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* python: (python.info). One line description of project
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Python 3.8.4, 七月 20, 2020

unknown

Copyright @copyright{} 2001-2020, Python Software Foundation
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@title Python
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@menu
* Python的新变化:: 
* Python 教程:: 
* Python安装和使用:: 
* Python语言参考:: 
* Python 标准库:: 
* 扩展和嵌入 Python 解释器:: 
* Python/C API 参考手册:: 
* 分发 Python 模块:: 
* 安装 Python 模块:: 
* Python 常用指引:: 
* Python 常见问题:: 
* 术语对照表:: 
* 文档说明:: 
* 处理错误:: 
* 版权所有:: 
* 历史和许可证:: 
* 分发 Python 模块（遗留版本）:: 
* 安装Python模块（旧版）:: 
* Python 模块索引:: 
* 索引:: 

@detailmenu
 --- The Detailed Node Listing ---

Python的新变化

* Python 3.8 有什么新变化: Python 3 8 有什么新变化. 
* Python 3.7 有什么新变化: Python 3 7 有什么新变化. 
* Python 3.6 有什么新变化: Python 3 6 有什么新变化. 
* Python 3.5 有什么新变化: Python 3 5 有什么新变化. 
* Python 3.4 有什么新变化: Python 3 4 有什么新变化. 
* Python 3.3 有什么新变化: Python 3 3 有什么新变化. 
* Python 3.2 有什么新变化: Python 3 2 有什么新变化. 
* Python 3.1 有什么新变化: Python 3 1 有什么新变化. 
* Python 3.0 有什么新变化: Python 3 0 有什么新变化. 
* Python 2.7 有什么新变化: Python 2 7 有什么新变化. 
* Python 2.6 有什么新变化: Python 2 6 有什么新变化. 
* Python 2.5 有什么新变化: Python 2 5 有什么新变化. 
* Python 2.4 有什么新变化: Python 2 4 有什么新变化. 
* Python 2.3 有什么新变化: Python 2 3 有什么新变化. 
* Python 2.2 有什么新变化: Python 2 2 有什么新变化. 
* Python 2.1 有什么新变化: Python 2 1 有什么新变化. 
* Python 2.0 有什么新变化: Python 2 0 有什么新变化. 
* 更新日志:: 

Python 3.8 有什么新变化

* 摘要 - 发布重点:: 
* 新的特性:: 
* 其他语言特性修改:: 
* 新增模块:: 
* 改进的模块:: 
* 性能优化:: 
* 构建和 C API 的改变:: 
* 弃用:: 
* API 与特性的移除:: 
* 移植到 Python 3.8: 移植到 Python 3 8. 
* Python 3.8.1 中的重要变化: Python 3 8 1 中的重要变化. 
* Python 3.8.2 中的重要变化: Python 3 8 2 中的重要变化. 
* Python 3.8.3 中的重要变化: Python 3 8 3 中的重要变化. 

新的特性

* 赋值表达式:: 
* 仅限位置形参:: 
* 用于已编译字节码文件的并行文件系统缓存:: 
* 调试构建使用与发布构建相同的 ABI:: 
* f-字符串支持 = 用于自动记录表达式和调试文档:: 
* PEP 578; Python 运行时审核钩子: PEP 578 Python 运行时审核钩子. 
* PEP 587; Python 初始化配置: PEP 587 Python 初始化配置. 
* Vectorcall; 用于 CPython 的快速调用协议: Vectorcall 用于 CPython 的快速调用协议. 
* 具有外部数据缓冲区的 pickle 协议 5:: 

改进的模块

* ast:: 
* asyncio:: 
* builtins:: 
* collections:: 
* cProfile:: 
* csv:: 
* curses:: 
* ctypes:: 
* datetime:: 
* functools:: 
* gc:: 
* gettext:: 
* gzip:: 
* IDLE 与 idlelib:: 
* inspect:: 
* io:: 
* itertools:: 
* json.tool: json tool. 
* logging:: 
* math:: 
* mmap:: 
* multiprocessing:: 
* os:: 
* os.path: os path. 
* pathlib:: 
* pickle:: 
* plistlib:: 
* pprint:: 
* py_compile:: 
* shlex:: 
* shutil:: 
* socket:: 
* ssl:: 
* statistics:: 
* sys:: 
* tarfile:: 
* threading:: 
* tokenize:: 
* tkinter:: 
* time:: 
* typing:: 
* unicodedata:: 
* unittest:: 
* venv:: 
* weakref:: 
* xml:: 
* xmlrpc:: 

移植到 Python 3.8

* Python 行为的改变:: 
* Python API 的变化:: 
* C API 的变化:: 
* CPython 字节码的改变:: 
* 演示和工具:: 

Python 3.7 有什么新变化

* 摘要 - 发布重点: 摘要 - 发布重点<2>. 
* 新的特性: 新的特性<2>. 
* 其他语言特性修改: 其他语言特性修改<2>. 
* 新增模块: 新增模块<2>. 
* 改进的模块: 改进的模块<2>. 
* C API 的改变:: 
* 构建的改变:: 
* 性能优化: 性能优化<2>. 
* 其他 CPython 实现的改变:: 
* 已弃用的 Python 行为:: 
* 已弃用的 Python 模块、函数和方法:: 
* 已弃用的 C API 函数和类型:: 
* 平台支持的移除:: 
* API 与特性的移除: API 与特性的移除<2>. 
* 移除的模块:: 
* Windows 专属的改变:: 
* 移植到 Python 3.7: 移植到 Python 3 7. 
* Python 3.7.1 中的重要变化: Python 3 7 1 中的重要变化. 
* Python 3.7.2 中的重要变化: Python 3 7 2 中的重要变化. 
* Python 3.7.6 中的重要变化: Python 3 7 6 中的重要变化. 

新的特性

* PEP 563：延迟的标注求值:: 
* PEP 538; 传统 C 区域强制转换: PEP 538 传统 C 区域强制转换. 
* PEP 540; 强制 UTF-8 运行时模式: PEP 540 强制 UTF-8 运行时模式. 
* PEP 553; 内置的 breakpoint(): PEP 553 内置的 breakpoint. 
* PEP 539; 用于线程局部存储的新 C API: PEP 539 用于线程局部存储的新 C API. 
* PEP 562; 定制对模块属性的访问: PEP 562 定制对模块属性的访问. 
* PEP 564; 具有纳秒级精度的新时间函数: PEP 564 具有纳秒级精度的新时间函数. 
* PEP 565; 在 __main__ 中显示 DeprecationWarning: PEP 565 在 __main__ 中显示 DeprecationWarning. 
* PEP 560; 对 typing 模块和泛型类型的核心支持: PEP 560 对 typing 模块和泛型类型的核心支持. 
* PEP 552; 基于哈希值的 .pyc 文件: PEP 552 基于哈希值的 pyc 文件. 
* PEP 545; Python 文档翻译: PEP 545 Python 文档翻译. 
* 开发运行时模式; -X dev: 开发运行时模式 -X dev. 

新增模块

* contextvars:: 
* dataclasses:: 
* importlib.resources: importlib resources. 

改进的模块

* argparse:: 
* asyncio: asyncio<2>. 
* binascii:: 
* calendar:: 
* collections: collections<2>. 
* compileall:: 
* concurrent.futures: concurrent futures. 
* contextlib:: 
* cProfile: cProfile<2>. 
* crypt:: 
* datetime: datetime<2>. 
* dbm:: 
* decimal:: 
* dis:: 
* distutils:: 
* enum:: 
* functools: functools<2>. 
* gc: gc<2>. 
* hmac:: 
* http.client: http client. 
* http.server: http server. 
* idlelib 与 IDLE:: 
* importlib:: 
* io: io<2>. 
* ipaddress:: 
* itertools: itertools<2>. 
* locale:: 
* logging: logging<2>. 
* math: math<2>. 
* mimetypes:: 
* msilib:: 
* multiprocessing: multiprocessing<2>. 
* os: os<2>. 
* pathlib: pathlib<2>. 
* pdb:: 
* py_compile: py_compile<2>. 
* pydoc:: 
* queue:: 
* re:: 
* signal:: 
* socket: socket<2>. 
* socketserver:: 
* sqlite3:: 
* ssl: ssl<2>. 
* string:: 
* subprocess:: 
* sys: sys<2>. 
* time: time<2>. 
* tkinter: tkinter<2>. 
* tracemalloc:: 
* types:: 
* unicodedata: unicodedata<2>. 
* unittest: unittest<2>. 
* unittest.mock: unittest mock. 
* urllib.parse: urllib parse. 
* uu:: 
* uuid:: 
* warnings:: 
* xml.etree: xml etree. 
* xmlrpc.server: xmlrpc server. 
* zipapp:: 
* zipfile:: 

已弃用的 Python 模块、函数和方法

* aifc:: 
* asyncio: asyncio<3>. 
* collections: collections<3>. 
* dbm: dbm<2>. 
* enum: enum<2>. 
* gettext: gettext<2>. 
* importlib: importlib<2>. 
* locale: locale<2>. 
* macpath:: 
* threading: threading<2>. 
* socket: socket<3>. 
* ssl: ssl<3>. 
* sunau:: 
* sys: sys<3>. 
* wave:: 

移植到 Python 3.7

* Python 行为的更改:: 
* Python API 的变化: Python API 的变化<2>. 
* C API 的变化: C API 的变化<2>. 
* CPython 字节码的改变: CPython 字节码的改变<2>. 
* Windows 专属的改变: Windows 专属的改变<2>. 
* 其他 CPython 实现的改变: 其他 CPython 实现的改变<2>. 

Python 3.6 有什么新变化

* 摘要 - 发布重点: 摘要 - 发布重点<3>. 
* 新的特性: 新的特性<3>. 
* 其他语言特性修改: 其他语言特性修改<3>. 
* 新增模块: 新增模块<3>. 
* 改进的模块: 改进的模块<3>. 
* 性能优化: 性能优化<3>. 
* 构建和 C API 的改变: 构建和 C API 的改变<2>. 
* 其他改进:: 
* 弃用: 弃用<2>. 
* 移除:: 
* 移植到Python 3.6: 移植到Python 3 6. 
* Python 3.6.2 中的重要变化: Python 3 6 2 中的重要变化. 
* Python 3.6.4 中的重要变化: Python 3 6 4 中的重要变化. 
* Python 3.6.5 中的重要变化: Python 3 6 5 中的重要变化. 
* Python 3.6.7 中的重要变化: Python 3 6 7 中的重要变化. 
* Python 3.6.10 中的重要变化: Python 3 6 10 中的重要变化. 

新的特性

* PEP 498; 格式化的字符串文字: PEP 498 格式化的字符串文字. 
* PEP 526; 变量注释的语法: PEP 526 变量注释的语法. 
* PEP 515; 数字文字中的下划线。: PEP 515 数字文字中的下划线。. 
* PEP 525; 异步生成器: PEP 525 异步生成器. 
* PEP 530; 异步推导: PEP 530 异步推导. 
* PEP 487; 自定义类创建: PEP 487 自定义类创建. 
* PEP 487; Descriptor Protocol Enhancements: PEP 487 Descriptor Protocol Enhancements. 
* PEP 519; 添加文件系统路径协议: PEP 519 添加文件系统路径协议. 
* PEP 495; 消除本地时间的歧义: PEP 495 消除本地时间的歧义. 
* PEP 529; 将Windows文件系统编码更改为UTF-8: PEP 529 将Windows文件系统编码更改为UTF-8. 
* PEP 528; 将Windows控制台编码更改为UTF-8: PEP 528 将Windows控制台编码更改为UTF-8. 
* PEP 520; 保留类属性定义顺序: PEP 520 保留类属性定义顺序. 
* PEP 468; 保留关键字参数顺序: PEP 468 保留关键字参数顺序. 
* 新的 dict 实现:: 
* PEP 523; 向CPython 添加框架评估API: PEP 523 向CPython 添加框架评估API. 
* PYTHONMALLOC 环境变量:: 
* DTrace 和 SystemTap 探测支持:: 

新增模块

* secrets:: 

改进的模块

* array:: 
* ast: ast<2>. 
* asyncio: asyncio<4>. 
* binascii: binascii<2>. 
* cmath:: 
* collections: collections<4>. 
* concurrent.futures: concurrent futures<2>. 
* contextlib: contextlib<2>. 
* datetime: datetime<3>. 
* decimal: decimal<2>. 
* distutils: distutils<2>. 
* email:: 
* encodings:: 
* enum: enum<3>. 
* faulthandler:: 
* fileinput:: 
* hashlib:: 
* http.client: http client<2>. 
* idlelib 与 IDLE: idlelib 与 IDLE<2>. 
* importlib: importlib<3>. 
* inspect: inspect<2>. 
* json:: 
* logging: logging<3>. 
* math: math<3>. 
* multiprocessing: multiprocessing<3>. 
* os: os<3>. 
* pathlib: pathlib<3>. 
* pdb: pdb<2>. 
* pickle: pickle<2>. 
* pickletools:: 
* pydoc: pydoc<2>. 
* random:: 
* re: re<2>. 
* readline:: 
* rlcompleter:: 
* shlex: shlex<2>. 
* site:: 
* sqlite3: sqlite3<2>. 
* socket: socket<4>. 
* socketserver: socketserver<2>. 
* ssl: ssl<4>. 
* statistics: statistics<2>. 
* struct:: 
* subprocess: subprocess<2>. 
* sys: sys<4>. 
* telnetlib:: 
* time: time<3>. 
* timeit:: 
* tkinter: tkinter<3>. 
* 回溯:: 
* tracemalloc: tracemalloc<2>. 
* typing: typing<2>. 
* unicodedata: unicodedata<3>. 
* unittest.mock: unittest mock<2>. 
* urllib.request: urllib request. 
* urllib.robotparser: urllib robotparser. 
* venv: venv<2>. 
* warnings: warnings<2>. 
* winreg:: 
* winsound:: 
* xmlrpc.client: xmlrpc client. 
* zipfile: zipfile<2>. 
* zlib:: 

弃用

* 新关键字:: 
* 已弃用的 Python 行为: 已弃用的 Python 行为<2>. 
* 已弃用的 Python 模块、函数和方法: 已弃用的 Python 模块、函数和方法<2>. 
* 已弃用的 C API 函数和类型: 已弃用的 C API 函数和类型<2>. 
* 弃用的构建选项:: 

已弃用的 Python 模块、函数和方法

* asynchat:: 
* asyncore:: 
* dbm: dbm<3>. 
* distutils: distutils<3>. 
* grp:: 
* importlib: importlib<4>. 
* os: os<4>. 
* re: re<3>. 
* ssl: ssl<5>. 
* tkinter: tkinter<4>. 
* venv: venv<3>. 

移除

* API 与特性的移除: API 与特性的移除<3>. 

移植到Python 3.6

* 'python' 命令行为的变化:: 
* Python API 的变化: Python API 的变化<3>. 
* C API 的变化: C API 的变化<3>. 
* CPython 字节码的改变: CPython 字节码的改变<3>. 

Python 3.6.2 中的重要变化

* New make regen-all build target:: 
* Removal of make touch build target:: 

Python 3.5 有什么新变化

* 摘要 - 发布重点: 摘要 - 发布重点<4>. 
* 新的特性: 新的特性<4>. 
* 其他语言特性修改: 其他语言特性修改<4>. 
* 新增模块: 新增模块<4>. 
* 改进的模块: 改进的模块<4>. 
* 其他模块级更改:: 
* 性能优化: 性能优化<4>. 
* 构建和 C API 的改变: 构建和 C API 的改变<3>. 
* 弃用: 弃用<3>. 
* 移除: 移除<2>. 
* 移植到Python 3.5: 移植到Python 3 5. 
* Python 3.5.4 的显著变化: Python 3 5 4 的显著变化. 

新的特性

* PEP 492 - 使用 async 和 await 语法实现协程:: 
* PEP 465 - 用于矩阵乘法的专用中缀运算符:: 
* PEP 448 - Additional Unpacking Generalizations:: 
* PEP 461 - percent formatting support for bytes and bytearray:: 
* PEP 484 - 类型提示:: 
* PEP 471 - os.scandir() function: PEP 471 - os scandir function -- a better and faster directory iterator. a better and faster directory iterator
* PEP 475; Retry system calls failing with EINTR: PEP 475 Retry system calls failing with EINTR. 
* PEP 479; Change StopIteration handling inside generators: PEP 479 Change StopIteration handling inside generators. 
* PEP 485; A function for testing approximate equality: PEP 485 A function for testing approximate equality. 
* PEP 486; Make the Python Launcher aware of virtual environments: PEP 486 Make the Python Launcher aware of virtual environments. 
* PEP 488; Elimination of PYO files: PEP 488 Elimination of PYO files. 
* PEP 489; Multi-phase extension module initialization: PEP 489 Multi-phase extension module initialization. 

新增模块

* typing: typing<3>. 
* zipapp: zipapp<2>. 

改进的模块

* argparse: argparse<2>. 
* asyncio: asyncio<5>. 
* bz2:: 
* cgi:: 
* cmath: cmath<2>. 
* code:: 
* collections: collections<5>. 
* collections.abc: collections abc. 
* compileall: compileall<2>. 
* concurrent.futures: concurrent futures<3>. 
* configparser:: 
* contextlib: contextlib<3>. 
* csv: csv<2>. 
* curses: curses<2>. 
* dbm: dbm<4>. 
* difflib:: 
* distutils: distutils<4>. 
* doctest:: 
* email: email<2>. 
* enum: enum<4>. 
* faulthandler: faulthandler<2>. 
* functools: functools<3>. 
* glob:: 
* gzip: gzip<2>. 
* heapq:: 
* http:: 
* http.client: http client<3>. 
* idlelib 与 IDLE: idlelib 与 IDLE<3>. 
* imaplib:: 
* imghdr:: 
* importlib: importlib<5>. 
* inspect: inspect<3>. 
* io: io<3>. 
* ipaddress: ipaddress<2>. 
* json: json<2>. 
* linecache:: 
* locale: locale<3>. 
* logging: logging<4>. 
* lzma:: 
* math: math<4>. 
* multiprocessing: multiprocessing<4>. 
* operator:: 
* os: os<5>. 
* pathlib: pathlib<4>. 
* pickle: pickle<3>. 
* poplib:: 
* re: re<4>. 
* readline: readline<2>. 
* selectors:: 
* shutil: shutil<2>. 
* signal: signal<2>. 
* smtpd:: 
* smtplib:: 
* sndhdr:: 
* socket: socket<5>. 
* ssl: ssl<6>. 
* sqlite3: sqlite3<3>. 
* subprocess: subprocess<3>. 
* sys: sys<5>. 
* sysconfig:: 
* tarfile: tarfile<2>. 
* threading: threading<3>. 
* time: time<4>. 
* timeit: timeit<2>. 
* tkinter: tkinter<5>. 
* 回溯: 回溯<2>. 
* types: types<2>. 
* unicodedata: unicodedata<4>. 
* unittest: unittest<3>. 
* unittest.mock: unittest mock<3>. 
* urllib:: 
* wsgiref:: 
* xmlrpc: xmlrpc<2>. 
* xml.sax: xml sax. 
* zipfile: zipfile<3>. 

ssl

* Memory BIO Support:: 
* Application-Layer Protocol Negotiation Support:: 
* Other Changes:: 

弃用

* 新关键字: 新关键字<2>. 
* 已弃用的 Python 行为: 已弃用的 Python 行为<3>. 
* 不支持的操作系统:: 
* 已弃用的 Python 模块、函数和方法: 已弃用的 Python 模块、函数和方法<3>. 

移除

* API 与特性的移除: API 与特性的移除<4>. 

移植到Python 3.5

* Python 行为的改变: Python 行为的改变<2>. 
* Python API 的变化: Python API 的变化<4>. 
* C API 的变化: C API 的变化<4>. 

Python 3.5.4 的显著变化

* New make regen-all build target: New make regen-all build target<2>. 
* Removal of make touch build target: Removal of make touch build target<2>. 

Python 3.4 有什么新变化

* 摘要 - 发布重点: 摘要 - 发布重点<5>. 
* 新的特性: 新的特性<5>. 
* 新增模块: 新增模块<5>. 
* 改进的模块: 改进的模块<5>. 
* CPython Implementation Changes:: 
* 弃用: 弃用<4>. 
* 移除: 移除<3>. 
* 移植到 Python 3.4: 移植到 Python 3 4. 
* 3.4.3 的变化: 3 4 3 的变化. 

新的特性

* PEP 453; Explicit Bootstrapping of PIP in Python Installations: PEP 453 Explicit Bootstrapping of PIP in Python Installations. 
* PEP 446; Newly Created File Descriptors Are Non-Inheritable: PEP 446 Newly Created File Descriptors Are Non-Inheritable. 
* Improvements to Codec Handling:: 
* PEP 451; A ModuleSpec Type for the Import System: PEP 451 A ModuleSpec Type for the Import System. 
* 其他语言特性修改: 其他语言特性修改<5>. 

PEP 453: Explicit Bootstrapping of PIP in Python Installations

* Bootstrapping pip By Default:: 
* 文档更改:: 

新增模块

* asyncio: asyncio<6>. 
* ensurepip:: 
* enum: enum<5>. 
* pathlib: pathlib<5>. 
* selectors: selectors<2>. 
* statistics: statistics<3>. 
* tracemalloc: tracemalloc<3>. 

改进的模块

* abc:: 
* aifc: aifc<2>. 
* argparse: argparse<3>. 
* audioop:: 
* base64:: 
* collections: collections<6>. 
* colorsys:: 
* contextlib: contextlib<4>. 
* dbm: dbm<5>. 
* dis: dis<2>. 
* doctest: doctest<2>. 
* email: email<3>. 
* filecmp:: 
* functools: functools<4>. 
* gc: gc<3>. 
* glob: glob<2>. 
* hashlib: hashlib<2>. 
* hmac: hmac<2>. 
* html:: 
* http: http<2>. 
* idlelib 与 IDLE: idlelib 与 IDLE<4>. 
* importlib: importlib<6>. 
* inspect: inspect<4>. 
* ipaddress: ipaddress<3>. 
* logging: logging<5>. 
* marshal:: 
* mmap: mmap<2>. 
* multiprocessing: multiprocessing<5>. 
* operator: operator<2>. 
* os: os<6>. 
* pdb: pdb<3>. 
* pickle: pickle<4>. 
* plistlib: plistlib<2>. 
* poplib: poplib<2>. 
* pprint: pprint<2>. 
* pty:: 
* pydoc: pydoc<3>. 
* re: re<5>. 
* resource:: 
* select:: 
* shelve:: 
* shutil: shutil<3>. 
* smtpd: smtpd<2>. 
* smtplib: smtplib<2>. 
* socket: socket<6>. 
* sqlite3: sqlite3<4>. 
* ssl: ssl<7>. 
* stat:: 
* struct: struct<2>. 
* subprocess: subprocess<4>. 
* sunau: sunau<2>. 
* sys: sys<6>. 
* tarfile: tarfile<3>. 
* textwrap:: 
* threading: threading<4>. 
* 回溯: 回溯<3>. 
* types: types<3>. 
* urllib: urllib<2>. 
* unittest: unittest<4>. 
* venv: venv<4>. 
* wave: wave<2>. 
* weakref: weakref<2>. 
* xml.etree: xml etree<2>. 
* zipfile: zipfile<4>. 

CPython Implementation Changes

* PEP 445; Customization of CPython Memory Allocators: PEP 445 Customization of CPython Memory Allocators. 
* PEP 442; Safe Object Finalization: PEP 442 Safe Object Finalization. 
* PEP 456; Secure and Interchangeable Hash Algorithm: PEP 456 Secure and Interchangeable Hash Algorithm. 
* PEP 436; Argument Clinic: PEP 436 Argument Clinic. 
* Other Build and C API Changes:: 
* 其他改进: 其他改进<2>. 
* Significant Optimizations:: 

弃用

* Deprecations in the Python API:: 
* Deprecated Features:: 

移除

* 不再支持的操作系统:: 
* API 与特性的移除: API 与特性的移除<5>. 
* Code Cleanups:: 

移植到 Python 3.4

* 'python' 命令行为的变化: 'python' 命令行为的变化<2>. 
* Python API 的变化: Python API 的变化<5>. 
* C API 的变化: C API 的变化<5>. 

3.4.3 的变化

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

Python 3.3 有什么新变化

* 摘要 - 发布重点: 摘要 - 发布重点<6>. 
* PEP 405; 虚拟环境: PEP 405 虚拟环境. 
* PEP 420; 隐式命名空间包: PEP 420 隐式命名空间包. 
* PEP 3118; 新的内存视图实现和缓冲协议文档: PEP 3118 新的内存视图实现和缓冲协议文档. 
* PEP 393; 灵活的字符串表示: PEP 393 灵活的字符串表示. 
* PEP 397; 适用于Windows的Python启动器: PEP 397 适用于Windows的Python启动器. 
* PEP 3151; 重写 OS 和 IO 异常的层次结构: PEP 3151 重写 OS 和 IO 异常的层次结构. 
* PEP 380; 委托给子生成器的语法: PEP 380 委托给子生成器的语法. 
* PEP 409; 清除异常上下文: PEP 409 清除异常上下文. 
* PEP 414; 显式的Unicode文本: PEP 414 显式的Unicode文本. 
* PEP 3155; 类和函数的限定名称: PEP 3155 类和函数的限定名称. 
* PEP 412; Key-Sharing Dictionary: PEP 412 Key-Sharing Dictionary. 
* PEP 362; 函数签名对象: PEP 362 函数签名对象. 
* PEP 421; 添加 sys.implementation: PEP 421 添加 sys implementation. 
* Using importlib as the Implementation of Import:: 
* 其他语言特性修改: 其他语言特性修改<6>. 
* A Finer-Grained Import Lock:: 
* Builtin functions and types:: 
* 新增模块: 新增模块<6>. 
* 改进的模块: 改进的模块<6>. 
* 性能优化: 性能优化<5>. 
* 构建和 C API 的改变: 构建和 C API 的改变<4>. 
* 弃用: 弃用<5>. 
* 移植到 Python 3.3: 移植到 Python 3 3. 

PEP 3118: 新的内存视图实现和缓冲协议文档

* 相关特性:: 
* API changes:: 

PEP 393: 灵活的字符串表示

* Functionality:: 
* Performance and resource usage:: 

PEP 421: 添加 sys.implementation

* SimpleNamespace:: 

Using importlib as the Implementation of Import

* New APIs:: 
* Visible Changes:: 

新增模块

* faulthandler: faulthandler<3>. 
* ipaddress: ipaddress<4>. 
* lzma: lzma<2>. 

改进的模块

* abc: abc<2>. 
* array: array<2>. 
* base64: base64<2>. 
* binascii: binascii<3>. 
* bz2: bz2<2>. 
* codecs:: 
* collections: collections<7>. 
* contextlib: contextlib<5>. 
* crypt: crypt<2>. 
* curses: curses<3>. 
* datetime: datetime<4>. 
* decimal: decimal<3>. 
* email: email<4>. 
* ftplib:: 
* functools: functools<5>. 
* gc: gc<4>. 
* hmac: hmac<3>. 
* http: http<3>. 
* html: html<2>. 
* imaplib: imaplib<2>. 
* inspect: inspect<5>. 
* io: io<4>. 
* itertools: itertools<3>. 
* logging: logging<6>. 
* math: math<5>. 
* mmap: mmap<3>. 
* multiprocessing: multiprocessing<6>. 
* nntplib:: 
* os: os<7>. 
* pdb: pdb<4>. 
* pickle: pickle<5>. 
* pydoc: pydoc<4>. 
* re: re<6>. 
* sched:: 
* select: select<2>. 
* shlex: shlex<3>. 
* shutil: shutil<4>. 
* signal: signal<3>. 
* smtpd: smtpd<3>. 
* smtplib: smtplib<3>. 
* socket: socket<7>. 
* socketserver: socketserver<3>. 
* sqlite3: sqlite3<5>. 
* ssl: ssl<8>. 
* stat: stat<2>. 
* struct: struct<3>. 
* subprocess: subprocess<5>. 
* sys: sys<7>. 
* tarfile: tarfile<4>. 
* tempfile:: 
* textwrap: textwrap<2>. 
* threading: threading<5>. 
* time: time<5>. 
* types: types<4>. 
* unittest: unittest<5>. 
* urllib: urllib<3>. 
* webbrowser:: 
* xml.etree.ElementTree: xml etree ElementTree. 
* zlib: zlib<2>. 

decimal

* 相关特性: 相关特性<2>. 
* API changes: API changes<2>. 

email

* Policy Framework:: 
* Provisional Policy with New Header API:: 
* Other API Changes:: 

弃用

* 不支持的操作系统: 不支持的操作系统<2>. 
* 已弃用的 Python 模块、函数和方法: 已弃用的 Python 模块、函数和方法<4>. 
* 已弃用的 C API 函数和类型: 已弃用的 C API 函数和类型<3>. 
* 弃用的功能:: 

移植到 Python 3.3

* Porting Python code:: 
* Porting C code:: 
* Building C extensions:: 
* Command Line Switch Changes:: 

Python 3.2 有什么新变化

* PEP 384; 定义稳定的ABI: PEP 384 定义稳定的ABI. 
* PEP 389; Argparse 命令行解析模块: PEP 389 Argparse 命令行解析模块. 
* PEP 391; 基于字典的日志配置: PEP 391 基于字典的日志配置. 
* PEP 3148; concurrent.futures 模块: PEP 3148 concurrent futures 模块. 
* PEP 3147; PYC 仓库目录: PEP 3147 PYC 仓库目录. 
* PEP 3149; ABI Version Tagged .so Files: PEP 3149 ABI Version Tagged so Files. 
* PEP 3333; Python Web服务器网关接口v1.0.1: PEP 3333 Python Web服务器网关接口v1 0 1. 
* 其他语言特性修改: 其他语言特性修改<7>. 
* 新增，改进和弃用的模块:: 
* 多线程:: 
* 性能优化: 性能优化<6>. 
* Unicode:: 
* 编解码器:: 
* 文档:: 
* IDLE:: 
* 代码库:: 
* 构建和 C API 的改变: 构建和 C API 的改变<5>. 
* 移植到 Python 3.2: 移植到 Python 3 2. 

新增，改进和弃用的模块

* email: email<5>. 
* elementtree:: 
* functools: functools<6>. 
* itertools: itertools<4>. 
* collections: collections<8>. 
* threading: threading<6>. 
* datetime 和 time:: 
* math: math<6>. 
* abc: abc<3>. 
* io: io<5>. 
* reprlib:: 
* logging: logging<7>. 
* csv: csv<3>. 
* contextlib: contextlib<6>. 
* decimal and fractions:: 
* ftp:: 
* popen:: 
* select: select<3>. 
* gzip 和 zipfile:: 
* tarfile: tarfile<5>. 
* hashlib: hashlib<3>. 
* ast: ast<3>. 
* os: os<8>. 
* shutil: shutil<5>. 
* sqlite3: sqlite3<6>. 
* html: html<3>. 
* socket: socket<8>. 
* ssl: ssl<9>. 
* nntp:: 
* certificates:: 
* imaplib: imaplib<3>. 
* http.client: http client<4>. 
* unittest: unittest<6>. 
* random: random<2>. 
* poplib: poplib<3>. 
* asyncore: asyncore<2>. 
* tempfile: tempfile<2>. 
* inspect: inspect<6>. 
* pydoc: pydoc<5>. 
* dis: dis<3>. 
* dbm: dbm<6>. 
* ctypes: ctypes<2>. 
* site: site<2>. 
* sysconfig: sysconfig<2>. 
* pdb: pdb<5>. 
* configparser: configparser<2>. 
* urllib.parse: urllib parse<2>. 
* mailbox:: 
* turtledemo:: 

Python 3.1 有什么新变化

* PEP 372; 有序字典: PEP 372 有序字典. 
* PEP 378; 千位分隔符的格式说明符: PEP 378 千位分隔符的格式说明符. 
* 其他语言特性修改: 其他语言特性修改<8>. 
* 新增，改进和弃用的模块: 新增，改进和弃用的模块<2>. 
* 性能优化: 性能优化<7>. 
* IDLE: IDLE<2>. 
* 构建和 C API 的改变: 构建和 C API 的改变<6>. 
* 移植到 Python 3.1: 移植到 Python 3 1. 

Python 3.0 有什么新变化

* 常见的绊脚石:: 
* Overview Of Syntax Changes:: 
* Changes Already Present In Python 2.6: Changes Already Present In Python 2 6. 
* Library Changes:: 
* PEP 3101; A New Approach To String Formatting: PEP 3101 A New Approach To String Formatting. 
* Changes To Exceptions:: 
* Miscellaneous Other Changes:: 
* 构建和 C API 的改变: 构建和 C API 的改变<7>. 
* 性能:: 
* 移植到 Python 3.0: 移植到 Python 3 0. 

常见的绊脚石

* Print Is A Function:: 
* Views And Iterators Instead Of Lists:: 
* Ordering Comparisons:: 
* 整数:: 
* Text Vs. Data Instead Of Unicode Vs. 8-bit: Text Vs Data Instead Of Unicode Vs 8-bit. 

Overview Of Syntax Changes

* 新语法:: 
* 修改的语法:: 
* 移除的语法:: 

Miscellaneous Other Changes

* Operators And Special Methods:: 
* Builtins:: 

Python 2.7 有什么新变化

* Python 2.x的未来: Python 2 x的未来. 
* Changes to the Handling of Deprecation Warnings:: 
* Python 3.1 Features: Python 3 1 Features. 
* PEP 372; Adding an Ordered Dictionary to collections: PEP 372 Adding an Ordered Dictionary to collections. 
* PEP 378; 千位分隔符的格式说明符: PEP 378 千位分隔符的格式说明符<2>. 
* PEP 389; The argparse Module for Parsing Command Lines: PEP 389 The argparse Module for Parsing Command Lines. 
* PEP 391; Dictionary-Based Configuration For Logging: PEP 391 Dictionary-Based Configuration For Logging. 
* PEP 3106; Dictionary Views: PEP 3106 Dictionary Views. 
* PEP 3137; The memoryview Object: PEP 3137 The memoryview Object. 
* 其他语言特性修改: 其他语言特性修改<9>. 
* 新增和改进的模块:: 
* 构建和 C API 的改变: 构建和 C API 的改变<8>. 
* Other Changes and Fixes:: 
* 移植到 Python 2.7: 移植到 Python 2 7. 
* New Features Added to Python 2.7 Maintenance Releases: New Features Added to Python 2 7 Maintenance Releases. 
* 致谢:: 

其他语言特性修改

* Interpreter Changes:: 
* 性能优化: 性能优化<8>. 

新增和改进的模块

* 新模块：importlib:: 
* 新模块：sysconfig:: 
* ttk; Themed Widgets for Tk: ttk Themed Widgets for Tk. 
* 更新的模块：unittest:: 
* 更新的模块：ElementTree 1.3: 更新的模块：ElementTree 1 3. 

构建和 C API 的改变

* 胶囊:: 
* 特定于 Windows 的更改：:: 
* 特定于 Mac OS X 的更改：:: 
* 特定于 FreeBSD 的更改：:: 

New Features Added to Python 2.7 Maintenance Releases

* Two new environment variables for debug mode:: 
* PEP 434; IDLE Enhancement Exception for All Branches: PEP 434 IDLE Enhancement Exception for All Branches. 
* PEP 466; Network Security Enhancements for Python 2.7: PEP 466 Network Security Enhancements for Python 2 7. 
* PEP 477; Backport ensurepip (PEP 453) to Python 2.7: PEP 477 Backport ensurepip PEP 453 to Python 2 7. 
* PEP 476; Enabling certificate verification by default for stdlib http clients: PEP 476 Enabling certificate verification by default for stdlib http clients<2>. 
* PEP 493：适用于Python 2.7 的 HTTPS 验证迁移工具: PEP 493：适用于Python 2 7 的 HTTPS 验证迁移工具. 
* New make regen-all build target: New make regen-all build target<3>. 
* Removal of make touch build target: Removal of make touch build target<3>. 

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

* Bootstrapping pip By Default: Bootstrapping pip By Default<2>. 
* 文档更改: 文档更改<2>. 

Python 2.6 有什么新变化

* Python 3.0: Python 3 0. 
* 开发过程的变化:: 
* PEP 343; "with" 语句: PEP 343 "with" 语句. 
* PEP 366; 从主模块显式相对导入: PEP 366 从主模块显式相对导入. 
* PEP 370; 分用户的 site-packages 目录: PEP 370 分用户的 site-packages 目录. 
* PEP 371; 多任务处理包: PEP 371 多任务处理包. 
* PEP 3101; 高级字符串格式: PEP 3101 高级字符串格式. 
* PEP 3105; print 改为函数: PEP 3105 print 改为函数. 
* PEP 3110; 异常处理的变更: PEP 3110 异常处理的变更. 
* PEP 3112; 字节字面值: PEP 3112 字节字面值. 
* PEP 3116; 新 I/O 库: PEP 3116 新 I/O 库. 
* PEP 3118; 修改缓冲区协议: PEP 3118 修改缓冲区协议. 
* PEP 3119; 抽象基类: PEP 3119 抽象基类. 
* PEP 3127; 整型文字支持和语法: PEP 3127 整型文字支持和语法. 
* PEP 3129; 类装饰器: PEP 3129 类装饰器. 
* PEP 3141; A Type Hierarchy for Numbers: PEP 3141 A Type Hierarchy for Numbers. 
* 其他语言特性修改: 其他语言特性修改<10>. 
* 新增和改进的模块: 新增和改进的模块<2>. 
* Deprecations and Removals:: 
* 构建和 C API 的改变: 构建和 C API 的改变<9>. 
* 移植到Python 2.6: 移植到Python 2 6. 
* 致谢: 致谢<2>. 

开发过程的变化

* New Issue Tracker; Roundup: New Issue Tracker Roundup. 
* 新的文档格式：使用 Sphinx 的 reStructuredText:: 

PEP 343: "with" 语句

* Writing Context Managers:: 
* contextlib 模块:: 

PEP 3141: A Type Hierarchy for Numbers

* fractions 模块:: 

其他语言特性修改

* 性能优化: 性能优化<9>. 
* Interpreter Changes: Interpreter Changes<2>. 

新增和改进的模块

* ast 模块:: 
* future_builtins 模块:: 
* The json module; JavaScript Object Notation: The json module JavaScript Object Notation. 
* plistlib 模块：属性列表解析器:: 
* ctypes Enhancements:: 
* Improved SSL Support:: 

构建和 C API 的改变

* 特定于 Windows 的更改：: 特定于 Windows 的更改：<2>. 
* 特定于 Mac OS X 的更改：: 特定于 Mac OS X 的更改：<2>. 
* 特定于 IRIX 的更改：:: 

Python 2.5 有什么新变化

* PEP 308; 条件表达式: PEP 308 条件表达式. 
* PEP 309; 部分功能应用: PEP 309 部分功能应用. 
* PEP 314; Python软件包的元数据 v1.1: PEP 314 Python软件包的元数据 v1 1. 
* PEP 328; 绝对导入和相对导入: PEP 328 绝对导入和相对导入. 
* PEP 338; 将模块作为脚本执行: PEP 338 将模块作为脚本执行. 
* PEP 341; 统一 try/except/finally: PEP 341 统一 try/except/finally. 
* PEP 342; 生成器的新特性: PEP 342 生成器的新特性. 
* PEP 343; "with" 语句: PEP 343 "with" 语句<2>. 
* PEP 352; 异常作为新型的类: PEP 352 异常作为新型的类. 
* PEP 353; 使用ssize_t作为索引类型: PEP 353 使用ssize_t作为索引类型. 
* PEP 357; '__index__' 方法: PEP 357 '__index__' 方法. 
* 其他语言特性修改: 其他语言特性修改<11>. 
* 新增，改进和删除的模块:: 
* 构建和 C API 的改变: 构建和 C API 的改变<10>. 
* 移植到Python 2.5: 移植到Python 2 5. 
* 致谢: 致谢<3>. 

PEP 343: "with" 语句

* Writing Context Managers: Writing Context Managers<2>. 
* contextlib 模块: contextlib 模块<2>. 

其他语言特性修改

* 交互解释器变更:: 
* 性能优化: 性能优化<10>. 

新增，改进和删除的模块

* ctypes 包:: 
* ElementTree 包:: 
* hashlib 包:: 
* sqlite3 包:: 
* wsgiref 包:: 

构建和 C API 的改变

* Port-Specific Changes:: 

Python 2.4 有什么新变化

* PEP 218; 内置集合对象: PEP 218 内置集合对象. 
* PEP 237; 统一长整数和整数: PEP 237 统一长整数和整数. 
* PEP 289; 生成器表达式: PEP 289 生成器表达式. 
* PEP 292; Simpler String Substitutions: PEP 292 Simpler String Substitutions. 
* PEP 318; Decorators for Functions and Methods: PEP 318 Decorators for Functions and Methods. 
* PEP 322; 反向迭代: PEP 322 反向迭代. 
* PEP 324; 新的子进程模块: PEP 324 新的子进程模块. 
* PEP 327; 十进制数据类型: PEP 327 十进制数据类型. 
* PEP 328; 多行导入: PEP 328 多行导入. 
* PEP 331; Locale-Independent Float/String Conversions: PEP 331 Locale-Independent Float/String Conversions. 
* 其他语言特性修改: 其他语言特性修改<12>. 
* 新增，改进和弃用的模块: 新增，改进和弃用的模块<3>. 
* 构建和 C API 的改变: 构建和 C API 的改变<11>. 
* 移植到 Python 2.4: 移植到 Python 2 4. 
* 致谢: 致谢<4>. 

PEP 327: 十进制数据类型

* 为什么需要十进制？:: 
* Decimal 类型:: 
* Context 类型:: 

其他语言特性修改

* 性能优化: 性能优化<11>. 

新增，改进和弃用的模块

* cookielib:: 
* doctest: doctest<3>. 

构建和 C API 的改变

* Port-Specific Changes: Port-Specific Changes<2>. 

Python 2.3 有什么新变化

* PEP 218; A Standard Set Datatype: PEP 218 A Standard Set Datatype. 
* PEP 255; Simple Generators: PEP 255 Simple Generators. 
* PEP 263; Source Code Encodings: PEP 263 Source Code Encodings. 
* PEP 273; 从ZIP压缩包导入模块: PEP 273 从ZIP压缩包导入模块. 
* PEP 277; Unicode file name support for Windows NT: PEP 277 Unicode file name support for Windows NT. 
* PEP 278; 通用换行支持: PEP 278 通用换行支持. 
* PEP 279; enumerate(): PEP 279 enumerate. 
* PEP 282; logging 包: PEP 282 logging 包. 
* PEP 285; 布尔类型: PEP 285 布尔类型. 
* PEP 293; Codec Error Handling Callbacks: PEP 293 Codec Error Handling Callbacks. 
* PEP 301; Distutils的软件包索引和元数据: PEP 301 Distutils的软件包索引和元数据. 
* PEP 302; New Import Hooks: PEP 302 New Import Hooks. 
* PEP 305; 逗号分隔文件: PEP 305 逗号分隔文件. 
* PEP 307; Pickle Enhancements: PEP 307 Pickle Enhancements. 
* 扩展切片:: 
* 其他语言特性修改: 其他语言特性修改<13>. 
* 新增，改进和弃用的模块: 新增，改进和弃用的模块<4>. 
* Pymalloc; A Specialized Object Allocator: Pymalloc A Specialized Object Allocator. 
* 构建和 C API 的改变: 构建和 C API 的改变<12>. 
* Other Changes and Fixes: Other Changes and Fixes<2>. 
* 移植到 Python 2.3: 移植到 Python 2 3. 
* 致谢: 致谢<5>. 

其他语言特性修改

* String Changes:: 
* 性能优化: 性能优化<12>. 

新增，改进和弃用的模块

* Date/Time 类型:: 
* optparse 模块:: 

构建和 C API 的改变

* Port-Specific Changes: Port-Specific Changes<3>. 

Python 2.2 有什么新变化

* 概述:: 
* PEPs 252 and 253; Type and Class Changes: PEPs 252 and 253 Type and Class Changes. 
* PEP 234; Iterators: PEP 234 Iterators. 
* PEP 255; Simple Generators: PEP 255 Simple Generators<2>. 
* PEP 237; 统一长整数和整数: PEP 237 统一长整数和整数<2>. 
* PEP 238; Changing the Division Operator: PEP 238 Changing the Division Operator. 
* Unicode Changes:: 
* PEP 227; Nested Scopes: PEP 227 Nested Scopes. 
* 新增和改进的模块: 新增和改进的模块<3>. 
* Interpreter Changes and Fixes:: 
* Other Changes and Fixes: Other Changes and Fixes<3>. 
* 致谢: 致谢<6>. 

PEPs 252 and 253: Type and Class Changes

* Old and New Classes:: 
* Descriptors:: 
* Multiple Inheritance; The Diamond Rule: Multiple Inheritance The Diamond Rule. 
* Attribute Access:: 
* Related Links:: 

Python 2.1 有什么新变化

* 概述: 概述<2>. 
* PEP 227; Nested Scopes: PEP 227 Nested Scopes<2>. 
* PEP 236; __future__ Directives: PEP 236 __future__ Directives. 
* PEP 207; Rich Comparisons: PEP 207 Rich Comparisons. 
* PEP 230; Warning Framework: PEP 230 Warning Framework. 
* PEP 229; New Build System: PEP 229 New Build System. 
* PEP 205; Weak References: PEP 205 Weak References. 
* PEP 232; Function Attributes: PEP 232 Function Attributes. 
* PEP 235; Importing Modules on Case-Insensitive Platforms: PEP 235 Importing Modules on Case-Insensitive Platforms. 
* PEP 217; Interactive Display Hook: PEP 217 Interactive Display Hook. 
* PEP 208; New Coercion Model: PEP 208 New Coercion Model. 
* PEP 241; Metadata in Python Packages: PEP 241 Metadata in Python Packages. 
* 新增和改进的模块: 新增和改进的模块<4>. 
* Other Changes and Fixes: Other Changes and Fixes<4>. 
* 致谢: 致谢<7>. 

Python 2.0 有什么新变化

* 概述: 概述<3>. 
* What About Python 1.6?: What About Python 1 6?. 
* 新开发流程:: 
* Unicode: Unicode<2>. 
* 列表推导式:: 
* Augmented Assignment:: 
* 字符串的方法:: 
* Garbage Collection of Cycles:: 
* 其他核心变化:: 
* 移植 Python 2.0: 移植 Python 2 0. 
* 扩展/嵌入更改:: 
* Distutils：使模块易于安装:: 
* XML 模块:: 
* 模块更改:: 
* 新增模块: 新增模块<7>. 
* IDLE 改进:: 
* 删除和弃用的模块:: 
* 致谢: 致谢<8>. 

其他核心变化

* Minor Language Changes:: 
* Changes to Built-in Functions:: 

XML 模块

* SAX2 Support:: 
* DOM Support:: 
* Relationship to PyXML:: 

更新日志

* Python 下一版:: 
* Python 3.8.4 final: Python 3 8 4 final. 
* Python 3.8.4 release candidate 1: Python 3 8 4 release candidate 1. 
* Python 3.8.3 final: Python 3 8 3 final. 
* Python 3.8.3 release candidate 1: Python 3 8 3 release candidate 1. 
* Python 3.8.2 正式版: Python 3 8 2 正式版. 
* Python 3.8.2 rc2: Python 3 8 2 rc2. 
* Python 3.8.2 rc1: Python 3 8 2 rc1. 
* Python 3.8.1 正式版: Python 3 8 1 正式版. 
* Python 3.8.1 rc1: Python 3 8 1 rc1. 
* Python 3.8.0 正式版: Python 3 8 0 正式版. 
* Python 3.8.0 rc1: Python 3 8 0 rc1. 
* Python 3.8.0 beta 4: Python 3 8 0 beta 4. 
* Python 3.8.0 beta 3: Python 3 8 0 beta 3. 
* Python 3.8.0 beta 2: Python 3 8 0 beta 2. 
* Python 3.8.0 beta 1: Python 3 8 0 beta 1. 
* Python 3.8.0 alpha 4: Python 3 8 0 alpha 4. 
* Python 3.8.0 alpha 3: Python 3 8 0 alpha 3. 
* Python 3.8.0 alpha 2: Python 3 8 0 alpha 2. 
* Python 3.8.0 alpha 1: Python 3 8 0 alpha 1. 
* Python 3.7.0 正式版: Python 3 7 0 正式版. 
* Python 3.7.0 rc1: Python 3 7 0 rc1. 
* Python 3.7.0 beta 5: Python 3 7 0 beta 5. 
* Python 3.7.0 beta 4: Python 3 7 0 beta 4. 
* Python 3.7.0 beta 3: Python 3 7 0 beta 3. 
* Python 3.7.0 beta 2: Python 3 7 0 beta 2. 
* Python 3.7.0 beta 1: Python 3 7 0 beta 1. 
* Python 3.7.0 alpha 4: Python 3 7 0 alpha 4. 
* Python 3.7.0 alpha 3: Python 3 7 0 alpha 3. 
* Python 3.7.0 alpha 2: Python 3 7 0 alpha 2. 
* Python 3.7.0 alpha 1: Python 3 7 0 alpha 1. 
* Python 3.6.6 正式版: Python 3 6 6 正式版. 
* Python 3.6.6 rc1: Python 3 6 6 rc1. 
* Python 3.6.5 正式版: Python 3 6 5 正式版. 
* Python 3.6.5 rc1: Python 3 6 5 rc1. 
* Python 3.6.4 正式版: Python 3 6 4 正式版. 
* Python 3.6.4 rc1: Python 3 6 4 rc1. 
* Python 3.6.3 正式版: Python 3 6 3 正式版. 
* Python 3.6.3 rc1: Python 3 6 3 rc1. 
* Python 3.6.2 正式版: Python 3 6 2 正式版. 
* Python 3.6.2 rc2: Python 3 6 2 rc2. 
* Python 3.6.2 rc1: Python 3 6 2 rc1. 
* Python 3.6.1 正式版: Python 3 6 1 正式版. 
* Python 3.6.1 rc1: Python 3 6 1 rc1. 
* Python 3.6.0 正式版: Python 3 6 0 正式版. 
* Python 3.6.0 rc2: Python 3 6 0 rc2. 
* Python 3.6.0 rc1: Python 3 6 0 rc1. 
* Python 3.6.0 beta 4: Python 3 6 0 beta 4. 
* Python 3.6.0 beta 3: Python 3 6 0 beta 3. 
* Python 3.6.0 beta 2: Python 3 6 0 beta 2. 
* Python 3.6.0 beta 1: Python 3 6 0 beta 1. 
* Python 3.6.0 alpha 4: Python 3 6 0 alpha 4. 
* Python 3.6.0 alpha 3: Python 3 6 0 alpha 3. 
* Python 3.6.0 alpha 2: Python 3 6 0 alpha 2. 
* Python 3.6.0 alpha 1: Python 3 6 0 alpha 1. 
* Python 3.5.5 正式版: Python 3 5 5 正式版. 
* Python 3.5.5 rc1: Python 3 5 5 rc1. 
* Python 3.5.4 正式版: Python 3 5 4 正式版. 
* Python 3.5.4 rc1: Python 3 5 4 rc1. 
* Python 3.5.3 正式版: Python 3 5 3 正式版. 
* Python 3.5.3 rc1: Python 3 5 3 rc1. 
* Python 3.5.2 正式版: Python 3 5 2 正式版. 
* Python 3.5.2 rc1: Python 3 5 2 rc1. 
* Python 3.5.1 正式版: Python 3 5 1 正式版. 
* Python 3.5.1 rc1: Python 3 5 1 rc1. 
* Python 3.5.0 正式版: Python 3 5 0 正式版. 
* Python 3.5.0 rc4: Python 3 5 0 rc4. 
* Python 3.5.0 rc3: Python 3 5 0 rc3. 
* Python 3.5.0 rc2: Python 3 5 0 rc2. 
* Python 3.5.0 rc1: Python 3 5 0 rc1. 
* Python 3.5.0 beta 4: Python 3 5 0 beta 4. 
* Python 3.5.0 beta 3: Python 3 5 0 beta 3. 
* Python 3.5.0 beta 2: Python 3 5 0 beta 2. 
* Python 3.5.0 beta 1: Python 3 5 0 beta 1. 
* Python 3.5.0 alpha 4: Python 3 5 0 alpha 4. 
* Python 3.5.0 alpha 3: Python 3 5 0 alpha 3. 
* Python 3.5.0 alpha 2: Python 3 5 0 alpha 2. 
* Python 3.5.0 alpha 1: Python 3 5 0 alpha 1. 

Python 下一版

* 安全:: 
* 核心与内置:: 
* 库:: 
* 构建:: 
* IDLE: IDLE<3>. 

Python 3.8.4 final

* 安全: 安全<2>. 
* 核心与内置: 核心与内置<2>. 
* 库: 库<2>. 
* IDLE: IDLE<4>. 

Python 3.8.4 release candidate 1

* 安全: 安全<3>. 
* 核心与内置: 核心与内置<3>. 
* 库: 库<3>. 
* 测试:: 
* 构建: 构建<2>. 
* Windows:: 
* macOS:: 
* IDLE: IDLE<5>. 
* 工具/示例:: 

Python 3.8.3 final

* 核心与内置: 核心与内置<4>. 
* 库: 库<4>. 
* 文档: 文档<2>. 
* Windows: Windows<2>. 
* C API:: 

Python 3.8.3 release candidate 1

* 安全: 安全<4>. 
* 核心与内置: 核心与内置<5>. 
* 库: 库<5>. 
* 文档: 文档<3>. 
* 测试: 测试<2>. 
* 构建: 构建<3>. 
* Windows: Windows<3>. 
* macOS: macOS<2>. 
* IDLE: IDLE<6>. 
* 工具/示例: 工具/示例<2>. 
* C API: C API<2>. 

Python 3.8.2 正式版

* 核心与内置: 核心与内置<6>. 
* 库: 库<6>. 
* 文档: 文档<4>. 
* IDLE: IDLE<7>. 

Python 3.8.2 rc2

* 安全: 安全<5>. 
* 核心与内置: 核心与内置<7>. 
* 库: 库<7>. 
* IDLE: IDLE<8>. 

Python 3.8.2 rc1

* 安全: 安全<6>. 
* 核心与内置: 核心与内置<8>. 
* 库: 库<8>. 
* 文档: 文档<5>. 
* 测试: 测试<3>. 
* 构建: 构建<4>. 
* Windows: Windows<4>. 
* IDLE: IDLE<9>. 

Python 3.8.1 正式版

* 核心与内置: 核心与内置<9>. 
* 库: 库<9>. 
* 测试: 测试<4>. 
* Windows: Windows<5>. 
* macOS: macOS<3>. 
* IDLE: IDLE<10>. 

Python 3.8.1 rc1

* 安全: 安全<7>. 
* 核心与内置: 核心与内置<10>. 
* 库: 库<10>. 
* 文档: 文档<6>. 
* 测试: 测试<5>. 
* 构建: 构建<5>. 
* Windows: Windows<6>. 
* macOS: macOS<4>. 
* IDLE: IDLE<11>. 
* C API: C API<3>. 

Python 3.8.0 正式版

* 核心与内置: 核心与内置<11>. 
* 库: 库<11>. 
* 文档: 文档<7>. 
* 测试: 测试<6>. 
* Windows: Windows<7>. 
* IDLE: IDLE<12>. 
* 工具/示例: 工具/示例<3>. 
* C API: C API<4>. 

Python 3.8.0 rc1

* 安全: 安全<8>. 
* 核心与内置: 核心与内置<12>. 
* 库: 库<12>. 
* 文档: 文档<8>. 
* 测试: 测试<7>. 
* 构建: 构建<6>. 
* Windows: Windows<8>. 
* macOS: macOS<5>. 
* IDLE: IDLE<13>. 
* 工具/示例: 工具/示例<4>. 
* C API: C API<5>. 

Python 3.8.0 beta 4

* 安全: 安全<9>. 
* 核心与内置: 核心与内置<13>. 
* 库: 库<13>. 
* 文档: 文档<9>. 
* 测试: 测试<8>. 
* 构建: 构建<7>. 
* Windows: Windows<9>. 
* macOS: macOS<6>. 
* IDLE: IDLE<14>. 
* 工具/示例: 工具/示例<5>. 
* C API: C API<6>. 

Python 3.8.0 beta 3

* 安全: 安全<10>. 
* 核心与内置: 核心与内置<14>. 
* 库: 库<14>. 
* 文档: 文档<10>. 
* 测试: 测试<9>. 
* 构建: 构建<8>. 
* Windows: Windows<10>. 
* IDLE: IDLE<15>. 
* 工具/示例: 工具/示例<6>. 

Python 3.8.0 beta 2

* 安全: 安全<11>. 
* 核心与内置: 核心与内置<15>. 
* 库: 库<15>. 
* 文档: 文档<11>. 
* 测试: 测试<10>. 
* 构建: 构建<9>. 
* Windows: Windows<11>. 
* macOS: macOS<7>. 
* IDLE: IDLE<16>. 
* C API: C API<7>. 

Python 3.8.0 beta 1

* 安全: 安全<12>. 
* 核心与内置: 核心与内置<16>. 
* 库: 库<16>. 
* 文档: 文档<12>. 
* 测试: 测试<11>. 
* 构建: 构建<10>. 
* Windows: Windows<12>. 
* macOS: macOS<8>. 
* IDLE: IDLE<17>. 
* 工具/示例: 工具/示例<7>. 
* C API: C API<8>. 

Python 3.8.0 alpha 4

* 安全: 安全<13>. 
* 核心与内置: 核心与内置<17>. 
* 库: 库<17>. 
* 文档: 文档<13>. 
* 测试: 测试<12>. 
* 构建: 构建<11>. 
* Windows: Windows<13>. 
* macOS: macOS<9>. 
* IDLE: IDLE<18>. 
* 工具/示例: 工具/示例<8>. 
* C API: C API<9>. 

Python 3.8.0 alpha 3

* 安全: 安全<14>. 
* 核心与内置: 核心与内置<18>. 
* 库: 库<18>. 
* 文档: 文档<14>. 
* 测试: 测试<13>. 
* 构建: 构建<12>. 
* Windows: Windows<14>. 
* IDLE: IDLE<19>. 
* 工具/示例: 工具/示例<9>. 
* C API: C API<10>. 

Python 3.8.0 alpha 2

* 核心与内置: 核心与内置<19>. 
* 库: 库<19>. 
* 文档: 文档<15>. 
* 测试: 测试<14>. 
* Windows: Windows<15>. 
* IDLE: IDLE<20>. 

Python 3.8.0 alpha 1

* 安全: 安全<15>. 
* 核心与内置: 核心与内置<20>. 
* 库: 库<20>. 
* 文档: 文档<16>. 
* 测试: 测试<15>. 
* 构建: 构建<13>. 
* Windows: Windows<16>. 
* macOS: macOS<10>. 
* IDLE: IDLE<21>. 
* 工具/示例: 工具/示例<10>. 
* C API: C API<11>. 

Python 3.7.0 正式版

* 库: 库<21>. 
* C API: C API<12>. 

Python 3.7.0 rc1

* 核心与内置: 核心与内置<21>. 
* 库: 库<22>. 
* 文档: 文档<17>. 
* 构建: 构建<14>. 
* Windows: Windows<17>. 
* IDLE: IDLE<22>. 

Python 3.7.0 beta 5

* 核心与内置: 核心与内置<22>. 
* 库: 库<23>. 
* 文档: 文档<18>. 
* 测试: 测试<16>. 
* 构建: 构建<15>. 
* macOS: macOS<11>. 
* IDLE: IDLE<23>. 

Python 3.7.0 beta 4

* 核心与内置: 核心与内置<23>. 
* 库: 库<24>. 
* 文档: 文档<19>. 
* 测试: 测试<17>. 
* 构建: 构建<16>. 
* Windows: Windows<18>. 
* macOS: macOS<12>. 
* IDLE: IDLE<24>. 
* 工具/示例: 工具/示例<11>. 

Python 3.7.0 beta 3

* 安全: 安全<16>. 
* 核心与内置: 核心与内置<24>. 
* 库: 库<25>. 
* 文档: 文档<20>. 
* 测试: 测试<18>. 
* 构建: 构建<17>. 
* Windows: Windows<19>. 
* macOS: macOS<13>. 
* IDLE: IDLE<25>. 
* 工具/示例: 工具/示例<12>. 
* C API: C API<13>. 

Python 3.7.0 beta 2

* 安全: 安全<17>. 
* 核心与内置: 核心与内置<25>. 
* 库: 库<26>. 
* 文档: 文档<21>. 
* 测试: 测试<19>. 
* 构建: 构建<18>. 
* Windows: Windows<20>. 
* macOS: macOS<14>. 
* IDLE: IDLE<26>. 
* 工具/示例: 工具/示例<13>. 

Python 3.7.0 beta 1

* 核心与内置: 核心与内置<26>. 
* 库: 库<27>. 
* 文档: 文档<22>. 
* 测试: 测试<20>. 
* 构建: 构建<19>. 
* Windows: Windows<21>. 
* macOS: macOS<15>. 
* C API: C API<14>. 

Python 3.7.0 alpha 4

* 核心与内置: 核心与内置<27>. 
* 库: 库<28>. 
* 文档: 文档<23>. 
* 测试: 测试<21>. 
* Windows: Windows<22>. 
* 工具/示例: 工具/示例<14>. 
* C API: C API<15>. 

Python 3.7.0 alpha 3

* 核心与内置: 核心与内置<28>. 
* 库: 库<29>. 
* 文档: 文档<24>. 
* 测试: 测试<22>. 
* 构建: 构建<20>. 
* Windows: Windows<23>. 
* macOS: macOS<16>. 
* IDLE: IDLE<27>. 
* 工具/示例: 工具/示例<15>. 
* C API: C API<16>. 

Python 3.7.0 alpha 2

* 核心与内置: 核心与内置<29>. 
* 库: 库<30>. 
* 文档: 文档<25>. 
* 构建: 构建<21>. 
* IDLE: IDLE<28>. 
* C API: C API<17>. 

Python 3.7.0 alpha 1

* 安全: 安全<18>. 
* 核心与内置: 核心与内置<30>. 
* 库: 库<31>. 
* 文档: 文档<26>. 
* 测试: 测试<23>. 
* 构建: 构建<22>. 
* Windows: Windows<24>. 
* IDLE: IDLE<29>. 
* 工具/示例: 工具/示例<16>. 
* C API: C API<18>. 

Python 3.6.6 rc1

* 核心与内置: 核心与内置<31>. 
* 库: 库<32>. 
* 文档: 文档<27>. 
* 测试: 测试<24>. 
* 构建: 构建<23>. 
* Windows: Windows<25>. 
* macOS: macOS<17>. 
* IDLE: IDLE<30>. 
* 工具/示例: 工具/示例<17>. 
* C API: C API<19>. 

Python 3.6.5 正式版

* 测试: 测试<25>. 
* 构建: 构建<24>. 

Python 3.6.5 rc1

* 安全: 安全<19>. 
* 核心与内置: 核心与内置<32>. 
* 库: 库<33>. 
* 文档: 文档<28>. 
* 测试: 测试<26>. 
* 构建: 构建<25>. 
* Windows: Windows<26>. 
* macOS: macOS<18>. 
* IDLE: IDLE<31>. 
* 工具/示例: 工具/示例<18>. 
* C API: C API<20>. 

Python 3.6.4 rc1

* 核心与内置: 核心与内置<33>. 
* 库: 库<34>. 
* 文档: 文档<29>. 
* 测试: 测试<27>. 
* 构建: 构建<26>. 
* Windows: Windows<27>. 
* macOS: macOS<19>. 
* IDLE: IDLE<32>. 
* 工具/示例: 工具/示例<19>. 
* C API: C API<21>. 

Python 3.6.3 正式版

* 库: 库<35>. 
* 构建: 构建<27>. 

Python 3.6.3 rc1

* 安全: 安全<20>. 
* 核心与内置: 核心与内置<34>. 
* 库: 库<36>. 
* 文档: 文档<30>. 
* 测试: 测试<28>. 
* 构建: 构建<28>. 
* Windows: Windows<28>. 
* IDLE: IDLE<33>. 
* 工具/示例: 工具/示例<20>. 

Python 3.6.2 rc2

* 安全: 安全<21>. 

Python 3.6.2 rc1

* 核心与内置: 核心与内置<35>. 
* 库: 库<37>. 
* 安全: 安全<22>. 
* 库: 库<38>. 
* IDLE: IDLE<34>. 
* C API: C API<22>. 
* 构建: 构建<29>. 
* 文档: 文档<31>. 
* 工具/示例: 工具/示例<21>. 
* 测试: 测试<29>. 
* Windows: Windows<29>. 

Python 3.6.1 正式版

* 核心与内置: 核心与内置<36>. 
* 构建: 构建<30>. 

Python 3.6.1 rc1

* 核心与内置: 核心与内置<37>. 
* 库: 库<39>. 
* IDLE: IDLE<35>. 
* Windows: Windows<30>. 
* C API: C API<23>. 
* 文档: 文档<32>. 
* 测试: 测试<30>. 
* 构建: 构建<31>. 

Python 3.6.0 rc2

* 核心与内置: 核心与内置<38>. 
* 工具/示例: 工具/示例<22>. 
* Windows: Windows<31>. 
* 构建: 构建<32>. 

Python 3.6.0 rc1

* 核心与内置: 核心与内置<39>. 
* 库: 库<40>. 
* C API: C API<24>. 
* 文档: 文档<33>. 
* 工具/示例: 工具/示例<23>. 

Python 3.6.0 beta 4

* 核心与内置: 核心与内置<40>. 
* 库: 库<41>. 
* 文档: 文档<34>. 
* 测试: 测试<31>. 
* 构建: 构建<33>. 

Python 3.6.0 beta 3

* 核心与内置: 核心与内置<41>. 
* 库: 库<42>. 
* Windows: Windows<32>. 
* 构建: 构建<34>. 
* 测试: 测试<32>. 

Python 3.6.0 beta 2

* 核心与内置: 核心与内置<42>. 
* 库: 库<43>. 
* Windows: Windows<33>. 
* C API: C API<25>. 
* 构建: 构建<35>. 
* 测试: 测试<33>. 

Python 3.6.0 beta 1

* 核心与内置: 核心与内置<43>. 
* 库: 库<44>. 
* IDLE: IDLE<36>. 
* C API: C API<26>. 
* 测试: 测试<34>. 
* 构建: 构建<36>. 
* 工具/示例: 工具/示例<24>. 
* Windows: Windows<34>. 

Python 3.6.0 alpha 4

* 核心与内置: 核心与内置<44>. 
* 库: 库<45>. 
* IDLE: IDLE<37>. 
* 测试: 测试<35>. 
* Windows: Windows<35>. 
* 构建: 构建<37>. 

Python 3.6.0 alpha 3

* 核心与内置: 核心与内置<45>. 
* 库: 库<46>. 
* 安全: 安全<23>. 
* 库: 库<47>. 
* 安全: 安全<24>. 
* 库: 库<48>. 
* IDLE: IDLE<38>. 
* C API: C API<27>. 
* 构建: 构建<38>. 
* 工具/示例: 工具/示例<25>. 
* 文档: 文档<35>. 
* 测试: 测试<36>. 

Python 3.6.0 alpha 2

* 核心与内置: 核心与内置<46>. 
* 库: 库<49>. 
* 安全: 安全<25>. 
* 库: 库<50>. 
* 安全: 安全<26>. 
* 库: 库<51>. 
* IDLE: IDLE<39>. 
* 文档: 文档<36>. 
* 测试: 测试<37>. 
* Windows: Windows<36>. 
* 构建: 构建<39>. 
* Windows: Windows<37>. 
* C API: C API<28>. 
* 工具/示例: 工具/示例<26>. 

Python 3.6.0 alpha 1

* 核心与内置: 核心与内置<47>. 
* 库: 库<52>. 
* 安全: 安全<27>. 
* 库: 库<53>. 
* 安全: 安全<28>. 
* 库: 库<54>. 
* 安全: 安全<29>. 
* 库: 库<55>. 
* IDLE: IDLE<40>. 
* 文档: 文档<37>. 
* 测试: 测试<38>. 
* 构建: 构建<40>. 
* Windows: Windows<38>. 
* 工具/示例: 工具/示例<27>. 
* C API: C API<29>. 

Python 3.5.5 rc1

* 安全: 安全<30>. 
* 核心与内置: 核心与内置<48>. 
* 库: 库<56>. 

Python 3.5.4 正式版

* 库: 库<57>. 

Python 3.5.4 rc1

* 安全: 安全<31>. 
* 核心与内置: 核心与内置<49>. 
* 库: 库<58>. 
* 文档: 文档<38>. 
* 测试: 测试<39>. 
* 构建: 构建<41>. 
* Windows: Windows<39>. 
* C API: C API<30>. 

Python 3.5.3 rc1

* 核心与内置: 核心与内置<50>. 
* 库: 库<59>. 
* 安全: 安全<32>. 
* 库: 库<60>. 
* 安全: 安全<33>. 
* 库: 库<61>. 
* IDLE: IDLE<41>. 
* C API: C API<31>. 
* 文档: 文档<39>. 
* 测试: 测试<40>. 
* 工具/示例: 工具/示例<28>. 
* Windows: Windows<40>. 
* 构建: 构建<42>. 

Python 3.5.2 正式版

* 核心与内置: 核心与内置<51>. 
* 测试: 测试<41>. 
* IDLE: IDLE<42>. 

Python 3.5.2 rc1

* 核心与内置: 核心与内置<52>. 
* 安全: 安全<34>. 
* 库: 库<62>. 
* 安全: 安全<35>. 
* 库: 库<63>. 
* 安全: 安全<36>. 
* 库: 库<64>. 
* 安全: 安全<37>. 
* 库: 库<65>. 
* 安全: 安全<38>. 
* 库: 库<66>. 
* IDLE: IDLE<43>. 
* 文档: 文档<40>. 
* 测试: 测试<42>. 
* 构建: 构建<43>. 
* Windows: Windows<41>. 
* 工具/示例: 工具/示例<29>. 
* Windows: Windows<42>. 

Python 3.5.1 正式版

* 核心与内置: 核心与内置<53>. 
* Windows: Windows<43>. 

Python 3.5.1 rc1

* 核心与内置: 核心与内置<54>. 
* 库: 库<67>. 
* IDLE: IDLE<44>. 
* 文档: 文档<41>. 
* 测试: 测试<43>. 
* 构建: 构建<44>. 
* Windows: Windows<44>. 
* 工具/示例: 工具/示例<30>. 

Python 3.5.0 正式版

* 构建: 构建<45>. 

Python 3.5.0 rc4

* 库: 库<68>. 
* 构建: 构建<46>. 

Python 3.5.0 rc3

* 核心与内置: 核心与内置<55>. 
* 库: 库<69>. 

Python 3.5.0 rc2

* 核心与内置: 核心与内置<56>. 
* 库: 库<70>. 

Python 3.5.0 rc1

* 核心与内置: 核心与内置<57>. 
* 库: 库<71>. 
* IDLE: IDLE<45>. 
* 文档: 文档<42>. 
* 测试: 测试<44>. 

Python 3.5.0 beta 4

* 核心与内置: 核心与内置<58>. 
* 库: 库<72>. 
* 构建: 构建<47>. 

Python 3.5.0 beta 3

* 核心与内置: 核心与内置<59>. 
* 库: 库<73>. 
* 测试: 测试<45>. 
* 文档: 文档<43>. 
* 构建: 构建<48>. 

Python 3.5.0 beta 2

* 核心与内置: 核心与内置<60>. 
* 库: 库<74>. 

Python 3.5.0 beta 1

* 核心与内置: 核心与内置<61>. 
* 库: 库<75>. 
* IDLE: IDLE<46>. 
* 测试: 测试<46>. 
* 文档: 文档<44>. 
* 工具/示例: 工具/示例<31>. 

Python 3.5.0 alpha 4

* 核心与内置: 核心与内置<62>. 
* 库: 库<76>. 
* 构建: 构建<49>. 
* 测试: 测试<47>. 
* 工具/示例: 工具/示例<32>. 
* C API: C API<32>. 

Python 3.5.0 alpha 3

* 核心与内置: 核心与内置<63>. 
* 库: 库<77>. 
* 构建: 构建<50>. 
* 测试: 测试<48>. 
* 工具/示例: 工具/示例<33>. 

Python 3.5.0 alpha 2

* 核心与内置: 核心与内置<64>. 
* 库: 库<78>. 
* 构建: 构建<51>. 
* C API: C API<33>. 
* Windows: Windows<45>. 

Python 3.5.0 alpha 1

* 核心与内置: 核心与内置<65>. 
* 库: 库<79>. 
* IDLE: IDLE<47>. 
* 构建: 构建<52>. 
* C API: C API<34>. 
* 文档: 文档<45>. 
* 测试: 测试<49>. 
* 工具/示例: 工具/示例<34>. 
* Windows: Windows<46>. 

Python 教程

* 课前甜点:: 
* 使用 Python 解释器:: 
* Python 的非正式介绍:: 
* 其他流程控制工具:: 
* 数据结构:: 
* 模块:: 
* 输入输出:: 
* 错误和异常:: 
* 类:: 
* 标准库简介:: 
* 标准库简介 —— 第二部分:: 
* 虚拟环境和包:: 
* 接下来？:: 
* 交互式编辑和编辑历史:: 
* 浮点算术：争议和限制:: 
* 附录:: 

使用 Python 解释器

* 调用解释器:: 
* 解释器的运行环境:: 

调用解释器

* 传入参数:: 
* 交互模式:: 

解释器的运行环境

* 源文件的字符编码:: 

Python 的非正式介绍

* Python 作为计算器使用:: 
* 走向编程的第一步:: 

Python 作为计算器使用

* 数字:: 
* 字符串:: 
* 列表:: 

其他流程控制工具

* if 语句:: 
* for 语句:: 
* range() 函数: range 函数. 
* break 和 continue 语句，以及循环中的 else 子句:: 
* pass 语句:: 
* 定义函数:: 
* 函数定义的更多形式:: 
* 小插曲：编码风格:: 

函数定义的更多形式

* 参数默认值:: 
* 关键字参数:: 
* 特殊参数:: 
* 任意的参数列表:: 
* 解包参数列表:: 
* Lambda 表达式:: 
* 文档字符串:: 
* 函数标注:: 

特殊参数

* 位置或关键字参数:: 
* 仅限位置参数:: 
* 仅限关键字参数:: 
* 函数示例:: 
* 概括:: 

数据结构

* 列表的更多特性:: 
* del 语句:: 
* 元组和序列:: 
* 集合:: 
* 字典:: 
* 循环的技巧:: 
* 深入条件控制:: 
* 比较序列和其他类型:: 

列表的更多特性

* 列表作为栈使用:: 
* 列表作为队列使用:: 
* 列表推导式: 列表推导式<2>. 
* 嵌套的列表推导式:: 

模块

* 更多有关模块的信息:: 
* 标准模块:: 
* dir() 函数: dir 函数. 
* 包:: 

更多有关模块的信息

* 以脚本的方式执行模块:: 
* 模块搜索路径:: 
* “编译过的”Python文件:: 

包

* 从包中导入 *:: 
* 子包参考:: 
* 多个目录中的包:: 

输入输出

* 更漂亮的输出格式:: 
* 读写文件:: 

更漂亮的输出格式

* 格式化字符串文字:: 
* 字符串的 format() 方法: 字符串的 format 方法. 
* 手动格式化字符串:: 
* 旧的字符串格式化方法:: 

读写文件

* 文件对象的方法:: 
* 使用 json 保存结构化数据:: 

错误和异常

* 语法错误:: 
* 异常:: 
* 处理异常:: 
* 抛出异常:: 
* 用户自定义异常:: 
* 定义清理操作:: 
* 预定义的清理操作:: 

类

* 名称和对象:: 
* Python 作用域和命名空间:: 
* 初探类:: 
* 补充说明:: 
* 继承:: 
* 私有变量:: 
* 杂项说明:: 
* 迭代器:: 
* 生成器:: 
* 生成器表达式:: 

Python 作用域和命名空间

* 作用域和命名空间示例:: 

初探类

* 类定义语法:: 
* 类对象:: 
* 实例对象:: 
* 方法对象:: 
* 类和实例变量:: 

继承

* 多重继承:: 

标准库简介

* 操作系统接口:: 
* 文件通配符:: 
* 命令行参数:: 
* 错误输出重定向和程序终止:: 
* 字符串模式匹配:: 
* 数学:: 
* 互联网访问:: 
* 日期和时间:: 
* 数据压缩:: 
* 性能测量:: 
* 质量控制:: 
* 自带电池:: 

标准库简介 —— 第二部分

* 格式化输出:: 
* 模板:: 
* 使用二进制数据记录格式:: 
* 多线程: 多线程<2>. 
* 日志记录:: 
* 弱引用:: 
* 用于操作列表的工具:: 
* 十进制浮点运算:: 

虚拟环境和包

* 概述: 概述<4>. 
* 创建虚拟环境:: 
* 使用pip管理包:: 

交互式编辑和编辑历史

* Tab 补全和编辑历史:: 
* 默认交互式解释器的替代品:: 

浮点算术：争议和限制

* 表示性错误:: 

附录

* 交互模式: 交互模式<2>. 

交互模式

* 错误处理:: 
* 可执行的Python脚本:: 
* 交互式启动文件:: 
* 定制模块:: 

Python安装和使用

* 命令行与环境:: 
* 在类Unix环境下使用Python:: 
* 在Windows上使用 Python:: 
* 在苹果系统上使用 Python:: 
* 编辑器和集成开发环境:: 

命令行与环境

* 命令行:: 
* 环境变量:: 

命令行

* 接口选项:: 
* 通用选项:: 
* 其他选项:: 
* 不应当使用的选项:: 

环境变量

* 调试模式变量:: 

在类Unix环境下使用Python

* 获得并安装Python的最新版本:: 
* 构建Python:: 
* 与Python相关的路径和文件:: 
* 杂项:: 

获得并安装Python的最新版本

* 在Linux中:: 
* 在FreeBSD和OpenBSD上:: 
* 在OpenSolaris系统上:: 

在Windows上使用 Python

* 完整安装程序:: 
* Microsoft Store包:: 
* nuget.org 安装包: nuget org 安装包. 
* 可嵌入的包:: 
* 替代捆绑包:: 
* 配置Python:: 
* UTF-8 模式:: 
* 适用于Windows的Python启动器:: 
* 查找模块:: 
* 附加模块:: 
* 在Windows上编译Python:: 
* 其他平台:: 

完整安装程序

* 安装步骤:: 
* 删除 MAX_PATH 限制:: 
* 无UI 安装:: 
* 免下载安装:: 
* 修改安装:: 

Microsoft Store包

* 已知的问题:: 

可嵌入的包

* Python应用程序:: 
* 嵌入Python:: 

配置Python

* 附录：设置环境变量:: 
* 查找Python可执行文件:: 

适用于Windows的Python启动器

* 入门:: 
* Shebang Lines:: 
* shebang lines 的参数:: 
* 自定义:: 
* 诊断:: 

入门

* 从命令行:: 
* 从虚拟环境:: 
* 从脚本:: 
* 从文件关联:: 

自定义

* 通过INI文件自定义:: 
* 自定义默认的Python版本:: 

附加模块

* PyWin32:: 
* cx_Freeze:: 
* WConio:: 

在苹果系统上使用 Python

* 获取和安装 MacPython:: 
* IDE:: 
* 安装额外的 Python 包:: 
* Mac 上的图形界面编程:: 
* 在 Mac 上分发 Python 应用程序:: 
* 其他资源:: 

获取和安装 MacPython

* 如何运行 Python 脚本:: 
* 运行有图形界面的脚本:: 
* 配置:: 

Python语言参考

* 概述: 概述<5>. 
* 词法分析:: 
* 数据模型:: 
* 执行模型:: 
* 导入系统:: 
* 表达式:: 
* 简单语句:: 
* 复合语句:: 
* 最高层级组件:: 
* 完整的语法规范:: 

概述

* 其他实现:: 
* 标注:: 

词法分析

* 行结构:: 
* 其他形符:: 
* 标识符和关键字:: 
* 字面值:: 
* 运算符:: 
* 分隔符:: 

行结构

* 逻辑行:: 
* 物理行:: 
* 注释:: 
* 编码声明:: 
* 显式的行拼接:: 
* 隐式的行拼接:: 
* 空白行:: 
* 缩进:: 
* 形符之间的空白:: 

标识符和关键字

* 关键字:: 
* 保留的标识符类:: 

字面值

* 字符串和字节串字面值:: 
* 字符串字面值拼接:: 
* 格式化字符串字面值:: 
* 数字字面值:: 
* 整型数字面值:: 
* 浮点数字面值:: 
* 虚数字面值:: 

数据模型

* 对象、值与类型:: 
* 标准类型层级结构:: 
* 特殊方法名称:: 
* 协程:: 

特殊方法名称

* 基本定制:: 
* 自定义属性访问:: 
* 自定义类创建:: 
* 自定义实例及子类检查:: 
* 模拟泛型类型:: 
* 模拟可调用对象:: 
* 模拟容器类型:: 
* 模拟数字类型:: 
* with 语句上下文管理器:: 
* 特殊方法查找:: 

自定义属性访问

* 自定义模块属性访问:: 
* 实现描述器:: 
* 调用描述器:: 
* __slots__:: 

__slots__

* 使用 __slots__ 的注意事项:: 

自定义类创建

* 元类:: 
* 解析 MRO 条目:: 
* 确定适当的元类:: 
* 准备类命名空间:: 
* 执行类主体:: 
* 创建类对象:: 
* 元类的作用:: 

协程

* 可等待对象:: 
* 协程对象:: 
* 异步迭代器:: 
* 异步上下文管理器:: 

执行模型

* 程序的结构:: 
* 命名与绑定:: 
* 异常: 异常<2>. 

命名与绑定

* 名称的绑定:: 
* 名称的解析:: 
* 内置命名空间和受限的执行:: 
* 与动态特性的交互:: 

导入系统

* importlib: importlib<7>. 
* 包: 包<2>. 
* 搜索:: 
* 加载:: 
* 基于路径的查找器:: 
* 替换标准导入系统:: 
* 包相对导入:: 
* 有关 __main__ 的特殊事项:: 
* 开放问题项:: 
* 参考文献:: 

包

* 常规包:: 
* 命名空间包:: 

搜索

* 模块缓存:: 
* 查找器和加载器:: 
* 导入钩子:: 
* 元路径:: 

加载

* 加载器:: 
* 子模块:: 
* 模块规格说明:: 
* 导入相关的模块属性:: 
* module.__path__: module __path__. 
* 模块的 repr:: 
* 已缓存字节码的失效:: 

基于路径的查找器

* 路径条目查找器:: 
* 路径条目查找器协议:: 

有关 __main__ 的特殊事项

* __main__.__spec__: __main__ __spec__. 

表达式

* 算术转换:: 
* 原子:: 
* 原型:: 
* await 表达式:: 
* 幂运算符:: 
* 一元算术和位运算:: 
* 二元算术运算符:: 
* 移位运算:: 
* 二元位运算:: 
* 比较运算:: 
* 布尔运算:: 
* 赋值表达式: 赋值表达式<2>. 
* 条件表达式:: 
* lambda 表达式:: 
* 表达式列表:: 
* 求值顺序:: 
* 运算符优先级:: 

原子

* 标识符（名称）:: 
* 字面值: 字面值<2>. 
* 带圆括号的形式:: 
* 列表、集合与字典的显示:: 
* 列表显示:: 
* 集合显示:: 
* 字典显示:: 
* 生成器表达式: 生成器表达式<2>. 
* yield 表达式:: 

yield 表达式

* 生成器-迭代器的方法:: 
* 例子:: 
* 异步生成器函数:: 
* 异步生成器-迭代器方法:: 

原型

* 属性引用:: 
* 抽取:: 
* 切片:: 
* 调用:: 

比较运算

* 值比较:: 
* 成员检测运算:: 
* 标识号比较:: 

简单语句

* 表达式语句:: 
* 赋值语句:: 
* assert 语句:: 
* pass 语句: pass 语句<2>. 
* del 语句: del 语句<2>. 
* return 语句:: 
* yield 语句:: 
* raise 语句:: 
* break 语句:: 
* continue 语句:: 
* import 语句:: 
* global 语句:: 
* nonlocal 语句:: 

赋值语句

* 增强赋值语句:: 
* 带标注的赋值语句:: 

import 语句

* future 语句:: 

复合语句

* if 语句: if 语句<2>. 
* while 语句:: 
* for 语句: for 语句<2>. 
* try 语句:: 
* with 语句:: 
* 函数定义:: 
* 类定义:: 
* 协程: 协程<2>. 

协程

* 协程函数定义:: 
* async for 语句:: 
* async with 语句:: 

最高层级组件

* 完整的 Python 程序:: 
* 文件输入:: 
* 交互式输入:: 
* 表达式输入:: 

Python 标准库

* 概述: 概述<6>. 
* 内置函数:: 
* 内置常量:: 
* 内置类型:: 
* 内置异常:: 
* 文本处理服务:: 
* 二进制数据服务:: 
* 数据类型:: 
* 数字和数学模块:: 
* 函数式编程模块:: 
* 文件和目录访问:: 
* 数据持久化:: 
* 数据压缩和存档:: 
* 文件格式:: 
* 加密服务:: 
* 通用操作系统服务:: 
* 并发执行:: 
* contextvars: contextvars --- Context Variables. Context Variables
* 网络和进程间通信:: 
* 互联网数据处理:: 
* 结构化标记处理工具:: 
* 互联网协议和支持:: 
* 多媒体服务:: 
* 国际化:: 
* 程序框架:: 
* Tk图形用户界面(GUI): Tk图形用户界面 GUI. 
* 开发工具:: 
* 调试和分析:: 
* 软件打包和分发:: 
* Python运行时服务:: 
* 自定义 Python 解释器:: 
* 导入模块:: 
* Python 语言服务:: 
* 杂项服务:: 
* Windows系统相关模块:: 
* Unix 专有服务:: 
* 被取代的模块:: 
* 未创建文档的模块:: 

概述

* 可用性注释:: 

内置常量

* 由 site 模块添加的常量:: 

内置类型

* 逻辑值检测:: 
* 布尔运算: 布尔运算 --- and or not. and, or, not
* 比较运算: 比较运算<2>. 
* 数字类型: 数字类型 --- int float complex. int, float, complex
* 迭代器类型:: 
* 序列类型: 序列类型 --- list tuple range. list, tuple, range
* 文本序列类型: 文本序列类型 --- str. str
* 二进制序列类型: 二进制序列类型 --- bytes bytearray memoryview. bytes, bytearray, memoryview
* 集合类型: 集合类型 --- set frozenset. set, frozenset
* 映射类型: 映射类型 --- dict. dict
* 上下文管理器类型:: 
* 其他内置类型:: 
* 特殊属性:: 

数字类型 --- int, float, complex

* 整数类型的按位运算:: 
* 整数类型的附加方法:: 
* 浮点类型的附加方法:: 
* 数字类型的哈希运算:: 

迭代器类型

* 生成器类型:: 

序列类型 --- list, tuple, range

* 通用序列操作:: 
* 不可变序列类型:: 
* 可变序列类型:: 
* 列表: 列表<2>. 
* 元组:: 
* range 对象:: 

文本序列类型 --- str

* 字符串的方法: 字符串的方法<2>. 
* printf 风格的字符串格式化:: 

二进制序列类型 --- bytes, bytearray, memoryview

* bytes 对象:: 
* bytearray 对象:: 
* bytes 和 bytearray 操作:: 
* printf 风格的字节串格式化:: 
* 内存视图:: 

映射类型 --- dict

* 字典视图对象:: 

其他内置类型

* 模块: 模块<2>. 
* 类与类实例:: 
* 函数:: 
* 方法:: 
* 代码对象:: 
* 类型对象:: 
* 空对象:: 
* 省略符对象:: 
* 未实现对象:: 
* 布尔值:: 
* 内部对象:: 

内置异常

* 基类:: 
* 具体异常:: 
* 警告:: 
* 异常层次结构:: 

具体异常

* OS 异常:: 

文本处理服务

* string: string --- 常见的字符串操作. 常见的字符串操作
* re: re --- 正则表达式操作. 正则表达式操作
* difflib: difflib --- 计算差异的辅助工具. 计算差异的辅助工具
* textwrap: textwrap --- 文本自动换行与填充. 文本自动换行与填充
* unicodedata: unicodedata --- Unicode 数据库. Unicode 数据库
* stringprep: stringprep --- 因特网字符串预备. 因特网字符串预备
* readline: readline --- GNU readline 接口. GNU readline 接口
* rlcompleter: rlcompleter --- GNU readline 的补全函数. GNU readline 的补全函数

string --- 常见的字符串操作

* 字符串常量:: 
* 自定义字符串格式化:: 
* 格式字符串语法:: 
* 模板字符串:: 
* 辅助函数:: 

格式字符串语法

* 格式规格迷你语言:: 
* 格式示例:: 

re --- 正则表达式操作

* 正则表达式语法:: 
* 模块内容:: 
* 正则表达式对象 （正则对象）:: 
* 匹配对象:: 
* 正则表达式例子:: 

正则表达式例子

* 检查对子:: 
* 模拟 scanf(): 模拟 scanf. 
* search() vs. match(): search vs match. 
* 制作一个电话本:: 
* 文字整理:: 
* 查找所有副词:: 
* 查找所有的副词及其位置:: 
* 原始字符串标记:: 
* 写一个词法分析器:: 

difflib --- 计算差异的辅助工具

* SequenceMatcher 对象:: 
* SequenceMatcher 的示例:: 
* Differ 对象:: 
* Differ 示例:: 
* difflib 的命令行接口:: 

readline --- GNU readline 接口

* 初始化文件:: 
* 行缓冲区:: 
* 历史文件:: 
* 历史列表:: 
* 启动钩子:: 
* Completion:: 
* 示例:: 

rlcompleter --- GNU readline 的补全函数

* Completer 对象:: 

二进制数据服务

* struct: struct --- 将字节串解读为打包的二进制数据. 将字节串解读为打包的二进制数据
* codecs: codecs --- 编解码器注册和相关基类. 编解码器注册和相关基类

struct --- 将字节串解读为打包的二进制数据

* 函数和异常:: 
* 格式字符串:: 
* 类: 类<2>. 

格式字符串

* 字节顺序，大小和对齐方式:: 
* 格式字符:: 
* 例子: 例子<2>. 

codecs --- 编解码器注册和相关基类

* 编解码器基类:: 
* 编码格式与 Unicode:: 
* 标准编码:: 
* Python 专属的编码格式:: 
* encodings.idna: encodings idna --- 应用程序中的国际化域名. 应用程序中的国际化域名
* encodings.mbcs: encodings mbcs --- Windows ANSI代码页. Windows ANSI代码页
* encodings.utf_8_sig: encodings utf_8_sig --- 带BOM签名的UTF-8编解码器. 带BOM签名的UTF-8编解码器

编解码器基类

* 错误处理方案:: 
* 无状态的编码和解码:: 
* 增量式的编码和解码:: 
* 流式的编码和解码:: 

增量式的编码和解码

* IncrementalEncoder 对象:: 
* IncrementalDecoder 对象:: 

流式的编码和解码

* StreamWriter 对象:: 
* StreamReader 对象:: 
* StreamReaderWriter 对象:: 
* StreamRecoder 对象:: 

Python 专属的编码格式

* 文字编码:: 
* 二进制转换:: 
* 文字转换:: 

数据类型

* datetime: datetime --- 基本的日期和时间类型. 基本的日期和时间类型
* calendar: calendar --- 日历相关函数. 日历相关函数
* collections: collections --- 容器数据类型. 容器数据类型
* collections.abc: collections abc --- 容器的抽象基类. 容器的抽象基类
* heapq: heapq --- 堆队列算法. 堆队列算法
* bisect: bisect --- 数组二分查找算法. 数组二分查找算法
* array: array --- 高效的数值数组. 高效的数值数组
* weakref: weakref --- 弱引用. 弱引用
* types: types --- 动态类型创建和内置类型名称. 动态类型创建和内置类型名称
* copy: copy --- 浅层 shallow 和深层 deep 复制操作. 浅层 (shallow) 和深层 (deep) 复制操作
* pprint: pprint --- 数据美化输出. 数据美化输出
* reprlib: reprlib --- 另一种 repr 实现. 另一种 repr() 实现
* enum: enum --- 对枚举的支持. 对枚举的支持

datetime --- 基本的日期和时间类型

* 感知型对象和简单型对象:: 
* 常量:: 
* 有效的类型:: 
* timedelta 类对象:: 
* date 对象:: 
* datetime 对象:: 
* time 对象:: 
* tzinfo 对象:: 
* timezone 对象:: 
* strftime() 和 strptime() 的行为: strftime 和 strptime 的行为. 

有效的类型

* 通用的特征属性:: 
* 确定一个对象是感知型还是简单型:: 

timedelta 类对象

* class;timedelta 用法示例: class timedelta 用法示例. 

date 对象

* class;date 用法示例: class date 用法示例. 

datetime 对象

* 用法示例; datetime: 用法示例 datetime. 

time 对象

* 用法示例; time: 用法示例 time. 

strftime() 和 strptime() 的行为

* strftime() 和 strptime() Format Codes: strftime 和 strptime Format Codes. 
* 技术细节:: 

collections --- 容器数据类型

* ChainMap 对象:: 
* Counter 对象:: 
* deque 对象:: 
* defaultdict 对象:: 
* namedtuple() 命名元组的工厂函数: namedtuple 命名元组的工厂函数. 
* OrderedDict 对象:: 
* UserDict 对象:: 
* UserList 对象:: 
* UserString 对象:: 

ChainMap 对象

* ChainMap 例子和方法:: 

deque 对象

* deque 用法:: 

defaultdict 对象

* defaultdict 例子:: 

OrderedDict 对象

* OrderedDict 例子和用法:: 

collections.abc --- 容器的抽象基类

* 容器抽象基类:: 

heapq --- 堆队列算法

* 基本示例:: 
* 优先队列实现说明:: 
* 理论:: 

bisect --- 数组二分查找算法

* 搜索有序列表:: 
* 其他示例:: 

weakref --- 弱引用

* 弱引用对象:: 
* 示例: 示例<2>. 
* 终结器对象:: 
* 比较终结器与 __del__() 方法: 比较终结器与 __del__ 方法. 

types --- 动态类型创建和内置类型名称

* 动态类型创建:: 
* 标准解释器类型:: 
* 附加工具类和函数:: 
* 协程工具函数:: 

pprint --- 数据美化输出

* PrettyPrinter 对象:: 
* 示例: 示例<3>. 

reprlib --- 另一种 repr() 实现

* Repr 对象:: 
* 子类化 Repr 对象:: 

enum --- 对枚举的支持

* 模块内容: 模块内容<2>. 
* 创建一个 Enum:: 
* 对枚举成员及其属性的程序化访问:: 
* 复制枚举成员和值:: 
* 确保唯一的枚举值:: 
* 使用自动设定的值:: 
* 迭代:: 
* 比较运算: 比较运算<3>. 
* 允许的枚举成员和属性:: 
* 受限的 Enum 子类化:: 
* 封存:: 
* 功能性 API:: 
* 派生的枚举:: 
* 何时使用 __new__() 与 __init__(): 何时使用 __new__ 与 __init__. 
* 有趣的示例:: 
* 各种枚举有何区别？:: 

派生的枚举

* IntEnum:: 
* IntFlag:: 
* Flag:: 
* 其他事项:: 

有趣的示例

* 省略值:: 
* OrderedEnum:: 
* DuplicateFreeEnum:: 
* Planet:: 
* TimePeriod:: 

省略值

* 使用 auto:: 
* 使用 object:: 
* 使用描述性字符串:: 
* 使用自定义的 __new__(): 使用自定义的 __new__. 

各种枚举有何区别？

* 枚举类:: 
* 枚举成员（即实例）:: 
* 细节要点:: 

细节要点

* 支持的 __dunder__ 名称:: 
* 支持的 _sunder_ 名称:: 
* Enum 成员类型:: 
* Enum 类和成员的布尔值:: 
* 带有方法的 Enum 类:: 
* 组合 Flag 的成员:: 

数字和数学模块

* numbers: numbers --- 数字的抽象基类. 数字的抽象基类
* math: math --- 数学函数. 数学函数
* cmath: cmath --- 关于复数的数学函数. 关于复数的数学函数
* decimal: decimal --- 十进制定点和浮点运算. 十进制定点和浮点运算
* fractions: fractions --- 分数. 分数
* random: random --- 生成伪随机数. 生成伪随机数
* statistics: statistics --- 数学统计函数. 数学统计函数

numbers --- 数字的抽象基类

* 数字的层次:: 
* 类型接口注释。:: 

类型接口注释。

* 加入更多数字的ABC:: 
* 实现算数运算:: 

math --- 数学函数

* 数论与表示函数:: 
* 幂函数与对数函数:: 
* 三角函数:: 
* 角度转换:: 
* 双曲函数:: 
* 特殊函数:: 
* 常量: 常量<2>. 

cmath --- 关于复数的数学函数

* 到极坐标和从极坐标的转换:: 
* 幂函数与对数函数: 幂函数与对数函数<2>. 
* 三角函数: 三角函数<2>. 
* 双曲函数: 双曲函数<2>. 
* 分类函数:: 
* 常量: 常量<3>. 

decimal --- 十进制定点和浮点运算

* 快速入门教程:: 
* Decimal 对象:: 
* 上下文对象:: 
* 常量: 常量<4>. 
* 舍入模式:: 
* 信号:: 
* 浮点数说明:: 
* 使用线程:: 
* 例程:: 
* Decimal 常见问题:: 

Decimal 对象

* 逻辑操作数:: 

浮点数说明

* 通过提升精度来解决舍入错误:: 
* 特殊的值:: 

random --- 生成伪随机数

* 簿记功能:: 
* 整数用函数:: 
* 序列用函数:: 
* 实值分布:: 
* 替代生成器:: 
* 关于再现性的说明:: 
* 例子和配方:: 

statistics --- 数学统计函数

* 平均值以及对中心位置的评估:: 
* 对分散程度的评估:: 
* 函数细节:: 
* 异常: 异常<3>. 
* NormalDist 对象:: 

NormalDist 对象

* NormalDist 示例和用法:: 

函数式编程模块

* itertools: itertools --- 为高效循环而创建迭代器的函数. 为高效循环而创建迭代器的函数
* functools: functools --- 高阶函数和可调用对象上的操作. 高阶函数和可调用对象上的操作
* operator: operator --- 标准运算符替代函数. 标准运算符替代函数

itertools --- 为高效循环而创建迭代器的函数

* Itertool函数:: 
* itertools 配方:: 

functools --- 高阶函数和可调用对象上的操作

* partial 对象:: 

operator --- 标准运算符替代函数

* 将运算符映射到函数:: 
* 原地运算符:: 

文件和目录访问

* pathlib: pathlib --- 面向对象的文件系统路径. 面向对象的文件系统路径
* os.path: os path --- 常用路径操作. 常用路径操作
* fileinput: fileinput --- 迭代来自多个输入流的行. 迭代来自多个输入流的行
* stat: stat --- 解析 stat 结果. 解析 stat() 结果
* filecmp: filecmp --- 文件及目录的比较. 文件及目录的比较
* tempfile: tempfile --- 生成临时文件和目录. 生成临时文件和目录
* glob: glob --- Unix 风格路径名模式扩展. Unix 风格路径名模式扩展
* fnmatch: fnmatch --- Unix 文件名模式匹配. Unix 文件名模式匹配
* linecache: linecache --- 随机读写文本行. 随机读写文本行
* shutil: shutil --- 高阶文件操作. 高阶文件操作

pathlib --- 面向对象的文件系统路径

* 基础使用:: 
* 纯路径:: 
* 具体路径:: 
* 对应的 os 模块的工具:: 

纯路径

* 通用性质:: 
* 运算符: 运算符<2>. 
* 访问个别部分:: 
* 方法和特征属性:: 

具体路径

* 方法: 方法<2>. 

filecmp --- 文件及目录的比较

* dircmp 类:: 

tempfile --- 生成临时文件和目录

* 例子: 例子<3>. 
* 已弃用的函数和变量:: 

shutil --- 高阶文件操作

* 目录和文件操作:: 
* 归档操作:: 
* 查询输出终端的尺寸:: 

目录和文件操作

* 依赖于具体平台的高效拷贝操作:: 
* copytree 示例:: 
* rmtree 示例:: 

归档操作

* 归档程序示例:: 
* 使用 base_dir 的归档程序示例:: 

数据持久化

* pickle: pickle --- Python 对象序列化. Python 对象序列化
* copyreg: copyreg --- 注册配合 pickle 模块使用的函数. 注册配合 pickle 模块使用的函数
* shelve: shelve --- Python 对象持久化. Python 对象持久化
* marshal: marshal --- 内部 Python 对象序列化. 内部 Python 对象序列化
* dbm: dbm --- Unix "数据库" 接口. Unix "数据库" 接口
* sqlite3: sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块. SQLite 数据库 DB-API 2.0 接口模块

pickle --- Python 对象序列化

* 与其他 Python 模块间的关系:: 
* 数据流格式:: 
* 模块接口:: 
* 可以被封存/解封的对象:: 
* 封存类实例:: 
* 类型，函数和其他对象的自定义归约:: 
* 外部缓冲区:: 
* 限制全局变量:: 
* 性能: 性能<2>. 
* 例子: 例子<4>. 

与其他 Python 模块间的关系

* 与 marshal 间的关系:: 
* 与 json 模块的比较:: 

封存类实例

* 持久化外部对象:: 
* Dispatch 表:: 
* 处理有状态的对象:: 

外部缓冲区

* 提供方 API:: 
* 使用方 API:: 
* 示例: 示例<4>. 

copyreg --- 注册配合 pickle 模块使用的函数

* 示例: 示例<5>. 

shelve --- Python 对象持久化

* 限制:: 
* 示例: 示例<6>. 

dbm --- Unix "数据库" 接口

* dbm.gnu: dbm gnu --- GNU 对 dbm 的重解析. GNU 对 dbm 的重解析
* dbm.ndbm: dbm ndbm --- 基于 ndbm 的接口. 基于 ndbm 的接口
* dbm.dumb: dbm dumb --- 便携式 DBM 实现. 便携式 DBM 实现

sqlite3 --- SQLite 数据库 DB-API 2.0 接口模块

* 模块函数和常量:: 
* 连接对象（Connection）:: 
* Cursor 对象:: 
* 行对象:: 
* 异常: 异常<4>. 
* SQLite 与 Python 类型:: 
* 控制事务:: 
* 有效使用 sqlite3:: 
* 常见问题:: 

SQLite 与 Python 类型

* 概述: 概述<7>. 
* 使用适配器将额外的 Python 类型保存在 SQLite 数据库中。:: 
* 将SQLite 值转换为自定义Python 类型:: 
* 默认适配器和转换器:: 

使用适配器将额外的 Python 类型保存在 SQLite 数据库中。

* 让对象自行适配:: 
* 注册可调用的适配器:: 

有效使用 sqlite3

* 使用快捷方式:: 
* 通过名称而不是索引访问索引:: 
* 使用连接作为上下文管理器:: 

常见问题

* 多线程: 多线程<3>. 

数据压缩和存档

* zlib: zlib --- 与 gzip 兼容的压缩. 与 gzip 兼容的压缩
* gzip: gzip --- 对 gzip 格式的支持. 对 gzip 格式的支持
* bz2: bz2 --- 对 bzip2 压缩算法的支持. 对 bzip2 压缩算法的支持
* lzma: lzma --- 用 LZMA 算法压缩. 用 LZMA 算法压缩
* zipfile: zipfile --- 使用ZIP存档. 使用ZIP存档
* tarfile: tarfile --- 读写tar归档文件. 读写tar归档文件

gzip --- 对 gzip 格式的支持

* 用法示例:: 
* 命令行界面:: 

命令行界面

* 命令行选项:: 

bz2 --- 对 bzip2 压缩算法的支持

* 文件压缩和解压:: 
* 增量压缩和解压:: 
* 一次性压缩或解压缩:: 
* 用法示例: 用法示例<2>. 

lzma --- 用 LZMA 算法压缩

* 读写压缩文件:: 
* 在内存中压缩和解压缩数据:: 
* 杂项: 杂项<2>. 
* 指定自定义的过滤器链:: 
* 例子: 例子<5>. 

zipfile --- 使用ZIP存档

* ZipFile 对象:: 
* Path 对象:: 
* PyZipFile 对象:: 
* ZipInfo 对象:: 
* 命令行界面: 命令行界面<2>. 
* 解压缩的障碍:: 

命令行界面

* 命令行选项: 命令行选项<2>. 

解压缩的障碍

* 由于文件本身:: 
* 文件系统限制:: 
* 资源限制:: 
* 中断:: 
* 提取的默认行为:: 

tarfile --- 读写tar归档文件

* TarFile 对象:: 
* TarInfo 对象:: 
* 命令行界面: 命令行界面<3>. 
* 例子: 例子<6>. 
* 受支持的 tar 格式:: 
* Unicode 问题:: 

命令行界面

* 命令行选项: 命令行选项<3>. 

文件格式

* csv: csv --- CSV 文件读写. CSV 文件读写
* configparser: configparser --- 配置文件解析器. 配置文件解析器
* netrc: netrc --- netrc 文件处理. netrc 文件处理
* xdrlib: xdrlib --- 编码与解码 XDR 数据. 编码与解码 XDR 数据
* plistlib: plistlib --- 生成与解析 Mac OS X plist 文件. 生成与解析 Mac OS X .plist 文件

csv --- CSV 文件读写

* 模块内容: 模块内容<3>. 
* 变种与格式参数:: 
* Reader 对象:: 
* Writer 对象:: 
* 例子: 例子<7>. 

configparser --- 配置文件解析器

* 快速起步:: 
* 支持的数据类型:: 
* 回退值:: 
* 受支持的 INI 文件结构:: 
* 值的插值:: 
* 映射协议访问:: 
* 定制解析器行为:: 
* 旧式 API 示例:: 
* ConfigParser 对象:: 
* RawConfigParser 对象:: 
* 异常: 异常<5>. 

netrc --- netrc 文件处理

* netrc 对象:: 

xdrlib --- 编码与解码 XDR 数据

* Packer 对象:: 
* Unpacker 对象:: 
* 异常: 异常<6>. 

plistlib --- 生成与解析 Mac OS X .plist 文件

* 例子: 例子<8>. 

加密服务

* hashlib: hashlib --- 安全哈希与消息摘要. 安全哈希与消息摘要
* hmac: hmac --- 基于密钥的消息验证. 基于密钥的消息验证
* secrets: secrets --- 生成安全随机数字用于管理密码. 生成安全随机数字用于管理密码

hashlib --- 安全哈希与消息摘要

* 哈希算法:: 
* SHAKE 可变长度摘要:: 
* 密钥派生:: 
* BLAKE2:: 

BLAKE2

* 创建哈希对象:: 
* 常量: 常量<5>. 
* 例子: 例子<9>. 
* 开发人员:: 

例子

* 简单哈希:: 
* 使用不同的摘要大小:: 
* 密钥哈希:: 
* 随机哈希:: 
* 个性化:: 
* 树形模式:: 

secrets --- 生成安全随机数字用于管理密码

* 随机数:: 
* 生成凭据:: 
* 其他功能:: 
* 应用技巧与最佳实践:: 

生成凭据

* 凭据应当使用多少个字节？:: 

通用操作系统服务

* os: os --- 多种操作系统接口. 多种操作系统接口
* io: io --- 处理流的核心工具. 处理流的核心工具
* time: time --- 时间的访问和转换. 时间的访问和转换
* argparse: argparse --- 命令行选项、参数和子命令解析器. 命令行选项、参数和子命令解析器
* getopt: getopt --- C 风格的命令行选项解析器. C 风格的命令行选项解析器
* logging: logging --- Python 的日志记录工具. Python 的日志记录工具
* logging.config: logging config --- 日志记录配置. 日志记录配置
* logging.handlers: logging handlers --- 日志处理. 日志处理
* getpass: getpass --- 便携式密码输入工具. 便携式密码输入工具
* curses: curses --- 终端字符单元显示的处理. 终端字符单元显示的处理
* curses.textpad: curses textpad --- Text input widget for curses programs. Text input widget for curses programs
* curses.ascii: curses ascii --- Utilities for ASCII characters. Utilities for ASCII characters
* curses.panel: curses panel --- A panel stack extension for curses. A panel stack extension for curses
* platform: platform --- 获取底层平台的标识数据. 获取底层平台的标识数据
* errno: errno --- 标准 errno 系统符号. 标准 errno 系统符号
* ctypes: ctypes --- Python 的外部函数库. Python 的外部函数库

os --- 多种操作系统接口

* 文件名，命令行参数，以及环境变量。:: 
* 进程参数:: 
* 创建文件对象:: 
* 文件描述符操作:: 
* 文件和目录:: 
* 进程管理:: 
* 调度器接口:: 
* 其他系统信息:: 
* 随机数: 随机数<2>. 

文件描述符操作

* 查询终端的尺寸:: 
* 文件描述符的继承:: 

文件和目录

* Linux 扩展属性:: 

io --- 处理流的核心工具

* 概述: 概述<8>. 
* 高阶模块接口:: 
* 类的层次结构:: 
* 性能: 性能<3>. 

概述

* 文本 I/O:: 
* 二进制 I/O:: 
* 原始 I/O:: 

高阶模块接口

* 内存中的流:: 

类的层次结构

* I/O 基类:: 
* 原始文件 I/O:: 
* 缓冲流:: 
* 文本 I/O: 文本 I/O<2>. 

性能

* 二进制 I/O: 二进制 I/O<2>. 
* 文本 I/O: 文本 I/O<3>. 
* 多线程: 多线程<4>. 
* 可重入性:: 

time --- 时间的访问和转换

* 函数: 函数<2>. 
* Clock ID 常量:: 
* 时区常量:: 

argparse --- 命令行选项、参数和子命令解析器

* 示例: 示例<7>. 
* ArgumentParser 对象:: 
* add_argument() 方法: add_argument 方法. 
* parse_args() 方法: parse_args 方法. 
* 其它实用工具:: 
* 升级 optparse 代码:: 

示例

* 创建一个解析器:: 
* 添加参数:: 
* 解析参数:: 

ArgumentParser 对象

* prog:: 
* usage:: 
* description:: 
* epilog:: 
* parents:: 
* formatter_class:: 
* prefix_chars:: 
* fromfile_prefix_chars:: 
* argument_default:: 
* allow_abbrev:: 
* conflict_handler:: 
* add_help:: 

add_argument() 方法

* name or flags:: 
* action:: 
* nargs:: 
* const:: 
* 默认值:: 
* type:: 
* choices:: 
* required:: 
* help:: 
* metavar:: 
* dest:: 
* Action 类:: 

parse_args() 方法

* 选项值语法:: 
* 无效的参数:: 
* 包含 - 的参数:: 
* 参数缩写（前缀匹配）:: 
* 在 sys.argv 以外: 在 sys argv 以外. 
* 命名空间对象:: 

其它实用工具

* 子命令:: 
* FileType 对象:: 
* 参数组:: 
* 互斥:: 
* 解析器默认值:: 
* 打印帮助:: 
* 部分解析:: 
* 自定义文件解析:: 
* 退出方法:: 
* 混合解析:: 

logging --- Python 的日志记录工具

* 记录器对象:: 
* 日志级别:: 
* 处理器对象:: 
* 格式器对象:: 
* Filter 对象:: 
* LogRecord 属性:: 
* LogRecord 属性: LogRecord 属性<2>. 
* LoggerAdapter 对象:: 
* 线程安全:: 
* 模块级别函数:: 
* 模块级属性:: 
* 与警告模块集成:: 

logging.config --- 日志记录配置

* 配置函数:: 
* 配置字典架构:: 
* Configuration file format:: 

配置字典架构

* 字典架构细节:: 
* 增量配置:: 
* 对象连接:: 
* 用户定义对象:: 
* Access to external objects:: 
* Access to internal objects:: 
* Import resolution and custom importers:: 

logging.handlers --- 日志处理

* StreamHandler:: 
* FileHandler:: 
* NullHandler:: 
* WatchedFileHandler:: 
* BaseRotatingHandler:: 
* RotatingFileHandler:: 
* TimedRotatingFileHandler:: 
* SocketHandler:: 
* DatagramHandler:: 
* SysLogHandler:: 
* NTEventLogHandler:: 
* SMTPHandler:: 
* MemoryHandler:: 
* HTTPHandler:: 
* QueueHandler:: 
* QueueListener:: 

curses --- 终端字符单元显示的处理

* 函数: 函数<3>. 
* Window Objects:: 
* 常量: 常量<6>. 

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

* 文本框对象:: 

curses.panel --- A panel stack extension for curses

* 函数: 函数<4>. 
* Panel Objects:: 

platform ---  获取底层平台的标识数据

* 跨平台:: 
* Java平台:: 
* Windows平台:: 
* Mac OS平台:: 
* Unix Platforms:: 

ctypes --- Python 的外部函数库

* ctypes 教程:: 
* ctypes reference:: 

ctypes 教程

* 载入动态连接库:: 
* 操作导入的动态链接库中的函数:: 
* 调用函数:: 
* 基础数据类型:: 
* 调用函数，继续:: 
* 使用自定义的数据类型调用函数:: 
* Specifying the required argument types (function prototypes): Specifying the required argument types function prototypes. 
* Return types:: 
* Passing pointers (or; passing parameters by reference): Passing pointers or passing parameters by reference. 
* Structures and unions:: 
* Structure/union alignment and byte order:: 
* Bit fields in structures and unions:: 
* Arrays:: 
* Pointers:: 
* Type conversions:: 
* Incomplete Types:: 
* Callback functions:: 
* Accessing values exported from dlls:: 
* Surprises:: 
* Variable-sized data types:: 

ctypes reference

* Finding shared libraries:: 
* Loading shared libraries:: 
* Foreign functions:: 
* Function prototypes:: 
* Utility functions:: 
* Data types:: 
* 基础数据类型: 基础数据类型<2>. 
* Structured data types:: 
* Arrays and pointers:: 

并发执行

* threading: threading --- 基于线程的并行. 基于线程的并行
* multiprocessing: multiprocessing --- 基于进程的并行. 基于进程的并行
* multiprocessing.shared_memory: multiprocessing shared_memory --- 可从进程直接访问的共享内存. 可从进程直接访问的共享内存
* concurrent 包:: 
* concurrent.futures: concurrent futures --- 启动并行任务. 启动并行任务
* subprocess: subprocess --- 子进程管理. 子进程管理
* sched: sched --- 事件调度器. 事件调度器
* queue: queue --- 一个同步的队列类. 一个同步的队列类
* _thread: _thread --- 底层多线程 API. 底层多线程 API
* _dummy_thread: _dummy_thread --- _thread 的替代模块. _thread 的替代模块
* dummy_threading: dummy_threading --- 可直接替代 threading 模块。. 可直接替代 threading 模块。

threading --- 基于线程的并行

* 线程本地数据:: 
* 线程对象:: 
* 锁对象:: 
* 递归锁对象:: 
* 条件对象:: 
* 信号量对象:: 
* 事件对象:: 
* 定时器对象:: 
* 栅栏对象:: 
* 在 with 语句中使用锁、条件和信号量:: 

信号量对象

* Semaphore 例子:: 

multiprocessing --- 基于进程的并行

* 概述: 概述<9>. 
* 参考:: 
* 编程指导:: 
* 例子: 例子<10>. 

概述

* Process 类:: 
* 上下文和启动方法:: 
* 在进程之间交换对象:: 
* 进程间同步:: 
* 进程间共享状态:: 
* 使用工作进程:: 

参考

* Process 和异常:: 
* 管道和队列:: 
* 杂项: 杂项<3>. 
* 连接对象（Connection）: 连接对象（Connection）<2>. 
* 同步原语:: 
* 共享 ctypes 对象:: 
* 管理器:: 
* 代理对象:: 
* 进程池:: 
* 监听者及客户端:: 
* 认证密码:: 
* 日志记录: 日志记录<2>. 
* multiprocessing.dummy 模块: multiprocessing dummy 模块. 

共享 ctypes 对象

* multiprocessing.sharedctypes 模块: multiprocessing sharedctypes 模块. 

管理器

* 自定义管理器:: 
* 使用远程管理器:: 

代理对象

* 清理:: 

监听者及客户端

* 地址格式:: 

编程指导

* 所有start方法:: 
* spawn 和 forkserver 启动方式:: 

concurrent.futures --- 启动并行任务

* 执行器对象:: 
* 线程池执行器:: 
* 进程池执行器:: 
* 期程对象:: 
* 模块函数:: 
* Exception类:: 

线程池执行器

* ThreadPoolExecutor 例子:: 

进程池执行器

* ProcessPoolExecutor 例子:: 

subprocess --- 子进程管理

* 使用 subprocess 模块:: 
* 安全考量:: 
* Popen 对象:: 
* Windows Popen 助手:: 
* Older high-level API:: 
* Replacing Older Functions with the subprocess Module:: 
* Legacy Shell Invocation Functions:: 
* 注释: 注释<2>. 

使用 subprocess 模块

* 常用参数:: 
* Popen 构造函数:: 
* 异常: 异常<7>. 

Windows Popen 助手

* Windows 常数:: 

Replacing Older Functions with the subprocess Module

* Replacing /bin/sh shell command substitution:: 
* Replacing shell pipeline:: 
* Replacing os.system(): Replacing os system. 
* Replacing the os.spawn family: Replacing the os spawn family. 
* Replacing os.popen()@comma{} os.popen2()@comma{} os.popen3(): Replacing os popen os popen2 os popen3. 
* Replacing functions from the popen2 module:: 

注释

* Converting an argument sequence to a string on Windows:: 

sched --- 事件调度器

* 调度器对象:: 

queue --- 一个同步的队列类

* Queue对象:: 
* SimpleQueue 对象:: 

contextvars --- Context Variables

* Context Variables:: 
* Manual Context Management:: 
* asyncio support:: 

网络和进程间通信

* asyncio: asyncio --- 异步 I/O. 异步 I/O
* socket: socket --- 底层网络接口. 底层网络接口
* ssl: ssl --- 套接字对象的TLS/SSL封装. 套接字对象的TLS/SSL封装
* select: select --- 等待 I/O 完成. 等待 I/O 完成
* selectors: selectors --- 高级 I/O 复用库. 高级 I/O 复用库
* asyncore: asyncore --- 异步socket处理器. 异步socket处理器
* asynchat: asynchat --- 异步 socket 指令/响应 处理器. 异步 socket 指令/响应 处理器
* signal: signal --- 设置异步事件处理程序. 设置异步事件处理程序
* mmap: mmap --- 内存映射文件支持. 内存映射文件支持

asyncio --- 异步 I/O

* 协程与任务:: 
* 流:: 
* Synchronization Primitives:: 
* 子进程集:: 
* 队列集:: 
* 异常: 异常<9>. 
* 事件循环:: 
* Futures:: 
* 传输和协议:: 
* 策略:: 
* 平台支持:: 
* 高级API索引:: 
* 底层API目录:: 
* 用 asyncio 开发:: 

协程与任务

* 协程: 协程<3>. 
* 可等待对象: 可等待对象<2>. 
* 运行 asyncio 程序:: 
* 创建任务:: 
* 休眠:: 
* 并发运行任务:: 
* 屏蔽取消操作:: 
* 超时:: 
* 简单等待:: 
* 来自其他线程的日程安排:: 
* 内省:: 
* Task 对象:: 
* 基于生成器的协程:: 

流

* StreamReader:: 
* StreamWriter:: 
* 例子: 例子<11>. 

例子

* TCP echo client using streams:: 
* TCP echo server using streams:: 
* Get HTTP headers:: 
* Register an open socket to wait for data using streams:: 

Synchronization Primitives

* Lock:: 
* Event:: 
* Condition:: 
* Semaphore:: 
* BoundedSemaphore:: 

子进程集

* Creating Subprocesses:: 
* 常量: 常量<7>. 
* Interacting with Subprocesses:: 

Interacting with Subprocesses

* Subprocess and Threads:: 
* 例子: 例子<12>. 

队列集

* Queue:: 
* 优先级队列:: 
* 后进先出队列:: 
* 异常: 异常<8>. 
* 例子: 例子<13>. 

事件循环

* 事件循环方法集:: 
* 回调处理:: 
* Server Objects:: 
* 事件循环实现:: 
* 例子: 例子<14>. 

事件循环方法集

* 运行和停止循环:: 
* 调度回调:: 
* 调度延迟回调:: 
* 创建 Futures 和 Tasks:: 
* 打开网络连接:: 
* 创建网络服务:: 
* 传输文件:: 
* TLS 升级:: 
* 监控文件描述符:: 
* 直接使用 socket 对象:: 
* DNS:: 
* 使用管道:: 
* Unix 信号:: 
* 在线程或者进程池中执行代码。:: 
* 错误处理API:: 
* 开启调试模式:: 
* 运行子进程:: 

例子

* call_soon() 的 Hello World 示例。: call_soon 的 Hello World 示例。. 
* 使用 call_later() 来展示当前的日期: 使用 call_later 来展示当前的日期. 
* 监控一个文件描述符的读事件:: 
* 为SIGINT和SIGTERM设置信号处理器:: 

Futures

* Future 函数:: 
* Future 对象:: 

传输和协议

* 传输:: 
* 协议:: 
* 例子: 例子<15>. 

传输

* 传输层级:: 
* 基础传输:: 
* 只读传输:: 
* 只写传输:: 
* 数据报传输:: 
* 子进程传输:: 

协议

* 基础协议:: 
* 基础协议: 基础协议<2>. 
* 流协议:: 
* 缓冲流协议:: 
* 数据报协议:: 
* 子进程协议:: 

例子

* TCP回应服务器:: 
* TCP回应客户端:: 
* UDP回应服务器:: 
* UDP回应客户端:: 
* 链接已存在的套接字:: 
* loop.subprocess_exec() and SubprocessProtocol: loop subprocess_exec and SubprocessProtocol. 

策略

* 获取和设置策略:: 
* 策略对象:: 
* 进程监视器:: 
* 自定义策略:: 

平台支持

* 所有平台:: 
* Windows: Windows<47>. 
* macOS: macOS<20>. 

Windows

* Windows的子进程支持:: 

高级API索引

* 任务:: 
* 队列集: 队列集<2>. 
* 子进程集: 子进程集<2>. 
* 流: 流<2>. 
* 同步:: 
* 异常: 异常<10>. 

底层API目录

* 获取事件循环:: 
* 事件循环方法集: 事件循环方法集<2>. 
* 传输: 传输<2>. 
* 协议: 协议<2>. 
* 事件循环策略:: 

用 asyncio 开发

* Debug 模式:: 
* 并发性和多线程:: 
* 运行阻塞的代码:: 
* 日志记录: 日志记录<3>. 
* 检测 never-awaited 协同程序:: 
* 检测就再也没异常:: 

socket --- 底层网络接口

* 套接字协议族:: 
* 模块内容: 模块内容<4>. 
* 套接字对象:: 
* 关于套接字超时的说明:: 
* 示例: 示例<8>. 

模块内容

* 异常: 异常<11>. 
* 常量: 常量<8>. 
* 函数: 函数<5>. 

函数

* 创建套接字:: 
* 其他功能: 其他功能<2>. 

关于套接字超时的说明

* 超时与 connect 方法:: 
* 超时与 accept 方法:: 

ssl --- 套接字对象的TLS/SSL封装

* Functions@comma{} Constants@comma{} and Exceptions: Functions Constants and Exceptions. 
* SSL Sockets:: 
* SSL Contexts:: 
* Certificates:: 
* 例子: 例子<16>. 
* Notes on non-blocking sockets:: 
* Memory BIO Support: Memory BIO Support<2>. 
* SSL session:: 
* Security considerations:: 
* TLS 1.3: TLS 1 3. 
* LibreSSL support:: 

Functions, Constants, and Exceptions

* Socket creation:: 
* 上下文创建:: 
* 异常: 异常<12>. 
* Random generation:: 
* Certificate handling:: 
* 常量: 常量<9>. 

Certificates

* Certificate chains:: 
* CA certificates:: 
* Combined key and certificate:: 
* Self-signed certificates:: 

例子

* Testing for SSL support:: 
* Client-side operation:: 
* Server-side operation:: 

Security considerations

* Best defaults:: 
* Manual settings:: 
* Multi-processing:: 

Manual settings

* Verifying certificates:: 
* Protocol versions:: 
* Cipher selection:: 

select --- 等待 I/O 完成

* /dev/poll 轮询对象:: 
* 边缘触发和水平触发的轮询 (epoll) 对象: 边缘触发和水平触发的轮询 epoll 对象. 
* Poll 对象:: 
* Kqueue 对象:: 
* Kevent 对象:: 

selectors --- 高级 I/O 复用库

* 概述: 概述<10>. 
* 类: 类<3>. 
* 例子: 例子<17>. 

asyncore --- 异步socket处理器

* asyncore Example basic HTTP client:: 
* asyncore Example basic echo server:: 

asynchat --- 异步 socket 指令/响应 处理器

* asynchat Example:: 

signal --- 设置异步事件处理程序

* 一般规则:: 
* 模块内容: 模块内容<5>. 
* 示例: 示例<9>. 
* Note on SIGPIPE:: 

一般规则

* 执行 Python 信号处理程序:: 
* 信号与线程:: 

mmap --- 内存映射文件支持

* MADV_* Constants:: 

互联网数据处理

* email: email --- 电子邮件与 MIME 处理包. 电子邮件与 MIME 处理包
* json: json --- JSON 编码和解码器. JSON 编码和解码器
* mailcap: mailcap --- Mailcap 文件处理. Mailcap 文件处理
* mailbox: mailbox --- Manipulate mailboxes in various formats. Manipulate mailboxes in various formats
* mimetypes: mimetypes --- Map filenames to MIME types. Map filenames to MIME types
* base64: base64 --- Base16 Base32 Base64 Base85 数据编码. Base16, Base32, Base64, Base85 数据编码
* binhex: binhex --- 对binhex4文件进行编码和解码. 对binhex4文件进行编码和解码
* binascii: binascii --- 二进制和 ASCII 码互转. 二进制和 ASCII 码互转
* quopri: quopri --- 编码与解码经过 MIME 转码的可打印数据. 编码与解码经过 MIME 转码的可打印数据
* uu: uu --- 对 uuencode 文件进行编码与解码. 对 uuencode 文件进行编码与解码

email --- 电子邮件与 MIME 处理包

* email.message; Representing an email message: email message Representing an email message. 
* email.parser; Parsing email messages: email parser Parsing email messages. 
* email.generator; Generating MIME documents: email generator Generating MIME documents. 
* email.policy; Policy Objects: email policy Policy Objects. 
* email.errors; 异常和缺陷类: email errors 异常和缺陷类. 
* email.headerregistry; Custom Header Objects: email headerregistry Custom Header Objects. 
* email.contentmanager; Managing MIME Content: email contentmanager Managing MIME Content. 
* email; 示例: email 示例. 
* email.message.Message; Representing an email message using the compat32 API: email message Message Representing an email message using the compat32 API. 
* email.mime; Creating email and MIME objects from scratch: email mime Creating email and MIME objects from scratch. 
* email.header; Internationalized headers: email header Internationalized headers. 
* email.charset; Representing character sets: email charset Representing character sets. 
* email.encoders; 编码器: email encoders 编码器. 
* email.utils; 其他工具: email utils 其他工具. 
* email.iterators; 迭代器: email iterators 迭代器. 

email.parser: Parsing email messages

* FeedParser API:: 
* Parser API:: 
* Additional notes:: 

email.contentmanager: Managing MIME Content

* Content Manager Instances:: 

json --- JSON 编码和解码器

* 基本使用:: 
* 编码器和解码器:: 
* 异常: 异常<13>. 
* 标准符合性和互操作性:: 
* 命令行界面: 命令行界面<4>. 

标准符合性和互操作性

* 字符编码:: 
* Infinite 和 NaN 数值:: 
* 对象中的重复名称:: 
* 顶级非对象，非数组值:: 
* 实现限制:: 

命令行界面

* 命令行选项: 命令行选项<4>. 

mailbox --- Manipulate mailboxes in various formats

* Mailbox 对象:: 
* Message objects:: 
* 异常: 异常<14>. 
* 例子: 例子<18>. 

Mailbox 对象

* Maildir:: 
* mbox:: 
* MH:: 
* Babyl:: 
* MMDF:: 

Message objects

* MaildirMessage:: 
* mboxMessage:: 
* MHMessage:: 
* BabylMessage:: 
* MMDFMessage:: 

mimetypes --- Map filenames to MIME types

* MimeTypes Objects:: 

binhex --- 对binhex4文件进行编码和解码

* 注释: 注释<3>. 

结构化标记处理工具

* html: html --- 超文本标记语言支持. 超文本标记语言支持
* html.parser: html parser --- 简单的 HTML 和 XHTML 解析器. 简单的 HTML 和 XHTML 解析器
* html.entities: html entities --- HTML 一般实体的定义. HTML 一般实体的定义
* XML处理模块:: 
* xml.etree.ElementTree: xml etree ElementTree --- ElementTree XML API. ElementTree XML API
* xml.dom: xml dom --- The Document Object Model API. The Document Object Model API
* xml.dom.minidom: xml dom minidom --- Minimal DOM implementation. Minimal DOM implementation
* xml.dom.pulldom: xml dom pulldom --- Support for building partial DOM trees. Support for building partial DOM trees
* xml.sax: xml sax --- Support for SAX2 parsers. Support for SAX2 parsers
* xml.sax.handler: xml sax handler --- Base classes for SAX handlers. Base classes for SAX handlers
* xml.sax.saxutils: xml sax saxutils --- SAX 工具集. SAX 工具集
* xml.sax.xmlreader: xml sax xmlreader --- Interface for XML parsers. Interface for XML parsers
* xml.parsers.expat: xml parsers expat --- Fast XML parsing using Expat. Fast XML parsing using Expat

html.parser --- 简单的 HTML 和 XHTML 解析器

* HTML 解析器的示例程序:: 
* HTMLParser 方法:: 
* 例子: 例子<19>. 

XML处理模块

* XML 漏洞:: 
* defusedxml 和 defusedexpat 软件包:: 

xml.etree.ElementTree ---  ElementTree XML API

* 教程:: 
* XPath支持:: 
* 参考: 参考<2>. 
* XInclude 支持:: 
* 参考: 参考<3>. 

教程

* XML树和元素:: 
* 解析XML:: 
* Pull API进行非阻塞解析:: 
* 查找感兴趣的元素:: 
* 修改XML文件:: 
* 构建XML文档:: 
* 使用命名空间解析XML:: 
* 其他资源: 其他资源<2>. 

XPath支持

* 示例: 示例<10>. 
* 支持的XPath语法:: 

参考

* 函数: 函数<6>. 

XInclude 支持

* 示例: 示例<11>. 

参考

* 函数: 函数<7>. 
* 元素对象:: 
* ElementTree 对象:: 
* QName Objects:: 
* TreeBuilder Objects:: 
* XMLParser对象:: 
* XMLPullParser对象:: 
* 异常: 异常<15>. 

xml.dom --- The Document Object Model API

* 模块内容: 模块内容<6>. 
* Objects in the DOM:: 
* 一致性:: 

Objects in the DOM

* DOMImplementation Objects:: 
* 节点对象:: 
* 节点列表对象:: 
* 文档类型对象:: 
* 文档对象:: 
* 元素对象: 元素对象<2>. 
* Attr 对象:: 
* NamedNodeMap 对象:: 
* 注释对象:: 
* Text 和 CDATASection 对象:: 
* ProcessingInstruction 对象:: 
* 异常: 异常<16>. 

一致性

* 类型映射:: 
* Accessor Methods:: 

xml.dom.minidom --- Minimal DOM implementation

* DOM Objects:: 
* DOM Example:: 
* minidom and the DOM standard:: 

xml.dom.pulldom --- Support for building partial DOM trees

* DOMEventStream Objects:: 

xml.sax --- Support for SAX2 parsers

* SAXException Objects:: 

xml.sax.handler --- Base classes for SAX handlers

* ContentHandler 对象:: 
* DTDHandler 对象:: 
* EntityResolver 对象:: 
* ErrorHandler 对象:: 

xml.sax.xmlreader --- Interface for XML parsers

* XMLReader 对象:: 
* IncrementalParser 对象:: 
* Locator 对象:: 
* InputSource 对象:: 
* The Attributes Interface:: 
* The AttributesNS Interface:: 

xml.parsers.expat --- Fast XML parsing using Expat

* XMLParser对象: XMLParser对象<2>. 
* ExpatError Exceptions:: 
* 示例: 示例<12>. 
* Content Model Descriptions:: 
* Expat error constants:: 

互联网协议和支持

* webbrowser: webbrowser --- 方便的Web浏览器控制器. 方便的Web浏览器控制器
* cgi: cgi --- Common Gateway Interface support. Common Gateway Interface support
* cgitb: cgitb --- 用于 CGI 脚本的回溯管理器. 用于 CGI 脚本的回溯管理器
* wsgiref: wsgiref --- WSGI Utilities and Reference Implementation. WSGI Utilities and Reference Implementation
* urllib: urllib --- URL 处理模块. URL 处理模块
* urllib.request: urllib request --- 用于打开 URL 的可扩展库. 用于打开 URL 的可扩展库
* urllib.response: urllib response --- urllib 使用的 Response 类. urllib 使用的 Response 类
* urllib.parse: urllib parse --- Parse URLs into components. Parse URLs into components
* urllib.error: urllib error --- urllib request 引发的异常类. urllib.request 引发的异常类
* urllib.robotparser: urllib robotparser --- robots txt 语法分析程序. robots.txt 语法分析程序
* http: http --- HTTP 模块. HTTP 模块
* http.client: http client --- HTTP 协议客户端. HTTP 协议客户端
* ftplib: ftplib --- FTP 协议客户端. FTP 协议客户端
* poplib: poplib --- POP3 protocol client. POP3 protocol client
* imaplib: imaplib --- IMAP4 protocol client. IMAP4 protocol client
* nntplib: nntplib --- NNTP protocol client. NNTP protocol client
* smtplib ---SMTP协议客户端:: 
* smtpd: smtpd --- SMTP 服务器. SMTP 服务器
* telnetlib: telnetlib --- Telnet client. Telnet client
* uuid: uuid --- UUID objects according to RFC 4122. UUID objects according to RFC 4122
* socketserver: socketserver --- A framework for network servers. A framework for network servers
* http.server: http server --- HTTP 服务器. HTTP 服务器
* http.cookies: http cookies --- HTTP状态管理. HTTP状态管理
* http.cookiejar —— HTTP 客户端的 Cookie 处理: http cookiejar —— HTTP 客户端的 Cookie 处理. 
* xmlrpc: xmlrpc --- XMLRPC 服务端与客户端模块. XMLRPC 服务端与客户端模块
* xmlrpc.client: xmlrpc client --- XML-RPC client access. XML-RPC client access
* xmlrpc.server: xmlrpc server --- Basic XML-RPC servers. Basic XML-RPC servers
* ipaddress: ipaddress --- IPv4/IPv6 操作库. IPv4/IPv6 操作库

webbrowser --- 方便的Web浏览器控制器

* 浏览器控制器对象:: 

cgi --- Common Gateway Interface support

* 概述: 概述<11>. 
* 使用cgi模块。:: 
* Higher Level Interface:: 
* 函数: 函数<8>. 
* Caring about security:: 
* Installing your CGI script on a Unix system:: 
* Testing your CGI script:: 
* Debugging CGI scripts:: 
* Common problems and solutions:: 

wsgiref --- WSGI Utilities and Reference Implementation

* wsgiref.util: wsgiref util -- WSGI environment utilities. WSGI environment utilities
* wsgiref.headers: wsgiref headers -- WSGI response header tools. WSGI response header tools
* wsgiref.simple_server: wsgiref simple_server -- a simple WSGI HTTP server. a simple WSGI HTTP server
* wsgiref.validate: wsgiref validate --- WSGI conformance checker. WSGI conformance checker
* wsgiref.handlers: wsgiref handlers -- server/gateway base classes. server/gateway base classes
* 例子: 例子<20>. 

urllib.request --- 用于打开 URL 的可扩展库

* Request 对象:: 
* OpenerDirector 对象:: 
* BaseHandler 对象:: 
* HTTPRedirectHandler 对象:: 
* HTTPCookieProcessor 对象:: 
* ProxyHandler 对象:: 
* HTTPPasswordMgr 对象:: 
* HTTPPasswordMgrWithPriorAuth 对象:: 
* AbstractBasicAuthHandler 对象:: 
* HTTPBasicAuthHandler 对象:: 
* ProxyBasicAuthHandler 对象:: 
* AbstractDigestAuthHandler 对象:: 
* HTTPDigestAuthHandler 对象:: 
* ProxyDigestAuthHandler 对象:: 
* HTTPHandler 对象:: 
* HTTPSHandler 对象:: 
* FileHandler 对象:: 
* DataHandler 对象:: 
* FTPHandler 对象:: 
* CacheFTPHandler 对象:: 
* UnknownHandler 对象:: 
* HTTPErrorProcessor 对象:: 
* 例子: 例子<21>. 
* Legacy interface:: 
* urllib.request Restrictions: urllib request Restrictions. 

urllib.parse --- Parse URLs into components

* URL 解析:: 
* 解析ASCII编码字节:: 
* 结构化解析结果:: 
* URL Quoting:: 

http --- HTTP 模块

* HTTP 状态码:: 

http.client --- HTTP 协议客户端

* HTTPConnection 对象:: 
* HTTPResponse 对象:: 
* 例子: 例子<22>. 
* HTTPMessage Objects:: 

ftplib --- FTP 协议客户端

* FTP Objects:: 
* FTP_TLS Objects:: 

poplib --- POP3 protocol client

* POP3 Objects:: 
* POP3 Example:: 

imaplib --- IMAP4 protocol client

* IMAP4 Objects:: 
* IMAP4 Example:: 

nntplib --- NNTP protocol client

* NNTP Objects:: 
* Utility functions: Utility functions<2>. 

NNTP Objects

* Attributes:: 
* 方法: 方法<3>. 

smtplib ---SMTP协议客户端

* SMTP Objects:: 
* SMTP Example:: 

smtpd --- SMTP 服务器

* SMTPServer 对象:: 
* DebuggingServer 对象:: 
* PureProxy对象:: 
* MailmanProxy 对象:: 
* SMTPChannel 对象:: 

telnetlib --- Telnet client

* Telnet Objects:: 
* Telnet Example:: 

uuid --- UUID objects according to RFC 4122

* 示例: 示例<13>. 

socketserver --- A framework for network servers

* Server Creation Notes:: 
* Server Objects: Server Objects<2>. 
* Request Handler Objects:: 
* 例子: 例子<23>. 

例子

* socketserver.TCPServer Example: socketserver TCPServer Example. 
* socketserver.UDPServer Example: socketserver UDPServer Example. 
* Asynchronous Mixins:: 

http.cookies --- HTTP状态管理

* Cookie 对象:: 
* Morsel 对象:: 
* 示例: 示例<14>. 

http.cookiejar —— HTTP 客户端的 Cookie 处理

* CookieJar 和 FileCookieJar 对象:: 
* FileCookieJar subclasses and co-operation with web browsers:: 
* CookiePolicy 对象:: 
* DefaultCookiePolicy 对象:: 
* Cookie 对象: Cookie 对象<2>. 
* 例子: 例子<24>. 

xmlrpc.client --- XML-RPC client access

* ServerProxy 对象:: 
* DateTime 对象:: 
* Binary 对象:: 
* Fault 对象:: 
* ProtocolError 对象:: 
* MultiCall 对象:: 
* Convenience Functions:: 
* Example of Client Usage:: 
* Example of Client and Server Usage:: 

xmlrpc.server --- Basic XML-RPC servers

* SimpleXMLRPCServer Objects:: 
* CGIXMLRPCRequestHandler:: 
* Documenting XMLRPC server:: 
* DocXMLRPCServer Objects:: 
* DocCGIXMLRPCRequestHandler:: 

SimpleXMLRPCServer Objects

* SimpleXMLRPCServer Example:: 

ipaddress --- IPv4/IPv6 操作库

* 方便的工厂函数:: 
* IP 地址:: 
* IP Network definitions:: 
* Interface objects:: 
* Other Module Level Functions:: 
* Custom Exceptions:: 

IP 地址

* 地址对象:: 
* Conversion to Strings and Integers:: 
* 运算符: 运算符<3>. 

运算符

* Comparison operators:: 
* Arithmetic operators:: 

IP Network definitions

* Prefix@comma{} net mask and host mask: Prefix net mask and host mask. 
* Network objects:: 
* 运算符: 运算符<4>. 

运算符

* Logical operators:: 
* 迭代: 迭代<2>. 
* Networks as containers of addresses:: 

Interface objects

* 运算符: 运算符<5>. 

运算符

* Logical operators: Logical operators<2>. 

多媒体服务

* audioop: audioop --- Manipulate raw audio data. Manipulate raw audio data
* aifc: aifc --- Read and write AIFF and AIFC files. Read and write AIFF and AIFC files
* sunau: sunau --- 读写 Sun AU 文件. 读写 Sun AU 文件
* wave: wave --- 读写WAV格式文件. 读写WAV格式文件
* chunk: chunk --- 读取 IFF 分块数据. 读取 IFF 分块数据
* colorsys: colorsys --- 颜色系统间的转换. 颜色系统间的转换
* imghdr: imghdr --- 推测图像类型. 推测图像类型
* sndhdr: sndhdr --- 推测声音文件的类型. 推测声音文件的类型
* ossaudiodev: ossaudiodev --- Access to OSS-compatible audio devices. Access to OSS-compatible audio devices

sunau --- 读写 Sun AU 文件

* AU_read 对象:: 
* AU_write 对象:: 

wave --- 读写WAV格式文件

* Wave_read对象:: 
* Wave_write 对象:: 

ossaudiodev --- Access to OSS-compatible audio devices

* Audio Device Objects:: 
* Mixer Device Objects:: 

国际化

* gettext: gettext --- 多语种国际化服务. 多语种国际化服务
* locale: locale --- 国际化服务. 国际化服务

gettext --- 多语种国际化服务

* GNU gettext API:: 
* Class-based API:: 
* Internationalizing your programs and modules:: 
* 致谢: 致谢<9>. 

Class-based API

* The NullTranslations class:: 
* The GNUTranslations class:: 
* Solaris message catalog support:: 
* The Catalog constructor:: 

Internationalizing your programs and modules

* Localizing your module:: 
* Localizing your application:: 
* Changing languages on the fly:: 
* Deferred translations:: 

locale --- 国际化服务

* Background@comma{} details@comma{} hints@comma{} tips and caveats: Background details hints tips and caveats. 
* For extension writers and programs that embed Python:: 
* Access to message catalogs:: 

程序框架

* turtle: turtle --- 海龟绘图. 海龟绘图
* cmd: cmd --- 支持面向行的命令解释器. 支持面向行的命令解释器
* shlex: shlex --- Simple lexical analysis. Simple lexical analysis

turtle --- 海龟绘图

* 概述: 概述<12>. 
* 可用的 Turtle 和 Screen 方法概览:: 
* RawTurtle/Turtle 方法和对应函数:: 
* TurtleScreen/Screen 方法及对应函数:: 
* 公共类:: 
* 帮助与配置:: 
* turtledemo: turtledemo --- 演示脚本集. 演示脚本集
* Python 2.6 之后的变化: Python 2 6 之后的变化. 
* Python 3.0 之后的变化: Python 3 0 之后的变化. 

可用的 Turtle 和 Screen 方法概览

* Turtle 方法:: 
* TurtleScreen/Screen 方法:: 

RawTurtle/Turtle 方法和对应函数

* 海龟动作:: 
* 获取海龟的状态:: 
* 度量单位设置:: 
* 画笔控制:: 
* 海龟状态:: 
* 使用事件:: 
* 特殊海龟方法:: 
* 复合形状:: 

画笔控制

* 绘图状态:: 
* 颜色控制:: 
* 填充:: 
* 更多绘图控制:: 

海龟状态

* 可见性:: 
* 外观:: 

TurtleScreen/Screen 方法及对应函数

* 窗口控制:: 
* 动画控制:: 
* 使用屏幕事件:: 
* 输入方法:: 
* 设置与特殊方法:: 
* Screen 专有方法@comma{} 而非继承自 TurtleScreen: Screen 专有方法 而非继承自 TurtleScreen. 

帮助与配置

* 如何使用帮助:: 
* 文档字符串翻译为不同的语言:: 
* 如何配置 Screen 和 Turtle:: 

cmd --- 支持面向行的命令解释器

* Cmd 对象:: 
* Cmd 例子:: 

shlex --- Simple lexical analysis

* shlex Objects:: 
* Parsing Rules:: 
* Improved Compatibility with Shells:: 

Tk图形用户界面(GUI)

* tkinter: tkinter --- Tcl/Tk的Python接口. Tcl/Tk的Python接口
* tkinter.ttk: tkinter ttk --- Tk主题小部件. Tk主题小部件
* tkinter.tix: tkinter tix --- Extension widgets for Tk. Extension widgets for Tk
* tkinter.scrolledtext: tkinter scrolledtext --- 滚动文字控件. 滚动文字控件
* IDLE: IDLE<48>. 
* 其他图形用户界面（GUI）包:: 

tkinter --- Tcl/Tk的Python接口

* Tkinter 模块:: 
* Tkinter Life Preserver:: 
* A (Very) Quick Look at Tcl/Tk: A Very Quick Look at Tcl/Tk. 
* Mapping Basic Tk into Tkinter:: 
* How Tk and Tkinter are Related:: 
* Handy Reference:: 
* File Handlers:: 

Tkinter Life Preserver

* How To Use This Section:: 
* A Simple Hello World Program:: 

Handy Reference

* Setting Options:: 
* The Packer:: 
* Packer Options:: 
* Coupling Widget Variables:: 
* The Window Manager:: 
* Tk Option Data Types:: 
* Bindings and Events:: 
* The index Parameter:: 
* Images:: 

tkinter.ttk --- Tk主题小部件

* 使用 Ttk:: 
* Ttk 部件:: 
* 控件:: 
* 组合框:: 
* Spinbox:: 
* 笔记本:: 
* Progressbar:: 
* Separator:: 
* Sizegrip:: 
* Treeview:: 
* Ttk Styling:: 

控件

* 标准选项:: 
* 可滚动控件选项:: 
* 标签选项:: 
* 兼容性选项:: 
* 控件状态:: 
* ttk.Widget: ttk Widget. 

组合框

* 选项:: 
* 虚拟事件:: 
* ttk.Combobox: ttk Combobox. 

Spinbox

* 选项: 选项<2>. 
* 虚拟事件: 虚拟事件<2>. 
* ttk.Spinbox: ttk Spinbox. 

笔记本

* 选项: 选项<3>. 
* Tab 选项:: 
* Tab Identifiers:: 
* Virtual Events:: 
* ttk.Notebook: ttk Notebook. 

Progressbar

* 选项: 选项<4>. 
* ttk.Progressbar: ttk Progressbar. 

Separator

* 选项: 选项<5>. 

Sizegrip

* Platform-specific notes:: 
* Bugs:: 

Treeview

* 选项: 选项<6>. 
* Item Options:: 
* Tag Options:: 
* Column Identifiers:: 
* Virtual Events: Virtual Events<2>. 
* ttk.Treeview: ttk Treeview. 

Ttk Styling

* Layouts:: 

tkinter.tix --- Extension widgets for Tk

* Using Tix:: 
* Tix Widgets:: 
* Tix Commands:: 

Tix Widgets

* Basic Widgets:: 
* File Selectors:: 
* Hierarchical ListBox:: 
* Tabular ListBox:: 
* Manager Widgets:: 
* Image Types:: 
* Miscellaneous Widgets:: 
* Form Geometry Manager:: 

IDLE

* 目录:: 
* 编辑和导航:: 
* 启动和代码执行:: 
* 帮助和偏好:: 

目录

* 文件菜单 （命令行和编辑器）:: 
* 编辑菜单（命令行和编辑器）:: 
* 格式菜单（仅 window 编辑器）:: 
* 运行菜单（仅 window 编辑器）:: 
* Shell 菜单（仅 window 编辑器）:: 
* 调试菜单（仅 window 编辑器）:: 
* 选项菜单（命令行和编辑器）:: 
* Window 菜单（命令行和编辑器）:: 
* 帮助菜单（命令行和编辑器）:: 
* 上下文菜单:: 

编辑和导航

* 编辑窗口:: 
* 按键绑定:: 
* 自动缩进:: 
* 完成:: 
* 提示:: 
* 代码上下文:: 
* Python Shell 窗口:: 
* 文本颜色:: 

启动和代码执行

* 命令行语法:: 
* 启动失败:: 
* 运行用户代码:: 
* Shell中的用户输出:: 
* 开发 tkinter 应用程序:: 
* 在没有子进程的情况下运行:: 

帮助和偏好

* 帮助源:: 
* 首选项设置:: 
* macOS 上的IDLE:: 
* 扩展:: 

开发工具

* typing: typing --- 类型标注支持. 类型标注支持
* pydoc: pydoc --- 文档生成器和在线帮助系统. 文档生成器和在线帮助系统
* doctest: doctest --- 测试交互性的Python示例. 测试交互性的Python示例
* unittest: unittest --- 单元测试框架. 单元测试框架
* unittest.mock: unittest mock --- 模拟对象库. 模拟对象库
* unittest.mock 上手指南: unittest mock 上手指南. 
* 2to3 - 自动将 Python 2 代码转为 Python 3 代码:: 
* test: test --- Python回归测试包. Python回归测试包
* test.support: test support --- Utilities for the Python test suite. Utilities for the Python test suite
* test.support.script_helper: test support script_helper --- Utilities for the Python execution tests. Utilities for the Python execution tests

typing --- 类型标注支持

* 类型别名:: 
* NewType:: 
* Callable:: 
* 泛型(Generic): 泛型 Generic. 
* 用户定义的泛型类型:: 
* Any 类型:: 
* Nominal vs structural subtyping:: 
* 类@comma{}函数和修饰器.: 类 函数和修饰器. 

doctest --- 测试交互性的Python示例

* 简单用法：检查Docstrings中的示例:: 
* Simple Usage; Checking Examples in a Text File: Simple Usage Checking Examples in a Text File. 
* How It Works:: 
* Basic API:: 
* Unittest API:: 
* Advanced API:: 
* 调试:: 
* Soapbox:: 

How It Works

* Which Docstrings Are Examined?:: 
* How are Docstring Examples Recognized?:: 
* What's the Execution Context?:: 
* What About Exceptions?:: 
* Option Flags:: 
* Directives:: 
* 警告: 警告<2>. 

Advanced API

* DocTest 对象:: 
* Example Objects:: 
* DocTestFinder 对象:: 
* DocTestParser 对象:: 
* DocTestRunner 对象:: 
* OutputChecker 对象:: 

unittest --- 单元测试框架

* 基本实例:: 
* 命令行界面: 命令行界面<5>. 
* 探索性测试:: 
* 组织你的测试代码:: 
* 复用已有的测试代码:: 
* 跳过测试与预计的失败:: 
* Distinguishing test iterations using subtests:: 
* 类与函数:: 
* Class and Module Fixtures:: 
* Signal Handling:: 

命令行界面

* 命令行选项: 命令行选项<5>. 

类与函数

* 测试用例:: 
* Grouping tests:: 
* Loading and running tests:: 

测试用例

* Deprecated aliases:: 

Loading and running tests

* load_tests Protocol:: 

Class and Module Fixtures

* setUpClass and tearDownClass:: 
* setUpModule and tearDownModule:: 

unittest.mock --- 模拟对象库

* 快速上手:: 
* Mock 类:: 
* The patchers:: 
* MagicMock and magic method support:: 
* Helpers:: 

Mock 类

* Calling:: 
* Deleting Attributes:: 
* Mock names and the name attribute:: 
* Attaching Mocks as Attributes:: 

The patchers

* patch:: 
* patch.object: patch object. 
* patch.dict: patch dict. 
* patch.multiple: patch multiple. 
* patch methods; start and stop: patch methods start and stop. 
* patch builtins:: 
* TEST_PREFIX:: 
* Nesting Patch Decorators:: 
* Where to patch:: 
* Patching Descriptors and Proxy Objects:: 

MagicMock and magic method support

* Mocking Magic Methods:: 
* Magic Mock:: 

Helpers

* sentinel:: 
* DEFAULT:: 
* call:: 
* create_autospec:: 
* ANY:: 
* FILTER_DIR:: 
* mock_open:: 
* Autospeccing:: 
* Sealing mocks:: 

unittest.mock 上手指南

* 使用 mock:: 
* Patch Decorators:: 
* Further Examples:: 

使用 mock

* 模拟方法调用:: 
* 对象上的方法调用的 mock:: 
* Mocking Classes:: 
* Naming your mocks:: 
* Tracking all Calls:: 
* Setting Return Values and Attributes:: 
* Raising exceptions with mocks:: 
* Side effect functions and iterables:: 
* Mocking asynchronous iterators:: 
* Mocking asynchronous context manager:: 
* Creating a Mock from an Existing Object:: 

Further Examples

* Mocking chained calls:: 
* Partial mocking:: 
* Mocking a Generator Method:: 
* Applying the same patch to every test method:: 
* Mocking Unbound Methods:: 
* Checking multiple calls with mock:: 
* Coping with mutable arguments:: 
* Nesting Patches:: 
* Mocking a dictionary with MagicMock:: 
* Mock subclasses and their attributes:: 
* Mocking imports with patch.dict: Mocking imports with patch dict. 
* Tracking order of calls and less verbose call assertions:: 
* More complex argument matching:: 

2to3 - 自动将 Python 2 代码转为 Python 3 代码

* 使用 2to3:: 
* 修复器:: 
* lib2to3 —— 2to3 支持库:: 

test ---  Python回归测试包

* Writing Unit Tests for the test package:: 
* Running tests using the command-line interface:: 

调试和分析

* 审计事件表:: 
* bdb: bdb --- Debugger framework. Debugger framework
* faulthandler: faulthandler --- Dump the Python traceback. Dump the Python traceback
* pdb: pdb --- Python的调试器. Python的调试器
* Python Profilers 分析器:: 
* timeit: timeit --- 测量小代码片段的执行时间. 测量小代码片段的执行时间
* trace: trace --- Trace or track Python statement execution. Trace or track Python statement execution
* tracemalloc: tracemalloc --- 跟踪内存分配. 跟踪内存分配

faulthandler --- Dump the Python traceback

* Dumping the traceback:: 
* Fault handler state:: 
* Dumping the tracebacks after a timeout:: 
* Dumping the traceback on a user signal:: 
* Issue with file descriptors:: 
* 示例: 示例<15>. 

pdb --- Python的调试器

* 调试器命令:: 

Python Profilers 分析器

* profile分析器简介:: 
* 实时用户手册:: 
* profile 和 cProfile 模块参考:: 
* Stats 类:: 
* 什么是确定性性能分析？:: 
* 局限性:: 
* 准确估量:: 
* 使用自定义计时器:: 

timeit --- 测量小代码片段的执行时间

* 基本示例: 基本示例<2>. 
* Python 接口:: 
* 命令行界面: 命令行界面<6>. 
* 例子: 例子<25>. 

trace --- Trace or track Python statement execution

* Command-Line Usage:: 
* 编程接口:: 

Command-Line Usage

* Main options:: 
* Modifiers:: 
* Filters:: 

tracemalloc --- 跟踪内存分配

* 例子: 例子<26>. 
* API:: 

例子

* 显示前10项:: 
* 计算差异:: 
* Get the traceback of a memory block:: 
* Pretty top:: 

API

* 函数: 函数<9>. 
* 域过滤器:: 
* 过滤器:: 
* Frame:: 
* 快照:: 
* 统计:: 
* StatisticDiff:: 
* 跟踪:: 
* 回溯: 回溯<4>. 

软件打包和分发

* distutils: distutils --- 构建和安装 Python 模块. 构建和安装 Python 模块
* ensurepip: ensurepip --- Bootstrapping the pip installer. Bootstrapping the pip installer
* venv: venv --- 创建虚拟环境. 创建虚拟环境
* zipapp: zipapp --- Manage executable Python zip archives. Manage executable Python zip archives

ensurepip --- Bootstrapping the pip installer

* Command line interface:: 
* Module API:: 

venv --- 创建虚拟环境

* 创建虚拟环境: 创建虚拟环境<2>. 
* API: API<2>. 
* 一个扩展 EnvBuilder 的例子:: 

zipapp --- Manage executable Python zip archives

* Basic Example:: 
* 命令行界面: 命令行界面<7>. 
* Python API:: 
* 例子: 例子<27>. 
* Specifying the Interpreter:: 
* Creating Standalone Applications with zipapp:: 
* The Python Zip Application Archive Format:: 

Creating Standalone Applications with zipapp

* Making a Windows executable:: 
* Caveats:: 

Python运行时服务

* sys: sys --- 系统相关的参数和函数. 系统相关的参数和函数
* sysconfig: sysconfig --- Provide access to Python's configuration information. Provide access to Python's configuration information
* builtins: builtins --- 内建对象. 内建对象
* __main__: __main__ --- 顶层脚本环境. 顶层脚本环境
* warnings: warnings --- Warning control. Warning control
* dataclasses: dataclasses --- 数据类. 数据类
* contextlib: contextlib --- 为 with语句上下文提供的工具. 为 with语句上下文提供的工具
* abc: abc --- 抽象基类. 抽象基类
* atexit: atexit --- 退出处理器. 退出处理器
* traceback: traceback --- 打印或检索堆栈回溯. 打印或检索堆栈回溯
* __future__: __future__ --- Future 语句定义. Future 语句定义
* gc: gc --- 垃圾回收器接口. 垃圾回收器接口
* inspect: inspect --- 检查对象. 检查对象
* site —— 指定域的配置钩子:: 

sysconfig --- Provide access to Python's configuration information

* 配置变量:: 
* 安装路径:: 
* 其他功能: 其他功能<3>. 
* Using sysconfig as a script:: 

warnings --- Warning control

* 警告类别:: 
* The Warnings Filter:: 
* 暂时禁止警告:: 
* 测试警告:: 
* Updating Code For New Versions of Dependencies:: 
* Available Functions:: 
* Available Context Managers:: 

The Warnings Filter

* Describing Warning Filters:: 
* 默认警告过滤器:: 
* Overriding the default filter:: 

dataclasses --- 数据类

* 模块级装饰器、类和函数:: 
* 初始化后处理:: 
* 类变量:: 
* 仅初始化变量:: 
* 冻结的实例:: 
* 继承: 继承<2>. 
* 默认工厂函数:: 
* 可变的默认值:: 
* 异常: 异常<17>. 

contextlib --- 为 with语句上下文提供的工具

* 工具:: 
* 例子和配方: 例子和配方<2>. 
* Single use@comma{} reusable and reentrant context managers: Single use reusable and reentrant context managers. 

例子和配方

* Supporting a variable number of context managers:: 
* Catching exceptions from __enter__ methods:: 
* Cleaning up in an __enter__ implementation:: 
* Replacing any use of try-finally and flag variables:: 
* Using a context manager as a function decorator:: 

Single use, reusable and reentrant context managers

* Reentrant context managers:: 
* Reusable context managers:: 

atexit --- 退出处理器

* atexit 示例:: 

traceback --- 打印或检索堆栈回溯

* TracebackException Objects:: 
* StackSummary Objects:: 
* FrameSummary Objects:: 
* Traceback Examples:: 

inspect --- 检查对象

* 类型和成员:: 
* Retrieving source code:: 
* Introspecting callables with the Signature object:: 
* 类与函数: 类与函数<2>. 
* The interpreter stack:: 
* Fetching attributes statically:: 
* Current State of Generators and Coroutines:: 
* Code Objects Bit Flags:: 
* 命令行界面: 命令行界面<8>. 

site —— 指定域的配置钩子

* Readline configuration:: 
* 模块内容: 模块内容<7>. 
* 命令行界面: 命令行界面<9>. 

自定义 Python 解释器

* code: code --- 解释器基类. 解释器基类
* codeop: codeop --- 编译Python代码. 编译Python代码

code --- 解释器基类

* 交互解释器对象:: 
* 交互式控制台对象:: 

导入模块

* zipimport: zipimport --- 从 Zip 存档中导入模块. 从 Zip 存档中导入模块
* pkgutil: pkgutil --- 包扩展工具. 包扩展工具
* modulefinder: modulefinder --- 查找脚本使用的模块. 查找脚本使用的模块
* runpy: runpy --- Locating and executing Python modules. Locating and executing Python modules
* importlib: importlib --- import 的实现. import 的实现
* Using importlib.metadata: Using importlib metadata. 

zipimport --- 从 Zip 存档中导入模块

* zipimporter 对象:: 
* 例子: 例子<28>. 

modulefinder --- 查找脚本使用的模块

* ModuleFinder 的示例用法:: 

importlib --- import 的实现

* 概述: 概述<13>. 
* 函数: 函数<10>. 
* importlib.abc —— 关于导入的抽象基类: importlib abc —— 关于导入的抽象基类. 
* importlib.resources: importlib resources -- 资源. 资源
* importlib.machinery: importlib machinery -- Importers and path hooks. Importers and path hooks
* importlib.util: importlib util -- Utility code for importers. Utility code for importers
* 例子: 例子<29>. 

例子

* Importing programmatically:: 
* Checking if a module can be imported:: 
* Importing a source file directly:: 
* Setting up an importer:: 
* Approximating importlib.import_module(): Approximating importlib import_module. 

Using importlib.metadata

* 概述: 概述<14>. 
* 功能性 API: 功能性 API<2>. 
* Distributions:: 
* Extending the search algorithm:: 

功能性 API

* Entry points:: 
* Distribution metadata:: 
* Distribution versions:: 
* Distribution files:: 
* Distribution requirements:: 

Python 语言服务

* parser: parser --- 访问 Python 解析树. 访问 Python 解析树
* ast: ast --- 抽象语法树. 抽象语法树
* symtable: symtable --- Access to the compiler's symbol tables. Access to the compiler's symbol tables
* symbol: symbol --- 与 Python 解析树一起使用的常量. 与 Python 解析树一起使用的常量
* token: token --- 与Python解析树一起使用的常量. 与Python解析树一起使用的常量
* keyword: keyword --- 检验Python关键字. 检验Python关键字
* tokenize: tokenize --- 对 Python 代码使用的标记解析器. 对 Python 代码使用的标记解析器
* tabnanny: tabnanny --- 模糊缩进检测. 模糊缩进检测
* pyclbr: pyclbr --- Python module browser support. Python module browser support
* py_compile: py_compile --- Compile Python source files. Compile Python source files
* compileall: compileall --- Byte-compile Python libraries. Byte-compile Python libraries
* dis: dis --- Python 字节码反汇编器. Python 字节码反汇编器
* pickletools: pickletools --- pickle 开发者工具集. pickle 开发者工具集

parser --- 访问 Python 解析树

* 创建 ST 对象:: 
* 转换 ST 对象:: 
* Queries on ST Objects:: 
* 异常和错误处理:: 
* ST 对象:: 
* 示例; compile() 的模拟: 示例 compile 的模拟. 

ast --- 抽象语法树

* 节点类:: 
* 抽象文法:: 
* ast 中的辅助函数:: 

symtable --- Access to the compiler's symbol tables

* Generating Symbol Tables:: 
* Examining Symbol Tables:: 

tokenize --- 对 Python 代码使用的标记解析器

* 对输入进行解析标记:: 
* Command-Line Usage: Command-Line Usage<2>. 
* 例子: 例子<30>. 

pyclbr --- Python module browser support

* 函数对象:: 
* 类对象: 类对象<2>. 

compileall --- Byte-compile Python libraries

* Command-line use:: 
* Public functions:: 

dis --- Python 字节码反汇编器

* 字节码分析:: 
* 分析函数:: 
* Python字节码说明:: 
* 操作码集合:: 

pickletools --- pickle 开发者工具集

* 命令行语法: 命令行语法<2>. 
* 编程接口: 编程接口<2>. 

命令行语法

* 命令行选项: 命令行选项<6>. 

杂项服务

* formatter: formatter --- 通用格式化输出. 通用格式化输出

formatter --- 通用格式化输出

* The Formatter Interface:: 
* Formatter Implementations:: 
* The Writer Interface:: 
* Writer Implementations:: 

Windows系统相关模块

* msilib: msilib --- Read and write Microsoft Installer files. Read and write Microsoft Installer files
* msvcrt: msvcrt --- 来自 MS VC++ 运行时的有用例程. 来自 MS VC++ 运行时的有用例程
* winreg: winreg --- Windows 注册表访问. Windows 注册表访问
* winsound: winsound --- Sound-playing interface for Windows. Sound-playing interface for Windows

msilib --- Read and write Microsoft Installer files

* Database Objects:: 
* View Objects:: 
* Summary Information Objects:: 
* Record Objects:: 
* Errors:: 
* CAB Objects:: 
* Directory Objects:: 
* 相关特性: 相关特性<3>. 
* GUI classes:: 
* Precomputed tables:: 

msvcrt --- 来自 MS VC++ 运行时的有用例程

* File Operations:: 
* Console I/O:: 
* Other Functions:: 

winreg --- Windows 注册表访问

* 函数: 函数<11>. 
* 常量: 常量<10>. 
* Registry Handle Objects:: 

常量

* HKEY_* Constants:: 
* Access Rights:: 
* Value Types:: 

Access Rights

* 64-bit Specific:: 

Unix 专有服务

* posix: posix --- 最常见的 POSIX 系统调用. 最常见的 POSIX 系统调用
* pwd: pwd --- 用户密码数据库. 用户密码数据库
* spwd: spwd --- The shadow password database. The shadow password database
* grp: grp --- 组数据库. 组数据库
* crypt: crypt --- Function to check Unix passwords. Function to check Unix passwords
* termios: termios --- POSIX 风格的 tty 控制. POSIX 风格的 tty 控制
* tty: tty --- 终端控制功能. 终端控制功能
* pty: pty --- 伪终端工具. 伪终端工具
* fcntl: fcntl --- The fcntl and ioctl system calls. The fcntl and ioctl system calls
* pipes: pipes --- 终端管道接口. 终端管道接口
* resource: resource --- Resource usage information. Resource usage information
* nis: nis --- Sun 的 NIS 黄页 接口. Sun 的 NIS (黄页) 接口
* Unix syslog 库例程:: 

posix --- 最常见的 POSIX 系统调用

* 大文件支持:: 
* 重要的模块内容:: 

crypt --- Function to check Unix passwords

* Hashing Methods:: 
* Module Attributes:: 
* 模块函数: 模块函数<2>. 
* 例子: 例子<31>. 

termios --- POSIX 风格的 tty 控制

* 示例: 示例<16>. 

pty --- 伪终端工具

* 示例: 示例<17>. 

pipes --- 终端管道接口

* 模板对象:: 

resource --- Resource usage information

* Resource Limits:: 
* Resource Usage:: 

Unix syslog 库例程

* 例子: 例子<32>. 

例子

* 简单示例:: 

被取代的模块

* optparse: optparse --- 解析器的命令行选项. 解析器的命令行选项
* imp: imp --- Access the import internals. Access the import internals

optparse --- 解析器的命令行选项

* 背景:: 
* 教程: 教程<2>. 
* 参考指南:: 
* Option Callbacks:: 
* Extending optparse:: 

背景

* 术语:: 
* What are options for?:: 
* 位置位置:: 

教程

* Understanding option actions:: 
* The store action:: 
* Handling boolean (flag) options: Handling boolean flag options. 
* Other actions:: 
* 默认值: 默认值<2>. 
* Generating help:: 
* Printing a version string:: 
* How optparse handles errors:: 
* Putting it all together:: 

Generating help

* Grouping Options:: 

参考指南

* 创建解析器:: 
* 填充解析器:: 
* 定义选项:: 
* Option attributes:: 
* Standard option actions:: 
* Standard option types:: 
* 解析参数: 解析参数<2>. 
* Querying and manipulating your option parser:: 
* Conflicts between options:: 
* 清理: 清理<2>. 
* Other methods:: 

Option Callbacks

* Defining a callback option:: 
* How callbacks are called:: 
* Raising errors in a callback:: 
* Callback example 1; trivial callback: Callback example 1 trivial callback. 
* Callback example 2; check option order: Callback example 2 check option order. 
* Callback example 3; check option order (generalized): Callback example 3 check option order generalized. 
* Callback example 4; check arbitrary condition: Callback example 4 check arbitrary condition. 
* Callback example 5; fixed arguments: Callback example 5 fixed arguments. 
* Callback example 6; variable arguments: Callback example 6 variable arguments. 

Extending optparse

* Adding new types:: 
* Adding new actions:: 

imp --- Access the import internals

* 例子: 例子<33>. 

未创建文档的模块

* 平台特定模块:: 

扩展和嵌入 Python 解释器

* 推荐的第三方工具:: 
* 不使用第三方工具创建扩展:: 
* 在更大的应用程序中嵌入 CPython 运行时:: 

不使用第三方工具创建扩展

* 使用 C 或 C++ 扩展 Python:: 
* 自定义扩展类型：教程:: 
* 定义扩展类型：已分类主题:: 
* 构建C/C++扩展:: 
* 在Windows平台编译C和C++扩展:: 

使用 C 或 C++ 扩展 Python

* 一个简单的例子:: 
* 关于错误和异常:: 
* 回到例子:: 
* 模块方法表和初始化函数:: 
* 编译和链接:: 
* 在C中调用Python函数:: 
* 提取扩展函数的参数:: 
* 给扩展函数的关键字参数:: 
* 构造任意值:: 
* 引用计数:: 
* 在C++中编写扩展:: 
* 给扩展模块提供C API:: 

引用计数

* Python中的引用计数:: 
* 拥有规则:: 
* 危险的薄冰:: 
* NULL指针:: 

自定义扩展类型：教程

* 基础:: 
* Adding data and methods to the Basic example:: 
* Providing finer control over data attributes:: 
* Supporting cyclic garbage collection:: 
* Subclassing other types:: 

定义扩展类型：已分类主题

* 终结和内存释放:: 
* 对象展示:: 
* Attribute Management:: 
* Object Comparison:: 
* Abstract Protocol Support:: 
* Weak Reference Support:: 
* 更多建议:: 

Attribute Management

* 泛型属性管理:: 
* Type-specific Attribute Management:: 

构建C/C++扩展

* 使用distutils构建C和C++扩展:: 
* 发布你的扩展模块:: 

在Windows平台编译C和C++扩展

* 菜谱式说明:: 
* Unix 和 Windows 之间的差异:: 
* DLL 的实际使用:: 

在更大的应用程序中嵌入 CPython 运行时

* 在其它应用程序嵌入 Python:: 

在其它应用程序嵌入 Python

* Very High Level Embedding:: 
* Beyond Very High Level Embedding; An overview: Beyond Very High Level Embedding An overview. 
* 纯嵌入:: 
* Extending Embedded Python:: 
* 在 C++ 中嵌入 Python:: 
* 在类 Unix 系统中编译和链接:: 

Python/C API 参考手册

* 概述: 概述<15>. 
* 稳定的应用程序二进制接口:: 
* The Very High Level Layer:: 
* 引用计数: 引用计数<3>. 
* 异常处理:: 
* 工具: 工具<2>. 
* 抽象对象层:: 
* 具体的对象层:: 
* Initialization@comma{} Finalization@comma{} and Threads: Initialization Finalization and Threads. 
* Python初始化配置:: 
* 内存管理:: 
* 对象实现支持:: 
* API 和 ABI 版本管理:: 

概述

* 代码标准:: 
* 包含文件:: 
* 有用的宏:: 
* 对象、类型和引用计数:: 
* 异常: 异常<18>. 
* 嵌入Python: 嵌入Python<2>. 
* 调试构建:: 

对象、类型和引用计数

* 引用计数: 引用计数<2>. 
* 类型:: 

引用计数

* Reference Count Details:: 

异常处理

* Printing and clearing:: 
* 抛出异常: 抛出异常<2>. 
* Issuing warnings:: 
* Querying the error indicator:: 
* Signal Handling: Signal Handling<2>. 
* Exception Classes:: 
* Exception Objects:: 
* Unicode Exception Objects:: 
* 递归控制:: 
* 标准异常:: 
* 标准警告类别:: 

工具

* 操作系统实用程序:: 
* 系统功能:: 
* 过程控制:: 
* 导入模块: 导入模块<2>. 
* 数据 marshal 操作支持:: 
* 解析参数并构建值变量:: 
* 字符串转换与格式化:: 
* 反射:: 
* 编解码器注册与支持功能:: 

解析参数并构建值变量

* 解析参数: 解析参数<3>. 
* 创建变量:: 

解析参数

* 字符串和缓存区:: 
* 数字: 数字<2>. 
* 其他对象:: 
* API 函数:: 

编解码器注册与支持功能

* Codec 查找API:: 
* 用于Unicode编码错误处理程序的注册表API:: 

抽象对象层

* 对象协议:: 
* 数字协议:: 
* 序列协议:: 
* 映射协议:: 
* 迭代器协议:: 
* 缓冲协议:: 
* 旧缓冲协议:: 

缓冲协议

* 缓冲区结构:: 
* Buffer request types:: 
* 复杂数组:: 
* Buffer-related functions:: 

Buffer request types

* request-independent fields:: 
* readonly@comma{} format: readonly format. 
* shape@comma{} strides@comma{} suboffsets: shape strides suboffsets. 
* 连续性的请求:: 
* 复合请求:: 

复杂数组

* NumPy-style; shape and strides: NumPy-style shape and strides. 
* PIL-style; shape@comma{} strides and suboffsets: PIL-style shape strides and suboffsets. 

具体的对象层

* 基本对象:: 
* 数值对象:: 
* 序列对象:: 
* 容器对象:: 
* 函数对象: 函数对象<2>. 
* 其他对象: 其他对象<2>. 

基本对象

* 类型对象: 类型对象<2>. 
* None 对象:: 

类型对象

* Creating Heap-Allocated Types:: 

数值对象

* 整数型对象:: 
* 布尔对象:: 
* 浮点数对象:: 
* 复数对象:: 

复数对象

* 表示复数的C结构体:: 
* 表示复数的Python对象:: 

序列对象

* bytes 对象: bytes 对象<2>. 
* 字节数组对象:: 
* Unicode Objects and Codecs:: 
* 元组对象:: 
* Struct Sequence Objects:: 
* 列表对象:: 

字节数组对象

* 类型检查宏:: 
* 直接 API 函数:: 
* 宏:: 

Unicode Objects and Codecs

* Unicode对象:: 
* Built-in Codecs:: 
* Methods and Slot Functions:: 

Unicode对象

* Unicode类型:: 
* Unicode字符属性:: 
* Creating and accessing Unicode strings:: 
* Deprecated Py_UNICODE APIs:: 
* Locale Encoding:: 
* File System Encoding:: 
* wchar_t Support:: 

Built-in Codecs

* Generic Codecs:: 
* UTF-8 Codecs:: 
* UTF-32 Codecs:: 
* UTF-16 Codecs:: 
* UTF-7 Codecs:: 
* Unicode-Escape Codecs:: 
* Raw-Unicode-Escape Codecs:: 
* Latin-1 Codecs:: 
* ASCII Codecs:: 
* Character Map Codecs:: 
* MBCS codecs for Windows:: 
* Methods & Slots:: 

容器对象

* 字典对象:: 
* 集合对象:: 

函数对象

* 函数对象: 函数对象<3>. 
* 实例方法对象:: 
* 方法对象: 方法对象<2>. 
* Cell 对象:: 
* 代码对象: 代码对象<2>. 

其他对象

* 文件对象:: 
* 模块对象:: 
* 迭代器对象:: 
* 描述符对象:: 
* 切片对象:: 
* Ellipsis 对象:: 
* MemoryView 对象:: 
* 弱引用对象: 弱引用对象<2>. 
* 胶囊: 胶囊<2>. 
* 生成器对象:: 
* 协程对象: 协程对象<2>. 
* 上下文变量对象:: 
* DateTime 对象: DateTime 对象<2>. 

模块对象

* Initializing C modules:: 
* Module lookup:: 

Initializing C modules

* Single-phase initialization:: 
* Multi-phase initialization:: 
* Low-level module creation functions:: 
* Support functions:: 

Initialization, Finalization, and Threads

* 在Python初始化之前:: 
* 全局配置变量:: 
* Initializing and finalizing the interpreter:: 
* Process-wide parameters:: 
* Thread State and the Global Interpreter Lock:: 
* Sub-interpreter support:: 
* 异步通知:: 
* 分析和跟踪:: 
* 高级调试器支持:: 
* Thread Local Storage Support:: 

Thread State and the Global Interpreter Lock

* Releasing the GIL from extension code:: 
* 非Python创建的线程:: 
* Cautions about fork(): Cautions about fork. 
* 高阶 API:: 
* Low-level API:: 

Sub-interpreter support

* 错误和警告:: 

Thread Local Storage Support

* Thread Specific Storage (TSS) API: Thread Specific Storage TSS API. 
* Thread Local Storage (TLS) API: Thread Local Storage TLS API. 

Thread Specific Storage (TSS) API

* Dynamic Allocation:: 
* 方法: 方法<4>. 

Python初始化配置

* PyWideStringList:: 
* PyStatus:: 
* PyPreConfig:: 
* Preinitialization with PyPreConfig:: 
* PyConfig:: 
* Initialization with PyConfig:: 
* Isolated Configuration:: 
* Python Configuration:: 
* 路径配置:: 
* Py_RunMain(): Py_RunMain. 
* Multi-Phase Initialization Private Provisional API:: 

内存管理

* 概述: 概述<16>. 
* 原始内存接口:: 
* 内存接口:: 
* 对象分配器:: 
* 默认内存分配器:: 
* 自定义内存分配器:: 
* pymalloc 分配器:: 
* tracemalloc C API:: 
* 例子: 例子<34>. 

pymalloc 分配器

* 自定义 pymalloc Arena 分配器:: 

对象实现支持

* 在堆上分配对象:: 
* Common Object Structures:: 
* 类型对象: 类型对象<3>. 
* Number Object Structures:: 
* Mapping Object Structures:: 
* Sequence Object Structures:: 
* Buffer Object Structures:: 
* Async Object Structures:: 
* Slot Type typedefs:: 
* 例子: 例子<35>. 
* 使对象类型支持循环垃圾回收:: 

类型对象

* 快速参考:: 
* PyTypeObject Definition:: 
* PyObject Slots:: 
* PyVarObject Slots:: 
* PyTypeObject Slots:: 
* Heap Types:: 

快速参考

* "tp 槽":: 
* sub-slots:: 
* slot typedefs:: 

分发 Python 模块

* 关键术语:: 
* 开源许可与协作:: 
* 安装工具:: 
* 阅读Python包用户指南:: 
* 我该如何...？: 我该如何 ？. 

我该如何...？

* ...为我的项目选择一个名字？: 为我的项目选择一个名字？. 
* ...创建和分发二进制扩展？: 创建和分发二进制扩展？. 

安装 Python 模块

* 关键术语: 关键术语<2>. 
* 基本使用: 基本使用<2>. 
* 我应如何 ...？: 我应如何 ？. 
* 常见的安装问题:: 

我应如何 ...？

* ... 在 Python 3.4 之前的 Python 版本中安装 pip ？: 在 Python 3 4 之前的 Python 版本中安装 pip ？. 
* ... 只为当前用户安装软件包？: 只为当前用户安装软件包？. 
* ... 安装科学计算类 Python 软件包？: 安装科学计算类 Python 软件包？. 
* ... 使用并行安装的多个 Python 版本？: 使用并行安装的多个 Python 版本？. 

常见的安装问题

* 在 Linux 的系统 Python 版本上安装:: 
* 未安装 pip:: 
* 安装二进制编译扩展:: 

Python 常用指引

* 将 Python 2 代码迁移到 Python 3:: 
* 将扩展模块移植到 Python 3:: 
* 用 Python 进行 Curses 编程:: 
* 描述器使用指南:: 
* 函数式编程指引:: 
* 日志常用指引:: 
* 日志操作手册:: 
* 正则表达式HOWTO:: 
* 套接字编程指南:: 
* 排序指南:: 
* Unicode 指南:: 
* HOWTO 使用 urllib 包获取网络资源:: 
* Argparse 教程:: 
* ipaddress模块介绍:: 
* Argument Clinic How-To:: 
* 使用 DTrace 和 SystemTap 检测CPython:: 

将 Python 2 代码迁移到 Python 3

* 简要说明:: 
* 详情:: 

详情

* 删除对Python 2.6及更早版本的支持: 删除对Python 2 6及更早版本的支持. 
* Make sure you specify the proper version support in your setup.py file: Make sure you specify the proper version support in your setup py file. 
* 良好的测试覆盖率:: 
* 了解Python 2 和 3之间的区别:: 
* 更新代码:: 
* Prevent compatibility regressions:: 
* Check which dependencies block your transition:: 
* Update your setup.py file to denote Python 3 compatibility: Update your setup py file to denote Python 3 compatibility. 
* Use continuous integration to stay compatible:: 
* 考虑使用可选的静态类型检查:: 

更新代码

* 除法:: 
* 文本与二进制数据:: 
* Use feature detection instead of version detection:: 

用 Python 进行 Curses 编程

* curses 是什么？:: 
* 开始和结束curses应用程序:: 
* 窗口和面板:: 
* 显示文字:: 
* 用户输入:: 
* 更多的信息:: 

curses 是什么？

* Python 的 curses 模块:: 

显示文字

* 属性和颜色:: 

描述器使用指南

* 摘要:: 
* 定义和简介:: 
* 描述器协议:: 
* 调用描述器: 调用描述器<2>. 
* 描述器示例:: 
* 属性:: 
* 函数和方法:: 
* 静态方法和类方法:: 

函数式编程指引

* 概述: 概述<17>. 
* 迭代器: 迭代器<2>. 
* 生成器表达式和列表推导式:: 
* 生成器: 生成器<2>. 
* 内置函数: 内置函数<2>. 
* itertools 模块:: 
* functools 模块:: 
* 小函数和 lambda 表达式:: 
* 修订记录和致谢:: 
* 参考文献: 参考文献<2>. 

概述

* 形式证明:: 
* 模块化:: 
* 易于调试和测试:: 
* 组合性:: 

迭代器

* 支持迭代器的数据类型:: 

生成器

* 向生成器传递值:: 

itertools 模块

* 创建新的迭代器:: 
* 对元素使用函数:: 
* 选择元素:: 
* 组合函数:: 
* 为元素分组:: 

functools 模块

* operator 模块:: 

参考文献

* 通用文献:: 
* Python 相关:: 
* Python 文档:: 

日志常用指引

* 日志基础教程:: 
* 进阶日志教程:: 
* 日志级别: 日志级别<2>. 
* 有用的处理程序:: 
* 记录日志中引发的异常:: 
* 使用任意对象作为消息:: 
* 优化:: 

日志基础教程

* 什么时候使用日志:: 
* 一个简单的例子: 一个简单的例子<2>. 
* 记录日志到文件:: 
* 从多个模块记录日志:: 
* 记录变量数据:: 
* 更改显示消息的格式:: 
* 在消息中显示日期/时间:: 
* 后续步骤:: 

进阶日志教程

* 记录流程:: 
* 记录器:: 
* 处理程序:: 
* 格式化程序:: 
* 配置日志记录:: 
* 如果没有提供配置会发生什么:: 
* 配置库的日志记录:: 

日志级别

* 自定义级别:: 

日志操作手册

* 在多个模块中记录日志:: 
* 在多个线程中记录日志:: 
* 多个日志处理器以及多种格式化器:: 
* 在多个地方记录日志:: 
* 日志服务器配置示例:: 
* 处理日志处理器的阻塞:: 
* 通过网络发送和接收日志:: 
* 在日志记录中添加上下文信息:: 
* 从多个进程记录至单个文件:: 
* 轮换日志文件:: 
* 使用其他日志格式化方式:: 
* Customizing LogRecord:: 
* Subclassing QueueHandler - a ZeroMQ example:: 
* Subclassing QueueListener - a ZeroMQ example:: 
* An example dictionary-based configuration:: 
* Using a rotator and namer to customize log rotation processing:: 
* A more elaborate multiprocessing example:: 
* Inserting a BOM into messages sent to a SysLogHandler:: 
* Implementing structured logging:: 
* Customizing handlers with dictConfig(): Customizing handlers with dictConfig. 
* Using particular formatting styles throughout your application:: 
* Configuring filters with dictConfig(): Configuring filters with dictConfig. 
* Customized exception formatting:: 
* Speaking logging messages:: 
* 缓冲日志消息并有条件地输出它们:: 
* 通过配置使用UTC (GMT) 格式化时间: 通过配置使用UTC GMT 格式化时间. 
* 使用上下文管理器的可选的日志记录:: 
* A CLI application starter template:: 
* A Qt GUI for logging:: 

在日志记录中添加上下文信息

* 使用日志适配器传递上下文信息:: 
* 使用过滤器传递上下文信息:: 

使用日志适配器传递上下文信息

* 使用除字典之外的其它对象传递上下文信息:: 

从多个进程记录至单个文件

* Using concurrent.futures.ProcessPoolExecutor: Using concurrent futures ProcessPoolExecutor. 

Using particular formatting styles throughout your application

* Using LogRecord factories:: 
* Using custom message objects:: 

正则表达式HOWTO

* 概述: 概述<18>. 
* 简单模式:: 
* 使用正则表达式:: 
* 更多模式能力:: 
* 修改字符串:: 
* 常见问题: 常见问题<2>. 
* 反馈:: 

简单模式

* 匹配字符:: 
* 重复:: 

使用正则表达式

* 编译正则表达式:: 
* 反斜杠灾难:: 
* 应用匹配:: 
* 模块级别函数: 模块级别函数<2>. 
* 编译标志:: 

更多模式能力

* 更多元字符:: 
* 分组:: 
* 非捕获和命名组:: 
* 前向断言:: 

修改字符串

* 分割字符串:: 
* 搜索和替换:: 

常见问题

* 使用字符串方法:: 
* match() 和 search(): match 和 search. 
* 贪婪与非贪婪:: 
* 使用 re.VERBOSE: 使用 re VERBOSE. 

套接字编程指南

* 套接字:: 
* 创建套接字: 创建套接字<2>. 
* 使用一个套接字:: 
* 断开连接:: 
* 非阻塞的套接字:: 

套接字

* 历史:: 

创建套接字

* 进程间通信:: 

使用一个套接字

* 二进制数据:: 

断开连接

* 套接字何时销毁:: 

排序指南

* 基本排序:: 
* 关键函数:: 
* Operator 模块函数:: 
* 升序和降序:: 
* 排序稳定性和排序复杂度:: 
* 使用装饰-排序-去装饰的旧方法:: 
* 使用 cmp 参数的旧方法:: 
* 其它:: 

Unicode 指南

* Unicode 概述:: 
* Python's Unicode Support:: 
* Reading and Writing Unicode Data:: 
* 致谢: 致谢<10>. 

Unicode 概述

* 定义:: 
* 编码:: 
* 参考文献: 参考文献<3>. 

Python's Unicode Support

* The String Type:: 
* Converting to Bytes:: 
* Unicode Literals in Python Source Code:: 
* Unicode Properties:: 
* Comparing Strings:: 
* Unicode Regular Expressions:: 
* 参考文献: 参考文献<4>. 

Reading and Writing Unicode Data

* Unicode filenames:: 
* Tips for Writing Unicode-aware Programs:: 
* 参考文献: 参考文献<5>. 

Tips for Writing Unicode-aware Programs

* Converting Between File Encodings:: 
* Files in an Unknown Encoding:: 

HOWTO 使用 urllib 包获取网络资源

* 概述: 概述<19>. 
* 提取URL:: 
* 处理异常: 处理异常<2>. 
* info and geturl:: 
* Openers and Handlers:: 
* 基本认证:: 
* 代理:: 
* Sockets and Layers:: 
* 备注:: 

提取URL

* 数据:: 
* Headers:: 

处理异常

* URLError:: 
* HTTPError:: 
* 包装起来:: 

HTTPError

* 错误代码:: 

包装起来

* 数字1:: 
* Number 2:: 

Argparse 教程

* 概念:: 
* 基础: 基础<2>. 
* 位置参数介绍:: 
* 可选参数介绍:: 
* 结合位置参数和可选参数:: 
* 进行一些小小的改进:: 
* 后记:: 

可选参数介绍

* 短选项:: 

进行一些小小的改进

* 矛盾的选项:: 

ipaddress模块介绍

* 创建 Address/Network/Interface 对象:: 
* 审查 Address/Network/Interface 对象:: 
* Network 作为 Address 列表:: 
* 比较运算: 比较运算<4>. 
* 将IP地址与其他模块一起使用:: 
* 实例创建失败时获取更多详细信息:: 

创建 Address/Network/Interface 对象

* 关于IP版本的说明:: 
* IP主机地址:: 
* 定义网络:: 
* 主机接口:: 

Argument Clinic How-To

* The Goals Of Argument Clinic:: 
* Basic Concepts And Usage:: 
* Converting Your First Function:: 
* Advanced Topics:: 

Advanced Topics

* Symbolic default values:: 
* Renaming the C functions and variables generated by Argument Clinic:: 
* Converting functions using PyArg_UnpackTuple:: 
* Optional Groups:: 
* Using real Argument Clinic converters@comma{} instead of "legacy converters": Using real Argument Clinic converters instead of "legacy converters". 
* Py_buffer:: 
* Advanced converters:: 
* Parameter default values:: 
* The NULL default value:: 
* Expressions specified as default values:: 
* Using a return converter:: 
* Cloning existing functions:: 
* Calling Python code:: 
* Using a "self converter":: 
* Writing a custom converter:: 
* Writing a custom return converter:: 
* METH_O and METH_NOARGS:: 
* tp_new and tp_init functions:: 
* Changing and redirecting Clinic's output:: 
* The #ifdef trick:: 
* Using Argument Clinic in Python files:: 

使用 DTrace 和 SystemTap 检测CPython

* 启用静态标记:: 
* 静态DTrace探针:: 
* 静态SystemTap标记:: 
* 可用的静态标记:: 
* SystemTap Tapsets:: 
* 例子: 例子<36>. 

Python 常见问题

* Python常见问题:: 
* 编程常见问题:: 
* 设计和历史常见问题:: 
* 代码库和插件 FAQ:: 
* 扩展/嵌入常见问题:: 
* Python在Windows上的常见问题:: 
* 图形用户界面（GUI）常见问题:: 
* “为什么我的电脑上安装了 Python ？”:: 

Python常见问题

* 一般信息:: 
* 现实世界中的 Python:: 

一般信息

* 什么是 Python？:: 
* 什么是 Python 软件基金会？:: 
* 使用 Python 是否存在版权限制？:: 
* 创造 Python 的最初理由是什么？:: 
* Python 适合做什么？:: 
* Python 版本的编号形式是怎样的？:: 
* 我应如何获取一份 Python 源代码的副本？:: 
* 我应如何获取 Python 的文档？:: 
* 我之前从未接触过编程。 哪里有 Python 的教程？:: 
* 是否有专门针对 Python 的新闻组或邮件列表？:: 
* 我应如何获取 Python 的公开测试版本？:: 
* 我应如何为 Python 提交错误报告和补丁？:: 
* 是否有任何公开发表的 Python 相关文章可以供我参考引用？:: 
* 是否有任何 Python 相关的书籍？:: 
* www.python.org 具体位于世界上的哪个地点？: www python org 具体位于世界上的哪个地点？. 
* 为何命名为 Python？:: 
* 我必须喜欢 "Monty Python 的飞行马戏团" 吗？:: 

现实世界中的 Python

* Python 有多稳定？:: 
* 有多少人在使用 Python？:: 
* 有哪些重要的项目是用 Python 开发的？:: 
* 在未来可以期待 Python 将有什么新进展？:: 
* 提议对 Python 加入不兼容的更改是否合理？:: 
* Python 是一种对编程初学者友好的语言吗？:: 

编程常见问题

* 一般问题:: 
* 核心语言:: 
* 数字和字符串:: 
* 性能: 性能<4>. 
* 序列（元组/列表）:: 
* 对象:: 
* 模块: 模块<3>. 

一般问题

* Python 有没有提供断点与单步调试等功能的，源码层次的调试器？:: 
* 有没有工具来帮助找寻漏洞或进行静态分析？:: 
* 我如何能够通过一个 Python 脚本创建一个独立运行的二进制文件？:: 
* 是否有 Python 程序规范代码标准或风格指南？:: 

核心语言

* 当变量有值时，为什么会出现UnboundLocalError？:: 
* Python中的局部变量和全局变量有哪些规则？:: 
* 为什么在具有不同值的循环中定义的lambdas都返回相同的结果？:: 
* 如何跨模块共享全局变量？:: 
* 导入模块的“最佳实践”是什么？:: 
* 为什么对象之间会共享默认值？:: 
* 如何将可选参数或关键字参数从一个函数传递到另一个函数？:: 
* 形参和实参之间有什么区别？:: 
* 为什么更改列表 'y' 也会更改列表 'x'？:: 
* 如何编写带输出参数的函数（通过引用调用）？:: 
* 如何在Python中创建高阶函数？:: 
* 如何在Python中复制对象？:: 
* 如何找到对象的方法或属性？:: 
* 我的代码如何才能发现对象的名称？:: 
* 逗号运算符的优先级是什么？:: 
* 是否有与 C 的 "?;" 三目运算符等价的东西？: 是否有与 C 的 "? " 三目运算符等价的东西？. 
* 是否可以用Python编写混淆的单行程序?:: 
* 函数参数列表中的斜杠（/）是什么意思？:: 

数字和字符串

* 如何指定十六进制和八进制整数？:: 
* 为什么-22 // 10返回-3？:: 
* 如何将字符串转换为数字？:: 
* 如何将数字转换为字符串？:: 
* 如何修改字符串？:: 
* 如何使用字符串调用函数/方法？:: 
* 是否有与Perl 的chomp() 等效的方法，用于从字符串中删除尾随换行符？: 是否有与Perl 的chomp 等效的方法，用于从字符串中删除尾随换行符？. 
* 是否有 scanf() 或 sscanf() 的对应物？: 是否有 scanf 或 sscanf 的对应物？. 
* 'UnicodeDecodeError' 或 'UnicodeEncodeError' 错误是什么意思？:: 

性能

* 我的程序太慢了。该如何加快速度？:: 
* 将多个字符串连接在一起的最有效方法是什么？:: 

序列（元组/列表）

* 如何在元组和列表之间进行转换？:: 
* 什么是负数序号？:: 
* 如何以相反的顺序迭代序列？:: 
* 如何从列表中删除重复项？:: 
* 如何在Python中创建数组？:: 
* 如何创建多维列表？:: 
* 如何将方法应用于一系列对象？:: 
* 为什么 a_tuple[i] += ['item'] 会在执行加法时引发异常？:: 
* 我想做一个复杂的排序：你能用Python做一个Schwartzian变换吗？:: 
* 如何按其他列表中的值对一个列表进行排序？:: 

对象

* 什么是类？:: 
* 什么是方法？:: 
* 什么是 self ？:: 
* 如何检查对象是否为给定类或其子类的一个实例？:: 
* 什么是委托？:: 
* 如何从覆盖基类的派生类调用基类中定义的方法?:: 
* 如何组织代码以便更改基类？:: 
* 如何创建静态类数据和静态类方法？:: 
* 如何在Python中重载构造函数（或方法）？:: 
* 我尝试使用 __spam ，但是得到一个关于 _SomeClassName__spam 的错误信息。:: 
* 类定义了 __del__ 方法，但是删除对象时没有调用它。:: 
* 如何获取给定类的所有实例的列表？:: 
* 为什么 id() 的结果看起来不是唯一的？: 为什么 id 的结果看起来不是唯一的？. 

模块

* 如何创建 .pyc 文件？: 如何创建 pyc 文件？. 
* 如何找到当前模块名称？:: 
* 如何让模块相互导入？:: 
* __import__('x.y.z') 返回 <module 'x'>; 如何获取z?: __import__ 'x y z' 返回 <module 'x'>; 如何获取z?. 
* 当我编辑了导入过的模块并重新导入它时，这些变化没有显示出来。为什么会这样？:: 

设计和历史常见问题

* 为什么Python使用缩进来分组语句？:: 
* 为什么简单的算术运算得到奇怪的结果？:: 
* 为什么浮点计算不准确？:: 
* 为什么Python字符串是不可变的？:: 
* 为什么必须在方法定义和调用中显式使用“self”？:: 
* 为什么不能在表达式中赋值？:: 
* 为什么Python对某些功能（例如list.index()）使用方法来实现，而其他功能（例如len(List)）使用函数实现？: 为什么Python对某些功能（例如list index ）使用方法来实现，而其他功能（例如len List ）使用函数实现？. 
* 为什么 join()是一个字符串方法而不是列表或元组方法？: 为什么 join 是一个字符串方法而不是列表或元组方法？. 
* 异常有多快？:: 
* 为什么Python中没有switch或case语句？:: 
* 难道不能在解释器中模拟线程，而非得依赖特定于操作系统的线程实现吗？:: 
* 为什么lambda表达式不能包含语句？:: 
* 可以将Python编译为机器代码，C或其他语言吗？:: 
* Python如何管理内存？:: 
* 为什么CPython不使用更传统的垃圾回收方案？:: 
* CPython退出时为什么不释放所有内存？:: 
* 为什么有单独的元组和列表数据类型？:: 
* 列表是如何在CPython中实现的？:: 
* 字典是如何在CPython中实现的？:: 
* 为什么字典key必须是不可变的？:: 
* 为什么 list.sort() 没有返回排序列表？: 为什么 list sort 没有返回排序列表？. 
* 如何在Python中指定和实施接口规范？:: 
* 为什么没有goto？:: 
* 为什么原始字符串（r-strings）不能以反斜杠结尾？:: 
* 为什么Python没有属性赋值的“with”语句？:: 
* 为什么 if/while/def/class语句需要冒号？:: 
* 为什么Python在列表和元组的末尾允许使用逗号？:: 

代码库和插件 FAQ

* 通用的代码库问题:: 
* 通用任务:: 
* 线程相关:: 
* 输入输出: 输入输出<2>. 
* 网络 / Internet 编程:: 
* 数据库:: 
* 数学和数字:: 

通用的代码库问题

* 如何找到可以用来做 XXX 的模块或应用？:: 
* math.py（socket.py，regex.py 等）的源文件在哪？: math py（socket py，regex py 等）的源文件在哪？. 
* 在 Unix 中怎样让 Python 脚本可执行？:: 
* Python 中有 curses/termcap 包吗？:: 
* Python 中存在类似 C 的 onexit() 函数的东西吗？: Python 中存在类似 C 的 onexit 函数的东西吗？. 
* 为什么我的信号处理函数不能工作？:: 

通用任务

* 怎样测试 Python 程序或组件？:: 
* 怎样用 docstring 创建文档？:: 
* 怎样一次只获取一个按键？:: 

线程相关

* 程序中怎样使用线程？:: 
* 我的线程都没有运行，为什么？:: 
* 如何将任务分配给多个工作线程？:: 
* 怎样修改全局变量是线程安全的？:: 
* 不能删除全局解释器锁吗？:: 

输入输出

* 怎样删除文件？（以及其他文件相关的问题……）:: 
* 怎样复制文件？:: 
* 怎样读取（或写入）二进制数据？:: 
* 似乎 os.popen() 创建的管道不能使用 os.read()，这是为什么？: 似乎 os popen 创建的管道不能使用 os read ，这是为什么？. 
* 怎样访问（RS232）串口？:: 
* 为什么关闭 sys.stdout（stdin，stderr）并不会真正关掉它？: 为什么关闭 sys stdout（stdin，stderr）并不会真正关掉它？. 

网络 / Internet 编程

* Python 中的 WWW 工具是什么？:: 
* 怎样模拟发送 CGI 表单（METHOD=POST）？:: 
* 生成 HTML 需要使用什么模块？:: 
* 怎样使用 Python 脚本发送邮件？:: 
* socket 的 connect() 方法怎样避免阻塞？: socket 的 connect 方法怎样避免阻塞？. 

数据库

* Python 中有数据库包的接口吗？:: 
* 在 Python 中如何实现持久化对象？:: 

数学和数字

* Python 中怎样生成随机数？:: 

扩展/嵌入常见问题

* 可以使用 C 语言创建自己的函数吗？:: 
* 可以使用 C++ 语言创建自己的函数吗？:: 
* C很难写，有没有其他选择？:: 
* 如何在 C 中执行任意 Python 语句？:: 
* 如何在 C 中对任意 Python 表达式求值？:: 
* 如何从Python对象中提取C的值？:: 
* 如何使用Py_BuildValue()创建任意长度的元组？: 如何使用Py_BuildValue 创建任意长度的元组？. 
* 如何从C调用对象的方法？:: 
* 如何捕获PyErr_Print()（或打印到stdout / stderr的任何内容）的输出？: 如何捕获PyErr_Print （或打印到stdout / stderr的任何内容）的输出？. 
* 如何从C访问用Python编写的模块？:: 
* 如何在 Python 中对接 C ++ 对象？:: 
* 我使用Setup文件添加了一个模块，为什么make失败了？:: 
* 如何调试扩展？:: 
* 我想在Linux系统上编译一个Python模块，但是缺少一些文件。为什么?:: 
* 如何区分“输入不完整”和“输入无效”？:: 
* 如何找到未定义的g++符号__builtin_new或__pure_virtual？:: 
* 能否创建一个对象类，其中部分方法在C中实现，而其他方法在Python中实现（例如通过继承）？:: 

Python在Windows上的常见问题

* 我怎样在Windows下运行一个Python程序？:: 
* 我怎么让 Python 脚本可执行？:: 
* 为什么有时候 Python 程序会启动缓慢？:: 
* 我怎样使用Python脚本制作可执行文件？:: 
* *.pyd 文件和DLL文件相同吗？: * pyd 文件和DLL文件相同吗？. 
* 我怎样将Python嵌入一个Windows程序？:: 
* 如何让编辑器不要在我的 Python 源代码中插入 tab ？:: 
* 如何在不阻塞的情况下检查按键？:: 

图形用户界面（GUI）常见问题

* 图形界面常见问题:: 
* Python 是否有平台无关的图形界面工具包？:: 
* 有哪些Python的GUI工具是某个平台专用的？:: 
* 有关Tkinter的问题:: 

Python 是否有平台无关的图形界面工具包？

* Tkinter:: 
* wxWidgets:: 
* Qt:: 
* Gtk+:: 
* Kivy:: 
* FLTK:: 
* OpenGL:: 

有关Tkinter的问题

* 我怎样“冻结”Tkinter程序？:: 
* 在等待 I/O 操作时能够处理 Tk 事件吗？:: 
* 在Tkinter中键绑定不工作：为什么？:: 

“为什么我的电脑上安装了 Python ？”

* 什么是 Python？: 什么是 Python？<2>. 
* 为什么我的电脑上安装了 Python ？:: 
* 我能删除 Python 吗？:: 

文档说明

* Python 文档的贡献者:: 

处理错误

* 文档 Bug:: 
* 使用 Python 的问题追踪系统:: 
* 开始为 Python 贡献您的知识:: 

历史和许可证

* 该软件的历史:: 
* 获取或以其他方式使用 Python 的条款和条件:: 
* 收录软件的许可与鸣谢:: 

获取或以其他方式使用 Python 的条款和条件

* 用于 PYTHON 3.8.4 的 PSF 许可协议: 用于 PYTHON 3 8 4 的 PSF 许可协议. 
* 用于 PYTHON 2.0 的 BEOPEN.COM 许可协议: 用于 PYTHON 2 0 的 BEOPEN COM 许可协议. 
* 用于 PYTHON 1.6.1 的 CNRI 许可协议: 用于 PYTHON 1 6 1 的 CNRI 许可协议. 
* 用于 PYTHON 0.9.0 至 1.2 的 CWI 许可协议: 用于 PYTHON 0 9 0 至 1 2 的 CWI 许可协议. 

收录软件的许可与鸣谢

* Mersenne Twister:: 
* 套接字: 套接字<2>. 
* 异步套接字服务:: 
* Cookie 管理:: 
* 执行追踪:: 
* UUencode 与 UUdecode 函数:: 
* XML 远程过程调用:: 
* test_epoll:: 
* Select kqueue:: 
* SipHash24:: 
* strtod 和 dtoa:: 
* OpenSSL:: 
* expat:: 
* libffi:: 
* zlib: zlib<3>. 
* cfuhash:: 
* libmpdec:: 
* W3C C14N 测试套件:: 

分发 Python 模块（遗留版本）

* An Introduction to Distutils:: 
* 编写安装脚本:: 
* 编写设置脚本的配置文件:: 
* Creating a Source Distribution:: 
* Creating Built Distributions:: 
* Distutils 示例:: 
* 扩展 Distutils:: 
* 命令参考:: 
* API参考引用:: 

An Introduction to Distutils

* 概念和术语:: 
* 一个简单的例子: 一个简单的例子<3>. 
* General Python terminology:: 
* Distutils-specific terminology:: 

编写安装脚本

* Listing whole packages:: 
* Listing individual modules:: 
* Describing extension modules:: 
* Relationships between Distributions and Packages:: 
* Installing Scripts:: 
* Installing Package Data:: 
* Installing Additional Files:: 
* Additional meta-data:: 
* Debugging the setup script:: 

Describing extension modules

* 扩展名和软件包:: 
* Extension source files:: 
* Preprocessor options:: 
* Library options:: 
* 其他选项: 其他选项<2>. 

Creating a Source Distribution

* Specifying the files to distribute:: 
* Manifest-related options:: 

Creating Built Distributions

* 创建RPM软件包:: 
* Creating Windows Installers:: 
* Cross-compiling on Windows:: 
* Vista User Access Control (UAC): Vista User Access Control UAC. 

Cross-compiling on Windows

* The Postinstallation script:: 

Distutils 示例

* 纯 Python 分发（通过 module）:: 
* 纯 Python 分发（通过 包）:: 
* 单个扩展模块:: 
* 检查一个包:: 
* 读取元数据:: 

扩展 Distutils

* 集成新的命令:: 
* 添加新的发布类型:: 

命令参考

* 安装模块; install 命令族: 安装模块 install 命令族. 
* 创建源码发行包; sdist 命令: 创建源码发行包 sdist 命令. 

安装模块: install 命令族

* install_data:: 
* install_scripts:: 

API参考引用

* distutils.core: distutils core --- 分发包功能的核心. 分发包功能的核心
* distutils.ccompiler: distutils ccompiler --- CCompiler基类. CCompiler基类
* distutils.unixccompiler: distutils unixccompiler --- Unix C Compiler. Unix C Compiler
* distutils.msvccompiler: distutils msvccompiler --- Microsoft Compiler. Microsoft Compiler
* distutils.bcppcompiler: distutils bcppcompiler --- Borland Compiler. Borland Compiler
* distutils.cygwincompiler: distutils cygwincompiler --- Cygwin Compiler. Cygwin Compiler
* distutils.archive_util: distutils archive_util --- Archiving utilities. Archiving utilities
* distutils.dep_util: distutils dep_util --- Dependency checking. Dependency checking
* distutils.dir_util: distutils dir_util --- Directory tree operations. Directory tree operations
* distutils.file_util: distutils file_util --- Single file operations. Single file operations
* distutils.util: distutils util --- Miscellaneous other utility functions. Miscellaneous other utility functions
* distutils.dist: distutils dist --- The Distribution class. The Distribution class
* distutils.extension: distutils extension --- The Extension class. The Extension class
* distutils.debug: distutils debug --- Distutils debug mode. Distutils debug mode
* distutils.errors: distutils errors --- Distutils exceptions. Distutils exceptions
* distutils.fancy_getopt: distutils fancy_getopt --- Wrapper around the standard getopt module. Wrapper around the standard getopt module
* distutils.filelist: distutils filelist --- The FileList class. The FileList class
* distutils.log: distutils log --- Simple PEP 282-style logging. Simple PEP 282-style logging
* distutils.spawn: distutils spawn --- Spawn a sub-process. Spawn a sub-process
* distutils.sysconfig: distutils sysconfig --- System configuration information. System configuration information
* distutils.text_file: distutils text_file --- The TextFile class. The TextFile class
* distutils.version: distutils version --- Version number classes. Version number classes
* distutils.cmd: distutils cmd --- Abstract base class for Distutils commands. Abstract base class for Distutils commands
* Creating a new Distutils command:: 
* distutils.command: distutils command --- Individual Distutils commands. Individual Distutils commands
* distutils.command.bdist: distutils command bdist --- Build a binary installer. Build a binary installer
* distutils.command.bdist_packager: distutils command bdist_packager --- Abstract base class for packagers. Abstract base class for packagers
* distutils.command.bdist_dumb: distutils command bdist_dumb --- Build a "dumb" installer. Build a "dumb" installer
* distutils.command.bdist_msi: distutils command bdist_msi --- Build a Microsoft Installer binary package. Build a Microsoft Installer binary package
* distutils.command.bdist_rpm: distutils command bdist_rpm --- Build a binary distribution as a Redhat RPM and SRPM. Build a binary distribution as a Redhat RPM and
                               SRPM
* distutils.command.bdist_wininst: distutils command bdist_wininst --- Build a Windows installer. Build a Windows installer
* distutils.command.sdist: distutils command sdist --- Build a source distribution. Build a source distribution
* distutils.command.build: distutils command build --- Build all files of a package. Build all files of a package
* distutils.command.build_clib: distutils command build_clib --- Build any C libraries in a package. Build any C libraries in a package
* distutils.command.build_ext: distutils command build_ext --- Build any extensions in a package. Build any extensions in a package
* distutils.command.build_py: distutils command build_py --- Build the py/ pyc files of a package. Build the .py/.pyc files of a package
* distutils.command.build_scripts: distutils command build_scripts --- Build the scripts of a package. Build the scripts of a package
* distutils.command.clean: distutils command clean --- Clean a package build area. Clean a package build area
* distutils.command.config: distutils command config --- Perform package configuration. Perform package configuration
* distutils.command.install: distutils command install --- Install a package. Install a package
* distutils.command.install_data: distutils command install_data --- Install data files from a package. Install data files from a package
* distutils.command.install_headers: distutils command install_headers --- Install C/C++ header files from a package. Install C/C++ header files from a package
* distutils.command.install_lib: distutils command install_lib --- Install library files from a package. Install library files from a package
* distutils.command.install_scripts: distutils command install_scripts --- Install script files from a package. Install script files from a package
* distutils.command.register: distutils command register --- Register a module with the Python Package Index. Register a module with the Python Package Index
* distutils.command.check: distutils command check --- Check the meta-data of a package. Check the meta-data of a package

安装Python模块（旧版）

* 概述: 概述<20>. 
* Standard Build and Install:: 
* Alternate Installation:: 
* 自定义安装:: 
* Distutils Configuration Files:: 
* Building Extensions; Tips and Tricks: Building Extensions Tips and Tricks. 

概述

* Distutils based source distributions:: 

Standard Build and Install

* Platform variations:: 
* Splitting the job up:: 
* How building works:: 
* How installation works:: 

Alternate Installation

* Alternate installation; the user scheme: Alternate installation the user scheme. 
* Alternate installation; the home scheme: Alternate installation the home scheme. 
* Alternate installation; Unix (the prefix scheme): Alternate installation Unix the prefix scheme. 
* Alternate installation; Windows (the prefix scheme): Alternate installation Windows the prefix scheme. 

自定义安装

* Modifying Python's Search Path:: 

Distutils Configuration Files

* Location and names of config files:: 
* Syntax of config files:: 

Building Extensions: Tips and Tricks

* Tweaking compiler/linker flags:: 
* Using non-Microsoft compilers on Windows:: 

Using non-Microsoft compilers on Windows

* Borland/CodeGear C++:: 
* GNU C / Cygwin / MinGW:: 

GNU C / Cygwin / MinGW

* Older Versions of Python and MinGW:: 

@end detailmenu
@end menu

@node Python的新变化,Python 教程,Top,Top
@anchor{whatsnew/index doc}@anchor{146}@anchor{whatsnew/index python-documentation-contents}@anchor{147}@anchor{whatsnew/index what-s-new-in-python}@anchor{148}@anchor{whatsnew/index whatsnew-index}@anchor{149}
@chapter Python的新变化


这个“Python 有什么新变化？”系列内容会带您浏览 Python 大版本之间重要的变化。在新版发布后，如果您希望掌握最新变化，请务必阅读这些内容。

@menu
* Python 3.8 有什么新变化: Python 3 8 有什么新变化. 
* Python 3.7 有什么新变化: Python 3 7 有什么新变化. 
* Python 3.6 有什么新变化: Python 3 6 有什么新变化. 
* Python 3.5 有什么新变化: Python 3 5 有什么新变化. 
* Python 3.4 有什么新变化: Python 3 4 有什么新变化. 
* Python 3.3 有什么新变化: Python 3 3 有什么新变化. 
* Python 3.2 有什么新变化: Python 3 2 有什么新变化. 
* Python 3.1 有什么新变化: Python 3 1 有什么新变化. 
* Python 3.0 有什么新变化: Python 3 0 有什么新变化. 
* Python 2.7 有什么新变化: Python 2 7 有什么新变化. 
* Python 2.6 有什么新变化: Python 2 6 有什么新变化. 
* Python 2.5 有什么新变化: Python 2 5 有什么新变化. 
* Python 2.4 有什么新变化: Python 2 4 有什么新变化. 
* Python 2.3 有什么新变化: Python 2 3 有什么新变化. 
* Python 2.2 有什么新变化: Python 2 2 有什么新变化. 
* Python 2.1 有什么新变化: Python 2 1 有什么新变化. 
* Python 2.0 有什么新变化: Python 2 0 有什么新变化. 
* 更新日志:: 

@end menu

@node Python 3 8 有什么新变化,Python 3 7 有什么新变化,,Python的新变化
@anchor{whatsnew/3 8 doc}@anchor{14a}@anchor{whatsnew/3 8 what-s-new-in-python-3-8}@anchor{14b}
@section Python 3.8 有什么新变化


@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number as a comment:
@c 
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer in :issue:`12345`.)
@c 
@c This saves the maintainer the effort of going through the Git log
@c when researching a change.

@*编者: 
Raymond Hettinger


本文解释了 Python 3.8 相比 3.7 的新增特性。 完整的详情可参阅 @ref{14c,,更新日志}。

Python 3.8已于2019年10月14日发布。

@c from datetime import date
@c from math import cos, radians
@c from unicodedata import normalize
@c import re
@c import math

@menu
* 摘要 - 发布重点:: 
* 新的特性:: 
* 其他语言特性修改:: 
* 新增模块:: 
* 改进的模块:: 
* 性能优化:: 
* 构建和 C API 的改变:: 
* 弃用:: 
* API 与特性的移除:: 
* 移植到 Python 3.8: 移植到 Python 3 8. 
* Python 3.8.1 中的重要变化: Python 3 8 1 中的重要变化. 
* Python 3.8.2 中的重要变化: Python 3 8 2 中的重要变化. 
* Python 3.8.3 中的重要变化: Python 3 8 3 中的重要变化. 

@end menu

@node 摘要 - 发布重点,新的特性,,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 summary-release-highlights}@anchor{14d}
@subsection 摘要 - 发布重点


@c This section singles out the most important changes in Python 3.8.
@c Brevity is key.

@c PEP-sized items next.

@node 新的特性,其他语言特性修改,摘要 - 发布重点,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 new-features}@anchor{14e}
@subsection 新的特性


@menu
* 赋值表达式:: 
* 仅限位置形参:: 
* 用于已编译字节码文件的并行文件系统缓存:: 
* 调试构建使用与发布构建相同的 ABI:: 
* f-字符串支持 = 用于自动记录表达式和调试文档:: 
* PEP 578; Python 运行时审核钩子: PEP 578 Python 运行时审核钩子. 
* PEP 587; Python 初始化配置: PEP 587 Python 初始化配置. 
* Vectorcall; 用于 CPython 的快速调用协议: Vectorcall 用于 CPython 的快速调用协议. 
* 具有外部数据缓冲区的 pickle 协议 5:: 

@end menu

@node 赋值表达式,仅限位置形参,,新的特性
@anchor{whatsnew/3 8 assignment-expressions}@anchor{14f}
@subsubsection 赋值表达式


新增的语法 @code{:=} 可在表达式内部为变量赋值。 它被昵称为“海象运算符”因为它很像是 海象的眼睛和长牙@footnote{https://en.wikipedia.org/wiki/Walrus#/media/File:Pacific_Walrus_-_Bull_(8247646168).jpg}。

在这个示例中，赋值表达式可以避免调用 @ref{150,,len()} 两次:

@example
if (n := len(a)) > 10:
    print(f"List is too long (@{n@} elements, expected <= 10)")
@end example

类似的益处还可出现在正则表达式匹配中需要使用两次匹配对象的情况中，一次检测用于匹配是否发生，另一次用于提取子分组:

@example
discount = 0.0
if (mo := re.search(r'(\d+)% discount', advertisement)):
    discount = float(mo.group(1)) / 100.0
@end example

此运算符也适用于配合 while 循环计算一个值来检测循环是否终止，而同一个值又在循环体中再次被使用的情况:

@example
# Loop over fixed length blocks
while (block := f.read(256)) != '@w{'}:
    process(block)
@end example

另一个值得介绍的用例出现于列表推导式中，在筛选条件中计算一个值，而同一个值又在表达式中需要被使用:

@example
[clean_name.title() for name in names
 if (clean_name := normalize('NFC', name)) in allowed_names]
@end example

请尽量将海象运算符的使用限制在清晰的场合中，以降低复杂性并提升可读性。

请参阅 
@geindex Python 提高建议; PEP 572
PEP 572@footnote{https://www.python.org/dev/peps/pep-0572} 了解详情。

（由 Morehouse 在 bpo-35224@footnote{https://bugs.python.org/issue35224} 中贡献。）

@node 仅限位置形参,用于已编译字节码文件的并行文件系统缓存,赋值表达式,新的特性
@anchor{whatsnew/3 8 positional-only-parameters}@anchor{151}
@subsubsection 仅限位置形参


新增了一个函数形参语法 @code{/} 用来指明某些函数形参必须使用仅限位置而非关键字参数的形式。 这种标记语法与通过 @code{help()} 所显示的使用 Larry Hastings 的 Argument Clinic@footnote{https://docs.python.org/3/howto/clinic.html} 工具标记的 C 函数相同。

在下面的例子中，形参 @emph{a} 和 @emph{b} 为仅限位置形参，@emph{c} 或 @emph{d} 可以是位置形参或关键字形参，而 @emph{e} 或 @emph{f} 要求为关键字形参:

@example
def f(a, b, /, c, d, *, e, f):
    print(a, b, c, d, e, f)
@end example

以下均为合法的调用:

@example
f(10, 20, 30, d=40, e=50, f=60)
@end example

但是，以下均为不合法的调用:

@example
f(10, b=20, c=30, d=40, e=50, f=60)   # b cannot be a keyword argument
f(10, 20, 30, 40, 50, f=60)           # e must be a keyword argument
@end example

这种标记形式的一个用例是它允许纯 Python 函数完整模拟现有的用 C 代码编写的函数的行为。 例如，内置的 @ref{152,,divmod()} 函数不接受关键字参数:

@example
def divmod(a, b, /):
    "Emulate the built in divmod() function"
    return (a // b, a % b)
@end example

另一个用例是在不需要形参名称时排除关键字参数。 例如，内置的 @ref{150,,len()} 函数的签名为 @code{len(obj, /)}。 这可以排除如下这种笨拙的调用形式:

@example
len(obj='hello')  # The "obj" keyword argument impairs readability
@end example

另一个益处是将形参标记为仅限位置形参将允许在未来修改形参名而不会破坏客户的代码。 例如，在 @ref{f5,,statistics} 模块中，形参名 @emph{dist} 在未来可能被修改。 这使得以下函数描述成为可能:

@example
def quantiles(dist, /, *, n=4, method='exclusive')
    ...
@end example

由于在 @code{/} 左侧的形参不会被公开为可用关键字，其他形参名仍可在 @code{**kwargs} 中使用:

@example
>>> def f(a, b, /, **kwargs):
...     print(a, b, kwargs)
...
>>> f(10, 20, a=1, b=2, c=3)         # a and b are used in two ways
10 20 @{'a': 1, 'b': 2, 'c': 3@}
@end example

这极大地简化了需要接受任意关键字参数的函数和方法的实现。 例如，以下是一段摘自 @ref{1e,,collections} 模块的代码:

@example
class Counter(dict):

    def __init__(self, iterable=None, /, **kwds):
        # Note "iterable" is a possible keyword argument
@end example

请参阅 
@geindex Python 提高建议; PEP 570
PEP 570@footnote{https://www.python.org/dev/peps/pep-0570} 了解详情。

（由 Pablo Galindo 在 bpo-36540@footnote{https://bugs.python.org/issue36540} 中贡献。）

@c TODO: Pablo will sprint on docs at PyCon US 2019.

@node 用于已编译字节码文件的并行文件系统缓存,调试构建使用与发布构建相同的 ABI,仅限位置形参,新的特性
@anchor{whatsnew/3 8 parallel-filesystem-cache-for-compiled-bytecode-files}@anchor{153}
@subsubsection 用于已编译字节码文件的并行文件系统缓存


新增的 
@geindex PYTHONPYCACHEPREFIX
@geindex 环境变量; PYTHONPYCACHEPREFIX
@ref{154,,PYTHONPYCACHEPREFIX} 设置 (也可使用 @ref{155,,-X} @code{pycache_prefix}) 可将隐式的字节码缓存配置为使用单独的并行文件系统树，而不是默认的每个源代码目录下的 @code{__pycache__} 子目录。

缓存的位置会在 @ref{156,,sys.pycache_prefix} 中报告 (@ref{157,,None} 表示默认位置即 @code{__pycache__} 子目录)。

（由 Carl Meyer 在 bpo-33499@footnote{https://bugs.python.org/issue33499} 中贡献。）

@node 调试构建使用与发布构建相同的 ABI,f-字符串支持 = 用于自动记录表达式和调试文档,用于已编译字节码文件的并行文件系统缓存,新的特性
@anchor{whatsnew/3 8 debug-build-uses-the-same-abi-as-release-build}@anchor{158}
@subsubsection 调试构建使用与发布构建相同的 ABI


Python 现在不论是以发布模式还是调试模式进行构建都将使用相同的 ABI。 在 Unix 上，当 Python 以调试模式构建时，现在将可以加载以发布模式构建的 C 扩展和使用稳定版 ABI 构建的 C 扩展。

发布构建和调试构建现在都是 ABI 兼容的：定义 @code{Py_DEBUG} 宏不会再启用 @code{Py_TRACE_REFS} 宏，它引入了唯一的 ABI 不兼容性。 @code{Py_TRACE_REFS} 宏添加了 @code{sys.getobjects()} 函数和 
@geindex PYTHONDUMPREFS
@geindex 环境变量; PYTHONDUMPREFS
@ref{159,,PYTHONDUMPREFS} 环境变量，它可以使用新的 @code{./configure --with-trace-refs} 构建选项来设置。 （由 Victor Stinner 在 bpo-36465@footnote{https://bugs.python.org/issue36465} 中贡献。）

在 Unix 上，C 扩展不会再被链接到 libpython，但 Android 和 Cygwin 例外。 现在静态链接的 Python 将可以加载使用共享库 Python 构建的 C 扩展。 （由 Victor Stinner 在 bpo-21536@footnote{https://bugs.python.org/issue21536} 中贡献。）

在 Unix 上，当 Python 以调试模式构建时，导入操作现在也会查找在发布模式下编译的 C 扩展以及使用稳定版 ABI 编译的 C 扩展。 （由 Victor Stinner 在 bpo-36722@footnote{https://bugs.python.org/issue36722} 中贡献。）

要将 Python 嵌入到一个应用中，必须将新增的 @code{--embed} 选项传给 @code{python3-config --libs --embed} 以获得 @code{-lpython3.8} (将应用链接到 libpython)。 要同时支持 3.8 和旧版本，请先尝试 @code{python3-config --libs --embed} 并在此命令失败时回退到 @code{python3-config --libs} (即不带 @code{--embed})。

增加一个 pkg-config @code{python-3.8-embed} 模块用来将 Python 嵌入到一个应用中: @code{pkg-config python-3.8-embed --libs} 包含 @code{-lpython3.8}。 要同时支持 3.8 和旧版本，请先尝试 @code{pkg-config python-X.Y-embed --libs} 并在此命令失败时回退到 @code{pkg-config python-X.Y --libs} (即不带 @code{--embed}) （请将 @code{X.Y} 替换为 Python 版本号）。

另一方面，@code{pkg-config python3.8 --libs} 不再包含 @code{-lpython3.8}。 C 扩展不可被链接到 libpython (但 Android 和 Cygwin 例外，这两者的情况由脚本处理)；此改变是故意被设为向下不兼容的。 （由 Victor Stinner 在 bpo-36721@footnote{https://bugs.python.org/issue36721} 中贡献。）

@node f-字符串支持 = 用于自动记录表达式和调试文档,PEP 578 Python 运行时审核钩子,调试构建使用与发布构建相同的 ABI,新的特性
@anchor{whatsnew/3 8 f-strings-support-for-self-documenting-expressions-and-debugging}@anchor{15a}
@subsubsection f-字符串支持 @code{=} 用于自动记录表达式和调试文档


增加 @code{=} 说明符用于 @ref{15b,,f-string}。 形式为 @code{f'@{expr=@}'} 的 f-字符串将扩展表示为表达式文本，加一个等于号，再加表达式的求值结果。 例如：

@example
>>> user = 'eric_idle'
>>> member_since = date(1975, 7, 31)
>>> f'@{user=@} @{member_since=@}'
"user='eric_idle' member_since=datetime.date(1975, 7, 31)"
@end example

通常的 @ref{15c,,f-字符串格式说明符} 允许更细致地控制所要显示的表达式结果:

@example
>>> delta = date.today() - member_since
>>> f'@{user=!s@}  @{delta.days=:,d@}'
'user=eric_idle  delta.days=16,075'
@end example

@code{=} 说明符将输出整个表达式，以便详细演示计算过程:

@example
>>> print(f'@{theta=@}  @{cos(radians(theta))=:.3f@}')
theta=30  cos(radians(theta))=0.866
@end example

（由 Eric V. Smith 和 Larry Hastings 在 bpo-36817@footnote{https://bugs.python.org/issue36817} 中贡献。）

@node PEP 578 Python 运行时审核钩子,PEP 587 Python 初始化配置,f-字符串支持 = 用于自动记录表达式和调试文档,新的特性
@anchor{whatsnew/3 8 pep-578-python-runtime-audit-hooks}@anchor{15d}
@subsubsection PEP 578: Python 运行时审核钩子


此 PEP 添加了审核钩子和已验证开放钩子。 两者在 Python 与本机代码中均可用。允许以纯 Python 代码编写的应用和框架利用额外的通知，同时允许嵌入开发人员或系统管理员部署始终启用审核的 Python 版本。

请参阅 
@geindex Python 提高建议; PEP 578
PEP 578@footnote{https://www.python.org/dev/peps/pep-0578} 了解详情。

@node PEP 587 Python 初始化配置,Vectorcall 用于 CPython 的快速调用协议,PEP 578 Python 运行时审核钩子,新的特性
@anchor{whatsnew/3 8 pep-587-python-initialization-configuration}@anchor{15e}
@subsubsection PEP 587: Python 初始化配置


@geindex Python 提高建议; PEP 587
PEP 587@footnote{https://www.python.org/dev/peps/pep-0587} 增加了一个新的 C API 用来配置 Python 初始化，提供对整个配置过程的更细致控制以及更好的错误报告。

新的结构：


@itemize *

@item 
@ref{15f,,PyConfig}

@item 
@ref{160,,PyPreConfig}

@item 
@ref{161,,PyStatus}

@item 
@ref{162,,PyWideStringList}
@end itemize

新的函数：


@itemize *

@item 
@ref{163,,PyConfig_Clear()}

@item 
@ref{164,,PyConfig_InitIsolatedConfig()}

@item 
@ref{165,,PyConfig_InitPythonConfig()}

@item 
@ref{166,,PyConfig_Read()}

@item 
@ref{167,,PyConfig_SetArgv()}

@item 
@ref{168,,PyConfig_SetBytesArgv()}

@item 
@ref{169,,PyConfig_SetBytesString()}

@item 
@ref{16a,,PyConfig_SetString()}

@item 
@ref{16b,,PyPreConfig_InitIsolatedConfig()}

@item 
@ref{16c,,PyPreConfig_InitPythonConfig()}

@item 
@ref{16d,,PyStatus_Error()}

@item 
@ref{16e,,PyStatus_Exception()}

@item 
@ref{16f,,PyStatus_Exit()}

@item 
@ref{170,,PyStatus_IsError()}

@item 
@ref{171,,PyStatus_IsExit()}

@item 
@ref{172,,PyStatus_NoMemory()}

@item 
@ref{173,,PyStatus_Ok()}

@item 
@ref{174,,PyWideStringList_Append()}

@item 
@ref{175,,PyWideStringList_Insert()}

@item 
@ref{176,,Py_BytesMain()}

@item 
@ref{177,,Py_ExitStatusException()}

@item 
@ref{178,,Py_InitializeFromConfig()}

@item 
@ref{179,,Py_PreInitialize()}

@item 
@ref{17a,,Py_PreInitializeFromArgs()}

@item 
@ref{17b,,Py_PreInitializeFromBytesArgs()}

@item 
@ref{17c,,Py_RunMain()}
@end itemize

此 PEP 还为这些内部结构添加了 @code{_PyRuntimeState.preconfig} (@ref{160,,PyPreConfig} 类型) 和 @code{PyInterpreterState.config} (@ref{15f,,PyConfig} 类型) 字段。 @code{PyInterpreterState.config} 成为新的引用配置，替代全局配置变量和其他私有变量。

请参阅 @ref{17d,,Python 初始化配置} 获取详细文档。

请参阅 
@geindex Python 提高建议; PEP 587
PEP 587@footnote{https://www.python.org/dev/peps/pep-0587} 了解详情。

（由 Victor Stinner 在 bpo-36763@footnote{https://bugs.python.org/issue36763} 中贡献。）

@node Vectorcall 用于 CPython 的快速调用协议,具有外部数据缓冲区的 pickle 协议 5,PEP 587 Python 初始化配置,新的特性
@anchor{whatsnew/3 8 vectorcall-a-fast-calling-protocol-for-cpython}@anchor{17e}
@subsubsection Vectorcall: 用于 CPython 的快速调用协议


添加 "vectorcall" 协议到 Python/C API。 它的目标是对已被应用于许多类的现有优化进行正式化。 任何实现可调用对象的扩展类型均可使用此协议。

此特性目前为暂定状态，计划在 Python 3.9 将其完全公开。

请参阅 
@geindex Python 提高建议; PEP 590
PEP 590@footnote{https://www.python.org/dev/peps/pep-0590} 了解详情。

（由 Jeroen Demeyer 和 Mark Shannon 在 bpo-36974@footnote{https://bugs.python.org/issue36974} 中贡献。）

@node 具有外部数据缓冲区的 pickle 协议 5,,Vectorcall 用于 CPython 的快速调用协议,新的特性
@anchor{whatsnew/3 8 pickle-protocol-5-with-out-of-band-data-buffers}@anchor{17f}
@subsubsection 具有外部数据缓冲区的 pickle 协议 5


当使用 @ref{ca,,pickle} 在 Python 进程间传输大量数据以充分发挥多核或多机处理的优势时，非常重要一点是通过减少内存拷贝来优化传输效率，并可能应用一些定制技巧例如针对特定数据的压缩。

@ref{ca,,pickle} 协议 5 引入了对于外部缓冲区的支持，这样 
@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} 兼容的数据可以与主 pickle 流分开进行传输，这是由通信层来确定的。

请参阅 
@geindex Python 提高建议; PEP 574
PEP 574@footnote{https://www.python.org/dev/peps/pep-0574} 了解详情。

（由 Antoine Pitrou 在 bpo-36785@footnote{https://bugs.python.org/issue36785} 中贡献。）

@node 其他语言特性修改,新增模块,新的特性,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 other-language-changes}@anchor{180}
@subsection 其他语言特性修改



@itemize *

@item 
在之前版本中 @ref{181,,continue} 语句不允许在 @ref{182,,finally} 子句中使用，这是因为具体实现存在一个问题。 在 Python 3.8 中此限制已被取消。 （由 Serhiy Storchaka 在 bpo-32489@footnote{https://bugs.python.org/issue32489} 中贡献。）

@item 
@ref{183,,bool}, @ref{184,,int} 和 @ref{185,,fractions.Fraction} 类型现在都有一个 @ref{186,,as_integer_ratio()} 方法，与 @ref{187,,float} 和 @ref{188,,decimal.Decimal} 中的已有方法类似。 这个微小的 API 扩展使得 @code{numerator, denominator = x.as_integer_ratio()} 这样的写法在多种数字类型上通用成为可能。 （由 Lisa Roach 在 bpo-33073@footnote{https://bugs.python.org/issue33073} 和 Raymond Hettinger 在 bpo-37819@footnote{https://bugs.python.org/issue37819} 中贡献。）

@item 
@ref{184,,int}, @ref{187,,float} 和 @ref{189,,complex} 的构造器现在会使用 @ref{18a,,__index__()} 特殊方法，如果该方法可用而对应的方法 method @ref{18b,,__int__()}, @ref{18c,,__float__()} 或 @ref{18d,,__complex__()} 方法不可用的话。 （由 Serhiy Storchaka 在 bpo-20092@footnote{https://bugs.python.org/issue20092} 中贡献。）

@item 
添加 @code{\N@{name@}} 转义符在 @ref{dd,,正则表达式} 中的支持:

@example
>>> notice = 'Copyright © 2019'
>>> copyright_year_pattern = re.compile(r'\N@{copyright sign@}\s*(\d@{4@})')
>>> int(copyright_year_pattern.search(notice).group(1))
2019
@end example

（由 Jonathan Eunice 和 Serhiy Storchaka 在 bpo-30688@footnote{https://bugs.python.org/issue30688} 中贡献。）

@item 
现在 dict 和 dictview 可以使用 @ref{18e,,reversed()} 按插入顺序反向迭代。 （由 Rémi Lapeyre 在 bpo-33462@footnote{https://bugs.python.org/issue33462} 中贡献。）

@item 
在函数调用中允许使用的关键字名称语法受到进一步的限制。 特别地，@code{f((keyword)=arg)} 不再被允许。 关键字参数赋值形式的左侧绝不允许一般标识符以外的其他内容。 （由 Benjamin Peterson 在 bpo-34641@footnote{https://bugs.python.org/issue34641} 中贡献。）

@item 
在 @ref{18f,,yield} 和 @ref{190,,return} 语句中的一般可迭代对象解包不再要求加圆括号。 这使得 @emph{yield} 和 @emph{return} 的语法与正常的赋值语法更为一致:

@example
>>> def parse(family):
        lastname, *members = family.split()
        return lastname.upper(), *members

>>> parse('simpsons homer marge bart lisa sally')
('SIMPSONS', 'homer', 'marge', 'bart', 'lisa', 'sally')
@end example

（由 David Cuthbert 和 Jordan Chapman 在 bpo-32117@footnote{https://bugs.python.org/issue32117} 中贡献。）

@item 
当类似 @code{[(10, 20) (30, 40)]} 这样在代码中少了一个逗号时，编译器将显示 @ref{191,,SyntaxWarning} 并附带更有帮助的提示。 这相比原来用 @ref{192,,TypeError} 来提示第一个元组是不可调用的更容易被理解。 （由 Serhiy Storchaka 在 bpo-15248@footnote{https://bugs.python.org/issue15248} 中贡献。）

@item 
@ref{193,,datetime.date} 或 @ref{194,,datetime.datetime} 和 @ref{195,,datetime.timedelta} 对象之间的算术运算现在将返回相应子类的实例而不是基类的实例。 这也会影响到在具体实现中（直接或间接地）使用了 @ref{195,,datetime.timedelta} 算术运算的返回类型，例如 @ref{196,,astimezone()}。 （由 Paul Ganssle 在 bpo-32417@footnote{https://bugs.python.org/issue32417} 中贡献。）

@item 
当 Python 解释器通过 Ctrl-C (SIGINT) 被中断并且所产生的 @ref{197,,KeyboardInterrupt} 异常未被捕获，Python 进程现在会通过一个 SIGINT 信号或是使得发起调用的进程能检测到它是由 Ctrl-C 操作杀死的正确退出代码来退出。 POSIX 和 Windows 上的终端会相应地使用此代码在交互式会话中终止脚本。 （由 Google 的 Gregory P. Smith 在 bpo-1054041@footnote{https://bugs.python.org/issue1054041} 中贡献。）

@item 
某些高级编程风格要求为现有的函数更新 @ref{198,,types.CodeType} 对象。 由于代码对象是不可变的，需要基于现有代码对象模型创建一个新的代码对象。 使用 19 个形参将会相当繁琐。 现在，新的 @code{replace()} 方法使得通过少量修改的形参创建克隆对象成为可能。

下面是一个修改 @ref{199,,statistics.mean()} 函数来防止 @emph{data} 形参被用作关键字参数的例子:

@example
>>> from statistics import mean
>>> mean(data=[10, 20, 90])
40
>>> mean.__code__ = mean.__code__.replace(co_posonlyargcount=1)
>>> mean(data=[10, 20, 90])
Traceback (most recent call last):
  ...
TypeError: mean() got some positional-only arguments passed as keyword arguments: 'data'
@end example

（由 Victor Stinner 在 bpo-37032@footnote{https://bugs.python.org/issue37032} 中贡献。）

@item 
对于整数，现在 @ref{19a,,pow()} 函数的三参数形式在底数与模数不可约的情况下允许指数为负值。 随后它会在指数为 @code{-1} 时计算底数的模乘逆元，并对其他负指数计算反模的适当幂次。 例如，要计算 38 模 137 的 模乘逆元@footnote{https://en.wikipedia.org/wiki/Modular_multiplicative_inverse} 则可写为:

@example
>>> pow(38, -1, 137)
119
>>> 119 * 38 % 137
1
@end example

模乘逆元在求解 线性丢番图方程@footnote{https://en.wikipedia.org/wiki/Diophantine_equation} 会被用到。 例如，想要求出 @code{4258𝑥 + 147𝑦 = 369} 的整数解，首先应重写为 @code{4258𝑥 ≡ 369 (mod 147)} 然后求解：

@example
>>> x = 369 * pow(4258, -1, 147) % 147
>>> y = (4258 * x - 369) // -147
>>> 4258 * x + 147 * y
369
@end example

（由 Mark Dickinson 在 bpo-36027@footnote{https://bugs.python.org/issue36027} 中贡献。）

@item 
字典推导式已与字典字面值实现同步，会先计算键再计算值:

@example
>>> # Dict comprehension
>>> cast = @{input('role? '): input('actor? ') for i in range(2)@}
role? King Arthur
actor? Chapman
role? Black Knight
actor? Cleese

>>> # Dict literal
>>> cast = @{input('role? '): input('actor? ')@}
role? Sir Robin
actor? Eric Idle
@end example

对执行顺序的保证对赋值表达式来说很有用，因为在键表达式中赋值的变量将可在值表达式中被使用:

@example
>>> names = ['Martin von Löwis', 'Łukasz Langa', 'Walter Dörwald']
>>> @{(n := normalize('NFC', name)).casefold() : n for name in names@}
@{'martin von löwis': 'Martin von Löwis',
 'łukasz langa': 'Łukasz Langa',
 'walter dörwald': 'Walter Dörwald'@}
@end example

（由 Jörn Heissler 在 bpo-35224@footnote{https://bugs.python.org/issue35224} 中贡献。）

@item 
@ref{19b,,object.__reduce__()} 方法现在可返回长度为二至六个元素的元组。 之前的上限为五个。 新增的第六个可选元素是签名为 @code{(obj, state)} 的可调用对象。 这样就允许直接控制特定对象的状态更新。 如果元素值不为 @emph{None}，该可调用对象将优先于对象的 @ref{19c,,__setstate__()} 方法。 （由 Pierre Glaser 和 Olivier Grisel 在 bpo-35900@footnote{https://bugs.python.org/issue35900} 中贡献。）
@end itemize

@node 新增模块,改进的模块,其他语言特性修改,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 new-modules}@anchor{19d}
@subsection 新增模块



@itemize *

@item 
新增的 @code{importlib.metadata} 模块提供了从第三方包读取元数据的（临时）支持。 例如，它可以提取一个已安装软件包的版本号、入口点列表等等:

@example
>>> # Note following example requires that the popular "requests"
>>> # package has been installed.
>>>
>>> from importlib.metadata import version, requires, files
>>> version('requests')
'2.22.0'
>>> list(requires('requests'))
['chardet (<3.1.0,>=3.0.2)']
>>> list(files('requests'))[:5]
[PackagePath('requests-2.22.0.dist-info/INSTALLER'),
 PackagePath('requests-2.22.0.dist-info/LICENSE'),
 PackagePath('requests-2.22.0.dist-info/METADATA'),
 PackagePath('requests-2.22.0.dist-info/RECORD'),
 PackagePath('requests-2.22.0.dist-info/WHEEL')]
@end example

（由 Barry Warsaw 和 Jason R. Coombs 在 bpo-34632@footnote{https://bugs.python.org/issue34632} 中贡献）。
@end itemize

@node 改进的模块,性能优化,新增模块,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 improved-modules}@anchor{19e}
@subsection 改进的模块


@menu
* ast:: 
* asyncio:: 
* builtins:: 
* collections:: 
* cProfile:: 
* csv:: 
* curses:: 
* ctypes:: 
* datetime:: 
* functools:: 
* gc:: 
* gettext:: 
* gzip:: 
* IDLE 与 idlelib:: 
* inspect:: 
* io:: 
* itertools:: 
* json.tool: json tool. 
* logging:: 
* math:: 
* mmap:: 
* multiprocessing:: 
* os:: 
* os.path: os path. 
* pathlib:: 
* pickle:: 
* plistlib:: 
* pprint:: 
* py_compile:: 
* shlex:: 
* shutil:: 
* socket:: 
* ssl:: 
* statistics:: 
* sys:: 
* tarfile:: 
* threading:: 
* tokenize:: 
* tkinter:: 
* time:: 
* typing:: 
* unicodedata:: 
* unittest:: 
* venv:: 
* weakref:: 
* xml:: 
* xmlrpc:: 

@end menu

@node ast,asyncio,,改进的模块
@anchor{whatsnew/3 8 ast}@anchor{19f}
@subsubsection ast


AST 节点现在具有 @code{end_lineno} 和 @code{end_col_offset} 属性，它们给出节点结束的精确位置。 （这只适用于具有 @code{lineno} 和 @code{col_offset} 属性的节点。）

新增函数 @ref{1a0,,ast.get_source_segment()} 返回指定 AST 节点的源代码。

（由 Ivan Levkivskyi 在 bpo-33416@footnote{https://bugs.python.org/issue33416} 中贡献。）

@ref{1a1,,ast.parse()} 函数具有一些新的旗标：


@itemize *

@item 
@code{type_comments=True} 导致其返回与特定 AST 节点相关联的 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} 和 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} 类型注释文本；

@item 
@code{mode='func_type'} 可被用于解析 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} "签名类型注释" (为函数定义 AST 节点而返回)；

@item 
@code{feature_version=(3, N)} 允许指定一个更早的 Python 3 版本。 例如，@code{feature_version=(3, 4)} 将把 @ref{1a2,,async} 和 @ref{1a3,,await} 视为非保留字。
@end itemize

（由 Guido van Rossum 在 bpo-35766@footnote{https://bugs.python.org/issue35766} 中贡献。）

@node asyncio,builtins,ast,改进的模块
@anchor{whatsnew/3 8 asyncio}@anchor{1a4}
@subsubsection asyncio


@ref{1a5,,asyncio.run()} 已经从暂定状态晋级为稳定 API。 此函数可被用于执行一个 @ref{1a6,,coroutine} 并返回结果，同时自动管理事件循环。 例如:

@example
import asyncio

async def main():
    await asyncio.sleep(0)
    return 42

asyncio.run(main())
@end example

这 @emph{大致} 等价于:

@example
import asyncio

async def main():
    await asyncio.sleep(0)
    return 42

loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
try:
    loop.run_until_complete(main())
finally:
    asyncio.set_event_loop(None)
    loop.close()
@end example

实际的实现要更复杂许多。 因此 @ref{1a5,,asyncio.run()} 应该作为运行 asyncio 程序的首选方式。

（由 Yury Selivanov 在 bpo-32314@footnote{https://bugs.python.org/issue32314} 中贡献。）

运行 @code{python -m asyncio} 将启动一个原生异步 REPL。 这允许快速体验具有最高层级 @ref{1a3,,await} 的代码。 这时不再需要直接调用 @code{asyncio.run()}，因为此操作会在每次发起调用时产生一个新事件循环：

@example
$ python -m asyncio
asyncio REPL 3.8.0
Use "await" directly instead of "asyncio.run()".
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> await asyncio.sleep(10, result='hello')
hello
@end example

（由 Yury Selivanov 在 bpo-37028@footnote{https://bugs.python.org/issue37028} 中贡献。）

The exception @ref{1a7,,asyncio.CancelledError} now inherits from
@ref{1a8,,BaseException} rather than @ref{1a9,,Exception} and no longer inherits
from @ref{1aa,,concurrent.futures.CancelledError}.
(Contributed by Yury Selivanov in bpo-32528@footnote{https://bugs.python.org/issue32528}.)

在 Windows 上，现在默认的事件循环为 @ref{1ab,,ProactorEventLoop}。 （由 Victor Stinner 在 bpo-34687@footnote{https://bugs.python.org/issue34687} 中贡献。）

@ref{1ab,,ProactorEventLoop} 现在也支持 UDP。 （由 Adam Meily 和 Andrew Svetlov 在 bpo-29883@footnote{https://bugs.python.org/issue29883} 中贡献。）

@ref{1ab,,ProactorEventLoop} 现在可通过 @ref{197,,KeyboardInterrupt} ("CTRL+C") 来中断。 （由 Vladimir Matveev 在 bpo-23057@footnote{https://bugs.python.org/issue23057} 中贡献。）

添加了 @ref{1ac,,asyncio.Task.get_coro()} 用来获取 @ref{1ad,,asyncio.Task} 中的已包装协程。 （由 Alex Grönholm 在 bpo-36999@footnote{https://bugs.python.org/issue36999} 中贡献。）

asyncio 任务现在可以被命名，或者是通过将 @code{name} 关键字参数传给 @ref{1ae,,asyncio.create_task()} 或 @ref{1af,,create_task()} 事件循环方法，或者是通过在任务对象上调用 @ref{1b0,,set_name()} 方法。 任务名称在 @ref{1ad,,asyncio.Task} 的 @code{repr()} 输出中可见，并且还可以使用 @ref{1b1,,get_name()} 方法来获取。 （由 Alex Grönholm 在 bpo-34270@footnote{https://bugs.python.org/issue34270} 中贡献。）

将对 Happy Eyeballs@footnote{https://en.wikipedia.org/wiki/Happy_Eyeballs} 的支持添加到 @ref{1b2,,asyncio.loop.create_connection()}。 要指定此行为，已增加了两个新的形参: @emph{happy_eyeballs_delay} 和 @emph{interleave}。 Happy Eyeballs 算法可提升支持 IPv4 和 IPv6 的应用的响应速度，具体做法是尝试同时使用两者进行连接。 （由 twisteroid ambassador 在 bpo-33530@footnote{https://bugs.python.org/issue33530} 中贡献。）

@node builtins,collections,asyncio,改进的模块
@anchor{whatsnew/3 8 builtins}@anchor{1b3}
@subsubsection builtins


内置的 @ref{1b4,,compile()} 已改进为可接受 @code{ast.PyCF_ALLOW_TOP_LEVEL_AWAIT} 旗标。 当传入此新旗标时，@ref{1b4,,compile()} 将允许通常被视为无效语法的最高层级 @code{await}, @code{async for} 和 @code{async with} 构造。 此后将可返回带有 @code{CO_COROUTINE} 旗标的异步代码对象。 （由 Matthias Bussonnier 在 bpo-34616@footnote{https://bugs.python.org/issue34616} 中贡献。）

@node collections,cProfile,builtins,改进的模块
@anchor{whatsnew/3 8 collections}@anchor{1b5}
@subsubsection collections


@ref{1b6,,collections.namedtuple()} 的 @ref{1b7,,_asdict()} 方法现在将返回 @ref{1b8,,dict} 而不是 @ref{1b9,,collections.OrderedDict}。 此项更改是由于普通字典自 Python 3.7 起已保证具有确定的元素顺序。 如果还需要 @code{OrderedDict} 的额外特性，建议的解决方案是将结果转换为需要的类型: @code{OrderedDict(nt._asdict())}。 （由 Raymond Hettinger 在 bpo-35864@footnote{https://bugs.python.org/issue35864} 中贡献。）

@node cProfile,csv,collections,改进的模块
@anchor{whatsnew/3 8 cprofile}@anchor{1ba}
@subsubsection cProfile


@ref{1bb,,cProfile.Profile} 类现在可被用作上下文管理器。 在运行时对一个代码块实现性能分析:

@example
import cProfile

with cProfile.Profile() as profiler:
      # code to be profiled
      ...
@end example

（由 Scott Sanderson 在 bpo-29235@footnote{https://bugs.python.org/issue29235} 中贡献。）

@node csv,curses,cProfile,改进的模块
@anchor{whatsnew/3 8 csv}@anchor{1bc}
@subsubsection csv


@ref{1bd,,csv.DictReader} 现在将返回 @ref{1b8,,dict} 而不是 @ref{1b9,,collections.OrderedDict}。 此工具现在会更快速且消耗更少内存同时仍然保留字段顺序。 （由 Michael Selik 在 bpo-34003@footnote{https://bugs.python.org/issue34003} 中贡献。）

@node curses,ctypes,csv,改进的模块
@anchor{whatsnew/3 8 curses}@anchor{1be}
@subsubsection curses


添加了一个新变量用于保存下层 ncurses 库的结构版信息: @ref{1bf,,ncurses_version}。 （由 Serhiy Storchaka 在 bpo-31680@footnote{https://bugs.python.org/issue31680} 中贡献。）

@node ctypes,datetime,curses,改进的模块
@anchor{whatsnew/3 8 ctypes}@anchor{1c0}
@subsubsection ctypes


在 Windows 上，@ref{1c1,,CDLL} 及其子类现在接受 @emph{winmode} 形参来指定用于底层 @code{LoadLibraryEx} 调用的旗标。 默认旗标被设为仅加载来自可信任位置的 DLL 依赖项，包括 DLL 的存放路径（如果加载初始 DLL 时使用了完整或部分路径）以及通过 @ref{1c2,,add_dll_directory()} 添加的路径。 （由 Steve Dower 在 bpo-36085@footnote{https://bugs.python.org/issue36085} 中贡献。）

@node datetime,functools,ctypes,改进的模块
@anchor{whatsnew/3 8 datetime}@anchor{1c3}
@subsubsection datetime


添加了新的替代构造器 @ref{1c4,,datetime.date.fromisocalendar()} 和 @ref{1c5,,datetime.datetime.fromisocalendar()}，它们分别基于 ISO 年份、周序号和周内日序号来构造 @code{date} 和 @ref{31,,datetime} 对象；这两者分别是其所对应类中 @code{isocalendar} 方法的逆操作。 （由 Paul Ganssle 在 bpo-36004@footnote{https://bugs.python.org/issue36004} 中贡献。）

@node functools,gc,datetime,改进的模块
@anchor{whatsnew/3 8 functools}@anchor{1c6}
@subsubsection functools


@ref{1c7,,functools.lru_cache()} 现在可直接作为装饰器而不是作为返回装饰器的函数。 因此这两种写法现在都被支持:

@example
@@lru_cache
def f(x):
    ...

@@lru_cache(maxsize=256)
def f(x):
    ...
@end example

（由 Raymond Hettinger 在 bpo-36772@footnote{https://bugs.python.org/issue36772} 中贡献。）

添加了新的 @ref{1c8,,functools.cached_property()} 装饰器，用于在实例生命周期内缓存的已计算特征属性。

@example
import functools
import statistics

class Dataset:
   def __init__(self, sequence_of_numbers):
      self.data = sequence_of_numbers

   @@functools.cached_property
   def variance(self):
      return statistics.variance(self.data)
@end example

（由 Carl Meyer 在 bpo-21145@footnote{https://bugs.python.org/issue21145} 中贡献）

添加了新的 @ref{1c9,,functools.singledispatchmethod()} 装饰器可使用 @ref{1ca,,single dispatch} 将方法转换为 @ref{1cb,,泛型函数}:

@example
from functools import singledispatchmethod
from contextlib import suppress

class TaskManager:

    def __init__(self, tasks):
        self.tasks = list(tasks)

    @@singledispatchmethod
    def discard(self, value):
        with suppress(ValueError):
            self.tasks.remove(value)

    @@discard.register(list)
    def _(self, tasks):
        targets = set(tasks)
        self.tasks = [x for x in self.tasks if x not in targets]
@end example

（由 Ethan Smith 在 bpo-32380@footnote{https://bugs.python.org/issue32380} 中贡献）

@node gc,gettext,functools,改进的模块
@anchor{whatsnew/3 8 gc}@anchor{1cc}
@subsubsection gc


@ref{1cd,,get_objects()} 现在能接受一个可选的 @emph{generation} 形参来指定一个用于获取对象的生成器。 （由 Pablo Galindo 在 bpo-36016@footnote{https://bugs.python.org/issue36016} 中贡献。）

@node gettext,gzip,gc,改进的模块
@anchor{whatsnew/3 8 gettext}@anchor{1ce}
@subsubsection gettext


添加了 @ref{1cf,,pgettext()} 及其变化形式。 （由 Franz Glasner, Éric Araujo 和 Cheryl Sabella 在 bpo-2504@footnote{https://bugs.python.org/issue2504} 中贡献。）

@node gzip,IDLE 与 idlelib,gettext,改进的模块
@anchor{whatsnew/3 8 gzip}@anchor{1d0}
@subsubsection gzip


添加 @emph{mtime} 形参到 @ref{1d1,,gzip.compress()} 用于可重现的输出。 （由 Guo Ci Teo 在 bpo-34898@footnote{https://bugs.python.org/issue34898} 中贡献。）

对于特定类型的无效或已损坏 gzip 文件现在将引发 @ref{1d2,,BadGzipFile} 而不是 @ref{1d3,,OSError}。 （由 Filip Gruszczyński, Michele Orrù 和 Zackery Spytz 在 bpo-6584@footnote{https://bugs.python.org/issue6584} 中贡献。）

@node IDLE 与 idlelib,inspect,gzip,改进的模块
@anchor{whatsnew/3 8 idle-and-idlelib}@anchor{1d4}
@subsubsection IDLE 与 idlelib


超过 N 行（默认值为 50）的输出将被折叠为一个按钮。 N 可以在 Settings 对话框的 General 页的 PyShell 部分中进行修改。 数量较少但是超长的行可以通过在输出上右击来折叠。 被折叠的输出可通过双击按钮来展开，或是通过右击按钮来放入剪贴板或是单独的窗口。 （由 Tal Einat 在 bpo-1529353@footnote{https://bugs.python.org/issue1529353} 中贡献。）

在 Run 菜单中增加了 "Run Customized" 以使用自定义设置来运行模块。 输入的任何命令行参数都会被加入 sys.argv。 它们在下次自定义运行时会再次显示在窗体中。 用户也可以禁用通常的 Shell 主模块重启。 （由 Cheryl Sabella, Terry Jan Reedy 等人在 bpo-5680@footnote{https://bugs.python.org/issue5680} 和 bpo-37627@footnote{https://bugs.python.org/issue37627} 中贡献。）

在 IDLE 编辑器窗口中增加了可选的行号。 窗口打开时默认不显示行号，除非在配置对话框的 General 选项卡中特别设置。 已打开窗口中的行号可以在 Options 菜单中显示和隐藏。 （由 Tal Einat 和 Saimadhav Heblikar 在 bpo-17535@footnote{https://bugs.python.org/issue17535} 中贡献。）

现在会使用 OS 本机编码格式在 Python 字符串和 Tcl 对象间进行转换。 这允许在 IDLE 中处理 emoji 和其他非 BMP 字符。 这些字符将可被显示或是从剪贴板复制和粘贴。 字符串从 Tcl 到 Python 的来回转换现在不会再发生失败。 （过去八年有许多人都为此付出过努力，问题最终由 Serhiy Storchaka 在 bpo-13153@footnote{https://bugs.python.org/issue13153} 中解决。）

上述修改已被反向移植到 3.7 维护发行版中。

@node inspect,io,IDLE 与 idlelib,改进的模块
@anchor{whatsnew/3 8 inspect}@anchor{1d5}
@subsubsection inspect


@ref{1d6,,inspect.getdoc()} 函数现在可以找到 @code{__slots__} 的文档字符串，如果该属性是一个元素值为文档字符串的 @ref{1b8,,dict} 的话。 这提供了类似于目前已有的 @ref{1d7,,property()}, @ref{1d8,,classmethod()} 和 @ref{1d9,,staticmethod()} 等函数的文档选项:

@example
class AudioClip:
    __slots__ = @{'bit_rate': 'expressed in kilohertz to one decimal place',
                 'duration': 'in seconds, rounded up to an integer'@}
    def __init__(self, bit_rate, duration):
        self.bit_rate = round(bit_rate / 1000.0, 1)
        self.duration = ceil(duration)
@end example

（由 Raymond Hettinger 在 bpo-36326@footnote{https://bugs.python.org/issue36326} 中贡献。）

@node io,itertools,inspect,改进的模块
@anchor{whatsnew/3 8 io}@anchor{1da}
@subsubsection io


在开发模式 (@ref{155,,-X} @code{env}) 和调试构建中，@ref{1db,,io.IOBase} 终结器现在会在 @code{close()} 方法失败时将异常写入日志。 发生的异常在发布构建中默认会被静默忽略。 （由 Victor Stinner 在 bpo-18748@footnote{https://bugs.python.org/issue18748} 中贡献。）

@node itertools,json tool,io,改进的模块
@anchor{whatsnew/3 8 itertools}@anchor{1dc}
@subsubsection itertools


@ref{1dd,,itertools.accumulate()} 函数增加了可选的 @emph{initial} 关键字参数用来指定一个初始值:

@example
>>> from itertools import accumulate
>>> list(accumulate([10, 5, 30, 15], initial=1000))
[1000, 1010, 1015, 1045, 1060]
@end example

（由 Lisa Roach 在 bpo-34659@footnote{https://bugs.python.org/issue34659} 中贡献。）

@node json tool,logging,itertools,改进的模块
@anchor{whatsnew/3 8 json-tool}@anchor{1de}
@subsubsection json.tool


添加选项 @code{--json-lines} 用于将每个输入行解析为单独的 JSON 对象。 （由 Weipeng Hong 在 bpo-31553@footnote{https://bugs.python.org/issue31553} 中贡献。）

@node logging,math,json tool,改进的模块
@anchor{whatsnew/3 8 logging}@anchor{1df}
@subsubsection logging


为 @ref{1e0,,logging.basicConfig()} 添加了 @emph{force} 关键字参数，当设为真值时，关联到根日志记录器的任何现有处理程序都将在执行由其他参数所指定的配置之前被移除并关闭。

这解决了一个长期存在的问题。 当一个日志处理器或 @emph{basicConfig()} 被调用时，对 @emph{basicConfig()} 的后续调用会被静默地忽略。 这导致使用交互提示符或 Jupyter 笔记本更新、试验或讲解各种日志配置选项变得相当困难。

（由 Raymond Hettinger 提议，由 Dong-hee Na 实现，并由 Vinay Sajip 在 bpo-33897@footnote{https://bugs.python.org/issue33897} 中完成审核。）

@node math,mmap,logging,改进的模块
@anchor{whatsnew/3 8 math}@anchor{1e1}
@subsubsection math


添加了新的函数 @ref{1e2,,math.dist()} 用于计算两点之间的欧几里得距离。 （由 Raymond Hettinger 在 bpo-33089@footnote{https://bugs.python.org/issue33089} 中贡献。）

扩展了 @ref{1e3,,math.hypot()} 函数以便处理更多的维度。 之前它仅支持 2-D 的情况。 （由 Raymond Hettinger 在 bpo-33089@footnote{https://bugs.python.org/issue33089} 中贡献。）

添加了新的函数 @ref{1e4,,math.prod()} 作为的 @ref{1e5,,sum()} 同类，该函数返回 'start' 值 (默认值: 1) 乘以一个数字可迭代对象的积:

@example
>>> prior = 0.8
>>> likelihoods = [0.625, 0.84, 0.30]
>>> math.prod(likelihoods, start=prior)
0.126
@end example

（由 Pablo Galindo 在 bpo-35606@footnote{https://bugs.python.org/issue35606} 中贡献。）

添加了两个新的组合函数 @ref{1e6,,math.perm()} 和 @ref{1e7,,math.comb()}:

@example
>>> math.perm(10, 3)    # Permutations of 10 things taken 3 at a time
720
>>> math.comb(10, 3)    # Combinations of 10 things taken 3 at a time
120
@end example

（由 Yash Aggarwal, Keller Fuchs, Serhiy Storchaka 和 Raymond Hettinger 在 bpo-37128@footnote{https://bugs.python.org/issue37128}, bpo-37178@footnote{https://bugs.python.org/issue37178} 和 bpo-35431@footnote{https://bugs.python.org/issue35431} 中贡献。）

添加了一个新函数 @ref{1e8,,math.isqrt()} 用于计算精确整数平方根而无需转换为浮点数。 该新函数支持任意大整数。 它的执行速度比 @code{floor(sqrt(n))} 快但是比 @ref{1e9,,math.sqrt()} 慢:

@example
>>> r = 650320427
>>> s = r ** 2
>>> isqrt(s - 1)         # correct
650320426
>>> floor(sqrt(s - 1))   # incorrect
650320427
@end example

（由 Mark Dickinson 在 bpo-36887@footnote{https://bugs.python.org/issue36887} 中贡献。）

函数 @ref{1ea,,math.factorial()} 不再接受非整数类参数。 （由 Pablo Galindo 在 bpo-33083@footnote{https://bugs.python.org/issue33083} 中贡献。）

@node mmap,multiprocessing,math,改进的模块
@anchor{whatsnew/3 8 mmap}@anchor{1eb}
@subsubsection mmap


@ref{1ec,,mmap.mmap} 类现在具有一个 @ref{1ed,,madvise()} 方法用于访问 @code{madvise()} 系统调用。 （由 Zackery Spytz 在 bpo-32941@footnote{https://bugs.python.org/issue32941} 中贡献。）

@node multiprocessing,os,mmap,改进的模块
@anchor{whatsnew/3 8 multiprocessing}@anchor{1ee}
@subsubsection multiprocessing


添加了新的 @ref{bc,,multiprocessing.shared_memory} 模块。 （由 Davin Potts 在 bpo-35813@footnote{https://bugs.python.org/issue35813} 中贡献。）

在macOS上，现在默认使用的启动方式是*spawn*启动方式。
（由 Victor Stinner 在 bpo-33725@footnote{https://bugs.python.org/issue33725} 中贡献。）

@node os,os path,multiprocessing,改进的模块
@anchor{whatsnew/3 8 os}@anchor{1ef}
@subsubsection os


在 Windows 上添加了新函数 @ref{1c2,,add_dll_directory()} 用于在导入扩展模块或使用 @ref{2b,,ctypes} 加载 DLL 时为本机依赖提供额外搜索路径 。 （由 Steve Dower 在 bpo-36085@footnote{https://bugs.python.org/issue36085} 中贡献。）

添加了新的 @ref{1f0,,os.memfd_create()} 函数用于包装 @code{memfd_create()} 系统调用。 （由 Zackery Spytz 和 Christian Heimes 在 bpo-26836@footnote{https://bugs.python.org/issue26836} 中贡献。）

在 Windows 上，大部分用于处理重解析点,（包括符号链接和目录连接）的手动逻辑已被委托给操作系统。 特别地，@ref{1f1,,os.stat()} 现在将会遍历操作系统所支持的任何内容，而 @ref{1f2,,os.lstat()} 将只打开被标识为“名称代理”的重解析点，而其要由 @ref{1f1,,os.stat()} 打开其他的重解析点。 在所有情况下，@code{stat_result.st_mode} 将只为符号链接而非其他种类的重解析点设置 @code{S_IFLNK}。 要标识其他种类的重解析点，请检查新的 @code{stat_result.st_reparse_tag} 属性。

在 Windows 上，@ref{1f3,,os.readlink()} 现在能够读取目录连接。 请注意 @ref{1f4,,islink()} 会对目录连接返回 @code{False}，因此首先检查 @code{islink} 的代码将连续把连接视为目录，而会处理 @ref{1f3,,os.readlink()} 所引发错误的代码现在会把连接视为链接。

（由 Steve Dower 在 bpo-37834@footnote{https://bugs.python.org/issue37834} 中贡献。）

@node os path,pathlib,os,改进的模块
@anchor{whatsnew/3 8 os-path}@anchor{1f5}
@subsubsection os.path


返回布尔值结果的 @ref{c5,,os.path} 函数例如 @ref{1f6,,exists()}, @ref{1f7,,lexists()}, @ref{1f8,,isdir()}, @ref{1f9,,isfile()}, @ref{1f4,,islink()}, 以及 @ref{1fa,,ismount()} 现在对于包含在 OS 层级无法表示的字符或字节的路径将会返回 @code{False} 而不是引发 @ref{1fb,,ValueError} 或其子类 @ref{1fc,,UnicodeEncodeError} 和 @ref{1fd,,UnicodeDecodeError}。 （由 Serhiy Storchaka 在 bpo-33721@footnote{https://bugs.python.org/issue33721} 中贡献。）

@ref{1fe,,expanduser()} 在 Windows 上现在改用 
@geindex USERPROFILE
@geindex 环境变量; USERPROFILE
@code{USERPROFILE} 环境变量而不再使用 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME}，后者通常不会为一般用户账户设置。 （由 Anthony Sottile 在 bpo-36264@footnote{https://bugs.python.org/issue36264} 中贡献。）

@ref{1f8,,isdir()} 在 Windows 上将不再为不存在的目录的链接返回 @code{True}。

@ref{1ff,,realpath()} 在 Windows 上现在会识别重解析点，包括符号链接和目录连接。

（由 Steve Dower 在 bpo-37834@footnote{https://bugs.python.org/issue37834} 中贡献。）

@node pathlib,pickle,os path,改进的模块
@anchor{whatsnew/3 8 pathlib}@anchor{200}
@subsubsection pathlib


返回布尔值结果的 @ref{201,,pathlib.Path} 方法例如 @ref{202,,exists()}, @ref{203,,is_dir()}, @ref{204,,is_file()}, @ref{205,,is_mount()}, @ref{206,,is_symlink()}, @ref{207,,is_block_device()}, @ref{208,,is_char_device()}, @ref{209,,is_fifo()}, @ref{20a,,is_socket()} 现在对于包含在 OS 层级无法表示的字符或字节的路径将会返回 @code{False} 而不是引发 @ref{1fb,,ValueError} 或其子类 @ref{1fc,,UnicodeEncodeError}。 （由 Serhiy Storchaka 在 bpo-33721@footnote{https://bugs.python.org/issue33721} 中贡献。）

添加了 @ref{20b,,pathlib.Path.link_to()} 用于创建指向某个路径的硬链接。 （由 Joannah Nanjekye 在 bpo-26978@footnote{https://bugs.python.org/issue26978} 中贡献。）

@node pickle,plistlib,pathlib,改进的模块
@anchor{whatsnew/3 8 pickle}@anchor{20c}
@subsubsection pickle


@ref{ca,,pickle} 扩展子类化针对 C 优化的 @ref{20d,,Pickler} 现在可通过定义特殊的 @ref{20e,,reducer_override()} 方法来重载函数和类的封存逻辑。 （由 Pierre Glaser 和 Olivier Grisel 在 bpo-35900@footnote{https://bugs.python.org/issue35900} 中贡献。）

@node plistlib,pprint,pickle,改进的模块
@anchor{whatsnew/3 8 plistlib}@anchor{20f}
@subsubsection plistlib


添加了新的 @ref{210,,plistlib.UID} 并启动了对读取和写入经过 NSKeyedArchiver 编码的二进制 plists 的支持。 （由 Jon Janzen 在 bpo-26707@footnote{https://bugs.python.org/issue26707} 中贡献。）

@node pprint,py_compile,plistlib,改进的模块
@anchor{whatsnew/3 8 pprint}@anchor{211}
@subsubsection pprint


@ref{d2,,pprint} 模块为一些函数添加了 @emph{sort_dicts} 形参。 默认情况下，这些函数会继续在渲染或打印之前对字典进行排序。 但是，如果 @emph{sort_dicts} 设为假值，则字典将保持键插入时的顺序。 这在调试期间与 JSON 输入进行比较时会很有用。

除此之外，还增加了一个方便的新函数 @ref{212,,pprint.pp()}，它类似于 @ref{213,,pprint.pprint()} 但它的 @emph{sort_dicts} 默认为 @code{False}:

@example
>>> from pprint import pprint, pp
>>> d = dict(source='input.txt', operation='filter', destination='output.txt')
>>> pp(d, width=40)                  # Original order
@{'source': 'input.txt',
 'operation': 'filter',
 'destination': 'output.txt'@}
>>> pprint(d, width=40)              # Keys sorted alphabetically
@{'destination': 'output.txt',
 'operation': 'filter',
 'source': 'input.txt'@}
@end example

（由 Rémi Lapeyre 在 bpo-30670@footnote{https://bugs.python.org/issue30670} 中贡献。）

@node py_compile,shlex,pprint,改进的模块
@anchor{whatsnew/3 8 py-compile}@anchor{214}
@subsubsection py_compile


@ref{215,,py_compile.compile()} 现在支持静默模式。 （由 Joannah Nanjekye 在 bpo-22640@footnote{https://bugs.python.org/issue22640} 中贡献。）

@node shlex,shutil,py_compile,改进的模块
@anchor{whatsnew/3 8 shlex}@anchor{216}
@subsubsection shlex


新增了 @ref{217,,shlex.join()} 函数作为 @ref{218,,shlex.split()} 的逆操作。 （由 Bo Bayles 在 bpo-32102@footnote{https://bugs.python.org/issue32102} 中贡献。）

@node shutil,socket,shlex,改进的模块
@anchor{whatsnew/3 8 shutil}@anchor{219}
@subsubsection shutil


@ref{21a,,shutil.copytree()} 现在接受新的 @code{dirs_exist_ok} 关键字参数。 （由 Josh Bronson 在 bpo-20849@footnote{https://bugs.python.org/issue20849} 中贡献。）

@ref{21b,,shutil.make_archive()} 现在对新的归档默认使用 modern pax (POSIX.1-2001) 格式以提升可移植性和标准一致性，此特性继承自对 @ref{101,,tarfile} 模块的相应更改。 （由 C.A.M. Gerlach 在 bpo-30661@footnote{https://bugs.python.org/issue30661} 中贡献。）

@ref{21c,,shutil.rmtree()} 在 Windows 上现在会移除目录连接而不会递归地先移除其中的内容。 （由 Steve Dower 在 bpo-37834@footnote{https://bugs.python.org/issue37834} 中贡献。）

@node socket,ssl,shutil,改进的模块
@anchor{whatsnew/3 8 socket}@anchor{21d}
@subsubsection socket


添加了便捷的 @ref{21e,,create_server()} 和 @ref{21f,,has_dualstack_ipv6()} 函数以自动化在创建服务器套接字时通常情况下所必须的任务，包括在同一套接字中同时接受 IPv4 和 IPv6 连接。 （由 Giampaolo Rodolà 在 bpo-17561@footnote{https://bugs.python.org/issue17561} 中贡献。）

@ref{220,,socket.if_nameindex()}, @ref{221,,socket.if_nametoindex()} 和 @ref{222,,socket.if_indextoname()} 函数已经在 Windows 上实现。 （由 Zackery Spytz 在 bpo-37007@footnote{https://bugs.python.org/issue37007} 中贡献。）

@node ssl,statistics,socket,改进的模块
@anchor{whatsnew/3 8 ssl}@anchor{223}
@subsubsection ssl


增加了 @ref{224,,post_handshake_auth} 和 @ref{225,,verify_client_post_handshake()} 分别启用和初始化 TLS 1.3 握手后验证。 （由 Christian Heimes 在 bpo-34670@footnote{https://bugs.python.org/issue34670} 中贡献。）

@node statistics,sys,ssl,改进的模块
@anchor{whatsnew/3 8 statistics}@anchor{226}
@subsubsection statistics


添加了 @ref{227,,statistics.fmean()} 作为 @ref{199,,statistics.mean()} 的更快速的浮点数版版本。 （由 Raymond Hettinger 和 Steven D'Aprano 在 bpo-35904@footnote{https://bugs.python.org/issue35904} 中贡献。）

添加了 @ref{228,,statistics.geometric_mean()} （由 Raymond Hettinger 在 bpo-27181@footnote{https://bugs.python.org/issue27181} 中贡献。）

添加了 @ref{229,,statistics.multimode()} 用于返回最常见值的列表。 （由 Raymond Hettinger 在 bpo-35892@footnote{https://bugs.python.org/issue35892} 中贡献。）

添加了 @ref{22a,,statistics.quantiles()} 用于将数据或分布划分为多个等概率区间（例如四分位、十分位或百分位）。 （由 Raymond Hettinger 在 bpo-36546@footnote{https://bugs.python.org/issue36546} 中贡献。）

添加了 @ref{22b,,statistics.NormalDist} 用于创建和操纵随机变量的正态分布。 （由 Raymond Hettinger 在 bpo-36018@footnote{https://bugs.python.org/issue36018} 中贡献。）

@example
>>> temperature_feb = NormalDist.from_samples([4, 12, -3, 2, 7, 14])
>>> temperature_feb.mean
6.0
>>> temperature_feb.stdev
6.356099432828281

>>> temperature_feb.cdf(3)            # Chance of being under 3 degrees
0.3184678262814532
>>> # Relative chance of being 7 degrees versus 10 degrees
>>> temperature_feb.pdf(7) / temperature_feb.pdf(10)
1.2039930378537762

>>> el_niño = NormalDist(4, 2.5)
>>> temperature_feb += el_niño        # Add in a climate effect
>>> temperature_feb
NormalDist(mu=10.0, sigma=6.830080526611674)

>>> temperature_feb * (9/5) + 32      # Convert to Fahrenheit
NormalDist(mu=50.0, sigma=12.294144947901014)
>>> temperature_feb.samples(3)        # Generate random samples
[7.672102882379219, 12.000027119750287, 4.647488369766392]
@end example

@node sys,tarfile,statistics,改进的模块
@anchor{whatsnew/3 8 sys}@anchor{22c}
@subsubsection sys


添加了新的 @ref{22d,,sys.unraisablehook()} 函数，可被重载以便控制如何处理“不可引发的异常”。 它会在发生了一个异常但 Python 没有办法处理时被调用。 例如，当一个析构器在垃圾回收时 (@ref{22e,,gc.collect()}) 所引发的异常。 （由 Victor Stinner 在 bpo-36829@footnote{https://bugs.python.org/issue36829} 中贡献。）

@node tarfile,threading,sys,改进的模块
@anchor{whatsnew/3 8 tarfile}@anchor{22f}
@subsubsection tarfile


@ref{101,,tarfile} 模块现在对新的归档默认使用 modern pax (POSIX.1-2001) 格式而不再是之前的 GNU 专属格式。 这通过标准化和可扩展格式的统一编码 (UTF-8) 提升了跨平台可移植性，还提供了其他一些益处。 （由 C.A.M. Gerlach 在 bpo-36268@footnote{https://bugs.python.org/issue36268} 中贡献。）

@node threading,tokenize,tarfile,改进的模块
@anchor{whatsnew/3 8 threading}@anchor{230}
@subsubsection threading


添加了新的 @ref{231,,threading.excepthook()} 函数用来处理未捕获的 @ref{232,,threading.Thread.run()} 异常。 它可被重载以便控制如何处理未捕获的 @ref{232,,threading.Thread.run()} 异常。 （由 Victor Stinner 在 bpo-1230540@footnote{https://bugs.python.org/issue1230540} 中贡献。）

添加了新的 @ref{233,,threading.get_native_id()} 函数以及 @ref{234,,threading.Thread} 类的 @ref{235,,native_id} 属性。 它们会返回内核所分配给当前线程的原生整数线程 ID。 此特性仅在特定平台上可用，参见 @ref{233,,get_native_id} 了解详情。 （由 Jake Tesler 在 bpo-36084@footnote{https://bugs.python.org/issue36084} 中贡献。）

@node tokenize,tkinter,threading,改进的模块
@anchor{whatsnew/3 8 tokenize}@anchor{236}
@subsubsection tokenize


当提供不带末尾新行的输入时，@ref{111,,tokenize} 模块现在会隐式地添加 @code{NEWLINE} 形符。 此行为现在已与 C 词法分析器的内部行为相匹配。 （由 Ammar Askar 在 bpo-33899@footnote{https://bugs.python.org/issue33899} 中贡献。）

@node tkinter,time,tokenize,改进的模块
@anchor{whatsnew/3 8 tkinter}@anchor{237}
@subsubsection tkinter


在 @code{tkinter.Spinbox} 中添加了方法 @code{selection_from()}, @code{selection_present()}, @code{selection_range()} 和 @code{selection_to()}。 （由 Juliette Monsel 在 bpo-34829@footnote{https://bugs.python.org/issue34829} 中贡献。）

在 @code{tkinter.Canvas} 类中添加了方法 @code{moveto()}。 （由 Juliette Monsel 在 bpo-23831@footnote{https://bugs.python.org/issue23831} 中贡献。）

@code{tkinter.PhotoImage} 类现在具有 @code{transparency_get()} 和 @code{transparency_set()} 方法。 （由 Zackery Spytz 在 bpo-25451@footnote{https://bugs.python.org/issue25451} 中贡献。）

@node time,typing,tkinter,改进的模块
@anchor{whatsnew/3 8 time}@anchor{238}
@subsubsection time


为 macOS 10.12 添加了新的时钟 @ref{239,,CLOCK_UPTIME_RAW}。 （由 Joannah Nanjekye 在 bpo-35702@footnote{https://bugs.python.org/issue35702} 中贡献。）

@node typing,unicodedata,time,改进的模块
@anchor{whatsnew/3 8 typing}@anchor{23a}
@subsubsection typing


@ref{119,,typing} 模块加入了一些新特性：


@itemize *

@item 
一个带有键专属类型的字典类型。 参见 
@geindex Python 提高建议; PEP 589
PEP 589@footnote{https://www.python.org/dev/peps/pep-0589} 和 @ref{23b,,typing.TypedDict}。 TypedDict 只使用字符串作为键。 默认情况下每个键都要求提供。 指定 "total=False" 以允许键作为可选项:

@example
class Location(TypedDict, total=False):
    lat_long: tuple
    grid_square: str
    xy_coordinate: tuple
@end example

@item 
Literal 类型。 参见 
@geindex Python 提高建议; PEP 586
PEP 586@footnote{https://www.python.org/dev/peps/pep-0586} 和 @ref{23c,,typing.Literal}。 Literal 类型指明一个形参或返回值被限定为一个或多个特定的字面值:

@example
def get_status(port: int) -> Literal['connected', 'disconnected']:
    ...
@end example

@item 
"Final" 变量、函数、方法和类。 参见 
@geindex Python 提高建议; PEP 591
PEP 591@footnote{https://www.python.org/dev/peps/pep-0591}, @ref{23d,,typing.Final} 和 @ref{23e,,typing.final()}。 final 限定符会指示静态类型检查器限制进行子类化、重载或重新赋值:

@example
pi: Final[float] = 3.1415926536
@end example

@item 
协议定义。 参见 
@geindex Python 提高建议; PEP 544
PEP 544@footnote{https://www.python.org/dev/peps/pep-0544}, @ref{23f,,typing.Protocol} 和 @ref{240,,typing.runtime_checkable()}。 简单的 ABC 例如 @ref{241,,typing.SupportsInt} 现在是 @code{Protocol} 的子类。

@item 
新的协议类 @ref{242,,typing.SupportsIndex}。

@item 
新的函数 @ref{243,,typing.get_origin()} 和 @ref{244,,typing.get_args()}。
@end itemize

@node unicodedata,unittest,typing,改进的模块
@anchor{whatsnew/3 8 unicodedata}@anchor{245}
@subsubsection unicodedata


@ref{11a,,unicodedata} 模块现在已升级为使用 Unicode 12.1.0@footnote{http://blog.unicode.org/2019/05/unicode-12-1-en.html} 发布版。

新的函数 @ref{246,,is_normalized()} 可被用来验证字符串是否为特定正规形式，通常会比实际进行字符串正规化要快得多。 （由 Max Belanger, David Euresti 和 Greg Price 在 bpo-32285@footnote{https://bugs.python.org/issue32285} 和 bpo-37966@footnote{https://bugs.python.org/issue37966} 中贡献。）

@node unittest,venv,unicodedata,改进的模块
@anchor{whatsnew/3 8 unittest}@anchor{247}
@subsubsection unittest


添加了 @ref{248,,AsyncMock} 以支持异步版本的 @ref{249,,Mock}。 同时也添加了相应的断言函数用于测试。 （由 Lisa Roach 在 bpo-26467@footnote{https://bugs.python.org/issue26467} 中贡献。）

unittest 添加了 @ref{24a,,addModuleCleanup()} 和 @ref{24b,,addClassCleanup()} 以支持对 @code{setUpModule()} 和 @ref{24c,,setUpClass()} 进行清理。 （由 Lisa Roach 在 bpo-24412@footnote{https://bugs.python.org/issue24412} 中贡献。）

一些模拟断言函数现在也会在失败时打印一个实际调用列表。 （由 Petter Strandmark 在 bpo-35047@footnote{https://bugs.python.org/issue35047} 中贡献。）

@ref{11b,,unittest} 模块已支持通过 @ref{24d,,unittest.IsolatedAsyncioTestCase} 来使用协程作为测试用例。 （由 Andrew Svetlov 在 bpo-32972@footnote{https://bugs.python.org/issue32972} 中贡献。）

示例:

@example
import unittest


class TestRequest(unittest.IsolatedAsyncioTestCase):

    async def asyncSetUp(self):
        self.connection = await AsyncConnection()

    async def test_get(self):
        response = await self.connection.get("https://example.com")
        self.assertEqual(response.status_code, 200)

    async def asyncTearDown(self):
        await self.connection.close()


if __name__ == "__main__":
    unittest.main()
@end example

@node venv,weakref,unittest,改进的模块
@anchor{whatsnew/3 8 venv}@anchor{24e}
@subsubsection venv


现在 @ref{125,,venv} 在所有平台上都会包含 @code{Activate.ps1} 脚本用于在 PowerShell Core 6.1 下激活虚拟环境。 （由 Brett Cannon 在 bpo-32718@footnote{https://bugs.python.org/issue32718} 中贡献。）

@node weakref,xml,venv,改进的模块
@anchor{whatsnew/3 8 weakref}@anchor{24f}
@subsubsection weakref


由 @ref{250,,weakref.proxy()} 返回的代理对象现在除其他算术运算符外也支持矩阵乘法运算符 @code{@@} 和 @code{@@=}。 （由 Mark Dickinson 在 bpo-36669@footnote{https://bugs.python.org/issue36669} 中贡献。）

@node xml,xmlrpc,weakref,改进的模块
@anchor{whatsnew/3 8 xml}@anchor{251}
@subsubsection xml


作为对 DTD 和外部实体检索的缓解，在默认情况下 @ref{135,,xml.dom.minidom} 和 @ref{13b,,xml.sax} 模块不再处理外部实体。 （由 Christian Heimes 在 bpo-17239@footnote{https://bugs.python.org/issue17239} 中贡献。）

@ref{137,,xml.etree.ElementTree} 模块中的 @code{.find*()} 方法支持通配符搜索例如 @code{@{*@}tag}，此搜索会忽略命名空间以及返回给定命名空间中所有标签的 @code{@{namespace@}*}。 （由 Stefan Behnel 在 bpo-28238@footnote{https://bugs.python.org/issue28238} 中贡献。）

@ref{137,,xml.etree.ElementTree} 模块提供了实现 C14N 2.0 的新函数 @code{–xml.etree.ElementTree.canonicalize()}。 （由 Stefan Behnel 在 bpo-13611@footnote{https://bugs.python.org/issue13611} 中贡献。）

@ref{252,,xml.etree.ElementTree.XMLParser} 的目标对象可通过新的回调方法 @code{start_ns()} 和 @code{end_ns()} 来接受命名空间声明事件。 此外，@ref{253,,xml.etree.ElementTree.TreeBuilder} 目标可被配置为处理有关注释和处理指令事件以将它们包含在所生成的树当中。 （由 Stefan Behnel 在 bpo-36676@footnote{https://bugs.python.org/issue36676} 和 bpo-36673@footnote{https://bugs.python.org/issue36673} 中贡献。）

@node xmlrpc,,xml,改进的模块
@anchor{whatsnew/3 8 xmlrpc}@anchor{254}
@subsubsection xmlrpc


@ref{255,,xmlrpc.client.ServerProxy} 现在支持可选的 @emph{headers} 关键字参数作为随同每次请求发送的 HTTP 标头序列。 此特征的作用之一是使得从默认的基础认证升级到更快速的会话认证成为可能。 （由 Cédric Krier 在 bpo-35153@footnote{https://bugs.python.org/issue35153} 中贡献。）

@node 性能优化,构建和 C API 的改变,改进的模块,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 optimizations}@anchor{256}
@subsection 性能优化



@itemize *

@item 
@ref{f9,,subprocess} 模块现在能在某些情况下使用 @ref{257,,os.posix_spawn()} 函数以获得更好的性能。 目前，它的使用仅限 macOS 和 Linux（使用 glibc 2.24 或更新版本），并要求满足以下条件：


@itemize *

@item 
@emph{close_fds} 为假值；

@item 
@emph{preexec_fn}, @emph{pass_fds}, @emph{cwd} 和 @emph{start_new_session} 形参未设置；

@item 
@emph{executable} 路径包含一个目录。
@end itemize

（由 Joannah Nanjekye 和 Victor Stinner 在 bpo-35537@footnote{https://bugs.python.org/issue35537} 中贡献。）

@item 
@ref{258,,shutil.copyfile()}, @ref{259,,shutil.copy()}, @ref{25a,,shutil.copy2()}, @ref{21a,,shutil.copytree()} 和 @ref{25b,,shutil.move()} 在 Linux 和 macOS 上会使用平台专属的 "fast-copy" 系统调用以提高效率。 "fast-copy" 意味着拷贝操作发生于内核中，从而避免在进行 "@code{outfd.write(infd.read())}" 等操作时使用 Python 中的用户空间缓冲区。 在 Windows 上 @ref{258,,shutil.copyfile()} 会使用更大的默认缓冲区（1 MiB 而不是 16 KiB）并且使用基于 @ref{25c,,memoryview()} 的 @ref{25d,,shutil.copyfileobj()} 版本。 在同一分区内拷贝一个 512 MiB 文件的速度提升在 Linux 上约为 +26%，在 macOS 上为 +50%，在 Windows 上为 +40%。 此外还将消耗更少的 CPU 周期。 参见 @ref{25e,,依赖于具体平台的高效拷贝操作} 一节。 （由 Giampaolo Rodolà 在 bpo-33671@footnote{https://bugs.python.org/issue33671} 中贡献。）

@item 
@ref{21a,,shutil.copytree()} 会根据其所用缓存的 @ref{1f1,,os.stat()} 值使用 @ref{25f,,os.scandir()} 函数及所有拷贝函数。 拷贝一个包含 8000 文件的目录的速度提升在 Linux 上约为 +9%，在 Windows 上为 +20%，对于 Windows SMB 共享目录则为 +30%。 此外 @ref{1f1,,os.stat()} 系统调用的次数也减少了 38%，使得 @ref{21a,,shutil.copytree()} 在网络文件系统上会特别快速。 （由Giampaolo Rodolà 在 bpo-33695@footnote{https://bugs.python.org/issue33695} 中贡献。）

@item 
@ref{ca,,pickle} 模块使用的默认协议现在为 Protocol 4，最早在 Python 3.4 中被引入。 它提供了比自 Python 3.0 起可用的 Protocol 3 更好的性能和更小的数据尺寸。

@item 
从 @code{PyGC_Head} 移除了一个 @code{Py_ssize_t} 成员。 所有跟踪 GC 的对象（例如 tuple, list, dict）大小减少了 4 或 8 字节。 （由 Inada Naoki 在 bpo-33597@footnote{https://bugs.python.org/issue33597} 中贡献。）

@item 
@ref{260,,uuid.UUID} 现在会使用 @code{__slots__} 以减少内存足迹。 （由 Wouter Bolsterlee 和 Tal Einat 在 bpo-30977@footnote{https://bugs.python.org/issue30977} 中贡献。）

@item 
@ref{261,,operator.itemgetter()} 的性能提升了 33%。 优化了参数处理，并为常见的在元组中单个非负整数索引的情况新增了一条快速路径（这是标准库中的典型用例）。 （由 Raymond Hettinger 在 bpo-35664@footnote{https://bugs.python.org/issue35664} 中贡献。

@item 
加快了在 @ref{1b6,,collections.namedtuple()} 中的字段查找。 它们现在的速度快了两倍以上，成为 Python 中最快的实例变量查找形式。 （由 Raymond Hettinger, Pablo Galindo 和 Joe Jevnik, Serhiy Storchaka 在 bpo-32492@footnote{https://bugs.python.org/issue32492} 中贡献。）

@item 
如果输入的可迭代对象的长度已知 (即输入对象实现了 @code{__len__})，@ref{262,,list} 构造器不会过度分配内部项缓冲区。 这使得所创建的列表资源占用平均减少了 12%。 （由 Raymond Hettinger 和 Pablo Galindo 在 bpo-33234@footnote{https://bugs.python.org/issue33234} 中贡献。）

@item 
类变量写入速度加倍。 当一个非冗余属性被更新时，之前存在一个更新 slots 的非必要调用。 （由 Stefan Behnel, Pablo Galindo Salgado, Raymond Hettinger, Neil Schemenauer, 和 Serhiy Storchaka 在 bpo-36012@footnote{https://bugs.python.org/issue36012} 中贡献。）

@item 
减少了传递给许多内置函数和方法的参数转换的开销。 这使得某些简单内置函数和方法的速度提升了 20--50%。 （由 Serhiy Storchaka 在 bpo-23867@footnote{https://bugs.python.org/issue23867}, bpo-35582@footnote{https://bugs.python.org/issue35582} 和 bpo-36127@footnote{https://bugs.python.org/issue36127} 中贡献。）

@item 
@code{LOAD_GLOBAL} 指令现在会使用新的 "per opcode cache" 机制。 它的速度现在提升了大约 40%。 （由 Yury Selivanov 和 Inada Naoki 在 bpo-26219@footnote{https://bugs.python.org/issue26219} 中贡献。）
@end itemize

@node 构建和 C API 的改变,弃用,性能优化,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 build-and-c-api-changes}@anchor{263}
@subsection 构建和 C API 的改变



@itemize *

@item 
默认的 @ref{264,,sys.abiflags} 成为一个空字符串：pymalloc 的 @code{m} 旗标不再有意义（无论是否启用 pymalloc 构建都是兼容 ABI 的）因此已被移除。 （由 Victor Stinner 在 bpo-36707@footnote{https://bugs.python.org/issue36707} 中贡献。）

改变的例子：


@itemize *

@item 
只会安装 @code{python3.8} 程序，不再有 @code{python3.8m} 程序。

@item 
只会安装 @code{python3.8-config} 脚本，不再有 @code{python3.8m-config} 脚本。

@item 
@code{m} 旗标已经从动态库文件名后缀中移除：包括标准库中的扩展模块以及第三方包所产生和安装的模块例如从 PyPI 下载的模块。 以 Linux 为例，Python 3.7 的后缀 @code{.cpython-37m-x86_64-linux-gnu.so} 在 Python 3.8 中改为 @code{.cpython-38-x86_64-linux-gnu.so}。
@end itemize

@item 
重新组织了所有头文件以更好地区分不同种类的 API：


@itemize *

@item 
@code{Include/*.h} 应为可移植的公有稳定版 C API。

@item 
@code{Include/cpython/*.h} 应为 CPython 专属的不稳定版 C API；公有 API，部分私有 API 附加 @code{_Py} or @code{_PY} 前缀。

@item 
@code{Include/internal/*.h} 应为 CPython 特别专属的私有内部 C API。 此 API 不具备向下兼容保证并且不应在 CPython 以外被使用。 它们的公开仅适用于特别限定的需求例如调试器和性能分析等必须直接访问 CPython 内部数据而不通过调用函数的应用。 此 API 现在是通过 @code{make install} 安装的。
@end itemize

（由 Victor Stinner 在 bpo-35134@footnote{https://bugs.python.org/issue35134} 和 bpo-35081@footnote{https://bugs.python.org/issue35081} 中贡献，相关工作由 Eric Snow 在 Python 3.7 中发起。）

@item 
某些宏已被转换为静态内联函数：形参类型和返回类型定义良好，它们不再会有与宏相关的问题，变量具有局部作用域。 例如：


@itemize *

@item 
@ref{265,,Py_INCREF()}, @ref{266,,Py_DECREF()}

@item 
@ref{267,,Py_XINCREF()}, @ref{268,,Py_XDECREF()}

@item 
@code{PyObject_INIT()}, @code{PyObject_INIT_VAR()}

@item 
私有函数: @code{_PyObject_GC_TRACK()}, @code{_PyObject_GC_UNTRACK()}, @code{_Py_Dealloc()}
@end itemize

（由 Victor Stinner 在 bpo-35059@footnote{https://bugs.python.org/issue35059} 中贡献。）

@item 
@code{PyByteArray_Init()} 和 @code{PyByteArray_Fini()} 函数已被移除。 它们自 Python 2.7.4 和 Python 3.2.0 起就没有任何用处，被排除在受限 API (稳定版 ABI) 之外，并且未被写入文档。 （由 Victor Stinner 在 bpo-35713@footnote{https://bugs.python.org/issue35713} 中贡献。）

@item 
@code{PyExceptionClass_Name()} 的结果类型现在是 @code{const char *} 而非 @code{char *}。 （由 Serhiy Storchaka 在 bpo-33818@footnote{https://bugs.python.org/issue33818} 中贡献。）

@item 
@code{Modules/Setup.dist} 与 @code{Modules/Setup} 两者的共存已被移除。 之前在更新 CPython 源码树时，开发者必须手动拷贝 @code{Modules/Setup.dist} (在源码树内) 到 @code{Modules/Setup} (在构建树内) 以反映上游的任何改变。 旧特性对打包者来说有一点益处，但代价是对追踪 CPython 开发进程的开发者造成经常性的麻烦，因为忘记拷贝该文件可能导致构建失败。

现在构建系统总是会从源码树内的 @code{Modules/Setup} 读取数据。 建议希望定制该文件的开发者在 CPython 的一个 git 分叉或补丁文件中维护他们的更改，就如他们对源码树做任何其他改变时一样。

（由 Antoine Pitrou 在 bpo-32430@footnote{https://bugs.python.org/issue32430} 中贡献。）

@item 
将 Python 数字转换为 C 整型的函数例如 @ref{269,,PyLong_AsLong()} 以及带有 @code{'i'} 之类整型转换格式单元的参数解析函数例如 @ref{26a,,PyArg_ParseTuple()} 现在如果可能将会使用 @ref{18a,,__index__()} 特殊方法而不是 @ref{18b,,__int__()}。 对于带有 @code{__int__()} 方法但没有 @code{__index__()} 方法的对象 (例如 @ref{188,,Decimal} 和 @ref{185,,Fraction}) 将会发出弃用警告。 对于实现了 @code{__index__()} 的对象 @ref{26b,,PyNumber_Check()} 现在将返回 @code{1}。 @ref{26c,,PyNumber_Long()}, @ref{26d,,PyNumber_Float()} 和 @ref{26e,,PyFloat_AsDouble()} 现在如果可能也将会使用 @code{__index__()} 方法。 （由 Serhiy Storchaka 在 bpo-36048@footnote{https://bugs.python.org/issue36048} 和 bpo-20092@footnote{https://bugs.python.org/issue20092} 中贡献。）

@item 
堆分配类型对象现在将增加它们在 @ref{26f,,PyObject_Init()} (及其对应的宏 @code{PyObject_INIT}) 中的引用计数而不是在 @ref{270,,PyType_GenericAlloc()} 中。 修改实例分配或中止分配的类型可能需要进行调整。 （由 Elizondo 在 bpo-35810@footnote{https://bugs.python.org/issue35810} 中贡献。）

@item 
新增函数 @ref{271,,PyCode_NewWithPosOnlyArgs()} 允许创建代码对象例如 @ref{272,,PyCode_New()}，但带有一个额外的 @emph{posonlyargcount} 形参以指明仅限位置参数的数量。 （由 Pablo Galindo 在 bpo-37221@footnote{https://bugs.python.org/issue37221} 中贡献。）

@item 
@ref{273,,Py_SetPath()} 现在会将 @ref{274,,sys.executable} 设为程序完整路径 (@ref{275,,Py_GetProgramFullPath()}) 而不是程序名称 (@ref{276,,Py_GetProgramName()})。 （由 Victor Stinner 在 bpo-38234@footnote{https://bugs.python.org/issue38234} 中贡献。）
@end itemize

@node 弃用,API 与特性的移除,构建和 C API 的改变,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 deprecated}@anchor{277}
@subsection 弃用



@itemize *

@item 
distutils 的 @code{bdist_wininst} 命令现在已弃用，请改用 @code{bdist_wheel} (wheel 包)。 （由 Victor Stinner 在 bpo-37481@footnote{https://bugs.python.org/issue37481} 中贡献。）

@item 
@ref{137,,ElementTree} 模块中的已弃用方法 @code{getchildren()} 和 @code{getiterator()} 现在会引发 @ref{278,,DeprecationWarning} 而不是 @ref{279,,PendingDeprecationWarning}。 它们将在 Python 3.9 中被移除。 （由 Serhiy Storchaka 在 bpo-29209@footnote{https://bugs.python.org/issue29209} 中贡献。）

@item 
将不是 @ref{27a,,concurrent.futures.ThreadPoolExecutor} 的实例的对象传给 @ref{27b,,loop.set_default_executor()} 已被弃用，并将在 Python 3.9 中被禁止。 （由 Elvis Pranskevichus 在 bpo-34075@footnote{https://bugs.python.org/issue34075} 中贡献。）

@item 
@ref{27c,,xml.dom.pulldom.DOMEventStream}, @ref{27d,,wsgiref.util.FileWrapper} 和 @ref{27e,,fileinput.FileInput} 的 @ref{27f,,__getitem__()} 方法已被弃用。

这些方法的实现会忽略它们的 @emph{index} 形参，并改为返回下一条目。 （由 Berker Peksag 在 bpo-9372@footnote{https://bugs.python.org/issue9372} 中贡献。）

@item 
@ref{280,,typing.NamedTuple} 类已弃用了 @code{_field_types} 属性而改用具有同样信息的 @code{__annotations__} 属性。 （由 Raymond Hettinger 在 bpo-36320@footnote{https://bugs.python.org/issue36320} 中贡献。）

@item 
@ref{8,,ast} 类 @code{Num}, @code{Str}, @code{Bytes}, @code{NameConstant} 和 @code{Ellipsis} 被视为已弃用并将在未来的 Python 版本中被移除。 应当改用 @code{Constant}。 （由 Serhiy Storchaka 在 bpo-32892@footnote{https://bugs.python.org/issue32892} 中贡献。）

@item 
@ref{281,,ast.NodeVisitor} 的方法 @code{visit_Num()}, @code{visit_Str()}, @code{visit_Bytes()}, @code{visit_NameConstant()} 和 @code{visit_Ellipsis()} 现在已被弃用，并且在未来的 Python 版本中将不再被调用。 添加 @code{visit_Constant()} 方法来处理所有常量节点。 （由 Serhiy Storchaka 在 bpo-36917@footnote{https://bugs.python.org/issue36917} 中贡献。）

@item 
@ref{282,,asyncio.coroutine()} @ref{283,,decorator} 已弃用并将在 3.10 版中被移除。 原有的 @code{@@asyncio.coroutine} 请改用 @ref{284,,async def} 来替代。 （由 Andrew Svetlov 在 bpo-36921@footnote{https://bugs.python.org/issue36921} 中贡献。）

@item 
在 @ref{a,,asyncio} 中，@emph{loop} 参数的显式传递已被弃用并且到 3.10 版时将会在以下函数中被移除: @ref{285,,asyncio.sleep()}, @ref{286,,asyncio.gather()}, @ref{287,,asyncio.shield()}, @ref{288,,asyncio.wait_for()}, @ref{289,,asyncio.wait()}, @ref{28a,,asyncio.as_completed()}, @ref{1ad,,asyncio.Task}, @ref{28b,,asyncio.Lock}, @ref{28c,,asyncio.Event}, @ref{28d,,asyncio.Condition}, @ref{28e,,asyncio.Semaphore}, @ref{28f,,asyncio.BoundedSemaphore}, @ref{290,,asyncio.Queue}, @ref{291,,asyncio.create_subprocess_exec()} 以及 @ref{292,,asyncio.create_subprocess_shell()}。

@item 
将协程对象显式传递给 @ref{289,,asyncio.wait()} 的做法已被弃用并且将在 3.11 版中被移除。 （由 Yury Selivanov 在 bpo-34790@footnote{https://bugs.python.org/issue34790} 中贡献。）

@item 
@ref{89,,gettext} 模块中的下列函数和方法已被弃用: @ref{293,,lgettext()}, @ref{294,,ldgettext()}, @ref{295,,lngettext()} 和 @ref{296,,ldngettext()}。 它们返回已编码的字节串，如果转换后的字符串存在编码问题你将可能遭遇预期之外的异常。 更好的做法是使用 Python 3 中返回 Unicode 字符串的操作作为替代。 前面的函数都早已不宜使用。

函数 @ref{297,,bind_textdomain_codeset()}，方法 @ref{298,,output_charset()} 和 @ref{299,,set_output_charset()}，以及函数 @ref{29a,,translation()} 和 @ref{29b,,install()} 的 @emph{codeset} 形参也忆被弃用，因为它们仅适用于 @code{l*gettext()} 函数。 （由 Serhiy Storchaka 在 bpo-33710@footnote{https://bugs.python.org/issue33710} 中贡献。）

@item 
@ref{234,,threading.Thread} 的 @code{isAlive()} 方法已弃用。 （由 Dong-hee Na 在 bpo-35283@footnote{https://bugs.python.org/issue35283} 中贡献。）

@item 
许多接受整数参数的内置和扩展模块的函数现在将对传入 @ref{188,,Decimal}, @ref{185,,Fraction} 以及任何其他可被转换为整数但会丢失精度（即具有 @ref{18b,,__int__()} 方法但没有 @ref{18a,,__index__()} 方法）的对象发出弃用警告。 在未来的版本中则将报错。 （由 Serhiy Storchaka 在 bpo-36048@footnote{https://bugs.python.org/issue36048} 中贡献。）

@item 
以下参数作为关键字参数传递的方式已被弃用：


@itemize -

@item 
@ref{29c,,functools.partialmethod()}, @ref{29d,,weakref.finalize()}, @ref{29e,,profile.Profile.runcall()}, @code{cProfile.Profile.runcall()}, @ref{29f,,bdb.Bdb.runcall()}, @ref{2a0,,trace.Trace.runfunc()} 与 @ref{2a1,,curses.wrapper()} 中的 @emph{func}。

@item 
@ref{2a2,,unittest.TestCase.addCleanup()} 中的 @emph{function}。

@item 
@ref{27a,,concurrent.futures.ThreadPoolExecutor} 和 @ref{2a3,,concurrent.futures.ProcessPoolExecutor} 的  @ref{2a4,,submit()} 方法中的 @emph{fn}。

@item 
@ref{2a5,,contextlib.ExitStack.callback()}, @code{contextlib.AsyncExitStack.callback()} 和 @ref{2a6,,contextlib.AsyncExitStack.push_async_callback()} 中的 @emph{callback}。

@item 
@code{multiprocessing.managers.Server} 和 @code{multiprocessing.managers.SharedMemoryServer} 的 @code{create()} 方法中的 @emph{c} 和 @emph{typeid}。

@item 
@ref{29d,,weakref.finalize()} 中的 @emph{obj}。
@end itemize

在未来版本的 Python 中，它们将成为 @ref{2a7,,仅限位置参数}。 （由 Serhiy Storchaka 在 bpo-36492@footnote{https://bugs.python.org/issue36492} 中贡献。）
@end itemize

@node API 与特性的移除,移植到 Python 3 8,弃用,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 api-and-feature-removals}@anchor{2a8}
@subsection API 与特性的移除


下列特性与 API 已从 Python 3.8 中移除：


@itemize *

@item 
自 Python 3.3 起，从 @ref{1e,,collections} 导入 ABC 的做法已弃用，而应当从 @ref{1f,,collections.abc} 执行导入。 从 collections 导入的操作在 3.8 中已标记为被移除，但将推迟到 3.9 中实施。 （参见 bpo-36952@footnote{https://bugs.python.org/issue36952}。）

@item 
@code{macpath} 模块，在 Python 3.7 中弃用，现已被移除。 （由 Victor Stinner 在 bpo-35471@footnote{https://bugs.python.org/issue35471} 中贡献。）

@item 
函数 @code{platform.popen()} 已被移除，它自 Python 3.3 起就已被弃用：请改用 @ref{2a9,,os.popen()}。 （由 Victor Stinner 在 bpo-35345@footnote{https://bugs.python.org/issue35345} 中贡献。）

@item 
函数 @code{time.clock()} 已被移除，它自 Python 3.3 起就已被弃用：请根据具体需求改用 @ref{2aa,,time.perf_counter()} 或 @ref{2ab,,time.process_time()} 以获得具有良好定义的行为。 （由 Matthias Bussonnier 在 bpo-36895@footnote{https://bugs.python.org/issue36895} 中贡献。）

@item 
@code{pyvenv} 脚本已被移除，推荐改用 @code{python3.8 -m venv} 来帮助消除容易混淆 @code{pyvenv} 脚本所关联的 Python 解释器这一问题。 （由 Brett Cannon 在 bpo-25427@footnote{https://bugs.python.org/issue25427} 中贡献。）

@item 
@code{parse_qs}, @code{parse_qsl} 和 @code{escape} 已从 @ref{16,,cgi} 模块中被移除。 这些函数自 Python 3.2 或更早就已被弃用。 它们应改为从 @code{urllib.parse} 和 @code{html} 模块导入。

@item 
@code{filemode} 函数已从 @ref{101,,tarfile} 模块中被移除。 该函数未被写入文档，自 Python 3.3 起就已弃用。

@item 
@ref{252,,XMLParser} 构造器不再接受 @emph{html} 参数。 它从来没有任何作用并在 Python 3.4 中已被弃用。 所有其他形参现在都是 @ref{2ac,,仅限关键字参数}。 （由 Serhiy Storchaka 在 bpo-29209@footnote{https://bugs.python.org/issue29209} 中贡献。）

@item 
@ref{252,,XMLParser} 的 @code{doctype()} 方法已被移除。 （由 Serhiy Storchaka 在 bpo-29209@footnote{https://bugs.python.org/issue29209} 中贡献。）

@item 
"unicode_internal" 编解码器已被移除。 （由 Inada Naoki 在 bpo-36297@footnote{https://bugs.python.org/issue36297} 中贡献。）

@item 
@ref{f2,,sqlite3} 模块的 @code{Cache} 和 @code{Statement} 对象已不再公开给用户。 （由 Aviv Palivoda 在 bpo-30262@footnote{https://bugs.python.org/issue30262} 中贡献。）

@item 
@ref{2ad,,fileinput.input()} 和 @ref{27e,,fileinput.FileInput()} 中自 Python 3.6 起就已被忽略并弃用的 @code{bufsize} 关键字参数已被移除。 由 Matthias Bussonnier 在 bpo-36952@footnote{https://bugs.python.org/issue36952} 中贡献。）

@item 
在 Python 3.7 中弃用的函数 @code{sys.set_coroutine_wrapper()} 和 @code{sys.get_coroutine_wrapper()} 已被移除。 （由 Matthias Bussonnier 在 bpo-36933@footnote{https://bugs.python.org/issue36933} 中贡献。）
@end itemize

@node 移植到 Python 3 8,Python 3 8 1 中的重要变化,API 与特性的移除,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 porting-to-python-3-8}@anchor{2ae}
@subsection 移植到 Python 3.8


本节列出了先前描述的更改以及可能需要更改代码的其他错误修正.

@menu
* Python 行为的改变:: 
* Python API 的变化:: 
* C API 的变化:: 
* CPython 字节码的改变:: 
* 演示和工具:: 

@end menu

@node Python 行为的改变,Python API 的变化,,移植到 Python 3 8
@anchor{whatsnew/3 8 changes-in-python-behavior}@anchor{2af}
@subsubsection Python 行为的改变



@itemize *

@item 
yield 表达式（包括 @code{yield} 和 @code{yield from} 子句）现在不允许在推导式和生成器表达式中使用（但 @code{for} 子句最左边的可迭代对象表达式除外）。 （由 Serhiy Storchaka 在 bpo-10544@footnote{https://bugs.python.org/issue10544} 中贡献。）

@item 
当标识号检测 (@code{is} 和 @code{is not}) 与特定类型的字面值 (例如字符串和数字) 一同使用时编译器现在会产生 @ref{191,,SyntaxWarning}。  这在 CPython 中通常是可行的，但并不被语言定义所保证。 该警告会建议用户改用相等性检测 (@code{==} and @code{!=})。 （由 Serhiy Storchaka 在 bpo-34850@footnote{https://bugs.python.org/issue34850} 中贡献。）

@item 
CPython 解释器在某些情况下可以忽略异常。 在 Python 3.8 中这种情况会更少发生。 特别地，从类型字典获取属性时引发的异常不会再被忽略。 （由 Serhiy Storchaka 在 bpo-35459@footnote{https://bugs.python.org/issue35459} 中贡献。）

@item 
从内置类型 @ref{183,,bool}, @ref{184,,int}, @ref{187,,float}, @ref{189,,complex} 和标准库的一些类中移除了 @code{__str__} 实现。 它们现在会从 @ref{2b0,,object} 继承 @code{__str__()}。 作为结果，在这些类的子类中定义 @code{__repr__()} 方法将会影响它们的字符串表示。 （由 Serhiy Storchaka 在 bpo-36793@footnote{https://bugs.python.org/issue36793} 中贡献。）

@item 
在 AIX 上，@ref{2b1,,sys.platform} 将不再包含主要版本号。 它将总是 @code{'aix'} 而不再是 @code{'aix3'} .. @code{'aix7'}。 由于较旧的 Python 版本会包含该版本号，因此推荐总是使用 @code{sys.platform.startswith('aix')}。 （由 M. Felt 在 bpo-36588@footnote{https://bugs.python.org/issue36588} 中贡献。）

@item 
现在 @ref{2b2,,PyEval_AcquireLock()} 和 @ref{2b3,,PyEval_AcquireThread()} 如果当解释器终结化时被调用将会终结当前线程，以使它们与 @ref{2b4,,PyEval_RestoreThread()}, @ref{2b5,,Py_END_ALLOW_THREADS()} 以及 @ref{2b6,,PyGILState_Ensure()} 保持一致。 如果不想要这样的行为，请通过检测 @code{_Py_IsFinalizing()} 或 @code{sys.is_finalizing()} 来保护该调用。 （由 Joannah Nanjekye 在 bpo-36475@footnote{https://bugs.python.org/issue36475} 中贡献。）
@end itemize

@node Python API 的变化,C API 的变化,Python 行为的改变,移植到 Python 3 8
@anchor{whatsnew/3 8 changes-in-the-python-api}@anchor{2b7}
@subsubsection Python API 的变化



@itemize *

@item 
在 Windows 上 @ref{2b8,,os.getcwdb()} 函数现在会使用 UTF-8 编码格式而不是 ANSI 代码页：请参看 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529} 了解具体原因。 该函数在 Windows 上不再被弃用。 （由 Victor Stinner 在 bpo-37412@footnote{https://bugs.python.org/issue37412} 中贡献。）

@item 
现在 @ref{2b9,,subprocess.Popen} 在某些情况下会使用 @ref{257,,os.posix_spawn()} 以获得更好的性能。 在适用于 Linux 的 Windows 子系统和 QEMU 用户模拟器上，使用 @ref{257,,os.posix_spawn()} 的 @code{Popen} 构造器不会再因为“找不到程序”这样的错误引发异常。 而是让子进程失败并返回一个非零的 @code{returncode}。 （由 Joannah Nanjekye 和 Victor Stinner 在 bpo-35537@footnote{https://bugs.python.org/issue35537} 中贡献。）

@item 
The @emph{preexec_fn} argument of * @ref{2b9,,subprocess.Popen} is no longer
compatible with subinterpreters. The use of the parameter in a
subinterpreter now raises @ref{2ba,,RuntimeError}.
(Contributed by Eric Snow in bpo-34651@footnote{https://bugs.python.org/issue34651}, modified by Christian Heimes
in bpo-37951@footnote{https://bugs.python.org/issue37951}.)

@item 
@code{imap.IMAP4.logout()} 方法不会再静默地忽略任意异常。 （由 Victor Stinner 在 bpo-36348@footnote{https://bugs.python.org/issue36348} 中贡献。）

@item 
函数 @code{platform.popen()} 已被移除，它自 Python 3.3 起就已被弃用：请改用 @ref{2a9,,os.popen()}。 （由 Victor Stinner 在 bpo-35345@footnote{https://bugs.python.org/issue35345} 中贡献。）

@item 
当传入多模数据时 @ref{2bb,,statistics.mode()} 函数不会再引发异常。 它将改为返回在输入数据中遇到的第一个模式。 （由 Raymond Hettinger 在 bpo-35892@footnote{https://bugs.python.org/issue35892} 中贡献。）

@item 
@ref{2bc,,tkinter.ttk.Treeview} 类的 @ref{2bd,,selection()} 方法不再接受参数。 带参数调用该方法来改变选择在 Python 3.6 中已弃用。 请使用专门方法例如 @ref{2be,,selection_set()} 来改变选择。 （由 Serhiy Storchaka 在 bpo-31508@footnote{https://bugs.python.org/issue31508} 中贡献。）

@item 
@ref{135,,xml.dom.minidom} 的 @code{writexml()}, @code{toxml()} 和 @code{toprettyxml()} 方法以及 @code{xml.etree} 的 @code{write()} 方法现在会保留用户指定的属性顺序。 （由 Diego Rojas 和 Raymond Hettinger 在 bpo-34160@footnote{https://bugs.python.org/issue34160} 中贡献。）

@item 
附带 @code{'r'} 旗标打开的 @ref{33,,dbm.dumb} 数据库现在将是只读的。 如果数据库不存在，附带 @code{'r'} 和 @code{'w'} 旗标的 @ref{2bf,,dbm.dumb.open()} 不会再创建数据库。 （由 Serhiy Storchaka 在 bpo-32749@footnote{https://bugs.python.org/issue32749} 中贡献。）

@item 
在 @ref{252,,XMLParser} 的子类中定义的 @code{doctype()} 方法将不会再被调用，并将导致发出 @ref{2c0,,RuntimeWarning} 而不是 @ref{278,,DeprecationWarning}。 请在目标上定义 @ref{2c1,,doctype()} 方法来处理 XML doctype 声明。 （由 Serhiy Storchaka 在 bpo-29209@footnote{https://bugs.python.org/issue29209} 中贡献。）

@item 
现在当自定义元类未在传给 @code{type.__new__} 的命名空间中提供 @code{__classcell__} 入口时将引发 @ref{2ba,,RuntimeError}。 在 Python 3.6--3.7 中是则是引发 @ref{278,,DeprecationWarning}。 （由 Serhiy Storchaka 在 bpo-23722@footnote{https://bugs.python.org/issue23722} 中贡献。）

@item 
@code{cProfile.Profile} 类现在可被用作上下文管理器。 （由 Scott Sanderson 在 bpo-29235@footnote{https://bugs.python.org/issue29235} 中贡献。）

@item 
@ref{258,,shutil.copyfile()}, @ref{259,,shutil.copy()}, @ref{25a,,shutil.copy2()}, @ref{21a,,shutil.copytree()} 和 @ref{25b,,shutil.move()} 会使用平台专属的 "fast-copy" 系统调用（参见 @ref{25e,,依赖于具体平台的高效拷贝操作} 一节）。

@item 
@ref{258,,shutil.copyfile()} 在 Windows 上的默认缓冲区大小从 16 KiB 改为 1 MiB。

@item 
@code{PyGC_Head} 结构已被完全改变。 所有接触到该结构的代码都应当被重写。 （参见 bpo-33597@footnote{https://bugs.python.org/issue33597}。）

@item 
@ref{2c2,,PyInterpreterState} 结构已被移入 "internal" 头文件（特别是 Include/internal/pycore_pystate.h）。 不透明的 @code{PyInterpreterState} 作为仅有 API（以及稳定版 ABI）的一部分仍然可用。 文档指明该结构的任何字段都不是公有的，因此我们希望没人在使用它们。 但是，如果你确实依赖其中某一个或更多个私有字段并且没有其他替代选项，则请开一个 BPO 问题。 我们将尽力帮助你进行调整（可能包括向公有 API 添加访问器函数）。 （参见 bpo-35886@footnote{https://bugs.python.org/issue35886}。）

@item 
现在所有平台下的 @ref{2c3,,mmap.flush()} 方法都会在成功时返回 @code{None} 并在错误时引发异常。 之前它的行为取决于具体平台： Windows 下会在成功时返回非零值；在失败时返回零。 Unix 下会在成功时返回零；在失败时引发错误。 （由 Berker Peksag 在 bpo-2122@footnote{https://bugs.python.org/issue2122} 中贡献。）

@item 
@ref{135,,xml.dom.minidom} 和 @ref{13b,,xml.sax} 模块默认将不再处理外部实体。 （由 Christian Heimes 在 bpo-17239@footnote{https://bugs.python.org/issue17239} 中贡献。）

@item 
从只读的 @ref{32,,dbm} 数据库 (@ref{33,,dbm.dumb}, @ref{34,,dbm.gnu} 或 @ref{35,,dbm.ndbm}) 删除键将会引发 @code{error} (@ref{2c4,,dbm.dumb.error}, @ref{2c5,,dbm.gnu.error} 或 @ref{2c6,,dbm.ndbm.error}) 而不是 @ref{2c7,,KeyError}。 （由 Xiang Zhang 在 bpo-33106@footnote{https://bugs.python.org/issue33106} 中贡献。）

@item 
简化了字面值的 AST。 所有常量将被表示为 @code{ast.Constant} 的实例。 实例化旧类 @code{Num}, @code{Str}, @code{Bytes}, @code{NameConstant} 和 @code{Ellipsis} 都将返回 @code{Constant} 的实例。 （由 Serhiy Storchaka 在 bpo-32892@footnote{https://bugs.python.org/issue32892} 中贡献。）

@item 
@ref{1fe,,expanduser()} 在 Windows 上现在改用 
@geindex USERPROFILE
@geindex 环境变量; USERPROFILE
@code{USERPROFILE} 环境变量而不再使用 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME}，后者通常不会为一般用户账户设置。 （由 Anthony Sottile 在 bpo-36264@footnote{https://bugs.python.org/issue36264} 中贡献。）

@item 
The exception @ref{1a7,,asyncio.CancelledError} now inherits from
@ref{1a8,,BaseException} rather than @ref{1a9,,Exception} and no longer inherits
from @ref{1aa,,concurrent.futures.CancelledError}.
(Contributed by Yury Selivanov in bpo-32528@footnote{https://bugs.python.org/issue32528}.)

@item 
当使用 @ref{1ad,,asyncio.Task} 的实例时，函数 @ref{288,,asyncio.wait_for()} 现在会正确地等待撤销。 在此之前当达到 @emph{timeout} 时，它会被撤销并立即返回。 （由 Elvis Pranskevichus 在 bpo-32751@footnote{https://bugs.python.org/issue32751} 中贡献。）

@item 
当将 'socket' 作为 @emph{name} 形参传入时，函数 @ref{2c8,,asyncio.BaseTransport.get_extra_info()} 现在会返回一个可安全使用的套接字对象。 （由 Yury Selivanov 在 bpo-37027@footnote{https://bugs.python.org/issue37027} 中贡献。）

@item 
@ref{2c9,,asyncio.BufferedProtocol} 已经晋级为稳定 API。
@end itemize
@anchor{whatsnew/3 8 bpo-36085-whatsnew}@anchor{2ca}

@itemize *

@item 
在 Windows 上对扩展模块的 DLL 依赖以及通过 @ref{2b,,ctypes}  加载的 DLL 的解析现在将更为安全。 只有系统路径、包含相信 DLL 或 PYD 文件的路径以及通过 @ref{1c2,,add_dll_directory()} 添加的目录才会被作为加载时依赖的搜索位置。 特别地，
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 和当前工作目录将不再被使用，对它们的修改将不再对正常的 DLL 解析产生影响。 如果你的应用依赖于这些机制，你应当先检查 @ref{1c2,,add_dll_directory()}，如果它存在就用它在加载你的库时添加你的 DLL 目录。 请注意 Windows 7 用户还需要确保 Windows 更新包 KB2533623 已安装（这一点也会由安装器进行验证）。 （由 Steve Dower 在 bpo-36085@footnote{https://bugs.python.org/issue36085} 中贡献。）

@item 
关联到 pgen 的头文件和函数在其被纯 Python 实现取代后已被移除。 （由 Pablo Galindo 在 bpo-36623@footnote{https://bugs.python.org/issue36623} 中贡献。）

@item 
@ref{198,,types.CodeType} 在构造器的第二个位置新增了一个形参 (@emph{posonlyargcount}) 以支持在 
@geindex Python 提高建议; PEP 570
PEP 570@footnote{https://www.python.org/dev/peps/pep-0570} 中定义的仅限位置参数。 第一个参数 (@emph{argcount}) 现在表示位置参数的总数量 (包括仅限位置参数)。 @ref{198,,types.CodeType} 中新增的 @code{replace()} 方法可用于让代码支持 future 特性。
@end itemize

@node C API 的变化,CPython 字节码的改变,Python API 的变化,移植到 Python 3 8
@anchor{whatsnew/3 8 changes-in-the-c-api}@anchor{2cb}
@subsubsection C API 的变化



@itemize *

@item 
@ref{2cc,,PyCompilerFlags} 结构体添加了一个新的 @emph{cf_feature_version} 字段。 它应当被初始化为 @code{PY_MINOR_VERSION}。 该字段默认会被忽略，当且仅当 @code{PyCF_ONLY_AST} 在 @emph{cf_flags} 中设置旗标时才会被使用。 （由 Guido van Rossum 在 bpo-35766@footnote{https://bugs.python.org/issue35766} 中贡献。）

@item 
@code{PyEval_ReInitThreads()} 函数已从 C API 中移除。 它不应当被显式地调用；请改用 @ref{2cd,,PyOS_AfterFork_Child()}。 （由 Victor Stinner 在 bpo-36728@footnote{https://bugs.python.org/issue36728} 中贡献。）

@item 
在 Unix 上，C 扩展不会再被链接到 libpython，但 Android 和 Cygwin 例外。 当 Python 被嵌入时，@code{libpython} 不可使用 @code{RTLD_LOCAL} 加载，而要改用 @code{RTLD_GLOBAL}。 之前使用 @code{RTLD_LOCAL} 已经不可能加载未链接到 @code{libpython} 的 C 扩展了，例如通过 @code{Modules/Setup} 的 @code{*shared*} 部分构建的标准库 C 扩展。 （由 Victor Stinner 在 bpo-21536@footnote{https://bugs.python.org/issue21536} 中贡献。）

@item 
在解析或构建值时（例如 @ref{26a,,PyArg_ParseTuple()}, @ref{2ce,,Py_BuildValue()}, @ref{2cf,,PyObject_CallFunction()} 等等）使用形如 @code{#} 的格式而不定义 @code{PY_SSIZE_T_CLEAN} 现在将会引发 @code{DeprecationWarning}。 它将在 3.10 或 4.0 中被移除。 请参阅 @ref{2d0,,解析参数并构建值变量} 了解详情。 （由 Inada Naoki 在 bpo-36381@footnote{https://bugs.python.org/issue36381} 中贡献。）

@item 
堆分配类型的实例（例如使用 @ref{2d1,,PyType_FromSpec()} 创建的实例）会保存一个对其类型对象的引用。 提升这些类型对象引用计数的操作已从 @ref{270,,PyType_GenericAlloc()} 移至更低层级的函数 @ref{26f,,PyObject_Init()} 和 @code{PyObject_INIT()}。 这使用通过This makes types created through @ref{2d1,,PyType_FromSpec()} 所创建类型的行为与管理代码中的其他类保持一致。

静态分配类型将不受影响。

在大部分情况下，这应该都不会有附带影响。 但是，在分配实例后手动提升引用计数的类型（也许是为了绕过漏洞）现在可能永远不会被销毁。 要避免这种情况，这些类需要在实例撤销分配期间在类型对象上调用 Py_DECREF。

要正确地将这些类型移植到 3.8，请应用以下修改：


@itemize *

@item 
在分配实例之后在类型对象上移除 @ref{265,,Py_INCREF} —— 如果有的话。 这可以发生在调用 @ref{2d2,,PyObject_New()}, @ref{2d3,,PyObject_NewVar()}, @ref{2d4,,PyObject_GC_New()}, @ref{2d5,,PyObject_GC_NewVar()} 或任何其他使用 @ref{26f,,PyObject_Init()} 或 @code{PyObject_INIT()} 的自定义分配器之后。

示例:

@example
static foo_struct *
foo_new(PyObject *type) @{
    foo_struct *foo = PyObject_GC_New(foo_struct, (PyTypeObject *) type);
    if (foo == NULL)
        return NULL;
#if PY_VERSION_HEX < 0x03080000
    // Workaround for Python issue 35810; no longer necessary in Python 3.8
    PY_INCREF(type)
#endif
    return foo;
@}
@end example

@item 
确保所有堆分配类型的自定义 @code{tp_dealloc} 函数会减少类型的引用计数。

示例:

@example
static void
foo_dealloc(foo_struct *instance) @{
    PyObject *type = Py_TYPE(instance);
    PyObject_GC_Del(instance);
#if PY_VERSION_HEX >= 0x03080000
    // This was not needed before Python 3.8 (Python issue 35810)
    Py_DECREF(type);
#endif
@}
@end example
@end itemize

（由 Eddie Elizondo 在 bpo-35810@footnote{https://bugs.python.org/issue35810} 中贡献。）

@item 
@code{Py_DEPRECATED()} 宏已经针对 MSVC 实现。 这个宏现在必须放在符号名称之前。

示例:

@example
Py_DEPRECATED(3.8) PyAPI_FUNC(int) Py_OldFunction(void);
@end example

（由 Zackery Spytz 在 bpo-33407@footnote{https://bugs.python.org/issue33407} 中贡献。）

@item 
解释器将不再假装支持跨发布版本的扩展类型二进制兼容性。 由第三方扩展模块所导出的 @ref{2d6,,PyTypeObject} 应该具有当前 Python 版本所要求的所有空位，包括 @ref{2d7,,tp_finalize} (@ref{2d8,,Py_TPFLAGS_HAVE_FINALIZE} 不会再在读取 @ref{2d7,,tp_finalize} 之前被检查)。

（由 Antoine Pitrou 在 bpo-32388@footnote{https://bugs.python.org/issue32388} 中贡献。）

@item 
@ref{272,,PyCode_New()} 在第二个位置添加了新的形参 (@emph{posonlyargcount}) 以支持 
@geindex Python 提高建议; PEP 570
PEP 570@footnote{https://www.python.org/dev/peps/pep-0570}，指明仅限位置参数的数量。

@item 
函数 @code{PyNode_AddChild()} 和 @code{PyParser_AddToken()} 现在接受两个额外的 @code{int} 参数 @emph{end_lineno} 和 @emph{end_col_offset}。

@item 
允许 MinGW 工具直接链接到 @code{python38.dll} 的 @code{libpython38.a} 文件已不再包含于标准的 Windows 分发包中。 如果你需要此文件，可使用 @code{gendef} 和 @code{dlltool} 工具来生成它，这些工具是 MinGW binutils 包的一部分：

@example
gendef - python38.dll > tmp.def
dlltool --dllname python38.dll --def tmp.def --output-lib libpython38.a
@end example

已安装的 @code{pythonXY.dll} 所在位置将取决于安装选项以及 Windows 的版本和语言。 请参阅 @ref{2d9,,在Windows上使用 Python} 了解更多信息。 该结果库应当放在与 @code{pythonXY.lib} 相同的目录下，这通常是你的 Python 安装路径下的 @code{libs} 目录。

（由 Steve Dower 在 bpo-37351@footnote{https://bugs.python.org/issue37351} 中贡献。）
@end itemize

@node CPython 字节码的改变,演示和工具,C API 的变化,移植到 Python 3 8
@anchor{whatsnew/3 8 cpython-bytecode-changes}@anchor{2da}
@subsubsection CPython 字节码的改变



@itemize *

@item 
解释器循环已通过将块堆栈展开逻辑移入编译器获得了简化。 编译器现在会发出显式指令来调整值堆栈并为 @ref{2db,,break}, @ref{181,,continue} 和 @ref{190,,return} 调用清除代码。

移除了操作码 @code{BREAK_LOOP}, @code{CONTINUE_LOOP}, @code{SETUP_LOOP} 和 @code{SETUP_EXCEPT}。 添加了新的操作码 @ref{2dc,,ROT_FOUR}, @ref{2dd,,BEGIN_FINALLY}, @ref{2de,,CALL_FINALLY} 和 @ref{2df,,POP_FINALLY}。 修改了 @ref{2e0,,END_FINALLY} 和 @ref{2e1,,WITH_CLEANUP_START} 的行为。

（由 Mark Shannon, Antoine Pitrou 和 Serhiy Storchaka 在 bpo-17611@footnote{https://bugs.python.org/issue17611} 中贡献。）

@item 
添加了新的操作码 @ref{2e2,,END_ASYNC_FOR} 用于处理当等待 @ref{2e3,,async for} 循环的下一项时引发的异常。 （由 Serhiy Storchaka 在 bpo-33041@footnote{https://bugs.python.org/issue33041} 中贡献。）

@item 
@ref{2e4,,MAP_ADD} 现在会预期值为栈的第一个元素而键为第二个元素。 作出此改变以使得字典推导式能如 
@geindex Python 提高建议; PEP 572
PEP 572@footnote{https://www.python.org/dev/peps/pep-0572} 所提议的那样，键总是会在值之前被求值。 （由 Jörn Heissler 在 bpo-35224@footnote{https://bugs.python.org/issue35224} 中贡献。）
@end itemize

@node 演示和工具,,CPython 字节码的改变,移植到 Python 3 8
@anchor{whatsnew/3 8 demos-and-tools}@anchor{2e5}
@subsubsection 演示和工具


添加了一个检测脚本用于对访问变量的不同方式进行计时: @code{Tools/scripts/var_access_benchmark.py}。 （由 Raymond Hettinger 在 bpo-35884@footnote{https://bugs.python.org/issue35884} 中贡献。）

以下是自 Python 3.3 以来性能提升情况的总结:

@example
Python version                       3.3     3.4     3.5     3.6     3.7     3.8
--------------                       ---     ---     ---     ---     ---     ---

Variable and attribute read access:
    read_local                       4.0     7.1     7.1     5.4     5.1     3.9
    read_nonlocal                    5.3     7.1     8.1     5.8     5.4     4.4
    read_global                     13.3    15.5    19.0    14.3    13.6     7.6
    read_builtin                    20.0    21.1    21.6    18.5    19.0     7.5
    read_classvar_from_class        20.5    25.6    26.5    20.7    19.5    18.4
    read_classvar_from_instance     18.5    22.8    23.5    18.8    17.1    16.4
    read_instancevar                26.8    32.4    33.1    28.0    26.3    25.4
    read_instancevar_slots          23.7    27.8    31.3    20.8    20.8    20.2
    read_namedtuple                 68.5    73.8    57.5    45.0    46.8    18.4
    read_boundmethod                29.8    37.6    37.9    29.6    26.9    27.7

Variable and attribute write access:
    write_local                      4.6     8.7     9.3     5.5     5.3     4.3
    write_nonlocal                   7.3    10.5    11.1     5.6     5.5     4.7
    write_global                    15.9    19.7    21.2    18.0    18.0    15.8
    write_classvar                  81.9    92.9    96.0   104.6   102.1    39.2
    write_instancevar               36.4    44.6    45.8    40.0    38.9    35.5
    write_instancevar_slots         28.7    35.6    36.1    27.3    26.6    25.7

Data structure read access:
    read_list                       19.2    24.2    24.5    20.8    20.8    19.0
    read_deque                      19.9    24.7    25.5    20.2    20.6    19.8
    read_dict                       19.7    24.3    25.7    22.3    23.0    21.0
    read_strdict                    17.9    22.6    24.3    19.5    21.2    18.9

Data structure write access:
    write_list                      21.2    27.1    28.5    22.5    21.6    20.0
    write_deque                     23.8    28.7    30.1    22.7    21.8    23.5
    write_dict                      25.9    31.4    33.3    29.3    29.2    24.7
    write_strdict                   22.9    28.4    29.9    27.5    25.2    23.1

Stack (or queue) operations:
    list_append_pop                144.2    93.4   112.7    75.4    74.2    50.8
    deque_append_pop                30.4    43.5    57.0    49.4    49.2    42.5
    deque_append_popleft            30.8    43.7    57.3    49.7    49.7    42.8

Timing loop:
    loop_overhead                    0.3     0.5     0.6     0.4     0.3     0.3
@end example

基准测试是在 Intel® Core™ i7-4960HQ 处理器@footnote{https://ark.intel.com/content/www/us/en/ark/products/76088/intel-core-i7-4960hq-processor-6m-cache-up-to-3-80-ghz.html} 上运行从 python.org@footnote{https://www.python.org/downloads/mac-osx/} 获取的 macOS 64 位版得到的数据。 基准测试脚本显示时间以纳秒为单位。

@node Python 3 8 1 中的重要变化,Python 3 8 2 中的重要变化,移植到 Python 3 8,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 notable-changes-in-python-3-8-1}@anchor{2e6}
@subsection Python 3.8.1 中的重要变化


出于重要的安全性考量，@ref{2e7,,asyncio.loop.create_datagram_endpoint()} 的 @emph{reuse_address} 形参不再被支持。 这是由 UDP 中的套接字选项 @code{SO_REUSEADDR} 的行为导致的。 更多细节请参阅 @code{loop.create_datagram_endpoint()} 的文档。 （由 Kyle Stanley, Antoine Pitrou 和 Yury Selivanov 在 bpo-37228@footnote{https://bugs.python.org/issue37228} 中贡献。。）

@node Python 3 8 2 中的重要变化,Python 3 8 3 中的重要变化,Python 3 8 1 中的重要变化,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 notable-changes-in-python-3-8-2}@anchor{2e8}
@subsection Python 3.8.2 中的重要变化


修复了 @ref{21a,,shutil.copytree()} 的 @code{ignore} 回调中的回归问题。 现在该参数的类型已改回 str 和 List[str]。 （由 Manuel Barkhau 和 Giampaolo Rodola 在 bpo-39390@footnote{https://bugs.python.org/issue39390} 中贡献。）

@node Python 3 8 3 中的重要变化,,Python 3 8 2 中的重要变化,Python 3 8 有什么新变化
@anchor{whatsnew/3 8 notable-changes-in-python-3-8-3}@anchor{2e9}
@subsection Python 3.8.3 中的重要变化


@ref{0,,__future__} 模块中的 future 旗标常量值已获得更新以防止与 compiler 旗标相冲突。 在之前版本中 @code{PyCF_ALLOW_TOP_LEVEL_AWAIT} 与 @code{CO_FUTURE_DIVISION} 存在冲突。 （由 Batuhan Taskaya 在 bpo-39562@footnote{https://bugs.python.org/issue39562} 中贡献）

@node Python 3 7 有什么新变化,Python 3 6 有什么新变化,Python 3 8 有什么新变化,Python的新变化
@anchor{whatsnew/3 7 doc}@anchor{2ea}@anchor{whatsnew/3 7 what-s-new-in-python-3-7}@anchor{2eb}
@section Python 3.7 有什么新变化


@*编者: 
Elvis Pranskevichus <@email{elvis@@magic.io}>


@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number as a comment:
@c 
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer in :issue:`12345`.)
@c 
@c This saves the maintainer the effort of going through the Git log
@c when researching a change.

本文解释了 Python 3.7 相比 3.6 的新增特性。Python 3.7 于 2018 年 6 月 27 日发布。完整的详情可参阅 @ref{14c,,更新日志}。

@menu
* 摘要 - 发布重点: 摘要 - 发布重点<2>. 
* 新的特性: 新的特性<2>. 
* 其他语言特性修改: 其他语言特性修改<2>. 
* 新增模块: 新增模块<2>. 
* 改进的模块: 改进的模块<2>. 
* C API 的改变:: 
* 构建的改变:: 
* 性能优化: 性能优化<2>. 
* 其他 CPython 实现的改变:: 
* 已弃用的 Python 行为:: 
* 已弃用的 Python 模块、函数和方法:: 
* 已弃用的 C API 函数和类型:: 
* 平台支持的移除:: 
* API 与特性的移除: API 与特性的移除<2>. 
* 移除的模块:: 
* Windows 专属的改变:: 
* 移植到 Python 3.7: 移植到 Python 3 7. 
* Python 3.7.1 中的重要变化: Python 3 7 1 中的重要变化. 
* Python 3.7.2 中的重要变化: Python 3 7 2 中的重要变化. 
* Python 3.7.6 中的重要变化: Python 3 7 6 中的重要变化. 

@end menu

@node 摘要 - 发布重点<2>,新的特性<2>,,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 summary-release-highlights}@anchor{2ec}
@subsection 摘要 - 发布重点


@c This section singles out the most important changes in Python 3.7.
@c Brevity is key.

新的语法特性：


@itemize *

@item 
@ref{2ed,,PEP 563}，类型标注延迟求值。
@end itemize

向后不兼容的语法更改：


@itemize *

@item 
@ref{1a2,,async} 和 @ref{1a3,,await} 现在是保留的关键字。
@end itemize

新的库模块：


@itemize *

@item 
@ref{25,,contextvars}: @ref{2ee,,PEP 567 -- 上下文变量}

@item 
@ref{30,,dataclasses}: @ref{2ef,,PEP 557 -- 数据类}

@item 
@ref{2f0,,importlib.resources}
@end itemize

新的内置特性：


@itemize *

@item 
@ref{2f1,,PEP 553}, 新的 @ref{2f2,,breakpoint()} 函数。
@end itemize

对 Python 数据模型的改进：


@itemize *

@item 
@ref{2f3,,PEP 562}, 自定义可访问的模块属性。

@item 
@ref{2f4,,PEP 560}, typing模块和泛型类型的核心支持。

@item 
@ref{2f5,,dict} 对象会保持插入时的顺序这个特性 正式宣布@footnote{https://mail.python.org/pipermail/python-dev/2017-December/151283.html} 成为 Python 语言官方规范的一部分。
@end itemize

标准库中的重大改进：


@itemize *

@item 
@ref{a,,asyncio} 模块添加了新的功能，重大改进请参阅 @ref{2f6,,可用性与性能提升}。

@item 
@ref{10a,,time} 模块现在提供 @ref{2f7,,纳秒级精度函数} 的支持。
@end itemize

CPython 实现的改进：


@itemize *

@item 
避免使用 ASCII 作为默认的文本编码：


@itemize *

@item 
@ref{2f8,,PEP 538}，传统 C 区域强制转换

@item 
@ref{2f9,,PEP 540}，强制 UTF-8 运行时模式
@end itemize

@item 
@ref{2fa,,PEP 552}，确定性的 .pyc 文件

@item 
@ref{2fb,,新的开发运行时模式}

@item 
@ref{2fc,,PEP 565}，改进的 @ref{278,,DeprecationWarning} 处理
@end itemize

C API 的改进：


@itemize *

@item 
@ref{2fd,,PEP 539}，用于线程本地存储的新 C API
@end itemize

文档的改进：


@itemize *

@item 
@ref{2fe,,PEP 545}, Python 文档翻译

@item 
新的文档翻译：Japanese@footnote{https://docs.python.org/ja/}，French@footnote{https://docs.python.org/fr/} 和 Korean@footnote{https://docs.python.org/ko/}。
@end itemize

此版本在诸多方面有显著的性能改进。@ref{2ff,,性能优化} 章节详细列出了它们。

和之前的 Python 版本存在兼容性的更改列表，请参阅 @ref{300,,移植到 Python 3.7} 章节。

@node 新的特性<2>,其他语言特性修改<2>,摘要 - 发布重点<2>,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 new-features}@anchor{301}
@subsection 新的特性


@menu
* PEP 563：延迟的标注求值:: 
* PEP 538; 传统 C 区域强制转换: PEP 538 传统 C 区域强制转换. 
* PEP 540; 强制 UTF-8 运行时模式: PEP 540 强制 UTF-8 运行时模式. 
* PEP 553; 内置的 breakpoint(): PEP 553 内置的 breakpoint. 
* PEP 539; 用于线程局部存储的新 C API: PEP 539 用于线程局部存储的新 C API. 
* PEP 562; 定制对模块属性的访问: PEP 562 定制对模块属性的访问. 
* PEP 564; 具有纳秒级精度的新时间函数: PEP 564 具有纳秒级精度的新时间函数. 
* PEP 565; 在 __main__ 中显示 DeprecationWarning: PEP 565 在 __main__ 中显示 DeprecationWarning. 
* PEP 560; 对 typing 模块和泛型类型的核心支持: PEP 560 对 typing 模块和泛型类型的核心支持. 
* PEP 552; 基于哈希值的 .pyc 文件: PEP 552 基于哈希值的 pyc 文件. 
* PEP 545; Python 文档翻译: PEP 545 Python 文档翻译. 
* 开发运行时模式; -X dev: 开发运行时模式 -X dev. 

@end menu

@node PEP 563：延迟的标注求值,PEP 538 传统 C 区域强制转换,,新的特性<2>
@anchor{whatsnew/3 7 pep-563-postponed-evaluation-of-annotations}@anchor{302}@anchor{whatsnew/3 7 whatsnew37-pep563}@anchor{2ed}
@subsubsection PEP 563：延迟的标注求值


随着 
@geindex Python 提高建议; PEP 3107
PEP 3107@footnote{https://www.python.org/dev/peps/pep-3107} 加入标注功能并在 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} 进一步细化，Python 中类型提示的出现揭示了两个明显的可用性问题：


@itemize *

@item 
标注只能使用在当前作用域中已经存在的名称，也就是说，它们不支持任何形式的前向引用；而且——

@item 
标注源码对 Python 程序的启动时间有不利的影响。
@end itemize

这两个问题都可以通过延迟标注求值来解决。在定义标注的时候，编译器并不会编译执行相应表达式的代码，而是保存与相应表达式的 AST 等价的字符串形式。如果有需要，标注可以在运行时使用 @ref{303,,typing.get_type_hints()} 进行解析。在不需要这种解析的通常情况下，标注的存储成本更低（因为解析器只需处理较短的字符串）且启动时间更短。

在可用性方面，标注现在支持向前引用，以使以下句法有效:

@example
class C:
    @@classmethod
    def from_string(cls, source: str) -> C:
        ...

    def validate_b(self, obj: B) -> bool:
        ...

class B:
    ...
@end example

由于此修改会破坏兼容性，在 Python 3.7 中此种新的行为需要在每个模块层级上使用 @ref{0,,__future__} 导入来启用:

@example
from __future__ import annotations
@end example

它将在 Python 4.0 中成为默认行为。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 563

@item PEP 563@footnote{https://www.python.org/dev/peps/pep-0563} -- 延迟的标注求值

PEP 由 Łukasz Langa 撰写并实现。
@end table


@node PEP 538 传统 C 区域强制转换,PEP 540 强制 UTF-8 运行时模式,PEP 563：延迟的标注求值,新的特性<2>
@anchor{whatsnew/3 7 pep-538-legacy-c-locale-coercion}@anchor{304}@anchor{whatsnew/3 7 whatsnew37-pep538}@anchor{2f8}
@subsubsection PEP 538: 传统 C 区域强制转换


Python 3 系列有一个持续的挑战就是为处理 7 比特位 ASCII 文本的假定编码确定合理的默认策略，目前的设定是在非 Windows 平台上使用默认的 C 或 POSIX 区域设置。

@geindex Python 提高建议; PEP 538
PEP 538@footnote{https://www.python.org/dev/peps/pep-0538} 更新了默认的解释器命令行接口，以自动将上述区域强制转换为可用的基于 UTF-8 的区域，具体描述可参见有关新增环境变量 
@geindex PYTHONCOERCECLOCALE
@geindex 环境变量; PYTHONCOERCECLOCALE
@ref{305,,PYTHONCOERCECLOCALE} 的文档。 以这种方式自动设置 @code{LC_CTYPE} 意味着核心解释器和能感知区域的 C 扩展 (例如 @ref{de,,readline}) 都将会假定 UTF-8 已被用作默认的文本编码，而不再是 ASCII。

@geindex Python 提高建议; PEP 11
PEP 11@footnote{https://www.python.org/dev/peps/pep-0011} 中的平台支持定义也已被更新以限制完整文本处理支持适当配置的基于非 ASCII 的语言区域。

作为此更改的一部分，当使用任何已定义的强制转换目标区域时 (目前为 @code{C.UTF-8}, @code{C.utf8} 和 @code{UTF-8}) @ref{306,,stdin} 和 @ref{307,,stdout} 默认的处理器现在将为 @code{surrogateescape} (而不是 @code{strict})。 而无论是什么区域，@ref{308,,stderr} 默认的处理器仍为 @code{backslashreplace}。

默认情况下区域强制转换会静默进行，但为了辅助调试潜在的区域相关集成问题，可以通过设置 @code{PYTHONCOERCECLOCALE=warn} 来请求显式地启用警告信息（直接在 @ref{308,,stderr} 上发出）。 此设置还会使得 Python 运行时在核心解释器初始化时如果传统 C 区域仍然处于激活状态时发出警告。

虽然 
@geindex Python 提高建议; PEP 538
PEP 538@footnote{https://www.python.org/dev/peps/pep-0538} 的区域强制转换的好处在于它还会同时影响扩展模块 (例如 GNU @code{readline}) 以及子进程 (包括运行非 Python 应用和旧版本 Python 的子进程)，但它也存在需要所运行系统必须存在适合的目标区域的缺点。 为了更好地处理没有可用适合的目标区域的情况 (例如在 RHEL/CentOS 7 上就会出现此情况)，Python 3.7 还实现了 @ref{2f9,,PEP 540; 强制 UTF-8 运行时模式}。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 538

@item PEP 538@footnote{https://www.python.org/dev/peps/pep-0538} -- 强制转换传统 C 区域到基于 UTF-8 的区域

PEP 由 Nick Coghlan 撰写并实现。
@end table


@node PEP 540 强制 UTF-8 运行时模式,PEP 553 内置的 breakpoint,PEP 538 传统 C 区域强制转换,新的特性<2>
@anchor{whatsnew/3 7 pep-540-forced-utf-8-runtime-mode}@anchor{309}@anchor{whatsnew/3 7 whatsnew37-pep540}@anchor{2f9}
@subsubsection PEP 540: 强制 UTF-8 运行时模式


新的 @ref{155,,-X} @code{utf8} 命令行选项和 
@geindex PYTHONUTF8
@geindex 环境变量; PYTHONUTF8
@ref{30a,,PYTHONUTF8} 环境变量可被用来启用 CPython 的 @emph{UTF-8 模式}。

当处于 UTF-8 模式时，CPython 会忽略区域设置，并默认使用 UTF-8 编码。 用于 @ref{306,,sys.stdin} 和 @ref{307,,sys.stdout} 流的错误处理器将设置为 @code{surrogateescape}。

强制 UTF-8 模式可被用来在嵌入的 Python 解释器中改变文本处理行为，而不会改变嵌入方应用的区域设置。

@geindex Python 提高建议; PEP 540
PEP 540@footnote{https://www.python.org/dev/peps/pep-0540} 的 UTF-8 模式的好处是不必关心运行所在系统中有哪些可用区域即可工作，但它也存在对扩展模块 (例如 GNU @code{readline})、运行非 Python 应用的子进程以及运行旧版本 Python 的子进程不起作用的缺点。 为了减小与这些组件通信时破坏文本数据的风险，Python 3.7 还实现了 @ref{2f9,,PEP 540; 强制 UTF-8 运行时模式})。

UTF-8 模式在语言区域为 @code{C} 或 @code{POSIX} 并且 
@geindex Python 提高建议; PEP 538
PEP 538@footnote{https://www.python.org/dev/peps/pep-0538} 区域强制转换特性无法将其修改为某种基于 UTF-8 的替代项时会被默认启用（无论修改失败是由于设置了 @code{PYTHONCOERCECLOCALE=0}, @code{LC_ALL} 还是由于缺少适合的目标区域）。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 540

@item PEP 540@footnote{https://www.python.org/dev/peps/pep-0540} -- 增加了新的 UTF-8 模式

PEP 由 Victor Stinner 撰写并实现
@end table


@node PEP 553 内置的 breakpoint,PEP 539 用于线程局部存储的新 C API,PEP 540 强制 UTF-8 运行时模式,新的特性<2>
@anchor{whatsnew/3 7 pep-553-built-in-breakpoint}@anchor{30b}@anchor{whatsnew/3 7 whatsnew37-pep553}@anchor{2f1}
@subsubsection PEP 553: 内置的 @code{breakpoint()}


Python 3.7 包含了新的内置 @ref{2f2,,breakpoint()} 函数，作为一种简单方便地进入 Python 调试器的方式。

内置 @code{breakpoint()} 会调用 @ref{30c,,sys.breakpointhook()}。 在默认情况下后者会导入 @ref{c9,,pdb} 然后再调用 @code{pdb.set_trace()}，但是通过将 @code{sys.breakpointhook()} 绑定到你选定的函数，@code{breakpoint()} 可以进入任何调试器。 此外，环境变量 
@geindex PYTHONBREAKPOINT
@geindex 环境变量; PYTHONBREAKPOINT
@ref{30d,,PYTHONBREAKPOINT} 可被设置为你选定的调试器的可调用对象。 设置 @code{PYTHONBREAKPOINT=0} 会完全禁用内置 @code{breakpoint()}。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 553

@item PEP 553@footnote{https://www.python.org/dev/peps/pep-0553} -- 内置的 breakpoint()

PEP 由 Barry Warsaw 撰写并实现
@end table


@node PEP 539 用于线程局部存储的新 C API,PEP 562 定制对模块属性的访问,PEP 553 内置的 breakpoint,新的特性<2>
@anchor{whatsnew/3 7 pep-539-new-c-api-for-thread-local-storage}@anchor{30e}@anchor{whatsnew/3 7 whatsnew37-pep539}@anchor{2fd}
@subsubsection PEP 539: 用于线程局部存储的新 C API


虽然 Python 已提供了用于线程局部存储支持的 C API；但原有的 @ref{30f,,线程局部存储 (TLS) API} 使用 @code{int} 来表示所有平台上的 TLS 密钥。 对于官方支持的平台而言这通常不是问题，但这既不符合 POSIX 标准，也不具备任何实际意义上的可移植性。

@geindex Python 提高建议; PEP 539
PEP 539@footnote{https://www.python.org/dev/peps/pep-0539} 通过向 CPython 提供了一个新的 @ref{310,,线程特定存储 (TSS) API} 来改变这一点，它取代了原有的 CPython 内部 TLS API 的使用，并且原有 API 已弃用。 TSS API 使用一种新类型 @ref{311,,Py_tss_t} 而非 @code{int} 来表示 TSS 密钥 -- 这是一种不透明类型，其定义可能依赖于下层的 TLS 实现。 因此，这将允许在以无法安全地转换为 @code{int} 的方式定义原生 TLS 密钥的平台上构建 CPython。

请注意在原生 TLS 密钥定义方式无法被安全地转换为 @code{int} 的平台上，原有 TLS API 中的全部函数将无法执行并会立即返回失败信息。 这样能清楚地表明原有 API 在无法可靠使用的平台上不受支持，并且不会再尝试添加此类支持。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 539

@item PEP 539@footnote{https://www.python.org/dev/peps/pep-0539} -- 在 CPython 中用于线程局部存储的新 C-API

PEP 由 Erik M. Bray 撰写；由 Masayuki Yamamoto 实现。
@end table


@node PEP 562 定制对模块属性的访问,PEP 564 具有纳秒级精度的新时间函数,PEP 539 用于线程局部存储的新 C API,新的特性<2>
@anchor{whatsnew/3 7 pep-562-customization-of-access-to-module-attributes}@anchor{312}@anchor{whatsnew/3 7 whatsnew37-pep562}@anchor{2f3}
@subsubsection PEP 562: 定制对模块属性的访问


Python 3.7 允许在模块上定义 @ref{313,,__getattr__()} 并且当以其他方式找不到某个模块属性时将会调用它。 在模块上定义 @ref{314,,__dir__()} 现在也是允许的。

一个典型的可能有用的例子是已弃用模块属性和惰性加载。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 562

@item PEP 562@footnote{https://www.python.org/dev/peps/pep-0562} -- 模块的 @code{__getattr__} 和 @code{__dir__}

PEP 由 Ivan Levkivskyi 撰写并实现
@end table


@node PEP 564 具有纳秒级精度的新时间函数,PEP 565 在 __main__ 中显示 DeprecationWarning,PEP 562 定制对模块属性的访问,新的特性<2>
@anchor{whatsnew/3 7 pep-564-new-time-functions-with-nanosecond-resolution}@anchor{315}@anchor{whatsnew/3 7 whatsnew37-pep564}@anchor{2f7}
@subsubsection PEP 564: 具有纳秒级精度的新时间函数


现代系统的时钟精度可以超过由 @ref{316,,time.time()} 函数及其变化形式所返回的浮点数的有限精度。 为了避免精度损失，
@geindex Python 提高建议; PEP 564
PEP 564@footnote{https://www.python.org/dev/peps/pep-0564} 在 @ref{10a,,time} 模块中增加了原有计时器函数的六个新“纳秒版”变化形式:


@itemize *

@item 
@ref{317,,time.clock_gettime_ns()}

@item 
@ref{318,,time.clock_settime_ns()}

@item 
@ref{319,,time.monotonic_ns()}

@item 
@ref{31a,,time.perf_counter_ns()}

@item 
@ref{31b,,time.process_time_ns()}

@item 
@ref{31c,,time.time_ns()}
@end itemize

这些新函数会以整数值的形式返回纳秒数。

测量@footnote{https://www.python.org/dev/peps/pep-0564/#annex-clocks-resolution-in-python} 表明在 Linux 和 Windows 上 @ref{31c,,time.time_ns()} 的精度大约比 @ref{316,,time.time()} 要高 3 倍。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 564

@item PEP 564@footnote{https://www.python.org/dev/peps/pep-0564} -- 增加具有纳秒级精度的新时间函数

PEP 由 Victor Stinner 撰写并实现
@end table


@node PEP 565 在 __main__ 中显示 DeprecationWarning,PEP 560 对 typing 模块和泛型类型的核心支持,PEP 564 具有纳秒级精度的新时间函数,新的特性<2>
@anchor{whatsnew/3 7 pep-565-show-deprecationwarning-in-main}@anchor{31d}@anchor{whatsnew/3 7 whatsnew37-pep565}@anchor{2fc}
@subsubsection PEP 565: 在 @code{__main__} 中显示 DeprecationWarning


@ref{278,,DeprecationWarning} 的默认处理方式已经被更改，这此警告默认只显示一次，仅有当直接在 @ref{1,,__main__} 模块中运行的代码触发它们时才会再次显示。 因此，单文件脚本开发者以及 Python 交互模式使用者应该会再次开始看到针对他们所使用 API 的已弃用警告，但被导入应用、库和框架模块所触发的已弃用警告默认将继续隐藏。

作为此项更改的结果，标准库现在允许开发者在三种不同的已弃用警告行为之间进行选择:


@itemize *

@item 
@ref{31e,,FutureWarning}: 默认情况下总是会显示，建议用于应用程序最终用户应该看到的警告信息（例如对于已弃用的应用程序配置的设置选项）。

@item 
@ref{278,,DeprecationWarning}: 默认情况下仅在 @ref{1,,__main__} 中以及当运行测试时会显示，建议用于其他 Python 开发者应该看到的警告信息，提示版本升级可能导致行为改变或者错误。

@item 
@ref{279,,PendingDeprecationWarning}: 默认情况下仅在运行测试时会显示，可用于提示未来版本升级将会改变警告类别为 @ref{278,,DeprecationWarning} 或 @ref{31e,,FutureWarning} 的情况。
@end itemize

在此之前 @ref{278,,DeprecationWarning} 和 @ref{279,,PendingDeprecationWarning} 都仅在运行测试时可见，这意味着主要编写单文件脚本或使用 Python 交互模式的开发者可能会因他们所用 API 突然出现的改变而感到惊讶。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 565

@item PEP 565@footnote{https://www.python.org/dev/peps/pep-0565} -- 在 @code{__main__} 中显示 DeprecationWarning

PEP 由 Nick Coghlan 撰写并实现
@end table


@node PEP 560 对 typing 模块和泛型类型的核心支持,PEP 552 基于哈希值的 pyc 文件,PEP 565 在 __main__ 中显示 DeprecationWarning,新的特性<2>
@anchor{whatsnew/3 7 pep-560-core-support-for-typing-module-and-generic-types}@anchor{31f}@anchor{whatsnew/3 7 whatsnew37-pep560}@anchor{2f4}
@subsubsection PEP 560: 对 @code{typing} 模块和泛型类型的核心支持


@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} 最初的设计方式使其不会向核心 CPython 解释器引入 @emph{任何} 更改。 现在类型提示和 @ref{119,,typing} 模块已被社区广泛使用，因此这个限制已被取消。 这个 PEP 引入了两个特殊方法 @ref{320,,__class_getitem__()} 和 @code{__mro_entries__}，这些方法现在被 @ref{119,,typing} 中的大多数类和特殊构造所使用。 结果就是与类型相关的各类操作的速度提升了 7 倍，泛型类型可以在没有元类冲突的情况下被使用，而 @ref{119,,typing} 模块中几个长期存在的错误也已被修正。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 560

@item PEP 560@footnote{https://www.python.org/dev/peps/pep-0560} -- 对 typing 模块和泛型类型的核心支持

PEP 由 Ivan Levkivskyi 撰写并实现
@end table


@node PEP 552 基于哈希值的 pyc 文件,PEP 545 Python 文档翻译,PEP 560 对 typing 模块和泛型类型的核心支持,新的特性<2>
@anchor{whatsnew/3 7 pep-552-hash-based-pyc-files}@anchor{321}@anchor{whatsnew/3 7 whatsnew37-pep552}@anchor{2fa}
@subsubsection PEP 552: 基于哈希值的 .pyc 文件


传统上 Python 检查字节码缓存文件 (即 @code{.pyc} 文件) 是否最新的方式是通过对源码元数据 (最后更改的时间戳和大小）和生成缓存时保存在其文件头中的源码元数据进行比较。 这种检查方法虽然有效，但也存在缺点。 当文件系统的时间戳太粗糙时，Python 有可能错过源码更新，导致用户感到困惑。 此外，在缓存文件中存在时间戳对于 构建可再现@footnote{https://reproducible-builds.org/} 并且基于内容的构建系统来说是有问题的。

@geindex Python 提高建议; PEP 552
PEP 552@footnote{https://www.python.org/dev/peps/pep-0552} 扩展了 pyc 格式以允许使用源文件的哈希值而非源文件的时间戳来检查有效性。 这种 @code{.pyc} 文件就称为“基于哈希值的”。 默认情况下，Python 仍然使用基于时间戳的有效性检查，不会在运行时生成基于哈希值的 @code{.pyc} 文件。 基于哈希值的 @code{.pyc} 文件可以使用 @ref{d7,,py_compile} 或 @ref{21,,compileall} 来生成。

基于哈希值的 @code{.pyc} 文件包含两种变体：已选定和未选定。 Python 会在运行时针对相应源码文件验证已选定基于哈希值的 @code{.pyc} 文件，但对未选定基于哈希值的 pyc 文件则不会这样做。 未选定基于哈希值的 @code{.pyc} 文件对于需要由 Python 外部的系统（例如构建系统）负责使 @code{.pyc} 文件保持最新的环境来说是一种有用的性能优化。

请参阅 @ref{322,,已缓存字节码的失效} 了解更多信息。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 552

@item PEP 552@footnote{https://www.python.org/dev/peps/pep-0552} -- 确定性的 pyc 文件

PEP 由 Benjamin Peterson 撰写并实现
@end table


@node PEP 545 Python 文档翻译,开发运行时模式 -X dev,PEP 552 基于哈希值的 pyc 文件,新的特性<2>
@anchor{whatsnew/3 7 pep-545-python-documentation-translations}@anchor{323}@anchor{whatsnew/3 7 whatsnew37-pep545}@anchor{2fe}
@subsubsection PEP 545: Python 文档翻译


@geindex Python 提高建议; PEP 545
PEP 545@footnote{https://www.python.org/dev/peps/pep-0545} 描述了创建和维护 Python 文档翻译的整个过程。

新增了三个新的翻译版本:


@itemize -

@item 
日语: @indicateurl{https://docs.python.org/ja/}

@item 
法语: @indicateurl{https://docs.python.org/fr/}

@item 
韩语: @indicateurl{https://docs.python.org/ko/}
@end itemize


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 545

@item PEP 545@footnote{https://www.python.org/dev/peps/pep-0545} -- Python 文档翻译

PEP 由 Julien Palard, Inada Naoki 和 Victor Stinner 撰写并实现。
@end table


@node 开发运行时模式 -X dev,,PEP 545 Python 文档翻译,新的特性<2>
@anchor{whatsnew/3 7 development-runtime-mode-x-dev}@anchor{324}@anchor{whatsnew/3 7 whatsnew37-devmode}@anchor{2fb}
@subsubsection 开发运行时模式: -X dev


新的 @ref{155,,-X} @code{dev} 命令行选项或新的 
@geindex PYTHONDEVMODE
@geindex 环境变量; PYTHONDEVMODE
@ref{325,,PYTHONDEVMODE} 环境变量可被用来启用 CPython 的 @emph{开发模式}。 在开发模式下，CPython 会执行额外的在默认情况下开销过大的运行时检查。 请参阅 @ref{155,,-X} @code{dev} 文档查看对于此模式效果的完整描述。

@node 其他语言特性修改<2>,新增模块<2>,新的特性<2>,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 other-language-changes}@anchor{326}
@subsection 其他语言特性修改



@itemize *

@item 
@ref{1a3,,await} 表达式和包含 @ref{2e3,,async for} 子句的推导式不允许在 @ref{15c,,格式化字符串字面值} 的表达式中使用。 在 Python 3.7 中此限制已被取消。

@item 
现在可以将超过 255 个参数传递给一个函数，而现在一个函数也可以拥有超过 255 个形参。 （由 Serhiy Storchaka 在 bpo-12844@footnote{https://bugs.python.org/issue12844} 和 bpo-18896@footnote{https://bugs.python.org/issue18896} 中贡献。）

@item 
现在 @ref{327,,bytes.fromhex()} 和 @ref{328,,bytearray.fromhex()} 会忽略所有 ASCII 空白符，而非仅是空格符. （由 Robert Xiao 在 bpo-28927@footnote{https://bugs.python.org/issue28927} 中贡献。）

@item 
@ref{329,,str}, @ref{32a,,bytes} 和 @ref{32b,,bytearray} 获得了对新 @ref{32c,,isascii()} 方法的支持，该方法可被用来测试是个字符串或字节串是否仅包含 ASCII 字符。 （由 INADA Naoki 在 bpo-32677@footnote{https://bugs.python.org/issue32677} 中贡献。）

@item 
现在当 @code{from ... import ...} 失败时 @ref{32d,,ImportError} 会显示模块名称和模块 @code{__file__} 路径。 （由 Matthias Bussonnier 在 bpo-29546@footnote{https://bugs.python.org/issue29546} 中贡献。）

@item 
现在已支持涉及将子模块绑定到一个名称的绝对导入的循环导入。 （由 Serhiy Storchaka 在 bpo-30024@footnote{https://bugs.python.org/issue30024} 中贡献。）

@item 
现在 @code{object.__format__(x, '@w{'})} 等价于 @code{str(x)} 而非 @code{format(str(self), '@w{'})}。 （由 Serhiy Storchaka d  bpo-28974@footnote{https://bugs.python.org/issue28974} 中贡献。）

@item 
为更好地支持栈跟踪的动态创建，现在 @ref{32e,,types.TracebackType} 可以从 Python 代码中被实例化，并且 @ref{32f,,回溯对象} 的 @code{tb_next} 属性现在是可写的。 （由 Nathaniel J. Smith 在 bpo-30579@footnote{https://bugs.python.org/issue30579} 中贡献。）

@item 
当使用 @ref{330,,-m} 开关时，现在 @code{sys.path[0]} 会主动扩展为完整的起始目录路径，而不是保持为空目录（这将允许在发生导入时从 @emph{当前} 工作目录导入） （由 Nick Coghlan 在 bpo-33053@footnote{https://bugs.python.org/issue33053} 中贡献。）

@item 
新的 @ref{155,,-X} @code{importtime} 选项或 
@geindex PYTHONPROFILEIMPORTTIME
@geindex 环境变量; PYTHONPROFILEIMPORTTIME
@ref{331,,PYTHONPROFILEIMPORTTIME} 环境变量可被用来显示每次模块导入的时间。 （由 Victor Stinner 在 bpo-31415@footnote{https://bugs.python.org/issue31415} 中贡献。）
@end itemize

@node 新增模块<2>,改进的模块<2>,其他语言特性修改<2>,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 new-modules}@anchor{332}
@subsection 新增模块


@menu
* contextvars:: 
* dataclasses:: 
* importlib.resources: importlib resources. 

@end menu

@node contextvars,dataclasses,,新增模块<2>
@anchor{whatsnew/3 7 contextvars}@anchor{333}@anchor{whatsnew/3 7 whatsnew37-pep567}@anchor{2ee}
@subsubsection contextvars


新的 @ref{25,,contextvars} 模块和一组 @ref{334,,新的 C API} 引入了对 @emph{上下文变量} 的支持。 上下文变量在概念上类似于线程局部变量。 与 TLS 不同，上下文变量能正确地支持异步代码。

@ref{a,,asyncio} 和 @ref{36,,decimal} 已得到更新以使用和支持开箱即用的上下文变量。 特别是激活的 decimal 上下文现在将存储在上下文变量中，它允许十进制运算在异步代码中使用正确的上下文。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 567

@item PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} -- 上下文变量

PEP 由 Yury Selivanov 撰写并实现
@end table


@node dataclasses,importlib resources,contextvars,新增模块<2>
@anchor{whatsnew/3 7 dataclasses}@anchor{335}@anchor{whatsnew/3 7 whatsnew37-pep557}@anchor{2ef}
@subsubsection dataclasses


新的 @ref{336,,dataclass()} 装饰器提供了一种声明 @emph{数据类} 的方式。  数据类使用变量标注来描述其属性。 它的构造器和其他魔术方法例如 @ref{337,,__repr__()}, @ref{338,,__eq__()} 以及 @ref{339,,__hash__()} 会自动地生成。

示例:

@example
@@dataclass
class Point:
    x: float
    y: float
    z: float = 0.0

p = Point(1.5, 2.5)
print(p)   # produces "Point(x=1.5, y=2.5, z=0.0)"
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 557

@item PEP 557@footnote{https://www.python.org/dev/peps/pep-0557} -- 数据类

PEP 由 Eric V. Smith 撰写并实现
@end table


@node importlib resources,,dataclasses,新增模块<2>
@anchor{whatsnew/3 7 importlib-resources}@anchor{33a}@anchor{whatsnew/3 7 whatsnew37-importlib-resources}@anchor{2f0}
@subsubsection importlib.resources


新的 @ref{9e,,importlib.resources} 模块提供了一些新的 API 和一个新的 ABC 用于访问、打开和读取包内的 @emph{资源}。 资源基本上类似于包内的文件，但它们不一定是物理文件系统中实际的文件。 模块加载器可以提供 @code{get_resource_reader()} 函数，它会返回一个 @ref{33b,,importlib.abc.ResourceReader} 实例来支持这个新 API。 内置的文件路径加载器和 zip 文件加载器都支持此特性。

由 Barry Warsaw 和 Brett Cannon 在 bpo-32248@footnote{https://bugs.python.org/issue32248} 中贡献。


@subsubheading 参见


importlib_resources@footnote{http://importlib-resources.readthedocs.io/en/latest/} -- 用于先前 Python 版本的 PyPI 下层接口。


@node 改进的模块<2>,C API 的改变,新增模块<2>,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 improved-modules}@anchor{33c}
@subsection 改进的模块


@menu
* argparse:: 
* asyncio: asyncio<2>. 
* binascii:: 
* calendar:: 
* collections: collections<2>. 
* compileall:: 
* concurrent.futures: concurrent futures. 
* contextlib:: 
* cProfile: cProfile<2>. 
* crypt:: 
* datetime: datetime<2>. 
* dbm:: 
* decimal:: 
* dis:: 
* distutils:: 
* enum:: 
* functools: functools<2>. 
* gc: gc<2>. 
* hmac:: 
* http.client: http client. 
* http.server: http server. 
* idlelib 与 IDLE:: 
* importlib:: 
* io: io<2>. 
* ipaddress:: 
* itertools: itertools<2>. 
* locale:: 
* logging: logging<2>. 
* math: math<2>. 
* mimetypes:: 
* msilib:: 
* multiprocessing: multiprocessing<2>. 
* os: os<2>. 
* pathlib: pathlib<2>. 
* pdb:: 
* py_compile: py_compile<2>. 
* pydoc:: 
* queue:: 
* re:: 
* signal:: 
* socket: socket<2>. 
* socketserver:: 
* sqlite3:: 
* ssl: ssl<2>. 
* string:: 
* subprocess:: 
* sys: sys<2>. 
* time: time<2>. 
* tkinter: tkinter<2>. 
* tracemalloc:: 
* types:: 
* unicodedata: unicodedata<2>. 
* unittest: unittest<2>. 
* unittest.mock: unittest mock. 
* urllib.parse: urllib parse. 
* uu:: 
* uuid:: 
* warnings:: 
* xml.etree: xml etree. 
* xmlrpc.server: xmlrpc server. 
* zipapp:: 
* zipfile:: 

@end menu

@node argparse,asyncio<2>,,改进的模块<2>
@anchor{whatsnew/3 7 argparse}@anchor{33d}
@subsubsection argparse


新的 @ref{33e,,ArgumentParser.parse_intermixed_args()} 方法允许混合选项与位置参数。 （由 paul.j3 在 bpo-14191@footnote{https://bugs.python.org/issue14191} 中提供。）

@node asyncio<2>,binascii,argparse,改进的模块<2>
@anchor{whatsnew/3 7 asyncio}@anchor{33f}@anchor{whatsnew/3 7 whatsnew37-asyncio}@anchor{2f6}
@subsubsection asyncio


@ref{a,,asyncio} 模块获得了许多新的特性、可用性和 @ref{340,,性能提升}。 重要的改变包括:


@itemize *

@item 
新的 @ref{341,,暂定} @ref{1a5,,asyncio.run()} 函数可被用于通过自动创建和销毁事件循环以基于同步代码运行协程。 （由 Yury Selivanov 在 bpo-32314@footnote{https://bugs.python.org/issue32314} 中贡献。）

@item 
asyncio 增加支持 @ref{25,,contextvars}. @ref{342,,loop.call_soon()}, @ref{343,,loop.call_soon_threadsafe()}, @ref{344,,loop.call_later()}, @ref{345,,loop.call_at()} 并且 @ref{346,,Future.add_done_callback()} 具有新的可选仅关键字参数 @emph{context}。 现在 @ref{1ad,,Tasks} 会自动跟踪其上下文。 详情参见 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567}。 （由 Yury Selivanov 在 bpo-32436@footnote{https://bugs.python.org/issue32436} 中贡献。）

@item 
增加了新的 @ref{1ae,,asyncio.create_task()} 函数作为 @code{asyncio.get_event_loop().create_task()} 的快捷方式。 （由 Andrew Svetlov 在 bpo-32311@footnote{https://bugs.python.org/issue32311} 中贡献。）

@item 
新的 @ref{347,,loop.start_tls()} 方法可用于升级现有的 TLS 连接。 （由 Yury Selivanov 在 bpo-23749@footnote{https://bugs.python.org/issue23749} 中贡献。）

@item 
新的 @ref{348,,loop.sock_recv_into()} 方法允许直接从套接字读取数据放入所提供的缓冲区，从而可以减少数据复制。 （由 Antoine Pitrou 在 bpo-31819@footnote{https://bugs.python.org/issue31819} 中贡献。）

@item 
新的 @ref{349,,asyncio.current_task()} 函数可返回当前运行的 @ref{1ad,,Task} 实例，以及新的 @ref{34a,,asyncio.all_tasks()} 函数可返回给定循环中所有现存 @code{Task} 实例的集合。 @ref{34b,,Task.current_task()} 和 @ref{34c,,Task.all_tasks()} 方法已弃用。 （由 Andrew Svetlov 在 bpo-32250@footnote{https://bugs.python.org/issue32250} 中贡献。）

@item 
新的 @emph{暂定} @ref{2c9,,BufferedProtocol} 类允许通过手动控制接收缓冲区来实现流式协议。 （由 Yury Selivanov 在 bpo-32251@footnote{https://bugs.python.org/issue32251} 中贡献。）

@item 
新的 @ref{34d,,asyncio.get_running_loop()} 函数可返回当前运行的循环，如果没有循环在运行则引发 @ref{2ba,,RuntimeError}。 这与 @ref{34e,,asyncio.get_event_loop()} 不同，后者在没有循环在运行时将 @emph{创建} 一个新的事件循环。 （由 Yury Selivanov 在 bpo-32269@footnote{https://bugs.python.org/issue32269} 中提供。）

@item 
新的 @ref{34f,,StreamWriter.wait_closed()} 协程方法允许执行等待直到流写入器被关闭。 新的 @ref{350,,StreamWriter.is_closing()} 方法可用于确定写入器是否被关闭。 （由 Andrew Svetlov 在 bpo-32391@footnote{https://bugs.python.org/issue32391} 中贡献。）

@item 
新的 @ref{351,,loop.sock_sendfile()} 协程方法允许在可能的情况下使用 @ref{352,,os.sendfile} 发送文件。 （由 Andrew Svetlov 在 bpo-32410@footnote{https://bugs.python.org/issue32410} 中贡献。）

@item 
新的 @ref{353,,Future.get_loop()} 和 @code{Task.get_loop()} 方法会返回创建 task 或 future 对象的事件循环的实例。 @ref{354,,Server.get_loop()} 允许为 @ref{355,,asyncio.Server} 对象执行同样操作。 （由 Yury Selivanov 在 bpo-32415@footnote{https://bugs.python.org/issue32415} 中，以及由 Srinivas Reddy Thatiparthy 在 bpo-32418@footnote{https://bugs.python.org/issue32418} 中贡献。）

@item 
现在可以控制 @ref{355,,asyncio.Server} 的实例如何开启服务。 之前，服务在创建后将立即开启服务。 新的 @emph{start_serving} 关键字参数已添加到 @ref{356,,loop.create_server()} 和 @ref{357,,loop.create_unix_server()}，并且 @ref{358,,Server.start_serving()}, 和 @ref{359,,Server.serve_forever()} 可被用来分离服务的实例化和服务的开启。 新的 @ref{35a,,Server.is_serving()} 方法会在服务开启时返回 @code{True}。 现在 @ref{355,,Server} 对象已是异步上下文管理器:

@example
srv = await loop.create_server(...)

async with srv:
    # some code

# At this point, srv is closed and no longer accepts new connections.
@end example

（由 Yury Selivanov 在 bpo-32662@footnote{https://bugs.python.org/issue32662} 中贡献。）

@item 
由 @ref{344,,loop.call_later()} 所返回的回调对象已获得新的 @ref{35b,,when()} 方法，该方法会返回一个排入计划日程的绝对时间戳。 （由 Andrew Svetlov 在 bpo-32741@footnote{https://bugs.python.org/issue32741} 中贡献。）

@item 
@ref{2e7,,loop.create_datagram_endpoint()} 方法已获得对 Unix 套接字的支持。 （由 Quentin Dawans 在 bpo-31245@footnote{https://bugs.python.org/issue31245} 中贡献。）

@item 
@ref{35c,,asyncio.open_connection()}, @ref{35d,,asyncio.start_server()} functions, @ref{1b2,,loop.create_connection()}, @ref{356,,loop.create_server()}, @ref{35e,,loop.create_accepted_socket()} 方法及其对应的 UNIX 套接字变体现在接受 @emph{ssl_handshake_timeout} 关键字参数。 （由 Neil Aspinall 在 bpo-29970@footnote{https://bugs.python.org/issue29970} 中贡献。）

@item 
新的 @ref{35f,,Handle.cancelled()} 方法会在回调被取消时返回 @code{True}。 （由 Marat Sharafutdinov 在 bpo-31943@footnote{https://bugs.python.org/issue31943} 中贡献。）

@item 
asyncio 源已被转换为使用 @ref{1a2,,async}/@ref{1a3,,await} 语法。 （由 Andrew Svetlov 在 bpo-32193@footnote{https://bugs.python.org/issue32193} 中贡献。）

@item 
新的 @ref{360,,ReadTransport.is_reading()} 方法可用于确定传输的读取状态。 此外，对 @ref{361,,ReadTransport.resume_reading()} 和 @ref{362,,ReadTransport.pause_reading()} 的调用现在是幂等的。 （由 Yury Selivanov 在 bpo-32356@footnote{https://bugs.python.org/issue32356} 中贡献。）

@item 
接受套接字路径的循环方法现在支持传入 @ref{363,,路径类对象}。 （由 Yury Selivanov 在 bpo-32066@footnote{https://bugs.python.org/issue32066} 中贡献。）

@item 
在 @ref{a,,asyncio} 中，Linux 上的 TCP 套接字现在创建时默认带有 @code{TCP_NODELAY} 旗标设置。 （由 Yury Selivanov 和 Victor Stinner 在 bpo-27456@footnote{https://bugs.python.org/issue27456} 中贡献。）

@item 
在被取消任务中发生的异常不会再被记录。 （由 Yury Selivanov 在 bpo-30508@footnote{https://bugs.python.org/issue30508} 中贡献。）

@item 
新的 @code{WindowsSelectorEventLoopPolicy} 和 @code{WindowsProactorEventLoopPolicy} 类。 （由 Yury Selivanov 在 bpo-33792@footnote{https://bugs.python.org/issue33792} 中贡献。）
@end itemize

部分 @code{asyncio} API 改为 @ref{364,,已弃用}。

@node binascii,calendar,asyncio<2>,改进的模块<2>
@anchor{whatsnew/3 7 binascii}@anchor{365}
@subsubsection binascii


@ref{366,,b2a_uu()} 函数现在接受可选的 @emph{backtick} 关键字参数。 当其为真值时，零会以 @code{'`'} 而非空格来表示。 （由 Xiang Zhang 在 bpo-30103@footnote{https://bugs.python.org/issue30103} 中贡献。）

@node calendar,collections<2>,binascii,改进的模块<2>
@anchor{whatsnew/3 7 calendar}@anchor{367}
@subsubsection calendar


@ref{368,,HTMLCalendar} 类具有新的类属性，可以简化所生成 HTML 日历中 CSS 类的自定义。 （由 Oz Tiram 在 bpo-30095@footnote{https://bugs.python.org/issue30095} 中贡献。）

@node collections<2>,compileall,calendar,改进的模块<2>
@anchor{whatsnew/3 7 collections}@anchor{369}
@subsubsection collections


@code{collections.namedtuple()} 现在支持默认值。 （由 Raymond Hettinger 在 bpo-32320@footnote{https://bugs.python.org/issue32320} 中贡献。）

@node compileall,concurrent futures,collections<2>,改进的模块<2>
@anchor{whatsnew/3 7 compileall}@anchor{36a}
@subsubsection compileall


@ref{36b,,compileall.compile_dir()} 增加了新的 @emph{invalidation_mode} 形参，可用于启用 @ref{2fa,,基于哈希值的 .pyc 有效性检测}。 失效模式也可以在命令行中使用新的 @code{--invalidation-mode} 参数来指定。 （由 Benjamin Peterson 在 bpo-31650@footnote{https://bugs.python.org/issue31650} 中贡献。）

@node concurrent futures,contextlib,compileall,改进的模块<2>
@anchor{whatsnew/3 7 concurrent-futures}@anchor{36c}
@subsubsection concurrent.futures


@ref{2a3,,ProcessPoolExecutor} 和 @ref{27a,,ThreadPoolExecutor} 现在支持新的 @emph{初始化器} 以及 @emph{initargs} 构造器参数。 （由 Antoine Pitrou 在 bpo-21423@footnote{https://bugs.python.org/issue21423} 中贡献。）

@ref{2a3,,ProcessPoolExecutor} 现在能通过新的 @emph{mp_context} 参数来接受多进程上下文。 （由 Thomas Moreau 在 bpo-31540@footnote{https://bugs.python.org/issue31540} 中贡献。）

@node contextlib,cProfile<2>,concurrent futures,改进的模块<2>
@anchor{whatsnew/3 7 contextlib}@anchor{36d}
@subsubsection contextlib


新的 @ref{36e,,nullcontext()} 是一个比 @ref{36f,,ExitStack} 更简单和快速的无操作上下文管理器。 （由 Jesse-Bakker 在 bpo-10049@footnote{https://bugs.python.org/issue10049} 中贡献。）

增加了新的 @ref{370,,asynccontextmanager()}, @ref{371,,AbstractAsyncContextManager} 和 @ref{372,,AsyncExitStack} 以补充它们所对应的同步项。 （由 Jelle Zijlstra 在 bpo-29679@footnote{https://bugs.python.org/issue29679} 和 bpo-30241@footnote{https://bugs.python.org/issue30241} 中，以及由 Alexander Mohr 和 Ilya Kulakov 在 bpo-29302@footnote{https://bugs.python.org/issue29302} 中贡献。）

@node cProfile<2>,crypt,contextlib,改进的模块<2>
@anchor{whatsnew/3 7 cprofile}@anchor{373}
@subsubsection cProfile


@ref{28,,cProfile} 命令行现在接受 @code{-m module_name} 作为脚本路径的替代。 （由 Sanyam Khurana 在 bpo-21862@footnote{https://bugs.python.org/issue21862} 中贡献。）

@node crypt,datetime<2>,cProfile<2>,改进的模块<2>
@anchor{whatsnew/3 7 crypt}@anchor{374}
@subsubsection crypt


@ref{29,,crypt} 模块现在支持 Blowfish 哈希方法。 （由 Serhiy Storchaka 在 bpo-31664@footnote{https://bugs.python.org/issue31664} 中贡献。）

@ref{375,,mksalt()} 函数现在允许指定哈希操作的轮数。 （由 Serhiy Storchaka 在 bpo-31702@footnote{https://bugs.python.org/issue31702} 中贡献。）

@node datetime<2>,dbm,crypt,改进的模块<2>
@anchor{whatsnew/3 7 datetime}@anchor{376}
@subsubsection datetime


新的 @ref{377,,datetime.fromisoformat()} 方法会基于由 @code{datetime.isoformat()} 所输出的某一特定格式字符串构建 @ref{194,,datetime} 对象。 （由 Paul Ganssle 在 bpo-15873@footnote{https://bugs.python.org/issue15873} 中贡献。）

@ref{378,,tzinfo} 类现在支持小于一分钟的偏移量。 （由 Alexander Belopolsky 在 bpo-5288@footnote{https://bugs.python.org/issue5288} 中贡献。）

@node dbm,decimal,datetime<2>,改进的模块<2>
@anchor{whatsnew/3 7 dbm}@anchor{379}
@subsubsection dbm


@ref{33,,dbm.dumb} 现在支持读取只读文件，并且在其未改变时不再写入索引文件。

@node decimal,dis,dbm,改进的模块<2>
@anchor{whatsnew/3 7 decimal}@anchor{37a}
@subsubsection decimal


@ref{36,,decimal} 模块现在使用 @ref{2ee,,上下文变量} 来储存十进制值上下文。 （由 Yury Selivanov 在 bpo-32630@footnote{https://bugs.python.org/issue32630} 中贡献。）

@node dis,distutils,decimal,改进的模块<2>
@anchor{whatsnew/3 7 dis}@anchor{37b}
@subsubsection dis


@ref{37c,,dis()} 函数现在能够反汇编嵌套的代码对象（推导式、生成器表达式和嵌套函数的代码，以及用于构建嵌套类的代码）。 反汇编递归的最大深度由新的 @emph{depth} 形参来控制。 （由 Serhiy Storchaka 在 bpo-11822@footnote{https://bugs.python.org/issue11822} 中贡献。）

@node distutils,enum,dis,改进的模块<2>
@anchor{whatsnew/3 7 distutils}@anchor{37d}
@subsubsection distutils


@code{README.rst} 现在包含在 distutils 的标准 README 列表之中，因而也包含在源码发布之中。 （由 Ryan Gonzalez 在 bpo-11913@footnote{https://bugs.python.org/issue11913} 中贡献。）

@node enum,functools<2>,distutils,改进的模块<2>
@anchor{whatsnew/3 7 enum}@anchor{37e}
@subsubsection enum


@ref{37f,,Enum} 增加了新的 @code{_ignore_} 类特征属性，该属性允许列出不应当成为枚举成员的特征属性名称。 （由 Ethan Furman 在 bpo-31801@footnote{https://bugs.python.org/issue31801} 中贡献。）

在 Python 3.8 中，尝试在 @code{Enum} 类中检查非 Enum 对象将引发 @ref{192,,TypeError} (例如 @code{1 in Color})；类似地，尝试在 @code{Flag} 成员中检查非 Flag 对象也将引发 @ref{192,,TypeError} (例如 @code{1 in Perm.RW})；目前，两种操作均会返回 @ref{380,,False} 并且已弃用。 （由 Ethan Furman 在 bpo-33217@footnote{https://bugs.python.org/issue33217} 中贡献。）

@node functools<2>,gc<2>,enum,改进的模块<2>
@anchor{whatsnew/3 7 functools}@anchor{381}
@subsubsection functools


@ref{382,,functools.singledispatch()} 现在支持使用类型标注来注册实现。 （由 Łukasz Langa 在 bpo-32227@footnote{https://bugs.python.org/issue32227} 中贡献。）

@node gc<2>,hmac,functools<2>,改进的模块<2>
@anchor{whatsnew/3 7 gc}@anchor{383}
@subsubsection gc


新的 @ref{384,,gc.freeze()} 函数允许冻结由垃圾回收器所跟踪的所有对象，并将它们从未来的集合中排除。 这可以在 POSIX @code{fork()} 调用之前使用以令 GC 友好地进行写入时复制或加速收集。 新的 @ref{385,,gc.unfreeze()} 函数会反转此操作。 此外，@ref{386,,gc.get_freeze_count()} 可被用于获取冻结对象的数量。 （由 Li Zekun 在 bpo-31558@footnote{https://bugs.python.org/issue31558} 中贡献。）

@node hmac,http client,gc<2>,改进的模块<2>
@anchor{whatsnew/3 7 hmac}@anchor{387}
@subsubsection hmac


@ref{8f,,hmac} 现在具有经优化的一次性 @ref{388,,digest()} 函数，其速度比 @code{HMAC()} 要快三倍。 （由 Christian Heimes 在 bpo-32433@footnote{https://bugs.python.org/issue32433} 中贡献。）

@node http client,http server,hmac,改进的模块<2>
@anchor{whatsnew/3 7 http-client}@anchor{389}
@subsubsection http.client


@ref{38a,,HTTPConnection} 和 @ref{38b,,HTTPSConnection} 现在支持新的 @emph{blocksize} 参数以提升上传吞吐量。 （由 Nir Soffer 在 bpo-31945@footnote{https://bugs.python.org/issue31945} 中贡献。）

@node http server,idlelib 与 IDLE,http client,改进的模块<2>
@anchor{whatsnew/3 7 http-server}@anchor{38c}
@subsubsection http.server


@ref{38d,,SimpleHTTPRequestHandler} 现在支持 HTTP @code{If-Modified-Since} 标头。 如果目标文件在该标点指定的时间之后未被修改则服务器会返回 304 响应状态。 （由 Pierre Quentel 在 bpo-29654@footnote{https://bugs.python.org/issue29654} 中贡献。）

@ref{38d,,SimpleHTTPRequestHandler} 接受新的 @emph{directory} 参数并增加了新的 @code{--directory} 命令行参数。 通过此形参，服务器可以对服务指定目录，默认情况下它使用当前工作目录。 （由 Stéphane Wirtel 和 Julien Palard 在 bpo-28707@footnote{https://bugs.python.org/issue28707} 中贡献。）

新的 @ref{38e,,ThreadingHTTPServer} 类使用线程来处理使用 @code{ThreadingMixin} 的请求。 它会在 @code{http.server} 附带 @code{-m} 运行时被使用。 （由 Julien Palard 在 bpo-31639@footnote{https://bugs.python.org/issue31639} 中贡献。）

@node idlelib 与 IDLE,importlib,http server,改进的模块<2>
@anchor{whatsnew/3 7 idlelib-and-idle}@anchor{38f}
@subsubsection idlelib 与 IDLE


多个对自动补全的修正。 （由 Louie Lu 在 bpo-15786@footnote{https://bugs.python.org/issue15786} 中贡献。）

Module Browser (在 File 菜单中，之前称为 Class Browser) 现在会在最高层级函数和类之外显示嵌套的函数和类。 （由 Guilherme Polo, Cheryl Sabella 和 Terry Jan Reedy 在 bpo-1612262@footnote{https://bugs.python.org/issue1612262} 中贡献。）

Settings 对话框 (Options 中的 Configure IDLE) 已经被部分重写以改进外观和功能。 （由 Cheryl Sabella 和 Terry Jan Reedy 在多个问题项中贡献。）

字体样本现在包括一组非拉丁字符以便用户能更好地查看所选特定字体的效果。 （由 Terry Jan Reedy 在 bpo-13802@footnote{https://bugs.python.org/issue13802} 中贡献。） 样本可以被修改以包括其他字符。 （由 Serhiy Storchaka 在 bpo-31860@footnote{https://bugs.python.org/issue31860} 中贡献。）

之前以扩展形式实现的 IDLE 特性已作为正常特性重新实现。 它们的设置已从 Extensions 选项卡移至其他对话框选项卡。 （由 Charles Wohlganger 和 Terry Jan Reedy 在 bpo-27099@footnote{https://bugs.python.org/issue27099} 中实现。）

编辑器代码上下文选项已经过修改。 Box 会显示所有上下文行直到最大行数。 点击一个上下文行会使编辑器跳转到该行。 自定义主题的上下文颜色已添加到 Settings 对话框的 Highlights 选项卡。 （由 Cheryl Sabella 和 Terry Jan Reedy 在 bpo-33642@footnote{https://bugs.python.org/issue33642}, bpo-33768@footnote{https://bugs.python.org/issue33768} 和 bpo-33679@footnote{https://bugs.python.org/issue33679} 中贡献。）

在 Windows 上，会有新的 API 调用将 tk 对 DPI 的调整告知 Windows。 在 Windows 8.1+ 或 10 上，如果 Python 二进制码的 DPI 兼容属性未改变，并且监视器分辨率大于 96 DPI，这应该会令文本和线条更清晰。 否则的话它应该不造成影响。 （由 Terry Jan Reedy 在 bpo-33656@footnote{https://bugs.python.org/issue33656} 中贡献。）

在 3.7.1 中新增:

超过 N 行（默认值为 50）的输出将被折叠为一个按钮。 N 可以在 Settings 对话框的 General 页的 PyShell 部分中进行修改。 数量较少但是超长的行可以通过在输出上右击来折叠。 被折叠的输出可通过双击按钮来展开，或是通过右击按钮来放入剪贴板或是单独的窗口。 （由 Tal Einat 在 bpo-1529353@footnote{https://bugs.python.org/issue1529353} 中贡献。）

上述修改已被反向移植到 3.6 维护发行版中。

在 3.7.4 中新增:

在 Run 菜单中增加了 "Run Customized" 以使用自定义设置来运行模块。 输入的任何命令行参数都会被加入 sys.argv。 它们在下次自定义运行时会再次显示在窗体中。 用户也可以禁用通常的 Shell 主模块重启。 （由 Cheryl Sabella, Terry Jan Reedy 等人在 bpo-5680@footnote{https://bugs.python.org/issue5680} 和 bpo-37627@footnote{https://bugs.python.org/issue37627} 中贡献。）

在 3.7.5 中新增:

在 IDLE 编辑器窗口中增加了可选的行序号。 窗口打开时默认不带行序号，除非在配置对话框的 General 选项卡中进行设置。 已打开窗口中的行序号可以在 Options 菜单中显示和隐藏。 （由 Tal Einat 和 Saimadhav Heblikar 在 bpo-17535@footnote{https://bugs.python.org/issue17535} 中贡献。）

@node importlib,io<2>,idlelib 与 IDLE,改进的模块<2>
@anchor{whatsnew/3 7 importlib}@anchor{390}
@subsubsection importlib


引入了 @ref{33b,,importlib.abc.ResourceReader} ABC 以支持从包中加载资源。 另请参阅 @ref{2f0,,importlib.resources}。 （由 Barry Warsaw, Brett Cannon 在 bpo-32248@footnote{https://bugs.python.org/issue32248} 中贡献。）

如果模块缺少规格描述 @ref{391,,importlib.reload()} 现在会引发 @ref{392,,ModuleNotFoundError}。 （由 Garvit Khatri 在 bpo-29851@footnote{https://bugs.python.org/issue29851} 中贡献。）

如果指定的父模块不是一个包 (即缺少 @code{__path__} 属性) @code{importlib.find_spec()} 现在会引发 @ref{392,,ModuleNotFoundError} 而非 @ref{393,,AttributeError}。 （由 Milan Oberkirch 在 bpo-30436@footnote{https://bugs.python.org/issue30436} 中贡献。）

新的 @code{importlib.source_hash()} 可被用来计算传入源的哈希值。 @ref{2fa,,基于哈希值的 .pyc 文件} 会嵌入此函数所返回的值。

@node io<2>,ipaddress,importlib,改进的模块<2>
@anchor{whatsnew/3 7 io}@anchor{394}
@subsubsection io


新的 @ref{395,,TextIOWrapper.reconfigure()} 方法可用于根据新的设置重新配置文本流。 （由 Antoine Pitrou 在 bpo-30526@footnote{https://bugs.python.org/issue30526} 以及 INADA Naoki 在 bpo-15216@footnote{https://bugs.python.org/issue15216} 中贡献。）

@node ipaddress,itertools<2>,io<2>,改进的模块<2>
@anchor{whatsnew/3 7 ipaddress}@anchor{396}
@subsubsection ipaddress


methods of @ref{397,,ipaddress.IPv6Network} 和 @ref{398,,ipaddress.IPv4Network} 中新的 @code{subnet_of()} 以及 @code{supernet_of()} 方法可用于网络包含测试。 （由 Michel Albert 和 Cheryl Sabella 在 bpo-20825@footnote{https://bugs.python.org/issue20825} 中贡献。）

@node itertools<2>,locale,ipaddress,改进的模块<2>
@anchor{whatsnew/3 7 itertools}@anchor{399}
@subsubsection itertools


@ref{39a,,itertools.islice()} 现在接受 @ref{18a,,类整数对象} 作为 start, stop 和 slice 参数。 （由 Will Roberts 在 bpo-30537@footnote{https://bugs.python.org/issue30537} 中贡献。）

@node locale,logging<2>,itertools<2>,改进的模块<2>
@anchor{whatsnew/3 7 locale}@anchor{39b}
@subsubsection locale


@ref{39c,,locale.format_string()} 中新的 @emph{monetary} 参数可用于转换所使用的千位分隔符和分组字符串。 （由 Garvit 在 bpo-10379@footnote{https://bugs.python.org/issue10379} 中贡献。）

现在 @ref{39d,,locale.getpreferredencoding()} 函数在 Android 上或是在 @ref{2f9,,强制 UTF-8 模式} 下总是返回 @code{'UTF-8'} 。

@node logging<2>,math<2>,locale,改进的模块<2>
@anchor{whatsnew/3 7 logging}@anchor{39e}
@subsubsection logging


@ref{39f,,Logger} 实例现在可以被 pickle。 （由 Vinay Sajip 在 bpo-30520@footnote{https://bugs.python.org/issue30520} 中贡献。）

新的 @ref{3a0,,StreamHandler.setStream()} 方法可用于在句柄创建之后替换日志流。 （由 Vinay Sajip 在 bpo-30522@footnote{https://bugs.python.org/issue30522} 中创建。）

现在可以在传递给 @ref{3a1,,logging.config.fileConfig()} 的配置信息中对句柄构造器指定关键字参数。 （由 Preston Landers 在 bpo-31080@footnote{https://bugs.python.org/issue31080} 中贡献。)

@node math<2>,mimetypes,logging<2>,改进的模块<2>
@anchor{whatsnew/3 7 math}@anchor{3a2}
@subsubsection math


新的 @ref{3a3,,math.remainder()} 函数实现了 IEEE 754 风格的余数运算。 （由 Mark Dickinson 在 bpo-29962@footnote{https://bugs.python.org/issue29962} 中贡献。）

@node mimetypes,msilib,math<2>,改进的模块<2>
@anchor{whatsnew/3 7 mimetypes}@anchor{3a4}
@subsubsection mimetypes


.bmp 的 MIME type 从 @code{'image/x-ms-bmp'} 改为 @code{'image/bmp'}。 （由 Nitish Chandra 在 bpo-22589@footnote{https://bugs.python.org/issue22589} 中贡献。）

@node msilib,multiprocessing<2>,mimetypes,改进的模块<2>
@anchor{whatsnew/3 7 msilib}@anchor{3a5}
@subsubsection msilib


新的 @ref{3a6,,Database.Close()} 方法可用于关闭 @abbr{MSI,last-in@comma{} first-out} 数据库。 （由 Berker Peksag 在 bpo-20486@footnote{https://bugs.python.org/issue20486} 中贡献。）

@node multiprocessing<2>,os<2>,msilib,改进的模块<2>
@anchor{whatsnew/3 7 multiprocessing}@anchor{3a7}
@subsubsection multiprocessing


新的 @ref{3a8,,Process.close()} 方法会显式地关闭进程对象并释放与其关联的所有资源。 如果底层进程仍在运行则将引发 @ref{1fb,,ValueError}。 （由 Antoine Pitrou 在 bpo-30596@footnote{https://bugs.python.org/issue30596} 中贡献。）

新的 @ref{3a9,,Process.kill()} 方法可用于在 Unix 上使用 @code{SIGKILL} 信号来终止进程。 （由 Vitor Pereira 在 bpo-30794@footnote{https://bugs.python.org/issue30794} 中贡献。）

由 @ref{3aa,,Process} 所创建的非守护线程现在会在进程退出时被合并。 （由 Antoine Pitrou 在 bpo-18966@footnote{https://bugs.python.org/issue18966} 中贡献。）

@node os<2>,pathlib<2>,multiprocessing<2>,改进的模块<2>
@anchor{whatsnew/3 7 os}@anchor{3ab}
@subsubsection os


@ref{3ac,,os.fwalk()} 现在接受 @ref{32a,,bytes} 类型的 @emph{path} 参数。 （由 Serhiy Storchaka 在 bpo-28682@footnote{https://bugs.python.org/issue28682} 中贡献。）

@ref{25f,,os.scandir()} 已获得对 @ref{3ad,,文件描述器} 的支持。 （由 Serhiy Storchaka 在 bpo-25996@footnote{https://bugs.python.org/issue25996} 中贡献。）

新的 @ref{3ae,,register_at_fork()} 函数允许注册 Python 回调以便在进程分叉中执行。 （由 Antoine Pitrou 在 bpo-16500@footnote{https://bugs.python.org/issue16500} 中贡献。）

增加了 @ref{3af,,os.preadv()} (结合了 @ref{3b0,,os.readv()} 与 @ref{3b1,,os.pread()} 的功能) 以及 @ref{3b2,,os.pwritev()} 函数 (结合了 @ref{3b3,,os.writev()} 和 @ref{3b4,,os.pwrite()} 的功能)。 （由 Pablo Galindo 在 bpo-31368@footnote{https://bugs.python.org/issue31368} 中贡献。）

@ref{3b5,,os.makedirs()} 的 mode 参数不再影响新创建的中间层级目录的文件权限。 （由 Serhiy Storchaka 在 bpo-19930@footnote{https://bugs.python.org/issue19930} 中贡献。）

@ref{3b6,,os.dup2()} 现在会返回新的文件描述器。 之前，返回的总是 @code{None}。 （由 Benjamin Peterson 在 bpo-32441@footnote{https://bugs.python.org/issue32441} 中贡献。）

在 Solaris 及其派生系统上 @ref{1f1,,os.stat()} 所返回的结构现在会包含 @ref{3b7,,st_fstype} 属性。 （由 Jesús Cea Avión 在 bpo-32659@footnote{https://bugs.python.org/issue32659} 中贡献。）

@node pathlib<2>,pdb,os<2>,改进的模块<2>
@anchor{whatsnew/3 7 pathlib}@anchor{3b8}
@subsubsection pathlib


在 POSIX 类系统上新的 @ref{205,,Path.is_mount()} 方法现在可用于确定一个路径是否为挂载点。 （由 Cooper Ry Lees 在 bpo-30897@footnote{https://bugs.python.org/issue30897} 中贡献。）

@node pdb,py_compile<2>,pathlib<2>,改进的模块<2>
@anchor{whatsnew/3 7 pdb}@anchor{3b9}
@subsubsection pdb


@ref{3ba,,pdb.set_trace()} 现在接受一个可选的限关键字参数 @emph{header}。 如果给出，它会在调试开始之前被打印到控制台。 （由 Barry Warsaw 在 bpo-31389@footnote{https://bugs.python.org/issue31389} 中贡献。）

@ref{c9,,pdb} 命令行现在接受 @code{-m module_name} 作为对脚本文件的替代。 （由 Mario Corchero 在 bpo-32206@footnote{https://bugs.python.org/issue32206} 中贡献。）

@node py_compile<2>,pydoc,pdb,改进的模块<2>
@anchor{whatsnew/3 7 py-compile}@anchor{3bb}
@subsubsection py_compile


@ref{215,,py_compile.compile()} -- 及其扩展形式 @ref{21,,compileall} -- 现在会通过无条件地为基于哈希值的有效性验证创建 @code{.pyc} 文件来支持 
@geindex SOURCE_DATE_EPOCH
@geindex 环境变量; SOURCE_DATE_EPOCH
@code{SOURCE_DATE_EPOCH} 环境变量。 这样可以确保当 @code{.pyc} 文件被主动创建时 可重现的生成@footnote{https://reproducible-builds.org/}。 （由 Bernhard M. Wiedemann 在 bpo-29708@footnote{https://bugs.python.org/issue29708} 中贡献。）

@node pydoc,queue,py_compile<2>,改进的模块<2>
@anchor{whatsnew/3 7 pydoc}@anchor{3bc}
@subsubsection pydoc


pydoc 服务器现在可以绑定到由新的 @code{-n} 命令行参数所指定的任意主机名。 （由 Feanil Patel 在 bpo-31128@footnote{https://bugs.python.org/issue31128} 中贡献。）

@node queue,re,pydoc,改进的模块<2>
@anchor{whatsnew/3 7 queue}@anchor{3bd}
@subsubsection queue


新的 @ref{3be,,SimpleQueue} 类是一个无界的 @abbr{FIFO,last-in@comma{} first-out} 队列。 （由 Antoine Pitrou 在 bpo-14976@footnote{https://bugs.python.org/issue14976} 中贡献。）

@node re,signal,queue,改进的模块<2>
@anchor{whatsnew/3 7 re}@anchor{3bf}
@subsubsection re


旗标 @ref{3c0,,re.ASCII}, @ref{3c1,,re.LOCALE} 和 @code{re.UNICODE} 可以在组的范围内设置。 （由 Serhiy Storchaka 在 bpo-31690@footnote{https://bugs.python.org/issue31690} 中贡献。）

@ref{3c2,,re.split()} 现在支持基于匹配一个空字符串的模式例如 @code{r'\b'}, @code{'^$'} 或 @code{(?=-)} 进行拆分。 （由 Serhiy Storchaka 在 bpo-25054@footnote{https://bugs.python.org/issue25054} 中贡献。）

使用 @ref{3c1,,re.LOCALE} 旗标编译的正则表达式不再依赖于编译时的区域设置。 区域设置仅在已编译正则表达式被使用时才被应用。 （由 Serhiy Storchaka 在 bpo-30215@footnote{https://bugs.python.org/issue30215} 中贡献。）

现在如果一个正则表达式包含语义将在未来发生改变的字符集构造，则会引发 @ref{31e,,FutureWarning}，例如嵌套集与集合操作等。 （由 Serhiy Storchaka 在 bpo-30349@footnote{https://bugs.python.org/issue30349} 中贡献。）

已编译正则表达式和匹配对象现在可以使用 @ref{3c3,,copy.copy()} 和 @ref{3c4,,copy.deepcopy()} 进行拷贝。 （由 Serhiy Storchaka 在 bpo-10076@footnote{https://bugs.python.org/issue10076} 中贡献。）

@node signal,socket<2>,re,改进的模块<2>
@anchor{whatsnew/3 7 signal}@anchor{3c5}
@subsubsection signal


@ref{3c6,,signal.set_wakeup_fd()} 函数新增的 @emph{warn_on_full_buffer} 参数可以指定当唤醒缓冲区溢出时 Python 是否要在 stderr 上打印警告信息。 （由 Nathaniel J. Smith 在 bpo-30050@footnote{https://bugs.python.org/issue30050} 中贡献。）

@node socket<2>,socketserver,signal,改进的模块<2>
@anchor{whatsnew/3 7 socket}@anchor{3c7}
@subsubsection socket


新增的 @ref{3c8,,socket.getblocking()} 方法会在套接字处于阻塞模式时返回 @code{True}，否则返回 @code{False}。 （由 Yury Selivanov 在 bpo-32373@footnote{https://bugs.python.org/issue32373} 中贡献。）

新的 @ref{3c9,,socket.close()} 函数可关闭所传入的套接字文件描述符。 应该用此函数来代替 @ref{3ca,,os.close()} 以获得更好的跨平台兼容性。 （由 Christian Heimes 在 bpo-32454@footnote{https://bugs.python.org/issue32454} 中贡献。）

@ref{ef,,socket} 模块现在会公开 @code{socket.TCP_CONGESTION} (Linux 2.6.13), @code{socket.TCP_USER_TIMEOUT} (Linux 2.6.37) 以及 @code{socket.TCP_NOTSENT_LOWAT} (Linux 3.12) 常量。 （由 Omar Sandoval 在 bpo-26273@footnote{https://bugs.python.org/issue26273} 以及 Nathaniel J. Smith 在 bpo-29728@footnote{https://bugs.python.org/issue29728} 中贡献。）

已加入对 @ref{3cb,,socket.AF_VSOCK} 套接字的支持以允许在虚拟机及其宿主机之间进行通讯。 （由 Cathy Avery 在 bpo-27584@footnote{https://bugs.python.org/issue27584} 中贡献。）

套接字现在默认会根据文件描述符自动检测所属族、类型和协议。 （由 Christian Heimes 在 bpo-28134@footnote{https://bugs.python.org/issue28134} 中贡献。）

@node socketserver,sqlite3,socket<2>,改进的模块<2>
@anchor{whatsnew/3 7 socketserver}@anchor{3cc}
@subsubsection socketserver


@code{socketserver.ThreadingMixIn.server_close()} 现在会等待所有非守护线程完成。 @code{socketserver.ForkingMixIn.server_close()} 现在会等待所有子进程完成。

为 @ref{3cd,,socketserver.ForkingMixIn} 和 @ref{3ce,,socketserver.ThreadingMixIn} 类增加了新的 @code{socketserver.ForkingMixIn.block_on_close} 类属性。 该类属性值设为 @code{False} 以保持 3.7 之前的行为。

@node sqlite3,ssl<2>,socketserver,改进的模块<2>
@anchor{whatsnew/3 7 sqlite3}@anchor{3cf}
@subsubsection sqlite3


现在当下层的 SQLite 库版本为 3.6.11 及以上时 @ref{3d0,,sqlite3.Connection} 会开放 @ref{3d1,,backup()} 方法。 （由 Lele Gaifax 在 bpo-27645@footnote{https://bugs.python.org/issue27645} 中贡献。）

@ref{3d2,,sqlite3.connect()} 的 @emph{database} 参数现在接受任何 @ref{363,,path-like object}，而不是只接受字符串。 （由 Anders Lorentsen 在 bpo-31843@footnote{https://bugs.python.org/issue31843} 中贡献。）

@node ssl<2>,string,sqlite3,改进的模块<2>
@anchor{whatsnew/3 7 ssl}@anchor{3d3}
@subsubsection ssl


@ref{f3,,ssl} 模块现在使用 OpenSSL 的内置 API 代替 @ref{3d4,,match_hostname()} 来检查主机名或 IP 地址。 值的验证会在 TLS 握手期间进行。 任何证书验证错误包括主机名检查失败现在将引发 @ref{3d5,,SSLCertVerificationError} 并使用正确的 TLS Alert 消息中止握手过程。 这个新异常包含有额外的信息。 主机名验证可通过 @ref{3d6,,SSLContext.hostname_checks_common_name} 进行自定义。 （由 Christian Heimes 在 bpo-31399@footnote{https://bugs.python.org/issue31399} 中贡献。）

@cartouche
@quotation 注解 
改进的主机名检测需要有兼容 OpenSSL 1.0.2 或 1.1 的 @emph{libssl} 实现。 因此，OpenSSL 0.9.8 和 1.0.1 不再被支持（请参阅 @ref{3d7,,平台支持的移除} 了解详情）。 目前 ssl 模块主要兼容 LibreSSL 2.7.2 及更高版本。
@end quotation
@end cartouche

@code{ssl} 模块不再以 SNI TLS 扩展发送 IP 地址。 （由 Christian Heimes 在 bpo-32185@footnote{https://bugs.python.org/issue32185} 中贡献。）

@ref{3d4,,match_hostname()} 不再支持部分通配符例如 @code{www*.example.org}。 （由 Mandeep Singh 在 bpo-23033@footnote{https://bugs.python.org/issue23033} 以及 Christian Heimes 在 bpo-31399@footnote{https://bugs.python.org/issue31399} 中贡献。）

@code{ssl} 模块默认的加密套件选择现在是使用黑名单方式而非硬编码的白名单。 Python 不会再重新启用已经被 OpenSSL 安全更新所阻止的加密。 默认的加密套件选择可以在编译时进行配置。 （由 Christian Heimes 在 bpo-31429@footnote{https://bugs.python.org/issue31429} 中贡献。）

现在已支持包含国际化域名 (IDN) 的服务器证书验证。 作为此更改的一部分，@ref{3d8,,SSLSocket.server_hostname} 属性现在会以预期的 A 标签形式 (@code{"xn--pythn-mua.org"}) 而不是以 U 标签形式 (@code{"pythön.org"}) 存储。 （由 Nathaniel J. Smith 与 Christian Heimes 在 bpo-28414@footnote{https://bugs.python.org/issue28414} 中贡献。）

@code{ssl} 模块对 TLS 1.3 和 OpenSSL 1.1.1 具有初步和实验性的支持。 在 Python 3.7.0 发布的时刻，OpenSSL 1.1.1 仍在开发中，而 TLS 1.3 尚未最终确定。 TLS 1.3 握手和协议行为与 TLS 1.2 及更早的版本略有差异，请参阅 @ref{3d9,,TLS 1.3}。 （由 Christian Heimes 在 bpo-32947@footnote{https://bugs.python.org/issue32947}, bpo-20995@footnote{https://bugs.python.org/issue20995}, bpo-29136@footnote{https://bugs.python.org/issue29136}, bpo-30622@footnote{https://bugs.python.org/issue30622} 以及 bpo-33618@footnote{https://bugs.python.org/issue33618} 中贡献。）

@ref{3da,,SSLSocket} 和 @ref{3db,,SSLObject} 不再具有公共构造器。 直接实例化从未成为有文档和受支持的特性。 实际必须通过 @ref{3dc,,SSLContext} 的方法 @ref{3dd,,wrap_socket()} 和 @ref{3de,,wrap_bio()} 来创建。 （由 Christian Heimes 在 bpo-32951@footnote{https://bugs.python.org/issue32951} 中贡献。）

用于设置最小和最大 TLS 协议版本的 OpenSSL 1.1 API 现已可用，名称分别为 @ref{3df,,SSLContext.minimum_version} 和 @ref{3e0,,SSLContext.maximum_version}。 受支持的协议由几个新增旗标指定，例如 @ref{3e1,,HAS_TLSv1_1}。 （由 Christian Heimes 在 bpo-32609@footnote{https://bugs.python.org/issue32609} 中贡献。）

@node string,subprocess,ssl<2>,改进的模块<2>
@anchor{whatsnew/3 7 string}@anchor{3e2}
@subsubsection string


@ref{3e3,,string.Template} 现在允许你有选择地分别修改带大括号的占位符和不带大括号的占位符所对应的正则表达式模式。 （由 Barry Warsaw 在 bpo-1198569@footnote{https://bugs.python.org/issue1198569} 中贡献。）

@node subprocess,sys<2>,string,改进的模块<2>
@anchor{whatsnew/3 7 subprocess}@anchor{3e4}
@subsubsection subprocess


@ref{3e5,,subprocess.run()} 函数接受新的 @emph{capture_output} 关键字参数。 当其为真值时，将会捕获 stdout 和 stderr。 这相当于将 @ref{3e6,,subprocess.PIPE} 作为 @emph{stdout} 和 @emph{stderr} 参数传入。 （由 Bo Bayles 在 bpo-32102@footnote{https://bugs.python.org/issue32102} 中贡献。）

@code{subprocess.run} 函数和 @ref{2b9,,subprocess.Popen} 构造器现在接受 @emph{text} 关键字参数作为 @emph{universal_newlines} 的别名。 （由 Andrew Clegg 在 bpo-31756@footnote{https://bugs.python.org/issue31756} 中贡献。）

在 Windows 中当重定向标准句柄时 @emph{close_fds} 的默认值由 @code{False} 改为 @code{True}。 现在可以在重定向标准句柄时将 @emph{close_fds} 设为真值。 参阅 @ref{2b9,,subprocess.Popen}。 这意味着现在 @emph{close_fds} 在所有受支持的平台上默认值均为 @code{True}。 （由 Segev Finer 在 bpo-19764@footnote{https://bugs.python.org/issue19764} 中贡献。）

在 @ref{3e7,,subprocess.call()}, @ref{3e5,,subprocess.run()} 期间或在 @ref{2b9,,Popen} 上下文管理器中，subprocess 模块现在能更优雅地处理 @ref{197,,KeyboardInterrupt}。 它现在会等待一小段时间以便子进程退出，然后再继续处理 @code{KeyboardInterrupt} 异常。 （由 Gregory P. Smith 在 bpo-25942@footnote{https://bugs.python.org/issue25942} 中贡献。）

@node sys<2>,time<2>,subprocess,改进的模块<2>
@anchor{whatsnew/3 7 sys}@anchor{3e8}
@subsubsection sys


新增 @ref{30c,,sys.breakpointhook()} 钩子函数，供内置的 @ref{2f2,,breakpoint()} 进行调用。 （由 Barry Warsaw 在 bpo-31353@footnote{https://bugs.python.org/issue31353} 中贡献。）

在 Android 中新增的 @ref{3e9,,sys.getandroidapilevel()} 会返回构建时的 Android API 版本。 （由 Victor Stinner 在 bpo-28740@footnote{https://bugs.python.org/issue28740} 中贡献。）

新的 @ref{3ea,,sys.get_coroutine_origin_tracking_depth()} 函数会返回当前协程的由新的 @ref{3eb,,sys.set_coroutine_origin_tracking_depth()} 所设定的原始跟踪深度。 @ref{a,,asyncio} 已转换为使用这个新 API 代替已弃用的 @code{sys.set_coroutine_wrapper()}。 （由 Nathaniel J. Smith 在 bpo-32591@footnote{https://bugs.python.org/issue32591} 中贡献。）

@node time<2>,tkinter<2>,sys<2>,改进的模块<2>
@anchor{whatsnew/3 7 time}@anchor{3ec}
@subsubsection time


@geindex Python 提高建议; PEP 564
PEP 564@footnote{https://www.python.org/dev/peps/pep-0564}  向 @ref{10a,,time} 模块增加六个具有纳秒级精度的新函数:


@itemize *

@item 
@ref{317,,time.clock_gettime_ns()}

@item 
@ref{318,,time.clock_settime_ns()}

@item 
@ref{319,,time.monotonic_ns()}

@item 
@ref{31a,,time.perf_counter_ns()}

@item 
@ref{31b,,time.process_time_ns()}

@item 
@ref{31c,,time.time_ns()}
@end itemize

增加了新的时钟标识符:


@itemize *

@item 
@ref{3ed,,time.CLOCK_BOOTTIME} (Linux): 与 @ref{3ee,,time.CLOCK_MONOTONIC} 相似，不同点在于它还包括任何系统挂起的时间。

@item 
@ref{3ef,,time.CLOCK_PROF} (FreeBSD, NetBSD 和 OpenBSD): 高精度的分进程 CPU 计时器。

@item 
@ref{3f0,,time.CLOCK_UPTIME} (FreeBSD, OpenBSD): 该时间的绝对值是系统运行且未挂起的时间，提供准确的正常运行时间度量。
@end itemize

新的 @ref{3f1,,time.thread_time()} 和 @ref{3f2,,time.thread_time_ns()} 函数可用于获取每线程的 CPU 时间度量。 （由 Antoine Pitrou 在 bpo-32025@footnote{https://bugs.python.org/issue32025} 中贡献。）

新的 @ref{3f3,,time.pthread_getcpuclockid()} 函数会返回特定线程中 CPU 时钟的时钟 ID。

@node tkinter<2>,tracemalloc,time<2>,改进的模块<2>
@anchor{whatsnew/3 7 tkinter}@anchor{3f4}
@subsubsection tkinter


新的 @ref{3f5,,tkinter.ttk.Spinbox} 类现已可用。 （由 Alan Moore 在 bpo-32585@footnote{https://bugs.python.org/issue32585} 中贡献。）

@node tracemalloc,types,tkinter<2>,改进的模块<2>
@anchor{whatsnew/3 7 tracemalloc}@anchor{3f6}
@subsubsection tracemalloc


@ref{3f7,,tracemalloc.Traceback} 的行为更接近正规的回溯，会对所有帧按从最旧到最新来排序。 @ref{3f8,,Traceback.format()} 现在接受负的 @emph{limit}，并会将结果截短至排在第 @code{abs(limit)} 位的旧帧。 如果要获得旧的行为，请在 @code{Traceback.format()} 中使用新的  @emph{most_recent_first} 参数。 （由 Jesse Bakker 在 bpo-32121@footnote{https://bugs.python.org/issue32121} 中贡献。）

@node types,unicodedata<2>,tracemalloc,改进的模块<2>
@anchor{whatsnew/3 7 types}@anchor{3f9}
@subsubsection types


新的 @ref{3fa,,WrapperDescriptorType}, @ref{3fb,,MethodWrapperType}, @ref{3fc,,MethodDescriptorType} 和 @ref{3fd,,ClassMethodDescriptorType} 类现已可用。 （由 Manuel Krebber 和 Guido van Rossum 在 bpo-29377@footnote{https://bugs.python.org/issue29377} 以及 Serhiy Storchaka 在 bpo-32265@footnote{https://bugs.python.org/issue32265} 中贡献。）

新的 @ref{3fe,,types.resolve_bases()} 函数会以 
@geindex Python 提高建议; PEP 560
PEP 560@footnote{https://www.python.org/dev/peps/pep-0560} 所规定的方式动态解析 MRO 条目。 （由 Ivan Levkivskyi 在 bpo-32717@footnote{https://bugs.python.org/issue32717} 中贡献。）

@node unicodedata<2>,unittest<2>,types,改进的模块<2>
@anchor{whatsnew/3 7 unicodedata}@anchor{3ff}
@subsubsection unicodedata


内部的 @ref{11a,,unicodedata} 数据库已升级为使用 Unicode 11@footnote{http://www.unicode.org/versions/Unicode11.0.0/}。 （由 Benjamin Peterson 贡献。）

@node unittest<2>,unittest mock,unicodedata<2>,改进的模块<2>
@anchor{whatsnew/3 7 unittest}@anchor{400}
@subsubsection unittest


新的 @code{-k} 命令行选项允许通过名称子字符串或类似于 Unix shell 的模式来筛选测试项。 例如，@code{python -m unittest -k foo} 将运行 @code{foo_tests.SomeTest.test_something}, @code{bar_tests.SomeTest.test_foo}，但不会运行 @code{bar_tests.FooTest.test_something}。 （由 Jonas Haag 在 bpo-32071@footnote{https://bugs.python.org/issue32071} 中贡献。）

@node unittest mock,urllib parse,unittest<2>,改进的模块<2>
@anchor{whatsnew/3 7 unittest-mock}@anchor{401}
@subsubsection unittest.mock


现在 @ref{402,,sentinel} 属性会在它们被 @ref{26,,复制} 或 @ref{ca,,封存} 时保存其标识。 （由 Serhiy Storchaka 在 bpo-20804@footnote{https://bugs.python.org/issue20804} 中贡献。）

新的 @ref{403,,seal()} 函数允许 @ref{249,,Mock} 对实例进行密封，这将禁止进一步创建属性模拟。 密封会以递归方式应用于自身模拟的所有属性。 （由 Mario Corchero 在 bpo-30541@footnote{https://bugs.python.org/issue30541} 中贡献。）

@node urllib parse,uu,unittest mock,改进的模块<2>
@anchor{whatsnew/3 7 urllib-parse}@anchor{404}
@subsubsection urllib.parse


@ref{405,,urllib.parse.quote()} 已经从 
@geindex RFC; RFC 2396
RFC 2396@footnote{https://tools.ietf.org/html/rfc2396.html} 更新为 
@geindex RFC; RFC 3986
RFC 3986@footnote{https://tools.ietf.org/html/rfc3986.html}，将 @code{~} 添加到默认情况下从未引用的字符集。 （由 Christian Theune 和 Ratnadeep Debnath 在 bpo-16285@footnote{https://bugs.python.org/issue16285} 中贡献。）

@node uu,uuid,urllib parse,改进的模块<2>
@anchor{whatsnew/3 7 uu}@anchor{406}
@subsubsection uu


@ref{407,,uu.encode()} 函数现在接受可选的 @emph{backtick} 关键字参数。 当其为真时，零会以 @code{'`'} 而非空格来表示。 （由 Xiang Zhang 在 bpo-30103@footnote{https://bugs.python.org/issue30103} 中贡献。）

@node uuid,warnings,uu,改进的模块<2>
@anchor{whatsnew/3 7 uuid}@anchor{408}
@subsubsection uuid


新的 @ref{409,,UUID.is_safe} 属性会从平台中继有关是否使用多进程安全模式来生成所需  UUID 的信息。 （由 Barry Warsaw 在 bpo-22807@footnote{https://bugs.python.org/issue22807} 中贡献。）

@ref{40a,,uuid.getnode()} 现在更倾向于统一管理的 MAC 地址而不是本地管理的 MAC 地址。 这样可以更好地保证从 @ref{40b,,uuid.uuid1()} 返回的 UUID 的全局唯一性。 如果只有本地管理的 MAC 地址可用，则返回首个找到的此类地址。 （由 Barry Warsaw 在 bpo-32107@footnote{https://bugs.python.org/issue32107} 中贡献。）

@node warnings,xml etree,uuid,改进的模块<2>
@anchor{whatsnew/3 7 warnings}@anchor{40c}
@subsubsection warnings


默认警告过滤器的初始化已进行以下更改:


@itemize *

@item 
通过命令行选项（包括 @ref{40d,,-b} 以及新的 CPython 专属的 @ref{155,,-X} @code{dev} 选项）启用的警告总是会通过 @ref{40e,,sys.warnoptions} 属性被传递给警告机制。

@item 
通过命令行或环境变量启用的警告过滤器现在具有以下优先顺序:

@quotation


@itemize *

@item 
用于 @ref{40d,,-b} (或 @code{-bb}) 的 @code{BytesWarning} 过滤器

@item 
通过 @ref{40f,,-W} 选项指定的任何过滤器

@item 
通过 
@geindex PYTHONWARNINGS
@geindex 环境变量; PYTHONWARNINGS
@ref{410,,PYTHONWARNINGS} 环境变量指定的任何过滤器

@item 
任何其他 CPython 专属过滤器（例如 @code{-X dev} 模式中新增的 @code{default} 过滤器）

@item 
由警告机制所定义的任何隐式过滤器
@end itemize
@end quotation

@item 
在 CPython 调试版本中，现在默认情况下会显示所有警告（隐式过滤器列表为空）
@end itemize

（由 Nick Coghlan 和 Victor Stinner 在 bpo-20361@footnote{https://bugs.python.org/issue20361}, bpo-32043@footnote{https://bugs.python.org/issue32043} 以及 bpo-32230@footnote{https://bugs.python.org/issue32230} 中贡献。）

在单文件脚本和交互式提示符中，默认情况下会再次显示已弃用警告。 详情参见 @ref{2fc,,PEP 565; 在 __main__ 中显示 DeprecationWarning}。 （由 Nick Coghlan 在 bpo-31975@footnote{https://bugs.python.org/issue31975} 中贡献。）

@node xml etree,xmlrpc server,warnings,改进的模块<2>
@anchor{whatsnew/3 7 xml-etree}@anchor{411}
@subsubsection xml.etree


@code{find()} 方法中的 @ref{412,,ElementPath} 描述词现在可以将当前节点文本与 @code{[. = "text"]} 进行比较，而不仅是子节点中的文本。 描述词还允许添加空格以提高可读性。 （由 Stefan Behnel 在 bpo-31648@footnote{https://bugs.python.org/issue31648} 中贡献。）

@node xmlrpc server,zipapp,xml etree,改进的模块<2>
@anchor{whatsnew/3 7 xmlrpc-server}@anchor{413}
@subsubsection xmlrpc.server


@code{SimpleXMLRPCDispatcher.register_function} 现在可以被用作装饰器。 （由 Xiang Zhang 在 bpo-7769@footnote{https://bugs.python.org/issue7769} 中贡献。）

@node zipapp,zipfile,xmlrpc server,改进的模块<2>
@anchor{whatsnew/3 7 zipapp}@anchor{414}
@subsubsection zipapp


函数 @ref{415,,create_archive()} 现在接受可选的 @emph{filter} 参数，以允许用户选择哪些文件应被加入归档包。 （由 Irmen de Jong 在 bpo-31072@footnote{https://bugs.python.org/issue31072} 中贡献。）

函数 @ref{415,,create_archive()} 现在接受可选的 @emph{compressed} 参数，以生成压缩归档包。 另外也加入了命令行选项 @code{--compress} 以支持压缩。 （由 Zhiming Wang 在 bpo-31638@footnote{https://bugs.python.org/issue31638} 中贡献。）

@node zipfile,,zipapp,改进的模块<2>
@anchor{whatsnew/3 7 zipfile}@anchor{416}
@subsubsection zipfile


@ref{417,,ZipFile} 现在接受新的 @emph{compresslevel} 形参，以控制压缩级别。 （由 Bo Bayles 在 bpo-21417@footnote{https://bugs.python.org/issue21417} 中贡献。）

@code{ZipFile} 所创建的归档包中的子目录现在会按字母表顺序保存。 （由 Bernhard M. Wiedemann 在 bpo-30693@footnote{https://bugs.python.org/issue30693} 中贡献。）

@node C API 的改变,构建的改变,改进的模块<2>,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 c-api-changes}@anchor{418}
@subsection C API 的改变


已实现了用于线程本地存储的新 API。 相关概述请参阅 @ref{2fd,,PEP 539; 用于线程局部存储的新 C API}，完整参考文档请查看 @ref{310,,Thread Specific Storage (TSS) API}。 （由 Masayuki Yamamoto 在 bpo-25658@footnote{https://bugs.python.org/issue25658} 中贡献。)

新的 @ref{2ee,,上下文变量} 功能开放了许多 @ref{334,,新的 C API}。

新的 @ref{419,,PyImport_GetModule()} 函数会返回之前所导入的具有给定名称的模块。 （由 Eric Snow 在 bpo-28411@footnote{https://bugs.python.org/issue28411} 中贡献。）

新的 @ref{41a,,Py_RETURN_RICHCOMPARE} 宏可以简化丰富比较函数的编写。 （由 Petr Victorin 在 bpo-23699@footnote{https://bugs.python.org/issue23699} 中贡献。）

新的 @ref{41b,,Py_UNREACHABLE} 宏可用于标记不可到达的代码路径。 （由 Barry Warsaw 在 bpo-31338@footnote{https://bugs.python.org/issue31338} 中贡献。）

@ref{114,,tracemalloc} 现在通过新的 @ref{41c,,PyTraceMalloc_Track()} 和 @ref{41d,,PyTraceMalloc_Untrack()} 函数公开了一个 C API。 （由 Victor Stinner 在 bpo-30054@footnote{https://bugs.python.org/issue30054} 中贡献。）

新的 @ref{41e,,import__find__load__start()} 和 @ref{41f,,import__find__load__done()} 静态标记可用于跟踪模块导入。 （由 Christian Heimes 在 bpo-31574@footnote{https://bugs.python.org/issue31574} 中贡献。）

结构体 @ref{420,,PyMemberDef}, @ref{421,,PyGetSetDef}, @ref{422,,PyStructSequence_Field}, @ref{423,,PyStructSequence_Desc} 和 @code{wrapperbase} 的字段 @code{name} 和 @code{doc} 现在的类型为 @code{const char *} 而不是 @code{char *}。 （由 Serhiy Storchaka 在 bpo-28761@footnote{https://bugs.python.org/issue28761} 中贡献。）

@ref{424,,PyUnicode_AsUTF8AndSize()} 和 @ref{425,,PyUnicode_AsUTF8()} 的结果类型现在是 @code{const char *} 而非 @code{char *}。 （由 Serhiy Storchaka 在 bpo-28769@footnote{https://bugs.python.org/issue28769} 中贡献。）

@ref{426,,PyMapping_Keys()}, @ref{427,,PyMapping_Values()} 和 @ref{428,,PyMapping_Items()} 的结果现在肯定是列表，而非可能是列表也可能是元组。 （由 Oren Milman 在 bpo-28280@footnote{https://bugs.python.org/issue28280} 中贡献。）

添加了函数 @ref{429,,PySlice_Unpack()} 和 @ref{42a,,PySlice_AdjustIndices()}。 （由 Serhiy Storchaka 在 bpo-27867@footnote{https://bugs.python.org/issue27867} 中贡献。）

@ref{42b,,PyOS_AfterFork()} 已弃用，建议改用新的 functions @ref{42c,,PyOS_BeforeFork()}, @ref{42d,,PyOS_AfterFork_Parent()} 和 @ref{2cd,,PyOS_AfterFork_Child()}。 （由 Antoine Pitrou 在 bpo-16500@footnote{https://bugs.python.org/issue16500} 中贡献。）

曾经作为公共 API 一部分的 @code{PyExc_RecursionErrorInst} 单例已被移除，因为它的成员永远不会被清理，可能在解释器的最终化过程中导致段错误。 由 Xavier de Gaye 在 bpo-22898@footnote{https://bugs.python.org/issue22898} 和 bpo-30697@footnote{https://bugs.python.org/issue30697} 中贡献。

添加 C API 对使用 timezone 的构造器 @ref{42e,,PyTimeZone_FromOffset()} 和 @ref{42f,,PyTimeZone_FromOffsetAndName()} 的时区的支持，以及通常 @ref{430,,PyDateTime_TimeZone_UTC} 使用 UTC 单例。 由 Paul Ganssle 在 bpo-10381@footnote{https://bugs.python.org/issue10381} 中贡献。

@code{PyThread_start_new_thread()} 和 @code{PyThread_get_thread_ident()} 的结果类型以及 @ref{431,,PyThreadState_SetAsyncExc()} 的 @emph{id} 参数类型由 @code{long} 改为 @code{unsigned long}。 （由 Serhiy Storchaka 在 bpo-6532@footnote{https://bugs.python.org/issue6532} 中贡献。）

现在 @ref{432,,PyUnicode_AsWideCharString()} 如果第二个参数为 @code{NULL} 并且 @code{wchar_t*} 字符串包含空字符则会引发 @ref{1fb,,ValueError}。 （由 Serhiy Storchaka 在 bpo-30708@footnote{https://bugs.python.org/issue30708} 中贡献。）

对启动顺序以及动态内存分配器管理的更改意味着早已记录在案的，对在调用大多数 C API 函数之前调用 @ref{433,,Py_Initialize()} 的要求的依赖现在变得更加强烈，未遵循此要求可能导致嵌入式应用程序中的段错误。 请参阅此文档的 @ref{300,,移植到 Python 3.7} 一节以及 C API 文档的 @ref{434,,在Python初始化之前} 一节了解更多细节。

新的 @ref{435,,PyInterpreterState_GetID()} 会返回给定解释器的唯一 ID。 （由 Eric Snow 在 bpo-29102@footnote{https://bugs.python.org/issue29102} 中贡献。）

现在当启用 @ref{2f9,,UTF-8 模式} 时 @ref{436,,Py_DecodeLocale()}, @ref{437,,Py_EncodeLocale()} 会使用 UTF-8 编码。 （由 Victor Stinner 在 bpo-29240@footnote{https://bugs.python.org/issue29240} 中贡献。）

@ref{438,,PyUnicode_DecodeLocaleAndSize()} 和 @ref{439,,PyUnicode_EncodeLocale()} 现在会为 @code{surrogateescape} 错误句柄使用当前区域编码。 （由 Victor Stinner 在 bpo-29240@footnote{https://bugs.python.org/issue29240} 中贡献。）

@ref{43a,,PyUnicode_FindChar()} 的 @emph{start} 和 @emph{end} 形参的行为现在调整为与字符串切片类似。 （由 Xiang Zhang 在 bpo-28822@footnote{https://bugs.python.org/issue28822} 中贡献。）

@node 构建的改变,性能优化<2>,C API 的改变,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 build-changes}@anchor{43b}
@subsection 构建的改变


对于 @code{--without-threads} 构建的支持已被移除。 @ref{109,,threading} 模块现在将总是可用。 （由 Antoine Pitrou 在 bpo-31370@footnote{https://bugs.python.org/issue31370} 中贡献。）

在非 OSX UNIX 平台上已不再包含用于构建 @ref{2b,,_ctypes} 模块的完整 libffi 副本。 现在当在此类平台上构建 @code{_ctypes} 时需要事先装有 libffi 的副本。 （由 Zachary Ware 在 bpo-27979@footnote{https://bugs.python.org/issue27979} 中贡献。）

Windows 构建过程不再依赖 Subversion 来拉取外部源码，而是改用一段 Python 脚本从 GitHub 下载 zip 文件。 如果未在系统中找到 Python 3.6 (通过 @code{py -3.6})，则会使用 NuGet 下载一份 32 位的 Python 副本用于此目的。 （由 Zachary Ware 在 bpo-30450@footnote{https://bugs.python.org/issue30450} 中贡献。）

@ref{f3,,ssl} 模块需要兼容 OpenSSL 1.0.2 或 1.1 的 libssl。 OpenSSL 1.0.1 的生命期已于 2016-12-31 终止且不再受支持。 LibreSSL 暂时也不受支持。 LibreSSL 发布版直到 2.6.4 版还缺少所需的 OpenSSL 1.0.2 API。

@node 性能优化<2>,其他 CPython 实现的改变,构建的改变,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 optimizations}@anchor{43c}@anchor{whatsnew/3 7 whatsnew37-perf}@anchor{2ff}
@subsection 性能优化


通过移植更多代码来使用 @code{METH_FASTCALL} 的约定，可以显著地减少调用 C 代码中实现的各类标准库的很多方法的开销。 （由 Victor Stinner 在 bpo-29300@footnote{https://bugs.python.org/issue29300}、bpo-29507@footnote{https://bugs.python.org/issue29507}、bpo-29452@footnote{https://bugs.python.org/issue29452} 以及 bpo-29286@footnote{https://bugs.python.org/issue29286} 中贡献。）

通过各种优化方式，使 Python 在 Linux 上的启动时间缩短了 10%，在 macOS 上缩短了 30%。 （由 Victor Stinner, INADA Naoki 在 bpo-29585@footnote{https://bugs.python.org/issue29585} 中，以及 Ivan Levkivskyi 在 bpo-31333@footnote{https://bugs.python.org/issue31333} 中贡献。）

由于避免创建绑定方法案例的字节码更改，方法调用速度现在加快了 20%。 （由 Yury Selivanov 和 INADA Naoki 在 bpo-26110@footnote{https://bugs.python.org/issue26110} 中贡献。）
@anchor{whatsnew/3 7 whatsnew37-asyncio-perf}@anchor{340}
对 @ref{a,,asyncio} 模块里面的一些常用函数做了显著的性能优化。


@itemize *

@item 
@ref{34e,,asyncio.get_event_loop()} 函数已经改用 C 重新实现，使其执行速度加快了 15 倍。 （由 Yury Selivanov 在 bpo-32296@footnote{https://bugs.python.org/issue32296} 中贡献。）

@item 
@ref{43d,,asyncio.Future} 回调管理已经过优化。 （由 Yury Selivanov 在 bpo-32348@footnote{https://bugs.python.org/issue32348} 中贡献。）

@item 
@ref{286,,asyncio.gather()} 的执行速度现在加快了 15%。 （由 Yury Selivanov 在 bpo-32355@footnote{https://bugs.python.org/issue32355} 中贡献。）

@item 
当 @emph{delay} 参数为零或负值时 @ref{285,,asyncio.sleep()} 的执行速度现在加快了 2 倍。 （由 Andrew Svetlov 在 bpo-32351@footnote{https://bugs.python.org/issue32351} 中贡献。）

@item 
asyncio 调试模式的执行开销已获减轻。 （由 Antoine Pitrou 在 bpo-31970@footnote{https://bugs.python.org/issue31970} 中贡献。）
@end itemize

作为 @ref{2f4,,PEP 560 工作} 的结果，@ref{119,,typing} 的导入时间已减少了 7 倍，许多与类型相关的操作现在会执行得更快。 （由 Ivan Levkivskyi 在 bpo-32226@footnote{https://bugs.python.org/issue32226} 中贡献。）

@ref{43e,,sorted()} 和 @ref{43f,,list.sort()} 已经过优化，在通常情况下执行速度可提升 40-75%。 （由 Elliot Gorokhovsky 在 bpo-28685@footnote{https://bugs.python.org/issue28685} 中贡献。）

@ref{440,,dict.copy()} 的执行速度现在加快了 5.5 倍。 （由 Yury Selivanov 在 bpo-31179@footnote{https://bugs.python.org/issue31179} 中贡献。）

当 @emph{name} 未找到并且 @emph{obj} 未重载 @ref{313,,object.__getattr__()} 或 @ref{441,,object.__getattribute__()} 时 @ref{442,,hasattr()} 和 @ref{443,,getattr()} 现在会比原来快大约 4 倍。 （由 INADA Naoki 在 bpo-32544@footnote{https://bugs.python.org/issue32544} 中贡献。）

在字符串中搜索特定的 Unicode 字符（例如乌克兰语字母“Є”）会比搜索其他字符慢上 25 倍。 而现在最坏情况下也只会慢上 3 倍。 （由 Serhiy Storchaka 在 bpo-24821@footnote{https://bugs.python.org/issue24821} 中贡献。）

@ref{1b6,,collections.namedtuple()} 工厂对象已经重写实现，使得创建具名元组的速度加快了 4 到 6 倍。 （由 Jelle Zijlstra 在 bpo-28638@footnote{https://bugs.python.org/issue28638} 中贡献，进一步的改进由 INADA Naoki, Serhiy Storchaka 和 Raymond Hettinger 贡献。）

现在 @code{date.fromordinal()} 和 @code{date.fromtimestamp()} 在通常情况下执行速度可提升 30%。 （由 Paul Ganssle 在 bpo-32403@footnote{https://bugs.python.org/issue32403} 中贡献。）

由于使用了 @ref{25f,,os.scandir()}，现在 @ref{3ac,,os.fwalk()} 函数执行速度提升了 2 倍。 （由 Serhiy Storchaka 在 bpo-25996@footnote{https://bugs.python.org/issue25996} 中贡献。）

由于使用了 @ref{25f,,os.scandir()} 函数，@ref{21c,,shutil.rmtree()} 函数的执行速度已经提升了 20--40%。 （由 Serhiy Storchaka 在 bpo-28564@footnote{https://bugs.python.org/issue28564} 中贡献。）

@ref{dd,,正则表达式} 忽略大小写的匹配和搜索已获得优化。 现在搜索某些模式的速度提升了 20 倍。 （由 Serhiy Storchaka 在 bpo-30285@footnote{https://bugs.python.org/issue30285} 中贡献。）

@ref{444,,re.compile()} 现在会将 @code{flags} 形参转换为 int 对象，如果它是 @code{RegexFlag} 的话。 它现在会和 Python 3.5 一样快，而比 Python 3.6 快大约 10%，实际速度取决于具体的模式。 （由 INADA Naoki 在 bpo-31671@footnote{https://bugs.python.org/issue31671} 中贡献。）

@ref{445,,selectors.EpollSelector}, @ref{446,,selectors.PollSelector} 和 @ref{447,,selectors.DevpollSelector} 这几个类的 @ref{448,,modify()} 方法在重负载下可以加快 10% 左右。 （由 Giampaolo Rodola' 在 bpo-30014@footnote{https://bugs.python.org/issue30014} 中贡献。）

常量折叠已经从窥孔优化器迁移至新的 AST 优化器，后者可以以更高的一致性来执行优化。 （由 Eugene Toder 和 INADA Naoki 在 bpo-29469@footnote{https://bugs.python.org/issue29469} 和 bpo-11549@footnote{https://bugs.python.org/issue11549} 中贡献。）

@ref{4,,abc} 中的大部分函数和方法已经用 C 重写。 这使得创建抽像基类以及调用其 @ref{449,,isinstance()} 和 @ref{44a,,issubclass()} 的速度加快了 1.5 倍。 这也使得 Python 启动耗时减少了 10%。 （由 Ivan Levkivskyi 和 INADA Naoki 在 bpo-31333@footnote{https://bugs.python.org/issue31333} 中贡献。）

在不构造子类时，通过使用快速路径构造器使得 @ref{193,,datetime.date} 和 @ref{194,,datetime.datetime} 的替代构造器获得了显著的速度提升。 （由 Paul Ganssle 在 bpo-32403@footnote{https://bugs.python.org/issue32403} 中贡献。）

在特定情况下 @ref{44b,,array.array} 实例的比较速度已获得很大提升。 现在当比较存放相同的整数类型的值的数组时会比原来快 10 到 70 倍。 （由 Adrian Wielgosik 在 bpo-24700@footnote{https://bugs.python.org/issue24700} 中贡献。）

在大多数平台上 @ref{44c,,math.erf()} 和 @ref{44d,,math.erfc()} 函数现在使用（更快的）C 库实现。 （由 Serhiy Storchaka 在 bpo-26121@footnote{https://bugs.python.org/issue26121} 中贡献。）

@node 其他 CPython 实现的改变,已弃用的 Python 行为,性能优化<2>,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 other-cpython-implementation-changes}@anchor{44e}
@subsection 其他 CPython 实现的改变



@itemize *

@item 
跟踪钩子现在可以选择不接收 @code{line} 而是选择从解释器接收 @code{opcode} 事件，具体做法是在被跟踪的帧上相应地设置新的 @code{f_trace_lines} 和 @code{f_trace_opcodes} 属性。 （由 Nick Coghlan 在 bpo-31344@footnote{https://bugs.python.org/issue31344} 中贡献。）

@item 
修复了一些命名空间包模块属性的一致性问题。 命名空间模块对象的 @code{__file__} 被设置为 @code{None}  (原先未设置)，对象的 @code{__spec__.origin} 也被设置为 @code{None} (之前为字符串 @code{"namespace"})。 参见 bpo-32305@footnote{https://bugs.python.org/issue32305}。 而且，命名空间模块对象的 @code{__spec__.loader} 被设置的值与 @code{__loader__} 相同 (原先前者被设置为 @code{None})。 参见 bpo-32303@footnote{https://bugs.python.org/issue32303}。

@item 
@ref{44f,,locals()} 字典现在以变量定义的词法顺序显示。 原先未定义顺序。 （由 Raymond Hettinger 在 bpo-32690@footnote{https://bugs.python.org/issue32690} 中贡献。）

@item 
@ref{39,,distutils} @code{upload} 命令不会再试图将行结束字符 CR 改为 CRLF。 这修复了 sdists 的一个以与 CR 等价的字节结束的数据损坏问题。 （由 Bo Bayles 在 bpo-32304@footnote{https://bugs.python.org/issue32304} 中贡献。）
@end itemize

@node 已弃用的 Python 行为,已弃用的 Python 模块、函数和方法,其他 CPython 实现的改变,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 deprecated-python-behavior}@anchor{450}
@subsection 已弃用的 Python 行为


在推导式和生成器表达式中的 yield 语句（包括 @code{yield} 和 @code{yield from} 子句）现在已弃用（最左端的 @code{for} 子句中的可迭代对象表达式除外）。 这确保了推导式总是立即返回适当类型的容器（而不是有可能返回 @ref{451,,generator iterator} 对象），这样生成器表达式不会试图将它们的隐式输出与任何来自显式 yield 表达式的输出交错起来。 在 Python 3.7 中，这样的表达式会在编译时引发 @ref{278,,DeprecationWarning}，在 Python 3.8 中则将引发 @ref{452,,SyntaxError}。 （由 Serhiy Storchaka 在 bpo-10544@footnote{https://bugs.python.org/issue10544} 中贡献。）

从 @ref{18d,,object.__complex__()} 返回一个 @ref{189,,complex} 的子类的行为已弃用并将在未来的 Python 版本中引发错误。 这使得 @code{__complex__()} 的行为与 @ref{18b,,object.__int__()} 和 @ref{18c,,object.__float__()} 保持一致。 （由 Serhiy Storchaka 在 bpo-28894@footnote{https://bugs.python.org/issue28894} 中贡献。）

@node 已弃用的 Python 模块、函数和方法,已弃用的 C API 函数和类型,已弃用的 Python 行为,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 deprecated-python-modules-functions-and-methods}@anchor{453}
@subsection 已弃用的 Python 模块、函数和方法


@menu
* aifc:: 
* asyncio: asyncio<3>. 
* collections: collections<3>. 
* dbm: dbm<2>. 
* enum: enum<2>. 
* gettext: gettext<2>. 
* importlib: importlib<2>. 
* locale: locale<2>. 
* macpath:: 
* threading: threading<2>. 
* socket: socket<3>. 
* ssl: ssl<3>. 
* sunau:: 
* sys: sys<3>. 
* wave:: 

@end menu

@node aifc,asyncio<3>,,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 aifc}@anchor{454}
@subsubsection aifc


@code{aifc.openfp()} 已弃用并将在 Python 3.9 中被移除。 请改用 @ref{455,,aifc.open()}。 （由 Brian Curtin 在 bpo-31985@footnote{https://bugs.python.org/issue31985} 中贡献。）

@node asyncio<3>,collections<3>,aifc,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id2}@anchor{456}@anchor{whatsnew/3 7 whatsnew37-asyncio-deprecated}@anchor{364}
@subsubsection asyncio


对 @ref{28b,,asyncio.Lock} 和其他 asyncio 同步原语的 @code{await} 实例的直接支持已弃用。 想要获取并释放同步资源必须使用异步上下文管理器。 （由 Andrew Svetlov 在 bpo-32253@footnote{https://bugs.python.org/issue32253} 中贡献。）

@ref{34b,,asyncio.Task.current_task()} 和 @ref{34c,,asyncio.Task.all_tasks()} 方法已弃用。 （由 Andrew Svetlov 在 bpo-32250@footnote{https://bugs.python.org/issue32250} 中贡献。）

@node collections<3>,dbm<2>,asyncio<3>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id3}@anchor{457}
@subsubsection collections


在 Python 3.8 中，@ref{1f,,collections.abc} 内的抽象基类将不会再通过常规的 @ref{1e,,collections} 模块公开。 这有助于更清晰地区别具体类与抽象基类。 （由 Serhiy Storchaka 在 bpo-25988@footnote{https://bugs.python.org/issue25988} 中贡献。）

@node dbm<2>,enum<2>,collections<3>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id4}@anchor{458}
@subsubsection dbm


@ref{33,,dbm.dumb} 现在支持读取只读文件，且当其未被更改时不会再写入索引文件。 现在如果索引文件丢失并在 @code{'r'} 与 @code{'w'} 模式下被重新创建，则会发出已弃用警告（在未来的 Python 发布版中将改为错误）。 （由 Serhiy Storchaka 在 bpo-28847@footnote{https://bugs.python.org/issue28847} 中贡献。）

@node enum<2>,gettext<2>,dbm<2>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id5}@anchor{459}
@subsubsection enum


在 Python 3.8 中，尝试在 @code{Enum} 类中检查非 Enum 对象将引发 @ref{192,,TypeError} (例如 @code{1 in Color})；类似地，尝试在 @code{Flag} 成员中检查非 Flag 对象也将引发 @ref{192,,TypeError} (例如 @code{1 in Perm.RW})；目前，两种操作均会返回 @ref{380,,False}。 （由 Ethan Furman 在 bpo-33217@footnote{https://bugs.python.org/issue33217} 中贡献。）

@node gettext<2>,importlib<2>,enum<2>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 gettext}@anchor{45a}
@subsubsection gettext


使用非整数值在 @ref{89,,gettext} 中选择复数形式现在已弃用。 它从未正确地发挥作用。 （由 Serhiy Storchaka 在 bpo-28692@footnote{https://bugs.python.org/issue28692} 中贡献。）

@node importlib<2>,locale<2>,gettext<2>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id6}@anchor{45b}
@subsubsection importlib


下列方法 @ref{45c,,MetaPathFinder.find_module()} (被 @ref{45d,,MetaPathFinder.find_spec() 替代}) 和 @ref{45e,,PathEntryFinder.find_loader()} (被 @ref{45f,,PathEntryFinder.find_spec() 替代}) 都在 Python 3.4 中已弃用，现在会引发 @ref{278,,DeprecationWarning}。 （由 Matthias Bussonnier 在 bpo-29576@footnote{https://bugs.python.org/issue29576} 中贡献）

@ref{460,,importlib.abc.ResourceLoader} ABC 已弃用，推荐改用 @ref{33b,,importlib.abc.ResourceReader}。

@node locale<2>,macpath,importlib<2>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id7}@anchor{461}
@subsubsection locale


@ref{462,,locale.format()} 已弃用，请改用 @ref{39c,,locale.format_string()}。 （由 Garvit 在 bpo-10379@footnote{https://bugs.python.org/issue10379} 中贡献。）

@node macpath,threading<2>,locale<2>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 macpath}@anchor{463}
@subsubsection macpath


@code{macpath} 现在已弃用，将在 Python 3.8 中被移除。 （由 Chi Hsuan Yen 在 bpo-9850@footnote{https://bugs.python.org/issue9850} 中贡献。）

@node threading<2>,socket<3>,macpath,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 threading}@anchor{464}
@subsubsection threading


@ref{68,,dummy_threading} 和 @ref{2,,_dummy_thread} 已弃用。 构建禁用线程的 Python 已不再可能。 请改用 @ref{109,,threading}。 （由 Antoine Pitrou 在 bpo-31370@footnote{https://bugs.python.org/issue31370} 中贡献。）

@node socket<3>,ssl<3>,threading<2>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id8}@anchor{465}
@subsubsection socket


@ref{466,,socket.htons()} 和 @ref{467,,socket.ntohs()} 中的静默参数截断已弃用。 在未来的 Python 版本中，如果传入的参数长度大于 16 比特位，将会引发异常。 （由 Oren Milman 在 bpo-28332@footnote{https://bugs.python.org/issue28332} 中贡献。）

@node ssl<3>,sunau,socket<3>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id9}@anchor{468}
@subsubsection ssl


@ref{469,,ssl.wrap_socket()} 已弃用。 请改用 @ref{3dd,,ssl.SSLContext.wrap_socket()}。 （由 Christian Heimes 在 bpo-28124@footnote{https://bugs.python.org/issue28124} 中贡献。）

@node sunau,sys<3>,ssl<3>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 sunau}@anchor{46a}
@subsubsection sunau


@ref{46b,,sunau.openfp()} 已弃用并将在 Python 3.9 中被移除。 请改用 @ref{46c,,sunau.open()}。 （由 Brian Curtin 在 bpo-31985@footnote{https://bugs.python.org/issue31985} 中贡献。）

@node sys<3>,wave,sunau,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 id10}@anchor{46d}
@subsubsection sys


已弃用 @code{sys.set_coroutine_wrapper()} 和 @code{sys.get_coroutine_wrapper()}。

未写入文档的 @code{sys.callstats()} 函数已弃用并将在未来的 Python 版本中被移除。 （由 Victor Stinner 在 bpo-28799@footnote{https://bugs.python.org/issue28799} 中贡献。）

@node wave,,sys<3>,已弃用的 Python 模块、函数和方法
@anchor{whatsnew/3 7 wave}@anchor{46e}
@subsubsection wave


@ref{46f,,wave.openfp()} 已弃用并将在 Python 3.9 中被移除。 请改用 @ref{470,,wave.open()}。 （由 Brian Curtin 在 bpo-31985@footnote{https://bugs.python.org/issue31985} 中贡献。）

@node 已弃用的 C API 函数和类型,平台支持的移除,已弃用的 Python 模块、函数和方法,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 deprecated-functions-and-types-of-the-c-api}@anchor{471}
@subsection 已弃用的 C API 函数和类型


如果 @code{Py_LIMITED_API} 未设定或设定为范围在 @code{0x03050400} 和 @code{0x03060000} (不含) 之间，或为 @code{0x03060100} 或更高的值，函数 @ref{472,,PySlice_GetIndicesEx()} 已弃用并被一个宏所替代。 （由 Serhiy Storchaka 在 bpo-27867@footnote{https://bugs.python.org/issue27867} 中贡献。）

@ref{42b,,PyOS_AfterFork()} 已弃用。 请改用 @ref{42c,,PyOS_BeforeFork()}, @ref{42d,,PyOS_AfterFork_Parent()} 或 @ref{2cd,,PyOS_AfterFork_Child()}。 （由 Antoine Pitrou 在 bpo-16500@footnote{https://bugs.python.org/issue16500} 中贡献。）

@node 平台支持的移除,API 与特性的移除<2>,已弃用的 C API 函数和类型,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 id11}@anchor{473}@anchor{whatsnew/3 7 platform-support-removals}@anchor{3d7}
@subsection 平台支持的移除



@itemize *

@item 
官方已不再支持 FreeBSD 9 及更旧的版本。

@item 
为了完整的 Unicode 支持，包括在扩展模块之内，*nix 平台现在至少应当提供 @code{C.UTF-8} (完整区域), @code{C.utf8} (完整区域) 或 @code{UTF-8} (@code{LC_CTYPE} 专属区域) 中的一个作为基于 @code{ASCII} 的传统 @code{C} 区域的替代。

@item 
OpenSSL 0.9.8 和 1.0.1 已不再受支持，这意味着在仍然使用这些版本的旧平台上构建带有 SSL/TLS 支持的 CPython 3.7 时，需要自定义构建选项以链接到更新的 OpenSSL 版本。

注意，此问题会影响到 Debian 8 (代号“jessie”) 和 Ubuntu 14.04 (代号“Trusty”) 等长期支持 Linux 发行版，因为它们默认仍然使用 OpenSSL 1.0.1。

Debian 9 (“stretch”) 和 Ubuntu 16.04 (“xenial”) 以及其他最新的长期支持 Linux 发行版 (例如 RHEL/CentOS 7.5, SLES 12-SP3) 都使用 OpenSSL 1.0.2 或更新的版本，因此继续在默认的构建配置中受到支持。

CPython 自己的 CI 配置文件@footnote{https://github.com/python/cpython/tree/3.8/.travis.yml} 提供了一个使用 CPython 测试套件中的 SSL 兼容性测试架构@footnote{https://github.com/python/cpython/tree/3.8/Tools/ssl/multissltests.py} 基于 OpenSSL 1.1.0 进行构建和链接的例子，而不是使用过时的系统所提供的 OpenSSL。
@end itemize

@node API 与特性的移除<2>,移除的模块,平台支持的移除,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 api-and-feature-removals}@anchor{474}
@subsection API 与特性的移除


下列特性与 API 已从 Python 3.7 中移除:


@itemize *

@item 
@code{os.stat_float_times()} 函数已被移除。 它在 Python 2.3 中被引入用于向下兼容 Python 2.2，并自 Python 3.1 起就已弃用。

@item 
在 @ref{475,,re.sub()} 的替换模块中由 @code{'\'} 与一个 ASCII 字母构成的未知转义在 Python 3.5 中已弃用，现在将会引发错误。

@item 
在 @ref{476,,tarfile.TarFile.add()} 中移除了对 @emph{exclude} 参数的支持。 它在 Python 2.7 和 3.2 中已弃用。 请改用 @emph{filter} 参数。

@item 
@code{ntpath} 模块中的 @code{splitunc()} 函数在 Python 3.1 中已弃用，现在已被移除。 请改用 @ref{477,,splitdrive()} 函数。

@item 
@ref{1b6,,collections.namedtuple()} 不再支持 @emph{verbose} 形参或 @code{_source} 属性，该属性会显示为具名元组类所生成的源代码。 这是加速类创建的设计优化的一部分。 （由 Jelle Zijlstra 在 bpo-28638@footnote{https://bugs.python.org/issue28638} 中贡献，进一步的改进由 INADA Naoki, Serhiy Storchaka 和 Raymond Hettinger 贡献。）

@item 
函数 @ref{183,,bool()}, @ref{187,,float()}, @ref{262,,list()} 和 @ref{478,,tuple()} 不再接受关键字参数。 @ref{184,,int()} 的第一个参数现在只能作为位置参数传入。

@item 
移除了之前在 Python 2.4 中已弃用的 @ref{cf,,plistlib} 模块的类 @code{Plist}, @code{Dict} 和 @code{_InternalDict}。 作为函数 @ref{479,,readPlist()} 和 @ref{47a,,readPlistFromBytes()} 返回结果的 Dict 值现在为普通 dict。 你不能再使用属性访问来获取这些字典的项。

@item 
@code{asyncio.windows_utils.socketpair()} 函数已被移除。 请改用 @ref{47b,,socket.socketpair()} 函数，它自 Python 3.5 起就在所有平台上可用。 @code{asyncio.windows_utils.socketpair} 在 Python 3.5 及更新版本上只是 @code{socket.socketpair} 的别名。

@item 
@ref{a,,asyncio} 不再将 @ref{e6,,selectors} 和 @code{_overlapped} 模块导出为 @code{asyncio.selectors} 和 @code{asyncio._overlapped}。 请将 @code{from asyncio import selectors} 替换为 @code{import selectors}。

@item 
现在已禁止直接实例化 @ref{3da,,ssl.SSLSocket} 和 @ref{3db,,ssl.SSLObject} 对象。 相应构造器从未写入文档、也从未作为公有构造器进行测试或设计。 用户应当使用 @ref{469,,ssl.wrap_socket()} 或 @ref{3dc,,ssl.SSLContext}。 （由 Christian Heimes 在 bpo-32951@footnote{https://bugs.python.org/issue32951} 中贡献。）

@item 
未被使用的 @ref{39,,distutils} @code{install_misc} 命令已被移除。 （由 Eric N. Vander Weele 在 bpo-29218@footnote{https://bugs.python.org/issue29218} 中贡献。）
@end itemize

@node 移除的模块,Windows 专属的改变,API 与特性的移除<2>,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 module-removals}@anchor{47c}
@subsection 移除的模块


@code{fpectl} 模块已被移除。 它从未被默认启用，从未在 x86-64 上正确发挥效果，并且它对 Python ABI 的改变会导致 C 扩展的意外损坏。 （由 Nathaniel J. Smith 在 bpo-29137@footnote{https://bugs.python.org/issue29137} 中贡献。）

@node Windows 专属的改变,移植到 Python 3 7,移除的模块,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 windows-only-changes}@anchor{47d}
@subsection Windows 专属的改变


Python 启动器（py.exe）可以接受 32 位或 64 位标记而 @strong{不必} 同时指定一个小版本。 因此 @code{py -3-32} 和 @code{py -3-64} 与 @code{py -3.7-32} 均为有效，并且现在还接受 -@emph{m}-64 和 -@emph{m.n}-64 来强制使用 64 位 python 命令，即使是本应使用 32 位的时候。 如果指定版本不可用则 py.exe 将报错退出。 （由 Steve Barnes 在 bpo-30291@footnote{https://bugs.python.org/issue30291} 中贡献。）

启动器可以运行 @code{py -0} 来列出已安装的所有 python，@emph{默认版本会以星号标出}。 运行 @code{py -0p} 将同时列出相应的路径。 如果运行 py 时指定了无法匹配的版本，它将显示 @emph{简短形式} 的可用版本列表。 （由 Steve Barnes 在 bpo-30362@footnote{https://bugs.python.org/issue30362} 中贡献。）

@node 移植到 Python 3 7,Python 3 7 1 中的重要变化,Windows 专属的改变,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 porting-to-python-3-7}@anchor{47e}@anchor{whatsnew/3 7 porting-to-python-37}@anchor{300}
@subsection 移植到 Python 3.7


本节列出了先前描述的更改以及可能需要更改代码的其他错误修正.

@menu
* Python 行为的更改:: 
* Python API 的变化: Python API 的变化<2>. 
* C API 的变化: C API 的变化<2>. 
* CPython 字节码的改变: CPython 字节码的改变<2>. 
* Windows 专属的改变: Windows 专属的改变<2>. 
* 其他 CPython 实现的改变: 其他 CPython 实现的改变<2>. 

@end menu

@node Python 行为的更改,Python API 的变化<2>,,移植到 Python 3 7
@anchor{whatsnew/3 7 changes-in-python-behavior}@anchor{47f}
@subsubsection Python 行为的更改



@itemize *

@item 
@ref{1a2,,async} 和 @ref{1a3,,await} 现在是保留关键字。 使用了这些名称作为标识符的代码现在将引发 @ref{452,,SyntaxError}。 （由 Jelle Zijlstra 在 bpo-30406@footnote{https://bugs.python.org/issue30406} 中贡献。）

@item 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479} 在 Python 3.7 中对所有代码启用，在协程和生成器中直接或间接引发的 @ref{480,,StopIteration} 异常会被转换为 @ref{2ba,,RuntimeError} 异常。 （由 Yury Selivanov 在 bpo-32670@footnote{https://bugs.python.org/issue32670} 中贡献。）

@item 
@ref{481,,object.__aiter__()} 方法不再能被声明为异步的。 （由 Yury Selivanov 在 bpo-31709@footnote{https://bugs.python.org/issue31709} 中贡献。）

@item 
由于一个疏忽，之前的 Python 版本会错误地接受以下语法:

@example
f(1 for x in [1],)

class C(1 for x in [1]):
    pass
@end example

现在 Python 3.7 会正确地引发 @ref{452,,SyntaxError}，因为生成器表达式总是必须直接包含于一对括号之内， 且前后都不能有逗号，仅在调用时可以忽略重复的括号。 （由 Serhiy Storchaka 在 bpo-32012@footnote{https://bugs.python.org/issue32012} 和 bpo-32023@footnote{https://bugs.python.org/issue32023} 中贡献。）

@item 
现在当使用 @ref{330,,-m} 开关时，会将初始工作目录添加到 @ref{482,,sys.path}，而不再是一个空字符串（即在每次导入时动态地指明当前工作目录）。 任何会检测该空字符串，或是以其他方式依赖之前行为的的程序将需要进行相应的更新（例如改为还要检测 @code{os.getcwd()} 或 @code{os.path.dirname(__main__.__file__)}，具体做法首先要取决于为何要对代码执行空字符串检测）。
@end itemize

@node Python API 的变化<2>,C API 的变化<2>,Python 行为的更改,移植到 Python 3 7
@anchor{whatsnew/3 7 changes-in-the-python-api}@anchor{483}
@subsubsection Python API 的变化



@itemize *

@item 
@code{socketserver.ThreadingMixIn.server_close()} 现在会等待所有非守护线程完成。 将新增的 @code{socketserver.ThreadingMixIn.block_on_close} 类属性设为 @code{False} 可获得 3.7 之前版本的行为。 （由 Victor Stinner 在 bpo-31233@footnote{https://bugs.python.org/issue31233} 和 bpo-33540@footnote{https://bugs.python.org/issue33540} 中贡献。）

@item 
@code{socketserver.ForkingMixIn.server_close()} 现在会等等所有子进程完成。 将新增的 @code{socketserver.ForkingMixIn.block_on_close} 类属性设为 @code{False} 可获得 3.7 之前版本的行为。 （由 Victor Stinner 在 bpo-31151@footnote{https://bugs.python.org/issue31151} 和 bpo-33540@footnote{https://bugs.python.org/issue33540} 中贡献。）

@item 
某些情况下 @ref{484,,locale.localeconv()} 函数现在会临时将 @code{LC_CTYPE} 区域设置为 @code{LC_NUMERIC} 的值。 （由 Victor Stinner 在 bpo-31900@footnote{https://bugs.python.org/issue31900} 中贡献。）

@item 
如果 @emph{path} 为字符串 @ref{485,,pkgutil.walk_packages()} 现在会引发 @ref{1fb,,ValueError}。 之前则是返回一个空列表。 （由 Sanyam Khurana 在 bpo-24744@footnote{https://bugs.python.org/issue24744} 中贡献。）

@item 
@ref{486,,string.Formatter.format()} 的格式字符串参数现在为 @ref{2a7,,仅限位置} 参数。 将其作为关键字参数传入的方式自 Python 3.5 起已弃用。 （由 Serhiy Storchaka 在 bpo-29193@footnote{https://bugs.python.org/issue29193} 中贡献。）

@item 
类 @ref{487,,http.cookies.Morsel} 的属性 @ref{488,,key}, @ref{489,,value} 和 @ref{48a,,coded_value} 现在均为只读。 对其赋值的操作自 Python 3.5 起已弃用。 要设置它们的值请使用 @ref{48b,,set()} 方法。 （由 Serhiy Storchaka 在 bpo-29192@footnote{https://bugs.python.org/issue29192} 中贡献。）

@item 
@ref{3b5,,os.makedirs()} 的 @emph{mode} 参数不会再影响新建中间层级目录的文件权限位。 要设置它们的文件权限位你可以在发起调用 @code{makedirs()} 之前设置 umask。 （由 Serhiy Storchaka 在 bpo-19930@footnote{https://bugs.python.org/issue19930} 中贡献。）

@item 
@ref{48c,,struct.Struct.format} 的类型现在是 @ref{329,,str} 而非 @ref{32a,,bytes}。 （由 Victor Stinner 在 bpo-21071@footnote{https://bugs.python.org/issue21071} 中贡献。）

@item 
@ref{48d,,parse_multipart()} 现在接受 @emph{encoding} 和 @emph{errors} 参数并返回与 @code{FieldStorage} 同样的结果：对于非文件字段，与键相关联的值是一个字符串列表，而非字节串。 （由 Pierre Quentel 在 bpo-29979@footnote{https://bugs.python.org/issue29979} 中贡献。）

@item 
由于 @ref{ef,,socket} 中的内部更改，在由旧版 Python 中的 @ref{48e,,socket.share} 所创建的套接字上调用 @ref{48f,,socket.fromshare()} 已不受支持。

@item 
@ref{1a8,,BaseException} 的 @code{repr} 已更改为不包含末尾的逗号。 大多数异常都会受此更改影响。 （由 Serhiy Storchaka 在 bpo-30399@footnote{https://bugs.python.org/issue30399} 中贡献。）

@item 
@ref{195,,datetime.timedelta} 的 @code{repr} 已更改为在输出中包含关键字参数。 （由 Utkarsh Upadhyay 在 bpo-30302@footnote{https://bugs.python.org/issue30302} 中贡献。）

@item 
因为 @ref{21c,,shutil.rmtree()} 现在是使用 @ref{25f,,os.scandir()} 函数实现的，用户指定的句柄 @emph{onerror} 现在被调用时如果列目录失败会附带第一个参数 @code{os.scandir} 而不是 @code{os.listdir}。

@item 
未来可能加入在正则表达式中对 Unicode 技术标准 #18@footnote{https://unicode.org/reports/tr18/} 中嵌套集合与集合操作的支持。 这会改变现有语法。 为了推动这项未来的改变，目前在有歧义的情况下会引发 @ref{31e,,FutureWarning}。 这包括以字面值 @code{'['} 开头或包含字面值字符序列 @code{'--'}, @code{'&&'}, @code{'~~'} 以及 @code{'||'}  的集合。 要避免警告，请用反斜杠对其进行转义。 （由 Serhiy Storchaka 在 bpo-30349@footnote{https://bugs.python.org/issue30349} 中贡献。）

@item 
基于可以匹配空字符串的 @ref{dd,,正则表达式} 对字符串进行拆分的结果已被更改。 例如基于 @code{r'\s*'} 的拆分现在不仅会像原先那样拆分空格符，而且会拆分所有非空格字符之前和字符串结尾处的空字符串。 通过将模式修改为 @code{r'\s+'} 可以恢复原先的行为。 自 Python 3.5 开始此类模式将会引发 @ref{31e,,FutureWarning}。

对于同时匹配空字符串和非空字符串的模式，在其他情况下搜索所有匹配的结果也可能会被更改。 例如在字符串 @code{'a\n\n'} 中，模式 @code{r'(?m)^\s*?$'} 将不仅会匹配位置 2 和 3 上的空字符串，还会匹配位置 2--3 上的字符串 @code{'\n'}。 想要只匹配空行，模式应当改写为 @code{r'(?m)^[^\S\n]*$'}。

@ref{475,,re.sub()} 现在会替换与前一个的非空匹配相邻的空匹配。 例如 @code{re.sub('x*', '-', 'abxd')} 现在会返回 @code{'-a-b--d-'} 而不是 @code{'-a-b-d-'} ('b' 和 'd' 之间的第一个减号是替换 'x'，而第二个减号则是替换 'x' 和 'd' 之间的空字符串)。

（由 Serhiy Storchaka 在 bpo-25054@footnote{https://bugs.python.org/issue25054} 和 bpo-32308@footnote{https://bugs.python.org/issue32308} 中贡献。）

@item 
@ref{490,,re.escape()} 更改为只转义正则表达式特殊字符，而不转义 ASCII 字母、数字和 @code{'_'} 以外的所有字符。 （由 Serhiy Storchaka 在 bpo-29995@footnote{https://bugs.python.org/issue29995} 中贡献。）

@item 
@ref{3f7,,tracemalloc.Traceback} 帧现在是按从最旧到最新排序，以便与 @ref{113,,traceback} 更为一致。 （由 Jesse Bakker 在 bpo-32121@footnote{https://bugs.python.org/issue32121} 中贡献。）

@item 
在支持 @ref{491,,socket.SOCK_NONBLOCK} 或 @ref{492,,socket.SOCK_CLOEXEC} 标志位的操作系统上，@ref{493,,socket.type} 不再应用它们。 因此，像 @code{if sock.type == socket.SOCK_STREAM} 之类的检测会在所有平台上按预期的方式工作。 （由 Yury Selivanov 在 bpo-32331@footnote{https://bugs.python.org/issue32331} 中贡献。）

@item 
在 Windows 上当重定向标准句柄时，@ref{2b9,,subprocess.Popen} 的 @emph{close_fds} 参数的默认值从 @ref{380,,False} 更改为 @ref{494,,True}。 如果你以前依赖于在使用带有标准 io 重定向的 @ref{2b9,,subprocess.Popen} 时所继承的句柄，则必须传入 @code{close_fds=False} 以保留原先的行为，或是使用 @ref{495,,STARTUPINFO.lpAttributeList}。

@item 
@ref{496,,importlib.machinery.PathFinder.invalidate_caches()} -- 此方法隐式地影响 @ref{497,,importlib.invalidate_caches()} -- 现在会删除 @ref{498,,sys.path_importer_cache} 中被设为 @code{None} 的条目。 （由 Brett Cannon 在 bpo-33169@footnote{https://bugs.python.org/issue33169} 中贡献。）

@item 
在 @ref{a,,asyncio} 中，@ref{499,,loop.sock_recv()}, @ref{49a,,loop.sock_sendall()}, @ref{49b,,loop.sock_accept()}, @ref{49c,,loop.getaddrinfo()}, @ref{49d,,loop.getnameinfo()} 已被更改为正确的协程方法以与培训五日文档相匹配。 之前，这些方法会返回 @ref{43d,,asyncio.Future} 实例。 （由 Yury Selivanov 在 bpo-32327@footnote{https://bugs.python.org/issue32327} 中贡献。）

@item 
@ref{49e,,asyncio.Server.sockets} 现在会返回服务器套接字列表的副本，而不是直接地返回它。 （由 Yury Selivanov 在 bpo-32662@footnote{https://bugs.python.org/issue32662} 中贡献。）

@item 
@ref{48c,,Struct.format} 现在是一个 @ref{329,,str} 实例而非 @ref{32a,,bytes} 实例。 （由 Victor Stinner 在 bpo-21071@footnote{https://bugs.python.org/issue21071} 中贡献。）

@item 
现在可以通过将 @code{required=True} 传给 @ref{49f,,ArgumentParser.add_subparsers()} 使得 @ref{6,,argparse} 子解析器成为必需的。 （由 Anthony Sottile 在 bpo-26510@footnote{https://bugs.python.org/issue26510} 中贡献。）

@item 
@ref{4a0,,ast.literal_eval()} 现在更为严格。 任意地加减数字已不再被允许。 （由 Serhiy Storchaka 在 bpo-31778@footnote{https://bugs.python.org/issue31778} 中贡献。）

@item 
当一个日期超出 @code{0001-01-01} 到 @code{9999-12-31} 范围时 @ref{4a1,,Calendar.itermonthdates} 现在将始终如一地引发异常，以便支持不能容忍此类异常的应用程序，可以使用新增的 @ref{4a2,,Calendar.itermonthdays3} 和 @ref{4a3,,Calendar.itermonthdays4}。 这些新方法返回元组，并且其不受 @ref{193,,datetime.date} 所支持的范围限制。 （由 Alexander Belopolsky 在 bpo-28292@footnote{https://bugs.python.org/issue28292} 中贡献。）

@item 
@ref{4a4,,collections.ChainMap} 现在会保留底层映射的顺序。 （由 Raymond Hettinger 在 bpo-32792@footnote{https://bugs.python.org/issue32792} 中贡献。）

@item 
如果在解释器关闭期间被调用，@ref{27a,,concurrent.futures.ThreadPoolExecutor} 和 @ref{2a3,,concurrent.futures.ProcessPoolExecutor} 的 @code{submit()} 方法现在会引发 @ref{2ba,,RuntimeError}。 （由 Mark Nemec 在 bpo-33097@footnote{https://bugs.python.org/issue33097} 中贡献。）

@item 
@ref{4a5,,configparser.ConfigParser} 构造器现在使用 @code{read_dict()} 来处理默认值，以使其行为与解析器的其余部分保持致。 在默认字典中的非字符串键和值现在会被隐式地转换为字符串。 （由 James Tocknell 在 bpo-23835@footnote{https://bugs.python.org/issue23835} 中贡献。）

@item 
一些未写入文档的内部导入已被移除。 一个例子是 @code{os.errno} 已不再可用；应改为直接使用 @code{import errno}。 请注意此类未写入文档的内部导入可能未经通知地随时被移除，甚至是在微版本号发行版中移除。
@end itemize

@node C API 的变化<2>,CPython 字节码的改变<2>,Python API 的变化<2>,移植到 Python 3 7
@anchor{whatsnew/3 7 changes-in-the-c-api}@anchor{4a6}
@subsubsection C API 的变化


函数 @ref{472,,PySlice_GetIndicesEx()} 被认为对于大小可变的序列来说并不安全。 如果切片索引不是 @ref{184,,int} 的实例，而是实现了 @code{__index__()} 方法的对象，则序列可以在其长度被传给 @code{PySlice_GetIndicesEx()} 之后调整大小。 这可能导致返回超出序列长度的索引号。 为了避免可能的问题，请使用新增的函数 @ref{429,,PySlice_Unpack()} 和 @ref{42a,,PySlice_AdjustIndices()}。 （由 Serhiy Storchaka 在 bpo-27867@footnote{https://bugs.python.org/issue27867} 中贡献。）

@node CPython 字节码的改变<2>,Windows 专属的改变<2>,C API 的变化<2>,移植到 Python 3 7
@anchor{whatsnew/3 7 cpython-bytecode-changes}@anchor{4a7}
@subsubsection CPython 字节码的改变


新增了两个操作码: @ref{4a8,,LOAD_METHOD} 和 @ref{4a9,,CALL_METHOD}。 （由 Yury Selivanov 和 INADA Naoki 在 bpo-26110@footnote{https://bugs.python.org/issue26110} 中贡献。）

@code{STORE_ANNOTATION} 操作码已被移除。 （由 Mark Shannon 在 bpo-32550@footnote{https://bugs.python.org/issue32550} 中贡献。）

@node Windows 专属的改变<2>,其他 CPython 实现的改变<2>,CPython 字节码的改变<2>,移植到 Python 3 7
@anchor{whatsnew/3 7 id12}@anchor{4aa}
@subsubsection Windows 专属的改变


用于重载 @ref{482,,sys.path} 的文件现在命名为 @code{<python-executable>._pth} 而不是 @code{'sys.path'}。 请参阅 @ref{4ab,,查找模块} 了解更多信息。 （由 Steve Dower 在 bpo-28137@footnote{https://bugs.python.org/issue28137} 中贡献。）

@node 其他 CPython 实现的改变<2>,,Windows 专属的改变<2>,移植到 Python 3 7
@anchor{whatsnew/3 7 id13}@anchor{4ac}
@subsubsection 其他 CPython 实现的改变


为了准备在未来对公开的 CPython 运行时初始化 API 进行潜在更改（请参阅 
@geindex Python 提高建议; PEP 432
PEP 432@footnote{https://www.python.org/dev/peps/pep-0432} 获取最初但略为过时的文稿），CPython 内部的启动和配置管理逻辑已经过大幅重构。 虽然这些更新旨在对嵌入式应用程序和常规的 CPython CLI 用户都完全透明，但它们在这里被提及是因为重构会改变解释器启动期间许多操作的内部顺序，因此可能提示出原先隐藏的缺陷，这可能存在于嵌入式应用程序中，或是在 CPython 自身内部。 （最初由 Nick Coghlan 和 Eric Snow 作为 bpo-22257@footnote{https://bugs.python.org/issue22257} 的一部分贡献，并由 Nick, Eric 和 Victor Stinner 在一系列其他问题报告中进一步更新）。 已知会受到影响的一些细节：


@itemize *

@item 
@ref{4ad,,PySys_AddWarnOptionUnicode()} 目前对嵌入式应用程序不可用，因为在调用 @cite{Py_Initialize} 之前需要创建  Unicode 对象。 请改用 @ref{4ae,,PySys_AddWarnOption()}。

@item 
嵌入式应用程序通过 @ref{4ae,,PySys_AddWarnOption()} 所添加的警告过滤器现在应该以更高的一致性优先于由解释器所设置的默认过滤器
@end itemize

由于默认警告过滤器的配置方式发生了变化，将 @ref{4af,,Py_BytesWarningFlag} 设置为大于一的值不再足以在发出 @ref{4b0,,BytesWarning} 消息的同时将其转换为异常。 而是改为必须设置旗标（以便首先发出警告），以及添加显式的 @code{error::BytesWarning} 警告过滤器来将其转换为异常。

由于编译器处理文档字符串的方式发生了变化，一个仅由文档字符串构成的函数体中隐式的 @code{return None} 现在被标记为在与文档字符串相同的行，而不是在函数的标题行。

当前异常状态已从帧对象移到协程对象。 这会简化解释器并修正由于在进入或退出生成器时具有交换异常状态而导致的一些模糊错误。 （由 Mark Shannon 在 bpo-25612@footnote{https://bugs.python.org/issue25612} 中贡献。）

@node Python 3 7 1 中的重要变化,Python 3 7 2 中的重要变化,移植到 Python 3 7,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 notable-changes-in-python-3-7-1}@anchor{4b1}
@subsection Python 3.7.1 中的重要变化


从 3.7.1 开始，@ref{433,,Py_Initialize()} 现在始终会读取并遵循与 @ref{4b2,,Py_Main()} 相同的环境设置（在更早的 Python 版本中，它会遵循一个错误定义的环境变量子集，而在 Python 3.7.0 中则会由于 bpo-34247@footnote{https://bugs.python.org/issue34247} 而完全不读取它们）。 如果不想要此行为，请在调用 @ref{433,,Py_Initialize()} 之前将 @ref{4b3,,Py_IgnoreEnvironmentFlag} 设为 1。

在 3.7.1 中，上下文变量的 C API 已 @ref{4b4,,获得更新} 以使用 @ref{4b5,,PyObject} 指针。 另请参阅 bpo-34762@footnote{https://bugs.python.org/issue34762}。

在 3.7.1 中，当提供不带末尾新行的输入时 @ref{111,,tokenize} 模块现在会隐式地添加 @code{NEWLINE} 形符。 此行为现在已与 C 词法分析器的内部行为相匹配。 （由 Ammar Askar 在 bpo-33899@footnote{https://bugs.python.org/issue33899} 中贡献。）

@node Python 3 7 2 中的重要变化,Python 3 7 6 中的重要变化,Python 3 7 1 中的重要变化,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 notable-changes-in-python-3-7-2}@anchor{4b6}
@subsection Python 3.7.2 中的重要变化


在 3.7.2 中，Windows 下的 @ref{125,,venv} 不再复制原来的二进制文件，而是改为创建名为 @code{python.exe} 和 @code{pythonw.exe} 的重定向脚本。 这解决了一个长期存在的问题，即所有虚拟环境在每次 Python 升级后都必须进行升级或是重新创建。 然而，要注意此发布版仍然要求重新创建虚拟环境以获得新的脚本。

@node Python 3 7 6 中的重要变化,,Python 3 7 2 中的重要变化,Python 3 7 有什么新变化
@anchor{whatsnew/3 7 notable-changes-in-python-3-7-6}@anchor{4b7}
@subsection Python 3.7.6 中的重要变化


出于重要的安全性考量，@ref{2e7,,asyncio.loop.create_datagram_endpoint()} 的 @emph{reuse_address} 形参不再被支持。 这是由 UDP 中的套接字选项 @code{SO_REUSEADDR} 的行为导致的。 更多细节请参阅 @code{loop.create_datagram_endpoint()} 的文档。 （由 Kyle Stanley, Antoine Pitrou 和 Yury Selivanov 在 bpo-37228@footnote{https://bugs.python.org/issue37228} 中贡献。。）

@node Python 3 6 有什么新变化,Python 3 5 有什么新变化,Python 3 7 有什么新变化,Python的新变化
@anchor{whatsnew/3 6 doc}@anchor{4b8}@anchor{whatsnew/3 6 what-s-new-in-python-3-6}@anchor{4b9}
@section Python 3.6 有什么新变化


@*编者: 
Elvis Pranskevichus <@email{elvis@@magic.io}>, Yury Selivanov <@email{yury@@magic.io}>


@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number as a comment:
@c 
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer in :issue:`12345`.)
@c 
@c This saves the maintainer the effort of going through the Mercurial log
@c when researching a change.

本文解释了与3.5相比，Python 3.6中的新功能。 Python 3.6于2016年12月23日发布。请参阅 changelog@footnote{https://docs.python.org/3.6/whatsnew/changelog.html} 以获取完整的更改列表。


@subsubheading 参见


@geindex Python 提高建议; PEP 494
PEP 494@footnote{https://www.python.org/dev/peps/pep-0494} - Python 3.6发布计划


@menu
* 摘要 - 发布重点: 摘要 - 发布重点<3>. 
* 新的特性: 新的特性<3>. 
* 其他语言特性修改: 其他语言特性修改<3>. 
* 新增模块: 新增模块<3>. 
* 改进的模块: 改进的模块<3>. 
* 性能优化: 性能优化<3>. 
* 构建和 C API 的改变: 构建和 C API 的改变<2>. 
* 其他改进:: 
* 弃用: 弃用<2>. 
* 移除:: 
* 移植到Python 3.6: 移植到Python 3 6. 
* Python 3.6.2 中的重要变化: Python 3 6 2 中的重要变化. 
* Python 3.6.4 中的重要变化: Python 3 6 4 中的重要变化. 
* Python 3.6.5 中的重要变化: Python 3 6 5 中的重要变化. 
* Python 3.6.7 中的重要变化: Python 3 6 7 中的重要变化. 
* Python 3.6.10 中的重要变化: Python 3 6 10 中的重要变化. 

@end menu

@node 摘要 - 发布重点<3>,新的特性<3>,,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 summary-release-highlights}@anchor{4ba}
@subsection 摘要 - 发布重点


新的语法特性：


@itemize *

@item 
@ref{4bb,,PEP 498}, 格式化的字符串文字

@item 
@ref{4bc,,PEP 515}, 数字文字中的下划线。

@item 
@ref{4bd,,PEP 526} , 变量注释的语法。

@item 
@ref{4be,,PEP 525}, 异步生成器。

@item 
@ref{4bf,,PEP 530}: 异步推导。
@end itemize

新的库模块：


@itemize *

@item 
@ref{e4,,secrets}: @ref{4c0,,PEP 506 -- Secrets模块被加入Python标准库}。
@end itemize

CPython 实现的改进：


@itemize *

@item 
The @ref{2f5,,dict} type has been reimplemented to use
a @ref{4c1,,more compact representation}
based on a proposal by Raymond Hettinger@footnote{https://mail.python.org/pipermail/python-dev/2012-December/123028.html}
and similar to the PyPy dict implementation@footnote{https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html}.  This resulted in dictionaries
using 20% to 25% less memory when compared to Python 3.5.

@item 
Customization of class creation has been simplified with the
@ref{4c2,,new protocol}.

@item 
The class attribute definition order is
@ref{4c3,,now preserved}.

@item 
The order of elements in @code{**kwargs} now
@ref{4c4,,corresponds to the order} in which keyword
arguments were passed to the function.

@item 
添加了 DTrace 和 SystemTap @ref{4c5,,探测支持}

@item 
The new @ref{4c6,,PYTHONMALLOC} environment variable
can now be used to debug the interpreter memory allocation and access
errors.
@end itemize

标准库中的重大改进：


@itemize *

@item 
The @ref{a,,asyncio} module has received new features, significant
usability and performance improvements, and a fair amount of bug fixes.
Starting with Python 3.6 the @code{asyncio} module is no longer provisional
and its API is considered stable.

@item 
A new @ref{4c7,,file system path protocol} has been
implemented to support @ref{363,,path-like objects}.
All standard library functions operating on paths have been updated to
work with the new protocol.

@item 
The @ref{31,,datetime} module has gained support for
@ref{4c8,,Local Time Disambiguation}.

@item 
The @ref{119,,typing} module received a number of
@ref{4c9,,improvements}.

@item 
The @ref{114,,tracemalloc} module has been significantly reworked
and is now used to provide better output for @ref{4ca,,ResourceWarning}
as well as provide better diagnostics for memory allocation errors.
See the @ref{4c6,,PYTHONMALLOC section} for more
information.
@end itemize

安全改进：


@itemize *

@item 
The new @ref{e4,,secrets} module has been added to simplify the generation of
cryptographically strong pseudo-random numbers suitable for
managing secrets such as account authentication, tokens, and similar.

@item 
On Linux, @ref{4cb,,os.urandom()} now blocks until the system urandom entropy
pool is initialized to increase the security. See the 
@geindex Python 提高建议; PEP 524
PEP 524@footnote{https://www.python.org/dev/peps/pep-0524} for the
rationale.

@item 
The @ref{8d,,hashlib} and @ref{f3,,ssl} modules now support OpenSSL 1.1.0.

@item 
The default settings and feature set of the @ref{f3,,ssl} module have been
improved.

@item 
The @ref{8d,,hashlib} module received support for the BLAKE2, SHA-3 and SHAKE
hash algorithms and the @ref{4cc,,scrypt()} key derivation function.
@end itemize

Windows改进：


@itemize *

@item 
@ref{4cd,,PEP 528} 和 @ref{4ce,,PEP 529}, 将Windows文件系统和控制台的编码更改为UTF-8

@item 
The @code{py.exe} launcher, when used interactively, no longer prefers
Python 2 over Python 3 when the user doesn't specify a version (via
command line arguments or a config file).  Handling of shebang lines
remains unchanged - "python" refers to Python 2 in that case.

@item 
@code{python.exe} and @code{pythonw.exe} have been marked as long-path aware,
which means that the 260 character path limit may no longer apply.
See @ref{4cf,,removing the MAX_PATH limitation} for details.

@item 
A @code{._pth} file can be added to force isolated mode and fully specify
all search paths to avoid registry and environment lookup. See
@ref{4ab,,the documentation} for more information.

@item 
A @code{python36.zip} file now works as a landmark to infer
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME}. See @ref{4ab,,the documentation} for
more information.
@end itemize

@node 新的特性<3>,其他语言特性修改<3>,摘要 - 发布重点<3>,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 new-features}@anchor{4d1}@anchor{whatsnew/3 6 pypy-dict-implementation}@anchor{4d2}
@subsection 新的特性


@menu
* PEP 498; 格式化的字符串文字: PEP 498 格式化的字符串文字. 
* PEP 526; 变量注释的语法: PEP 526 变量注释的语法. 
* PEP 515; 数字文字中的下划线。: PEP 515 数字文字中的下划线。. 
* PEP 525; 异步生成器: PEP 525 异步生成器. 
* PEP 530; 异步推导: PEP 530 异步推导. 
* PEP 487; 自定义类创建: PEP 487 自定义类创建. 
* PEP 487; Descriptor Protocol Enhancements: PEP 487 Descriptor Protocol Enhancements. 
* PEP 519; 添加文件系统路径协议: PEP 519 添加文件系统路径协议. 
* PEP 495; 消除本地时间的歧义: PEP 495 消除本地时间的歧义. 
* PEP 529; 将Windows文件系统编码更改为UTF-8: PEP 529 将Windows文件系统编码更改为UTF-8. 
* PEP 528; 将Windows控制台编码更改为UTF-8: PEP 528 将Windows控制台编码更改为UTF-8. 
* PEP 520; 保留类属性定义顺序: PEP 520 保留类属性定义顺序. 
* PEP 468; 保留关键字参数顺序: PEP 468 保留关键字参数顺序. 
* 新的 dict 实现:: 
* PEP 523; 向CPython 添加框架评估API: PEP 523 向CPython 添加框架评估API. 
* PYTHONMALLOC 环境变量:: 
* DTrace 和 SystemTap 探测支持:: 

@end menu

@node PEP 498 格式化的字符串文字,PEP 526 变量注释的语法,,新的特性<3>
@anchor{whatsnew/3 6 pep-498-formatted-string-literals}@anchor{4d3}@anchor{whatsnew/3 6 whatsnew36-pep498}@anchor{4bb}
@subsubsection PEP 498: 格式化的字符串文字


@geindex Python 提高建议; PEP 498
PEP 498@footnote{https://www.python.org/dev/peps/pep-0498} introduces a new kind of string literals: @emph{f-strings}, or
@ref{15c,,formatted string literals}.

Formatted string literals are prefixed with @code{'f'} and are similar to
the format strings accepted by @ref{4d4,,str.format()}.  They contain replacement
fields surrounded by curly braces.  The replacement fields are expressions,
which are evaluated at run time, and then formatted using the
@ref{4d5,,format()} protocol:

@example
>>> name = "Fred"
>>> f"He said his name is @{name@}."
'He said his name is Fred.'
>>> width = 10
>>> precision = 4
>>> value = decimal.Decimal("12.34567")
>>> f"result: @{value:@{width@}.@{precision@}@}"  # nested fields
'result:      12.35'
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 498

@item PEP 498@footnote{https://www.python.org/dev/peps/pep-0498} -- 文字字符串插值。

PEP 由 Eric V. Smith 撰写并实现
@end table

@ref{15c,,Feature documentation}.


@node PEP 526 变量注释的语法,PEP 515 数字文字中的下划线。,PEP 498 格式化的字符串文字,新的特性<3>
@anchor{whatsnew/3 6 pep-526-syntax-for-variable-annotations}@anchor{4d6}@anchor{whatsnew/3 6 whatsnew36-pep526}@anchor{4bd}
@subsubsection PEP 526: 变量注释的语法


@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} introduced the standard for type annotations of function
parameters, a.k.a. type hints. This PEP adds syntax to Python for annotating
the types of variables including class variables and instance variables:

@example
primes: List[int] = []

captain: str  # Note: no initial value!

class Starship:
    stats: Dict[str, int] = @{@}
@end example

Just as for function annotations, the Python interpreter does not attach any
particular meaning to variable annotations and only stores them in the
@code{__annotations__} attribute of a class or module.

In contrast to variable declarations in statically typed languages,
the goal of annotation syntax is to provide an easy way to specify structured
type metadata for third party tools and libraries via the abstract syntax tree
and the @code{__annotations__} attribute.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 526

@item PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} -- 变量注释的语法。

PEP 由 Ryan Gonzalez, Philip House, Ivan Levkivskyi, Lisa Roach, 和 Guido van Rossum 撰写，由 Ivan Levkivskyi 实现。
@end table

Tools that use or will use the new syntax:
mypy@footnote{http://www.mypy-lang.org/},
pytype@footnote{https://github.com/google/pytype}, PyCharm, etc.


@node PEP 515 数字文字中的下划线。,PEP 525 异步生成器,PEP 526 变量注释的语法,新的特性<3>
@anchor{whatsnew/3 6 pep-515-underscores-in-numeric-literals}@anchor{4d7}@anchor{whatsnew/3 6 whatsnew36-pep515}@anchor{4bc}
@subsubsection PEP 515: 数字文字中的下划线。


@geindex Python 提高建议; PEP 515
PEP 515@footnote{https://www.python.org/dev/peps/pep-0515} adds the ability to use underscores in numeric literals for
improved readability.  For example:

@example
>>> 1_000_000_000_000_000
1000000000000000
>>> 0x_FF_FF_FF_FF
4294967295
@end example

Single underscores are allowed between digits and after any base
specifier.  Leading, trailing, or multiple underscores in a row are not
allowed.

The @ref{4d8,,string formatting} language also now has support
for the @code{'_'} option to signal the use of an underscore for a thousands
separator for floating point presentation types and for integer
presentation type @code{'d'}.  For integer presentation types @code{'b'},
@code{'o'}, @code{'x'}, and @code{'X'}, underscores will be inserted every 4
digits:

@example
>>> '@{:_@}'.format(1000000)
'1_000_000'
>>> '@{:_x@}'.format(0xFFFFFFFF)
'ffff_ffff'
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 515

@item PEP 515@footnote{https://www.python.org/dev/peps/pep-0515} -- 数字文字中的下划线。

PEP 由 Georg Brandl 和 Serhiy Storchaka 撰写
@end table


@node PEP 525 异步生成器,PEP 530 异步推导,PEP 515 数字文字中的下划线。,新的特性<3>
@anchor{whatsnew/3 6 pep-525-asynchronous-generators}@anchor{4d9}@anchor{whatsnew/3 6 whatsnew36-pep525}@anchor{4be}
@subsubsection PEP 525: 异步生成器


@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} introduced support for native coroutines and @code{async} / @code{await}
syntax to Python 3.5.  A notable limitation of the Python 3.5 implementation
is that it was not possible to use @code{await} and @code{yield} in the same
function body.  In Python 3.6 this restriction has been lifted, making it
possible to define @emph{asynchronous generators}:

@example
async def ticker(delay, to):
    """Yield numbers from 0 to *to* every *delay* seconds."""
    for i in range(to):
        yield i
        await asyncio.sleep(delay)
@end example

The new syntax allows for faster and more concise code.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 525

@item PEP 525@footnote{https://www.python.org/dev/peps/pep-0525} -- 异步生成器

PEP 由 Yury Selivanov 撰写并实现
@end table


@node PEP 530 异步推导,PEP 487 自定义类创建,PEP 525 异步生成器,新的特性<3>
@anchor{whatsnew/3 6 pep-530-asynchronous-comprehensions}@anchor{4da}@anchor{whatsnew/3 6 whatsnew36-pep530}@anchor{4bf}
@subsubsection PEP 530: 异步推导


@geindex Python 提高建议; PEP 530
PEP 530@footnote{https://www.python.org/dev/peps/pep-0530} adds support for using @code{async for} in list, set, dict
comprehensions and generator expressions:

@example
result = [i async for i in aiter() if i % 2]
@end example

Additionally, @code{await} expressions are supported in all kinds
of comprehensions:

@example
result = [await fun() for fun in funcs if await condition()]
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 530

@item PEP 530@footnote{https://www.python.org/dev/peps/pep-0530} -- 异步推导

PEP 由 Yury Selivanov 撰写并实现
@end table


@node PEP 487 自定义类创建,PEP 487 Descriptor Protocol Enhancements,PEP 530 异步推导,新的特性<3>
@anchor{whatsnew/3 6 pep-487-simpler-customization-of-class-creation}@anchor{4db}@anchor{whatsnew/3 6 whatsnew36-pep487}@anchor{4c2}
@subsubsection PEP 487: 自定义类创建


It is now possible to customize subclass creation without using a metaclass.
The new @code{__init_subclass__} classmethod will be called on the base class
whenever a new subclass is created:

@example
class PluginBase:
    subclasses = []

    def __init_subclass__(cls, **kwargs):
        super().__init_subclass__(**kwargs)
        cls.subclasses.append(cls)

class Plugin1(PluginBase):
    pass

class Plugin2(PluginBase):
    pass
@end example

In order to allow zero-argument @ref{4dc,,super()} calls to work correctly from
@ref{4dd,,__init_subclass__()} implementations, custom metaclasses must
ensure that the new @code{__classcell__} namespace entry is propagated to
@code{type.__new__} (as described in @ref{4de,,创建类对象}).


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 487

@item PEP 487@footnote{https://www.python.org/dev/peps/pep-0487} -- 自定义类创建

PEP 由 Martin Teichmann 撰写并实现。
@end table

@ref{4df,,Feature documentation}


@node PEP 487 Descriptor Protocol Enhancements,PEP 519 添加文件系统路径协议,PEP 487 自定义类创建,新的特性<3>
@anchor{whatsnew/3 6 pep-487-descriptor-protocol-enhancements}@anchor{4e0}@anchor{whatsnew/3 6 whatsnew36-pep487-descriptors}@anchor{4e1}
@subsubsection PEP 487: Descriptor Protocol Enhancements


@geindex Python 提高建议; PEP 487
PEP 487@footnote{https://www.python.org/dev/peps/pep-0487} extends the descriptor protocol to include the new optional
@ref{4e2,,__set_name__()} method.  Whenever a new class is defined, the new
method will be called on all descriptors included in the definition, providing
them with a reference to the class being defined and the name given to the
descriptor within the class namespace.  In other words, instances of
descriptors can now know the attribute name of the descriptor in the
owner class:

@example
class IntField:
    def __get__(self, instance, owner):
        return instance.__dict__[self.name]

    def __set__(self, instance, value):
        if not isinstance(value, int):
            raise ValueError(f'expecting integer in @{self.name@}')
        instance.__dict__[self.name] = value

    # this is the new initializer:
    def __set_name__(self, owner, name):
        self.name = name

class Model:
    int_field = IntField()
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 487

@item PEP 487@footnote{https://www.python.org/dev/peps/pep-0487} -- 自定义类创建

PEP 由 Martin Teichmann 撰写并实现。
@end table

@ref{4e3,,Feature documentation}


@node PEP 519 添加文件系统路径协议,PEP 495 消除本地时间的歧义,PEP 487 Descriptor Protocol Enhancements,新的特性<3>
@anchor{whatsnew/3 6 pep-519-adding-a-file-system-path-protocol}@anchor{4e4}@anchor{whatsnew/3 6 whatsnew36-pep519}@anchor{4c7}
@subsubsection PEP 519: 添加文件系统路径协议


File system paths have historically been represented as @ref{329,,str}
or @ref{32a,,bytes} objects. This has led to people who write code which
operate on file system paths to assume that such objects are only one
of those two types (an @ref{184,,int} representing a file descriptor
does not count as that is not a file path). Unfortunately that
assumption prevents alternative object representations of file system
paths like @ref{c8,,pathlib} from working with pre-existing code,
including Python's standard library.

To fix this situation, a new interface represented by
@ref{4e5,,os.PathLike} has been defined. By implementing the
@ref{4e6,,__fspath__()} method, an object signals that it
represents a path. An object can then provide a low-level
representation of a file system path as a @ref{329,,str} or
@ref{32a,,bytes} object. This means an object is considered
@ref{363,,path-like} if it implements
@ref{4e5,,os.PathLike} or is a @ref{329,,str} or @ref{32a,,bytes} object
which represents a file system path. Code can use @ref{4e7,,os.fspath()},
@ref{4e8,,os.fsdecode()}, or @ref{4e9,,os.fsencode()} to explicitly get a
@ref{329,,str} and/or @ref{32a,,bytes} representation of a path-like
object.

The built-in @ref{4ea,,open()} function has been updated to accept
@ref{4e5,,os.PathLike} objects, as have all relevant functions in the
@ref{c4,,os} and @ref{c5,,os.path} modules, and most other functions and
classes in the standard library.  The @ref{4eb,,os.DirEntry} class
and relevant classes in @ref{c8,,pathlib} have also been updated to
implement @ref{4e5,,os.PathLike}.

The hope is that updating the fundamental functions for operating
on file system paths will lead to third-party code to implicitly
support all @ref{363,,path-like objects} without any
code changes, or at least very minimal ones (e.g. calling
@ref{4e7,,os.fspath()} at the beginning of code before operating on a
path-like object).

Here are some examples of how the new interface allows for
@ref{201,,pathlib.Path} to be used more easily and transparently with
pre-existing code:

@example
>>> import pathlib
>>> with open(pathlib.Path("README")) as f:
...     contents = f.read()
...
>>> import os.path
>>> os.path.splitext(pathlib.Path("some_file.txt"))
('some_file', '.txt')
>>> os.path.join("/a/b", pathlib.Path("c"))
'/a/b/c'
>>> import os
>>> os.fspath(pathlib.Path("some_file.txt"))
'some_file.txt'
@end example

(Implemented by Brett Cannon, Ethan Furman, Dusty Phillips, and Jelle Zijlstra.)


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 519

@item PEP 519@footnote{https://www.python.org/dev/peps/pep-0519} -- 添加文件系统路径协议

PEP 由 Brett Cannon 和 Koos Zevenhoven 撰写。
@end table


@node PEP 495 消除本地时间的歧义,PEP 529 将Windows文件系统编码更改为UTF-8,PEP 519 添加文件系统路径协议,新的特性<3>
@anchor{whatsnew/3 6 pep-495-local-time-disambiguation}@anchor{4ec}@anchor{whatsnew/3 6 whatsnew36-pep495}@anchor{4c8}
@subsubsection PEP 495: 消除本地时间的歧义


In most world locations, there have been and will be times when local clocks
are moved back.  In those times, intervals are introduced in which local
clocks show the same time twice in the same day. In these situations, the
information displayed on a local clock (or stored in a Python datetime
instance) is insufficient to identify a particular moment in time.

@geindex Python 提高建议; PEP 495
PEP 495@footnote{https://www.python.org/dev/peps/pep-0495} adds the new @emph{fold} attribute to instances of
@ref{194,,datetime.datetime} and @ref{4ed,,datetime.time} classes to differentiate
between two moments in time for which local times are the same:

@example
>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0
@end example

The values of the @ref{4ee,,fold} attribute have the
value @code{0} for all instances except those that represent the second
(chronologically) moment in time in an ambiguous case.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 495

@item PEP 495@footnote{https://www.python.org/dev/peps/pep-0495} -- 消除本地时间的歧义

PEP 由 Alexander Belopolsky 和 Tim Peters 撰写，由 Alexander Belopolsky 实现。
@end table


@node PEP 529 将Windows文件系统编码更改为UTF-8,PEP 528 将Windows控制台编码更改为UTF-8,PEP 495 消除本地时间的歧义,新的特性<3>
@anchor{whatsnew/3 6 pep-529-change-windows-filesystem-encoding-to-utf-8}@anchor{4ef}@anchor{whatsnew/3 6 whatsnew36-pep529}@anchor{4ce}
@subsubsection PEP 529: 将Windows文件系统编码更改为UTF-8


Representing filesystem paths is best performed with str (Unicode) rather than
bytes. However, there are some situations where using bytes is sufficient and
correct.

Prior to Python 3.6, data loss could result when using bytes paths on Windows.
With this change, using bytes to represent paths is now supported on Windows,
provided those bytes are encoded with the encoding returned by
@ref{4f0,,sys.getfilesystemencoding()}, which now defaults to @code{'utf-8'}.

Applications that do not use str to represent paths should use
@ref{4e9,,os.fsencode()} and @ref{4e8,,os.fsdecode()} to ensure their bytes are
correctly encoded. To revert to the previous behaviour, set
@geindex PYTHONLEGACYWINDOWSFSENCODING
@geindex 环境变量; PYTHONLEGACYWINDOWSFSENCODING
@ref{4f1,,PYTHONLEGACYWINDOWSFSENCODING} or call
@ref{4f2,,sys._enablelegacywindowsfsencoding()}.

有关详细信息和可能需要的代码修改的讨论，请参见 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529} 。

@node PEP 528 将Windows控制台编码更改为UTF-8,PEP 520 保留类属性定义顺序,PEP 529 将Windows文件系统编码更改为UTF-8,新的特性<3>
@anchor{whatsnew/3 6 pep-528-change-windows-console-encoding-to-utf-8}@anchor{4f3}@anchor{whatsnew/3 6 whatsnew36-pep528}@anchor{4cd}
@subsubsection PEP 528: 将Windows控制台编码更改为UTF-8


The default console on Windows will now accept all Unicode characters and
provide correctly read str objects to Python code. @code{sys.stdin},
@code{sys.stdout} and @code{sys.stderr} now default to utf-8 encoding.

This change only applies when using an interactive console, and not when
redirecting files or pipes. To revert to the previous behaviour for interactive
console use, set 
@geindex PYTHONLEGACYWINDOWSSTDIO
@geindex 环境变量; PYTHONLEGACYWINDOWSSTDIO
@ref{4f4,,PYTHONLEGACYWINDOWSSTDIO}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 528

@item PEP 528@footnote{https://www.python.org/dev/peps/pep-0528} -- 将Windows控制台编码更改为UTF-8

PEP 由 Steve Dower 撰写并实现。
@end table


@node PEP 520 保留类属性定义顺序,PEP 468 保留关键字参数顺序,PEP 528 将Windows控制台编码更改为UTF-8,新的特性<3>
@anchor{whatsnew/3 6 pep-520-preserving-class-attribute-definition-order}@anchor{4f5}@anchor{whatsnew/3 6 whatsnew36-pep520}@anchor{4c3}
@subsubsection PEP 520: 保留类属性定义顺序


Attributes in a class definition body have a natural ordering: the same
order in which the names appear in the source.  This order is now
preserved in the new class's @ref{4f6,,__dict__} attribute.

Also, the effective default class @emph{execution} namespace (returned from
@ref{4f7,,type.__prepare__()}) is now an insertion-order-preserving
mapping.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 520

@item PEP 520@footnote{https://www.python.org/dev/peps/pep-0520} -- 保留类属性定义顺序

PEP 由 Eric Snow 撰写并实现
@end table


@node PEP 468 保留关键字参数顺序,新的 dict 实现,PEP 520 保留类属性定义顺序,新的特性<3>
@anchor{whatsnew/3 6 pep-468-preserving-keyword-argument-order}@anchor{4f8}@anchor{whatsnew/3 6 whatsnew36-pep468}@anchor{4c4}
@subsubsection PEP 468: 保留关键字参数顺序


@code{**kwargs} in a function signature is now guaranteed to be an
insertion-order-preserving mapping.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 468

@item PEP 468@footnote{https://www.python.org/dev/peps/pep-0468} -- 保留关键字参数顺序

PEP 由 Eric Snow 撰写并实现
@end table


@node 新的 dict 实现,PEP 523 向CPython 添加框架评估API,PEP 468 保留关键字参数顺序,新的特性<3>
@anchor{whatsnew/3 6 new-dict-implementation}@anchor{4f9}@anchor{whatsnew/3 6 whatsnew36-compactdict}@anchor{4c1}
@subsubsection 新的 dict 实现


The @ref{2f5,,dict} type now uses a "compact" representation
based on a proposal by Raymond Hettinger@footnote{https://mail.python.org/pipermail/python-dev/2012-December/123028.html}
which was first implemented by PyPy@footnote{https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html}.
The memory usage of the new @ref{1b8,,dict()} is between 20% and 25% smaller
compared to Python 3.5.

The order-preserving aspect of this new implementation is considered an
implementation detail and should not be relied upon (this may change in
the future, but it is desired to have this new dict implementation in
the language for a few releases before changing the language spec to mandate
order-preserving semantics for all current and future Python
implementations; this also helps preserve backwards-compatibility
with older versions of the language where random iteration order is
still in effect, e.g. Python 3.5).

(Contributed by INADA Naoki in bpo-27350@footnote{https://bugs.python.org/issue27350}. Idea
originally suggested by Raymond Hettinger@footnote{https://mail.python.org/pipermail/python-dev/2012-December/123028.html}.)

@node PEP 523 向CPython 添加框架评估API,PYTHONMALLOC 环境变量,新的 dict 实现,新的特性<3>
@anchor{whatsnew/3 6 pep-523-adding-a-frame-evaluation-api-to-cpython}@anchor{4fa}@anchor{whatsnew/3 6 whatsnew36-pep523}@anchor{4fb}
@subsubsection PEP 523: 向CPython 添加框架评估API


While Python provides extensive support to customize how code
executes, one place it has not done so is in the evaluation of frame
objects.  If you wanted some way to intercept frame evaluation in
Python there really wasn't any way without directly manipulating
function pointers for defined functions.

@geindex Python 提高建议; PEP 523
PEP 523@footnote{https://www.python.org/dev/peps/pep-0523} changes this by providing an API to make frame
evaluation pluggable at the C level. This will allow for tools such
as debuggers and JITs to intercept frame evaluation before the
execution of Python code begins. This enables the use of alternative
evaluation implementations for Python code, tracking frame
evaluation, etc.

This API is not part of the limited C API and is marked as private to
signal that usage of this API is expected to be limited and only
applicable to very select, low-level use-cases. Semantics of the
API will change with Python as necessary.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 523

@item PEP 523@footnote{https://www.python.org/dev/peps/pep-0523} -- 向CPython 添加框架评估API

PEP 由 Brett Cannon 和 Dino Viehland 撰写。
@end table


@node PYTHONMALLOC 环境变量,DTrace 和 SystemTap 探测支持,PEP 523 向CPython 添加框架评估API,新的特性<3>
@anchor{whatsnew/3 6 pythonmalloc-environment-variable}@anchor{4fc}@anchor{whatsnew/3 6 whatsnew36-pythonmalloc}@anchor{4c6}
@subsubsection PYTHONMALLOC 环境变量


The new 
@geindex PYTHONMALLOC
@geindex 环境变量; PYTHONMALLOC
@ref{4fd,,PYTHONMALLOC} environment variable allows setting the Python
memory allocators and installing debug hooks.

It is now possible to install debug hooks on Python memory allocators on Python
compiled in release mode using @code{PYTHONMALLOC=debug}. Effects of debug hooks:


@itemize *

@item 
新分配的内存中填充字节 @code{0xCB}

@item 
释放的内存中填充了字节 @code{0xDB}

@item 
Detect violations of the Python memory allocator API. For example,
@ref{4fe,,PyObject_Free()} called on a memory block allocated by
@ref{4ff,,PyMem_Malloc()}.

@item 
在缓冲区开始之前检测写操作（缓冲区下溢）

@item 
在缓冲区结束后检测写操作（缓冲区溢出）

@item 
Check that the @ref{500,,GIL} is held when allocator
functions of @ref{501,,PYMEM_DOMAIN_OBJ} (ex: @ref{502,,PyObject_Malloc()}) and
@ref{503,,PYMEM_DOMAIN_MEM} (ex: @ref{4ff,,PyMem_Malloc()}) domains are called.
@end itemize

检查是否保留了 GIL 也是Python 3.6 的新特性。

See the @ref{504,,PyMem_SetupDebugHooks()} function for debug hooks on Python
memory allocators.

It is now also possible to force the usage of the @code{malloc()} allocator of
the C library for all Python memory allocations using @code{PYTHONMALLOC=malloc}.
This is helpful when using external memory debuggers like Valgrind on
a Python compiled in release mode.

On error, the debug hooks on Python memory allocators now use the
@ref{114,,tracemalloc} module to get the traceback where a memory block was
allocated.

Example of fatal error on buffer overflow using
@code{python3.6 -X tracemalloc=5} (store 5 frames in traces):

@example
Debug memory block at address p=0x7fbcd41666f8: API 'o'
    4 bytes originally requested
    The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
    The 8 pad bytes at tail=0x7fbcd41666fc are not all FORBIDDENBYTE (0xfb):
        at tail+0: 0x02 *** OUCH
        at tail+1: 0xfb
        at tail+2: 0xfb
        at tail+3: 0xfb
        at tail+4: 0xfb
        at tail+5: 0xfb
        at tail+6: 0xfb
        at tail+7: 0xfb
    The block was made by call #1233329 to debug malloc/realloc.
    Data at p: 1a 2b 30 00

Memory block allocated at (most recent call first):
  File "test/test_bytes.py", line 323
  File "unittest/case.py", line 600
  File "unittest/case.py", line 648
  File "unittest/suite.py", line 122
  File "unittest/suite.py", line 84

Fatal Python error: bad trailing pad byte

Current thread 0x00007fbcdbd32700 (most recent call first):
  File "test/test_bytes.py", line 323 in test_hex
  File "unittest/case.py", line 600 in run
  File "unittest/case.py", line 648 in __call__
  File "unittest/suite.py", line 122 in run
  File "unittest/suite.py", line 84 in __call__
  File "unittest/suite.py", line 122 in run
  File "unittest/suite.py", line 84 in __call__
  ...
@end example

（由 Victor Stinner 在 bpo-26516@footnote{https://bugs.python.org/issue26516} 和 bpo-26564@footnote{https://bugs.python.org/issue26564} 中贡献。）

@node DTrace 和 SystemTap 探测支持,,PYTHONMALLOC 环境变量,新的特性<3>
@anchor{whatsnew/3 6 dtrace-and-systemtap-probing-support}@anchor{505}@anchor{whatsnew/3 6 whatsnew36-tracing}@anchor{4c5}
@subsubsection DTrace 和 SystemTap 探测支持


Python can now be built @code{--with-dtrace} which enables static markers
for the following events in the interpreter:


@itemize *

@item 
函数调用/返回

@item 
垃圾收集开始/完成

@item 
执行的代码行。
@end itemize

This can be used to instrument running interpreters in production,
without the need to recompile specific debug builds or providing
application-specific profiling/debugging code.

更多信息，请参见 @ref{506,,使用 DTrace 和 SystemTap 检测CPython} 。

当前的实现已在 Linux 和 macOS 上进行了测试。将来可能会添加其他标记。

(Contributed by Łukasz Langa in bpo-21590@footnote{https://bugs.python.org/issue21590}, based on patches by
Jesús Cea Avión, David Malcolm, and Nikhil Benesch.)

@node 其他语言特性修改<3>,新增模块<3>,新的特性<3>,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 other-language-changes}@anchor{507}
@subsection 其他语言特性修改


对Python 语言核心进行的小改动：


@itemize *

@item 
A @code{global} or @code{nonlocal} statement must now textually appear
before the first use of the affected name in the same scope.
Previously this was a @ref{191,,SyntaxWarning}.

@item 
It is now possible to set a @ref{508,,special method} to
@code{None} to indicate that the corresponding operation is not available.
For example, if a class sets @ref{509,,__iter__()} to @code{None}, the class
is not iterable.
(Contributed by Andrew Barnert and Ivan Levkivskyi in bpo-25958@footnote{https://bugs.python.org/issue25958}.)

@item 
Long sequences of repeated traceback lines are now abbreviated as
@code{"[Previous line repeated @{count@} more times]"} (see
@ref{50a,,回溯} for an example).
(Contributed by Emanuel Barry in bpo-26823@footnote{https://bugs.python.org/issue26823}.)

@item 
Import now raises the new exception @ref{392,,ModuleNotFoundError}
(subclass of @ref{32d,,ImportError}) when it cannot find a module.  Code
that currently checks for ImportError (in try-except) will still work.
(Contributed by Eric Snow in bpo-15767@footnote{https://bugs.python.org/issue15767}.)

@item 
Class methods relying on zero-argument @code{super()} will now work correctly
when called from metaclass methods during class creation.
(Contributed by Martin Teichmann in bpo-23722@footnote{https://bugs.python.org/issue23722}.)
@end itemize

@node 新增模块<3>,改进的模块<3>,其他语言特性修改<3>,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 new-modules}@anchor{50b}
@subsection 新增模块


@menu
* secrets:: 

@end menu

@node secrets,,,新增模块<3>
@anchor{whatsnew/3 6 secrets}@anchor{50c}@anchor{whatsnew/3 6 whatsnew36-pep506}@anchor{4c0}
@subsubsection secrets


The main purpose of the new @ref{e4,,secrets} module is to provide an obvious way
to reliably generate cryptographically strong pseudo-random values suitable
for managing secrets, such as account authentication, tokens, and similar.

@cartouche
@quotation 警告 
Note that the pseudo-random generators in the @ref{dc,,random} module
should @emph{NOT} be used for security purposes.  Use @ref{e4,,secrets}
on Python 3.6+ and @ref{4cb,,os.urandom()} on Python 3.5 and earlier.
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 506

@item PEP 506@footnote{https://www.python.org/dev/peps/pep-0506} -- Secrets模块被加入Python标准库

PEP 由 Steven D'Aprano 撰写并实现。
@end table


@node 改进的模块<3>,性能优化<3>,新增模块<3>,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 improved-modules}@anchor{50d}
@subsection 改进的模块


@menu
* array:: 
* ast: ast<2>. 
* asyncio: asyncio<4>. 
* binascii: binascii<2>. 
* cmath:: 
* collections: collections<4>. 
* concurrent.futures: concurrent futures<2>. 
* contextlib: contextlib<2>. 
* datetime: datetime<3>. 
* decimal: decimal<2>. 
* distutils: distutils<2>. 
* email:: 
* encodings:: 
* enum: enum<3>. 
* faulthandler:: 
* fileinput:: 
* hashlib:: 
* http.client: http client<2>. 
* idlelib 与 IDLE: idlelib 与 IDLE<2>. 
* importlib: importlib<3>. 
* inspect: inspect<2>. 
* json:: 
* logging: logging<3>. 
* math: math<3>. 
* multiprocessing: multiprocessing<3>. 
* os: os<3>. 
* pathlib: pathlib<3>. 
* pdb: pdb<2>. 
* pickle: pickle<2>. 
* pickletools:: 
* pydoc: pydoc<2>. 
* random:: 
* re: re<2>. 
* readline:: 
* rlcompleter:: 
* shlex: shlex<2>. 
* site:: 
* sqlite3: sqlite3<2>. 
* socket: socket<4>. 
* socketserver: socketserver<2>. 
* ssl: ssl<4>. 
* statistics: statistics<2>. 
* struct:: 
* subprocess: subprocess<2>. 
* sys: sys<4>. 
* telnetlib:: 
* time: time<3>. 
* timeit:: 
* tkinter: tkinter<3>. 
* 回溯:: 
* tracemalloc: tracemalloc<2>. 
* typing: typing<2>. 
* unicodedata: unicodedata<3>. 
* unittest.mock: unittest mock<2>. 
* urllib.request: urllib request. 
* urllib.robotparser: urllib robotparser. 
* venv: venv<2>. 
* warnings: warnings<2>. 
* winreg:: 
* winsound:: 
* xmlrpc.client: xmlrpc client. 
* zipfile: zipfile<2>. 
* zlib:: 

@end menu

@node array,ast<2>,,改进的模块<3>
@anchor{whatsnew/3 6 array}@anchor{50e}
@subsubsection array


Exhausted iterators of @ref{44b,,array.array} will now stay exhausted even
if the iterated array is extended.  This is consistent with the behavior
of other mutable sequences.

由 Serhiy Storchaka 在 bpo-26492@footnote{https://bugs.python.org/issue26492} 中贡献。

@node ast<2>,asyncio<4>,array,改进的模块<3>
@anchor{whatsnew/3 6 ast}@anchor{50f}
@subsubsection ast


The new @code{ast.Constant} AST node has been added.  It can be used
by external AST optimizers for the purposes of constant folding.

由 Victor Stinner 在 bpo-26146@footnote{https://bugs.python.org/issue26146} 中贡献。

@node asyncio<4>,binascii<2>,ast<2>,改进的模块<3>
@anchor{whatsnew/3 6 asyncio}@anchor{510}
@subsubsection asyncio


Starting with Python 3.6 the @code{asyncio} module is no longer provisional and its
API is considered stable.

Notable changes in the @ref{a,,asyncio} module since Python 3.5.0
(all backported to 3.5.x due to the provisional status):


@itemize *

@item 
The @ref{34e,,get_event_loop()} function has been changed to
always return the currently running loop when called from coroutines
and callbacks.
(Contributed by Yury Selivanov in bpo-28613@footnote{https://bugs.python.org/issue28613}.)

@item 
The @ref{511,,ensure_future()} function and all functions that
use it, such as @ref{512,,loop.run_until_complete()},
now accept all kinds of @ref{513,,awaitable objects}.
(Contributed by Yury Selivanov.)

@item 
New @ref{514,,run_coroutine_threadsafe()} function to submit
coroutines to event loops from other threads.
(Contributed by Vincent Michel.)

@item 
New @ref{515,,Transport.is_closing()}
method to check if the transport is closing or closed.
(Contributed by Yury Selivanov.)

@item 
The @ref{356,,loop.create_server()}
method can now accept a list of hosts.
(Contributed by Yann Sionneau.)

@item 
New @ref{516,,loop.create_future()}
method to create Future objects.  This allows alternative event
loop implementations, such as
uvloop@footnote{https://github.com/MagicStack/uvloop}, to provide a faster
@ref{43d,,asyncio.Future} implementation.
(Contributed by Yury Selivanov in bpo-27041@footnote{https://bugs.python.org/issue27041}.)

@item 
New @ref{517,,loop.get_exception_handler()}
method to get the current exception handler.
(Contributed by Yury Selivanov in bpo-27040@footnote{https://bugs.python.org/issue27040}.)

@item 
New @ref{518,,StreamReader.readuntil()}
method to read data from the stream until a separator bytes
sequence appears.
(Contributed by Mark Korenberg.)

@item 
The performance of @ref{519,,StreamReader.readexactly()}
has been improved.
(Contributed by Mark Korenberg in bpo-28370@footnote{https://bugs.python.org/issue28370}.)

@item 
The @ref{49c,,loop.getaddrinfo()}
method is optimized to avoid calling the system @code{getaddrinfo}
function if the address is already resolved.
(Contributed by A. Jesse Jiryu Davis.)

@item 
The @ref{51a,,loop.stop()}
method has been changed to stop the loop immediately after
the current iteration.  Any new callbacks scheduled as a result
of the last iteration will be discarded.
(Contributed by Guido van Rossum in bpo-25593@footnote{https://bugs.python.org/issue25593}.)

@item 
@code{Future.set_exception}
will now raise @ref{192,,TypeError} when passed an instance of
the @ref{480,,StopIteration} exception.
(Contributed by Chris Angelico in bpo-26221@footnote{https://bugs.python.org/issue26221}.)

@item 
New @ref{35e,,loop.connect_accepted_socket()}
method to be used by servers that accept connections outside of asyncio,
but that use asyncio to handle them.
(Contributed by Jim Fulton in bpo-27392@footnote{https://bugs.python.org/issue27392}.)

@item 
@code{TCP_NODELAY} flag is now set for all TCP transports by default.
(Contributed by Yury Selivanov in bpo-27456@footnote{https://bugs.python.org/issue27456}.)

@item 
New @ref{51b,,loop.shutdown_asyncgens()}
to properly close pending asynchronous generators before closing the
loop.
(Contributed by Yury Selivanov in bpo-28003@footnote{https://bugs.python.org/issue28003}.)

@item 
@ref{43d,,Future} and @ref{1ad,,Task}
classes now have an optimized C implementation which makes asyncio
code up to 30% faster.
(Contributed by Yury Selivanov and INADA Naoki in bpo-26081@footnote{https://bugs.python.org/issue26081}
and bpo-28544@footnote{https://bugs.python.org/issue28544}.)
@end itemize

@node binascii<2>,cmath,asyncio<4>,改进的模块<3>
@anchor{whatsnew/3 6 binascii}@anchor{51c}
@subsubsection binascii


The @ref{51d,,b2a_base64()} function now accepts an optional @emph{newline}
keyword argument to control whether the newline character is appended to the
return value.
(Contributed by Victor Stinner in bpo-25357@footnote{https://bugs.python.org/issue25357}.)

@node cmath,collections<4>,binascii<2>,改进的模块<3>
@anchor{whatsnew/3 6 cmath}@anchor{51e}
@subsubsection cmath


The new @ref{51f,,cmath.tau} (@emph{τ}) constant has been added.
(Contributed by Lisa Roach in bpo-12345@footnote{https://bugs.python.org/issue12345}, see 
@geindex Python 提高建议; PEP 628
PEP 628@footnote{https://www.python.org/dev/peps/pep-0628} for details.)

New constants: @ref{520,,cmath.inf} and @ref{521,,cmath.nan} to
match @ref{522,,math.inf} and @ref{523,,math.nan}, and also @ref{524,,cmath.infj}
and @ref{525,,cmath.nanj} to match the format used by complex repr.
(Contributed by Mark Dickinson in bpo-23229@footnote{https://bugs.python.org/issue23229}.)

@node collections<4>,concurrent futures<2>,cmath,改进的模块<3>
@anchor{whatsnew/3 6 collections}@anchor{526}
@subsubsection collections


The new @ref{527,,Collection} abstract base class has been
added to represent sized iterable container classes.
(Contributed by Ivan Levkivskyi, docs by Neil Girdhar in bpo-27598@footnote{https://bugs.python.org/issue27598}.)

The new @ref{528,,Reversible} abstract base class represents
iterable classes that also provide the @ref{529,,__reversed__()} method.
(Contributed by Ivan Levkivskyi in bpo-25987@footnote{https://bugs.python.org/issue25987}.)

The new @ref{52a,,AsyncGenerator} abstract base class represents
asynchronous generators.
(Contributed by Yury Selivanov in bpo-28720@footnote{https://bugs.python.org/issue28720}.)

The @ref{1b6,,namedtuple()} function now accepts an optional
keyword argument @emph{module}, which, when specified, is used for
the @code{__module__} attribute of the returned named tuple class.
(Contributed by Raymond Hettinger in bpo-17941@footnote{https://bugs.python.org/issue17941}.)

The @emph{verbose} and @emph{rename} arguments for
@ref{1b6,,namedtuple()} are now keyword-only.
(Contributed by Raymond Hettinger in bpo-25628@footnote{https://bugs.python.org/issue25628}.)

Recursive @ref{52b,,collections.deque} instances can now be pickled.
(Contributed by Serhiy Storchaka in bpo-26482@footnote{https://bugs.python.org/issue26482}.)

@node concurrent futures<2>,contextlib<2>,collections<4>,改进的模块<3>
@anchor{whatsnew/3 6 concurrent-futures}@anchor{52c}
@subsubsection concurrent.futures


The @ref{27a,,ThreadPoolExecutor}
class constructor now accepts an optional @emph{thread_name_prefix} argument
to make it possible to customize the names of the threads created by the
pool.
(Contributed by Gregory P. Smith in bpo-27664@footnote{https://bugs.python.org/issue27664}.)

@node contextlib<2>,datetime<3>,concurrent futures<2>,改进的模块<3>
@anchor{whatsnew/3 6 contextlib}@anchor{52d}
@subsubsection contextlib


The @ref{52e,,contextlib.AbstractContextManager} class has been added to
provide an abstract base class for context managers.  It provides a
sensible default implementation for @cite{__enter__()} which returns
@code{self} and leaves @cite{__exit__()} an abstract method.  A matching
class has been added to the @ref{119,,typing} module as
@ref{52f,,typing.ContextManager}.
(Contributed by Brett Cannon in bpo-25609@footnote{https://bugs.python.org/issue25609}.)

@node datetime<3>,decimal<2>,contextlib<2>,改进的模块<3>
@anchor{whatsnew/3 6 datetime}@anchor{530}
@subsubsection datetime


The @ref{194,,datetime} and @ref{4ed,,time} classes have
the new @code{fold} attribute used to disambiguate local time
when necessary.  Many functions in the @ref{31,,datetime} have been
updated to support local time disambiguation.
See @ref{4c8,,Local Time Disambiguation} section for more
information.
(Contributed by Alexander Belopolsky in bpo-24773@footnote{https://bugs.python.org/issue24773}.)

The @ref{531,,datetime.strftime()} and
@ref{532,,date.strftime()} methods now support
ISO 8601 date directives @code{%G}, @code{%u} and @code{%V}.
(Contributed by Ashley Anderson in bpo-12006@footnote{https://bugs.python.org/issue12006}.)

The @ref{533,,datetime.isoformat()} function
now accepts an optional @emph{timespec} argument that specifies the number
of additional components of the time value to include.
(Contributed by Alessandro Cucci and Alexander Belopolsky in bpo-19475@footnote{https://bugs.python.org/issue19475}.)

The @ref{534,,datetime.combine()} now
accepts an optional @emph{tzinfo} argument.
(Contributed by Alexander Belopolsky in bpo-27661@footnote{https://bugs.python.org/issue27661}.)

@node decimal<2>,distutils<2>,datetime<3>,改进的模块<3>
@anchor{whatsnew/3 6 decimal}@anchor{535}
@subsubsection decimal


New @ref{536,,Decimal.as_integer_ratio()}
method that returns a pair @code{(n, d)} of integers that represent the given
@ref{188,,Decimal} instance as a fraction, in lowest terms and
with a positive denominator:

@example
>>> Decimal('-3.14').as_integer_ratio()
(-157, 50)
@end example

（由 Stefan Krah 和 Mark Dickinson  在 bpo-25928@footnote{https://bugs.python.org/issue25928} 中贡献。）

@node distutils<2>,email,decimal<2>,改进的模块<3>
@anchor{whatsnew/3 6 distutils}@anchor{537}
@subsubsection distutils


The @code{default_format} attribute has been removed from
@code{distutils.command.sdist.sdist} and the @code{formats}
attribute defaults to @code{['gztar']}. Although not anticipated,
any code relying on the presence of @code{default_format} may
need to be adapted. See bpo-27819@footnote{https://bugs.python.org/issue27819} for more details.

@node email,encodings,distutils<2>,改进的模块<3>
@anchor{whatsnew/3 6 email}@anchor{538}
@subsubsection email


The new email API, enabled via the @emph{policy} keyword to various constructors, is
no longer provisional.  The @ref{69,,email} documentation has been reorganized and
rewritten to focus on the new API, while retaining the old documentation for
the legacy API.  (Contributed by R. David Murray in bpo-24277@footnote{https://bugs.python.org/issue24277}.)

The @ref{73,,email.mime} classes now all accept an optional @emph{policy} keyword.
(Contributed by Berker Peksag in bpo-27331@footnote{https://bugs.python.org/issue27331}.)

The @ref{539,,DecodedGenerator} now supports the @emph{policy}
keyword.

There is a new @ref{75,,policy} attribute,
@ref{53a,,message_factory}, that controls what class is used
by default when the parser creates new message objects.  For the
@ref{53b,,email.policy.compat32} policy this is @ref{53c,,Message},
for the new policies it is @ref{53d,,EmailMessage}.
(Contributed by R. David Murray in bpo-20476@footnote{https://bugs.python.org/issue20476}.)

@node encodings,enum<3>,email,改进的模块<3>
@anchor{whatsnew/3 6 encodings}@anchor{53e}
@subsubsection encodings


On Windows, added the @code{'oem'} encoding to use @code{CP_OEMCP}, and the @code{'ansi'}
alias for the existing @code{'mbcs'} encoding, which uses the @code{CP_ACP} code page.
(Contributed by Steve Dower in bpo-27959@footnote{https://bugs.python.org/issue27959}.)

@node enum<3>,faulthandler,encodings,改进的模块<3>
@anchor{whatsnew/3 6 enum}@anchor{53f}
@subsubsection enum


Two new enumeration base classes have been added to the @ref{7b,,enum} module:
@ref{540,,Flag} and @code{IntFlags}.  Both are used to define
constants that can be combined using the bitwise operators.
(Contributed by Ethan Furman in bpo-23591@footnote{https://bugs.python.org/issue23591}.)

Many standard library modules have been updated to use the
@code{IntFlags} class for their constants.

The new @ref{541,,enum.auto} value can be used to assign values to enum
members automatically:

@example
>>> from enum import Enum, auto
>>> class Color(Enum):
...     red = auto()
...     blue = auto()
...     green = auto()
...
>>> list(Color)
[<Color.red: 1>, <Color.blue: 2>, <Color.green: 3>]
@end example

@node faulthandler,fileinput,enum<3>,改进的模块<3>
@anchor{whatsnew/3 6 faulthandler}@anchor{542}
@subsubsection faulthandler


On Windows, the @ref{7d,,faulthandler} module now installs a handler for Windows
exceptions: see @ref{543,,faulthandler.enable()}. (Contributed by Victor Stinner in
bpo-23848@footnote{https://bugs.python.org/issue23848}.)

@node fileinput,hashlib,faulthandler,改进的模块<3>
@anchor{whatsnew/3 6 fileinput}@anchor{544}
@subsubsection fileinput


@ref{545,,hook_encoded()} now supports the @emph{errors} argument.
(Contributed by Joseph Hackman in bpo-25788@footnote{https://bugs.python.org/issue25788}.)

@node hashlib,http client<2>,fileinput,改进的模块<3>
@anchor{whatsnew/3 6 hashlib}@anchor{546}
@subsubsection hashlib


@ref{8d,,hashlib} supports OpenSSL 1.1.0.  The minimum recommend version is 1.0.2.
(Contributed by Christian Heimes in bpo-26470@footnote{https://bugs.python.org/issue26470}.)

BLAKE2 hash functions were added to the module. @ref{547,,blake2b()}
and @ref{548,,blake2s()} are always available and support the full
feature set of BLAKE2.
(Contributed by Christian Heimes in bpo-26798@footnote{https://bugs.python.org/issue26798} based on code by
Dmitry Chestnykh and Samuel Neves. Documentation written by Dmitry Chestnykh.)

The SHA-3 hash functions @code{sha3_224()}, @code{sha3_256()},
@code{sha3_384()}, @code{sha3_512()}, and SHAKE hash functions
@code{shake_128()} and @code{shake_256()} were added.
(Contributed by Christian Heimes in bpo-16113@footnote{https://bugs.python.org/issue16113}. Keccak Code Package
by Guido Bertoni, Joan Daemen, Michaël Peeters, Gilles Van Assche, and
Ronny Van Keer.)

The password-based key derivation function @ref{4cc,,scrypt()} is now
available with OpenSSL 1.1.0 and newer.
(Contributed by Christian Heimes in bpo-27928@footnote{https://bugs.python.org/issue27928}.)

@node http client<2>,idlelib 与 IDLE<2>,hashlib,改进的模块<3>
@anchor{whatsnew/3 6 http-client}@anchor{549}
@subsubsection http.client


@ref{54a,,HTTPConnection.request()} and
@ref{54b,,endheaders()} both now support
chunked encoding request bodies.
(Contributed by Demian Brecht and Rolf Krahl in bpo-12319@footnote{https://bugs.python.org/issue12319}.)

@node idlelib 与 IDLE<2>,importlib<3>,http client<2>,改进的模块<3>
@anchor{whatsnew/3 6 idlelib-and-idle}@anchor{54c}
@subsubsection idlelib 与 IDLE


The idlelib package is being modernized and refactored to make IDLE look and
work better and to make the code easier to understand, test, and improve. Part
of making IDLE look better, especially on Linux and Mac, is using ttk widgets,
mostly in the dialogs.  As a result, IDLE no longer runs with tcl/tk 8.4.  It
now requires tcl/tk 8.5 or 8.6.  We recommend running the latest release of
either.

'Modernizing' includes renaming and consolidation of idlelib modules. The
renaming of files with partial uppercase names is similar to the renaming of,
for instance, Tkinter and TkFont to tkinter and tkinter.font in 3.0.  As a
result, imports of idlelib files that worked in 3.5 will usually not work in
3.6.  At least a module name change will be needed (see idlelib/README.txt),
sometimes more.  (Name changes contributed by Al Swiegart and Terry Reedy in
bpo-24225@footnote{https://bugs.python.org/issue24225}.  Most idlelib patches since have been and will be part of the
process.)

In compensation, the eventual result with be that some idlelib classes will be
easier to use, with better APIs and docstrings explaining them.  Additional
useful information will be added to idlelib when available.

在 3.6.2 中新增:

多个对自动补全的修正。 （由 Louie Lu 在 bpo-15786@footnote{https://bugs.python.org/issue15786} 中贡献。）

在 3.6.3 中新增:

Module Browser (在 File 菜单中，之前称为 Class Browser) 现在会在最高层级函数和类之外显示嵌套的函数和类。 （由 Guilherme Polo, Cheryl Sabella 和 Terry Jan Reedy 在 bpo-1612262@footnote{https://bugs.python.org/issue1612262} 中贡献。）

之前以扩展形式实现的 IDLE 特性已作为正常特性重新实现。 它们的设置已从 Extensions 选项卡移至其他对话框选项卡。 （由 Charles Wohlganger 和 Terry Jan Reedy 在 bpo-27099@footnote{https://bugs.python.org/issue27099} 中实现。）

Settings 对话框 (Options 中的 Configure IDLE) 已经被部分重写以改进外观和功能。 （由 Cheryl Sabella 和 Terry Jan Reedy 在多个问题项中贡献。）

在 3.6.4 中新增:

字体样本现在包括一组非拉丁字符以便用户能更好地查看所选特定字体的效果。 （由 Terry Jan Reedy 在 bpo-13802@footnote{https://bugs.python.org/issue13802} 中贡献。） 样本可以被修改以包括其他字符。 （由 Serhiy Storchaka 在 bpo-31860@footnote{https://bugs.python.org/issue31860} 中贡献。）

在 3.6.6 中新增:

编辑器代码上下文选项已经过修改。 Box 会显示所有上下文行直到最大行数。 点击一个上下文行会使编辑器跳转到该行。 自定义主题的上下文颜色已添加到 Settings 对话框的 Highlights 选项卡。 （由 Cheryl Sabella 和 Terry Jan Reedy 在 bpo-33642@footnote{https://bugs.python.org/issue33642}, bpo-33768@footnote{https://bugs.python.org/issue33768} 和 bpo-33679@footnote{https://bugs.python.org/issue33679} 中贡献。）

在 Windows 上，会有新的 API 调用将 tk 对 DPI 的调整告知 Windows。 在 Windows 8.1+ 或 10 上，如果 Python 二进制码的 DPI 兼容属性未改变，并且监视器分辨率大于 96 DPI，这应该会令文本和线条更清晰。 否则的话它应该不造成影响。 （由 Terry Jan Reedy 在 bpo-33656@footnote{https://bugs.python.org/issue33656} 中贡献。）

在 3.6.7 中新增:

超过 N 行（默认值为 50）的输出将被折叠为一个按钮。 N 可以在 Settings 对话框的 General 页的 PyShell 部分中进行修改。 数量较少但是超长的行可以通过在输出上右击来折叠。 被折叠的输出可通过双击按钮来展开，或是通过右击按钮来放入剪贴板或是单独的窗口。 （由 Tal Einat 在 bpo-1529353@footnote{https://bugs.python.org/issue1529353} 中贡献。）

@node importlib<3>,inspect<2>,idlelib 与 IDLE<2>,改进的模块<3>
@anchor{whatsnew/3 6 importlib}@anchor{54d}
@subsubsection importlib


Import now raises the new exception @ref{392,,ModuleNotFoundError}
(subclass of @ref{32d,,ImportError}) when it cannot find a module.  Code
that current checks for @code{ImportError} (in try-except) will still work.
(Contributed by Eric Snow in bpo-15767@footnote{https://bugs.python.org/issue15767}.)

@ref{54e,,importlib.util.LazyLoader} now calls
@ref{54f,,create_module()} on the wrapped loader, removing the
restriction that @ref{550,,importlib.machinery.BuiltinImporter} and
@ref{551,,importlib.machinery.ExtensionFileLoader} couldn't be used with
@ref{54e,,importlib.util.LazyLoader}.

@ref{552,,importlib.util.cache_from_source()},
@ref{553,,importlib.util.source_from_cache()}, and
@ref{554,,importlib.util.spec_from_file_location()} now accept a
@ref{363,,path-like object}.

@node inspect<2>,json,importlib<3>,改进的模块<3>
@anchor{whatsnew/3 6 inspect}@anchor{555}
@subsubsection inspect


The @ref{556,,inspect.signature()} function now reports the
implicit @code{.0} parameters generated by the compiler for comprehension and
generator expression scopes as if they were positional-only parameters called
@code{implicit0}. (Contributed by Jelle Zijlstra in bpo-19611@footnote{https://bugs.python.org/issue19611}.)

To reduce code churn when upgrading from Python 2.7 and the legacy
@ref{557,,inspect.getargspec()} API, the previously documented deprecation of
@ref{558,,inspect.getfullargspec()} has been reversed. While this function is
convenient for single/source Python 2/3 code bases, the richer
@ref{556,,inspect.signature()} interface remains the recommended approach for new
code. (Contributed by Nick Coghlan in bpo-27172@footnote{https://bugs.python.org/issue27172})

@node json,logging<3>,inspect<2>,改进的模块<3>
@anchor{whatsnew/3 6 json}@anchor{559}
@subsubsection json


@ref{55a,,json.load()} and @ref{55b,,json.loads()} now support binary input.  Encoded
JSON should be represented using either UTF-8, UTF-16, or UTF-32.
(Contributed by Serhiy Storchaka in bpo-17909@footnote{https://bugs.python.org/issue17909}.)

@node logging<3>,math<3>,json,改进的模块<3>
@anchor{whatsnew/3 6 logging}@anchor{55c}
@subsubsection logging


The new @ref{55d,,WatchedFileHandler.reopenIfNeeded()}
method has been added to add the ability to check if the log file needs to
be reopened.
(Contributed by Marian Horban in bpo-24884@footnote{https://bugs.python.org/issue24884}.)

@node math<3>,multiprocessing<3>,logging<3>,改进的模块<3>
@anchor{whatsnew/3 6 math}@anchor{55e}
@subsubsection math


The tau (@emph{τ}) constant has been added to the @ref{b1,,math} and @ref{19,,cmath}
modules.
(Contributed by Lisa Roach in bpo-12345@footnote{https://bugs.python.org/issue12345}, see 
@geindex Python 提高建议; PEP 628
PEP 628@footnote{https://www.python.org/dev/peps/pep-0628} for details.)

@node multiprocessing<3>,os<3>,math<3>,改进的模块<3>
@anchor{whatsnew/3 6 multiprocessing}@anchor{55f}
@subsubsection multiprocessing


@ref{560,,Proxy Objects} returned by
@code{multiprocessing.Manager()} can now be nested.
(Contributed by Davin Potts in bpo-6766@footnote{https://bugs.python.org/issue6766}.)

@node os<3>,pathlib<3>,multiprocessing<3>,改进的模块<3>
@anchor{whatsnew/3 6 os}@anchor{561}
@subsubsection os


See the summary of @ref{4c7,,PEP 519} for details on how the
@ref{c4,,os} and @ref{c5,,os.path} modules now support
@ref{363,,path-like objects}.

@ref{25f,,scandir()} now supports @ref{32a,,bytes} paths on Windows.

A new @ref{562,,close()} method allows explicitly closing a
@ref{25f,,scandir()} iterator.  The @ref{25f,,scandir()} iterator now
supports the @ref{563,,context manager} protocol.  If a @code{scandir()}
iterator is neither exhausted nor explicitly closed a @ref{4ca,,ResourceWarning}
will be emitted in its destructor.
(Contributed by Serhiy Storchaka in bpo-25994@footnote{https://bugs.python.org/issue25994}.)

On Linux, @ref{4cb,,os.urandom()} now blocks until the system urandom entropy pool
is initialized to increase the security. See the 
@geindex Python 提高建议; PEP 524
PEP 524@footnote{https://www.python.org/dev/peps/pep-0524} for the rationale.

The Linux @code{getrandom()} syscall (get random bytes) is now exposed as the new
@ref{564,,os.getrandom()} function.
(Contributed by Victor Stinner, part of the 
@geindex Python 提高建议; PEP 524
PEP 524@footnote{https://www.python.org/dev/peps/pep-0524})

@node pathlib<3>,pdb<2>,os<3>,改进的模块<3>
@anchor{whatsnew/3 6 pathlib}@anchor{565}
@subsubsection pathlib


@ref{c8,,pathlib} now supports @ref{363,,path-like objects}.
(Contributed by Brett Cannon in bpo-27186@footnote{https://bugs.python.org/issue27186}.)

See the summary of @ref{4c7,,PEP 519} for details.

@node pdb<2>,pickle<2>,pathlib<3>,改进的模块<3>
@anchor{whatsnew/3 6 pdb}@anchor{566}
@subsubsection pdb


The @ref{567,,Pdb} class constructor has a new optional @emph{readrc} argument
to control whether @code{.pdbrc} files should be read.

@node pickle<2>,pickletools,pdb<2>,改进的模块<3>
@anchor{whatsnew/3 6 pickle}@anchor{568}
@subsubsection pickle


Objects that need @code{__new__} called with keyword arguments can now be pickled
using @ref{569,,pickle protocols} older than protocol version 4.
Protocol version 4 already supports this case.  (Contributed by Serhiy
Storchaka in bpo-24164@footnote{https://bugs.python.org/issue24164}.)

@node pickletools,pydoc<2>,pickle<2>,改进的模块<3>
@anchor{whatsnew/3 6 pickletools}@anchor{56a}
@subsubsection pickletools


@ref{56b,,pickletools.dis()} now outputs the implicit memo index for the
@code{MEMOIZE} opcode.
(Contributed by Serhiy Storchaka in bpo-25382@footnote{https://bugs.python.org/issue25382}.)

@node pydoc<2>,random,pickletools,改进的模块<3>
@anchor{whatsnew/3 6 pydoc}@anchor{56c}
@subsubsection pydoc


The @ref{d9,,pydoc} module has learned to respect the @code{MANPAGER}
environment variable.
(Contributed by Matthias Klose in bpo-8637@footnote{https://bugs.python.org/issue8637}.)

@ref{56d,,help()} and @ref{d9,,pydoc} can now list named tuple fields in the
order they were defined rather than alphabetically.
(Contributed by Raymond Hettinger in bpo-24879@footnote{https://bugs.python.org/issue24879}.)

@node random,re<2>,pydoc<2>,改进的模块<3>
@anchor{whatsnew/3 6 random}@anchor{56e}
@subsubsection random


The new @ref{56f,,choices()} function returns a list of elements of
specified size from the given population with optional weights.
(Contributed by Raymond Hettinger in bpo-18844@footnote{https://bugs.python.org/issue18844}.)

@node re<2>,readline,random,改进的模块<3>
@anchor{whatsnew/3 6 re}@anchor{570}
@subsubsection re


Added support of modifier spans in regular expressions.  Examples:
@code{'(?i:p)ython'} matches @code{'python'} and @code{'Python'}, but not @code{'PYTHON'};
@code{'(?i)g(?-i:v)r'} matches @code{'GvR'} and @code{'gvr'}, but not @code{'GVR'}.
(Contributed by Serhiy Storchaka in bpo-433028@footnote{https://bugs.python.org/issue433028}.)

Match object groups can be accessed by @code{__getitem__}, which is
equivalent to @code{group()}.  So @code{mo['name']} is now equivalent to
@code{mo.group('name')}.  (Contributed by Eric Smith in bpo-24454@footnote{https://bugs.python.org/issue24454}.)

@code{Match} objects now support
@ref{18a,,index-like objects} as group
indices.
(Contributed by Jeroen Demeyer and Xiang Zhang in bpo-27177@footnote{https://bugs.python.org/issue27177}.)

@node readline,rlcompleter,re<2>,改进的模块<3>
@anchor{whatsnew/3 6 readline}@anchor{571}
@subsubsection readline


Added @ref{572,,set_auto_history()} to enable or disable
automatic addition of input to the history list.  (Contributed by
Tyler Crompton in bpo-26870@footnote{https://bugs.python.org/issue26870}.)

@node rlcompleter,shlex<2>,readline,改进的模块<3>
@anchor{whatsnew/3 6 rlcompleter}@anchor{573}
@subsubsection rlcompleter


Private and special attribute names now are omitted unless the prefix starts
with underscores.  A space or a colon is added after some completed keywords.
(Contributed by Serhiy Storchaka in bpo-25011@footnote{https://bugs.python.org/issue25011} and bpo-25209@footnote{https://bugs.python.org/issue25209}.)

@node shlex<2>,site,rlcompleter,改进的模块<3>
@anchor{whatsnew/3 6 shlex}@anchor{574}
@subsubsection shlex


The @ref{575,,shlex} has much
@ref{576,,improved shell compatibility}
through the new @emph{punctuation_chars} argument to control which characters
are treated as punctuation.
(Contributed by Vinay Sajip in bpo-1521950@footnote{https://bugs.python.org/issue1521950}.)

@node site,sqlite3<2>,shlex<2>,改进的模块<3>
@anchor{whatsnew/3 6 site}@anchor{577}
@subsubsection site


When specifying paths to add to @ref{482,,sys.path} in a @cite{.pth} file,
you may now specify file paths on top of directories (e.g. zip files).
(Contributed by Wolfgang Langner in bpo-26587@footnote{https://bugs.python.org/issue26587}).

@node sqlite3<2>,socket<4>,site,改进的模块<3>
@anchor{whatsnew/3 6 sqlite3}@anchor{578}
@subsubsection sqlite3


@ref{579,,sqlite3.Cursor.lastrowid} now supports the @code{REPLACE} statement.
(Contributed by Alex LordThorsen in bpo-16864@footnote{https://bugs.python.org/issue16864}.)

@node socket<4>,socketserver<2>,sqlite3<2>,改进的模块<3>
@anchor{whatsnew/3 6 socket}@anchor{57a}
@subsubsection socket


The @ref{57b,,ioctl()} function now supports the
@ref{57c,,SIO_LOOPBACK_FAST_PATH} control code.
(Contributed by Daniel Stokes in bpo-26536@footnote{https://bugs.python.org/issue26536}.)

The @ref{57d,,getsockopt()} constants @code{SO_DOMAIN},
@code{SO_PROTOCOL}, @code{SO_PEERSEC}, and @code{SO_PASSSEC} are now supported.
(Contributed by Christian Heimes in bpo-26907@footnote{https://bugs.python.org/issue26907}.)

The @ref{57e,,setsockopt()} now supports the
@code{setsockopt(level, optname, None, optlen: int)} form.
(Contributed by Christian Heimes in bpo-27744@footnote{https://bugs.python.org/issue27744}.)

The socket module now supports the address family
@ref{57f,,AF_ALG} to interface with Linux Kernel crypto API. @code{ALG_*},
@code{SOL_ALG} and @ref{580,,sendmsg_afalg()} were added.
(Contributed by Christian Heimes in bpo-27744@footnote{https://bugs.python.org/issue27744} with support from
Victor Stinner.)

New Linux constants @code{TCP_USER_TIMEOUT} and @code{TCP_CONGESTION} were added.
(Contributed by Omar Sandoval, issue:@cite{26273}).

@node socketserver<2>,ssl<4>,socket<4>,改进的模块<3>
@anchor{whatsnew/3 6 socketserver}@anchor{581}
@subsubsection socketserver


Servers based on the @ref{f0,,socketserver} module, including those
defined in @ref{97,,http.server}, @ref{140,,xmlrpc.server} and
@ref{12f,,wsgiref.simple_server}, now support the @ref{563,,context manager}
protocol.
(Contributed by Aviv Palivoda in bpo-26404@footnote{https://bugs.python.org/issue26404}.)

The @code{wfile} attribute of
@ref{582,,StreamRequestHandler} classes now implements
the @ref{583,,io.BufferedIOBase} writable interface.  In particular,
calling @ref{584,,write()} is now guaranteed to send the
data in full.  (Contributed by Martin Panter in bpo-26721@footnote{https://bugs.python.org/issue26721}.)

@node ssl<4>,statistics<2>,socketserver<2>,改进的模块<3>
@anchor{whatsnew/3 6 ssl}@anchor{585}
@subsubsection ssl


@ref{f3,,ssl} supports OpenSSL 1.1.0.  The minimum recommend version is 1.0.2.
(Contributed by Christian Heimes in bpo-26470@footnote{https://bugs.python.org/issue26470}.)

3DES has been removed from the default cipher suites and ChaCha20 Poly1305
cipher suites have been added.
(Contributed by Christian Heimes in bpo-27850@footnote{https://bugs.python.org/issue27850} and bpo-27766@footnote{https://bugs.python.org/issue27766}.)

@ref{3dc,,SSLContext} has better default configuration for options
and ciphers.
(Contributed by Christian Heimes in bpo-28043@footnote{https://bugs.python.org/issue28043}.)

SSL session can be copied from one client-side connection to another
with the new @ref{586,,SSLSession} class.  TLS session resumption can
speed up the initial handshake, reduce latency and improve performance
(Contributed by Christian Heimes in bpo-19500@footnote{https://bugs.python.org/issue19500} based on a draft by
Alex Warhawk.)

The new @ref{587,,get_ciphers()} method can be used to
get a list of enabled ciphers in order of cipher priority.

All constants and flags have been converted to @ref{588,,IntEnum} and
@code{IntFlags}.
(Contributed by Christian Heimes in bpo-28025@footnote{https://bugs.python.org/issue28025}.)

Server and client-side specific TLS protocols for @ref{3dc,,SSLContext}
were added.
(Contributed by Christian Heimes in bpo-28085@footnote{https://bugs.python.org/issue28085}.)

@node statistics<2>,struct,ssl<4>,改进的模块<3>
@anchor{whatsnew/3 6 statistics}@anchor{589}
@subsubsection statistics


A new @ref{58a,,harmonic_mean()} function has been added.
(Contributed by Steven D'Aprano in bpo-27181@footnote{https://bugs.python.org/issue27181}.)

@node struct,subprocess<2>,statistics<2>,改进的模块<3>
@anchor{whatsnew/3 6 struct}@anchor{58b}
@subsubsection struct


@ref{f8,,struct} now supports IEEE 754 half-precision floats via the @code{'e'}
format specifier.
(Contributed by Eli Stevens, Mark Dickinson in bpo-11734@footnote{https://bugs.python.org/issue11734}.)

@node subprocess<2>,sys<4>,struct,改进的模块<3>
@anchor{whatsnew/3 6 subprocess}@anchor{58c}
@subsubsection subprocess


@ref{2b9,,subprocess.Popen} destructor now emits a @ref{4ca,,ResourceWarning} warning
if the child process is still running. Use the context manager protocol (@code{with
proc: ...}) or explicitly call the @ref{58d,,wait()} method to
read the exit status of the child process. (Contributed by Victor Stinner in
bpo-26741@footnote{https://bugs.python.org/issue26741}.)

The @ref{2b9,,subprocess.Popen} constructor and all functions that pass arguments
through to it now accept @emph{encoding} and @emph{errors} arguments. Specifying either
of these will enable text mode for the @emph{stdin}, @emph{stdout} and @emph{stderr} streams.
(Contributed by Steve Dower in bpo-6135@footnote{https://bugs.python.org/issue6135}.)

@node sys<4>,telnetlib,subprocess<2>,改进的模块<3>
@anchor{whatsnew/3 6 sys}@anchor{58e}
@subsubsection sys


The new @ref{58f,,getfilesystemencodeerrors()} function returns the name of
the error mode used to convert between Unicode filenames and bytes filenames.
(Contributed by Steve Dower in bpo-27781@footnote{https://bugs.python.org/issue27781}.)

On Windows the return value of the @ref{590,,getwindowsversion()} function
now includes the @emph{platform_version} field which contains the accurate major
version, minor version and build number of the current operating system,
rather than the version that is being emulated for the process
(Contributed by Steve Dower in bpo-27932@footnote{https://bugs.python.org/issue27932}.)

@node telnetlib,time<3>,sys<4>,改进的模块<3>
@anchor{whatsnew/3 6 telnetlib}@anchor{591}
@subsubsection telnetlib


@ref{592,,Telnet} is now a context manager (contributed by
Stéphane Wirtel in bpo-25485@footnote{https://bugs.python.org/issue25485}).

@node time<3>,timeit,telnetlib,改进的模块<3>
@anchor{whatsnew/3 6 time}@anchor{593}
@subsubsection time


The @ref{594,,struct_time} attributes @code{tm_gmtoff} and
@code{tm_zone} are now available on all platforms.

@node timeit,tkinter<3>,time<3>,改进的模块<3>
@anchor{whatsnew/3 6 timeit}@anchor{595}
@subsubsection timeit


The new @ref{596,,Timer.autorange()} convenience
method has been added to call @ref{597,,Timer.timeit()}
repeatedly so that the total run time is greater or equal to 200 milliseconds.
(Contributed by Steven D'Aprano in bpo-6422@footnote{https://bugs.python.org/issue6422}.)

@ref{10b,,timeit} now warns when there is substantial (4x) variance
between best and worst times.
(Contributed by Serhiy Storchaka in bpo-23552@footnote{https://bugs.python.org/issue23552}.)

@node tkinter<3>,回溯,timeit,改进的模块<3>
@anchor{whatsnew/3 6 tkinter}@anchor{598}
@subsubsection tkinter


Added methods @code{trace_add()},
@code{trace_remove()} and @code{trace_info()}
in the @code{tkinter.Variable} class.  They replace old methods
@code{trace_variable()}, @code{trace()},
@code{trace_vdelete()} and
@code{trace_vinfo()} that use obsolete Tcl commands and might
not work in future versions of Tcl.
(Contributed by Serhiy Storchaka in bpo-22115@footnote{https://bugs.python.org/issue22115}).

@node 回溯,tracemalloc<2>,tkinter<3>,改进的模块<3>
@anchor{whatsnew/3 6 traceback}@anchor{599}@anchor{whatsnew/3 6 whatsnew36-traceback}@anchor{50a}
@subsubsection 回溯


Both the traceback module and the interpreter's builtin exception display now
abbreviate long sequences of repeated lines in tracebacks as shown in the
following example:

@example
>>> def f(): f()
...
>>> f()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in f
  File "<stdin>", line 1, in f
  File "<stdin>", line 1, in f
  [Previous line repeated 995 more times]
RecursionError: maximum recursion depth exceeded
@end example

（由  Emanuel Barry在 bpo-26823@footnote{https://bugs.python.org/issue26823} 中贡献。）

@node tracemalloc<2>,typing<2>,回溯,改进的模块<3>
@anchor{whatsnew/3 6 tracemalloc}@anchor{59a}
@subsubsection tracemalloc


The @ref{114,,tracemalloc} module now supports tracing memory allocations in
multiple different address spaces.

The new @ref{59b,,DomainFilter} filter class has been added
to filter block traces by their address space (domain).

（由 Victor Stinner 在 bpo-26588@footnote{https://bugs.python.org/issue26588} 中贡献。）

@node typing<2>,unicodedata<3>,tracemalloc<2>,改进的模块<3>
@anchor{whatsnew/3 6 typing}@anchor{59c}@anchor{whatsnew/3 6 whatsnew36-typing}@anchor{4c9}
@subsubsection typing


Since the @ref{119,,typing} module is @ref{341,,provisional},
all changes introduced in Python 3.6 have also been
backported to Python 3.5.x.

The @ref{119,,typing} module has a much improved support for generic type
aliases.  For example @code{Dict[str, Tuple[S, T]]} is now a valid
type annotation.
(Contributed by Guido van Rossum in Github #195@footnote{https://github.com/python/typing/pull/195}.)

The @ref{52f,,typing.ContextManager} class has been added for
representing @ref{52e,,contextlib.AbstractContextManager}.
(Contributed by Brett Cannon in bpo-25609@footnote{https://bugs.python.org/issue25609}.)

The @ref{59d,,typing.Collection} class has been added for
representing @ref{527,,collections.abc.Collection}.
(Contributed by Ivan Levkivskyi in bpo-27598@footnote{https://bugs.python.org/issue27598}.)

The @ref{59e,,typing.ClassVar} type construct has been added to
mark class variables.  As introduced in 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526}, a variable annotation
wrapped in ClassVar indicates that a given attribute is intended to be used as
a class variable and should not be set on instances of that class.
(Contributed by Ivan Levkivskyi in Github #280@footnote{https://github.com/python/typing/pull/280}.)

A new @ref{59f,,TYPE_CHECKING} constant that is assumed to be
@code{True} by the static type checkers, but is @code{False} at runtime.
(Contributed by Guido van Rossum in Github #230@footnote{https://github.com/python/typing/issues/230}.)

A new @ref{5a0,,NewType()} helper function has been added to create
lightweight distinct types for annotations:

@example
from typing import NewType

UserId = NewType('UserId', int)
some_id = UserId(524313)
@end example

The static type checker will treat the new type as if it were a subclass
of the original type.  (Contributed by Ivan Levkivskyi in Github #189@footnote{https://github.com/python/typing/issues/189}.)

@node unicodedata<3>,unittest mock<2>,typing<2>,改进的模块<3>
@anchor{whatsnew/3 6 unicodedata}@anchor{5a1}
@subsubsection unicodedata


The @ref{11a,,unicodedata} module now uses data from Unicode 9.0.0@footnote{http://unicode.org/versions/Unicode9.0.0/}.
(Contributed by Benjamin Peterson.)

@node unittest mock<2>,urllib request,unicodedata<3>,改进的模块<3>
@anchor{whatsnew/3 6 unittest-mock}@anchor{5a2}
@subsubsection unittest.mock


The @ref{249,,Mock} class has the following improvements:


@itemize *

@item 
Two new methods, @ref{5a3,,Mock.assert_called()} and @ref{5a4,,Mock.assert_called_once()} to check if the mock object
was called.
(Contributed by Amit Saha in bpo-26323@footnote{https://bugs.python.org/issue26323}.)

@item 
The @ref{5a5,,Mock.reset_mock()} method
now has two optional keyword only arguments: @emph{return_value} and
@emph{side_effect}.
(Contributed by Kushal Das in bpo-21271@footnote{https://bugs.python.org/issue21271}.)
@end itemize

@node urllib request,urllib robotparser,unittest mock<2>,改进的模块<3>
@anchor{whatsnew/3 6 urllib-request}@anchor{5a6}
@subsubsection urllib.request


If a HTTP request has a file or iterable body (other than a
bytes object) but no @code{Content-Length} header, rather than
throwing an error, @code{AbstractHTTPHandler} now
falls back to use chunked transfer encoding.
(Contributed by Demian Brecht and Rolf Krahl in bpo-12319@footnote{https://bugs.python.org/issue12319}.)

@node urllib robotparser,venv<2>,urllib request,改进的模块<3>
@anchor{whatsnew/3 6 urllib-robotparser}@anchor{5a7}
@subsubsection urllib.robotparser


@ref{5a8,,RobotFileParser} now supports the @code{Crawl-delay} and
@code{Request-rate} extensions.
(Contributed by Nikolay Bogoychev in bpo-16099@footnote{https://bugs.python.org/issue16099}.)

@node venv<2>,warnings<2>,urllib robotparser,改进的模块<3>
@anchor{whatsnew/3 6 venv}@anchor{5a9}
@subsubsection venv


@ref{125,,venv} accepts a new parameter @code{--prompt}. This parameter provides an
alternative prefix for the virtual environment. (Proposed by Łukasz Balcerzak
and ported to 3.6 by Stéphane Wirtel in bpo-22829@footnote{https://bugs.python.org/issue22829}.)

@node warnings<2>,winreg,venv<2>,改进的模块<3>
@anchor{whatsnew/3 6 warnings}@anchor{5aa}
@subsubsection warnings


A new optional @emph{source} parameter has been added to the
@ref{5ab,,warnings.warn_explicit()} function: the destroyed object which emitted a
@ref{4ca,,ResourceWarning}. A @emph{source} attribute has also been added to
@code{warnings.WarningMessage} (contributed by Victor Stinner in
bpo-26568@footnote{https://bugs.python.org/issue26568} and bpo-26567@footnote{https://bugs.python.org/issue26567}).

When a @ref{4ca,,ResourceWarning} warning is logged, the @ref{114,,tracemalloc} module is now
used to try to retrieve the traceback where the destroyed object was allocated.

Example with the script @code{example.py}:

@example
import warnings

def func():
    return open(__file__)

f = func()
f = None
@end example

Output of the command @code{python3.6 -Wd -X tracemalloc=5 example.py}:

@example
example.py:7: ResourceWarning: unclosed file <_io.TextIOWrapper name='example.py' mode='r' encoding='UTF-8'>
  f = None
Object allocated at (most recent call first):
  File "example.py", lineno 4
    return open(__file__)
  File "example.py", lineno 6
    f = func()
@end example

The "Object allocated at" traceback is new and is only displayed if
@ref{114,,tracemalloc} is tracing Python memory allocations and if the
@ref{126,,warnings} module was already imported.

@node winreg,winsound,warnings<2>,改进的模块<3>
@anchor{whatsnew/3 6 winreg}@anchor{5ac}
@subsubsection winreg


Added the 64-bit integer type @ref{5ad,,REG_QWORD}.
(Contributed by Clement Rouault in bpo-23026@footnote{https://bugs.python.org/issue23026}.)

@node winsound,xmlrpc client,winreg,改进的模块<3>
@anchor{whatsnew/3 6 winsound}@anchor{5ae}
@subsubsection winsound


Allowed keyword arguments to be passed to @ref{5af,,Beep},
@ref{5b0,,MessageBeep}, and @ref{5b1,,PlaySound} (bpo-27982@footnote{https://bugs.python.org/issue27982}).

@node xmlrpc client,zipfile<2>,winsound,改进的模块<3>
@anchor{whatsnew/3 6 xmlrpc-client}@anchor{5b2}
@subsubsection xmlrpc.client


The @ref{13f,,xmlrpc.client} module now supports unmarshalling
additional data types used by the Apache XML-RPC implementation
for numerics and @code{None}.
(Contributed by Serhiy Storchaka in bpo-26885@footnote{https://bugs.python.org/issue26885}.)

@node zipfile<2>,zlib,xmlrpc client,改进的模块<3>
@anchor{whatsnew/3 6 zipfile}@anchor{5b3}
@subsubsection zipfile


A new @ref{5b4,,ZipInfo.from_file()} class method
allows making a @ref{5b5,,ZipInfo} instance from a filesystem file.
A new @ref{5b6,,ZipInfo.is_dir()} method can be used
to check if the @ref{5b5,,ZipInfo} instance represents a directory.
(Contributed by Thomas Kluyver in bpo-26039@footnote{https://bugs.python.org/issue26039}.)

The @ref{5b7,,ZipFile.open()} method can now be used to
write data into a ZIP file, as well as for extracting data.
(Contributed by Thomas Kluyver in bpo-26039@footnote{https://bugs.python.org/issue26039}.)

@node zlib,,zipfile<2>,改进的模块<3>
@anchor{whatsnew/3 6 zlib}@anchor{5b8}
@subsubsection zlib


The @ref{5b9,,compress()} and @ref{5ba,,decompress()} functions now accept
keyword arguments.
(Contributed by Aviv Palivoda in bpo-26243@footnote{https://bugs.python.org/issue26243} and
Xiang Zhang in bpo-16764@footnote{https://bugs.python.org/issue16764} respectively.)

@node 性能优化<3>,构建和 C API 的改变<2>,改进的模块<3>,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 optimizations}@anchor{5bb}
@subsection 性能优化



@itemize *

@item 
The Python interpreter now uses a 16-bit wordcode instead of bytecode which
made a number of opcode optimizations possible.
(Contributed by Demur Rumed with input and reviews from
Serhiy Storchaka and Victor Stinner in bpo-26647@footnote{https://bugs.python.org/issue26647} and bpo-28050@footnote{https://bugs.python.org/issue28050}.)

@item 
The @ref{43d,,asyncio.Future} class now has an optimized C implementation.
(Contributed by Yury Selivanov and INADA Naoki in bpo-26081@footnote{https://bugs.python.org/issue26081}.)

@item 
The @ref{1ad,,asyncio.Task} class now has an optimized
C implementation. (Contributed by Yury Selivanov in bpo-28544@footnote{https://bugs.python.org/issue28544}.)

@item 
Various implementation improvements in the @ref{119,,typing} module
(such as caching of generic types) allow up to 30 times performance
improvements and reduced memory footprint.

@item 
The ASCII decoder is now up to 60 times as fast for error handlers
@code{surrogateescape}, @code{ignore} and @code{replace} (Contributed
by Victor Stinner in bpo-24870@footnote{https://bugs.python.org/issue24870}).

@item 
The ASCII and the Latin1 encoders are now up to 3 times as fast for the
error handler @code{surrogateescape}
(Contributed by Victor Stinner in bpo-25227@footnote{https://bugs.python.org/issue25227}).

@item 
The UTF-8 encoder is now up to 75 times as fast for error handlers
@code{ignore}, @code{replace}, @code{surrogateescape}, @code{surrogatepass} (Contributed
by Victor Stinner in bpo-25267@footnote{https://bugs.python.org/issue25267}).

@item 
The UTF-8 decoder is now up to 15 times as fast for error handlers
@code{ignore}, @code{replace} and @code{surrogateescape} (Contributed
by Victor Stinner in bpo-25301@footnote{https://bugs.python.org/issue25301}).

@item 
@code{bytes % args} is now up to 2 times faster. (Contributed by Victor Stinner
in bpo-25349@footnote{https://bugs.python.org/issue25349}).

@item 
@code{bytearray % args} is now between 2.5 and 5 times faster. (Contributed by
Victor Stinner in bpo-25399@footnote{https://bugs.python.org/issue25399}).

@item 
Optimize @ref{327,,bytes.fromhex()} and @ref{328,,bytearray.fromhex()}: they are now
between 2x and 3.5x faster. (Contributed by Victor Stinner in bpo-25401@footnote{https://bugs.python.org/issue25401}).

@item 
Optimize @code{bytes.replace(b'@w{'}, b'.')} and @code{bytearray.replace(b'@w{'}, b'.')}:
up to 80% faster. (Contributed by Josh Snider in bpo-26574@footnote{https://bugs.python.org/issue26574}).

@item 
Allocator functions of the @ref{4ff,,PyMem_Malloc()} domain
(@ref{503,,PYMEM_DOMAIN_MEM}) now use the @ref{5bc,,pymalloc memory allocator} instead of @code{malloc()} function of the C library. The
pymalloc allocator is optimized for objects smaller or equal to 512 bytes
with a short lifetime, and use @code{malloc()} for larger memory blocks.
(Contributed by Victor Stinner in bpo-26249@footnote{https://bugs.python.org/issue26249}).

@item 
@ref{5bd,,pickle.load()} and @ref{5be,,pickle.loads()} are now up to 10% faster when
deserializing many small objects (Contributed by Victor Stinner in
bpo-27056@footnote{https://bugs.python.org/issue27056}).

@item 
Passing @ref{5bf,,keyword arguments} to a function has an
overhead in comparison with passing @ref{5c0,,positional arguments}.  Now in extension functions implemented with using
Argument Clinic this overhead is significantly decreased.
(Contributed by Serhiy Storchaka in bpo-27574@footnote{https://bugs.python.org/issue27574}).

@item 
Optimized @ref{5c1,,glob()} and @ref{5c2,,iglob()} functions in the
@ref{8a,,glob} module; they are now about 3--6 times faster.
(Contributed by Serhiy Storchaka in bpo-25596@footnote{https://bugs.python.org/issue25596}).

@item 
Optimized globbing in @ref{c8,,pathlib} by using @ref{25f,,os.scandir()};
it is now about 1.5--4 times faster.
(Contributed by Serhiy Storchaka in bpo-26032@footnote{https://bugs.python.org/issue26032}).

@item 
@ref{137,,xml.etree.ElementTree} parsing, iteration and deepcopy performance
has been significantly improved.
(Contributed by Serhiy Storchaka in bpo-25638@footnote{https://bugs.python.org/issue25638}, bpo-25873@footnote{https://bugs.python.org/issue25873},
and bpo-25869@footnote{https://bugs.python.org/issue25869}.)

@item 
Creation of @ref{185,,fractions.Fraction} instances from floats and
decimals is now 2 to 3 times faster.
(Contributed by Serhiy Storchaka in bpo-25971@footnote{https://bugs.python.org/issue25971}.)
@end itemize

@node 构建和 C API 的改变<2>,其他改进,性能优化<3>,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 build-and-c-api-changes}@anchor{5c3}
@subsection 构建和 C API 的改变



@itemize *

@item 
Python now requires some C99 support in the toolchain to build.
Most notably, Python now uses standard integer types and macros in
place of custom macros like @code{PY_LONG_LONG}.
For more information, see 
@geindex Python 提高建议; PEP 7
PEP 7@footnote{https://www.python.org/dev/peps/pep-0007} and bpo-17884@footnote{https://bugs.python.org/issue17884}.

@item 
Cross-compiling CPython with the Android NDK and the Android API level set to
21 (Android 5.0 Lollipop) or greater runs successfully. While Android is not
yet a supported platform, the Python test suite runs on the Android emulator
with only about 16 tests failures. See the Android meta-issue bpo-26865@footnote{https://bugs.python.org/issue26865}.

@item 
The @code{--enable-optimizations} configure flag has been added. Turning it on
will activate expensive optimizations like PGO.
(Original patch by Alecsandru Patrascu of Intel in bpo-26359@footnote{https://bugs.python.org/issue26359}.)

@item 
The @ref{500,,GIL} must now be held when allocator
functions of @ref{501,,PYMEM_DOMAIN_OBJ} (ex: @ref{502,,PyObject_Malloc()}) and
@ref{503,,PYMEM_DOMAIN_MEM} (ex: @ref{4ff,,PyMem_Malloc()}) domains are called.

@item 
New @ref{5c4,,Py_FinalizeEx()} API which indicates if flushing buffered data
failed.
(Contributed by Martin Panter in bpo-5319@footnote{https://bugs.python.org/issue5319}.)

@item 
@ref{5c5,,PyArg_ParseTupleAndKeywords()} now supports @ref{2a7,,positional-only parameters}.  Positional-only parameters are
defined by empty names.
(Contributed by Serhiy Storchaka in bpo-26282@footnote{https://bugs.python.org/issue26282}).

@item 
@code{PyTraceback_Print} method now abbreviates long sequences of repeated lines
as @code{"[Previous line repeated @{count@} more times]"}.
(Contributed by Emanuel Barry in bpo-26823@footnote{https://bugs.python.org/issue26823}.)

@item 
The new @ref{5c6,,PyErr_SetImportErrorSubclass()} function allows for
specifying a subclass of @ref{32d,,ImportError} to raise.
(Contributed by Eric Snow in bpo-15767@footnote{https://bugs.python.org/issue15767}.)

@item 
The new @ref{5c7,,PyErr_ResourceWarning()} function can be used to generate
a @ref{4ca,,ResourceWarning} providing the source of the resource allocation.
(Contributed by Victor Stinner in bpo-26567@footnote{https://bugs.python.org/issue26567}.)

@item 
The new @ref{5c8,,PyOS_FSPath()} function returns the file system
representation of a @ref{363,,path-like object}.
(Contributed by Brett Cannon in bpo-27186@footnote{https://bugs.python.org/issue27186}.)

@item 
The @ref{5c9,,PyUnicode_FSConverter()} and @ref{5ca,,PyUnicode_FSDecoder()}
functions will now accept @ref{363,,path-like objects}.
@end itemize

@node 其他改进,弃用<2>,构建和 C API 的改变<2>,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 other-improvements}@anchor{5cb}
@subsection 其他改进



@itemize *

@item 
When @ref{5cc,,--version} (short form: @ref{5cd,,-V}) is supplied twice,
Python prints @ref{5ce,,sys.version} for detailed information.

@example
$ ./python -VV
Python 3.6.0b4+ (3.6:223967b49e49+, Nov 21 2016, 20:55:04)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)]
@end example
@end itemize

@node 弃用<2>,移除,其他改进,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 deprecated}@anchor{5cf}
@subsection 弃用


@menu
* 新关键字:: 
* 已弃用的 Python 行为: 已弃用的 Python 行为<2>. 
* 已弃用的 Python 模块、函数和方法: 已弃用的 Python 模块、函数和方法<2>. 
* 已弃用的 C API 函数和类型: 已弃用的 C API 函数和类型<2>. 
* 弃用的构建选项:: 

@end menu

@node 新关键字,已弃用的 Python 行为<2>,,弃用<2>
@anchor{whatsnew/3 6 new-keywords}@anchor{5d0}
@subsubsection 新关键字


@code{async} and @code{await} are not recommended to be used as variable, class,
function or module names.  Introduced by 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} in Python 3.5, they will
become proper keywords in Python 3.7.  Starting in Python 3.6, the use of
@code{async} or @code{await} as names will generate a @ref{278,,DeprecationWarning}.

@node 已弃用的 Python 行为<2>,已弃用的 Python 模块、函数和方法<2>,新关键字,弃用<2>
@anchor{whatsnew/3 6 deprecated-python-behavior}@anchor{5d1}
@subsubsection 已弃用的 Python 行为


Raising the @ref{480,,StopIteration} exception inside a generator will now
generate a @ref{278,,DeprecationWarning}, and will trigger a @ref{2ba,,RuntimeError}
in Python 3.7.  See @ref{5d2,,PEP 479; Change StopIteration handling inside generators} for details.

The @ref{481,,__aiter__()} method is now expected to return an asynchronous
iterator directly instead of returning an awaitable as previously.
Doing the former will trigger a @ref{278,,DeprecationWarning}.  Backward
compatibility will be removed in Python 3.7.
(Contributed by Yury Selivanov in bpo-27243@footnote{https://bugs.python.org/issue27243}.)

A backslash-character pair that is not a valid escape sequence now generates
a @ref{278,,DeprecationWarning}.  Although this will eventually become a
@ref{452,,SyntaxError}, that will not be for several Python releases.
(Contributed by Emanuel Barry in bpo-27364@footnote{https://bugs.python.org/issue27364}.)

When performing a relative import, falling back on @code{__name__} and
@code{__path__} from the calling module when @code{__spec__} or
@code{__package__} are not defined now raises an @ref{5d3,,ImportWarning}.
(Contributed by Rose Ames in bpo-25791@footnote{https://bugs.python.org/issue25791}.)

@node 已弃用的 Python 模块、函数和方法<2>,已弃用的 C API 函数和类型<2>,已弃用的 Python 行为<2>,弃用<2>
@anchor{whatsnew/3 6 deprecated-python-modules-functions-and-methods}@anchor{5d4}
@subsubsection 已弃用的 Python 模块、函数和方法


@menu
* asynchat:: 
* asyncore:: 
* dbm: dbm<3>. 
* distutils: distutils<3>. 
* grp:: 
* importlib: importlib<4>. 
* os: os<4>. 
* re: re<3>. 
* ssl: ssl<5>. 
* tkinter: tkinter<4>. 
* venv: venv<3>. 

@end menu

@node asynchat,asyncore,,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 asynchat}@anchor{5d5}
@subsubsection asynchat


The @ref{9,,asynchat} has been deprecated in favor of @ref{a,,asyncio}.
(Contributed by Mariatta in bpo-25002@footnote{https://bugs.python.org/issue25002}.)

@node asyncore,dbm<3>,asynchat,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 asyncore}@anchor{5d6}
@subsubsection asyncore


The @ref{b,,asyncore} has been deprecated in favor of @ref{a,,asyncio}.
(Contributed by Mariatta in bpo-25002@footnote{https://bugs.python.org/issue25002}.)

@node dbm<3>,distutils<3>,asyncore,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 dbm}@anchor{5d7}
@subsubsection dbm


Unlike other @ref{32,,dbm} implementations, the @ref{33,,dbm.dumb} module
creates databases with the @code{'rw'} mode and allows modifying the database
opened with the @code{'r'} mode.  This behavior is now deprecated and will
be removed in 3.8.
(Contributed by Serhiy Storchaka in bpo-21708@footnote{https://bugs.python.org/issue21708}.)

@node distutils<3>,grp,dbm<3>,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 id2}@anchor{5d8}
@subsubsection distutils


The undocumented @code{extra_path} argument to the
@code{Distribution} constructor is now considered deprecated
and will raise a warning if set.   Support for this parameter will be
removed in a future Python release.  See bpo-27919@footnote{https://bugs.python.org/issue27919} for details.

@node grp,importlib<4>,distutils<3>,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 grp}@anchor{5d9}
@subsubsection grp


The support of non-integer arguments in @ref{5da,,getgrgid()} has been
deprecated.
(Contributed by Serhiy Storchaka in bpo-26129@footnote{https://bugs.python.org/issue26129}.)

@node importlib<4>,os<4>,grp,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 id3}@anchor{5db}
@subsubsection importlib


The @ref{5dc,,importlib.machinery.SourceFileLoader.load_module()} and
@ref{5dd,,importlib.machinery.SourcelessFileLoader.load_module()} methods
are now deprecated. They were the only remaining implementations of
@ref{5de,,importlib.abc.Loader.load_module()} in @ref{9b,,importlib} that had not
been deprecated in previous versions of Python in favour of
@ref{5df,,importlib.abc.Loader.exec_module()}.

The @ref{5e0,,importlib.machinery.WindowsRegistryFinder} class is now
deprecated. As of 3.6.0, it is still added to @ref{5e1,,sys.meta_path} by
default (on Windows), but this may change in future releases.

@node os<4>,re<3>,importlib<4>,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 id4}@anchor{5e2}
@subsubsection os


Undocumented support of general @ref{5e3,,bytes-like objects}
as paths in @ref{c4,,os} functions, @ref{1b4,,compile()} and similar functions is
now deprecated.
(Contributed by Serhiy Storchaka in bpo-25791@footnote{https://bugs.python.org/issue25791} and bpo-26754@footnote{https://bugs.python.org/issue26754}.)

@node re<3>,ssl<5>,os<4>,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 id5}@anchor{5e4}
@subsubsection re


Support for inline flags @code{(?letters)} in the middle of the regular
expression has been deprecated and will be removed in a future Python
version.  Flags at the start of a regular expression are still allowed.
(Contributed by Serhiy Storchaka in bpo-22493@footnote{https://bugs.python.org/issue22493}.)

@node ssl<5>,tkinter<4>,re<3>,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 id6}@anchor{5e5}
@subsubsection ssl


OpenSSL 0.9.8, 1.0.0 and 1.0.1 are deprecated and no longer supported.
In the future the @ref{f3,,ssl} module will require at least OpenSSL 1.0.2 or
1.1.0.

SSL-related arguments like @code{certfile}, @code{keyfile} and @code{check_hostname}
in @ref{84,,ftplib}, @ref{94,,http.client}, @ref{98,,imaplib}, @ref{d0,,poplib},
and @ref{ed,,smtplib} have been deprecated in favor of @code{context}.
(Contributed by Christian Heimes in bpo-28022@footnote{https://bugs.python.org/issue28022}.)

A couple of protocols and functions of the @ref{f3,,ssl} module are now
deprecated. Some features will no longer be available in future versions
of OpenSSL. Other features are deprecated in favor of a different API.
(Contributed by Christian Heimes in bpo-28022@footnote{https://bugs.python.org/issue28022} and bpo-26470@footnote{https://bugs.python.org/issue26470}.)

@node tkinter<4>,venv<3>,ssl<5>,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 id7}@anchor{5e6}
@subsubsection tkinter


The @ref{10e,,tkinter.tix} module is now deprecated.  @ref{10c,,tkinter} users
should use @ref{10f,,tkinter.ttk} instead.

@node venv<3>,,tkinter<4>,已弃用的 Python 模块、函数和方法<2>
@anchor{whatsnew/3 6 id8}@anchor{5e7}
@subsubsection venv


The @code{pyvenv} script has been deprecated in favour of @code{python3 -m venv}.
This prevents confusion as to what Python interpreter @code{pyvenv} is
connected to and thus what Python interpreter will be used by the virtual
environment.  (Contributed by Brett Cannon in bpo-25154@footnote{https://bugs.python.org/issue25154}.)

@node 已弃用的 C API 函数和类型<2>,弃用的构建选项,已弃用的 Python 模块、函数和方法<2>,弃用<2>
@anchor{whatsnew/3 6 deprecated-functions-and-types-of-the-c-api}@anchor{5e8}
@subsubsection 已弃用的 C API 函数和类型


Undocumented functions @code{PyUnicode_AsEncodedObject()},
@code{PyUnicode_AsDecodedObject()}, @code{PyUnicode_AsEncodedUnicode()}
and @code{PyUnicode_AsDecodedUnicode()} are deprecated now.
Use the @ref{5e9,,generic codec based API} instead.

@node 弃用的构建选项,,已弃用的 C API 函数和类型<2>,弃用<2>
@anchor{whatsnew/3 6 deprecated-build-options}@anchor{5ea}
@subsubsection 弃用的构建选项


The @code{--with-system-ffi} configure flag is now on by default on non-macOS
UNIX platforms.  It may be disabled by using @code{--without-system-ffi}, but
using the flag is deprecated and will not be accepted in Python 3.7.
macOS is unaffected by this change.  Note that many OS distributors already
use the @code{--with-system-ffi} flag when building their system Python.

@node 移除,移植到Python 3 6,弃用<2>,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 removed}@anchor{5eb}
@subsection 移除


@menu
* API 与特性的移除: API 与特性的移除<3>. 

@end menu

@node API 与特性的移除<3>,,,移除
@anchor{whatsnew/3 6 api-and-feature-removals}@anchor{5ec}
@subsubsection API 与特性的移除



@itemize *

@item 
Unknown escapes consisting of @code{'\'} and an ASCII letter in
regular expressions will now cause an error.  In replacement templates for
@ref{475,,re.sub()} they are still allowed, but deprecated.
The @ref{3c1,,re.LOCALE} flag can now only be used with binary patterns.

@item 
@code{inspect.getmoduleinfo()} was removed (was deprecated since CPython 3.3).
@ref{5ed,,inspect.getmodulename()} should be used for obtaining the module
name for a given path.
(Contributed by Yury Selivanov in bpo-13248@footnote{https://bugs.python.org/issue13248}.)

@item 
@code{traceback.Ignore} class and @code{traceback.usage}, @code{traceback.modname},
@code{traceback.fullmodname}, @code{traceback.find_lines_from_code},
@code{traceback.find_lines}, @code{traceback.find_strings},
@code{traceback.find_executable_lines} methods were removed from the
@ref{113,,traceback} module. They were undocumented methods deprecated since
Python 3.2 and equivalent functionality is available from private methods.

@item 
The @code{tk_menuBar()} and @code{tk_bindForTraversal()} dummy methods in
@ref{10c,,tkinter} widget classes were removed (corresponding Tk commands
were obsolete since Tk 4.0).

@item 
The @ref{5b7,,open()} method of the @ref{417,,zipfile.ZipFile}
class no longer supports the @code{'U'} mode (was deprecated since Python 3.4).
Use @ref{5ee,,io.TextIOWrapper} for reading compressed text files in
@ref{5ef,,universal newlines} mode.

@item 
The undocumented @code{IN}, @code{CDROM}, @code{DLFCN}, @code{TYPES}, @code{CDIO}, and
@code{STROPTS} modules have been removed.  They had been available in the
platform specific @code{Lib/plat-*/} directories, but were chronically out of
date, inconsistently available across platforms, and unmaintained.  The
script that created these modules is still available in the source
distribution at Tools/scripts/h2py.py@footnote{https://github.com/python/cpython/tree/3.8/Tools/scripts/h2py.py}.

@item 
The deprecated @code{asynchat.fifo} class has been removed.
@end itemize

@node 移植到Python 3 6,Python 3 6 2 中的重要变化,移除,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 porting-to-python-3-6}@anchor{5f0}
@subsection 移植到Python 3.6


本节列出了先前描述的更改以及可能需要更改代码的其他错误修正.

@menu
* 'python' 命令行为的变化:: 
* Python API 的变化: Python API 的变化<3>. 
* C API 的变化: C API 的变化<3>. 
* CPython 字节码的改变: CPython 字节码的改变<3>. 

@end menu

@node 'python' 命令行为的变化,Python API 的变化<3>,,移植到Python 3 6
@anchor{whatsnew/3 6 changes-in-python-command-behavior}@anchor{5f1}
@subsubsection  'python' 命令行为的变化



@itemize *

@item 
The output of a special Python build with defined @code{COUNT_ALLOCS},
@code{SHOW_ALLOC_COUNT} or @code{SHOW_TRACK_COUNT} macros is now off by
default.  It can be re-enabled using the @code{-X showalloccount} option.
It now outputs to @code{stderr} instead of @code{stdout}.
(Contributed by Serhiy Storchaka in bpo-23034@footnote{https://bugs.python.org/issue23034}.)
@end itemize

@node Python API 的变化<3>,C API 的变化<3>,'python' 命令行为的变化,移植到Python 3 6
@anchor{whatsnew/3 6 changes-in-the-python-api}@anchor{5f2}
@subsubsection Python API 的变化



@itemize *

@item 
@ref{4ea,,open()} will no longer allow combining the @code{'U'} mode flag
with @code{'+'}.
(Contributed by Jeff Balogh and John O'Connor in bpo-2091@footnote{https://bugs.python.org/issue2091}.)

@item 
@ref{f2,,sqlite3} no longer implicitly commits an open transaction before DDL
statements.

@item 
On Linux, @ref{4cb,,os.urandom()} now blocks until the system urandom entropy pool
is initialized to increase the security.

@item 
When @ref{5df,,importlib.abc.Loader.exec_module()} is defined,
@ref{54f,,importlib.abc.Loader.create_module()} must also be defined.

@item 
@ref{5f3,,PyErr_SetImportError()} now sets @ref{192,,TypeError} when its @strong{msg}
argument is not set. Previously only @code{NULL} was returned.

@item 
The format of the @code{co_lnotab} attribute of code objects changed to support
a negative line number delta. By default, Python does not emit bytecode with
a negative line number delta. Functions using @code{frame.f_lineno},
@code{PyFrame_GetLineNumber()} or @code{PyCode_Addr2Line()} are not affected.
Functions directly decoding @code{co_lnotab} should be updated to use a signed
8-bit integer type for the line number delta, but this is only required to
support applications using a negative line number delta. See
@code{Objects/lnotab_notes.txt} for the @code{co_lnotab} format and how to decode
it, and see the 
@geindex Python 提高建议; PEP 511
PEP 511@footnote{https://www.python.org/dev/peps/pep-0511} for the rationale.

@item 
The functions in the @ref{21,,compileall} module now return booleans instead
of @code{1} or @code{0} to represent success or failure, respectively. Thanks to
booleans being a subclass of integers, this should only be an issue if you
were doing identity checks for @code{1} or @code{0}. See bpo-25768@footnote{https://bugs.python.org/issue25768}.

@item 
Reading the @code{port} attribute of
@ref{5f4,,urllib.parse.urlsplit()} and @ref{5f5,,urlparse()} results
now raises @ref{1fb,,ValueError} for out-of-range values, rather than
returning @ref{157,,None}.  See bpo-20059@footnote{https://bugs.python.org/issue20059}.

@item 
The @ref{9a,,imp} module now raises a @ref{278,,DeprecationWarning} instead of
@ref{279,,PendingDeprecationWarning}.

@item 
The following modules have had missing APIs added to their @code{__all__}
attributes to match the documented APIs:
@ref{15,,calendar}, @ref{16,,cgi}, @ref{2a,,csv},
@ref{137,,ElementTree}, @ref{7b,,enum},
@ref{80,,fileinput}, @ref{84,,ftplib}, @ref{aa,,logging}, @ref{ae,,mailbox},
@ref{b2,,mimetypes}, @ref{c3,,optparse}, @ref{cf,,plistlib}, @ref{ec,,smtpd},
@ref{f9,,subprocess}, @ref{101,,tarfile}, @ref{109,,threading} and
@ref{127,,wave}.  This means they will export new symbols when @code{import *}
is used.
(Contributed by Joel Taddei and Jacek Kołodziej in bpo-23883@footnote{https://bugs.python.org/issue23883}.)

@item 
When performing a relative import, if @code{__package__} does not compare equal
to @code{__spec__.parent} then @ref{5d3,,ImportWarning} is raised.
(Contributed by Brett Cannon in bpo-25791@footnote{https://bugs.python.org/issue25791}.)

@item 
When a relative import is performed and no parent package is known, then
@ref{32d,,ImportError} will be raised. Previously, @ref{5f6,,SystemError} could be
raised. (Contributed by Brett Cannon in bpo-18018@footnote{https://bugs.python.org/issue18018}.)

@item 
Servers based on the @ref{f0,,socketserver} module, including those
defined in @ref{97,,http.server}, @ref{140,,xmlrpc.server} and
@ref{12f,,wsgiref.simple_server}, now only catch exceptions derived
from @ref{1a9,,Exception}. Therefore if a request handler raises
an exception like @ref{5f7,,SystemExit} or @ref{197,,KeyboardInterrupt},
@ref{5f8,,handle_error()} is no longer called, and
the exception will stop a single-threaded server. (Contributed by
Martin Panter in bpo-23430@footnote{https://bugs.python.org/issue23430}.)

@item 
@ref{5f9,,spwd.getspnam()} now raises a @ref{5fa,,PermissionError} instead of
@ref{2c7,,KeyError} if the user doesn't have privileges.

@item 
The @ref{5fb,,socket.socket.close()} method now raises an exception if
an error (e.g. @code{EBADF}) was reported by the underlying system call.
(Contributed by Martin Panter in bpo-26685@footnote{https://bugs.python.org/issue26685}.)

@item 
The @emph{decode_data} argument for the @ref{5fc,,smtpd.SMTPChannel} and
@ref{5fd,,smtpd.SMTPServer} constructors is now @code{False} by default.
This means that the argument passed to
@ref{5fe,,process_message()} is now a bytes object by
default, and @code{process_message()} will be passed keyword arguments.
Code that has already been updated in accordance with the deprecation
warning generated by 3.5 will not be affected.

@item 
All optional arguments of the @ref{5ff,,dump()}, @ref{600,,dumps()},
@ref{55a,,load()} and @ref{55b,,loads()} functions and
@ref{601,,JSONEncoder} and @ref{602,,JSONDecoder} class
constructors in the @ref{a4,,json} module are now @ref{2ac,,keyword-only}.
(Contributed by Serhiy Storchaka in bpo-18726@footnote{https://bugs.python.org/issue18726}.)

@item 
@ref{603,,type} 的子类如果未重载 @code{type.__new__}，将不再能使用一个参数的形式来获取对象的类型。

@item 
As part of 
@geindex Python 提高建议; PEP 487
PEP 487@footnote{https://www.python.org/dev/peps/pep-0487}, the handling of keyword arguments passed to
@ref{603,,type} (other than the metaclass hint, @code{metaclass}) is now
consistently delegated to @ref{4dd,,object.__init_subclass__()}. This means that
@code{type.__new__()} and @code{type.__init__()} both now accept arbitrary
keyword arguments, but @ref{4dd,,object.__init_subclass__()} (which is called from
@code{type.__new__()}) will reject them by default. Custom metaclasses
accepting additional keyword arguments will need to adjust their calls to
@code{type.__new__()} (whether direct or via @ref{4dc,,super}) accordingly.

@item 
In @code{distutils.command.sdist.sdist}, the @code{default_format}
attribute has been removed and is no longer honored. Instead, the
gzipped tarfile format is the default on all platforms and no
platform-specific selection is made.
In environments where distributions are
built on Windows and zip distributions are required, configure
the project with a @code{setup.cfg} file containing the following:

@example
[sdist]
formats=zip
@end example

This behavior has also been backported to earlier Python versions
by Setuptools 26.0.0.

@item 
In the @ref{120,,urllib.request} module and the
@ref{54a,,http.client.HTTPConnection.request()} method, if no Content-Length
header field has been specified and the request body is a file object,
it is now sent with HTTP 1.1 chunked encoding. If a file object has to
be sent to a HTTP 1.0 server, the Content-Length value now has to be
specified by the caller.
(Contributed by Demian Brecht and Rolf Krahl with tweaks from
Martin Panter in bpo-12319@footnote{https://bugs.python.org/issue12319}.)

@item 
The @ref{1bd,,DictReader} now returns rows of type
@ref{1b9,,OrderedDict}.
(Contributed by Steve Holden in bpo-27842@footnote{https://bugs.python.org/issue27842}.)

@item 
The @ref{604,,crypt.METHOD_CRYPT} will no longer be added to @code{crypt.methods}
if unsupported by the platform.
(Contributed by Victor Stinner in bpo-25287@footnote{https://bugs.python.org/issue25287}.)

@item 
The @emph{verbose} and @emph{rename} arguments for
@ref{1b6,,namedtuple()} are now keyword-only.
(Contributed by Raymond Hettinger in bpo-25628@footnote{https://bugs.python.org/issue25628}.)

@item 
On Linux, @ref{605,,ctypes.util.find_library()} now looks in
@code{LD_LIBRARY_PATH} for shared libraries.
(Contributed by Vinay Sajip in bpo-9998@footnote{https://bugs.python.org/issue9998}.)

@item 
The @ref{606,,imaplib.IMAP4} class now handles flags containing the
@code{']'} character in messages sent from the server to improve
real-world compatibility.
(Contributed by Lita Cho in bpo-21815@footnote{https://bugs.python.org/issue21815}.)

@item 
The @code{mmap.write()} function now returns the number
of bytes written like other write methods.
(Contributed by Jakub Stasiak in bpo-26335@footnote{https://bugs.python.org/issue26335}.)

@item 
The @ref{607,,pkgutil.iter_modules()} and @ref{485,,pkgutil.walk_packages()}
functions now return @ref{608,,ModuleInfo} named tuples.
(Contributed by Ramchandra Apte in bpo-17211@footnote{https://bugs.python.org/issue17211}.)

@item 
@ref{475,,re.sub()} now raises an error for invalid numerical group
references in replacement templates even if the pattern is not
found in the string.  The error message for invalid group references
now includes the group index and the position of the reference.
(Contributed by SilentGhost, Serhiy Storchaka in bpo-25953@footnote{https://bugs.python.org/issue25953}.)

@item 
@ref{417,,zipfile.ZipFile} will now raise @ref{609,,NotImplementedError} for
unrecognized compression values.  Previously a plain @ref{2ba,,RuntimeError}
was raised.  Additionally, calling @ref{417,,ZipFile} methods
on a closed ZipFile or calling the @ref{60a,,write()} method
on a ZipFile created with mode @code{'r'} will raise a @ref{1fb,,ValueError}.
Previously, a @ref{2ba,,RuntimeError} was raised in those scenarios.

@item 
when custom metaclasses are combined with zero-argument @ref{4dc,,super()} or
direct references from methods to the implicit @code{__class__} closure
variable, the implicit @code{__classcell__} namespace entry must now be passed
up to @code{type.__new__} for initialisation. Failing to do so will result in
a @ref{278,,DeprecationWarning} in Python 3.6 and a @ref{2ba,,RuntimeError} in
Python 3.8.

@item 
With the introduction of @ref{392,,ModuleNotFoundError}, import system consumers
may start expecting import system replacements to raise that more specific
exception when appropriate, rather than the less-specific @ref{32d,,ImportError}.
To provide future compatibility with such consumers, implementors of
alternative import systems that completely replace @ref{60b,,__import__()} will
need to update their implementations to raise the new subclass when a module
can't be found at all. Implementors of compliant plugins to the default
import system shouldn't need to make any changes, as the default import
system will raise the new subclass when appropriate.
@end itemize

@node C API 的变化<3>,CPython 字节码的改变<3>,Python API 的变化<3>,移植到Python 3 6
@anchor{whatsnew/3 6 changes-in-the-c-api}@anchor{60c}
@subsubsection C API 的变化



@itemize *

@item 
The @ref{4ff,,PyMem_Malloc()} allocator family now uses the @ref{5bc,,pymalloc allocator} rather than the system @code{malloc()}. Applications calling
@ref{4ff,,PyMem_Malloc()} without holding the GIL can now crash. Set the
@geindex PYTHONMALLOC
@geindex 环境变量; PYTHONMALLOC
@ref{4fd,,PYTHONMALLOC} environment variable to @code{debug} to validate the
usage of memory allocators in your application. See bpo-26249@footnote{https://bugs.python.org/issue26249}.

@item 
@ref{60d,,Py_Exit()} (and the main interpreter) now override the exit status
with 120 if flushing buffered data failed.  See bpo-5319@footnote{https://bugs.python.org/issue5319}.
@end itemize

@node CPython 字节码的改变<3>,,C API 的变化<3>,移植到Python 3 6
@anchor{whatsnew/3 6 cpython-bytecode-changes}@anchor{60e}
@subsubsection CPython 字节码的改变


There have been several major changes to the @ref{60f,,bytecode} in Python 3.6.


@itemize *

@item 
The Python interpreter now uses a 16-bit wordcode instead of bytecode.
(Contributed by Demur Rumed with input and reviews from
Serhiy Storchaka and Victor Stinner in bpo-26647@footnote{https://bugs.python.org/issue26647} and bpo-28050@footnote{https://bugs.python.org/issue28050}.)

@item 
The new @ref{610,,FORMAT_VALUE} and @ref{611,,BUILD_STRING} opcodes as part
of the  @ref{4bb,,formatted string literal} implementation.
(Contributed by Eric Smith in bpo-25483@footnote{https://bugs.python.org/issue25483} and
Serhiy Storchaka in bpo-27078@footnote{https://bugs.python.org/issue27078}.)

@item 
The new @ref{612,,BUILD_CONST_KEY_MAP} opcode to optimize the creation
of dictionaries with constant keys.
(Contributed by Serhiy Storchaka in bpo-27140@footnote{https://bugs.python.org/issue27140}.)

@item 
The function call opcodes have been heavily reworked for better performance
and simpler implementation.
The @ref{613,,MAKE_FUNCTION}, @ref{614,,CALL_FUNCTION},
@ref{615,,CALL_FUNCTION_KW} and @ref{616,,BUILD_MAP_UNPACK_WITH_CALL} opcodes
have been modified, the new @ref{617,,CALL_FUNCTION_EX} and
@ref{618,,BUILD_TUPLE_UNPACK_WITH_CALL} have been added, and
@code{CALL_FUNCTION_VAR}, @code{CALL_FUNCTION_VAR_KW} and @code{MAKE_CLOSURE} opcodes
have been removed.
(Contributed by Demur Rumed in bpo-27095@footnote{https://bugs.python.org/issue27095}, and Serhiy Storchaka in
bpo-27213@footnote{https://bugs.python.org/issue27213}, bpo-28257@footnote{https://bugs.python.org/issue28257}.)

@item 
The new @ref{619,,SETUP_ANNOTATIONS} and @code{STORE_ANNOTATION} opcodes
have been added to support the new @ref{61a,,variable annotation} syntax.
(Contributed by Ivan Levkivskyi in bpo-27985@footnote{https://bugs.python.org/issue27985}.)
@end itemize

@node Python 3 6 2 中的重要变化,Python 3 6 4 中的重要变化,移植到Python 3 6,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 notable-changes-in-python-3-6-2}@anchor{61b}
@subsection Python 3.6.2 中的重要变化


@menu
* New make regen-all build target:: 
* Removal of make touch build target:: 

@end menu

@node New make regen-all build target,Removal of make touch build target,,Python 3 6 2 中的重要变化
@anchor{whatsnew/3 6 new-make-regen-all-build-target}@anchor{61c}
@subsubsection New @code{make regen-all} build target


To simplify cross-compilation, and to ensure that CPython can reliably be
compiled without requiring an existing version of Python to already be
available, the autotools-based build system no longer attempts to implicitly
recompile generated files based on file modification times.

Instead, a new @code{make regen-all} command has been added to force regeneration
of these files when desired (e.g. after an initial version of Python has
already been built based on the pregenerated versions).

More selective regeneration targets are also defined - see
Makefile.pre.in@footnote{https://github.com/python/cpython/tree/3.8/Makefile.pre.in} for details.

（由 Victor Stinner 在 bpo-23404@footnote{https://bugs.python.org/issue23404} 中贡献。）


3.6.2 新版功能.


@node Removal of make touch build target,,New make regen-all build target,Python 3 6 2 中的重要变化
@anchor{whatsnew/3 6 removal-of-make-touch-build-target}@anchor{61d}
@subsubsection Removal of @code{make touch} build target


The @code{make touch} build target previously used to request implicit regeneration
of generated files by updating their modification times has been removed.

It has been replaced by the new @code{make regen-all} target.

（由 Victor Stinner 在 bpo-23404@footnote{https://bugs.python.org/issue23404} 中贡献。）


在 3.6.2 版更改.


@node Python 3 6 4 中的重要变化,Python 3 6 5 中的重要变化,Python 3 6 2 中的重要变化,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 notable-changes-in-python-3-6-4}@anchor{61e}
@subsection Python 3.6.4 中的重要变化


The @code{PyExc_RecursionErrorInst} singleton that was part of the public API
has been removed as its members being never cleared may cause a segfault
during finalization of the interpreter.
(Contributed by Xavier de Gaye in bpo-22898@footnote{https://bugs.python.org/issue22898} and bpo-30697@footnote{https://bugs.python.org/issue30697}.)

@node Python 3 6 5 中的重要变化,Python 3 6 7 中的重要变化,Python 3 6 4 中的重要变化,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 notable-changes-in-python-3-6-5}@anchor{61f}
@subsection Python 3.6.5 中的重要变化


The @ref{484,,locale.localeconv()} function now sets temporarily the @code{LC_CTYPE}
locale to the @code{LC_NUMERIC} locale in some cases.
(Contributed by Victor Stinner in bpo-31900@footnote{https://bugs.python.org/issue31900}.)

@node Python 3 6 7 中的重要变化,Python 3 6 10 中的重要变化,Python 3 6 5 中的重要变化,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 notable-changes-in-python-3-6-7}@anchor{620}
@subsection Python 3.6.7 中的重要变化


In 3.6.7 the @ref{111,,tokenize} module now implicitly emits a @code{NEWLINE} token
when provided with input that does not have a trailing new line.  This behavior
now matches what the C tokenizer does internally.
(Contributed by Ammar Askar in bpo-33899@footnote{https://bugs.python.org/issue33899}.)

@node Python 3 6 10 中的重要变化,,Python 3 6 7 中的重要变化,Python 3 6 有什么新变化
@anchor{whatsnew/3 6 notable-changes-in-python-3-6-10}@anchor{621}
@subsection Python 3.6.10 中的重要变化


出于重要的安全性考量，@ref{2e7,,asyncio.loop.create_datagram_endpoint()} 的 @emph{reuse_address} 形参不再被支持。 这是由 UDP 中的套接字选项 @code{SO_REUSEADDR} 的行为导致的。 更多细节请参阅 @code{loop.create_datagram_endpoint()} 的文档。 （由 Kyle Stanley, Antoine Pitrou 和 Yury Selivanov 在 bpo-37228@footnote{https://bugs.python.org/issue37228} 中贡献。。）

@node Python 3 5 有什么新变化,Python 3 4 有什么新变化,Python 3 6 有什么新变化,Python的新变化
@anchor{whatsnew/3 5 doc}@anchor{622}@anchor{whatsnew/3 5 what-s-new-in-python-3-5}@anchor{623}
@section Python 3.5 有什么新变化


@*编者: 
Elvis Pranskevichus <@email{elvis@@magic.io}>, Yury Selivanov <@email{yury@@magic.io}>


@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number as a comment:
@c 
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer in :issue:`12345`.)
@c 
@c This saves the maintainer the effort of going through the Mercurial log
@c when researching a change.

This article explains the new features in Python 3.5, compared to 3.4.
Python 3.5 was released on September 13, 2015.  See the
changelog@footnote{https://docs.python.org/3.5/whatsnew/changelog.html} for a full
list of changes.


@subsubheading 参见


@geindex Python 提高建议; PEP 478
PEP 478@footnote{https://www.python.org/dev/peps/pep-0478} - Python 3.5 发布计划


@menu
* 摘要 - 发布重点: 摘要 - 发布重点<4>. 
* 新的特性: 新的特性<4>. 
* 其他语言特性修改: 其他语言特性修改<4>. 
* 新增模块: 新增模块<4>. 
* 改进的模块: 改进的模块<4>. 
* 其他模块级更改:: 
* 性能优化: 性能优化<4>. 
* 构建和 C API 的改变: 构建和 C API 的改变<3>. 
* 弃用: 弃用<3>. 
* 移除: 移除<2>. 
* 移植到Python 3.5: 移植到Python 3 5. 
* Python 3.5.4 的显著变化: Python 3 5 4 的显著变化. 

@end menu

@node 摘要 - 发布重点<4>,新的特性<4>,,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 summary-release-highlights}@anchor{624}
@subsection 摘要 - 发布重点


新的语法特性：


@itemize *

@item 
@ref{625,,PEP 492}, 使用 async 和 await 语法实现协程。

@item 
@ref{626,,PEP 465}, 新的矩阵乘法运算符: @code{a @@ b}.

@item 
@ref{627,,PEP 448}, additional unpacking generalizations.
@end itemize

新的库模块：


@itemize *

@item 
@ref{119,,typing}: @ref{628,,PEP 484 -- 类型提示}.

@item 
@ref{141,,zipapp}: @ref{629,,PEP 441 改进Python ZIP应用程序支持}.
@end itemize

新的内置特性：


@itemize *

@item 
@code{bytes % args}, @code{bytearray % args}: @ref{62a,,PEP 461} --
Adding @code{%} formatting to bytes and bytearray.

@item 
New @ref{62b,,bytes.hex()}, @ref{62c,,bytearray.hex()} and @ref{62d,,memoryview.hex()}
methods. (Contributed by Arnon Yaari in bpo-9951@footnote{https://bugs.python.org/issue9951}.)

@item 
@ref{25c,,memoryview} now supports tuple indexing (including multi-dimensional).
(Contributed by Antoine Pitrou in bpo-23632@footnote{https://bugs.python.org/issue23632}.)

@item 
Generators have a new @code{gi_yieldfrom} attribute, which returns the
object being iterated by @code{yield from} expressions. (Contributed
by Benno Leslie and Yury Selivanov in bpo-24450@footnote{https://bugs.python.org/issue24450}.)

@item 
A new @ref{62e,,RecursionError} exception is now raised when maximum
recursion depth is reached.  (Contributed by Georg Brandl
in bpo-19235@footnote{https://bugs.python.org/issue19235}.)
@end itemize

CPython 实现的改进：


@itemize *

@item 
When the @code{LC_TYPE} locale is the POSIX locale (@code{C} locale),
@ref{306,,sys.stdin} and @ref{307,,sys.stdout} now use the
@code{surrogateescape} error handler, instead of the @code{strict} error handler.
(Contributed by Victor Stinner in bpo-19977@footnote{https://bugs.python.org/issue19977}.)

@item 
@code{.pyo} files are no longer used and have been replaced by a more flexible
scheme that includes the optimization level explicitly in @code{.pyc} name.
(See @ref{62f,,PEP 488 overview}.)

@item 
Builtin and extension modules are now initialized in a multi-phase process,
which is similar to how Python modules are loaded.
(See @ref{630,,PEP 489 overview}.)
@end itemize

标准库中的重大改进：


@itemize *

@item 
@ref{1b9,,collections.OrderedDict} is now
@ref{631,,implemented in C}, which makes it
4 to 100 times faster.

@item 
The @ref{f3,,ssl} module gained
@ref{632,,support for Memory BIO}, which decouples SSL
protocol handling from network IO.

@item 
The new @ref{25f,,os.scandir()} function provides a
@ref{633,,better and significantly faster way}
of directory traversal.

@item 
@ref{1c7,,functools.lru_cache()} has been mostly
@ref{634,,reimplemented in C}, yielding much better
performance.

@item 
The new @ref{3e5,,subprocess.run()} function provides a
@ref{635,,streamlined way to run subprocesses}.

@item 
The @ref{113,,traceback} module has been significantly
@ref{636,,enhanced} for improved
performance and developer convenience.
@end itemize

安全改进：


@itemize *

@item 
SSLv3 is now disabled throughout the standard library.
It can still be enabled by instantiating a @ref{3dc,,ssl.SSLContext}
manually.  (See bpo-22638@footnote{https://bugs.python.org/issue22638} for more details; this change was
backported to CPython 3.4 and 2.7.)

@item 
HTTP cookie parsing is now stricter, in order to protect
against potential injection attacks. (Contributed by Antoine Pitrou
in bpo-22796@footnote{https://bugs.python.org/issue22796}.)
@end itemize

Windows改进：


@itemize *

@item 
A new installer for Windows has replaced the old MSI.
See @ref{2d9,,在Windows上使用 Python} for more information.

@item 
Windows builds now use Microsoft Visual C++ 14.0, and extension modules
should use the same.
@end itemize

Please read on for a comprehensive list of user-facing changes, including many
other smaller improvements, CPython optimizations, deprecations, and potential
porting issues.

@node 新的特性<4>,其他语言特性修改<4>,摘要 - 发布重点<4>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 new-features}@anchor{637}
@subsection 新的特性


@menu
* PEP 492 - 使用 async 和 await 语法实现协程:: 
* PEP 465 - 用于矩阵乘法的专用中缀运算符:: 
* PEP 448 - Additional Unpacking Generalizations:: 
* PEP 461 - percent formatting support for bytes and bytearray:: 
* PEP 484 - 类型提示:: 
* PEP 471 - os.scandir() function: PEP 471 - os scandir function -- a better and faster directory iterator. a better and faster directory iterator
* PEP 475; Retry system calls failing with EINTR: PEP 475 Retry system calls failing with EINTR. 
* PEP 479; Change StopIteration handling inside generators: PEP 479 Change StopIteration handling inside generators. 
* PEP 485; A function for testing approximate equality: PEP 485 A function for testing approximate equality. 
* PEP 486; Make the Python Launcher aware of virtual environments: PEP 486 Make the Python Launcher aware of virtual environments. 
* PEP 488; Elimination of PYO files: PEP 488 Elimination of PYO files. 
* PEP 489; Multi-phase extension module initialization: PEP 489 Multi-phase extension module initialization. 

@end menu

@node PEP 492 - 使用 async 和 await 语法实现协程,PEP 465 - 用于矩阵乘法的专用中缀运算符,,新的特性<4>
@anchor{whatsnew/3 5 pep-492-coroutines-with-async-and-await-syntax}@anchor{638}@anchor{whatsnew/3 5 whatsnew-pep-492}@anchor{625}
@subsubsection PEP 492 - 使用 async 和 await 语法实现协程


@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} greatly improves support for asynchronous programming in Python
by adding @ref{513,,awaitable objects},
@ref{639,,coroutine functions},
@ref{63a,,asynchronous iteration},
and @ref{63b,,asynchronous context managers}.

Coroutine functions are declared using the new @ref{284,,async def} syntax:

@example
>>> async def coro():
...     return 'spam'
@end example

Inside a coroutine function, the new @ref{1a3,,await} expression can be used
to suspend coroutine execution until the result is available.  Any object
can be @emph{awaited}, as long as it implements the @ref{513,,awaitable} protocol by
defining the @ref{63c,,__await__()} method.

PEP 492 also adds @ref{2e3,,async for} statement for convenient iteration
over asynchronous iterables.

An example of a rudimentary HTTP client written using the new syntax:

@example
import asyncio

async def http_get(domain):
    reader, writer = await asyncio.open_connection(domain, 80)

    writer.write(b'\r\n'.join([
        b'GET / HTTP/1.1',
        b'Host: %b' % domain.encode('latin-1'),
        b'Connection: close',
        b'@w{'}, b'@w{'}
    ]))

    async for line in reader:
        print('>>>', line)

    writer.close()

loop = asyncio.get_event_loop()
try:
    loop.run_until_complete(http_get('example.com'))
finally:
    loop.close()
@end example

Similarly to asynchronous iteration, there is a new syntax for asynchronous
context managers.  The following script:

@example
import asyncio

async def coro(name, lock):
    print('coro @{@}: waiting for lock'.format(name))
    async with lock:
        print('coro @{@}: holding the lock'.format(name))
        await asyncio.sleep(1)
        print('coro @{@}: releasing the lock'.format(name))

loop = asyncio.get_event_loop()
lock = asyncio.Lock()
coros = asyncio.gather(coro(1, lock), coro(2, lock))
try:
    loop.run_until_complete(coros)
finally:
    loop.close()
@end example

将输出：

@example
coro 2: waiting for lock
coro 2: holding the lock
coro 1: waiting for lock
coro 2: releasing the lock
coro 1: holding the lock
coro 1: releasing the lock
@end example

Note that both @ref{2e3,,async for} and @ref{63d,,async with} can only
be used inside a coroutine function declared with @ref{284,,async def}.

Coroutine functions are intended to be run inside a compatible event loop,
such as the @ref{63e,,asyncio loop}.

@cartouche
@quotation 注解 

在 3.5.2 版更改: Starting with CPython 3.5.2, @code{__aiter__} can directly return
@ref{63f,,asynchronous iterators}.  Returning
an @ref{513,,awaitable} object will result in a
@ref{279,,PendingDeprecationWarning}.

See more details in the @ref{640,,异步迭代器} documentation
section.

@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 492

@item PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} -- 使用 async 和 await 语法实现协程

PEP 由 Yury Selivanov 撰写并实现
@end table


@node PEP 465 - 用于矩阵乘法的专用中缀运算符,PEP 448 - Additional Unpacking Generalizations,PEP 492 - 使用 async 和 await 语法实现协程,新的特性<4>
@anchor{whatsnew/3 5 pep-465-a-dedicated-infix-operator-for-matrix-multiplication}@anchor{641}@anchor{whatsnew/3 5 whatsnew-pep-465}@anchor{626}
@subsubsection PEP 465 - 用于矩阵乘法的专用中缀运算符


@geindex Python 提高建议; PEP 465
PEP 465@footnote{https://www.python.org/dev/peps/pep-0465} adds the @code{@@} infix operator for matrix multiplication.
Currently, no builtin Python types implement the new operator, however, it
can be implemented by defining @ref{642,,__matmul__()}, @ref{643,,__rmatmul__()},
and @ref{644,,__imatmul__()} for regular, reflected, and in-place matrix
multiplication.  The semantics of these methods is similar to that of
methods defining other infix arithmetic operators.

矩阵乘法在数学，科学，工程学的许多领域中是一种常见的操作，使用 @code{@@} 运算符可以编写更简洁的代码：

@example
S = (H @@ beta - r).T @@ inv(H @@ V @@ H.T) @@ (H @@ beta - r)
@end example

代替：

@example
S = dot((dot(H, beta) - r).T,
        dot(inv(dot(dot(H, V), H.T)), dot(H, beta) - r))
@end example

NumPy 1.10 支持新的运算符：

@example
>>> import numpy

>>> x = numpy.ones(3)
>>> x
array([ 1., 1., 1.])

>>> m = numpy.eye(3)
>>> m
array([[ 1., 0., 0.],
       [ 0., 1., 0.],
       [ 0., 0., 1.]])

>>> x @@ m
array([ 1., 1., 1.])
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 465

@item PEP 465@footnote{https://www.python.org/dev/peps/pep-0465} -- 用于矩阵乘法的专用中缀运算符

PEP 由 Nathaniel J. Smith 撰写，由 Benjamin Peterson 实现。
@end table


@node PEP 448 - Additional Unpacking Generalizations,PEP 461 - percent formatting support for bytes and bytearray,PEP 465 - 用于矩阵乘法的专用中缀运算符,新的特性<4>
@anchor{whatsnew/3 5 pep-448-additional-unpacking-generalizations}@anchor{645}@anchor{whatsnew/3 5 whatsnew-pep-448}@anchor{627}
@subsubsection PEP 448 - Additional Unpacking Generalizations


@geindex Python 提高建议; PEP 448
PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} extends the allowed uses of the @code{*} iterable unpacking
operator and @code{**} dictionary unpacking operator.  It is now possible
to use an arbitrary number of unpackings in @ref{646,,function calls}:

@example
>>> print(*[1], *[2], 3, *[4, 5])
1 2 3 4 5

>>> def fn(a, b, c, d):
...     print(a, b, c, d)
...

>>> fn(**@{'a': 1, 'c': 3@}, **@{'b': 2, 'd': 4@})
1 2 3 4
@end example

Similarly, tuple, list, set, and dictionary displays allow multiple
unpackings (see @ref{647,,表达式列表} and @ref{648,,字典显示}):

@example
>>> *range(4), 4
(0, 1, 2, 3, 4)

>>> [*range(4), 4]
[0, 1, 2, 3, 4]

>>> @{*range(4), 4, *(5, 6, 7)@}
@{0, 1, 2, 3, 4, 5, 6, 7@}

>>> @{'x': 1, **@{'y': 2@}@}
@{'x': 1, 'y': 2@}
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 448

@item PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} -- Additional Unpacking Generalizations

PEP 由 Joshua Landau 撰写 ，由 Neil Girdhar，Thomas Wouters 和 Joshua Landau 实现。
@end table


@node PEP 461 - percent formatting support for bytes and bytearray,PEP 484 - 类型提示,PEP 448 - Additional Unpacking Generalizations,新的特性<4>
@anchor{whatsnew/3 5 pep-461-percent-formatting-support-for-bytes-and-bytearray}@anchor{649}@anchor{whatsnew/3 5 whatsnew-pep-461}@anchor{62a}
@subsubsection PEP 461 - percent formatting support for bytes and bytearray


@geindex Python 提高建议; PEP 461
PEP 461@footnote{https://www.python.org/dev/peps/pep-0461} adds support for the @code{%}
@ref{64a,,interpolation operator} to @ref{32a,,bytes}
and @ref{32b,,bytearray}.

While interpolation is usually thought of as a string operation, there are
cases where interpolation on @code{bytes} or @code{bytearrays} makes sense, and the
work needed to make up for this missing functionality detracts from the
overall readability of the code.  This issue is particularly important when
dealing with wire format protocols, which are often a mixture of binary
and ASCII compatible text.

示例:

@example
>>> b'Hello %b!' % b'World'
b'Hello World!'

>>> b'x=%i y=%f' % (1, 2.5)
b'x=1 y=2.500000'
@end example

Unicode is not allowed for @code{%b}, but it is accepted by @code{%a} (equivalent of
@code{repr(obj).encode('ascii', 'backslashreplace')}):

@example
>>> b'Hello %b!' % 'World'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: %b requires bytes, or an object that implements __bytes__, not 'str'

>>> b'price: %a' % '10€'
b"price: '10\\u20ac'"
@end example

Note that @code{%s} and @code{%r} conversion types, although supported, should
only be used in codebases that need compatibility with Python 2.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 461

@item PEP 461@footnote{https://www.python.org/dev/peps/pep-0461} -- Adding % formatting to bytes and bytearray

PEP 由 Ethan Furman 撰写 ，由 Neil Schemenauer 和 Ethan Furman 实现。
@end table


@node PEP 484 - 类型提示,PEP 471 - os scandir function -- a better and faster directory iterator,PEP 461 - percent formatting support for bytes and bytearray,新的特性<4>
@anchor{whatsnew/3 5 pep-484-type-hints}@anchor{64b}@anchor{whatsnew/3 5 whatsnew-pep-484}@anchor{628}
@subsubsection PEP 484 - 类型提示


Function annotation syntax has been a Python feature since version 3.0
(
@geindex Python 提高建议; PEP 3107
PEP 3107@footnote{https://www.python.org/dev/peps/pep-3107}), however the semantics of annotations has been left undefined.

Experience has shown that the majority of function annotation
uses were to provide type hints to function parameters and return values.  It
became evident that it would be beneficial for Python users, if the
standard library included the base definitions and tools for type annotations.

@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} introduces a @ref{341,,provisional module} to
provide these standard definitions and tools, along with some conventions
for situations where annotations are not available.

For example, here is a simple function whose argument and return type
are declared in the annotations:

@example
def greeting(name: str) -> str:
    return 'Hello ' + name
@end example

While these annotations are available at runtime through the usual
@code{__annotations__} attribute, @emph{no automatic type checking happens at
runtime}.  Instead, it is assumed that a separate off-line type checker
(e.g. mypy@footnote{http://mypy-lang.org}) will be used for on-demand
source code analysis.

The type system supports unions, generic types, and a special type
named @ref{64c,,Any} which is consistent with (i.e. assignable to
and from) all types.


@subsubheading 参见



@itemize *

@item 
@ref{119,,typing} 模块文档

@item 

@table @asis

@geindex Python 提高建议; PEP 484

@item PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} -- 类型提示

PEP 由 Guido van Rossum，Jukka Lehtosalo 和 Łukasz Langa 撰写，由 Guido van Rossum 实现。
@end table

@item 

@table @asis

@geindex Python 提高建议; PEP 483

@item PEP 483@footnote{https://www.python.org/dev/peps/pep-0483} -- 类型提示理论

PEP 由 Yury Selivanov 撰写
@end table
@end itemize


@node PEP 471 - os scandir function -- a better and faster directory iterator,PEP 475 Retry system calls failing with EINTR,PEP 484 - 类型提示,新的特性<4>
@anchor{whatsnew/3 5 pep-471-os-scandir-function-a-better-and-faster-directory-iterator}@anchor{64d}@anchor{whatsnew/3 5 whatsnew-pep-471}@anchor{633}
@subsubsection PEP 471 - os.scandir() function -- a better and faster directory iterator


@geindex Python 提高建议; PEP 471
PEP 471@footnote{https://www.python.org/dev/peps/pep-0471} adds a new directory iteration function, @ref{25f,,os.scandir()},
to the standard library.  Additionally, @ref{64e,,os.walk()} is now
implemented using @code{scandir}, which makes it 3 to 5 times faster
on POSIX systems and 7 to 20 times faster on Windows systems.  This is
largely achieved by greatly reducing the number of calls to @ref{1f1,,os.stat()}
required to walk a directory tree.

Additionally, @code{scandir} returns an iterator, as opposed to returning
a list of file names, which improves memory efficiency when iterating
over very large directories.

The following example shows a simple use of @ref{25f,,os.scandir()} to display all
the files (excluding directories) in the given @emph{path} that don't start with
@code{'.'}. The @ref{64f,,entry.is_file()} call will generally
not make an additional system call:

@example
for entry in os.scandir(path):
    if not entry.name.startswith('.') and entry.is_file():
        print(entry.name)
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 471

@item PEP 471@footnote{https://www.python.org/dev/peps/pep-0471} -- os.scandir() function -- a better and faster directory iterator

PEP 由 Ben Hoyt 在 Victor Stinner 的帮助下撰写并实现
@end table


@node PEP 475 Retry system calls failing with EINTR,PEP 479 Change StopIteration handling inside generators,PEP 471 - os scandir function -- a better and faster directory iterator,新的特性<4>
@anchor{whatsnew/3 5 pep-475-retry-system-calls-failing-with-eintr}@anchor{650}@anchor{whatsnew/3 5 whatsnew-pep-475}@anchor{651}
@subsubsection PEP 475: Retry system calls failing with EINTR


An @ref{652,,errno.EINTR} error code is returned whenever a system call, that
is waiting for I/O, is interrupted by a signal.  Previously, Python would
raise @ref{653,,InterruptedError} in such cases.  This meant that, when writing a
Python application, the developer had two choices:


@enumerate 

@item 
Ignore the @code{InterruptedError}.

@item 
Handle the @code{InterruptedError} and attempt to restart the interrupted
system call at every call site.
@end enumerate

The first option makes an application fail intermittently.
The second option adds a large amount of boilerplate that makes the
code nearly unreadable.  Compare:

@example
print("Hello World")
@end example

和:

@example
while True:
    try:
        print("Hello World")
        break
    except InterruptedError:
        continue
@end example

@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475} implements automatic retry of system calls on
@code{EINTR}.  This removes the burden of dealing with @code{EINTR}
or @ref{653,,InterruptedError} in user code in most situations and makes
Python programs, including the standard library, more robust.  Note that
the system call is only retried if the signal handler does not raise an
exception.

Below is a list of functions which are now retried when interrupted
by a signal:


@itemize *

@item 
@ref{4ea,,open()} 和 @ref{654,,io.open()};

@item 
@ref{7d,,faulthandler} 模块的功能

@item 
@ref{c4,,os} 函数: @ref{655,,fchdir()}, @ref{656,,fchmod()}, @ref{657,,fchown()}, @ref{658,,fdatasync()}, @ref{659,,fstat()}, @ref{65a,,fstatvfs()}, @ref{65b,,fsync()}, @ref{65c,,ftruncate()}, @ref{65d,,mkfifo()}, @ref{65e,,mknod()}, @ref{65f,,open()}, @ref{660,,posix_fadvise()}, @ref{661,,posix_fallocate()}, @ref{3b1,,pread()}, @ref{3b4,,pwrite()}, @ref{662,,read()}, @ref{3b0,,readv()}, @ref{352,,sendfile()}, @ref{663,,wait3()}, @ref{664,,wait4()}, @ref{665,,wait()}, @ref{666,,waitid()}, @ref{667,,waitpid()}, @ref{668,,write()}, @ref{3b3,,writev()};

@item 
特例: @ref{3ca,,os.close()} 和 @ref{3b6,,os.dup2()} 现在会忽略 @ref{652,,EINTR} 错误; 不重试系统调用（请参阅PEP了解基本原理）

@item 
@ref{e5,,select} 函数: @ref{669,,devpoll.poll()}, @ref{66a,,epoll.poll()}, @ref{66b,,kqueue.control()}, @ref{66c,,poll.poll()}, @ref{66d,,select()};

@item 
@ref{66e,,socket} 类的方法: @ref{66f,,accept()}, @ref{670,,connect()} （除了非阻塞套接字）, @ref{671,,recv()}, @ref{672,,recvfrom()}, @ref{673,,recvmsg()}, @ref{674,,send()}, @ref{675,,sendall()}, @ref{676,,sendmsg()}, @ref{677,,sendto()};

@item 
@ref{678,,signal.sigtimedwait()} 和 @ref{679,,signal.sigwaitinfo()};

@item 
@ref{67a,,time.sleep()}.
@end itemize


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 475

@item PEP 475@footnote{https://www.python.org/dev/peps/pep-0475} -- Retry system calls failing with EINTR

PEP and implementation written by Charles-François Natali and
Victor Stinner, with the help of Antoine Pitrou (the French connection).
@end table


@node PEP 479 Change StopIteration handling inside generators,PEP 485 A function for testing approximate equality,PEP 475 Retry system calls failing with EINTR,新的特性<4>
@anchor{whatsnew/3 5 pep-479-change-stopiteration-handling-inside-generators}@anchor{67b}@anchor{whatsnew/3 5 whatsnew-pep-479}@anchor{5d2}
@subsubsection PEP 479: Change StopIteration handling inside generators


The interaction of generators and @ref{480,,StopIteration} in Python 3.4 and
earlier was sometimes surprising, and could conceal obscure bugs.  Previously,
@code{StopIteration} raised accidentally inside a generator function was
interpreted as the end of the iteration by the loop construct driving the
generator.

@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479} changes the behavior of generators: when a @code{StopIteration}
exception is raised inside a generator, it is replaced with a
@ref{2ba,,RuntimeError} before it exits the generator frame.  The main goal of
this change is to ease debugging in the situation where an unguarded
@ref{67c,,next()} call raises @code{StopIteration} and causes the iteration controlled
by the generator to terminate silently. This is particularly pernicious in
combination with the @code{yield from} construct.

This is a backwards incompatible change, so to enable the new behavior,
a @ref{67d,,__future__} import is necessary:

@example
>>> from __future__ import generator_stop

>>> def gen():
...     next(iter([]))
...     yield
...
>>> next(gen())
Traceback (most recent call last):
  File "<stdin>", line 2, in gen
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: generator raised StopIteration
@end example

Without a @code{__future__} import, a @ref{279,,PendingDeprecationWarning} will be
raised whenever a @ref{480,,StopIteration} exception is raised inside a generator.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 479

@item PEP 479@footnote{https://www.python.org/dev/peps/pep-0479} -- Change StopIteration handling inside generators

PEP 由 Chris Angelico 和 Guido van Rossum 撰写，由 Chris Angelico，Yury Selivanov 和 Nick Coghlan 实现。
@end table


@node PEP 485 A function for testing approximate equality,PEP 486 Make the Python Launcher aware of virtual environments,PEP 479 Change StopIteration handling inside generators,新的特性<4>
@anchor{whatsnew/3 5 pep-485-a-function-for-testing-approximate-equality}@anchor{67e}@anchor{whatsnew/3 5 whatsnew-pep-485}@anchor{67f}
@subsubsection PEP 485: A function for testing approximate equality


@geindex Python 提高建议; PEP 485
PEP 485@footnote{https://www.python.org/dev/peps/pep-0485} adds the @ref{680,,math.isclose()} and @ref{681,,cmath.isclose()}
functions which tell whether two values are approximately equal or
"close" to each other.  Whether or not two values are considered
close is determined according to given absolute and relative tolerances.
Relative tolerance is the maximum allowed difference between @code{isclose}
arguments, relative to the larger absolute value:

@example
>>> import math
>>> a = 5.0
>>> b = 4.99998
>>> math.isclose(a, b, rel_tol=1e-5)
True
>>> math.isclose(a, b, rel_tol=1e-6)
False
@end example

It is also possible to compare two values using absolute tolerance, which
must be a non-negative value:

@example
>>> import math
>>> a = 5.0
>>> b = 4.99998
>>> math.isclose(a, b, abs_tol=0.00003)
True
>>> math.isclose(a, b, abs_tol=0.00001)
False
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 485

@item PEP 485@footnote{https://www.python.org/dev/peps/pep-0485} —— 用于测试近似相等的函数

PEP 由 Christopher Barker 撰写，由 Chris Barker 和 Tal Einat 实现。
@end table


@node PEP 486 Make the Python Launcher aware of virtual environments,PEP 488 Elimination of PYO files,PEP 485 A function for testing approximate equality,新的特性<4>
@anchor{whatsnew/3 5 pep-486-make-the-python-launcher-aware-of-virtual-environments}@anchor{682}@anchor{whatsnew/3 5 whatsnew-pep-486}@anchor{683}
@subsubsection PEP 486: Make the Python Launcher aware of virtual environments


@geindex Python 提高建议; PEP 486
PEP 486@footnote{https://www.python.org/dev/peps/pep-0486} makes the Windows launcher (see 
@geindex Python 提高建议; PEP 397
PEP 397@footnote{https://www.python.org/dev/peps/pep-0397}) aware of an active
virtual environment. When the default interpreter would be used and the
@code{VIRTUAL_ENV} environment variable is set, the interpreter in the virtual
environment will be used.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 486

@item PEP 486@footnote{https://www.python.org/dev/peps/pep-0486} -- Make the Python Launcher aware of virtual environments

PEP 由 Paul Moore 撰写并实现
@end table


@node PEP 488 Elimination of PYO files,PEP 489 Multi-phase extension module initialization,PEP 486 Make the Python Launcher aware of virtual environments,新的特性<4>
@anchor{whatsnew/3 5 pep-488-elimination-of-pyo-files}@anchor{684}@anchor{whatsnew/3 5 whatsnew-pep-488}@anchor{62f}
@subsubsection PEP 488: Elimination of PYO files


@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} does away with the concept of @code{.pyo} files. This means that
@code{.pyc} files represent both unoptimized and optimized bytecode. To prevent the
need to constantly regenerate bytecode files, @code{.pyc} files now have an
optional @code{opt-} tag in their name when the bytecode is optimized. This has the
side-effect of no more bytecode file name clashes when running under either
@ref{685,,-O} or @ref{686,,-OO}. Consequently, bytecode files generated from
@ref{685,,-O}, and @ref{686,,-OO} may now exist simultaneously.
@ref{552,,importlib.util.cache_from_source()} has an updated API to help with
this change.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 488

@item PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} -- Elimination of PYO files

PEP 由 Brett Cannon 撰写并实现。
@end table


@node PEP 489 Multi-phase extension module initialization,,PEP 488 Elimination of PYO files,新的特性<4>
@anchor{whatsnew/3 5 pep-489-multi-phase-extension-module-initialization}@anchor{687}@anchor{whatsnew/3 5 whatsnew-pep-489}@anchor{630}
@subsubsection PEP 489: Multi-phase extension module initialization


@geindex Python 提高建议; PEP 489
PEP 489@footnote{https://www.python.org/dev/peps/pep-0489} updates extension module initialization to take advantage of the
two step module loading mechanism introduced by 
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451} in Python 3.4.

This change brings the import semantics of extension modules that opt-in to
using the new mechanism much closer to those of Python source and bytecode
modules, including the ability to use any valid identifier as a module name,
rather than being restricted to ASCII.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 489

@item PEP 489@footnote{https://www.python.org/dev/peps/pep-0489} -- Multi-phase extension module initialization

PEP 由 Petr Viktorin , Stefan Behnel 和 Nick Coghlan 撰写，由 Petr Viktorin 实现。
@end table


@node 其他语言特性修改<4>,新增模块<4>,新的特性<4>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 other-language-changes}@anchor{688}
@subsection 其他语言特性修改


对Python 语言核心进行的小改动：


@itemize *

@item 
Added the @code{"namereplace"} error handlers.  The @code{"backslashreplace"}
error handlers now work with decoding and translating.
(Contributed by Serhiy Storchaka in bpo-19676@footnote{https://bugs.python.org/issue19676} and bpo-22286@footnote{https://bugs.python.org/issue22286}.)

@item 
The @ref{40d,,-b} option now affects comparisons of @ref{32a,,bytes} with
@ref{184,,int}.  (Contributed by Serhiy Storchaka in bpo-23681@footnote{https://bugs.python.org/issue23681}.)

@item 
New Kazakh @code{kz1048} and Tajik @code{koi8_t} @ref{689,,codecs}.
(Contributed by Serhiy Storchaka in bpo-22682@footnote{https://bugs.python.org/issue22682} and bpo-22681@footnote{https://bugs.python.org/issue22681}.)

@item 
Property docstrings are now writable. This is especially useful for
@ref{1b6,,collections.namedtuple()} docstrings.
(Contributed by Berker Peksag in bpo-24064@footnote{https://bugs.python.org/issue24064}.)

@item 
Circular imports involving relative imports are now supported.
(Contributed by Brett Cannon and Antoine Pitrou in bpo-17636@footnote{https://bugs.python.org/issue17636}.)
@end itemize

@node 新增模块<4>,改进的模块<4>,其他语言特性修改<4>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 new-modules}@anchor{68a}
@subsection 新增模块


@menu
* typing: typing<3>. 
* zipapp: zipapp<2>. 

@end menu

@node typing<3>,zipapp<2>,,新增模块<4>
@anchor{whatsnew/3 5 typing}@anchor{68b}
@subsubsection typing


The new @ref{119,,typing} @ref{341,,provisional} module
provides standard definitions and tools for function type annotations.
See @ref{628,,Type Hints} for more information.

@node zipapp<2>,,typing<3>,新增模块<4>
@anchor{whatsnew/3 5 whatsnew-zipapp}@anchor{629}@anchor{whatsnew/3 5 zipapp}@anchor{68c}
@subsubsection zipapp


The new @ref{141,,zipapp} module (specified in 
@geindex Python 提高建议; PEP 441
PEP 441@footnote{https://www.python.org/dev/peps/pep-0441}) provides an API and
command line tool for creating executable Python Zip Applications, which
were introduced in Python 2.6 in bpo-1739468@footnote{https://bugs.python.org/issue1739468}, but which were not well
publicized, either at the time or since.

With the new module, bundling your application is as simple as putting all
the files, including a @code{__main__.py} file, into a directory @code{myapp}
and running:

@example
$ python -m zipapp myapp
$ python myapp.pyz
@end example

The module implementation has been contributed by Paul Moore in
bpo-23491@footnote{https://bugs.python.org/issue23491}.


@subsubheading 参见


@geindex Python 提高建议; PEP 441
PEP 441@footnote{https://www.python.org/dev/peps/pep-0441} -- Improving Python ZIP Application Support


@node 改进的模块<4>,其他模块级更改,新增模块<4>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 improved-modules}@anchor{68d}
@subsection 改进的模块


@menu
* argparse: argparse<2>. 
* asyncio: asyncio<5>. 
* bz2:: 
* cgi:: 
* cmath: cmath<2>. 
* code:: 
* collections: collections<5>. 
* collections.abc: collections abc. 
* compileall: compileall<2>. 
* concurrent.futures: concurrent futures<3>. 
* configparser:: 
* contextlib: contextlib<3>. 
* csv: csv<2>. 
* curses: curses<2>. 
* dbm: dbm<4>. 
* difflib:: 
* distutils: distutils<4>. 
* doctest:: 
* email: email<2>. 
* enum: enum<4>. 
* faulthandler: faulthandler<2>. 
* functools: functools<3>. 
* glob:: 
* gzip: gzip<2>. 
* heapq:: 
* http:: 
* http.client: http client<3>. 
* idlelib 与 IDLE: idlelib 与 IDLE<3>. 
* imaplib:: 
* imghdr:: 
* importlib: importlib<5>. 
* inspect: inspect<3>. 
* io: io<3>. 
* ipaddress: ipaddress<2>. 
* json: json<2>. 
* linecache:: 
* locale: locale<3>. 
* logging: logging<4>. 
* lzma:: 
* math: math<4>. 
* multiprocessing: multiprocessing<4>. 
* operator:: 
* os: os<5>. 
* pathlib: pathlib<4>. 
* pickle: pickle<3>. 
* poplib:: 
* re: re<4>. 
* readline: readline<2>. 
* selectors:: 
* shutil: shutil<2>. 
* signal: signal<2>. 
* smtpd:: 
* smtplib:: 
* sndhdr:: 
* socket: socket<5>. 
* ssl: ssl<6>. 
* sqlite3: sqlite3<3>. 
* subprocess: subprocess<3>. 
* sys: sys<5>. 
* sysconfig:: 
* tarfile: tarfile<2>. 
* threading: threading<3>. 
* time: time<4>. 
* timeit: timeit<2>. 
* tkinter: tkinter<5>. 
* 回溯: 回溯<2>. 
* types: types<2>. 
* unicodedata: unicodedata<4>. 
* unittest: unittest<3>. 
* unittest.mock: unittest mock<3>. 
* urllib:: 
* wsgiref:: 
* xmlrpc: xmlrpc<2>. 
* xml.sax: xml sax. 
* zipfile: zipfile<3>. 

@end menu

@node argparse<2>,asyncio<5>,,改进的模块<4>
@anchor{whatsnew/3 5 argparse}@anchor{68e}
@subsubsection argparse


The @ref{68f,,ArgumentParser} class now allows disabling
@ref{690,,abbreviated usage} of long options by setting
@ref{691,,allow_abbrev} to @code{False}.  (Contributed by Jonathan Paugh,
Steven Bethard, paul j3 and Daniel Eriksson in bpo-14910@footnote{https://bugs.python.org/issue14910}.)

@node asyncio<5>,bz2,argparse<2>,改进的模块<4>
@anchor{whatsnew/3 5 asyncio}@anchor{692}
@subsubsection asyncio


Since the @ref{a,,asyncio} module is @ref{341,,provisional},
all changes introduced in Python 3.5 have also been backported to Python 3.4.x.

Notable changes in the @ref{a,,asyncio} module since Python 3.4.0:


@itemize *

@item 
New debugging APIs: @ref{693,,loop.set_debug()}
and @ref{694,,loop.get_debug()} methods.
(Contributed by Victor Stinner.)

@item 
The proactor event loop now supports SSL.
(Contributed by Antoine Pitrou and Victor Stinner in bpo-22560@footnote{https://bugs.python.org/issue22560}.)

@item 
A new @ref{695,,loop.is_closed()} method to
check if the event loop is closed.
(Contributed by Victor Stinner in bpo-21326@footnote{https://bugs.python.org/issue21326}.)

@item 
A new @ref{1af,,loop.create_task()}
to conveniently create and schedule a new @ref{1ad,,Task}
for a coroutine.  The @code{create_task} method is also used by all
asyncio functions that wrap coroutines into tasks, such as
@ref{289,,asyncio.wait()}, @ref{286,,asyncio.gather()}, etc.
(Contributed by Victor Stinner.)

@item 
A new @ref{696,,transport.get_write_buffer_limits()}
method to inquire for @emph{high-} and @emph{low-} water limits of the flow
control.
(Contributed by Victor Stinner.)

@item 
The @code{async()} function is deprecated in favor of
@ref{511,,ensure_future()}.
(Contributed by Yury Selivanov.)

@item 
New @ref{697,,loop.set_task_factory()} and
@ref{698,,loop.get_task_factory()}
methods to customize the task factory that @ref{1af,,loop.create_task()} method uses.  (Contributed by Yury
Selivanov.)

@item 
New @ref{699,,Queue.join()} and
@ref{69a,,Queue.task_done()} queue methods.
(Contributed by Victor Stinner.)

@item 
The @code{JoinableQueue} class was removed, in favor of the
@ref{290,,asyncio.Queue} class.
(Contributed by Victor Stinner.)
@end itemize

3.5.1 中的更新：


@itemize *

@item 
The @ref{511,,ensure_future()} function and all functions that
use it, such as @ref{512,,loop.run_until_complete()},
now accept all kinds of @ref{513,,awaitable objects}.
(Contributed by Yury Selivanov.)

@item 
New @ref{514,,run_coroutine_threadsafe()} function to submit
coroutines to event loops from other threads.
(Contributed by Vincent Michel.)

@item 
New @ref{515,,Transport.is_closing()}
method to check if the transport is closing or closed.
(Contributed by Yury Selivanov.)

@item 
The @ref{356,,loop.create_server()}
method can now accept a list of hosts.
(Contributed by Yann Sionneau.)
@end itemize

3.5.2 中的更新：


@itemize *

@item 
New @ref{516,,loop.create_future()}
method to create Future objects.  This allows alternative event
loop implementations, such as
uvloop@footnote{https://github.com/MagicStack/uvloop}, to provide a faster
@ref{43d,,asyncio.Future} implementation.
(Contributed by Yury Selivanov.)

@item 
New @ref{517,,loop.get_exception_handler()}
method to get the current exception handler.
(Contributed by Yury Selivanov.)

@item 
New @ref{518,,StreamReader.readuntil()}
method to read data from the stream until a separator bytes
sequence appears.
(Contributed by Mark Korenberg.)

@item 
The @ref{1b2,,loop.create_connection()}
and @ref{356,,loop.create_server()}
methods are optimized to avoid calling the system @code{getaddrinfo}
function if the address is already resolved.
(Contributed by A. Jesse Jiryu Davis.)

@item 
The @ref{69b,,loop.sock_connect(sock@comma{} address)}
no longer requires the @emph{address} to be resolved prior to the call.
(Contributed by A. Jesse Jiryu Davis.)
@end itemize

@node bz2,cgi,asyncio<5>,改进的模块<4>
@anchor{whatsnew/3 5 bz2}@anchor{69c}
@subsubsection bz2


The @ref{69d,,BZ2Decompressor.decompress}
method now accepts an optional @emph{max_length} argument to limit the maximum
size of decompressed data. (Contributed by Nikolaus Rath in bpo-15955@footnote{https://bugs.python.org/issue15955}.)

@node cgi,cmath<2>,bz2,改进的模块<4>
@anchor{whatsnew/3 5 cgi}@anchor{69e}
@subsubsection cgi


The @code{FieldStorage} class now supports the @ref{563,,context manager}
protocol.  (Contributed by Berker Peksag in bpo-20289@footnote{https://bugs.python.org/issue20289}.)

@node cmath<2>,code,cgi,改进的模块<4>
@anchor{whatsnew/3 5 cmath}@anchor{69f}
@subsubsection cmath


A new function @ref{681,,isclose()} provides a way to test for approximate
equality.  (Contributed by Chris Barker and Tal Einat in bpo-24270@footnote{https://bugs.python.org/issue24270}.)

@node code,collections<5>,cmath<2>,改进的模块<4>
@anchor{whatsnew/3 5 code}@anchor{6a0}
@subsubsection code


The @ref{6a1,,InteractiveInterpreter.showtraceback()}
method now prints the full chained traceback, just like the interactive
interpreter.  (Contributed by Claudiu Popa in bpo-17442@footnote{https://bugs.python.org/issue17442}.)

@node collections<5>,collections abc,code,改进的模块<4>
@anchor{whatsnew/3 5 collections}@anchor{6a2}
@subsubsection collections

@anchor{whatsnew/3 5 whatsnew-ordereddict}@anchor{631}
The @ref{1b9,,OrderedDict} class is now implemented in C, which
makes it 4 to 100 times faster.  (Contributed by Eric Snow in bpo-16991@footnote{https://bugs.python.org/issue16991}.)

@code{OrderedDict.items()},
@code{OrderedDict.keys()},
@code{OrderedDict.values()} views now support
@ref{18e,,reversed()} iteration.
(Contributed by Serhiy Storchaka in bpo-19505@footnote{https://bugs.python.org/issue19505}.)

The @ref{52b,,deque} class now defines
@ref{6a3,,index()}, @ref{6a4,,insert()}, and
@ref{6a5,,copy()}, and supports the @code{+} and @code{*} operators.
This allows deques to be recognized as a @ref{6a6,,MutableSequence}
and improves their substitutability for lists.
(Contributed by Raymond Hettinger in bpo-23704@footnote{https://bugs.python.org/issue23704}.)

Docstrings produced by @ref{1b6,,namedtuple()} can now be updated:

@example
Point = namedtuple('Point', ['x', 'y'])
Point.__doc__ += ': Cartesian coodinate'
Point.x.__doc__ = 'abscissa'
Point.y.__doc__ = 'ordinate'
@end example

（由 Berker Peksag 在 bpo-24064@footnote{https://bugs.python.org/issue24064} 中贡献。）

The @ref{6a7,,UserString} class now implements the
@ref{6a8,,__getnewargs__()}, @ref{6a9,,__rmod__()}, @ref{6aa,,casefold()},
@ref{6ab,,format_map()}, @ref{6ac,,isprintable()}, and @ref{6ad,,maketrans()}
methods to match the corresponding methods of @ref{329,,str}.
(Contributed by Joe Jevnik in bpo-22189@footnote{https://bugs.python.org/issue22189}.)

@node collections abc,compileall<2>,collections<5>,改进的模块<4>
@anchor{whatsnew/3 5 collections-abc}@anchor{6ae}
@subsubsection collections.abc


The @code{Sequence.index()} method now
accepts @emph{start} and @emph{stop} arguments to match the corresponding methods
of @ref{478,,tuple}, @ref{262,,list}, etc.
(Contributed by Devin Jeanpierre in bpo-23086@footnote{https://bugs.python.org/issue23086}.)

A new @ref{6af,,Generator} abstract base class. (Contributed
by Stefan Behnel in bpo-24018@footnote{https://bugs.python.org/issue24018}.)

New @ref{6b0,,Awaitable}, @ref{6b1,,Coroutine},
@ref{6b2,,AsyncIterator}, and
@ref{6b3,,AsyncIterable} abstract base classes.
(Contributed by Yury Selivanov in bpo-24184@footnote{https://bugs.python.org/issue24184}.)

For earlier Python versions, a backport of the new ABCs is available in an
external PyPI package@footnote{https://pypi.org/project/backports_abc}.

@node compileall<2>,concurrent futures<3>,collections abc,改进的模块<4>
@anchor{whatsnew/3 5 compileall}@anchor{6b4}
@subsubsection compileall


A new @ref{21,,compileall} option, @code{-j @emph{N}}, allows running @emph{N} workers
simultaneously to perform parallel bytecode compilation.
The @ref{36b,,compile_dir()} function has a corresponding @code{workers}
parameter.  (Contributed by Claudiu Popa in bpo-16104@footnote{https://bugs.python.org/issue16104}.)

Another new option, @code{-r}, allows controlling the maximum recursion
level for subdirectories.  (Contributed by Claudiu Popa in bpo-19628@footnote{https://bugs.python.org/issue19628}.)

The @code{-q} command line option can now be specified more than once, in
which case all output, including errors, will be suppressed.  The corresponding
@code{quiet} parameter in @ref{36b,,compile_dir()},
@ref{6b5,,compile_file()}, and @ref{6b6,,compile_path()} can now
accept an integer value indicating the level of output suppression.
(Contributed by Thomas Kluyver in bpo-21338@footnote{https://bugs.python.org/issue21338}.)

@node concurrent futures<3>,configparser,compileall<2>,改进的模块<4>
@anchor{whatsnew/3 5 concurrent-futures}@anchor{6b7}
@subsubsection concurrent.futures


The @ref{6b8,,Executor.map()} method now accepts a
@emph{chunksize} argument to allow batching of tasks to improve performance when
@ref{2a3,,ProcessPoolExecutor()} is used.
(Contributed by Dan O'Reilly in bpo-11271@footnote{https://bugs.python.org/issue11271}.)

The number of workers in the @ref{27a,,ThreadPoolExecutor}
constructor is optional now.  The default value is 5 times the number of CPUs.
(Contributed by Claudiu Popa in bpo-21527@footnote{https://bugs.python.org/issue21527}.)

@node configparser,contextlib<3>,concurrent futures<3>,改进的模块<4>
@anchor{whatsnew/3 5 configparser}@anchor{6b9}
@subsubsection configparser


@ref{23,,configparser} now provides a way to customize the conversion
of values by specifying a dictionary of converters in the
@ref{4a5,,ConfigParser} constructor, or by defining them
as methods in @code{ConfigParser} subclasses.  Converters defined in
a parser instance are inherited by its section proxies.

示例:

@example
>>> import configparser
>>> conv = @{@}
>>> conv['list'] = lambda v: [e.strip() for e in v.split() if e.strip()]
>>> cfg = configparser.ConfigParser(converters=conv)
>>> cfg.read_string("""
... [s]
... list = a b c d e f g
... """)
>>> cfg.get('s', 'list')
'a b c d e f g'
>>> cfg.getlist('s', 'list')
['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> section = cfg['s']
>>> section.getlist('list')
['a', 'b', 'c', 'd', 'e', 'f', 'g']
@end example

（由 Łukasz Langa 在 bpo-18159@footnote{https://bugs.python.org/issue18159} 中贡献。）

@node contextlib<3>,csv<2>,configparser,改进的模块<4>
@anchor{whatsnew/3 5 contextlib}@anchor{6ba}
@subsubsection contextlib


The new @ref{6bb,,redirect_stderr()} @ref{563,,context manager} (similar to
@ref{6bc,,redirect_stdout()}) makes it easier for utility scripts to
handle inflexible APIs that write their output to @ref{308,,sys.stderr} and
don't provide any options to redirect it:

@example
>>> import contextlib, io, logging
>>> f = io.StringIO()
>>> with contextlib.redirect_stderr(f):
...     logging.warning('warning')
...
>>> f.getvalue()
'WARNING:root:warning\n'
@end example

（由 Berker Peksag 在 bpo-22389@footnote{https://bugs.python.org/issue22389} 中贡献。）

@node csv<2>,curses<2>,contextlib<3>,改进的模块<4>
@anchor{whatsnew/3 5 csv}@anchor{6bd}
@subsubsection csv


The @ref{6be,,writerow()} method now supports arbitrary iterables,
not just sequences.  (Contributed by Serhiy Storchaka in bpo-23171@footnote{https://bugs.python.org/issue23171}.)

@node curses<2>,dbm<4>,csv<2>,改进的模块<4>
@anchor{whatsnew/3 5 curses}@anchor{6bf}
@subsubsection curses


The new @ref{6c0,,update_lines_cols()} function updates the 
@geindex LINES
@geindex 环境变量; LINES
@code{LINES}
and 
@geindex COLS
@geindex 环境变量; COLS
@code{COLS} environment variables.  This is useful for detecting
manual screen resizing.  (Contributed by Arnon Yaari in bpo-4254@footnote{https://bugs.python.org/issue4254}.)

@node dbm<4>,difflib,curses<2>,改进的模块<4>
@anchor{whatsnew/3 5 dbm}@anchor{6c1}
@subsubsection dbm


@ref{2bf,,dumb.open} always creates a new database when the flag
has the value @code{"n"}.  (Contributed by Claudiu Popa in bpo-18039@footnote{https://bugs.python.org/issue18039}.)

@node difflib,distutils<4>,dbm<4>,改进的模块<4>
@anchor{whatsnew/3 5 difflib}@anchor{6c2}
@subsubsection difflib


The charset of HTML documents generated by
@ref{6c3,,HtmlDiff.make_file()}
can now be customized by using a new @emph{charset} keyword-only argument.
The default charset of HTML document changed from @code{"ISO-8859-1"}
to @code{"utf-8"}.
(Contributed by Berker Peksag in bpo-2052@footnote{https://bugs.python.org/issue2052}.)

The @ref{6c4,,diff_bytes()} function can now compare lists of byte
strings.  This fixes a regression from Python 2.
(Contributed by Terry J. Reedy and Greg Ward in bpo-17445@footnote{https://bugs.python.org/issue17445}.)

@node distutils<4>,doctest,difflib,改进的模块<4>
@anchor{whatsnew/3 5 distutils}@anchor{6c5}
@subsubsection distutils


Both the @code{build} and @code{build_ext} commands now accept a @code{-j} option to
enable parallel building of extension modules.
(Contributed by Antoine Pitrou in bpo-5309@footnote{https://bugs.python.org/issue5309}.)

The @ref{39,,distutils} module now supports @code{xz} compression, and can be
enabled by passing @code{xztar} as an argument to @code{bdist --format}.
(Contributed by Serhiy Storchaka in bpo-16314@footnote{https://bugs.python.org/issue16314}.)

@node doctest,email<2>,distutils<4>,改进的模块<4>
@anchor{whatsnew/3 5 doctest}@anchor{6c6}
@subsubsection doctest


The @ref{6c7,,DocTestSuite()} function returns an empty
@ref{6c8,,unittest.TestSuite} if @emph{module} contains no docstrings, instead of
raising @ref{1fb,,ValueError}.  (Contributed by Glenn Jones in bpo-15916@footnote{https://bugs.python.org/issue15916}.)

@node email<2>,enum<4>,doctest,改进的模块<4>
@anchor{whatsnew/3 5 email}@anchor{6c9}
@subsubsection email


A new policy option @ref{6ca,,Policy.mangle_from_}
controls whether or not lines that start with @code{"From "} in email bodies are
prefixed with a @code{">"} character by generators.  The default is @code{True} for
@ref{53b,,compat32} and @code{False} for all other policies.
(Contributed by Milan Oberkirch in bpo-20098@footnote{https://bugs.python.org/issue20098}.)

A new
@ref{6cb,,Message.get_content_disposition()}
method provides easy access to a canonical value for the
@code{Content-Disposition} header.
(Contributed by Abhilash Raj in bpo-21083@footnote{https://bugs.python.org/issue21083}.)

A new policy option @ref{6cc,,EmailPolicy.utf8}
can be set to @code{True} to encode email headers using the UTF-8 charset instead
of using encoded words.  This allows @code{Messages} to be formatted according to
@geindex RFC; RFC 6532
RFC 6532@footnote{https://tools.ietf.org/html/rfc6532.html} and used with an SMTP server that supports the 
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html}
@code{SMTPUTF8} extension.  (Contributed by R. David Murray in
bpo-24211@footnote{https://bugs.python.org/issue24211}.)

The @ref{6cd,,mime.text.MIMEText} constructor now
accepts a @ref{6ce,,charset.Charset} instance.
(Contributed by Claude Paroz and Berker Peksag in bpo-16324@footnote{https://bugs.python.org/issue16324}.)

@node enum<4>,faulthandler<2>,email<2>,改进的模块<4>
@anchor{whatsnew/3 5 enum}@anchor{6cf}
@subsubsection enum


The @ref{37f,,Enum} callable has a new parameter @emph{start} to
specify the initial number of enum values if only @emph{names} are provided:

@example
>>> Animal = enum.Enum('Animal', 'cat dog', start=10)
>>> Animal.cat
<Animal.cat: 10>
>>> Animal.dog
<Animal.dog: 11>
@end example

（由 Ethan Furman 在 bpo-21706@footnote{https://bugs.python.org/issue21706} 中贡献。）

@node faulthandler<2>,functools<3>,enum<4>,改进的模块<4>
@anchor{whatsnew/3 5 faulthandler}@anchor{6d0}
@subsubsection faulthandler


The @ref{543,,enable()}, @ref{6d1,,register()},
@ref{6d2,,dump_traceback()} and
@ref{6d3,,dump_traceback_later()} functions now accept file
descriptors in addition to file-like objects.
(Contributed by Wei Wu in bpo-23566@footnote{https://bugs.python.org/issue23566}.)

@node functools<3>,glob,faulthandler<2>,改进的模块<4>
@anchor{whatsnew/3 5 functools}@anchor{6d4}
@subsubsection functools

@anchor{whatsnew/3 5 whatsnew-lrucache}@anchor{634}
Most of the @ref{1c7,,lru_cache()} machinery is now implemented in C, making
it significantly faster.  (Contributed by Matt Joiner, Alexey Kachayev, and
Serhiy Storchaka in bpo-14373@footnote{https://bugs.python.org/issue14373}.)

@node glob,gzip<2>,functools<3>,改进的模块<4>
@anchor{whatsnew/3 5 glob}@anchor{6d5}
@subsubsection glob


The @ref{5c2,,iglob()} and @ref{5c1,,glob()} functions now support recursive
search in subdirectories, using the @code{"**"} pattern.
(Contributed by Serhiy Storchaka in bpo-13968@footnote{https://bugs.python.org/issue13968}.)

@node gzip<2>,heapq,glob,改进的模块<4>
@anchor{whatsnew/3 5 gzip}@anchor{6d6}
@subsubsection gzip


The @emph{mode} argument of the @ref{6d7,,GzipFile} constructor now
accepts @code{"x"} to request exclusive creation.
(Contributed by Tim Heaney in bpo-19222@footnote{https://bugs.python.org/issue19222}.)

@node heapq,http,gzip<2>,改进的模块<4>
@anchor{whatsnew/3 5 heapq}@anchor{6d8}
@subsubsection heapq


Element comparison in @ref{6d9,,merge()} can now be customized by
passing a @ref{6da,,key function} in a new optional @emph{key} keyword argument,
and a new optional @emph{reverse} keyword argument can be used to reverse element
comparison:

@example
>>> import heapq
>>> a = ['9', '777', '55555']
>>> b = ['88', '6666']
>>> list(heapq.merge(a, b, key=len))
['9', '88', '777', '6666', '55555']
>>> list(heapq.merge(reversed(a), reversed(b), key=len, reverse=True))
['55555', '6666', '777', '88', '9']
@end example

（由 Raymond Hettinger 在 bpo-13742@footnote{https://bugs.python.org/issue13742} 中贡献。）

@node http,http client<3>,heapq,改进的模块<4>
@anchor{whatsnew/3 5 http}@anchor{6db}
@subsubsection http


A new @ref{6dc,,HTTPStatus} enum that defines a set of
HTTP status codes, reason phrases and long descriptions written in English.
(Contributed by Demian Brecht in bpo-21793@footnote{https://bugs.python.org/issue21793}.)

@node http client<3>,idlelib 与 IDLE<3>,http,改进的模块<4>
@anchor{whatsnew/3 5 http-client}@anchor{6dd}
@subsubsection http.client


@ref{6de,,HTTPConnection.getresponse()}
now raises a @ref{6df,,RemoteDisconnected} exception when a
remote server connection is closed unexpectedly.  Additionally, if a
@ref{6e0,,ConnectionError} (of which @code{RemoteDisconnected}
is a subclass) is raised, the client socket is now closed automatically,
and will reconnect on the next request:

@example
import http.client
conn = http.client.HTTPConnection('www.python.org')
for retries in range(3):
    try:
        conn.request('GET', '/')
        resp = conn.getresponse()
    except http.client.RemoteDisconnected:
        pass
@end example

（由 Martin Panter 在 bpo-3566@footnote{https://bugs.python.org/issue3566} 中贡献。）

@node idlelib 与 IDLE<3>,imaplib,http client<3>,改进的模块<4>
@anchor{whatsnew/3 5 idlelib-and-idle}@anchor{6e1}
@subsubsection idlelib 与 IDLE


Since idlelib implements the IDLE shell and editor and is not intended for
import by other programs, it gets improvements with every release.  See
@code{Lib/idlelib/NEWS.txt} for a cumulative list of changes since 3.4.0,
as well as changes made in future 3.5.x releases. This file is also available
from the IDLE Help ‣ About IDLE dialog.

@node imaplib,imghdr,idlelib 与 IDLE<3>,改进的模块<4>
@anchor{whatsnew/3 5 imaplib}@anchor{6e2}
@subsubsection imaplib


The @ref{606,,IMAP4} class now supports the @ref{563,,context manager} protocol.
When used in a @ref{6e3,,with} statement, the IMAP4 @code{LOGOUT}
command will be called automatically at the end of the block.
(Contributed by Tarek Ziadé and Serhiy Storchaka in bpo-4972@footnote{https://bugs.python.org/issue4972}.)

The @ref{98,,imaplib} module now supports 
@geindex RFC; RFC 5161
RFC 5161@footnote{https://tools.ietf.org/html/rfc5161.html} (ENABLE Extension)
and 
@geindex RFC; RFC 6855
RFC 6855@footnote{https://tools.ietf.org/html/rfc6855.html} (UTF-8 Support) via the @ref{6e4,,IMAP4.enable()}
method.  A new @ref{6e5,,IMAP4.utf8_enabled}
attribute tracks whether or not 
@geindex RFC; RFC 6855
RFC 6855@footnote{https://tools.ietf.org/html/rfc6855.html} support is enabled.
(Contributed by Milan Oberkirch, R. David Murray, and Maciej Szulik in
bpo-21800@footnote{https://bugs.python.org/issue21800}.)

The @ref{98,,imaplib} module now automatically encodes non-ASCII string usernames
and passwords using UTF-8, as recommended by the RFCs.  (Contributed by Milan
Oberkirch in bpo-21800@footnote{https://bugs.python.org/issue21800}.)

@node imghdr,importlib<5>,imaplib,改进的模块<4>
@anchor{whatsnew/3 5 imghdr}@anchor{6e6}
@subsubsection imghdr


The @ref{6e7,,what()} function now recognizes the
OpenEXR@footnote{http://www.openexr.com} format
(contributed by Martin Vignali and Claudiu Popa in bpo-20295@footnote{https://bugs.python.org/issue20295}),
and the WebP@footnote{https://en.wikipedia.org/wiki/WebP} format
(contributed by Fabrice Aneche and Claudiu Popa in bpo-20197@footnote{https://bugs.python.org/issue20197}.)

@node importlib<5>,inspect<3>,imghdr,改进的模块<4>
@anchor{whatsnew/3 5 importlib}@anchor{6e8}
@subsubsection importlib


The @ref{54e,,util.LazyLoader} class allows for
lazy loading of modules in applications where startup time is important.
(Contributed by Brett Cannon in bpo-17621@footnote{https://bugs.python.org/issue17621}.)

The @ref{6e9,,abc.InspectLoader.source_to_code()}
method is now a static method.  This makes it easier to initialize a module
object with code compiled from a string by running
@code{exec(code, module.__dict__)}.
(Contributed by Brett Cannon in bpo-21156@footnote{https://bugs.python.org/issue21156}.)

The new @ref{6ea,,util.module_from_spec()}
function is now the preferred way to create a new module.  As opposed to
creating a @ref{6eb,,types.ModuleType} instance directly, this new function
will set the various import-controlled attributes based on the passed-in
spec object.  (Contributed by Brett Cannon in bpo-20383@footnote{https://bugs.python.org/issue20383}.)

@node inspect<3>,io<3>,importlib<5>,改进的模块<4>
@anchor{whatsnew/3 5 inspect}@anchor{6ec}
@subsubsection inspect


Both the @ref{6ed,,Signature} and @ref{6ee,,Parameter} classes are
now picklable and hashable.  (Contributed by Yury Selivanov in bpo-20726@footnote{https://bugs.python.org/issue20726}
and bpo-20334@footnote{https://bugs.python.org/issue20334}.)

A new
@ref{6ef,,BoundArguments.apply_defaults()}
method provides a way to set default values for missing arguments:

@example
>>> def foo(a, b='ham', *args): pass
>>> ba = inspect.signature(foo).bind('spam')
>>> ba.apply_defaults()
>>> ba.arguments
OrderedDict([('a', 'spam'), ('b', 'ham'), ('args', ())])
@end example

（由 Yury Selivanov 在 bpo-24190@footnote{https://bugs.python.org/issue24190} 中贡献。）

A new class method
@ref{6f0,,Signature.from_callable()} makes
subclassing of @ref{6ed,,Signature} easier.  (Contributed
by Yury Selivanov and Eric Snow in bpo-17373@footnote{https://bugs.python.org/issue17373}.)

The @ref{556,,signature()} function now accepts a @emph{follow_wrapped}
optional keyword argument, which, when set to @code{False}, disables automatic
following of @code{__wrapped__} links.
(Contributed by Yury Selivanov in bpo-20691@footnote{https://bugs.python.org/issue20691}.)

A set of new functions to inspect
@ref{639,,coroutine functions} and
@ref{1a6,,coroutine objects} has been added:
@ref{6f1,,iscoroutine()}, @ref{6f2,,iscoroutinefunction()},
@ref{6f3,,isawaitable()}, @ref{6f4,,getcoroutinelocals()},
and @ref{6f5,,getcoroutinestate()}.
(Contributed by Yury Selivanov in bpo-24017@footnote{https://bugs.python.org/issue24017} and bpo-24400@footnote{https://bugs.python.org/issue24400}.)

The @ref{6f6,,stack()}, @ref{6f7,,trace()},
@ref{6f8,,getouterframes()}, and @ref{6f9,,getinnerframes()}
functions now return a list of named tuples.
(Contributed by Daniel Shahaf in bpo-16808@footnote{https://bugs.python.org/issue16808}.)

@node io<3>,ipaddress<2>,inspect<3>,改进的模块<4>
@anchor{whatsnew/3 5 io}@anchor{6fa}
@subsubsection io


A new @ref{6fb,,BufferedIOBase.readinto1()}
method, that uses at most one call to the underlying raw stream's
@ref{6fc,,RawIOBase.read()} or
@ref{6fd,,RawIOBase.readinto()} methods.
(Contributed by Nikolaus Rath in bpo-20578@footnote{https://bugs.python.org/issue20578}.)

@node ipaddress<2>,json<2>,io<3>,改进的模块<4>
@anchor{whatsnew/3 5 ipaddress}@anchor{6fe}
@subsubsection ipaddress


Both the @ref{398,,IPv4Network} and @ref{397,,IPv6Network} classes
now accept an @code{(address, netmask)} tuple argument, so as to easily construct
network objects from existing addresses:

@example
>>> import ipaddress
>>> ipaddress.IPv4Network(('127.0.0.0', 8))
IPv4Network('127.0.0.0/8')
>>> ipaddress.IPv4Network(('127.0.0.0', '255.0.0.0'))
IPv4Network('127.0.0.0/8')
@end example

（由 Peter Moody 和 Antoine Pitrou 在 bpo-16531@footnote{https://bugs.python.org/issue16531} 中贡献。）

A new @code{reverse_pointer} attribute for the
@ref{398,,IPv4Network} and @ref{397,,IPv6Network} classes
returns the name of the reverse DNS PTR record:

@example
>>> import ipaddress
>>> addr = ipaddress.IPv4Address('127.0.0.1')
>>> addr.reverse_pointer
'1.0.0.127.in-addr.arpa'
>>> addr6 = ipaddress.IPv6Address('::1')
>>> addr6.reverse_pointer
'1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa'
@end example

（由 Leon Weber 在 bpo-20480@footnote{https://bugs.python.org/issue20480} 中贡献。）

@node json<2>,linecache,ipaddress<2>,改进的模块<4>
@anchor{whatsnew/3 5 json}@anchor{6ff}
@subsubsection json


The @ref{a5,,json.tool} command line interface now preserves the order of keys in
JSON objects passed in input.  The new @code{--sort-keys} option can be used
to sort the keys alphabetically. (Contributed by Berker Peksag
in bpo-21650@footnote{https://bugs.python.org/issue21650}.)

JSON decoder now raises @ref{700,,JSONDecodeError} instead of
@ref{1fb,,ValueError} to provide better context information about the error.
(Contributed by Serhiy Storchaka in bpo-19361@footnote{https://bugs.python.org/issue19361}.)

@node linecache,locale<3>,json<2>,改进的模块<4>
@anchor{whatsnew/3 5 linecache}@anchor{701}
@subsubsection linecache


A new @ref{702,,lazycache()} function can be used to capture information
about a non-file-based module to permit getting its lines later via
@ref{703,,getline()}. This avoids doing I/O until a line is actually
needed, without having to carry the module globals around indefinitely.
(Contributed by Robert Collins in bpo-17911@footnote{https://bugs.python.org/issue17911}.)

@node locale<3>,logging<4>,linecache,改进的模块<4>
@anchor{whatsnew/3 5 locale}@anchor{704}
@subsubsection locale


A new @ref{705,,delocalize()} function can be used to convert a string into
a normalized number string, taking the @code{LC_NUMERIC} settings into account:

@example
>>> import locale
>>> locale.setlocale(locale.LC_NUMERIC, 'de_DE.UTF-8')
'de_DE.UTF-8'
>>> locale.delocalize('1.234,56')
'1234.56'
>>> locale.setlocale(locale.LC_NUMERIC, 'en_US.UTF-8')
'en_US.UTF-8'
>>> locale.delocalize('1,234.56')
'1234.56'
@end example

（由 Cédric Krier 在 bpo-13918@footnote{https://bugs.python.org/issue13918} 中贡献。）

@node logging<4>,lzma,locale<3>,改进的模块<4>
@anchor{whatsnew/3 5 logging}@anchor{706}
@subsubsection logging


All logging methods (@ref{39f,,Logger} @ref{707,,log()},
@ref{708,,exception()}, @ref{709,,critical()},
@ref{70a,,debug()}, etc.), now accept exception instances
as an @emph{exc_info} argument, in addition to boolean values and exception
tuples:

@example
>>> import logging
>>> try:
...     1/0
... except ZeroDivisionError as ex:
...     logging.error('exception', exc_info=ex)
ERROR:root:exception
@end example

（由 Yury Selivanov 在 bpo-20537@footnote{https://bugs.python.org/issue20537} 中贡献。）

The @ref{70b,,handlers.HTTPHandler} class now
accepts an optional @ref{3dc,,ssl.SSLContext} instance to configure SSL
settings used in an HTTP connection.
(Contributed by Alex Gaynor in bpo-22788@footnote{https://bugs.python.org/issue22788}.)

The @ref{70c,,handlers.QueueListener} class now
takes a @emph{respect_handler_level} keyword argument which, if set to @code{True},
will pass messages to handlers taking handler levels into account.
(Contributed by Vinay Sajip.)

@node lzma,math<4>,logging<4>,改进的模块<4>
@anchor{whatsnew/3 5 lzma}@anchor{70d}
@subsubsection lzma


The @ref{70e,,LZMADecompressor.decompress()}
method now accepts an optional @emph{max_length} argument to limit the maximum
size of decompressed data.
(Contributed by Martin Panter in bpo-15955@footnote{https://bugs.python.org/issue15955}.)

@node math<4>,multiprocessing<4>,lzma,改进的模块<4>
@anchor{whatsnew/3 5 math}@anchor{70f}
@subsubsection math


Two new constants have been added to the @ref{b1,,math} module: @ref{522,,inf}
and @ref{523,,nan}.  (Contributed by Mark Dickinson in bpo-23185@footnote{https://bugs.python.org/issue23185}.)

A new function @ref{680,,isclose()} provides a way to test for approximate
equality. (Contributed by Chris Barker and Tal Einat in bpo-24270@footnote{https://bugs.python.org/issue24270}.)

A new @ref{710,,gcd()} function has been added.  The @ref{711,,fractions.gcd()}
function is now deprecated. (Contributed by Mark Dickinson and Serhiy
Storchaka in bpo-22486@footnote{https://bugs.python.org/issue22486}.)

@node multiprocessing<4>,operator,math<4>,改进的模块<4>
@anchor{whatsnew/3 5 multiprocessing}@anchor{712}
@subsubsection multiprocessing


@ref{713,,sharedctypes.synchronized()}
objects now support the @ref{563,,context manager} protocol.
(Contributed by Charles-François Natali in bpo-21565@footnote{https://bugs.python.org/issue21565}.)

@node operator,os<5>,multiprocessing<4>,改进的模块<4>
@anchor{whatsnew/3 5 operator}@anchor{714}
@subsubsection operator


@ref{715,,attrgetter()}, @ref{261,,itemgetter()},
and @ref{716,,methodcaller()} objects now support pickling.
(Contributed by Josh Rosenberg and Serhiy Storchaka in bpo-22955@footnote{https://bugs.python.org/issue22955}.)

New @ref{717,,matmul()} and @ref{718,,imatmul()} functions
to perform matrix multiplication.
(Contributed by Benjamin Peterson in bpo-21176@footnote{https://bugs.python.org/issue21176}.)

@node os<5>,pathlib<4>,operator,改进的模块<4>
@anchor{whatsnew/3 5 os}@anchor{719}
@subsubsection os


The new @ref{25f,,scandir()} function returning an iterator of
@ref{4eb,,DirEntry} objects has been added.  If possible, @ref{25f,,scandir()}
extracts file attributes while scanning a directory, removing the need to
perform subsequent system calls to determine file type or attributes, which may
significantly improve performance.  (Contributed by Ben Hoyt with the help
of Victor Stinner in bpo-22524@footnote{https://bugs.python.org/issue22524}.)

On Windows, a new
@ref{71a,,stat_result.st_file_attributes}
attribute is now available.  It corresponds to the @code{dwFileAttributes} member
of the @code{BY_HANDLE_FILE_INFORMATION} structure returned by
@code{GetFileInformationByHandle()}.  (Contributed by Ben Hoyt in bpo-21719@footnote{https://bugs.python.org/issue21719}.)

The @ref{4cb,,urandom()} function now uses the @code{getrandom()} syscall on Linux 3.17
or newer, and @code{getentropy()} on OpenBSD 5.6 and newer, removing the need to
use @code{/dev/urandom} and avoiding failures due to potential file descriptor
exhaustion.  (Contributed by Victor Stinner in bpo-22181@footnote{https://bugs.python.org/issue22181}.)

New @ref{71b,,get_blocking()} and @ref{71c,,set_blocking()} functions allow
getting and setting a file descriptor's blocking mode (@ref{71d,,O_NONBLOCK}.)
(Contributed by Victor Stinner in bpo-22054@footnote{https://bugs.python.org/issue22054}.)

The @ref{71e,,truncate()} and @ref{65c,,ftruncate()} functions are now supported
on Windows.  (Contributed by Steve Dower in bpo-23668@footnote{https://bugs.python.org/issue23668}.)

There is a new @ref{71f,,os.path.commonpath()} function returning the longest
common sub-path of each passed pathname.  Unlike the
@ref{720,,os.path.commonprefix()} function, it always returns a valid
path:

@example
>>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
'/usr/l'

>>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
'/usr'
@end example

（由 Rafik Draoui 和 Serhiy Storchaka 在 bpo-10395@footnote{https://bugs.python.org/issue10395} 中贡献。）

@node pathlib<4>,pickle<3>,os<5>,改进的模块<4>
@anchor{whatsnew/3 5 pathlib}@anchor{721}
@subsubsection pathlib


The new @ref{722,,Path.samefile()} method can be used
to check whether the path points to the same file as another path, which can
be either another @ref{201,,Path} object, or a string:

@example
>>> import pathlib
>>> p1 = pathlib.Path('/etc/hosts')
>>> p2 = pathlib.Path('/etc/../etc/hosts')
>>> p1.samefile(p2)
True
@end example

（由 Vajrasky Kok 和 Antoine Pitrou 在 bpo-19775@footnote{https://bugs.python.org/issue19775} 中贡献。）

The @ref{723,,Path.mkdir()} method now accepts a new optional
@emph{exist_ok} argument to match @code{mkdir -p} and @ref{3b5,,os.makedirs()}
functionality.  (Contributed by Berker Peksag in bpo-21539@footnote{https://bugs.python.org/issue21539}.)

There is a new @ref{724,,Path.expanduser()} method to
expand @code{~} and @code{~user} prefixes.  (Contributed by Serhiy Storchaka and
Claudiu Popa in bpo-19776@footnote{https://bugs.python.org/issue19776}.)

A new @ref{725,,Path.home()} class method can be used to get
a @ref{201,,Path} instance representing the user’s home
directory.
(Contributed by Victor Salgado and Mayank Tripathi in bpo-19777@footnote{https://bugs.python.org/issue19777}.)

New @ref{726,,Path.write_text()},
@ref{727,,Path.read_text()},
@ref{728,,Path.write_bytes()},
@ref{729,,Path.read_bytes()} methods to simplify
read/write operations on files.

The following code snippet will create or rewrite existing file
@code{~/spam42}:

@example
>>> import pathlib
>>> p = pathlib.Path('~/spam42')
>>> p.expanduser().write_text('ham')
3
@end example

（由 Christopher Welborn 在 bpo-20218@footnote{https://bugs.python.org/issue20218} 中贡献。）

@node pickle<3>,poplib,pathlib<4>,改进的模块<4>
@anchor{whatsnew/3 5 pickle}@anchor{72a}
@subsubsection pickle


Nested objects, such as unbound methods or nested classes, can now be pickled
using @ref{569,,pickle protocols} older than protocol version 4.
Protocol version 4 already supports these cases.  (Contributed by Serhiy
Storchaka in bpo-23611@footnote{https://bugs.python.org/issue23611}.)

@node poplib,re<4>,pickle<3>,改进的模块<4>
@anchor{whatsnew/3 5 poplib}@anchor{72b}
@subsubsection poplib


A new @ref{72c,,POP3.utf8()} command enables 
@geindex RFC; RFC 6856
RFC 6856@footnote{https://tools.ietf.org/html/rfc6856.html}
(Internationalized Email) support, if a POP server supports it.
(Contributed by Milan OberKirch in bpo-21804@footnote{https://bugs.python.org/issue21804}.)

@node re<4>,readline<2>,poplib,改进的模块<4>
@anchor{whatsnew/3 5 re}@anchor{72d}
@subsubsection re


References and conditional references to groups with fixed length are now
allowed in lookbehind assertions:

@example
>>> import re
>>> pat = re.compile(r'(a|b).(?<=\1)c')
>>> pat.match('aac')
<_sre.SRE_Match object; span=(0, 3), match='aac'>
>>> pat.match('bbc')
<_sre.SRE_Match object; span=(0, 3), match='bbc'>
@end example

（由 Serhiy Storchaka 在 bpo-9179@footnote{https://bugs.python.org/issue9179} 中贡献。）

The number of capturing groups in regular expressions is no longer limited to
100.  (Contributed by Serhiy Storchaka in bpo-22437@footnote{https://bugs.python.org/issue22437}.)

The @ref{475,,sub()} and @ref{72e,,subn()} functions now replace unmatched
groups with empty strings instead of raising an exception.
(Contributed by Serhiy Storchaka in bpo-1519638@footnote{https://bugs.python.org/issue1519638}.)

The @ref{72f,,re.error} exceptions have new attributes,
@ref{730,,msg}, @ref{731,,pattern},
@ref{732,,pos}, @ref{733,,lineno},
and @ref{734,,colno}, that provide better context
information about the error:

@example
>>> re.compile("""
...     (?x)
...     .++
... """)
Traceback (most recent call last):
   ...
sre_constants.error: multiple repeat at position 16 (line 3, column 7)
@end example

（由 Serhiy Storchaka 在 bpo-22578@footnote{https://bugs.python.org/issue22578} 中贡献。）

@node readline<2>,selectors,re<4>,改进的模块<4>
@anchor{whatsnew/3 5 readline}@anchor{735}
@subsubsection readline


A new @ref{736,,append_history_file()} function can be used to append
the specified number of trailing elements in history to the given file.
(Contributed by Bruno Cauet in bpo-22940@footnote{https://bugs.python.org/issue22940}.)

@node selectors,shutil<2>,readline<2>,改进的模块<4>
@anchor{whatsnew/3 5 selectors}@anchor{737}
@subsubsection selectors


The new @ref{447,,DevpollSelector} supports efficient
@code{/dev/poll} polling on Solaris.
(Contributed by Giampaolo Rodola' in bpo-18931@footnote{https://bugs.python.org/issue18931}.)

@node shutil<2>,signal<2>,selectors,改进的模块<4>
@anchor{whatsnew/3 5 shutil}@anchor{738}
@subsubsection shutil


The @ref{25b,,move()} function now accepts a @emph{copy_function} argument,
allowing, for example, the @ref{259,,copy()} function to be used instead of
the default @ref{25a,,copy2()} if there is a need to ignore file metadata
when moving.
(Contributed by Claudiu Popa in bpo-19840@footnote{https://bugs.python.org/issue19840}.)

The @ref{21b,,make_archive()} function now supports the @emph{xztar} format.
(Contributed by Serhiy Storchaka in bpo-5411@footnote{https://bugs.python.org/issue5411}.)

@node signal<2>,smtpd,shutil<2>,改进的模块<4>
@anchor{whatsnew/3 5 signal}@anchor{739}
@subsubsection signal


On Windows, the @ref{3c6,,set_wakeup_fd()} function now also supports
socket handles.  (Contributed by Victor Stinner in bpo-22018@footnote{https://bugs.python.org/issue22018}.)

Various @code{SIG*} constants in the @ref{ea,,signal} module have been converted into
@ref{7b,,Enums}.  This allows meaningful names to be printed
during debugging, instead of integer "magic numbers".
(Contributed by Giampaolo Rodola' in bpo-21076@footnote{https://bugs.python.org/issue21076}.)

@node smtpd,smtplib,signal<2>,改进的模块<4>
@anchor{whatsnew/3 5 smtpd}@anchor{73a}
@subsubsection smtpd


Both the @ref{5fd,,SMTPServer} and @ref{5fc,,SMTPChannel} classes now
accept a @emph{decode_data} keyword argument to determine if the @code{DATA} portion of
the SMTP transaction is decoded using the @code{"utf-8"} codec or is instead
provided to the
@ref{5fe,,SMTPServer.process_message()}
method as a byte string.  The default is @code{True} for backward compatibility
reasons, but will change to @code{False} in Python 3.6.  If @emph{decode_data} is set
to @code{False}, the @code{process_message} method must be prepared to accept keyword
arguments.
(Contributed by Maciej Szulik in bpo-19662@footnote{https://bugs.python.org/issue19662}.)

The @ref{5fd,,SMTPServer} class now advertises the @code{8BITMIME} extension
(
@geindex RFC; RFC 6152
RFC 6152@footnote{https://tools.ietf.org/html/rfc6152.html}) if @emph{decode_data} has been set @code{True}.  If the client
specifies @code{BODY=8BITMIME} on the @code{MAIL} command, it is passed to
@ref{5fe,,SMTPServer.process_message()}
via the @emph{mail_options} keyword.
(Contributed by Milan Oberkirch and R.  David Murray in bpo-21795@footnote{https://bugs.python.org/issue21795}.)

The @ref{5fd,,SMTPServer} class now also supports the @code{SMTPUTF8}
extension (
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html}: Internationalized Email).  If the client specified
@code{SMTPUTF8 BODY=8BITMIME} on the @code{MAIL} command, they are passed to
@ref{5fe,,SMTPServer.process_message()}
via the @emph{mail_options} keyword.  It is the responsibility of the
@code{process_message} method to correctly handle the @code{SMTPUTF8} data.
(Contributed by Milan Oberkirch in bpo-21725@footnote{https://bugs.python.org/issue21725}.)

It is now possible to provide, directly or via name resolution, IPv6
addresses in the @ref{5fd,,SMTPServer} constructor, and have it
successfully connect.  (Contributed by Milan Oberkirch in bpo-14758@footnote{https://bugs.python.org/issue14758}.)

@node smtplib,sndhdr,smtpd,改进的模块<4>
@anchor{whatsnew/3 5 smtplib}@anchor{73b}
@subsubsection smtplib


A new @ref{73c,,SMTP.auth()} method provides a convenient way to
implement custom authentication mechanisms. (Contributed by Milan
Oberkirch in bpo-15014@footnote{https://bugs.python.org/issue15014}.)

The @ref{73d,,SMTP.set_debuglevel()} method now
accepts an additional debuglevel (2), which enables timestamps in debug
messages. (Contributed by Gavin Chappell and Maciej Szulik in bpo-16914@footnote{https://bugs.python.org/issue16914}.)

Both the @ref{73e,,SMTP.sendmail()} and
@ref{73f,,SMTP.send_message()} methods now
support 
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html} (SMTPUTF8).
(Contributed by Milan Oberkirch and R. David Murray in bpo-22027@footnote{https://bugs.python.org/issue22027}.)

@node sndhdr,socket<5>,smtplib,改进的模块<4>
@anchor{whatsnew/3 5 sndhdr}@anchor{740}
@subsubsection sndhdr


The @ref{741,,what()} and @ref{742,,whathdr()} functions  now return
a @ref{1b6,,namedtuple()}.  (Contributed by Claudiu Popa in
bpo-18615@footnote{https://bugs.python.org/issue18615}.)

@node socket<5>,ssl<6>,sndhdr,改进的模块<4>
@anchor{whatsnew/3 5 socket}@anchor{743}
@subsubsection socket


Functions with timeouts now use a monotonic clock, instead of a system clock.
(Contributed by Victor Stinner in bpo-22043@footnote{https://bugs.python.org/issue22043}.)

A new @ref{744,,socket.sendfile()} method allows
sending a file over a socket by using the high-performance @ref{352,,os.sendfile()}
function on UNIX, resulting in uploads being from 2 to 3 times faster than when
using plain @ref{674,,socket.send()}.
(Contributed by Giampaolo Rodola' in bpo-17552@footnote{https://bugs.python.org/issue17552}.)

The @ref{675,,socket.sendall()} method no longer resets the
socket timeout every time bytes are received or sent.  The socket timeout is
now the maximum total duration to send all data.
(Contributed by Victor Stinner in bpo-23853@footnote{https://bugs.python.org/issue23853}.)

The @emph{backlog} argument of the @ref{745,,socket.listen()}
method is now optional.  By default it is set to
@ref{746,,SOMAXCONN} or to @code{128}, whichever is less.
(Contributed by Charles-François Natali in bpo-21455@footnote{https://bugs.python.org/issue21455}.)

@node ssl<6>,sqlite3<3>,socket<5>,改进的模块<4>
@anchor{whatsnew/3 5 ssl}@anchor{747}
@subsubsection ssl


@menu
* Memory BIO Support:: 
* Application-Layer Protocol Negotiation Support:: 
* Other Changes:: 

@end menu

@node Memory BIO Support,Application-Layer Protocol Negotiation Support,,ssl<6>
@anchor{whatsnew/3 5 memory-bio-support}@anchor{748}@anchor{whatsnew/3 5 whatsnew-sslmemorybio}@anchor{632}
@subsubsection Memory BIO Support


（由 Geert Jansen 在 bpo-21965@footnote{https://bugs.python.org/issue21965} 中贡献。）

The new @ref{3db,,SSLObject} class has been added to provide SSL protocol
support for cases when the network I/O capabilities of @ref{3da,,SSLSocket}
are not necessary or are suboptimal.  @code{SSLObject} represents
an SSL protocol instance, but does not implement any network I/O methods, and
instead provides a memory buffer interface.  The new @ref{749,,MemoryBIO}
class can be used to pass data between Python and an SSL protocol instance.

The memory BIO SSL support is primarily intended to be used in frameworks
implementing asynchronous I/O for which @ref{3da,,SSLSocket}'s readiness
model ("select/poll") is inefficient.

A new @ref{3de,,SSLContext.wrap_bio()} method can be used
to create a new @code{SSLObject} instance.

@node Application-Layer Protocol Negotiation Support,Other Changes,Memory BIO Support,ssl<6>
@anchor{whatsnew/3 5 application-layer-protocol-negotiation-support}@anchor{74a}
@subsubsection Application-Layer Protocol Negotiation Support


（由 Benjamin Peterson 在 bpo-20188@footnote{https://bugs.python.org/issue20188} 中贡献。）

Where OpenSSL support is present, the @ref{f3,,ssl} module now implements
the @emph{Application-Layer Protocol Negotiation} TLS extension as described
in 
@geindex RFC; RFC 7301
RFC 7301@footnote{https://tools.ietf.org/html/rfc7301.html}.

The new @ref{74b,,SSLContext.set_alpn_protocols()}
can be used to specify which protocols a socket should advertise during
the TLS handshake.

The new
@ref{74c,,SSLSocket.selected_alpn_protocol()}
returns the protocol that was selected during the TLS handshake.
The @ref{74d,,HAS_ALPN} flag indicates whether ALPN support is present.

@node Other Changes,,Application-Layer Protocol Negotiation Support,ssl<6>
@anchor{whatsnew/3 5 other-changes}@anchor{74e}
@subsubsection Other Changes


There is a new @ref{74f,,SSLSocket.version()} method to
query the actual protocol version in use.
(Contributed by Antoine Pitrou in bpo-20421@footnote{https://bugs.python.org/issue20421}.)

The @ref{3da,,SSLSocket} class now implements
a @code{SSLSocket.sendfile()} method.
(Contributed by Giampaolo Rodola' in bpo-17552@footnote{https://bugs.python.org/issue17552}.)

The @code{SSLSocket.send()} method now raises either
the @ref{750,,ssl.SSLWantReadError} or @ref{751,,ssl.SSLWantWriteError} exception on a
non-blocking socket if the operation would block. Previously, it would return
@code{0}.  (Contributed by Nikolaus Rath in bpo-20951@footnote{https://bugs.python.org/issue20951}.)

The @ref{752,,cert_time_to_seconds()} function now interprets the input time
as UTC and not as local time, per 
@geindex RFC; RFC 5280
RFC 5280@footnote{https://tools.ietf.org/html/rfc5280.html}.  Additionally, the return
value is always an @ref{184,,int}. (Contributed by Akira Li in bpo-19940@footnote{https://bugs.python.org/issue19940}.)

New @code{SSLObject.shared_ciphers()} and
@ref{753,,SSLSocket.shared_ciphers()} methods return
the list of ciphers sent by the client during the handshake.
(Contributed by Benjamin Peterson in bpo-23186@footnote{https://bugs.python.org/issue23186}.)

The @ref{754,,SSLSocket.do_handshake()},
@ref{755,,SSLSocket.read()},
@code{SSLSocket.shutdown()}, and
@ref{756,,SSLSocket.write()} methods of the @ref{3da,,SSLSocket}
class no longer reset the socket timeout every time bytes are received or sent.
The socket timeout is now the maximum total duration of the method.
(Contributed by Victor Stinner in bpo-23853@footnote{https://bugs.python.org/issue23853}.)

The @ref{3d4,,match_hostname()} function now supports matching of IP addresses.
(Contributed by Antoine Pitrou in bpo-23239@footnote{https://bugs.python.org/issue23239}.)

@node sqlite3<3>,subprocess<3>,ssl<6>,改进的模块<4>
@anchor{whatsnew/3 5 sqlite3}@anchor{757}
@subsubsection sqlite3


The @ref{758,,Row} class now fully supports the sequence protocol,
in particular @ref{18e,,reversed()} iteration and slice indexing.
(Contributed by Claudiu Popa in bpo-10203@footnote{https://bugs.python.org/issue10203}; by Lucas Sinclair,
Jessica McKellar, and  Serhiy Storchaka in bpo-13583@footnote{https://bugs.python.org/issue13583}.)

@node subprocess<3>,sys<5>,sqlite3<3>,改进的模块<4>
@anchor{whatsnew/3 5 subprocess}@anchor{759}@anchor{whatsnew/3 5 whatsnew-subprocess}@anchor{635}
@subsubsection subprocess


The new @ref{3e5,,run()} function has been added.
It runs the specified command and returns a
@ref{75a,,CompletedProcess} object, which describes a finished
process.  The new API is more consistent and is the recommended approach
to invoking subprocesses in Python code that does not need to maintain
compatibility with earlier Python versions.
(Contributed by Thomas Kluyver in bpo-23342@footnote{https://bugs.python.org/issue23342}.)

示例:

@example
>>> subprocess.run(["ls", "-l"])  # doesn't capture output
CompletedProcess(args=['ls', '-l'], returncode=0)

>>> subprocess.run("exit 1", shell=True, check=True)
Traceback (most recent call last):
  ...
subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1

>>> subprocess.run(["ls", "-l", "/dev/null"], stdout=subprocess.PIPE)
CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,
stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n')
@end example

@node sys<5>,sysconfig,subprocess<3>,改进的模块<4>
@anchor{whatsnew/3 5 sys}@anchor{75b}
@subsubsection sys


A new @code{set_coroutine_wrapper()} function allows setting a global
hook that will be called whenever a @ref{1a6,,coroutine object}
is created by an @ref{284,,async def} function.  A corresponding
@code{get_coroutine_wrapper()} can be used to obtain a currently set
wrapper.  Both functions are @ref{341,,provisional},
and are intended for debugging purposes only.  (Contributed by Yury Selivanov
in bpo-24017@footnote{https://bugs.python.org/issue24017}.)

A new @ref{75c,,is_finalizing()} function can be used to check if the Python
interpreter is @ref{75d,,shutting down}.
(Contributed by Antoine Pitrou in bpo-22696@footnote{https://bugs.python.org/issue22696}.)

@node sysconfig,tarfile<2>,sys<5>,改进的模块<4>
@anchor{whatsnew/3 5 sysconfig}@anchor{75e}
@subsubsection sysconfig


The name of the user scripts directory on Windows now includes the first
two components of the Python version. (Contributed by Paul Moore
in bpo-23437@footnote{https://bugs.python.org/issue23437}.)

@node tarfile<2>,threading<3>,sysconfig,改进的模块<4>
@anchor{whatsnew/3 5 tarfile}@anchor{75f}
@subsubsection tarfile


The @emph{mode} argument of the @ref{760,,open()} function now accepts @code{"x"}
to request exclusive creation.  (Contributed by Berker Peksag in bpo-21717@footnote{https://bugs.python.org/issue21717}.)

The @ref{761,,TarFile.extractall()} and
@ref{762,,TarFile.extract()} methods now take a keyword
argument @emph{numeric_owner}.  If set to @code{True}, the extracted files and
directories will be owned by the numeric @code{uid} and @code{gid} from the tarfile.
If set to @code{False} (the default, and the behavior in versions prior to 3.5),
they will be owned by the named user and group in the tarfile.
(Contributed by Michael Vogt and Eric Smith in bpo-23193@footnote{https://bugs.python.org/issue23193}.)

The @ref{763,,TarFile.list()} now accepts an optional
@emph{members} keyword argument that can be set to a subset of the list returned
by @ref{764,,TarFile.getmembers()}.
(Contributed by Serhiy Storchaka in bpo-21549@footnote{https://bugs.python.org/issue21549}.)

@node threading<3>,time<4>,tarfile<2>,改进的模块<4>
@anchor{whatsnew/3 5 threading}@anchor{765}
@subsubsection threading


Both the @ref{766,,Lock.acquire()} and
@ref{767,,RLock.acquire()} methods
now use a monotonic clock for timeout management.
(Contributed by Victor Stinner in bpo-22043@footnote{https://bugs.python.org/issue22043}.)

@node time<4>,timeit<2>,threading<3>,改进的模块<4>
@anchor{whatsnew/3 5 time}@anchor{768}
@subsubsection time


The @ref{769,,monotonic()} function is now always available.
(Contributed by Victor Stinner in bpo-22043@footnote{https://bugs.python.org/issue22043}.)

@node timeit<2>,tkinter<5>,time<4>,改进的模块<4>
@anchor{whatsnew/3 5 timeit}@anchor{76a}
@subsubsection timeit


A new command line option @code{-u} or @code{--unit=@emph{U}} can be used to specify the time
unit for the timer output.  Supported options are @code{usec}, @code{msec},
or @code{sec}.  (Contributed by Julian Gindi in bpo-18983@footnote{https://bugs.python.org/issue18983}.)

The @ref{76b,,timeit()} function has a new @emph{globals} parameter for
specifying the namespace in which the code will be running.
(Contributed by Ben Roberts in bpo-2527@footnote{https://bugs.python.org/issue2527}.)

@node tkinter<5>,回溯<2>,timeit<2>,改进的模块<4>
@anchor{whatsnew/3 5 tkinter}@anchor{76c}
@subsubsection tkinter


The @code{tkinter._fix} module used for setting up the Tcl/Tk environment
on Windows has been replaced by a private function in the @code{_tkinter}
module which makes no permanent changes to environment variables.
(Contributed by Zachary Ware in bpo-20035@footnote{https://bugs.python.org/issue20035}.)

@node 回溯<2>,types<2>,tkinter<5>,改进的模块<4>
@anchor{whatsnew/3 5 traceback}@anchor{76d}@anchor{whatsnew/3 5 whatsnew-traceback}@anchor{636}
@subsubsection 回溯


New @ref{76e,,walk_stack()} and @ref{76f,,walk_tb()}
functions to conveniently traverse frame and traceback objects.
(Contributed by Robert Collins in bpo-17911@footnote{https://bugs.python.org/issue17911}.)

New lightweight classes: @ref{770,,TracebackException},
@ref{771,,StackSummary}, and @ref{772,,FrameSummary}.
(Contributed by Robert Collins in bpo-17911@footnote{https://bugs.python.org/issue17911}.)

Both the @ref{773,,print_tb()} and @ref{774,,print_stack()} functions
now support negative values for the @emph{limit} argument.
(Contributed by Dmitry Kazakov in bpo-22619@footnote{https://bugs.python.org/issue22619}.)

@node types<2>,unicodedata<4>,回溯<2>,改进的模块<4>
@anchor{whatsnew/3 5 types}@anchor{775}
@subsubsection types


A new @ref{776,,coroutine()} function to transform
@ref{451,,generator} and
@ref{6af,,generator-like} objects into
@ref{513,,awaitables}.
(Contributed by Yury Selivanov in bpo-24017@footnote{https://bugs.python.org/issue24017}.)

A new type called @ref{777,,CoroutineType}, which is used for
@ref{1a6,,coroutine} objects created by @ref{284,,async def} functions.
(Contributed by Yury Selivanov in bpo-24400@footnote{https://bugs.python.org/issue24400}.)

@node unicodedata<4>,unittest<3>,types<2>,改进的模块<4>
@anchor{whatsnew/3 5 unicodedata}@anchor{778}
@subsubsection unicodedata


The @ref{11a,,unicodedata} module now uses data from Unicode 8.0.0@footnote{http://unicode.org/versions/Unicode8.0.0/}.

@node unittest<3>,unittest mock<3>,unicodedata<4>,改进的模块<4>
@anchor{whatsnew/3 5 unittest}@anchor{779}
@subsubsection unittest


The @ref{77a,,TestLoader.loadTestsFromModule()}
method now accepts a keyword-only argument @emph{pattern} which is passed to
@code{load_tests} as the third argument.  Found packages are now checked for
@code{load_tests} regardless of whether their path matches @emph{pattern}, because it
is impossible for a package name to match the default pattern.
(Contributed by Robert Collins and Barry A. Warsaw in bpo-16662@footnote{https://bugs.python.org/issue16662}.)

Unittest discovery errors now are exposed in the
@ref{77b,,TestLoader.errors} attribute of the
@ref{77c,,TestLoader} instance.
(Contributed by Robert Collins in bpo-19746@footnote{https://bugs.python.org/issue19746}.)

A new command line option @code{--locals} to show local variables in
tracebacks.  (Contributed by Robert Collins in bpo-22936@footnote{https://bugs.python.org/issue22936}.)

@node unittest mock<3>,urllib,unittest<3>,改进的模块<4>
@anchor{whatsnew/3 5 unittest-mock}@anchor{77d}
@subsubsection unittest.mock


The @ref{249,,Mock} class has the following improvements:


@itemize *

@item 
The class constructor has a new @emph{unsafe} parameter, which causes mock
objects to raise @ref{393,,AttributeError} on attribute names starting
with @code{"assert"}.
(Contributed by Kushal Das in bpo-21238@footnote{https://bugs.python.org/issue21238}.)

@item 
A new @ref{77e,,Mock.assert_not_called()}
method to check if the mock object was called.
(Contributed by Kushal Das in bpo-21262@footnote{https://bugs.python.org/issue21262}.)
@end itemize

The @ref{77f,,MagicMock} class now supports @ref{780,,__truediv__()},
@ref{781,,__divmod__()} and @ref{642,,__matmul__()} operators.
(Contributed by Johannes Baiter in bpo-20968@footnote{https://bugs.python.org/issue20968}, and Håkan Lövdahl
in bpo-23581@footnote{https://bugs.python.org/issue23581} and bpo-23568@footnote{https://bugs.python.org/issue23568}.)

It is no longer necessary to explicitly pass @code{create=True} to the
@ref{782,,patch()} function when patching builtin names.
(Contributed by Kushal Das in bpo-17660@footnote{https://bugs.python.org/issue17660}.)

@node urllib,wsgiref,unittest mock<3>,改进的模块<4>
@anchor{whatsnew/3 5 urllib}@anchor{783}
@subsubsection urllib


A new
@ref{784,,request.HTTPPasswordMgrWithPriorAuth}
class allows HTTP Basic Authentication credentials to be managed so as to
eliminate unnecessary @code{401} response handling, or to unconditionally send
credentials on the first request in order to communicate with servers that
return a @code{404} response instead of a @code{401} if the @code{Authorization} header
is not sent. (Contributed by Matej Cepl in bpo-19494@footnote{https://bugs.python.org/issue19494} and Akshit Khurana in
bpo-7159@footnote{https://bugs.python.org/issue7159}.)

A new @emph{quote_via} argument for the
@ref{785,,parse.urlencode()}
function provides a way to control the encoding of query parts if needed.
(Contributed by Samwyse and Arnon Yaari in bpo-13866@footnote{https://bugs.python.org/issue13866}.)

The @ref{786,,request.urlopen()} function accepts an
@ref{3dc,,ssl.SSLContext} object as a @emph{context} argument, which will be used for
the HTTPS connection.  (Contributed by Alex Gaynor in bpo-22366@footnote{https://bugs.python.org/issue22366}.)

The @ref{787,,parse.urljoin()} was updated to use the
@geindex RFC; RFC 3986
RFC 3986@footnote{https://tools.ietf.org/html/rfc3986.html} semantics for the resolution of relative URLs, rather than
@geindex RFC; RFC 1808
RFC 1808@footnote{https://tools.ietf.org/html/rfc1808.html} and 
@geindex RFC; RFC 2396
RFC 2396@footnote{https://tools.ietf.org/html/rfc2396.html}.
(Contributed by Demian Brecht and Senthil Kumaran in bpo-22118@footnote{https://bugs.python.org/issue22118}.)

@node wsgiref,xmlrpc<2>,urllib,改进的模块<4>
@anchor{whatsnew/3 5 wsgiref}@anchor{788}
@subsubsection wsgiref


The @emph{headers} argument of the @ref{789,,headers.Headers}
class constructor is now optional.
(Contributed by Pablo Torres Navarrete and SilentGhost in bpo-5800@footnote{https://bugs.python.org/issue5800}.)

@node xmlrpc<2>,xml sax,wsgiref,改进的模块<4>
@anchor{whatsnew/3 5 xmlrpc}@anchor{78a}
@subsubsection xmlrpc


The @ref{255,,client.ServerProxy} class now supports
the @ref{563,,context manager} protocol.
(Contributed by Claudiu Popa in bpo-20627@footnote{https://bugs.python.org/issue20627}.)

The @ref{255,,client.ServerProxy} constructor now accepts
an optional @ref{3dc,,ssl.SSLContext} instance.
(Contributed by Alex Gaynor in bpo-22960@footnote{https://bugs.python.org/issue22960}.)

@node xml sax,zipfile<3>,xmlrpc<2>,改进的模块<4>
@anchor{whatsnew/3 5 xml-sax}@anchor{78b}
@subsubsection xml.sax


SAX parsers now support a character stream of the
@ref{78c,,xmlreader.InputSource} object.
(Contributed by Serhiy Storchaka in bpo-2175@footnote{https://bugs.python.org/issue2175}.)

@ref{78d,,parseString()} now accepts a @ref{329,,str} instance.
(Contributed by Serhiy Storchaka in bpo-10590@footnote{https://bugs.python.org/issue10590}.)

@node zipfile<3>,,xml sax,改进的模块<4>
@anchor{whatsnew/3 5 zipfile}@anchor{78e}
@subsubsection zipfile


ZIP output can now be written to unseekable streams.
(Contributed by Serhiy Storchaka in bpo-23252@footnote{https://bugs.python.org/issue23252}.)

The @emph{mode} argument of @ref{5b7,,ZipFile.open()} method now
accepts @code{"x"} to request exclusive creation.
(Contributed by Serhiy Storchaka in bpo-21717@footnote{https://bugs.python.org/issue21717}.)

@node 其他模块级更改,性能优化<4>,改进的模块<4>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 other-module-level-changes}@anchor{78f}
@subsection 其他模块级更改


Many functions in the @ref{b3,,mmap}, @ref{c6,,ossaudiodev}, @ref{ef,,socket},
@ref{f3,,ssl}, and @ref{1c,,codecs} modules now accept writable
@ref{5e3,,bytes-like objects}.
(Contributed by Serhiy Storchaka in bpo-23001@footnote{https://bugs.python.org/issue23001}.)

@node 性能优化<4>,构建和 C API 的改变<3>,其他模块级更改,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 optimizations}@anchor{790}
@subsection 性能优化


The @ref{64e,,os.walk()} function has been sped up by 3 to 5 times on POSIX systems,
and by 7 to 20 times on Windows.  This was done using the new @ref{25f,,os.scandir()}
function, which exposes file information from the underlying @code{readdir} or
@code{FindFirstFile}/@code{FindNextFile} system calls.  (Contributed by
Ben Hoyt with help from Victor Stinner in bpo-23605@footnote{https://bugs.python.org/issue23605}.)

Construction of @code{bytes(int)} (filled by zero bytes) is faster and uses less
memory for large objects. @code{calloc()} is used instead of @code{malloc()} to
allocate memory for these objects.
(Contributed by Victor Stinner in bpo-21233@footnote{https://bugs.python.org/issue21233}.)

Some operations on @ref{a2,,ipaddress} @ref{398,,IPv4Network} and
@ref{397,,IPv6Network} have been massively sped up, such as
@ref{791,,subnets()}, @ref{792,,supernet()},
@ref{793,,summarize_address_range()}, @ref{794,,collapse_addresses()}.
The speed up can range from 3 to 15 times.
(Contributed by Antoine Pitrou, Michel Albert, and Markus in
bpo-21486@footnote{https://bugs.python.org/issue21486}, bpo-21487@footnote{https://bugs.python.org/issue21487}, bpo-20826@footnote{https://bugs.python.org/issue20826}, bpo-23266@footnote{https://bugs.python.org/issue23266}.)

Pickling of @ref{a2,,ipaddress} objects was optimized to produce significantly
smaller output.  (Contributed by Serhiy Storchaka in bpo-23133@footnote{https://bugs.python.org/issue23133}.)

Many operations on @ref{795,,io.BytesIO} are now 50% to 100% faster.
(Contributed by Serhiy Storchaka in bpo-15381@footnote{https://bugs.python.org/issue15381} and David Wilson in
bpo-22003@footnote{https://bugs.python.org/issue22003}.)

The @ref{796,,marshal.dumps()} function is now faster: 65--85% with versions 3
and 4, 20--25% with versions 0 to 2 on typical data, and up to 5 times in
best cases.
(Contributed by Serhiy Storchaka in bpo-20416@footnote{https://bugs.python.org/issue20416} and bpo-23344@footnote{https://bugs.python.org/issue23344}.)

The UTF-32 encoder is now 3 to 7 times faster.
(Contributed by Serhiy Storchaka in bpo-15027@footnote{https://bugs.python.org/issue15027}.)

Regular expressions are now parsed up to 10% faster.
(Contributed by Serhiy Storchaka in bpo-19380@footnote{https://bugs.python.org/issue19380}.)

The @ref{600,,json.dumps()} function was optimized to run with
@code{ensure_ascii=False} as fast as with @code{ensure_ascii=True}.
(Contributed by Naoki Inada in bpo-23206@footnote{https://bugs.python.org/issue23206}.)

The @ref{797,,PyObject_IsInstance()} and @ref{798,,PyObject_IsSubclass()}
functions have been sped up in the common case that the second argument
has @ref{603,,type} as its metaclass.
(Contributed Georg Brandl by in bpo-22540@footnote{https://bugs.python.org/issue22540}.)

Method caching was slightly improved, yielding up to 5% performance
improvement in some benchmarks.
(Contributed by Antoine Pitrou in bpo-22847@footnote{https://bugs.python.org/issue22847}.)

Objects from the @ref{dc,,random} module now use 50% less memory on 64-bit
builds.  (Contributed by Serhiy Storchaka in bpo-23488@footnote{https://bugs.python.org/issue23488}.)

The @ref{1d7,,property()} getter calls are up to 25% faster.
(Contributed by Joe Jevnik in bpo-23910@footnote{https://bugs.python.org/issue23910}.)

Instantiation of @ref{185,,fractions.Fraction} is now up to 30% faster.
(Contributed by Stefan Behnel in bpo-22464@footnote{https://bugs.python.org/issue22464}.)

String methods @ref{799,,find()}, @ref{79a,,rfind()}, @ref{79b,,split()},
@ref{79c,,partition()} and the @ref{79d,,in} string operator are now significantly
faster for searching 1-character substrings.
(Contributed by Serhiy Storchaka in bpo-23573@footnote{https://bugs.python.org/issue23573}.)

@node 构建和 C API 的改变<3>,弃用<3>,性能优化<4>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 build-and-c-api-changes}@anchor{79e}
@subsection 构建和 C API 的改变


增加了 @code{calloc} 函数


@itemize *

@item 
@ref{79f,,PyMem_RawCalloc()},

@item 
@ref{7a0,,PyMem_Calloc()},

@item 
@ref{7a1,,PyObject_Calloc()}.
@end itemize

(Victor Stinner 贡献于 bpo-21233@footnote{https://bugs.python.org/issue21233}.)

新的 encoding/decoding 帮助函数:


@itemize *

@item 
@ref{436,,Py_DecodeLocale()} (替代 @code{_Py_char2wchar()}),

@item 
@ref{437,,Py_EncodeLocale()} (替代 @code{_Py_wchar2char()}).
@end itemize

（由 Victor Stinner 在 bpo-18395@footnote{https://bugs.python.org/issue18395} 中贡献。）

A new @ref{7a2,,PyCodec_NameReplaceErrors()} function to replace the unicode
encode error with @code{\N@{...@}} escapes.
(Contributed by Serhiy Storchaka in bpo-19676@footnote{https://bugs.python.org/issue19676}.)

A new @ref{7a3,,PyErr_FormatV()} function similar to @ref{7a4,,PyErr_Format()},
but accepts a @code{va_list} argument.
(Contributed by Antoine Pitrou in bpo-18711@footnote{https://bugs.python.org/issue18711}.)

A new @code{PyExc_RecursionError} exception.
(Contributed by Georg Brandl in bpo-19235@footnote{https://bugs.python.org/issue19235}.)

New @ref{7a5,,PyModule_FromDefAndSpec()}, @ref{7a6,,PyModule_FromDefAndSpec2()},
and @ref{7a7,,PyModule_ExecDef()} functions introduced by 
@geindex Python 提高建议; PEP 489
PEP 489@footnote{https://www.python.org/dev/peps/pep-0489} --
multi-phase extension module initialization.
(Contributed by Petr Viktorin in bpo-24268@footnote{https://bugs.python.org/issue24268}.)

New @ref{7a8,,PyNumber_MatrixMultiply()} and
@ref{7a9,,PyNumber_InPlaceMatrixMultiply()} functions to perform matrix
multiplication.
(Contributed by Benjamin Peterson in bpo-21176@footnote{https://bugs.python.org/issue21176}.  See also 
@geindex Python 提高建议; PEP 465
PEP 465@footnote{https://www.python.org/dev/peps/pep-0465}
for details.)

The @ref{2d7,,PyTypeObject.tp_finalize} slot is now part of the stable ABI.

Windows builds now require Microsoft Visual C++ 14.0, which
is available as part of Visual Studio 2015@footnote{https://www.visualstudio.com/}.

Extension modules now include a platform information tag in their filename on
some platforms (the tag is optional, and CPython will import extensions without
it, although if the tag is present and mismatched, the extension won't be
loaded):


@itemize *

@item 
On Linux, extension module filenames end with
@code{.cpython-<major><minor>m-<architecture>-<os>.pyd}:


@itemize *

@item 
@code{<major>} is the major number of the Python version;
for Python 3.5 this is @code{3}.

@item 
@code{<minor>} is the minor number of the Python version;
for Python 3.5 this is @code{5}.

@item 
@code{<architecture>} is the hardware architecture the extension module
was built to run on. It's most commonly either @code{i386} for 32-bit Intel
platforms or @code{x86_64} for 64-bit Intel (and AMD) platforms.

@item 
@code{<os>} is always @code{linux-gnu}, except for extensions built to
talk to the 32-bit ABI on 64-bit platforms, in which case it is
@code{linux-gnu32} (and @code{<architecture>} will be @code{x86_64}).
@end itemize

@item 
On Windows, extension module filenames end with
@code{<debug>.cp<major><minor>-<platform>.pyd}:


@itemize *

@item 
@code{<major>} is the major number of the Python version;
for Python 3.5 this is @code{3}.

@item 
@code{<minor>} is the minor number of the Python version;
for Python 3.5 this is @code{5}.

@item 
@code{<platform>} is the platform the extension module was built for,
either @code{win32} for Win32, @code{win_amd64} for Win64, @code{win_ia64} for
Windows Itanium 64, and @code{win_arm} for Windows on ARM.

@item 
If built in debug mode, @code{<debug>} will be @code{_d},
otherwise it will be blank.
@end itemize

@item 
On OS X platforms, extension module filenames now end with @code{-darwin.so}.

@item 
On all other platforms, extension module filenames are the same as they were
with Python 3.4.
@end itemize

@node 弃用<3>,移除<2>,构建和 C API 的改变<3>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 deprecated}@anchor{7aa}
@subsection 弃用


@menu
* 新关键字: 新关键字<2>. 
* 已弃用的 Python 行为: 已弃用的 Python 行为<3>. 
* 不支持的操作系统:: 
* 已弃用的 Python 模块、函数和方法: 已弃用的 Python 模块、函数和方法<3>. 

@end menu

@node 新关键字<2>,已弃用的 Python 行为<3>,,弃用<3>
@anchor{whatsnew/3 5 new-keywords}@anchor{7ab}
@subsubsection 新关键字


@code{async} and @code{await} are not recommended to be used as variable, class,
function or module names.  Introduced by 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} in Python 3.5, they will
become proper keywords in Python 3.7.

@node 已弃用的 Python 行为<3>,不支持的操作系统,新关键字<2>,弃用<3>
@anchor{whatsnew/3 5 deprecated-python-behavior}@anchor{7ac}
@subsubsection 已弃用的 Python 行为


Raising the @ref{480,,StopIteration} exception inside a generator will now generate a silent
@ref{279,,PendingDeprecationWarning}, which will become a non-silent deprecation
warning in Python 3.6 and will trigger a @ref{2ba,,RuntimeError} in Python 3.7.
See @ref{5d2,,PEP 479; Change StopIteration handling inside generators}
for details.

@node 不支持的操作系统,已弃用的 Python 模块、函数和方法<3>,已弃用的 Python 行为<3>,弃用<3>
@anchor{whatsnew/3 5 unsupported-operating-systems}@anchor{7ad}
@subsubsection 不支持的操作系统


Windows XP is no longer supported by Microsoft, thus, per 
@geindex Python 提高建议; PEP 11
PEP 11@footnote{https://www.python.org/dev/peps/pep-0011}, CPython
3.5 is no longer officially supported on this OS.

@node 已弃用的 Python 模块、函数和方法<3>,,不支持的操作系统,弃用<3>
@anchor{whatsnew/3 5 deprecated-python-modules-functions-and-methods}@anchor{7ae}
@subsubsection 已弃用的 Python 模块、函数和方法


The @ref{82,,formatter} module has now graduated to full deprecation and is still
slated for removal in Python 3.6.

The @code{asyncio.async()} function is deprecated in favor of
@ref{511,,ensure_future()}.

The @ref{ec,,smtpd} module has in the past always decoded the DATA portion of
email messages using the @code{utf-8} codec.  This can now be controlled by the
new @emph{decode_data} keyword to @ref{5fd,,SMTPServer}.  The default value is
@code{True}, but this default is deprecated.  Specify the @emph{decode_data} keyword
with an appropriate value to avoid the deprecation warning.

Directly assigning values to the @ref{488,,key},
@ref{489,,value} and
@ref{48a,,coded_value} of @ref{487,,http.cookies.Morsel}
objects is deprecated.  Use the @ref{48b,,set()} method
instead.  In addition, the undocumented @emph{LegalChars} parameter of
@ref{48b,,set()} is deprecated, and is now ignored.

Passing a format string as keyword argument @emph{format_string} to the
@ref{486,,format()} method of the @ref{7af,,string.Formatter}
class has been deprecated.
(Contributed by Serhiy Storchaka in bpo-23671@footnote{https://bugs.python.org/issue23671}.)

The @code{platform.dist()} and @code{platform.linux_distribution()} functions
are now deprecated.  Linux distributions use too many different ways of
describing themselves, so the functionality is left to a package.
(Contributed by Vajrasky Kok and Berker Peksag in bpo-1322@footnote{https://bugs.python.org/issue1322}.)

The previously undocumented @code{from_function} and @code{from_builtin} methods of
@ref{6ed,,inspect.Signature} are deprecated.  Use the new
@ref{6f0,,Signature.from_callable()}
method instead. (Contributed by Yury Selivanov in bpo-24248@footnote{https://bugs.python.org/issue24248}.)

The @ref{557,,inspect.getargspec()} function is deprecated and scheduled to be
removed in Python 3.6.  (See bpo-20438@footnote{https://bugs.python.org/issue20438} for details.)

The @ref{a0,,inspect} @ref{558,,getfullargspec()},
@ref{7b0,,getcallargs()}, and @ref{7b1,,formatargspec()} functions are
deprecated in favor of the @ref{556,,inspect.signature()} API. (Contributed by Yury
Selivanov in bpo-20438@footnote{https://bugs.python.org/issue20438}.)

@ref{7b2,,getargvalues()} and @ref{7b3,,formatargvalues()} functions
were inadvertently marked as deprecated with the release of Python 3.5.0.

Use of @ref{3c1,,re.LOCALE} flag with str patterns or @ref{3c0,,re.ASCII} is now
deprecated.  (Contributed by Serhiy Storchaka in bpo-22407@footnote{https://bugs.python.org/issue22407}.)

Use of unrecognized special sequences consisting of @code{'\'} and an ASCII letter
in regular expression patterns and replacement patterns now raises a
deprecation warning and will be forbidden in Python 3.6.
(Contributed by Serhiy Storchaka in bpo-23622@footnote{https://bugs.python.org/issue23622}.)

The undocumented and unofficial @emph{use_load_tests} default argument of the
@ref{77a,,unittest.TestLoader.loadTestsFromModule()} method now is
deprecated and ignored.
(Contributed by Robert Collins and Barry A. Warsaw in bpo-16662@footnote{https://bugs.python.org/issue16662}.)

@node 移除<2>,移植到Python 3 5,弃用<3>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 removed}@anchor{7b4}
@subsection 移除


@menu
* API 与特性的移除: API 与特性的移除<4>. 

@end menu

@node API 与特性的移除<4>,,,移除<2>
@anchor{whatsnew/3 5 api-and-feature-removals}@anchor{7b5}
@subsubsection API 与特性的移除


The following obsolete and previously deprecated APIs and features have been
removed:


@itemize *

@item 
The @code{__version__} attribute has been dropped from the email package.  The
email code hasn't been shipped separately from the stdlib for a long time,
and the @code{__version__} string was not updated in the last few releases.

@item 
The internal @code{Netrc} class in the @ref{84,,ftplib} module was deprecated in
3.4, and has now been removed.
(Contributed by Matt Chaput in bpo-6623@footnote{https://bugs.python.org/issue6623}.)

@item 
The concept of @code{.pyo} files has been removed.

@item 
The JoinableQueue class in the provisional @ref{a,,asyncio} module was
deprecated in 3.4.4 and is now removed.
(Contributed by A. Jesse Jiryu Davis in bpo-23464@footnote{https://bugs.python.org/issue23464}.)
@end itemize

@node 移植到Python 3 5,Python 3 5 4 的显著变化,移除<2>,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 porting-to-python-3-5}@anchor{7b6}
@subsection 移植到Python 3.5


本节列出了先前描述的更改以及可能需要更改代码的其他错误修正.

@menu
* Python 行为的改变: Python 行为的改变<2>. 
* Python API 的变化: Python API 的变化<4>. 
* C API 的变化: C API 的变化<4>. 

@end menu

@node Python 行为的改变<2>,Python API 的变化<4>,,移植到Python 3 5
@anchor{whatsnew/3 5 changes-in-python-behavior}@anchor{7b7}
@subsubsection Python 行为的改变



@itemize *

@item 
由于一个疏忽，之前的 Python 版本会错误地接受以下语法:

@example
f(1 for x in [1], *args)
f(1 for x in [1], **kwargs)
@end example

Python 3.5 now correctly raises a @ref{452,,SyntaxError}, as generator
expressions must be put in parentheses if not a sole argument to a function.
@end itemize

@node Python API 的变化<4>,C API 的变化<4>,Python 行为的改变<2>,移植到Python 3 5
@anchor{whatsnew/3 5 changes-in-the-python-api}@anchor{7b8}
@subsubsection Python API 的变化



@itemize *

@item 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}: System calls are now retried when interrupted by a signal instead
of raising @ref{653,,InterruptedError} if the Python signal handler does not
raise an exception.

@item 
Before Python 3.5, a @ref{4ed,,datetime.time} object was considered to be false
if it represented midnight in UTC.  This behavior was considered obscure and
error-prone and has been removed in Python 3.5.  See bpo-13936@footnote{https://bugs.python.org/issue13936} for full
details.

@item 
The @code{ssl.SSLSocket.send()} method now raises either
@ref{750,,ssl.SSLWantReadError} or @ref{751,,ssl.SSLWantWriteError}
on a non-blocking socket if the operation would block.  Previously,
it would return @code{0}.  (Contributed by Nikolaus Rath in bpo-20951@footnote{https://bugs.python.org/issue20951}.)

@item 
The @code{__name__} attribute of generators is now set from the function name,
instead of being set from the code name. Use @code{gen.gi_code.co_name} to
retrieve the code name. Generators also have a new @code{__qualname__}
attribute, the qualified name, which is now used for the representation
of a generator (@code{repr(gen)}).
(Contributed by Victor Stinner in bpo-21205@footnote{https://bugs.python.org/issue21205}.)

@item 
The deprecated "strict" mode and argument of @ref{7b9,,HTMLParser},
@code{HTMLParser.error()}, and the @code{HTMLParserError} exception have been
removed.  (Contributed by Ezio Melotti in bpo-15114@footnote{https://bugs.python.org/issue15114}.)
The @emph{convert_charrefs} argument of @ref{7b9,,HTMLParser} is
now @code{True} by default.  (Contributed by Berker Peksag in bpo-21047@footnote{https://bugs.python.org/issue21047}.)

@item 
Although it is not formally part of the API, it is worth noting for porting
purposes (ie: fixing tests) that error messages that were previously of the
form "'sometype' does not support the buffer protocol" are now of the form "a
@ref{5e3,,bytes-like object} is required, not 'sometype'".
(Contributed by Ezio Melotti in bpo-16518@footnote{https://bugs.python.org/issue16518}.)

@item 
If the current directory is set to a directory that no longer exists then
@ref{7ba,,FileNotFoundError} will no longer be raised and instead
@ref{7bb,,find_spec()} will return @code{None}
@strong{without} caching @code{None} in @ref{498,,sys.path_importer_cache}, which is
different than the typical case (bpo-22834@footnote{https://bugs.python.org/issue22834}).

@item 
HTTP status code and messages from @ref{94,,http.client} and @ref{97,,http.server}
were refactored into a common @ref{6dc,,HTTPStatus} enum.  The values in
@ref{94,,http.client} and @ref{97,,http.server} remain available for backwards
compatibility.  (Contributed by Demian Brecht in bpo-21793@footnote{https://bugs.python.org/issue21793}.)

@item 
When an import loader defines @code{importlib.machinery.Loader.exec_module()}
it is now expected to also define
@code{create_module()} (raises a
@ref{278,,DeprecationWarning} now, will be an error in Python 3.6). If the loader
inherits from @ref{7bc,,importlib.abc.Loader} then there is nothing to do, else
simply define @code{create_module()} to return
@code{None}.  (Contributed by Brett Cannon in bpo-23014@footnote{https://bugs.python.org/issue23014}.)

@item 
The @ref{3c2,,re.split()} function always ignored empty pattern matches, so the
@code{"x*"} pattern worked the same as @code{"x+"}, and the @code{"\b"} pattern never
worked.  Now @ref{3c2,,re.split()} raises a warning if the pattern could match
an empty string.  For compatibility, use patterns that never match an empty
string (e.g. @code{"x+"} instead of @code{"x*"}).  Patterns that could only match
an empty string (such as @code{"\b"}) now raise an error.
(Contributed by Serhiy Storchaka in bpo-22818@footnote{https://bugs.python.org/issue22818}.)

@item 
The @ref{487,,http.cookies.Morsel} dict-like interface has been made self
consistent:  morsel comparison now takes the @ref{488,,key}
and @ref{489,,value} into account,
@ref{7bd,,copy()} now results in a
@ref{487,,Morsel} instance rather than a @ref{1b8,,dict}, and
@ref{7be,,update()} will now raise an exception if any of the
keys in the update dictionary are invalid.  In addition, the undocumented
@emph{LegalChars} parameter of @ref{48b,,set()} is deprecated and
is now ignored.  (Contributed by Demian Brecht in bpo-2211@footnote{https://bugs.python.org/issue2211}.)

@item 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} has removed @code{.pyo} files from Python and introduced the optional
@code{opt-} tag in @code{.pyc} file names. The
@ref{552,,importlib.util.cache_from_source()} has gained an @emph{optimization}
parameter to help control the @code{opt-} tag. Because of this, the
@emph{debug_override} parameter of the function is now deprecated. @cite{.pyo} files
are also no longer supported as a file argument to the Python interpreter and
thus serve no purpose when distributed on their own (i.e. sourceless code
distribution). Due to the fact that the magic number for bytecode has changed
in Python 3.5, all old @cite{.pyo} files from previous versions of Python are
invalid regardless of this PEP.

@item 
The @ref{ef,,socket} module now exports the @ref{7bf,,CAN_RAW_FD_FRAMES}
constant on linux 3.6 and greater.

@item 
The @ref{752,,ssl.cert_time_to_seconds()} function now interprets the input time
as UTC and not as local time, per 
@geindex RFC; RFC 5280
RFC 5280@footnote{https://tools.ietf.org/html/rfc5280.html}.  Additionally, the return
value is always an @ref{184,,int}. (Contributed by Akira Li in bpo-19940@footnote{https://bugs.python.org/issue19940}.)

@item 
The @code{pygettext.py} Tool now uses the standard +NNNN format for timezones in
the POT-Creation-Date header.

@item 
The @ref{ed,,smtplib} module now uses @ref{308,,sys.stderr} instead of the previous
module-level @code{stderr} variable for debug output.  If your (test)
program depends on patching the module-level variable to capture the debug
output, you will need to update it to capture sys.stderr instead.

@item 
The @ref{7c0,,str.startswith()} and @ref{7c1,,str.endswith()} methods no longer return
@code{True} when finding the empty string and the indexes are completely out of
range.  (Contributed by Serhiy Storchaka in bpo-24284@footnote{https://bugs.python.org/issue24284}.)

@item 
The @ref{1d6,,inspect.getdoc()} function now returns documentation strings
inherited from base classes.  Documentation strings no longer need to be
duplicated if the inherited documentation is appropriate.  To suppress an
inherited string, an empty string must be specified (or the documentation
may be filled in).  This change affects the output of the @ref{d9,,pydoc}
module and the @ref{56d,,help()} function.
(Contributed by Serhiy Storchaka in bpo-15582@footnote{https://bugs.python.org/issue15582}.)

@item 
Nested @ref{7c2,,functools.partial()} calls are now flattened.  If you were
relying on the previous behavior, you can now either add an attribute to a
@ref{7c2,,functools.partial()} object or you can create a subclass of
@ref{7c2,,functools.partial()}.
(Contributed by Alexander Belopolsky in bpo-7830@footnote{https://bugs.python.org/issue7830}.)
@end itemize

@node C API 的变化<4>,,Python API 的变化<4>,移植到Python 3 5
@anchor{whatsnew/3 5 changes-in-the-c-api}@anchor{7c3}
@subsubsection C API 的变化



@itemize *

@item 
The undocumented @code{format} member of the
(non-public) @code{PyMemoryViewObject} structure has been removed.
All extensions relying on the relevant parts in @code{memoryobject.h}
must be rebuilt.

@item 
The @code{PyMemAllocator} structure was renamed to
@ref{7c4,,PyMemAllocatorEx} and a new @code{calloc} field was added.

@item 
Removed non-documented macro @code{PyObject_REPR} which leaked references.
Use format character @code{%R} in @ref{7c5,,PyUnicode_FromFormat()}-like functions
to format the @ref{7c6,,repr()} of the object.
(Contributed by Serhiy Storchaka in bpo-22453@footnote{https://bugs.python.org/issue22453}.)

@item 
Because the lack of the @code{__module__} attribute breaks pickling and
introspection, a deprecation warning is now raised for builtin types without
the @code{__module__} attribute.  This would be an AttributeError in
the future.
(Contributed by Serhiy Storchaka in bpo-20204@footnote{https://bugs.python.org/issue20204}.)

@item 
As part of the 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} implementation, the @code{tp_reserved} slot of
@ref{2d6,,PyTypeObject} was replaced with a
@code{tp_as_async} slot.  Refer to @ref{7c7,,协程对象} for
new types, structures and functions.
@end itemize

@node Python 3 5 4 的显著变化,,移植到Python 3 5,Python 3 5 有什么新变化
@anchor{whatsnew/3 5 notable-changes-in-python-3-5-4}@anchor{7c8}
@subsection Python 3.5.4 的显著变化


@menu
* New make regen-all build target: New make regen-all build target<2>. 
* Removal of make touch build target: Removal of make touch build target<2>. 

@end menu

@node New make regen-all build target<2>,Removal of make touch build target<2>,,Python 3 5 4 的显著变化
@anchor{whatsnew/3 5 new-make-regen-all-build-target}@anchor{7c9}
@subsubsection New @code{make regen-all} build target


To simplify cross-compilation, and to ensure that CPython can reliably be
compiled without requiring an existing version of Python to already be
available, the autotools-based build system no longer attempts to implicitly
recompile generated files based on file modification times.

Instead, a new @code{make regen-all} command has been added to force regeneration
of these files when desired (e.g. after an initial version of Python has
already been built based on the pregenerated versions).

More selective regeneration targets are also defined - see
Makefile.pre.in@footnote{https://github.com/python/cpython/tree/3.8/Makefile.pre.in} for details.

（由 Victor Stinner 在 bpo-23404@footnote{https://bugs.python.org/issue23404} 中贡献。）


3.5.4 新版功能.


@node Removal of make touch build target<2>,,New make regen-all build target<2>,Python 3 5 4 的显著变化
@anchor{whatsnew/3 5 removal-of-make-touch-build-target}@anchor{7ca}
@subsubsection Removal of @code{make touch} build target


The @code{make touch} build target previously used to request implicit regeneration
of generated files by updating their modification times has been removed.

It has been replaced by the new @code{make regen-all} target.

（由 Victor Stinner 在 bpo-23404@footnote{https://bugs.python.org/issue23404} 中贡献。）


在 3.5.4 版更改.


@node Python 3 4 有什么新变化,Python 3 3 有什么新变化,Python 3 5 有什么新变化,Python的新变化
@anchor{whatsnew/3 4 doc}@anchor{7cb}@anchor{whatsnew/3 4 what-s-new-in-python-3-4}@anchor{7cc}
@section Python 3.4 有什么新变化


@*作者: 
R. David Murray <@email{rdmurray@@bitdance.com}> (Editor)


@c Rules for maintenance:
@c 
@c * Anyone can add text to this document, but the maintainer reserves the
@c right to rewrite any additions. In particular, for obscure or esoteric
@c features, the maintainer may reduce any addition to a simple reference to
@c the new documentation rather than explaining the feature inline.
@c 
@c * While the maintainer will periodically go through Misc/NEWS
@c and add changes, it's best not to rely on this. We know from experience
@c that any changes that aren't in the What's New documentation around the
@c time of the original release will remain largely unknown to the community
@c for years, even if they're added later. We also know from experience that
@c other priorities can arise, and the maintainer will run out of time to do
@c updates -- in such cases, end users will be much better served by partial
@c notifications that at least give a hint about new features to
@c investigate.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS. The What's New should focus on changes that
@c are visible to Python *users* and that *require* a feature release (i.e.
@c most bug fixes should only be recorded in Misc/NEWS)
@c 
@c * PEPs should not be marked Final until they have an entry in What's New.
@c A placeholder entry that is just a section header and a link to the PEP
@c (e.g ":pep:`397` has been implemented") is acceptable. If a PEP has been
@c implemented and noted in What's New, don't forget to mark it as Final!
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to add just a very brief note about a change.  For
@c example: "The :ref:`~socket.transmogrify()` function was added to the
@c :mod:`socket` module."  The maintainer will research the change and
@c write the necessary text (if appropriate). The advantage of doing this
@c is that even if no more descriptive text is ever added, readers will at
@c least have a notification that the new feature exists and a link to the
@c relevant documentation.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number as a comment:
@c 
@c The :ref:`~socket.transmogrify()` function was added to the
@c :mod:`socket` module.  (Contributed by P.Y. Developer in :issue:`12345`.)
@c 
@c This saves the maintainer the effort of going through the Mercurial log
@c when researching a change.
@c 
@c * Cross referencing tip: :ref:`mod.attr` will display as ``mod.attr``,
@c while :ref:`~mod.attr` will display as ``attr``.

This article explains the new features in Python 3.4, compared to 3.3.
Python 3.4 was released on March 16, 2014.  For full details, see the
changelog@footnote{https://docs.python.org/3.4/whatsnew/changelog.html}.


@subsubheading 参见


@geindex Python 提高建议; PEP 429
PEP 429@footnote{https://www.python.org/dev/peps/pep-0429} -- Python 3.4 发布计划


@menu
* 摘要 - 发布重点: 摘要 - 发布重点<5>. 
* 新的特性: 新的特性<5>. 
* 新增模块: 新增模块<5>. 
* 改进的模块: 改进的模块<5>. 
* CPython Implementation Changes:: 
* 弃用: 弃用<4>. 
* 移除: 移除<3>. 
* 移植到 Python 3.4: 移植到 Python 3 4. 
* 3.4.3 的变化: 3 4 3 的变化. 

@end menu

@node 摘要 - 发布重点<5>,新的特性<5>,,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 summary-release-highlights}@anchor{7cd}
@subsection 摘要 - 发布重点


@c This section singles out the most important changes in Python 3.4.
@c Brevity is key.

新的语法特性：


@itemize *

@item 
No new syntax features were added in Python 3.4.
@end itemize

其他的新特性


@itemize *

@item 
@ref{7ce,,pip 能够随时可用} (
@geindex Python 提高建议; PEP 453
PEP 453@footnote{https://www.python.org/dev/peps/pep-0453}).

@item 
@ref{7cf,,Newly created file descriptors are non-inheritable}
(
@geindex Python 提高建议; PEP 446
PEP 446@footnote{https://www.python.org/dev/peps/pep-0446}).

@item 
command line option for @ref{7d0,,isolated mode}
(bpo-16499@footnote{https://bugs.python.org/issue16499}).

@item 
@ref{7d1,,improvements in the handling of codecs}
that are not text encodings (multiple issues).

@item 
@ref{7d2,,A ModuleSpec Type} for the Import System
(
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}).  (Affects importer authors.)

@item 
The @ref{b0,,marshal} format has been made @ref{7d3,,more compact and efficient} (bpo-16475@footnote{https://bugs.python.org/issue16475}).
@end itemize

新的库模块：


@itemize *

@item 
@ref{a,,asyncio}: @ref{7d4,,New provisional API for asynchronous IO} (
@geindex Python 提高建议; PEP 3156
PEP 3156@footnote{https://www.python.org/dev/peps/pep-3156}).

@item 
@ref{7a,,ensurepip}: @ref{7d5,,Bootstrapping the pip installer}
(
@geindex Python 提高建议; PEP 453
PEP 453@footnote{https://www.python.org/dev/peps/pep-0453}).

@item 
@ref{7b,,enum}: @ref{7d6,,Support for enumeration types}
(
@geindex Python 提高建议; PEP 435
PEP 435@footnote{https://www.python.org/dev/peps/pep-0435}).

@item 
@ref{c8,,pathlib}: @ref{7d7,,Object-oriented filesystem paths}
(
@geindex Python 提高建议; PEP 428
PEP 428@footnote{https://www.python.org/dev/peps/pep-0428}).

@item 
@ref{e6,,selectors}: @ref{7d8,,High-level and efficient I/O multiplexing}, built upon the @ref{e5,,select} module primitives (part
of 
@geindex Python 提高建议; PEP 3156
PEP 3156@footnote{https://www.python.org/dev/peps/pep-3156}).

@item 
@ref{f5,,statistics}: A basic @ref{7d9,,numerically stable statistics library} (
@geindex Python 提高建议; PEP 450
PEP 450@footnote{https://www.python.org/dev/peps/pep-0450}).

@item 
@ref{114,,tracemalloc}: @ref{7da,,Trace Python memory allocations} (
@geindex Python 提高建议; PEP 454
PEP 454@footnote{https://www.python.org/dev/peps/pep-0454}).
@end itemize

Significantly improved library modules:


@itemize *

@item 
@ref{7db,,Single-dispatch generic functions} in
@ref{85,,functools} (
@geindex Python 提高建议; PEP 443
PEP 443@footnote{https://www.python.org/dev/peps/pep-0443}).

@item 
New @ref{ca,,pickle} @ref{7dc,,protocol 4} (
@geindex Python 提高建议; PEP 3154
PEP 3154@footnote{https://www.python.org/dev/peps/pep-3154}).

@item 
@ref{b7,,multiprocessing} now has @ref{7dd,,an option to avoid using os.fork on Unix} (bpo-8713@footnote{https://bugs.python.org/issue8713}).

@item 
@ref{69,,email} has a new submodule, @ref{6b,,contentmanager}, and
a new @ref{53c,,Message} subclass
(@code{EmailMessage}) that @ref{7de,,simplify MIME handling} (bpo-18891@footnote{https://bugs.python.org/issue18891}).

@item 
The @ref{a0,,inspect} and @ref{d9,,pydoc} modules are now capable of
correct introspection of a much wider variety of callable objects,
which improves the output of the Python @ref{56d,,help()} system.

@item 
The @ref{a2,,ipaddress} module API has been declared stable
@end itemize

安全改进：


@itemize *

@item 
@ref{7df,,Secure and interchangeable hash algorithm}
(
@geindex Python 提高建议; PEP 456
PEP 456@footnote{https://www.python.org/dev/peps/pep-0456}).

@item 
@ref{7cf,,Make newly created file descriptors non-inheritable}
(
@geindex Python 提高建议; PEP 446
PEP 446@footnote{https://www.python.org/dev/peps/pep-0446}) to avoid leaking file descriptors to child processes.

@item 
New command line option for @ref{7d0,,isolated mode},
(bpo-16499@footnote{https://bugs.python.org/issue16499}).

@item 
@ref{b7,,multiprocessing} now has @ref{7dd,,an option to avoid using os.fork on Unix}.  @emph{spawn} and @emph{forkserver} are
more secure because they avoid sharing data with child processes.

@item 
@ref{b7,,multiprocessing} child processes on Windows no longer inherit
all of the parent's inheritable handles, only the necessary ones.

@item 
A new @ref{7e0,,hashlib.pbkdf2_hmac()} function provides
the PKCS#5 password-based key derivation function 2@footnote{https://en.wikipedia.org/wiki/PBKDF2}.

@item 
@ref{7e1,,TLSv1.1 and TLSv1.2 support} for @ref{f3,,ssl}.

@item 
@ref{7e2,,Retrieving certificates from the Windows system cert store support} for @ref{f3,,ssl}.

@item 
@ref{7e3,,Server-side SNI (Server Name Indication) support} for @ref{f3,,ssl}.

@item 
The @ref{3dc,,ssl.SSLContext} class has a @ref{7e4,,lot of improvements}.

@item 
All modules in the standard library that support SSL now support server
certificate verification, including hostname matching
(@ref{3d4,,ssl.match_hostname()}) and CRLs (Certificate Revocation lists, see
@ref{7e5,,ssl.SSLContext.load_verify_locations()}).
@end itemize

CPython 实现的改进：


@itemize *

@item 
@ref{7e6,,Safe object finalization} (
@geindex Python 提高建议; PEP 442
PEP 442@footnote{https://www.python.org/dev/peps/pep-0442}).

@item 
Leveraging 
@geindex Python 提高建议; PEP 442
PEP 442@footnote{https://www.python.org/dev/peps/pep-0442}, in most cases @ref{7e6,,module globals are no longer set to None during finalization} (bpo-18214@footnote{https://bugs.python.org/issue18214}).

@item 
@ref{7e7,,Configurable memory allocators} (
@geindex Python 提高建议; PEP 445
PEP 445@footnote{https://www.python.org/dev/peps/pep-0445}).

@item 
@ref{7e8,,Argument Clinic} (
@geindex Python 提高建议; PEP 436
PEP 436@footnote{https://www.python.org/dev/peps/pep-0436}).
@end itemize

Please read on for a comprehensive list of user-facing changes, including many
other smaller improvements, CPython optimizations, deprecations, and potential
porting issues.

@node 新的特性<5>,新增模块<5>,摘要 - 发布重点<5>,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 new-features}@anchor{7e9}
@subsection 新的特性


@menu
* PEP 453; Explicit Bootstrapping of PIP in Python Installations: PEP 453 Explicit Bootstrapping of PIP in Python Installations. 
* PEP 446; Newly Created File Descriptors Are Non-Inheritable: PEP 446 Newly Created File Descriptors Are Non-Inheritable. 
* Improvements to Codec Handling:: 
* PEP 451; A ModuleSpec Type for the Import System: PEP 451 A ModuleSpec Type for the Import System. 
* 其他语言特性修改: 其他语言特性修改<5>. 

@end menu

@node PEP 453 Explicit Bootstrapping of PIP in Python Installations,PEP 446 Newly Created File Descriptors Are Non-Inheritable,,新的特性<5>
@anchor{whatsnew/3 4 pep-453-explicit-bootstrapping-of-pip-in-python-installations}@anchor{7ea}@anchor{whatsnew/3 4 whatsnew-pep-453}@anchor{7ce}
@subsubsection PEP 453: Explicit Bootstrapping of PIP in Python Installations


@menu
* Bootstrapping pip By Default:: 
* 文档更改:: 

@end menu

@node Bootstrapping pip By Default,文档更改,,PEP 453 Explicit Bootstrapping of PIP in Python Installations
@anchor{whatsnew/3 4 bootstrapping-pip-by-default}@anchor{7eb}
@subsubsection Bootstrapping pip By Default


The new @ref{7a,,ensurepip} module (defined in 
@geindex Python 提高建议; PEP 453
PEP 453@footnote{https://www.python.org/dev/peps/pep-0453}) provides a standard
cross-platform mechanism to bootstrap the pip installer into Python
installations and virtual environments. The version of @code{pip} included
with Python 3.4.0 is @code{pip} 1.5.4, and future 3.4.x maintenance releases
will update the bundled version to the latest version of @code{pip} that is
available at the time of creating the release candidate.

By default, the commands @code{pipX} and @code{pipX.Y} will be installed on all
platforms (where X.Y stands for the version of the Python installation),
along with the @code{pip} Python package and its dependencies. On Windows and
in virtual environments on all platforms, the unversioned @code{pip} command
will also be installed. On other platforms, the system wide unversioned
@code{pip} command typically refers to the separately installed Python 2
version.

The @code{pyvenv} command line utility and the @ref{125,,venv}
module make use of the @ref{7a,,ensurepip} module to make @code{pip} readily
available in virtual environments. When using the command line utility,
@code{pip} is installed by default, while when using the @ref{125,,venv} module
@ref{7ec,,API} installation of @code{pip} must be requested explicitly.

For CPython @ref{7ed,,source builds on POSIX systems},
the @code{make install} and @code{make altinstall} commands bootstrap @code{pip} by
default.  This behaviour can be controlled through configure options, and
overridden through Makefile options.

On Windows and Mac OS X, the CPython installers now default to installing
@code{pip} along with CPython itself (users may opt out of installing it
during the installation process). Window users will need to opt in to the
automatic @code{PATH} modifications to have @code{pip} available from the command
line by default, otherwise it can still be accessed through the Python
launcher for Windows as @code{py -m pip}.

As discussed in the PEP@footnote{https://www.python.org/dev/peps/pep-0453/#recommendations-for-downstream-distributors}, platform packagers may choose not to install
these commands by default, as long as, when invoked, they provide clear and
simple directions on how to install them on that platform (usually using
the system package manager).

@cartouche
@quotation 注解 
To avoid conflicts between parallel Python 2 and Python 3 installations,
only the versioned @code{pip3} and @code{pip3.4} commands are bootstrapped by
default when @code{ensurepip} is invoked directly - the @code{--default-pip}
option is needed to also request the unversioned @code{pip} command.
@code{pyvenv} and the Windows installer ensure that the unqualified @code{pip}
command is made available in those environments, and @code{pip} can always be
invoked via the @code{-m} switch rather than directly to avoid ambiguity on
systems with multiple Python installations.
@end quotation
@end cartouche

@node 文档更改,,Bootstrapping pip By Default,PEP 453 Explicit Bootstrapping of PIP in Python Installations
@anchor{whatsnew/3 4 documentation-changes}@anchor{7ee}
@subsubsection 文档更改


As part of this change, the @ref{7ef,,安装 Python 模块} and
@ref{7f0,,分发 Python 模块} sections of the documentation have been
completely redesigned as short getting started and FAQ documents. Most
packaging documentation has now been moved out to the Python Packaging
Authority maintained Python Packaging User Guide@footnote{https://packaging.python.org} and the documentation of the individual
projects.

However, as this migration is currently still incomplete, the legacy
versions of those guides remaining available as @ref{7f1,,安装Python模块（旧版）}
and @ref{7f2,,分发 Python 模块（遗留版本）}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 453

@item PEP 453@footnote{https://www.python.org/dev/peps/pep-0453} -- Python安装中pip的显式引导

PEP 由Donald Stufft 和 Nick Coghlan 撰写，由 Donald Stufft，Nick Coghlan，Martin von Löwis 和 Ned Deily 实现。
@end table


@node PEP 446 Newly Created File Descriptors Are Non-Inheritable,Improvements to Codec Handling,PEP 453 Explicit Bootstrapping of PIP in Python Installations,新的特性<5>
@anchor{whatsnew/3 4 pep-446-newly-created-file-descriptors-are-non-inheritable}@anchor{7f3}@anchor{whatsnew/3 4 whatsnew-pep-446}@anchor{7cf}
@subsubsection PEP 446: Newly Created File Descriptors Are Non-Inheritable


@geindex Python 提高建议; PEP 446
PEP 446@footnote{https://www.python.org/dev/peps/pep-0446} makes newly created file descriptors @ref{7f4,,non-inheritable}.  In general, this is the behavior an application will
want: when launching a new process, having currently open files also
open in the new process can lead to all sorts of hard to find bugs,
and potentially to security issues.

However, there are occasions when inheritance is desired.  To support
these cases, the following new functions and methods are available:


@itemize *

@item 
@ref{7f5,,os.get_inheritable()}, @ref{7f6,,os.set_inheritable()}

@item 
@ref{7f7,,os.get_handle_inheritable()}, @ref{7f8,,os.set_handle_inheritable()}

@item 
@ref{7f9,,socket.socket.get_inheritable()}, @ref{7fa,,socket.socket.set_inheritable()}
@end itemize


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 446

@item PEP 446@footnote{https://www.python.org/dev/peps/pep-0446} -- Make newly created file descriptors non-inheritable

PEP 由 Victor Stinner 撰写并实现。
@end table


@node Improvements to Codec Handling,PEP 451 A ModuleSpec Type for the Import System,PEP 446 Newly Created File Descriptors Are Non-Inheritable,新的特性<5>
@anchor{whatsnew/3 4 codec-handling-improvements}@anchor{7d1}@anchor{whatsnew/3 4 improvements-to-codec-handling}@anchor{7fb}
@subsubsection Improvements to Codec Handling


Since it was first introduced, the @ref{1c,,codecs} module has always been
intended to operate as a type-neutral dynamic encoding and decoding
system. However, its close coupling with the Python text model, especially
the type restricted convenience methods on the builtin @ref{329,,str},
@ref{32a,,bytes} and @ref{32b,,bytearray} types, has historically obscured that
fact.

As a key step in clarifying the situation, the @ref{7fc,,codecs.encode()} and
@ref{7fd,,codecs.decode()} convenience functions are now properly documented in
Python 2.7, 3.3 and 3.4. These functions have existed in the @ref{1c,,codecs}
module (and have been covered by the regression test suite) since Python 2.4,
but were previously only discoverable through runtime introspection.

Unlike the convenience methods on @ref{329,,str}, @ref{32a,,bytes} and
@ref{32b,,bytearray}, the @ref{1c,,codecs} convenience functions support arbitrary
codecs in both Python 2 and Python 3, rather than being limited to Unicode text
encodings (in Python 3) or @code{basestring} <-> @code{basestring} conversions (in
Python 2).

In Python 3.4, the interpreter is able to identify the known non-text
encodings provided in the standard library and direct users towards these
general purpose convenience functions when appropriate:

@example
>>> b"abcdef".decode("hex")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
LookupError: 'hex' is not a text encoding; use codecs.decode() to handle arbitrary codecs

>>> "hello".encode("rot13")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
LookupError: 'rot13' is not a text encoding; use codecs.encode() to handle arbitrary codecs

>>> open("foo.txt", encoding="hex")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
LookupError: 'hex' is not a text encoding; use codecs.open() to handle arbitrary codecs
@end example

In a related change, whenever it is feasible without breaking backwards
compatibility, exceptions raised during encoding and decoding operations
are wrapped in a chained exception of the same type that mentions the
name of the codec responsible for producing the error:

@example
>>> import codecs

>>> codecs.decode(b"abcdefgh", "hex")
Traceback (most recent call last):
  File "/usr/lib/python3.4/encodings/hex_codec.py", line 20, in hex_decode
    return (binascii.a2b_hex(input), len(input))
binascii.Error: Non-hexadecimal digit found

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
binascii.Error: decoding with 'hex' codec failed (Error: Non-hexadecimal digit found)

>>> codecs.encode("hello", "bz2")
Traceback (most recent call last):
  File "/usr/lib/python3.4/encodings/bz2_codec.py", line 17, in bz2_encode
    return (bz2.compress(input), len(input))
  File "/usr/lib/python3.4/bz2.py", line 498, in compress
    return comp.compress(data) + comp.flush()
TypeError: 'str' does not support the buffer interface

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: encoding with 'bz2' codec failed (TypeError: 'str' does not support the buffer interface)
@end example

Finally, as the examples above show, these improvements have permitted
the restoration of the convenience aliases for the non-Unicode codecs that
were themselves restored in Python 3.2. This means that encoding binary data
to and from its hexadecimal representation (for example) can now be written
as:

@example
>>> from codecs import encode, decode
>>> encode(b"hello", "hex")
b'68656c6c6f'
>>> decode(b"68656c6c6f", "hex")
b'hello'
@end example

The binary and text transforms provided in the standard library are detailed
in @ref{7fe,,二进制转换} and @ref{7ff,,文字转换}.

(Contributed by Nick Coghlan in bpo-7475@footnote{https://bugs.python.org/issue7475}, bpo-17827@footnote{https://bugs.python.org/issue17827},
bpo-17828@footnote{https://bugs.python.org/issue17828} and bpo-19619@footnote{https://bugs.python.org/issue19619}.)

@node PEP 451 A ModuleSpec Type for the Import System,其他语言特性修改<5>,Improvements to Codec Handling,新的特性<5>
@anchor{whatsnew/3 4 pep-451-a-modulespec-type-for-the-import-system}@anchor{800}@anchor{whatsnew/3 4 whatsnew-pep-451}@anchor{7d2}
@subsubsection PEP 451: A ModuleSpec Type for the Import System


@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451} provides an encapsulation of the information about a module that the
import machinery will use to load it (that is, a module specification).  This
helps simplify both the import implementation and several import-related APIs.
The change is also a stepping stone for several future import-related improvements@footnote{https://mail.python.org/pipermail/python-dev/2013-November/130111.html}.

The public-facing changes from the PEP are entirely backward-compatible.
Furthermore, they should be transparent to everyone but importer authors.  Key
finder and loader methods have been deprecated, but they will continue working.
New importers should use the new methods described in the PEP.  Existing
importers should be updated to implement the new methods.  See the
@ref{801,,弃用} section for a list of methods that should be replaced and
their replacements.

@node 其他语言特性修改<5>,,PEP 451 A ModuleSpec Type for the Import System,新的特性<5>
@anchor{whatsnew/3 4 other-language-changes}@anchor{802}
@subsubsection 其他语言特性修改


对Python 语言核心进行的小改动：


@itemize *

@item 
Unicode database updated to UCD version 6.3.

@item 
@ref{803,,min()} and @ref{804,,max()} now accept a @emph{default} keyword-only argument that
can be used to specify the value they return if the iterable they are
evaluating has no elements.  (Contributed by Julian Berman in
bpo-18111@footnote{https://bugs.python.org/issue18111}.)

@item 
Module objects are now @ref{128,,weakref}'able.

@item 
Module @code{__file__} attributes (and related values) should now always
contain absolute paths by default, with the sole exception of
@code{__main__.__file__} when a script has been executed directly using
a relative path.  (Contributed by Brett Cannon in bpo-18416@footnote{https://bugs.python.org/issue18416}.)

@item 
All the UTF-* codecs (except UTF-7) now reject surrogates during both
encoding and decoding unless the @code{surrogatepass} error handler is used,
with the exception of the UTF-16 decoder (which accepts valid surrogate pairs)
and the UTF-16 encoder (which produces them while encoding non-BMP characters).
(Contributed by Victor Stinner, Kang-Hao (Kenny) Lu and Serhiy Storchaka in
bpo-12892@footnote{https://bugs.python.org/issue12892}.)

@item 
New German EBCDIC @ref{689,,codec} @code{cp273}.  (Contributed
by Michael Bierenfeld and Andrew Kuchling in bpo-1097797@footnote{https://bugs.python.org/issue1097797}.)

@item 
New Ukrainian @ref{689,,codec} @code{cp1125}.  (Contributed by
Serhiy Storchaka in bpo-19668@footnote{https://bugs.python.org/issue19668}.)

@item 
@ref{32a,,bytes}.join() and @ref{32b,,bytearray}.join() now accept arbitrary
buffer objects as arguments.  (Contributed by Antoine Pitrou in
bpo-15958@footnote{https://bugs.python.org/issue15958}.)

@item 
The @ref{184,,int} constructor now accepts any object that has an @code{__index__}
method for its @emph{base} argument.  (Contributed by Mark Dickinson in
bpo-16772@footnote{https://bugs.python.org/issue16772}.)

@item 
Frame objects now have a @ref{805,,clear()} method that clears all
references to local variables from the frame.  (Contributed by Antoine Pitrou
in bpo-17934@footnote{https://bugs.python.org/issue17934}.)

@item 
@ref{25c,,memoryview} is now registered as a @ref{1f,,Sequence},
and supports the @ref{18e,,reversed()} builtin.  (Contributed by Nick Coghlan
and Claudiu Popa in bpo-18690@footnote{https://bugs.python.org/issue18690} and bpo-19078@footnote{https://bugs.python.org/issue19078}.)

@item 
Signatures reported by @ref{56d,,help()} have been modified and improved in
several cases as a result of the introduction of Argument Clinic and other
changes to the @ref{a0,,inspect} and @ref{d9,,pydoc} modules.

@item 
@ref{806,,__length_hint__()} is now part of the formal language
specification (see 
@geindex Python 提高建议; PEP 424
PEP 424@footnote{https://www.python.org/dev/peps/pep-0424}).  (Contributed by Armin Ronacher in
bpo-16148@footnote{https://bugs.python.org/issue16148}.)
@end itemize

@node 新增模块<5>,改进的模块<5>,新的特性<5>,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 new-modules}@anchor{807}
@subsection 新增模块


@menu
* asyncio: asyncio<6>. 
* ensurepip:: 
* enum: enum<5>. 
* pathlib: pathlib<5>. 
* selectors: selectors<2>. 
* statistics: statistics<3>. 
* tracemalloc: tracemalloc<3>. 

@end menu

@node asyncio<6>,ensurepip,,新增模块<5>
@anchor{whatsnew/3 4 asyncio}@anchor{808}@anchor{whatsnew/3 4 whatsnew-asyncio}@anchor{7d4}
@subsubsection asyncio


The new @ref{a,,asyncio} module (defined in 
@geindex Python 提高建议; PEP 3156
PEP 3156@footnote{https://www.python.org/dev/peps/pep-3156}) provides a standard
pluggable event loop model for Python, providing solid asynchronous IO
support in the standard library, and making it easier for other event loop
implementations to interoperate with the standard library and each other.

For Python 3.4, this module is considered a @ref{341,,provisional API}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3156

@item PEP 3156@footnote{https://www.python.org/dev/peps/pep-3156} -- Asynchronous IO Support Rebooted: the "asyncio" Module

PEP 由 Guido van Rossum 领导编写和实现。
@end table


@node ensurepip,enum<5>,asyncio<6>,新增模块<5>
@anchor{whatsnew/3 4 ensurepip}@anchor{809}@anchor{whatsnew/3 4 whatsnew-ensurepip}@anchor{7d5}
@subsubsection ensurepip


The new @ref{7a,,ensurepip} module is the primary infrastructure for the
@geindex Python 提高建议; PEP 453
PEP 453@footnote{https://www.python.org/dev/peps/pep-0453} implementation.  In the normal course of events end users will not
need to interact with this module, but it can be used to manually bootstrap
@code{pip} if the automated bootstrapping into an installation or virtual
environment was declined.

@ref{7a,,ensurepip} includes a bundled copy of @code{pip}, up-to-date as of the first
release candidate of the release of CPython with which it ships (this applies
to both maintenance releases and feature releases).  @code{ensurepip} does not
access the internet.  If the installation has Internet access, after
@code{ensurepip} is run the bundled @code{pip} can be used to upgrade @code{pip} to a
more recent release than the bundled one.  (Note that such an upgraded version
of @code{pip} is considered to be a separately installed package and will not be
removed if Python is uninstalled.)

The module is named @emph{ensure}pip because if called when @code{pip} is already
installed, it does nothing.  It also has an @code{--upgrade} option that will
cause it to install the bundled copy of @code{pip} if the existing installed
version of @code{pip} is older than the bundled copy.

@node enum<5>,pathlib<5>,ensurepip,新增模块<5>
@anchor{whatsnew/3 4 enum}@anchor{80a}@anchor{whatsnew/3 4 whatsnew-enum}@anchor{7d6}
@subsubsection enum


The new @ref{7b,,enum} module (defined in 
@geindex Python 提高建议; PEP 435
PEP 435@footnote{https://www.python.org/dev/peps/pep-0435}) provides a standard
implementation of enumeration types, allowing other modules (such as
@ref{ef,,socket}) to provide more informative error messages and better
debugging support by replacing opaque integer constants with backwards
compatible enumeration values.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 435

@item PEP 435@footnote{https://www.python.org/dev/peps/pep-0435} -- Adding an Enum type to the Python standard library

PEP 由 Barry Warsaw，Eli Bendersky 和 Ethan Furman 撰写 ，由 Ethan Furman 实现。
@end table


@node pathlib<5>,selectors<2>,enum<5>,新增模块<5>
@anchor{whatsnew/3 4 pathlib}@anchor{80b}@anchor{whatsnew/3 4 whatsnew-pathlib}@anchor{7d7}
@subsubsection pathlib


The new @ref{c8,,pathlib} module offers classes representing filesystem paths
with semantics appropriate for different operating systems.  Path classes are
divided between @emph{pure paths}, which provide purely computational operations
without I/O, and @emph{concrete paths}, which inherit from pure paths but also
provide I/O operations.

For Python 3.4, this module is considered a @ref{341,,provisional API}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 428

@item PEP 428@footnote{https://www.python.org/dev/peps/pep-0428} -- The pathlib module -- object-oriented filesystem paths

PEP 由 Antoine Pitrou 撰写并实现
@end table


@node selectors<2>,statistics<3>,pathlib<5>,新增模块<5>
@anchor{whatsnew/3 4 selectors}@anchor{80c}@anchor{whatsnew/3 4 whatsnew-selectors}@anchor{7d8}
@subsubsection selectors


The new @ref{e6,,selectors} module (created as part of implementing 
@geindex Python 提高建议; PEP 3156
PEP 3156@footnote{https://www.python.org/dev/peps/pep-3156})
allows high-level and efficient I/O multiplexing, built upon the
@ref{e5,,select} module primitives.

@node statistics<3>,tracemalloc<3>,selectors<2>,新增模块<5>
@anchor{whatsnew/3 4 statistics}@anchor{80d}@anchor{whatsnew/3 4 whatsnew-statistics}@anchor{7d9}
@subsubsection statistics


The new @ref{f5,,statistics} module (defined in 
@geindex Python 提高建议; PEP 450
PEP 450@footnote{https://www.python.org/dev/peps/pep-0450}) offers some core
statistics functionality directly in the standard library. This module
supports calculation of the mean, median, mode, variance and standard
deviation of a data series.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 450

@item PEP 450@footnote{https://www.python.org/dev/peps/pep-0450} -- Adding A Statistics Module To The Standard Library

PEP 由 Steven D'Aprano 撰写并实现。
@end table


@node tracemalloc<3>,,statistics<3>,新增模块<5>
@anchor{whatsnew/3 4 tracemalloc}@anchor{80e}@anchor{whatsnew/3 4 whatsnew-tracemalloc}@anchor{7da}
@subsubsection tracemalloc


The new @ref{114,,tracemalloc} module (defined in 
@geindex Python 提高建议; PEP 454
PEP 454@footnote{https://www.python.org/dev/peps/pep-0454}) is a debug tool to
trace memory blocks allocated by Python. It provides the following information:


@itemize *

@item 
Trace where an object was allocated

@item 
Statistics on allocated memory blocks per filename and per line number:
total size, number and average size of allocated memory blocks

@item 
Compute the differences between two snapshots to detect memory leaks
@end itemize


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 454

@item PEP 454@footnote{https://www.python.org/dev/peps/pep-0454} -- Add a new tracemalloc module to trace Python memory allocations

PEP 由 Victor Stinner 撰写并实现
@end table


@node 改进的模块<5>,CPython Implementation Changes,新增模块<5>,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 improved-modules}@anchor{80f}
@subsection 改进的模块


@menu
* abc:: 
* aifc: aifc<2>. 
* argparse: argparse<3>. 
* audioop:: 
* base64:: 
* collections: collections<6>. 
* colorsys:: 
* contextlib: contextlib<4>. 
* dbm: dbm<5>. 
* dis: dis<2>. 
* doctest: doctest<2>. 
* email: email<3>. 
* filecmp:: 
* functools: functools<4>. 
* gc: gc<3>. 
* glob: glob<2>. 
* hashlib: hashlib<2>. 
* hmac: hmac<2>. 
* html:: 
* http: http<2>. 
* idlelib 与 IDLE: idlelib 与 IDLE<4>. 
* importlib: importlib<6>. 
* inspect: inspect<4>. 
* ipaddress: ipaddress<3>. 
* logging: logging<5>. 
* marshal:: 
* mmap: mmap<2>. 
* multiprocessing: multiprocessing<5>. 
* operator: operator<2>. 
* os: os<6>. 
* pdb: pdb<3>. 
* pickle: pickle<4>. 
* plistlib: plistlib<2>. 
* poplib: poplib<2>. 
* pprint: pprint<2>. 
* pty:: 
* pydoc: pydoc<3>. 
* re: re<5>. 
* resource:: 
* select:: 
* shelve:: 
* shutil: shutil<3>. 
* smtpd: smtpd<2>. 
* smtplib: smtplib<2>. 
* socket: socket<6>. 
* sqlite3: sqlite3<4>. 
* ssl: ssl<7>. 
* stat:: 
* struct: struct<2>. 
* subprocess: subprocess<4>. 
* sunau: sunau<2>. 
* sys: sys<6>. 
* tarfile: tarfile<3>. 
* textwrap:: 
* threading: threading<4>. 
* 回溯: 回溯<3>. 
* types: types<3>. 
* urllib: urllib<2>. 
* unittest: unittest<4>. 
* venv: venv<4>. 
* wave: wave<2>. 
* weakref: weakref<2>. 
* xml.etree: xml etree<2>. 
* zipfile: zipfile<4>. 

@end menu

@node abc,aifc<2>,,改进的模块<5>
@anchor{whatsnew/3 4 abc}@anchor{810}
@subsubsection abc


New function @ref{811,,abc.get_cache_token()} can be used to know when to invalidate
caches that are affected by changes in the object graph.  (Contributed
by Łukasz Langa in bpo-16832@footnote{https://bugs.python.org/issue16832}.)

New class @ref{812,,ABC} has @ref{813,,ABCMeta} as its meta class.
Using @code{ABC} as a base class has essentially the same effect as specifying
@code{metaclass=abc.ABCMeta}, but is simpler to type and easier to read.
(Contributed by Bruno Dupuis in bpo-16049@footnote{https://bugs.python.org/issue16049}.)

@node aifc<2>,argparse<3>,abc,改进的模块<5>
@anchor{whatsnew/3 4 aifc}@anchor{814}
@subsubsection aifc


The @ref{815,,getparams()} method now returns a namedtuple rather than a
plain tuple.  (Contributed by Claudiu Popa in bpo-17818@footnote{https://bugs.python.org/issue17818}.)

@ref{455,,aifc.open()} now supports the context management protocol: when used in a
@ref{6e3,,with} block, the @ref{816,,close()} method of the returned
object will be called automatically at the end of the block.  (Contributed by
Serhiy Storchacha in bpo-16486@footnote{https://bugs.python.org/issue16486}.)

The @ref{817,,writeframesraw()} and @ref{818,,writeframes()}
methods now accept any @ref{5e3,,bytes-like object}.  (Contributed by Serhiy
Storchaka in bpo-8311@footnote{https://bugs.python.org/issue8311}.)

@node argparse<3>,audioop,aifc<2>,改进的模块<5>
@anchor{whatsnew/3 4 argparse}@anchor{819}
@subsubsection argparse


The @ref{81a,,FileType} class now accepts @emph{encoding} and
@emph{errors} arguments, which are passed through to @ref{4ea,,open()}.  (Contributed
by Lucas Maystre in bpo-11175@footnote{https://bugs.python.org/issue11175}.)

@node audioop,base64,argparse<3>,改进的模块<5>
@anchor{whatsnew/3 4 audioop}@anchor{81b}
@subsubsection audioop


@ref{d,,audioop} now supports 24-bit samples.  (Contributed by Serhiy Storchaka
in bpo-12866@footnote{https://bugs.python.org/issue12866}.)

New @ref{81c,,byteswap()} function converts big-endian samples to
little-endian and vice versa.  (Contributed by Serhiy Storchaka in
bpo-19641@footnote{https://bugs.python.org/issue19641}.)

All @ref{d,,audioop} functions now accept any @ref{5e3,,bytes-like object}.  Strings
are not accepted: they didn't work before, now they raise an error right away.
(Contributed by Serhiy Storchaka in bpo-16685@footnote{https://bugs.python.org/issue16685}.)

@node base64,collections<6>,audioop,改进的模块<5>
@anchor{whatsnew/3 4 base64}@anchor{81d}
@subsubsection base64


The encoding and decoding functions in @ref{e,,base64} now accept any
@ref{5e3,,bytes-like object} in cases where it previously required a
@ref{32a,,bytes} or @ref{32b,,bytearray} instance.  (Contributed by Nick Coghlan in
bpo-17839@footnote{https://bugs.python.org/issue17839}.)

New functions @ref{81e,,a85encode()}, @ref{81f,,a85decode()},
@ref{820,,b85encode()}, and @ref{821,,b85decode()} provide the ability to
encode and decode binary data from and to @code{Ascii85} and the git/mercurial
@code{Base85} formats, respectively.  The @code{a85} functions have options that can
be used to make them compatible with the variants of the @code{Ascii85} encoding,
including the Adobe variant.  (Contributed by Martin Morrison, the Mercurial
project, Serhiy Storchaka, and Antoine Pitrou in bpo-17618@footnote{https://bugs.python.org/issue17618}.)

@node collections<6>,colorsys,base64,改进的模块<5>
@anchor{whatsnew/3 4 collections}@anchor{822}
@subsubsection collections


The @ref{823,,ChainMap.new_child()} method now accepts an @emph{m} argument specifying
the child map to add to the chain.  This allows an existing mapping and/or a
custom mapping type to be used for the child.  (Contributed by Vinay Sajip in
bpo-16613@footnote{https://bugs.python.org/issue16613}.)

@node colorsys,contextlib<4>,collections<6>,改进的模块<5>
@anchor{whatsnew/3 4 colorsys}@anchor{824}
@subsubsection colorsys


The number of digits in the coefficients for the RGB --- YIQ conversions have
been expanded so that they match the FCC NTSC versions.  The change in
results should be less than 1% and may better match results found elsewhere.
(Contributed by Brian Landers and Serhiy Storchaka in bpo-14323@footnote{https://bugs.python.org/issue14323}.)

@node contextlib<4>,dbm<5>,colorsys,改进的模块<5>
@anchor{whatsnew/3 4 contextlib}@anchor{825}
@subsubsection contextlib


The new @ref{826,,contextlib.suppress} context manager helps to clarify the
intent of code that deliberately suppresses exceptions from a single
statement.  (Contributed by Raymond Hettinger in bpo-15806@footnote{https://bugs.python.org/issue15806} and
Zero Piraeus in bpo-19266@footnote{https://bugs.python.org/issue19266}.)

The new @ref{6bc,,contextlib.redirect_stdout()} context manager makes it easier
for utility scripts to handle inflexible APIs that write their output to
@ref{307,,sys.stdout} and don't provide any options to redirect it.  Using the
context manager, the @ref{307,,sys.stdout} output can be redirected to any
other stream or, in conjunction with @ref{827,,io.StringIO}, to a string.
The latter can be especially useful, for example, to capture output
from a function that was written to implement a command line interface.
It is recommended only for utility scripts because it affects the
global state of @ref{307,,sys.stdout}.  (Contributed by Raymond Hettinger
in bpo-15805@footnote{https://bugs.python.org/issue15805}.)

The @ref{24,,contextlib} documentation has also been updated to include a
@ref{828,,discussion} of the
differences between single use, reusable and reentrant context managers.

@node dbm<5>,dis<2>,contextlib<4>,改进的模块<5>
@anchor{whatsnew/3 4 dbm}@anchor{829}
@subsubsection dbm


@ref{82a,,dbm.open()} objects now support the context management protocol.  When
used in a @ref{6e3,,with} statement, the @code{close} method of the database
object will be called automatically at the end of the block.  (Contributed by
Claudiu Popa and Nick Coghlan in bpo-19282@footnote{https://bugs.python.org/issue19282}.)

@node dis<2>,doctest<2>,dbm<5>,改进的模块<5>
@anchor{whatsnew/3 4 dis}@anchor{82b}
@subsubsection dis


Functions @ref{82c,,show_code()}, @ref{37c,,dis()}, @ref{82d,,distb()}, and
@ref{82e,,disassemble()} now accept a keyword-only @emph{file} argument that
controls where they write their output.

The @ref{38,,dis} module is now built around an @ref{82f,,Instruction} class
that provides object oriented access to the details of each individual bytecode
operation.

A new method, @ref{830,,get_instructions()}, provides an iterator that emits
the Instruction stream for a given piece of Python code.  Thus it is now
possible to write a program that inspects and manipulates a bytecode
object in ways different from those provided by the @ref{38,,dis} module
itself.  For example:

@example
>>> import dis
>>> for instr in dis.get_instructions(lambda x: x + 1):
...     print(instr.opname)
LOAD_FAST
LOAD_CONST
BINARY_ADD
RETURN_VALUE
@end example

The various display tools in the @ref{38,,dis} module have been rewritten to use
these new components.

In addition, a new application-friendly class @ref{831,,Bytecode} provides
an object-oriented API for inspecting bytecode in both in human-readable form
and for iterating over instructions.  The @ref{831,,Bytecode} constructor
takes the same arguments that @code{get_instruction()} does (plus an
optional @emph{current_offset}), and the resulting object can be iterated to produce
@ref{82f,,Instruction} objects.  But it also has a @ref{832,,dis}
method, equivalent to calling @ref{37c,,dis} on the constructor argument, but
returned as a multi-line string:

@example
>>> bytecode = dis.Bytecode(lambda x: x + 1, current_offset=3)
>>> for instr in bytecode:
...     print('@{@} (@{@})'.format(instr.opname, instr.opcode))
LOAD_FAST (124)
LOAD_CONST (100)
BINARY_ADD (23)
RETURN_VALUE (83)
>>> bytecode.dis().splitlines()       
['  1           0 LOAD_FAST                0 (x)',
 '      -->     3 LOAD_CONST               1 (1)',
 '              6 BINARY_ADD',
 '              7 RETURN_VALUE']
@end example

@ref{831,,Bytecode} also has a class method,
@ref{833,,from_traceback()}, that provides the ability to manipulate a
traceback (that is, @code{print(Bytecode.from_traceback(tb).dis())} is equivalent
to @code{distb(tb)}).

(Contributed by Nick Coghlan, Ryan Kelly and Thomas Kluyver in bpo-11816@footnote{https://bugs.python.org/issue11816}
and Claudiu Popa in bpo-17916@footnote{https://bugs.python.org/issue17916}.)

New function @ref{834,,stack_effect()} computes the effect on the Python stack
of a given opcode and argument, information that is not otherwise available.
(Contributed by Larry Hastings in bpo-19722@footnote{https://bugs.python.org/issue19722}.)

@node doctest<2>,email<3>,dis<2>,改进的模块<5>
@anchor{whatsnew/3 4 doctest}@anchor{835}
@subsubsection doctest


A new @ref{836,,option flag}, @ref{837,,FAIL_FAST}, halts
test running as soon as the first failure is detected.  (Contributed by R.
David Murray and Daniel Urban in bpo-16522@footnote{https://bugs.python.org/issue16522}.)

The @ref{67,,doctest} command line interface now uses @ref{6,,argparse}, and has two
new options, @code{-o} and @code{-f}.  @code{-o} allows @ref{836,,doctest options} to be specified on the command line, and @code{-f} is a
shorthand for @code{-o FAIL_FAST} (to parallel the similar option supported by the
@ref{11b,,unittest} CLI).  (Contributed by R. David Murray in bpo-11390@footnote{https://bugs.python.org/issue11390}.)

@ref{67,,doctest} will now find doctests in extension module @code{__doc__} strings.
(Contributed by Zachary Ware in bpo-3158@footnote{https://bugs.python.org/issue3158}.)

@node email<3>,filecmp,doctest<2>,改进的模块<5>
@anchor{whatsnew/3 4 email}@anchor{838}
@subsubsection email


@ref{839,,as_string()} now accepts a @emph{policy} argument to
override the default policy of the message when generating a string
representation of it.  This means that @code{as_string} can now be used in more
circumstances, instead of having to create and use a @ref{6e,,generator} in
order to pass formatting parameters to its @code{flatten} method.  (Contributed by
R. David Murray in bpo-18600@footnote{https://bugs.python.org/issue18600}.)

New method @ref{83a,,as_bytes()} added to produce a bytes
representation of the message in a fashion similar to how @code{as_string}
produces a string representation.  It does not accept the @emph{maxheaderlen}
argument, but does accept the @emph{unixfrom} and @emph{policy} arguments. The
@ref{53c,,Message} @ref{83b,,__bytes__()} method
calls it, meaning that @code{bytes(mymsg)} will now produce the intuitive
result:  a bytes object containing the fully formatted message.  (Contributed
by R. David Murray in bpo-18600@footnote{https://bugs.python.org/issue18600}.)

The @ref{83c,,Message.set_param()} message now accepts a @emph{replace} keyword argument.
When specified, the associated header will be updated without changing
its location in the list of headers.  For backward compatibility, the default
is @code{False}.  (Contributed by R. David Murray in bpo-18891@footnote{https://bugs.python.org/issue18891}.)
@anchor{whatsnew/3 4 whatsnew-email-contentmanager}@anchor{7de}
A pair of new subclasses of @ref{53c,,Message} have been added
(@ref{53d,,EmailMessage} and @ref{83d,,MIMEPart}), along with a new sub-module,
@ref{6b,,contentmanager} and a new @ref{75,,policy} attribute
@ref{83e,,content_manager}.  All documentation is
currently in the new module, which is being added as part of email's new
@ref{341,,provisional API}.  These classes provide a number of new methods that
make extracting content from and inserting content into email messages much
easier.  For details, see the @ref{6b,,contentmanager} documentation and
the @ref{83f,,email; 示例}.  These API additions complete the
bulk of the work that was planned as part of the email6 project.  The currently
provisional API is scheduled to become final in Python 3.5 (possibly with a few
minor additions in the area of error handling).  (Contributed by R. David
Murray in bpo-18891@footnote{https://bugs.python.org/issue18891}.)

@node filecmp,functools<4>,email<3>,改进的模块<5>
@anchor{whatsnew/3 4 filecmp}@anchor{840}
@subsubsection filecmp


A new @ref{841,,clear_cache()} function provides the ability to clear the
@ref{7f,,filecmp} comparison cache, which uses @ref{1f1,,os.stat()} information to
determine if the file has changed since the last compare.  This can be used,
for example, if the file might have been changed and re-checked in less time
than the resolution of a particular filesystem's file modification time field.
(Contributed by Mark Levitt in bpo-18149@footnote{https://bugs.python.org/issue18149}.)

New module attribute @ref{842,,DEFAULT_IGNORES} provides the list of
directories that are used as the default value for the @emph{ignore} parameter of
the @ref{843,,dircmp()} function.  (Contributed by Eli Bendersky in
bpo-15442@footnote{https://bugs.python.org/issue15442}.)

@node functools<4>,gc<3>,filecmp,改进的模块<5>
@anchor{whatsnew/3 4 functools}@anchor{844}
@subsubsection functools


The new @ref{29c,,partialmethod()} descriptor brings partial argument
application to descriptors, just as @ref{7c2,,partial()} provides
for normal callables. The new descriptor also makes it easier to get
arbitrary callables (including @ref{7c2,,partial()} instances)
to behave like normal instance methods when included in a class definition.
(Contributed by Alon Horev and Nick Coghlan in bpo-4331@footnote{https://bugs.python.org/issue4331}.)
@anchor{whatsnew/3 4 whatsnew-singledispatch}@anchor{7db}
The new @ref{382,,singledispatch()} decorator brings support for
single-dispatch generic functions to the Python standard library. Where
object oriented programming focuses on grouping multiple operations on a
common set of data into a class, a generic function focuses on grouping
multiple implementations of an operation that allows it to work with
@emph{different} kinds of data.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 443

@item PEP 443@footnote{https://www.python.org/dev/peps/pep-0443} -- Single-dispatch generic functions

PEP 由 Łukasz Langa 撰写并实现。
@end table


@ref{845,,total_ordering()} now supports a return value of
@ref{846,,NotImplemented} from the underlying comparison function.  (Contributed
by Katie Miller in bpo-10042@footnote{https://bugs.python.org/issue10042}.)

A pure-python version of the @ref{7c2,,partial()} function is now in the
stdlib; in CPython it is overridden by the C accelerated version, but it is
available for other implementations to use.  (Contributed by Brian Thorne in
bpo-12428@footnote{https://bugs.python.org/issue12428}.)

@node gc<3>,glob<2>,functools<4>,改进的模块<5>
@anchor{whatsnew/3 4 gc}@anchor{847}
@subsubsection gc


New function @ref{848,,get_stats()} returns a list of three per-generation
dictionaries containing the collections statistics since interpreter startup.
(Contributed by Antoine Pitrou in bpo-16351@footnote{https://bugs.python.org/issue16351}.)

@node glob<2>,hashlib<2>,gc<3>,改进的模块<5>
@anchor{whatsnew/3 4 glob}@anchor{849}
@subsubsection glob


A new function @ref{84a,,escape()} provides a way to escape special characters
in a filename so that they do not become part of the globbing expansion but are
instead matched literally.  (Contributed by Serhiy Storchaka in bpo-8402@footnote{https://bugs.python.org/issue8402}.)

@node hashlib<2>,hmac<2>,glob<2>,改进的模块<5>
@anchor{whatsnew/3 4 hashlib}@anchor{84b}
@subsubsection hashlib


A new @ref{7e0,,hashlib.pbkdf2_hmac()} function provides
the PKCS#5 password-based key derivation function 2@footnote{https://en.wikipedia.org/wiki/PBKDF2}.  (Contributed by Christian
Heimes in bpo-18582@footnote{https://bugs.python.org/issue18582}.)

The @ref{84c,,name} attribute of @ref{8d,,hashlib} hash objects is now
a formally supported interface.  It has always existed in CPython's
@ref{8d,,hashlib} (although it did not return lower case names for all supported
hashes), but it was not a public interface and so some other Python
implementations have not previously supported it.  (Contributed by Jason R.
Coombs in bpo-18532@footnote{https://bugs.python.org/issue18532}.)

@node hmac<2>,html,hashlib<2>,改进的模块<5>
@anchor{whatsnew/3 4 hmac}@anchor{84d}
@subsubsection hmac


@ref{8f,,hmac} now accepts @code{bytearray} as well as @code{bytes} for the @emph{key}
argument to the @ref{84e,,new()} function, and the @emph{msg} parameter to both the
@ref{84e,,new()} function and the @ref{84f,,update()} method now
accepts any type supported by the @ref{8d,,hashlib} module.  (Contributed
by Jonas Borgström in bpo-18240@footnote{https://bugs.python.org/issue18240}.)

The @emph{digestmod} argument to the @ref{84e,,hmac.new()} function may now be any hash
digest name recognized by @ref{8d,,hashlib}.  In addition, the current behavior in
which the value of @emph{digestmod} defaults to @code{MD5} is deprecated: in a
future version of Python there will be no default value.  (Contributed by
Christian Heimes in bpo-17276@footnote{https://bugs.python.org/issue17276}.)

With the addition of @ref{850,,block_size} and @ref{851,,name}
attributes (and the formal documentation of the @ref{852,,digest_size}
attribute), the @ref{8f,,hmac} module now conforms fully to the 
@geindex Python 提高建议; PEP 247
PEP 247@footnote{https://www.python.org/dev/peps/pep-0247} API.
(Contributed by Christian Heimes in bpo-18775@footnote{https://bugs.python.org/issue18775}.)

@node html,http<2>,hmac<2>,改进的模块<5>
@anchor{whatsnew/3 4 html}@anchor{853}
@subsubsection html


New function @ref{854,,unescape()} function converts HTML5 character references to
the corresponding Unicode characters.  (Contributed by Ezio Melotti in
bpo-2927@footnote{https://bugs.python.org/issue2927}.)

@ref{7b9,,HTMLParser} accepts a new keyword argument
@emph{convert_charrefs} that, when @code{True}, automatically converts all character
references.  For backward-compatibility, its value defaults to @code{False}, but
it will change to @code{True} in a future version of Python, so you are invited to
set it explicitly and update your code to use this new feature.  (Contributed
by Ezio Melotti in bpo-13633@footnote{https://bugs.python.org/issue13633}.)

The @emph{strict} argument of @ref{7b9,,HTMLParser} is now deprecated.
(Contributed by Ezio Melotti in bpo-15114@footnote{https://bugs.python.org/issue15114}.)

@node http<2>,idlelib 与 IDLE<4>,html,改进的模块<5>
@anchor{whatsnew/3 4 http}@anchor{855}
@subsubsection http


@ref{856,,send_error()} now accepts an
optional additional @emph{explain} parameter which can be used to provide an
extended error description, overriding the hardcoded default if there is one.
This extended error description will be formatted using the
@code{error_message_format} attribute and sent as the body
of the error response.  (Contributed by Karl Cow in bpo-12921@footnote{https://bugs.python.org/issue12921}.)

The @ref{97,,http.server} @ref{857,,command line interface} now has
a @code{-b/--bind} option that causes the server to listen on a specific address.
(Contributed by Malte Swart in bpo-17764@footnote{https://bugs.python.org/issue17764}.)

@node idlelib 与 IDLE<4>,importlib<6>,http<2>,改进的模块<5>
@anchor{whatsnew/3 4 idlelib-and-idle}@anchor{858}
@subsubsection idlelib 与 IDLE


Since idlelib implements the IDLE shell and editor and is not intended for
import by other programs, it gets improvements with every release. See
@code{Lib/idlelib/NEWS.txt} for a cumulative list of changes since 3.3.0,
as well as changes made in future 3.4.x releases. This file is also available
from the IDLE Help ‣ About IDLE dialog.

@node importlib<6>,inspect<4>,idlelib 与 IDLE<4>,改进的模块<5>
@anchor{whatsnew/3 4 importlib}@anchor{859}
@subsubsection importlib


The @ref{85a,,InspectLoader} ABC defines a new method,
@ref{6e9,,source_to_code()} that accepts source
data and a path and returns a code object.  The default implementation
is equivalent to @code{compile(data, path, 'exec', dont_inherit=True)}.
(Contributed by Eric Snow and Brett Cannon in bpo-15627@footnote{https://bugs.python.org/issue15627}.)

@ref{85a,,InspectLoader} also now has a default implementation
for the @ref{85b,,get_code()} method.  However,
it will normally be desirable to override the default implementation
for performance reasons.  (Contributed by Brett Cannon in bpo-18072@footnote{https://bugs.python.org/issue18072}.)

The @ref{391,,reload()} function has been moved from @ref{9a,,imp} to
@ref{9b,,importlib} as part of the @ref{9a,,imp} module deprecation.  (Contributed by
Berker Peksag in bpo-18193@footnote{https://bugs.python.org/issue18193}.)

@ref{9f,,importlib.util} now has a @ref{85c,,MAGIC_NUMBER} attribute
providing access to the bytecode version number.  This replaces the
@ref{85d,,get_magic()} function in the deprecated @ref{9a,,imp} module.
(Contributed by Brett Cannon in bpo-18192@footnote{https://bugs.python.org/issue18192}.)

New @ref{9f,,importlib.util} functions @ref{552,,cache_from_source()}
and @ref{553,,source_from_cache()} replace the same-named functions
in the deprecated @ref{9a,,imp} module.  (Contributed by Brett Cannon in
bpo-18194@footnote{https://bugs.python.org/issue18194}.)

The @ref{9b,,importlib} bootstrap @code{NamespaceLoader} now conforms to
the @ref{85a,,InspectLoader} ABC, which means that @code{runpy} and
@code{python -m} can now be used with namespace packages.  (Contributed
by Brett Cannon in bpo-18058@footnote{https://bugs.python.org/issue18058}.)

@ref{9f,,importlib.util} has a new function @ref{85e,,decode_source()}
that decodes source from bytes using universal newline processing.  This is
useful for implementing @ref{85f,,InspectLoader.get_source()} methods.

@ref{551,,importlib.machinery.ExtensionFileLoader} now has a
@ref{860,,get_filename()} method.  This was
inadvertently omitted in the original implementation.  (Contributed by Eric
Snow in bpo-19152@footnote{https://bugs.python.org/issue19152}.)

@node inspect<4>,ipaddress<3>,importlib<6>,改进的模块<5>
@anchor{whatsnew/3 4 inspect}@anchor{861}
@subsubsection inspect


The @ref{a0,,inspect} module now offers a basic @ref{862,,command line interface} to quickly display source code and other
information for modules, classes and functions.  (Contributed by Claudiu Popa
and Nick Coghlan in bpo-18626@footnote{https://bugs.python.org/issue18626}.)

@ref{863,,unwrap()} makes it easy to unravel wrapper function chains
created by @ref{864,,functools.wraps()} (and any other API that sets the
@code{__wrapped__} attribute on a wrapper function).  (Contributed by
Daniel Urban, Aaron Iles and Nick Coghlan in bpo-13266@footnote{https://bugs.python.org/issue13266}.)

As part of the implementation of the new @ref{7b,,enum} module, the
@ref{a0,,inspect} module now has substantially better support for custom
@code{__dir__} methods and dynamic class attributes provided through
metaclasses.  (Contributed by Ethan Furman in bpo-18929@footnote{https://bugs.python.org/issue18929} and
bpo-19030@footnote{https://bugs.python.org/issue19030}.)

@ref{558,,getfullargspec()} and @ref{557,,getargspec()}
now use the @ref{556,,signature()} API. This allows them to
support a much broader range of callables, including those with
@code{__signature__} attributes, those with metadata provided by argument
clinic, @ref{7c2,,functools.partial()} objects and more. Note that, unlike
@ref{556,,signature()}, these functions still ignore @code{__wrapped__}
attributes, and report the already bound first argument for bound methods,
so it is still necessary to update your code to use
@ref{556,,signature()} directly if those features are desired.
(Contributed by Yury Selivanov in bpo-17481@footnote{https://bugs.python.org/issue17481}.)

@ref{556,,signature()} now supports duck types of CPython functions,
which adds support for functions compiled with Cython.  (Contributed
by Stefan Behnel and Yury Selivanov in bpo-17159@footnote{https://bugs.python.org/issue17159}.)

@node ipaddress<3>,logging<5>,inspect<4>,改进的模块<5>
@anchor{whatsnew/3 4 ipaddress}@anchor{865}
@subsubsection ipaddress


@ref{a2,,ipaddress} was added to the standard library in Python 3.3 as a
@ref{341,,provisional API}. With the release of Python 3.4, this qualification
has been removed: @ref{a2,,ipaddress} is now considered a stable API, covered
by the normal standard library requirements to maintain backwards
compatibility.

A new @ref{866,,is_global} property is @code{True} if
an address is globally routeable.  (Contributed by Peter Moody in
bpo-17400@footnote{https://bugs.python.org/issue17400}.)

@node logging<5>,marshal,ipaddress<3>,改进的模块<5>
@anchor{whatsnew/3 4 logging}@anchor{867}
@subsubsection logging


The @ref{868,,TimedRotatingFileHandler} has a new @emph{atTime}
parameter that can be used to specify the time of day when rollover should
happen.  (Contributed by Ronald Oussoren in bpo-9556@footnote{https://bugs.python.org/issue9556}.)

@ref{869,,SocketHandler} and
@ref{86a,,DatagramHandler} now support Unix domain sockets (by
setting @emph{port} to @code{None}).  (Contributed by Vinay Sajip in commit
ce46195b56a9.)

@ref{3a1,,fileConfig()} now accepts a
@ref{86b,,configparser.RawConfigParser} subclass instance for the @emph{fname}
parameter.  This facilitates using a configuration file when logging
configuration is just a part of the overall application configuration, or where
the application modifies the configuration before passing it to
@ref{3a1,,fileConfig()}.  (Contributed by Vinay Sajip in
bpo-16110@footnote{https://bugs.python.org/issue16110}.)

Logging configuration data received from a socket via the
@ref{86c,,logging.config.listen()} function can now be validated before being
processed by supplying a verification function as the argument to the new
@emph{verify} keyword argument.  (Contributed by Vinay Sajip in bpo-15452@footnote{https://bugs.python.org/issue15452}.)

@node marshal,mmap<2>,logging<5>,改进的模块<5>
@anchor{whatsnew/3 4 marshal}@anchor{86d}@anchor{whatsnew/3 4 whatsnew-marshal-3}@anchor{7d3}
@subsubsection marshal


The default @ref{b0,,marshal} version has been bumped to 3.  The code implementing
the new version restores the Python2 behavior of recording only one copy of
interned strings and preserving the interning on deserialization, and extends
this "one copy" ability to any object type (including handling recursive
references).  This reduces both the size of @code{.pyc} files and the amount of
memory a module occupies in memory when it is loaded from a @code{.pyc} (or
@code{.pyo}) file.  (Contributed by Kristján Valur Jónsson in bpo-16475@footnote{https://bugs.python.org/issue16475},
with additional speedups by Antoine Pitrou in bpo-19219@footnote{https://bugs.python.org/issue19219}.)

@node mmap<2>,multiprocessing<5>,marshal,改进的模块<5>
@anchor{whatsnew/3 4 mmap}@anchor{86e}
@subsubsection mmap


mmap objects can now be @ref{128,,weakref}ed.  (Contributed by Valerie Lambert in
bpo-4885@footnote{https://bugs.python.org/issue4885}.)

@node multiprocessing<5>,operator<2>,mmap<2>,改进的模块<5>
@anchor{whatsnew/3 4 multiprocessing}@anchor{86f}
@subsubsection multiprocessing

@anchor{whatsnew/3 4 whatsnew-multiprocessing-no-fork}@anchor{7dd}
On Unix two new @ref{870,,start methods},
@code{spawn} and @code{forkserver}, have been added for starting processes using
@ref{b7,,multiprocessing}.  These make the mixing of processes with threads more
robust, and the @code{spawn} method matches the semantics that multiprocessing has
always used on Windows.  New function
@ref{871,,get_all_start_methods()} reports all start methods
available on the platform, @ref{872,,get_start_method()} reports
the current start method, and @ref{873,,set_start_method()} sets
the start method.  (Contributed by Richard Oudkerk in bpo-8713@footnote{https://bugs.python.org/issue8713}.)

@ref{b7,,multiprocessing} also now has the concept of a @code{context}, which
determines how child processes are created.  New function
@ref{874,,get_context()} returns a context that uses a specified
start method.  It has the same API as the @ref{b7,,multiprocessing} module itself,
so you can use it to create @ref{875,,Pool}s and other
objects that will operate within that context.  This allows a framework and an
application or different parts of the same application to use multiprocessing
without interfering with each other.  (Contributed by Richard Oudkerk in
bpo-18999@footnote{https://bugs.python.org/issue18999}.)

Except when using the old @emph{fork} start method, child processes no longer
inherit unneeded handles/file descriptors from their parents (part of
bpo-8713@footnote{https://bugs.python.org/issue8713}).

@ref{b7,,multiprocessing} now relies on @ref{e2,,runpy} (which implements the
@code{-m} switch) to initialise @code{__main__} appropriately in child processes
when using the @code{spawn} or @code{forkserver} start methods. This resolves some
edge cases where combining multiprocessing, the @code{-m} command line switch,
and explicit relative imports could cause obscure failures in child
processes.  (Contributed by Nick Coghlan in bpo-19946@footnote{https://bugs.python.org/issue19946}.)

@node operator<2>,os<6>,multiprocessing<5>,改进的模块<5>
@anchor{whatsnew/3 4 operator}@anchor{876}
@subsubsection operator


New function @ref{877,,length_hint()} provides an implementation of the
specification for how the @ref{806,,__length_hint__()} special method should
be used, as part of the 
@geindex Python 提高建议; PEP 424
PEP 424@footnote{https://www.python.org/dev/peps/pep-0424} formal specification of this language
feature.  (Contributed by Armin Ronacher in bpo-16148@footnote{https://bugs.python.org/issue16148}.)

There is now a pure-python version of the @ref{c2,,operator} module available for
reference and for use by alternate implementations of Python.  (Contributed by
Zachary Ware in bpo-16694@footnote{https://bugs.python.org/issue16694}.)

@node os<6>,pdb<3>,operator<2>,改进的模块<5>
@anchor{whatsnew/3 4 os}@anchor{878}
@subsubsection os


There are new functions to get and set the @ref{7f4,,inheritable flag} of a file descriptor (@ref{7f5,,os.get_inheritable()},
@ref{7f6,,os.set_inheritable()}) or a Windows handle
(@ref{7f7,,os.get_handle_inheritable()}, @ref{7f8,,os.set_handle_inheritable()}).

New function @ref{879,,cpu_count()} reports the number of CPUs available on the
platform on which Python is running (or @code{None} if the count can't be
determined).  The @ref{87a,,multiprocessing.cpu_count()} function is now implemented
in terms of this function).  (Contributed by Trent Nelson, Yogesh Chaudhari,
Victor Stinner, and Charles-François Natali in bpo-17914@footnote{https://bugs.python.org/issue17914}.)

@ref{87b,,os.path.samestat()} is now available on the Windows platform (and the
@ref{87c,,os.path.samefile()} implementation is now shared between Unix and
Windows).  (Contributed by Brian Curtin in bpo-11939@footnote{https://bugs.python.org/issue11939}.)

@ref{1fa,,os.path.ismount()} now recognizes volumes mounted below a drive
root on Windows.  (Contributed by Tim Golden in bpo-9035@footnote{https://bugs.python.org/issue9035}.)

@ref{65f,,os.open()} supports two new flags on platforms that provide them,
@ref{87d,,O_PATH} (un-opened file descriptor), and @ref{87e,,O_TMPFILE}
(unnamed temporary file; as of 3.4.0 release available only on Linux systems
with a kernel version of 3.11 or newer that have uapi headers).  (Contributed
by Christian Heimes in bpo-18673@footnote{https://bugs.python.org/issue18673} and Benjamin Peterson, respectively.)

@node pdb<3>,pickle<4>,os<6>,改进的模块<5>
@anchor{whatsnew/3 4 pdb}@anchor{87f}
@subsubsection pdb


@ref{c9,,pdb} has been enhanced to handle generators, @ref{18f,,yield}, and
@code{yield from} in a more useful fashion.  This is especially helpful when
debugging @ref{a,,asyncio} based programs.  (Contributed by Andrew Svetlov and
Xavier de Gaye in bpo-16596@footnote{https://bugs.python.org/issue16596}.)

The @code{print} command has been removed from @ref{c9,,pdb}, restoring access to the
Python @ref{880,,print()} function from the pdb command line.  Python2's @code{pdb} did
not have a @code{print} command; instead, entering @code{print} executed the
@code{print} statement.  In Python3 @code{print} was mistakenly made an alias for the
pdb @ref{881,,p} command.  @code{p}, however, prints the @code{repr} of its argument,
not the @code{str} like the Python2 @code{print} command did.  Worse, the Python3
@code{pdb print} command shadowed the Python3 @code{print} function, making it
inaccessible at the @code{pdb} prompt.  (Contributed by Connor Osborn in
bpo-18764@footnote{https://bugs.python.org/issue18764}.)

@node pickle<4>,plistlib<2>,pdb<3>,改进的模块<5>
@anchor{whatsnew/3 4 pickle}@anchor{882}@anchor{whatsnew/3 4 whatsnew-protocol-4}@anchor{7dc}
@subsubsection pickle


@ref{ca,,pickle} now supports (but does not use by default) a new pickle protocol,
protocol 4.  This new protocol addresses a number of issues that were present
in previous protocols, such as the serialization of nested classes, very large
strings and containers, and classes whose @ref{883,,__new__()} method takes
keyword-only arguments.  It also provides some efficiency improvements.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3154

@item PEP 3154@footnote{https://www.python.org/dev/peps/pep-3154} -- Pickle protocol 4

PEP 由 Antoine Pitrou 撰写，并由 Alexandre Vassalotti 实现
@end table


@node plistlib<2>,poplib<2>,pickle<4>,改进的模块<5>
@anchor{whatsnew/3 4 plistlib}@anchor{884}
@subsubsection plistlib


@ref{cf,,plistlib} now has an API that is similar to the standard pattern for
stdlib serialization protocols, with new @ref{885,,load()},
@ref{886,,dump()}, @ref{887,,loads()}, and @ref{888,,dumps()}
functions.  (The older API is now deprecated.)  In addition to the already
supported XML plist format (@ref{889,,FMT_XML}), it also now supports
the binary plist format (@ref{88a,,FMT_BINARY}).  (Contributed by Ronald
Oussoren and others in bpo-14455@footnote{https://bugs.python.org/issue14455}.)

@node poplib<2>,pprint<2>,plistlib<2>,改进的模块<5>
@anchor{whatsnew/3 4 poplib}@anchor{88b}
@subsubsection poplib


Two new methods have been added to @ref{d0,,poplib}: @ref{88c,,capa()},
which returns the list of capabilities advertised by the POP server, and
@ref{88d,,stls()}, which switches a clear-text POP3 session into an
encrypted POP3 session if the POP server supports it.  (Contributed by Lorenzo
Catucci in bpo-4473@footnote{https://bugs.python.org/issue4473}.)

@node pprint<2>,pty,poplib<2>,改进的模块<5>
@anchor{whatsnew/3 4 pprint}@anchor{88e}
@subsubsection pprint


The @ref{d2,,pprint} module's @ref{88f,,PrettyPrinter} class and its
@ref{890,,pformat()}, and @ref{213,,pprint()} functions have a new
option, @emph{compact}, that controls how the output is formatted.  Currently
setting @emph{compact} to @code{True} means that sequences will be printed with as many
sequence elements as will fit within @emph{width} on each (indented) line.
(Contributed by Serhiy Storchaka in bpo-19132@footnote{https://bugs.python.org/issue19132}.)

Long strings are now wrapped using Python's normal line continuation
syntax.  (Contributed by Antoine Pitrou in bpo-17150@footnote{https://bugs.python.org/issue17150}.)

@node pty,pydoc<3>,pprint<2>,改进的模块<5>
@anchor{whatsnew/3 4 pty}@anchor{891}
@subsubsection pty


@ref{892,,pty.spawn()} now returns the status value from @ref{667,,os.waitpid()} on
the child process, instead of @code{None}.  (Contributed by Gregory P. Smith.)

@node pydoc<3>,re<5>,pty,改进的模块<5>
@anchor{whatsnew/3 4 pydoc}@anchor{893}
@subsubsection pydoc


The @ref{d9,,pydoc} module is now based directly on the @ref{556,,inspect.signature()}
introspection API, allowing it to provide signature information for a wider
variety of callable objects. This change also means that @code{__wrapped__}
attributes are now taken into account when displaying help information.
(Contributed by Larry Hastings in bpo-19674@footnote{https://bugs.python.org/issue19674}.)

The @ref{d9,,pydoc} module no longer displays the @code{self} parameter for
already bound methods. Instead, it aims to always display the exact current
signature of the supplied callable.  (Contributed by Larry Hastings in
bpo-20710@footnote{https://bugs.python.org/issue20710}.)

In addition to the changes that have been made to @ref{d9,,pydoc} directly,
its handling of custom @code{__dir__} methods and various descriptor
behaviours has also been improved substantially by the underlying changes in
the @ref{a0,,inspect} module.

As the @ref{56d,,help()} builtin is based on @ref{d9,,pydoc}, the above changes also
affect the behaviour of @ref{56d,,help()}.

@node re<5>,resource,pydoc<3>,改进的模块<5>
@anchor{whatsnew/3 4 re}@anchor{894}
@subsubsection re


New @ref{895,,fullmatch()} function and @code{regex.fullmatch()} method anchor
the pattern at both ends of the string to match.  This provides a way to be
explicit about the goal of the match, which avoids a class of subtle bugs where
@code{$} characters get lost during code changes or the addition of alternatives
to an existing regular expression.  (Contributed by Matthew Barnett in
bpo-16203@footnote{https://bugs.python.org/issue16203}.)

The repr of @ref{896,,regex objects} now includes the pattern
and the flags; the repr of @ref{897,,match objects} now
includes the start, end, and the part of the string that matched.  (Contributed
by Hugo Lopes Tavares and Serhiy Storchaka in bpo-13592@footnote{https://bugs.python.org/issue13592} and
bpo-17087@footnote{https://bugs.python.org/issue17087}.)

@node resource,select,re<5>,改进的模块<5>
@anchor{whatsnew/3 4 resource}@anchor{898}
@subsubsection resource


New @ref{899,,prlimit()} function, available on Linux platforms with a
kernel version of 2.6.36 or later and glibc of 2.13 or later, provides the
ability to query or set the resource limits for processes other than the one
making the call.  (Contributed by Christian Heimes in bpo-16595@footnote{https://bugs.python.org/issue16595}.)

On Linux kernel version 2.6.36 or later, there are also some new
Linux specific constants: @ref{89a,,RLIMIT_MSGQUEUE},
@ref{89b,,RLIMIT_NICE}, @ref{89c,,RLIMIT_RTPRIO},
@ref{89d,,RLIMIT_RTTIME}, and @ref{89e,,RLIMIT_SIGPENDING}.
(Contributed by Christian Heimes in bpo-19324@footnote{https://bugs.python.org/issue19324}.)

On FreeBSD version 9 and later, there some new FreeBSD specific constants:
@ref{89f,,RLIMIT_SBSIZE}, @ref{8a0,,RLIMIT_SWAP}, and
@ref{8a1,,RLIMIT_NPTS}.  (Contributed by Claudiu Popa in
bpo-19343@footnote{https://bugs.python.org/issue19343}.)

@node select,shelve,resource,改进的模块<5>
@anchor{whatsnew/3 4 select}@anchor{8a2}
@subsubsection select


@ref{8a3,,epoll} objects now support the context management protocol.
When used in a @ref{6e3,,with} statement, the @ref{8a4,,close()}
method will be called automatically at the end of the block.  (Contributed
by Serhiy Storchaka in bpo-16488@footnote{https://bugs.python.org/issue16488}.)

@ref{8a5,,devpoll} objects now have @ref{8a6,,fileno()} and
@ref{8a7,,close()} methods, as well as a new attribute
@ref{8a8,,closed}.  (Contributed by Victor Stinner in
bpo-18794@footnote{https://bugs.python.org/issue18794}.)

@node shelve,shutil<3>,select,改进的模块<5>
@anchor{whatsnew/3 4 shelve}@anchor{8a9}
@subsubsection shelve


@ref{8aa,,Shelf} instances may now be used in @ref{6e3,,with} statements,
and will be automatically closed at the end of the @code{with} block.
(Contributed by Filip Gruszczyński in bpo-13896@footnote{https://bugs.python.org/issue13896}.)

@node shutil<3>,smtpd<2>,shelve,改进的模块<5>
@anchor{whatsnew/3 4 shutil}@anchor{8ab}
@subsubsection shutil


@ref{258,,copyfile()} now raises a specific @ref{8ac,,Error} subclass,
@ref{8ad,,SameFileError}, when the source and destination are the same
file, which allows an application to take appropriate action on this specific
error.  (Contributed by Atsuo Ishimoto and Hynek Schlawack in
bpo-1492704@footnote{https://bugs.python.org/issue1492704}.)

@node smtpd<2>,smtplib<2>,shutil<3>,改进的模块<5>
@anchor{whatsnew/3 4 smtpd}@anchor{8ae}
@subsubsection smtpd


The @ref{5fd,,SMTPServer} and @ref{5fc,,SMTPChannel} classes now
accept a @emph{map} keyword argument which, if specified, is passed in to
@ref{8af,,asynchat.async_chat} as its @emph{map} argument.  This allows an application
to avoid affecting the global socket map.  (Contributed by Vinay Sajip in
bpo-11959@footnote{https://bugs.python.org/issue11959}.)

@node smtplib<2>,socket<6>,smtpd<2>,改进的模块<5>
@anchor{whatsnew/3 4 smtplib}@anchor{8b0}
@subsubsection smtplib


@ref{8b1,,SMTPException} is now a subclass of @ref{1d3,,OSError}, which allows
both socket level errors and SMTP protocol level errors to be caught in one
try/except statement by code that only cares whether or not an error occurred.
(Contributed by Ned Jackson Lovely in bpo-2118@footnote{https://bugs.python.org/issue2118}.)

@node socket<6>,sqlite3<4>,smtplib<2>,改进的模块<5>
@anchor{whatsnew/3 4 socket}@anchor{8b2}
@subsubsection socket


The socket module now supports the @ref{8b3,,CAN_BCM} protocol on
platforms that support it.  (Contributed by Brian Thorne in bpo-15359@footnote{https://bugs.python.org/issue15359}.)

Socket objects have new methods to get or set their @ref{7f4,,inheritable flag}, @ref{7f9,,get_inheritable()} and
@ref{7fa,,set_inheritable()}.

The @code{socket.AF_*} and @code{socket.SOCK_*} constants are now enumeration values
using the new @ref{7b,,enum} module.  This allows meaningful names to be printed
during debugging, instead of integer "magic numbers".

The @ref{8b4,,AF_LINK} constant is now available on BSD and OSX.

@ref{8b5,,inet_pton()} and @ref{8b6,,inet_ntop()} are now supported
on Windows.  (Contributed by Atsuo Ishimoto in bpo-7171@footnote{https://bugs.python.org/issue7171}.)

@node sqlite3<4>,ssl<7>,socket<6>,改进的模块<5>
@anchor{whatsnew/3 4 sqlite3}@anchor{8b7}
@subsubsection sqlite3


A new boolean parameter to the @ref{3d2,,connect()} function, @emph{uri}, can be
used to indicate that the @emph{database} parameter is a @code{uri} (see the SQLite URI documentation@footnote{https://www.sqlite.org/uri.html}).  (Contributed by poq in
bpo-13773@footnote{https://bugs.python.org/issue13773}.)

@node ssl<7>,stat,sqlite3<4>,改进的模块<5>
@anchor{whatsnew/3 4 ssl}@anchor{8b8}
@subsubsection ssl

@anchor{whatsnew/3 4 whatsnew-tls-11-12}@anchor{7e1}
@ref{8b9,,PROTOCOL_TLSv1_1} and @ref{8ba,,PROTOCOL_TLSv1_2} (TLSv1.1 and
TLSv1.2 support) have been added; support for these protocols is only available if
Python is linked with OpenSSL 1.0.1 or later.  (Contributed by Michele Orrù and
Antoine Pitrou in bpo-16692@footnote{https://bugs.python.org/issue16692}.)
@anchor{whatsnew/3 4 whatsnew34-sslcontext}@anchor{7e4}
New function @ref{8bb,,create_default_context()} provides a standard way to
obtain an @ref{3dc,,SSLContext} whose settings are intended to be a
reasonable balance between compatibility and security.  These settings are
more stringent than the defaults provided by the @ref{3dc,,SSLContext}
constructor, and may be adjusted in the future, without prior deprecation, if
best-practice security requirements change.  The new recommended best
practice for using stdlib libraries that support SSL is to use
@ref{8bb,,create_default_context()} to obtain an @ref{3dc,,SSLContext}
object, modify it if needed, and then pass it as the @emph{context} argument
of the appropriate stdlib API.  (Contributed by Christian Heimes
in bpo-19689@footnote{https://bugs.python.org/issue19689}.)

@ref{3dc,,SSLContext} method @ref{7e5,,load_verify_locations()}
accepts a new optional argument @emph{cadata}, which can be used to provide PEM or
DER encoded certificates directly via strings or bytes, respectively.
(Contributed by Christian Heimes in bpo-18138@footnote{https://bugs.python.org/issue18138}.)

New function @ref{8bc,,get_default_verify_paths()} returns
a named tuple of the paths and environment variables that the
@ref{8bd,,set_default_verify_paths()} method uses to set
OpenSSL's default @code{cafile} and @code{capath}.  This can be an aid in
debugging default verification issues.  (Contributed by Christian Heimes
in bpo-18143@footnote{https://bugs.python.org/issue18143}.)

@ref{3dc,,SSLContext} has a new method,
@ref{8be,,cert_store_stats()}, that reports the number of loaded
@code{X.509} certs, @code{X.509 CA} certs, and certificate revocation lists
(@code{crl}s), as well as a @ref{8bf,,get_ca_certs()} method that
returns a list of the loaded @code{CA} certificates.  (Contributed by Christian
Heimes in bpo-18147@footnote{https://bugs.python.org/issue18147}.)

If OpenSSL 0.9.8 or later is available, @ref{3dc,,SSLContext} has a new
attribute @ref{8c0,,verify_flags} that can be used to control the
certificate verification process by setting it to some combination of the new
constants @ref{8c1,,VERIFY_DEFAULT}, @ref{8c2,,VERIFY_CRL_CHECK_LEAF},
@ref{8c3,,VERIFY_CRL_CHECK_CHAIN}, or @ref{8c4,,VERIFY_X509_STRICT}.
OpenSSL does not do any CRL verification by default.  (Contributed by
Christien Heimes in bpo-8813@footnote{https://bugs.python.org/issue8813}.)

New @ref{3dc,,SSLContext} method @ref{8c5,,load_default_certs()}
loads a set of default "certificate authority" (CA) certificates from default
locations, which vary according to the platform.  It can be used to load both
TLS web server authentication certificates
(@code{purpose=}@ref{8c6,,SERVER_AUTH}) for a client to use to verify a
server, and certificates for a server to use in verifying client certificates
(@code{purpose=}@ref{8c7,,CLIENT_AUTH}).  (Contributed by Christian
Heimes in bpo-19292@footnote{https://bugs.python.org/issue19292}.)
@anchor{whatsnew/3 4 whatsnew34-win-cert-store}@anchor{7e2}
Two new windows-only functions, @ref{8c8,,enum_certificates()} and
@ref{8c9,,enum_crls()} provide the ability to retrieve certificates,
certificate information, and CRLs from the Windows cert store.  (Contributed
by Christian Heimes in bpo-17134@footnote{https://bugs.python.org/issue17134}.)
@anchor{whatsnew/3 4 whatsnew34-sni}@anchor{7e3}
Support for server-side SNI (Server Name Indication) using the new
@ref{8ca,,ssl.SSLContext.set_servername_callback()} method.
(Contributed by Daniel Black in bpo-8109@footnote{https://bugs.python.org/issue8109}.)

The dictionary returned by @ref{8cb,,SSLSocket.getpeercert()} contains additional
@code{X509v3} extension items: @code{crlDistributionPoints}, @code{calIssuers}, and
@code{OCSP} URIs.  (Contributed by Christian Heimes in bpo-18379@footnote{https://bugs.python.org/issue18379}.)

@node stat,struct<2>,ssl<7>,改进的模块<5>
@anchor{whatsnew/3 4 stat}@anchor{8cc}
@subsubsection stat


The @ref{f4,,stat} module is now backed by a C implementation in @code{_stat}. A C
implementation is required as most of the values aren't standardized and
are platform-dependent.  (Contributed by Christian Heimes in bpo-11016@footnote{https://bugs.python.org/issue11016}.)

The module supports new @ref{8cd,,ST_MODE} flags, @ref{8ce,,S_IFDOOR},
@ref{8cf,,S_IFPORT}, and @ref{8d0,,S_IFWHT}.  (Contributed by
Christian Hiemes in bpo-11016@footnote{https://bugs.python.org/issue11016}.)

@node struct<2>,subprocess<4>,stat,改进的模块<5>
@anchor{whatsnew/3 4 struct}@anchor{8d1}
@subsubsection struct


New function @ref{8d2,,iter_unpack} and a new
@ref{8d3,,struct.Struct.iter_unpack()} method on compiled formats provide streamed
unpacking of a buffer containing repeated instances of a given format of data.
(Contributed by Antoine Pitrou in bpo-17804@footnote{https://bugs.python.org/issue17804}.)

@node subprocess<4>,sunau<2>,struct<2>,改进的模块<5>
@anchor{whatsnew/3 4 subprocess}@anchor{8d4}
@subsubsection subprocess


@ref{8d5,,check_output()} now accepts an @emph{input} argument that can
be used to provide the contents of @code{stdin} for the command that is run.
(Contributed by Zack Weinberg in bpo-16624@footnote{https://bugs.python.org/issue16624}.)

@code{getstatus()} and @ref{8d6,,getstatusoutput()} now
work on Windows.  This change was actually inadvertently made in 3.3.4.
(Contributed by Tim Golden in bpo-10197@footnote{https://bugs.python.org/issue10197}.)

@node sunau<2>,sys<6>,subprocess<4>,改进的模块<5>
@anchor{whatsnew/3 4 sunau}@anchor{8d7}
@subsubsection sunau


The @code{getparams()} method now returns a namedtuple rather than a
plain tuple.  (Contributed by Claudiu Popa in bpo-18901@footnote{https://bugs.python.org/issue18901}.)

@ref{46c,,sunau.open()} now supports the context management protocol: when used in a
@ref{6e3,,with} block, the @code{close} method of the returned object will be
called automatically at the end of the block.  (Contributed by Serhiy Storchaka
in bpo-18878@footnote{https://bugs.python.org/issue18878}.)

@ref{8d8,,AU_write.setsampwidth()} now supports 24 bit samples, thus adding
support for writing 24 sample using the module.  (Contributed by
Serhiy Storchaka in bpo-19261@footnote{https://bugs.python.org/issue19261}.)

The @ref{8d9,,writeframesraw()} and
@ref{8da,,writeframes()} methods now accept any @ref{5e3,,bytes-like object}.  (Contributed by Serhiy Storchaka in bpo-8311@footnote{https://bugs.python.org/issue8311}.)

@node sys<6>,tarfile<3>,sunau<2>,改进的模块<5>
@anchor{whatsnew/3 4 sys}@anchor{8db}
@subsubsection sys


New function @ref{8dc,,sys.getallocatedblocks()} returns the current number of
blocks allocated by the interpreter.  (In CPython with the default
@code{--with-pymalloc} setting, this is allocations made through the
@ref{502,,PyObject_Malloc()} API.)  This can be useful for tracking memory leaks,
especially if automated via a test suite.  (Contributed by Antoine Pitrou
in bpo-13390@footnote{https://bugs.python.org/issue13390}.)

When the Python interpreter starts in @ref{8dd,,interactive mode}, it checks for an @ref{8de,,__interactivehook__} attribute
on the @ref{fd,,sys} module.  If the attribute exists, its value is called with no
arguments just before interactive mode is started.  The check is made after the
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP} file is read, so it can be set there.  The @ref{eb,,site}
module @ref{8e0,,sets it} to a function that enables tab
completion and history saving (in @code{~/.python-history}) if the platform
supports @ref{de,,readline}.  If you do not want this (new) behavior, you can
override it in 
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP}, @code{sitecustomize}, or
@code{usercustomize} by deleting this attribute from @ref{fd,,sys} (or setting it
to some other callable).  (Contributed by Éric Araujo and Antoine Pitrou in
bpo-5845@footnote{https://bugs.python.org/issue5845}.)

@node tarfile<3>,textwrap,sys<6>,改进的模块<5>
@anchor{whatsnew/3 4 tarfile}@anchor{8e1}
@subsubsection tarfile


The @ref{101,,tarfile} module now supports a simple @ref{8e2,,命令行界面} when
called as a script directly or via @code{-m}.  This can be used to create and
extract tarfile archives.  (Contributed by Berker Peksag in bpo-13477@footnote{https://bugs.python.org/issue13477}.)

@node textwrap,threading<4>,tarfile<3>,改进的模块<5>
@anchor{whatsnew/3 4 textwrap}@anchor{8e3}
@subsubsection textwrap


The @ref{8e4,,TextWrapper} class has two new attributes/constructor
arguments: @ref{8e5,,max_lines}, which limits the number of
lines in the output, and @ref{8e6,,placeholder}, which is a
string that will appear at the end of the output if it has been truncated
because of @emph{max_lines}.  Building on these capabilities, a new convenience
function @ref{8e7,,shorten()} collapses all of the whitespace in the input
to single spaces and produces a single line of a given @emph{width} that ends with
the @emph{placeholder} (by default, @code{[...]}).  (Contributed by Antoine Pitrou and
Serhiy Storchaka in bpo-18585@footnote{https://bugs.python.org/issue18585} and bpo-18725@footnote{https://bugs.python.org/issue18725}.)

@node threading<4>,回溯<3>,textwrap,改进的模块<5>
@anchor{whatsnew/3 4 threading}@anchor{8e8}
@subsubsection threading


The @ref{234,,Thread} object representing the main thread can be
obtained from the new @ref{8e9,,main_thread()} function.  In normal
conditions this will be the thread from which the Python interpreter was
started.  (Contributed by Andrew Svetlov in bpo-18882@footnote{https://bugs.python.org/issue18882}.)

@node 回溯<3>,types<3>,threading<4>,改进的模块<5>
@anchor{whatsnew/3 4 traceback}@anchor{8ea}
@subsubsection 回溯


A new @ref{8eb,,traceback.clear_frames()} function takes a traceback object
and clears the local variables in all of the frames it references,
reducing the amount of memory consumed.  (Contributed by Andrew Kuchling in
bpo-1565525@footnote{https://bugs.python.org/issue1565525}.)

@node types<3>,urllib<2>,回溯<3>,改进的模块<5>
@anchor{whatsnew/3 4 types}@anchor{8ec}
@subsubsection types


A new @ref{8ed,,DynamicClassAttribute()} descriptor provides a way to define
an attribute that acts normally when looked up through an instance object, but
which is routed to the @emph{class} @code{__getattr__} when looked up through the
class.  This allows one to have properties active on a class, and have virtual
attributes on the class with the same name (see @code{Enum} for an example).
(Contributed by Ethan Furman in bpo-19030@footnote{https://bugs.python.org/issue19030}.)

@node urllib<2>,unittest<4>,types<3>,改进的模块<5>
@anchor{whatsnew/3 4 urllib}@anchor{8ee}
@subsubsection urllib


@ref{120,,urllib.request} now supports @code{data:} URLs via the
@ref{8ef,,DataHandler} class.  (Contributed by Mathias Panzenböck
in bpo-16423@footnote{https://bugs.python.org/issue16423}.)

The http method that will be used by a @ref{8f0,,Request} class
can now be specified by setting a @ref{8f1,,method}
class attribute on the subclass.  (Contributed by Jason R Coombs in
bpo-18978@footnote{https://bugs.python.org/issue18978}.)

@ref{8f0,,Request} objects are now reusable: if the
@ref{8f2,,full_url} or @ref{8f3,,data}
attributes are modified, all relevant internal properties are updated.  This
means, for example, that it is now possible to use the same
@ref{8f0,,Request} object in more than one
@ref{8f4,,OpenerDirector.open()} call with different @emph{data} arguments, or to
modify a @ref{8f0,,Request}'s @code{url} rather than recomputing it
from scratch.  There is also a new
@ref{8f5,,remove_header()} method that can be used to remove
headers from a @ref{8f0,,Request}.  (Contributed by Alexey
Kachayev in bpo-16464@footnote{https://bugs.python.org/issue16464}, Daniel Wozniak in bpo-17485@footnote{https://bugs.python.org/issue17485}, and Damien Brecht
and Senthil Kumaran in bpo-17272@footnote{https://bugs.python.org/issue17272}.)

@ref{8f6,,HTTPError} objects now have a
@ref{8f7,,headers} attribute that provides access to the
HTTP response headers associated with the error.  (Contributed by
Berker Peksag in bpo-15701@footnote{https://bugs.python.org/issue15701}.)

@node unittest<4>,venv<4>,urllib<2>,改进的模块<5>
@anchor{whatsnew/3 4 unittest}@anchor{8f8}
@subsubsection unittest


The @ref{8f9,,TestCase} class has a new method,
@ref{8fa,,subTest()}, that produces a context manager whose
@ref{6e3,,with} block becomes a "sub-test".  This context manager allows a test
method to dynamically generate subtests  by, say, calling the @code{subTest}
context manager inside a loop.  A single test method can thereby produce an
indefinite number of separately-identified and separately-counted tests, all of
which will run even if one or more of them fail.  For example:

@example
class NumbersTest(unittest.TestCase):
    def test_even(self):
        for i in range(6):
            with self.subTest(i=i):
                self.assertEqual(i % 2, 0)
@end example

will result in six subtests, each identified in the unittest verbose output
with a label consisting of the variable name @code{i} and a particular value for
that variable (@code{i=0}, @code{i=1}, etc).  See @ref{8fb,,Distinguishing test iterations using subtests} for the full
version of this example.  (Contributed by Antoine Pitrou in bpo-16997@footnote{https://bugs.python.org/issue16997}.)

@ref{8fc,,unittest.main()} now accepts an iterable of test names for
@emph{defaultTest}, where previously it only accepted a single test name as a
string.  (Contributed by Jyrki Pulliainen in bpo-15132@footnote{https://bugs.python.org/issue15132}.)

If @ref{8fd,,SkipTest} is raised during test discovery (that is, at the
module level in the test file), it is now reported as a skip instead of an
error.  (Contributed by Zach Ware in bpo-16935@footnote{https://bugs.python.org/issue16935}.)

@ref{8fe,,discover()} now sorts the discovered files to provide
consistent test ordering.  (Contributed by Martin Melin and Jeff Ramnani in
bpo-16709@footnote{https://bugs.python.org/issue16709}.)

@ref{6c8,,TestSuite} now drops references to tests as soon as the test
has been run, if the test is successful.  On Python interpreters that do
garbage collection, this allows the tests to be garbage collected if nothing
else is holding a reference to the test.  It is possible to override this
behavior by creating a @ref{6c8,,TestSuite} subclass that defines a
custom @code{_removeTestAtIndex} method.  (Contributed by Tom Wardill, Matt
McClure, and Andrew Svetlov in bpo-11798@footnote{https://bugs.python.org/issue11798}.)

A new test assertion context-manager, @ref{8ff,,assertLogs()},
will ensure that a given block of code emits a log message using the
@ref{aa,,logging} module.  By default the message can come from any logger and
have a priority of @code{INFO} or higher, but both the logger name and an
alternative minimum logging level may be specified.  The object returned by the
context manager can be queried for the @ref{900,,LogRecord}s and/or
formatted messages that were logged.  (Contributed by Antoine Pitrou in
bpo-18937@footnote{https://bugs.python.org/issue18937}.)

Test discovery now works with namespace packages (Contributed by Claudiu Popa
in bpo-17457@footnote{https://bugs.python.org/issue17457}.)

@ref{11c,,unittest.mock} objects now inspect their specification signatures when
matching calls, which means an argument can now be matched by either position
or name, instead of only by position.  (Contributed by Antoine Pitrou in
bpo-17015@footnote{https://bugs.python.org/issue17015}.)

@code{mock_open()} objects now have @code{readline} and @code{readlines}
methods.  (Contributed by Toshio Kuratomi in bpo-17467@footnote{https://bugs.python.org/issue17467}.)

@node venv<4>,wave<2>,unittest<4>,改进的模块<5>
@anchor{whatsnew/3 4 venv}@anchor{901}
@subsubsection venv


@ref{125,,venv} now includes activation scripts for the @code{csh} and @code{fish}
shells.  (Contributed by Andrew Svetlov in bpo-15417@footnote{https://bugs.python.org/issue15417}.)

@ref{902,,EnvBuilder} and the @ref{903,,create()} convenience function
take a new keyword argument @emph{with_pip}, which defaults to @code{False}, that
controls whether or not @ref{902,,EnvBuilder} ensures that @code{pip} is
installed in the virtual environment.  (Contributed by Nick Coghlan in
bpo-19552@footnote{https://bugs.python.org/issue19552} as part of the 
@geindex Python 提高建议; PEP 453
PEP 453@footnote{https://www.python.org/dev/peps/pep-0453} implementation.)

@node wave<2>,weakref<2>,venv<4>,改进的模块<5>
@anchor{whatsnew/3 4 wave}@anchor{904}
@subsubsection wave


The @code{getparams()} method now returns a namedtuple rather than a
plain tuple.  (Contributed by Claudiu Popa in bpo-17487@footnote{https://bugs.python.org/issue17487}.)

@ref{470,,wave.open()} now supports the context management protocol.  (Contributed
by Claudiu Popa in bpo-17616@footnote{https://bugs.python.org/issue17616}.)

@ref{127,,wave} can now @ref{905,,write output to unseekable files}.  (Contributed by David Jones, Guilherme Polo, and Serhiy
Storchaka in bpo-5202@footnote{https://bugs.python.org/issue5202}.)

The @ref{906,,writeframesraw()} and
@ref{907,,writeframes()} methods now accept any @ref{5e3,,bytes-like object}.  (Contributed by Serhiy Storchaka in bpo-8311@footnote{https://bugs.python.org/issue8311}.)

@node weakref<2>,xml etree<2>,wave<2>,改进的模块<5>
@anchor{whatsnew/3 4 weakref}@anchor{908}
@subsubsection weakref


New @ref{909,,WeakMethod} class simulates weak references to bound
methods.  (Contributed by Antoine Pitrou in bpo-14631@footnote{https://bugs.python.org/issue14631}.)

New @ref{29d,,finalize} class makes it possible to register a callback
to be invoked when an object is garbage collected, without needing to
carefully manage the lifecycle of the weak reference itself.  (Contributed by
Richard Oudkerk in bpo-15528@footnote{https://bugs.python.org/issue15528}.)

The callback, if any, associated with a @ref{90a,,ref} is now
exposed via the @ref{90b,,__callback__} attribute.  (Contributed
by Mark Dickinson in bpo-17643@footnote{https://bugs.python.org/issue17643}.)

@node xml etree<2>,zipfile<4>,weakref<2>,改进的模块<5>
@anchor{whatsnew/3 4 xml-etree}@anchor{90c}
@subsubsection xml.etree


A new parser, @ref{90d,,XMLPullParser}, allows a
non-blocking applications to parse XML documents.  An example can be
seen at @ref{90e,,Pull API进行非阻塞解析}.  (Contributed by Antoine
Pitrou in bpo-17741@footnote{https://bugs.python.org/issue17741}.)

The @ref{137,,xml.etree.ElementTree} @ref{90f,,tostring()} and
@ref{910,,tostringlist()} functions, and the
@ref{911,,ElementTree}
@ref{912,,write()} method, now have a
@emph{short_empty_elements} @ref{2ac,,keyword-only parameter}
providing control over whether elements with no content are written in
abbreviated (@code{<tag />}) or expanded (@code{<tag></tag>}) form.  (Contributed by
Ariel Poliak and Serhiy Storchaka in bpo-14377@footnote{https://bugs.python.org/issue14377}.)

@node zipfile<4>,,xml etree<2>,改进的模块<5>
@anchor{whatsnew/3 4 zipfile}@anchor{913}
@subsubsection zipfile


The @ref{914,,writepy()} method of the
@ref{915,,PyZipFile} class has a new @emph{filterfunc} option that can be
used to control which directories and files are added to the archive.  For
example, this could be used to exclude test files from the archive.
(Contributed by Christian Tismer in bpo-19274@footnote{https://bugs.python.org/issue19274}.)

The @emph{allowZip64} parameter to @ref{417,,ZipFile} and
@code{PyZipfile} is now @code{True} by default.  (Contributed by
William Mallard in bpo-17201@footnote{https://bugs.python.org/issue17201}.)

@node CPython Implementation Changes,弃用<4>,改进的模块<5>,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 cpython-implementation-changes}@anchor{916}
@subsection CPython Implementation Changes


@menu
* PEP 445; Customization of CPython Memory Allocators: PEP 445 Customization of CPython Memory Allocators. 
* PEP 442; Safe Object Finalization: PEP 442 Safe Object Finalization. 
* PEP 456; Secure and Interchangeable Hash Algorithm: PEP 456 Secure and Interchangeable Hash Algorithm. 
* PEP 436; Argument Clinic: PEP 436 Argument Clinic. 
* Other Build and C API Changes:: 
* 其他改进: 其他改进<2>. 
* Significant Optimizations:: 

@end menu

@node PEP 445 Customization of CPython Memory Allocators,PEP 442 Safe Object Finalization,,CPython Implementation Changes
@anchor{whatsnew/3 4 pep-445-customization-of-cpython-memory-allocators}@anchor{917}@anchor{whatsnew/3 4 whatsnew-pep-445}@anchor{7e7}
@subsubsection PEP 445: Customization of CPython Memory Allocators


@geindex Python 提高建议; PEP 445
PEP 445@footnote{https://www.python.org/dev/peps/pep-0445} adds new C level interfaces to customize memory allocation in
the CPython interpreter.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 445

@item PEP 445@footnote{https://www.python.org/dev/peps/pep-0445} -- Add new APIs to customize Python memory allocators

PEP 由 Victor Stinner 撰写并实现。
@end table


@node PEP 442 Safe Object Finalization,PEP 456 Secure and Interchangeable Hash Algorithm,PEP 445 Customization of CPython Memory Allocators,CPython Implementation Changes
@anchor{whatsnew/3 4 pep-442-safe-object-finalization}@anchor{918}@anchor{whatsnew/3 4 whatsnew-pep-442}@anchor{7e6}
@subsubsection PEP 442: Safe Object Finalization


@geindex Python 提高建议; PEP 442
PEP 442@footnote{https://www.python.org/dev/peps/pep-0442} removes the current limitations and quirks of object finalization
in CPython. With it, objects with @ref{919,,__del__()} methods, as well as
generators with @ref{182,,finally} clauses, can be finalized when they are
part of a reference cycle.

As part of this change, module globals are no longer forcibly set to
@ref{157,,None} during interpreter shutdown in most cases, instead relying
on the normal operation of the cyclic garbage collector.  This avoids a
whole class of interpreter-shutdown-time errors, usually involving
@code{__del__} methods, that have plagued Python since the cyclic GC
was first introduced.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 442

@item PEP 442@footnote{https://www.python.org/dev/peps/pep-0442} -- Safe object finalization

PEP 由 Antoine Pitrou 撰写并实现
@end table


@node PEP 456 Secure and Interchangeable Hash Algorithm,PEP 436 Argument Clinic,PEP 442 Safe Object Finalization,CPython Implementation Changes
@anchor{whatsnew/3 4 pep-456-secure-and-interchangeable-hash-algorithm}@anchor{91a}@anchor{whatsnew/3 4 whatsnew-pep-456}@anchor{7df}
@subsubsection PEP 456: Secure and Interchangeable Hash Algorithm


@geindex Python 提高建议; PEP 456
PEP 456@footnote{https://www.python.org/dev/peps/pep-0456} follows up on earlier security fix work done on Python's hash
algorithm to address certain DOS attacks to which public facing APIs backed by
dictionary lookups may be subject.  (See bpo-14621@footnote{https://bugs.python.org/issue14621} for the start of the
current round of improvements.)  The PEP unifies CPython's hash code to make it
easier for a packager to substitute a different hash algorithm, and switches
Python's default implementation to a SipHash implementation on platforms that
have a 64 bit data type.  Any performance differences in comparison with the
older FNV algorithm are trivial.

The PEP adds additional fields to the @ref{91b,,sys.hash_info} named tuple to
describe the hash algorithm in use by the currently executing binary.  Otherwise,
the PEP does not alter any existing CPython APIs.

@node PEP 436 Argument Clinic,Other Build and C API Changes,PEP 456 Secure and Interchangeable Hash Algorithm,CPython Implementation Changes
@anchor{whatsnew/3 4 pep-436-argument-clinic}@anchor{91c}@anchor{whatsnew/3 4 whatsnew-pep-436}@anchor{7e8}
@subsubsection PEP 436: Argument Clinic


"Argument Clinic" (
@geindex Python 提高建议; PEP 436
PEP 436@footnote{https://www.python.org/dev/peps/pep-0436}) is now part of the CPython build process
and can be used to simplify the process of defining and maintaining
accurate signatures for builtins and standard library extension modules
implemented in C.

Some standard library extension modules have been converted to use Argument
Clinic in Python 3.4, and @ref{d9,,pydoc} and @ref{a0,,inspect} have been updated
accordingly.

It is expected that signature metadata for programmatic introspection will
be added to additional callables implemented in C as part of Python 3.4
maintenance releases.

@cartouche
@quotation 注解 
The Argument Clinic PEP is not fully up to date with the state of the
implementation. This has been deemed acceptable by the release manager
and core development team in this case, as Argument Clinic will not
be made available as a public API for third party use in Python 3.4.
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 436

@item PEP 436@footnote{https://www.python.org/dev/peps/pep-0436} -- The Argument Clinic DSL

PEP 由 Larry Hastings 撰写并实现
@end table


@node Other Build and C API Changes,其他改进<2>,PEP 436 Argument Clinic,CPython Implementation Changes
@anchor{whatsnew/3 4 other-build-and-c-api-changes}@anchor{91d}
@subsubsection Other Build and C API Changes



@itemize *

@item 
The new @ref{91e,,PyType_GetSlot()} function has been added to the stable ABI,
allowing retrieval of function pointers from named type slots when using
the limited API.  (Contributed by Martin von Löwis in bpo-17162@footnote{https://bugs.python.org/issue17162}.)

@item 
The new @ref{91f,,Py_SetStandardStreamEncoding()} pre-initialization API
allows applications embedding the CPython interpreter to reliably force
a particular encoding and error handler for the standard streams.
(Contributed by Bastien Montagne and Nick Coghlan in bpo-16129@footnote{https://bugs.python.org/issue16129}.)

@item 
Most Python C APIs that don't mutate string arguments are now correctly
marked as accepting @code{const char *} rather than @code{char *}.  (Contributed
by Serhiy Storchaka in bpo-1772673@footnote{https://bugs.python.org/issue1772673}.)

@item 
A new shell version of @code{python-config} can be used even when a python
interpreter is not available (for example, in cross compilation scenarios).

@item 
@ref{7c5,,PyUnicode_FromFormat()} now supports width and precision
specifications for @code{%s}, @code{%A}, @code{%U}, @code{%V}, @code{%S}, and @code{%R}.
(Contributed by Ysj Ray and Victor Stinner in bpo-7330@footnote{https://bugs.python.org/issue7330}.)

@item 
New function @ref{920,,PyStructSequence_InitType2()} supplements the
existing @ref{921,,PyStructSequence_InitType()} function.  The difference
is that it returns @code{0} on success and @code{-1} on failure.

@item 
The CPython source can now be compiled using the address sanity checking
features of recent versions of GCC and clang:  the false alarms in the small
object allocator have been silenced.  (Contributed by Dhiru Kholia in
bpo-18596@footnote{https://bugs.python.org/issue18596}.)

@item 
The Windows build now uses Address Space Layout Randomization@footnote{https://en.wikipedia.org/wiki/Address_space_layout_randomization} and Data Execution Prevention@footnote{https://en.wikipedia.org/wiki/Data_Execution_Prevention}.  (Contributed by
Christian Heimes in bpo-16632@footnote{https://bugs.python.org/issue16632}.)

@item 
New function @ref{922,,PyObject_LengthHint()} is the C API equivalent
of @ref{877,,operator.length_hint()}.  (Contributed by Armin Ronacher in
bpo-16148@footnote{https://bugs.python.org/issue16148}.)
@end itemize

@node 其他改进<2>,Significant Optimizations,Other Build and C API Changes,CPython Implementation Changes
@anchor{whatsnew/3 4 other-improvements}@anchor{923}@anchor{whatsnew/3 4 other-improvements-3-4}@anchor{924}
@subsubsection 其他改进

@anchor{whatsnew/3 4 whatsnew-isolated-mode}@anchor{7d0}

@itemize *

@item 
The @ref{925,,python} command has a new @ref{926,,option}, @code{-I}, which causes it to run in "isolated mode",
which means that @ref{482,,sys.path} contains neither the script's directory nor
the user's @code{site-packages} directory, and all 
@geindex PYTHON*
@geindex 环境变量; PYTHON*
@code{PYTHON*} environment
variables are ignored (it implies both @code{-s} and @code{-E}).  Other
restrictions may also be applied in the future, with the goal being to
isolate the execution of a script from the user's environment.  This is
appropriate, for example, when Python is used to run a system script.  On
most POSIX systems it can and should be used in the @code{#!} line of system
scripts.  (Contributed by Christian Heimes in bpo-16499@footnote{https://bugs.python.org/issue16499}.)

@item 
Tab-completion is now enabled by default in the interactive interpreter
on systems that support @ref{de,,readline}.  History is also enabled by default,
and is written to (and read from) the file @code{~/.python-history}.
(Contributed by Antoine Pitrou and Éric Araujo in bpo-5845@footnote{https://bugs.python.org/issue5845}.)

@item 
Invoking the Python interpreter with @code{--version} now outputs the version to
standard output instead of standard error (bpo-18338@footnote{https://bugs.python.org/issue18338}). Similar changes
were made to @ref{6,,argparse} (bpo-18920@footnote{https://bugs.python.org/issue18920}) and other modules that have
script-like invocation capabilities (bpo-18922@footnote{https://bugs.python.org/issue18922}).

@item 
The CPython Windows installer now adds @code{.py} to the 
@geindex PATHEXT
@geindex 环境变量; PATHEXT
@code{PATHEXT}
variable when extensions are registered, allowing users to run a python
script at the windows command prompt by just typing its name without the
@code{.py} extension.  (Contributed by Paul Moore in bpo-18569@footnote{https://bugs.python.org/issue18569}.)

@item 
A new @code{make} target coverage-report@footnote{https://devguide.python.org/coverage/#measuring-coverage-of-c-code-with-gcov-and-lcov}
will build python, run the test suite, and generate an HTML coverage report
for the C codebase using @code{gcov} and lcov@footnote{http://ltp.sourceforge.net/coverage/lcov.php}.

@item 
The @code{-R} option to the @ref{927,,python regression test suite} now
also checks for memory allocation leaks, using
@ref{8dc,,sys.getallocatedblocks()}.  (Contributed by Antoine Pitrou in
bpo-13390@footnote{https://bugs.python.org/issue13390}.)

@item 
@code{python -m} now works with namespace packages.

@item 
The @ref{f4,,stat} module is now implemented in C, which means it gets the
values for its constants from the C header files, instead of having the
values hard-coded in the python module as was previously the case.

@item 
Loading multiple python modules from a single OS module (@code{.so}, @code{.dll})
now works correctly (previously it silently returned the first python
module in the file).  (Contributed by Václav Šmilauer in bpo-16421@footnote{https://bugs.python.org/issue16421}.)

@item 
A new opcode, @ref{928,,LOAD_CLASSDEREF}, has been added to fix a bug in the
loading of free variables in class bodies that could be triggered by certain
uses of @ref{4f7,,__prepare__}.  (Contributed by Benjamin Peterson in
bpo-17853@footnote{https://bugs.python.org/issue17853}.)

@item 
A number of MemoryError-related crashes were identified and fixed by Victor
Stinner using his 
@geindex Python 提高建议; PEP 445
PEP 445@footnote{https://www.python.org/dev/peps/pep-0445}-based @code{pyfailmalloc} tool (bpo-18408@footnote{https://bugs.python.org/issue18408},
bpo-18520@footnote{https://bugs.python.org/issue18520}).

@item 
The @code{pyvenv} command now accepts a @code{--copies} option
to use copies rather than symlinks even on systems where symlinks are the
default.  (Contributed by Vinay Sajip in bpo-18807@footnote{https://bugs.python.org/issue18807}.)

@item 
The @code{pyvenv} command also accepts a @code{--without-pip}
option to suppress the otherwise-automatic bootstrapping of pip into
the virtual environment.  (Contributed by Nick Coghlan in bpo-19552@footnote{https://bugs.python.org/issue19552}
as part of the 
@geindex Python 提高建议; PEP 453
PEP 453@footnote{https://www.python.org/dev/peps/pep-0453} implementation.)

@item 
The encoding name is now optional in the value set for the
@geindex PYTHONIOENCODING
@geindex 环境变量; PYTHONIOENCODING
@ref{929,,PYTHONIOENCODING} environment variable.  This makes it possible to
set just the error handler, without changing the default encoding.
(Contributed by Serhiy Storchaka in bpo-18818@footnote{https://bugs.python.org/issue18818}.)

@item 
The @ref{14,,bz2}, @ref{ad,,lzma}, and @ref{8c,,gzip} module @code{open} functions now
support @code{x} (exclusive creation) mode.  (Contributed by Tim Heaney and
Vajrasky Kok in bpo-19201@footnote{https://bugs.python.org/issue19201}, bpo-19222@footnote{https://bugs.python.org/issue19222}, and bpo-19223@footnote{https://bugs.python.org/issue19223}.)
@end itemize

@node Significant Optimizations,,其他改进<2>,CPython Implementation Changes
@anchor{whatsnew/3 4 significant-optimizations}@anchor{92a}
@subsubsection Significant Optimizations



@itemize *

@item 
The UTF-32 decoder is now 3x to 4x faster.  (Contributed by Serhiy Storchaka
in bpo-14625@footnote{https://bugs.python.org/issue14625}.)

@item 
The cost of hash collisions for sets is now reduced.  Each hash table
probe now checks a series of consecutive, adjacent key/hash pairs before
continuing to make random probes through the hash table.  This exploits
cache locality to make collision resolution less expensive.
The collision resolution scheme can be described as a hybrid of linear
probing and open addressing.  The number of additional linear probes
defaults to nine.  This can be changed at compile-time by defining
LINEAR_PROBES to be any value.  Set LINEAR_PROBES=0 to turn-off
linear probing entirely.  (Contributed by Raymond Hettinger in
bpo-18771@footnote{https://bugs.python.org/issue18771}.)

@item 
The interpreter starts about 30% faster. A couple of measures lead to the
speedup. The interpreter loads fewer modules on startup, e.g. the @ref{dd,,re},
@ref{1e,,collections} and @ref{a9,,locale} modules and their dependencies are no
longer imported by default. The marshal module has been improved to load
compiled Python code faster.  (Contributed by Antoine Pitrou, Christian
Heimes and Victor Stinner in bpo-19219@footnote{https://bugs.python.org/issue19219}, bpo-19218@footnote{https://bugs.python.org/issue19218}, bpo-19209@footnote{https://bugs.python.org/issue19209},
bpo-19205@footnote{https://bugs.python.org/issue19205} and bpo-9548@footnote{https://bugs.python.org/issue9548}.)

@item 
@ref{92b,,bz2.BZ2File} is now as fast or faster than the Python2 version for
most cases.  @ref{92c,,lzma.LZMAFile} has also been optimized.  (Contributed by
Serhiy Storchaka and Nadeem Vawda in bpo-16034@footnote{https://bugs.python.org/issue16034}.)

@item 
@ref{92d,,random.getrandbits()} is 20%-40% faster for small integers (the most
common use case).  (Contributed by Serhiy Storchaka in bpo-16674@footnote{https://bugs.python.org/issue16674}.)

@item 
By taking advantage of the new storage format for strings, pickling of
strings is now significantly faster.  (Contributed by Victor Stinner and
Antoine Pitrou in bpo-15596@footnote{https://bugs.python.org/issue15596}.)

@item 
A performance issue in @code{io.FileIO.readall()} has been solved.  This
particularly affects Windows, and significantly speeds up the case of piping
significant amounts of data through @ref{f9,,subprocess}.  (Contributed
by Richard Oudkerk in bpo-15758@footnote{https://bugs.python.org/issue15758}.)

@item 
@ref{92e,,html.escape()} is now 10x faster.  (Contributed by Matt Bryant in
bpo-18020@footnote{https://bugs.python.org/issue18020}.)

@item 
On Windows, the native @code{VirtualAlloc} is now used instead of the CRT
@code{malloc} in @code{obmalloc}.  Artificial benchmarks show about a 3% memory
savings.

@item 
@ref{4cb,,os.urandom()} now uses a lazily-opened persistent file descriptor
so as to avoid using many file descriptors when run in parallel from
multiple threads.  (Contributed by Antoine Pitrou in bpo-18756@footnote{https://bugs.python.org/issue18756}.)
@end itemize

@node 弃用<4>,移除<3>,CPython Implementation Changes,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 deprecated}@anchor{92f}@anchor{whatsnew/3 4 deprecated-3-4}@anchor{801}
@subsection 弃用


This section covers various APIs and other features that have been deprecated
in Python 3.4, and will be removed in Python 3.5 or later.  In most (but not
all) cases, using the deprecated APIs will produce a @ref{278,,DeprecationWarning}
when the interpreter is run with deprecation warnings enabled (for example, by
using @code{-Wd}).

@menu
* Deprecations in the Python API:: 
* Deprecated Features:: 

@end menu

@node Deprecations in the Python API,Deprecated Features,,弃用<4>
@anchor{whatsnew/3 4 deprecations-in-the-python-api}@anchor{930}
@subsubsection Deprecations in the Python API



@itemize *

@item 
As mentioned in @ref{7d2,,PEP 451; A ModuleSpec Type for the Import System}, a number of @ref{9b,,importlib}
methods and functions are deprecated: @ref{931,,importlib.find_loader()} is
replaced by @ref{932,,importlib.util.find_spec()};
@ref{933,,importlib.machinery.PathFinder.find_module()} is replaced by
@ref{934,,importlib.machinery.PathFinder.find_spec()};
@ref{45c,,importlib.abc.MetaPathFinder.find_module()} is replaced by
@ref{45d,,importlib.abc.MetaPathFinder.find_spec()};
@ref{45e,,importlib.abc.PathEntryFinder.find_loader()} and
@ref{935,,find_module()} are replaced by
@ref{45f,,importlib.abc.PathEntryFinder.find_spec()}; all of the @code{xxxLoader} ABC
@code{load_module} methods (@ref{5de,,importlib.abc.Loader.load_module()},
@ref{936,,importlib.abc.InspectLoader.load_module()},
@ref{937,,importlib.abc.FileLoader.load_module()},
@ref{938,,importlib.abc.SourceLoader.load_module()}) should no longer be
implemented, instead loaders should implement an
@code{exec_module} method
(@ref{5df,,importlib.abc.Loader.exec_module()},
@ref{939,,importlib.abc.InspectLoader.exec_module()}
@ref{93a,,importlib.abc.SourceLoader.exec_module()}) and let the import system
take care of the rest; and
@ref{93b,,importlib.abc.Loader.module_repr()},
@ref{93c,,importlib.util.module_for_loader()}, @ref{93d,,importlib.util.set_loader()},
and @ref{93e,,importlib.util.set_package()} are no longer needed because their
functions are now handled automatically by the import system.

@item 
The @ref{9a,,imp} module is pending deprecation. To keep compatibility with
Python 2/3 code bases, the module's removal is currently not scheduled.

@item 
The @ref{82,,formatter} module is pending deprecation and is slated for removal
in Python 3.6.

@item 
@code{MD5} as the default @emph{digestmod} for the @ref{84e,,hmac.new()} function is
deprecated.  Python 3.6 will require an explicit digest name or constructor as
@emph{digestmod} argument.

@item 
The internal @code{Netrc} class in the @ref{84,,ftplib} module has been documented
as deprecated in its docstring for quite some time.  It now emits a
@ref{278,,DeprecationWarning} and will be removed completely in Python 3.5.

@item 
The undocumented @emph{endtime} argument to @ref{58d,,subprocess.Popen.wait()} should
not have been exposed and is hopefully not in use; it is deprecated and
will mostly likely be removed in Python 3.5.

@item 
The @emph{strict} argument of @ref{7b9,,HTMLParser} is deprecated.

@item 
The @ref{cf,,plistlib} @ref{479,,readPlist()},
@ref{93f,,writePlist()}, @ref{47a,,readPlistFromBytes()}, and
@ref{940,,writePlistToBytes()} functions are deprecated in favor of the
corresponding new functions @ref{885,,load()}, @ref{886,,dump()},
@ref{887,,loads()}, and @ref{888,,dumps()}.  @ref{941,,Data()}
is deprecated in favor of just using the @ref{32a,,bytes} constructor.

@item 
The @ref{fe,,sysconfig} key @code{SO} is deprecated, it has been replaced by
@code{EXT_SUFFIX}.

@item 
The @code{U} mode accepted by various @code{open} functions is deprecated.
In Python3 it does not do anything useful, and should be replaced by
appropriate uses of @ref{5ee,,io.TextIOWrapper} (if needed) and its @emph{newline}
argument.

@item 
The @emph{parser} argument of @ref{942,,xml.etree.ElementTree.iterparse()} has
been deprecated, as has the @emph{html} argument of
@ref{252,,XMLParser()}.  To prepare for the removal of the
latter, all arguments to @code{XMLParser} should be passed by keyword.
@end itemize

@node Deprecated Features,,Deprecations in the Python API,弃用<4>
@anchor{whatsnew/3 4 deprecated-features}@anchor{943}
@subsubsection Deprecated Features



@itemize *

@item 
Running @ref{944,,IDLE} with the @code{-n} flag (no subprocess) is deprecated.
However, the feature will not be removed until bpo-18823@footnote{https://bugs.python.org/issue18823} is resolved.

@item 
The site module adding a "site-python" directory to sys.path, if it
exists, is deprecated (bpo-19375@footnote{https://bugs.python.org/issue19375}).
@end itemize

@node 移除<3>,移植到 Python 3 4,弃用<4>,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 removed}@anchor{945}
@subsection 移除


@menu
* 不再支持的操作系统:: 
* API 与特性的移除: API 与特性的移除<5>. 
* Code Cleanups:: 

@end menu

@node 不再支持的操作系统,API 与特性的移除<5>,,移除<3>
@anchor{whatsnew/3 4 operating-systems-no-longer-supported}@anchor{946}
@subsubsection 不再支持的操作系统


从源代码和构建工具中删除了对以下操作系统的支持：


@itemize *

@item 
OS/2 (bpo-16135@footnote{https://bugs.python.org/issue16135}).

@item 
Windows 2000（变更集e52df05b496a）。

@item 
Windows系统中 @code{COMSPEC} 指向 @code{command.com} 的版本（ bpo-14470@footnote{https://bugs.python.org/issue14470} ）。

@item 
VMS (bpo-16136@footnote{https://bugs.python.org/issue16136}).
@end itemize

@node API 与特性的移除<5>,Code Cleanups,不再支持的操作系统,移除<3>
@anchor{whatsnew/3 4 api-and-feature-removals}@anchor{947}
@subsubsection API 与特性的移除


The following obsolete and previously deprecated APIs and features have been
removed:


@itemize *

@item 
The unmaintained @code{Misc/TextMate} and @code{Misc/vim} directories have been
removed (see the devguide@footnote{https://devguide.python.org}
for suggestions on what to use instead).

@item 
The @code{SO} makefile macro is removed (it was replaced by the
@code{SHLIB_SUFFIX} and @code{EXT_SUFFIX} macros) (bpo-16754@footnote{https://bugs.python.org/issue16754}).

@item 
The @code{PyThreadState.tick_counter} field has been removed; its value has
been meaningless since Python 3.2, when the "new GIL" was introduced
(bpo-19199@footnote{https://bugs.python.org/issue19199}).

@item 
@code{PyLoader} and @code{PyPycLoader} have been removed from @ref{9b,,importlib}.
(Contributed by Taras Lyapun in bpo-15641@footnote{https://bugs.python.org/issue15641}.)

@item 
The @emph{strict} argument to @ref{38a,,HTTPConnection} and
@ref{38b,,HTTPSConnection} has been removed.  HTTP 0.9-style
"Simple Responses" are no longer supported.

@item 
The deprecated @ref{8f0,,urllib.request.Request} getter and setter methods
@code{add_data}, @code{has_data}, @code{get_data}, @code{get_type}, @code{get_host},
@code{get_selector}, @code{set_proxy}, @code{get_origin_req_host}, and
@code{is_unverifiable} have been removed (use direct attribute access instead).

@item 
Support for loading the deprecated @code{TYPE_INT64} has been removed from
@ref{b0,,marshal}.  (Contributed by Dan Riti in bpo-15480@footnote{https://bugs.python.org/issue15480}.)

@item 
@ref{6ed,,inspect.Signature}: positional-only parameters are now required
to have a valid name.

@item 
@ref{948,,object.__format__()} no longer accepts non-empty format strings, it now
raises a @ref{192,,TypeError} instead.  Using a non-empty string has been
deprecated since Python 3.2.  This change has been made to prevent a
situation where previously working (but incorrect) code would start failing
if an object gained a __format__ method, which means that your code may now
raise a @ref{192,,TypeError} if you are using an @code{'s'} format code with objects
that do not have a __format__ method that handles it.  See bpo-7994@footnote{https://bugs.python.org/issue7994} for
background.

@item 
@code{difflib.SequenceMatcher.isbjunk()} and
@code{difflib.SequenceMatcher.isbpopular()} were deprecated in 3.2, and have
now been removed: use @code{x in sm.bjunk} and
@code{x in sm.bpopular}, where @emph{sm} is a @ref{949,,SequenceMatcher} object
(bpo-13248@footnote{https://bugs.python.org/issue13248}).
@end itemize

@node Code Cleanups,,API 与特性的移除<5>,移除<3>
@anchor{whatsnew/3 4 code-cleanups}@anchor{94a}
@subsubsection Code Cleanups



@itemize *

@item 
The unused and undocumented internal @code{Scanner} class has been removed from
the @ref{d9,,pydoc} module.

@item 
The private and effectively unused @code{_gestalt} module has been removed,
along with the private @ref{ce,,platform} functions @code{_mac_ver_lookup},
@code{_mac_ver_gstalt}, and @code{_bcd2str}, which would only have ever been called
on badly broken OSX systems (see bpo-18393@footnote{https://bugs.python.org/issue18393}).

@item 
The hardcoded copies of certain @ref{f4,,stat} constants that were included in
the @ref{101,,tarfile} module namespace have been removed.
@end itemize

@node 移植到 Python 3 4,3 4 3 的变化,移除<3>,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 porting-to-python-3-4}@anchor{94b}
@subsection 移植到 Python 3.4


本节列出了先前描述的更改以及可能需要更改代码的其他错误修正.

@menu
* 'python' 命令行为的变化: 'python' 命令行为的变化<2>. 
* Python API 的变化: Python API 的变化<5>. 
* C API 的变化: C API 的变化<5>. 

@end menu

@node 'python' 命令行为的变化<2>,Python API 的变化<5>,,移植到 Python 3 4
@anchor{whatsnew/3 4 changes-in-python-command-behavior}@anchor{94c}
@subsubsection  'python' 命令行为的变化



@itemize *

@item 
In a posix shell, setting the 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} environment variable to
an empty value is equivalent to not setting it at all.  However, setting
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} to an empty value was @emph{not} equivalent to not setting it
at all: setting 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} to an empty value was equivalent to
setting it to @code{.}, which leads to confusion when reasoning by analogy to
how 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} works.  The behavior now conforms to the posix convention
for 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH}.

@item 
The [X refs, Y blocks] output of a debug (@code{--with-pydebug}) build of the
CPython interpreter is now off by default.  It can be re-enabled using the
@code{-X showrefcount} option.  (Contributed by Ezio Melotti in bpo-17323@footnote{https://bugs.python.org/issue17323}.)

@item 
The python command and most stdlib scripts (as well as @ref{6,,argparse}) now
output @code{--version} information to @code{stdout} instead of @code{stderr} (for
issue list see @ref{924,,其他改进} above).
@end itemize

@node Python API 的变化<5>,C API 的变化<5>,'python' 命令行为的变化<2>,移植到 Python 3 4
@anchor{whatsnew/3 4 changes-in-the-python-api}@anchor{94e}
@subsubsection Python API 的变化



@itemize *

@item 
The ABCs defined in @ref{9c,,importlib.abc} now either raise the appropriate
exception or return a default value instead of raising
@ref{609,,NotImplementedError} blindly. This will only affect code calling
@ref{4dc,,super()} and falling through all the way to the ABCs. For compatibility,
catch both @ref{609,,NotImplementedError} or the appropriate exception as needed.

@item 
The module type now initializes the @ref{94f,,__package__} and @ref{950,,__loader__}
attributes to @code{None} by default. To determine if these attributes were set
in a backwards-compatible fashion, use e.g.
@code{getattr(module, '__loader__', None) is not None}.  (bpo-17115@footnote{https://bugs.python.org/issue17115}.)

@item 
@ref{93c,,importlib.util.module_for_loader()} now sets @code{__loader__} and
@code{__package__} unconditionally to properly support reloading. If this is not
desired then you will need to set these attributes manually. You can use
@code{importlib.util.module_to_load()} for module management.

@item 
Import now resets relevant attributes (e.g. @code{__name__}, @code{__loader__},
@code{__package__}, @code{__file__}, @code{__cached__}) unconditionally when reloading.
Note that this restores a pre-3.3 behavior in that it means a module is
re-found when re-loaded (bpo-19413@footnote{https://bugs.python.org/issue19413}).

@item 
Frozen packages no longer set @code{__path__} to a list containing the package
name, they now set it to an empty list.  The previous behavior could cause
the import system to do the wrong thing on submodule imports if there was
also a directory with the same name as the frozen package.  The correct way
to determine if a module is a package or not is to use @code{hasattr(module,
'__path__')} (bpo-18065@footnote{https://bugs.python.org/issue18065}).

@item 
Frozen modules no longer define a @code{__file__} attribute. It's semantically
incorrect for frozen modules to set the attribute as they are not loaded from
any explicit location. If you must know that a module comes from frozen code
then you can see if the module's @code{__spec__.location} is set to @code{'frozen'},
check if the loader is a subclass of
@ref{951,,importlib.machinery.FrozenImporter},
or if Python 2 compatibility is necessary you can use @code{imp.is_frozen()}.

@item 
@ref{215,,py_compile.compile()} now raises @ref{952,,FileExistsError} if the file path
it would write to is a symlink or a non-regular file. This is to act as a
warning that import will overwrite those files with a regular file regardless
of what type of file path they were originally.

@item 
@ref{953,,importlib.abc.SourceLoader.get_source()} no longer raises
@ref{32d,,ImportError} when the source code being loaded triggers a
@ref{452,,SyntaxError} or @ref{1fd,,UnicodeDecodeError}. As @ref{32d,,ImportError} is
meant to be raised only when source code cannot be found but it should, it was
felt to be over-reaching/overloading of that meaning when the source code is
found but improperly structured. If you were catching ImportError before and
wish to continue to ignore syntax or decoding issues, catch all three
exceptions now.

@item 
@ref{954,,functools.update_wrapper()} and @ref{864,,functools.wraps()} now correctly
set the @code{__wrapped__} attribute to the function being wrapped, even if
that function also had its @code{__wrapped__} attribute set. This means
@code{__wrapped__} attributes now correctly link a stack of decorated
functions rather than every @code{__wrapped__} attribute in the chain
referring to the innermost function. Introspection libraries that
assumed the previous behaviour was intentional can use
@ref{863,,inspect.unwrap()} to access the first function in the chain that has
no @code{__wrapped__} attribute.

@item 
@ref{558,,inspect.getfullargspec()} has been reimplemented on top of
@ref{556,,inspect.signature()} and hence handles a much wider variety of callable
objects than it did in the past. It is expected that additional builtin and
extension module callables will gain signature metadata over the course of
the Python 3.4 series. Code that assumes that
@ref{558,,inspect.getfullargspec()} will fail on non-Python callables may need
to be adjusted accordingly.

@item 
@ref{955,,importlib.machinery.PathFinder} now passes on the current working
directory to objects in @ref{956,,sys.path_hooks} for the empty string. This
results in @ref{498,,sys.path_importer_cache} never containing @code{'@w{'}}, thus
iterating through @ref{498,,sys.path_importer_cache} based on @ref{482,,sys.path}
will not find all keys. A module's @code{__file__} when imported in the current
working directory will also now have an absolute path, including when using
@code{-m} with the interpreter (except for @code{__main__.__file__} when a script
has been executed directly using a relative path) (Contributed by Brett
Cannon in bpo-18416@footnote{https://bugs.python.org/issue18416}).  is specified on the command-line)
(bpo-18416@footnote{https://bugs.python.org/issue18416}).

@item 
The removal of the @emph{strict} argument to @ref{38a,,HTTPConnection}
and @ref{38b,,HTTPSConnection} changes the meaning of the
remaining arguments if you are specifying them positionally rather than by
keyword.  If you've been paying attention to deprecation warnings your code
should already be specifying any additional arguments via keywords.

@item 
Strings between @code{from __future__ import ...} statements now @emph{always} raise
a @ref{452,,SyntaxError}.  Previously if there was no leading docstring, an
interstitial string would sometimes be ignored.  This brings CPython into
compliance with the language spec; Jython and PyPy already were.
(bpo-17434@footnote{https://bugs.python.org/issue17434}).

@item 
@ref{8cb,,ssl.SSLSocket.getpeercert()} and @ref{754,,ssl.SSLSocket.do_handshake()}
now raise an @ref{1d3,,OSError} with @code{ENOTCONN} when the @code{SSLSocket} is not
connected, instead of the previous behavior of raising an
@ref{393,,AttributeError}.  In addition, @ref{8cb,,getpeercert()}
will raise a @ref{1fb,,ValueError} if the handshake has not yet been done.

@item 
@ref{957,,base64.b32decode()} now raises a @ref{958,,binascii.Error} when the
input string contains non-b32-alphabet characters, instead of a
@ref{192,,TypeError}.  This particular @ref{192,,TypeError} was missed when the other
@ref{192,,TypeError}s were converted.  (Contributed by Serhiy Storchaka in
bpo-18011@footnote{https://bugs.python.org/issue18011}.)  Note: this change was also inadvertently applied in Python
3.3.3.

@item 
The @code{file} attribute is now automatically closed when
the creating @code{cgi.FieldStorage} instance is garbage collected. If you
were pulling the file object out separately from the @code{cgi.FieldStorage}
instance and not keeping the instance alive, then you should either store the
entire @code{cgi.FieldStorage} instance or read the contents of the file
before the @code{cgi.FieldStorage} instance is garbage collected.

@item 
Calling @code{read} or @code{write} on a closed SSL socket now raises an
informative @ref{1fb,,ValueError} rather than the previous more mysterious
@ref{393,,AttributeError} (bpo-9177@footnote{https://bugs.python.org/issue9177}).

@item 
@ref{959,,slice.indices()} no longer produces an @ref{95a,,OverflowError} for huge
values.  As a consequence of this fix, @ref{959,,slice.indices()} now raises a
@ref{1fb,,ValueError} if given a negative length; previously it returned nonsense
values (bpo-14794@footnote{https://bugs.python.org/issue14794}).

@item 
The @ref{189,,complex} constructor, unlike the @ref{19,,cmath} functions, was
incorrectly accepting @ref{187,,float} values if an object's @code{__complex__}
special method returned one.  This now raises a @ref{192,,TypeError}.
(bpo-16290@footnote{https://bugs.python.org/issue16290}.)

@item 
The @ref{184,,int} constructor in 3.2 and 3.3 erroneously accepts @ref{187,,float}
values for the @emph{base} parameter.  It is unlikely anyone was doing this, but
if so, it will now raise a @ref{192,,TypeError} (bpo-16772@footnote{https://bugs.python.org/issue16772}).

@item 
Defaults for keyword-only arguments are now evaluated @emph{after} defaults for
regular keyword arguments, instead of before.  Hopefully no one wrote any
code that depends on the previous buggy behavior (bpo-16967@footnote{https://bugs.python.org/issue16967}).

@item 
Stale thread states are now cleared after @ref{95b,,fork()}.  This may cause
some system resources to be released that previously were incorrectly kept
perpetually alive (for example, database connections kept in thread-local
storage).  (bpo-17094@footnote{https://bugs.python.org/issue17094}.)

@item 
Parameter names in @code{__annotations__} dicts are now mangled properly,
similarly to @code{__kwdefaults__}.  (Contributed by Yury Selivanov in
bpo-20625@footnote{https://bugs.python.org/issue20625}.)

@item 
@ref{84c,,hashlib.hash.name} now always returns the identifier in lower case.
Previously some builtin hashes had uppercase names, but now that it is a
formal public interface the naming has been made consistent (bpo-18532@footnote{https://bugs.python.org/issue18532}).

@item 
Because @ref{6c8,,unittest.TestSuite} now drops references to tests after they
are run, test harnesses that re-use a @ref{6c8,,TestSuite} to re-run
a set of tests may fail.   Test suites should not be re-used in this fashion
since it means state is retained between test runs, breaking the test
isolation that @ref{11b,,unittest} is designed to provide.  However, if the lack
of isolation is considered acceptable, the old behavior can be restored by
creating a @ref{6c8,,TestSuite} subclass that defines a
@code{_removeTestAtIndex} method that does nothing (see
@ref{95c,,TestSuite.__iter__()}) (bpo-11798@footnote{https://bugs.python.org/issue11798}).

@item 
@ref{11b,,unittest} now uses @ref{6,,argparse} for command line parsing.  There are
certain invalid command forms that used to work that are no longer allowed;
in theory this should not cause backward compatibility issues since the
disallowed command forms didn't make any sense and are unlikely to be in use.

@item 
The @ref{3c2,,re.split()}, @ref{95d,,re.findall()}, and @ref{475,,re.sub()} functions, and
the @code{group()} and @code{groups()} methods of
@code{match} objects now always return a @emph{bytes} object when the string
to be matched is a @ref{5e3,,bytes-like object}.  Previously the return type
matched the input type, so if your code was depending on the return value
being, say, a @code{bytearray}, you will need to change your code.

@item 
@ref{d,,audioop} functions now raise an error immediately if passed string
input, instead of failing randomly later on (bpo-16685@footnote{https://bugs.python.org/issue16685}).

@item 
The new @emph{convert_charrefs} argument to @ref{7b9,,HTMLParser}
currently defaults to @code{False} for backward compatibility, but will
eventually be changed to default to @code{True}.  It is recommended that you add
this keyword, with the appropriate value, to any
@ref{7b9,,HTMLParser} calls in your code (bpo-13633@footnote{https://bugs.python.org/issue13633}).

@item 
Since the @emph{digestmod} argument to the @ref{84e,,hmac.new()} function will in the
future have no default, all calls to @ref{84e,,hmac.new()} should be changed to
explicitly specify a @emph{digestmod} (bpo-17276@footnote{https://bugs.python.org/issue17276}).

@item 
Calling @ref{95e,,sysconfig.get_config_var()} with the @code{SO} key, or looking
@code{SO} up in the results of a call to @ref{95f,,sysconfig.get_config_vars()}
is deprecated.  This key should be replaced by @code{EXT_SUFFIX} or
@code{SHLIB_SUFFIX}, depending on the context (bpo-19555@footnote{https://bugs.python.org/issue19555}).

@item 
Any calls to @code{open} functions that specify @code{U} should be modified.
@code{U} is ineffective in Python3 and will eventually raise an error if used.
Depending on the function, the equivalent of its old Python2 behavior can be
achieved using either a @emph{newline} argument, or if necessary by wrapping the
stream in @ref{5ee,,TextIOWrapper} to use its @emph{newline} argument
(bpo-15204@footnote{https://bugs.python.org/issue15204}).

@item 
If you use @code{pyvenv} in a script and desire that pip
@emph{not} be installed, you must add @code{--without-pip} to your command
invocation.

@item 
The default behavior of @ref{5ff,,json.dump()} and @ref{600,,json.dumps()} when
an indent is specified has changed: it no longer produces trailing
spaces after the item separating commas at the ends of lines.  This
will matter only if you have tests that are doing white-space-sensitive
comparisons of such output (bpo-16333@footnote{https://bugs.python.org/issue16333}).

@item 
@ref{67,,doctest} now looks for doctests in extension module @code{__doc__}
strings, so if your doctest test discovery includes extension modules that
have things that look like doctests in them you may see test failures you've
never seen before when running your tests (bpo-3158@footnote{https://bugs.python.org/issue3158}).

@item 
The @ref{1f,,collections.abc} module has been slightly refactored as
part of the Python startup improvements.  As a consequence of this, it is no
longer the case that importing @ref{1e,,collections} automatically imports
@ref{1f,,collections.abc}.  If your program depended on the (undocumented)
implicit import, you will need to add an explicit @code{import collections.abc}
(bpo-20784@footnote{https://bugs.python.org/issue20784}).
@end itemize

@node C API 的变化<5>,,Python API 的变化<5>,移植到 Python 3 4
@anchor{whatsnew/3 4 changes-in-the-c-api}@anchor{960}
@subsubsection C API 的变化



@itemize *

@item 
@ref{961,,PyEval_EvalFrameEx()}, @ref{962,,PyObject_Repr()}, and
@ref{963,,PyObject_Str()}, along with some other internal C APIs, now include
a debugging assertion that ensures they are not used in situations where
they may silently discard a currently active exception. In cases where
discarding the active exception is expected and desired (for example,
because it has already been saved locally with @ref{964,,PyErr_Fetch()} or
is being deliberately replaced with a different exception), an explicit
@ref{965,,PyErr_Clear()} call will be needed to avoid triggering the
assertion when invoking these operations (directly or indirectly) and
running against a version of Python that is compiled with assertions
enabled.

@item 
@ref{5f3,,PyErr_SetImportError()} now sets @ref{192,,TypeError} when its @strong{msg}
argument is not set. Previously only @code{NULL} was returned with no exception
set.

@item 
The result of the @ref{966,,PyOS_ReadlineFunctionPointer} callback must
now be a string allocated by @ref{967,,PyMem_RawMalloc()} or
@ref{968,,PyMem_RawRealloc()}, or @code{NULL} if an error occurred, instead of a
string allocated by @ref{4ff,,PyMem_Malloc()} or @ref{969,,PyMem_Realloc()}
(bpo-16742@footnote{https://bugs.python.org/issue16742})

@item 
@ref{96a,,PyThread_set_key_value()} now always set the value. In Python
3.3, the function did nothing if the key already exists (if the current
value is a non-@code{NULL} pointer).

@item 
The @code{f_tstate} (thread state) field of the @ref{96b,,PyFrameObject}
structure has been removed to fix a bug: see bpo-14432@footnote{https://bugs.python.org/issue14432} for the
rationale.
@end itemize

@node 3 4 3 的变化,,移植到 Python 3 4,Python 3 4 有什么新变化
@anchor{whatsnew/3 4 changed-in-3-4-3}@anchor{96c}
@subsection 3.4.3 的变化


@menu
* PEP 476; Enabling certificate verification by default for stdlib http clients: PEP 476 Enabling certificate verification by default for stdlib http clients. 

@end menu

@node PEP 476 Enabling certificate verification by default for stdlib http clients,,,3 4 3 的变化
@anchor{whatsnew/3 4 pep-476}@anchor{96d}@anchor{whatsnew/3 4 pep-476-enabling-certificate-verification-by-default-for-stdlib-http-clients}@anchor{96e}
@subsubsection PEP 476: Enabling certificate verification by default for stdlib http clients


@ref{94,,http.client} and modules which use it, such as @ref{120,,urllib.request} and
@ref{13f,,xmlrpc.client}, will now verify that the server presents a certificate
which is signed by a CA in the platform trust store and whose hostname matches
the hostname being requested by default, significantly improving security for
many applications.

For applications which require the old previous behavior, they can pass an
alternate context:

@example
import urllib.request
import ssl

# This disables all verification
context = ssl._create_unverified_context()

# This allows using a specific certificate for the host, which doesn't need
# to be in the trust store
context = ssl.create_default_context(cafile="/path/to/file.crt")

urllib.request.urlopen("https://invalid-cert", context=context)
@end example

@node Python 3 3 有什么新变化,Python 3 2 有什么新变化,Python 3 4 有什么新变化,Python的新变化
@anchor{whatsnew/3 3 doc}@anchor{96f}@anchor{whatsnew/3 3 what-s-new-in-python-3-3}@anchor{970}
@section Python 3.3 有什么新变化


@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number as a comment:
@c 
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer in :issue:`12345`.)
@c 
@c This saves the maintainer the effort of going through the Mercurial log
@c when researching a change.

本文介绍了Python 3.3相比 3.2 的新增特性。Python 3.3于2012年9月29日发布。有关完整详细信息，请参见 changelog@footnote{https://docs.python.org/3.3/whatsnew/changelog.html}。


@subsubheading 参见


@geindex Python 提高建议; PEP 398
PEP 398@footnote{https://www.python.org/dev/peps/pep-0398} - Python 3.3 发布计划


@menu
* 摘要 - 发布重点: 摘要 - 发布重点<6>. 
* PEP 405; 虚拟环境: PEP 405 虚拟环境. 
* PEP 420; 隐式命名空间包: PEP 420 隐式命名空间包. 
* PEP 3118; 新的内存视图实现和缓冲协议文档: PEP 3118 新的内存视图实现和缓冲协议文档. 
* PEP 393; 灵活的字符串表示: PEP 393 灵活的字符串表示. 
* PEP 397; 适用于Windows的Python启动器: PEP 397 适用于Windows的Python启动器. 
* PEP 3151; 重写 OS 和 IO 异常的层次结构: PEP 3151 重写 OS 和 IO 异常的层次结构. 
* PEP 380; 委托给子生成器的语法: PEP 380 委托给子生成器的语法. 
* PEP 409; 清除异常上下文: PEP 409 清除异常上下文. 
* PEP 414; 显式的Unicode文本: PEP 414 显式的Unicode文本. 
* PEP 3155; 类和函数的限定名称: PEP 3155 类和函数的限定名称. 
* PEP 412; Key-Sharing Dictionary: PEP 412 Key-Sharing Dictionary. 
* PEP 362; 函数签名对象: PEP 362 函数签名对象. 
* PEP 421; 添加 sys.implementation: PEP 421 添加 sys implementation. 
* Using importlib as the Implementation of Import:: 
* 其他语言特性修改: 其他语言特性修改<6>. 
* A Finer-Grained Import Lock:: 
* Builtin functions and types:: 
* 新增模块: 新增模块<6>. 
* 改进的模块: 改进的模块<6>. 
* 性能优化: 性能优化<5>. 
* 构建和 C API 的改变: 构建和 C API 的改变<4>. 
* 弃用: 弃用<5>. 
* 移植到 Python 3.3: 移植到 Python 3 3. 

@end menu

@node 摘要 - 发布重点<6>,PEP 405 虚拟环境,,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 summary-release-highlights}@anchor{971}
@subsection 摘要 - 发布重点


@c This section singles out the most important changes in Python 3.3.
@c Brevity is key.

新的语法特性：


@itemize *

@item 
New @code{yield from} expression for @ref{972,,generator delegation}.

@item 
The @code{u'unicode'} syntax is accepted again for @ref{329,,str} objects.
@end itemize

新的库模块：


@itemize *

@item 
@ref{7d,,faulthandler} （帮助调试低级崩溃）

@item 
@ref{a2,,ipaddress} (high-level objects representing IP addresses and masks)

@item 
@ref{ad,,lzma} (compress data using the XZ / LZMA algorithm)

@item 
@ref{11c,,unittest.mock} (replace parts of your system under test with mock objects)

@item 
@ref{125,,venv} (Python @ref{973,,virtual environments}, as in the
popular @code{virtualenv} package)
@end itemize

新的内置特性：


@itemize *

@item 
重写 @ref{974,,I/O 异常的层次结构}.
@end itemize

实现的改进：


@itemize *

@item 
基于 @ref{9b,,importlib} 重写 @ref{975,,import machinery}

@item 
More compact @ref{976,,unicode strings}.

@item 
More compact @ref{977,,attribute dictionaries}.
@end itemize

显着改进的库模块：


@itemize *

@item 
C Accelerator for the @ref{978,,decimal} module.

@item 
Better unicode handling in the @ref{979,,email} module
(@ref{97a,,provisional}).
@end itemize

安全改进：


@itemize *

@item 
Hash randomization is switched on by default.
@end itemize

Please read on for a comprehensive list of user-facing changes.

@node PEP 405 虚拟环境,PEP 420 隐式命名空间包,摘要 - 发布重点<6>,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-405}@anchor{973}@anchor{whatsnew/3 3 pep-405-virtual-environments}@anchor{97b}
@subsection PEP 405: 虚拟环境


Virtual environments help create separate Python setups while sharing a
system-wide base install, for ease of maintenance.  Virtual environments
have their own set of private site packages (i.e. locally-installed
libraries), and are optionally segregated from the system-wide site
packages.  Their concept and implementation are inspired by the popular
@code{virtualenv} third-party package, but benefit from tighter integration
with the interpreter core.

This PEP adds the @ref{125,,venv} module for programmatic access, and the
@code{pyvenv} script for command-line access and
administration.  The Python interpreter checks for a @code{pyvenv.cfg},
file whose existence signals the base of a virtual environment's directory
tree.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 405

@item PEP 405@footnote{https://www.python.org/dev/peps/pep-0405} - Python虚拟环境

PEP 由 Carl Meyer 撰写 ; 由 Carl Meyer 和 Vinay Sajip 实现。
@end table


@node PEP 420 隐式命名空间包,PEP 3118 新的内存视图实现和缓冲协议文档,PEP 405 虚拟环境,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-420-implicit-namespace-packages}@anchor{97c}
@subsection PEP 420: 隐式命名空间包


Native support for package directories that don't require @code{__init__.py}
marker files and can automatically span multiple path segments (inspired by
various third party approaches to namespace packages, as described in
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420})


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 420

@item PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} - 隐式命名空间包

PEP 由 Eric V. Smith 撰写，由 Eric V. Smith 和 Barry Warsaw 实现
@end table


@node PEP 3118 新的内存视图实现和缓冲协议文档,PEP 393 灵活的字符串表示,PEP 420 隐式命名空间包,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-3118-new-memoryview-implementation-and-buffer-protocol-documentation}@anchor{97d}@anchor{whatsnew/3 3 pep-3118-update}@anchor{97e}
@subsection PEP 3118: 新的内存视图实现和缓冲协议文档


The implementation of 
@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} has been significantly improved.

The new memoryview implementation comprehensively fixes all ownership and
lifetime issues of dynamically allocated fields in the Py_buffer struct
that led to multiple crash reports. Additionally, several functions that
crashed or returned incorrect results for non-contiguous or multi-dimensional
input have been fixed.

The memoryview object now has a PEP-3118 compliant getbufferproc()
that checks the consumer's request type. Many new features have been
added, most of them work in full generality for non-contiguous arrays
and arrays with suboffsets.

The documentation has been updated, clearly spelling out responsibilities
for both exporters and consumers. Buffer request flags are grouped into
basic and compound flags. The memory layout of non-contiguous and
multi-dimensional NumPy-style arrays is explained.

@menu
* 相关特性:: 
* API changes:: 

@end menu

@node 相关特性,API changes,,PEP 3118 新的内存视图实现和缓冲协议文档
@anchor{whatsnew/3 3 features}@anchor{97f}
@subsubsection 相关特性



@itemize *

@item 
All native single character format specifiers in struct module syntax
(optionally prefixed with '@@') are now supported.

@item 
With some restrictions, the cast() method allows changing of format and
shape of C-contiguous arrays.

@item 
Multi-dimensional list representations are supported for any array type.

@item 
Multi-dimensional comparisons are supported for any array type.

@item 
One-dimensional memoryviews of hashable (read-only) types with formats B,
b or c are now hashable.  (Contributed by Antoine Pitrou in bpo-13411@footnote{https://bugs.python.org/issue13411}.)

@item 
Arbitrary slicing of any 1-D arrays type is supported. For example, it
is now possible to reverse a memoryview in O(1) by using a negative step.
@end itemize

@node API changes,,相关特性,PEP 3118 新的内存视图实现和缓冲协议文档
@anchor{whatsnew/3 3 api-changes}@anchor{980}
@subsubsection API changes



@itemize *

@item 
The maximum number of dimensions is officially limited to 64.

@item 
The representation of empty shape, strides and suboffsets is now
an empty tuple instead of @code{None}.

@item 
Accessing a memoryview element with format 'B' (unsigned bytes)
now returns an integer (in accordance with the struct module syntax).
For returning a bytes object the view must be cast to 'c' first.

@item 
memoryview comparisons now use the logical structure of the operands
and compare all array elements by value. All format strings in struct
module syntax are supported. Views with unrecognised format strings
are still permitted, but will always compare as unequal, regardless
of view contents.

@item 
For further changes see @ref{981,,Build and C API Changes} and @ref{982,,Porting C code}.
@end itemize

（由 Stefan Krah 在 bpo-10181@footnote{https://bugs.python.org/issue10181} 中贡献。）


@subsubheading 参见


@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} - 修改缓冲区协议


@node PEP 393 灵活的字符串表示,PEP 397 适用于Windows的Python启动器,PEP 3118 新的内存视图实现和缓冲协议文档,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-393}@anchor{976}@anchor{whatsnew/3 3 pep-393-flexible-string-representation}@anchor{983}
@subsection PEP 393: 灵活的字符串表示


The Unicode string type is changed to support multiple internal
representations, depending on the character with the largest Unicode ordinal
(1, 2, or 4 bytes) in the represented string.  This allows a space-efficient
representation in common cases, but gives access to full UCS-4 on all
systems.  For compatibility with existing APIs, several representations may
exist in parallel; over time, this compatibility should be phased out.

On the Python side, there should be no downside to this change.

On the C API side, 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393} is fully backward compatible.  The legacy API
should remain available at least five years.  Applications using the legacy
API will not fully benefit of the memory reduction, or - worse - may use
a bit more memory, because Python may have to maintain two versions of each
string (in the legacy format and in the new efficient storage).

@menu
* Functionality:: 
* Performance and resource usage:: 

@end menu

@node Functionality,Performance and resource usage,,PEP 393 灵活的字符串表示
@anchor{whatsnew/3 3 functionality}@anchor{984}
@subsubsection Functionality


Changes introduced by 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393} are the following:


@itemize *

@item 
Python now always supports the full range of Unicode code points, including
non-BMP ones (i.e. from @code{U+0000} to @code{U+10FFFF}).  The distinction between
narrow and wide builds no longer exists and Python now behaves like a wide
build, even under Windows.

@item 
With the death of narrow builds, the problems specific to narrow builds have
also been fixed, for example:


@itemize *

@item 
@ref{150,,len()} now always returns 1 for non-BMP characters,
so @code{len('\U0010FFFF') == 1};

@item 
surrogate pairs are not recombined in string literals,
so @code{'\uDBFF\uDFFF' != '\U0010FFFF'};

@item 
indexing or slicing non-BMP characters returns the expected value,
so @code{'\U0010FFFF'[0]} now returns @code{'\U0010FFFF'} and not @code{'\uDBFF'};

@item 
all other functions in the standard library now correctly handle
non-BMP code points.
@end itemize

@item 
The value of @ref{985,,sys.maxunicode} is now always @code{1114111} (@code{0x10FFFF}
in hexadecimal).  The @code{PyUnicode_GetMax()} function still returns
either @code{0xFFFF} or @code{0x10FFFF} for backward compatibility, and it should
not be used with the new Unicode API (see bpo-13054@footnote{https://bugs.python.org/issue13054}).

@item 
The @code{./configure} flag @code{--with-wide-unicode} has been removed.
@end itemize

@node Performance and resource usage,,Functionality,PEP 393 灵活的字符串表示
@anchor{whatsnew/3 3 performance-and-resource-usage}@anchor{986}
@subsubsection Performance and resource usage


The storage of Unicode strings now depends on the highest code point in the string:


@itemize *

@item 
pure ASCII and Latin1 strings (@code{U+0000-U+00FF}) use 1 byte per code point;

@item 
BMP strings (@code{U+0000-U+FFFF}) use 2 bytes per code point;

@item 
non-BMP strings (@code{U+10000-U+10FFFF}) use 4 bytes per code point.
@end itemize

The net effect is that for most applications, memory usage of string
storage should decrease significantly - especially compared to former
wide unicode builds - as, in many cases, strings will be pure ASCII
even in international contexts (because many strings store non-human
language data, such as XML fragments, HTTP headers, JSON-encoded data,
etc.).  We also hope that it will, for the same reasons, increase CPU
cache efficiency on non-trivial applications. The memory usage of
Python 3.3 is two to three times smaller than Python 3.2, and a little
bit better than Python 2.7, on a Django benchmark (see the PEP for
details).


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 393

@item PEP 393@footnote{https://www.python.org/dev/peps/pep-0393} - 灵活的字符串表示

PEP 由 Martin von Löwis 撰写 ; 由 Torsten Becker 和 Martin von Löwis 实现。
@end table


@node PEP 397 适用于Windows的Python启动器,PEP 3151 重写 OS 和 IO 异常的层次结构,PEP 393 灵活的字符串表示,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-397}@anchor{987}@anchor{whatsnew/3 3 pep-397-python-launcher-for-windows}@anchor{988}
@subsection PEP 397: 适用于Windows的Python启动器


The Python 3.3 Windows installer now includes a @code{py} launcher application
that can be used to launch Python applications in a version independent
fashion.

This launcher is invoked implicitly when double-clicking @code{*.py} files.
If only a single Python version is installed on the system, that version
will be used to run the file. If multiple versions are installed, the most
recent version is used by default, but this can be overridden by including
a Unix-style "shebang line" in the Python script.

The launcher can also be used explicitly from the command line as the @code{py}
application. Running @code{py} follows the same version selection rules as
implicitly launching scripts, but a more specific version can be selected
by passing appropriate arguments (such as @code{-3} to request Python 3 when
Python 2 is also installed, or @code{-2.6} to specifically request an earlier
Python version when a more recent version is installed).

In addition to the launcher, the Windows installer now includes an
option to add the newly installed Python to the system PATH.  (Contributed
by Brian Curtin in bpo-3561@footnote{https://bugs.python.org/issue3561}.)


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 397

@item PEP 397@footnote{https://www.python.org/dev/peps/pep-0397} - 适用于Windows的Python启动器

PEP 由 Mark Hammond 和 Martin v. Löwis 撰写 ; 由 Vinay Sajip实现。
@end table

Launcher documentation: @ref{989,,适用于Windows的Python启动器}

Installer PATH modification: @ref{98a,,查找Python可执行文件}


@node PEP 3151 重写 OS 和 IO 异常的层次结构,PEP 380 委托给子生成器的语法,PEP 397 适用于Windows的Python启动器,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-3151}@anchor{974}@anchor{whatsnew/3 3 pep-3151-reworking-the-os-and-io-exception-hierarchy}@anchor{98b}
@subsection PEP 3151: 重写 OS 和 IO 异常的层次结构


The hierarchy of exceptions raised by operating system errors is now both
simplified and finer-grained.

You don't have to worry anymore about choosing the appropriate exception
type between @ref{1d3,,OSError}, @ref{98c,,IOError}, @ref{98d,,EnvironmentError},
@ref{98e,,WindowsError}, @code{mmap.error}, @ref{98f,,socket.error} or
@ref{990,,select.error}.  All these exception types are now only one:
@ref{1d3,,OSError}.  The other names are kept as aliases for compatibility
reasons.

Also, it is now easier to catch a specific error condition.  Instead of
inspecting the @code{errno} attribute (or @code{args[0]}) for a particular
constant from the @ref{7c,,errno} module, you can catch the adequate
@ref{1d3,,OSError} subclass.  The available subclasses are the following:


@itemize *

@item 
@ref{991,,BlockingIOError}

@item 
@ref{992,,ChildProcessError}

@item 
@ref{6e0,,ConnectionError}

@item 
@ref{952,,FileExistsError}

@item 
@ref{7ba,,FileNotFoundError}

@item 
@ref{653,,InterruptedError}

@item 
@ref{993,,IsADirectoryError}

@item 
@ref{994,,NotADirectoryError}

@item 
@ref{5fa,,PermissionError}

@item 
@ref{995,,ProcessLookupError}

@item 
@ref{996,,TimeoutError}
@end itemize

And the @ref{6e0,,ConnectionError} itself has finer-grained subclasses:


@itemize *

@item 
@ref{997,,BrokenPipeError}

@item 
@ref{998,,ConnectionAbortedError}

@item 
@ref{999,,ConnectionRefusedError}

@item 
@ref{99a,,ConnectionResetError}
@end itemize

Thanks to the new exceptions, common usages of the @ref{7c,,errno} can now be
avoided.  For example, the following code written for Python 3.2:

@example
from errno import ENOENT, EACCES, EPERM

try:
    with open("document.txt") as f:
        content = f.read()
except IOError as err:
    if err.errno == ENOENT:
        print("document.txt file is missing")
    elif err.errno in (EACCES, EPERM):
        print("You are not allowed to read document.txt")
    else:
        raise
@end example

can now be written without the @ref{7c,,errno} import and without manual
inspection of exception attributes:

@example
try:
    with open("document.txt") as f:
        content = f.read()
except FileNotFoundError:
    print("document.txt file is missing")
except PermissionError:
    print("You are not allowed to read document.txt")
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3151

@item PEP 3151@footnote{https://www.python.org/dev/peps/pep-3151} - 重写 OS 和 IO 异常的层次结构

PEP 由 Antoine Pitrou 撰写并实现
@end table


@geindex yield; yield from (in What's New)

@node PEP 380 委托给子生成器的语法,PEP 409 清除异常上下文,PEP 3151 重写 OS 和 IO 异常的层次结构,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-380}@anchor{972}@anchor{whatsnew/3 3 pep-380-syntax-for-delegating-to-a-subgenerator}@anchor{99b}
@subsection PEP 380: 委托给子生成器的语法


PEP 380 adds the @code{yield from} expression, allowing a @ref{99c,,generator} to
delegate
part of its operations to another generator. This allows a section of code
containing @ref{18f,,yield} to be factored out and placed in another generator.
Additionally, the subgenerator is allowed to return with a value, and the
value is made available to the delegating generator.

While designed primarily for use in delegating to a subgenerator, the @code{yield
from} expression actually allows delegation to arbitrary subiterators.

For simple iterators, @code{yield from iterable} is essentially just a shortened
form of @code{for item in iterable: yield item}:

@example
>>> def g(x):
...     yield from range(x, 0, -1)
...     yield from range(x)
...
>>> list(g(5))
[5, 4, 3, 2, 1, 0, 1, 2, 3, 4]
@end example

However, unlike an ordinary loop, @code{yield from} allows subgenerators to
receive sent and thrown values directly from the calling scope, and
return a final value to the outer generator:

@example
>>> def accumulate():
...     tally = 0
...     while 1:
...         next = yield
...         if next is None:
...             return tally
...         tally += next
...
>>> def gather_tallies(tallies):
...     while 1:
...         tally = yield from accumulate()
...         tallies.append(tally)
...
>>> tallies = []
>>> acc = gather_tallies(tallies)
>>> next(acc)  # Ensure the accumulator is ready to accept values
>>> for i in range(4):
...     acc.send(i)
...
>>> acc.send(None)  # Finish the first tally
>>> for i in range(5):
...     acc.send(i)
...
>>> acc.send(None)  # Finish the second tally
>>> tallies
[6, 10]
@end example

The main principle driving this change is to allow even generators that are
designed to be used with the @code{send} and @code{throw} methods to be split into
multiple subgenerators as easily as a single large function can be split into
multiple subfunctions.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 380

@item PEP 380@footnote{https://www.python.org/dev/peps/pep-0380} - 委托给子生成器的语法

PEP 由 Greg Ewing 撰写，由 Greg Ewing 实现。由 Renaud Blanch，Ryan Kelly 和 Nick Coghlan 集成到3.3，由 Zbigniew Jędrzejewski-Szmek 和 Nick Coghlan 编写文档
@end table


@node PEP 409 清除异常上下文,PEP 414 显式的Unicode文本,PEP 380 委托给子生成器的语法,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-409-suppressing-exception-context}@anchor{99d}
@subsection PEP 409: 清除异常上下文


PEP 409 introduces new syntax that allows the display of the chained
exception context to be disabled. This allows cleaner error messages in
applications that convert between exception types:

@example
>>> class D:
...     def __init__(self, extra):
...         self._extra_attributes = extra
...     def __getattr__(self, attr):
...         try:
...             return self._extra_attributes[attr]
...         except KeyError:
...             raise AttributeError(attr) from None
...
>>> D(@{@}).x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 8, in __getattr__
AttributeError: x
@end example

Without the @code{from None} suffix to suppress the cause, the original
exception would be displayed by default:

@example
>>> class C:
...     def __init__(self, extra):
...         self._extra_attributes = extra
...     def __getattr__(self, attr):
...         try:
...             return self._extra_attributes[attr]
...         except KeyError:
...             raise AttributeError(attr)
...
>>> C(@{@}).x
Traceback (most recent call last):
  File "<stdin>", line 6, in __getattr__
KeyError: 'x'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 8, in __getattr__
AttributeError: x
@end example

No debugging capability is lost, as the original exception context remains
available if needed (for example, if an intervening library has incorrectly
suppressed valuable underlying details):

@example
>>> try:
...     D(@{@}).x
... except AttributeError as exc:
...     print(repr(exc.__context__))
...
KeyError('x',)
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 409

@item PEP 409@footnote{https://www.python.org/dev/peps/pep-0409} - 清除异常上下文

PEP 由 Ethan Furman 撰写 ，由 Ethan Furman 和 Nick Coghlan 实现。
@end table


@node PEP 414 显式的Unicode文本,PEP 3155 类和函数的限定名称,PEP 409 清除异常上下文,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-414-explicit-unicode-literals}@anchor{99e}
@subsection PEP 414: 显式的Unicode文本


To ease the transition from Python 2 for Unicode aware Python applications
that make heavy use of Unicode literals, Python 3.3 once again supports the
"@code{u}" prefix for string literals. This prefix has no semantic significance
in Python 3, it is provided solely to reduce the number of purely mechanical
changes in migrating to Python 3, making it easier for developers to focus on
the more significant semantic changes (such as the stricter default
separation of binary and text data).


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 414

@item PEP 414@footnote{https://www.python.org/dev/peps/pep-0414} - 显式的Unicode文本

PEP 由 Armin Ronacher 撰写
@end table


@node PEP 3155 类和函数的限定名称,PEP 412 Key-Sharing Dictionary,PEP 414 显式的Unicode文本,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-3155-qualified-name-for-classes-and-functions}@anchor{99f}
@subsection PEP 3155: 类和函数的限定名称


Functions and class objects have a new @code{__qualname__} attribute representing
the "path" from the module top-level to their definition.  For global functions
and classes, this is the same as @code{__name__}.  For other functions and classes,
it provides better information about where they were actually defined, and
how they might be accessible from the global scope.

Example with (non-bound) methods:

@example
>>> class C:
...     def meth(self):
...         pass
>>> C.meth.__name__
'meth'
>>> C.meth.__qualname__
'C.meth'
@end example

Example with nested classes:

@example
>>> class C:
...     class D:
...         def meth(self):
...             pass
...
>>> C.D.__name__
'D'
>>> C.D.__qualname__
'C.D'
>>> C.D.meth.__name__
'meth'
>>> C.D.meth.__qualname__
'C.D.meth'
@end example

Example with nested functions:

@example
>>> def outer():
...     def inner():
...         pass
...     return inner
...
>>> outer().__name__
'inner'
>>> outer().__qualname__
'outer.<locals>.inner'
@end example

The string representation of those objects is also changed to include the
new, more precise information:

@example
>>> str(C.D)
"<class '__main__.C.D'>"
>>> str(C.D.meth)
'<function C.D.meth at 0x7f46b9fe31e0>'
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3155

@item PEP 3155@footnote{https://www.python.org/dev/peps/pep-3155} - 类和函数的限定名称

PEP 由 Antoine Pitrou 撰写并实现
@end table


@node PEP 412 Key-Sharing Dictionary,PEP 362 函数签名对象,PEP 3155 类和函数的限定名称,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-412}@anchor{977}@anchor{whatsnew/3 3 pep-412-key-sharing-dictionary}@anchor{9a0}
@subsection PEP 412: Key-Sharing Dictionary


Dictionaries used for the storage of objects' attributes are now able to
share part of their internal storage between each other (namely, the part
which stores the keys and their respective hashes).  This reduces the memory
consumption of programs creating many instances of non-builtin types.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 412

@item PEP 412@footnote{https://www.python.org/dev/peps/pep-0412} - Key-Sharing Dictionary

PEP 由 Mark Shannon 撰写并实现。
@end table


@node PEP 362 函数签名对象,PEP 421 添加 sys implementation,PEP 412 Key-Sharing Dictionary,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-362-function-signature-object}@anchor{9a1}
@subsection PEP 362: 函数签名对象


A new function @ref{556,,inspect.signature()} makes introspection of python
callables easy and straightforward.  A broad range of callables is supported:
python functions, decorated or not, classes, and @ref{7c2,,functools.partial()}
objects.  New classes @ref{6ed,,inspect.Signature}, @ref{6ee,,inspect.Parameter}
and @ref{9a2,,inspect.BoundArguments} hold information about the call signatures,
such as, annotations, default values, parameters kinds, and bound arguments,
which considerably simplifies writing decorators and any code that validates
or amends calling signatures or arguments.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 362

@item PEP 362@footnote{https://www.python.org/dev/peps/pep-0362}: -  函数签名对象

PEP 由 Brett Cannon，Yury Selivanov，Larry Hastings，Jiwon Seo 撰写，由 Yury Selivanov 实现
@end table


@node PEP 421 添加 sys implementation,Using importlib as the Implementation of Import,PEP 362 函数签名对象,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 pep-421-adding-sys-implementation}@anchor{9a3}
@subsection PEP 421: 添加 sys.implementation


A new attribute on the @ref{fd,,sys} module exposes details specific to the
implementation of the currently running interpreter.  The initial set of
attributes on @ref{9a4,,sys.implementation} are @code{name}, @code{version},
@code{hexversion}, and @code{cache_tag}.

The intention of @code{sys.implementation} is to consolidate into one namespace
the implementation-specific data used by the standard library.  This allows
different Python implementations to share a single standard library code base
much more easily.  In its initial state, @code{sys.implementation} holds only a
small portion of the implementation-specific data.  Over time that ratio will
shift in order to make the standard library more portable.

One example of improved standard library portability is @code{cache_tag}.  As of
Python 3.3, @code{sys.implementation.cache_tag} is used by @ref{9b,,importlib} to
support 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} compliance.  Any Python implementation that uses
@code{importlib} for its built-in import system may use @code{cache_tag} to control
the caching behavior for modules.

@menu
* SimpleNamespace:: 

@end menu

@node SimpleNamespace,,,PEP 421 添加 sys implementation
@anchor{whatsnew/3 3 simplenamespace}@anchor{9a5}
@subsubsection SimpleNamespace


The implementation of @code{sys.implementation} also introduces a new type to
Python: @ref{9a6,,types.SimpleNamespace}.  In contrast to a mapping-based
namespace, like @ref{1b8,,dict}, @code{SimpleNamespace} is attribute-based, like
@ref{2b0,,object}.  However, unlike @code{object}, @code{SimpleNamespace} instances
are writable.  This means that you can add, remove, and modify the namespace
through normal attribute access.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 421

@item PEP 421@footnote{https://www.python.org/dev/peps/pep-0421} - 添加 sys.implementation

PEP 由 Eric Snow 撰写并实现
@end table


@node Using importlib as the Implementation of Import,其他语言特性修改<6>,PEP 421 添加 sys implementation,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 importlib}@anchor{975}@anchor{whatsnew/3 3 using-importlib-as-the-implementation-of-import}@anchor{9a7}
@subsection Using importlib as the Implementation of Import


bpo-2377@footnote{https://bugs.python.org/issue2377} - Replace __import__ w/ importlib.__import__
bpo-13959@footnote{https://bugs.python.org/issue13959} - Re-implement parts of @ref{9a,,imp} in pure Python
bpo-14605@footnote{https://bugs.python.org/issue14605} - Make import machinery explicit
bpo-14646@footnote{https://bugs.python.org/issue14646} - Require loaders set __loader__ and __package__

The @ref{60b,,__import__()} function is now powered by @ref{9a8,,importlib.__import__()}.
This work leads to the completion of "phase 2" of 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}. There are
multiple benefits to this change. First, it has allowed for more of the
machinery powering import to be exposed instead of being implicit and hidden
within the C code. It also provides a single implementation for all Python VMs
supporting Python 3.3 to use, helping to end any VM-specific deviations in
import semantics. And finally it eases the maintenance of import, allowing for
future growth to occur.

For the common user, there should be no visible change in semantics.  For
those whose code currently manipulates import or calls import
programmatically, the code changes that might possibly be required are covered
in the @ref{9a9,,Porting Python code} section of this document.

@menu
* New APIs:: 
* Visible Changes:: 

@end menu

@node New APIs,Visible Changes,,Using importlib as the Implementation of Import
@anchor{whatsnew/3 3 new-apis}@anchor{9aa}
@subsubsection New APIs


One of the large benefits of this work is the exposure of what goes into
making the import statement work. That means the various importers that were
once implicit are now fully exposed as part of the @ref{9b,,importlib} package.

The abstract base classes defined in @ref{9c,,importlib.abc} have been expanded
to properly delineate between @ref{9ab,,meta path finders}
and @ref{9ac,,path entry finders} by introducing
@ref{9ad,,importlib.abc.MetaPathFinder} and
@ref{9ae,,importlib.abc.PathEntryFinder}, respectively. The old ABC of
@ref{9af,,importlib.abc.Finder} is now only provided for backwards-compatibility
and does not enforce any method requirements.

In terms of finders, @ref{9b0,,importlib.machinery.FileFinder} exposes the
mechanism used to search for source and bytecode files of a module. Previously
this class was an implicit member of @ref{956,,sys.path_hooks}.

For loaders, the new abstract base class @ref{9b1,,importlib.abc.FileLoader} helps
write a loader that uses the file system as the storage mechanism for a module's
code. The loader for source files
(@ref{9b2,,importlib.machinery.SourceFileLoader}), sourceless bytecode files
(@ref{9b3,,importlib.machinery.SourcelessFileLoader}), and extension modules
(@ref{551,,importlib.machinery.ExtensionFileLoader}) are now available for
direct use.

@ref{32d,,ImportError} now has @code{name} and @code{path} attributes which are set when
there is relevant data to provide. The message for failed imports will also
provide the full name of the module now instead of just the tail end of the
module's name.

The @ref{497,,importlib.invalidate_caches()} function will now call the method with
the same name on all finders cached in @ref{498,,sys.path_importer_cache} to help
clean up any stored state as necessary.

@node Visible Changes,,New APIs,Using importlib as the Implementation of Import
@anchor{whatsnew/3 3 visible-changes}@anchor{9b4}
@subsubsection Visible Changes


For potential required changes to code, see the @ref{9a9,,Porting Python code}
section.

Beyond the expanse of what @ref{9b,,importlib} now exposes, there are other
visible changes to import. The biggest is that @ref{5e1,,sys.meta_path} and
@ref{956,,sys.path_hooks} now store all of the meta path finders and path entry
hooks used by import.  Previously the finders were implicit and hidden within
the C code of import instead of being directly exposed. This means that one can
now easily remove or change the order of the various finders to fit one's needs.

Another change is that all modules have a @code{__loader__} attribute, storing the
loader used to create the module. 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} has been updated to make this
attribute mandatory for loaders to implement, so in the future once 3rd-party
loaders have been updated people will be able to rely on the existence of the
attribute. Until such time, though, import is setting the module post-load.

Loaders are also now expected to set the @code{__package__} attribute from
@geindex Python 提高建议; PEP 366
PEP 366@footnote{https://www.python.org/dev/peps/pep-0366}. Once again, import itself is already setting this on all loaders
from @ref{9b,,importlib} and import itself is setting the attribute post-load.

@code{None} is now inserted into @ref{498,,sys.path_importer_cache} when no finder
can be found on @ref{956,,sys.path_hooks}. Since @ref{9b5,,imp.NullImporter} is not
directly exposed on @ref{956,,sys.path_hooks} it could no longer be relied upon to
always be available to use as a value representing no finder found.

All other changes relate to semantic changes which should be taken into
consideration when updating code for Python 3.3, and thus should be read about
in the @ref{9a9,,Porting Python code} section of this document.

(Implementation by Brett Cannon)

@node 其他语言特性修改<6>,A Finer-Grained Import Lock,Using importlib as the Implementation of Import,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 other-language-changes}@anchor{9b6}
@subsection 其他语言特性修改


对Python 语言核心进行的小改动：


@itemize *

@item 
Added support for Unicode name aliases and named sequences.
Both @ref{9b7,,unicodedata.lookup()} and @code{'\N@{...@}'} now resolve name aliases,
and @ref{9b7,,unicodedata.lookup()} resolves named sequences too.

（由 Ezio Melotti 在 bpo-12753@footnote{https://bugs.python.org/issue12753} 中贡献。）

@item 
Unicode database updated to UCD version 6.1.0

@item 
Equality comparisons on @ref{9b8,,range()} objects now return a result reflecting
the equality of the underlying sequences generated by those range objects.
(bpo-13201@footnote{https://bugs.python.org/issue13201})

@item 
The @code{count()}, @code{find()}, @code{rfind()}, @code{index()} and @code{rindex()}
methods of @ref{32a,,bytes} and @ref{32b,,bytearray} objects now accept an
integer between 0 and 255 as their first argument.

（由 Petri Lehtinen 在 bpo-12170@footnote{https://bugs.python.org/issue12170} 中贡献。）

@item 
The @code{rjust()}, @code{ljust()}, and @code{center()} methods of @ref{32a,,bytes}
and @ref{32b,,bytearray} now accept a @ref{32b,,bytearray} for the @code{fill}
argument.  (Contributed by Petri Lehtinen in bpo-12380@footnote{https://bugs.python.org/issue12380}.)

@item 
New methods have been added to @ref{262,,list} and @ref{32b,,bytearray}:
@code{copy()} and @code{clear()} (bpo-10516@footnote{https://bugs.python.org/issue10516}).  Consequently,
@ref{6a6,,MutableSequence} now also defines a
@code{clear()} method (bpo-11388@footnote{https://bugs.python.org/issue11388}).

@item 
Raw bytes literals can now be written @code{rb"..."} as well as @code{br"..."}.

（由 Antoine Pitrou 在 bpo-13748@footnote{https://bugs.python.org/issue13748} 中贡献。）

@item 
@ref{9b9,,dict.setdefault()} now does only one lookup for the given key, making
it atomic when used with built-in types.

（由 Filip Gruszczyński 在 bpo-13521@footnote{https://bugs.python.org/issue13521} 中贡献。）

@item 
The error messages produced when a function call does not match the function
signature have been significantly improved.

（由 Benjamin Peterson 贡献。）
@end itemize

@node A Finer-Grained Import Lock,Builtin functions and types,其他语言特性修改<6>,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 a-finer-grained-import-lock}@anchor{9ba}
@subsection A Finer-Grained Import Lock


Previous versions of CPython have always relied on a global import lock.
This led to unexpected annoyances, such as deadlocks when importing a module
would trigger code execution in a different thread as a side-effect.
Clumsy workarounds were sometimes employed, such as the
@ref{9bb,,PyImport_ImportModuleNoBlock()} C API function.

In Python 3.3, importing a module takes a per-module lock.  This correctly
serializes importation of a given module from multiple threads (preventing
the exposure of incompletely initialized modules), while eliminating the
aforementioned annoyances.

（由 Antoine Pitrou 在 bpo-9260@footnote{https://bugs.python.org/issue9260} 中贡献。）

@node Builtin functions and types,新增模块<6>,A Finer-Grained Import Lock,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 builtin-functions-and-types}@anchor{9bc}
@subsection Builtin functions and types



@itemize *

@item 
@ref{4ea,,open()} gets a new @emph{opener} parameter: the underlying file descriptor
for the file object is then obtained by calling @emph{opener} with (@emph{file},
@emph{flags}). It can be used to use custom flags like @ref{9bd,,os.O_CLOEXEC} for
example. The @code{'x'} mode was added: open for exclusive creation, failing if
the file already exists.

@item 
@ref{880,,print()}: added the @emph{flush} keyword argument. If the @emph{flush} keyword
argument is true, the stream is forcibly flushed.

@item 
@ref{9be,,hash()}: hash randomization is enabled by default, see
@ref{339,,object.__hash__()} and 
@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED}.

@item 
The @ref{329,,str} type gets a new @ref{6aa,,casefold()} method: return a
casefolded copy of the string, casefolded strings may be used for caseless
matching. For example, @code{'ß'.casefold()} returns @code{'ss'}.

@item 
The sequence documentation has been substantially rewritten to better
explain the binary/text sequence distinction and to provide specific
documentation sections for the individual builtin sequence types
(bpo-4966@footnote{https://bugs.python.org/issue4966}).
@end itemize

@node 新增模块<6>,改进的模块<6>,Builtin functions and types,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 new-modules}@anchor{9c0}
@subsection 新增模块


@menu
* faulthandler: faulthandler<3>. 
* ipaddress: ipaddress<4>. 
* lzma: lzma<2>. 

@end menu

@node faulthandler<3>,ipaddress<4>,,新增模块<6>
@anchor{whatsnew/3 3 faulthandler}@anchor{9c1}
@subsubsection faulthandler


This new debug module @ref{7d,,faulthandler} contains functions to dump Python tracebacks explicitly,
on a fault (a crash like a segmentation fault), after a timeout, or on a user
signal. Call @ref{543,,faulthandler.enable()} to install fault handlers for the
@code{SIGSEGV}, @code{SIGFPE}, @code{SIGABRT}, @code{SIGBUS}, and
@code{SIGILL} signals. You can also enable them at startup by setting the
@geindex PYTHONFAULTHANDLER
@geindex 环境变量; PYTHONFAULTHANDLER
@ref{9c2,,PYTHONFAULTHANDLER} environment variable or by using @ref{155,,-X}
@code{faulthandler} command line option.

Example of a segmentation fault on Linux:

@example
$ python -q -X faulthandler
>>> import ctypes
>>> ctypes.string_at(0)
Fatal Python error: Segmentation fault

Current thread 0x00007fb899f39700:
  File "/home/python/cpython/Lib/ctypes/__init__.py", line 486 in string_at
  File "<stdin>", line 1 in <module>
Segmentation fault
@end example

@node ipaddress<4>,lzma<2>,faulthandler<3>,新增模块<6>
@anchor{whatsnew/3 3 ipaddress}@anchor{9c3}
@subsubsection ipaddress


The new @ref{a2,,ipaddress} module provides tools for creating and manipulating
objects representing IPv4 and IPv6 addresses, networks and interfaces (i.e.
an IP address associated with a specific IP subnet).

（由 Google 和 Peter Moody 在 bpo-3144@footnote{https://bugs.python.org/issue3144} 中贡献。）

@node lzma<2>,,ipaddress<4>,新增模块<6>
@anchor{whatsnew/3 3 lzma}@anchor{9c4}
@subsubsection lzma


The newly-added @ref{ad,,lzma} module provides data compression and decompression
using the LZMA algorithm, including support for the @code{.xz} and @code{.lzma}
file formats.

（由 Nadeem Vawda 和 Per Øyvind Karlsen 在 bpo-6715@footnote{https://bugs.python.org/issue6715} 中贡献。）

@node 改进的模块<6>,性能优化<5>,新增模块<6>,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 improved-modules}@anchor{9c5}
@subsection 改进的模块


@menu
* abc: abc<2>. 
* array: array<2>. 
* base64: base64<2>. 
* binascii: binascii<3>. 
* bz2: bz2<2>. 
* codecs:: 
* collections: collections<7>. 
* contextlib: contextlib<5>. 
* crypt: crypt<2>. 
* curses: curses<3>. 
* datetime: datetime<4>. 
* decimal: decimal<3>. 
* email: email<4>. 
* ftplib:: 
* functools: functools<5>. 
* gc: gc<4>. 
* hmac: hmac<3>. 
* http: http<3>. 
* html: html<2>. 
* imaplib: imaplib<2>. 
* inspect: inspect<5>. 
* io: io<4>. 
* itertools: itertools<3>. 
* logging: logging<6>. 
* math: math<5>. 
* mmap: mmap<3>. 
* multiprocessing: multiprocessing<6>. 
* nntplib:: 
* os: os<7>. 
* pdb: pdb<4>. 
* pickle: pickle<5>. 
* pydoc: pydoc<4>. 
* re: re<6>. 
* sched:: 
* select: select<2>. 
* shlex: shlex<3>. 
* shutil: shutil<4>. 
* signal: signal<3>. 
* smtpd: smtpd<3>. 
* smtplib: smtplib<3>. 
* socket: socket<7>. 
* socketserver: socketserver<3>. 
* sqlite3: sqlite3<5>. 
* ssl: ssl<8>. 
* stat: stat<2>. 
* struct: struct<3>. 
* subprocess: subprocess<5>. 
* sys: sys<7>. 
* tarfile: tarfile<4>. 
* tempfile:: 
* textwrap: textwrap<2>. 
* threading: threading<5>. 
* time: time<5>. 
* types: types<4>. 
* unittest: unittest<5>. 
* urllib: urllib<3>. 
* webbrowser:: 
* xml.etree.ElementTree: xml etree ElementTree. 
* zlib: zlib<2>. 

@end menu

@node abc<2>,array<2>,,改进的模块<6>
@anchor{whatsnew/3 3 abc}@anchor{9c6}
@subsubsection abc


Improved support for abstract base classes containing descriptors composed with
abstract methods. The recommended approach to declaring abstract descriptors is
now to provide @code{__isabstractmethod__} as a dynamically updated
property. The built-in descriptors have been updated accordingly.

@quotation


@itemize *

@item 
@ref{9c7,,abc.abstractproperty} has been deprecated, use @ref{1d7,,property}
with @ref{9c8,,abc.abstractmethod()} instead.

@item 
@ref{9c9,,abc.abstractclassmethod} has been deprecated, use
@ref{1d8,,classmethod} with @ref{9c8,,abc.abstractmethod()} instead.

@item 
@ref{9ca,,abc.abstractstaticmethod} has been deprecated, use
@ref{1d9,,staticmethod} with @ref{9c8,,abc.abstractmethod()} instead.
@end itemize
@end quotation

（由 Pablo Galindo 在 bpo-11610@footnote{https://bugs.python.org/issue11610} 中贡献。）

@ref{9cb,,abc.ABCMeta.register()} now returns the registered subclass, which means
it can now be used as a class decorator (bpo-10868@footnote{https://bugs.python.org/issue10868}).

@node array<2>,base64<2>,abc<2>,改进的模块<6>
@anchor{whatsnew/3 3 array}@anchor{9cc}
@subsubsection array


The @ref{7,,array} module supports the @code{long long} type using @code{q} and
@code{Q} type codes.

（由 Oren Tirosh 和 Hirokazu Yamamoto 在 bpo-1172711@footnote{https://bugs.python.org/issue1172711} 中贡献。）

@node base64<2>,binascii<3>,array<2>,改进的模块<6>
@anchor{whatsnew/3 3 base64}@anchor{9cd}
@subsubsection base64


ASCII-only Unicode strings are now accepted by the decoding functions of the
@ref{e,,base64} modern interface. For example, @code{base64.b64decode('YWJj')}
returns @code{b'abc'}.  (Contributed by Catalin Iacob in bpo-13641@footnote{https://bugs.python.org/issue13641}.)

@node binascii<3>,bz2<2>,base64<2>,改进的模块<6>
@anchor{whatsnew/3 3 binascii}@anchor{9ce}
@subsubsection binascii


In addition to the binary objects they normally accept, the @code{a2b_} functions
now all also accept ASCII-only strings as input.  (Contributed by Antoine
Pitrou in bpo-13637@footnote{https://bugs.python.org/issue13637}.)

@node bz2<2>,codecs,binascii<3>,改进的模块<6>
@anchor{whatsnew/3 3 bz2}@anchor{9cf}
@subsubsection bz2


The @ref{14,,bz2} module has been rewritten from scratch. In the process, several
new features have been added:


@itemize *

@item 
New @ref{9d0,,bz2.open()} function: open a bzip2-compressed file in binary or
text mode.

@item 
@ref{92b,,bz2.BZ2File} can now read from and write to arbitrary file-like
objects, by means of its constructor's @emph{fileobj} argument.

（由 Nadeem Vawda 在 bpo-5863@footnote{https://bugs.python.org/issue5863} 中贡献。）

@item 
@ref{92b,,bz2.BZ2File} and @ref{9d1,,bz2.decompress()} can now decompress
multi-stream inputs (such as those produced by the @code{pbzip2} tool).
@ref{92b,,bz2.BZ2File} can now also be used to create this type of file, using
the @code{'a'} (append) mode.

（由 Nir Aides 在 bpo-1625@footnote{https://bugs.python.org/issue1625} 中贡献。）

@item 
@ref{92b,,bz2.BZ2File} now implements all of the @ref{583,,io.BufferedIOBase} API,
except for the @code{detach()} and @code{truncate()} methods.
@end itemize

@node codecs,collections<7>,bz2<2>,改进的模块<6>
@anchor{whatsnew/3 3 codecs}@anchor{9d2}
@subsubsection codecs


The @ref{78,,mbcs} codec has been rewritten to handle correctly
@code{replace} and @code{ignore} error handlers on all Windows versions.  The
@ref{78,,mbcs} codec now supports all error handlers, instead of only
@code{replace} to encode and @code{ignore} to decode.

A new Windows-only codec has been added: @code{cp65001} (bpo-13216@footnote{https://bugs.python.org/issue13216}). It is the
Windows code page 65001 (Windows UTF-8, @code{CP_UTF8}).  For example, it is used
by @code{sys.stdout} if the console output code page is set to cp65001 (e.g., using
@code{chcp 65001} command).

Multibyte CJK decoders now resynchronize faster.  They only ignore the first
byte of an invalid byte sequence. For example, @code{b'\xff\n'.decode('gb2312',
'replace')} now returns a @code{\n} after the replacement character.

(bpo-12016@footnote{https://bugs.python.org/issue12016})

Incremental CJK codec encoders are no longer reset at each call to their
encode() methods. For example:

@example
>>> import codecs
>>> encoder = codecs.getincrementalencoder('hz')('strict')
>>> b'@w{'}.join(encoder.encode(x) for x in '\u52ff\u65bd\u65bc\u4eba\u3002 Bye.')
b'~@{NpJ)l6HK!#~@} Bye.'
@end example

This example gives @code{b'~@{Np~@}~@{J)~@}~@{l6~@}~@{HK~@}~@{!#~@} Bye.'} with older Python
versions.

(bpo-12100@footnote{https://bugs.python.org/issue12100})

The @code{unicode_internal} codec has been deprecated.

@node collections<7>,contextlib<5>,codecs,改进的模块<6>
@anchor{whatsnew/3 3 collections}@anchor{9d3}
@subsubsection collections


Addition of a new @ref{4a4,,ChainMap} class to allow treating a
number of mappings as a single unit.  (Written by Raymond Hettinger for
bpo-11089@footnote{https://bugs.python.org/issue11089}, made public in bpo-11297@footnote{https://bugs.python.org/issue11297}.)

The abstract base classes have been moved in a new @ref{1f,,collections.abc}
module, to better differentiate between the abstract and the concrete
collections classes.  Aliases for ABCs are still present in the
@ref{1e,,collections} module to preserve existing imports.  (bpo-11085@footnote{https://bugs.python.org/issue11085})

@c XXX addition of __slots__ to ABCs not recorded here: internal detail

The @ref{9d4,,Counter} class now supports the unary @code{+} and @code{-}
operators, as well as the in-place operators @code{+=}, @code{-=}, @code{|=}, and
@code{&=}.  (Contributed by Raymond Hettinger in bpo-13121@footnote{https://bugs.python.org/issue13121}.)

@node contextlib<5>,crypt<2>,collections<7>,改进的模块<6>
@anchor{whatsnew/3 3 contextlib}@anchor{9d5}
@subsubsection contextlib


@ref{36f,,ExitStack} now provides a solid foundation for
programmatic manipulation of context managers and similar cleanup
functionality. Unlike the previous @code{contextlib.nested} API (which was
deprecated and removed), the new API is designed to work correctly
regardless of whether context managers acquire their resources in
their @code{__init__} method (for example, file objects) or in their
@code{__enter__} method (for example, synchronisation objects from the
@ref{109,,threading} module).

(bpo-13585@footnote{https://bugs.python.org/issue13585})

@node crypt<2>,curses<3>,contextlib<5>,改进的模块<6>
@anchor{whatsnew/3 3 crypt}@anchor{9d6}
@subsubsection crypt


Addition of salt and modular crypt format (hashing method) and the @ref{375,,mksalt()}
function to the @ref{29,,crypt} module.

(bpo-10924@footnote{https://bugs.python.org/issue10924})

@node curses<3>,datetime<4>,crypt<2>,改进的模块<6>
@anchor{whatsnew/3 3 curses}@anchor{9d7}
@subsubsection curses


@quotation


@itemize *

@item 
If the @ref{2c,,curses} module is linked to the ncursesw library, use Unicode
functions when Unicode strings or characters are passed (e.g.
@code{waddwstr()}), and bytes functions otherwise (e.g. @code{waddstr()}).

@item 
Use the locale encoding instead of @code{utf-8} to encode Unicode strings.

@item 
@code{curses.window} has a new @ref{9d8,,curses.window.encoding} attribute.

@item 
The @code{curses.window} class has a new @ref{9d9,,get_wch()}
method to get a wide character

@item 
The @ref{2c,,curses} module has a new @ref{9da,,unget_wch()} function to
push a wide character so the next @ref{9d9,,get_wch()} will return
it
@end itemize
@end quotation

（由 Iñigo Serna 在 bpo-6755@footnote{https://bugs.python.org/issue6755} 中贡献。）

@node datetime<4>,decimal<3>,curses<3>,改进的模块<6>
@anchor{whatsnew/3 3 datetime}@anchor{9db}
@subsubsection datetime


@quotation


@itemize *

@item 
Equality comparisons between naive and aware @ref{194,,datetime}
instances now return @ref{380,,False} instead of raising @ref{192,,TypeError}
(bpo-15006@footnote{https://bugs.python.org/issue15006}).

@item 
New @ref{9dc,,datetime.datetime.timestamp()} method: Return POSIX timestamp
corresponding to the @ref{194,,datetime} instance.

@item 
The @ref{531,,datetime.datetime.strftime()} method supports formatting years
older than 1000.

@item 
The @ref{196,,datetime.datetime.astimezone()} method can now be
called without arguments to convert datetime instance to the system
timezone.
@end itemize
@end quotation

@node decimal<3>,email<4>,datetime<4>,改进的模块<6>
@anchor{whatsnew/3 3 decimal}@anchor{9dd}@anchor{whatsnew/3 3 new-decimal}@anchor{978}
@subsubsection decimal



@table @asis

@item bpo-7652@footnote{https://bugs.python.org/issue7652} - integrate fast native decimal arithmetic.

C-module and libmpdec written by Stefan Krah.
@end table

The new C version of the decimal module integrates the high speed libmpdec
library for arbitrary precision correctly-rounded decimal floating point
arithmetic. libmpdec conforms to IBM's General Decimal Arithmetic Specification.

Performance gains range from 10x for database applications to 100x for
numerically intensive applications. These numbers are expected gains
for standard precisions used in decimal floating point arithmetic. Since
the precision is user configurable, the exact figures may vary. For example,
in integer bignum arithmetic the differences can be significantly higher.

The following table is meant as an illustration. Benchmarks are available
at @indicateurl{http://www.bytereef.org/mpdecimal/quickstart.html}.

@quotation


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} 
@headitem

@tab

decimal.py

@tab

_decimal

@tab

加速

@item

pi

@tab

42.02秒

@tab

0.345秒

@tab

120倍

@item

telco

@tab

172.19秒

@tab

5.68秒

@tab

30倍

@item

psycopg

@tab

3.57秒

@tab

0.29秒

@tab

12倍

@end multitable

@end quotation

@menu
* 相关特性: 相关特性<2>. 
* API changes: API changes<2>. 

@end menu

@node 相关特性<2>,API changes<2>,,decimal<3>
@anchor{whatsnew/3 3 id1}@anchor{9de}
@subsubsection 相关特性



@itemize *

@item 
The @ref{9df,,FloatOperation} signal optionally enables stricter
semantics for mixing floats and Decimals.

@item 
If Python is compiled without threads, the C version automatically
disables the expensive thread local context machinery. In this case,
the variable @ref{9e0,,HAVE_THREADS} is set to @code{False}.
@end itemize

@node API changes<2>,,相关特性<2>,decimal<3>
@anchor{whatsnew/3 3 id2}@anchor{9e1}
@subsubsection API changes



@itemize *

@item 
C模块上下文限制（如下表），具体取决于计算机体系结构：

@quotation


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

@tab

32位

@tab

64位

@item

@code{MAX_PREC}

@tab

@code{425000000}

@tab

@code{999999999999999999}

@item

@code{MAX_EMAX}

@tab

@code{425000000}

@tab

@code{999999999999999999}

@item

@code{MIN_EMIN}

@tab

@code{-425000000}

@tab

@code{-999999999999999999}

@end multitable

@end quotation

@item 
In the context templates (@ref{9e2,,DefaultContext},
@ref{9e3,,BasicContext} and @ref{9e4,,ExtendedContext})
the magnitude of @code{Emax} and
@code{Emin} has changed to @code{999999}.

@item 
The @ref{188,,Decimal} constructor in decimal.py does not observe
the context limits and converts values with arbitrary exponents or precision
exactly. Since the C version has internal limits, the following scheme is
used: If possible, values are converted exactly, otherwise
@ref{9e5,,InvalidOperation} is raised and the result is NaN. In the
latter case it is always possible to use @ref{9e6,,create_decimal()}
in order to obtain a rounded or inexact value.

@item 
The power function in decimal.py is always correctly-rounded. In the
C version, it is defined in terms of the correctly-rounded
@ref{9e7,,exp()} and @ref{9e8,,ln()} functions,
but the final result is only "almost always correctly rounded".

@item 
In the C version, the context dictionary containing the signals is a
@ref{9e9,,MutableMapping}.  For speed reasons,
@code{flags} and @code{traps} always
refer to the same @ref{9e9,,MutableMapping} that the context
was initialized with. If a new signal dictionary is assigned,
@code{flags} and @code{traps}
are updated with the new values, but they do not reference the RHS
dictionary.

@item 
Pickling a @ref{9ea,,Context} produces a different output in order
to have a common interchange format for the Python and C versions.

@item 
The order of arguments in the @ref{9ea,,Context} constructor has been
changed to match the order displayed by @ref{7c6,,repr()}.

@item 
The @code{watchexp} parameter in the @ref{9eb,,quantize()} method
is deprecated.
@end itemize

@node email<4>,ftplib,decimal<3>,改进的模块<6>
@anchor{whatsnew/3 3 email}@anchor{9ec}@anchor{whatsnew/3 3 new-email}@anchor{979}
@subsubsection email


@menu
* Policy Framework:: 
* Provisional Policy with New Header API:: 
* Other API Changes:: 

@end menu

@node Policy Framework,Provisional Policy with New Header API,,email<4>
@anchor{whatsnew/3 3 policy-framework}@anchor{9ed}
@subsubsection Policy Framework


The email package now has a @ref{75,,policy} framework.  A
@ref{9ee,,Policy} is an object with several methods and properties
that control how the email package behaves.  The primary policy for Python 3.3
is the @ref{9ef,,Compat32} policy, which provides backward
compatibility with the email package in Python 3.2.  A @code{policy} can be
specified when an email message is parsed by a @ref{74,,parser}, or when a
@ref{53c,,Message} object is created, or when an email is
serialized using a @ref{6e,,generator}.  Unless overridden, a policy passed
to a @code{parser} is inherited by all the @code{Message} object and sub-objects
created by the @code{parser}.  By default a @code{generator} will use the policy of
the @code{Message} object it is serializing.  The default policy is
@ref{53b,,compat32}.

The minimum set of controls implemented by all @code{policy} objects are:

@quotation


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

max_line_length

@tab

The maximum length, excluding the linesep character(s),
individual lines may have when a @code{Message} is
serialized.  Defaults to 78.

@item

linesep

@tab

The character used to separate individual lines when a
@code{Message} is serialized.  Defaults to @code{\n}.

@item

cte_type

@tab

@code{7bit} or @code{8bit}.  @code{8bit} applies only to a
@code{Bytes} @code{generator}, and means that non-ASCII may
be used where allowed by the protocol (or where it
exists in the original input).

@item

raise_on_defect

@tab

Causes a @code{parser} to raise error when defects are
encountered instead of adding them to the @code{Message}
object's @code{defects} list.

@end multitable

@end quotation

A new policy instance, with new settings, is created using the
@ref{9f0,,clone()} method of policy objects.  @code{clone} takes
any of the above controls as keyword arguments.  Any control not specified in
the call retains its default value.  Thus you can create a policy that uses
@code{\r\n} linesep characters like this:

@example
mypolicy = compat32.clone(linesep='\r\n')
@end example

Policies can be used to make the generation of messages in the format needed by
your application simpler.  Instead of having to remember to specify
@code{linesep='\r\n'} in all the places you call a @code{generator}, you can specify
it once, when you set the policy used by the @code{parser} or the @code{Message},
whichever your program uses to create @code{Message} objects.  On the other hand,
if you need to generate messages in multiple forms, you can still specify the
parameters in the appropriate @code{generator} call.  Or you can have custom
policy instances for your different cases, and pass those in when you create
the @code{generator}.

@node Provisional Policy with New Header API,Other API Changes,Policy Framework,email<4>
@anchor{whatsnew/3 3 provisional-policy-with-new-header-api}@anchor{9f1}
@subsubsection Provisional Policy with New Header API


While the policy framework is worthwhile all by itself, the main motivation for
introducing it is to allow the creation of new policies that implement new
features for the email package in a way that maintains backward compatibility
for those who do not use the new policies.  Because the new policies introduce a
new API, we are releasing them in Python 3.3 as a @ref{97a,,provisional policy}.  Backwards incompatible changes (up to and including
removal of the code) may occur if deemed necessary by the core developers.

The new policies are instances of @ref{9f2,,EmailPolicy},
and add the following additional controls:

@quotation


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

refold_source

@tab

Controls whether or not headers parsed by a
@ref{74,,parser} are refolded by the
@ref{6e,,generator}.  It can be @code{none}, @code{long},
or @code{all}.  The default is @code{long}, which means that
source headers with a line longer than
@code{max_line_length} get refolded.  @code{none} means no
line get refolded, and @code{all} means that all lines
get refolded.

@item

header_factory

@tab

A callable that take a @code{name} and @code{value} and
produces a custom header object.

@end multitable

@end quotation

The @code{header_factory} is the key to the new features provided by the new
policies.  When one of the new policies is used, any header retrieved from
a @code{Message} object is an object produced by the @code{header_factory}, and any
time you set a header on a @code{Message} it becomes an object produced by
@code{header_factory}.  All such header objects have a @code{name} attribute equal
to the header name.  Address and Date headers have additional attributes
that give you access to the parsed data of the header.  This means you can now
do things like this:

@example
>>> m = Message(policy=SMTP)
>>> m['To'] = 'Éric <foo@@example.com>'
>>> m['to']
'Éric <foo@@example.com>'
>>> m['to'].addresses
(Address(display_name='Éric', username='foo', domain='example.com'),)
>>> m['to'].addresses[0].username
'foo'
>>> m['to'].addresses[0].display_name
'Éric'
>>> m['Date'] = email.utils.localtime()
>>> m['Date'].datetime
datetime.datetime(2012, 5, 25, 21, 39, 24, 465484, tzinfo=datetime.timezone(datetime.timedelta(-1, 72000), 'EDT'))
>>> m['Date']
'Fri, 25 May 2012 21:44:27 -0400'
>>> print(m)
To: =?utf-8?q?=C3=89ric?= <foo@@example.com>
Date: Fri, 25 May 2012 21:44:27 -0400
@end example

You will note that the unicode display name is automatically encoded as
@code{utf-8} when the message is serialized, but that when the header is accessed
directly, you get the unicode version.  This eliminates any need to deal with
the @ref{6f,,email.header} @ref{9f3,,decode_header()} or
@ref{9f4,,make_header()} functions.

You can also create addresses from parts:

@example
>>> m['cc'] = [Group('pals', [Address('Bob', 'bob', 'example.com'),
...                           Address('Sally', 'sally', 'example.com')]),
...            Address('Bonzo', addr_spec='bonz@@laugh.com')]
>>> print(m)
To: =?utf-8?q?=C3=89ric?= <foo@@example.com>
Date: Fri, 25 May 2012 21:44:27 -0400
cc: pals: Bob <bob@@example.com>, Sally <sally@@example.com>;, Bonzo <bonz@@laugh.com>
@end example

Decoding to unicode is done automatically:

@example
>>> m2 = message_from_string(str(m))
>>> m2['to']
'Éric <foo@@example.com>'
@end example

When you parse a message, you can use the @code{addresses} and @code{groups}
attributes of the header objects to access the groups and individual
addresses:

@example
>>> m2['cc'].addresses
(Address(display_name='Bob', username='bob', domain='example.com'), Address(display_name='Sally', username='sally', domain='example.com'), Address(display_name='Bonzo', username='bonz', domain='laugh.com'))
>>> m2['cc'].groups
(Group(display_name='pals', addresses=(Address(display_name='Bob', username='bob', domain='example.com'), Address(display_name='Sally', username='sally', domain='example.com')), Group(display_name=None, addresses=(Address(display_name='Bonzo', username='bonz', domain='laugh.com'),))
@end example

In summary, if you use one of the new policies, header manipulation works the
way it ought to:  your application works with unicode strings, and the email
package transparently encodes and decodes the unicode to and from the RFC
standard Content Transfer Encodings.

@node Other API Changes,,Provisional Policy with New Header API,email<4>
@anchor{whatsnew/3 3 other-api-changes}@anchor{9f5}
@subsubsection Other API Changes


New @ref{9f6,,BytesHeaderParser}, added to the @ref{74,,parser}
module to complement @ref{9f7,,HeaderParser} and complete the Bytes
API.

New utility functions:

@quotation


@itemize *

@item 
@ref{9f8,,format_datetime()}: given a @ref{194,,datetime},
produce a string formatted for use in an email header.

@item 
@ref{9f9,,parsedate_to_datetime()}: given a date string from
an email header, convert it into an aware @ref{194,,datetime},
or a naive @ref{194,,datetime} if the offset is @code{-0000}.

@item 
@ref{9fa,,localtime()}: With no argument, returns the
current local time as an aware @ref{194,,datetime} using the local
@ref{9fb,,timezone}.  Given an aware @ref{194,,datetime},
converts it into an aware @ref{194,,datetime} using the
local @ref{9fb,,timezone}.
@end itemize
@end quotation

@node ftplib,functools<5>,email<4>,改进的模块<6>
@anchor{whatsnew/3 3 ftplib}@anchor{9fc}
@subsubsection ftplib



@itemize *

@item 
@ref{9fd,,ftplib.FTP} now accepts a @code{source_address} keyword argument to
specify the @code{(host, port)} to use as the source address in the bind call
when creating the outgoing socket.  (Contributed by Giampaolo Rodolà
in bpo-8594@footnote{https://bugs.python.org/issue8594}.)

@item 
The @ref{9fe,,FTP_TLS} class now provides a new
@ref{9ff,,ccc()} function to revert control channel back to
plaintext.  This can be useful to take advantage of firewalls that know how
to handle NAT with non-secure FTP without opening fixed ports.  (Contributed
by Giampaolo Rodolà in bpo-12139@footnote{https://bugs.python.org/issue12139}.)

@item 
Added @ref{a00,,ftplib.FTP.mlsd()} method which provides a parsable directory
listing format and deprecates @ref{a01,,ftplib.FTP.nlst()} and
@ref{a02,,ftplib.FTP.dir()}.  (Contributed by Giampaolo Rodolà in bpo-11072@footnote{https://bugs.python.org/issue11072}.)
@end itemize

@node functools<5>,gc<4>,ftplib,改进的模块<6>
@anchor{whatsnew/3 3 functools}@anchor{a03}
@subsubsection functools


The @ref{1c7,,functools.lru_cache()} decorator now accepts a @code{typed} keyword
argument (that defaults to @code{False} to ensure that it caches values of
different types that compare equal in separate cache slots.  (Contributed
by Raymond Hettinger in bpo-13227@footnote{https://bugs.python.org/issue13227}.)

@node gc<4>,hmac<3>,functools<5>,改进的模块<6>
@anchor{whatsnew/3 3 gc}@anchor{a04}
@subsubsection gc


It is now possible to register callbacks invoked by the garbage collector
before and after collection using the new @ref{a05,,callbacks} list.

@node hmac<3>,http<3>,gc<4>,改进的模块<6>
@anchor{whatsnew/3 3 hmac}@anchor{a06}
@subsubsection hmac


A new @ref{a07,,compare_digest()} function has been added to prevent side
channel attacks on digests through timing analysis.  (Contributed by Nick
Coghlan and Christian Heimes in bpo-15061@footnote{https://bugs.python.org/issue15061}.)

@node http<3>,html<2>,hmac<3>,改进的模块<6>
@anchor{whatsnew/3 3 http}@anchor{a08}
@subsubsection http


@ref{a09,,http.server.BaseHTTPRequestHandler} now buffers the headers and writes
them all at once when @ref{a0a,,end_headers()} is
called.  A new method @ref{a0b,,flush_headers()}
can be used to directly manage when the accumulated headers are sent.
(Contributed by Andrew Schaaf in bpo-3709@footnote{https://bugs.python.org/issue3709}.)

@ref{97,,http.server} now produces valid @code{HTML 4.01 strict} output.
(Contributed by Ezio Melotti in bpo-13295@footnote{https://bugs.python.org/issue13295}.)

@ref{a0c,,http.client.HTTPResponse} now has a
@ref{a0d,,readinto()} method, which means it can be used
as an @ref{a0e,,io.RawIOBase} class.  (Contributed by John Kuhn in
bpo-13464@footnote{https://bugs.python.org/issue13464}.)

@node html<2>,imaplib<2>,http<3>,改进的模块<6>
@anchor{whatsnew/3 3 html}@anchor{a0f}
@subsubsection html


@ref{7b9,,html.parser.HTMLParser} is now able to parse broken markup without
raising errors, therefore the @emph{strict} argument of the constructor and the
@code{HTMLParseError} exception are now deprecated.
The ability to parse broken markup is the result of a number of bug fixes that
are also available on the latest bug fix releases of Python 2.7/3.2.
(Contributed by Ezio Melotti in bpo-15114@footnote{https://bugs.python.org/issue15114}, and bpo-14538@footnote{https://bugs.python.org/issue14538},
bpo-13993@footnote{https://bugs.python.org/issue13993}, bpo-13960@footnote{https://bugs.python.org/issue13960}, bpo-13358@footnote{https://bugs.python.org/issue13358}, bpo-1745761@footnote{https://bugs.python.org/issue1745761},
bpo-755670@footnote{https://bugs.python.org/issue755670}, bpo-13357@footnote{https://bugs.python.org/issue13357}, bpo-12629@footnote{https://bugs.python.org/issue12629}, bpo-1200313@footnote{https://bugs.python.org/issue1200313},
bpo-670664@footnote{https://bugs.python.org/issue670664}, bpo-13273@footnote{https://bugs.python.org/issue13273}, bpo-12888@footnote{https://bugs.python.org/issue12888}, bpo-7311@footnote{https://bugs.python.org/issue7311}.)

A new @ref{a10,,html5} dictionary that maps HTML5 named character
references to the equivalent Unicode character(s) (e.g. @code{html5['gt;'] ==
'>'}) has been added to the @ref{91,,html.entities} module.  The dictionary is
now also used by @ref{7b9,,HTMLParser}.  (Contributed by Ezio
Melotti in bpo-11113@footnote{https://bugs.python.org/issue11113} and bpo-15156@footnote{https://bugs.python.org/issue15156}.)

@node imaplib<2>,inspect<5>,html<2>,改进的模块<6>
@anchor{whatsnew/3 3 imaplib}@anchor{a11}
@subsubsection imaplib


The @ref{a12,,IMAP4_SSL} constructor now accepts an SSLContext
parameter to control parameters of the secure channel.

（由 Sijin Joseph 在 bpo-8808@footnote{https://bugs.python.org/issue8808} 中贡献。）

@node inspect<5>,io<4>,imaplib<2>,改进的模块<6>
@anchor{whatsnew/3 3 inspect}@anchor{a13}
@subsubsection inspect


A new @ref{a14,,getclosurevars()} function has been added. This function
reports the current binding of all names referenced from the function body and
where those names were resolved, making it easier to verify correct internal
state when testing code that relies on stateful closures.

（由  Meador Inge 和 Nick Coghlan 在 bpo-13062@footnote{https://bugs.python.org/issue13062} 中贡献。）

A new @ref{a15,,getgeneratorlocals()} function has been added. This
function reports the current binding of local variables in the generator's
stack frame, making it easier to verify correct internal state when testing
generators.

（由 Meador Inge 在 bpo-15153@footnote{https://bugs.python.org/issue15153} 中贡献。）

@node io<4>,itertools<3>,inspect<5>,改进的模块<6>
@anchor{whatsnew/3 3 io}@anchor{a16}
@subsubsection io


The @ref{654,,open()} function has a new @code{'x'} mode that can be used to
exclusively create a new file, and raise a @ref{952,,FileExistsError} if the file
already exists. It is based on the C11 'x' mode to fopen().

（由 David Townshend 在 bpo-12760@footnote{https://bugs.python.org/issue12760} 中贡献。）

The constructor of the @ref{5ee,,TextIOWrapper} class has a new
@emph{write_through} optional argument. If @emph{write_through} is @code{True}, calls to
@code{write()} are guaranteed not to be buffered: any data
written on the @ref{5ee,,TextIOWrapper} object is immediately handled to its
underlying binary buffer.

@node itertools<3>,logging<6>,io<4>,改进的模块<6>
@anchor{whatsnew/3 3 itertools}@anchor{a17}
@subsubsection itertools


@ref{1dd,,accumulate()} now takes an optional @code{func} argument for
providing a user-supplied binary function.

@node logging<6>,math<5>,itertools<3>,改进的模块<6>
@anchor{whatsnew/3 3 logging}@anchor{a18}
@subsubsection logging


The @ref{1e0,,basicConfig()} function now supports an optional @code{handlers}
argument taking an iterable of handlers to be added to the root logger.

A class level attribute @code{append_nul} has
been added to @ref{a19,,SysLogHandler} to allow control of the
appending of the @code{NUL} (@code{\000}) byte to syslog records, since for some
daemons it is required while for others it is passed through to the log.

@node math<5>,mmap<3>,logging<6>,改进的模块<6>
@anchor{whatsnew/3 3 math}@anchor{a1a}
@subsubsection math


The @ref{b1,,math} module has a new function, @ref{a1b,,log2()},  which returns
the base-2 logarithm of @emph{x}.

(Written by Mark Dickinson in bpo-11888@footnote{https://bugs.python.org/issue11888}.)

@node mmap<3>,multiprocessing<6>,math<5>,改进的模块<6>
@anchor{whatsnew/3 3 mmap}@anchor{a1c}
@subsubsection mmap


The @ref{a1d,,read()} method is now more compatible with other file-like
objects: if the argument is omitted or specified as @code{None}, it returns the
bytes from the current file position to the end of the mapping.  (Contributed
by Petri Lehtinen in bpo-12021@footnote{https://bugs.python.org/issue12021}.)

@node multiprocessing<6>,nntplib,mmap<3>,改进的模块<6>
@anchor{whatsnew/3 3 multiprocessing}@anchor{a1e}
@subsubsection multiprocessing


The new @ref{a1f,,multiprocessing.connection.wait()} function allows polling
multiple objects (such as connections, sockets and pipes) with a timeout.
(Contributed by Richard Oudkerk in bpo-12328@footnote{https://bugs.python.org/issue12328}.)

@code{multiprocessing.Connection} objects can now be transferred over
multiprocessing connections.
(Contributed by Richard Oudkerk in bpo-4892@footnote{https://bugs.python.org/issue4892}.)

@ref{3aa,,multiprocessing.Process} now accepts a @code{daemon} keyword argument
to override the default behavior of inheriting the @code{daemon} flag from
the parent process (bpo-6064@footnote{https://bugs.python.org/issue6064}).

New attribute @ref{a20,,multiprocessing.Process.sentinel} allows a
program to wait on multiple @ref{3aa,,Process} objects at one
time using the appropriate OS primitives (for example, @ref{e5,,select} on
posix systems).

New methods @ref{a21,,multiprocessing.pool.Pool.starmap()} and
@ref{a22,,starmap_async()} provide
@ref{a23,,itertools.starmap()} equivalents to the existing
@ref{a24,,multiprocessing.pool.Pool.map()} and
@ref{a25,,map_async()} functions.  (Contributed by Hynek
Schlawack in bpo-12708@footnote{https://bugs.python.org/issue12708}.)

@node nntplib,os<7>,multiprocessing<6>,改进的模块<6>
@anchor{whatsnew/3 3 nntplib}@anchor{a26}
@subsubsection nntplib


The @ref{a27,,nntplib.NNTP} class now supports the context management protocol to
unconditionally consume @ref{98f,,socket.error} exceptions and to close the NNTP
connection when done:

@example
>>> from nntplib import NNTP
>>> with NNTP('news.gmane.org') as n:
...     n.group('gmane.comp.python.committers')
...
('211 1755 1 1755 gmane.comp.python.committers', 1755, 1, 1755, 'gmane.comp.python.committers')
>>>
@end example

（由 Giampaolo Rodolà 在 bpo-9795@footnote{https://bugs.python.org/issue9795} 中贡献。）

@node os<7>,pdb<4>,nntplib,改进的模块<6>
@anchor{whatsnew/3 3 os}@anchor{a28}
@subsubsection os



@itemize *

@item 
The @ref{c4,,os} module has a new @ref{a29,,pipe2()} function that makes it
possible to create a pipe with @ref{9bd,,O_CLOEXEC} or
@ref{71d,,O_NONBLOCK} flags set atomically. This is especially useful to
avoid race conditions in multi-threaded programs.

@item 
The @ref{c4,,os} module has a new @ref{352,,sendfile()} function which provides
an efficient "zero-copy" way for copying data from one file (or socket)
descriptor to another. The phrase "zero-copy" refers to the fact that all of
the copying of data between the two descriptors is done entirely by the
kernel, with no copying of data into userspace buffers. @ref{352,,sendfile()}
can be used to efficiently copy data from a file on disk to a network socket,
e.g. for downloading a file.

(Patch submitted by Ross Lagerwall and Giampaolo Rodolà in bpo-10882@footnote{https://bugs.python.org/issue10882}.)

@item 
To avoid race conditions like symlink attacks and issues with temporary
files and directories, it is more reliable (and also faster) to manipulate
file descriptors instead of file names. Python 3.3 enhances existing functions
and introduces new functions to work on file descriptors (bpo-4761@footnote{https://bugs.python.org/issue4761},
bpo-10755@footnote{https://bugs.python.org/issue10755} and bpo-14626@footnote{https://bugs.python.org/issue14626}).


@itemize -

@item 
The @ref{c4,,os} module has a new @ref{3ac,,fwalk()} function similar to
@ref{64e,,walk()} except that it also yields file descriptors referring to the
directories visited. This is especially useful to avoid symlink races.

@item 
The following functions get new optional @emph{dir_fd} (@ref{a2a,,paths relative to directory descriptors}) and/or @emph{follow_symlinks} (@ref{a2b,,not following symlinks}):
@ref{a2c,,access()}, @ref{a2d,,chflags()}, @ref{a2e,,chmod()}, @ref{a2f,,chown()},
@ref{a30,,link()}, @ref{1f2,,lstat()}, @ref{a31,,mkdir()}, @ref{65d,,mkfifo()},
@ref{65e,,mknod()}, @ref{65f,,open()}, @ref{1f3,,readlink()}, @ref{a32,,remove()},
@ref{a33,,rename()}, @ref{a34,,replace()}, @ref{a35,,rmdir()}, @ref{1f1,,stat()},
@ref{a36,,symlink()}, @ref{a37,,unlink()}, @ref{a38,,utime()}.  Platform
support for using these parameters can be checked via the sets
@ref{a39,,os.supports_dir_fd} and @code{os.supports_follows_symlinks}.

@item 
The following functions now support a file descriptor for their path argument:
@ref{a3a,,chdir()}, @ref{a2e,,chmod()}, @ref{a2f,,chown()},
@ref{a3b,,execve()}, @ref{a3c,,listdir()}, @ref{a3d,,pathconf()}, @ref{1f6,,exists()},
@ref{1f1,,stat()}, @ref{a3e,,statvfs()}, @ref{a38,,utime()}.  Platform support
for this can be checked via the @ref{a3f,,os.supports_fd} set.
@end itemize

@item 
@ref{a2c,,access()} accepts an @code{effective_ids} keyword argument to turn on
using the effective uid/gid rather than the real uid/gid in the access check.
Platform support for this can be checked via the
@ref{a40,,supports_effective_ids} set.

@item 
The @ref{c4,,os} module has two new functions: @ref{a41,,getpriority()} and
@ref{a42,,setpriority()}. They can be used to get or set process
niceness/priority in a fashion similar to @ref{a43,,os.nice()} but extended to all
processes instead of just the current one.

(Patch submitted by Giampaolo Rodolà in bpo-10784@footnote{https://bugs.python.org/issue10784}.)

@item 
The new @ref{a34,,os.replace()} function allows cross-platform renaming of a
file with overwriting the destination.  With @ref{a33,,os.rename()}, an existing
destination file is overwritten under POSIX, but raises an error under
Windows.
(Contributed by Antoine Pitrou in bpo-8828@footnote{https://bugs.python.org/issue8828}.)

@item 
The stat family of functions (@ref{1f1,,stat()}, @ref{659,,fstat()},
and @ref{1f2,,lstat()}) now support reading a file's timestamps
with nanosecond precision.  Symmetrically, @ref{a38,,utime()}
can now write file timestamps with nanosecond precision.  (Contributed by
Larry Hastings in bpo-14127@footnote{https://bugs.python.org/issue14127}.)

@item 
The new @ref{a44,,os.get_terminal_size()} function queries the size of the
terminal attached to a file descriptor. See also
@ref{a45,,shutil.get_terminal_size()}.
(Contributed by Zbigniew Jędrzejewski-Szmek in bpo-13609@footnote{https://bugs.python.org/issue13609}.)
@end itemize

@c XXX sort out this mess after beta1


@itemize *

@item 
New functions to support Linux extended attributes (bpo-12720@footnote{https://bugs.python.org/issue12720}):
@ref{a46,,getxattr()}, @ref{a47,,listxattr()}, @ref{a48,,removexattr()},
@ref{a49,,setxattr()}.

@item 
New interface to the scheduler. These functions
control how a process is allocated CPU time by the operating system. New
functions:
@ref{a4a,,sched_get_priority_max()}, @ref{a4b,,sched_get_priority_min()},
@ref{a4c,,sched_getaffinity()}, @ref{a4d,,sched_getparam()},
@ref{a4e,,sched_getscheduler()}, @ref{a4f,,sched_rr_get_interval()},
@ref{a50,,sched_setaffinity()}, @ref{a51,,sched_setparam()},
@ref{a52,,sched_setscheduler()}, @ref{a53,,sched_yield()},

@item 
New functions to control the file system:


@itemize *

@item 
@ref{660,,posix_fadvise()}: Announces an intention to access data in a
specific pattern thus allowing the kernel to make optimizations.

@item 
@ref{661,,posix_fallocate()}: Ensures that enough disk space is allocated
for a file.

@item 
@ref{a54,,sync()}: Force write of everything to disk.
@end itemize

@item 
Additional new  posix functions:


@itemize *

@item 
@ref{a55,,lockf()}: Apply, test or remove a POSIX lock on an open file descriptor.

@item 
@ref{3b1,,pread()}: Read from a file descriptor at an offset, the file
offset remains unchanged.

@item 
@ref{3b4,,pwrite()}: Write to a file descriptor from an offset, leaving
the file offset unchanged.

@item 
@ref{3b0,,readv()}: Read from a file descriptor into a number of writable buffers.

@item 
@ref{71e,,truncate()}: Truncate the file corresponding to @emph{path}, so that
it is at most @emph{length} bytes in size.

@item 
@ref{666,,waitid()}: Wait for the completion of one or more child processes.

@item 
@ref{3b3,,writev()}: Write the contents of @emph{buffers} to a file descriptor,
where @emph{buffers} is an arbitrary sequence of buffers.

@item 
@ref{a56,,getgrouplist()} (bpo-9344@footnote{https://bugs.python.org/issue9344}): Return list of group ids that
specified user belongs to.
@end itemize

@item 
@ref{a57,,times()} and @ref{a58,,uname()}: Return type changed from a tuple to
a tuple-like object with named attributes.

@item 
Some platforms now support additional constants for the @ref{a59,,lseek()}
function, such as @code{os.SEEK_HOLE} and @code{os.SEEK_DATA}.

@item 
New constants @ref{a5a,,RTLD_LAZY}, @ref{a5b,,RTLD_NOW},
@ref{a5c,,RTLD_GLOBAL}, @ref{a5d,,RTLD_LOCAL}, @ref{a5e,,RTLD_NODELETE},
@ref{a5f,,RTLD_NOLOAD}, and @ref{a60,,RTLD_DEEPBIND} are available on
platforms that support them.   These are for use with the
@ref{a61,,sys.setdlopenflags()} function, and supersede the similar constants
defined in @ref{2b,,ctypes} and @code{DLFCN}.  (Contributed by Victor Stinner
in bpo-13226@footnote{https://bugs.python.org/issue13226}.)

@item 
@ref{a36,,os.symlink()} now accepts (and ignores) the @code{target_is_directory}
keyword argument on non-Windows platforms, to ease cross-platform support.
@end itemize

@node pdb<4>,pickle<5>,os<7>,改进的模块<6>
@anchor{whatsnew/3 3 pdb}@anchor{a62}
@subsubsection pdb


Tab-completion is now available not only for command names, but also their
arguments.  For example, for the @code{break} command, function and file names
are completed.

（由 Georg Brandl 在 bpo-14210@footnote{https://bugs.python.org/issue14210} 中贡献）

@node pickle<5>,pydoc<4>,pdb<4>,改进的模块<6>
@anchor{whatsnew/3 3 pickle}@anchor{a63}
@subsubsection pickle


@ref{20d,,pickle.Pickler} objects now have an optional
@ref{a64,,dispatch_table} attribute allowing per-pickler
reduction functions to be set.

（由 Richard Oudkerk 在 bpo-14166@footnote{https://bugs.python.org/issue14166} 中贡献。）

@node pydoc<4>,re<6>,pickle<5>,改进的模块<6>
@anchor{whatsnew/3 3 pydoc}@anchor{a65}
@subsubsection pydoc


The Tk GUI and the @code{serve()} function have been removed from the
@ref{d9,,pydoc} module: @code{pydoc -g} and @code{serve()} have been deprecated
in Python 3.2.

@node re<6>,sched,pydoc<4>,改进的模块<6>
@anchor{whatsnew/3 3 re}@anchor{a66}
@subsubsection re


@ref{329,,str} regular expressions now support @code{\u} and @code{\U} escapes.

（由 Serhiy Storchaka 在 bpo-3665@footnote{https://bugs.python.org/issue3665} 中贡献。）

@node sched,select<2>,re<6>,改进的模块<6>
@anchor{whatsnew/3 3 sched}@anchor{a67}
@subsubsection sched



@itemize *

@item 
@ref{a68,,run()} now accepts a @emph{blocking} parameter which when
set to false makes the method execute the scheduled events due to expire
soonest (if any) and then return immediately.
This is useful in case you want to use the @ref{a69,,scheduler} in
non-blocking applications.  (Contributed by Giampaolo Rodolà in bpo-13449@footnote{https://bugs.python.org/issue13449}.)

@item 
@ref{a69,,scheduler} class can now be safely used in multi-threaded
environments.  (Contributed by Josiah Carlson and Giampaolo Rodolà in
bpo-8684@footnote{https://bugs.python.org/issue8684}.)

@item 
@emph{timefunc} and @emph{delayfunct} parameters of @ref{a69,,scheduler} class
constructor are now optional and defaults to @ref{316,,time.time()} and
@ref{67a,,time.sleep()} respectively.  (Contributed by Chris Clark in
bpo-13245@footnote{https://bugs.python.org/issue13245}.)

@item 
@ref{a6a,,enter()} and @ref{a6b,,enterabs()}
@emph{argument} parameter is now optional.  (Contributed by Chris Clark in
bpo-13245@footnote{https://bugs.python.org/issue13245}.)

@item 
@ref{a6a,,enter()} and @ref{a6b,,enterabs()}
now accept a @emph{kwargs} parameter.  (Contributed by Chris Clark in
bpo-13245@footnote{https://bugs.python.org/issue13245}.)
@end itemize

@node select<2>,shlex<3>,sched,改进的模块<6>
@anchor{whatsnew/3 3 select}@anchor{a6c}
@subsubsection select


Solaris and derivative platforms have a new class @ref{8a5,,select.devpoll}
for high performance asynchronous sockets via @code{/dev/poll}.
(Contributed by Jesús Cea Avión in bpo-6397@footnote{https://bugs.python.org/issue6397}.)

@node shlex<3>,shutil<4>,select<2>,改进的模块<6>
@anchor{whatsnew/3 3 shlex}@anchor{a6d}
@subsubsection shlex


The previously undocumented helper function @code{quote} from the
@ref{cc,,pipes} modules has been moved to the @ref{e8,,shlex} module and
documented.  @ref{a6e,,quote()} properly escapes all characters in a string
that might be otherwise given special meaning by the shell.

@node shutil<4>,signal<3>,shlex<3>,改进的模块<6>
@anchor{whatsnew/3 3 shutil}@anchor{a6f}
@subsubsection shutil



@itemize *

@item 
新的函数：


@itemize *

@item 
@ref{a70,,disk_usage()}: provides total, used and free disk space
statistics.  (Contributed by Giampaolo Rodolà in bpo-12442@footnote{https://bugs.python.org/issue12442}.)

@item 
@ref{a71,,chown()}: allows one to change user and/or group of the given
path also specifying the user/group names and not only their numeric
ids.  (Contributed by Sandro Tosi in bpo-12191@footnote{https://bugs.python.org/issue12191}.)

@item 
@ref{a45,,shutil.get_terminal_size()}: returns the size of the terminal window
to which the interpreter is attached.  (Contributed by Zbigniew
Jędrzejewski-Szmek in bpo-13609@footnote{https://bugs.python.org/issue13609}.)
@end itemize

@item 
@ref{25a,,copy2()} and @ref{a72,,copystat()} now preserve file
timestamps with nanosecond precision on platforms that support it.
They also preserve file "extended attributes" on Linux.  (Contributed
by Larry Hastings in bpo-14127@footnote{https://bugs.python.org/issue14127} and  bpo-15238@footnote{https://bugs.python.org/issue15238}.)

@item 
Several functions now take an optional @code{symlinks} argument: when that
parameter is true, symlinks aren't dereferenced and the operation instead
acts on the symlink itself (or creates one, if relevant).
(Contributed by Hynek Schlawack in bpo-12715@footnote{https://bugs.python.org/issue12715}.)

@item 
When copying files to a different file system, @ref{25b,,move()} now
handles symlinks the way the posix @code{mv} command does, recreating the
symlink rather than copying the target file contents.  (Contributed by
Jonathan Niehof in bpo-9993@footnote{https://bugs.python.org/issue9993}.)  @ref{25b,,move()} now also returns
the @code{dst} argument as its result.

@item 
@ref{21c,,rmtree()} is now resistant to symlink attacks on platforms
which support the new @code{dir_fd} parameter in @ref{65f,,os.open()} and
@ref{a37,,os.unlink()}.  (Contributed by Martin von Löwis and Hynek Schlawack
in bpo-4489@footnote{https://bugs.python.org/issue4489}.)
@end itemize

@node signal<3>,smtpd<3>,shutil<4>,改进的模块<6>
@anchor{whatsnew/3 3 signal}@anchor{a73}
@subsubsection signal



@itemize *

@item 
The @ref{ea,,signal} module has new functions:


@itemize *

@item 
@ref{a74,,pthread_sigmask()}: fetch and/or change the signal mask of the
calling thread (Contributed by Jean-Paul Calderone in bpo-8407@footnote{https://bugs.python.org/issue8407});

@item 
@ref{a75,,pthread_kill()}: send a signal to a thread;

@item 
@ref{a76,,sigpending()}: examine pending functions;

@item 
@ref{a77,,sigwait()}: wait a signal;

@item 
@ref{679,,sigwaitinfo()}: wait for a signal, returning detailed
information about it;

@item 
@ref{678,,sigtimedwait()}: like @ref{679,,sigwaitinfo()} but with a
timeout.
@end itemize

@item 
The signal handler writes the signal number as a single byte instead of
a nul byte into the wakeup file descriptor. So it is possible to wait more
than one signal and know which signals were raised.

@item 
@ref{a78,,signal.signal()} and @ref{a79,,signal.siginterrupt()} raise an OSError,
instead of a RuntimeError: OSError has an errno attribute.
@end itemize

@node smtpd<3>,smtplib<3>,signal<3>,改进的模块<6>
@anchor{whatsnew/3 3 smtpd}@anchor{a7a}
@subsubsection smtpd


The @ref{ec,,smtpd} module now supports 
@geindex RFC; RFC 5321
RFC 5321@footnote{https://tools.ietf.org/html/rfc5321.html} (extended SMTP) and 
@geindex RFC; RFC 1870
RFC 1870@footnote{https://tools.ietf.org/html/rfc1870.html}
(size extension).  Per the standard, these extensions are enabled if and only
if the client initiates the session with an @code{EHLO} command.

(Initial @code{ELHO} support by Alberto Trevino.  Size extension by Juhana
Jauhiainen.  Substantial additional work on the patch contributed by Michele
Orrù and Dan Boswell.  bpo-8739@footnote{https://bugs.python.org/issue8739})

@node smtplib<3>,socket<7>,smtpd<3>,改进的模块<6>
@anchor{whatsnew/3 3 smtplib}@anchor{a7b}
@subsubsection smtplib


The @ref{a7c,,SMTP}, @ref{a7d,,SMTP_SSL}, and
@ref{a7e,,LMTP} classes now accept a @code{source_address} keyword argument
to specify the @code{(host, port)} to use as the source address in the bind call
when creating the outgoing socket.  (Contributed by Paulo Scardine in
bpo-11281@footnote{https://bugs.python.org/issue11281}.)

@ref{a7c,,SMTP} now supports the context management protocol, allowing an
@code{SMTP} instance to be used in a @code{with} statement.  (Contributed
by Giampaolo Rodolà in bpo-11289@footnote{https://bugs.python.org/issue11289}.)

The @ref{a7d,,SMTP_SSL} constructor and the @ref{a7f,,starttls()}
method now accept an SSLContext parameter to control parameters of the secure
channel.  (Contributed by Kasun Herath in bpo-8809@footnote{https://bugs.python.org/issue8809}.)

@node socket<7>,socketserver<3>,smtplib<3>,改进的模块<6>
@anchor{whatsnew/3 3 socket}@anchor{a80}
@subsubsection socket



@itemize *

@item 
The @ref{66e,,socket} class now exposes additional methods to process
ancillary data when supported by the underlying platform:


@itemize *

@item 
@ref{676,,sendmsg()}

@item 
@ref{673,,recvmsg()}

@item 
@ref{a81,,recvmsg_into()}
@end itemize

(Contributed by David Watson in bpo-6560@footnote{https://bugs.python.org/issue6560}, based on an earlier patch by
Heiko Wundram)

@item 
The @ref{66e,,socket} class now supports the PF_CAN protocol family
(@indicateurl{https://en.wikipedia.org/wiki/Socketcan}), on Linux
(@indicateurl{https://lwn.net/Articles/253425}).

(Contributed by Matthias Fuchs, updated by Tiago Gonçalves in bpo-10141@footnote{https://bugs.python.org/issue10141}.)

@item 
The @ref{66e,,socket} class now supports the PF_RDS protocol family
(@indicateurl{https://en.wikipedia.org/wiki/Reliable_Datagram_Sockets} and
@indicateurl{https://oss.oracle.com/projects/rds/}).

@item 
The @ref{66e,,socket} class now supports the @code{PF_SYSTEM} protocol
family on OS X.  (Contributed by Michael Goderbauer in bpo-13777@footnote{https://bugs.python.org/issue13777}.)

@item 
New function @ref{a82,,sethostname()} allows the hostname to be set
on unix systems if the calling process has sufficient privileges.
(Contributed by Ross Lagerwall in bpo-10866@footnote{https://bugs.python.org/issue10866}.)
@end itemize

@node socketserver<3>,sqlite3<5>,socket<7>,改进的模块<6>
@anchor{whatsnew/3 3 socketserver}@anchor{a83}
@subsubsection socketserver


@ref{a84,,BaseServer} now has an overridable method
@ref{a85,,service_actions()} that is called by the
@ref{a86,,serve_forever()} method in the service loop.
@ref{3cd,,ForkingMixIn} now uses this to clean up zombie
child processes.  (Contributed by Justin Warkentin in bpo-11109@footnote{https://bugs.python.org/issue11109}.)

@node sqlite3<5>,ssl<8>,socketserver<3>,改进的模块<6>
@anchor{whatsnew/3 3 sqlite3}@anchor{a87}
@subsubsection sqlite3


New @ref{3d0,,sqlite3.Connection} method
@ref{a88,,set_trace_callback()} can be used to capture a trace of
all sql commands processed by sqlite.  (Contributed by Torsten Landschoff
in bpo-11688@footnote{https://bugs.python.org/issue11688}.)

@node ssl<8>,stat<2>,sqlite3<5>,改进的模块<6>
@anchor{whatsnew/3 3 ssl}@anchor{a89}
@subsubsection ssl



@itemize *

@item 
The @ref{f3,,ssl} module has two new random generation functions:


@itemize *

@item 
@ref{a8a,,RAND_bytes()}: generate cryptographically strong
pseudo-random bytes.

@item 
@ref{a8b,,RAND_pseudo_bytes()}: generate pseudo-random bytes.
@end itemize

（由 Victor Stinner 在 bpo-12049@footnote{https://bugs.python.org/issue12049} 中贡献。）

@item 
The @ref{f3,,ssl} module now exposes a finer-grained exception hierarchy
in order to make it easier to inspect the various kinds of errors.
(Contributed by Antoine Pitrou in bpo-11183@footnote{https://bugs.python.org/issue11183}.)

@item 
@ref{a8c,,load_cert_chain()} now accepts a @emph{password} argument
to be used if the private key is encrypted.
(Contributed by Adam Simpkins in bpo-12803@footnote{https://bugs.python.org/issue12803}.)

@item 
Diffie-Hellman key exchange, both regular and Elliptic Curve-based, is
now supported through the @ref{a8d,,load_dh_params()} and
@ref{a8e,,set_ecdh_curve()} methods.
(Contributed by Antoine Pitrou in bpo-13626@footnote{https://bugs.python.org/issue13626} and bpo-13627@footnote{https://bugs.python.org/issue13627}.)

@item 
SSL sockets have a new @ref{a8f,,get_channel_binding()} method
allowing the implementation of certain authentication mechanisms such as
SCRAM-SHA-1-PLUS.  (Contributed by Jacek Konieczny in bpo-12551@footnote{https://bugs.python.org/issue12551}.)

@item 
You can query the SSL compression algorithm used by an SSL socket, thanks
to its new @ref{a90,,compression()} method.  The new attribute
@ref{a91,,OP_NO_COMPRESSION} can be used to disable compression.
(Contributed by Antoine Pitrou in bpo-13634@footnote{https://bugs.python.org/issue13634}.)

@item 
Support has been added for the Next Protocol Negotiation extension using
the @ref{a92,,ssl.SSLContext.set_npn_protocols()} method.
(Contributed by Colin Marc in bpo-14204@footnote{https://bugs.python.org/issue14204}.)

@item 
SSL errors can now be introspected more easily thanks to
@ref{a93,,library} and @ref{a94,,reason} attributes.
(Contributed by Antoine Pitrou in bpo-14837@footnote{https://bugs.python.org/issue14837}.)

@item 
The @ref{a95,,get_server_certificate()} function now supports IPv6.
(Contributed by Charles-François Natali in bpo-11811@footnote{https://bugs.python.org/issue11811}.)

@item 
New attribute @ref{a96,,OP_CIPHER_SERVER_PREFERENCE} allows setting
SSLv3 server sockets to use the server's cipher ordering preference rather
than the client's (bpo-13635@footnote{https://bugs.python.org/issue13635}).
@end itemize

@node stat<2>,struct<3>,ssl<8>,改进的模块<6>
@anchor{whatsnew/3 3 stat}@anchor{a97}
@subsubsection stat


The undocumented tarfile.filemode function has been moved to
@ref{a98,,stat.filemode()}. It can be used to convert a file's mode to a string of
the form '-rwxrwxrwx'.

（由 Giampaolo Rodolà 在 bpo-14807@footnote{https://bugs.python.org/issue14807} 中贡献。）

@node struct<3>,subprocess<5>,stat<2>,改进的模块<6>
@anchor{whatsnew/3 3 struct}@anchor{a99}
@subsubsection struct


The @ref{f8,,struct} module now supports @code{ssize_t} and @code{size_t} via the
new codes @code{n} and @code{N}, respectively.  (Contributed by Antoine Pitrou
in bpo-3163@footnote{https://bugs.python.org/issue3163}.)

@node subprocess<5>,sys<7>,struct<3>,改进的模块<6>
@anchor{whatsnew/3 3 subprocess}@anchor{a9a}
@subsubsection subprocess


Command strings can now be bytes objects on posix platforms.  (Contributed by
Victor Stinner in bpo-8513@footnote{https://bugs.python.org/issue8513}.)

A new constant @ref{a9b,,DEVNULL} allows suppressing output in a
platform-independent fashion.  (Contributed by Ross Lagerwall in
bpo-5870@footnote{https://bugs.python.org/issue5870}.)

@node sys<7>,tarfile<4>,subprocess<5>,改进的模块<6>
@anchor{whatsnew/3 3 sys}@anchor{a9c}
@subsubsection sys


The @ref{fd,,sys} module has a new @ref{a9d,,thread_info} @ref{a9e,,named tuple} holding information about the thread implementation
(bpo-11223@footnote{https://bugs.python.org/issue11223}).

@node tarfile<4>,tempfile,sys<7>,改进的模块<6>
@anchor{whatsnew/3 3 tarfile}@anchor{a9f}
@subsubsection tarfile


@ref{101,,tarfile} now supports @code{lzma} encoding via the @ref{ad,,lzma} module.
(Contributed by Lars Gustäbel in bpo-5689@footnote{https://bugs.python.org/issue5689}.)

@node tempfile,textwrap<2>,tarfile<4>,改进的模块<6>
@anchor{whatsnew/3 3 tempfile}@anchor{aa0}
@subsubsection tempfile


@ref{aa1,,tempfile.SpooledTemporaryFile}'s
@code{truncate()} method now accepts
a @code{size} parameter.  (Contributed by Ryan Kelly in bpo-9957@footnote{https://bugs.python.org/issue9957}.)

@node textwrap<2>,threading<5>,tempfile,改进的模块<6>
@anchor{whatsnew/3 3 textwrap}@anchor{aa2}
@subsubsection textwrap


The @ref{108,,textwrap} module has a new @ref{aa3,,indent()} that makes
it straightforward to add a common prefix to selected lines in a block
of text  (bpo-13857@footnote{https://bugs.python.org/issue13857}).

@node threading<5>,time<5>,textwrap<2>,改进的模块<6>
@anchor{whatsnew/3 3 threading}@anchor{aa4}
@subsubsection threading


@ref{aa5,,threading.Condition}, @ref{aa6,,threading.Semaphore},
@ref{aa7,,threading.BoundedSemaphore}, @ref{aa8,,threading.Event}, and
@ref{aa9,,threading.Timer}, all of which used to be factory functions returning a
class instance, are now classes and may be subclassed.  (Contributed by Éric
Araujo in bpo-10968@footnote{https://bugs.python.org/issue10968}.)

The @ref{234,,threading.Thread} constructor now accepts a @code{daemon} keyword
argument to override the default behavior of inheriting the @code{daemon} flag
value from the parent thread (bpo-6064@footnote{https://bugs.python.org/issue6064}).

The formerly private function @code{_thread.get_ident} is now available as the
public function @ref{aaa,,threading.get_ident()}.  This eliminates several cases of
direct access to the @code{_thread} module in the stdlib.  Third party code that
used @code{_thread.get_ident} should likewise be changed to use the new public
interface.

@node time<5>,types<4>,threading<5>,改进的模块<6>
@anchor{whatsnew/3 3 time}@anchor{aab}
@subsubsection time


The 
@geindex Python 提高建议; PEP 418
PEP 418@footnote{https://www.python.org/dev/peps/pep-0418} added new functions to the @ref{10a,,time} module:


@itemize *

@item 
@ref{aac,,get_clock_info()}: Get information on a clock.

@item 
@ref{769,,monotonic()}: Monotonic clock (cannot go backward), not affected
by system clock updates.

@item 
@ref{2aa,,perf_counter()}: Performance counter with the highest available
resolution to measure a short duration.

@item 
@ref{2ab,,process_time()}: Sum of the system and user CPU time of the
current process.
@end itemize

Other new functions:


@itemize *

@item 
@ref{aad,,clock_getres()}, @ref{aae,,clock_gettime()} and
@ref{aaf,,clock_settime()} functions with @code{CLOCK_xxx} constants.
(Contributed by Victor Stinner in bpo-10278@footnote{https://bugs.python.org/issue10278}.)
@end itemize

To improve cross platform consistency, @ref{67a,,sleep()} now raises a
@ref{1fb,,ValueError} when passed a negative sleep value.  Previously this was an
error on posix, but produced an infinite sleep on Windows.

@node types<4>,unittest<5>,time<5>,改进的模块<6>
@anchor{whatsnew/3 3 types}@anchor{ab0}
@subsubsection types


Add a new @ref{ab1,,types.MappingProxyType} class: Read-only proxy of a mapping.
(bpo-14386@footnote{https://bugs.python.org/issue14386})

The new functions @ref{ab2,,types.new_class()} and @ref{ab3,,types.prepare_class()} provide support
for 
@geindex Python 提高建议; PEP 3115
PEP 3115@footnote{https://www.python.org/dev/peps/pep-3115} compliant dynamic type creation. (bpo-14588@footnote{https://bugs.python.org/issue14588})

@node unittest<5>,urllib<3>,types<4>,改进的模块<6>
@anchor{whatsnew/3 3 unittest}@anchor{ab4}
@subsubsection unittest


@ref{ab5,,assertRaises()}, @ref{ab6,,assertRaisesRegex()}, @ref{ab7,,assertWarns()}, and
@ref{ab8,,assertWarnsRegex()} now accept a keyword argument @emph{msg} when used as
context managers.  (Contributed by Ezio Melotti and Winston Ewert in
bpo-10775@footnote{https://bugs.python.org/issue10775}.)

@ref{ab9,,unittest.TestCase.run()} now returns the @ref{aba,,TestResult}
object.

@node urllib<3>,webbrowser,unittest<5>,改进的模块<6>
@anchor{whatsnew/3 3 urllib}@anchor{abb}
@subsubsection urllib


The @ref{8f0,,Request} class, now accepts a @emph{method} argument
used by @ref{abc,,get_method()} to determine what HTTP method
should be used.  For example, this will send a @code{'HEAD'} request:

@example
>>> urlopen(Request('https://www.python.org', method='HEAD'))
@end example

(bpo-1673007@footnote{https://bugs.python.org/issue1673007})

@node webbrowser,xml etree ElementTree,urllib<3>,改进的模块<6>
@anchor{whatsnew/3 3 webbrowser}@anchor{abd}
@subsubsection webbrowser


The @ref{129,,webbrowser} module supports more "browsers": Google Chrome (named
@code{chrome}, @code{chromium}, @code{chrome-browser} or
@code{chromium-browser} depending on the version and operating system),
and the generic launchers @code{xdg-open}, from the FreeDesktop.org
project, and @code{gvfs-open}, which is the default URI handler for GNOME
3.  (The former contributed by Arnaud Calmettes in bpo-13620@footnote{https://bugs.python.org/issue13620}, the latter
by Matthias Klose in bpo-14493@footnote{https://bugs.python.org/issue14493}.)

@node xml etree ElementTree,zlib<2>,webbrowser,改进的模块<6>
@anchor{whatsnew/3 3 xml-etree-elementtree}@anchor{abe}
@subsubsection xml.etree.ElementTree


The @ref{137,,xml.etree.ElementTree} module now imports its C accelerator by
default; there is no longer a need to explicitly import
@code{xml.etree.cElementTree} (this module stays for backwards compatibility,
but is now deprecated).  In addition,  the @code{iter} family of methods of
@ref{abf,,Element} has been optimized (rewritten in C).
The module's documentation has also been greatly improved with added examples
and a more detailed reference.

@node zlib<2>,,xml etree ElementTree,改进的模块<6>
@anchor{whatsnew/3 3 zlib}@anchor{ac0}
@subsubsection zlib


New attribute @ref{ac1,,zlib.Decompress.eof} makes it possible to distinguish
between a properly-formed compressed stream and an incomplete or truncated one.
(Contributed by Nadeem Vawda in bpo-12646@footnote{https://bugs.python.org/issue12646}.)

New attribute @ref{ac2,,zlib.ZLIB_RUNTIME_VERSION} reports the version string of
the underlying @code{zlib} library that is loaded at runtime.  (Contributed by
Torsten Landschoff in bpo-12306@footnote{https://bugs.python.org/issue12306}.)

@node 性能优化<5>,构建和 C API 的改变<4>,改进的模块<6>,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 optimizations}@anchor{ac3}
@subsection 性能优化


Major performance enhancements have been added:


@itemize *

@item 
Thanks to 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393}, some operations on Unicode strings have been optimized:


@itemize *

@item 
the memory footprint is divided by 2 to 4 depending on the text

@item 
encode an ASCII string to UTF-8 doesn't need to encode characters anymore,
the UTF-8 representation is shared with the ASCII representation

@item 
the UTF-8 encoder has been optimized

@item 
repeating a single ASCII letter and getting a substring of an ASCII string
is 4 times faster
@end itemize

@item 
UTF-8 is now 2x to 4x faster.  UTF-16 encoding is now up to 10x faster.

(Contributed by Serhiy Storchaka, bpo-14624@footnote{https://bugs.python.org/issue14624}, bpo-14738@footnote{https://bugs.python.org/issue14738} and
bpo-15026@footnote{https://bugs.python.org/issue15026}.)
@end itemize

@node 构建和 C API 的改变<4>,弃用<5>,性能优化<5>,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 build-and-c-api-changes}@anchor{981}
@subsection 构建和 C API 的改变


Changes to Python's build process and to the C API include:


@itemize *

@item 
新的 
@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} 相关功能：


@itemize *

@item 
@ref{ac4,,PyMemoryView_FromMemory()}
@end itemize

@item 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393} 添加了新的 Unicode 类型，宏和函数


@itemize *

@item 
高阶 API


@itemize *

@item 
@ref{ac5,,PyUnicode_CopyCharacters()}

@item 
@ref{43a,,PyUnicode_FindChar()}

@item 
@ref{ac6,,PyUnicode_GetLength()}, @ref{ac7,,PyUnicode_GET_LENGTH}

@item 
@ref{ac8,,PyUnicode_New()}

@item 
@ref{ac9,,PyUnicode_Substring()}

@item 
@ref{aca,,PyUnicode_ReadChar()}, @ref{acb,,PyUnicode_WriteChar()}
@end itemize

@item 
低阶 API:


@itemize *

@item 
@ref{acc,,Py_UCS1}, @ref{acd,,Py_UCS2}, @ref{ace,,Py_UCS4} 类型

@item 
@ref{acf,,PyASCIIObject} 和 @ref{ad0,,PyCompactUnicodeObject} 结构

@item 
@ref{ad1,,PyUnicode_READY}

@item 
@ref{ad2,,PyUnicode_FromKindAndData()}

@item 
@ref{ad3,,PyUnicode_AsUCS4()}, @ref{ad4,,PyUnicode_AsUCS4Copy()}

@item 
@ref{ad5,,PyUnicode_DATA}, @ref{ad6,,PyUnicode_1BYTE_DATA},
@ref{ad7,,PyUnicode_2BYTE_DATA}, @ref{ad8,,PyUnicode_4BYTE_DATA}

@item 
@ref{ad9,,PyUnicode_KIND} 使用 @code{PyUnicode_Kind} 枚举: @ref{ada,,PyUnicode_WCHAR_KIND}, @ref{adb,,PyUnicode_1BYTE_KIND}, @ref{adc,,PyUnicode_2BYTE_KIND}, @ref{add,,PyUnicode_4BYTE_KIND}

@item 
@ref{ade,,PyUnicode_READ}, @ref{adf,,PyUnicode_READ_CHAR}, @ref{ae0,,PyUnicode_WRITE}

@item 
@ref{ae1,,PyUnicode_MAX_CHAR_VALUE}
@end itemize
@end itemize

@item 
@ref{26a,,PyArg_ParseTuple} 现在接受 @code{c} 格式的 @ref{32b,,bytearray} (bpo-12380@footnote{https://bugs.python.org/issue12380})。
@end itemize

@node 弃用<5>,移植到 Python 3 3,构建和 C API 的改变<4>,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 deprecated}@anchor{ae2}
@subsection 弃用


@menu
* 不支持的操作系统: 不支持的操作系统<2>. 
* 已弃用的 Python 模块、函数和方法: 已弃用的 Python 模块、函数和方法<4>. 
* 已弃用的 C API 函数和类型: 已弃用的 C API 函数和类型<3>. 
* 弃用的功能:: 

@end menu

@node 不支持的操作系统<2>,已弃用的 Python 模块、函数和方法<4>,,弃用<5>
@anchor{whatsnew/3 3 unsupported-operating-systems}@anchor{ae3}
@subsubsection 不支持的操作系统


由于缺少维护人员，不再支持 OS/2 和 VMS 系统 。

由于维护负担，将 @code{COMSPEC} 设置为 @code{command.com} 的 Windows平台（含Windows 2000）不再受支持。

OSF支持在3.2中被弃用，现在已经被完全删除。

@node 已弃用的 Python 模块、函数和方法<4>,已弃用的 C API 函数和类型<3>,不支持的操作系统<2>,弃用<5>
@anchor{whatsnew/3 3 deprecated-python-modules-functions-and-methods}@anchor{ae4}
@subsubsection 已弃用的 Python 模块、函数和方法



@itemize *

@item 
Passing a non-empty string to @code{object.__format__()} is deprecated, and
will produce a @ref{192,,TypeError} in Python 3.4 (bpo-9856@footnote{https://bugs.python.org/issue9856}).

@item 
The @code{unicode_internal} codec has been deprecated because of the
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393}, use UTF-8, UTF-16 (@code{utf-16-le} or @code{utf-16-be}), or UTF-32
(@code{utf-32-le} or @code{utf-32-be})

@item 
@ref{a01,,ftplib.FTP.nlst()} and @ref{a02,,ftplib.FTP.dir()}: use
@ref{a00,,ftplib.FTP.mlsd()}

@item 
@code{platform.popen()}: use the @ref{f9,,subprocess} module. Check especially
the @ref{ae5,,Replacing Older Functions with the subprocess Module} section (bpo-11377@footnote{https://bugs.python.org/issue11377}).

@item 
bpo-13374@footnote{https://bugs.python.org/issue13374}: The Windows bytes API has been deprecated in the @ref{c4,,os}
module. Use Unicode filenames, instead of bytes filenames, to not depend on
the ANSI code page anymore and to support any filename.

@item 
bpo-13988@footnote{https://bugs.python.org/issue13988}: The @code{xml.etree.cElementTree} module is deprecated.  The
accelerator is used automatically whenever available.

@item 
The behaviour of @code{time.clock()} depends on the platform: use the new
@ref{2aa,,time.perf_counter()} or @ref{2ab,,time.process_time()} function instead,
depending on your requirements, to have a well defined behaviour.

@item 
The @code{os.stat_float_times()} function is deprecated.

@item 
@ref{4,,abc} module:


@itemize *

@item 
@ref{9c7,,abc.abstractproperty} has been deprecated, use @ref{1d7,,property}
with @ref{9c8,,abc.abstractmethod()} instead.

@item 
@ref{9c9,,abc.abstractclassmethod} has been deprecated, use
@ref{1d8,,classmethod} with @ref{9c8,,abc.abstractmethod()} instead.

@item 
@ref{9ca,,abc.abstractstaticmethod} has been deprecated, use
@ref{1d9,,staticmethod} with @ref{9c8,,abc.abstractmethod()} instead.
@end itemize

@item 
@ref{9b,,importlib} package:


@itemize *

@item 
@ref{ae6,,importlib.abc.SourceLoader.path_mtime()} is now deprecated in favour of
@ref{ae7,,importlib.abc.SourceLoader.path_stats()} as bytecode files now store
both the modification time and size of the source file the bytecode file was
compiled from.
@end itemize
@end itemize

@node 已弃用的 C API 函数和类型<3>,弃用的功能,已弃用的 Python 模块、函数和方法<4>,弃用<5>
@anchor{whatsnew/3 3 deprecated-functions-and-types-of-the-c-api}@anchor{ae8}
@subsubsection 已弃用的 C API 函数和类型


@ref{ae9,,Py_UNICODE} 已经在 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393} 弃用，并将于 Python 4 中移除。所有使用此类型的函数都已弃用：

Unicode functions and methods using @ref{ae9,,Py_UNICODE} and
@ref{ae9,,Py_UNICODE*} types:


@itemize *

@item 
@ref{aea,,PyUnicode_FromUnicode}: 使用 @ref{aeb,,PyUnicode_FromWideChar()} 或 @ref{ad2,,PyUnicode_FromKindAndData()}

@item 
@ref{aec,,PyUnicode_AS_UNICODE}, @ref{aed,,PyUnicode_AsUnicode()}, @ref{aee,,PyUnicode_AsUnicodeAndSize()}: 使用 @ref{432,,PyUnicode_AsWideCharString()}

@item 
@ref{aef,,PyUnicode_AS_DATA}: 使用 @ref{ad5,,PyUnicode_DATA} 以及 @ref{ade,,PyUnicode_READ}  和 @ref{ae0,,PyUnicode_WRITE}

@item 
@ref{af0,,PyUnicode_GET_SIZE}, @ref{af1,,PyUnicode_GetSize()}: 使用 @ref{ac7,,PyUnicode_GET_LENGTH} 或 @ref{ac6,,PyUnicode_GetLength()}

@item 
@ref{af2,,PyUnicode_GET_DATA_SIZE}: 使用 @code{PyUnicode_GET_LENGTH(str) * PyUnicode_KIND(str)} (仅适用于现成的字符串)

@item 
@ref{af3,,PyUnicode_AsUnicodeCopy()}: 使用 @ref{ad4,,PyUnicode_AsUCS4Copy()} 或 @ref{432,,PyUnicode_AsWideCharString()}

@item 
@code{PyUnicode_GetMax()}
@end itemize

Functions and macros manipulating Py_UNICODE* strings:


@itemize *

@item 
@code{Py_UNICODE_strlen}: 使用 @ref{ac6,,PyUnicode_GetLength()} 或 @ref{ac7,,PyUnicode_GET_LENGTH}

@item 
@code{Py_UNICODE_strcat}: 使用 @ref{ac5,,PyUnicode_CopyCharacters()} 或 @ref{7c5,,PyUnicode_FromFormat()}

@item 
@code{Py_UNICODE_strcpy}, @code{Py_UNICODE_strncpy}, @code{Py_UNICODE_COPY}: 使用 @ref{ac5,,PyUnicode_CopyCharacters()} 或 @ref{ac9,,PyUnicode_Substring()}

@item 
@code{Py_UNICODE_strcmp}: 使用 @ref{af4,,PyUnicode_Compare()}

@item 
@code{Py_UNICODE_strncmp}: 使用 @ref{af5,,PyUnicode_Tailmatch()}

@item 
@code{Py_UNICODE_strchr}, @code{Py_UNICODE_strrchr}: 使用 @ref{43a,,PyUnicode_FindChar()}

@item 
@code{Py_UNICODE_FILL}: 使用 @ref{af6,,PyUnicode_Fill()}

@item 
@code{Py_UNICODE_MATCH}
@end itemize

编码器:


@itemize *

@item 
@ref{af7,,PyUnicode_Encode()}: 使用 @code{PyUnicode_AsEncodedObject()}

@item 
@ref{af8,,PyUnicode_EncodeUTF7()}

@item 
@ref{af9,,PyUnicode_EncodeUTF8()}: 使用 @ref{425,,PyUnicode_AsUTF8()} 或 @ref{afa,,PyUnicode_AsUTF8String()}

@item 
@ref{afb,,PyUnicode_EncodeUTF32()}

@item 
@ref{afc,,PyUnicode_EncodeUTF16()}

@item 
@code{PyUnicode_EncodeUnicodeEscape:()} 使用 @ref{afd,,PyUnicode_AsUnicodeEscapeString()}

@item 
@code{PyUnicode_EncodeRawUnicodeEscape:()} 使用 @ref{afe,,PyUnicode_AsRawUnicodeEscapeString()}

@item 
@ref{aff,,PyUnicode_EncodeLatin1()}: 使用 @ref{b00,,PyUnicode_AsLatin1String()}

@item 
@ref{b01,,PyUnicode_EncodeASCII()}: 使用 @ref{b02,,PyUnicode_AsASCIIString()}

@item 
@ref{b03,,PyUnicode_EncodeCharmap()}

@item 
@ref{b04,,PyUnicode_TranslateCharmap()}

@item 
@ref{b05,,PyUnicode_EncodeMBCS()}: 使用 @ref{b06,,PyUnicode_AsMBCSString()} 或 @ref{b07,,PyUnicode_EncodeCodePage()} (和 @code{CP_ACP} code_page)

@item 
@code{PyUnicode_EncodeDecimal()},
@ref{b08,,PyUnicode_TransformDecimalToASCII()}
@end itemize

@node 弃用的功能,,已弃用的 C API 函数和类型<3>,弃用<5>
@anchor{whatsnew/3 3 deprecated-features}@anchor{b09}
@subsubsection 弃用的功能


The @ref{7,,array} module's @code{'u'} format code is now deprecated and will be
removed in Python 4 together with the rest of the (@ref{ae9,,Py_UNICODE}) API.

@node 移植到 Python 3 3,,弃用<5>,Python 3 3 有什么新变化
@anchor{whatsnew/3 3 porting-to-python-3-3}@anchor{b0a}
@subsection 移植到 Python 3.3


本节列出了先前描述的更改以及可能需要更改代码的其他错误修正.

@menu
* Porting Python code:: 
* Porting C code:: 
* Building C extensions:: 
* Command Line Switch Changes:: 

@end menu

@node Porting Python code,Porting C code,,移植到 Python 3 3
@anchor{whatsnew/3 3 porting-python-code}@anchor{9a9}@anchor{whatsnew/3 3 portingpythoncode}@anchor{b0b}
@subsubsection Porting Python code



@itemize *

@item 
Hash randomization is enabled by default. Set the 
@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED}
environment variable to @code{0} to disable hash randomization. See also the
@ref{339,,object.__hash__()} method.

@item 
bpo-12326@footnote{https://bugs.python.org/issue12326}: On Linux, sys.platform doesn't contain the major version
anymore. It is now always 'linux', instead of 'linux2' or 'linux3' depending
on the Linux version used to build Python. Replace sys.platform == 'linux2'
with sys.platform.startswith('linux'), or directly sys.platform == 'linux' if
you don't need to support older Python versions.

@item 
bpo-13847@footnote{https://bugs.python.org/issue13847}, bpo-14180@footnote{https://bugs.python.org/issue14180}: @ref{10a,,time} and @ref{31,,datetime}:
@ref{95a,,OverflowError} is now raised instead of @ref{1fb,,ValueError} if a
timestamp is out of range. @ref{1d3,,OSError} is now raised if C functions
@code{gmtime()} or @code{localtime()} failed.

@item 
The default finders used by import now utilize a cache of what is contained
within a specific directory. If you create a Python source file or sourceless
bytecode file, make sure to call @ref{497,,importlib.invalidate_caches()} to clear
out the cache for the finders to notice the new file.

@item 
@ref{32d,,ImportError} now uses the full name of the module that was attempted to
be imported. Doctests that check ImportErrors' message will need to be
updated to use the full name of the module instead of just the tail of the
name.

@item 
The @emph{index} argument to @ref{60b,,__import__()} now defaults to 0 instead of -1
and no longer support negative values. It was an oversight when 
@geindex Python 提高建议; PEP 328
PEP 328@footnote{https://www.python.org/dev/peps/pep-0328} was
implemented that the default value remained -1. If you need to continue to
perform a relative import followed by an absolute import, then perform the
relative import using an index of 1, followed by another import using an
index of 0. It is preferred, though, that you use
@ref{b0c,,importlib.import_module()} rather than call @ref{60b,,__import__()} directly.

@item 
@ref{60b,,__import__()} no longer allows one to use an index value other than 0
for top-level modules. E.g. @code{__import__('sys', level=1)} is now an error.

@item 
Because @ref{5e1,,sys.meta_path} and @ref{956,,sys.path_hooks} now have finders on
them by default, you will most likely want to use @code{list.insert()} instead
of @code{list.append()} to add to those lists.

@item 
Because @code{None} is now inserted into @ref{498,,sys.path_importer_cache}, if you
are clearing out entries in the dictionary of paths that do not have a
finder, you will need to remove keys paired with values of @code{None} @strong{and}
@ref{9b5,,imp.NullImporter} to be backwards-compatible. This will lead to extra
overhead on older versions of Python that re-insert @code{None} into
@ref{498,,sys.path_importer_cache} where it represents the use of implicit
finders, but semantically it should not change anything.

@item 
@ref{9af,,importlib.abc.Finder} no longer specifies a @cite{find_module()} abstract
method that must be implemented. If you were relying on subclasses to
implement that method, make sure to check for the method's existence first.
You will probably want to check for @cite{find_loader()} first, though, in the
case of working with @ref{9ac,,path entry finders}.

@item 
@ref{cd,,pkgutil} has been converted to use @ref{9b,,importlib} internally. This
eliminates many edge cases where the old behaviour of the 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} import
emulation failed to match the behaviour of the real import system. The
import emulation itself is still present, but is now deprecated. The
@ref{b0d,,pkgutil.iter_importers()} and @ref{485,,pkgutil.walk_packages()} functions
special case the standard import hooks so they are still supported even
though they do not provide the non-standard @code{iter_modules()} method.

@item 
A longstanding RFC-compliance bug (bpo-1079@footnote{https://bugs.python.org/issue1079}) in the parsing done by
@ref{9f3,,email.header.decode_header()} has been fixed.  Code that uses the
standard idiom to convert encoded headers into unicode
(@code{str(make_header(decode_header(h))}) will see no change, but code that
looks at the individual tuples returned by decode_header will see that
whitespace that precedes or follows @code{ASCII} sections is now included in the
@code{ASCII} section.  Code that builds headers using @code{make_header} should
also continue to work without change, since @code{make_header} continues to add
whitespace between @code{ASCII} and non-@code{ASCII} sections if it is not already
present in the input strings.

@item 
@ref{b0e,,email.utils.formataddr()} now does the correct content transfer
encoding when passed non-@code{ASCII} display names.  Any code that depended on
the previous buggy behavior that preserved the non-@code{ASCII} unicode in the
formatted output string will need to be changed (bpo-1690608@footnote{https://bugs.python.org/issue1690608}).

@item 
@ref{b0f,,poplib.POP3.quit()} may now raise protocol errors like all other
@code{poplib} methods.  Code that assumes @code{quit} does not raise
@ref{b10,,poplib.error_proto} errors may need to be changed if errors on @code{quit}
are encountered by a particular application (bpo-11291@footnote{https://bugs.python.org/issue11291}).

@item 
The @code{strict} argument to @ref{b11,,email.parser.Parser}, deprecated since
Python 2.4, has finally been removed.

@item 
The deprecated method @code{unittest.TestCase.assertSameElements} has been
removed.

@item 
The deprecated variable @code{time.accept2dyear} has been removed.

@item 
The deprecated @code{Context._clamp} attribute has been removed from the
@ref{36,,decimal} module.  It was previously replaced by the public attribute
@code{clamp}.  (See bpo-8540@footnote{https://bugs.python.org/issue8540}.)

@item 
The undocumented internal helper class @code{SSLFakeFile} has been removed
from @ref{ed,,smtplib}, since its functionality has long been provided directly
by @ref{b12,,socket.socket.makefile()}.

@item 
Passing a negative value to @ref{67a,,time.sleep()} on Windows now raises an
error instead of sleeping forever.  It has always raised an error on posix.

@item 
The @code{ast.__version__} constant has been removed.  If you need to
make decisions affected by the AST version, use @ref{b13,,sys.version_info}
to make the decision.

@item 
Code that used to work around the fact that the @ref{109,,threading} module used
factory functions by subclassing the private classes will need to change to
subclass the now-public classes.

@item 
The undocumented debugging machinery in the threading module has been
removed, simplifying the code.  This should have no effect on production
code, but is mentioned here in case any application debug frameworks were
interacting with it (bpo-13550@footnote{https://bugs.python.org/issue13550}).
@end itemize

@node Porting C code,Building C extensions,Porting Python code,移植到 Python 3 3
@anchor{whatsnew/3 3 porting-c-code}@anchor{982}
@subsubsection Porting C code



@itemize *

@item 
In the course of changes to the buffer API the undocumented
@code{smalltable} member of the
@ref{b14,,Py_buffer} structure has been removed and the
layout of the @code{PyMemoryViewObject} has changed.

All extensions relying on the relevant parts in @code{memoryobject.h}
or @code{object.h} must be rebuilt.

@item 
Due to @ref{976,,PEP 393}, the @ref{ae9,,Py_UNICODE} type and all
functions using this type are deprecated (but will stay available for
at least five years).  If you were using low-level Unicode APIs to
construct and access unicode objects and you want to benefit of the
memory footprint reduction provided by 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393}, you have to convert
your code to the new @ref{b15,,Unicode API}.

However, if you only have been using high-level functions such as
@ref{b16,,PyUnicode_Concat()}, @ref{b17,,PyUnicode_Join()} or
@ref{7c5,,PyUnicode_FromFormat()}, your code will automatically take
advantage of the new unicode representations.

@item 
@ref{b18,,PyImport_GetMagicNumber()} now returns @code{-1} upon failure.

@item 
As a negative value for the @emph{level} argument to @ref{60b,,__import__()} is no
longer valid, the same now holds for @ref{b19,,PyImport_ImportModuleLevel()}.
This also means that the value of @emph{level} used by
@ref{b1a,,PyImport_ImportModuleEx()} is now @code{0} instead of @code{-1}.
@end itemize

@node Building C extensions,Command Line Switch Changes,Porting C code,移植到 Python 3 3
@anchor{whatsnew/3 3 building-c-extensions}@anchor{b1b}
@subsubsection Building C extensions



@itemize *

@item 
The range of possible file names for C extensions has been narrowed.
Very rarely used spellings have been suppressed: under POSIX, files
named @code{xxxmodule.so}, @code{xxxmodule.abi3.so} and
@code{xxxmodule.cpython-*.so} are no longer recognized as implementing
the @code{xxx} module.  If you had been generating such files, you have
to switch to the other spellings (i.e., remove the @code{module} string
from the file names).

(implemented in bpo-14040@footnote{https://bugs.python.org/issue14040}.)
@end itemize

@node Command Line Switch Changes,,Building C extensions,移植到 Python 3 3
@anchor{whatsnew/3 3 command-line-switch-changes}@anchor{b1c}
@subsubsection Command Line Switch Changes



@itemize *

@item 
The -Q command-line flag and related artifacts have been removed.  Code
checking sys.flags.division_warning will need updating.

（bpo-10998@footnote{https://bugs.python.org/issue10998}，由 Éric Araujo 贡献。）

@item 
When @code{python} is started with @ref{b1d,,-S}, @code{import site}
will no longer add site-specific paths to the module search paths.  In
previous versions, it did.

(bpo-11591@footnote{https://bugs.python.org/issue11591}, contributed by Carl Meyer with editions by Éric Araujo.)
@end itemize

@node Python 3 2 有什么新变化,Python 3 1 有什么新变化,Python 3 3 有什么新变化,Python的新变化
@anchor{whatsnew/3 2 doc}@anchor{b1e}@anchor{whatsnew/3 2 what-s-new-in-python-3-2}@anchor{b1f}
@section Python 3.2 有什么新变化


@*作者: 
Raymond Hettinger


@c $Id$
@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten.  (Note, during release candidate phase or just before
@c a beta release, please use the tracker instead -- this helps avoid
@c merge conflicts.   If you must add a suggested entry directly,
@c please put it in an XXX comment and the maintainer will take notice).
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.  It's helpful to
@c add the issue number:
@c 
@c   XXX Describe the transmogrify() function added to the socket
@c   module.
@c 
@c   (Contributed by P.Y. Developer; :issue:`12345`.)
@c 
@c This saves the maintainer the effort of going through the SVN log
@c when researching a change.

This article explains the new features in Python 3.2 as compared to 3.1.  It
focuses on a few highlights and gives a few examples.  For full details, see the
Misc/NEWS@footnote{https://github.com/python/cpython/blob/076ca6c3c8df3030307e548d9be792ce3c1c6eea/Misc/NEWS}
file.


@subsubheading 参见


@geindex Python 提高建议; PEP 392
PEP 392@footnote{https://www.python.org/dev/peps/pep-0392} - Python 3.2 发布计划


@menu
* PEP 384; 定义稳定的ABI: PEP 384 定义稳定的ABI. 
* PEP 389; Argparse 命令行解析模块: PEP 389 Argparse 命令行解析模块. 
* PEP 391; 基于字典的日志配置: PEP 391 基于字典的日志配置. 
* PEP 3148; concurrent.futures 模块: PEP 3148 concurrent futures 模块. 
* PEP 3147; PYC 仓库目录: PEP 3147 PYC 仓库目录. 
* PEP 3149; ABI Version Tagged .so Files: PEP 3149 ABI Version Tagged so Files. 
* PEP 3333; Python Web服务器网关接口v1.0.1: PEP 3333 Python Web服务器网关接口v1 0 1. 
* 其他语言特性修改: 其他语言特性修改<7>. 
* 新增，改进和弃用的模块:: 
* 多线程:: 
* 性能优化: 性能优化<6>. 
* Unicode:: 
* 编解码器:: 
* 文档:: 
* IDLE:: 
* 代码库:: 
* 构建和 C API 的改变: 构建和 C API 的改变<5>. 
* 移植到 Python 3.2: 移植到 Python 3 2. 

@end menu

@node PEP 384 定义稳定的ABI,PEP 389 Argparse 命令行解析模块,,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 pep-384-defining-a-stable-abi}@anchor{b20}
@subsection PEP 384: 定义稳定的ABI


In the past, extension modules built for one Python version were often
not usable with other Python versions. Particularly on Windows, every
feature release of Python required rebuilding all extension modules that
one wanted to use. This requirement was the result of the free access to
Python interpreter internals that extension modules could use.

With Python 3.2, an alternative approach becomes available: extension
modules which restrict themselves to a limited API (by defining
Py_LIMITED_API) cannot use many of the internals, but are constrained
to a set of API functions that are promised to be stable for several
releases. As a consequence, extension modules built for 3.2 in that
mode will also work with 3.3, 3.4, and so on. Extension modules that
make use of details of memory structures can still be built, but will
need to be recompiled for every feature release.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 384

@item PEP 384@footnote{https://www.python.org/dev/peps/pep-0384} - 定义稳定的ABI

PEP 由  Martin von Löwis 撰写
@end table


@node PEP 389 Argparse 命令行解析模块,PEP 391 基于字典的日志配置,PEP 384 定义稳定的ABI,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 pep-389-argparse-command-line-parsing-module}@anchor{b21}
@subsection PEP 389: Argparse 命令行解析模块


A new module for command line parsing, @ref{6,,argparse}, was introduced to
overcome the limitations of @ref{c3,,optparse} which did not provide support for
positional arguments (not just options), subcommands, required options and other
common patterns of specifying and validating options.

This module has already had widespread success in the community as a
third-party module.  Being more fully featured than its predecessor, the
@ref{6,,argparse} module is now the preferred module for command-line processing.
The older module is still being kept available because of the substantial amount
of legacy code that depends on it.

Here's an annotated example parser showing features like limiting results to a
set of choices, specifying a @emph{metavar} in the help screen, validating that one
or more positional arguments is present, and making a required option:

@example
import argparse
parser = argparse.ArgumentParser(
            description = 'Manage servers',         # main description for help
            epilog = 'Tested on Solaris and Linux') # displayed after help
parser.add_argument('action',                       # argument name
            choices = ['deploy', 'start', 'stop'],  # three allowed values
            help = 'action on each target')         # help msg
parser.add_argument('targets',
            metavar = 'HOSTNAME',                   # var name used in help msg
            nargs = '+',                            # require one or more targets
            help = 'url for target machines')       # help msg explanation
parser.add_argument('-u', '--user',                 # -u or --user option
            required = True,                        # make it a required argument
            help = 'login as user')
@end example

Example of calling the parser on a command string:

@example
>>> cmd = 'deploy sneezy.example.com sleepy.example.com -u skycaptain'
>>> result = parser.parse_args(cmd.split())
>>> result.action
'deploy'
>>> result.targets
['sneezy.example.com', 'sleepy.example.com']
>>> result.user
'skycaptain'
@end example

Example of the parser's automatically generated help:

@example
>>> parser.parse_args('-h'.split())

usage: manage_cloud.py [-h] -u USER
                       @{deploy,start,stop@} HOSTNAME [HOSTNAME ...]

Manage servers

positional arguments:
  @{deploy,start,stop@}   action on each target
  HOSTNAME              url for target machines

optional arguments:
  -h, --help            show this help message and exit
  -u USER, --user USER  login as user

Tested on Solaris and Linux
@end example

An especially nice @ref{6,,argparse} feature is the ability to define subparsers,
each with their own argument patterns and help displays:

@example
import argparse
parser = argparse.ArgumentParser(prog='HELM')
subparsers = parser.add_subparsers()

parser_l = subparsers.add_parser('launch', help='Launch Control')   # first subgroup
parser_l.add_argument('-m', '--missiles', action='store_true')
parser_l.add_argument('-t', '--torpedos', action='store_true')

parser_m = subparsers.add_parser('move', help='Move Vessel',        # second subgroup
                                 aliases=('steer', 'turn'))         # equivalent names
parser_m.add_argument('-c', '--course', type=int, required=True)
parser_m.add_argument('-s', '--speed', type=int, default=0)
@end example

@example
$ ./helm.py --help                         # top level help (launch and move)
$ ./helm.py launch --help                  # help for launch options
$ ./helm.py launch --missiles              # set missiles=True and torpedos=False
$ ./helm.py steer --course 180 --speed 5   # set movement parameters
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 389

@item PEP 389@footnote{https://www.python.org/dev/peps/pep-0389} - 新的命令行解析模块

PEP 由 Steven Bethard 撰写
@end table

@ref{b22,,升级 optparse 代码} for details on the differences from @ref{c3,,optparse}.


@node PEP 391 基于字典的日志配置,PEP 3148 concurrent futures 模块,PEP 389 Argparse 命令行解析模块,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 pep-391-dictionary-based-configuration-for-logging}@anchor{b23}
@subsection PEP 391:  基于字典的日志配置


The @ref{aa,,logging} module provided two kinds of configuration, one style with
function calls for each option or another style driven by an external file saved
in a @code{ConfigParser} format.  Those options did not provide the flexibility
to create configurations from JSON or YAML files, nor did they support
incremental configuration, which is needed for specifying logger options from a
command line.

To support a more flexible style, the module now offers
@ref{b24,,logging.config.dictConfig()} for specifying logging configuration with
plain Python dictionaries.  The configuration options include formatters,
handlers, filters, and loggers.  Here's a working example of a configuration
dictionary:

@example
@{"version": 1,
 "formatters": @{"brief": @{"format": "%(levelname)-8s: %(name)-15s: %(message)s"@},
                "full": @{"format": "%(asctime)s %(name)-15s %(levelname)-8s %(message)s"@}
                @},
 "handlers": @{"console": @{
                   "class": "logging.StreamHandler",
                   "formatter": "brief",
                   "level": "INFO",
                   "stream": "ext://sys.stdout"@},
              "console_priority": @{
                   "class": "logging.StreamHandler",
                   "formatter": "full",
                   "level": "ERROR",
                   "stream": "ext://sys.stderr"@}
              @},
 "root": @{"level": "DEBUG", "handlers": ["console", "console_priority"]@}@}
@end example

If that dictionary is stored in a file called @code{conf.json}, it can be
loaded and called with code like this:

@example
>>> import json, logging.config
>>> with open('conf.json') as f:
...     conf = json.load(f)
...
>>> logging.config.dictConfig(conf)
>>> logging.info("Transaction completed normally")
INFO    : root           : Transaction completed normally
>>> logging.critical("Abnormal termination")
2011-02-17 11:14:36,694 root            CRITICAL Abnormal termination
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 391

@item PEP 391@footnote{https://www.python.org/dev/peps/pep-0391} - 基于字典的日志配置

PEP 由 Vinay Sajip 撰写
@end table


@node PEP 3148 concurrent futures 模块,PEP 3147 PYC 仓库目录,PEP 391 基于字典的日志配置,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 pep-3148-the-concurrent-futures-module}@anchor{b25}
@subsection PEP 3148:  @code{concurrent.futures} 模块


Code for creating and managing concurrency is being collected in a new top-level
namespace, @emph{concurrent}.  Its first member is a @emph{futures} package which provides
a uniform high-level interface for managing threads and processes.

The design for @ref{22,,concurrent.futures} was inspired by the
@emph{java.util.concurrent} package.  In that model, a running call and its result
are represented by a @ref{b26,,Future} object that abstracts
features common to threads, processes, and remote procedure calls.  That object
supports status checks (running or done), timeouts, cancellations, adding
callbacks, and access to results or exceptions.

The primary offering of the new module is a pair of executor classes for
launching and managing calls.  The goal of the executors is to make it easier to
use existing tools for making parallel calls. They save the effort needed to
setup a pool of resources, launch the calls, create a results queue, add
time-out handling, and limit the total number of threads, processes, or remote
procedure calls.

Ideally, each application should share a single executor across multiple
components so that process and thread limits can be centrally managed.  This
solves the design challenge that arises when each component has its own
competing strategy for resource management.

Both classes share a common interface with three methods:
@ref{2a4,,submit()} for scheduling a callable and
returning a @ref{b26,,Future} object;
@ref{6b8,,map()} for scheduling many asynchronous calls
at a time, and @ref{b27,,shutdown()} for freeing
resources.  The class is a @ref{563,,context manager} and can be used in a
@ref{6e3,,with} statement to assure that resources are automatically released
when currently pending futures are done executing.

A simple of example of @ref{27a,,ThreadPoolExecutor} is a
launch of four parallel threads for copying files:

@example
import concurrent.futures, shutil
with concurrent.futures.ThreadPoolExecutor(max_workers=4) as e:
    e.submit(shutil.copy, 'src1.txt', 'dest1.txt')
    e.submit(shutil.copy, 'src2.txt', 'dest2.txt')
    e.submit(shutil.copy, 'src3.txt', 'dest3.txt')
    e.submit(shutil.copy, 'src3.txt', 'dest4.txt')
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3148

@item PEP 3148@footnote{https://www.python.org/dev/peps/pep-3148} -- futures - 异步执行指令

PEP 由 Brian Quinlan 撰写
@end table

@ref{b28,,Code for Threaded Parallel URL reads}, an
example using threads to fetch multiple web pages in parallel.

@ref{b29,,Code for computing prime numbers in parallel}, an example demonstrating
@ref{2a3,,ProcessPoolExecutor}.


@node PEP 3147 PYC 仓库目录,PEP 3149 ABI Version Tagged so Files,PEP 3148 concurrent futures 模块,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 pep-3147-pyc-repository-directories}@anchor{b2a}
@subsection PEP 3147:  PYC 仓库目录


Python's scheme for caching bytecode in @emph{.pyc} files did not work well in
environments with multiple Python interpreters.  If one interpreter encountered
a cached file created by another interpreter, it would recompile the source and
overwrite the cached file, thus losing the benefits of caching.

The issue of "pyc fights" has become more pronounced as it has become
commonplace for Linux distributions to ship with multiple versions of Python.
These conflicts also arise with CPython alternatives such as Unladen Swallow.

To solve this problem, Python's import machinery has been extended to use
distinct filenames for each interpreter.  Instead of Python 3.2 and Python 3.3 and
Unladen Swallow each competing for a file called "mymodule.pyc", they will now
look for "mymodule.cpython-32.pyc", "mymodule.cpython-33.pyc", and
"mymodule.unladen10.pyc".  And to prevent all of these new files from
cluttering source directories, the @emph{pyc} files are now collected in a
"__pycache__" directory stored under the package directory.

Aside from the filenames and target directories, the new scheme has a few
aspects that are visible to the programmer:


@itemize *

@item 
Imported modules now have a @ref{b2b,,__cached__} attribute which stores the name
of the actual file that was imported:

@example
>>> import collections
>>> collections.__cached__ 
'c:/py32/lib/__pycache__/collections.cpython-32.pyc'
@end example

@item 
The tag that is unique to each interpreter is accessible from the @ref{9a,,imp}
module:

@example
>>> import imp
>>> imp.get_tag() 
'cpython-32'
@end example

@item 
Scripts that try to deduce source filename from the imported file now need to
be smarter.  It is no longer sufficient to simply strip the "c" from a ".pyc"
filename.  Instead, use the new functions in the @ref{9a,,imp} module:

@example
>>> imp.source_from_cache('c:/py32/lib/__pycache__/collections.cpython-32.pyc')
'c:/py32/lib/collections.py'
>>> imp.cache_from_source('c:/py32/lib/collections.py') 
'c:/py32/lib/__pycache__/collections.cpython-32.pyc'
@end example

@item 
The @ref{d7,,py_compile} and @ref{21,,compileall} modules have been updated to
reflect the new naming convention and target directory.  The command-line
invocation of @emph{compileall} has new options: @code{-i} for
specifying a list of files and directories to compile and @code{-b} which causes
bytecode files to be written to their legacy location rather than
@emph{__pycache__}.

@item 
The @ref{9c,,importlib.abc} module has been updated with new @ref{b2c,,abstract base classes} for loading bytecode files.  The obsolete
ABCs, @code{PyLoader} and
@code{PyPycLoader}, have been deprecated (instructions on how
to stay Python 3.1 compatible are included with the documentation).
@end itemize


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3147

@item PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} - PYC 仓库目录

PEP 由 Barry Warsaw 撰写
@end table


@node PEP 3149 ABI Version Tagged so Files,PEP 3333 Python Web服务器网关接口v1 0 1,PEP 3147 PYC 仓库目录,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 pep-3149-abi-version-tagged-so-files}@anchor{b2d}
@subsection PEP 3149: ABI Version Tagged .so Files


The PYC repository directory allows multiple bytecode cache files to be
co-located.  This PEP implements a similar mechanism for shared object files by
giving them a common directory and distinct names for each version.

The common directory is "pyshared" and the file names are made distinct by
identifying the Python implementation (such as CPython, PyPy, Jython, etc.), the
major and minor version numbers, and optional build flags (such as "d" for
debug, "m" for pymalloc, "u" for wide-unicode).  For an arbitrary package "foo",
you may see these files when the distribution package is installed:

@example
/usr/share/pyshared/foo.cpython-32m.so
/usr/share/pyshared/foo.cpython-33md.so
@end example

In Python itself, the tags are accessible from functions in the @ref{fe,,sysconfig}
module:

@example
>>> import sysconfig
>>> sysconfig.get_config_var('SOABI')       # find the version tag
'cpython-32mu'
>>> sysconfig.get_config_var('EXT_SUFFIX')  # find the full filename extension
'.cpython-32mu.so'
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3149

@item PEP 3149@footnote{https://www.python.org/dev/peps/pep-3149} - ABI Version Tagged .so Files

PEP 由 Barry Warsaw 撰写
@end table


@node PEP 3333 Python Web服务器网关接口v1 0 1,其他语言特性修改<7>,PEP 3149 ABI Version Tagged so Files,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 pep-3333-python-web-server-gateway-interface-v1-0-1}@anchor{b2e}
@subsection PEP 3333: Python Web服务器网关接口v1.0.1


This informational PEP clarifies how bytes/text issues are to be handled by the
WSGI protocol.  The challenge is that string handling in Python 3 is most
conveniently handled with the @ref{329,,str} type even though the HTTP protocol
is itself bytes oriented.

The PEP differentiates so-called @emph{native strings} that are used for
request/response headers and metadata versus @emph{byte strings} which are used for
the bodies of requests and responses.

The @emph{native strings} are always of type @ref{329,,str} but are restricted to code
points between @emph{U+0000} through @emph{U+00FF} which are translatable to bytes using
@emph{Latin-1} encoding.  These strings are used for the keys and values in the
environment dictionary and for response headers and statuses in the
@code{start_response()} function.  They must follow 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html} with respect to
encoding. That is, they must either be @emph{ISO-8859-1} characters or use
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html} MIME encoding.

For developers porting WSGI applications from Python 2, here are the salient
points:


@itemize *

@item 
If the app already used strings for headers in Python 2, no change is needed.

@item 
If instead, the app encoded output headers or decoded input headers, then the
headers will need to be re-encoded to Latin-1.  For example, an output header
encoded in utf-8 was using @code{h.encode('utf-8')} now needs to convert from
bytes to native strings using @code{h.encode('utf-8').decode('latin-1')}.

@item 
Values yielded by an application or sent using the @code{write()} method
must be byte strings.  The @code{start_response()} function and environ
must use native strings.  The two cannot be mixed.
@end itemize

For server implementers writing CGI-to-WSGI pathways or other CGI-style
protocols, the users must to be able access the environment using native strings
even though the underlying platform may have a different convention.  To bridge
this gap, the @ref{12c,,wsgiref} module has a new function,
@ref{b2f,,wsgiref.handlers.read_environ()} for transcoding CGI variables from
@ref{b30,,os.environ} into native strings and returning a new dictionary.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3333

@item PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333} - Python Web服务器网关接口v1.0.1

PEP 由 Phillip Eby 撰写
@end table


@node 其他语言特性修改<7>,新增，改进和弃用的模块,PEP 3333 Python Web服务器网关接口v1 0 1,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 other-language-changes}@anchor{b31}
@subsection 其他语言特性修改


对Python 语言核心进行的小改动：


@itemize *

@item 
String formatting for @ref{4d5,,format()} and @ref{4d4,,str.format()} gained new
capabilities for the format character @strong{#}.  Previously, for integers in
binary, octal, or hexadecimal, it caused the output to be prefixed with '0b',
'0o', or '0x' respectively.  Now it can also handle floats, complex, and
Decimal, causing the output to always have a decimal point even when no digits
follow it.

@example
>>> format(20, '#o')
'0o24'
>>> format(12.34, '#5.0f')
'  12.'
@end example

(Suggested by Mark Dickinson and implemented by Eric Smith in bpo-7094@footnote{https://bugs.python.org/issue7094}.)

@item 
There is also a new @ref{6ab,,str.format_map()} method that extends the
capabilities of the existing @ref{4d4,,str.format()} method by accepting arbitrary
@ref{b32,,mapping} objects.  This new method makes it possible to use string
formatting with any of Python's many dictionary-like objects such as
@ref{b33,,defaultdict}, @ref{8aa,,Shelf},
@ref{4a5,,ConfigParser}, or @ref{32,,dbm}.  It is also useful with
custom @ref{1b8,,dict} subclasses that normalize keys before look-up or that
supply a @ref{b34,,__missing__()} method for unknown keys:

@example
>>> import shelve
>>> d = shelve.open('tmp.shl')
>>> 'The @{project_name@} status is @{status@} as of @{date@}'.format_map(d)
'The testing project status is green as of February 15, 2011'

>>> class LowerCasedDict(dict):
...     def __getitem__(self, key):
...         return dict.__getitem__(self, key.lower())
>>> lcd = LowerCasedDict(part='widgets', quantity=10)
>>> 'There are @{QUANTITY@} @{Part@} in stock'.format_map(lcd)
'There are 10 widgets in stock'

>>> class PlaceholderDict(dict):
...     def __missing__(self, key):
...         return '<@{@}>'.format(key)
>>> 'Hello @{name@}, welcome to @{location@}'.format_map(PlaceholderDict())
'Hello <name>, welcome to <location>'
@end example
@end itemize

@quotation

(Suggested by Raymond Hettinger and implemented by Eric Smith in
bpo-6081@footnote{https://bugs.python.org/issue6081}.)
@end quotation


@itemize *

@item 
The interpreter can now be started with a quiet option, @code{-q}, to prevent
the copyright and version information from being displayed in the interactive
mode.  The option can be introspected using the @ref{b35,,sys.flags} attribute:

@example
$ python -q
>>> sys.flags
sys.flags(debug=0, division_warning=0, inspect=0, interactive=0,
optimize=0, dont_write_bytecode=0, no_user_site=0, no_site=0,
ignore_environment=0, verbose=0, bytes_warning=0, quiet=1)
@end example

（由 Marcin Wojdyr 在 bpo-1772833@footnote{https://bugs.python.org/issue1772833} 中贡献。）

@item 
The @ref{442,,hasattr()} function works by calling @ref{443,,getattr()} and detecting
whether an exception is raised.  This technique allows it to detect methods
created dynamically by @ref{313,,__getattr__()} or @ref{441,,__getattribute__()} which
would otherwise be absent from the class dictionary.  Formerly, @emph{hasattr}
would catch any exception, possibly masking genuine errors.  Now, @emph{hasattr}
has been tightened to only catch @ref{393,,AttributeError} and let other
exceptions pass through:

@example
>>> class A:
...     @@property
...     def f(self):
...         return 1 // 0
...
>>> a = A()
>>> hasattr(a, 'f')
Traceback (most recent call last):
  ...
ZeroDivisionError: integer division or modulo by zero
@end example

(Discovered by Yury Selivanov and fixed by Benjamin Peterson; bpo-9666@footnote{https://bugs.python.org/issue9666}.)

@item 
The @ref{329,,str()} of a float or complex number is now the same as its
@ref{7c6,,repr()}. Previously, the @ref{329,,str()} form was shorter but that just
caused confusion and is no longer needed now that the shortest possible
@ref{7c6,,repr()} is displayed by default:

@example
>>> import math
>>> repr(math.pi)
'3.141592653589793'
>>> str(math.pi)
'3.141592653589793'
@end example

(Proposed and implemented by Mark Dickinson; bpo-9337@footnote{https://bugs.python.org/issue9337}.)

@item 
@ref{25c,,memoryview} objects now have a @ref{b36,,release()} method
and they also now support the context management protocol.  This allows timely
release of any resources that were acquired when requesting a buffer from the
original object.

@example
>>> with memoryview(b'abcdefgh') as v:
...     print(v.tolist())
[97, 98, 99, 100, 101, 102, 103, 104]
@end example

(Added by Antoine Pitrou; bpo-9757@footnote{https://bugs.python.org/issue9757}.)

@item 
Previously it was illegal to delete a name from the local namespace if it
occurs as a free variable in a nested block:

@example
def outer(x):
    def inner():
        return x
    inner()
    del x
@end example

This is now allowed.  Remember that the target of an @ref{b37,,except} clause
is cleared, so this code which used to work with Python 2.6, raised a
@ref{452,,SyntaxError} with Python 3.1 and now works again:

@example
def f():
    def print_error():
        print(e)
    try:
        something
    except Exception as e:
        print_error()
        # implicit "del e" here
@end example

(See bpo-4617@footnote{https://bugs.python.org/issue4617}.)

@item 
The internal @code{structsequence} tool now creates subclasses of tuple.
This means that C structures like those returned by @ref{1f1,,os.stat()},
@ref{b38,,time.gmtime()}, and @ref{b13,,sys.version_info} now work like a
@ref{a9e,,named tuple} and now work with functions and methods that
expect a tuple as an argument.  This is a big step forward in making the C
structures as flexible as their pure Python counterparts:

@example
>>> import sys
>>> isinstance(sys.version_info, tuple)
True
>>> 'Version %d.%d.%d %s(%d)' % sys.version_info 
'Version 3.2.0 final(0)'
@end example

(Suggested by Arfrever Frehtes Taifersar Arahesis and implemented
by Benjamin Peterson in bpo-8413@footnote{https://bugs.python.org/issue8413}.)

@item 
Warnings are now easier to control using the 
@geindex PYTHONWARNINGS
@geindex 环境变量; PYTHONWARNINGS
@ref{410,,PYTHONWARNINGS}
environment variable as an alternative to using @code{-W} at the command line:

@example
$ export PYTHONWARNINGS='ignore::RuntimeWarning::,once::UnicodeWarning::'
@end example

(Suggested by Barry Warsaw and implemented by Philip Jenvey in bpo-7301@footnote{https://bugs.python.org/issue7301}.)

@item 
A new warning category, @ref{4ca,,ResourceWarning}, has been added.  It is
emitted when potential issues with resource consumption or cleanup
are detected.  It is silenced by default in normal release builds but
can be enabled through the means provided by the @ref{126,,warnings}
module, or on the command line.

A @ref{4ca,,ResourceWarning} is issued at interpreter shutdown if the
@ref{b39,,gc.garbage} list isn't empty, and if @ref{b3a,,gc.DEBUG_UNCOLLECTABLE} is
set, all uncollectable objects are printed.  This is meant to make the
programmer aware that their code contains object finalization issues.

A @ref{4ca,,ResourceWarning} is also issued when a @ref{b3b,,file object} is destroyed
without having been explicitly closed.  While the deallocator for such
object ensures it closes the underlying operating system resource
(usually, a file descriptor), the delay in deallocating the object could
produce various issues, especially under Windows.  Here is an example
of enabling the warning from the command line:

@example
$ python -q -Wdefault
>>> f = open("foo", "wb")
>>> del f
__main__:1: ResourceWarning: unclosed file <_io.BufferedWriter name='foo'>
@end example

(Added by Antoine Pitrou and Georg Brandl in bpo-10093@footnote{https://bugs.python.org/issue10093} and bpo-477863@footnote{https://bugs.python.org/issue477863}.)

@item 
@ref{9b8,,range} objects now support @emph{index} and @emph{count} methods. This is part
of an effort to make more objects fully implement the
@code{collections.Sequence} @ref{b2c,,abstract base class}.  As a result, the
language will have a more uniform API.  In addition, @ref{9b8,,range} objects
now support slicing and negative indices, even with values larger than
@ref{b3c,,sys.maxsize}.  This makes @emph{range} more interoperable with lists:

@example
>>> range(0, 100, 2).count(10)
1
>>> range(0, 100, 2).index(10)
5
>>> range(0, 100, 2)[5]
10
>>> range(0, 100, 2)[0:5]
range(0, 10, 2)
@end example

（由 Daniel Stutzbach 在 bpo-9213@footnote{https://bugs.python.org/issue9213} 中贡献，由 Alexander Belopolsky 在 bpo-2690@footnote{https://bugs.python.org/issue2690} 中贡献，由 Nick Coghlan 在 bpo-10889@footnote{https://bugs.python.org/issue10889} 中贡献。）

@item 
The @ref{b3d,,callable()} builtin function from Py2.x was resurrected.  It provides
a concise, readable alternative to using an @ref{b2c,,abstract base class} in an
expression like @code{isinstance(x, collections.Callable)}:

@example
>>> callable(max)
True
>>> callable(20)
False
@end example

（见 bpo-10518@footnote{https://bugs.python.org/issue10518} ）

@item 
Python's import mechanism can now load modules installed in directories with
non-ASCII characters in the path name.  This solved an aggravating problem
with home directories for users with non-ASCII characters in their usernames.
@end itemize

@quotation

(Required extensive work by Victor Stinner in bpo-9425@footnote{https://bugs.python.org/issue9425}.)
@end quotation

@node 新增，改进和弃用的模块,多线程,其他语言特性修改<7>,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 new-improved-and-deprecated-modules}@anchor{b3e}
@subsection 新增，改进和弃用的模块


Python's standard library has undergone significant maintenance efforts and
quality improvements.

The biggest news for Python 3.2 is that the @ref{69,,email} package, @ref{ae,,mailbox}
module, and @ref{c0,,nntplib} modules now work correctly with the bytes/text model
in Python 3.  For the first time, there is correct handling of messages with
mixed encodings.

Throughout the standard library, there has been more careful attention to
encodings and text versus bytes issues.  In particular, interactions with the
operating system are now better able to exchange non-ASCII data using the
Windows MBCS encoding, locale-aware encodings, or UTF-8.

Another significant win is the addition of substantially better support for
@emph{SSL} connections and security certificates.

In addition, more classes now implement a @ref{563,,context manager} to support
convenient and reliable resource clean-up using a @ref{6e3,,with} statement.

@menu
* email: email<5>. 
* elementtree:: 
* functools: functools<6>. 
* itertools: itertools<4>. 
* collections: collections<8>. 
* threading: threading<6>. 
* datetime 和 time:: 
* math: math<6>. 
* abc: abc<3>. 
* io: io<5>. 
* reprlib:: 
* logging: logging<7>. 
* csv: csv<3>. 
* contextlib: contextlib<6>. 
* decimal and fractions:: 
* ftp:: 
* popen:: 
* select: select<3>. 
* gzip 和 zipfile:: 
* tarfile: tarfile<5>. 
* hashlib: hashlib<3>. 
* ast: ast<3>. 
* os: os<8>. 
* shutil: shutil<5>. 
* sqlite3: sqlite3<6>. 
* html: html<3>. 
* socket: socket<8>. 
* ssl: ssl<9>. 
* nntp:: 
* certificates:: 
* imaplib: imaplib<3>. 
* http.client: http client<4>. 
* unittest: unittest<6>. 
* random: random<2>. 
* poplib: poplib<3>. 
* asyncore: asyncore<2>. 
* tempfile: tempfile<2>. 
* inspect: inspect<6>. 
* pydoc: pydoc<5>. 
* dis: dis<3>. 
* dbm: dbm<6>. 
* ctypes: ctypes<2>. 
* site: site<2>. 
* sysconfig: sysconfig<2>. 
* pdb: pdb<5>. 
* configparser: configparser<2>. 
* urllib.parse: urllib parse<2>. 
* mailbox:: 
* turtledemo:: 

@end menu

@node email<5>,elementtree,,新增，改进和弃用的模块
@anchor{whatsnew/3 2 email}@anchor{b3f}
@subsubsection email


The usability of the @ref{69,,email} package in Python 3 has been mostly fixed by
the extensive efforts of R. David Murray.  The problem was that emails are
typically read and stored in the form of @ref{32a,,bytes} rather than @ref{329,,str}
text, and they may contain multiple encodings within a single email.  So, the
email package had to be extended to parse and generate email messages in bytes
format.


@itemize *

@item 
New functions @ref{b40,,message_from_bytes()} and
@ref{b41,,message_from_binary_file()}, and new classes
@ref{b42,,BytesFeedParser} and @ref{b43,,BytesParser}
allow binary message data to be parsed into model objects.

@item 
Given bytes input to the model, @ref{b44,,get_payload()}
will by default decode a message body that has a
@code{Content-Transfer-Encoding} of @emph{8bit} using the charset
specified in the MIME headers and return the resulting string.

@item 
Given bytes input to the model, @ref{b45,,Generator} will
convert message bodies that have a @code{Content-Transfer-Encoding} of
@emph{8bit} to instead have a @emph{7bit} @code{Content-Transfer-Encoding}.

Headers with unencoded non-ASCII bytes are deemed to be 
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html}-encoded
using the @emph{unknown-8bit} character set.

@item 
A new class @ref{b46,,BytesGenerator} produces bytes as output,
preserving any unchanged non-ASCII data that was present in the input used to
build the model, including message bodies with a
@code{Content-Transfer-Encoding} of @emph{8bit}.

@item 
The @ref{ed,,smtplib} @ref{a7c,,SMTP} class now accepts a byte string
for the @emph{msg} argument to the @ref{73e,,sendmail()} method,
and a new method, @ref{73f,,send_message()} accepts a
@ref{53c,,Message} object and can optionally obtain the
@emph{from_addr} and @emph{to_addrs} addresses directly from the object.
@end itemize

(Proposed and implemented by R. David Murray, bpo-4661@footnote{https://bugs.python.org/issue4661} and bpo-10321@footnote{https://bugs.python.org/issue10321}.)

@node elementtree,functools<6>,email<5>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 elementtree}@anchor{b47}
@subsubsection elementtree


The @ref{137,,xml.etree.ElementTree} package and its @code{xml.etree.cElementTree}
counterpart have been updated to version 1.3.

Several new and useful functions and methods have been added:


@itemize *

@item 
@ref{b48,,xml.etree.ElementTree.fromstringlist()} which builds an XML document
from a sequence of fragments

@item 
@ref{b49,,xml.etree.ElementTree.register_namespace()} for registering a global
namespace prefix

@item 
@ref{910,,xml.etree.ElementTree.tostringlist()} for string representation
including all sublists

@item 
@ref{b4a,,xml.etree.ElementTree.Element.extend()} for appending a sequence of zero
or more elements

@item 
@ref{b4b,,xml.etree.ElementTree.Element.iterfind()} searches an element and
subelements

@item 
@ref{b4c,,xml.etree.ElementTree.Element.itertext()} creates a text iterator over
an element and its subelements

@item 
@ref{b4d,,xml.etree.ElementTree.TreeBuilder.end()} closes the current element

@item 
@ref{2c1,,xml.etree.ElementTree.TreeBuilder.doctype()} handles a doctype
declaration
@end itemize

两个方法被弃用：


@itemize *

@item 
@code{xml.etree.ElementTree.getchildren()} 被 @code{list(elem)} 替代。

@item 
@code{xml.etree.ElementTree.getiterator()} 被 @code{Element.iter} 替代。
@end itemize

For details of the update, see Introducing ElementTree@footnote{http://effbot.org/zone/elementtree-13-intro.htm} on Fredrik Lundh's website.

（由 Florent Xicluna 和 Fredrik Lundh 在 bpo-6472@footnote{https://bugs.python.org/issue6472} 中贡献。）

@node functools<6>,itertools<4>,elementtree,新增，改进和弃用的模块
@anchor{whatsnew/3 2 functools}@anchor{b4e}
@subsubsection functools



@itemize *

@item 
The @ref{85,,functools} module includes a new decorator for caching function
calls.  @ref{1c7,,functools.lru_cache()} can save repeated queries to an external
resource whenever the results are expected to be the same.

For example, adding a caching decorator to a database query function can save
database accesses for popular searches:

@example
>>> import functools
>>> @@functools.lru_cache(maxsize=300)
... def get_phone_number(name):
...     c = conn.cursor()
...     c.execute('SELECT phonenumber FROM phonelist WHERE name=?', (name,))
...     return c.fetchone()[0]
@end example

@example
>>> for name in user_requests:        
...     get_phone_number(name)        # cached lookup
@end example

To help with choosing an effective cache size, the wrapped function is
instrumented for tracking cache statistics:

@example
>>> get_phone_number.cache_info()     
CacheInfo(hits=4805, misses=980, maxsize=300, currsize=300)
@end example

If the phonelist table gets updated, the outdated contents of the cache can be
cleared with:

@example
>>> get_phone_number.cache_clear()
@end example

(Contributed by Raymond Hettinger and incorporating design ideas from Jim
Baker, Miki Tebeka, and Nick Coghlan; see recipe 498245@footnote{https://code.activestate.com/recipes/498245}, recipe 577479@footnote{https://code.activestate.com/recipes/577479}, bpo-10586@footnote{https://bugs.python.org/issue10586}, and
bpo-10593@footnote{https://bugs.python.org/issue10593}.)

@item 
The @ref{864,,functools.wraps()} decorator now adds a @code{__wrapped__} attribute
pointing to the original callable function.  This allows wrapped functions to
be introspected.  It also copies @code{__annotations__} if defined.  And now
it also gracefully skips over missing attributes such as @code{__doc__} which
might not be defined for the wrapped callable.

In the above example, the cache can be removed by recovering the original
function:

@example
>>> get_phone_number = get_phone_number.__wrapped__    # uncached function
@end example

(By Nick Coghlan and Terrence Cole; bpo-9567@footnote{https://bugs.python.org/issue9567}, bpo-3445@footnote{https://bugs.python.org/issue3445}, and
bpo-8814@footnote{https://bugs.python.org/issue8814}.)

@item 
To help write classes with rich comparison methods, a new decorator
@ref{845,,functools.total_ordering()} will use existing equality and inequality
methods to fill in the remaining methods.

For example, supplying @emph{__eq__} and @emph{__lt__} will enable
@ref{845,,total_ordering()} to fill-in @emph{__le__}, @emph{__gt__} and @emph{__ge__}:

@example
@@total_ordering
class Student:
    def __eq__(self, other):
        return ((self.lastname.lower(), self.firstname.lower()) ==
                (other.lastname.lower(), other.firstname.lower()))

    def __lt__(self, other):
        return ((self.lastname.lower(), self.firstname.lower()) <
                (other.lastname.lower(), other.firstname.lower()))
@end example

With the @emph{total_ordering} decorator, the remaining comparison methods
are filled in automatically.

（由 Raymond Hettinger 贡献。）

@item 
To aid in porting programs from Python 2, the @ref{b4f,,functools.cmp_to_key()}
function converts an old-style comparison function to
modern @ref{6da,,key function}:

@example
>>> # locale-aware sort order
>>> sorted(iterable, key=cmp_to_key(locale.strcoll)) 
@end example

For sorting examples and a brief sorting tutorial, see the Sorting HowTo@footnote{https://wiki.python.org/moin/HowTo/Sorting/} tutorial.

（由 Raymond Hettinger 贡献。）
@end itemize

@node itertools<4>,collections<8>,functools<6>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 itertools}@anchor{b50}
@subsubsection itertools



@itemize *

@item 
The @ref{a3,,itertools} module has a new @ref{1dd,,accumulate()} function
modeled on APL's @emph{scan} operator and Numpy's @emph{accumulate} function:

@example
>>> from itertools import accumulate
>>> list(accumulate([8, 2, 50]))
[8, 10, 60]
@end example

@example
>>> prob_dist = [0.1, 0.4, 0.2, 0.3]
>>> list(accumulate(prob_dist))      # cumulative probability distribution
[0.1, 0.5, 0.7, 1.0]
@end example

For an example using @ref{1dd,,accumulate()}, see the @ref{b51,,examples for the random module}.

(Contributed by Raymond Hettinger and incorporating design suggestions
from Mark Dickinson.)
@end itemize

@node collections<8>,threading<6>,itertools<4>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 collections}@anchor{b52}
@subsubsection collections



@itemize *

@item 
The @ref{9d4,,collections.Counter} class now has two forms of in-place
subtraction, the existing @emph{-=} operator for saturating subtraction@footnote{https://en.wikipedia.org/wiki/Saturation_arithmetic} and the new
@ref{b53,,subtract()} method for regular subtraction.  The
former is suitable for multisets@footnote{https://en.wikipedia.org/wiki/Multiset}
which only have positive counts, and the latter is more suitable for use cases
that allow negative counts:

@example
>>> from collections import Counter
>>> tally = Counter(dogs=5, cats=3)
>>> tally -= Counter(dogs=2, cats=8)    # saturating subtraction
>>> tally
Counter(@{'dogs': 3@})
@end example

@example
>>> tally = Counter(dogs=5, cats=3)
>>> tally.subtract(dogs=2, cats=8)      # regular subtraction
>>> tally
Counter(@{'dogs': 3, 'cats': -5@})
@end example

（由 Raymond Hettinger 贡献。）

@item 
The @ref{1b9,,collections.OrderedDict} class has a new method
@ref{b54,,move_to_end()} which takes an existing key and
moves it to either the first or last position in the ordered sequence.

The default is to move an item to the last position.  This is equivalent of
renewing an entry with @code{od[k] = od.pop(k)}.

A fast move-to-end operation is useful for resequencing entries.  For example,
an ordered dictionary can be used to track order of access by aging entries
from the oldest to the most recently accessed.

@example
>>> from collections import OrderedDict
>>> d = OrderedDict.fromkeys(['a', 'b', 'X', 'd', 'e'])
>>> list(d)
['a', 'b', 'X', 'd', 'e']
>>> d.move_to_end('X')
>>> list(d)
['a', 'b', 'd', 'e', 'X']
@end example

（由 Raymond Hettinger 贡献。）

@item 
The @ref{52b,,collections.deque} class grew two new methods
@ref{b55,,count()} and @ref{b56,,reverse()} that
make them more substitutable for @ref{262,,list} objects:

@example
>>> from collections import deque
>>> d = deque('simsalabim')
>>> d.count('s')
2
>>> d.reverse()
>>> d
deque(['m', 'i', 'b', 'a', 'l', 'a', 's', 'm', 'i', 's'])
@end example

（由 Raymond Hettinger 贡献。）
@end itemize

@node threading<6>,datetime 和 time,collections<8>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 threading}@anchor{b57}
@subsubsection threading


The @ref{109,,threading} module has a new @ref{b58,,Barrier}
synchronization class for making multiple threads wait until all of them have
reached a common barrier point.  Barriers are useful for making sure that a task
with multiple preconditions does not run until all of the predecessor tasks are
complete.

Barriers can work with an arbitrary number of threads.  This is a generalization
of a Rendezvous@footnote{https://en.wikipedia.org/wiki/Synchronous_rendezvous} which
is defined for only two threads.

Implemented as a two-phase cyclic barrier, @ref{b58,,Barrier} objects
are suitable for use in loops.  The separate @emph{filling} and @emph{draining} phases
assure that all threads get released (drained) before any one of them can loop
back and re-enter the barrier.  The barrier fully resets after each cycle.

Example of using barriers:

@example
from threading import Barrier, Thread

def get_votes(site):
    ballots = conduct_election(site)
    all_polls_closed.wait()        # do not count until all polls are closed
    totals = summarize(ballots)
    publish(site, totals)

all_polls_closed = Barrier(len(sites))
for site in sites:
    Thread(target=get_votes, args=(site,)).start()
@end example

In this example, the barrier enforces a rule that votes cannot be counted at any
polling site until all polls are closed.  Notice how a solution with a barrier
is similar to one with @ref{b59,,threading.Thread.join()}, but the threads stay alive
and continue to do work (summarizing ballots) after the barrier point is
crossed.

If any of the predecessor tasks can hang or be delayed, a barrier can be created
with an optional @emph{timeout} parameter.  Then if the timeout period elapses before
all the predecessor tasks reach the barrier point, all waiting threads are
released and a @ref{b5a,,BrokenBarrierError} exception is raised:

@example
def get_votes(site):
    ballots = conduct_election(site)
    try:
        all_polls_closed.wait(timeout=midnight - time.now())
    except BrokenBarrierError:
        lockbox = seal_ballots(ballots)
        queue.put(lockbox)
    else:
        totals = summarize(ballots)
        publish(site, totals)
@end example

In this example, the barrier enforces a more robust rule.  If some election
sites do not finish before midnight, the barrier times-out and the ballots are
sealed and deposited in a queue for later handling.

See Barrier Synchronization Patterns@footnote{http://osl.cs.illinois.edu/media/papers/karmani-2009-barrier_synchronization_pattern.pdf}
for more examples of how barriers can be used in parallel computing.  Also, there is
a simple but thorough explanation of barriers in The Little Book of Semaphores@footnote{https://greenteapress.com/semaphores/LittleBookOfSemaphores.pdf}, @emph{section 3.6}.

(Contributed by Kristján Valur Jónsson with an API review by Jeffrey Yasskin in
bpo-8777@footnote{https://bugs.python.org/issue8777}.)

@node datetime 和 time,math<6>,threading<6>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 datetime-and-time}@anchor{b5b}
@subsubsection datetime 和 time



@itemize *

@item 
The @ref{31,,datetime} module has a new type @ref{9fb,,timezone} that
implements the @ref{378,,tzinfo} interface by returning a fixed UTC
offset and timezone name. This makes it easier to create timezone-aware
datetime objects:

@example
>>> from datetime import datetime, timezone

>>> datetime.now(timezone.utc)
datetime.datetime(2010, 12, 8, 21, 4, 2, 923754, tzinfo=datetime.timezone.utc)

>>> datetime.strptime("01/01/2000 12:00 +0000", "%m/%d/%Y %H:%M %z")
datetime.datetime(2000, 1, 1, 12, 0, tzinfo=datetime.timezone.utc)
@end example

@item 
Also, @ref{195,,timedelta} objects can now be multiplied by
@ref{187,,float} and divided by @ref{187,,float} and @ref{184,,int} objects.
And @ref{195,,timedelta} objects can now divide one another.

@item 
The @ref{532,,datetime.date.strftime()} method is no longer restricted to years
after 1900.  The new supported year range is from 1000 to 9999 inclusive.

@item 
Whenever a two-digit year is used in a time tuple, the interpretation has been
governed by @code{time.accept2dyear}.  The default is @code{True} which means that
for a two-digit year, the century is guessed according to the POSIX rules
governing the @code{%y} strptime format.

Starting with Py3.2, use of the century guessing heuristic will emit a
@ref{278,,DeprecationWarning}.  Instead, it is recommended that
@code{time.accept2dyear} be set to @code{False} so that large date ranges
can be used without guesswork:

@example
>>> import time, warnings
>>> warnings.resetwarnings()      # remove the default warning filters

>>> time.accept2dyear = True      # guess whether 11 means 11 or 2011
>>> time.asctime((11, 1, 1, 12, 34, 56, 4, 1, 0))
Warning (from warnings module):
  ...
DeprecationWarning: Century info guessed for a 2-digit year.
'Fri Jan  1 12:34:56 2011'

>>> time.accept2dyear = False     # use the full range of allowable dates
>>> time.asctime((11, 1, 1, 12, 34, 56, 4, 1, 0))
'Fri Jan  1 12:34:56 11'
@end example

Several functions now have significantly expanded date ranges.  When
@code{time.accept2dyear} is false, the @ref{b5c,,time.asctime()} function will
accept any year that fits in a C int, while the @ref{b5d,,time.mktime()} and
@ref{b5e,,time.strftime()} functions will accept the full range supported by the
corresponding operating system functions.
@end itemize

(Contributed by Alexander Belopolsky and Victor Stinner in bpo-1289118@footnote{https://bugs.python.org/issue1289118},
bpo-5094@footnote{https://bugs.python.org/issue5094}, bpo-6641@footnote{https://bugs.python.org/issue6641}, bpo-2706@footnote{https://bugs.python.org/issue2706}, bpo-1777412@footnote{https://bugs.python.org/issue1777412}, bpo-8013@footnote{https://bugs.python.org/issue8013},
and bpo-10827@footnote{https://bugs.python.org/issue10827}.)

@c XXX https://bugs.python.org/issue?%40search_text=datetime&%40sort=-activity

@node math<6>,abc<3>,datetime 和 time,新增，改进和弃用的模块
@anchor{whatsnew/3 2 math}@anchor{b5f}
@subsubsection math


The @ref{b1,,math} module has been updated with six new functions inspired by the
C99 standard.

The @ref{b60,,isfinite()} function provides a reliable and fast way to detect
special values.  It returns @code{True} for regular numbers and @code{False} for @emph{Nan} or
@emph{Infinity}:

@example
>>> from math import isfinite
>>> [isfinite(x) for x in (123, 4.56, float('Nan'), float('Inf'))]
[True, True, False, False]
@end example

The @ref{b61,,expm1()} function computes @code{e**x-1} for small values of @emph{x}
without incurring the loss of precision that usually accompanies the subtraction
of nearly equal quantities:

@example
>>> from math import expm1
>>> expm1(0.013671875)   # more accurate way to compute e**x-1 for a small x
0.013765762467652909
@end example

The @ref{44c,,erf()} function computes a probability integral or Gaussian error function@footnote{https://en.wikipedia.org/wiki/Error_function}.  The
complementary error function, @ref{44d,,erfc()}, is @code{1 - erf(x)}:

@example
>>> from math import erf, erfc, sqrt
>>> erf(1.0/sqrt(2.0))   # portion of normal distribution within 1 standard deviation
0.682689492137086
>>> erfc(1.0/sqrt(2.0))  # portion of normal distribution outside 1 standard deviation
0.31731050786291404
>>> erf(1.0/sqrt(2.0)) + erfc(1.0/sqrt(2.0))
1.0
@end example

The @ref{b62,,gamma()} function is a continuous extension of the factorial
function.  See @indicateurl{https://en.wikipedia.org/wiki/Gamma_function} for details.  Because
the function is related to factorials, it grows large even for small values of
@emph{x}, so there is also a @ref{b63,,lgamma()} function for computing the natural
logarithm of the gamma function:

@example
>>> from math import gamma, lgamma
>>> gamma(7.0)           # six factorial
720.0
>>> lgamma(801.0)        # log(800 factorial)
4551.950730698041
@end example

（由 Mark Dickinson 贡献）

@node abc<3>,io<5>,math<6>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 abc}@anchor{b64}
@subsubsection abc


The @ref{4,,abc} module now supports @ref{9c9,,abstractclassmethod()} and
@ref{9ca,,abstractstaticmethod()}.

These tools make it possible to define an @ref{b2c,,abstract base class} that
requires a particular @ref{1d8,,classmethod()} or @ref{1d9,,staticmethod()} to be
implemented:

@example
class Temperature(metaclass=abc.ABCMeta):
    @@abc.abstractclassmethod
    def from_fahrenheit(cls, t):
        ...
    @@abc.abstractclassmethod
    def from_celsius(cls, t):
        ...
@end example

(Patch submitted by Daniel Urban; bpo-5867@footnote{https://bugs.python.org/issue5867}.)

@node io<5>,reprlib,abc<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 io}@anchor{b65}
@subsubsection io


The @ref{795,,io.BytesIO} has a new method, @ref{b66,,getbuffer()}, which
provides functionality similar to @ref{25c,,memoryview()}.  It creates an editable
view of the data without making a copy.  The buffer's random access and support
for slice notation are well-suited to in-place editing:

@example
>>> REC_LEN, LOC_START, LOC_LEN = 34, 7, 11

>>> def change_location(buffer, record_number, location):
...     start = record_number * REC_LEN + LOC_START
...     buffer[start: start+LOC_LEN] = location

>>> import io

>>> byte_stream = io.BytesIO(
...     b'G3805  storeroom  Main chassis    '
...     b'X7899  shipping   Reserve cog     '
...     b'L6988  receiving  Primary sprocket'
... )
>>> buffer = byte_stream.getbuffer()
>>> change_location(buffer, 1, b'warehouse  ')
>>> change_location(buffer, 0, b'showroom   ')
>>> print(byte_stream.getvalue())
b'G3805  showroom   Main chassis    '
b'X7899  warehouse  Reserve cog     '
b'L6988  receiving  Primary sprocket'
@end example

（由 Antoine Pitrou 在 bpo-5506@footnote{https://bugs.python.org/issue5506} 中贡献。）

@node reprlib,logging<7>,io<5>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 reprlib}@anchor{b67}
@subsubsection reprlib


When writing a @ref{337,,__repr__()} method for a custom container, it is easy to
forget to handle the case where a member refers back to the container itself.
Python's builtin objects such as @ref{262,,list} and @ref{b68,,set} handle
self-reference by displaying "..." in the recursive part of the representation
string.

To help write such @ref{337,,__repr__()} methods, the @ref{df,,reprlib} module has a new
decorator, @ref{b69,,recursive_repr()}, for detecting recursive calls to
@ref{337,,__repr__()} and substituting a placeholder string instead:

@example
>>> class MyList(list):
...     @@recursive_repr()
...     def __repr__(self):
...         return '<' + '|'.join(map(repr, self)) + '>'
...
>>> m = MyList('abc')
>>> m.append(m)
>>> m.append('x')
>>> print(m)
<'a'|'b'|'c'|...|'x'>
@end example

（由 Raymond Hettinger 在 bpo-9826@footnote{https://bugs.python.org/issue9826} 和  bpo-9840@footnote{https://bugs.python.org/issue9840} 中贡献。）

@node logging<7>,csv<3>,reprlib,新增，改进和弃用的模块
@anchor{whatsnew/3 2 logging}@anchor{b6a}
@subsubsection logging


In addition to dictionary-based configuration described above, the
@ref{aa,,logging} package has many other improvements.

The logging documentation has been augmented by a @ref{b6b,,basic tutorial}, an @ref{b6c,,advanced tutorial}, and a @ref{b6d,,cookbook} of
logging recipes.  These documents are the fastest way to learn about logging.

The @ref{1e0,,logging.basicConfig()} set-up function gained a @emph{style} argument to
support three different types of string formatting.  It defaults to "%" for
traditional %-formatting, can be set to "@{" for the new @ref{4d4,,str.format()} style, or
can be set to "$" for the shell-style formatting provided by
@ref{3e3,,string.Template}.  The following three configurations are equivalent:

@example
>>> from logging import basicConfig
>>> basicConfig(style='%', format="%(name)s -> %(levelname)s: %(message)s")
>>> basicConfig(style='@{', format="@{name@} -> @{levelname@} @{message@}")
>>> basicConfig(style='$', format="$name -> $levelname: $message")
@end example

If no configuration is set-up before a logging event occurs, there is now a
default configuration using a @ref{b6e,,StreamHandler} directed to
@ref{308,,sys.stderr} for events of @code{WARNING} level or higher.  Formerly, an
event occurring before a configuration was set-up would either raise an
exception or silently drop the event depending on the value of
@code{logging.raiseExceptions}.  The new default handler is stored in
@ref{b6f,,logging.lastResort}.

The use of filters has been simplified.  Instead of creating a
@ref{b70,,Filter} object, the predicate can be any Python callable that
returns @code{True} or @code{False}.

There were a number of other improvements that add flexibility and simplify
configuration.  See the module documentation for a full listing of changes in
Python 3.2.

@node csv<3>,contextlib<6>,logging<7>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 csv}@anchor{b71}
@subsubsection csv


The @ref{2a,,csv} module now supports a new dialect, @ref{b72,,unix_dialect},
which applies quoting for all fields and a traditional Unix style with @code{'\n'} as
the line terminator.  The registered dialect name is @code{unix}.

The @ref{b73,,csv.DictWriter} has a new method,
@ref{b74,,writeheader()} for writing-out an initial row to document
the field names:

@example
>>> import csv, sys
>>> w = csv.DictWriter(sys.stdout, ['name', 'dept'], dialect='unix')
>>> w.writeheader()
"name","dept"
>>> w.writerows([
...     @{'name': 'tom', 'dept': 'accounting'@},
...     @{'name': 'susan', 'dept': 'Salesl'@}])
"tom","accounting"
"susan","sales"
@end example

(New dialect suggested by Jay Talbot in bpo-5975@footnote{https://bugs.python.org/issue5975}, and the new method
suggested by Ed Abraham in bpo-1537721@footnote{https://bugs.python.org/issue1537721}.)

@node contextlib<6>,decimal and fractions,csv<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 contextlib}@anchor{b75}
@subsubsection contextlib


There is a new and slightly mind-blowing tool
@ref{b76,,ContextDecorator} that is helpful for creating a
@ref{563,,context manager} that does double duty as a function decorator.

As a convenience, this new functionality is used by
@ref{b77,,contextmanager()} so that no extra effort is needed to support
both roles.

The basic idea is that both context managers and function decorators can be used
for pre-action and post-action wrappers.  Context managers wrap a group of
statements using a @ref{6e3,,with} statement, and function decorators wrap a
group of statements enclosed in a function.  So, occasionally there is a need to
write a pre-action or post-action wrapper that can be used in either role.

For example, it is sometimes useful to wrap functions or groups of statements
with a logger that can track the time of entry and time of exit.  Rather than
writing both a function decorator and a context manager for the task, the
@ref{b77,,contextmanager()} provides both capabilities in a single
definition:

@example
from contextlib import contextmanager
import logging

logging.basicConfig(level=logging.INFO)

@@contextmanager
def track_entry_and_exit(name):
    logging.info('Entering: %s', name)
    yield
    logging.info('Exiting: %s', name)
@end example

Formerly, this would have only been usable as a context manager:

@example
with track_entry_and_exit('widget loader'):
    print('Some time consuming activity goes here')
    load_widget()
@end example

Now, it can be used as a decorator as well:

@example
@@track_entry_and_exit('widget loader')
def activity():
    print('Some time consuming activity goes here')
    load_widget()
@end example

Trying to fulfill two roles at once places some limitations on the technique.
Context managers normally have the flexibility to return an argument usable by
a @ref{6e3,,with} statement, but there is no parallel for function decorators.

In the above example, there is not a clean way for the @emph{track_entry_and_exit}
context manager to return a logging instance for use in the body of enclosed
statements.

（由 Michael Foord 在 bpo-9110@footnote{https://bugs.python.org/issue9110} 中贡献。）

@node decimal and fractions,ftp,contextlib<6>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 decimal-and-fractions}@anchor{b78}
@subsubsection decimal and fractions


Mark Dickinson crafted an elegant and efficient scheme for assuring that
different numeric datatypes will have the same hash value whenever their actual
values are equal (bpo-8188@footnote{https://bugs.python.org/issue8188}):

@example
assert hash(Fraction(3, 2)) == hash(1.5) == \
       hash(Decimal("1.5")) == hash(complex(1.5, 0))
@end example

Some of the hashing details are exposed through a new attribute,
@ref{91b,,sys.hash_info}, which describes the bit width of the hash value, the
prime modulus, the hash values for @emph{infinity} and @emph{nan}, and the multiplier
used for the imaginary part of a number:

@example
>>> sys.hash_info 
sys.hash_info(width=64, modulus=2305843009213693951, inf=314159, nan=0, imag=1000003)
@end example

An early decision to limit the inter-operability of various numeric types has
been relaxed.  It is still unsupported (and ill-advised) to have implicit
mixing in arithmetic expressions such as @code{Decimal('1.1') + float('1.1')}
because the latter loses information in the process of constructing the binary
float.  However, since existing floating point value can be converted losslessly
to either a decimal or rational representation, it makes sense to add them to
the constructor and to support mixed-type comparisons.


@itemize *

@item 
The @ref{188,,decimal.Decimal} constructor now accepts @ref{187,,float} objects
directly so there in no longer a need to use the @ref{b79,,from_float()}
method (bpo-8257@footnote{https://bugs.python.org/issue8257}).

@item 
Mixed type comparisons are now fully supported so that
@ref{188,,Decimal} objects can be directly compared with @ref{187,,float}
and @ref{185,,fractions.Fraction} (bpo-2531@footnote{https://bugs.python.org/issue2531} and bpo-8188@footnote{https://bugs.python.org/issue8188}).
@end itemize

Similar changes were made to @ref{185,,fractions.Fraction} so that the
@ref{b7a,,from_float()} and @ref{b7b,,from_decimal()}
methods are no longer needed (bpo-8294@footnote{https://bugs.python.org/issue8294}):

@example
>>> from decimal import Decimal
>>> from fractions import Fraction
>>> Decimal(1.1)
Decimal('1.100000000000000088817841970012523233890533447265625')
>>> Fraction(1.1)
Fraction(2476979795053773, 2251799813685248)
@end example

Another useful change for the @ref{36,,decimal} module is that the
@code{Context.clamp} attribute is now public.  This is useful in creating
contexts that correspond to the decimal interchange formats specified in IEEE
754 (see bpo-8540@footnote{https://bugs.python.org/issue8540}).

（由 Mark Dickinson 和 Raymond Hettinger贡献。）

@node ftp,popen,decimal and fractions,新增，改进和弃用的模块
@anchor{whatsnew/3 2 ftp}@anchor{b7c}
@subsubsection ftp


The @ref{9fd,,ftplib.FTP} class now supports the context management protocol to
unconditionally consume @ref{98f,,socket.error} exceptions and to close the FTP
connection when done:

@example
>>> from ftplib import FTP
>>> with FTP("ftp1.at.proftpd.org") as ftp:
        ftp.login()
        ftp.dir()

'230 Anonymous login ok, restrictions apply.'
dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 .
dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 ..
dr-xr-xr-x   5 ftp      ftp          4096 May  6 10:43 CentOS
dr-xr-xr-x   3 ftp      ftp            18 Jul 10  2008 Fedora
@end example

Other file-like objects such as @ref{1ec,,mmap.mmap} and @ref{2ad,,fileinput.input()}
also grew auto-closing context managers:

@example
with fileinput.input(files=('log1.txt', 'log2.txt')) as f:
    for line in f:
        process(line)
@end example

（由 Tarek Ziadé 和 Giampaolo Rodolà 在 bpo-4972`贡献，由 Georg Brandl 在 :issue:`8046@footnote{https://bugs.python.org/issue4972`贡献，由 Georg Brandl 在 :issue:`8046} 和 bpo-1286@footnote{https://bugs.python.org/issue1286} 贡献。）

The @ref{9fe,,FTP_TLS} class now accepts a @emph{context} parameter, which is a
@ref{3dc,,ssl.SSLContext} object allowing bundling SSL configuration options,
certificates and private keys into a single (potentially long-lived) structure.

（由 Giampaolo Rodolà 在 bpo-8806@footnote{https://bugs.python.org/issue8806} 中贡献。）

@node popen,select<3>,ftp,新增，改进和弃用的模块
@anchor{whatsnew/3 2 popen}@anchor{b7d}
@subsubsection popen


The @ref{2a9,,os.popen()} and @ref{2b9,,subprocess.Popen()} functions now support
@ref{6e3,,with} statements for auto-closing of the file descriptors.

（由 Antoine Pitrou 和 Brian Curtin 在 bpo-7461@footnote{https://bugs.python.org/issue7461} 和 bpo-10554@footnote{https://bugs.python.org/issue10554} 中贡献。）

@node select<3>,gzip 和 zipfile,popen,新增，改进和弃用的模块
@anchor{whatsnew/3 2 select}@anchor{b7e}
@subsubsection select


The @ref{e5,,select} module now exposes a new, constant attribute,
@ref{b7f,,PIPE_BUF}, which gives the minimum number of bytes which are
guaranteed not to block when @ref{66d,,select.select()} says a pipe is ready
for writing.

@example
>>> import select
>>> select.PIPE_BUF  
512
@end example

(Available on Unix systems. Patch by Sébastien Sablé in bpo-9862@footnote{https://bugs.python.org/issue9862})

@node gzip 和 zipfile,tarfile<5>,select<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 gzip-and-zipfile}@anchor{b80}
@subsubsection gzip 和 zipfile


@ref{6d7,,gzip.GzipFile} now implements the @ref{583,,io.BufferedIOBase}
@ref{b2c,,abstract base class} (except for @code{truncate()}).  It also has a
@ref{b81,,peek()} method and supports unseekable as well as
zero-padded file objects.

The @ref{8c,,gzip} module also gains the @ref{1d1,,compress()} and
@ref{b82,,decompress()} functions for easier in-memory compression and
decompression.  Keep in mind that text needs to be encoded as @ref{32a,,bytes}
before compressing and decompressing:

@example
>>> import gzip
>>> s = 'Three shall be the number thou shalt count, '
>>> s += 'and the number of the counting shall be three'
>>> b = s.encode()                        # convert to utf-8
>>> len(b)
89
>>> c = gzip.compress(b)
>>> len(c)
77
>>> gzip.decompress(c).decode()[:42]      # decompress and convert to text
'Three shall be the number thou shalt count'
@end example

（由 Anand B. Pillai 在 bpo-3488@footnote{https://bugs.python.org/issue3488} 中贡献，由Antoine Pitrou, Nir Aides 和 Brian Curtin 在 bpo-9962@footnote{https://bugs.python.org/issue9962}，bpo-1675951@footnote{https://bugs.python.org/issue1675951} ，bpo-7471@footnote{https://bugs.python.org/issue7471} 和 bpo-2846@footnote{https://bugs.python.org/issue2846} 中贡献。）

Also, the @code{zipfile.ZipExtFile} class was reworked internally to represent
files stored inside an archive.  The new implementation is significantly faster
and can be wrapped in an @ref{b83,,io.BufferedReader} object for more speedups.  It
also solves an issue where interleaved calls to @emph{read} and @emph{readline} gave the
wrong results.

(Patch submitted by Nir Aides in bpo-7610@footnote{https://bugs.python.org/issue7610}.)

@node tarfile<5>,hashlib<3>,gzip 和 zipfile,新增，改进和弃用的模块
@anchor{whatsnew/3 2 tarfile}@anchor{b84}
@subsubsection tarfile


The @ref{b85,,TarFile} class can now be used as a context manager.  In
addition, its @ref{476,,add()} method has a new option, @emph{filter},
that controls which files are added to the archive and allows the file metadata
to be edited.

The new @emph{filter} option replaces the older, less flexible @emph{exclude} parameter
which is now deprecated.  If specified, the optional @emph{filter} parameter needs to
be a @ref{5bf,,keyword argument}.  The user-supplied filter function accepts a
@ref{b86,,TarInfo} object and returns an updated
@ref{b86,,TarInfo} object, or if it wants the file to be excluded, the
function can return @code{None}:

@example
>>> import tarfile, glob

>>> def myfilter(tarinfo):
...     if tarinfo.isfile():             # only save real files
...         tarinfo.uname = 'monty'      # redact the user name
...         return tarinfo

>>> with tarfile.open(name='myarchive.tar.gz', mode='w:gz') as tf:
...     for filename in glob.glob('*.txt'):
...         tf.add(filename, filter=myfilter)
...     tf.list()
-rw-r--r-- monty/501        902 2011-01-26 17:59:11 annotations.txt
-rw-r--r-- monty/501        123 2011-01-26 17:59:11 general_questions.txt
-rw-r--r-- monty/501       3514 2011-01-26 17:59:11 prion.txt
-rw-r--r-- monty/501        124 2011-01-26 17:59:11 py_todo.txt
-rw-r--r-- monty/501       1399 2011-01-26 17:59:11 semaphore_notes.txt
@end example

(Proposed by Tarek Ziadé and implemented by Lars Gustäbel in bpo-6856@footnote{https://bugs.python.org/issue6856}.)

@node hashlib<3>,ast<3>,tarfile<5>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 hashlib}@anchor{b87}
@subsubsection hashlib


The @ref{8d,,hashlib} module has two new constant attributes listing the hashing
algorithms guaranteed to be present in all implementations and those available
on the current implementation:

@example
>>> import hashlib

>>> hashlib.algorithms_guaranteed
@{'sha1', 'sha224', 'sha384', 'sha256', 'sha512', 'md5'@}

>>> hashlib.algorithms_available
@{'md2', 'SHA256', 'SHA512', 'dsaWithSHA', 'mdc2', 'SHA224', 'MD4', 'sha256',
'sha512', 'ripemd160', 'SHA1', 'MDC2', 'SHA', 'SHA384', 'MD2',
'ecdsa-with-SHA1','md4', 'md5', 'sha1', 'DSA-SHA', 'sha224',
'dsaEncryption', 'DSA', 'RIPEMD160', 'sha', 'MD5', 'sha384'@}
@end example

（由 Carl Chenet 在 bpo-7418@footnote{https://bugs.python.org/issue7418} 中建议。）

@node ast<3>,os<8>,hashlib<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 ast}@anchor{b88}
@subsubsection ast


The @ref{8,,ast} module has a wonderful a general-purpose tool for safely
evaluating expression strings using the Python literal
syntax.  The @ref{4a0,,ast.literal_eval()} function serves as a secure alternative to
the builtin @ref{b89,,eval()} function which is easily abused.  Python 3.2 adds
@ref{32a,,bytes} and @ref{b68,,set} literals to the list of supported types:
strings, bytes, numbers, tuples, lists, dicts, sets, booleans, and @code{None}.

@example
>>> from ast import literal_eval

>>> request = "@{'req': 3, 'func': 'pow', 'args': (2, 0.5)@}"
>>> literal_eval(request)
@{'args': (2, 0.5), 'req': 3, 'func': 'pow'@}

>>> request = "os.system('do something harmful')"
>>> literal_eval(request)
Traceback (most recent call last):
  ...
ValueError: malformed node or string: <_ast.Call object at 0x101739a10>
@end example

（由Benjamin Peterson 和 Georg Brandl 实现。）

@node os<8>,shutil<5>,ast<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 os}@anchor{b8a}
@subsubsection os


Different operating systems use various encodings for filenames and environment
variables.  The @ref{c4,,os} module provides two new functions,
@ref{4e9,,fsencode()} and @ref{4e8,,fsdecode()}, for encoding and decoding
filenames:

@example
>>> import os
>>> filename = 'Sehenswürdigkeiten'
>>> os.fsencode(filename)
b'Sehensw\xc3\xbcrdigkeiten'
@end example

Some operating systems allow direct access to encoded bytes in the
environment.  If so, the @ref{b8b,,os.supports_bytes_environ} constant will be
true.

For direct access to encoded environment variables (if available),
use the new @ref{b8c,,os.getenvb()} function or use @ref{b8d,,os.environb}
which is a bytes version of @ref{b30,,os.environ}.

（由 Victor Stinner 贡献。）

@node shutil<5>,sqlite3<6>,os<8>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 shutil}@anchor{b8e}
@subsubsection shutil


The @ref{21a,,shutil.copytree()} function has two new options:


@itemize *

@item 
@emph{ignore_dangling_symlinks}: when @code{symlinks=False} so that the function
copies a file pointed to by a symlink, not the symlink itself. This option
will silence the error raised if the file doesn't exist.

@item 
@emph{copy_function}: is a callable that will be used to copy files.
@ref{25a,,shutil.copy2()} is used by default.
@end itemize

（由 Tarek Ziadé 贡献。）

In addition, the @ref{e9,,shutil} module now supports @ref{b8f,,archiving operations} for zipfiles, uncompressed tarfiles, gzipped tarfiles,
and bzipped tarfiles.  And there are functions for registering additional
archiving file formats (such as xz compressed tarfiles or custom formats).

The principal functions are @ref{21b,,make_archive()} and
@ref{b90,,unpack_archive()}.  By default, both operate on the current
directory (which can be set by @ref{a3a,,os.chdir()}) and on any sub-directories.
The archive filename needs to be specified with a full pathname.  The archiving
step is non-destructive (the original files are left unchanged).

@example
>>> import shutil, pprint

>>> os.chdir('mydata')  # change to the source directory
>>> f = shutil.make_archive('/var/backup/mydata',
...                         'zip')      # archive the current directory
>>> f                                   # show the name of archive
'/var/backup/mydata.zip'
>>> os.chdir('tmp')                     # change to an unpacking
>>> shutil.unpack_archive('/var/backup/mydata.zip')  # recover the data

>>> pprint.pprint(shutil.get_archive_formats())  # display known formats
[('bztar', "bzip2'ed tar-file"),
 ('gztar', "gzip'ed tar-file"),
 ('tar', 'uncompressed tar file'),
 ('zip', 'ZIP file')]

>>> shutil.register_archive_format(     # register a new archive format
...     name='xz',
...     function=xz.compress,           # callable archiving function
...     extra_args=[('level', 8)],      # arguments to the function
...     description='xz compression'
... )
@end example

（由 Tarek Ziadé 贡献。）

@node sqlite3<6>,html<3>,shutil<5>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 sqlite3}@anchor{b91}
@subsubsection sqlite3


The @ref{f2,,sqlite3} module was updated to pysqlite version 2.6.0.  It has two new capabilities.


@itemize *

@item 
The @code{sqlite3.Connection.in_transit} attribute is true if there is an
active transaction for uncommitted changes.

@item 
The @ref{b92,,sqlite3.Connection.enable_load_extension()} and
@ref{b93,,sqlite3.Connection.load_extension()} methods allows you to load SQLite
extensions from ".so" files.  One well-known extension is the fulltext-search
extension distributed with SQLite.
@end itemize

（由 R. David Murray 和 Shashwat Anand 在 bpo-8845@footnote{https://bugs.python.org/issue8845} 中贡献。）

@node html<3>,socket<8>,sqlite3<6>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 html}@anchor{b94}
@subsubsection html


A new @ref{90,,html} module was introduced with only a single function,
@ref{92e,,escape()}, which is used for escaping reserved characters from HTML
markup:

@example
>>> import html
>>> html.escape('x > 2 && x < 7')
'x &gt; 2 &amp;&amp; x &lt; 7'
@end example

@node socket<8>,ssl<9>,html<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 socket}@anchor{b95}
@subsubsection socket


The @ref{ef,,socket} module has two new improvements.


@itemize *

@item 
Socket objects now have a @ref{b96,,detach()} method which puts
the socket into closed state without actually closing the underlying file
descriptor.  The latter can then be reused for other purposes.
(Added by Antoine Pitrou; bpo-8524@footnote{https://bugs.python.org/issue8524}.)

@item 
@ref{b97,,socket.create_connection()} now supports the context management protocol
to unconditionally consume @ref{98f,,socket.error} exceptions and to close the
socket when done.
(Contributed by Giampaolo Rodolà; bpo-9794@footnote{https://bugs.python.org/issue9794}.)
@end itemize

@node ssl<9>,nntp,socket<8>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 ssl}@anchor{b98}
@subsubsection ssl


The @ref{f3,,ssl} module added a number of features to satisfy common requirements
for secure (encrypted, authenticated) internet connections:


@itemize *

@item 
A new class, @ref{3dc,,SSLContext}, serves as a container for persistent
SSL data, such as protocol settings, certificates, private keys, and various
other options. It includes a @ref{3dd,,wrap_socket()} for creating
an SSL socket from an SSL context.

@item 
A new function, @ref{3d4,,ssl.match_hostname()}, supports server identity
verification for higher-level protocols by implementing the rules of HTTPS
(from 
@geindex RFC; RFC 2818
RFC 2818@footnote{https://tools.ietf.org/html/rfc2818.html}) which are also suitable for other protocols.

@item 
The @ref{469,,ssl.wrap_socket()} constructor function now takes a @emph{ciphers}
argument.  The @emph{ciphers} string lists the allowed encryption algorithms using
the format described in the OpenSSL documentation@footnote{https://www.openssl.org/docs/manmaster/man1/ciphers.html#CIPHER-LIST-FORMAT}.

@item 
When linked against recent versions of OpenSSL, the @ref{f3,,ssl} module now
supports the Server Name Indication extension to the TLS protocol, allowing
multiple "virtual hosts" using different certificates on a single IP port.
This extension is only supported in client mode, and is activated by passing
the @emph{server_hostname} argument to @ref{3dd,,ssl.SSLContext.wrap_socket()}.

@item 
Various options have been added to the @ref{f3,,ssl} module, such as
@ref{b99,,OP_NO_SSLv2} which disables the insecure and obsolete SSLv2
protocol.

@item 
The extension now loads all the OpenSSL ciphers and digest algorithms.  If
some SSL certificates cannot be verified, they are reported as an "unknown
algorithm" error.

@item 
The version of OpenSSL being used is now accessible using the module
attributes @ref{b9a,,ssl.OPENSSL_VERSION} (a string),
@ref{b9b,,ssl.OPENSSL_VERSION_INFO} (a 5-tuple), and
@ref{b9c,,ssl.OPENSSL_VERSION_NUMBER} (an integer).
@end itemize

（由 Antoine Pitrou 在 bpo-8850@footnote{https://bugs.python.org/issue8850},  bpo-1589@footnote{https://bugs.python.org/issue1589}, bpo-8322@footnote{https://bugs.python.org/issue8322}, bpo-5639@footnote{https://bugs.python.org/issue5639}, bpo-4870@footnote{https://bugs.python.org/issue4870}, bpo-8484@footnote{https://bugs.python.org/issue8484} 和 bpo-8321@footnote{https://bugs.python.org/issue8321} 中贡献。）

@node nntp,certificates,ssl<9>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 nntp}@anchor{b9d}
@subsubsection nntp


The @ref{c0,,nntplib} module has a revamped implementation with better bytes and
text semantics as well as more practical APIs.  These improvements break
compatibility with the nntplib version in Python 3.1, which was partly
dysfunctional in itself.

Support for secure connections through both implicit (using
@ref{b9e,,nntplib.NNTP_SSL}) and explicit (using @ref{b9f,,nntplib.NNTP.starttls()})
TLS has also been added.

（由 Antoine Pitrou 在 bpo-9360@footnote{https://bugs.python.org/issue9360} 中贡献，由 Andrew Vant 在 bpo-1926@footnote{https://bugs.python.org/issue1926} 中贡献。）

@node certificates,imaplib<3>,nntp,新增，改进和弃用的模块
@anchor{whatsnew/3 2 certificates}@anchor{ba0}
@subsubsection certificates


@ref{38b,,http.client.HTTPSConnection}, @ref{ba1,,urllib.request.HTTPSHandler}
and @ref{786,,urllib.request.urlopen()} now take optional arguments to allow for
server certificate checking against a set of Certificate Authorities,
as recommended in public uses of HTTPS.

(Added by Antoine Pitrou, bpo-9003@footnote{https://bugs.python.org/issue9003}.)

@node imaplib<3>,http client<4>,certificates,新增，改进和弃用的模块
@anchor{whatsnew/3 2 imaplib}@anchor{ba2}
@subsubsection imaplib


Support for explicit TLS on standard IMAP4 connections has been added through
the new @ref{ba3,,imaplib.IMAP4.starttls} method.

（由 Lorenzo M. Catucci 和 Antoine Pitrou 在 bpo-4471@footnote{https://bugs.python.org/issue4471} 中贡献。）

@node http client<4>,unittest<6>,imaplib<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 http-client}@anchor{ba4}
@subsubsection http.client


There were a number of small API improvements in the @ref{94,,http.client} module.
The old-style HTTP 0.9 simple responses are no longer supported and the @emph{strict}
parameter is deprecated in all classes.

The @ref{38a,,HTTPConnection} and
@ref{38b,,HTTPSConnection} classes now have a @emph{source_address}
parameter for a (host, port) tuple indicating where the HTTP connection is made
from.

Support for certificate checking and HTTPS virtual hosts were added to
@ref{38b,,HTTPSConnection}.

The @ref{54a,,request()} method on connection objects
allowed an optional @emph{body} argument so that a @ref{b3b,,file object} could be used
to supply the content of the request.  Conveniently, the @emph{body} argument now
also accepts an @ref{ba5,,iterable} object so long as it includes an explicit
@code{Content-Length} header.  This extended interface is much more flexible than
before.

To establish an HTTPS connection through a proxy server, there is a new
@ref{ba6,,set_tunnel()} method that sets the host and
port for HTTP Connect tunneling.

To match the behavior of @ref{97,,http.server}, the HTTP client library now also
encodes headers with ISO-8859-1 (Latin-1) encoding.  It was already doing that
for incoming headers, so now the behavior is consistent for both incoming and
outgoing traffic. (See work by Armin Ronacher in bpo-10980@footnote{https://bugs.python.org/issue10980}.)

@node unittest<6>,random<2>,http client<4>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 unittest}@anchor{ba7}
@subsubsection unittest


The unittest module has a number of improvements supporting test discovery for
packages, easier experimentation at the interactive prompt, new testcase
methods, improved diagnostic messages for test failures, and better method
names.


@itemize *

@item 
The command-line call @code{python -m unittest} can now accept file paths
instead of module names for running specific tests (bpo-10620@footnote{https://bugs.python.org/issue10620}).  The new
test discovery can find tests within packages, locating any test importable
from the top-level directory.  The top-level directory can be specified with
the @cite{-t} option, a pattern for matching files with @code{-p}, and a directory to
start discovery with @code{-s}:

@example
$ python -m unittest discover -s my_proj_dir -p _test.py
@end example

（由 Michael Foord 贡献）

@item 
Experimentation at the interactive prompt is now easier because the
@code{unittest.case.TestCase} class can now be instantiated without
arguments:

@example
>>> from unittest import TestCase
>>> TestCase().assertEqual(pow(2, 3), 8)
@end example

（由 Michael Foord 贡献）

@item 
The @ref{11b,,unittest} module has two new methods,
@ref{ab7,,assertWarns()} and
@ref{ab8,,assertWarnsRegex()} to verify that a given warning type
is triggered by the code under test:

@example
with self.assertWarns(DeprecationWarning):
    legacy_function('XYZ')
@end example

（由 Antoine Pitrou 在 bpo-9754@footnote{https://bugs.python.org/issue9754} 中贡献。）

Another new method, @ref{ba8,,assertCountEqual()} is used to
compare two iterables to determine if their element counts are equal (whether
the same elements are present with the same number of occurrences regardless
of order):

@example
def test_anagram(self):
    self.assertCountEqual('algorithm', 'logarithm')
@end example

（由 Raymond Hettinger 贡献。）

@item 
A principal feature of the unittest module is an effort to produce meaningful
diagnostics when a test fails.  When possible, the failure is recorded along
with a diff of the output.  This is especially helpful for analyzing log files
of failed test runs. However, since diffs can sometime be voluminous, there is
a new @ref{ba9,,maxDiff} attribute that sets maximum length of
diffs displayed.

@item 
In addition, the method names in the module have undergone a number of clean-ups.

For example, @ref{baa,,assertRegex()} is the new name for
@code{assertRegexpMatches()} which was misnamed because the
test uses @ref{bab,,re.search()}, not @ref{bac,,re.match()}.  Other methods using
regular expressions are now named using short form "Regex" in preference to
"Regexp" -- this matches the names used in other unittest implementations,
matches Python's old name for the @ref{dd,,re} module, and it has unambiguous
camel-casing.

（由 Raymond Hettinger 贡献并由 Ezio Melotti 实现。）

@item 
To improve consistency, some long-standing method aliases are being
deprecated in favor of the preferred names:

@quotation


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

旧名称

@tab

首选名称

@item

@code{assert_()}

@tab

@ref{bad,,assertTrue()}

@item

@code{assertEquals()}

@tab

@ref{bae,,assertEqual()}

@item

@code{assertNotEquals()}

@tab

@ref{baf,,assertNotEqual()}

@item

@code{assertAlmostEquals()}

@tab

@ref{bb0,,assertAlmostEqual()}

@item

@code{assertNotAlmostEquals()}

@tab

@ref{bb1,,assertNotAlmostEqual()}

@end multitable

@end quotation

Likewise, the @code{TestCase.fail*} methods deprecated in Python 3.1 are expected
to be removed in Python 3.3.  Also see the @ref{bb2,,Deprecated aliases} section in
the @ref{11b,,unittest} documentation.

（由 Ezio Melotti 在 bpo-9424@footnote{https://bugs.python.org/issue9424} 中贡献。）

@item 
The @code{assertDictContainsSubset()} method was deprecated
because it was misimplemented with the arguments in the wrong order.  This
created hard-to-debug optical illusions where tests like
@code{TestCase().assertDictContainsSubset(@{'a':1, 'b':2@}, @{'a':1@})} would fail.

（由 Raymond Hettinger 贡献。）
@end itemize

@node random<2>,poplib<3>,unittest<6>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 random}@anchor{bb3}
@subsubsection random


The integer methods in the @ref{dc,,random} module now do a better job of producing
uniform distributions.  Previously, they computed selections with
@code{int(n*random())} which had a slight bias whenever @emph{n} was not a power of two.
Now, multiple selections are made from a range up to the next power of two and a
selection is kept only when it falls within the range @code{0 <= x < n}.  The
functions and methods affected are @ref{bb4,,randrange()},
@ref{bb5,,randint()}, @ref{bb6,,choice()}, @ref{bb7,,shuffle()} and
@ref{bb8,,sample()}.

（由 Raymond Hettinger 在 bpo-9025@footnote{https://bugs.python.org/issue9025} 中贡献。）

@node poplib<3>,asyncore<2>,random<2>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 poplib}@anchor{bb9}
@subsubsection poplib


@ref{bba,,POP3_SSL} class now accepts a @emph{context} parameter, which is a
@ref{3dc,,ssl.SSLContext} object allowing bundling SSL configuration options,
certificates and private keys into a single (potentially long-lived)
structure.

（由 Giampaolo Rodolà 在 bpo-8807@footnote{https://bugs.python.org/issue8807} 中贡献。）

@node asyncore<2>,tempfile<2>,poplib<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 asyncore}@anchor{bbb}
@subsubsection asyncore


@ref{bbc,,asyncore.dispatcher} now provides a
@ref{bbd,,handle_accepted()} method
returning a @cite{(sock@comma{} addr)} pair which is called when a connection has actually
been established with a new remote endpoint. This is supposed to be used as a
replacement for old @ref{bbe,,handle_accept()} and avoids
the user  to call @ref{bbf,,accept()} directly.

（由 Giampaolo Rodolà 在 bpo-6706@footnote{https://bugs.python.org/issue6706} 中贡献。）

@node tempfile<2>,inspect<6>,asyncore<2>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 tempfile}@anchor{bc0}
@subsubsection tempfile


The @ref{103,,tempfile} module has a new context manager,
@ref{bc1,,TemporaryDirectory} which provides easy deterministic
cleanup of temporary directories:

@example
with tempfile.TemporaryDirectory() as tmpdirname:
    print('created temporary dir:', tmpdirname)
@end example

（由 Neil Schemenauer 和 Nick Coghlan 在 bpo-5178@footnote{https://bugs.python.org/issue5178} 中贡献。）

@node inspect<6>,pydoc<5>,tempfile<2>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 inspect}@anchor{bc2}
@subsubsection inspect



@itemize *

@item 
The @ref{a0,,inspect} module has a new function
@ref{bc3,,getgeneratorstate()} to easily identify the current state of a
generator-iterator:

@example
>>> from inspect import getgeneratorstate
>>> def gen():
...     yield 'demo'
>>> g = gen()
>>> getgeneratorstate(g)
'GEN_CREATED'
>>> next(g)
'demo'
>>> getgeneratorstate(g)
'GEN_SUSPENDED'
>>> next(g, None)
>>> getgeneratorstate(g)
'GEN_CLOSED'
@end example

（由 Rodolpho Eckhardt 和 Nick Coghlan 在 bpo-10220@footnote{https://bugs.python.org/issue10220} 中贡献。）

@item 
To support lookups without the possibility of activating a dynamic attribute,
the @ref{a0,,inspect} module has a new function, @ref{bc4,,getattr_static()}.
Unlike @ref{442,,hasattr()}, this is a true read-only search, guaranteed not to
change state while it is searching:

@example
>>> class A:
...     @@property
...     def f(self):
...         print('Running')
...         return 10
...
>>> a = A()
>>> getattr(a, 'f')
Running
10
>>> inspect.getattr_static(a, 'f')
<property object at 0x1022bd788>
@end example
@end itemize

@quotation

（由 Michael Foord 贡献）
@end quotation

@node pydoc<5>,dis<3>,inspect<6>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 pydoc}@anchor{bc5}
@subsubsection pydoc


The @ref{d9,,pydoc} module now provides a much-improved Web server interface, as
well as a new command-line option @code{-b} to automatically open a browser window
to display that server:

@example
$ pydoc3.2 -b
@end example

（由 Ron Adam 在 bpo-2001@footnote{https://bugs.python.org/issue2001} 中贡献。）

@node dis<3>,dbm<6>,pydoc<5>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 dis}@anchor{bc6}
@subsubsection dis


The @ref{38,,dis} module gained two new functions for inspecting code,
@ref{bc7,,code_info()} and @ref{82c,,show_code()}.  Both provide detailed code
object information for the supplied function, method, source code string or code
object.  The former returns a string and the latter prints it:

@example
>>> import dis, random
>>> dis.show_code(random.choice)
Name:              choice
Filename:          /Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/random.py
Argument count:    2
Kw-only arguments: 0
Number of locals:  3
Stack size:        11
Flags:             OPTIMIZED, NEWLOCALS, NOFREE
Constants:
   0: 'Choose a random element from a non-empty sequence.'
   1: 'Cannot choose from an empty sequence'
Names:
   0: _randbelow
   1: len
   2: ValueError
   3: IndexError
Variable names:
   0: self
   1: seq
   2: i
@end example

In addition, the @ref{37c,,dis()} function now accepts string arguments
so that the common idiom @code{dis(compile(s, '@w{'}, 'eval'))} can be shortened
to @code{dis(s)}:

@example
>>> dis('3*x+1 if x%2==1 else x//2')
  1           0 LOAD_NAME                0 (x)
              3 LOAD_CONST               0 (2)
              6 BINARY_MODULO
              7 LOAD_CONST               1 (1)
             10 COMPARE_OP               2 (==)
             13 POP_JUMP_IF_FALSE       28
             16 LOAD_CONST               2 (3)
             19 LOAD_NAME                0 (x)
             22 BINARY_MULTIPLY
             23 LOAD_CONST               1 (1)
             26 BINARY_ADD
             27 RETURN_VALUE
        >>   28 LOAD_NAME                0 (x)
             31 LOAD_CONST               0 (2)
             34 BINARY_FLOOR_DIVIDE
             35 RETURN_VALUE
@end example

Taken together, these improvements make it easier to explore how CPython is
implemented and to see for yourself what the language syntax does
under-the-hood.

（由 Nick Coghlan 在 bpo-9147@footnote{https://bugs.python.org/issue9147} 中贡献。）

@node dbm<6>,ctypes<2>,dis<3>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 dbm}@anchor{bc8}
@subsubsection dbm


All database modules now support the @code{get()} and @code{setdefault()} methods.

（由 Ray Allen 在 bpo-9523@footnote{https://bugs.python.org/issue9523} 中建议。）

@node ctypes<2>,site<2>,dbm<6>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 ctypes}@anchor{bc9}
@subsubsection ctypes


A new type, @ref{bca,,ctypes.c_ssize_t} represents the C @code{ssize_t} datatype.

@node site<2>,sysconfig<2>,ctypes<2>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 site}@anchor{bcb}
@subsubsection site


The @ref{eb,,site} module has three new functions useful for reporting on the
details of a given Python installation.


@itemize *

@item 
@ref{bcc,,getsitepackages()} lists all global site-packages directories.

@item 
@ref{bcd,,getuserbase()} reports on the user's base directory where data can
be stored.

@item 
@ref{bce,,getusersitepackages()} reveals the user-specific site-packages
directory path.
@end itemize

@example
>>> import site
>>> site.getsitepackages()
['/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/site-packages',
 '/Library/Frameworks/Python.framework/Versions/3.2/lib/site-python',
 '/Library/Python/3.2/site-packages']
>>> site.getuserbase()
'/Users/raymondhettinger/Library/Python/3.2'
>>> site.getusersitepackages()
'/Users/raymondhettinger/Library/Python/3.2/lib/python/site-packages'
@end example

Conveniently, some of site's functionality is accessible directly from the
command-line:

@example
$ python -m site --user-base
/Users/raymondhettinger/.local
$ python -m site --user-site
/Users/raymondhettinger/.local/lib/python3.2/site-packages
@end example

（由 Tarek Ziadé 在 bpo-6693@footnote{https://bugs.python.org/issue6693} 中贡献。）

@node sysconfig<2>,pdb<5>,site<2>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 sysconfig}@anchor{bcf}
@subsubsection sysconfig


The new @ref{fe,,sysconfig} module makes it straightforward to discover
installation paths and configuration variables that vary across platforms and
installations.

The module offers access simple access functions for platform and version
information:


@itemize *

@item 
@ref{bd0,,get_platform()} returning values like @emph{linux-i586} or
@emph{macosx-10.6-ppc}.

@item 
@ref{bd1,,get_python_version()} returns a Python version string
such as "3.2".
@end itemize

It also provides access to the paths and variables corresponding to one of
seven named schemes used by @ref{39,,distutils}.  Those include @emph{posix_prefix},
@emph{posix_home}, @emph{posix_user}, @emph{nt}, @emph{nt_user}, @emph{os2}, @emph{os2_home}:


@itemize *

@item 
@ref{bd2,,get_paths()} makes a dictionary containing installation paths
for the current installation scheme.

@item 
@ref{95f,,get_config_vars()} returns a dictionary of platform specific
variables.
@end itemize

还有一个方便的命令行界面：

@example
C:\Python32>python -m sysconfig
Platform: "win32"
Python version: "3.2"
Current installation scheme: "nt"

Paths:
        data = "C:\Python32"
        include = "C:\Python32\Include"
        platinclude = "C:\Python32\Include"
        platlib = "C:\Python32\Lib\site-packages"
        platstdlib = "C:\Python32\Lib"
        purelib = "C:\Python32\Lib\site-packages"
        scripts = "C:\Python32\Scripts"
        stdlib = "C:\Python32\Lib"

Variables:
        BINDIR = "C:\Python32"
        BINLIBDEST = "C:\Python32\Lib"
        EXE = ".exe"
        INCLUDEPY = "C:\Python32\Include"
        LIBDEST = "C:\Python32\Lib"
        SO = ".pyd"
        VERSION = "32"
        abiflags = ""
        base = "C:\Python32"
        exec_prefix = "C:\Python32"
        platbase = "C:\Python32"
        prefix = "C:\Python32"
        projectbase = "C:\Python32"
        py_version = "3.2"
        py_version_nodot = "32"
        py_version_short = "3.2"
        srcdir = "C:\Python32"
        userbase = "C:\Documents and Settings\Raymond\Application Data\Python"
@end example

（由TarekZiadé 移出Distutils。）

@node pdb<5>,configparser<2>,sysconfig<2>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 pdb}@anchor{bd3}
@subsubsection pdb


The @ref{c9,,pdb} debugger module gained a number of usability improvements:


@itemize *

@item 
@code{pdb.py} now has a @code{-c} option that executes commands as given in a
@code{.pdbrc} script file.

@item 
A @code{.pdbrc} script file can contain @code{continue} and @code{next} commands
that continue debugging.

@item 
The @code{Pdb} class constructor now accepts a @emph{nosigint} argument.

@item 
New commands: @code{l(list)}, @code{ll(long list)} and @code{source} for
listing source code.

@item 
New commands: @code{display} and @code{undisplay} for showing or hiding
the value of an expression if it has changed.

@item 
New command: @code{interact} for starting an interactive interpreter containing
the global and local  names found in the current scope.

@item 
Breakpoints can be cleared by breakpoint number.
@end itemize

（由Georg Brandl, Antonio Cuni 和 Ilya Sandler 贡献。）

@node configparser<2>,urllib parse<2>,pdb<5>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 configparser}@anchor{bd4}
@subsubsection configparser


The @ref{23,,configparser} module was modified to improve usability and
predictability of the default parser and its supported INI syntax.  The old
@code{ConfigParser} class was removed in favor of @code{SafeConfigParser}
which has in turn been renamed to @ref{4a5,,ConfigParser}. Support
for inline comments is now turned off by default and section or option
duplicates are not allowed in a single configuration source.

Config parsers gained a new API based on the mapping protocol:

@example
>>> parser = ConfigParser()
>>> parser.read_string("""
... [DEFAULT]
... location = upper left
... visible = yes
... editable = no
... color = blue
...
... [main]
... title = Main Menu
... color = green
...
... [options]
... title = Options
... """)
>>> parser['main']['color']
'green'
>>> parser['main']['editable']
'no'
>>> section = parser['options']
>>> section['title']
'Options'
>>> section['title'] = 'Options (editable: %(editable)s)'
>>> section['title']
'Options (editable: no)'
@end example

The new API is implemented on top of the classical API, so custom parser
subclasses should be able to use it without modifications.

The INI file structure accepted by config parsers can now be customized. Users
can specify alternative option/value delimiters and comment prefixes, change the
name of the @emph{DEFAULT} section or switch the interpolation syntax.

There is support for pluggable interpolation including an additional interpolation
handler @ref{bd5,,ExtendedInterpolation}:

@example
>>> parser = ConfigParser(interpolation=ExtendedInterpolation())
>>> parser.read_dict(@{'buildout': @{'directory': '/home/ambv/zope9'@},
...                   'custom': @{'prefix': '/usr/local'@}@})
>>> parser.read_string("""
... [buildout]
... parts =
...   zope9
...   instance
... find-links =
...   $@{buildout:directory@}/downloads/dist
...
... [zope9]
... recipe = plone.recipe.zope9install
... location = /opt/zope
...
... [instance]
... recipe = plone.recipe.zope9instance
... zope9-location = $@{zope9:location@}
... zope-conf = $@{custom:prefix@}/etc/zope.conf
... """)
>>> parser['buildout']['find-links']
'\n/home/ambv/zope9/downloads/dist'
>>> parser['instance']['zope-conf']
'/usr/local/etc/zope.conf'
>>> instance = parser['instance']
>>> instance['zope-conf']
'/usr/local/etc/zope.conf'
>>> instance['zope9-location']
'/opt/zope'
@end example

A number of smaller features were also introduced, like support for specifying
encoding in read operations, specifying fallback values for get-functions, or
reading directly from dictionaries and strings.

(All changes contributed by Łukasz Langa.)

@c XXX consider showing a difflib example

@node urllib parse<2>,mailbox,configparser<2>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 urllib-parse}@anchor{bd6}
@subsubsection urllib.parse


A number of usability improvements were made for the @ref{11f,,urllib.parse} module.

The @ref{5f5,,urlparse()} function now supports IPv6@footnote{https://en.wikipedia.org/wiki/IPv6} addresses as described in 
@geindex RFC; RFC 2732
RFC 2732@footnote{https://tools.ietf.org/html/rfc2732.html}:

@example
>>> import urllib.parse
>>> urllib.parse.urlparse('http://[dead:beef:cafe:5417:affe:8FA3:deaf:feed]/foo/') 
ParseResult(scheme='http',
            netloc='[dead:beef:cafe:5417:affe:8FA3:deaf:feed]',
            path='/foo/',
            params='@w{'},
            query='@w{'},
            fragment='@w{'})
@end example

The @ref{bd7,,urldefrag()} function now returns a @ref{a9e,,named tuple}:

@example
>>> r = urllib.parse.urldefrag('http://python.org/about/#target')
>>> r
DefragResult(url='http://python.org/about/', fragment='target')
>>> r[0]
'http://python.org/about/'
>>> r.fragment
'target'
@end example

And, the @ref{785,,urlencode()} function is now much more flexible,
accepting either a string or bytes type for the @emph{query} argument.  If it is a
string, then the @emph{safe}, @emph{encoding}, and @emph{error} parameters are sent to
@ref{bd8,,quote_plus()} for encoding:

@example
>>> urllib.parse.urlencode([
...      ('type', 'telenovela'),
...      ('name', '¿Dónde Está Elisa?')],
...      encoding='latin-1')
'type=telenovela&name=%BFD%F3nde+Est%E1+Elisa%3F'
@end example

As detailed in @ref{bd9,,解析ASCII编码字节}, all the @ref{11f,,urllib.parse}
functions now accept ASCII-encoded byte strings as input, so long as they are
not mixed with regular strings.  If ASCII-encoded byte strings are given as
parameters, the return types will also be an ASCII-encoded byte strings:

@example
>>> urllib.parse.urlparse(b'http://www.python.org:80/about/') 
ParseResultBytes(scheme=b'http', netloc=b'www.python.org:80',
                 path=b'/about/', params=b'@w{'}, query=b'@w{'}, fragment=b'@w{'})
@end example

(Work by Nick Coghlan, Dan Mahn, and Senthil Kumaran in bpo-2987@footnote{https://bugs.python.org/issue2987},
bpo-5468@footnote{https://bugs.python.org/issue5468}, and bpo-9873@footnote{https://bugs.python.org/issue9873}.)

@node mailbox,turtledemo,urllib parse<2>,新增，改进和弃用的模块
@anchor{whatsnew/3 2 mailbox}@anchor{bda}
@subsubsection mailbox


Thanks to a concerted effort by R. David Murray, the @ref{ae,,mailbox} module has
been fixed for Python 3.2.  The challenge was that mailbox had been originally
designed with a text interface, but email messages are best represented with
@ref{32a,,bytes} because various parts of a message may have different encodings.

The solution harnessed the @ref{69,,email} package's binary support for parsing
arbitrary email messages.  In addition, the solution required a number of API
changes.

As expected, the @ref{bdb,,add()} method for
@ref{bdc,,mailbox.Mailbox} objects now accepts binary input.

@ref{827,,StringIO} and text file input are deprecated.  Also, string input
will fail early if non-ASCII characters are used.  Previously it would fail when
the email was processed in a later step.

There is also support for binary output.  The @ref{bdd,,get_file()}
method now returns a file in the binary mode (where it used to incorrectly set
the file to text-mode).  There is also a new @ref{bde,,get_bytes()}
method that returns a @ref{32a,,bytes} representation of a message corresponding
to a given @emph{key}.

It is still possible to get non-binary output using the old API's
@ref{bdf,,get_string()} method, but that approach
is not very useful.  Instead, it is best to extract messages from
a @ref{be0,,Message} object or to load them from binary input.

(Contributed by R. David Murray, with efforts from Steffen Daode Nurpmeso and an
initial patch by Victor Stinner in bpo-9124@footnote{https://bugs.python.org/issue9124}.)

@node turtledemo,,mailbox,新增，改进和弃用的模块
@anchor{whatsnew/3 2 turtledemo}@anchor{be1}
@subsubsection turtledemo


The demonstration code for the @ref{116,,turtle} module was moved from the @emph{Demo}
directory to main library.  It includes over a dozen sample scripts with
lively displays.  Being on @ref{482,,sys.path}, it can now be run directly
from the command-line:

@example
$ python -m turtledemo
@end example

(Moved from the Demo directory by Alexander Belopolsky in bpo-10199@footnote{https://bugs.python.org/issue10199}.)

@node 多线程,性能优化<6>,新增，改进和弃用的模块,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 multi-threading}@anchor{be2}
@subsection 多线程



@itemize *

@item 
The mechanism for serializing execution of concurrently running Python threads
(generally known as the @ref{be3,,GIL} or @ref{500,,Global Interpreter Lock}) has
been rewritten.  Among the objectives were more predictable switching
intervals and reduced overhead due to lock contention and the number of
ensuing system calls.  The notion of a "check interval" to allow thread
switches has been abandoned and replaced by an absolute duration expressed in
seconds.  This parameter is tunable through @ref{be4,,sys.setswitchinterval()}.
It currently defaults to 5 milliseconds.

Additional details about the implementation can be read from a python-dev mailing-list message@footnote{https://mail.python.org/pipermail/python-dev/2009-October/093321.html}
(however, "priority requests" as exposed in this message have not been kept
for inclusion).

（由 Antoine Pitrou 贡献。）

@item 
Regular and recursive locks now accept an optional @emph{timeout} argument to their
@ref{766,,acquire()} method.  (Contributed by Antoine Pitrou;
bpo-7316@footnote{https://bugs.python.org/issue7316}.)

@item 
Similarly, @ref{be5,,threading.Semaphore.acquire()} also gained a @emph{timeout}
argument.  (Contributed by Torsten Landschoff; bpo-850728@footnote{https://bugs.python.org/issue850728}.)

@item 
Regular and recursive lock acquisitions can now be interrupted by signals on
platforms using Pthreads.  This means that Python programs that deadlock while
acquiring locks can be successfully killed by repeatedly sending SIGINT to the
process (by pressing @code{Ctrl+C} in most shells).
(Contributed by Reid Kleckner; bpo-8844@footnote{https://bugs.python.org/issue8844}.)
@end itemize

@node 性能优化<6>,Unicode,多线程,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 optimizations}@anchor{be6}
@subsection 性能优化


A number of small performance enhancements have been added:


@itemize *

@item 
Python's peephole optimizer now recognizes patterns such @code{x in @{1, 2, 3@}} as
being a test for membership in a set of constants.  The optimizer recasts the
@ref{b68,,set} as a @ref{be7,,frozenset} and stores the pre-built constant.

Now that the speed penalty is gone, it is practical to start writing
membership tests using set-notation.  This style is both semantically clear
and operationally fast:

@example
extension = name.rpartition('.')[2]
if extension in @{'xml', 'html', 'xhtml', 'css'@}:
    handle(name)
@end example

(Patch and additional tests contributed by Dave Malcolm; bpo-6690@footnote{https://bugs.python.org/issue6690}).

@item 
Serializing and unserializing data using the @ref{ca,,pickle} module is now
several times faster.

（由 Alexandre Vassalotti, Antoine Pitrou 和 Unladen Swallow 团队在 bpo-9410@footnote{https://bugs.python.org/issue9410} 和 bpo-3873@footnote{https://bugs.python.org/issue3873} 中贡献。）

@item 
The Timsort algorithm@footnote{https://en.wikipedia.org/wiki/Timsort} used in
@ref{43f,,list.sort()} and @ref{43e,,sorted()} now runs faster and uses less memory
when called with a @ref{6da,,key function}.  Previously, every element of
a list was wrapped with a temporary object that remembered the key value
associated with each element.  Now, two arrays of keys and values are
sorted in parallel.  This saves the memory consumed by the sort wrappers,
and it saves time lost to delegating comparisons.

(Patch by Daniel Stutzbach in bpo-9915@footnote{https://bugs.python.org/issue9915}.)

@item 
JSON decoding performance is improved and memory consumption is reduced
whenever the same string is repeated for multiple keys.  Also, JSON encoding
now uses the C speedups when the @code{sort_keys} argument is true.

（由Antoine Pitrou 在 bpo-7451@footnote{https://bugs.python.org/issue7451} 中贡献，由 Raymond Hettinger 和 Antoine Pitrou 在 bpo-10314@footnote{https://bugs.python.org/issue10314} 中贡献。）

@item 
Recursive locks (created with the @ref{be8,,threading.RLock()} API) now benefit
from a C implementation which makes them as fast as regular locks, and between
10x and 15x faster than their previous pure Python implementation.

（由 Antoine Pitrou 在 bpo-3001@footnote{https://bugs.python.org/issue3001} 中贡献。）

@item 
The fast-search algorithm in stringlib is now used by the @code{split()},
@code{rsplit()}, @code{splitlines()} and @code{replace()} methods on
@ref{32a,,bytes}, @ref{32b,,bytearray} and @ref{329,,str} objects. Likewise, the
algorithm is also used by @code{rfind()}, @code{rindex()}, @code{rsplit()} and
@code{rpartition()}.

(Patch by Florent Xicluna in bpo-7622@footnote{https://bugs.python.org/issue7622} and bpo-7462@footnote{https://bugs.python.org/issue7462}.)

@item 
Integer to string conversions now work two "digits" at a time, reducing the
number of division and modulo operations.

(bpo-6713@footnote{https://bugs.python.org/issue6713} by Gawain Bolton, Mark Dickinson, and Victor Stinner.)
@end itemize

There were several other minor optimizations. Set differencing now runs faster
when one operand is much larger than the other (patch by Andress Bennetts in
bpo-8685@footnote{https://bugs.python.org/issue8685}).  The @code{array.repeat()} method has a faster implementation
(bpo-1569291@footnote{https://bugs.python.org/issue1569291} by Alexander Belopolsky). The @code{BaseHTTPRequestHandler}
has more efficient buffering (bpo-3709@footnote{https://bugs.python.org/issue3709} by Andrew Schaaf).  The
@ref{715,,operator.attrgetter()} function has been sped-up (bpo-10160@footnote{https://bugs.python.org/issue10160} by
Christos Georgiou).  And @code{ConfigParser} loads multi-line arguments a bit
faster (bpo-7113@footnote{https://bugs.python.org/issue7113} by Łukasz Langa).

@node Unicode,编解码器,性能优化<6>,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 unicode}@anchor{be9}
@subsection Unicode


Python has been updated to Unicode 6.0.0@footnote{http://unicode.org/versions/Unicode6.0.0/}.  The update to the standard adds
over 2,000 new characters including emoji@footnote{https://en.wikipedia.org/wiki/Emoji}
symbols which are important for mobile phones.

In addition, the updated standard has altered the character properties for two
Kannada characters (U+0CF1, U+0CF2) and one New Tai Lue numeric character
(U+19DA), making the former eligible for use in identifiers while disqualifying
the latter.  For more information, see Unicode Character Database Changes@footnote{http://www.unicode.org/versions/Unicode6.0.0/#Database_Changes}.

@node 编解码器,文档,Unicode,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 codecs}@anchor{bea}
@subsection 编解码器


Support was added for @emph{cp720} Arabic DOS encoding (bpo-1616979@footnote{https://bugs.python.org/issue1616979}).

MBCS encoding no longer ignores the error handler argument. In the default
strict mode, it raises an @ref{1fd,,UnicodeDecodeError} when it encounters an
undecodable byte sequence and an @ref{1fc,,UnicodeEncodeError} for an unencodable
character.

The MBCS codec supports @code{'strict'} and @code{'ignore'} error handlers for
decoding, and @code{'strict'} and @code{'replace'} for encoding.

To emulate Python3.1 MBCS encoding, select the @code{'ignore'} handler for decoding
and the @code{'replace'} handler for encoding.

On Mac OS X, Python decodes command line arguments with @code{'utf-8'} rather than
the locale encoding.

By default, @ref{101,,tarfile} uses @code{'utf-8'} encoding on Windows (instead of
@code{'mbcs'}) and the @code{'surrogateescape'} error handler on all operating
systems.

@node 文档,IDLE,编解码器,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 documentation}@anchor{beb}
@subsection 文档


The documentation continues to be improved.


@itemize *

@item 
A table of quick links has been added to the top of lengthy sections such as
@ref{bec,,内置函数}.  In the case of @ref{a3,,itertools}, the links are
accompanied by tables of cheatsheet-style summaries to provide an overview and
memory jog without having to read all of the docs.

@item 
In some cases, the pure Python source code can be a helpful adjunct to the
documentation, so now many modules now feature quick links to the latest
version of the source code.  For example, the @ref{85,,functools} module
documentation has a quick link at the top labeled:

@quotation

@strong{源代码} Lib/functools.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/functools.py}.
@end quotation

（由 Raymond Hettinger 贡献，参见 rationale@footnote{https://rhettinger.wordpress.com/2011/01/28/open-your-source-more/}。）

@item 
The docs now contain more examples and recipes.  In particular, @ref{dd,,re}
module has an extensive section, @ref{bed,,正则表达式例子}.  Likewise, the
@ref{a3,,itertools} module continues to be updated with new
@ref{bee,,itertools 配方}.

@item 
The @ref{31,,datetime} module now has an auxiliary implementation in pure Python.
No functionality was changed.  This just provides an easier-to-read alternate
implementation.

（由 Alexander Belopolsky 在 bpo-9528@footnote{https://bugs.python.org/issue9528} 中贡献。）

@item 
The unmaintained @code{Demo} directory has been removed.  Some demos were
integrated into the documentation, some were moved to the @code{Tools/demo}
directory, and others were removed altogether.

（由 Georg Brandl 在 bpo-7962@footnote{https://bugs.python.org/issue7962} 中贡献）
@end itemize

@node IDLE,代码库,文档,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 idle}@anchor{bef}
@subsection IDLE



@itemize *

@item 
The format menu now has an option to clean source files by stripping
trailing whitespace.

（由 Raymond Hettinger 在 bpo-5150@footnote{https://bugs.python.org/issue5150} 中贡献。）

@item 
IDLE on Mac OS X now works with both Carbon AquaTk and Cocoa AquaTk.

（由 Kevin Walzer, Ned Deily 和 Ronald Oussoren 在 bpo-6075@footnote{https://bugs.python.org/issue6075} 中贡献。）
@end itemize

@node 代码库,构建和 C API 的改变<5>,IDLE,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 code-repository}@anchor{bf0}
@subsection 代码库


In addition to the existing Subversion code repository at @indicateurl{http://svn.python.org}
there is now a Mercurial@footnote{https://www.mercurial-scm.org/} repository at
@indicateurl{https://hg.python.org/}.

After the 3.2 release, there are plans to switch to Mercurial as the primary
repository.  This distributed version control system should make it easier for
members of the community to create and share external changesets.  See
@geindex Python 提高建议; PEP 385
PEP 385@footnote{https://www.python.org/dev/peps/pep-0385} for details.

To learn to use the new version control system, see the Quick Start@footnote{https://www.mercurial-scm.org/wiki/QuickStart} or the Guide to Mercurial Workflows@footnote{https://www.mercurial-scm.org/guide}.

@node 构建和 C API 的改变<5>,移植到 Python 3 2,代码库,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 build-and-c-api-changes}@anchor{bf1}
@subsection 构建和 C API 的改变


Changes to Python's build process and to the C API include:


@itemize *

@item 
The @emph{idle}, @emph{pydoc} and @emph{2to3} scripts are now installed with a
version-specific suffix on @code{make altinstall} (bpo-10679@footnote{https://bugs.python.org/issue10679}).

@item 
The C functions that access the Unicode Database now accept and return
characters from the full Unicode range, even on narrow unicode builds
(Py_UNICODE_TOLOWER, Py_UNICODE_ISDECIMAL, and others).  A visible difference
in Python is that @ref{bf2,,unicodedata.numeric()} now returns the correct value
for large code points, and @ref{7c6,,repr()} may consider more characters as
printable.

(Reported by Bupjoe Lee and fixed by Amaury Forgeot D'Arc; bpo-5127@footnote{https://bugs.python.org/issue5127}.)

@item 
Computed gotos are now enabled by default on supported compilers (which are
detected by the configure script).  They can still be disabled selectively by
specifying @code{--without-computed-gotos}.

（由 Antoine Pitrou 在 bpo-9203@footnote{https://bugs.python.org/issue9203} 中贡献。）

@item 
The option @code{--with-wctype-functions} was removed.  The built-in unicode
database is now used for all functions.

（由 Amaury Forgeot d'Arc 在 bpo-9210@footnote{https://bugs.python.org/issue9210} 中贡献。）

@item 
Hash values are now values of a new type, @code{Py_hash_t}, which is
defined to be the same size as a pointer.  Previously they were of type long,
which on some 64-bit operating systems is still only 32 bits long.  As a
result of this fix, @ref{b68,,set} and @ref{1b8,,dict} can now hold more than
@code{2**32} entries on builds with 64-bit pointers (previously, they could grow
to that size but their performance degraded catastrophically).

(Suggested by Raymond Hettinger and implemented by Benjamin Peterson;
bpo-9778@footnote{https://bugs.python.org/issue9778}.)

@item 
A new macro @code{Py_VA_COPY} copies the state of the variable argument
list.  It is equivalent to C99 @emph{va_copy} but available on all Python platforms
(bpo-2443@footnote{https://bugs.python.org/issue2443}).

@item 
A new C API function @ref{bf3,,PySys_SetArgvEx()} allows an embedded interpreter
to set @ref{bf4,,sys.argv} without also modifying @ref{482,,sys.path}
(bpo-5753@footnote{https://bugs.python.org/issue5753}).

@item 
@code{PyEval_CallObject} is now only available in macro form.  The
function declaration, which was kept for backwards compatibility reasons, is
now removed -- the macro was introduced in 1997 (bpo-8276@footnote{https://bugs.python.org/issue8276}).

@item 
There is a new function @ref{bf5,,PyLong_AsLongLongAndOverflow()} which
is analogous to @ref{bf6,,PyLong_AsLongAndOverflow()}.  They both serve to
convert Python @ref{184,,int} into a native fixed-width type while providing
detection of cases where the conversion won't fit (bpo-7767@footnote{https://bugs.python.org/issue7767}).

@item 
The @ref{bf7,,PyUnicode_CompareWithASCIIString()} function now returns @emph{not
equal} if the Python string is @emph{NUL} terminated.

@item 
There is a new function @ref{bf8,,PyErr_NewExceptionWithDoc()} that is
like @ref{bf9,,PyErr_NewException()} but allows a docstring to be specified.
This lets C exceptions have the same self-documenting capabilities as
their pure Python counterparts (bpo-7033@footnote{https://bugs.python.org/issue7033}).

@item 
When compiled with the @code{--with-valgrind} option, the pymalloc
allocator will be automatically disabled when running under Valgrind.  This
gives improved memory leak detection when running under Valgrind, while taking
advantage of pymalloc at other times (bpo-2422@footnote{https://bugs.python.org/issue2422}).

@item 
Removed the @code{O?} format from the @emph{PyArg_Parse} functions.  The format is no
longer used and it had never been documented (bpo-8837@footnote{https://bugs.python.org/issue8837}).
@end itemize

There were a number of other small changes to the C-API.  See the
Misc/NEWS@footnote{https://github.com/python/cpython/tree/3.8/Misc/NEWS} file for a complete list.

Also, there were a number of updates to the Mac OS X build, see
Mac/BuildScript/README.txt@footnote{https://github.com/python/cpython/tree/3.8/Mac/BuildScript/README.txt} for details.  For users running a 32/64-bit
build, there is a known problem with the default Tcl/Tk on Mac OS X 10.6.
Accordingly, we recommend installing an updated alternative such as
ActiveState Tcl/Tk 8.5.9@footnote{https://www.activestate.com/activetcl/downloads}.
See @indicateurl{https://www.python.org/download/mac/tcltk/} for additional details.

@node 移植到 Python 3 2,,构建和 C API 的改变<5>,Python 3 2 有什么新变化
@anchor{whatsnew/3 2 porting-to-python-3-2}@anchor{bfa}
@subsection 移植到 Python 3.2


This section lists previously described changes and other bugfixes that may
require changes to your code:


@itemize *

@item 
The @ref{23,,configparser} module has a number of clean-ups.  The major change is
to replace the old @code{ConfigParser} class with long-standing preferred
alternative @code{SafeConfigParser}.  In addition there are a number of
smaller incompatibilities:


@itemize *

@item 
The interpolation syntax is now validated on
@ref{bfb,,get()} and
@ref{bfc,,set()} operations. In the default
interpolation scheme, only two tokens with percent signs are valid: @code{%(name)s}
and @code{%%}, the latter being an escaped percent sign.

@item 
The @ref{bfc,,set()} and
@ref{bfd,,add_section()} methods now verify that
values are actual strings.  Formerly, unsupported types could be introduced
unintentionally.

@item 
Duplicate sections or options from a single source now raise either
@ref{bfe,,DuplicateSectionError} or
@ref{bff,,DuplicateOptionError}.  Formerly, duplicates would
silently overwrite a previous entry.

@item 
Inline comments are now disabled by default so now the @strong{;} character
can be safely used in values.

@item 
Comments now can be indented.  Consequently, for @strong{;} or @strong{#} to appear at
the start of a line in multiline values, it has to be interpolated.  This
keeps comment prefix characters in values from being mistaken as comments.

@item 
@code{""} is now a valid value and is no longer automatically converted to an
empty string. For empty strings, use @code{"option ="} in a line.
@end itemize

@item 
The @ref{c0,,nntplib} module was reworked extensively, meaning that its APIs
are often incompatible with the 3.1 APIs.

@item 
@ref{32b,,bytearray} objects can no longer be used as filenames; instead,
they should be converted to @ref{32a,,bytes}.

@item 
The @code{array.tostring()} and @code{array.fromstring()} have been renamed to
@code{array.tobytes()} and @code{array.frombytes()} for clarity.  The old names
have been deprecated. (See bpo-8990@footnote{https://bugs.python.org/issue8990}.)

@item 
@code{PyArg_Parse*()} 函数:


@itemize *

@item 
"t#" format has been removed: use "s#" or "s*" instead

@item 
"w" and "w#" formats has been removed: use "w*" instead
@end itemize

@item 
The @code{PyCObject} type, deprecated in 3.1, has been removed.  To wrap
opaque C pointers in Python objects, the @ref{c00,,PyCapsule} API should be used
instead; the new type has a well-defined interface for passing typing safety
information and a less complicated signature for calling a destructor.

@item 
The @code{sys.setfilesystemencoding()} function was removed because
it had a flawed design.

@item 
The @ref{c01,,random.seed()} function and method now salt string seeds with an
sha512 hash function.  To access the previous version of @emph{seed} in order to
reproduce Python 3.1 sequences, set the @emph{version} argument to @emph{1},
@code{random.seed(s, version=1)}.

@item 
The previously deprecated @code{string.maketrans()} function has been removed
in favor of the static methods @ref{c02,,bytes.maketrans()} and
@ref{c03,,bytearray.maketrans()}.  This change solves the confusion around which
types were supported by the @ref{f6,,string} module.  Now, @ref{329,,str},
@ref{32a,,bytes}, and @ref{32b,,bytearray} each have their own @strong{maketrans} and
@strong{translate} methods with intermediate translation tables of the appropriate
type.

（由Georg Brandl在 bpo-5675@footnote{https://bugs.python.org/issue5675} 中贡献）

@item 
The previously deprecated @code{contextlib.nested()} function has been removed
in favor of a plain @ref{6e3,,with} statement which can accept multiple
context managers.  The latter technique is faster (because it is built-in),
and it does a better job finalizing multiple context managers when one of them
raises an exception:

@example
with open('mylog.txt') as infile, open('a.out', 'w') as outfile:
    for line in infile:
        if '<critical>' in line:
            outfile.write(line)
@end example

(Contributed by Georg Brandl and Mattias Brändström;
appspot issue 53094@footnote{https://codereview.appspot.com/53094}.)

@item 
@ref{c04,,struct.pack()} now only allows bytes for the @code{s} string pack code.
Formerly, it would accept text arguments and implicitly encode them to bytes
using UTF-8.  This was problematic because it made assumptions about the
correct encoding and because a variable-length encoding can fail when writing
to fixed length segment of a structure.

Code such as @code{struct.pack('<6sHHBBB', 'GIF87a', x, y)} should be rewritten
with to use bytes instead of text, @code{struct.pack('<6sHHBBB', b'GIF87a', x, y)}.

(Discovered by David Beazley and fixed by Victor Stinner; bpo-10783@footnote{https://bugs.python.org/issue10783}.)

@item 
The @ref{137,,xml.etree.ElementTree} class now raises an
@ref{c05,,xml.etree.ElementTree.ParseError} when a parse fails. Previously it
raised an @ref{c06,,xml.parsers.expat.ExpatError}.

@item 
The new, longer @ref{329,,str()} value on floats may break doctests which rely on
the old output format.

@item 
In @ref{2b9,,subprocess.Popen}, the default value for @emph{close_fds} is now
@code{True} under Unix; under Windows, it is @code{True} if the three standard
streams are set to @code{None}, @code{False} otherwise.  Previously, @emph{close_fds}
was always @code{False} by default, which produced difficult to solve bugs
or race conditions when open file descriptors would leak into the child
process.

@item 
Support for legacy HTTP 0.9 has been removed from @ref{120,,urllib.request}
and @ref{94,,http.client}.  Such support is still present on the server side
(in @ref{97,,http.server}).

（由 Antoine Pitrou 在 bpo-10711@footnote{https://bugs.python.org/issue10711} 中贡献。）

@item 
SSL sockets in timeout mode now raise @ref{c07,,socket.timeout} when a timeout
occurs, rather than a generic @ref{c08,,SSLError}.

（由 Antoine Pitrou 在 bpo-10272@footnote{https://bugs.python.org/issue10272} 中贡献。）

@item 
The misleading functions @ref{2b2,,PyEval_AcquireLock()} and
@ref{c09,,PyEval_ReleaseLock()} have been officially deprecated.  The
thread-state aware APIs (such as @ref{c0a,,PyEval_SaveThread()}
and @ref{2b4,,PyEval_RestoreThread()}) should be used instead.

@item 
Due to security risks, @code{asyncore.handle_accept()} has been deprecated, and
a new function, @code{asyncore.handle_accepted()}, was added to replace it.

（由 Giampaolo Rodola 在 bpo-6706@footnote{https://bugs.python.org/issue6706} 中贡献。）

@item 
Due to the new @ref{be3,,GIL} implementation, @ref{c0b,,PyEval_InitThreads()}
cannot be called before @ref{433,,Py_Initialize()} anymore.
@end itemize

@node Python 3 1 有什么新变化,Python 3 0 有什么新变化,Python 3 2 有什么新变化,Python的新变化
@anchor{whatsnew/3 1 doc}@anchor{c0c}@anchor{whatsnew/3 1 what-s-new-in-python-3-1}@anchor{c0d}
@section Python 3.1 有什么新变化


@*作者: 
Raymond Hettinger


@c $Id$
@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number as a comment:
@c 
@c % Patch 12345
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer.)
@c 
@c This saves the maintainer the effort of going through the SVN log
@c when researching a change.

This article explains the new features in Python 3.1, compared to 3.0.

@menu
* PEP 372; 有序字典: PEP 372 有序字典. 
* PEP 378; 千位分隔符的格式说明符: PEP 378 千位分隔符的格式说明符. 
* 其他语言特性修改: 其他语言特性修改<8>. 
* 新增，改进和弃用的模块: 新增，改进和弃用的模块<2>. 
* 性能优化: 性能优化<7>. 
* IDLE: IDLE<2>. 
* 构建和 C API 的改变: 构建和 C API 的改变<6>. 
* 移植到 Python 3.1: 移植到 Python 3 1. 

@end menu

@node PEP 372 有序字典,PEP 378 千位分隔符的格式说明符,,Python 3 1 有什么新变化
@anchor{whatsnew/3 1 pep-372-ordered-dictionaries}@anchor{c0e}
@subsection PEP 372: 有序字典


Regular Python dictionaries iterate over key/value pairs in arbitrary order.
Over the years, a number of authors have written alternative implementations
that remember the order that the keys were originally inserted.  Based on
the experiences from those implementations, a new
@ref{1b9,,collections.OrderedDict} class has been introduced.

The OrderedDict API is substantially the same as regular dictionaries
but will iterate over keys and values in a guaranteed order depending on
when a key was first inserted.  If a new entry overwrites an existing entry,
the original insertion position is left unchanged.  Deleting an entry and
reinserting it will move it to the end.

The standard library now supports use of ordered dictionaries in several
modules.  The @ref{23,,configparser} module uses them by default.  This lets
configuration files be read, modified, and then written back in their original
order.  The @emph{_asdict()} method for @ref{1b6,,collections.namedtuple()} now
returns an ordered dictionary with the values appearing in the same order as
the underlying tuple indices.  The @ref{a4,,json} module is being built-out with
an @emph{object_pairs_hook} to allow OrderedDicts to be built by the decoder.
Support was also added for third-party tools like PyYAML@footnote{http://pyyaml.org/}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 372

@item PEP 372@footnote{https://www.python.org/dev/peps/pep-0372} - 有序字典

PEP 由 Armin Ronacher 和 Raymond Hettinger 撰写，由 Raymond Hettinger 实现。
@end table


@node PEP 378 千位分隔符的格式说明符,其他语言特性修改<8>,PEP 372 有序字典,Python 3 1 有什么新变化
@anchor{whatsnew/3 1 pep-378-format-specifier-for-thousands-separator}@anchor{c0f}
@subsection PEP 378: 千位分隔符的格式说明符


The built-in @ref{4d5,,format()} function and the @ref{4d4,,str.format()} method use
a mini-language that now includes a simple, non-locale aware way to format
a number with a thousands separator.  That provides a way to humanize a
program's output, improving its professional appearance and readability:

@example
>>> format(1234567, ',d')
'1,234,567'
>>> format(1234567.89, ',.2f')
'1,234,567.89'
>>> format(12345.6 + 8901234.12j, ',f')
'12,345.600000+8,901,234.120000j'
>>> format(Decimal('1234567.89'), ',f')
'1,234,567.89'
@end example

The supported types are @ref{184,,int}, @ref{187,,float}, @ref{189,,complex}
and @ref{188,,decimal.Decimal}.

Discussions are underway about how to specify alternative separators
like dots, spaces, apostrophes, or underscores.  Locale-aware applications
should use the existing @emph{n} format specifier which already has some support
for thousands separators.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 378

@item PEP 378@footnote{https://www.python.org/dev/peps/pep-0378} - 千位分隔符的格式说明符

PEP 由 Raymond Hettinger 撰写，并由 Eric Smith 和 Mark Dickinson 实现
@end table


@node 其他语言特性修改<8>,新增，改进和弃用的模块<2>,PEP 378 千位分隔符的格式说明符,Python 3 1 有什么新变化
@anchor{whatsnew/3 1 other-language-changes}@anchor{c10}
@subsection 其他语言特性修改


对Python 语言核心进行的小改动：


@itemize *

@item 
Directories and zip archives containing a @code{__main__.py}
file can now be executed directly by passing their name to the
interpreter. The directory/zipfile is automatically inserted as the
first entry in sys.path.  (Suggestion and initial patch by Andy Chu;
revised patch by Phillip J. Eby and Nick Coghlan; bpo-1739468@footnote{https://bugs.python.org/issue1739468}.)

@item 
The @ref{184,,int()} type gained a @code{bit_length} method that returns the
number of bits necessary to represent its argument in binary:

@example
>>> n = 37
>>> bin(37)
'0b100101'
>>> n.bit_length()
6
>>> n = 2**123-1
>>> n.bit_length()
123
>>> (n+1).bit_length()
124
@end example

（由 Fredrik Johansson, Victor Stinner, Raymond Hettinger 和 Mark Dickinson 在 bpo-3439@footnote{https://bugs.python.org/issue3439} 中贡献。）

@item 
The fields in @ref{4d5,,format()} strings can now be automatically
numbered:

@example
>>> 'Sir @{@} of @{@}'.format('Gallahad', 'Camelot')
'Sir Gallahad of Camelot'
@end example

Formerly, the string would have required numbered fields such as:
@code{'Sir @{0@} of @{1@}'}.

（由 Eric Smith在 bpo-5237@footnote{https://bugs.python.org/issue5237} 中贡献）

@item 
The @code{string.maketrans()} function is deprecated and is replaced by new
static methods, @ref{c02,,bytes.maketrans()} and @ref{c03,,bytearray.maketrans()}.
This change solves the confusion around which types were supported by the
@ref{f6,,string} module. Now, @ref{329,,str}, @ref{32a,,bytes}, and
@ref{32b,,bytearray} each have their own @strong{maketrans} and @strong{translate}
methods with intermediate translation tables of the appropriate type.

（由Georg Brandl在 bpo-5675@footnote{https://bugs.python.org/issue5675} 中贡献）

@item 
The syntax of the @ref{6e3,,with} statement now allows multiple context
managers in a single statement:

@example
>>> with open('mylog.txt') as infile, open('a.out', 'w') as outfile:
...     for line in infile:
...         if '<critical>' in line:
...             outfile.write(line)
@end example

With the new syntax, the @code{contextlib.nested()} function is no longer
needed and is now deprecated.

(Contributed by Georg Brandl and Mattias Brändström;
appspot issue 53094@footnote{https://codereview.appspot.com/53094}.)

@item 
@code{round(x, n)} now returns an integer if @emph{x} is an integer.
Previously it returned a float:

@example
>>> round(1123, -2)
1100
@end example

（由 Mark Dickinson在 bpo-4707@footnote{https://bugs.python.org/issue4707} 贡献）

@item 
Python now uses David Gay's algorithm for finding the shortest floating
point representation that doesn't change its value.  This should help
mitigate some of the confusion surrounding binary floating point
numbers.

The significance is easily seen with a number like @code{1.1} which does not
have an exact equivalent in binary floating point.  Since there is no exact
equivalent, an expression like @code{float('1.1')} evaluates to the nearest
representable value which is @code{0x1.199999999999ap+0} in hex or
@code{1.100000000000000088817841970012523233890533447265625} in decimal. That
nearest value was and still is used in subsequent floating point
calculations.

What is new is how the number gets displayed.  Formerly, Python used a
simple approach.  The value of @code{repr(1.1)} was computed as @code{format(1.1,
'.17g')} which evaluated to @code{'1.1000000000000001'}. The advantage of
using 17 digits was that it relied on IEEE-754 guarantees to assure that
@code{eval(repr(1.1))} would round-trip exactly to its original value.  The
disadvantage is that many people found the output to be confusing (mistaking
intrinsic limitations of binary floating point representation as being a
problem with Python itself).

The new algorithm for @code{repr(1.1)} is smarter and returns @code{'1.1'}.
Effectively, it searches all equivalent string representations (ones that
get stored with the same underlying float value) and returns the shortest
representation.

The new algorithm tends to emit cleaner representations when possible, but
it does not change the underlying values.  So, it is still the case that
@code{1.1 + 2.2 != 3.3} even though the representations may suggest otherwise.

The new algorithm depends on certain features in the underlying floating
point implementation.  If the required features are not found, the old
algorithm will continue to be used.  Also, the text pickle protocols
assure cross-platform portability by using the old algorithm.

（由 Eric Smith 和 Mark Dickinson 在 bpo-1580@footnote{https://bugs.python.org/issue1580} 贡献）
@end itemize

@node 新增，改进和弃用的模块<2>,性能优化<7>,其他语言特性修改<8>,Python 3 1 有什么新变化
@anchor{whatsnew/3 1 new-improved-and-deprecated-modules}@anchor{c11}
@subsection 新增，改进和弃用的模块



@itemize *

@item 
Added a @ref{9d4,,collections.Counter} class to support convenient
counting of unique items in a sequence or iterable:

@example
>>> Counter(['red', 'blue', 'red', 'green', 'blue', 'blue'])
Counter(@{'blue': 3, 'red': 2, 'green': 1@})
@end example

（由 Raymond Hettinger 在 bpo-1696199@footnote{https://bugs.python.org/issue1696199} 中贡献。）

@item 
Added a new module, @ref{10f,,tkinter.ttk} for access to the Tk themed widget set.
The basic idea of ttk is to separate, to the extent possible, the code
implementing a widget's behavior from the code implementing its appearance.

（由 Guilherme Polo 在 bpo-2983@footnote{https://bugs.python.org/issue2983} 中贡献。）

@item 
The @ref{6d7,,gzip.GzipFile} and @ref{92b,,bz2.BZ2File} classes now support
the context management protocol:

@example
>>> # Automatically close file after writing
>>> with gzip.GzipFile(filename, "wb") as f:
...     f.write(b"xxx")
@end example

（由 Antoine Pitrou 贡献。）

@item 
The @ref{36,,decimal} module now supports methods for creating a
decimal object from a binary @ref{187,,float}.  The conversion is
exact but can sometimes be surprising:

@example
>>> Decimal.from_float(1.1)
Decimal('1.100000000000000088817841970012523233890533447265625')
@end example

The long decimal result shows the actual binary fraction being
stored for @emph{1.1}.  The fraction has many digits because @emph{1.1} cannot
be exactly represented in binary.

（由Raymond Hettinger 和 Mark Dickinson贡献。）

@item 
The @ref{a3,,itertools} module grew two new functions.  The
@ref{c12,,itertools.combinations_with_replacement()} function is one of
four for generating combinatorics including permutations and Cartesian
products.  The @ref{c13,,itertools.compress()} function mimics its namesake
from APL.  Also, the existing @ref{c14,,itertools.count()} function now has
an optional @emph{step} argument and can accept any type of counting
sequence including @ref{185,,fractions.Fraction} and
@ref{188,,decimal.Decimal}:

@example
>>> [p+q for p,q in combinations_with_replacement('LOVE', 2)]
['LL', 'LO', 'LV', 'LE', 'OO', 'OV', 'OE', 'VV', 'VE', 'EE']

>>> list(compress(data=range(10), selectors=[0,0,1,1,0,1,0,1,0,0]))
[2, 3, 5, 7]

>>> c = count(start=Fraction(1,2), step=Fraction(1,6))
>>> [next(c), next(c), next(c), next(c)]
[Fraction(1, 2), Fraction(2, 3), Fraction(5, 6), Fraction(1, 1)]
@end example

（由 Raymond Hettinger 贡献。）

@item 
@ref{1b6,,collections.namedtuple()} now supports a keyword argument
@emph{rename} which lets invalid fieldnames be automatically converted to
positional names in the form _0, _1, etc.  This is useful when
the field names are being created by an external source such as a
CSV header, SQL field list, or user input:

@example
>>> query = input()
SELECT region, dept, count(*) FROM main GROUPBY region, dept

>>> cursor.execute(query)
>>> query_fields = [desc[0] for desc in cursor.description]
>>> UserQuery = namedtuple('UserQuery', query_fields, rename=True)
>>> pprint.pprint([UserQuery(*row) for row in cursor])
[UserQuery(region='South', dept='Shipping', _2=185),
 UserQuery(region='North', dept='Accounting', _2=37),
 UserQuery(region='West', dept='Sales', _2=419)]
@end example

（由 Raymond Hettinger 在 bpo-1818@footnote{https://bugs.python.org/issue1818} 中贡献。）

@item 
The @ref{475,,re.sub()}, @ref{72e,,re.subn()} and @ref{3c2,,re.split()} functions now
accept a flags parameter.

（由 Gregory Smith 贡献）

@item 
The @ref{aa,,logging} module now implements a simple @ref{c15,,logging.NullHandler}
class for applications that are not using logging but are calling
library code that does.  Setting-up a null handler will suppress
spurious warnings such as "No handlers could be found for logger foo":

@example
>>> h = logging.NullHandler()
>>> logging.getLogger("foo").addHandler(h)
@end example

（由 Vinay Sajip 在 bpo-4384@footnote{https://bugs.python.org/issue4384} 中贡献。）

@item 
The @ref{e2,,runpy} module which supports the @code{-m} command line switch
now supports the execution of packages by looking for and executing
a @code{__main__} submodule when a package name is supplied.

（由 Andi Vajda 在 bpo-4195@footnote{https://bugs.python.org/issue4195} 中贡献。）

@item 
The @ref{c9,,pdb} module can now access and display source code loaded via
@ref{143,,zipimport} (or any other conformant 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} loader).

（由 Alexander Belopolsky 在 bpo-4201@footnote{https://bugs.python.org/issue4201} 中贡献。）

@item 
@ref{7c2,,functools.partial} objects can now be pickled.
@end itemize

@quotation

(Suggested by Antoine Pitrou and Jesse Noller.  Implemented by
Jack Diederich; bpo-5228@footnote{https://bugs.python.org/issue5228}.)
@end quotation


@itemize *

@item 
Add @ref{d9,,pydoc} help topics for symbols so that @code{help('@@')}
works as expected in the interactive environment.

（由 David Laban 在 bpo-4739@footnote{https://bugs.python.org/issue4739} 中贡献。）

@item 
The @ref{11b,,unittest} module now supports skipping individual tests or classes
of tests. And it supports marking a test as an expected failure, a test that
is known to be broken, but shouldn't be counted as a failure on a
TestResult:

@example
class TestGizmo(unittest.TestCase):

    @@unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
    def test_gizmo_on_windows(self):
        ...

    @@unittest.expectedFailure
    def test_gimzo_without_required_library(self):
        ...
@end example

Also, tests for exceptions have been builtout to work with context managers
using the @ref{6e3,,with} statement:

@example
def test_division_by_zero(self):
    with self.assertRaises(ZeroDivisionError):
        x / 0
@end example

In addition, several new assertion methods were added including
@code{assertSetEqual()}, @code{assertDictEqual()},
@code{assertDictContainsSubset()}, @code{assertListEqual()},
@code{assertTupleEqual()}, @code{assertSequenceEqual()},
@code{assertRaisesRegexp()}, @code{assertIsNone()},
and @code{assertIsNotNone()}.

（由Benjamin Peterson 和 Antoine Pitrou 贡献。）

@item 
The @ref{a1,,io} module has three new constants for the @code{seek()}
method @code{SEEK_SET}, @code{SEEK_CUR}, and @code{SEEK_END}.

@item 
The @ref{b13,,sys.version_info} tuple is now a named tuple:

@example
>>> sys.version_info
sys.version_info(major=3, minor=1, micro=0, releaselevel='alpha', serial=2)
@end example

（由 Ross Light 在 bpo-4285@footnote{https://bugs.python.org/issue4285} 中贡献。）

@item 
The @ref{c0,,nntplib} and @ref{98,,imaplib} modules now support IPv6.

（由 Derek Morr 在 bpo-1655@footnote{https://bugs.python.org/issue1655} 和 bpo-1664@footnote{https://bugs.python.org/issue1664} 中贡献。）

@item 
The @ref{ca,,pickle} module has been adapted for better interoperability with
Python 2.x when used with protocol 2 or lower.  The reorganization of the
standard library changed the formal reference for many objects.  For
example, @code{__builtin__.set} in Python 2 is called @code{builtins.set} in Python
3. This change confounded efforts to share data between different versions of
Python.  But now when protocol 2 or lower is selected, the pickler will
automatically use the old Python 2 names for both loading and dumping. This
remapping is turned-on by default but can be disabled with the @emph{fix_imports}
option:

@example
>>> s = @{1, 2, 3@}
>>> pickle.dumps(s, protocol=0)
b'c__builtin__\nset\np0\n((lp1\nL1L\naL2L\naL3L\natp2\nRp3\n.'
>>> pickle.dumps(s, protocol=0, fix_imports=False)
b'cbuiltins\nset\np0\n((lp1\nL1L\naL2L\naL3L\natp2\nRp3\n.'
@end example

An unfortunate but unavoidable side-effect of this change is that protocol 2
pickles produced by Python 3.1 won't be readable with Python 3.0. The latest
pickle protocol, protocol 3, should be used when migrating data between
Python 3.x implementations, as it doesn't attempt to remain compatible with
Python 2.x.

（由 Alexandre Vassalotti 和 Antoine Pitrou 在 bpo-6137@footnote{https://bugs.python.org/issue6137} 中贡献。）

@item 
A new module, @ref{9b,,importlib} was added.  It provides a complete, portable,
pure Python reference implementation of the @ref{c16,,import} statement and its
counterpart, the @ref{60b,,__import__()} function.  It represents a substantial
step forward in documenting and defining the actions that take place during
imports.

（由 Brett Cannon 贡献。）
@end itemize

@node 性能优化<7>,IDLE<2>,新增，改进和弃用的模块<2>,Python 3 1 有什么新变化
@anchor{whatsnew/3 1 optimizations}@anchor{c17}
@subsection 性能优化


Major performance enhancements have been added:


@itemize *

@item 
The new I/O library (as defined in 
@geindex Python 提高建议; PEP 3116
PEP 3116@footnote{https://www.python.org/dev/peps/pep-3116}) was mostly written in
Python and quickly proved to be a problematic bottleneck in Python 3.0.
In Python 3.1, the I/O library has been entirely rewritten in C and is
2 to 20 times faster depending on the task at hand. The pure Python
version is still available for experimentation purposes through
the @code{_pyio} module.

（由 Amaury Forgeot d'Arc 和 Antoine Pitrou 贡献。）

@item 
Added a heuristic so that tuples and dicts containing only untrackable objects
are not tracked by the garbage collector. This can reduce the size of
collections and therefore the garbage collection overhead on long-running
programs, depending on their particular use of datatypes.

（由 Antoine Pitrou 在 bpo-4688@footnote{https://bugs.python.org/issue4688} 中贡献。）

@item 
Enabling a configure option named @code{--with-computed-gotos}
on compilers that support it (notably: gcc, SunPro, icc), the bytecode
evaluation loop is compiled with a new dispatch mechanism which gives
speedups of up to 20%, depending on the system, the compiler, and
the benchmark.

（由 Antoine Pitrou 以及其他一些参与者在 bpo-4753@footnote{https://bugs.python.org/issue4753} 中贡献。）

@item 
The decoding of UTF-8, UTF-16 and LATIN-1 is now two to four times
faster.

（由 Antoine Pitrou 和 Amaury Forgeot d'Arc 在 bpo-4868@footnote{https://bugs.python.org/issue4868} 中贡献。）

@item 
The @ref{a4,,json} module now has a C extension to substantially improve
its performance.  In addition, the API was modified so that json works
only with @ref{329,,str}, not with @ref{32a,,bytes}.  That change makes the
module closely match the JSON specification@footnote{http://json.org/}
which is defined in terms of Unicode.

（由 Bob Ippolito 在 bpo-4136@footnote{https://bugs.python.org/issue4136} 中贡献。并由 Antoine Pitrou 和 Benjamin Peterson 转换为Py3.1）

@item 
Unpickling now interns the attribute names of pickled objects.  This saves
memory and allows pickles to be smaller.

（由 Jake McGuire 和 Antoine Pitrou 在 bpo-5084@footnote{https://bugs.python.org/issue5084} 中贡献。）
@end itemize

@node IDLE<2>,构建和 C API 的改变<6>,性能优化<7>,Python 3 1 有什么新变化
@anchor{whatsnew/3 1 idle}@anchor{c18}
@subsection IDLE



@itemize *

@item 
IDLE's format menu now provides an option to strip trailing whitespace
from a source file.

（由 Roger D. Serwy 在 bpo-5150@footnote{https://bugs.python.org/issue5150} 中贡献。）
@end itemize

@node 构建和 C API 的改变<6>,移植到 Python 3 1,IDLE<2>,Python 3 1 有什么新变化
@anchor{whatsnew/3 1 build-and-c-api-changes}@anchor{c19}
@subsection 构建和 C API 的改变


Changes to Python's build process and to the C API include:


@itemize *

@item 
Integers are now stored internally either in base 2**15 or in base
2**30, the base being determined at build time.  Previously, they
were always stored in base 2**15.  Using base 2**30 gives
significant performance improvements on 64-bit machines, but
benchmark results on 32-bit machines have been mixed.  Therefore,
the default is to use base 2**30 on 64-bit machines and base 2**15
on 32-bit machines; on Unix, there's a new configure option
@code{--enable-big-digits} that can be used to override this default.

Apart from the performance improvements this change should be invisible to
end users, with one exception: for testing and debugging purposes there's a
new @ref{c1a,,sys.int_info} that provides information about the
internal format, giving the number of bits per digit and the size in bytes
of the C type used to store each digit:

@example
>>> import sys
>>> sys.int_info
sys.int_info(bits_per_digit=30, sizeof_digit=4)
@end example

（由 Mark Dickinson在 bpo-4258@footnote{https://bugs.python.org/issue4258} 贡献）

@item 
The @ref{c1b,,PyLong_AsUnsignedLongLong()} function now handles a negative
@emph{pylong} by raising @ref{95a,,OverflowError} instead of @ref{192,,TypeError}.

（由 Mark Dickinson 和 Lisandro Dalcrin 在 bpo-5175@footnote{https://bugs.python.org/issue5175} 中贡献。）

@item 
Deprecated @code{PyNumber_Int()}.  Use @ref{26c,,PyNumber_Long()} instead.

（由 Mark Dickinson在 bpo-4910@footnote{https://bugs.python.org/issue4910} 贡献）

@item 
Added a new @ref{c1c,,PyOS_string_to_double()} function to replace the
deprecated functions @code{PyOS_ascii_strtod()} and @code{PyOS_ascii_atof()}.

（由 Mark Dickinson 在 bpo-5914@footnote{https://bugs.python.org/issue5914} 贡献）

@item 
Added @ref{c00,,PyCapsule} as a replacement for the @code{PyCObject} API.
The principal difference is that the new type has a well defined interface
for passing typing safety information and a less complicated signature
for calling a destructor.  The old type had a problematic API and is now
deprecated.

（由 Larry Hastings 在 bpo-5630@footnote{https://bugs.python.org/issue5630} 中贡献。）
@end itemize

@node 移植到 Python 3 1,,构建和 C API 的改变<6>,Python 3 1 有什么新变化
@anchor{whatsnew/3 1 porting-to-python-3-1}@anchor{c1d}
@subsection 移植到 Python 3.1


This section lists previously described changes and other bugfixes
that may require changes to your code:


@itemize *

@item 
The new floating point string representations can break existing doctests.
For example:

@example
def e():
    '@w{'}'Compute the base of natural logarithms.

    >>> e()
    2.7182818284590451

    '@w{'}'
    return sum(1/math.factorial(x) for x in reversed(range(30)))

doctest.testmod()

**********************************************************************
Failed example:
    e()
Expected:
    2.7182818284590451
Got:
    2.718281828459045
**********************************************************************
@end example

@item 
The automatic name remapping in the pickle module for protocol 2 or lower can
make Python 3.1 pickles unreadable in Python 3.0.  One solution is to use
protocol 3.  Another solution is to set the @emph{fix_imports} option to @code{False}.
See the discussion above for more details.
@end itemize

@node Python 3 0 有什么新变化,Python 2 7 有什么新变化,Python 3 1 有什么新变化,Python的新变化
@anchor{whatsnew/3 0 doc}@anchor{c1e}@anchor{whatsnew/3 0 what-s-new-in-python-3-0}@anchor{c1f}
@section Python 3.0 有什么新变化


@c XXX Add trademark info for Apple, Microsoft.

@*作者: 
Guido van Rossum


@c $Id$
@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.  (Note: I didn't get to this for 3.0.
@c GvR.)
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.  (Due to time
@c constraints I haven't managed to do this for 3.0.  GvR.)
@c 
@c * It's helpful to add the bug/patch number as a comment:
@c 
@c % Patch 12345
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer.)
@c 
@c This saves the maintainer the effort of going through the SVN log
@c when researching a change.  (Again, I didn't get to this for 3.0.
@c GvR.)

This article explains the new features in Python 3.0, compared to 2.6.
Python 3.0, also known as "Python 3000" or "Py3K", is the first ever
@emph{intentionally backwards incompatible} Python release.  There are more
changes than in a typical release, and more that are important for all
Python users.  Nevertheless, after digesting the changes, you'll find
that Python really hasn't changed all that much -- by and large, we're
mostly fixing well-known annoyances and warts, and removing a lot of
old cruft.

This article doesn't attempt to provide a complete specification of
all new features, but instead tries to give a convenient overview.
For full details, you should refer to the documentation for Python
3.0, and/or the many PEPs referenced in the text. If you want to
understand the complete implementation and design rationale for a
particular feature, PEPs usually have more details than the regular
documentation; but note that PEPs usually are not kept up-to-date once
a feature has been fully implemented.

Due to time constraints this document is not as complete as it should
have been.  As always for a new release, the @code{Misc/NEWS} file in the
source distribution contains a wealth of detailed information about
every small thing that was changed.

@c Compare with previous release in 2 - 3 sentences here.

@c add hyperlink when the documentation becomes available online.

@c ======================================================================

@c Large, PEP-level features and changes should be described here.

@c Should there be a new section here for 3k migration?

@c Or perhaps a more general section describing module changes/deprecation?

@c sets module deprecated

@c ======================================================================

@menu
* 常见的绊脚石:: 
* Overview Of Syntax Changes:: 
* Changes Already Present In Python 2.6: Changes Already Present In Python 2 6. 
* Library Changes:: 
* PEP 3101; A New Approach To String Formatting: PEP 3101 A New Approach To String Formatting. 
* Changes To Exceptions:: 
* Miscellaneous Other Changes:: 
* 构建和 C API 的改变: 构建和 C API 的改变<7>. 
* 性能:: 
* 移植到 Python 3.0: 移植到 Python 3 0. 

@end menu

@node 常见的绊脚石,Overview Of Syntax Changes,,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 common-stumbling-blocks}@anchor{c20}
@subsection 常见的绊脚石


This section lists those few changes that are most likely to trip you
up if you're used to Python 2.5.

@menu
* Print Is A Function:: 
* Views And Iterators Instead Of Lists:: 
* Ordering Comparisons:: 
* 整数:: 
* Text Vs. Data Instead Of Unicode Vs. 8-bit: Text Vs Data Instead Of Unicode Vs 8-bit. 

@end menu

@node Print Is A Function,Views And Iterators Instead Of Lists,,常见的绊脚石
@anchor{whatsnew/3 0 print-is-a-function}@anchor{c21}
@subsubsection Print Is A Function


The @code{print} statement has been replaced with a @ref{880,,print()}
function, with keyword arguments to replace most of the special syntax
of the old @code{print} statement (
@geindex Python 提高建议; PEP 3105
PEP 3105@footnote{https://www.python.org/dev/peps/pep-3105}).  Examples:

@example
Old: print "The answer is", 2*2
New: print("The answer is", 2*2)

Old: print x,           # Trailing comma suppresses newline
New: print(x, end=" ")  # Appends a space instead of a newline

Old: print              # Prints a newline
New: print()            # You must call the function!

Old: print >>sys.stderr, "fatal error"
New: print("fatal error", file=sys.stderr)

Old: print (x, y)       # prints repr((x, y))
New: print((x, y))      # Not the same as print(x, y)!
@end example

You can also customize the separator between items, e.g.:

@example
print("There are <", 2**32, "> possibilities!", sep="")
@end example

which produces:

@example
There are <4294967296> possibilities!
@end example

注意


@itemize *

@item 
The @ref{880,,print()} function doesn't support the "softspace" feature of
the old @code{print} statement.  For example, in Python 2.x,
@code{print "A\n", "B"} would write @code{"A\nB\n"}; but in Python 3.0,
@code{print("A\n", "B")} writes @code{"A\n B\n"}.

@item 
Initially, you'll be finding yourself typing the old @code{print x}
a lot in interactive mode.  Time to retrain your fingers to type
@code{print(x)} instead!

@item 
When using the @code{2to3} source-to-source conversion tool, all
@code{print} statements are automatically converted to
@ref{880,,print()} function calls, so this is mostly a non-issue for
larger projects.
@end itemize

@node Views And Iterators Instead Of Lists,Ordering Comparisons,Print Is A Function,常见的绊脚石
@anchor{whatsnew/3 0 views-and-iterators-instead-of-lists}@anchor{c22}
@subsubsection Views And Iterators Instead Of Lists


Some well-known APIs no longer return lists:


@itemize *

@item 
@ref{1b8,,dict} methods @ref{c23,,dict.keys()}, @ref{c24,,dict.items()} and
@ref{c25,,dict.values()} return "views" instead of lists.  For example,
this no longer works: @code{k = d.keys(); k.sort()}.  Use @code{k =
sorted(d)} instead (this works in Python 2.5 too and is just
as efficient).

@item 
Also, the @code{dict.iterkeys()}, @code{dict.iteritems()} and
@code{dict.itervalues()} methods are no longer supported.

@item 
@ref{c26,,map()} and @ref{c27,,filter()} return iterators.  If you really need
a list and the input sequences are all of equal length, a quick
fix is to wrap @ref{c26,,map()} in @ref{262,,list()}, e.g. @code{list(map(...))},
but a better fix is
often to use a list comprehension (especially when the original code
uses @ref{c28,,lambda}), or rewriting the code so it doesn't need a
list at all.  Particularly tricky is @ref{c26,,map()} invoked for the
side effects of the function; the correct transformation is to use a
regular @ref{c29,,for} loop (since creating a list would just be
wasteful).

If the input sequences are not of equal length, @ref{c26,,map()} will
stop at the termination of the shortest of the sequences. For full
compatibility with @ref{c26,,map()} from Python 2.x, also wrap the sequences in
@ref{c2a,,itertools.zip_longest()}, e.g. @code{map(func, *sequences)} becomes
@code{list(map(func, itertools.zip_longest(*sequences)))}.

@item 
@ref{9b8,,range()} now behaves like @code{xrange()} used to behave, except
it works with values of arbitrary size.  The latter no longer
exists.

@item 
@ref{c2b,,zip()} now returns an iterator.
@end itemize

@node Ordering Comparisons,整数,Views And Iterators Instead Of Lists,常见的绊脚石
@anchor{whatsnew/3 0 ordering-comparisons}@anchor{c2c}
@subsubsection Ordering Comparisons


Python 3.0 has simplified the rules for ordering comparisons:


@itemize *

@item 
The ordering comparison operators (@code{<}, @code{<=}, @code{>=}, @code{>})
raise a TypeError exception when the operands don't have a
meaningful natural ordering.  Thus, expressions like @code{1 < '@w{'}}, @code{0
> None} or @code{len <= len} are no longer valid, and e.g. @code{None <
None} raises @ref{192,,TypeError} instead of returning
@code{False}.  A corollary is that sorting a heterogeneous list
no longer makes sense -- all the elements must be comparable to each
other.  Note that this does not apply to the @code{==} and @code{!=}
operators: objects of different incomparable types always compare
unequal to each other.

@item 
@code{builtin.sorted()} and @ref{43f,,list.sort()} no longer accept the
@emph{cmp} argument providing a comparison function.  Use the @emph{key}
argument instead. N.B. the @emph{key} and @emph{reverse} arguments are now
"keyword-only".

@item 
The @code{cmp()} function should be treated as gone, and the @code{__cmp__()}
special method is no longer supported.  Use @ref{c2d,,__lt__()} for sorting,
@ref{338,,__eq__()} with @ref{339,,__hash__()}, and other rich comparisons as needed.
(If you really need the @code{cmp()} functionality, you could use the
expression @code{(a > b) - (a < b)} as the equivalent for @code{cmp(a, b)}.)
@end itemize

@node 整数,Text Vs Data Instead Of Unicode Vs 8-bit,Ordering Comparisons,常见的绊脚石
@anchor{whatsnew/3 0 integers}@anchor{c2e}
@subsubsection 整数



@itemize *

@item 
@geindex Python 提高建议; PEP 237
PEP 237@footnote{https://www.python.org/dev/peps/pep-0237}: Essentially, @code{long} renamed to @ref{184,,int}.
That is, there is only one built-in integral type, named
@ref{184,,int}; but it behaves mostly like the old @code{long} type.

@item 
@geindex Python 提高建议; PEP 238
PEP 238@footnote{https://www.python.org/dev/peps/pep-0238}: An expression like @code{1/2} returns a float.  Use
@code{1//2} to get the truncating behavior.  (The latter syntax has
existed for years, at least since Python 2.2.)

@item 
The @code{sys.maxint} constant was removed, since there is no
longer a limit to the value of integers.  However, @ref{b3c,,sys.maxsize}
can be used as an integer larger than any practical list or string
index.  It conforms to the implementation's "natural" integer size
and is typically the same as @code{sys.maxint} in previous releases
on the same platform (assuming the same build options).

@item 
The @ref{7c6,,repr()} of a long integer doesn't include the trailing @code{L}
anymore, so code that unconditionally strips that character will
chop off the last digit instead.  (Use @ref{329,,str()} instead.)

@item 
Octal literals are no longer of the form @code{0720}; use @code{0o720}
instead.
@end itemize

@node Text Vs Data Instead Of Unicode Vs 8-bit,,整数,常见的绊脚石
@anchor{whatsnew/3 0 text-vs-data-instead-of-unicode-vs-8-bit}@anchor{c2f}
@subsubsection Text Vs. Data Instead Of Unicode Vs. 8-bit


Everything you thought you knew about binary data and Unicode has
changed.


@itemize *

@item 
Python 3.0 uses the concepts of @emph{text} and (binary) @emph{data} instead
of Unicode strings and 8-bit strings.  All text is Unicode; however
@emph{encoded} Unicode is represented as binary data.  The type used to
hold text is @ref{329,,str}, the type used to hold data is
@ref{32a,,bytes}.  The biggest difference with the 2.x situation is
that any attempt to mix text and data in Python 3.0 raises
@ref{192,,TypeError}, whereas if you were to mix Unicode and 8-bit
strings in Python 2.x, it would work if the 8-bit string happened to
contain only 7-bit (ASCII) bytes, but you would get
@ref{1fd,,UnicodeDecodeError} if it contained non-ASCII values.  This
value-specific behavior has caused numerous sad faces over the
years.

@item 
As a consequence of this change in philosophy, pretty much all code
that uses Unicode, encodings or binary data most likely has to
change.  The change is for the better, as in the 2.x world there
were numerous bugs having to do with mixing encoded and unencoded
text.  To be prepared in Python 2.x, start using @code{unicode}
for all unencoded text, and @ref{329,,str} for binary or encoded data
only.  Then the @code{2to3} tool will do most of the work for you.

@item 
You can no longer use @code{u"..."} literals for Unicode text.
However, you must use @code{b"..."} literals for binary data.

@item 
As the @ref{329,,str} and @ref{32a,,bytes} types cannot be mixed, you
must always explicitly convert between them.  Use @ref{c30,,str.encode()}
to go from @ref{329,,str} to @ref{32a,,bytes}, and @ref{c31,,bytes.decode()}
to go from @ref{32a,,bytes} to @ref{329,,str}.  You can also use
@code{bytes(s, encoding=...)} and @code{str(b, encoding=...)},
respectively.

@item 
Like @ref{329,,str}, the @ref{32a,,bytes} type is immutable.  There is a
separate @emph{mutable} type to hold buffered binary data,
@ref{32b,,bytearray}.  Nearly all APIs that accept @ref{32a,,bytes} also
accept @ref{32b,,bytearray}.  The mutable API is based on
@code{collections.MutableSequence}.

@item 
All backslashes in raw string literals are interpreted literally.
This means that @code{'\U'} and @code{'\u'} escapes in raw strings are not
treated specially.  For example, @code{r'\u20ac'} is a string of 6
characters in Python 3.0, whereas in 2.6, @code{ur'\u20ac'} was the
single "euro" character.  (Of course, this change only affects raw
string literals; the euro character is @code{'\u20ac'} in Python 3.0.)

@item 
The built-in @code{basestring} abstract type was removed.  Use
@ref{329,,str} instead.  The @ref{329,,str} and @ref{32a,,bytes} types
don't have functionality enough in common to warrant a shared base
class.  The @code{2to3} tool (see below) replaces every occurrence of
@code{basestring} with @ref{329,,str}.

@item 
Files opened as text files (still the default mode for @ref{4ea,,open()})
always use an encoding to map between strings (in memory) and bytes
(on disk).  Binary files (opened with a @code{b} in the mode argument)
always use bytes in memory.  This means that if a file is opened
using an incorrect mode or encoding, I/O will likely fail loudly,
instead of silently producing incorrect data.  It also means that
even Unix users will have to specify the correct mode (text or
binary) when opening a file.  There is a platform-dependent default
encoding, which on Unixy platforms can be set with the @code{LANG}
environment variable (and sometimes also with some other
platform-specific locale-related environment variables).  In many
cases, but not all, the system default is UTF-8; you should never
count on this default.  Any application reading or writing more than
pure ASCII text should probably have a way to override the encoding.
There is no longer any need for using the encoding-aware streams
in the @ref{1c,,codecs} module.

@item 
The initial values of @ref{306,,sys.stdin}, @ref{307,,sys.stdout} and
@ref{308,,sys.stderr} are now unicode-only text files (i.e., they are
instances of @ref{c32,,io.TextIOBase}).  To read and write bytes data
with these streams, you need to use their @ref{c33,,io.TextIOBase.buffer}
attribute.

@item 
Filenames are passed to and returned from APIs as (Unicode) strings.
This can present platform-specific problems because on some
platforms filenames are arbitrary byte strings.  (On the other hand,
on Windows filenames are natively stored as Unicode.)  As a
work-around, most APIs (e.g. @ref{4ea,,open()} and many functions in the
@ref{c4,,os} module) that take filenames accept @ref{32a,,bytes} objects
as well as strings, and a few APIs have a way to ask for a
@ref{32a,,bytes} return value.  Thus, @ref{a3c,,os.listdir()} returns a
list of @ref{32a,,bytes} instances if the argument is a @ref{32a,,bytes}
instance, and @ref{2b8,,os.getcwdb()} returns the current working
directory as a @ref{32a,,bytes} instance.  Note that when
@ref{a3c,,os.listdir()} returns a list of strings, filenames that
cannot be decoded properly are omitted rather than raising
@ref{c34,,UnicodeError}.

@item 
Some system APIs like @ref{b30,,os.environ} and @ref{bf4,,sys.argv} can
also present problems when the bytes made available by the system is
not interpretable using the default encoding.  Setting the @code{LANG}
variable and rerunning the program is probably the best approach.

@item 
@geindex Python 提高建议; PEP 3138
PEP 3138@footnote{https://www.python.org/dev/peps/pep-3138}: The @ref{7c6,,repr()} of a string no longer escapes
non-ASCII characters.  It still escapes control characters and code
points with non-printable status in the Unicode standard, however.

@item 
@geindex Python 提高建议; PEP 3120
PEP 3120@footnote{https://www.python.org/dev/peps/pep-3120}: The default source encoding is now UTF-8.

@item 
@geindex Python 提高建议; PEP 3131
PEP 3131@footnote{https://www.python.org/dev/peps/pep-3131}: Non-ASCII letters are now allowed in identifiers.
(However, the standard library remains ASCII-only with the exception
of contributor names in comments.)

@item 
The @code{StringIO} and @code{cStringIO} modules are gone.  Instead,
import the @ref{a1,,io} module and use @ref{827,,io.StringIO} or
@ref{795,,io.BytesIO} for text and data respectively.

@item 
See also the @ref{c35,,Unicode 指南}, which was updated for Python 3.0.
@end itemize

@node Overview Of Syntax Changes,Changes Already Present In Python 2 6,常见的绊脚石,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 overview-of-syntax-changes}@anchor{c36}
@subsection Overview Of Syntax Changes


This section gives a brief overview of every @emph{syntactic} change in
Python 3.0.

@menu
* 新语法:: 
* 修改的语法:: 
* 移除的语法:: 

@end menu

@node 新语法,修改的语法,,Overview Of Syntax Changes
@anchor{whatsnew/3 0 new-syntax}@anchor{c37}
@subsubsection 新语法



@itemize *

@item 
@geindex Python 提高建议; PEP 3107
PEP 3107@footnote{https://www.python.org/dev/peps/pep-3107}: Function argument and return value annotations.  This
provides a standardized way of annotating a function's parameters
and return value.  There are no semantics attached to such
annotations except that they can be introspected at runtime using
the @code{__annotations__} attribute.  The intent is to encourage
experimentation through metaclasses, decorators or frameworks.

@item 
@geindex Python 提高建议; PEP 3102
PEP 3102@footnote{https://www.python.org/dev/peps/pep-3102}: Keyword-only arguments.  Named parameters occurring
after @code{*args} in the parameter list @emph{must} be specified using
keyword syntax in the call.  You can also use a bare @code{*} in the
parameter list to indicate that you don't accept a variable-length
argument list, but you do have keyword-only arguments.

@item 
Keyword arguments are allowed after the list of base classes in a
class definition.  This is used by the new convention for specifying
a metaclass (see next section), but can be used for other purposes
as well, as long as the metaclass supports it.

@item 
@geindex Python 提高建议; PEP 3104
PEP 3104@footnote{https://www.python.org/dev/peps/pep-3104}: @ref{c38,,nonlocal} statement.  Using @code{nonlocal x}
you can now assign directly to a variable in an outer (but
non-global) scope.  @code{nonlocal} is a new reserved word.

@item 
@geindex Python 提高建议; PEP 3132
PEP 3132@footnote{https://www.python.org/dev/peps/pep-3132}: Extended Iterable Unpacking.  You can now write things
like @code{a, b, *rest = some_sequence}.  And even @code{*rest, a =
stuff}.  The @code{rest} object is always a (possibly empty) list; the
right-hand side may be any iterable.  Example:

@example
(a, *rest, b) = range(5)
@end example

This sets @emph{a} to @code{0}, @emph{b} to @code{4}, and @emph{rest} to @code{[1, 2, 3]}.

@item 
Dictionary comprehensions: @code{@{k: v for k, v in stuff@}} means the
same thing as @code{dict(stuff)} but is more flexible.  (This is
@geindex Python 提高建议; PEP 274
PEP 274@footnote{https://www.python.org/dev/peps/pep-0274} vindicated. :-)

@item 
Set literals, e.g. @code{@{1, 2@}}.  Note that @code{@{@}} is an empty
dictionary; use @code{set()} for an empty set.  Set comprehensions are
also supported; e.g., @code{@{x for x in stuff@}} means the same thing as
@code{set(stuff)} but is more flexible.

@item 
New octal literals, e.g. @code{0o720} (already in 2.6).  The old octal
literals (@code{0720}) are gone.

@item 
New binary literals, e.g. @code{0b1010} (already in 2.6), and
there is a new corresponding built-in function, @ref{c39,,bin()}.

@item 
Bytes literals are introduced with a leading @code{b} or @code{B}, and
there is a new corresponding built-in function, @ref{32a,,bytes()}.
@end itemize

@node 修改的语法,移除的语法,新语法,Overview Of Syntax Changes
@anchor{whatsnew/3 0 changed-syntax}@anchor{c3a}
@subsubsection 修改的语法



@itemize *

@item 
@geindex Python 提高建议; PEP 3109
PEP 3109@footnote{https://www.python.org/dev/peps/pep-3109} and 
@geindex Python 提高建议; PEP 3134
PEP 3134@footnote{https://www.python.org/dev/peps/pep-3134}: new @ref{c3b,,raise} statement syntax:
@code{raise [@emph{expr} [from @emph{expr}]]}.  See below.

@item 
@code{as} and @ref{6e3,,with} are now reserved words.  (Since
2.6, actually.)

@item 
@code{True}, @code{False}, and @code{None} are reserved words.  (2.6 partially enforced
the restrictions on @code{None} already.)

@item 
Change from @ref{b37,,except} @emph{exc}, @emph{var} to
@code{except} @emph{exc} @code{as} @emph{var}.  See 
@geindex Python 提高建议; PEP 3110
PEP 3110@footnote{https://www.python.org/dev/peps/pep-3110}.

@item 
@geindex Python 提高建议; PEP 3115
PEP 3115@footnote{https://www.python.org/dev/peps/pep-3115}: New Metaclass Syntax.  Instead of:

@example
class C:
    __metaclass__ = M
    ...
@end example

you must now use:

@example
class C(metaclass=M):
    ...
@end example

The module-global @code{__metaclass__} variable is no longer
supported.  (It was a crutch to make it easier to default to
new-style classes without deriving every class from
@ref{2b0,,object}.)

@item 
List comprehensions no longer support the syntactic form
@code{[... for @emph{var} in @emph{item1}, @emph{item2}, ...]}.  Use
@code{[... for @emph{var} in (@emph{item1}, @emph{item2}, ...)]} instead.
Also note that list comprehensions have different semantics: they
are closer to syntactic sugar for a generator expression inside a
@ref{262,,list()} constructor, and in particular the loop control
variables are no longer leaked into the surrounding scope.

@item 
The @emph{ellipsis} (@code{...}) can be used as an atomic expression
anywhere.  (Previously it was only allowed in slices.)  Also, it
@emph{must} now be spelled as @code{...}.  (Previously it could also be
spelled as @code{. . .}, by a mere accident of the grammar.)
@end itemize

@node 移除的语法,,修改的语法,Overview Of Syntax Changes
@anchor{whatsnew/3 0 removed-syntax}@anchor{c3c}
@subsubsection 移除的语法



@itemize *

@item 
@geindex Python 提高建议; PEP 3113
PEP 3113@footnote{https://www.python.org/dev/peps/pep-3113}: Tuple parameter unpacking removed.  You can no longer
write @code{def foo(a, (b, c)): ...}.
Use @code{def foo(a, b_c): b, c = b_c} instead.

@item 
Removed backticks (use @ref{7c6,,repr()} instead).

@item 
Removed @code{<>} (use @code{!=} instead).

@item 
Removed keyword: @ref{c3d,,exec()} is no longer a keyword; it remains as
a function.  (Fortunately the function syntax was also accepted in
2.x.)  Also note that @ref{c3d,,exec()} no longer takes a stream argument;
instead of @code{exec(f)} you can use @code{exec(f.read())}.

@item 
Integer literals no longer support a trailing @code{l} or @code{L}.

@item 
String literals no longer support a leading @code{u} or @code{U}.

@item 
The @ref{c3e,,from} @emph{module} @ref{c16,,import} @code{*} syntax is only
allowed at the module level, no longer inside functions.

@item 
The only acceptable syntax for relative imports is @code{from .[@emph{module}]
import @emph{name}}.  All @ref{c16,,import} forms not starting with @code{.} are
interpreted as absolute imports.  (
@geindex Python 提高建议; PEP 328
PEP 328@footnote{https://www.python.org/dev/peps/pep-0328})

@item 
Classic classes are gone.
@end itemize

@node Changes Already Present In Python 2 6,Library Changes,Overview Of Syntax Changes,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 changes-already-present-in-python-2-6}@anchor{c3f}
@subsection Changes Already Present In Python 2.6


Since many users presumably make the jump straight from Python 2.5 to
Python 3.0, this section reminds the reader of new features that were
originally designed for Python 3.0 but that were back-ported to Python
2.6.  The corresponding sections in @ref{c40,,Python 2.6 有什么新变化} should be
consulted for longer descriptions.


@itemize *

@item 
@ref{c41,,PEP 343; "with" 语句}.  The @ref{6e3,,with} statement is now a standard
feature and no longer needs to be imported from the @ref{0,,__future__}.
Also check out @ref{c42,,Writing Context Managers} and
@ref{c43,,contextlib 模块}.

@item 
@ref{c44,,PEP 366; 从主模块显式相对导入}.  This enhances the usefulness of the @ref{330,,-m}
option when the referenced module lives in a package.

@item 
@ref{c45,,PEP 370; 分用户的 site-packages 目录}.

@item 
@ref{c46,,PEP 371; 多任务处理包}.

@item 
@ref{c47,,PEP 3101; 高级字符串格式}.  Note: the 2.6 description mentions the
@ref{4d5,,format()} method for both 8-bit and Unicode strings.  In 3.0,
only the @ref{329,,str} type (text strings with Unicode support)
supports this method; the @ref{32a,,bytes} type does not.  The plan is
to eventually make this the only API for string formatting, and to
start deprecating the @code{%} operator in Python 3.1.

@item 
@ref{c48,,PEP 3105; print 改为函数}.  This is now a standard feature and no longer needs
to be imported from @ref{0,,__future__}.  More details were given above.

@item 
@ref{c49,,PEP 3110; 异常处理的变更}.  The @ref{b37,,except} @emph{exc} @code{as} @emph{var}
syntax is now standard and @code{except} @emph{exc}, @emph{var} is no
longer supported.  (Of course, the @code{as} @emph{var} part is still
optional.)

@item 
@ref{c4a,,PEP 3112; 字节字面值}.  The @code{b"..."} string literal notation (and its
variants like @code{b'...'}, @code{b"""..."""}, and @code{br"..."}) now
produces a literal of type @ref{32a,,bytes}.

@item 
@ref{c4b,,PEP 3116; 新 I/O 库}.  The @ref{a1,,io} module is now the standard way of
doing file I/O.  The built-in @ref{4ea,,open()} function is now an
alias for @ref{654,,io.open()} and has additional keyword arguments
@emph{encoding}, @emph{errors}, @emph{newline} and @emph{closefd}.  Also note that an
invalid @emph{mode} argument now raises @ref{1fb,,ValueError}, not
@ref{98c,,IOError}.  The binary file object underlying a text file
object can be accessed as @code{f.buffer} (but beware that the
text object maintains a buffer of itself in order to speed up
the encoding and decoding operations).

@item 
@ref{c4c,,PEP 3118; 修改缓冲区协议}.  The old builtin @code{buffer()} is now really gone;
the new builtin @ref{25c,,memoryview()} provides (mostly) similar
functionality.

@item 
@ref{c4d,,PEP 3119; 抽象基类}.  The @ref{4,,abc} module and the ABCs defined in the
@ref{1e,,collections} module plays a somewhat more prominent role in
the language now, and built-in collection types like @ref{1b8,,dict}
and @ref{262,,list} conform to the @code{collections.MutableMapping}
and @code{collections.MutableSequence} ABCs, respectively.

@item 
@ref{c4e,,PEP 3127; 整型文字支持和语法}.  As mentioned above, the new octal literal
notation is the only one supported, and binary literals have been
added.

@item 
@ref{c4f,,PEP 3129; 类装饰器}.

@item 
@ref{c50,,PEP 3141; A Type Hierarchy for Numbers}.  The @ref{c1,,numbers} module is another new use of
ABCs, defining Python's "numeric tower".  Also note the new
@ref{83,,fractions} module which implements @ref{c51,,numbers.Rational}.
@end itemize

@node Library Changes,PEP 3101 A New Approach To String Formatting,Changes Already Present In Python 2 6,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 library-changes}@anchor{c52}
@subsection Library Changes


Due to time constraints, this document does not exhaustively cover the
very extensive changes to the standard library.  
@geindex Python 提高建议; PEP 3108
PEP 3108@footnote{https://www.python.org/dev/peps/pep-3108} is the
reference for the major changes to the library.  Here's a capsule
review:


@itemize *

@item 
Many old modules were removed.  Some, like @code{gopherlib} (no
longer used) and @code{md5} (replaced by @ref{8d,,hashlib}), were
already deprecated by 
@geindex Python 提高建议; PEP 4
PEP 4@footnote{https://www.python.org/dev/peps/pep-0004}.  Others were removed as a result
of the removal of support for various platforms such as Irix, BeOS
and Mac OS 9 (see 
@geindex Python 提高建议; PEP 11
PEP 11@footnote{https://www.python.org/dev/peps/pep-0011}).  Some modules were also selected for
removal in Python 3.0 due to lack of use or because a better
replacement exists.  See 
@geindex Python 提高建议; PEP 3108
PEP 3108@footnote{https://www.python.org/dev/peps/pep-3108} for an exhaustive list.

@item 
The @code{bsddb3} package was removed because its presence in the
core standard library has proved over time to be a particular burden
for the core developers due to testing instability and Berkeley DB's
release schedule.  However, the package is alive and well,
externally maintained at @indicateurl{https://www.jcea.es/programacion/pybsddb.htm}.

@item 
Some modules were renamed because their old name disobeyed
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008}, or for various other reasons.  Here's the list:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

旧名称

@tab

新名称

@item

_winreg

@tab

winreg

@item

ConfigParser

@tab

configparser

@item

copy_reg

@tab

copyreg

@item

Queue

@tab

queue

@item

SocketServer

@tab

socketserver

@item

markupbase

@tab

_markupbase

@item

repr

@tab

reprlib

@item

test.test_support

@tab

test.support

@end multitable


@item 
A common pattern in Python 2.x is to have one version of a module
implemented in pure Python, with an optional accelerated version
implemented as a C extension; for example, @ref{ca,,pickle} and
@code{cPickle}.  This places the burden of importing the accelerated
version and falling back on the pure Python version on each user of
these modules.  In Python 3.0, the accelerated versions are
considered implementation details of the pure Python versions.
Users should always import the standard version, which attempts to
import the accelerated version and falls back to the pure Python
version.  The @ref{ca,,pickle} / @code{cPickle} pair received this
treatment.  The @ref{d3,,profile} module is on the list for 3.1.  The
@code{StringIO} module has been turned into a class in the @ref{a1,,io}
module.

@item 
Some related modules have been grouped into packages, and usually
the submodule names have been simplified.  The resulting new
packages are:


@itemize *

@item 
@ref{32,,dbm} (@code{anydbm}, @code{dbhash}, @ref{32,,dbm},
@code{dumbdbm}, @code{gdbm}, @code{whichdb}).

@item 
@ref{90,,html} (@code{HTMLParser}, @code{htmlentitydefs}).

@item 
@ref{93,,http} (@code{httplib}, @code{BaseHTTPServer},
@code{CGIHTTPServer}, @code{SimpleHTTPServer}, @code{Cookie},
@code{cookielib}).

@item 
@ref{10c,,tkinter} (all @code{Tkinter}-related modules except
@ref{116,,turtle}).  The target audience of @ref{116,,turtle} doesn't
really care about @ref{10c,,tkinter}.  Also note that as of Python
2.6, the functionality of @ref{116,,turtle} has been greatly enhanced.

@item 
@ref{11d,,urllib} (@ref{11d,,urllib}, @code{urllib2}, @code{urlparse},
@code{robotparse}).

@item 
@code{xmlrpc} (@code{xmlrpclib}, @code{DocXMLRPCServer},
@code{SimpleXMLRPCServer}).
@end itemize
@end itemize

Some other changes to standard library modules, not covered by
@geindex Python 提高建议; PEP 3108
PEP 3108@footnote{https://www.python.org/dev/peps/pep-3108}:


@itemize *

@item 
Killed @code{sets}.  Use the built-in @ref{b68,,set()} class.

@item 
Cleanup of the @ref{fd,,sys} module: removed @code{sys.exitfunc()},
@code{sys.exc_clear()}, @code{sys.exc_type}, @code{sys.exc_value},
@code{sys.exc_traceback}.  (Note that @ref{c53,,sys.last_type}
etc. remain.)

@item 
Cleanup of the @ref{44b,,array.array} type: the @code{read()} and
@code{write()} methods are gone; use @code{fromfile()} and
@code{tofile()} instead.  Also, the @code{'c'} typecode for array is
gone -- use either @code{'b'} for bytes or @code{'u'} for Unicode
characters.

@item 
Cleanup of the @ref{c2,,operator} module: removed
@code{sequenceIncludes()} and @code{isCallable()}.

@item 
Cleanup of the @code{thread} module: @code{acquire_lock()} and
@code{release_lock()} are gone; use @code{acquire()} and
@code{release()} instead.

@item 
Cleanup of the @ref{dc,,random} module: removed the @code{jumpahead()} API.

@item 
The @code{new} module is gone.

@item 
The functions @code{os.tmpnam()}, @code{os.tempnam()} and
@code{os.tmpfile()} have been removed in favor of the @ref{103,,tempfile}
module.

@item 
The @ref{111,,tokenize} module has been changed to work with bytes.  The
main entry point is now @ref{c54,,tokenize.tokenize()}, instead of
generate_tokens.

@item 
@code{string.letters} and its friends (@code{string.lowercase} and
@code{string.uppercase}) are gone.  Use
@ref{c55,,string.ascii_letters} etc. instead.  (The reason for the
removal is that @code{string.letters} and friends had
locale-specific behavior, which is a bad idea for such
attractively-named global "constants".)

@item 
Renamed module @code{__builtin__} to @ref{13,,builtins} (removing the
underscores, adding an 's').  The @code{__builtins__} variable
found in most global namespaces is unchanged.  To modify a builtin,
you should use @ref{13,,builtins}, not @code{__builtins__}!
@end itemize

@node PEP 3101 A New Approach To String Formatting,Changes To Exceptions,Library Changes,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 pep-3101-a-new-approach-to-string-formatting}@anchor{c56}
@subsection @strong{PEP 3101}: A New Approach To String Formatting


@geindex Python 提高建议; PEP 3101


@itemize *

@item 
A new system for  built-in string formatting operations replaces the
@code{%} string  formatting operator.   (However, the @code{%}  operator is
still supported;  it will  be deprecated in  Python 3.1  and removed
from the language at some later time.)  Read 
@geindex Python 提高建议; PEP 3101
PEP 3101@footnote{https://www.python.org/dev/peps/pep-3101} for the full
scoop.
@end itemize

@node Changes To Exceptions,Miscellaneous Other Changes,PEP 3101 A New Approach To String Formatting,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 changes-to-exceptions}@anchor{c57}
@subsection Changes To Exceptions


The APIs for raising and catching exception have been cleaned up and
new powerful features added:


@itemize *

@item 
@geindex Python 提高建议; PEP 352
PEP 352@footnote{https://www.python.org/dev/peps/pep-0352}: All exceptions must be derived (directly or indirectly)
from @ref{1a8,,BaseException}.  This is the root of the exception
hierarchy.  This is not new as a recommendation, but the
@emph{requirement} to inherit from @ref{1a8,,BaseException} is new.  (Python
2.6 still allowed classic classes to be raised, and placed no
restriction on what you can catch.)  As a consequence, string
exceptions are finally truly and utterly dead.

@item 
Almost all exceptions should actually derive from @ref{1a9,,Exception};
@ref{1a8,,BaseException} should only be used as a base class for
exceptions that should only be handled at the top level, such as
@ref{5f7,,SystemExit} or @ref{197,,KeyboardInterrupt}.  The recommended
idiom for handling all exceptions except for this latter category is
to use @ref{b37,,except} @ref{1a9,,Exception}.

@item 
@code{StandardError} was removed.

@item 
Exceptions no longer behave as sequences.  Use the @code{args}
attribute instead.

@item 
@geindex Python 提高建议; PEP 3109
PEP 3109@footnote{https://www.python.org/dev/peps/pep-3109}: Raising exceptions.  You must now use @code{raise
@emph{Exception}(@emph{args})} instead of @code{raise @emph{Exception}, @emph{args}}.
Additionally, you can no longer explicitly specify a traceback;
instead, if you @emph{have} to do this, you can assign directly to the
@code{__traceback__} attribute (see below).

@item 
@geindex Python 提高建议; PEP 3110
PEP 3110@footnote{https://www.python.org/dev/peps/pep-3110}: Catching exceptions.  You must now use
@code{except @emph{SomeException} as @emph{variable}} instead
of @code{except @emph{SomeException}, @emph{variable}}.  Moreover, the
@emph{variable} is explicitly deleted when the @ref{b37,,except} block
is left.

@item 
@geindex Python 提高建议; PEP 3134
PEP 3134@footnote{https://www.python.org/dev/peps/pep-3134}: Exception chaining.  There are two cases: implicit
chaining and explicit chaining.  Implicit chaining happens when an
exception is raised in an @ref{b37,,except} or @ref{182,,finally}
handler block.  This usually happens due to a bug in the handler
block; we call this a @emph{secondary} exception.  In this case, the
original exception (that was being handled) is saved as the
@code{__context__} attribute of the secondary exception.
Explicit chaining is invoked with this syntax:

@example
raise SecondaryException() from primary_exception
@end example

(where @emph{primary_exception} is any expression that produces an
exception object, probably an exception that was previously caught).
In this case, the primary exception is stored on the
@code{__cause__} attribute of the secondary exception.  The
traceback printed when an unhandled exception occurs walks the chain
of @code{__cause__} and @code{__context__} attributes and prints a
separate traceback for each component of the chain, with the primary
exception at the top.  (Java users may recognize this behavior.)

@item 
@geindex Python 提高建议; PEP 3134
PEP 3134@footnote{https://www.python.org/dev/peps/pep-3134}: Exception objects now store their traceback as the
@code{__traceback__} attribute.  This means that an exception
object now contains all the information pertaining to an exception,
and there are fewer reasons to use @ref{c58,,sys.exc_info()} (though the
latter is not removed).

@item 
A few exception messages are improved when Windows fails to load an
extension module.  For example, @code{error code 193} is now @code{%1 is
not a valid Win32 application}.  Strings now deal with non-English
locales.
@end itemize

@node Miscellaneous Other Changes,构建和 C API 的改变<7>,Changes To Exceptions,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 miscellaneous-other-changes}@anchor{c59}
@subsection Miscellaneous Other Changes


@menu
* Operators And Special Methods:: 
* Builtins:: 

@end menu

@node Operators And Special Methods,Builtins,,Miscellaneous Other Changes
@anchor{whatsnew/3 0 operators-and-special-methods}@anchor{c5a}
@subsubsection Operators And Special Methods



@itemize *

@item 
@code{!=} now returns the opposite of @code{==}, unless @code{==} returns
@ref{846,,NotImplemented}.

@item 
The concept of "unbound methods" has been removed from the language.
When referencing a method as a class attribute, you now get a plain
function object.

@item 
@code{__getslice__()}, @code{__setslice__()} and @code{__delslice__()}
were killed.  The syntax @code{a[i:j]} now translates to
@code{a.__getitem__(slice(i, j))} (or @ref{c5b,,__setitem__()} or
@ref{c5c,,__delitem__()}, when used as an assignment or deletion target,
respectively).

@item 
@geindex Python 提高建议; PEP 3114
PEP 3114@footnote{https://www.python.org/dev/peps/pep-3114}: the standard @ref{67c,,next()} method has been renamed to
@ref{c5d,,__next__()}.

@item 
The @code{__oct__()} and @code{__hex__()} special methods are removed
-- @ref{c5e,,oct()} and @ref{c5f,,hex()} use @ref{18a,,__index__()} now to convert
the argument to an integer.

@item 
Removed support for @code{__members__} and @code{__methods__}.

@item 
The function attributes named @code{func_X} have been renamed to
use the @code{__X__} form, freeing up these names in the function
attribute namespace for user-defined attributes.  To wit,
@code{func_closure}, @code{func_code}, @code{func_defaults},
@code{func_dict}, @code{func_doc}, @code{func_globals},
@code{func_name} were renamed to @code{__closure__},
@code{__code__}, @code{__defaults__}, @ref{4f6,,__dict__},
@code{__doc__}, @code{__globals__}, @ref{c60,,__name__},
respectively.

@item 
@code{__nonzero__()} is now @ref{c61,,__bool__()}.
@end itemize

@node Builtins,,Operators And Special Methods,Miscellaneous Other Changes
@anchor{whatsnew/3 0 builtins}@anchor{c62}
@subsubsection Builtins



@itemize *

@item 
@geindex Python 提高建议; PEP 3135
PEP 3135@footnote{https://www.python.org/dev/peps/pep-3135}: New @ref{4dc,,super()}.  You can now invoke @ref{4dc,,super()}
without arguments and (assuming this is in a regular instance method
defined inside a @ref{c63,,class} statement) the right class and
instance will automatically be chosen.  With arguments, the behavior
of @ref{4dc,,super()} is unchanged.

@item 
@geindex Python 提高建议; PEP 3111
PEP 3111@footnote{https://www.python.org/dev/peps/pep-3111}: @code{raw_input()} was renamed to @ref{c64,,input()}.  That
is, the new @ref{c64,,input()} function reads a line from
@ref{306,,sys.stdin} and returns it with the trailing newline stripped.
It raises @ref{c65,,EOFError} if the input is terminated prematurely.
To get the old behavior of @ref{c64,,input()}, use @code{eval(input())}.

@item 
A new built-in function @ref{67c,,next()} was added to call the
@ref{c5d,,__next__()} method on an object.

@item 
The @ref{c66,,round()} function rounding strategy and return type have
changed.  Exact halfway cases are now rounded to the nearest even
result instead of away from zero.  (For example, @code{round(2.5)} now
returns @code{2} rather than @code{3}.)  @code{round(x[, n])} now
delegates to @code{x.__round__([n])} instead of always returning a
float.  It generally returns an integer when called with a single
argument and a value of the same type as @code{x} when called with two
arguments.

@item 
Moved @code{intern()} to @ref{c67,,sys.intern()}.

@item 
Removed: @code{apply()}.  Instead of @code{apply(f, args)} use
@code{f(*args)}.

@item 
Removed @ref{b3d,,callable()}.  Instead of @code{callable(f)} you can use
@code{isinstance(f, collections.Callable)}.  The @code{operator.isCallable()}
function is also gone.

@item 
Removed @code{coerce()}.  This function no longer serves a purpose
now that classic classes are gone.

@item 
Removed @code{execfile()}.  Instead of @code{execfile(fn)} use
@code{exec(open(fn).read())}.

@item 
Removed the @code{file} type.  Use @ref{4ea,,open()}.  There are now several
different kinds of streams that open can return in the @ref{a1,,io} module.

@item 
Removed @code{reduce()}.  Use @ref{c68,,functools.reduce()} if you really
need it; however, 99 percent of the time an explicit @ref{c29,,for}
loop is more readable.

@item 
Removed @code{reload()}.  Use @ref{c69,,imp.reload()}.

@item 
Removed. @code{dict.has_key()} -- use the @ref{79d,,in} operator
instead.
@end itemize

@c ======================================================================

@node 构建和 C API 的改变<7>,性能,Miscellaneous Other Changes,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 build-and-c-api-changes}@anchor{c6a}
@subsection 构建和 C API 的改变


Due to time constraints, here is a @emph{very} incomplete list of changes
to the C API.


@itemize *

@item 
Support for several platforms was dropped, including but not limited
to Mac OS 9, BeOS, RISCOS, Irix, and Tru64.

@item 
@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118}: New Buffer API.

@item 
@geindex Python 提高建议; PEP 3121
PEP 3121@footnote{https://www.python.org/dev/peps/pep-3121}: Extension Module Initialization & Finalization.

@item 
@geindex Python 提高建议; PEP 3123
PEP 3123@footnote{https://www.python.org/dev/peps/pep-3123}: Making @ref{c6b,,PyObject_HEAD} conform to standard C.

@item 
No more C API support for restricted execution.

@item 
@code{PyNumber_Coerce()}, @code{PyNumber_CoerceEx()},
@code{PyMember_Get()}, and @code{PyMember_Set()} C APIs are removed.

@item 
New C API @ref{9bb,,PyImport_ImportModuleNoBlock()}, works like
@ref{c6c,,PyImport_ImportModule()} but won't block on the import lock
(returning an error instead).

@item 
Renamed the boolean conversion C-level slot and method:
@code{nb_nonzero} is now @code{nb_bool}.

@item 
Removed @code{METH_OLDARGS} and @code{WITH_CYCLE_GC} from the C API.
@end itemize

@c ======================================================================

@node 性能,移植到 Python 3 0,构建和 C API 的改变<7>,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 performance}@anchor{c6d}
@subsection 性能


The net result of the 3.0 generalizations is that Python 3.0 runs the
pystone benchmark around 10% slower than Python 2.5.  Most likely the
biggest cause is the removal of special-casing for small integers.
There's room for improvement, but it will happen after 3.0 is
released!

@c ======================================================================

@node 移植到 Python 3 0,,性能,Python 3 0 有什么新变化
@anchor{whatsnew/3 0 porting-to-python-3-0}@anchor{c6e}
@subsection 移植到 Python 3.0


For porting existing Python 2.5 or 2.6 source code to Python 3.0, the
best strategy is the following:


@enumerate 0

@item 
(Prerequisite:) Start with excellent test coverage.

@item 
Port to Python 2.6.  This should be no more work than the average
port from Python 2.x to Python 2.(x+1).  Make sure all your tests
pass.

@item 
(Still using 2.6:) Turn on the @code{-3} command line switch.
This enables warnings about features that will be removed (or
change) in 3.0.  Run your test suite again, and fix code that you
get warnings about until there are no warnings left, and all your
tests still pass.

@item 
Run the @code{2to3} source-to-source translator over your source code
tree.  (See @ref{c6f,,2to3 - 自动将 Python 2 代码转为 Python 3 代码} for more on this tool.)  Run the
result of the translation under Python 3.0.  Manually fix up any
remaining issues, fixing problems until all tests pass again.
@end enumerate

It is not recommended to try to write source code that runs unchanged
under both Python 2.6 and 3.0; you'd have to use a very contorted
coding style, e.g. avoiding @code{print} statements, metaclasses,
and much more.  If you are maintaining a library that needs to support
both Python 2.6 and Python 3.0, the best approach is to modify step 3
above by editing the 2.6 version of the source code and running the
@code{2to3} translator again, rather than editing the 3.0 version of the
source code.

For porting C extensions to Python 3.0, please see @ref{c70,,将扩展模块移植到 Python 3}.

@c ======================================================================

@node Python 2 7 有什么新变化,Python 2 6 有什么新变化,Python 3 0 有什么新变化,Python的新变化
@anchor{whatsnew/2 7 doc}@anchor{c71}@anchor{whatsnew/2 7 what-s-new-in-python-2-7}@anchor{c72}
@section Python 2.7 有什么新变化


@*作者: 
A.M. Kuchling (amk at amk.ca)


@c hyperlink all the methods & functions.

@c T_STRING_INPLACE not described in main docs

@c $Id$
@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.  Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number in a parenthetical comment.
@c 
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer; :issue:`12345`.)
@c 
@c This saves the maintainer some effort going through the SVN logs
@c when researching a change.

本文介绍了Python 2.7 的新功能。 Python 2.7 于2010年7月3日发布。

Numeric handling has been improved in many ways, for both
floating-point numbers and for the @ref{188,,Decimal} class.
There are some useful additions to the standard library, such as a
greatly enhanced @ref{11b,,unittest} module, the @ref{6,,argparse} module
for parsing command-line options, convenient @ref{1b9,,OrderedDict}
and @ref{9d4,,Counter} classes in the @ref{1e,,collections} module,
and many other improvements.

Python 2.7 is planned to be the last of the 2.x releases, so we worked
on making it a good release for the long term.  To help with porting
to Python 3, several new features from the Python 3.x series have been
included in 2.7.

This article doesn't attempt to provide a complete specification of
the new features, but instead provides a convenient overview.  For
full details, you should refer to the documentation for Python 2.7 at
@indicateurl{https://docs.python.org}. If you want to understand the rationale for
the design and implementation, refer to the PEP for a particular new
feature or the issue on @indicateurl{https://bugs.python.org} in which a change was
discussed.  Whenever possible, "What's New in Python" links to the
bug/patch item for each change.

@menu
* Python 2.x的未来: Python 2 x的未来. 
* Changes to the Handling of Deprecation Warnings:: 
* Python 3.1 Features: Python 3 1 Features. 
* PEP 372; Adding an Ordered Dictionary to collections: PEP 372 Adding an Ordered Dictionary to collections. 
* PEP 378; 千位分隔符的格式说明符: PEP 378 千位分隔符的格式说明符<2>. 
* PEP 389; The argparse Module for Parsing Command Lines: PEP 389 The argparse Module for Parsing Command Lines. 
* PEP 391; Dictionary-Based Configuration For Logging: PEP 391 Dictionary-Based Configuration For Logging. 
* PEP 3106; Dictionary Views: PEP 3106 Dictionary Views. 
* PEP 3137; The memoryview Object: PEP 3137 The memoryview Object. 
* 其他语言特性修改: 其他语言特性修改<9>. 
* 新增和改进的模块:: 
* 构建和 C API 的改变: 构建和 C API 的改变<8>. 
* Other Changes and Fixes:: 
* 移植到 Python 2.7: 移植到 Python 2 7. 
* New Features Added to Python 2.7 Maintenance Releases: New Features Added to Python 2 7 Maintenance Releases. 
* 致谢:: 

@end menu

@node Python 2 x的未来,Changes to the Handling of Deprecation Warnings,,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 the-future-for-python-2-x}@anchor{c73}@anchor{whatsnew/2 7 whatsnew27-python31}@anchor{c74}
@subsection Python 2.x的未来


Python 2.7 是 2.x 系列中的最后一个主版本，因为Python 维护人员已将新功能开发工作的重点转移到了 Python 3.x 系列中。这意味着，尽管 Python 2 会继续修复bug并更新，以便在新的硬件和支持操作系统版本上正确构建，但不会有新的功能发布。

然而，尽管在 Python 2.7 和 Python 3 之间有一个很大的公共子集，并且迁移到该公共子集或直接迁移到 Python 3 所涉及的许多更改可以安全地自动化完成。但是一些其他更改（特别是那些与Unicode处理相关的更改）可能需要仔细考虑，并且最好用自动化回归测试套件进行健壮性测试，以便有效地迁移。

这意味着 Python2.7 将长期保留，为尚未移植到 Python 3 的生产系统提供一个稳定且受支持的基础平台。Python 2.7系列的预期完整生命周期在 
@geindex Python 提高建议; PEP 373
PEP 373@footnote{https://www.python.org/dev/peps/pep-0373} 中有详细介绍。

长期保留 2.7 版的的一些关键后果：


@itemize *

@item 
如上所述，与早期的2.x版本相比，2.7版本的维护时间更长。目前，预计核心开发团队将继续支持Python 2.7（接收安全更新和其他错误修复），直到至少2020年（首次发布后10年，相比之下，通常的支持期为18--24个月）。

@item 
随着 Python 2.7 标准库的老化，有效地利用 Python 包索引（直接或通过重新分发者）对 Python 2 用户来说变得更加重要。除了各种任务的第三方包之外，可用的包还包括与 Python 2 兼容的 Python 3 标准库中的新模块和功能的后端移植，以及各种工具和库，这些工具和库可以让用户更容易迁移到 Python 3。 Python 包用户指南@footnote{https://packaging.python.org} 提供了从 Python 包索引的下载和安装软件的指导。

@item 
虽然现在增强 Python 2 的首选方法是在Python包索引上发布新包，但这种方法不一定适用于所有情况，尤其是与网络安全相关的情况。在一些特殊情况下，如果在PyPI上发布新的或更新的包无法得到充分的处理，则可以使用Python增强建议过程来提出直接在Python 2标准库中添加新功能。任何此类添加及其添加的维护版本将在下面的 @ref{c75,,New Features Added to Python 2.7 Maintenance Releases} 部分中注明。
@end itemize

对于希望从 Python2 迁移到 Python3 的项目，或者对于希望同时支持 Python2 和 Python3 用户的库和框架开发人员，可以使用各种工具和指南来帮助决定合适的方法并管理所涉及的一些技术细节。建议从 @ref{c76,,将 Python 2 代码迁移到 Python 3} 操作指南开始。

@node Changes to the Handling of Deprecation Warnings,Python 3 1 Features,Python 2 x的未来,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 changes-to-the-handling-of-deprecation-warnings}@anchor{c77}
@subsection Changes to the Handling of Deprecation Warnings


For Python 2.7, a policy decision was made to silence warnings only of
interest to developers by default.  @ref{278,,DeprecationWarning} and its
descendants are now ignored unless otherwise requested, preventing
users from seeing warnings triggered by an application.  This change
was also made in the branch that became Python 3.2. (Discussed
on stdlib-sig and carried out in bpo-7319@footnote{https://bugs.python.org/issue7319}.)

In previous releases, @ref{278,,DeprecationWarning} messages were
enabled by default, providing Python developers with a clear
indication of where their code may break in a future major version
of Python.

However, there are increasingly many users of Python-based
applications who are not directly involved in the development of
those applications.  @ref{278,,DeprecationWarning} messages are
irrelevant to such users, making them worry about an application
that's actually working correctly and burdening application developers
with responding to these concerns.

You can re-enable display of @ref{278,,DeprecationWarning} messages by
running Python with the @ref{40f,,-Wdefault} (short form:
@ref{40f,,-Wd}) switch, or by setting the 
@geindex PYTHONWARNINGS
@geindex 环境变量; PYTHONWARNINGS
@ref{410,,PYTHONWARNINGS}
environment variable to @code{"default"} (or @code{"d"}) before running
Python.  Python code can also re-enable them
by calling @code{warnings.simplefilter('default')}.

The @code{unittest} module also automatically reenables deprecation warnings
when running tests.

@node Python 3 1 Features,PEP 372 Adding an Ordered Dictionary to collections,Changes to the Handling of Deprecation Warnings,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 python-3-1-features}@anchor{c78}
@subsection Python 3.1 Features


就像 Python2.6 集成了 Python3.0 的特性一样，2.7版也集成了 Python3.1 中的一些新特性。2.x 系列继续提供迁移到3.x系列的工具。

3.1 功能的部分列表，这些功能已反向移植到 2.7：


@itemize *

@item 
The syntax for set literals (@code{@{1,2,3@}} is a mutable set).

@item 
Dictionary and set comprehensions (@code{@{i: i*2 for i in range(3)@}}).

@item 
Multiple context managers in a single @ref{6e3,,with} statement.

@item 
A new version of the @ref{a1,,io} library, rewritten in C for performance.

@item 
The ordered-dictionary type described in @ref{c79,,PEP 372; Adding an Ordered Dictionary to collections}.

@item 
The new @code{","} format specifier described in @ref{c7a,,PEP 378; 千位分隔符的格式说明符}.

@item 
The @ref{25c,,memoryview} object.

@item 
A small subset of the @ref{9b,,importlib} module,
@ref{c7b,,described below}.

@item 
The @ref{7c6,,repr()} of a float @code{x} is shorter in many cases: it's now
based on the shortest decimal string that's guaranteed to round back
to @code{x}.  As in previous versions of Python, it's guaranteed that
@code{float(repr(x))} recovers @code{x}.

@item 
Float-to-string and string-to-float conversions are correctly rounded.
The @ref{c66,,round()} function is also now correctly rounded.

@item 
The @ref{c00,,PyCapsule} type, used to provide a C API for extension modules.

@item 
The @ref{bf6,,PyLong_AsLongAndOverflow()} C API function.
@end itemize

Other new Python3-mode warnings include:


@itemize *

@item 
@code{operator.isCallable()} and @code{operator.sequenceIncludes()},
which are not supported in 3.x, now trigger warnings.

@item 
The @code{-3} switch now automatically
enables the @code{-Qwarn} switch that causes warnings
about using classic division with integers and long integers.
@end itemize

@c ========================================================================

@c Large, PEP-level features and changes should be described here.

@c ========================================================================

@node PEP 372 Adding an Ordered Dictionary to collections,PEP 378 千位分隔符的格式说明符<2>,Python 3 1 Features,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 pep-0372}@anchor{c79}@anchor{whatsnew/2 7 pep-372-adding-an-ordered-dictionary-to-collections}@anchor{c7c}
@subsection PEP 372: Adding an Ordered Dictionary to collections


Regular Python dictionaries iterate over key/value pairs in arbitrary order.
Over the years, a number of authors have written alternative implementations
that remember the order that the keys were originally inserted.  Based on
the experiences from those implementations, 2.7 introduces a new
@ref{1b9,,OrderedDict} class in the @ref{1e,,collections} module.

The @ref{1b9,,OrderedDict} API provides the same interface as regular
dictionaries but iterates over keys and values in a guaranteed order
depending on when a key was first inserted:

@example
>>> from collections import OrderedDict
>>> d = OrderedDict([('first', 1),
...                  ('second', 2),
...                  ('third', 3)])
>>> d.items()
[('first', 1), ('second', 2), ('third', 3)]
@end example

If a new entry overwrites an existing entry, the original insertion
position is left unchanged:

@example
>>> d['second'] = 4
>>> d.items()
[('first', 1), ('second', 4), ('third', 3)]
@end example

Deleting an entry and reinserting it will move it to the end:

@example
>>> del d['second']
>>> d['second'] = 5
>>> d.items()
[('first', 1), ('third', 3), ('second', 5)]
@end example

The @ref{c7d,,popitem()} method has an optional @emph{last}
argument that defaults to @code{True}.  If @emph{last} is true, the most recently
added key is returned and removed; if it's false, the
oldest key is selected:

@example
>>> od = OrderedDict([(x,0) for x in range(20)])
>>> od.popitem()
(19, 0)
>>> od.popitem()
(18, 0)
>>> od.popitem(last=False)
(0, 0)
>>> od.popitem(last=False)
(1, 0)
@end example

Comparing two ordered dictionaries checks both the keys and values,
and requires that the insertion order was the same:

@example
>>> od1 = OrderedDict([('first', 1),
...                    ('second', 2),
...                    ('third', 3)])
>>> od2 = OrderedDict([('third', 3),
...                    ('first', 1),
...                    ('second', 2)])
>>> od1 == od2
False
>>> # Move 'third' key to the end
>>> del od2['third']; od2['third'] = 3
>>> od1 == od2
True
@end example

Comparing an @ref{1b9,,OrderedDict} with a regular dictionary
ignores the insertion order and just compares the keys and values.

How does the @ref{1b9,,OrderedDict} work?  It maintains a
doubly-linked list of keys, appending new keys to the list as they're inserted.
A secondary dictionary maps keys to their corresponding list node, so
deletion doesn't have to traverse the entire linked list and therefore
remains O(1).

The standard library now supports use of ordered dictionaries in several
modules.


@itemize *

@item 
The @code{ConfigParser} module uses them by default, meaning that
configuration files can now be read, modified, and then written back
in their original order.

@item 
The @ref{1b7,,_asdict()} method for
@ref{1b6,,collections.namedtuple()} now returns an ordered dictionary with the
values appearing in the same order as the underlying tuple indices.

@item 
The @ref{a4,,json} module's @ref{602,,JSONDecoder} class
constructor was extended with an @emph{object_pairs_hook} parameter to
allow @code{OrderedDict} instances to be built by the decoder.
Support was also added for third-party tools like
PyYAML@footnote{http://pyyaml.org/}.
@end itemize


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 372

@item PEP 372@footnote{https://www.python.org/dev/peps/pep-0372} - 将有序词典添加到集合中

PEP 由 Armin Ronacher 和 Raymond Hettinger 撰写，由 Raymond Hettinger 实现。
@end table


@node PEP 378 千位分隔符的格式说明符<2>,PEP 389 The argparse Module for Parsing Command Lines,PEP 372 Adding an Ordered Dictionary to collections,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 pep-0378}@anchor{c7a}@anchor{whatsnew/2 7 pep-378-format-specifier-for-thousands-separator}@anchor{c7e}
@subsection PEP 378: 千位分隔符的格式说明符


To make program output more readable, it can be useful to add
separators to large numbers, rendering them as
18,446,744,073,709,551,616 instead of 18446744073709551616.

The fully general solution for doing this is the @ref{a9,,locale} module,
which can use different separators ("," in North America, "." in
Europe) and different grouping sizes, but @ref{a9,,locale} is complicated
to use and unsuitable for multi-threaded applications where different
threads are producing output for different locales.

Therefore, a simple comma-grouping mechanism has been added to the
mini-language used by the @ref{4d4,,str.format()} method.  When
formatting a floating-point number, simply include a comma between the
width and the precision:

@example
>>> '@{:20,.2f@}'.format(18446744073709551616.0)
'18,446,744,073,709,551,616.00'
@end example

When formatting an integer, include the comma after the width:

@example
>>> '@{:20,d@}'.format(18446744073709551616)
'18,446,744,073,709,551,616'
@end example

This mechanism is not adaptable at all; commas are always used as the
separator and the grouping is always into three-digit groups.  The
comma-formatting mechanism isn't as general as the @ref{a9,,locale}
module, but it's easier to use.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 378

@item PEP 378@footnote{https://www.python.org/dev/peps/pep-0378} - 千位分隔符的格式说明符

PEP 由 Raymond Hettinger 撰写，由 Eric Smith 实现
@end table


@node PEP 389 The argparse Module for Parsing Command Lines,PEP 391 Dictionary-Based Configuration For Logging,PEP 378 千位分隔符的格式说明符<2>,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 pep-389-the-argparse-module-for-parsing-command-lines}@anchor{c7f}
@subsection PEP 389: The argparse Module for Parsing Command Lines


The @ref{6,,argparse} module for parsing command-line arguments was
added as a more powerful replacement for the
@ref{c3,,optparse} module.

This means Python now supports three different modules for parsing
command-line arguments: @ref{87,,getopt}, @ref{c3,,optparse}, and
@ref{6,,argparse}.  The @ref{87,,getopt} module closely resembles the C
library's @code{getopt()} function, so it remains useful if you're writing a
Python prototype that will eventually be rewritten in C.
@ref{c3,,optparse} becomes redundant, but there are no plans to remove it
because there are many scripts still using it, and there's no
automated way to update these scripts.  (Making the @ref{6,,argparse}
API consistent with @ref{c3,,optparse}'s interface was discussed but
rejected as too messy and difficult.)

In short, if you're writing a new script and don't need to worry
about compatibility with earlier versions of Python, use
@ref{6,,argparse} instead of @ref{c3,,optparse}.

Here's an example:

@example
import argparse

parser = argparse.ArgumentParser(description='Command-line example.')

# Add optional switches
parser.add_argument('-v', action='store_true', dest='is_verbose',
                    help='produce verbose output')
parser.add_argument('-o', action='store', dest='output',
                    metavar='FILE',
                    help='direct output to FILE instead of stdout')
parser.add_argument('-C', action='store', type=int, dest='context',
                    metavar='NUM', default=0,
                    help='display NUM lines of added context')

# Allow any number of additional arguments.
parser.add_argument(nargs='*', action='store', dest='inputs',
                    help='input filenames (default is stdin)')

args = parser.parse_args()
print args.__dict__
@end example

Unless you override it, @code{-h} and @code{--help} switches
are automatically added, and produce neatly formatted output:

@example
-> ./python.exe argparse-example.py --help
usage: argparse-example.py [-h] [-v] [-o FILE] [-C NUM] [inputs [inputs ...]]

Command-line example.

positional arguments:
  inputs      input filenames (default is stdin)

optional arguments:
  -h, --help  show this help message and exit
  -v          produce verbose output
  -o FILE     direct output to FILE instead of stdout
  -C NUM      display NUM lines of added context
@end example

As with @ref{c3,,optparse}, the command-line switches and arguments
are returned as an object with attributes named by the @emph{dest} parameters:

@example
-> ./python.exe argparse-example.py -v
@{'output': None,
 'is_verbose': True,
 'context': 0,
 'inputs': []@}

-> ./python.exe argparse-example.py -v -o /tmp/output -C 4 file1 file2
@{'output': '/tmp/output',
 'is_verbose': True,
 'context': 4,
 'inputs': ['file1', 'file2']@}
@end example

@ref{6,,argparse} has much fancier validation than @ref{c3,,optparse}; you
can specify an exact number of arguments as an integer, 0 or more
arguments by passing @code{'*'}, 1 or more by passing @code{'+'}, or an
optional argument with @code{'?'}.  A top-level parser can contain
sub-parsers to define subcommands that have different sets of
switches, as in @code{svn commit}, @code{svn checkout}, etc.  You can
specify an argument's type as @ref{81a,,FileType}, which will
automatically open files for you and understands that @code{'-'} means
standard input or output.


@subsubheading 参见



@table @asis

@item @ref{6,,argparse} documentation

argparse 模块的文档页面。

@item @ref{b22,,升级 optparse 代码}

Part of the Python documentation, describing how to convert
code that uses @ref{c3,,optparse}.

@geindex Python 提高建议; PEP 389

@item PEP 389@footnote{https://www.python.org/dev/peps/pep-0389} - argparse - 新的命令行解析模块

PEP 由 Steven Bethard 撰写并实现。
@end table


@node PEP 391 Dictionary-Based Configuration For Logging,PEP 3106 Dictionary Views,PEP 389 The argparse Module for Parsing Command Lines,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 pep-391-dictionary-based-configuration-for-logging}@anchor{c80}
@subsection PEP 391: Dictionary-Based Configuration For Logging


The @ref{aa,,logging} module is very flexible; applications can define
a tree of logging subsystems, and each logger in this tree can filter
out certain messages, format them differently, and direct messages to
a varying number of handlers.

All this flexibility can require a lot of configuration.  You can
write Python statements to create objects and set their properties,
but a complex set-up requires verbose but boring code.
@ref{aa,,logging} also supports a @code{fileConfig()}
function that parses a file, but the file format doesn't support
configuring filters, and it's messier to generate programmatically.

Python 2.7 adds a @code{dictConfig()} function that
uses a dictionary to configure logging.  There are many ways to
produce a dictionary from different sources: construct one with code;
parse a file containing JSON; or use a YAML parsing library if one is
installed.  For more information see @ref{c81,,配置函数}.

The following example configures two loggers, the root logger and a
logger named "network".  Messages sent to the root logger will be
sent to the system log using the syslog protocol, and messages
to the "network" logger will be written to a @code{network.log} file
that will be rotated once the log reaches 1MB.

@example
import logging
import logging.config

configdict = @{
 'version': 1,    # Configuration schema in use; must be 1 for now
 'formatters': @{
     'standard': @{
         'format': ('%(asctime)s %(name)-15s '
                    '%(levelname)-8s %(message)s')@}@},

 'handlers': @{'netlog': @{'backupCount': 10,
                     'class': 'logging.handlers.RotatingFileHandler',
                     'filename': '/logs/network.log',
                     'formatter': 'standard',
                     'level': 'INFO',
                     'maxBytes': 1000000@},
              'syslog': @{'class': 'logging.handlers.SysLogHandler',
                         'formatter': 'standard',
                         'level': 'ERROR'@}@},

 # Specify all the subordinate loggers
 'loggers': @{
             'network': @{
                         'handlers': ['netlog']
             @}
 @},
 # Specify properties of the root logger
 'root': @{
          'handlers': ['syslog']
 @},
@}

# Set up configuration
logging.config.dictConfig(configdict)

# As an example, log two error messages
logger = logging.getLogger('/')
logger.error('Database not found')

netlogger = logging.getLogger('network')
netlogger.error('Connection failed')
@end example

Three smaller enhancements to the @ref{aa,,logging} module, all
implemented by Vinay Sajip, are:

@c rev79293


@itemize *

@item 
The @ref{a19,,SysLogHandler} class now supports
syslogging over TCP.  The constructor has a @emph{socktype} parameter
giving the type of socket to use, either @ref{c82,,socket.SOCK_DGRAM}
for UDP or @ref{c83,,socket.SOCK_STREAM} for TCP.  The default
protocol remains UDP.

@item 
@ref{39f,,Logger} instances gained a @ref{c84,,getChild()}
method that retrieves a descendant logger using a relative path.
For example, once you retrieve a logger by doing @code{log = getLogger('app')},
calling @code{log.getChild('network.listen')} is equivalent to
@code{getLogger('app.network.listen')}.

@item 
The @ref{c85,,LoggerAdapter} class gained an
@code{isEnabledFor()} method that takes a
@emph{level} and returns whether the underlying logger would
process a message of that level of importance.
@end itemize

@c XXX: Logger objects don't have a class declaration so the link don't work


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 391

@item PEP 391@footnote{https://www.python.org/dev/peps/pep-0391} - 基于字典的日志配置

PEP 由 Vinay Sajip 撰写并实现
@end table


@node PEP 3106 Dictionary Views,PEP 3137 The memoryview Object,PEP 391 Dictionary-Based Configuration For Logging,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 pep-3106-dictionary-views}@anchor{c86}
@subsection PEP 3106: Dictionary Views


The dictionary methods @ref{c23,,keys()}, @ref{c25,,values()}, and
@ref{c24,,items()} are different in Python 3.x.  They return an object
called a @emph{view} instead of a fully materialized list.

It's not possible to change the return values of @ref{c23,,keys()},
@ref{c25,,values()}, and @ref{c24,,items()} in Python 2.7 because
too much code would break.  Instead the 3.x versions were added
under the new names @code{viewkeys()}, @code{viewvalues()},
and @code{viewitems()}.

@example
>>> d = dict((i*10, chr(65+i)) for i in range(26))
>>> d
@{0: 'A', 130: 'N', 10: 'B', 140: 'O', 20: ..., 250: 'Z'@}
>>> d.viewkeys()
dict_keys([0, 130, 10, 140, 20, 150, 30, ..., 250])
@end example

Views can be iterated over, but the key and item views also behave
like sets.  The @code{&} operator performs intersection, and @code{|}
performs a union:

@example
>>> d1 = dict((i*10, chr(65+i)) for i in range(26))
>>> d2 = dict((i**.5, i) for i in range(1000))
>>> d1.viewkeys() & d2.viewkeys()
set([0.0, 10.0, 20.0, 30.0])
>>> d1.viewkeys() | range(0, 30)
set([0, 1, 130, 3, 4, 5, 6, ..., 120, 250])
@end example

The view keeps track of the dictionary and its contents change as the
dictionary is modified:

@example
>>> vk = d.viewkeys()
>>> vk
dict_keys([0, 130, 10, ..., 250])
>>> d[260] = '&'
>>> vk
dict_keys([0, 130, 260, 10, ..., 250])
@end example

However, note that you can't add or remove keys while you're iterating
over the view:

@example
>>> for k in vk:
...     d[k*2] = k
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: dictionary changed size during iteration
@end example

You can use the view methods in Python 2.x code, and the 2to3
converter will change them to the standard @ref{c23,,keys()},
@ref{c25,,values()}, and @ref{c24,,items()} methods.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3106

@item PEP 3106@footnote{https://www.python.org/dev/peps/pep-3106} - 改造 dict.keys(), .values() 和 .items()

PEP written by Guido van Rossum.
Backported to 2.7 by Alexandre Vassalotti; bpo-1967@footnote{https://bugs.python.org/issue1967}.
@end table


@node PEP 3137 The memoryview Object,其他语言特性修改<9>,PEP 3106 Dictionary Views,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 pep-3137-the-memoryview-object}@anchor{c87}
@subsection PEP 3137: The memoryview Object


The @ref{25c,,memoryview} object provides a view of another object's
memory content that matches the @ref{32a,,bytes} type's interface.

@example
>>> import string
>>> m = memoryview(string.letters)
>>> m
<memory at 0x37f850>
>>> len(m)           # Returns length of underlying object
52
>>> m[0], m[25], m[26]   # Indexing returns one byte
('a', 'z', 'A')
>>> m2 = m[0:26]         # Slicing returns another memoryview
>>> m2
<memory at 0x37f080>
@end example

The content of the view can be converted to a string of bytes or
a list of integers:

@example
>>> m2.tobytes()
'abcdefghijklmnopqrstuvwxyz'
>>> m2.tolist()
[97, 98, 99, 100, 101, 102, 103, ... 121, 122]
>>>
@end example

@ref{25c,,memoryview} objects allow modifying the underlying object if
it's a mutable object.

@example
>>> m2[0] = 75
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot modify read-only memory
>>> b = bytearray(string.letters)  # Creating a mutable object
>>> b
bytearray(b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
>>> mb = memoryview(b)
>>> mb[0] = '*'         # Assign to view, changing the bytearray.
>>> b[0:5]              # The bytearray has been changed.
bytearray(b'*bcde')
>>>
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3137

@item PEP 3137@footnote{https://www.python.org/dev/peps/pep-3137} - 不变字节和可变缓冲区

PEP written by Guido van Rossum.
Implemented by Travis Oliphant, Antoine Pitrou and others.
Backported to 2.7 by Antoine Pitrou; bpo-2396@footnote{https://bugs.python.org/issue2396}.
@end table


@node 其他语言特性修改<9>,新增和改进的模块,PEP 3137 The memoryview Object,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 other-language-changes}@anchor{c88}
@subsection 其他语言特性修改


对Python 语言核心进行的小改动：


@itemize *

@item 
The syntax for set literals has been backported from Python 3.x.
Curly brackets are used to surround the contents of the resulting
mutable set; set literals are
distinguished from dictionaries by not containing colons and values.
@code{@{@}} continues to represent an empty dictionary; use
@code{set()} for an empty set.

@example
>>> @{1, 2, 3, 4, 5@}
set([1, 2, 3, 4, 5])
>>> set() # empty set
set([])
>>> @{@}    # empty dict
@{@}
@end example

Backported by Alexandre Vassalotti; bpo-2335@footnote{https://bugs.python.org/issue2335}.

@item 
Dictionary and set comprehensions are another feature backported from
3.x, generalizing list/generator comprehensions to use
the literal syntax for sets and dictionaries.

@example
>>> @{x: x*x for x in range(6)@}
@{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25@}
>>> @{('a'*x) for x in range(6)@}
set(['@w{'}, 'a', 'aa', 'aaa', 'aaaa', 'aaaaa'])
@end example

Backported by Alexandre Vassalotti; bpo-2333@footnote{https://bugs.python.org/issue2333}.

@item 
The @ref{6e3,,with} statement can now use multiple context managers
in one statement.  Context managers are processed from left to right
and each one is treated as beginning a new @code{with} statement.
This means that:

@example
with A() as a, B() as b:
    ... suite of statements ...
@end example

相当于:

@example
with A() as a:
    with B() as b:
        ... suite of statements ...
@end example

The @code{contextlib.nested()} function provides a very similar
function, so it's no longer necessary and has been deprecated.

(Proposed in @indicateurl{https://codereview.appspot.com/53094}; implemented by
Georg Brandl.)

@item 
Conversions between floating-point numbers and strings are
now correctly rounded on most platforms.  These conversions occur
in many different places: @ref{329,,str()} on
floats and complex numbers; the @ref{187,,float} and @ref{189,,complex}
constructors;
numeric formatting; serializing and
deserializing floats and complex numbers using the
@ref{b0,,marshal}, @ref{ca,,pickle}
and @ref{a4,,json} modules;
parsing of float and imaginary literals in Python code;
and @ref{188,,Decimal}-to-float conversion.

Related to this, the @ref{7c6,,repr()} of a floating-point number @emph{x}
now returns a result based on the shortest decimal string that's
guaranteed to round back to @emph{x} under correct rounding (with
round-half-to-even rounding mode).  Previously it gave a string
based on rounding x to 17 decimal digits.

@c maybe add an example?

The rounding library responsible for this improvement works on
Windows and on Unix platforms using the gcc, icc, or suncc
compilers.  There may be a small number of platforms where correct
operation of this code cannot be guaranteed, so the code is not
used on such systems.  You can find out which code is being used
by checking @ref{c89,,sys.float_repr_style},  which will be @code{short}
if the new code is in use and @code{legacy} if it isn't.

Implemented by Eric Smith and Mark Dickinson, using David Gay's
@code{dtoa.c} library; bpo-7117@footnote{https://bugs.python.org/issue7117}.

@item 
Conversions from long integers and regular integers to floating
point now round differently, returning the floating-point number
closest to the number.  This doesn't matter for small integers that
can be converted exactly, but for large numbers that will
unavoidably lose precision, Python 2.7 now approximates more
closely.  For example, Python 2.6 computed the following:

@example
>>> n = 295147905179352891391
>>> float(n)
2.9514790517935283e+20
>>> n - long(float(n))
65535L
@end example

Python 2.7's floating-point result is larger, but much closer to the
true value:

@example
>>> n = 295147905179352891391
>>> float(n)
2.9514790517935289e+20
>>> n - long(float(n))
-1L
@end example

(Implemented by Mark Dickinson; bpo-3166@footnote{https://bugs.python.org/issue3166}.)

Integer division is also more accurate in its rounding behaviours.  (Also
implemented by Mark Dickinson; bpo-1811@footnote{https://bugs.python.org/issue1811}.)

@item 
Implicit coercion for complex numbers has been removed; the interpreter
will no longer ever attempt to call a @code{__coerce__()} method on complex
objects.  (Removed by Meador Inge and Mark Dickinson; bpo-5211@footnote{https://bugs.python.org/issue5211}.)

@item 
The @ref{4d4,,str.format()} method now supports automatic numbering of the replacement
fields.  This makes using @ref{4d4,,str.format()} more closely resemble using
@code{%s} formatting:

@example
>>> '@{@}:@{@}:@{@}'.format(2009, 04, 'Sunday')
'2009:4:Sunday'
>>> '@{@}:@{@}:@{day@}'.format(2009, 4, day='Sunday')
'2009:4:Sunday'
@end example

The auto-numbering takes the fields from left to right, so the first @code{@{...@}}
specifier will use the first argument to @ref{4d4,,str.format()}, the next
specifier will use the next argument, and so on.  You can't mix auto-numbering
and explicit numbering -- either number all of your specifier fields or none
of them -- but you can mix auto-numbering and named fields, as in the second
example above.  (Contributed by Eric Smith; bpo-5237@footnote{https://bugs.python.org/issue5237}.)

Complex numbers now correctly support usage with @ref{4d5,,format()},
and default to being right-aligned.
Specifying a precision or comma-separation applies to both the real
and imaginary parts of the number, but a specified field width and
alignment is applied to the whole of the resulting @code{1.5+3j}
output.  (Contributed by Eric Smith; bpo-1588@footnote{https://bugs.python.org/issue1588} and bpo-7988@footnote{https://bugs.python.org/issue7988}.)

The 'F' format code now always formats its output using uppercase characters,
so it will now produce 'INF' and 'NAN'.
(Contributed by Eric Smith; bpo-3382@footnote{https://bugs.python.org/issue3382}.)

A low-level change: the @ref{948,,object.__format__()} method now triggers
a @ref{279,,PendingDeprecationWarning} if it's passed a format string,
because the @ref{948,,__format__()} method for @ref{2b0,,object} converts
the object to a string representation and formats that.  Previously
the method silently applied the format string to the string
representation, but that could hide mistakes in Python code.  If
you're supplying formatting information such as an alignment or
precision, presumably you're expecting the formatting to be applied
in some object-specific way.  (Fixed by Eric Smith; bpo-7994@footnote{https://bugs.python.org/issue7994}.)

@item 
The @ref{184,,int()} and @code{long()} types gained a @code{bit_length}
method that returns the number of bits necessary to represent
its argument in binary:

@example
>>> n = 37
>>> bin(n)
'0b100101'
>>> n.bit_length()
6
>>> n = 2**123-1
>>> n.bit_length()
123
>>> (n+1).bit_length()
124
@end example

(Contributed by Fredrik Johansson and Victor Stinner; bpo-3439@footnote{https://bugs.python.org/issue3439}.)

@item 
The @ref{c16,,import} statement will no longer try an absolute import
if a relative import (e.g. @code{from .os import sep}) fails.  This
fixes a bug, but could possibly break certain @code{import}
statements that were only working by accident.  (Fixed by Meador Inge;
bpo-7902@footnote{https://bugs.python.org/issue7902}.)

@item 
It's now possible for a subclass of the built-in @code{unicode} type
to override the @code{__unicode__()} method.  (Implemented by
Victor Stinner; bpo-1583863@footnote{https://bugs.python.org/issue1583863}.)

@item 
The @ref{32b,,bytearray} type's @ref{c8a,,translate()} method now accepts
@code{None} as its first argument.  (Fixed by Georg Brandl;
bpo-4759@footnote{https://bugs.python.org/issue4759}.)

@c XXX bytearray doesn't seem to be documented

@item 
When using @code{@@classmethod} and @code{@@staticmethod} to wrap
methods as class or static methods, the wrapper object now
exposes the wrapped function as their @code{__func__} attribute.
(Contributed by Amaury Forgeot d'Arc, after a suggestion by
George Sakkis; bpo-5982@footnote{https://bugs.python.org/issue5982}.)

@item 
When a restricted set of attributes were set using @code{__slots__},
deleting an unset attribute would not raise @ref{393,,AttributeError}
as you would expect.  Fixed by Benjamin Peterson; bpo-7604@footnote{https://bugs.python.org/issue7604}.)

@item 
Two new encodings are now supported: "cp720", used primarily for
Arabic text; and "cp858", a variant of CP 850 that adds the euro
symbol.  (CP720 contributed by Alexander Belchenko and Amaury
Forgeot d'Arc in bpo-1616979@footnote{https://bugs.python.org/issue1616979}; CP858 contributed by Tim Hatch in
bpo-8016@footnote{https://bugs.python.org/issue8016}.)

@item 
The @code{file} object will now set the @code{filename} attribute
on the @ref{98c,,IOError} exception when trying to open a directory
on POSIX platforms (noted by Jan Kaliszewski; bpo-4764@footnote{https://bugs.python.org/issue4764}), and
now explicitly checks for and forbids writing to read-only file objects
instead of trusting the C library to catch and report the error
(fixed by Stefan Krah; bpo-5677@footnote{https://bugs.python.org/issue5677}).

@item 
The Python tokenizer now translates line endings itself, so the
@ref{1b4,,compile()} built-in function now accepts code using any
line-ending convention.  Additionally, it no longer requires that the
code end in a newline.

@item 
Extra parentheses in function definitions are illegal in Python 3.x,
meaning that you get a syntax error from @code{def f((x)): pass}.  In
Python3-warning mode, Python 2.7 will now warn about this odd usage.
(Noted by James Lingard; bpo-7362@footnote{https://bugs.python.org/issue7362}.)

@item 
It's now possible to create weak references to old-style class
objects.  New-style classes were always weak-referenceable.  (Fixed
by Antoine Pitrou; bpo-8268@footnote{https://bugs.python.org/issue8268}.)

@item 
When a module object is garbage-collected, the module's dictionary is
now only cleared if no one else is holding a reference to the
dictionary (bpo-7140@footnote{https://bugs.python.org/issue7140}).
@end itemize

@c ======================================================================

@menu
* Interpreter Changes:: 
* 性能优化: 性能优化<8>. 

@end menu

@node Interpreter Changes,性能优化<8>,,其他语言特性修改<9>
@anchor{whatsnew/2 7 interpreter-changes}@anchor{c8b}@anchor{whatsnew/2 7 new-27-interpreter}@anchor{c8c}
@subsubsection Interpreter Changes


A new environment variable, 
@geindex PYTHONWARNINGS
@geindex 环境变量; PYTHONWARNINGS
@ref{410,,PYTHONWARNINGS},
allows controlling warnings.  It should be set to a string
containing warning settings, equivalent to those
used with the @ref{40f,,-W} switch, separated by commas.
(Contributed by Brian Curtin; bpo-7301@footnote{https://bugs.python.org/issue7301}.)

For example, the following setting will print warnings every time
they occur, but turn warnings from the @code{Cookie} module into an
error.  (The exact syntax for setting an environment variable varies
across operating systems and shells.)

@example
export PYTHONWARNINGS=all,error:::Cookie:0
@end example

@c ======================================================================

@node 性能优化<8>,,Interpreter Changes,其他语言特性修改<9>
@anchor{whatsnew/2 7 optimizations}@anchor{c8d}
@subsubsection 性能优化


Several performance enhancements have been added:


@itemize *

@item 
A new opcode was added to perform the initial setup for
@ref{6e3,,with} statements, looking up the @ref{c8e,,__enter__()} and
@ref{c8f,,__exit__()} methods.  (Contributed by Benjamin Peterson.)

@item 
The garbage collector now performs better for one common usage
pattern: when many objects are being allocated without deallocating
any of them.  This would previously take quadratic
time for garbage collection, but now the number of full garbage collections
is reduced as the number of objects on the heap grows.
The new logic only performs a full garbage collection pass when
the middle generation has been collected 10 times and when the
number of survivor objects from the middle generation exceeds 10% of
the number of objects in the oldest generation.  (Suggested by Martin
von Löwis and implemented by Antoine Pitrou; bpo-4074@footnote{https://bugs.python.org/issue4074}.)

@item 
The garbage collector tries to avoid tracking simple containers
which can't be part of a cycle. In Python 2.7, this is now true for
tuples and dicts containing atomic types (such as ints, strings,
etc.). Transitively, a dict containing tuples of atomic types won't
be tracked either. This helps reduce the cost of each
garbage collection by decreasing the number of objects to be
considered and traversed by the collector.
(Contributed by Antoine Pitrou; bpo-4688@footnote{https://bugs.python.org/issue4688}.)

@item 
Long integers are now stored internally either in base 2**15 or in base
2**30, the base being determined at build time.  Previously, they
were always stored in base 2**15.  Using base 2**30 gives
significant performance improvements on 64-bit machines, but
benchmark results on 32-bit machines have been mixed.  Therefore,
the default is to use base 2**30 on 64-bit machines and base 2**15
on 32-bit machines; on Unix, there's a new configure option
@code{--enable-big-digits} that can be used to override this default.

Apart from the performance improvements this change should be
invisible to end users, with one exception: for testing and
debugging purposes there's a new structseq @code{sys.long_info} that
provides information about the internal format, giving the number of
bits per digit and the size in bytes of the C type used to store
each digit:

@example
>>> import sys
>>> sys.long_info
sys.long_info(bits_per_digit=30, sizeof_digit=4)
@end example

（由 Mark Dickinson在 bpo-4258@footnote{https://bugs.python.org/issue4258} 贡献）

Another set of changes made long objects a few bytes smaller: 2 bytes
smaller on 32-bit systems and 6 bytes on 64-bit.
(Contributed by Mark Dickinson; bpo-5260@footnote{https://bugs.python.org/issue5260}.)

@item 
The division algorithm for long integers has been made faster
by tightening the inner loop, doing shifts instead of multiplications,
and fixing an unnecessary extra iteration.
Various benchmarks show speedups of between 50% and 150% for long
integer divisions and modulo operations.
(Contributed by Mark Dickinson; bpo-5512@footnote{https://bugs.python.org/issue5512}.)
Bitwise operations are also significantly faster (initial patch by
Gregory Smith; bpo-1087418@footnote{https://bugs.python.org/issue1087418}).

@item 
The implementation of @code{%} checks for the left-side operand being
a Python string and special-cases it; this results in a 1--3%
performance increase for applications that frequently use @code{%}
with strings, such as templating libraries.
(Implemented by Collin Winter; bpo-5176@footnote{https://bugs.python.org/issue5176}.)

@item 
List comprehensions with an @code{if} condition are compiled into
faster bytecode.  (Patch by Antoine Pitrou, back-ported to 2.7
by Jeffrey Yasskin; bpo-4715@footnote{https://bugs.python.org/issue4715}.)

@item 
Converting an integer or long integer to a decimal string was made
faster by special-casing base 10 instead of using a generalized
conversion function that supports arbitrary bases.
(Patch by Gawain Bolton; bpo-6713@footnote{https://bugs.python.org/issue6713}.)

@item 
The @code{split()}, @code{replace()}, @code{rindex()},
@code{rpartition()}, and @code{rsplit()} methods of string-like types
(strings, Unicode strings, and @ref{32b,,bytearray} objects) now use a
fast reverse-search algorithm instead of a character-by-character
scan.  This is sometimes faster by a factor of 10.  (Added by
Florent Xicluna; bpo-7462@footnote{https://bugs.python.org/issue7462} and bpo-7622@footnote{https://bugs.python.org/issue7622}.)

@item 
The @ref{ca,,pickle} and @code{cPickle} modules now automatically
intern the strings used for attribute names, reducing memory usage
of the objects resulting from unpickling.  (Contributed by Jake
McGuire; bpo-5084@footnote{https://bugs.python.org/issue5084}.)

@item 
The @code{cPickle} module now special-cases dictionaries,
nearly halving the time required to pickle them.
(Contributed by Collin Winter; bpo-5670@footnote{https://bugs.python.org/issue5670}.)
@end itemize

@c ======================================================================

@node 新增和改进的模块,构建和 C API 的改变<8>,其他语言特性修改<9>,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 new-and-improved-modules}@anchor{c90}
@subsection 新增和改进的模块


As in every release, Python's standard library received a number of
enhancements and bug fixes.  Here's a partial list of the most notable
changes, sorted alphabetically by module name. Consult the
@code{Misc/NEWS} file in the source tree for a more complete list of
changes, or look through the Subversion logs for all the details.


@itemize *

@item 
The @ref{f,,bdb} module's base debugging class @ref{c91,,Bdb}
gained a feature for skipping modules.  The constructor
now takes an iterable containing glob-style patterns such as
@code{django.*}; the debugger will not step into stack frames
from a module that matches one of these patterns.
(Contributed by Maru Newby after a suggestion by
Senthil Kumaran; bpo-5142@footnote{https://bugs.python.org/issue5142}.)

@item 
The @ref{10,,binascii} module now supports the buffer API, so it can be
used with @ref{25c,,memoryview} instances and other similar buffer objects.
(Backported from 3.x by Florent Xicluna; bpo-7703@footnote{https://bugs.python.org/issue7703}.)

@item 
Updated module: the @code{bsddb} module has been updated from 4.7.2devel9
to version 4.8.4 of
the pybsddb package@footnote{https://www.jcea.es/programacion/pybsddb.htm}.
The new version features better Python 3.x compatibility, various bug fixes,
and adds several new BerkeleyDB flags and methods.
(Updated by Jesús Cea Avión; bpo-8156@footnote{https://bugs.python.org/issue8156}.  The pybsddb
changelog can be read at @indicateurl{http://hg.jcea.es/pybsddb/file/tip/ChangeLog}.)

@item 
The @ref{14,,bz2} module's @ref{92b,,BZ2File} now supports the context
management protocol, so you can write @code{with bz2.BZ2File(...) as f:}.
(Contributed by Hagen Fürstenau; bpo-3860@footnote{https://bugs.python.org/issue3860}.)

@item 
New class: the @ref{9d4,,Counter} class in the @ref{1e,,collections}
module is useful for tallying data.  @ref{9d4,,Counter} instances
behave mostly like dictionaries but return zero for missing keys instead of
raising a @ref{2c7,,KeyError}:

@example
>>> from collections import Counter
>>> c = Counter()
>>> for letter in 'here is a sample of english text':
...   c[letter] += 1
...
>>> c 
Counter(@{' ': 6, 'e': 5, 's': 3, 'a': 2, 'i': 2, 'h': 2,
'l': 2, 't': 2, 'g': 1, 'f': 1, 'm': 1, 'o': 1, 'n': 1,
'p': 1, 'r': 1, 'x': 1@})
>>> c['e']
5
>>> c['z']
0
@end example

There are three additional @ref{9d4,,Counter} methods.
@ref{c92,,most_common()} returns the N most common
elements and their counts.  @ref{c93,,elements()}
returns an iterator over the contained elements, repeating each
element as many times as its count.
@ref{b53,,subtract()} takes an iterable and
subtracts one for each element instead of adding; if the argument is
a dictionary or another @code{Counter}, the counts are
subtracted.

@example
>>> c.most_common(5)
[(' ', 6), ('e', 5), ('s', 3), ('a', 2), ('i', 2)]
>>> c.elements() ->
   'a', 'a', ' ', ' ', ' ', ' ', ' ', ' ',
   'e', 'e', 'e', 'e', 'e', 'g', 'f', 'i', 'i',
   'h', 'h', 'm', 'l', 'l', 'o', 'n', 'p', 's',
   's', 's', 'r', 't', 't', 'x'
>>> c['e']
5
>>> c.subtract('very heavy on the letter e')
>>> c['e']    # Count is now lower
-1
@end example

Contributed by Raymond Hettinger; bpo-1696199@footnote{https://bugs.python.org/issue1696199}.

@c revision 79660

New class: @ref{1b9,,OrderedDict} is described in the earlier
section @ref{c79,,PEP 372; Adding an Ordered Dictionary to collections}.

New method: The @ref{52b,,deque} data type now has a
@ref{b55,,count()} method that returns the number of
contained elements equal to the supplied argument @emph{x}, and a
@ref{b56,,reverse()} method that reverses the elements
of the deque in-place.  @ref{52b,,deque} also exposes its maximum
length as the read-only @ref{c94,,maxlen} attribute.
(Both features added by Raymond Hettinger.)

The @ref{1b6,,namedtuple} class now has an optional @emph{rename} parameter.
If @emph{rename} is true, field names that are invalid because they've
been repeated or aren't legal Python identifiers will be
renamed to legal names that are derived from the field's
position within the list of fields:

@example
>>> from collections import namedtuple
>>> T = namedtuple('T', ['field1', '$illegal', 'for', 'field2'], rename=True)
>>> T._fields
('field1', '_1', '_2', 'field2')
@end example

(Added by Raymond Hettinger; bpo-1818@footnote{https://bugs.python.org/issue1818}.)

Finally, the @code{Mapping} abstract base class now
returns @ref{846,,NotImplemented} if a mapping is compared to
another type that isn't a @code{Mapping}.
(Fixed by Daniel Stutzbach; bpo-8729@footnote{https://bugs.python.org/issue8729}.)

@item 
Constructors for the parsing classes in the @code{ConfigParser} module now
take an @emph{allow_no_value} parameter, defaulting to false; if true,
options without values will be allowed.  For example:

@example
>>> import ConfigParser, StringIO
>>> sample_config = """
... [mysqld]
... user = mysql
... pid-file = /var/run/mysqld/mysqld.pid
... skip-bdb
... """
>>> config = ConfigParser.RawConfigParser(allow_no_value=True)
>>> config.readfp(StringIO.StringIO(sample_config))
>>> config.get('mysqld', 'user')
'mysql'
>>> print config.get('mysqld', 'skip-bdb')
None
>>> print config.get('mysqld', 'unknown')
Traceback (most recent call last):
  ...
NoOptionError: No option 'unknown' in section: 'mysqld'
@end example

(Contributed by Mats Kindahl; bpo-7005@footnote{https://bugs.python.org/issue7005}.)

@item 
Deprecated function: @code{contextlib.nested()}, which allows
handling more than one context manager with a single @ref{6e3,,with}
statement, has been deprecated, because the @code{with} statement
now supports multiple context managers.

@item 
The @code{cookielib} module now ignores cookies that have an invalid
version field, one that doesn't contain an integer value.  (Fixed by
John J. Lee; bpo-3924@footnote{https://bugs.python.org/issue3924}.)

@item 
The @ref{26,,copy} module's @ref{3c4,,deepcopy()} function will now
correctly copy bound instance methods.  (Implemented by
Robert Collins; bpo-1515@footnote{https://bugs.python.org/issue1515}.)

@item 
The @ref{2b,,ctypes} module now always converts @code{None} to a C @code{NULL}
pointer for arguments declared as pointers.  (Changed by Thomas
Heller; bpo-4606@footnote{https://bugs.python.org/issue4606}.)  The underlying libffi library@footnote{https://sourceware.org/libffi/} has been updated to version
3.0.9, containing various fixes for different platforms.  (Updated
by Matthias Klose; bpo-8142@footnote{https://bugs.python.org/issue8142}.)

@item 
New method: the @ref{31,,datetime} module's @ref{195,,timedelta} class
gained a @ref{c95,,total_seconds()} method that returns the
number of seconds in the duration.  (Contributed by Brian Quinlan; bpo-5788@footnote{https://bugs.python.org/issue5788}.)

@item 
New method: the @ref{188,,Decimal} class gained a
@ref{b79,,from_float()} class method that performs an exact
conversion of a floating-point number to a @ref{188,,Decimal}.
This exact conversion strives for the
closest decimal approximation to the floating-point representation's value;
the resulting decimal value will therefore still include the inaccuracy,
if any.
For example, @code{Decimal.from_float(0.1)} returns
@code{Decimal('0.1000000000000000055511151231257827021181583404541015625')}.
(Implemented by Raymond Hettinger; bpo-4796@footnote{https://bugs.python.org/issue4796}.)

Comparing instances of @ref{188,,Decimal} with floating-point
numbers now produces sensible results based on the numeric values
of the operands.  Previously such comparisons would fall back to
Python's default rules for comparing objects, which produced arbitrary
results based on their type.  Note that you still cannot combine
@code{Decimal} and floating-point in other operations such as addition,
since you should be explicitly choosing how to convert between float and
@ref{188,,Decimal}.  (Fixed by Mark Dickinson; bpo-2531@footnote{https://bugs.python.org/issue2531}.)

The constructor for @ref{188,,Decimal} now accepts
floating-point numbers (added by Raymond Hettinger; bpo-8257@footnote{https://bugs.python.org/issue8257})
and non-European Unicode characters such as Arabic-Indic digits
(contributed by Mark Dickinson; bpo-6595@footnote{https://bugs.python.org/issue6595}).

Most of the methods of the @ref{9ea,,Context} class now accept integers
as well as @ref{188,,Decimal} instances; the only exceptions are the
@ref{c96,,canonical()} and @ref{c97,,is_canonical()}
methods.  (Patch by Juan José Conti; bpo-7633@footnote{https://bugs.python.org/issue7633}.)

When using @ref{188,,Decimal} instances with a string's
@ref{4d4,,format()} method, the default alignment was previously
left-alignment.  This has been changed to right-alignment, which is
more sensible for numeric types.  (Changed by Mark Dickinson; bpo-6857@footnote{https://bugs.python.org/issue6857}.)

Comparisons involving a signaling NaN value (or @code{sNAN}) now signal
@code{InvalidOperation} instead of silently returning a true or
false value depending on the comparison operator.  Quiet NaN values
(or @code{NaN}) are now hashable.  (Fixed by Mark Dickinson;
bpo-7279@footnote{https://bugs.python.org/issue7279}.)

@item 
The @ref{37,,difflib} module now produces output that is more
compatible with modern @code{diff}/@code{patch} tools
through one small change, using a tab character instead of spaces as
a separator in the header giving the filename.  (Fixed by Anatoly
Techtonik; bpo-7585@footnote{https://bugs.python.org/issue7585}.)

@item 
The Distutils @code{sdist} command now always regenerates the
@code{MANIFEST} file, since even if the @code{MANIFEST.in} or
@code{setup.py} files haven't been modified, the user might have
created some new files that should be included.
(Fixed by Tarek Ziadé; bpo-8688@footnote{https://bugs.python.org/issue8688}.)

@item 
The @ref{67,,doctest} module's @code{IGNORE_EXCEPTION_DETAIL} flag
will now ignore the name of the module containing the exception
being tested.  (Patch by Lennart Regebro; bpo-7490@footnote{https://bugs.python.org/issue7490}.)

@item 
The @ref{69,,email} module's @ref{53c,,Message} class will
now accept a Unicode-valued payload, automatically converting the
payload to the encoding specified by @code{output_charset}.
(Added by R. David Murray; bpo-1368247@footnote{https://bugs.python.org/issue1368247}.)

@item 
The @ref{185,,Fraction} class now accepts a single float or
@ref{188,,Decimal} instance, or two rational numbers, as
arguments to its constructor.  (Implemented by Mark Dickinson;
rationals added in bpo-5812@footnote{https://bugs.python.org/issue5812}, and float/decimal in
bpo-8294@footnote{https://bugs.python.org/issue8294}.)

Ordering comparisons (@code{<}, @code{<=}, @code{>}, @code{>=}) between
fractions and complex numbers now raise a @ref{192,,TypeError}.
This fixes an oversight, making the @ref{185,,Fraction}
match the other numeric types.

@c revision 79455

@item 
New class: @ref{9fe,,FTP_TLS} in
the @ref{84,,ftplib} module provides secure FTP
connections using TLS encapsulation of authentication as well as
subsequent control and data transfers.
(Contributed by Giampaolo Rodola; bpo-2054@footnote{https://bugs.python.org/issue2054}.)

The @ref{c98,,storbinary()} method for binary uploads can now restart
uploads thanks to an added @emph{rest} parameter (patch by Pablo Mouzo;
bpo-6845@footnote{https://bugs.python.org/issue6845}.)

@item 
New class decorator: @ref{845,,total_ordering()} in the @ref{85,,functools}
module takes a class that defines an @ref{338,,__eq__()} method and one of
@ref{c2d,,__lt__()}, @ref{c99,,__le__()}, @ref{c9a,,__gt__()}, or @ref{c9b,,__ge__()},
and generates the missing comparison methods.  Since the
@code{__cmp__()} method is being deprecated in Python 3.x,
this decorator makes it easier to define ordered classes.
(Added by Raymond Hettinger; bpo-5479@footnote{https://bugs.python.org/issue5479}.)

New function: @ref{b4f,,cmp_to_key()} will take an old-style comparison
function that expects two arguments and return a new callable that
can be used as the @emph{key} parameter to functions such as
@ref{43e,,sorted()}, @ref{803,,min()} and @ref{804,,max()}, etc.  The primary
intended use is to help with making code compatible with Python 3.x.
(Added by Raymond Hettinger.)

@item 
New function: the @ref{86,,gc} module's @ref{c9c,,is_tracked()} returns
true if a given instance is tracked by the garbage collector, false
otherwise. (Contributed by Antoine Pitrou; bpo-4688@footnote{https://bugs.python.org/issue4688}.)

@item 
The @ref{8c,,gzip} module's @ref{6d7,,GzipFile} now supports the context
management protocol, so you can write @code{with gzip.GzipFile(...) as f:}
(contributed by Hagen Fürstenau; bpo-3860@footnote{https://bugs.python.org/issue3860}), and it now implements
the @ref{583,,io.BufferedIOBase} ABC, so you can wrap it with
@ref{b83,,io.BufferedReader} for faster processing
(contributed by Nir Aides; bpo-7471@footnote{https://bugs.python.org/issue7471}).
It's also now possible to override the modification time
recorded in a gzipped file by providing an optional timestamp to
the constructor.  (Contributed by Jacques Frechet; bpo-4272@footnote{https://bugs.python.org/issue4272}.)

Files in gzip format can be padded with trailing zero bytes; the
@ref{8c,,gzip} module will now consume these trailing bytes.  (Fixed by
Tadek Pietraszek and Brian Curtin; bpo-2846@footnote{https://bugs.python.org/issue2846}.)

@item 
New attribute: the @ref{8d,,hashlib} module now has an @code{algorithms}
attribute containing a tuple naming the supported algorithms.
In Python 2.7, @code{hashlib.algorithms} contains
@code{('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512')}.
(Contributed by Carl Chenet; bpo-7418@footnote{https://bugs.python.org/issue7418}.)

@item 
The default @code{HTTPResponse} class used by the @code{httplib} module now
supports buffering, resulting in much faster reading of HTTP responses.
(Contributed by Kristján Valur Jónsson; bpo-4879@footnote{https://bugs.python.org/issue4879}.)

The @code{HTTPConnection} and @code{HTTPSConnection} classes
now support a @emph{source_address} parameter, a @code{(host, port)} 2-tuple
giving the source address that will be used for the connection.
(Contributed by Eldon Ziegler; bpo-3972@footnote{https://bugs.python.org/issue3972}.)

@item 
The @code{ihooks} module now supports relative imports.  Note that
@code{ihooks} is an older module for customizing imports,
superseded by the @code{imputil} module added in Python 2.0.
(Relative import support added by Neil Schemenauer.)

@c revision 75423

@item 
The @ref{98,,imaplib} module now supports IPv6 addresses.
(Contributed by Derek Morr; bpo-1655@footnote{https://bugs.python.org/issue1655}.)

@item 
New function: the @ref{a0,,inspect} module's @ref{7b0,,getcallargs()}
takes a callable and its positional and keyword arguments,
and figures out which of the callable's parameters will receive each argument,
returning a dictionary mapping argument names to their values.  For example:

@example
>>> from inspect import getcallargs
>>> def f(a, b=1, *pos, **named):
...     pass
>>> getcallargs(f, 1, 2, 3)
@{'a': 1, 'b': 2, 'pos': (3,), 'named': @{@}@}
>>> getcallargs(f, a=2, x=4)
@{'a': 2, 'b': 1, 'pos': (), 'named': @{'x': 4@}@}
>>> getcallargs(f)
Traceback (most recent call last):
...
TypeError: f() takes at least 1 argument (0 given)
@end example

由 Georg Sakkis 在 bpo-3135@footnote{https://bugs.python.org/issue3135} 中贡献。

@item 
Updated module: The @ref{a1,,io} library has been upgraded to the version shipped with
Python 3.1.  For 3.1, the I/O library was entirely rewritten in C
and is 2 to 20 times faster depending on the task being performed.  The
original Python version was renamed to the @code{_pyio} module.

One minor resulting change: the @ref{c32,,io.TextIOBase} class now
has an @code{errors} attribute giving the error setting
used for encoding and decoding errors (one of @code{'strict'}, @code{'replace'},
@code{'ignore'}).

The @ref{c9d,,io.FileIO} class now raises an @ref{1d3,,OSError} when passed
an invalid file descriptor.  (Implemented by Benjamin Peterson;
bpo-4991@footnote{https://bugs.python.org/issue4991}.)  The @ref{c9e,,truncate()} method now preserves the
file position; previously it would change the file position to the
end of the new file.  (Fixed by Pascal Chambon; bpo-6939@footnote{https://bugs.python.org/issue6939}.)

@item 
New function: @code{itertools.compress(data, selectors)} takes two
iterators.  Elements of @emph{data} are returned if the corresponding
value in @emph{selectors} is true:

@example
itertools.compress('ABCDEF', [1,0,1,0,1,1]) =>
  A, C, E, F
@end example

@c maybe here is better to use >>> list(itertools.compress(...)) instead

New function: @code{itertools.combinations_with_replacement(iter, r)}
returns all the possible @emph{r}-length combinations of elements from the
iterable @emph{iter}.  Unlike @ref{c9f,,combinations()}, individual elements
can be repeated in the generated combinations:

@example
itertools.combinations_with_replacement('abc', 2) =>
  ('a', 'a'), ('a', 'b'), ('a', 'c'),
  ('b', 'b'), ('b', 'c'), ('c', 'c')
@end example

Note that elements are treated as unique depending on their position
in the input, not their actual values.

The @ref{c14,,itertools.count()} function now has a @emph{step} argument that
allows incrementing by values other than 1.  @ref{c14,,count()} also
now allows keyword arguments, and using non-integer values such as
floats or @ref{188,,Decimal} instances.  (Implemented by Raymond
Hettinger; bpo-5032@footnote{https://bugs.python.org/issue5032}.)

@ref{c9f,,itertools.combinations()} and @ref{ca0,,itertools.product()}
previously raised @ref{1fb,,ValueError} for values of @emph{r} larger than
the input iterable.  This was deemed a specification error, so they
now return an empty iterator.  (Fixed by Raymond Hettinger; bpo-4816@footnote{https://bugs.python.org/issue4816}.)

@item 
Updated module: The @ref{a4,,json} module was upgraded to version 2.0.9 of the
simplejson package, which includes a C extension that makes
encoding and decoding faster.
(Contributed by Bob Ippolito; bpo-4136@footnote{https://bugs.python.org/issue4136}.)

To support the new @ref{1b9,,collections.OrderedDict} type, @ref{55a,,json.load()}
now has an optional @emph{object_pairs_hook} parameter that will be called
with any object literal that decodes to a list of pairs.
(Contributed by Raymond Hettinger; bpo-5381@footnote{https://bugs.python.org/issue5381}.)

@item 
The @ref{ae,,mailbox} module's @ref{ca1,,Maildir} class now records the
timestamp on the directories it reads, and only re-reads them if the
modification time has subsequently changed.  This improves
performance by avoiding unneeded directory scans.  (Fixed by
A.M. Kuchling and Antoine Pitrou; bpo-1607951@footnote{https://bugs.python.org/issue1607951}, bpo-6896@footnote{https://bugs.python.org/issue6896}.)

@item 
New functions: the @ref{b1,,math} module gained
@ref{44c,,erf()} and @ref{44d,,erfc()} for the error function and the complementary error function,
@ref{b61,,expm1()} which computes @code{e**x - 1} with more precision than
using @ref{ca2,,exp()} and subtracting 1,
@ref{b62,,gamma()} for the Gamma function, and
@ref{b63,,lgamma()} for the natural log of the Gamma function.
(Contributed by Mark Dickinson and nirinA raseliarison; bpo-3366@footnote{https://bugs.python.org/issue3366}.)

@item 
The @ref{b7,,multiprocessing} module's @code{Manager*} classes
can now be passed a callable that will be called whenever
a subprocess is started, along with a set of arguments that will be
passed to the callable.
(Contributed by lekma; bpo-5585@footnote{https://bugs.python.org/issue5585}.)

The @code{Pool} class, which controls a pool of worker processes,
now has an optional @emph{maxtasksperchild} parameter.  Worker processes
will perform the specified number of tasks and then exit, causing the
@code{Pool} to start a new worker.  This is useful if tasks may leak
memory or other resources, or if some tasks will cause the worker to
become very large.
(Contributed by Charles Cazabon; bpo-6963@footnote{https://bugs.python.org/issue6963}.)

@item 
The @ref{c0,,nntplib} module now supports IPv6 addresses.
(Contributed by Derek Morr; bpo-1664@footnote{https://bugs.python.org/issue1664}.)

@item 
New functions: the @ref{c4,,os} module wraps the following POSIX system
calls: @ref{ca3,,getresgid()} and @ref{ca4,,getresuid()}, which return the
real, effective, and saved GIDs and UIDs;
@ref{ca5,,setresgid()} and @ref{ca6,,setresuid()}, which set
real, effective, and saved GIDs and UIDs to new values;
@ref{ca7,,initgroups()}, which initialize the group access list
for the current process.  (GID/UID functions
contributed by Travis H.; bpo-6508@footnote{https://bugs.python.org/issue6508}.  Support for initgroups added
by Jean-Paul Calderone; bpo-7333@footnote{https://bugs.python.org/issue7333}.)

The @ref{95b,,os.fork()} function now re-initializes the import lock in
the child process; this fixes problems on Solaris when @ref{95b,,fork()}
is called from a thread.  (Fixed by Zsolt Cserna; bpo-7242@footnote{https://bugs.python.org/issue7242}.)

@item 
In the @ref{c5,,os.path} module, the @ref{ca8,,normpath()} and
@ref{ca9,,abspath()} functions now preserve Unicode; if their input path
is a Unicode string, the return value is also a Unicode string.
(@ref{ca8,,normpath()} fixed by Matt Giuca in bpo-5827@footnote{https://bugs.python.org/issue5827};
@ref{ca9,,abspath()} fixed by Ezio Melotti in bpo-3426@footnote{https://bugs.python.org/issue3426}.)

@item 
The @ref{d9,,pydoc} module now has help for the various symbols that Python
uses.  You can now do @code{help('<<')} or @code{help('@@')}, for example.
(Contributed by David Laban; bpo-4739@footnote{https://bugs.python.org/issue4739}.)

@item 
The @ref{dd,,re} module's @ref{3c2,,split()}, @ref{475,,sub()}, and @ref{72e,,subn()}
now accept an optional @emph{flags} argument, for consistency with the
other functions in the module.  (Added by Gregory P. Smith.)

@item 
New function: @ref{caa,,run_path()} in the @ref{e2,,runpy} module
will execute the code at a provided @emph{path} argument.  @emph{path} can be
the path of a Python source file (@code{example.py}), a compiled
bytecode file (@code{example.pyc}), a directory
(@code{./package/}), or a zip archive (@code{example.zip}).  If a
directory or zip path is provided, it will be added to the front of
@code{sys.path} and the module @ref{1,,__main__} will be imported.  It's
expected that the directory or zip contains a @code{__main__.py};
if it doesn't, some other @code{__main__.py} might be imported from
a location later in @code{sys.path}.  This makes more of the machinery
of @ref{e2,,runpy} available to scripts that want to mimic the way
Python's command line processes an explicit path name.
(Added by Nick Coghlan; bpo-6816@footnote{https://bugs.python.org/issue6816}.)

@item 
New function: in the @ref{e9,,shutil} module, @ref{21b,,make_archive()}
takes a filename, archive type (zip or tar-format), and a directory
path, and creates an archive containing the directory's contents.
(Added by Tarek Ziadé.)

@ref{e9,,shutil}'s @ref{258,,copyfile()} and @ref{21a,,copytree()}
functions now raise a @code{SpecialFileError} exception when
asked to copy a named pipe.  Previously the code would treat
named pipes like a regular file by opening them for reading, and
this would block indefinitely.  (Fixed by Antoine Pitrou; bpo-3002@footnote{https://bugs.python.org/issue3002}.)

@item 
The @ref{ea,,signal} module no longer re-installs the signal handler
unless this is truly necessary, which fixes a bug that could make it
impossible to catch the EINTR signal robustly.  (Fixed by
Charles-Francois Natali; bpo-8354@footnote{https://bugs.python.org/issue8354}.)

@item 
New functions: in the @ref{eb,,site} module, three new functions
return various site- and user-specific paths.
@ref{bcc,,getsitepackages()} returns a list containing all
global site-packages directories,
@ref{bce,,getusersitepackages()} returns the path of the user's
site-packages directory, and
@ref{bcd,,getuserbase()} returns the value of the 
@geindex USER_BASE
@geindex 环境变量; USER_BASE
@code{USER_BASE}
environment variable, giving the path to a directory that can be used
to store data.
(Contributed by Tarek Ziadé; bpo-6693@footnote{https://bugs.python.org/issue6693}.)

The @ref{eb,,site} module now reports exceptions occurring
when the @code{sitecustomize} module is imported, and will no longer
catch and swallow the @ref{197,,KeyboardInterrupt} exception.  (Fixed by
Victor Stinner; bpo-3137@footnote{https://bugs.python.org/issue3137}.)

@item 
The @ref{b97,,create_connection()} function
gained a @emph{source_address} parameter, a @code{(host, port)} 2-tuple
giving the source address that will be used for the connection.
(Contributed by Eldon Ziegler; bpo-3972@footnote{https://bugs.python.org/issue3972}.)

The @ref{cab,,recv_into()} and @ref{cac,,recvfrom_into()}
methods will now write into objects that support the buffer API, most usefully
the @ref{32b,,bytearray} and @ref{25c,,memoryview} objects.  (Implemented by
Antoine Pitrou; bpo-8104@footnote{https://bugs.python.org/issue8104}.)

@item 
The @code{SocketServer} module's @code{TCPServer} class now
supports socket timeouts and disabling the Nagle algorithm.
The @code{disable_nagle_algorithm} class attribute
defaults to @code{False}; if overridden to be true,
new request connections will have the TCP_NODELAY option set to
prevent buffering many small sends into a single TCP packet.
The @code{timeout} class attribute can hold
a timeout in seconds that will be applied to the request socket; if
no request is received within that time, @code{handle_timeout()}
will be called and @code{handle_request()} will return.
(Contributed by Kristján Valur Jónsson; bpo-6192@footnote{https://bugs.python.org/issue6192} and bpo-6267@footnote{https://bugs.python.org/issue6267}.)

@item 
Updated module: the @ref{f2,,sqlite3} module has been updated to
version 2.6.0 of the pysqlite package@footnote{https://github.com/ghaering/pysqlite}. Version 2.6.0 includes a number of bugfixes, and adds
the ability to load SQLite extensions from shared libraries.
Call the @code{enable_load_extension(True)} method to enable extensions,
and then call @ref{b93,,load_extension()} to load a particular shared library.
(Updated by Gerhard Häring.)

@item 
The @ref{f3,,ssl} module's @ref{3da,,SSLSocket} objects now support the
buffer API, which fixed a test suite failure (fix by Antoine Pitrou;
bpo-7133@footnote{https://bugs.python.org/issue7133}) and automatically set
OpenSSL's @code{SSL_MODE_AUTO_RETRY}, which will prevent an error
code being returned from @code{recv()} operations that trigger an SSL
renegotiation (fix by Antoine Pitrou; bpo-8222@footnote{https://bugs.python.org/issue8222}).

The @ref{469,,ssl.wrap_socket()} constructor function now takes a
@emph{ciphers} argument that's a string listing the encryption algorithms
to be allowed; the format of the string is described
in the OpenSSL documentation@footnote{https://www.openssl.org/docs/manmaster/man1/ciphers.html#CIPHER-LIST-FORMAT}.
(Added by Antoine Pitrou; bpo-8322@footnote{https://bugs.python.org/issue8322}.)

Another change makes the extension load all of OpenSSL's ciphers and
digest algorithms so that they're all available.  Some SSL
certificates couldn't be verified, reporting an "unknown algorithm"
error.  (Reported by Beda Kosata, and fixed by Antoine Pitrou;
bpo-8484@footnote{https://bugs.python.org/issue8484}.)

The version of OpenSSL being used is now available as the module
attributes @ref{b9a,,ssl.OPENSSL_VERSION} (a string),
@ref{b9b,,ssl.OPENSSL_VERSION_INFO} (a 5-tuple), and
@ref{b9c,,ssl.OPENSSL_VERSION_NUMBER} (an integer).  (Added by Antoine
Pitrou; bpo-8321@footnote{https://bugs.python.org/issue8321}.)

@item 
The @ref{f8,,struct} module will no longer silently ignore overflow
errors when a value is too large for a particular integer format
code (one of @code{bBhHiIlLqQ}); it now always raises a
@ref{cad,,struct.error} exception.  (Changed by Mark Dickinson;
bpo-1523@footnote{https://bugs.python.org/issue1523}.)  The @ref{c04,,pack()} function will also
attempt to use @ref{18a,,__index__()} to convert and pack non-integers
before trying the @ref{18b,,__int__()} method or reporting an error.
(Changed by Mark Dickinson; bpo-8300@footnote{https://bugs.python.org/issue8300}.)

@item 
New function: the @ref{f9,,subprocess} module's
@ref{8d5,,check_output()} runs a command with a specified set of arguments
and returns the command's output as a string when the command runs without
error, or raises a @ref{cae,,CalledProcessError} exception otherwise.

@example
>>> subprocess.check_output(['df', '-h', '.'])
'Filesystem     Size   Used  Avail Capacity  Mounted on\n
/dev/disk0s2    52G    49G   3.0G    94%    /\n'

>>> subprocess.check_output(['df', '-h', '/bogus'])
  ...
subprocess.CalledProcessError: Command '['df', '-h', '/bogus']' returned non-zero exit status 1
@end example

（由 Gregory P. Smith 贡献）

The @ref{f9,,subprocess} module will now retry its internal system calls
on receiving an @code{EINTR} signal.  (Reported by several people; final
patch by Gregory P. Smith in bpo-1068268@footnote{https://bugs.python.org/issue1068268}.)

@item 
New function: @ref{caf,,is_declared_global()} in the @ref{fc,,symtable} module
returns true for variables that are explicitly declared to be global,
false for ones that are implicitly global.
(Contributed by Jeremy Hylton.)

@item 
The @ref{ff,,syslog} module will now use the value of @code{sys.argv[0]} as the
identifier instead of the previous default value of @code{'python'}.
(Changed by Sean Reifschneider; bpo-8451@footnote{https://bugs.python.org/issue8451}.)

@item 
The @code{sys.version_info} value is now a named tuple, with attributes
named @code{major}, @code{minor}, @code{micro},
@code{releaselevel}, and @code{serial}.  (Contributed by Ross
Light; bpo-4285@footnote{https://bugs.python.org/issue4285}.)

@ref{590,,sys.getwindowsversion()} also returns a named tuple,
with attributes named @code{major}, @code{minor}, @code{build},
@ref{ce,,platform}, @code{service_pack}, @code{service_pack_major},
@code{service_pack_minor}, @code{suite_mask}, and
@code{product_type}.  (Contributed by Brian Curtin; bpo-7766@footnote{https://bugs.python.org/issue7766}.)

@item 
The @ref{101,,tarfile} module's default error handling has changed, to
no longer suppress fatal errors.  The default error level was previously 0,
which meant that errors would only result in a message being written to the
debug log, but because the debug log is not activated by default,
these errors go unnoticed.  The default error level is now 1,
which raises an exception if there's an error.
(Changed by Lars Gustäbel; bpo-7357@footnote{https://bugs.python.org/issue7357}.)

@ref{101,,tarfile} now supports filtering the @ref{b86,,TarInfo}
objects being added to a tar file.  When you call @ref{476,,add()},
you may supply an optional @emph{filter} argument
that's a callable.  The @emph{filter} callable will be passed the
@ref{b86,,TarInfo} for every file being added, and can modify and return it.
If the callable returns @code{None}, the file will be excluded from the
resulting archive.  This is more powerful than the existing
@emph{exclude} argument, which has therefore been deprecated.
(Added by Lars Gustäbel; bpo-6856@footnote{https://bugs.python.org/issue6856}.)
The @ref{b85,,TarFile} class also now supports the context management protocol.
(Added by Lars Gustäbel; bpo-7232@footnote{https://bugs.python.org/issue7232}.)

@item 
The @ref{cb0,,wait()} method of the @ref{aa8,,threading.Event} class
now returns the internal flag on exit.  This means the method will usually
return true because @ref{cb0,,wait()} is supposed to block until the
internal flag becomes true.  The return value will only be false if
a timeout was provided and the operation timed out.
(Contributed by Tim Lesher; bpo-1674032@footnote{https://bugs.python.org/issue1674032}.)

@item 
The Unicode database provided by the @ref{11a,,unicodedata} module is
now used internally to determine which characters are numeric,
whitespace, or represent line breaks.  The database also
includes information from the @code{Unihan.txt} data file (patch
by Anders Chrigström and Amaury Forgeot d'Arc; bpo-1571184@footnote{https://bugs.python.org/issue1571184})
and has been updated to version 5.2.0 (updated by
Florent Xicluna; bpo-8024@footnote{https://bugs.python.org/issue8024}).

@item 
The @code{urlparse} module's @code{urlsplit()} now handles
unknown URL schemes in a fashion compliant with 
@geindex RFC; RFC 3986
RFC 3986@footnote{https://tools.ietf.org/html/rfc3986.html}: if the
URL is of the form @code{"<something>://..."}, the text before the
@code{://} is treated as the scheme, even if it's a made-up scheme that
the module doesn't know about.  This change may break code that
worked around the old behaviour.  For example, Python 2.6.4 or 2.5
will return the following:

@example
>>> import urlparse
>>> urlparse.urlsplit('invented://host/filename?query')
('invented', '@w{'}, '//host/filename?query', '@w{'}, '@w{'})
@end example

Python 2.7 (and Python 2.6.5) will return:

@example
>>> import urlparse
>>> urlparse.urlsplit('invented://host/filename?query')
('invented', 'host', '/filename?query', '@w{'}, '@w{'})
@end example

(Python 2.7 actually produces slightly different output, since it
returns a named tuple instead of a standard tuple.)

The @code{urlparse} module also supports IPv6 literal addresses as defined by
@geindex RFC; RFC 2732
RFC 2732@footnote{https://tools.ietf.org/html/rfc2732.html} (contributed by Senthil Kumaran; bpo-2987@footnote{https://bugs.python.org/issue2987}).

@example
>>> urlparse.urlparse('http://[1080::8:800:200C:417A]/foo')
ParseResult(scheme='http', netloc='[1080::8:800:200C:417A]',
            path='/foo', params='@w{'}, query='@w{'}, fragment='@w{'})
@end example

@item 
New class: the @ref{cb1,,WeakSet} class in the @ref{128,,weakref}
module is a set that only holds weak references to its elements; elements
will be removed once there are no references pointing to them.
(Originally implemented in Python 3.x by Raymond Hettinger, and backported
to 2.7 by Michael Foord.)

@item 
The ElementTree library, @code{xml.etree}, no longer escapes
ampersands and angle brackets when outputting an XML processing
instruction (which looks like @code{<?xml-stylesheet href="#style1"?>})
or comment (which looks like @code{<!-- comment -->}).
(Patch by Neil Muller; bpo-2746@footnote{https://bugs.python.org/issue2746}.)

@item 
The XML-RPC client and server, provided by the @code{xmlrpclib} and
@code{SimpleXMLRPCServer} modules, have improved performance by
supporting HTTP/1.1 keep-alive and by optionally using gzip encoding
to compress the XML being exchanged.  The gzip compression is
controlled by the @code{encode_threshold} attribute of
@code{SimpleXMLRPCRequestHandler}, which contains a size in bytes;
responses larger than this will be compressed.
(Contributed by Kristján Valur Jónsson; bpo-6267@footnote{https://bugs.python.org/issue6267}.)

@item 
The @ref{142,,zipfile} module's @ref{417,,ZipFile} now supports the context
management protocol, so you can write @code{with zipfile.ZipFile(...) as f:}.
(Contributed by Brian Curtin; bpo-5511@footnote{https://bugs.python.org/issue5511}.)

@ref{142,,zipfile} now also supports archiving empty directories and
extracts them correctly.  (Fixed by Kuba Wieczorek; bpo-4710@footnote{https://bugs.python.org/issue4710}.)
Reading files out of an archive is faster, and interleaving
@ref{cb2,,read()} and @code{readline()} now works correctly.
(Contributed by Nir Aides; bpo-7610@footnote{https://bugs.python.org/issue7610}.)

The @ref{cb3,,is_zipfile()} function now
accepts a file object, in addition to the path names accepted in earlier
versions.  (Contributed by Gabriel Genellina; bpo-4756@footnote{https://bugs.python.org/issue4756}.)

The @ref{cb4,,writestr()} method now has an optional @emph{compress_type} parameter
that lets you override the default compression method specified in the
@ref{417,,ZipFile} constructor.  (Contributed by Ronald Oussoren;
bpo-6003@footnote{https://bugs.python.org/issue6003}.)
@end itemize

@c ======================================================================

@c whole new modules get described in subsections here

@menu
* 新模块：importlib:: 
* 新模块：sysconfig:: 
* ttk; Themed Widgets for Tk: ttk Themed Widgets for Tk. 
* 更新的模块：unittest:: 
* 更新的模块：ElementTree 1.3: 更新的模块：ElementTree 1 3. 

@end menu

@node 新模块：importlib,新模块：sysconfig,,新增和改进的模块
@anchor{whatsnew/2 7 importlib-section}@anchor{c7b}@anchor{whatsnew/2 7 new-module-importlib}@anchor{cb5}
@subsubsection 新模块：importlib


Python 3.1 includes the @ref{9b,,importlib} package, a re-implementation
of the logic underlying Python's @ref{c16,,import} statement.
@ref{9b,,importlib} is useful for implementors of Python interpreters and
to users who wish to write new importers that can participate in the
import process.  Python 2.7 doesn't contain the complete
@ref{9b,,importlib} package, but instead has a tiny subset that contains
a single function, @ref{b0c,,import_module()}.

@code{import_module(name, package=None)} imports a module.  @emph{name} is
a string containing the module or package's name.  It's possible to do
relative imports by providing a string that begins with a @code{.}
character, such as @code{..utils.errors}.  For relative imports, the
@emph{package} argument must be provided and is the name of the package that
will be used as the anchor for
the relative import.  @ref{b0c,,import_module()} both inserts the imported
module into @code{sys.modules} and returns the module object.

Here are some examples:

@example
>>> from importlib import import_module
>>> anydbm = import_module('anydbm')  # Standard absolute import
>>> anydbm
<module 'anydbm' from '/p/python/Lib/anydbm.py'>
>>> # Relative import
>>> file_util = import_module('..file_util', 'distutils.command')
>>> file_util
<module 'distutils.file_util' from '/python/Lib/distutils/file_util.pyc'>
@end example

@ref{9b,,importlib} was implemented by Brett Cannon and introduced in
Python 3.1.

@node 新模块：sysconfig,ttk Themed Widgets for Tk,新模块：importlib,新增和改进的模块
@anchor{whatsnew/2 7 new-module-sysconfig}@anchor{cb6}
@subsubsection 新模块：sysconfig


The @ref{fe,,sysconfig} module has been pulled out of the Distutils
package, becoming a new top-level module in its own right.
@ref{fe,,sysconfig} provides functions for getting information about
Python's build process: compiler switches, installation paths, the
platform name, and whether Python is running from its source
directory.

Some of the functions in the module are:


@itemize *

@item 
@ref{95e,,get_config_var()} returns variables from Python's
Makefile and the @code{pyconfig.h} file.

@item 
@ref{95f,,get_config_vars()} returns a dictionary containing
all of the configuration variables.

@item 
@ref{cb7,,get_path()} returns the configured path for
a particular type of module: the standard library,
site-specific modules, platform-specific modules, etc.

@item 
@ref{cb8,,is_python_build()} returns true if you're running a
binary from a Python source tree, and false otherwise.
@end itemize

Consult the @ref{fe,,sysconfig} documentation for more details and for
a complete list of functions.

The Distutils package and @ref{fe,,sysconfig} are now maintained by Tarek
Ziadé, who has also started a Distutils2 package (source repository at
@indicateurl{https://hg.python.org/distutils2/}) for developing a next-generation
version of Distutils.

@node ttk Themed Widgets for Tk,更新的模块：unittest,新模块：sysconfig,新增和改进的模块
@anchor{whatsnew/2 7 ttk-themed-widgets-for-tk}@anchor{cb9}
@subsubsection ttk: Themed Widgets for Tk


Tcl/Tk 8.5 includes a set of themed widgets that re-implement basic Tk
widgets but have a more customizable appearance and can therefore more
closely resemble the native platform's widgets.  This widget
set was originally called Tile, but was renamed to Ttk (for "themed Tk")
on being added to Tcl/Tck release 8.5.

To learn more, read the @code{ttk} module documentation.  You may also
wish to read the Tcl/Tk manual page describing the
Ttk theme engine, available at
@indicateurl{https://www.tcl.tk/man/tcl8.5/TkCmd/ttk_intro.htm}. Some
screenshots of the Python/Ttk code in use are at
@indicateurl{https://code.google.com/archive/p/python-ttk/wikis/Screenshots.wiki}.

The @code{ttk} module was written by Guilherme Polo and added in
bpo-2983@footnote{https://bugs.python.org/issue2983}.  An alternate version called @code{Tile.py}, written by
Martin Franklin and maintained by Kevin Walzer, was proposed for
inclusion in bpo-2618@footnote{https://bugs.python.org/issue2618}, but the authors argued that Guilherme
Polo's work was more comprehensive.

@node 更新的模块：unittest,更新的模块：ElementTree 1 3,ttk Themed Widgets for Tk,新增和改进的模块
@anchor{whatsnew/2 7 unittest-section}@anchor{cba}@anchor{whatsnew/2 7 updated-module-unittest}@anchor{cbb}
@subsubsection 更新的模块：unittest


The @ref{11b,,unittest} module was greatly enhanced; many
new features were added.  Most of these features were implemented
by Michael Foord, unless otherwise noted.  The enhanced version of
the module is downloadable separately for use with Python versions 2.4 to 2.6,
packaged as the @code{unittest2} package, from
@indicateurl{https://pypi.org/project/unittest2}.

When used from the command line, the module can automatically discover
tests.  It's not as fancy as py.test@footnote{http://pytest.org} or
nose@footnote{https://nose.readthedocs.io/}, but provides a
simple way to run tests kept within a set of package directories.  For example,
the following command will search the @code{test/} subdirectory for
any importable test files named @code{test*.py}:

@example
python -m unittest discover -s test
@end example

Consult the @ref{11b,,unittest} module documentation for more details.
(Developed in bpo-6001@footnote{https://bugs.python.org/issue6001}.)

The @ref{8fc,,main()} function supports some other new options:


@itemize *

@item 
@ref{cbc,,-b} or @code{--buffer} will buffer the standard output
and standard error streams during each test.  If the test passes,
any resulting output will be discarded; on failure, the buffered
output will be displayed.

@item 
@ref{cbd,,-c} or @code{--catch} will cause the control-C interrupt
to be handled more gracefully.  Instead of interrupting the test
process immediately, the currently running test will be completed
and then the partial results up to the interruption will be reported.
If you're impatient, a second press of control-C will cause an immediate
interruption.

This control-C handler tries to avoid causing problems when the code
being tested or the tests being run have defined a signal handler of
their own, by noticing that a signal handler was already set and
calling it.  If this doesn't work for you, there's a
@ref{cbe,,removeHandler()} decorator that can be used to mark tests that
should have the control-C handling disabled.

@item 
@ref{cbf,,-f} or @code{--failfast} makes
test execution stop immediately when a test fails instead of
continuing to execute further tests.  (Suggested by Cliff Dyer and
implemented by Michael Foord; bpo-8074@footnote{https://bugs.python.org/issue8074}.)
@end itemize

The progress messages now show 'x' for expected failures
and 'u' for unexpected successes when run in verbose mode.
(Contributed by Benjamin Peterson.)

Test cases can raise the @ref{8fd,,SkipTest} exception to skip a
test (bpo-1034053@footnote{https://bugs.python.org/issue1034053}).

The error messages for @ref{bae,,assertEqual()},
@ref{bad,,assertTrue()}, and @ref{cc0,,assertFalse()}
failures now provide more information.  If you set the
@ref{cc1,,longMessage} attribute of your @ref{8f9,,TestCase} classes to
true, both the standard error message and any additional message you
provide will be printed for failures.  (Added by Michael Foord; bpo-5663@footnote{https://bugs.python.org/issue5663}.)

The @ref{ab5,,assertRaises()} method now
returns a context handler when called without providing a callable
object to run.  For example, you can write this:

@example
with self.assertRaises(KeyError):
    @{@}['foo']
@end example

(Implemented by Antoine Pitrou; bpo-4444@footnote{https://bugs.python.org/issue4444}.)

@c rev 78774

Module- and class-level setup and teardown fixtures are now supported.
Modules can contain @code{setUpModule()} and @code{tearDownModule()}
functions.  Classes can have @ref{24c,,setUpClass()} and
@ref{cc2,,tearDownClass()} methods that must be defined as class methods
(using @code{@@classmethod} or equivalent).  These functions and
methods are invoked when the test runner switches to a test case in a
different module or class.

The methods @ref{2a2,,addCleanup()} and
@ref{cc3,,doCleanups()} were added.
@ref{2a2,,addCleanup()} lets you add cleanup functions that
will be called unconditionally (after @ref{cc4,,setUp()} if
@ref{cc4,,setUp()} fails, otherwise after @ref{cc5,,tearDown()}). This allows
for much simpler resource allocation and deallocation during tests
(bpo-5679@footnote{https://bugs.python.org/issue5679}).

A number of new methods were added that provide more specialized
tests.  Many of these methods were written by Google engineers
for use in their test suites; Gregory P. Smith, Michael Foord, and
GvR worked on merging them into Python's version of @ref{11b,,unittest}.


@itemize *

@item 
@ref{cc6,,assertIsNone()} and @ref{cc7,,assertIsNotNone()} take one
expression and verify that the result is or is not @code{None}.

@item 
@ref{cc8,,assertIs()} and @ref{cc9,,assertIsNot()}
take two values and check whether the two values evaluate to the same object or not.
(Added by Michael Foord; bpo-2578@footnote{https://bugs.python.org/issue2578}.)

@item 
@ref{cca,,assertIsInstance()} and
@ref{ccb,,assertNotIsInstance()} check whether
the resulting object is an instance of a particular class, or of
one of a tuple of classes.  (Added by Georg Brandl; bpo-7031@footnote{https://bugs.python.org/issue7031}.)

@item 
@ref{ccc,,assertGreater()}, @ref{ccd,,assertGreaterEqual()},
@ref{cce,,assertLess()}, and @ref{ccf,,assertLessEqual()} compare
two quantities.

@item 
@ref{cd0,,assertMultiLineEqual()} compares two strings, and if they're
not equal, displays a helpful comparison that highlights the
differences in the two strings.  This comparison is now used by
default when Unicode strings are compared with @ref{bae,,assertEqual()}.

@item 
@code{assertRegexpMatches()} and
@code{assertNotRegexpMatches()} checks whether the
first argument is a string matching or not matching the regular
expression provided as the second argument (bpo-8038@footnote{https://bugs.python.org/issue8038}).

@item 
@code{assertRaisesRegexp()} checks whether a particular exception
is raised, and then also checks that the string representation of
the exception matches the provided regular expression.

@item 
@ref{cd1,,assertIn()} and @ref{cd2,,assertNotIn()}
tests whether @emph{first} is or is not in  @emph{second}.

@item 
@code{assertItemsEqual()} tests whether two provided sequences
contain the same elements.

@item 
@ref{cd3,,assertSetEqual()} compares whether two sets are equal, and
only reports the differences between the sets in case of error.

@item 
Similarly, @ref{cd4,,assertListEqual()} and @ref{cd5,,assertTupleEqual()}
compare the specified types and explain any differences without necessarily
printing their full values; these methods are now used by default
when comparing lists and tuples using @ref{bae,,assertEqual()}.
More generally, @ref{cd6,,assertSequenceEqual()} compares two sequences
and can optionally check whether both sequences are of a
particular type.

@item 
@ref{cd7,,assertDictEqual()} compares two dictionaries and reports the
differences; it's now used by default when you compare two dictionaries
using @ref{bae,,assertEqual()}.  @code{assertDictContainsSubset()} checks whether
all of the key/value pairs in @emph{first} are found in @emph{second}.

@item 
@ref{bb0,,assertAlmostEqual()} and @ref{bb1,,assertNotAlmostEqual()} test
whether @emph{first} and @emph{second} are approximately equal.  This method
can either round their difference to an optionally-specified number
of @emph{places} (the default is 7) and compare it to zero, or require
the difference to be smaller than a supplied @emph{delta} value.

@item 
@ref{cd8,,loadTestsFromName()} properly honors the
@ref{cd9,,suiteClass} attribute of
the @ref{77c,,TestLoader}. (Fixed by Mark Roddy; bpo-6866@footnote{https://bugs.python.org/issue6866}.)

@item 
A new hook lets you extend the @ref{bae,,assertEqual()} method to handle
new data types.  The @ref{cda,,addTypeEqualityFunc()} method takes a type
object and a function. The function will be used when both of the
objects being compared are of the specified type.  This function
should compare the two objects and raise an exception if they don't
match; it's a good idea for the function to provide additional
information about why the two objects aren't matching, much as the new
sequence comparison methods do.
@end itemize

@ref{8fc,,unittest.main()} now takes an optional @code{exit} argument.  If
false, @ref{8fc,,main()} doesn't call @ref{cdb,,sys.exit()}, allowing
@ref{8fc,,main()} to be used from the interactive interpreter.
(Contributed by J. Pablo Fernández; bpo-3379@footnote{https://bugs.python.org/issue3379}.)

@ref{aba,,TestResult} has new @ref{cdc,,startTestRun()} and
@ref{cdd,,stopTestRun()} methods that are called immediately before
and after a test run.  (Contributed by Robert Collins; bpo-5728@footnote{https://bugs.python.org/issue5728}.)

With all these changes, the @code{unittest.py} was becoming awkwardly
large, so the module was turned into a package and the code split into
several files (by Benjamin Peterson).  This doesn't affect how the
module is imported or used.


@subsubheading 参见



@table @asis

@item @indicateurl{http://www.voidspace.org.uk/python/articles/unittest2.shtml}

Describes the new features, how to use them, and the
rationale for various design decisions.  (By Michael Foord.)
@end table


@node 更新的模块：ElementTree 1 3,,更新的模块：unittest,新增和改进的模块
@anchor{whatsnew/2 7 elementtree-section}@anchor{cde}@anchor{whatsnew/2 7 updated-module-elementtree-1-3}@anchor{cdf}
@subsubsection 更新的模块：ElementTree 1.3


The version of the ElementTree library included with Python was updated to
version 1.3.  Some of the new features are:


@itemize *

@item 
The various parsing functions now take a @emph{parser} keyword argument
giving an @ref{252,,XMLParser} instance that will
be used.  This makes it possible to override the file's internal encoding:

@example
p = ET.XMLParser(encoding='utf-8')
t = ET.XML("""<root/>""", parser=p)
@end example

Errors in parsing XML now raise a @code{ParseError} exception, whose
instances have a @code{position} attribute
containing a (@emph{line}, @emph{column}) tuple giving the location of the problem.

@item 
ElementTree's code for converting trees to a string has been
significantly reworked, making it roughly twice as fast in many
cases.  The @ref{912,,ElementTree.write()}
and @code{Element.write()} methods now have a @emph{method} parameter that can be
"xml" (the default), "html", or "text".  HTML mode will output empty
elements as @code{<empty></empty>} instead of @code{<empty/>}, and text
mode will skip over elements and only output the text chunks.  If
you set the @code{tag} attribute of an element to @code{None} but
leave its children in place, the element will be omitted when the
tree is written out, so you don't need to do more extensive rearrangement
to remove a single element.

Namespace handling has also been improved.  All @code{xmlns:<whatever>}
declarations are now output on the root element, not scattered throughout
the resulting XML.  You can set the default namespace for a tree
by setting the @code{default_namespace} attribute and can
register new prefixes with @ref{b49,,register_namespace()}.  In XML mode,
you can use the true/false @emph{xml_declaration} parameter to suppress the
XML declaration.

@item 
New @ref{abf,,Element} method:
@ref{b4a,,extend()} appends the items from a
sequence to the element's children.  Elements themselves behave like
sequences, so it's easy to move children from one element to
another:

@example
from xml.etree import ElementTree as ET

t = ET.XML("""<list>
  <item>1</item> <item>2</item>  <item>3</item>
</list>""")
new = ET.XML('<root/>')
new.extend(t)

# Outputs <root><item>1</item>...</root>
print ET.tostring(new)
@end example

@item 
New @code{Element} method:
@ref{ce0,,iter()} yields the children of the
element as a generator.  It's also possible to write @code{for child in
elem:} to loop over an element's children.  The existing method
@code{getiterator()} is now deprecated, as is @code{getchildren()}
which constructs and returns a list of children.

@item 
New @code{Element} method:
@ref{b4c,,itertext()} yields all chunks of
text that are descendants of the element.  For example:

@example
t = ET.XML("""<list>
  <item>1</item> <item>2</item>  <item>3</item>
</list>""")

# Outputs ['\n  ', '1', ' ', '2', '  ', '3', '\n']
print list(t.itertext())
@end example

@item 
Deprecated: using an element as a Boolean (i.e., @code{if elem:}) would
return true if the element had any children, or false if there were
no children.  This behaviour is confusing -- @code{None} is false, but
so is a childless element? -- so it will now trigger a
@ref{31e,,FutureWarning}.  In your code, you should be explicit: write
@code{len(elem) != 0} if you're interested in the number of children,
or @code{elem is not None}.
@end itemize

Fredrik Lundh develops ElementTree and produced the 1.3 version;
you can read his article describing 1.3 at
@indicateurl{http://effbot.org/zone/elementtree-13-intro.htm}.
Florent Xicluna updated the version included with
Python, after discussions on python-dev and in bpo-6472@footnote{https://bugs.python.org/issue6472}.)

@c ======================================================================

@node 构建和 C API 的改变<8>,Other Changes and Fixes,新增和改进的模块,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 build-and-c-api-changes}@anchor{ce1}
@subsection 构建和 C API 的改变


Changes to Python's build process and to the C API include:


@itemize *

@item 
The latest release of the GNU Debugger, GDB 7, can be scripted using Python@footnote{https://sourceware.org/gdb/current/onlinedocs/gdb/Python.html}.
When you begin debugging an executable program P, GDB will look for
a file named @code{P-gdb.py} and automatically read it.  Dave Malcolm
contributed a @code{python-gdb.py} that adds a number of
commands useful when debugging Python itself.  For example,
@code{py-up} and @code{py-down} go up or down one Python stack frame,
which usually corresponds to several C stack frames.  @code{py-print}
prints the value of a Python variable, and @code{py-bt} prints the
Python stack trace.  (Added as a result of bpo-8032@footnote{https://bugs.python.org/issue8032}.)

@item 
If you use the @code{.gdbinit} file provided with Python,
the "pyo" macro in the 2.7 version now works correctly when the thread being
debugged doesn't hold the GIL; the macro now acquires it before printing.
(Contributed by Victor Stinner; bpo-3632@footnote{https://bugs.python.org/issue3632}.)

@item 
@ref{ce2,,Py_AddPendingCall()} is now thread-safe, letting any
worker thread submit notifications to the main Python thread.  This
is particularly useful for asynchronous IO operations.
(Contributed by Kristján Valur Jónsson; bpo-4293@footnote{https://bugs.python.org/issue4293}.)

@item 
New function: @ref{ce3,,PyCode_NewEmpty()} creates an empty code object;
only the filename, function name, and first line number are required.
This is useful for extension modules that are attempting to
construct a more useful traceback stack.  Previously such
extensions needed to call @ref{272,,PyCode_New()}, which had many
more arguments.  (Added by Jeffrey Yasskin.)

@item 
New function: @ref{bf8,,PyErr_NewExceptionWithDoc()} creates a new
exception class, just as the existing @ref{bf9,,PyErr_NewException()} does,
but takes an extra @code{char *} argument containing the docstring for the
new exception class.  (Added by 'lekma' on the Python bug tracker;
bpo-7033@footnote{https://bugs.python.org/issue7033}.)

@item 
New function: @ref{ce4,,PyFrame_GetLineNumber()} takes a frame object
and returns the line number that the frame is currently executing.
Previously code would need to get the index of the bytecode
instruction currently executing, and then look up the line number
corresponding to that address.  (Added by Jeffrey Yasskin.)

@item 
New functions: @ref{bf6,,PyLong_AsLongAndOverflow()} and
@ref{bf5,,PyLong_AsLongLongAndOverflow()}  approximates a Python long
integer as a C @code{long} or @code{long long}.
If the number is too large to fit into
the output type, an @emph{overflow} flag is set and returned to the caller.
(Contributed by Case Van Horsen; bpo-7528@footnote{https://bugs.python.org/issue7528} and bpo-7767@footnote{https://bugs.python.org/issue7767}.)

@item 
New function: stemming from the rewrite of string-to-float conversion,
a new @ref{c1c,,PyOS_string_to_double()} function was added.  The old
@code{PyOS_ascii_strtod()} and @code{PyOS_ascii_atof()} functions
are now deprecated.

@item 
New function: @ref{bf3,,PySys_SetArgvEx()} sets the value of
@code{sys.argv} and can optionally update @code{sys.path} to include the
directory containing the script named by @code{sys.argv[0]} depending
on the value of an @emph{updatepath} parameter.

This function was added to close a security hole for applications
that embed Python.  The old function, @ref{ce5,,PySys_SetArgv()}, would
always update @code{sys.path}, and sometimes it would add the current
directory.  This meant that, if you ran an application embedding
Python in a directory controlled by someone else, attackers could
put a Trojan-horse module in the directory (say, a file named
@code{os.py}) that your application would then import and run.

If you maintain a C/C++ application that embeds Python, check
whether you're calling @ref{ce5,,PySys_SetArgv()} and carefully consider
whether the application should be using @ref{bf3,,PySys_SetArgvEx()}
with @emph{updatepath} set to false.

Security issue reported as CVE-2008-5983@footnote{https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983};
discussed in bpo-5753@footnote{https://bugs.python.org/issue5753}, and fixed by Antoine Pitrou.

@item 
New macros: the Python header files now define the following macros:
@code{Py_ISALNUM},
@code{Py_ISALPHA},
@code{Py_ISDIGIT},
@code{Py_ISLOWER},
@code{Py_ISSPACE},
@code{Py_ISUPPER},
@code{Py_ISXDIGIT},
@code{Py_TOLOWER}, and @code{Py_TOUPPER}.
All of these functions are analogous to the C
standard macros for classifying characters, but ignore the current
locale setting, because in
several places Python needs to analyze characters in a
locale-independent way.  (Added by Eric Smith;
bpo-5793@footnote{https://bugs.python.org/issue5793}.)

@c XXX these macros don't seem to be described in the c-api docs.

@item 
Removed function: @code{PyEval_CallObject} is now only available
as a macro.  A function version was being kept around to preserve
ABI linking compatibility, but that was in 1997; it can certainly be
deleted by now.  (Removed by Antoine Pitrou; bpo-8276@footnote{https://bugs.python.org/issue8276}.)

@item 
New format codes: the @code{PyFormat_FromString()},
@code{PyFormat_FromStringV()}, and @ref{7a4,,PyErr_Format()} functions now
accept @code{%lld} and @code{%llu} format codes for displaying
C's @code{long long} types.
(Contributed by Mark Dickinson; bpo-7228@footnote{https://bugs.python.org/issue7228}.)

@item 
The complicated interaction between threads and process forking has
been changed.  Previously, the child process created by
@ref{95b,,os.fork()} might fail because the child is created with only a
single thread running, the thread performing the @ref{95b,,os.fork()}.
If other threads were holding a lock, such as Python's import lock,
when the fork was performed, the lock would still be marked as
"held" in the new process.  But in the child process nothing would
ever release the lock, since the other threads weren't replicated,
and the child process would no longer be able to perform imports.

Python 2.7 acquires the import lock before performing an
@ref{95b,,os.fork()}, and will also clean up any locks created using the
@ref{109,,threading} module.  C extension modules that have internal
locks, or that call @code{fork()} themselves, will not benefit
from this clean-up.

(Fixed by Thomas Wouters; bpo-1590864@footnote{https://bugs.python.org/issue1590864}.)

@item 
The @ref{ce6,,Py_Finalize()} function now calls the internal
@code{threading._shutdown()} function; this prevents some exceptions from
being raised when an interpreter shuts down.
(Patch by Adam Olsen; bpo-1722344@footnote{https://bugs.python.org/issue1722344}.)

@item 
When using the @ref{420,,PyMemberDef} structure to define attributes
of a type, Python will no longer let you try to delete or set a
@code{T_STRING_INPLACE} attribute.

@c rev 79644

@item 
Global symbols defined by the @ref{2b,,ctypes} module are now prefixed
with @code{Py}, or with @code{_ctypes}.  (Implemented by Thomas
Heller; bpo-3102@footnote{https://bugs.python.org/issue3102}.)

@item 
New configure option: the @code{--with-system-expat} switch allows
building the @code{pyexpat} module to use the system Expat library.
(Contributed by Arfrever Frehtes Taifersar Arahesis; bpo-7609@footnote{https://bugs.python.org/issue7609}.)

@item 
New configure option: the
@code{--with-valgrind} option will now disable the pymalloc
allocator, which is difficult for the Valgrind memory-error detector
to analyze correctly.
Valgrind will therefore be better at detecting memory leaks and
overruns. (Contributed by James Henstridge; bpo-2422@footnote{https://bugs.python.org/issue2422}.)

@item 
New configure option: you can now supply an empty string to
@code{--with-dbmliborder=} in order to disable all of the various
DBM modules.  (Added by Arfrever Frehtes Taifersar Arahesis;
bpo-6491@footnote{https://bugs.python.org/issue6491}.)

@item 
The @code{configure} script now checks for floating-point rounding bugs
on certain 32-bit Intel chips and defines a @code{X87_DOUBLE_ROUNDING}
preprocessor definition.  No code currently uses this definition,
but it's available if anyone wishes to use it.
(Added by Mark Dickinson; bpo-2937@footnote{https://bugs.python.org/issue2937}.)

@code{configure} also now sets a 
@geindex LDCXXSHARED
@geindex 环境变量; LDCXXSHARED
@code{LDCXXSHARED} Makefile
variable for supporting C++ linking.  (Contributed by Arfrever
Frehtes Taifersar Arahesis; bpo-1222585@footnote{https://bugs.python.org/issue1222585}.)

@item 
The build process now creates the necessary files for pkg-config
support.  (Contributed by Clinton Roy; bpo-3585@footnote{https://bugs.python.org/issue3585}.)

@item 
The build process now supports Subversion 1.7.  (Contributed by
Arfrever Frehtes Taifersar Arahesis; bpo-6094@footnote{https://bugs.python.org/issue6094}.)
@end itemize

@menu
* 胶囊:: 
* 特定于 Windows 的更改：:: 
* 特定于 Mac OS X 的更改：:: 
* 特定于 FreeBSD 的更改：:: 

@end menu

@node 胶囊,特定于 Windows 的更改：,,构建和 C API 的改变<8>
@anchor{whatsnew/2 7 capsules}@anchor{ce7}@anchor{whatsnew/2 7 whatsnew27-capsules}@anchor{ce8}
@subsubsection 胶囊


Python 3.1 adds a new C datatype, @ref{c00,,PyCapsule}, for providing a
C API to an extension module.  A capsule is essentially the holder of
a C @code{void *} pointer, and is made available as a module attribute; for
example, the @ref{ef,,socket} module's API is exposed as @code{socket.CAPI},
and @ref{11a,,unicodedata} exposes @code{ucnhash_CAPI}.  Other extensions
can import the module, access its dictionary to get the capsule
object, and then get the @code{void *} pointer, which will usually point
to an array of pointers to the module's various API functions.

There is an existing data type already used for this,
@code{PyCObject}, but it doesn't provide type safety.  Evil code
written in pure Python could cause a segmentation fault by taking a
@code{PyCObject} from module A and somehow substituting it for the
@code{PyCObject} in module B.   Capsules know their own name,
and getting the pointer requires providing the name:

@example
void *vtable;

if (!PyCapsule_IsValid(capsule, "mymodule.CAPI") @{
        PyErr_SetString(PyExc_ValueError, "argument type invalid");
        return NULL;
@}

vtable = PyCapsule_GetPointer(capsule, "mymodule.CAPI");
@end example

You are assured that @code{vtable} points to whatever you're expecting.
If a different capsule was passed in, @ref{ce9,,PyCapsule_IsValid()} would
detect the mismatched name and return false.  Refer to
@ref{cea,,给扩展模块提供C API} for more information on using these objects.

Python 2.7 now uses capsules internally to provide various
extension-module APIs, but the @code{PyCObject_AsVoidPtr()} was
modified to handle capsules, preserving compile-time compatibility
with the @code{CObject} interface.  Use of
@code{PyCObject_AsVoidPtr()} will signal a
@ref{279,,PendingDeprecationWarning}, which is silent by default.

Implemented in Python 3.1 and backported to 2.7 by Larry Hastings;
discussed in bpo-5630@footnote{https://bugs.python.org/issue5630}.

@c ======================================================================

@node 特定于 Windows 的更改：,特定于 Mac OS X 的更改：,胶囊,构建和 C API 的改变<8>
@anchor{whatsnew/2 7 port-specific-changes-windows}@anchor{ceb}
@subsubsection 特定于 Windows 的更改：



@itemize *

@item 
The @ref{b6,,msvcrt} module now contains some constants from
the @code{crtassem.h} header file:
@code{CRT_ASSEMBLY_VERSION},
@code{VC_ASSEMBLY_PUBLICKEYTOKEN},
and @code{LIBRARIES_ASSEMBLY_NAME_PREFIX}.
(Contributed by David Cournapeau; bpo-4365@footnote{https://bugs.python.org/issue4365}.)

@item 
The @code{_winreg} module for accessing the registry now implements
the @code{CreateKeyEx()} and @code{DeleteKeyEx()}
functions, extended versions of previously-supported functions that
take several extra arguments.  The @code{DisableReflectionKey()},
@code{EnableReflectionKey()}, and @code{QueryReflectionKey()}
were also tested and documented.
(Implemented by Brian Curtin: bpo-7347@footnote{https://bugs.python.org/issue7347}.)

@item 
The new @code{_beginthreadex()} API is used to start threads, and
the native thread-local storage functions are now used.
(Contributed by Kristján Valur Jónsson; bpo-3582@footnote{https://bugs.python.org/issue3582}.)

@item 
The @ref{cec,,os.kill()} function now works on Windows.  The signal value
can be the constants @code{CTRL_C_EVENT},
@code{CTRL_BREAK_EVENT}, or any integer.  The first two constants
will send @code{Control-C} and @code{Control-Break} keystroke events to
subprocesses; any other value will use the @code{TerminateProcess()}
API.  (Contributed by Miki Tebeka; bpo-1220212@footnote{https://bugs.python.org/issue1220212}.)

@item 
The @ref{a3c,,os.listdir()} function now correctly fails
for an empty path.  (Fixed by Hirokazu Yamamoto; bpo-5913@footnote{https://bugs.python.org/issue5913}.)

@item 
The @code{mimelib} module will now read the MIME database from
the Windows registry when initializing.
(Patch by Gabriel Genellina; bpo-4969@footnote{https://bugs.python.org/issue4969}.)
@end itemize

@c ======================================================================

@node 特定于 Mac OS X 的更改：,特定于 FreeBSD 的更改：,特定于 Windows 的更改：,构建和 C API 的改变<8>
@anchor{whatsnew/2 7 port-specific-changes-mac-os-x}@anchor{ced}
@subsubsection 特定于 Mac OS X 的更改：



@itemize *

@item 
The path @code{/Library/Python/2.7/site-packages} is now appended to
@code{sys.path}, in order to share added packages between the system
installation and a user-installed copy of the same version.
(Changed by Ronald Oussoren; bpo-4865@footnote{https://bugs.python.org/issue4865}.)

@quotation


在 2.7.13 版更改: As of 2.7.13, this change was removed.
@code{/Library/Python/2.7/site-packages}, the site-packages directory
used by the Apple-supplied system Python 2.7 is no longer appended to
@code{sys.path} for user-installed Pythons such as from the python.org
installers.  As of macOS 10.12, Apple changed how the system
site-packages directory is configured, which could cause installation
of pip components, like setuptools, to fail.  Packages installed for
the system Python will no longer be shared with user-installed
Pythons. (bpo-28440@footnote{https://bugs.python.org/issue28440})

@end quotation
@end itemize

@node 特定于 FreeBSD 的更改：,,特定于 Mac OS X 的更改：,构建和 C API 的改变<8>
@anchor{whatsnew/2 7 port-specific-changes-freebsd}@anchor{cee}
@subsubsection 特定于 FreeBSD 的更改：



@itemize *

@item 
FreeBSD 7.1's @code{SO_SETFIB} constant, used with
@code{getsockopt()}/@code{setsockopt()} to select an
alternate routing table, is now available in the @ref{ef,,socket}
module.  (Added by Kyle VanderBeek; bpo-8235@footnote{https://bugs.python.org/issue8235}.)
@end itemize

@node Other Changes and Fixes,移植到 Python 2 7,构建和 C API 的改变<8>,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 other-changes-and-fixes}@anchor{cef}
@subsection Other Changes and Fixes



@itemize *

@item 
Two benchmark scripts, @code{iobench} and @code{ccbench}, were
added to the @code{Tools} directory.  @code{iobench} measures the
speed of the built-in file I/O objects returned by @ref{4ea,,open()}
while performing various operations, and @code{ccbench} is a
concurrency benchmark that tries to measure computing throughput,
thread switching latency, and IO processing bandwidth when
performing several tasks using a varying number of threads.

@item 
The @code{Tools/i18n/msgfmt.py} script now understands plural
forms in @code{.po} files.  (Fixed by Martin von Löwis;
bpo-5464@footnote{https://bugs.python.org/issue5464}.)

@item 
When importing a module from a @code{.pyc} or @code{.pyo} file
with an existing @code{.py} counterpart, the @code{co_filename}
attributes of the resulting code objects are overwritten when the
original filename is obsolete.  This can happen if the file has been
renamed, moved, or is accessed through different paths.  (Patch by
Ziga Seilnacht and Jean-Paul Calderone; bpo-1180193@footnote{https://bugs.python.org/issue1180193}.)

@item 
The @code{regrtest.py} script now takes a @code{--randseed=}
switch that takes an integer that will be used as the random seed
for the @code{-r} option that executes tests in random order.
The @code{-r} option also reports the seed that was used
(Added by Collin Winter.)

@item 
Another @code{regrtest.py} switch is @code{-j}, which
takes an integer specifying how many tests run in parallel. This
allows reducing the total runtime on multi-core machines.
This option is compatible with several other options, including the
@code{-R} switch which is known to produce long runtimes.
(Added by Antoine Pitrou, bpo-6152@footnote{https://bugs.python.org/issue6152}.)  This can also be used
with a new @code{-F} switch that runs selected tests in a loop
until they fail.  (Added by Antoine Pitrou; bpo-7312@footnote{https://bugs.python.org/issue7312}.)

@item 
When executed as a script, the @code{py_compile.py} module now
accepts @code{'-'} as an argument, which will read standard input for
the list of filenames to be compiled.  (Contributed by Piotr
Ożarowski; bpo-8233@footnote{https://bugs.python.org/issue8233}.)
@end itemize

@c ======================================================================

@node 移植到 Python 2 7,New Features Added to Python 2 7 Maintenance Releases,Other Changes and Fixes,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 porting-to-python-2-7}@anchor{cf0}
@subsection 移植到 Python 2.7


This section lists previously described changes and other bugfixes
that may require changes to your code:


@itemize *

@item 
The @ref{9b8,,range()} function processes its arguments more
consistently; it will now call @ref{18b,,__int__()} on non-float,
non-integer arguments that are supplied to it.  (Fixed by Alexander
Belopolsky; bpo-1533@footnote{https://bugs.python.org/issue1533}.)

@item 
The string @ref{4d5,,format()} method changed the default precision used
for floating-point and complex numbers from 6 decimal
places to 12, which matches the precision used by @ref{329,,str()}.
(Changed by Eric Smith; bpo-5920@footnote{https://bugs.python.org/issue5920}.)

@item 
Because of an optimization for the @ref{6e3,,with} statement, the special
methods @ref{c8e,,__enter__()} and @ref{c8f,,__exit__()} must belong to the object's
type, and cannot be directly attached to the object's instance.  This
affects new-style classes (derived from @ref{2b0,,object}) and C extension
types.  (bpo-6101@footnote{https://bugs.python.org/issue6101}.)

@item 
Due to a bug in Python 2.6, the @emph{exc_value} parameter to
@ref{c8f,,__exit__()} methods was often the string representation of the
exception, not an instance.  This was fixed in 2.7, so @emph{exc_value}
will be an instance as expected.  (Fixed by Florent Xicluna;
bpo-7853@footnote{https://bugs.python.org/issue7853}.)

@item 
When a restricted set of attributes were set using @code{__slots__},
deleting an unset attribute would not raise @ref{393,,AttributeError}
as you would expect.  Fixed by Benjamin Peterson; bpo-7604@footnote{https://bugs.python.org/issue7604}.)
@end itemize

In the standard library:


@itemize *

@item 
Operations with @ref{194,,datetime} instances that resulted in a year
falling outside the supported range didn't always raise
@ref{95a,,OverflowError}.  Such errors are now checked more carefully
and will now raise the exception. (Reported by Mark Leander, patch
by Anand B. Pillai and Alexander Belopolsky; bpo-7150@footnote{https://bugs.python.org/issue7150}.)

@item 
When using @ref{188,,Decimal} instances with a string's
@ref{4d5,,format()} method, the default alignment was previously
left-alignment.  This has been changed to right-alignment, which might
change the output of your programs.
(Changed by Mark Dickinson; bpo-6857@footnote{https://bugs.python.org/issue6857}.)

Comparisons involving a signaling NaN value (or @code{sNAN}) now signal
@ref{9e5,,InvalidOperation} instead of silently returning a true or
false value depending on the comparison operator.  Quiet NaN values
(or @code{NaN}) are now hashable.  (Fixed by Mark Dickinson;
bpo-7279@footnote{https://bugs.python.org/issue7279}.)

@item 
The ElementTree library, @code{xml.etree}, no longer escapes
ampersands and angle brackets when outputting an XML processing
instruction (which looks like @cite{<?xml-stylesheet href="#style1"?>})
or comment (which looks like @cite{<!-- comment -->}).
(Patch by Neil Muller; bpo-2746@footnote{https://bugs.python.org/issue2746}.)

@item 
The @code{readline()} method of @code{StringIO} objects now does
nothing when a negative length is requested, as other file-like
objects do.  (bpo-7348@footnote{https://bugs.python.org/issue7348}).

@item 
The @ref{ff,,syslog} module will now use the value of @code{sys.argv[0]} as the
identifier instead of the previous default value of @code{'python'}.
(Changed by Sean Reifschneider; bpo-8451@footnote{https://bugs.python.org/issue8451}.)

@item 
The @ref{101,,tarfile} module's default error handling has changed, to
no longer suppress fatal errors.  The default error level was previously 0,
which meant that errors would only result in a message being written to the
debug log, but because the debug log is not activated by default,
these errors go unnoticed.  The default error level is now 1,
which raises an exception if there's an error.
(Changed by Lars Gustäbel; bpo-7357@footnote{https://bugs.python.org/issue7357}.)

@item 
The @code{urlparse} module's @code{urlsplit()} now handles
unknown URL schemes in a fashion compliant with 
@geindex RFC; RFC 3986
RFC 3986@footnote{https://tools.ietf.org/html/rfc3986.html}: if the
URL is of the form @code{"<something>://..."}, the text before the
@code{://} is treated as the scheme, even if it's a made-up scheme that
the module doesn't know about.  This change may break code that
worked around the old behaviour.  For example, Python 2.6.4 or 2.5
will return the following:

@example
>>> import urlparse
>>> urlparse.urlsplit('invented://host/filename?query')
('invented', '@w{'}, '//host/filename?query', '@w{'}, '@w{'})
@end example

Python 2.7 (and Python 2.6.5) will return:

@example
>>> import urlparse
>>> urlparse.urlsplit('invented://host/filename?query')
('invented', 'host', '/filename?query', '@w{'}, '@w{'})
@end example

(Python 2.7 actually produces slightly different output, since it
returns a named tuple instead of a standard tuple.)
@end itemize

对于C 扩展模块：


@itemize *

@item 
C extensions that use integer format codes with the @code{PyArg_Parse*}
family of functions will now raise a @ref{192,,TypeError} exception
instead of triggering a @ref{278,,DeprecationWarning} (bpo-5080@footnote{https://bugs.python.org/issue5080}).

@item 
Use the new @ref{c1c,,PyOS_string_to_double()} function instead of the old
@code{PyOS_ascii_strtod()} and @code{PyOS_ascii_atof()} functions,
which are now deprecated.
@end itemize

对于嵌入Python的应用程序：


@itemize *

@item 
The @ref{bf3,,PySys_SetArgvEx()} function was added, letting
applications close a security hole when the existing
@ref{ce5,,PySys_SetArgv()} function was used.  Check whether you're
calling @ref{ce5,,PySys_SetArgv()} and carefully consider whether the
application should be using @ref{bf3,,PySys_SetArgvEx()} with
@emph{updatepath} set to false.
@end itemize

@c ======================================================================

@node New Features Added to Python 2 7 Maintenance Releases,致谢,移植到 Python 2 7,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 new-features-added-to-python-2-7-maintenance-releases}@anchor{cf1}@anchor{whatsnew/2 7 py27-maintenance-enhancements}@anchor{c75}
@subsection New Features Added to Python 2.7 Maintenance Releases


New features may be added to Python 2.7 maintenance releases when the
situation genuinely calls for it. Any such additions must go through
the Python Enhancement Proposal process, and make a compelling case for why
they can't be adequately addressed by either adding the new feature solely to
Python 3, or else by publishing it on the Python Package Index.

In addition to the specific proposals listed below, there is a general
exemption allowing new @code{-3} warnings to be added in any Python 2.7
maintenance release.

@menu
* Two new environment variables for debug mode:: 
* PEP 434; IDLE Enhancement Exception for All Branches: PEP 434 IDLE Enhancement Exception for All Branches. 
* PEP 466; Network Security Enhancements for Python 2.7: PEP 466 Network Security Enhancements for Python 2 7. 
* PEP 477; Backport ensurepip (PEP 453) to Python 2.7: PEP 477 Backport ensurepip PEP 453 to Python 2 7. 
* PEP 476; Enabling certificate verification by default for stdlib http clients: PEP 476 Enabling certificate verification by default for stdlib http clients<2>. 
* PEP 493：适用于Python 2.7 的 HTTPS 验证迁移工具: PEP 493：适用于Python 2 7 的 HTTPS 验证迁移工具. 
* New make regen-all build target: New make regen-all build target<3>. 
* Removal of make touch build target: Removal of make touch build target<3>. 

@end menu

@node Two new environment variables for debug mode,PEP 434 IDLE Enhancement Exception for All Branches,,New Features Added to Python 2 7 Maintenance Releases
@anchor{whatsnew/2 7 two-new-environment-variables-for-debug-mode}@anchor{cf2}
@subsubsection Two new environment variables for debug mode


In debug mode, the @code{[xxx refs]} statistic is not written by default, the
@geindex PYTHONSHOWREFCOUNT
@geindex 环境变量; PYTHONSHOWREFCOUNT
@code{PYTHONSHOWREFCOUNT} environment variable now must also be set.
(Contributed by Victor Stinner; bpo-31733@footnote{https://bugs.python.org/issue31733}.)

When Python is compiled with @code{COUNT_ALLOC} defined, allocation counts are no
longer dumped by default anymore: the 
@geindex PYTHONSHOWALLOCCOUNT
@geindex 环境变量; PYTHONSHOWALLOCCOUNT
@code{PYTHONSHOWALLOCCOUNT} environment
variable must now also be set. Moreover, allocation counts are now dumped into
stderr, rather than stdout. (Contributed by Victor Stinner; bpo-31692@footnote{https://bugs.python.org/issue31692}.)


2.7.15 新版功能.


@node PEP 434 IDLE Enhancement Exception for All Branches,PEP 466 Network Security Enhancements for Python 2 7,Two new environment variables for debug mode,New Features Added to Python 2 7 Maintenance Releases
@anchor{whatsnew/2 7 pep-434-idle-enhancement-exception-for-all-branches}@anchor{cf3}
@subsubsection PEP 434: IDLE Enhancement Exception for All Branches


@geindex Python 提高建议; PEP 434
PEP 434@footnote{https://www.python.org/dev/peps/pep-0434} describes a general exemption for changes made to the IDLE
development environment shipped along with Python. This exemption makes it
possible for the IDLE developers to provide a more consistent user
experience across all supported versions of Python 2 and 3.

For details of any IDLE changes, refer to the NEWS file for the specific
release.

@node PEP 466 Network Security Enhancements for Python 2 7,PEP 477 Backport ensurepip PEP 453 to Python 2 7,PEP 434 IDLE Enhancement Exception for All Branches,New Features Added to Python 2 7 Maintenance Releases
@anchor{whatsnew/2 7 pep-466-network-security-enhancements-for-python-2-7}@anchor{cf4}
@subsubsection PEP 466: Network Security Enhancements for Python 2.7


@geindex Python 提高建议; PEP 466
PEP 466@footnote{https://www.python.org/dev/peps/pep-0466} describes a number of network security enhancement proposals
that have been approved for inclusion in Python 2.7 maintenance releases,
with the first of those changes appearing in the Python 2.7.7 release.

@geindex Python 提高建议; PEP 466
PEP 466@footnote{https://www.python.org/dev/peps/pep-0466} Python 2.7.7 中添加的相关功能：


@itemize *

@item 
@ref{a07,,hmac.compare_digest()} was backported from Python 3 to make a timing
attack resistant comparison operation available to Python 2 applications.
(Contributed by Alex Gaynor; bpo-21306@footnote{https://bugs.python.org/issue21306}.)

@item 
OpenSSL 1.0.1g was upgraded in the official Windows installers published on
python.org. (Contributed by Zachary Ware; bpo-21462@footnote{https://bugs.python.org/issue21462}.)
@end itemize

@geindex Python 提高建议; PEP 466
PEP 466@footnote{https://www.python.org/dev/peps/pep-0466} Python 2.7.8 中添加的相关功能：


@itemize *

@item 
@ref{7e0,,hashlib.pbkdf2_hmac()} was backported from Python 3 to make a hashing
algorithm suitable for secure password storage broadly available to Python
2 applications. (Contributed by Alex Gaynor; bpo-21304@footnote{https://bugs.python.org/issue21304}.)

@item 
OpenSSL 1.0.1h was upgraded for the official Windows installers published on
python.org. (contributed by Zachary Ware in bpo-21671@footnote{https://bugs.python.org/issue21671} for CVE-2014-0224)
@end itemize

@geindex Python 提高建议; PEP 466
PEP 466@footnote{https://www.python.org/dev/peps/pep-0466} Python 2.7.9 中添加的相关功能：


@itemize *

@item 
Most of Python 3.4's @ref{f3,,ssl} module was backported. This means @ref{f3,,ssl}
now supports Server Name Indication, TLS1.x settings, access to the platform
certificate store, the @ref{3dc,,SSLContext} class, and other
features. (Contributed by Alex Gaynor and David Reid; bpo-21308@footnote{https://bugs.python.org/issue21308}.)

Refer to the "Version added: 2.7.9" notes in the module documentation for
specific details.

@item 
@ref{4cb,,os.urandom()} was changed to cache a file descriptor to @code{/dev/urandom}
instead of reopening @code{/dev/urandom} on every call. (Contributed by Alex
Gaynor; bpo-21305@footnote{https://bugs.python.org/issue21305}.)

@item 
@ref{cf5,,hashlib.algorithms_guaranteed} and
@ref{cf6,,hashlib.algorithms_available} were backported from Python 3 to make
it easier for Python 2 applications to select the strongest available hash
algorithm. (Contributed by Alex Gaynor in bpo-21307@footnote{https://bugs.python.org/issue21307})
@end itemize

@node PEP 477 Backport ensurepip PEP 453 to Python 2 7,PEP 476 Enabling certificate verification by default for stdlib http clients<2>,PEP 466 Network Security Enhancements for Python 2 7,New Features Added to Python 2 7 Maintenance Releases
@anchor{whatsnew/2 7 pep-477-backport-ensurepip-pep-453-to-python-2-7}@anchor{cf7}
@subsubsection PEP 477: Backport ensurepip (PEP 453) to Python 2.7


@geindex Python 提高建议; PEP 477
PEP 477@footnote{https://www.python.org/dev/peps/pep-0477} approves the inclusion of the 
@geindex Python 提高建议; PEP 453
PEP 453@footnote{https://www.python.org/dev/peps/pep-0453} ensurepip module and the
improved documentation that was enabled by it in the Python 2.7 maintenance
releases, appearing first in the Python 2.7.9 release.

@menu
* Bootstrapping pip By Default: Bootstrapping pip By Default<2>. 
* 文档更改: 文档更改<2>. 

@end menu

@node Bootstrapping pip By Default<2>,文档更改<2>,,PEP 477 Backport ensurepip PEP 453 to Python 2 7
@anchor{whatsnew/2 7 bootstrapping-pip-by-default}@anchor{cf8}
@subsubsection Bootstrapping pip By Default


The new @ref{7a,,ensurepip} module (defined in 
@geindex Python 提高建议; PEP 453
PEP 453@footnote{https://www.python.org/dev/peps/pep-0453}) provides a standard
cross-platform mechanism to bootstrap the pip installer into Python
installations. The version of @code{pip} included with Python 2.7.9 is @code{pip}
1.5.6, and future 2.7.x maintenance releases will update the bundled version to
the latest version of @code{pip} that is available at the time of creating the
release candidate.

By default, the commands @code{pip}, @code{pipX} and @code{pipX.Y} will be installed on
all platforms (where X.Y stands for the version of the Python installation),
along with the @code{pip} Python package and its dependencies.

For CPython @ref{7ed,,source builds on POSIX systems},
the @code{make install} and @code{make altinstall} commands do not bootstrap @code{pip}
by default.  This behaviour can be controlled through configure options, and
overridden through Makefile options.

On Windows and Mac OS X, the CPython installers now default to installing
@code{pip} along with CPython itself (users may opt out of installing it
during the installation process). Window users will need to opt in to the
automatic @code{PATH} modifications to have @code{pip} available from the command
line by default, otherwise it can still be accessed through the Python
launcher for Windows as @code{py -m pip}.

As discussed in the PEP@footnote{https://www.python.org/dev/peps/pep-0477/#disabling-ensurepip-by-downstream-distributors}, platform packagers may choose not to install
these commands by default, as long as, when invoked, they provide clear and
simple directions on how to install them on that platform (usually using
the system package manager).

@node 文档更改<2>,,Bootstrapping pip By Default<2>,PEP 477 Backport ensurepip PEP 453 to Python 2 7
@anchor{whatsnew/2 7 documentation-changes}@anchor{cf9}@anchor{whatsnew/2 7 id1}@anchor{cfa}
@subsubsection 文档更改


As part of this change, the @ref{7ef,,安装 Python 模块} and
@ref{7f0,,分发 Python 模块} sections of the documentation have been
completely redesigned as short getting started and FAQ documents. Most
packaging documentation has now been moved out to the Python Packaging
Authority maintained Python Packaging User Guide@footnote{http://packaging.python.org} and the documentation of the individual
projects.

However, as this migration is currently still incomplete, the legacy
versions of those guides remaining available as @ref{7f1,,安装Python模块（旧版）}
and @ref{7f2,,分发 Python 模块（遗留版本）}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 453

@item PEP 453@footnote{https://www.python.org/dev/peps/pep-0453} -- Python安装中pip的显式引导

PEP 由Donald Stufft 和 Nick Coghlan 撰写，由 Donald Stufft，Nick Coghlan，Martin von Löwis 和 Ned Deily 实现。
@end table


@node PEP 476 Enabling certificate verification by default for stdlib http clients<2>,PEP 493：适用于Python 2 7 的 HTTPS 验证迁移工具,PEP 477 Backport ensurepip PEP 453 to Python 2 7,New Features Added to Python 2 7 Maintenance Releases
@anchor{whatsnew/2 7 pep-476-enabling-certificate-verification-by-default-for-stdlib-http-clients}@anchor{cfb}
@subsubsection PEP 476: Enabling certificate verification by default for stdlib http clients


@geindex Python 提高建议; PEP 476
PEP 476@footnote{https://www.python.org/dev/peps/pep-0476} updated @code{httplib} and modules which use it, such as
@code{urllib2} and @code{xmlrpclib}, to now verify that the server
presents a certificate which is signed by a Certificate Authority in the
platform trust store and whose hostname matches the hostname being requested
by default, significantly improving security for many applications. This
change was made in the Python 2.7.9 release.

For applications which require the old previous behavior, they can pass an
alternate context:

@example
import urllib2
import ssl

# This disables all verification
context = ssl._create_unverified_context()

# This allows using a specific certificate for the host, which doesn't need
# to be in the trust store
context = ssl.create_default_context(cafile="/path/to/file.crt")

urllib2.urlopen("https://invalid-cert", context=context)
@end example

@node PEP 493：适用于Python 2 7 的 HTTPS 验证迁移工具,New make regen-all build target<3>,PEP 476 Enabling certificate verification by default for stdlib http clients<2>,New Features Added to Python 2 7 Maintenance Releases
@anchor{whatsnew/2 7 pep-493-https-verification-migration-tools-for-python-2-7}@anchor{cfc}
@subsubsection PEP 493：适用于Python 2.7 的 HTTPS 验证迁移工具


@geindex Python 提高建议; PEP 493
PEP 493@footnote{https://www.python.org/dev/peps/pep-0493} provides additional migration tools to support a more incremental
infrastructure upgrade process for environments containing applications and
services relying on the historically permissive processing of server
certificates when establishing client HTTPS connections.  These additions were
made in the Python 2.7.12 release.

These tools are intended for use in cases where affected applications and
services can't be modified to explicitly pass a more permissive SSL context
when establishing the connection.

For applications and services which can't be modified at all, the new
@code{PYTHONHTTPSVERIFY} environment variable may be set to @code{0} to revert an
entire Python process back to the default permissive behaviour of Python 2.7.8
and earlier.

For cases where the connection establishment code can't be modified, but the
overall application can be, the new @code{ssl._https_verify_certificates()}
function can be used to adjust the default behaviour at runtime.

@node New make regen-all build target<3>,Removal of make touch build target<3>,PEP 493：适用于Python 2 7 的 HTTPS 验证迁移工具,New Features Added to Python 2 7 Maintenance Releases
@anchor{whatsnew/2 7 new-make-regen-all-build-target}@anchor{cfd}
@subsubsection New @code{make regen-all} build target


To simplify cross-compilation, and to ensure that CPython can reliably be
compiled without requiring an existing version of Python to already be
available, the autotools-based build system no longer attempts to implicitly
recompile generated files based on file modification times.

Instead, a new @code{make regen-all} command has been added to force regeneration
of these files when desired (e.g. after an initial version of Python has
already been built based on the pregenerated versions).

More selective regeneration targets are also defined - see
Makefile.pre.in@footnote{https://github.com/python/cpython/tree/3.8/Makefile.pre.in} for details.

（由 Victor Stinner 在 bpo-23404@footnote{https://bugs.python.org/issue23404} 中贡献。）


2.7.14 新版功能.


@node Removal of make touch build target<3>,,New make regen-all build target<3>,New Features Added to Python 2 7 Maintenance Releases
@anchor{whatsnew/2 7 removal-of-make-touch-build-target}@anchor{cfe}
@subsubsection Removal of @code{make touch} build target


The @code{make touch} build target previously used to request implicit regeneration
of generated files by updating their modification times has been removed.

It has been replaced by the new @code{make regen-all} target.

（由 Victor Stinner 在 bpo-23404@footnote{https://bugs.python.org/issue23404} 中贡献。）


在 2.7.14 版更改.


@c ======================================================================

@node 致谢,,New Features Added to Python 2 7 Maintenance Releases,Python 2 7 有什么新变化
@anchor{whatsnew/2 7 acknowledgements}@anchor{cff}@anchor{whatsnew/2 7 acks27}@anchor{d00}
@subsection 致谢


作者要感谢以下人员为本文的各种草案提供建议，更正和帮助： Nick Coghlan, Philip Jenvey, Ryan Lovett, R. David Murray, Hugh Secker-Walker.

@node Python 2 6 有什么新变化,Python 2 5 有什么新变化,Python 2 7 有什么新变化,Python的新变化
@anchor{whatsnew/2 6 doc}@anchor{d01}@anchor{whatsnew/2 6 what-s-new-in-python-2-6}@anchor{d02}@anchor{whatsnew/2 6 whats-new-in-2-6}@anchor{c40}
@section Python 2.6 有什么新变化


@c XXX add trademark info for Apple, Microsoft, SourceForge.

@*作者: 
A.M. Kuchling (amk at amk.ca)


@c $Id$
@c Rules for maintenance:
@c 
@c * Anyone can add text to this document.  Do not spend very much time
@c on the wording of your changes, because your text will probably
@c get rewritten to some degree.
@c 
@c * The maintainer will go through Misc/NEWS periodically and add
@c changes; it's therefore more important to add your changes to
@c Misc/NEWS than to this file.
@c 
@c * This is not a complete list of every single change; completeness
@c is the purpose of Misc/NEWS.  Some changes I consider too small
@c or esoteric to include.  If such a change is added to the text,
@c I'll just remove it.  (This is another reason you shouldn't spend
@c too much time on writing your addition.)
@c 
@c * If you want to draw your new text to the attention of the
@c maintainer, add 'XXX' to the beginning of the paragraph or
@c section.
@c 
@c * It's OK to just add a fragmentary note about a change.  For
@c example: "XXX Describe the transmogrify() function added to the
@c socket module."  The maintainer will research the change and
@c write the necessary text.
@c 
@c * You can comment out your additions if you like, but it's not
@c necessary (especially when a final release is some months away).
@c 
@c * Credit the author of a patch or bugfix.   Just the name is
@c sufficient; the e-mail address isn't necessary.
@c 
@c * It's helpful to add the bug/patch number in a parenthetical comment.
@c 
@c XXX Describe the transmogrify() function added to the socket
@c module.
@c (Contributed by P.Y. Developer; :issue:`12345`.)
@c 
@c This saves the maintainer some effort going through the SVN logs
@c when researching a change.

This article explains the new features in Python 2.6, released on October 1
2008.  The release schedule is described in 
@geindex Python 提高建议; PEP 361
PEP 361@footnote{https://www.python.org/dev/peps/pep-0361}.

The major theme of Python 2.6 is preparing the migration path to
Python 3.0, a major redesign of the language.  Whenever possible,
Python 2.6 incorporates new features and syntax from 3.0 while
remaining compatible with existing code by not removing older features
or syntax.  When it's not possible to do that, Python 2.6 tries to do
what it can, adding compatibility functions in a
@code{future_builtins} module and a @code{-3} switch to warn about
usages that will become unsupported in 3.0.

Some significant new packages have been added to the standard library,
such as the @ref{b7,,multiprocessing} and @ref{a4,,json} modules, but
there aren't many new features that aren't related to Python 3.0 in
some way.

Python 2.6 also sees a number of improvements and bugfixes throughout
the source.  A search through the change logs finds there were 259
patches applied and 612 bugs fixed between Python 2.5 and 2.6.  Both
figures are likely to be underestimates.

This article doesn't attempt to provide a complete specification of
the new features, but instead provides a convenient overview.  For
full details, you should refer to the documentation for Python 2.6. If
you want to understand the rationale for the design and
implementation, refer to the PEP for a particular new feature.
Whenever possible, "What's New in Python" links to the bug/patch item
for each change.

@c Compare with previous release in 2 - 3 sentences here.
@c add hyperlink when the documentation becomes available online.

@c ========================================================================

@c Large, PEP-level features and changes should be described here.

@c ========================================================================

@menu
* Python 3.0: Python 3 0. 
* 开发过程的变化:: 
* PEP 343; "with" 语句: PEP 343 "with" 语句. 
* PEP 366; 从主模块显式相对导入: PEP 366 从主模块显式相对导入. 
* PEP 370; 分用户的 site-packages 目录: PEP 370 分用户的 site-packages 目录. 
* PEP 371; 多任务处理包: PEP 371 多任务处理包. 
* PEP 3101; 高级字符串格式: PEP 3101 高级字符串格式. 
* PEP 3105; print 改为函数: PEP 3105 print 改为函数. 
* PEP 3110; 异常处理的变更: PEP 3110 异常处理的变更. 
* PEP 3112; 字节字面值: PEP 3112 字节字面值. 
* PEP 3116; 新 I/O 库: PEP 3116 新 I/O 库. 
* PEP 3118; 修改缓冲区协议: PEP 3118 修改缓冲区协议. 
* PEP 3119; 抽象基类: PEP 3119 抽象基类. 
* PEP 3127; 整型文字支持和语法: PEP 3127 整型文字支持和语法. 
* PEP 3129; 类装饰器: PEP 3129 类装饰器. 
* PEP 3141; A Type Hierarchy for Numbers: PEP 3141 A Type Hierarchy for Numbers. 
* 其他语言特性修改: 其他语言特性修改<10>. 
* 新增和改进的模块: 新增和改进的模块<2>. 
* Deprecations and Removals:: 
* 构建和 C API 的改变: 构建和 C API 的改变<9>. 
* 移植到Python 2.6: 移植到Python 2 6. 
* 致谢: 致谢<2>. 

@end menu

@node Python 3 0,开发过程的变化,,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 python-3-0}@anchor{d03}
@subsection Python 3.0


The development cycle for Python versions 2.6 and 3.0 was
synchronized, with the alpha and beta releases for both versions being
made on the same days.  The development of 3.0 has influenced many
features in 2.6.

Python 3.0 is a far-ranging redesign of Python that breaks
compatibility with the 2.x series.  This means that existing Python
code will need some conversion in order to run on
Python 3.0.  However, not all the changes in 3.0 necessarily break
compatibility.  In cases where new features won't cause existing code
to break, they've been backported to 2.6 and are described in this
document in the appropriate place.  Some of the 3.0-derived features
are:


@itemize *

@item 
A @ref{18d,,__complex__()} method for converting objects to a complex number.

@item 
Alternate syntax for catching exceptions: @code{except TypeError as exc}.

@item 
The addition of @ref{c68,,functools.reduce()} as a synonym for the built-in
@code{reduce()} function.
@end itemize

Python 3.0 adds several new built-in functions and changes the
semantics of some existing builtins.  Functions that are new in 3.0
such as @ref{c39,,bin()} have simply been added to Python 2.6, but existing
builtins haven't been changed; instead, the @code{future_builtins}
module has versions with the new 3.0 semantics.  Code written to be
compatible with 3.0 can do @code{from future_builtins import hex, map} as
necessary.

A new command-line switch, @code{-3}, enables warnings
about features that will be removed in Python 3.0.  You can run code
with this switch to see how much work will be necessary to port
code to 3.0.  The value of this switch is available
to Python code as the boolean variable @code{sys.py3kwarning},
and to C extension code as @code{Py_Py3kWarningFlag}.


@subsubheading 参见


The 3xxx series of PEPs, which contains proposals for Python 3.0.
@geindex Python 提高建议; PEP 3000
PEP 3000@footnote{https://www.python.org/dev/peps/pep-3000} describes the development process for Python 3.0.
Start with 
@geindex Python 提高建议; PEP 3100
PEP 3100@footnote{https://www.python.org/dev/peps/pep-3100} that describes the general goals for Python
3.0, and then explore the higher-numbered PEPS that propose
specific features.


@node 开发过程的变化,PEP 343 "with" 语句,Python 3 0,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 changes-to-the-development-process}@anchor{d04}
@subsection 开发过程的变化


While 2.6 was being developed, the Python development process
underwent two significant changes: we switched from SourceForge's
issue tracker to a customized Roundup installation, and the
documentation was converted from LaTeX to reStructuredText.

@menu
* New Issue Tracker; Roundup: New Issue Tracker Roundup. 
* 新的文档格式：使用 Sphinx 的 reStructuredText:: 

@end menu

@node New Issue Tracker Roundup,新的文档格式：使用 Sphinx 的 reStructuredText,,开发过程的变化
@anchor{whatsnew/2 6 new-issue-tracker-roundup}@anchor{d05}
@subsubsection New Issue Tracker: Roundup


For a long time, the Python developers had been growing increasingly
annoyed by SourceForge's bug tracker.  SourceForge's hosted solution
doesn't permit much customization; for example, it wasn't possible to
customize the life cycle of issues.

The infrastructure committee of the Python Software Foundation
therefore posted a call for issue trackers, asking volunteers to set
up different products and import some of the bugs and patches from
SourceForge.  Four different trackers were examined: Jira@footnote{https://www.atlassian.com/software/jira/},
Launchpad@footnote{https://launchpad.net/},
Roundup@footnote{http://roundup.sourceforge.net/}, and
Trac@footnote{https://trac.edgewall.org/}.
The committee eventually settled on Jira
and Roundup as the two candidates.  Jira is a commercial product that
offers no-cost hosted instances to free-software projects; Roundup
is an open-source project that requires volunteers
to administer it and a server to host it.

After posting a call for volunteers, a new Roundup installation was
set up at @indicateurl{https://bugs.python.org}.  One installation of Roundup can
host multiple trackers, and this server now also hosts issue trackers
for Jython and for the Python web site.  It will surely find
other uses in the future.  Where possible,
this edition of "What's New in Python" links to the bug/patch
item for each change.

Hosting of the Python bug tracker is kindly provided by
Upfront Systems@footnote{http://www.upfrontsoftware.co.za}
of Stellenbosch, South Africa.  Martin von Löwis put a
lot of effort into importing existing bugs and patches from
SourceForge; his scripts for this import operation are at
@indicateurl{http://svn.python.org/view/tracker/importer/} and may be useful to
other projects wishing to move from SourceForge to Roundup.


@subsubheading 参见



@table @asis

@item @indicateurl{https://bugs.python.org}

Python 的错误追踪器

@item @indicateurl{http://bugs.jython.org}:

Jython 的错误追踪器

@item @indicateurl{http://roundup.sourceforge.net/}

Roundup 下载和文档。

@item @indicateurl{http://svn.python.org/view/tracker/importer/}

Martin von Löwis 的转换脚本。
@end table


@node 新的文档格式：使用 Sphinx 的 reStructuredText,,New Issue Tracker Roundup,开发过程的变化
@anchor{whatsnew/2 6 new-documentation-format-restructuredtext-using-sphinx}@anchor{d06}
@subsubsection 新的文档格式：使用 Sphinx 的 reStructuredText


The Python documentation was written using LaTeX since the project
started around 1989.  In the 1980s and early 1990s, most documentation
was printed out for later study, not viewed online. LaTeX was widely
used because it provided attractive printed output while remaining
straightforward to write once the basic rules of the markup were
learned.

Today LaTeX is still used for writing publications destined for
printing, but the landscape for programming tools has shifted.  We no
longer print out reams of documentation; instead, we browse through it
online and HTML has become the most important format to support.
Unfortunately, converting LaTeX to HTML is fairly complicated and Fred
L. Drake Jr., the long-time Python documentation editor, spent a lot
of time maintaining the conversion process.  Occasionally people would
suggest converting the documentation into SGML and later XML, but
performing a good conversion is a major task and no one ever committed
the time required to finish the job.

During the 2.6 development cycle, Georg Brandl put a lot of effort
into building a new toolchain for processing the documentation.  The
resulting package is called Sphinx, and is available from
@indicateurl{http://sphinx-doc.org/}.

Sphinx concentrates on HTML output, producing attractively styled and
modern HTML; printed output is still supported through conversion to
LaTeX.  The input format is reStructuredText, a markup syntax
supporting custom extensions and directives that is commonly used in
the Python community.

Sphinx is a standalone package that can be used for writing, and
almost two dozen other projects
(listed on the Sphinx web site@footnote{https://www.sphinx-doc.org/en/master/examples.html})
have adopted Sphinx as their documentation tool.


@subsubheading 参见



@table @asis

@item Documenting Python@footnote{https://devguide.python.org/documenting/}

描述如何编写Python文档。

@item Sphinx@footnote{http://sphinx-doc.org/}

Sphinx工具链的文档和代码。

@item Docutils@footnote{http://docutils.sourceforge.net}

reStructuredText 的基础解析器和工具集。
@end table


@node PEP 343 "with" 语句,PEP 366 从主模块显式相对导入,开发过程的变化,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-0343}@anchor{c41}@anchor{whatsnew/2 6 pep-343-the-with-statement}@anchor{d07}
@subsection PEP 343: "with" 语句


The previous version, Python 2.5, added the '@ref{6e3,,with}'
statement as an optional feature, to be enabled by a @code{from __future__
import with_statement} directive.  In 2.6 the statement no longer needs to
be specially enabled; this means that @code{with} is now always a
keyword.  The rest of this section is a copy of the corresponding
section from the "What's New in Python 2.5" document; if you're
familiar with the '@code{with}' statement
from Python 2.5, you can skip this section.

The '@ref{6e3,,with}' statement clarifies code that previously would use
@code{try...finally} blocks to ensure that clean-up code is executed.  In this
section, I'll discuss the statement as it will commonly be used.  In the next
section, I'll examine the implementation details and show how to write objects
for use with this statement.

The '@ref{6e3,,with}' statement is a control-flow structure whose basic
structure is:

@example
with expression [as variable]:
    with-block
@end example

The expression is evaluated, and it should result in an object that supports the
context management protocol (that is, has @ref{c8e,,__enter__()} and @ref{c8f,,__exit__()}
methods).

The object's @ref{c8e,,__enter__()} is called before @emph{with-block} is executed and
therefore can run set-up code. It also may return a value that is bound to the
name @emph{variable}, if given.  (Note carefully that @emph{variable} is @emph{not} assigned
the result of @emph{expression}.)

After execution of the @emph{with-block} is finished, the object's @ref{c8f,,__exit__()}
method is called, even if the block raised an exception, and can therefore run
clean-up code.

Some standard Python objects now support the context management protocol and can
be used with the '@ref{6e3,,with}' statement. File objects are one example:

@example
with open('/etc/passwd', 'r') as f:
    for line in f:
        print line
        ... more processing code ...
@end example

After this statement has executed, the file object in @emph{f} will have been
automatically closed, even if the @ref{c29,,for} loop raised an exception
part-way through the block.

@cartouche
@quotation 注解 
In this case, @emph{f} is the same object created by @ref{4ea,,open()}, because
@code{file.__enter__()} returns @emph{self}.
@end quotation
@end cartouche

The @ref{109,,threading} module's locks and condition variables  also support the
'@ref{6e3,,with}' statement:

@example
lock = threading.Lock()
with lock:
    # Critical section of code
    ...
@end example

The lock is acquired before the block is executed and always released once  the
block is complete.

The @code{localcontext()} function in the @ref{36,,decimal} module makes it easy
to save and restore the current decimal context, which encapsulates the desired
precision and rounding characteristics for computations:

@example
from decimal import Decimal, Context, localcontext

# Displays with default precision of 28 digits
v = Decimal('578')
print v.sqrt()

with localcontext(Context(prec=16)):
    # All code in this block uses a precision of 16 digits.
    # The original context is restored on exiting the block.
    print v.sqrt()
@end example

@menu
* Writing Context Managers:: 
* contextlib 模块:: 

@end menu

@node Writing Context Managers,contextlib 模块,,PEP 343 "with" 语句
@anchor{whatsnew/2 6 new-26-context-managers}@anchor{c42}@anchor{whatsnew/2 6 writing-context-managers}@anchor{d08}
@subsubsection Writing Context Managers


Under the hood, the '@ref{6e3,,with}' statement is fairly complicated. Most
people will only use '@code{with}' in company with existing objects and
don't need to know these details, so you can skip the rest of this section if
you like.  Authors of new objects will need to understand the details of the
underlying implementation and should keep reading.

A high-level explanation of the context management protocol is:


@itemize *

@item 
The expression is evaluated and should result in an object called a "context
manager".  The context manager must have @ref{c8e,,__enter__()} and @ref{c8f,,__exit__()}
methods.

@item 
The context manager's @ref{c8e,,__enter__()} method is called.  The value returned
is assigned to @emph{VAR}.  If no @code{as VAR} clause is present, the value is simply
discarded.

@item 
The code in @emph{BLOCK} is executed.

@item 
If @emph{BLOCK} raises an exception, the context manager's @ref{c8f,,__exit__()} method
is called with three arguments, the exception details (@code{type, value, traceback},
the same values returned by @ref{c58,,sys.exc_info()}, which can also be @code{None}
if no exception occurred).  The method's return value controls whether an exception
is re-raised: any false value re-raises the exception, and @code{True} will result
in suppressing it.  You'll only rarely want to suppress the exception, because
if you do the author of the code containing the '@ref{6e3,,with}' statement will
never realize anything went wrong.

@item 
If @emph{BLOCK} didn't raise an exception,  the @ref{c8f,,__exit__()} method is still
called, but @emph{type}, @emph{value}, and @emph{traceback} are all @code{None}.
@end itemize

Let's think through an example.  I won't present detailed code but will only
sketch the methods necessary for a database that supports transactions.

(For people unfamiliar with database terminology: a set of changes to the
database are grouped into a transaction.  Transactions can be either committed,
meaning that all the changes are written into the database, or rolled back,
meaning that the changes are all discarded and the database is unchanged.  See
any database textbook for more information.)

Let's assume there's an object representing a database connection. Our goal will
be to let the user write code like this:

@example
db_connection = DatabaseConnection()
with db_connection as cursor:
    cursor.execute('insert into ...')
    cursor.execute('delete from ...')
    # ... more operations ...
@end example

The transaction should be committed if the code in the block runs flawlessly or
rolled back if there's an exception. Here's the basic interface for
@code{DatabaseConnection} that I'll assume:

@example
class DatabaseConnection:
    # Database interface
    def cursor(self):
        "Returns a cursor object and starts a new transaction"
    def commit(self):
        "Commits current transaction"
    def rollback(self):
        "Rolls back current transaction"
@end example

The @ref{c8e,,__enter__()} method is pretty easy, having only to start a new
transaction.  For this application the resulting cursor object would be a useful
result, so the method will return it.  The user can then add @code{as cursor} to
their '@ref{6e3,,with}' statement to bind the cursor to a variable name.

@example
class DatabaseConnection:
    ...
    def __enter__(self):
        # Code to start a new transaction
        cursor = self.cursor()
        return cursor
@end example

The @ref{c8f,,__exit__()} method is the most complicated because it's where most of
the work has to be done.  The method has to check if an exception occurred.  If
there was no exception, the transaction is committed.  The transaction is rolled
back if there was an exception.

In the code below, execution will just fall off the end of the function,
returning the default value of @code{None}.  @code{None} is false, so the exception
will be re-raised automatically.  If you wished, you could be more explicit and
add a @ref{190,,return} statement at the marked location.

@example
class DatabaseConnection:
    ...
    def __exit__(self, type, value, tb):
        if tb is None:
            # No exception, so commit
            self.commit()
        else:
            # Exception occurred, so rollback.
            self.rollback()
            # return False
@end example

@node contextlib 模块,,Writing Context Managers,PEP 343 "with" 语句
@anchor{whatsnew/2 6 new-module-contextlib}@anchor{c43}@anchor{whatsnew/2 6 the-contextlib-module}@anchor{d09}
@subsubsection contextlib 模块


The @ref{24,,contextlib} module provides some functions and a decorator that
are useful when writing objects for use with the '@ref{6e3,,with}' statement.

The decorator is called @code{contextmanager()}, and lets you write a single
generator function instead of defining a new class.  The generator should yield
exactly one value.  The code up to the @ref{18f,,yield} will be executed as the
@ref{c8e,,__enter__()} method, and the value yielded will be the method's return
value that will get bound to the variable in the '@ref{6e3,,with}' statement's
@code{as} clause, if any.  The code after the @code{yield} will be
executed in the @ref{c8f,,__exit__()} method.  Any exception raised in the block will
be raised by the @code{yield} statement.

Using this decorator, our database example from the previous section
could be written as:

@example
from contextlib import contextmanager

@@contextmanager
def db_transaction(connection):
    cursor = connection.cursor()
    try:
        yield cursor
    except:
        connection.rollback()
        raise
    else:
        connection.commit()

db = DatabaseConnection()
with db_transaction(db) as cursor:
    ...
@end example

The @ref{24,,contextlib} module also has a @code{nested(mgr1, mgr2, ...)} function
that combines a number of context managers so you don't need to write nested
'@ref{6e3,,with}' statements.  In this example, the single '@code{with}'
statement both starts a database transaction and acquires a thread lock:

@example
lock = threading.Lock()
with nested (db_transaction(db), lock) as (cursor, locked):
    ...
@end example

Finally, the @code{closing()} function returns its argument so that it can be
bound to a variable, and calls the argument's @code{.close()} method at the end
of the block.

@example
import urllib, sys
from contextlib import closing

with closing(urllib.urlopen('http://www.yahoo.com')) as f:
    for line in f:
        sys.stdout.write(line)
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 343

@item PEP 343@footnote{https://www.python.org/dev/peps/pep-0343} - "with" 语句

PEP written by Guido van Rossum and Nick Coghlan; implemented by Mike Bland,
Guido van Rossum, and Neal Norwitz.  The PEP shows the code generated for a
'@ref{6e3,,with}' statement, which can be helpful in learning how the statement
works.
@end table

@ref{24,,contextlib} 模块的文档。


@c ======================================================================

@node PEP 366 从主模块显式相对导入,PEP 370 分用户的 site-packages 目录,PEP 343 "with" 语句,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-0366}@anchor{c44}@anchor{whatsnew/2 6 pep-366-explicit-relative-imports-from-a-main-module}@anchor{d0a}
@subsection PEP 366: 从主模块显式相对导入


Python's @ref{330,,-m} switch allows running a module as a script.
When you ran a module that was located inside a package, relative
imports didn't work correctly.

The fix for Python 2.6 adds a @ref{94f,,__package__} attribute to
modules.  When this attribute is present, relative imports will be
relative to the value of this attribute instead of the
@ref{d0b,,__name__} attribute.

PEP 302-style importers can then set @ref{94f,,__package__} as necessary.
The @ref{e2,,runpy} module that implements the @ref{330,,-m} switch now
does this, so relative imports will now work correctly in scripts
running from inside a package.

@c ======================================================================

@node PEP 370 分用户的 site-packages 目录,PEP 371 多任务处理包,PEP 366 从主模块显式相对导入,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-0370}@anchor{c45}@anchor{whatsnew/2 6 pep-370-per-user-site-packages-directory}@anchor{d0c}
@subsection PEP 370: 分用户的 site-packages 目录


When you run Python, the module search path @code{sys.path} usually
includes a directory whose path ends in @code{"site-packages"}.  This
directory is intended to hold locally-installed packages available to
all users using a machine or a particular site installation.

Python 2.6 introduces a convention for user-specific site directories.
The directory varies depending on the platform:


@itemize *

@item 
Unix and Mac OS X: @code{~/.local/}

@item 
Windows: @code{%APPDATA%/Python}
@end itemize

Within this directory, there will be version-specific subdirectories,
such as @code{lib/python2.6/site-packages} on Unix/Mac OS and
@code{Python26/site-packages} on Windows.

If you don't like the default directory, it can be overridden by an
environment variable.  
@geindex PYTHONUSERBASE
@geindex 环境变量; PYTHONUSERBASE
@ref{d0d,,PYTHONUSERBASE} sets the root
directory used for all Python versions supporting this feature.  On
Windows, the directory for application-specific data can be changed by
setting the 
@geindex APPDATA
@geindex 环境变量; APPDATA
@code{APPDATA} environment variable.  You can also
modify the @code{site.py} file for your Python installation.

The feature can be disabled entirely by running Python with the
@ref{d0e,,-s} option or setting the 
@geindex PYTHONNOUSERSITE
@geindex 环境变量; PYTHONNOUSERSITE
@ref{d0f,,PYTHONNOUSERSITE}
environment variable.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 370

@item PEP 370@footnote{https://www.python.org/dev/peps/pep-0370} - 分用户的 site-packages 目录

PEP 由 Christian Heimes 撰写并实现
@end table


@c ======================================================================

@node PEP 371 多任务处理包,PEP 3101 高级字符串格式,PEP 370 分用户的 site-packages 目录,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-0371}@anchor{c46}@anchor{whatsnew/2 6 pep-371-the-multiprocessing-package}@anchor{d10}
@subsection PEP 371: 多任务处理包


The new @ref{b7,,multiprocessing} package lets Python programs create new
processes that will perform a computation and return a result to the
parent.  The parent and child processes can communicate using queues
and pipes, synchronize their operations using locks and semaphores,
and can share simple arrays of data.

The @ref{b7,,multiprocessing} module started out as an exact emulation of
the @ref{109,,threading} module using processes instead of threads.  That
goal was discarded along the path to Python 2.6, but the general
approach of the module is still similar.  The fundamental class
is the @code{Process}, which is passed a callable object and
a collection of arguments.  The @code{start()} method
sets the callable running in a subprocess, after which you can call
the @code{is_alive()} method to check whether the subprocess is still running
and the @code{join()} method to wait for the process to exit.

Here's a simple example where the subprocess will calculate a
factorial.  The function doing the calculation is written strangely so
that it takes significantly longer when the input argument is a
multiple of 4.

@example
import time
from multiprocessing import Process, Queue


def factorial(queue, N):
    "Compute a factorial."
    # If N is a multiple of 4, this function will take much longer.
    if (N % 4) == 0:
        time.sleep(.05 * N/4)

    # Calculate the result
    fact = 1L
    for i in range(1, N+1):
        fact = fact * i

    # Put the result on the queue
    queue.put(fact)

if __name__ == '__main__':
    queue = Queue()

    N = 5

    p = Process(target=factorial, args=(queue, N))
    p.start()
    p.join()

    result = queue.get()
    print 'Factorial', N, '=', result
@end example

A @ref{d11,,Queue} is used to communicate the result of the factorial.
The @ref{d11,,Queue} object is stored in a global variable.
The child process will use the value of the variable when the child
was created; because it's a @ref{d11,,Queue}, parent and child can use
the object to communicate.  (If the parent were to change the value of
the global variable, the child's value would be unaffected, and vice
versa.)

Two other classes, @code{Pool} and @code{Manager}, provide
higher-level interfaces.  @code{Pool} will create a fixed number of
worker processes, and requests can then be distributed to the workers
by calling @code{apply()} or @code{apply_async()} to add a single request,
and @ref{c26,,map()} or @code{map_async()} to add a number of
requests.  The following code uses a @code{Pool} to spread requests
across 5 worker processes and retrieve a list of results:

@example
from multiprocessing import Pool

def factorial(N, dictionary):
    "Compute a factorial."
    ...
p = Pool(5)
result = p.map(factorial, range(1, 1000, 10))
for v in result:
    print v
@end example

This produces the following output:

@example
1
39916800
51090942171709440000
8222838654177922817725562880000000
33452526613163807108170062053440751665152000000000
...
@end example

The other high-level interface, the @code{Manager} class, creates a
separate server process that can hold master copies of Python data
structures.  Other processes can then access and modify these data
structures using proxy objects.  The following example creates a
shared dictionary by calling the @ref{1b8,,dict()} method; the worker
processes then insert values into the dictionary.  (Locking is not
done for you automatically, which doesn't matter in this example.
@code{Manager}'s methods also include @code{Lock()}, @code{RLock()},
and @code{Semaphore()} to create shared locks.)

@example
import time
from multiprocessing import Pool, Manager

def factorial(N, dictionary):
    "Compute a factorial."
    # Calculate the result
    fact = 1L
    for i in range(1, N+1):
        fact = fact * i

    # Store result in dictionary
    dictionary[N] = fact

if __name__ == '__main__':
    p = Pool(5)
    mgr = Manager()
    d = mgr.dict()         # Create shared dictionary

    # Run tasks using the pool
    for N in range(1, 1000, 10):
        p.apply_async(factorial, (N, d))

    # Mark pool as closed -- no more tasks can be added.
    p.close()

    # Wait for tasks to exit
    p.join()

    # Output results
    for k, v in sorted(d.items()):
        print k, v
@end example

This will produce the output:

@example
1 1
11 39916800
21 51090942171709440000
31 8222838654177922817725562880000000
41 33452526613163807108170062053440751665152000000000
51 15511187532873822802242430164693032110632597200169861120000...
@end example


@subsubheading 参见


@ref{b7,,multiprocessing} 模块的文档。


@table @asis

@geindex Python 提高建议; PEP 371

@item PEP 371@footnote{https://www.python.org/dev/peps/pep-0371} - 添加多任务处理包

PEP 由 Jesse Noller 和 Richard Oudkerk 撰写，由 Richard Oudkerk 和 Jesse Noller 实现
@end table


@c ======================================================================

@node PEP 3101 高级字符串格式,PEP 3105 print 改为函数,PEP 371 多任务处理包,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3101}@anchor{c47}@anchor{whatsnew/2 6 pep-3101-advanced-string-formatting}@anchor{d12}
@subsection PEP 3101: 高级字符串格式


In Python 3.0, the @cite{%} operator is supplemented by a more powerful string
formatting method, @ref{4d5,,format()}.  Support for the @ref{4d4,,str.format()} method
has been backported to Python 2.6.

In 2.6, both 8-bit and Unicode strings have a @cite{.format()} method that
treats the string as a template and takes the arguments to be formatted.
The formatting template uses curly brackets (@cite{@{}, @cite{@}}) as special characters:

@example
>>> # Substitute positional argument 0 into the string.
>>> "User ID: @{0@}".format("root")
'User ID: root'
>>> # Use the named keyword arguments
>>> "User ID: @{uid@}   Last seen: @{last_login@}".format(
...    uid="root",
...    last_login = "5 Mar 2008 07:20")
'User ID: root   Last seen: 5 Mar 2008 07:20'
@end example

Curly brackets can be escaped by doubling them:

@example
>>> "Empty dict: @{@{@}@}".format()
"Empty dict: @{@}"
@end example

Field names can be integers indicating positional arguments, such as
@code{@{0@}}, @code{@{1@}}, etc. or names of keyword arguments.  You can also
supply compound field names that read attributes or access dictionary keys:

@example
>>> import sys
>>> print 'Platform: @{0.platform@}\nPython version: @{0.version@}'.format(sys)
Platform: darwin
Python version: 2.6a1+ (trunk:61261M, Mar  5 2008, 20:29:41)
[GCC 4.0.1 (Apple Computer, Inc. build 5367)]'

>>> import mimetypes
>>> 'Content-type: @{0[.mp4]@}'.format(mimetypes.types_map)
'Content-type: video/mp4'
@end example

Note that when using dictionary-style notation such as @code{[.mp4]}, you
don't need to put any quotation marks around the string; it will look
up the value using @code{.mp4} as the key.  Strings beginning with a
number will be converted to an integer.  You can't write more
complicated expressions inside a format string.

So far we've shown how to specify which field to substitute into the
resulting string.  The precise formatting used is also controllable by
adding a colon followed by a format specifier.  For example:

@example
>>> # Field 0: left justify, pad to 15 characters
>>> # Field 1: right justify, pad to 6 characters
>>> fmt = '@{0:15@} $@{1:>6@}'
>>> fmt.format('Registration', 35)
'Registration    $    35'
>>> fmt.format('Tutorial', 50)
'Tutorial        $    50'
>>> fmt.format('Banquet', 125)
'Banquet         $   125'
@end example

Format specifiers can reference other fields through nesting:

@example
>>> fmt = '@{0:@{1@}@}'
>>> width = 15
>>> fmt.format('Invoice #1234', width)
'Invoice #1234  '
>>> width = 35
>>> fmt.format('Invoice #1234', width)
'Invoice #1234                      '
@end example

可以指定所需宽度内的字段对齐方式：


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

字符

@tab

效果

@item

< (默认)

@tab

左对齐

@item

>

@tab

右对齐

@item

^

@tab

居中对齐

@item

=

@tab

（仅适用于数字类型）在符号后加空格。

@end multitable


Format specifiers can also include a presentation type, which
controls how the value is formatted.  For example, floating-point numbers
can be formatted as a general number or in exponential notation:

@example
>>> '@{0:g@}'.format(3.75)
'3.75'
>>> '@{0:e@}'.format(3.75)
'3.750000e+00'
@end example

A variety of presentation types are available.  Consult the 2.6
documentation for a @ref{d13,,complete list}; here's a sample:


@multitable {xxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{b}

@tab

二进制。输出以2为底的数字。

@item

@code{c}

@tab

字符。在打印之前将整数转换为相应的Unicode字符。

@item

@code{d}

@tab

十进制整数。 输出以 10 为基数的数字。

@item

@code{o}

@tab

八进制格式。 输出以 8 为基数的数字。

@item

@code{x}

@tab

十六进制格式。 输出以 16 为基数的数字，使用小写字母表示 9 以上的数码。

@item

@code{e}

@tab

指数表示法。用字母 'e' 以科学计数法打印数字以表示指数。

@item

@code{g}

@tab

General format. This prints the number as a fixed-point number, unless
the number is too large, in which case it switches to 'e' exponent
notation.

@item

@code{n}

@tab

Number. This is the same as 'g' (for floats) or 'd' (for integers),
except that it uses the current locale setting to insert the appropriate
number separator characters.

@item

@code{%}

@tab

Percentage. Multiplies the number by 100 and displays in fixed ('f')
format, followed by a percent sign.

@end multitable


Classes and types can define a @ref{948,,__format__()} method to control how they're
formatted.  It receives a single argument, the format specifier:

@example
def __format__(self, format_spec):
    if isinstance(format_spec, unicode):
        return unicode(str(self))
    else:
        return str(self)
@end example

There's also a @ref{4d5,,format()} builtin that will format a single
value.  It calls the type's @ref{948,,__format__()} method with the
provided specifier:

@example
>>> format(75.6564, '.2f')
'75.66'
@end example


@subsubheading 参见



@table @asis

@item @ref{d13,,格式字符串语法}

格式字段的参考文档。

@geindex Python 提高建议; PEP 3101

@item PEP 3101@footnote{https://www.python.org/dev/peps/pep-3101} - 高级字符串格式

PEP 由 Eric V. Smith 撰写并实现
@end table


@c ======================================================================

@node PEP 3105 print 改为函数,PEP 3110 异常处理的变更,PEP 3101 高级字符串格式,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3105}@anchor{c48}@anchor{whatsnew/2 6 pep-3105-print-as-a-function}@anchor{d14}
@subsection PEP 3105: @code{print} 改为函数


The @code{print} statement becomes the @ref{880,,print()} function in Python 3.0.
Making @ref{880,,print()} a function makes it possible to replace the function
by doing @code{def print(...)} or importing a new function from somewhere else.

Python 2.6 has a @code{__future__} import that removes @code{print} as language
syntax, letting you use the functional form instead.  For example:

@example
>>> from __future__ import print_function
>>> print('# of entries', len(dictionary), file=sys.stderr)
@end example

The signature of the new function is:

@example
def print(*args, sep=' ', end='\n', file=None)
@end example

The parameters are:

@quotation


@itemize *

@item 
@emph{args}: positional arguments whose values will be printed out.

@item 
@emph{sep}: the separator, which will be printed between arguments.

@item 
@emph{end}: the ending text, which will be printed after all of the
arguments have been output.

@item 
@emph{file}: the file object to which the output will be sent.
@end itemize
@end quotation


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3105

@item PEP 3105@footnote{https://www.python.org/dev/peps/pep-3105} - print 改为函数

PEP 由 Georg Brandl 撰写
@end table


@c ======================================================================

@node PEP 3110 异常处理的变更,PEP 3112 字节字面值,PEP 3105 print 改为函数,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3110}@anchor{c49}@anchor{whatsnew/2 6 pep-3110-exception-handling-changes}@anchor{d15}
@subsection PEP 3110: 异常处理的变更


One error that Python programmers occasionally make
is writing the following code:

@example
try:
    ...
except TypeError, ValueError:  # Wrong!
    ...
@end example

The author is probably trying to catch both @ref{192,,TypeError} and
@ref{1fb,,ValueError} exceptions, but this code actually does something
different: it will catch @ref{192,,TypeError} and bind the resulting
exception object to the local name @code{"ValueError"}.  The
@ref{1fb,,ValueError} exception will not be caught at all.  The correct
code specifies a tuple of exceptions:

@example
try:
    ...
except (TypeError, ValueError):
    ...
@end example

This error happens because the use of the comma here is ambiguous:
does it indicate two different nodes in the parse tree, or a single
node that's a tuple?

Python 3.0 makes this unambiguous by replacing the comma with the word
"as".  To catch an exception and store the exception object in the
variable @code{exc}, you must write:

@example
try:
    ...
except TypeError as exc:
    ...
@end example

Python 3.0 will only support the use of "as", and therefore interprets
the first example as catching two different exceptions.  Python 2.6
supports both the comma and "as", so existing code will continue to
work.  We therefore suggest using "as" when writing new Python code
that will only be executed with 2.6.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3110

@item PEP 3110@footnote{https://www.python.org/dev/peps/pep-3110} - 在 Python 3000 中捕获异常

PEP 由 Collin Winter 撰写并实现
@end table


@c ======================================================================

@node PEP 3112 字节字面值,PEP 3116 新 I/O 库,PEP 3110 异常处理的变更,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3112}@anchor{c4a}@anchor{whatsnew/2 6 pep-3112-byte-literals}@anchor{d16}
@subsection PEP 3112: 字节字面值


Python 3.0 adopts Unicode as the language's fundamental string type and
denotes 8-bit literals differently, either as @code{b'string'}
or using a @ref{32a,,bytes} constructor.  For future compatibility,
Python 2.6 adds @ref{32a,,bytes} as a synonym for the @ref{329,,str} type,
and it also supports the @code{b'@w{'}} notation.

The 2.6 @ref{329,,str} differs from 3.0's @ref{32a,,bytes} type in various
ways; most notably, the constructor is completely different.  In 3.0,
@code{bytes([65, 66, 67])} is 3 elements long, containing the bytes
representing @code{ABC}; in 2.6, @code{bytes([65, 66, 67])} returns the
12-byte string representing the @ref{329,,str()} of the list.

The primary use of @ref{32a,,bytes} in 2.6 will be to write tests of
object type such as @code{isinstance(x, bytes)}.  This will help the 2to3
converter, which can't tell whether 2.x code intends strings to
contain either characters or 8-bit bytes; you can now
use either @ref{32a,,bytes} or @ref{329,,str} to represent your intention
exactly, and the resulting code will also be correct in Python 3.0.

There's also a @code{__future__} import that causes all string literals
to become Unicode strings.  This means that @code{\u} escape sequences
can be used to include Unicode characters:

@example
from __future__ import unicode_literals

s = ('\u751f\u3080\u304e\u3000\u751f\u3054'
     '\u3081\u3000\u751f\u305f\u307e\u3054')

print len(s)               # 12 Unicode characters
@end example

At the C level, Python 3.0 will rename the existing 8-bit
string type, called @code{PyStringObject} in Python 2.x,
to @ref{d17,,PyBytesObject}.  Python 2.6 uses @code{#define}
to support using the names @ref{d17,,PyBytesObject()},
@ref{d18,,PyBytes_Check()}, @ref{d19,,PyBytes_FromStringAndSize()},
and all the other functions and macros used with strings.

Instances of the @ref{32a,,bytes} type are immutable just
as strings are.  A new @ref{32b,,bytearray} type stores a mutable
sequence of bytes:

@example
>>> bytearray([65, 66, 67])
bytearray(b'ABC')
>>> b = bytearray(u'\u21ef\u3244', 'utf-8')
>>> b
bytearray(b'\xe2\x87\xaf\xe3\x89\x84')
>>> b[0] = '\xe3'
>>> b
bytearray(b'\xe3\x87\xaf\xe3\x89\x84')
>>> unicode(str(b), 'utf-8')
u'\u31ef \u3244'
@end example

Byte arrays support most of the methods of string types, such as
@code{startswith()}/@code{endswith()}, @code{find()}/@code{rfind()},
and some of the methods of lists, such as @code{append()},
@code{pop()},  and @code{reverse()}.

@example
>>> b = bytearray('ABC')
>>> b.append('d')
>>> b.append(ord('e'))
>>> b
bytearray(b'ABCde')
@end example

There's also a corresponding C API, with
@ref{d1a,,PyByteArray_FromObject()},
@ref{d1b,,PyByteArray_FromStringAndSize()},
and various other functions.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3112

@item PEP 3112@footnote{https://www.python.org/dev/peps/pep-3112} - Python 3000 中的字节字面值

PEP 由 Jason Orendorff 撰写， 补丁2.6 由 Christian Heimes 撰写。
@end table


@c ======================================================================

@node PEP 3116 新 I/O 库,PEP 3118 修改缓冲区协议,PEP 3112 字节字面值,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3116}@anchor{c4b}@anchor{whatsnew/2 6 pep-3116-new-i-o-library}@anchor{d1c}
@subsection PEP 3116: 新 I/O 库


Python's built-in file objects support a number of methods, but
file-like objects don't necessarily support all of them.  Objects that
imitate files usually support @code{read()} and @code{write()}, but they
may not support @ref{de,,readline()}, for example.  Python 3.0 introduces
a layered I/O library in the @ref{a1,,io} module that separates buffering
and text-handling features from the fundamental read and write
operations.

There are three levels of abstract base classes provided by
the @ref{a1,,io} module:


@itemize *

@item 
@code{RawIOBase} defines raw I/O operations: @code{read()},
@code{readinto()},
@code{write()}, @code{seek()}, @code{tell()}, @code{truncate()},
and @code{close()}.
Most of the methods of this class will often map to a single system call.
There are also @code{readable()}, @code{writable()}, and @code{seekable()}
methods for determining what operations a given object will allow.

Python 3.0 has concrete implementations of this class for files and
sockets, but Python 2.6 hasn't restructured its file and socket objects
in this way.

@c XXX should 2.6 register them in io.py?

@item 
@code{BufferedIOBase} is an abstract base class that
buffers data in memory to reduce the number of
system calls used, making I/O processing more efficient.
It supports all of the methods of @code{RawIOBase},
and adds a @code{raw} attribute holding the underlying raw object.

There are five concrete classes implementing this ABC.
@code{BufferedWriter} and @code{BufferedReader} are for objects
that support write-only or read-only usage that have a @code{seek()}
method for random access.  @code{BufferedRandom} objects support
read and write access upon the same underlying stream, and
@code{BufferedRWPair} is for objects such as TTYs that have both
read and write operations acting upon unconnected streams of data.
The @code{BytesIO} class supports reading, writing, and seeking
over an in-memory buffer.

@geindex universal newlines; What's new

@item 
@code{TextIOBase}: Provides functions for reading and writing
strings (remember, strings will be Unicode in Python 3.0),
and supporting @ref{5ef,,universal newlines}.  @code{TextIOBase} defines
the @ref{de,,readline()} method and supports iteration upon
objects.

There are two concrete implementations.  @code{TextIOWrapper}
wraps a buffered I/O object, supporting all of the methods for
text I/O and adding a @code{buffer} attribute for access
to the underlying object.  @code{StringIO} simply buffers
everything in memory without ever writing anything to disk.

(In Python 2.6, @ref{827,,io.StringIO} is implemented in
pure Python, so it's pretty slow.   You should therefore stick with the
existing @code{StringIO} module or @code{cStringIO} for now.  At some
point Python 3.0's @ref{a1,,io} module will be rewritten into C for speed,
and perhaps the C implementation will be  backported to the 2.x releases.)
@end itemize

In Python 2.6, the underlying implementations haven't been
restructured to build on top of the @ref{a1,,io} module's classes.  The
module is being provided to make it easier to write code that's
forward-compatible with 3.0, and to save developers the effort of writing
their own implementations of buffering and text I/O.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3116

@item PEP 3116@footnote{https://www.python.org/dev/peps/pep-3116} - 新 I/O

PEP written by Daniel Stutzbach, Mike Verdone, and Guido van Rossum.
Code by Guido van Rossum, Georg Brandl, Walter Doerwald,
Jeremy Hylton, Martin von Löwis, Tony Lownds, and others.
@end table


@c ======================================================================

@node PEP 3118 修改缓冲区协议,PEP 3119 抽象基类,PEP 3116 新 I/O 库,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3118}@anchor{c4c}@anchor{whatsnew/2 6 pep-3118-revised-buffer-protocol}@anchor{d1d}
@subsection PEP 3118: 修改缓冲区协议


The buffer protocol is a C-level API that lets Python types
exchange pointers into their internal representations.  A
memory-mapped file can be viewed as a buffer of characters, for
example, and this lets another module such as @ref{dd,,re}
treat memory-mapped files as a string of characters to be searched.

The primary users of the buffer protocol are numeric-processing
packages such as NumPy, which expose the internal representation
of arrays so that callers can write data directly into an array instead
of going through a slower API.  This PEP updates the buffer protocol in light of experience
from NumPy development, adding a number of new features
such as indicating the shape of an array or locking a memory region.

The most important new C API function is
@code{PyObject_GetBuffer(PyObject *obj, Py_buffer *view, int flags)}, which
takes an object and a set of flags, and fills in the
@code{Py_buffer} structure with information
about the object's memory representation.  Objects
can use this operation to lock memory in place
while an external caller could be modifying the contents,
so there's a corresponding @code{PyBuffer_Release(Py_buffer *view)} to
indicate that the external caller is done.

@c XXX PyObject_GetBuffer not documented in c-api

The @emph{flags} argument to @ref{d1e,,PyObject_GetBuffer()} specifies
constraints upon the memory returned.  Some examples are:

@quotation


@itemize *

@item 
@code{PyBUF_WRITABLE} indicates that the memory must be writable.

@item 
@code{PyBUF_LOCK} requests a read-only or exclusive lock on the memory.

@item 
@code{PyBUF_C_CONTIGUOUS} and @code{PyBUF_F_CONTIGUOUS}
requests a C-contiguous (last dimension varies the fastest) or
Fortran-contiguous (first dimension varies the fastest) array layout.
@end itemize
@end quotation

Two new argument codes for @ref{26a,,PyArg_ParseTuple()},
@code{s*} and @code{z*}, return locked buffer objects for a parameter.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3118

@item PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} - 修改缓冲区协议

PEP 由 Travis Oliphant 和 Carl Banks 撰写，由 Travis Oliphant 实现。
@end table


@c ======================================================================

@node PEP 3119 抽象基类,PEP 3127 整型文字支持和语法,PEP 3118 修改缓冲区协议,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3119}@anchor{c4d}@anchor{whatsnew/2 6 pep-3119-abstract-base-classes}@anchor{d1f}
@subsection PEP 3119: 抽象基类


Some object-oriented languages such as Java support interfaces,
declaring that a class has a given set of methods or supports a given
access protocol.  Abstract Base Classes (or ABCs) are an equivalent
feature for Python. The ABC support consists of an @ref{4,,abc} module
containing a metaclass called @code{ABCMeta}, special handling of
this metaclass by the @ref{449,,isinstance()} and @ref{44a,,issubclass()}
builtins, and a collection of basic ABCs that the Python developers
think will be widely useful.  Future versions of Python will probably
add more ABCs.

Let's say you have a particular class and wish to know whether it supports
dictionary-style access.  The phrase "dictionary-style" is vague, however.
It probably means that accessing items with @code{obj[1]} works.
Does it imply that setting items with @code{obj[2] = value} works?
Or that the object will have @code{keys()}, @code{values()}, and @code{items()}
methods?  What about the iterative variants  such as @code{iterkeys()}?  @ref{26,,copy()}
and @code{update()}?  Iterating over the object with @ref{d20,,iter()}?

The Python 2.6 @ref{1e,,collections} module includes a number of
different ABCs that represent these distinctions.  @code{Iterable}
indicates that a class defines @ref{509,,__iter__()}, and
@code{Container} means the class defines a @ref{d21,,__contains__()}
method and therefore supports @code{x in y} expressions.  The basic
dictionary interface of getting items, setting items, and
@code{keys()}, @code{values()}, and @code{items()}, is defined by the
@code{MutableMapping} ABC.

You can derive your own classes from a particular ABC
to indicate they support that ABC's interface:

@example
import collections

class Storage(collections.MutableMapping):
    ...
@end example

Alternatively, you could write the class without deriving from
the desired ABC and instead register the class by
calling the ABC's @code{register()} method:

@example
import collections

class Storage:
    ...

collections.MutableMapping.register(Storage)
@end example

For classes that you write, deriving from the ABC is probably clearer.
The @code{register()}  method is useful when you've written a new
ABC that can describe an existing type or class, or if you want
to declare that some third-party class implements an ABC.
For example, if you defined a @code{PrintableType} ABC,
it's legal to do:

@example
# Register Python's types
PrintableType.register(int)
PrintableType.register(float)
PrintableType.register(str)
@end example

Classes should obey the semantics specified by an ABC, but
Python can't check this; it's up to the class author to
understand the ABC's requirements and to implement the code accordingly.

To check whether an object supports a particular interface, you can
now write:

@example
def func(d):
    if not isinstance(d, collections.MutableMapping):
        raise ValueError("Mapping object expected, not %r" % d)
@end example

Don't feel that you must now begin writing lots of checks as in the
above example.  Python has a strong tradition of duck-typing, where
explicit type-checking is never done and code simply calls methods on
an object, trusting that those methods will be there and raising an
exception if they aren't.  Be judicious in checking for ABCs and only
do it where it's absolutely necessary.

You can write your own ABCs by using @code{abc.ABCMeta} as the
metaclass in a class definition:

@example
from abc import ABCMeta, abstractmethod

class Drawable():
    __metaclass__ = ABCMeta

    @@abstractmethod
    def draw(self, x, y, scale=1.0):
        pass

    def draw_doubled(self, x, y):
        self.draw(x, y, scale=2.0)


class Square(Drawable):
    def draw(self, x, y, scale):
        ...
@end example

In the @code{Drawable} ABC above, the @code{draw_doubled()} method
renders the object at twice its size and can be implemented in terms
of other methods described in @code{Drawable}.  Classes implementing
this ABC therefore don't need to provide their own implementation
of @code{draw_doubled()}, though they can do so.  An implementation
of @code{draw()} is necessary, though; the ABC can't provide
a useful generic implementation.

You can apply the @code{@@abstractmethod} decorator to methods such as
@code{draw()} that must be implemented; Python will then raise an
exception for classes that don't define the method.
Note that the exception is only raised when you actually
try to create an instance of a subclass lacking the method:

@example
>>> class Circle(Drawable):
...     pass
...
>>> c = Circle()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Can't instantiate abstract class Circle with abstract methods draw
>>>
@end example

Abstract data attributes can be declared using the
@code{@@abstractproperty} decorator:

@example
from abc import abstractproperty
...

@@abstractproperty
def readonly(self):
   return self._x
@end example

Subclasses must then define a @code{readonly()} property.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3119

@item PEP 3119@footnote{https://www.python.org/dev/peps/pep-3119} - 引入抽象基类

PEP written by Guido van Rossum and Talin.
Implemented by Guido van Rossum.
Backported to 2.6 by Benjamin Aranguren, with Alex Martelli.
@end table


@c ======================================================================

@node PEP 3127 整型文字支持和语法,PEP 3129 类装饰器,PEP 3119 抽象基类,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3127}@anchor{c4e}@anchor{whatsnew/2 6 pep-3127-integer-literal-support-and-syntax}@anchor{d22}
@subsection PEP 3127: 整型文字支持和语法


Python 3.0 changes the syntax for octal (base-8) integer literals,
prefixing them with "0o" or "0O" instead of a leading zero, and adds
support for binary (base-2) integer literals, signalled by a "0b" or
"0B" prefix.

Python 2.6 doesn't drop support for a leading 0 signalling
an octal number, but it does add support for "0o" and "0b":

@example
>>> 0o21, 2*8 + 1
(17, 17)
>>> 0b101111
47
@end example

The @ref{c5e,,oct()} builtin still returns numbers
prefixed with a leading zero, and a new @ref{c39,,bin()}
builtin returns the binary representation for a number:

@example
>>> oct(42)
'052'
>>> future_builtins.oct(42)
'0o52'
>>> bin(173)
'0b10101101'
@end example

The @ref{184,,int()} and @code{long()} builtins will now accept the "0o"
and "0b" prefixes when base-8 or base-2 are requested, or when the
@emph{base} argument is zero (signalling that the base used should be
determined from the string):

@example
>>> int ('0o52', 0)
42
>>> int('1101', 2)
13
>>> int('0b1101', 2)
13
>>> int('0b1101', 0)
13
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3127

@item PEP 3127@footnote{https://www.python.org/dev/peps/pep-3127} - 整型文字支持和语法

PEP written by Patrick Maupin; backported to 2.6 by
Eric Smith.
@end table


@c ======================================================================

@node PEP 3129 类装饰器,PEP 3141 A Type Hierarchy for Numbers,PEP 3127 整型文字支持和语法,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3129}@anchor{c4f}@anchor{whatsnew/2 6 pep-3129-class-decorators}@anchor{d23}
@subsection PEP 3129: 类装饰器


Decorators have been extended from functions to classes.  It's now legal to
write:

@example
@@foo
@@bar
class A:
  pass
@end example

这相当于:

@example
class A:
  pass

A = foo(bar(A))
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3129

@item PEP 3129@footnote{https://www.python.org/dev/peps/pep-3129} - 类装饰器

PEP 由 Collin Winter 撰写
@end table


@c ======================================================================

@node PEP 3141 A Type Hierarchy for Numbers,其他语言特性修改<10>,PEP 3129 类装饰器,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 pep-3141}@anchor{c50}@anchor{whatsnew/2 6 pep-3141-a-type-hierarchy-for-numbers}@anchor{d24}
@subsection PEP 3141: A Type Hierarchy for Numbers


Python 3.0 adds several abstract base classes for numeric types
inspired by Scheme's numeric tower.  These classes were backported to
2.6 as the @ref{c1,,numbers} module.

The most general ABC is @code{Number}.  It defines no operations at
all, and only exists to allow checking if an object is a number by
doing @code{isinstance(obj, Number)}.

@code{Complex} is a subclass of @code{Number}.  Complex numbers
can undergo the basic operations of addition, subtraction,
multiplication, division, and exponentiation, and you can retrieve the
real and imaginary parts and obtain a number's conjugate.  Python's built-in
complex type is an implementation of @code{Complex}.

@code{Real} further derives from @code{Complex}, and adds
operations that only work on real numbers: @code{floor()}, @code{trunc()},
rounding, taking the remainder mod N, floor division,
and comparisons.

@code{Rational} numbers derive from @code{Real}, have
@code{numerator} and @code{denominator} properties, and can be
converted to floats.  Python 2.6 adds a simple rational-number class,
@code{Fraction}, in the @ref{83,,fractions} module.  (It's called
@code{Fraction} instead of @code{Rational} to avoid
a name clash with @ref{c51,,numbers.Rational}.)

@code{Integral} numbers derive from @code{Rational}, and
can be shifted left and right with @code{<<} and @code{>>},
combined using bitwise operations such as @code{&} and @code{|},
and can be used as array indexes and slice boundaries.

In Python 3.0, the PEP slightly redefines the existing builtins
@ref{c66,,round()}, @ref{d25,,math.floor()}, @ref{d26,,math.ceil()}, and adds a new
one, @ref{d27,,math.trunc()}, that's been backported to Python 2.6.
@ref{d27,,math.trunc()} rounds toward zero, returning the closest
@code{Integral} that's between the function's argument and zero.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3141

@item PEP 3141@footnote{https://www.python.org/dev/peps/pep-3141} - A Type Hierarchy for Numbers

PEP 由 Jeffrey Yasskin 撰写
@end table

Scheme's numerical tower@footnote{https://www.gnu.org/software/guile/manual/html_node/Numerical-Tower.html#Numerical-Tower}, from the Guile manual.

Scheme's number datatypes@footnote{http://schemers.org/Documents/Standards/R5RS/HTML/r5rs-Z-H-9.html#%_sec_6.2} from the R5RS Scheme specification.


@menu
* fractions 模块:: 

@end menu

@node fractions 模块,,,PEP 3141 A Type Hierarchy for Numbers
@anchor{whatsnew/2 6 the-fractions-module}@anchor{d28}
@subsubsection @code{fractions} 模块


To fill out the hierarchy of numeric types, the @ref{83,,fractions}
module provides a rational-number class.  Rational numbers store their
values as a numerator and denominator forming a fraction, and can
exactly represent numbers such as @code{2/3} that floating-point numbers
can only approximate.

The @code{Fraction} constructor takes two @code{Integral} values
that will be the numerator and denominator of the resulting fraction.

@example
>>> from fractions import Fraction
>>> a = Fraction(2, 3)
>>> b = Fraction(2, 5)
>>> float(a), float(b)
(0.66666666666666663, 0.40000000000000002)
>>> a+b
Fraction(16, 15)
>>> a/b
Fraction(5, 3)
@end example

For converting floating-point numbers to rationals,
the float type now has an @code{as_integer_ratio()} method that returns
the numerator and denominator for a fraction that evaluates to the same
floating-point value:

@example
>>> (2.5) .as_integer_ratio()
(5, 2)
>>> (3.1415) .as_integer_ratio()
(7074029114692207L, 2251799813685248L)
>>> (1./3) .as_integer_ratio()
(6004799503160661L, 18014398509481984L)
@end example

Note that values that can only be approximated by floating-point
numbers, such as 1./3, are not simplified to the number being
approximated; the fraction attempts to match the floating-point value
@strong{exactly}.

The @ref{83,,fractions} module is based upon an implementation by Sjoerd
Mullender that was in Python's @code{Demo/classes/} directory for a
long time.  This implementation was significantly updated by Jeffrey
Yasskin.

@node 其他语言特性修改<10>,新增和改进的模块<2>,PEP 3141 A Type Hierarchy for Numbers,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 other-language-changes}@anchor{d29}
@subsection 其他语言特性修改


对Python 语言核心进行的小改动：


@itemize *

@item 
Directories and zip archives containing a @code{__main__.py} file
can now be executed directly by passing their name to the
interpreter. The directory or zip archive is automatically inserted
as the first entry in sys.path.  (Suggestion and initial patch by
Andy Chu, subsequently revised by Phillip J. Eby and Nick Coghlan;
bpo-1739468@footnote{https://bugs.python.org/issue1739468}.)

@item 
The @ref{442,,hasattr()} function was catching and ignoring all errors,
under the assumption that they meant a @ref{313,,__getattr__()} method
was failing somehow and the return value of @ref{442,,hasattr()} would
therefore be @code{False}.  This logic shouldn't be applied to
@ref{197,,KeyboardInterrupt} and @ref{5f7,,SystemExit}, however; Python 2.6
will no longer discard such exceptions when @ref{442,,hasattr()}
encounters them.  (Fixed by Benjamin Peterson; bpo-2196@footnote{https://bugs.python.org/issue2196}.)

@item 
When calling a function using the @code{**} syntax to provide keyword
arguments, you are no longer required to use a Python dictionary;
any mapping will now work:

@example
>>> def f(**kw):
...    print sorted(kw)
...
>>> ud=UserDict.UserDict()
>>> ud['a'] = 1
>>> ud['b'] = 'string'
>>> f(**ud)
['a', 'b']
@end example

（由 Alexander Belopolsky 在 bpo-1686487@footnote{https://bugs.python.org/issue1686487} 中贡献。）

It's also become legal to provide keyword arguments after a @code{*args} argument
to a function call.

@example
>>> def f(*args, **kw):
...     print args, kw
...
>>> f(1,2,3, *(4,5,6), keyword=13)
(1, 2, 3, 4, 5, 6) @{'keyword': 13@}
@end example

Previously this would have been a syntax error.
(Contributed by Amaury Forgeot d'Arc; bpo-3473@footnote{https://bugs.python.org/issue3473}.)

@item 
A new builtin, @code{next(iterator, [default])} returns the next item
from the specified iterator.  If the @emph{default} argument is supplied,
it will be returned if @emph{iterator} has been exhausted; otherwise,
the @ref{480,,StopIteration} exception will be raised.  (Backported
in bpo-2719@footnote{https://bugs.python.org/issue2719}.)

@item 
Tuples now have @code{index()} and @code{count()} methods matching the
list type's @code{index()} and @code{count()} methods:

@example
>>> t = (0,1,2,3,4,0,1,2)
>>> t.index(3)
3
>>> t.count(0)
2
@end example

（由 Raymond Hettinger 贡献）

@item 
The built-in types now have improved support for extended slicing syntax,
accepting various combinations of @code{(start, stop, step)}.
Previously, the support was partial and certain corner cases wouldn't work.
(Implemented by Thomas Wouters.)

@c Revision 57619

@item 
Properties now have three attributes, @code{getter}, @code{setter}
and @code{deleter}, that are decorators providing useful shortcuts
for adding a getter, setter or deleter function to an existing
property. You would use them like this:

@example
class C(object):
    @@property
    def x(self):
        return self._x

    @@x.setter
    def x(self, value):
        self._x = value

    @@x.deleter
    def x(self):
        del self._x

class D(C):
    @@C.x.getter
    def x(self):
        return self._x * 2

    @@x.setter
    def x(self, value):
        self._x = value / 2
@end example

@item 
Several methods of the built-in set types now accept multiple iterables:
@code{intersection()},
@code{intersection_update()},
@code{union()}, @code{update()},
@code{difference()} and @code{difference_update()}.

@example
>>> s=set('1234567890')
>>> s.intersection('abc123', 'cdf246')  # Intersection between all inputs
set(['2'])
>>> s.difference('246', '789')
set(['1', '0', '3', '5'])
@end example

（由 Raymond Hettinger 贡献。）

@item 
Many floating-point features were added.  The @ref{187,,float()} function
will now turn the string @code{nan} into an
IEEE 754 Not A Number value, and @code{+inf} and @code{-inf} into
positive or negative infinity.  This works on any platform with
IEEE 754 semantics.  (Contributed by Christian Heimes; bpo-1635@footnote{https://bugs.python.org/issue1635}.)

Other functions in the @ref{b1,,math} module, @code{isinf()} and
@code{isnan()}, return true if their floating-point argument is
infinite or Not A Number.  (bpo-1640@footnote{https://bugs.python.org/issue1640})

Conversion functions were added to convert floating-point numbers
into hexadecimal strings (bpo-3008@footnote{https://bugs.python.org/issue3008}).  These functions
convert floats to and from a string representation without
introducing rounding errors from the conversion between decimal and
binary.  Floats have a @ref{c5f,,hex()} method that returns a string
representation, and the @code{float.fromhex()} method converts a string
back into a number:

@example
>>> a = 3.75
>>> a.hex()
'0x1.e000000000000p+1'
>>> float.fromhex('0x1.e000000000000p+1')
3.75
>>> b=1./3
>>> b.hex()
'0x1.5555555555555p-2'
@end example

@item 
A numerical nicety: when creating a complex number from two floats
on systems that support signed zeros (-0 and +0), the
@ref{189,,complex()} constructor will now preserve the sign
of the zero.  (Fixed by Mark T. Dickinson; bpo-1507@footnote{https://bugs.python.org/issue1507}.)

@item 
Classes that inherit a @ref{339,,__hash__()} method from a parent class
can set @code{__hash__ = None} to indicate that the class isn't
hashable.  This will make @code{hash(obj)} raise a @ref{192,,TypeError}
and the class will not be indicated as implementing the
@code{Hashable} ABC.

You should do this when you've defined a @code{__cmp__()} or
@ref{338,,__eq__()} method that compares objects by their value rather
than by identity.  All objects have a default hash method that uses
@code{id(obj)} as the hash value.  There's no tidy way to remove the
@ref{339,,__hash__()} method inherited from a parent class, so
assigning @code{None} was implemented as an override.  At the
C level, extensions can set @code{tp_hash} to
@ref{d2a,,PyObject_HashNotImplemented()}.
(Fixed by Nick Coghlan and Amaury Forgeot d'Arc; bpo-2235@footnote{https://bugs.python.org/issue2235}.)

@item 
The @ref{d2b,,GeneratorExit} exception now subclasses
@ref{1a8,,BaseException} instead of @ref{1a9,,Exception}.  This means
that an exception handler that does @code{except Exception:}
will not inadvertently catch @ref{d2b,,GeneratorExit}.
(Contributed by Chad Austin; bpo-1537@footnote{https://bugs.python.org/issue1537}.)

@item 
Generator objects now have a @code{gi_code} attribute that refers to
the original code object backing the generator.
(Contributed by Collin Winter; bpo-1473257@footnote{https://bugs.python.org/issue1473257}.)

@item 
The @ref{1b4,,compile()} built-in function now accepts keyword arguments
as well as positional parameters.  (Contributed by Thomas Wouters;
bpo-1444529@footnote{https://bugs.python.org/issue1444529}.)

@item 
The @ref{189,,complex()} constructor now accepts strings containing
parenthesized complex numbers, meaning that @code{complex(repr(cplx))}
will now round-trip values.  For example, @code{complex('(3+4j)')}
now returns the value (3+4j).  (bpo-1491866@footnote{https://bugs.python.org/issue1491866})

@item 
The string @code{translate()} method now accepts @code{None} as the
translation table parameter, which is treated as the identity
transformation.   This makes it easier to carry out operations
that only delete characters.  (Contributed by Bengt Richter and
implemented by Raymond Hettinger; bpo-1193128@footnote{https://bugs.python.org/issue1193128}.)

@item 
The built-in @ref{d2c,,dir()} function now checks for a @ref{314,,__dir__()}
method on the objects it receives.  This method must return a list
of strings containing the names of valid attributes for the object,
and lets the object control the value that @ref{d2c,,dir()} produces.
Objects that have @ref{313,,__getattr__()} or @ref{441,,__getattribute__()}
methods can use this to advertise pseudo-attributes they will honor.
(bpo-1591665@footnote{https://bugs.python.org/issue1591665})

@item 
Instance method objects have new attributes for the object and function
comprising the method; the new synonym for @code{im_self} is
@code{__self__}, and @code{im_func} is also available as @code{__func__}.
The old names are still supported in Python 2.6, but are gone in 3.0.

@item 
An obscure change: when you use the @ref{44f,,locals()} function inside a
@ref{c63,,class} statement, the resulting dictionary no longer returns free
variables.  (Free variables, in this case, are variables referenced in the
@code{class} statement  that aren't attributes of the class.)
@end itemize

@c ======================================================================

@menu
* 性能优化: 性能优化<9>. 
* Interpreter Changes: Interpreter Changes<2>. 

@end menu

@node 性能优化<9>,Interpreter Changes<2>,,其他语言特性修改<10>
@anchor{whatsnew/2 6 optimizations}@anchor{d2d}
@subsubsection 性能优化



@itemize *

@item 
The @ref{126,,warnings} module has been rewritten in C.  This makes
it possible to invoke warnings from the parser, and may also
make the interpreter's startup faster.
(Contributed by Neal Norwitz and Brett Cannon; bpo-1631171@footnote{https://bugs.python.org/issue1631171}.)

@item 
Type objects now have a cache of methods that can reduce
the work required to find the correct method implementation
for a particular class; once cached, the interpreter doesn't need to
traverse base classes to figure out the right method to call.
The cache is cleared if a base class or the class itself is modified,
so the cache should remain correct even in the face of Python's dynamic
nature.
(Original optimization implemented by Armin Rigo, updated for
Python 2.6 by Kevin Jacobs; bpo-1700288@footnote{https://bugs.python.org/issue1700288}.)

By default, this change is only applied to types that are included with
the Python core.  Extension modules may not necessarily be compatible with
this cache,
so they must explicitly add @code{Py_TPFLAGS_HAVE_VERSION_TAG}
to the module's @code{tp_flags} field to enable the method cache.
(To be compatible with the method cache, the extension module's code
must not directly access and modify the @code{tp_dict} member of
any of the types it implements.  Most modules don't do this,
but it's impossible for the Python interpreter to determine that.
See bpo-1878@footnote{https://bugs.python.org/issue1878} for some discussion.)

@item 
Function calls that use keyword arguments are significantly faster
by doing a quick pointer comparison, usually saving the time of a
full string comparison.  (Contributed by Raymond Hettinger, after an
initial implementation by Antoine Pitrou; bpo-1819@footnote{https://bugs.python.org/issue1819}.)

@item 
All of the functions in the @ref{f8,,struct} module have been rewritten in
C, thanks to work at the Need For Speed sprint.
(Contributed by Raymond Hettinger.)

@item 
Some of the standard built-in types now set a bit in their type
objects.  This speeds up checking whether an object is a subclass of
one of these types.  (Contributed by Neal Norwitz.)

@item 
Unicode strings now use faster code for detecting
whitespace and line breaks; this speeds up the @code{split()} method
by about 25% and @code{splitlines()} by 35%.
(Contributed by Antoine Pitrou.)  Memory usage is reduced
by using pymalloc for the Unicode string's data.

@item 
The @code{with} statement now stores the @ref{c8f,,__exit__()} method on the stack,
producing a small speedup.  (Implemented by Jeffrey Yasskin.)

@item 
To reduce memory usage, the garbage collector will now clear internal
free lists when garbage-collecting the highest generation of objects.
This may return memory to the operating system sooner.
@end itemize

@c ======================================================================

@node Interpreter Changes<2>,,性能优化<9>,其他语言特性修改<10>
@anchor{whatsnew/2 6 interpreter-changes}@anchor{d2e}@anchor{whatsnew/2 6 new-26-interpreter}@anchor{d2f}
@subsubsection Interpreter Changes


Two command-line options have been reserved for use by other Python
implementations.  The @ref{d30,,-J} switch has been reserved for use by
Jython for Jython-specific options, such as switches that are passed to
the underlying JVM.  @ref{155,,-X} has been reserved for options
specific to a particular implementation of Python such as CPython,
Jython, or IronPython.  If either option is used with Python 2.6, the
interpreter will report that the option isn't currently used.

Python can now be prevented from writing @code{.pyc} or @code{.pyo}
files by supplying the @ref{d31,,-B} switch to the Python interpreter,
or by setting the 
@geindex PYTHONDONTWRITEBYTECODE
@geindex 环境变量; PYTHONDONTWRITEBYTECODE
@ref{d32,,PYTHONDONTWRITEBYTECODE} environment
variable before running the interpreter.  This setting is available to
Python programs as the @code{sys.dont_write_bytecode} variable, and
Python code can change the value to modify the interpreter's
behaviour.  (Contributed by Neal Norwitz and Georg Brandl.)

The encoding used for standard input, output, and standard error can
be specified by setting the 
@geindex PYTHONIOENCODING
@geindex 环境变量; PYTHONIOENCODING
@ref{929,,PYTHONIOENCODING} environment
variable before running the interpreter.  The value should be a string
in the form @code{<encoding>} or @code{<encoding>:<errorhandler>}.
The @emph{encoding} part specifies the encoding's name, e.g. @code{utf-8} or
@code{latin-1}; the optional @emph{errorhandler} part specifies
what to do with characters that can't be handled by the encoding,
and  should be one of "error", "ignore", or "replace".   (Contributed
by Martin von Löwis.)

@c ======================================================================

@node 新增和改进的模块<2>,Deprecations and Removals,其他语言特性修改<10>,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 new-and-improved-modules}@anchor{d33}
@subsection 新增和改进的模块


As in every release, Python's standard library received a number of
enhancements and bug fixes.  Here's a partial list of the most notable
changes, sorted alphabetically by module name. Consult the
@code{Misc/NEWS} file in the source tree for a more complete list of
changes, or look through the Subversion logs for all the details.


@itemize *

@item 
The @ref{b,,asyncore} and @ref{9,,asynchat} modules are
being actively maintained again, and a number of patches and bugfixes
were applied.  (Maintained by Josiah Carlson; see bpo-1736190@footnote{https://bugs.python.org/issue1736190} for
one patch.)

@item 
The @code{bsddb} module also has a new maintainer, Jesús Cea Avión, and the package
is now available as a standalone package.  The web page for the package is
www.jcea.es/programacion/pybsddb.htm@footnote{https://www.jcea.es/programacion/pybsddb.htm}.
The plan is to remove the package from the standard library
in Python 3.0, because its pace of releases is much more frequent than
Python's.

The @code{bsddb.dbshelve} module now uses the highest pickling protocol
available, instead of restricting itself to protocol 1.
(Contributed by W. Barnes.)

@item 
The @ref{16,,cgi} module will now read variables from the query string
of an HTTP POST request.  This makes it possible to use form actions
with URLs that include query strings such as
"/cgi-bin/add.py?category=1".  (Contributed by Alexandre Fiori and
Nubis; bpo-1817@footnote{https://bugs.python.org/issue1817}.)

The @code{parse_qs()} and @code{parse_qsl()} functions have been
relocated from the @ref{16,,cgi} module to the @code{urlparse} module.
The versions still available in the @ref{16,,cgi} module will
trigger @ref{279,,PendingDeprecationWarning} messages in 2.6
(bpo-600362@footnote{https://bugs.python.org/issue600362}).

@item 
The @ref{19,,cmath} module underwent extensive revision,
contributed by Mark Dickinson and Christian Heimes.
Five new functions were added:


@itemize *

@item 
@code{polar()} converts a complex number to polar form, returning
the modulus and argument of the complex number.

@item 
@code{rect()} does the opposite, turning a modulus, argument pair
back into the corresponding complex number.

@item 
@code{phase()} returns the argument (also called the angle) of a complex
number.

@item 
@code{isnan()} returns True if either
the real or imaginary part of its argument is a NaN.

@item 
@code{isinf()} returns True if either the real or imaginary part of
its argument is infinite.
@end itemize

The revisions also improved the numerical soundness of the
@ref{19,,cmath} module.  For all functions, the real and imaginary
parts of the results are accurate to within a few units of least
precision (ulps) whenever possible.  See bpo-1381@footnote{https://bugs.python.org/issue1381} for the
details.  The branch cuts for @code{asinh()}, @code{atanh()}: and
@code{atan()} have also been corrected.

The tests for the module have been greatly expanded; nearly 2000 new
test cases exercise the algebraic functions.

On IEEE 754 platforms, the @ref{19,,cmath} module now handles IEEE 754
special values and floating-point exceptions in a manner consistent
with Annex 'G' of the C99 standard.

@item 
A new data type in the @ref{1e,,collections} module: @code{namedtuple(typename,
fieldnames)} is a factory function that creates subclasses of the standard tuple
whose fields are accessible by name as well as index.  For example:

@example
>>> var_type = collections.namedtuple('variable',
...             'id name type size')
>>> # Names are separated by spaces or commas.
>>> # 'id, name, type, size' would also work.
>>> var_type._fields
('id', 'name', 'type', 'size')

>>> var = var_type(1, 'frequency', 'int', 4)
>>> print var[0], var.id    # Equivalent
1 1
>>> print var[2], var.type  # Equivalent
int int
>>> var._asdict()
@{'size': 4, 'type': 'int', 'id': 1, 'name': 'frequency'@}
>>> v2 = var._replace(name='amplitude')
>>> v2
variable(id=1, name='amplitude', type='int', size=4)
@end example

Several places in the standard library that returned tuples have
been modified to return @code{namedtuple} instances.  For example,
the @code{Decimal.as_tuple()} method now returns a named tuple with
@code{sign}, @code{digits}, and @code{exponent} fields.

（由 Raymond Hettinger 贡献。）

@item 
Another change to the @ref{1e,,collections} module is that the
@code{deque} type now supports an optional @emph{maxlen} parameter;
if supplied, the deque's size will be restricted to no more
than @emph{maxlen} items.  Adding more items to a full deque causes
old items to be discarded.

@example
>>> from collections import deque
>>> dq=deque(maxlen=3)
>>> dq
deque([], maxlen=3)
>>> dq.append(1); dq.append(2); dq.append(3)
>>> dq
deque([1, 2, 3], maxlen=3)
>>> dq.append(4)
>>> dq
deque([2, 3, 4], maxlen=3)
@end example

（由 Raymond Hettinger 贡献。）

@item 
The @code{Cookie} module's @code{Morsel} objects now support an
@code{httponly} attribute.  In some browsers. cookies with this attribute
set cannot be accessed or manipulated by JavaScript code.
(Contributed by Arvin Schnell; bpo-1638033@footnote{https://bugs.python.org/issue1638033}.)

@item 
A new window method in the @ref{2c,,curses} module,
@code{chgat()}, changes the display attributes for a certain number of
characters on a single line.  (Contributed by Fabian Kreutz.)

@example
# Boldface text starting at y=0,x=21
# and affecting the rest of the line.
stdscr.chgat(0, 21, curses.A_BOLD)
@end example

The @code{Textbox} class in the @ref{2f,,curses.textpad} module
now supports editing in insert mode as well as overwrite mode.
Insert mode is enabled by supplying a true value for the @emph{insert_mode}
parameter when creating the @code{Textbox} instance.

@item 
The @ref{31,,datetime} module's @code{strftime()} methods now support a
@code{%f} format code that expands to the number of microseconds in the
object, zero-padded on
the left to six places.  (Contributed by Skip Montanaro; bpo-1158@footnote{https://bugs.python.org/issue1158}.)

@item 
The @ref{36,,decimal} module was updated to version 1.66 of
the General Decimal Specification@footnote{http://speleotrove.com/decimal/decarith.html}.  New features
include some methods for some basic mathematical functions such as
@code{exp()} and @code{log10()}:

@example
>>> Decimal(1).exp()
Decimal("2.718281828459045235360287471")
>>> Decimal("2.7182818").ln()
Decimal("0.9999999895305022877376682436")
>>> Decimal(1000).log10()
Decimal("3")
@end example

The @code{as_tuple()} method of @code{Decimal} objects now returns a
named tuple with @code{sign}, @code{digits}, and @code{exponent} fields.

(Implemented by Facundo Batista and Mark Dickinson.  Named tuple
support added by Raymond Hettinger.)

@item 
The @ref{37,,difflib} module's @code{SequenceMatcher} class
now returns named tuples representing matches,
with @code{a}, @code{b}, and @code{size} attributes.
(Contributed by Raymond Hettinger.)

@item 
An optional @code{timeout} parameter, specifying a timeout measured in
seconds, was added to the @ref{9fd,,ftplib.FTP} class constructor as
well as the @code{connect()} method.  (Added by Facundo Batista.)
Also, the @code{FTP} class's @code{storbinary()} and
@code{storlines()} now take an optional @emph{callback} parameter that
will be called with each block of data after the data has been sent.
(Contributed by Phil Schwartz; bpo-1221598@footnote{https://bugs.python.org/issue1221598}.)

@item 
The @code{reduce()} built-in function is also available in the
@ref{85,,functools} module.  In Python 3.0, the builtin has been
dropped and @code{reduce()} is only available from @ref{85,,functools};
currently there are no plans to drop the builtin in the 2.x series.
(Patched by Christian Heimes; bpo-1739906@footnote{https://bugs.python.org/issue1739906}.)

@item 
When possible, the @ref{88,,getpass} module will now use
@code{/dev/tty} to print a prompt message and read the password,
falling back to standard error and standard input.  If the
password may be echoed to the terminal, a warning is printed before
the prompt is displayed.  (Contributed by Gregory P. Smith.)

@item 
The @ref{5c1,,glob.glob()} function can now return Unicode filenames if
a Unicode path was used and Unicode filenames are matched within the
directory.  (bpo-1001604@footnote{https://bugs.python.org/issue1001604})

@item 
A new function in the @ref{8e,,heapq} module, @code{merge(iter1, iter2, ...)},
takes any number of iterables returning data in sorted
order, and returns a new generator that returns the contents of all
the iterators, also in sorted order.  For example:

@example
>>> list(heapq.merge([1, 3, 5, 9], [2, 8, 16]))
[1, 2, 3, 5, 8, 9, 16]
@end example

Another new function, @code{heappushpop(heap, item)},
pushes @emph{item} onto @emph{heap}, then pops off and returns the smallest item.
This is more efficient than making a call to @code{heappush()} and then
@code{heappop()}.

@ref{8e,,heapq} is now implemented to only use less-than comparison,
instead of the less-than-or-equal comparison it previously used.
This makes @ref{8e,,heapq}'s usage of a type match the
@ref{43f,,list.sort()} method.
(Contributed by Raymond Hettinger.)

@item 
An optional @code{timeout} parameter, specifying a timeout measured in
seconds, was added to the @code{httplib.HTTPConnection} and
@code{HTTPSConnection} class constructors.  (Added by Facundo
Batista.)

@item 
Most of the @ref{a0,,inspect} module's functions, such as
@code{getmoduleinfo()} and @code{getargs()}, now return named tuples.
In addition to behaving like tuples, the elements of the  return value
can also be accessed as attributes.
(Contributed by Raymond Hettinger.)

Some new functions in the module include
@code{isgenerator()}, @code{isgeneratorfunction()},
and @code{isabstract()}.

@item 
The @ref{a3,,itertools} module gained several new functions.

@code{izip_longest(iter1, iter2, ...[, fillvalue])} makes tuples from
each of the elements; if some of the iterables are shorter than
others, the missing values are set to @emph{fillvalue}.  For example:

@example
>>> tuple(itertools.izip_longest([1,2,3], [1,2,3,4,5]))
((1, 1), (2, 2), (3, 3), (None, 4), (None, 5))
@end example

@code{product(iter1, iter2, ..., [repeat=N])} returns the Cartesian product
of the supplied iterables, a set of tuples containing
every possible combination of the elements returned from each iterable.

@example
>>> list(itertools.product([1,2,3], [4,5,6]))
[(1, 4), (1, 5), (1, 6),
 (2, 4), (2, 5), (2, 6),
 (3, 4), (3, 5), (3, 6)]
@end example

The optional @emph{repeat} keyword argument is used for taking the
product of an iterable or a set of iterables with themselves,
repeated @emph{N} times.  With a single iterable argument, @emph{N}-tuples
are returned:

@example
>>> list(itertools.product([1,2], repeat=3))
[(1, 1, 1), (1, 1, 2), (1, 2, 1), (1, 2, 2),
 (2, 1, 1), (2, 1, 2), (2, 2, 1), (2, 2, 2)]
@end example

With two iterables, @emph{2N}-tuples are returned.

@example
>>> list(itertools.product([1,2], [3,4], repeat=2))
[(1, 3, 1, 3), (1, 3, 1, 4), (1, 3, 2, 3), (1, 3, 2, 4),
 (1, 4, 1, 3), (1, 4, 1, 4), (1, 4, 2, 3), (1, 4, 2, 4),
 (2, 3, 1, 3), (2, 3, 1, 4), (2, 3, 2, 3), (2, 3, 2, 4),
 (2, 4, 1, 3), (2, 4, 1, 4), (2, 4, 2, 3), (2, 4, 2, 4)]
@end example

@code{combinations(iterable, r)} returns sub-sequences of length @emph{r} from
the elements of @emph{iterable}.

@example
>>> list(itertools.combinations('123', 2))
[('1', '2'), ('1', '3'), ('2', '3')]
>>> list(itertools.combinations('123', 3))
[('1', '2', '3')]
>>> list(itertools.combinations('1234', 3))
[('1', '2', '3'), ('1', '2', '4'),
 ('1', '3', '4'), ('2', '3', '4')]
@end example

@code{permutations(iter[, r])} returns all the permutations of length @emph{r} of
the iterable's elements.  If @emph{r} is not specified, it will default to the
number of elements produced by the iterable.

@example
>>> list(itertools.permutations([1,2,3,4], 2))
[(1, 2), (1, 3), (1, 4),
 (2, 1), (2, 3), (2, 4),
 (3, 1), (3, 2), (3, 4),
 (4, 1), (4, 2), (4, 3)]
@end example

@code{itertools.chain(*iterables)} is an existing function in
@ref{a3,,itertools} that gained a new constructor in Python 2.6.
@code{itertools.chain.from_iterable(iterable)} takes a single
iterable that should return other iterables.  @code{chain()} will
then return all the elements of the first iterable, then
all the elements of the second, and so on.

@example
>>> list(itertools.chain.from_iterable([[1,2,3], [4,5,6]]))
[1, 2, 3, 4, 5, 6]
@end example

(All contributed by Raymond Hettinger.)

@item 
The @ref{aa,,logging} module's @code{FileHandler} class
and its subclasses @code{WatchedFileHandler}, @code{RotatingFileHandler},
and @code{TimedRotatingFileHandler} now
have an optional @emph{delay} parameter to their constructors.  If @emph{delay}
is true, opening of the log file is deferred until the first
@code{emit()} call is made.  (Contributed by Vinay Sajip.)

@code{TimedRotatingFileHandler} also has a @emph{utc} constructor
parameter.  If the argument is true, UTC time will be used
in determining when midnight occurs and in generating filenames;
otherwise local time will be used.

@item 
Several new functions were added to the @ref{b1,,math} module:


@itemize *

@item 
@ref{d34,,isinf()} and @ref{d35,,isnan()} determine whether a given float
is a (positive or negative) infinity or a NaN (Not a Number), respectively.

@item 
@ref{d36,,copysign()} copies the sign bit of an IEEE 754 number,
returning the absolute value of @emph{x} combined with the sign bit of
@emph{y}.  For example, @code{math.copysign(1, -0.0)} returns -1.0.
(Contributed by Christian Heimes.)

@item 
@ref{1ea,,factorial()} computes the factorial of a number.
(Contributed by Raymond Hettinger; bpo-2138@footnote{https://bugs.python.org/issue2138}.)

@item 
@ref{d37,,fsum()} adds up the stream of numbers from an iterable,
and is careful to avoid loss of precision through using partial sums.
(Contributed by Jean Brouwers, Raymond Hettinger, and Mark Dickinson;
bpo-2819@footnote{https://bugs.python.org/issue2819}.)

@item 
@ref{d38,,acosh()}, @ref{d39,,asinh()}
and @ref{d3a,,atanh()} compute the inverse hyperbolic functions.

@item 
@ref{d3b,,log1p()} returns the natural logarithm of @emph{1+x}
(base @emph{e}).

@item 
@code{trunc()} rounds a number toward zero, returning the closest
@code{Integral} that's between the function's argument and zero.
Added as part of the backport of
@ref{c50,,PEP 3141's type hierarchy for numbers}.
@end itemize

@item 
The @ref{b1,,math} module has been improved to give more consistent
behaviour across platforms, especially with respect to handling of
floating-point exceptions and IEEE 754 special values.

Whenever possible, the module follows the recommendations of the C99
standard about 754's special values.  For example, @code{sqrt(-1.)}
should now give a @ref{1fb,,ValueError} across almost all platforms,
while @code{sqrt(float('NaN'))} should return a NaN on all IEEE 754
platforms.  Where Annex 'F' of the C99 standard recommends signaling
'divide-by-zero' or 'invalid', Python will raise @ref{1fb,,ValueError}.
Where Annex 'F' of the C99 standard recommends signaling 'overflow',
Python will raise @ref{95a,,OverflowError}.  (See bpo-711019@footnote{https://bugs.python.org/issue711019} and
bpo-1640@footnote{https://bugs.python.org/issue1640}.)

（由 Christian Heimes 和 Mark Dickinson 贡献。）

@item 
@ref{1ec,,mmap} objects now have a @code{rfind()} method that searches for a
substring beginning at the end of the string and searching
backwards.  The @code{find()} method also gained an @emph{end} parameter
giving an index at which to stop searching.
(Contributed by John Lenton.)

@item 
The @ref{c2,,operator} module gained a
@code{methodcaller()} function that takes a name and an optional
set of arguments, returning a callable that will call
the named function on any arguments passed to it.  For example:

@example
>>> # Equivalent to lambda s: s.replace('old', 'new')
>>> replacer = operator.methodcaller('replace', 'old', 'new')
>>> replacer('old wine in old bottles')
'new wine in new bottles'
@end example

（由 Gregory Petrosyan 提供建议，之后由 Georg Brandl 贡献。）

The @code{attrgetter()} function now accepts dotted names and performs
the corresponding attribute lookups:

@example
>>> inst_name = operator.attrgetter(
...        '__class__.__name__')
>>> inst_name('@w{'})
'str'
>>> inst_name(help)
'_Helper'
@end example

（由 Barry Warsaw 提供建议，之后由 Georg Brandl 贡献。）

@item 
The @ref{c4,,os} module now wraps several new system calls.
@code{fchmod(fd, mode)} and @code{fchown(fd, uid, gid)} change the mode
and ownership of an opened file, and @code{lchmod(path, mode)} changes
the mode of a symlink.  (Contributed by Georg Brandl and Christian
Heimes.)

@code{chflags()} and @code{lchflags()} are wrappers for the
corresponding system calls (where they're available), changing the
flags set on a file.  Constants for the flag values are defined in
the @ref{f4,,stat} module; some possible values include
@code{UF_IMMUTABLE} to signal the file may not be changed and
@code{UF_APPEND} to indicate that data can only be appended to the
file.  (Contributed by M. Levinson.)

@code{os.closerange(low, high)} efficiently closes all file descriptors
from @emph{low} to @emph{high}, ignoring any errors and not including @emph{high} itself.
This function is now used by the @ref{f9,,subprocess} module to make starting
processes faster.  (Contributed by Georg Brandl; bpo-1663329@footnote{https://bugs.python.org/issue1663329}.)

@item 
The @code{os.environ} object's @code{clear()} method will now unset the
environment variables using @ref{d3c,,os.unsetenv()} in addition to clearing
the object's keys.  (Contributed by Martin Horcicka; bpo-1181@footnote{https://bugs.python.org/issue1181}.)

@item 
The @ref{64e,,os.walk()} function now has a @code{followlinks} parameter. If
set to True, it will follow symlinks pointing to directories and
visit the directory's contents.  For backward compatibility, the
parameter's default value is false.  Note that the function can fall
into an infinite recursion if there's a symlink that points to a
parent directory.  (bpo-1273829@footnote{https://bugs.python.org/issue1273829})

@item 
In the @ref{c5,,os.path} module, the @code{splitext()} function
has been changed to not split on leading period characters.
This produces better results when operating on Unix's dot-files.
For example, @code{os.path.splitext('.ipython')}
now returns @code{('.ipython', '@w{'})} instead of @code{('@w{'}, '.ipython')}.
(bpo-1115886@footnote{https://bugs.python.org/issue1115886})

A new function, @code{os.path.relpath(path, start='.')}, returns a relative path
from the @code{start} path, if it's supplied, or from the current
working directory to the destination @code{path}.  (Contributed by
Richard Barran; bpo-1339796@footnote{https://bugs.python.org/issue1339796}.)

On Windows, @ref{d3d,,os.path.expandvars()} will now expand environment variables
given in the form "%var%", and "~user" will be expanded into the
user's home directory path.  (Contributed by Josiah Carlson;
bpo-957650@footnote{https://bugs.python.org/issue957650}.)

@item 
The Python debugger provided by the @ref{c9,,pdb} module
gained a new command: "run" restarts the Python program being debugged
and can optionally take new command-line arguments for the program.
(Contributed by Rocky Bernstein; bpo-1393667@footnote{https://bugs.python.org/issue1393667}.)

@item 
The @ref{d3e,,pdb.post_mortem()} function, used to begin debugging a
traceback, will now use the traceback returned by @ref{c58,,sys.exc_info()}
if no traceback is supplied.   (Contributed by Facundo Batista;
bpo-1106316@footnote{https://bugs.python.org/issue1106316}.)

@item 
The @ref{cb,,pickletools} module now has an @code{optimize()} function
that takes a string containing a pickle and removes some unused
opcodes, returning a shorter pickle that contains the same data structure.
(Contributed by Raymond Hettinger.)

@item 
A @code{get_data()} function was added to the @ref{cd,,pkgutil}
module that returns the contents of resource files included
with an installed Python package.  For example:

@example
>>> import pkgutil
>>> print pkgutil.get_data('test', 'exception_hierarchy.txt')
BaseException
 +-- SystemExit
 +-- KeyboardInterrupt
 +-- GeneratorExit
 +-- Exception
      +-- StopIteration
      +-- StandardError
 ...
@end example

（由 Paul Moore 在 bpo-2439@footnote{https://bugs.python.org/issue2439} 中贡献。）

@item 
The @code{pyexpat} module's @code{Parser} objects now allow setting
their @code{buffer_size} attribute to change the size of the buffer
used to hold character data.
(Contributed by Achim Gaedke; bpo-1137@footnote{https://bugs.python.org/issue1137}.)

@item 
The @code{Queue} module now provides queue variants that retrieve entries
in different orders.  The @code{PriorityQueue} class stores
queued items in a heap and retrieves them in priority order,
and @code{LifoQueue} retrieves the most recently added entries first,
meaning that it behaves like a stack.
(Contributed by Raymond Hettinger.)

@item 
The @ref{dc,,random} module's @code{Random} objects can
now be pickled on a 32-bit system and unpickled on a 64-bit
system, and vice versa.  Unfortunately, this change also means
that Python 2.6's @code{Random} objects can't be unpickled correctly
on earlier versions of Python.
(Contributed by Shawn Ligocki; bpo-1727780@footnote{https://bugs.python.org/issue1727780}.)

The new @code{triangular(low, high, mode)} function returns random
numbers following a triangular distribution.   The returned values
are between @emph{low} and @emph{high}, not including @emph{high} itself, and
with @emph{mode} as the most frequently occurring value
in the distribution.  (Contributed by Wladmir van der Laan and
Raymond Hettinger; bpo-1681432@footnote{https://bugs.python.org/issue1681432}.)

@item 
Long regular expression searches carried out by the  @ref{dd,,re}
module will check for signals being delivered, so
time-consuming searches can now be interrupted.
(Contributed by Josh Hoyt and Ralf Schmitt; bpo-846388@footnote{https://bugs.python.org/issue846388}.)

The regular expression module is implemented by compiling bytecodes
for a tiny regex-specific virtual machine.  Untrusted code
could create malicious strings of bytecode directly and cause crashes,
so Python 2.6 includes a verifier for the regex bytecode.
(Contributed by Guido van Rossum from work for Google App Engine;
bpo-3487@footnote{https://bugs.python.org/issue3487}.)

@item 
The @ref{e1,,rlcompleter} module's @code{Completer.complete()} method
will now ignore exceptions triggered while evaluating a name.
(Fixed by Lorenz Quack; bpo-2250@footnote{https://bugs.python.org/issue2250}.)

@item 
The @ref{e3,,sched} module's @code{scheduler} instances now
have a read-only @ref{da,,queue} attribute that returns the
contents of the scheduler's queue, represented as a list of
named tuples with the fields @code{(time, priority, action, argument)}.
(Contributed by Raymond Hettinger; bpo-1861@footnote{https://bugs.python.org/issue1861}.)

@item 
The @ref{e5,,select} module now has wrapper functions
for the Linux @code{epoll()} and BSD @code{kqueue()} system calls.
@code{modify()} method was added to the existing @code{poll}
objects; @code{pollobj.modify(fd, eventmask)} takes a file descriptor
or file object and an event mask, modifying the recorded event mask
for that file.
(Contributed by Christian Heimes; bpo-1657@footnote{https://bugs.python.org/issue1657}.)

@item 
The @ref{21a,,shutil.copytree()} function now has an optional @emph{ignore} argument
that takes a callable object.  This callable will receive each directory path
and a list of the directory's contents, and returns a list of names that
will be ignored, not copied.

The @ref{e9,,shutil} module also provides an @code{ignore_patterns()}
function for use with this new parameter.  @code{ignore_patterns()}
takes an arbitrary number of glob-style patterns and returns a
callable that will ignore any files and directories that match any
of these patterns.  The following example copies a directory tree,
but skips both @code{.svn} directories and Emacs backup files,
which have names ending with '~':

@example
shutil.copytree('Doc/library', '/tmp/library',
                ignore=shutil.ignore_patterns('*~', '.svn'))
@end example

（由 Tarek Ziadé 在 bpo-2663@footnote{https://bugs.python.org/issue2663} 中贡献。）

@item 
Integrating signal handling with GUI handling event loops
like those used by Tkinter or GTk+ has long been a problem; most
software ends up polling, waking up every fraction of a second to check
if any GUI events have occurred.
The @ref{ea,,signal} module can now make this more efficient.
Calling @code{signal.set_wakeup_fd(fd)} sets a file descriptor
to be used; when a signal is received, a byte is written to that
file descriptor.  There's also a C-level function,
@ref{d3f,,PySignal_SetWakeupFd()}, for setting the descriptor.

Event loops will use this by opening a pipe to create two descriptors,
one for reading and one for writing.  The writable descriptor
will be passed to @code{set_wakeup_fd()}, and the readable descriptor
will be added to the list of descriptors monitored by the event loop via
@code{select()} or @code{poll()}.
On receiving a signal, a byte will be written and the main event loop
will be woken up, avoiding the need to poll.

（由 Adam Olsen 在 bpo-1583@footnote{https://bugs.python.org/issue1583} 中贡献。）

The @code{siginterrupt()} function is now available from Python code,
and allows changing whether signals can interrupt system calls or not.
(Contributed by Ralf Schmitt.)

The @code{setitimer()} and @code{getitimer()} functions have also been
added (where they're available).  @code{setitimer()}
allows setting interval timers that will cause a signal to be
delivered to the process after a specified time, measured in
wall-clock time, consumed process time, or combined process+system
time.  (Contributed by Guilherme Polo; bpo-2240@footnote{https://bugs.python.org/issue2240}.)

@item 
The @ref{ed,,smtplib} module now supports SMTP over SSL thanks to the
addition of the @code{SMTP_SSL} class. This class supports an
interface identical to the existing @code{SMTP} class.
(Contributed by Monty Taylor.)  Both class constructors also have an
optional @code{timeout} parameter that specifies a timeout for the
initial connection attempt, measured in seconds.  (Contributed by
Facundo Batista.)

An implementation of the LMTP protocol (
@geindex RFC; RFC 2033
RFC 2033@footnote{https://tools.ietf.org/html/rfc2033.html}) was also added
to the module.  LMTP is used in place of SMTP when transferring
e-mail between agents that don't manage a mail queue.  (LMTP
implemented by Leif Hedstrom; bpo-957003@footnote{https://bugs.python.org/issue957003}.)

@code{SMTP.starttls()} now complies with 
@geindex RFC; RFC 3207
RFC 3207@footnote{https://tools.ietf.org/html/rfc3207.html} and forgets any
knowledge obtained from the server not obtained from the TLS
negotiation itself.  (Patch contributed by Bill Fenner;
bpo-829951@footnote{https://bugs.python.org/issue829951}.)

@item 
The @ref{ef,,socket} module now supports TIPC (@indicateurl{http://tipc.sourceforge.net/}),
a high-performance non-IP-based protocol designed for use in clustered
environments.  TIPC addresses are 4- or 5-tuples.
(Contributed by Alberto Bertogli; bpo-1646@footnote{https://bugs.python.org/issue1646}.)

A new function, @code{create_connection()}, takes an address and
connects to it using an optional timeout value, returning the
connected socket object.  This function also looks up the address's
type and connects to it using IPv4 or IPv6 as appropriate.  Changing
your code to use @code{create_connection()} instead of
@code{socket(socket.AF_INET, ...)} may be all that's required to make
your code work with IPv6.

@item 
The base classes in the @code{SocketServer} module now support
calling a @code{handle_timeout()} method after a span of inactivity
specified by the server's @code{timeout} attribute.  (Contributed
by Michael Pomraning.)  The @code{serve_forever()} method
now takes an optional poll interval measured in seconds,
controlling how often the server will check for a shutdown request.
(Contributed by Pedro Werneck and Jeffrey Yasskin;
bpo-742598@footnote{https://bugs.python.org/issue742598}, bpo-1193577@footnote{https://bugs.python.org/issue1193577}.)

@item 
The @ref{f2,,sqlite3} module, maintained by Gerhard Häring,
has been updated from version 2.3.2 in Python 2.5 to
version 2.4.1.

@item 
The @ref{f8,,struct} module now supports the C99 @code{_Bool} type,
using the format character @code{'?'}.
(Contributed by David Remahl.)

@item 
The @code{Popen} objects provided by the @ref{f9,,subprocess} module
now have @code{terminate()}, @code{kill()}, and @code{send_signal()} methods.
On Windows, @code{send_signal()} only supports the @code{SIGTERM}
signal, and all these methods are aliases for the Win32 API function
@code{TerminateProcess()}.
(Contributed by Christian Heimes.)

@item 
A new variable in the @ref{fd,,sys} module, @code{float_info}, is an
object containing information derived from the @code{float.h} file
about the platform's floating-point support.  Attributes of this
object include @code{mant_dig} (number of digits in the mantissa),
@code{epsilon} (smallest difference between 1.0 and the next
largest value representable), and several others.  (Contributed by
Christian Heimes; bpo-1534@footnote{https://bugs.python.org/issue1534}.)

Another new variable, @code{dont_write_bytecode}, controls whether Python
writes any @code{.pyc} or @code{.pyo} files on importing a module.
If this variable is true, the compiled files are not written.  The
variable is initially set on start-up by supplying the @ref{d31,,-B}
switch to the Python interpreter, or by setting the
@geindex PYTHONDONTWRITEBYTECODE
@geindex 环境变量; PYTHONDONTWRITEBYTECODE
@ref{d32,,PYTHONDONTWRITEBYTECODE} environment variable before
running the interpreter.  Python code can subsequently
change the value of this variable to control whether bytecode files
are written or not.
(Contributed by Neal Norwitz and Georg Brandl.)

Information about the command-line arguments supplied to the Python
interpreter is available by reading attributes of a named
tuple available as @code{sys.flags}.  For example, the @code{verbose}
attribute is true if Python
was executed in verbose mode, @code{debug} is true in debugging mode, etc.
These attributes are all read-only.
(Contributed by Christian Heimes.)

A new function, @code{getsizeof()}, takes a Python object and returns
the amount of memory used by the object, measured in bytes.  Built-in
objects return correct results; third-party extensions may not,
but can define a @code{__sizeof__()} method to return the
object's size.
(Contributed by Robert Schuppenies; bpo-2898@footnote{https://bugs.python.org/issue2898}.)

It's now possible to determine the current profiler and tracer functions
by calling @ref{d40,,sys.getprofile()} and @ref{d41,,sys.gettrace()}.
(Contributed by Georg Brandl; bpo-1648@footnote{https://bugs.python.org/issue1648}.)

@item 
The @ref{101,,tarfile} module now supports POSIX.1-2001 (pax) tarfiles in
addition to the POSIX.1-1988 (ustar) and GNU tar formats that were
already supported.  The default format is GNU tar; specify the
@code{format} parameter to open a file using a different format:

@example
tar = tarfile.open("output.tar", "w",
                   format=tarfile.PAX_FORMAT)
@end example

The new @code{encoding} and @code{errors} parameters specify an encoding and
an error handling scheme for character conversions.  @code{'strict'},
@code{'ignore'}, and @code{'replace'} are the three standard ways Python can
handle errors,;
@code{'utf-8'} is a special value that replaces bad characters with
their UTF-8 representation.  (Character conversions occur because the
PAX format supports Unicode filenames, defaulting to UTF-8 encoding.)

The @code{TarFile.add()} method now accepts an @code{exclude} argument that's
a function that can be used to exclude certain filenames from
an archive.
The function must take a filename and return true if the file
should be excluded or false if it should be archived.
The function is applied to both the name initially passed to @code{add()}
and to the names of files in recursively-added directories.

(All changes contributed by Lars Gustäbel).

@item 
An optional @code{timeout} parameter was added to the
@ref{592,,telnetlib.Telnet} class constructor, specifying a timeout
measured in seconds.  (Added by Facundo Batista.)

@item 
The @ref{d42,,tempfile.NamedTemporaryFile} class usually deletes
the temporary file it created when the file is closed.  This
behaviour can now be changed by passing @code{delete=False} to the
constructor.  (Contributed by Damien Miller; bpo-1537850@footnote{https://bugs.python.org/issue1537850}.)

A new class, @code{SpooledTemporaryFile}, behaves like
a temporary file but stores its data in memory until a maximum size is
exceeded.  On reaching that limit, the contents will be written to
an on-disk temporary file.  (Contributed by Dustin J. Mitchell.)

The @code{NamedTemporaryFile} and @code{SpooledTemporaryFile} classes
both work as context managers, so you can write
@code{with tempfile.NamedTemporaryFile() as tmp: ...}.
(Contributed by Alexander Belopolsky; bpo-2021@footnote{https://bugs.python.org/issue2021}.)

@item 
The @code{test.test_support} module gained a number
of context managers useful for writing tests.
@code{EnvironmentVarGuard()} is a
context manager that temporarily changes environment variables and
automatically restores them to their old values.

Another context manager, @code{TransientResource}, can surround calls
to resources that may or may not be available; it will catch and
ignore a specified list of exceptions.  For example,
a network test may ignore certain failures when connecting to an
external web site:

@example
with test_support.TransientResource(IOError,
                                errno=errno.ETIMEDOUT):
    f = urllib.urlopen('https://sf.net')
    ...
@end example

Finally, @code{check_warnings()} resets the @code{warning} module's
warning filters and returns an object that will record all warning
messages triggered (bpo-3781@footnote{https://bugs.python.org/issue3781}):

@example
with test_support.check_warnings() as wrec:
    warnings.simplefilter("always")
    # ... code that triggers a warning ...
    assert str(wrec.message) == "function is outdated"
    assert len(wrec.warnings) == 1, "Multiple warnings raised"
@end example

（由 Brett Cannon 贡献。）

@item 
The @ref{108,,textwrap} module can now preserve existing whitespace
at the beginnings and ends of the newly-created lines
by specifying @code{drop_whitespace=False}
as an argument:

@example
>>> S = """This  sentence  has a bunch   of
...   extra   whitespace."""
>>> print textwrap.fill(S, width=15)
This  sentence
has a bunch
of    extra
whitespace.
>>> print textwrap.fill(S, drop_whitespace=False, width=15)
This  sentence
  has a bunch
   of    extra
   whitespace.
>>>
@end example

（由 Dwayne Bailey 在 bpo-1581073@footnote{https://bugs.python.org/issue1581073} 中贡献。）

@item 
The @ref{109,,threading} module API is being changed to use properties
such as @code{daemon} instead of @code{setDaemon()} and
@code{isDaemon()} methods, and some methods have been renamed to use
underscores instead of camel-case; for example, the
@code{activeCount()} method is renamed to @code{active_count()}.  Both
the 2.6 and 3.0 versions of the module support the same properties
and renamed methods, but don't remove the old methods.  No date has been set
for the deprecation of the old APIs in Python 3.x; the old APIs won't
be removed in any 2.x version.
(Carried out by several people, most notably Benjamin Peterson.)

The @ref{109,,threading} module's @code{Thread} objects
gained an @code{ident} property that returns the thread's
identifier, a nonzero integer.  (Contributed by Gregory P. Smith;
bpo-2871@footnote{https://bugs.python.org/issue2871}.)

@item 
The @ref{10b,,timeit} module now accepts callables as well as strings
for the statement being timed and for the setup code.
Two convenience functions were added for creating
@code{Timer} instances:
@code{repeat(stmt, setup, time, repeat, number)} and
@code{timeit(stmt, setup, time, number)} create an instance and call
the corresponding method. (Contributed by Erik Demaine;
bpo-1533909@footnote{https://bugs.python.org/issue1533909}.)

@item 
The @code{Tkinter} module now accepts lists and tuples for options,
separating the elements by spaces before passing the resulting value to
Tcl/Tk.
(Contributed by Guilherme Polo; bpo-2906@footnote{https://bugs.python.org/issue2906}.)

@item 
The @ref{116,,turtle} module for turtle graphics was greatly enhanced by
Gregor Lingl.  New features in the module include:


@itemize *

@item 
Better animation of turtle movement and rotation.

@item 
Control over turtle movement using the new @code{delay()},
@code{tracer()}, and @code{speed()} methods.

@item 
The ability to set new shapes for the turtle, and to
define a new coordinate system.

@item 
Turtles now have an @code{undo()} method that can roll back actions.

@item 
Simple support for reacting to input events such as mouse and keyboard
activity, making it possible to write simple games.

@item 
A @code{turtle.cfg} file can be used to customize the starting appearance
of the turtle's screen.

@item 
The module's docstrings can be replaced by new docstrings that have been
translated into another language.
@end itemize

(bpo-1513695@footnote{https://bugs.python.org/issue1513695})

@item 
An optional @code{timeout} parameter was added to the
@code{urllib.urlopen()} function and the
@code{urllib.ftpwrapper} class constructor, as well as the
@code{urllib2.urlopen()} function.  The parameter specifies a timeout
measured in seconds.   For example:

@example
>>> u = urllib2.urlopen("http://slow.example.com",
                        timeout=3)
Traceback (most recent call last):
  ...
urllib2.URLError: <urlopen error timed out>
>>>
@end example

(Added by Facundo Batista.)

@item 
The Unicode database provided by the @ref{11a,,unicodedata} module
has been updated to version 5.1.0.  (Updated by
Martin von Löwis; bpo-3811@footnote{https://bugs.python.org/issue3811}.)

@item 
The @ref{126,,warnings} module's @code{formatwarning()} and @code{showwarning()}
gained an optional @emph{line} argument that can be used to supply the
line of source code.  (Added as part of bpo-1631171@footnote{https://bugs.python.org/issue1631171}, which re-implemented
part of the @ref{126,,warnings} module in C code.)

A new function, @code{catch_warnings()}, is a context manager
intended for testing purposes that lets you temporarily modify the
warning filters and then restore their original values (bpo-3781@footnote{https://bugs.python.org/issue3781}).

@item 
The XML-RPC @code{SimpleXMLRPCServer} and @code{DocXMLRPCServer}
classes can now be prevented from immediately opening and binding to
their socket by passing @code{False} as the @emph{bind_and_activate}
constructor parameter.  This can be used to modify the instance's
@code{allow_reuse_address} attribute before calling the
@code{server_bind()} and @code{server_activate()} methods to
open the socket and begin listening for connections.
(Contributed by Peter Parente; bpo-1599845@footnote{https://bugs.python.org/issue1599845}.)

@code{SimpleXMLRPCServer} also has a @code{_send_traceback_header}
attribute; if true, the exception and formatted traceback are returned
as HTTP headers "X-Exception" and "X-Traceback".  This feature is
for debugging purposes only and should not be used on production servers
because the tracebacks might reveal passwords or other sensitive
information.  (Contributed by Alan McIntyre as part of his
project for Google's Summer of Code 2007.)

@item 
The @code{xmlrpclib} module no longer automatically converts
@ref{193,,datetime.date} and @ref{4ed,,datetime.time} to the
@code{xmlrpclib.DateTime} type; the conversion semantics were
not necessarily correct for all applications.  Code using
@code{xmlrpclib} should convert @code{date} and @ref{4ed,,time}
instances. (bpo-1330538@footnote{https://bugs.python.org/issue1330538})  The code can also handle
dates before 1900 (contributed by Ralf Schmitt; bpo-2014@footnote{https://bugs.python.org/issue2014})
and 64-bit integers represented by using @code{<i8>} in XML-RPC responses
(contributed by Riku Lindblad; bpo-2985@footnote{https://bugs.python.org/issue2985}).

@item 
The @ref{142,,zipfile} module's @code{ZipFile} class now has
@code{extract()} and @code{extractall()} methods that will unpack
a single file or all the files in the archive to the current directory, or
to a specified directory:

@example
z = zipfile.ZipFile('python-251.zip')

# Unpack a single file, writing it relative
# to the /tmp directory.
z.extract('Python/sysmodule.c', '/tmp')

# Unpack all the files in the archive.
z.extractall()
@end example

（由 Alan McIntyre 在 bpo-467924@footnote{https://bugs.python.org/issue467924} 中贡献。）

The @ref{4ea,,open()}, @code{read()} and @code{extract()} methods can now
take either a filename or a @code{ZipInfo} object.  This is useful when an
archive accidentally contains a duplicated filename.
(Contributed by Graham Horler; bpo-1775025@footnote{https://bugs.python.org/issue1775025}.)

Finally, @ref{142,,zipfile} now supports using Unicode filenames
for archived files.  (Contributed by Alexey Borzenkov; bpo-1734346@footnote{https://bugs.python.org/issue1734346}.)
@end itemize

@c ======================================================================

@c whole new modules get described in subsections here

@menu
* ast 模块:: 
* future_builtins 模块:: 
* The json module; JavaScript Object Notation: The json module JavaScript Object Notation. 
* plistlib 模块：属性列表解析器:: 
* ctypes Enhancements:: 
* Improved SSL Support:: 

@end menu

@node ast 模块,future_builtins 模块,,新增和改进的模块<2>
@anchor{whatsnew/2 6 the-ast-module}@anchor{d43}
@subsubsection @code{ast} 模块


The @ref{8,,ast} module provides an Abstract Syntax Tree
representation of Python code, and Armin Ronacher
contributed a set of helper functions that perform a variety of
common tasks.  These will be useful for HTML templating
packages, code analyzers, and similar tools that process
Python code.

The @code{parse()} function takes an expression and returns an AST.
The @code{dump()} function outputs a representation of a tree, suitable
for debugging:

@example
import ast

t = ast.parse("""
d = @{@}
for i in 'abcdefghijklm':
    d[i + i] = ord(i) - ord('a') + 1
print d
""")
print ast.dump(t)
@end example

This outputs a deeply nested tree:

@example
Module(body=[
  Assign(targets=[
    Name(id='d', ctx=Store())
   ], value=Dict(keys=[], values=[]))
  For(target=Name(id='i', ctx=Store()),
      iter=Str(s='abcdefghijklm'), body=[
    Assign(targets=[
      Subscript(value=
        Name(id='d', ctx=Load()),
          slice=
          Index(value=
            BinOp(left=Name(id='i', ctx=Load()), op=Add(),
             right=Name(id='i', ctx=Load()))), ctx=Store())
     ], value=
     BinOp(left=
      BinOp(left=
       Call(func=
        Name(id='ord', ctx=Load()), args=[
          Name(id='i', ctx=Load())
         ], keywords=[], starargs=None, kwargs=None),
       op=Sub(), right=Call(func=
        Name(id='ord', ctx=Load()), args=[
          Str(s='a')
         ], keywords=[], starargs=None, kwargs=None)),
       op=Add(), right=Num(n=1)))
    ], orelse=[])
   Print(dest=None, values=[
     Name(id='d', ctx=Load())
   ], nl=True)
 ])
@end example

The @code{literal_eval()} method takes a string or an AST
representing a literal expression, parses and evaluates it, and
returns the resulting value.  A literal expression is a Python
expression containing only strings, numbers, dictionaries,
etc. but no statements or function calls.  If you need to
evaluate an expression but cannot accept the security risk of using an
@ref{b89,,eval()} call, @code{literal_eval()} will handle it safely:

@example
>>> literal = '("a", "b", @{2:4, 3:8, 1:2@})'
>>> print ast.literal_eval(literal)
('a', 'b', @{1: 2, 2: 4, 3: 8@})
>>> print ast.literal_eval('"a" + "b"')
Traceback (most recent call last):
  ...
ValueError: malformed string
@end example

The module also includes @code{NodeVisitor} and
@code{NodeTransformer} classes for traversing and modifying an AST,
and functions for common transformations such as changing line
numbers.

@c ======================================================================

@node future_builtins 模块,The json module JavaScript Object Notation,ast 模块,新增和改进的模块<2>
@anchor{whatsnew/2 6 the-future-builtins-module}@anchor{d44}
@subsubsection @code{future_builtins} 模块


Python 3.0 makes many changes to the repertoire of built-in
functions, and most of the changes can't be introduced in the Python
2.x series because they would break compatibility.
The @code{future_builtins} module provides versions
of these built-in functions that can be imported when writing
3.0-compatible code.

The functions in this module currently include:


@itemize *

@item 
@code{ascii(obj)}: equivalent to @ref{7c6,,repr()}.  In Python 3.0,
@ref{7c6,,repr()} will return a Unicode string, while @ref{d45,,ascii()} will
return a pure ASCII bytestring.

@item 
@code{filter(predicate, iterable)},
@code{map(func, iterable1, ...)}: the 3.0 versions
return iterators, unlike the 2.x builtins which return lists.

@item 
@code{hex(value)}, @code{oct(value)}: instead of calling the
@code{__hex__()} or @code{__oct__()} methods, these versions will
call the @ref{18a,,__index__()} method and convert the result to hexadecimal
or octal.  @ref{c5e,,oct()} will use the new @code{0o} notation for its
result.
@end itemize

@c ======================================================================

@node The json module JavaScript Object Notation,plistlib 模块：属性列表解析器,future_builtins 模块,新增和改进的模块<2>
@anchor{whatsnew/2 6 the-json-module-javascript-object-notation}@anchor{d46}
@subsubsection The @code{json} module: JavaScript Object Notation


The new @ref{a4,,json} module supports the encoding and decoding of Python types in
JSON (Javascript Object Notation). JSON is a lightweight interchange format
often used in web applications. For more information about JSON, see
@indicateurl{http://www.json.org}.

@ref{a4,,json} comes with support for decoding and encoding most built-in Python
types. The following example encodes and decodes a dictionary:

@example
>>> import json
>>> data = @{"spam": "foo", "parrot": 42@}
>>> in_json = json.dumps(data) # Encode the data
>>> in_json
'@{"parrot": 42, "spam": "foo"@}'
>>> json.loads(in_json) # Decode into a Python object
@{"spam": "foo", "parrot": 42@}
@end example

It's also possible to write your own decoders and encoders to support
more types. Pretty-printing of the JSON strings is also supported.

@ref{a4,,json} (originally called simplejson) was written by Bob
Ippolito.

@c ======================================================================

@node plistlib 模块：属性列表解析器,ctypes Enhancements,The json module JavaScript Object Notation,新增和改进的模块<2>
@anchor{whatsnew/2 6 the-plistlib-module-a-property-list-parser}@anchor{d47}
@subsubsection @code{plistlib} 模块：属性列表解析器


The @code{.plist} format is commonly used on Mac OS X to
store basic data types (numbers, strings, lists,
and dictionaries) by serializing them into an XML-based format.
It resembles the XML-RPC serialization of data types.

Despite being primarily used on Mac OS X, the format
has nothing Mac-specific about it and the Python implementation works
on any platform that Python supports, so the @ref{cf,,plistlib} module
has been promoted to the standard library.

Using the module is simple:

@example
import sys
import plistlib
import datetime

# Create data structure
data_struct = dict(lastAccessed=datetime.datetime.now(),
                   version=1,
                   categories=('Personal','Shared','Private'))

# Create string containing XML.
plist_str = plistlib.writePlistToString(data_struct)
new_struct = plistlib.readPlistFromString(plist_str)
print data_struct
print new_struct

# Write data structure to a file and read it back.
plistlib.writePlist(data_struct, '/tmp/customizations.plist')
new_struct = plistlib.readPlist('/tmp/customizations.plist')

# read/writePlist accepts file-like objects as well as paths.
plistlib.writePlist(data_struct, sys.stdout)
@end example

@c ======================================================================

@node ctypes Enhancements,Improved SSL Support,plistlib 模块：属性列表解析器,新增和改进的模块<2>
@anchor{whatsnew/2 6 ctypes-enhancements}@anchor{d48}
@subsubsection ctypes Enhancements


Thomas Heller continued to maintain and enhance the
@ref{2b,,ctypes} module.

@ref{2b,,ctypes} now supports a @code{c_bool} datatype
that represents the C99 @code{bool} type.  (Contributed by David Remahl;
bpo-1649190@footnote{https://bugs.python.org/issue1649190}.)

The @ref{2b,,ctypes} string, buffer and array types have improved
support for extended slicing syntax,
where various combinations of @code{(start, stop, step)} are supplied.
(Implemented by Thomas Wouters.)

@c Revision 57769

All @ref{2b,,ctypes} data types now support
@code{from_buffer()} and @code{from_buffer_copy()}
methods that create a ctypes instance based on a
provided buffer object.  @code{from_buffer_copy()} copies
the contents of the object,
while @code{from_buffer()} will share the same memory area.

A new calling convention tells @ref{2b,,ctypes} to clear the @code{errno} or
Win32 LastError variables at the outset of each wrapped call.
(Implemented by Thomas Heller; bpo-1798@footnote{https://bugs.python.org/issue1798}.)

You can now retrieve the Unix @code{errno} variable after a function
call.  When creating a wrapped function, you can supply
@code{use_errno=True} as a keyword parameter to the @code{DLL()} function
and then call the module-level methods @code{set_errno()} and
@code{get_errno()} to set and retrieve the error value.

The Win32 LastError variable is similarly supported by
the @code{DLL()}, @code{OleDLL()}, and @code{WinDLL()} functions.
You supply @code{use_last_error=True} as a keyword parameter
and then call the module-level methods @code{set_last_error()}
and @code{get_last_error()}.

The @code{byref()} function, used to retrieve a pointer to a ctypes
instance, now has an optional @emph{offset} parameter that is a byte
count that will be added to the returned pointer.

@c ======================================================================

@node Improved SSL Support,,ctypes Enhancements,新增和改进的模块<2>
@anchor{whatsnew/2 6 improved-ssl-support}@anchor{d49}
@subsubsection Improved SSL Support


Bill Janssen made extensive improvements to Python 2.6's support for
the Secure Sockets Layer by adding a new module, @ref{f3,,ssl}, that's
built atop the OpenSSL@footnote{https://www.openssl.org/} library.
This new module provides more control over the protocol negotiated,
the X.509 certificates used, and has better support for writing SSL
servers (as opposed to clients) in Python.  The existing SSL support
in the @ref{ef,,socket} module hasn't been removed and continues to work,
though it will be removed in Python 3.0.

To use the new module, you must first create a TCP connection in the
usual way and then pass it to the @ref{469,,ssl.wrap_socket()} function.
It's possible to specify whether a certificate is required, and to
obtain certificate info by calling the @code{getpeercert()} method.


@subsubheading 参见


@ref{f3,,ssl} 模块的文档。


@c ======================================================================

@node Deprecations and Removals,构建和 C API 的改变<9>,新增和改进的模块<2>,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 deprecations-and-removals}@anchor{d4a}
@subsection Deprecations and Removals



@itemize *

@item 
String exceptions have been removed.  Attempting to use them raises a
@ref{192,,TypeError}.

@item 
Changes to the @ref{1a9,,Exception} interface
as dictated by 
@geindex Python 提高建议; PEP 352
PEP 352@footnote{https://www.python.org/dev/peps/pep-0352} continue to be made.  For 2.6,
the @code{message} attribute is being deprecated in favor of the
@code{args} attribute.

@item 
(3.0-warning mode) Python 3.0 will feature a reorganized standard
library that will drop many outdated modules and rename others.
Python 2.6 running in 3.0-warning mode will warn about these modules
when they are imported.

The list of deprecated modules is:
@code{audiodev},
@code{bgenlocations},
@code{buildtools},
@code{bundlebuilder},
@code{Canvas},
@code{compiler},
@code{dircache},
@code{dl},
@code{fpformat},
@code{gensuitemodule},
@code{ihooks},
@code{imageop},
@code{imgfile},
@code{linuxaudiodev},
@code{mhlib},
@code{mimetools},
@code{multifile},
@code{new},
@code{pure},
@code{statvfs},
@code{sunaudiodev},
@code{test.testall}, and
@code{toaiff}.

@item 
@code{gopherlib} 模块已被移除。

@item 
The @code{MimeWriter} module and @code{mimify} module
have been deprecated; use the @ref{69,,email}
package instead.

@item 
The @code{md5} module has been deprecated; use the @ref{8d,,hashlib} module
instead.

@item 
The @code{posixfile} module has been deprecated; @ref{d4b,,fcntl.lockf()}
provides better locking.

@item 
The @code{popen2} module has been deprecated; use the @ref{f9,,subprocess}
module.

@item 
@code{rgbimg} 模块已被移除。

@item 
The @code{sets} module has been deprecated; it's better to
use the built-in @ref{b68,,set} and @ref{be7,,frozenset} types.

@item 
The @code{sha} module has been deprecated; use the @ref{8d,,hashlib} module
instead.
@end itemize

@c ======================================================================

@node 构建和 C API 的改变<9>,移植到Python 2 6,Deprecations and Removals,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 build-and-c-api-changes}@anchor{d4c}
@subsection 构建和 C API 的改变


Changes to Python's build process and to the C API include:


@itemize *

@item 
Python now must be compiled with C89 compilers (after 19
years!).  This means that the Python source tree has dropped its
own implementations of @code{memmove()} and @code{strerror()}, which
are in the C89 standard library.

@item 
Python 2.6 can be built with Microsoft Visual Studio 2008 (version
9.0), and this is the new default compiler.  See the
@code{PCbuild} directory for the build files.  (Implemented by
Christian Heimes.)

@item 
On Mac OS X, Python 2.6 can be compiled as a 4-way universal build.
The @code{configure} script
can take a @code{--with-universal-archs=[32-bit|64-bit|all]}
switch, controlling whether the binaries are built for 32-bit
architectures (x86, PowerPC), 64-bit (x86-64 and PPC-64), or both.
(Contributed by Ronald Oussoren.)

@item 
The BerkeleyDB module now has a C API object, available as
@code{bsddb.db.api}.   This object can be used by other C extensions
that wish to use the @code{bsddb} module for their own purposes.
(Contributed by Duncan Grisby.)

@item 
The new buffer interface, previously described in
@ref{d1d,,the PEP 3118 section},
adds @ref{d1e,,PyObject_GetBuffer()} and @ref{d4d,,PyBuffer_Release()},
as well as a few other functions.

@item 
Python's use of the C stdio library is now thread-safe, or at least
as thread-safe as the underlying library is.  A long-standing potential
bug occurred if one thread closed a file object while another thread
was reading from or writing to the object.  In 2.6 file objects
have a reference count, manipulated by the
@code{PyFile_IncUseCount()} and @code{PyFile_DecUseCount()}
functions.  File objects can't be closed unless the reference count
is zero.  @code{PyFile_IncUseCount()} should be called while the GIL
is still held, before carrying out an I/O operation using the
@code{FILE *} pointer, and @code{PyFile_DecUseCount()} should be called
immediately after the GIL is re-acquired.
(Contributed by Antoine Pitrou and Gregory P. Smith.)

@item 
Importing modules simultaneously in two different threads no longer
deadlocks; it will now raise an @ref{32d,,ImportError}.  A new API
function, @ref{9bb,,PyImport_ImportModuleNoBlock()}, will look for a
module in @code{sys.modules} first, then try to import it after
acquiring an import lock.  If the import lock is held by another
thread, an @ref{32d,,ImportError} is raised.
(Contributed by Christian Heimes.)

@item 
Several functions return information about the platform's
floating-point support.  @ref{d4e,,PyFloat_GetMax()} returns
the maximum representable floating point value,
and @ref{d4f,,PyFloat_GetMin()} returns the minimum
positive value.  @ref{d50,,PyFloat_GetInfo()} returns an object
containing more information from the @code{float.h} file, such as
@code{"mant_dig"} (number of digits in the mantissa), @code{"epsilon"}
(smallest difference between 1.0 and the next largest value
representable), and several others.
(Contributed by Christian Heimes; bpo-1534@footnote{https://bugs.python.org/issue1534}.)

@item 
C functions and methods that use
@ref{d51,,PyComplex_AsCComplex()} will now accept arguments that
have a @ref{18d,,__complex__()} method.  In particular, the functions in the
@ref{19,,cmath} module will now accept objects with this method.
This is a backport of a Python 3.0 change.
(Contributed by Mark Dickinson; bpo-1675423@footnote{https://bugs.python.org/issue1675423}.)

@item 
Python's C API now includes two functions for case-insensitive string
comparisons, @code{PyOS_stricmp(char*, char*)}
and @code{PyOS_strnicmp(char*, char*, Py_ssize_t)}.
(Contributed by Christian Heimes; bpo-1635@footnote{https://bugs.python.org/issue1635}.)

@item 
Many C extensions define their own little macro for adding
integers and strings to the module's dictionary in the
@code{init*} function.  Python 2.6 finally defines standard macros
for adding values to a module, @ref{d52,,PyModule_AddStringMacro}
and @code{PyModule_AddIntMacro()}.  (Contributed by
Christian Heimes.)

@item 
Some macros were renamed in both 3.0 and 2.6 to make it clearer that
they are macros,
not functions.  @code{Py_Size()} became @code{Py_SIZE()},
@code{Py_Type()} became @code{Py_TYPE()}, and
@code{Py_Refcnt()} became @code{Py_REFCNT()}.
The mixed-case macros are still available
in Python 2.6 for backward compatibility.
(bpo-1629@footnote{https://bugs.python.org/issue1629})

@item 
Distutils now places C extensions it builds in a
different directory when running on a debug version of Python.
(Contributed by Collin Winter; bpo-1530959@footnote{https://bugs.python.org/issue1530959}.)

@item 
Several basic data types, such as integers and strings, maintain
internal free lists of objects that can be re-used.  The data
structures for these free lists now follow a naming convention: the
variable is always named @code{free_list}, the counter is always named
@code{numfree}, and a macro @code{Py<typename>_MAXFREELIST} is
always defined.

@item 
A new Makefile target, "make patchcheck", prepares the Python source tree
for making a patch: it fixes trailing whitespace in all modified
@code{.py} files, checks whether the documentation has been changed,
and reports whether the @code{Misc/ACKS} and @code{Misc/NEWS} files
have been updated.
(Contributed by Brett Cannon.)

Another new target, "make profile-opt", compiles a Python binary
using GCC's profile-guided optimization.  It compiles Python with
profiling enabled, runs the test suite to obtain a set of profiling
results, and then compiles using these results for optimization.
(Contributed by Gregory P. Smith.)
@end itemize

@c ======================================================================

@menu
* 特定于 Windows 的更改：: 特定于 Windows 的更改：<2>. 
* 特定于 Mac OS X 的更改：: 特定于 Mac OS X 的更改：<2>. 
* 特定于 IRIX 的更改：:: 

@end menu

@node 特定于 Windows 的更改：<2>,特定于 Mac OS X 的更改：<2>,,构建和 C API 的改变<9>
@anchor{whatsnew/2 6 port-specific-changes-windows}@anchor{d53}
@subsubsection 特定于 Windows 的更改：



@itemize *

@item 
The support for Windows 95, 98, ME and NT4 has been dropped.
Python 2.6 requires at least Windows 2000 SP4.

@item 
The new default compiler on Windows is Visual Studio 2008 (version
9.0). The build directories for Visual Studio 2003 (version 7.1) and
2005 (version 8.0) were moved into the PC/ directory. The new
@code{PCbuild} directory supports cross compilation for X64, debug
builds and Profile Guided Optimization (PGO). PGO builds are roughly
10% faster than normal builds.  (Contributed by Christian Heimes
with help from Amaury Forgeot d'Arc and Martin von Löwis.)

@item 
The @ref{b6,,msvcrt} module now supports
both the normal and wide char variants of the console I/O
API.  The @code{getwch()} function reads a keypress and returns a Unicode
value, as does the @code{getwche()} function.  The @code{putwch()} function
takes a Unicode character and writes it to the console.
(Contributed by Christian Heimes.)

@item 
@ref{d3d,,os.path.expandvars()} will now expand environment variables in
the form "%var%", and "~user" will be expanded into the user's home
directory path.  (Contributed by Josiah Carlson; bpo-957650@footnote{https://bugs.python.org/issue957650}.)

@item 
The @ref{ef,,socket} module's socket objects now have an
@code{ioctl()} method that provides a limited interface to the
@code{WSAIoctl()} system interface.

@item 
The @code{_winreg} module now has a function,
@code{ExpandEnvironmentStrings()},
that expands environment variable references such as @code{%NAME%}
in an input string.  The handle objects provided by this
module now support the context protocol, so they can be used
in @ref{6e3,,with} statements. (Contributed by Christian Heimes.)

@code{_winreg} also has better support for x64 systems,
exposing the @code{DisableReflectionKey()}, @code{EnableReflectionKey()},
and @code{QueryReflectionKey()} functions, which enable and disable
registry reflection for 32-bit processes running on 64-bit systems.
(bpo-1753245@footnote{https://bugs.python.org/issue1753245})

@item 
The @ref{b5,,msilib} module's @code{Record} object
gained @code{GetInteger()} and @code{GetString()} methods that
return field values as an integer or a string.
(Contributed by Floris Bruynooghe; bpo-2125@footnote{https://bugs.python.org/issue2125}.)
@end itemize

@c ======================================================================

@node 特定于 Mac OS X 的更改：<2>,特定于 IRIX 的更改：,特定于 Windows 的更改：<2>,构建和 C API 的改变<9>
@anchor{whatsnew/2 6 port-specific-changes-mac-os-x}@anchor{d54}
@subsubsection 特定于 Mac OS X 的更改：



@itemize *

@item 
现在，在编译Python的框架版本时，可以为 @code{configure} 脚本添加 @code{--with-framework-name=} 选项来指定要使用的框架名称。

@item 
@code{macfs} 模块已被删除。这反过来要求删除 @code{macostools.touched()} 函数，因为它依赖于 @code{macfs} 模块。 (bpo-1490190@footnote{https://bugs.python.org/issue1490190})

@item 
许多其他 Mac OS 模块已弃用并将在 Python 3.0 中被删除: @code{_builtinSuites}, @code{aepack}, @code{aetools}, @code{aetypes}, @code{applesingle}, @code{appletrawmain}, @code{appletrunner}, @code{argvemulator}, @code{Audio_mac}, @code{autoGIL}, @code{Carbon}, @code{cfmfile}, @code{CodeWarrior}, @code{ColorPicker}, @code{EasyDialogs}, @code{Explorer}, @code{Finder}, @code{FrameWork}, @code{findertools}, @code{ic}, @code{icglue}, @code{icopen}, @code{macerrors}, @code{MacOS}, @code{macfs}, @code{macostools}, @code{macresource}, @code{MiniAEFrame}, @code{Nav}, @code{Netscape}, @code{OSATerminology}, @code{pimp}, @code{PixMapWrapper}, @code{StdSuites}, @code{SystemEvents}, @code{Terminal} 和 @code{terminalcommand}。
@end itemize

@c ======================================================================

@node 特定于 IRIX 的更改：,,特定于 Mac OS X 的更改：<2>,构建和 C API 的改变<9>
@anchor{whatsnew/2 6 port-specific-changes-irix}@anchor{d55}
@subsubsection 特定于 IRIX 的更改：


许多旧的 IRIX 专用模块已被弃用，并将在Python 3.0中删除： @code{al} 和 @code{AL}, @code{cd}, @code{cddb}, @code{cdplayer}, @code{CL} 和 @code{cl}, @code{DEVICE}, @code{ERRNO}, @code{FILE}, @code{FL} 和 @code{fl}, @code{flp}, @code{fm}, @code{GET}, @code{GLWS}, @code{GL} 和 @code{gl}, @code{IN}, @code{IOCTL}, @code{jpeg}, @code{panelparser}, @code{readcd}, @code{SV} 和 @code{sv}, @code{torgb}, @code{videoreader}, 和 @code{WAIT}.

@c ======================================================================

@node 移植到Python 2 6,致谢<2>,构建和 C API 的改变<9>,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 porting-to-python-2-6}@anchor{d56}
@subsection 移植到Python 2.6


This section lists previously described changes and other bugfixes
that may require changes to your code:


@itemize *

@item 
Classes that aren't supposed to be hashable should
set @code{__hash__ = None} in their definitions to indicate
the fact.

@item 
String exceptions have been removed.  Attempting to use them raises a
@ref{192,,TypeError}.

@item 
The @ref{d57,,__init__()} method of @ref{52b,,collections.deque}
now clears any existing contents of the deque
before adding elements from the iterable.  This change makes the
behavior match @code{list.__init__()}.

@item 
@ref{d57,,object.__init__()} previously accepted arbitrary arguments and
keyword arguments, ignoring them.  In Python 2.6, this is no longer
allowed and will result in a @ref{192,,TypeError}.  This will affect
@ref{d57,,__init__()} methods that end up calling the corresponding
method on @ref{2b0,,object} (perhaps through using @ref{4dc,,super()}).
See bpo-1683368@footnote{https://bugs.python.org/issue1683368} for discussion.

@item 
The @code{Decimal} constructor now accepts leading and trailing
whitespace when passed a string.  Previously it would raise an
@code{InvalidOperation} exception.  On the other hand, the
@code{create_decimal()} method of @code{Context} objects now
explicitly disallows extra whitespace, raising a
@code{ConversionSyntax} exception.

@item 
Due to an implementation accident, if you passed a file path to
the built-in  @ref{60b,,__import__()} function, it would actually import
the specified file.  This was never intended to work, however, and
the implementation now explicitly checks for this case and raises
an @ref{32d,,ImportError}.

@item 
C API: the @ref{d58,,PyImport_Import()} and @ref{c6c,,PyImport_ImportModule()}
functions now default to absolute imports, not relative imports.
This will affect C extensions that import other modules.

@item 
C API: extension data types that shouldn't be hashable
should define their @code{tp_hash} slot to
@ref{d2a,,PyObject_HashNotImplemented()}.

@item 
The @ref{ef,,socket} module exception @ref{98f,,socket.error} now inherits
from @ref{98c,,IOError}.  Previously it wasn't a subclass of
@code{StandardError} but now it is, through @ref{98c,,IOError}.
(Implemented by Gregory P. Smith; bpo-1706815@footnote{https://bugs.python.org/issue1706815}.)

@item 
The @code{xmlrpclib} module no longer automatically converts
@ref{193,,datetime.date} and @ref{4ed,,datetime.time} to the
@code{xmlrpclib.DateTime} type; the conversion semantics were
not necessarily correct for all applications.  Code using
@code{xmlrpclib} should convert @code{date} and @ref{4ed,,time}
instances. (bpo-1330538@footnote{https://bugs.python.org/issue1330538})

@item 
(3.0-warning mode) The @ref{1a9,,Exception} class now warns
when accessed using slicing or index access; having
@ref{1a9,,Exception} behave like a tuple is being phased out.

@item 
(3.0-warning mode) inequality comparisons between two dictionaries
or two objects that don't implement comparison methods are reported
as warnings.  @code{dict1 == dict2} still works, but @code{dict1 < dict2}
is being phased out.

Comparisons between cells, which are an implementation detail of Python's
scoping rules, also cause warnings because such comparisons are forbidden
entirely in 3.0.
@end itemize

@c ======================================================================

@node 致谢<2>,,移植到Python 2 6,Python 2 6 有什么新变化
@anchor{whatsnew/2 6 acknowledgements}@anchor{d59}@anchor{whatsnew/2 6 acks}@anchor{d5a}
@subsection 致谢


作者感谢以下人员对本文各种草稿给予的建议，更正和协助： Georg Brandl, Steve Brown, Nick Coghlan, Ralph Corderoy, Jim Jewett, Kent Johnson, Chris Lambacher,  Martin Michlmayr, Antoine Pitrou, Brian Warner.

@node Python 2 5 有什么新变化,Python 2 4 有什么新变化,Python 2 6 有什么新变化,Python的新变化
@anchor{whatsnew/2 5 doc}@anchor{d5b}@anchor{whatsnew/2 5 what-s-new-in-python-2-5}@anchor{d5c}
@section Python 2.5 有什么新变化


@*作者: 
A.M. Kuchling


@c $Id: whatsnew25.tex 56611 2007-07-29 08:26:10Z georg.brandl $

@c Fix XXX comments

This article explains the new features in Python 2.5.  The final release of
Python 2.5 is scheduled for August 2006; 
@geindex Python 提高建议; PEP 356
PEP 356@footnote{https://www.python.org/dev/peps/pep-0356} describes the planned
release schedule.

The changes in Python 2.5 are an interesting mix of language and library
improvements. The library enhancements will be more important to Python's user
community, I think, because several widely-useful packages were added.  New
modules include ElementTree for XML processing (@code{xml.etree}),
the SQLite database module (@code{sqlite}), and the @ref{2b,,ctypes}
module for calling C functions.

The language changes are of middling significance.  Some pleasant new features
were added, but most of them aren't features that you'll use every day.
Conditional expressions were finally added to the language using a novel syntax;
see section @ref{d5d,,PEP 308; 条件表达式}.  The new '@ref{6e3,,with}' statement will make
writing cleanup code easier (section @ref{d5e,,PEP 343; "with" 语句}).  Values can now be passed
into generators (section @ref{d5f,,PEP 342; 生成器的新特性}).  Imports are now visible as either
absolute or relative (section @ref{d60,,PEP 328; 绝对导入和相对导入}).  Some corner cases of exception
handling are handled better (section @ref{d61,,PEP 341; 统一 try/except/finally}).  All these improvements
are worthwhile, but they're improvements to one specific language feature or
another; none of them are broad modifications to Python's semantics.

As well as the language and library additions, other improvements and bugfixes
were made throughout the source tree.  A search through the SVN change logs
finds there were 353 patches applied and 458 bugs fixed between Python 2.4 and
2.5.  (Both figures are likely to be underestimates.)

This article doesn't try to be a complete specification of the new features;
instead changes are briefly introduced using helpful examples.  For full
details, you should always refer to the documentation for Python 2.5 at
@indicateurl{https://docs.python.org}. If you want to understand the complete implementation
and design rationale, refer to the PEP for a particular new feature.

Comments, suggestions, and error reports for this document are welcome; please
e-mail them to the author or open a bug in the Python bug tracker.

@c ======================================================================

@menu
* PEP 308; 条件表达式: PEP 308 条件表达式. 
* PEP 309; 部分功能应用: PEP 309 部分功能应用. 
* PEP 314; Python软件包的元数据 v1.1: PEP 314 Python软件包的元数据 v1 1. 
* PEP 328; 绝对导入和相对导入: PEP 328 绝对导入和相对导入. 
* PEP 338; 将模块作为脚本执行: PEP 338 将模块作为脚本执行. 
* PEP 341; 统一 try/except/finally: PEP 341 统一 try/except/finally. 
* PEP 342; 生成器的新特性: PEP 342 生成器的新特性. 
* PEP 343; "with" 语句: PEP 343 "with" 语句<2>. 
* PEP 352; 异常作为新型的类: PEP 352 异常作为新型的类. 
* PEP 353; 使用ssize_t作为索引类型: PEP 353 使用ssize_t作为索引类型. 
* PEP 357; '__index__' 方法: PEP 357 '__index__' 方法. 
* 其他语言特性修改: 其他语言特性修改<11>. 
* 新增，改进和删除的模块:: 
* 构建和 C API 的改变: 构建和 C API 的改变<10>. 
* 移植到Python 2.5: 移植到Python 2 5. 
* 致谢: 致谢<3>. 

@end menu

@node PEP 308 条件表达式,PEP 309 部分功能应用,,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-308}@anchor{d5d}@anchor{whatsnew/2 5 pep-308-conditional-expressions}@anchor{d62}
@subsection PEP 308: 条件表达式


For a long time, people have been requesting a way to write conditional
expressions, which are expressions that return value A or value B depending on
whether a Boolean value is true or false.  A conditional expression lets you
write a single assignment statement that has the same effect as the following:

@example
if condition:
    x = true_value
else:
    x = false_value
@end example

There have been endless tedious discussions of syntax on both python-dev and
comp.lang.python.  A vote was even held that found the majority of voters wanted
conditional expressions in some form, but there was no syntax that was preferred
by a clear majority. Candidates included C's @code{cond ? true_v : false_v}, @code{if
cond then true_v else false_v}, and 16 other variations.

Guido van Rossum 最终选择了一种令人惊讶的语法：

@example
x = true_value if condition else false_value
@end example

Evaluation is still lazy as in existing Boolean expressions, so the order of
evaluation jumps around a bit.  The @emph{condition} expression in the middle is
evaluated first, and the @emph{true_value} expression is evaluated only if the
condition was true.  Similarly, the @emph{false_value} expression is only evaluated
when the condition is false.

This syntax may seem strange and backwards; why does the condition go in the
@emph{middle} of the expression, and not in the front as in C's @code{c ? x : y}?  The
decision was checked by applying the new syntax to the modules in the standard
library and seeing how the resulting code read.  In many cases where a
conditional expression is used, one value seems to be the 'common case' and one
value is an 'exceptional case', used only on rarer occasions when the condition
isn't met.  The conditional syntax makes this pattern a bit more obvious:

@example
contents = ((doc + '\n') if doc else '@w{'})
@end example

I read the above statement as meaning "here @emph{contents} is  usually assigned a
value of @code{doc+'\n'}; sometimes  @emph{doc} is empty, in which special case an empty
string is returned."   I doubt I will use conditional expressions very often
where there  isn't a clear common and uncommon case.

There was some discussion of whether the language should require surrounding
conditional expressions with parentheses.  The decision was made to @emph{not}
require parentheses in the Python language's grammar, but as a matter of style I
think you should always use them. Consider these two statements:

@example
# First version -- no parens
level = 1 if logging else 0

# Second version -- with parens
level = (1 if logging else 0)
@end example

In the first version, I think a reader's eye might group the statement into
'level = 1', 'if logging', 'else 0', and think that the condition decides
whether the assignment to @emph{level} is performed.  The second version reads
better, in my opinion, because it makes it clear that the assignment is always
performed and the choice is being made between two values.

Another reason for including the brackets: a few odd combinations of list
comprehensions and lambdas could look like incorrect conditional expressions.
See 
@geindex Python 提高建议; PEP 308
PEP 308@footnote{https://www.python.org/dev/peps/pep-0308} for some examples.  If you put parentheses around your
conditional expressions, you won't run into this case.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 308

@item PEP 308@footnote{https://www.python.org/dev/peps/pep-0308} - 条件表达式

PEP 由 Guido van Rossum 和 Raymond D 撰写，由 Thomas Wouters 实现。
@end table


@c ======================================================================

@node PEP 309 部分功能应用,PEP 314 Python软件包的元数据 v1 1,PEP 308 条件表达式,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-309}@anchor{d63}@anchor{whatsnew/2 5 pep-309-partial-function-application}@anchor{d64}
@subsection PEP 309: 部分功能应用


The @ref{85,,functools} module is intended to contain tools for functional-style
programming.

One useful tool in this module is the @code{partial()} function. For programs
written in a functional style, you'll sometimes want to construct variants of
existing functions that have some of the parameters filled in.  Consider a
Python function @code{f(a, b, c)}; you could create a new function @code{g(b, c)} that
was equivalent to @code{f(1, b, c)}.  This is called "partial function
application".

@code{partial()} takes the arguments @code{(function, arg1, arg2, ... kwarg1=value1,
kwarg2=value2)}.  The resulting object is callable, so you can just call it to
invoke @emph{function} with the filled-in arguments.

这里有一个很小但很现实的例子:

@example
import functools

def log (message, subsystem):
    "Write the contents of 'message' to the specified subsystem."
    print '%s: %s' % (subsystem, message)
    ...

server_log = functools.partial(log, subsystem='server')
server_log('Unable to open socket')
@end example

Here's another example, from a program that uses PyGTK.  Here a context-sensitive
pop-up menu is being constructed dynamically.  The callback provided
for the menu option is a partially applied version of the @code{open_item()}
method, where the first argument has been provided.

@example
...
class Application:
    def open_item(self, path):
       ...
    def init (self):
        open_func = functools.partial(self.open_item, item_path)
        popup_menu.append( ("Open", open_func, 1) )
@end example

Another function in the @ref{85,,functools} module is the
@code{update_wrapper(wrapper, wrapped)} function that helps you write
well-behaved decorators.  @code{update_wrapper()} copies the name, module, and
docstring attribute to a wrapper function so that tracebacks inside the wrapped
function are easier to understand.  For example, you might write:

@example
def my_decorator(f):
    def wrapper(*args, **kwds):
        print 'Calling decorated function'
        return f(*args, **kwds)
    functools.update_wrapper(wrapper, f)
    return wrapper
@end example

@code{wraps()} is a decorator that can be used inside your own decorators to copy
the wrapped function's information.  An alternate  version of the previous
example would be:

@example
def my_decorator(f):
    @@functools.wraps(f)
    def wrapper(*args, **kwds):
        print 'Calling decorated function'
        return f(*args, **kwds)
    return wrapper
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 309

@item PEP 309@footnote{https://www.python.org/dev/peps/pep-0309} - Partial Function Application

PEP由 Peter Harris 提出并撰写；由 Hye-Shik Chang 和 Nick Coghlan 实现，并由 Raymond Hettinger 适配。
@end table


@c ======================================================================

@node PEP 314 Python软件包的元数据 v1 1,PEP 328 绝对导入和相对导入,PEP 309 部分功能应用,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-314}@anchor{d65}@anchor{whatsnew/2 5 pep-314-metadata-for-python-software-packages-v1-1}@anchor{d66}
@subsection PEP 314: Python软件包的元数据 v1.1


Some simple dependency support was added to Distutils.  The @code{setup()}
function now has @code{requires}, @code{provides}, and @code{obsoletes} keyword
parameters.  When you build a source distribution using the @code{sdist} command,
the dependency information will be recorded in the @code{PKG-INFO} file.

Another new keyword parameter is @code{download_url}, which should be set to a URL
for the package's source code.  This means it's now possible to look up an entry
in the package index, determine the dependencies for a package, and download the
required packages.

@example
VERSION = '1.0'
setup(name='PyPackage',
      version=VERSION,
      requires=['numarray', 'zlib (>=1.1.4)'],
      obsoletes=['OldPackage']
      download_url=('http://www.example.com/pypackage/dist/pkg-%s.tar.gz'
                    % VERSION),
     )
@end example

Another new enhancement to the Python package index at
@indicateurl{https://pypi.org} is storing source and binary archives for a
package.  The new @code{upload} Distutils command will upload a package to
the repository.

Before a package can be uploaded, you must be able to build a distribution using
the @code{sdist} Distutils command.  Once that works, you can run @code{python
setup.py upload} to add your package to the PyPI archive.  Optionally you can
GPG-sign the package by supplying the @code{--sign} and @code{--identity}
options.

Package uploading was implemented by Martin von Löwis and Richard Jones.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 314

@item PEP 314@footnote{https://www.python.org/dev/peps/pep-0314} - Python软件包的元数据 v1.1

PEP 由 A.M. Kuchling, Richard Jones 和 Fred Drake 提出并撰写，由 Richard Jones 和 Fred Drake 实现
@end table


@c ======================================================================

@node PEP 328 绝对导入和相对导入,PEP 338 将模块作为脚本执行,PEP 314 Python软件包的元数据 v1 1,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-328}@anchor{d60}@anchor{whatsnew/2 5 pep-328-absolute-and-relative-imports}@anchor{d67}
@subsection PEP 328: 绝对导入和相对导入


The simpler part of 
@geindex Python 提高建议; PEP 328
PEP 328@footnote{https://www.python.org/dev/peps/pep-0328} was implemented in Python 2.4: parentheses could now
be used to enclose the names imported from a module using the @code{from ... import
...} statement, making it easier to import many different names.

The more complicated part has been implemented in Python 2.5: importing a module
can be specified to use absolute or package-relative imports.  The plan is to
move toward making absolute imports the default in future versions of Python.

Let's say you have a package directory like this:

@example
pkg/
pkg/__init__.py
pkg/main.py
pkg/string.py
@end example

This defines a package named @code{pkg} containing the @code{pkg.main} and
@code{pkg.string} submodules.

Consider the code in the @code{main.py} module.  What happens if it executes
the statement @code{import string}?  In Python 2.4 and earlier, it will first look
in the package's directory to perform a relative import, finds
@code{pkg/string.py}, imports the contents of that file as the
@code{pkg.string} module, and that module is bound to the name @code{string} in the
@code{pkg.main} module's namespace.

That's fine if @code{pkg.string} was what you wanted.  But what if you wanted
Python's standard @ref{f6,,string} module?  There's no clean way to ignore
@code{pkg.string} and look for the standard module; generally you had to look at
the contents of @code{sys.modules}, which is slightly unclean.    Holger Krekel's
@code{py.std} package provides a tidier way to perform imports from the standard
library, @code{import py; py.std.string.join()}, but that package isn't available
on all Python installations.

Reading code which relies on relative imports is also less clear, because a
reader may be confused about which module, @ref{f6,,string} or @code{pkg.string},
is intended to be used.  Python users soon learned not to duplicate the names of
standard library modules in the names of their packages' submodules, but you
can't protect against having your submodule's name being used for a new module
added in a future version of Python.

In Python 2.5, you can switch @ref{c16,,import}'s behaviour to  absolute imports
using a @code{from __future__ import absolute_import} directive.  This absolute-import
behaviour will become the default in a future version (probably Python
2.7).  Once absolute imports  are the default, @code{import string} will always
find the standard library's version. It's suggested that users should begin
using absolute imports as much as possible, so it's preferable to begin writing
@code{from pkg import string} in your code.

Relative imports are still possible by adding a leading period  to the module
name when using the @code{from ... import} form:

@example
# Import names from pkg.string
from .string import name1, name2
# Import pkg.string
from . import string
@end example

This imports the @ref{f6,,string} module relative to the current package, so in
@code{pkg.main} this will import @emph{name1} and @emph{name2} from @code{pkg.string}.
Additional leading periods perform the relative import starting from the parent
of the current package.  For example, code in the @code{A.B.C} module can do:

@example
from . import D                 # Imports A.B.D
from .. import E                # Imports A.E
from ..F import G               # Imports A.F.G
@end example

Leading periods cannot be used with the @code{import modname}  form of the import
statement, only the @code{from ... import} form.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 328

@item PEP 328@footnote{https://www.python.org/dev/peps/pep-0328} - 导入：多行和绝对/相对导入

PEP 由 Aahz 撰写，由 Thomas Wouters 实现。

@item @indicateurl{https://pylib.readthedocs.io/}

The py library by Holger Krekel, which contains the @code{py.std} package.
@end table


@c ======================================================================

@node PEP 338 将模块作为脚本执行,PEP 341 统一 try/except/finally,PEP 328 绝对导入和相对导入,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-338}@anchor{d68}@anchor{whatsnew/2 5 pep-338-executing-modules-as-scripts}@anchor{d69}
@subsection PEP 338: 将模块作为脚本执行


The @ref{330,,-m} switch added in Python 2.4 to execute a module as a script
gained a few more abilities.  Instead of being implemented in C code inside the
Python interpreter, the switch now uses an implementation in a new module,
@ref{e2,,runpy}.

The @ref{e2,,runpy} module implements a more sophisticated import mechanism so that
it's now possible to run modules in a package such as @code{pychecker.checker}.
The module also supports alternative import mechanisms such as the
@ref{143,,zipimport} module.  This means you can add a .zip archive's path to
@code{sys.path} and then use the @ref{330,,-m} switch to execute code from the
archive.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 338

@item PEP 338@footnote{https://www.python.org/dev/peps/pep-0338} - 将模块作为脚本执行

PEP 由 Nick Coghlan 撰写并实现。
@end table


@c ======================================================================

@node PEP 341 统一 try/except/finally,PEP 342 生成器的新特性,PEP 338 将模块作为脚本执行,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-341}@anchor{d61}@anchor{whatsnew/2 5 pep-341-unified-try-except-finally}@anchor{d6a}
@subsection PEP 341: 统一 try/except/finally


Until Python 2.5, the @ref{d6b,,try} statement came in two flavours. You could
use a @ref{182,,finally} block to ensure that code is always executed, or one or
more @ref{b37,,except} blocks to catch  specific exceptions.  You couldn't
combine both @code{except} blocks and a @code{finally} block, because
generating the right bytecode for the combined version was complicated and it
wasn't clear what the semantics of the combined statement should be.

Guido van Rossum spent some time working with Java, which does support the
equivalent of combining @ref{b37,,except} blocks and a @ref{182,,finally} block,
and this clarified what the statement should mean.  In Python 2.5, you can now
write:

@example
try:
    block-1 ...
except Exception1:
    handler-1 ...
except Exception2:
    handler-2 ...
else:
    else-block
finally:
    final-block
@end example

The code in @emph{block-1} is executed.  If the code raises an exception, the various
@ref{b37,,except} blocks are tested: if the exception is of class
@code{Exception1}, @emph{handler-1} is executed; otherwise if it's of class
@code{Exception2}, @emph{handler-2} is executed, and so forth.  If no exception is
raised, the @emph{else-block} is executed.

No matter what happened previously, the @emph{final-block} is executed once the code
block is complete and any raised exceptions handled. Even if there's an error in
an exception handler or the @emph{else-block} and a new exception is raised, the code
in the @emph{final-block} is still run.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 341

@item PEP 341@footnote{https://www.python.org/dev/peps/pep-0341} - 统一 try-except 和 try-finally

PEP 由 Georg Brandl 撰写，由 Thomas Lee 实现。
@end table


@c ======================================================================

@node PEP 342 生成器的新特性,PEP 343 "with" 语句<2>,PEP 341 统一 try/except/finally,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-342}@anchor{d5f}@anchor{whatsnew/2 5 pep-342-new-generator-features}@anchor{d6c}
@subsection PEP 342: 生成器的新特性


Python 2.5 adds a simple way to pass values @emph{into} a generator. As introduced in
Python 2.3, generators only produce output; once a generator's code was invoked
to create an iterator, there was no way to pass any new information into the
function when its execution is resumed.  Sometimes the ability to pass in some
information would be useful.  Hackish solutions to this include making the
generator's code look at a global variable and then changing the global
variable's value, or passing in some mutable object that callers then modify.

To refresh your memory of basic generators, here's a simple example:

@example
def counter (maximum):
    i = 0
    while i < maximum:
        yield i
        i += 1
@end example

When you call @code{counter(10)}, the result is an iterator that returns the values
from 0 up to 9.  On encountering the @ref{18f,,yield} statement, the iterator
returns the provided value and suspends the function's execution, preserving the
local variables. Execution resumes on the following call to the iterator's
@ref{67c,,next()} method, picking up after the @code{yield} statement.

In Python 2.3, @ref{18f,,yield} was a statement; it didn't return any value.  In
2.5, @code{yield} is now an expression, returning a value that can be
assigned to a variable or otherwise operated on:

@example
val = (yield i)
@end example

I recommend that you always put parentheses around a @ref{18f,,yield} expression
when you're doing something with the returned value, as in the above example.
The parentheses aren't always necessary, but it's easier to always add them
instead of having to remember when they're needed.

(
@geindex Python 提高建议; PEP 342
PEP 342@footnote{https://www.python.org/dev/peps/pep-0342} explains the exact rules, which are that a
@ref{18f,,yield}-expression must always be parenthesized except when it
occurs at the top-level
expression on the right-hand side of an assignment.  This means you can write
@code{val = yield i} but have to use parentheses when there's an operation, as in
@code{val = (yield i) + 12}.)

Values are sent into a generator by calling its @code{send(value)} method.  The
generator's code is then resumed and the @ref{18f,,yield} expression returns the
specified @emph{value}.  If the regular @ref{67c,,next()} method is called, the
@code{yield} returns @ref{157,,None}.

Here's the previous example, modified to allow changing the value of the
internal counter.

@example
def counter (maximum):
    i = 0
    while i < maximum:
        val = (yield i)
        # If value provided, change counter
        if val is not None:
            i = val
        else:
            i += 1
@end example

And here's an example of changing the counter:

@example
>>> it = counter(10)
>>> print it.next()
0
>>> print it.next()
1
>>> print it.send(8)
8
>>> print it.next()
9
>>> print it.next()
Traceback (most recent call last):
  File "t.py", line 15, in ?
    print it.next()
StopIteration
@end example

@ref{18f,,yield} will usually return @ref{157,,None}, so you should always check
for this case.  Don't just use its value in expressions unless you're sure that
the @code{send()} method will be the only method used to resume your generator
function.

In addition to @code{send()}, there are two other new methods on generators:


@itemize *

@item 
@code{throw(type, value=None, traceback=None)} is used to raise an exception
inside the generator; the exception is raised by the @ref{18f,,yield} expression
where the generator's execution is paused.

@item 
@code{close()} raises a new @ref{d2b,,GeneratorExit} exception inside the generator
to terminate the iteration.  On receiving this exception, the generator's code
must either raise @ref{d2b,,GeneratorExit} or @ref{480,,StopIteration}.  Catching the
@ref{d2b,,GeneratorExit} exception and returning a value is illegal and will trigger
a @ref{2ba,,RuntimeError}; if the function raises some other exception, that
exception is propagated to the caller.  @code{close()} will also be called by
Python's garbage collector when the generator is garbage-collected.

If you need to run cleanup code when a @ref{d2b,,GeneratorExit} occurs, I suggest
using a @code{try: ... finally:} suite instead of  catching @ref{d2b,,GeneratorExit}.
@end itemize

这些改变的累积效应是，让生成器从单向的信息生产者变成了既是生产者，又是消费者。

Generators also become @emph{coroutines}, a more generalized form of subroutines.
Subroutines are entered at one point and exited at another point (the top of the
function, and a @ref{190,,return} statement), but coroutines can be entered,
exited, and resumed at many different points (the @ref{18f,,yield} statements).
We'll have to figure out patterns for using coroutines effectively in Python.

The addition of the @code{close()} method has one side effect that isn't obvious.
@code{close()} is called when a generator is garbage-collected, so this means the
generator's code gets one last chance to run before the generator is destroyed.
This last chance means that @code{try...finally} statements in generators can now
be guaranteed to work; the @ref{182,,finally} clause will now always get a
chance to run.  The syntactic restriction that you couldn't mix @ref{18f,,yield}
statements with a @code{try...finally} suite has therefore been removed.  This
seems like a minor bit of language trivia, but using generators and
@code{try...finally} is actually necessary in order to implement the
@ref{6e3,,with} statement described by 
@geindex Python 提高建议; PEP 343
PEP 343@footnote{https://www.python.org/dev/peps/pep-0343}.  I'll look at this new statement
in the following  section.

Another even more esoteric effect of this change: previously, the
@code{gi_frame} attribute of a generator was always a frame object. It's now
possible for @code{gi_frame} to be @code{None} once the generator has been
exhausted.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 342

@item PEP 342@footnote{https://www.python.org/dev/peps/pep-0342} - 通过增强型生成器实现协程

PEP 由 Guido van Rossum 和 Phillip J. Eby 撰写，由 Phillip J. Eby 实现。包括一些更高级的使用生成器作为协程的示例。

这些功能的早期版本在 
@geindex Python 提高建议; PEP 288
PEP 288@footnote{https://www.python.org/dev/peps/pep-0288} （由 Raymond Hettinger 撰写） 和 
@geindex Python 提高建议; PEP 325
PEP 325@footnote{https://www.python.org/dev/peps/pep-0325} （由 Samuele Pedroni 撰写）中提出。

@item @indicateurl{https://en.wikipedia.org/wiki/Coroutine}

协程的Wikipedia条目。

@item @indicateurl{http://www.sidhe.org/~dan/blog/archives/000178.html}

An explanation of coroutines from a Perl point of view, written by Dan Sugalski.
@end table


@c ======================================================================

@node PEP 343 "with" 语句<2>,PEP 352 异常作为新型的类,PEP 342 生成器的新特性,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-343}@anchor{d5e}@anchor{whatsnew/2 5 pep-343-the-with-statement}@anchor{d6d}
@subsection PEP 343: "with" 语句


The '@ref{6e3,,with}' statement clarifies code that previously would use
@code{try...finally} blocks to ensure that clean-up code is executed.  In this
section, I'll discuss the statement as it will commonly be used.  In the next
section, I'll examine the implementation details and show how to write objects
for use with this statement.

The '@ref{6e3,,with}' statement is a new control-flow structure whose basic
structure is:

@example
with expression [as variable]:
    with-block
@end example

The expression is evaluated, and it should result in an object that supports the
context management protocol (that is, has @ref{c8e,,__enter__()} and @ref{c8f,,__exit__()}
methods.

The object's @ref{c8e,,__enter__()} is called before @emph{with-block} is executed and
therefore can run set-up code. It also may return a value that is bound to the
name @emph{variable}, if given.  (Note carefully that @emph{variable} is @emph{not} assigned
the result of @emph{expression}.)

After execution of the @emph{with-block} is finished, the object's @ref{c8f,,__exit__()}
method is called, even if the block raised an exception, and can therefore run
clean-up code.

To enable the statement in Python 2.5, you need to add the following directive
to your module:

@example
from __future__ import with_statement
@end example

该语句在Python 2.6 中始终启用。

Some standard Python objects now support the context management protocol and can
be used with the '@ref{6e3,,with}' statement. File objects are one example:

@example
with open('/etc/passwd', 'r') as f:
    for line in f:
        print line
        ... more processing code ...
@end example

After this statement has executed, the file object in @emph{f} will have been
automatically closed, even if the @ref{c29,,for} loop raised an exception
part-way through the block.

@cartouche
@quotation 注解 
In this case, @emph{f} is the same object created by @ref{4ea,,open()}, because
@code{file.__enter__()} returns @emph{self}.
@end quotation
@end cartouche

The @ref{109,,threading} module's locks and condition variables  also support the
'@ref{6e3,,with}' statement:

@example
lock = threading.Lock()
with lock:
    # Critical section of code
    ...
@end example

The lock is acquired before the block is executed and always released once  the
block is complete.

The new @code{localcontext()} function in the @ref{36,,decimal} module makes it easy
to save and restore the current decimal context, which encapsulates the desired
precision and rounding characteristics for computations:

@example
from decimal import Decimal, Context, localcontext

# Displays with default precision of 28 digits
v = Decimal('578')
print v.sqrt()

with localcontext(Context(prec=16)):
    # All code in this block uses a precision of 16 digits.
    # The original context is restored on exiting the block.
    print v.sqrt()
@end example

@menu
* Writing Context Managers: Writing Context Managers<2>. 
* contextlib 模块: contextlib 模块<2>. 

@end menu

@node Writing Context Managers<2>,contextlib 模块<2>,,PEP 343 "with" 语句<2>
@anchor{whatsnew/2 5 new-25-context-managers}@anchor{d6e}@anchor{whatsnew/2 5 writing-context-managers}@anchor{d6f}
@subsubsection Writing Context Managers


Under the hood, the '@ref{6e3,,with}' statement is fairly complicated. Most
people will only use '@code{with}' in company with existing objects and
don't need to know these details, so you can skip the rest of this section if
you like.  Authors of new objects will need to understand the details of the
underlying implementation and should keep reading.

A high-level explanation of the context management protocol is:


@itemize *

@item 
The expression is evaluated and should result in an object called a "context
manager".  The context manager must have @ref{c8e,,__enter__()} and @ref{c8f,,__exit__()}
methods.

@item 
The context manager's @ref{c8e,,__enter__()} method is called.  The value returned
is assigned to @emph{VAR}.  If no @code{'as VAR'} clause is present, the value is simply
discarded.

@item 
The code in @emph{BLOCK} is executed.

@item 
If @emph{BLOCK} raises an exception, the @code{__exit__(type, value, traceback)}
is called with the exception details, the same values returned by
@ref{c58,,sys.exc_info()}.  The method's return value controls whether the exception
is re-raised: any false value re-raises the exception, and @code{True} will result
in suppressing it.  You'll only rarely want to suppress the exception, because
if you do the author of the code containing the '@ref{6e3,,with}' statement will
never realize anything went wrong.

@item 
If @emph{BLOCK} didn't raise an exception,  the @ref{c8f,,__exit__()} method is still
called, but @emph{type}, @emph{value}, and @emph{traceback} are all @code{None}.
@end itemize

Let's think through an example.  I won't present detailed code but will only
sketch the methods necessary for a database that supports transactions.

(For people unfamiliar with database terminology: a set of changes to the
database are grouped into a transaction.  Transactions can be either committed,
meaning that all the changes are written into the database, or rolled back,
meaning that the changes are all discarded and the database is unchanged.  See
any database textbook for more information.)

Let's assume there's an object representing a database connection. Our goal will
be to let the user write code like this:

@example
db_connection = DatabaseConnection()
with db_connection as cursor:
    cursor.execute('insert into ...')
    cursor.execute('delete from ...')
    # ... more operations ...
@end example

The transaction should be committed if the code in the block runs flawlessly or
rolled back if there's an exception. Here's the basic interface for
@code{DatabaseConnection} that I'll assume:

@example
class DatabaseConnection:
    # Database interface
    def cursor (self):
        "Returns a cursor object and starts a new transaction"
    def commit (self):
        "Commits current transaction"
    def rollback (self):
        "Rolls back current transaction"
@end example

The @ref{c8e,,__enter__()} method is pretty easy, having only to start a new
transaction.  For this application the resulting cursor object would be a useful
result, so the method will return it.  The user can then add @code{as cursor} to
their '@ref{6e3,,with}' statement to bind the cursor to a variable name.

@example
class DatabaseConnection:
    ...
    def __enter__ (self):
        # Code to start a new transaction
        cursor = self.cursor()
        return cursor
@end example

The @ref{c8f,,__exit__()} method is the most complicated because it's where most of
the work has to be done.  The method has to check if an exception occurred.  If
there was no exception, the transaction is committed.  The transaction is rolled
back if there was an exception.

In the code below, execution will just fall off the end of the function,
returning the default value of @code{None}.  @code{None} is false, so the exception
will be re-raised automatically.  If you wished, you could be more explicit and
add a @ref{190,,return} statement at the marked location.

@example
class DatabaseConnection:
    ...
    def __exit__ (self, type, value, tb):
        if tb is None:
            # No exception, so commit
            self.commit()
        else:
            # Exception occurred, so rollback.
            self.rollback()
            # return False
@end example

@node contextlib 模块<2>,,Writing Context Managers<2>,PEP 343 "with" 语句<2>
@anchor{whatsnew/2 5 contextlibmod}@anchor{d70}@anchor{whatsnew/2 5 the-contextlib-module}@anchor{d71}
@subsubsection contextlib 模块


The new @ref{24,,contextlib} module provides some functions and a decorator that
are useful for writing objects for use with the '@ref{6e3,,with}' statement.

The decorator is called @code{contextmanager()}, and lets you write a single
generator function instead of defining a new class.  The generator should yield
exactly one value.  The code up to the @ref{18f,,yield} will be executed as the
@ref{c8e,,__enter__()} method, and the value yielded will be the method's return
value that will get bound to the variable in the '@ref{6e3,,with}' statement's
@code{as} clause, if any.  The code after the @ref{18f,,yield} will be
executed in the @ref{c8f,,__exit__()} method.  Any exception raised in the block will
be raised by the @code{yield} statement.

Our database example from the previous section could be written  using this
decorator as:

@example
from contextlib import contextmanager

@@contextmanager
def db_transaction (connection):
    cursor = connection.cursor()
    try:
        yield cursor
    except:
        connection.rollback()
        raise
    else:
        connection.commit()

db = DatabaseConnection()
with db_transaction(db) as cursor:
    ...
@end example

The @ref{24,,contextlib} module also has a @code{nested(mgr1, mgr2, ...)} function
that combines a number of context managers so you don't need to write nested
'@ref{6e3,,with}' statements.  In this example, the single '@code{with}'
statement both starts a database transaction and acquires a thread lock:

@example
lock = threading.Lock()
with nested (db_transaction(db), lock) as (cursor, locked):
    ...
@end example

Finally, the @code{closing(object)} function returns @emph{object} so that it can be
bound to a variable, and calls @code{object.close} at the end of the block.

@example
import urllib, sys
from contextlib import closing

with closing(urllib.urlopen('http://www.yahoo.com')) as f:
    for line in f:
        sys.stdout.write(line)
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 343

@item PEP 343@footnote{https://www.python.org/dev/peps/pep-0343} - "with" 语句

PEP written by Guido van Rossum and Nick Coghlan; implemented by Mike Bland,
Guido van Rossum, and Neal Norwitz.  The PEP shows the code generated for a
'@ref{6e3,,with}' statement, which can be helpful in learning how the statement
works.
@end table

@ref{24,,contextlib} 模块的文档。


@c ======================================================================

@node PEP 352 异常作为新型的类,PEP 353 使用ssize_t作为索引类型,PEP 343 "with" 语句<2>,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-352}@anchor{d72}@anchor{whatsnew/2 5 pep-352-exceptions-as-new-style-classes}@anchor{d73}
@subsection PEP 352: 异常作为新型的类


Exception classes can now be new-style classes, not just classic classes, and
the built-in @ref{1a9,,Exception} class and all the standard built-in exceptions
(@ref{d74,,NameError}, @ref{1fb,,ValueError}, etc.) are now new-style classes.

The inheritance hierarchy for exceptions has been rearranged a bit. In 2.5, the
inheritance relationships are:

@example
BaseException       # New in Python 2.5
|- KeyboardInterrupt
|- SystemExit
|- Exception
   |- (all other current built-in exceptions)
@end example

This rearrangement was done because people often want to catch all exceptions
that indicate program errors.  @ref{197,,KeyboardInterrupt} and @ref{5f7,,SystemExit}
aren't errors, though, and usually represent an explicit action such as the user
hitting @code{Control-C} or code calling @ref{cdb,,sys.exit()}.  A bare @code{except:} will
catch all exceptions, so you commonly need to list @ref{197,,KeyboardInterrupt} and
@ref{5f7,,SystemExit} in order to re-raise them.  The usual pattern is:

@example
try:
    ...
except (KeyboardInterrupt, SystemExit):
    raise
except:
    # Log error...
    # Continue running program...
@end example

In Python 2.5, you can now write @code{except Exception} to achieve the same
result, catching all the exceptions that usually indicate errors  but leaving
@ref{197,,KeyboardInterrupt} and @ref{5f7,,SystemExit} alone.  As in previous versions,
a bare @code{except:} still catches all exceptions.

The goal for Python 3.0 is to require any class raised as an exception to derive
from @ref{1a8,,BaseException} or some descendant of @ref{1a8,,BaseException}, and future
releases in the Python 2.x series may begin to enforce this constraint.
Therefore, I suggest you begin making all your exception classes derive from
@ref{1a9,,Exception} now.  It's been suggested that the bare @code{except:} form should
be removed in Python 3.0, but Guido van Rossum hasn't decided whether to do this
or not.

Raising of strings as exceptions, as in the statement @code{raise "Error
occurred"}, is deprecated in Python 2.5 and will trigger a warning.  The aim is
to be able to remove the string-exception feature in a few releases.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 352

@item PEP 352@footnote{https://www.python.org/dev/peps/pep-0352} - 异常所需的超类

PEP 由 Brett Cannon 和 Guido van Rossum 撰写，由 Brett Cannon 实现
@end table


@c ======================================================================

@node PEP 353 使用ssize_t作为索引类型,PEP 357 '__index__' 方法,PEP 352 异常作为新型的类,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-353}@anchor{d75}@anchor{whatsnew/2 5 pep-353-using-ssize-t-as-the-index-type}@anchor{d76}
@subsection PEP 353: 使用ssize_t作为索引类型


A wide-ranging change to Python's C API, using a new  @code{Py_ssize_t} type
definition instead of @code{int},  will permit the interpreter to handle more
data on 64-bit platforms. This change doesn't affect Python's capacity on 32-bit
platforms.

Various pieces of the Python interpreter used C's @code{int} type to store
sizes or counts; for example, the number of items in a list or tuple were stored
in an @code{int}.  The C compilers for most 64-bit platforms still define
@code{int} as a 32-bit type, so that meant that lists could only hold up to
@code{2**31 - 1} = 2147483647 items. (There are actually a few different
programming models that 64-bit C compilers can use -- see
@indicateurl{http://www.unix.org/version2/whatsnew/lp64_wp.html} for a discussion -- but the
most commonly available model leaves @code{int} as 32 bits.)

A limit of 2147483647 items doesn't really matter on a 32-bit platform because
you'll run out of memory before hitting the length limit. Each list item
requires space for a pointer, which is 4 bytes, plus space for a
@ref{4b5,,PyObject} representing the item.  2147483647*4 is already more bytes
than a 32-bit address space can contain.

It's possible to address that much memory on a 64-bit platform, however.  The
pointers for a list that size would only require 16 GiB of space, so it's not
unreasonable that Python programmers might construct lists that large.
Therefore, the Python interpreter had to be changed to use some type other than
@code{int}, and this will be a 64-bit type on 64-bit platforms.  The change
will cause incompatibilities on 64-bit machines, so it was deemed worth making
the transition now, while the number of 64-bit users is still relatively small.
(In 5 or 10 years, we may @emph{all} be on 64-bit machines, and the transition would
be more painful then.)

This change most strongly affects authors of C extension modules.   Python
strings and container types such as lists and tuples  now use
@code{Py_ssize_t} to store their size.   Functions such as
@ref{d77,,PyList_Size()}  now return @code{Py_ssize_t}.  Code in extension modules
may therefore need to have some variables changed to @code{Py_ssize_t}.

The @ref{26a,,PyArg_ParseTuple()} and @ref{2ce,,Py_BuildValue()} functions have a new
conversion code, @code{n}, for @code{Py_ssize_t}.   @ref{26a,,PyArg_ParseTuple()}'s
@code{s#} and @code{t#} still output @code{int} by default, but you can define the
macro  @code{PY_SSIZE_T_CLEAN} before including @code{Python.h}  to make
them return @code{Py_ssize_t}.

@geindex Python 提高建议; PEP 353
PEP 353@footnote{https://www.python.org/dev/peps/pep-0353} has a section on conversion guidelines that  extension authors should
read to learn about supporting 64-bit platforms.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 353

@item PEP 353@footnote{https://www.python.org/dev/peps/pep-0353} - 使用ssize_t作为索引类型

PEP 由 Martin von Löwis 撰写并实现。
@end table


@c ======================================================================

@node PEP 357 '__index__' 方法,其他语言特性修改<11>,PEP 353 使用ssize_t作为索引类型,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 pep-357}@anchor{d78}@anchor{whatsnew/2 5 pep-357-the-index-method}@anchor{d79}
@subsection PEP 357: '__index__' 方法


The NumPy developers had a problem that could only be solved by adding a new
special method, @ref{18a,,__index__()}.  When using slice notation, as in
@code{[start:stop:step]}, the values of the @emph{start}, @emph{stop}, and @emph{step} indexes
must all be either integers or long integers.  NumPy defines a variety of
specialized integer types corresponding to unsigned and signed integers of 8,
16, 32, and 64 bits, but there was no way to signal that these types could be
used as slice indexes.

Slicing can't just use the existing @ref{18b,,__int__()} method because that method
is also used to implement coercion to integers.  If slicing used
@ref{18b,,__int__()}, floating-point numbers would also become legal slice indexes
and that's clearly an undesirable behaviour.

Instead, a new special method called @ref{18a,,__index__()} was added.  It takes no
arguments and returns an integer giving the slice index to use.  For example:

@example
class C:
    def __index__ (self):
        return self.value
@end example

The return value must be either a Python integer or long integer. The
interpreter will check that the type returned is correct, and raises a
@ref{192,,TypeError} if this requirement isn't met.

A corresponding @code{nb_index} slot was added to the C-level
@ref{d7a,,PyNumberMethods} structure to let C extensions implement this protocol.
@code{PyNumber_Index(obj)} can be used in extension code to call the
@ref{18a,,__index__()} function and retrieve its result.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 357

@item PEP 357@footnote{https://www.python.org/dev/peps/pep-0357} - 允许将任何对象用于切片

PEP 由 Travis Oliphant 撰写并实现。
@end table


@c ======================================================================

@node 其他语言特性修改<11>,新增，改进和删除的模块,PEP 357 '__index__' 方法,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 other-lang}@anchor{d7b}@anchor{whatsnew/2 5 other-language-changes}@anchor{d7c}
@subsection 其他语言特性修改


Here are all of the changes that Python 2.5 makes to the core Python language.


@itemize *

@item 
The @ref{1b8,,dict} type has a new hook for letting subclasses provide a default
value when a key isn't contained in the dictionary. When a key isn't found, the
dictionary's @code{__missing__(key)} method will be called.  This hook is used
to implement the new @code{defaultdict} class in the @ref{1e,,collections}
module.  The following example defines a dictionary  that returns zero for any
missing key:

@example
class zerodict (dict):
    def __missing__ (self, key):
        return 0

d = zerodict(@{1:1, 2:2@})
print d[1], d[2]   # Prints 1, 2
print d[3], d[4]   # Prints 0, 0
@end example

@item 
Both 8-bit and Unicode strings have new @code{partition(sep)}  and
@code{rpartition(sep)} methods that simplify a common use case.

The @code{find(S)} method is often used to get an index which is then used to
slice the string and obtain the pieces that are before and after the separator.
@code{partition(sep)} condenses this pattern into a single method call that
returns a 3-tuple containing the substring before the separator, the separator
itself, and the substring after the separator.  If the separator isn't found,
the first element of the tuple is the entire string and the other two elements
are empty.  @code{rpartition(sep)} also returns a 3-tuple but starts searching
from the end of the string; the @code{r} stands for 'reverse'.

几个例子:

@example
>>> ('http://www.python.org').partition('://')
('http', '://', 'www.python.org')
>>> ('file:/usr/share/doc/index.html').partition('://')
('file:/usr/share/doc/index.html', '@w{'}, '@w{'})
>>> (u'Subject: a quick question').partition(':')
(u'Subject', u':', u' a quick question')
>>> 'www.python.org'.rpartition('.')
('www.python', '.', 'org')
>>> 'www.python.org'.rpartition(':')
('@w{'}, '@w{'}, 'www.python.org')
@end example

(Implemented by Fredrik Lundh following a suggestion by Raymond Hettinger.)

@item 
The @code{startswith()} and @code{endswith()} methods of string types now accept
tuples of strings to check for.

@example
def is_image_file (filename):
    return filename.endswith(('.gif', '.jpg', '.tiff'))
@end example

(Implemented by Georg Brandl following a suggestion by Tom Lynn.)

@c RFE #1491485

@item 
The @ref{803,,min()} and @ref{804,,max()} built-in functions gained a @code{key} keyword
parameter analogous to the @code{key} argument for @code{sort()}.  This parameter
supplies a function that takes a single argument and is called for every value
in the list; @ref{803,,min()}/@ref{804,,max()} will return the element with the
smallest/largest return value from this function. For example, to find the
longest string in a list, you can do:

@example
L = ['medium', 'longest', 'short']
# Prints 'longest'
print max(L, key=len)
# Prints 'short', because lexicographically 'short' has the largest value
print max(L)
@end example

（由 Steven Bethard 和 Raymond Hettinger 贡献。）

@item 
Two new built-in functions, @ref{d7d,,any()} and @ref{d7e,,all()}, evaluate whether an
iterator contains any true or false values.  @ref{d7d,,any()} returns @ref{494,,True}
if any value returned by the iterator is true; otherwise it will return
@ref{380,,False}.  @ref{d7e,,all()} returns @ref{494,,True} only if all of the values
returned by the iterator evaluate as true. (Suggested by Guido van Rossum, and
implemented by Raymond Hettinger.)

@item 
The result of a class's @ref{339,,__hash__()} method can now be either a long
integer or a regular integer.  If a long integer is returned, the hash of that
value is taken.  In earlier versions the hash value was required to be a
regular integer, but in 2.5 the @ref{d7f,,id()} built-in was changed to always
return non-negative numbers, and users often seem to use @code{id(self)} in
@ref{339,,__hash__()} methods (though this is discouraged).

@c Bug #1536021

@item 
ASCII is now the default encoding for modules.  It's now  a syntax error if a
module contains string literals with 8-bit characters but doesn't have an
encoding declaration.  In Python 2.4 this triggered a warning, not a syntax
error.  See 
@geindex Python 提高建议; PEP 263
PEP 263@footnote{https://www.python.org/dev/peps/pep-0263}  for how to declare a module's encoding; for example, you
might add  a line like this near the top of the source file:

@example
# -*- coding: latin1 -*-
@end example

@item 
A new warning, @ref{d80,,UnicodeWarning}, is triggered when  you attempt to
compare a Unicode string and an 8-bit string  that can't be converted to Unicode
using the default ASCII encoding.   The result of the comparison is false:

@example
>>> chr(128) == unichr(128)   # Can't convert chr(128) to Unicode
__main__:1: UnicodeWarning: Unicode equal comparison failed
  to convert both arguments to Unicode - interpreting them
  as being unequal
False
>>> chr(127) == unichr(127)   # chr(127) can be converted
True
@end example

Previously this would raise a @ref{1fd,,UnicodeDecodeError} exception, but in 2.5
this could result in puzzling problems when accessing a dictionary.  If you
looked up @code{unichr(128)} and @code{chr(128)} was being used as a key, you'd get a
@ref{1fd,,UnicodeDecodeError} exception.  Other changes in 2.5 resulted in this
exception being raised instead of suppressed by the code in @code{dictobject.c}
that implements dictionaries.

Raising an exception for such a comparison is strictly correct, but the change
might have broken code, so instead  @ref{d80,,UnicodeWarning} was introduced.

（由 Marc-André Lemburg 实现。）

@item 
One error that Python programmers sometimes make is forgetting to include an
@code{__init__.py} module in a package directory. Debugging this mistake can be
confusing, and usually requires running Python with the @ref{d81,,-v} switch to
log all the paths searched. In Python 2.5, a new @ref{5d3,,ImportWarning} warning is
triggered when an import would have picked up a directory as a package but no
@code{__init__.py} was found.  This warning is silently ignored by default;
provide the @ref{40f,,-Wd} option when running the Python executable to display
the warning message. (Implemented by Thomas Wouters.)

@item 
The list of base classes in a class definition can now be empty.   As an
example, this is now legal:

@example
class C():
    pass
@end example

（由 Brett Cannon 实现。）
@end itemize

@c ======================================================================

@menu
* 交互解释器变更:: 
* 性能优化: 性能优化<10>. 

@end menu

@node 交互解释器变更,性能优化<10>,,其他语言特性修改<11>
@anchor{whatsnew/2 5 interactive}@anchor{d82}@anchor{whatsnew/2 5 interactive-interpreter-changes}@anchor{d83}
@subsubsection 交互解释器变更


In the interactive interpreter, @code{quit} and @code{exit}  have long been strings so
that new users get a somewhat helpful message when they try to quit:

@example
>>> quit
'Use Ctrl-D (i.e. EOF) to exit.'
@end example

In Python 2.5, @code{quit} and @code{exit} are now objects that still produce string
representations of themselves, but are also callable. Newbies who try @code{quit()}
or @code{exit()} will now exit the interpreter as they expect.  (Implemented by
Georg Brandl.)

The Python executable now accepts the standard long options  @ref{d84,,--help}
and @ref{5cc,,--version}; on Windows,  it also accepts the @ref{d85,,/?} option
for displaying a help message. (Implemented by Georg Brandl.)

@c ======================================================================

@node 性能优化<10>,,交互解释器变更,其他语言特性修改<11>
@anchor{whatsnew/2 5 optimizations}@anchor{d86}@anchor{whatsnew/2 5 opts}@anchor{d87}
@subsubsection 性能优化


Several of the optimizations were developed at the NeedForSpeed sprint, an event
held in Reykjavik, Iceland, from May 21--28 2006. The sprint focused on speed
enhancements to the CPython implementation and was funded by EWT LLC with local
support from CCP Games.  Those optimizations added at this sprint are specially
marked in the following list.


@itemize *

@item 
When they were introduced  in Python 2.4, the built-in @ref{b68,,set} and
@ref{be7,,frozenset} types were built on top of Python's dictionary type.   In 2.5
the internal data structure has been customized for implementing sets, and as a
result sets will use a third less memory and are somewhat faster. (Implemented
by Raymond Hettinger.)

@item 
The speed of some Unicode operations, such as finding substrings, string
splitting, and character map encoding and decoding, has been improved.
(Substring search and splitting improvements were added by Fredrik Lundh and
Andrew Dalke at the NeedForSpeed sprint. Character maps were improved by Walter
Dörwald and Martin von Löwis.)

@c Patch 1313939, 1359618

@item 
The @code{long(str, base)} function is now faster on long digit strings
because fewer intermediate results are calculated.  The peak is for strings of
around 800--1000 digits where  the function is 6 times faster. (Contributed by
Alan McIntyre and committed at the NeedForSpeed sprint.)

@c Patch 1442927

@item 
It's now illegal to mix iterating over a file  with @code{for line in file} and
calling  the file object's @code{read()}/@ref{de,,readline()}/@code{readlines()}
methods.  Iteration uses an internal buffer and the  @code{read*()} methods
don't use that buffer.   Instead they would return the data following the
buffer, causing the data to appear out of order.  Mixing iteration and these
methods will now trigger a @ref{1fb,,ValueError} from the @code{read*()} method.
(Implemented by Thomas Wouters.)

@c Patch 1397960

@item 
The @ref{f8,,struct} module now compiles structure format  strings into an
internal representation and caches this representation, yielding a 20% speedup.
(Contributed by Bob Ippolito at the NeedForSpeed sprint.)

@item 
The @ref{dd,,re} module got a 1 or 2% speedup by switching to  Python's allocator
functions instead of the system's  @code{malloc()} and @code{free()}.
(Contributed by Jack Diederich at the NeedForSpeed sprint.)

@item 
The code generator's peephole optimizer now performs simple constant folding
in expressions.  If you write something like @code{a = 2+3}, the code generator
will do the arithmetic and produce code corresponding to @code{a = 5}.  (Proposed
and implemented  by Raymond Hettinger.)

@item 
Function calls are now faster because code objects now keep  the most recently
finished frame (a "zombie frame") in an internal field of the code object,
reusing it the next time the code object is invoked.  (Original patch by Michael
Hudson, modified by Armin Rigo and Richard Jones; committed at the NeedForSpeed
sprint.)  Frame objects are also slightly smaller, which may improve cache
locality and reduce memory usage a bit.  (Contributed by Neal Norwitz.)

@c Patch 876206

@c Patch 1337051

@item 
Python's built-in exceptions are now new-style classes, a change that speeds
up instantiation considerably.  Exception handling in Python 2.5 is therefore
about 30% faster than in 2.4. (Contributed by Richard Jones, Georg Brandl and
Sean Reifschneider at the NeedForSpeed sprint.)

@item 
Importing now caches the paths tried, recording whether  they exist or not so
that the interpreter makes fewer  @code{open()} and @code{stat()} calls on
startup. (Contributed by Martin von Löwis and Georg Brandl.)

@c Patch 921466
@end itemize

@c ======================================================================

@node 新增，改进和删除的模块,构建和 C API 的改变<10>,其他语言特性修改<11>,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 modules}@anchor{d88}@anchor{whatsnew/2 5 new-improved-and-removed-modules}@anchor{d89}
@subsection 新增，改进和删除的模块


The standard library received many enhancements and bug fixes in Python 2.5.
Here's a partial list of the most notable changes, sorted alphabetically by
module name. Consult the @code{Misc/NEWS} file in the source tree for a more
complete list of changes, or look through the SVN logs for all the details.


@itemize *

@item 
The @ref{d,,audioop} module now supports the a-LAW encoding, and the code for
u-LAW encoding has been improved.  (Contributed by Lars Immisch.)

@item 
The @ref{1c,,codecs} module gained support for incremental codecs.  The
@code{codec.lookup()} function now returns a @code{CodecInfo} instance instead
of a tuple. @code{CodecInfo} instances behave like a 4-tuple to preserve
backward compatibility but also have the attributes @code{encode},
@code{decode}, @code{incrementalencoder}, @code{incrementaldecoder},
@code{streamwriter}, and @code{streamreader}.  Incremental codecs  can receive
input and produce output in multiple chunks; the output is the same as if the
entire input was fed to the non-incremental codec. See the @ref{1c,,codecs} module
documentation for details. (Designed and implemented by Walter Dörwald.)

@c Patch  1436130

@item 
The @ref{1e,,collections} module gained a new type, @code{defaultdict}, that
subclasses the standard @ref{1b8,,dict} type.  The new type mostly behaves like a
dictionary but constructs a default value when a key isn't present,
automatically adding it to the dictionary for the requested key value.

The first argument to @code{defaultdict}'s constructor is a factory function
that gets called whenever a key is requested but not found. This factory
function receives no arguments, so you can use built-in type constructors such
as @ref{262,,list()} or @ref{184,,int()}.  For example,  you can make an index of words
based on their initial letter like this:

@example
words = """Nel mezzo del cammin di nostra vita
mi ritrovai per una selva oscura
che la diritta via era smarrita""".lower().split()

index = defaultdict(list)

for w in words:
    init_letter = w[0]
    index[init_letter].append(w)
@end example

打印 @code{index} 导致以下输出:

@example
defaultdict(<type 'list'>, @{'c': ['cammin', 'che'], 'e': ['era'],
        'd': ['del', 'di', 'diritta'], 'm': ['mezzo', 'mi'],
        'l': ['la'], 'o': ['oscura'], 'n': ['nel', 'nostra'],
        'p': ['per'], 's': ['selva', 'smarrita'],
        'r': ['ritrovai'], 'u': ['una'], 'v': ['vita', 'via']@}
@end example

（由 Guido van Rossum 贡献。）

@item 
The @code{deque} double-ended queue type supplied by the @ref{1e,,collections}
module now has a @code{remove(value)} method that removes the first occurrence
of @emph{value} in the queue, raising @ref{1fb,,ValueError} if the value isn't found.
(Contributed by Raymond Hettinger.)

@item 
New module: The @ref{24,,contextlib} module contains helper functions for use
with the new '@ref{6e3,,with}' statement.  See section @ref{d70,,contextlib 模块}
for more about this module.

@item 
New module: The @ref{28,,cProfile} module is a C implementation of  the existing
@ref{d3,,profile} module that has much lower overhead. The module's interface is
the same as @ref{d3,,profile}: you run @code{cProfile.run('main()')} to profile a
function, can save profile data to a file, etc.  It's not yet known if the
Hotshot profiler, which is also written in C but doesn't match the
@ref{d3,,profile} module's interface, will continue to be maintained in future
versions of Python.  (Contributed by Armin Rigo.)

Also, the @ref{d4,,pstats} module for analyzing the data measured by the profiler
now supports directing the output to any file object by supplying a @emph{stream}
argument to the @code{Stats} constructor. (Contributed by Skip Montanaro.)

@item 
The @ref{2a,,csv} module, which parses files in comma-separated value format,
received several enhancements and a number of bugfixes.  You can now set the
maximum size in bytes of a field by calling the
@code{csv.field_size_limit(new_limit)} function; omitting the @emph{new_limit}
argument will return the currently-set limit.  The @code{reader} class now has
a @code{line_num} attribute that counts the number of physical lines read from
the source; records can span multiple physical lines, so @code{line_num} is not
the same as the number of records read.

The CSV parser is now stricter about multi-line quoted fields. Previously, if a
line ended within a quoted field without a terminating newline character, a
newline would be inserted into the returned field. This behavior caused problems
when reading files that contained carriage return characters within fields, so
the code was changed to return the field without inserting newlines. As a
consequence, if newlines embedded within fields are important, the input should
be split into lines in a manner that preserves the newline characters.

（由Skip Montanaro 和 Andrew McNamara 贡献。）

@item 
The @ref{194,,datetime} class in the @ref{31,,datetime}  module now has a
@code{strptime(string, format)}  method for parsing date strings, contributed
by Josh Spoerri. It uses the same format characters as @ref{d8a,,time.strptime()} and
@ref{b5e,,time.strftime()}:

@example
from datetime import datetime

ts = datetime.strptime('10:13:15 2006-03-07',
                       '%H:%M:%S %Y-%m-%d')
@end example

@item 
The @code{SequenceMatcher.get_matching_blocks()} method in the @ref{37,,difflib}
module now guarantees to return a minimal list of blocks describing matching
subsequences.  Previously, the algorithm would occasionally break a block of
matching elements into two list entries. (Enhancement by Tim Peters.)

@item 
The @ref{67,,doctest} module gained a @code{SKIP} option that keeps an example from
being executed at all.  This is intended for code snippets that are usage
examples intended for the reader and aren't actually test cases.

An @emph{encoding} parameter was added to the @code{testfile()} function and the
@code{DocFileSuite} class to specify the file's encoding.  This makes it
easier to use non-ASCII characters in  tests contained within a docstring.
(Contributed by Bjorn Tillenius.)

@c Patch 1080727

@item 
@ref{69,,email} 包已经升级到 4.0版 （由 Barry Warsaw 贡献）

@c XXX need to provide some more detail here

@geindex universal newlines; What's new

@item 
The @ref{80,,fileinput} module was made more flexible. Unicode filenames are now
supported, and a @emph{mode} parameter that defaults to @code{"r"} was added to the
@ref{c64,,input()} function to allow opening files in binary or @ref{5ef,,universal newlines} mode.  Another new parameter, @emph{openhook}, lets you use a function
other than @ref{4ea,,open()}  to open the input files.  Once you're iterating over
the set of files, the @code{FileInput} object's new @code{fileno()} returns
the file descriptor for the currently opened file. (Contributed by Georg
Brandl.)

@item 
In the @ref{86,,gc} module, the new @code{get_count()} function returns a 3-tuple
containing the current collection counts for the three GC generations.  This is
accounting information for the garbage collector; when these counts reach a
specified threshold, a garbage collection sweep will be made.  The existing
@ref{22e,,gc.collect()} function now takes an optional @emph{generation} argument of 0, 1,
or 2 to specify which generation to collect. (Contributed by Barry Warsaw.)

@item 
The @code{nsmallest()} and  @code{nlargest()} functions in the @ref{8e,,heapq}
module  now support a @code{key} keyword parameter similar to the one provided by
the @ref{803,,min()}/@ref{804,,max()} functions and the @code{sort()} methods.  For
example:

@example
>>> import heapq
>>> L = ["short", 'medium', 'longest', 'longer still']
>>> heapq.nsmallest(2, L)  # Return two lowest elements, lexicographically
['longer still', 'longest']
>>> heapq.nsmallest(2, L, key=len)   # Return two shortest elements
['short', 'medium']
@end example

（由 Raymond Hettinger 贡献。）

@item 
The @ref{39a,,itertools.islice()} function now accepts @code{None} for the start and
step arguments.  This makes it more compatible with the attributes of slice
objects, so that you can now write the following:

@example
s = slice(5)     # Create slice object
itertools.islice(iterable, s.start, s.stop, s.step)
@end example

（由 Raymond Hettinger 贡献。）

@item 
The @ref{4d5,,format()} function in the @ref{a9,,locale} module has been modified and
two new functions were added, @code{format_string()} and @code{currency()}.

The @ref{4d5,,format()} function's @emph{val} parameter could previously be a string as
long as no more than one %char specifier appeared; now the parameter must be
exactly one %char specifier with no surrounding text.  An optional @emph{monetary}
parameter was also added which, if @code{True}, will use the locale's rules for
formatting currency in placing a separator between groups of three digits.

To format strings with multiple %char specifiers, use the new
@code{format_string()} function that works like @ref{4d5,,format()} but also supports
mixing %char specifiers with arbitrary text.

A new @code{currency()} function was also added that formats a number according
to the current locale's settings.

（由Georg Brandl 贡献。）

@c Patch 1180296

@item 
The @ref{ae,,mailbox} module underwent a massive rewrite to add the capability to
modify mailboxes in addition to reading them.  A new set of classes that include
@code{mbox}, @code{MH}, and @code{Maildir} are used to read mailboxes, and
have an @code{add(message)} method to add messages, @code{remove(key)} to
remove messages, and @code{lock()}/@code{unlock()} to lock/unlock the mailbox.
The following example converts a maildir-format mailbox into an mbox-format
one:

@example
import mailbox

# 'factory=None' uses email.Message.Message as the class representing
# individual messages.
src = mailbox.Maildir('maildir', factory=None)
dest = mailbox.mbox('/tmp/mbox')

for msg in src:
    dest.add(msg)
@end example

(Contributed by Gregory K. Johnson.  Funding was provided by Google's 2005
Summer of Code.)

@item 
New module: the @ref{b5,,msilib} module allows creating Microsoft Installer
@code{.msi} files and CAB files.  Some support for reading the @code{.msi}
database is also included. (Contributed by Martin von Löwis.)

@item 
The @ref{bf,,nis} module now supports accessing domains other than the system
default domain by supplying a @emph{domain} argument to the @ref{d8b,,nis.match()} and
@ref{d8c,,nis.maps()} functions. (Contributed by Ben Bell.)

@item 
The @ref{c2,,operator} module's @code{itemgetter()}  and @code{attrgetter()}
functions now support multiple fields.   A call such as
@code{operator.attrgetter('a', 'b')} will return a function  that retrieves the
@code{a} and @code{b} attributes.  Combining  this new feature with the
@code{sort()} method's @code{key} parameter  lets you easily sort lists using
multiple fields. (Contributed by Raymond Hettinger.)

@item 
The @ref{c3,,optparse} module was updated to version 1.5.1 of the Optik library.
The @code{OptionParser} class gained an @code{epilog} attribute, a string
that will be printed after the help message, and a @code{destroy()} method to
break reference cycles created by the object. (Contributed by Greg Ward.)

@item 
The @ref{c4,,os} module underwent several changes.  The @code{stat_float_times}
variable now defaults to true, meaning that @ref{1f1,,os.stat()} will now return time
values as floats.  (This doesn't necessarily mean that @ref{1f1,,os.stat()} will
return times that are precise to fractions of a second; not all systems support
such precision.)

Constants named @ref{d8d,,os.SEEK_SET}, @ref{d8e,,os.SEEK_CUR}, and
@ref{d8f,,os.SEEK_END} have been added; these are the parameters to the
@ref{a59,,os.lseek()} function.  Two new constants for locking are
@ref{d90,,os.O_SHLOCK} and @ref{d91,,os.O_EXLOCK}.

Two new functions, @code{wait3()} and @code{wait4()}, were added.  They're similar
the @code{waitpid()} function which waits for a child process to exit and returns
a tuple of the process ID and its exit status, but @code{wait3()} and
@code{wait4()} return additional information.  @code{wait3()} doesn't take a
process ID as input, so it waits for any child process to exit and returns a
3-tuple of @emph{process-id}, @emph{exit-status}, @emph{resource-usage} as returned from the
@ref{d92,,resource.getrusage()} function. @code{wait4(pid)} does take a process ID.
(Contributed by Chad J. Schroeder.)

On FreeBSD, the @ref{1f1,,os.stat()} function now returns  times with nanosecond
resolution, and the returned object now has @code{st_gen} and
@code{st_birthtime}. The @code{st_flags} attribute is also available, if the
platform supports it. (Contributed by Antti Louko and  Diego Pettenò.)

@c (Patch 1180695, 1212117)

@item 
The Python debugger provided by the @ref{c9,,pdb} module can now store lists of
commands to execute when a breakpoint is reached and execution stops.  Once
breakpoint #1 has been created, enter @code{commands 1} and enter a series of
commands to be executed, finishing the list with @code{end}.  The command list can
include commands that resume execution, such as @code{continue} or @code{next}.
(Contributed by Grégoire Dooms.)

@c Patch 790710

@item 
The @ref{ca,,pickle} and @code{cPickle} modules no longer accept a return value
of @code{None} from the @ref{19b,,__reduce__()} method; the method must return a tuple
of arguments instead.  The ability to return @code{None} was deprecated in Python
2.4, so this completes the removal of the feature.

@item 
The @ref{cd,,pkgutil} module, containing various utility functions for finding
packages, was enhanced to support 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}'s import hooks and now also works for
packages stored in ZIP-format archives. (Contributed by Phillip J. Eby.)

@item 
The pybench benchmark suite by Marc-André Lemburg is now included in the
@code{Tools/pybench} directory.  The pybench suite is an improvement on the
commonly used @code{pystone.py} program because pybench provides a more
detailed measurement of the interpreter's speed.  It times particular operations
such as function calls, tuple slicing, method lookups, and numeric operations,
instead of performing many different operations and reducing the result to a
single number as @code{pystone.py} does.

@item 
The @code{pyexpat} module now uses version 2.0 of the Expat parser.
(Contributed by Trent Mick.)

@item 
The @ref{d11,,Queue} class provided by the @code{Queue} module gained two new
methods.  @code{join()} blocks until all items in the queue have been retrieved
and all processing work on the items  have been completed.  Worker threads call
the other new method,  @code{task_done()}, to signal that processing for an item
has been completed.  (Contributed by Raymond Hettinger.)

@item 
The old @code{regex} and @code{regsub} modules, which have been  deprecated
ever since Python 2.0, have finally been deleted.   Other deleted modules:
@code{statcache}, @code{tzparse}, @code{whrandom}.

@item 
Also deleted: the @code{lib-old} directory, which includes ancient modules
such as @code{dircmp} and @code{ni}, was removed.  @code{lib-old} wasn't on the
default @code{sys.path}, so unless your programs explicitly added the directory to
@code{sys.path}, this removal shouldn't affect your code.

@item 
The @ref{e1,,rlcompleter} module is no longer  dependent on importing the
@ref{de,,readline} module and therefore now works on non-Unix platforms. (Patch
from Robert Kiendl.)

@c Patch #1472854

@item 
The @code{SimpleXMLRPCServer} and @code{DocXMLRPCServer}  classes now have a
@code{rpc_paths} attribute that constrains XML-RPC operations to a limited set
of URL paths; the default is to allow only @code{'/'} and @code{'/RPC2'}.  Setting
@code{rpc_paths} to @code{None} or an empty tuple disables  this path checking.

@c Bug #1473048

@item 
The @ref{ef,,socket} module now supports @code{AF_NETLINK} sockets on Linux,
thanks to a patch from Philippe Biondi.   Netlink sockets are a Linux-specific
mechanism for communications between a user-space process and kernel code; an
introductory  article about them is at @indicateurl{https://www.linuxjournal.com/article/7356}.
In Python code, netlink addresses are represented as a tuple of 2 integers,
@code{(pid, group_mask)}.

Two new methods on socket objects, @code{recv_into(buffer)} and
@code{recvfrom_into(buffer)}, store the received data in an object  that
supports the buffer protocol instead of returning the data as a string.  This
means you can put the data directly into an array or a memory-mapped file.

Socket objects also gained @code{getfamily()}, @code{gettype()}, and
@code{getproto()} accessor methods to retrieve the family, type, and protocol
values for the socket.

@item 
New module: the @ref{f1,,spwd} module provides functions for accessing the shadow
password database on systems that support  shadow passwords.

@item 
The @ref{f8,,struct} is now faster because it  compiles format strings into
@code{Struct} objects with @code{pack()} and @code{unpack()} methods.  This is
similar to how the @ref{dd,,re} module lets you create compiled regular expression
objects.  You can still use the module-level  @code{pack()} and @code{unpack()}
functions; they'll create  @code{Struct} objects and cache them.  Or you can
use  @code{Struct} instances directly:

@example
s = struct.Struct('ih3s')

data = s.pack(1972, 187, 'abc')
year, number, name = s.unpack(data)
@end example

You can also pack and unpack data to and from buffer objects directly using the
@code{pack_into(buffer, offset, v1, v2, ...)} and @code{unpack_from(buffer,
offset)} methods.  This lets you store data directly into an array or a
memory-mapped file.

(@code{Struct} objects were implemented by Bob Ippolito at the NeedForSpeed
sprint.  Support for buffer objects was added by Martin Blais, also at the
NeedForSpeed sprint.)

@item 
The Python developers switched from CVS to Subversion during the 2.5
development process.  Information about the exact build version is available as
the @code{sys.subversion} variable, a 3-tuple of @code{(interpreter-name, branch-name,
revision-range)}.  For example, at the time of writing my copy of 2.5 was
reporting @code{('CPython', 'trunk', '45313:45315')}.

This information is also available to C extensions via the
@ref{d93,,Py_GetBuildInfo()} function that returns a  string of build information
like this: @code{"trunk:45355:45356M, Apr 13 2006, 07:42:19"}.   (Contributed by
Barry Warsaw.)

@item 
Another new function, @ref{d94,,sys._current_frames()}, returns the current stack
frames for all running threads as a dictionary mapping thread identifiers to the
topmost stack frame currently active in that thread at the time the function is
called.  (Contributed by Tim Peters.)

@item 
The @code{TarFile} class in the @ref{101,,tarfile} module now has an
@code{extractall()} method that extracts all members from the archive into the
current working directory.  It's also possible to set a different directory as
the extraction target, and to unpack only a subset of the archive's members.

The compression used for a tarfile opened in stream mode can now be autodetected
using the mode @code{'r|*'}. (Contributed by Lars Gustäbel.)

@c patch 918101

@item 
The @ref{109,,threading} module now lets you set the stack size used when new
threads are created. The @code{stack_size([*size*])} function returns the
currently configured stack size, and supplying the optional @emph{size} parameter
sets a new value.  Not all platforms support changing the stack size, but
Windows, POSIX threading, and OS/2 all do. (Contributed by Andrew MacIntyre.)

@c Patch 1454481

@item 
The @ref{11a,,unicodedata} module has been updated to use version 4.1.0 of the
Unicode character database.  Version 3.2.0 is required  by some specifications,
so it's still available as  @ref{d95,,unicodedata.ucd_3_2_0}.

@item 
New module: the  @ref{124,,uuid} module generates  universally unique identifiers
(UUIDs) according to 
@geindex RFC; RFC 4122
RFC 4122@footnote{https://tools.ietf.org/html/rfc4122.html}.  The RFC defines several different UUID
versions that are generated from a starting string, from system properties, or
purely randomly.  This module contains a @code{UUID} class and  functions
named @code{uuid1()}, @code{uuid3()}, @code{uuid4()},  and  @code{uuid5()} to
generate different versions of UUID.  (Version 2 UUIDs  are not specified in
@geindex RFC; RFC 4122
RFC 4122@footnote{https://tools.ietf.org/html/rfc4122.html} and are not supported by this module.)

@example
>>> import uuid
>>> # make a UUID based on the host ID and current time
>>> uuid.uuid1()
UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

>>> # make a UUID using an MD5 hash of a namespace UUID and a name
>>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')

>>> # make a random UUID
>>> uuid.uuid4()
UUID('16fd2706-8baf-433b-82eb-8c7fada847da')

>>> # make a UUID using a SHA-1 hash of a namespace UUID and a name
>>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')
@end example

（由 Ka-Ping Yee 贡献。）

@item 
The @ref{128,,weakref} module's @code{WeakKeyDictionary} and
@code{WeakValueDictionary} types gained new methods for iterating over the
weak references contained in the dictionary.  @code{iterkeyrefs()} and
@code{keyrefs()} methods were added to @code{WeakKeyDictionary}, and
@code{itervaluerefs()} and @code{valuerefs()} were added to
@code{WeakValueDictionary}.  (Contributed by Fred L. Drake, Jr.)

@item 
The @ref{129,,webbrowser} module received a number of enhancements. It's now
usable as a script with @code{python -m webbrowser}, taking a URL as the argument;
there are a number of switches  to control the behaviour (@code{-n} for a new
browser window,  @code{-t} for a new tab).  New module-level functions,
@code{open_new()} and @code{open_new_tab()}, were added  to support this.  The
module's @ref{4ea,,open()} function supports an additional feature, an @emph{autoraise}
parameter that signals whether to raise the open window when possible. A number
of additional browsers were added to the supported list such as Firefox, Opera,
Konqueror, and elinks.  (Contributed by Oleg Broytmann and Georg Brandl.)

@c Patch #754022

@item 
The @code{xmlrpclib} module now supports returning  @ref{194,,datetime} objects
for the XML-RPC date type.  Supply  @code{use_datetime=True} to the @code{loads()}
function or the @code{Unmarshaller} class to enable this feature. (Contributed
by Skip Montanaro.)

@c Patch 1120353

@item 
The @ref{142,,zipfile} module now supports the ZIP64 version of the  format,
meaning that a .zip archive can now be larger than 4 GiB and can contain
individual files larger than 4 GiB.  (Contributed by Ronald Oussoren.)

@c Patch 1446489

@item 
The @ref{144,,zlib} module's @code{Compress} and @code{Decompress} objects now
support a @ref{26,,copy()} method that makes a copy of the  object's internal state
and returns a new  @code{Compress} or @code{Decompress} object.
(Contributed by Chris AtLee.)

@c Patch 1435422
@end itemize

@c ======================================================================

@menu
* ctypes 包:: 
* ElementTree 包:: 
* hashlib 包:: 
* sqlite3 包:: 
* wsgiref 包:: 

@end menu

@node ctypes 包,ElementTree 包,,新增，改进和删除的模块
@anchor{whatsnew/2 5 module-ctypes}@anchor{d96}@anchor{whatsnew/2 5 the-ctypes-package}@anchor{d97}
@subsubsection ctypes 包


The @ref{2b,,ctypes} package, written by Thomas Heller, has been added  to the
standard library.  @ref{2b,,ctypes} lets you call arbitrary functions  in shared
libraries or DLLs.  Long-time users may remember the @code{dl} module, which
provides functions for loading shared libraries and calling functions in them.
The @ref{2b,,ctypes} package is much fancier.

To load a shared library or DLL, you must create an instance of the
@code{CDLL} class and provide the name or path of the shared library or DLL.
Once that's done, you can call arbitrary functions by accessing them as
attributes of the @code{CDLL} object.

@example
import ctypes

libc = ctypes.CDLL('libc.so.6')
result = libc.printf("Line of output\n")
@end example

Type constructors for the various C types are provided: @code{c_int()},
@code{c_float()}, @code{c_double()}, @code{c_char_p()} (equivalent to @code{char
*}), and so forth.  Unlike Python's types, the C versions are all mutable; you
can assign to their @code{value} attribute to change the wrapped value.  Python
integers and strings will be automatically converted to the corresponding C
types, but for other types you  must call the correct type constructor.  (And I
mean @emph{must};  getting it wrong will often result in the interpreter crashing
with a segmentation fault.)

You shouldn't use @code{c_char_p()} with a Python string when the C function will
be modifying the memory area, because Python strings are  supposed to be
immutable; breaking this rule will cause puzzling bugs.  When you need a
modifiable memory area, use @code{create_string_buffer()}:

@example
s = "this is a string"
buf = ctypes.create_string_buffer(s)
libc.strfry(buf)
@end example

C functions are assumed to return integers, but you can set the @code{restype}
attribute of the function object to  change this:

@example
>>> libc.atof('2.71828')
-1783957616
>>> libc.atof.restype = ctypes.c_double
>>> libc.atof('2.71828')
2.71828
@end example

@ref{2b,,ctypes} also provides a wrapper for Python's C API  as the
@code{ctypes.pythonapi} object.  This object does @emph{not}  release the global
interpreter lock before calling a function, because the lock must be held when
calling into the interpreter's code.   There's a @code{py_object()} type
constructor that will create a  @ref{4b5,,PyObject *} pointer.  A simple usage:

@example
import ctypes

d = @{@}
ctypes.pythonapi.PyObject_SetItem(ctypes.py_object(d),
          ctypes.py_object("abc"),  ctypes.py_object(1))
# d is now @{'abc', 1@}.
@end example

Don't forget to use @code{py_object()}; if it's omitted you end  up with a
segmentation fault.

@ref{2b,,ctypes} has been around for a while, but people still write  and
distribution hand-coded extension modules because you can't rely on
@ref{2b,,ctypes} being present. Perhaps developers will begin to write  Python
wrappers atop a library accessed through @ref{2b,,ctypes} instead of extension
modules, now that @ref{2b,,ctypes} is included with core Python.


@subsubheading 参见



@table @asis

@item @indicateurl{http://starship.python.net/crew/theller/ctypes/}

ctypes的主页，含教程， 参考和常见问题解答。
@end table

@ref{2b,,ctypes} 模块的文档。


@c ======================================================================

@node ElementTree 包,hashlib 包,ctypes 包,新增，改进和删除的模块
@anchor{whatsnew/2 5 module-etree}@anchor{d98}@anchor{whatsnew/2 5 the-elementtree-package}@anchor{d99}
@subsubsection ElementTree 包


A subset of Fredrik Lundh's ElementTree library for processing XML has been
added to the standard library as @code{xml.etree}.  The available modules are
@code{ElementTree}, @code{ElementPath}, and @code{ElementInclude} from
ElementTree 1.2.6.    The @code{cElementTree} accelerator module is also
included.

The rest of this section will provide a brief overview of using ElementTree.
Full documentation for ElementTree is available at
@indicateurl{http://effbot.org/zone/element-index.htm}.

ElementTree represents an XML document as a tree of element nodes. The text
content of the document is stored as the @code{text} and @code{tail}
attributes of  (This is one of the major differences between ElementTree and
the Document Object Model; in the DOM there are many different types of node,
including @code{TextNode}.)

The most commonly used parsing function is @code{parse()}, that takes either a
string (assumed to contain a filename) or a file-like object and returns an
@code{ElementTree} instance:

@example
from xml.etree import ElementTree as ET

tree = ET.parse('ex-1.xml')

feed = urllib.urlopen(
          'http://planet.python.org/rss10.xml')
tree = ET.parse(feed)
@end example

Once you have an @code{ElementTree} instance, you can call its @code{getroot()}
method to get the root @code{Element} node.

There's also an @code{XML()} function that takes a string literal and returns an
@code{Element} node (not an @code{ElementTree}).   This function provides a
tidy way to incorporate XML fragments, approaching the convenience of an XML
literal:

@example
svg = ET.XML("""<svg width="10px" version="1.0">
             </svg>""")
svg.set('height', '320px')
svg.append(elem1)
@end example

Each XML element supports some dictionary-like and some list-like access
methods.  Dictionary-like operations are used to access attribute values, and
list-like operations are used to access child nodes.


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@item

@code{elem[n]}

@tab

返回第n个子元素

@item

@code{elem[m:n]}

@tab

返回第m至第n个子元素的列表。

@item

@code{len(elem)}

@tab

返回子元素的个数

@item

@code{list(elem)}

@tab

返回子元素的列表

@item

@code{elem.append(elem2)}

@tab

将 @emph{elem2} 添加为子级。

@item

@code{elem.insert(index, elem2)}

@tab

在指定位置插入 @emph{elem2} 。

@item

@code{del elem[n]}

@tab

删除第n个子元素

@item

@code{elem.keys()}

@tab

返回属性名称的列表。

@item

@code{elem.get(name)}

@tab

返回 @emph{name} 属性的值。

@item

@code{elem.set(name, value)}

@tab

为 @emph{name} 属性设置新值

@item

@code{elem.attrib}

@tab

检索包含属性的字典。

@item

@code{del elem.attrib[name]}

@tab

删除 元素 @emph{name} 的属性

@end multitable


Comments and processing instructions are also represented as @code{Element}
nodes.  To check if a node is a comment or processing instructions:

@example
if elem.tag is ET.Comment:
    ...
elif elem.tag is ET.ProcessingInstruction:
    ...
@end example

To generate XML output, you should call the @code{ElementTree.write()} method.
Like @code{parse()}, it can take either a string or a file-like object:

@example
# Encoding is US-ASCII
tree.write('output.xml')

# Encoding is UTF-8
f = open('output.xml', 'w')
tree.write(f, encoding='utf-8')
@end example

(Caution: the default encoding used for output is ASCII.  For general XML work,
where an element's name may contain arbitrary Unicode characters, ASCII isn't a
very useful encoding because it will raise an exception if an element's name
contains any characters with values greater than 127.  Therefore, it's best to
specify a different encoding such as UTF-8 that can handle any Unicode
character.)

This section is only a partial description of the ElementTree interfaces. Please
read the package's official documentation for more details.


@subsubheading 参见



@table @asis

@item @indicateurl{http://effbot.org/zone/element-index.htm}

ElementTree 的官方文档
@end table


@c ======================================================================

@node hashlib 包,sqlite3 包,ElementTree 包,新增，改进和删除的模块
@anchor{whatsnew/2 5 module-hashlib}@anchor{d9a}@anchor{whatsnew/2 5 the-hashlib-package}@anchor{d9b}
@subsubsection hashlib 包


A new @ref{8d,,hashlib} module, written by Gregory P. Smith,  has been added to
replace the @code{md5} and @code{sha} modules.  @ref{8d,,hashlib} adds support for
additional secure hashes (SHA-224, SHA-256, SHA-384, and SHA-512). When
available, the module uses OpenSSL for fast platform optimized implementations
of algorithms.

The old @code{md5} and @code{sha} modules still exist as wrappers around hashlib
to preserve backwards compatibility.  The new module's interface is very close
to that of the old modules, but not identical. The most significant difference
is that the constructor functions for creating new hashing objects are named
differently.

@example
# Old versions
h = md5.md5()
h = md5.new()

# New version
h = hashlib.md5()

# Old versions
h = sha.sha()
h = sha.new()

# New version
h = hashlib.sha1()

# Hash that weren't previously available
h = hashlib.sha224()
h = hashlib.sha256()
h = hashlib.sha384()
h = hashlib.sha512()

# Alternative form
h = hashlib.new('md5')          # Provide algorithm as a string
@end example

Once a hash object has been created, its methods are the same as before:
@code{update(string)} hashes the specified string into the  current digest
state, @code{digest()} and @code{hexdigest()} return the digest value as a binary
string or a string of hex digits, and @ref{26,,copy()} returns a new hashing object
with the same digest state.


@subsubheading 参见


@ref{8d,,hashlib} 模块的文档。


@c ======================================================================

@node sqlite3 包,wsgiref 包,hashlib 包,新增，改进和删除的模块
@anchor{whatsnew/2 5 module-sqlite}@anchor{d9c}@anchor{whatsnew/2 5 the-sqlite3-package}@anchor{d9d}
@subsubsection sqlite3 包


The pysqlite module (@indicateurl{http://www.pysqlite.org}), a wrapper for the SQLite embedded
database, has been added to the standard library under the package name
@ref{f2,,sqlite3}.

SQLite 是一个C语言库，它可以提供一种轻量级的基于磁盘的数据库，这种数据库不需要独立的服务器进程，也允许需要使用一种非标准的 SQL 查询语言来访问它。一些应用程序可以使用 SQLite 作为内部数据存储。可以用它来创建一个应用程序原型，然后再迁移到更大的数据库，比如 PostgreSQL 或 Oracle。

pysqlite was written by Gerhard Häring and provides a SQL interface compliant
with the DB-API 2.0 specification described by 
@geindex Python 提高建议; PEP 249
PEP 249@footnote{https://www.python.org/dev/peps/pep-0249}.

If you're compiling the Python source yourself, note that the source tree
doesn't include the SQLite code, only the wrapper module. You'll need to have
the SQLite libraries and headers installed before compiling Python, and the
build process will compile the module when the necessary headers are available.

To use the module, you must first create a @code{Connection} object that
represents the database.  Here the data will be stored in the
@code{/tmp/example} file:

@example
conn = sqlite3.connect('/tmp/example')
@end example

你也可以使用 @code{:memory:} 来创建一个内存中的数据库

Once you have a @code{Connection}, you can create a @code{Cursor}  object
and call its @code{execute()} method to perform SQL commands:

@example
c = conn.cursor()

# Create table
c.execute('@w{'}'create table stocks
(date text, trans text, symbol text,
 qty real, price real)'@w{'}')

# Insert a row of data
c.execute("""insert into stocks
          values ('2006-01-05','BUY','RHAT',100,35.14)""")
@end example

Usually your SQL operations will need to use values from Python variables.  You
shouldn't assemble your query using Python's string operations because doing so
is insecure; it makes your program vulnerable to an SQL injection attack.

Instead, use the DB-API's parameter substitution.  Put @code{?} as a placeholder
wherever you want to use a value, and then provide a tuple of values as the
second argument to the cursor's @code{execute()} method.  (Other database modules
may use a different placeholder, such as @code{%s} or @code{:1}.) For example:

@example
# Never do this -- insecure!
symbol = 'IBM'
c.execute("... where symbol = '%s'" % symbol)

# Do this instead
t = (symbol,)
c.execute('select * from stocks where symbol=?', t)

# Larger example
for t in (('2006-03-28', 'BUY', 'IBM', 1000, 45.00),
          ('2006-04-05', 'BUY', 'MSOFT', 1000, 72.00),
          ('2006-04-06', 'SELL', 'IBM', 500, 53.00),
         ):
    c.execute('insert into stocks values (?,?,?,?,?)', t)
@end example

To retrieve data after executing a SELECT statement, you can either  treat the
cursor as an iterator, call the cursor's @code{fetchone()} method to retrieve a
single matching row,  or call @code{fetchall()} to get a list of the matching
rows.

下面是一个使用迭代器形式的例子：

@example
>>> c = conn.cursor()
>>> c.execute('select * from stocks order by price')
>>> for row in c:
...    print row
...
(u'2006-01-05', u'BUY', u'RHAT', 100, 35.140000000000001)
(u'2006-03-28', u'BUY', u'IBM', 1000, 45.0)
(u'2006-04-06', u'SELL', u'IBM', 500, 53.0)
(u'2006-04-05', u'BUY', u'MSOFT', 1000, 72.0)
>>>
@end example

For more information about the SQL dialect supported by SQLite, see
@indicateurl{https://www.sqlite.org}.


@subsubheading 参见



@table @asis

@item @indicateurl{http://www.pysqlite.org}

pysqlite 的主页

@item @indicateurl{https://www.sqlite.org}

SQLite的主页；它的文档详细描述了它所支持的 SQL 方言的语法和可用的数据类型。
@end table

@ref{f2,,sqlite3} 模块的文档。


@table @asis

@geindex Python 提高建议; PEP 249

@item PEP 249@footnote{https://www.python.org/dev/peps/pep-0249} - DB-API 2.0 规范

PEP 由 Marc-André Lemburg 撰写。
@end table


@c ======================================================================

@node wsgiref 包,,sqlite3 包,新增，改进和删除的模块
@anchor{whatsnew/2 5 module-wsgiref}@anchor{d9e}@anchor{whatsnew/2 5 the-wsgiref-package}@anchor{d9f}
@subsubsection wsgiref 包


The Web Server Gateway Interface (WSGI) v1.0 defines a standard interface
between web servers and Python web applications and is described in 
@geindex Python 提高建议; PEP 333
PEP 333@footnote{https://www.python.org/dev/peps/pep-0333}.
The @ref{12c,,wsgiref} package is a reference implementation of the WSGI
specification.

@c XXX should this be in a :pep:`333` section instead?

The package includes a basic HTTP server that will run a WSGI application; this
server is useful for debugging but isn't intended for  production use.  Setting
up a server takes only a few lines of code:

@example
from wsgiref import simple_server

wsgi_app = ...

host = '@w{'}
port = 8000
httpd = simple_server.make_server(host, port, wsgi_app)
httpd.serve_forever()
@end example

@c XXX discuss structure of WSGI applications?

@c XXX provide an example using Django or some other framework?


@subsubheading 参见



@table @asis

@item @indicateurl{http://www.wsgi.org}

WSGI相关资源的核心网站。

@geindex Python 提高建议; PEP 333

@item PEP 333@footnote{https://www.python.org/dev/peps/pep-0333} - Python Web服务器网关接口 v1.0

PEP 由 Phillip J. Eby 撰写
@end table


@c ======================================================================

@node 构建和 C API 的改变<10>,移植到Python 2 5,新增，改进和删除的模块,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 build-and-c-api-changes}@anchor{da0}@anchor{whatsnew/2 5 build-api}@anchor{da1}
@subsection 构建和 C API 的改变


Changes to Python's build process and to the C API include:


@itemize *

@item 
The Python source tree was converted from CVS to Subversion,  in a complex
migration procedure that was supervised and flawlessly carried out by Martin von
Löwis.  The procedure was developed as 
@geindex Python 提高建议; PEP 347
PEP 347@footnote{https://www.python.org/dev/peps/pep-0347}.

@item 
Coverity, a company that markets a source code analysis tool called Prevent,
provided the results of their examination of the Python source code.  The
analysis found about 60 bugs that  were quickly fixed.  Many of the bugs were
refcounting problems, often occurring in error-handling code.  See
@indicateurl{https://scan.coverity.com} for the statistics.

@item 
The largest change to the C API came from 
@geindex Python 提高建议; PEP 353
PEP 353@footnote{https://www.python.org/dev/peps/pep-0353}, which modifies the
interpreter to use a @code{Py_ssize_t} type definition instead of
@code{int}.  See the earlier section @ref{d75,,PEP 353; 使用ssize_t作为索引类型} for a discussion of this
change.

@item 
The design of the bytecode compiler has changed a great deal,  no longer
generating bytecode by traversing the parse tree.  Instead the parse tree is
converted to an abstract syntax tree (or AST), and it is  the abstract syntax
tree that's traversed to produce the bytecode.

It's possible for Python code to obtain AST objects by using the
@ref{1b4,,compile()} built-in and specifying @code{_ast.PyCF_ONLY_AST} as the value of
the  @emph{flags} parameter:

@example
from _ast import PyCF_ONLY_AST
ast = compile("""a=0
for i in range(10):
    a += i
""", "<string>", 'exec', PyCF_ONLY_AST)

assignment = ast.body[0]
for_loop = ast.body[1]
@end example

No official documentation has been written for the AST code yet, but 
@geindex Python 提高建议; PEP 339
PEP 339@footnote{https://www.python.org/dev/peps/pep-0339}
discusses the design.  To start learning about the code, read the definition of
the various AST nodes in @code{Parser/Python.asdl}.  A Python script reads this
file and generates a set of C structure definitions in
@code{Include/Python-ast.h}.  The @code{PyParser_ASTFromString()} and
@code{PyParser_ASTFromFile()}, defined in @code{Include/pythonrun.h}, take
Python source as input and return the root of an AST representing the contents.
This AST can then be turned into a code object by @code{PyAST_Compile()}.  For
more information, read the source code, and then ask questions on python-dev.

The AST code was developed under Jeremy Hylton's management, and implemented by
(in alphabetical order) Brett Cannon, Nick Coghlan, Grant Edwards, John
Ehresman, Kurt Kaiser, Neal Norwitz, Tim Peters, Armin Rigo, and Neil
Schemenauer, plus the participants in a number of AST sprints at conferences
such as PyCon.

@c List of names taken from Jeremy's python-dev post at

@c https://mail.python.org/pipermail/python-dev/2005-October/057500.html

@item 
Evan Jones's patch to obmalloc, first described in a talk at PyCon DC 2005,
was applied.  Python 2.4 allocated small objects in 256K-sized arenas, but never
freed arenas.  With this patch, Python will free arenas when they're empty.  The
net effect is that on some platforms, when you allocate many objects, Python's
memory usage may actually drop when you delete them and the memory may be
returned to the operating system.  (Implemented by Evan Jones, and reworked by
Tim Peters.)

Note that this change means extension modules must be more careful when
allocating memory.  Python's API has many different functions for allocating
memory that are grouped into families.  For example, @ref{4ff,,PyMem_Malloc()},
@ref{969,,PyMem_Realloc()}, and @ref{da2,,PyMem_Free()} are one family that allocates
raw memory, while @ref{502,,PyObject_Malloc()}, @ref{da3,,PyObject_Realloc()}, and
@ref{4fe,,PyObject_Free()} are another family that's supposed to be used for
creating Python objects.

Previously these different families all reduced to the platform's
@code{malloc()} and @code{free()} functions.  This meant  it didn't matter if
you got things wrong and allocated memory with the @code{PyMem()} function but
freed it with the @ref{4b5,,PyObject()} function.  With 2.5's changes to obmalloc,
these families now do different things and mismatches will probably result in a
segfault.  You should carefully test your C extension modules with Python 2.5.

@item 
The built-in set types now have an official C API.  Call @ref{da4,,PySet_New()}
and @ref{da5,,PyFrozenSet_New()} to create a new set, @ref{da6,,PySet_Add()} and
@ref{da7,,PySet_Discard()} to add and remove elements, and @ref{da8,,PySet_Contains()}
and @ref{da9,,PySet_Size()} to examine the set's state. (Contributed by Raymond
Hettinger.)

@item 
C code can now obtain information about the exact revision of the Python
interpreter by calling the  @ref{d93,,Py_GetBuildInfo()} function that returns a
string of build information like this: @code{"trunk:45355:45356M, Apr 13 2006,
07:42:19"}.   (Contributed by Barry Warsaw.)

@item 
Two new macros can be used to indicate C functions that are local to the
current file so that a faster calling convention can be used.
@code{Py_LOCAL(type)} declares the function as returning a value of the
specified @emph{type} and uses a fast-calling qualifier.
@code{Py_LOCAL_INLINE(type)} does the same thing and also requests the
function be inlined.  If @code{PY_LOCAL_AGGRESSIVE()} is defined before
@code{python.h} is included, a set of more aggressive optimizations are enabled
for the module; you should benchmark the results to find out if these
optimizations actually make the code faster.  (Contributed by Fredrik Lundh at
the NeedForSpeed sprint.)

@item 
@code{PyErr_NewException(name, base, dict)} can now accept a tuple of base
classes as its @emph{base} argument.  (Contributed by Georg Brandl.)

@item 
The @code{PyErr_Warn()} function for issuing warnings is now deprecated in
favour of @code{PyErr_WarnEx(category, message, stacklevel)} which lets you
specify the number of stack frames separating this function and the caller.  A
@emph{stacklevel} of 1 is the function calling @ref{daa,,PyErr_WarnEx()}, 2 is the
function above that, and so forth.  (Added by Neal Norwitz.)

@item 
The CPython interpreter is still written in C, but  the code can now be
compiled with a C++ compiler without errors.   (Implemented by Anthony Baxter,
Martin von Löwis, Skip Montanaro.)

@item 
The @code{PyRange_New()} function was removed.  It was never documented, never
used in the core code, and had dangerously lax error checking.  In the unlikely
case that your extensions were using it, you can replace it by something like
the following:

@example
range = PyObject_CallFunction((PyObject*) &PyRange_Type, "lll",
                              start, stop, step);
@end example
@end itemize

@c ======================================================================

@menu
* Port-Specific Changes:: 

@end menu

@node Port-Specific Changes,,,构建和 C API 的改变<10>
@anchor{whatsnew/2 5 port-specific-changes}@anchor{dab}@anchor{whatsnew/2 5 ports}@anchor{dac}
@subsubsection Port-Specific Changes



@itemize *

@item 
MacOS X (10.3 and higher): dynamic loading of modules now uses the
@code{dlopen()} function instead of MacOS-specific functions.

@item 
MacOS X: an @code{--enable-universalsdk} switch was added to the
@code{configure} script that compiles the interpreter as a universal binary
able to run on both PowerPC and Intel processors. (Contributed by Ronald
Oussoren; bpo-2573@footnote{https://bugs.python.org/issue2573}.)

@item 
Windows: @code{.dll} is no longer supported as a filename extension for
extension modules.  @code{.pyd} is now the only filename extension that will be
searched for.
@end itemize

@c ======================================================================

@node 移植到Python 2 5,致谢<3>,构建和 C API 的改变<10>,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 porting}@anchor{dad}@anchor{whatsnew/2 5 porting-to-python-2-5}@anchor{dae}
@subsection 移植到Python 2.5


This section lists previously described changes that may require changes to your
code:


@itemize *

@item 
ASCII is now the default encoding for modules.  It's now  a syntax error if a
module contains string literals with 8-bit characters but doesn't have an
encoding declaration.  In Python 2.4 this triggered a warning, not a syntax
error.

@item 
Previously, the @code{gi_frame} attribute of a generator was always a frame
object.  Because of the 
@geindex Python 提高建议; PEP 342
PEP 342@footnote{https://www.python.org/dev/peps/pep-0342} changes described in section @ref{d5f,,PEP 342; 生成器的新特性},
it's now possible for @code{gi_frame} to be @code{None}.

@item 
A new warning, @ref{d80,,UnicodeWarning}, is triggered when  you attempt to
compare a Unicode string and an 8-bit string that can't be converted to Unicode
using the default ASCII encoding.  Previously such comparisons would raise a
@ref{1fd,,UnicodeDecodeError} exception.

@item 
Library: the @ref{2a,,csv} module is now stricter about multi-line quoted fields.
If your files contain newlines embedded within fields, the input should be split
into lines in a manner which preserves the newline characters.

@item 
Library: the @ref{a9,,locale} module's  @ref{4d5,,format()} function's would
previously  accept any string as long as no more than one %char specifier
appeared.  In Python 2.5, the argument must be exactly one %char specifier with
no surrounding text.

@item 
Library: The @ref{ca,,pickle} and @code{cPickle} modules no longer accept a
return value of @code{None} from the @ref{19b,,__reduce__()} method; the method must
return a tuple of arguments instead.  The modules also no longer accept the
deprecated @emph{bin} keyword parameter.

@item 
Library: The @code{SimpleXMLRPCServer} and @code{DocXMLRPCServer}  classes now
have a @code{rpc_paths} attribute that constrains XML-RPC operations to a
limited set of URL paths; the default is to allow only @code{'/'} and @code{'/RPC2'}.
Setting  @code{rpc_paths} to @code{None} or an empty tuple disables  this path
checking.

@item 
C API: Many functions now use @code{Py_ssize_t}  instead of @code{int} to
allow processing more data on 64-bit machines.  Extension code may need to make
the same change to avoid warnings and to support 64-bit machines.  See the
earlier section @ref{d75,,PEP 353; 使用ssize_t作为索引类型} for a discussion of this change.

@item 
C API:  The obmalloc changes mean that  you must be careful to not mix usage
of the @code{PyMem_*()} and @code{PyObject_*()} families of functions. Memory
allocated with  one family's @code{*_Malloc()} must be  freed with the
corresponding family's @code{*_Free()} function.
@end itemize

@c ======================================================================

@node 致谢<3>,,移植到Python 2 5,Python 2 5 有什么新变化
@anchor{whatsnew/2 5 acknowledgements}@anchor{daf}
@subsection 致谢


作者感谢以下人员对本文各种草稿给予的建议，更正和协助： Georg Brandl, Nick Coghlan, Phillip J. Eby, Lars Gustäbel, Raymond Hettinger, Ralf W. Grosse-Kunstleve, Kent Johnson, Iain Lowe, Martin von Löwis, Fredrik Lundh, Andrew McNamara, Skip Montanaro, Gustavo Niemeyer, Paul Prescod, James Pryor, Mike Rovner, Scott Weikart, Barry Warsaw, Thomas Wouters.

@node Python 2 4 有什么新变化,Python 2 3 有什么新变化,Python 2 5 有什么新变化,Python的新变化
@anchor{whatsnew/2 4 doc}@anchor{db0}@anchor{whatsnew/2 4 what-s-new-in-python-2-4}@anchor{db1}
@section Python 2.4 有什么新变化


@*作者: 
A.M. Kuchling


@c $Id: whatsnew24.tex 54632 2007-03-31 11:59:54Z georg.brandl $

@c Don't write extensive text for new sections; I'll do that.

@c Feel free to add commented-out reminders of things that need

@c to be covered.  --amk

本文介绍了2005年3月30日发布的 Python 2.4.1 的新功能。

Python 2.4 is a medium-sized release.  It doesn't introduce as many changes as
the radical Python 2.2, but introduces more features than the conservative 2.3
release.  The most significant new language features are function decorators and
generator expressions; most other changes are to the standard library.

According to the CVS change logs, there were 481 patches applied and 502 bugs
fixed between Python 2.3 and 2.4.  Both figures are likely to be underestimates.

This article doesn't attempt to provide a complete specification of every single
new feature, but instead provides a brief introduction to each feature.  For
full details, you should refer to the documentation for Python 2.4, such as the
Python Library Reference and the Python Reference Manual.  Often you will be
referred to the PEP for a particular new feature for explanations of the
implementation and design rationale.

@c ======================================================================

@menu
* PEP 218; 内置集合对象: PEP 218 内置集合对象. 
* PEP 237; 统一长整数和整数: PEP 237 统一长整数和整数. 
* PEP 289; 生成器表达式: PEP 289 生成器表达式. 
* PEP 292; Simpler String Substitutions: PEP 292 Simpler String Substitutions. 
* PEP 318; Decorators for Functions and Methods: PEP 318 Decorators for Functions and Methods. 
* PEP 322; 反向迭代: PEP 322 反向迭代. 
* PEP 324; 新的子进程模块: PEP 324 新的子进程模块. 
* PEP 327; 十进制数据类型: PEP 327 十进制数据类型. 
* PEP 328; 多行导入: PEP 328 多行导入. 
* PEP 331; Locale-Independent Float/String Conversions: PEP 331 Locale-Independent Float/String Conversions. 
* 其他语言特性修改: 其他语言特性修改<12>. 
* 新增，改进和弃用的模块: 新增，改进和弃用的模块<3>. 
* 构建和 C API 的改变: 构建和 C API 的改变<11>. 
* 移植到 Python 2.4: 移植到 Python 2 4. 
* 致谢: 致谢<4>. 

@end menu

@node PEP 218 内置集合对象,PEP 237 统一长整数和整数,,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-218-built-in-set-objects}@anchor{db2}
@subsection PEP 218: 内置集合对象


Python 2.3 introduced the @code{sets} module.  C implementations of set data
types have now been added to the Python core as two new built-in types,
@code{set(iterable)} and @code{frozenset(iterable)}.  They provide high speed
operations for membership testing, for eliminating duplicates from sequences,
and for mathematical operations like unions, intersections, differences, and
symmetric differences.

@example
>>> a = set('abracadabra')              # form a set from a string
>>> 'z' in a                            # fast membership testing
False
>>> a                                   # unique letters in a
set(['a', 'r', 'b', 'c', 'd'])
>>> '@w{'}.join(a)                          # convert back into a string
'arbcd'

>>> b = set('alacazam')                 # form a second set
>>> a - b                               # letters in a but not in b
set(['r', 'd', 'b'])
>>> a | b                               # letters in either a or b
set(['a', 'c', 'r', 'd', 'b', 'm', 'z', 'l'])
>>> a & b                               # letters in both a and b
set(['a', 'c'])
>>> a ^ b                               # letters in a or b but not both
set(['r', 'd', 'b', 'm', 'z', 'l'])

>>> a.add('z')                          # add a new element
>>> a.update('wxy')                     # add multiple new elements
>>> a
set(['a', 'c', 'b', 'd', 'r', 'w', 'y', 'x', 'z'])
>>> a.remove('x')                       # take one element out
>>> a
set(['a', 'c', 'b', 'd', 'r', 'w', 'y', 'z'])
@end example

The @ref{be7,,frozenset()} type is an immutable version of @ref{b68,,set()}. Since it is
immutable and hashable, it may be used as a dictionary key or as a member of
another set.

The @code{sets} module remains in the standard library, and may be useful if you
wish to subclass the @code{Set} or @code{ImmutableSet} classes.  There are
currently no plans to deprecate the module.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 218

@item PEP 218@footnote{https://www.python.org/dev/peps/pep-0218} - 添加内置Set对象类型

最初由 Greg Wilson 提出，由 Raymond Hettinger 最终实现。
@end table


@c ======================================================================

@node PEP 237 统一长整数和整数,PEP 289 生成器表达式,PEP 218 内置集合对象,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-237-unifying-long-integers-and-integers}@anchor{db3}
@subsection PEP 237: 统一长整数和整数


The lengthy transition process for this PEP, begun in Python 2.2, takes another
step forward in Python 2.4.  In 2.3, certain integer operations that would
behave differently after int/long unification triggered @ref{31e,,FutureWarning}
warnings and returned values limited to 32 or 64 bits (depending on your
platform).  In 2.4, these expressions no longer produce a warning and instead
produce a different result that's usually a long integer.

The problematic expressions are primarily left shifts and lengthy hexadecimal
and octal constants.  For example, @code{2 << 32} results in a warning in 2.3,
evaluating to 0 on 32-bit platforms.  In Python 2.4, this expression now returns
the correct answer, 8589934592.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 237

@item PEP 237@footnote{https://www.python.org/dev/peps/pep-0237} - 统一长整数和整数

原始PEP由 Moshe Zadka 和 GvR 撰写，2.4 的变更由 Kalle Svensson 实现。
@end table


@c ======================================================================

@node PEP 289 生成器表达式,PEP 292 Simpler String Substitutions,PEP 237 统一长整数和整数,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-289-generator-expressions}@anchor{db4}
@subsection PEP 289: 生成器表达式


The iterator feature introduced in Python 2.2 and the @ref{a3,,itertools} module
make it easier to write programs that loop through large data sets without
having the entire data set in memory at one time.  List comprehensions don't fit
into this picture very well because they produce a Python list object containing
all of the items.  This unavoidably pulls all of the objects into memory, which
can be a problem if your data set is very large.  When trying to write a
functionally-styled program, it would be natural to write something like:

@example
links = [link for link in get_all_links() if not link.followed]
for link in links:
    ...
@end example

代替：

@example
for link in get_all_links():
    if link.followed:
        continue
    ...
@end example

The first form is more concise and perhaps more readable, but if you're dealing
with a large number of link objects you'd have to write the second form to avoid
having all link objects in memory at the same time.

Generator expressions work similarly to list comprehensions but don't
materialize the entire list; instead they create a generator that will return
elements one by one.  The above example could be written as:

@example
links = (link for link in get_all_links() if not link.followed)
for link in links:
    ...
@end example

Generator expressions always have to be written inside parentheses, as in the
above example.  The parentheses signalling a function call also count, so if you
want to create an iterator that will be immediately passed to a function you
could write:

@example
print sum(obj.count for obj in list_all_objects())
@end example

Generator expressions differ from list comprehensions in various small ways.
Most notably, the loop variable (@emph{obj} in the above example) is not accessible
outside of the generator expression.  List comprehensions leave the variable
assigned to its last value; future versions of Python will change this, making
list comprehensions match generator expressions in this respect.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 289

@item PEP 289@footnote{https://www.python.org/dev/peps/pep-0289} - 生成器表达式

Proposed by Raymond Hettinger and implemented by Jiwon Seo with early efforts
steered by Hye-Shik Chang.
@end table


@c ======================================================================

@node PEP 292 Simpler String Substitutions,PEP 318 Decorators for Functions and Methods,PEP 289 生成器表达式,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-292-simpler-string-substitutions}@anchor{db5}
@subsection PEP 292: Simpler String Substitutions


Some new classes in the standard library provide an alternative mechanism for
substituting variables into strings; this style of substitution may be better
for applications where untrained users need to edit templates.

The usual way of substituting variables by name is the @code{%} operator:

@example
>>> '%(page)i: %(title)s' % @{'page':2, 'title': 'The Best of Times'@}
'2: The Best of Times'
@end example

When writing the template string, it can be easy to forget the @code{i} or @code{s}
after the closing parenthesis.  This isn't a big problem if the template is in a
Python module, because you run the code, get an "Unsupported format character"
@ref{1fb,,ValueError}, and fix the problem.  However, consider an application such
as Mailman where template strings or translations are being edited by users who
aren't aware of the Python language.  The format string's syntax is complicated
to explain to such users, and if they make a mistake, it's difficult to provide
helpful feedback to them.

PEP 292 adds a @code{Template} class to the @ref{f6,,string} module that uses
@code{$} to indicate a substitution:

@example
>>> import string
>>> t = string.Template('$page: $title')
>>> t.substitute(@{'page':2, 'title': 'The Best of Times'@})
'2: The Best of Times'
@end example

If a key is missing from the dictionary, the @code{substitute()} method will
raise a @ref{2c7,,KeyError}.  There's also a @code{safe_substitute()} method that
ignores missing keys:

@example
>>> t = string.Template('$page: $title')
>>> t.safe_substitute(@{'page':3@})
'3: $title'
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 292

@item PEP 292@footnote{https://www.python.org/dev/peps/pep-0292} - Simpler String Substitutions

由 Barry Warsaw 撰写并实现
@end table


@c ======================================================================

@node PEP 318 Decorators for Functions and Methods,PEP 322 反向迭代,PEP 292 Simpler String Substitutions,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-318-decorators-for-functions-and-methods}@anchor{db6}
@subsection PEP 318: Decorators for Functions and Methods


Python 2.2 extended Python's object model by adding static methods and class
methods, but it didn't extend Python's syntax to provide any new way of defining
static or class methods.  Instead, you had to write a @ref{db7,,def} statement
in the usual way, and pass the resulting method to a @ref{1d9,,staticmethod()} or
@ref{1d8,,classmethod()} function that would wrap up the function as a method of the
new type. Your code would look like this:

@example
class C:
   def meth (cls):
       ...

   meth = classmethod(meth)   # Rebind name to wrapped-up class method
@end example

If the method was very long, it would be easy to miss or forget the
@ref{1d8,,classmethod()} invocation after the function body.

The intention was always to add some syntax to make such definitions more
readable, but at the time of 2.2's release a good syntax was not obvious.  Today
a good syntax @emph{still} isn't obvious but users are asking for easier access to
the feature; a new syntactic feature has been added to meet this need.

The new feature is called "function decorators".  The name comes from the idea
that @ref{1d8,,classmethod()}, @ref{1d9,,staticmethod()}, and friends are storing
additional information on a function object; they're @emph{decorating} functions with
more details.

The notation borrows from Java and uses the @code{'@@'} character as an indicator.
Using the new syntax, the example above would be written:

@example
class C:

   @@classmethod
   def meth (cls):
       ...
@end example

The @code{@@classmethod} is shorthand for the @code{meth=classmethod(meth)} assignment.
More generally, if you have the following:

@example
@@A
@@B
@@C
def f ():
    ...
@end example

It's equivalent to the following pre-decorator code:

@example
def f(): ...
f = A(B(C(f)))
@end example

Decorators must come on the line before a function definition, one decorator per
line, and can't be on the same line as the def statement, meaning that @code{@@A def
f(): ...} is illegal.  You can only decorate function definitions, either at
the module level or inside a class; you can't decorate class definitions.

A decorator is just a function that takes the function to be decorated as an
argument and returns either the same function or some new object.  The return
value of the decorator need not be callable (though it typically is), unless
further decorators will be applied to the result.  It's easy to write your own
decorators.  The following simple example just sets an attribute on the function
object:

@example
>>> def deco(func):
...    func.attr = 'decorated'
...    return func
...
>>> @@deco
... def f(): pass
...
>>> f
<function f at 0x402ef0d4>
>>> f.attr
'decorated'
>>>
@end example

As a slightly more realistic example, the following decorator checks that the
supplied argument is an integer:

@example
def require_int (func):
    def wrapper (arg):
        assert isinstance(arg, int)
        return func(arg)

    return wrapper

@@require_int
def p1 (arg):
    print arg

@@require_int
def p2(arg):
    print arg*2
@end example

An example in 
@geindex Python 提高建议; PEP 318
PEP 318@footnote{https://www.python.org/dev/peps/pep-0318} contains a fancier version of this idea that lets you
both specify the required type and check the returned type.

Decorator functions can take arguments.  If arguments are supplied, your
decorator function is called with only those arguments and must return a new
decorator function; this function must take a single function and return a
function, as previously described.  In other words, @code{@@A @@B @@C(args)} becomes:

@example
def f(): ...
_deco = C(args)
f = A(B(_deco(f)))
@end example

Getting this right can be slightly brain-bending, but it's not too difficult.

A small related change makes the @code{func_name} attribute of functions
writable.  This attribute is used to display function names in tracebacks, so
decorators should change the name of any new function that's constructed and
returned.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 318

@item PEP 318@footnote{https://www.python.org/dev/peps/pep-0318} - Decorators for Functions, Methods and Classes

Written  by Kevin D. Smith, Jim Jewett, and Skip Montanaro.  Several people
wrote patches implementing function decorators, but the one that was actually
checked in was patch #979728, written by Mark Russell.

@item @indicateurl{https://wiki.python.org/moin/PythonDecoratorLibrary}

该Wiki页面包含几个装饰器示例。
@end table


@c ======================================================================

@node PEP 322 反向迭代,PEP 324 新的子进程模块,PEP 318 Decorators for Functions and Methods,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-322-reverse-iteration}@anchor{db8}
@subsection PEP 322: 反向迭代


A new built-in function, @code{reversed(seq)}, takes a sequence and returns an
iterator that loops over the elements of the sequence  in reverse order.

@example
>>> for i in reversed(xrange(1,4)):
...    print i
...
3
2
1
@end example

Compared to extended slicing, such as @code{range(1,4)[::-1]}, @ref{18e,,reversed()} is
easier to read, runs faster, and uses substantially less memory.

Note that @ref{18e,,reversed()} only accepts sequences, not arbitrary iterators.  If
you want to reverse an iterator, first convert it to  a list with @ref{262,,list()}.

@example
>>> input = open('/etc/passwd', 'r')
>>> for line in reversed(list(input)):
...   print line
...
root:*:0:0:System Administrator:/var/root:/bin/tcsh
  ...
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 322

@item PEP 322@footnote{https://www.python.org/dev/peps/pep-0322} - 反向迭代

由 Raymond Hettinger 撰写并实现。
@end table


@c ======================================================================

@node PEP 324 新的子进程模块,PEP 327 十进制数据类型,PEP 322 反向迭代,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-324-new-subprocess-module}@anchor{db9}
@subsection PEP 324: 新的子进程模块


The standard library provides a number of ways to execute a subprocess, offering
different features and different levels of complexity.
@code{os.system(command)} is easy to use, but slow (it runs a shell process
which executes the command) and dangerous (you have to be careful about escaping
the shell's metacharacters).  The @code{popen2} module offers classes that can
capture standard output and standard error from the subprocess, but the naming
is confusing.  The @ref{f9,,subprocess} module cleans  this up, providing a unified
interface that offers all the features you might need.

Instead of @code{popen2}'s collection of classes, @ref{f9,,subprocess} contains a
single class called @code{Popen}  whose constructor supports a number of
different keyword arguments.

@example
class Popen(args, bufsize=0, executable=None,
            stdin=None, stdout=None, stderr=None,
            preexec_fn=None, close_fds=False, shell=False,
            cwd=None, env=None, universal_newlines=False,
            startupinfo=None, creationflags=0):
@end example

@emph{args} is commonly a sequence of strings that will be the arguments to the
program executed as the subprocess.  (If the @emph{shell} argument is true, @emph{args}
can be a string which will then be passed on to the shell for interpretation,
just as @ref{dba,,os.system()} does.)

@emph{stdin}, @emph{stdout}, and @emph{stderr} specify what the subprocess's input, output, and
error streams will be.  You can provide a file object or a file descriptor, or
you can use the constant @code{subprocess.PIPE} to create a pipe between the
subprocess and the parent.

@geindex universal newlines; What's new

The constructor has a number of handy options:


@itemize *

@item 
@emph{close_fds} requests that all file descriptors be closed before running the
subprocess.

@item 
@emph{cwd} specifies the working directory in which the subprocess will be executed
(defaulting to whatever the parent's working directory is).

@item 
@emph{env} is a dictionary specifying environment variables.

@item 
@emph{preexec_fn} is a function that gets called before the child is started.

@item 
@emph{universal_newlines} opens the child's input and output using Python's
@ref{5ef,,universal newlines} feature.
@end itemize

Once you've created the @code{Popen} instance,  you can call its @code{wait()}
method to pause until the subprocess has exited, @code{poll()} to check if it's
exited without pausing,  or @code{communicate(data)} to send the string @emph{data}
to the subprocess's standard input.   @code{communicate(data)}  then reads any
data that the subprocess has sent to its standard output  or standard error,
returning a tuple @code{(stdout_data, stderr_data)}.

@code{call()} is a shortcut that passes its arguments along to the @code{Popen}
constructor, waits for the command to complete, and returns the status code of
the subprocess.  It can serve as a safer analog to @ref{dba,,os.system()}:

@example
sts = subprocess.call(['dpkg', '-i', '/tmp/new-package.deb'])
if sts == 0:
    # Success
    ...
else:
    # dpkg returned an error
    ...
@end example

The command is invoked without use of the shell.  If you really do want to  use
the shell, you can add @code{shell=True} as a keyword argument and provide a string
instead of a sequence:

@example
sts = subprocess.call('dpkg -i /tmp/new-package.deb', shell=True)
@end example

The PEP takes various examples of shell and Python code and shows how they'd be
translated into Python code that uses @ref{f9,,subprocess}.  Reading this section
of the PEP is highly recommended.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 324

@item PEP 324@footnote{https://www.python.org/dev/peps/pep-0324} - 子进程 - 新的进程模块

由 Peter Åstrand 在 Fredrik Lundh 等人的协助下撰写并实现。
@end table


@c ======================================================================

@node PEP 327 十进制数据类型,PEP 328 多行导入,PEP 324 新的子进程模块,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-327-decimal-data-type}@anchor{dbb}
@subsection PEP 327: 十进制数据类型


Python has always supported floating-point (FP) numbers, based on the underlying
C @code{double} type, as a data type.  However, while most programming
languages provide a floating-point type, many people (even programmers) are
unaware that floating-point numbers don't represent certain decimal fractions
accurately.  The new @code{Decimal} type can represent these fractions
accurately, up to a user-specified precision limit.

@menu
* 为什么需要十进制？:: 
* Decimal 类型:: 
* Context 类型:: 

@end menu

@node 为什么需要十进制？,Decimal 类型,,PEP 327 十进制数据类型
@anchor{whatsnew/2 4 why-is-decimal-needed}@anchor{dbc}
@subsubsection 为什么需要十进制？


The limitations arise from the representation used for floating-point numbers.
FP numbers are made up of three components:


@itemize *

@item 
The sign, which is positive or negative.

@item 
The mantissa, which is a single-digit binary number   followed by a fractional
part.  For example, @code{1.01} in base-2 notation is @code{1 + 0/2 + 1/4}, or 1.25 in
decimal notation.

@item 
The exponent, which tells where the decimal point is located in the number
represented.
@end itemize

For example, the number 1.25 has positive sign, a mantissa value of 1.01 (in
binary), and an exponent of 0 (the decimal point doesn't need to be shifted).
The number 5 has the same sign and mantissa, but the exponent is 2 because the
mantissa is multiplied by 4 (2 to the power of the exponent 2); 1.25 * 4 equals
5.

Modern systems usually provide floating-point support that conforms to a
standard called IEEE 754.  C's @code{double} type is usually implemented as a
64-bit IEEE 754 number, which uses 52 bits of space for the mantissa.  This
means that numbers can only be specified to 52 bits of precision.  If you're
trying to represent numbers whose expansion repeats endlessly, the expansion is
cut off after 52 bits. Unfortunately, most software needs to produce output in
base 10, and common fractions in base 10 are often repeating decimals in binary.
For example, 1.1 decimal is binary @code{1.0001100110011 ...}; .1 = 1/16 + 1/32 +
1/256 plus an infinite number of additional terms.  IEEE 754 has to chop off
that infinitely repeated decimal after 52 digits, so the representation is
slightly inaccurate.

Sometimes you can see this inaccuracy when the number is printed:

@example
>>> 1.1
1.1000000000000001
@end example

The inaccuracy isn't always visible when you print the number because the
FP-to-decimal-string conversion is provided by the C library, and most C libraries try
to produce sensible output.  Even if it's not displayed, however, the inaccuracy
is still there and subsequent operations can magnify the error.

For many applications this doesn't matter.  If I'm plotting points and
displaying them on my monitor, the difference between 1.1 and 1.1000000000000001
is too small to be visible.  Reports often limit output to a certain number of
decimal places, and if you round the number to two or three or even eight
decimal places, the error is never apparent.  However, for applications where it
does matter,  it's a lot of work to implement your own custom arithmetic
routines.

因此，创建了 @code{Decimal} 类型。

@node Decimal 类型,Context 类型,为什么需要十进制？,PEP 327 十进制数据类型
@anchor{whatsnew/2 4 the-decimal-type}@anchor{dbd}
@subsubsection @code{Decimal} 类型


A new module, @ref{36,,decimal}, was added to Python's standard library.  It
contains two classes, @code{Decimal} and @code{Context}.  @code{Decimal}
instances represent numbers, and @code{Context} instances are used to wrap up
various settings such as the precision and default rounding mode.

@code{Decimal} instances are immutable, like regular Python integers and FP
numbers; once it's been created, you can't change the value an instance
represents.  @code{Decimal} instances can be created from integers or
strings:

@example
>>> import decimal
>>> decimal.Decimal(1972)
Decimal("1972")
>>> decimal.Decimal("1.1")
Decimal("1.1")
@end example

You can also provide tuples containing the sign, the mantissa represented  as a
tuple of decimal digits, and the exponent:

@example
>>> decimal.Decimal((1, (1, 4, 7, 5), -2))
Decimal("-14.75")
@end example

Cautionary note: the sign bit is a Boolean value, so 0 is positive and 1 is
negative.

Converting from floating-point numbers poses a bit of a problem: should the FP
number representing 1.1 turn into the decimal number for exactly 1.1, or for 1.1
plus whatever inaccuracies are introduced? The decision was to dodge the issue
and leave such a conversion out of the API.  Instead, you should convert the
floating-point number into a string using the desired precision and pass the
string to the @code{Decimal} constructor:

@example
>>> f = 1.1
>>> decimal.Decimal(str(f))
Decimal("1.1")
>>> decimal.Decimal('%.12f' % f)
Decimal("1.100000000000")
@end example

Once you have @code{Decimal} instances, you can perform the usual mathematical
operations on them.  One limitation: exponentiation requires an integer
exponent:

@example
>>> a = decimal.Decimal('35.72')
>>> b = decimal.Decimal('1.73')
>>> a+b
Decimal("37.45")
>>> a-b
Decimal("33.99")
>>> a*b
Decimal("61.7956")
>>> a/b
Decimal("20.64739884393063583815028902")
>>> a ** 2
Decimal("1275.9184")
>>> a**b
Traceback (most recent call last):
  ...
decimal.InvalidOperation: x ** (non-integer)
@end example

You can combine @code{Decimal} instances with integers, but not with
floating-point numbers:

@example
>>> a + 4
Decimal("39.72")
>>> a + 4.5
Traceback (most recent call last):
  ...
TypeError: You can interact Decimal only with int, long or Decimal data types.
>>>
@end example

@code{Decimal} numbers can be used with the @ref{b1,,math} and @ref{19,,cmath}
modules, but note that they'll be immediately converted to  floating-point
numbers before the operation is performed, resulting in a possible loss of
precision and accuracy.  You'll also get back a regular floating-point number
and not a @code{Decimal}.

@example
>>> import math, cmath
>>> d = decimal.Decimal('123456789012.345')
>>> math.sqrt(d)
351364.18288201344
>>> cmath.sqrt(-d)
351364.18288201344j
@end example

@code{Decimal} instances have a @code{sqrt()} method that returns a
@code{Decimal}, but if you need other things such as trigonometric functions
you'll have to implement them.

@example
>>> d.sqrt()
Decimal("351364.1828820134592177245001")
@end example

@node Context 类型,,Decimal 类型,PEP 327 十进制数据类型
@anchor{whatsnew/2 4 the-context-type}@anchor{dbe}
@subsubsection @code{Context} 类型


Instances of the @code{Context} class encapsulate several settings for
decimal operations:


@itemize *

@item 
@code{prec} is the precision, the number of decimal places.

@item 
@code{rounding} specifies the rounding mode.  The @ref{36,,decimal} module has
constants for the various possibilities: @code{ROUND_DOWN},
@code{ROUND_CEILING},  @code{ROUND_HALF_EVEN}, and various others.

@item 
@code{traps} is a dictionary specifying what happens on encountering certain
error conditions: either  an exception is raised or  a value is returned.  Some
examples of error conditions are division by zero, loss of precision, and
overflow.
@end itemize

There's a thread-local default context available by calling @code{getcontext()};
you can change the properties of this context to alter the default precision,
rounding, or trap handling.  The following example shows the effect of changing
the precision of the default context:

@example
>>> decimal.getcontext().prec
28
>>> decimal.Decimal(1) / decimal.Decimal(7)
Decimal("0.1428571428571428571428571429")
>>> decimal.getcontext().prec = 9
>>> decimal.Decimal(1) / decimal.Decimal(7)
Decimal("0.142857143")
@end example

The default action for error conditions is selectable; the module can either
return a special value such as infinity or not-a-number, or exceptions can be
raised:

@example
>>> decimal.Decimal(1) / decimal.Decimal(0)
Traceback (most recent call last):
  ...
decimal.DivisionByZero: x / 0
>>> decimal.getcontext().traps[decimal.DivisionByZero] = False
>>> decimal.Decimal(1) / decimal.Decimal(0)
Decimal("Infinity")
>>>
@end example

The @code{Context} instance also has various methods for formatting  numbers
such as @code{to_eng_string()} and @code{to_sci_string()}.

For more information, see the documentation for the @ref{36,,decimal} module, which
includes a quick-start tutorial and a reference.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 327

@item PEP 327@footnote{https://www.python.org/dev/peps/pep-0327} - 十进数据类型

由 Facundo Batista 撰写，由Facundo Batista, Eric Price, Raymond Hettinger, Aahz 和 Tim Peters 实现。

@item @indicateurl{http://www.lahey.com/float.htm}

The article uses Fortran code to illustrate many of the problems that
floating-point inaccuracy can cause.

@item @indicateurl{http://speleotrove.com/decimal/}

A description of a decimal-based representation.  This representation is being
proposed as a standard, and underlies the new Python decimal type.  Much of this
material was written by Mike Cowlishaw, designer of the Rexx language.
@end table


@c ======================================================================

@node PEP 328 多行导入,PEP 331 Locale-Independent Float/String Conversions,PEP 327 十进制数据类型,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-328-multi-line-imports}@anchor{dbf}
@subsection PEP 328: 多行导入


One language change is a small syntactic tweak aimed at making it easier to
import many names from a module.  In a @code{from module import names} statement,
@emph{names} is a sequence of names separated by commas.  If the sequence is  very
long, you can either write multiple imports from the same module, or you can use
backslashes to escape the line endings like this:

@example
from SimpleXMLRPCServer import SimpleXMLRPCServer,\
            SimpleXMLRPCRequestHandler,\
            CGIXMLRPCRequestHandler,\
            resolve_dotted_attribute
@end example

The syntactic change in Python 2.4 simply allows putting the names within
parentheses.  Python ignores newlines within a parenthesized expression, so the
backslashes are no longer needed:

@example
from SimpleXMLRPCServer import (SimpleXMLRPCServer,
                                SimpleXMLRPCRequestHandler,
                                CGIXMLRPCRequestHandler,
                                resolve_dotted_attribute)
@end example

The PEP also proposes that all @ref{c16,,import} statements be absolute imports,
with a leading @code{.} character to indicate a relative import.  This part of the
PEP was not implemented for Python 2.4, but was completed for Python 2.5.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 328

@item PEP 328@footnote{https://www.python.org/dev/peps/pep-0328} - 导入：多行和绝对/相对导入

由 Aahz 撰写，多行导入由 Dima Dorfman 实现。
@end table


@c ======================================================================

@node PEP 331 Locale-Independent Float/String Conversions,其他语言特性修改<12>,PEP 328 多行导入,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 pep-331-locale-independent-float-string-conversions}@anchor{dc0}
@subsection PEP 331: Locale-Independent Float/String Conversions


The @ref{a9,,locale} modules lets Python software select various conversions and
display conventions that are localized to a particular country or language.
However, the module was careful to not change the numeric locale because various
functions in Python's implementation required that the numeric locale remain set
to the @code{'C'} locale.  Often this was because the code was using the C
library's @code{atof()} function.

Not setting the numeric locale caused trouble for extensions that used third-party
C libraries, however, because they wouldn't have the correct locale set.
The motivating example was GTK+, whose user interface widgets weren't displaying
numbers in the current locale.

The solution described in the PEP is to add three new functions to the Python
API that perform ASCII-only conversions, ignoring the locale setting:


@itemize *

@item 
@code{PyOS_ascii_strtod(str, ptr)}  and @code{PyOS_ascii_atof(str, ptr)}
both convert a string to a C @code{double}.

@item 
@code{PyOS_ascii_formatd(buffer, buf_len, format, d)} converts a
@code{double} to an ASCII string.
@end itemize

The code for these functions came from the GLib library
(@indicateurl{https://developer.gnome.org/glib/stable/}), whose developers kindly
relicensed the relevant functions and donated them to the Python Software
Foundation.  The @ref{a9,,locale} module  can now change the numeric locale,
letting extensions such as GTK+  produce the correct results.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 331

@item PEP 331@footnote{https://www.python.org/dev/peps/pep-0331} - Locale-Independent Float/String Conversions

由Christian R. Reis撰写，由 Gustavo Carneiro 实现。
@end table


@c ======================================================================

@node 其他语言特性修改<12>,新增，改进和弃用的模块<3>,PEP 331 Locale-Independent Float/String Conversions,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 other-language-changes}@anchor{dc1}
@subsection 其他语言特性修改


Here are all of the changes that Python 2.4 makes to the core Python language.


@itemize *

@item 
Decorators for functions and methods were added (
@geindex Python 提高建议; PEP 318
PEP 318@footnote{https://www.python.org/dev/peps/pep-0318}).

@item 
Built-in @ref{b68,,set()} and @ref{be7,,frozenset()} types were  added (
@geindex Python 提高建议; PEP 218
PEP 218@footnote{https://www.python.org/dev/peps/pep-0218}).
Other new built-ins include the @code{reversed(seq)} function (
@geindex Python 提高建议; PEP 322
PEP 322@footnote{https://www.python.org/dev/peps/pep-0322}).

@item 
Generator expressions were added (
@geindex Python 提高建议; PEP 289
PEP 289@footnote{https://www.python.org/dev/peps/pep-0289}).

@item 
Certain numeric expressions no longer return values restricted to 32 or 64
bits (
@geindex Python 提高建议; PEP 237
PEP 237@footnote{https://www.python.org/dev/peps/pep-0237}).

@item 
You can now put parentheses around the list of names in a @code{from module import
names} statement (
@geindex Python 提高建议; PEP 328
PEP 328@footnote{https://www.python.org/dev/peps/pep-0328}).

@item 
The @ref{dc2,,dict.update()} method now accepts the same argument forms as the
@ref{1b8,,dict} constructor.  This includes any mapping, any iterable of key/value
pairs, and keyword arguments. (Contributed by Raymond Hettinger.)

@item 
The string methods @code{ljust()}, @code{rjust()}, and @code{center()} now take
an optional argument for specifying a fill character other than a space.
(Contributed by Raymond Hettinger.)

@item 
Strings also gained an @code{rsplit()} method that works like the @code{split()}
method but splits from the end of the string.   (Contributed by Sean
Reifschneider.)

@example
>>> 'www.python.org'.split('.', 1)
['www', 'python.org']
'www.python.org'.rsplit('.', 1)
['www.python', 'org']
@end example

@item 
Three keyword parameters, @emph{cmp}, @emph{key}, and @emph{reverse}, were added to the
@code{sort()} method of lists. These parameters make some common usages of
@code{sort()} simpler. All of these parameters are optional.

For the @emph{cmp} parameter, the value should be a comparison function that takes
two parameters and returns -1, 0, or +1 depending on how the parameters compare.
This function will then be used to sort the list.  Previously this was the only
parameter that could be provided to @code{sort()}.

@emph{key} should be a single-parameter function that takes a list element and
returns a comparison key for the element.  The list is then sorted using the
comparison keys.  The following example sorts a list case-insensitively:

@example
>>> L = ['A', 'b', 'c', 'D']
>>> L.sort()                 # Case-sensitive sort
>>> L
['A', 'D', 'b', 'c']
>>> # Using 'key' parameter to sort list
>>> L.sort(key=lambda x: x.lower())
>>> L
['A', 'b', 'c', 'D']
>>> # Old-fashioned way
>>> L.sort(cmp=lambda x,y: cmp(x.lower(), y.lower()))
>>> L
['A', 'b', 'c', 'D']
@end example

The last example, which uses the @emph{cmp} parameter, is the old way to perform a
case-insensitive sort.  It works but is slower than using a @emph{key} parameter.
Using @emph{key} calls @code{lower()} method once for each element in the list while
using @emph{cmp} will call it twice for each comparison, so using @emph{key} saves on
invocations of the @code{lower()} method.

For simple key functions and comparison functions, it is often possible to avoid
a @ref{c28,,lambda} expression by using an unbound method instead.  For example,
the above case-insensitive sort is best written as:

@example
>>> L.sort(key=str.lower)
>>> L
['A', 'b', 'c', 'D']
@end example

Finally, the @emph{reverse} parameter takes a Boolean value.  If the value is true,
the list will be sorted into reverse order. Instead of @code{L.sort();
L.reverse()}, you can now write @code{L.sort(reverse=True)}.

The results of sorting are now guaranteed to be stable.  This means that two
entries with equal keys will be returned in the same order as they were input.
For example, you can sort a list of people by name, and then sort the list by
age, resulting in a list sorted by age where people with the same age are in
name-sorted order.

(All changes to @code{sort()} contributed by Raymond Hettinger.)

@item 
There is a new built-in function @code{sorted(iterable)} that works like the
in-place @ref{43f,,list.sort()} method but can be used in expressions.  The
differences are:

@item 
the input may be any iterable;

@item 
a newly formed copy is sorted, leaving the original intact; and

@item 
the expression returns the new sorted copy

@example
>>> L = [9,7,8,3,2,4,1,6,5]
>>> [10+i for i in sorted(L)]       # usable in a list comprehension
[11, 12, 13, 14, 15, 16, 17, 18, 19]
>>> L                               # original is left unchanged
[9,7,8,3,2,4,1,6,5]
>>> sorted('Monty Python')          # any iterable may be an input
[' ', 'M', 'P', 'h', 'n', 'n', 'o', 'o', 't', 't', 'y', 'y']

>>> # List the contents of a dict sorted by key values
>>> colormap = dict(red=1, blue=2, green=3, black=4, yellow=5)
>>> for k, v in sorted(colormap.iteritems()):
...     print k, v
...
black 4
blue 2
green 3
red 1
yellow 5
@end example

（由 Raymond Hettinger 贡献。）

@item 
Integer operations will no longer trigger an @code{OverflowWarning}. The
@code{OverflowWarning} warning will disappear in Python 2.5.

@item 
The interpreter gained a new switch, @ref{330,,-m}, that takes a name, searches
for the corresponding  module on @code{sys.path}, and runs the module as a script.
For example,  you can now run the Python profiler with @code{python -m profile}.
(Contributed by Nick Coghlan.)

@item 
The @code{eval(expr, globals, locals)} and @code{execfile(filename, globals,
locals)} functions and the @code{exec} statement now accept any mapping type
for the @emph{locals} parameter.  Previously this had to be a regular Python
dictionary.  (Contributed by Raymond Hettinger.)

@item 
The @ref{c2b,,zip()} built-in function and @code{itertools.izip()} now return an
empty list if called with no arguments. Previously they raised a
@ref{192,,TypeError} exception.  This makes them more suitable for use with variable
length argument lists:

@example
>>> def transpose(array):
...    return zip(*array)
...
>>> transpose([(1,2,3), (4,5,6)])
[(1, 4), (2, 5), (3, 6)]
>>> transpose([])
[]
@end example

（由 Raymond Hettinger 贡献。）

@item 
Encountering a failure while importing a module no longer leaves a partially-initialized
module object in @code{sys.modules}.  The incomplete module object left
behind would fool further imports of the same module into succeeding, leading to
confusing errors.   (Fixed by Tim Peters.)

@item 
@ref{157,,None} is now a constant; code that binds a new value to  the name
@code{None} is now a syntax error. (Contributed by Raymond Hettinger.)
@end itemize

@c ======================================================================

@menu
* 性能优化: 性能优化<11>. 

@end menu

@node 性能优化<11>,,,其他语言特性修改<12>
@anchor{whatsnew/2 4 optimizations}@anchor{dc3}
@subsubsection 性能优化



@itemize *

@item 
The inner loops for list and tuple slicing were optimized and now run about
one-third faster.  The inner loops for dictionaries were also optimized,
resulting in performance boosts for @code{keys()}, @code{values()}, @code{items()},
@code{iterkeys()}, @code{itervalues()}, and @code{iteritems()}. (Contributed by
Raymond Hettinger.)

@item 
The machinery for growing and shrinking lists was optimized for speed and for
space efficiency.  Appending and popping from lists now runs faster due to more
efficient code paths and less frequent use of the underlying system
@code{realloc()}.  List comprehensions also benefit.   @code{list.extend()} was
also optimized and no longer converts its argument into a temporary list before
extending the base list.  (Contributed by Raymond Hettinger.)

@item 
@ref{262,,list()}, @ref{478,,tuple()}, @ref{c26,,map()}, @ref{c27,,filter()}, and @ref{c2b,,zip()} now
run several times faster with non-sequence arguments that supply a
@ref{dc4,,__len__()} method.  (Contributed by Raymond Hettinger.)

@item 
The methods @code{list.__getitem__()}, @code{dict.__getitem__()}, and
@code{dict.__contains__()} are now implemented as @code{method_descriptor}
objects rather than @code{wrapper_descriptor} objects.  This form of  access
doubles their performance and makes them more suitable for use as arguments to
functionals: @code{map(mydict.__getitem__, keylist)}. (Contributed by Raymond
Hettinger.)

@item 
Added a new opcode, @code{LIST_APPEND}, that simplifies the generated bytecode
for list comprehensions and speeds them up by about a third.  (Contributed by
Raymond Hettinger.)

@item 
The peephole bytecode optimizer has been improved to  produce shorter, faster
bytecode; remarkably, the resulting bytecode is  more readable.  (Enhanced by
Raymond Hettinger.)

@item 
String concatenations in statements of the form @code{s = s + "abc"} and @code{s +=
"abc"} are now performed more efficiently in certain circumstances.  This
optimization won't be present in other Python implementations such as Jython, so
you shouldn't rely on it; using the @code{join()} method of strings is still
recommended when you want to efficiently glue a large number of strings
together. (Contributed by Armin Rigo.)
@end itemize

The net result of the 2.4 optimizations is that Python 2.4 runs the pystone
benchmark around 5% faster than Python 2.3 and 35% faster than Python 2.2.
(pystone is not a particularly good benchmark, but it's the most commonly used
measurement of Python's performance.  Your own applications may show greater or
smaller benefits from Python 2.4.)

@c pystone is almost useless for comparing different versions of Python;
@c instead, it excels at predicting relative Python performance on different
@c machines.  So, this section would be more informative if it used other tools
@c such as pybench and parrotbench.  For a more application oriented benchmark,
@c try comparing the timings of test_decimal.py under 2.3 and 2.4.

@c ======================================================================

@node 新增，改进和弃用的模块<3>,构建和 C API 的改变<11>,其他语言特性修改<12>,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 new-improved-and-deprecated-modules}@anchor{dc5}
@subsection 新增，改进和弃用的模块


As usual, Python's standard library received a number of enhancements and bug
fixes.  Here's a partial list of the most notable changes, sorted alphabetically
by module name. Consult the @code{Misc/NEWS} file in the source tree for a more
complete list of changes, or look through the CVS logs for all the details.


@itemize *

@item 
The @ref{b,,asyncore} module's @code{loop()} function now has a @emph{count} parameter
that lets you perform a limited number of passes through the polling loop.  The
default is still to loop forever.

@item 
The @ref{e,,base64} module now has more complete 
@geindex RFC; RFC 3548
RFC 3548@footnote{https://tools.ietf.org/html/rfc3548.html} support for Base64,
Base32, and Base16 encoding and decoding, including optional case folding and
optional alternative alphabets. (Contributed by Barry Warsaw.)

@item 
The @ref{12,,bisect} module now has an underlying C implementation for improved
performance. (Contributed by Dmitry Vasiliev.)

@item 
由 Hye-Shik Chang 维护的东亚编解码器的 CJKCodecs 集合已集成到 2.4 中。新的编码为：

@item 
汉语（大陆）: gb2312, gbk, gb18030, big5hkscs, hz

@item 
汉语（台湾）: big5, cp950

@item 

@table @asis

@item 日语: cp932, euc-jis-2004, euc-jp, euc-jisx0213, iso-2022-jp,

iso-2022-jp-1, iso-2022-jp-2, iso-2022-jp-3, iso-2022-jp-ext, iso-2022-jp-2004,
shift-jis, shift-jisx0213, shift-jis-2004
@end table

@item 
韩语: cp949, euc-kr, johab, iso-2022-kr

@item 
添加了其他一些新的编码：HP Roman8, ISO_8859-11, ISO_8859-16, PCTP-154 和 TIS-620

@item 
The UTF-8 and UTF-16 codecs now cope better with receiving partial input.
Previously the @code{StreamReader} class would try to read more data, making
it impossible to resume decoding from the stream.  The @code{read()} method will
now return as much data as it can and future calls will resume decoding where
previous ones left off.  (Implemented by Walter Dörwald.)

@item 
There is a new @ref{1e,,collections} module for  various specialized collection
datatypes.  Currently it contains just one type, @code{deque}, a double-ended
queue that supports efficiently adding and removing elements from either
end:

@example
>>> from collections import deque
>>> d = deque('ghi')        # make a new deque with three items
>>> d.append('j')           # add a new entry to the right side
>>> d.appendleft('f')       # add a new entry to the left side
>>> d                       # show the representation of the deque
deque(['f', 'g', 'h', 'i', 'j'])
>>> d.pop()                 # return and remove the rightmost item
'j'
>>> d.popleft()             # return and remove the leftmost item
'f'
>>> list(d)                 # list the contents of the deque
['g', 'h', 'i']
>>> 'h' in d                # search the deque
True
@end example

Several modules, such as the @code{Queue} and @ref{109,,threading} modules, now take
advantage of @ref{52b,,collections.deque} for improved performance.  (Contributed
by Raymond Hettinger.)

@item 
The @code{ConfigParser} classes have been enhanced slightly. The @code{read()}
method now returns a list of the files that were successfully parsed, and the
@ref{b68,,set()} method raises @ref{192,,TypeError} if passed a @emph{value} argument that
isn't a string.   (Contributed by John Belmonte and David Goodger.)

@item 
The @ref{2c,,curses} module now supports the ncurses extension
@code{use_default_colors()}.  On platforms where the terminal supports
transparency, this makes it possible to use a transparent background.
(Contributed by Jörg Lehmann.)

@item 
The @ref{37,,difflib} module now includes an @code{HtmlDiff} class that creates
an HTML table showing a side by side comparison of two versions of a text.
(Contributed by Dan Gass.)

@item 
The @ref{69,,email} package was updated to version 3.0,  which dropped various
deprecated APIs and removes support for Python versions earlier than 2.3.  The
3.0 version of the package uses a new incremental parser for MIME messages,
available in the @code{email.FeedParser} module.  The new parser doesn't require
reading the entire message into memory, and doesn't raise exceptions if a
message is malformed; instead it records any problems in the  @code{defect}
attribute of the message.  (Developed by Anthony Baxter, Barry Warsaw, Thomas
Wouters, and others.)

@item 
The @ref{8e,,heapq} module has been converted to C.  The resulting tenfold
improvement in speed makes the module suitable for handling high volumes of
data.  In addition, the module has two new functions @code{nlargest()} and
@code{nsmallest()} that use heaps to find the N largest or smallest values in a
dataset without the expense of a full sort.  (Contributed by Raymond Hettinger.)

@item 
The @code{httplib} module now contains constants for HTTP status codes defined
in various HTTP-related RFC documents.  Constants have names such as
@code{OK}, @code{CREATED}, @code{CONTINUE}, and
@code{MOVED_PERMANENTLY}; use pydoc to get a full list.  (Contributed by
Andrew Eland.)

@item 
The @ref{98,,imaplib} module now supports IMAP's THREAD command (contributed by
Yves Dionne) and new @code{deleteacl()} and @code{myrights()} methods (contributed
by Arnaud Mazin).

@item 
The @ref{a3,,itertools} module gained a @code{groupby(iterable[, *func*])}
function. @emph{iterable} is something that can be iterated over to return a stream
of elements, and the optional @emph{func} parameter is a function that takes an
element and returns a key value; if omitted, the key is simply the element
itself.  @code{groupby()} then groups the elements into subsequences which have
matching values of the key, and returns a series of 2-tuples containing the key
value and an iterator over the subsequence.

Here's an example to make this clearer.  The @emph{key} function simply returns
whether a number is even or odd, so the result of @code{groupby()} is to return
consecutive runs of odd or even numbers.

@example
>>> import itertools
>>> L = [2, 4, 6, 7, 8, 9, 11, 12, 14]
>>> for key_val, it in itertools.groupby(L, lambda x: x % 2):
...    print key_val, list(it)
...
0 [2, 4, 6]
1 [7]
0 [8]
1 [9, 11]
0 [12, 14]
>>>
@end example

@code{groupby()} is typically used with sorted input.  The logic for
@code{groupby()} is similar to the Unix @code{uniq} filter which makes it handy for
eliminating, counting, or identifying duplicate elements:

@example
>>> word = 'abracadabra'
>>> letters = sorted(word)   # Turn string into a sorted list of letters
>>> letters
['a', 'a', 'a', 'a', 'a', 'b', 'b', 'c', 'd', 'r', 'r']
>>> for k, g in itertools.groupby(letters):
...    print k, list(g)
...
a ['a', 'a', 'a', 'a', 'a']
b ['b', 'b']
c ['c']
d ['d']
r ['r', 'r']
>>> # List unique letters
>>> [k for k, g in groupby(letters)]
['a', 'b', 'c', 'd', 'r']
>>> # Count letter occurrences
>>> [(k, len(list(g))) for k, g in groupby(letters)]
[('a', 5), ('b', 2), ('c', 1), ('d', 1), ('r', 2)]
@end example

（由 Hye-Shik Chang 贡献。）

@item 
@ref{a3,,itertools} also gained a function named @code{tee(iterator, N)} that
returns @emph{N} independent iterators that replicate @emph{iterator}.  If @emph{N} is omitted,
the default is 2.

@example
>>> L = [1,2,3]
>>> i1, i2 = itertools.tee(L)
>>> i1,i2
(<itertools.tee object at 0x402c2080>, <itertools.tee object at 0x402c2090>)
>>> list(i1)               # Run the first iterator to exhaustion
[1, 2, 3]
>>> list(i2)               # Run the second iterator to exhaustion
[1, 2, 3]
@end example

Note that @code{tee()} has to keep copies of the values returned  by the
iterator; in the worst case, it may need to keep all of them.   This should
therefore be used carefully if the leading iterator can run far ahead of the
trailing iterator in a long stream of inputs. If the separation is large, then
you might as well use  @ref{262,,list()} instead.  When the iterators track closely
with one another, @code{tee()} is ideal.  Possible applications include
bookmarking, windowing, or lookahead iterators. (Contributed by Raymond
Hettinger.)

@item 
A number of functions were added to the @ref{a9,,locale}  module, such as
@code{bind_textdomain_codeset()} to specify a particular encoding and a family of
@code{l*gettext()} functions that return messages in the chosen encoding.
(Contributed by Gustavo Niemeyer.)

@item 
Some keyword arguments were added to the @ref{aa,,logging} package's
@code{basicConfig()} function to simplify log configuration.  The default
behavior is to log messages to standard error, but various keyword arguments can
be specified to log to a particular file, change the logging format, or set the
logging level. For example:

@example
import logging
logging.basicConfig(filename='/var/log/application.log',
    level=0,  # Log all messages
    format='%(levelname):%(process):%(thread):%(message)')
@end example

Other additions to the @ref{aa,,logging} package include a @code{log(level, msg)}
convenience method, as well as a @code{TimedRotatingFileHandler} class that
rotates its log files at a timed interval.  The module already had
@code{RotatingFileHandler}, which rotated logs once the file exceeded a
certain size.  Both classes derive from a new @code{BaseRotatingHandler} class
that can be used to implement other rotating handlers.

（更改由 Vinay Sajip 实现。）

@item 
The @ref{b0,,marshal} module now shares interned strings on unpacking a  data
structure.  This may shrink the size of certain pickle strings, but the primary
effect is to make @code{.pyc} files significantly smaller. (Contributed by
Martin von Löwis.)

@item 
The @ref{c0,,nntplib} module's @code{NNTP} class gained @code{description()} and
@code{descriptions()} methods to retrieve  newsgroup descriptions for a single
group or for a range of groups. (Contributed by Jürgen A. Erhard.)

@item 
Two new functions were added to the @ref{c2,,operator} module,
@code{attrgetter(attr)} and @code{itemgetter(index)}. Both functions return
callables that take a single argument and return the corresponding attribute or
item; these callables make excellent data extractors when used with @ref{c26,,map()}
or @ref{43e,,sorted()}.  For example:

@example
>>> L = [('c', 2), ('d', 1), ('a', 4), ('b', 3)]
>>> map(operator.itemgetter(0), L)
['c', 'd', 'a', 'b']
>>> map(operator.itemgetter(1), L)
[2, 1, 4, 3]
>>> sorted(L, key=operator.itemgetter(1)) # Sort list by second tuple item
[('d', 1), ('c', 2), ('b', 3), ('a', 4)]
@end example

（由 Raymond Hettinger 贡献。）

@item 
The @ref{c3,,optparse} module was updated in various ways.  The module now passes
its messages through @ref{dc6,,gettext.gettext()}, making it possible to
internationalize Optik's help and error messages.  Help messages for options can
now include the string @code{'%default'}, which will be replaced by the option's
default value.  (Contributed by Greg Ward.)

@item 
The long-term plan is to deprecate the @code{rfc822} module in some future
Python release in favor of the @ref{69,,email} package. To this end, the
@code{email.Utils.formatdate()} function has been changed to make it usable as a
replacement for @code{rfc822.formatdate()}.  You may want to write new e-mail
processing code with this in mind.  (Change implemented by Anthony Baxter.)

@item 
A new @code{urandom(n)} function was added to the @ref{c4,,os} module, returning
a string containing @emph{n} bytes of random data.  This function provides access to
platform-specific sources of randomness such as @code{/dev/urandom} on Linux or
the Windows CryptoAPI.  (Contributed by Trevor Perrin.)

@item 
Another new function: @code{os.path.lexists(path)}  returns true if the file
specified by @emph{path} exists, whether or not it's a symbolic link.  This differs
from the existing @code{os.path.exists(path)} function, which returns false if
@emph{path} is a symlink that points to a destination that doesn't exist.
(Contributed by Beni Cherniavsky.)

@item 
A new @code{getsid()} function was added to the @ref{d1,,posix} module that
underlies the @ref{c4,,os} module. (Contributed by J. Raynor.)

@item 
The @ref{d0,,poplib} module now supports POP over SSL.  (Contributed by Hector
Urtubia.)

@item 
The @ref{d3,,profile} module can now profile C extension functions. (Contributed
by Nick Bastin.)

@item 
The @ref{dc,,random} module has a new method called @code{getrandbits(N)} that
returns a long integer @emph{N} bits in length.  The existing @code{randrange()}
method now uses @code{getrandbits()} where appropriate, making generation of
arbitrarily large random numbers more efficient.  (Contributed by Raymond
Hettinger.)

@item 
The regular expression language accepted by the @ref{dd,,re} module was extended
with simple conditional expressions, written as @code{(?(group)A|B)}.  @emph{group} is
either a numeric group ID or a group name defined with @code{(?P<group>...)}
earlier in the expression.  If the specified group matched, the regular
expression pattern @emph{A} will be tested against the string; if the group didn't
match, the pattern @emph{B} will be used instead. (Contributed by Gustavo Niemeyer.)

@item 
The @ref{dd,,re} module is also no longer recursive, thanks to a massive amount
of work by Gustavo Niemeyer.  In a recursive regular expression engine, certain
patterns result in a large amount of C stack space being consumed, and it was
possible to overflow the stack. For example, if you matched a 30000-byte string
of @code{a} characters against the expression @code{(a|b)+}, one stack frame was
consumed per character.  Python 2.3 tried to check for stack overflow and raise
a @ref{2ba,,RuntimeError} exception, but certain patterns could sidestep the
checking and if you were unlucky Python could segfault. Python 2.4's regular
expression engine can match this pattern without problems.

@item 
The @ref{ea,,signal} module now performs tighter error-checking on the parameters
to the @ref{a78,,signal.signal()} function.  For example, you can't set a handler on
the @code{SIGKILL} signal; previous versions of Python would quietly accept
this, but 2.4 will raise a @ref{2ba,,RuntimeError} exception.

@item 
Two new functions were added to the @ref{ef,,socket} module. @code{socketpair()}
returns a pair of connected sockets and @code{getservbyport(port)} looks up the
service name for a given port number. (Contributed by Dave Cole and Barry
Warsaw.)

@item 
The @code{sys.exitfunc()} function has been deprecated.  Code should be using
the existing @ref{c,,atexit} module, which correctly handles calling multiple exit
functions.  Eventually @code{sys.exitfunc()} will become a purely internal
interface, accessed only by @ref{c,,atexit}.

@item 
The @ref{101,,tarfile} module now generates GNU-format tar files by default.
(Contributed by Lars Gustäbel.)

@item 
The @ref{109,,threading} module now has an elegantly simple way to support
thread-local data.  The module contains a @code{local} class whose attribute
values are local to different threads.

@example
import threading

data = threading.local()
data.number = 42
data.url = ('www.python.org', 80)
@end example

Other threads can assign and retrieve their own values for the @code{number}
and @code{url} attributes.  You can subclass @code{local} to initialize
attributes or to add methods. (Contributed by Jim Fulton.)

@item 
The @ref{10b,,timeit} module now automatically disables periodic garbage
collection during the timing loop.  This change makes consecutive timings more
comparable.  (Contributed by Raymond Hettinger.)

@item 
The @ref{128,,weakref} module now supports a wider variety of objects including
Python functions, class instances, sets, frozensets, deques, arrays, files,
sockets, and regular expression pattern objects. (Contributed by Raymond
Hettinger.)

@item 
The @code{xmlrpclib} module now supports a multi-call extension for
transmitting multiple XML-RPC calls in a single HTTP operation. (Contributed by
Brian Quinlan.)

@item 
@code{mpz}, @code{rotor} 和 @code{xreadlines} 模块已被移除。
@end itemize

@c ======================================================================

@c whole new modules get described in subsections here

@c =====================

@menu
* cookielib:: 
* doctest: doctest<3>. 

@end menu

@node cookielib,doctest<3>,,新增，改进和弃用的模块<3>
@anchor{whatsnew/2 4 cookielib}@anchor{dc7}
@subsubsection cookielib


The @code{cookielib} library supports client-side handling for HTTP cookies,
mirroring the @code{Cookie} module's server-side cookie support. Cookies are
stored in cookie jars; the library transparently stores cookies offered by the
web server in the cookie jar, and fetches the cookie from the jar when
connecting to the server. As in web browsers, policy objects control whether
cookies are accepted or not.

In order to store cookies across sessions, two implementations of cookie jars
are provided: one that stores cookies in the Netscape format so applications can
use the Mozilla or Lynx cookie files, and one that stores cookies in the same
format as the Perl libwww library.

@code{urllib2} has been changed to interact with @code{cookielib}:
@code{HTTPCookieProcessor} manages a cookie jar that is used when accessing
URLs.

该模块由  John J. Lee 贡献。

@c ==================

@node doctest<3>,,cookielib,新增，改进和弃用的模块<3>
@anchor{whatsnew/2 4 doctest}@anchor{dc8}
@subsubsection doctest


The @ref{67,,doctest} module underwent considerable refactoring thanks to Edward
Loper and Tim Peters.  Testing can still be as simple as running
@ref{dc9,,doctest.testmod()}, but the refactorings allow customizing the module's
operation in various ways

The new @code{DocTestFinder} class extracts the tests from a given  object's
docstrings:

@example
def f (x, y):
    """>>> f(2,2)
4
>>> f(3,2)
6
    """
    return x*y

finder = doctest.DocTestFinder()

# Get list of DocTest instances
tests = finder.find(f)
@end example

The new @code{DocTestRunner} class then runs individual tests and can produce
a summary of the results:

@example
runner = doctest.DocTestRunner()
for t in tests:
    tried, failed = runner.run(t)

runner.summarize(verbose=1)
@end example

The above example produces the following output:

@example
1 items passed all tests:
   2 tests in f
2 tests in 1 items.
2 passed and 0 failed.
Test passed.
@end example

@code{DocTestRunner} uses an instance of the @code{OutputChecker} class to
compare the expected output with the actual output.  This class takes a number
of different flags that customize its behaviour; ambitious users can also write
a completely new subclass of @code{OutputChecker}.

The default output checker provides a number of handy features. For example,
with the @ref{dca,,doctest.ELLIPSIS} option flag, an ellipsis (@code{...}) in the
expected output matches any substring,  making it easier to accommodate outputs
that vary in minor ways:

@example
def o (n):
    """>>> o(1)
<__main__.C instance at 0x...>
>>>
"""
@end example

Another special string, @code{<BLANKLINE>}, matches a blank line:

@example
def p (n):
    """>>> p(1)
<BLANKLINE>
>>>
"""
@end example

Another new capability is producing a diff-style display of the output by
specifying the @ref{dcb,,doctest.REPORT_UDIFF} (unified diffs),
@ref{dcc,,doctest.REPORT_CDIFF} (context diffs), or @ref{dcd,,doctest.REPORT_NDIFF}
(delta-style) option flags.  For example:

@example
def g (n):
    """>>> g(4)
here
is
a
lengthy
>>>"""
    L = 'here is a rather lengthy list of words'.split()
    for word in L[:n]:
        print word
@end example

Running the above function's tests with @ref{dcb,,doctest.REPORT_UDIFF} specified,
you get the following output:

@example
**********************************************************************
File "t.py", line 15, in g
Failed example:
    g(4)
Differences (unified diff with -expected +actual):
    @@@@ -2,3 +2,3 @@@@
     is
     a
    -lengthy
    +rather
**********************************************************************
@end example

@c ======================================================================

@node 构建和 C API 的改变<11>,移植到 Python 2 4,新增，改进和弃用的模块<3>,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 build-and-c-api-changes}@anchor{dce}
@subsection 构建和 C API 的改变


Some of the changes to Python's build process and to the C API are:


@itemize *

@item 
Three new convenience macros were added for common return values from
extension functions: @ref{dcf,,Py_RETURN_NONE}, @ref{dd0,,Py_RETURN_TRUE}, and
@ref{dd1,,Py_RETURN_FALSE}. (Contributed by Brett Cannon.)

@item 
Another new macro, @code{Py_CLEAR(obj)},  decreases the reference count of
@emph{obj} and sets @emph{obj} to the null pointer.  (Contributed by Jim Fulton.)

@item 
A new function, @code{PyTuple_Pack(N, obj1, obj2, ..., objN)}, constructs
tuples from a variable length argument list of Python objects.  (Contributed by
Raymond Hettinger.)

@item 
A new function, @code{PyDict_Contains(d, k)}, implements fast dictionary
lookups without masking exceptions raised during the look-up process.
(Contributed by Raymond Hettinger.)

@item 
The @code{Py_IS_NAN(X)} macro returns 1 if  its float or double argument
@emph{X} is a NaN.   (Contributed by Tim Peters.)

@item 
C code can avoid unnecessary locking by using the new
@ref{dd2,,PyEval_ThreadsInitialized()} function to tell  if any thread operations
have been performed.  If this function  returns false, no lock operations are
needed. (Contributed by Nick Coghlan.)

@item 
A new function, @ref{dd3,,PyArg_VaParseTupleAndKeywords()}, is the same as
@ref{5c5,,PyArg_ParseTupleAndKeywords()} but takes a  @code{va_list} instead of a
number of arguments. (Contributed by Greg Chapman.)

@item 
A new method flag, @code{METH_COEXISTS}, allows a function defined in slots
to co-exist with a @ref{dd4,,PyCFunction} having the same name.  This can halve
the access time for a method such as @code{set.__contains__()}.  (Contributed by
Raymond Hettinger.)

@item 
Python can now be built with additional profiling for the interpreter itself,
intended as an aid to people developing the Python core.  Providing
@code{--enable-profiling} to the @code{configure} script will let you
profile the interpreter with @code{gprof}, and providing the
@code{--with-tsc} switch enables profiling using the Pentium's
Time-Stamp-Counter register.  Note that the @code{--with-tsc} switch is slightly
misnamed, because the profiling feature also works on the PowerPC platform,
though that processor architecture doesn't call that register "the TSC
register".  (Contributed by Jeremy Hylton.)

@item 
The @code{tracebackobject} type has been renamed to
@code{PyTracebackObject}.
@end itemize

@c ======================================================================

@menu
* Port-Specific Changes: Port-Specific Changes<2>. 

@end menu

@node Port-Specific Changes<2>,,,构建和 C API 的改变<11>
@anchor{whatsnew/2 4 port-specific-changes}@anchor{dd5}
@subsubsection Port-Specific Changes



@itemize *

@item 
The Windows port now builds under MSVC++ 7.1 as well as version 6.
(Contributed by Martin von Löwis.)
@end itemize

@c ======================================================================

@node 移植到 Python 2 4,致谢<4>,构建和 C API 的改变<11>,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 porting-to-python-2-4}@anchor{dd6}
@subsection 移植到 Python 2.4


This section lists previously described changes that may require changes to your
code:


@itemize *

@item 
Left shifts and hexadecimal/octal constants that are too  large no longer
trigger a @ref{31e,,FutureWarning} and return  a value limited to 32 or 64 bits;
instead they return a long integer.

@item 
Integer operations will no longer trigger an @code{OverflowWarning}. The
@code{OverflowWarning} warning will disappear in Python 2.5.

@item 
The @ref{c2b,,zip()} built-in function and @code{itertools.izip()} now return  an
empty list instead of raising a @ref{192,,TypeError} exception if called with no
arguments.

@item 
You can no longer compare the @code{date} and @ref{194,,datetime} instances
provided by the @ref{31,,datetime} module.  Two  instances of different classes
will now always be unequal, and  relative comparisons (@code{<}, @code{>}) will raise
a @ref{192,,TypeError}.

@item 
@code{dircache.listdir()} now passes exceptions to the caller instead of
returning empty lists.

@item 
@code{LexicalHandler.startDTD()} used to receive the public and system IDs in
the wrong order.  This has been corrected; applications relying on the wrong
order need to be fixed.

@item 
@ref{dd7,,fcntl.ioctl()} now warns if the @emph{mutate}  argument is omitted and
relevant.

@item 
The @ref{101,,tarfile} module now generates GNU-format tar files by default.

@item 
Encountering a failure while importing a module no longer leaves a
partially-initialized module object in @code{sys.modules}.

@item 
@ref{157,,None} is now a constant; code that binds a new value to  the name
@code{None} is now a syntax error.

@item 
The @code{signals.signal()} function now raises a @ref{2ba,,RuntimeError} exception
for certain illegal values; previously these errors would pass silently.  For
example, you can no longer set a handler on the @code{SIGKILL} signal.
@end itemize

@c ======================================================================

@node 致谢<4>,,移植到 Python 2 4,Python 2 4 有什么新变化
@anchor{whatsnew/2 4 acknowledgements}@anchor{dd8}@anchor{whatsnew/2 4 acks}@anchor{dd9}
@subsection 致谢


作者感谢以下人员对本文各种草稿给予的建议，更正和协助：Koray Can, Hye-Shik Chang, Michael Dyck, Raymond Hettinger, Brian Hurt, Hamish Lawson, Fredrik Lundh, Sean Reifschneider, Sadruddin Rejeb.

@node Python 2 3 有什么新变化,Python 2 2 有什么新变化,Python 2 4 有什么新变化,Python的新变化
@anchor{whatsnew/2 3 doc}@anchor{dda}@anchor{whatsnew/2 3 what-s-new-in-python-2-3}@anchor{ddb}
@section Python 2.3 有什么新变化


@*作者: 
A.M. Kuchling


@c $Id: whatsnew23.tex 54631 2007-03-31 11:58:36Z georg.brandl $

This article explains the new features in Python 2.3.  Python 2.3 was released
on July 29, 2003.

The main themes for Python 2.3 are polishing some of the features added in 2.2,
adding various small but useful enhancements to the core language, and expanding
the standard library.  The new object model introduced in the previous version
has benefited from 18 months of bugfixes and from optimization efforts that have
improved the performance of new-style classes.  A few new built-in functions
have been added such as @ref{1e5,,sum()} and @ref{ddc,,enumerate()}.  The @ref{79d,,in}
operator can now be used for substring searches (e.g. @code{"ab" in "abc"} returns
@ref{494,,True}).

Some of the many new library features include Boolean, set, heap, and date/time
data types, the ability to import modules from ZIP-format archives, metadata
support for the long-awaited Python catalog, an updated version of IDLE, and
modules for logging messages, wrapping text, parsing CSV files, processing
command-line options, using BerkeleyDB databases...  the list of new and
enhanced modules is lengthy.

This article doesn't attempt to provide a complete specification of the new
features, but instead provides a convenient overview.  For full details, you
should refer to the documentation for Python 2.3, such as the Python Library
Reference and the Python Reference Manual.  If you want to understand the
complete implementation and design rationale, refer to the PEP for a particular
new feature.

@c ======================================================================

@menu
* PEP 218; A Standard Set Datatype: PEP 218 A Standard Set Datatype. 
* PEP 255; Simple Generators: PEP 255 Simple Generators. 
* PEP 263; Source Code Encodings: PEP 263 Source Code Encodings. 
* PEP 273; 从ZIP压缩包导入模块: PEP 273 从ZIP压缩包导入模块. 
* PEP 277; Unicode file name support for Windows NT: PEP 277 Unicode file name support for Windows NT. 
* PEP 278; 通用换行支持: PEP 278 通用换行支持. 
* PEP 279; enumerate(): PEP 279 enumerate. 
* PEP 282; logging 包: PEP 282 logging 包. 
* PEP 285; 布尔类型: PEP 285 布尔类型. 
* PEP 293; Codec Error Handling Callbacks: PEP 293 Codec Error Handling Callbacks. 
* PEP 301; Distutils的软件包索引和元数据: PEP 301 Distutils的软件包索引和元数据. 
* PEP 302; New Import Hooks: PEP 302 New Import Hooks. 
* PEP 305; 逗号分隔文件: PEP 305 逗号分隔文件. 
* PEP 307; Pickle Enhancements: PEP 307 Pickle Enhancements. 
* 扩展切片:: 
* 其他语言特性修改: 其他语言特性修改<13>. 
* 新增，改进和弃用的模块: 新增，改进和弃用的模块<4>. 
* Pymalloc; A Specialized Object Allocator: Pymalloc A Specialized Object Allocator. 
* 构建和 C API 的改变: 构建和 C API 的改变<12>. 
* Other Changes and Fixes: Other Changes and Fixes<2>. 
* 移植到 Python 2.3: 移植到 Python 2 3. 
* 致谢: 致谢<5>. 

@end menu

@node PEP 218 A Standard Set Datatype,PEP 255 Simple Generators,,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-218-a-standard-set-datatype}@anchor{ddd}
@subsection PEP 218: A Standard Set Datatype


The new @code{sets} module contains an implementation of a set datatype.  The
@code{Set} class is for mutable sets, sets that can have members added and
removed.  The @code{ImmutableSet} class is for sets that can't be modified,
and instances of @code{ImmutableSet} can therefore be used as dictionary keys.
Sets are built on top of dictionaries, so the elements within a set must be
hashable.

这是一个简单的示例：

@example
>>> import sets
>>> S = sets.Set([1,2,3])
>>> S
Set([1, 2, 3])
>>> 1 in S
True
>>> 0 in S
False
>>> S.add(5)
>>> S.remove(3)
>>> S
Set([1, 2, 5])
>>>
@end example

The union and intersection of sets can be computed with the @code{union()} and
@code{intersection()} methods; an alternative notation uses the bitwise operators
@code{&} and @code{|}. Mutable sets also have in-place versions of these methods,
@code{union_update()} and @code{intersection_update()}.

@example
>>> S1 = sets.Set([1,2,3])
>>> S2 = sets.Set([4,5,6])
>>> S1.union(S2)
Set([1, 2, 3, 4, 5, 6])
>>> S1 | S2                  # Alternative notation
Set([1, 2, 3, 4, 5, 6])
>>> S1.intersection(S2)
Set([])
>>> S1 & S2                  # Alternative notation
Set([])
>>> S1.union_update(S2)
>>> S1
Set([1, 2, 3, 4, 5, 6])
>>>
@end example

It's also possible to take the symmetric difference of two sets.  This is the
set of all elements in the union that aren't in the intersection.  Another way
of putting it is that the symmetric difference contains all elements that are in
exactly one set.  Again, there's an alternative notation (@code{^}), and an
in-place version with the ungainly name @code{symmetric_difference_update()}.

@example
>>> S1 = sets.Set([1,2,3,4])
>>> S2 = sets.Set([3,4,5,6])
>>> S1.symmetric_difference(S2)
Set([1, 2, 5, 6])
>>> S1 ^ S2
Set([1, 2, 5, 6])
>>>
@end example

There are also @code{issubset()} and @code{issuperset()} methods for checking
whether one set is a subset or superset of another:

@example
>>> S1 = sets.Set([1,2,3])
>>> S2 = sets.Set([2,3])
>>> S2.issubset(S1)
True
>>> S1.issubset(S2)
False
>>> S1.issuperset(S2)
True
>>>
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 218

@item PEP 218@footnote{https://www.python.org/dev/peps/pep-0218} - 添加内置Set对象类型

PEP 由 Greg V. Wilson 撰写 ; 由 Greg V. Wilson, Alex Martelli 和 GvR 实现。
@end table


@c ======================================================================

@node PEP 255 Simple Generators,PEP 263 Source Code Encodings,PEP 218 A Standard Set Datatype,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-255-simple-generators}@anchor{dde}@anchor{whatsnew/2 3 section-generators}@anchor{ddf}
@subsection PEP 255: Simple Generators


In Python 2.2, generators were added as an optional feature, to be enabled by a
@code{from __future__ import generators} directive.  In 2.3 generators no longer
need to be specially enabled, and are now always present; this means that
@ref{18f,,yield} is now always a keyword.  The rest of this section is a copy of
the description of generators from the "What's New in Python 2.2" document; if
you read it back when Python 2.2 came out, you can skip the rest of this
section.

You're doubtless familiar with how function calls work in Python or C. When you
call a function, it gets a private namespace where its local variables are
created.  When the function reaches a @ref{190,,return} statement, the local
variables are destroyed and the resulting value is returned to the caller.  A
later call to the same function will get a fresh new set of local variables.
But, what if the local variables weren't thrown away on exiting a function?
What if you could later resume the function where it left off?  This is what
generators provide; they can be thought of as resumable functions.

Here's the simplest example of a generator function:

@example
def generate_ints(N):
    for i in range(N):
        yield i
@end example

A new keyword, @ref{18f,,yield}, was introduced for generators.  Any function
containing a @code{yield} statement is a generator function; this is
detected by Python's bytecode compiler which compiles the function specially as
a result.

When you call a generator function, it doesn't return a single value; instead it
returns a generator object that supports the iterator protocol.  On executing
the @ref{18f,,yield} statement, the generator outputs the value of @code{i},
similar to a @ref{190,,return} statement.  The big difference between
@code{yield} and a @code{return} statement is that on reaching a
@code{yield} the generator's state of execution is suspended and local
variables are preserved.  On the next call to the generator's @code{.next()}
method, the function will resume executing immediately after the
@code{yield} statement.  (For complicated reasons, the @code{yield}
statement isn't allowed inside the @ref{d6b,,try} block of a
@code{try}...@code{finally} statement; read 
@geindex Python 提高建议; PEP 255
PEP 255@footnote{https://www.python.org/dev/peps/pep-0255} for a full
explanation of the interaction between @code{yield} and exceptions.)

Here's a sample usage of the @code{generate_ints()} generator:

@example
>>> gen = generate_ints(3)
>>> gen
<generator object at 0x8117f90>
>>> gen.next()
0
>>> gen.next()
1
>>> gen.next()
2
>>> gen.next()
Traceback (most recent call last):
  File "stdin", line 1, in ?
  File "stdin", line 2, in generate_ints
StopIteration
@end example

You could equally write @code{for i in generate_ints(5)}, or @code{a,b,c =
generate_ints(3)}.

Inside a generator function, the @ref{190,,return} statement can only be used
without a value, and signals the end of the procession of values; afterwards the
generator cannot return any further values. @code{return} with a value, such
as @code{return 5}, is a syntax error inside a generator function.  The end of the
generator's results can also be indicated by raising @ref{480,,StopIteration}
manually, or by just letting the flow of execution fall off the bottom of the
function.

You could achieve the effect of generators manually by writing your own class
and storing all the local variables of the generator as instance variables.  For
example, returning a list of integers could be done by setting @code{self.count} to
0, and having the @ref{67c,,next()} method increment @code{self.count} and return it.
However, for a moderately complicated generator, writing a corresponding class
would be much messier. @code{Lib/test/test_generators.py} contains a number of
more interesting examples.  The simplest one implements an in-order traversal of
a tree using generators recursively.

@example
# A recursive generator that generates Tree leaves in in-order.
def inorder(t):
    if t:
        for x in inorder(t.left):
            yield x
        yield t.label
        for x in inorder(t.right):
            yield x
@end example

Two other examples in @code{Lib/test/test_generators.py} produce solutions for
the N-Queens problem (placing $N$ queens on an $NxN$ chess board so that no
queen threatens another) and the Knight's Tour (a route that takes a knight to
every square of an $NxN$ chessboard without visiting any square twice).

The idea of generators comes from other programming languages, especially Icon
(@indicateurl{https://www.cs.arizona.edu/icon/}), where the idea of generators is central.  In
Icon, every expression and function call behaves like a generator.  One example
from "An Overview of the Icon Programming Language" at
@indicateurl{https://www.cs.arizona.edu/icon/docs/ipd266.htm} gives an idea of what this looks
like:

@example
sentence := "Store it in the neighboring harbor"
if (i := find("or", sentence)) > 5 then write(i)
@end example

In Icon the @code{find()} function returns the indexes at which the substring
"or" is found: 3, 23, 33.  In the @ref{de0,,if} statement, @code{i} is first
assigned a value of 3, but 3 is less than 5, so the comparison fails, and Icon
retries it with the second value of 23.  23 is greater than 5, so the comparison
now succeeds, and the code prints the value 23 to the screen.

Python doesn't go nearly as far as Icon in adopting generators as a central
concept.  Generators are considered part of the core Python language, but
learning or using them isn't compulsory; if they don't solve any problems that
you have, feel free to ignore them. One novel feature of Python's interface as
compared to Icon's is that a generator's state is represented as a concrete
object (the iterator) that can be passed around to other functions or stored in
a data structure.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 255

@item PEP 255@footnote{https://www.python.org/dev/peps/pep-0255} - 简单生成器

Written by Neil Schemenauer, Tim Peters, Magnus Lie Hetland.  Implemented mostly
by Neil Schemenauer and Tim Peters, with other fixes from the Python Labs crew.
@end table


@c ======================================================================

@node PEP 263 Source Code Encodings,PEP 273 从ZIP压缩包导入模块,PEP 255 Simple Generators,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-263-source-code-encodings}@anchor{de1}@anchor{whatsnew/2 3 section-encodings}@anchor{de2}
@subsection PEP 263: Source Code Encodings


Python source files can now be declared as being in different character set
encodings.  Encodings are declared by including a specially formatted comment in
the first or second line of the source file.  For example, a UTF-8 file can be
declared with:

@example
#!/usr/bin/env python
# -*- coding: UTF-8 -*-
@end example

Without such an encoding declaration, the default encoding used is 7-bit ASCII.
Executing or importing modules that contain string literals with 8-bit
characters and have no encoding declaration will result in a
@ref{278,,DeprecationWarning} being signalled by Python 2.3; in 2.4 this will be a
syntax error.

The encoding declaration only affects Unicode string literals, which will be
converted to Unicode using the specified encoding.  Note that Python identifiers
are still restricted to ASCII characters, so you can't have variable names that
use characters outside of the usual alphanumerics.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 263

@item PEP 263@footnote{https://www.python.org/dev/peps/pep-0263} - Defining Python Source Code Encodings

由 Marc-André Lemburg 和 Martin von Löwis 撰写 ; 由 Suzuki Hisao 和 Martin von Löwis 实现。
@end table


@c ======================================================================

@node PEP 273 从ZIP压缩包导入模块,PEP 277 Unicode file name support for Windows NT,PEP 263 Source Code Encodings,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-273-importing-modules-from-zip-archives}@anchor{de3}
@subsection PEP 273: 从ZIP压缩包导入模块


The new @ref{143,,zipimport} module adds support for importing modules from a
ZIP-format archive.  You don't need to import the module explicitly; it will be
automatically imported if a ZIP archive's filename is added to @code{sys.path}.
For example:

@example
amk@@nyman:~/src/python$ unzip -l /tmp/example.zip
Archive:  /tmp/example.zip
  Length     Date   Time    Name
 --------    ----   ----    ----
     8467  11-26-02 22:30   jwzthreading.py
 --------                   -------
     8467                   1 file
amk@@nyman:~/src/python$ ./python
Python 2.3 (#1, Aug 1 2003, 19:54:32)
>>> import sys
>>> sys.path.insert(0, '/tmp/example.zip')  # Add .zip file to front of path
>>> import jwzthreading
>>> jwzthreading.__file__
'/tmp/example.zip/jwzthreading.py'
>>>
@end example

An entry in @code{sys.path} can now be the filename of a ZIP archive. The ZIP
archive can contain any kind of files, but only files named @code{*.py},
@code{*.pyc}, or @code{*.pyo} can be imported.  If an archive only contains
@code{*.py} files, Python will not attempt to modify the archive by adding the
corresponding @code{*.pyc} file, meaning that if a ZIP archive doesn't contain
@code{*.pyc} files, importing may be rather slow.

A path within the archive can also be specified to only import from a
subdirectory; for example, the path @code{/tmp/example.zip/lib/} would only
import from the @code{lib/} subdirectory within the archive.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 273

@item PEP 273@footnote{https://www.python.org/dev/peps/pep-0273} -  从ZIP压缩包导入模块

Written by James C. Ahlstrom,  who also provided an implementation. Python 2.3
follows the specification in 
@geindex Python 提高建议; PEP 273
PEP 273@footnote{https://www.python.org/dev/peps/pep-0273},  but uses an implementation written by
Just van Rossum  that uses the import hooks described in 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}. See section
@ref{de4,,PEP 302; New Import Hooks} for a description of the new import hooks.
@end table


@c ======================================================================

@node PEP 277 Unicode file name support for Windows NT,PEP 278 通用换行支持,PEP 273 从ZIP压缩包导入模块,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-277-unicode-file-name-support-for-windows-nt}@anchor{de5}
@subsection PEP 277: Unicode file name support for Windows NT


On Windows NT, 2000, and XP, the system stores file names as Unicode strings.
Traditionally, Python has represented file names as byte strings, which is
inadequate because it renders some file names inaccessible.

Python now allows using arbitrary Unicode strings (within the limitations of the
file system) for all functions that expect file names, most notably the
@ref{4ea,,open()} built-in function. If a Unicode string is passed to
@ref{a3c,,os.listdir()}, Python now returns a list of Unicode strings.  A new
function, @code{os.getcwdu()}, returns the current directory as a Unicode string.

Byte strings still work as file names, and on Windows Python will transparently
convert them to Unicode using the @code{mbcs} encoding.

Other systems also allow Unicode strings as file names but convert them to byte
strings before passing them to the system, which can cause a @ref{c34,,UnicodeError}
to be raised. Applications can test whether arbitrary Unicode strings are
supported as file names by checking @ref{de6,,os.path.supports_unicode_filenames},
a Boolean value.

Under MacOS, @ref{a3c,,os.listdir()} may now return Unicode filenames.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 277

@item PEP 277@footnote{https://www.python.org/dev/peps/pep-0277} - Unicode file name support for Windows NT

由 Neil Hodgson 撰写 ; 由 Neil Hodgson, Martin von Löwis 和 Mark Hammond 实现。
@end table


@c ======================================================================

@geindex universal newlines; What's new

@node PEP 278 通用换行支持,PEP 279 enumerate,PEP 277 Unicode file name support for Windows NT,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-278-universal-newline-support}@anchor{de7}
@subsection PEP 278: 通用换行支持


The three major operating systems used today are Microsoft Windows, Apple's
Macintosh OS, and the various Unix derivatives.  A minor irritation of
cross-platform work  is that these three platforms all use different characters to
mark the ends of lines in text files.  Unix uses the linefeed (ASCII character
10), MacOS uses the carriage return (ASCII character 13), and Windows uses a
two-character sequence of a carriage return plus a newline.

Python's file objects can now support end of line conventions other than the
one followed by the platform on which Python is running. Opening a file with
the mode @code{'U'} or @code{'rU'} will open a file for reading in @ref{5ef,,universal newlines} mode.  All three line ending conventions will be translated to a
@code{'\n'} in the strings returned by the various file methods such as
@code{read()} and @ref{de,,readline()}.

Universal newline support is also used when importing modules and when executing
a file with the @code{execfile()} function.  This means that Python modules can
be shared between all three operating systems without needing to convert the
line-endings.

This feature can be disabled when compiling Python by specifying the
@code{--without-universal-newlines} switch when running Python's
@code{configure} script.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 278

@item PEP 278@footnote{https://www.python.org/dev/peps/pep-0278} - 通用换行支持

由 Jack Jansen 撰写并实现。
@end table


@c ======================================================================

@node PEP 279 enumerate,PEP 282 logging 包,PEP 278 通用换行支持,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-279-enumerate}@anchor{de8}@anchor{whatsnew/2 3 section-enumerate}@anchor{de9}
@subsection PEP 279: enumerate()


A new built-in function, @ref{ddc,,enumerate()}, will make certain loops a bit
clearer.  @code{enumerate(thing)}, where @emph{thing} is either an iterator or a
sequence, returns an iterator that will return @code{(0, thing[0])}, @code{(1,
thing[1])}, @code{(2, thing[2])}, and so forth.

A common idiom to change every element of a list looks like this:

@example
for i in range(len(L)):
    item = L[i]
    # ... compute some result based on item ...
    L[i] = result
@end example

可以使用 @ref{ddc,,enumerate()} 重写为：

@example
for i, item in enumerate(L):
    # ... compute some result based on item ...
    L[i] = result
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 279

@item PEP 279@footnote{https://www.python.org/dev/peps/pep-0279} - 内置函数 enumerate()

由 Raymond D. Hettinger 撰写并实现。
@end table


@c ======================================================================

@node PEP 282 logging 包,PEP 285 布尔类型,PEP 279 enumerate,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-282-the-logging-package}@anchor{dea}
@subsection PEP 282: logging 包


A standard package for writing logs, @ref{aa,,logging}, has been added to Python
2.3.  It provides a powerful and flexible mechanism for generating logging
output which can then be filtered and processed in various ways.  A
configuration file written in a standard format can be used to control the
logging behavior of a program.  Python includes handlers that will write log
records to standard error or to a file or socket, send them to the system log,
or even e-mail them to a particular address; of course, it's also possible to
write your own handler classes.

The @code{Logger} class is the primary class. Most application code will deal
with one or more @code{Logger} objects, each one used by a particular
subsystem of the application. Each @code{Logger} is identified by a name, and
names are organized into a hierarchy using @code{.}  as the component separator.
For example, you might have @code{Logger} instances named @code{server},
@code{server.auth} and @code{server.network}.  The latter two instances are below
@code{server} in the hierarchy.  This means that if you turn up the verbosity for
@code{server} or direct @code{server} messages to a different handler, the changes
will also apply to records logged to @code{server.auth} and @code{server.network}.
There's also a root @code{Logger} that's the parent of all other loggers.

For simple uses, the @ref{aa,,logging} package contains some convenience functions
that always use the root log:

@example
import logging

logging.debug('Debugging information')
logging.info('Informational message')
logging.warning('Warning:config file %s not found', 'server.conf')
logging.error('Error occurred')
logging.critical('Critical error -- shutting down')
@end example

This produces the following output:

@example
WARNING:root:Warning:config file server.conf not found
ERROR:root:Error occurred
CRITICAL:root:Critical error -- shutting down
@end example

In the default configuration, informational and debugging messages are
suppressed and the output is sent to standard error.  You can enable the display
of informational and debugging messages by calling the @code{setLevel()} method
on the root logger.

Notice the @code{warning()} call's use of string formatting operators; all of the
functions for logging messages take the arguments @code{(msg, arg1, arg2, ...)} and
log the string resulting from @code{msg % (arg1, arg2, ...)}.

There's also an @code{exception()} function that records the most recent
traceback.  Any of the other functions will also record the traceback if you
specify a true value for the keyword argument @emph{exc_info}.

@example
def f():
    try:    1/0
    except: logging.exception('Problem recorded')

f()
@end example

This produces the following output:

@example
ERROR:root:Problem recorded
Traceback (most recent call last):
  File "t.py", line 6, in f
    1/0
ZeroDivisionError: integer division or modulo by zero
@end example

Slightly more advanced programs will use a logger other than the root logger.
The @code{getLogger(name)} function is used to get a particular log, creating
it if it doesn't exist yet. @code{getLogger(None)} returns the root logger.

@example
log = logging.getLogger('server')
 ...
log.info('Listening on port %i', port)
 ...
log.critical('Disk full')
 ...
@end example

Log records are usually propagated up the hierarchy, so a message logged to
@code{server.auth} is also seen by @code{server} and @code{root}, but a @code{Logger}
can prevent this by setting its @code{propagate} attribute to @ref{380,,False}.

There are more classes provided by the @ref{aa,,logging} package that can be
customized.  When a @code{Logger} instance is told to log a message, it
creates a @code{LogRecord} instance that is sent to any number of different
@code{Handler} instances.  Loggers and handlers can also have an attached list
of filters, and each filter can cause the @code{LogRecord} to be ignored or
can modify the record before passing it along.  When they're finally output,
@code{LogRecord} instances are converted to text by a @code{Formatter}
class.  All of these classes can be replaced by your own specially-written
classes.

With all of these features the @ref{aa,,logging} package should provide enough
flexibility for even the most complicated applications.  This is only an
incomplete overview of its features, so please see the package's reference
documentation for all of the details.  Reading 
@geindex Python 提高建议; PEP 282
PEP 282@footnote{https://www.python.org/dev/peps/pep-0282} will also be helpful.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 282

@item PEP 282@footnote{https://www.python.org/dev/peps/pep-0282} - Logging 系统

由 Vinay Sajip 和 Trent Mick 撰写 ; 由 Vinay Sajip 实现。
@end table


@c ======================================================================

@node PEP 285 布尔类型,PEP 293 Codec Error Handling Callbacks,PEP 282 logging 包,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-285-a-boolean-type}@anchor{deb}@anchor{whatsnew/2 3 section-bool}@anchor{dec}
@subsection PEP 285: 布尔类型


A Boolean type was added to Python 2.3.  Two new constants were added to the
@code{__builtin__} module, @ref{494,,True} and @ref{380,,False}.  (@ref{494,,True} and
@ref{380,,False} constants were added to the built-ins in Python 2.2.1, but the
2.2.1 versions are simply set to integer values of 1 and 0 and aren't a
different type.)

The type object for this new type is named @ref{183,,bool}; the constructor for it
takes any Python value and converts it to @ref{494,,True} or @ref{380,,False}.

@example
>>> bool(1)
True
>>> bool(0)
False
>>> bool([])
False
>>> bool( (1,) )
True
@end example

Most of the standard library modules and built-in functions have been changed to
return Booleans.

@example
>>> obj = []
>>> hasattr(obj, 'append')
True
>>> isinstance(obj, list)
True
>>> isinstance(obj, tuple)
False
@end example

Python's Booleans were added with the primary goal of making code clearer.  For
example, if you're reading a function and encounter the statement @code{return 1},
you might wonder whether the @code{1} represents a Boolean truth value, an index,
or a coefficient that multiplies some other quantity.  If the statement is
@code{return True}, however, the meaning of the return value is quite clear.

Python's Booleans were @emph{not} added for the sake of strict type-checking.  A very
strict language such as Pascal would also prevent you performing arithmetic with
Booleans, and would require that the expression in an @ref{de0,,if} statement
always evaluate to a Boolean result.  Python is not this strict and never will
be, as 
@geindex Python 提高建议; PEP 285
PEP 285@footnote{https://www.python.org/dev/peps/pep-0285} explicitly says.  This means you can still use any expression
in an @code{if} statement, even ones that evaluate to a list or tuple or
some random object.  The Boolean type is a subclass of the @ref{184,,int} class so
that arithmetic using a Boolean still works.

@example
>>> True + 1
2
>>> False + 1
1
>>> False * 75
0
>>> True * 75
75
@end example

To sum up @ref{494,,True} and @ref{380,,False} in a sentence: they're alternative
ways to spell the integer values 1 and 0, with the single difference that
@ref{329,,str()} and @ref{7c6,,repr()} return the strings @code{'True'} and @code{'False'}
instead of @code{'1'} and @code{'0'}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 285

@item PEP 285@footnote{https://www.python.org/dev/peps/pep-0285} - 添加布尔类型

由 GvR 撰写并实现。
@end table


@c ======================================================================

@node PEP 293 Codec Error Handling Callbacks,PEP 301 Distutils的软件包索引和元数据,PEP 285 布尔类型,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-293-codec-error-handling-callbacks}@anchor{ded}
@subsection PEP 293: Codec Error Handling Callbacks


When encoding a Unicode string into a byte string, unencodable characters may be
encountered.  So far, Python has allowed specifying the error processing as
either "strict" (raising @ref{c34,,UnicodeError}), "ignore" (skipping the
character), or "replace" (using a question mark in the output string), with
"strict" being the default behavior. It may be desirable to specify alternative
processing of such errors, such as inserting an XML character reference or HTML
entity reference into the converted string.

Python now has a flexible framework to add different processing strategies.  New
error handlers can be added with @ref{dee,,codecs.register_error()}, and codecs then
can access the error handler with @ref{def,,codecs.lookup_error()}. An equivalent C
API has been added for codecs written in C. The error handler gets the necessary
state information such as the string being converted, the position in the string
where the error was detected, and the target encoding.  The handler can then
either raise an exception or return a replacement string.

Two additional error handlers have been implemented using this framework:
"backslashreplace" uses Python backslash quoting to represent unencodable
characters and "xmlcharrefreplace" emits XML character references.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 293

@item PEP 293@footnote{https://www.python.org/dev/peps/pep-0293} - Codec Error Handling Callbacks

由 Walter Dörwald 撰写并实现。
@end table


@c ======================================================================

@node PEP 301 Distutils的软件包索引和元数据,PEP 302 New Import Hooks,PEP 293 Codec Error Handling Callbacks,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-301-package-index-and-metadata-for-distutils}@anchor{df0}@anchor{whatsnew/2 3 section-pep301}@anchor{df1}
@subsection PEP 301: Distutils的软件包索引和元数据


Support for the long-requested Python catalog makes its first appearance in 2.3.

The heart of the catalog is the new Distutils @code{register} command.
Running @code{python setup.py register} will collect the metadata describing a
package, such as its name, version, maintainer, description, &c., and send it to
a central catalog server.  The resulting catalog is available from
@indicateurl{https://pypi.org}.

To make the catalog a bit more useful, a new optional @emph{classifiers} keyword
argument has been added to the Distutils @code{setup()} function.  A list of
Trove@footnote{http://catb.org/~esr/trove/}-style strings can be supplied to help
classify the software.

Here's an example @code{setup.py} with classifiers, written to be compatible
with older versions of the Distutils:

@example
from distutils import core
kw = @{'name': "Quixote",
      'version': "0.5.1",
      'description': "A highly Pythonic Web application framework",
      # ...
      @}

if (hasattr(core, 'setup_keywords') and
    'classifiers' in core.setup_keywords):
    kw['classifiers'] = \
        ['Topic :: Internet :: WWW/HTTP :: Dynamic Content',
         'Environment :: No Input/Output (Daemon)',
         'Intended Audience :: Developers'],

core.setup(**kw)
@end example

The full list of classifiers can be obtained by running  @code{python setup.py
register --list-classifiers}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 301

@item PEP 301@footnote{https://www.python.org/dev/peps/pep-0301} - Distutils 的软件包索引和元数据

由 Richard Jones 撰写并实现。
@end table


@c ======================================================================

@node PEP 302 New Import Hooks,PEP 305 逗号分隔文件,PEP 301 Distutils的软件包索引和元数据,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-302-new-import-hooks}@anchor{df2}@anchor{whatsnew/2 3 section-pep302}@anchor{de4}
@subsection PEP 302: New Import Hooks


While it's been possible to write custom import hooks ever since the
@code{ihooks} module was introduced in Python 1.3, no one has ever been really
happy with it because writing new import hooks is difficult and messy.  There
have been various proposed alternatives such as the @code{imputil} and @code{iu}
modules, but none of them has ever gained much acceptance, and none of them were
easily usable from C code.

@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} borrows ideas from its predecessors, especially from Gordon
McMillan's @code{iu} module.  Three new items  are added to the @ref{fd,,sys}
module:


@itemize *

@item 
@code{sys.path_hooks} is a list of callable objects; most  often they'll be
classes.  Each callable takes a string containing a path and either returns an
importer object that will handle imports from this path or raises an
@ref{32d,,ImportError} exception if it can't handle this path.

@item 
@code{sys.path_importer_cache} caches importer objects for each path, so
@code{sys.path_hooks} will only need to be traversed once for each path.

@item 
@code{sys.meta_path} is a list of importer objects that will be traversed before
@code{sys.path} is checked.  This list is initially empty, but user code can add
objects to it.  Additional built-in and frozen modules can be imported by an
object added to this list.
@end itemize

Importer objects must have a single method, @code{find_module(fullname,
path=None)}.  @emph{fullname} will be a module or package name, e.g. @code{string} or
@code{distutils.core}.  @code{find_module()} must return a loader object that has a
single method, @code{load_module(fullname)}, that creates and returns the
corresponding module object.

Pseudo-code for Python's new import logic, therefore, looks something like this
(simplified a bit; see 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} for the full details):

@example
for mp in sys.meta_path:
    loader = mp(fullname)
    if loader is not None:
        <module> = loader.load_module(fullname)

for path in sys.path:
    for hook in sys.path_hooks:
        try:
            importer = hook(path)
        except ImportError:
            # ImportError, so try the other path hooks
            pass
        else:
            loader = importer.find_module(fullname)
            <module> = loader.load_module(fullname)

# Not found!
raise ImportError
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 302

@item PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} - 新导入钩

由 Just van Rossum 和 Paul Moore 撰写 ; 由 Just van Rossum 实现。
@end table


@c ======================================================================

@node PEP 305 逗号分隔文件,PEP 307 Pickle Enhancements,PEP 302 New Import Hooks,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-305-comma-separated-files}@anchor{df3}@anchor{whatsnew/2 3 section-pep305}@anchor{df4}
@subsection PEP 305: 逗号分隔文件


Comma-separated files are a format frequently used for exporting data from
databases and spreadsheets.  Python 2.3 adds a parser for comma-separated files.

Comma-separated format is deceptively simple at first glance:

@example
Costs,150,200,3.95
@end example

Read a line and call @code{line.split(',')}: what could be simpler? But toss in
string data that can contain commas, and things get more complicated:

@example
"Costs",150,200,3.95,"Includes taxes, shipping, and sundry items"
@end example

A big ugly regular expression can parse this, but using the new  @ref{2a,,csv}
package is much simpler:

@example
import csv

input = open('datafile', 'rb')
reader = csv.reader(input)
for line in reader:
    print line
@end example

The @code{reader()} function takes a number of different options. The field
separator isn't limited to the comma and can be changed to any character, and so
can the quoting and line-ending characters.

Different dialects of comma-separated files can be defined and registered;
currently there are two dialects, both used by Microsoft Excel. A separate
@ref{df5,,csv.writer} class will generate comma-separated files from a succession
of tuples or lists, quoting strings that contain the delimiter.


@subsubheading 参见



@table @asis

@item 该实现在“Python 增强提议” - PEP @cite{305} (CSV 文件 API)  中被提出

由 Kevin Altis, Dave Cole, Andrew McNamara, Skip Montanaro, Cliff Wells 撰写并实现。
@end table


@c ======================================================================

@node PEP 307 Pickle Enhancements,扩展切片,PEP 305 逗号分隔文件,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pep-307-pickle-enhancements}@anchor{df6}@anchor{whatsnew/2 3 section-pep307}@anchor{df7}
@subsection PEP 307: Pickle Enhancements


The @ref{ca,,pickle} and @code{cPickle} modules received some attention during the
2.3 development cycle.  In 2.2, new-style classes could be pickled without
difficulty, but they weren't pickled very compactly; 
@geindex Python 提高建议; PEP 307
PEP 307@footnote{https://www.python.org/dev/peps/pep-0307} quotes a trivial
example where a new-style class results in a pickled string three times longer
than that for a classic class.

The solution was to invent a new pickle protocol.  The @ref{df8,,pickle.dumps()}
function has supported a text-or-binary flag  for a long time.  In 2.3, this
flag is redefined from a Boolean to an integer: 0 is the old text-mode pickle
format, 1 is the old binary format, and now 2 is a new 2.3-specific format.  A
new constant, @ref{df9,,pickle.HIGHEST_PROTOCOL}, can be used to select the
fanciest protocol available.

Unpickling is no longer considered a safe operation.  2.2's @ref{ca,,pickle}
provided hooks for trying to prevent unsafe classes from being unpickled
(specifically, a @code{__safe_for_unpickling__} attribute), but none of this
code was ever audited and therefore it's all been ripped out in 2.3.  You should
not unpickle untrusted data in any version of Python.

To reduce the pickling overhead for new-style classes, a new interface for
customizing pickling was added using three special methods:
@ref{dfa,,__getstate__()}, @ref{19c,,__setstate__()}, and @ref{6a8,,__getnewargs__()}.  Consult
@geindex Python 提高建议; PEP 307
PEP 307@footnote{https://www.python.org/dev/peps/pep-0307} for the full semantics  of these methods.

As a way to compress pickles yet further, it's now possible to use integer codes
instead of long strings to identify pickled classes. The Python Software
Foundation will maintain a list of standardized codes; there's also a range of
codes for private use.  Currently no codes have been specified.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 307

@item PEP 307@footnote{https://www.python.org/dev/peps/pep-0307} - Extensions to the pickle protocol

PEP 由 Guido van Rossum 和 Tim Peters 撰写和实现。
@end table


@c ======================================================================

@node 扩展切片,其他语言特性修改<13>,PEP 307 Pickle Enhancements,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 extended-slices}@anchor{dfb}@anchor{whatsnew/2 3 section-slices}@anchor{dfc}
@subsection 扩展切片


Ever since Python 1.4, the slicing syntax has supported an optional third "step"
or "stride" argument.  For example, these are all legal Python syntax:
@code{L[1:10:2]}, @code{L[:-1:1]}, @code{L[::-1]}.  This was added to Python at the
request of the developers of Numerical Python, which uses the third argument
extensively.  However, Python's built-in list, tuple, and string sequence types
have never supported this feature, raising a @ref{192,,TypeError} if you tried it.
Michael Hudson contributed a patch to fix this shortcoming.

For example, you can now easily extract the elements of a list that have even
indexes:

@example
>>> L = range(10)
>>> L[::2]
[0, 2, 4, 6, 8]
@end example

Negative values also work to make a copy of the same list in reverse order:

@example
>>> L[::-1]
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
@end example

This also works for tuples, arrays, and strings:

@example
>>> s='abcd'
>>> s[::2]
'ac'
>>> s[::-1]
'dcba'
@end example

If you have a mutable sequence such as a list or an array you can assign to or
delete an extended slice, but there are some differences between assignment to
extended and regular slices.  Assignment to a regular slice can be used to
change the length of the sequence:

@example
>>> a = range(3)
>>> a
[0, 1, 2]
>>> a[1:3] = [4, 5, 6]
>>> a
[0, 4, 5, 6]
@end example

Extended slices aren't this flexible.  When assigning to an extended slice, the
list on the right hand side of the statement must contain the same number of
items as the slice it is replacing:

@example
>>> a = range(4)
>>> a
[0, 1, 2, 3]
>>> a[::2]
[0, 2]
>>> a[::2] = [0, -1]
>>> a
[0, 1, -1, 3]
>>> a[::2] = [0,1,2]
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
ValueError: attempt to assign sequence of size 3 to extended slice of size 2
@end example

Deletion is more straightforward:

@example
>>> a = range(4)
>>> a
[0, 1, 2, 3]
>>> a[::2]
[0, 2]
>>> del a[::2]
>>> a
[1, 3]
@end example

One can also now pass slice objects to the @ref{27f,,__getitem__()} methods of the
built-in sequences:

@example
>>> range(10).__getitem__(slice(0, 5, 2))
[0, 2, 4]
@end example

Or use slice objects directly in subscripts:

@example
>>> range(10)[slice(0, 5, 2)]
[0, 2, 4]
@end example

To simplify implementing sequences that support extended slicing, slice objects
now have a method @code{indices(length)} which, given the length of a sequence,
returns a @code{(start, stop, step)} tuple that can be passed directly to
@ref{9b8,,range()}. @code{indices()} handles omitted and out-of-bounds indices in a
manner consistent with regular slices (and this innocuous phrase hides a welter
of confusing details!).  The method is intended to be used like this:

@example
class FakeSeq:
    ...
    def calc_item(self, i):
        ...
    def __getitem__(self, item):
        if isinstance(item, slice):
            indices = item.indices(len(self))
            return FakeSeq([self.calc_item(i) for i in range(*indices)])
        else:
            return self.calc_item(i)
@end example

From this example you can also see that the built-in @ref{dfd,,slice} object is
now the type object for the slice type, and is no longer a function.  This is
consistent with Python 2.2, where @ref{184,,int}, @ref{329,,str}, etc., underwent
the same change.

@c ======================================================================

@node 其他语言特性修改<13>,新增，改进和弃用的模块<4>,扩展切片,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 other-language-changes}@anchor{dfe}
@subsection 其他语言特性修改


Here are all of the changes that Python 2.3 makes to the core Python language.


@itemize *

@item 
The @ref{18f,,yield} statement is now always a keyword, as described in
section @ref{ddf,,PEP 255; Simple Generators} of this document.

@item 
A new built-in function @ref{ddc,,enumerate()} was added, as described in section
@ref{de9,,PEP 279; enumerate()} of this document.

@item 
Two new constants, @ref{494,,True} and @ref{380,,False} were added along with the
built-in @ref{183,,bool} type, as described in section @ref{dec,,PEP 285; 布尔类型} of this
document.

@item 
The @ref{184,,int()} type constructor will now return a long integer instead of
raising an @ref{95a,,OverflowError} when a string or floating-point number is too
large to fit into an integer.  This can lead to the paradoxical result that
@code{isinstance(int(expression), int)} is false, but that seems unlikely to cause
problems in practice.

@item 
Built-in types now support the extended slicing syntax, as described in
section @ref{dfc,,扩展切片} of this document.

@item 
A new built-in function, @code{sum(iterable, start=0)},  adds up the numeric
items in the iterable object and returns their sum.  @ref{1e5,,sum()} only accepts
numbers, meaning that you can't use it to concatenate a bunch of strings.
(Contributed by Alex Martelli.)

@item 
@code{list.insert(pos, value)} used to  insert @emph{value} at the front of the list
when @emph{pos} was negative.  The behaviour has now been changed to be consistent
with slice indexing, so when @emph{pos} is -1 the value will be inserted before the
last element, and so forth.

@item 
@code{list.index(value)}, which searches for @emph{value}  within the list and returns
its index, now takes optional  @emph{start} and @emph{stop} arguments to limit the search
to  only part of the list.

@item 
Dictionaries have a new method, @code{pop(key[, *default*])}, that returns
the value corresponding to @emph{key} and removes that key/value pair from the
dictionary.  If the requested key isn't present in the dictionary, @emph{default} is
returned if it's specified and @ref{2c7,,KeyError} raised if it isn't.

@example
>>> d = @{1:2@}
>>> d
@{1: 2@}
>>> d.pop(4)
Traceback (most recent call last):
  File "stdin", line 1, in ?
KeyError: 4
>>> d.pop(1)
2
>>> d.pop(1)
Traceback (most recent call last):
  File "stdin", line 1, in ?
KeyError: 'pop(): dictionary is empty'
>>> d
@{@}
>>>
@end example

There's also a new class method,  @code{dict.fromkeys(iterable, value)}, that
creates a dictionary with keys taken from the supplied iterator @emph{iterable} and
all values set to @emph{value}, defaulting to @code{None}.

(Patches contributed by Raymond Hettinger.)

Also, the @ref{1b8,,dict()} constructor now accepts keyword arguments to simplify
creating small dictionaries:

@example
>>> dict(red=1, blue=2, green=3, black=4)
@{'blue': 2, 'black': 4, 'green': 3, 'red': 1@}
@end example

（由 Just van Rossum 贡献。）

@item 
The @ref{dff,,assert} statement no longer checks the @code{__debug__} flag, so
you can no longer disable assertions by assigning to @code{__debug__}. Running
Python with the @ref{685,,-O} switch will still generate code that doesn't
execute any assertions.

@item 
Most type objects are now callable, so you can use them to create new objects
such as functions, classes, and modules.  (This means that the @code{new} module
can be deprecated in a future Python version, because you can now use the type
objects available in the @ref{118,,types} module.) For example, you can create a new
module object with the following code:

@example
>>> import types
>>> m = types.ModuleType('abc','docstring')
>>> m
<module 'abc' (built-in)>
>>> m.__doc__
'docstring'
@end example

@item 
A new warning, @ref{279,,PendingDeprecationWarning} was added to indicate features
which are in the process of being deprecated.  The warning will @emph{not} be printed
by default.  To check for use of features that will be deprecated in the future,
supply @ref{40f,,-Walways;;PendingDeprecationWarning;;} on the command line or
use @ref{e00,,warnings.filterwarnings()}.

@item 
The process of deprecating string-based exceptions, as in @code{raise "Error
occurred"}, has begun.  Raising a string will now trigger
@ref{279,,PendingDeprecationWarning}.

@item 
Using @code{None} as a variable name will now result in a @ref{191,,SyntaxWarning}
warning.  In a future version of Python, @code{None} may finally become a keyword.

@item 
The @code{xreadlines()} method of file objects, introduced in Python 2.1, is no
longer necessary because files now behave as their own iterator.
@code{xreadlines()} was originally introduced as a faster way to loop over all
the lines in a file, but now you can simply write @code{for line in file_obj}.
File objects also have a new read-only @code{encoding} attribute that gives the
encoding used by the file; Unicode strings written to the file will be
automatically  converted to bytes using the given encoding.

@item 
The method resolution order used by new-style classes has changed, though
you'll only notice the difference if you have a really complicated inheritance
hierarchy.  Classic classes are unaffected by this change.  Python 2.2
originally used a topological sort of a class's ancestors, but 2.3 now uses the
C3 algorithm as described in the paper "A Monotonic Superclass Linearization for Dylan"@footnote{http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.19.3910}. To
understand the motivation for this change,  read Michele Simionato's article
"Python 2.3 Method Resolution Order"@footnote{http://www.phyast.pitt.edu/~micheles/mro.html}, or
read the thread on python-dev starting with the message at
@indicateurl{https://mail.python.org/pipermail/python-dev/2002-October/029035.html}. Samuele
Pedroni first pointed out the problem and also implemented the fix by coding the
C3 algorithm.

@item 
Python runs multithreaded programs by switching between threads after
executing N bytecodes.  The default value for N has been increased from 10 to
100 bytecodes, speeding up single-threaded applications by reducing the
switching overhead.  Some multithreaded applications may suffer slower response
time, but that's easily fixed by setting the limit back to a lower number using
@code{sys.setcheckinterval(N)}. The limit can be retrieved with the new
@ref{e01,,sys.getcheckinterval()} function.

@item 
One minor but far-reaching change is that the names of extension types defined
by the modules included with Python now contain the module and a @code{'.'} in
front of the type name.  For example, in Python 2.2, if you created a socket and
printed its @code{__class__}, you'd get this output:

@example
>>> s = socket.socket()
>>> s.__class__
<type 'socket'>
@end example

In 2.3, you get this:

@example
>>> s.__class__
<type '_socket.socket'>
@end example

@item 
One of the noted incompatibilities between old- and new-style classes has been
removed: you can now assign to the @ref{c60,,__name__} and @ref{e02,,__bases__}
attributes of new-style classes.  There are some restrictions on what can be
assigned to @ref{e02,,__bases__} along the lines of those relating to assigning to
an instance's @ref{e03,,__class__} attribute.
@end itemize

@c ======================================================================

@menu
* String Changes:: 
* 性能优化: 性能优化<12>. 

@end menu

@node String Changes,性能优化<12>,,其他语言特性修改<13>
@anchor{whatsnew/2 3 string-changes}@anchor{e04}
@subsubsection String Changes



@itemize *

@item 
The @ref{79d,,in} operator now works differently for strings. Previously, when
evaluating @code{X in Y} where @emph{X} and @emph{Y} are strings, @emph{X} could only be a single
character. That's now changed; @emph{X} can be a string of any length, and @code{X in Y}
will return @ref{494,,True} if @emph{X} is a substring of @emph{Y}.  If @emph{X} is the empty
string, the result is always @ref{494,,True}.

@example
>>> 'ab' in 'abcd'
True
>>> 'ad' in 'abcd'
False
>>> '@w{'} in 'abcd'
True
@end example

Note that this doesn't tell you where the substring starts; if you need that
information, use the @code{find()} string method.

@item 
The @code{strip()}, @code{lstrip()}, and @code{rstrip()} string methods now have
an optional argument for specifying the characters to strip.  The default is
still to remove all whitespace characters:

@example
>>> '   abc '.strip()
'abc'
>>> '><><abc<><><>'.strip('<>')
'abc'
>>> '><><abc<><><>\n'.strip('<>')
'abc<><><>\n'
>>> u'\u4000\u4001abc\u4000'.strip(u'\u4000')
u'\u4001abc'
>>>
@end example

(Suggested by Simon Brunning and implemented by Walter Dörwald.)

@item 
The @code{startswith()} and @code{endswith()} string methods now accept negative
numbers for the @emph{start} and @emph{end} parameters.

@item 
Another new string method is @code{zfill()}, originally a function in the
@ref{f6,,string} module.  @code{zfill()} pads a numeric string with zeros on the
left until it's the specified width. Note that the @code{%} operator is still more
flexible and powerful than @code{zfill()}.

@example
>>> '45'.zfill(4)
'0045'
>>> '12345'.zfill(4)
'12345'
>>> 'goofy'.zfill(6)
'0goofy'
@end example

（由 Walter Dörwald 贡献。）

@item 
A new type object, @code{basestring}, has been added. Both 8-bit strings and
Unicode strings inherit from this type, so @code{isinstance(obj, basestring)} will
return @ref{494,,True} for either kind of string.  It's a completely abstract
type, so you can't create @code{basestring} instances.

@item 
Interned strings are no longer immortal and will now be garbage-collected in
the usual way when the only reference to them is from the internal dictionary of
interned strings.  (Implemented by Oren Tirosh.)
@end itemize

@c ======================================================================

@node 性能优化<12>,,String Changes,其他语言特性修改<13>
@anchor{whatsnew/2 3 optimizations}@anchor{e05}
@subsubsection 性能优化



@itemize *

@item 
The creation of new-style class instances has been made much faster; they're
now faster than classic classes!

@item 
The @code{sort()} method of list objects has been extensively rewritten by Tim
Peters, and the implementation is significantly faster.

@item 
Multiplication of large long integers is now much faster thanks to an
implementation of Karatsuba multiplication, an algorithm that scales better than
the O(n*n) required for the grade-school multiplication algorithm.  (Original
patch by Christopher A. Craig, and significantly reworked by Tim Peters.)

@item 
The @code{SET_LINENO} opcode is now gone.  This may provide a small speed
increase, depending on your compiler's idiosyncrasies. See section
@ref{e06,,Other Changes and Fixes} for a longer explanation. (Removed by Michael Hudson.)

@item 
@code{xrange()} objects now have their own iterator, making @code{for i in
xrange(n)} slightly faster than @code{for i in range(n)}.  (Patch by Raymond
Hettinger.)

@item 
A number of small rearrangements have been made in various hotspots to improve
performance, such as inlining a function or removing some code.  (Implemented
mostly by GvR, but lots of people have contributed single changes.)
@end itemize

The net result of the 2.3 optimizations is that Python 2.3 runs the  pystone
benchmark around 25% faster than Python 2.2.

@c ======================================================================

@node 新增，改进和弃用的模块<4>,Pymalloc A Specialized Object Allocator,其他语言特性修改<13>,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 new-improved-and-deprecated-modules}@anchor{e07}
@subsection 新增，改进和弃用的模块


As usual, Python's standard library received a number of enhancements and bug
fixes.  Here's a partial list of the most notable changes, sorted alphabetically
by module name. Consult the @code{Misc/NEWS} file in the source tree for a more
complete list of changes, or look through the CVS logs for all the details.


@itemize *

@item 
The @ref{7,,array} module now supports arrays of Unicode characters using the
@code{'u'} format character.  Arrays also now support using the @code{+=} assignment
operator to add another array's contents, and the @code{*=} assignment operator to
repeat an array. (Contributed by Jason Orendorff.)

@item 
The @code{bsddb} module has been replaced by version 4.1.6 of the PyBSDDB@footnote{http://pybsddb.sourceforge.net} package, providing a more complete interface
to the transactional features of the BerkeleyDB library.

The old version of the module has been renamed to  @code{bsddb185} and is no
longer built automatically; you'll  have to edit @code{Modules/Setup} to enable
it.  Note that the new @code{bsddb} package is intended to be compatible with
the  old module, so be sure to file bugs if you discover any incompatibilities.
When upgrading to Python 2.3, if the new interpreter is compiled with a new
version of  the underlying BerkeleyDB library, you will almost certainly have to
convert your database files to the new version.  You can do this fairly easily
with the new scripts @code{db2pickle.py} and @code{pickle2db.py} which you
will find in the distribution's @code{Tools/scripts} directory.  If you've
already been using the PyBSDDB package and importing it as @code{bsddb3}, you
will have to change your @code{import} statements to import it as @code{bsddb}.

@item 
The new @ref{14,,bz2} module is an interface to the bz2 data compression library.
bz2-compressed data is usually smaller than  corresponding
@ref{144,,zlib}-compressed data. (Contributed by Gustavo Niemeyer.)

@item 
A set of standard date/time types has been added in the new @ref{31,,datetime}
module.  See the following section for more details.

@item 
The Distutils @code{Extension} class now supports an extra constructor
argument named @emph{depends} for listing additional source files that an extension
depends on.  This lets Distutils recompile the module if any of the dependency
files are modified.  For example, if @code{sampmodule.c} includes the header
file @code{sample.h}, you would create the @code{Extension} object like
this:

@example
ext = Extension("samp",
                sources=["sampmodule.c"],
                depends=["sample.h"])
@end example

Modifying @code{sample.h} would then cause the module to be recompiled.
(Contributed by Jeremy Hylton.)

@item 
Other minor changes to Distutils: it now checks for the 
@geindex CC
@geindex 环境变量; CC
@code{CC},
@geindex CFLAGS
@geindex 环境变量; CFLAGS
@code{CFLAGS}, 
@geindex CPP
@geindex 环境变量; CPP
@code{CPP}, 
@geindex LDFLAGS
@geindex 环境变量; LDFLAGS
@code{LDFLAGS}, and 
@geindex CPPFLAGS
@geindex 环境变量; CPPFLAGS
@code{CPPFLAGS}
environment variables, using them to override the settings in Python's
configuration (contributed by Robert Weber).

@item 
Previously the @ref{67,,doctest} module would only search the docstrings of
public methods and functions for test cases, but it now also examines private
ones as well.  The @code{DocTestSuite()} function creates a
@ref{6c8,,unittest.TestSuite} object from a set of @ref{67,,doctest} tests.

@item 
The new @code{gc.get_referents(object)} function returns a list of all the
objects referenced by @emph{object}.

@item 
The @ref{87,,getopt} module gained a new function, @code{gnu_getopt()}, that
supports the same arguments as the existing @ref{87,,getopt()} function but uses
GNU-style scanning mode. The existing @ref{87,,getopt()} stops processing options as
soon as a non-option argument is encountered, but in GNU-style mode processing
continues, meaning that options and arguments can be mixed.  For example:

@example
>>> getopt.getopt(['-f', 'filename', 'output', '-v'], 'f:v')
([('-f', 'filename')], ['output', '-v'])
>>> getopt.gnu_getopt(['-f', 'filename', 'output', '-v'], 'f:v')
([('-f', 'filename'), ('-v', '@w{'})], ['output'])
@end example

（由 Peter Åstrand 贡献。）

@item 
The @ref{8b,,grp}, @ref{d6,,pwd}, and @ref{e0,,resource} modules now return enhanced
tuples:

@example
>>> import grp
>>> g = grp.getgrnam('amk')
>>> g.gr_name, g.gr_gid
('amk', 500)
@end example

@item 
The @ref{8c,,gzip} module can now handle files exceeding 2 GiB.

@item 
The new @ref{8e,,heapq} module contains an implementation of a heap queue
algorithm.  A heap is an array-like data structure that keeps items in a
partially sorted order such that, for every index @emph{k}, @code{heap[k] <=
heap[2*k+1]} and @code{heap[k] <= heap[2*k+2]}.  This makes it quick to remove the
smallest item, and inserting a new item while maintaining the heap property is
O(lg n).  (See @indicateurl{https://xlinux.nist.gov/dads//HTML/priorityque.html} for more
information about the priority queue data structure.)

The @ref{8e,,heapq} module provides @code{heappush()} and @code{heappop()} functions
for adding and removing items while maintaining the heap property on top of some
other mutable Python sequence type.  Here's an example that uses a Python list:

@example
>>> import heapq
>>> heap = []
>>> for item in [3, 7, 5, 11, 1]:
...    heapq.heappush(heap, item)
...
>>> heap
[1, 3, 5, 11, 7]
>>> heapq.heappop(heap)
1
>>> heapq.heappop(heap)
3
>>> heap
[5, 7, 11]
@end example

（由 Kevin O'Connor 贡献。）

@item 
The IDLE integrated development environment has been updated using the code
from the IDLEfork project (@indicateurl{http://idlefork.sourceforge.net}).  The most notable feature is
that the code being developed is now executed in a subprocess, meaning that
there's no longer any need for manual @code{reload()} operations. IDLE's core code
has been incorporated into the standard library as the @code{idlelib} package.

@item 
The @ref{98,,imaplib} module now supports IMAP over SSL. (Contributed by Piers
Lauder and Tino Lange.)

@item 
The @ref{a3,,itertools} contains a number of useful functions for use with
iterators, inspired by various functions provided by the ML and Haskell
languages.  For example, @code{itertools.ifilter(predicate, iterator)} returns all
elements in the iterator for which the function @code{predicate()} returns
@ref{494,,True}, and @code{itertools.repeat(obj, N)} returns @code{obj} @emph{N} times.
There are a number of other functions in the module; see the package's reference
documentation for details.
(Contributed by Raymond Hettinger.)

@item 
Two new functions in the @ref{b1,,math} module, @code{degrees(rads)} and
@code{radians(degs)}, convert between radians and degrees.  Other functions in
the @ref{b1,,math} module such as @ref{e08,,math.sin()} and @ref{e09,,math.cos()} have always
required input values measured in radians.  Also, an optional @emph{base} argument
was added to @ref{e0a,,math.log()} to make it easier to compute logarithms for bases
other than @code{e} and @code{10}.  (Contributed by Raymond Hettinger.)

@item 
Several new POSIX functions (@code{getpgid()}, @code{killpg()}, @code{lchown()},
@code{loadavg()}, @code{major()}, @code{makedev()}, @code{minor()}, and
@code{mknod()}) were added to the @ref{d1,,posix} module that underlies the
@ref{c4,,os} module. (Contributed by Gustavo Niemeyer, Geert Jansen, and Denis S.
Otkidach.)

@item 
In the @ref{c4,,os} module, the @code{*stat()} family of functions can now report
fractions of a second in a timestamp.  Such time stamps are represented as
floats, similar to the value returned by @ref{316,,time.time()}.

During testing, it was found that some applications will break if time stamps
are floats.  For compatibility, when using the tuple interface of the
@code{stat_result} time stamps will be represented as integers. When using
named fields (a feature first introduced in Python 2.2), time stamps are still
represented as integers, unless @code{os.stat_float_times()} is invoked to enable
float return values:

@example
>>> os.stat("/tmp").st_mtime
1034791200
>>> os.stat_float_times(True)
>>> os.stat("/tmp").st_mtime
1034791200.6335014
@end example

In Python 2.4, the default will change to always returning floats.

Application developers should enable this feature only if all their libraries
work properly when confronted with floating point time stamps, or if they use
the tuple API. If used, the feature should be activated on an application level
instead of trying to enable it on a per-use basis.

@item 
The @ref{c3,,optparse} module contains a new parser for command-line arguments
that can convert option values to a particular Python type  and will
automatically generate a usage message.  See the following section for  more
details.

@item 
The old and never-documented @code{linuxaudiodev} module has been deprecated,
and a new version named @ref{c6,,ossaudiodev} has been added.  The module was
renamed because the OSS sound drivers can be used on platforms other than Linux,
and the interface has also been tidied and brought up to date in various ways.
(Contributed by Greg Ward and Nicholas FitzRoy-Dale.)

@item 
The new @ref{ce,,platform} module contains a number of functions that try to
determine various properties of the platform you're running on.  There are
functions for getting the architecture, CPU type, the Windows OS version, and
even the Linux distribution version. (Contributed by Marc-André Lemburg.)

@item 
The parser objects provided by the @code{pyexpat} module can now optionally
buffer character data, resulting in fewer calls to your character data handler
and therefore faster performance.  Setting the parser object's
@code{buffer_text} attribute to @ref{494,,True} will enable buffering.

@item 
The @code{sample(population, k)} function was added to the @ref{dc,,random}
module.  @emph{population} is a sequence or @code{xrange} object containing the
elements of a population, and @code{sample()} chooses @emph{k} elements from the
population without replacing chosen elements.  @emph{k} can be any value up to
@code{len(population)}. For example:

@example
>>> days = ['Mo', 'Tu', 'We', 'Th', 'Fr', 'St', 'Sn']
>>> random.sample(days, 3)      # Choose 3 elements
['St', 'Sn', 'Th']
>>> random.sample(days, 7)      # Choose 7 elements
['Tu', 'Th', 'Mo', 'We', 'St', 'Fr', 'Sn']
>>> random.sample(days, 7)      # Choose 7 again
['We', 'Mo', 'Sn', 'Fr', 'Tu', 'St', 'Th']
>>> random.sample(days, 8)      # Can't choose eight
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "random.py", line 414, in sample
      raise ValueError, "sample larger than population"
ValueError: sample larger than population
>>> random.sample(xrange(1,10000,2), 10)   # Choose ten odd nos. under 10000
[3407, 3805, 1505, 7023, 2401, 2267, 9733, 3151, 8083, 9195]
@end example

The @ref{dc,,random} module now uses a new algorithm, the Mersenne Twister,
implemented in C.  It's faster and more extensively studied than the previous
algorithm.

(All changes contributed by Raymond Hettinger.)

@item 
The @ref{de,,readline} module also gained a number of new functions:
@code{get_history_item()}, @code{get_current_history_length()}, and
@code{redisplay()}.

@item 
The @code{rexec} and @code{Bastion} modules have been declared dead, and
attempts to import them will fail with a @ref{2ba,,RuntimeError}.  New-style classes
provide new ways to break out of the restricted execution environment provided
by @code{rexec}, and no one has interest in fixing them or time to do so.  If
you have applications using @code{rexec}, rewrite them to use something else.

(Sticking with Python 2.2 or 2.1 will not make your applications any safer
because there are known bugs in the @code{rexec} module in those versions.  To
repeat: if you're using @code{rexec}, stop using it immediately.)

@item 
The @code{rotor} module has been deprecated because the  algorithm it uses for
encryption is not believed to be secure.  If you need encryption, use one of the
several AES Python modules that are available separately.

@item 
The @ref{e9,,shutil} module gained a @code{move(src, dest)} function that
recursively moves a file or directory to a new location.

@item 
Support for more advanced POSIX signal handling was added to the @ref{ea,,signal}
but then removed again as it proved impossible to make it work reliably across
platforms.

@item 
The @ref{ef,,socket} module now supports timeouts.  You can call the
@code{settimeout(t)} method on a socket object to set a timeout of @emph{t} seconds.
Subsequent socket operations that take longer than @emph{t} seconds to complete will
abort and raise a @ref{c07,,socket.timeout} exception.

The original timeout implementation was by Tim O'Malley.  Michael Gilfix
integrated it into the Python @ref{ef,,socket} module and shepherded it through a
lengthy review.  After the code was checked in, Guido van Rossum rewrote parts
of it.  (This is a good example of a collaborative development process in
action.)

@item 
On Windows, the @ref{ef,,socket} module now ships with Secure  Sockets Layer
(SSL) support.

@item 
The value of the C @code{PYTHON_API_VERSION} macro is now exposed at the
Python level as @code{sys.api_version}.  The current exception can be cleared by
calling the new @code{sys.exc_clear()} function.

@item 
The new @ref{101,,tarfile} module  allows reading from and writing to
@code{tar}-format archive files. (Contributed by Lars Gustäbel.)

@item 
The new @ref{108,,textwrap} module contains functions for wrapping strings
containing paragraphs of text.  The @code{wrap(text, width)} function takes a
string and returns a list containing the text split into lines of no more than
the chosen width.  The @code{fill(text, width)} function returns a single
string, reformatted to fit into lines no longer than the chosen width. (As you
can guess, @code{fill()} is built on top of @code{wrap()}.  For example:

@example
>>> import textwrap
>>> paragraph = "Not a whit, we defy augury: ... more text ..."
>>> textwrap.wrap(paragraph, 60)
["Not a whit, we defy augury: there's a special providence in",
 "the fall of a sparrow. If it be now, 'tis not to come; if it",
 ...]
>>> print textwrap.fill(paragraph, 35)
Not a whit, we defy augury: there's
a special providence in the fall of
a sparrow. If it be now, 'tis not
to come; if it be not to come, it
will be now; if it be not now, yet
it will come: the readiness is all.
>>>
@end example

The module also contains a @code{TextWrapper} class that actually implements
the text wrapping strategy.   Both the @code{TextWrapper} class and the
@code{wrap()} and @code{fill()} functions support a number of additional keyword
arguments for fine-tuning the formatting; consult the module's documentation
for details. (Contributed by Greg Ward.)

@item 
The @code{thread} and @ref{109,,threading} modules now have companion modules,
@code{dummy_thread} and @ref{68,,dummy_threading}, that provide a do-nothing
implementation of the @code{thread} module's interface for platforms where
threads are not supported.  The intention is to simplify thread-aware modules
(ones that @emph{don't} rely on threads to run) by putting the following code at the
top:

@example
try:
    import threading as _threading
except ImportError:
    import dummy_threading as _threading
@end example

In this example, @code{_threading} is used as the module name to make it clear
that the module being used is not necessarily the actual @ref{109,,threading}
module. Code can call functions and use classes in @code{_threading} whether or
not threads are supported, avoiding an @ref{de0,,if} statement and making the
code slightly clearer.  This module will not magically make multithreaded code
run without threads; code that waits for another thread to return or to do
something will simply hang forever.

@item 
The @ref{10a,,time} module's @code{strptime()} function has long been an annoyance
because it uses the platform C library's @code{strptime()} implementation, and
different platforms sometimes have odd bugs.  Brett Cannon contributed a
portable implementation that's written in pure Python and should behave
identically on all platforms.

@item 
The new @ref{10b,,timeit} module helps measure how long snippets of Python code
take to execute.  The @code{timeit.py} file can be run directly from the
command line, or the module's @code{Timer} class can be imported and used
directly.  Here's a short example that figures out whether it's faster to
convert an 8-bit string to Unicode by appending an empty Unicode string to it or
by using the @code{unicode()} function:

@example
import timeit

timer1 = timeit.Timer('unicode("abc")')
timer2 = timeit.Timer('"abc" + u""')

# Run three trials
print timer1.repeat(repeat=3, number=100000)
print timer2.repeat(repeat=3, number=100000)

# On my laptop this outputs:
# [0.36831796169281006, 0.37441694736480713, 0.35304892063140869]
# [0.17574405670166016, 0.18193507194519043, 0.17565798759460449]
@end example

@item 
The @code{Tix} module has received various bug fixes and updates for the
current version of the Tix package.

@item 
The @code{Tkinter} module now works with a thread-enabled  version of Tcl.
Tcl's threading model requires that widgets only be accessed from the thread in
which they're created; accesses from another thread can cause Tcl to panic.  For
certain Tcl interfaces, @code{Tkinter} will now automatically avoid this  when a
widget is accessed from a different thread by marshalling a command, passing it
to the correct thread, and waiting for the results.  Other interfaces can't be
handled automatically but @code{Tkinter} will now raise an exception on such an
access so that you can at least find out about the problem.  See
@indicateurl{https://mail.python.org/pipermail/python-dev/2002-December/031107.html} for a more
detailed explanation of this change.  (Implemented by Martin von Löwis.)

@item 
Calling Tcl methods through @code{_tkinter} no longer  returns only strings.
Instead, if Tcl returns other objects those objects are converted to their
Python equivalent, if one exists, or wrapped with a @code{_tkinter.Tcl_Obj}
object if no Python equivalent exists. This behavior can be controlled through
the @code{wantobjects()} method of @code{tkapp} objects.

When using @code{_tkinter} through the @code{Tkinter} module (as most Tkinter
applications will), this feature is always activated. It should not cause
compatibility problems, since Tkinter would always convert string results to
Python types where possible.

If any incompatibilities are found, the old behavior can be restored by setting
the @code{wantobjects} variable in the @code{Tkinter} module to false before
creating the first @code{tkapp} object.

@example
import Tkinter
Tkinter.wantobjects = 0
@end example

Any breakage caused by this change should be reported as a bug.

@item 
The @code{UserDict} module has a new @code{DictMixin} class which defines
all dictionary methods for classes that already have a minimum mapping
interface.  This greatly simplifies writing classes that need to be
substitutable for dictionaries, such as the classes in  the @ref{e7,,shelve}
module.

Adding the mix-in as a superclass provides the full dictionary interface
whenever the class defines @ref{27f,,__getitem__()}, @ref{c5b,,__setitem__()},
@ref{c5c,,__delitem__()}, and @code{keys()}. For example:

@example
>>> import UserDict
>>> class SeqDict(UserDict.DictMixin):
...     """Dictionary lookalike implemented with lists."""
...     def __init__(self):
...         self.keylist = []
...         self.valuelist = []
...     def __getitem__(self, key):
...         try:
...             i = self.keylist.index(key)
...         except ValueError:
...             raise KeyError
...         return self.valuelist[i]
...     def __setitem__(self, key, value):
...         try:
...             i = self.keylist.index(key)
...             self.valuelist[i] = value
...         except ValueError:
...             self.keylist.append(key)
...             self.valuelist.append(value)
...     def __delitem__(self, key):
...         try:
...             i = self.keylist.index(key)
...         except ValueError:
...             raise KeyError
...         self.keylist.pop(i)
...         self.valuelist.pop(i)
...     def keys(self):
...         return list(self.keylist)
...
>>> s = SeqDict()
>>> dir(s)      # See that other dictionary methods are implemented
['__cmp__', '__contains__', '__delitem__', '__doc__', '__getitem__',
 '__init__', '__iter__', '__len__', '__module__', '__repr__',
 '__setitem__', 'clear', 'get', 'has_key', 'items', 'iteritems',
 'iterkeys', 'itervalues', 'keylist', 'keys', 'pop', 'popitem',
 'setdefault', 'update', 'valuelist', 'values']
@end example

（由 Raymond Hettinger 贡献。）

@item 
The DOM implementation in @ref{135,,xml.dom.minidom} can now generate XML output
in a particular encoding by providing an optional encoding argument to the
@code{toxml()} and @code{toprettyxml()} methods of DOM nodes.

@item 
The @code{xmlrpclib} module now supports an XML-RPC extension for handling nil
data values such as Python's @code{None}.  Nil values are always supported on
unmarshalling an XML-RPC response.  To generate requests containing @code{None},
you must supply a true value for the @emph{allow_none} parameter when creating a
@code{Marshaller} instance.

@item 
The new @code{DocXMLRPCServer} module allows writing self-documenting XML-RPC
servers. Run it in demo mode (as a program) to see it in action.   Pointing the
Web browser to the RPC server produces pydoc-style documentation; pointing
xmlrpclib to the server allows invoking the actual methods. (Contributed by
Brian Quinlan.)

@item 
Support for internationalized domain names (RFCs 3454, 3490, 3491, and 3492)
has been added. The "idna" encoding can be used to convert between a Unicode
domain name and the ASCII-compatible encoding (ACE) of that name.

@example
>@{@}>@{@}> u"www.Alliancefrançaise.nu".encode("idna")
'www.xn--alliancefranaise-npb.nu'
@end example

The @ref{ef,,socket} module has also been extended to transparently convert
Unicode hostnames to the ACE version before passing them to the C library.
Modules that deal with hostnames such as @code{httplib} and @ref{84,,ftplib})
also support Unicode host names; @code{httplib} also sends HTTP @code{Host}
headers using the ACE version of the domain name.  @ref{11d,,urllib} supports
Unicode URLs with non-ASCII host names as long as the @code{path} part of the URL
is ASCII only.

To implement this change, the @ref{f7,,stringprep} module, the  @code{mkstringprep}
tool and the @code{punycode} encoding have been added.
@end itemize

@c ======================================================================

@menu
* Date/Time 类型:: 
* optparse 模块:: 

@end menu

@node Date/Time 类型,optparse 模块,,新增，改进和弃用的模块<4>
@anchor{whatsnew/2 3 date-time-type}@anchor{e0b}
@subsubsection Date/Time 类型


Date and time types suitable for expressing timestamps were added as the
@ref{31,,datetime} module.  The types don't support different calendars or many
fancy features, and just stick to the basics of representing time.

The three primary types are: @code{date}, representing a day, month, and year;
@ref{4ed,,time}, consisting of hour, minute, and second; and @ref{194,,datetime},
which contains all the attributes of both @code{date} and @ref{4ed,,time}.
There's also a @code{timedelta} class representing differences between two
points in time, and time zone logic is implemented by classes inheriting from
the abstract @code{tzinfo} class.

You can create instances of @code{date} and @ref{4ed,,time} by either supplying
keyword arguments to the appropriate constructor, e.g.
@code{datetime.date(year=1972, month=10, day=15)}, or by using one of a number of
class methods.  For example, the @code{date.today()} class method returns the
current local date.

Once created, instances of the date/time classes are all immutable. There are a
number of methods for producing formatted strings from objects:

@example
>>> import datetime
>>> now = datetime.datetime.now()
>>> now.isoformat()
'2002-12-30T21:27:03.994956'
>>> now.ctime()  # Only available on date, datetime
'Mon Dec 30 21:27:03 2002'
>>> now.strftime('%Y %d %b')
'2002 30 Dec'
@end example

The @code{replace()} method allows modifying one or more fields  of a
@code{date} or @ref{194,,datetime} instance, returning a new instance:

@example
>>> d = datetime.datetime.now()
>>> d
datetime.datetime(2002, 12, 30, 22, 15, 38, 827738)
>>> d.replace(year=2001, hour = 12)
datetime.datetime(2001, 12, 30, 12, 15, 38, 827738)
>>>
@end example

Instances can be compared, hashed, and converted to strings (the result is the
same as that of @code{isoformat()}).  @code{date} and @ref{194,,datetime}
instances can be subtracted from each other, and added to @code{timedelta}
instances.  The largest missing feature is that there's no standard library
support for parsing strings and getting back a @code{date} or
@ref{194,,datetime}.

For more information, refer to the module's reference documentation.
(Contributed by Tim Peters.)

@c ======================================================================

@node optparse 模块,,Date/Time 类型,新增，改进和弃用的模块<4>
@anchor{whatsnew/2 3 the-optparse-module}@anchor{e0c}
@subsubsection optparse 模块


The @ref{87,,getopt} module provides simple parsing of command-line arguments.  The
new @ref{c3,,optparse} module (originally named Optik) provides more elaborate
command-line parsing that follows the Unix conventions, automatically creates
the output for @code{--help}, and can perform different actions for different
options.

You start by creating an instance of @code{OptionParser} and telling it what
your program's options are.

@example
import sys
from optparse import OptionParser

op = OptionParser()
op.add_option('-i', '--input',
              action='store', type='string', dest='input',
              help='set input filename')
op.add_option('-l', '--length',
              action='store', type='int', dest='length',
              help='set maximum length of output')
@end example

Parsing a command line is then done by calling the @code{parse_args()} method.

@example
options, args = op.parse_args(sys.argv[1:])
print options
print args
@end example

This returns an object containing all of the option values, and a list of
strings containing the remaining arguments.

Invoking the script with the various arguments now works as you'd expect it to.
Note that the length argument is automatically converted to an integer.

@example
$ ./python opt.py -i data arg1
<Values at 0x400cad4c: @{'input': 'data', 'length': None@}>
['arg1']
$ ./python opt.py --input=data --length=4
<Values at 0x400cad2c: @{'input': 'data', 'length': 4@}>
[]
$
@end example

The help message is automatically generated for you:

@example
$ ./python opt.py --help
usage: opt.py [options]

options:
  -h, --help            show this help message and exit
  -iINPUT, --input=INPUT
                        set input filename
  -lLENGTH, --length=LENGTH
                        set maximum length of output
$
@end example

有关更多详细信息，请参见模块的文档。

Optik was written by Greg Ward, with suggestions from the readers of the Getopt
SIG.

@c ======================================================================

@node Pymalloc A Specialized Object Allocator,构建和 C API 的改变<12>,新增，改进和弃用的模块<4>,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 pymalloc-a-specialized-object-allocator}@anchor{e0d}@anchor{whatsnew/2 3 section-pymalloc}@anchor{e0e}
@subsection Pymalloc: A Specialized Object Allocator


Pymalloc, a specialized object allocator written by Vladimir Marangozov, was a
feature added to Python 2.1.  Pymalloc is intended to be faster than the system
@code{malloc()} and to have less memory overhead for allocation patterns typical
of Python programs. The allocator uses C's @code{malloc()} function to get large
pools of memory and then fulfills smaller memory requests from these pools.

In 2.1 and 2.2, pymalloc was an experimental feature and wasn't enabled by
default; you had to explicitly enable it when compiling Python by providing the
@code{--with-pymalloc} option to the @code{configure} script.  In 2.3,
pymalloc has had further enhancements and is now enabled by default; you'll have
to supply @code{--without-pymalloc} to disable it.

This change is transparent to code written in Python; however, pymalloc may
expose bugs in C extensions.  Authors of C extension modules should test their
code with pymalloc enabled, because some incorrect code may cause core dumps at
runtime.

There's one particularly common error that causes problems.  There are a number
of memory allocation functions in Python's C API that have previously just been
aliases for the C library's @code{malloc()} and @code{free()}, meaning that if
you accidentally called mismatched functions the error wouldn't be noticeable.
When the object allocator is enabled, these functions aren't aliases of
@code{malloc()} and @code{free()} any more, and calling the wrong function to
free memory may get you a core dump.  For example, if memory was allocated using
@ref{502,,PyObject_Malloc()}, it has to be freed using @ref{4fe,,PyObject_Free()}, not
@code{free()}.  A few modules included with Python fell afoul of this and had to
be fixed; doubtless there are more third-party modules that will have the same
problem.

As part of this change, the confusing multiple interfaces for allocating memory
have been consolidated down into two API families. Memory allocated with one
family must not be manipulated with functions from the other family.  There is
one family for allocating chunks of memory and another family of functions
specifically for allocating Python objects.


@itemize *

@item 
To allocate and free an undistinguished chunk of memory use the "raw memory"
family: @ref{4ff,,PyMem_Malloc()}, @ref{969,,PyMem_Realloc()}, and @ref{da2,,PyMem_Free()}.

@item 
The "object memory" family is the interface to the pymalloc facility described
above and is biased towards a large number of "small" allocations:
@ref{502,,PyObject_Malloc()}, @ref{da3,,PyObject_Realloc()}, and @ref{4fe,,PyObject_Free()}.

@item 
To allocate and free Python objects, use the "object" family
@ref{2d2,,PyObject_New()}, @ref{2d3,,PyObject_NewVar()}, and @ref{e0f,,PyObject_Del()}.
@end itemize

Thanks to lots of work by Tim Peters, pymalloc in 2.3 also provides debugging
features to catch memory overwrites and doubled frees in both extension modules
and in the interpreter itself.  To enable this support, compile a debugging
version of the Python interpreter by running @code{configure} with
@code{--with-pydebug}.

To aid extension writers, a header file @code{Misc/pymemcompat.h} is
distributed with the source to Python 2.3 that allows Python extensions to use
the 2.3 interfaces to memory allocation while compiling against any version of
Python since 1.5.2.  You would copy the file from Python's source distribution
and bundle it with the source of your extension.


@subsubheading 参见



@table @asis

@item @indicateurl{https://hg.python.org/cpython/file/default/Objects/obmalloc.c}

For the full details of the pymalloc implementation, see the comments at
the top of the file @code{Objects/obmalloc.c} in the Python source code.
The above link points to the file within the python.org SVN browser.
@end table


@c ======================================================================

@node 构建和 C API 的改变<12>,Other Changes and Fixes<2>,Pymalloc A Specialized Object Allocator,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 build-and-c-api-changes}@anchor{e10}
@subsection 构建和 C API 的改变


Changes to Python's build process and to the C API include:


@itemize *

@item 
The cycle detection implementation used by the garbage collection has proven
to be stable, so it's now been made mandatory.  You can no longer compile Python
without it, and the @code{--with-cycle-gc} switch to @code{configure} has
been removed.

@item 
Python can now optionally be built as a shared library
(@code{libpython2.3.so}) by supplying @code{--enable-shared} when running
Python's @code{configure} script.  (Contributed by Ondrej Palkovsky.)

@item 
The @code{DL_EXPORT} and @code{DL_IMPORT} macros are now deprecated.
Initialization functions for Python extension modules should now be declared
using the new macro @code{PyMODINIT_FUNC}, while the Python core will
generally use the @code{PyAPI_FUNC} and @code{PyAPI_DATA} macros.

@item 
The interpreter can be compiled without any docstrings for the built-in
functions and modules by supplying @code{--without-doc-strings} to the
@code{configure} script. This makes the Python executable about 10% smaller,
but will also mean that you can't get help for Python's built-ins.  (Contributed
by Gustavo Niemeyer.)

@item 
The @code{PyArg_NoArgs()} macro is now deprecated, and code that uses it
should be changed.  For Python 2.2 and later, the method definition table can
specify the @ref{e11,,METH_NOARGS} flag, signalling that there are no arguments,
and the argument checking can then be removed.  If compatibility with pre-2.2
versions of Python is important, the code could use @code{PyArg_ParseTuple(args,
"")} instead, but this will be slower than using @ref{e11,,METH_NOARGS}.

@item 
@ref{26a,,PyArg_ParseTuple()} accepts new format characters for various sizes of
unsigned integers: @code{B} for @code{unsigned char}, @code{H} for @code{unsigned
short int},  @code{I} for @code{unsigned int},  and @code{K} for @code{unsigned
long long}.

@item 
A new function, @code{PyObject_DelItemString(mapping, char *key)} was added
as shorthand for @code{PyObject_DelItem(mapping, PyString_New(key))}.

@item 
File objects now manage their internal string buffer differently, increasing
it exponentially when needed.  This results in the benchmark tests in
@code{Lib/test/test_bufio.py} speeding up considerably (from 57 seconds to 1.7
seconds, according to one measurement).

@item 
It's now possible to define class and static methods for a C extension type by
setting either the @ref{e12,,METH_CLASS} or @ref{e13,,METH_STATIC} flags in a
method's @ref{e14,,PyMethodDef} structure.

@item 
Python now includes a copy of the Expat XML parser's source code, removing any
dependence on a system version or local installation of Expat.

@item 
If you dynamically allocate type objects in your extension, you should be
aware of a change in the rules relating to the @code{__module__} and
@ref{c60,,__name__} attributes.  In summary, you will want to ensure the type's
dictionary contains a @code{'__module__'} key; making the module name the part of
the type name leading up to the final period will no longer have the desired
effect.  For more detail, read the API reference documentation or the  source.
@end itemize

@c ======================================================================

@menu
* Port-Specific Changes: Port-Specific Changes<3>. 

@end menu

@node Port-Specific Changes<3>,,,构建和 C API 的改变<12>
@anchor{whatsnew/2 3 port-specific-changes}@anchor{e15}
@subsubsection Port-Specific Changes


Support for a port to IBM's OS/2 using the EMX runtime environment was merged
into the main Python source tree.  EMX is a POSIX emulation layer over the OS/2
system APIs.  The Python port for EMX tries to support all the POSIX-like
capability exposed by the EMX runtime, and mostly succeeds; @code{fork()} and
@ref{7e,,fcntl()} are restricted by the limitations of the underlying emulation
layer.  The standard OS/2 port, which uses IBM's Visual Age compiler, also
gained support for case-sensitive import semantics as part of the integration of
the EMX port into CVS.  (Contributed by Andrew MacIntyre.)

On MacOS, most toolbox modules have been weaklinked to improve backward
compatibility.  This means that modules will no longer fail to load if a single
routine is missing on the current OS version. Instead calling the missing
routine will raise an exception. (Contributed by Jack Jansen.)

The RPM spec files, found in the @code{Misc/RPM/} directory in the Python
source distribution, were updated for 2.3.  (Contributed by Sean Reifschneider.)

Other new platforms now supported by Python include AtheOS
(@indicateurl{http://www.atheos.cx/}), GNU/Hurd, and OpenVMS.

@c ======================================================================

@node Other Changes and Fixes<2>,移植到 Python 2 3,构建和 C API 的改变<12>,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 other-changes-and-fixes}@anchor{e16}@anchor{whatsnew/2 3 section-other}@anchor{e06}
@subsection Other Changes and Fixes


As usual, there were a bunch of other improvements and bugfixes scattered
throughout the source tree.  A search through the CVS change logs finds there
were 523 patches applied and 514 bugs fixed between Python 2.2 and 2.3.  Both
figures are likely to be underestimates.

Some of the more notable changes are:


@itemize *

@item 
If the 
@geindex PYTHONINSPECT
@geindex 环境变量; PYTHONINSPECT
@ref{e17,,PYTHONINSPECT} environment variable is set, the Python
interpreter will enter the interactive prompt after running a Python program, as
if Python had been invoked with the @ref{e18,,-i} option. The environment
variable can be set before running the Python interpreter, or it can be set by
the Python program as part of its execution.

@item 
The @code{regrtest.py} script now provides a way to allow "all resources
except @emph{foo}."  A resource name passed to the @code{-u} option can now be
prefixed with a hyphen (@code{'-'}) to mean "remove this resource."  For example,
the option '@code{-uall,-bsddb}' could be used to enable the use of all resources
except @code{bsddb}.

@item 
The tools used to build the documentation now work under Cygwin as well as
Unix.

@item 
The @code{SET_LINENO} opcode has been removed.  Back in the mists of time, this
opcode was needed to produce line numbers in tracebacks and support trace
functions (for, e.g., @ref{c9,,pdb}). Since Python 1.5, the line numbers in
tracebacks have been computed using a different mechanism that works with
"python -O".  For Python 2.3 Michael Hudson implemented a similar scheme to
determine when to call the trace function, removing the need for @code{SET_LINENO}
entirely.

It would be difficult to detect any resulting difference from Python code, apart
from a slight speed up when Python is run without @ref{685,,-O}.

C extensions that access the @code{f_lineno} field of frame objects should
instead call @code{PyCode_Addr2Line(f->f_code, f->f_lasti)}. This will have the
added effect of making the code work as desired under "python -O" in earlier
versions of Python.

A nifty new feature is that trace functions can now assign to the
@code{f_lineno} attribute of frame objects, changing the line that will be
executed next.  A @code{jump} command has been added to the @ref{c9,,pdb} debugger
taking advantage of this new feature. (Implemented by Richie Hindle.)
@end itemize

@c ======================================================================

@node 移植到 Python 2 3,致谢<5>,Other Changes and Fixes<2>,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 porting-to-python-2-3}@anchor{e19}
@subsection 移植到 Python 2.3


This section lists previously described changes that may require changes to your
code:


@itemize *

@item 
@ref{18f,,yield} is now always a keyword; if it's used as a variable name in
your code, a different name must be chosen.

@item 
For strings @emph{X} and @emph{Y}, @code{X in Y} now works if @emph{X} is more than one
character long.

@item 
The @ref{184,,int()} type constructor will now return a long integer instead of
raising an @ref{95a,,OverflowError} when a string or floating-point number is too
large to fit into an integer.

@item 
If you have Unicode strings that contain 8-bit characters, you must declare
the file's encoding (UTF-8, Latin-1, or whatever) by adding a comment to the top
of the file.  See section @ref{de2,,PEP 263; Source Code Encodings} for more information.

@item 
Calling Tcl methods through @code{_tkinter} no longer  returns only strings.
Instead, if Tcl returns other objects those objects are converted to their
Python equivalent, if one exists, or wrapped with a @code{_tkinter.Tcl_Obj}
object if no Python equivalent exists.

@item 
Large octal and hex literals such as @code{0xffffffff} now trigger a
@ref{31e,,FutureWarning}. Currently they're stored as 32-bit numbers and result in a
negative value, but in Python 2.4 they'll become positive long integers.

There are a few ways to fix this warning.  If you really need a positive number,
just add an @code{L} to the end of the literal.  If you're trying to get a 32-bit
integer with low bits set and have previously used an expression such as @code{~(1
<< 31)}, it's probably clearest to start with all bits set and clear the
desired upper bits. For example, to clear just the top bit (bit 31), you could
write @code{0xffffffffL &~(1L<<31)}.

@item 
You can no longer disable assertions by assigning to @code{__debug__}.

@item 
The Distutils @code{setup()} function has gained various new keyword arguments
such as @emph{depends}.  Old versions of the Distutils will abort if passed unknown
keywords.  A solution is to check for the presence of the new
@code{get_distutil_options()} function in your @code{setup.py} and only uses the
new keywords with a version of the Distutils that supports them:

@example
from distutils import core

kw = @{'sources': 'foo.c', ...@}
if hasattr(core, 'get_distutil_options'):
    kw['depends'] = ['foo.h']
ext = Extension(**kw)
@end example

@item 
Using @code{None} as a variable name will now result in a @ref{191,,SyntaxWarning}
warning.

@item 
Names of extension types defined by the modules included with Python now
contain the module and a @code{'.'} in front of the type name.
@end itemize

@c ======================================================================

@node 致谢<5>,,移植到 Python 2 3,Python 2 3 有什么新变化
@anchor{whatsnew/2 3 acknowledgements}@anchor{e1a}@anchor{whatsnew/2 3 acks}@anchor{e1b}
@subsection 致谢


作者感谢以下人员为本文的各种草案提供建议，更正和帮助： Jeff Bauer, Simon Brunning, Brett Cannon, Michael Chermside, Andrew Dalke, Scott David Daniels, Fred L. Drake, Jr., David Fraser,  Kelly Gerber, Raymond Hettinger, Michael Hudson, Chris Lambert, Detlef Lannert, Martin von Löwis, Andrew MacIntyre, Lalo Martins, Chad Netzer, Gustavo Niemeyer, Neal Norwitz, Hans Nowak, Chris Reedy, Francesco Ricciardi, Vinay Sajip, Neil Schemenauer, Roman Suzi, Jason Tishler, Just van Rossum.

@node Python 2 2 有什么新变化,Python 2 1 有什么新变化,Python 2 3 有什么新变化,Python的新变化
@anchor{whatsnew/2 2 doc}@anchor{e1c}@anchor{whatsnew/2 2 what-s-new-in-python-2-2}@anchor{e1d}
@section Python 2.2 有什么新变化


@*作者: 
A.M. Kuchling


@c $Id: whatsnew22.tex 37315 2004-09-10 19:33:00Z akuchling $

@menu
* 概述:: 
* PEPs 252 and 253; Type and Class Changes: PEPs 252 and 253 Type and Class Changes. 
* PEP 234; Iterators: PEP 234 Iterators. 
* PEP 255; Simple Generators: PEP 255 Simple Generators<2>. 
* PEP 237; 统一长整数和整数: PEP 237 统一长整数和整数<2>. 
* PEP 238; Changing the Division Operator: PEP 238 Changing the Division Operator. 
* Unicode Changes:: 
* PEP 227; Nested Scopes: PEP 227 Nested Scopes. 
* 新增和改进的模块: 新增和改进的模块<3>. 
* Interpreter Changes and Fixes:: 
* Other Changes and Fixes: Other Changes and Fixes<3>. 
* 致谢: 致谢<6>. 

@end menu

@node 概述,PEPs 252 and 253 Type and Class Changes,,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 introduction}@anchor{e1e}
@subsection 概述


This article explains the new features in Python 2.2.2, released on October 14,
2002.  Python 2.2.2 is a bugfix release of Python 2.2, originally released on
December 21, 2001.

Python 2.2 can be thought of as the "cleanup release".  There are some features
such as generators and iterators that are completely new, but most of the
changes, significant and far-reaching though they may be, are aimed at cleaning
up irregularities and dark corners of the language design.

This article doesn't attempt to provide a complete specification of the new
features, but instead provides a convenient overview.  For full details, you
should refer to the documentation for Python 2.2, such as the Python Library Reference@footnote{https://docs.python.org/2.2/lib/lib.html} and the Python Reference Manual@footnote{https://docs.python.org/2.2/ref/ref.html}.  If you want to
understand the complete implementation and design rationale for a change, refer
to the PEP for a particular new feature.

@c see also, now defunct
@c 
@c http://www.unixreview.com/documents/s=1356/urm0109h/0109h.htm
@c    "What's So Special About Python 2.2?" is also about the new 2.2 features, and
@c    was written by Cameron Laird and Kathryn Soraiz.

@c ======================================================================

@node PEPs 252 and 253 Type and Class Changes,PEP 234 Iterators,概述,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 peps-252-and-253-type-and-class-changes}@anchor{e1f}
@subsection PEPs 252 and 253: Type and Class Changes


The largest and most far-reaching changes in Python 2.2 are to Python's model of
objects and classes.  The changes should be backward compatible, so it's likely
that your code will continue to run unchanged, but the changes provide some
amazing new capabilities. Before beginning this, the longest and most
complicated section of this article, I'll provide an overview of the changes and
offer some comments.

A long time ago I wrote a Web page listing flaws in Python's design.  One of the
most significant flaws was that it's impossible to subclass Python types
implemented in C.  In particular, it's not possible to subclass built-in types,
so you can't just subclass, say, lists in order to add a single useful method to
them. The @code{UserList} module provides a class that supports all of the
methods of lists and that can be subclassed further, but there's lots of C code
that expects a regular Python list and won't accept a @code{UserList}
instance.

Python 2.2 fixes this, and in the process adds some exciting new capabilities.
A brief summary:


@itemize *

@item 
You can subclass built-in types such as lists and even integers, and your
subclasses should work in every place that requires the original type.

@item 
It's now possible to define static and class methods, in addition to the
instance methods available in previous versions of Python.

@item 
It's also possible to automatically call methods on accessing or setting an
instance attribute by using a new mechanism called @emph{properties}.  Many uses
of @ref{313,,__getattr__()} can be rewritten to use properties instead, making the
resulting code simpler and faster.  As a small side benefit, attributes can now
have docstrings, too.

@item 
The list of legal attributes for an instance can be limited to a particular
set using @emph{slots}, making it possible to safeguard against typos and
perhaps make more optimizations possible in future versions of Python.
@end itemize

Some users have voiced concern about all these changes.  Sure, they say, the new
features are neat and lend themselves to all sorts of tricks that weren't
possible in previous versions of Python, but they also make the language more
complicated.  Some people have said that they've always recommended Python for
its simplicity, and feel that its simplicity is being lost.

Personally, I think there's no need to worry.  Many of the new features are
quite esoteric, and you can write a lot of Python code without ever needed to be
aware of them.  Writing a simple class is no more difficult than it ever was, so
you don't need to bother learning or teaching them unless they're actually
needed.  Some very complicated tasks that were previously only possible from C
will now be possible in pure Python, and to my mind that's all for the better.

I'm not going to attempt to cover every single corner case and small change that
were required to make the new features work.  Instead this section will paint
only the broad strokes.  See section @ref{e20,,Related Links}, "Related Links", for
further sources of information about Python 2.2's new object model.

@menu
* Old and New Classes:: 
* Descriptors:: 
* Multiple Inheritance; The Diamond Rule: Multiple Inheritance The Diamond Rule. 
* Attribute Access:: 
* Related Links:: 

@end menu

@node Old and New Classes,Descriptors,,PEPs 252 and 253 Type and Class Changes
@anchor{whatsnew/2 2 old-and-new-classes}@anchor{e21}
@subsubsection Old and New Classes


First, you should know that Python 2.2 really has two kinds of classes: classic
or old-style classes, and new-style classes.  The old-style class model is
exactly the same as the class model in earlier versions of Python.  All the new
features described in this section apply only to new-style classes. This
divergence isn't intended to last forever; eventually old-style classes will be
dropped, possibly in Python 3.0.

So how do you define a new-style class?  You do it by subclassing an existing
new-style class.  Most of Python's built-in types, such as integers, lists,
dictionaries, and even files, are new-style classes now.  A new-style class
named @ref{2b0,,object}, the base class for all built-in types, has also been
added so if no built-in type is suitable, you can just subclass
@ref{2b0,,object}:

@example
class C(object):
    def __init__ (self):
        ...
    ...
@end example

This means that @ref{c63,,class} statements that don't have any base classes are
always classic classes in Python 2.2.  (Actually you can also change this by
setting a module-level variable named @code{__metaclass__} --- see 
@geindex Python 提高建议; PEP 253
PEP 253@footnote{https://www.python.org/dev/peps/pep-0253}
for the details --- but it's easier to just subclass @ref{2b0,,object}.)

The type objects for the built-in types are available as built-ins, named using
a clever trick.  Python has always had built-in functions named @ref{184,,int()},
@ref{187,,float()}, and @ref{329,,str()}.  In 2.2, they aren't functions any more, but
type objects that behave as factories when called.

@example
>>> int
<type 'int'>
>>> int('123')
123
@end example

To make the set of types complete, new type objects such as @ref{1b8,,dict()} and
@code{file()} have been added.  Here's a more interesting example, adding a
@code{lock()} method to file objects:

@example
class LockableFile(file):
    def lock (self, operation, length=0, start=0, whence=0):
        import fcntl
        return fcntl.lockf(self.fileno(), operation,
                           length, start, whence)
@end example

The now-obsolete @code{posixfile} module contained a class that emulated all of
a file object's methods and also added a @code{lock()} method, but this class
couldn't be passed to internal functions that expected a built-in file,
something which is possible with our new @code{LockableFile}.

@node Descriptors,Multiple Inheritance The Diamond Rule,Old and New Classes,PEPs 252 and 253 Type and Class Changes
@anchor{whatsnew/2 2 descriptors}@anchor{e22}
@subsubsection Descriptors


In previous versions of Python, there was no consistent way to discover what
attributes and methods were supported by an object. There were some informal
conventions, such as defining @code{__members__} and @code{__methods__}
attributes that were lists of names, but often the author of an extension type
or a class wouldn't bother to define them.  You could fall back on inspecting
the @ref{4f6,,__dict__} of an object, but when class inheritance or an arbitrary
@ref{313,,__getattr__()} hook were in use this could still be inaccurate.

The one big idea underlying the new class model is that an API for describing
the attributes of an object using @emph{descriptors} has been formalized.
Descriptors specify the value of an attribute, stating whether it's a method or
a field.  With the descriptor API, static methods and class methods become
possible, as well as more exotic constructs.

Attribute descriptors are objects that live inside class objects, and have a few
attributes of their own:


@itemize *

@item 
@ref{c60,,__name__} is the attribute's name.

@item 
@code{__doc__} is the attribute's docstring.

@item 
@code{__get__(object)} is a method that retrieves the attribute value from
@emph{object}.

@item 
@code{__set__(object, value)} sets the attribute on @emph{object} to @emph{value}.

@item 
@code{__delete__(object, value)} deletes the @emph{value}  attribute of @emph{object}.
@end itemize

For example, when you write @code{obj.x}, the steps that Python actually performs
are:

@example
descriptor = obj.__class__.x
descriptor.__get__(obj)
@end example

For methods, @code{descriptor.__get__()} returns a temporary object that's
callable, and wraps up the instance and the method to be called on it. This is
also why static methods and class methods are now possible; they have
descriptors that wrap up just the method, or the method and the class.  As a
brief explanation of these new kinds of methods, static methods aren't passed
the instance, and therefore resemble regular functions.  Class methods are
passed the class of the object, but not the object itself.  Static and class
methods are defined like this:

@example
class C(object):
    def f(arg1, arg2):
        ...
    f = staticmethod(f)

    def g(cls, arg1, arg2):
        ...
    g = classmethod(g)
@end example

The @ref{1d9,,staticmethod()} function takes the function @code{f()}, and returns it
wrapped up in a descriptor so it can be stored in the class object.  You might
expect there to be special syntax for creating such methods (@code{def static f},
@code{defstatic f()}, or something like that) but no such syntax has been defined
yet; that's been left for future versions of Python.

More new features, such as slots and properties, are also implemented as new
kinds of descriptors, and it's not difficult to write a descriptor class that
does something novel.  For example, it would be possible to write a descriptor
class that made it possible to write Eiffel-style preconditions and
postconditions for a method.  A class that used this feature might be defined
like this:

@example
from eiffel import eiffelmethod

class C(object):
    def f(self, arg1, arg2):
        # The actual function
        ...
    def pre_f(self):
        # Check preconditions
        ...
    def post_f(self):
        # Check postconditions
        ...

    f = eiffelmethod(f, pre_f, post_f)
@end example

Note that a person using the new @code{eiffelmethod()} doesn't have to understand
anything about descriptors.  This is why I think the new features don't increase
the basic complexity of the language. There will be a few wizards who need to
know about it in order to write @code{eiffelmethod()} or the ZODB or whatever,
but most users will just write code on top of the resulting libraries and ignore
the implementation details.

@node Multiple Inheritance The Diamond Rule,Attribute Access,Descriptors,PEPs 252 and 253 Type and Class Changes
@anchor{whatsnew/2 2 multiple-inheritance-the-diamond-rule}@anchor{e23}
@subsubsection Multiple Inheritance: The Diamond Rule


Multiple inheritance has also been made more useful through changing the rules
under which names are resolved.  Consider this set of classes (diagram taken
from 
@geindex Python 提高建议; PEP 253
PEP 253@footnote{https://www.python.org/dev/peps/pep-0253} by Guido van Rossum):

@example
      class A:
        ^ ^  def save(self): ...
       /   \
      /     \
     /       \
    /         \
class B     class C:
    ^         ^  def save(self): ...
     \       /
      \     /
       \   /
        \ /
      class D
@end example

The lookup rule for classic classes is simple but not very smart; the base
classes are searched depth-first, going from left to right.  A reference to
@code{D.save()} will search the classes @code{D}, @code{B}, and then
@code{A}, where @code{save()} would be found and returned.  @code{C.save()}
would never be found at all.  This is bad, because if @code{C}'s @code{save()}
method is saving some internal state specific to @code{C}, not calling it will
result in that state never getting saved.

New-style classes follow a different algorithm that's a bit more complicated to
explain, but does the right thing in this situation. (Note that Python 2.3
changes this algorithm to one that produces the same results in most cases, but
produces more useful results for really complicated inheritance graphs.)


@enumerate 

@item 
List all the base classes, following the classic lookup rule and include a
class multiple times if it's visited repeatedly.  In the above example, the list
of visited classes is [@code{D}, @code{B}, @code{A}, @code{C},
@code{A}].

@item 
Scan the list for duplicated classes.  If any are found, remove all but one
occurrence, leaving the @emph{last} one in the list.  In the above example, the list
becomes [@code{D}, @code{B}, @code{C}, @code{A}] after dropping
duplicates.
@end enumerate

Following this rule, referring to @code{D.save()} will return @code{C.save()},
which is the behaviour we're after.  This lookup rule is the same as the one
followed by Common Lisp.  A new built-in function, @ref{4dc,,super()}, provides a way
to get at a class's superclasses without having to reimplement Python's
algorithm. The most commonly used form will be  @code{super(class, obj)}, which
returns  a bound superclass object (not the actual class object).  This form
will be used in methods to call a method in the superclass; for example,
@code{D}'s @code{save()} method would look like this:

@example
class D (B,C):
    def save (self):
        # Call superclass .save()
        super(D, self).save()
        # Save D's private information here
        ...
@end example

@ref{4dc,,super()} can also return unbound superclass objects when called as
@code{super(class)} or @code{super(class1, class2)}, but this probably won't
often be useful.

@node Attribute Access,Related Links,Multiple Inheritance The Diamond Rule,PEPs 252 and 253 Type and Class Changes
@anchor{whatsnew/2 2 attribute-access}@anchor{e24}
@subsubsection Attribute Access


A fair number of sophisticated Python classes define hooks for attribute access
using @ref{313,,__getattr__()}; most commonly this is done for convenience, to make
code more readable by automatically mapping an attribute access such as
@code{obj.parent} into a method call such as @code{obj.get_parent}.  Python 2.2 adds
some new ways of controlling attribute access.

First, @code{__getattr__(attr_name)} is still supported by new-style classes,
and nothing about it has changed.  As before, it will be called when an attempt
is made to access @code{obj.foo} and no attribute named @code{foo} is found in the
instance's dictionary.

New-style classes also support a new method,
@code{__getattribute__(attr_name)}.  The difference between the two methods is
that @ref{441,,__getattribute__()} is @emph{always} called whenever any attribute is
accessed, while the old @ref{313,,__getattr__()} is only called if @code{foo} isn't
found in the instance's dictionary.

However, Python 2.2's support for @emph{properties} will often be a simpler way
to trap attribute references.  Writing a @ref{313,,__getattr__()} method is
complicated because to avoid recursion you can't use regular attribute accesses
inside them, and instead have to mess around with the contents of
@ref{4f6,,__dict__}. @ref{313,,__getattr__()} methods also end up being called by Python
when it checks for other methods such as @ref{337,,__repr__()} or @code{__coerce__()},
and so have to be written with this in mind. Finally, calling a function on
every attribute access results in a sizable performance loss.

@ref{1d7,,property} is a new built-in type that packages up three functions that
get, set, or delete an attribute, and a docstring.  For example, if you want to
define a @code{size} attribute that's computed, but also settable, you could
write:

@example
class C(object):
    def get_size (self):
        result = ... computation ...
        return result
    def set_size (self, size):
        ... compute something based on the size
        and set internal state appropriately ...

    # Define a property.  The 'delete this attribute'
    # method is defined as None, so the attribute
    # can't be deleted.
    size = property(get_size, set_size,
                    None,
                    "Storage size of this instance")
@end example

That is certainly clearer and easier to write than a pair of
@ref{313,,__getattr__()}/@ref{e25,,__setattr__()} methods that check for the @code{size}
attribute and handle it specially while retrieving all other attributes from the
instance's @ref{4f6,,__dict__}.  Accesses to @code{size} are also the only ones
which have to perform the work of calling a function, so references to other
attributes run at their usual speed.

Finally, it's possible to constrain the list of attributes that can be
referenced on an object using the new @ref{e26,,__slots__} class attribute. Python
objects are usually very dynamic; at any time it's possible to define a new
attribute on an instance by just doing @code{obj.new_attr=1}.   A new-style class
can define a class attribute named @ref{e26,,__slots__} to limit the legal
attributes  to a particular set of names.  An example will make this clear:

@example
>>> class C(object):
...     __slots__ = ('template', 'name')
...
>>> obj = C()
>>> print obj.template
None
>>> obj.template = 'Test'
>>> print obj.template
Test
>>> obj.newattr = None
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'C' object has no attribute 'newattr'
@end example

Note how you get an @ref{393,,AttributeError} on the attempt to assign to an
attribute not listed in @ref{e26,,__slots__}.

@node Related Links,,Attribute Access,PEPs 252 and 253 Type and Class Changes
@anchor{whatsnew/2 2 related-links}@anchor{e27}@anchor{whatsnew/2 2 sect-rellinks}@anchor{e20}
@subsubsection Related Links


This section has just been a quick overview of the new features, giving enough
of an explanation to start you programming, but many details have been
simplified or ignored.  Where should you go to get a more complete picture?

@indicateurl{https://docs.python.org/dev/howto/descriptor.html} is a lengthy tutorial introduction to
the descriptor features, written by Guido van Rossum. If my description has
whetted your appetite, go read this tutorial next, because it goes into much
more detail about the new features while still remaining quite easy to read.

Next, there are two relevant PEPs, 
@geindex Python 提高建议; PEP 252
PEP 252@footnote{https://www.python.org/dev/peps/pep-0252} and 
@geindex Python 提高建议; PEP 253
PEP 253@footnote{https://www.python.org/dev/peps/pep-0253}.  
@geindex Python 提高建议; PEP 252
PEP 252@footnote{https://www.python.org/dev/peps/pep-0252} is
titled "Making Types Look More Like Classes", and covers the descriptor API.
@geindex Python 提高建议; PEP 253
PEP 253@footnote{https://www.python.org/dev/peps/pep-0253} is titled "Subtyping Built-in Types", and describes the changes to
type objects that make it possible to subtype built-in objects.  
@geindex Python 提高建议; PEP 253
PEP 253@footnote{https://www.python.org/dev/peps/pep-0253} is
the more complicated PEP of the two, and at a few points the necessary
explanations of types and meta-types may cause your head to explode.  Both PEPs
were written and implemented by Guido van Rossum, with substantial assistance
from the rest of the Zope Corp. team.

Finally, there's the ultimate authority: the source code.  Most of the machinery
for the type handling is in @code{Objects/typeobject.c}, but you should only
resort to it after all other avenues have been exhausted, including posting a
question to python-list or python-dev.

@c ======================================================================

@node PEP 234 Iterators,PEP 255 Simple Generators<2>,PEPs 252 and 253 Type and Class Changes,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 pep-234-iterators}@anchor{e28}
@subsection PEP 234: Iterators


Another significant addition to 2.2 is an iteration interface at both the C and
Python levels.  Objects can define how they can be looped over by callers.

In Python versions up to 2.1, the usual way to make @code{for item in obj} work is
to define a @ref{27f,,__getitem__()} method that looks something like this:

@example
def __getitem__(self, index):
    return <next item>
@end example

@ref{27f,,__getitem__()} is more properly used to define an indexing operation on an
object so that you can write @code{obj[5]} to retrieve the sixth element.  It's a
bit misleading when you're using this only to support @ref{c29,,for} loops.
Consider some file-like object that wants to be looped over; the @emph{index}
parameter is essentially meaningless, as the class probably assumes that a
series of @ref{27f,,__getitem__()} calls will be made with @emph{index} incrementing by
one each time.  In other words, the presence of the @ref{27f,,__getitem__()} method
doesn't mean that using @code{file[5]}  to randomly access the sixth element will
work, though it really should.

In Python 2.2, iteration can be implemented separately, and @ref{27f,,__getitem__()}
methods can be limited to classes that really do support random access.  The
basic idea of iterators is  simple.  A new built-in function, @code{iter(obj)}
or @code{iter(C, sentinel)}, is used to get an iterator. @code{iter(obj)} returns
an iterator for the object @emph{obj}, while @code{iter(C, sentinel)} returns an
iterator that will invoke the callable object @emph{C} until it returns @emph{sentinel} to
signal that the iterator is done.

Python classes can define an @ref{509,,__iter__()} method, which should create and
return a new iterator for the object; if the object is its own iterator, this
method can just return @code{self}.  In particular, iterators will usually be their
own iterators.  Extension types implemented in C can implement a @ref{e29,,tp_iter}
function in order to return an iterator, and extension types that want to behave
as iterators can define a @ref{e2a,,tp_iternext} function.

So, after all this, what do iterators actually do?  They have one required
method, @ref{67c,,next()}, which takes no arguments and returns the next value.  When
there are no more values to be returned, calling @ref{67c,,next()} should raise the
@ref{480,,StopIteration} exception.

@example
>>> L = [1,2,3]
>>> i = iter(L)
>>> print i
<iterator object at 0x8116870>
>>> i.next()
1
>>> i.next()
2
>>> i.next()
3
>>> i.next()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
StopIteration
>>>
@end example

In 2.2, Python's @ref{c29,,for} statement no longer expects a sequence; it
expects something for which @ref{d20,,iter()} will return an iterator. For backward
compatibility and convenience, an iterator is automatically constructed for
sequences that don't implement @ref{509,,__iter__()} or a @ref{e29,,tp_iter} slot, so
@code{for i in [1,2,3]} will still work.  Wherever the Python interpreter loops
over a sequence, it's been changed to use the iterator protocol.  This means you
can do things like this:

@example
>>> L = [1,2,3]
>>> i = iter(L)
>>> a,b,c = i
>>> a,b,c
(1, 2, 3)
@end example

Iterator support has been added to some of Python's basic types.   Calling
@ref{d20,,iter()} on a dictionary will return an iterator which loops over its keys:

@example
>>> m = @{'Jan': 1, 'Feb': 2, 'Mar': 3, 'Apr': 4, 'May': 5, 'Jun': 6,
...      'Jul': 7, 'Aug': 8, 'Sep': 9, 'Oct': 10, 'Nov': 11, 'Dec': 12@}
>>> for key in m: print key, m[key]
...
Mar 3
Feb 2
Aug 8
Sep 9
May 5
Jun 6
Jul 7
Jan 1
Apr 4
Nov 11
Dec 12
Oct 10
@end example

That's just the default behaviour.  If you want to iterate over keys, values, or
key/value pairs, you can explicitly call the @code{iterkeys()},
@code{itervalues()}, or @code{iteritems()} methods to get an appropriate iterator.
In a minor related change, the @ref{79d,,in} operator now works on dictionaries,
so @code{key in dict} is now equivalent to @code{dict.has_key(key)}.

Files also provide an iterator, which calls the @ref{de,,readline()} method until
there are no more lines in the file.  This means you can now read each line of a
file using code like this:

@example
for line in file:
    # do something for each line
    ...
@end example

Note that you can only go forward in an iterator; there's no way to get the
previous element, reset the iterator, or make a copy of it. An iterator object
could provide such additional capabilities, but the iterator protocol only
requires a @ref{67c,,next()} method.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 234

@item PEP 234@footnote{https://www.python.org/dev/peps/pep-0234} - Iterators

由 Ka-Ping Yee 和 GvR 撰写；由 Python Labs 小组（主要由 GvR 和 Tim Peters）实现。
@end table


@c ======================================================================

@node PEP 255 Simple Generators<2>,PEP 237 统一长整数和整数<2>,PEP 234 Iterators,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 pep-255-simple-generators}@anchor{e2b}
@subsection PEP 255: Simple Generators


Generators are another new feature, one that interacts with the introduction of
iterators.

You're doubtless familiar with how function calls work in Python or C.  When you
call a function, it gets a private namespace where its local variables are
created.  When the function reaches a @ref{190,,return} statement, the local
variables are destroyed and the resulting value is returned to the caller.  A
later call to the same function will get a fresh new set of local variables.
But, what if the local variables weren't thrown away on exiting a function?
What if you could later resume the function where it left off?  This is what
generators provide; they can be thought of as resumable functions.

Here's the simplest example of a generator function:

@example
def generate_ints(N):
    for i in range(N):
        yield i
@end example

A new keyword, @ref{18f,,yield}, was introduced for generators.  Any function
containing a @code{yield} statement is a generator function; this is
detected by Python's bytecode compiler which compiles the function specially as
a result.  Because a new keyword was introduced, generators must be explicitly
enabled in a module by including a @code{from __future__ import generators}
statement near the top of the module's source code.  In Python 2.3 this
statement will become unnecessary.

When you call a generator function, it doesn't return a single value; instead it
returns a generator object that supports the iterator protocol.  On executing
the @ref{18f,,yield} statement, the generator outputs the value of @code{i},
similar to a @ref{190,,return} statement.  The big difference between
@code{yield} and a @code{return} statement is that on reaching a
@code{yield} the generator's state of execution is suspended and local
variables are preserved.  On the next call to the generator's @code{next()} method,
the function will resume executing immediately after the @code{yield}
statement.  (For complicated reasons, the @code{yield} statement isn't
allowed inside the @code{try} block of a
@ref{d6b,,try}...@ref{182,,finally} statement; read 
@geindex Python 提高建议; PEP 255
PEP 255@footnote{https://www.python.org/dev/peps/pep-0255} for a full
explanation of the interaction between @code{yield} and exceptions.)

Here's a sample usage of the @code{generate_ints()} generator:

@example
>>> gen = generate_ints(3)
>>> gen
<generator object at 0x8117f90>
>>> gen.next()
0
>>> gen.next()
1
>>> gen.next()
2
>>> gen.next()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "<stdin>", line 2, in generate_ints
StopIteration
@end example

You could equally write @code{for i in generate_ints(5)}, or @code{a,b,c =
generate_ints(3)}.

Inside a generator function, the @ref{190,,return} statement can only be used
without a value, and signals the end of the procession of values; afterwards the
generator cannot return any further values. @code{return} with a value, such
as @code{return 5}, is a syntax error inside a generator function.  The end of the
generator's results can also be indicated by raising @ref{480,,StopIteration}
manually, or by just letting the flow of execution fall off the bottom of the
function.

You could achieve the effect of generators manually by writing your own class
and storing all the local variables of the generator as instance variables.  For
example, returning a list of integers could be done by setting @code{self.count} to
0, and having the @ref{67c,,next()} method increment @code{self.count} and return it.
However, for a moderately complicated generator, writing a corresponding class
would be much messier. @code{Lib/test/test_generators.py} contains a number of
more interesting examples.  The simplest one implements an in-order traversal of
a tree using generators recursively.

@example
# A recursive generator that generates Tree leaves in in-order.
def inorder(t):
    if t:
        for x in inorder(t.left):
            yield x
        yield t.label
        for x in inorder(t.right):
            yield x
@end example

Two other examples in @code{Lib/test/test_generators.py} produce solutions for
the N-Queens problem (placing $N$ queens on an $NxN$ chess board so that no
queen threatens another) and the Knight's Tour (a route that takes a knight to
every square of an $NxN$ chessboard without visiting any square twice).

The idea of generators comes from other programming languages, especially Icon
(@indicateurl{https://www.cs.arizona.edu/icon/}), where the idea of generators is central.  In
Icon, every expression and function call behaves like a generator.  One example
from "An Overview of the Icon Programming Language" at
@indicateurl{https://www.cs.arizona.edu/icon/docs/ipd266.htm} gives an idea of what this looks
like:

@example
sentence := "Store it in the neighboring harbor"
if (i := find("or", sentence)) > 5 then write(i)
@end example

In Icon the @code{find()} function returns the indexes at which the substring
"or" is found: 3, 23, 33.  In the @ref{de0,,if} statement, @code{i} is first
assigned a value of 3, but 3 is less than 5, so the comparison fails, and Icon
retries it with the second value of 23.  23 is greater than 5, so the comparison
now succeeds, and the code prints the value 23 to the screen.

Python doesn't go nearly as far as Icon in adopting generators as a central
concept.  Generators are considered a new part of the core Python language, but
learning or using them isn't compulsory; if they don't solve any problems that
you have, feel free to ignore them. One novel feature of Python's interface as
compared to Icon's is that a generator's state is represented as a concrete
object (the iterator) that can be passed around to other functions or stored in
a data structure.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 255

@item PEP 255@footnote{https://www.python.org/dev/peps/pep-0255} - 简单生成器

Written by Neil Schemenauer, Tim Peters, Magnus Lie Hetland.  Implemented mostly
by Neil Schemenauer and Tim Peters, with other fixes from the Python Labs crew.
@end table


@c ======================================================================

@node PEP 237 统一长整数和整数<2>,PEP 238 Changing the Division Operator,PEP 255 Simple Generators<2>,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 pep-237-unifying-long-integers-and-integers}@anchor{e2c}
@subsection PEP 237: 统一长整数和整数


In recent versions, the distinction between regular integers, which are 32-bit
values on most machines, and long integers, which can be of arbitrary size, was
becoming an annoyance.  For example, on platforms that support files larger than
@code{2**32} bytes, the @code{tell()} method of file objects has to return a long
integer. However, there were various bits of Python that expected plain integers
and would raise an error if a long integer was provided instead.  For example,
in Python 1.5, only regular integers could be used as a slice index, and
@code{'abc'[1L:]} would raise a @ref{192,,TypeError} exception with the message 'slice
index must be int'.

Python 2.2 will shift values from short to long integers as required. The 'L'
suffix is no longer needed to indicate a long integer literal, as now the
compiler will choose the appropriate type.  (Using the 'L' suffix will be
discouraged in future 2.x versions of Python, triggering a warning in Python
2.4, and probably dropped in Python 3.0.)  Many operations that used to raise an
@ref{95a,,OverflowError} will now return a long integer as their result.  For
example:

@example
>>> 1234567890123
1234567890123L
>>> 2 ** 64
18446744073709551616L
@end example

In most cases, integers and long integers will now be treated identically.  You
can still distinguish them with the @ref{603,,type()} built-in function, but that's
rarely needed.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 237

@item PEP 237@footnote{https://www.python.org/dev/peps/pep-0237} - 统一长整数和整数

由 Moshe Zadka 和 Guido van Rossum 撰写 ; 大部分由 Guido van Rossum 实现。
@end table


@c ======================================================================

@node PEP 238 Changing the Division Operator,Unicode Changes,PEP 237 统一长整数和整数<2>,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 pep-238-changing-the-division-operator}@anchor{e2d}
@subsection PEP 238: Changing the Division Operator


The most controversial change in Python 2.2 heralds the start of an effort to
fix an old design flaw that's been in Python from the beginning. Currently
Python's division operator, @code{/}, behaves like C's division operator when
presented with two integer arguments: it returns an integer result that's
truncated down when there would be a fractional part.  For example, @code{3/2} is
1, not 1.5, and @code{(-1)/2} is -1, not -0.5.  This means that the results of
division can vary unexpectedly depending on the type of the two operands and
because Python is dynamically typed, it can be difficult to determine the
possible types of the operands.

(The controversy is over whether this is @emph{really} a design flaw, and whether
it's worth breaking existing code to fix this.  It's caused endless discussions
on python-dev, and in July 2001 erupted into a storm of acidly sarcastic
postings on @code{comp.lang.python}. I won't argue for either side here
and will stick to describing what's  implemented in 2.2.  Read 
@geindex Python 提高建议; PEP 238
PEP 238@footnote{https://www.python.org/dev/peps/pep-0238} for a
summary of arguments and counter-arguments.)

Because this change might break code, it's being introduced very gradually.
Python 2.2 begins the transition, but the switch won't be complete until Python
3.0.

First, I'll borrow some terminology from 
@geindex Python 提高建议; PEP 238
PEP 238@footnote{https://www.python.org/dev/peps/pep-0238}.  "True division" is the
division that most non-programmers are familiar with: 3/2 is 1.5, 1/4 is 0.25,
and so forth.  "Floor division" is what Python's @code{/} operator currently does
when given integer operands; the result is the floor of the value returned by
true division.  "Classic division" is the current mixed behaviour of @code{/}; it
returns the result of floor division when the operands are integers, and returns
the result of true division when one of the operands is a floating-point number.

Here are the changes 2.2 introduces:


@itemize *

@item 
A new operator, @code{//}, is the floor division operator. (Yes, we know it looks
like C++'s comment symbol.)  @code{//} @emph{always} performs floor division no matter
what the types of its operands are, so @code{1 // 2} is 0 and @code{1.0 // 2.0} is
also 0.0.

@code{//} is always available in Python 2.2; you don't need to enable it using a
@code{__future__} statement.

@item 
By including a @code{from __future__ import division} in a module, the @code{/}
operator will be changed to return the result of true division, so @code{1/2} is
0.5.  Without the @code{__future__} statement, @code{/} still means classic division.
The default meaning of @code{/} will not change until Python 3.0.

@item 
Classes can define methods called @ref{780,,__truediv__()} and @ref{e2e,,__floordiv__()}
to overload the two division operators.  At the C level, there are also slots in
the @ref{d7a,,PyNumberMethods} structure so extension types can define the two
operators.

@item 
Python 2.2 supports some command-line arguments for testing whether code will
work with the changed division semantics.  Running python with @code{-Q
warn} will cause a warning to be issued whenever division is applied to two
integers.  You can use this to find code that's affected by the change and fix
it.  By default, Python 2.2 will simply perform classic division without a
warning; the warning will be turned on by default in Python 2.3.
@end itemize


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 238

@item PEP 238@footnote{https://www.python.org/dev/peps/pep-0238} - Changing the Division Operator

由 Moshe Zadka 和 Guido van Rossum 撰写 ; 由 Guido van Rossum 实现。
@end table


@c ======================================================================

@node Unicode Changes,PEP 227 Nested Scopes,PEP 238 Changing the Division Operator,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 unicode-changes}@anchor{e2f}
@subsection Unicode Changes


Python's Unicode support has been enhanced a bit in 2.2.  Unicode strings are
usually stored as UCS-2, as 16-bit unsigned integers. Python 2.2 can also be
compiled to use UCS-4, 32-bit unsigned integers, as its internal encoding by
supplying @code{--enable-unicode=ucs4} to the configure script.   (It's also
possible to specify @code{--disable-unicode} to completely disable Unicode
support.)

When built to use UCS-4 (a "wide Python"), the interpreter can natively handle
Unicode characters from U+000000 to U+110000, so the range of legal values for
the @code{unichr()} function is expanded accordingly.  Using an interpreter
compiled to use UCS-2 (a "narrow Python"), values greater than 65535 will still
cause @code{unichr()} to raise a @ref{1fb,,ValueError} exception. This is all
described in 
@geindex Python 提高建议; PEP 261
PEP 261@footnote{https://www.python.org/dev/peps/pep-0261}, "Support for 'wide' Unicode characters"; consult it for
further details.

Another change is simpler to explain. Since their introduction, Unicode strings
have supported an @code{encode()} method to convert the string to a selected
encoding such as UTF-8 or Latin-1.  A symmetric @code{decode([*encoding*])}
method has been added to 8-bit strings (though not to Unicode strings) in 2.2.
@code{decode()} assumes that the string is in the specified encoding and decodes
it, returning whatever is returned by the codec.

Using this new feature, codecs have been added for tasks not directly related to
Unicode.  For example, codecs have been added for uu-encoding, MIME's base64
encoding, and compression with the @ref{144,,zlib} module:

@example
>>> s = """Here is a lengthy piece of redundant, overly verbose,
... and repetitive text.
... """
>>> data = s.encode('zlib')
>>> data
'x\x9c\r\xc9\xc1\r\x80 \x10\x04\xc0?Ul...'
>>> data.decode('zlib')
'Here is a lengthy piece of redundant, overly verbose,\nand repetitive text.\n'
>>> print s.encode('uu')
begin 666 <data>
M2&5R92!I<R!A(&QE;F=T:'D@@<&EE8V4@@;V8@@<F5D=6YD86YT+"!O=F5R;'D@@
>=F5R8F]S92P*86YD(')E<&5T:71I=F4@@=&5X="X*

end
>>> "sheesh".encode('rot-13')
'furrfu'
@end example

To convert a class instance to Unicode, a @code{__unicode__()} method can be
defined by a class, analogous to @ref{e30,,__str__()}.

@code{encode()}, @code{decode()}, and @code{__unicode__()} were implemented by
Marc-André Lemburg.  The changes to support using UCS-4 internally were
implemented by Fredrik Lundh and Martin von Löwis.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 261

@item PEP 261@footnote{https://www.python.org/dev/peps/pep-0261} - Support for 'wide' Unicode characters

Written by Paul Prescod.
@end table


@c ======================================================================

@node PEP 227 Nested Scopes,新增和改进的模块<3>,Unicode Changes,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 pep-227-nested-scopes}@anchor{e31}
@subsection PEP 227: Nested Scopes


In Python 2.1, statically nested scopes were added as an optional feature, to be
enabled by a @code{from __future__ import nested_scopes} directive.  In 2.2 nested
scopes no longer need to be specially enabled, and are now always present.  The
rest of this section is a copy of the description of nested scopes from my
"What's New in Python 2.1" document; if you read it when 2.1 came out, you can
skip the rest of this section.

The largest change introduced in Python 2.1, and made complete in 2.2, is to
Python's scoping rules.  In Python 2.0, at any given time there are at most
three namespaces used to look up variable names: local, module-level, and the
built-in namespace.  This often surprised people because it didn't match their
intuitive expectations.  For example, a nested recursive function definition
doesn't work:

@example
def f():
    ...
    def g(value):
        ...
        return g(value-1) + 1
    ...
@end example

The function @code{g()} will always raise a @ref{d74,,NameError} exception, because
the binding of the name @code{g} isn't in either its local namespace or in the
module-level namespace.  This isn't much of a problem in practice (how often do
you recursively define interior functions like this?), but this also made using
the @ref{c28,,lambda} expression clumsier, and this was a problem in practice.
In code which uses @code{lambda} you can often find local variables being
copied by passing them as the default values of arguments.

@example
def find(self, name):
    "Return list of any entries equal to 'name'"
    L = filter(lambda x, name=name: x == name,
               self.list_attribute)
    return L
@end example

The readability of Python code written in a strongly functional style suffers
greatly as a result.

The most significant change to Python 2.2 is that static scoping has been added
to the language to fix this problem.  As a first effect, the @code{name=name}
default argument is now unnecessary in the above example.  Put simply, when a
given variable name is not assigned a value within a function (by an assignment,
or the @ref{db7,,def}, @ref{c63,,class}, or @ref{c16,,import} statements),
references to the variable will be looked up in the local namespace of the
enclosing scope.  A more detailed explanation of the rules, and a dissection of
the implementation, can be found in the PEP.

This change may cause some compatibility problems for code where the same
variable name is used both at the module level and as a local variable within a
function that contains further function definitions. This seems rather unlikely
though, since such code would have been pretty confusing to read in the first
place.

One side effect of the change is that the @code{from module import *} and
@code{exec} statements have been made illegal inside a function scope under
certain conditions.  The Python reference manual has said all along that @code{from
module import *} is only legal at the top level of a module, but the CPython
interpreter has never enforced this before.  As part of the implementation of
nested scopes, the compiler which turns Python source into bytecodes has to
generate different code to access variables in a containing scope.  @code{from
module import *} and @code{exec} make it impossible for the compiler to
figure this out, because they add names to the local namespace that are
unknowable at compile time. Therefore, if a function contains function
definitions or @ref{c28,,lambda} expressions with free variables, the compiler
will flag this by raising a @ref{452,,SyntaxError} exception.

To make the preceding explanation a bit clearer, here's an example:

@example
x = 1
def f():
    # The next line is a syntax error
    exec 'x=2'
    def g():
        return x
@end example

Line 4 containing the @code{exec} statement is a syntax error, since
@code{exec} would define a new local variable named @code{x} whose value should
be accessed by @code{g()}.

This shouldn't be much of a limitation, since @code{exec} is rarely used in
most Python code (and when it is used, it's often a sign of a poor design
anyway).


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 227

@item PEP 227@footnote{https://www.python.org/dev/peps/pep-0227} - Statically Nested Scopes

由 Jeremy Hylton 撰写并实现。
@end table


@c ======================================================================

@node 新增和改进的模块<3>,Interpreter Changes and Fixes,PEP 227 Nested Scopes,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 new-and-improved-modules}@anchor{e32}
@subsection 新增和改进的模块



@itemize *

@item 
The @code{xmlrpclib} module was contributed to the standard library by Fredrik
Lundh, providing support for writing XML-RPC clients.  XML-RPC is a simple
remote procedure call protocol built on top of HTTP and XML. For example, the
following snippet retrieves a list of RSS channels from the O'Reilly Network,
and then  lists the recent headlines for one channel:

@example
import xmlrpclib
s = xmlrpclib.Server(
      'http://www.oreillynet.com/meerkat/xml-rpc/server.php')
channels = s.meerkat.getChannels()
# channels is a list of dictionaries, like this:
# [@{'id': 4, 'title': 'Freshmeat Daily News'@}
#  @{'id': 190, 'title': '32Bits Online'@},
#  @{'id': 4549, 'title': '3DGamers'@}, ... ]

# Get the items for one channel
items = s.meerkat.getItems( @{'channel': 4@} )

# 'items' is another list of dictionaries, like this:
# [@{'link': 'http://freshmeat.net/releases/52719/',
#   'description': 'A utility which converts HTML to XSL FO.',
#   'title': 'html2fo 0.3 (Default)'@}, ... ]
@end example

The @code{SimpleXMLRPCServer} module makes it easy to create straightforward
XML-RPC servers.  See @indicateurl{http://xmlrpc.scripting.com/} for more information about XML-RPC.

@item 
The new @ref{8f,,hmac} module implements the HMAC algorithm described by
@geindex RFC; RFC 2104
RFC 2104@footnote{https://tools.ietf.org/html/rfc2104.html}. (Contributed by Gerhard Häring.)

@item 
Several functions that originally returned lengthy tuples now return
pseudo-sequences that still behave like tuples but also have mnemonic attributes such
as memberst_mtime or @code{tm_year}. The enhanced functions include
@ref{f4,,stat()}, @code{fstat()}, @code{statvfs()}, and @code{fstatvfs()} in the
@ref{c4,,os} module, and @code{localtime()}, @code{gmtime()}, and @code{strptime()} in
the @ref{10a,,time} module.

For example, to obtain a file's size using the old tuples, you'd end up writing
something like @code{file_size = os.stat(filename)[stat.ST_SIZE]}, but now this can
be written more clearly as @code{file_size = os.stat(filename).st_size}.

The original patch for this feature was contributed by Nick Mathewson.

@item 
The Python profiler has been extensively reworked and various errors in its
output have been corrected.  (Contributed by Fred L. Drake, Jr. and Tim Peters.)

@item 
The @ref{ef,,socket} module can be compiled to support IPv6; specify the
@code{--enable-ipv6} option to Python's configure script.  (Contributed by
Jun-ichiro "itojun" Hagino.)

@item 
Two new format characters were added to the @ref{f8,,struct} module for 64-bit
integers on platforms that support the C @code{long long} type.  @code{q} is for
a signed 64-bit integer, and @code{Q} is for an unsigned one.  The value is
returned in Python's long integer type.  (Contributed by Tim Peters.)

@item 
In the interpreter's interactive mode, there's a new built-in function
@ref{56d,,help()} that uses the @ref{d9,,pydoc} module introduced in Python 2.1 to
provide interactive help. @code{help(object)} displays any available help text
about @emph{object}.  @ref{56d,,help()} with no argument puts you in an online help
utility, where you can enter the names of functions, classes, or modules to read
their help text. (Contributed by Guido van Rossum, using Ka-Ping Yee's
@ref{d9,,pydoc} module.)

@item 
Various bugfixes and performance improvements have been made to the SRE engine
underlying the @ref{dd,,re} module.  For example, the @ref{475,,re.sub()} and
@ref{3c2,,re.split()} functions have been rewritten in C.  Another contributed patch
speeds up certain Unicode character ranges by a factor of two, and a new
@code{finditer()}  method that returns an iterator over all the non-overlapping
matches in  a given string.  (SRE is maintained by Fredrik Lundh.  The
BIGCHARSET patch was contributed by Martin von Löwis.)

@item 
The @ref{ed,,smtplib} module now supports 
@geindex RFC; RFC 2487
RFC 2487@footnote{https://tools.ietf.org/html/rfc2487.html}, "Secure SMTP over TLS", so
it's now possible to encrypt the SMTP traffic between a Python program and the
mail transport agent being handed a message.  @ref{ed,,smtplib} also supports SMTP
authentication.  (Contributed by Gerhard Häring.)

@item 
The @ref{98,,imaplib} module, maintained by Piers Lauder, has support for several
new extensions: the NAMESPACE extension defined in 
@geindex RFC; RFC 2342
RFC 2342@footnote{https://tools.ietf.org/html/rfc2342.html}, SORT, GETACL and
SETACL.  (Contributed by Anthony Baxter and Michel Pelletier.)

@item 
The @code{rfc822} module's parsing of email addresses is now compliant with
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}, an update to 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html}.  (The module's name is @emph{not} going to be
changed to @code{rfc2822}.)  A new package, @ref{69,,email}, has also been added for
parsing and generating e-mail messages.  (Contributed by Barry Warsaw, and
arising out of his work on Mailman.)

@item 
The @ref{37,,difflib} module now contains a new @code{Differ} class for
producing human-readable lists of changes (a "delta") between two sequences of
lines of text.  There are also two generator functions, @code{ndiff()} and
@code{restore()}, which respectively return a delta from two sequences, or one of
the original sequences from a delta. (Grunt work contributed by David Goodger,
from ndiff.py code by Tim Peters who then did the generatorization.)

@item 
New constants @code{ascii_letters}, @code{ascii_lowercase}, and
@code{ascii_uppercase} were added to the @ref{f6,,string} module.  There were
several modules in the standard library that used @code{string.letters} to
mean the ranges A-Za-z, but that assumption is incorrect when locales are in
use, because @code{string.letters} varies depending on the set of legal
characters defined by the current locale.  The buggy modules have all been fixed
to use @code{ascii_letters} instead. (Reported by an unknown person; fixed by
Fred L. Drake, Jr.)

@item 
The @ref{b2,,mimetypes} module now makes it easier to use alternative MIME-type
databases by the addition of a @code{MimeTypes} class, which takes a list of
filenames to be parsed.  (Contributed by Fred L. Drake, Jr.)

@item 
A @code{Timer} class was added to the @ref{109,,threading} module that allows
scheduling an activity to happen at some future time.  (Contributed by Itamar
Shtull-Trauring.)
@end itemize

@c ======================================================================

@node Interpreter Changes and Fixes,Other Changes and Fixes<3>,新增和改进的模块<3>,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 interpreter-changes-and-fixes}@anchor{e33}
@subsection Interpreter Changes and Fixes


Some of the changes only affect people who deal with the Python interpreter at
the C level because they're writing Python extension modules, embedding the
interpreter, or just hacking on the interpreter itself. If you only write Python
code, none of the changes described here will affect you very much.


@itemize *

@item 
Profiling and tracing functions can now be implemented in C, which can operate
at much higher speeds than Python-based functions and should reduce the overhead
of profiling and tracing.  This  will be of interest to authors of development
environments for Python.  Two new C functions were added to Python's API,
@ref{e34,,PyEval_SetProfile()} and @ref{e35,,PyEval_SetTrace()}. The existing
@ref{e36,,sys.setprofile()} and @ref{e37,,sys.settrace()} functions still exist, and have
simply been changed to use the new C-level interface.  (Contributed by Fred L.
Drake, Jr.)

@item 
Another low-level API, primarily of interest to implementors of Python
debuggers and development tools, was added. @ref{e38,,PyInterpreterState_Head()} and
@ref{e39,,PyInterpreterState_Next()} let a caller walk through all the existing
interpreter objects; @ref{e3a,,PyInterpreterState_ThreadHead()} and
@ref{e3b,,PyThreadState_Next()} allow looping over all the thread states for a given
interpreter.  (Contributed by David Beazley.)

@item 
The C-level interface to the garbage collector has been changed to make it
easier to write extension types that support garbage collection and to debug
misuses of the functions. Various functions have slightly different semantics,
so a bunch of functions had to be renamed.  Extensions that use the old API will
still compile but will @emph{not} participate in garbage collection, so updating them
for 2.2 should be considered fairly high priority.

To upgrade an extension module to the new API, perform the following steps:

@item 
Rename @code{Py_TPFLAGS_GC()} to @code{PyTPFLAGS_HAVE_GC()}.

@item 

@table @asis

@item Use @ref{2d4,,PyObject_GC_New()} or @ref{2d5,,PyObject_GC_NewVar()} to allocate

objects, and @ref{e3c,,PyObject_GC_Del()} to deallocate them.
@end table

@item 

@table @asis

@item Rename @code{PyObject_GC_Init()} to @ref{e3d,,PyObject_GC_Track()} and

@code{PyObject_GC_Fini()} to @ref{e3e,,PyObject_GC_UnTrack()}.
@end table

@item 
Remove @code{PyGC_HEAD_SIZE()} from object size calculations.

@item 
Remove calls to @code{PyObject_AS_GC()} and @code{PyObject_FROM_GC()}.

@item 
A new @code{et} format sequence was added to @ref{26a,,PyArg_ParseTuple()}; @code{et}
takes both a parameter and an encoding name, and converts the parameter to the
given encoding if the parameter turns out to be a Unicode string, or leaves it
alone if it's an 8-bit string, assuming it to already be in the desired
encoding.  This differs from the @code{es} format character, which assumes that
8-bit strings are in Python's default ASCII encoding and converts them to the
specified new encoding. (Contributed by M.-A. Lemburg, and used for the MBCS
support on Windows described in the following section.)

@item 
A different argument parsing function, @ref{e3f,,PyArg_UnpackTuple()}, has been
added that's simpler and presumably faster.  Instead of specifying a format
string, the caller simply gives the minimum and maximum number of arguments
expected, and a set of pointers to @ref{4b5,,PyObject*} variables that will be
filled in with argument values.

@item 
Two new flags @ref{e11,,METH_NOARGS} and @ref{e40,,METH_O} are available in method
definition tables to simplify implementation of methods with no arguments or a
single untyped argument. Calling such methods is more efficient than calling a
corresponding method that uses @ref{e41,,METH_VARARGS}.  Also, the old
@code{METH_OLDARGS} style of writing C methods is  now officially deprecated.

@item 
Two new wrapper functions, @ref{e42,,PyOS_snprintf()} and @ref{e43,,PyOS_vsnprintf()}
were added to provide  cross-platform implementations for the relatively new
@code{snprintf()} and @code{vsnprintf()} C lib APIs. In contrast to the standard
@code{sprintf()} and @code{vsprintf()} functions, the Python versions check the
bounds of the buffer used to protect against buffer overruns. (Contributed by
M.-A. Lemburg.)

@item 
The @ref{e44,,_PyTuple_Resize()} function has lost an unused parameter, so now it
takes 2 parameters instead of 3.  The third argument was never used, and can
simply be discarded when porting code from earlier versions to Python 2.2.
@end itemize

@c ======================================================================

@node Other Changes and Fixes<3>,致谢<6>,Interpreter Changes and Fixes,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 other-changes-and-fixes}@anchor{e45}
@subsection Other Changes and Fixes


As usual there were a bunch of other improvements and bugfixes scattered
throughout the source tree.  A search through the CVS change logs finds there
were 527 patches applied and 683 bugs fixed between Python 2.1 and 2.2; 2.2.1
applied 139 patches and fixed 143 bugs; 2.2.2 applied 106 patches and fixed 82
bugs.  These figures are likely to be underestimates.

Some of the more notable changes are:


@itemize *

@item 
The code for the MacOS port for Python, maintained by Jack Jansen, is now kept
in the main Python CVS tree, and many changes have been made to support MacOS X.

The most significant change is the ability to build Python as a framework,
enabled by supplying the @code{--enable-framework} option to the configure
script when compiling Python.  According to Jack Jansen, "This installs a
self-contained Python installation plus the OS X framework "glue" into
@code{/Library/Frameworks/Python.framework} (or another location of choice).
For now there is little immediate added benefit to this (actually, there is the
disadvantage that you have to change your PATH to be able to find Python), but
it is the basis for creating a full-blown Python application, porting the
MacPython IDE, possibly using Python as a standard OSA scripting language and
much more."

Most of the MacPython toolbox modules, which interface to MacOS APIs such as
windowing, QuickTime, scripting, etc. have been ported to OS X, but they've been
left commented out in @code{setup.py}.  People who want to experiment with
these modules can uncomment them manually.

@c Jack's original comments:
@c The main change is the possibility to build Python as a
@c framework. This installs a self-contained Python installation plus the
@c OSX framework "glue" into /Library/Frameworks/Python.framework (or
@c another location of choice). For now there is little immediate added
@c benefit to this (actually, there is the disadvantage that you have to
@c change your PATH to be able to find Python), but it is the basis for
@c creating a fullblown Python application, porting the MacPython IDE,
@c possibly using Python as a standard OSA scripting language and much
@c more. You enable this with "configure --enable-framework".
@c The other change is that most MacPython toolbox modules, which
@c interface to all the MacOS APIs such as windowing, quicktime,
@c scripting, etc. have been ported. Again, most of these are not of
@c immediate use, as they need a full application to be really useful, so
@c they have been commented out in setup.py. People wanting to experiment
@c can uncomment them. Gestalt and Internet Config modules are enabled by
@c default.

@item 
Keyword arguments passed to built-in functions that don't take them now cause a
@ref{192,,TypeError} exception to be raised, with the message "@emph{function} takes no
keyword arguments".

@item 
Weak references, added in Python 2.1 as an extension module, are now part of
the core because they're used in the implementation of new-style classes.  The
@ref{e46,,ReferenceError} exception has therefore moved from the @ref{128,,weakref}
module to become a built-in exception.

@item 
A new script, @code{Tools/scripts/cleanfuture.py} by Tim Peters,
automatically removes obsolete @code{__future__} statements from Python source
code.

@item 
An additional @emph{flags} argument has been added to the built-in function
@ref{1b4,,compile()}, so the behaviour of @code{__future__} statements can now be
correctly observed in simulated shells, such as those presented by IDLE and
other development environments.  This is described in 
@geindex Python 提高建议; PEP 264
PEP 264@footnote{https://www.python.org/dev/peps/pep-0264}. (Contributed
by Michael Hudson.)

@item 
The new license introduced with Python 1.6 wasn't GPL-compatible.  This is
fixed by some minor textual changes to the 2.2 license, so it's now legal to
embed Python inside a GPLed program again.  Note that Python itself is not
GPLed, but instead is under a license that's essentially equivalent to the BSD
license, same as it always was.  The license changes were also applied to the
Python 2.0.1 and 2.1.1 releases.

@item 
When presented with a Unicode filename on Windows, Python will now convert it
to an MBCS encoded string, as used by the Microsoft file APIs.  As MBCS is
explicitly used by the file APIs, Python's choice of ASCII as the default
encoding turns out to be an annoyance.  On Unix, the locale's character set is
used if @code{locale.nl_langinfo(CODESET)} is available.  (Windows support was
contributed by Mark Hammond with assistance from Marc-André Lemburg. Unix
support was added by Martin von Löwis.)

@item 
Large file support is now enabled on Windows.  (Contributed by Tim Peters.)

@item 
The @code{Tools/scripts/ftpmirror.py} script now parses a @code{.netrc}
file, if you have one. (Contributed by Mike Romberg.)

@item 
Some features of the object returned by the @code{xrange()} function are now
deprecated, and trigger warnings when they're accessed; they'll disappear in
Python 2.3. @code{xrange} objects tried to pretend they were full sequence
types by supporting slicing, sequence multiplication, and the @ref{79d,,in}
operator, but these features were rarely used and therefore buggy.  The
@code{tolist()} method and the @code{start}, @code{stop}, and @code{step}
attributes are also being deprecated.  At the C level, the fourth argument to
the @code{PyRange_New()} function, @code{repeat}, has also been deprecated.

@item 
There were a bunch of patches to the dictionary implementation, mostly to fix
potential core dumps if a dictionary contains objects that sneakily changed
their hash value, or mutated the dictionary they were contained in. For a while
python-dev fell into a gentle rhythm of Michael Hudson finding a case that
dumped core, Tim Peters fixing the bug, Michael finding another case, and round
and round it went.

@item 
On Windows, Python can now be compiled with Borland C thanks to a number of
patches contributed by Stephen Hansen, though the result isn't fully functional
yet.  (But this @emph{is} progress...)

@item 
Another Windows enhancement: Wise Solutions generously offered PythonLabs use
of their InstallerMaster 8.1 system.  Earlier PythonLabs Windows installers used
Wise 5.0a, which was beginning to show its age.  (Packaged up by Tim Peters.)

@item 
Files ending in @code{.pyw} can now be imported on Windows. @code{.pyw} is a
Windows-only thing, used to indicate that a script needs to be run using
PYTHONW.EXE instead of PYTHON.EXE in order to prevent a DOS console from popping
up to display the output.  This patch makes it possible to import such scripts,
in case they're also usable as modules.  (Implemented by David Bolen.)

@item 
On platforms where Python uses the C @code{dlopen()} function  to load
extension modules, it's now possible to set the flags used  by @code{dlopen()}
using the @ref{e47,,sys.getdlopenflags()} and @ref{a61,,sys.setdlopenflags()} functions.
(Contributed by Bram Stolk.)

@item 
The @ref{19a,,pow()} built-in function no longer supports 3 arguments when
floating-point numbers are supplied. @code{pow(x, y, z)} returns @code{(x**y) % z},
but this is never useful for floating point numbers, and the final result varies
unpredictably depending on the platform.  A call such as @code{pow(2.0, 8.0, 7.0)}
will now raise a @ref{192,,TypeError} exception.
@end itemize

@c ======================================================================

@node 致谢<6>,,Other Changes and Fixes<3>,Python 2 2 有什么新变化
@anchor{whatsnew/2 2 acknowledgements}@anchor{e48}
@subsection 致谢


作者感谢以下人员为本文的各种草案提供建议，更正和帮助： Fred Bremmer, Keith Briggs, Andrew Dalke, Fred L. Drake, Jr., Carel Fellinger, David Goodger, Mark Hammond, Stephen Hansen, Michael Hudson, Jack Jansen, Marc-André Lemburg, Martin von Löwis, Fredrik Lundh, Michael McLay, Nick Mathewson, Paul Moore, Gustavo Niemeyer, Don O'Donnell, Joonas Paalasma, Tim Peters, Jens Quade, Tom Reinhardt, Neil Schemenauer, Guido van Rossum, Greg Ward, Edward Welbourne.

@node Python 2 1 有什么新变化,Python 2 0 有什么新变化,Python 2 2 有什么新变化,Python的新变化
@anchor{whatsnew/2 1 doc}@anchor{e49}@anchor{whatsnew/2 1 what-s-new-in-python-2-1}@anchor{e4a}
@section Python 2.1 有什么新变化


@*作者: 
A.M. Kuchling


@c $Id: whatsnew21.tex 50964 2006-07-30 03:03:43Z fred.drake $

@menu
* 概述: 概述<2>. 
* PEP 227; Nested Scopes: PEP 227 Nested Scopes<2>. 
* PEP 236; __future__ Directives: PEP 236 __future__ Directives. 
* PEP 207; Rich Comparisons: PEP 207 Rich Comparisons. 
* PEP 230; Warning Framework: PEP 230 Warning Framework. 
* PEP 229; New Build System: PEP 229 New Build System. 
* PEP 205; Weak References: PEP 205 Weak References. 
* PEP 232; Function Attributes: PEP 232 Function Attributes. 
* PEP 235; Importing Modules on Case-Insensitive Platforms: PEP 235 Importing Modules on Case-Insensitive Platforms. 
* PEP 217; Interactive Display Hook: PEP 217 Interactive Display Hook. 
* PEP 208; New Coercion Model: PEP 208 New Coercion Model. 
* PEP 241; Metadata in Python Packages: PEP 241 Metadata in Python Packages. 
* 新增和改进的模块: 新增和改进的模块<4>. 
* Other Changes and Fixes: Other Changes and Fixes<4>. 
* 致谢: 致谢<7>. 

@end menu

@node 概述<2>,PEP 227 Nested Scopes<2>,,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 introduction}@anchor{e4b}
@subsection 概述


This article explains the new features in Python 2.1.  While there aren't as
many changes in 2.1 as there were in Python 2.0, there are still some pleasant
surprises in store.  2.1 is the first release to be steered through the use of
Python Enhancement Proposals, or PEPs, so most of the sizable changes have
accompanying PEPs that provide more complete documentation and a design
rationale for the change.  This article doesn't attempt to document the new
features completely, but simply provides an overview of the new features for
Python programmers. Refer to the Python 2.1 documentation, or to the specific
PEP, for more details about any new feature that particularly interests you.

One recent goal of the Python development team has been to accelerate the pace
of new releases, with a new release coming every 6 to 9 months. 2.1 is the first
release to come out at this faster pace, with the first alpha appearing in
January, 3 months after the final version of 2.0 was released.

Python 2.1 的最终版本于2001年4月17日发布。

@c ======================================================================

@node PEP 227 Nested Scopes<2>,PEP 236 __future__ Directives,概述<2>,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-227-nested-scopes}@anchor{e4c}
@subsection PEP 227: Nested Scopes


The largest change in Python 2.1 is to Python's scoping rules.  In Python 2.0,
at any given time there are at most three namespaces used to look up variable
names: local, module-level, and the built-in namespace.  This often surprised
people because it didn't match their intuitive expectations.  For example, a
nested recursive function definition doesn't work:

@example
def f():
    ...
    def g(value):
        ...
        return g(value-1) + 1
    ...
@end example

The function @code{g()} will always raise a @ref{d74,,NameError} exception, because
the binding of the name @code{g} isn't in either its local namespace or in the
module-level namespace.  This isn't much of a problem in practice (how often do
you recursively define interior functions like this?), but this also made using
the @ref{c28,,lambda} expression clumsier, and this was a problem in practice.
In code which uses @ref{c28,,lambda} you can often find local variables being
copied by passing them as the default values of arguments.

@example
def find(self, name):
    "Return list of any entries equal to 'name'"
    L = filter(lambda x, name=name: x == name,
               self.list_attribute)
    return L
@end example

The readability of Python code written in a strongly functional style suffers
greatly as a result.

The most significant change to Python 2.1 is that static scoping has been added
to the language to fix this problem.  As a first effect, the @code{name=name}
default argument is now unnecessary in the above example.  Put simply, when a
given variable name is not assigned a value within a function (by an assignment,
or the @ref{db7,,def}, @ref{c63,,class}, or @ref{c16,,import} statements),
references to the variable will be looked up in the local namespace of the
enclosing scope.  A more detailed explanation of the rules, and a dissection of
the implementation, can be found in the PEP.

This change may cause some compatibility problems for code where the same
variable name is used both at the module level and as a local variable within a
function that contains further function definitions. This seems rather unlikely
though, since such code would have been pretty confusing to read in the first
place.

One side effect of the change is that the @code{from module import *} and
@code{exec} statements have been made illegal inside a function scope under
certain conditions.  The Python reference manual has said all along that @code{from
module import *} is only legal at the top level of a module, but the CPython
interpreter has never enforced this before.  As part of the implementation of
nested scopes, the compiler which turns Python source into bytecodes has to
generate different code to access variables in a containing scope.  @code{from
module import *} and @code{exec} make it impossible for the compiler to
figure this out, because they add names to the local namespace that are
unknowable at compile time. Therefore, if a function contains function
definitions or @ref{c28,,lambda} expressions with free variables, the compiler
will flag this by raising a @ref{452,,SyntaxError} exception.

To make the preceding explanation a bit clearer, here's an example:

@example
x = 1
def f():
    # The next line is a syntax error
    exec 'x=2'
    def g():
        return x
@end example

Line 4 containing the @code{exec} statement is a syntax error, since
@code{exec} would define a new local variable named @code{x} whose value should
be accessed by @code{g()}.

This shouldn't be much of a limitation, since @code{exec} is rarely used in
most Python code (and when it is used, it's often a sign of a poor design
anyway).

Compatibility concerns have led to nested scopes being introduced gradually; in
Python 2.1, they aren't enabled by default, but can be turned on within a module
by using a future statement as described in 
@geindex Python 提高建议; PEP 236
PEP 236@footnote{https://www.python.org/dev/peps/pep-0236}.  (See the following section
for further discussion of 
@geindex Python 提高建议; PEP 236
PEP 236@footnote{https://www.python.org/dev/peps/pep-0236}.)  In Python 2.2, nested scopes will become
the default and there will be no way to turn them off, but users will have had
all of 2.1's lifetime to fix any breakage resulting from their introduction.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 227

@item PEP 227@footnote{https://www.python.org/dev/peps/pep-0227} - Statically Nested Scopes

由 Jeremy Hylton 撰写并实现。
@end table


@c ======================================================================

@node PEP 236 __future__ Directives,PEP 207 Rich Comparisons,PEP 227 Nested Scopes<2>,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-236-future-directives}@anchor{e4d}
@subsection PEP 236: __future__ Directives


The reaction to nested scopes was widespread concern about the dangers of
breaking code with the 2.1 release, and it was strong enough to make the
Pythoneers take a more conservative approach.  This approach consists of
introducing a convention for enabling optional functionality in release N that
will become compulsory in release N+1.

The syntax uses a @code{from...import} statement using the reserved module name
@ref{0,,__future__}.  Nested scopes can be enabled by the following statement:

@example
from __future__ import nested_scopes
@end example

While it looks like a normal @ref{c16,,import} statement, it's not; there are
strict rules on where such a future statement can be put. They can only be at
the top of a module, and must precede any Python code or regular
@code{import} statements.  This is because such statements can affect how
the Python bytecode compiler parses code and generates bytecode, so they must
precede any statement that will result in bytecodes being produced.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 236

@item PEP 236@footnote{https://www.python.org/dev/peps/pep-0236} - Back to the @ref{0,,__future__}

由 Tim Peters 撰写，主要由 Jeremy Hylton 实现。
@end table


@c ======================================================================

@node PEP 207 Rich Comparisons,PEP 230 Warning Framework,PEP 236 __future__ Directives,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-207-rich-comparisons}@anchor{e4e}
@subsection PEP 207: Rich Comparisons


In earlier versions, Python's support for implementing comparisons on user-defined
classes and extension types was quite simple. Classes could implement a
@code{__cmp__()} method that was given two instances of a class, and could only
return 0 if they were equal or +1 or -1 if they weren't; the method couldn't
raise an exception or return anything other than a Boolean value.  Users of
Numeric Python often found this model too weak and restrictive, because in the
number-crunching programs that numeric Python is used for, it would be more
useful to be able to perform elementwise comparisons of two matrices, returning
a matrix containing the results of a given comparison for each element.  If the
two matrices are of different sizes, then the compare has to be able to raise an
exception to signal the error.

In Python 2.1, rich comparisons were added in order to support this need.
Python classes can now individually overload each of the @code{<}, @code{<=}, @code{>},
@code{>=}, @code{==}, and @code{!=} operations.  The new magic method names are:


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

方法名称

@item

@code{<}

@tab

@ref{c2d,,__lt__()}

@item

@code{<=}

@tab

@ref{c99,,__le__()}

@item

@code{>}

@tab

@ref{c9a,,__gt__()}

@item

@code{>=}

@tab

@ref{c9b,,__ge__()}

@item

@code{==}

@tab

@ref{338,,__eq__()}

@item

@code{!=}

@tab

@ref{e4f,,__ne__()}

@end multitable


(The magic methods are named after the corresponding Fortran operators @code{.LT.}.
@code{.LE.}, &c.  Numeric programmers are almost certainly quite familiar with
these names and will find them easy to remember.)

Each of these magic methods is of the form @code{method(self, other)}, where
@code{self} will be the object on the left-hand side of the operator, while
@code{other} will be the object on the right-hand side.  For example, the
expression @code{A < B} will cause @code{A.__lt__(B)} to be called.

Each of these magic methods can return anything at all: a Boolean, a matrix, a
list, or any other Python object.  Alternatively they can raise an exception if
the comparison is impossible, inconsistent, or otherwise meaningless.

The built-in @code{cmp(A,B)} function can use the rich comparison machinery,
and now accepts an optional argument specifying which comparison operation to
use; this is given as one of the strings @code{"<"}, @code{"<="}, @code{">"}, @code{">="},
@code{"=="}, or @code{"!="}.  If called without the optional third argument,
@code{cmp()} will only return -1, 0, or +1 as in previous versions of Python;
otherwise it will call the appropriate method and can return any Python object.

There are also corresponding changes of interest to C programmers; there's a new
slot @code{tp_richcmp} in type objects and an API for performing a given rich
comparison.  I won't cover the C API here, but will refer you to 
@geindex Python 提高建议; PEP 207
PEP 207@footnote{https://www.python.org/dev/peps/pep-0207}, or to
2.1's C API documentation, for the full list of related functions.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 207

@item PEP 207@footnote{https://www.python.org/dev/peps/pep-0207} - Rich Comparisons

Written by Guido van Rossum, heavily based on earlier work by David Ascher, and
implemented by Guido van Rossum.
@end table


@c ======================================================================

@node PEP 230 Warning Framework,PEP 229 New Build System,PEP 207 Rich Comparisons,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-230-warning-framework}@anchor{e50}
@subsection PEP 230: Warning Framework


Over its 10 years of existence, Python has accumulated a certain number of
obsolete modules and features along the way.  It's difficult to know when a
feature is safe to remove, since there's no way of knowing how much code uses it
--- perhaps no programs depend on the feature, or perhaps many do.  To enable
removing old features in a more structured way, a warning framework was added.
When the Python developers want to get rid of a feature, it will first trigger a
warning in the next version of Python.  The following Python version can then
drop the feature, and users will have had a full release cycle to remove uses of
the old feature.

Python 2.1 adds the warning framework to be used in this scheme.  It adds a
@ref{126,,warnings} module that provide functions to issue warnings, and to filter
out warnings that you don't want to be displayed. Third-party modules can also
use this framework to deprecate old features that they no longer wish to
support.

For example, in Python 2.1 the @code{regex} module is deprecated, so importing
it causes a warning to be printed:

@example
>>> import regex
__main__:1: DeprecationWarning: the regex module
         is deprecated; please use the re module
>>>
@end example

Warnings can be issued by calling the @ref{e51,,warnings.warn()} function:

@example
warnings.warn("feature X no longer supported")
@end example

The first parameter is the warning message; an additional optional parameters
can be used to specify a particular warning category.

Filters can be added to disable certain warnings; a regular expression pattern
can be applied to the message or to the module name in order to suppress a
warning.  For example, you may have a program that uses the @code{regex} module
and not want to spare the time to convert it to use the @ref{dd,,re} module right
now.  The warning can be suppressed by calling

@example
import warnings
warnings.filterwarnings(action = 'ignore',
                        message='.*regex module is deprecated',
                        category=DeprecationWarning,
                        module = '__main__')
@end example

This adds a filter that will apply only to warnings of the class
@ref{278,,DeprecationWarning} triggered in the @ref{1,,__main__} module, and applies
a regular expression to only match the message about the @code{regex} module
being deprecated, and will cause such warnings to be ignored.  Warnings can also
be printed only once, printed every time the offending code is executed, or
turned into exceptions that will cause the program to stop (unless the
exceptions are caught in the usual way, of course).

Functions were also added to Python's C API for issuing warnings; refer to PEP
230 or to Python's API documentation for the details.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 5

@item PEP 5@footnote{https://www.python.org/dev/peps/pep-0005} - Guidelines for Language Evolution

Written by Paul Prescod, to specify procedures to be followed when removing old
features from Python.  The policy described in this PEP hasn't been officially
adopted, but the eventual policy probably won't be too different from Prescod's
proposal.

@geindex Python 提高建议; PEP 230

@item PEP 230@footnote{https://www.python.org/dev/peps/pep-0230} - Warning Framework

由 Guido van Rossum 撰写并实现。
@end table


@c ======================================================================

@node PEP 229 New Build System,PEP 205 Weak References,PEP 230 Warning Framework,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-229-new-build-system}@anchor{e52}
@subsection PEP 229: New Build System


When compiling Python, the user had to go in and edit the @code{Modules/Setup}
file in order to enable various additional modules; the default set is
relatively small and limited to modules that compile on most Unix platforms.
This means that on Unix platforms with many more features, most notably Linux,
Python installations often don't contain all useful modules they could.

Python 2.0 added the Distutils, a set of modules for distributing and installing
extensions.  In Python 2.1, the Distutils are used to compile much of the
standard library of extension modules, autodetecting which ones are supported on
the current machine.  It's hoped that this will make Python installations easier
and more featureful.

Instead of having to edit the @code{Modules/Setup} file in order to enable
modules, a @code{setup.py} script in the top directory of the Python source
distribution is run at build time, and attempts to discover which modules can be
enabled by examining the modules and header files on the system.  If a module is
configured in @code{Modules/Setup}, the @code{setup.py} script won't attempt
to compile that module and will defer to the @code{Modules/Setup} file's
contents.  This provides a way to specific any strange command-line flags or
libraries that are required for a specific platform.

In another far-reaching change to the build mechanism, Neil Schemenauer
restructured things so Python now uses a single makefile that isn't recursive,
instead of makefiles in the top directory and in each of the @code{Python/},
@code{Parser/}, @code{Objects/}, and @code{Modules/} subdirectories.  This
makes building Python faster and also makes hacking the Makefiles clearer and
simpler.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 229

@item PEP 229@footnote{https://www.python.org/dev/peps/pep-0229} - Using Distutils to Build Python

由 A.M. Kuchling 撰写并实现。
@end table


@c ======================================================================

@node PEP 205 Weak References,PEP 232 Function Attributes,PEP 229 New Build System,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-205-weak-references}@anchor{e53}
@subsection PEP 205: Weak References


Weak references, available through the @ref{128,,weakref} module, are a minor but
useful new data type in the Python programmer's toolbox.

Storing a reference to an object (say, in a dictionary or a list) has the side
effect of keeping that object alive forever.  There are a few specific cases
where this behaviour is undesirable, object caches being the most common one,
and another being circular references in data structures such as trees.

For example, consider a memoizing function that caches the results of another
function @code{f(x)} by storing the function's argument and its result in a
dictionary:

@example
_cache = @{@}
def memoize(x):
    if _cache.has_key(x):
        return _cache[x]

    retval = f(x)

    # Cache the returned object
    _cache[x] = retval

    return retval
@end example

This version works for simple things such as integers, but it has a side effect;
the @code{_cache} dictionary holds a reference to the return values, so they'll
never be deallocated until the Python process exits and cleans up. This isn't
very noticeable for integers, but if @code{f()} returns an object, or a data
structure that takes up a lot of memory, this can be a problem.

Weak references provide a way to implement a cache that won't keep objects alive
beyond their time.  If an object is only accessible through weak references, the
object will be deallocated and the weak references will now indicate that the
object it referred to no longer exists.  A weak reference to an object @emph{obj} is
created by calling @code{wr = weakref.ref(obj)}.  The object being referred to is
returned by calling the weak reference as if it were a function: @code{wr()}.  It
will return the referenced object, or @code{None} if the object no longer exists.

This makes it possible to write a @code{memoize()} function whose cache doesn't
keep objects alive, by storing weak references in the cache.

@example
_cache = @{@}
def memoize(x):
    if _cache.has_key(x):
        obj = _cache[x]()
        # If weak reference object still exists,
        # return it
        if obj is not None: return obj

    retval = f(x)

    # Cache a weak reference
    _cache[x] = weakref.ref(retval)

    return retval
@end example

The @ref{128,,weakref} module also allows creating proxy objects which behave like
weak references --- an object referenced only by proxy objects is deallocated --
but instead of requiring an explicit call to retrieve the object, the proxy
transparently forwards all operations to the object as long as the object still
exists.  If the object is deallocated, attempting to use a proxy will cause a
@code{weakref.ReferenceError} exception to be raised.

@example
proxy = weakref.proxy(obj)
proxy.attr   # Equivalent to obj.attr
proxy.meth() # Equivalent to obj.meth()
del obj
proxy.attr   # raises weakref.ReferenceError
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 205

@item PEP 205@footnote{https://www.python.org/dev/peps/pep-0205} - 弱引用

由 Fred L. Drake, Jr 撰写并实现。
@end table


@c ======================================================================

@node PEP 232 Function Attributes,PEP 235 Importing Modules on Case-Insensitive Platforms,PEP 205 Weak References,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-232-function-attributes}@anchor{e54}
@subsection PEP 232: Function Attributes


In Python 2.1, functions can now have arbitrary information attached to them.
People were often using docstrings to hold information about functions and
methods, because the @code{__doc__} attribute was the only way of attaching any
information to a function.  For example, in the Zope Web application server,
functions are marked as safe for public access by having a docstring, and in
John Aycock's SPARK parsing framework, docstrings hold parts of the BNF grammar
to be parsed.  This overloading is unfortunate, since docstrings are really
intended to hold a function's documentation; for example, it means you can't
properly document functions intended for private use in Zope.

Arbitrary attributes can now be set and retrieved on functions using the regular
Python syntax:

@example
def f(): pass

f.publish = 1
f.secure = 1
f.grammar = "A ::= B (C D)*"
@end example

The dictionary containing attributes can be accessed as the function's
@ref{4f6,,__dict__}. Unlike the @ref{4f6,,__dict__} attribute of class instances, in
functions you can actually assign a new dictionary to @ref{4f6,,__dict__}, though
the new value is restricted to a regular Python dictionary; you @emph{can't} be
tricky and set it to a @code{UserDict} instance, or any other random object
that behaves like a mapping.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 232

@item PEP 232@footnote{https://www.python.org/dev/peps/pep-0232} - Function Attributes

由 Barry Warsaw 撰写并实现
@end table


@c ======================================================================

@node PEP 235 Importing Modules on Case-Insensitive Platforms,PEP 217 Interactive Display Hook,PEP 232 Function Attributes,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-235-importing-modules-on-case-insensitive-platforms}@anchor{e55}
@subsection PEP 235: Importing Modules on Case-Insensitive Platforms


Some operating systems have filesystems that are case-insensitive, MacOS and
Windows being the primary examples; on these systems, it's impossible to
distinguish the filenames @code{FILE.PY} and @code{file.py}, even though they do store
the file's name  in its original case (they're case-preserving, too).

In Python 2.1, the @ref{c16,,import} statement will work to simulate case-sensitivity
on case-insensitive platforms.  Python will now search for the first
case-sensitive match by default, raising an @ref{32d,,ImportError} if no such file
is found, so @code{import file} will not import a module named @code{FILE.PY}.
Case-insensitive matching can be requested by setting the 
@geindex PYTHONCASEOK
@geindex 环境变量; PYTHONCASEOK
@ref{e56,,PYTHONCASEOK}
environment variable before starting the Python interpreter.

@c ======================================================================

@node PEP 217 Interactive Display Hook,PEP 208 New Coercion Model,PEP 235 Importing Modules on Case-Insensitive Platforms,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-217-interactive-display-hook}@anchor{e57}
@subsection PEP 217: Interactive Display Hook


When using the Python interpreter interactively, the output of commands is
displayed using the built-in @ref{7c6,,repr()} function. In Python 2.1, the variable
@ref{e58,,sys.displayhook()} can be set to a callable object which will be called
instead of @ref{7c6,,repr()}. For example, you can set it to a special
pretty-printing function:

@example
>>> # Create a recursive data structure
... L = [1,2,3]
>>> L.append(L)
>>> L # Show Python's default output
[1, 2, 3, [...]]
>>> # Use pprint.pprint() as the display function
... import sys, pprint
>>> sys.displayhook = pprint.pprint
>>> L
[1, 2, 3,  <Recursion on list with id=135143996>]
>>>
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 217

@item PEP 217@footnote{https://www.python.org/dev/peps/pep-0217} - Display Hook for Interactive Use

由 Moshe Zadka 撰写并实现
@end table


@c ======================================================================

@node PEP 208 New Coercion Model,PEP 241 Metadata in Python Packages,PEP 217 Interactive Display Hook,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-208-new-coercion-model}@anchor{e59}
@subsection PEP 208: New Coercion Model


How numeric coercion is done at the C level was significantly modified.  This
will only affect the authors of C extensions to Python, allowing them more
flexibility in writing extension types that support numeric operations.

Extension types can now set the type flag @code{Py_TPFLAGS_CHECKTYPES} in their
@code{PyTypeObject} structure to indicate that they support the new coercion model.
In such extension types, the numeric slot functions can no longer assume that
they'll be passed two arguments of the same type; instead they may be passed two
arguments of differing types, and can then perform their own internal coercion.
If the slot function is passed a type it can't handle, it can indicate the
failure by returning a reference to the @code{Py_NotImplemented} singleton value.
The numeric functions of the other type will then be tried, and perhaps they can
handle the operation; if the other type also returns @code{Py_NotImplemented}, then
a @ref{192,,TypeError} will be raised.  Numeric methods written in Python can also
return @code{Py_NotImplemented}, causing the interpreter to act as if the method
did not exist (perhaps raising a @ref{192,,TypeError}, perhaps trying another
object's numeric methods).


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 208

@item PEP 208@footnote{https://www.python.org/dev/peps/pep-0208} - Reworking the Coercion Model

Written and implemented by Neil Schemenauer, heavily based upon earlier work by
Marc-André Lemburg.  Read this to understand the fine points of how numeric
operations will now be processed at the C level.
@end table


@c ======================================================================

@node PEP 241 Metadata in Python Packages,新增和改进的模块<4>,PEP 208 New Coercion Model,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 pep-241-metadata-in-python-packages}@anchor{e5a}
@subsection PEP 241: Metadata in Python Packages


A common complaint from Python users is that there's no single catalog of all
the Python modules in existence.  T. Middleton's Vaults of Parnassus at
@indicateurl{http://www.vex.net/parnassus/} are the largest catalog of Python modules, but
registering software at the Vaults is optional, and many people don't bother.

As a first small step toward fixing the problem, Python software packaged using
the Distutils @code{sdist} command will include a file named
@code{PKG-INFO} containing information about the package such as its name,
version, and author (metadata, in cataloguing terminology).  
@geindex Python 提高建议; PEP 241
PEP 241@footnote{https://www.python.org/dev/peps/pep-0241} contains
the full list of fields that can be present in the @code{PKG-INFO} file.  As
people began to package their software using Python 2.1, more and more packages
will include metadata, making it possible to build automated cataloguing systems
and experiment with them.  With the result experience, perhaps it'll be possible
to design a really good catalog and then build support for it into Python 2.2.
For example, the Distutils @code{sdist} and @code{bdist_*} commands
could support an @code{upload} option that would automatically upload your
package to a catalog server.

You can start creating packages containing @code{PKG-INFO} even if you're not
using Python 2.1, since a new release of the Distutils will be made for users of
earlier Python versions.  Version 1.0.2 of the Distutils includes the changes
described in 
@geindex Python 提高建议; PEP 241
PEP 241@footnote{https://www.python.org/dev/peps/pep-0241}, as well as various bugfixes and enhancements.  It will be
available from the Distutils SIG at @indicateurl{https://www.python.org/community/sigs/current/distutils-sig/}.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 241

@item PEP 241@footnote{https://www.python.org/dev/peps/pep-0241} - Metadata for Python Software Packages

由 A.M. Kuchling 撰写并实现。

@geindex Python 提高建议; PEP 243

@item PEP 243@footnote{https://www.python.org/dev/peps/pep-0243} - Module Repository Upload Mechanism

Written by Sean Reifschneider, this draft PEP describes a proposed mechanism for
uploading  Python packages to a central server.
@end table


@c ======================================================================

@node 新增和改进的模块<4>,Other Changes and Fixes<4>,PEP 241 Metadata in Python Packages,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 new-and-improved-modules}@anchor{e5b}
@subsection 新增和改进的模块



@itemize *

@item 
Ka-Ping Yee contributed two new modules: @code{inspect.py}, a module for
getting information about live Python code, and @code{pydoc.py}, a module for
interactively converting docstrings to HTML or text.  As a bonus,
@code{Tools/scripts/pydoc}, which is now automatically installed, uses
@code{pydoc.py} to display documentation given a Python module, package, or
class name.  For example, @code{pydoc xml.dom} displays the following:

@example
Python Library Documentation: package xml.dom in xml

NAME
    xml.dom - W3C Document Object Model implementation for Python.

FILE
    /usr/local/lib/python2.1/xml/dom/__init__.pyc

DESCRIPTION
    The Python mapping of the Document Object Model is documented in the
    Python Library Reference in the section on the xml.dom package.

    This package contains the following modules:
      ...
@end example

@code{pydoc} also includes a Tk-based interactive help browser.   @code{pydoc}
quickly becomes addictive; try it out!

@item 
Two different modules for unit testing were added to the standard library.
The @ref{67,,doctest} module, contributed by Tim Peters, provides a testing
framework based on running embedded examples in docstrings and comparing the
results against the expected output.  PyUnit, contributed by Steve Purcell, is a
unit testing framework inspired by JUnit, which was in turn an adaptation of
Kent Beck's Smalltalk testing framework.  See @indicateurl{http://pyunit.sourceforge.net/} for
more information about PyUnit.

@item 
The @ref{37,,difflib} module contains a class, @code{SequenceMatcher}, which
compares two sequences and computes the changes required to transform one
sequence into the other.  For example, this module can be used to write a tool
similar to the Unix @code{diff} program, and in fact the sample program
@code{Tools/scripts/ndiff.py} demonstrates how to write such a script.

@item 
@ref{2e,,curses.panel}, a wrapper for the panel library, part of ncurses and of
SYSV curses, was contributed by Thomas Gellekum.  The panel library provides
windows with the additional feature of depth. Windows can be moved higher or
lower in the depth ordering, and the panel library figures out where panels
overlap and which sections are visible.

@item 
The PyXML package has gone through a few releases since Python 2.0, and Python
2.1 includes an updated version of the @ref{133,,xml} package.  Some of the
noteworthy changes include support for Expat 1.2 and later versions, the ability
for Expat parsers to handle files in any encoding supported by Python, and
various bugfixes for SAX, DOM, and the @code{minidom} module.

@item 
Ping also contributed another hook for handling uncaught exceptions.
@ref{e5c,,sys.excepthook()} can be set to a callable object.  When an exception isn't
caught by any @ref{d6b,,try}...@ref{b37,,except} blocks, the exception will be
passed to @ref{e5c,,sys.excepthook()}, which can then do whatever it likes.  At the
Ninth Python Conference, Ping demonstrated an application for this hook:
printing an extended traceback that not only lists the stack frames, but also
lists the function arguments and the local variables for each frame.

@item 
Various functions in the @ref{10a,,time} module, such as @code{asctime()} and
@code{localtime()}, require a floating point argument containing the time in
seconds since the epoch.  The most common use of these functions is to work with
the current time, so the floating point argument has been made optional; when a
value isn't provided, the current time will be used.  For example, log file
entries usually need a string containing the current time; in Python 2.1,
@code{time.asctime()} can be used, instead of the lengthier
@code{time.asctime(time.localtime(time.time()))} that was previously required.

This change was proposed and implemented by Thomas Wouters.

@item 
The @ref{84,,ftplib} module now defaults to retrieving files in passive mode,
because passive mode is more likely to work from behind a firewall.  This
request came from the Debian bug tracking system, since other Debian packages
use @ref{84,,ftplib} to retrieve files and then don't work from behind a firewall.
It's deemed unlikely that this will cause problems for anyone, because Netscape
defaults to passive mode and few people complain, but if passive mode is
unsuitable for your application or network setup, call @code{set_pasv(0)} on
FTP objects to disable passive mode.

@item 
Support for raw socket access has been added to the @ref{ef,,socket} module,
contributed by Grant Edwards.

@item 
The @ref{d4,,pstats} module now contains a simple interactive statistics browser
for displaying timing profiles for Python programs, invoked when the module is
run as a script.  Contributed by  Eric S. Raymond.

@item 
A new implementation-dependent function, @code{sys._getframe([depth])}, has
been added to return a given frame object from the current call stack.
@ref{e5d,,sys._getframe()} returns the frame at the top of the call stack;  if the
optional integer argument @emph{depth} is supplied, the function returns the frame
that is @emph{depth} calls below the top of the stack.  For example,
@code{sys._getframe(1)} returns the caller's frame object.

This function is only present in CPython, not in Jython or the .NET
implementation.  Use it for debugging, and resist the temptation to put it into
production code.
@end itemize

@c ======================================================================

@node Other Changes and Fixes<4>,致谢<7>,新增和改进的模块<4>,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 other-changes-and-fixes}@anchor{e5e}
@subsection Other Changes and Fixes


There were relatively few smaller changes made in Python 2.1 due to the shorter
release cycle.  A search through the CVS change logs turns up 117 patches
applied, and 136 bugs fixed; both figures are likely to be underestimates.  Some
of the more notable changes are:


@itemize *

@item 
A specialized object allocator is now optionally available, that should be
faster than the system @code{malloc()} and have less memory overhead.  The
allocator uses C's @code{malloc()} function to get large pools of memory, and
then fulfills smaller memory requests from these pools.  It can be enabled by
providing the @code{--with-pymalloc} option to the @code{configure}
script; see @code{Objects/obmalloc.c} for the implementation details.

Authors of C extension modules should test their code with the object allocator
enabled, because some incorrect code may break, causing core dumps at runtime.
There are a bunch of memory allocation functions in Python's C API that have
previously been just aliases for the C library's @code{malloc()} and
@code{free()}, meaning that if you accidentally called mismatched functions, the
error wouldn't be noticeable.  When the object allocator is enabled, these
functions aren't aliases of @code{malloc()} and @code{free()} any more, and
calling the wrong function to free memory will get you a core dump.  For
example, if memory was allocated using @code{PyMem_New()}, it has to be freed
using @code{PyMem_Del()}, not @code{free()}.  A few modules included with Python
fell afoul of this and had to be fixed; doubtless there are more third-party
modules that will have the same problem.

The object allocator was contributed by Vladimir Marangozov.

@item 
The speed of line-oriented file I/O has been improved because people often
complain about its lack of speed, and because it's often been used as a naïve
benchmark.  The @ref{de,,readline()} method of file objects has therefore been
rewritten to be much faster.  The exact amount of the speedup will vary from
platform to platform depending on how slow the C library's @code{getc()} was, but
is around 66%, and potentially much faster on some particular operating systems.
Tim Peters did much of the benchmarking and coding for this change, motivated by
a discussion in comp.lang.python.

A new module and method for file objects was also added, contributed by Jeff
Epler. The new method, @code{xreadlines()}, is similar to the existing
@code{xrange()} built-in.  @code{xreadlines()} returns an opaque sequence object
that only supports being iterated over, reading a line on every iteration but
not reading the entire file into memory as the existing @code{readlines()} method
does. You'd use it like this:

@example
for line in sys.stdin.xreadlines():
    # ... do something for each line ...
    ...
@end example

For a fuller discussion of the line I/O changes, see the python-dev summary for
January 1--15, 2001 at @indicateurl{https://mail.python.org/pipermail/python-dev/2001-January/}.

@item 
A new method, @code{popitem()}, was added to dictionaries to enable
destructively iterating through the contents of a dictionary; this can be faster
for large dictionaries because there's no need to construct a list containing
all the keys or values. @code{D.popitem()} removes a random @code{(key, value)} pair
from the dictionary @code{D} and returns it as a 2-tuple.  This was implemented
mostly by Tim Peters and Guido van Rossum, after a suggestion and preliminary
patch by Moshe Zadka.

@item 
Modules can now control which names are imported when @code{from module import *}
is used, by defining an @code{__all__} attribute containing a list of names that
will be imported.  One common complaint is that if the module imports other
modules such as @ref{fd,,sys} or @ref{f6,,string}, @code{from module import *} will add
them to the importing module's namespace.  To fix this, simply list the public
names in @code{__all__}:

@example
# List public names
__all__ = ['Database', 'open']
@end example

A stricter version of this patch was first suggested and implemented by Ben
Wolfson, but after some python-dev discussion, a weaker final version was
checked in.

@item 
Applying @ref{7c6,,repr()} to strings previously used octal escapes for
non-printable characters; for example, a newline was @code{'\012'}.  This was a
vestigial trace of Python's C ancestry, but today octal is of very little
practical use.  Ka-Ping Yee suggested using hex escapes instead of octal ones,
and using the @code{\n}, @code{\t}, @code{\r} escapes for the appropriate characters,
and implemented this new formatting.

@item 
Syntax errors detected at compile-time can now raise exceptions containing the
filename and line number of the error, a pleasant side effect of the compiler
reorganization done by Jeremy Hylton.

@item 
C extensions which import other modules have been changed to use
@code{PyImport_ImportModule()}, which means that they will use any import hooks
that have been installed.  This is also encouraged for third-party extensions
that need to import some other module from C code.

@item 
The size of the Unicode character database was shrunk by another 340K thanks
to Fredrik Lundh.

@item 
Some new ports were contributed: MacOS X (by Steven Majewski), Cygwin (by
Jason Tishler); RISCOS (by Dietmar Schwertberger); Unixware 7  (by Billy G.
Allie).
@end itemize

And there's the usual list of minor bugfixes, minor memory leaks, docstring
edits, and other tweaks, too lengthy to be worth itemizing; see the CVS logs for
the full details if you want them.

@c ======================================================================

@node 致谢<7>,,Other Changes and Fixes<4>,Python 2 1 有什么新变化
@anchor{whatsnew/2 1 acknowledgements}@anchor{e5f}
@subsection 致谢


作者感谢以下人员对本文的各种草案提出建议： Graeme Cross, David Goodger, Jay Graves, Michael Hudson, Marc-André Lemburg, Fredrik Lundh, Neil Schemenauer, Thomas Wouters.

@node Python 2 0 有什么新变化,更新日志,Python 2 1 有什么新变化,Python的新变化
@anchor{whatsnew/2 0 doc}@anchor{e60}@anchor{whatsnew/2 0 what-s-new-in-python-2-0}@anchor{e61}
@section Python 2.0 有什么新变化


@*作者: 
A.M. Kuchling 和 Moshe Zadka


@c $Id: whatsnew20.tex 50964 2006-07-30 03:03:43Z fred.drake $

@menu
* 概述: 概述<3>. 
* What About Python 1.6?: What About Python 1 6?. 
* 新开发流程:: 
* Unicode: Unicode<2>. 
* 列表推导式:: 
* Augmented Assignment:: 
* 字符串的方法:: 
* Garbage Collection of Cycles:: 
* 其他核心变化:: 
* 移植 Python 2.0: 移植 Python 2 0. 
* 扩展/嵌入更改:: 
* Distutils：使模块易于安装:: 
* XML 模块:: 
* 模块更改:: 
* 新增模块: 新增模块<7>. 
* IDLE 改进:: 
* 删除和弃用的模块:: 
* 致谢: 致谢<8>. 

@end menu

@node 概述<3>,What About Python 1 6?,,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 introduction}@anchor{e62}
@subsection 概述


A new release of Python, version 2.0, was released on October 16, 2000. This
article covers the exciting new features in 2.0, highlights some other useful
changes, and points out a few incompatible changes that may require rewriting
code.

Python's development never completely stops between releases, and a steady flow
of bug fixes and improvements are always being submitted. A host of minor fixes,
a few optimizations, additional docstrings, and better error messages went into
2.0; to list them all would be impossible, but they're certainly significant.
Consult the publicly-available CVS logs if you want to see the full list.  This
progress is due to the five developers working for  PythonLabs are now getting
paid to spend their days fixing bugs, and also due to the improved communication
resulting  from moving to SourceForge.

@c ======================================================================

@node What About Python 1 6?,新开发流程,概述<3>,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 what-about-python-1-6}@anchor{e63}
@subsection What About Python 1.6?


Python 1.6 can be thought of as the Contractual Obligations Python release.
After the core development team left CNRI in May 2000, CNRI requested that a 1.6
release be created, containing all the work on Python that had been performed at
CNRI.  Python 1.6 therefore represents the state of the CVS tree as of May 2000,
with the most significant new feature being Unicode support.  Development
continued after May, of course, so the 1.6 tree received a few fixes to ensure
that it's forward-compatible with Python 2.0.  1.6 is therefore part of Python's
evolution, and not a side branch.

So, should you take much interest in Python 1.6?  Probably not.  The 1.6final
and 2.0beta1 releases were made on the same day (September 5, 2000), the plan
being to finalize Python 2.0 within a month or so.  If you have applications to
maintain, there seems little point in breaking things by moving to 1.6, fixing
them, and then having another round of breakage within a month by moving to 2.0;
you're better off just going straight to 2.0.  Most of the really interesting
features described in this document are only in 2.0, because a lot of work was
done between May and September.

@c ======================================================================

@node 新开发流程,Unicode<2>,What About Python 1 6?,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 new-development-process}@anchor{e64}
@subsection 新开发流程


The most important change in Python 2.0 may not be to the code at all, but to
how Python is developed: in May 2000 the Python developers began using the tools
made available by SourceForge for storing  source code, tracking bug reports,
and managing the queue of patch submissions.  To report bugs or submit patches
for Python 2.0, use the bug tracking and patch manager tools available from
Python's project page, located at @indicateurl{https://sourceforge.net/projects/python/}.

The most important of the services now hosted at SourceForge is the Python CVS
tree, the version-controlled repository containing the source code for Python.
Previously, there were roughly 7 or so people who had write access to the CVS
tree, and all patches had to be inspected and checked in by one of the people on
this short list. Obviously, this wasn't very scalable.  By moving the CVS tree
to SourceForge, it became possible to grant write access to more people; as of
September 2000 there were 27 people able to check in changes, a fourfold
increase.  This makes possible large-scale changes that wouldn't be attempted if
they'd have to be filtered through the small group of core developers.  For
example, one day Peter Schneider-Kamp took it into his head to drop K&R C
compatibility and convert the C source for Python to ANSI C. After getting
approval on the python-dev mailing list, he launched into a flurry of checkins
that lasted about a week, other developers joined in to help, and the job was
done.  If there were only 5 people with write access, probably that task would
have been viewed as "nice, but not worth the time and effort needed" and it
would never have gotten done.

The shift to using SourceForge's services has resulted in a remarkable increase
in the speed of development.  Patches now get submitted, commented on, revised
by people other than the original submitter, and bounced back and forth between
people until the patch is deemed worth checking in.  Bugs are tracked in one
central location and can be assigned to a specific person for fixing, and we can
count the number of open bugs to measure progress.  This didn't come without a
cost: developers now have more e-mail to deal with, more mailing lists to
follow, and special tools had to be written for the new environment. For
example, SourceForge sends default patch and bug notification e-mail messages
that are completely unhelpful, so Ka-Ping Yee wrote an HTML screen-scraper that
sends more useful messages.

The ease of adding code caused a few initial growing pains, such as code was
checked in before it was ready or without getting clear agreement from the
developer group.  The approval process that has emerged is somewhat similar to
that used by the Apache group. Developers can vote +1, +0, -0, or -1 on a patch;
+1 and -1 denote acceptance or rejection, while +0 and -0 mean the developer is
mostly indifferent to the change, though with a slight positive or negative
slant.  The most significant change from the Apache model is that the voting is
essentially advisory, letting Guido van Rossum, who has Benevolent Dictator For
Life status, know what the general opinion is. He can still ignore the result of
a vote, and approve or reject a change even if the community disagrees with him.

Producing an actual patch is the last step in adding a new feature, and is
usually easy compared to the earlier task of coming up with a good design.
Discussions of new features can often explode into lengthy mailing list threads,
making the discussion hard to follow, and no one can read every posting to
python-dev.  Therefore, a relatively formal process has been set up to write
Python Enhancement Proposals (PEPs), modelled on the Internet RFC process.  PEPs
are draft documents that describe a proposed new feature, and are continually
revised until the community reaches a consensus, either accepting or rejecting
the proposal.  Quoting from the introduction to 
@geindex Python 提高建议; PEP 1
PEP 1@footnote{https://www.python.org/dev/peps/pep-0001}, "PEP Purpose and
Guidelines":

@quotation

PEP stands for Python Enhancement Proposal.  A PEP is a design document
providing information to the Python community, or describing a new feature for
Python.  The PEP should provide a concise technical specification of the feature
and a rationale for the feature.

We intend PEPs to be the primary mechanisms for proposing new features, for
collecting community input on an issue, and for documenting the design decisions
that have gone into Python.  The PEP author is responsible for building
consensus within the community and documenting dissenting opinions.
@end quotation

Read the rest of 
@geindex Python 提高建议; PEP 1
PEP 1@footnote{https://www.python.org/dev/peps/pep-0001} for the details of the PEP editorial process, style, and
format.  PEPs are kept in the Python CVS tree on SourceForge, though they're not
part of the Python 2.0 distribution, and are also available in HTML form from
@indicateurl{https://www.python.org/dev/peps/}.  As of September 2000, there are 25 PEPS, ranging
from 
@geindex Python 提高建议; PEP 201
PEP 201@footnote{https://www.python.org/dev/peps/pep-0201}, "Lockstep Iteration", to PEP 225, "Elementwise/Objectwise
Operators".

@c ======================================================================

@node Unicode<2>,列表推导式,新开发流程,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 unicode}@anchor{e65}
@subsection Unicode


The largest new feature in Python 2.0 is a new fundamental data type: Unicode
strings.  Unicode uses 16-bit numbers to represent characters instead of the
8-bit number used by ASCII, meaning that 65,536 distinct characters can be
supported.

The final interface for Unicode support was arrived at through countless
often-stormy discussions on the python-dev mailing list, and mostly implemented by
Marc-André Lemburg, based on a Unicode string type implementation by Fredrik
Lundh.  A detailed explanation of the interface was written up as 
@geindex Python 提高建议; PEP 100
PEP 100@footnote{https://www.python.org/dev/peps/pep-0100},
"Python Unicode Integration". This article will simply cover the most
significant points about the Unicode interfaces.

In Python source code, Unicode strings are written as @code{u"string"}.  Arbitrary
Unicode characters can be written using a new escape sequence, @code{\uHHHH}, where
@emph{HHHH} is a 4-digit hexadecimal number from 0000 to FFFF.  The existing
@code{\xHHHH} escape sequence can also be used, and octal escapes can be used for
characters up to U+01FF, which is represented by @code{\777}.

Unicode strings, just like regular strings, are an immutable sequence type.
They can be indexed and sliced, but not modified in place. Unicode strings have
an @code{encode( [encoding] )} method that returns an 8-bit string in the desired
encoding.  Encodings are named by strings, such as @code{'ascii'}, @code{'utf-8'},
@code{'iso-8859-1'}, or whatever.  A codec API is defined for implementing and
registering new encodings that are then available throughout a Python program.
If an encoding isn't specified, the default encoding is usually 7-bit ASCII,
though it can be changed for your Python installation by calling the
@code{sys.setdefaultencoding(encoding)} function in a customized version of
@code{site.py}.

Combining 8-bit and Unicode strings always coerces to Unicode, using the default
ASCII encoding; the result of @code{'a' + u'bc'} is @code{u'abc'}.

New built-in functions have been added, and existing built-ins modified to
support Unicode:


@itemize *

@item 
@code{unichr(ch)} returns a Unicode string 1 character long, containing the
character @emph{ch}.

@item 
@code{ord(u)}, where @emph{u} is a 1-character regular or Unicode string, returns the
number of the character as an integer.

@item 
@code{unicode(string [, encoding]  [, errors] )} creates a Unicode string
from an 8-bit string.  @code{encoding} is a string naming the encoding to use. The
@code{errors} parameter specifies the treatment of characters that are invalid for
the current encoding; passing @code{'strict'} as the value causes an exception to
be raised on any encoding error, while @code{'ignore'} causes errors to be silently
ignored and @code{'replace'} uses U+FFFD, the official replacement character, in
case of any problems.

@item 
The @code{exec} statement, and various built-ins such as @code{eval()},
@code{getattr()}, and @code{setattr()} will also accept Unicode strings as well as
regular strings.  (It's possible that the process of fixing this missed some
built-ins; if you find a built-in function that accepts strings but doesn't
accept Unicode strings at all, please report it as a bug.)
@end itemize

A new module, @ref{11a,,unicodedata}, provides an interface to Unicode character
properties.  For example, @code{unicodedata.category(u'A')} returns the 2-character
string 'Lu', the 'L' denoting it's a letter, and 'u' meaning that it's
uppercase. @code{unicodedata.bidirectional(u'\u0660')} returns 'AN', meaning that
U+0660 is an Arabic number.

The @ref{1c,,codecs} module contains functions to look up existing encodings and
register new ones.  Unless you want to implement a new encoding, you'll most
often use the @code{codecs.lookup(encoding)} function, which returns a
4-element tuple: @code{(encode_func, decode_func, stream_reader, stream_writer)}.


@itemize *

@item 
@emph{encode_func} is a function that takes a Unicode string, and returns a 2-tuple
@code{(string, length)}.  @emph{string} is an 8-bit string containing a portion (perhaps
all) of the Unicode string converted into the given encoding, and @emph{length} tells
you how much of the Unicode string was converted.

@item 
@emph{decode_func} is the opposite of @emph{encode_func}, taking an 8-bit string and
returning a 2-tuple @code{(ustring, length)}, consisting of the resulting Unicode
string @emph{ustring} and the integer @emph{length} telling how much of the 8-bit string
was consumed.

@item 
@emph{stream_reader} is a class that supports decoding input from a stream.
@emph{stream_reader(file_obj)} returns an object that supports the @code{read()},
@ref{de,,readline()}, and @code{readlines()} methods.  These methods will all
translate from the given encoding and return Unicode strings.

@item 
@emph{stream_writer}, similarly, is a class that supports encoding output to a
stream.  @emph{stream_writer(file_obj)} returns an object that supports the
@code{write()} and @code{writelines()} methods.  These methods expect Unicode
strings, translating them to the given encoding on output.
@end itemize

For example, the following code writes a Unicode string into a file,  encoding
it as UTF-8:

@example
import codecs

unistr = u'\u0660\u2000ab ...'

(UTF8_encode, UTF8_decode,
 UTF8_streamreader, UTF8_streamwriter) = codecs.lookup('UTF-8')

output = UTF8_streamwriter( open( '/tmp/output', 'wb') )
output.write( unistr )
output.close()
@end example

The following code would then read UTF-8 input from the file:

@example
input = UTF8_streamreader( open( '/tmp/output', 'rb') )
print repr(input.read())
input.close()
@end example

Unicode-aware regular expressions are available through the @ref{dd,,re} module,
which has a new underlying implementation called SRE written by Fredrik Lundh of
Secret Labs AB.

A @code{-U} command line option was added which causes the Python compiler to
interpret all string literals as Unicode string literals. This is intended to be
used in testing and future-proofing your Python code, since some future version
of Python may drop support for 8-bit strings and provide only Unicode strings.

@c ======================================================================

@node 列表推导式,Augmented Assignment,Unicode<2>,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 list-comprehensions}@anchor{e66}
@subsection 列表推导式


Lists are a workhorse data type in Python, and many programs manipulate a list
at some point.  Two common operations on lists are to loop over them, and either
pick out the elements that meet a certain criterion, or apply some function to
each element.  For example, given a list of strings, you might want to pull out
all the strings containing a given substring, or strip off trailing whitespace
from each line.

The existing @ref{c26,,map()} and @ref{c27,,filter()} functions can be used for this
purpose, but they require a function as one of their arguments.  This is fine if
there's an existing built-in function that can be passed directly, but if there
isn't, you have to create a little function to do the required work, and
Python's scoping rules make the result ugly if the little function needs
additional information.  Take the first example in the previous paragraph,
finding all the strings in the list containing a given substring.  You could
write the following to do it:

@example
# Given the list L, make a list of all strings
# containing the substring S.
sublist = filter( lambda s, substring=S:
                     string.find(s, substring) != -1,
                  L)
@end example

Because of Python's scoping rules, a default argument is used so that the
anonymous function created by the @ref{c28,,lambda} expression knows what
substring is being searched for.  List comprehensions make this cleaner:

@example
sublist = [ s for s in L if string.find(s, S) != -1 ]
@end example

List comprehensions have the form:

@example
[ expression for expr in sequence1
             for expr2 in sequence2 ...
             for exprN in sequenceN
             if condition ]
@end example

The @code{for}...@code{in} clauses contain the sequences to be
iterated over.  The sequences do not have to be the same length, because they
are @emph{not} iterated over in parallel, but from left to right; this is explained
more clearly in the following paragraphs.  The elements of the generated list
will be the successive values of @emph{expression}.  The final @code{if} clause
is optional; if present, @emph{expression} is only evaluated and added to the result
if @emph{condition} is true.

To make the semantics very clear, a list comprehension is equivalent to the
following Python code:

@example
for expr1 in sequence1:
    for expr2 in sequence2:
    ...
        for exprN in sequenceN:
             if (condition):
                  # Append the value of
                  # the expression to the
                  # resulting list.
@end example

This means that when there are multiple @code{for}...@code{in}
clauses, the resulting list will be equal to the product of the lengths of all
the sequences.  If you have two lists of length 3, the output list is 9 elements
long:

@example
seq1 = 'abc'
seq2 = (1,2,3)
>>> [ (x,y) for x in seq1 for y in seq2]
[('a', 1), ('a', 2), ('a', 3), ('b', 1), ('b', 2), ('b', 3), ('c', 1),
('c', 2), ('c', 3)]
@end example

To avoid introducing an ambiguity into Python's grammar, if @emph{expression} is
creating a tuple, it must be surrounded with parentheses.  The first list
comprehension below is a syntax error, while the second one is correct:

@example
# Syntax error
[ x,y for x in seq1 for y in seq2]
# Correct
[ (x,y) for x in seq1 for y in seq2]
@end example

The idea of list comprehensions originally comes from the functional programming
language Haskell (@indicateurl{https://www.haskell.org}).  Greg Ewing argued most effectively
for adding them to Python and wrote the initial list comprehension patch, which
was then discussed for a seemingly endless time on the python-dev mailing list
and kept up-to-date by Skip Montanaro.

@c ======================================================================

@node Augmented Assignment,字符串的方法,列表推导式,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 augmented-assignment}@anchor{e67}
@subsection Augmented Assignment


Augmented assignment operators, another long-requested feature, have been added
to Python 2.0.  Augmented assignment operators include @code{+=}, @code{-=}, @code{*=},
and so forth.  For example, the statement @code{a += 2} increments the value of the
variable  @code{a} by 2, equivalent to the slightly lengthier @code{a = a + 2}.

The full list of supported assignment operators is @code{+=}, @code{-=}, @code{*=},
@code{/=}, @code{%=}, @code{**=}, @code{&=}, @code{|=}, @code{^=}, @code{>>=}, and @code{<<=}.  Python
classes can override the augmented assignment operators by defining methods
named @ref{e68,,__iadd__()}, @ref{e69,,__isub__()}, etc.  For example, the following
@code{Number} class stores a number and supports using += to create a new
instance with an incremented value.

@c The empty groups below prevent conversion to guillemets.

@example
class Number:
    def __init__(self, value):
        self.value = value
    def __iadd__(self, increment):
        return Number( self.value + increment)

n = Number(5)
n += 3
print n.value
@end example

The @ref{e68,,__iadd__()} special method is called with the value of the increment,
and should return a new instance with an appropriately modified value; this
return value is bound as the new value of the variable on the left-hand side.

Augmented assignment operators were first introduced in the C programming
language, and most C-derived languages, such as @code{awk}, C++, Java, Perl,
and PHP also support them.  The augmented assignment patch was implemented by
Thomas Wouters.

@c ======================================================================

@node 字符串的方法,Garbage Collection of Cycles,Augmented Assignment,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 string-methods}@anchor{e6a}
@subsection 字符串的方法


Until now string-manipulation functionality was in the @ref{f6,,string} module,
which was usually a front-end for the @code{strop} module written in C.  The
addition of Unicode posed a difficulty for the @code{strop} module, because the
functions would all need to be rewritten in order to accept either 8-bit or
Unicode strings.  For functions such as @code{string.replace()}, which takes 3
string arguments, that means eight possible permutations, and correspondingly
complicated code.

Instead, Python 2.0 pushes the problem onto the string type, making string
manipulation functionality available through methods on both 8-bit strings and
Unicode strings.

@example
>>> 'andrew'.capitalize()
'Andrew'
>>> 'hostname'.replace('os', 'linux')
'hlinuxtname'
>>> 'moshe'.find('sh')
2
@end example

One thing that hasn't changed, a noteworthy April Fools' joke notwithstanding,
is that Python strings are immutable. Thus, the string methods return new
strings, and do not modify the string on which they operate.

The old @ref{f6,,string} module is still around for backwards compatibility, but it
mostly acts as a front-end to the new string methods.

Two methods which have no parallel in pre-2.0 versions, although they did exist
in JPython for quite some time, are @code{startswith()} and @code{endswith()}.
@code{s.startswith(t)} is equivalent to @code{s[:len(t)] == t}, while
@code{s.endswith(t)} is equivalent to @code{s[-len(t):] == t}.

One other method which deserves special mention is @code{join()}.  The
@code{join()} method of a string receives one parameter, a sequence of strings,
and is equivalent to the @code{string.join()} function from the old @ref{f6,,string}
module, with the arguments reversed. In other words, @code{s.join(seq)} is
equivalent to the old @code{string.join(seq, s)}.

@c ======================================================================

@node Garbage Collection of Cycles,其他核心变化,字符串的方法,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 garbage-collection-of-cycles}@anchor{e6b}
@subsection Garbage Collection of Cycles


The C implementation of Python uses reference counting to implement garbage
collection.  Every Python object maintains a count of the number of references
pointing to itself, and adjusts the count as references are created or
destroyed.  Once the reference count reaches zero, the object is no longer
accessible, since you need to have a reference to an object to access it, and if
the count is zero, no references exist any longer.

Reference counting has some pleasant properties: it's easy to understand and
implement, and the resulting implementation is portable, fairly fast, and reacts
well with other libraries that implement their own memory handling schemes.  The
major problem with reference counting is that it sometimes doesn't realise that
objects are no longer accessible, resulting in a memory leak.  This happens when
there are cycles of references.

Consider the simplest possible cycle,  a class instance which has a reference to
itself:

@example
instance = SomeClass()
instance.myself = instance
@end example

After the above two lines of code have been executed, the reference count of
@code{instance} is 2; one reference is from the variable named @code{'instance'}, and
the other is from the @code{myself} attribute of the instance.

If the next line of code is @code{del instance}, what happens?  The reference count
of @code{instance} is decreased by 1, so it has a reference count of 1; the
reference in the @code{myself} attribute still exists.  Yet the instance is no
longer accessible through Python code, and it could be deleted.  Several objects
can participate in a cycle if they have references to each other, causing all of
the objects to be leaked.

Python 2.0 fixes this problem by periodically executing a cycle detection
algorithm which looks for inaccessible cycles and deletes the objects involved.
A new @ref{86,,gc} module provides functions to perform a garbage collection,
obtain debugging statistics, and tuning the collector's parameters.

Running the cycle detection algorithm takes some time, and therefore will result
in some additional overhead.  It is hoped that after we've gotten experience
with the cycle collection from using 2.0, Python 2.1 will be able to minimize
the overhead with careful tuning.  It's not yet obvious how much performance is
lost, because benchmarking this is tricky and depends crucially on how often the
program creates and destroys objects.  The detection of cycles can be disabled
when Python is compiled, if you can't afford even a tiny speed penalty or
suspect that the cycle collection is buggy, by specifying the
@code{--without-cycle-gc} switch when running the @code{configure}
script.

Several people tackled this problem and contributed to a solution.  An early
implementation of the cycle detection approach was written by Toby Kelsey.  The
current algorithm was suggested by Eric Tiedemann during a visit to CNRI, and
Guido van Rossum and Neil Schemenauer wrote two different implementations, which
were later integrated by Neil.  Lots of other people offered suggestions along
the way; the March 2000 archives of the python-dev mailing list contain most of
the relevant discussion, especially in the threads titled "Reference cycle
collection for Python" and "Finalization again".

@c ======================================================================

@node 其他核心变化,移植 Python 2 0,Garbage Collection of Cycles,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 other-core-changes}@anchor{e6c}
@subsection 其他核心变化


Various minor changes have been made to Python's syntax and built-in functions.
None of the changes are very far-reaching, but they're handy conveniences.

@menu
* Minor Language Changes:: 
* Changes to Built-in Functions:: 

@end menu

@node Minor Language Changes,Changes to Built-in Functions,,其他核心变化
@anchor{whatsnew/2 0 minor-language-changes}@anchor{e6d}
@subsubsection Minor Language Changes


A new syntax makes it more convenient to call a given function with a tuple of
arguments and/or a dictionary of keyword arguments. In Python 1.5 and earlier,
you'd use the @code{apply()} built-in function: @code{apply(f, args, kw)} calls the
function @code{f()} with the argument tuple @emph{args} and the keyword arguments in
the dictionary @emph{kw}.  @code{apply()}  is the same in 2.0, but thanks to a patch
from Greg Ewing, @code{f(*args, **kw)} is a shorter and clearer way to achieve the
same effect.  This syntax is symmetrical with the syntax for defining
functions:

@example
def f(*args, **kw):
    # args is a tuple of positional args,
    # kw is a dictionary of keyword args
    ...
@end example

The @code{print} statement can now have its output directed to a file-like
object by following the @code{print} with  @code{>> file}, similar to the
redirection operator in Unix shells. Previously you'd either have to use the
@code{write()} method of the file-like object, which lacks the convenience and
simplicity of @code{print}, or you could assign a new value to
@code{sys.stdout} and then restore the old value.  For sending output to standard
error, it's much easier to write this:

@example
print >> sys.stderr, "Warning: action field not supplied"
@end example

Modules can now be renamed on importing them, using the syntax @code{import module
as name} or @code{from module import name as othername}.  The patch was submitted
by Thomas Wouters.

A new format style is available when using the @code{%} operator; '%r' will insert
the @ref{7c6,,repr()} of its argument.  This was also added from symmetry
considerations, this time for symmetry with the existing '%s' format style,
which inserts the @ref{329,,str()} of its argument.  For example, @code{'%r %s' % ('abc',
'abc')} returns a string containing @code{'abc' abc}.

Previously there was no way to implement a class that overrode Python's built-in
@ref{79d,,in} operator and implemented a custom version.  @code{obj in seq} returns
true if @emph{obj} is present in the sequence @emph{seq}; Python computes this by simply
trying every index of the sequence until either @emph{obj} is found or an
@ref{e6e,,IndexError} is encountered.  Moshe Zadka contributed a patch which adds a
@ref{d21,,__contains__()} magic method for providing a custom implementation for
@code{in}. Additionally, new built-in objects written in C can define what
@code{in} means for them via a new slot in the sequence protocol.

Earlier versions of Python used a recursive algorithm for deleting objects.
Deeply nested data structures could cause the interpreter to fill up the C stack
and crash; Christian Tismer rewrote the deletion logic to fix this problem.  On
a related note, comparing recursive objects recursed infinitely and crashed;
Jeremy Hylton rewrote the code to no longer crash, producing a useful result
instead.  For example, after this code:

@example
a = []
b = []
a.append(a)
b.append(b)
@end example

The comparison @code{a==b} returns true, because the two recursive data structures
are isomorphic. See the thread "trashcan and PR#7" in the April 2000 archives of
the python-dev mailing list for the discussion leading up to this
implementation, and some useful relevant links.    Note that comparisons can now
also raise exceptions. In earlier versions of Python, a comparison operation
such as @code{cmp(a,b)} would always produce an answer, even if a user-defined
@code{__cmp__()} method encountered an error, since the resulting exception would
simply be silently swallowed.

@c Starting URL:

@c https://www.python.org/pipermail/python-dev/2000-April/004834.html

Work has been done on porting Python to 64-bit Windows on the Itanium processor,
mostly by Trent Mick of ActiveState.  (Confusingly, @code{sys.platform} is still
@code{'win32'} on Win64 because it seems that for ease of porting, MS Visual C++
treats code as 32 bit on Itanium.) PythonWin also supports Windows CE; see the
Python CE page at @indicateurl{http://pythonce.sourceforge.net/} for more information.

Another new platform is Darwin/MacOS X; initial support for it is in Python 2.0.
Dynamic loading works, if you specify "configure --with-dyld --with-suffix=.x".
Consult the README in the Python source distribution for more instructions.

An attempt has been made to alleviate one of Python's warts, the often-confusing
@ref{d74,,NameError} exception when code refers to a local variable before the
variable has been assigned a value.  For example, the following code raises an
exception on the @code{print} statement in both 1.5.2 and 2.0; in 1.5.2 a
@ref{d74,,NameError} exception is raised, while 2.0 raises a new
@ref{e6f,,UnboundLocalError} exception. @ref{e6f,,UnboundLocalError} is a subclass of
@ref{d74,,NameError}, so any existing code that expects @ref{d74,,NameError} to be
raised should still work.

@example
def f():
    print "i=",i
    i = i + 1
f()
@end example

Two new exceptions, @ref{e70,,TabError} and @ref{e71,,IndentationError}, have been
introduced.  They're both subclasses of @ref{452,,SyntaxError}, and are raised when
Python code is found to be improperly indented.

@node Changes to Built-in Functions,,Minor Language Changes,其他核心变化
@anchor{whatsnew/2 0 changes-to-built-in-functions}@anchor{e72}
@subsubsection Changes to Built-in Functions


A new built-in, @code{zip(seq1, seq2, ...)}, has been added.  @ref{c2b,,zip()}
returns a list of tuples where each tuple contains the i-th element from each of
the argument sequences.  The difference between @ref{c2b,,zip()} and @code{map(None,
seq1, seq2)} is that @ref{c26,,map()} pads the sequences with @code{None} if the
sequences aren't all of the same length, while @ref{c2b,,zip()} truncates the
returned list to the length of the shortest argument sequence.

The @ref{184,,int()} and @code{long()} functions now accept an optional "base"
parameter when the first argument is a string. @code{int('123', 10)} returns 123,
while @code{int('123', 16)} returns 291.  @code{int(123, 16)} raises a
@ref{192,,TypeError} exception with the message "can't convert non-string with
explicit base".

A new variable holding more detailed version information has been added to the
@ref{fd,,sys} module.  @code{sys.version_info} is a tuple @code{(major, minor, micro,
level, serial)} For example, in a hypothetical 2.0.1beta1, @code{sys.version_info}
would be @code{(2, 0, 1, 'beta', 1)}. @emph{level} is a string such as @code{"alpha"},
@code{"beta"}, or @code{"final"} for a final release.

Dictionaries have an odd new method, @code{setdefault(key, default)}, which
behaves similarly to the existing @code{get()} method.  However, if the key is
missing, @code{setdefault()} both returns the value of @emph{default} as @code{get()}
would do, and also inserts it into the dictionary as the value for @emph{key}.  Thus,
the following lines of code:

@example
if dict.has_key( key ): return dict[key]
else:
    dict[key] = []
    return dict[key]
@end example

can be reduced to a single @code{return dict.setdefault(key, [])} statement.

The interpreter sets a maximum recursion depth in order to catch runaway
recursion before filling the C stack and causing a core dump or GPF..
Previously this limit was fixed when you compiled Python, but in 2.0 the maximum
recursion depth can be read and modified using @ref{e73,,sys.getrecursionlimit()} and
@ref{e74,,sys.setrecursionlimit()}. The default value is 1000, and a rough maximum
value for a given platform can be found by running a new script,
@code{Misc/find_recursionlimit.py}.

@c ======================================================================

@node 移植 Python 2 0,扩展/嵌入更改,其他核心变化,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 porting-to-2-0}@anchor{e75}
@subsection 移植 Python 2.0


New Python releases try hard to be compatible with previous releases, and the
record has been pretty good.  However, some changes are considered useful
enough, usually because they fix initial design decisions that turned out to be
actively mistaken, that breaking backward compatibility can't always be avoided.
This section lists the changes in Python 2.0 that may cause old Python code to
break.

The change which will probably break the most code is tightening up the
arguments accepted by some methods.  Some methods would take multiple arguments
and treat them as a tuple, particularly various list methods such as
@code{append()} and @code{insert()}. In earlier versions of Python, if @code{L} is
a list, @code{L.append( 1,2 )} appends the tuple @code{(1,2)} to the list.  In Python
2.0 this causes a @ref{192,,TypeError} exception to be raised, with the message:
'append requires exactly 1 argument; 2 given'.  The fix is to simply add an
extra set of parentheses to pass both values as a tuple:  @code{L.append( (1,2) )}.

The earlier versions of these methods were more forgiving because they used an
old function in Python's C interface to parse their arguments; 2.0 modernizes
them to use @code{PyArg_ParseTuple()}, the current argument parsing function,
which provides more helpful error messages and treats multi-argument calls as
errors.  If you absolutely must use 2.0 but can't fix your code, you can edit
@code{Objects/listobject.c} and define the preprocessor symbol
@code{NO_STRICT_LIST_APPEND} to preserve the old behaviour; this isn't recommended.

Some of the functions in the @ref{ef,,socket} module are still forgiving in this
way.  For example, @code{socket.connect( ('hostname', 25) )()} is the correct
form, passing a tuple representing an IP address, but @code{socket.connect(
'hostname', 25 )()} also works. @code{socket.connect_ex()} and @code{socket.bind()}
are similarly easy-going.  2.0alpha1 tightened these functions up, but because
the documentation actually used the erroneous multiple argument form, many
people wrote code which would break with the stricter checking.  GvR backed out
the changes in the face of public reaction, so for the @ref{ef,,socket} module, the
documentation was fixed and the multiple argument form is simply marked as
deprecated; it @emph{will} be tightened up again in a future Python version.

The @code{\x} escape in string literals now takes exactly 2 hex digits.  Previously
it would consume all the hex digits following the 'x' and take the lowest 8 bits
of the result, so @code{\x123456} was equivalent to @code{\x56}.

The @ref{393,,AttributeError} and @ref{d74,,NameError} exceptions have a more friendly
error message, whose text will be something like @code{'Spam' instance has no
attribute 'eggs'} or @code{name 'eggs' is not defined}.  Previously the error
message was just the missing attribute name @code{eggs}, and code written to take
advantage of this fact will break in 2.0.

Some work has been done to make integers and long integers a bit more
interchangeable.  In 1.5.2, large-file support was added for Solaris, to allow
reading files larger than 2 GiB; this made the @code{tell()} method of file
objects return a long integer instead of a regular integer.  Some code would
subtract two file offsets and attempt to use the result to multiply a sequence
or slice a string, but this raised a @ref{192,,TypeError}.  In 2.0, long integers
can be used to multiply or slice a sequence, and it'll behave as you'd
intuitively expect it to; @code{3L * 'abc'} produces 'abcabcabc', and
@code{(0,1,2,3)[2L:4L]} produces (2,3). Long integers can also be used in various
contexts where previously only integers were accepted, such as in the
@code{seek()} method of file objects, and in the formats supported by the @code{%}
operator (@code{%d}, @code{%i}, @code{%x}, etc.).  For example, @code{"%d" % 2L**64} will
produce the string @code{18446744073709551616}.

The subtlest long integer change of all is that the @ref{329,,str()} of a long
integer no longer has a trailing 'L' character, though @ref{7c6,,repr()} still
includes it.  The 'L' annoyed many people who wanted to print long integers that
looked just like regular integers, since they had to go out of their way to chop
off the character.  This is no longer a problem in 2.0, but code which does
@code{str(longval)[:-1]} and assumes the 'L' is there, will now lose the final
digit.

Taking the @ref{7c6,,repr()} of a float now uses a different formatting precision
than @ref{329,,str()}.  @ref{7c6,,repr()} uses @code{%.17g} format string for C's
@code{sprintf()}, while @ref{329,,str()} uses @code{%.12g} as before.  The effect is that
@ref{7c6,,repr()} may occasionally show more decimal places than  @ref{329,,str()}, for
certain numbers.  For example, the number 8.1 can't be represented exactly in
binary, so @code{repr(8.1)} is @code{'8.0999999999999996'}, while str(8.1) is
@code{'8.1'}.

The @code{-X} command-line option, which turned all standard exceptions into
strings instead of classes, has been removed; the standard exceptions will now
always be classes.  The @code{exceptions} module containing the standard
exceptions was translated from Python to a built-in C module, written by Barry
Warsaw and Fredrik Lundh.

@c Commented out for now -- I don't think anyone will care.
@c The pattern and match objects provided by SRE are C types, not Python
@c class instances as in 1.5.  This means you can no longer inherit from
@c \class{RegexObject} or \class{MatchObject}, but that shouldn't be much
@c of a problem since no one should have been doing that in the first
@c place.

@c ======================================================================

@node 扩展/嵌入更改,Distutils：使模块易于安装,移植 Python 2 0,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 extending-embedding-changes}@anchor{e76}
@subsection 扩展/嵌入更改


Some of the changes are under the covers, and will only be apparent to people
writing C extension modules or embedding a Python interpreter in a larger
application.  If you aren't dealing with Python's C API, you can safely skip
this section.

The version number of the Python C API was incremented, so C extensions compiled
for 1.5.2 must be recompiled in order to work with 2.0.  On Windows, it's not
possible for Python 2.0 to import a third party extension built for Python 1.5.x
due to how Windows DLLs work, so Python will raise an exception and the import
will fail.

Users of Jim Fulton's ExtensionClass module will be pleased to find out that
hooks have been added so that ExtensionClasses are now supported by
@ref{449,,isinstance()} and @ref{44a,,issubclass()}. This means you no longer have to
remember to write code such as @code{if type(obj) == myExtensionClass}, but can use
the more natural @code{if isinstance(obj, myExtensionClass)}.

The @code{Python/importdl.c} file, which was a mass of #ifdefs to support
dynamic loading on many different platforms, was cleaned up and reorganised by
Greg Stein.  @code{importdl.c} is now quite small, and platform-specific code
has been moved into a bunch of @code{Python/dynload_*.c} files.  Another
cleanup: there were also a number of @code{my*.h} files in the Include/
directory that held various portability hacks; they've been merged into a single
file, @code{Include/pyport.h}.

Vladimir Marangozov's long-awaited malloc restructuring was completed, to make
it easy to have the Python interpreter use a custom allocator instead of C's
standard @code{malloc()}.  For documentation, read the comments in
@code{Include/pymem.h} and @code{Include/objimpl.h}.  For the lengthy
discussions during which the interface was hammered out, see the Web archives of
the 'patches' and 'python-dev' lists at python.org.

Recent versions of the GUSI development environment for MacOS support POSIX
threads.  Therefore, Python's POSIX threading support now works on the
Macintosh.  Threading support using the user-space GNU @code{pth} library was also
contributed.

Threading support on Windows was enhanced, too.  Windows supports thread locks
that use kernel objects only in case of contention; in the common case when
there's no contention, they use simpler functions which are an order of
magnitude faster.  A threaded version of Python 1.5.2 on NT is twice as slow as
an unthreaded version; with the 2.0 changes, the difference is only 10%.  These
improvements were contributed by Yakov Markovitch.

Python 2.0's source now uses only ANSI C prototypes, so compiling Python now
requires an ANSI C compiler, and can no longer be done using a compiler that
only supports K&R C.

Previously the Python virtual machine used 16-bit numbers in its bytecode,
limiting the size of source files.  In particular, this affected the maximum
size of literal lists and dictionaries in Python source; occasionally people who
are generating Python code would run into this limit.  A patch by Charles G.
Waldman raises the limit from @code{2^16} to @code{2^@{32@}}.

Three new convenience functions intended for adding constants to a module's
dictionary at module initialization time were added: @code{PyModule_AddObject()},
@code{PyModule_AddIntConstant()}, and @code{PyModule_AddStringConstant()}.  Each
of these functions takes a module object, a null-terminated C string containing
the name to be added, and a third argument for the value to be assigned to the
name.  This third argument is, respectively, a Python object, a C long, or a C
string.

A wrapper API was added for Unix-style signal handlers. @code{PyOS_getsig()} gets
a signal handler and @code{PyOS_setsig()} will set a new handler.

@c ======================================================================

@node Distutils：使模块易于安装,XML 模块,扩展/嵌入更改,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 distutils-making-modules-easy-to-install}@anchor{e77}
@subsection Distutils：使模块易于安装


Before Python 2.0, installing modules was a tedious affair -- there was no way
to figure out automatically where Python is installed, or what compiler options
to use for extension modules.  Software authors had to go through an arduous
ritual of editing Makefiles and configuration files, which only really work on
Unix and leave Windows and MacOS unsupported.  Python users faced wildly
differing installation instructions which varied between different extension
packages, which made administering a Python installation something of  a chore.

The SIG for distribution utilities, shepherded by Greg Ward, has created the
Distutils, a system to make package installation much easier.  They form the
@ref{39,,distutils} package, a new part of Python's standard library. In the best
case, installing a Python module from source will require the same steps: first
you simply mean unpack the tarball or zip archive, and the run "@code{python
setup.py install}".  The platform will be automatically detected, the compiler
will be recognized, C extension modules will be compiled, and the distribution
installed into the proper directory.  Optional command-line arguments provide
more control over the installation process, the distutils package offers many
places to override defaults -- separating the build from the install, building
or installing in non-default directories, and more.

In order to use the Distutils, you need to write a @code{setup.py} script.  For
the simple case, when the software contains only .py files, a minimal
@code{setup.py} can be just a few lines long:

@example
from distutils.core import setup
setup (name = "foo", version = "1.0",
       py_modules = ["module1", "module2"])
@end example

The @code{setup.py} file isn't much more complicated if the software consists
of a few packages:

@example
from distutils.core import setup
setup (name = "foo", version = "1.0",
       packages = ["package", "package.subpackage"])
@end example

A C extension can be the most complicated case; here's an example taken from
the PyXML package:

@example
from distutils.core import setup, Extension

expat_extension = Extension('xml.parsers.pyexpat',
     define_macros = [('XML_NS', None)],
     include_dirs = [ 'extensions/expat/xmltok',
                      'extensions/expat/xmlparse' ],
     sources = [ 'extensions/pyexpat.c',
                 'extensions/expat/xmltok/xmltok.c',
                 'extensions/expat/xmltok/xmlrole.c', ]
       )
setup (name = "PyXML", version = "0.5.4",
       ext_modules =[ expat_extension ] )
@end example

The Distutils can also take care of creating source and binary distributions.
The "sdist" command, run by "@code{python setup.py sdist}', builds a source
distribution such as @code{foo-1.0.tar.gz}. Adding new commands isn't
difficult, "bdist_rpm" and "bdist_wininst" commands have already been
contributed to create an RPM distribution and a Windows installer for the
software, respectively.  Commands to create other distribution formats such as
Debian packages and Solaris @code{.pkg} files are in various stages of
development.

All this is documented in a new manual, @emph{Distributing Python Modules}, that
joins the basic set of Python documentation.

@c ======================================================================

@node XML 模块,模块更改,Distutils：使模块易于安装,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 xml-modules}@anchor{e78}
@subsection XML 模块


Python 1.5.2 included a simple XML parser in the form of the @code{xmllib}
module, contributed by Sjoerd Mullender.  Since 1.5.2's release, two different
interfaces for processing XML have become common: SAX2 (version 2 of the Simple
API for XML) provides an event-driven interface with some similarities to
@code{xmllib}, and the DOM (Document Object Model) provides a tree-based
interface, transforming an XML document into a tree of nodes that can be
traversed and modified.  Python 2.0 includes a SAX2 interface and a stripped-down
DOM interface as part of the @ref{133,,xml} package. Here we will give a brief
overview of these new interfaces; consult the Python documentation or the source
code for complete details. The Python XML SIG is also working on improved
documentation.

@menu
* SAX2 Support:: 
* DOM Support:: 
* Relationship to PyXML:: 

@end menu

@node SAX2 Support,DOM Support,,XML 模块
@anchor{whatsnew/2 0 sax2-support}@anchor{e79}
@subsubsection SAX2 Support


SAX defines an event-driven interface for parsing XML.  To use SAX, you must
write a SAX handler class.  Handler classes inherit from various classes
provided by SAX, and override various methods that will then be called by the
XML parser.  For example, the @code{startElement()} and @code{endElement()}
methods are called for every starting and end tag encountered by the parser, the
@code{characters()} method is called for every chunk of character data, and so
forth.

The advantage of the event-driven approach is that the whole document doesn't
have to be resident in memory at any one time, which matters if you are
processing really huge documents.  However, writing the SAX handler class can
get very complicated if you're trying to modify the document structure in some
elaborate way.

For example, this little example program defines a handler that prints a message
for every starting and ending tag, and then parses the file @code{hamlet.xml}
using it:

@example
from xml import sax

class SimpleHandler(sax.ContentHandler):
    def startElement(self, name, attrs):
        print 'Start of element:', name, attrs.keys()

    def endElement(self, name):
        print 'End of element:', name

# Create a parser object
parser = sax.make_parser()

# Tell it what handler to use
handler = SimpleHandler()
parser.setContentHandler( handler )

# Parse a file!
parser.parse( 'hamlet.xml' )
@end example

For more information, consult the Python documentation, or the XML HOWTO at
@indicateurl{http://pyxml.sourceforge.net/topics/howto/xml-howto.html}.

@node DOM Support,Relationship to PyXML,SAX2 Support,XML 模块
@anchor{whatsnew/2 0 dom-support}@anchor{e7a}
@subsubsection DOM Support


The Document Object Model is a tree-based representation for an XML document.  A
top-level @code{Document} instance is the root of the tree, and has a single
child which is the top-level @code{Element} instance. This @code{Element}
has children nodes representing character data and any sub-elements, which may
have further children of their own, and so forth.  Using the DOM you can
traverse the resulting tree any way you like, access element and attribute
values, insert and delete nodes, and convert the tree back into XML.

The DOM is useful for modifying XML documents, because you can create a DOM
tree, modify it by adding new nodes or rearranging subtrees, and then produce a
new XML document as output.  You can also construct a DOM tree manually and
convert it to XML, which can be a more flexible way of producing XML output than
simply writing @code{<tag1>}...@code{</tag1>} to a file.

The DOM implementation included with Python lives in the @ref{135,,xml.dom.minidom}
module.  It's a lightweight implementation of the Level 1 DOM with support for
XML namespaces.  The  @code{parse()} and @code{parseString()} convenience
functions are provided for generating a DOM tree:

@example
from xml.dom import minidom
doc = minidom.parse('hamlet.xml')
@end example

@code{doc} is a @code{Document} instance.  @code{Document}, like all the other
DOM classes such as @code{Element} and @code{Text}, is a subclass of the
@code{Node} base class.  All the nodes in a DOM tree therefore support certain
common methods, such as @code{toxml()} which returns a string containing the XML
representation of the node and its children.  Each class also has special
methods of its own; for example, @code{Element} and @code{Document}
instances have a method to find all child elements with a given tag name.
Continuing from the previous 2-line example:

@example
perslist = doc.getElementsByTagName( 'PERSONA' )
print perslist[0].toxml()
print perslist[1].toxml()
@end example

For the @emph{Hamlet} XML file, the above few lines output:

@example
<PERSONA>CLAUDIUS, king of Denmark. </PERSONA>
<PERSONA>HAMLET, son to the late, and nephew to the present king.</PERSONA>
@end example

The root element of the document is available as @code{doc.documentElement}, and
its children can be easily modified by deleting, adding, or removing nodes:

@example
root = doc.documentElement

# Remove the first child
root.removeChild( root.childNodes[0] )

# Move the new first child to the end
root.appendChild( root.childNodes[0] )

# Insert the new first child (originally,
# the third child) before the 20th child.
root.insertBefore( root.childNodes[0], root.childNodes[20] )
@end example

Again, I will refer you to the Python documentation for a complete listing of
the different @code{Node} classes and their various methods.

@node Relationship to PyXML,,DOM Support,XML 模块
@anchor{whatsnew/2 0 relationship-to-pyxml}@anchor{e7b}
@subsubsection Relationship to PyXML


The XML Special Interest Group has been working on XML-related Python code for a
while.  Its code distribution, called PyXML, is available from the SIG's Web
pages at @indicateurl{https://www.python.org/community/sigs/current/xml-sig}. The PyXML distribution also used
the package name @code{xml}.  If you've written programs that used PyXML, you're
probably wondering about its compatibility with the 2.0 @ref{133,,xml} package.

The answer is that Python 2.0's @ref{133,,xml} package isn't compatible with PyXML,
but can be made compatible by installing a recent version PyXML.  Many
applications can get by with the XML support that is included with Python 2.0,
but more complicated applications will require that the full PyXML package will
be installed.  When installed, PyXML versions 0.6.0 or greater will replace the
@ref{133,,xml} package shipped with Python, and will be a strict superset of the
standard package, adding a bunch of additional features.  Some of the additional
features in PyXML include:


@itemize *

@item 
4DOM, a full DOM implementation from FourThought, Inc.

@item 
The xmlproc validating parser, written by Lars Marius Garshol.

@item 
The @code{sgmlop} parser accelerator module, written by Fredrik Lundh.
@end itemize

@c ======================================================================

@node 模块更改,新增模块<7>,XML 模块,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 module-changes}@anchor{e7c}
@subsection 模块更改


Lots of improvements and bugfixes were made to Python's extensive standard
library; some of the affected modules include @ref{de,,readline},
@code{ConfigParser}, @ref{16,,cgi}, @ref{15,,calendar}, @ref{d1,,posix}, @ref{de,,readline},
@code{xmllib}, @ref{5,,aifc}, @code{chunk, wave}, @ref{dc,,random}, @ref{e7,,shelve},
and @ref{c0,,nntplib}.  Consult the CVS logs for the exact patch-by-patch details.

Brian Gallew contributed OpenSSL support for the @ref{ef,,socket} module.  OpenSSL
is an implementation of the Secure Socket Layer, which encrypts the data being
sent over a socket.  When compiling Python, you can edit @code{Modules/Setup}
to include SSL support, which adds an additional function to the @ref{ef,,socket}
module: @code{socket.ssl(socket, keyfile, certfile)}, which takes a socket
object and returns an SSL socket.  The @code{httplib} and @ref{11d,,urllib} modules
were also changed to support @code{https://} URLs, though no one has implemented
FTP or SMTP over SSL.

The @code{httplib} module has been rewritten by Greg Stein to support HTTP/1.1.
Backward compatibility with the 1.5 version of @code{httplib} is provided,
though using HTTP/1.1 features such as pipelining will require rewriting code to
use a different set of interfaces.

The @code{Tkinter} module now supports Tcl/Tk version 8.1, 8.2, or 8.3, and
support for the older 7.x versions has been dropped.  The Tkinter module now
supports displaying Unicode strings in Tk widgets. Also, Fredrik Lundh
contributed an optimization which makes operations like @code{create_line} and
@code{create_polygon} much faster, especially when using lots of coordinates.

The @ref{2c,,curses} module has been greatly extended, starting from Oliver
Andrich's enhanced version, to provide many additional functions from ncurses
and SYSV curses, such as colour, alternative character set support, pads, and
mouse support.  This means the module is no longer compatible with operating
systems that only have BSD curses, but there don't seem to be any currently
maintained OSes that fall into this category.

As mentioned in the earlier discussion of 2.0's Unicode support, the underlying
implementation of the regular expressions provided by the @ref{dd,,re} module has
been changed.  SRE, a new regular expression engine written by Fredrik Lundh and
partially funded by Hewlett Packard, supports matching against both 8-bit
strings and Unicode strings.

@c ======================================================================

@node 新增模块<7>,IDLE 改进,模块更改,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 new-modules}@anchor{e7d}
@subsection 新增模块


A number of new modules were added.  We'll simply list them with brief
descriptions; consult the 2.0 documentation for the details of a particular
module.


@itemize *

@item 
@ref{c,,atexit}:  For registering functions to be called before the Python
interpreter exits. Code that currently sets @code{sys.exitfunc} directly should be
changed to  use the @ref{c,,atexit} module instead, importing @ref{c,,atexit} and
calling @ref{e7e,,atexit.register()} with  the function to be called on exit.
(Contributed by Skip Montanaro.)

@item 
@ref{1c,,codecs}, @code{encodings}, @ref{11a,,unicodedata}:  Added as part of the new
Unicode support.

@item 
@ref{7f,,filecmp}: Supersedes the old @code{cmp}, @code{cmpcache} and
@code{dircmp} modules, which have now become deprecated. (Contributed by Gordon
MacMillan and Moshe Zadka.)

@item 
@ref{89,,gettext}: This module provides internationalization (I18N) and
localization (L10N) support for Python programs by providing an interface to the
GNU gettext message catalog library. (Integrated by Barry Warsaw, from separate
contributions by Martin  von Löwis, Peter Funk, and James Henstridge.)

@item 
@code{linuxaudiodev}: Support for the @code{/dev/audio} device on Linux, a
twin to the existing @code{sunaudiodev} module. (Contributed by Peter Bosch,
with fixes by Jeremy Hylton.)

@item 
@ref{b3,,mmap}: An interface to memory-mapped files on both Windows and Unix.  A
file's contents can be mapped directly into memory, at which point it behaves
like a mutable string, so its contents can be read and modified.  They can even
be passed to functions that expect ordinary strings, such as the @ref{dd,,re}
module. (Contributed by Sam Rushing, with some extensions by A.M. Kuchling.)

@item 
@code{pyexpat}: An interface to the Expat XML parser. (Contributed by Paul
Prescod.)

@item 
@code{robotparser}: Parse a @code{robots.txt} file, which is used for writing
Web spiders that politely avoid certain areas of a Web site.  The parser accepts
the contents of a @code{robots.txt} file, builds a set of rules from it, and
can then answer questions about the fetchability of a given URL.  (Contributed
by Skip Montanaro.)

@item 
@ref{100,,tabnanny}: A module/script to  check Python source code for ambiguous
indentation. (Contributed by Tim Peters.)

@item 
@code{UserString}: A base class useful for deriving objects that behave like
strings.

@item 
@ref{129,,webbrowser}: A module that provides a platform independent way to launch
a web browser on a specific URL. For each platform, various browsers are tried
in a specific order. The user can alter which browser is launched by setting the
@emph{BROWSER} environment variable.  (Originally inspired by Eric S. Raymond's patch
to @ref{11d,,urllib} which added similar functionality, but the final module comes
from code originally  implemented by Fred Drake as
@code{Tools/idle/BrowserControl.py}, and adapted for the standard library by
Fred.)

@item 
@code{_winreg}: An interface to the Windows registry.  @code{_winreg} is an
adaptation of functions that have been part of PythonWin since 1995, but has now
been added to the core  distribution, and enhanced to support Unicode.
@code{_winreg} was written by Bill Tutt and Mark Hammond.

@item 
@ref{142,,zipfile}: A module for reading and writing ZIP-format archives.  These
are archives produced by @code{PKZIP} on DOS/Windows or @code{zip} on
Unix, not to be confused with @code{gzip}-format files (which are
supported by the @ref{8c,,gzip} module) (Contributed by James C. Ahlstrom.)

@item 
@code{imputil}: A module that provides a simpler way for writing customized
import hooks, in comparison to the existing @code{ihooks} module.  (Implemented
by Greg Stein, with much discussion on python-dev along the way.)
@end itemize

@c ======================================================================

@node IDLE 改进,删除和弃用的模块,新增模块<7>,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 idle-improvements}@anchor{e7f}
@subsection IDLE 改进


IDLE is the official Python cross-platform IDE, written using Tkinter. Python
2.0 includes IDLE 0.6, which adds a number of new features and improvements.  A
partial list:


@itemize *

@item 
UI improvements and optimizations, especially in the area of syntax
highlighting and auto-indentation.

@item 
The class browser now shows more information, such as the top level functions
in a module.

@item 
Tab width is now a user settable option. When opening an existing Python file,
IDLE automatically detects the indentation conventions, and adapts.

@item 
There is now support for calling browsers on various platforms, used to open
the Python documentation in a browser.

@item 
IDLE now has a command line, which is largely similar to  the vanilla Python
interpreter.

@item 
Call tips were added in many places.

@item 
IDLE can now be installed as a package.

@item 
In the editor window, there is now a line/column bar at the bottom.

@item 
Three new keystroke commands: Check module (@code{Alt-F5}), Import module (@code{F5}) and
Run script (@code{Ctrl-F5}).
@end itemize

@c ======================================================================

@node 删除和弃用的模块,致谢<8>,IDLE 改进,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 deleted-and-deprecated-modules}@anchor{e80}
@subsection 删除和弃用的模块


A few modules have been dropped because they're obsolete, or because there are
now better ways to do the same thing.  The @code{stdwin} module is gone; it was
for a platform-independent windowing toolkit that's no longer developed.

A number of modules have been moved to the @code{lib-old} subdirectory:
@code{cmp}, @code{cmpcache}, @code{dircmp}, @code{dump},  @code{find},
@code{grep}, @code{packmail},  @code{poly}, @code{util}, @code{whatsound},
@code{zmod}.  If you have code which relies on a module  that's been moved to
@code{lib-old}, you can simply add that directory to @code{sys.path}   to get them
back, but you're encouraged to update any code that uses these modules.

@node 致谢<8>,,删除和弃用的模块,Python 2 0 有什么新变化
@anchor{whatsnew/2 0 acknowledgements}@anchor{e81}
@subsection 致谢


作者感谢以下人士对本文的各种草稿提出建议： David Bolen, Mark Hammond, Gregg Hauser, Jeremy Hylton, Fredrik Lundh, Detlef Lannert, Aahz Maruch, Skip Montanaro, Vladimir Marangozov, Tobias Polzin, Guido van Rossum, Neil Schemenauer, and Russ Schmidt.

这个“更新日志”是 Misc/NEWS.d@footnote{https://github.com/python/cpython/tree/3.8/Misc/NEWS.d} 目录下文件 构建@footnote{https://pypi.org/project/blurb} 的 HTML 版本，它包含了对当前 Python 版本进行的 @emph{所有} 重要的更改。

@node 更新日志,,Python 2 0 有什么新变化,Python的新变化
@anchor{whatsnew/changelog doc}@anchor{e82}@anchor{whatsnew/changelog changelog}@anchor{14c}@anchor{whatsnew/changelog id1}@anchor{e83}
@section 更新日志


@menu
* Python 下一版:: 
* Python 3.8.4 final: Python 3 8 4 final. 
* Python 3.8.4 release candidate 1: Python 3 8 4 release candidate 1. 
* Python 3.8.3 final: Python 3 8 3 final. 
* Python 3.8.3 release candidate 1: Python 3 8 3 release candidate 1. 
* Python 3.8.2 正式版: Python 3 8 2 正式版. 
* Python 3.8.2 rc2: Python 3 8 2 rc2. 
* Python 3.8.2 rc1: Python 3 8 2 rc1. 
* Python 3.8.1 正式版: Python 3 8 1 正式版. 
* Python 3.8.1 rc1: Python 3 8 1 rc1. 
* Python 3.8.0 正式版: Python 3 8 0 正式版. 
* Python 3.8.0 rc1: Python 3 8 0 rc1. 
* Python 3.8.0 beta 4: Python 3 8 0 beta 4. 
* Python 3.8.0 beta 3: Python 3 8 0 beta 3. 
* Python 3.8.0 beta 2: Python 3 8 0 beta 2. 
* Python 3.8.0 beta 1: Python 3 8 0 beta 1. 
* Python 3.8.0 alpha 4: Python 3 8 0 alpha 4. 
* Python 3.8.0 alpha 3: Python 3 8 0 alpha 3. 
* Python 3.8.0 alpha 2: Python 3 8 0 alpha 2. 
* Python 3.8.0 alpha 1: Python 3 8 0 alpha 1. 
* Python 3.7.0 正式版: Python 3 7 0 正式版. 
* Python 3.7.0 rc1: Python 3 7 0 rc1. 
* Python 3.7.0 beta 5: Python 3 7 0 beta 5. 
* Python 3.7.0 beta 4: Python 3 7 0 beta 4. 
* Python 3.7.0 beta 3: Python 3 7 0 beta 3. 
* Python 3.7.0 beta 2: Python 3 7 0 beta 2. 
* Python 3.7.0 beta 1: Python 3 7 0 beta 1. 
* Python 3.7.0 alpha 4: Python 3 7 0 alpha 4. 
* Python 3.7.0 alpha 3: Python 3 7 0 alpha 3. 
* Python 3.7.0 alpha 2: Python 3 7 0 alpha 2. 
* Python 3.7.0 alpha 1: Python 3 7 0 alpha 1. 
* Python 3.6.6 正式版: Python 3 6 6 正式版. 
* Python 3.6.6 rc1: Python 3 6 6 rc1. 
* Python 3.6.5 正式版: Python 3 6 5 正式版. 
* Python 3.6.5 rc1: Python 3 6 5 rc1. 
* Python 3.6.4 正式版: Python 3 6 4 正式版. 
* Python 3.6.4 rc1: Python 3 6 4 rc1. 
* Python 3.6.3 正式版: Python 3 6 3 正式版. 
* Python 3.6.3 rc1: Python 3 6 3 rc1. 
* Python 3.6.2 正式版: Python 3 6 2 正式版. 
* Python 3.6.2 rc2: Python 3 6 2 rc2. 
* Python 3.6.2 rc1: Python 3 6 2 rc1. 
* Python 3.6.1 正式版: Python 3 6 1 正式版. 
* Python 3.6.1 rc1: Python 3 6 1 rc1. 
* Python 3.6.0 正式版: Python 3 6 0 正式版. 
* Python 3.6.0 rc2: Python 3 6 0 rc2. 
* Python 3.6.0 rc1: Python 3 6 0 rc1. 
* Python 3.6.0 beta 4: Python 3 6 0 beta 4. 
* Python 3.6.0 beta 3: Python 3 6 0 beta 3. 
* Python 3.6.0 beta 2: Python 3 6 0 beta 2. 
* Python 3.6.0 beta 1: Python 3 6 0 beta 1. 
* Python 3.6.0 alpha 4: Python 3 6 0 alpha 4. 
* Python 3.6.0 alpha 3: Python 3 6 0 alpha 3. 
* Python 3.6.0 alpha 2: Python 3 6 0 alpha 2. 
* Python 3.6.0 alpha 1: Python 3 6 0 alpha 1. 
* Python 3.5.5 正式版: Python 3 5 5 正式版. 
* Python 3.5.5 rc1: Python 3 5 5 rc1. 
* Python 3.5.4 正式版: Python 3 5 4 正式版. 
* Python 3.5.4 rc1: Python 3 5 4 rc1. 
* Python 3.5.3 正式版: Python 3 5 3 正式版. 
* Python 3.5.3 rc1: Python 3 5 3 rc1. 
* Python 3.5.2 正式版: Python 3 5 2 正式版. 
* Python 3.5.2 rc1: Python 3 5 2 rc1. 
* Python 3.5.1 正式版: Python 3 5 1 正式版. 
* Python 3.5.1 rc1: Python 3 5 1 rc1. 
* Python 3.5.0 正式版: Python 3 5 0 正式版. 
* Python 3.5.0 rc4: Python 3 5 0 rc4. 
* Python 3.5.0 rc3: Python 3 5 0 rc3. 
* Python 3.5.0 rc2: Python 3 5 0 rc2. 
* Python 3.5.0 rc1: Python 3 5 0 rc1. 
* Python 3.5.0 beta 4: Python 3 5 0 beta 4. 
* Python 3.5.0 beta 3: Python 3 5 0 beta 3. 
* Python 3.5.0 beta 2: Python 3 5 0 beta 2. 
* Python 3.5.0 beta 1: Python 3 5 0 beta 1. 
* Python 3.5.0 alpha 4: Python 3 5 0 alpha 4. 
* Python 3.5.0 alpha 3: Python 3 5 0 alpha 3. 
* Python 3.5.0 alpha 2: Python 3 5 0 alpha 2. 
* Python 3.5.0 alpha 1: Python 3 5 0 alpha 1. 

@end menu

@node Python 下一版,Python 3 8 4 final,,更新日志
@anchor{whatsnew/changelog python-next}@anchor{e84}
@subsection Python 下一版


@emph{发布日期: XXXX-XX-XX}

@menu
* 安全:: 
* 核心与内置:: 
* 库:: 
* 构建:: 
* IDLE: IDLE<3>. 

@end menu

@node 安全,核心与内置,,Python 下一版
@anchor{whatsnew/changelog security}@anchor{e85}
@subsubsection 安全



@itemize -

@item 
bpo-41304@footnote{https://bugs.python.org/issue41304}: Fixes @code{python3x._pth} being ignored on Windows, caused by the
fix for bpo-29778@footnote{https://bugs.python.org/issue29778} (CVE-2020-15801).

@item 
bpo-39603@footnote{https://bugs.python.org/issue39603}: Prevent http header injection by rejecting control characters
in http.client.putrequest(...).
@end itemize

@node 核心与内置,库,安全,Python 下一版
@anchor{whatsnew/changelog core-and-builtins}@anchor{e86}
@subsubsection 核心与内置



@itemize -

@item 
bpo-41295@footnote{https://bugs.python.org/issue41295}: Resolve a regression in CPython 3.8.4 where defining
"__setattr__" in a multi-inheritance setup and calling up the hierarchy
chain could fail if builtins/extension types were involved in the base
types.
@end itemize

@node 库,构建,核心与内置,Python 下一版
@anchor{whatsnew/changelog library}@anchor{e87}
@subsubsection 库



@itemize -

@item 
bpo-41288@footnote{https://bugs.python.org/issue41288}: Unpickling invalid NEWOBJ_EX opcode with the C implementation
raises now UnpicklingError instead of crashing.

@item 
bpo-39017@footnote{https://bugs.python.org/issue39017}: Avoid infinite loop when reading specially crafted TAR files
using the tarfile module (CVE-2019-20907).
@end itemize

@node 构建,IDLE<3>,库,Python 下一版
@anchor{whatsnew/changelog build}@anchor{e88}
@subsubsection 构建



@itemize -

@item 
bpo-41302@footnote{https://bugs.python.org/issue41302}: Enable building Python 3.8 with libmpdec-2.5.0 to ease
maintenance for Linux distributions. Patch by Felix Yan.
@end itemize

@node IDLE<3>,,构建,Python 下一版
@anchor{whatsnew/changelog idle}@anchor{e89}
@subsubsection IDLE



@itemize -

@item 
bpo-41300@footnote{https://bugs.python.org/issue41300}: Save files with non-ascii chars. Fix regression released in
3.9.0b4 and 3.8.4.
@end itemize

@node Python 3 8 4 final,Python 3 8 4 release candidate 1,Python 下一版,更新日志
@anchor{whatsnew/changelog python-3-8-4-final}@anchor{e8a}
@subsection Python 3.8.4 final


@emph{Release date: 2020-07-13}

@menu
* 安全: 安全<2>. 
* 核心与内置: 核心与内置<2>. 
* 库: 库<2>. 
* IDLE: IDLE<4>. 

@end menu

@node 安全<2>,核心与内置<2>,,Python 3 8 4 final
@anchor{whatsnew/changelog id2}@anchor{e8b}
@subsubsection 安全



@itemize -

@item 
bpo-41162@footnote{https://bugs.python.org/issue41162}: Audit hooks are now cleared later during finalization to avoid
missing events.

@item 
bpo-29778@footnote{https://bugs.python.org/issue29778}: Ensure @code{python3.dll} is loaded from correct locations
when Python is embedded (CVE-2020-15523).
@end itemize

@node 核心与内置<2>,库<2>,安全<2>,Python 3 8 4 final
@anchor{whatsnew/changelog id3}@anchor{e8c}
@subsubsection 核心与内置



@itemize -

@item 
bpo-41247@footnote{https://bugs.python.org/issue41247}: Always cache the running loop holder when running
@code{asyncio.set_running_loop}.

@item 
bpo-41252@footnote{https://bugs.python.org/issue41252}: Fix incorrect refcounting in _ssl.c's
@code{_servername_callback()}.

@item 
bpo-41218@footnote{https://bugs.python.org/issue41218}: Python 3.8.3 had a regression where compiling with
ast.PyCF_ALLOW_TOP_LEVEL_AWAIT would aggressively mark list comprehension
with CO_COROUTINE. Now only list comprehension making use of async/await
will tagged as so.

@item 
bpo-41175@footnote{https://bugs.python.org/issue41175}: Guard against a NULL pointer dereference within bytearrayobject
triggered by the @code{bytearray() + bytearray()} operation.

@item 
bpo-39960@footnote{https://bugs.python.org/issue39960}: The "hackcheck" that prevents sneaking around a type's
__setattr__() by calling the superclass method was rewritten to allow C
implemented heap types.
@end itemize

@node 库<2>,IDLE<4>,核心与内置<2>,Python 3 8 4 final
@anchor{whatsnew/changelog id4}@anchor{e8d}
@subsubsection 库



@itemize -

@item 
bpo-41235@footnote{https://bugs.python.org/issue41235}: Fix the error handling in
@ref{a8d,,ssl.SSLContext.load_dh_params()}.

@item 
bpo-41193@footnote{https://bugs.python.org/issue41193}: The @code{write_history()} atexit function of the readline
completer now ignores any @ref{1d3,,OSError} to ignore error if the filesystem
is read-only, instead of only ignoring @ref{7ba,,FileNotFoundError} and
@ref{5fa,,PermissionError}.

@item 
bpo-41043@footnote{https://bugs.python.org/issue41043}: Fixed the use of @ref{5c1,,glob()} in the stdlib: literal part
of the path is now always correctly escaped.

@item 
bpo-39384@footnote{https://bugs.python.org/issue39384}: Fixed email.contentmanager to allow set_content() to set a null
string.
@end itemize

@node IDLE<4>,,库<2>,Python 3 8 4 final
@anchor{whatsnew/changelog id5}@anchor{e8e}
@subsubsection IDLE



@itemize -

@item 
bpo-37765@footnote{https://bugs.python.org/issue37765}: Add keywords to module name completion list.  Rewrite
Completions section of IDLE doc.

@item 
bpo-41152@footnote{https://bugs.python.org/issue41152}: The encoding of @code{stdin}, @code{stdout} and @code{stderr} in IDLE is
now always UTF-8.
@end itemize

@node Python 3 8 4 release candidate 1,Python 3 8 3 final,Python 3 8 4 final,更新日志
@anchor{whatsnew/changelog python-3-8-4-release-candidate-1}@anchor{e8f}
@subsection Python 3.8.4 release candidate 1


@emph{Release date: 2020-06-29}

@menu
* 安全: 安全<3>. 
* 核心与内置: 核心与内置<3>. 
* 库: 库<3>. 
* 测试:: 
* 构建: 构建<2>. 
* Windows:: 
* macOS:: 
* IDLE: IDLE<5>. 
* 工具/示例:: 

@end menu

@node 安全<3>,核心与内置<3>,,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog id6}@anchor{e90}
@subsubsection 安全



@itemize -

@item 
bpo-41004@footnote{https://bugs.python.org/issue41004}: The __hash__() methods of  ipaddress.IPv4Interface and
ipaddress.IPv6Interface incorrectly generated constant hash values of 32
and 128 respectively. This resulted in always causing hash collisions. The
fix uses hash() to generate hash values for the tuple of (address, mask
length, network address).

@item 
bpo-39073@footnote{https://bugs.python.org/issue39073}: Disallow CR or LF in email.headerregistry.Address arguments to
guard against header injection attacks.
@end itemize

@node 核心与内置<3>,库<3>,安全<3>,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog id7}@anchor{e91}
@subsubsection 核心与内置



@itemize -

@item 
bpo-41094@footnote{https://bugs.python.org/issue41094}: Fix decoding errors with audit when open files with non-ASCII
names on non-UTF-8 locale.

@item 
bpo-41056@footnote{https://bugs.python.org/issue41056}: Fixes a reference to deallocated stack space during startup
when constructing sys.path involving a relative symlink when code was
supplied via -c.  (discovered via Coverity)

@item 
bpo-35975@footnote{https://bugs.python.org/issue35975}: Stefan Behnel reported that cf_feature_version is used even
when PyCF_ONLY_AST is not set. This is against the intention and against
the documented behavior, so it's been fixed.

@item 
bpo-40957@footnote{https://bugs.python.org/issue40957}: Fix refleak in _Py_fopen_obj() when PySys_Audit() fails

@item 
bpo-40870@footnote{https://bugs.python.org/issue40870}: Raise @ref{1fb,,ValueError} when validating custom AST's where the
constants @code{True}, @code{False} and @code{None} are used within a
@code{ast.Name} node.

@item 
bpo-40826@footnote{https://bugs.python.org/issue40826}: Fix GIL usage in @code{PyOS_Readline()}: lock the GIL to set
an exception and pass the Python thread state when checking if there is a
pending signal.

@item 
bpo-40824@footnote{https://bugs.python.org/issue40824}: Unexpected errors in calling the @code{__iter__} method are no
longer masked by @code{TypeError} in the @ref{79d,,in} operator and functions
@ref{e92,,contains()}, @ref{e93,,indexOf()} and
@ref{e94,,countOf()} of the @ref{c2,,operator} module.

@item 
bpo-40663@footnote{https://bugs.python.org/issue40663}: Correctly generate annotations where parentheses are omitted
but required (e.g: @code{Type[(str, int, *other))]}.
@end itemize

@node 库<3>,测试,核心与内置<3>,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog id8}@anchor{e95}
@subsubsection 库



@itemize -

@item 
bpo-41138@footnote{https://bugs.python.org/issue41138}: Fixed the @ref{112,,trace} module CLI for Python source files with
non-UTF-8 encoding.

@item 
bpo-31938@footnote{https://bugs.python.org/issue31938}: Fix default-value signatures of several functions in the
@ref{e5,,select} module - by Anthony Sottile.

@item 
bpo-41068@footnote{https://bugs.python.org/issue41068}: Fixed reading files with non-ASCII names from ZIP archive
directly after writing them.

@item 
bpo-41058@footnote{https://bugs.python.org/issue41058}: @code{pdb.find_function()} now correctly determines the source
file encoding.

@item 
bpo-41056@footnote{https://bugs.python.org/issue41056}: Fix a NULL pointer dereference within the ssl module during a
MemoryError in the keylog callback. (discovered by Coverity)

@item 
bpo-41048@footnote{https://bugs.python.org/issue41048}: @ref{e96,,mimetypes.read_mime_types()} function reads the rule file
using UTF-8 encoding, not the locale encoding. Patch by Srinivas Reddy
Thatiparthy.

@item 
bpo-40448@footnote{https://bugs.python.org/issue40448}: @ref{7a,,ensurepip} now disables the use of @code{pip} cache when
installing the bundled versions of @code{pip} and @code{setuptools}.  Patch by
Krzysztof Konopko.

@item 
bpo-40855@footnote{https://bugs.python.org/issue40855}: The standard deviation and variance functions in the statistics
module were ignoring their mu and xbar arguments.

@item 
bpo-40807@footnote{https://bugs.python.org/issue40807}: Stop codeop._maybe_compile, used by code.InteractiveInterpreter
(and IDLE). from from emitting each warning three times.

@item 
bpo-40834@footnote{https://bugs.python.org/issue40834}: Fix truncate when sending str object
with_xxsubinterpreters.channel_send.

@item 
bpo-38488@footnote{https://bugs.python.org/issue38488}: Update ensurepip to install pip 20.1.1 and setuptools 47.1.0.

@item 
bpo-40767@footnote{https://bugs.python.org/issue40767}: @ref{129,,webbrowser} now properly finds the default browser in
pure Wayland systems by checking the WAYLAND_DISPLAY environment variable.
Patch contributed by Jérémy Attali.

@item 
bpo-40795@footnote{https://bugs.python.org/issue40795}: @ref{2b,,ctypes} module: If ctypes fails to convert the result of
a callback or if a ctypes callback function raises an exception,
sys.unraisablehook is now called with an exception set. Previously, the
error was logged into stderr by @ref{e97,,PyErr_Print()}.

@item 
bpo-30008@footnote{https://bugs.python.org/issue30008}: Fix @ref{f3,,ssl} code to be compatible with OpenSSL 1.1.x builds
that use @code{no-deprecated} and @code{--api=1.1.0}.

@item 
bpo-40614@footnote{https://bugs.python.org/issue40614}: @ref{1a1,,ast.parse()} will not parse self documenting expressions
in f-strings when passed @code{feature_version} is less than @code{(3, 8)}.

@item 
bpo-40626@footnote{https://bugs.python.org/issue40626}: Add h5 file extension as MIME Type application/x-hdf5, as per
HDF Group recommendation for HDF5 formatted data files. Patch contributed
by Mark Schwab.

@item 
bpo-25872@footnote{https://bugs.python.org/issue25872}: @ref{a8,,linecache} could crash with a @ref{2c7,,KeyError} when
accessed from multiple threads. Fix by Michael Graczyk.

@item 
bpo-40597@footnote{https://bugs.python.org/issue40597}: If text content lines are longer than policy.max_line_length,
always use a content-encoding to make sure they are wrapped.

@item 
bpo-40515@footnote{https://bugs.python.org/issue40515}: The @ref{f3,,ssl} and @ref{8d,,hashlib} modules now actively check
that OpenSSL is build with thread support. Python 3.7.0 made thread
support mandatory and no longer works safely with a no-thread builds.

@item 
bpo-13097@footnote{https://bugs.python.org/issue13097}: @code{ctypes} now raises an @code{ArgumentError} when a callback is
invoked with more than 1024 arguments.

@item 
bpo-40457@footnote{https://bugs.python.org/issue40457}: The ssl module now support OpenSSL builds without TLS 1.0 and
1.1 methods.

@item 
bpo-39830@footnote{https://bugs.python.org/issue39830}: Add @ref{e98,,zipfile.Path} to @code{__all__} in the @ref{142,,zipfile}
module.

@item 
bpo-40025@footnote{https://bugs.python.org/issue40025}: Raise TypeError when _generate_next_value_ is defined after
members. Patch by Ethan Onstott.

@item 
bpo-39244@footnote{https://bugs.python.org/issue39244}: Fixed @code{multiprocessing.context.get_all_start_methods} to
properly return the default method first on macOS.

@item 
bpo-39040@footnote{https://bugs.python.org/issue39040}: Fix parsing of invalid mime headers parameters by collapsing
whitespace between encoded words in a bare-quote-string.

@item 
bpo-35714@footnote{https://bugs.python.org/issue35714}: @ref{cad,,struct.error} is now raised if there is a null character
in a @ref{f8,,struct} format string.

@item 
bpo-36290@footnote{https://bugs.python.org/issue36290}: AST nodes are now raising @ref{192,,TypeError} on conflicting
keyword arguments. Patch contributed by Rémi Lapeyre.

@item 
bpo-29620@footnote{https://bugs.python.org/issue29620}: @ref{ab7,,assertWarns()} no longer raises a
@code{RuntimeException} when accessing a module's @code{__warningregistry__}
causes importation of a new module, or when a new module is imported in
another thread. Patch by Kernc.

@item 
bpo-34226@footnote{https://bugs.python.org/issue34226}: Fix @ref{48d,,cgi.parse_multipart} without content_length. Patch by
Roger Duran
@end itemize

@node 测试,构建<2>,库<3>,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog tests}@anchor{e99}
@subsubsection 测试



@itemize -

@item 
bpo-41085@footnote{https://bugs.python.org/issue41085}: Fix integer overflow in the @ref{e9a,,array.array.index()} method on
64-bit Windows for index larger than @code{2**31}.

@item 
bpo-38377@footnote{https://bugs.python.org/issue38377}: On Linux, skip tests using multiprocessing if the current user
cannot create a file in @code{/dev/shm/} directory. Add the
@code{skip_if_broken_multiprocessing_synchronize()} function
to the @ref{106,,test.support} module.

@item 
bpo-41009@footnote{https://bugs.python.org/issue41009}: Fix use of @code{support.require_@{linux|mac|freebsd@}_version()}
decorators as class decorator.

@item 
bpo-41003@footnote{https://bugs.python.org/issue41003}: Fix @code{test_copyreg} when @code{numpy} is installed:
@code{test.pickletester} now saves/restores warnings filters when importing
@code{numpy}, to ignore filters installed by @code{numpy}.

@item 
bpo-40964@footnote{https://bugs.python.org/issue40964}: Disable remote @ref{98,,imaplib} tests, host cyrus.andrew.cmu.edu
is blocking incoming connections.

@item 
bpo-40055@footnote{https://bugs.python.org/issue40055}: distutils.tests now saves/restores warnings filters to leave
them unchanged. Importing tests imports docutils which imports
pkg_resources which adds a warnings filter.

@item 
bpo-34401@footnote{https://bugs.python.org/issue34401}: Make test_gdb properly run on HP-UX. Patch by Michael Osipov.
@end itemize

@node 构建<2>,Windows,测试,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog id9}@anchor{e9b}
@subsubsection 构建



@itemize -

@item 
bpo-40204@footnote{https://bugs.python.org/issue40204}: Pin Sphinx version to 2.3.1 in @code{Doc/Makefile}.

@item 
bpo-40653@footnote{https://bugs.python.org/issue40653}: Move _dirnameW out of HAVE_SYMLINK to fix a potential compiling
issue.
@end itemize

@node Windows,macOS,构建<2>,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog windows}@anchor{e9c}
@subsubsection Windows



@itemize -

@item 
bpo-41074@footnote{https://bugs.python.org/issue41074}: Fixed support of non-ASCII names in functions
@ref{e9d,,msilib.OpenDatabase()} and @ref{e9e,,msilib.init_database()} and non-ASCII
SQL in method @ref{e9f,,msilib.Database.OpenView()}.

@item 
bpo-40164@footnote{https://bugs.python.org/issue40164}: Updates Windows OpenSSL to 1.1.1g

@item 
bpo-39631@footnote{https://bugs.python.org/issue39631}: Changes the registered MIME type for @code{.py} files on Windows
to @code{text/x-python} instead of @code{text/plain}.

@item 
bpo-40677@footnote{https://bugs.python.org/issue40677}: Manually define IO_REPARSE_TAG_APPEXECLINK in case some old
Windows SDK doesn't have it.

@item 
bpo-40650@footnote{https://bugs.python.org/issue40650}: Include winsock2.h in pytime.c for timeval.

@item 
bpo-39148@footnote{https://bugs.python.org/issue39148}: Add IPv6 support to @ref{a,,asyncio} datagram endpoints in
ProactorEventLoop. Change the raised exception for unknown address
families to ValueError as it's not coming from Windows API.
@end itemize

@node macOS,IDLE<5>,Windows,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog macos}@anchor{ea0}
@subsubsection macOS



@itemize -

@item 
bpo-39580@footnote{https://bugs.python.org/issue39580}: Avoid opening Finder window if running installer from the
command line. Patch contributed by Rick Heil.

@item 
bpo-41100@footnote{https://bugs.python.org/issue41100}: Fix configure error when building on macOS 11. Note that the
current Python release was released shortly after the first developer
preview of macOS 11 (Big Sur); there are other known issues with building
and running on the developer preview. Big Sur is expected to be fully
supported in a future bugfix release of Python 3.8.x and with 3.9.0.

@item 
bpo-41005@footnote{https://bugs.python.org/issue41005}: fixed an XDG settings issue not allowing macos to open browser
in webbrowser.py

@item 
bpo-40741@footnote{https://bugs.python.org/issue40741}: Update macOS installer to use SQLite 3.32.2.
@end itemize

@node IDLE<5>,工具/示例,macOS,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog id10}@anchor{ea1}
@subsubsection IDLE



@itemize -

@item 
bpo-41144@footnote{https://bugs.python.org/issue41144}: Make Open Module open a special module such as os.path.

@item 
bpo-39885@footnote{https://bugs.python.org/issue39885}: Make context menu Cut and Copy work again when right-clicking
within a selection.

@item 
bpo-40723@footnote{https://bugs.python.org/issue40723}: Make test_idle pass when run after import.
@end itemize

@node 工具/示例,,IDLE<5>,Python 3 8 4 release candidate 1
@anchor{whatsnew/changelog tools-demos}@anchor{ea2}
@subsubsection 工具/示例



@itemize -

@item 
bpo-40479@footnote{https://bugs.python.org/issue40479}: Update multissltest helper to test with latest OpenSSL 1.0.2,
1.1.0, 1.1.1, and 3.0.0-alpha.

@item 
bpo-40163@footnote{https://bugs.python.org/issue40163}: Fix multissltest tool. OpenSSL has changed download URL for old
releases. The multissltest tool now tries to download from current and old
download URLs.
@end itemize

@node Python 3 8 3 final,Python 3 8 3 release candidate 1,Python 3 8 4 release candidate 1,更新日志
@anchor{whatsnew/changelog python-3-8-3-final}@anchor{ea3}
@subsection Python 3.8.3 final


@emph{Release date: 2020-05-13}

@menu
* 核心与内置: 核心与内置<4>. 
* 库: 库<4>. 
* 文档: 文档<2>. 
* Windows: Windows<2>. 
* C API:: 

@end menu

@node 核心与内置<4>,库<4>,,Python 3 8 3 final
@anchor{whatsnew/changelog id11}@anchor{ea4}
@subsubsection 核心与内置



@itemize -

@item 
bpo-40527@footnote{https://bugs.python.org/issue40527}: Fix command line argument parsing: no longer write errors
multiple times into stderr.

@item 
bpo-40417@footnote{https://bugs.python.org/issue40417}: Fix imp module deprecation warning when PyImport_ReloadModule
is called. Patch by Robert Rouhani.

@item 
bpo-39562@footnote{https://bugs.python.org/issue39562}: The constant values of future flags in the @ref{0,,__future__}
module are updated in order to prevent collision with compiler flags.
Previously @code{PyCF_ALLOW_TOP_LEVEL_AWAIT} was clashing with
@code{CO_FUTURE_DIVISION}.
@end itemize

@node 库<4>,文档<2>,核心与内置<4>,Python 3 8 3 final
@anchor{whatsnew/changelog id12}@anchor{ea5}
@subsubsection 库



@itemize -

@item 
bpo-40559@footnote{https://bugs.python.org/issue40559}: Fix possible memory leak in the C implementation of
@ref{1ad,,asyncio.Task}.

@item 
bpo-40355@footnote{https://bugs.python.org/issue40355}: Improve error reporting in @ref{4a0,,ast.literal_eval()} in the
presence of malformed @code{ast.Dict} nodes instead of silently ignoring
any non-conforming elements. Patch by Curtis Bucher.

@item 
bpo-40459@footnote{https://bugs.python.org/issue40459}: @ref{ea6,,platform.win32_ver()} now produces correct @emph{ptype} strings
instead of empty strings.

@item 
bpo-40398@footnote{https://bugs.python.org/issue40398}: @ref{244,,typing.get_args()} now always returns an empty tuple for
special generic aliases.
@end itemize

@node 文档<2>,Windows<2>,库<4>,Python 3 8 3 final
@anchor{whatsnew/changelog documentation}@anchor{ea7}
@subsubsection 文档



@itemize -

@item 
bpo-40561@footnote{https://bugs.python.org/issue40561}: Provide docstrings for webbrowser open functions.

@item 
bpo-39435@footnote{https://bugs.python.org/issue39435}: Fix an incorrect signature for @ref{5be,,pickle.loads()} in the docs
@end itemize

@node Windows<2>,C API,文档<2>,Python 3 8 3 final
@anchor{whatsnew/changelog id13}@anchor{ea8}
@subsubsection Windows



@itemize -

@item 
bpo-40458@footnote{https://bugs.python.org/issue40458}: Increase reserved stack space to prevent overflow crash on
Windows.
@end itemize

@node C API,,Windows<2>,Python 3 8 3 final
@anchor{whatsnew/changelog c-api}@anchor{ea9}
@subsubsection C API



@itemize -

@item 
bpo-40412@footnote{https://bugs.python.org/issue40412}: Nullify inittab_copy during finalization, preventing future
interpreter initializations in an embedded situation from crashing. Patch
by Gregory Szorc.
@end itemize

@node Python 3 8 3 release candidate 1,Python 3 8 2 正式版,Python 3 8 3 final,更新日志
@anchor{whatsnew/changelog python-3-8-3-release-candidate-1}@anchor{eaa}
@subsection Python 3.8.3 release candidate 1


@emph{发布日期: 2020-04-29}

@menu
* 安全: 安全<4>. 
* 核心与内置: 核心与内置<5>. 
* 库: 库<5>. 
* 文档: 文档<3>. 
* 测试: 测试<2>. 
* 构建: 构建<3>. 
* Windows: Windows<3>. 
* macOS: macOS<2>. 
* IDLE: IDLE<6>. 
* 工具/示例: 工具/示例<2>. 
* C API: C API<2>. 

@end menu

@node 安全<4>,核心与内置<5>,,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id14}@anchor{eab}
@subsubsection 安全



@itemize -

@item 
bpo-40121@footnote{https://bugs.python.org/issue40121}: Fixes audit events raised on creating a new socket.

@item 
bpo-38576@footnote{https://bugs.python.org/issue38576}: Disallow control characters in hostnames in http.client,
addressing CVE-2019-18348. Such potentially malicious header injection
URLs now cause a InvalidURL to be raised.

@item 
bpo-39503@footnote{https://bugs.python.org/issue39503}: CVE-2020-8492: The
@ref{eac,,AbstractBasicAuthHandler} class of the
@ref{120,,urllib.request} module uses an inefficient regular expression which
can be exploited by an attacker to cause a denial of service. Fix the
regex to prevent the catastrophic backtracking. Vulnerability reported by
Ben Caller and Matt Schwager.
@end itemize

@node 核心与内置<5>,库<5>,安全<4>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id15}@anchor{ead}
@subsubsection 核心与内置



@itemize -

@item 
bpo-20526@footnote{https://bugs.python.org/issue20526}: Fix @ref{eae,,PyThreadState_Clear()}. @code{PyThreadState.frame} is
a borrowed reference, not a strong reference: @code{PyThreadState_Clear()}
must not call @code{Py_CLEAR(tstate->frame)}.

@item 
bpo-39965@footnote{https://bugs.python.org/issue39965}: Correctly raise @code{SyntaxError} if @emph{await} is used inside
non-async functions and @code{PyCF_ALLOW_TOP_LEVEL_AWAIT} is set (like in the
asyncio REPL). Patch by Pablo Galindo.

@item 
bpo-39562@footnote{https://bugs.python.org/issue39562}: Allow executing asynchronous comprehensions on the top level
when the @code{PyCF_ALLOW_TOP_LEVEL_AWAIT} flag is given. Patch by Batuhan
Taskaya.

@item 
bpo-38894@footnote{https://bugs.python.org/issue38894}: Fix a bug that was causing incomplete results when calling
@code{pathlib.Path.glob} in the presence of symlinks that point to files
where the user does not have read access. Patch by Pablo Galindo and Matt
Wozniski.

@item 
bpo-39871@footnote{https://bugs.python.org/issue39871}: Fix a possible @ref{5f6,,SystemError} in
@code{math.@{atan2,copysign,remainder@}()} when the first argument cannot be
converted to a @ref{187,,float}. Patch by Zachary Spytz.

@item 
bpo-39776@footnote{https://bugs.python.org/issue39776}: Fix race condition where threads created by PyGILState_Ensure()
could get a duplicate id.

This affects consumers of tstate->id like the contextvar caching
machinery, which could return invalid cached objects under heavy thread
load (observed in embedded scenarios).

@item 
bpo-39778@footnote{https://bugs.python.org/issue39778}: Fixed a crash due to incorrect handling of weak references in
@code{collections.OrderedDict} classes. Patch by Pablo Galindo.

@item 
bpo-39520@footnote{https://bugs.python.org/issue39520}: Fix unparsing of ext slices with no items (@code{foo[:,]}). Patch
by Batuhan Taskaya.

@item 
bpo-22490@footnote{https://bugs.python.org/issue22490}: Don't leak environment variable @code{__PYVENV_LAUNCHER__} into
the interpreter session on macOS.
@end itemize

@node 库<5>,文档<3>,核心与内置<5>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id16}@anchor{eaf}
@subsubsection 库



@itemize -

@item 
bpo-40138@footnote{https://bugs.python.org/issue40138}: Fix the Windows implementation of @ref{667,,os.waitpid()} for exit
code larger than @code{INT_MAX >> 8}. The exit status is now interpreted as
an unsigned number.

@item 
bpo-39942@footnote{https://bugs.python.org/issue39942}: Set "__main__" as the default module name when "__name__" is
missing in @ref{eb0,,typing.TypeVar}. Patch by Weipeng Hong.

@item 
bpo-40330@footnote{https://bugs.python.org/issue40330}: In @code{ShareableList.__setitem__()}, check the size of a new
string item after encoding it to utf-8, not before.

@item 
bpo-40287@footnote{https://bugs.python.org/issue40287}: Fixed @code{SpooledTemporaryFile.seek()} to return the position.

@item 
bpo-40260@footnote{https://bugs.python.org/issue40260}: Ensure @ref{b4,,modulefinder} uses @ref{eb1,,io.open_code()} and
respects coding comments.

@item 
bpo-40196@footnote{https://bugs.python.org/issue40196}: Fix a bug in the @ref{fc,,symtable} module that was causing
incorrectly report global variables as local. Patch by Pablo Galindo.

@item 
bpo-40126@footnote{https://bugs.python.org/issue40126}: Fixed reverting multiple patches in unittest.mock. Patcher's
@code{__exit__()} is now never called if its @code{__enter__()} is failed.
Returning true from @code{__exit__()} silences now the exception.

@item 
bpo-40089@footnote{https://bugs.python.org/issue40089}: Fix threading._after_fork(): if fork was not called by a thread
spawned by threading.Thread, threading._after_fork() now creates a
_MainThread instance for _main_thread, instead of a _DummyThread instance.

@item 
bpo-39503@footnote{https://bugs.python.org/issue39503}: @ref{eac,,AbstractBasicAuthHandler} of
@ref{120,,urllib.request} now parses all WWW-Authenticate HTTP headers and
accepts multiple challenges per header: use the realm of the first Basic
challenge.

@item 
bpo-40014@footnote{https://bugs.python.org/issue40014}: Fix @code{os.getgrouplist()}: if @code{getgrouplist()} function fails
because the group list is too small, retry with a larger group list. On
failure, the glibc implementation of @code{getgrouplist()} sets @code{ngroups}
to the total number of groups. For other implementations, double the group
list size.

@item 
bpo-40016@footnote{https://bugs.python.org/issue40016}: In re docstring, clarify the relationship between inline and
argument compile flags.

@item 
bpo-39953@footnote{https://bugs.python.org/issue39953}: Update internal table of OpenSSL error codes in the @code{ssl}
module.

@item 
bpo-39360@footnote{https://bugs.python.org/issue39360}: Ensure all workers exit when finalizing a
@code{multiprocessing.Pool} implicitly via the module finalization
handlers of multiprocessing. This fixes a deadlock situation that can be
experienced when the Pool is not properly finalized via the context
manager or a call to @code{multiprocessing.Pool.terminate}. Patch by Batuhan
Taskaya and Pablo Galindo.

@item 
bpo-39652@footnote{https://bugs.python.org/issue39652}: The column name found in @code{sqlite3.Cursor.description} is now
truncated on the first '[' only if the PARSE_COLNAMES option is set.

@item 
bpo-39915@footnote{https://bugs.python.org/issue39915}: Ensure @ref{eb2,,unittest.mock.AsyncMock.await_args_list} has call
objects in the order of awaited arguments instead of using
@ref{eb3,,unittest.mock.Mock.call_args} which has the last value of the call.
Patch by Karthikeyan Singaravelan.

@item 
bpo-38662@footnote{https://bugs.python.org/issue38662}: The @code{ensurepip} module now invokes @code{pip} via the @code{runpy}
module. Hence it is no longer tightly coupled with the internal API of the
bundled @code{pip} version, allowing easier updates to a newer @code{pip}
version both internally and for distributors.

@item 
bpo-39916@footnote{https://bugs.python.org/issue39916}: More reliable use of @code{os.scandir()} in @code{Path.glob()}. It no
longer emits a ResourceWarning when interrupted.

@item 
bpo-39850@footnote{https://bugs.python.org/issue39850}: @ref{b7,,multiprocessing} now supports abstract socket addresses
(if abstract sockets are supported in the running platform). Patch by
Pablo Galindo.

@item 
bpo-39828@footnote{https://bugs.python.org/issue39828}: Fix @ref{a5,,json.tool} to catch @ref{997,,BrokenPipeError}. Patch by
Dong-hee Na.

@item 
bpo-13487@footnote{https://bugs.python.org/issue13487}: Avoid a possible @emph{"RuntimeError: dictionary changed size during
iteration"} from @ref{eb4,,inspect.getmodule()} when it tried to loop through
@ref{eb5,,sys.modules}.

@item 
bpo-39794@footnote{https://bugs.python.org/issue39794}: Add --without-decimal-contextvar build option.  This enables a
thread-local rather than a coroutine local context.

@item 
bpo-39769@footnote{https://bugs.python.org/issue39769}: The @ref{36b,,compileall.compile_dir()} function's @emph{ddir} parameter
and the compileall command line flag @code{-d} no longer write the wrong
pathname to the generated pyc file for submodules beneath the root of the
directory tree being compiled.  This fixes a regression introduced with
Python 3.5.

@item 
bpo-39517@footnote{https://bugs.python.org/issue39517}: Fix runpy.run_path() when using pathlike objects

@item 
bpo-39764@footnote{https://bugs.python.org/issue39764}: Fix AttributeError when calling get_stack on a PyAsyncGenObject
Task

@item 
bpo-30566@footnote{https://bugs.python.org/issue30566}: Fix @ref{e6e,,IndexError} when trying to decode an invalid string
with punycode codec.

@item 
bpo-39667@footnote{https://bugs.python.org/issue39667}: Correct performance degradation in @code{zipfile.Path} as found in
zipp 3.0. While retaining compatibility, this change discourages the use
of @code{zipfile.Path.open} due to the signature change in Python 3.9. For
compatibility across Python 3.8 and later versions, consider using
@code{zipp.Path} on Python 3.8.x and earlier.

@item 
bpo-39548@footnote{https://bugs.python.org/issue39548}: Fix handling of header in
@ref{eb6,,urllib.request.AbstractDigestAuthHandler} when the optional
@code{qop} parameter is not present.

@item 
bpo-38971@footnote{https://bugs.python.org/issue38971}: Open issue in the BPO indicated a desire to make the
implementation of codecs.open() at parity with io.open(), which implements
a try/except to assure file stream gets closed before an exception is
raised.

@item 
bpo-38410@footnote{https://bugs.python.org/issue38410}: Properly handle @ref{eb7,,sys.audit()} failures in
@ref{eb8,,sys.set_asyncgen_hooks()}. Based on patch by Zackery Spytz.

@item 
bpo-36541@footnote{https://bugs.python.org/issue36541}: lib2to3 now recognizes named assignment expressions (the walrus
operator, @code{:=})

@item 
bpo-31758@footnote{https://bugs.python.org/issue31758}: Prevent crashes when using an uninitialized
@code{_elementtree.XMLParser} object. Patch by Oren Milman.
@end itemize

@node 文档<3>,测试<2>,库<5>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id17}@anchor{eb9}
@subsubsection 文档



@itemize -

@item 
bpo-27635@footnote{https://bugs.python.org/issue27635}: The pickle documentation incorrectly claimed that @code{__new__}
isn't called by default when unpickling.

@item 
bpo-39879@footnote{https://bugs.python.org/issue39879}: Updated @ref{eba,,数据模型} docs to include @ref{1b8,,dict()} insertion
order preservation. Patch by Furkan Onder and Samy Lahfa.

@item 
bpo-39868@footnote{https://bugs.python.org/issue39868}: Updated the Language Reference for 
@geindex Python 提高建议; PEP 572
PEP 572@footnote{https://www.python.org/dev/peps/pep-0572}.

@item 
bpo-13790@footnote{https://bugs.python.org/issue13790}: Change 'string' to 'specification' in format doc.

@item 
bpo-17422@footnote{https://bugs.python.org/issue17422}: The language reference no longer restricts default class
namespaces to dicts only.

@item 
bpo-39530@footnote{https://bugs.python.org/issue39530}: Fix misleading documentation about mixed-type numeric
comparisons.

@item 
bpo-39718@footnote{https://bugs.python.org/issue39718}: Update @ref{110,,token} documentation to reflect additions in
Python 3.8

@item 
bpo-39677@footnote{https://bugs.python.org/issue39677}: Changed operand name of @strong{MAKE_FUNCTION} from @emph{argc} to
@emph{flags} for module @ref{38,,dis}

@item 
bpo-38387@footnote{https://bugs.python.org/issue38387}: Document @ref{ebb,,PyDoc_STRVAR} macro in the C-API reference.
@end itemize

@node 测试<2>,构建<3>,文档<3>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id18}@anchor{ebc}
@subsubsection 测试



@itemize -

@item 
bpo-40436@footnote{https://bugs.python.org/issue40436}: test_gdb and test.pythoninfo now check gdb command exit code.

@item 
bpo-40162@footnote{https://bugs.python.org/issue40162}: Update Travis CI configuration to OpenSSL 1.1.1f.

@item 
bpo-40146@footnote{https://bugs.python.org/issue40146}: Update OpenSSL to 1.1.1f in Azure Pipelines.

@item 
bpo-40019@footnote{https://bugs.python.org/issue40019}: test_gdb now skips tests if it detects that gdb failed to read
debug information because the Python binary is optimized.

@item 
bpo-27807@footnote{https://bugs.python.org/issue27807}: @code{test_site.test_startup_imports()} is now skipped if a path
of @ref{482,,sys.path} contains a @code{.pth} file.

@item 
bpo-39793@footnote{https://bugs.python.org/issue39793}: Use the same domain when testing @code{make_msgid}. Patch by
Batuhan Taskaya.

@item 
bpo-1812@footnote{https://bugs.python.org/issue1812}: Fix newline handling in doctest.testfile when loading from a
package whose loader has a get_data method. Patch by Peter Donis.

@item 
bpo-37957@footnote{https://bugs.python.org/issue37957}: test.regrtest now can receive a list of test patterns to ignore
(using the -i/--ignore argument) or a file with a list of patterns to
ignore (using the --ignore-file argument). Patch by Pablo Galindo.

@item 
bpo-38502@footnote{https://bugs.python.org/issue38502}: test.regrtest now uses process groups in the multiprocessing
mode (-jN command line option) if process groups are available: if
@ref{ebd,,os.setsid()} and @ref{ebe,,os.killpg()} functions are available.
@end itemize

@node 构建<3>,Windows<3>,测试<2>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id19}@anchor{ebf}
@subsubsection 构建



@itemize -

@item 
bpo-38360@footnote{https://bugs.python.org/issue38360}: Support single-argument form of macOS -isysroot flag.

@item 
bpo-40204@footnote{https://bugs.python.org/issue40204}: Pin Sphinx version to 1.8.2 in @code{Doc/Makefile}.

@item 
bpo-40158@footnote{https://bugs.python.org/issue40158}: Fix CPython MSBuild Properties in NuGet Package
(build/native/python.props)

@item 
bpo-38527@footnote{https://bugs.python.org/issue38527}: Fix configure check on Solaris for "float word ordering":
sometimes, the correct "grep" command was not being used. Patch by Arnon
Yaari.
@end itemize

@node Windows<3>,macOS<2>,构建<3>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id20}@anchor{ec0}
@subsubsection Windows



@itemize -

@item 
bpo-40164@footnote{https://bugs.python.org/issue40164}: Updates Windows to OpenSSL 1.1.1f

@item 
bpo-39930@footnote{https://bugs.python.org/issue39930}: Ensures the required @code{vcruntime140.dll} is included in
install packages.

@item 
bpo-39847@footnote{https://bugs.python.org/issue39847}: Avoid hang when computer is hibernated whilst waiting for a
mutex (for lock-related objects from @ref{109,,threading}) around 49-day
uptime.

@item 
bpo-38597@footnote{https://bugs.python.org/issue38597}: @ref{39,,distutils} will no longer statically link
@code{vcruntime140.dll} when a redistributable version is unavailable.
All future releases of CPython will include a copy of this DLL to ensure
distributed extensions can continue to load.

@item 
bpo-38380@footnote{https://bugs.python.org/issue38380}: Update Windows builds to use SQLite 3.31.1

@item 
bpo-39789@footnote{https://bugs.python.org/issue39789}: Update Windows release build machines to Visual Studio 2019
(MSVC 14.2).

@item 
bpo-34803@footnote{https://bugs.python.org/issue34803}: Package for nuget.org now includes repository reference and
bundled icon image.
@end itemize

@node macOS<2>,IDLE<6>,Windows<3>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id21}@anchor{ec1}
@subsubsection macOS



@itemize -

@item 
bpo-40164@footnote{https://bugs.python.org/issue40164}: Update macOS installer builds to use OpenSSL 1.1.1g.

@item 
bpo-38380@footnote{https://bugs.python.org/issue38380}: Update macOS builds to use SQLite 3.31.1
@end itemize

@node IDLE<6>,工具/示例<2>,macOS<2>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id22}@anchor{ec2}
@subsubsection IDLE



@itemize -

@item 
bpo-27115@footnote{https://bugs.python.org/issue27115}: For 'Go to Line', use a Query box subclass with IDLE standard
behavior and improved error checking.

@item 
bpo-39885@footnote{https://bugs.python.org/issue39885}: Since clicking to get an IDLE context menu moves the cursor,
any text selection should be and now is cleared.

@item 
bpo-39852@footnote{https://bugs.python.org/issue39852}: Edit "Go to line" now clears any selection, preventing
accidental deletion. It also updates Ln and Col on the status bar.

@item 
bpo-39781@footnote{https://bugs.python.org/issue39781}: Selecting code context lines no longer causes a jump.

@item 
bpo-38439@footnote{https://bugs.python.org/issue38439}: Add a 256×256 pixel IDLE icon to support more modern
environments. Created by Andrew Clover. Delete the unused macOS idle.icns
icon file.

@item 
bpo-38689@footnote{https://bugs.python.org/issue38689}: IDLE will no longer freeze when inspect.signature fails when
fetching a calltip.
@end itemize

@node 工具/示例<2>,C API<2>,IDLE<6>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id23}@anchor{ec3}
@subsubsection 工具/示例



@itemize -

@item 
bpo-40179@footnote{https://bugs.python.org/issue40179}: Fixed translation of @code{#elif} in Argument Clinic.

@item 
bpo-36184@footnote{https://bugs.python.org/issue36184}: Port python-gdb.py to FreeBSD. python-gdb.py now checks for
"take_gil" function name to check if a frame tries to acquire the GIL,
instead of checking for "pthread_cond_timedwait" which is specific to
Linux and can be a different condition than the GIL.

@item 
bpo-39889@footnote{https://bugs.python.org/issue39889}: Fixed @code{unparse.py} for extended slices containing a single
element (e.g. @code{a[i:j,]}). Remove redundant tuples when index with a
tuple (e.g. @code{a[i, j]}).
@end itemize

@node C API<2>,,工具/示例<2>,Python 3 8 3 release candidate 1
@anchor{whatsnew/changelog id24}@anchor{ec4}
@subsubsection C API



@itemize -

@item 
bpo-35370@footnote{https://bugs.python.org/issue35370}: If @ref{ec5,,PySys_Audit()} fails in @ref{e34,,PyEval_SetProfile()}
or @ref{e35,,PyEval_SetTrace()}, log the error as an unraisable exception.

@item 
bpo-39884@footnote{https://bugs.python.org/issue39884}: @ref{ec6,,PyDescr_NewMethod()} and @code{PyCFunction_NewEx()} now
include the method name in the SystemError "bad call flags" error message
to ease debug.

@item 
bpo-38643@footnote{https://bugs.python.org/issue38643}: @ref{ec7,,PyNumber_ToBase()} now raises a @ref{5f6,,SystemError}
instead of crashing when called with invalid base.

@item 
bpo-38913@footnote{https://bugs.python.org/issue38913}: Fixed segfault in @code{Py_BuildValue()} called with a format
containing "#" and undefined PY_SSIZE_T_CLEAN whwn an exception is set.
@end itemize

@node Python 3 8 2 正式版,Python 3 8 2 rc2,Python 3 8 3 release candidate 1,更新日志
@anchor{whatsnew/changelog python-3-8-2-final}@anchor{ec8}
@subsection Python 3.8.2 正式版


@emph{发布日期: 2020-02-24}

@menu
* 核心与内置: 核心与内置<6>. 
* 库: 库<6>. 
* 文档: 文档<4>. 
* IDLE: IDLE<7>. 

@end menu

@node 核心与内置<6>,库<6>,,Python 3 8 2 正式版
@anchor{whatsnew/changelog id25}@anchor{ec9}
@subsubsection 核心与内置



@itemize -

@item 
bpo-39382@footnote{https://bugs.python.org/issue39382}: Fix a use-after-free in the single inheritance path of
@code{issubclass()}, when the @code{__bases__} of an object has a single
reference, and so does its first item. Patch by Yonatan Goldschmidt.

@item 
bpo-39427@footnote{https://bugs.python.org/issue39427}: Document all possibilities for the @code{-X} options in the
command line help section. Patch by Pablo Galindo.
@end itemize

@node 库<6>,文档<4>,核心与内置<6>,Python 3 8 2 正式版
@anchor{whatsnew/changelog id26}@anchor{eca}
@subsubsection 库



@itemize -

@item 
bpo-39649@footnote{https://bugs.python.org/issue39649}: Remove obsolete check for @code{__args__} in
bdb.Bdb.format_stack_entry.

@item 
bpo-39681@footnote{https://bugs.python.org/issue39681}: Fix a regression where the C pickle module wouldn't allow
unpickling from a file-like object that doesn't expose a readinto()
method.

@item 
bpo-39546@footnote{https://bugs.python.org/issue39546}: Fix a regression in @ref{68f,,ArgumentParser} where
@code{allow_abbrev=False} was ignored for long options that used a prefix
character other than "-".

@item 
bpo-39432@footnote{https://bugs.python.org/issue39432}: Implement PEP-489 algorithm for non-ascii "PyInit_..." symbol
names in distutils to make it export the correct init symbol also on
Windows.
@end itemize

@node 文档<4>,IDLE<7>,库<6>,Python 3 8 2 正式版
@anchor{whatsnew/changelog id27}@anchor{ecb}
@subsubsection 文档



@itemize -

@item 
bpo-17422@footnote{https://bugs.python.org/issue17422}: The language reference now specifies restrictions on class
namespaces. Adapted from a patch by Ethan Furman.

@item 
bpo-39572@footnote{https://bugs.python.org/issue39572}: Updated documentation of @code{total} flag of TypeDict.

@item 
bpo-39654@footnote{https://bugs.python.org/issue39654}: In pyclbr doc, update 'class' to 'module' where appropriate and
add readmodule comment. Patch by Hakan Çelik.
@end itemize

@node IDLE<7>,,文档<4>,Python 3 8 2 正式版
@anchor{whatsnew/changelog id28}@anchor{ecc}
@subsubsection IDLE



@itemize -

@item 
bpo-39663@footnote{https://bugs.python.org/issue39663}: Add tests for pyparse find_good_parse_start().
@end itemize

@node Python 3 8 2 rc2,Python 3 8 2 rc1,Python 3 8 2 正式版,更新日志
@anchor{whatsnew/changelog python-3-8-2-release-candidate-2}@anchor{ecd}
@subsection Python 3.8.2 rc2


@emph{发布日期:: 2020-02-17}

@menu
* 安全: 安全<5>. 
* 核心与内置: 核心与内置<7>. 
* 库: 库<7>. 
* IDLE: IDLE<8>. 

@end menu

@node 安全<5>,核心与内置<7>,,Python 3 8 2 rc2
@anchor{whatsnew/changelog id29}@anchor{ece}
@subsubsection 安全



@itemize -

@item 
bpo-39184@footnote{https://bugs.python.org/issue39184}: Add audit events to functions in @ref{7e,,fcntl}, @ref{b6,,msvcrt}, @ref{c4,,os},
@ref{e0,,resource}, @ref{e9,,shutil}, @ref{ea,,signal} and @ref{ff,,syslog}.
@end itemize

@node 核心与内置<7>,库<7>,安全<5>,Python 3 8 2 rc2
@anchor{whatsnew/changelog id30}@anchor{ecf}
@subsubsection 核心与内置



@itemize -

@item 
bpo-39619@footnote{https://bugs.python.org/issue39619}: Enable use of @ref{ed0,,os.chroot()} on HP-UX systems.

@item 
bpo-39606@footnote{https://bugs.python.org/issue39606}: Fix regression caused by fix for bpo-39386@footnote{https://bugs.python.org/issue39386}, that prevented
calling @code{aclose} on an async generator that had already been closed or
exhausted.

@item 
bpo-39453@footnote{https://bugs.python.org/issue39453}: Fixed a possible crash in @code{list.__contains__()} when a list
is changed during comparing items. Patch by Dong-hee Na.

@item 
bpo-39219@footnote{https://bugs.python.org/issue39219}: Syntax errors raised in the tokenizer now always set correct
"text" and "offset" attributes.
@end itemize

@node 库<7>,IDLE<8>,核心与内置<7>,Python 3 8 2 rc2
@anchor{whatsnew/changelog id31}@anchor{ed1}
@subsubsection 库



@itemize -

@item 
bpo-27657@footnote{https://bugs.python.org/issue27657}: The original fix for bpo-27657@footnote{https://bugs.python.org/issue27657}, "Fix urlparse() with numeric
paths" (GH-16839) included in 3.8.1, inadvertently introduced a behavior
change that broke several third-party packages relying on the original
undefined parsing behavior. The change is reverted in 3.8.2, restoring the
behavior of 3.8.0 and earlier releases.

@item 
bpo-39474@footnote{https://bugs.python.org/issue39474}: Fixed starting position of AST for expressions like @code{(a)(b)},
@code{(a)[b]} and @code{(a).b}.

@item 
bpo-21016@footnote{https://bugs.python.org/issue21016}: The @ref{d9,,pydoc} and @ref{112,,trace} modules now use the
@ref{fe,,sysconfig} module to get the path to the Python standard library, to
support uncommon installation path like @code{/usr/lib64/python3.9/} on
Fedora. Patch by Jan Matějek.

@item 
bpo-39595@footnote{https://bugs.python.org/issue39595}: Improved performance of zipfile.Path for files with a large
number of entries. Also improved performance and fixed minor issue as
published with importlib_metadata 1.5@footnote{https://importlib-metadata.readthedocs.io/en/latest/changelog%20(links).html#v1-5-0}.
@end itemize

@node IDLE<8>,,库<7>,Python 3 8 2 rc2
@anchor{whatsnew/changelog id32}@anchor{ed2}
@subsubsection IDLE



@itemize -

@item 
bpo-39600@footnote{https://bugs.python.org/issue39600}: In the font configuration window, remove duplicated font names.
@end itemize

@node Python 3 8 2 rc1,Python 3 8 1 正式版,Python 3 8 2 rc2,更新日志
@anchor{whatsnew/changelog python-3-8-2-release-candidate-1}@anchor{ed3}
@subsection Python 3.8.2 rc1


@emph{发布日期:: 2020-02-10}

@menu
* 安全: 安全<6>. 
* 核心与内置: 核心与内置<8>. 
* 库: 库<8>. 
* 文档: 文档<5>. 
* 测试: 测试<3>. 
* 构建: 构建<4>. 
* Windows: Windows<4>. 
* IDLE: IDLE<9>. 

@end menu

@node 安全<6>,核心与内置<8>,,Python 3 8 2 rc1
@anchor{whatsnew/changelog id33}@anchor{ed4}
@subsubsection 安全



@itemize -

@item 
bpo-39401@footnote{https://bugs.python.org/issue39401}: Avoid unsafe load of @code{api-ms-win-core-path-l1-1-0.dll} at
startup on Windows 7.

@item 
bpo-39184@footnote{https://bugs.python.org/issue39184}: Add audit events to command execution functions in os and pty
modules.
@end itemize

@node 核心与内置<8>,库<8>,安全<6>,Python 3 8 2 rc1
@anchor{whatsnew/changelog id34}@anchor{ed5}
@subsubsection 核心与内置



@itemize -

@item 
bpo-39579@footnote{https://bugs.python.org/issue39579}: Change the ending column offset of @code{Attribute} nodes
constructed in @code{ast_for_dotted_name} to point at the end of the current
node and not at the end of the last @code{NAME} node.

@item 
bpo-39510@footnote{https://bugs.python.org/issue39510}: Fix segfault in @code{readinto()} method on closed BufferedReader.

@item 
bpo-39492@footnote{https://bugs.python.org/issue39492}: Fix a reference cycle in the C Pickler that was preventing the
garbage collection of deleted, pickled objects.

@item 
bpo-39421@footnote{https://bugs.python.org/issue39421}: Fix possible crashes when operating with the functions in the
@ref{8e,,heapq} module and custom comparison operators.

@item 
bpo-39386@footnote{https://bugs.python.org/issue39386}: Prevent double awaiting of async iterator.

@item 
bpo-39235@footnote{https://bugs.python.org/issue39235}: Fix AST end location for lone generator expression in function
call, e.g. f(i for i in a).

@item 
bpo-39209@footnote{https://bugs.python.org/issue39209}: Correctly handle multi-line tokens in interactive mode. Patch
by Pablo Galindo.

@item 
bpo-39216@footnote{https://bugs.python.org/issue39216}: Fix constant folding optimization for positional only arguments
- by Anthony Sottile.

@item 
bpo-39215@footnote{https://bugs.python.org/issue39215}: Fix @code{SystemError} when nested function has annotation on
positional-only argument - by Anthony Sottile.

@item 
bpo-38588@footnote{https://bugs.python.org/issue38588}: Fix possible crashes in dict and list when calling
@ref{ed6,,PyObject_RichCompareBool()}.

@item 
bpo-38610@footnote{https://bugs.python.org/issue38610}: Fix possible crashes in several list methods by holding strong
references to list elements when calling
@ref{ed6,,PyObject_RichCompareBool()}.
@end itemize

@node 库<8>,文档<5>,核心与内置<8>,Python 3 8 2 rc1
@anchor{whatsnew/changelog id35}@anchor{ed7}
@subsubsection 库



@itemize -

@item 
bpo-39590@footnote{https://bugs.python.org/issue39590}: Collections.deque now holds strong references during
deque.__contains__ and deque.count, fixing crashes.

@item 
bpo-38149@footnote{https://bugs.python.org/issue38149}: @ref{eb7,,sys.audit()} is now called only once per call of
@ref{5c1,,glob.glob()} and @ref{5c2,,glob.iglob()}.

@item 
bpo-39450@footnote{https://bugs.python.org/issue39450}: Striped whitespace from docstring before returning it from
@code{unittest.case.shortDescription()}.

@item 
bpo-39493@footnote{https://bugs.python.org/issue39493}: Mark @code{typing.IO.closed} as a property

@item 
bpo-39485@footnote{https://bugs.python.org/issue39485}: Fix a bug in @ref{ed8,,unittest.mock.create_autospec()} that would
complain about the wrong number of arguments for custom descriptors
defined in an extension module returning functions.

@item 
bpo-39082@footnote{https://bugs.python.org/issue39082}: Allow AsyncMock to correctly patch static/class methods

@item 
bpo-39430@footnote{https://bugs.python.org/issue39430}: Fixed race condition in lazy imports in @ref{101,,tarfile}.

@item 
bpo-39390@footnote{https://bugs.python.org/issue39390}: Fixed a regression with the @code{ignore} callback of
@ref{21a,,shutil.copytree()}. The argument types are now str and List[str]
again.

@item 
bpo-39389@footnote{https://bugs.python.org/issue39389}: Write accurate compression level metadata in @ref{8c,,gzip}
archives, rather than always signaling maximum compression.

@item 
bpo-39274@footnote{https://bugs.python.org/issue39274}: @code{bool(fraction.Fraction)} now returns a boolean even if
(numerator != 0) does not return a boolean (ex: numpy number).

@item 
bpo-39297@footnote{https://bugs.python.org/issue39297}: Improved performance of importlib.metadata distribution
discovery and resilients to inaccessible sys.path entries
(importlib_metadata v1.4.0).

@item 
bpo-39242@footnote{https://bugs.python.org/issue39242}: Updated the Gmane domain from news.gmane.org to news.gmane.io
which is used for examples of @ref{a27,,NNTP} news reader server
and nntplib tests.

@item 
bpo-38907@footnote{https://bugs.python.org/issue38907}: In http.server script, restore binding to IPv4 on Windows.

@item 
bpo-39152@footnote{https://bugs.python.org/issue39152}: Fix ttk.Scale.configure([name]) to return configuration tuple
for name or all options.  Giovanni Lombardo contributed part of the patch.

@item 
bpo-39198@footnote{https://bugs.python.org/issue39198}: If an exception were to be thrown in @code{Logger.isEnabledFor}
(say, by asyncio timeouts or stopit) , the @ref{aa,,logging} global lock may not
be released appropriately, resulting in deadlock.  This change wraps that
block of code with @code{try...finally} to ensure the lock is released.

@item 
bpo-39191@footnote{https://bugs.python.org/issue39191}: Perform a check for running loop before starting a new task in
@code{loop.run_until_complete()} to fail fast; it prevents the side effect of
new task spawning before exception raising.

@item 
bpo-38871@footnote{https://bugs.python.org/issue38871}: Correctly parenthesize filter-based statements that contain
lambda expressions in mod:@ref{a7,,lib2to3}. Patch by Dong-hee Na.

@item 
bpo-39142@footnote{https://bugs.python.org/issue39142}: A change was made to logging.config.dictConfig to avoid
converting instances of named tuples to ConvertingTuple. It's assumed that
named tuples are too specialised to be treated like ordinary tuples; if a
user of named tuples requires ConvertingTuple functionality, they will
have to implement that themselves in their named tuple class.

@item 
bpo-39129@footnote{https://bugs.python.org/issue39129}: Fix import path for @code{asyncio.TimeoutError}

@item 
bpo-39057@footnote{https://bugs.python.org/issue39057}: @code{urllib.request.proxy_bypass_environment()} now ignores
leading dots and no longer ignores a trailing newline.

@item 
bpo-39056@footnote{https://bugs.python.org/issue39056}: Fixed handling invalid warning category in the -W option.  No
longer import the re module if it is not needed.

@item 
bpo-39055@footnote{https://bugs.python.org/issue39055}: @ref{ed9,,base64.b64decode()} with @code{validate=True} raises now a
binascii.Error if the input ends with a single @code{\n}.

@item 
bpo-39033@footnote{https://bugs.python.org/issue39033}: Fix @ref{d74,,NameError} in @ref{143,,zipimport}. Patch by Karthikeyan
Singaravelan.

@item 
bpo-38878@footnote{https://bugs.python.org/issue38878}: Fixed __subclasshook__ of @ref{4e5,,os.PathLike} to return a
correct result upon inheritence. Patch by Bar Harel.

@item 
bpo-35182@footnote{https://bugs.python.org/issue35182}: Fixed @code{Popen.communicate()} subsequent call crash when the
child process has already closed any piped standard stream, but still
continues to be running. Patch by Andriy Maletsky.

@item 
bpo-38473@footnote{https://bugs.python.org/issue38473}: Use signature from inner mock for autospecced methods attached
with @code{unittest.mock.attach_mock()}. Patch by Karthikeyan Singaravelan.

@item 
bpo-38293@footnote{https://bugs.python.org/issue38293}: Add @ref{3c3,,copy.copy()} and @ref{3c4,,copy.deepcopy()} support to
@ref{1d7,,property()} objects.
@end itemize

@node 文档<5>,测试<3>,库<8>,Python 3 8 2 rc1
@anchor{whatsnew/changelog id36}@anchor{eda}
@subsubsection 文档



@itemize -

@item 
bpo-39153@footnote{https://bugs.python.org/issue39153}: Clarify refcounting semantics for the following functions: -
PyObject_SetItem - PyMapping_SetItemString - PyDict_SetItem -
PyDict_SetItemString

@item 
bpo-39392@footnote{https://bugs.python.org/issue39392}: Explain that when filling with turtle, overlap regions may be
left unfilled.

@item 
bpo-39381@footnote{https://bugs.python.org/issue39381}: Mention in docs that @ref{34e,,asyncio.get_event_loop()} implicitly
creates new event loop only if called from the main thread.

@item 
bpo-38918@footnote{https://bugs.python.org/issue38918}: Add an entry for @code{__module__} in the "function" & "method"
sections of the inspect docs types and members table@footnote{https://docs.python.org/3/library/inspect.html#types-and-members}

@item 
bpo-3530@footnote{https://bugs.python.org/issue3530}: In the @ref{8,,ast} module documentation, fix a misleading
@code{NodeTransformer} example and add advice on when to use the
@code{fix_missing_locations} function.
@end itemize

@node 测试<3>,构建<4>,文档<5>,Python 3 8 2 rc1
@anchor{whatsnew/changelog id37}@anchor{edb}
@subsubsection 测试



@itemize -

@item 
bpo-39502@footnote{https://bugs.python.org/issue39502}: Skip test_zipfile.test_add_file_after_2107() if
@ref{edc,,time.localtime()} fails with @ref{95a,,OverflowError}. It is the case on
AIX 6.1 for example.

@item 
bpo-38546@footnote{https://bugs.python.org/issue38546}: Fix test_ressources_gced_in_workers() of
test_concurrent_futures: explicitly stop the manager to prevent leaking a
child process running in the background after the test completes.
@end itemize

@node 构建<4>,Windows<4>,测试<3>,Python 3 8 2 rc1
@anchor{whatsnew/changelog id38}@anchor{edd}
@subsubsection 构建



@itemize -

@item 
bpo-39144@footnote{https://bugs.python.org/issue39144}: The ctags and etags build targets both include Modules/_ctypes
and Python standard library source files.
@end itemize

@node Windows<4>,IDLE<9>,构建<4>,Python 3 8 2 rc1
@anchor{whatsnew/changelog id39}@anchor{ede}
@subsubsection Windows



@itemize -

@item 
bpo-39439@footnote{https://bugs.python.org/issue39439}: Honor the Python path when a virtualenv is active on Windows.

@item 
bpo-39393@footnote{https://bugs.python.org/issue39393}: Improve the error message when attempting to load a DLL with
unresolved dependencies.

@item 
bpo-38883@footnote{https://bugs.python.org/issue38883}: @ref{725,,home()} and
@ref{724,,expanduser()} on Windows now prefer
@geindex USERPROFILE
@geindex 环境变量; USERPROFILE
@code{USERPROFILE} and no longer use 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME}, which is not
normally set for regular user accounts. This makes them again behave like
@ref{1fe,,os.path.expanduser()}, which was changed to ignore 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME} in
3.8, see bpo-36264@footnote{https://bugs.python.org/issue36264}.

@item 
bpo-39185@footnote{https://bugs.python.org/issue39185}: The build.bat script has additional options for very-quiet
output (-q) and very-verbose output (-vv)
@end itemize

@node IDLE<9>,,Windows<4>,Python 3 8 2 rc1
@anchor{whatsnew/changelog id40}@anchor{edf}
@subsubsection IDLE



@itemize -

@item 
bpo-30780@footnote{https://bugs.python.org/issue30780}: Add remaining configdialog tests for buttons and highlights and
keys tabs.

@item 
bpo-39388@footnote{https://bugs.python.org/issue39388}: IDLE Settings Cancel button now cancels pending changes

@item 
bpo-39050@footnote{https://bugs.python.org/issue39050}: Make IDLE Settings dialog Help button work again.

@item 
bpo-34118@footnote{https://bugs.python.org/issue34118}: Tag memoryview, range, and tuple as classes, the same as list,
etcetera, in the library manual built-in functions list.

@item 
bpo-38792@footnote{https://bugs.python.org/issue38792}: Close an IDLE shell calltip if a @ref{197,,KeyboardInterrupt} or
shell restart occurs.  Patch by Zackery Spytz.

@item 
bpo-32989@footnote{https://bugs.python.org/issue32989}: Add tests for editor newline_and_indent_event method. Remove
dead code from pyparse find_good_parse_start method.
@end itemize

@node Python 3 8 1 正式版,Python 3 8 1 rc1,Python 3 8 2 rc1,更新日志
@anchor{whatsnew/changelog python-3-8-1-final}@anchor{ee0}
@subsection Python 3.8.1 正式版


@emph{发布日期: 2019-12-18}

@menu
* 核心与内置: 核心与内置<9>. 
* 库: 库<9>. 
* 测试: 测试<4>. 
* Windows: Windows<5>. 
* macOS: macOS<3>. 
* IDLE: IDLE<10>. 

@end menu

@node 核心与内置<9>,库<9>,,Python 3 8 1 正式版
@anchor{whatsnew/changelog id41}@anchor{ee1}
@subsubsection 核心与内置



@itemize -

@item 
bpo-39080@footnote{https://bugs.python.org/issue39080}: Fix the value of @emph{end_col_offset} for Starred Expression AST
nodes when they are among the elements in the @emph{args} attribute of Call AST
nodes.

@item 
bpo-39031@footnote{https://bugs.python.org/issue39031}: When parsing an "elif" node, lineno and col_offset of the node
now point to the "elif" keyword and not to its condition, making it
consistent with the "if" node. Patch by Lysandros Nikolaou.

@item 
bpo-39008@footnote{https://bugs.python.org/issue39008}: @ref{ec5,,PySys_Audit()} now requires @code{Py_ssize_t} to be used
for size arguments in the format string, regardless of whether
@code{PY_SSIZE_T_CLEAN} was defined at include time.
@end itemize

@node 库<9>,测试<4>,核心与内置<9>,Python 3 8 1 正式版
@anchor{whatsnew/changelog id42}@anchor{ee2}
@subsubsection 库



@itemize -

@item 
bpo-39022@footnote{https://bugs.python.org/issue39022}: Update importlib.metadata to include improvements from
importlib_metadata 1.3 including better serialization of EntryPoints and
improved documentation for custom finders.

@item 
bpo-38811@footnote{https://bugs.python.org/issue38811}: Fix an unhandled exception in @ref{c8,,pathlib} when
@ref{a30,,os.link()} is missing. Patch by Toke Høiland-Jørgensen.

@item 
bpo-36406@footnote{https://bugs.python.org/issue36406}: Handle namespace packages in @ref{67,,doctest}. Patch by
Karthikeyan Singaravelan.
@end itemize

@node 测试<4>,Windows<5>,库<9>,Python 3 8 1 正式版
@anchor{whatsnew/changelog id43}@anchor{ee3}
@subsubsection 测试



@itemize -

@item 
bpo-38546@footnote{https://bugs.python.org/issue38546}: Multiprocessing and concurrent.futures tests now stop the
resource tracker process when tests complete.
@end itemize

@node Windows<5>,macOS<3>,测试<4>,Python 3 8 1 正式版
@anchor{whatsnew/changelog id44}@anchor{ee4}
@subsubsection Windows



@itemize -

@item 
bpo-39007@footnote{https://bugs.python.org/issue39007}: Add auditing events to functions in @ref{12a,,winreg}.
@end itemize

@node macOS<3>,IDLE<10>,Windows<5>,Python 3 8 1 正式版
@anchor{whatsnew/changelog id45}@anchor{ee5}
@subsubsection macOS



@itemize -

@item 
bpo-38295@footnote{https://bugs.python.org/issue38295}: Prevent failure of test_relative_path in test_py_compile on
macOS Catalina.
@end itemize

@node IDLE<10>,,macOS<3>,Python 3 8 1 正式版
@anchor{whatsnew/changelog id46}@anchor{ee6}
@subsubsection IDLE



@itemize -

@item 
bpo-38944@footnote{https://bugs.python.org/issue38944}: Escape key now closes IDLE completion windows.  Patch by Johnny
Najera.

@item 
bpo-38943@footnote{https://bugs.python.org/issue38943}: Fix IDLE autocomplete windows not always appearing on some
systems. Patch by Johnny Najera.
@end itemize

@node Python 3 8 1 rc1,Python 3 8 0 正式版,Python 3 8 1 正式版,更新日志
@anchor{whatsnew/changelog python-3-8-1-release-candidate-1}@anchor{ee7}
@subsection Python 3.8.1 rc1


@emph{发布日期: 2019-12-09}

@menu
* 安全: 安全<7>. 
* 核心与内置: 核心与内置<10>. 
* 库: 库<10>. 
* 文档: 文档<6>. 
* 测试: 测试<5>. 
* 构建: 构建<5>. 
* Windows: Windows<6>. 
* macOS: macOS<4>. 
* IDLE: IDLE<11>. 
* C API: C API<3>. 

@end menu

@node 安全<7>,核心与内置<10>,,Python 3 8 1 rc1
@anchor{whatsnew/changelog id47}@anchor{ee8}
@subsubsection 安全



@itemize -

@item 
bpo-38945@footnote{https://bugs.python.org/issue38945}: Newline characters have been escaped when performing uu
encoding to prevent them from overflowing into to content section of the
encoded file. This prevents malicious or accidental modification of data
during the decoding process.

@item 
bpo-37228@footnote{https://bugs.python.org/issue37228}: Due to significant security concerns, the @emph{reuse_address}
parameter of @ref{2e7,,asyncio.loop.create_datagram_endpoint()} is no longer
supported. This is because of the behavior of @code{SO_REUSEADDR} in UDP. For
more details, see the documentation for
@code{loop.create_datagram_endpoint()}. (Contributed by Kyle Stanley, Antoine
Pitrou, and Yury Selivanov in bpo-37228@footnote{https://bugs.python.org/issue37228}.)

@item 
bpo-38722@footnote{https://bugs.python.org/issue38722}: @ref{e2,,runpy} now uses @ref{eb1,,io.open_code()} to open code files.
Patch by Jason Killen.

@item 
bpo-38804@footnote{https://bugs.python.org/issue38804}: Fixes a ReDoS vulnerability in @ref{95,,http.cookiejar}. Patch by
Ben Caller.

@item 
bpo-38622@footnote{https://bugs.python.org/issue38622}: Add additional audit events for the @ref{2b,,ctypes} module.

@item 
bpo-38418@footnote{https://bugs.python.org/issue38418}: 修复 @ref{dba,,os.system()} 的审计事件被命名为 @code{os.system} 。
@end itemize

@node 核心与内置<10>,库<10>,安全<7>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id48}@anchor{ee9}
@subsubsection 核心与内置



@itemize -

@item 
bpo-38673@footnote{https://bugs.python.org/issue38673}: In REPL mode, don't switch to PS2 if the line starts with
comment or whitespace. Based on work by Batuhan Taşkaya.

@item 
bpo-38922@footnote{https://bugs.python.org/issue38922}: Calling @code{replace} on a code object now raises the
@code{code.__new__} audit event.

@item 
bpo-38920@footnote{https://bugs.python.org/issue38920}: Add audit hooks for when @ref{e5c,,sys.excepthook()} and
@ref{22d,,sys.unraisablehook()} are invoked

@item 
bpo-38892@footnote{https://bugs.python.org/issue38892}: Improve documentation for audit events table and functions.

@item 
bpo-38707@footnote{https://bugs.python.org/issue38707}: @code{MainThread.native_id} is now correctly reset in child
processes spawned using @ref{3aa,,multiprocessing.Process}, instead of
retaining the parent's value.

@item 
bpo-38640@footnote{https://bugs.python.org/issue38640}: Fixed a bug in the compiler that was causing to raise in the
presence of break statements and continue statements inside always false
while loops. Patch by Pablo Galindo.

@item 
bpo-38535@footnote{https://bugs.python.org/issue38535}: 修复了装饰器中不带参数调用的AST节点的行号和列偏移量。

@item 
bpo-38525@footnote{https://bugs.python.org/issue38525}: 修复了使用空 @code{dict} 对象的反向迭代器时的分段错误。由 Dong-hee Na 和 Inada Naoki 补丁修复

@item 
bpo-35409@footnote{https://bugs.python.org/issue35409}: Ignore GeneratorExit exceptions when throwing an exception into
the aclose coroutine of an asynchronous generator.
@end itemize

@node 库<10>,文档<6>,核心与内置<10>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id49}@anchor{eea}
@subsubsection 库



@itemize -

@item 
bpo-39006@footnote{https://bugs.python.org/issue39006}: Fix asyncio when the ssl module is missing: only check for
ssl.SSLSocket instance if the ssl module is available.

@item 
bpo-38708@footnote{https://bugs.python.org/issue38708}: Fix a potential IndexError in email parser when parsing an
empty msg-id.

@item 
bpo-38698@footnote{https://bugs.python.org/issue38698}: Add a new @code{InvalidMessageID} token to email parser to
represent invalid Message-ID headers.  Also, add defects when there is
remaining value after parsing the header.

@item 
bpo-38979@footnote{https://bugs.python.org/issue38979}: Return class from @code{ContextVar.__class_getitem__} to simplify
subclassing.

@item 
bpo-38986@footnote{https://bugs.python.org/issue38986}: Make repr of C accelerated TaskWakeupMethWrapper the same as of
pure Python version.

@item 
bpo-38529@footnote{https://bugs.python.org/issue38529}: Drop too noisy asyncio warning about deletion of a stream
without explicit @code{.close()} call.

@item 
bpo-38634@footnote{https://bugs.python.org/issue38634}: The @ref{de,,readline} module now detects if Python is linked to
libedit at runtime on all platforms.  Previously, the check was only done
on macOS.

@item 
bpo-33684@footnote{https://bugs.python.org/issue33684}: Fix @code{json.tool} failed to read a JSON file with non-ASCII
characters when locale encoding is not UTF-8.

@item 
bpo-38698@footnote{https://bugs.python.org/issue38698}: Prevent UnboundLocalError to pop up in parse_message_id

parse_message_id() was improperly using a token defined inside an
exception handler, which was raising @ref{e6f,,UnboundLocalError} on parsing an
invalid value. Patch by Claudiu Popa.

@item 
bpo-26730@footnote{https://bugs.python.org/issue26730}: Fix @code{SpooledTemporaryFile.rollover()} might corrupt the file
when it is in text mode. Patch by Serhiy Storchaka.

@item 
bpo-38668@footnote{https://bugs.python.org/issue38668}: Calling func:@ref{21a,,shutil.copytree} to copy a directory tree from
one directory to another subdirectory resulted in an endless loop and a
RecursionError. A fix was added to consume an iterator and create the list
of the entries to be copied, avoiding the recursion for newly created
directories. Patch by Bruno P. Kinoshita.

@item 
bpo-37838@footnote{https://bugs.python.org/issue37838}: @ref{303,,typing.get_type_hints()} properly handles functions
decorated with @ref{864,,functools.wraps()}.

@item 
bpo-38859@footnote{https://bugs.python.org/issue38859}: AsyncMock now returns StopAsyncIteration on the exaustion of a
side_effects iterable. Since PEP-479 its Impossible to raise a
StopIteration exception from a coroutine.

@item 
bpo-38857@footnote{https://bugs.python.org/issue38857}: AsyncMock fix for return values that are awaitable types.  This
also covers side_effect iterable values that happend to be awaitable, and
wraps callables that return an awaitable type. Before these awaitables
were being awaited instead of being returned as is.

@item 
bpo-38821@footnote{https://bugs.python.org/issue38821}: Fix unhandled exceptions in @ref{6,,argparse} when
internationalizing error messages for arguments with @code{nargs} set to
special (non-integer) values. Patch by Federico Bond.

@item 
bpo-38820@footnote{https://bugs.python.org/issue38820}: Make Python compatible with OpenSSL 3.0.0.
@ref{8cb,,ssl.SSLSocket.getpeercert()} no longer returns IPv6 addresses with a
trailing new line.

@item 
bpo-38807@footnote{https://bugs.python.org/issue38807}: Update @ref{192,,TypeError} messages for @ref{eeb,,os.path.join()} to
include @ref{4e5,,os.PathLike} objects as acceptable input types.

@item 
bpo-38785@footnote{https://bugs.python.org/issue38785}: Prevent asyncio from crashing if parent @code{__init__} is not
called from a constructor of object derived from @code{asyncio.Future}.

@item 
bpo-38723@footnote{https://bugs.python.org/issue38723}: @ref{c9,,pdb} now uses @ref{eb1,,io.open_code()} to trigger auditing
events.

@item 
bpo-27805@footnote{https://bugs.python.org/issue27805}: Allow opening pipes and other non-seekable files in append mode
with @ref{4ea,,open()}.

@item 
bpo-38686@footnote{https://bugs.python.org/issue38686}: Added support for multiple @code{qop} values in
@ref{eb6,,urllib.request.AbstractDigestAuthHandler}.

@item 
bpo-38334@footnote{https://bugs.python.org/issue38334}: 修复了在加密的 @code{zipfile.ZipExtFile} 上向后搜索的问题。

@item 
bpo-34679@footnote{https://bugs.python.org/issue34679}: asynci.ProactorEventLoop.close() 现在仅调用主线程中的 signal.set_wakeup_fd()

@item 
bpo-31202@footnote{https://bugs.python.org/issue31202}: @code{pathlib.WindowsPath.glob()} 的结果现在与文本部分的式样匹配。

@item 
bpo-38521@footnote{https://bugs.python.org/issue38521}: Fixed erroneous equality comparison in statistics.NormalDist().

@item 
bpo-38478@footnote{https://bugs.python.org/issue38478}: Fixed a bug in @code{inspect.signature.bind()} that was causing
it to fail when handling a keyword argument with same name as
positional-only parameter. Patch by Pablo Galindo.

@item 
bpo-33604@footnote{https://bugs.python.org/issue33604}: Fixed @ref{84e,,hmac.new} and @code{hmac.HMAC} to raise TypeError instead of
ValueError when the digestmod parameter, now required in 3.8, is omitted.
Also clarified the hmac module documentation and docstrings.

@item 
bpo-38422@footnote{https://bugs.python.org/issue38422}: Clarify docstrings of pathlib suffix(es)

@item 
bpo-36993@footnote{https://bugs.python.org/issue36993}: Improve error reporting for corrupt zip files with bad zip64
extra data. Patch by Daniel Hillier.

@item 
bpo-36820@footnote{https://bugs.python.org/issue36820}: Break cycle generated when saving an exception in socket.py,
codeop.py and dyld.py as they keep alive not only the exception but user
objects through the @code{__traceback__} attribute. Patch by Mario Corchero.

@item 
bpo-34776@footnote{https://bugs.python.org/issue34776}: Fix dataclasses to support forward references in type
annotations

@item 
bpo-33348@footnote{https://bugs.python.org/issue33348}: lib2to3 now recognizes expressions after @code{*} and @code{**} like in
@code{f(*[] or [])}.

@item 
bpo-27657@footnote{https://bugs.python.org/issue27657}: Fix urllib.parse.urlparse() with numeric paths. A string like
"path:80" is no longer parsed as a path but as a scheme ("path") and a
path ("80").
@end itemize

@node 文档<6>,测试<5>,库<10>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id50}@anchor{eec}
@subsubsection 文档



@itemize -

@item 
bpo-38816@footnote{https://bugs.python.org/issue38816}: Provides more details about the interaction between
@code{fork()} and CPython's runtime, focusing just on the C-API.  This
includes cautions about where @code{fork()} should and shouldn't be
called.

@item 
bpo-38351@footnote{https://bugs.python.org/issue38351}: Modernize @ref{69,,email} examples from %-formatting to f-strings.

@item 
bpo-38778@footnote{https://bugs.python.org/issue38778}: Document the fact that @ref{2ba,,RuntimeError} is raised if
@ref{95b,,os.fork()} is called in a subinterpreter.

@item 
bpo-38592@footnote{https://bugs.python.org/issue38592}: Add Brazilian Portuguese to the language switcher at Python
Documentation website.
@end itemize

@node 测试<5>,构建<5>,文档<6>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id51}@anchor{eed}
@subsubsection 测试



@itemize -

@item 
bpo-38547@footnote{https://bugs.python.org/issue38547}: Fix test_pty: if the process is the session leader, closing the
master file descriptor raises a SIGHUP signal: simply ignore SIGHUP when
running the tests.

@item 
bpo-38992@footnote{https://bugs.python.org/issue38992}: Fix a test for @ref{d37,,math.fsum()} that was failing due to
constant folding.

@item 
bpo-38965@footnote{https://bugs.python.org/issue38965}: Fix test_faulthandler on GCC 10. Use the "volatile" keyword in
@code{faulthandler._stack_overflow()} to prevent tail call optimization on
any compiler, rather than relying on compiler specific pragma.

@item 
bpo-38875@footnote{https://bugs.python.org/issue38875}: test_capi: trashcan tests now require the test "cpu" resource.

@item 
bpo-38841@footnote{https://bugs.python.org/issue38841}: Skip asyncio test_create_datagram_endpoint_existing_sock_unix
on platforms lacking a functional bind() for named unix domain sockets.

@item 
bpo-38669@footnote{https://bugs.python.org/issue38669}: Raise @ref{192,,TypeError} when passing target as a string with
@ref{eee,,unittest.mock.patch.object()}.

@item 
bpo-35998@footnote{https://bugs.python.org/issue35998}: Fix a race condition in test_asyncio.test_start_tls_server_1().
Previously, there was a race condition between the test main() function
which replaces the protocol and the test ServerProto protocol which sends
ANSWER once it gets HELLO. Now, only the test main() function is
responsible to send data, ServerProto no longer sends data.
@end itemize

@node 构建<5>,Windows<6>,测试<5>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id52}@anchor{eef}
@subsubsection 构建



@itemize -

@item 
bpo-37404@footnote{https://bugs.python.org/issue37404}: @ref{a,,asyncio} now raises @code{TyperError} when calling
incompatible methods with an @ref{3da,,ssl.SSLSocket} socket.  Patch by Ido
Michael.

@item 
bpo-38809@footnote{https://bugs.python.org/issue38809}: On Windows, build scripts will now recognize and use python.exe
from an active virtual env.

@item 
bpo-38684@footnote{https://bugs.python.org/issue38684}: Fix _hashlib build when Blake2 is disabled, but OpenSSL
supports it.

@item 
bpo-37415@footnote{https://bugs.python.org/issue37415}: Fix stdatomic.h header check for ICC compiler: the ICC
implementation lacks atomic_uintptr_t type which is needed by Python.
@end itemize

@node Windows<6>,macOS<4>,构建<5>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id53}@anchor{ef0}
@subsubsection Windows



@itemize -

@item 
bpo-33125@footnote{https://bugs.python.org/issue33125}: Add support for building and releasing Windows ARM64 packages.

@item 
bpo-38589@footnote{https://bugs.python.org/issue38589}: Fixes HTML Help shortcut when Windows is not installed to C
drive

@item 
bpo-38453@footnote{https://bugs.python.org/issue38453}: Ensure ntpath.realpath() correctly resolves relative paths.

@item 
bpo-38519@footnote{https://bugs.python.org/issue38519}: Restores the internal C headers that were missing from the
nuget.org and Microsoft Store packages.

@item 
bpo-38492@footnote{https://bugs.python.org/issue38492}: 删除 pythonw.exe 依赖的 Microsoft C++ 执行库。
@end itemize

@node macOS<4>,IDLE<11>,Windows<6>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id54}@anchor{ef1}
@subsubsection macOS



@itemize -

@item 
bpo-37931@footnote{https://bugs.python.org/issue37931}: Fixed a crash on OSX dynamic builds that occurred when
re-initializing the posix module after a Py_Finalize if the environment
had changed since the previous @code{import posix}. Patch by Benoît Hudson.
@end itemize

@node IDLE<11>,C API<3>,macOS<4>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id55}@anchor{ef2}
@subsubsection IDLE



@itemize -

@item 
bpo-38862@footnote{https://bugs.python.org/issue38862}: 'Strip Trailing Whitespace' on the Format menu removes extra
newlines at the end of non-shell files.

@item 
bpo-26353@footnote{https://bugs.python.org/issue26353}: Stop adding newline when saving an IDLE shell window.

@item 
bpo-38636@footnote{https://bugs.python.org/issue38636}: Fix IDLE Format menu tab toggle and file indent width. These
functions (default shortcuts Alt-T and Alt-U) were mistakenly disabled in
3.7.5 and 3.8.0.

@item 
bpo-4630@footnote{https://bugs.python.org/issue4630}: Add an option to toggle IDLE's cursor blink for shell, editor,
and output windows.  See Settings, General, Window Preferences, Cursor
Blink. Patch by Zachary Spytz.

@item 
bpo-38598@footnote{https://bugs.python.org/issue38598}: Do not try to compile IDLE shell or output windows
@end itemize

@node C API<3>,,IDLE<11>,Python 3 8 1 rc1
@anchor{whatsnew/changelog id56}@anchor{ef3}
@subsubsection C API



@itemize -

@item 
bpo-37633@footnote{https://bugs.python.org/issue37633}: Re-export some function compatibility wrappers for macros in
@code{pythonrun.h}.

@item 
bpo-38540@footnote{https://bugs.python.org/issue38540}: Fixed possible leak in @ref{ef4,,PyArg_Parse()} and similar
functions for format units @code{"es#"} and @code{"et#"} when the macro
@code{PY_SSIZE_T_CLEAN} is not defined.

@item 
bpo-36389@footnote{https://bugs.python.org/issue36389}: The @code{_PyObject_CheckConsistency()} function is now also
available in release mode. For example, it can be used to debug a crash in
the @code{visit_decref()} function of the GC.
@end itemize

@node Python 3 8 0 正式版,Python 3 8 0 rc1,Python 3 8 1 rc1,更新日志
@anchor{whatsnew/changelog python-3-8-0-final}@anchor{ef5}
@subsection Python 3.8.0 正式版


@emph{发布日期: 2019-10-14}

@menu
* 核心与内置: 核心与内置<11>. 
* 库: 库<11>. 
* 文档: 文档<7>. 
* 测试: 测试<6>. 
* Windows: Windows<7>. 
* IDLE: IDLE<12>. 
* 工具/示例: 工具/示例<3>. 
* C API: C API<4>. 

@end menu

@node 核心与内置<11>,库<11>,,Python 3 8 0 正式版
@anchor{whatsnew/changelog id57}@anchor{ef6}
@subsubsection 核心与内置



@itemize -

@item 
bpo-38469@footnote{https://bugs.python.org/issue38469}: Fixed a bug where the scope of named expressions was not being
resolved correctly in the presence of the @emph{global} keyword. Patch by Pablo
Galindo.

@item 
bpo-38379@footnote{https://bugs.python.org/issue38379}: When cyclic garbage collection (gc) runs finalizers that
resurrect unreachable objects, the current gc run ends, without collecting
any cyclic trash.  However, the statistics reported by @code{collect()} and
@code{get_stats()} claimed that all cyclic trash found was collected, and
that the resurrected objects were collected.   Changed the stats to report
that none were collected.
@end itemize

@node 库<11>,文档<7>,核心与内置<11>,Python 3 8 0 正式版
@anchor{whatsnew/changelog id58}@anchor{ef7}
@subsubsection 库



@itemize -

@item 
bpo-38449@footnote{https://bugs.python.org/issue38449}: Revert GH-15522, which introduces a regression in
@ref{ef8,,mimetypes.guess_type()} due to improper handling of filenames as
urls.

@item 
bpo-38431@footnote{https://bugs.python.org/issue38431}: Fix @code{__repr__} method for @code{dataclasses.InitVar} to
support typing objects, patch by Samuel Colvin.

@item 
bpo-38109@footnote{https://bugs.python.org/issue38109}: Add missing @ref{8ce,,stat.S_IFDOOR}, @ref{8cf,,stat.S_IFPORT},
@ref{8d0,,stat.S_IFWHT}, @ref{ef9,,stat.S_ISDOOR()}, @ref{efa,,stat.S_ISPORT()}, and
@ref{efb,,stat.S_ISWHT()} values to the Python implementation of @ref{f4,,stat}.

@item 
bpo-38405@footnote{https://bugs.python.org/issue38405}: Nested subclasses of @ref{280,,typing.NamedTuple} are now
pickleable.

@item 
bpo-38332@footnote{https://bugs.python.org/issue38332}: Prevent @ref{2c7,,KeyError} thrown by @code{_encoded_words.decode()}
when given an encoded-word with invalid content-type encoding from
propagating all the way to @code{email.message.get()}.

@item 
bpo-38341@footnote{https://bugs.python.org/issue38341}: Add @ref{efc,,smtplib.SMTPNotSupportedError} to the @ref{ed,,smtplib}
exported names.

@item 
bpo-13153@footnote{https://bugs.python.org/issue13153}: OS native encoding is now used for converting between Python
strings and Tcl objects.  This allows to display, copy and paste to
clipboard emoji and other non-BMP characters.  Converting strings from Tcl
to Python and back now never fails (except MemoryError).
@end itemize

@node 文档<7>,测试<6>,库<11>,Python 3 8 0 正式版
@anchor{whatsnew/changelog id59}@anchor{efd}
@subsubsection 文档



@itemize -

@item 
bpo-38294@footnote{https://bugs.python.org/issue38294}: Add list of no-longer-escaped chars to re.escape documentation.
@end itemize

@node 测试<6>,Windows<7>,文档<7>,Python 3 8 0 正式版
@anchor{whatsnew/changelog id60}@anchor{efe}
@subsubsection 测试



@itemize -

@item 
bpo-37531@footnote{https://bugs.python.org/issue37531}: On timeout, regrtest no longer attempts to call
@code{popen.communicate()} again: it can hang until all child processes using
stdout and stderr pipes completes. Kill the worker process and ignores its
output. Change also the faulthandler timeout of the main process from 1
minute to 5 minutes, for Python slowest buildbots.
@end itemize

@node Windows<7>,IDLE<12>,测试<6>,Python 3 8 0 正式版
@anchor{whatsnew/changelog id61}@anchor{eff}
@subsubsection Windows



@itemize -

@item 
bpo-38344@footnote{https://bugs.python.org/issue38344}: Fix error message in activate.bat.

@item 
bpo-38359@footnote{https://bugs.python.org/issue38359}: Ensures @code{pyw.exe} launcher reads correct registry key.

@item 
bpo-38355@footnote{https://bugs.python.org/issue38355}: Fixes @code{ntpath.realpath} failing on @code{sys.executable}.
@end itemize

@node IDLE<12>,工具/示例<3>,Windows<7>,Python 3 8 0 正式版
@anchor{whatsnew/changelog id62}@anchor{f00}
@subsubsection IDLE



@itemize -

@item 
bpo-36698@footnote{https://bugs.python.org/issue36698}: IDLE no longer fails when write non-encodable characters to
stderr.  It now escapes them with a backslash, as the regular Python
interpreter. Added the @code{errors} field to the standard streams.
@end itemize

@node 工具/示例<3>,C API<4>,IDLE<12>,Python 3 8 0 正式版
@anchor{whatsnew/changelog id63}@anchor{f01}
@subsubsection 工具/示例



@itemize -

@item 
bpo-38118@footnote{https://bugs.python.org/issue38118}: Update Valgrind suppression file to ignore a false alarm in
@ref{f02,,PyUnicode_Decode()} when using GCC builtin strcmp().

@item 
bpo-38347@footnote{https://bugs.python.org/issue38347}: pathfix.py: Assume all files that end on '.py' are Python
scripts when working recursively.
@end itemize

@node C API<4>,,工具/示例<3>,Python 3 8 0 正式版
@anchor{whatsnew/changelog id64}@anchor{f03}
@subsubsection C API



@itemize -

@item 
bpo-38395@footnote{https://bugs.python.org/issue38395}: Fix a crash in @ref{250,,weakref.proxy} objects due to incorrect
lifetime management when calling some associated methods that may delete
the last reference to object being referenced by the proxy. Patch by Pablo
Galindo.
@end itemize

@node Python 3 8 0 rc1,Python 3 8 0 beta 4,Python 3 8 0 正式版,更新日志
@anchor{whatsnew/changelog python-3-8-0-release-candidate-1}@anchor{f04}
@subsection Python 3.8.0 rc1


@emph{发布日期: 2019-10-01}

@menu
* 安全: 安全<8>. 
* 核心与内置: 核心与内置<12>. 
* 库: 库<12>. 
* 文档: 文档<8>. 
* 测试: 测试<7>. 
* 构建: 构建<6>. 
* Windows: Windows<8>. 
* macOS: macOS<5>. 
* IDLE: IDLE<13>. 
* 工具/示例: 工具/示例<4>. 
* C API: C API<5>. 

@end menu

@node 安全<8>,核心与内置<12>,,Python 3 8 0 rc1
@anchor{whatsnew/changelog id65}@anchor{f05}
@subsubsection 安全



@itemize -

@item 
bpo-38243@footnote{https://bugs.python.org/issue38243}: 在将文档页渲染为 HTML 时会对 @ref{f06,,xmlrpc.server.DocXMLRPCServer} 的服务器标题进行转义。 （由 Dong-hee Na 在 bpo-38243@footnote{https://bugs.python.org/issue38243} 中贡献。）

@item 
bpo-38174@footnote{https://bugs.python.org/issue38174}: 将厂商化的 expat 库版本更新至 2.2.8，这解决了 CVE-2019-15903。

@item 
bpo-37764@footnote{https://bugs.python.org/issue37764}: 修复了 email._header_value_parser.get_unstructured 在邮件头不包含末尾空格，以及在其包含无效的已编码字等特定情况下进入无限循环的问题。 由 Ashwin Ramaswami 贡献补丁。
@end itemize

@node 核心与内置<12>,库<12>,安全<8>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id66}@anchor{f07}
@subsubsection 核心与内置



@itemize -

@item 
bpo-38006@footnote{https://bugs.python.org/issue38006}: Fix a bug due to the interaction of weakrefs and the cyclic
garbage collector. We must clear any weakrefs in garbage in order to
prevent their callbacks from executing and causing a crash.

@item 
bpo-38317@footnote{https://bugs.python.org/issue38317}: Fix warnings options priority: @code{PyConfig.warnoptions} has the
highest priority, as stated in the 
@geindex Python 提高建议; PEP 587
PEP 587@footnote{https://www.python.org/dev/peps/pep-0587}.

@item 
bpo-36871@footnote{https://bugs.python.org/issue36871}: 改进了 mock 的 assert_has_calls 和 assert_has_awaits 方法的错误处理。 修复了一个漏洞，它会在将预期的调用绑定到 mock 的规格时静默接收所遇到的任何错误，从而产生误导性的错误输出。

@item 
bpo-38236@footnote{https://bugs.python.org/issue38236}: Python now dumps path configuration if it fails to import the
Python codecs of the filesystem and stdio encodings.

@item 
bpo-38013@footnote{https://bugs.python.org/issue38013}: Allow to call @code{async_generator_athrow().throw(...)} even for
non-started async generator helper. It fixes annoying warning at the end
of @ref{1a5,,asyncio.run()} call.

@item 
bpo-38124@footnote{https://bugs.python.org/issue38124}: Fix an off-by-one error in PyState_AddModule that could cause
out-of-bounds memory access.

@item 
bpo-38005@footnote{https://bugs.python.org/issue38005}: 修复InterpreterID 和 ChannelID的创建和对比.

@item 
bpo-37994@footnote{https://bugs.python.org/issue37994}: Fixed silencing arbitrary errors if an attribute lookup fails
in several sites. Only AttributeError should be silenced.

@item 
bpo-37990@footnote{https://bugs.python.org/issue37990}: Fix elapsed time in gc stats was not printed correctly.  This
bug was a regression in 3.8b4.

@item 
bpo-37966@footnote{https://bugs.python.org/issue37966}: The implementation of @ref{246,,is_normalized()} has
been greatly sped up on strings that aren't normalized, by implementing
the full normalization-quick-check algorithm from the Unicode standard.

@item 
bpo-20490@footnote{https://bugs.python.org/issue20490}: Improve import error message for partially initialized module
on circular @code{from} imports - by Anthony Sottile.

@item 
bpo-37409@footnote{https://bugs.python.org/issue37409}: Ensure explicit relative imports from interactive sessions and
scripts (having no parent package) always raise ImportError, rather than
treating the current module as the package. Patch by Ben Lewis.

@item 
bpo-37619@footnote{https://bugs.python.org/issue37619}: When adding a wrapper descriptor from one class to a different
class (for example, setting @code{__add__ = str.__add__} on an @code{int}
subclass), an exception is correctly raised when the operator is called.

@item 
bpo-30773@footnote{https://bugs.python.org/issue30773}: Prohibit parallel running of aclose() / asend() / athrow(). Fix
ag_running to reflect the actual running status of the AG.
@end itemize

@node 库<12>,文档<8>,核心与内置<12>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id67}@anchor{f08}
@subsubsection 库



@itemize -

@item 
bpo-38319@footnote{https://bugs.python.org/issue38319}: 修复 套接字 和 shutil 模块中使用的sendfile() 在 32-bit 架构上会产生 OverflowError for files >= 2GiB . (补丁由Giampaolo Rodola提供)

@item 
bpo-38242@footnote{https://bugs.python.org/issue38242}: 回滚新的 asyncio Streams API

@item 
bpo-38019@footnote{https://bugs.python.org/issue38019}: Correctly handle pause/resume reading of closed asyncio unix
pipe.

@item 
bpo-38163@footnote{https://bugs.python.org/issue38163}: Child mocks will now detect their type as either synchronous or
asynchronous, asynchronous child mocks will be AsyncMocks and synchronous
child mocks will be either MagicMock or Mock (depending on their parent
type).

@item 
bpo-38161@footnote{https://bugs.python.org/issue38161}: Removes _AwaitEvent from AsyncMock.

@item 
bpo-38216@footnote{https://bugs.python.org/issue38216}: Allow the rare code that wants to send invalid http requests
from the @ref{94,,http.client} library a way to do so.  The fixes for bpo-30458@footnote{https://bugs.python.org/issue30458}
led to breakage for some projects that were relying on this ability to
test their own behavior in the face of bad requests.

@item 
bpo-38108@footnote{https://bugs.python.org/issue38108}: Any synchronous magic methods on an AsyncMock now return a
MagicMock. Any asynchronous magic methods on a MagicMock now return an
AsyncMock.

@item 
bpo-38248@footnote{https://bugs.python.org/issue38248}: asyncio: Fix inconsistent immediate Task cancellation

@item 
bpo-38237@footnote{https://bugs.python.org/issue38237}: The arguments for the builtin pow function are more
descriptive. They can now also be passed in as keywords.

@item 
bpo-38191@footnote{https://bugs.python.org/issue38191}: Constructors of @ref{280,,NamedTuple} and
@ref{23b,,TypedDict} types now accept arbitrary keyword argument
names, including "cls", "self", "typename", "_typename", "fields" and
"_fields".  Passing positional arguments by keyword is deprecated.

@item 
bpo-38185@footnote{https://bugs.python.org/issue38185}: Fixed case-insensitive string comparison in
@ref{758,,sqlite3.Row} indexing.

@item 
bpo-38136@footnote{https://bugs.python.org/issue38136}: Changes AsyncMock call count and await count to be two
different counters. Now await count only counts when a coroutine has been
awaited, not when it has been called, and vice-versa. Update the
documentation around this.

@item 
bpo-37828@footnote{https://bugs.python.org/issue37828}: Fix default mock name in
@ref{5a3,,unittest.mock.Mock.assert_called()} exceptions. Patch by Abraham
Toriz Cruz.

@item 
bpo-38175@footnote{https://bugs.python.org/issue38175}: Fix a memory leak in comparison of @ref{758,,sqlite3.Row}
objects.

@item 
bpo-33936@footnote{https://bugs.python.org/issue33936}: _hashlib no longer calls obsolete OpenSSL initialization
function with OpenSSL 1.1.0+.

@item 
bpo-34706@footnote{https://bugs.python.org/issue34706}: Preserve subclassing in inspect.Signature.from_callable.

@item 
bpo-38153@footnote{https://bugs.python.org/issue38153}: Names of hashing algorithms frome OpenSSL are now normalized to
follow Python's naming conventions. For example OpenSSL uses sha3-512
instead of sha3_512 or blake2b512 instead of blake2b.

@item 
bpo-38115@footnote{https://bugs.python.org/issue38115}: Fix a bug in dis.findlinestarts() where it would return invalid
bytecode offsets. Document that a code object's co_lnotab can contain
invalid bytecode offsets.

@item 
bpo-38148@footnote{https://bugs.python.org/issue38148}: Add slots to @ref{a,,asyncio} transport classes, which can reduce
memory usage.

@item 
bpo-36991@footnote{https://bugs.python.org/issue36991}: Fixes a potential incorrect AttributeError exception escaping
ZipFile.extract() in some unsupported input error situations.

@item 
bpo-38134@footnote{https://bugs.python.org/issue38134}: Remove obsolete copy of PBKDF2_HMAC_fast. All supported OpenSSL
versions contain a fast implementation.

@item 
bpo-38132@footnote{https://bugs.python.org/issue38132}: The OpenSSL hashlib wrapper uses a simpler implementation.
Several Macros and pointless caches are gone. The hash name now comes from
OpenSSL's EVP. The algorithm name stays the same, except it is now always
lower case.

@item 
bpo-38008@footnote{https://bugs.python.org/issue38008}: Fix parent class check in protocols to correctly identify the
module that provides a builtin protocol, instead of assuming they all come
from the @ref{1f,,collections.abc} module

@item 
bpo-37405@footnote{https://bugs.python.org/issue37405}: Fixed regression bug for socket.getsockname() for non-CAN_ISOTP
AF_CAN address family sockets by returning a 1-tuple instead of string.

@item 
bpo-38121@footnote{https://bugs.python.org/issue38121}: Update parameter names on functions in importlib.metadata
matching the changes in the 0.22 release of importlib_metadata.

@item 
bpo-38110@footnote{https://bugs.python.org/issue38110}: The os.closewalk() implementation now uses the libc fdwalk()
API on platforms where it is available.

@item 
bpo-38093@footnote{https://bugs.python.org/issue38093}: Fixes AsyncMock so it doesn't crash when used with
AsyncContextManagers or AsyncIterators.

@item 
bpo-37488@footnote{https://bugs.python.org/issue37488}: Add warning to @code{datetime.utctimetuple()},
@code{datetime.utcnow()} and @code{datetime.utcfromtimestamp()} .

@item 
bpo-38086@footnote{https://bugs.python.org/issue38086}: Update importlib.metadata with changes from importlib_metadata 0.21@footnote{https://gitlab.com/python-devs/importlib_metadata/blob/0.21/importlib_metadata/docs/changelog.rst}.

@item 
bpo-37251@footnote{https://bugs.python.org/issue37251}: Remove @code{__code__} check in AsyncMock that incorrectly evaluated
function specs as async objects but failed to evaluate classes with
@code{__await__} but no @code{__code__} attribute defined as async objects.

@item 
bpo-38037@footnote{https://bugs.python.org/issue38037}: Fix reference counters in the @ref{ea,,signal} module.

@item 
bpo-38066@footnote{https://bugs.python.org/issue38066}: Hide internal asyncio.Stream methods: feed_eof(), feed_data(),
set_exception() and set_transport().

@item 
bpo-38059@footnote{https://bugs.python.org/issue38059}: inspect.py now uses sys.exit() instead of exit()

@item 
bpo-37953@footnote{https://bugs.python.org/issue37953}: In @ref{119,,typing}, improved the @code{__hash__} and @code{__eq__}
methods for @code{ForwardReferences}.

@item 
bpo-38026@footnote{https://bugs.python.org/issue38026}: Fixed @ref{bc4,,inspect.getattr_static()} used @code{isinstance} while
it should avoid dynamic lookup.

@item 
bpo-38010@footnote{https://bugs.python.org/issue38010}: In @code{importlib.metadata} sync with @code{importlib_metadata}
0.20, clarifying behavior of @code{files()} and fixing issue where only one
requirement was returned for @code{requires()} on @code{dist-info} packages.

@item 
bpo-38006@footnote{https://bugs.python.org/issue38006}: weakref.WeakValueDictionary defines a local remove() function
used as callback for weak references. This function was created with a
closure. Modify the implementation to avoid the closure.

@item 
bpo-34410@footnote{https://bugs.python.org/issue34410}: Fixed a crash in the @code{tee()} iterator when re-enter it.
RuntimeError is now raised in this case.

@item 
bpo-37140@footnote{https://bugs.python.org/issue37140}: Fix a ctypes regression of Python 3.8. When a ctypes.Structure
is passed by copy to a function, ctypes internals created a temporary
object which had the side effect of calling the structure finalizer
(__del__) twice. The Python semantics requires a finalizer to be called
exactly once. Fix ctypes internals to no longer call the finalizer twice.

@item 
bpo-37972@footnote{https://bugs.python.org/issue37972}: Subscripts to the @ref{f09,,unittest.mock.call} objects now receive the
same chaining mechanism as any other custom attributes, so that the
following usage no longer raises a @ref{192,,TypeError}:

call().foo().__getitem__('bar')

Patch by blhsing

@item 
bpo-22347@footnote{https://bugs.python.org/issue22347}: Update mimetypes.guess_type to allow proper parsing of URLs
with only a host name. Patch by Dong-hee Na.

@item 
bpo-37885@footnote{https://bugs.python.org/issue37885}: venv: Don't generate unset variable warning on deactivate.

@item 
bpo-37785@footnote{https://bugs.python.org/issue37785}: Fix xgettext warnings in @ref{6,,argparse}.

@item 
bpo-11953@footnote{https://bugs.python.org/issue11953}: Completing WSA* error codes in @ref{ef,,socket}.

@item 
bpo-37424@footnote{https://bugs.python.org/issue37424}: Fixes a possible hang when using a timeout on
@ref{3e5,,subprocess.run()} while capturing output.  If the child process spawned
its own children or otherwise connected its stdout or stderr handles with
another process, we could hang after the timeout was reached and our child
was killed when attempting to read final output from the pipes.

@item 
bpo-37212@footnote{https://bugs.python.org/issue37212}: @ref{f09,,unittest.mock.call()} now preserves the order of keyword
arguments in repr output. Patch by Karthikeyan Singaravelan.

@item 
bpo-37305@footnote{https://bugs.python.org/issue37305}: Add .webmanifest -> application/manifest+json to list of
recognized file types and content type headers

@item 
bpo-21872@footnote{https://bugs.python.org/issue21872}: Fix @ref{ad,,lzma}: module decompresses data incompletely. When
decompressing a FORMAT_ALONE format file, and it doesn't have the end
marker, sometimes the last one to dozens bytes can't be output. Patch by
Ma Lin.

@item 
bpo-37206@footnote{https://bugs.python.org/issue37206}: Default values which cannot be represented as Python objects no
longer improperly represented as @code{None} in function signatures.

@item 
bpo-12144@footnote{https://bugs.python.org/issue12144}: Ensure cookies with @code{expires} attribute are handled in
@code{CookieJar.make_cookies()}.

@item 
bpo-31163@footnote{https://bugs.python.org/issue31163}: pathlib.Path instance's rename and replace methods now return
the new Path instance.

@item 
bpo-25068@footnote{https://bugs.python.org/issue25068}: @ref{f0a,,urllib.request.ProxyHandler} now lowercases the keys of
the passed dictionary.

@item 
bpo-21315@footnote{https://bugs.python.org/issue21315}: Email headers containing RFC2047 encoded words are parsed
despite the missing whitespace, and a defect registered. Also missing
trailing whitespace after encoded words is now registered as a defect.

@item 
bpo-36250@footnote{https://bugs.python.org/issue36250}: Ignore @code{ValueError} from @code{signal} with @code{interaction} in
non-main thread.

@item 
bpo-35168@footnote{https://bugs.python.org/issue35168}: @ref{f0b,,shlex.shlex.punctuation_chars} is now a read-only
property.

@item 
bpo-20504@footnote{https://bugs.python.org/issue20504}: Fixes a bug in @ref{16,,cgi} module when a multipart/form-data
request has no @code{Content-Length} header.

@item 
bpo-34519@footnote{https://bugs.python.org/issue34519}: Add additional aliases for HP Roman 8. Patch by Michael Osipov.
@end itemize

@node 文档<8>,测试<7>,库<12>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id68}@anchor{f0c}
@subsubsection 文档



@itemize -

@item 
bpo-26868@footnote{https://bugs.python.org/issue26868}: Fix example usage of @ref{f0d,,PyModule_AddObject()} to properly
handle errors.

@item 
bpo-36797@footnote{https://bugs.python.org/issue36797}: Fix a dead link in the distutils API Reference.

@item 
bpo-37977@footnote{https://bugs.python.org/issue37977}: Warn more strongly and clearly about pickle insecurity

@item 
bpo-37937@footnote{https://bugs.python.org/issue37937}: Mention @code{frame.f_trace} in @ref{e37,,sys.settrace()} docs.

@item 
bpo-36260@footnote{https://bugs.python.org/issue36260}: Add decompression pitfalls to zipfile module documentation.

@item 
bpo-36960@footnote{https://bugs.python.org/issue36960}: Restructured the @ref{31,,datetime} docs in the interest of making
them more user-friendly and improving readability. Patch by Brad Solomon.

@item 
bpo-23460@footnote{https://bugs.python.org/issue23460}: The documentation for decimal string formatting using the @code{:g}
specifier has been updated to reflect the correct exponential notation
cutoff point. Original patch contributed by Tuomas Suutari.

@item 
bpo-35803@footnote{https://bugs.python.org/issue35803}: Document and test that @code{tempfile} functions may accept a
@ref{363,,path-like object} for the @code{dir} argument.  Patch by Anthony
Sottile.

@item 
bpo-33944@footnote{https://bugs.python.org/issue33944}: Added a note about the intended use of code in .pth files.

@item 
bpo-34293@footnote{https://bugs.python.org/issue34293}: Fix the Doc/Makefile regarding PAPER environment variable and
PDF builds
@end itemize

@node 测试<7>,构建<6>,文档<8>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id69}@anchor{f0e}
@subsubsection 测试



@itemize -

@item 
bpo-38239@footnote{https://bugs.python.org/issue38239}: Fix test_gdb for Link Time Optimization (LTO) builds.

@item 
bpo-38275@footnote{https://bugs.python.org/issue38275}: test_ssl now handles disabled TLS/SSL versions better.
OpenSSL's crypto policy and run-time settings are recognized and tests for
disabled versions are skipped. Tests also accept more TLS minimum_versions
for platforms that override OpenSSL's default with strict settings.

@item 
bpo-38271@footnote{https://bugs.python.org/issue38271}: The private keys for test_ssl were encrypted with 3DES in
traditional PKCS#5 format. 3DES and the digest algorithm of PKCS#5 are
blocked by some strict crypto policies. Use PKCS#8 format with AES256
encryption instead.

@item 
bpo-38270@footnote{https://bugs.python.org/issue38270}: test.support now has a helper function to check for
availibility of a hash digest function. Several tests are refactored avoid
MD5 and use SHA256 instead. Other tests are marked to use MD5 and skipped
when MD5 is disabled.

@item 
bpo-37123@footnote{https://bugs.python.org/issue37123}: Multiprocessing test test_mymanager() now also expects
-SIGTERM, not only exitcode 0. BaseManager._finalize_manager() sends
SIGTERM to the manager process if it takes longer than 1 second to stop,
which happens on slow buildbots.

@item 
bpo-38212@footnote{https://bugs.python.org/issue38212}: Multiprocessing tests: increase
test_queue_feeder_donot_stop_onexc() timeout from 1 to 60 seconds.

@item 
bpo-38117@footnote{https://bugs.python.org/issue38117}: 使用OpenSSL 1.1.1d进行测试

@item 
bpo-37531@footnote{https://bugs.python.org/issue37531}: Enhance regrtest multiprocess timeout: write a message when
killing a worker process, catch popen.kill() and popen.wait() exceptions,
put a timeout on the second call to popen.communicate().

@item 
bpo-37876@footnote{https://bugs.python.org/issue37876}: Add tests for ROT-13 codec.

@item 
bpo-37252@footnote{https://bugs.python.org/issue37252}: Fix assertions in @code{test_close} and
@code{test_events_mask_overflow} devpoll tests.

@item 
bpo-34001@footnote{https://bugs.python.org/issue34001}: Make test_ssl pass with LibreSSL. LibreSSL handles minimum and
maximum TLS version differently than OpenSSL.

@item 
bpo-36919@footnote{https://bugs.python.org/issue36919}: Make @code{test_source_encoding.test_issue2301} implementation
independent. The test will work now for both CPython and IronPython.

@item 
bpo-34596@footnote{https://bugs.python.org/issue34596}: Fallback to a default reason when @ref{f0f,,unittest.skip()} is
uncalled. Patch by Naitree Zhu.
@end itemize

@node 构建<6>,Windows<8>,测试<7>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id70}@anchor{f10}
@subsubsection 构建



@itemize -

@item 
bpo-38301@footnote{https://bugs.python.org/issue38301}: In Solaris family, we must be sure to use @code{-D_REENTRANT}.
Patch by Jesús Cea Avión.

@item 
bpo-36210@footnote{https://bugs.python.org/issue36210}: Update optional extension module detection for AIX. ossaudiodev
and spwd are not applicable for AIX, and are no longer reported as
missing. 3rd-party packaging of ncurses (with ASIS support) conflicts with
officially supported AIX curses library, so configure AIX to use
libcurses.a. However, skip trying to build _curses_panel.

patch by M Felt

@item 
bpo-36002@footnote{https://bugs.python.org/issue36002}: Locate @code{llvm-profdata} and @code{llvm-ar} binaries using
@code{AC_PATH_TOOL} rather than @code{AC_PATH_TARGET_TOOL}.

@item 
bpo-37936@footnote{https://bugs.python.org/issue37936}: The @code{.gitignore} file systematically keeps "rooted", with
a non-trailing slash, all the rules that are meant to apply to files in a
specific place in the repo.  Previously, when the intended file to ignore
happened to be at the root of the repo, we'd most often accidentally also
ignore files and directories with the same name anywhere in the tree.

@item 
bpo-37936@footnote{https://bugs.python.org/issue37936}: The @code{.gitignore} file no longer applies to any files that
are in fact tracked in the Git repository.  Patch by Greg Price.
@end itemize

@node Windows<8>,macOS<5>,构建<6>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id71}@anchor{f11}
@subsubsection Windows



@itemize -

@item 
bpo-38117@footnote{https://bugs.python.org/issue38117}: 将绑定的OpenSSL更新到1.1.1d

@item 
bpo-38092@footnote{https://bugs.python.org/issue38092}: Reduce overhead when using multiprocessing in a Windows virtual
environment.

@item 
bpo-38133@footnote{https://bugs.python.org/issue38133}: Allow py.exe launcher to locate installations from the
Microsoft Store and improve display of active virtual environments.

@item 
bpo-38114@footnote{https://bugs.python.org/issue38114}: The @code{pip.ini} is no longer included in the Nuget package.

@item 
bpo-36634@footnote{https://bugs.python.org/issue36634}: @ref{879,,os.cpu_count()} now returns active processors rather than
maximum processors.

@item 
bpo-36634@footnote{https://bugs.python.org/issue36634}: venv activate.bat now works when the existing variables contain
double quote characters.

@item 
bpo-38081@footnote{https://bugs.python.org/issue38081}: Prevent error calling @ref{1ff,,os.path.realpath()} on @code{'NUL'}.

@item 
bpo-38087@footnote{https://bugs.python.org/issue38087}: Fix case sensitivity in test_pathlib and test_ntpath.

@item 
bpo-38088@footnote{https://bugs.python.org/issue38088}: Fixes distutils not finding vcruntime140.dll with only the v142
toolset installed.

@item 
bpo-37283@footnote{https://bugs.python.org/issue37283}: Ensure command-line and unattend.xml setting override
previously detected states in Windows installer.

@item 
bpo-38030@footnote{https://bugs.python.org/issue38030}: Fixes @ref{1f1,,os.stat()} failing for block devices on Windows

@item 
bpo-38020@footnote{https://bugs.python.org/issue38020}: Fixes potential crash when calling @ref{1f3,,os.readlink()} (or
indirectly through @ref{1ff,,realpath()}) on a file that is not a
supported link.

@item 
bpo-37705@footnote{https://bugs.python.org/issue37705}: Improve the implementation of @code{winerror_to_errno()}.

@item 
bpo-37702@footnote{https://bugs.python.org/issue37702}: Fix memory leak on Windows in creating an SSLContext object or
running urllib.request.urlopen('@indicateurl{https://}...').

@item 
bpo-37445@footnote{https://bugs.python.org/issue37445}: Include the @code{FORMAT_MESSAGE_IGNORE_INSERTS} flag in
@code{FormatMessageW()} calls.

@item 
bpo-37380@footnote{https://bugs.python.org/issue37380}: Don't collect unfinished processes with @code{subprocess._active}
on Windows to cleanup later. Patch by Ruslan Kuprieiev.

@item 
bpo-32587@footnote{https://bugs.python.org/issue32587}: Make @ref{f12,,winreg.REG_MULTI_SZ} support zero-length strings.
@end itemize

@node macOS<5>,IDLE<13>,Windows<8>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id72}@anchor{f13}
@subsubsection macOS



@itemize -

@item 
bpo-38117@footnote{https://bugs.python.org/issue38117}: 在MacOS安装程序中将OpenSSL更新为1.1.1d。

@item 
bpo-38089@footnote{https://bugs.python.org/issue38089}: Move Azure Pipelines to latest VM versions and make macOS tests
optional
@end itemize

@node IDLE<13>,工具/示例<4>,macOS<5>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id73}@anchor{f14}
@subsubsection IDLE



@itemize -

@item 
bpo-35379@footnote{https://bugs.python.org/issue35379}: When exiting IDLE, catch any AttributeError.  One happens when
EditorWindow.close is called twice.  Printing a traceback, when IDLE is
run from a terminal, is useless and annoying.

@item 
bpo-38183@footnote{https://bugs.python.org/issue38183}: To avoid problems, test_idle ignores the user config directory.
It no longer tries to create or access .idlerc or any files within. Users
must run IDLE to discover problems with saving settings.

@item 
bpo-38077@footnote{https://bugs.python.org/issue38077}: IDLE no longer adds 'argv' to the user namespace when
initializing it.  This bug only affected 3.7.4 and 3.8.0b2 to 3.8.0b4.

@item 
bpo-38041@footnote{https://bugs.python.org/issue38041}: Shell restart lines now fill the window width, always start
with '=', and avoid wrapping unnecessarily. The line will still wrap if
the included file name is long relative to the width.

@item 
bpo-35771@footnote{https://bugs.python.org/issue35771}: To avoid occasional spurious test_idle failures on slower
machines, increase the @code{hover_delay} in test_tooltip.

@item 
bpo-37902@footnote{https://bugs.python.org/issue37902}: Add mousewheel scrolling for IDLE module, path, and stack
browsers. Patch by George Zhang.
@end itemize

@node 工具/示例<4>,C API<5>,IDLE<13>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id74}@anchor{f15}
@subsubsection 工具/示例



@itemize -

@item 
bpo-37803@footnote{https://bugs.python.org/issue37803}: pdb's @code{--help} and @code{--version} long options now work.

@item 
bpo-37064@footnote{https://bugs.python.org/issue37064}: Add option -k to pathscript.py script: preserve shebang flags.
Add option -a to pathscript.py script: add flags.
@end itemize

@node C API<5>,,工具/示例<4>,Python 3 8 0 rc1
@anchor{whatsnew/changelog id75}@anchor{f16}
@subsubsection C API



@itemize -

@item 
bpo-38234@footnote{https://bugs.python.org/issue38234}: @ref{273,,Py_SetPath()} now sets @ref{274,,sys.executable} to the
program full path (@ref{275,,Py_GetProgramFullPath()}) rather than to the
program name (@ref{276,,Py_GetProgramName()}).

@item 
bpo-38234@footnote{https://bugs.python.org/issue38234}: Python ignored arguments passed to @ref{273,,Py_SetPath()},
@ref{f17,,Py_SetPythonHome()} and @ref{f18,,Py_SetProgramName()}: fix Python
initialization to use specified arguments.

@item 
bpo-38205@footnote{https://bugs.python.org/issue38205}: The @ref{41b,,Py_UNREACHABLE()} macro now calls
@ref{f19,,Py_FatalError()}.

@item 
bpo-37879@footnote{https://bugs.python.org/issue37879}: Fix subtype_dealloc to suppress the type decref when the base
type is a C heap type
@end itemize

@node Python 3 8 0 beta 4,Python 3 8 0 beta 3,Python 3 8 0 rc1,更新日志
@anchor{whatsnew/changelog python-3-8-0-beta-4}@anchor{f1a}
@subsection Python 3.8.0 beta 4


@emph{发布日期: 2019-08-29}

@menu
* 安全: 安全<9>. 
* 核心与内置: 核心与内置<13>. 
* 库: 库<13>. 
* 文档: 文档<9>. 
* 测试: 测试<8>. 
* 构建: 构建<7>. 
* Windows: Windows<9>. 
* macOS: macOS<6>. 
* IDLE: IDLE<14>. 
* 工具/示例: 工具/示例<5>. 
* C API: C API<6>. 

@end menu

@node 安全<9>,核心与内置<13>,,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id76}@anchor{f1b}
@subsubsection 安全



@itemize -

@item 
bpo-34155@footnote{https://bugs.python.org/issue34155}: Fix parsing of invalid email addresses with more than one @code{@@}
(e.g. a@@b@@c.com.) to not return the part before 2nd @code{@@} as valid email
address. Patch by maxking & jpic.
@end itemize

@node 核心与内置<13>,库<13>,安全<9>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id77}@anchor{f1c}
@subsubsection 核心与内置



@itemize -

@item 
bpo-37947@footnote{https://bugs.python.org/issue37947}: Adjust correctly the recursion level in the symtable generation
for named expressions. Patch by Pablo Galindo.

@item 
bpo-37830@footnote{https://bugs.python.org/issue37830}: Fixed compilation of @ref{2db,,break} and @ref{181,,continue}
in the @ref{182,,finally} block when the corresponding @ref{d6b,,try}
block contains @ref{190,,return} with a non-constant value.

@item 
bpo-32912@footnote{https://bugs.python.org/issue32912}: Reverted bpo-32912@footnote{https://bugs.python.org/issue32912}: emitting @ref{191,,SyntaxWarning} instead
of @ref{278,,DeprecationWarning} for invalid escape sequences in string and
bytes literals.

@item 
bpo-37757@footnote{https://bugs.python.org/issue37757}: 
@geindex Python 提高建议; PEP 572
PEP 572@footnote{https://www.python.org/dev/peps/pep-0572}: As described in the PEP, assignment expressions now
raise @ref{452,,SyntaxError} when their interaction with comprehension scoping
results in an ambiguous target scope.

The @code{TargetScopeError} subclass originally proposed by the PEP has been
removed in favour of just raising regular syntax errors for the disallowed
cases.

@item 
bpo-36311@footnote{https://bugs.python.org/issue36311}: Decoding bytes objects larger than 2GiB is faster and no longer
fails when a multibyte characters spans a chunk boundary.

@item 
bpo-37433@footnote{https://bugs.python.org/issue37433}: Fix @code{SyntaxError} indicator printing too many spaces for
multi-line strings - by Anthony Sottile.

@item 
bpo-20523@footnote{https://bugs.python.org/issue20523}: @code{pdb.Pdb} supports ~/.pdbrc in Windows 7. Patch by Tim Hopper
and Dan Lidral-Porter.
@end itemize

@node 库<13>,文档<9>,核心与内置<13>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id78}@anchor{f1d}
@subsubsection 库



@itemize -

@item 
bpo-37834@footnote{https://bugs.python.org/issue37834}: Prevent shutil.rmtree exception when built on non-Windows
system without fd system call support, like older versions of macOS.

@item 
bpo-37965@footnote{https://bugs.python.org/issue37965}: Fix C compiler warning caused by
distutils.ccompiler.CCompiler.has_function.

@item 
bpo-37960@footnote{https://bugs.python.org/issue37960}: @code{repr()} of buffered and text streams now silences only
expected exceptions when get the value of "name" and "mode" attributes.

@item 
bpo-37951@footnote{https://bugs.python.org/issue37951}: Most features of the subprocess module now work again in
subinterpreters. Only @emph{preexec_fn} is restricted in subinterpreters.

@item 
bpo-36205@footnote{https://bugs.python.org/issue36205}: Fix the rusage implementation of time.process_time() to
correctly report the sum of the system and user CPU time.

@item 
bpo-37950@footnote{https://bugs.python.org/issue37950}: Fix @ref{f1e,,ast.dump()} when call with incompletely initialized
node.

@item 
bpo-34679@footnote{https://bugs.python.org/issue34679}: Restores instantiation of Windows IOCP event loops from the
non-main thread.

@item 
bpo-36917@footnote{https://bugs.python.org/issue36917}: Add default implementation of the
@code{ast.NodeVisitor.visit_Constant()} method which emits a deprecation
warning and calls corresponding methody @code{visit_Num()}, @code{visit_Str()},
etc.

@item 
bpo-37798@footnote{https://bugs.python.org/issue37798}: Update test_statistics.py to verify that the statistics module
works well for both C and Python implementations. Patch by Dong-hee Na

@item 
bpo-26589@footnote{https://bugs.python.org/issue26589}: Added a new status code to the http module: 451
UNAVAILABLE_FOR_LEGAL_REASONS

@item 
bpo-37915@footnote{https://bugs.python.org/issue37915}: Fix a segmentation fault that appeared when comparing instances
of @code{datetime.timezone} and @code{datetime.tzinfo} objects. Patch by Pablo
Galindo.

@item 
bpo-37868@footnote{https://bugs.python.org/issue37868}: Fix dataclasses.is_dataclass when given an instance that never
raises AttributeError in __getattr__.  That is, an object that returns
something for __dataclass_fields__ even if it's not a dataclass.

@item 
bpo-37811@footnote{https://bugs.python.org/issue37811}: Fix @code{socket} module's @code{socket.connect(address)} function
being unable to establish connection in case of interrupted system call.
The problem was observed on all OSes which @code{poll(2)} system call can
take only non-negative integers and -1 as a timeout value.

@item 
bpo-21131@footnote{https://bugs.python.org/issue21131}: Fix @code{faulthandler.register(chain=True)} stack. faulthandler
now allocates a dedicated stack of @code{SIGSTKSZ*2} bytes, instead of just
@code{SIGSTKSZ} bytes. Calling the previous signal handler in faulthandler
signal handler uses more than @code{SIGSTKSZ} bytes of stack memory on some
platforms.

@item 
bpo-37798@footnote{https://bugs.python.org/issue37798}: Add C fastpath for statistics.NormalDist.inv_cdf() Patch by
Dong-hee Na

@item 
bpo-37819@footnote{https://bugs.python.org/issue37819}: Add Fraction.as_integer_ratio() to match the corresponding
methods in bool, int, float, and decimal.

@item 
bpo-37810@footnote{https://bugs.python.org/issue37810}: Fix @ref{37,,difflib} @code{?} hint in diff output when dealing with
tabs.  Patch by Anthony Sottile.

@item 
bpo-37772@footnote{https://bugs.python.org/issue37772}: In @code{zipfile.Path}, when adding implicit dirs, ensure that
ancestral directories are added and that duplicates are excluded.

@item 
bpo-28292@footnote{https://bugs.python.org/issue28292}: Mark calendar.py helper functions as being private.  The
follows PEP 8 guidance to maintain the style conventions in the module and
it addresses a known case of user confusion.

@item 
bpo-18049@footnote{https://bugs.python.org/issue18049}: Add definition of THREAD_STACK_SIZE for AIX in
Python/thread_pthread.h The default thread stacksize caused crashes with
the default recursion limit Patch by M Felt

@item 
bpo-37738@footnote{https://bugs.python.org/issue37738}: Fix the implementation of curses @code{addch(str, color_pair)}:
pass the color pair to @code{setcchar()}, instead of always passing 0 as the
color pair.

@item 
bpo-37723@footnote{https://bugs.python.org/issue37723}: Fix performance regression on regular expression parsing with
huge character sets. Patch by Yann Vaginay.

@item 
bpo-32178@footnote{https://bugs.python.org/issue32178}: Fix IndexError in @ref{69,,email} package when trying to parse
invalid address fields starting with @code{:}.

@item 
bpo-37685@footnote{https://bugs.python.org/issue37685}: Fixed comparisons of @ref{195,,datetime.timedelta} and
@ref{9fb,,datetime.timezone}.

@item 
bpo-37695@footnote{https://bugs.python.org/issue37695}: Correct @ref{9da,,curses.unget_wch()} error message.  Patch by
Anthony Sottile.

@item 
bpo-37354@footnote{https://bugs.python.org/issue37354}: Make Activate.ps1 Powershell script static to allow for signing
it.

@item 
bpo-37664@footnote{https://bugs.python.org/issue37664}: Update wheels bundled with ensurepip (pip 19.2.3 and setuptools
41.2.0)

@item 
bpo-37642@footnote{https://bugs.python.org/issue37642}: Allowed the pure Python implementation of
@ref{9fb,,datetime.timezone} to represent sub-minute offsets close to
minimum and maximum boundaries, specifically in the ranges (23:59, 24:00)
and (-23:59, 24:00). Patch by Ngalim Siregar

@item 
bpo-16970@footnote{https://bugs.python.org/issue16970}: Adding a value error when an invalid value in passed to nargs
Patch by Robert Leenders

@item 
bpo-37587@footnote{https://bugs.python.org/issue37587}: Make json.loads faster for long strings. (Patch by Marco
Paolini)

@item 
bpo-18378@footnote{https://bugs.python.org/issue18378}: Recognize "UTF-8" as a valid value for LC_CTYPE in
locale._parse_localename.

@item 
bpo-37531@footnote{https://bugs.python.org/issue37531}: "python3 -m test -jN --timeout=TIMEOUT" now kills a worker
process if it runs longer than @emph{TIMEOUT} seconds.

@item 
bpo-37482@footnote{https://bugs.python.org/issue37482}: Fix serialization of display name in originator or destination
address fields with both encoded words and special chars.

@item 
bpo-37372@footnote{https://bugs.python.org/issue37372}: Fix error unpickling datetime.time objects from Python 2 with
seconds>=24. Patch by Justin Blanchard.

@item 
bpo-37085@footnote{https://bugs.python.org/issue37085}: Add the optional Linux SocketCAN Broadcast Manager constants,
used as flags to configure the BCM behaviour, in the socket module.  Patch
by Karl Ding.

@item 
bpo-36871@footnote{https://bugs.python.org/issue36871}: Ensure method signature is used instead of constructor
signature of a class while asserting mock object against method calls.
Patch by Karthikeyan Singaravelan.

@item 
bpo-36582@footnote{https://bugs.python.org/issue36582}: Fix @code{UserString.encode()} to correctly return @code{bytes}
rather than a @code{UserString} instance.

@item 
bpo-34775@footnote{https://bugs.python.org/issue34775}: Division handling of PurePath now returns NotImplemented
instead of raising a TypeError when passed something other than an
instance of str or PurePath. Patch by Roger Aiudi.
@end itemize

@node 文档<9>,测试<8>,库<13>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id79}@anchor{f1f}
@subsubsection 文档



@itemize -

@item 
bpo-37979@footnote{https://bugs.python.org/issue37979}: Added a link to dateutil.parser.isoparse in the
datetime.fromisoformat documentation. Patch by Paul Ganssle

@item 
bpo-37759@footnote{https://bugs.python.org/issue37759}: Beginning edits to Whatsnew 3.8

@item 
bpo-37726@footnote{https://bugs.python.org/issue37726}: Stop recommending getopt in the tutorial for command line
argument parsing and promote argparse.

@item 
bpo-37256@footnote{https://bugs.python.org/issue37256}: Fix wording of arguments for @code{Request} in
@ref{120,,urllib.request}

@item 
bpo-37004@footnote{https://bugs.python.org/issue37004}: In the documentation for difflib, a note was added explicitly
warning that the results of SequenceMatcher's ratio method may depend on
the order of the input strings.

@item 
bpo-36487@footnote{https://bugs.python.org/issue36487}: Make C-API docs clear about what the "main" interpreter is.
@end itemize

@node 测试<8>,构建<7>,文档<9>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id80}@anchor{f20}
@subsubsection 测试



@itemize -

@item 
bpo-37805@footnote{https://bugs.python.org/issue37805}: Add tests for json.dump(..., skipkeys=True). Patch by Dong-hee
Na.
@end itemize

@node 构建<7>,Windows<9>,测试<8>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id81}@anchor{f21}
@subsubsection 构建



@itemize -

@item 
bpo-37707@footnote{https://bugs.python.org/issue37707}: Mark some individual tests to skip when --pgo is used.  The
tests marked increase the PGO task time significantly and likely don't
help improve optimization of the final executable.
@end itemize

@node Windows<9>,macOS<6>,构建<7>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id82}@anchor{f22}
@subsubsection Windows



@itemize -

@item 
bpo-37549@footnote{https://bugs.python.org/issue37549}: @ref{f23,,os.dup()} no longer fails for standard streams on Windows
7.

@item 
bpo-1311@footnote{https://bugs.python.org/issue1311}: The @code{nul} file on Windows now returns True from
@ref{1f6,,exists()} and a valid result from @ref{1f1,,os.stat()} with
@code{S_IFCHR} set.

@item 
bpo-9949@footnote{https://bugs.python.org/issue9949}: Enable support for following symlinks in @code{os.realpath()}.

@item 
bpo-37834@footnote{https://bugs.python.org/issue37834}: Treat all name surrogate reparse points on Windows in
@ref{1f2,,os.lstat()} and other reparse points as regular files in
@ref{1f1,,os.stat()}.

@item 
bpo-36266@footnote{https://bugs.python.org/issue36266}: Add the module name in the formatted error message when DLL
load fail happens during module import in
@code{_PyImport_FindSharedFuncptrWindows()}. Patch by Srinivas Nyayapati.

@item 
bpo-25172@footnote{https://bugs.python.org/issue25172}: Trying to import the @ref{29,,crypt} module on Windows will result
in an @ref{32d,,ImportError} with a message explaining that the module isn't
supported on Windows. On other platforms, if the underlying @code{_crypt}
module is not available, the ImportError will include a message explaining
the problem.

@item 
bpo-37778@footnote{https://bugs.python.org/issue37778}: Fixes the icons used for file associations to the Microsoft
Store package.

@item 
bpo-37734@footnote{https://bugs.python.org/issue37734}: Fix use of registry values to launch Python from Microsoft
Store app.

@item 
bpo-28269@footnote{https://bugs.python.org/issue28269}: Replace use of @code{strcasecmp()} for the system function
@code{_stricmp()}. Patch by Minmin Gong.
@end itemize

@node macOS<6>,IDLE<14>,Windows<9>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id83}@anchor{f24}
@subsubsection macOS



@itemize -

@item 
bpo-18049@footnote{https://bugs.python.org/issue18049}: Increase the default stack size of threads from 5MB to 16MB on
macOS, to match the stack size of the main thread. This avoids crashes on
deep recursion in threads.
@end itemize

@node IDLE<14>,工具/示例<5>,macOS<6>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id84}@anchor{f25}
@subsubsection IDLE



@itemize -

@item 
bpo-37824@footnote{https://bugs.python.org/issue37824}: Properly handle user input warnings in IDLE shell. Cease
turning SyntaxWarnings into SyntaxErrors.

@item 
bpo-37929@footnote{https://bugs.python.org/issue37929}: IDLE Settings dialog now closes properly when there is no shell
window.

@item 
bpo-37849@footnote{https://bugs.python.org/issue37849}: Fixed completions list appearing too high or low when shown
above the current line.

@item 
bpo-36419@footnote{https://bugs.python.org/issue36419}: Refactor IDLE autocomplete and improve testing.

@item 
bpo-37748@footnote{https://bugs.python.org/issue37748}: Reorder the Run menu.  Put the most common choice, Run Module,
at the top.
@end itemize

@node 工具/示例<5>,C API<6>,IDLE<14>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id85}@anchor{f26}
@subsubsection 工具/示例



@itemize -

@item 
bpo-37942@footnote{https://bugs.python.org/issue37942}: Improve ArgumentClinic converter for floats.

@item 
bpo-37034@footnote{https://bugs.python.org/issue37034}: Argument Clinic now uses the argument name on errors with
keyword-only argument instead of their position. Patch contributed by Rémi
Lapeyre.
@end itemize

@node C API<6>,,工具/示例<5>,Python 3 8 0 beta 4
@anchor{whatsnew/changelog id86}@anchor{f27}
@subsubsection C API



@itemize -

@item 
bpo-36763@footnote{https://bugs.python.org/issue36763}: Options added by @code{PySys_AddXOption()} are now handled the
same way than @code{PyConfig.xoptions} and command line @code{-X} options.

@item 
bpo-37926@footnote{https://bugs.python.org/issue37926}: Fix a crash in @code{PySys_SetArgvEx(0, NULL, 0)}.
@end itemize

@node Python 3 8 0 beta 3,Python 3 8 0 beta 2,Python 3 8 0 beta 4,更新日志
@anchor{whatsnew/changelog python-3-8-0-beta-3}@anchor{f28}
@subsection Python 3.8.0 beta 3


@emph{发布日期: 2019-07-29}

@menu
* 安全: 安全<10>. 
* 核心与内置: 核心与内置<14>. 
* 库: 库<14>. 
* 文档: 文档<10>. 
* 测试: 测试<9>. 
* 构建: 构建<8>. 
* Windows: Windows<10>. 
* IDLE: IDLE<15>. 
* 工具/示例: 工具/示例<6>. 

@end menu

@node 安全<10>,核心与内置<14>,,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id87}@anchor{f29}
@subsubsection 安全



@itemize -

@item 
bpo-37461@footnote{https://bugs.python.org/issue37461}: Fix an infinite loop when parsing specially crafted email
headers. Patch by Abhilash Raj.
@end itemize

@node 核心与内置<14>,库<14>,安全<10>,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id88}@anchor{f2a}
@subsubsection 核心与内置



@itemize -

@item 
bpo-37593@footnote{https://bugs.python.org/issue37593}: Swap the positions of the @emph{posonlyargs} and @emph{args} parameters
in the constructor of @code{ast.parameters} nodes.

@item 
bpo-36974@footnote{https://bugs.python.org/issue36974}: Implemented separate vectorcall functions for every calling
convention of builtin functions and methods. This improves performance for
calls.
@end itemize

@node 库<14>,文档<10>,核心与内置<14>,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id89}@anchor{f2b}
@subsubsection 库



@itemize -

@item 
bpo-37697@footnote{https://bugs.python.org/issue37697}: Syncronize @code{importlib.metadata} with importlib_metadata 0.19@footnote{https://gitlab.com/python-devs/importlib_metadata/-/milestones/20},
improving handling of EGG-INFO files and fixing a crash when entry point
names contained colons.

@item 
bpo-37691@footnote{https://bugs.python.org/issue37691}: Let math.dist() accept coordinates as sequences (or iterables)
rather than just tuples.

@item 
bpo-37664@footnote{https://bugs.python.org/issue37664}: Update wheels bundled with ensurepip (pip 19.2.1 and setuptools
41.0.1)

@item 
bpo-36324@footnote{https://bugs.python.org/issue36324}: Make internal attributes for statistics.NormalDist() private.

@item 
bpo-37491@footnote{https://bugs.python.org/issue37491}: Fix @code{IndexError} when parsing email headers with unexpectedly
ending bare-quoted string value. Patch by Abhilash Raj.

@item 
bpo-37579@footnote{https://bugs.python.org/issue37579}: Return @ref{846,,NotImplemented} in Python implementation of
@code{__eq__} for @ref{195,,timedelta} and @ref{4ed,,time}
when the other object being compared is not of the same type to match C
implementation. Patch by Karthikeyan Singaravelan.

@item 
bpo-21478@footnote{https://bugs.python.org/issue21478}: Record calls to parent when autospecced object is attached to a
mock using @code{unittest.mock.attach_mock()}. Patch by Karthikeyan
Singaravelan.

@item 
bpo-37502@footnote{https://bugs.python.org/issue37502}: pickle.loads() no longer raises TypeError when the buffers
argument is set to None

@item 
bpo-37520@footnote{https://bugs.python.org/issue37520}: Correct behavior for zipfile.Path.parent when the path object
identifies a subdirectory.

@item 
bpo-18374@footnote{https://bugs.python.org/issue18374}: Fix the @code{.col_offset} attribute of nested @code{ast.BinOp}
instances which had a too large value in some situations.

@item 
bpo-37421@footnote{https://bugs.python.org/issue37421}: Fix @code{multiprocessing.util.get_temp_dir()} finalizer: clear
also the 'tempdir' configuration of the current process, so next call to
@code{get_temp_dir()} will create a new temporary directory, rather than
reusing the removed temporary directory.

@item 
bpo-37481@footnote{https://bugs.python.org/issue37481}: The distutils @code{bdist_wininst} command is deprecated in Python
3.8, use @code{bdist_wheel} (wheel packages) instead.

@item 
bpo-26967@footnote{https://bugs.python.org/issue26967}: An @ref{68f,,ArgumentParser} with
@code{allow_abbrev=False} no longer disables grouping of short flags, such as
@code{-vv}, but only disables abbreviation of long flags as documented. Patch
by Zac Hatfield-Dodds.

@item 
bpo-37347@footnote{https://bugs.python.org/issue37347}: @ref{f2c,,sqlite3.Connection.create_aggregate()},
@ref{f2d,,sqlite3.Connection.create_function()},
@ref{f2e,,sqlite3.Connection.set_authorizer()},
@ref{f2f,,sqlite3.Connection.set_progress_handler()}
@ref{a88,,sqlite3.Connection.set_trace_callback()} methods lead to segfaults if
some of these methods are called twice with an equal object but not the
same. Now callbacks are stored more carefully. Patch by Aleksandr Balezin.

@item 
bpo-36564@footnote{https://bugs.python.org/issue36564}: Fix infinite loop in email header folding logic that would be
triggered when an email policy's max_line_length is not long enough to
include the required markup and any values in the message. Patch by Paul
Ganssle
@end itemize

@node 文档<10>,测试<9>,库<14>,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id90}@anchor{f30}
@subsubsection 文档



@itemize -

@item 
bpo-32910@footnote{https://bugs.python.org/issue32910}: Remove implementation-specific behaviour of how venv's
Deactivate works.

@item 
bpo-37284@footnote{https://bugs.python.org/issue37284}: Add a brief note to indicate that any new
@code{sys.implementation} required attributes must go through the PEP
process.

@item 
bpo-30088@footnote{https://bugs.python.org/issue30088}: Documented that @ref{ca1,,mailbox.Maildir} constructor doesn't
attempt to verify the maildir folder layout correctness. Patch by
Sviatoslav Sydorenko.

@item 
bpo-37521@footnote{https://bugs.python.org/issue37521}: Fix @ref{9b,,importlib} examples to insert any newly created modules
via importlib.util.module_from_spec() immediately into sys.modules instead
of after calling loader.exec_module().

Thanks to Benjamin Mintz for finding the bug.

@item 
bpo-37456@footnote{https://bugs.python.org/issue37456}: Slash ('/') is now part of syntax.

@item 
bpo-37487@footnote{https://bugs.python.org/issue37487}: Fix PyList_GetItem index description to include 0.

@item 
bpo-37149@footnote{https://bugs.python.org/issue37149}: Replace the dead link to the Tkinter 8.5 reference by John
Shipman, New Mexico Tech, with a link to the archive.org copy.

@item 
bpo-37478@footnote{https://bugs.python.org/issue37478}: Added possible exceptions to the description of os.chdir().
@end itemize

@node 测试<9>,构建<8>,文档<10>,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id91}@anchor{f31}
@subsubsection 测试



@itemize -

@item 
bpo-37558@footnote{https://bugs.python.org/issue37558}: Fix test_shared_memory_cleaned_after_process_termination name
handling

@item 
bpo-37526@footnote{https://bugs.python.org/issue37526}: Add @ref{f32,,test.support.catch_threading_exception()}: context
manager catching @ref{234,,threading.Thread} exception using
@ref{231,,threading.excepthook()}.

@item 
bpo-37421@footnote{https://bugs.python.org/issue37421}: test_concurrent_futures now explicitly stops the ForkServer
instance if it's running.

@item 
bpo-37421@footnote{https://bugs.python.org/issue37421}: multiprocessing tests now stop the ForkServer instance if it's
running: close the "alive" file descriptor to ask the server to stop and
then remove its UNIX address.
@end itemize

@node 构建<8>,Windows<10>,测试<9>,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id92}@anchor{f33}
@subsubsection 构建



@itemize -

@item 
bpo-36044@footnote{https://bugs.python.org/issue36044}: Reduce the number of unit tests run for the PGO generation
task.  This speeds up the task by a factor of about 15x.  Running the full
unit test suite is slow.  This change may result in a slightly less
optimized build since not as many code branches will be executed.  If you
are willing to wait for the much slower build, the old behavior can be
restored using './configure [..] PROFILE_TASK="-m test --pgo-extended"'.
We make no guarantees as to which PGO task set produces a faster build.
Users who care should run their own relevant benchmarks as results can
depend on the environment, workload, and compiler tool chain.
@end itemize

@node Windows<10>,IDLE<15>,构建<8>,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id93}@anchor{f34}
@subsubsection Windows



@itemize -

@item 
bpo-37672@footnote{https://bugs.python.org/issue37672}: Switch Windows Store package's pip to use bundled
@code{pip.ini} instead of 
@geindex PIP_USER
@geindex 环境变量; PIP_USER
@code{PIP_USER} variable.
@end itemize

@node IDLE<15>,工具/示例<6>,Windows<10>,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id94}@anchor{f35}
@subsubsection IDLE



@itemize -

@item 
bpo-37692@footnote{https://bugs.python.org/issue37692}: Improve highlight config sample with example shell interaction
and better labels for shell elements.

@item 
bpo-37628@footnote{https://bugs.python.org/issue37628}: Settings dialog no longer expands with font size.

@item 
bpo-37627@footnote{https://bugs.python.org/issue37627}: Initialize the Customize Run dialog with the command line
arguments most recently entered before.  The user can optionally edit
before submitting them.

@item 
bpo-33610@footnote{https://bugs.python.org/issue33610}: Fix code context not showing the correct context when first
toggled on.

@item 
bpo-37530@footnote{https://bugs.python.org/issue37530}: Optimize code context to reduce unneeded background activity.
Font and highlight changes now occur along with text changes instead of
after a random delay.

@item 
bpo-27452@footnote{https://bugs.python.org/issue27452}: Cleanup @code{config.py} by inlining @code{RemoveFile} and
simplifying the handling of @code{file} in @code{CreateConfigHandlers}.

@item 
bpo-17535@footnote{https://bugs.python.org/issue17535}: Add optional line numbers for IDLE editor windows.  Windows
open without line numbers unless set otherwise in the General tab of the
configuration dialog.

@item 
bpo-26806@footnote{https://bugs.python.org/issue26806}: To compensate for stack frames added by IDLE and avoid possible
problems with low recursion limits, add 30 to limits in the user code
execution process.  Subtract 30 when reporting recursion limits to make
this addition mostly transparent.

@item 
bpo-36390@footnote{https://bugs.python.org/issue36390}: Gather Format menu functions into format.py.  Combine
paragraph.py, rstrip.py, and format methods from editor.py.
@end itemize

@node 工具/示例<6>,,IDLE<15>,Python 3 8 0 beta 3
@anchor{whatsnew/changelog id95}@anchor{f36}
@subsubsection 工具/示例



@itemize -

@item 
bpo-37675@footnote{https://bugs.python.org/issue37675}: 2to3 now works when run from a zipped standard library.
@end itemize

@node Python 3 8 0 beta 2,Python 3 8 0 beta 1,Python 3 8 0 beta 3,更新日志
@anchor{whatsnew/changelog python-3-8-0-beta-2}@anchor{f37}
@subsection Python 3.8.0 beta 2


@emph{发布日期: 2019-07-04}

@menu
* 安全: 安全<11>. 
* 核心与内置: 核心与内置<15>. 
* 库: 库<15>. 
* 文档: 文档<11>. 
* 测试: 测试<10>. 
* 构建: 构建<9>. 
* Windows: Windows<11>. 
* macOS: macOS<7>. 
* IDLE: IDLE<16>. 
* C API: C API<7>. 

@end menu

@node 安全<11>,核心与内置<15>,,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id96}@anchor{f38}
@subsubsection 安全



@itemize -

@item 
bpo-37363@footnote{https://bugs.python.org/issue37363}: Adds audit events for the range of supported run commands (see
@ref{f39,,命令行与环境}).

@item 
bpo-37463@footnote{https://bugs.python.org/issue37463}: ssl.match_hostname() no longer accepts IPv4 addresses with
additional text after the address and only quad-dotted notation without
trailing whitespaces. Some inet_aton() implementations ignore whitespace
and all data after whitespace, e.g. '127.0.0.1 whatever'.

@item 
bpo-37363@footnote{https://bugs.python.org/issue37363}: Adds audit events for @ref{7a,,ensurepip}, @ref{84,,ftplib},
@ref{8a,,glob}, @ref{98,,imaplib}, @ref{c0,,nntplib}, @ref{c9,,pdb}, @ref{d0,,poplib},
@ref{e9,,shutil}, @ref{ed,,smtplib}, @ref{f2,,sqlite3}, @ref{f9,,subprocess},
@ref{102,,telnetlib}, @ref{103,,tempfile} and @ref{129,,webbrowser}, as well as
@ref{a3c,,os.listdir()}, @ref{25f,,os.scandir()} and @ref{2f2,,breakpoint()}.

@item 
bpo-37364@footnote{https://bugs.python.org/issue37364}: @ref{eb1,,io.open_code()} is now used when reading @code{.pth}
files.

@item 
bpo-34631@footnote{https://bugs.python.org/issue34631}: 在Windows安装程序中将OpenSSL更新为1.1.1c
@end itemize

@node 核心与内置<15>,库<15>,安全<11>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id97}@anchor{f3a}
@subsubsection 核心与内置



@itemize -

@item 
bpo-37467@footnote{https://bugs.python.org/issue37467}: Fix @ref{e5c,,sys.excepthook()} and @code{PyErr_Display()} if a
filename is a bytes string. For example, for a SyntaxError exception where
the filename attribute is a bytes string.

@item 
bpo-37417@footnote{https://bugs.python.org/issue37417}: @code{bytearray.extend()} now correctly handles errors that
arise during iteration. Patch by Brandt Bucher.

@item 
bpo-24214@footnote{https://bugs.python.org/issue24214}: Improved support of the surrogatepass error handler in the
UTF-8 and UTF-16 incremental decoders.

@item 
bpo-35224@footnote{https://bugs.python.org/issue35224}: Reverse evaluation order of key: value in dict comprehensions
as proposed in PEP 572. I.e. in @code{@{k: v for ...@}}, @code{k} will be
evaluated before @code{v}.

@item 
bpo-37316@footnote{https://bugs.python.org/issue37316}: Fix the @ref{ec5,,PySys_Audit()} call in @ref{1ec,,mmap.mmap}.

@item 
bpo-37269@footnote{https://bugs.python.org/issue37269}: Fix a bug in the peephole optimizer that was not treating
correctly constant conditions with binary operators. Patch by Pablo
Galindo.

@item 
bpo-37213@footnote{https://bugs.python.org/issue37213}: Handle correctly negative line offsets in the peephole
optimizer. Patch by Pablo Galindo.

@item 
bpo-37219@footnote{https://bugs.python.org/issue37219}: Remove errorneous optimization for empty set differences.

@item 
bpo-36922@footnote{https://bugs.python.org/issue36922}: Slot functions optimize any callable with
@code{Py_TPFLAGS_METHOD_DESCRIPTOR} instead of only instances of
@code{function}.

@item 
bpo-36974@footnote{https://bugs.python.org/issue36974}: The slot @code{tp_vectorcall_offset} is inherited unconditionally
to support @code{super().__call__()} when the base class uses vectorcall.

@item 
bpo-37160@footnote{https://bugs.python.org/issue37160}: @ref{233,,threading.get_native_id()} now also supports NetBSD.

@item 
bpo-37077@footnote{https://bugs.python.org/issue37077}: Add @ref{233,,threading.get_native_id()} support for AIX. Patch by
M. Felt
@end itemize

@node 库<15>,文档<11>,核心与内置<15>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id98}@anchor{f3b}
@subsubsection 库



@itemize -

@item 
bpo-37440@footnote{https://bugs.python.org/issue37440}: http.client now enables TLS 1.3 post-handshake authentication
for default context or if a cert_file is passed to HTTPSConnection.

@item 
bpo-37437@footnote{https://bugs.python.org/issue37437}: Update vendorized expat version to 2.2.7.

@item 
bpo-37428@footnote{https://bugs.python.org/issue37428}: SSLContext.post_handshake_auth = True no longer sets
SSL_VERIFY_POST_HANDSHAKE verify flag for client connections. Although the
option is documented as ignored for clients, OpenSSL implicitly enables
cert chain validation when the flag is set.

@item 
bpo-37420@footnote{https://bugs.python.org/issue37420}: @ref{a50,,os.sched_setaffinity()} now correctly handles errors that
arise during iteration over its @code{mask} argument. Patch by Brandt Bucher.

@item 
bpo-37412@footnote{https://bugs.python.org/issue37412}: The @ref{2b8,,os.getcwdb()} function now uses the UTF-8 encoding on
Windows, rather than the ANSI code page: see 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529} for the rationale.
The function is no longer deprecated on Windows.

@item 
bpo-29412@footnote{https://bugs.python.org/issue29412}: Fix IndexError in parsing a header value ending unexpectedly.
Patch by Abhilash Raj.

@item 
bpo-36546@footnote{https://bugs.python.org/issue36546}: The @emph{dist} argument for statistics.quantiles() is now
positional only. The current name doesn't reflect that the argument can be
either a dataset or a distribution.  Marking the parameter as positional
avoids confusion and makes it possible to change the name later.

@item 
bpo-37394@footnote{https://bugs.python.org/issue37394}: Fix a bug that was causing the @ref{da,,queue} module to fail if
the accelerator module was not available. Patch by Pablo Galindo.

@item 
bpo-33972@footnote{https://bugs.python.org/issue33972}: Email with single part but content-type set to @code{multipart/*}
doesn't raise AttributeError anymore.

@item 
bpo-37280@footnote{https://bugs.python.org/issue37280}: Use threadpool for reading from file for sendfile fallback
mode.

@item 
bpo-37279@footnote{https://bugs.python.org/issue37279}: Fix asyncio sendfile support when sendfile sends extra data in
fallback mode.

@item 
bpo-19865@footnote{https://bugs.python.org/issue19865}: @ref{f3c,,ctypes.create_unicode_buffer()} now also supports
non-BMP characters on platforms with 16-bit @code{wchar_t} (for
example, Windows and AIX).

@item 
bpo-37210@footnote{https://bugs.python.org/issue37210}: Allow pure Python implementation of @ref{ca,,pickle} to work even
when the C @code{_pickle} module is unavailable.

@item 
bpo-35922@footnote{https://bugs.python.org/issue35922}: Fix @code{RobotFileParser.crawl_delay()} and
@code{RobotFileParser.request_rate()} to return @code{None} rather than raise
@ref{393,,AttributeError} when no relevant rule is defined in the robots.txt
file.  Patch by Rémi Lapeyre.

@item 
bpo-35766@footnote{https://bugs.python.org/issue35766}: Change the format of feature_version to be a (major, minor)
tuple.

@item 
bpo-36607@footnote{https://bugs.python.org/issue36607}: Eliminate @ref{2ba,,RuntimeError} raised by
@ref{34a,,asyncio.all_tasks()} if internal tasks weak set is changed by
another thread during iteration.

@item 
bpo-18748@footnote{https://bugs.python.org/issue18748}: @code{_pyio.IOBase} destructor now does nothing if getting
the @code{closed} attribute fails to better mimick @code{_io.IOBase}
finalizer.

@item 
bpo-36402@footnote{https://bugs.python.org/issue36402}: Fix a race condition at Python shutdown when waiting for
threads. Wait until the Python thread state of all non-daemon threads get
deleted (join all non-daemon threads), rather than just wait until
non-daemon Python threads complete.

@item 
bpo-34886@footnote{https://bugs.python.org/issue34886}: Fix an unintended ValueError from @ref{3e5,,subprocess.run()} when
checking for conflicting @ref{c64,,input} and @code{stdin} or @code{capture_output} and
@code{stdout} or @code{stderr} args when they were explicitly provided but with
@ref{157,,None} values within a passed in @code{**kwargs} dict rather than as passed
directly by name. Patch contributed by Rémi Lapeyre.

@item 
bpo-37173@footnote{https://bugs.python.org/issue37173}: The exception message for @code{inspect.getfile()} now correctly
reports the passed class rather than the builtins module.

@item 
bpo-37178@footnote{https://bugs.python.org/issue37178}: Give math.perm() a one argument form that means the same as
math.factorial().

@item 
bpo-37178@footnote{https://bugs.python.org/issue37178}: For math.perm(n, k), let k default to n, giving the same result
as factorial.

@item 
bpo-37163@footnote{https://bugs.python.org/issue37163}: Deprecated passing @code{obj} argument of
@ref{f3d,,dataclasses.replace()} as keyword argument.

@item 
bpo-37165@footnote{https://bugs.python.org/issue37165}: Converted _collections._count_elements to use the Argument
Clinic.

@item 
bpo-34767@footnote{https://bugs.python.org/issue34767}: Do not always create a @ref{52b,,collections.deque} in
@ref{28b,,asyncio.Lock}.

@item 
bpo-37158@footnote{https://bugs.python.org/issue37158}: Speed-up statistics.fmean() by switching from a function to a
generator.

@item 
bpo-37150@footnote{https://bugs.python.org/issue37150}: @code{argparse._ActionsContainer.add_argument} now throws error, if
someone accidentally pass FileType class object instead of instance of
FileType as @ref{603,,type} argument

@item 
bpo-35621@footnote{https://bugs.python.org/issue35621}: Support running asyncio subprocesses when execution event loop
in a thread on UNIX.

@item 
bpo-36520@footnote{https://bugs.python.org/issue36520}: Lengthy email headers with UTF-8 characters are now properly
encoded when they are folded. Patch by Jeffrey Kintscher.

@item 
bpo-30835@footnote{https://bugs.python.org/issue30835}: Fixed a bug in email parsing where a message with invalid bytes
in content-transfer-encoding of a multipart message can cause an
AttributeError. Patch by Andrew Donnellan.

@item 
bpo-35805@footnote{https://bugs.python.org/issue35805}: Add parser for Message-ID header and add it to default
HeaderRegistry. This should prevent folding of Message-ID using RFC 2048
encoded words.

@item 
bpo-35070@footnote{https://bugs.python.org/issue35070}: posix.getgrouplist() now works correctly when the user belongs
to NGROUPS_MAX supplemental groups. Patch by Jeffrey Kintscher.

@item 
bpo-32627@footnote{https://bugs.python.org/issue32627}: Fix compile error when @code{_uuid} headers conflicting included.

@item 
bpo-11122@footnote{https://bugs.python.org/issue11122}: Distutils won't check for rpmbuild in specified paths only.

@item 
bpo-4963@footnote{https://bugs.python.org/issue4963}: Fixed non-deterministic behavior related to mimetypes extension
mapping and module reinitialization.
@end itemize

@node 文档<11>,测试<10>,库<15>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id99}@anchor{f3e}
@subsubsection 文档



@itemize -

@item 
bpo-34903@footnote{https://bugs.python.org/issue34903}: Documented that in @ref{f3f,,datetime.datetime.strptime()}, the
leading zero in some two-digit formats is optional. Patch by Mike Gleen.
@end itemize

@node 测试<10>,构建<9>,文档<11>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id100}@anchor{f40}
@subsubsection 测试



@itemize -

@item 
bpo-37421@footnote{https://bugs.python.org/issue37421}: test_distutils.test_build_ext() is now able to remove the
temporary directory on Windows: don't import the newly built C extension
("xx") in the current process, but test it in a separated process.

@item 
bpo-37421@footnote{https://bugs.python.org/issue37421}: test_concurrent_futures now cleans up multiprocessing to remove
immediately temporary directories created by
multiprocessing.util.get_temp_dir().

@item 
bpo-37421@footnote{https://bugs.python.org/issue37421}: test_winconsoleio doesn't leak a temporary file anymore: use
tempfile.TemporaryFile() to remove it when the test completes.

@item 
bpo-37421@footnote{https://bugs.python.org/issue37421}: multiprocessing tests now explicitly call @code{_run_finalizers()}
to immediately remove temporary directories created by tests.

@item 
bpo-37199@footnote{https://bugs.python.org/issue37199}: Fix test failures when IPv6 is unavailable or disabled.

@item 
bpo-37335@footnote{https://bugs.python.org/issue37335}: Remove no longer necessary code from c locale coercion tests

@item 
bpo-37421@footnote{https://bugs.python.org/issue37421}: Fix test_shutil to no longer leak temporary files.

@item 
bpo-37411@footnote{https://bugs.python.org/issue37411}: Fix test_wsgiref.testEnviron() to no longer depend on the
environment variables (don't fail if "X" variable is set).

@item 
bpo-37400@footnote{https://bugs.python.org/issue37400}: Fix test_os.test_chown(): use os.getgroups() rather than
grp.getgrall() to get groups. Rename also the test to test_chown_gid().

@item 
bpo-37359@footnote{https://bugs.python.org/issue37359}: Add --cleanup option to python3 -m test to remove
@code{test_python_*} directories of previous failed jobs. Add "make
cleantest" to run @code{python3 -m test --cleanup}.

@item 
bpo-37362@footnote{https://bugs.python.org/issue37362}: test_gdb no longer fails if it gets an "unexpected" message on
stderr: it now ignores stderr. The purpose of test_gdb is to test that
python-gdb.py commands work as expected, not to test gdb.

@item 
bpo-35998@footnote{https://bugs.python.org/issue35998}: Avoid TimeoutError in test_asyncio: test_start_tls_server_1()

@item 
bpo-37278@footnote{https://bugs.python.org/issue37278}: Fix test_asyncio ProactorLoopCtrlC: join the thread to prevent
leaking a running thread and leaking a reference.

@item 
bpo-37261@footnote{https://bugs.python.org/issue37261}: Fix @ref{f41,,test.support.catch_unraisable_exception()}: its
__exit__() method now ignores unraisable exception raised when clearing
its @code{unraisable} attribute.

@item 
bpo-37169@footnote{https://bugs.python.org/issue37169}: Rewrite @code{_PyObject_IsFreed()} unit tests.

@item 
bpo-37153@footnote{https://bugs.python.org/issue37153}: @code{test_venv.test_mutiprocessing()} now explicitly calls
@code{pool.terminate()} to wait until the pool completes.

@item 
bpo-28009@footnote{https://bugs.python.org/issue28009}: Modify the test_uuid logic to test when a program is available
AND can be used to obtain a MACADDR as basis for an UUID. Patch by M. Felt
@end itemize

@node 构建<9>,Windows<11>,测试<10>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id101}@anchor{f42}
@subsubsection 构建



@itemize -

@item 
bpo-37189@footnote{https://bugs.python.org/issue37189}: Many @code{PyRun_XXX()} functions like @ref{f43,,PyRun_String()} were
no longer exported in @code{libpython38.dll} by mistake. Export them again to
fix the ABI compatibiliy.
@end itemize

@node Windows<11>,macOS<7>,构建<9>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id102}@anchor{f44}
@subsubsection Windows



@itemize -

@item 
bpo-10945@footnote{https://bugs.python.org/issue10945}: 正式取消对在非Windows系统上创建 bdist_wininst 安装程序的支持。

@item 
bpo-37369@footnote{https://bugs.python.org/issue37369}: Fixes path for @ref{274,,sys.executable} when running from the
Microsoft Store.

@item 
bpo-37351@footnote{https://bugs.python.org/issue37351}: Removes libpython38.a from standard Windows distribution.

@item 
bpo-35360@footnote{https://bugs.python.org/issue35360}: 更新 Windows 构建以使用 SQLite 3.28.0.

@item 
bpo-37267@footnote{https://bugs.python.org/issue37267}: On Windows, @ref{f23,,os.dup()} no longer creates an inheritable fd
when handling a character file.

@item 
bpo-36779@footnote{https://bugs.python.org/issue36779}: Ensure @code{time.tzname} is correct on Windows when the active
code page is set to CP_UTF7 or CP_UTF8.
@end itemize

@node macOS<7>,IDLE<16>,Windows<11>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id103}@anchor{f45}
@subsubsection macOS



@itemize -

@item 
bpo-34602@footnote{https://bugs.python.org/issue34602}: Avoid test suite failures on macOS by no longer calling
resource.setrlimit to increase the process stack size limit at runtime.
The runtime change is no longer needed since the interpreter is being
built with a larger default stack size.

@item 
bpo-35360@footnote{https://bugs.python.org/issue35360}: 更新macOS安装程序以使用SQLite 3.28.0.

@item 
bpo-34631@footnote{https://bugs.python.org/issue34631}: 在MacOS安装程序中将OpenSSL更新为1.1.1c。
@end itemize

@node IDLE<16>,C API<7>,macOS<7>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id104}@anchor{f46}
@subsubsection IDLE



@itemize -

@item 
bpo-37325@footnote{https://bugs.python.org/issue37325}: Fix tab focus traversal order for help source and custom run
dialogs.

@item 
bpo-37321@footnote{https://bugs.python.org/issue37321}: Both subprocess connection error messages now refer to the
'Startup failure' section of the IDLE doc.

@item 
bpo-37177@footnote{https://bugs.python.org/issue37177}: Properly 'attach' search dialogs to their main window so that
they behave like other dialogs and do not get hidden behind their main
window.

@item 
bpo-37039@footnote{https://bugs.python.org/issue37039}: Adjust "Zoom Height" to individual screens by momemtarily
maximizing the window on first use with a particular screen.  Changing
screen settings may invalidate the saved height.  While a window is
maximized, "Zoom Height" has no effect.

@item 
bpo-35763@footnote{https://bugs.python.org/issue35763}: Make calltip reminder about '/' meaning positional-only less
obtrusive by only adding it when there is room on the first line.

@item 
bpo-5680@footnote{https://bugs.python.org/issue5680}: Add 'Run... Customized' to the Run menu to run a module with
customized settings.  Any 'command line arguments' entered are added to
sys.argv. One can suppress the normal Shell main module restart.
@end itemize

@node C API<7>,,IDLE<16>,Python 3 8 0 beta 2
@anchor{whatsnew/changelog id105}@anchor{f47}
@subsubsection C API



@itemize -

@item 
bpo-36763@footnote{https://bugs.python.org/issue36763}: Add @code{PyConfig_SetWideStringList()} function.

@item 
bpo-28805@footnote{https://bugs.python.org/issue28805}: The @ref{f48,,METH_FASTCALL} calling convention has been
documented.

@item 
bpo-37221@footnote{https://bugs.python.org/issue37221}: @code{tp_print} is put back at the end of the @code{PyTypeObject}
structure to restore support for old code (in particular generated by
Cython) setting @code{tp_print = 0}. Note that @code{tp_print} will be removed
entirely in Python 3.9.

@item 
bpo-37221@footnote{https://bugs.python.org/issue37221}: The new function @ref{271,,PyCode_NewWithPosOnlyArgs()} allows to
create code objects like @ref{272,,PyCode_New()}, but with an extra
@emph{posonlyargcount} parameter for indicating the number of positonal-only
arguments.

@item 
bpo-37215@footnote{https://bugs.python.org/issue37215}: Fix dtrace issue introduce by bpo-36842@footnote{https://bugs.python.org/issue36842}

@item 
bpo-37191@footnote{https://bugs.python.org/issue37191}: Python.h does not need compiler support for intermingled
declarations (GCC's @code{-Wdeclaration-after-statement}), which were added
in 3.8.0 Beta 1. Note that in Python 3.9, intermingled declarations will
be needed again.

@item 
bpo-37170@footnote{https://bugs.python.org/issue37170}: Fix the cast on error in
@ref{f49,,PyLong_AsUnsignedLongLongMask()}.
@end itemize

@node Python 3 8 0 beta 1,Python 3 8 0 alpha 4,Python 3 8 0 beta 2,更新日志
@anchor{whatsnew/changelog python-3-8-0-beta-1}@anchor{f4a}
@subsection Python 3.8.0 beta 1


@emph{发布日期: 2019-06-04}

@menu
* 安全: 安全<12>. 
* 核心与内置: 核心与内置<16>. 
* 库: 库<16>. 
* 文档: 文档<12>. 
* 测试: 测试<11>. 
* 构建: 构建<10>. 
* Windows: Windows<12>. 
* macOS: macOS<8>. 
* IDLE: IDLE<17>. 
* 工具/示例: 工具/示例<7>. 
* C API: C API<8>. 

@end menu

@node 安全<12>,核心与内置<16>,,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id106}@anchor{f4b}
@subsubsection 安全



@itemize -

@item 
bpo-35907@footnote{https://bugs.python.org/issue35907}: CVE-2019-9948: Avoid file reading by disallowing
@code{local-file://} and @code{local_file://} URL schemes in
@code{URLopener().open()} and @code{URLopener().retrieve()} of
@ref{120,,urllib.request}.

@item 
bpo-33529@footnote{https://bugs.python.org/issue33529}: Prevent fold function used in email header encoding from
entering infinite loop when there are too many non-ASCII characters in a
header.

@item 
bpo-33164@footnote{https://bugs.python.org/issue33164}: Updated blake2 implementation which uses secure memset
implementation provided by platform.
@end itemize

@node 核心与内置<16>,库<16>,安全<12>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id107}@anchor{f4c}
@subsubsection 核心与内置



@itemize -

@item 
bpo-35814@footnote{https://bugs.python.org/issue35814}: Allow unpacking in the right hand side of annotated
assignments. In particular, @code{t: Tuple[int, ...] = x, y, *z} is now
allowed.

@item 
bpo-37126@footnote{https://bugs.python.org/issue37126}: All structseq objects are now tracked by the garbage collector.
Patch by Pablo Galindo.

@item 
bpo-37122@footnote{https://bugs.python.org/issue37122}: Make the @emph{co_argcount} attribute of code objects represent the
total number of positional arguments (including positional-only
arguments). The value of @emph{co_posonlyargcount} can be used to distinguish
which arguments are positional only, and the difference (@emph{co_argcount} -
@emph{co_posonlyargcount}) is the number of positional-or-keyword arguments.
Patch by Pablo Galindo.

@item 
bpo-20092@footnote{https://bugs.python.org/issue20092}: Constructors of @ref{184,,int}, @ref{187,,float} and
@ref{189,,complex} will now use the @ref{18a,,__index__()} special
method, if available and the corresponding method @ref{18b,,__int__()},
@ref{18c,,__float__()} or @ref{18d,,__complex__()} is not available.

@item 
bpo-37087@footnote{https://bugs.python.org/issue37087}: Add native thread ID (TID) support to OpenBSD.

@item 
bpo-26219@footnote{https://bugs.python.org/issue26219}: Implemented per opcode cache mechanism and @code{LOAD_GLOBAL}
instruction use it. @code{LOAD_GLOBAL} is now about 40% faster. Contributed
by Yury Selivanov, and Inada Naoki.

@item 
bpo-37072@footnote{https://bugs.python.org/issue37072}: Fix crash in PyAST_FromNodeObject() when flags is NULL.

@item 
bpo-37029@footnote{https://bugs.python.org/issue37029}: Freeing a great many small objects could take time quadratic in
the number of arenas, due to using linear search to keep @code{obmalloc.c}'s
list of usable arenas sorted by order of number of free memory pools.
This is accomplished without search now, leaving the worst-case time
linear in the number of arenas.  For programs where this quite visibly
matters (typically with more than 100 thousand small objects alive
simultaneously), this can greatly reduce the time needed to release their
memory.

@item 
bpo-26423@footnote{https://bugs.python.org/issue26423}: Fix possible overflow in @code{wrap_lenfunc()} when @code{sizeof(long)
< sizeof(Py_ssize_t)} (e.g., 64-bit Windows).

@item 
bpo-37050@footnote{https://bugs.python.org/issue37050}: Improve the AST for "debug" f-strings, which use '=' to print
out the source of the expression being evaluated.  Delete expr_text from
the FormattedValue node, and instead use a Constant string node (possibly
merged with adjacent constant expressions inside the f-string).

@item 
bpo-22385@footnote{https://bugs.python.org/issue22385}: The @ref{62b,,bytes.hex}, @ref{62c,,bytearray.hex}, and @ref{62d,,memoryview.hex} methods
as well as the @ref{f4d,,binascii.hexlify} and @code{b2a_hex} functions now have the
ability to include an optional separator between hex bytes.  This
functionality was inspired by MicroPython's hexlify implementation.

@item 
bpo-26836@footnote{https://bugs.python.org/issue26836}: Add @ref{1f0,,os.memfd_create()}.

@item 
bpo-37032@footnote{https://bugs.python.org/issue37032}: Added new @code{replace()} method to the code type
(@ref{198,,types.CodeType}).

@item 
bpo-37007@footnote{https://bugs.python.org/issue37007}: Implement @ref{220,,socket.if_nameindex()},
@ref{221,,socket.if_nametoindex()}, and @ref{222,,socket.if_indextoname()} on
Windows.

@item 
bpo-36829@footnote{https://bugs.python.org/issue36829}: @ref{f4e,,PyErr_WriteUnraisable()} now creates a traceback object
if there is no current traceback. Moreover, call
@ref{f4f,,PyErr_NormalizeException()} and @ref{f50,,PyException_SetTraceback()}
to normalize the exception value. Ignore any error.

@item 
bpo-36878@footnote{https://bugs.python.org/issue36878}: Only accept text after @code{# type: ignore} if the first character
is ASCII. This is to disallow things like @code{# type: ignoreé}.

@item 
bpo-36878@footnote{https://bugs.python.org/issue36878}: Store text appearing after a @code{# type: ignore} comment in the
AST. For example a type ignore like @code{# type: ignore[E1000]} will have the
string @code{"[E1000]"} stored in its AST node.

@item 
bpo-2180@footnote{https://bugs.python.org/issue2180}: Treat line continuation at EOF as a @code{SyntaxError} by Anthony
Sottile.

@item 
bpo-36907@footnote{https://bugs.python.org/issue36907}: Fix a crash when calling a C function with a keyword dict
(@code{f(**kwargs)}) and changing the dict @code{kwargs} while that function is
running.

@item 
bpo-36946@footnote{https://bugs.python.org/issue36946}: Fix possible signed integer overflow when handling slices.

@item 
bpo-36826@footnote{https://bugs.python.org/issue36826}: Add NamedExpression kind support to ast_unparse.c

@item 
bpo-1875@footnote{https://bugs.python.org/issue1875}: A @ref{452,,SyntaxError} is now raised if a code blocks that will be
optimized away (e.g. if conditions that are always false) contains syntax
errors. Patch by Pablo Galindo.

@item 
bpo-36027@footnote{https://bugs.python.org/issue36027}: Allow computation of modular inverses via three-argument
@code{pow}: the second argument is now permitted to be negative in the case
where the first and third arguments are relatively prime.

@item 
bpo-36861@footnote{https://bugs.python.org/issue36861}: Update the Unicode database to version 12.1.0.

@item 
bpo-28866@footnote{https://bugs.python.org/issue28866}: Avoid caching attributes of classes which type defines mro() to
avoid a hard cache invalidation problem.

@item 
bpo-36851@footnote{https://bugs.python.org/issue36851}: The @code{FrameType} stack is now correctly cleaned up if the
execution ends with a return and the stack is not empty.

@item 
bpo-34616@footnote{https://bugs.python.org/issue34616}: The @code{compile()} builtin functions now support the
@code{ast.PyCF_ALLOW_TOP_LEVEL_AWAIT} flag,  which allow to compile sources
that  contains top-level @code{await}, @code{async with} or @code{async for}. This
is useful to evaluate async-code from with an already async functions; for
example in a custom REPL.

@item 
bpo-36842@footnote{https://bugs.python.org/issue36842}: Implement PEP 578, adding sys.audit, io.open_code and related
APIs.

@item 
bpo-27639@footnote{https://bugs.python.org/issue27639}: Correct return type for UserList slicing operations. Patch by
Michael Blahay, Erick Cervantes, and vaultah

@item 
bpo-36737@footnote{https://bugs.python.org/issue36737}: Move PyRuntimeState.warnings into per-interpreter state (via
"module state").

@item 
bpo-36793@footnote{https://bugs.python.org/issue36793}: Removed @code{__str__} implementations from builtin types
@ref{183,,bool}, @ref{184,,int}, @ref{187,,float}, @ref{189,,complex} and few
classes from the standard library. They now inherit @code{__str__()} from
@ref{2b0,,object}.

@item 
bpo-36817@footnote{https://bugs.python.org/issue36817}: Add a @code{=} feature f-strings for debugging. This can precede
@code{!s}, @code{!r}, or @code{!a}. It produces the text of the expression,
followed by an equal sign, followed by the repr of the value of the
expression. So @code{f'@{3*9+15=@}'} would be equal to the string
@code{'3*9+15=42'}.  If @code{=} is specified, the default conversion is set to
@code{!r}, unless a format spec is given, in which case the formatting
behavior is unchanged, and __format__ will be used.

@item 
bpo-24048@footnote{https://bugs.python.org/issue24048}: Save the live exception during import.c's @code{remove_module()}.

@item 
bpo-27987@footnote{https://bugs.python.org/issue27987}: pymalloc returns memory blocks aligned by 16 bytes, instead of
8 bytes, on 64-bit platforms to conform x86-64 ABI. Recent compilers
assume this alignment more often. Patch by Inada Naoki.

@item 
bpo-36601@footnote{https://bugs.python.org/issue36601}: A long-since-meaningless check for @code{getpid() == main_pid} was
removed from Python's internal C signal handler.

@item 
bpo-36594@footnote{https://bugs.python.org/issue36594}: Fix incorrect use of @code{%p} in format strings. Patch by Zackery
Spytz.

@item 
bpo-36045@footnote{https://bugs.python.org/issue36045}: builtins.help() now prefixes @code{async} for async functions

@item 
bpo-36084@footnote{https://bugs.python.org/issue36084}: Add native thread ID (TID) to threading.Thread objects
(supported platforms: Windows, FreeBSD, Linux, macOS)

@item 
bpo-36035@footnote{https://bugs.python.org/issue36035}: Added fix for broken symlinks in combination with pathlib

@item 
bpo-35983@footnote{https://bugs.python.org/issue35983}: Added new trashcan macros to deal with a double deallocation
that could occur when the @code{tp_dealloc} of a subclass calls the
@code{tp_dealloc} of a base class and that base class uses the trashcan
mechanism. Patch by Jeroen Demeyer.

@item 
bpo-20602@footnote{https://bugs.python.org/issue20602}: Do not clear @ref{b35,,sys.flags} and @ref{f51,,sys.float_info}
during shutdown. Patch by Zackery Spytz.

@item 
bpo-26826@footnote{https://bugs.python.org/issue26826}: Expose @code{copy_file_range()} as a low level API in the
@ref{c4,,os} module.

@item 
bpo-32388@footnote{https://bugs.python.org/issue32388}: Remove cross-version binary compatibility requirement in
tp_flags.

@item 
bpo-31862@footnote{https://bugs.python.org/issue31862}: Port binascii to PEP 489 multiphase initialization. Patch by
Marcel Plch.
@end itemize

@node 库<16>,文档<12>,核心与内置<16>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id108}@anchor{f52}
@subsubsection 库



@itemize -

@item 
bpo-37128@footnote{https://bugs.python.org/issue37128}: Added @ref{1e6,,math.perm()}.

@item 
bpo-37120@footnote{https://bugs.python.org/issue37120}: Add SSLContext.num_tickets to control the number of TLSv1.3
session tickets.

@item 
bpo-12202@footnote{https://bugs.python.org/issue12202}: Fix the error handling in
@ref{f53,,msilib.SummaryInformation.GetProperty()}. Patch by Zackery Spytz.

@item 
bpo-26835@footnote{https://bugs.python.org/issue26835}: The fcntl module now contains file sealing constants for
sealing of memfds.

@item 
bpo-29262@footnote{https://bugs.python.org/issue29262}: Add @code{get_origin()} and @code{get_args()} introspection helpers
to @code{typing} module.

@item 
bpo-12639@footnote{https://bugs.python.org/issue12639}: @ref{f54,,msilib.Directory.start_component()} no longer fails if
@emph{keyfile} is not @code{None}.

@item 
bpo-36999@footnote{https://bugs.python.org/issue36999}: Add the @code{asyncio.Task.get_coro()} method to publicly expose
the tasks's coroutine object.

@item 
bpo-35246@footnote{https://bugs.python.org/issue35246}: Make @ref{291,,asyncio.create_subprocess_exec()} accept path-like
arguments.

@item 
bpo-35279@footnote{https://bugs.python.org/issue35279}: Change default @emph{max_workers} of @code{ThreadPoolExecutor} from
@code{cpu_count() * 5} to @code{min(32, cpu_count() + 4))}.  Previous value was
unreasonably large on many cores machines.

@item 
bpo-37076@footnote{https://bugs.python.org/issue37076}: @ref{f55,,_thread.start_new_thread()} now logs uncaught exception
raised by the function using @ref{22d,,sys.unraisablehook()}, rather than
@ref{e5c,,sys.excepthook()}, so the hook gets access to the function which
raised the exception.

@item 
bpo-33725@footnote{https://bugs.python.org/issue33725}: On macOS, the @ref{b7,,multiprocessing} module now uses @emph{spawn}
start method by default.

@item 
bpo-37054@footnote{https://bugs.python.org/issue37054}: Fix destructor @code{_pyio.BytesIO} and
@code{_pyio.TextIOWrapper}: initialize their @code{_buffer} attribute as
soon as possible (in the class body), because it's used by @code{__del__()}
which calls @code{close()}.

@item 
bpo-37058@footnote{https://bugs.python.org/issue37058}: PEP 544: Add @code{Protocol} and @code{@@runtime_checkable} to the
@code{typing} module.

@item 
bpo-36933@footnote{https://bugs.python.org/issue36933}: The functions @code{sys.set_coroutine_wrapper} and
@code{sys.get_coroutine_wrapper} that were deprecated and marked for removal
in 3.8 have been removed.

@item 
bpo-37047@footnote{https://bugs.python.org/issue37047}: Handle late binding and attribute access in
@ref{248,,unittest.mock.AsyncMock} setup for autospeccing. Document newly
implemented async methods in @ref{77f,,unittest.mock.MagicMock}.

@item 
bpo-37049@footnote{https://bugs.python.org/issue37049}: PEP 589: Add @code{TypedDict} to the @code{typing} module.

@item 
bpo-37046@footnote{https://bugs.python.org/issue37046}: PEP 586: Add @code{Literal} to the @code{typing} module.

@item 
bpo-37045@footnote{https://bugs.python.org/issue37045}: PEP 591: Add @code{Final} qualifier and @code{@@final} decorator to
the @code{typing} module.

@item 
bpo-37035@footnote{https://bugs.python.org/issue37035}: Don't log OSError based exceptions if a fatal error has
occurred in asyncio transport. Peer can generate almost any OSError, user
cannot avoid these exceptions by fixing own code. Errors are still
propagated to user code, it's just logging them is pointless and pollute
asyncio logs.

@item 
bpo-37001@footnote{https://bugs.python.org/issue37001}: @ref{f56,,symtable.symtable()} now accepts the same input types for
source code as the built-in @ref{1b4,,compile()} function. Patch by Dino
Viehland.

@item 
bpo-37028@footnote{https://bugs.python.org/issue37028}: Implement asyncio REPL

@item 
bpo-37027@footnote{https://bugs.python.org/issue37027}: Return safe to use proxy socket object from
transport.get_extra_info('socket')

@item 
bpo-32528@footnote{https://bugs.python.org/issue32528}: Make asyncio.CancelledError a BaseException.

This will address the common mistake many asyncio users make: an "except
Exception" clause breaking Tasks cancellation.

In addition to this change, we stop inheriting asyncio.TimeoutError and
asyncio.InvalidStateError from their concurrent.futures.* counterparts.
There's no point for these exceptions to share the inheritance chain.

@item 
bpo-1230540@footnote{https://bugs.python.org/issue1230540}: Add a new @ref{231,,threading.excepthook()} function which handles
uncaught @ref{232,,threading.Thread.run()} exception. It can be overridden to
control how uncaught @ref{232,,threading.Thread.run()} exceptions are handled.

@item 
bpo-36996@footnote{https://bugs.python.org/issue36996}: Handle @ref{782,,unittest.mock.patch()} used as a decorator on async
functions.

@item 
bpo-37008@footnote{https://bugs.python.org/issue37008}: Add support for calling @ref{67c,,next()} with the mock resulting
from @ref{f57,,unittest.mock.mock_open()}

@item 
bpo-27737@footnote{https://bugs.python.org/issue27737}: Allow whitespace only header encoding in @code{email.header} - by
Batuhan Taskaya

@item 
bpo-36969@footnote{https://bugs.python.org/issue36969}: PDB command @code{args} now  display positional only arguments.
Patch contributed by Rémi Lapeyre.

@item 
bpo-36969@footnote{https://bugs.python.org/issue36969}: PDB command @code{args} now  display keyword only arguments. Patch
contributed by Rémi Lapeyre.

@item 
bpo-36983@footnote{https://bugs.python.org/issue36983}: Add missing names to @code{typing.__all__}: @code{ChainMap},
@code{ForwardRef}, @code{OrderedDict} - by Anthony Sottile.

@item 
bpo-36972@footnote{https://bugs.python.org/issue36972}: Add SupportsIndex protocol to the typing module to allow type
checking to detect classes that can be passed to @ref{c5f,,hex()}, @ref{c5e,,oct()} and
@ref{c39,,bin()}.

@item 
bpo-32972@footnote{https://bugs.python.org/issue32972}: Implement @code{unittest.IsolatedAsyncioTestCase} to help testing
asyncio-based code.

@item 
bpo-36952@footnote{https://bugs.python.org/issue36952}: @ref{2ad,,fileinput.input()} and @ref{27e,,fileinput.FileInput}
@strong{bufsize} argument has been removed (was deprecated and ignored since
Python 3.6), and as a result the @strong{mode} and @strong{openhook} arguments have
been made keyword-only.

@item 
bpo-36952@footnote{https://bugs.python.org/issue36952}: Starting with Python 3.3, importing ABCs from
@ref{1e,,collections} is deprecated, and import should be done from
@ref{1f,,collections.abc}. Still being able to import from @ref{1e,,collections}
was marked for removal in 3.8, but has been delayed to 3.9; documentation
and @code{DeprecationWarning} clarified.

@item 
bpo-36949@footnote{https://bugs.python.org/issue36949}: Implement __repr__ for WeakSet objects.

@item 
bpo-36948@footnote{https://bugs.python.org/issue36948}: Fix @ref{d74,,NameError} in
@ref{f58,,urllib.request.URLopener.retrieve()}. Patch by Karthikeyan
Singaravelan.

@item 
bpo-33524@footnote{https://bugs.python.org/issue33524}: Fix the folding of email header when the max_line_length is 0
or None and the header contains non-ascii characters.  Contributed by
Licht Takeuchi (@@Licht-T).

@item 
bpo-24564@footnote{https://bugs.python.org/issue24564}: @ref{a72,,shutil.copystat()} now ignores @ref{f59,,errno.EINVAL} on
@ref{a49,,os.setxattr()} which may occur when copying files on filesystems
without extended attributes support.

Original patch by Giampaolo Rodola, updated by Ying Wang.

@item 
bpo-36888@footnote{https://bugs.python.org/issue36888}: Python child processes can now access the status of their
parent process using multiprocessing.process.parent_process

@item 
bpo-36921@footnote{https://bugs.python.org/issue36921}: Deprecate @code{@@coroutine} for sake of @code{async def}.

@item 
bpo-25652@footnote{https://bugs.python.org/issue25652}: Fix bug in @code{__rmod__} of @code{UserString} - by Batuhan Taskaya.

@item 
bpo-36916@footnote{https://bugs.python.org/issue36916}: Remove a message about an unhandled exception in a task when
writer.write() is used without await and writer.drain() fails with an
exception.

@item 
bpo-36889@footnote{https://bugs.python.org/issue36889}: Introduce @code{asyncio.Stream} class that merges
@ref{f5a,,asyncio.StreamReader} and @ref{f5b,,asyncio.StreamWriter}
functionality. @code{asyncio.Stream} can work in readonly, writeonly and
readwrite modes. Provide @code{asyncio.connect()},
@code{asyncio.connect_unix()}, @code{asyncio.connect_read_pipe()} and
@code{asyncio.connect_write_pipe()} factories to open
@code{asyncio.Stream} connections. Provide @code{asyncio.StreamServer}
and @code{UnixStreamServer} to serve servers with asyncio.Stream API.
Modify @ref{292,,asyncio.create_subprocess_shell()} and
@ref{291,,asyncio.create_subprocess_exec()} to use @code{asyncio.Stream}
instead of deprecated @code{StreamReader} and @code{StreamWriter}.
Deprecate @ref{f5a,,asyncio.StreamReader} and @ref{f5b,,asyncio.StreamWriter}.
Deprecate usage of private classes, e.g.
@code{asyncio.FlowControlMixing} and
@code{asyncio.StreamReaderProtocol} outside of asyncio package.

@item 
bpo-36845@footnote{https://bugs.python.org/issue36845}: Added validation of integer prefixes to the construction of IP
networks and interfaces in the ipaddress module.

@item 
bpo-23378@footnote{https://bugs.python.org/issue23378}: Add an extend action to argparser.

@item 
bpo-36867@footnote{https://bugs.python.org/issue36867}: Fix a bug making a SharedMemoryManager instance and its parent
process use two separate resource_tracker processes.

@item 
bpo-23896@footnote{https://bugs.python.org/issue23896}: Adds a grammar to lib2to3.pygram that contains exec as a
function not as statement.

@item 
bpo-36895@footnote{https://bugs.python.org/issue36895}: The function @code{time.clock()} was deprecated in 3.3 in favor of
@code{time.perf_counter()} and marked for removal in 3.8, it has removed.

@item 
bpo-35545@footnote{https://bugs.python.org/issue35545}: Fix asyncio discarding IPv6 scopes when ensuring hostname
resolutions internally

@item 
bpo-36887@footnote{https://bugs.python.org/issue36887}: Add new function @ref{1e8,,math.isqrt()} to compute integer square
roots.

@item 
bpo-34632@footnote{https://bugs.python.org/issue34632}: Introduce the @code{importlib.metadata} module with (provisional)
support for reading metadata from third-party packages.

@item 
bpo-36878@footnote{https://bugs.python.org/issue36878}: When using @code{type_comments=True} in @ref{1a1,,ast.parse}, treat @code{# type:
ignore} followed by a non-alphanumeric character and then arbitrary text
as a type ignore, instead of requiring nothing but whitespace or another
comment. This is to permit formations such as @code{# type: ignore[E1000]}.

@item 
bpo-36778@footnote{https://bugs.python.org/issue36778}: @code{cp65001} encoding (Windows code page 65001) becomes an alias
to @code{utf_8} encoding.

@item 
bpo-36867@footnote{https://bugs.python.org/issue36867}: The multiprocessing.resource_tracker replaces the
multiprocessing.semaphore_tracker module. Other than semaphores,
resource_tracker also tracks shared_memory segments.

@item 
bpo-30262@footnote{https://bugs.python.org/issue30262}: The @code{Cache} and @code{Statement} objects of the @ref{f2,,sqlite3}
module are not exposed to the user.  Patch by Aviv Palivoda.

@item 
bpo-24538@footnote{https://bugs.python.org/issue24538}: In @ref{a72,,shutil.copystat()}, first copy extended file attributes and
then file permissions, since extended attributes can only be set on the
destination while it is still writeable.

@item 
bpo-36829@footnote{https://bugs.python.org/issue36829}: Add new @ref{22d,,sys.unraisablehook()} function which can be
overridden to control how "unraisable exceptions" are handled. It is
called when an exception has occurred but there is no way for Python to
handle it. For example, when a destructor raises an exception or during
garbage collection (@ref{22e,,gc.collect()}).

@item 
bpo-36832@footnote{https://bugs.python.org/issue36832}: Introducing @code{zipfile.Path}, a pathlib-compatible wrapper for
traversing zip files.

@item 
bpo-36814@footnote{https://bugs.python.org/issue36814}: Fix an issue where os.posix_spawnp() would incorrectly raise a
TypeError when file_actions is None.

@item 
bpo-33110@footnote{https://bugs.python.org/issue33110}: Handle exceptions raised by functions added by
concurrent.futures add_done_callback correctly when the Future has already
completed.

@item 
bpo-26903@footnote{https://bugs.python.org/issue26903}: Limit @code{max_workers} in @code{ProcessPoolExecutor} to 61 to work
around a WaitForMultipleObjects limitation.

@item 
bpo-36813@footnote{https://bugs.python.org/issue36813}: Fix @ref{70c,,QueueListener} to call
@code{queue.task_done()} upon stopping. Patch by Bar Harel.

@item 
bpo-36806@footnote{https://bugs.python.org/issue36806}: Forbid creation of asyncio stream objects like StreamReader,
StreamWriter, Process, and their protocols outside of asyncio package.

@item 
bpo-36802@footnote{https://bugs.python.org/issue36802}: Provide both sync and async calls for StreamWriter.write() and
StreamWriter.close()

@item 
bpo-36801@footnote{https://bugs.python.org/issue36801}: Properly handle SSL connection closing in asyncio
StreamWriter.drain() call.

@item 
bpo-36785@footnote{https://bugs.python.org/issue36785}: Implement PEP 574 (pickle protocol 5 with out-of-band buffers).

@item 
bpo-36772@footnote{https://bugs.python.org/issue36772}: functools.lru_cache() can now be used as a straight decorator
in addition to its existing usage as a function that returns a decorator.

@item 
bpo-6584@footnote{https://bugs.python.org/issue6584}: Add a @ref{1d2,,BadGzipFile} exception to the @ref{8c,,gzip}
module.

@item 
bpo-36748@footnote{https://bugs.python.org/issue36748}: Optimized write buffering in C implementation of
@code{TextIOWrapper}. Writing ASCII string to @code{TextIOWrapper} with ascii,
latin1, or utf-8 encoding is about 20% faster.  Patch by Inada Naoki.

@item 
bpo-8138@footnote{https://bugs.python.org/issue8138}: Don't mark @code{wsgiref.simple_server.SimpleServer} as
multi-threaded since @code{wsgiref.simple_server.WSGIServer} is
single-threaded.

@item 
bpo-22640@footnote{https://bugs.python.org/issue22640}: @ref{215,,py_compile.compile()} now supports silent mode. Patch by
Joannah Nanjekye

@item 
bpo-29183@footnote{https://bugs.python.org/issue29183}: Fix double exceptions in @ref{f5c,,wsgiref.handlers.BaseHandler}
by calling its @code{close()} method only
when no exception is raised.

@item 
bpo-36548@footnote{https://bugs.python.org/issue36548}: Improved the repr of regular expression flags.

@item 
bpo-36542@footnote{https://bugs.python.org/issue36542}: The signature of Python functions can now be overridden by
specifying the @code{__text_signature__} attribute.

@item 
bpo-36533@footnote{https://bugs.python.org/issue36533}: Reinitialize logging.Handler locks in forked child processes
instead of attempting to acquire them all in the parent before forking
only to be released in the child process.  The acquire/release pattern was
leading to deadlocks in code that has implemented any form of chained
logging handlers that depend upon one another as the lock acquisition
order cannot be guaranteed.

@item 
bpo-35252@footnote{https://bugs.python.org/issue35252}: Throw a TypeError instead of an AssertionError when using an
invalid type annotation with singledispatch.

@item 
bpo-35900@footnote{https://bugs.python.org/issue35900}: Allow reduction methods to return a 6-item tuple where the 6th
item specifies a custom state-setting method that's called instead of the
regular @code{__setstate__} method.

@item 
bpo-35900@footnote{https://bugs.python.org/issue35900}: enable custom reduction callback registration for functions and
classes in _pickle.c, using the new Pickler's attribute
@code{reducer_override}

@item 
bpo-36368@footnote{https://bugs.python.org/issue36368}: Fix a bug crashing SharedMemoryManager instances in interactive
sessions after a ctrl-c (KeyboardInterrupt) was sent

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Fix mmap fail for VxWorks

@item 
bpo-27497@footnote{https://bugs.python.org/issue27497}: @ref{b74,,csv.DictWriter.writeheader()} now returns the return value
of the underlying @code{csv.Writer.writerow()} method. Patch contributed by
Ashish Nitin Patil.

@item 
bpo-36239@footnote{https://bugs.python.org/issue36239}: Parsing .mo files now ignores comments starting and ending with
#-#-#-#-#.

@item 
bpo-26707@footnote{https://bugs.python.org/issue26707}: Enable plistlib to read and write binary plist files that were
created as a KeyedArchive file. Specifically, this allows the plistlib to
process 0x80 tokens as UID objects.

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Add posix module support for VxWorks.

@item 
bpo-35125@footnote{https://bugs.python.org/issue35125}: Asyncio: Remove inner callback on outer cancellation in shield

@item 
bpo-35721@footnote{https://bugs.python.org/issue35721}: Fix @code{asyncio.SelectorEventLoop.subprocess_exec()} leaks
file descriptors if @code{Popen} fails and called with
@code{stdin=subprocess.PIPE}. Patch by Niklas Fiekas.

@item 
bpo-31855@footnote{https://bugs.python.org/issue31855}: @ref{f57,,unittest.mock.mock_open()} results now respects the
argument of read([size]). Patch contributed by Rémi Lapeyre.

@item 
bpo-35431@footnote{https://bugs.python.org/issue35431}: Implement @ref{1e7,,math.comb()} that returns binomial coefficient,
that computes the number of ways to choose k items from n items without
repetition and without order. Patch by Yash Aggarwal and Keller Fuchs.

@item 
bpo-26660@footnote{https://bugs.python.org/issue26660}: Fixed permission errors in
@ref{bc1,,TemporaryDirectory} clean up. Previously
@code{TemporaryDirectory.cleanup()} failed when non-writeable or
non-searchable files or directories were created inside a temporary
directory.

@item 
bpo-34271@footnote{https://bugs.python.org/issue34271}: Add debugging helpers to ssl module. It's now possible to dump
key material and to trace TLS protocol. The default and stdlib contexts
also support SSLKEYLOGFILE env var.

@item 
bpo-26467@footnote{https://bugs.python.org/issue26467}: Added AsyncMock to support using unittest to mock asyncio
coroutines. Patch by Lisa Roach.

@item 
bpo-33569@footnote{https://bugs.python.org/issue33569}: dataclasses.InitVar: Exposes the type used to create the init
var.

@item 
bpo-34424@footnote{https://bugs.python.org/issue34424}: Fix serialization of messages containing encoded strings when
the policy.linesep is set to a multi-character string. Patch by Jens
Troeger.

@item 
bpo-34303@footnote{https://bugs.python.org/issue34303}: Performance of @ref{c68,,functools.reduce()} is slightly improved.
Patch by Sergey Fedoseev.

@item 
bpo-33361@footnote{https://bugs.python.org/issue33361}: Fix a bug in @ref{f5d,,codecs.StreamRecoder} where seeking might
leave old data in a buffer and break subsequent read calls. Patch by Ammar
Askar.

@item 
bpo-22454@footnote{https://bugs.python.org/issue22454}: The @ref{e8,,shlex} module now exposes @ref{217,,shlex.join()}, the
inverse of @ref{218,,shlex.split()}. Patch by Bo Bayles.

@item 
bpo-31922@footnote{https://bugs.python.org/issue31922}: @code{asyncio.AbstractEventLoop.create_datagram_endpoint()}: Do
not connect UDP socket when broadcast is allowed. This allows to receive
replies after a UDP broadcast.

@item 
bpo-24882@footnote{https://bugs.python.org/issue24882}: Change ThreadPoolExecutor to use existing idle threads before
spinning up new ones.

@item 
bpo-31961@footnote{https://bugs.python.org/issue31961}: Added support for bytes and path-like objects in
@ref{2b9,,subprocess.Popen()} on Windows.  The @emph{args} parameter now accepts a
@ref{363,,path-like object} if @emph{shell} is @code{False} and a sequence containing
bytes and path-like objects. The @emph{executable} parameter now accepts a
bytes and @ref{363,,path-like object}. The @emph{cwd} parameter now accepts a
bytes object. Based on patch by Anders Lorentsen.

@item 
bpo-33123@footnote{https://bugs.python.org/issue33123}: @ref{f5e,,pathlib.Path.unlink} now accepts a @emph{missing_ok}
parameter to avoid a @ref{7ba,,FileNotFoundError} from being raised. Patch by
Robert Buchholz.

@item 
bpo-32941@footnote{https://bugs.python.org/issue32941}: Allow @ref{1ec,,mmap.mmap} objects to access the madvise() system
call (through @ref{1ed,,mmap.mmap.madvise()}).

@item 
bpo-22102@footnote{https://bugs.python.org/issue22102}: Added support for ZIP files with disks set to 0. Such files are
commonly created by builtin tools on Windows when use ZIP64 extension.
Patch by Francisco Facioni.

@item 
bpo-32515@footnote{https://bugs.python.org/issue32515}: trace.py can now run modules via python3 -m trace -t --module
module_name

@item 
bpo-32299@footnote{https://bugs.python.org/issue32299}: Changed @ref{f5f,,unittest.mock.patch.dict()} to return the patched
dictionary when used as context manager. Patch by Vadim Tsander.

@item 
bpo-27141@footnote{https://bugs.python.org/issue27141}: Added a @code{__copy__()} to @code{collections.UserList} and
@code{collections.UserDict} in order to correctly implement shallow copying
of the objects. Patch by Bar Harel.

@item 
bpo-31829@footnote{https://bugs.python.org/issue31829}: @code{\r}, @code{\0} and @code{\x1a} (end-of-file on Windows) are now
escaped in protocol 0 pickles of Unicode strings. This allows to load them
without loss from files open in text mode in Python 2.

@item 
bpo-23395@footnote{https://bugs.python.org/issue23395}: @code{_thread.interrupt_main()} now avoids setting the Python
error status if the @code{SIGINT} signal is ignored or not handled by Python.
@end itemize

@node 文档<12>,测试<11>,库<16>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id109}@anchor{f60}
@subsubsection 文档



@itemize -

@item 
bpo-36896@footnote{https://bugs.python.org/issue36896}: Clarify that some types have unstable constructor signature
between Python versions.

@item 
bpo-36686@footnote{https://bugs.python.org/issue36686}: Improve documentation of the stdin, stdout, and stderr
arguments of of the @code{asyncio.subprocess_exec} function to specify which
values are supported. Also mention that decoding as text is not supported.

Add a few tests to verify that the various values passed to the std*
arguments actually work.

@item 
bpo-36984@footnote{https://bugs.python.org/issue36984}: Improve version added references in @code{typing} module - by
Anthony Sottile.

@item 
bpo-36868@footnote{https://bugs.python.org/issue36868}: What's new now mentions SSLContext.hostname_checks_common_name
instead of SSLContext.host_flags.

@item 
bpo-35924@footnote{https://bugs.python.org/issue35924}: Add a note to the @code{curses.addstr()} documentation to warn
that multiline strings can cause segfaults because of an ncurses bug.

@item 
bpo-36783@footnote{https://bugs.python.org/issue36783}: Added C API Documentation for Time_FromTimeAndFold and
PyDateTime_FromDateAndTimeAndFold as per PEP 495. Patch by Edison
Abahurire.

@item 
bpo-36797@footnote{https://bugs.python.org/issue36797}: More of the legacy distutils documentation has been either
pruned, or else more clearly marked as being retained solely until the
setuptools documentation covers it independently.

@item 
bpo-22865@footnote{https://bugs.python.org/issue22865}: Add detail to the documentation on the @ref{892,,pty.spawn} function.

@item 
bpo-35397@footnote{https://bugs.python.org/issue35397}: Remove deprecation and document urllib.parse.unwrap(). Patch
contributed by Rémi Lapeyre.

@item 
bpo-32995@footnote{https://bugs.python.org/issue32995}: Added the context variable in glossary.

@item 
bpo-33519@footnote{https://bugs.python.org/issue33519}: Clarify that @ref{26,,copy()} is not part of the @code{MutableSequence} ABC.

@item 
bpo-33482@footnote{https://bugs.python.org/issue33482}: Make @code{codecs.StreamRecoder.writelines} take a list of bytes.

@item 
bpo-25735@footnote{https://bugs.python.org/issue25735}: Added documentation for func factorial to indicate that returns
integer values

@item 
bpo-20285@footnote{https://bugs.python.org/issue20285}: Expand object.__doc__ (docstring) to make it clearer. Modify
pydoc.py so that help(object) lists object methods (for other classes,
help omits methods of the object base class.)
@end itemize

@node 测试<11>,构建<10>,文档<12>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id110}@anchor{f61}
@subsubsection 测试



@itemize -

@item 
bpo-37069@footnote{https://bugs.python.org/issue37069}: Modify test_coroutines, test_cprofile, test_generators,
test_raise, test_ssl and test_yield_from to use
@ref{f41,,test.support.catch_unraisable_exception()} rather than
@ref{f62,,test.support.captured_stderr()}.

@item 
bpo-37098@footnote{https://bugs.python.org/issue37098}: Fix test_memfd_create on older Linux Kernels.

@item 
bpo-37081@footnote{https://bugs.python.org/issue37081}: 使用OpenSSL 1.1.1c进行测试

@item 
bpo-36829@footnote{https://bugs.python.org/issue36829}: Add @ref{f41,,test.support.catch_unraisable_exception()}: context
manager catching unraisable exception using @ref{22d,,sys.unraisablehook()}.

@item 
bpo-36915@footnote{https://bugs.python.org/issue36915}: The main regrtest process now always removes all temporary
directories of worker processes even if they crash or if they are killed
on KeyboardInterrupt (CTRL+c).

@item 
bpo-36719@footnote{https://bugs.python.org/issue36719}: "python3 -m test -jN ..." now continues the execution of next
tests when a worker process crash (CHILD_ERROR state). Previously, the
test suite stopped immediately. Use --failfast to stop at the first error.

@item 
bpo-36816@footnote{https://bugs.python.org/issue36816}: Update Lib/test/selfsigned_pythontestdotnet.pem to match
self-signed.pythontest.net's new TLS certificate.

@item 
bpo-35925@footnote{https://bugs.python.org/issue35925}: Skip httplib and nntplib networking tests when they would
otherwise fail due to a modern OS or distro with a default OpenSSL policy
of rejecting connections to servers with weak certificates.

@item 
bpo-36782@footnote{https://bugs.python.org/issue36782}: Add tests for several C API functions in the @ref{31,,datetime}
module. Patch by Edison Abahurire.

@item 
bpo-36342@footnote{https://bugs.python.org/issue36342}: Fix test_multiprocessing in test_venv if platform lacks
functioning sem_open.
@end itemize

@node 构建<10>,Windows<12>,测试<11>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id111}@anchor{f63}
@subsubsection 构建



@itemize -

@item 
bpo-36721@footnote{https://bugs.python.org/issue36721}: To embed Python into an application, a new @code{--embed} option
must be passed to @code{python3-config --libs --embed} to get @code{-lpython3.8}
(link the application to libpython). To support both 3.8 and older, try
@code{python3-config --libs --embed} first and fallback to @code{python3-config
--libs} (without @code{--embed}) if the previous command fails.

增加一个 pkg-config @code{python-3.8-embed} 模块用来将 Python 嵌入到一个应用中: @code{pkg-config python-3.8-embed --libs} 包含 @code{-lpython3.8}。 要同时支持 3.8 和旧版本，请先尝试 @code{pkg-config python-X.Y-embed --libs} 并在此命令失败时回退到 @code{pkg-config python-X.Y --libs} (即不带 @code{--embed}) （请将 @code{X.Y} 替换为 Python 版本号）。

On the other hand, @code{pkg-config python3.8 --libs} no longer contains
@code{-lpython3.8}. C extensions must not be linked to libpython (except on
Android, case handled by the script); this change is backward incompatible
on purpose.

@item 
bpo-36786@footnote{https://bugs.python.org/issue36786}: "make install" now runs compileall in parallel.
@end itemize

@node Windows<12>,macOS<8>,构建<10>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id112}@anchor{f64}
@subsubsection Windows



@itemize -

@item 
bpo-36965@footnote{https://bugs.python.org/issue36965}: include of STATUS_CONTROL_C_EXIT without depending on MSC
compiler

@item 
bpo-35926@footnote{https://bugs.python.org/issue35926}: 在Windows安装程序中将OpenSSL更新为1.1.1b

@item 
bpo-29883@footnote{https://bugs.python.org/issue29883}: Add Windows support for UDP transports for the Proactor Event
Loop. Patch by Adam Meily.

@item 
bpo-33407@footnote{https://bugs.python.org/issue33407}: The @code{Py_DEPRECATED()} macro has been implemented for
MSVC.
@end itemize

@node macOS<8>,IDLE<17>,Windows<12>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id113}@anchor{f65}
@subsubsection macOS



@itemize -

@item 
bpo-36231@footnote{https://bugs.python.org/issue36231}: Support building Python on macOS without /usr/include
installed. As of macOS 10.14, system header files are only available
within an SDK provided by either the Command Line Tools or the Xcode app.
@end itemize

@node IDLE<17>,工具/示例<7>,macOS<8>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id114}@anchor{f66}
@subsubsection IDLE



@itemize -

@item 
bpo-35610@footnote{https://bugs.python.org/issue35610}: Replace now redundant .context_use_ps1 with .prompt_last_line.
This finishes change started in bpo-31858@footnote{https://bugs.python.org/issue31858}.

@item 
bpo-37038@footnote{https://bugs.python.org/issue37038}: Make idlelib.run runnable; add test clause.

@item 
bpo-36958@footnote{https://bugs.python.org/issue36958}: Print any argument other than None or int passed to SystemExit
or sys.exit().

@item 
bpo-36807@footnote{https://bugs.python.org/issue36807}: When saving a file, call os.fsync() so bits are flushed to e.g.
USB drive.

@item 
bpo-32411@footnote{https://bugs.python.org/issue32411}: In browser.py, remove extraneous sorting by line number since
dictionary was created in line number order.
@end itemize

@node 工具/示例<7>,C API<8>,IDLE<17>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id115}@anchor{f67}
@subsubsection 工具/示例



@itemize -

@item 
bpo-37053@footnote{https://bugs.python.org/issue37053}: Handle strings like u"bar" correctly in
Tools/parser/unparse.py. Patch by Chih-Hsuan Yen.
@end itemize

@node C API<8>,,工具/示例<7>,Python 3 8 0 beta 1
@anchor{whatsnew/changelog id116}@anchor{f68}
@subsubsection C API



@itemize -

@item 
bpo-36763@footnote{https://bugs.python.org/issue36763}: Implement the 
@geindex Python 提高建议; PEP 587
PEP 587@footnote{https://www.python.org/dev/peps/pep-0587} "Python Initialization Configuration".

@item 
bpo-36379@footnote{https://bugs.python.org/issue36379}: Fix crashes when attempting to use the @emph{modulo} parameter when
@code{__ipow__} is implemented in C.

@item 
bpo-37107@footnote{https://bugs.python.org/issue37107}: Update @ref{f69,,PyObject_CallMethodObjArgs()} and
@code{_PyObject_CallMethodIdObjArgs} to use @code{_PyObject_GetMethod} to avoid
creating a bound method object in many cases. Patch by Michael J.
Sullivan.

@item 
bpo-36974@footnote{https://bugs.python.org/issue36974}: Implement 
@geindex Python 提高建议; PEP 590
PEP 590@footnote{https://www.python.org/dev/peps/pep-0590}: Vectorcall: a fast calling protocol for
CPython. This is a new protocol to optimize calls of custom callable
objects.

@item 
bpo-36763@footnote{https://bugs.python.org/issue36763}: @code{Py_Main()} now returns the exitcode rather than calling
@code{Py_Exit(exitcode)} when calling @code{PyErr_Print()} if the current
exception type is @code{SystemExit}.

@item 
bpo-36922@footnote{https://bugs.python.org/issue36922}: Add new type flag @code{Py_TPFLAGS_METHOD_DESCRIPTOR} for objects
behaving like unbound methods. These are objects supporting the
optimization given by the @code{LOAD_METHOD}/@code{CALL_METHOD} opcodes. See PEP
590.

@item 
bpo-36728@footnote{https://bugs.python.org/issue36728}: The @code{PyEval_ReInitThreads()} function has been removed
from the C API. It should not be called explicitly: use
@ref{2cd,,PyOS_AfterFork_Child()} instead.
@end itemize

@node Python 3 8 0 alpha 4,Python 3 8 0 alpha 3,Python 3 8 0 beta 1,更新日志
@anchor{whatsnew/changelog python-3-8-0-alpha-4}@anchor{f6a}
@subsection Python 3.8.0 alpha 4


@emph{发布日期: 2019-05-06}

@menu
* 安全: 安全<13>. 
* 核心与内置: 核心与内置<17>. 
* 库: 库<17>. 
* 文档: 文档<13>. 
* 测试: 测试<12>. 
* 构建: 构建<11>. 
* Windows: Windows<13>. 
* macOS: macOS<9>. 
* IDLE: IDLE<18>. 
* 工具/示例: 工具/示例<8>. 
* C API: C API<9>. 

@end menu

@node 安全<13>,核心与内置<17>,,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id117}@anchor{f6b}
@subsubsection 安全



@itemize -

@item 
bpo-36742@footnote{https://bugs.python.org/issue36742}: 于函数 urlsplit() 中修复了对于预规格化字符的不当处理过程。

@item 
bpo-30458@footnote{https://bugs.python.org/issue30458}: Address CVE-2019-9740 by disallowing URL paths with embedded
whitespace or control characters through into the underlying http client
request.  Such potentially malicious header injection URLs now cause an
http.client.InvalidURL exception to be raised.

@item 
bpo-35755@footnote{https://bugs.python.org/issue35755}: @ref{f6c,,shutil.which()} now uses @code{os.confstr("CS_PATH")} if
available and if the 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} environment variable is not set.
Remove also the current directory from @code{posixpath.defpath}. On Unix,
@ref{f6c,,shutil.which()} and the @ref{f9,,subprocess} module no longer search the
executable in the current directory if the 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} environment
variable is not set.
@end itemize

@node 核心与内置<17>,库<17>,安全<13>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id118}@anchor{f6d}
@subsubsection 核心与内置



@itemize -

@item 
bpo-36722@footnote{https://bugs.python.org/issue36722}: In debug build, import now also looks for C extensions compiled
in release mode and for C extensions compiled in the stable ABI.

@item 
bpo-32849@footnote{https://bugs.python.org/issue32849}: Fix Python Initialization code on FreeBSD to detect properly
when stdin file descriptor (fd 0) is invalid.

@item 
bpo-36623@footnote{https://bugs.python.org/issue36623}: Remove parser headers and related function declarations that
lack implementations after the removal of pgen.

@item 
bpo-20180@footnote{https://bugs.python.org/issue20180}: @code{dict.pop()} is now up to 33% faster thanks to Argument
Clinic. Patch by Inada Naoki.

@item 
bpo-36611@footnote{https://bugs.python.org/issue36611}: Debug memory allocators: disable serialno field by default from
debug hooks on Python memory allocators to reduce the memory footprint by
5%. Enable @ref{114,,tracemalloc} to get the traceback where a memory block
has been allocated when a fatal memory error is logged to decide where to
put a breakpoint. Compile Python with @code{PYMEM_DEBUG_SERIALNO} defined to
get back the field.

@item 
bpo-36588@footnote{https://bugs.python.org/issue36588}: On AIX, @ref{2b1,,sys.platform} doesn't contain the major version
anymore. Always return @code{'aix'}, instead of @code{'aix3'} .. @code{'aix7'}.
Since older Python versions include the version number, it is recommended
to always use @code{sys.platform.startswith('aix')}. Contributed by M. Felt.

@item 
bpo-36549@footnote{https://bugs.python.org/issue36549}: Change str.capitalize to use titlecase for the first character
instead of uppercase.

@item 
bpo-36540@footnote{https://bugs.python.org/issue36540}: Implement 
@geindex Python 提高建议; PEP 570
PEP 570@footnote{https://www.python.org/dev/peps/pep-0570} (Python positional-only parameters). Patch
by Pablo Galindo.

@item 
bpo-36475@footnote{https://bugs.python.org/issue36475}: @ref{2b2,,PyEval_AcquireLock()} and @ref{2b3,,PyEval_AcquireThread()}
now terminate the current thread if called while the interpreter is
finalizing, making them consistent with @ref{2b4,,PyEval_RestoreThread()},
@ref{2b5,,Py_END_ALLOW_THREADS()}, and @ref{2b6,,PyGILState_Ensure()}.

@item 
bpo-36504@footnote{https://bugs.python.org/issue36504}: 在 _ctypes.c's @code{PyCArrayType_new()} 中修复了“有符号整数”类型的溢出。

@item 
bpo-20844@footnote{https://bugs.python.org/issue20844}: 修复了含有经编码的 cookie 和换行符的脚本位于 Windows 平台可能运行失败的问题。

@item 
bpo-24214@footnote{https://bugs.python.org/issue24214}: 修复了UTF-8增量解码器对surrogatepass的错误回调方法的支持

@item 
bpo-36452@footnote{https://bugs.python.org/issue36452}: Changing @code{dict} keys during iteration of the dict itself,
@code{keys()}, @code{values()}, or @code{items()} will now be detected in certain
corner cases where keys are deleted/added so that the number of keys isn't
changed. A @ref{2ba,,RuntimeError} will be raised after @code{len(dict)} iterations.
Contributed by Thomas Perl.

@item 
bpo-36459@footnote{https://bugs.python.org/issue36459}: 修复了由于tokenizer.c中的 @code{tok_nextc()} 方法可能导致的两次 @code{PyMem_FREE()} 调用。

@item 
bpo-36433@footnote{https://bugs.python.org/issue36433}: 修复了位于 classmethoddescr_call 的类型错误信息

@item 
bpo-36430@footnote{https://bugs.python.org/issue36430}: 修复了函数 @ref{c14,,itertools.count()} 中的潜在引用对象泄漏。

@item 
bpo-36440@footnote{https://bugs.python.org/issue36440}: Include node names in @code{ParserError} messages, instead of
numeric IDs. Patch by A. Skrobov.

@item 
bpo-36143@footnote{https://bugs.python.org/issue36143}: Regenerate @ref{a6,,keyword} from the Grammar and Tokens file
using pgen. Patch by Pablo Galindo.

@item 
bpo-18372@footnote{https://bugs.python.org/issue18372}: Add missing @ref{e3d,,PyObject_GC_Track()} calls in the
@ref{ca,,pickle} module. Patch by Zackery Spytz.
@end itemize

@node 库<17>,文档<13>,核心与内置<17>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id119}@anchor{f6e}
@subsubsection 库



@itemize -

@item 
bpo-35952@footnote{https://bugs.python.org/issue35952}: Fix pythoninfo when the compiler is missing.

@item 
bpo-28238@footnote{https://bugs.python.org/issue28238}: The @code{.find*()} methods of xml.etree.ElementTree can now
search for wildcards like @code{@{*@}tag} and @code{@{ns@}*} that match a tag in any
namespace or all tags in a namespace.  Patch by Stefan Behnel.

@item 
bpo-26978@footnote{https://bugs.python.org/issue26978}: @code{pathlib.path.link_to()} is now implemented. It creates a hard
link pointing to a path.

@item 
bpo-1613500@footnote{https://bugs.python.org/issue1613500}: @ref{27e,,fileinput.FileInput} now uses the input file mode to
correctly set the output file mode (previously it was hardcoded to
@code{'w'})  when @code{inplace=True} is passed to its constructor.

@item 
bpo-36734@footnote{https://bugs.python.org/issue36734}: Fix compilation of @code{faulthandler.c} on HP-UX. Initialize
@code{stack_t current_stack} to zero using @code{memset()}.

@item 
bpo-13611@footnote{https://bugs.python.org/issue13611}: The xml.etree.ElementTree packages gained support for C14N 2.0
serialisation. Patch by Stefan Behnel.

@item 
bpo-36669@footnote{https://bugs.python.org/issue36669}: Add missing matrix multiplication operator support to
weakref.proxy.

@item 
bpo-36676@footnote{https://bugs.python.org/issue36676}: The XMLParser() in xml.etree.ElementTree provides namespace
prefix context to the parser target if it defines the callback methods
"start_ns()" and/or "end_ns()". Patch by Stefan Behnel.

@item 
bpo-36673@footnote{https://bugs.python.org/issue36673}: The TreeBuilder and XMLPullParser in xml.etree.ElementTree
gained support for parsing comments and processing instructions. Patch by
Stefan Behnel.

@item 
bpo-36650@footnote{https://bugs.python.org/issue36650}: The C version of functools.lru_cache() was treating calls with
an empty @code{**kwargs} dictionary as being distinct from calls with no
keywords at all. This did not result in an incorrect answer, but it did
trigger an unexpected cache miss.

@item 
bpo-28552@footnote{https://bugs.python.org/issue28552}: Fix @ref{62,,distutils.sysconfig} if @ref{274,,sys.executable} is
@code{None} or an empty string: use @ref{f6f,,os.getcwd()} to initialize
@code{project_base}.  Fix also the distutils build command: don't use
@ref{274,,sys.executable} if it is @code{None} or an empty string.

@item 
bpo-35755@footnote{https://bugs.python.org/issue35755}: @ref{f6c,,shutil.which()} and
@code{distutils.spawn.find_executable()} now use @code{os.confstr("CS_PATH")}
if available instead of @ref{f70,,os.defpath}, if the @code{PATH} environment
variable is not set. Moreover, don't use @code{os.confstr("CS_PATH")} nor
@ref{f70,,os.defpath} if the @code{PATH} environment variable is set to an empty
string.

@item 
bpo-25430@footnote{https://bugs.python.org/issue25430}: improve performance of @code{IPNetwork.__contains__()}

@item 
bpo-30485@footnote{https://bugs.python.org/issue30485}: Path expressions in xml.etree.ElementTree can now avoid
explicit namespace prefixes for tags (or the "@{namespace@}tag" notation) by
passing a default namespace with an empty string prefix.

@item 
bpo-36613@footnote{https://bugs.python.org/issue36613}: Fix @ref{a,,asyncio} wait() not removing callback if exception

@item 
bpo-36598@footnote{https://bugs.python.org/issue36598}: Fix @code{isinstance} check for Mock objects with spec when the
code is executed under tracing. Patch by Karthikeyan Singaravelan.

@item 
bpo-18748@footnote{https://bugs.python.org/issue18748}: In development mode (@ref{155,,-X} @code{dev}) and in debug build,
the @ref{1db,,io.IOBase} destructor now logs @code{close()} exceptions. These
exceptions are silent by default in release mode.

@item 
bpo-36575@footnote{https://bugs.python.org/issue36575}: The @code{_lsprof} module now uses internal timer same to
@code{time.perf_counter()} by default. @code{gettimeofday(2)} was used on Unix.
New timer has better resolution on most Unix platforms and timings are no
longer impacted by system clock updates since @code{perf_counter()} is
monotonic. Patch by Inada Naoki.

@item 
bpo-33461@footnote{https://bugs.python.org/issue33461}: @code{json.loads} now emits @code{DeprecationWarning} when
@code{encoding} option is specified.  Patch by Matthias Bussonnier.

@item 
bpo-36559@footnote{https://bugs.python.org/issue36559}: The random module now prefers the lean internal _sha512 module
over hashlib for seed(version=2) to optimize import time.

@item 
bpo-17561@footnote{https://bugs.python.org/issue17561}: Set backlog=None as the default for socket.create_server.

@item 
bpo-34373@footnote{https://bugs.python.org/issue34373}: Fix @ref{b5d,,time.mktime()} error handling on AIX for year before
1970.

@item 
bpo-36232@footnote{https://bugs.python.org/issue36232}: Improve error message when trying to open existing DBM database
that actually doesn't exist. Patch by Marco Rougeth.

@item 
bpo-36546@footnote{https://bugs.python.org/issue36546}: Add statistics.quantiles()

@item 
bpo-36050@footnote{https://bugs.python.org/issue36050}: Optimized @code{http.client.HTTPResponse.read()} for large
response. Patch by Inada Naoki.

@item 
bpo-36522@footnote{https://bugs.python.org/issue36522}: If @emph{debuglevel} is set to >0 in @ref{94,,http.client}, print all
values for headers with multiple values for the same header name. Patch by
Matt Houglum.

@item 
bpo-36492@footnote{https://bugs.python.org/issue36492}: Deprecated passing required arguments like @emph{func} as keyword
arguments in functions which should accept arbitrary keyword arguments and
pass them to other function. Arbitrary keyword arguments (even with names
"self" and "func") can now be passed to these functions if the required
arguments are passed as positional arguments.

@item 
bpo-27181@footnote{https://bugs.python.org/issue27181}: Add statistics.geometric_mean().

@item 
bpo-30427@footnote{https://bugs.python.org/issue30427}: @code{os.path.normcase()} relies on @code{os.fspath()} to check the
type of its argument. Redundant checks have been removed from its
@code{posixpath.normcase()} and @code{ntpath.normcase()} implementations. Patch
by Wolfgang Maier.

@item 
bpo-36385@footnote{https://bugs.python.org/issue36385}: Stop rejecting IPv4 octets for being ambiguously octal. Leading
zeros are ignored, and no longer are assumed to specify octal octets.
Octets are always decimal numbers. Octets must still be no more than three
digits, including leading zeroes.

@item 
bpo-36434@footnote{https://bugs.python.org/issue36434}: Errors during writing to a ZIP file no longer prevent to
properly close it.

@item 
bpo-36407@footnote{https://bugs.python.org/issue36407}: Fixed wrong indentation writing for CDATA section in
xml.dom.minidom. Patch by Vladimir Surjaninov.

@item 
bpo-36326@footnote{https://bugs.python.org/issue36326}: inspect.getdoc() can now find docstrings for member objects
when __slots__ is a dictionary.

@item 
bpo-36366@footnote{https://bugs.python.org/issue36366}: Calling @code{stop()} on an unstarted or stopped
@ref{782,,unittest.mock.patch()} object will now return @ref{157,,None} instead of
raising @ref{2ba,,RuntimeError}, making the method idempotent. Patch by
Karthikeyan Singaravelan.

@item 
bpo-36348@footnote{https://bugs.python.org/issue36348}: The @code{imap.IMAP4.logout()} method no longer ignores silently
arbitrary exceptions.

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Add time module support and fix test_time faiures for VxWorks.

@item 
bpo-36227@footnote{https://bugs.python.org/issue36227}: Added support for keyword arguments @code{default_namespace} and
@code{xml_declaration} in functions ElementTree.tostring() and
ElementTree.tostringlist().

@item 
bpo-36004@footnote{https://bugs.python.org/issue36004}: Added new alternate constructors
@ref{1c4,,datetime.date.fromisocalendar()} and
@ref{1c5,,datetime.datetime.fromisocalendar()}, which construct date objects
from ISO year, week number and weekday; these are the inverse of each
class's @code{isocalendar} method. Patch by Paul Ganssle.

@item 
bpo-35936@footnote{https://bugs.python.org/issue35936}: @ref{b4,,modulefinder} no longer depends on the deprecated
@ref{9a,,imp} module, and the initializer for
@ref{f71,,modulefinder.ModuleFinder} now has immutable default arguments.
Patch by Brandt Bucher.

@item 
bpo-35376@footnote{https://bugs.python.org/issue35376}: @ref{b4,,modulefinder} correctly handles modules that have the
same name as a bad package. Patch by Brandt Bucher.

@item 
bpo-17396@footnote{https://bugs.python.org/issue17396}: @ref{b4,,modulefinder} no longer crashes when encountering syntax
errors in followed imports. Patch by Brandt Bucher.

@item 
bpo-35934@footnote{https://bugs.python.org/issue35934}: Added @ref{21e,,create_server()} and
@ref{21f,,has_dualstack_ipv6()} convenience functions to automate the
necessary tasks usually involved when creating a server socket, including
accepting both IPv4 and IPv6 connections on the same socket.  (Contributed
by Giampaolo Rodola in bpo-17561@footnote{https://bugs.python.org/issue17561}.)

@item 
bpo-23078@footnote{https://bugs.python.org/issue23078}: Add support for @ref{1d8,,classmethod()} and @ref{1d9,,staticmethod()} to
@ref{ed8,,unittest.mock.create_autospec()}.  Initial patch by Felipe Ochoa.

@item 
bpo-35416@footnote{https://bugs.python.org/issue35416}: Fix potential resource warnings in distutils. Patch by Mickaël
Schoentgen.

@item 
bpo-25451@footnote{https://bugs.python.org/issue25451}: Add transparency methods to @code{tkinter.PhotoImage}.  Patch
by Zackery Spytz.

@item 
bpo-35082@footnote{https://bugs.python.org/issue35082}: Don't return deleted attributes when calling dir on a
@ref{249,,unittest.mock.Mock}.

@item 
bpo-34547@footnote{https://bugs.python.org/issue34547}: @ref{f5c,,wsgiref.handlers.BaseHandler} now handles abrupt client
connection terminations gracefully. Patch by Petter Strandmark.

@item 
bpo-31658@footnote{https://bugs.python.org/issue31658}: @ref{f72,,xml.sax.parse()} now supports @ref{363,,path-like}. Patch by Mickaël Schoentgen.

@item 
bpo-34139@footnote{https://bugs.python.org/issue34139}: Remove stale unix datagram socket before binding

@item 
bpo-33530@footnote{https://bugs.python.org/issue33530}: Implemented Happy Eyeballs in @code{asyncio.create_connection()}.
Added two new arguments, @emph{happy_eyeballs_delay} and @emph{interleave}, to
specify Happy Eyeballs behavior.

@item 
bpo-33291@footnote{https://bugs.python.org/issue33291}: Do not raise AttributeError when calling the inspect functions
isgeneratorfunction, iscoroutinefunction, isasyncgenfunction on a method
created from an arbitrary callable. Instead, return False.

@item 
bpo-31310@footnote{https://bugs.python.org/issue31310}: Fix the multiprocessing.semaphore_tracker so it is reused by
child processes

@item 
bpo-31292@footnote{https://bugs.python.org/issue31292}: 为包含 @code{include} 指令的文件修复 @code{setup.py check --restructuredtext}。
@end itemize

@node 文档<13>,测试<12>,库<17>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id120}@anchor{f73}
@subsubsection 文档



@itemize -

@item 
bpo-36625@footnote{https://bugs.python.org/issue36625}: Remove obsolete comments from docstrings in fractions.Fraction

@item 
bpo-30840@footnote{https://bugs.python.org/issue30840}: Document relative imports

@item 
bpo-36523@footnote{https://bugs.python.org/issue36523}: Add docstring for io.IOBase.writelines().

@item 
bpo-36425@footnote{https://bugs.python.org/issue36425}: 新增的文档翻译: 简体中文@footnote{https://docs.python.org/zh-cn/}.

@item 
bpo-36345@footnote{https://bugs.python.org/issue36345}: Avoid the duplication of code from @code{Tools/scripts/serve.py}
in using the @code{literalinclude} directive for the basic
wsgiref-based web server in the documentation of @ref{12c,,wsgiref}.
Contributed by Stéphane Wirtel.

@item 
bpo-36345@footnote{https://bugs.python.org/issue36345}: Using the code of the @code{Tools/scripts/serve.py} script as an
example in the @ref{12c,,wsgiref} documentation.  Contributed by Stéphane
Wirtel.

@item 
bpo-36157@footnote{https://bugs.python.org/issue36157}: Added Documention for  PyInterpreterState_Main().

@item 
bpo-33043@footnote{https://bugs.python.org/issue33043}: Updates the docs.python.org page with the addition of a
'Contributing to Docs' link at the end of the page (between 'Reporting
Bugs' and 'About Documentation'). Updates the 'Found a Bug' page with
additional links and information in the Documentation Bugs section.

@item 
bpo-35581@footnote{https://bugs.python.org/issue35581}: @@typing.type_check_only now allows type stubs to mark functions
and classes not available during runtime.

@item 
bpo-33832@footnote{https://bugs.python.org/issue33832}: Add glossary entry for 'magic method'.

@item 
bpo-32913@footnote{https://bugs.python.org/issue32913}: Added re.Match.groupdict example to regex HOWTO.
@end itemize

@node 测试<12>,构建<11>,文档<13>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id121}@anchor{f74}
@subsubsection 测试



@itemize -

@item 
bpo-36719@footnote{https://bugs.python.org/issue36719}: regrtest now always detects uncollectable objects. Previously,
the check was only enabled by @code{--findleaks}. The check now also works
with @code{-jN/--multiprocess N}. @code{--findleaks} becomes a deprecated alias
to @code{--fail-env-changed}.

@item 
bpo-36725@footnote{https://bugs.python.org/issue36725}: When using mulitprocessing mode (-jN), regrtest now better
reports errors if a worker process fails, and it exits immediately on a
worker thread failure or when interrupted.

@item 
bpo-36454@footnote{https://bugs.python.org/issue36454}: Change test_time.test_monotonic() to test only the lower bound
of elapsed time after a sleep command rather than the upper bound. This
prevents unnecessary test failures on slow buildbots. Patch by Victor
Stinner.

@item 
bpo-32424@footnote{https://bugs.python.org/issue32424}: Improve test coverage for xml.etree.ElementTree. Patch by
Gordon P. Hemsley.

@item 
bpo-32424@footnote{https://bugs.python.org/issue32424}: Fix typo in test_cyclic_gc() test for xml.etree.ElementTree.
Patch by Gordon P. Hemsley.

@item 
bpo-36635@footnote{https://bugs.python.org/issue36635}: Add a new @code{_testinternalcapi} module to test the internal
C API.

@item 
bpo-36629@footnote{https://bugs.python.org/issue36629}: Fix @code{test_imap4_host_default_value()} of @code{test_imaplib}:
catch also @ref{f75,,errno.ENETUNREACH} error.

@item 
bpo-36611@footnote{https://bugs.python.org/issue36611}: Fix @code{test_sys.test_getallocatedblocks()} when
@ref{114,,tracemalloc} is enabled.

@item 
bpo-36560@footnote{https://bugs.python.org/issue36560}: Fix reference leak hunting in regrtest: compute also deltas (of
reference count, allocated memory blocks, file descriptor count) during
warmup, to ensure that everything is initialized before starting to hunt
reference leaks.

@item 
bpo-36565@footnote{https://bugs.python.org/issue36565}: Fix reference hunting (@code{python3 -m test -R 3:3}) when Python
has no built-in abc module.

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Port test_resource to VxWorks: skip tests cases setting
RLIMIT_FSIZE and RLIMIT_CPU.

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Fix test_tabnanny on VxWorks: adjust ENOENT error message.

@item 
bpo-36436@footnote{https://bugs.python.org/issue36436}: Fix @code{_testcapi.pymem_buffer_overflow()}: handle memory
allocation failure.

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Fix test_utf8_mode on VxWorks: Python always use UTF-8 on
VxWorks.

@item 
bpo-36341@footnote{https://bugs.python.org/issue36341}: Fix tests that may fail with PermissionError upon calling
bind() on AF_UNIX sockets.
@end itemize

@node 构建<11>,Windows<13>,测试<12>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id122}@anchor{f76}
@subsubsection 构建



@itemize -

@item 
bpo-36747@footnote{https://bugs.python.org/issue36747}: Remove the stale scriptsinstall Makefile target.

@item 
bpo-21536@footnote{https://bugs.python.org/issue21536}: On Unix, C extensions are no longer linked to libpython except
on Android and Cygwin.

It is now possible for a statically linked Python to load a C extension
built using a shared library Python.

When Python is embedded, @code{libpython} must not be loaded with
@code{RTLD_LOCAL}, but @code{RTLD_GLOBAL} instead. Previously, using
@code{RTLD_LOCAL}, it was already not possible to load C extensions which
were not linked to @code{libpython}, such as C extensions of the standard
library built by the @code{*shared*} section of @code{Modules/Setup}.

distutils, python-config and python-config.py have been modified.

@item 
bpo-36707@footnote{https://bugs.python.org/issue36707}: @code{./configure --with-pymalloc} no longer adds the @code{m} flag
to SOABI (sys.implementation.cache_tag). Enabling or disabling pymalloc
has no impact on the ABI.

@item 
bpo-36635@footnote{https://bugs.python.org/issue36635}: Change @code{PyAPI_FUNC(type)}, @code{PyAPI_DATA(type)} and
@code{PyMODINIT_FUNC} macros of @code{pyport.h} when @code{Py_BUILD_CORE_MODULE} is
defined. The @code{Py_BUILD_CORE_MODULE} define must be now be used to build
a C extension as a dynamic library accessing Python internals: export the
PyInit_xxx() function in DLL exports on Windows.

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Don't build the @code{_crypt} extension on VxWorks.

@item 
bpo-36618@footnote{https://bugs.python.org/issue36618}: Add @code{-fmax-type-align=8} to CFLAGS when clang compiler is
detected. The pymalloc memory allocator aligns memory on 8 bytes. On
x86-64, clang expects alignment on 16 bytes by default and so uses MOVAPS
instruction which can lead to segmentation fault. Instruct clang that
Python is limited to alignment on 8 bytes to use MOVUPS instruction
instead: slower but don't trigger a SIGSEGV if the memory is not aligned
on 16 bytes. Sadly, the flag must be added to @code{CFLAGS} and not just
@code{CFLAGS_NODIST}, since third party C extensions can have the same issue.

@item 
bpo-36605@footnote{https://bugs.python.org/issue36605}: @code{make tags} and @code{make TAGS} now also parse
@code{Modules/_io/*.c} and @code{Modules/_io/*.h}.

@item 
bpo-36465@footnote{https://bugs.python.org/issue36465}: Release builds and debug builds are now ABI compatible:
defining the @code{Py_DEBUG} macro no longer implies the @code{Py_TRACE_REFS}
macro, which introduces the only ABI incompatibility. The
@code{Py_TRACE_REFS} macro, which adds the @code{sys.getobjects()} function
and the 
@geindex PYTHONDUMPREFS
@geindex 环境变量; PYTHONDUMPREFS
@ref{159,,PYTHONDUMPREFS} environment variable, can be set using
the new @code{./configure --with-trace-refs} build option.

@item 
bpo-36577@footnote{https://bugs.python.org/issue36577}: setup.py now correctly reports missing OpenSSL headers and
libraries again.

@item 
bpo-36544@footnote{https://bugs.python.org/issue36544}: Fix regression introduced in bpo-36146@footnote{https://bugs.python.org/issue36146} refactoring setup.py

@item 
bpo-36508@footnote{https://bugs.python.org/issue36508}: @code{python-config --ldflags} no longer includes flags of the
@code{LINKFORSHARED} variable. The @code{LINKFORSHARED} variable must only be
used to build executables.

@item 
bpo-36503@footnote{https://bugs.python.org/issue36503}: Remove references to "aix3" and "aix4". Patch by M. Felt.
@end itemize

@node Windows<13>,macOS<9>,构建<11>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id123}@anchor{f77}
@subsubsection Windows



@itemize -

@item 
bpo-35920@footnote{https://bugs.python.org/issue35920}: Added platform.win32_edition() and platform.win32_is_iot().
Added support for cross-compiling packages for Windows ARM32. Skip tests
that are not expected to work on Windows IoT Core ARM32.

@item 
bpo-36649@footnote{https://bugs.python.org/issue36649}: Remove trailing spaces for registry keys when installed via the
Store.

@item 
bpo-34144@footnote{https://bugs.python.org/issue34144}: Fixed activate.bat to correctly update codepage when chcp.com
returns dots in output. Patch by Lorenz Mende.

@item 
bpo-36509@footnote{https://bugs.python.org/issue36509}: Added preset-iot layout for Windows IoT ARM containers. This
layout doesn't contain UI components like tkinter or IDLE. It also doesn't
contain files to support on-target builds since Windows ARM32 builds must
be cross-compiled when using MSVC.

@item 
bpo-35941@footnote{https://bugs.python.org/issue35941}: enum_certificates function of the ssl module now returns
certificates from all available certificate stores inside windows in a
query instead of returning only certificates from the system wide
certificate store. This includes certificates from these certificate
stores: local machine, local machine enterprise, local machine group
policy, current user, current user group policy, services, users.
ssl.enum_crls() function is changed in the same way to return all
certificate revocation lists inside the windows certificate revocation
list stores.

@item 
bpo-36441@footnote{https://bugs.python.org/issue36441}: Fixes creating a venv when debug binaries are installed.

@item 
bpo-36085@footnote{https://bugs.python.org/issue36085}: Enable better DLL resolution on Windows by using safe DLL
search paths and adding @ref{1c2,,os.add_dll_directory()}.

@item 
bpo-36010@footnote{https://bugs.python.org/issue36010}: Add the venv standard library module to the nuget distribution
for Windows.

@item 
bpo-29515@footnote{https://bugs.python.org/issue29515}: Add the following socket module constants on Windows:
IPPROTO_AH IPPROTO_CBT IPPROTO_DSTOPTS IPPROTO_EGP IPPROTO_ESP
IPPROTO_FRAGMENT IPPROTO_GGP IPPROTO_HOPOPTS IPPROTO_ICLFXBM
IPPROTO_ICMPV6 IPPROTO_IDP IPPROTO_IGMP IPPROTO_IGP IPPROTO_IPV4
IPPROTO_IPV6 IPPROTO_L2TP IPPROTO_MAX IPPROTO_ND IPPROTO_NONE IPPROTO_PGM
IPPROTO_PIM IPPROTO_PUP IPPROTO_RDP IPPROTO_ROUTING IPPROTO_SCTP
IPPROTO_ST

@item 
bpo-35947@footnote{https://bugs.python.org/issue35947}: Added current version of libffi to cpython-source-deps. Change
_ctypes to use current version of libffi on Windows.

@item 
bpo-34060@footnote{https://bugs.python.org/issue34060}: Report system load when running test suite on Windows. Patch by
Ammar Askar. Based on prior work by Jeremy Kloth.

@item 
bpo-31512@footnote{https://bugs.python.org/issue31512}: With the Windows 10 Creators Update, non-elevated users can now
create symlinks as long as the computer has Developer Mode enabled.
@end itemize

@node macOS<9>,IDLE<18>,Windows<13>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id124}@anchor{f78}
@subsubsection macOS



@itemize -

@item 
bpo-34602@footnote{https://bugs.python.org/issue34602}: Avoid failures setting macOS stack resource limit with
resource.setrlimit. This reverts an earlier fix for bpo-18075@footnote{https://bugs.python.org/issue18075} which forced
a non-default stack size when building the interpreter executable on
macOS.
@end itemize

@node IDLE<18>,工具/示例<8>,macOS<9>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id125}@anchor{f79}
@subsubsection IDLE



@itemize -

@item 
bpo-36429@footnote{https://bugs.python.org/issue36429}: Fix starting IDLE with pyshell. Add idlelib.pyshell alias at
top; remove pyshell alias at bottom. Remove obsolete __name__=='__main__'
command.
@end itemize

@node 工具/示例<8>,C API<9>,IDLE<18>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id126}@anchor{f7a}
@subsubsection 工具/示例



@itemize -

@item 
bpo-14546@footnote{https://bugs.python.org/issue14546}: Fix the argument handling in Tools/scripts/lll.py.
@end itemize

@node C API<9>,,工具/示例<8>,Python 3 8 0 alpha 4
@anchor{whatsnew/changelog id127}@anchor{f7b}
@subsubsection C API



@itemize -

@item 
bpo-36763@footnote{https://bugs.python.org/issue36763}: Fix memory leak in @ref{91f,,Py_SetStandardStreamEncoding()}:
release memory if the function is called twice.

@item 
bpo-36641@footnote{https://bugs.python.org/issue36641}: @code{PyDoc_VAR(name)} and
@code{PyDoc_STRVAR(name,str)} now create @code{static const char name[]}
instead of @code{static char name[]}.  Patch by Inada Naoki.

@item 
bpo-36389@footnote{https://bugs.python.org/issue36389}: Change the value of @code{CLEANBYTE}, @code{DEADDYTE} and
@code{FORBIDDENBYTE} internal constants used by debug hooks on Python memory
allocators (@ref{504,,PyMem_SetupDebugHooks()} function). Byte patterns
@code{0xCB}, @code{0xDB} and @code{0xFB} have been replaced with @code{0xCD}, @code{0xDD}
and @code{0xFD} to use the same values than Windows CRT debug @code{malloc()}
and @code{free()}.

@item 
bpo-36443@footnote{https://bugs.python.org/issue36443}: Since Python 3.7.0, calling @ref{436,,Py_DecodeLocale()} before
@ref{433,,Py_Initialize()} produces mojibake if the @code{LC_CTYPE} locale is
coerced and/or if the UTF-8 Mode is enabled by the user configuration. The
LC_CTYPE coercion and UTF-8 Mode are now disabled by default to fix the
mojibake issue. They must now be enabled explicitly (opt-in) using the new
@code{_Py_PreInitialize()} API with @code{_PyPreConfig}.

@item 
bpo-36025@footnote{https://bugs.python.org/issue36025}: Fixed an accidental change to the datetime C API where the
arguments to the @ref{f7c,,PyDate_FromTimestamp()} function were incorrectly
interpreted as a single timestamp rather than an arguments tuple, which
causes existing code to start raising @ref{192,,TypeError}. The
backwards-incompatible change was only present in alpha releases of Python
3.8. Patch by Paul Ganssle.

@item 
bpo-35810@footnote{https://bugs.python.org/issue35810}: Modify @code{PyObject_Init} to correctly increase the refcount of
heap- allocated Type objects. Also fix the refcounts of the heap-allocated
types that were either doing this manually or not decreasing the type's
refcount in tp_dealloc
@end itemize

@node Python 3 8 0 alpha 3,Python 3 8 0 alpha 2,Python 3 8 0 alpha 4,更新日志
@anchor{whatsnew/changelog python-3-8-0-alpha-3}@anchor{f7d}
@subsection Python 3.8.0 alpha 3


@emph{发布日期： 2019-03-25}

@menu
* 安全: 安全<14>. 
* 核心与内置: 核心与内置<18>. 
* 库: 库<18>. 
* 文档: 文档<14>. 
* 测试: 测试<13>. 
* 构建: 构建<12>. 
* Windows: Windows<14>. 
* IDLE: IDLE<19>. 
* 工具/示例: 工具/示例<9>. 
* C API: C API<10>. 

@end menu

@node 安全<14>,核心与内置<18>,,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id128}@anchor{f7e}
@subsubsection 安全



@itemize -

@item 
bpo-36216@footnote{https://bugs.python.org/issue36216}: Changes urlsplit() to raise ValueError when the URL contains
characters that decompose under IDNA encoding (NFKC-normalization) into
characters that affect how the URL is parsed.

@item 
bpo-35121@footnote{https://bugs.python.org/issue35121}: Don't send cookies of domain A without Domain attribute to
domain B when domain A is a suffix match of domain B while using a
cookiejar with @ref{f7f,,http.cookiejar.DefaultCookiePolicy} policy. Patch
by Karthikeyan Singaravelan.
@end itemize

@node 核心与内置<18>,库<18>,安全<14>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id129}@anchor{f80}
@subsubsection 核心与内置



@itemize -

@item 
bpo-36421@footnote{https://bugs.python.org/issue36421}: Fix a possible double decref in _ctypes.c's
@code{PyCArrayType_new()}.

@item 
bpo-36412@footnote{https://bugs.python.org/issue36412}: Fix a possible crash when creating a new dictionary.

@item 
bpo-36398@footnote{https://bugs.python.org/issue36398}: Fix a possible crash in @code{structseq_repr()}.

@item 
bpo-36256@footnote{https://bugs.python.org/issue36256}: Fix bug in parsermodule when parsing a state in a DFA that has
two or more arcs with labels of the same type. Patch by Pablo Galindo.

@item 
bpo-36365@footnote{https://bugs.python.org/issue36365}: repr(structseq) is no longer limited to 512 bytes.

@item 
bpo-36374@footnote{https://bugs.python.org/issue36374}: Fix a possible null pointer dereference in
@code{merge_consts_recursive()}. Patch by Zackery Spytz.

@item 
bpo-36236@footnote{https://bugs.python.org/issue36236}: 在 Python 初始化时，如果当前目录被移除，则它将不再会被添加到 @ref{482,,sys.path} 中。

@item 
bpo-36352@footnote{https://bugs.python.org/issue36352}: Python initialization now fails with an error, rather than
silently truncating paths, if a path is too long.

@item 
bpo-36301@footnote{https://bugs.python.org/issue36301}: Python initialization now fails if decoding @code{pybuilddir.txt}
configuration file fails at startup.

@item 
bpo-36333@footnote{https://bugs.python.org/issue36333}: Fix leak in _PyRuntimeState_Fini. Contributed by Stéphane
Wirtel.

@item 
bpo-36332@footnote{https://bugs.python.org/issue36332}: The builtin @ref{1b4,,compile()} can now handle AST objects that
contain assignment expressions. Patch by Pablo Galindo.

@item 
bpo-36282@footnote{https://bugs.python.org/issue36282}: Improved error message for too much positional arguments in
some builtin functions.

@item 
bpo-30040@footnote{https://bugs.python.org/issue30040}: New empty dict uses fewer memory for now.  It used more memory
than empty dict created by @code{dict.clear()}.  And empty dict creation and
deletion is about 2x faster.  Patch by Inada Naoki.

@item 
bpo-36262@footnote{https://bugs.python.org/issue36262}: 修复了在 @code{float(str)}, @code{complex(str)}, @ref{5bd,,pickle.load()}, @ref{f81,,marshal.load()} 等所用的函数 @code{_Py_dg_strtod()} 中进行从字符串到浮点数的转换时偶有发生的一个内存泄漏问题。

@item 
bpo-36252@footnote{https://bugs.python.org/issue36252}: Update Unicode databases to version 12.0.0.

@item 
bpo-36218@footnote{https://bugs.python.org/issue36218}: Fix a segfault occurring when sorting a list of heterogeneous
values. Patch contributed by Rémi Lapeyre and Elliot Gorokhovsky.

@item 
bpo-36188@footnote{https://bugs.python.org/issue36188}: Cleaned up left-over vestiges of Python 2 unbound method
handling in method objects and documentation. Patch by Martijn Pieters

@item 
bpo-36124@footnote{https://bugs.python.org/issue36124}: Add a new interpreter-specific dict and expose it in the C-API
via PyInterpreterState_GetDict().  This parallels PyThreadState_GetDict().
However, extension modules should continue using PyModule_GetState() for
their own internal per-interpreter state.

@item 
bpo-35975@footnote{https://bugs.python.org/issue35975}: Add a @code{feature_version} flag to @code{ast.parse()} (documented)
and @code{compile()} (hidden) that allows tweaking the parser to support
older versions of the grammar. In particular, if @code{feature_version} is 5
or 6, the hacks for the @code{async} and @code{await} keyword from PEP 492 are
reinstated. (For 7 or higher, these are unconditionally treated as
keywords, but they are still special tokens rather than @code{NAME} tokens
that the parser driver recognizes.)

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Use UTF-8 as the system encoding on VxWorks.

@item 
bpo-36048@footnote{https://bugs.python.org/issue36048}: The @ref{18a,,__index__()} special method will be used
instead of @ref{18b,,__int__()} for implicit conversion of Python
numbers to C integers.  Using the @code{__int__()} method in implicit
conversions has been deprecated.

@item 
bpo-35808@footnote{https://bugs.python.org/issue35808}: Retire pgen and use a modified version of pgen2 to generate the
parser. Patch by Pablo Galindo.
@end itemize

@node 库<18>,文档<14>,核心与内置<18>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id130}@anchor{f82}
@subsubsection 库



@itemize -

@item 
bpo-36401@footnote{https://bugs.python.org/issue36401}: The class documentation created by pydoc now has a separate
section for readonly properties.

@item 
bpo-36320@footnote{https://bugs.python.org/issue36320}: The typing.NamedTuple() class has deprecated the _field_types
attribute in favor of the __annotations__ attribute which carried the same
information. Also, both attributes were converted from OrderedDict to a
regular dict.

@item 
bpo-34745@footnote{https://bugs.python.org/issue34745}: Fix @ref{a,,asyncio} ssl memory issues caused by circular
references

@item 
bpo-36324@footnote{https://bugs.python.org/issue36324}: Add method to statistics.NormalDist for computing the inverse
cumulative normal distribution.

@item 
bpo-36321@footnote{https://bugs.python.org/issue36321}: collections.namedtuple() misspelled the name of an attribute.
To be consistent with typing.NamedTuple, the attribute name should have
been "_field_defaults" instead of "_fields_defaults".  For backwards
compatibility, both spellings are now created.  The misspelled version may
be removed in the future.

@item 
bpo-36297@footnote{https://bugs.python.org/issue36297}: "unicode_internal" codec is removed.  It was deprecated since
Python 3.3. Patch by Inada Naoki.

@item 
bpo-36298@footnote{https://bugs.python.org/issue36298}: Raise ModuleNotFoundError in pyclbr when a module can't be
found. Thanks to 'mental' for the bug report.

@item 
bpo-36268@footnote{https://bugs.python.org/issue36268}: Switch the default format used for writing tars with
mod:@ref{101,,tarfile} to the modern POSIX.1-2001 pax standard, from the
vendor-specific GNU. Contributed by C.A.M. Gerlach.

@item 
bpo-36285@footnote{https://bugs.python.org/issue36285}: Fix integer overflows in the array module. Patch by Stephan
Hohe.

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Add _signal module support for VxWorks.

@item 
bpo-36272@footnote{https://bugs.python.org/issue36272}: @ref{aa,,logging} does not silently ignore RecursionError anymore.
Patch contributed by Rémi Lapeyre.

@item 
bpo-36280@footnote{https://bugs.python.org/issue36280}: Add a kind field to ast.Constant. It is 'u' if the literal has
a 'u' prefix (i.e. a Python 2 style unicode literal), else None.

@item 
bpo-35931@footnote{https://bugs.python.org/issue35931}: The @ref{c9,,pdb} @code{debug} command now gracefully handles all
exceptions.

@item 
bpo-36251@footnote{https://bugs.python.org/issue36251}: Fix format strings used for stderrprinter and re.Match reprs.
Patch by Stephan Hohe.

@item 
bpo-36235@footnote{https://bugs.python.org/issue36235}: Fix @code{CFLAGS} in @code{customize_compiler()} of
@code{distutils.sysconfig}: when the @code{CFLAGS} environment variable is
defined, don't override @code{CFLAGS} variable with the @code{OPT} variable
anymore. Initial patch written by David Malcolm.

@item 
bpo-35807@footnote{https://bugs.python.org/issue35807}: Update ensurepip to install pip 19.0.3 and setuptools 40.8.0.

@item 
bpo-36139@footnote{https://bugs.python.org/issue36139}: Release GIL when closing @ref{1ec,,mmap} objects.

@item 
bpo-36179@footnote{https://bugs.python.org/issue36179}: Fix two unlikely reference leaks in _hashopenssl. The leaks
only occur in out-of-memory cases.

@item 
bpo-36169@footnote{https://bugs.python.org/issue36169}: Add overlap() method to statistics.NormalDist.  Computes the
overlapping coefficient for two normal distributions.

@item 
bpo-36103@footnote{https://bugs.python.org/issue36103}: Default buffer size used by @code{shutil.copyfileobj()} is changed
from 16 KiB to 64 KiB on non-Windows platform to reduce system call
overhead. Contributed by Inada Naoki.

@item 
bpo-36130@footnote{https://bugs.python.org/issue36130}: Fix @code{pdb} with @code{skip=...} when stepping into a frame
without a @code{__name__} global.  Patch by Anthony Sottile.

@item 
bpo-35652@footnote{https://bugs.python.org/issue35652}: shutil.copytree(copy_function=...) erroneously pass DirEntry
instead of a path string.

@item 
bpo-35178@footnote{https://bugs.python.org/issue35178}: Ensure custom @ref{f83,,warnings.formatwarning()} function can
receive @code{line} as positional argument. Based on patch by Tashrif Billah.

@item 
bpo-36106@footnote{https://bugs.python.org/issue36106}: Resolve potential name clash with libm's sinpi(). Patch by
Dmitrii Pasechnik.

@item 
bpo-36091@footnote{https://bugs.python.org/issue36091}: Clean up reference to async generator in Lib/types. Patch by
Henry Chen.

@item 
bpo-36043@footnote{https://bugs.python.org/issue36043}: @code{FileCookieJar} supports @ref{363,,path-like object}.
Contributed by Stéphane Wirtel

@item 
bpo-35899@footnote{https://bugs.python.org/issue35899}: Enum has been fixed to correctly handle empty strings and
strings with non-Latin characters (ie. 'α', 'א') without crashing.
Original patch contributed by Maxwell. Assisted by Stéphane Wirtel.

@item 
bpo-21269@footnote{https://bugs.python.org/issue21269}: Add @code{args} and @code{kwargs} properties to mock call objects.
Contributed by Kumar Akshay.

@item 
bpo-30670@footnote{https://bugs.python.org/issue30670}: @ref{212,,pprint.pp} has been added to pretty-print objects with
dictionary keys being sorted with their insertion order by default.
Parameter @emph{sort_dicts} has been added to @ref{213,,pprint.pprint}, @ref{890,,pprint.pformat}
and @ref{88f,,pprint.PrettyPrinter}. Contributed by Rémi Lapeyre.

@item 
bpo-35843@footnote{https://bugs.python.org/issue35843}: Implement @code{__getitem__} for @code{_NamespacePath}.  Patch by
Anthony Sottile.

@item 
bpo-35802@footnote{https://bugs.python.org/issue35802}: Clean up code which checked presence of @code{os.stat} /
@code{os.lstat} / @code{os.chmod} which are always present.  Patch by Anthony
Sottile.

@item 
bpo-35715@footnote{https://bugs.python.org/issue35715}: Librates the return value of a ProcessPoolExecutor
_process_worker after it's no longer needed to free memory

@item 
bpo-35493@footnote{https://bugs.python.org/issue35493}: Use @ref{a1f,,multiprocessing.connection.wait()} instead of polling
each 0.2 seconds for worker updates in @code{multiprocessing.Pool}.
Patch by Pablo Galindo.

@item 
bpo-35661@footnote{https://bugs.python.org/issue35661}: Store the venv prompt in pyvenv.cfg.

@item 
bpo-35121@footnote{https://bugs.python.org/issue35121}: Don't set cookie for a request when the request path is a
prefix match of the cookie's path attribute but doesn't end with "/".
Patch by Karthikeyan Singaravelan.

@item 
bpo-21478@footnote{https://bugs.python.org/issue21478}: Calls to a child function created with
@ref{ed8,,unittest.mock.create_autospec()} should propagate to the parent.
Patch by Karthikeyan Singaravelan.

@item 
bpo-35198@footnote{https://bugs.python.org/issue35198}: Fix C++ extension compilation on AIX
@end itemize

@node 文档<14>,测试<13>,库<18>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id131}@anchor{f84}
@subsubsection 文档



@itemize -

@item 
bpo-36329@footnote{https://bugs.python.org/issue36329}: Declare the path of the Python binary for the usage of
@code{Tools/scripts/serve.py} when executing @code{make -C Doc/ serve}.
Contributed by Stéphane Wirtel

@item 
bpo-36138@footnote{https://bugs.python.org/issue36138}: Improve documentation about converting datetime.timedelta to
scalars.

@item 
bpo-21314@footnote{https://bugs.python.org/issue21314}: A new entry was added to the Core Language Section of the
Programming FAQ, which explaines the usage of slash(/) in the signature of
a function. Patch by Lysandros Nikolaou
@end itemize

@node 测试<13>,构建<12>,文档<14>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id132}@anchor{f85}
@subsubsection 测试



@itemize -

@item 
bpo-36234@footnote{https://bugs.python.org/issue36234}: test_posix.PosixUidGidTests: add tests for invalid uid/gid type
(str). Initial patch written by David Malcolm.

@item 
bpo-29571@footnote{https://bugs.python.org/issue29571}: Fix @code{test_re.test_locale_flag()}:  use
@code{locale.getpreferredencoding()} rather than @code{locale.getlocale()} to
get the locale encoding. With some locales, @code{locale.getlocale()} returns
the wrong encoding.

@item 
bpo-36123@footnote{https://bugs.python.org/issue36123}: Fix race condition in test_socket.
@end itemize

@node 构建<12>,Windows<14>,测试<13>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id133}@anchor{f86}
@subsubsection 构建



@itemize -

@item 
bpo-36356@footnote{https://bugs.python.org/issue36356}: Fix leaks that led to build failure when configured with
address sanitizer.

@item 
bpo-36146@footnote{https://bugs.python.org/issue36146}: Add @code{TEST_EXTENSIONS} constant to @code{setup.py} to allow to
not build test extensions like @code{_testcapi}.

@item 
bpo-36146@footnote{https://bugs.python.org/issue36146}: Fix setup.py on macOS: only add @code{/usr/include/ffi} to include
directories of _ctypes, not for all extensions.

@item 
bpo-31904@footnote{https://bugs.python.org/issue31904}: Enable build system to cross-build for VxWorks RTOS.
@end itemize

@node Windows<14>,IDLE<19>,构建<12>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id134}@anchor{f87}
@subsubsection Windows



@itemize -

@item 
bpo-36312@footnote{https://bugs.python.org/issue36312}: Fixed decoders for the following code pages: 50220, 50221,
50222, 50225, 50227, 50229, 57002 through 57011, 65000 and 42.

@item 
bpo-36264@footnote{https://bugs.python.org/issue36264}: Don't honor POSIX @code{HOME} in @code{os.path.expanduser} on
windows.  Patch by Anthony Sottile.

@item 
bpo-24643@footnote{https://bugs.python.org/issue24643}: Fix name collisions due to @code{#define timezone _timezone} in
PC/pyconfig.h.
@end itemize

@node IDLE<19>,工具/示例<9>,Windows<14>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id135}@anchor{f88}
@subsubsection IDLE



@itemize -

@item 
bpo-36405@footnote{https://bugs.python.org/issue36405}: Use dict unpacking in idlelib.

@item 
bpo-36396@footnote{https://bugs.python.org/issue36396}: Remove fgBg param of idlelib.config.GetHighlight(). This param
was only used twice and changed the return type.

@item 
bpo-36176@footnote{https://bugs.python.org/issue36176}: 修复 IDLE 自动补全和 calltip 悬浮窗的颜色. 避免与 Linux 暗色主题冲突 (略微加深了calltip 的背景颜色).

@item 
bpo-23205@footnote{https://bugs.python.org/issue23205}: For the grep module, add tests for findfiles, refactor
findfiles to be a module-level function, and refactor findfiles to use
os.walk.

@item 
bpo-23216@footnote{https://bugs.python.org/issue23216}: 将文档字符串添加到IDLE 的搜索模块。

@item 
bpo-36152@footnote{https://bugs.python.org/issue36152}: Remove colorizer.ColorDelegator.close_when_done and the
corresponding argument of .close().  In IDLE, both have always been None
or False since 2007.

@item 
bpo-32129@footnote{https://bugs.python.org/issue32129}: Avoid blurry IDLE application icon on macOS with Tk 8.6. Patch
by Kevin Walzer.

@item 
bpo-36096@footnote{https://bugs.python.org/issue36096}: Refactor class variables to instance variables in colorizer.

@item 
bpo-30348@footnote{https://bugs.python.org/issue30348}: Increase test coverage of idlelib.autocomplete by 30%. Patch by
Louie Lu
@end itemize

@node 工具/示例<9>,C API<10>,IDLE<19>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id136}@anchor{f89}
@subsubsection 工具/示例



@itemize -

@item 
bpo-35132@footnote{https://bugs.python.org/issue35132}: Fix py-list and py-bt commands of python-gdb.py on gdb7.

@item 
bpo-32217@footnote{https://bugs.python.org/issue32217}: Fix freeze script on Windows.
@end itemize

@node C API<10>,,工具/示例<9>,Python 3 8 0 alpha 3
@anchor{whatsnew/changelog id137}@anchor{f8a}
@subsubsection C API



@itemize -

@item 
bpo-36381@footnote{https://bugs.python.org/issue36381}: Raise @code{DeprecationWarning} when '#' formats are used for
building or parsing values without @code{PY_SSIZE_T_CLEAN}.

@item 
bpo-36142@footnote{https://bugs.python.org/issue36142}: The whole coreconfig.h header is now excluded from
Py_LIMITED_API. Move functions definitions into a new internal
pycore_coreconfig.h header.
@end itemize

@node Python 3 8 0 alpha 2,Python 3 8 0 alpha 1,Python 3 8 0 alpha 3,更新日志
@anchor{whatsnew/changelog python-3-8-0-alpha-2}@anchor{f8b}
@subsection Python 3.8.0 alpha 2


@emph{发布日期: 2019-02-25}

@menu
* 核心与内置: 核心与内置<19>. 
* 库: 库<19>. 
* 文档: 文档<15>. 
* 测试: 测试<14>. 
* Windows: Windows<15>. 
* IDLE: IDLE<20>. 

@end menu

@node 核心与内置<19>,库<19>,,Python 3 8 0 alpha 2
@anchor{whatsnew/changelog id138}@anchor{f8c}
@subsubsection 核心与内置



@itemize -

@item 
bpo-36052@footnote{https://bugs.python.org/issue36052}: Raise a @ref{452,,SyntaxError} when assigning a value to
@ref{f8d,,__debug__} with the Assignment Operator. Contributed by Stéphane Wirtel
and Pablo Galindo.

@item 
bpo-36012@footnote{https://bugs.python.org/issue36012}: Doubled the speed of class variable writes.  When a non-dunder
attribute was updated, there was an unnecessary call to update slots.

@item 
bpo-35942@footnote{https://bugs.python.org/issue35942}: The error message emitted when returning invalid types from
@code{__fspath__} in interfaces that allow passing @ref{4e5,,PathLike}
objects has been improved and now it does explain the origin of the error.

@item 
bpo-36016@footnote{https://bugs.python.org/issue36016}: @code{gc.get_objects} can now receive an optional parameter
indicating a generation to get objects from. Patch by Pablo Galindo.

@item 
bpo-1054041@footnote{https://bugs.python.org/issue1054041}: When the main interpreter exits due to an uncaught
KeyboardInterrupt, the process now exits in the appropriate manner for its
parent process to detect that a SIGINT or ^C terminated the process.  This
allows shells and batch scripts to understand that the user has asked them
to stop.

@item 
bpo-35992@footnote{https://bugs.python.org/issue35992}: Fix @code{__class_getitem__()} not being called on a class with a
custom non-subscriptable metaclass.

@item 
bpo-35993@footnote{https://bugs.python.org/issue35993}: Fix a crash on fork when using subinterpreters. Contributed by
Stéphane Wirtel

@item 
bpo-35991@footnote{https://bugs.python.org/issue35991}: Fix a potential double free in Modules/_randommodule.c.

@item 
bpo-35961@footnote{https://bugs.python.org/issue35961}: Fix a crash in slice_richcompare(): use strong references
rather than stolen references for the two temporary internal tuples.

@item 
bpo-35911@footnote{https://bugs.python.org/issue35911}: Enable the creation of cell objects by adding a
@code{cell.__new__} method, and expose the type @code{cell} in @code{Lib/types.py}
under the name CellType. Patch by Pierre Glaser.

@item 
bpo-12822@footnote{https://bugs.python.org/issue12822}: Use monotonic clock for @code{pthread_cond_timedwait} when
@code{pthread_condattr_setclock} and @code{CLOCK_MONOTONIC} are available.

@item 
bpo-15248@footnote{https://bugs.python.org/issue15248}: The compiler emits now syntax warnings in the case when a comma
is likely missed before tuple or list.

@item 
bpo-35886@footnote{https://bugs.python.org/issue35886}: The implementation of PyInterpreterState has been moved into
the internal header files (guarded by Py_BUILD_CORE).

@item 
bpo-31506@footnote{https://bugs.python.org/issue31506}: Clarify the errors reported when @code{object.__new__} and
@code{object.__init__} receive more than one argument. Contributed by Sanyam
Khurana.

@item 
bpo-35724@footnote{https://bugs.python.org/issue35724}: Signal-handling is now guaranteed to happen relative to the
main interpreter.

@item 
bpo-33608@footnote{https://bugs.python.org/issue33608}: We added a new internal _Py_AddPendingCall() that operates
relative to the provided interpreter.  This allows us to use the existing
implementation to ask another interpreter to do work that cannot be done
in the current interpreter, like decref an object the other interpreter
owns.  The existing Py_AddPendingCall() only operates relative to the main
interpreter.

@item 
bpo-33989@footnote{https://bugs.python.org/issue33989}: Fix a possible crash in @ref{43f,,list.sort()} when sorting objects
with @code{ob_type->tp_richcompare == NULL}.  Patch by Zackery Spytz.
@end itemize

@node 库<19>,文档<15>,核心与内置<19>,Python 3 8 0 alpha 2
@anchor{whatsnew/changelog id139}@anchor{f8e}
@subsubsection 库



@itemize -

@item 
bpo-35512@footnote{https://bugs.python.org/issue35512}: @ref{f5f,,unittest.mock.patch.dict()} used as a decorator with
string target resolves the target during function call instead of during
decorator construction. Patch by Karthikeyan Singaravelan.

@item 
bpo-36018@footnote{https://bugs.python.org/issue36018}: Add statistics.NormalDist, a tool for creating and manipulating
normal distributions of random variable.  Features a composite class that
treats the mean and standard deviation of measurement data as single
entity.

@item 
bpo-35904@footnote{https://bugs.python.org/issue35904}: Added statistics.fmean() as a faster, floating point variant of
the existing mean() function.

@item 
bpo-35918@footnote{https://bugs.python.org/issue35918}: Removed broken @code{has_key} method from
multiprocessing.managers.SyncManager.dict. Contributed by Rémi Lapeyre.

@item 
bpo-18283@footnote{https://bugs.python.org/issue18283}: Add support for bytes to @ref{f6c,,shutil.which()}.

@item 
bpo-35960@footnote{https://bugs.python.org/issue35960}: Fix @ref{f8f,,dataclasses.field()} throwing away empty mapping
objects passed as metadata.

@item 
bpo-35500@footnote{https://bugs.python.org/issue35500}: Write expected and actual call parameters on separate lines in
@ref{f90,,unittest.mock.Mock.assert_called_with()} assertion errors.
Contributed by Susan Su.

@item 
bpo-35931@footnote{https://bugs.python.org/issue35931}: The @ref{c9,,pdb} @code{debug} command now gracefully handles syntax
errors.

@item 
bpo-24209@footnote{https://bugs.python.org/issue24209}: In http.server script, rely on getaddrinfo to bind to preferred
address based on the bind parameter. Now default bind or binding to a name
may bind to IPv6 or dual-stack, depending on the environment.

@item 
bpo-35321@footnote{https://bugs.python.org/issue35321}: Set @code{__spec__.origin} of  @code{_frozen_importlib} to frozen so
that it matches the behavior of @code{_frozen_importlib_external}.  Patch by
Nina Zakharenko.

@item 
bpo-35378@footnote{https://bugs.python.org/issue35378}: Fix a reference issue inside @code{multiprocessing.Pool} that
caused the pool to remain alive if it was deleted without being closed or
terminated explicitly. A new strong reference is added to the pool
iterators to link the lifetime of the pool to the lifetime of its
iterators so the pool does not get destroyed if a pool iterator is still
alive.

@item 
bpo-34294@footnote{https://bugs.python.org/issue34294}: re module, fix wrong capturing groups in rare cases.
@ref{bab,,re.search()}, @ref{95d,,re.findall()}, @ref{475,,re.sub()} and other functions
that scan through string looking for a match, should reset capturing
groups between two match attempts. Patch by Ma Lin.

@item 
bpo-35615@footnote{https://bugs.python.org/issue35615}: @ref{128,,weakref}: Fix a RuntimeError when copying a
WeakKeyDictionary or a WeakValueDictionary, due to some keys or values
disappearing while iterating.

@item 
bpo-35606@footnote{https://bugs.python.org/issue35606}: Implement @ref{1e4,,math.prod()} as analogous function to
@ref{1e5,,sum()} that returns the product of a 'start' value (default: 1) times
an iterable of numbers. Patch by Pablo Galindo.

@item 
bpo-32417@footnote{https://bugs.python.org/issue32417}: Performing arithmetic between @ref{194,,datetime.datetime}
subclasses and @ref{195,,datetime.timedelta} now returns an object of the
same type as the @ref{194,,datetime.datetime} subclass. As a result,
@ref{196,,datetime.datetime.astimezone()} and alternate constructors like
@ref{f91,,datetime.datetime.now()} and @code{datetime.fromtimestamp()} called
with a @code{tz} argument now @emph{also} retain their subclass.

@item 
bpo-35153@footnote{https://bugs.python.org/issue35153}: Add @emph{headers} optional keyword-only parameter to
@ref{255,,xmlrpc.client.ServerProxy}, @code{xmlrpc.client.Transport} and
@code{xmlrpc.client.SafeTransport}.  Patch by Cédric Krier.

@item 
bpo-34572@footnote{https://bugs.python.org/issue34572}: Fix C implementation of pickle.loads to use importlib's locking
mechanisms, and thereby avoid using partially-loaded modules. Patch by Tim
Burgess.
@end itemize

@node 文档<15>,测试<14>,库<19>,Python 3 8 0 alpha 2
@anchor{whatsnew/changelog id140}@anchor{f92}
@subsubsection 文档



@itemize -

@item 
bpo-36083@footnote{https://bugs.python.org/issue36083}: Fix formatting of --check-hash-based-pycs options in the
manpage Synopsis.

@item 
bpo-36007@footnote{https://bugs.python.org/issue36007}: Bump minimum sphinx version to 1.8.  Patch by Anthony Sottile.

@item 
bpo-22062@footnote{https://bugs.python.org/issue22062}: Update documentation and docstrings for pathlib. Original patch
by Mike Short.
@end itemize

@node 测试<14>,Windows<15>,文档<15>,Python 3 8 0 alpha 2
@anchor{whatsnew/changelog id141}@anchor{f93}
@subsubsection 测试



@itemize -

@item 
bpo-27313@footnote{https://bugs.python.org/issue27313}: Avoid test_ttk_guionly ComboboxTest failure with macOS Cocoa
Tk.

@item 
bpo-36019@footnote{https://bugs.python.org/issue36019}: Add test.support.TEST_HTTP_URL and replace references of
@indicateurl{http://www.example.com} by this new constant. Contributed by Stéphane
Wirtel.

@item 
bpo-36037@footnote{https://bugs.python.org/issue36037}: Fix test_ssl for strict OpenSSL configuration like RHEL8 strict
crypto policy. Use older TLS version for minimum TLS version of the server
SSL context if needed, to test TLS version older than default minimum TLS
version.

@item 
bpo-35798@footnote{https://bugs.python.org/issue35798}: Added @ref{f94,,test.support.check_syntax_warning()}.

@item 
bpo-35505@footnote{https://bugs.python.org/issue35505}: Make test_imap4_host_default_value independent on whether the
local IMAP server is running.

@item 
bpo-35917@footnote{https://bugs.python.org/issue35917}: multiprocessing: provide unit tests for SyncManager and
SharedMemoryManager classes + all the shareable types which are supposed
to be supported by them.  (patch by Giampaolo Rodola)

@item 
bpo-35704@footnote{https://bugs.python.org/issue35704}: Skip @code{test_shutil.test_unpack_archive_xztar} to prevent a
MemoryError on 32-bit AIX when MAXDATA setting is less than 0x20000000.

Patch by Michael Felt (aixtools)

@item 
bpo-34720@footnote{https://bugs.python.org/issue34720}: Assert m_state != NULL to mimic GC traversal functions that do
not correctly handle module creation when the module state has not been
created.
@end itemize

@node Windows<15>,IDLE<20>,测试<14>,Python 3 8 0 alpha 2
@anchor{whatsnew/changelog id142}@anchor{f95}
@subsubsection Windows



@itemize -

@item 
bpo-35976@footnote{https://bugs.python.org/issue35976}: Added ARM build support to Windows build files in PCBuild.

@item 
bpo-35692@footnote{https://bugs.python.org/issue35692}: @code{pathlib} no longer raises when checking file and directory
existence on drives that are not ready

@item 
bpo-35872@footnote{https://bugs.python.org/issue35872}: Uses the base Python executable when invoking venv in a virtual
environment

@item 
bpo-35873@footnote{https://bugs.python.org/issue35873}: Prevents venv paths being inherited by child processes

@item 
bpo-35299@footnote{https://bugs.python.org/issue35299}: Fix sysconfig detection of the source directory and distutils
handling of pyconfig.h during PGO profiling
@end itemize

@node IDLE<20>,,Windows<15>,Python 3 8 0 alpha 2
@anchor{whatsnew/changelog id143}@anchor{f96}
@subsubsection IDLE



@itemize -

@item 
bpo-24310@footnote{https://bugs.python.org/issue24310}: IDLE -- 文档设置对话框字体选项卡示例。

@item 
bpo-35833@footnote{https://bugs.python.org/issue35833}: Revise IDLE doc for control codes sent to Shell. Add a code
example block.

@item 
bpo-35689@footnote{https://bugs.python.org/issue35689}: Add docstrings and unittests for colorizer.py.
@end itemize

@node Python 3 8 0 alpha 1,Python 3 7 0 正式版,Python 3 8 0 alpha 2,更新日志
@anchor{whatsnew/changelog python-3-8-0-alpha-1}@anchor{f97}
@subsection Python 3.8.0 alpha 1


@emph{发布日期: 2019-02-03}

@menu
* 安全: 安全<15>. 
* 核心与内置: 核心与内置<20>. 
* 库: 库<20>. 
* 文档: 文档<16>. 
* 测试: 测试<15>. 
* 构建: 构建<13>. 
* Windows: Windows<16>. 
* macOS: macOS<10>. 
* IDLE: IDLE<21>. 
* 工具/示例: 工具/示例<10>. 
* C API: C API<11>. 

@end menu

@node 安全<15>,核心与内置<20>,,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id144}@anchor{f98}
@subsubsection 安全



@itemize -

@item 
bpo-35746@footnote{https://bugs.python.org/issue35746}: [CVE-2019-5010] Fix a NULL pointer deref in ssl module. The
cert parser did not handle CRL distribution points with empty DP or URI
correctly. A malicious or buggy certificate can result into segfault.
Vulnerability (TALOS-2018-0758) reported by Colin Read and Nicolas Edet of
Cisco.

@item 
bpo-34812@footnote{https://bugs.python.org/issue34812}: The @ref{f99,,-I} command line option (run Python in isolated
mode) is now also copied by the @ref{b7,,multiprocessing} and
@ref{39,,distutils} modules when spawning child processes. Previously, only
@ref{f9a,,-E} and @ref{d0e,,-s} options (enabled by @ref{f99,,-I}) were
copied.

@item 
bpo-34791@footnote{https://bugs.python.org/issue34791}: The xml.sax and xml.dom.domreg no longer use environment
variables to override parser implementations when
sys.flags.ignore_environment is set by -E or -I arguments.

@item 
bpo-17239@footnote{https://bugs.python.org/issue17239}: The xml.sax and xml.dom.minidom parsers no longer processes
external entities by default. External DTD and ENTITY declarations no
longer load files or create network connections.

@item 
bpo-34623@footnote{https://bugs.python.org/issue34623}: CVE-2018-14647: The C accelerated _elementtree module now
initializes hash randomization salt from _Py_HashSecret instead of
libexpat's default CSPRNG.

@item 
bpo-34405@footnote{https://bugs.python.org/issue34405}: 将Windows内部版本更新到OpenSSL 1.1.0i

@item 
bpo-33871@footnote{https://bugs.python.org/issue33871}: 修复了使用 @ref{352,,os.sendfile()} 在macOS上发送部分文件的错误。使用 @emph{trailers} 参数可能导致从输入文件发送的字节数多于指定的数量。

@item 
bpo-32533@footnote{https://bugs.python.org/issue32533}: Fixed thread-safety of error handling in _ssl.

@item 
bpo-33136@footnote{https://bugs.python.org/issue33136}: Harden ssl module against LibreSSL CVE-2018-8970.
X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new
test ensures that NULL bytes are not allowed.

@item 
bpo-33001@footnote{https://bugs.python.org/issue33001}: Minimal fix to prevent buffer overrun in os.symlink on Windows

@item 
bpo-32981@footnote{https://bugs.python.org/issue32981}: Regexes in difflib and poplib were vulnerable to catastrophic
backtracking. These regexes formed potential DOS vectors (REDOS). They
have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch
by Jamie Davis.

@item 
bpo-28414@footnote{https://bugs.python.org/issue28414}: The ssl module now allows users to perform their own IDN
en/decoding when using SNI.
@end itemize

@node 核心与内置<20>,库<20>,安全<15>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id145}@anchor{f9b}
@subsubsection 核心与内置



@itemize -

@item 
bpo-35877@footnote{https://bugs.python.org/issue35877}: Make parenthesis optional for named expressions in while
statement. Patch by Karthikeyan Singaravelan.

@item 
bpo-35814@footnote{https://bugs.python.org/issue35814}: Allow same right hand side expressions in annotated assignments
as in normal ones. In particular, @code{x: Tuple[int, int] = 1, 2} (without
parentheses on the right) is now allowed.

@item 
bpo-35766@footnote{https://bugs.python.org/issue35766}: Add the option to parse PEP 484 type comments in the ast
module. (Off by default.) This is merging the key functionality of the
third party fork thereof,
[typed_ast](@indicateurl{https://github.com/python/typed_ast}).

@item 
bpo-35713@footnote{https://bugs.python.org/issue35713}: Reorganize Python initialization to get working exceptions and
sys.stderr earlier.

@item 
bpo-33416@footnote{https://bugs.python.org/issue33416}: Add end line and end column position information to the Python
AST nodes. This is a C-level backwards incompatible change.

@item 
bpo-35720@footnote{https://bugs.python.org/issue35720}: Fixed a minor memory leak in pymain_parse_cmdline_impl function
in Modules/main.c

@item 
bpo-35634@footnote{https://bugs.python.org/issue35634}: @code{func(**kwargs)} will now raise an error when @code{kwargs} is a
mapping containing multiple entries with the same key. An error was
already raised when other keyword arguments are passed before @code{**kwargs}
since Python 3.6.

@item 
bpo-35623@footnote{https://bugs.python.org/issue35623}: 修复了在排序超长列表时崩溃的问题。 补丁作者 Stephan Hohe。

@item 
bpo-35214@footnote{https://bugs.python.org/issue35214}: 添加了 clang Memory Sanitizer 构建工具以绕过来自 posix, socket, time, test_io 和 test_faulthandler 的误报问题。

@item 
bpo-35560@footnote{https://bugs.python.org/issue35560}: 修复了在调试版中使用 "n" 格式进行零留空和小宽度的浮点格式化时 @ref{4d5,,format()} 内的一个断言错误。 发布版未受影响。 补丁作者 Karthikeyan Singaravelan。

@item 
bpo-35552@footnote{https://bugs.python.org/issue35552}: Format characters @code{%s} and @code{%V} in
@ref{7c5,,PyUnicode_FromFormat()} and @code{%s} in @ref{f9c,,PyBytes_FromFormat()}
no longer read memory past the limit if @emph{precision} is specified.

@item 
bpo-35504@footnote{https://bugs.python.org/issue35504}: 修复了在删除特定属性时的段错误和 @ref{5f6,,SystemError} 问题。 补丁作者 Zackery Spytz。

@item 
bpo-35504@footnote{https://bugs.python.org/issue35504}: Fixed a SystemError when delete the characters_written
attribute of an OSError.

@item 
bpo-35494@footnote{https://bugs.python.org/issue35494}: Improved syntax error messages for unbalanced parentheses in
f-string.

@item 
bpo-35444@footnote{https://bugs.python.org/issue35444}: Fixed error handling in pickling methods when fail to look up
builtin "getattr". Sped up pickling iterators.

@item 
bpo-35436@footnote{https://bugs.python.org/issue35436}: Fix various issues with memory allocation error handling.
Patch by Zackery Spytz.

@item 
bpo-35423@footnote{https://bugs.python.org/issue35423}: Separate the signal handling trigger in the eval loop from the
"pending calls" machinery. There is no semantic change and the difference
in performance is insignificant.

@item 
bpo-35357@footnote{https://bugs.python.org/issue35357}: Internal attributes' names of unittest.mock._Call and
unittest.mock.MagicProxy (name, parent & from_kall) are now prefixed with
_mock_ in order to prevent clashes with widely used object attributes.
Fixed minor typo in test function name.

@item 
bpo-35372@footnote{https://bugs.python.org/issue35372}: Fixed the code page decoder for input longer than 2 GiB
containing undecodable bytes.

@item 
bpo-35336@footnote{https://bugs.python.org/issue35336}: Fix PYTHONCOERCECLOCALE=1 environment variable: only coerce the
C locale if the LC_CTYPE locale is "C".

@item 
bpo-31241@footnote{https://bugs.python.org/issue31241}: The @emph{lineno} and @emph{col_offset} attributes of AST nodes for list
comprehensions, generator expressions and tuples are now point to the
opening parenthesis or square brace. For tuples without parenthesis they
point to the position of the first item.

@item 
bpo-33954@footnote{https://bugs.python.org/issue33954}: For @ref{4d4,,str.format()}, @code{float.__format__()} and
@code{complex.__format__()} methods for non-ASCII decimal point when using
the "n" formatter.

@item 
bpo-35269@footnote{https://bugs.python.org/issue35269}: Fix a possible segfault involving a newly-created coroutine.
Patch by Zackery Spytz.

@item 
bpo-35224@footnote{https://bugs.python.org/issue35224}: Implement 
@geindex Python 提高建议; PEP 572
PEP 572@footnote{https://www.python.org/dev/peps/pep-0572} (assignment expressions). Patch by Emily
Morehouse.

@item 
bpo-32492@footnote{https://bugs.python.org/issue32492}: Speed up @code{namedtuple} attribute access by 1.6x using a C
fast-path for the name descriptors. Patch by Pablo Galindo.

@item 
bpo-35214@footnote{https://bugs.python.org/issue35214}: Fixed an out of bounds memory access when parsing a truncated
unicode escape sequence at the end of a string such as @code{'\N'}.  It would
read one byte beyond the end of the memory allocation.

@item 
bpo-35214@footnote{https://bugs.python.org/issue35214}: The interpreter and extension modules have had annotations
added so that they work properly under clang's Memory Sanitizer.  A new
configure flag --with-memory-sanitizer has been added to make test builds
of this nature easier to perform.

@item 
bpo-35193@footnote{https://bugs.python.org/issue35193}: Fix an off by one error in the bytecode peephole optimizer
where it could read bytes beyond the end of bounds of an array when
removing unreachable code. This bug was present in every release of Python
3.6 and 3.7 until now.

@item 
bpo-35169@footnote{https://bugs.python.org/issue35169}: Improved error messages for forbidden assignments.

@item 
bpo-34022@footnote{https://bugs.python.org/issue34022}: Fix handling of hash-based bytecode files in @ref{143,,zipimport}.
Patch by Elvis Pranskevichus.

@item 
bpo-28401@footnote{https://bugs.python.org/issue28401}: Debug builds will no longer to attempt to import extension
modules built for the ABI as they were never compatible to begin with.
Patch by Stefano Rivera.

@item 
bpo-29341@footnote{https://bugs.python.org/issue29341}: Clarify in the docstrings of @ref{c4,,os} methods that path-like
objects are also accepted as input parameters.

@item 
bpo-35050@footnote{https://bugs.python.org/issue35050}: @ref{ef,,socket}: Fix off-by-one bug in length check for
@code{AF_ALG} name and type.

@item 
bpo-29743@footnote{https://bugs.python.org/issue29743}: Raise @ref{1fb,,ValueError} instead of @ref{95a,,OverflowError} in case
of a negative @code{_length_} in a @ref{f9d,,ctypes.Array} subclass.  Also
raise @ref{192,,TypeError} instead of @ref{393,,AttributeError} for non-integer
@code{_length_}. Original patch by Oren Milman.

@item 
bpo-16806@footnote{https://bugs.python.org/issue16806}: Fix @code{lineno} and @code{col_offset} for multi-line string tokens.

@item 
bpo-35029@footnote{https://bugs.python.org/issue35029}: @ref{191,,SyntaxWarning} raised as an exception at code generation
time will be now replaced with a @ref{452,,SyntaxError} for better error
reporting.

@item 
bpo-34983@footnote{https://bugs.python.org/issue34983}: Expose @ref{f9e,,symtable.Symbol.is_nonlocal()} in the symtable
module. Patch by Pablo Galindo.

@item 
bpo-34974@footnote{https://bugs.python.org/issue34974}: @ref{32a,,bytes} and @ref{32b,,bytearray} constructors no longer
convert unexpected exceptions (e.g. @ref{f9f,,MemoryError} and
@ref{197,,KeyboardInterrupt}) to @ref{192,,TypeError}.

@item 
bpo-34939@footnote{https://bugs.python.org/issue34939}: Allow annotated names in module namespace that are declared
global before the annotation happens. Patch by Pablo Galindo.

@item 
bpo-34973@footnote{https://bugs.python.org/issue34973}: Fixed crash in @ref{32a,,bytes()} when the @ref{262,,list} argument is
mutated while it is iterated.

@item 
bpo-34876@footnote{https://bugs.python.org/issue34876}: The @emph{lineno} and @emph{col_offset} attributes of the AST for
decorated function and class refer now to the position of the
corresponding @code{def}, @code{async def} and @code{class} instead of the position
of the first decorator. This leads to more correct line reporting in
tracing. This is the only case when the position of child AST nodes can
precede the position of the parent AST node.

@item 
bpo-34879@footnote{https://bugs.python.org/issue34879}: Fix a possible null pointer dereference in bytesobject.c.
Patch by Zackery Spytz.

@item 
bpo-34784@footnote{https://bugs.python.org/issue34784}: Fix the implementation of PyStructSequence_NewType in order to
create heap allocated StructSequences.

@item 
bpo-32912@footnote{https://bugs.python.org/issue32912}: A @ref{191,,SyntaxWarning} is now emitted instead of a
@ref{278,,DeprecationWarning} for invalid escape sequences in string and bytes
literals.

@item 
bpo-34854@footnote{https://bugs.python.org/issue34854}: 修复问题——当编译包含一个没有默认值的关键字参数的 lambda 的字符串注解时可导致崩溃。

@item 
bpo-34850@footnote{https://bugs.python.org/issue34850}: The compiler now produces a @ref{191,,SyntaxWarning} when identity
checks (@code{is} and @code{is not}) are used with certain types of literals
(e.g. strings, ints).  These can often work by accident in CPython, but
are not guaranteed by the language spec.  The warning advises users to use
equality tests (@code{==} and @code{!=}) instead.

@item 
bpo-34824@footnote{https://bugs.python.org/issue34824}: Fix a possible null pointer dereference in Modules/_ssl.c.
Patch by Zackery Spytz.

@item 
bpo-30156@footnote{https://bugs.python.org/issue30156}: The C function @code{property_descr_get()} uses a "cached" tuple
to optimize function calls. But this tuple can be discovered in debug mode
with @code{sys.getobjects()}. Remove the optimization, it's not really
worth it and it causes 3 different crashes last years.

@item 
bpo-34762@footnote{https://bugs.python.org/issue34762}: Fix contextvars C API to use PyObject* pointer types.

@item 
bpo-34751@footnote{https://bugs.python.org/issue34751}: The hash function for tuples is now based on xxHash which gives
better collision results on (formerly) pathological cases. Additionally,
on 64-bit systems it improves tuple hashes in general. Patch by Jeroen
Demeyer with substantial contributions by Tim Peters.

@item 
bpo-34735@footnote{https://bugs.python.org/issue34735}: Fix a memory leak in Modules/timemodule.c.  Patch by Zackery
Spytz.

@item 
bpo-34683@footnote{https://bugs.python.org/issue34683}: Fixed a bug where some SyntaxError error pointed to locations
that were off-by-one.

@item 
bpo-34651@footnote{https://bugs.python.org/issue34651}: Only allow the main interpreter to fork.  The avoids the
possibility of affecting the main interpreter, which is critical to
operation of the runtime.

@item 
bpo-34653@footnote{https://bugs.python.org/issue34653}: Remove unused function PyParser_SimpleParseStringFilename.

@item 
bpo-32236@footnote{https://bugs.python.org/issue32236}: Warn that line buffering is not supported if @ref{4ea,,open()} is
called with binary mode and @code{buffering=1}.

@item 
bpo-34641@footnote{https://bugs.python.org/issue34641}: Further restrict the syntax of the left-hand side of keyword
arguments in function calls. In particular, @code{f((keyword)=arg)} is now
disallowed.

@item 
bpo-34637@footnote{https://bugs.python.org/issue34637}: Make the @emph{start} argument to @emph{sum()} visible as a keyword
argument.

@item 
bpo-1621@footnote{https://bugs.python.org/issue1621}: Do not assume signed integer overflow behavior (C undefined
behavior) when performing set hash table resizing.

@item 
bpo-34588@footnote{https://bugs.python.org/issue34588}: Fix an off-by-one in the recursive call pruning feature of
traceback formatting.

@item 
bpo-34485@footnote{https://bugs.python.org/issue34485}: On Windows, the LC_CTYPE is now set to the user preferred
locale at startup. Previously, the LC_CTYPE locale was "C" at startup, but
changed when calling setlocale(LC_CTYPE, "") or setlocale(LC_ALL, "").

@item 
bpo-34485@footnote{https://bugs.python.org/issue34485}: Standard streams like sys.stdout now use the "surrogateescape"
error handler, instead of "strict", on the POSIX locale (when the C locale
is not coerced and the UTF-8 Mode is disabled).

@item 
bpo-34485@footnote{https://bugs.python.org/issue34485}: Fix the error handler of standard streams like sys.stdout:
PYTHONIOENCODING=":" is now ignored instead of setting the error handler
to "strict".

@item 
bpo-34485@footnote{https://bugs.python.org/issue34485}: Python now gets the locale encoding with C code to initialize
the encoding of standard streams like sys.stdout. Moreover, the encoding
is now initialized to the Python codec name to get a normalized encoding
name and to ensure that the codec is loaded. The change avoids importing
_bootlocale and _locale modules at startup by default.

@item 
bpo-34527@footnote{https://bugs.python.org/issue34527}: On FreeBSD, Py_DecodeLocale() and Py_EncodeLocale() now also
forces the ASCII encoding if the LC_CTYPE locale is "POSIX", not only if
the LC_CTYPE locale is "C".

@item 
bpo-34527@footnote{https://bugs.python.org/issue34527}: The UTF-8 Mode is now also enabled by the "POSIX" locale, not
only by the "C" locale.

@item 
bpo-34403@footnote{https://bugs.python.org/issue34403}: On HP-UX with C or POSIX locale, sys.getfilesystemencoding()
now returns "ascii" instead of "roman8" (when the UTF-8 Mode is disabled
and the C locale is not coerced).

@item 
bpo-34523@footnote{https://bugs.python.org/issue34523}: The Python filesystem encoding is now read earlier during the
Python initialization.

@item 
bpo-12458@footnote{https://bugs.python.org/issue12458}: Tracebacks show now correct line number for subexpressions in
multiline expressions. Tracebacks show now the line number of the first
line for multiline expressions instead of the line number of the last
subexpression.

@item 
bpo-34408@footnote{https://bugs.python.org/issue34408}: Prevent a null pointer dereference and resource leakage in
@code{PyInterpreterState_New()}.

@item 
bpo-34400@footnote{https://bugs.python.org/issue34400}: Fix undefined behavior in parsetok.c.  Patch by Zackery Spytz.

@item 
bpo-33073@footnote{https://bugs.python.org/issue33073}: Added as_integer_ratio to ints to make them more interoperable
with floats.

@item 
bpo-34377@footnote{https://bugs.python.org/issue34377}: 更新valgrind的抑制列表，使用 @code{_PyObject_Free}/@code{_PyObject_Realloc} 代替 @code{PyObject_Free}/@code{PyObject_Realloc} 。

@item 
bpo-34353@footnote{https://bugs.python.org/issue34353}: Added the "socket" option in the @ref{a98,,stat.filemode()} Python
implementation to match the C implementation.

@item 
bpo-34320@footnote{https://bugs.python.org/issue34320}: 修复问题——@code{dict(od)} 不会复制 OrderedDict 的迭代顺序。

@item 
bpo-34113@footnote{https://bugs.python.org/issue34113}: Fixed crash on debug builds when opcode stack was adjusted with
negative numbers. Patch by Constantin Petrisor.

@item 
bpo-34100@footnote{https://bugs.python.org/issue34100}: Compiler now merges constants in tuples and frozensets
recursively. Code attributes like @code{co_names} are merged too.

@item 
bpo-34151@footnote{https://bugs.python.org/issue34151}: Performance of list concatenation, repetition and slicing
operations is slightly improved. Patch by Sergey Fedoseev.

@item 
bpo-34170@footnote{https://bugs.python.org/issue34170}: -X dev: 即使启用了开发模式，现在也可以使用PYTHONMALLOC重载内存分配器。

@item 
bpo-33237@footnote{https://bugs.python.org/issue33237}: Improved @ref{393,,AttributeError} message for partially
initialized module.

@item 
bpo-34149@footnote{https://bugs.python.org/issue34149}: Fix min and max functions to get default behavior when key is
None.

@item 
bpo-34125@footnote{https://bugs.python.org/issue34125}: Profiling of unbound built-in methods now works when
@code{**kwargs} is given.

@item 
bpo-34141@footnote{https://bugs.python.org/issue34141}: Optimized pickling atomic types (None, bool, int, float, bytes,
str).

@item 
bpo-34126@footnote{https://bugs.python.org/issue34126}: 修复在分析某些未绑定的方法的无效调用时崩溃的问题。由Jeroen Demeyer修复。

@item 
bpo-24618@footnote{https://bugs.python.org/issue24618}: 修复了当创建代码对象时使用的变量名元组太小或参数太多导致读取无效内存的问题。

@item 
bpo-34068@footnote{https://bugs.python.org/issue34068}: 在调用 @ref{fa0,,io.IOBase.close()} 时确保 @ref{fa1,,closed} 属性未设置有效的异常。 由Zackery Spytz和Serhiy Storchaka修复。

@item 
bpo-34087@footnote{https://bugs.python.org/issue34087}: 修复由unicode转换为数值类型时缓冲区溢出的问题。

@item 
bpo-34080@footnote{https://bugs.python.org/issue34080}: 修复了编译器在标记化过程中引发一些不常见错误时内存泄漏的问题。

@item 
bpo-34066@footnote{https://bugs.python.org/issue34066}: 调用 @code{open()} 和进入  @code{with open()} 的 @strong{with} 语句块内时禁止使用 Ctrl-C 中断。

@item 
bpo-34042@footnote{https://bugs.python.org/issue34042}: 修复 dict.copy() 以维护正确的总引用计数（由sys.gettotalrefcount()报告）。

@item 
bpo-33418@footnote{https://bugs.python.org/issue33418}: Fix potential memory leak in function object when it creates
reference cycle.

@item 
bpo-33985@footnote{https://bugs.python.org/issue33985}: 实现contextvars.ContextVar.name 属性。

@item 
bpo-33956@footnote{https://bugs.python.org/issue33956}: Update vendored Expat library copy to version 2.2.5.

@item 
bpo-24596@footnote{https://bugs.python.org/issue24596}: 执行 @ref{e97,,PyErr_Print()} 之前，在 @ref{fa2,,PyRun_SimpleFileExFlags()} 内减少模块对象的引用。 由Zackery Spytz修复。

@item 
bpo-33451@footnote{https://bugs.python.org/issue33451}: 执行 @code{PyEval_EvalCode()} 前先关闭直接执行的pyc文件。

@item 
bpo-1617161@footnote{https://bugs.python.org/issue1617161}: The hash of @code{BuiltinMethodType} instances (methods of
built-in classes) now depends on the hash of the identity of @emph{__self__}
instead of its value. The hash and equality of @code{ModuleType} and
@code{MethodWrapperType} instances (methods of user-defined classes and
some methods of built-in classes like @code{str.__add__}) now depend on the
hash and equality of the identity of @emph{__self__} instead of its value.
@code{MethodWrapperType} instances no longer support ordering.

@item 
bpo-33824@footnote{https://bugs.python.org/issue33824}: 修复"LC_ALL=C python3.7 -V"：在读取Python配置后编码发生更改时，正确重置命令行解析器。

@item 
bpo-33803@footnote{https://bugs.python.org/issue33803}: Fix a crash in hamt.c caused by enabling GC tracking for an
object that hadn't all of its fields set to NULL.

@item 
bpo-33738@footnote{https://bugs.python.org/issue33738}: Seven macro incompatibilities with the Limited API were fixed,
and the macros @ref{fa3,,PyIter_Check()}, @ref{fa4,,PyIndex_Check()} and
@code{PyExceptionClass_Name()} were added as functions. A script for
automatic macro checks was added.

@item 
bpo-33786@footnote{https://bugs.python.org/issue33786}: Fix asynchronous generators to handle GeneratorExit in athrow()
correctly

@item 
bpo-30167@footnote{https://bugs.python.org/issue30167}: @code{PyRun_SimpleFileExFlags} removes @code{__cached__} from module
in addition to @code{__file__}.

@item 
bpo-33706@footnote{https://bugs.python.org/issue33706}: Fix a crash in Python initialization when parsing the command
line options. Thanks Christoph Gohlke for the bug report and the fix!

@item 
bpo-33597@footnote{https://bugs.python.org/issue33597}: Reduce @code{PyGC_Head} size from 3 words to 2 words.

@item 
bpo-30654@footnote{https://bugs.python.org/issue30654}: Fixed reset of the SIGINT handler to SIG_DFL on interpreter
shutdown even when there was a custom handler set previously. Patch by
Philipp Kerling.

@item 
bpo-33622@footnote{https://bugs.python.org/issue33622}: Fixed a leak when the garbage collector fails to add an object
with the @code{__del__} method or referenced by it into the
@ref{b39,,gc.garbage} list. @code{PyGC_Collect()} can now be called when an
exception is set and preserves it.

@item 
bpo-33462@footnote{https://bugs.python.org/issue33462}: Make dict and dict views reversible. Patch by Rémi Lapeyre.

@item 
bpo-23722@footnote{https://bugs.python.org/issue23722}: A @ref{2ba,,RuntimeError} is now raised when the custom metaclass
doesn't provide the @code{__classcell__} entry in the namespace passed to
@code{type.__new__}.  A @ref{278,,DeprecationWarning} was emitted in Python
3.6--3.7.

@item 
bpo-33499@footnote{https://bugs.python.org/issue33499}: Add 
@geindex PYTHONPYCACHEPREFIX
@geindex 环境变量; PYTHONPYCACHEPREFIX
@ref{154,,PYTHONPYCACHEPREFIX} environment variable and
@ref{155,,-X} @code{pycache_prefix} command-line option to set an alternate
root directory for writing module bytecode cache files.

@item 
bpo-25711@footnote{https://bugs.python.org/issue25711}: The @ref{143,,zipimport} module has been rewritten in pure Python.

@item 
bpo-33509@footnote{https://bugs.python.org/issue33509}: Fix module_globals parameter of warnings.warn_explicit(): don't
crash if module_globals is not a dict.

@item 
bpo-31849@footnote{https://bugs.python.org/issue31849}: Fix signed/unsigned comparison warning in pyhash.c.

@item 
bpo-33475@footnote{https://bugs.python.org/issue33475}: Fixed miscellaneous bugs in converting annotations to strings
and optimized parentheses in the string representation.

@item 
bpo-20104@footnote{https://bugs.python.org/issue20104}: Added support for the @code{setpgroup}, @code{resetids}, @code{setsigmask},
@code{setsigdef} and @code{scheduler} parameters of @code{posix_spawn}. Patch by Pablo
Galindo.

@item 
bpo-33391@footnote{https://bugs.python.org/issue33391}: Fix a leak in set_symmetric_difference().

@item 
bpo-33363@footnote{https://bugs.python.org/issue33363}: 在异步函数外使用`@w{`}async with`@w{`} 和 @code{async for}  时抛出SyntaxError异常。

@item 
bpo-28055@footnote{https://bugs.python.org/issue28055}: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

@item 
bpo-33128@footnote{https://bugs.python.org/issue33128}: 修复导致PathFinder在sys.meta_path上出现两次的错误。由Pablo Galindo Salgado提供补丁。

@item 
bpo-33331@footnote{https://bugs.python.org/issue33331}: Modules imported last are now cleared first at interpreter
shutdown.

@item 
bpo-33312@footnote{https://bugs.python.org/issue33312}: Fixed clang ubsan (undefined behavior sanitizer) warnings in
dictobject.c by adjusting how the internal struct _dictkeysobject shared
keys structure is declared.

@item 
bpo-33305@footnote{https://bugs.python.org/issue33305}: Improved syntax error messages for invalid numerical literals.

@item 
bpo-33306@footnote{https://bugs.python.org/issue33306}: Improved syntax error messages for unbalanced parentheses.

@item 
bpo-33234@footnote{https://bugs.python.org/issue33234}: The list constructor will pre-size and not over-allocate when
the input length is known.

@item 
bpo-33270@footnote{https://bugs.python.org/issue33270}: Intern the names for all anonymous code objects.  Patch by
Zackery Spytz.

@item 
bpo-30455@footnote{https://bugs.python.org/issue30455}: The C and Python code and the documentation related to tokens
are now generated from a single source file @code{Grammar/Tokens}.

@item 
bpo-33176@footnote{https://bugs.python.org/issue33176}: Add a @code{toreadonly()} method to memoryviews.

@item 
bpo-33231@footnote{https://bugs.python.org/issue33231}: 修复 @code{normalizestring()} 中潜在的内存泄漏。

@item 
bpo-33205@footnote{https://bugs.python.org/issue33205}: Change dict growth function from
@code{round_up_to_power_2(used*2+hashtable_size/2)} to
@code{round_up_to_power_2(used*3)}.  Previously, dict is shrinked only when
@code{used == 0}. Now dict has more chance to be shrinked.

@item 
bpo-29922@footnote{https://bugs.python.org/issue29922}: Improved error messages in 'async with' when @code{__aenter__()}
or @code{__aexit__()} return non-awaitable object.

@item 
bpo-33199@footnote{https://bugs.python.org/issue33199}: Fix @code{ma_version_tag} in dict implementation is uninitialized
when copying from key-sharing dict.

@item 
bpo-33053@footnote{https://bugs.python.org/issue33053}: When using the -m switch, sys.path[0] is now explicitly
expanded as the @emph{starting} working directory, rather than being left as
the empty path (which allows imports from the current working directory at
the time of the import)

@item 
bpo-33138@footnote{https://bugs.python.org/issue33138}: Changed standard error message for non-pickleable and
non-copyable types. It now says "cannot pickle" instead of "can't pickle"
or "cannot serialize".

@item 
bpo-33018@footnote{https://bugs.python.org/issue33018}: Improve consistency of errors raised by @code{issubclass()} when
called with a non-class and an abstract base class as the first and second
arguments, respectively. Patch by Josh Bronson.

@item 
bpo-33083@footnote{https://bugs.python.org/issue33083}: @code{math.factorial} no longer accepts arguments that are not
int-like. Patch by Pablo Galindo.

@item 
bpo-33041@footnote{https://bugs.python.org/issue33041}: Added new opcode @ref{2e2,,END_ASYNC_FOR} and fixes the
following issues:


@itemize *

@item 
Setting global @ref{fa5,,StopAsyncIteration} no longer breaks @code{async for}
loops.

@item 
Jumping into an @code{async for} loop is now disabled.

@item 
Jumping out of an @code{async for} loop no longer corrupts the stack.
@end itemize

@item 
bpo-25750@footnote{https://bugs.python.org/issue25750}: Fix rare Python crash due to bad refcounting in
@code{type_getattro()} if a descriptor deletes itself from the class. Patch
by Jeroen Demeyer.

@item 
bpo-33041@footnote{https://bugs.python.org/issue33041}: Fixed bytecode generation for "async for" with a complex
target. A StopAsyncIteration raised on assigning or unpacking will be now
propagated instead of stopping the iteration.

@item 
bpo-33026@footnote{https://bugs.python.org/issue33026}: Fixed jumping out of "with" block by setting f_lineno.

@item 
bpo-33005@footnote{https://bugs.python.org/issue33005}: Fix a crash on fork when using a custom memory allocator (ex:
using PYTHONMALLOC env var). _PyGILState_Reinit() and
_PyInterpreterState_Enable() now use the default RAW memory allocator to
allocate a new interpreters mutex on fork.

@item 
bpo-32911@footnote{https://bugs.python.org/issue32911}: Due to unexpected compatibility issues discovered during
downstream beta testing, reverted bpo-29463@footnote{https://bugs.python.org/issue29463}. @code{docstring} field is
removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes
which was added in 3.7a1.  Docstring expression is restored as a first
statement in their body. Based on patch by Inada Naoki.

@item 
bpo-17288@footnote{https://bugs.python.org/issue17288}: Prevent jumps from 'return' and 'exception' trace events.

@item 
bpo-32946@footnote{https://bugs.python.org/issue32946}: Importing names from already imported module with "from ...
import ..." is now 30% faster if the module is not a package.

@item 
bpo-32932@footnote{https://bugs.python.org/issue32932}: Make error message more revealing when there are non-str
objects in @code{__all__}.

@item 
bpo-32925@footnote{https://bugs.python.org/issue32925}: Optimized iterating and containing test for literal lists
consisting of non-constants: @code{x in [a, b]} and @code{for x in [a, b]}. The
case of all constant elements already was optimized.

@item 
bpo-32889@footnote{https://bugs.python.org/issue32889}: Update Valgrind suppression list to account for the rename of
@code{Py_ADDRESS_IN_RANG} to @code{address_in_range}.

@item 
bpo-32836@footnote{https://bugs.python.org/issue32836}: Don't use temporary variables in cases of list/dict/set
comprehensions

@item 
bpo-31356@footnote{https://bugs.python.org/issue31356}: Remove the new API added in bpo-31356@footnote{https://bugs.python.org/issue31356} (gc.ensure_disabled()
context manager).

@item 
bpo-32305@footnote{https://bugs.python.org/issue32305}: For namespace packages, ensure that both @code{__file__} and
@code{__spec__.origin} are set to None.

@item 
bpo-32303@footnote{https://bugs.python.org/issue32303}: Make sure @code{__spec__.loader} matches @code{__loader__} for
namespace packages.

@item 
bpo-32711@footnote{https://bugs.python.org/issue32711}: Fix the warning messages for Python/ast_unparse.c. Patch by
Stéphane Wirtel

@item 
bpo-32583@footnote{https://bugs.python.org/issue32583}: Fix possible crashing in builtin Unicode decoders caused by
write out-of-bound errors when using customized decode error handlers.

@item 
bpo-32489@footnote{https://bugs.python.org/issue32489}: A @ref{181,,continue} statement is now allowed in the
@ref{182,,finally} clause.

@item 
bpo-17611@footnote{https://bugs.python.org/issue17611}: Simplified the interpreter loop by moving the logic of
unrolling the stack of blocks into the compiler. The compiler emits now
explicit instructions for adjusting the stack of values and calling the
cleaning up code for @ref{2db,,break}, @ref{181,,continue} and
@ref{190,,return}.

Removed opcodes @code{BREAK_LOOP}, @code{CONTINUE_LOOP},
@code{SETUP_LOOP} and @code{SETUP_EXCEPT}. Added new opcodes
@ref{2dc,,ROT_FOUR}, @ref{2dd,,BEGIN_FINALLY} and @ref{2de,,CALL_FINALLY} and
@ref{2df,,POP_FINALLY}. Changed the behavior of @ref{2e0,,END_FINALLY} and
@ref{2e1,,WITH_CLEANUP_START}.

@item 
bpo-32285@footnote{https://bugs.python.org/issue32285}: New function unicodedata.is_normalized, which can check whether
a string is in a specific normal form.

@item 
bpo-10544@footnote{https://bugs.python.org/issue10544}: Yield expressions are now disallowed in comprehensions and
generator expressions except the expression for the outermost iterable.

@item 
bpo-32117@footnote{https://bugs.python.org/issue32117}: Iterable unpacking is now allowed without parentheses in yield
and return statements, e.g. @code{yield 1, 2, 3, *rest}. Thanks to David
Cuthbert for the change and Jordan Chapman for added tests.

@item 
bpo-31902@footnote{https://bugs.python.org/issue31902}: Fix the @code{col_offset} attribute for ast nodes
@code{ast.AsyncFor}, @code{ast.AsyncFunctionDef}, and @code{ast.AsyncWith}.
Previously, @code{col_offset} pointed to the keyword after @code{async}.

@item 
bpo-25862@footnote{https://bugs.python.org/issue25862}: 修复 @code{io.TextIOWrapper} 的 @code{tell()} 方法内的错误断言。

@item 
bpo-21983@footnote{https://bugs.python.org/issue21983}: Fix a crash in @ref{fa6,,ctypes.cast()} in case the type argument is a
ctypes structured data type. Patch by Eryk Sun and Oren Milman.

@item 
bpo-31577@footnote{https://bugs.python.org/issue31577}: Fix a crash in @ref{a38,,os.utime()} in case of a bad ns argument. Patch
by Oren Milman.

@item 
bpo-29832@footnote{https://bugs.python.org/issue29832}: Remove references to 'getsockaddrarg' from various socket error
messages. Patch by Oren Milman.
@end itemize

@node 库<20>,文档<16>,核心与内置<20>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id146}@anchor{fa7}
@subsubsection 库



@itemize -

@item 
bpo-35845@footnote{https://bugs.python.org/issue35845}: Add 'order' parameter to memoryview.tobytes().

@item 
bpo-35864@footnote{https://bugs.python.org/issue35864}: The _asdict() method for collections.namedtuple now returns a
regular dict instead of an OrderedDict.

@item 
bpo-35537@footnote{https://bugs.python.org/issue35537}: An ExitStack is now used internally within subprocess.POpen to
clean up pipe file handles. No behavior change in normal operation. But if
closing one handle were ever to cause an exception, the others will now be
closed instead of leaked.  (patch by Giampaolo Rodola)

@item 
bpo-35847@footnote{https://bugs.python.org/issue35847}: RISC-V needed the CTYPES_PASS_BY_REF_HACK.  Fixes ctypes
Structure test_pass_by_value.

@item 
bpo-35813@footnote{https://bugs.python.org/issue35813}: Shared memory submodule added to multiprocessing to avoid need
for serialization between processes

@item 
bpo-35780@footnote{https://bugs.python.org/issue35780}: Fix lru_cache() errors arising in recursive, reentrant, or
multi-threaded code. These errors could result in orphan links and in the
cache being trapped in a state with fewer than the specified maximum
number of links. Fix handling of negative maxsize which should have been
treated as zero. Fix errors in toggling the "full" status flag. Fix
misordering of links when errors are encountered.  Sync-up the C code and
pure Python code for the space saving path in functions with a single
positional argument. In this common case, the space overhead of an lru
cache entry is reduced by almost half.  Fix counting of cache misses. In
error cases, the miss count was out of sync with the actual number of
times the underlying user function was called.

@item 
bpo-35537@footnote{https://bugs.python.org/issue35537}: @ref{257,,os.posix_spawn()} and @ref{fa8,,os.posix_spawnp()} now have a
@emph{setsid} parameter.

@item 
bpo-23846@footnote{https://bugs.python.org/issue23846}: @ref{1ab,,asyncio.ProactorEventLoop} now catches and logs send
errors when the self-pipe is full.

@item 
bpo-34323@footnote{https://bugs.python.org/issue34323}: @ref{a,,asyncio}: Enhance @code{IocpProactor.close()} log: wait 1
second before the first log, then log every second. Log also the number of
seconds since @code{close()} was called.

@item 
bpo-35674@footnote{https://bugs.python.org/issue35674}: Add a new @ref{fa8,,os.posix_spawnp()} function. Patch by Joannah
Nanjekye.

@item 
bpo-35733@footnote{https://bugs.python.org/issue35733}: @code{ast.Constant(boolean)} no longer an instance of
@code{ast.Num}.  Patch by Anthony Sottile.

@item 
bpo-35726@footnote{https://bugs.python.org/issue35726}: QueueHandler.prepare() now makes a copy of the record before
modifying and enqueueing it, to avoid affecting other handlers in the
chain.

@item 
bpo-35719@footnote{https://bugs.python.org/issue35719}: Sped up multi-argument @ref{b1,,math} functions atan2(),
copysign(), remainder() and hypot() by 1.3--2.5 times.

@item 
bpo-35717@footnote{https://bugs.python.org/issue35717}: Fix KeyError exception raised when using enums and compile.
Patch contributed by Rémi Lapeyre.

@item 
bpo-35699@footnote{https://bugs.python.org/issue35699}: Fixed detection of Visual Studio Build Tools 2017 in distutils

@item 
bpo-32710@footnote{https://bugs.python.org/issue32710}: Fix memory leaks in asyncio ProactorEventLoop on overlapped
operation failure.

@item 
bpo-35702@footnote{https://bugs.python.org/issue35702}: The @ref{239,,time.CLOCK_UPTIME_RAW} constant is now available for
macOS 10.12.

@item 
bpo-32710@footnote{https://bugs.python.org/issue32710}: Fix a memory leak in asyncio in the ProactorEventLoop when
@code{ReadFile()} or @code{WSASend()} overlapped operation fail immediately:
release the internal buffer.

@item 
bpo-35682@footnote{https://bugs.python.org/issue35682}: Fix @code{asyncio.ProactorEventLoop.sendfile()}: don't attempt to
set the result of an internal future if it's already done.

@item 
bpo-35283@footnote{https://bugs.python.org/issue35283}: Add a deprecated warning for the
@code{threading.Thread.isAlive()} method. Patch by Dong-hee Na.

@item 
bpo-35664@footnote{https://bugs.python.org/issue35664}: Improve operator.itemgetter() performance by 33% with optimized
argument handling and with adding a fast path for the common case of a
single non-negative integer index into a tuple (which is the typical use
case in the standard library).

@item 
bpo-35643@footnote{https://bugs.python.org/issue35643}: 修复了 Modules/_sha3/cleanup.py 中的一个 SyntaxWarning: invalid escape sequence。 补丁作者 Mickaël Schoentgen。

@item 
bpo-35619@footnote{https://bugs.python.org/issue35619}: Improved support of custom data descriptors in @ref{56d,,help()} and
@ref{d9,,pydoc}.

@item 
bpo-28503@footnote{https://bugs.python.org/issue28503}: 当库函数可用时 @ref{29,,crypt} 模块现在将在内部使用 @code{crypt_r()} 而非 @ref{29,,crypt()}。

@item 
bpo-35614@footnote{https://bugs.python.org/issue35614}: Fixed help() on metaclasses. Patch by Sanyam Khurana.

@item 
bpo-35568@footnote{https://bugs.python.org/issue35568}: Expose @code{raise(signum)} as @code{raise_signal}

@item 
bpo-35588@footnote{https://bugs.python.org/issue35588}: The floor division and modulo operations and the @ref{152,,divmod()}
function on @ref{185,,fractions.Fraction} types are 2--4x faster. Patch by
Stefan Behnel.

@item 
bpo-35585@footnote{https://bugs.python.org/issue35585}: 加快构建按值枚举的速度，例如 http.HTTPStatus(200)。

@item 
bpo-30561@footnote{https://bugs.python.org/issue30561}: random.gammavariate(1.0, beta) now computes the same result as
random.expovariate(1.0 / beta).  This synchonizes the two algorithms and
eliminates some idiosyncrasies in the old implementation.  It does however
produce a difference stream of random variables than it used to.

@item 
bpo-35537@footnote{https://bugs.python.org/issue35537}: The @ref{f9,,subprocess} module can now use the
@ref{257,,os.posix_spawn()} function in some cases for better performance.

@item 
bpo-35526@footnote{https://bugs.python.org/issue35526}: Delaying the 'joke' of barry_as_FLUFL.mandatory to Python
version 4.0

@item 
bpo-35523@footnote{https://bugs.python.org/issue35523}: Remove @ref{2b,,ctypes} callback workaround: no longer create a
callback at startup. Avoid SELinux alert on @code{import ctypes} and @code{import
uuid}.

@item 
bpo-31784@footnote{https://bugs.python.org/issue31784}: @ref{40b,,uuid.uuid1()} now calls @ref{31c,,time.time_ns()} rather than
@code{int(time.time() * 1e9)}.

@item 
bpo-35513@footnote{https://bugs.python.org/issue35513}: @code{unittest.runner} 的 @code{TextTestRunner} 现在将使用 @ref{2aa,,time.perf_counter()} 而非 @ref{316,,time.time()} 来计量一个测试的执行时间: @ref{316,,time.time()} 可以回退，而 @ref{2aa,,time.perf_counter()} 为单调递增。

@item 
bpo-35502@footnote{https://bugs.python.org/issue35502}: 修复了构建树未完成的情况下 @ref{253,,xml.etree.ElementTree.TreeBuilder} 中的引用泄漏（特别是在解析 XML 期间引发错误的时候）。

@item 
bpo-35348@footnote{https://bugs.python.org/issue35348}: Make @ref{fa9,,platform.architecture()} parsing of @code{file} command
output more reliable: add the @code{-b} option to the @code{file} command to
omit the filename, force the usage of the C locale, and search also the
"shared object" pattern.

@item 
bpo-35491@footnote{https://bugs.python.org/issue35491}: @ref{b7,,multiprocessing}: Add @code{Pool.__repr__()} and enhance
@code{BaseProcess.__repr__()} (add pid and parent pid) to ease debugging.
Pool state constant values are now strings instead of integers, for
example @code{RUN} value becomes @code{'RUN'} instead of @code{0}.

@item 
bpo-35477@footnote{https://bugs.python.org/issue35477}: @code{multiprocessing.Pool.__enter__()} now fails if the pool is
not running: @code{with pool:} fails if used more than once.

@item 
bpo-31446@footnote{https://bugs.python.org/issue31446}: 复制被传递给 CreateProcessW 的命令行，因为此函数能改变输入缓存的内容。

@item 
bpo-35471@footnote{https://bugs.python.org/issue35471}: Python2.4 取消了对MacOS 9 的支持。Python3.7 中已弃用 macpath 模块。该模块现在已移除。

@item 
bpo-23057@footnote{https://bugs.python.org/issue23057}: Unblock Proactor event loop when keyboard interrupt is received
on Windows

@item 
bpo-35052@footnote{https://bugs.python.org/issue35052}: Fix xml.dom.minidom cloneNode() on a document with an entity:
pass the correct arguments to the user data handler of an entity.

@item 
bpo-20239@footnote{https://bugs.python.org/issue20239}: Allow repeated assignment deletion of
@ref{249,,unittest.mock.Mock} attributes. Patch by Pablo Galindo.

@item 
bpo-17185@footnote{https://bugs.python.org/issue17185}: 在 mock 上设置 @code{__signature__} 以便 @ref{a0,,inspect} 能获得签名。 补丁作者为 Karthikeyan Singaravelan。

@item 
bpo-35445@footnote{https://bugs.python.org/issue35445}: Memory errors during creating posix.environ no longer ignored.

@item 
bpo-35415@footnote{https://bugs.python.org/issue35415}: Validate fileno= argument to socket.socket().

@item 
bpo-35424@footnote{https://bugs.python.org/issue35424}: @code{multiprocessing.Pool} destructor now emits
@ref{4ca,,ResourceWarning} if the pool is still running.

@item 
bpo-35330@footnote{https://bugs.python.org/issue35330}: When a @code{Mock} instance was used to wrap an object, if
@code{side_effect} is used in one of the mocks of it methods, don't call the
original implementation and return the result of using the side effect the
same way that it is done with return_value.

@item 
bpo-35346@footnote{https://bugs.python.org/issue35346}: 从 @ref{ce,,platform} 模块中删除 MacOS 9 和 Rhapsody 支持。Rhapsody 上一次发布是在2000年。MacOS 9 上一次发布是在2001年。

@item 
bpo-10496@footnote{https://bugs.python.org/issue10496}: @code{check_environ()} of
@code{distutils.utils} now catches @ref{2c7,,KeyError} on calling
@ref{faa,,pwd.getpwuid()}: don't create the @code{HOME} environment variable in
this case.

@item 
bpo-10496@footnote{https://bugs.python.org/issue10496}: @code{posixpath.expanduser()} now returns the input @emph{path}
unchanged if the @code{HOME} environment variable is not set and the current
user has no home directory (if the current user identifier doesn't exist
in the password database). This change fix the @ref{eb,,site} module if the
current user doesn't exist in the password database (if the user has no
home directory).

@item 
bpo-35389@footnote{https://bugs.python.org/issue35389}: @ref{fab,,platform.libc_ver()} now uses
@code{os.confstr('CS_GNU_LIBC_VERSION')} if available and the @emph{executable}
parameter is not set.

@item 
bpo-35394@footnote{https://bugs.python.org/issue35394}: Add empty slots to asyncio abstract protocols.

@item 
bpo-35310@footnote{https://bugs.python.org/issue35310}: Fix a bug in @ref{66d,,select.select()} where, in some cases, the
file descriptor sequences were returned unmodified after a signal
interruption, even though the file descriptors might not be ready yet.
@ref{66d,,select.select()} will now always return empty lists if a timeout has
occurred.  Patch by Oran Avraham.

@item 
bpo-35380@footnote{https://bugs.python.org/issue35380}: Enable TCP_NODELAY on Windows for proactor asyncio event loop.

@item 
bpo-35341@footnote{https://bugs.python.org/issue35341}: Add generic version of @code{collections.OrderedDict} to the
@code{typing} module. Patch by Ismo Toijala.

@item 
bpo-35371@footnote{https://bugs.python.org/issue35371}: Fixed possible crash in @code{os.utime()} on Windows when pass
incorrect arguments.

@item 
bpo-35346@footnote{https://bugs.python.org/issue35346}: @ref{fac,,platform.uname()} now redirects @code{stderr} to
@ref{fad,,os.devnull} when running external programs like @code{cmd /c ver}.

@item 
bpo-35066@footnote{https://bugs.python.org/issue35066}: Previously, calling the strftime() method on a datetime object
with a trailing '%' in the format string would result in an exception.
However, this only occurred when the datetime C module was being used; the
python implementation did not match this behavior. Datetime is now PEP-399
compliant, and will not throw an exception on a trailing '%'.

@item 
bpo-35345@footnote{https://bugs.python.org/issue35345}: The function @code{platform.popen} has been removed, it was
deprecated since Python 3.3: use @ref{2a9,,os.popen()} instead.

@item 
bpo-35344@footnote{https://bugs.python.org/issue35344}: On macOS, @ref{fae,,platform.platform()} now uses
@ref{faf,,platform.mac_ver()}, if it returns a non-empty release string, to get
the macOS version rather than the darwin version.

@item 
bpo-35312@footnote{https://bugs.python.org/issue35312}: Make @code{lib2to3.pgen2.parse.ParseError} round-trip pickle-able.
Patch by Anthony Sottile.

@item 
bpo-35308@footnote{https://bugs.python.org/issue35308}: Fix regression in @code{webbrowser} where default browsers may be
preferred over browsers in the @code{BROWSER} environment variable.

@item 
bpo-24746@footnote{https://bugs.python.org/issue24746}: Avoid stripping trailing whitespace in doctest fancy diff.
Original patch by R. David Murray & Jairo Trad. Enhanced by Sanyam
Khurana.

@item 
bpo-28604@footnote{https://bugs.python.org/issue28604}: @ref{484,,locale.localeconv()} now sets temporarily the @code{LC_CTYPE}
locale to the @code{LC_MONETARY} locale if the two locales are different and
monetary strings are non-ASCII. This temporary change affects other
threads.

@item 
bpo-35277@footnote{https://bugs.python.org/issue35277}: Update ensurepip to install pip 18.1 and setuptools 40.6.2.

@item 
bpo-24209@footnote{https://bugs.python.org/issue24209}: Adds IPv6 support when invoking http.server directly.

@item 
bpo-35226@footnote{https://bugs.python.org/issue35226}: Recursively check arguments when testing for equality of
@ref{f09,,unittest.mock.call} objects and add note that tracking of
parameters used to create ancestors of mocks in @code{mock_calls} is not
possible.

@item 
bpo-29564@footnote{https://bugs.python.org/issue29564}: The warnings module now suggests to enable tracemalloc if the
source is specified, the tracemalloc module is available, but tracemalloc
is not tracing memory allocations.

@item 
bpo-35189@footnote{https://bugs.python.org/issue35189}: Modify the following fnctl function to retry if interrupted by
a signal (EINTR): flock, lockf, fnctl

@item 
bpo-30064@footnote{https://bugs.python.org/issue30064}: Use add_done_callback() in sock_* asyncio API to unsubscribe
reader/writer early on calcellation.

@item 
bpo-35186@footnote{https://bugs.python.org/issue35186}: Removed the "built with" comment added when @code{setup.py upload}
is used with either @code{bdist_rpm} or @code{bdist_dumb}.

@item 
bpo-35152@footnote{https://bugs.python.org/issue35152}: Allow sending more than 2 GB at once on a multiprocessing
connection on non-Windows systems.

@item 
bpo-35062@footnote{https://bugs.python.org/issue35062}: Fix incorrect parsing of
@code{_io.IncrementalNewlineDecoder}'s @emph{translate} argument.

@item 
bpo-35065@footnote{https://bugs.python.org/issue35065}: Remove @code{StreamReaderProtocol._untrack_reader}. The call to
@code{_untrack_reader} is currently performed too soon, causing the protocol to
forget about the reader before @code{connection_lost} can run and feed the EOF
to the reader.

@item 
bpo-34160@footnote{https://bugs.python.org/issue34160}: ElementTree and minidom now preserve the attribute order
specified by the user.

@item 
bpo-35079@footnote{https://bugs.python.org/issue35079}: Improve difflib.SequenceManager.get_matching_blocks doc by
adding 'non-overlapping' and changing '!=' to '<'.

@item 
bpo-33710@footnote{https://bugs.python.org/issue33710}: Deprecated @code{l*gettext()} functions and methods in the
@ref{89,,gettext} module. They return encoded bytes instead of Unicode
strings and are artifacts from Python 2 times. Also deprecated functions
and methods related to setting the charset for @code{l*gettext()} functions
and methods.

@item 
bpo-35017@footnote{https://bugs.python.org/issue35017}: @ref{a86,,socketserver.BaseServer.serve_forever()} now exits
immediately if it's @ref{fb0,,shutdown()} method is
called while it is polling for new events.

@item 
bpo-35024@footnote{https://bugs.python.org/issue35024}: @ref{9b,,importlib} no longer logs @code{wrote} redundantly
after @code{(created|could not create)} is already logged.
Patch by Quentin Agren.

@item 
bpo-35047@footnote{https://bugs.python.org/issue35047}: @code{unittest.mock} now includes mock calls in exception messages
if @code{assert_not_called}, @code{assert_called_once}, or
@code{assert_called_once_with} fails. Patch by Petter Strandmark.

@item 
bpo-31047@footnote{https://bugs.python.org/issue31047}: Fix @code{ntpath.abspath} regression where it didn't remove a
trailing separator on Windows. Patch by Tim Graham.

@item 
bpo-35053@footnote{https://bugs.python.org/issue35053}: tracemalloc now tries to update the traceback when an object is
reused from a "free list" (optimization for faster object creation, used
by the builtin list type for example).

@item 
bpo-31553@footnote{https://bugs.python.org/issue31553}: Add the --json-lines option to json.tool. Patch by hongweipeng.

@item 
bpo-34794@footnote{https://bugs.python.org/issue34794}: Fixed a leak in Tkinter when pass the Python wrapper around
Tcl_Obj back to Tcl/Tk.

@item 
bpo-34909@footnote{https://bugs.python.org/issue34909}: Enum: fix grandchildren subclassing when parent mixed with
concrete data types.

@item 
bpo-35022@footnote{https://bugs.python.org/issue35022}: @ref{77f,,unittest.mock.MagicMock} now supports the
@code{__fspath__} method (from @ref{4e5,,os.PathLike}).

@item 
bpo-35008@footnote{https://bugs.python.org/issue35008}: Fixed references leaks when call the @code{__setstate__()} method
of @ref{abf,,xml.etree.ElementTree.Element} in the C implementation for
already initialized element.

@item 
bpo-23420@footnote{https://bugs.python.org/issue23420}: Verify the value for the parameter '-s' of the cProfile CLI.
Patch by Robert Kuska

@item 
bpo-33947@footnote{https://bugs.python.org/issue33947}: dataclasses now handle recursive reprs without raising
RecursionError.

@item 
bpo-34890@footnote{https://bugs.python.org/issue34890}: Make @ref{6f2,,inspect.iscoroutinefunction()},
@ref{fb1,,inspect.isgeneratorfunction()} and @ref{fb2,,inspect.isasyncgenfunction()}
work with @ref{7c2,,functools.partial()}. Patch by Pablo Galindo.

@item 
bpo-34521@footnote{https://bugs.python.org/issue34521}: Use @ref{fb3,,socket.CMSG_SPACE()} to calculate ancillary data size
instead of @ref{fb4,,socket.CMSG_LEN()} in
@code{multiprocessing.reduction.recvfds()} as 
@geindex RFC; RFC 3542
RFC 3542@footnote{https://tools.ietf.org/html/rfc3542.html} requires the use
of the former for portable applications.

@item 
bpo-31522@footnote{https://bugs.python.org/issue31522}: The @code{mailbox.mbox.get_string} function @emph{from_} parameter can
now successfully be set to a non-default value.

@item 
bpo-34970@footnote{https://bugs.python.org/issue34970}: Protect tasks weak set manipulation in @code{asyncio.all_tasks()}

@item 
bpo-34969@footnote{https://bugs.python.org/issue34969}: gzip: Add --fast, --best on the gzip CLI, these parameters will
be used for the fast compression method (quick) or the best method
compress (slower, but smaller file). Also, change the default compression
level to 6 (tradeoff).

@item 
bpo-16965@footnote{https://bugs.python.org/issue16965}: The @ref{fb5,,2to3} @ref{fb6,,execfile} fixer now opens the file
with mode @code{'rb'}.  Patch by Zackery Spytz.

@item 
bpo-34966@footnote{https://bugs.python.org/issue34966}: @ref{d9,,pydoc} now supports aliases not only to methods defined
in the end class, but also to inherited methods.  The docstring is not
duplicated for aliases.

@item 
bpo-34926@footnote{https://bugs.python.org/issue34926}: @ref{fb7,,mimetypes.MimeTypes.guess_type()} now accepts
@ref{363,,path-like object} in addition to url strings. Patch by Mayank
Asthana.

@item 
bpo-23831@footnote{https://bugs.python.org/issue23831}: Add @code{moveto()} method to the @code{tkinter.Canvas} widget. Patch
by Juliette Monsel.

@item 
bpo-34941@footnote{https://bugs.python.org/issue34941}: Methods @code{find()}, @code{findtext()} and @code{findall()} of the
@code{Element} class in the @ref{137,,xml.etree.ElementTree} module are now able
to find children which are instances of @code{Element} subclasses.

@item 
bpo-32680@footnote{https://bugs.python.org/issue32680}: @ref{a7c,,smtplib.SMTP} objects now always have a @code{sock}
attribute present

@item 
bpo-34769@footnote{https://bugs.python.org/issue34769}: Fix for async generators not finalizing when event loop is in
debug mode and garbage collector runs in another thread.

@item 
bpo-34936@footnote{https://bugs.python.org/issue34936}: Fix @code{TclError} in @code{tkinter.Spinbox.selection_element()}.
Patch by Juliette Monsel.

@item 
bpo-34829@footnote{https://bugs.python.org/issue34829}: Add methods @code{selection_from}, @code{selection_range},
@code{selection_present} and @code{selection_to} to the @code{tkinter.Spinbox} for
consistency with the @code{tkinter.Entry} widget. Patch by Juliette Monsel.

@item 
bpo-34911@footnote{https://bugs.python.org/issue34911}: Added @emph{secure_protocols} argument to
@emph{http.cookiejar.DefaultCookiePolicy} to allow for tweaking of protocols
and also to add support by default for @emph{wss}, the secure websocket
protocol.

@item 
bpo-34922@footnote{https://bugs.python.org/issue34922}: Fixed integer overflow in the @ref{fb8,,digest()}
and @ref{fb9,,hexdigest()} methods for the SHAKE algorithm in
the @ref{8d,,hashlib} module.

@item 
bpo-34925@footnote{https://bugs.python.org/issue34925}: 25% speedup in argument parsing for the functions in the bisect
module.

@item 
bpo-34900@footnote{https://bugs.python.org/issue34900}: Fixed @ref{fba,,unittest.TestCase.debug()} when used to call test
methods with subtests.  Patch by Bruno Oliveira.

@item 
bpo-34844@footnote{https://bugs.python.org/issue34844}: logging.Formatter enhancement - Ensure styles and fmt matches
in logging.Formatter - Added validate method in each format style class:
StrFormatStyle, PercentStyle, StringTemplateStyle. - This method is called
in the constructor of logging.Formatter class - Also re-raise the KeyError
in the format method of each style class, so it would a bit clear that
it's an error with the invalid format fields.

@item 
bpo-34897@footnote{https://bugs.python.org/issue34897}: Adjust test.support.missing_compiler_executable check so that a
nominal command name of "" is ignored. Patch by Michael Felt.

@item 
bpo-34871@footnote{https://bugs.python.org/issue34871}: Fix inspect module polluted @code{sys.modules} when parsing
@code{__text_signature__} of callable.

@item 
bpo-34898@footnote{https://bugs.python.org/issue34898}: Add @code{mtime} argument to @ref{1d1,,gzip.compress} for reproducible
output. Patch by Guo Ci Teo.

@item 
bpo-28441@footnote{https://bugs.python.org/issue28441}: On Cygwin and MinGW, ensure that @code{sys.executable} always
includes the full filename in the path, including the @code{.exe} suffix
(unless it is a symbolic link).

@item 
bpo-34866@footnote{https://bugs.python.org/issue34866}: Adding @code{max_num_fields} to @code{cgi.FieldStorage} to make DOS
attacks harder by limiting the number of @code{MiniFieldStorage} objects
created by @code{FieldStorage}.

@item 
bpo-34711@footnote{https://bugs.python.org/issue34711}: http.server ensures it reports HTTPStatus.NOT_FOUND when the
local path ends with "/" and is not a directory, even if the underlying OS
(e.g. AIX) accepts such paths as a valid file reference. Patch by Michael
Felt.

@item 
bpo-34872@footnote{https://bugs.python.org/issue34872}: Fix self-cancellation in C implementation of asyncio.Task

@item 
bpo-34849@footnote{https://bugs.python.org/issue34849}: Don't log waiting for @code{selector.select} in asyncio loop
iteration. The waiting is pretty normal for any asyncio program, logging
its time just adds a noise to logs without any useful information
provided.

@item 
bpo-34022@footnote{https://bugs.python.org/issue34022}: The 
@geindex SOURCE_DATE_EPOCH
@geindex 环境变量; SOURCE_DATE_EPOCH
@code{SOURCE_DATE_EPOCH} environment variable no longer
overrides the value of the @emph{invalidation_mode} argument to
@ref{215,,py_compile.compile()}, and determines its default value instead.

@item 
bpo-34819@footnote{https://bugs.python.org/issue34819}: 使用一个单一时钟计算 @code{Executor.map()} 和 @code{as_completed()} 中的超时，以防止当系统时钟被修改时因偏离导致的超时。

@item 
bpo-34758@footnote{https://bugs.python.org/issue34758}: Add .wasm -> application/wasm to list of recognized file types
and content type headers

@item 
bpo-34789@footnote{https://bugs.python.org/issue34789}: @ref{fbb,,xml.sax.make_parser()} now accepts any iterable as its
@emph{parser_list} argument.  Patch by Andrés Delfino.

@item 
bpo-34334@footnote{https://bugs.python.org/issue34334}: In @code{QueueHandler}, clear @code{exc_text} from
@code{LogRecord} to prevent traceback from being written twice.

@item 
bpo-34687@footnote{https://bugs.python.org/issue34687}: On Windows, asyncio now uses ProactorEventLoop, instead of
SelectorEventLoop, by default.

@item 
bpo-5950@footnote{https://bugs.python.org/issue5950}: Support reading zip files with archive comments in
@ref{143,,zipimport}.

@item 
bpo-32892@footnote{https://bugs.python.org/issue32892}: The parser now represents all constants as
@code{ast.Constant} instead of using specific constant AST types
(@code{Num}, @code{Str}, @code{Bytes}, @code{NameConstant} and @code{Ellipsis}). These
classes are considered deprecated and will be removed in future Python
versions.

@item 
bpo-34728@footnote{https://bugs.python.org/issue34728}: Add deprecation warning when @code{loop} is used in methods:
@ref{285,,asyncio.sleep}, @ref{289,,asyncio.wait} and @ref{288,,asyncio.wait_for}.

@item 
bpo-34738@footnote{https://bugs.python.org/issue34738}: ZIP files created by @ref{39,,distutils} will now include entries
for directories.

@item 
bpo-34659@footnote{https://bugs.python.org/issue34659}: Add an optional @emph{initial} argument to itertools.accumulate().

@item 
bpo-29577@footnote{https://bugs.python.org/issue29577}: Support multiple mixin classes when creating Enums.

@item 
bpo-34670@footnote{https://bugs.python.org/issue34670}: Add SSLContext.post_handshake_auth and
SSLSocket.verify_client_post_handshake for TLS 1.3's post handshake
authentication feature.

@item 
bpo-32718@footnote{https://bugs.python.org/issue32718}: The Activate.ps1 script from venv works with PowerShell Core
6.1 and is now available under all operating systems.

@item 
bpo-31177@footnote{https://bugs.python.org/issue31177}: Fix bug that prevented using @ref{5a5,,reset_mock} on mock instances with deleted attributes

@item 
bpo-34672@footnote{https://bugs.python.org/issue34672}: Add a workaround, so the @code{'Z'} @ref{b5e,,time.strftime()}
specifier on the musl C library can work in some cases.

@item 
bpo-34666@footnote{https://bugs.python.org/issue34666}: Implement @code{asyncio.StreamWriter.awrite} and
@code{asyncio.StreamWriter.aclose()} coroutines.  Methods are needed for
providing a consistent stream API with control flow switched on by
default.

@item 
bpo-6721@footnote{https://bugs.python.org/issue6721}: Acquire the logging module's commonly used internal locks while
fork()ing to avoid deadlocks in the child process.

@item 
bpo-34658@footnote{https://bugs.python.org/issue34658}: Fix a rare interpreter unhandled exception state SystemError
only seen when using subprocess with a preexec_fn while an after_parent
handler has been registered with os.register_at_fork and the fork system
call fails.

@item 
bpo-34652@footnote{https://bugs.python.org/issue34652}: Ensure @ref{fbc,,os.lchmod()} is never defined on Linux.

@item 
bpo-34638@footnote{https://bugs.python.org/issue34638}: Store a weak reference to stream reader to break strong
references loop between reader and protocol.  It allows to detect and
close the socket if the stream is deleted (garbage collected) without
@code{close()} call.

@item 
bpo-34536@footnote{https://bugs.python.org/issue34536}: @code{Enum._missing_}:  raise @ref{1fb,,ValueError} if None returned and
@ref{192,,TypeError} if non-member is returned.

@item 
bpo-34636@footnote{https://bugs.python.org/issue34636}: Speed up re scanning of many non-matching characters for s w
and d within bytes objects. (microoptimization)

@item 
bpo-24412@footnote{https://bugs.python.org/issue24412}: Add @ref{24a,,addModuleCleanup()} and
@ref{24b,,addClassCleanup()} to unittest to support
cleanups for @code{setUpModule()} and
@ref{24c,,setUpClass()}. Patch by Lisa Roach.

@item 
bpo-34630@footnote{https://bugs.python.org/issue34630}: Don't log SSL certificate errors in asyncio code (connection
error logging is skipped already).

@item 
bpo-32490@footnote{https://bugs.python.org/issue32490}: Prevent filename duplication in @ref{f9,,subprocess} exception
messages.  Patch by Zackery Spytz.

@item 
bpo-34363@footnote{https://bugs.python.org/issue34363}: dataclasses.asdict() and .astuple() now handle namedtuples
correctly.

@item 
bpo-34625@footnote{https://bugs.python.org/issue34625}: Update vendorized expat library version to 2.2.6.

@item 
bpo-32270@footnote{https://bugs.python.org/issue32270}: The subprocess module no longer mistakenly closes redirected
fds even when they were in pass_fds when outside of the default @{0, 1, 2@}
set.

@item 
bpo-34622@footnote{https://bugs.python.org/issue34622}: Create a dedicated @code{asyncio.CancelledError},
@code{asyncio.InvalidStateError} and @code{asyncio.TimeoutError} exception
classes.  Inherit them from corresponding exceptions from
@code{concurrent.futures} package. Extract @code{asyncio} exceptions into a
separate file.

@item 
bpo-34610@footnote{https://bugs.python.org/issue34610}: Fixed iterator of @code{multiprocessing.managers.DictProxy}.

@item 
bpo-34421@footnote{https://bugs.python.org/issue34421}: Fix distutils logging for non-ASCII strings.  This caused
installation issues on Windows.

@item 
bpo-34604@footnote{https://bugs.python.org/issue34604}: Fix possible mojibake in the error message of @ref{fbd,,pwd.getpwnam}
and @ref{fbe,,grp.getgrnam} using string representation because of invisible
characters or trailing whitespaces. Patch by William Grzybowski.

@item 
bpo-30977@footnote{https://bugs.python.org/issue30977}: Make uuid.UUID use @code{__slots__} to reduce its memory
footprint. Based on original patch by Wouter Bolsterlee.

@item 
bpo-34574@footnote{https://bugs.python.org/issue34574}: OrderedDict iterators are not exhausted during pickling
anymore. Patch by Sergey Fedoseev.

@item 
bpo-8110@footnote{https://bugs.python.org/issue8110}: Refactored @ref{f9,,subprocess} to check for Windows-specific
modules rather than @code{sys.platform == 'win32'}.

@item 
bpo-34530@footnote{https://bugs.python.org/issue34530}: @code{distutils.spawn.find_executable()} now falls back on
@ref{f70,,os.defpath} if the @code{PATH} environment variable is not set.

@item 
bpo-34563@footnote{https://bugs.python.org/issue34563}: On Windows, fix multiprocessing.Connection for very large read:
fix _winapi.PeekNamedPipe() and _winapi.ReadFile() for read larger than
INT_MAX (usually 2^31-1).

@item 
bpo-34558@footnote{https://bugs.python.org/issue34558}: Correct typo in Lib/ctypes/_aix.py

@item 
bpo-34282@footnote{https://bugs.python.org/issue34282}: Move @code{Enum._convert} to @code{EnumMeta._convert_} and fix enum
members getting shadowed by parent attributes.

@item 
bpo-22872@footnote{https://bugs.python.org/issue22872}: When the queue is closed, @ref{1fb,,ValueError} is now raised by
@ref{fbf,,multiprocessing.Queue.put()} and @ref{fc0,,multiprocessing.Queue.get()}
instead of @ref{fc1,,AssertionError} and @ref{1d3,,OSError}, respectively. Patch
by Zackery Spytz.

@item 
bpo-34515@footnote{https://bugs.python.org/issue34515}: Fix parsing non-ASCII identifiers in
@code{lib2to3.pgen2.tokenize} (PEP 3131).

@item 
bpo-13312@footnote{https://bugs.python.org/issue13312}: Avoids a possible integer underflow (undefined behavior) in the
time module's year handling code when passed a very low negative year
value.

@item 
bpo-34472@footnote{https://bugs.python.org/issue34472}: Improved compatibility for streamed files in @ref{142,,zipfile}.
Previously an optional signature was not being written and certain ZIP
applications were not supported. Patch by Silas Sewell.

@item 
bpo-34454@footnote{https://bugs.python.org/issue34454}: Fix the .fromisoformat() methods of datetime types crashing
when given unicode with non-UTF-8-encodable code points.  Specifically,
datetime.fromisoformat() now accepts surrogate unicode code points used as
the separator. Report and tests by Alexey Izbyshev, patch by Paul Ganssle.

@item 
bpo-6700@footnote{https://bugs.python.org/issue6700}: Fix inspect.getsourcelines for module level frames/tracebacks.
Patch by Vladimir Matveev.

@item 
bpo-34171@footnote{https://bugs.python.org/issue34171}: Running the @ref{112,,trace} module no longer creates the
@code{trace.cover} file.

@item 
bpo-34441@footnote{https://bugs.python.org/issue34441}: Fix crash when an @code{ABC}-derived class with invalid
@code{__subclasses__} is passed as the second argument to
@ref{44a,,issubclass()}. Patch by Alexey Izbyshev.

@item 
bpo-34427@footnote{https://bugs.python.org/issue34427}: Fix infinite loop in @code{a.extend(a)} for @code{MutableSequence}
subclasses.

@item 
bpo-34412@footnote{https://bugs.python.org/issue34412}: Make @ref{fc2,,signal.strsignal()} work on HP-UX. Patch by Michael
Osipov.

@item 
bpo-20849@footnote{https://bugs.python.org/issue20849}: shutil.copytree now accepts a new @code{dirs_exist_ok} keyword
argument. Patch by Josh Bronson.

@item 
bpo-31715@footnote{https://bugs.python.org/issue31715}: Associate @code{.mjs} file extension with
@code{application/javascript} MIME Type.

@item 
bpo-34384@footnote{https://bugs.python.org/issue34384}: @ref{1f3,,os.readlink()} now accepts @ref{363,,path-like} and @ref{32a,,bytes} objects on Windows.

@item 
bpo-22602@footnote{https://bugs.python.org/issue22602}: The UTF-7 decoder now raises @ref{1fd,,UnicodeDecodeError} for
ill-formed sequences starting with "+" (as specified in RFC 2152).  Patch
by Zackery Spytz.

@item 
bpo-2122@footnote{https://bugs.python.org/issue2122}: The @ref{2c3,,mmap.flush()} method now returns
@code{None} on success, raises an exception on error under all platforms.

@item 
bpo-34341@footnote{https://bugs.python.org/issue34341}: Appending to the ZIP archive with the ZIP64 extension no longer
grows the size of extra fields of existing entries.

@item 
bpo-34333@footnote{https://bugs.python.org/issue34333}: 修复在 @ref{fc3,,pathlib.PurePath.with_suffix()} 内使用%-formatting 格式化错误信息的错误。

@item 
bpo-18540@footnote{https://bugs.python.org/issue18540}: The @ref{606,,imaplib.IMAP4} and @ref{a12,,imaplib.IMAP4_SSL}
classes now resolve to the local host IP correctly when the default value
of @emph{host} parameter (@code{'@w{'}}) is used.

@item 
bpo-26502@footnote{https://bugs.python.org/issue26502}: Implement @code{traceback.FrameSummary.__len__()} method to
preserve compatibility with the old tuple API.

@item 
bpo-34318@footnote{https://bugs.python.org/issue34318}: @ref{ab5,,assertRaises()},
@ref{ab6,,assertRaisesRegex()},
@ref{ab7,,assertWarns()} and
@ref{ab8,,assertWarnsRegex()} no longer success if the
passed callable is None. They no longer ignore unknown keyword arguments
in the context manager mode. A DeprecationWarning was raised in these
cases since Python 3.5.

@item 
bpo-9372@footnote{https://bugs.python.org/issue9372}: Deprecate @ref{27f,,__getitem__()} methods of
@ref{27c,,xml.dom.pulldom.DOMEventStream}, @ref{27d,,wsgiref.util.FileWrapper}
and @ref{27e,,fileinput.FileInput}.

@item 
bpo-33613@footnote{https://bugs.python.org/issue33613}: Fix a race condition in @code{multiprocessing.semaphore_tracker}
when the tracker receives SIGINT before it can register signal handlers
for ignoring it.

@item 
bpo-34248@footnote{https://bugs.python.org/issue34248}: Report filename in the exception raised when the database file
cannot be opened by @ref{fc4,,dbm.gnu.open()} and @ref{fc5,,dbm.ndbm.open()} due to
OS-related error. Patch by Zsolt Cserna.

@item 
bpo-33089@footnote{https://bugs.python.org/issue33089}: Add math.dist() to compute the Euclidean distance between two
points.

@item 
bpo-34246@footnote{https://bugs.python.org/issue34246}: @ref{73f,,smtplib.SMTP.send_message()} no longer modifies the
content of the @emph{mail_options} argument. Patch by Pablo S. Blum de Aguiar.

@item 
bpo-31047@footnote{https://bugs.python.org/issue31047}: Fix @code{ntpath.abspath} for invalid paths on windows. Patch by
Franz Woellert.

@item 
bpo-32321@footnote{https://bugs.python.org/issue32321}: Add pure Python fallback for functools.reduce. Patch by Robert
Wright.

@item 
bpo-34270@footnote{https://bugs.python.org/issue34270}: The default asyncio task class now always has a name which can
be get or set using two new methods (@ref{1b1,,get_name()} and
@ref{1b0,,set_name()}) and is visible in the @ref{7c6,,repr()} output.
An initial name can also be set using the new @code{name} keyword argument to
@ref{1ae,,asyncio.create_task()} or the
@code{create_task()} method of the event loop.
If no initial name is set, the default Task implementation generates a
name like @code{Task-1} using a monotonic counter.

@item 
bpo-34263@footnote{https://bugs.python.org/issue34263}: asyncio's event loop will not pass timeouts longer than one day
to epoll/select etc.

@item 
bpo-34035@footnote{https://bugs.python.org/issue34035}: Fix several AttributeError in zipfile seek() methods. Patch by
Mickaël Schoentgen.

@item 
bpo-32215@footnote{https://bugs.python.org/issue32215}: Fix performance regression in @ref{f2,,sqlite3} when a DML
statement appeared in a different line than the rest of the SQL query.

@item 
bpo-34075@footnote{https://bugs.python.org/issue34075}: Deprecate passing non-ThreadPoolExecutor instances to
@code{AbstractEventLoop.set_default_executor()}.

@item 
bpo-34251@footnote{https://bugs.python.org/issue34251}: Restore @code{msilib.Win64} to preserve backwards compatibility
since it's already used by @ref{39,,distutils}' @code{bdist_msi} command.

@item 
bpo-19891@footnote{https://bugs.python.org/issue19891}: Ignore errors caused by missing / non-writable homedir while
writing history during exit of an interactive session.  Patch by Anthony
Sottile.

@item 
bpo-33089@footnote{https://bugs.python.org/issue33089}: Enhanced math.hypot() to support more than two dimensions.

@item 
bpo-34228@footnote{https://bugs.python.org/issue34228}: tracemalloc: PYTHONTRACEMALLOC=0 environment variable and -X
tracemalloc=0 command line option are now allowed to disable explicitly
tracemalloc at startup.

@item 
bpo-13041@footnote{https://bugs.python.org/issue13041}: Use @ref{a45,,shutil.get_terminal_size()} to calculate the terminal
width correctly in the @code{argparse.HelpFormatter} class.  Initial patch by
Zbyszek Jędrzejewski-Szmek.

@item 
bpo-34213@footnote{https://bugs.python.org/issue34213}: Allow frozen dataclasses to have a field named "object".
Previously this conflicted with an internal use of "object".

@item 
bpo-34052@footnote{https://bugs.python.org/issue34052}: @ref{f2c,,sqlite3.Connection.create_aggregate()},
@ref{f2d,,sqlite3.Connection.create_function()},
@ref{f2e,,sqlite3.Connection.set_authorizer()},
@ref{f2f,,sqlite3.Connection.set_progress_handler()} methods raises TypeError
when unhashable objects are passed as callable. These methods now don't
pass such objects to SQLite API. Previous behavior could lead to
segfaults. Patch by Sergey Fedoseev.

@item 
bpo-34197@footnote{https://bugs.python.org/issue34197}: Attributes @emph{skipinitialspace}, @emph{doublequote} and @emph{strict} of
the @emph{dialect} attribute of the @ref{2a,,csv} reader are now @ref{183,,bool}
instances instead of integers 0 or 1.

@item 
bpo-32788@footnote{https://bugs.python.org/issue32788}: Errors other than @ref{192,,TypeError} raised in methods
@code{__adapt__()} and @code{__conform__()} in the @ref{f2,,sqlite3} module are now
propagated to the user.

@item 
bpo-21446@footnote{https://bugs.python.org/issue21446}: The @ref{fc6,,reload} fixer now uses @ref{391,,importlib.reload()}
instead of deprecated @ref{c69,,imp.reload()}.

@item 
bpo-940286@footnote{https://bugs.python.org/issue940286}: pydoc's @code{Helper.showtopic()} method now prints the cross
references of a topic correctly.

@item 
bpo-34164@footnote{https://bugs.python.org/issue34164}: @ref{957,,base64.b32decode()} could raise UnboundLocalError or
OverflowError for incorrect padding.  Now it always raises
@code{base64.Error} in these cases.

@item 
bpo-33729@footnote{https://bugs.python.org/issue33729}: Fixed issues with arguments parsing in @ref{8d,,hashlib}.

@item 
bpo-34097@footnote{https://bugs.python.org/issue34097}: ZipFile can zip files older than 1980-01-01 and newer than
2107-12-31 using a new @code{strict_timestamps} parameter at the cost of
setting the timestamp to the limit.

@item 
bpo-34108@footnote{https://bugs.python.org/issue34108}: Remove extraneous CR in 2to3 refactor.

@item 
bpo-34070@footnote{https://bugs.python.org/issue34070}: Make sure to only check if the handle is a tty, when opening a
file with @code{buffering=-1}.

@item 
bpo-27494@footnote{https://bugs.python.org/issue27494}: Reverted bpo-27494@footnote{https://bugs.python.org/issue27494}. 2to3 rejects now a trailing comma in
generator expressions.

@item 
bpo-33967@footnote{https://bugs.python.org/issue33967}: functools.singledispatch now raises TypeError instead of
IndexError when no positional arguments are passed.

@item 
bpo-34041@footnote{https://bugs.python.org/issue34041}: Add the parameter @emph{deterministic} to the
@ref{f2d,,sqlite3.Connection.create_function()} method. Patch by Sergey
Fedoseev.

@item 
bpo-34056@footnote{https://bugs.python.org/issue34056}: Ensure the loader shim created by @code{imp.load_module} always
returns bytes from its @code{get_data()} function. This fixes using
@code{imp.load_module} with 
@geindex Python 提高建议; PEP 552
PEP 552@footnote{https://www.python.org/dev/peps/pep-0552} hash-based pycs.

@item 
bpo-34054@footnote{https://bugs.python.org/issue34054}: The multiprocessing module now uses the monotonic clock
@ref{769,,time.monotonic()} instead of the system clock @ref{316,,time.time()} to
implement timeout.

@item 
bpo-34043@footnote{https://bugs.python.org/issue34043}: Optimize tarfile uncompress performance about 15% when gzip is
used.

@item 
bpo-34044@footnote{https://bugs.python.org/issue34044}: @code{subprocess.Popen} now copies the @emph{startupinfo} argument to
leave it unchanged: it will modify the copy, so that the same
@code{STARTUPINFO} object can be used multiple times.

@item 
bpo-34010@footnote{https://bugs.python.org/issue34010}: Fixed a performance regression for reading streams with
tarfile. The buffered read should use a list, instead of appending to a
bytes object.

@item 
bpo-34019@footnote{https://bugs.python.org/issue34019}: webbrowser: Correct the arguments passed to Opera Browser when
opening a new URL using the @code{webbrowser} module. Patch by Bumsik Kim.

@item 
bpo-34003@footnote{https://bugs.python.org/issue34003}: csv.DictReader now creates dicts instead of OrderedDicts. Patch
by Michael Selik.

@item 
bpo-33978@footnote{https://bugs.python.org/issue33978}: Closed existing logging handlers before reconfiguration via
fileConfig and dictConfig. Patch by Karthikeyan Singaravelan.

@item 
bpo-14117@footnote{https://bugs.python.org/issue14117}: Make minor tweaks to turtledemo. The 'wikipedia' example is now
'rosette', describing what it draws.  The 'penrose' print output is
reduced. The'1024' output of 'tree' is eliminated.

@item 
bpo-33974@footnote{https://bugs.python.org/issue33974}: Fixed passing lists and tuples of strings containing special
characters @code{"}, @code{\}, @code{@{}, @code{@}} and @code{\n} as options to
@ref{10f,,ttk} widgets.

@item 
bpo-27500@footnote{https://bugs.python.org/issue27500}: Fix getaddrinfo to resolve IPv6 addresses correctly.

@item 
bpo-24567@footnote{https://bugs.python.org/issue24567}: Improve random.choices() to handle subnormal input weights that
could occasionally trigger an IndexError.

@item 
bpo-33871@footnote{https://bugs.python.org/issue33871}: Fixed integer overflow in @ref{3b0,,os.readv()}, @ref{3b3,,os.writev()},
@ref{3af,,os.preadv()} and @ref{3b2,,os.pwritev()} and in @ref{352,,os.sendfile()} with
@emph{headers} or @emph{trailers} arguments (on BSD-based OSes and macOS).

@item 
bpo-25007@footnote{https://bugs.python.org/issue25007}: Add @ref{3c3,,copy.copy()} and @ref{3c4,,copy.deepcopy()} support to zlib
compressors and decompressors.  Patch by Zackery Spytz.

@item 
bpo-33929@footnote{https://bugs.python.org/issue33929}: multiprocessing: Fix a race condition in Popen of
multiprocessing.popen_spawn_win32. The child process now duplicates the
read end of pipe instead of "stealing" it. Previously, the read end of
pipe was "stolen" by the child process, but it leaked a handle if the
child process had been terminated before it could steal the handle from
the parent process.

@item 
bpo-33899@footnote{https://bugs.python.org/issue33899}: Tokenize module now implicitly emits a NEWLINE when provided
with input that does not have a trailing new line.  This behavior now
matches what the C tokenizer does internally.  Contributed by Ammar Askar.

@item 
bpo-33897@footnote{https://bugs.python.org/issue33897}: Added a 'force' keyword argument to logging.basicConfig().

@item 
bpo-33695@footnote{https://bugs.python.org/issue33695}: @ref{21a,,shutil.copytree()} uses @ref{25f,,os.scandir()} function and
all copy functions depending from it use cached @ref{1f1,,os.stat()} values.
The speedup for copying a directory with 8000 files is around +9% on
Linux, +20% on Windows and + 30% on a Windows SMB share. Also the number
of @ref{1f1,,os.stat()} syscalls is reduced by 38% making
@ref{21a,,shutil.copytree()} especially faster on network filesystems.
(Contributed by Giampaolo Rodola' in bpo-33695@footnote{https://bugs.python.org/issue33695}.)

@item 
bpo-33916@footnote{https://bugs.python.org/issue33916}: bz2 and lzma: When Decompressor.__init__() is called twice,
free the old lock to not leak memory.

@item 
bpo-32568@footnote{https://bugs.python.org/issue32568}: Make select.epoll() and its documentation consistent regarding
@emph{sizehint} and @emph{flags}.

@item 
bpo-33833@footnote{https://bugs.python.org/issue33833}: Fixed bug in asyncio where ProactorSocketTransport logs
AssertionError if force closed during write.

@item 
bpo-33663@footnote{https://bugs.python.org/issue33663}: Convert content length to string before putting to header.

@item 
bpo-33721@footnote{https://bugs.python.org/issue33721}: @ref{c5,,os.path} functions that return a boolean result like
@ref{1f6,,exists()}, @ref{1f7,,lexists()}, @ref{1f8,,isdir()},
@ref{1f9,,isfile()}, @ref{1f4,,islink()}, and
@ref{1fa,,ismount()}, and @ref{201,,pathlib.Path} methods that return a
boolean result like @ref{202,,exists()},
@ref{203,,is_dir()}, @ref{204,,is_file()},
@ref{205,,is_mount()}, @ref{206,,is_symlink()},
@ref{207,,is_block_device()},
@ref{208,,is_char_device()}, @ref{209,,is_fifo()},
@ref{20a,,is_socket()} now return @code{False} instead of raising
@ref{1fb,,ValueError} or its subclasses @ref{1fc,,UnicodeEncodeError} and
@ref{1fd,,UnicodeDecodeError} for paths that contain characters or bytes
unrepresentable at the OS level.

@item 
bpo-26544@footnote{https://bugs.python.org/issue26544}: Fixed implementation of @ref{fab,,platform.libc_ver()}. It almost
always returned version '2.9' for glibc.

@item 
bpo-33843@footnote{https://bugs.python.org/issue33843}: Remove deprecated @code{cgi.escape}, @code{cgi.parse_qs} and
@code{cgi.parse_qsl}.

@item 
bpo-33842@footnote{https://bugs.python.org/issue33842}: Remove @code{tarfile.filemode} which is deprecated since Python
3.3.

@item 
bpo-30167@footnote{https://bugs.python.org/issue30167}: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by
Steve Weber.

@item 
bpo-33805@footnote{https://bugs.python.org/issue33805}: Improve error message of dataclasses.replace() when an InitVar
is not specified

@item 
bpo-33687@footnote{https://bugs.python.org/issue33687}: Fix the call to @code{os.chmod()} for @code{uu.decode()} if a mode is
given or decoded. Patch by Timo Furrer.

@item 
bpo-33812@footnote{https://bugs.python.org/issue33812}: Datetime instance d with non-None tzinfo, but with
d.tzinfo.utcoffset(d) returning None is now treated as naive by the
astimezone() method.

@item 
bpo-32108@footnote{https://bugs.python.org/issue32108}: In configparser, don't clear section when it is assigned to
itself.

@item 
bpo-27397@footnote{https://bugs.python.org/issue27397}: Make email module properly handle invalid-length base64
strings.

@item 
bpo-33578@footnote{https://bugs.python.org/issue33578}: Implement multibyte encoder/decoder state methods

@item 
bpo-30805@footnote{https://bugs.python.org/issue30805}: Avoid race condition with debug logging

@item 
bpo-33476@footnote{https://bugs.python.org/issue33476}: Fix _header_value_parser.py when address group is missing final
';'. Contributed by Enrique Perez-Terron

@item 
bpo-33694@footnote{https://bugs.python.org/issue33694}: asyncio: Fix a race condition causing data loss on
pause_reading()/resume_reading() when using the ProactorEventLoop.

@item 
bpo-32493@footnote{https://bugs.python.org/issue32493}: Correct test for @code{uuid_enc_be} availability in
@code{configure.ac}. Patch by Michael Felt.

@item 
bpo-33792@footnote{https://bugs.python.org/issue33792}: Add asyncio.WindowsSelectorEventLoopPolicy and
asyncio.WindowsProactorEventLoopPolicy.

@item 
bpo-33274@footnote{https://bugs.python.org/issue33274}: W3C DOM Level 1 specifies return value of
Element.removeAttributeNode() as "The Attr node that was removed."
xml.dom.minidom now complies with this requirement.

@item 
bpo-33778@footnote{https://bugs.python.org/issue33778}: Update @code{unicodedata}'s database to Unicode version 11.0.0.

@item 
bpo-33165@footnote{https://bugs.python.org/issue33165}: Added a stacklevel parameter to logging calls to allow use of
wrapper/helper functions for logging APIs.

@item 
bpo-33770@footnote{https://bugs.python.org/issue33770}: improve base64 exception message for encoded inputs of invalid
length

@item 
bpo-33769@footnote{https://bugs.python.org/issue33769}: asyncio/start_tls: Fix error message; cancel callbacks in case
of an unhandled error; mark SSLTransport as closed if it is aborted.

@item 
bpo-33767@footnote{https://bugs.python.org/issue33767}: The concatenation (@code{+}) and repetition (@code{*}) sequence
operations now raise @ref{192,,TypeError} instead of @ref{5f6,,SystemError} when
performed on @ref{1ec,,mmap.mmap} objects.  Patch by Zackery Spytz.

@item 
bpo-33734@footnote{https://bugs.python.org/issue33734}: asyncio/ssl: Fix AttributeError, increase default handshake
timeout

@item 
bpo-31014@footnote{https://bugs.python.org/issue31014}: Fixed creating a controller for @ref{129,,webbrowser} when a user
specifies a path to an entry in the BROWSER environment variable.  Based
on patch by John Still.

@item 
bpo-2504@footnote{https://bugs.python.org/issue2504}: Add gettext.pgettext() and variants.

@item 
bpo-33197@footnote{https://bugs.python.org/issue33197}: Add description property for _ParameterKind

@item 
bpo-32751@footnote{https://bugs.python.org/issue32751}: When cancelling the task due to a timeout,
@ref{288,,asyncio.wait_for()} will now wait until the cancellation is complete.

@item 
bpo-32684@footnote{https://bugs.python.org/issue32684}: Fix gather to propagate cancellation of itself even with
return_exceptions.

@item 
bpo-33654@footnote{https://bugs.python.org/issue33654}: Support protocol type switching in SSLTransport.set_protocol().

@item 
bpo-33674@footnote{https://bugs.python.org/issue33674}: Pause the transport as early as possible to further reduce the
risk of data_received() being called before connection_made().

@item 
bpo-33671@footnote{https://bugs.python.org/issue33671}: @ref{258,,shutil.copyfile()}, @ref{259,,shutil.copy()},
@ref{25a,,shutil.copy2()}, @ref{21a,,shutil.copytree()} and @ref{25b,,shutil.move()} use
platform-specific fast-copy syscalls on Linux and macOS in order to copy
the file more efficiently. On Windows @ref{258,,shutil.copyfile()} uses a
bigger default buffer size (1 MiB instead of 16 KiB) and a
@ref{25c,,memoryview()}-based variant of @ref{25d,,shutil.copyfileobj()} is used.
The speedup for copying a 512MiB file is about +26% on Linux, +50% on
macOS and +40% on Windows. Also, much less CPU cycles are consumed.
(Contributed by Giampaolo Rodola' in bpo-25427@footnote{https://bugs.python.org/issue25427}.)

@item 
bpo-33674@footnote{https://bugs.python.org/issue33674}: Fix a race condition in SSLProtocol.connection_made() of
asyncio.sslproto: start immediately the handshake instead of using
call_soon(). Previously, data_received() could be called before the
handshake started, causing the handshake to hang or fail.

@item 
bpo-31647@footnote{https://bugs.python.org/issue31647}: Fixed bug where calling write_eof() on a
_SelectorSocketTransport after it's already closed raises AttributeError.

@item 
bpo-32610@footnote{https://bugs.python.org/issue32610}: Make asyncio.all_tasks() return only pending tasks.

@item 
bpo-32410@footnote{https://bugs.python.org/issue32410}: Avoid blocking on file IO in sendfile fallback code

@item 
bpo-33469@footnote{https://bugs.python.org/issue33469}: Fix RuntimeError after closing loop that used run_in_executor

@item 
bpo-33672@footnote{https://bugs.python.org/issue33672}: Fix Task.__repr__ crash with Cython's bogus coroutines

@item 
bpo-33654@footnote{https://bugs.python.org/issue33654}: Fix transport.set_protocol() to support switching between
asyncio.Protocol and asyncio.BufferedProtocol.  Fix loop.start_tls() to
work with asyncio.BufferedProtocols.

@item 
bpo-33652@footnote{https://bugs.python.org/issue33652}: Pickles of type variables and subscripted generics are now
future-proof and compatible with older Python versions.

@item 
bpo-32493@footnote{https://bugs.python.org/issue32493}: Fixed @ref{40b,,uuid.uuid1()} on FreeBSD.

@item 
bpo-33238@footnote{https://bugs.python.org/issue33238}: Add @code{InvalidStateError} to @ref{22,,concurrent.futures}.
@code{Future.set_result} and @code{Future.set_exception} now raise
@code{InvalidStateError} if the futures are not pending or running. Patch by
Jason Haydaman.

@item 
bpo-33618@footnote{https://bugs.python.org/issue33618}: Finalize and document preliminary and experimental TLS 1.3
support with OpenSSL 1.1.1

@item 
bpo-33625@footnote{https://bugs.python.org/issue33625}: Release GIL on @ref{fbe,,grp.getgrnam}, @ref{5da,,grp.getgrgid}, @ref{fbd,,pwd.getpwnam}
and @ref{faa,,pwd.getpwuid} if reentrant variants of these functions are available.
Patch by William Grzybowski.

@item 
bpo-33623@footnote{https://bugs.python.org/issue33623}: Fix possible SIGSGV when asyncio.Future is created in __del__

@item 
bpo-11874@footnote{https://bugs.python.org/issue11874}: Use a better regex when breaking usage into wrappable parts.
Avoids bogus assertion errors from custom metavar strings.

@item 
bpo-30877@footnote{https://bugs.python.org/issue30877}: Fixed a bug in the Python implementation of the JSON decoder
that prevented the cache of parsed strings from clearing after finishing
the decoding. Based on patch by c-fos.

@item 
bpo-33604@footnote{https://bugs.python.org/issue33604}: Remove HMAC default to md5 marked for removal in 3.8 (removal
originally planned in 3.6, bump to 3.8 in gh-7062).

@item 
bpo-33582@footnote{https://bugs.python.org/issue33582}: Emit a deprecation warning for inspect.formatargspec

@item 
bpo-21145@footnote{https://bugs.python.org/issue21145}: Add @code{functools.cached_property} decorator, for computed
properties cached for the life of the instance.

@item 
bpo-33570@footnote{https://bugs.python.org/issue33570}: Change TLS 1.3 cipher suite settings for compatibility with
OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers
enabled by default.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Do not simplify arguments to @ref{fc7,,typing.Union}. Now
@code{Union[Manager, Employee]} is not simplified to @code{Employee} at runtime.
Such simplification previously caused several bugs and limited
possibilities for introspection.

@item 
bpo-12486@footnote{https://bugs.python.org/issue12486}: @ref{fc8,,tokenize.generate_tokens()} is now documented as a public
API to tokenize unicode strings. It was previously present but
undocumented.

@item 
bpo-33540@footnote{https://bugs.python.org/issue33540}: Add a new @code{block_on_close} class attribute to
@code{ForkingMixIn} and @code{ThreadingMixIn} classes of @ref{f0,,socketserver}.

@item 
bpo-33548@footnote{https://bugs.python.org/issue33548}: tempfile._candidate_tempdir_list should consider common TEMP
locations

@item 
bpo-33109@footnote{https://bugs.python.org/issue33109}: argparse subparsers are once again not required by default,
reverting the change in behavior introduced by bpo-26510@footnote{https://bugs.python.org/issue26510} in 3.7.0a2.

@item 
bpo-33541@footnote{https://bugs.python.org/issue33541}: Remove unused private method @code{_strptime.LocaleTime.__pad}
(a.k.a. @code{_LocaleTime__pad}).

@item 
bpo-33536@footnote{https://bugs.python.org/issue33536}: dataclasses.make_dataclass now checks for invalid field names
and duplicate fields. Also, added a check for invalid field
specifications.

@item 
bpo-33542@footnote{https://bugs.python.org/issue33542}: Prevent @code{uuid.get_node} from using a DUID instead of a MAC on
Windows. Patch by Zvi Effron

@item 
bpo-26819@footnote{https://bugs.python.org/issue26819}: Fix race condition with @code{ReadTransport.resume_reading} in
Windows proactor event loop.

@item 
Fix failure in @ref{303,,typing.get_type_hints()} when ClassVar was provided as a
string forward reference.

@item 
bpo-33516@footnote{https://bugs.python.org/issue33516}: @ref{77f,,unittest.mock.MagicMock} now supports the @code{__round__}
magic method.

@item 
bpo-28612@footnote{https://bugs.python.org/issue28612}: Added support for Site Maps to urllib's @code{RobotFileParser} as
@ref{fc9,,RobotFileParser.site_maps()}. Patch by Lady Red, based
on patch by Peter Wirtz.

@item 
bpo-28167@footnote{https://bugs.python.org/issue28167}: Remove platform.linux_distribution, which was deprecated since
3.5.

@item 
bpo-33504@footnote{https://bugs.python.org/issue33504}: Switch the default dictionary implementation for
@ref{23,,configparser} from @ref{1b9,,collections.OrderedDict} to the standard
@ref{1b8,,dict} type.

@item 
bpo-33505@footnote{https://bugs.python.org/issue33505}: Optimize asyncio.ensure_future() by reordering if checks: 1.17x
faster.

@item 
bpo-33497@footnote{https://bugs.python.org/issue33497}: Add errors param to cgi.parse_multipart and make an encoding in
FieldStorage use the given errors (needed for Twisted).  Patch by Amber
Brown.

@item 
bpo-29235@footnote{https://bugs.python.org/issue29235}: The @code{cProfile.Profile} class can now be used as a
context manager. Patch by Scott Sanderson.

@item 
bpo-33495@footnote{https://bugs.python.org/issue33495}: Change dataclasses.Fields repr to use the repr of each of its
members, instead of str.  This makes it more clear what each field
actually represents.  This is especially true for the 'type' member.

@item 
bpo-26103@footnote{https://bugs.python.org/issue26103}: Correct @code{inspect.isdatadescriptor} to look for @code{__set__} or
@code{__delete__}.  Patch by Aaron Hall.

@item 
bpo-29209@footnote{https://bugs.python.org/issue29209}: Removed the @code{doctype()} method and the @emph{html} parameter of
the constructor of @ref{252,,XMLParser}.  The
@code{doctype()} method defined in a subclass will no longer be called.
Deprecated methods @code{getchildren()} and @code{getiterator()} in the
@ref{137,,ElementTree} module emit now a @ref{278,,DeprecationWarning}
instead of @ref{279,,PendingDeprecationWarning}.

@item 
bpo-33453@footnote{https://bugs.python.org/issue33453}: Fix dataclasses to work if using literal string type
annotations or if using PEP 563 "Postponed Evaluation of Annotations".
Only specific string prefixes are detected for both ClassVar ("ClassVar"
and "typing.ClassVar") and InitVar ("InitVar" and "dataclasses.InitVar").

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Minor fixes in typing module: add annotations to
@code{NamedTuple.__new__}, pass @code{*args} and @code{**kwds} in
@code{Generic.__new__}.  Original PRs by Paulius Šarka and Chad Dombrova.

@item 
bpo-33365@footnote{https://bugs.python.org/issue33365}: Print the header values besides the header keys instead just
the header keys if @emph{debuglevel} is set to >0 in @ref{94,,http.client}. Patch
by Marco Strigl.

@item 
bpo-20087@footnote{https://bugs.python.org/issue20087}: Updated alias mapping with glibc 2.27 supported locales.

@item 
bpo-33422@footnote{https://bugs.python.org/issue33422}: Fix trailing quotation marks getting deleted when looking up
byte/string literals on pydoc. Patch by Andrés Delfino.

@item 
bpo-28167@footnote{https://bugs.python.org/issue28167}: The function @code{platform.linux_distribution} and
@code{platform.dist} now trigger a @code{DeprecationWarning} and have been
marked for removal in Python 3.8

@item 
bpo-33281@footnote{https://bugs.python.org/issue33281}: Fix ctypes.util.find_library regression on macOS.

@item 
bpo-33311@footnote{https://bugs.python.org/issue33311}: Text and html output generated by cgitb does not display
parentheses if the current call is done directly in the module. Patch by
Stéphane Blondon.

@item 
bpo-27300@footnote{https://bugs.python.org/issue27300}: The file classes in @emph{tempfile} now accept an @emph{errors} parameter
that complements the already existing @emph{encoding}.  Patch by Stephan Hohe.

@item 
bpo-32933@footnote{https://bugs.python.org/issue32933}: @ref{f57,,unittest.mock.mock_open()} now supports iteration over the
file contents. Patch by Tony Flury.

@item 
bpo-33217@footnote{https://bugs.python.org/issue33217}: Raise @ref{192,,TypeError} when looking up non-Enum objects in Enum
classes and Enum members.

@item 
bpo-33197@footnote{https://bugs.python.org/issue33197}: Update error message when constructing invalid
inspect.Parameters Patch by Dong-hee Na.

@item 
bpo-33383@footnote{https://bugs.python.org/issue33383}: Fixed crash in the get() method of the @ref{35,,dbm.ndbm} database
object when it is called with a single argument.

@item 
bpo-33375@footnote{https://bugs.python.org/issue33375}: The warnings module now finds the Python file associated with a
warning from the code object, rather than the frame's global namespace.
This is consistent with how tracebacks and pdb find filenames, and should
work better for dynamically executed code.

@item 
bpo-33336@footnote{https://bugs.python.org/issue33336}: @code{imaplib} now allows @code{MOVE} command in @code{IMAP4.uid()} (RFC
6851: IMAP MOVE Extension) and potentially as a name of supported method
of @code{IMAP4} object.

@item 
bpo-32455@footnote{https://bugs.python.org/issue32455}: Added @emph{jump} parameter to @ref{834,,dis.stack_effect()}.

@item 
bpo-27485@footnote{https://bugs.python.org/issue27485}: Rename and deprecate undocumented functions in
@ref{11f,,urllib.parse()}.

@item 
bpo-33332@footnote{https://bugs.python.org/issue33332}: Add @code{signal.valid_signals()} to expose the POSIX sigfillset()
functionality.

@item 
bpo-33251@footnote{https://bugs.python.org/issue33251}: @code{ConfigParser.items()} was fixed so that key-value pairs passed
in via @ref{fca,,vars} are not included in the resulting output.

@item 
bpo-33329@footnote{https://bugs.python.org/issue33329}: Fix multiprocessing regression on newer glibcs

@item 
bpo-33334@footnote{https://bugs.python.org/issue33334}: @ref{834,,dis.stack_effect()} now supports all defined opcodes
including NOP and EXTENDED_ARG.

@item 
bpo-991266@footnote{https://bugs.python.org/issue991266}: Fix quoting of the @code{Comment} attribute of
@ref{fcb,,http.cookies.SimpleCookie}.

@item 
bpo-33131@footnote{https://bugs.python.org/issue33131}: Upgrade bundled version of pip to 10.0.1.

@item 
bpo-33308@footnote{https://bugs.python.org/issue33308}: Fixed a crash in the @ref{c7,,parser} module when converting an ST
object to a tree of tuples or lists with @code{line_info=False} and
@code{col_info=True}.

@item 
bpo-23403@footnote{https://bugs.python.org/issue23403}: lib2to3 now uses pickle protocol 4 for pre-computed grammars.

@item 
bpo-33266@footnote{https://bugs.python.org/issue33266}: lib2to3 now recognizes @code{rf'...'} strings.

@item 
bpo-11594@footnote{https://bugs.python.org/issue11594}: Ensure line-endings are respected when using lib2to3.

@item 
bpo-33254@footnote{https://bugs.python.org/issue33254}: Have @ref{fcc,,importlib.resources.contents()} and
@ref{fcd,,importlib.abc.ResourceReader.contents()} return an @ref{ba5,,iterable}
instead of an @ref{fce,,iterator}.

@item 
bpo-33265@footnote{https://bugs.python.org/issue33265}: @code{contextlib.ExitStack} and @code{contextlib.AsyncExitStack} now
use a method instead of a wrapper function for exit callbacks.

@item 
bpo-33263@footnote{https://bugs.python.org/issue33263}: Fix FD leak in @code{_SelectorSocketTransport}  Patch by Vlad
Starostin.

@item 
bpo-33256@footnote{https://bugs.python.org/issue33256}: Fix display of @code{<module>} call in the html produced by
@code{cgitb.html()}. Patch by Stéphane Blondon.

@item 
bpo-33144@footnote{https://bugs.python.org/issue33144}: @code{random.Random()} and its subclassing mechanism got optimized
to check only once at class/subclass instantiation time whether its
@code{getrandbits()} method can be relied on by other methods, including
@code{randrange()}, for the generation of arbitrarily large random integers.
Patch by Wolfgang Maier.

@item 
bpo-33185@footnote{https://bugs.python.org/issue33185}: Fixed regression when running pydoc with the @ref{330,,-m}
switch. (The regression was introduced in 3.7.0b3 by the resolution of
bpo-33053@footnote{https://bugs.python.org/issue33053})

This fix also changed pydoc to add @code{os.getcwd()} to @ref{482,,sys.path}
when necessary, rather than adding @code{"."}.

@item 
bpo-29613@footnote{https://bugs.python.org/issue29613}: Added support for the @code{SameSite} cookie flag to the
@code{http.cookies} module.

@item 
bpo-33169@footnote{https://bugs.python.org/issue33169}: Delete entries of @code{None} in @ref{498,,sys.path_importer_cache}
when @code{importlib.machinery.invalidate_caches()} is called.

@item 
bpo-33203@footnote{https://bugs.python.org/issue33203}: @code{random.Random.choice()} now raises @code{IndexError} for empty
sequences consistently even when called from subclasses without a
@code{getrandbits()} implementation.

@item 
bpo-33224@footnote{https://bugs.python.org/issue33224}: Update difflib.mdiff() for 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479}.  Convert an uncaught
StopIteration in a generator into a return-statement.

@item 
bpo-33209@footnote{https://bugs.python.org/issue33209}: End framing at the end of C implementation of
@ref{fcf,,pickle.Pickler.dump()}.

@item 
bpo-32861@footnote{https://bugs.python.org/issue32861}: The urllib.robotparser's @code{__str__} representation now
includes wildcard entries and the "Crawl-delay" and "Request-rate" fields.
Also removes extra newlines that were being appended to the end of the
string. Patch by Michael Lazar.

@item 
bpo-23403@footnote{https://bugs.python.org/issue23403}: @code{DEFAULT_PROTOCOL} in @ref{ca,,pickle} was bumped to 4. Protocol
4 is described in 
@geindex Python 提高建议; PEP 3154
PEP 3154@footnote{https://www.python.org/dev/peps/pep-3154} and available since Python 3.4. It offers
better performance and smaller size compared to protocol 3 introduced in
Python 3.0.

@item 
bpo-20104@footnote{https://bugs.python.org/issue20104}: Improved error handling and fixed a reference leak in
@ref{257,,os.posix_spawn()}.

@item 
bpo-33106@footnote{https://bugs.python.org/issue33106}: Deleting a key from a read-only dbm database raises module
specific error instead of KeyError.

@item 
bpo-33175@footnote{https://bugs.python.org/issue33175}: In dataclasses, Field.__set_name__ now looks up the
__set_name__ special method on the class, not the instance, of the default
value.

@item 
bpo-32380@footnote{https://bugs.python.org/issue32380}: Create functools.singledispatchmethod to support generic single
dispatch on descriptors and methods.

@item 
bpo-33141@footnote{https://bugs.python.org/issue33141}: Have Field objects pass through __set_name__ to their default
values, if they have their own __set_name__.

@item 
bpo-33096@footnote{https://bugs.python.org/issue33096}: Allow ttk.Treeview.insert to insert iid that has a false
boolean value. Note iid=0 and iid=False would be same. Patch by Garvit
Khatri.

@item 
bpo-32873@footnote{https://bugs.python.org/issue32873}: Treat type variables and special typing forms as immutable by
copy and pickle.  This fixes several minor issues and inconsistencies, and
improves backwards compatibility with Python 3.6.

@item 
bpo-33134@footnote{https://bugs.python.org/issue33134}: When computing dataclass's __hash__, use the lookup table to
contain the function which returns the __hash__ value.  This is an
improvement over looking up a string, and then testing that string to see
what to do.

@item 
bpo-33127@footnote{https://bugs.python.org/issue33127}: ssl模块现在使用LibreSSL 2.7.1编译。

@item 
bpo-32505@footnote{https://bugs.python.org/issue32505}: 如果数据类的成员变量的类型为Field，但没有类型注解，则引发TypeError。

@item 
bpo-33078@footnote{https://bugs.python.org/issue33078}: 修复在OSX平台因为依赖sem_getvalue而导致的失败。

@item 
bpo-33116@footnote{https://bugs.python.org/issue33116}: 将'Field'添加到dataclasses.__all__。

@item 
bpo-32896@footnote{https://bugs.python.org/issue32896}: Fix an error where subclassing a dataclass with a field that
uses a default_factory would generate an incorrect class.

@item 
bpo-33100@footnote{https://bugs.python.org/issue33100}: Dataclasses: If a field has a default value that's a
MemberDescriptorType, then it's from that field being in __slots__, not an
actual default value.

@item 
bpo-32953@footnote{https://bugs.python.org/issue32953}: If a non-dataclass inherits from a frozen dataclass, allow
attributes to be added to the derived class.  Only attributes from the
frozen dataclass cannot be assigned to.  Require all dataclasses in a
hierarchy to be either all frozen or all non-frozen.

@item 
bpo-33097@footnote{https://bugs.python.org/issue33097}: Raise RuntimeError when @code{executor.submit} is called during
interpreter shutdown.

@item 
bpo-32968@footnote{https://bugs.python.org/issue32968}: Modulo and floor division involving Fraction and float should
return float.

@item 
bpo-33061@footnote{https://bugs.python.org/issue33061}: 添加丢失的 @code{NoReturn} 到typing.py的 @code{__all__}

@item 
bpo-33078@footnote{https://bugs.python.org/issue33078}: Fix the size handling in multiprocessing.Queue when a pickling
error occurs.

@item 
bpo-33064@footnote{https://bugs.python.org/issue33064}: lib2to3 now properly supports trailing commas after @code{*args}
and @code{**kwargs} in function signatures.

@item 
bpo-33056@footnote{https://bugs.python.org/issue33056}: FIX properly close leaking fds in
concurrent.futures.ProcessPoolExecutor.

@item 
bpo-33021@footnote{https://bugs.python.org/issue33021}: Release the GIL during fstat() calls, avoiding hang of all
threads when calling mmap.mmap(), os.urandom(), and random.seed().  Patch
by Nir Soffer.

@item 
bpo-31804@footnote{https://bugs.python.org/issue31804}: Avoid failing in multiprocessing.Process if the standard
streams are closed or None at exit.

@item 
bpo-33034@footnote{https://bugs.python.org/issue33034}: Providing an explicit error message when casting the port
property to anything that is not an integer value using @code{urlparse()} and
@code{urlsplit()}. Patch by Matt Eaton.

@item 
bpo-30249@footnote{https://bugs.python.org/issue30249}: Improve struct.unpack_from() exception messages for problems
with the buffer size and offset.

@item 
bpo-33037@footnote{https://bugs.python.org/issue33037}: Skip sending/receiving data after SSL transport closing.

@item 
bpo-27683@footnote{https://bugs.python.org/issue27683}: Fix a regression in @ref{a2,,ipaddress} that result of
@code{hosts()} is empty when the network is constructed by a tuple
containing an integer mask and only 1 bit left for addresses.

@item 
bpo-22674@footnote{https://bugs.python.org/issue22674}: Add the strsignal() function in the signal module that returns
the system description of the given signal, as returned by strsignal(3).

@item 
bpo-32999@footnote{https://bugs.python.org/issue32999}: Fix C implementation of @code{ABC.__subclasscheck__(cls,
subclass)} crashed when @code{subclass} is not a type object.

@item 
bpo-33009@footnote{https://bugs.python.org/issue33009}: Fix inspect.signature() for single-parameter partialmethods.

@item 
bpo-32969@footnote{https://bugs.python.org/issue32969}: Expose several missing constants in zlib and fix corresponding
documentation.

@item 
bpo-32056@footnote{https://bugs.python.org/issue32056}: Improved exceptions raised for invalid number of channels and
sample width when read an audio file in modules @ref{5,,aifc}, @ref{127,,wave}
and @ref{fa,,sunau}.

@item 
bpo-32970@footnote{https://bugs.python.org/issue32970}: Improved disassembly of the MAKE_FUNCTION instruction.

@item 
bpo-32844@footnote{https://bugs.python.org/issue32844}: Fix wrong redirection of a low descriptor (0 or 1) to stderr in
subprocess if another low descriptor is closed.

@item 
bpo-32960@footnote{https://bugs.python.org/issue32960}: For dataclasses, disallow inheriting frozen from non-frozen
classes, and also disallow inheriting non-frozen from frozen classes. This
restriction will be relaxed at a future date.

@item 
bpo-32713@footnote{https://bugs.python.org/issue32713}: Fixed tarfile.itn handling of out-of-bounds float values. Patch
by Joffrey Fuhrer.

@item 
bpo-32257@footnote{https://bugs.python.org/issue32257}: The ssl module now contains OP_NO_RENEGOTIATION constant,
available with OpenSSL 1.1.0h or 1.1.1.

@item 
bpo-32951@footnote{https://bugs.python.org/issue32951}: Direct instantiation of SSLSocket and SSLObject objects is now
prohibited. The constructors were never documented, tested, or designed as
public constructors. Users were suppose to use ssl.wrap_socket() or
SSLContext.

@item 
bpo-32929@footnote{https://bugs.python.org/issue32929}: Remove the tri-state parameter "hash", and add the boolean
"unsafe_hash". If unsafe_hash is True, add a __hash__ function, but if a
__hash__ exists, raise TypeError.  If unsafe_hash is False, add a __hash__
based on the values of eq= and frozen=.  The unsafe_hash=False behavior is
the same as the old hash=None behavior.  unsafe_hash=False is the default,
just as hash=None used to be.

@item 
bpo-32947@footnote{https://bugs.python.org/issue32947}: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3
for future compatibility with OpenSSL 1.1.1.

@item 
bpo-32146@footnote{https://bugs.python.org/issue32146}: Document the interaction between frozen executables and the
spawn and forkserver start methods in multiprocessing.

@item 
bpo-30622@footnote{https://bugs.python.org/issue30622}: The ssl module now detects missing NPN support in LibreSSL.

@item 
bpo-32922@footnote{https://bugs.python.org/issue32922}: dbm.open() now encodes filename with the filesystem encoding
rather than default encoding.

@item 
bpo-32759@footnote{https://bugs.python.org/issue32759}: Free unused arenas in multiprocessing.heap.

@item 
bpo-32859@footnote{https://bugs.python.org/issue32859}: In @code{os.dup2}, don't check every call whether the @code{dup3}
syscall exists or not.

@item 
bpo-32556@footnote{https://bugs.python.org/issue32556}: nt._getfinalpathname, nt._getvolumepathname and
nt._getdiskusage now correctly convert from bytes.

@item 
bpo-21060@footnote{https://bugs.python.org/issue21060}: Rewrite confusing message from setup.py upload from "No dist
file created in earlier command" to the more helpful "Must create and
upload files in one command".

@item 
bpo-32857@footnote{https://bugs.python.org/issue32857}: In @ref{10c,,tkinter}, @code{after_cancel(None)} now raises a
@ref{1fb,,ValueError} instead of canceling the first scheduled function.
Patch by Cheryl Sabella.

@item 
bpo-32852@footnote{https://bugs.python.org/issue32852}: Make sure sys.argv remains as a list when running trace.

@item 
bpo-31333@footnote{https://bugs.python.org/issue31333}: @code{_abc} module is added.  It is a speedup module with C
implementations for various functions and methods in @code{abc}.  Creating an
ABC subclass and calling @code{isinstance} or @code{issubclass} with an ABC
subclass are up to 1.5x faster. In addition, this makes Python start-up up
to 10% faster.

Note that the new implementation hides internal registry and caches,
previously accessible via private attributes @code{_abc_registry},
@code{_abc_cache}, and @code{_abc_negative_cache}.  There are three debugging
helper methods that can be used instead @code{_dump_registry},
@code{_abc_registry_clear}, and @code{_abc_caches_clear}.

@item 
bpo-32841@footnote{https://bugs.python.org/issue32841}: Fixed @ref{28d,,asyncio.Condition} issue which silently ignored
cancellation after notifying and cancelling a conditional lock. Patch by
Bar Harel.

@item 
bpo-32819@footnote{https://bugs.python.org/issue32819}: ssl.match_hostname() has been simplified and no longer depends
on re and ipaddress module for wildcard and IP addresses. Error reporting
for invalid wildcards has been improved.

@item 
bpo-19675@footnote{https://bugs.python.org/issue19675}: @code{multiprocessing.Pool} no longer leaks processes if its
initialization fails.

@item 
bpo-32394@footnote{https://bugs.python.org/issue32394}: socket: Remove
TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version
Windows during run-time.

@item 
bpo-31787@footnote{https://bugs.python.org/issue31787}: Fixed refleaks of @code{__init__()} methods in various modules.
(Contributed by Oren Milman)

@item 
bpo-30157@footnote{https://bugs.python.org/issue30157}: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when
only the last field is quoted.  Patch by Jake Davis.

@item 
bpo-30688@footnote{https://bugs.python.org/issue30688}: Added support of @code{\N@{name@}} escapes in regular expressions.
Based on patch by Jonathan Eunice.

@item 
bpo-32792@footnote{https://bugs.python.org/issue32792}: collections.ChainMap() preserves the order of the underlying
mappings.

@item 
bpo-32775@footnote{https://bugs.python.org/issue32775}: @ref{fd0,,fnmatch.translate()} no longer produces patterns which
contain set operations. Sets starting with '[' or containing '--', '&&',
'~~' or '||' will be interpreted differently in regular expressions in
future versions. Currently they emit warnings. fnmatch.translate() now
avoids producing patterns containing such sets by accident.

@item 
bpo-32622@footnote{https://bugs.python.org/issue32622}: Implement native fast sendfile for Windows proactor event loop.

@item 
bpo-32777@footnote{https://bugs.python.org/issue32777}: Fix a rare but potential pre-exec child process deadlock in
subprocess on POSIX systems when marking file descriptors inheritable on
exec in the child process.  This bug appears to have been introduced in
3.4.

@item 
bpo-32647@footnote{https://bugs.python.org/issue32647}: The ctypes module used to depend on indirect linking for
dlopen. The shared extension is now explicitly linked against libdl on
platforms with dl.

@item 
bpo-32749@footnote{https://bugs.python.org/issue32749}: A @ref{33,,dbm.dumb} database opened with flags 'r' is now
read-only. @ref{2bf,,dbm.dumb.open()} with flags 'r' and 'w' no longer creates
a database if it does not exist.

@item 
bpo-32741@footnote{https://bugs.python.org/issue32741}: Implement @code{asyncio.TimerHandle.when()} method.

@item 
bpo-32691@footnote{https://bugs.python.org/issue32691}: Use mod_spec.parent when running modules with pdb

@item 
bpo-32734@footnote{https://bugs.python.org/issue32734}: Fixed @code{asyncio.Lock()} safety issue which allowed acquiring
and locking the same lock multiple times, without it being free. Patch by
Bar Harel.

@item 
bpo-32727@footnote{https://bugs.python.org/issue32727}: Do not include name field in SMTP envelope from address. Patch
by Stéphane Wirtel

@item 
bpo-31453@footnote{https://bugs.python.org/issue31453}: Add TLSVersion constants and SSLContext.maximum_version /
minimum_version attributes. The new API wraps OpenSSL 1.1
@indicateurl{https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html}
feature.

@item 
bpo-24334@footnote{https://bugs.python.org/issue24334}: Internal implementation details of ssl module were cleaned up.
The SSLSocket has one less layer of indirection. Owner and session
information are now handled by the SSLSocket and SSLObject constructor.
Channel binding implementation has been simplified.

@item 
bpo-31848@footnote{https://bugs.python.org/issue31848}: Fix the error handling in Aifc_read.initfp() when the SSND
chunk is not found. Patch by Zackery Spytz.

@item 
bpo-32585@footnote{https://bugs.python.org/issue32585}: Add Ttk spinbox widget to @ref{10f,,tkinter.ttk}.  Patch by Alan D
Moore.

@item 
bpo-32512@footnote{https://bugs.python.org/issue32512}: @ref{d3,,profile} CLI accepts @code{-m module_name} as an alternative
to script path.

@item 
bpo-8525@footnote{https://bugs.python.org/issue8525}: help() on a type now displays builtin subclasses. This is
intended primarily to help with notification of more specific exception
subclasses.

Patch by Sanyam Khurana.

@item 
bpo-31639@footnote{https://bugs.python.org/issue31639}: http.server now exposes a ThreadingHTTPServer class and uses it
when the module is run with @code{-m} to cope with web browsers pre-opening
sockets.

@item 
bpo-29877@footnote{https://bugs.python.org/issue29877}: compileall: import ProcessPoolExecutor only when needed,
preventing hangs on low resource platforms

@item 
bpo-32221@footnote{https://bugs.python.org/issue32221}: Various functions returning tuple containing IPv6 addresses now
omit @code{%scope} part since the same information is already encoded in
@emph{scopeid} tuple item. Especially this speeds up @code{socket.recvfrom()}
when it receives multicast packet since useless resolving of network
interface name is omitted.

@item 
bpo-32147@footnote{https://bugs.python.org/issue32147}: @ref{fd1,,binascii.unhexlify()} is now up to 2 times faster. Patch
by Sergey Fedoseev.

@item 
bpo-30693@footnote{https://bugs.python.org/issue30693}: The TarFile class now recurses directories in a reproducible
way.

@item 
bpo-30693@footnote{https://bugs.python.org/issue30693}: The ZipFile class now recurses directories in a reproducible
way.

@item 
bpo-31680@footnote{https://bugs.python.org/issue31680}: Added @ref{1bf,,curses.ncurses_version}.

@item 
bpo-31908@footnote{https://bugs.python.org/issue31908}: Fix output of cover files for @code{trace} module command-line
tool. Previously emitted cover files only when @code{--missing} option was
used. Patch by Michael Selik.

@item 
bpo-31608@footnote{https://bugs.python.org/issue31608}: Raise a @code{TypeError} instead of crashing if a
@code{collections.deque} subclass returns a non-deque from @code{__new__}. Patch
by Oren Milman.

@item 
bpo-31425@footnote{https://bugs.python.org/issue31425}: Add support for sockets of the AF_QIPCRTR address family,
supported by the Linux kernel. This is used to communicate with services,
such as GPS or radio, running on Qualcomm devices. Patch by Bjorn
Andersson.

@item 
bpo-22005@footnote{https://bugs.python.org/issue22005}: Implemented unpickling instances of
@ref{194,,datetime}, @ref{193,,date} and
@ref{4ed,,time} pickled by Python 2. @code{encoding='latin1'} should
be used for successful decoding.

@item 
bpo-27645@footnote{https://bugs.python.org/issue27645}: @ref{3d0,,sqlite3.Connection} now exposes a
@ref{3d1,,backup} method, if the underlying SQLite
library is at version 3.6.11 or higher.  Patch by Lele Gaifax.

@item 
bpo-16865@footnote{https://bugs.python.org/issue16865}: Support arrays >=2GiB in @ref{2b,,ctypes}.  Patch by Segev Finer.

@item 
bpo-31508@footnote{https://bugs.python.org/issue31508}: Removed support of arguments in
@ref{2bd,,tkinter.ttk.Treeview.selection}. It was deprecated in 3.6.  Use
specialized methods like @code{selection_set} for changing the selection.

@item 
bpo-29456@footnote{https://bugs.python.org/issue29456}: Fix bugs in hangul normalization: u1176, u11a7 and u11c3
@end itemize

@node 文档<16>,测试<15>,库<20>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id147}@anchor{fd2}
@subsubsection 文档



@itemize -

@item 
bpo-21257@footnote{https://bugs.python.org/issue21257}: Document @ref{fd3,,http.client.parse_headers()}.

@item 
bpo-34764@footnote{https://bugs.python.org/issue34764}: Improve example of iter() with 2nd sentinel argument.

@item 
bpo-35564@footnote{https://bugs.python.org/issue35564}: Explicitly set master_doc variable in conf.py for compliance
with Sphinx 2.0

@item 
bpo-35511@footnote{https://bugs.python.org/issue35511}: Specified that profile.Profile class doesn't not support enable
or disable methods. Also, elaborated that Profile object as a context
manager is only supported in cProfile module.

@item 
bpo-10536@footnote{https://bugs.python.org/issue10536}: Enhance the gettext docs. Patch by Éric Araujo

@item 
bpo-35089@footnote{https://bugs.python.org/issue35089}: Remove mention of @code{typing.io} and @code{typing.re}. Their types
should be imported from @code{typing} directly.

@item 
bpo-35038@footnote{https://bugs.python.org/issue35038}: Fix the documentation about an unexisting @code{f_restricted}
attribute in the frame object. Patch by Stéphane Wirtel

@item 
bpo-35042@footnote{https://bugs.python.org/issue35042}: Replace PEP XYZ by the pep role and allow to use the direct
links to the PEPs.

@item 
bpo-35044@footnote{https://bugs.python.org/issue35044}: Fix the documentation with the role @code{exc} for the
appropriated exception. Patch by Stéphane Wirtel

@item 
bpo-35035@footnote{https://bugs.python.org/issue35035}: Rename documentation for @ref{76,,email.utils} to
@code{email.utils.rst}.

@item 
bpo-34967@footnote{https://bugs.python.org/issue34967}: Use app.add_object_type() instead of the deprecated Sphinx
function app.description_unit()

@item 
bpo-34913@footnote{https://bugs.python.org/issue34913}: Add documentation about the new command line interface of the
gzip module.

@item 
bpo-32174@footnote{https://bugs.python.org/issue32174}: chm document displays non-ASCII charaters properly on some MBCS
Windows systems.

@item 
bpo-11233@footnote{https://bugs.python.org/issue11233}: Create availability directive for documentation.  Original
patch by Georg Brandl.

@item 
bpo-34790@footnote{https://bugs.python.org/issue34790}: Document how passing coroutines to asyncio.wait() can be
confusing.

@item 
bpo-34552@footnote{https://bugs.python.org/issue34552}: Make clear that @code{==} operator sometimes is equivalent to
@code{is}. The @code{<}, @code{<=}, @code{>} and @code{>=} operators are only defined where
they make sense.

@item 
bpo-28617@footnote{https://bugs.python.org/issue28617}: Fixed info in the stdtypes docs concerning the types that
support membership tests.

@item 
bpo-20177@footnote{https://bugs.python.org/issue20177}: Migrate datetime.date.fromtimestamp to Argument Clinic. Patch
by Tim Hoffmann.

@item 
bpo-34065@footnote{https://bugs.python.org/issue34065}: Fix wrongly written basicConfig documentation markup syntax

@item 
bpo-33460@footnote{https://bugs.python.org/issue33460}: replaced ellipsis with correct error codes in tutorial chapter
3.

@item 
bpo-33847@footnote{https://bugs.python.org/issue33847}: Add '@@' operator entry to index.

@item 
bpo-33409@footnote{https://bugs.python.org/issue33409}: Clarified the relationship between 
@geindex Python 提高建议; PEP 538
PEP 538@footnote{https://www.python.org/dev/peps/pep-0538}'s
PYTHONCOERCECLOCALE and PEP 540's PYTHONUTF8 mode.

@item 
bpo-33197@footnote{https://bugs.python.org/issue33197}: Add versionadded tag to the documentation of
ParameterKind.description

@item 
bpo-17045@footnote{https://bugs.python.org/issue17045}: Improve the C-API doc for PyTypeObject.  This includes adding
several quick-reference tables and a lot of missing slot/typedef entries.
The existing entries were also cleaned up with a slightly more consistent
format.

@item 
bpo-33736@footnote{https://bugs.python.org/issue33736}: Improve the documentation of @ref{35c,,asyncio.open_connection()},
@ref{35d,,asyncio.start_server()} and their UNIX socket counterparts.

@item 
bpo-23859@footnote{https://bugs.python.org/issue23859}: Document that @ref{289,,asyncio.wait()} does not cancel its futures on
timeout.

@item 
bpo-32436@footnote{https://bugs.python.org/issue32436}: Document 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} changes to asyncio.

@item 
bpo-33604@footnote{https://bugs.python.org/issue33604}: 更新HMAC md5默认报告DeprecationWarning，并将在3.8移除。

@item 
bpo-33594@footnote{https://bugs.python.org/issue33594}: Document @code{getargspec}, @code{from_function} and @code{from_builtin}
as deprecated in their respective docstring, and include version since
deprecation in DeprecationWarning message.

@item 
bpo-33503@footnote{https://bugs.python.org/issue33503}: 修复错误的pypi链接

@item 
bpo-33421@footnote{https://bugs.python.org/issue33421}: 为`@w{`}typing.AsyncContextManager`@w{`}添加缺失的文档。

@item 
bpo-33487@footnote{https://bugs.python.org/issue33487}: BZ2file now emit a DeprecationWarning when buffering=None is
passed, the deprecation message and documentation also now explicitly
state it is deprecated since 3.0.

@item 
bpo-33378@footnote{https://bugs.python.org/issue33378}: Add Korean language switcher for @indicateurl{https://docs.python.org/3/}

@item 
bpo-33276@footnote{https://bugs.python.org/issue33276}: Clarify that the @code{__path__} attribute on modules cannot be
just any value.

@item 
bpo-33201@footnote{https://bugs.python.org/issue33201}: Modernize documentation for writing C extension types.

@item 
bpo-33195@footnote{https://bugs.python.org/issue33195}: Deprecate @code{Py_UNICODE} usage in @code{c-api/arg} document.
@code{Py_UNICODE} related APIs are deprecated since Python 3.3, but it is
missed in the document.

@item 
bpo-33126@footnote{https://bugs.python.org/issue33126}: Document PyBuffer_ToContiguous().

@item 
bpo-27212@footnote{https://bugs.python.org/issue27212}: Modify documentation for the @code{islice()} recipe to consume
initial values up to the start index.

@item 
bpo-28247@footnote{https://bugs.python.org/issue28247}: Update @ref{141,,zipapp} documentation to describe how to make
standalone applications.

@item 
bpo-18802@footnote{https://bugs.python.org/issue18802}: Documentation changes for ipaddress.  Patch by Jon Foster and
Berker Peksag.

@item 
bpo-27428@footnote{https://bugs.python.org/issue27428}: Update documentation to clarify that @code{WindowsRegistryFinder}
implements @code{MetaPathFinder}. (Patch by Himanshu Lakhara)

@item 
bpo-28124@footnote{https://bugs.python.org/issue28124}: The ssl module function ssl.wrap_socket() has been
de-emphasized and deprecated in favor of the more secure and efficient
SSLContext.wrap_socket() method.

@item 
bpo-17232@footnote{https://bugs.python.org/issue17232}: Clarify docs for -O and -OO.  Patch by Terry Reedy.

@item 
bpo-32436@footnote{https://bugs.python.org/issue32436}: Add documentation for the contextvars module (PEP 567).

@item 
bpo-32800@footnote{https://bugs.python.org/issue32800}: Update link to w3c doc for xml default namespaces.

@item 
bpo-11015@footnote{https://bugs.python.org/issue11015}: Update @ref{106,,test.support} documentation.

@item 
bpo-32613@footnote{https://bugs.python.org/issue32613}: Update the faq/windows.html to use the py command from PEP 397
instead of python.

@item 
bpo-8722@footnote{https://bugs.python.org/issue8722}: Document @ref{313,,__getattr__()} behavior when property @code{get()}
method raises @ref{393,,AttributeError}.

@item 
bpo-32614@footnote{https://bugs.python.org/issue32614}: Modify RE examples in documentation to use raw strings to
prevent @ref{278,,DeprecationWarning} and add text to REGEX HOWTO to highlight
the deprecation.

@item 
bpo-20709@footnote{https://bugs.python.org/issue20709}: Remove the paragraph where we explain that os.utime() does not
support a directory as path under Windows. Patch by Jan-Philip Gehrcke

@item 
bpo-32722@footnote{https://bugs.python.org/issue32722}: Remove the bad example in the tutorial of the Generator
Expression. Patch by Stéphane Wirtel

@item 
bpo-31972@footnote{https://bugs.python.org/issue31972}: Improve docstrings for @ref{fd4,,pathlib.PurePath} subclasses.

@item 
bpo-30607@footnote{https://bugs.python.org/issue30607}: Use the externalized @code{python-docs-theme} package when
building the documentation.

@item 
bpo-8243@footnote{https://bugs.python.org/issue8243}: Add a note about curses.addch and curses.addstr exception
behavior when writing outside a window, or pad.

@item 
bpo-32337@footnote{https://bugs.python.org/issue32337}: Update documentation related with @code{dict} order.

@item 
bpo-25041@footnote{https://bugs.python.org/issue25041}: Document @code{AF_PACKET} in the @ref{ef,,socket} module.

@item 
bpo-31432@footnote{https://bugs.python.org/issue31432}: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED
flags for ssl.SSLContext.verify_mode.
@end itemize

@node 测试<15>,构建<13>,文档<16>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id148}@anchor{fd5}
@subsubsection 测试



@itemize -

@item 
bpo-35772@footnote{https://bugs.python.org/issue35772}: Fix sparse file tests of test_tarfile on ppc64 with the tmpfs
filesystem. Fix the function testing if the filesystem supports sparse
files: create a file which contains data and "holes", instead of creating
a file which contains no data. tmpfs effective block size is a page size
(tmpfs lives in the page cache). RHEL uses 64 KiB pages on aarch64, ppc64,
ppc64le, only s390x and x86_64 use 4 KiB pages, whereas the test punch
holes of 4 KiB.

@item 
bpo-35045@footnote{https://bugs.python.org/issue35045}: Make ssl tests less strict and also accept TLSv1 as system
default. The changes unbreaks test_min_max_version on Fedora 29.

@item 
bpo-32710@footnote{https://bugs.python.org/issue32710}: @code{test_asyncio/test_sendfile.py} now resets the event loop
policy using @code{tearDownModule()} as done in other tests, to prevent a
warning when running tests on Windows.

@item 
bpo-33717@footnote{https://bugs.python.org/issue33717}: test.pythoninfo now logs information of all clocks, not only
time.time() and time.perf_counter().

@item 
bpo-35488@footnote{https://bugs.python.org/issue35488}: Add a test to pathlib's Path.match() to verify it does not
support glob-style ** recursive pattern matching.

@item 
bpo-31731@footnote{https://bugs.python.org/issue31731}: Fix a race condition in @code{check_interrupted_write()} of
test_io: create directly the thread with SIGALRM signal blocked, rather
than blocking the signal later from the thread. Previously, it was
possible that the thread gets the signal before the signal is blocked.

@item 
bpo-35424@footnote{https://bugs.python.org/issue35424}: Fix test_multiprocessing_main_handling: use
@code{multiprocessing.Pool} with a context manager and then explicitly
join the pool.

@item 
bpo-35519@footnote{https://bugs.python.org/issue35519}: Rename @code{test.bisect} module to @code{test.bisect_cmd} to
avoid conflict with @ref{12,,bisect} module when running directly a test like
@code{./python Lib/test/test_xmlrpc.py}.

@item 
bpo-35513@footnote{https://bugs.python.org/issue35513}: Replace @ref{316,,time.time()} with @ref{769,,time.monotonic()} in tests
to measure time delta.

@item 
bpo-34279@footnote{https://bugs.python.org/issue34279}: @ref{fd6,,test.support.run_unittest()} no longer raise
@code{TestDidNotRun} if the test result contains skipped tests. The
exception is now only raised if no test have been run and no test have
been skipped.

@item 
bpo-35412@footnote{https://bugs.python.org/issue35412}: Add testcase to @code{test_future4}: check unicode literal.

@item 
bpo-26704@footnote{https://bugs.python.org/issue26704}: 添加了对一个实例方法进行双重修补的测试演示。 补丁作者为 Anthony Sottile。

@item 
bpo-33725@footnote{https://bugs.python.org/issue33725}: test_multiprocessing_fork may crash on recent versions of
macOS.  Until the issue is resolved, skip the test on macOS.

@item 
bpo-35352@footnote{https://bugs.python.org/issue35352}: Modify test_asyncio to use the certificate set from the test
directory.

@item 
bpo-35317@footnote{https://bugs.python.org/issue35317}: Fix @code{mktime()} overflow error in @code{test_email}: run
@code{test_localtime_daylight_true_dst_true()} and
@code{test_localtime_daylight_false_dst_true()} with a specific timezone.

@item 
bpo-21263@footnote{https://bugs.python.org/issue21263}: After several reports that test_gdb does not work properly on
macOS and since gdb is not shipped by default anymore, test_gdb is now
skipped on macOS when LLVM Clang has been used to compile Python. Patch by
Lysandros Nikolaou

@item 
bpo-34279@footnote{https://bugs.python.org/issue34279}: regrtest issue a warning when no tests have been executed in a
particular test file. Also, a new final result state is issued if no test
have been executed across all test files. Patch by Pablo Galindo.

@item 
bpo-34962@footnote{https://bugs.python.org/issue34962}: make docstest in Doc now passes., and is enforced in CI

@item 
bpo-23596@footnote{https://bugs.python.org/issue23596}: Use argparse for the command line of the gzip module. Patch by
Antony Lee

@item 
bpo-34537@footnote{https://bugs.python.org/issue34537}: Fix @code{test_gdb.test_strings()} when @code{LC_ALL=C} and GDB was
compiled with Python 3.6 or earlier.

@item 
bpo-34587@footnote{https://bugs.python.org/issue34587}: test_socket: Remove RDSTest.testCongestion(). The test tries to
fill the receiver's socket buffer and expects an error. But the RDS
protocol doesn't require that. Moreover, the Linux implementation of RDS
expects that the producer of the messages reduces its rate, it's not the
role of the receiver to trigger an error. The test fails on Fedora 28 by
design, so just remove it.

@item 
bpo-34661@footnote{https://bugs.python.org/issue34661}: Fix test_shutil if unzip doesn't support -t.

@item 
bpo-34200@footnote{https://bugs.python.org/issue34200}: Fixed non-deterministic flakiness of test_pkg by not using the
scary test.support.module_cleanup() logic to save and restore sys.modules
contents between test cases.

@item 
bpo-34569@footnote{https://bugs.python.org/issue34569}: The experimental PEP 554 data channels now correctly pass
negative PyLong objects between subinterpreters on 32-bit systems. Patch
by Michael Felt.

@item 
bpo-34594@footnote{https://bugs.python.org/issue34594}: Fix usage of hardcoded @code{errno} values in the tests.

@item 
bpo-34579@footnote{https://bugs.python.org/issue34579}: Fix test_embed for AIX Patch by Michael Felt

@item 
bpo-34542@footnote{https://bugs.python.org/issue34542}: Use 3072 RSA keys and SHA-256 signature for test certs and
keys.

@item 
bpo-11193@footnote{https://bugs.python.org/issue11193}: Remove special condition for AIX in
@code{test_subprocess.test_undecodable_env}

@item 
bpo-34347@footnote{https://bugs.python.org/issue34347}: Fix @code{test_utf8_mode.test_cmd_line} for AIX

@item 
bpo-34490@footnote{https://bugs.python.org/issue34490}: On AIX with AF_UNIX family sockets getsockname() does not
provide 'sockname', so skip calls to transport.get_extra_info('sockname')

@item 
bpo-34391@footnote{https://bugs.python.org/issue34391}: Fix ftplib test for TLS 1.3 by reading from data socket.

@item 
bpo-11192@footnote{https://bugs.python.org/issue11192}: Fix @code{test_socket} on AIX AIX 6.1 and later IPv6 zone id
supports only supported by inet_pton6_zone() Switch to runtime-based
platform.system() to establish current platform  rather than build-time
based sys.platform()

@item 
bpo-34399@footnote{https://bugs.python.org/issue34399}: Update all RSA keys and DH params to use at least 2048 bits.

@item 
bpo-34373@footnote{https://bugs.python.org/issue34373}: Fix @code{test_mktime} and @code{test_pthread_getcpuclickid} tests
for AIX Add range checking for @code{_PyTime_localtime} for AIX Patch by
Michael Felt

@item 
bpo-11191@footnote{https://bugs.python.org/issue11191}: Skip the distutils test 'test_search_cpp' when using XLC as
compiler patch by aixtools (Michael Felt)

@item 
Improved an error message when mock assert_has_calls fails.

@item 
bpo-33746@footnote{https://bugs.python.org/issue33746}: Fix test_unittest when run in verbose mode.

@item 
bpo-33901@footnote{https://bugs.python.org/issue33901}: Fix test_dbm_gnu on macOS with gdbm 1.15: add a larger value to
make sure that the file size changes.

@item 
bpo-33873@footnote{https://bugs.python.org/issue33873}: Fix a bug in @code{regrtest} that caused an extra test to run if
--huntrleaks/-R was used. Exit with error in case that invalid parameters
are specified to --huntrleaks/-R (at least one warmup run and one
repetition must be used).

@item 
bpo-33562@footnote{https://bugs.python.org/issue33562}: Check that a global asyncio event loop policy is not left
behind by any tests.

@item 
bpo-33655@footnote{https://bugs.python.org/issue33655}: 忽略运行在BSD平台的ZFS上时test_posix_fallocate的失败。

@item 
bpo-32962@footnote{https://bugs.python.org/issue32962}: Fixed test_gdb when Python is compiled with flags -mcet
-fcf-protection -O0.

@item 
bpo-33358@footnote{https://bugs.python.org/issue33358}: Fix @code{test_embed.test_pre_initialization_sys_options()} when
the interpreter is built with @code{--enable-shared}.

@item 
bpo-32872@footnote{https://bugs.python.org/issue32872}: Avoid regrtest compatibility issue with namespace packages.

@item 
bpo-32517@footnote{https://bugs.python.org/issue32517}: Fix failing @code{test_asyncio} on macOS 10.12.2+ due to transport
of @code{KqueueSelector} loop was not being closed.

@item 
bpo-32663@footnote{https://bugs.python.org/issue32663}: Making sure the @code{SMTPUTF8SimTests} class of tests gets run in
test_smtplib.py.

@item 
bpo-27643@footnote{https://bugs.python.org/issue27643}: Test_C test case needs "signed short" bitfields, but the IBM
XLC compiler (on AIX) does not support this Skip the code and test when
AIX and XLC are used

Applicable to Python2-2.7 and later

@item 
bpo-19417@footnote{https://bugs.python.org/issue19417}: Add test_bdb.py.

@item 
bpo-31809@footnote{https://bugs.python.org/issue31809}: Add tests to verify connection with secp ECDH curves.
@end itemize

@node 构建<13>,Windows<16>,测试<15>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id149}@anchor{fd7}
@subsubsection 构建



@itemize -

@item 
bpo-34691@footnote{https://bugs.python.org/issue34691}: The _contextvars module is now built into the core Python
library on Windows.

@item 
bpo-35683@footnote{https://bugs.python.org/issue35683}: Improved Azure Pipelines build steps and now verifying layouts
correctly

@item 
bpo-35642@footnote{https://bugs.python.org/issue35642}: Remove asynciomodule.c from pythoncore.vcxproj

@item 
bpo-35550@footnote{https://bugs.python.org/issue35550}: Fix incorrect Solaris #ifdef checks to look for __sun && __SVR4
instead of sun when compiling.

@item 
bpo-35499@footnote{https://bugs.python.org/issue35499}: @code{make profile-opt} no longer replaces @code{CFLAGS_NODIST} with
@code{CFLAGS}. It now adds profile-guided optimization (PGO) flags to
@code{CFLAGS_NODIST}: existing @code{CFLAGS_NODIST} flags are kept.

@item 
bpo-35257@footnote{https://bugs.python.org/issue35257}: Avoid leaking the linker flags from Link Time Optimizations
(LTO) into distutils when compiling C extensions.

@item 
bpo-35351@footnote{https://bugs.python.org/issue35351}: When building Python with clang and LTO, LTO flags are no
longer passed into CFLAGS to build third-party C extensions through
distutils.

@item 
bpo-35139@footnote{https://bugs.python.org/issue35139}: Fix a compiler error when statically linking @code{pyexpat} in
@code{Modules/Setup}.

@item 
bpo-35059@footnote{https://bugs.python.org/issue35059}: PCbuild: Set InlineFunctionExpansion to OnlyExplicitInline
("/Ob1" option) in pyproject.props in Debug mode to expand functions
marked as inline. This change should make Python compiled in Debug mode a
little bit faster on Windows.

@item 
bpo-35011@footnote{https://bugs.python.org/issue35011}: Restores the use of pyexpatns.h to isolate our embedded copy of
the expat C library so that its symbols do not conflict at link or dynamic
loading time with an embedding application or other extension modules with
their own version of libexpat.

@item 
bpo-28015@footnote{https://bugs.python.org/issue28015}: Have --with-lto works correctly with clang.

@item 
bpo-34765@footnote{https://bugs.python.org/issue34765}: Update the outdated install-sh file to the latest revision from
automake v1.16.1

@item 
bpo-34585@footnote{https://bugs.python.org/issue34585}: Check for floating-point byte order in configure.ac using
compilation tests instead of executing code, so that these checks work in
cross-compiled builds.

@item 
bpo-34710@footnote{https://bugs.python.org/issue34710}: Fixed SSL module build with OpenSSL & pedantic CFLAGS.

@item 
bpo-34582@footnote{https://bugs.python.org/issue34582}: Add JUnit XML output for regression tests and update Azure
DevOps builds.

@item 
bpo-34081@footnote{https://bugs.python.org/issue34081}: Make Sphinx warnings as errors in the Docs Makefile.

@item 
bpo-34555@footnote{https://bugs.python.org/issue34555}: Fix for case where it was not possible to have both
@code{HAVE_LINUX_VM_SOCKETS_H} and @code{HAVE_SOCKADDR_ALG} be undefined.

@item 
bpo-33015@footnote{https://bugs.python.org/issue33015}: Fix an undefined behaviour in the pthread implementation of
@code{PyThread_start_new_thread()}: add a function wrapper to always
return @code{NULL}.

@item 
bpo-34245@footnote{https://bugs.python.org/issue34245}: The Python shared library is now installed with write
permission (mode 0755), which is the standard way of installing such
libraries.

@item 
bpo-34121@footnote{https://bugs.python.org/issue34121}: Fix detection of C11 atomic support on clang.

@item 
bpo-32430@footnote{https://bugs.python.org/issue32430}: Rename Modules/Setup.dist to Modules/Setup, and remove the
necessity to copy the former manually to the latter when updating the
local source tree.

@item 
bpo-30345@footnote{https://bugs.python.org/issue30345}: Add -g to LDFLAGS when compiling with LTO to get debug symbols.

@item 
bpo-5755@footnote{https://bugs.python.org/issue5755}: Move @code{-Wstrict-prototypes} option to @code{CFLAGS_NODIST} from
@code{OPT}. This option emitted annoying warnings when building extension
modules written in C++.

@item 
bpo-33614@footnote{https://bugs.python.org/issue33614}: Ensures module definition files for the stable ABI on Windows
are correctly regenerated.

@item 
bpo-33648@footnote{https://bugs.python.org/issue33648}: The --with-c-locale-warning configuration flag has been
removed. It has had no effect for about a year.

@item 
bpo-33522@footnote{https://bugs.python.org/issue33522}: Enable CI builds on Visual Studio Team Services at
@indicateurl{https://python.visualstudio.com/cpython}

@item 
bpo-33512@footnote{https://bugs.python.org/issue33512}: configure's check for "long double" has been simplified

@item 
bpo-33483@footnote{https://bugs.python.org/issue33483}: C compiler is now correctly detected from the standard
environment variables. --without-gcc and --with-icc options have been
removed.

@item 
bpo-33394@footnote{https://bugs.python.org/issue33394}: Enable the verbose build for extension modules, when GNU make
is passed macros on the command line.

@item 
bpo-33393@footnote{https://bugs.python.org/issue33393}: Update config.guess and config.sub files.

@item 
bpo-33377@footnote{https://bugs.python.org/issue33377}: Add new triplets for mips r6 and riscv variants (used in
extension suffixes).

@item 
bpo-32232@footnote{https://bugs.python.org/issue32232}: By default, modules configured in @code{Modules/Setup} are no longer
built with @code{-DPy_BUILD_CORE}. Instead, modules that specifically need that
preprocessor definition include it in their individual entries.

@item 
bpo-33182@footnote{https://bugs.python.org/issue33182}: The embedding tests can once again be built with clang 6.0

@item 
bpo-33163@footnote{https://bugs.python.org/issue33163}: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

@item 
bpo-33012@footnote{https://bugs.python.org/issue33012}: gcc 8 has added a new warning heuristic to detect invalid
function casts and a stock python build seems to hit that warning quite
often.  The most common is the cast of a METH_NOARGS function (that uses
just one argument) to a PyCFunction. Fix this by adding a dummy argument
to all functions that implement METH_NOARGS.

@item 
bpo-32898@footnote{https://bugs.python.org/issue32898}: Fix the python debug build when using COUNT_ALLOCS.

@item 
bpo-29442@footnote{https://bugs.python.org/issue29442}: Replace optparse with argparse in setup.py
@end itemize

@node Windows<16>,macOS<10>,构建<13>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id150}@anchor{fd8}
@subsubsection Windows



@itemize -

@item 
bpo-35890@footnote{https://bugs.python.org/issue35890}: Fix API calling consistency of GetVersionEx and wcstok.

@item 
bpo-32560@footnote{https://bugs.python.org/issue32560}: The @code{py} launcher now forwards its @code{STARTUPINFO} structure
to child processes.

@item 
bpo-35854@footnote{https://bugs.python.org/issue35854}: Fix EnvBuilder and --symlinks in venv on Windows

@item 
bpo-35811@footnote{https://bugs.python.org/issue35811}: Avoid propagating venv settings when launching via py.exe

@item 
bpo-35797@footnote{https://bugs.python.org/issue35797}: Fix default executable used by the multiprocessing module

@item 
bpo-35758@footnote{https://bugs.python.org/issue35758}: Allow building on ARM with MSVC.

@item 
bpo-29734@footnote{https://bugs.python.org/issue29734}: Fix handle leaks in os.stat on Windows.

@item 
bpo-35596@footnote{https://bugs.python.org/issue35596}: Use unchecked PYCs for the embeddable distro to avoid zipimport
restrictions.

@item 
bpo-35596@footnote{https://bugs.python.org/issue35596}: Fix vcruntime140.dll being added to embeddable distro multiple
times.

@item 
bpo-35402@footnote{https://bugs.python.org/issue35402}: 更新 Windows 构建以使用 Tcl 和 Tk 8.6.9

@item 
bpo-35401@footnote{https://bugs.python.org/issue35401}: 将Windows内部版本更新到OpenSSL 1.1.0j

@item 
bpo-34977@footnote{https://bugs.python.org/issue34977}: venv on Windows will now use a python.exe redirector rather
than copying the actual binaries from the base environment.

@item 
bpo-34977@footnote{https://bugs.python.org/issue34977}: Adds support for building a Windows App Store package

@item 
bpo-35067@footnote{https://bugs.python.org/issue35067}: Remove _distutils_findvs module and use vswhere.exe instead.

@item 
bpo-32557@footnote{https://bugs.python.org/issue32557}: Allow shutil.disk_usage to take a file path on Windows

@item 
bpo-34770@footnote{https://bugs.python.org/issue34770}: Fix a possible null pointer dereference in pyshellext.cpp.

@item 
bpo-34603@footnote{https://bugs.python.org/issue34603}: Fix returning structs from functions produced by MSVC

@item 
bpo-34581@footnote{https://bugs.python.org/issue34581}: Guard MSVC-specific code in socketmodule.c with @code{#ifdef
_MSC_VER}.

@item 
bpo-34532@footnote{https://bugs.python.org/issue34532}: Fixes exit code of list version arguments for py.exe.

@item 
bpo-34062@footnote{https://bugs.python.org/issue34062}: Fixed the '--list' and '--list-paths' arguments for the py.exe
launcher

@item 
bpo-34225@footnote{https://bugs.python.org/issue34225}: Ensure INCLUDE and LIB directories do not end with a backslash.

@item 
bpo-34011@footnote{https://bugs.python.org/issue34011}: A suite of code has been changed which copied across DLLs and
init.tcl from the running Python location into a venv being created. These
copies are needed only when running from a Python source build, and the
copying code is now only run when that is the case, rather than whenever a
venv is created.

@item 
bpo-34006@footnote{https://bugs.python.org/issue34006}: Revert line length limit for Windows help docs. The line-length
limit is not needed because the pages appear in a separate app rather than
on a browser tab.  It can also interact badly with the DPI setting.

@item 
bpo-31546@footnote{https://bugs.python.org/issue31546}: Restore running PyOS_InputHook while waiting for user input at
the prompt. The restores integration of interactive GUI windows (such as
Matplotlib figures) with the prompt on Windows.

@item 
bpo-30237@footnote{https://bugs.python.org/issue30237}: Output error when ReadConsole is canceled by
CancelSynchronousIo instead of crashing.

@item 
bpo-33895@footnote{https://bugs.python.org/issue33895}: GIL is released while calling functions that acquire Windows
loader lock.

@item 
bpo-33720@footnote{https://bugs.python.org/issue33720}: Reduces maximum marshal recursion depth on release builds.

@item 
bpo-29097@footnote{https://bugs.python.org/issue29097}: Fix bug where @code{datetime.fromtimestamp()} erroneously throws
an @ref{1d3,,OSError} on Windows for values between 0 and 86400. Patch by
Ammar Askar.

@item 
bpo-33316@footnote{https://bugs.python.org/issue33316}: PyThread_release_lock always fails

@item 
bpo-33184@footnote{https://bugs.python.org/issue33184}: 在Windows安装程序中将OpenSSL更新为1.1.0h.

@item 
bpo-32890@footnote{https://bugs.python.org/issue32890}: Fix usage of GetLastError() instead of errno in os.execve() and
os.truncate().

@item 
bpo-33016@footnote{https://bugs.python.org/issue33016}: Fix potential use of uninitialized memory in
nt._getfinalpathname

@item 
bpo-32903@footnote{https://bugs.python.org/issue32903}: Fix a memory leak in os.chdir() on Windows if the current
directory is set to a UNC path.

@item 
bpo-32901@footnote{https://bugs.python.org/issue32901}: Update Tcl and Tk versions to 8.6.8

@item 
bpo-31966@footnote{https://bugs.python.org/issue31966}: Fixed WindowsConsoleIO.write() for writing empty data.

@item 
bpo-32409@footnote{https://bugs.python.org/issue32409}: Ensures activate.bat can handle Unicode contents.

@item 
bpo-32457@footnote{https://bugs.python.org/issue32457}: Improves handling of denormalized executable path when
launching Python.

@item 
bpo-32370@footnote{https://bugs.python.org/issue32370}: Use the correct encoding for ipconfig output in the uuid
module. Patch by Segev Finer.

@item 
bpo-29248@footnote{https://bugs.python.org/issue29248}: Fix @ref{1f3,,os.readlink()} on Windows, which was mistakenly
treating the @code{PrintNameOffset} field of the reparse data buffer as a
number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

@item 
bpo-1104@footnote{https://bugs.python.org/issue1104}: Correctly handle string length in
@code{msilib.SummaryInfo.GetProperty()} to prevent it from truncating the
last character.
@end itemize

@node macOS<10>,IDLE<21>,Windows<16>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id151}@anchor{fd9}
@subsubsection macOS



@itemize -

@item 
bpo-35401@footnote{https://bugs.python.org/issue35401}: 在MacOS安装程序中将OpenSSL更新为1.1.0j。

@item 
bpo-35025@footnote{https://bugs.python.org/issue35025}: Properly guard the use of the @code{CLOCK_GETTIME} et al. macros
in @code{timemodule} on macOS.

@item 
bpo-24658@footnote{https://bugs.python.org/issue24658}: On macOS, fix reading from and writing into a file with a size
larger than 2 GiB.

@item 
bpo-34405@footnote{https://bugs.python.org/issue34405}: 在MacOS安装程序中将OpenSSL更新为1.1.0i 。

@item 
bpo-33635@footnote{https://bugs.python.org/issue33635}: In macOS stat on some file descriptors (/dev/fd/3 f.e) will
result in bad file descriptor OSError. Guard against this exception was
added in is_dir, is_file and similar methods. DirEntry.is_dir can also
throw this exception so _RecursiveWildcardSelector._iterate_directories
was also extended with the same error ignoring pattern.

@item 
bpo-13631@footnote{https://bugs.python.org/issue13631}: The .editrc file in user's home directory is now processed
correctly during the readline initialization through editline emulation on
macOS.

@item 
bpo-33184@footnote{https://bugs.python.org/issue33184}: 在MacOS安装程序中将OpenSSL更新为1.1.0h。

@item 
bpo-32726@footnote{https://bugs.python.org/issue32726}: Build and link with private copy of Tcl/Tk 8.6 for the macOS
10.6+ installer. The 10.9+ installer variant already does this.  This
means that the Python 3.7 provided by the python.org macOS installers no
longer need or use any external versions of Tcl/Tk, either system-provided
or user-installed, such as ActiveTcl.

@item 
bpo-32901@footnote{https://bugs.python.org/issue32901}: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

@item 
bpo-31903@footnote{https://bugs.python.org/issue31903}: In @code{_scproxy}, drop the GIL when calling into
@code{SystemConfiguration} to avoid deadlocks.
@end itemize

@node IDLE<21>,工具/示例<10>,macOS<10>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id152}@anchor{fda}
@subsubsection IDLE



@itemize -

@item 
bpo-35770@footnote{https://bugs.python.org/issue35770}: IDLE macosx deletes Options => Configure IDLE. It previously
deleted Window => Zoom Height by mistake. (Zoom Height is now on the
Options menu).  On Mac, the settings dialog is accessed via Preferences on
the IDLE menu.

@item 
bpo-35769@footnote{https://bugs.python.org/issue35769}: 将 IDLE 的新文件名从 'Untitled' 更改为 'untitled'

@item 
bpo-35660@footnote{https://bugs.python.org/issue35660}: Fix imports in idlelib.window.

@item 
bpo-35641@footnote{https://bugs.python.org/issue35641}: 当函数没有文档字符串时正确地格式化 @code{calltip}。

@item 
bpo-33987@footnote{https://bugs.python.org/issue33987}: Use ttk Frame for ttk widgets.

@item 
bpo-34055@footnote{https://bugs.python.org/issue34055}: Fix erroneous 'smart' indents and newlines in IDLE Shell.

@item 
bpo-35591@footnote{https://bugs.python.org/issue35591}: Find Selection now works when selection not found.

@item 
bpo-35196@footnote{https://bugs.python.org/issue35196}: Speed up squeezer line counting.

@item 
bpo-35598@footnote{https://bugs.python.org/issue35598}: Update config_key: use PEP 8 names and ttk widgets, make some
objects global, and add tests.

@item 
bpo-28097@footnote{https://bugs.python.org/issue28097}: Add Previous/Next History entries to Shell menu.

@item 
bpo-35208@footnote{https://bugs.python.org/issue35208}: Squeezer now properly counts wrapped lines before newlines.

@item 
bpo-35555@footnote{https://bugs.python.org/issue35555}: Gray out Code Context menu entry when it's not applicable.

@item 
bpo-35521@footnote{https://bugs.python.org/issue35521}: Document the IDLE editor code context feature. Add some
internal references within the IDLE doc.

@item 
bpo-22703@footnote{https://bugs.python.org/issue22703}: The Code Context menu label now toggles between Show/Hide Code
Context. The Zoom Height menu now toggles between Zoom/Restore Height.
Zoom Height has moved from the Window menu to the Options menu.

@item 
bpo-35213@footnote{https://bugs.python.org/issue35213}: Where appropriate, use 'macOS' in idlelib.

@item 
bpo-34864@footnote{https://bugs.python.org/issue34864}: On macOS, warn if the system preference "Prefer tabs when
opening documents" is set to "Always".

@item 
bpo-34864@footnote{https://bugs.python.org/issue34864}: Document two IDLE on MacOS issues. The System Preferences Dock
"prefer tabs always" setting disables some IDLE features.  Menus are a bit
different than as described for Windows and Linux.

@item 
bpo-35202@footnote{https://bugs.python.org/issue35202}: Remove unused imports from lib/idlelib

@item 
bpo-33000@footnote{https://bugs.python.org/issue33000}: Document that IDLE's shell has no line limit. A program that
runs indefinitely can overfill memory.

@item 
bpo-23220@footnote{https://bugs.python.org/issue23220}: Explain how IDLE's Shell displays output.

@item 
bpo-35099@footnote{https://bugs.python.org/issue35099}: Improve the doc about IDLE running user code.   The section is
renamed from "IDLE -- console differences" is renamed "Running user code".
It mostly covers the implications of using custom sys.stdxxx objects.

@item 
bpo-35097@footnote{https://bugs.python.org/issue35097}: Add IDLE doc subsection explaining editor windows. Topics
include opening, title and status bar, .py* extension, and running.

@item 
bpo-35093@footnote{https://bugs.python.org/issue35093}: Document the IDLE document viewer in the IDLE doc. Add a
paragraph in "Help and preferences", "Help sources" subsection.

@item 
bpo-35088@footnote{https://bugs.python.org/issue35088}: Update idlelib.help.copy_string docstring. We now use git and
backporting instead of hg and forward merging.

@item 
bpo-35087@footnote{https://bugs.python.org/issue35087}: Update idlelib help files for the current doc build. The main
change is the elimination of chapter-section numbers.

@item 
bpo-34548@footnote{https://bugs.python.org/issue34548}: Use configured color theme for read-only text views.

@item 
bpo-1529353@footnote{https://bugs.python.org/issue1529353}: Enable "squeezing" of long outputs in the shell, to avoid
performance degradation and to clean up the history without losing it.
Squeezed outputs may be copied, viewed in a separate window, and
"unsqueezed".

@item 
bpo-34047@footnote{https://bugs.python.org/issue34047}: Fixed mousewheel scrolling direction on macOS.

@item 
bpo-34275@footnote{https://bugs.python.org/issue34275}: Make IDLE calltips always visible on Mac. Some MacOS-tk
combinations need .update_idletasks(). Patch by Kevin Walzer.

@item 
bpo-34120@footnote{https://bugs.python.org/issue34120}: Fix unresponsiveness after closing certain windows and dialogs.

@item 
bpo-33975@footnote{https://bugs.python.org/issue33975}: Avoid small type when running htests. Since part of the purpose
of human-viewed tests is to determine that widgets look right, it is
important that they look the same for testing as when running IDLE.

@item 
bpo-33905@footnote{https://bugs.python.org/issue33905}: Add test for idlelib.stackview.StackBrowser.

@item 
bpo-33924@footnote{https://bugs.python.org/issue33924}: Change mainmenu.menudefs key 'windows' to 'window'. Every other
menudef key is lowercase version of main menu entry.

@item 
bpo-33906@footnote{https://bugs.python.org/issue33906}: Rename idlelib.windows as window Match Window on the main menu
and remove last plural module name.

@item 
bpo-33917@footnote{https://bugs.python.org/issue33917}: Fix and document idlelib/idle_test/template.py. The revised
file compiles, runs, and tests OK.  idle_test/README.txt explains how to
use it to create new IDLE test files.

@item 
bpo-33904@footnote{https://bugs.python.org/issue33904}: IDLE: In rstrip, rename class RstripExtension as Rstrip

@item 
bpo-33907@footnote{https://bugs.python.org/issue33907}: For consistency and clarity, rename an IDLE module and classes.
Module calltips and its class CallTips are now calltip and Calltip. In
module calltip_w, class CallTip is now CalltipWindow.

@item 
bpo-33856@footnote{https://bugs.python.org/issue33856}: Add "help" in the welcome message of IDLE

@item 
bpo-33839@footnote{https://bugs.python.org/issue33839}: IDLE: refactor ToolTip and CallTip and add documentation and
tests

@item 
bpo-33855@footnote{https://bugs.python.org/issue33855}: Minimally test all IDLE modules. Add missing files, import
module, instantiate classes, and check coverage. Check existing files.

@item 
bpo-33656@footnote{https://bugs.python.org/issue33656}: On Windows, add API call saying that tk scales for DPI. On
Windows 8.1+ or 10, with DPI compatibility properties of the Python binary
unchanged, and a monitor resolution greater than 96 DPI, this should make
text and lines sharper.  It should otherwise have no effect.

@item 
bpo-33768@footnote{https://bugs.python.org/issue33768}: Clicking on a context line moves that line to the top of the
editor window.

@item 
bpo-33763@footnote{https://bugs.python.org/issue33763}: IDLE: Use read-only text widget for code context instead of
label widget.

@item 
bpo-33664@footnote{https://bugs.python.org/issue33664}: Scroll IDLE editor text by lines. Previously, the mouse wheel
and scrollbar slider moved text by a fixed number of pixels, resulting in
partial lines at the top of the editor box.  The change also applies to
the shell and grep output windows, but not to read-only text views.

@item 
bpo-33679@footnote{https://bugs.python.org/issue33679}: Enable theme-specific color configuration for Code Context. Use
the Highlights tab to see the setting for built-in themes or add settings
to custom themes.

@item 
bpo-33642@footnote{https://bugs.python.org/issue33642}: Display up to maxlines non-blank lines for Code Context. If
there is no current context, show a single blank line.

@item 
bpo-33628@footnote{https://bugs.python.org/issue33628}: IDLE: Cleanup codecontext.py and its test.

@item 
bpo-33564@footnote{https://bugs.python.org/issue33564}: IDLE's code context now recognizes async as a block opener.

@item 
bpo-21474@footnote{https://bugs.python.org/issue21474}: Update word/identifier definition from ascii to unicode. In
text and entry boxes, this affects selection by double-click, movement
left/right by control-left/right, and deletion left/right by
control-BACKSPACE/DEL.

@item 
bpo-33204@footnote{https://bugs.python.org/issue33204}: IDLE: consistently color invalid string prefixes. A 'u' string
prefix cannot be paired with either 'r' or 'f'. Consistently color as much
of the prefix, starting at the right, as is valid. Revise and extend
colorizer test.

@item 
bpo-32984@footnote{https://bugs.python.org/issue32984}: Set @code{__file__} while running a startup file.  Like Python,
IDLE optionally runs one startup file in the Shell window before
presenting the first interactive input prompt.  For IDLE, @code{-s} runs a
file named in environmental variable  
@geindex IDLESTARTUP
@geindex 环境变量; IDLESTARTUP
@code{IDLESTARTUP} or
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP}; @code{-r file} runs @code{file}.  Python sets
@code{__file__} to the startup file name before running the file and unsets
it before the first prompt.  IDLE now does the same when run normally,
without the @code{-n} option.

@item 
bpo-32940@footnote{https://bugs.python.org/issue32940}: Simplify and rename StringTranslatePseudoMapping in pyparse.

@item 
bpo-32916@footnote{https://bugs.python.org/issue32916}: Change @code{str} to @code{code} in pyparse.

@item 
bpo-32905@footnote{https://bugs.python.org/issue32905}: Remove unused code in pyparse module.

@item 
bpo-32874@footnote{https://bugs.python.org/issue32874}: Add tests for pyparse.

@item 
bpo-32837@footnote{https://bugs.python.org/issue32837}: Using the system and place-dependent default encoding for
open() is a bad idea for IDLE's system and location-independent files.

@item 
bpo-32826@footnote{https://bugs.python.org/issue32826}: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI
test test_file_buttons() only looks at initial ascii-only lines, but
failed on systems where open() defaults to 'ascii' because readline()
internally reads and decodes far enough ahead to encounter a non-ascii
character in CREDITS.txt.

@item 
bpo-32831@footnote{https://bugs.python.org/issue32831}: Add docstrings and tests for codecontext.

@item 
bpo-32765@footnote{https://bugs.python.org/issue32765}: Update configdialog General tab docstring to add new widgets to
the widget list.
@end itemize

@node 工具/示例<10>,C API<11>,IDLE<21>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id153}@anchor{fdb}
@subsubsection 工具/示例



@itemize -

@item 
bpo-35884@footnote{https://bugs.python.org/issue35884}: Add a benchmark script for timing various ways to access
variables: @code{Tools/scripts/var_access_benchmark.py}.

@item 
bpo-34989@footnote{https://bugs.python.org/issue34989}: python-gdb.py now handles errors on computing the line number
of a Python frame.

@item 
bpo-20260@footnote{https://bugs.python.org/issue20260}: Argument Clinic now has non-bitwise unsigned int converters.

@item 
bpo-32962@footnote{https://bugs.python.org/issue32962}: python-gdb now catches @code{UnicodeDecodeError} exceptions when
calling @code{string()}.

@item 
bpo-32962@footnote{https://bugs.python.org/issue32962}: python-gdb now catches ValueError on read_var(): when Python
has no debug symbols for example.

@item 
bpo-33189@footnote{https://bugs.python.org/issue33189}: @code{pygettext.py} now recognizes only literal strings as
docstrings and translatable strings, and rejects bytes literals and
f-string expressions.

@item 
bpo-31920@footnote{https://bugs.python.org/issue31920}: Fixed handling directories as arguments in the @code{pygettext}
script. Based on patch by Oleg Krasnikov.

@item 
bpo-29673@footnote{https://bugs.python.org/issue29673}: Fix pystackv and pystack gdbinit macros.

@item 
bpo-25427@footnote{https://bugs.python.org/issue25427}: Remove the pyvenv script in favor of @code{python3 -m venv} in
order to lower confusion as to what Python interpreter a virtual
environment will be created for.

@item 
bpo-32885@footnote{https://bugs.python.org/issue32885}: Add an @code{-n} flag for @code{Tools/scripts/pathfix.py} to disable
automatic backup creation (files with @code{~} suffix).

@item 
bpo-32222@footnote{https://bugs.python.org/issue32222}: Fix pygettext not extracting docstrings for functions with type
annotated arguments. Patch by Toby Harradine.

@item 
bpo-31583@footnote{https://bugs.python.org/issue31583}: Fix 2to3 for using with --add-suffix option but without
--output-dir option for relative path to files in current directory.
@end itemize

@node C API<11>,,工具/示例<10>,Python 3 8 0 alpha 1
@anchor{whatsnew/changelog id154}@anchor{fdc}
@subsubsection C API



@itemize -

@item 
bpo-35713@footnote{https://bugs.python.org/issue35713}: The @code{PyByteArray_Init()} and @code{PyByteArray_Fini()}
functions have been removed. They did nothing since Python 2.7.4 and
Python 3.2.0, were excluded from the limited API (stable ABI), and were
not documented.

@item 
bpo-33817@footnote{https://bugs.python.org/issue33817}: Fixed @ref{fdd,,_PyBytes_Resize()} for empty bytes objects.

@item 
bpo-35322@footnote{https://bugs.python.org/issue35322}: Fix memory leak in @ref{439,,PyUnicode_EncodeLocale()} and
@ref{fde,,PyUnicode_EncodeFSDefault()} on error handling.

@item 
bpo-35059@footnote{https://bugs.python.org/issue35059}: The following C macros have been converted to static inline
functions: @ref{265,,Py_INCREF()}, @ref{266,,Py_DECREF()}, @ref{267,,Py_XINCREF()},
@ref{268,,Py_XDECREF()}, @code{PyObject_INIT()},
@code{PyObject_INIT_VAR()}.

@item 
bpo-35296@footnote{https://bugs.python.org/issue35296}: @code{make install} now also installs the internal API:
@code{Include/internal/*.h} header files.

@item 
bpo-35081@footnote{https://bugs.python.org/issue35081}: Internal APIs surrounded by @code{#ifdef Py_BUILD_CORE} have been
moved from @code{Include/*.h} headers to new header files
@code{Include/internal/pycore_*.h}.

@item 
bpo-35259@footnote{https://bugs.python.org/issue35259}: 基于 Py_LIMITED_API 有条件地声明 @ref{5c4,,Py_FinalizeEx()} (3.6 中新增)。 补丁作者 Arthur Neufeld。

@item 
bpo-35081@footnote{https://bugs.python.org/issue35081}: The @code{_PyObject_GC_TRACK()} and
@code{_PyObject_GC_UNTRACK()} macros have been removed from the public C
API.

@item 
bpo-35134@footnote{https://bugs.python.org/issue35134}: Creation of a new @code{Include/cpython/} subdirectory.

@item 
bpo-34725@footnote{https://bugs.python.org/issue34725}: Adds _Py_SetProgramFullPath so embedders may override
sys.executable

@item 
bpo-34910@footnote{https://bugs.python.org/issue34910}: Ensure that @ref{fdf,,PyObject_Print()} always returns @code{-1} on
error.  Patch by Zackery Spytz.

@item 
bpo-34523@footnote{https://bugs.python.org/issue34523}: Py_DecodeLocale() and Py_EncodeLocale() now use the UTF-8
encoding on Windows if Py_LegacyWindowsFSEncodingFlag is zero.

@item 
bpo-34193@footnote{https://bugs.python.org/issue34193}: Fix pluralization in TypeError messages in getargs.c and
typeobject.c: '1 argument' instead of '1 arguments' and '1 element'
instead of '1 elements'.

@item 
bpo-34127@footnote{https://bugs.python.org/issue34127}: Return grammatically correct error message based on argument
count. Patch by Karthikeyan Singaravelan.

@item 
bpo-23927@footnote{https://bugs.python.org/issue23927}: Fixed @ref{5f6,,SystemError} in
@ref{5c5,,PyArg_ParseTupleAndKeywords()} when the @code{w*} format unit is used
for optional parameter.

@item 
bpo-32455@footnote{https://bugs.python.org/issue32455}: Added @code{PyCompile_OpcodeStackEffectWithJump()}.

@item 
bpo-34008@footnote{https://bugs.python.org/issue34008}: Py_Main() can again be called after Py_Initialize(), as in
Python 3.6.

@item 
bpo-32500@footnote{https://bugs.python.org/issue32500}: Fixed error messages for @ref{fe0,,PySequence_Size()},
@ref{fe1,,PySequence_GetItem()}, @ref{fe2,,PySequence_SetItem()} and
@ref{fe3,,PySequence_DelItem()} called with a mapping and
@ref{fe4,,PyMapping_Size()} called with a sequence.

@item 
bpo-33818@footnote{https://bugs.python.org/issue33818}: @code{PyExceptionClass_Name()} will now return @code{const char
*} instead of @code{char *}.

@item 
bpo-33042@footnote{https://bugs.python.org/issue33042}: Embedding applications may once again call
PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to
calling Py_Initialize.

@item 
bpo-32374@footnote{https://bugs.python.org/issue32374}: Document that m_traverse for multi-phase initialized modules
can be called with m_state=NULL, and add a sanity check

@item 
bpo-30863@footnote{https://bugs.python.org/issue30863}: @ref{fe5,,PyUnicode_AsWideChar()} and
@ref{432,,PyUnicode_AsWideCharString()} no longer cache the @code{wchar_t*}
representation of string objects.
@end itemize

@node Python 3 7 0 正式版,Python 3 7 0 rc1,Python 3 8 0 alpha 1,更新日志
@anchor{whatsnew/changelog python-3-7-0-final}@anchor{fe6}
@subsection Python 3.7.0 正式版


@emph{发布日期: 2018-06-27}

@menu
* 库: 库<21>. 
* C API: C API<12>. 

@end menu

@node 库<21>,C API<12>,,Python 3 7 0 正式版
@anchor{whatsnew/changelog id155}@anchor{fe7}
@subsubsection 库



@itemize -

@item 
bpo-33851@footnote{https://bugs.python.org/issue33851}: Fix @ref{fe8,,ast.get_docstring()} for a node that lacks a
docstring.
@end itemize

@node C API<12>,,库<21>,Python 3 7 0 正式版
@anchor{whatsnew/changelog id156}@anchor{fe9}
@subsubsection C API



@itemize -

@item 
bpo-33932@footnote{https://bugs.python.org/issue33932}: Calling Py_Initialize() twice does nothing, instead of failing
with a fatal error: restore the Python 3.6 behaviour.
@end itemize

@node Python 3 7 0 rc1,Python 3 7 0 beta 5,Python 3 7 0 正式版,更新日志
@anchor{whatsnew/changelog python-3-7-0-release-candidate-1}@anchor{fea}
@subsection Python 3.7.0 rc1


@emph{发布日期: 2018-06-12}

@menu
* 核心与内置: 核心与内置<21>. 
* 库: 库<22>. 
* 文档: 文档<17>. 
* 构建: 构建<14>. 
* Windows: Windows<17>. 
* IDLE: IDLE<22>. 

@end menu

@node 核心与内置<21>,库<22>,,Python 3 7 0 rc1
@anchor{whatsnew/changelog id157}@anchor{feb}
@subsubsection 核心与内置



@itemize -

@item 
bpo-33803@footnote{https://bugs.python.org/issue33803}: Fix a crash in hamt.c caused by enabling GC tracking for an
object that hadn't all of its fields set to NULL.

@item 
bpo-33706@footnote{https://bugs.python.org/issue33706}: Fix a crash in Python initialization when parsing the command
line options. Thanks Christoph Gohlke for the bug report and the fix!

@item 
bpo-30654@footnote{https://bugs.python.org/issue30654}: Fixed reset of the SIGINT handler to SIG_DFL on interpreter
shutdown even when there was a custom handler set previously. Patch by
Philipp Kerling.

@item 
bpo-31849@footnote{https://bugs.python.org/issue31849}: Fix signed/unsigned comparison warning in pyhash.c.
@end itemize

@node 库<22>,文档<17>,核心与内置<21>,Python 3 7 0 rc1
@anchor{whatsnew/changelog id158}@anchor{fec}
@subsubsection 库



@itemize -

@item 
bpo-30167@footnote{https://bugs.python.org/issue30167}: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by
Steve Weber.

@item 
bpo-33812@footnote{https://bugs.python.org/issue33812}: Datetime instance d with non-None tzinfo, but with
d.tzinfo.utcoffset(d) returning None is now treated as naive by the
astimezone() method.

@item 
bpo-30805@footnote{https://bugs.python.org/issue30805}: Avoid race condition with debug logging

@item 
bpo-33694@footnote{https://bugs.python.org/issue33694}: asyncio: Fix a race condition causing data loss on
pause_reading()/resume_reading() when using the ProactorEventLoop.

@item 
bpo-32493@footnote{https://bugs.python.org/issue32493}: Correct test for @code{uuid_enc_be} availability in
@code{configure.ac}. Patch by Michael Felt.

@item 
bpo-33792@footnote{https://bugs.python.org/issue33792}: Add asyncio.WindowsSelectorEventLoopPolicy and
asyncio.WindowsProactorEventLoopPolicy.

@item 
bpo-33778@footnote{https://bugs.python.org/issue33778}: Update @code{unicodedata}'s database to Unicode version 11.0.0.

@item 
bpo-33770@footnote{https://bugs.python.org/issue33770}: improve base64 exception message for encoded inputs of invalid
length

@item 
bpo-33769@footnote{https://bugs.python.org/issue33769}: asyncio/start_tls: Fix error message; cancel callbacks in case
of an unhandled error; mark SSLTransport as closed if it is aborted.

@item 
bpo-33767@footnote{https://bugs.python.org/issue33767}: The concatenation (@code{+}) and repetition (@code{*}) sequence
operations now raise @ref{192,,TypeError} instead of @ref{5f6,,SystemError} when
performed on @ref{1ec,,mmap.mmap} objects.  Patch by Zackery Spytz.

@item 
bpo-33734@footnote{https://bugs.python.org/issue33734}: asyncio/ssl: Fix AttributeError, increase default handshake
timeout

@item 
bpo-11874@footnote{https://bugs.python.org/issue11874}: Use a better regex when breaking usage into wrappable parts.
Avoids bogus assertion errors from custom metavar strings.

@item 
bpo-33582@footnote{https://bugs.python.org/issue33582}: Emit a deprecation warning for inspect.formatargspec
@end itemize

@node 文档<17>,构建<14>,库<22>,Python 3 7 0 rc1
@anchor{whatsnew/changelog id159}@anchor{fed}
@subsubsection 文档



@itemize -

@item 
bpo-33409@footnote{https://bugs.python.org/issue33409}: Clarified the relationship between 
@geindex Python 提高建议; PEP 538
PEP 538@footnote{https://www.python.org/dev/peps/pep-0538}'s
PYTHONCOERCECLOCALE and PEP 540's PYTHONUTF8 mode.

@item 
bpo-33736@footnote{https://bugs.python.org/issue33736}: Improve the documentation of @ref{35c,,asyncio.open_connection()},
@ref{35d,,asyncio.start_server()} and their UNIX socket counterparts.

@item 
bpo-31432@footnote{https://bugs.python.org/issue31432}: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED
flags for ssl.SSLContext.verify_mode.
@end itemize

@node 构建<14>,Windows<17>,文档<17>,Python 3 7 0 rc1
@anchor{whatsnew/changelog id160}@anchor{fee}
@subsubsection 构建



@itemize -

@item 
bpo-5755@footnote{https://bugs.python.org/issue5755}: Move @code{-Wstrict-prototypes} option to @code{CFLAGS_NODIST} from
@code{OPT}. This option emitted annoying warnings when building extension
modules written in C++.
@end itemize

@node Windows<17>,IDLE<22>,构建<14>,Python 3 7 0 rc1
@anchor{whatsnew/changelog id161}@anchor{fef}
@subsubsection Windows



@itemize -

@item 
bpo-33720@footnote{https://bugs.python.org/issue33720}: Reduces maximum marshal recursion depth on release builds.
@end itemize

@node IDLE<22>,,Windows<17>,Python 3 7 0 rc1
@anchor{whatsnew/changelog id162}@anchor{ff0}
@subsubsection IDLE



@itemize -

@item 
bpo-33656@footnote{https://bugs.python.org/issue33656}: On Windows, add API call saying that tk scales for DPI. On
Windows 8.1+ or 10, with DPI compatibility properties of the Python binary
unchanged, and a monitor resolution greater than 96 DPI, this should make
text and lines sharper.  It should otherwise have no effect.

@item 
bpo-33768@footnote{https://bugs.python.org/issue33768}: Clicking on a context line moves that line to the top of the
editor window.

@item 
bpo-33763@footnote{https://bugs.python.org/issue33763}: IDLE: Use read-only text widget for code context instead of
label widget.

@item 
bpo-33664@footnote{https://bugs.python.org/issue33664}: Scroll IDLE editor text by lines. Previously, the mouse wheel
and scrollbar slider moved text by a fixed number of pixels, resulting in
partial lines at the top of the editor box.  The change also applies to
the shell and grep output windows, but not to read-only text views.

@item 
bpo-33679@footnote{https://bugs.python.org/issue33679}: Enable theme-specific color configuration for Code Context. Use
the Highlights tab to see the setting for built-in themes or add settings
to custom themes.

@item 
bpo-33642@footnote{https://bugs.python.org/issue33642}: Display up to maxlines non-blank lines for Code Context. If
there is no current context, show a single blank line.
@end itemize

@node Python 3 7 0 beta 5,Python 3 7 0 beta 4,Python 3 7 0 rc1,更新日志
@anchor{whatsnew/changelog python-3-7-0-beta-5}@anchor{ff1}
@subsection Python 3.7.0 beta 5


@emph{发布日期: 2018-05-30}

@menu
* 核心与内置: 核心与内置<22>. 
* 库: 库<23>. 
* 文档: 文档<18>. 
* 测试: 测试<16>. 
* 构建: 构建<15>. 
* macOS: macOS<11>. 
* IDLE: IDLE<23>. 

@end menu

@node 核心与内置<22>,库<23>,,Python 3 7 0 beta 5
@anchor{whatsnew/changelog id163}@anchor{ff2}
@subsubsection 核心与内置



@itemize -

@item 
bpo-33622@footnote{https://bugs.python.org/issue33622}: Fixed a leak when the garbage collector fails to add an object
with the @code{__del__} method or referenced by it into the
@ref{b39,,gc.garbage} list. @code{PyGC_Collect()} can now be called when an
exception is set and preserves it.

@item 
bpo-33509@footnote{https://bugs.python.org/issue33509}: Fix module_globals parameter of warnings.warn_explicit(): don't
crash if module_globals is not a dict.

@item 
bpo-20104@footnote{https://bugs.python.org/issue20104}: The new @ref{257,,os.posix_spawn} added in 3.7.0b1 was removed as we are
still working on what the API should look like.  Expect this in 3.8
instead.

@item 
bpo-33475@footnote{https://bugs.python.org/issue33475}: Fixed miscellaneous bugs in converting annotations to strings
and optimized parentheses in the string representation.

@item 
bpo-33391@footnote{https://bugs.python.org/issue33391}: Fix a leak in set_symmetric_difference().

@item 
bpo-28055@footnote{https://bugs.python.org/issue28055}: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

@item 
bpo-32911@footnote{https://bugs.python.org/issue32911}: Due to unexpected compatibility issues discovered during
downstream beta testing, reverted bpo-29463@footnote{https://bugs.python.org/issue29463}. @code{docstring} field is
removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes
which was added in 3.7a1.  Docstring expression is restored as a first
statement in their body. Based on patch by Inada Naoki.

@item 
bpo-21983@footnote{https://bugs.python.org/issue21983}: Fix a crash in @ref{fa6,,ctypes.cast()} in case the type argument is a
ctypes structured data type. Patch by Eryk Sun and Oren Milman.
@end itemize

@node 库<23>,文档<18>,核心与内置<22>,Python 3 7 0 beta 5
@anchor{whatsnew/changelog id164}@anchor{ff3}
@subsubsection 库



@itemize -

@item 
bpo-32751@footnote{https://bugs.python.org/issue32751}: When cancelling the task due to a timeout,
@ref{288,,asyncio.wait_for()} will now wait until the cancellation is complete.

@item 
bpo-32684@footnote{https://bugs.python.org/issue32684}: Fix gather to propagate cancellation of itself even with
return_exceptions.

@item 
bpo-33654@footnote{https://bugs.python.org/issue33654}: Support protocol type switching in SSLTransport.set_protocol().

@item 
bpo-33674@footnote{https://bugs.python.org/issue33674}: Pause the transport as early as possible to further reduce the
risk of data_received() being called before connection_made().

@item 
bpo-33674@footnote{https://bugs.python.org/issue33674}: Fix a race condition in SSLProtocol.connection_made() of
asyncio.sslproto: start immediately the handshake instead of using
call_soon(). Previously, data_received() could be called before the
handshake started, causing the handshake to hang or fail.

@item 
bpo-31647@footnote{https://bugs.python.org/issue31647}: Fixed bug where calling write_eof() on a
_SelectorSocketTransport after it's already closed raises AttributeError.

@item 
bpo-32610@footnote{https://bugs.python.org/issue32610}: Make asyncio.all_tasks() return only pending tasks.

@item 
bpo-32410@footnote{https://bugs.python.org/issue32410}: Avoid blocking on file IO in sendfile fallback code

@item 
bpo-33469@footnote{https://bugs.python.org/issue33469}: Fix RuntimeError after closing loop that used run_in_executor

@item 
bpo-33672@footnote{https://bugs.python.org/issue33672}: Fix Task.__repr__ crash with Cython's bogus coroutines

@item 
bpo-33654@footnote{https://bugs.python.org/issue33654}: Fix transport.set_protocol() to support switching between
asyncio.Protocol and asyncio.BufferedProtocol.  Fix loop.start_tls() to
work with asyncio.BufferedProtocols.

@item 
bpo-33652@footnote{https://bugs.python.org/issue33652}: Pickles of type variables and subscripted generics are now
future-proof and compatible with older Python versions.

@item 
bpo-32493@footnote{https://bugs.python.org/issue32493}: Fixed @ref{40b,,uuid.uuid1()} on FreeBSD.

@item 
bpo-33618@footnote{https://bugs.python.org/issue33618}: Finalize and document preliminary and experimental TLS 1.3
support with OpenSSL 1.1.1

@item 
bpo-33623@footnote{https://bugs.python.org/issue33623}: Fix possible SIGSGV when asyncio.Future is created in __del__

@item 
bpo-30877@footnote{https://bugs.python.org/issue30877}: Fixed a bug in the Python implementation of the JSON decoder
that prevented the cache of parsed strings from clearing after finishing
the decoding. Based on patch by c-fos.

@item 
bpo-33570@footnote{https://bugs.python.org/issue33570}: Change TLS 1.3 cipher suite settings for compatibility with
OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers
enabled by default.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Do not simplify arguments to @ref{fc7,,typing.Union}. Now
@code{Union[Manager, Employee]} is not simplified to @code{Employee} at runtime.
Such simplification previously caused several bugs and limited
possibilities for introspection.

@item 
bpo-33540@footnote{https://bugs.python.org/issue33540}: Add a new @code{block_on_close} class attribute to
@code{ForkingMixIn} and @code{ThreadingMixIn} classes of @ref{f0,,socketserver}.

@item 
bpo-33548@footnote{https://bugs.python.org/issue33548}: tempfile._candidate_tempdir_list should consider common TEMP
locations

@item 
bpo-33109@footnote{https://bugs.python.org/issue33109}: argparse subparsers are once again not required by default,
reverting the change in behavior introduced by bpo-26510@footnote{https://bugs.python.org/issue26510} in 3.7.0a2.

@item 
bpo-33536@footnote{https://bugs.python.org/issue33536}: dataclasses.make_dataclass now checks for invalid field names
and duplicate fields. Also, added a check for invalid field
specifications.

@item 
bpo-33542@footnote{https://bugs.python.org/issue33542}: Prevent @code{uuid.get_node} from using a DUID instead of a MAC on
Windows. Patch by Zvi Effron

@item 
bpo-26819@footnote{https://bugs.python.org/issue26819}: Fix race condition with @code{ReadTransport.resume_reading} in
Windows proactor event loop.

@item 
Fix failure in @ref{303,,typing.get_type_hints()} when ClassVar was provided as a
string forward reference.

@item 
bpo-33505@footnote{https://bugs.python.org/issue33505}: Optimize asyncio.ensure_future() by reordering if checks: 1.17x
faster.

@item 
bpo-33497@footnote{https://bugs.python.org/issue33497}: Add errors param to cgi.parse_multipart and make an encoding in
FieldStorage use the given errors (needed for Twisted).  Patch by Amber
Brown.

@item 
bpo-33495@footnote{https://bugs.python.org/issue33495}: Change dataclasses.Fields repr to use the repr of each of its
members, instead of str.  This makes it more clear what each field
actually represents.  This is especially true for the 'type' member.

@item 
bpo-33453@footnote{https://bugs.python.org/issue33453}: Fix dataclasses to work if using literal string type
annotations or if using PEP 563 "Postponed Evaluation of Annotations".
Only specific string prefixes are detected for both ClassVar ("ClassVar"
and "typing.ClassVar") and InitVar ("InitVar" and "dataclasses.InitVar").

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Minor fixes in typing module: add annotations to
@code{NamedTuple.__new__}, pass @code{*args} and @code{**kwds} in
@code{Generic.__new__}.  Original PRs by Paulius Šarka and Chad Dombrova.

@item 
bpo-20087@footnote{https://bugs.python.org/issue20087}: Updated alias mapping with glibc 2.27 supported locales.

@item 
bpo-33422@footnote{https://bugs.python.org/issue33422}: Fix trailing quotation marks getting deleted when looking up
byte/string literals on pydoc. Patch by Andrés Delfino.

@item 
bpo-28167@footnote{https://bugs.python.org/issue28167}: The function @code{platform.linux_distribution} and
@code{platform.dist} now trigger a @code{DeprecationWarning} and have been
marked for removal in Python 3.8

@item 
bpo-33197@footnote{https://bugs.python.org/issue33197}: Update error message when constructing invalid
inspect.Parameters Patch by Dong-hee Na.

@item 
bpo-33263@footnote{https://bugs.python.org/issue33263}: Fix FD leak in @code{_SelectorSocketTransport}  Patch by Vlad
Starostin.

@item 
bpo-32861@footnote{https://bugs.python.org/issue32861}: The urllib.robotparser's @code{__str__} representation now
includes wildcard entries and the "Crawl-delay" and "Request-rate" fields.
Patch by Michael Lazar.

@item 
bpo-32257@footnote{https://bugs.python.org/issue32257}: The ssl module now contains OP_NO_RENEGOTIATION constant,
available with OpenSSL 1.1.0h or 1.1.1.

@item 
bpo-16865@footnote{https://bugs.python.org/issue16865}: Support arrays >=2GiB in @ref{2b,,ctypes}.  Patch by Segev Finer.
@end itemize

@node 文档<18>,测试<16>,库<23>,Python 3 7 0 beta 5
@anchor{whatsnew/changelog id165}@anchor{ff4}
@subsubsection 文档



@itemize -

@item 
bpo-23859@footnote{https://bugs.python.org/issue23859}: Document that @ref{289,,asyncio.wait()} does not cancel its futures on
timeout.

@item 
bpo-32436@footnote{https://bugs.python.org/issue32436}: Document 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} changes to asyncio.

@item 
bpo-33604@footnote{https://bugs.python.org/issue33604}: 更新HMAC md5默认报告DeprecationWarning，并将在3.8移除。

@item 
bpo-33503@footnote{https://bugs.python.org/issue33503}: 修复错误的pypi链接

@item 
bpo-33421@footnote{https://bugs.python.org/issue33421}: 为`@w{`}typing.AsyncContextManager`@w{`}添加缺失的文档。
@end itemize

@node 测试<16>,构建<15>,文档<18>,Python 3 7 0 beta 5
@anchor{whatsnew/changelog id166}@anchor{ff5}
@subsubsection 测试



@itemize -

@item 
bpo-33655@footnote{https://bugs.python.org/issue33655}: 忽略运行在BSD平台的ZFS上时test_posix_fallocate的失败。

@item 
bpo-32604@footnote{https://bugs.python.org/issue32604}:  删除_xxsubinterpreters模块（用于测试）和相关的帮助程序。该模块最初最初是在3.7b1中添加的。
@end itemize

@node 构建<15>,macOS<11>,测试<16>,Python 3 7 0 beta 5
@anchor{whatsnew/changelog id167}@anchor{ff6}
@subsubsection 构建



@itemize -

@item 
bpo-33614@footnote{https://bugs.python.org/issue33614}: Ensures module definition files for the stable ABI on Windows
are correctly regenerated.

@item 
bpo-33522@footnote{https://bugs.python.org/issue33522}: Enable CI builds on Visual Studio Team Services at
@indicateurl{https://python.visualstudio.com/cpython}

@item 
bpo-33012@footnote{https://bugs.python.org/issue33012}: Add @code{-Wno-cast-function-type} for gcc 8 for silencing
warnings about function casts like casting to PyCFunction in method
definition lists.
@end itemize

@node macOS<11>,IDLE<23>,构建<15>,Python 3 7 0 beta 5
@anchor{whatsnew/changelog id168}@anchor{ff7}
@subsubsection macOS



@itemize -

@item 
bpo-13631@footnote{https://bugs.python.org/issue13631}: The .editrc file in user's home directory is now processed
correctly during the readline initialization through editline emulation on
macOS.
@end itemize

@node IDLE<23>,,macOS<11>,Python 3 7 0 beta 5
@anchor{whatsnew/changelog id169}@anchor{ff8}
@subsubsection IDLE



@itemize -

@item 
bpo-33628@footnote{https://bugs.python.org/issue33628}: IDLE: Cleanup codecontext.py and its test.

@item 
bpo-33564@footnote{https://bugs.python.org/issue33564}: IDLE's code context now recognizes async as a block opener.

@item 
bpo-32831@footnote{https://bugs.python.org/issue32831}: Add docstrings and tests for codecontext.
@end itemize

@node Python 3 7 0 beta 4,Python 3 7 0 beta 3,Python 3 7 0 beta 5,更新日志
@anchor{whatsnew/changelog python-3-7-0-beta-4}@anchor{ff9}
@subsection Python 3.7.0 beta 4


@emph{发布日期: 2018-05-02}

@menu
* 核心与内置: 核心与内置<23>. 
* 库: 库<24>. 
* 文档: 文档<19>. 
* 测试: 测试<17>. 
* 构建: 构建<16>. 
* Windows: Windows<18>. 
* macOS: macOS<12>. 
* IDLE: IDLE<24>. 
* 工具/示例: 工具/示例<11>. 

@end menu

@node 核心与内置<23>,库<24>,,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id170}@anchor{ffa}
@subsubsection 核心与内置



@itemize -

@item 
bpo-33363@footnote{https://bugs.python.org/issue33363}: 在异步函数外使用`@w{`}async with`@w{`} 和 @code{async for}  时抛出SyntaxError异常。

@item 
bpo-33128@footnote{https://bugs.python.org/issue33128}: 修复导致PathFinder在sys.meta_path上出现两次的错误。由Pablo Galindo Salgado提供补丁。

@item 
bpo-33312@footnote{https://bugs.python.org/issue33312}: Fixed clang ubsan (undefined behavior sanitizer) warnings in
dictobject.c by adjusting how the internal struct _dictkeysobject shared
keys structure is declared.

@item 
bpo-33231@footnote{https://bugs.python.org/issue33231}: 修复 @code{normalizestring()} 中潜在的内存泄漏。

@item 
bpo-33205@footnote{https://bugs.python.org/issue33205}: Change dict growth function from
@code{round_up_to_power_2(used*2+hashtable_size/2)} to
@code{round_up_to_power_2(used*3)}.  Previously, dict is shrinked only when
@code{used == 0}. Now dict has more chance to be shrinked.

@item 
bpo-29922@footnote{https://bugs.python.org/issue29922}: Improved error messages in 'async with' when @code{__aenter__()}
or @code{__aexit__()} return non-awaitable object.

@item 
bpo-33199@footnote{https://bugs.python.org/issue33199}: Fix @code{ma_version_tag} in dict implementation is uninitialized
when copying from key-sharing dict.
@end itemize

@node 库<24>,文档<19>,核心与内置<23>,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id171}@anchor{ffb}
@subsubsection 库



@itemize -

@item 
bpo-33281@footnote{https://bugs.python.org/issue33281}: Fix ctypes.util.find_library regression on macOS.

@item 
bpo-33383@footnote{https://bugs.python.org/issue33383}: Fixed crash in the get() method of the @ref{35,,dbm.ndbm} database
object when it is called with a single argument.

@item 
bpo-33329@footnote{https://bugs.python.org/issue33329}: Fix multiprocessing regression on newer glibcs

@item 
bpo-991266@footnote{https://bugs.python.org/issue991266}: Fix quoting of the @code{Comment} attribute of
@ref{fcb,,http.cookies.SimpleCookie}.

@item 
bpo-33131@footnote{https://bugs.python.org/issue33131}: Upgrade bundled version of pip to 10.0.1.

@item 
bpo-33308@footnote{https://bugs.python.org/issue33308}: Fixed a crash in the @ref{c7,,parser} module when converting an ST
object to a tree of tuples or lists with @code{line_info=False} and
@code{col_info=True}.

@item 
bpo-33266@footnote{https://bugs.python.org/issue33266}: lib2to3 now recognizes @code{rf'...'} strings.

@item 
bpo-11594@footnote{https://bugs.python.org/issue11594}: Ensure line-endings are respected when using lib2to3.

@item 
bpo-33254@footnote{https://bugs.python.org/issue33254}: Have @ref{fcc,,importlib.resources.contents()} and
@ref{fcd,,importlib.abc.ResourceReader.contents()} return an @ref{ba5,,iterable}
instead of an @ref{fce,,iterator}.

@item 
bpo-33256@footnote{https://bugs.python.org/issue33256}: Fix display of @code{<module>} call in the html produced by
@code{cgitb.html()}. Patch by Stéphane Blondon.

@item 
bpo-33185@footnote{https://bugs.python.org/issue33185}: Fixed regression when running pydoc with the @ref{330,,-m}
switch. (The regression was introduced in 3.7.0b3 by the resolution of
bpo-33053@footnote{https://bugs.python.org/issue33053}) This fix also changed pydoc to add @code{os.getcwd()} to
@ref{482,,sys.path} when necessary, rather than adding @code{"."}.

@item 
bpo-33169@footnote{https://bugs.python.org/issue33169}: Delete entries of @code{None} in @ref{498,,sys.path_importer_cache}
when @code{importlib.machinery.invalidate_caches()} is called.

@item 
bpo-33217@footnote{https://bugs.python.org/issue33217}: Deprecate looking up non-Enum objects in Enum classes and Enum
members (will raise @ref{192,,TypeError} in 3.8+).

@item 
bpo-33203@footnote{https://bugs.python.org/issue33203}: @code{random.Random.choice()} now raises @code{IndexError} for empty
sequences consistently even when called from subclasses without a
@code{getrandbits()} implementation.

@item 
bpo-33224@footnote{https://bugs.python.org/issue33224}: Update difflib.mdiff() for 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479}.  Convert an uncaught
StopIteration in a generator into a return-statement.

@item 
bpo-33209@footnote{https://bugs.python.org/issue33209}: End framing at the end of C implementation of
@ref{fcf,,pickle.Pickler.dump()}.

@item 
bpo-20104@footnote{https://bugs.python.org/issue20104}: Improved error handling and fixed a reference leak in
@ref{257,,os.posix_spawn()}.

@item 
bpo-33175@footnote{https://bugs.python.org/issue33175}: In dataclasses, Field.__set_name__ now looks up the
__set_name__ special method on the class, not the instance, of the default
value.

@item 
bpo-33097@footnote{https://bugs.python.org/issue33097}: Raise RuntimeError when @code{executor.submit} is called during
interpreter shutdown.

@item 
bpo-31908@footnote{https://bugs.python.org/issue31908}: Fix output of cover files for @code{trace} module command-line
tool. Previously emitted cover files only when @code{--missing} option was
used. Patch by Michael Selik.
@end itemize

@node 文档<19>,测试<17>,库<24>,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id172}@anchor{ffc}
@subsubsection 文档



@itemize -

@item 
bpo-33378@footnote{https://bugs.python.org/issue33378}: Add Korean language switcher for @indicateurl{https://docs.python.org/3/}

@item 
bpo-33276@footnote{https://bugs.python.org/issue33276}: Clarify that the @code{__path__} attribute on modules cannot be
just any value.

@item 
bpo-33201@footnote{https://bugs.python.org/issue33201}: Modernize documentation for writing C extension types.

@item 
bpo-33195@footnote{https://bugs.python.org/issue33195}: Deprecate @code{Py_UNICODE} usage in @code{c-api/arg} document.
@code{Py_UNICODE} related APIs are deprecated since Python 3.3, but it is
missed in the document.

@item 
bpo-8243@footnote{https://bugs.python.org/issue8243}: Add a note about curses.addch and curses.addstr exception
behavior when writing outside a window, or pad.

@item 
bpo-32337@footnote{https://bugs.python.org/issue32337}: Update documentation related with @code{dict} order.
@end itemize

@node 测试<17>,构建<16>,文档<19>,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id173}@anchor{ffd}
@subsubsection 测试



@itemize -

@item 
bpo-33358@footnote{https://bugs.python.org/issue33358}: Fix @code{test_embed.test_pre_initialization_sys_options()} when
the interpreter is built with @code{--enable-shared}.
@end itemize

@node 构建<16>,Windows<18>,测试<17>,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id174}@anchor{ffe}
@subsubsection 构建



@itemize -

@item 
bpo-33394@footnote{https://bugs.python.org/issue33394}: Enable the verbose build for extension modules, when GNU make
is passed macros on the command line.

@item 
bpo-33393@footnote{https://bugs.python.org/issue33393}: Update config.guess and config.sub files.

@item 
bpo-33377@footnote{https://bugs.python.org/issue33377}: Add new triplets for mips r6 and riscv variants (used in
extension suffixes).

@item 
bpo-32232@footnote{https://bugs.python.org/issue32232}: By default, modules configured in @code{Modules/Setup} are no longer
built with @code{-DPy_BUILD_CORE}. Instead, modules that specifically need that
preprocessor definition include it in their individual entries.

@item 
bpo-33182@footnote{https://bugs.python.org/issue33182}: The embedding tests can once again be built with clang 6.0
@end itemize

@node Windows<18>,macOS<12>,构建<16>,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id175}@anchor{fff}
@subsubsection Windows



@itemize -

@item 
bpo-33184@footnote{https://bugs.python.org/issue33184}: 在Windows安装程序中将OpenSSL更新为1.1.0h.
@end itemize

@node macOS<12>,IDLE<24>,Windows<18>,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id176}@anchor{1000}
@subsubsection macOS



@itemize -

@item 
bpo-33184@footnote{https://bugs.python.org/issue33184}: 在MacOS安装程序中将OpenSSL更新为1.1.0h。
@end itemize

@node IDLE<24>,工具/示例<11>,macOS<12>,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id177}@anchor{1001}
@subsubsection IDLE



@itemize -

@item 
bpo-21474@footnote{https://bugs.python.org/issue21474}: Update word/identifier definition from ascii to unicode. In
text and entry boxes, this affects selection by double-click, movement
left/right by control-left/right, and deletion left/right by
control-BACKSPACE/DEL.

@item 
bpo-33204@footnote{https://bugs.python.org/issue33204}: IDLE: consistently color invalid string prefixes. A 'u' string
prefix cannot be paired with either 'r' or 'f'. Consistently color as much
of the prefix, starting at the right, as is valid. Revise and extend
colorizer test.
@end itemize

@node 工具/示例<11>,,IDLE<24>,Python 3 7 0 beta 4
@anchor{whatsnew/changelog id178}@anchor{1002}
@subsubsection 工具/示例



@itemize -

@item 
bpo-33189@footnote{https://bugs.python.org/issue33189}: @code{pygettext.py} now recognizes only literal strings as
docstrings and translatable strings, and rejects bytes literals and
f-string expressions.

@item 
bpo-31920@footnote{https://bugs.python.org/issue31920}: Fixed handling directories as arguments in the @code{pygettext}
script. Based on patch by Oleg Krasnikov.

@item 
bpo-29673@footnote{https://bugs.python.org/issue29673}: Fix pystackv and pystack gdbinit macros.

@item 
bpo-31583@footnote{https://bugs.python.org/issue31583}: Fix 2to3 for using with --add-suffix option but without
--output-dir option for relative path to files in current directory.
@end itemize

@node Python 3 7 0 beta 3,Python 3 7 0 beta 2,Python 3 7 0 beta 4,更新日志
@anchor{whatsnew/changelog python-3-7-0-beta-3}@anchor{1003}
@subsection Python 3.7.0 beta 3


@emph{发布日期: 2018-03-29}

@menu
* 安全: 安全<16>. 
* 核心与内置: 核心与内置<24>. 
* 库: 库<25>. 
* 文档: 文档<20>. 
* 测试: 测试<18>. 
* 构建: 构建<17>. 
* Windows: Windows<19>. 
* macOS: macOS<13>. 
* IDLE: IDLE<25>. 
* 工具/示例: 工具/示例<12>. 
* C API: C API<13>. 

@end menu

@node 安全<16>,核心与内置<24>,,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id179}@anchor{1004}
@subsubsection 安全



@itemize -

@item 
bpo-33136@footnote{https://bugs.python.org/issue33136}: Harden ssl module against LibreSSL CVE-2018-8970.
X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new
test ensures that NULL bytes are not allowed.

@item 
bpo-33001@footnote{https://bugs.python.org/issue33001}: Minimal fix to prevent buffer overrun in os.symlink on Windows

@item 
bpo-32981@footnote{https://bugs.python.org/issue32981}: Regexes in difflib and poplib were vulnerable to catastrophic
backtracking. These regexes formed potential DOS vectors (REDOS). They
have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch
by Jamie Davis.
@end itemize

@node 核心与内置<24>,库<25>,安全<16>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id180}@anchor{1005}
@subsubsection 核心与内置



@itemize -

@item 
bpo-33053@footnote{https://bugs.python.org/issue33053}: When using the -m switch, sys.path[0] is now explicitly
expanded as the @emph{starting} working directory, rather than being left as
the empty path (which allows imports from the current working directory at
the time of the import)

@item 
bpo-33018@footnote{https://bugs.python.org/issue33018}: Improve consistency of errors raised by @code{issubclass()} when
called with a non-class and an abstract base class as the first and second
arguments, respectively. Patch by Josh Bronson.

@item 
bpo-33041@footnote{https://bugs.python.org/issue33041}: Fixed jumping when the function contains an @code{async for} loop.

@item 
bpo-33026@footnote{https://bugs.python.org/issue33026}: Fixed jumping out of "with" block by setting f_lineno.

@item 
bpo-33005@footnote{https://bugs.python.org/issue33005}: Fix a crash on fork when using a custom memory allocator (ex:
using PYTHONMALLOC env var). _PyGILState_Reinit() and
_PyInterpreterState_Enable() now use the default RAW memory allocator to
allocate a new interpreters mutex on fork.

@item 
bpo-17288@footnote{https://bugs.python.org/issue17288}: Prevent jumps from 'return' and 'exception' trace events.

@item 
bpo-32836@footnote{https://bugs.python.org/issue32836}: Don't use temporary variables in cases of list/dict/set
comprehensions
@end itemize

@node 库<25>,文档<20>,核心与内置<24>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id181}@anchor{1006}
@subsubsection 库



@itemize -

@item 
bpo-33141@footnote{https://bugs.python.org/issue33141}: Have Field objects pass through __set_name__ to their default
values, if they have their own __set_name__.

@item 
bpo-33096@footnote{https://bugs.python.org/issue33096}: Allow ttk.Treeview.insert to insert iid that has a false
boolean value. Note iid=0 and iid=False would be same. Patch by Garvit
Khatri.

@item 
bpo-32873@footnote{https://bugs.python.org/issue32873}: Treat type variables and special typing forms as immutable by
copy and pickle.  This fixes several minor issues and inconsistencies, and
improves backwards compatibility with Python 3.6.

@item 
bpo-33134@footnote{https://bugs.python.org/issue33134}: When computing dataclass's __hash__, use the lookup table to
contain the function which returns the __hash__ value.  This is an
improvement over looking up a string, and then testing that string to see
what to do.

@item 
bpo-33127@footnote{https://bugs.python.org/issue33127}: ssl模块现在使用LibreSSL 2.7.1编译。

@item 
bpo-32505@footnote{https://bugs.python.org/issue32505}: 如果数据类的成员变量的类型为Field，但没有类型注解，则引发TypeError。

@item 
bpo-33078@footnote{https://bugs.python.org/issue33078}: 修复在OSX平台因为依赖sem_getvalue而导致的失败。

@item 
bpo-33116@footnote{https://bugs.python.org/issue33116}: 将'Field'添加到dataclasses.__all__。

@item 
bpo-32896@footnote{https://bugs.python.org/issue32896}: Fix an error where subclassing a dataclass with a field that
uses a default_factory would generate an incorrect class.

@item 
bpo-33100@footnote{https://bugs.python.org/issue33100}: Dataclasses: If a field has a default value that's a
MemberDescriptorType, then it's from that field being in __slots__, not an
actual default value.

@item 
bpo-32953@footnote{https://bugs.python.org/issue32953}: If a non-dataclass inherits from a frozen dataclass, allow
attributes to be added to the derived class.  Only attributes from the
frozen dataclass cannot be assigned to.  Require all dataclasses in a
hierarchy to be either all frozen or all non-frozen.

@item 
bpo-33061@footnote{https://bugs.python.org/issue33061}: 添加丢失的 @code{NoReturn} 到typing.py的 @code{__all__}

@item 
bpo-33078@footnote{https://bugs.python.org/issue33078}: Fix the size handling in multiprocessing.Queue when a pickling
error occurs.

@item 
bpo-33064@footnote{https://bugs.python.org/issue33064}: lib2to3 now properly supports trailing commas after @code{*args}
and @code{**kwargs} in function signatures.

@item 
bpo-33056@footnote{https://bugs.python.org/issue33056}: FIX properly close leaking fds in
concurrent.futures.ProcessPoolExecutor.

@item 
bpo-33021@footnote{https://bugs.python.org/issue33021}: Release the GIL during fstat() calls, avoiding hang of all
threads when calling mmap.mmap(), os.urandom(), and random.seed().  Patch
by Nir Soffer.

@item 
bpo-31804@footnote{https://bugs.python.org/issue31804}: Avoid failing in multiprocessing.Process if the standard
streams are closed or None at exit.

@item 
bpo-33037@footnote{https://bugs.python.org/issue33037}: Skip sending/receiving data after SSL transport closing.

@item 
bpo-27683@footnote{https://bugs.python.org/issue27683}: Fix a regression in @ref{a2,,ipaddress} that result of
@code{hosts()} is empty when the network is constructed by a tuple
containing an integer mask and only 1 bit left for addresses.

@item 
bpo-32999@footnote{https://bugs.python.org/issue32999}: Fix C implementation of @code{ABC.__subclasscheck__(cls,
subclass)} crashed when @code{subclass} is not a type object.

@item 
bpo-33009@footnote{https://bugs.python.org/issue33009}: Fix inspect.signature() for single-parameter partialmethods.

@item 
bpo-32969@footnote{https://bugs.python.org/issue32969}: Expose several missing constants in zlib and fix corresponding
documentation.

@item 
bpo-32056@footnote{https://bugs.python.org/issue32056}: Improved exceptions raised for invalid number of channels and
sample width when read an audio file in modules @ref{5,,aifc}, @ref{127,,wave}
and @ref{fa,,sunau}.

@item 
bpo-32844@footnote{https://bugs.python.org/issue32844}: Fix wrong redirection of a low descriptor (0 or 1) to stderr in
subprocess if another low descriptor is closed.

@item 
bpo-32857@footnote{https://bugs.python.org/issue32857}: In @ref{10c,,tkinter}, @code{after_cancel(None)} now raises a
@ref{1fb,,ValueError} instead of canceling the first scheduled function.
Patch by Cheryl Sabella.

@item 
bpo-31639@footnote{https://bugs.python.org/issue31639}: http.server now exposes a ThreadedHTTPServer class and uses it
when the module is run with @code{-m} to cope with web browsers pre-opening
sockets.

@item 
bpo-27645@footnote{https://bugs.python.org/issue27645}: @ref{3d0,,sqlite3.Connection} now exposes a
@ref{3d1,,backup} method, if the underlying SQLite
library is at version 3.6.11 or higher.  Patch by Lele Gaifax.
@end itemize

@node 文档<20>,测试<18>,库<25>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id182}@anchor{1007}
@subsubsection 文档



@itemize -

@item 
bpo-33126@footnote{https://bugs.python.org/issue33126}: Document PyBuffer_ToContiguous().

@item 
bpo-27212@footnote{https://bugs.python.org/issue27212}: Modify documentation for the @code{islice()} recipe to consume
initial values up to the start index.

@item 
bpo-28247@footnote{https://bugs.python.org/issue28247}: Update @ref{141,,zipapp} documentation to describe how to make
standalone applications.

@item 
bpo-18802@footnote{https://bugs.python.org/issue18802}: Documentation changes for ipaddress.  Patch by Jon Foster and
Berker Peksag.

@item 
bpo-27428@footnote{https://bugs.python.org/issue27428}: Update documentation to clarify that @code{WindowsRegistryFinder}
implements @code{MetaPathFinder}. (Patch by Himanshu Lakhara)
@end itemize

@node 测试<18>,构建<17>,文档<20>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id183}@anchor{1008}
@subsubsection 测试



@itemize -

@item 
bpo-32872@footnote{https://bugs.python.org/issue32872}: Avoid regrtest compatibility issue with namespace packages.

@item 
bpo-32517@footnote{https://bugs.python.org/issue32517}: Fix failing @code{test_asyncio} on macOS 10.12.2+ due to transport
of @code{KqueueSelector} loop was not being closed.

@item 
bpo-19417@footnote{https://bugs.python.org/issue19417}: Add test_bdb.py.
@end itemize

@node 构建<17>,Windows<19>,测试<18>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id184}@anchor{1009}
@subsubsection 构建



@itemize -

@item 
bpo-33163@footnote{https://bugs.python.org/issue33163}: Upgrade pip to 9.0.3 and setuptools to v39.0.1.
@end itemize

@node Windows<19>,macOS<13>,构建<17>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id185}@anchor{100a}
@subsubsection Windows



@itemize -

@item 
bpo-33016@footnote{https://bugs.python.org/issue33016}: Fix potential use of uninitialized memory in
nt._getfinalpathname

@item 
bpo-32903@footnote{https://bugs.python.org/issue32903}: Fix a memory leak in os.chdir() on Windows if the current
directory is set to a UNC path.
@end itemize

@node macOS<13>,IDLE<25>,Windows<19>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id186}@anchor{100b}
@subsubsection macOS



@itemize -

@item 
bpo-32726@footnote{https://bugs.python.org/issue32726}: Build and link with private copy of Tcl/Tk 8.6 for the macOS
10.6+ installer. The 10.9+ installer variant already does this.  This
means that the Python 3.7 provided by the python.org macOS installers no
longer need or use any external versions of Tcl/Tk, either system-provided
or user-installed, such as ActiveTcl.
@end itemize

@node IDLE<25>,工具/示例<12>,macOS<13>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id187}@anchor{100c}
@subsubsection IDLE



@itemize -

@item 
bpo-32984@footnote{https://bugs.python.org/issue32984}: Set @code{__file__} while running a startup file.  Like Python,
IDLE optionally runs one startup file in the Shell window before
presenting the first interactive input prompt.  For IDLE, @code{-s} runs a
file named in environmental variable  
@geindex IDLESTARTUP
@geindex 环境变量; IDLESTARTUP
@code{IDLESTARTUP} or
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP}; @code{-r file} runs @code{file}.  Python sets
@code{__file__} to the startup file name before running the file and unsets
it before the first prompt.  IDLE now does the same when run normally,
without the @code{-n} option.

@item 
bpo-32940@footnote{https://bugs.python.org/issue32940}: Simplify and rename StringTranslatePseudoMapping in pyparse.
@end itemize

@node 工具/示例<12>,C API<13>,IDLE<25>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id188}@anchor{100d}
@subsubsection 工具/示例



@itemize -

@item 
bpo-32885@footnote{https://bugs.python.org/issue32885}: Add an @code{-n} flag for @code{Tools/scripts/pathfix.py} to disable
automatic backup creation (files with @code{~} suffix).
@end itemize

@node C API<13>,,工具/示例<12>,Python 3 7 0 beta 3
@anchor{whatsnew/changelog id189}@anchor{100e}
@subsubsection C API



@itemize -

@item 
bpo-33042@footnote{https://bugs.python.org/issue33042}: Embedding applications may once again call
PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to
calling Py_Initialize.

@item 
bpo-32374@footnote{https://bugs.python.org/issue32374}: Document that m_traverse for multi-phase initialized modules
can be called with m_state=NULL, and add a sanity check
@end itemize

@node Python 3 7 0 beta 2,Python 3 7 0 beta 1,Python 3 7 0 beta 3,更新日志
@anchor{whatsnew/changelog python-3-7-0-beta-2}@anchor{100f}
@subsection Python 3.7.0 beta 2


@emph{发布日期: 2018-02-27}

@menu
* 安全: 安全<17>. 
* 核心与内置: 核心与内置<25>. 
* 库: 库<26>. 
* 文档: 文档<21>. 
* 测试: 测试<19>. 
* 构建: 构建<18>. 
* Windows: Windows<20>. 
* macOS: macOS<14>. 
* IDLE: IDLE<26>. 
* 工具/示例: 工具/示例<13>. 

@end menu

@node 安全<17>,核心与内置<25>,,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id190}@anchor{1010}
@subsubsection 安全



@itemize -

@item 
bpo-28414@footnote{https://bugs.python.org/issue28414}: The ssl module now allows users to perform their own IDN
en/decoding when using SNI.
@end itemize

@node 核心与内置<25>,库<26>,安全<17>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id191}@anchor{1011}
@subsubsection 核心与内置



@itemize -

@item 
bpo-32889@footnote{https://bugs.python.org/issue32889}: Update Valgrind suppression list to account for the rename of
@code{Py_ADDRESS_IN_RANG} to @code{address_in_range}.

@item 
bpo-31356@footnote{https://bugs.python.org/issue31356}: Remove the new API added in bpo-31356@footnote{https://bugs.python.org/issue31356} (gc.ensure_disabled()
context manager).

@item 
bpo-32305@footnote{https://bugs.python.org/issue32305}: For namespace packages, ensure that both @code{__file__} and
@code{__spec__.origin} are set to None.

@item 
bpo-32303@footnote{https://bugs.python.org/issue32303}: Make sure @code{__spec__.loader} matches @code{__loader__} for
namespace packages.

@item 
bpo-32711@footnote{https://bugs.python.org/issue32711}: Fix the warning messages for Python/ast_unparse.c. Patch by
Stéphane Wirtel

@item 
bpo-32583@footnote{https://bugs.python.org/issue32583}: Fix possible crashing in builtin Unicode decoders caused by
write out-of-bound errors when using customized decode error handlers.
@end itemize

@node 库<26>,文档<21>,核心与内置<25>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id192}@anchor{1012}
@subsubsection 库



@itemize -

@item 
bpo-32960@footnote{https://bugs.python.org/issue32960}: For dataclasses, disallow inheriting frozen from non-frozen
classes, and also disallow inheriting non-frozen from frozen classes. This
restriction will be relaxed at a future date.

@item 
bpo-32713@footnote{https://bugs.python.org/issue32713}: Fixed tarfile.itn handling of out-of-bounds float values. Patch
by Joffrey Fuhrer.

@item 
bpo-32951@footnote{https://bugs.python.org/issue32951}: Direct instantiation of SSLSocket and SSLObject objects is now
prohibited. The constructors were never documented, tested, or designed as
public constructors. Users were suppose to use ssl.wrap_socket() or
SSLContext.

@item 
bpo-32929@footnote{https://bugs.python.org/issue32929}: Remove the tri-state parameter "hash", and add the boolean
"unsafe_hash". If unsafe_hash is True, add a __hash__ function, but if a
__hash__ exists, raise TypeError.  If unsafe_hash is False, add a __hash__
based on the values of eq= and frozen=.  The unsafe_hash=False behavior is
the same as the old hash=None behavior.  unsafe_hash=False is the default,
just as hash=None used to be.

@item 
bpo-32947@footnote{https://bugs.python.org/issue32947}: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3
for future compatibility with OpenSSL 1.1.1.

@item 
bpo-30622@footnote{https://bugs.python.org/issue30622}: The ssl module now detects missing NPN support in LibreSSL.

@item 
bpo-32922@footnote{https://bugs.python.org/issue32922}: dbm.open() now encodes filename with the filesystem encoding
rather than default encoding.

@item 
bpo-32859@footnote{https://bugs.python.org/issue32859}: In @code{os.dup2}, don't check every call whether the @code{dup3}
syscall exists or not.

@item 
bpo-32556@footnote{https://bugs.python.org/issue32556}: nt._getfinalpathname, nt._getvolumepathname and
nt._getdiskusage now correctly convert from bytes.

@item 
bpo-25988@footnote{https://bugs.python.org/issue25988}: Emit a @ref{278,,DeprecationWarning} when using or importing an ABC
directly from @ref{1e,,collections} rather than from @ref{1f,,collections.abc}.

@item 
bpo-21060@footnote{https://bugs.python.org/issue21060}: Rewrite confusing message from setup.py upload from "No dist
file created in earlier command" to the more helpful "Must create and
upload files in one command".

@item 
bpo-32852@footnote{https://bugs.python.org/issue32852}: Make sure sys.argv remains as a list when running trace.

@item 
bpo-31333@footnote{https://bugs.python.org/issue31333}: @code{_abc} module is added.  It is a speedup module with C
implementations for various functions and methods in @code{abc}.  Creating an
ABC subclass and calling @code{isinstance} or @code{issubclass} with an ABC
subclass are up to 1.5x faster. In addition, this makes Python start-up up
to 10% faster. Note that the new implementation hides internal registry
and caches, previously accessible via private attributes
@code{_abc_registry}, @code{_abc_cache}, and @code{_abc_negative_cache}.  There are
three debugging helper methods that can be used instead
@code{_dump_registry}, @code{_abc_registry_clear}, and @code{_abc_caches_clear}.

@item 
bpo-32841@footnote{https://bugs.python.org/issue32841}: Fixed @ref{28d,,asyncio.Condition} issue which silently ignored
cancellation after notifying and cancelling a conditional lock. Patch by
Bar Harel.

@item 
bpo-32819@footnote{https://bugs.python.org/issue32819}: ssl.match_hostname() has been simplified and no longer depends
on re and ipaddress module for wildcard and IP addresses. Error reporting
for invalid wildcards has been improved.

@item 
bpo-32394@footnote{https://bugs.python.org/issue32394}: socket: Remove
TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version
Windows during run-time.

@item 
bpo-31787@footnote{https://bugs.python.org/issue31787}: Fixed refleaks of @code{__init__()} methods in various modules.
(Contributed by Oren Milman)

@item 
bpo-30157@footnote{https://bugs.python.org/issue30157}: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when
only the last field is quoted.  Patch by Jake Davis.

@item 
bpo-32792@footnote{https://bugs.python.org/issue32792}: collections.ChainMap() preserves the order of the underlying
mappings.

@item 
bpo-32775@footnote{https://bugs.python.org/issue32775}: @ref{fd0,,fnmatch.translate()} no longer produces patterns which
contain set operations. Sets starting with '[' or containing '--', '&&',
'~~' or '||' will be interpreted differently in regular expressions in
future versions. Currently they emit warnings. fnmatch.translate() now
avoids producing patterns containing such sets by accident.

@item 
bpo-32622@footnote{https://bugs.python.org/issue32622}: Implement native fast sendfile for Windows proactor event loop.

@item 
bpo-32777@footnote{https://bugs.python.org/issue32777}: Fix a rare but potential pre-exec child process deadlock in
subprocess on POSIX systems when marking file descriptors inheritable on
exec in the child process.  This bug appears to have been introduced in
3.4.

@item 
bpo-32647@footnote{https://bugs.python.org/issue32647}: The ctypes module used to depend on indirect linking for
dlopen. The shared extension is now explicitly linked against libdl on
platforms with dl.

@item 
bpo-32741@footnote{https://bugs.python.org/issue32741}: Implement @code{asyncio.TimerHandle.when()} method.

@item 
bpo-32691@footnote{https://bugs.python.org/issue32691}: Use mod_spec.parent when running modules with pdb

@item 
bpo-32734@footnote{https://bugs.python.org/issue32734}: Fixed @code{asyncio.Lock()} safety issue which allowed acquiring
and locking the same lock multiple times, without it being free. Patch by
Bar Harel.

@item 
bpo-32727@footnote{https://bugs.python.org/issue32727}: Do not include name field in SMTP envelope from address. Patch
by Stéphane Wirtel

@item 
bpo-31453@footnote{https://bugs.python.org/issue31453}: Add TLSVersion constants and SSLContext.maximum_version /
minimum_version attributes. The new API wraps OpenSSL 1.1
@indicateurl{https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html}
feature.

@item 
bpo-24334@footnote{https://bugs.python.org/issue24334}: Internal implementation details of ssl module were cleaned up.
The SSLSocket has one less layer of indirection. Owner and session
information are now handled by the SSLSocket and SSLObject constructor.
Channel binding implementation has been simplified.

@item 
bpo-31848@footnote{https://bugs.python.org/issue31848}: Fix the error handling in Aifc_read.initfp() when the SSND
chunk is not found. Patch by Zackery Spytz.

@item 
bpo-32585@footnote{https://bugs.python.org/issue32585}: Add Ttk spinbox widget to @ref{10f,,tkinter.ttk}.  Patch by Alan D
Moore.

@item 
bpo-32221@footnote{https://bugs.python.org/issue32221}: Various functions returning tuple containing IPv6 addresses now
omit @code{%scope} part since the same information is already encoded in
@emph{scopeid} tuple item. Especially this speeds up @code{socket.recvfrom()}
when it receives multicast packet since useless resolving of network
interface name is omitted.

@item 
bpo-30693@footnote{https://bugs.python.org/issue30693}: The TarFile class now recurses directories in a reproducible
way.

@item 
bpo-30693@footnote{https://bugs.python.org/issue30693}: The ZipFile class now recurses directories in a reproducible
way.
@end itemize

@node 文档<21>,测试<19>,库<26>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id193}@anchor{1013}
@subsubsection 文档



@itemize -

@item 
bpo-28124@footnote{https://bugs.python.org/issue28124}: The ssl module function ssl.wrap_socket() has been
de-emphasized and deprecated in favor of the more secure and efficient
SSLContext.wrap_socket() method.

@item 
bpo-17232@footnote{https://bugs.python.org/issue17232}: Clarify docs for -O and -OO.  Patch by Terry Reedy.

@item 
bpo-32436@footnote{https://bugs.python.org/issue32436}: Add documentation for the contextvars module (PEP 567).

@item 
bpo-32800@footnote{https://bugs.python.org/issue32800}: Update link to w3c doc for xml default namespaces.

@item 
bpo-11015@footnote{https://bugs.python.org/issue11015}: Update @ref{106,,test.support} documentation.

@item 
bpo-8722@footnote{https://bugs.python.org/issue8722}: Document @ref{313,,__getattr__()} behavior when property @code{get()}
method raises @ref{393,,AttributeError}.

@item 
bpo-32614@footnote{https://bugs.python.org/issue32614}: Modify RE examples in documentation to use raw strings to
prevent @ref{278,,DeprecationWarning} and add text to REGEX HOWTO to highlight
the deprecation.

@item 
bpo-31972@footnote{https://bugs.python.org/issue31972}: Improve docstrings for @ref{fd4,,pathlib.PurePath} subclasses.
@end itemize

@node 测试<19>,构建<18>,文档<21>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id194}@anchor{1014}
@subsubsection 测试



@itemize -

@item 
bpo-31809@footnote{https://bugs.python.org/issue31809}: Add tests to verify connection with secp ECDH curves.
@end itemize

@node 构建<18>,Windows<20>,测试<19>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id195}@anchor{1015}
@subsubsection 构建



@itemize -

@item 
bpo-32898@footnote{https://bugs.python.org/issue32898}: Fix the python debug build when using COUNT_ALLOCS.
@end itemize

@node Windows<20>,macOS<14>,构建<18>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id196}@anchor{1016}
@subsubsection Windows



@itemize -

@item 
bpo-32901@footnote{https://bugs.python.org/issue32901}: Update Tcl and Tk versions to 8.6.8

@item 
bpo-31966@footnote{https://bugs.python.org/issue31966}: Fixed WindowsConsoleIO.write() for writing empty data.

@item 
bpo-32409@footnote{https://bugs.python.org/issue32409}: Ensures activate.bat can handle Unicode contents.

@item 
bpo-32457@footnote{https://bugs.python.org/issue32457}: Improves handling of denormalized executable path when
launching Python.

@item 
bpo-32370@footnote{https://bugs.python.org/issue32370}: Use the correct encoding for ipconfig output in the uuid
module. Patch by Segev Finer.

@item 
bpo-29248@footnote{https://bugs.python.org/issue29248}: Fix @ref{1f3,,os.readlink()} on Windows, which was mistakenly
treating the @code{PrintNameOffset} field of the reparse data buffer as a
number of characters instead of bytes. Patch by Craig Holmquist and SSE4.
@end itemize

@node macOS<14>,IDLE<26>,Windows<20>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id197}@anchor{1017}
@subsubsection macOS



@itemize -

@item 
bpo-32901@footnote{https://bugs.python.org/issue32901}: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.
@end itemize

@node IDLE<26>,工具/示例<13>,macOS<14>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id198}@anchor{1018}
@subsubsection IDLE



@itemize -

@item 
bpo-32916@footnote{https://bugs.python.org/issue32916}: Change @code{str} to @code{code} in pyparse.

@item 
bpo-32905@footnote{https://bugs.python.org/issue32905}: Remove unused code in pyparse module.

@item 
bpo-32874@footnote{https://bugs.python.org/issue32874}: Add tests for pyparse.

@item 
bpo-32837@footnote{https://bugs.python.org/issue32837}: Using the system and place-dependent default encoding for
open() is a bad idea for IDLE's system and location-independent files.

@item 
bpo-32826@footnote{https://bugs.python.org/issue32826}: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI
test test_file_buttons() only looks at initial ascii-only lines, but
failed on systems where open() defaults to 'ascii' because readline()
internally reads and decodes far enough ahead to encounter a non-ascii
character in CREDITS.txt.

@item 
bpo-32765@footnote{https://bugs.python.org/issue32765}: Update configdialog General tab docstring to add new widgets to
the widget list.
@end itemize

@node 工具/示例<13>,,IDLE<26>,Python 3 7 0 beta 2
@anchor{whatsnew/changelog id199}@anchor{1019}
@subsubsection 工具/示例



@itemize -

@item 
bpo-32222@footnote{https://bugs.python.org/issue32222}: Fix pygettext not extracting docstrings for functions with type
annotated arguments. Patch by Toby Harradine.
@end itemize

@node Python 3 7 0 beta 1,Python 3 7 0 alpha 4,Python 3 7 0 beta 2,更新日志
@anchor{whatsnew/changelog python-3-7-0-beta-1}@anchor{101a}
@subsection Python 3.7.0 beta 1


@emph{发布日期: 2018-01-30}

@menu
* 核心与内置: 核心与内置<26>. 
* 库: 库<27>. 
* 文档: 文档<22>. 
* 测试: 测试<20>. 
* 构建: 构建<19>. 
* Windows: Windows<21>. 
* macOS: macOS<15>. 
* C API: C API<14>. 

@end menu

@node 核心与内置<26>,库<27>,,Python 3 7 0 beta 1
@anchor{whatsnew/changelog id200}@anchor{101b}
@subsubsection 核心与内置



@itemize -

@item 
bpo-32703@footnote{https://bugs.python.org/issue32703}: Fix coroutine's ResourceWarning when there's an active error
set when it's being finalized.

@item 
bpo-32650@footnote{https://bugs.python.org/issue32650}: Pdb and other debuggers dependent on bdb.py will correctly step
over (next command) native coroutines. Patch by Pablo Galindo.

@item 
bpo-28685@footnote{https://bugs.python.org/issue28685}: Optimize list.sort() and sorted() by using type specialized
comparisons when possible.

@item 
bpo-32685@footnote{https://bugs.python.org/issue32685}: Improve suggestion when the Python 2 form of print statement is
either present on the same line as the header of a compound statement or
else terminated by a semi-colon instead of a newline. Patch by Nitish
Chandra.

@item 
bpo-32697@footnote{https://bugs.python.org/issue32697}: Python now explicitly preserves the definition order of
keyword-only parameters.  It's always preserved their order, but this
behavior was never guaranteed before; this behavior is now guaranteed and
tested.

@item 
bpo-32690@footnote{https://bugs.python.org/issue32690}: The locals() dictionary now displays in the lexical order that
variables were defined.  Previously, the order was reversed.

@item 
bpo-32677@footnote{https://bugs.python.org/issue32677}: Add @code{.isascii()} method to @code{str}, @code{bytes} and
@code{bytearray}. It can be used to test that string contains only ASCII
characters.

@item 
bpo-32670@footnote{https://bugs.python.org/issue32670}: Enforce 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479} for all code. This means that manually
raising a StopIteration exception from a generator is prohibited for all
code, regardless of whether 'from __future__ import generator_stop' was
used or not.

@item 
bpo-32591@footnote{https://bugs.python.org/issue32591}: Added built-in support for tracking the origin of coroutine
objects; see sys.set_coroutine_origin_tracking_depth and
CoroutineType.cr_origin. This replaces the asyncio debug mode's use of
coroutine wrapping for native coroutine objects.

@item 
bpo-31368@footnote{https://bugs.python.org/issue31368}: Expose preadv and pwritev system calls in the os module. Patch
by Pablo Galindo

@item 
bpo-32544@footnote{https://bugs.python.org/issue32544}: @code{hasattr(obj, name)} and @code{getattr(obj, name, default)} are
about 4 times faster than before when @code{name} is not found and @code{obj}
doesn't override @code{__getattr__} or @code{__getattribute__}.

@item 
bpo-26163@footnote{https://bugs.python.org/issue26163}: Improved frozenset() hash to create more distinct hash values
when faced with datasets containing many similar values.

@item 
bpo-32550@footnote{https://bugs.python.org/issue32550}: Remove the STORE_ANNOTATION bytecode.

@item 
bpo-20104@footnote{https://bugs.python.org/issue20104}: Expose posix_spawn as a low level API in the os module.
(removed before 3.7.0rc1)

@item 
bpo-24340@footnote{https://bugs.python.org/issue24340}: Fixed estimation of the code stack size.

@item 
bpo-32436@footnote{https://bugs.python.org/issue32436}: Implement 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} Context Variables.

@item 
bpo-18533@footnote{https://bugs.python.org/issue18533}: @code{repr()} on a dict containing its own @code{values()} or
@code{items()} no longer raises @code{RecursionError}; OrderedDict similarly.
Instead, use @code{...}, as for other recursive structures.  Patch by Ben
North.

@item 
bpo-20891@footnote{https://bugs.python.org/issue20891}: Py_Initialize() now creates the GIL. The GIL is no longer
created "on demand" to fix a race condition when PyGILState_Ensure() is
called in a non-Python thread.

@item 
bpo-32028@footnote{https://bugs.python.org/issue32028}: Leading whitespace is now correctly ignored when generating
suggestions for converting Py2 print statements to Py3 builtin print
function calls. Patch by Sanyam Khurana.

@item 
bpo-31179@footnote{https://bugs.python.org/issue31179}: Make dict.copy() up to 5.5 times faster.

@item 
bpo-31113@footnote{https://bugs.python.org/issue31113}: Get rid of recursion in the compiler for normal control flow.
@end itemize

@node 库<27>,文档<22>,核心与内置<26>,Python 3 7 0 beta 1
@anchor{whatsnew/changelog id201}@anchor{101c}
@subsubsection 库



@itemize -

@item 
bpo-25988@footnote{https://bugs.python.org/issue25988}: Deprecate exposing the contents of collections.abc in the
regular collections module.

@item 
bpo-31429@footnote{https://bugs.python.org/issue31429}: The default cipher suite selection of the ssl module now uses a
blacklist approach rather than a hard-coded whitelist. Python no longer
re-enables ciphers that have been blocked by OpenSSL security update.
Default cipher suite selection can be configured on compile time.

@item 
bpo-30306@footnote{https://bugs.python.org/issue30306}: contextlib.contextmanager now releases the arguments passed to
the underlying generator as soon as the context manager is entered.
Previously it would keep them alive for as long as the context manager was
alive, even when not being used as a function decorator. Patch by Martin
Teichmann.

@item 
bpo-21417@footnote{https://bugs.python.org/issue21417}: Added support for setting the compression level for
zipfile.ZipFile.

@item 
bpo-32251@footnote{https://bugs.python.org/issue32251}: Implement asyncio.BufferedProtocol (provisional API).

@item 
bpo-32513@footnote{https://bugs.python.org/issue32513}: In dataclasses, allow easier overriding of dunder methods
without specifying decorator parameters.

@item 
bpo-32660@footnote{https://bugs.python.org/issue32660}: @ref{104,,termios} makes available @code{FIONREAD}, @code{FIONCLEX},
@code{FIOCLEX}, @code{FIOASYNC} and @code{FIONBIO} also under Solaris/derivatives.

@item 
bpo-27931@footnote{https://bugs.python.org/issue27931}: Fix email address header parsing error when the username is an
empty quoted string. Patch by Xiang Zhang.

@item 
bpo-32659@footnote{https://bugs.python.org/issue32659}: Under Solaris and derivatives, @ref{101d,,os.stat_result} provides
a st_fstype attribute.

@item 
bpo-32662@footnote{https://bugs.python.org/issue32662}: Implement Server.start_serving(), Server.serve_forever(), and
Server.is_serving() methods.  Add 'start_serving' keyword parameter to
loop.create_server() and loop.create_unix_server().

@item 
bpo-32391@footnote{https://bugs.python.org/issue32391}: Implement @ref{34f,,asyncio.StreamWriter.wait_closed()} and
@ref{350,,asyncio.StreamWriter.is_closing()} methods

@item 
bpo-32643@footnote{https://bugs.python.org/issue32643}: Make Task._step, Task._wakeup and Future._schedule_callbacks
methods private.

@item 
bpo-32630@footnote{https://bugs.python.org/issue32630}: Refactor decimal module to use contextvars to store decimal
context.

@item 
bpo-32622@footnote{https://bugs.python.org/issue32622}: Add @code{asyncio.AbstractEventLoop.sendfile()} method.

@item 
bpo-32304@footnote{https://bugs.python.org/issue32304}: distutils' upload command no longer corrupts tar files ending
with a CR byte, and no longer tries to convert CR to CRLF in any of the
upload text fields.

@item 
bpo-32502@footnote{https://bugs.python.org/issue32502}: uuid.uuid1 no longer raises an exception if a 64-bit hardware
address is encountered.

@item 
bpo-32596@footnote{https://bugs.python.org/issue32596}: @code{concurrent.futures} imports @code{ThreadPoolExecutor} and
@code{ProcessPoolExecutor} lazily (using 
@geindex Python 提高建议; PEP 562
PEP 562@footnote{https://www.python.org/dev/peps/pep-0562}). It makes @code{import
asyncio} about 15% faster because asyncio uses only
@code{ThreadPoolExecutor} by default.

@item 
bpo-31801@footnote{https://bugs.python.org/issue31801}: Add @code{_ignore_} to @code{Enum} so temporary variables can be used
during class construction without being turned into members.

@item 
bpo-32576@footnote{https://bugs.python.org/issue32576}: Use queue.SimpleQueue() in places where it can be invoked from
a weakref callback.

@item 
bpo-32574@footnote{https://bugs.python.org/issue32574}: Fix memory leak in asyncio.Queue, when the queue has limited
size and it is full, the cancelation of queue.put() can cause a memory
leak. Patch by: José Melero.

@item 
bpo-32521@footnote{https://bugs.python.org/issue32521}: The nis module is now compatible with new libnsl and headers
location.

@item 
bpo-32467@footnote{https://bugs.python.org/issue32467}: collections.abc.ValuesView now inherits from
collections.abc.Collection.

@item 
bpo-32473@footnote{https://bugs.python.org/issue32473}: Improve ABCMeta._dump_registry() output readability

@item 
bpo-32102@footnote{https://bugs.python.org/issue32102}: New argument @code{capture_output} for subprocess.run

@item 
bpo-32521@footnote{https://bugs.python.org/issue32521}: glibc has removed Sun RPC. Use replacement libtirpc headers and
library in nis module.

@item 
bpo-32493@footnote{https://bugs.python.org/issue32493}: UUID module fixes build for FreeBSD/OpenBSD

@item 
bpo-32503@footnote{https://bugs.python.org/issue32503}: Pickling with protocol 4 no longer creates too small frames.

@item 
bpo-29237@footnote{https://bugs.python.org/issue29237}: Create enum for pstats sorting options

@item 
bpo-32454@footnote{https://bugs.python.org/issue32454}: Add close(fd) function to the socket module.

@item 
bpo-25942@footnote{https://bugs.python.org/issue25942}: The subprocess module is now more graceful when handling a
Ctrl-C KeyboardInterrupt during subprocess.call, subprocess.run, or a
Popen context manager.  It now waits a short amount of time for the child
(presumed to have also gotten the SIGINT) to exit, before continuing the
KeyboardInterrupt exception handling.  This still includes a SIGKILL in
the call() and run() APIs, but at least the child had a chance first.

@item 
bpo-32433@footnote{https://bugs.python.org/issue32433}: The hmac module now has hmac.digest(), which provides an
optimized HMAC digest.

@item 
bpo-28134@footnote{https://bugs.python.org/issue28134}: Sockets now auto-detect family, type and protocol from file
descriptor by default.

@item 
bpo-32404@footnote{https://bugs.python.org/issue32404}: Fix bug where @ref{101e,,datetime.datetime.fromtimestamp()} did not
call __new__ in @ref{194,,datetime.datetime} subclasses.

@item 
bpo-32403@footnote{https://bugs.python.org/issue32403}: Improved speed of @ref{193,,datetime.date} and
@ref{194,,datetime.datetime} alternate constructors.

@item 
bpo-32228@footnote{https://bugs.python.org/issue32228}: Ensure that @code{truncate()} preserves the file position (as
reported by @code{tell()}) after writes longer than the buffer size.

@item 
bpo-32410@footnote{https://bugs.python.org/issue32410}: Implement @code{loop.sock_sendfile} for asyncio event loop.

@item 
bpo-22908@footnote{https://bugs.python.org/issue22908}: Added seek and tell to the ZipExtFile class. This only works if
the file object used to open the zipfile is seekable.

@item 
bpo-32373@footnote{https://bugs.python.org/issue32373}: Add socket.getblocking() method.

@item 
bpo-32248@footnote{https://bugs.python.org/issue32248}: Add @ref{9e,,importlib.resources} and
@ref{33b,,importlib.abc.ResourceReader} as the unified API for reading
resources contained within packages.  Loaders wishing to support resource
reading must implement the @code{get_resource_reader()} method.
File-based and zipimport-based loaders both implement these APIs.
@ref{460,,importlib.abc.ResourceLoader} is deprecated in favor of these new
APIs.

@item 
bpo-32320@footnote{https://bugs.python.org/issue32320}: collections.namedtuple() now supports default values.

@item 
bpo-29302@footnote{https://bugs.python.org/issue29302}: Add contextlib.AsyncExitStack. Patch by Alexander Mohr and Ilya
Kulakov.

@item 
bpo-31961@footnote{https://bugs.python.org/issue31961}: @emph{Removed in Python 3.7.0b2.} The @emph{args} argument of
subprocess.Popen can now be a @ref{363,,path-like object}. If @emph{args} is given
as a sequence, it's first element can now be a @ref{363,,path-like object} as
well.

@item 
bpo-31900@footnote{https://bugs.python.org/issue31900}: The @ref{484,,locale.localeconv()} function now sets temporarily the
@code{LC_CTYPE} locale to the @code{LC_NUMERIC} locale to decode
@code{decimal_point} and @code{thousands_sep} byte strings if they are non-ASCII
or longer than 1 byte, and the @code{LC_NUMERIC} locale is different than the
@code{LC_CTYPE} locale. This temporary change affects other threads. Same
change for the @ref{4d4,,str.format()} method when formatting a number
(@ref{184,,int}, @ref{187,,float}, @ref{187,,float} and subclasses) with the
@code{n} type (ex: @code{'@{:n@}'.format(1234)}).

@item 
bpo-31853@footnote{https://bugs.python.org/issue31853}: Use super().method instead of socket.method in SSLSocket.  They
were there most likely for legacy reasons.

@item 
bpo-31399@footnote{https://bugs.python.org/issue31399}: The ssl module now uses OpenSSL's X509_VERIFY_PARAM_set1_host()
and X509_VERIFY_PARAM_set1_ip() API to verify hostname and IP addresses.
Subject common name fallback can be disabled with
SSLContext.hostname_checks_common_name.

@item 
bpo-14976@footnote{https://bugs.python.org/issue14976}: Add a queue.SimpleQueue class, an unbounded FIFO queue with a
reentrant C implementation of put().
@end itemize

@node 文档<22>,测试<20>,库<27>,Python 3 7 0 beta 1
@anchor{whatsnew/changelog id202}@anchor{101f}
@subsubsection 文档



@itemize -

@item 
bpo-32724@footnote{https://bugs.python.org/issue32724}: Add references to some commands in the documentation of Pdb.
Patch by Stéphane Wirtel

@item 
bpo-32649@footnote{https://bugs.python.org/issue32649}: Complete the C API documentation, profiling and tracing part
with the newly added per-opcode events.

@item 
bpo-17799@footnote{https://bugs.python.org/issue17799}: Explain real behaviour of sys.settrace and sys.setprofile and
their C-API counterparts regarding which type of events are received in
each function. Patch by Pablo Galindo Salgado.
@end itemize

@node 测试<20>,构建<19>,文档<22>,Python 3 7 0 beta 1
@anchor{whatsnew/changelog id203}@anchor{1020}
@subsubsection 测试



@itemize -

@item 
bpo-32721@footnote{https://bugs.python.org/issue32721}: Fix test_hashlib to not fail if the _md5 module is not built.

@item 
bpo-28414@footnote{https://bugs.python.org/issue28414}: Add test cases for IDNA 2003 and 2008 host names. IDNA 2003
internationalized host names are working since bpo-31399@footnote{https://bugs.python.org/issue31399} has landed. IDNA
2008 are still broken.

@item 
bpo-32604@footnote{https://bugs.python.org/issue32604}: Add a new "_xxsubinterpreters" extension module that exposes
the existing subinterpreter C-API and a new cross-interpreter data sharing
mechanism. The module is primarily intended for more thorough testing of
the existing subinterpreter support. Note that the _xxsubinterpreters
module has been removed in 3.7.0rc1.

@item 
bpo-32602@footnote{https://bugs.python.org/issue32602}: Add test certs and test for ECDSA cert and EC/RSA dual mode.

@item 
bpo-32549@footnote{https://bugs.python.org/issue32549}: On Travis CI, Python now Compiles and uses a local copy of
OpenSSL 1.1.0g for testing.
@end itemize

@node 构建<19>,Windows<21>,测试<20>,Python 3 7 0 beta 1
@anchor{whatsnew/changelog id204}@anchor{1021}
@subsubsection 构建



@itemize -

@item 
bpo-32635@footnote{https://bugs.python.org/issue32635}: Fix segfault of the crypt module when libxcrypt is provided
instead of libcrypt at the system.

@item 
bpo-32598@footnote{https://bugs.python.org/issue32598}: Use autoconf to detect OpenSSL libs, headers and supported
features. The ax_check_openssl M4 macro uses pkg-config to locate OpenSSL
and falls back to manual search.

@item 
bpo-32593@footnote{https://bugs.python.org/issue32593}: 放弃对 FreeBSD 9 及更早版本的支持。

@item 
bpo-29708@footnote{https://bugs.python.org/issue29708}: If the 
@geindex SOURCE_DATE_EPOCH
@geindex 环境变量; SOURCE_DATE_EPOCH
@code{SOURCE_DATE_EPOCH} environment variable is set,
@ref{d7,,py_compile} will always create hash-based @code{.pyc} files.
@end itemize

@node Windows<21>,macOS<15>,构建<19>,Python 3 7 0 beta 1
@anchor{whatsnew/changelog id205}@anchor{1022}
@subsubsection Windows



@itemize -

@item 
bpo-32588@footnote{https://bugs.python.org/issue32588}: Create standalone _distutils_findvs module and add missing
_queue module to installer.

@item 
bpo-29911@footnote{https://bugs.python.org/issue29911}: Ensure separate Modify and Uninstall buttons are displayed.

@item 
bpo-32507@footnote{https://bugs.python.org/issue32507}: Use app-local UCRT install rather than the proper update for
old versions of Windows.
@end itemize

@node macOS<15>,C API<14>,Windows<21>,Python 3 7 0 beta 1
@anchor{whatsnew/changelog id206}@anchor{1023}
@subsubsection macOS



@itemize -

@item 
bpo-32726@footnote{https://bugs.python.org/issue32726}: Provide an additional, more modern macOS installer variant that
supports macOS 10.9+ systems in 64-bit mode only.  Upgrade the supplied
third-party libraries to OpenSSL 1.1.0g and to SQLite 3.22.0.  The 10.9+
installer now links with and supplies its own copy of Tcl/Tk 8.6.

@item 
bpo-28440@footnote{https://bugs.python.org/issue28440}: No longer add /Library/Python/3.x/site-packages to sys.path for
macOS framework builds to avoid future conflicts.
@end itemize

@node C API<14>,,macOS<15>,Python 3 7 0 beta 1
@anchor{whatsnew/changelog id207}@anchor{1024}
@subsubsection C API



@itemize -

@item 
bpo-32681@footnote{https://bugs.python.org/issue32681}: Fix uninitialized variable 'res' in the C implementation of
os.dup2. Patch by Stéphane Wirtel

@item 
bpo-10381@footnote{https://bugs.python.org/issue10381}: Add C API access to the @code{datetime.timezone} constructor and
@code{datetime.timzone.UTC} singleton.
@end itemize

@node Python 3 7 0 alpha 4,Python 3 7 0 alpha 3,Python 3 7 0 beta 1,更新日志
@anchor{whatsnew/changelog python-3-7-0-alpha-4}@anchor{1025}
@subsection Python 3.7.0 alpha 4


@emph{发布日期: 2018-01-08}

@menu
* 核心与内置: 核心与内置<27>. 
* 库: 库<28>. 
* 文档: 文档<23>. 
* 测试: 测试<21>. 
* Windows: Windows<22>. 
* 工具/示例: 工具/示例<14>. 
* C API: C API<15>. 

@end menu

@node 核心与内置<27>,库<28>,,Python 3 7 0 alpha 4
@anchor{whatsnew/changelog id208}@anchor{1026}
@subsubsection 核心与内置



@itemize -

@item 
bpo-31975@footnote{https://bugs.python.org/issue31975}: The default warning filter list now starts with a
"default::DeprecationWarning:__main__" entry, so deprecation warnings are
once again shown by default in single-file scripts and at the interactive
prompt.

@item 
bpo-32226@footnote{https://bugs.python.org/issue32226}: @code{__class_getitem__} is now an automatic class method.

@item 
bpo-32399@footnote{https://bugs.python.org/issue32399}: Add AIX uuid library support for RFC4122 using uuid_create() in
libc.a

@item 
bpo-32390@footnote{https://bugs.python.org/issue32390}: Fix the compilation failure on AIX after the f_fsid field has
been added to the object returned by os.statvfs() (bpo-32143@footnote{https://bugs.python.org/issue32143}). Original
patch by Michael Felt.

@item 
bpo-32379@footnote{https://bugs.python.org/issue32379}: Make MRO computation faster when a class inherits from a single
base.

@item 
bpo-32259@footnote{https://bugs.python.org/issue32259}: The error message of a TypeError raised when unpack
non-iterable is now more specific.

@item 
bpo-27169@footnote{https://bugs.python.org/issue27169}: The @code{__debug__} constant is now optimized out at compile
time. This fixes also bpo-22091@footnote{https://bugs.python.org/issue22091}.

@item 
bpo-32329@footnote{https://bugs.python.org/issue32329}: The @ref{1027,,-R} option now turns on hash randomization when
the 
@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED} environment variable is set to @code{0}.
Previously, the option was ignored. Moreover,
@code{sys.flags.hash_randomization} is now properly set to 0 when hash
randomization is turned off by @code{PYTHONHASHSEED=0}.

@item 
bpo-30416@footnote{https://bugs.python.org/issue30416}: The optimizer is now protected from spending much time doing
complex calculations and consuming much memory for creating large
constants in constant folding. Increased limits for constants that can be
produced in constant folding.

@item 
bpo-32282@footnote{https://bugs.python.org/issue32282}: Fix an unnecessary ifdef in the include of VersionHelpers.h in
socketmodule on Windows.

@item 
bpo-30579@footnote{https://bugs.python.org/issue30579}: Implement TracebackType.__new__ to allow Python-level creation
of traceback objects, and make TracebackType.tb_next mutable.

@item 
bpo-32260@footnote{https://bugs.python.org/issue32260}: Don't byte swap the input keys to the SipHash algorithm on
big-endian platforms. This should ensure siphash gives consistent results
across platforms.

@item 
bpo-31506@footnote{https://bugs.python.org/issue31506}: Improve the error message logic for object.__new__ and
object.__init__. Patch by Sanyam Khurana.

@item 
bpo-20361@footnote{https://bugs.python.org/issue20361}: @code{-b} and @code{-bb} now inject @code{'default::BytesWarning'} and
@code{error::BytesWarning} entries into @code{sys.warnoptions}, ensuring that
they take precedence over any other warning filters configured via the
@code{-W} option or the @code{PYTHONWARNINGS} environment variable.

@item 
bpo-32230@footnote{https://bugs.python.org/issue32230}: @code{-X dev} now injects a @code{'default'} entry into
sys.warnoptions, ensuring that it behaves identically to actually passing
@code{-Wdefault} at the command line.

@item 
bpo-29240@footnote{https://bugs.python.org/issue29240}: Add a new UTF-8 mode: implementation of the 
@geindex Python 提高建议; PEP 540
PEP 540@footnote{https://www.python.org/dev/peps/pep-0540}.

@item 
bpo-32226@footnote{https://bugs.python.org/issue32226}: 
@geindex Python 提高建议; PEP 560
PEP 560@footnote{https://www.python.org/dev/peps/pep-0560}: Add support for @code{__mro_entries__} and
@code{__class_getitem__}. Implemented by Ivan Levkivskyi.

@item 
bpo-32225@footnote{https://bugs.python.org/issue32225}: 
@geindex Python 提高建议; PEP 562
PEP 562@footnote{https://www.python.org/dev/peps/pep-0562}: Add support for module @code{__getattr__} and
@code{__dir__}. Implemented by Ivan Levkivskyi.

@item 
bpo-31901@footnote{https://bugs.python.org/issue31901}: The @ref{c,,atexit} module now has its callback stored per
interpreter.

@item 
bpo-31650@footnote{https://bugs.python.org/issue31650}: Implement 
@geindex Python 提高建议; PEP 552
PEP 552@footnote{https://www.python.org/dev/peps/pep-0552} (Deterministic pycs). Python now supports
invalidating bytecode cache files bashed on a source content hash rather
than source last-modified time.

@item 
bpo-29469@footnote{https://bugs.python.org/issue29469}: Move constant folding from bytecode layer to AST layer.
Original patch by Eugene Toder.
@end itemize

@node 库<28>,文档<23>,核心与内置<27>,Python 3 7 0 alpha 4
@anchor{whatsnew/changelog id209}@anchor{1028}
@subsubsection 库



@itemize -

@item 
bpo-32506@footnote{https://bugs.python.org/issue32506}: Now that dict is defined as keeping insertion order, drop
OrderedDict and just use plain dict.

@item 
bpo-32279@footnote{https://bugs.python.org/issue32279}: Add params to dataclasses.make_dataclasses(): init, repr, eq,
order, hash, and frozen.  Pass them through to dataclass().

@item 
bpo-32278@footnote{https://bugs.python.org/issue32278}: Make type information optional on dataclasses.make_dataclass().
If omitted, the string 'typing.Any' is used.

@item 
bpo-32499@footnote{https://bugs.python.org/issue32499}: Add dataclasses.is_dataclass(obj), which returns True if obj is
a dataclass or an instance of one.

@item 
bpo-32468@footnote{https://bugs.python.org/issue32468}: Improve frame repr() to mention filename, code name and current
line number.

@item 
bpo-23749@footnote{https://bugs.python.org/issue23749}: asyncio: Implement loop.start_tls()

@item 
bpo-32441@footnote{https://bugs.python.org/issue32441}: Return the new file descriptor (i.e., the second argument) from
@code{os.dup2}. Previously, @code{None} was always returned.

@item 
bpo-32422@footnote{https://bugs.python.org/issue32422}: @code{functools.lru_cache} uses less memory (3 words for each
cached key) and takes about 1/3 time for cyclic GC.

@item 
bpo-31721@footnote{https://bugs.python.org/issue31721}: Prevent Python crash from happening when Future._log_traceback
is set to True manually.  Now it can only be set to False, or a ValueError
is raised.

@item 
bpo-32415@footnote{https://bugs.python.org/issue32415}: asyncio: Add Task.get_loop() and Future.get_loop()

@item 
bpo-26133@footnote{https://bugs.python.org/issue26133}: Don't unsubscribe signals in asyncio UNIX event loop on
interpreter shutdown.

@item 
bpo-32363@footnote{https://bugs.python.org/issue32363}: Make asyncio.Task.set_exception() and set_result() raise
NotImplementedError. Task._step() and Future.__await__() raise proper
exceptions when they are in an invalid state, instead of raising an
AssertionError.

@item 
bpo-32357@footnote{https://bugs.python.org/issue32357}: Optimize asyncio.iscoroutine() and loop.create_task() for
non-native coroutines (e.g. async/await compiled with Cython).
'loop.create_task(python_coroutine)' used to be 20% faster than
'loop.create_task(cython_coroutine)'.  Now, the latter is as fast.

@item 
bpo-32356@footnote{https://bugs.python.org/issue32356}: asyncio.transport.resume_reading() and pause_reading() are now
idempotent. New transport.is_reading() method is added.

@item 
bpo-32355@footnote{https://bugs.python.org/issue32355}: Optimize asyncio.gather(); now up to 15% faster.

@item 
bpo-32351@footnote{https://bugs.python.org/issue32351}: Use fastpath in asyncio.sleep if delay<0 (2x boost)

@item 
bpo-32348@footnote{https://bugs.python.org/issue32348}: Optimize asyncio.Future schedule/add/remove callback.  The
optimization shows 3-6% performance improvements of async/await code.

@item 
bpo-32331@footnote{https://bugs.python.org/issue32331}: Fix socket.settimeout() and socket.setblocking() to keep
socket.type as is. Fix socket.socket() constructor to reset any bit flags
applied to socket's type.  This change only affects OSes that have
SOCK_NONBLOCK and/or SOCK_CLOEXEC.

@item 
bpo-32248@footnote{https://bugs.python.org/issue32248}: Add @ref{33b,,importlib.abc.ResourceReader} as an ABC for loaders
to provide a unified API for reading resources contained within packages.
Also add @ref{9e,,importlib.resources} as the port of
@code{importlib_resources}.

@item 
bpo-32311@footnote{https://bugs.python.org/issue32311}: Implement asyncio.create_task(coro) shortcut

@item 
bpo-32327@footnote{https://bugs.python.org/issue32327}: Convert asyncio functions that were documented as coroutines to
coroutines. Affected functions: loop.sock_sendall, loop.sock_recv,
loop.sock_accept, loop.getaddrinfo, loop.getnameinfo.

@item 
bpo-32323@footnote{https://bugs.python.org/issue32323}: @ref{5f4,,urllib.parse.urlsplit()} does not convert zone-id
(scope) to lower case for scoped IPv6 addresses in hostnames now.

@item 
bpo-32302@footnote{https://bugs.python.org/issue32302}: Fix bdist_wininst of distutils for CRT v142: it binary
compatible with CRT v140.

@item 
bpo-29711@footnote{https://bugs.python.org/issue29711}: Fix @code{stop_serving} in asyncio proactor loop kill all
listening servers

@item 
bpo-32308@footnote{https://bugs.python.org/issue32308}: @ref{475,,re.sub()} now replaces empty matches adjacent to a
previous non-empty match.

@item 
bpo-29970@footnote{https://bugs.python.org/issue29970}: Abort asyncio SSLProtocol connection if handshake not complete
within 10s

@item 
bpo-32314@footnote{https://bugs.python.org/issue32314}: Implement asyncio.run().

@item 
bpo-17852@footnote{https://bugs.python.org/issue17852}: Revert incorrect fix based on misunderstanding of
_Py_PyAtExit() semantics.

@item 
bpo-32296@footnote{https://bugs.python.org/issue32296}: Implement asyncio._get_running_loop() and get_event_loop() in
C. This makes them 4x faster.

@item 
bpo-32250@footnote{https://bugs.python.org/issue32250}: Implement @code{asyncio.current_task()} and
@code{asyncio.all_tasks()}. Add helpers intended to be used by alternative
task implementations: @code{asyncio._register_task}, @code{asyncio._enter_task},
@code{asyncio._leave_task} and @code{asyncio._unregister_task}. Deprecate
@code{asyncio.Task.current_task()} and @code{asyncio.Task.all_tasks()}.

@item 
bpo-32255@footnote{https://bugs.python.org/issue32255}: A single empty field is now always quoted when written into a
CSV file. This allows to distinguish an empty row from a row consisting of
a single empty field. Patch by Licht Takeuchi.

@item 
bpo-32277@footnote{https://bugs.python.org/issue32277}: Raise @code{NotImplementedError} instead of @code{SystemError} on
platforms where @code{chmod(..., follow_symlinks=False)} is not supported.
Patch by Anthony Sottile.

@item 
bpo-30050@footnote{https://bugs.python.org/issue30050}: New argument warn_on_full_buffer to signal.set_wakeup_fd lets
you control whether Python prints a warning on stderr when the wakeup fd
buffer overflows.

@item 
bpo-29137@footnote{https://bugs.python.org/issue29137}: The @code{fpectl} library has been removed. It was never enabled
by default, never worked correctly on x86-64, and it changed the Python
ABI in ways that caused unexpected breakage of C extensions.

@item 
bpo-32273@footnote{https://bugs.python.org/issue32273}: Move asyncio.test_utils to test.test_asyncio.

@item 
bpo-32272@footnote{https://bugs.python.org/issue32272}: Remove asyncio.async() function.

@item 
bpo-32269@footnote{https://bugs.python.org/issue32269}: Add asyncio.get_running_loop() function.

@item 
bpo-32265@footnote{https://bugs.python.org/issue32265}: All class and static methods of builtin types now are correctly
classified by inspect.classify_class_attrs() and grouped in pydoc ouput.
Added types.ClassMethodDescriptorType for unbound class methods of builtin
types.

@item 
bpo-32253@footnote{https://bugs.python.org/issue32253}: Deprecate @code{yield from lock}, @code{await lock}, @code{with (yield
from lock)} and @code{with await lock} for asyncio synchronization
primitives.

@item 
bpo-22589@footnote{https://bugs.python.org/issue22589}: Changed MIME type of .bmp from 'image/x-ms-bmp' to 'image/bmp'

@item 
bpo-32193@footnote{https://bugs.python.org/issue32193}: Convert asyncio to use @emph{async/await} syntax. Old styled @code{yield
from} is still supported too.

@item 
bpo-32206@footnote{https://bugs.python.org/issue32206}: Add support to run modules with pdb

@item 
bpo-32227@footnote{https://bugs.python.org/issue32227}: @code{functools.singledispatch} now supports registering
implementations using type annotations.

@item 
bpo-15873@footnote{https://bugs.python.org/issue15873}: Added new alternate constructors
@ref{377,,datetime.datetime.fromisoformat()},
@ref{1029,,datetime.time.fromisoformat()} and
@ref{102a,,datetime.date.fromisoformat()} as the inverse operation of each
classes's respective @code{isoformat} methods.

@item 
bpo-32199@footnote{https://bugs.python.org/issue32199}: The getnode() ip getter now uses 'ip link' instead of 'ip link
list'.

@item 
bpo-32143@footnote{https://bugs.python.org/issue32143}: os.statvfs() includes the f_fsid field from statvfs(2)

@item 
bpo-26439@footnote{https://bugs.python.org/issue26439}: Fix ctypes.util.find_library() for AIX by implementing
ctypes._aix.find_library() Patch by: Michael Felt

@item 
bpo-31993@footnote{https://bugs.python.org/issue31993}: The pickler now uses less memory when serializing large bytes
and str objects into a file.  Pickles created with protocol 4 will require
less memory for unpickling large bytes and str objects.

@item 
bpo-27456@footnote{https://bugs.python.org/issue27456}: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

@item 
bpo-31778@footnote{https://bugs.python.org/issue31778}: ast.literal_eval() is now more strict. Addition and subtraction
of arbitrary numbers no longer allowed.

@item 
bpo-31802@footnote{https://bugs.python.org/issue31802}: Importing native path module (@code{posixpath}, @code{ntpath}) now
works even if the @code{os} module still is not imported.

@item 
bpo-30241@footnote{https://bugs.python.org/issue30241}: Add contextlib.AbstractAsyncContextManager. Patch by Jelle
Zijlstra.

@item 
bpo-31699@footnote{https://bugs.python.org/issue31699}: Fix deadlocks in
@ref{2a3,,concurrent.futures.ProcessPoolExecutor} when task arguments or
results cause pickling or unpickling errors. This should make sure that
calls to the @code{ProcessPoolExecutor} API always eventually return.

@item 
bpo-15216@footnote{https://bugs.python.org/issue15216}: @code{TextIOWrapper.reconfigure()} supports changing @emph{encoding},
@emph{errors}, and @emph{newline}.
@end itemize

@node 文档<23>,测试<21>,库<28>,Python 3 7 0 alpha 4
@anchor{whatsnew/changelog id210}@anchor{102b}
@subsubsection 文档



@itemize -

@item 
bpo-32418@footnote{https://bugs.python.org/issue32418}: Add get_loop() method to Server and AbstractServer classes.
@end itemize

@node 测试<21>,Windows<22>,文档<23>,Python 3 7 0 alpha 4
@anchor{whatsnew/changelog id211}@anchor{102c}
@subsubsection 测试



@itemize -

@item 
bpo-32252@footnote{https://bugs.python.org/issue32252}: Fix faulthandler_suppress_crash_report() used to prevent core
dump files when testing crashes. getrlimit() returns zero on success.

@item 
bpo-32002@footnote{https://bugs.python.org/issue32002}: Adjust C locale coercion testing for the empty locale and POSIX
locale cases to more readily adjust to platform dependent behaviour.
@end itemize

@node Windows<22>,工具/示例<14>,测试<21>,Python 3 7 0 alpha 4
@anchor{whatsnew/changelog id212}@anchor{102d}
@subsubsection Windows



@itemize -

@item 
bpo-19764@footnote{https://bugs.python.org/issue19764}: Implement support for @code{subprocess.Popen(close_fds=True)} on
Windows. Patch by Segev Finer.
@end itemize

@node 工具/示例<14>,C API<15>,Windows<22>,Python 3 7 0 alpha 4
@anchor{whatsnew/changelog id213}@anchor{102e}
@subsubsection 工具/示例



@itemize -

@item 
bpo-24960@footnote{https://bugs.python.org/issue24960}: 2to3 and lib2to3 can now read pickled grammar files using
pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and
lib2to3 work when run from a zipfile.
@end itemize

@node C API<15>,,工具/示例<14>,Python 3 7 0 alpha 4
@anchor{whatsnew/changelog id214}@anchor{102f}
@subsubsection C API



@itemize -

@item 
bpo-32030@footnote{https://bugs.python.org/issue32030}: Py_Initialize() doesn't reset the memory allocators to default
if the @code{PYTHONMALLOC} environment variable is not set.

@item 
bpo-29084@footnote{https://bugs.python.org/issue29084}: Undocumented C API for OrderedDict has been excluded from the
limited C API. It was added by mistake and actually never worked in the
limited C API.

@item 
bpo-32264@footnote{https://bugs.python.org/issue32264}: Moved the pygetopt.h header into internal/, since it has no
public APIs.

@item 
bpo-32241@footnote{https://bugs.python.org/issue32241}: @ref{f18,,Py_SetProgramName()} and @ref{f17,,Py_SetPythonHome()} now
take the @code{const wchar *} arguments instead of @code{wchar *}.
@end itemize

@node Python 3 7 0 alpha 3,Python 3 7 0 alpha 2,Python 3 7 0 alpha 4,更新日志
@anchor{whatsnew/changelog python-3-7-0-alpha-3}@anchor{1030}
@subsection Python 3.7.0 alpha 3


@emph{发布日期: 2017-12-05}

@menu
* 核心与内置: 核心与内置<28>. 
* 库: 库<29>. 
* 文档: 文档<24>. 
* 测试: 测试<22>. 
* 构建: 构建<20>. 
* Windows: Windows<23>. 
* macOS: macOS<16>. 
* IDLE: IDLE<27>. 
* 工具/示例: 工具/示例<15>. 
* C API: C API<16>. 

@end menu

@node 核心与内置<28>,库<29>,,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id215}@anchor{1031}
@subsubsection 核心与内置



@itemize -

@item 
bpo-32176@footnote{https://bugs.python.org/issue32176}: co_flags.CO_NOFREE is now always set correctly by the code
object constructor based on freevars and cellvars, rather than needing to
be set correctly by the caller. This ensures it will be cleared
automatically when additional cell references are injected into a modified
code object and function.

@item 
bpo-10544@footnote{https://bugs.python.org/issue10544}: Yield expressions are now deprecated in comprehensions and
generator expressions. They are still permitted in the definition of the
outermost iterable, as that is evaluated directly in the enclosing scope.

@item 
bpo-32137@footnote{https://bugs.python.org/issue32137}: The repr of deeply nested dict now raises a RecursionError
instead of crashing due to a stack overflow.

@item 
bpo-32096@footnote{https://bugs.python.org/issue32096}: Revert memory allocator changes in the C API: move structures
back from _PyRuntime to Objects/obmalloc.c. The memory allocators are once
again initialized statically, and so PyMem_RawMalloc() and
Py_DecodeLocale() can be called before _PyRuntime_Initialize().

@item 
bpo-32043@footnote{https://bugs.python.org/issue32043}: Add a new "developer mode": new "-X dev" command line option to
enable debug checks at runtime.

@item 
bpo-32023@footnote{https://bugs.python.org/issue32023}: SyntaxError is now correctly raised when a generator expression
without parenthesis is used instead of an inheritance list in a class
definition. The duplication of the parentheses can be omitted only on
calls.

@item 
bpo-32012@footnote{https://bugs.python.org/issue32012}: SyntaxError is now correctly raised when a generator expression
without parenthesis is passed as an argument, but followed by a trailing
comma. A generator expression always needs to be directly inside a set of
parentheses and cannot have a comma on either side.

@item 
bpo-28180@footnote{https://bugs.python.org/issue28180}: A new internal @code{_Py_SetLocaleFromEnv(category)} helper
function has been added in order to improve the consistency of behaviour
across different @code{libc} implementations (e.g. Android doesn't support
setting the locale from the environment by default).

@item 
bpo-31949@footnote{https://bugs.python.org/issue31949}: Fixed several issues in printing tracebacks
(PyTraceBack_Print()). Setting sys.tracebacklimit to 0 or less now
suppresses printing tracebacks. Setting sys.tracebacklimit to None now
causes using the default limit. Setting sys.tracebacklimit to an integer
larger than LONG_MAX now means using the limit LONG_MAX rather than the
default limit. Fixed integer overflows in the case of more than 2**31
traceback items on Windows. Fixed output errors handling.

@item 
bpo-30696@footnote{https://bugs.python.org/issue30696}: Fix the interactive interpreter looping endlessly when no
memory.

@item 
bpo-20047@footnote{https://bugs.python.org/issue20047}: Bytearray methods partition() and rpartition() now accept only
bytes-like objects as separator, as documented.  In particular they now
raise TypeError rather of returning a bogus result when an integer is
passed as a separator.

@item 
bpo-21720@footnote{https://bugs.python.org/issue21720}: BytesWarning no longer emitted when the @emph{fromlist} argument of
@code{__import__()} or the @code{__all__} attribute of the module contain bytes
instances.

@item 
bpo-31845@footnote{https://bugs.python.org/issue31845}: Environment variables are once more read correctly at
interpreter startup.

@item 
bpo-28936@footnote{https://bugs.python.org/issue28936}: Ensure that lexically first syntax error involving a parameter
and @code{global} or @code{nonlocal} is detected first at a given scope. Patch
by Ivan Levkivskyi.

@item 
bpo-31825@footnote{https://bugs.python.org/issue31825}: Fixed OverflowError in the 'unicode-escape' codec and in
codecs.escape_decode() when decode an escaped non-ascii byte.

@item 
bpo-31618@footnote{https://bugs.python.org/issue31618}: The per-frame tracing logic added in 3.7a1 has been altered so
that @code{frame->f_lineno} is updated before either @code{"line"} or
@code{"opcode"} events are emitted. Previously, opcode events were emitted
first, and therefore would occasionally see stale line numbers on the
frame. The behavior of this feature has changed slightly as a result: when
both @code{f_trace_lines} and @code{f_trace_opcodes} are enabled, line events
now occur first.

@item 
bpo-28603@footnote{https://bugs.python.org/issue28603}: Print the full context/cause chain of exceptions on interpreter
exit, even if an exception in the chain is unhashable or compares equal to
later ones. Patch by Zane Bitter.

@item 
bpo-31786@footnote{https://bugs.python.org/issue31786}: Fix timeout rounding in the select module to round correctly
negative timeouts between -1.0 and 0.0. The functions now block waiting
for events as expected. Previously, the call was incorrectly non-blocking.
Patch by Pablo Galindo.

@item 
bpo-31781@footnote{https://bugs.python.org/issue31781}: Prevent crashes when calling methods of an uninitialized
@code{zipimport.zipimporter} object. Patch by Oren Milman.

@item 
bpo-30399@footnote{https://bugs.python.org/issue30399}: Standard repr() of BaseException with a single argument no
longer contains redundant trailing comma.

@item 
bpo-31626@footnote{https://bugs.python.org/issue31626}: Fixed a bug in debug memory allocator.  There was a write to
freed memory after shrinking a memory block.

@item 
bpo-30817@footnote{https://bugs.python.org/issue30817}: @code{PyErr_PrintEx()} clears now the ignored exception that may be
raised by @code{_PySys_SetObjectId()}, for example when no memory.
@end itemize

@node 库<29>,文档<24>,核心与内置<28>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id216}@anchor{1032}
@subsubsection 库



@itemize -

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Two minor fixes for @code{typing} module: allow shallow copying
instances of generic classes, improve interaction of @code{__init_subclass__}
with generics. Original PRs by Ivan Levkivskyi.

@item 
bpo-32214@footnote{https://bugs.python.org/issue32214}: PEP 557, Data Classes. Provides a decorator which adds
boilerplate methods to classes which use type annotations so specify
fields.

@item 
bpo-27240@footnote{https://bugs.python.org/issue27240}: The header folding algorithm for the new email policies has
been rewritten, which also fixes bpo-30788@footnote{https://bugs.python.org/issue30788}, bpo-31831@footnote{https://bugs.python.org/issue31831}, and bpo-32182@footnote{https://bugs.python.org/issue32182}.  In
particular, RFC2231 folding is now done correctly.

@item 
bpo-32186@footnote{https://bugs.python.org/issue32186}: io.FileIO.readall() and io.FileIO.read() now release the GIL
when getting the file size. Fixed hang of all threads with inaccessible
NFS server. Patch by Nir Soffer.

@item 
bpo-321010@footnote{https://bugs.python.org/issue321010}: Add @code{sys.flags.dev_mode} flag

@item 
bpo-32154@footnote{https://bugs.python.org/issue32154}: The @code{asyncio.windows_utils.socketpair()} function has been
removed: use directly @ref{47b,,socket.socketpair()} which is available on all
platforms since Python 3.5 (before, it wasn't available on Windows).
@code{asyncio.windows_utils.socketpair()} was just an alias to
@code{socket.socketpair} on Python 3.5 and newer.

@item 
bpo-32089@footnote{https://bugs.python.org/issue32089}: warnings: In development (-X dev) and debug mode (pydebug
build), use the "default" action for ResourceWarning, rather than the
"always" action, in the default warnings filters.

@item 
bpo-32107@footnote{https://bugs.python.org/issue32107}: @code{uuid.getnode()} now preferentially returns universally
administered MAC addresses if available, over locally administered MAC
addresses.  This makes a better guarantee for global uniqueness of UUIDs
returned from @code{uuid.uuid1()}.  If only locally administered MAC
addresses are available, the first such one found is returned.

@item 
bpo-23033@footnote{https://bugs.python.org/issue23033}: Wildcard is now supported in hostname when it is one and only
character in the left most segment of hostname in second argument of
@ref{3d4,,ssl.match_hostname()}.  Patch by Mandeep Singh.

@item 
bpo-12239@footnote{https://bugs.python.org/issue12239}: Make @ref{f53,,msilib.SummaryInformation.GetProperty()} return
@code{None} when the value of property is @code{VT_EMPTY}.  Initial patch by
Mark Mc Mahon.

@item 
bpo-28334@footnote{https://bugs.python.org/issue28334}: Use @ref{1fe,,os.path.expanduser()} to find the @code{~/.netrc} file in
@ref{1033,,netrc.netrc}.  If it does not exist, @ref{7ba,,FileNotFoundError} is
raised.  Patch by Dimitri Merejkowsky.

@item 
bpo-32121@footnote{https://bugs.python.org/issue32121}: Made @code{tracemalloc.Traceback} behave more like the traceback
module, sorting the frames from oldest to most recent.
@code{Traceback.format()} now accepts negative @emph{limit}, truncating the result
to the @code{abs(limit)} oldest frames. To get the old behaviour, one can use
the new @emph{most_recent_first} argument to @code{Traceback.format()}. (Patch by
Jesse Bakker.)

@item 
bpo-31325@footnote{https://bugs.python.org/issue31325}: Fix wrong usage of @ref{1b6,,collections.namedtuple()} in the
@ref{1034,,RobotFileParser.parse()}
method. Initial patch by Robin Wellner.

@item 
bpo-12382@footnote{https://bugs.python.org/issue12382}: @ref{e9d,,msilib.OpenDatabase()} now raises a better exception
message when it couldn't open or create an MSI file.  Initial patch by
William Tisäter.

@item 
bpo-19610@footnote{https://bugs.python.org/issue19610}: @code{setup()} now warns about invalid types for some fields. The
@code{distutils.dist.Distribution} class now warns when @code{classifiers},
@code{keywords} and @code{platforms} fields are not specified as a list or a
string.

@item 
bpo-32071@footnote{https://bugs.python.org/issue32071}: Added the @code{-k} command-line option to @code{python -m unittest}
to run only tests that match the given pattern(s).

@item 
bpo-10049@footnote{https://bugs.python.org/issue10049}: Added @emph{nullcontext} no-op context manager to contextlib. This
provides a simpler and faster alternative to ExitStack() when handling
optional context managers.

@item 
bpo-28684@footnote{https://bugs.python.org/issue28684}: The new test.support.skip_unless_bind_unix_socket() decorator
is used here to skip asyncio tests that fail because the platform lacks a
functional bind() function for unix domain sockets (as it is the case for
non root users on the recent Android versions that run now SELinux in
enforcing mode).

@item 
bpo-32110@footnote{https://bugs.python.org/issue32110}: @code{codecs.StreamReader.read(n)} now returns not more than @emph{n}
characters/bytes for non-negative @emph{n}. This makes it compatible with
@code{read()} methods of other file-like objects.

@item 
bpo-27535@footnote{https://bugs.python.org/issue27535}: The warnings module doesn't leak memory anymore in the hidden
warnings registry for the "ignore" action of warnings filters.
warn_explicit() function doesn't add the warning key to the registry
anymore for the "ignore" action.

@item 
bpo-32088@footnote{https://bugs.python.org/issue32088}: warnings:  When Python is build is debug mode (@code{Py_DEBUG}),
@ref{278,,DeprecationWarning}, @ref{279,,PendingDeprecationWarning} and
@ref{5d3,,ImportWarning} warnings are now displayed by default.

@item 
bpo-1647489@footnote{https://bugs.python.org/issue1647489}: Fixed searching regular expression patterns that could match
an empty string. Non-empty string can now be correctly found after
matching an empty string.

@item 
bpo-25054@footnote{https://bugs.python.org/issue25054}: Added support of splitting on a pattern that could match an
empty string.

@item 
bpo-32072@footnote{https://bugs.python.org/issue32072}: Fixed issues with binary plists: Fixed saving bytearrays.
Identical objects will be saved only once. Equal references will be load
as identical objects. Added support for saving and loading recursive data
structures.

@item 
bpo-32069@footnote{https://bugs.python.org/issue32069}: Drop legacy SSL transport from asyncio, ssl.MemoryBIO is always
used anyway.

@item 
bpo-32066@footnote{https://bugs.python.org/issue32066}: asyncio: Support pathlib.Path in create_unix_connection; sock
arg should be optional

@item 
bpo-32046@footnote{https://bugs.python.org/issue32046}: Updates 2to3 to convert from operator.isCallable(obj) to
callable(obj). Patch by Dong-hee Na.

@item 
bpo-32018@footnote{https://bugs.python.org/issue32018}: inspect.signature should follow 
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008}, if the parameter has
an annotation and a default value. Patch by Dong-hee Na.

@item 
bpo-32025@footnote{https://bugs.python.org/issue32025}: Add time.thread_time() and time.thread_time_ns()

@item 
bpo-32037@footnote{https://bugs.python.org/issue32037}: Integers that fit in a signed 32-bit integer will be now
pickled with protocol 0 using the INT opcode.  This will decrease the size
of a pickle, speed up pickling and unpickling, and make these integers be
unpickled as int instances in Python 2.

@item 
bpo-32034@footnote{https://bugs.python.org/issue32034}: Make asyncio.IncompleteReadError and LimitOverrunError
pickleable.

@item 
bpo-32015@footnote{https://bugs.python.org/issue32015}: Fixed the looping of asyncio in the case of reconnection the
socket during waiting async read/write from/to the socket.

@item 
bpo-32011@footnote{https://bugs.python.org/issue32011}: Restored support of loading marshal files with the TYPE_INT64
code. These files can be produced in Python 2.7.

@item 
bpo-28369@footnote{https://bugs.python.org/issue28369}: Enhance add_reader/writer check that socket is not used by some
transport. Before, only cases when add_reader/writer were called with an
int FD were supported.  Now the check is implemented correctly for all
file-like objects.

@item 
bpo-31976@footnote{https://bugs.python.org/issue31976}: Fix race condition when flushing a file is slow, which can
cause a segfault if closing the file from another thread.

@item 
bpo-31985@footnote{https://bugs.python.org/issue31985}: Formally deprecated aifc.openfp, sunau.openfp, and wave.openfp.
Since change 7bc817d5ba917528e8bd07ec461c635291e7b06a in 1993, openfp in
each of the three modules had been pointing to that module's open function
as a matter of backwards compatibility, though it had been both untested
and undocumented.

@item 
bpo-21862@footnote{https://bugs.python.org/issue21862}: cProfile command line now accepts @code{-m module_name} as an
alternative to script path. Patch by Sanyam Khurana.

@item 
bpo-31970@footnote{https://bugs.python.org/issue31970}: Reduce performance overhead of asyncio debug mode.

@item 
bpo-31843@footnote{https://bugs.python.org/issue31843}: @emph{database} argument of sqlite3.connect() now accepts a
@ref{363,,path-like object}, instead of just a string.

@item 
bpo-31945@footnote{https://bugs.python.org/issue31945}: Add Configurable @emph{blocksize} to @code{HTTPConnection} and
@code{HTTPSConnection} for improved upload throughput.  Patch by Nir Soffer.

@item 
bpo-31943@footnote{https://bugs.python.org/issue31943}: Add a @code{cancelled()} method to @ref{1035,,asyncio.Handle}.  Patch
by Marat Sharafutdinov.

@item 
bpo-9678@footnote{https://bugs.python.org/issue9678}: Fixed determining the MAC address in the uuid module: Using
ifconfig on NetBSD and OpenBSD. Using arp on Linux, FreeBSD, NetBSD and
OpenBSD. Based on patch by Takayuki Shimizukawa.

@item 
bpo-30057@footnote{https://bugs.python.org/issue30057}: Fix potential missed signal in signal.signal().

@item 
bpo-31933@footnote{https://bugs.python.org/issue31933}: Fix Blake2 params leaf_size and node_offset on big endian
platforms. Patch by Jack O'Connor.

@item 
bpo-21423@footnote{https://bugs.python.org/issue21423}: Add an initializer argument to @{Process,Thread@}PoolExecutor

@item 
bpo-31927@footnote{https://bugs.python.org/issue31927}: Fixed compilation of the socket module on NetBSD 8.  Fixed
assertion failure or reading arbitrary data when parse a AF_BLUETOOTH
address on NetBSD and DragonFly BSD.

@item 
bpo-27666@footnote{https://bugs.python.org/issue27666}: Fixed stack corruption in curses.box() and curses.ungetmouse()
when the size of types chtype or mmask_t is less than the size of C long.
curses.box() now accepts characters as arguments.  Based on patch by Steve
Fink.

@item 
bpo-31917@footnote{https://bugs.python.org/issue31917}: Add 3 new clock identifiers: @ref{3ed,,time.CLOCK_BOOTTIME},
@ref{3ef,,time.CLOCK_PROF} and @ref{3f0,,time.CLOCK_UPTIME}.

@item 
bpo-31897@footnote{https://bugs.python.org/issue31897}: plistlib now catches more errors when read binary plists and
raises InvalidFileException instead of unexpected exceptions.

@item 
bpo-25720@footnote{https://bugs.python.org/issue25720}: Fix the method for checking pad state of curses WINDOW. Patch
by Masayuki Yamamoto.

@item 
bpo-31893@footnote{https://bugs.python.org/issue31893}: Fixed the layout of the kqueue_event structure on OpenBSD and
NetBSD. Fixed the comparison of the kqueue_event objects.

@item 
bpo-31891@footnote{https://bugs.python.org/issue31891}: Fixed building the curses module on NetBSD.

@item 
bpo-31884@footnote{https://bugs.python.org/issue31884}: added required constants to subprocess module for setting
priority on windows

@item 
bpo-28281@footnote{https://bugs.python.org/issue28281}: Remove year (1-9999) limits on the Calendar.weekday() function.
Patch by Mark Gollahon.

@item 
bpo-31702@footnote{https://bugs.python.org/issue31702}: crypt.mksalt() now allows to specify the number of rounds for
SHA-256 and SHA-512 hashing.

@item 
bpo-30639@footnote{https://bugs.python.org/issue30639}: @ref{1036,,inspect.getfile()} no longer computes the repr of unknown
objects to display in an error message, to protect against badly behaved
custom reprs.

@item 
bpo-30768@footnote{https://bugs.python.org/issue30768}: Fix the pthread+semaphore implementation of
PyThread_acquire_lock_timed() when called with timeout > 0 and
intr_flag=0: recompute the timeout if sem_timedwait() is interrupted by a
signal (EINTR). See also the 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}.

@item 
bpo-31854@footnote{https://bugs.python.org/issue31854}: Add @code{mmap.ACCESS_DEFAULT} constant.

@item 
bpo-31834@footnote{https://bugs.python.org/issue31834}: Use optimized code for BLAKE2 only with SSSE3+. The pure SSE2
implementation is slower than the pure C reference implementation.

@item 
bpo-28292@footnote{https://bugs.python.org/issue28292}: Calendar.itermonthdates() will now consistently raise an
exception when a date falls outside of the 0001-01-01 through 9999-12-31
range.  To support applications that cannot tolerate such exceptions, the
new methods itermonthdays3() and itermonthdays4() are added.  The new
methods return tuples and are not restricted by the range supported by
datetime.date.

@item 
bpo-28564@footnote{https://bugs.python.org/issue28564}: The shutil.rmtree() function has been sped up to 20--40%. This
was done using the os.scandir() function.

@item 
bpo-28416@footnote{https://bugs.python.org/issue28416}: Instances of pickle.Pickler subclass with the persistent_id()
method and pickle.Unpickler subclass with the persistent_load() method no
longer create reference cycles.

@item 
bpo-31653@footnote{https://bugs.python.org/issue31653}: Don't release the GIL if we can acquire a multiprocessing
semaphore immediately.

@item 
bpo-28326@footnote{https://bugs.python.org/issue28326}: Fix multiprocessing.Process when stdout and/or stderr is closed
or None.

@item 
bpo-20825@footnote{https://bugs.python.org/issue20825}: Add @code{subnet_of} and @code{superset_of} containment tests to
@ref{397,,ipaddress.IPv6Network} and @ref{398,,ipaddress.IPv4Network}. Patch
by Michel Albert and Cheryl Sabella.

@item 
bpo-31827@footnote{https://bugs.python.org/issue31827}: Remove the os.stat_float_times() function. It was introduced in
Python 2.3 for backward compatibility with Python 2.2, and was deprecated
since Python 3.1.

@item 
bpo-31756@footnote{https://bugs.python.org/issue31756}: Add a @code{subprocess.Popen(text=False)} keyword argument to
@ref{f9,,subprocess} functions to be more explicit about when the library should
attempt to decode outputs into text. Patch by Andrew Clegg.

@item 
bpo-31819@footnote{https://bugs.python.org/issue31819}: Add AbstractEventLoop.sock_recv_into().

@item 
bpo-31457@footnote{https://bugs.python.org/issue31457}: If nested log adapters are used, the inner @code{process()}
methods are no longer omitted.

@item 
bpo-31457@footnote{https://bugs.python.org/issue31457}: The @code{manager} property on LoggerAdapter objects is now
properly settable.

@item 
bpo-31806@footnote{https://bugs.python.org/issue31806}: Fix timeout rounding in time.sleep(), threading.Lock.acquire()
and socket.socket.settimeout() to round correctly negative timeouts
between -1.0 and 0.0. The functions now block waiting for events as
expected. Previously, the call was incorrectly non-blocking. Patch by
Pablo Galindo.

@item 
bpo-31803@footnote{https://bugs.python.org/issue31803}: time.clock() and time.get_clock_info('clock') now emit a
DeprecationWarning warning.

@item 
bpo-31800@footnote{https://bugs.python.org/issue31800}: Extended support for parsing UTC offsets. strptime '%z' can now
parse the output generated by datetime.isoformat, including seconds and
microseconds.

@item 
bpo-28603@footnote{https://bugs.python.org/issue28603}: traceback: Fix a TypeError that occurred during printing of
exception tracebacks when either the current exception or an exception in
its context/cause chain is unhashable. Patch by Zane Bitter.

@item 
bpo-30541@footnote{https://bugs.python.org/issue30541}: Add new function to seal a mock and prevent the automatically
creation of child mocks. Patch by Mario Corchero.

@item 
bpo-31784@footnote{https://bugs.python.org/issue31784}: Implement the 
@geindex Python 提高建议; PEP 564
PEP 564@footnote{https://www.python.org/dev/peps/pep-0564}, add new 6 new functions with
nanosecond resolution to the @ref{10a,,time} module:
@ref{317,,clock_gettime_ns()}, @ref{318,,clock_settime_ns()},
@ref{319,,monotonic_ns()}, @ref{31a,,perf_counter_ns()},
@ref{31b,,process_time_ns()}, @ref{31c,,time_ns()}.

@item 
bpo-30143@footnote{https://bugs.python.org/issue30143}: 2to3 now generates a code that uses abstract collection classes
from collections.abc rather than collections.

@item 
bpo-31770@footnote{https://bugs.python.org/issue31770}: Prevent a crash when calling the @code{__init__()} method of a
@code{sqlite3.Cursor} object more than once. Patch by Oren Milman.

@item 
bpo-31764@footnote{https://bugs.python.org/issue31764}: Prevent a crash in @code{sqlite3.Cursor.close()} in case the
@code{Cursor} object is uninitialized. Patch by Oren Milman.

@item 
bpo-31752@footnote{https://bugs.python.org/issue31752}: Fix possible crash in timedelta constructor called with custom
integers.

@item 
bpo-31620@footnote{https://bugs.python.org/issue31620}: an empty asyncio.Queue now doesn't leak memory when queue.get
pollers timeout

@item 
bpo-31690@footnote{https://bugs.python.org/issue31690}: Allow the flags re.ASCII, re.LOCALE, and re.UNICODE to be used
as group flags for regular expressions.

@item 
bpo-30349@footnote{https://bugs.python.org/issue30349}: FutureWarning is now emitted if a regular expression contains
character set constructs that will change semantically in the future
(nested sets and set operations).

@item 
bpo-31664@footnote{https://bugs.python.org/issue31664}: Added support for the Blowfish hashing in the crypt module.

@item 
bpo-31632@footnote{https://bugs.python.org/issue31632}: Fix method set_protocol() of class _SSLProtocolTransport in
asyncio module. This method was previously modifying a wrong reference to
the protocol.

@item 
bpo-15037@footnote{https://bugs.python.org/issue15037}: Added a workaround for getkey() in curses for ncurses 5.7 and
earlier.

@item 
bpo-31307@footnote{https://bugs.python.org/issue31307}: Allow use of bytes objects for arguments to
@ref{1037,,configparser.ConfigParser.read()}. Patch by Vincent Michel.

@item 
bpo-31334@footnote{https://bugs.python.org/issue31334}: Fix @code{poll.poll([timeout])} in the @code{select} module for
arbitrary negative timeouts on all OSes where it can only be a
non-negative integer or -1. Patch by Riccardo Coccioli.

@item 
bpo-31310@footnote{https://bugs.python.org/issue31310}: multiprocessing's semaphore tracker should be launched again if
crashed.

@item 
bpo-31308@footnote{https://bugs.python.org/issue31308}: Make multiprocessing's forkserver process immune to Ctrl-C and
other user interruptions. If it crashes, restart it when necessary.

@item 
bpo-31245@footnote{https://bugs.python.org/issue31245}: Added support for AF_UNIX socket in asyncio
@code{create_datagram_endpoint}.

@item 
bpo-30553@footnote{https://bugs.python.org/issue30553}: Add HTTP/2 status code 421 (Misdirected Request) to
@ref{6dc,,http.HTTPStatus}. Patch by Vitor Pereira.
@end itemize

@node 文档<24>,测试<22>,库<29>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id217}@anchor{1038}
@subsubsection 文档



@itemize -

@item 
bpo-32105@footnote{https://bugs.python.org/issue32105}: Added asyncio.BaseEventLoop.connect_accepted_socket
versionadded marker.
@end itemize

@node 测试<22>,构建<20>,文档<24>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id218}@anchor{1039}
@subsubsection 测试



@itemize -

@item 
bpo-31380@footnote{https://bugs.python.org/issue31380}: Skip test_httpservers test_undecodable_file on macOS: fails on
APFS.

@item 
bpo-31705@footnote{https://bugs.python.org/issue31705}: Skip test_socket.test_sha256() on Linux kernel older than 4.5.
The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged
into the kernel 4.5.

@item 
bpo-32138@footnote{https://bugs.python.org/issue32138}: Skip on Android test_faulthandler tests that raise SIGSEGV and
remove the test.support.requires_android_level decorator.

@item 
bpo-32136@footnote{https://bugs.python.org/issue32136}: The runtime embedding tests have been split out from
@code{Lib/test/test_capi.py} into a new @code{Lib/test/test_embed.py} file.

@item 
bpo-28668@footnote{https://bugs.python.org/issue28668}: test.support.requires_multiprocessing_queue is removed. Skip
tests with test.support.import_module('multiprocessing.synchronize')
instead when the semaphore implementation is broken or missing.

@item 
bpo-32126@footnote{https://bugs.python.org/issue32126}: Skip test_get_event_loop_new_process in
test.test_asyncio.test_events when sem_open() is not functional.

@item 
bpo-31174@footnote{https://bugs.python.org/issue31174}: Fix test_tools.test_unparse: DirectoryTestCase now stores the
names sample to always test the same files. It prevents false alarms when
hunting reference leaks.
@end itemize

@node 构建<20>,Windows<23>,测试<22>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id219}@anchor{103a}
@subsubsection 构建



@itemize -

@item 
bpo-28538@footnote{https://bugs.python.org/issue28538}: Revert the previous changes, the if_nameindex structure is
defined by Unified Headers.

@item 
bpo-28762@footnote{https://bugs.python.org/issue28762}: Revert the last commit, the F_LOCK macro is defined by Android
Unified Headers.

@item 
bpo-29040@footnote{https://bugs.python.org/issue29040}: Support building Android with Unified Headers. The first NDK
release to support Unified Headers is android-ndk-r14.

@item 
bpo-32059@footnote{https://bugs.python.org/issue32059}: @code{detect_modules()} in @code{setup.py} now also searches the
sysroot paths when cross-compiling.

@item 
bpo-31957@footnote{https://bugs.python.org/issue31957}: Fixes Windows SDK version detection when building for Windows.

@item 
bpo-31609@footnote{https://bugs.python.org/issue31609}: Fixes quotes in PCbuild/clean.bat

@item 
bpo-31934@footnote{https://bugs.python.org/issue31934}: Abort the build when building out of a not clean source tree.

@item 
bpo-31926@footnote{https://bugs.python.org/issue31926}: Fixed Argument Clinic sometimes causing compilation errors when
there was more than one function and/or method in a .c file with the same
name.

@item 
bpo-28791@footnote{https://bugs.python.org/issue28791}: 更新 Windows 构建以使用 SQLite 3.21.0.

@item 
bpo-28791@footnote{https://bugs.python.org/issue28791}: 更新 OS X 安装程序以使用 SQLite 3.21.0.

@item 
bpo-28643@footnote{https://bugs.python.org/issue28643}: Record profile-opt build progress with stamp files.

@item 
bpo-31866@footnote{https://bugs.python.org/issue31866}: Finish removing support for AtheOS.
@end itemize

@node Windows<23>,macOS<16>,构建<20>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id220}@anchor{103b}
@subsubsection Windows



@itemize -

@item 
bpo-1102@footnote{https://bugs.python.org/issue1102}: Return @code{None} when @code{View.Fetch()} returns
@code{ERROR_NO_MORE_ITEMS} instead of raising @code{MSIError}. Initial patch by
Anthony Tuininga.

@item 
bpo-31944@footnote{https://bugs.python.org/issue31944}: Fixes Modify button in Apps and Features dialog.

@item 
bpo-20486@footnote{https://bugs.python.org/issue20486}: Implement the @code{Database.Close()} method to help closing MSI
database objects.

@item 
bpo-31857@footnote{https://bugs.python.org/issue31857}: Make the behavior of USE_STACKCHECK deterministic in a
multi-threaded environment.
@end itemize

@node macOS<16>,IDLE<27>,Windows<23>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id221}@anchor{103c}
@subsubsection macOS



@itemize -

@item 
bpo-31392@footnote{https://bugs.python.org/issue31392}: 更新 macOS 安装程序以使用OpenSSL 1.0.2m
@end itemize

@node IDLE<27>,工具/示例<15>,macOS<16>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id222}@anchor{103d}
@subsubsection IDLE



@itemize -

@item 
bpo-32207@footnote{https://bugs.python.org/issue32207}: Improve tk event exception tracebacks in IDLE. When tk event
handling is driven by IDLE's run loop, a confusing and distracting
queue.EMPTY traceback context is no longer added to tk event exception
tracebacks.  The traceback is now the same as when event handling is
driven by user code.  Patch based on a suggestion by Serhiy Storchaka.

@item 
bpo-32164@footnote{https://bugs.python.org/issue32164}: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet
in configdialog was replaced by ttk.Notebook.

@item 
bpo-32100@footnote{https://bugs.python.org/issue32100}: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch
mostly by Cheryl Sabella.

@item 
bpo-31858@footnote{https://bugs.python.org/issue31858}: IDLE -- Restrict shell prompt manipulation to the shell. Editor
and output windows only see an empty last prompt line.  This simplifies
the code and fixes a minor bug when newline is inserted. Sys.ps1, if
present, is read on Shell start-up, but is not set or changed.

@item 
bpo-31860@footnote{https://bugs.python.org/issue31860}: The font sample in the IDLE configuration dialog is now
editable. Changes persist while IDLE remains open

@item 
bpo-31836@footnote{https://bugs.python.org/issue31836}: Test_code_module now passes if run after test_idle, which sets
ps1. The code module uses sys.ps1 if present or sets it to '>>> ' if not.
Test_code_module now properly tests both behaviors.  Ditto for ps2.

@item 
bpo-28603@footnote{https://bugs.python.org/issue28603}: Fix a TypeError that caused a shell restart when printing a
traceback that includes an exception that is unhashable. Patch by Zane
Bitter.

@item 
bpo-13802@footnote{https://bugs.python.org/issue13802}: Use non-Latin characters in the IDLE's Font settings sample.
Even if one selects a font that defines a limited subset of the unicode
Basic Multilingual Plane, tcl/tk will use other fonts that define a
character. The expanded example give users of non-Latin characters a
better idea of what they might see in IDLE's shell and editors. To make
room for the expanded sample, frames on the Font tab are re-arranged.  The
Font/Tabs help explains a bit about the additions.
@end itemize

@node 工具/示例<15>,C API<16>,IDLE<27>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id223}@anchor{103e}
@subsubsection 工具/示例



@itemize -

@item 
bpo-32159@footnote{https://bugs.python.org/issue32159}: Remove CVS and Subversion tools: remove svneol.py and
treesync.py scripts. CPython migrated from CVS to Subversion, to
Mercurial, and then to Git. CVS and Subversion are no longer used to
develop CPython.

@item 
bpo-30722@footnote{https://bugs.python.org/issue30722}: Make redemo work with Python 3.6 and newer versions. Also,
remove the @code{LOCALE} option since it doesn't work with string patterns in
Python 3. Patch by Christoph Sarnowski.
@end itemize

@node C API<16>,,工具/示例<15>,Python 3 7 0 alpha 3
@anchor{whatsnew/changelog id224}@anchor{103f}
@subsubsection C API



@itemize -

@item 
bpo-20891@footnote{https://bugs.python.org/issue20891}: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in
a non-Python thread before PyEval_InitThreads(), only call
PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.

@item 
bpo-32125@footnote{https://bugs.python.org/issue32125}: The @code{Py_UseClassExceptionsFlag} flag has been removed. It was
deprecated and wasn't used anymore since Python 2.0.

@item 
bpo-25612@footnote{https://bugs.python.org/issue25612}: Move the current exception state from the frame object to the
co-routine. This simplifies the interpreter and fixes a couple of obscure
bugs caused by having swap exception state when entering or exiting a
generator.

@item 
bpo-23699@footnote{https://bugs.python.org/issue23699}: Add Py_RETURN_RICHCOMPARE macro to reduce boilerplate code in
rich comparison functions.

@item 
bpo-30697@footnote{https://bugs.python.org/issue30697}: The @code{PyExc_RecursionErrorInst} singleton is removed and
@code{PyErr_NormalizeException()} does not use it anymore. This singleton is
persistent and its members being never cleared may cause a segfault during
finalization of the interpreter. See also bpo-22898@footnote{https://bugs.python.org/issue22898}.
@end itemize

@node Python 3 7 0 alpha 2,Python 3 7 0 alpha 1,Python 3 7 0 alpha 3,更新日志
@anchor{whatsnew/changelog python-3-7-0-alpha-2}@anchor{1040}
@subsection Python 3.7.0 alpha 2


@emph{发布日期: 2017-10-16}

@menu
* 核心与内置: 核心与内置<29>. 
* 库: 库<30>. 
* 文档: 文档<25>. 
* 构建: 构建<21>. 
* IDLE: IDLE<28>. 
* C API: C API<17>. 

@end menu

@node 核心与内置<29>,库<30>,,Python 3 7 0 alpha 2
@anchor{whatsnew/changelog id225}@anchor{1041}
@subsubsection 核心与内置



@itemize -

@item 
bpo-31558@footnote{https://bugs.python.org/issue31558}: @code{gc.freeze()} is a new API that allows for moving all objects
currently tracked by the garbage collector to a permanent generation,
effectively removing them from future collection events. This can be used
to protect those objects from having their PyGC_Head mutated. In effect,
this enables great copy-on-write stability at fork().

@item 
bpo-31642@footnote{https://bugs.python.org/issue31642}: Restored blocking "from package import module" by setting
sys.modules["package.module"] to None.

@item 
bpo-31708@footnote{https://bugs.python.org/issue31708}: Allow use of asynchronous generator expressions in synchronous
functions.

@item 
bpo-31709@footnote{https://bugs.python.org/issue31709}: 取消对异步__Aiter__的支持。

@item 
bpo-30404@footnote{https://bugs.python.org/issue30404}: The -u option now makes the stdout and stderr streams
unbuffered rather than line-buffered.

@item 
bpo-31619@footnote{https://bugs.python.org/issue31619}: Fixed a ValueError when convert a string with large number of
underscores to integer with binary base.

@item 
bpo-31602@footnote{https://bugs.python.org/issue31602}: Fix an assertion failure in @code{zipimporter.get_source()} in case
of a bad @ref{5ba,,zlib.decompress()}. Patch by Oren Milman.

@item 
bpo-31592@footnote{https://bugs.python.org/issue31592}: Fixed an assertion failure in Python parser in case of a bad
@ref{1042,,unicodedata.normalize()}. Patch by Oren Milman.

@item 
bpo-31588@footnote{https://bugs.python.org/issue31588}: Raise a @ref{192,,TypeError} with a helpful error message when class
creation fails due to a metaclass with a bad @code{__prepare__()} method.
Patch by Oren Milman.

@item 
bpo-31574@footnote{https://bugs.python.org/issue31574}: Importlib was instrumented with two dtrace probes to profile
import timing.

@item 
bpo-31566@footnote{https://bugs.python.org/issue31566}: Fix an assertion failure in @code{_warnings.warn()} in case of a bad
@code{__name__} global. Patch by Oren Milman.

@item 
bpo-31506@footnote{https://bugs.python.org/issue31506}: Improved the error message logic for object.__new__ and
object.__init__.

@item 
bpo-31505@footnote{https://bugs.python.org/issue31505}: Fix an assertion failure in @ref{a4,,json}, in case
@code{_json.make_encoder()} received a bad @code{encoder()} argument. Patch by Oren
Milman.

@item 
bpo-31492@footnote{https://bugs.python.org/issue31492}: Fix assertion failures in case of failing to import from a
module with a bad @code{__name__} attribute, and in case of failing to access
an attribute of such a module. Patch by Oren Milman.

@item 
bpo-31478@footnote{https://bugs.python.org/issue31478}: Fix an assertion failure in @code{_random.Random.seed()} in case the
argument has a bad @code{__abs__()} method. Patch by Oren Milman.

@item 
bpo-31336@footnote{https://bugs.python.org/issue31336}: Speed up class creation by 10-20% by reducing the overhead in
the necessary special method lookups.  Patch by Stefan Behnel.

@item 
bpo-31415@footnote{https://bugs.python.org/issue31415}: Add @code{-X importtime} option to show how long each import
takes. It can be used to optimize application's startup time.  Support the
@geindex PYTHONPROFILEIMPORTTIME
@geindex 环境变量; PYTHONPROFILEIMPORTTIME
@ref{331,,PYTHONPROFILEIMPORTTIME} as an equivalent way to enable this.

@item 
bpo-31410@footnote{https://bugs.python.org/issue31410}: Optimized calling wrapper and classmethod descriptors.

@item 
bpo-31353@footnote{https://bugs.python.org/issue31353}: 
@geindex Python 提高建议; PEP 553
PEP 553@footnote{https://www.python.org/dev/peps/pep-0553} - Add a new built-in called @code{breakpoint()} which
calls @code{sys.breakpointhook()}.  By default this imports @code{pdb} and calls
@code{pdb.set_trace()}, but users may override @code{sys.breakpointhook()} to
call whatever debugger they want.  The original value of the hook is saved
in @code{sys.__breakpointhook__}.

@item 
bpo-17852@footnote{https://bugs.python.org/issue17852}: Maintain a list of open buffered files, flush them before
exiting the interpreter.  Based on a patch from Armin Rigo.

@item 
bpo-31315@footnote{https://bugs.python.org/issue31315}: Fix an assertion failure in imp.create_dynamic(), when
spec.name is not a string. Patch by Oren Milman.

@item 
bpo-31311@footnote{https://bugs.python.org/issue31311}: Fix a crash in the @code{__setstate__()} method of
@ref{1043,,ctypes._CData}, in case of a bad @code{__dict__}. Patch by Oren Milman.

@item 
bpo-31293@footnote{https://bugs.python.org/issue31293}: Fix crashes in true division and multiplication of a timedelta
object by a float with a bad as_integer_ratio() method. Patch by Oren
Milman.

@item 
bpo-31285@footnote{https://bugs.python.org/issue31285}: Fix an assertion failure in @ref{5ab,,warnings.warn_explicit}, when the
return value of the received loader's get_source() has a bad splitlines()
method. Patch by Oren Milman.

@item 
bpo-30406@footnote{https://bugs.python.org/issue30406}: Make @code{async} and @code{await} proper keywords, as specified in
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492}.
@end itemize

@node 库<30>,文档<25>,核心与内置<29>,Python 3 7 0 alpha 2
@anchor{whatsnew/changelog id226}@anchor{1044}
@subsubsection 库



@itemize -

@item 
bpo-30058@footnote{https://bugs.python.org/issue30058}: Fixed buffer overflow in select.kqueue.control().

@item 
bpo-31672@footnote{https://bugs.python.org/issue31672}: @code{idpattern} in @code{string.Template} matched some non-ASCII
characters. Now it uses @code{-i} regular expression local flag to avoid
non-ASCII characters.

@item 
bpo-31701@footnote{https://bugs.python.org/issue31701}: On Windows, faulthandler.enable() now ignores MSC and COM
exceptions.

@item 
bpo-31728@footnote{https://bugs.python.org/issue31728}: Prevent crashes in @code{_elementtree} due to unsafe cleanup of
@code{Element.text} and @code{Element.tail}. Patch by Oren Milman.

@item 
bpo-31671@footnote{https://bugs.python.org/issue31671}: Now @code{re.compile()} converts passed RegexFlag to normal int
object before compiling. bm_regex_compile benchmark shows 14% performance
improvements.

@item 
bpo-30397@footnote{https://bugs.python.org/issue30397}: The types of compiled regular objects and match objects are now
exposed as @code{re.Pattern} and @code{re.Match}.  This adds information in pydoc
output for the re module.

@item 
bpo-31675@footnote{https://bugs.python.org/issue31675}: Fixed memory leaks in Tkinter's methods splitlist() and split()
when pass a string larger than 2 GiB.

@item 
bpo-31673@footnote{https://bugs.python.org/issue31673}: Fixed typo in the name of Tkinter's method adderrorinfo().

@item 
bpo-31648@footnote{https://bugs.python.org/issue31648}: Improvements to path predicates in ElementTree: Allow
whitespace around predicate parts, i.e. "[a = 'text']" instead of
requiring the less readable "[a='text']". Add support for text comparison
of the current node, like "[.='text']". Patch by Stefan Behnel.

@item 
bpo-30806@footnote{https://bugs.python.org/issue30806}: Fix the string representation of a netrc object.

@item 
bpo-31638@footnote{https://bugs.python.org/issue31638}: Add optional argument @code{compressed} to
@code{zipapp.create_archive}, and add option @code{--compress} to the command
line interface of @code{zipapp}.

@item 
bpo-25351@footnote{https://bugs.python.org/issue25351}: Avoid venv activate failures with undefined variables

@item 
bpo-20519@footnote{https://bugs.python.org/issue20519}: Avoid ctypes use (if possible) and improve import time for
uuid.

@item 
bpo-28293@footnote{https://bugs.python.org/issue28293}: The regular expression cache is no longer completely dumped
when it is full.

@item 
bpo-31596@footnote{https://bugs.python.org/issue31596}: Added pthread_getcpuclockid() to the time module

@item 
bpo-27494@footnote{https://bugs.python.org/issue27494}: Make 2to3 accept a trailing comma in generator expressions. For
example, @code{set(x for x in [],)} is now allowed.

@item 
bpo-30347@footnote{https://bugs.python.org/issue30347}: Stop crashes when concurrently iterate over itertools.groupby()
iterators.

@item 
bpo-30346@footnote{https://bugs.python.org/issue30346}: An iterator produced by itertools.groupby() iterator now
becomes exhausted after advancing the groupby iterator.

@item 
bpo-31556@footnote{https://bugs.python.org/issue31556}: Cancel asyncio.wait_for future faster if timeout <= 0

@item 
bpo-31540@footnote{https://bugs.python.org/issue31540}: Allow passing a context object in
@ref{2a3,,concurrent.futures.ProcessPoolExecutor} constructor. Also, free
job resources in @ref{2a3,,concurrent.futures.ProcessPoolExecutor} earlier
to improve memory usage when a worker waits for new jobs.

@item 
bpo-31516@footnote{https://bugs.python.org/issue31516}: @code{threading.current_thread()} should not return a dummy thread
at shutdown.

@item 
bpo-31525@footnote{https://bugs.python.org/issue31525}: In the sqlite module, require the sqlite3_prepare_v2 API. Thus,
the sqlite module now requires sqlite version at least 3.3.9.

@item 
bpo-26510@footnote{https://bugs.python.org/issue26510}: argparse subparsers are now required by default.  This matches
behaviour in Python 2. For optional subparsers, use the new parameter
@code{add_subparsers(required=False)}. Patch by Anthony Sottile. (As of
3.7.0rc1, the default was changed to not required as had been the case
since Python 3.3.)

@item 
bpo-27541@footnote{https://bugs.python.org/issue27541}: Reprs of subclasses of some collection and iterator classes
(@ref{32b,,bytearray}, @ref{44b,,array.array}, @ref{52b,,collections.deque},
@ref{b33,,collections.defaultdict}, @ref{c14,,itertools.count}, @ref{1045,,itertools.repeat}) now
contain actual type name insteads of hardcoded name of the base class.

@item 
bpo-31351@footnote{https://bugs.python.org/issue31351}: python -m ensurepip now exits with non-zero exit code if pip
bootstrapping has failed.

@item 
bpo-31389@footnote{https://bugs.python.org/issue31389}: @code{pdb.set_trace()} now takes an optional keyword-only argument
@code{header}. If given, this is printed to the console just before debugging
begins.
@end itemize

@node 文档<25>,构建<21>,库<30>,Python 3 7 0 alpha 2
@anchor{whatsnew/changelog id227}@anchor{1046}
@subsubsection 文档



@itemize -

@item 
bpo-31537@footnote{https://bugs.python.org/issue31537}: Fix incorrect usage of @code{get_history_length} in readline
documentation example code. Patch by Brad Smith.

@item 
bpo-30085@footnote{https://bugs.python.org/issue30085}: The operator functions without double underscores are preferred
for clarity. The one with underscores are only kept for
back-compatibility.
@end itemize

@node 构建<21>,IDLE<28>,文档<25>,Python 3 7 0 alpha 2
@anchor{whatsnew/changelog id228}@anchor{1047}
@subsubsection 构建



@itemize -

@item 
bpo-31696@footnote{https://bugs.python.org/issue31696}: Improve compiler version information in @ref{5ce,,sys.version}
when Python is built with Clang.

@item 
bpo-31625@footnote{https://bugs.python.org/issue31625}: Stop using ranlib on static libraries. Instead, we assume ar
supports the 's' flag.

@item 
bpo-31624@footnote{https://bugs.python.org/issue31624}: 删除对 BSD/OS 的支持。

@item 
bpo-22140@footnote{https://bugs.python.org/issue22140}: Prevent double substitution of prefix in python-config.sh.

@item 
bpo-31569@footnote{https://bugs.python.org/issue31569}: Correct PCBuild/ case to PCbuild/ in build scripts and
documentation.

@item 
bpo-31536@footnote{https://bugs.python.org/issue31536}: Avoid wholesale rebuild after @code{make regen-all} if nothing
changed.
@end itemize

@node IDLE<28>,C API<17>,构建<21>,Python 3 7 0 alpha 2
@anchor{whatsnew/changelog id229}@anchor{1048}
@subsubsection IDLE



@itemize -

@item 
bpo-31460@footnote{https://bugs.python.org/issue31460}: Simplify the API of IDLE's Module Browser. Passing a widget
instead of an flist with a root widget opens the option of creating a
browser frame that is only part of a window.  Passing a full file name
instead of pieces assumed to come from a .py file opens the possibility of
browsing python files that do not end in .py.

@item 
bpo-31649@footnote{https://bugs.python.org/issue31649}: IDLE - Make _htest, _utest parameters keyword only.

@item 
bpo-31559@footnote{https://bugs.python.org/issue31559}: Remove test order dependence in idle_test.test_browser.

@item 
bpo-31459@footnote{https://bugs.python.org/issue31459}: Rename IDLE's module browser from Class Browser to Module
Browser. The original module-level class and method browser became a
module browser, with the addition of module-level functions, years ago.
Nested classes and functions were added yesterday.  For
back-compatibility, the virtual event <<open-class-browser>>, which
appears on the Keys tab of the Settings dialog, is not changed. Patch by
Cheryl Sabella.

@item 
bpo-31500@footnote{https://bugs.python.org/issue31500}: Default fonts now are scaled on HiDPI displays.

@item 
bpo-1612262@footnote{https://bugs.python.org/issue1612262}: IDLE module browser now shows nested classes and functions.
Original patches for code and tests by Guilherme Polo and Cheryl Sabella,
respectively.
@end itemize

@node C API<17>,,IDLE<28>,Python 3 7 0 alpha 2
@anchor{whatsnew/changelog id230}@anchor{1049}
@subsubsection C API



@itemize -

@item 
bpo-28280@footnote{https://bugs.python.org/issue28280}: Make @code{PyMapping_Keys()}, @code{PyMapping_Values()} and
@code{PyMapping_Items()} always return a @ref{262,,list} (rather than a @ref{262,,list} or a
@ref{478,,tuple}). Patch by Oren Milman.

@item 
bpo-31532@footnote{https://bugs.python.org/issue31532}: Fix memory corruption due to allocator mix in getpath.c between
Py_GetPath() and Py_SetPath()

@item 
bpo-25658@footnote{https://bugs.python.org/issue25658}: Implement 
@geindex Python 提高建议; PEP 539
PEP 539@footnote{https://www.python.org/dev/peps/pep-0539} for Thread Specific Storage (TSS) API: it
is a new Thread Local Storage (TLS) API to CPython which would supersede
use of the existing TLS API within the CPython interpreter, while
deprecating the existing API. PEP written by Erik M. Bray, patch by
Masayuki Yamamoto.
@end itemize

@node Python 3 7 0 alpha 1,Python 3 6 6 正式版,Python 3 7 0 alpha 2,更新日志
@anchor{whatsnew/changelog python-3-7-0-alpha-1}@anchor{104a}
@subsection Python 3.7.0 alpha 1


@emph{发布日期: 2017-09-19}

@menu
* 安全: 安全<18>. 
* 核心与内置: 核心与内置<30>. 
* 库: 库<31>. 
* 文档: 文档<26>. 
* 测试: 测试<23>. 
* 构建: 构建<22>. 
* Windows: Windows<24>. 
* IDLE: IDLE<29>. 
* 工具/示例: 工具/示例<16>. 
* C API: C API<18>. 

@end menu

@node 安全<18>,核心与内置<30>,,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id231}@anchor{104b}
@subsubsection 安全



@itemize -

@item 
bpo-29781@footnote{https://bugs.python.org/issue29781}: SSLObject.version() now correctly returns None when handshake
over BIO has not been performed yet.

@item 
bpo-29505@footnote{https://bugs.python.org/issue29505}: Add fuzz tests for float(str), int(str), unicode(str); for
oss-fuzz.

@item 
bpo-30947@footnote{https://bugs.python.org/issue30947}: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to
get security fixes.

@item 
bpo-30730@footnote{https://bugs.python.org/issue30730}: Prevent environment variables injection in subprocess on
Windows.  Prevent passing other environment variables and command
arguments.

@item 
bpo-30694@footnote{https://bugs.python.org/issue30694}: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple
security vulnerabilities including: CVE-2017-9233 (External entity
infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix),
CVE-2016-0718 (Fix regression bugs from 2.2.0's fix to CVE-2016-0718) and
CVE-2012-0876 (Counter hash flooding with SipHash). Note: the
CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn't
impact Python, since Python already gets entropy from the OS to set the
expat secret using @code{XML_SetHashSalt()}.

@item 
bpo-30500@footnote{https://bugs.python.org/issue30500}: Fix urllib.parse.splithost() to correctly parse fragments. For
example, @code{splithost('//127.0.0.1#@@evil.com/')} now correctly returns the
@code{127.0.0.1} host, instead of treating @code{@@evil.com} as the host in an
authentication (@code{login@@host}).

@item 
bpo-29591@footnote{https://bugs.python.org/issue29591}: Update expat copy from 2.1.1 to 2.2.0 to get fixes of
CVE-2016-0718 and CVE-2016-4472. See
@indicateurl{https://sourceforge.net/p/expat/bugs/537/} for more information.
@end itemize

@node 核心与内置<30>,库<31>,安全<18>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id232}@anchor{104c}
@subsubsection 核心与内置



@itemize -

@item 
bpo-31490@footnote{https://bugs.python.org/issue31490}: Fix an assertion failure in @ref{2b,,ctypes} class definition, in case
the class has an attribute whose name is specified in @code{_anonymous_} but
not in @code{_fields_}. Patch by Oren Milman.

@item 
bpo-31471@footnote{https://bugs.python.org/issue31471}: Fix an assertion failure in @ref{2b9,,subprocess.Popen()} on Windows, in
case the env argument has a bad keys() method. Patch by Oren Milman.

@item 
bpo-31418@footnote{https://bugs.python.org/issue31418}: Fix an assertion failure in @code{PyErr_WriteUnraisable()} in case
of an exception with a bad @code{__module__} attribute. Patch by Oren Milman.

@item 
bpo-31416@footnote{https://bugs.python.org/issue31416}: Fix assertion failures in case of a bad warnings.filters or
warnings.defaultaction. Patch by Oren Milman.

@item 
bpo-28411@footnote{https://bugs.python.org/issue28411}: Change direct usage of PyInterpreterState.modules to
PyImport_GetModuleDict(). Also introduce more uniformity in other code
that deals with sys.modules. This helps reduce complications when working
on sys.modules.

@item 
bpo-28411@footnote{https://bugs.python.org/issue28411}: Switch to the abstract API when dealing with
@code{PyInterpreterState.modules}. This allows later support for all dict
subclasses and other Mapping implementations.  Also add a
@code{PyImport_GetModule()} function to reduce a bunch of duplicated code.

@item 
bpo-31411@footnote{https://bugs.python.org/issue31411}: Raise a TypeError instead of SystemError in case
warnings.onceregistry is not a dictionary. Patch by Oren Milman.

@item 
bpo-31344@footnote{https://bugs.python.org/issue31344}: For finer control of tracing behaviour when testing the
interpreter, two new frame attributes have been added to control the
emission of particular trace events: @code{f_trace_lines} (@code{True} by
default) to turn off per-line trace events; and @code{f_trace_opcodes}
(@code{False} by default) to turn on per-opcode trace events.

@item 
bpo-31373@footnote{https://bugs.python.org/issue31373}: Fix several possible instances of undefined behavior due to
floating-point demotions.

@item 
bpo-30465@footnote{https://bugs.python.org/issue30465}: Location information (@code{lineno} and @code{col_offset}) in
f-strings is now (mostly) correct.  This fixes tools like flake8 from
showing warnings on the wrong line (typically the first line of the file).

@item 
bpo-30860@footnote{https://bugs.python.org/issue30860}: Consolidate CPython's global runtime state under a single
struct.  This improves discoverability of the runtime state.

@item 
bpo-31347@footnote{https://bugs.python.org/issue31347}: Fix possible undefined behavior in _PyObject_FastCall_Prepend.

@item 
bpo-31343@footnote{https://bugs.python.org/issue31343}: Include sys/sysmacros.h for major(), minor(), and makedev().
GNU C libray plans to remove the functions from sys/types.h.

@item 
bpo-31291@footnote{https://bugs.python.org/issue31291}: Fix an assertion failure in @ref{104d,,zipimport.zipimporter.get_data} on
Windows, when the return value of @code{pathname.replace('/','\\')} isn't a
string. Patch by Oren Milman.

@item 
bpo-31271@footnote{https://bugs.python.org/issue31271}: Fix an assertion failure in the write() method of
@ref{5ee,,io.TextIOWrapper}, when the encoder doesn't return a bytes object. Patch
by Oren Milman.

@item 
bpo-31243@footnote{https://bugs.python.org/issue31243}: Fix a crash in some methods of @ref{5ee,,io.TextIOWrapper}, when the
decoder's state is invalid. Patch by Oren Milman.

@item 
bpo-30721@footnote{https://bugs.python.org/issue30721}: @code{print} now shows correct usage hint for using Python 2
redirection syntax.  Patch by Sanyam Khurana.

@item 
bpo-31070@footnote{https://bugs.python.org/issue31070}: Fix a race condition in importlib _get_module_lock().

@item 
bpo-30747@footnote{https://bugs.python.org/issue30747}: Add a non-dummy implementation of _Py_atomic_store and
_Py_atomic_load on MSVC.

@item 
bpo-31095@footnote{https://bugs.python.org/issue31095}: Fix potential crash during GC caused by @code{tp_dealloc} which
doesn't call @code{PyObject_GC_UnTrack()}.

@item 
bpo-31071@footnote{https://bugs.python.org/issue31071}: Avoid masking original TypeError in call with * unpacking when
other arguments are passed.

@item 
bpo-30978@footnote{https://bugs.python.org/issue30978}: str.format_map() now passes key lookup exceptions through.
Previously any exception was replaced with a KeyError exception.

@item 
bpo-30808@footnote{https://bugs.python.org/issue30808}: Use _Py_atomic API for concurrency-sensitive signal state.

@item 
bpo-30876@footnote{https://bugs.python.org/issue30876}: Relative import from unloaded package now reimports the package
instead of failing with SystemError.  Relative import from non-package now
fails with ImportError rather than SystemError.

@item 
bpo-30703@footnote{https://bugs.python.org/issue30703}: Improve signal delivery. Avoid using Py_AddPendingCall from
signal handler, to avoid calling signal-unsafe functions. The tests I'm
adding here fail without the rest of the patch, on Linux and OS X. This
means our signal delivery logic had defects (some signals could be lost).

@item 
bpo-30765@footnote{https://bugs.python.org/issue30765}: Avoid blocking in pthread_mutex_lock() when
PyThread_acquire_lock() is asked not to block.

@item 
bpo-31161@footnote{https://bugs.python.org/issue31161}: Make sure the 'Missing parentheses' syntax error message is
only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

@item 
bpo-30814@footnote{https://bugs.python.org/issue30814}: Fixed a race condition when import a submodule from a package.

@item 
bpo-30736@footnote{https://bugs.python.org/issue30736}: The internal unicodedata database has been upgraded to Unicode
10.0.

@item 
bpo-30604@footnote{https://bugs.python.org/issue30604}: Move co_extra_freefuncs from per-thread to per-interpreter to
avoid crashes.

@item 
bpo-30597@footnote{https://bugs.python.org/issue30597}: @code{print} now shows expected input in custom error message when
used as a Python 2 statement. Patch by Sanyam Khurana.

@item 
bpo-30682@footnote{https://bugs.python.org/issue30682}: Removed a too-strict assertion that failed for certain
f-strings, such as eval("f'\n'") and eval("f'\r'").

@item 
bpo-30501@footnote{https://bugs.python.org/issue30501}: The compiler now produces more optimal code for complex
condition expressions in the "if", "while" and "assert" statement, the
"if" expression, and generator expressions and comprehensions.

@item 
bpo-28180@footnote{https://bugs.python.org/issue28180}: Implement 
@geindex Python 提高建议; PEP 538
PEP 538@footnote{https://www.python.org/dev/peps/pep-0538} (legacy C locale coercion). This means
that when a suitable coercion target locale is available, both the core
interpreter and locale-aware C extensions will assume the use of UTF-8 as
the default text encoding, rather than ASCII.

@item 
bpo-30486@footnote{https://bugs.python.org/issue30486}: Allows setting cell values for __closure__. Patch by Lisa
Roach.

@item 
bpo-30537@footnote{https://bugs.python.org/issue30537}: itertools.islice now accepts integer-like objects (having an
__index__ method) as start, stop, and slice arguments

@item 
bpo-25324@footnote{https://bugs.python.org/issue25324}: Tokens needed for parsing in Python moved to C. @code{COMMENT},
@code{NL} and @code{ENCODING}. This way the tokens and tok_names in the token
module don't get changed when you import the tokenize module.

@item 
bpo-29104@footnote{https://bugs.python.org/issue29104}: Fixed parsing backslashes in f-strings.

@item 
bpo-27945@footnote{https://bugs.python.org/issue27945}: Fixed various segfaults with dict when input collections are
mutated during searching, inserting or comparing.  Based on patches by
Duane Griffin and Tim Mitchell.

@item 
bpo-25794@footnote{https://bugs.python.org/issue25794}: Fixed type.__setattr__() and type.__delattr__() for
non-interned attribute names.  Based on patch by Eryk Sun.

@item 
bpo-30039@footnote{https://bugs.python.org/issue30039}: If a KeyboardInterrupt happens when the interpreter is in the
middle of resuming a chain of nested 'yield from' or 'await' calls, it's
now correctly delivered to the innermost frame.

@item 
bpo-28974@footnote{https://bugs.python.org/issue28974}: @code{object.__format__(x, '@w{'})} is now equivalent to @code{str(x)}
rather than @code{format(str(self), '@w{'})}.

@item 
bpo-30024@footnote{https://bugs.python.org/issue30024}: Circular imports involving absolute imports with binding a
submodule to a name are now supported.

@item 
bpo-12414@footnote{https://bugs.python.org/issue12414}: sys.getsizeof() on a code object now returns the sizes which
includes the code struct and sizes of objects which it references. Patch
by Dong-hee Na.

@item 
bpo-29839@footnote{https://bugs.python.org/issue29839}: len() now raises ValueError rather than OverflowError if
__len__() returned a large negative integer.

@item 
bpo-11913@footnote{https://bugs.python.org/issue11913}: README.rst is now included in the list of distutils standard
READMEs and therefore included in source distributions.

@item 
bpo-29914@footnote{https://bugs.python.org/issue29914}: Fixed default implementations of __reduce__ and
__reduce_ex__(). object.__reduce__() no longer takes arguments,
object.__reduce_ex__() now requires one argument.

@item 
bpo-29949@footnote{https://bugs.python.org/issue29949}: Fix memory usage regression of set and frozenset object.

@item 
bpo-29935@footnote{https://bugs.python.org/issue29935}: Fixed error messages in the index() method of tuple, list and
deque when pass indices of wrong type.

@item 
bpo-29816@footnote{https://bugs.python.org/issue29816}: Shift operation now has less opportunity to raise
OverflowError. ValueError always is raised rather than OverflowError for
negative counts. Shifting zero with non-negative count always returns
zero.

@item 
bpo-24821@footnote{https://bugs.python.org/issue24821}: Fixed the slowing down to 25 times in the searching of some
unlucky Unicode characters.

@item 
bpo-29102@footnote{https://bugs.python.org/issue29102}: Add a unique ID to PyInterpreterState.  This makes it easier to
identify each subinterpreter.

@item 
bpo-29894@footnote{https://bugs.python.org/issue29894}: The deprecation warning is emitted if __complex__ returns an
instance of a strict subclass of complex.  In a future versions of Python
this can be an error.

@item 
bpo-29859@footnote{https://bugs.python.org/issue29859}: Show correct error messages when any of the pthread_* calls in
thread_pthread.h fails.

@item 
bpo-29849@footnote{https://bugs.python.org/issue29849}: Fix a memory leak when an ImportError is raised during from
import.

@item 
bpo-28856@footnote{https://bugs.python.org/issue28856}: Fix an oversight that %b format for bytes should support
objects follow the buffer protocol.

@item 
bpo-29723@footnote{https://bugs.python.org/issue29723}: The @code{sys.path[0]} initialization change for bpo-29139@footnote{https://bugs.python.org/issue29139} caused
a regression by revealing an inconsistency in how sys.path is initialized
when executing @code{__main__} from a zipfile, directory, or other import
location. The interpreter now consistently avoids ever adding the import
location's parent directory to @code{sys.path}, and ensures no other
@code{sys.path} entries are inadvertently modified when inserting the import
location named on the command line.

@item 
bpo-29568@footnote{https://bugs.python.org/issue29568}: Escaped percent "%%" in the format string for classic string
formatting no longer allows any characters between two percents.

@item 
bpo-29714@footnote{https://bugs.python.org/issue29714}: Fix a regression that bytes format may fail when containing
zero bytes inside.

@item 
bpo-29695@footnote{https://bugs.python.org/issue29695}: bool(), float(), list() and tuple() no longer take keyword
arguments. The first argument of int() can now be passes only as
positional argument.

@item 
bpo-28893@footnote{https://bugs.python.org/issue28893}: Set correct __cause__ for errors about invalid awaitables
returned from __aiter__ and __anext__.

@item 
bpo-28876@footnote{https://bugs.python.org/issue28876}: @code{bool(range)} works even if @code{len(range)} raises
@ref{95a,,OverflowError}.

@item 
bpo-29683@footnote{https://bugs.python.org/issue29683}: Fixes to memory allocation in _PyCode_SetExtra.  Patch by Brian
Coleman.

@item 
bpo-29684@footnote{https://bugs.python.org/issue29684}: Fix minor regression of PyEval_CallObjectWithKeywords. It
should raise TypeError when kwargs is not a dict.  But it might cause segv
when args=NULL and kwargs is not a dict.

@item 
bpo-28598@footnote{https://bugs.python.org/issue28598}: Support __rmod__ for subclasses of str being called before
str.__mod__. Patch by Martijn Pieters.

@item 
bpo-29607@footnote{https://bugs.python.org/issue29607}: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by
Matthieu Dartiailh.

@item 
bpo-29602@footnote{https://bugs.python.org/issue29602}: Fix incorrect handling of signed zeros in complex constructor
for complex subclasses and for inputs having a __complex__ method. Patch
by Serhiy Storchaka.

@item 
bpo-29347@footnote{https://bugs.python.org/issue29347}: Fixed possibly dereferencing undefined pointers when creating
weakref objects.

@item 
bpo-29463@footnote{https://bugs.python.org/issue29463}: Add @code{docstring} field to Module, ClassDef, FunctionDef, and
AsyncFunctionDef ast nodes.  docstring is not first stmt in their body
anymore.  It affects @code{co_firstlineno} and @code{co_lnotab} of code object
for module and class. (Reverted in bpo-32911@footnote{https://bugs.python.org/issue32911}.)

@item 
bpo-29438@footnote{https://bugs.python.org/issue29438}: Fixed use-after-free problem in key sharing dict.

@item 
bpo-29546@footnote{https://bugs.python.org/issue29546}: Set the 'path' and 'name' attribute on ImportError for @code{from
... import ...}.

@item 
bpo-29546@footnote{https://bugs.python.org/issue29546}: Improve from-import error message with location

@item 
bpo-29478@footnote{https://bugs.python.org/issue29478}: If max_line_length=None is specified while using the Compat32
policy, it is no longer ignored.  Patch by Mircea Cosbuc.

@item 
bpo-29319@footnote{https://bugs.python.org/issue29319}: Prevent RunMainFromImporter overwriting sys.path[0].

@item 
bpo-29337@footnote{https://bugs.python.org/issue29337}: Fixed possible BytesWarning when compare the code objects.
Warnings could be emitted at compile time.

@item 
bpo-29327@footnote{https://bugs.python.org/issue29327}: Fixed a crash when pass the iterable keyword argument to
sorted().

@item 
bpo-29034@footnote{https://bugs.python.org/issue29034}: Fix memory leak and use-after-free in os module
(path_converter).

@item 
bpo-29159@footnote{https://bugs.python.org/issue29159}: Fix regression in bytes(x) when x.__index__() raises Exception.

@item 
bpo-29049@footnote{https://bugs.python.org/issue29049}: Call _PyObject_GC_TRACK() lazily when calling Python function.
Calling function is up to 5% faster.

@item 
bpo-28927@footnote{https://bugs.python.org/issue28927}: bytes.fromhex() and bytearray.fromhex() now ignore all ASCII
whitespace, not only spaces.  Patch by Robert Xiao.

@item 
bpo-28932@footnote{https://bugs.python.org/issue28932}: Do not include <sys/random.h> if it does not exist.

@item 
bpo-25677@footnote{https://bugs.python.org/issue25677}: Correct the positioning of the syntax error caret for indented
blocks. Based on patch by Michael Layzell.

@item 
bpo-29000@footnote{https://bugs.python.org/issue29000}: Fixed bytes formatting of octals with zero padding in alternate
form.

@item 
bpo-18896@footnote{https://bugs.python.org/issue18896}: Python function can now have more than 255 parameters.
collections.namedtuple() now supports tuples with more than 255 elements.

@item 
bpo-28596@footnote{https://bugs.python.org/issue28596}: The preferred encoding is UTF-8 on Android. Patch written by
Chi Hsuan Yen.

@item 
bpo-22257@footnote{https://bugs.python.org/issue22257}: Clean up interpreter startup (see 
@geindex Python 提高建议; PEP 432
PEP 432@footnote{https://www.python.org/dev/peps/pep-0432}).

@item 
bpo-26919@footnote{https://bugs.python.org/issue26919}: On Android, operating system data is now always encoded/decoded
to/from UTF-8, instead of the locale encoding to avoid inconsistencies
with os.fsencode() and os.fsdecode() which are already using UTF-8.

@item 
bpo-28991@footnote{https://bugs.python.org/issue28991}: functools.lru_cache() was susceptible to an obscure reentrancy
bug triggerable by a monkey-patched len() function.

@item 
bpo-28147@footnote{https://bugs.python.org/issue28147}: Fix a memory leak in split-table dictionaries: setattr() must
not convert combined table into split table. Patch written by INADA Naoki.

@item 
bpo-28739@footnote{https://bugs.python.org/issue28739}: f-string expressions are no longer accepted as docstrings and
by ast.literal_eval() even if they do not include expressions.

@item 
bpo-28512@footnote{https://bugs.python.org/issue28512}: Fixed setting the offset attribute of SyntaxError by
PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

@item 
bpo-28918@footnote{https://bugs.python.org/issue28918}: Fix the cross compilation of xxlimited when Python has been
built with Py_DEBUG defined.

@item 
bpo-23722@footnote{https://bugs.python.org/issue23722}: Rather than silently producing a class that doesn't support
zero-argument @code{super()} in methods, failing to pass the new
@code{__classcell__} namespace entry up to @code{type.__new__} now results in a
@code{DeprecationWarning} and a class that supports zero-argument
@code{super()}.

@item 
bpo-28797@footnote{https://bugs.python.org/issue28797}: Modifying the class __dict__ inside the __set_name__ method of
a descriptor that is used inside that class no longer prevents calling the
__set_name__ method of other descriptors.

@item 
bpo-28799@footnote{https://bugs.python.org/issue28799}: Remove the @code{PyEval_GetCallStats()} function and deprecate the
untested and undocumented @code{sys.callstats()} function. Remove the
@code{CALL_PROFILE} special build: use the @ref{e36,,sys.setprofile()} function,
@ref{28,,cProfile} or @ref{d3,,profile} to profile function calls.

@item 
bpo-12844@footnote{https://bugs.python.org/issue12844}: More than 255 arguments can now be passed to a function.

@item 
bpo-28782@footnote{https://bugs.python.org/issue28782}: Fix a bug in the implementation @code{yield from} when checking if
the next instruction is YIELD_FROM. Regression introduced by WORDCODE
(bpo-26647@footnote{https://bugs.python.org/issue26647}).

@item 
bpo-28774@footnote{https://bugs.python.org/issue28774}: Fix error position of the unicode error in ASCII and Latin1
encoders when a string returned by the error handler contains multiple
non-encodable characters (non-ASCII for the ASCII codec, characters out of
the U+0000-U+00FF range for Latin1).

@item 
bpo-28731@footnote{https://bugs.python.org/issue28731}: Optimize _PyDict_NewPresized() to create correct size dict.
Improve speed of dict literal with constant keys up to 30%.

@item 
bpo-28532@footnote{https://bugs.python.org/issue28532}: Show sys.version when -V option is supplied twice.

@item 
bpo-27100@footnote{https://bugs.python.org/issue27100}: The with-statement now checks for __enter__ before it checks
for __exit__. This gives less confusing error messages when both methods
are missing. Patch by Jonathan Ellington.

@item 
bpo-28746@footnote{https://bugs.python.org/issue28746}: Fix the set_inheritable() file descriptor method on platforms
that do not have the ioctl FIOCLEX and FIONCLEX commands.

@item 
bpo-26920@footnote{https://bugs.python.org/issue26920}: Fix not getting the locale's charset upon initializing the
interpreter, on platforms that do not have langinfo.

@item 
bpo-28648@footnote{https://bugs.python.org/issue28648}: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X
when decode astral characters.  Patch by Xiang Zhang.

@item 
bpo-28665@footnote{https://bugs.python.org/issue28665}: Improve speed of the STORE_DEREF opcode by 40%.

@item 
bpo-19398@footnote{https://bugs.python.org/issue19398}: Extra slash no longer added to sys.path components in case of
empty compile-time PYTHONPATH components.

@item 
bpo-28621@footnote{https://bugs.python.org/issue28621}: Sped up converting int to float by reusing faster bits counting
implementation.  Patch by Adrian Wielgosik.

@item 
bpo-28580@footnote{https://bugs.python.org/issue28580}: Optimize iterating split table values. Patch by Xiang Zhang.

@item 
bpo-28583@footnote{https://bugs.python.org/issue28583}: PyDict_SetDefault didn't combine split table when needed. Patch
by Xiang Zhang.

@item 
bpo-28128@footnote{https://bugs.python.org/issue28128}: Deprecation warning for invalid str and byte escape sequences
now prints better information about where the error occurs. Patch by
Serhiy Storchaka and Eric Smith.

@item 
bpo-28509@footnote{https://bugs.python.org/issue28509}: dict.update() no longer allocate unnecessary large memory.

@item 
bpo-28426@footnote{https://bugs.python.org/issue28426}: Fixed potential crash in PyUnicode_AsDecodedObject() in debug
build.

@item 
bpo-28517@footnote{https://bugs.python.org/issue28517}: Fixed of-by-one error in the peephole optimizer that caused
keeping unreachable code.

@item 
bpo-28214@footnote{https://bugs.python.org/issue28214}: Improved exception reporting for problematic __set_name__
attributes.

@item 
bpo-23782@footnote{https://bugs.python.org/issue23782}: Fixed possible memory leak in _PyTraceback_Add() and exception
loss in PyTraceBack_Here().

@item 
bpo-28183@footnote{https://bugs.python.org/issue28183}: Optimize and cleanup dict iteration.

@item 
bpo-26081@footnote{https://bugs.python.org/issue26081}: Added C implementation of asyncio.Future. Original patch by
Yury Selivanov.

@item 
bpo-28379@footnote{https://bugs.python.org/issue28379}: Added sanity checks and tests for PyUnicode_CopyCharacters().
Patch by Xiang Zhang.

@item 
bpo-28376@footnote{https://bugs.python.org/issue28376}: The type of long range iterator is now registered as Iterator.
Patch by Oren Milman.

@item 
bpo-28376@footnote{https://bugs.python.org/issue28376}: Creating instances of range_iterator by calling range_iterator
type now is disallowed.  Calling iter() on range instance is the only way.
Patch by Oren Milman.

@item 
bpo-26906@footnote{https://bugs.python.org/issue26906}: Resolving special methods of uninitialized type now causes
implicit initialization of the type instead of a fail.

@item 
bpo-18287@footnote{https://bugs.python.org/issue18287}: PyType_Ready() now checks that tp_name is not NULL. Original
patch by Niklas Koep.

@item 
bpo-24098@footnote{https://bugs.python.org/issue24098}: Fixed possible crash when AST is changed in process of
compiling it.

@item 
bpo-28201@footnote{https://bugs.python.org/issue28201}: Dict reduces possibility of 2nd conflict in hash table when
hashes have same lower bits.

@item 
bpo-28350@footnote{https://bugs.python.org/issue28350}: String constants with null character no longer interned.

@item 
bpo-26617@footnote{https://bugs.python.org/issue26617}: Fix crash when GC runs during weakref callbacks.

@item 
bpo-27942@footnote{https://bugs.python.org/issue27942}: String constants now interned recursively in tuples and
frozensets.

@item 
bpo-28289@footnote{https://bugs.python.org/issue28289}: ImportError.__init__ now resets not specified attributes.

@item 
bpo-21578@footnote{https://bugs.python.org/issue21578}: Fixed misleading error message when ImportError called with
invalid keyword args.

@item 
bpo-28203@footnote{https://bugs.python.org/issue28203}: Fix incorrect type in complex(1.0, @{2:3@}) error message. Patch
by Soumya Sharma.

@item 
bpo-28086@footnote{https://bugs.python.org/issue28086}: Single var-positional argument of tuple subtype was passed
unscathed to the C-defined function.  Now it is converted to exact tuple.

@item 
bpo-28214@footnote{https://bugs.python.org/issue28214}: Now __set_name__ is looked up on the class instead of the
instance.

@item 
bpo-27955@footnote{https://bugs.python.org/issue27955}: Fallback on reading /dev/urandom device when the getrandom()
syscall fails with EPERM, for example when blocked by SECCOMP.

@item 
bpo-28192@footnote{https://bugs.python.org/issue28192}: Don't import readline in isolated mode.

@item 
bpo-27441@footnote{https://bugs.python.org/issue27441}: Remove some redundant assignments to ob_size in longobject.c.
Thanks Oren Milman.

@item 
bpo-27222@footnote{https://bugs.python.org/issue27222}: Clean up redundant code in long_rshift function. Thanks Oren
Milman.

@item 
Upgrade internal unicode databases to Unicode version 9.0.0.

@item 
bpo-28131@footnote{https://bugs.python.org/issue28131}: Fix a regression in zipimport's compile_source().  zipimport
should use the same optimization level as the interpreter.

@item 
bpo-28126@footnote{https://bugs.python.org/issue28126}: Replace Py_MEMCPY with memcpy(). Visual Studio can properly
optimize memcpy().

@item 
bpo-28120@footnote{https://bugs.python.org/issue28120}: Fix dict.pop() for splitted dictionary when trying to remove a
"pending key" (Not yet inserted in split-table). Patch by Xiang Zhang.

@item 
bpo-26182@footnote{https://bugs.python.org/issue26182}: Raise DeprecationWarning when async and await keywords are used
as variable/attribute/class/function name.

@item 
bpo-26182@footnote{https://bugs.python.org/issue26182}: Fix a refleak in code that raises DeprecationWarning.

@item 
bpo-28721@footnote{https://bugs.python.org/issue28721}: Fix asynchronous generators aclose() and athrow() to handle
StopAsyncIteration propagation properly.

@item 
bpo-26110@footnote{https://bugs.python.org/issue26110}: Speed-up method calls: add LOAD_METHOD and CALL_METHOD opcodes.
@end itemize

@node 库<31>,文档<26>,核心与内置<30>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id233}@anchor{104e}
@subsubsection 库



@itemize -

@item 
bpo-31499@footnote{https://bugs.python.org/issue31499}: xml.etree: Fix a crash when a parser is part of a reference
cycle.

@item 
bpo-31482@footnote{https://bugs.python.org/issue31482}: @code{random.seed()} now works with bytes in version=1

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: typing.get_type_hints now finds the right globalns for classes
and modules by default (when no @code{globalns} was specified by the caller).

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Speed improvements to the @code{typing} module.  Original PRs by
Ivan Levkivskyi and Mitar.

@item 
bpo-31544@footnote{https://bugs.python.org/issue31544}: The C accelerator module of ElementTree ignored exceptions
raised when looking up TreeBuilder target methods in XMLParser().

@item 
bpo-31234@footnote{https://bugs.python.org/issue31234}: socket.create_connection() now fixes manually a reference
cycle: clear the variable storing the last exception on success.

@item 
bpo-31457@footnote{https://bugs.python.org/issue31457}: LoggerAdapter objects can now be nested.

@item 
bpo-31431@footnote{https://bugs.python.org/issue31431}: SSLContext.check_hostname now automatically sets
SSLContext.verify_mode to ssl.CERT_REQUIRED instead of failing with a
ValueError.

@item 
bpo-31233@footnote{https://bugs.python.org/issue31233}: socketserver.ThreadingMixIn now keeps a list of non-daemonic
threads to wait until all these threads complete in server_close().

@item 
bpo-28638@footnote{https://bugs.python.org/issue28638}: Changed the implementation strategy for
collections.namedtuple() to substantially reduce the use of exec() in
favor of precomputed methods. As a result, the @emph{verbose} parameter and
@emph{_source} attribute are no longer supported.  The benefits include 1)
having a smaller memory footprint for applications using multiple named
tuples, 2) faster creation of the named tuple class (approx 4x to 6x
depending on how it is measured), and 3) minor speed-ups for instance
creation using __new__, _make, and _replace.  (The primary patch
contributor is Jelle Zijlstra with further improvements by INADA Naoki,
Serhiy Storchaka, and Raymond Hettinger.)

@item 
bpo-31400@footnote{https://bugs.python.org/issue31400}: Improves SSL error handling to avoid losing error numbers.

@item 
bpo-27629@footnote{https://bugs.python.org/issue27629}: Make return types of SSLContext.wrap_bio() and
SSLContext.wrap_socket() customizable.

@item 
bpo-28958@footnote{https://bugs.python.org/issue28958}: ssl.SSLContext() now uses OpenSSL error information when a
context cannot be instantiated.

@item 
bpo-28182@footnote{https://bugs.python.org/issue28182}: The SSL module now raises SSLCertVerificationError when OpenSSL
fails to verify the peer's certificate. The exception contains more
information about the error.

@item 
bpo-27340@footnote{https://bugs.python.org/issue27340}: SSLSocket.sendall() now uses memoryview to create slices of
data. This fixes support for all bytes-like object. It is also more
efficient and avoids costly copies.

@item 
bpo-14191@footnote{https://bugs.python.org/issue14191}: A new function
@code{argparse.ArgumentParser.parse_intermixed_args} provides the ability to
parse command lines where there user intermixes options and positional
arguments.

@item 
bpo-31178@footnote{https://bugs.python.org/issue31178}: Fix string concatenation bug in rare error path in the
subprocess module

@item 
bpo-31350@footnote{https://bugs.python.org/issue31350}: Micro-optimize @code{asyncio._get_running_loop()} to become up
to 10% faster.

@item 
bpo-31170@footnote{https://bugs.python.org/issue31170}: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of
partial characters for UTF-8 input (libexpat bug 115):
@indicateurl{https://github.com/libexpat/libexpat/issues/115}

@item 
bpo-29136@footnote{https://bugs.python.org/issue29136}: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

@item 
bpo-1198569@footnote{https://bugs.python.org/issue1198569}: @code{string.Template} subclasses can optionally define
@code{braceidpattern} if they want to specify different placeholder patterns
inside and outside the braces.  If None (the default) it falls back to
@code{idpattern}.

@item 
bpo-31326@footnote{https://bugs.python.org/issue31326}: concurrent.futures.ProcessPoolExecutor.shutdown() now
explicitly closes the call queue. Moreover, shutdown(wait=True) now also
join the call queue thread, to prevent leaking a dangling thread.

@item 
bpo-27144@footnote{https://bugs.python.org/issue27144}: The @code{map()} and @code{as_completed()} iterators in
@code{concurrent.futures} now avoid keeping a reference to yielded objects.

@item 
bpo-31281@footnote{https://bugs.python.org/issue31281}: Fix @code{fileinput.FileInput(files, inplace=True)} when @code{files}
contain @code{pathlib.Path} objects.

@item 
bpo-10746@footnote{https://bugs.python.org/issue10746}: Fix ctypes producing wrong 
@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} type codes for integer
types.

@item 
bpo-27584@footnote{https://bugs.python.org/issue27584}: @code{AF_VSOCK} has been added to the socket interface which
allows communication between virtual machines and their host.

@item 
bpo-22536@footnote{https://bugs.python.org/issue22536}: The subprocess module now sets the filename when
FileNotFoundError is raised on POSIX systems due to the executable or cwd
not being found.

@item 
bpo-29741@footnote{https://bugs.python.org/issue29741}: Update some methods in the _pyio module to also accept integer
types. Patch by Oren Milman.

@item 
bpo-31249@footnote{https://bugs.python.org/issue31249}: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor
now breaks a reference cycle between an exception object and the WorkItem
object.

@item 
bpo-31247@footnote{https://bugs.python.org/issue31247}: xmlrpc.server now explicitly breaks reference cycles when using
sys.exc_info() in code handling exceptions.

@item 
bpo-23835@footnote{https://bugs.python.org/issue23835}: configparser: reading defaults in the @code{ConfigParser()}
constructor is now using @code{read_dict()}, making its behavior consistent
with the rest of the parser.  Non-string keys and values in the defaults
dictionary are now being implicitly converted to strings.  Patch by James
Tocknell.

@item 
bpo-31238@footnote{https://bugs.python.org/issue31238}: pydoc: the stop() method of the private ServerThread class now
waits until DocServer.serve_until_quit() completes and then explicitly
sets its docserver attribute to None to break a reference cycle.

@item 
bpo-5001@footnote{https://bugs.python.org/issue5001}: Many asserts in @ref{b7,,multiprocessing} are now more informative, and
some error types have been changed to more specific ones.

@item 
bpo-31109@footnote{https://bugs.python.org/issue31109}: Convert zipimport to use Argument Clinic.

@item 
bpo-30102@footnote{https://bugs.python.org/issue30102}: The ssl and hashlib modules now call
OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function
detects CPU features and enables optimizations on some CPU architectures
such as POWER8. Patch is based on research from Gustavo Serra Scalet.

@item 
bpo-18966@footnote{https://bugs.python.org/issue18966}: Non-daemonic threads created by a multiprocessing.Process are
now joined on child exit.

@item 
bpo-31183@footnote{https://bugs.python.org/issue31183}: @ref{38,,dis} now works with asynchronous generator and coroutine
objects. Patch by George Collins based on diagnosis by Luciano Ramalho.

@item 
bpo-5001@footnote{https://bugs.python.org/issue5001}: There are a number of uninformative asserts in the
@ref{b7,,multiprocessing} module, as noted in issue 5001. This change fixes two of
the most potentially problematic ones, since they are in error-reporting
code, in the @code{multiprocessing.managers.convert_to_error} function. (It
also makes more informative a ValueError message.) The only potentially
problematic change is that the AssertionError is now a TypeError; however,
this should also help distinguish it from an AssertionError being
@emph{reported} by the function/its caller (such as in issue 31169). - Patch by
Allen W. Smith (drallensmith on github).

@item 
bpo-31185@footnote{https://bugs.python.org/issue31185}: Fixed miscellaneous errors in asyncio speedup module.

@item 
bpo-31151@footnote{https://bugs.python.org/issue31151}: socketserver.ForkingMixIn.server_close() now waits until all
child processes completed to prevent leaking zombie processes.

@item 
bpo-31072@footnote{https://bugs.python.org/issue31072}: Add an @code{include_file} parameter to
@code{zipapp.create_archive()}

@item 
bpo-24700@footnote{https://bugs.python.org/issue24700}: Optimize array.array comparison. It is now from 10x up to 70x
faster when comparing arrays holding values of the same integer type.

@item 
bpo-31135@footnote{https://bugs.python.org/issue31135}: ttk: fix the destroy() method of LabeledScale and OptionMenu
classes. Call the parent destroy() method even if the used attribute
doesn't exist. The LabeledScale.destroy() method now also explicitly
clears label and scale attributes to help the garbage collector to destroy
all widgets.

@item 
bpo-31107@footnote{https://bugs.python.org/issue31107}: Fix @code{copyreg._slotnames()} mangled attribute calculation for
classes whose name begins with an underscore. Patch by Shane Harvey.

@item 
bpo-31080@footnote{https://bugs.python.org/issue31080}: Allow @ref{3a1,,logging.config.fileConfig} to accept kwargs and/or args.

@item 
bpo-30897@footnote{https://bugs.python.org/issue30897}: @code{pathlib.Path} objects now include an @code{is_mount()} method
(only implemented on POSIX).  This is similar to @code{os.path.ismount(p)}.
Patch by Cooper Ry Lees.

@item 
bpo-31061@footnote{https://bugs.python.org/issue31061}: Fixed a crash when using asyncio and threads.

@item 
bpo-30987@footnote{https://bugs.python.org/issue30987}: Added support for CAN ISO-TP protocol in the socket module.

@item 
bpo-30522@footnote{https://bugs.python.org/issue30522}: Added a @code{setStream} method to @code{logging.StreamHandler} to
allow the stream to be set after creation.

@item 
bpo-30502@footnote{https://bugs.python.org/issue30502}: Fix handling of long oids in ssl.  Based on patch by Christian
Heimes.

@item 
bpo-5288@footnote{https://bugs.python.org/issue5288}: Support tzinfo objects with sub-minute offsets.

@item 
bpo-30919@footnote{https://bugs.python.org/issue30919}: Fix shared memory performance regression in multiprocessing in
3.x. Shared memory used anonymous memory mappings in 2.x, while 3.x mmaps
actual files. Try to be careful to do as little disk I/O as possible.

@item 
bpo-26732@footnote{https://bugs.python.org/issue26732}: Fix too many fds in processes started with the "forkserver"
method. A child process would inherit as many fds as the number of
still-running children.

@item 
bpo-29403@footnote{https://bugs.python.org/issue29403}: Fix @code{unittest.mock}'s autospec to not fail on method-bound
builtin functions.  Patch by Aaron Gallagher.

@item 
bpo-30961@footnote{https://bugs.python.org/issue30961}: Fix decrementing a borrowed reference in tracemalloc.

@item 
bpo-19896@footnote{https://bugs.python.org/issue19896}: Fix multiprocessing.sharedctypes to recognize typecodes @code{'q'}
and @code{'Q'}.

@item 
bpo-30946@footnote{https://bugs.python.org/issue30946}: Remove obsolete code in readline module for platforms where GNU
readline is older than 2.1 or where select() is not available.

@item 
bpo-25684@footnote{https://bugs.python.org/issue25684}: Change @code{ttk.OptionMenu} radiobuttons to be unique across
instances of @code{OptionMenu}.

@item 
bpo-30886@footnote{https://bugs.python.org/issue30886}: Fix multiprocessing.Queue.join_thread(): it now waits until the
thread completes, even if the thread was started by the same process which
created the queue.

@item 
bpo-29854@footnote{https://bugs.python.org/issue29854}: Fix segfault in readline when using readline's history-size
option.  Patch by Nir Soffer.

@item 
bpo-30794@footnote{https://bugs.python.org/issue30794}: Added multiprocessing.Process.kill method to terminate using
the SIGKILL signal on Unix.

@item 
bpo-30319@footnote{https://bugs.python.org/issue30319}: socket.close() now ignores ECONNRESET error.

@item 
bpo-30828@footnote{https://bugs.python.org/issue30828}: Fix out of bounds write in
@code{asyncio.CFuture.remove_done_callback()}.

@item 
bpo-30302@footnote{https://bugs.python.org/issue30302}: Use keywords in the @code{repr} of @code{datetime.timedelta}.

@item 
bpo-30807@footnote{https://bugs.python.org/issue30807}: signal.setitimer() may disable the timer when passed a tiny
value. Tiny values (such as 1e-6) are valid non-zero values for
setitimer(), which is specified as taking microsecond-resolution
intervals. However, on some platform, our conversion routine could convert
1e-6 into a zero interval, therefore disabling the timer instead of
(re-)scheduling it.

@item 
bpo-30441@footnote{https://bugs.python.org/issue30441}: Fix bug when modifying os.environ while iterating over it

@item 
bpo-29585@footnote{https://bugs.python.org/issue29585}: Avoid importing @code{sysconfig} from @code{site} to improve startup
speed. Python startup is about 5% faster on Linux and 30% faster on macOS.

@item 
bpo-29293@footnote{https://bugs.python.org/issue29293}: Add missing parameter "n" on
multiprocessing.Condition.notify(). The doc claims
multiprocessing.Condition behaves like threading.Condition, but its
notify() method lacked the optional "n" argument (to specify the number of
sleepers to wake up) that threading.Condition.notify() accepts.

@item 
bpo-30532@footnote{https://bugs.python.org/issue30532}: Fix email header value parser dropping folding white space in
certain cases.

@item 
bpo-30596@footnote{https://bugs.python.org/issue30596}: Add a @code{close()} method to @code{multiprocessing.Process}.

@item 
bpo-9146@footnote{https://bugs.python.org/issue9146}: Fix a segmentation fault in _hashopenssl when standard hash
functions such as md5 are not available in the linked OpenSSL library.  As
in some special FIPS-140 build environments.

@item 
bpo-29169@footnote{https://bugs.python.org/issue29169}: Update zlib to 1.2.11.

@item 
bpo-30119@footnote{https://bugs.python.org/issue30119}: ftplib.FTP.putline() now throws ValueError on commands that
contains CR or LF. Patch by Dong-hee Na.

@item 
bpo-30879@footnote{https://bugs.python.org/issue30879}: os.listdir() and os.scandir() now emit bytes names when called
with bytes-like argument.

@item 
bpo-30746@footnote{https://bugs.python.org/issue30746}: Prohibited the '=' character in environment variable names in
@code{os.putenv()} and @code{os.spawn*()}.

@item 
bpo-30664@footnote{https://bugs.python.org/issue30664}: The description of a unittest subtest now preserves the order
of keyword arguments of TestCase.subTest().

@item 
bpo-21071@footnote{https://bugs.python.org/issue21071}: struct.Struct.format type is now @ref{329,,str} instead of
@ref{32a,,bytes}.

@item 
bpo-29212@footnote{https://bugs.python.org/issue29212}: Fix concurrent.futures.thread.ThreadPoolExecutor threads to
have a non repr() based thread name by default when no thread_name_prefix
is supplied. They will now identify themselves as
"ThreadPoolExecutor-y_n".

@item 
bpo-29755@footnote{https://bugs.python.org/issue29755}: Fixed the lgettext() family of functions in the gettext module.
They now always return bytes.

@item 
bpo-30616@footnote{https://bugs.python.org/issue30616}: Functional API of enum allows to create empty enums. Patched by
Dong-hee Na

@item 
bpo-30038@footnote{https://bugs.python.org/issue30038}: Fix race condition between signal delivery and wakeup file
descriptor. Patch by Nathaniel Smith.

@item 
bpo-23894@footnote{https://bugs.python.org/issue23894}: lib2to3 now recognizes @code{rb'...'} and @code{f'...'} strings.

@item 
bpo-24744@footnote{https://bugs.python.org/issue24744}: pkgutil.walk_packages function now raises ValueError if @emph{path}
is a string. Patch by Sanyam Khurana.

@item 
bpo-24484@footnote{https://bugs.python.org/issue24484}: Avoid race condition in multiprocessing cleanup.

@item 
bpo-30589@footnote{https://bugs.python.org/issue30589}: Fix multiprocessing.Process.exitcode to return the opposite of
the signal number when the process is killed by a signal (instead of 255)
when using the "forkserver" method.

@item 
bpo-28994@footnote{https://bugs.python.org/issue28994}: The traceback no longer displayed for SystemExit raised in a
callback registered by atexit.

@item 
bpo-30508@footnote{https://bugs.python.org/issue30508}: Don't log exceptions if Task/Future "cancel()" method was
called.

@item 
bpo-30645@footnote{https://bugs.python.org/issue30645}: Fix path calculation in @code{imp.load_package()}, fixing it for
cases when a package is only shipped with bytecodes. Patch by Alexandru
Ardelean.

@item 
bpo-11822@footnote{https://bugs.python.org/issue11822}: The dis.dis() function now is able to disassemble nested code
objects.

@item 
bpo-30624@footnote{https://bugs.python.org/issue30624}: selectors does not take KeyboardInterrupt and SystemExit into
account, leaving a fd in a bad state in case of error. Patch by Giampaolo
Rodola'.

@item 
bpo-30595@footnote{https://bugs.python.org/issue30595}: multiprocessing.Queue.get() with a timeout now polls its reader
in non-blocking mode if it succeeded to acquire the lock but the acquire
took longer than the timeout.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Updates to typing module: Add generic AsyncContextManager, add
support for ContextManager on all versions. Original PRs by Jelle Zijlstra
and Ivan Levkivskyi

@item 
bpo-30605@footnote{https://bugs.python.org/issue30605}: re.compile() no longer raises a BytesWarning when compiling a
bytes instance with misplaced inline modifier.  Patch by Roy Williams.

@item 
bpo-29870@footnote{https://bugs.python.org/issue29870}: Fix ssl sockets leaks when connection is aborted in asyncio/ssl
implementation. Patch by Michaël Sghaïer.

@item 
bpo-29743@footnote{https://bugs.python.org/issue29743}: Closing transport during handshake process leaks open socket.
Patch by Nikolay Kim

@item 
bpo-27585@footnote{https://bugs.python.org/issue27585}: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu
Sornay.

@item 
bpo-30014@footnote{https://bugs.python.org/issue30014}: modify() method of poll(), epoll() and devpoll() based classes
of selectors module is around 10% faster.  Patch by Giampaolo Rodola'.

@item 
bpo-30418@footnote{https://bugs.python.org/issue30418}: On Windows, subprocess.Popen.communicate() now also ignore
EINVAL on stdin.write() if the child process is still running but closed
the pipe.

@item 
bpo-30463@footnote{https://bugs.python.org/issue30463}: Addded empty __slots__ to abc.ABC.  This allows subclassers to
deny __dict__ and __weakref__ creation.  Patch by Aaron Hall.

@item 
bpo-30520@footnote{https://bugs.python.org/issue30520}: Loggers are now pickleable.

@item 
bpo-30557@footnote{https://bugs.python.org/issue30557}: faulthandler now correctly filters and displays exception codes
on Windows

@item 
bpo-30526@footnote{https://bugs.python.org/issue30526}: Add TextIOWrapper.reconfigure() and a
TextIOWrapper.write_through attribute.

@item 
bpo-30245@footnote{https://bugs.python.org/issue30245}: Fix possible overflow when organize struct.pack_into error
message.  Patch by Yuan Liu.

@item 
bpo-30378@footnote{https://bugs.python.org/issue30378}: Fix the problem that logging.handlers.SysLogHandler cannot
handle IPv6 addresses.

@item 
bpo-16500@footnote{https://bugs.python.org/issue16500}: Allow registering at-fork handlers.

@item 
bpo-30470@footnote{https://bugs.python.org/issue30470}: Deprecate invalid ctypes call protection on Windows.  Patch by
Mariatta Wijaya.

@item 
bpo-30414@footnote{https://bugs.python.org/issue30414}: multiprocessing.Queue._feed background running thread do not
break from main loop on exception.

@item 
bpo-30003@footnote{https://bugs.python.org/issue30003}: Fix handling escape characters in HZ codec.  Based on patch by
Ma Lin.

@item 
bpo-30149@footnote{https://bugs.python.org/issue30149}: inspect.signature() now supports callables with
variable-argument parameters wrapped with partialmethod. Patch by Dong-hee
Na.

@item 
bpo-30436@footnote{https://bugs.python.org/issue30436}: importlib.find_spec() raises ModuleNotFoundError instead of
AttributeError if the specified parent module is not a package (i.e. lacks
a __path__ attribute).

@item 
bpo-30301@footnote{https://bugs.python.org/issue30301}: Fix AttributeError when using SimpleQueue.empty() under @emph{spawn}
and @emph{forkserver} start methods.

@item 
bpo-30375@footnote{https://bugs.python.org/issue30375}: Warnings emitted when compile a regular expression now always
point to the line in the user code.  Previously they could point into
inners of the re module if emitted from inside of groups or conditionals.

@item 
bpo-30329@footnote{https://bugs.python.org/issue30329}: imaplib and poplib now catch the Windows socket WSAEINVAL error
(code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted.
This error occurs sometimes on SSL connections.

@item 
bpo-29196@footnote{https://bugs.python.org/issue29196}: Removed previously deprecated in Python 2.4 classes Plist, Dict
and _InternalDict in the plistlib module.  Dict values in the result of
functions readPlist() and readPlistFromBytes() are now normal dicts.  You
no longer can use attribute access to access items of these dictionaries.

@item 
bpo-9850@footnote{https://bugs.python.org/issue9850}: The @code{macpath} is now deprecated and will be removed in
Python 3.8.

@item 
bpo-30299@footnote{https://bugs.python.org/issue30299}: Compiling regular expression in debug mode on CPython now
displays the compiled bytecode in human readable form.

@item 
bpo-30048@footnote{https://bugs.python.org/issue30048}: Fixed @code{Task.cancel()} can be ignored when the task is running
coroutine and the coroutine returned without any more @code{await}.

@item 
bpo-30266@footnote{https://bugs.python.org/issue30266}: contextlib.AbstractContextManager now supports
anti-registration by setting __enter__ = None or __exit__ = None,
following the pattern introduced in bpo-25958@footnote{https://bugs.python.org/issue25958}. Patch by Jelle Zijlstra.

@item 
bpo-30340@footnote{https://bugs.python.org/issue30340}: Enhanced regular expressions optimization. This increased the
performance of matching some patterns up to 25 times.

@item 
bpo-30298@footnote{https://bugs.python.org/issue30298}: Weaken the condition of deprecation warnings for inline
modifiers. Now allowed several subsequential inline modifiers at the start
of the pattern (e.g. @code{'(?i)(?s)...'}).  In verbose mode whitespaces and
comments now are allowed before and between inline modifiers (e.g. @code{'(?x)
(?i) (?s)...'}).

@item 
bpo-30285@footnote{https://bugs.python.org/issue30285}: Optimized case-insensitive matching and searching of regular
expressions.

@item 
bpo-29990@footnote{https://bugs.python.org/issue29990}: Fix range checking in GB18030 decoder.  Original patch by Ma
Lin.

@item 
bpo-29979@footnote{https://bugs.python.org/issue29979}: rewrite cgi.parse_multipart, reusing the FieldStorage class and
making its results consistent with those of FieldStorage for
multipart/form-data requests. Patch by Pierre Quentel.

@item 
bpo-30243@footnote{https://bugs.python.org/issue30243}: Removed the __init__ methods of _json's scanner and encoder.
Misusing them could cause memory leaks or crashes.  Now scanner and
encoder objects are completely initialized in the __new__ methods.

@item 
bpo-30215@footnote{https://bugs.python.org/issue30215}: Compiled regular expression objects with the re.LOCALE flag no
longer depend on the locale at compile time.  Only the locale at matching
time affects the result of matching.

@item 
bpo-30185@footnote{https://bugs.python.org/issue30185}: Avoid KeyboardInterrupt tracebacks in forkserver helper process
when Ctrl-C is received.

@item 
bpo-30103@footnote{https://bugs.python.org/issue30103}: binascii.b2a_uu() and uu.encode() now support using @code{'`'} as
zero instead of space.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Various updates to typing module: add typing.NoReturn type, use
WrapperDescriptorType, minor bug-fixes.  Original PRs by Jim
Fasarakis-Hilliard and Ivan Levkivskyi.

@item 
bpo-30205@footnote{https://bugs.python.org/issue30205}: Fix getsockname() for unbound AF_UNIX sockets on Linux.

@item 
bpo-30228@footnote{https://bugs.python.org/issue30228}: The seek() and tell() methods of io.FileIO now set the internal
seekable attribute to avoid one syscall on open() (in buffered or text
mode).

@item 
bpo-30190@footnote{https://bugs.python.org/issue30190}: unittest's assertAlmostEqual and assertNotAlmostEqual provide a
better message in case of failure which includes the difference between
left and right arguments.  (patch by Giampaolo Rodola')

@item 
bpo-30101@footnote{https://bugs.python.org/issue30101}: Add support for curses.A_ITALIC.

@item 
bpo-29822@footnote{https://bugs.python.org/issue29822}: inspect.isabstract() now works during __init_subclass__.  Patch
by Nate Soares.

@item 
bpo-29960@footnote{https://bugs.python.org/issue29960}: Preserve generator state when _random.Random.setstate() raises
an exception. Patch by Bryan Olson.

@item 
bpo-30070@footnote{https://bugs.python.org/issue30070}: Fixed leaks and crashes in errors handling in the parser
module.

@item 
bpo-22352@footnote{https://bugs.python.org/issue22352}: Column widths in the output of dis.dis() are now adjusted for
large line numbers and instruction offsets.

@item 
bpo-30061@footnote{https://bugs.python.org/issue30061}: Fixed crashes in IOBase methods __next__() and readlines() when
readline() or __next__() respectively return non-sizeable object. Fixed
possible other errors caused by not checking results of PyObject_Size(),
PySequence_Size(), or PyMapping_Size().

@item 
bpo-30218@footnote{https://bugs.python.org/issue30218}: Fix PathLike support for shutil.unpack_archive. Patch by Jelle
Zijlstra.

@item 
bpo-10076@footnote{https://bugs.python.org/issue10076}: Compiled regular expression and match objects in the re module
now support copy.copy() and copy.deepcopy() (they are considered atomic).

@item 
bpo-30068@footnote{https://bugs.python.org/issue30068}: _io._IOBase.readlines will check if it's closed first when hint
is present.

@item 
bpo-29694@footnote{https://bugs.python.org/issue29694}: Fixed race condition in pathlib mkdir with flags parents=True.
Patch by Armin Rigo.

@item 
bpo-29692@footnote{https://bugs.python.org/issue29692}: Fixed arbitrary unchaining of RuntimeError exceptions in
contextlib.contextmanager.  Patch by Siddharth Velankar.

@item 
bpo-26187@footnote{https://bugs.python.org/issue26187}: Test that sqlite3 trace callback is not called multiple times
when schema is changing.  Indirectly fixed by switching to use
sqlite3_prepare_v2() in bpo-9303@footnote{https://bugs.python.org/issue9303}.  Patch by Aviv Palivoda.

@item 
bpo-30017@footnote{https://bugs.python.org/issue30017}: Allowed calling the close() method of the zip entry writer
object multiple times.  Writing to a closed writer now always produces a
ValueError.

@item 
bpo-29998@footnote{https://bugs.python.org/issue29998}: Pickling and copying ImportError now preserves name and path
attributes.

@item 
bpo-29995@footnote{https://bugs.python.org/issue29995}: re.escape() now escapes only regex special characters.

@item 
bpo-29962@footnote{https://bugs.python.org/issue29962}: Add math.remainder operation, implementing remainder as
specified in IEEE 754.

@item 
bpo-29649@footnote{https://bugs.python.org/issue29649}: Improve struct.pack_into() exception messages for problems with
the buffer size and offset.  Patch by Andrew Nester.

@item 
bpo-29654@footnote{https://bugs.python.org/issue29654}: Support If-Modified-Since HTTP header (browser cache).  Patch
by Pierre Quentel.

@item 
bpo-29931@footnote{https://bugs.python.org/issue29931}: Fixed comparison check for ipaddress.ip_interface objects.
Patch by Sanjay Sundaresan.

@item 
bpo-29953@footnote{https://bugs.python.org/issue29953}: Fixed memory leaks in the replace() method of datetime and time
objects when pass out of bound fold argument.

@item 
bpo-29942@footnote{https://bugs.python.org/issue29942}: Fix a crash in itertools.chain.from_iterable when encountering
long runs of empty iterables.

@item 
bpo-10030@footnote{https://bugs.python.org/issue10030}: Sped up reading encrypted ZIP files by 2 times.

@item 
bpo-29204@footnote{https://bugs.python.org/issue29204}: Element.getiterator() and the html parameter of XMLParser()
were deprecated only in the documentation (since Python 3.2 and 3.4
correspondintly). Now using them emits a deprecation warning.

@item 
bpo-27863@footnote{https://bugs.python.org/issue27863}: Fixed multiple crashes in ElementTree caused by race conditions
and wrong types.

@item 
bpo-25996@footnote{https://bugs.python.org/issue25996}: Added support of file descriptors in os.scandir() on Unix.
os.fwalk() is sped up by 2 times by using os.scandir().

@item 
bpo-28699@footnote{https://bugs.python.org/issue28699}: Fixed a bug in pools in multiprocessing.pool that raising an
exception at the very first of an iterable may swallow the exception or
make the program hang. Patch by Davin Potts and Xiang Zhang.

@item 
bpo-23890@footnote{https://bugs.python.org/issue23890}: unittest.TestCase.assertRaises() now manually breaks a
reference cycle to not keep objects alive longer than expected.

@item 
bpo-29901@footnote{https://bugs.python.org/issue29901}: The zipapp module now supports general path-like objects, not
just pathlib.Path.

@item 
bpo-25803@footnote{https://bugs.python.org/issue25803}: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when
the OS gives priority to errors such as EACCES over EEXIST.

@item 
bpo-29861@footnote{https://bugs.python.org/issue29861}: Release references to tasks, their arguments and their results
as soon as they are finished in multiprocessing.Pool.

@item 
bpo-19930@footnote{https://bugs.python.org/issue19930}: The mode argument of os.makedirs() no longer affects the file
permission bits of newly-created intermediate-level directories.

@item 
bpo-29884@footnote{https://bugs.python.org/issue29884}: faulthandler: Restore the old sigaltstack during teardown.
Patch by Christophe Zeitouny.

@item 
bpo-25455@footnote{https://bugs.python.org/issue25455}: Fixed crashes in repr of recursive buffered file-like objects.

@item 
bpo-29800@footnote{https://bugs.python.org/issue29800}: Fix crashes in partial.__repr__ if the keys of partial.keywords
are not strings.  Patch by Michael Seifert.

@item 
bpo-8256@footnote{https://bugs.python.org/issue8256}: Fixed possible failing or crashing input() if attributes
"encoding" or "errors" of sys.stdin or sys.stdout are not set or are not
strings.

@item 
bpo-28692@footnote{https://bugs.python.org/issue28692}: Using non-integer value for selecting a plural form in gettext
is now deprecated.

@item 
bpo-26121@footnote{https://bugs.python.org/issue26121}: Use C library implementation for math functions erf() and
erfc().

@item 
bpo-29619@footnote{https://bugs.python.org/issue29619}: os.stat() and os.DirEntry.inode() now convert inode (st_ino)
using unsigned integers.

@item 
bpo-28298@footnote{https://bugs.python.org/issue28298}: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting
big intables (objects that have __int__) as elements.

@item 
bpo-29645@footnote{https://bugs.python.org/issue29645}: Speed up importing the webbrowser module.
webbrowser.register() is now thread-safe.

@item 
bpo-28231@footnote{https://bugs.python.org/issue28231}: The zipfile module now accepts path-like objects for external
paths.

@item 
bpo-26915@footnote{https://bugs.python.org/issue26915}: index() and count() methods of collections.abc.Sequence now
check identity before checking equality when do comparisons.

@item 
bpo-28682@footnote{https://bugs.python.org/issue28682}: Added support for bytes paths in os.fwalk().

@item 
bpo-29728@footnote{https://bugs.python.org/issue29728}: Add new @code{socket.TCP_NOTSENT_LOWAT} (Linux 3.12) constant.
Patch by Nathaniel J. Smith.

@item 
bpo-29623@footnote{https://bugs.python.org/issue29623}: Allow use of path-like object as a single argument in
ConfigParser.read(). Patch by David Ellis.

@item 
bpo-9303@footnote{https://bugs.python.org/issue9303}: Migrate sqlite3 module to _v2 API.  Patch by Aviv Palivoda.

@item 
bpo-28963@footnote{https://bugs.python.org/issue28963}: Fix out of bound iteration in
asyncio.Future.remove_done_callback implemented in C.

@item 
bpo-29704@footnote{https://bugs.python.org/issue29704}: asyncio.subprocess.SubprocessStreamProtocol no longer closes
before all pipes are closed.

@item 
bpo-29271@footnote{https://bugs.python.org/issue29271}: Fix Task.current_task and Task.all_tasks implemented in C to
accept None argument as their pure Python implementation.

@item 
bpo-29703@footnote{https://bugs.python.org/issue29703}: Fix asyncio to support instantiation of new event loops in
child processes.

@item 
bpo-29615@footnote{https://bugs.python.org/issue29615}: SimpleXMLRPCDispatcher no longer chains KeyError (or any other
exception) to exception(s) raised in the dispatched methods. Patch by Petr
Motejlek.

@item 
bpo-7769@footnote{https://bugs.python.org/issue7769}: Method register_function() of
xmlrpc.server.SimpleXMLRPCDispatcher and its subclasses can now be used as
a decorator.

@item 
bpo-29376@footnote{https://bugs.python.org/issue29376}: Fix assertion error in threading._DummyThread.is_alive().

@item 
bpo-28624@footnote{https://bugs.python.org/issue28624}: Add a test that checks that cwd parameter of Popen() accepts
PathLike objects.  Patch by Sayan Chowdhury.

@item 
bpo-28518@footnote{https://bugs.python.org/issue28518}: Start a transaction implicitly before a DML statement. Patch by
Aviv Palivoda.

@item 
bpo-29742@footnote{https://bugs.python.org/issue29742}: get_extra_info() raises exception if get called on closed ssl
transport. Patch by Nikolay Kim.

@item 
bpo-16285@footnote{https://bugs.python.org/issue16285}: urllib.parse.quote is now based on RFC 3986 and hence includes
'~' in the set of characters that is not quoted by default. Patch by
Christian Theune and Ratnadeep Debnath.

@item 
bpo-29532@footnote{https://bugs.python.org/issue29532}: Altering a kwarg dictionary passed to functools.partial() no
longer affects a partial object after creation.

@item 
bpo-29110@footnote{https://bugs.python.org/issue29110}: Fix file object leak in aifc.open() when file is given as a
filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

@item 
bpo-22807@footnote{https://bugs.python.org/issue22807}: Add uuid.SafeUUID and uuid.UUID.is_safe to relay information
from the platform about whether generated UUIDs are generated with a
multiprocessing safe method.

@item 
bpo-29576@footnote{https://bugs.python.org/issue29576}: Improve some deprecations in importlib. Some deprecated methods
now emit DeprecationWarnings and have better descriptive messages.

@item 
bpo-29534@footnote{https://bugs.python.org/issue29534}: Fixed different behaviour of Decimal.from_float() for _decimal
and _pydecimal. Thanks Andrew Nester.

@item 
bpo-10379@footnote{https://bugs.python.org/issue10379}: locale.format_string now supports the 'monetary' keyword
argument, and locale.format is deprecated.

@item 
bpo-29851@footnote{https://bugs.python.org/issue29851}: importlib.reload() now raises ModuleNotFoundError if the module
lacks a spec.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Various updates to typing module: typing.Counter,
typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle
Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

@item 
bpo-29100@footnote{https://bugs.python.org/issue29100}: Fix datetime.fromtimestamp() regression introduced in Python
3.6.0: check minimum and maximum years.

@item 
bpo-29416@footnote{https://bugs.python.org/issue29416}: Prevent infinite loop in pathlib.Path.mkdir

@item 
bpo-29444@footnote{https://bugs.python.org/issue29444}: Fixed out-of-bounds buffer access in the group() method of the
match object. Based on patch by WGH.

@item 
bpo-29377@footnote{https://bugs.python.org/issue29377}: Add WrapperDescriptorType, MethodWrapperType, and
MethodDescriptorType built-in types to types module. Original patch by
Manuel Krebber.

@item 
bpo-29218@footnote{https://bugs.python.org/issue29218}: Unused install_misc command is now removed.  It has been
documented as unused since 2000.  Patch by Eric N. Vander Weele.

@item 
bpo-29368@footnote{https://bugs.python.org/issue29368}: The extend() method is now called instead of the append()
method when unpickle collections.deque and other list-like objects. This
can speed up unpickling to 2 times.

@item 
bpo-29338@footnote{https://bugs.python.org/issue29338}: The help of a builtin or extension class now includes the
constructor signature if __text_signature__ is provided for the class.

@item 
bpo-29335@footnote{https://bugs.python.org/issue29335}: Fix subprocess.Popen.wait() when the child process has exited
to a stopped instead of terminated state (ex: when under ptrace).

@item 
bpo-29290@footnote{https://bugs.python.org/issue29290}: Fix a regression in argparse that help messages would wrap at
non-breaking spaces.

@item 
bpo-28735@footnote{https://bugs.python.org/issue28735}: Fixed the comparison of mock.MagickMock with mock.ANY.

@item 
bpo-29197@footnote{https://bugs.python.org/issue29197}: Removed deprecated function ntpath.splitunc().

@item 
bpo-29210@footnote{https://bugs.python.org/issue29210}: Removed support of deprecated argument "exclude" in
tarfile.TarFile.add().

@item 
bpo-29219@footnote{https://bugs.python.org/issue29219}: Fixed infinite recursion in the repr of uninitialized
ctypes.CDLL instances.

@item 
bpo-29192@footnote{https://bugs.python.org/issue29192}: Removed deprecated features in the http.cookies module.

@item 
bpo-29193@footnote{https://bugs.python.org/issue29193}: A format string argument for string.Formatter.format() is now
positional-only.

@item 
bpo-29195@footnote{https://bugs.python.org/issue29195}: Removed support of deprecated undocumented keyword arguments in
methods of regular expression objects.

@item 
bpo-28969@footnote{https://bugs.python.org/issue28969}: Fixed race condition in C implementation of
functools.lru_cache. KeyError could be raised when cached function with
full cache was simultaneously called from different threads with the same
uncached arguments.

@item 
bpo-20804@footnote{https://bugs.python.org/issue20804}: The unittest.mock.sentinel attributes now preserve their
identity when they are copied or pickled.

@item 
bpo-29142@footnote{https://bugs.python.org/issue29142}: In urllib.request, suffixes in no_proxy environment variable
with leading dots could match related hostnames again (e.g. .b.c matches
a.b.c). Patch by Milan Oberkirch.

@item 
bpo-28961@footnote{https://bugs.python.org/issue28961}: Fix unittest.mock._Call helper: don't ignore the name parameter
anymore. Patch written by Jiajun Huang.

@item 
bpo-15812@footnote{https://bugs.python.org/issue15812}: inspect.getframeinfo() now correctly shows the first line of a
context. Patch by Sam Breese.

@item 
bpo-28985@footnote{https://bugs.python.org/issue28985}: Update authorizer constants in sqlite3 module. Patch by
Dingyuan Wang.

@item 
bpo-29079@footnote{https://bugs.python.org/issue29079}: Prevent infinite loop in pathlib.resolve() on Windows

@item 
bpo-13051@footnote{https://bugs.python.org/issue13051}: Fixed recursion errors in large or resized
curses.textpad.Textbox.  Based on patch by Tycho Andersen.

@item 
bpo-9770@footnote{https://bugs.python.org/issue9770}: curses.ascii predicates now work correctly with negative
integers.

@item 
bpo-28427@footnote{https://bugs.python.org/issue28427}: old keys should not remove new values from WeakValueDictionary
when collecting from another thread.

@item 
bpo-28923@footnote{https://bugs.python.org/issue28923}: Remove editor artifacts from Tix.py.

@item 
bpo-28871@footnote{https://bugs.python.org/issue28871}: Fixed a crash when deallocate deep ElementTree.

@item 
bpo-19542@footnote{https://bugs.python.org/issue19542}: Fix bugs in WeakValueDictionary.setdefault() and
WeakValueDictionary.pop() when a GC collection happens in another thread.

@item 
bpo-20191@footnote{https://bugs.python.org/issue20191}: Fixed a crash in resource.prlimit() when passing a sequence
that doesn't own its elements as limits.

@item 
bpo-16255@footnote{https://bugs.python.org/issue16255}: subprocess.Popen uses /system/bin/sh on Android as the shell,
instead of /bin/sh.

@item 
bpo-28779@footnote{https://bugs.python.org/issue28779}: multiprocessing.set_forkserver_preload() would crash the
forkserver process if a preloaded module instantiated some multiprocessing
objects such as locks.

@item 
bpo-26937@footnote{https://bugs.python.org/issue26937}: The chown() method of the tarfile.TarFile class does not fail
now when the grp module cannot be imported, as for example on Android
platforms.

@item 
bpo-28847@footnote{https://bugs.python.org/issue28847}: dbm.dumb now supports reading read-only files and no longer
writes the index file when it is not changed.  A deprecation warning is
now emitted if the index file is missed and recreated in the 'r' and 'w'
modes (will be an error in future Python releases).

@item 
bpo-27030@footnote{https://bugs.python.org/issue27030}: Unknown escapes consisting of @code{'\'} and an ASCII letter in
re.sub() replacement templates regular expressions now are errors.

@item 
bpo-28835@footnote{https://bugs.python.org/issue28835}: Fix a regression introduced in warnings.catch_warnings(): call
warnings.showwarning() if it was overridden inside the context manager.

@item 
bpo-27172@footnote{https://bugs.python.org/issue27172}: To assist with upgrades from 2.7, the previously documented
deprecation of @code{inspect.getfullargspec()} has been reversed. This
decision may be revisited again after the Python 2.7 branch is no longer
officially supported.

@item 
bpo-28740@footnote{https://bugs.python.org/issue28740}: Add sys.getandroidapilevel(): return the build time API version
of Android as an integer. Function only available on Android.

@item 
bpo-26273@footnote{https://bugs.python.org/issue26273}: Add new @code{socket.TCP_CONGESTION} (Linux 2.6.13) and
@code{socket.TCP_USER_TIMEOUT} (Linux 2.6.37) constants. Patch written by
Omar Sandoval.

@item 
bpo-28752@footnote{https://bugs.python.org/issue28752}: Restored the __reduce__() methods of datetime objects.

@item 
bpo-28727@footnote{https://bugs.python.org/issue28727}: Regular expression patterns, _sre.SRE_Pattern objects created
by re.compile(), become comparable (only x==y and x!=y operators). This
change should fix the bpo-18383@footnote{https://bugs.python.org/issue18383}: don't duplicate warning filters when
the warnings module is reloaded (thing usually only done in unit tests).

@item 
bpo-20572@footnote{https://bugs.python.org/issue20572}: Remove the subprocess.Popen.wait endtime parameter.  It was
deprecated in 3.4 and undocumented prior to that.

@item 
bpo-25659@footnote{https://bugs.python.org/issue25659}: In ctypes, prevent a crash calling the from_buffer() and
from_buffer_copy() methods on abstract classes like Array.

@item 
bpo-28548@footnote{https://bugs.python.org/issue28548}: In the "http.server" module, parse the protocol version if
possible, to avoid using HTTP 0.9 in some error responses.

@item 
bpo-19717@footnote{https://bugs.python.org/issue19717}: Makes Path.resolve() succeed on paths that do not exist. Patch
by Vajrasky Kok

@item 
bpo-28563@footnote{https://bugs.python.org/issue28563}: Fixed possible DoS and arbitrary code execution when handle
plural form selections in the gettext module.  The expression parser now
supports exact syntax supported by GNU gettext.

@item 
bpo-28387@footnote{https://bugs.python.org/issue28387}: Fixed possible crash in _io.TextIOWrapper deallocator when the
garbage collector is invoked in other thread.  Based on patch by Sebastian
Cufre.

@item 
bpo-27517@footnote{https://bugs.python.org/issue27517}: LZMA compressor and decompressor no longer raise exceptions if
given empty data twice.  Patch by Benjamin Fogle.

@item 
bpo-28549@footnote{https://bugs.python.org/issue28549}: Fixed segfault in curses's addch() with ncurses6.

@item 
bpo-28449@footnote{https://bugs.python.org/issue28449}: tarfile.open() with mode "r" or "r:" now tries to open a tar
file with compression before trying to open it without compression.
Otherwise it had 50% chance failed with ignore_zeros=True.

@item 
bpo-23262@footnote{https://bugs.python.org/issue23262}: The webbrowser module now supports Firefox 36+ and derived
browsers.  Based on patch by Oleg Broytman.

@item 
bpo-24241@footnote{https://bugs.python.org/issue24241}: The webbrowser in an X environment now prefers using the
default browser directly. Also, the webbrowser register() function now has
a documented 'preferred' argument, to specify browsers to be returned by
get() with no arguments. Patch by David Steele

@item 
bpo-27939@footnote{https://bugs.python.org/issue27939}: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
by representing the scale as float value internally in Tk.  tkinter.IntVar
now works if float value is set to underlying Tk variable.

@item 
bpo-28255@footnote{https://bugs.python.org/issue28255}: calendar.TextCalendar.prweek() no longer prints a space after a
weeks's calendar.  calendar.TextCalendar.pryear() no longer prints
redundant newline after a year's calendar.  Based on patch by Xiang Zhang.

@item 
bpo-28255@footnote{https://bugs.python.org/issue28255}: calendar.TextCalendar.prmonth() no longer prints a space at the
start of new line after printing a month's calendar.  Patch by Xiang
Zhang.

@item 
bpo-20491@footnote{https://bugs.python.org/issue20491}: The textwrap.TextWrapper class now honors non-breaking spaces.
Based on patch by Kaarle Ritvanen.

@item 
bpo-28353@footnote{https://bugs.python.org/issue28353}: os.fwalk() no longer fails on broken links.

@item 
bpo-28430@footnote{https://bugs.python.org/issue28430}: Fix iterator of C implemented asyncio.Future doesn't accept
non-None value is passed to it.send(val).

@item 
bpo-27025@footnote{https://bugs.python.org/issue27025}: Generated names for Tkinter widgets now start by the "!" prefix
for readability.

@item 
bpo-25464@footnote{https://bugs.python.org/issue25464}: Fixed HList.header_exists() in tkinter.tix module by addin a
workaround to Tix library bug.

@item 
bpo-28488@footnote{https://bugs.python.org/issue28488}: shutil.make_archive() no longer adds entry "./" to ZIP archive.

@item 
bpo-25953@footnote{https://bugs.python.org/issue25953}: re.sub() now raises an error for invalid numerical group
reference in replacement template even if the pattern is not found in the
string.  Error message for invalid group reference now includes the group
index and the position of the reference. Based on patch by SilentGhost.

@item 
bpo-28469@footnote{https://bugs.python.org/issue28469}: timeit now uses the sequence 1, 2, 5, 10, 20, 50,... instead of
1, 10, 100,... for autoranging.

@item 
bpo-28115@footnote{https://bugs.python.org/issue28115}: Command-line interface of the zipfile module now uses argparse.
Added support of long options.

@item 
bpo-18219@footnote{https://bugs.python.org/issue18219}: Optimize csv.DictWriter for large number of columns. Patch by
Mariatta Wijaya.

@item 
bpo-28448@footnote{https://bugs.python.org/issue28448}: Fix C implemented asyncio.Future didn't work on Windows.

@item 
bpo-23214@footnote{https://bugs.python.org/issue23214}: In the "io" module, the argument to BufferedReader and
BytesIO's read1() methods is now optional and can be -1, matching the
BufferedIOBase specification.

@item 
bpo-28480@footnote{https://bugs.python.org/issue28480}: Fix error building socket module when multithreading is
disabled.

@item 
bpo-28240@footnote{https://bugs.python.org/issue28240}: timeit: remove @code{-c/--clock} and @code{-t/--time} command line
options which were deprecated since Python 3.3.

@item 
bpo-28240@footnote{https://bugs.python.org/issue28240}: timeit now repeats the benchmarks 5 times instead of only 3 to
make benchmarks more reliable.

@item 
bpo-28240@footnote{https://bugs.python.org/issue28240}: timeit autorange now uses a single loop iteration if the
benchmark takes less than 10 seconds, instead of 10 iterations. "python3
-m timeit -s 'import time' 'time.sleep(1)'" now takes 4 seconds instead of
40 seconds.

@item 
Distutils.sdist now looks for README and setup.py files with case
sensitivity. This behavior matches that found in Setuptools 6.0 and later.
See setuptools 100@footnote{https://github.com/pypa/setuptools/issues/100} for
rationale.

@item 
bpo-24452@footnote{https://bugs.python.org/issue24452}: Make webbrowser support Chrome on Mac OS X. Patch by Ned
Batchelder.

@item 
bpo-20766@footnote{https://bugs.python.org/issue20766}: Fix references leaked by pdb in the handling of SIGINT
handlers.

@item 
bpo-27998@footnote{https://bugs.python.org/issue27998}: Fixed bytes path support in os.scandir() on Windows. Patch by
Eryk Sun.

@item 
bpo-28317@footnote{https://bugs.python.org/issue28317}: The disassembler now decodes FORMAT_VALUE argument.

@item 
bpo-28380@footnote{https://bugs.python.org/issue28380}: unittest.mock Mock autospec functions now properly support
assert_called, assert_not_called, and assert_called_once.

@item 
bpo-28229@footnote{https://bugs.python.org/issue28229}: lzma module now supports pathlib.

@item 
bpo-28321@footnote{https://bugs.python.org/issue28321}: Fixed writing non-BMP characters with binary format in
plistlib.

@item 
bpo-28225@footnote{https://bugs.python.org/issue28225}: bz2 module now supports pathlib.  Initial patch by Ethan
Furman.

@item 
bpo-28227@footnote{https://bugs.python.org/issue28227}: gzip now supports pathlib.  Patch by Ethan Furman.

@item 
bpo-28332@footnote{https://bugs.python.org/issue28332}: Deprecated silent truncations in socket.htons and socket.ntohs.
Original patch by Oren Milman.

@item 
bpo-27358@footnote{https://bugs.python.org/issue27358}: Optimized merging var-keyword arguments and improved error
message when passing a non-mapping as a var-keyword argument.

@item 
bpo-28257@footnote{https://bugs.python.org/issue28257}: Improved error message when passing a non-iterable as a
var-positional argument.  Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

@item 
bpo-28322@footnote{https://bugs.python.org/issue28322}: Fixed possible crashes when unpickle itertools objects from
incorrect pickle data.  Based on patch by John Leitch.

@item 
bpo-28228@footnote{https://bugs.python.org/issue28228}: imghdr now supports pathlib.

@item 
bpo-28226@footnote{https://bugs.python.org/issue28226}: compileall now supports pathlib.

@item 
bpo-28314@footnote{https://bugs.python.org/issue28314}: Fix function declaration (C flags) for the getiterator() method
of xml.etree.ElementTree.Element.

@item 
bpo-28148@footnote{https://bugs.python.org/issue28148}: Stop using localtime() and gmtime() in the time module.
Introduced platform independent _PyTime_localtime API that is similar to
POSIX localtime_r, but available on all platforms.  Patch by Ed Schouten.

@item 
bpo-28253@footnote{https://bugs.python.org/issue28253}: Fixed calendar functions for extreme months: 0001-01 and
9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so
that they don't call itermonthdates() which can cause datetime.date
under/overflow.

@item 
bpo-28275@footnote{https://bugs.python.org/issue28275}: Fixed possible use after free in the decompress() methods of
the LZMADecompressor and BZ2Decompressor classes. Original patch by John
Leitch.

@item 
bpo-27897@footnote{https://bugs.python.org/issue27897}: Fixed possible crash in sqlite3.Connection.create_collation()
if pass invalid string-like object as a name.  Patch by Xiang Zhang.

@item 
bpo-18844@footnote{https://bugs.python.org/issue18844}: random.choices() now has k as a keyword-only argument to
improve the readability of common cases and come into line with the
signature used in other languages.

@item 
bpo-18893@footnote{https://bugs.python.org/issue18893}: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py.
Patch by Madison May.

@item 
bpo-27611@footnote{https://bugs.python.org/issue27611}: Fixed support of default root window in the tkinter.tix module.
Added the master parameter in the DisplayStyle constructor.

@item 
bpo-27348@footnote{https://bugs.python.org/issue27348}: In the traceback module, restore the formatting of exception
messages like "Exception: None".  This fixes a regression introduced in
3.5a2.

@item 
bpo-25651@footnote{https://bugs.python.org/issue25651}: Allow falsy values to be used for msg parameter of subTest().

@item 
bpo-27778@footnote{https://bugs.python.org/issue27778}: Fix a memory leak in os.getrandom() when the getrandom() is
interrupted by a signal and a signal handler raises a Python exception.

@item 
bpo-28200@footnote{https://bugs.python.org/issue28200}: Fix memory leak on Windows in the os module (fix
path_converter() function).

@item 
bpo-25400@footnote{https://bugs.python.org/issue25400}: RobotFileParser now correctly returns default values for
crawl_delay and request_rate.  Initial patch by Peter Wirtz.

@item 
bpo-27932@footnote{https://bugs.python.org/issue27932}: Prevent memory leak in win32_ver().

@item 
Fix UnboundLocalError in socket._sendfile_use_sendfile.

@item 
bpo-28075@footnote{https://bugs.python.org/issue28075}: Check for ERROR_ACCESS_DENIED in Windows implementation of
os.stat().  Patch by Eryk Sun.

@item 
bpo-22493@footnote{https://bugs.python.org/issue22493}: Warning message emitted by using inline flags in the middle of
regular expression now contains a (truncated) regex pattern. Patch by Tim
Graham.

@item 
bpo-25270@footnote{https://bugs.python.org/issue25270}: Prevent codecs.escape_encode() from raising SystemError when an
empty bytestring is passed.

@item 
bpo-28181@footnote{https://bugs.python.org/issue28181}: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

@item 
bpo-25895@footnote{https://bugs.python.org/issue25895}: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by
Gergely Imreh and Markus Holtermann.

@item 
bpo-28114@footnote{https://bugs.python.org/issue28114}: Fix a crash in parse_envlist() when env contains byte strings.
Patch by Eryk Sun.

@item 
bpo-27599@footnote{https://bugs.python.org/issue27599}: Fixed buffer overrun in binascii.b2a_qp() and
binascii.a2b_qp().

@item 
bpo-27906@footnote{https://bugs.python.org/issue27906}: Fix socket accept exhaustion during high TCP traffic. Patch by
Kevin Conway.

@item 
bpo-28174@footnote{https://bugs.python.org/issue28174}: Handle when SO_REUSEPORT isn't properly supported. Patch by
Seth Michael Larson.

@item 
bpo-26654@footnote{https://bugs.python.org/issue26654}: Inspect functools.partial in asyncio.Handle.__repr__. Patch by
iceboy.

@item 
bpo-26909@footnote{https://bugs.python.org/issue26909}: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

@item 
bpo-28176@footnote{https://bugs.python.org/issue28176}: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

@item 
bpo-27759@footnote{https://bugs.python.org/issue27759}: Fix selectors incorrectly retain invalid file descriptors.
Patch by Mark Williams.

@item 
bpo-28325@footnote{https://bugs.python.org/issue28325}: Remove vestigial MacOS 9 macurl2path module and its tests.

@item 
bpo-28368@footnote{https://bugs.python.org/issue28368}: Refuse monitoring processes if the child watcher has no loop
attached. Patch by Vincent Michel.

@item 
bpo-28369@footnote{https://bugs.python.org/issue28369}: Raise RuntimeError when transport's FD is used with add_reader,
add_writer, etc.

@item 
bpo-28370@footnote{https://bugs.python.org/issue28370}: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг
Марк.

@item 
bpo-28371@footnote{https://bugs.python.org/issue28371}: Deprecate passing asyncio.Handles to run_in_executor.

@item 
bpo-28372@footnote{https://bugs.python.org/issue28372}: Fix asyncio to support formatting of non-python coroutines.

@item 
bpo-28399@footnote{https://bugs.python.org/issue28399}: Remove UNIX socket from FS before binding. Patch by Коренберг
Марк.

@item 
bpo-27972@footnote{https://bugs.python.org/issue27972}: Prohibit Tasks to await on themselves.

@item 
bpo-24142@footnote{https://bugs.python.org/issue24142}: Reading a corrupt config file left configparser in an invalid
state. Original patch by Florian Höch.

@item 
bpo-29581@footnote{https://bugs.python.org/issue29581}: ABCMeta.__new__ now accepts @code{**kwargs}, allowing abstract
base classes to use keyword parameters in __init_subclass__. Patch by Nate
Soares.

@item 
bpo-25532@footnote{https://bugs.python.org/issue25532}: inspect.unwrap() will now only try to unwrap an object
sys.getrecursionlimit() times, to protect against objects which create a
new object on every attribute access.

@item 
bpo-30177@footnote{https://bugs.python.org/issue30177}: path.resolve(strict=False) no longer cuts the path after the
first element not present in the filesystem.  Patch by Antoine Pietri.
@end itemize

@node 文档<26>,测试<23>,库<31>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id234}@anchor{104f}
@subsubsection 文档



@itemize -

@item 
bpo-31294@footnote{https://bugs.python.org/issue31294}: Fix incomplete code snippet in the ZeroMQSocketListener and
ZeroMQSocketHandler examples and adapt them to Python 3.

@item 
bpo-21649@footnote{https://bugs.python.org/issue21649}: Add RFC 7525 and Mozilla server side TLS links to SSL
documentation.

@item 
bpo-31128@footnote{https://bugs.python.org/issue31128}: Allow the pydoc server to bind to arbitrary hostnames.

@item 
bpo-30803@footnote{https://bugs.python.org/issue30803}: Clarify doc on truth value testing. Original patch by Peter
Thomassen.

@item 
bpo-30176@footnote{https://bugs.python.org/issue30176}: Add missing attribute related constants in curses
documentation.

@item 
bpo-30052@footnote{https://bugs.python.org/issue30052}: the link targets for @ref{32a,,bytes()} and @ref{32b,,bytearray()} are
now their respective type definitions, rather than the corresponding
builtin function entries. Use @ref{1050,,bytes} and
@ref{1051,,bytearray} to reference the latter. In order to
ensure this and future cross-reference updates are applied automatically,
the daily documentation builds now disable the default output caching
features in Sphinx.

@item 
bpo-26985@footnote{https://bugs.python.org/issue26985}: Add missing info of code object in inspect documentation.

@item 
bpo-19824@footnote{https://bugs.python.org/issue19824}: Improve the documentation for, and links to, template strings
by emphasizing their utility for internationalization, and by clarifying
some usage constraints. (See also: bpo-20314@footnote{https://bugs.python.org/issue20314}, bpo-12518@footnote{https://bugs.python.org/issue12518})

@item 
bpo-28929@footnote{https://bugs.python.org/issue28929}: Link the documentation to its source file on GitHub.

@item 
bpo-25008@footnote{https://bugs.python.org/issue25008}: Document smtpd.py as effectively deprecated and add a pointer
to aiosmtpd, a third-party asyncio-based replacement.

@item 
bpo-26355@footnote{https://bugs.python.org/issue26355}: Add canonical header link on each page to corresponding major
version of the documentation. Patch by Matthias Bussonnier.

@item 
bpo-29349@footnote{https://bugs.python.org/issue29349}: Fix Python 2 syntax in code for building the documentation.

@item 
bpo-23722@footnote{https://bugs.python.org/issue23722}: The data model reference and the porting section in the 3.6
What's New guide now cover the additional @code{__classcell__} handling
needed for custom metaclasses to fully support 
@geindex Python 提高建议; PEP 487
PEP 487@footnote{https://www.python.org/dev/peps/pep-0487} and
zero-argument @code{super()}.

@item 
bpo-28513@footnote{https://bugs.python.org/issue28513}: Documented command-line interface of zipfile.
@end itemize

@node 测试<23>,构建<22>,文档<26>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id235}@anchor{1052}
@subsubsection 测试



@itemize -

@item 
bpo-29639@footnote{https://bugs.python.org/issue29639}: test.support.HOST is now "localhost", a new HOSTv4 constant has
been added for your @code{127.0.0.1} needs, similar to the existing HOSTv6
constant.

@item 
bpo-31320@footnote{https://bugs.python.org/issue31320}: Silence traceback in test_ssl

@item 
bpo-31346@footnote{https://bugs.python.org/issue31346}: Prefer PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER protocols
for SSLContext.

@item 
bpo-25674@footnote{https://bugs.python.org/issue25674}: Remove sha256.tbs-internet.com ssl test

@item 
bpo-30715@footnote{https://bugs.python.org/issue30715}: Address ALPN callback changes for OpenSSL 1.1.0f. The latest
version behaves like OpenSSL 1.0.2 and no longer aborts handshake.

@item 
bpo-30822@footnote{https://bugs.python.org/issue30822}: regrtest: Exclude tzdata from regrtest --all. When running the
test suite using --use=all / -u all, exclude tzdata since it makes
test_datetime too slow (15-20 min on some buildbots) which then times out
on some buildbots. Fix also regrtest command line parser to allow passing
-u extralargefile to run test_zipfile64.

@item 
bpo-30695@footnote{https://bugs.python.org/issue30695}: Add the @code{set_nomemory(start, stop)} and @code{remove_mem_hooks()}
functions to the _testcapi module.

@item 
bpo-30357@footnote{https://bugs.python.org/issue30357}: test_thread: setUp() now uses support.threading_setup() and
support.threading_cleanup() to wait until threads complete to avoid random
side effects on following tests. Initial patch written by Grzegorz
Grzywacz.

@item 
bpo-30197@footnote{https://bugs.python.org/issue30197}: Enhanced functions swap_attr() and swap_item() in the
test.support module. They now work when delete replaced attribute or item
inside the with statement.  The old value of the attribute or item (or
None if it doesn't exist) now will be assigned to the target of the "as"
clause, if there is one.

@item 
bpo-24932@footnote{https://bugs.python.org/issue24932}: Use proper command line parsing in _testembed

@item 
bpo-28950@footnote{https://bugs.python.org/issue28950}: Disallow -j0 to be combined with -T/-l in regrtest command line
arguments.

@item 
bpo-28683@footnote{https://bugs.python.org/issue28683}: Fix the tests that bind() a unix socket and raise
PermissionError on Android for a non-root user.

@item 
bpo-26936@footnote{https://bugs.python.org/issue26936}: Fix the test_socket failures on Android - getservbyname(),
getservbyport() and getaddrinfo() are broken on some Android API levels.

@item 
bpo-28666@footnote{https://bugs.python.org/issue28666}: Now test.support.rmtree is able to remove unwritable or
unreadable directories.

@item 
bpo-23839@footnote{https://bugs.python.org/issue23839}: Various caches now are cleared before running every test file.

@item 
bpo-26944@footnote{https://bugs.python.org/issue26944}: Fix test_posix for Android where 'id -G' is entirely wrong or
missing the effective gid.

@item 
bpo-28409@footnote{https://bugs.python.org/issue28409}: regrtest: fix the parser of command line arguments.

@item 
bpo-28217@footnote{https://bugs.python.org/issue28217}: Adds _testconsole module to test console input.

@item 
bpo-26939@footnote{https://bugs.python.org/issue26939}: Add the support.setswitchinterval() function to fix
test_functools hanging on the Android armv7 qemu emulator.
@end itemize

@node 构建<22>,Windows<24>,测试<23>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id236}@anchor{1053}
@subsubsection 构建



@itemize -

@item 
bpo-31354@footnote{https://bugs.python.org/issue31354}: Allow --with-lto to be used on all builds, not just @code{make
profile-opt}.

@item 
bpo-31370@footnote{https://bugs.python.org/issue31370}: Remove support for building --without-threads. This option is
not really useful anymore in the 21st century. Removing lots of
conditional paths allows us to simplify the code base, including in
difficult to maintain low-level internal code.

@item 
bpo-31341@footnote{https://bugs.python.org/issue31341}: Per 
@geindex Python 提高建议; PEP 11
PEP 11@footnote{https://www.python.org/dev/peps/pep-0011}, support for the IRIX operating system was
removed.

@item 
bpo-30854@footnote{https://bugs.python.org/issue30854}: Fix compile error when compiling --without-threads. Patch by
Masayuki Yamamoto.

@item 
bpo-30687@footnote{https://bugs.python.org/issue30687}: Locate msbuild.exe on Windows when building rather than
vcvarsall.bat

@item 
bpo-20210@footnote{https://bugs.python.org/issue20210}: Support the @emph{disabled} marker in Setup files. Extension modules
listed after this marker are not built at all, neither by the Makefile nor
by setup.py.

@item 
bpo-29941@footnote{https://bugs.python.org/issue29941}: Add @code{--with-assertions} configure flag to explicitly enable C
@code{assert()} checks. Defaults to off. @code{--with-pydebug} implies
@code{--with-assertions}.

@item 
bpo-28787@footnote{https://bugs.python.org/issue28787}: Fix out-of-tree builds of Python when configured with
@code{--with--dtrace}.

@item 
bpo-29243@footnote{https://bugs.python.org/issue29243}: Prevent unnecessary rebuilding of Python during @code{make test},
@code{make install} and some other make targets when configured with
@code{--enable-optimizations}.

@item 
bpo-23404@footnote{https://bugs.python.org/issue23404}: Don't regenerate generated files based on file modification
time anymore: the action is now explicit. Replace @code{make touch} with
@code{make regen-all}.

@item 
bpo-29643@footnote{https://bugs.python.org/issue29643}: Fix @code{--enable-optimization} didn't work.

@item 
bpo-27593@footnote{https://bugs.python.org/issue27593}: sys.version and the platform module python_build(),
python_branch(), and python_revision() functions now use git information
rather than hg when building from a repo.

@item 
bpo-29572@footnote{https://bugs.python.org/issue29572}: 更新Windows 构建和OS X安装程序以使用OpenSSL 1.0.2k。

@item 
bpo-27659@footnote{https://bugs.python.org/issue27659}: Prohibit implicit C function declarations: use
@code{-Werror=implicit-function-declaration} when possible (GCC and Clang,
but it depends on the compiler version). Patch written by Chi Hsuan Yen.

@item 
bpo-29384@footnote{https://bugs.python.org/issue29384}: Remove old Be OS helper scripts.

@item 
bpo-26851@footnote{https://bugs.python.org/issue26851}: Set Android compilation and link flags.

@item 
bpo-28768@footnote{https://bugs.python.org/issue28768}: Fix implicit declaration of function _setmode. Patch by
Masayuki Yamamoto

@item 
bpo-29080@footnote{https://bugs.python.org/issue29080}: Removes hard dependency on hg.exe from PCBuild/build.bat

@item 
bpo-23903@footnote{https://bugs.python.org/issue23903}: Added missed names to PC/python3.def.

@item 
bpo-28762@footnote{https://bugs.python.org/issue28762}: lockf() is available on Android API level 24, but the F_LOCK
macro is not defined in android-ndk-r13.

@item 
bpo-28538@footnote{https://bugs.python.org/issue28538}: Fix the compilation error that occurs because if_nameindex() is
available on Android API level 24, but the if_nameindex structure is not
defined.

@item 
bpo-20211@footnote{https://bugs.python.org/issue20211}: Do not add the directory for installing C header files and the
directory for installing object code libraries to the cross compilation
search paths. Original patch by Thomas Petazzoni.

@item 
bpo-28849@footnote{https://bugs.python.org/issue28849}: Do not define sys.implementation._multiarch on Android.

@item 
bpo-10656@footnote{https://bugs.python.org/issue10656}: Fix out-of-tree building on AIX.  Patch by Tristan Carel and
Michael Haubenwallner.

@item 
bpo-26359@footnote{https://bugs.python.org/issue26359}: Rename --with-optimiations to --enable-optimizations.

@item 
bpo-28444@footnote{https://bugs.python.org/issue28444}: Fix missing extensions modules when cross compiling.

@item 
bpo-28208@footnote{https://bugs.python.org/issue28208}: 更新Windows 构建和OS X 安装程序以使用SQLite 3.14.2.

@item 
bpo-28248@footnote{https://bugs.python.org/issue28248}: 更新Windows 构建和OS X安装程序以使用OpenSSL 1.0.2j.

@item 
bpo-21124@footnote{https://bugs.python.org/issue21124}: Fix building the _struct module on Cygwin by passing @code{NULL}
instead of @code{&PyType_Type} to PyVarObject_HEAD_INIT.  Patch by Masayuki
Yamamoto.

@item 
bpo-13756@footnote{https://bugs.python.org/issue13756}: Fix building extensions modules on Cygwin.  Patch by Roumen
Petrov, based on original patch by Jason Tishler.

@item 
bpo-21085@footnote{https://bugs.python.org/issue21085}: Add configure check for siginfo_t.si_band, which Cygwin does
not provide. Patch by Masayuki Yamamoto with review and rebase by Erik
Bray.

@item 
bpo-28258@footnote{https://bugs.python.org/issue28258}: Fixed build with Estonian locale (python-config and distclean
targets in Makefile).  Patch by Arfrever Frehtes Taifersar Arahesis.

@item 
bpo-26661@footnote{https://bugs.python.org/issue26661}: setup.py now detects system libffi with multiarch wrapper.

@item 
bpo-27979@footnote{https://bugs.python.org/issue27979}: A full copy of libffi is no longer bundled for use when
building _ctypes on non-OSX UNIX platforms.  An installed copy of libffi
is now required when building _ctypes on such platforms.

@item 
bpo-15819@footnote{https://bugs.python.org/issue15819}: Remove redundant include search directory option for building
outside the source tree.

@item 
bpo-28676@footnote{https://bugs.python.org/issue28676}: Prevent missing 'getentropy' declaration warning on macOS.
Patch by Gareth Rees.
@end itemize

@node Windows<24>,IDLE<29>,构建<22>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id237}@anchor{1054}
@subsubsection Windows



@itemize -

@item 
bpo-31392@footnote{https://bugs.python.org/issue31392}: 更新Windows 构建以使用OpenSSL 1.1.0f

@item 
bpo-30389@footnote{https://bugs.python.org/issue30389}: Adds detection of Visual Studio 2017 to distutils on Windows.

@item 
bpo-31358@footnote{https://bugs.python.org/issue31358}: zlib is no longer bundled in the CPython source, instead it is
downloaded on demand just like bz2, lzma, OpenSSL, Tcl/Tk, and SQLite.

@item 
bpo-31340@footnote{https://bugs.python.org/issue31340}: Change to building with MSVC v141 (included with Visual Studio
2017)

@item 
bpo-30581@footnote{https://bugs.python.org/issue30581}: os.cpu_count() now returns the correct number of processors on
Windows when the number of logical processors is greater than 64.

@item 
bpo-30916@footnote{https://bugs.python.org/issue30916}: Pre-build OpenSSL, Tcl and Tk and include the binaries in the
build.

@item 
bpo-30731@footnote{https://bugs.python.org/issue30731}: Add a missing xmlns to python.manifest so that it matches the
schema.

@item 
bpo-30291@footnote{https://bugs.python.org/issue30291}: Allow requiring 64-bit interpreters from py.exe using -64
suffix. Contributed by Steve (Gadget) Barnes.

@item 
bpo-30362@footnote{https://bugs.python.org/issue30362}: Adds list options (-0, -0p) to py.exe launcher. Contributed by
Steve Barnes.

@item 
bpo-23451@footnote{https://bugs.python.org/issue23451}: Fix socket deprecation warnings in socketmodule.c. Patch by
Segev Finer.

@item 
bpo-30450@footnote{https://bugs.python.org/issue30450}: The build process on Windows no longer depends on Subversion,
instead pulling external code from GitHub via a Python script.  If Python
3.6 is not found on the system (via @code{py -3.6}), NuGet is used to
download a copy of 32-bit Python.

@item 
bpo-29579@footnote{https://bugs.python.org/issue29579}: Removes readme.txt from the installer.

@item 
bpo-25778@footnote{https://bugs.python.org/issue25778}: winreg does not truncate string correctly (Patch by Eryk Sun)

@item 
bpo-28896@footnote{https://bugs.python.org/issue28896}: Deprecate WindowsRegistryFinder and disable it by default

@item 
bpo-28522@footnote{https://bugs.python.org/issue28522}: Fixes mishandled buffer reallocation in getpathp.c

@item 
bpo-28402@footnote{https://bugs.python.org/issue28402}: Adds signed catalog files for stdlib on Windows.

@item 
bpo-28333@footnote{https://bugs.python.org/issue28333}: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk
Sun)

@item 
bpo-28251@footnote{https://bugs.python.org/issue28251}: Improvements to help manuals on Windows.

@item 
bpo-28110@footnote{https://bugs.python.org/issue28110}: launcher.msi has different product codes between 32-bit and
64-bit

@item 
bpo-28161@footnote{https://bugs.python.org/issue28161}: Opening CON for write access fails

@item 
bpo-28162@footnote{https://bugs.python.org/issue28162}: WindowsConsoleIO readall() fails if first line starts with
Ctrl+Z

@item 
bpo-28163@footnote{https://bugs.python.org/issue28163}: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle

@item 
bpo-28164@footnote{https://bugs.python.org/issue28164}: _PyIO_get_console_type fails for various paths

@item 
bpo-28137@footnote{https://bugs.python.org/issue28137}: Renames Windows path file to ._pth

@item 
bpo-28138@footnote{https://bugs.python.org/issue28138}: Windows ._pth file should allow import site
@end itemize

@node IDLE<29>,工具/示例<16>,Windows<24>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id238}@anchor{1055}
@subsubsection IDLE



@itemize -

@item 
bpo-31493@footnote{https://bugs.python.org/issue31493}: IDLE code context -- fix code update and font update timers.
Canceling timers prevents a warning message when test_idle completes.

@item 
bpo-31488@footnote{https://bugs.python.org/issue31488}: IDLE - Update non-key options in former extension classes. When
applying configdialog changes, call .reload for each feature class. Change
ParenMatch so updated options affect existing instances attached to
existing editor windows.

@item 
bpo-31477@footnote{https://bugs.python.org/issue31477}: IDLE - Improve rstrip entry in doc. Strip trailing whitespace
strips more than blank spaces.  Multiline string literals are not skipped.

@item 
bpo-31480@footnote{https://bugs.python.org/issue31480}: IDLE - make tests pass with zzdummy extension disabled by
default.

@item 
bpo-31421@footnote{https://bugs.python.org/issue31421}: Document how IDLE runs tkinter programs. IDLE calls tcl/tk
update in the background in order to make live interaction and
experimentation with tkinter applications much easier.

@item 
bpo-31414@footnote{https://bugs.python.org/issue31414}: IDLE -- fix tk entry box tests by deleting first. Adding to an
int entry is not the same as deleting and inserting because int('@w{'}) will
fail.

@item 
bpo-31051@footnote{https://bugs.python.org/issue31051}: Rearrange IDLE configdialog GenPage into Window, Editor, and
Help sections.

@item 
bpo-30617@footnote{https://bugs.python.org/issue30617}: IDLE - Add docstrings and tests for outwin subclass of editor.
Move some data and functions from the class to module level. Patch by
Cheryl Sabella.

@item 
bpo-31287@footnote{https://bugs.python.org/issue31287}: IDLE - Do not modify tkinter.message in test_configdialog.

@item 
bpo-27099@footnote{https://bugs.python.org/issue27099}: Convert IDLE's built-in 'extensions' to regular features. About
10 IDLE features were implemented as supposedly optional extensions. Their
different behavior could be confusing or worse for users and not good for
maintenance. Hence the conversion. The main difference for users is that
user configurable key bindings for builtin features are now handled
uniformly. Now, editing a binding in a keyset only affects its value in
the keyset. All bindings are defined together in the system-specific
default keysets in config-extensions.def. All custom keysets are saved as
a whole in config-extension.cfg.  All take effect as soon as one clicks
Apply or Ok. The affected events are '<<force-open-completions>>',
'<<expand-word>>', '<<force-open-calltip>>', '<<flash-paren>>',
'<<format-paragraph>>', '<<run-module>>', '<<check-module>>', and
'<<zoom-height>>'.  Any (global) customizations made before 3.6.3 will not
affect their keyset-specific customization after 3.6.3. and vice versa.
Initial patch by Charles Wohlganger.

@item 
bpo-31206@footnote{https://bugs.python.org/issue31206}: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by
Cheryl Sabella.

@item 
bpo-31001@footnote{https://bugs.python.org/issue31001}: Add tests for configdialog highlight tab.  Patch by Cheryl
Sabella.

@item 
bpo-31205@footnote{https://bugs.python.org/issue31205}: IDLE: Factor KeysPage(Frame) class from ConfigDialog.  The
slightly modified tests continue to pass.  Patch by Cheryl Sabella.

@item 
bpo-31130@footnote{https://bugs.python.org/issue31130}: IDLE -- stop leaks in test_configdialog. Initial patch by
Victor Stinner.

@item 
bpo-31002@footnote{https://bugs.python.org/issue31002}: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

@item 
bpo-19903@footnote{https://bugs.python.org/issue19903}: IDLE: Calltips use @ref{556,,inspect.signature} instead of
@ref{558,,inspect.getfullargspec}. This improves calltips for builtins converted to
use Argument Clinic. Patch by Louie Lu.

@item 
bpo-31083@footnote{https://bugs.python.org/issue31083}: IDLE - Add an outline of a TabPage class in configdialog.
Update existing classes to match outline. Initial patch by Cheryl Sabella.

@item 
bpo-31050@footnote{https://bugs.python.org/issue31050}: Factor GenPage(Frame) class from ConfigDialog. The slightly
modified tests continue to pass. Patch by Cheryl Sabella.

@item 
bpo-31004@footnote{https://bugs.python.org/issue31004}: IDLE - Factor FontPage(Frame) class from ConfigDialog. Slightly
modified tests continue to pass. Fix General tests. Patch mostly by Cheryl
Sabella.

@item 
bpo-30781@footnote{https://bugs.python.org/issue30781}: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan
Reedy and Cheryl Sabella.

@item 
bpo-31060@footnote{https://bugs.python.org/issue31060}: IDLE - Finish rearranging methods of ConfigDialog Grouping
methods pertaining to each tab and the buttons will aid writing tests and
improving the tabs and will enable splitting the groups into classes.

@item 
bpo-30853@footnote{https://bugs.python.org/issue30853}: IDLE -- Factor a VarTrace class out of ConfigDialog. Instance
tracers manages pairs consisting of a tk variable and a callback function.
When tracing is turned on, setting the variable calls the function.  Test
coverage for the new class is 100%.

@item 
bpo-31003@footnote{https://bugs.python.org/issue31003}: IDLE: Add more tests for General tab.

@item 
bpo-30993@footnote{https://bugs.python.org/issue30993}: IDLE - Improve configdialog font page and tests. In
configdialog: Document causal pathways in create_font_tab docstring.
Simplify some attribute names. Move set_samples calls to var_changed_font
(idea from Cheryl Sabella).  Move related functions to positions after the
create widgets function. In test_configdialog: Fix test_font_set so not
order dependent.  Fix renamed test_indent_scale so it tests the widget.
Adjust tests for movement of set_samples call.  Add tests for load
functions.  Put all font tests in one class and tab indent tests in
another.  Except for two lines, these tests completely cover the related
functions.

@item 
bpo-30981@footnote{https://bugs.python.org/issue30981}: IDLE -- Add more configdialog font page tests.

@item 
bpo-28523@footnote{https://bugs.python.org/issue28523}: IDLE: replace 'colour' with 'color' in configdialog.

@item 
bpo-30917@footnote{https://bugs.python.org/issue30917}: Add tests for idlelib.config.IdleConf. Increase coverage from
46% to 96%. Patch by Louie Lu.

@item 
bpo-30934@footnote{https://bugs.python.org/issue30934}: Document coverage details for idlelib tests. Add section to
idlelib/idle-test/README.txt. Include check that branches are taken both
ways. Exclude IDLE-specific code that does not run during unit tests.

@item 
bpo-30913@footnote{https://bugs.python.org/issue30913}: IDLE: Document ConfigDialog tk Vars, methods, and widgets in
docstrings This will facilitate improving the dialog and splitting up the
class. Original patch by Cheryl Sabella.

@item 
bpo-30899@footnote{https://bugs.python.org/issue30899}: IDLE: Add tests for ConfigParser subclasses in config. Patch by
Louie Lu.

@item 
bpo-30881@footnote{https://bugs.python.org/issue30881}: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

@item 
bpo-30851@footnote{https://bugs.python.org/issue30851}: IDLE: Remove unused variables in configdialog.  One is a
duplicate, one is set but cannot be altered by users. Patch by Cheryl
Sabella.

@item 
bpo-30870@footnote{https://bugs.python.org/issue30870}: IDLE: In Settings dialog, select font with Up, Down keys as
well as mouse. Initial patch by Louie Lu.

@item 
bpo-8231@footnote{https://bugs.python.org/issue8231}: IDLE: call config.IdleConf.GetUserCfgDir only once.

@item 
bpo-30779@footnote{https://bugs.python.org/issue30779}: IDLE: Factor ConfigChanges class from configdialog, put in
config; test. * In config, put dump test code in a function; run it and
unittest in   'if __name__ == '__main__'. * Add class config.ConfigChanges
based on changes_class_v4.py on bpo issue. * Add class
test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise
configdialog to use ConfigChanges; see tracker msg297804. * Revise
test_configdialog to match configdialog changes. * Remove configdialog
functions unused or moved to ConfigChanges. Cheryl Sabella contributed
parts of the patch.

@item 
bpo-30777@footnote{https://bugs.python.org/issue30777}: IDLE: configdialog - Add docstrings and fix comments. Patch by
Cheryl Sabella.

@item 
bpo-30495@footnote{https://bugs.python.org/issue30495}: IDLE: Improve textview with docstrings, PEP8 names, and more
tests. Patch by Cheryl Sabella.

@item 
bpo-30723@footnote{https://bugs.python.org/issue30723}: IDLE: Make several improvements to parenmatch. Add 'parens'
style to highlight both opener and closer. Make 'default' style, which is
not default, a synonym for 'opener'. Make time-delay work the same with
all styles. Add help for config dialog extensions tab, including help for
parenmatch. Add new tests.  Original patch by Charles Wohlganger.

@item 
bpo-30674@footnote{https://bugs.python.org/issue30674}: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

@item 
bpo-21519@footnote{https://bugs.python.org/issue21519}: IDLE's basic custom key entry dialog now detects duplicates
properly. Original patch by Saimadhav Heblikar.

@item 
bpo-29910@footnote{https://bugs.python.org/issue29910}: IDLE no longer deletes a character after commenting out a
region by a key shortcut.  Add @code{return 'break'} for this and other
potential conflicts between IDLE and default key bindings.

@item 
bpo-30728@footnote{https://bugs.python.org/issue30728}: Review and change idlelib.configdialog names. Lowercase method
and attribute names. Replace 'colour' with 'color', expand overly cryptic
names, delete unneeded underscores. Replace @code{import *} with specific
imports. Patches by Cheryl Sabella.

@item 
bpo-6739@footnote{https://bugs.python.org/issue6739}: IDLE: Verify user-entered key sequences by trying to bind them
with tk. Add tests for all 3 validation functions. Original patch by G
Polo.  Tests added by Cheryl Sabella.

@item 
bpo-15786@footnote{https://bugs.python.org/issue15786}: Fix several problems with IDLE's autocompletion box. The
following should now work: clicking on selection box items; using the
scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no
longer happen. Patch by Louie Lu.

@item 
bpo-25514@footnote{https://bugs.python.org/issue25514}: Add doc subsubsection about IDLE failure to start. Popup
no-connection message directs users to this section.

@item 
bpo-30642@footnote{https://bugs.python.org/issue30642}: Fix reference leaks in IDLE tests. Patches by Louie Lu and
Terry Jan Reedy.

@item 
bpo-30495@footnote{https://bugs.python.org/issue30495}: Add docstrings for textview.py and use PEP8 names. Patches by
Cheryl Sabella and Terry Jan Reedy.

@item 
bpo-30290@footnote{https://bugs.python.org/issue30290}: Help-about: use pep8 names and add tests. Increase coverage to
100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

@item 
bpo-30303@footnote{https://bugs.python.org/issue30303}: Add _utest option to textview; add new tests. Increase coverage
to 100%. Patches by Louie Lu and Terry Jan Reedy.

@item 
bpo-29071@footnote{https://bugs.python.org/issue29071}: IDLE colors f-string prefixes (but not invalid ur prefixes).

@item 
bpo-28572@footnote{https://bugs.python.org/issue28572}: Add 10% to coverage of IDLE's test_configdialog. Update and
augment description of the configuration system.
@end itemize

@node 工具/示例<16>,C API<18>,IDLE<29>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id239}@anchor{1056}
@subsubsection 工具/示例



@itemize -

@item 
bpo-30983@footnote{https://bugs.python.org/issue30983}: gdb integration commands (py-bt, etc.) work on optimized shared
builds now, too.  
@geindex Python 提高建议; PEP 523
PEP 523@footnote{https://www.python.org/dev/peps/pep-0523} introduced _PyEval_EvalFrameDefault which
inlines PyEval_EvalFrameEx on non-debug shared builds.  This broke the
ability to use py-bt, py-up, and a few other Python-specific gdb
integrations. The problem is fixed by only looking for
_PyEval_EvalFrameDefault frames in python-gdb.py.  Original patch by Bruno
"Polaco" Penteado.

@item 
bpo-29748@footnote{https://bugs.python.org/issue29748}: Added the slice index converter in Argument Clinic.

@item 
bpo-24037@footnote{https://bugs.python.org/issue24037}: Argument Clinic now uses the converter @code{bool(accept=@{int@})}
rather than @ref{184,,int} for semantical booleans.  This avoids repeating the
default value for Python and C and will help in converting to @ref{183,,bool} in
future.

@item 
bpo-29367@footnote{https://bugs.python.org/issue29367}: python-gdb.py now supports also @code{method-wrapper}
(@code{wrapperobject}) objects.

@item 
bpo-28023@footnote{https://bugs.python.org/issue28023}: Fix python-gdb.py didn't support new dict implementation.

@item 
bpo-15369@footnote{https://bugs.python.org/issue15369}: The pybench and pystone microbenchmark have been removed from
Tools. Please use the new Python benchmark suite
@indicateurl{https://github.com/python/performance} which is more reliable and includes
a portable version of pybench working on Python 2 and Python 3.

@item 
bpo-28102@footnote{https://bugs.python.org/issue28102}: The zipfile module CLI now prints usage to stderr. Patch by
Stephen J. Turnbull.
@end itemize

@node C API<18>,,工具/示例<16>,Python 3 7 0 alpha 1
@anchor{whatsnew/changelog id240}@anchor{1057}
@subsubsection C API



@itemize -

@item 
bpo-31338@footnote{https://bugs.python.org/issue31338}: Added the @code{Py_UNREACHABLE()} macro for code paths which are
never expected to be reached.  This and a few other useful macros are now
documented in the C API manual.

@item 
bpo-30832@footnote{https://bugs.python.org/issue30832}: Remove own implementation for thread-local storage. CPython has
provided the own implementation for thread-local storage (TLS) on
Python/thread.c, it's used in the case which a platform has not supplied
native TLS.  However, currently all supported platforms (Windows and
pthreads) have provided native TLS and defined the Py_HAVE_NATIVE_TLS
macro with unconditional in any case.

@item 
bpo-30708@footnote{https://bugs.python.org/issue30708}: PyUnicode_AsWideCharString() now raises a ValueError if the
second argument is NULL and the wchar_t* string contains null characters.

@item 
bpo-16500@footnote{https://bugs.python.org/issue16500}: Deprecate PyOS_AfterFork() and add PyOS_BeforeFork(),
PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

@item 
bpo-6532@footnote{https://bugs.python.org/issue6532}: The type of results of PyThread_start_new_thread() and
PyThread_get_thread_ident(), and the id parameter of
PyThreadState_SetAsyncExc() changed from "long" to "unsigned long".

@item 
bpo-27867@footnote{https://bugs.python.org/issue27867}: Function PySlice_GetIndicesEx() is deprecated and replaced with
a macro if Py_LIMITED_API is not set or set to the value between
0x03050400 and 0x03060000 (not including) or 0x03060100 or higher.  Added
functions PySlice_Unpack() and PySlice_AdjustIndices().

@item 
bpo-29083@footnote{https://bugs.python.org/issue29083}: Fixed the declaration of some public API functions.
PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in
limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and
Py_BuildValue() were not available in limited API of version < 3.3 when
PY_SSIZE_T_CLEAN is defined.

@item 
bpo-28769@footnote{https://bugs.python.org/issue28769}: The result of PyUnicode_AsUTF8AndSize() and PyUnicode_AsUTF8()
is now of type @code{const char *} rather of @code{char *}.

@item 
bpo-29058@footnote{https://bugs.python.org/issue29058}: All stable API extensions added after Python 3.2 are now
available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of
the minimum Python version supporting this API.

@item 
bpo-28822@footnote{https://bugs.python.org/issue28822}: The index parameters @emph{start} and @emph{end} of PyUnicode_FindChar()
are now adjusted to behave like @code{str[start:end]}.

@item 
bpo-28808@footnote{https://bugs.python.org/issue28808}: PyUnicode_CompareWithASCIIString() now never raises exceptions.

@item 
bpo-28761@footnote{https://bugs.python.org/issue28761}: The fields name and doc of structures PyMemberDef, PyGetSetDef,
PyStructSequence_Field, PyStructSequence_Desc, and wrapperbase are now of
type @code{const char *} rather of @code{char *}.

@item 
bpo-28748@footnote{https://bugs.python.org/issue28748}: Private variable _Py_PackageContext is now of type @code{const char
*} rather of @code{char *}.

@item 
bpo-19569@footnote{https://bugs.python.org/issue19569}: Compiler warnings are now emitted if use most of deprecated
functions.

@item 
bpo-28426@footnote{https://bugs.python.org/issue28426}: Deprecated undocumented functions PyUnicode_AsEncodedObject(),
PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and
PyUnicode_AsEncodedUnicode().
@end itemize

@node Python 3 6 6 正式版,Python 3 6 6 rc1,Python 3 7 0 alpha 1,更新日志
@anchor{whatsnew/changelog python-3-6-6-final}@anchor{1058}
@subsection Python 3.6.6 正式版


@emph{发布日期: 2018-06-27}

在 3.6.6 版本中没有新的更改。

@node Python 3 6 6 rc1,Python 3 6 5 正式版,Python 3 6 6 正式版,更新日志
@anchor{whatsnew/changelog python-3-6-6-release-candidate-1}@anchor{1059}
@subsection Python 3.6.6 rc1


@emph{发布日期: 2018-06-11}

@menu
* 核心与内置: 核心与内置<31>. 
* 库: 库<32>. 
* 文档: 文档<27>. 
* 测试: 测试<24>. 
* 构建: 构建<23>. 
* Windows: Windows<25>. 
* macOS: macOS<17>. 
* IDLE: IDLE<30>. 
* 工具/示例: 工具/示例<17>. 
* C API: C API<19>. 

@end menu

@node 核心与内置<31>,库<32>,,Python 3 6 6 rc1
@anchor{whatsnew/changelog id241}@anchor{105a}
@subsubsection 核心与内置



@itemize -

@item 
bpo-33786@footnote{https://bugs.python.org/issue33786}: Fix asynchronous generators to handle GeneratorExit in athrow()
correctly

@item 
bpo-30654@footnote{https://bugs.python.org/issue30654}: Fixed reset of the SIGINT handler to SIG_DFL on interpreter
shutdown even when there was a custom handler set previously. Patch by
Philipp Kerling.

@item 
bpo-33622@footnote{https://bugs.python.org/issue33622}: Fixed a leak when the garbage collector fails to add an object
with the @code{__del__} method or referenced by it into the
@ref{b39,,gc.garbage} list. @code{PyGC_Collect()} can now be called when an
exception is set and preserves it.

@item 
bpo-31849@footnote{https://bugs.python.org/issue31849}: Fix signed/unsigned comparison warning in pyhash.c.

@item 
bpo-33391@footnote{https://bugs.python.org/issue33391}: Fix a leak in set_symmetric_difference().

@item 
bpo-28055@footnote{https://bugs.python.org/issue28055}: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

@item 
bpo-33231@footnote{https://bugs.python.org/issue33231}: 修复 @code{normalizestring()} 中潜在的内存泄漏。

@item 
bpo-29922@footnote{https://bugs.python.org/issue29922}: Improved error messages in 'async with' when @code{__aenter__()}
or @code{__aexit__()} return non-awaitable object.

@item 
bpo-33199@footnote{https://bugs.python.org/issue33199}: Fix @code{ma_version_tag} in dict implementation is uninitialized
when copying from key-sharing dict.

@item 
bpo-33041@footnote{https://bugs.python.org/issue33041}: Fixed jumping when the function contains an @code{async for} loop.

@item 
bpo-32282@footnote{https://bugs.python.org/issue32282}: Fix an unnecessary ifdef in the include of VersionHelpers.h in
socketmodule on Windows.

@item 
bpo-21983@footnote{https://bugs.python.org/issue21983}: Fix a crash in @ref{fa6,,ctypes.cast()} in case the type argument is a
ctypes structured data type. Patch by Eryk Sun and Oren Milman.
@end itemize

@node 库<32>,文档<27>,核心与内置<31>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id242}@anchor{105b}
@subsubsection 库



@itemize -

@item 
bpo-30167@footnote{https://bugs.python.org/issue30167}: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by
Steve Weber.

@item 
bpo-33812@footnote{https://bugs.python.org/issue33812}: Datetime instance d with non-None tzinfo, but with
d.tzinfo.utcoffset(d) returning None is now treated as naive by the
astimezone() method.

@item 
bpo-30805@footnote{https://bugs.python.org/issue30805}: Avoid race condition with debug logging

@item 
bpo-33767@footnote{https://bugs.python.org/issue33767}: The concatenation (@code{+}) and repetition (@code{*}) sequence
operations now raise @ref{192,,TypeError} instead of @ref{5f6,,SystemError} when
performed on @ref{1ec,,mmap.mmap} objects.  Patch by Zackery Spytz.

@item 
bpo-32684@footnote{https://bugs.python.org/issue32684}: Fix gather to propagate cancellation of itself even with
return_exceptions.

@item 
bpo-33674@footnote{https://bugs.python.org/issue33674}: Fix a race condition in SSLProtocol.connection_made() of
asyncio.sslproto: start immediately the handshake instead of using
call_soon(). Previously, data_received() could be called before the
handshake started, causing the handshake to hang or fail.

@item 
bpo-31647@footnote{https://bugs.python.org/issue31647}: Fixed bug where calling write_eof() on a
_SelectorSocketTransport after it's already closed raises AttributeError.

@item 
bpo-33672@footnote{https://bugs.python.org/issue33672}: Fix Task.__repr__ crash with Cython's bogus coroutines

@item 
bpo-33469@footnote{https://bugs.python.org/issue33469}: Fix RuntimeError after closing loop that used run_in_executor

@item 
bpo-11874@footnote{https://bugs.python.org/issue11874}: Use a better regex when breaking usage into wrappable parts.
Avoids bogus assertion errors from custom metavar strings.

@item 
bpo-30877@footnote{https://bugs.python.org/issue30877}: Fixed a bug in the Python implementation of the JSON decoder
that prevented the cache of parsed strings from clearing after finishing
the decoding. Based on patch by c-fos.

@item 
bpo-33548@footnote{https://bugs.python.org/issue33548}: tempfile._candidate_tempdir_list should consider common TEMP
locations

@item 
bpo-33542@footnote{https://bugs.python.org/issue33542}: Prevent @code{uuid.get_node} from using a DUID instead of a MAC on
Windows. Patch by Zvi Effron

@item 
bpo-26819@footnote{https://bugs.python.org/issue26819}: Fix race condition with @code{ReadTransport.resume_reading} in
Windows proactor event loop.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Minor fixes in typing module: add annotations to
@code{NamedTuple.__new__}, pass @code{*args} and @code{**kwds} in
@code{Generic.__new__}.  Original PRs by Paulius Šarka and Chad Dombrova.

@item 
bpo-20087@footnote{https://bugs.python.org/issue20087}: Updated alias mapping with glibc 2.27 supported locales.

@item 
bpo-33422@footnote{https://bugs.python.org/issue33422}: Fix trailing quotation marks getting deleted when looking up
byte/string literals on pydoc. Patch by Andrés Delfino.

@item 
bpo-33197@footnote{https://bugs.python.org/issue33197}: Update error message when constructing invalid
inspect.Parameters Patch by Dong-hee Na.

@item 
bpo-33383@footnote{https://bugs.python.org/issue33383}: Fixed crash in the get() method of the @ref{35,,dbm.ndbm} database
object when it is called with a single argument.

@item 
bpo-33329@footnote{https://bugs.python.org/issue33329}: Fix multiprocessing regression on newer glibcs

@item 
bpo-991266@footnote{https://bugs.python.org/issue991266}: Fix quoting of the @code{Comment} attribute of
@ref{fcb,,http.cookies.SimpleCookie}.

@item 
bpo-33131@footnote{https://bugs.python.org/issue33131}: Upgrade bundled version of pip to 10.0.1.

@item 
bpo-33308@footnote{https://bugs.python.org/issue33308}: Fixed a crash in the @ref{c7,,parser} module when converting an ST
object to a tree of tuples or lists with @code{line_info=False} and
@code{col_info=True}.

@item 
bpo-33263@footnote{https://bugs.python.org/issue33263}: Fix FD leak in @code{_SelectorSocketTransport}  Patch by Vlad
Starostin.

@item 
bpo-33256@footnote{https://bugs.python.org/issue33256}: Fix display of @code{<module>} call in the html produced by
@code{cgitb.html()}. Patch by Stéphane Blondon.

@item 
bpo-33203@footnote{https://bugs.python.org/issue33203}: @code{random.Random.choice()} now raises @code{IndexError} for empty
sequences consistently even when called from subclasses without a
@code{getrandbits()} implementation.

@item 
bpo-33224@footnote{https://bugs.python.org/issue33224}: Update difflib.mdiff() for 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479}.  Convert an uncaught
StopIteration in a generator into a return-statement.

@item 
bpo-33209@footnote{https://bugs.python.org/issue33209}: End framing at the end of C implementation of
@ref{fcf,,pickle.Pickler.dump()}.

@item 
bpo-32861@footnote{https://bugs.python.org/issue32861}: The urllib.robotparser's @code{__str__} representation now
includes wildcard entries and the "Crawl-delay" and "Request-rate" fields.
Patch by Michael Lazar.

@item 
bpo-33096@footnote{https://bugs.python.org/issue33096}: Allow ttk.Treeview.insert to insert iid that has a false
boolean value. Note iid=0 and iid=False would be same. Patch by Garvit
Khatri.

@item 
bpo-33127@footnote{https://bugs.python.org/issue33127}: ssl模块现在使用LibreSSL 2.7.1编译。

@item 
bpo-33021@footnote{https://bugs.python.org/issue33021}: Release the GIL during fstat() calls, avoiding hang of all
threads when calling mmap.mmap(), os.urandom(), and random.seed().  Patch
by Nir Soffer.

@item 
bpo-27683@footnote{https://bugs.python.org/issue27683}: Fix a regression in @ref{a2,,ipaddress} that result of
@code{hosts()} is empty when the network is constructed by a tuple
containing an integer mask and only 1 bit left for addresses.

@item 
bpo-32844@footnote{https://bugs.python.org/issue32844}: Fix wrong redirection of a low descriptor (0 or 1) to stderr in
subprocess if another low descriptor is closed.

@item 
bpo-31908@footnote{https://bugs.python.org/issue31908}: Fix output of cover files for @code{trace} module command-line
tool. Previously emitted cover files only when @code{--missing} option was
used. Patch by Michael Selik.

@item 
bpo-31457@footnote{https://bugs.python.org/issue31457}: If nested log adapters are used, the inner @code{process()}
methods are no longer omitted.

@item 
bpo-16865@footnote{https://bugs.python.org/issue16865}: Support arrays >=2GiB in @ref{2b,,ctypes}.  Patch by Segev Finer.

@item 
bpo-31238@footnote{https://bugs.python.org/issue31238}: pydoc: the stop() method of the private ServerThread class now
waits until DocServer.serve_until_quit() completes and then explicitly
sets its docserver attribute to None to break a reference cycle.
@end itemize

@node 文档<27>,测试<24>,库<32>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id243}@anchor{105c}
@subsubsection 文档



@itemize -

@item 
bpo-33503@footnote{https://bugs.python.org/issue33503}: 修复错误的pypi链接

@item 
bpo-33421@footnote{https://bugs.python.org/issue33421}: 为`@w{`}typing.AsyncContextManager`@w{`}添加缺失的文档。

@item 
bpo-33378@footnote{https://bugs.python.org/issue33378}: Add Korean language switcher for @indicateurl{https://docs.python.org/3/}

@item 
bpo-33276@footnote{https://bugs.python.org/issue33276}: Clarify that the @code{__path__} attribute on modules cannot be
just any value.

@item 
bpo-33201@footnote{https://bugs.python.org/issue33201}: Modernize documentation for writing C extension types.

@item 
bpo-33195@footnote{https://bugs.python.org/issue33195}: Deprecate @code{Py_UNICODE} usage in @code{c-api/arg} document.
@code{Py_UNICODE} related APIs are deprecated since Python 3.3, but it is
missed in the document.

@item 
bpo-33126@footnote{https://bugs.python.org/issue33126}: Document PyBuffer_ToContiguous().

@item 
bpo-27212@footnote{https://bugs.python.org/issue27212}: Modify documentation for the @code{islice()} recipe to consume
initial values up to the start index.

@item 
bpo-28247@footnote{https://bugs.python.org/issue28247}: Update @ref{141,,zipapp} documentation to describe how to make
standalone applications.

@item 
bpo-18802@footnote{https://bugs.python.org/issue18802}: Documentation changes for ipaddress.  Patch by Jon Foster and
Berker Peksag.

@item 
bpo-27428@footnote{https://bugs.python.org/issue27428}: Update documentation to clarify that @code{WindowsRegistryFinder}
implements @code{MetaPathFinder}. (Patch by Himanshu Lakhara)

@item 
bpo-8243@footnote{https://bugs.python.org/issue8243}: Add a note about curses.addch and curses.addstr exception
behavior when writing outside a window, or pad.

@item 
bpo-31432@footnote{https://bugs.python.org/issue31432}: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED
flags for ssl.SSLContext.verify_mode.
@end itemize

@node 测试<24>,构建<23>,文档<27>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id244}@anchor{105d}
@subsubsection 测试



@itemize -

@item 
bpo-33655@footnote{https://bugs.python.org/issue33655}: 忽略运行在BSD平台的ZFS上时test_posix_fallocate的失败。

@item 
bpo-19417@footnote{https://bugs.python.org/issue19417}: Add test_bdb.py.
@end itemize

@node 构建<23>,Windows<25>,测试<24>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id245}@anchor{105e}
@subsubsection 构建



@itemize -

@item 
bpo-5755@footnote{https://bugs.python.org/issue5755}: Move @code{-Wstrict-prototypes} option to @code{CFLAGS_NODIST} from
@code{OPT}. This option emitted annoying warnings when building extension
modules written in C++.

@item 
bpo-33614@footnote{https://bugs.python.org/issue33614}: Ensures module definition files for the stable ABI on Windows
are correctly regenerated.

@item 
bpo-33522@footnote{https://bugs.python.org/issue33522}: Enable CI builds on Visual Studio Team Services at
@indicateurl{https://python.visualstudio.com/cpython}

@item 
bpo-33012@footnote{https://bugs.python.org/issue33012}: Add @code{-Wno-cast-function-type} for gcc 8 for silencing
warnings about function casts like casting to PyCFunction in method
definition lists.

@item 
bpo-33394@footnote{https://bugs.python.org/issue33394}: Enable the verbose build for extension modules, when GNU make
is passed macros on the command line.
@end itemize

@node Windows<25>,macOS<17>,构建<23>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id246}@anchor{105f}
@subsubsection Windows



@itemize -

@item 
bpo-33184@footnote{https://bugs.python.org/issue33184}: 更新Windows 构建以使用OpenSSL 1.0.2o.
@end itemize

@node macOS<17>,IDLE<30>,Windows<25>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id247}@anchor{1060}
@subsubsection macOS



@itemize -

@item 
bpo-33184@footnote{https://bugs.python.org/issue33184}: 更新macOS 安装程序以使用OpenSSL 1.0.2o.
@end itemize

@node IDLE<30>,工具/示例<17>,macOS<17>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id248}@anchor{1061}
@subsubsection IDLE



@itemize -

@item 
bpo-33656@footnote{https://bugs.python.org/issue33656}: On Windows, add API call saying that tk scales for DPI. On
Windows 8.1+ or 10, with DPI compatibility properties of the Python binary
unchanged, and a monitor resolution greater than 96 DPI, this should make
text and lines sharper.  It should otherwise have no effect.

@item 
bpo-33768@footnote{https://bugs.python.org/issue33768}: Clicking on a context line moves that line to the top of the
editor window.

@item 
bpo-33763@footnote{https://bugs.python.org/issue33763}: IDLE: Use read-only text widget for code context instead of
label widget.

@item 
bpo-33664@footnote{https://bugs.python.org/issue33664}: Scroll IDLE editor text by lines. Previously, the mouse wheel
and scrollbar slider moved text by a fixed number of pixels, resulting in
partial lines at the top of the editor box.  The change also applies to
the shell and grep output windows, but not to read-only text views.

@item 
bpo-33679@footnote{https://bugs.python.org/issue33679}: Enable theme-specific color configuration for Code Context. Use
the Highlights tab to see the setting for built-in themes or add settings
to custom themes.

@item 
bpo-33642@footnote{https://bugs.python.org/issue33642}: Display up to maxlines non-blank lines for Code Context. If
there is no current context, show a single blank line.

@item 
bpo-33628@footnote{https://bugs.python.org/issue33628}: IDLE: Cleanup codecontext.py and its test.

@item 
bpo-33564@footnote{https://bugs.python.org/issue33564}: IDLE's code context now recognizes async as a block opener.

@item 
bpo-29706@footnote{https://bugs.python.org/issue29706}: IDLE now colors async and await as keywords in 3.6. They become
full keywords in 3.7.

@item 
bpo-21474@footnote{https://bugs.python.org/issue21474}: Update word/identifier definition from ascii to unicode. In
text and entry boxes, this affects selection by double-click, movement
left/right by control-left/right, and deletion left/right by
control-BACKSPACE/DEL.

@item 
bpo-33204@footnote{https://bugs.python.org/issue33204}: IDLE: consistently color invalid string prefixes. A 'u' string
prefix cannot be paired with either 'r' or 'f'. Consistently color as much
of the prefix, starting at the right, as is valid. Revise and extend
colorizer test.

@item 
bpo-32831@footnote{https://bugs.python.org/issue32831}: Add docstrings and tests for codecontext.
@end itemize

@node 工具/示例<17>,C API<19>,IDLE<30>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id249}@anchor{1062}
@subsubsection 工具/示例



@itemize -

@item 
bpo-33189@footnote{https://bugs.python.org/issue33189}: @code{pygettext.py} now recognizes only literal strings as
docstrings and translatable strings, and rejects bytes literals and
f-string expressions.

@item 
bpo-31920@footnote{https://bugs.python.org/issue31920}: Fixed handling directories as arguments in the @code{pygettext}
script. Based on patch by Oleg Krasnikov.

@item 
bpo-29673@footnote{https://bugs.python.org/issue29673}: Fix pystackv and pystack gdbinit macros.

@item 
bpo-32885@footnote{https://bugs.python.org/issue32885}: Add an @code{-n} flag for @code{Tools/scripts/pathfix.py} to disable
automatic backup creation (files with @code{~} suffix).

@item 
bpo-31583@footnote{https://bugs.python.org/issue31583}: Fix 2to3 for using with --add-suffix option but without
--output-dir option for relative path to files in current directory.
@end itemize

@node C API<19>,,工具/示例<17>,Python 3 6 6 rc1
@anchor{whatsnew/changelog id250}@anchor{1063}
@subsubsection C API



@itemize -

@item 
bpo-32374@footnote{https://bugs.python.org/issue32374}: Document that m_traverse for multi-phase initialized modules
can be called with m_state=NULL, and add a sanity check
@end itemize

@node Python 3 6 5 正式版,Python 3 6 5 rc1,Python 3 6 6 rc1,更新日志
@anchor{whatsnew/changelog python-3-6-5-final}@anchor{1064}
@subsection Python 3.6.5 正式版


@emph{发布日期: 2018-03-28}

@menu
* 测试: 测试<25>. 
* 构建: 构建<24>. 

@end menu

@node 测试<25>,构建<24>,,Python 3 6 5 正式版
@anchor{whatsnew/changelog id251}@anchor{1065}
@subsubsection 测试



@itemize -

@item 
bpo-32872@footnote{https://bugs.python.org/issue32872}: Avoid regrtest compatibility issue with namespace packages.
@end itemize

@node 构建<24>,,测试<25>,Python 3 6 5 正式版
@anchor{whatsnew/changelog id252}@anchor{1066}
@subsubsection 构建



@itemize -

@item 
bpo-33163@footnote{https://bugs.python.org/issue33163}: Upgrade pip to 9.0.3 and setuptools to v39.0.1.
@end itemize

@node Python 3 6 5 rc1,Python 3 6 4 正式版,Python 3 6 5 正式版,更新日志
@anchor{whatsnew/changelog python-3-6-5-release-candidate-1}@anchor{1067}
@subsection Python 3.6.5 rc1


@emph{发布日期: 2018-03-13}

@menu
* 安全: 安全<19>. 
* 核心与内置: 核心与内置<32>. 
* 库: 库<33>. 
* 文档: 文档<28>. 
* 测试: 测试<26>. 
* 构建: 构建<25>. 
* Windows: Windows<26>. 
* macOS: macOS<18>. 
* IDLE: IDLE<31>. 
* 工具/示例: 工具/示例<18>. 
* C API: C API<20>. 

@end menu

@node 安全<19>,核心与内置<32>,,Python 3 6 5 rc1
@anchor{whatsnew/changelog id253}@anchor{1068}
@subsubsection 安全



@itemize -

@item 
bpo-33001@footnote{https://bugs.python.org/issue33001}: Minimal fix to prevent buffer overrun in os.symlink on Windows

@item 
bpo-32981@footnote{https://bugs.python.org/issue32981}: Regexes in difflib and poplib were vulnerable to catastrophic
backtracking. These regexes formed potential DOS vectors (REDOS). They
have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch
by Jamie Davis.
@end itemize

@node 核心与内置<32>,库<33>,安全<19>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id254}@anchor{1069}
@subsubsection 核心与内置



@itemize -

@item 
bpo-33026@footnote{https://bugs.python.org/issue33026}: Fixed jumping out of "with" block by setting f_lineno.

@item 
bpo-17288@footnote{https://bugs.python.org/issue17288}: Prevent jumps from 'return' and 'exception' trace events.

@item 
bpo-32889@footnote{https://bugs.python.org/issue32889}: Update Valgrind suppression list to account for the rename of
@code{Py_ADDRESS_IN_RANG} to @code{address_in_range}.

@item 
bpo-32650@footnote{https://bugs.python.org/issue32650}: Pdb and other debuggers dependent on bdb.py will correctly step
over (next command) native coroutines. Patch by Pablo Galindo.

@item 
bpo-32685@footnote{https://bugs.python.org/issue32685}: Improve suggestion when the Python 2 form of print statement is
either present on the same line as the header of a compound statement or
else terminated by a semi-colon instead of a newline. Patch by Nitish
Chandra.

@item 
bpo-32583@footnote{https://bugs.python.org/issue32583}: Fix possible crashing in builtin Unicode decoders caused by
write out-of-bound errors when using customized decode error handlers.

@item 
bpo-26163@footnote{https://bugs.python.org/issue26163}: Improved frozenset() hash to create more distinct hash values
when faced with datasets containing many similar values.

@item 
bpo-27169@footnote{https://bugs.python.org/issue27169}: The @code{__debug__} constant is now optimized out at compile
time. This fixes also bpo-22091@footnote{https://bugs.python.org/issue22091}.

@item 
bpo-32329@footnote{https://bugs.python.org/issue32329}: @code{sys.flags.hash_randomization} is now properly set to 0 when
hash randomization is turned off by @code{PYTHONHASHSEED=0}.

@item 
bpo-30416@footnote{https://bugs.python.org/issue30416}: The optimizer is now protected from spending much time doing
complex calculations and consuming much memory for creating large
constants in constant folding.

@item 
bpo-18533@footnote{https://bugs.python.org/issue18533}: @code{repr()} on a dict containing its own @code{values()} or
@code{items()} no longer raises @code{RecursionError}; OrderedDict similarly.
Instead, use @code{...}, as for other recursive structures.  Patch by Ben
North.

@item 
bpo-32028@footnote{https://bugs.python.org/issue32028}: Leading whitespace is now correctly ignored when generating
suggestions for converting Py2 print statements to Py3 builtin print
function calls. Patch by Sanyam Khurana.

@item 
bpo-32137@footnote{https://bugs.python.org/issue32137}: The repr of deeply nested dict now raises a RecursionError
instead of crashing due to a stack overflow.
@end itemize

@node 库<33>,文档<28>,核心与内置<32>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id255}@anchor{106a}
@subsubsection 库



@itemize -

@item 
bpo-33064@footnote{https://bugs.python.org/issue33064}: lib2to3 now properly supports trailing commas after @code{*args}
and @code{**kwargs} in function signatures.

@item 
bpo-31804@footnote{https://bugs.python.org/issue31804}: Avoid failing in multiprocessing.Process if the standard
streams are closed or None at exit.

@item 
bpo-33037@footnote{https://bugs.python.org/issue33037}: Skip sending/receiving data after SSL transport closing.

@item 
bpo-30353@footnote{https://bugs.python.org/issue30353}: Fix ctypes pass-by-value for structs on 64-bit Cygwin/MinGW.

@item 
bpo-33009@footnote{https://bugs.python.org/issue33009}: Fix inspect.signature() for single-parameter partialmethods.

@item 
bpo-32969@footnote{https://bugs.python.org/issue32969}: Expose several missing constants in zlib and fix corresponding
documentation.

@item 
bpo-32713@footnote{https://bugs.python.org/issue32713}: Fixed tarfile.itn handling of out-of-bounds float values. Patch
by Joffrey Fuhrer.

@item 
bpo-30622@footnote{https://bugs.python.org/issue30622}: The ssl module now detects missing NPN support in LibreSSL.

@item 
bpo-32922@footnote{https://bugs.python.org/issue32922}: dbm.open() now encodes filename with the filesystem encoding
rather than default encoding.

@item 
bpo-32859@footnote{https://bugs.python.org/issue32859}: In @code{os.dup2}, don't check every call whether the @code{dup3}
syscall exists or not.

@item 
bpo-21060@footnote{https://bugs.python.org/issue21060}: Rewrite confusing message from setup.py upload from "No dist
file created in earlier command" to the more helpful "Must create and
upload files in one command".

@item 
bpo-32857@footnote{https://bugs.python.org/issue32857}: In @ref{10c,,tkinter}, @code{after_cancel(None)} now raises a
@ref{1fb,,ValueError} instead of canceling the first scheduled function.
Patch by Cheryl Sabella.

@item 
bpo-32852@footnote{https://bugs.python.org/issue32852}: Make sure sys.argv remains as a list when running trace.

@item 
bpo-32841@footnote{https://bugs.python.org/issue32841}: Fixed @ref{28d,,asyncio.Condition} issue which silently ignored
cancellation after notifying and cancelling a conditional lock. Patch by
Bar Harel.

@item 
bpo-31787@footnote{https://bugs.python.org/issue31787}: Fixed refleaks of @code{__init__()} methods in various modules.
(Contributed by Oren Milman)

@item 
bpo-30157@footnote{https://bugs.python.org/issue30157}: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when
only the last field is quoted.  Patch by Jake Davis.

@item 
bpo-32394@footnote{https://bugs.python.org/issue32394}: socket: Remove TCP_FASTOPEN, TCP_KEEPCNT flags on older version
Windows during run-time.

@item 
bpo-32777@footnote{https://bugs.python.org/issue32777}: Fix a rare but potential pre-exec child process deadlock in
subprocess on POSIX systems when marking file descriptors inheritable on
exec in the child process.  This bug appears to have been introduced in
3.4.

@item 
bpo-32647@footnote{https://bugs.python.org/issue32647}: The ctypes module used to depend on indirect linking for
dlopen. The shared extension is now explicitly linked against libdl on
platforms with dl.

@item 
bpo-32734@footnote{https://bugs.python.org/issue32734}: Fixed @code{asyncio.Lock()} safety issue which allowed acquiring
and locking the same lock multiple times, without it being free. Patch by
Bar Harel.

@item 
bpo-32727@footnote{https://bugs.python.org/issue32727}: Do not include name field in SMTP envelope from address. Patch
by Stéphane Wirtel

@item 
bpo-27931@footnote{https://bugs.python.org/issue27931}: Fix email address header parsing error when the username is an
empty quoted string. Patch by Xiang Zhang.

@item 
bpo-32304@footnote{https://bugs.python.org/issue32304}: distutils' upload command no longer corrupts tar files ending
with a CR byte, and no longer tries to convert CR to CRLF in any of the
upload text fields.

@item 
bpo-32502@footnote{https://bugs.python.org/issue32502}: uuid.uuid1 no longer raises an exception if a 64-bit hardware
address is encountered.

@item 
bpo-31848@footnote{https://bugs.python.org/issue31848}: Fix the error handling in Aifc_read.initfp() when the SSND
chunk is not found. Patch by Zackery Spytz.

@item 
bpo-32555@footnote{https://bugs.python.org/issue32555}: On FreeBSD and Solaris, os.strerror() now always decode the
byte string from the current locale encoding, rather than using
ASCII/surrogateescape in some cases.

@item 
bpo-32521@footnote{https://bugs.python.org/issue32521}: The nis module is now compatible with new libnsl and headers
location.

@item 
bpo-32473@footnote{https://bugs.python.org/issue32473}: Improve ABCMeta._dump_registry() output readability

@item 
bpo-32521@footnote{https://bugs.python.org/issue32521}: glibc has removed Sun RPC. Use replacement libtirpc headers and
library in nis module.

@item 
bpo-32228@footnote{https://bugs.python.org/issue32228}: Ensure that @code{truncate()} preserves the file position (as
reported by @code{tell()}) after writes longer than the buffer size.

@item 
bpo-26133@footnote{https://bugs.python.org/issue26133}: Don't unsubscribe signals in asyncio UNIX event loop on
interpreter shutdown.

@item 
bpo-32185@footnote{https://bugs.python.org/issue32185}: The SSL module no longer sends IP addresses in SNI TLS
extension on platforms with OpenSSL 1.0.2+ or inet_pton.

@item 
bpo-32323@footnote{https://bugs.python.org/issue32323}: @ref{5f4,,urllib.parse.urlsplit()} does not convert zone-id
(scope) to lower case for scoped IPv6 addresses in hostnames now.

@item 
bpo-32302@footnote{https://bugs.python.org/issue32302}: Fix bdist_wininst of distutils for CRT v142: it binary
compatible with CRT v140.

@item 
bpo-32255@footnote{https://bugs.python.org/issue32255}: A single empty field is now always quoted when written into a
CSV file. This allows to distinguish an empty row from a row consisting of
a single empty field. Patch by Licht Takeuchi.

@item 
bpo-32277@footnote{https://bugs.python.org/issue32277}: Raise @code{NotImplementedError} instead of @code{SystemError} on
platforms where @code{chmod(..., follow_symlinks=False)} is not supported.
Patch by Anthony Sottile.

@item 
bpo-32199@footnote{https://bugs.python.org/issue32199}: The getnode() ip getter now uses 'ip link' instead of 'ip link
list'.

@item 
bpo-27456@footnote{https://bugs.python.org/issue27456}: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

@item 
bpo-31900@footnote{https://bugs.python.org/issue31900}: The @ref{484,,locale.localeconv()} function now sets temporarily the
@code{LC_CTYPE} locale to the @code{LC_NUMERIC} locale to decode
@code{decimal_point} and @code{thousands_sep} byte strings if they are non-ASCII
or longer than 1 byte, and the @code{LC_NUMERIC} locale is different than the
@code{LC_CTYPE} locale. This temporary change affects other threads. Same
change for the @ref{4d4,,str.format()} method when formatting a number
(@ref{184,,int}, @ref{187,,float}, @ref{187,,float} and subclasses) with the
@code{n} type (ex: @code{'@{:n@}'.format(1234)}).

@item 
bpo-31802@footnote{https://bugs.python.org/issue31802}: Importing native path module (@code{posixpath}, @code{ntpath}) now
works even if the @code{os} module still is not imported.
@end itemize

@node 文档<28>,测试<26>,库<33>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id256}@anchor{106b}
@subsubsection 文档



@itemize -

@item 
bpo-17232@footnote{https://bugs.python.org/issue17232}: Clarify docs for -O and -OO.  Patch by Terry Reedy.

@item 
bpo-32800@footnote{https://bugs.python.org/issue32800}: Update link to w3c doc for xml default namespaces.

@item 
bpo-8722@footnote{https://bugs.python.org/issue8722}: Document @ref{313,,__getattr__()} behavior when property @code{get()}
method raises @ref{393,,AttributeError}.

@item 
bpo-32614@footnote{https://bugs.python.org/issue32614}: Modify RE examples in documentation to use raw strings to
prevent @ref{278,,DeprecationWarning} and add text to REGEX HOWTO to highlight
the deprecation.

@item 
bpo-31972@footnote{https://bugs.python.org/issue31972}: Improve docstrings for @ref{fd4,,pathlib.PurePath} subclasses.

@item 
bpo-17799@footnote{https://bugs.python.org/issue17799}: Explain real behaviour of sys.settrace and sys.setprofile and
their C-API counterparts regarding which type of events are received in
each function. Patch by Pablo Galindo Salgado.
@end itemize

@node 测试<26>,构建<25>,文档<28>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id257}@anchor{106c}
@subsubsection 测试



@itemize -

@item 
bpo-32517@footnote{https://bugs.python.org/issue32517}: Fix failing @code{test_asyncio} on macOS 10.12.2+ due to transport
of @code{KqueueSelector} loop was not being closed.

@item 
bpo-32721@footnote{https://bugs.python.org/issue32721}: Fix test_hashlib to not fail if the _md5 module is not built.

@item 
bpo-32252@footnote{https://bugs.python.org/issue32252}: Fix faulthandler_suppress_crash_report() used to prevent core
dump files when testing crashes. getrlimit() returns zero on success.

@item 
bpo-31518@footnote{https://bugs.python.org/issue31518}: Debian Unstable has disabled TLS 1.0 and 1.1 for
SSLv23_METHOD(). Change TLS/SSL protocol of some tests to PROTOCOL_TLS or
PROTOCOL_TLSv1_2 to make them pass on Debian.
@end itemize

@node 构建<25>,Windows<26>,测试<26>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id258}@anchor{106d}
@subsubsection 构建



@itemize -

@item 
bpo-32635@footnote{https://bugs.python.org/issue32635}: Fix segfault of the crypt module when libxcrypt is provided
instead of libcrypt at the system.
@end itemize

@node Windows<26>,macOS<18>,构建<25>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id259}@anchor{106e}
@subsubsection Windows



@itemize -

@item 
bpo-33016@footnote{https://bugs.python.org/issue33016}: Fix potential use of uninitialized memory in
nt._getfinalpathname

@item 
bpo-32903@footnote{https://bugs.python.org/issue32903}: Fix a memory leak in os.chdir() on Windows if the current
directory is set to a UNC path.

@item 
bpo-31966@footnote{https://bugs.python.org/issue31966}: Fixed WindowsConsoleIO.write() for writing empty data.

@item 
bpo-32409@footnote{https://bugs.python.org/issue32409}: Ensures activate.bat can handle Unicode contents.

@item 
bpo-32457@footnote{https://bugs.python.org/issue32457}: Improves handling of denormalized executable path when
launching Python.

@item 
bpo-32370@footnote{https://bugs.python.org/issue32370}: Use the correct encoding for ipconfig output in the uuid
module. Patch by Segev Finer.

@item 
bpo-29248@footnote{https://bugs.python.org/issue29248}: Fix @ref{1f3,,os.readlink()} on Windows, which was mistakenly
treating the @code{PrintNameOffset} field of the reparse data buffer as a
number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

@item 
bpo-32588@footnote{https://bugs.python.org/issue32588}: Create standalone _distutils_findvs module.
@end itemize

@node macOS<18>,IDLE<31>,Windows<26>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id260}@anchor{106f}
@subsubsection macOS



@itemize -

@item 
bpo-32726@footnote{https://bugs.python.org/issue32726}: Provide an additional, more modern macOS installer variant that
supports macOS 10.9+ systems in 64-bit mode only. Upgrade the supplied
third-party libraries to OpenSSL 1.0.2n, XZ 5.2.3, and SQLite 3.22.0. The
10.9+ installer now links with and supplies its own copy of Tcl/Tk 8.6.8.
@end itemize

@node IDLE<31>,工具/示例<18>,macOS<18>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id261}@anchor{1070}
@subsubsection IDLE



@itemize -

@item 
bpo-32984@footnote{https://bugs.python.org/issue32984}: Set @code{__file__} while running a startup file.  Like Python,
IDLE optionally runs one startup file in the Shell window before
presenting the first interactive input prompt.  For IDLE, @code{-s} runs a
file named in environmental variable  
@geindex IDLESTARTUP
@geindex 环境变量; IDLESTARTUP
@code{IDLESTARTUP} or
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP}; @code{-r file} runs @code{file}.  Python sets
@code{__file__} to the startup file name before running the file and unsets
it before the first prompt.  IDLE now does the same when run normally,
without the @code{-n} option.

@item 
bpo-32940@footnote{https://bugs.python.org/issue32940}: Simplify and rename StringTranslatePseudoMapping in pyparse.

@item 
bpo-32916@footnote{https://bugs.python.org/issue32916}: Change @code{str} to @code{code} in pyparse.

@item 
bpo-32905@footnote{https://bugs.python.org/issue32905}: Remove unused code in pyparse module.

@item 
bpo-32874@footnote{https://bugs.python.org/issue32874}: Add tests for pyparse.

@item 
bpo-32837@footnote{https://bugs.python.org/issue32837}: Using the system and place-dependent default encoding for
open() is a bad idea for IDLE's system and location-independent files.

@item 
bpo-32826@footnote{https://bugs.python.org/issue32826}: Add "encoding=utf-8" to open() in IDLE's test_help_about. GUI
test test_file_buttons() only looks at initial ascii-only lines, but
failed on systems where open() defaults to 'ascii' because readline()
internally reads and decodes far enough ahead to encounter a non-ascii
character in CREDITS.txt.

@item 
bpo-32765@footnote{https://bugs.python.org/issue32765}: Update configdialog General tab docstring to add new widgets to
the widget list.
@end itemize

@node 工具/示例<18>,C API<20>,IDLE<31>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id262}@anchor{1071}
@subsubsection 工具/示例



@itemize -

@item 
bpo-24960@footnote{https://bugs.python.org/issue24960}: 2to3 and lib2to3 can now read pickled grammar files using
pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and
lib2to3 work when run from a zipfile.

@item 
bpo-32222@footnote{https://bugs.python.org/issue32222}: Fix pygettext not extracting docstrings for functions with type
annotated arguments. Patch by Toby Harradine.
@end itemize

@node C API<20>,,工具/示例<18>,Python 3 6 5 rc1
@anchor{whatsnew/changelog id263}@anchor{1072}
@subsubsection C API



@itemize -

@item 
bpo-29084@footnote{https://bugs.python.org/issue29084}: Undocumented C API for OrderedDict has been excluded from the
limited C API. It was added by mistake and actually never worked in the
limited C API.
@end itemize

@node Python 3 6 4 正式版,Python 3 6 4 rc1,Python 3 6 5 rc1,更新日志
@anchor{whatsnew/changelog python-3-6-4-final}@anchor{1073}
@subsection Python 3.6.4 正式版


@emph{发布日期: 2017-12-18}

从 3.6.4 rc1 到 3.6.4 正式版中没有新的代码更改。

@node Python 3 6 4 rc1,Python 3 6 3 正式版,Python 3 6 4 正式版,更新日志
@anchor{whatsnew/changelog python-3-6-4-release-candidate-1}@anchor{1074}
@subsection Python 3.6.4 rc1


@emph{发布日期: 2017-12-05}

@menu
* 核心与内置: 核心与内置<33>. 
* 库: 库<34>. 
* 文档: 文档<29>. 
* 测试: 测试<27>. 
* 构建: 构建<26>. 
* Windows: Windows<27>. 
* macOS: macOS<19>. 
* IDLE: IDLE<32>. 
* 工具/示例: 工具/示例<19>. 
* C API: C API<21>. 

@end menu

@node 核心与内置<33>,库<34>,,Python 3 6 4 rc1
@anchor{whatsnew/changelog id264}@anchor{1075}
@subsubsection 核心与内置



@itemize -

@item 
bpo-32176@footnote{https://bugs.python.org/issue32176}: co_flags.CO_NOFREE is now always set correctly by the code
object constructor based on freevars and cellvars, rather than needing to
be set correctly by the caller. This ensures it will be cleared
automatically when additional cell references are injected into a modified
code object and function.

@item 
bpo-31949@footnote{https://bugs.python.org/issue31949}: Fixed several issues in printing tracebacks
(PyTraceBack_Print()). Setting sys.tracebacklimit to 0 or less now
suppresses printing tracebacks. Setting sys.tracebacklimit to None now
causes using the default limit. Setting sys.tracebacklimit to an integer
larger than LONG_MAX now means using the limit LONG_MAX rather than the
default limit. Fixed integer overflows in the case of more than 2**31
traceback items on Windows. Fixed output errors handling.

@item 
bpo-30696@footnote{https://bugs.python.org/issue30696}: Fix the interactive interpreter looping endlessly when no
memory.

@item 
bpo-20047@footnote{https://bugs.python.org/issue20047}: Bytearray methods partition() and rpartition() now accept only
bytes-like objects as separator, as documented.  In particular they now
raise TypeError rather of returning a bogus result when an integer is
passed as a separator.

@item 
bpo-31852@footnote{https://bugs.python.org/issue31852}: Fix a segmentation fault caused by a combination of the async
soft keyword and continuation lines.

@item 
bpo-21720@footnote{https://bugs.python.org/issue21720}: BytesWarning no longer emitted when the @emph{fromlist} argument of
@code{__import__()} or the @code{__all__} attribute of the module contain bytes
instances.

@item 
bpo-31825@footnote{https://bugs.python.org/issue31825}: Fixed OverflowError in the 'unicode-escape' codec and in
codecs.escape_decode() when decode an escaped non-ascii byte.

@item 
bpo-28603@footnote{https://bugs.python.org/issue28603}: Print the full context/cause chain of exceptions on interpreter
exit, even if an exception in the chain is unhashable or compares equal to
later ones. Patch by Zane Bitter.

@item 
bpo-31786@footnote{https://bugs.python.org/issue31786}: Fix timeout rounding in the select module to round correctly
negative timeouts between -1.0 and 0.0. The functions now block waiting
for events as expected. Previously, the call was incorrectly non-blocking.
Patch by Pablo Galindo.

@item 
bpo-31642@footnote{https://bugs.python.org/issue31642}: Restored blocking "from package import module" by setting
sys.modules["package.module"] to None.

@item 
bpo-31626@footnote{https://bugs.python.org/issue31626}: Fixed a bug in debug memory allocator.  There was a write to
freed memory after shrinking a memory block.

@item 
bpo-31619@footnote{https://bugs.python.org/issue31619}: Fixed a ValueError when convert a string with large number of
underscores to integer with binary base.

@item 
bpo-31592@footnote{https://bugs.python.org/issue31592}: Fixed an assertion failure in Python parser in case of a bad
@ref{1042,,unicodedata.normalize()}. Patch by Oren Milman.

@item 
bpo-31588@footnote{https://bugs.python.org/issue31588}: Raise a @ref{192,,TypeError} with a helpful error message when class
creation fails due to a metaclass with a bad @code{__prepare__()} method.
Patch by Oren Milman.

@item 
bpo-31566@footnote{https://bugs.python.org/issue31566}: Fix an assertion failure in @code{_warnings.warn()} in case of a bad
@code{__name__} global. Patch by Oren Milman.

@item 
bpo-31505@footnote{https://bugs.python.org/issue31505}: Fix an assertion failure in @ref{a4,,json}, in case
@code{_json.make_encoder()} received a bad @code{encoder()} argument. Patch by Oren
Milman.

@item 
bpo-31492@footnote{https://bugs.python.org/issue31492}: Fix assertion failures in case of failing to import from a
module with a bad @code{__name__} attribute, and in case of failing to access
an attribute of such a module. Patch by Oren Milman.

@item 
bpo-31490@footnote{https://bugs.python.org/issue31490}: Fix an assertion failure in @ref{2b,,ctypes} class definition, in case
the class has an attribute whose name is specified in @code{_anonymous_} but
not in @code{_fields_}. Patch by Oren Milman.

@item 
bpo-31478@footnote{https://bugs.python.org/issue31478}: Fix an assertion failure in @code{_random.Random.seed()} in case the
argument has a bad @code{__abs__()} method. Patch by Oren Milman.

@item 
bpo-31315@footnote{https://bugs.python.org/issue31315}: Fix an assertion failure in imp.create_dynamic(), when
spec.name is not a string. Patch by Oren Milman.

@item 
bpo-31311@footnote{https://bugs.python.org/issue31311}: Fix a crash in the @code{__setstate__()} method of
@ref{1043,,ctypes._CData}, in case of a bad @code{__dict__}. Patch by Oren Milman.

@item 
bpo-31293@footnote{https://bugs.python.org/issue31293}: Fix crashes in true division and multiplication of a timedelta
object by a float with a bad as_integer_ratio() method. Patch by Oren
Milman.

@item 
bpo-31285@footnote{https://bugs.python.org/issue31285}: Fix an assertion failure in @ref{5ab,,warnings.warn_explicit}, when the
return value of the received loader's get_source() has a bad splitlines()
method. Patch by Oren Milman.

@item 
bpo-30817@footnote{https://bugs.python.org/issue30817}: @code{PyErr_PrintEx()} clears now the ignored exception that may be
raised by @code{_PySys_SetObjectId()}, for example when no memory.
@end itemize

@node 库<34>,文档<29>,核心与内置<33>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id265}@anchor{1076}
@subsubsection 库



@itemize -

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Two minor fixes for @code{typing} module: allow shallow copying
instances of generic classes, improve interaction of @code{__init_subclass__}
with generics. Original PRs by Ivan Levkivskyi.

@item 
bpo-27240@footnote{https://bugs.python.org/issue27240}: The header folding algorithm for the new email policies has
been rewritten, which also fixes bpo-30788@footnote{https://bugs.python.org/issue30788}, bpo-31831@footnote{https://bugs.python.org/issue31831}, and bpo-32182@footnote{https://bugs.python.org/issue32182}.  In
particular, RFC2231 folding is now done correctly.

@item 
bpo-32186@footnote{https://bugs.python.org/issue32186}: io.FileIO.readall() and io.FileIO.read() now release the GIL
when getting the file size. Fixed hang of all threads with inaccessible
NFS server. Patch by Nir Soffer.

@item 
bpo-12239@footnote{https://bugs.python.org/issue12239}: Make @ref{f53,,msilib.SummaryInformation.GetProperty()} return
@code{None} when the value of property is @code{VT_EMPTY}.  Initial patch by
Mark Mc Mahon.

@item 
bpo-31325@footnote{https://bugs.python.org/issue31325}: Fix wrong usage of @ref{1b6,,collections.namedtuple()} in the
@ref{1034,,RobotFileParser.parse()}
method. Initial patch by Robin Wellner.

@item 
bpo-12382@footnote{https://bugs.python.org/issue12382}: @ref{e9d,,msilib.OpenDatabase()} now raises a better exception
message when it couldn't open or create an MSI file.  Initial patch by
William Tisäter.

@item 
bpo-32110@footnote{https://bugs.python.org/issue32110}: @code{codecs.StreamReader.read(n)} now returns not more than @emph{n}
characters/bytes for non-negative @emph{n}. This makes it compatible with
@code{read()} methods of other file-like objects.

@item 
bpo-32072@footnote{https://bugs.python.org/issue32072}: Fixed issues with binary plists: Fixed saving bytearrays.
Identical objects will be saved only once. Equal references will be load
as identical objects. Added support for saving and loading recursive data
structures.

@item 
bpo-32034@footnote{https://bugs.python.org/issue32034}: Make asyncio.IncompleteReadError and LimitOverrunError
pickleable.

@item 
bpo-32015@footnote{https://bugs.python.org/issue32015}: Fixed the looping of asyncio in the case of reconnection the
socket during waiting async read/write from/to the socket.

@item 
bpo-32011@footnote{https://bugs.python.org/issue32011}: Restored support of loading marshal files with the TYPE_INT64
code. These files can be produced in Python 2.7.

@item 
bpo-31970@footnote{https://bugs.python.org/issue31970}: Reduce performance overhead of asyncio debug mode.

@item 
bpo-9678@footnote{https://bugs.python.org/issue9678}: Fixed determining the MAC address in the uuid module: Using
ifconfig on NetBSD and OpenBSD. Using arp on Linux, FreeBSD, NetBSD and
OpenBSD. Based on patch by Takayuki Shimizukawa.

@item 
bpo-30057@footnote{https://bugs.python.org/issue30057}: Fix potential missed signal in signal.signal().

@item 
bpo-31933@footnote{https://bugs.python.org/issue31933}: Fix Blake2 params leaf_size and node_offset on big endian
platforms. Patch by Jack O'Connor.

@item 
bpo-31927@footnote{https://bugs.python.org/issue31927}: Fixed compilation of the socket module on NetBSD 8.  Fixed
assertion failure or reading arbitrary data when parse a AF_BLUETOOTH
address on NetBSD and DragonFly BSD.

@item 
bpo-27666@footnote{https://bugs.python.org/issue27666}: Fixed stack corruption in curses.box() and curses.ungetmouse()
when the size of types chtype or mmask_t is less than the size of C long.
curses.box() now accepts characters as arguments.  Based on patch by Steve
Fink.

@item 
bpo-31897@footnote{https://bugs.python.org/issue31897}: plistlib now catches more errors when read binary plists and
raises InvalidFileException instead of unexpected exceptions.

@item 
bpo-25720@footnote{https://bugs.python.org/issue25720}: Fix the method for checking pad state of curses WINDOW. Patch
by Masayuki Yamamoto.

@item 
bpo-31893@footnote{https://bugs.python.org/issue31893}: Fixed the layout of the kqueue_event structure on OpenBSD and
NetBSD. Fixed the comparison of the kqueue_event objects.

@item 
bpo-31891@footnote{https://bugs.python.org/issue31891}: Fixed building the curses module on NetBSD.

@item 
bpo-28416@footnote{https://bugs.python.org/issue28416}: Instances of pickle.Pickler subclass with the persistent_id()
method and pickle.Unpickler subclass with the persistent_load() method no
longer create reference cycles.

@item 
bpo-28326@footnote{https://bugs.python.org/issue28326}: Fix multiprocessing.Process when stdout and/or stderr is closed
or None.

@item 
bpo-31457@footnote{https://bugs.python.org/issue31457}: If nested log adapters are used, the inner @code{process()}
methods are no longer omitted.

@item 
bpo-31457@footnote{https://bugs.python.org/issue31457}: The @code{manager} property on LoggerAdapter objects is now
properly settable.

@item 
bpo-31806@footnote{https://bugs.python.org/issue31806}: Fix timeout rounding in time.sleep(), threading.Lock.acquire()
and socket.socket.settimeout() to round correctly negative timeouts
between -1.0 and 0.0. The functions now block waiting for events as
expected. Previously, the call was incorrectly non-blocking. Patch by
Pablo Galindo.

@item 
bpo-28603@footnote{https://bugs.python.org/issue28603}: traceback: Fix a TypeError that occurred during printing of
exception tracebacks when either the current exception or an exception in
its context/cause chain is unhashable. Patch by Zane Bitter.

@item 
bpo-30058@footnote{https://bugs.python.org/issue30058}: Fixed buffer overflow in select.kqueue.control().

@item 
bpo-31770@footnote{https://bugs.python.org/issue31770}: Prevent a crash when calling the @code{__init__()} method of a
@code{sqlite3.Cursor} object more than once. Patch by Oren Milman.

@item 
bpo-31672@footnote{https://bugs.python.org/issue31672}: @code{idpattern} in @code{string.Template} matched some non-ASCII
characters. Now it uses @code{-i} regular expression local flag to avoid
non-ASCII characters.

@item 
bpo-31764@footnote{https://bugs.python.org/issue31764}: Prevent a crash in @code{sqlite3.Cursor.close()} in case the
@code{Cursor} object is uninitialized. Patch by Oren Milman.

@item 
bpo-31752@footnote{https://bugs.python.org/issue31752}: Fix possible crash in timedelta constructor called with custom
integers.

@item 
bpo-31701@footnote{https://bugs.python.org/issue31701}: On Windows, faulthandler.enable() now ignores MSC and COM
exceptions.

@item 
bpo-31728@footnote{https://bugs.python.org/issue31728}: Prevent crashes in @code{_elementtree} due to unsafe cleanup of
@code{Element.text} and @code{Element.tail}. Patch by Oren Milman.

@item 
bpo-31620@footnote{https://bugs.python.org/issue31620}: an empty asyncio.Queue now doesn't leak memory when queue.get
pollers timeout

@item 
bpo-31632@footnote{https://bugs.python.org/issue31632}: Fix method set_protocol() of class _SSLProtocolTransport in
asyncio module. This method was previously modifying a wrong reference to
the protocol.

@item 
bpo-31675@footnote{https://bugs.python.org/issue31675}: Fixed memory leaks in Tkinter's methods splitlist() and split()
when pass a string larger than 2 GiB.

@item 
bpo-31673@footnote{https://bugs.python.org/issue31673}: Fixed typo in the name of Tkinter's method adderrorinfo().

@item 
bpo-30806@footnote{https://bugs.python.org/issue30806}: Fix the string representation of a netrc object.

@item 
bpo-15037@footnote{https://bugs.python.org/issue15037}: Added a workaround for getkey() in curses for ncurses 5.7 and
earlier.

@item 
bpo-25351@footnote{https://bugs.python.org/issue25351}: Avoid venv activate failures with undefined variables

@item 
bpo-25532@footnote{https://bugs.python.org/issue25532}: inspect.unwrap() will now only try to unwrap an object
sys.getrecursionlimit() times, to protect against objects which create a
new object on every attribute access.

@item 
bpo-30347@footnote{https://bugs.python.org/issue30347}: Stop crashes when concurrently iterate over itertools.groupby()
iterators.

@item 
bpo-31516@footnote{https://bugs.python.org/issue31516}: @code{threading.current_thread()} should not return a dummy thread
at shutdown.

@item 
bpo-31351@footnote{https://bugs.python.org/issue31351}: python -m ensurepip now exits with non-zero exit code if pip
bootstrapping has failed.

@item 
bpo-31482@footnote{https://bugs.python.org/issue31482}: @code{random.seed()} now works with bytes in version=1

@item 
bpo-31334@footnote{https://bugs.python.org/issue31334}: Fix @code{poll.poll([timeout])} in the @code{select} module for
arbitrary negative timeouts on all OSes where it can only be a
non-negative integer or -1. Patch by Riccardo Coccioli.

@item 
bpo-31310@footnote{https://bugs.python.org/issue31310}: multiprocessing's semaphore tracker should be launched again if
crashed.

@item 
bpo-31308@footnote{https://bugs.python.org/issue31308}: Make multiprocessing's forkserver process immune to Ctrl-C and
other user interruptions. If it crashes, restart it when necessary.
@end itemize

@node 文档<29>,测试<27>,库<34>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id266}@anchor{1077}
@subsubsection 文档



@itemize -

@item 
bpo-32105@footnote{https://bugs.python.org/issue32105}: Added asyncio.BaseEventLoop.connect_accepted_socket
versionadded marker.

@item 
bpo-31537@footnote{https://bugs.python.org/issue31537}: Fix incorrect usage of @code{get_history_length} in readline
documentation example code. Patch by Brad Smith.

@item 
bpo-30085@footnote{https://bugs.python.org/issue30085}: The operator functions without double underscores are preferred
for clarity. The one with underscores are only kept for
back-compatibility.
@end itemize

@node 测试<27>,构建<26>,文档<29>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id267}@anchor{1078}
@subsubsection 测试



@itemize -

@item 
bpo-31380@footnote{https://bugs.python.org/issue31380}: Skip test_httpservers test_undecodable_file on macOS: fails on
APFS.

@item 
bpo-31705@footnote{https://bugs.python.org/issue31705}: Skip test_socket.test_sha256() on Linux kernel older than 4.5.
The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged
into the kernel 4.5.

@item 
bpo-31174@footnote{https://bugs.python.org/issue31174}: Fix test_tools.test_unparse: DirectoryTestCase now stores the
names sample to always test the same files. It prevents false alarms when
hunting reference leaks.

@item 
bpo-30695@footnote{https://bugs.python.org/issue30695}: Add the @code{set_nomemory(start, stop)} and @code{remove_mem_hooks()}
functions to the _testcapi module.
@end itemize

@node 构建<26>,Windows<27>,测试<27>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id268}@anchor{1079}
@subsubsection 构建



@itemize -

@item 
bpo-32059@footnote{https://bugs.python.org/issue32059}: @code{detect_modules()} in @code{setup.py} now also searches the
sysroot paths when cross-compiling.

@item 
bpo-31957@footnote{https://bugs.python.org/issue31957}: Fixes Windows SDK version detection when building for Windows.

@item 
bpo-31609@footnote{https://bugs.python.org/issue31609}: Fixes quotes in PCbuild/clean.bat

@item 
bpo-31934@footnote{https://bugs.python.org/issue31934}: Abort the build when building out of a not clean source tree.

@item 
bpo-31926@footnote{https://bugs.python.org/issue31926}: Fixed Argument Clinic sometimes causing compilation errors when
there was more than one function and/or method in a .c file with the same
name.

@item 
bpo-28791@footnote{https://bugs.python.org/issue28791}: 更新 Windows 构建以使用 SQLite 3.21.0.

@item 
bpo-28791@footnote{https://bugs.python.org/issue28791}: 更新 OS X 安装程序以使用 SQLite 3.21.0.

@item 
bpo-22140@footnote{https://bugs.python.org/issue22140}: Prevent double substitution of prefix in python-config.sh.

@item 
bpo-31536@footnote{https://bugs.python.org/issue31536}: Avoid wholesale rebuild after @code{make regen-all} if nothing
changed.
@end itemize

@node Windows<27>,macOS<19>,构建<26>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id269}@anchor{107a}
@subsubsection Windows



@itemize -

@item 
bpo-1102@footnote{https://bugs.python.org/issue1102}: Return @code{None} when @code{View.Fetch()} returns
@code{ERROR_NO_MORE_ITEMS} instead of raising @code{MSIError}. Initial patch by
Anthony Tuininga.

@item 
bpo-31944@footnote{https://bugs.python.org/issue31944}: Fixes Modify button in Apps and Features dialog.
@end itemize

@node macOS<19>,IDLE<32>,Windows<27>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id270}@anchor{107b}
@subsubsection macOS



@itemize -

@item 
bpo-31392@footnote{https://bugs.python.org/issue31392}: 更新 macOS 安装程序以使用OpenSSL 1.0.2m
@end itemize

@node IDLE<32>,工具/示例<19>,macOS<19>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id271}@anchor{107c}
@subsubsection IDLE



@itemize -

@item 
bpo-32207@footnote{https://bugs.python.org/issue32207}: Improve tk event exception tracebacks in IDLE. When tk event
handling is driven by IDLE's run loop, a confusing and distracting
queue.EMPTY traceback context is no longer added to tk event exception
tracebacks.  The traceback is now the same as when event handling is
driven by user code.  Patch based on a suggestion by Serhiy Storchaka.

@item 
bpo-32164@footnote{https://bugs.python.org/issue32164}: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet
in configdialog was replaced by ttk.Notebook.

@item 
bpo-32100@footnote{https://bugs.python.org/issue32100}: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch
mostly by Cheryl Sabella.

@item 
bpo-31858@footnote{https://bugs.python.org/issue31858}: IDLE -- Restrict shell prompt manipulation to the shell. Editor
and output windows only see an empty last prompt line.  This simplifies
the code and fixes a minor bug when newline is inserted. Sys.ps1, if
present, is read on Shell start-up, but is not set or changed.

@item 
bpo-31860@footnote{https://bugs.python.org/issue31860}: The font sample in the IDLE configuration dialog is now
editable. Changes persist while IDLE remains open

@item 
bpo-31836@footnote{https://bugs.python.org/issue31836}: Test_code_module now passes if run after test_idle, which sets
ps1. The code module uses sys.ps1 if present or sets it to '>>> ' if not.
Test_code_module now properly tests both behaviors.  Ditto for ps2.

@item 
bpo-28603@footnote{https://bugs.python.org/issue28603}: Fix a TypeError that caused a shell restart when printing a
traceback that includes an exception that is unhashable. Patch by Zane
Bitter.

@item 
bpo-13802@footnote{https://bugs.python.org/issue13802}: Use non-Latin characters in the IDLE's Font settings sample.
Even if one selects a font that defines a limited subset of the unicode
Basic Multilingual Plane, tcl/tk will use other fonts that define a
character. The expanded example give users of non-Latin characters a
better idea of what they might see in IDLE's shell and editors. To make
room for the expanded sample, frames on the Font tab are re-arranged. The
Font/Tabs help explains a bit about the additions.

@item 
bpo-31460@footnote{https://bugs.python.org/issue31460}: Simplify the API of IDLE's Module Browser. Passing a widget
instead of an flist with a root widget opens the option of creating a
browser frame that is only part of a window.  Passing a full file name
instead of pieces assumed to come from a .py file opens the possibility of
browsing python files that do not end in .py.

@item 
bpo-31649@footnote{https://bugs.python.org/issue31649}: IDLE - Make _htest, _utest parameters keyword only.

@item 
bpo-31559@footnote{https://bugs.python.org/issue31559}: Remove test order dependence in idle_test.test_browser.

@item 
bpo-31459@footnote{https://bugs.python.org/issue31459}: Rename IDLE's module browser from Class Browser to Module
Browser. The original module-level class and method browser became a
module browser, with the addition of module-level functions, years ago.
Nested classes and functions were added yesterday.  For
back-compatibility, the virtual event <<open-class-browser>>, which
appears on the Keys tab of the Settings dialog, is not changed. Patch by
Cheryl Sabella.

@item 
bpo-31500@footnote{https://bugs.python.org/issue31500}: Default fonts now are scaled on HiDPI displays.

@item 
bpo-1612262@footnote{https://bugs.python.org/issue1612262}: IDLE module browser now shows nested classes and functions.
Original patches for code and tests by Guilherme Polo and Cheryl Sabella,
respectively.
@end itemize

@node 工具/示例<19>,C API<21>,IDLE<32>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id272}@anchor{107d}
@subsubsection 工具/示例



@itemize -

@item 
bpo-30722@footnote{https://bugs.python.org/issue30722}: Make redemo work with Python 3.6 and newer versions. Also,
remove the @code{LOCALE} option since it doesn't work with string patterns in
Python 3. Patch by Christoph Sarnowski.
@end itemize

@node C API<21>,,工具/示例<19>,Python 3 6 4 rc1
@anchor{whatsnew/changelog id273}@anchor{107e}
@subsubsection C API



@itemize -

@item 
bpo-20891@footnote{https://bugs.python.org/issue20891}: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in
a non-Python thread before PyEval_InitThreads(), only call
PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.

@item 
bpo-31532@footnote{https://bugs.python.org/issue31532}: Fix memory corruption due to allocator mix in getpath.c between
Py_GetPath() and Py_SetPath()

@item 
bpo-30697@footnote{https://bugs.python.org/issue30697}: The @code{PyExc_RecursionErrorInst} singleton is removed and
@code{PyErr_NormalizeException()} does not use it anymore. This singleton is
persistent and its members being never cleared may cause a segfault during
finalization of the interpreter. See also bpo-22898@footnote{https://bugs.python.org/issue22898}.
@end itemize

@node Python 3 6 3 正式版,Python 3 6 3 rc1,Python 3 6 4 rc1,更新日志
@anchor{whatsnew/changelog python-3-6-3-final}@anchor{107f}
@subsection Python 3.6.3 正式版


@emph{发布日期: 2017-10-03}

@menu
* 库: 库<35>. 
* 构建: 构建<27>. 

@end menu

@node 库<35>,构建<27>,,Python 3 6 3 正式版
@anchor{whatsnew/changelog id274}@anchor{1080}
@subsubsection 库



@itemize -

@item 
bpo-31641@footnote{https://bugs.python.org/issue31641}: Re-allow arbitrary iterables in
@ref{1081,,concurrent.futures.as_completed()}. Fixes regression in 3.6.3rc1.
@end itemize

@node 构建<27>,,库<35>,Python 3 6 3 正式版
@anchor{whatsnew/changelog id275}@anchor{1082}
@subsubsection 构建



@itemize -

@item 
bpo-31662@footnote{https://bugs.python.org/issue31662}: Fix typos in Windows @code{uploadrelease.bat} script. Fix Windows
Doc build issues in @code{Doc/make.bat}.

@item 
bpo-31423@footnote{https://bugs.python.org/issue31423}: Fix building the PDF documentation with newer versions of
Sphinx.
@end itemize

@node Python 3 6 3 rc1,Python 3 6 2 正式版,Python 3 6 3 正式版,更新日志
@anchor{whatsnew/changelog python-3-6-3-release-candidate-1}@anchor{1083}
@subsection Python 3.6.3 rc1


@emph{发布日期: 2017-09-18}

@menu
* 安全: 安全<20>. 
* 核心与内置: 核心与内置<34>. 
* 库: 库<36>. 
* 文档: 文档<30>. 
* 测试: 测试<28>. 
* 构建: 构建<28>. 
* Windows: Windows<28>. 
* IDLE: IDLE<33>. 
* 工具/示例: 工具/示例<20>. 

@end menu

@node 安全<20>,核心与内置<34>,,Python 3 6 3 rc1
@anchor{whatsnew/changelog id276}@anchor{1084}
@subsubsection 安全



@itemize -

@item 
bpo-29781@footnote{https://bugs.python.org/issue29781}: SSLObject.version() now correctly returns None when handshake
over BIO has not been performed yet.

@item 
bpo-30947@footnote{https://bugs.python.org/issue30947}: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to
get security fixes.
@end itemize

@node 核心与内置<34>,库<36>,安全<20>,Python 3 6 3 rc1
@anchor{whatsnew/changelog id277}@anchor{1085}
@subsubsection 核心与内置



@itemize -

@item 
bpo-31471@footnote{https://bugs.python.org/issue31471}: Fix an assertion failure in @ref{2b9,,subprocess.Popen()} on Windows, in
case the env argument has a bad keys() method. Patch by Oren Milman.

@item 
bpo-31418@footnote{https://bugs.python.org/issue31418}: Fix an assertion failure in @code{PyErr_WriteUnraisable()} in case
of an exception with a bad @code{__module__} attribute. Patch by Oren Milman.

@item 
bpo-31416@footnote{https://bugs.python.org/issue31416}: Fix assertion failures in case of a bad warnings.filters or
warnings.defaultaction. Patch by Oren Milman.

@item 
bpo-31411@footnote{https://bugs.python.org/issue31411}: Raise a TypeError instead of SystemError in case
warnings.onceregistry is not a dictionary. Patch by Oren Milman.

@item 
bpo-31373@footnote{https://bugs.python.org/issue31373}: Fix several possible instances of undefined behavior due to
floating-point demotions.

@item 
bpo-30465@footnote{https://bugs.python.org/issue30465}: Location information (@code{lineno} and @code{col_offset}) in
f-strings is now (mostly) correct.  This fixes tools like flake8 from
showing warnings on the wrong line (typically the first line of the file).

@item 
bpo-31343@footnote{https://bugs.python.org/issue31343}: Include sys/sysmacros.h for major(), minor(), and makedev().
GNU C libray plans to remove the functions from sys/types.h.

@item 
bpo-31291@footnote{https://bugs.python.org/issue31291}: Fix an assertion failure in @ref{104d,,zipimport.zipimporter.get_data} on
Windows, when the return value of @code{pathname.replace('/','\\')} isn't a
string. Patch by Oren Milman.

@item 
bpo-31271@footnote{https://bugs.python.org/issue31271}: Fix an assertion failure in the write() method of
@ref{5ee,,io.TextIOWrapper}, when the encoder doesn't return a bytes object. Patch
by Oren Milman.

@item 
bpo-31243@footnote{https://bugs.python.org/issue31243}: Fix a crash in some methods of @ref{5ee,,io.TextIOWrapper}, when the
decoder's state is invalid. Patch by Oren Milman.

@item 
bpo-30721@footnote{https://bugs.python.org/issue30721}: @code{print} now shows correct usage hint for using Python 2
redirection syntax.  Patch by Sanyam Khurana.

@item 
bpo-31070@footnote{https://bugs.python.org/issue31070}: Fix a race condition in importlib _get_module_lock().

@item 
bpo-31095@footnote{https://bugs.python.org/issue31095}: Fix potential crash during GC caused by @code{tp_dealloc} which
doesn't call @code{PyObject_GC_UnTrack()}.

@item 
bpo-31071@footnote{https://bugs.python.org/issue31071}: Avoid masking original TypeError in call with * unpacking when
other arguments are passed.

@item 
bpo-30978@footnote{https://bugs.python.org/issue30978}: str.format_map() now passes key lookup exceptions through.
Previously any exception was replaced with a KeyError exception.

@item 
bpo-30808@footnote{https://bugs.python.org/issue30808}: Use _Py_atomic API for concurrency-sensitive signal state.

@item 
bpo-30876@footnote{https://bugs.python.org/issue30876}: Relative import from unloaded package now reimports the package
instead of failing with SystemError.  Relative import from non-package now
fails with ImportError rather than SystemError.

@item 
bpo-30703@footnote{https://bugs.python.org/issue30703}: Improve signal delivery. Avoid using Py_AddPendingCall from
signal handler, to avoid calling signal-unsafe functions. The tests I'm
adding here fail without the rest of the patch, on Linux and OS X. This
means our signal delivery logic had defects (some signals could be lost).

@item 
bpo-30765@footnote{https://bugs.python.org/issue30765}: Avoid blocking in pthread_mutex_lock() when
PyThread_acquire_lock() is asked not to block.

@item 
bpo-31161@footnote{https://bugs.python.org/issue31161}: Make sure the 'Missing parentheses' syntax error message is
only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

@item 
bpo-30814@footnote{https://bugs.python.org/issue30814}: Fixed a race condition when import a submodule from a package.

@item 
bpo-30597@footnote{https://bugs.python.org/issue30597}: @code{print} now shows expected input in custom error message when
used as a Python 2 statement. Patch by Sanyam Khurana.
@end itemize

@node 库<36>,文档<30>,核心与内置<34>,Python 3 6 3 rc1
@anchor{whatsnew/changelog id278}@anchor{1086}
@subsubsection 库



@itemize -

@item 
bpo-31499@footnote{https://bugs.python.org/issue31499}: xml.etree: Fix a crash when a parser is part of a reference
cycle.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: typing.get_type_hints now finds the right globalns for classes
and modules by default (when no @code{globalns} was specified by the caller).

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Speed improvements to the @code{typing} module.  Original PRs by
Ivan Levkivskyi and Mitar.

@item 
bpo-31544@footnote{https://bugs.python.org/issue31544}: The C accelerator module of ElementTree ignored exceptions
raised when looking up TreeBuilder target methods in XMLParser().

@item 
bpo-31234@footnote{https://bugs.python.org/issue31234}: socket.create_connection() now fixes manually a reference
cycle: clear the variable storing the last exception on success.

@item 
bpo-31457@footnote{https://bugs.python.org/issue31457}: LoggerAdapter objects can now be nested.

@item 
bpo-31400@footnote{https://bugs.python.org/issue31400}: Improves SSL error handling to avoid losing error numbers.

@item 
bpo-28958@footnote{https://bugs.python.org/issue28958}: ssl.SSLContext() now uses OpenSSL error information when a
context cannot be instantiated.

@item 
bpo-27340@footnote{https://bugs.python.org/issue27340}: SSLSocket.sendall() now uses memoryview to create slices of
data. This fixes support for all bytes-like object. It is also more
efficient and avoids costly copies.

@item 
bpo-31178@footnote{https://bugs.python.org/issue31178}: Fix string concatenation bug in rare error path in the
subprocess module

@item 
bpo-31350@footnote{https://bugs.python.org/issue31350}: Micro-optimize @code{asyncio._get_running_loop()} to become up
to 10% faster.

@item 
bpo-31170@footnote{https://bugs.python.org/issue31170}: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of
partial characters for UTF-8 input (libexpat bug 115):
@indicateurl{https://github.com/libexpat/libexpat/issues/115}

@item 
bpo-29136@footnote{https://bugs.python.org/issue29136}: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

@item 
bpo-29212@footnote{https://bugs.python.org/issue29212}: Fix concurrent.futures.thread.ThreadPoolExecutor threads to
have a non repr() based thread name by default when no thread_name_prefix
is supplied. They will now identify themselves as
"ThreadPoolExecutor-y_n".

@item 
bpo-9146@footnote{https://bugs.python.org/issue9146}: Fix a segmentation fault in _hashopenssl when standard hash
functions such as md5 are not available in the linked OpenSSL library.  As
in some special FIPS-140 build environments.

@item 
bpo-27144@footnote{https://bugs.python.org/issue27144}: The @code{map()} and @code{as_completed()} iterators in
@code{concurrent.futures} now avoid keeping a reference to yielded objects.

@item 
bpo-10746@footnote{https://bugs.python.org/issue10746}: Fix ctypes producing wrong 
@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} type codes for integer
types.

@item 
bpo-22536@footnote{https://bugs.python.org/issue22536}: The subprocess module now sets the filename when
FileNotFoundError is raised on POSIX systems due to the executable or cwd
not being found.

@item 
bpo-31249@footnote{https://bugs.python.org/issue31249}: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor
now breaks a reference cycle between an exception object and the WorkItem
object.

@item 
bpo-31247@footnote{https://bugs.python.org/issue31247}: xmlrpc.server now explicitly breaks reference cycles when using
sys.exc_info() in code handling exceptions.

@item 
bpo-30102@footnote{https://bugs.python.org/issue30102}: The ssl and hashlib modules now call
OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function
detects CPU features and enables optimizations on some CPU architectures
such as POWER8. Patch is based on research from Gustavo Serra Scalet.

@item 
bpo-31185@footnote{https://bugs.python.org/issue31185}: Fixed miscellaneous errors in asyncio speedup module.

@item 
bpo-31135@footnote{https://bugs.python.org/issue31135}: ttk: fix the destroy() method of LabeledScale and OptionMenu
classes. Call the parent destroy() method even if the used attribute
doesn't exist. The LabeledScale.destroy() method now also explicitly
clears label and scale attributes to help the garbage collector to destroy
all widgets.

@item 
bpo-31107@footnote{https://bugs.python.org/issue31107}: Fix @code{copyreg._slotnames()} mangled attribute calculation for
classes whose name begins with an underscore. Patch by Shane Harvey.

@item 
bpo-31061@footnote{https://bugs.python.org/issue31061}: Fixed a crash when using asyncio and threads.

@item 
bpo-30502@footnote{https://bugs.python.org/issue30502}: Fix handling of long oids in ssl.  Based on patch by Christian
Heimes.

@item 
bpo-30119@footnote{https://bugs.python.org/issue30119}: ftplib.FTP.putline() now throws ValueError on commands that
contains CR or LF. Patch by Dong-hee Na.

@item 
bpo-30595@footnote{https://bugs.python.org/issue30595}: multiprocessing.Queue.get() with a timeout now polls its reader
in non-blocking mode if it succeeded to acquire the lock but the acquire
took longer than the timeout.

@item 
bpo-29403@footnote{https://bugs.python.org/issue29403}: Fix @code{unittest.mock}'s autospec to not fail on method-bound
builtin functions.  Patch by Aaron Gallagher.

@item 
bpo-30961@footnote{https://bugs.python.org/issue30961}: Fix decrementing a borrowed reference in tracemalloc.

@item 
bpo-25684@footnote{https://bugs.python.org/issue25684}: Change @code{ttk.OptionMenu} radiobuttons to be unique across
instances of @code{OptionMenu}.

@item 
bpo-30886@footnote{https://bugs.python.org/issue30886}: Fix multiprocessing.Queue.join_thread(): it now waits until the
thread completes, even if the thread was started by the same process which
created the queue.

@item 
bpo-29854@footnote{https://bugs.python.org/issue29854}: Fix segfault in readline when using readline's history-size
option.  Patch by Nir Soffer.

@item 
bpo-30319@footnote{https://bugs.python.org/issue30319}: socket.close() now ignores ECONNRESET error.

@item 
bpo-30828@footnote{https://bugs.python.org/issue30828}: Fix out of bounds write in
@code{asyncio.CFuture.remove_done_callback()}.

@item 
bpo-30807@footnote{https://bugs.python.org/issue30807}: signal.setitimer() may disable the timer when passed a tiny
value. Tiny values (such as 1e-6) are valid non-zero values for
setitimer(), which is specified as taking microsecond-resolution
intervals. However, on some platform, our conversion routine could convert
1e-6 into a zero interval, therefore disabling the timer instead of
(re-)scheduling it.

@item 
bpo-30441@footnote{https://bugs.python.org/issue30441}: Fix bug when modifying os.environ while iterating over it

@item 
bpo-30532@footnote{https://bugs.python.org/issue30532}: Fix email header value parser dropping folding white space in
certain cases.

@item 
bpo-30879@footnote{https://bugs.python.org/issue30879}: os.listdir() and os.scandir() now emit bytes names when called
with bytes-like argument.

@item 
bpo-30746@footnote{https://bugs.python.org/issue30746}: Prohibited the '=' character in environment variable names in
@code{os.putenv()} and @code{os.spawn*()}.

@item 
bpo-29755@footnote{https://bugs.python.org/issue29755}: Fixed the lgettext() family of functions in the gettext module.
They now always return bytes.
@end itemize

@node 文档<30>,测试<28>,库<36>,Python 3 6 3 rc1
@anchor{whatsnew/changelog id279}@anchor{1087}
@subsubsection 文档



@itemize -

@item 
bpo-31294@footnote{https://bugs.python.org/issue31294}: Fix incomplete code snippet in the ZeroMQSocketListener and
ZeroMQSocketHandler examples and adapt them to Python 3.

@item 
bpo-21649@footnote{https://bugs.python.org/issue21649}: Add RFC 7525 and Mozilla server side TLS links to SSL
documentation.

@item 
bpo-30803@footnote{https://bugs.python.org/issue30803}: Clarify doc on truth value testing. Original patch by Peter
Thomassen.
@end itemize

@node 测试<28>,构建<28>,文档<30>,Python 3 6 3 rc1
@anchor{whatsnew/changelog id280}@anchor{1088}
@subsubsection 测试



@itemize -

@item 
bpo-31320@footnote{https://bugs.python.org/issue31320}: Silence traceback in test_ssl

@item 
bpo-25674@footnote{https://bugs.python.org/issue25674}: Remove sha256.tbs-internet.com ssl test

@item 
bpo-30715@footnote{https://bugs.python.org/issue30715}: Address ALPN callback changes for OpenSSL 1.1.0f. The latest
version behaves like OpenSSL 1.0.2 and no longer aborts handshake.

@item 
bpo-30822@footnote{https://bugs.python.org/issue30822}: regrtest: Exclude tzdata from regrtest --all. When running the
test suite using --use=all / -u all, exclude tzdata since it makes
test_datetime too slow (15-20 min on some buildbots) which then times out
on some buildbots. Fix also regrtest command line parser to allow passing
-u extralargefile to run test_zipfile64.
@end itemize

@node 构建<28>,Windows<28>,测试<28>,Python 3 6 3 rc1
@anchor{whatsnew/changelog id281}@anchor{1089}
@subsubsection 构建



@itemize -

@item 
bpo-30854@footnote{https://bugs.python.org/issue30854}: Fix compile error when compiling --without-threads. Patch by
Masayuki Yamamoto.
@end itemize

@node Windows<28>,IDLE<33>,构建<28>,Python 3 6 3 rc1
@anchor{whatsnew/changelog id282}@anchor{108a}
@subsubsection Windows



@itemize -

@item 
bpo-30389@footnote{https://bugs.python.org/issue30389}: Adds detection of Visual Studio 2017 to distutils on Windows.

@item 
bpo-31340@footnote{https://bugs.python.org/issue31340}: Change to building with MSVC v141 (included with Visual Studio
2017)

@item 
bpo-30581@footnote{https://bugs.python.org/issue30581}: os.cpu_count() now returns the correct number of processors on
Windows when the number of logical processors is greater than 64.

@item 
bpo-30731@footnote{https://bugs.python.org/issue30731}: Add a missing xmlns to python.manifest so that it matches the
schema.
@end itemize

@node IDLE<33>,工具/示例<20>,Windows<28>,Python 3 6 3 rc1
@anchor{whatsnew/changelog id283}@anchor{108b}
@subsubsection IDLE



@itemize -

@item 
bpo-31493@footnote{https://bugs.python.org/issue31493}: IDLE code context -- fix code update and font update timers.
Canceling timers prevents a warning message when test_idle completes.

@item 
bpo-31488@footnote{https://bugs.python.org/issue31488}: IDLE - Update non-key options in former extension classes. When
applying configdialog changes, call .reload for each feature class. Change
ParenMatch so updated options affect existing instances attached to
existing editor windows.

@item 
bpo-31477@footnote{https://bugs.python.org/issue31477}: IDLE - Improve rstrip entry in doc. Strip trailing whitespace
strips more than blank spaces.  Multiline string literals are not skipped.

@item 
bpo-31480@footnote{https://bugs.python.org/issue31480}: IDLE - make tests pass with zzdummy extension disabled by
default.

@item 
bpo-31421@footnote{https://bugs.python.org/issue31421}: Document how IDLE runs tkinter programs. IDLE calls tcl/tk
update in the background in order to make live interaction and
experimentation with tkinter applications much easier.

@item 
bpo-31414@footnote{https://bugs.python.org/issue31414}: IDLE -- fix tk entry box tests by deleting first. Adding to an
int entry is not the same as deleting and inserting because int('@w{'}) will
fail.

@item 
bpo-31051@footnote{https://bugs.python.org/issue31051}: Rearrange IDLE configdialog GenPage into Window, Editor, and
Help sections.

@item 
bpo-30617@footnote{https://bugs.python.org/issue30617}: IDLE - Add docstrings and tests for outwin subclass of editor.
Move some data and functions from the class to module level. Patch by
Cheryl Sabella.

@item 
bpo-31287@footnote{https://bugs.python.org/issue31287}: IDLE - Do not modify tkinter.message in test_configdialog.

@item 
bpo-27099@footnote{https://bugs.python.org/issue27099}: Convert IDLE's built-in 'extensions' to regular features. About
10 IDLE features were implemented as supposedly optional extensions. Their
different behavior could be confusing or worse for users and not good for
maintenance. Hence the conversion. The main difference for users is that
user configurable key bindings for builtin features are now handled
uniformly. Now, editing a binding in a keyset only affects its value in
the keyset. All bindings are defined together in the system-specific
default keysets in config-extensions.def. All custom keysets are saved as
a whole in config-extension.cfg.  All take effect as soon as one clicks
Apply or Ok. The affected events are '<<force-open-completions>>',
'<<expand-word>>', '<<force-open-calltip>>', '<<flash-paren>>',
'<<format-paragraph>>', '<<run-module>>', '<<check-module>>', and
'<<zoom-height>>'.  Any (global) customizations made before 3.6.3 will not
affect their keyset-specific customization after 3.6.3. and vice versa.
Initial patch by Charles Wohlganger.

@item 
bpo-31206@footnote{https://bugs.python.org/issue31206}: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by
Cheryl Sabella.

@item 
bpo-31001@footnote{https://bugs.python.org/issue31001}: Add tests for configdialog highlight tab.  Patch by Cheryl
Sabella.

@item 
bpo-31205@footnote{https://bugs.python.org/issue31205}: IDLE: Factor KeysPage(Frame) class from ConfigDialog.  The
slightly modified tests continue to pass.  Patch by Cheryl Sabella.

@item 
bpo-31130@footnote{https://bugs.python.org/issue31130}: IDLE -- stop leaks in test_configdialog. Initial patch by
Victor Stinner.

@item 
bpo-31002@footnote{https://bugs.python.org/issue31002}: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

@item 
bpo-19903@footnote{https://bugs.python.org/issue19903}: IDLE: Calltips use @ref{556,,inspect.signature} instead of
@ref{558,,inspect.getfullargspec}. This improves calltips for builtins converted to
use Argument Clinic. Patch by Louie Lu.

@item 
bpo-31083@footnote{https://bugs.python.org/issue31083}: IDLE - Add an outline of a TabPage class in configdialog.
Update existing classes to match outline. Initial patch by Cheryl Sabella.

@item 
bpo-31050@footnote{https://bugs.python.org/issue31050}: Factor GenPage(Frame) class from ConfigDialog. The slightly
modified tests continue to pass. Patch by Cheryl Sabella.

@item 
bpo-31004@footnote{https://bugs.python.org/issue31004}: IDLE - Factor FontPage(Frame) class from ConfigDialog. Slightly
modified tests continue to pass. Fix General tests. Patch mostly by Cheryl
Sabella.

@item 
bpo-30781@footnote{https://bugs.python.org/issue30781}: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan
Reedy and Cheryl Sabella.

@item 
bpo-31060@footnote{https://bugs.python.org/issue31060}: IDLE - Finish rearranging methods of ConfigDialog Grouping
methods pertaining to each tab and the buttons will aid writing tests and
improving the tabs and will enable splitting the groups into classes.

@item 
bpo-30853@footnote{https://bugs.python.org/issue30853}: IDLE -- Factor a VarTrace class out of ConfigDialog. Instance
tracers manages pairs consisting of a tk variable and a callback function.
When tracing is turned on, setting the variable calls the function.  Test
coverage for the new class is 100%.

@item 
bpo-31003@footnote{https://bugs.python.org/issue31003}: IDLE: Add more tests for General tab.

@item 
bpo-30993@footnote{https://bugs.python.org/issue30993}: IDLE - Improve configdialog font page and tests. In
configdialog: Document causal pathways in create_font_tab docstring.
Simplify some attribute names. Move set_samples calls to var_changed_font
(idea from Cheryl Sabella).  Move related functions to positions after the
create widgets function. In test_configdialog: Fix test_font_set so not
order dependent.  Fix renamed test_indent_scale so it tests the widget.
Adjust tests for movement of set_samples call.  Add tests for load
functions.  Put all font tests in one class and tab indent tests in
another.  Except for two lines, these tests completely cover the related
functions.

@item 
bpo-30981@footnote{https://bugs.python.org/issue30981}: IDLE -- Add more configdialog font page tests.

@item 
bpo-28523@footnote{https://bugs.python.org/issue28523}: IDLE: replace 'colour' with 'color' in configdialog.

@item 
bpo-30917@footnote{https://bugs.python.org/issue30917}: Add tests for idlelib.config.IdleConf. Increase coverage from
46% to 96%. Patch by Louie Lu.

@item 
bpo-30934@footnote{https://bugs.python.org/issue30934}: Document coverage details for idlelib tests. Add section to
idlelib/idle-test/README.txt. Include check that branches are taken both
ways. Exclude IDLE-specific code that does not run during unit tests.

@item 
bpo-30913@footnote{https://bugs.python.org/issue30913}: IDLE: Document ConfigDialog tk Vars, methods, and widgets in
docstrings This will facilitate improving the dialog and splitting up the
class. Original patch by Cheryl Sabella.

@item 
bpo-30899@footnote{https://bugs.python.org/issue30899}: IDLE: Add tests for ConfigParser subclasses in config. Patch by
Louie Lu.

@item 
bpo-30881@footnote{https://bugs.python.org/issue30881}: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

@item 
bpo-30851@footnote{https://bugs.python.org/issue30851}: IDLE: Remove unused variables in configdialog.  One is a
duplicate, one is set but cannot be altered by users. Patch by Cheryl
Sabella.

@item 
bpo-30870@footnote{https://bugs.python.org/issue30870}: IDLE: In Settings dialog, select font with Up, Down keys as
well as mouse. Initial patch by Louie Lu.

@item 
bpo-8231@footnote{https://bugs.python.org/issue8231}: IDLE: call config.IdleConf.GetUserCfgDir only once.

@item 
bpo-30779@footnote{https://bugs.python.org/issue30779}: IDLE: Factor ConfigChanges class from configdialog, put in
config; test. * In config, put dump test code in a function; run it and
unittest in   'if __name__ == '__main__'. * Add class config.ConfigChanges
based on changes_class_v4.py on bpo issue. * Add class
test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise
configdialog to use ConfigChanges; see tracker msg297804. * Revise
test_configdialog to match configdialog changes. * Remove configdialog
functions unused or moved to ConfigChanges. Cheryl Sabella contributed
parts of the patch.

@item 
bpo-30777@footnote{https://bugs.python.org/issue30777}: IDLE: configdialog - Add docstrings and fix comments. Patch by
Cheryl Sabella.

@item 
bpo-30495@footnote{https://bugs.python.org/issue30495}: IDLE: Improve textview with docstrings, PEP8 names, and more
tests. Patch by Cheryl Sabella.

@item 
bpo-30723@footnote{https://bugs.python.org/issue30723}: IDLE: Make several improvements to parenmatch. Add 'parens'
style to highlight both opener and closer. Make 'default' style, which is
not default, a synonym for 'opener'. Make time-delay work the same with
all styles. Add help for config dialog extensions tab, including help for
parenmatch. Add new tests.  Original patch by Charles Wohlganger.

@item 
bpo-30674@footnote{https://bugs.python.org/issue30674}: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

@item 
bpo-21519@footnote{https://bugs.python.org/issue21519}: IDLE's basic custom key entry dialog now detects duplicates
properly. Original patch by Saimadhav Heblikar.

@item 
bpo-29910@footnote{https://bugs.python.org/issue29910}: IDLE no longer deletes a character after commenting out a
region by a key shortcut.  Add @code{return 'break'} for this and other
potential conflicts between IDLE and default key bindings.

@item 
bpo-30728@footnote{https://bugs.python.org/issue30728}: Review and change idlelib.configdialog names. Lowercase method
and attribute names. Replace 'colour' with 'color', expand overly cryptic
names, delete unneeded underscores. Replace @code{import *} with specific
imports. Patches by Cheryl Sabella.

@item 
bpo-6739@footnote{https://bugs.python.org/issue6739}: IDLE: Verify user-entered key sequences by trying to bind them
with tk. Add tests for all 3 validation functions. Original patch by G
Polo.  Tests added by Cheryl Sabella.
@end itemize

@node 工具/示例<20>,,IDLE<33>,Python 3 6 3 rc1
@anchor{whatsnew/changelog id284}@anchor{108c}
@subsubsection 工具/示例



@itemize -

@item 
bpo-30983@footnote{https://bugs.python.org/issue30983}: gdb integration commands (py-bt, etc.) work on optimized shared
builds now, too.  
@geindex Python 提高建议; PEP 523
PEP 523@footnote{https://www.python.org/dev/peps/pep-0523} introduced _PyEval_EvalFrameDefault which
inlines PyEval_EvalFrameEx on non-debug shared builds.  This broke the
ability to use py-bt, py-up, and a few other Python-specific gdb
integrations. The problem is fixed by only looking for
_PyEval_EvalFrameDefault frames in python-gdb.py.  Original patch by Bruno
"Polaco" Penteado.
@end itemize

@node Python 3 6 2 正式版,Python 3 6 2 rc2,Python 3 6 3 rc1,更新日志
@anchor{whatsnew/changelog python-3-6-2-final}@anchor{108d}
@subsection Python 3.6.2 正式版


@emph{发布日期: 2017-07-17}

自rc2起没有更改

@node Python 3 6 2 rc2,Python 3 6 2 rc1,Python 3 6 2 正式版,更新日志
@anchor{whatsnew/changelog python-3-6-2-release-candidate-2}@anchor{108e}
@subsection Python 3.6.2 rc2


@emph{发布日期: 2017-07-07}

@menu
* 安全: 安全<21>. 

@end menu

@node 安全<21>,,,Python 3 6 2 rc2
@anchor{whatsnew/changelog id285}@anchor{108f}
@subsubsection 安全



@itemize -

@item 
bpo-30730@footnote{https://bugs.python.org/issue30730}: Prevent environment variables injection in subprocess on
Windows.  Prevent passing other environment variables and command
arguments.

@item 
bpo-30694@footnote{https://bugs.python.org/issue30694}: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple
security vulnerabilities including: CVE-2017-9233 (External entity
infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix),
CVE-2016-0718 (Fix regression bugs from 2.2.0's fix to CVE-2016-0718) and
CVE-2012-0876 (Counter hash flooding with SipHash). Note: the
CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn't
impact Python, since Python already gets entropy from the OS to set the
expat secret using @code{XML_SetHashSalt()}.

@item 
bpo-30500@footnote{https://bugs.python.org/issue30500}: Fix urllib.parse.splithost() to correctly parse fragments. For
example, @code{splithost('//127.0.0.1#@@evil.com/')} now correctly returns the
@code{127.0.0.1} host, instead of treating @code{@@evil.com} as the host in an
authentication (@code{login@@host}).
@end itemize

@node Python 3 6 2 rc1,Python 3 6 1 正式版,Python 3 6 2 rc2,更新日志
@anchor{whatsnew/changelog python-3-6-2-release-candidate-1}@anchor{1090}
@subsection Python 3.6.2 rc1


@emph{发布日期: 2017-06-17}

@menu
* 核心与内置: 核心与内置<35>. 
* 库: 库<37>. 
* 安全: 安全<22>. 
* 库: 库<38>. 
* IDLE: IDLE<34>. 
* C API: C API<22>. 
* 构建: 构建<29>. 
* 文档: 文档<31>. 
* 工具/示例: 工具/示例<21>. 
* 测试: 测试<29>. 
* Windows: Windows<29>. 

@end menu

@node 核心与内置<35>,库<37>,,Python 3 6 2 rc1
@anchor{whatsnew/changelog id286}@anchor{1091}
@subsubsection 核心与内置



@itemize -

@item 
bpo-30682@footnote{https://bugs.python.org/issue30682}: Removed a too-strict assertion that failed for certain
f-strings, such as eval("f'\n'") and eval("f'\r'").

@item 
bpo-30604@footnote{https://bugs.python.org/issue30604}: Move co_extra_freefuncs to not be per-thread to avoid crashes

@item 
bpo-29104@footnote{https://bugs.python.org/issue29104}: Fixed parsing backslashes in f-strings.

@item 
bpo-27945@footnote{https://bugs.python.org/issue27945}: Fixed various segfaults with dict when input collections are
mutated during searching, inserting or comparing.  Based on patches by
Duane Griffin and Tim Mitchell.

@item 
bpo-25794@footnote{https://bugs.python.org/issue25794}: Fixed type.__setattr__() and type.__delattr__() for
non-interned attribute names.  Based on patch by Eryk Sun.

@item 
bpo-30039@footnote{https://bugs.python.org/issue30039}: If a KeyboardInterrupt happens when the interpreter is in the
middle of resuming a chain of nested 'yield from' or 'await' calls, it's
now correctly delivered to the innermost frame.

@item 
bpo-12414@footnote{https://bugs.python.org/issue12414}: sys.getsizeof() on a code object now returns the sizes which
includes the code struct and sizes of objects which it references. Patch
by Dong-hee Na.

@item 
bpo-29949@footnote{https://bugs.python.org/issue29949}: Fix memory usage regression of set and frozenset object.

@item 
bpo-29935@footnote{https://bugs.python.org/issue29935}: Fixed error messages in the index() method of tuple, list and
deque when pass indices of wrong type.

@item 
bpo-29859@footnote{https://bugs.python.org/issue29859}: Show correct error messages when any of the pthread_* calls in
thread_pthread.h fails.

@item 
bpo-28876@footnote{https://bugs.python.org/issue28876}: @code{bool(range)} works even if @code{len(range)} raises
@ref{95a,,OverflowError}.

@item 
bpo-29600@footnote{https://bugs.python.org/issue29600}: Fix wrapping coroutine return values in StopIteration.

@item 
bpo-28856@footnote{https://bugs.python.org/issue28856}: Fix an oversight that %b format for bytes should support
objects follow the buffer protocol.

@item 
bpo-29714@footnote{https://bugs.python.org/issue29714}: Fix a regression that bytes format may fail when containing
zero bytes inside.

@item 
bpo-29478@footnote{https://bugs.python.org/issue29478}: If max_line_length=None is specified while using the Compat32
policy, it is no longer ignored.  Patch by Mircea Cosbuc.
@end itemize

@node 库<37>,安全<22>,核心与内置<35>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id287}@anchor{1092}
@subsubsection 库



@itemize -

@item 
bpo-30616@footnote{https://bugs.python.org/issue30616}: Functional API of enum allows to create empty enums. Patched by
Dong-hee Na

@item 
bpo-30038@footnote{https://bugs.python.org/issue30038}: Fix race condition between signal delivery and wakeup file
descriptor. Patch by Nathaniel Smith.

@item 
bpo-23894@footnote{https://bugs.python.org/issue23894}: lib2to3 now recognizes @code{rb'...'} and @code{f'...'} strings.

@item 
bpo-23890@footnote{https://bugs.python.org/issue23890}: unittest.TestCase.assertRaises() now manually breaks a
reference cycle to not keep objects alive longer than expected.

@item 
bpo-30149@footnote{https://bugs.python.org/issue30149}: inspect.signature() now supports callables with
variable-argument parameters wrapped with partialmethod. Patch by Dong-hee
Na.

@item 
bpo-30645@footnote{https://bugs.python.org/issue30645}: Fix path calculation in imp.load_package(), fixing it for cases
when a package is only shipped with bytecodes. Patch by Alexandru
Ardelean.

@item 
bpo-29931@footnote{https://bugs.python.org/issue29931}: Fixed comparison check for ipaddress.ip_interface objects.
Patch by Sanjay Sundaresan.

@item 
bpo-30605@footnote{https://bugs.python.org/issue30605}: re.compile() no longer raises a BytesWarning when compiling a
bytes instance with misplaced inline modifier.  Patch by Roy Williams.
@end itemize

@node 安全<22>,库<38>,库<37>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id288}@anchor{1093}
@subsubsection 安全



@itemize -

@item 
bpo-29591@footnote{https://bugs.python.org/issue29591}: Update expat copy from 2.1.1 to 2.2.0 to get fixes of
CVE-2016-0718 and CVE-2016-4472. See
@indicateurl{https://sourceforge.net/p/expat/bugs/537/} for more information.
@end itemize

@node 库<38>,IDLE<34>,安全<22>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id289}@anchor{1094}
@subsubsection 库



@itemize -

@item 
bpo-24484@footnote{https://bugs.python.org/issue24484}: Avoid race condition in multiprocessing cleanup (#2159)

@item 
bpo-28994@footnote{https://bugs.python.org/issue28994}: The traceback no longer displayed for SystemExit raised in a
callback registered by atexit.

@item 
bpo-30508@footnote{https://bugs.python.org/issue30508}: Don't log exceptions if Task/Future "cancel()" method was
called.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Updates to typing module: Add generic AsyncContextManager, add
support for ContextManager on all versions. Original PRs by Jelle Zijlstra
and Ivan Levkivskyi

@item 
bpo-29870@footnote{https://bugs.python.org/issue29870}: Fix ssl sockets leaks when connection is aborted in asyncio/ssl
implementation. Patch by Michaël Sghaïer.

@item 
bpo-29743@footnote{https://bugs.python.org/issue29743}: Closing transport during handshake process leaks open socket.
Patch by Nikolay Kim

@item 
bpo-27585@footnote{https://bugs.python.org/issue27585}: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu
Sornay.

@item 
bpo-30418@footnote{https://bugs.python.org/issue30418}: On Windows, subprocess.Popen.communicate() now also ignore
EINVAL on stdin.write() if the child process is still running but closed
the pipe.

@item 
bpo-29822@footnote{https://bugs.python.org/issue29822}: inspect.isabstract() now works during __init_subclass__.  Patch
by Nate Soares.

@item 
bpo-29581@footnote{https://bugs.python.org/issue29581}: ABCMeta.__new__ now accepts @code{**kwargs}, allowing abstract
base classes to use keyword parameters in __init_subclass__. Patch by Nate
Soares.

@item 
bpo-30557@footnote{https://bugs.python.org/issue30557}: faulthandler now correctly filters and displays exception codes
on Windows

@item 
bpo-30378@footnote{https://bugs.python.org/issue30378}: Fix the problem that logging.handlers.SysLogHandler cannot
handle IPv6 addresses.

@item 
bpo-29960@footnote{https://bugs.python.org/issue29960}: Preserve generator state when _random.Random.setstate() raises
an exception. Patch by Bryan Olson.

@item 
bpo-30414@footnote{https://bugs.python.org/issue30414}: multiprocessing.Queue._feed background running thread do not
break from main loop on exception.

@item 
bpo-30003@footnote{https://bugs.python.org/issue30003}: Fix handling escape characters in HZ codec.  Based on patch by
Ma Lin.

@item 
bpo-30301@footnote{https://bugs.python.org/issue30301}: Fix AttributeError when using SimpleQueue.empty() under @emph{spawn}
and @emph{forkserver} start methods.

@item 
bpo-30329@footnote{https://bugs.python.org/issue30329}: imaplib and poplib now catch the Windows socket WSAEINVAL error
(code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted.
This error occurs sometimes on SSL connections.

@item 
bpo-30375@footnote{https://bugs.python.org/issue30375}: Warnings emitted when compile a regular expression now always
point to the line in the user code.  Previously they could point into
inners of the re module if emitted from inside of groups or conditionals.

@item 
bpo-30048@footnote{https://bugs.python.org/issue30048}: Fixed @code{Task.cancel()} can be ignored when the task is running
coroutine and the coroutine returned without any more @code{await}.

@item 
bpo-30266@footnote{https://bugs.python.org/issue30266}: contextlib.AbstractContextManager now supports
anti-registration by setting __enter__ = None or __exit__ = None,
following the pattern introduced in bpo-25958@footnote{https://bugs.python.org/issue25958}. Patch by Jelle Zijlstra.

@item 
bpo-30298@footnote{https://bugs.python.org/issue30298}: Weaken the condition of deprecation warnings for inline
modifiers. Now allowed several subsequential inline modifiers at the start
of the pattern (e.g. @code{'(?i)(?s)...'}).  In verbose mode whitespaces and
comments now are allowed before and between inline modifiers (e.g. @code{'(?x)
(?i) (?s)...'}).

@item 
bpo-29990@footnote{https://bugs.python.org/issue29990}: Fix range checking in GB18030 decoder.  Original patch by Ma
Lin.

@item 
bpo-26293@footnote{https://bugs.python.org/issue26293}: Change resulted because of zipfile breakage. (See also:
bpo-29094@footnote{https://bugs.python.org/issue29094})

@item 
bpo-30243@footnote{https://bugs.python.org/issue30243}: Removed the __init__ methods of _json's scanner and encoder.
Misusing them could cause memory leaks or crashes.  Now scanner and
encoder objects are completely initialized in the __new__ methods.

@item 
bpo-30185@footnote{https://bugs.python.org/issue30185}: Avoid KeyboardInterrupt tracebacks in forkserver helper process
when Ctrl-C is received.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Various updates to typing module: add typing.NoReturn type, use
WrapperDescriptorType, minor bug-fixes.  Original PRs by Jim
Fasarakis-Hilliard and Ivan Levkivskyi.

@item 
bpo-30205@footnote{https://bugs.python.org/issue30205}: Fix getsockname() for unbound AF_UNIX sockets on Linux.

@item 
bpo-30070@footnote{https://bugs.python.org/issue30070}: Fixed leaks and crashes in errors handling in the parser
module.

@item 
bpo-30061@footnote{https://bugs.python.org/issue30061}: Fixed crashes in IOBase methods __next__() and readlines() when
readline() or __next__() respectively return non-sizeable object. Fixed
possible other errors caused by not checking results of PyObject_Size(),
PySequence_Size(), or PyMapping_Size().

@item 
bpo-30017@footnote{https://bugs.python.org/issue30017}: Allowed calling the close() method of the zip entry writer
object multiple times.  Writing to a closed writer now always produces a
ValueError.

@item 
bpo-30068@footnote{https://bugs.python.org/issue30068}: _io._IOBase.readlines will check if it's closed first when hint
is present.

@item 
bpo-29694@footnote{https://bugs.python.org/issue29694}: Fixed race condition in pathlib mkdir with flags parents=True.
Patch by Armin Rigo.

@item 
bpo-29692@footnote{https://bugs.python.org/issue29692}: Fixed arbitrary unchaining of RuntimeError exceptions in
contextlib.contextmanager.  Patch by Siddharth Velankar.

@item 
bpo-29998@footnote{https://bugs.python.org/issue29998}: Pickling and copying ImportError now preserves name and path
attributes.

@item 
bpo-29953@footnote{https://bugs.python.org/issue29953}: Fixed memory leaks in the replace() method of datetime and time
objects when pass out of bound fold argument.

@item 
bpo-29942@footnote{https://bugs.python.org/issue29942}: Fix a crash in itertools.chain.from_iterable when encountering
long runs of empty iterables.

@item 
bpo-27863@footnote{https://bugs.python.org/issue27863}: Fixed multiple crashes in ElementTree caused by race conditions
and wrong types.

@item 
bpo-28699@footnote{https://bugs.python.org/issue28699}: Fixed a bug in pools in multiprocessing.pool that raising an
exception at the very first of an iterable may swallow the exception or
make the program hang. Patch by Davin Potts and Xiang Zhang.

@item 
bpo-25803@footnote{https://bugs.python.org/issue25803}: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when
the OS gives priority to errors such as EACCES over EEXIST.

@item 
bpo-29861@footnote{https://bugs.python.org/issue29861}: Release references to tasks, their arguments and their results
as soon as they are finished in multiprocessing.Pool.

@item 
bpo-29884@footnote{https://bugs.python.org/issue29884}: faulthandler: Restore the old sigaltstack during teardown.
Patch by Christophe Zeitouny.

@item 
bpo-25455@footnote{https://bugs.python.org/issue25455}: Fixed crashes in repr of recursive buffered file-like objects.

@item 
bpo-29800@footnote{https://bugs.python.org/issue29800}: Fix crashes in partial.__repr__ if the keys of partial.keywords
are not strings.  Patch by Michael Seifert.

@item 
bpo-29742@footnote{https://bugs.python.org/issue29742}: get_extra_info() raises exception if get called on closed ssl
transport. Patch by Nikolay Kim.

@item 
bpo-8256@footnote{https://bugs.python.org/issue8256}: Fixed possible failing or crashing input() if attributes
"encoding" or "errors" of sys.stdin or sys.stdout are not set or are not
strings.

@item 
bpo-28298@footnote{https://bugs.python.org/issue28298}: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting
big intables (objects that have __int__) as elements.  Patch by Oren
Milman.

@item 
bpo-28231@footnote{https://bugs.python.org/issue28231}: The zipfile module now accepts path-like objects for external
paths.

@item 
bpo-26915@footnote{https://bugs.python.org/issue26915}: index() and count() methods of collections.abc.Sequence now
check identity before checking equality when do comparisons.

@item 
bpo-29615@footnote{https://bugs.python.org/issue29615}: SimpleXMLRPCDispatcher no longer chains KeyError (or any other
exception) to exception(s) raised in the dispatched methods. Patch by Petr
Motejlek.

@item 
bpo-30177@footnote{https://bugs.python.org/issue30177}: path.resolve(strict=False) no longer cuts the path after the
first element not present in the filesystem.  Patch by Antoine Pietri.
@end itemize

@node IDLE<34>,C API<22>,库<38>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id290}@anchor{1095}
@subsubsection IDLE



@itemize -

@item 
bpo-15786@footnote{https://bugs.python.org/issue15786}: Fix several problems with IDLE's autocompletion box. The
following should now work: clicking on selection box items; using the
scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no
longer happen. Patch by Louie Lu.

@item 
bpo-25514@footnote{https://bugs.python.org/issue25514}: Add doc subsubsection about IDLE failure to start. Popup
no-connection message directs users to this section.

@item 
bpo-30642@footnote{https://bugs.python.org/issue30642}: Fix reference leaks in IDLE tests. Patches by Louie Lu and
Terry Jan Reedy.

@item 
bpo-30495@footnote{https://bugs.python.org/issue30495}: Add docstrings for textview.py and use PEP8 names. Patches by
Cheryl Sabella and Terry Jan Reedy.

@item 
bpo-30290@footnote{https://bugs.python.org/issue30290}: Help-about: use pep8 names and add tests. Increase coverage to
100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

@item 
bpo-30303@footnote{https://bugs.python.org/issue30303}: Add _utest option to textview; add new tests. Increase coverage
to 100%. Patches by Louie Lu and Terry Jan Reedy.
@end itemize

@node C API<22>,构建<29>,IDLE<34>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id291}@anchor{1096}
@subsubsection C API



@itemize -

@item 
bpo-27867@footnote{https://bugs.python.org/issue27867}: Function PySlice_GetIndicesEx() no longer replaced with a macro
if Py_LIMITED_API is not set.
@end itemize

@node 构建<29>,文档<31>,C API<22>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id292}@anchor{1097}
@subsubsection 构建



@itemize -

@item 
bpo-29941@footnote{https://bugs.python.org/issue29941}: Add @code{--with-assertions} configure flag to explicitly enable C
@code{assert()} checks. Defaults to off. @code{--with-pydebug} implies
@code{--with-assertions}.

@item 
bpo-28787@footnote{https://bugs.python.org/issue28787}: Fix out-of-tree builds of Python when configured with
@code{--with--dtrace}.

@item 
bpo-29243@footnote{https://bugs.python.org/issue29243}: Prevent unnecessary rebuilding of Python during @code{make test},
@code{make install} and some other make targets when configured with
@code{--enable-optimizations}.

@item 
bpo-23404@footnote{https://bugs.python.org/issue23404}: Don't regenerate generated files based on file modification
time anymore: the action is now explicit. Replace @code{make touch} with
@code{make regen-all}.

@item 
bpo-29643@footnote{https://bugs.python.org/issue29643}: Fix @code{--enable-optimization} didn't work.
@end itemize

@node 文档<31>,工具/示例<21>,构建<29>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id293}@anchor{1098}
@subsubsection 文档



@itemize -

@item 
bpo-30176@footnote{https://bugs.python.org/issue30176}: Add missing attribute related constants in curses
documentation.

@item 
bpo-30052@footnote{https://bugs.python.org/issue30052}: the link targets for @ref{32a,,bytes()} and @ref{32b,,bytearray()} are
now their respective type definitions, rather than the corresponding
builtin function entries. Use @ref{1050,,bytes} and
@ref{1051,,bytearray} to reference the latter. In order to
ensure this and future cross-reference updates are applied automatically,
the daily documentation builds now disable the default output caching
features in Sphinx.

@item 
bpo-26985@footnote{https://bugs.python.org/issue26985}: Add missing info of code object in inspect documentation.
@end itemize

@node 工具/示例<21>,测试<29>,文档<31>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id294}@anchor{1099}
@subsubsection 工具/示例



@itemize -

@item 
bpo-29367@footnote{https://bugs.python.org/issue29367}: python-gdb.py now supports also @code{method-wrapper}
(@code{wrapperobject}) objects.
@end itemize

@node 测试<29>,Windows<29>,工具/示例<21>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id295}@anchor{109a}
@subsubsection 测试



@itemize -

@item 
bpo-30357@footnote{https://bugs.python.org/issue30357}: test_thread: setUp() now uses support.threading_setup() and
support.threading_cleanup() to wait until threads complete to avoid random
side effects on following tests. Initial patch written by Grzegorz
Grzywacz.

@item 
bpo-30197@footnote{https://bugs.python.org/issue30197}: Enhanced functions swap_attr() and swap_item() in the
test.support module. They now work when delete replaced attribute or item
inside the with statement.  The old value of the attribute or item (or
None if it doesn't exist) now will be assigned to the target of the "as"
clause, if there is one.
@end itemize

@node Windows<29>,,测试<29>,Python 3 6 2 rc1
@anchor{whatsnew/changelog id296}@anchor{109b}
@subsubsection Windows



@itemize -

@item 
bpo-30687@footnote{https://bugs.python.org/issue30687}: Locate msbuild.exe on Windows when building rather than
vcvarsall.bat

@item 
bpo-30450@footnote{https://bugs.python.org/issue30450}: The build process on Windows no longer depends on Subversion,
instead pulling external code from GitHub via a Python script.  If Python
3.6 is not found on the system (via @code{py -3.6}), NuGet is used to
download a copy of 32-bit Python.
@end itemize

@node Python 3 6 1 正式版,Python 3 6 1 rc1,Python 3 6 2 rc1,更新日志
@anchor{whatsnew/changelog python-3-6-1-final}@anchor{109c}
@subsection Python 3.6.1 正式版


@emph{发布日期: 2017-03-21}

@menu
* 核心与内置: 核心与内置<36>. 
* 构建: 构建<30>. 

@end menu

@node 核心与内置<36>,构建<30>,,Python 3 6 1 正式版
@anchor{whatsnew/changelog id297}@anchor{109d}
@subsubsection 核心与内置



@itemize -

@item 
bpo-29723@footnote{https://bugs.python.org/issue29723}: The @code{sys.path[0]} initialization change for bpo-29139@footnote{https://bugs.python.org/issue29139} caused
a regression by revealing an inconsistency in how sys.path is initialized
when executing @code{__main__} from a zipfile, directory, or other import
location. The interpreter now consistently avoids ever adding the import
location's parent directory to @code{sys.path}, and ensures no other
@code{sys.path} entries are inadvertently modified when inserting the import
location named on the command line.
@end itemize

@node 构建<30>,,核心与内置<36>,Python 3 6 1 正式版
@anchor{whatsnew/changelog id298}@anchor{109e}
@subsubsection 构建



@itemize -

@item 
bpo-27593@footnote{https://bugs.python.org/issue27593}: fix format of git information used in sys.version

@item 
Fix incompatible comment in python.h
@end itemize

@node Python 3 6 1 rc1,Python 3 6 0 正式版,Python 3 6 1 正式版,更新日志
@anchor{whatsnew/changelog python-3-6-1-release-candidate-1}@anchor{109f}
@subsection Python 3.6.1 rc1


@emph{发布日期: 2017-03-04}

@menu
* 核心与内置: 核心与内置<37>. 
* 库: 库<39>. 
* IDLE: IDLE<35>. 
* Windows: Windows<30>. 
* C API: C API<23>. 
* 文档: 文档<32>. 
* 测试: 测试<30>. 
* 构建: 构建<31>. 

@end menu

@node 核心与内置<37>,库<39>,,Python 3 6 1 rc1
@anchor{whatsnew/changelog id299}@anchor{10a0}
@subsubsection 核心与内置



@itemize -

@item 
bpo-28893@footnote{https://bugs.python.org/issue28893}: Set correct __cause__ for errors about invalid awaitables
returned from __aiter__ and __anext__.

@item 
bpo-29683@footnote{https://bugs.python.org/issue29683}: Fixes to memory allocation in _PyCode_SetExtra.  Patch by Brian
Coleman.

@item 
bpo-29684@footnote{https://bugs.python.org/issue29684}: Fix minor regression of PyEval_CallObjectWithKeywords. It
should raise TypeError when kwargs is not a dict.  But it might cause segv
when args=NULL and kwargs is not a dict.

@item 
bpo-28598@footnote{https://bugs.python.org/issue28598}: Support __rmod__ for subclasses of str being called before
str.__mod__. Patch by Martijn Pieters.

@item 
bpo-29607@footnote{https://bugs.python.org/issue29607}: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by
Matthieu Dartiailh.

@item 
bpo-29602@footnote{https://bugs.python.org/issue29602}: Fix incorrect handling of signed zeros in complex constructor
for complex subclasses and for inputs having a __complex__ method. Patch
by Serhiy Storchaka.

@item 
bpo-29347@footnote{https://bugs.python.org/issue29347}: Fixed possibly dereferencing undefined pointers when creating
weakref objects.

@item 
bpo-29438@footnote{https://bugs.python.org/issue29438}: Fixed use-after-free problem in key sharing dict.

@item 
bpo-29319@footnote{https://bugs.python.org/issue29319}: Prevent RunMainFromImporter overwriting sys.path[0].

@item 
bpo-29337@footnote{https://bugs.python.org/issue29337}: Fixed possible BytesWarning when compare the code objects.
Warnings could be emitted at compile time.

@item 
bpo-29327@footnote{https://bugs.python.org/issue29327}: Fixed a crash when pass the iterable keyword argument to
sorted().

@item 
bpo-29034@footnote{https://bugs.python.org/issue29034}: Fix memory leak and use-after-free in os module
(path_converter).

@item 
bpo-29159@footnote{https://bugs.python.org/issue29159}: Fix regression in bytes(x) when x.__index__() raises Exception.

@item 
bpo-28932@footnote{https://bugs.python.org/issue28932}: Do not include <sys/random.h> if it does not exist.

@item 
bpo-25677@footnote{https://bugs.python.org/issue25677}: Correct the positioning of the syntax error caret for indented
blocks. Based on patch by Michael Layzell.

@item 
bpo-29000@footnote{https://bugs.python.org/issue29000}: Fixed bytes formatting of octals with zero padding in alternate
form.

@item 
bpo-26919@footnote{https://bugs.python.org/issue26919}: On Android, operating system data is now always encoded/decoded
to/from UTF-8, instead of the locale encoding to avoid inconsistencies
with os.fsencode() and os.fsdecode() which are already using UTF-8.

@item 
bpo-28991@footnote{https://bugs.python.org/issue28991}: functools.lru_cache() was susceptible to an obscure reentrancy
bug triggerable by a monkey-patched len() function.

@item 
bpo-28739@footnote{https://bugs.python.org/issue28739}: f-string expressions are no longer accepted as docstrings and
by ast.literal_eval() even if they do not include expressions.

@item 
bpo-28512@footnote{https://bugs.python.org/issue28512}: Fixed setting the offset attribute of SyntaxError by
PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

@item 
bpo-28918@footnote{https://bugs.python.org/issue28918}: Fix the cross compilation of xxlimited when Python has been
built with Py_DEBUG defined.

@item 
bpo-28731@footnote{https://bugs.python.org/issue28731}: Optimize _PyDict_NewPresized() to create correct size dict.
Improve speed of dict literal with constant keys up to 30%.
@end itemize

@node 库<39>,IDLE<35>,核心与内置<37>,Python 3 6 1 rc1
@anchor{whatsnew/changelog id300}@anchor{10a1}
@subsubsection 库



@itemize -

@item 
bpo-29169@footnote{https://bugs.python.org/issue29169}: Update zlib to 1.2.11.

@item 
bpo-29623@footnote{https://bugs.python.org/issue29623}: Allow use of path-like object as a single argument in
ConfigParser.read(). Patch by David Ellis.

@item 
bpo-28963@footnote{https://bugs.python.org/issue28963}: Fix out of bound iteration in
asyncio.Future.remove_done_callback implemented in C.

@item 
bpo-29704@footnote{https://bugs.python.org/issue29704}: asyncio.subprocess.SubprocessStreamProtocol no longer closes
before all pipes are closed.

@item 
bpo-29271@footnote{https://bugs.python.org/issue29271}: Fix Task.current_task and Task.all_tasks implemented in C to
accept None argument as their pure Python implementation.

@item 
bpo-29703@footnote{https://bugs.python.org/issue29703}: Fix asyncio to support instantiation of new event loops in
child processes.

@item 
bpo-29376@footnote{https://bugs.python.org/issue29376}: Fix assertion error in threading._DummyThread.is_alive().

@item 
bpo-28624@footnote{https://bugs.python.org/issue28624}: Add a test that checks that cwd parameter of Popen() accepts
PathLike objects.  Patch by Sayan Chowdhury.

@item 
bpo-28518@footnote{https://bugs.python.org/issue28518}: Start a transaction implicitly before a DML statement. Patch by
Aviv Palivoda.

@item 
bpo-29532@footnote{https://bugs.python.org/issue29532}: Altering a kwarg dictionary passed to functools.partial() no
longer affects a partial object after creation.

@item 
bpo-29110@footnote{https://bugs.python.org/issue29110}: Fix file object leak in aifc.open() when file is given as a
filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Various updates to typing module: typing.Counter,
typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle
Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

@item 
bpo-29100@footnote{https://bugs.python.org/issue29100}: Fix datetime.fromtimestamp() regression introduced in Python
3.6.0: check minimum and maximum years.

@item 
bpo-29519@footnote{https://bugs.python.org/issue29519}: Fix weakref spewing exceptions during interpreter shutdown when
used with a rare combination of multiprocessing and custom codecs.

@item 
bpo-29416@footnote{https://bugs.python.org/issue29416}: Prevent infinite loop in pathlib.Path.mkdir

@item 
bpo-29444@footnote{https://bugs.python.org/issue29444}: Fixed out-of-bounds buffer access in the group() method of the
match object. Based on patch by WGH.

@item 
bpo-29335@footnote{https://bugs.python.org/issue29335}: Fix subprocess.Popen.wait() when the child process has exited
to a stopped instead of terminated state (ex: when under ptrace).

@item 
bpo-29290@footnote{https://bugs.python.org/issue29290}: Fix a regression in argparse that help messages would wrap at
non-breaking spaces.

@item 
bpo-28735@footnote{https://bugs.python.org/issue28735}: Fixed the comparison of mock.MagickMock with mock.ANY.

@item 
bpo-29316@footnote{https://bugs.python.org/issue29316}: Restore the provisional status of typing module, add
corresponding note to documentation. Patch by Ivan L.

@item 
bpo-29219@footnote{https://bugs.python.org/issue29219}: Fixed infinite recursion in the repr of uninitialized
ctypes.CDLL instances.

@item 
bpo-29011@footnote{https://bugs.python.org/issue29011}: Fix an important omission by adding Deque to the typing module.

@item 
bpo-28969@footnote{https://bugs.python.org/issue28969}: Fixed race condition in C implementation of
functools.lru_cache. KeyError could be raised when cached function with
full cache was simultaneously called from different threads with the same
uncached arguments.

@item 
bpo-29142@footnote{https://bugs.python.org/issue29142}: In urllib.request, suffixes in no_proxy environment variable
with leading dots could match related hostnames again (e.g. .b.c matches
a.b.c). Patch by Milan Oberkirch.

@item 
bpo-28961@footnote{https://bugs.python.org/issue28961}: Fix unittest.mock._Call helper: don't ignore the name parameter
anymore. Patch written by Jiajun Huang.

@item 
bpo-29203@footnote{https://bugs.python.org/issue29203}: functools.lru_cache() now respects 
@geindex Python 提高建议; PEP 468
PEP 468@footnote{https://www.python.org/dev/peps/pep-0468} and preserves the
order of keyword arguments.  f(a=1, b=2) is now cached separately from
f(b=2, a=1) since both calls could potentially give different results.

@item 
bpo-15812@footnote{https://bugs.python.org/issue15812}: inspect.getframeinfo() now correctly shows the first line of a
context. Patch by Sam Breese.

@item 
bpo-29094@footnote{https://bugs.python.org/issue29094}: Offsets in a ZIP file created with extern file object and modes
"w" and "x" now are relative to the start of the file.

@item 
bpo-29085@footnote{https://bugs.python.org/issue29085}: Allow random.Random.seed() to use high quality OS randomness
rather than the pid and time.

@item 
bpo-29061@footnote{https://bugs.python.org/issue29061}: Fixed bug in secrets.randbelow() which would hang when given a
negative input.  Patch by Brendan Donegan.

@item 
bpo-29079@footnote{https://bugs.python.org/issue29079}: Prevent infinite loop in pathlib.resolve() on Windows

@item 
bpo-13051@footnote{https://bugs.python.org/issue13051}: Fixed recursion errors in large or resized
curses.textpad.Textbox.  Based on patch by Tycho Andersen.

@item 
bpo-29119@footnote{https://bugs.python.org/issue29119}: Fix weakrefs in the pure python version of
collections.OrderedDict move_to_end() method. Contributed by Andra
Bogildea.

@item 
bpo-9770@footnote{https://bugs.python.org/issue9770}: curses.ascii predicates now work correctly with negative
integers.

@item 
bpo-28427@footnote{https://bugs.python.org/issue28427}: old keys should not remove new values from WeakValueDictionary
when collecting from another thread.

@item 
bpo-28923@footnote{https://bugs.python.org/issue28923}: Remove editor artifacts from Tix.py.

@item 
bpo-29055@footnote{https://bugs.python.org/issue29055}: Neaten-up empty population error on random.choice() by
suppressing the upstream exception.

@item 
bpo-28871@footnote{https://bugs.python.org/issue28871}: Fixed a crash when deallocate deep ElementTree.

@item 
bpo-19542@footnote{https://bugs.python.org/issue19542}: Fix bugs in WeakValueDictionary.setdefault() and
WeakValueDictionary.pop() when a GC collection happens in another thread.

@item 
bpo-20191@footnote{https://bugs.python.org/issue20191}: Fixed a crash in resource.prlimit() when passing a sequence
that doesn't own its elements as limits.

@item 
bpo-28779@footnote{https://bugs.python.org/issue28779}: multiprocessing.set_forkserver_preload() would crash the
forkserver process if a preloaded module instantiated some multiprocessing
objects such as locks.

@item 
bpo-28847@footnote{https://bugs.python.org/issue28847}: dbm.dumb now supports reading read-only files and no longer
writes the index file when it is not changed.

@item 
bpo-26937@footnote{https://bugs.python.org/issue26937}: The chown() method of the tarfile.TarFile class does not fail
now when the grp module cannot be imported, as for example on Android
platforms.
@end itemize

@node IDLE<35>,Windows<30>,库<39>,Python 3 6 1 rc1
@anchor{whatsnew/changelog id301}@anchor{10a2}
@subsubsection IDLE



@itemize -

@item 
bpo-29071@footnote{https://bugs.python.org/issue29071}: IDLE colors f-string prefixes (but not invalid ur prefixes).

@item 
bpo-28572@footnote{https://bugs.python.org/issue28572}: Add 10% to coverage of IDLE's test_configdialog. Update and
augment description of the configuration system.
@end itemize

@node Windows<30>,C API<23>,IDLE<35>,Python 3 6 1 rc1
@anchor{whatsnew/changelog id302}@anchor{10a3}
@subsubsection Windows



@itemize -

@item 
bpo-29579@footnote{https://bugs.python.org/issue29579}: Removes readme.txt from the installer

@item 
bpo-29326@footnote{https://bugs.python.org/issue29326}: Ignores blank lines in ._pth files (Patch by Alexey Izbyshev)

@item 
bpo-28164@footnote{https://bugs.python.org/issue28164}: Correctly handle special console filenames (patch by Eryk Sun)

@item 
bpo-29409@footnote{https://bugs.python.org/issue29409}: Implement 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529} for io.FileIO (Patch by Eryk Sun)

@item 
bpo-29392@footnote{https://bugs.python.org/issue29392}: Prevent crash when passing invalid arguments into msvcrt
module.

@item 
bpo-25778@footnote{https://bugs.python.org/issue25778}: winreg does not truncate string correctly (Patch by Eryk Sun)

@item 
bpo-28896@footnote{https://bugs.python.org/issue28896}: Deprecate WindowsRegistryFinder and disable it by default.
@end itemize

@node C API<23>,文档<32>,Windows<30>,Python 3 6 1 rc1
@anchor{whatsnew/changelog id303}@anchor{10a4}
@subsubsection C API



@itemize -

@item 
bpo-27867@footnote{https://bugs.python.org/issue27867}: Function PySlice_GetIndicesEx() is replaced with a macro if
Py_LIMITED_API is not set or set to the value between 0x03050400 and
0x03060000 (not including) or 0x03060100 or higher.

@item 
bpo-29083@footnote{https://bugs.python.org/issue29083}: Fixed the declaration of some public API functions.
PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in
limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and
Py_BuildValue() were not available in limited API of version < 3.3 when
PY_SSIZE_T_CLEAN is defined.

@item 
bpo-29058@footnote{https://bugs.python.org/issue29058}: All stable API extensions added after Python 3.2 are now
available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of
the minimum Python version supporting this API.
@end itemize

@node 文档<32>,测试<30>,C API<23>,Python 3 6 1 rc1
@anchor{whatsnew/changelog id304}@anchor{10a5}
@subsubsection 文档



@itemize -

@item 
bpo-28929@footnote{https://bugs.python.org/issue28929}: Link the documentation to its source file on GitHub.

@item 
bpo-25008@footnote{https://bugs.python.org/issue25008}: Document smtpd.py as effectively deprecated and add a pointer
to aiosmtpd, a third-party asyncio-based replacement.

@item 
bpo-26355@footnote{https://bugs.python.org/issue26355}: Add canonical header link on each page to corresponding major
version of the documentation. Patch by Matthias Bussonnier.

@item 
bpo-29349@footnote{https://bugs.python.org/issue29349}: Fix Python 2 syntax in code for building the documentation.
@end itemize

@node 测试<30>,构建<31>,文档<32>,Python 3 6 1 rc1
@anchor{whatsnew/changelog id305}@anchor{10a6}
@subsubsection 测试



@itemize -

@item 
bpo-28087@footnote{https://bugs.python.org/issue28087}: Skip test_asyncore and test_eintr poll failures on macOS. Skip
some tests of select.poll when running on macOS due to unresolved issues
with the underlying system poll function on some macOS versions.

@item 
bpo-29571@footnote{https://bugs.python.org/issue29571}: to match the behaviour of the @code{re.LOCALE} flag,
test_re.test_locale_flag now uses @code{locale.getpreferredencoding(False)}
to determine the candidate encoding for the test regex (allowing it to
correctly skip the test when the default locale encoding is a multi-byte
encoding)

@item 
bpo-28950@footnote{https://bugs.python.org/issue28950}: Disallow -j0 to be combined with -T/-l in regrtest command line
arguments.

@item 
bpo-28683@footnote{https://bugs.python.org/issue28683}: Fix the tests that bind() a unix socket and raise
PermissionError on Android for a non-root user.

@item 
bpo-26939@footnote{https://bugs.python.org/issue26939}: Add the support.setswitchinterval() function to fix
test_functools hanging on the Android armv7 qemu emulator.
@end itemize

@node 构建<31>,,测试<30>,Python 3 6 1 rc1
@anchor{whatsnew/changelog id306}@anchor{10a7}
@subsubsection 构建



@itemize -

@item 
bpo-27593@footnote{https://bugs.python.org/issue27593}: sys.version and the platform module python_build(),
python_branch(), and python_revision() functions now use git information
rather than hg when building from a repo.

@item 
bpo-29572@footnote{https://bugs.python.org/issue29572}: 更新Windows 构建和OS X安装程序以使用OpenSSL 1.0.2k。

@item 
bpo-26851@footnote{https://bugs.python.org/issue26851}: Set Android compilation and link flags.

@item 
bpo-28768@footnote{https://bugs.python.org/issue28768}: Fix implicit declaration of function _setmode. Patch by
Masayuki Yamamoto

@item 
bpo-29080@footnote{https://bugs.python.org/issue29080}: Removes hard dependency on hg.exe from PCBuild/build.bat

@item 
bpo-23903@footnote{https://bugs.python.org/issue23903}: Added missed names to PC/python3.def.

@item 
bpo-28762@footnote{https://bugs.python.org/issue28762}: lockf() is available on Android API level 24, but the F_LOCK
macro is not defined in android-ndk-r13.

@item 
bpo-28538@footnote{https://bugs.python.org/issue28538}: Fix the compilation error that occurs because if_nameindex() is
available on Android API level 24, but the if_nameindex structure is not
defined.

@item 
bpo-20211@footnote{https://bugs.python.org/issue20211}: Do not add the directory for installing C header files and the
directory for installing object code libraries to the cross compilation
search paths. Original patch by Thomas Petazzoni.

@item 
bpo-28849@footnote{https://bugs.python.org/issue28849}: Do not define sys.implementation._multiarch on Android.
@end itemize

@node Python 3 6 0 正式版,Python 3 6 0 rc2,Python 3 6 1 rc1,更新日志
@anchor{whatsnew/changelog python-3-6-0-final}@anchor{10a8}
@subsection Python 3.6.0 正式版


@emph{发布日期: 2016-12-23}

自rc2起没有更改

@node Python 3 6 0 rc2,Python 3 6 0 rc1,Python 3 6 0 正式版,更新日志
@anchor{whatsnew/changelog python-3-6-0-release-candidate-2}@anchor{10a9}
@subsection Python 3.6.0 rc2


@emph{发布日期: 2016-12-16}

@menu
* 核心与内置: 核心与内置<38>. 
* 工具/示例: 工具/示例<22>. 
* Windows: Windows<31>. 
* 构建: 构建<32>. 

@end menu

@node 核心与内置<38>,工具/示例<22>,,Python 3 6 0 rc2
@anchor{whatsnew/changelog id307}@anchor{10aa}
@subsubsection 核心与内置



@itemize -

@item 
bpo-28147@footnote{https://bugs.python.org/issue28147}: Fix a memory leak in split-table dictionaries: setattr() must
not convert combined table into split table. Patch written by INADA Naoki.

@item 
bpo-28990@footnote{https://bugs.python.org/issue28990}: Fix asyncio SSL hanging if connection is closed before
handshake is completed. (Patch by HoHo-Ho)
@end itemize

@node 工具/示例<22>,Windows<31>,核心与内置<38>,Python 3 6 0 rc2
@anchor{whatsnew/changelog id308}@anchor{10ab}
@subsubsection 工具/示例



@itemize -

@item 
bpo-28770@footnote{https://bugs.python.org/issue28770}: Fix python-gdb.py for fastcalls.
@end itemize

@node Windows<31>,构建<32>,工具/示例<22>,Python 3 6 0 rc2
@anchor{whatsnew/changelog id309}@anchor{10ac}
@subsubsection Windows



@itemize -

@item 
bpo-28896@footnote{https://bugs.python.org/issue28896}: Deprecate WindowsRegistryFinder.
@end itemize

@node 构建<32>,,Windows<31>,Python 3 6 0 rc2
@anchor{whatsnew/changelog id310}@anchor{10ad}
@subsubsection 构建



@itemize -

@item 
bpo-28898@footnote{https://bugs.python.org/issue28898}: Prevent gdb build errors due to HAVE_LONG_LONG redefinition.
@end itemize

@node Python 3 6 0 rc1,Python 3 6 0 beta 4,Python 3 6 0 rc2,更新日志
@anchor{whatsnew/changelog python-3-6-0-release-candidate-1}@anchor{10ae}
@subsection Python 3.6.0 rc1


@emph{发布日期: 2016-12-06}

@menu
* 核心与内置: 核心与内置<39>. 
* 库: 库<40>. 
* C API: C API<24>. 
* 文档: 文档<33>. 
* 工具/示例: 工具/示例<23>. 

@end menu

@node 核心与内置<39>,库<40>,,Python 3 6 0 rc1
@anchor{whatsnew/changelog id311}@anchor{10af}
@subsubsection 核心与内置



@itemize -

@item 
bpo-23722@footnote{https://bugs.python.org/issue23722}: Rather than silently producing a class that doesn't support
zero-argument @code{super()} in methods, failing to pass the new
@code{__classcell__} namespace entry up to @code{type.__new__} now results in a
@code{DeprecationWarning} and a class that supports zero-argument
@code{super()}.

@item 
bpo-28797@footnote{https://bugs.python.org/issue28797}: Modifying the class __dict__ inside the __set_name__ method of
a descriptor that is used inside that class no longer prevents calling the
__set_name__ method of other descriptors.

@item 
bpo-28782@footnote{https://bugs.python.org/issue28782}: Fix a bug in the implementation @code{yield from} when checking if
the next instruction is YIELD_FROM. Regression introduced by WORDCODE
(bpo-26647@footnote{https://bugs.python.org/issue26647}).
@end itemize

@node 库<40>,C API<24>,核心与内置<39>,Python 3 6 0 rc1
@anchor{whatsnew/changelog id312}@anchor{10b0}
@subsubsection 库



@itemize -

@item 
bpo-27030@footnote{https://bugs.python.org/issue27030}: Unknown escapes in re.sub() replacement template are allowed
again.  But they still are deprecated and will be disabled in 3.7.

@item 
bpo-28835@footnote{https://bugs.python.org/issue28835}: Fix a regression introduced in warnings.catch_warnings(): call
warnings.showwarning() if it was overridden inside the context manager.

@item 
bpo-27172@footnote{https://bugs.python.org/issue27172}: To assist with upgrades from 2.7, the previously documented
deprecation of @code{inspect.getfullargspec()} has been reversed. This
decision may be revisited again after the Python 2.7 branch is no longer
officially supported.

@item 
bpo-26273@footnote{https://bugs.python.org/issue26273}: Add new @code{socket.TCP_CONGESTION} (Linux 2.6.13) and
@code{socket.TCP_USER_TIMEOUT} (Linux 2.6.37) constants. Patch written by
Omar Sandoval.

@item 
bpo-24142@footnote{https://bugs.python.org/issue24142}: Reading a corrupt config file left configparser in an invalid
state. Original patch by Florian Höch.

@item 
bpo-28843@footnote{https://bugs.python.org/issue28843}: Fix asyncio C Task to handle exceptions __traceback__.
@end itemize

@node C API<24>,文档<33>,库<40>,Python 3 6 0 rc1
@anchor{whatsnew/changelog id313}@anchor{10b1}
@subsubsection C API



@itemize -

@item 
bpo-28808@footnote{https://bugs.python.org/issue28808}: PyUnicode_CompareWithASCIIString() now never raises exceptions.
@end itemize

@node 文档<33>,工具/示例<23>,C API<24>,Python 3 6 0 rc1
@anchor{whatsnew/changelog id314}@anchor{10b2}
@subsubsection 文档



@itemize -

@item 
bpo-23722@footnote{https://bugs.python.org/issue23722}: The data model reference and the porting section in the What's
New guide now cover the additional @code{__classcell__} handling needed for
custom metaclasses to fully support 
@geindex Python 提高建议; PEP 487
PEP 487@footnote{https://www.python.org/dev/peps/pep-0487} and zero-argument
@code{super()}.
@end itemize

@node 工具/示例<23>,,文档<33>,Python 3 6 0 rc1
@anchor{whatsnew/changelog id315}@anchor{10b3}
@subsubsection 工具/示例



@itemize -

@item 
bpo-28023@footnote{https://bugs.python.org/issue28023}: Fix python-gdb.py didn't support new dict implementation.
@end itemize

@node Python 3 6 0 beta 4,Python 3 6 0 beta 3,Python 3 6 0 rc1,更新日志
@anchor{whatsnew/changelog python-3-6-0-beta-4}@anchor{10b4}
@subsection Python 3.6.0 beta 4


@emph{发布日期: 2016-11-21}

@menu
* 核心与内置: 核心与内置<40>. 
* 库: 库<41>. 
* 文档: 文档<34>. 
* 测试: 测试<31>. 
* 构建: 构建<33>. 

@end menu

@node 核心与内置<40>,库<41>,,Python 3 6 0 beta 4
@anchor{whatsnew/changelog id316}@anchor{10b5}
@subsubsection 核心与内置



@itemize -

@item 
bpo-28532@footnote{https://bugs.python.org/issue28532}: Show sys.version when -V option is supplied twice.

@item 
bpo-27100@footnote{https://bugs.python.org/issue27100}: The with-statement now checks for __enter__ before it checks
for __exit__. This gives less confusing error messages when both methods
are missing. Patch by Jonathan Ellington.

@item 
bpo-28746@footnote{https://bugs.python.org/issue28746}: Fix the set_inheritable() file descriptor method on platforms
that do not have the ioctl FIOCLEX and FIONCLEX commands.

@item 
bpo-26920@footnote{https://bugs.python.org/issue26920}: Fix not getting the locale's charset upon initializing the
interpreter, on platforms that do not have langinfo.

@item 
bpo-28648@footnote{https://bugs.python.org/issue28648}: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X
when decode astral characters.  Patch by Xiang Zhang.

@item 
bpo-19398@footnote{https://bugs.python.org/issue19398}: Extra slash no longer added to sys.path components in case of
empty compile-time PYTHONPATH components.

@item 
bpo-28665@footnote{https://bugs.python.org/issue28665}: Improve speed of the STORE_DEREF opcode by 40%.

@item 
bpo-28583@footnote{https://bugs.python.org/issue28583}: PyDict_SetDefault didn't combine split table when needed. Patch
by Xiang Zhang.

@item 
bpo-27243@footnote{https://bugs.python.org/issue27243}: Change PendingDeprecationWarning -> DeprecationWarning. As it
was agreed in the issue, __aiter__ returning an awaitable should result in
PendingDeprecationWarning in 3.5 and in DeprecationWarning in 3.6.

@item 
bpo-26182@footnote{https://bugs.python.org/issue26182}: Fix a refleak in code that raises DeprecationWarning.

@item 
bpo-28721@footnote{https://bugs.python.org/issue28721}: Fix asynchronous generators aclose() and athrow() to handle
StopAsyncIteration propagation properly.
@end itemize

@node 库<41>,文档<34>,核心与内置<40>,Python 3 6 0 beta 4
@anchor{whatsnew/changelog id317}@anchor{10b6}
@subsubsection 库



@itemize -

@item 
bpo-28752@footnote{https://bugs.python.org/issue28752}: Restored the __reduce__() methods of datetime objects.

@item 
bpo-28727@footnote{https://bugs.python.org/issue28727}: Regular expression patterns, _sre.SRE_Pattern objects created
by re.compile(), become comparable (only x==y and x!=y operators). This
change should fix the bpo-18383@footnote{https://bugs.python.org/issue18383}: don't duplicate warning filters when
the warnings module is reloaded (thing usually only done in unit tests).

@item 
bpo-20572@footnote{https://bugs.python.org/issue20572}: The subprocess.Popen.wait method's undocumented endtime
parameter now raises a DeprecationWarning.

@item 
bpo-25659@footnote{https://bugs.python.org/issue25659}: In ctypes, prevent a crash calling the from_buffer() and
from_buffer_copy() methods on abstract classes like Array.

@item 
bpo-19717@footnote{https://bugs.python.org/issue19717}: Makes Path.resolve() succeed on paths that do not exist. Patch
by Vajrasky Kok

@item 
bpo-28563@footnote{https://bugs.python.org/issue28563}: Fixed possible DoS and arbitrary code execution when handle
plural form selections in the gettext module.  The expression parser now
supports exact syntax supported by GNU gettext.

@item 
bpo-28387@footnote{https://bugs.python.org/issue28387}: Fixed possible crash in _io.TextIOWrapper deallocator when the
garbage collector is invoked in other thread.  Based on patch by Sebastian
Cufre.

@item 
bpo-28600@footnote{https://bugs.python.org/issue28600}: Optimize loop.call_soon.

@item 
bpo-28613@footnote{https://bugs.python.org/issue28613}: Fix get_event_loop() return the current loop if called from
coroutines/callbacks.

@item 
bpo-28634@footnote{https://bugs.python.org/issue28634}: Fix asyncio.isfuture() to support unittest.Mock.

@item 
bpo-26081@footnote{https://bugs.python.org/issue26081}: Fix refleak in _asyncio.Future.__iter__().throw.

@item 
bpo-28639@footnote{https://bugs.python.org/issue28639}: Fix inspect.isawaitable to always return bool Patch by Justin
Mayfield.

@item 
bpo-28652@footnote{https://bugs.python.org/issue28652}: Make loop methods reject socket kinds they do not support.

@item 
bpo-28653@footnote{https://bugs.python.org/issue28653}: Fix a refleak in functools.lru_cache.

@item 
bpo-28703@footnote{https://bugs.python.org/issue28703}: Fix asyncio.iscoroutinefunction to handle Mock objects.

@item 
bpo-28704@footnote{https://bugs.python.org/issue28704}: Fix create_unix_server to support Path-like objects (PEP 519).

@item 
bpo-28720@footnote{https://bugs.python.org/issue28720}: Add collections.abc.AsyncGenerator.
@end itemize

@node 文档<34>,测试<31>,库<41>,Python 3 6 0 beta 4
@anchor{whatsnew/changelog id318}@anchor{10b7}
@subsubsection 文档



@itemize -

@item 
bpo-28513@footnote{https://bugs.python.org/issue28513}: Documented command-line interface of zipfile.
@end itemize

@node 测试<31>,构建<33>,文档<34>,Python 3 6 0 beta 4
@anchor{whatsnew/changelog id319}@anchor{10b8}
@subsubsection 测试



@itemize -

@item 
bpo-28666@footnote{https://bugs.python.org/issue28666}: Now test.support.rmtree is able to remove unwritable or
unreadable directories.

@item 
bpo-23839@footnote{https://bugs.python.org/issue23839}: Various caches now are cleared before running every test file.
@end itemize

@node 构建<33>,,测试<31>,Python 3 6 0 beta 4
@anchor{whatsnew/changelog id320}@anchor{10b9}
@subsubsection 构建



@itemize -

@item 
bpo-10656@footnote{https://bugs.python.org/issue10656}: Fix out-of-tree building on AIX.  Patch by Tristan Carel and
Michael Haubenwallner.

@item 
bpo-26359@footnote{https://bugs.python.org/issue26359}: Rename --with-optimiations to --enable-optimizations.

@item 
bpo-28676@footnote{https://bugs.python.org/issue28676}: Prevent missing 'getentropy' declaration warning on macOS.
Patch by Gareth Rees.
@end itemize

@node Python 3 6 0 beta 3,Python 3 6 0 beta 2,Python 3 6 0 beta 4,更新日志
@anchor{whatsnew/changelog python-3-6-0-beta-3}@anchor{10ba}
@subsection Python 3.6.0 beta 3


@emph{发布日期: 2016-10-31}

@menu
* 核心与内置: 核心与内置<41>. 
* 库: 库<42>. 
* Windows: Windows<32>. 
* 构建: 构建<34>. 
* 测试: 测试<32>. 

@end menu

@node 核心与内置<41>,库<42>,,Python 3 6 0 beta 3
@anchor{whatsnew/changelog id321}@anchor{10bb}
@subsubsection 核心与内置



@itemize -

@item 
bpo-28128@footnote{https://bugs.python.org/issue28128}: Deprecation warning for invalid str and byte escape sequences
now prints better information about where the error occurs. Patch by
Serhiy Storchaka and Eric Smith.

@item 
bpo-28509@footnote{https://bugs.python.org/issue28509}: dict.update() no longer allocate unnecessary large memory.

@item 
bpo-28426@footnote{https://bugs.python.org/issue28426}: Fixed potential crash in PyUnicode_AsDecodedObject() in debug
build.

@item 
bpo-28517@footnote{https://bugs.python.org/issue28517}: Fixed of-by-one error in the peephole optimizer that caused
keeping unreachable code.

@item 
bpo-28214@footnote{https://bugs.python.org/issue28214}: Improved exception reporting for problematic __set_name__
attributes.

@item 
bpo-23782@footnote{https://bugs.python.org/issue23782}: Fixed possible memory leak in _PyTraceback_Add() and exception
loss in PyTraceBack_Here().

@item 
bpo-28471@footnote{https://bugs.python.org/issue28471}: Fix "Python memory allocator called without holding the GIL"
crash in socket.setblocking.
@end itemize

@node 库<42>,Windows<32>,核心与内置<41>,Python 3 6 0 beta 3
@anchor{whatsnew/changelog id322}@anchor{10bc}
@subsubsection 库



@itemize -

@item 
bpo-27517@footnote{https://bugs.python.org/issue27517}: LZMA compressor and decompressor no longer raise exceptions if
given empty data twice.  Patch by Benjamin Fogle.

@item 
bpo-28549@footnote{https://bugs.python.org/issue28549}: Fixed segfault in curses's addch() with ncurses6.

@item 
bpo-28449@footnote{https://bugs.python.org/issue28449}: tarfile.open() with mode "r" or "r:" now tries to open a tar
file with compression before trying to open it without compression.
Otherwise it had 50% chance failed with ignore_zeros=True.

@item 
bpo-23262@footnote{https://bugs.python.org/issue23262}: The webbrowser module now supports Firefox 36+ and derived
browsers.  Based on patch by Oleg Broytman.

@item 
bpo-27939@footnote{https://bugs.python.org/issue27939}: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
by representing the scale as float value internally in Tk.  tkinter.IntVar
now works if float value is set to underlying Tk variable.

@item 
bpo-18844@footnote{https://bugs.python.org/issue18844}: The various ways of specifying weights for random.choices() now
produce the same result sequences.

@item 
bpo-28255@footnote{https://bugs.python.org/issue28255}: calendar.TextCalendar().prmonth() no longer prints a space at
the start of new line after printing a month's calendar.  Patch by Xiang
Zhang.

@item 
bpo-20491@footnote{https://bugs.python.org/issue20491}: The textwrap.TextWrapper class now honors non-breaking spaces.
Based on patch by Kaarle Ritvanen.

@item 
bpo-28353@footnote{https://bugs.python.org/issue28353}: os.fwalk() no longer fails on broken links.

@item 
bpo-28430@footnote{https://bugs.python.org/issue28430}: Fix iterator of C implemented asyncio.Future doesn't accept
non-None value is passed to it.send(val).

@item 
bpo-27025@footnote{https://bugs.python.org/issue27025}: Generated names for Tkinter widgets now start by the "!" prefix
for readability.

@item 
bpo-25464@footnote{https://bugs.python.org/issue25464}: Fixed HList.header_exists() in tkinter.tix module by addin a
workaround to Tix library bug.

@item 
bpo-28488@footnote{https://bugs.python.org/issue28488}: shutil.make_archive() no longer adds entry "./" to ZIP archive.

@item 
bpo-25953@footnote{https://bugs.python.org/issue25953}: re.sub() now raises an error for invalid numerical group
reference in replacement template even if the pattern is not found in the
string.  Error message for invalid group reference now includes the group
index and the position of the reference. Based on patch by SilentGhost.

@item 
bpo-18219@footnote{https://bugs.python.org/issue18219}: Optimize csv.DictWriter for large number of columns. Patch by
Mariatta Wijaya.

@item 
bpo-28448@footnote{https://bugs.python.org/issue28448}: Fix C implemented asyncio.Future didn't work on Windows.

@item 
bpo-28480@footnote{https://bugs.python.org/issue28480}: Fix error building socket module when multithreading is
disabled.

@item 
bpo-24452@footnote{https://bugs.python.org/issue24452}: Make webbrowser support Chrome on Mac OS X.

@item 
bpo-20766@footnote{https://bugs.python.org/issue20766}: Fix references leaked by pdb in the handling of SIGINT
handlers.

@item 
bpo-28492@footnote{https://bugs.python.org/issue28492}: Fix how StopIteration exception is raised in _asyncio.Future.

@item 
bpo-28500@footnote{https://bugs.python.org/issue28500}: Fix asyncio to handle async gens GC from another thread.

@item 
bpo-26923@footnote{https://bugs.python.org/issue26923}: Fix asyncio.Gather to refuse being cancelled once all children
are done. Patch by Johannes Ebke.

@item 
bpo-26796@footnote{https://bugs.python.org/issue26796}: Don't configure the number of workers for default threadpool
executor. Initial patch by Hans Lawrenz.

@item 
bpo-28544@footnote{https://bugs.python.org/issue28544}: Implement asyncio.Task in C.
@end itemize

@node Windows<32>,构建<34>,库<42>,Python 3 6 0 beta 3
@anchor{whatsnew/changelog id323}@anchor{10bd}
@subsubsection Windows



@itemize -

@item 
bpo-28522@footnote{https://bugs.python.org/issue28522}: Fixes mishandled buffer reallocation in getpathp.c
@end itemize

@node 构建<34>,测试<32>,Windows<32>,Python 3 6 0 beta 3
@anchor{whatsnew/changelog id324}@anchor{10be}
@subsubsection 构建



@itemize -

@item 
bpo-28444@footnote{https://bugs.python.org/issue28444}: Fix missing extensions modules when cross compiling.

@item 
bpo-28208@footnote{https://bugs.python.org/issue28208}: 更新Windows 构建和OS X 安装程序以使用SQLite 3.14.2.

@item 
bpo-28248@footnote{https://bugs.python.org/issue28248}: 更新Windows 构建和OS X安装程序以使用OpenSSL 1.0.2j.
@end itemize

@node 测试<32>,,构建<34>,Python 3 6 0 beta 3
@anchor{whatsnew/changelog id325}@anchor{10bf}
@subsubsection 测试



@itemize -

@item 
bpo-26944@footnote{https://bugs.python.org/issue26944}: Fix test_posix for Android where 'id -G' is entirely wrong or
missing the effective gid.

@item 
bpo-28409@footnote{https://bugs.python.org/issue28409}: regrtest: fix the parser of command line arguments.
@end itemize

@node Python 3 6 0 beta 2,Python 3 6 0 beta 1,Python 3 6 0 beta 3,更新日志
@anchor{whatsnew/changelog python-3-6-0-beta-2}@anchor{10c0}
@subsection Python 3.6.0 beta 2


@emph{发布日期: 2016-10-10}

@menu
* 核心与内置: 核心与内置<42>. 
* 库: 库<43>. 
* Windows: Windows<33>. 
* C API: C API<25>. 
* 构建: 构建<35>. 
* 测试: 测试<33>. 

@end menu

@node 核心与内置<42>,库<43>,,Python 3 6 0 beta 2
@anchor{whatsnew/changelog id326}@anchor{10c1}
@subsubsection 核心与内置



@itemize -

@item 
bpo-28183@footnote{https://bugs.python.org/issue28183}: Optimize and cleanup dict iteration.

@item 
bpo-26081@footnote{https://bugs.python.org/issue26081}: Added C implementation of asyncio.Future. Original patch by
Yury Selivanov.

@item 
bpo-28379@footnote{https://bugs.python.org/issue28379}: Added sanity checks and tests for PyUnicode_CopyCharacters().
Patch by Xiang Zhang.

@item 
bpo-28376@footnote{https://bugs.python.org/issue28376}: The type of long range iterator is now registered as Iterator.
Patch by Oren Milman.

@item 
bpo-28376@footnote{https://bugs.python.org/issue28376}: Creating instances of range_iterator by calling range_iterator
type now is deprecated.  Patch by Oren Milman.

@item 
bpo-28376@footnote{https://bugs.python.org/issue28376}: The constructor of range_iterator now checks that step is not
0. Patch by Oren Milman.

@item 
bpo-26906@footnote{https://bugs.python.org/issue26906}: Resolving special methods of uninitialized type now causes
implicit initialization of the type instead of a fail.

@item 
bpo-18287@footnote{https://bugs.python.org/issue18287}: PyType_Ready() now checks that tp_name is not NULL. Original
patch by Niklas Koep.

@item 
bpo-24098@footnote{https://bugs.python.org/issue24098}: Fixed possible crash when AST is changed in process of
compiling it.

@item 
bpo-28201@footnote{https://bugs.python.org/issue28201}: Dict reduces possibility of 2nd conflict in hash table when
hashes have same lower bits.

@item 
bpo-28350@footnote{https://bugs.python.org/issue28350}: String constants with null character no longer interned.

@item 
bpo-26617@footnote{https://bugs.python.org/issue26617}: Fix crash when GC runs during weakref callbacks.

@item 
bpo-27942@footnote{https://bugs.python.org/issue27942}: String constants now interned recursively in tuples and
frozensets.

@item 
bpo-21578@footnote{https://bugs.python.org/issue21578}: Fixed misleading error message when ImportError called with
invalid keyword args.

@item 
bpo-28203@footnote{https://bugs.python.org/issue28203}: Fix incorrect type in complex(1.0, @{2:3@}) error message. Patch
by Soumya Sharma.

@item 
bpo-28086@footnote{https://bugs.python.org/issue28086}: Single var-positional argument of tuple subtype was passed
unscathed to the C-defined function.  Now it is converted to exact tuple.

@item 
bpo-28214@footnote{https://bugs.python.org/issue28214}: Now __set_name__ is looked up on the class instead of the
instance.

@item 
bpo-27955@footnote{https://bugs.python.org/issue27955}: Fallback on reading /dev/urandom device when the getrandom()
syscall fails with EPERM, for example when blocked by SECCOMP.

@item 
bpo-28192@footnote{https://bugs.python.org/issue28192}: Don't import readline in isolated mode.

@item 
Upgrade internal unicode databases to Unicode version 9.0.0.

@item 
bpo-28131@footnote{https://bugs.python.org/issue28131}: Fix a regression in zipimport's compile_source().  zipimport
should use the same optimization level as the interpreter.

@item 
bpo-28126@footnote{https://bugs.python.org/issue28126}: Replace Py_MEMCPY with memcpy(). Visual Studio can properly
optimize memcpy().

@item 
bpo-28120@footnote{https://bugs.python.org/issue28120}: Fix dict.pop() for splitted dictionary when trying to remove a
"pending key" (Not yet inserted in split-table). Patch by Xiang Zhang.

@item 
bpo-26182@footnote{https://bugs.python.org/issue26182}: Raise DeprecationWarning when async and await keywords are used
as variable/attribute/class/function name.
@end itemize

@node 库<43>,Windows<33>,核心与内置<42>,Python 3 6 0 beta 2
@anchor{whatsnew/changelog id327}@anchor{10c2}
@subsubsection 库



@itemize -

@item 
bpo-27998@footnote{https://bugs.python.org/issue27998}: Fixed bytes path support in os.scandir() on Windows. Patch by
Eryk Sun.

@item 
bpo-28317@footnote{https://bugs.python.org/issue28317}: The disassembler now decodes FORMAT_VALUE argument.

@item 
bpo-26293@footnote{https://bugs.python.org/issue26293}: Fixed writing ZIP files that starts not from the start of the
file.  Offsets in ZIP file now are relative to the start of the archive in
conforming to the specification.

@item 
bpo-28380@footnote{https://bugs.python.org/issue28380}: unittest.mock Mock autospec functions now properly support
assert_called, assert_not_called, and assert_called_once.

@item 
bpo-27181@footnote{https://bugs.python.org/issue27181}: remove statistics.geometric_mean and defer until 3.7.

@item 
bpo-28229@footnote{https://bugs.python.org/issue28229}: lzma module now supports pathlib.

@item 
bpo-28321@footnote{https://bugs.python.org/issue28321}: Fixed writing non-BMP characters with binary format in
plistlib.

@item 
bpo-28225@footnote{https://bugs.python.org/issue28225}: bz2 module now supports pathlib.  Initial patch by Ethan
Furman.

@item 
bpo-28227@footnote{https://bugs.python.org/issue28227}: gzip now supports pathlib.  Patch by Ethan Furman.

@item 
bpo-27358@footnote{https://bugs.python.org/issue27358}: Optimized merging var-keyword arguments and improved error
message when passing a non-mapping as a var-keyword argument.

@item 
bpo-28257@footnote{https://bugs.python.org/issue28257}: Improved error message when passing a non-iterable as a
var-positional argument.  Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

@item 
bpo-28322@footnote{https://bugs.python.org/issue28322}: Fixed possible crashes when unpickle itertools objects from
incorrect pickle data.  Based on patch by John Leitch.

@item 
bpo-28228@footnote{https://bugs.python.org/issue28228}: imghdr now supports pathlib.

@item 
bpo-28226@footnote{https://bugs.python.org/issue28226}: compileall now supports pathlib.

@item 
bpo-28314@footnote{https://bugs.python.org/issue28314}: Fix function declaration (C flags) for the getiterator() method
of xml.etree.ElementTree.Element.

@item 
bpo-28148@footnote{https://bugs.python.org/issue28148}: Stop using localtime() and gmtime() in the time module.
Introduced platform independent _PyTime_localtime API that is similar to
POSIX localtime_r, but available on all platforms.  Patch by Ed Schouten.

@item 
bpo-28253@footnote{https://bugs.python.org/issue28253}: Fixed calendar functions for extreme months: 0001-01 and
9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so
that they don't call itermonthdates() which can cause datetime.date
under/overflow.

@item 
bpo-28275@footnote{https://bugs.python.org/issue28275}: Fixed possible use after free in the decompress() methods of
the LZMADecompressor and BZ2Decompressor classes. Original patch by John
Leitch.

@item 
bpo-27897@footnote{https://bugs.python.org/issue27897}: Fixed possible crash in sqlite3.Connection.create_collation()
if pass invalid string-like object as a name.  Patch by Xiang Zhang.

@item 
bpo-18844@footnote{https://bugs.python.org/issue18844}: random.choices() now has k as a keyword-only argument to
improve the readability of common cases and come into line with the
signature used in other languages.

@item 
bpo-18893@footnote{https://bugs.python.org/issue18893}: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py.
Patch by Madison May.

@item 
bpo-27611@footnote{https://bugs.python.org/issue27611}: Fixed support of default root window in the tkinter.tix module.
Added the master parameter in the DisplayStyle constructor.

@item 
bpo-27348@footnote{https://bugs.python.org/issue27348}: In the traceback module, restore the formatting of exception
messages like "Exception: None".  This fixes a regression introduced in
3.5a2.

@item 
bpo-25651@footnote{https://bugs.python.org/issue25651}: Allow falsy values to be used for msg parameter of subTest().

@item 
bpo-27778@footnote{https://bugs.python.org/issue27778}: Fix a memory leak in os.getrandom() when the getrandom() is
interrupted by a signal and a signal handler raises a Python exception.

@item 
bpo-28200@footnote{https://bugs.python.org/issue28200}: Fix memory leak on Windows in the os module (fix
path_converter() function).

@item 
bpo-25400@footnote{https://bugs.python.org/issue25400}: RobotFileParser now correctly returns default values for
crawl_delay and request_rate.  Initial patch by Peter Wirtz.

@item 
bpo-27932@footnote{https://bugs.python.org/issue27932}: Prevent memory leak in win32_ver().

@item 
Fix UnboundLocalError in socket._sendfile_use_sendfile.

@item 
bpo-28075@footnote{https://bugs.python.org/issue28075}: Check for ERROR_ACCESS_DENIED in Windows implementation of
os.stat().  Patch by Eryk Sun.

@item 
bpo-22493@footnote{https://bugs.python.org/issue22493}: Warning message emitted by using inline flags in the middle of
regular expression now contains a (truncated) regex pattern. Patch by Tim
Graham.

@item 
bpo-25270@footnote{https://bugs.python.org/issue25270}: Prevent codecs.escape_encode() from raising SystemError when an
empty bytestring is passed.

@item 
bpo-28181@footnote{https://bugs.python.org/issue28181}: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

@item 
bpo-25895@footnote{https://bugs.python.org/issue25895}: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by
Gergely Imreh and Markus Holtermann.

@item 
bpo-28114@footnote{https://bugs.python.org/issue28114}: Fix a crash in parse_envlist() when env contains byte strings.
Patch by Eryk Sun.

@item 
bpo-27599@footnote{https://bugs.python.org/issue27599}: Fixed buffer overrun in binascii.b2a_qp() and
binascii.a2b_qp().

@item 
bpo-27906@footnote{https://bugs.python.org/issue27906}: Fix socket accept exhaustion during high TCP traffic. Patch by
Kevin Conway.

@item 
bpo-28174@footnote{https://bugs.python.org/issue28174}: Handle when SO_REUSEPORT isn't properly supported. Patch by
Seth Michael Larson.

@item 
bpo-26654@footnote{https://bugs.python.org/issue26654}: Inspect functools.partial in asyncio.Handle.__repr__. Patch by
iceboy.

@item 
bpo-26909@footnote{https://bugs.python.org/issue26909}: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

@item 
bpo-28176@footnote{https://bugs.python.org/issue28176}: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

@item 
bpo-27759@footnote{https://bugs.python.org/issue27759}: Fix selectors incorrectly retain invalid file descriptors.
Patch by Mark Williams.

@item 
bpo-28368@footnote{https://bugs.python.org/issue28368}: Refuse monitoring processes if the child watcher has no loop
attached. Patch by Vincent Michel.

@item 
bpo-28369@footnote{https://bugs.python.org/issue28369}: Raise RuntimeError when transport's FD is used with add_reader,
add_writer, etc.

@item 
bpo-28370@footnote{https://bugs.python.org/issue28370}: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг
Марк.

@item 
bpo-28371@footnote{https://bugs.python.org/issue28371}: Deprecate passing asyncio.Handles to run_in_executor.

@item 
bpo-28372@footnote{https://bugs.python.org/issue28372}: Fix asyncio to support formatting of non-python coroutines.

@item 
bpo-28399@footnote{https://bugs.python.org/issue28399}: Remove UNIX socket from FS before binding. Patch by Коренберг
Марк.

@item 
bpo-27972@footnote{https://bugs.python.org/issue27972}: Prohibit Tasks to await on themselves.
@end itemize

@node Windows<33>,C API<25>,库<43>,Python 3 6 0 beta 2
@anchor{whatsnew/changelog id328}@anchor{10c3}
@subsubsection Windows



@itemize -

@item 
bpo-28402@footnote{https://bugs.python.org/issue28402}: Adds signed catalog files for stdlib on Windows.

@item 
bpo-28333@footnote{https://bugs.python.org/issue28333}: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk
Sun)

@item 
bpo-28251@footnote{https://bugs.python.org/issue28251}: Improvements to help manuals on Windows.

@item 
bpo-28110@footnote{https://bugs.python.org/issue28110}: launcher.msi has different product codes between 32-bit and
64-bit

@item 
bpo-28161@footnote{https://bugs.python.org/issue28161}: Opening CON for write access fails

@item 
bpo-28162@footnote{https://bugs.python.org/issue28162}: WindowsConsoleIO readall() fails if first line starts with
Ctrl+Z

@item 
bpo-28163@footnote{https://bugs.python.org/issue28163}: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle

@item 
bpo-28164@footnote{https://bugs.python.org/issue28164}: _PyIO_get_console_type fails for various paths

@item 
bpo-28137@footnote{https://bugs.python.org/issue28137}: Renames Windows path file to ._pth

@item 
bpo-28138@footnote{https://bugs.python.org/issue28138}: Windows ._pth file should allow import site
@end itemize

@node C API<25>,构建<35>,Windows<33>,Python 3 6 0 beta 2
@anchor{whatsnew/changelog id329}@anchor{10c4}
@subsubsection C API



@itemize -

@item 
bpo-28426@footnote{https://bugs.python.org/issue28426}: Deprecated undocumented functions PyUnicode_AsEncodedObject(),
PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and
PyUnicode_AsEncodedUnicode().
@end itemize

@node 构建<35>,测试<33>,C API<25>,Python 3 6 0 beta 2
@anchor{whatsnew/changelog id330}@anchor{10c5}
@subsubsection 构建



@itemize -

@item 
bpo-28258@footnote{https://bugs.python.org/issue28258}: Fixed build with Estonian locale (python-config and distclean
targets in Makefile).  Patch by Arfrever Frehtes Taifersar Arahesis.

@item 
bpo-26661@footnote{https://bugs.python.org/issue26661}: setup.py now detects system libffi with multiarch wrapper.

@item 
bpo-15819@footnote{https://bugs.python.org/issue15819}: Remove redundant include search directory option for building
outside the source tree.
@end itemize

@node 测试<33>,,构建<35>,Python 3 6 0 beta 2
@anchor{whatsnew/changelog id331}@anchor{10c6}
@subsubsection 测试



@itemize -

@item 
bpo-28217@footnote{https://bugs.python.org/issue28217}: Adds _testconsole module to test console input.
@end itemize

@node Python 3 6 0 beta 1,Python 3 6 0 alpha 4,Python 3 6 0 beta 2,更新日志
@anchor{whatsnew/changelog python-3-6-0-beta-1}@anchor{10c7}
@subsection Python 3.6.0 beta 1


@emph{发布日期： 2016-09-12}

@menu
* 核心与内置: 核心与内置<43>. 
* 库: 库<44>. 
* IDLE: IDLE<36>. 
* C API: C API<26>. 
* 测试: 测试<34>. 
* 构建: 构建<36>. 
* 工具/示例: 工具/示例<24>. 
* Windows: Windows<34>. 

@end menu

@node 核心与内置<43>,库<44>,,Python 3 6 0 beta 1
@anchor{whatsnew/changelog id332}@anchor{10c8}
@subsubsection 核心与内置



@itemize -

@item 
bpo-23722@footnote{https://bugs.python.org/issue23722}: The __class__ cell used by zero-argument super() is now
initialized from type.__new__ rather than __build_class__, so class
methods relying on that will now work correctly when called from metaclass
methods during class creation. Patch by Martin Teichmann.

@item 
bpo-25221@footnote{https://bugs.python.org/issue25221}: Fix corrupted result from PyLong_FromLong(0) when Python is
compiled with NSMALLPOSINTS = 0.

@item 
bpo-27080@footnote{https://bugs.python.org/issue27080}: Implement formatting support for 
@geindex Python 提高建议; PEP 515
PEP 515@footnote{https://www.python.org/dev/peps/pep-0515}.  Initial patch by
Chris Angelico.

@item 
bpo-27199@footnote{https://bugs.python.org/issue27199}: In tarfile, expose copyfileobj bufsize to improve throughput.
Patch by Jason Fried.

@item 
bpo-27948@footnote{https://bugs.python.org/issue27948}: In f-strings, only allow backslashes inside the braces (where
the expressions are).  This is a breaking change from the 3.6 alpha
releases, where backslashes are allowed anywhere in an f-string.  Also,
require that expressions inside f-strings be enclosed within literal
braces, and not escapes like @code{f'\x7b"hi"\x7d'}.

@item 
bpo-28046@footnote{https://bugs.python.org/issue28046}: Remove platform-specific directories from sys.path.

@item 
bpo-28071@footnote{https://bugs.python.org/issue28071}: Add early-out for differencing from an empty set.

@item 
bpo-25758@footnote{https://bugs.python.org/issue25758}: Prevents zipimport from unnecessarily encoding a filename
(patch by Eryk Sun)

@item 
bpo-25856@footnote{https://bugs.python.org/issue25856}: The __module__ attribute of extension classes and functions now
is interned. This leads to more compact pickle data with protocol 4.

@item 
bpo-27213@footnote{https://bugs.python.org/issue27213}: Rework CALL_FUNCTION* opcodes to produce shorter and more
efficient bytecode. Patch by Demur Rumed, design by Serhiy Storchaka,
reviewed by Serhiy Storchaka and Victor Stinner.

@item 
bpo-26331@footnote{https://bugs.python.org/issue26331}: Implement tokenizing support for 
@geindex Python 提高建议; PEP 515
PEP 515@footnote{https://www.python.org/dev/peps/pep-0515}. Patch by Georg
Brandl.

@item 
bpo-27999@footnote{https://bugs.python.org/issue27999}: Make "global after use" a SyntaxError, and ditto for nonlocal.
Patch by Ivan Levkivskyi.

@item 
bpo-28003@footnote{https://bugs.python.org/issue28003}: Implement 
@geindex Python 提高建议; PEP 525
PEP 525@footnote{https://www.python.org/dev/peps/pep-0525} -- Asynchronous Generators.

@item 
bpo-27985@footnote{https://bugs.python.org/issue27985}: Implement 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} -- Syntax for Variable Annotations. Patch
by Ivan Levkivskyi.

@item 
bpo-26058@footnote{https://bugs.python.org/issue26058}: Add a new private version to the builtin dict type, incremented
at each dictionary creation and at each dictionary change. Implementation
of the PEP 509.

@item 
bpo-27364@footnote{https://bugs.python.org/issue27364}: A backslash-character pair that is not a valid escape sequence
now generates a DeprecationWarning.  Patch by Emanuel Barry.

@item 
bpo-27350@footnote{https://bugs.python.org/issue27350}: @ref{1b8,,dict} implementation is changed like PyPy. It is more compact
and preserves insertion order. (Concept developed by Raymond Hettinger and
patch by Inada Naoki.)

@item 
bpo-27911@footnote{https://bugs.python.org/issue27911}: Remove unnecessary error checks in
@code{exec_builtin_or_dynamic()}.

@item 
bpo-27078@footnote{https://bugs.python.org/issue27078}: Added BUILD_STRING opcode.  Optimized f-strings evaluation.

@item 
bpo-17884@footnote{https://bugs.python.org/issue17884}: Python now requires systems with inttypes.h and stdint.h

@item 
bpo-27961@footnote{https://bugs.python.org/issue27961}: Require platforms to support @code{long long}. Python hasn't
compiled without @code{long long} for years, so this is basically a
formality.

@item 
bpo-27355@footnote{https://bugs.python.org/issue27355}: Removed support for Windows CE.  It was never finished, and
Windows CE is no longer a relevant platform for Python.

@item 
Implement 
@geindex Python 提高建议; PEP 523
PEP 523@footnote{https://www.python.org/dev/peps/pep-0523}.

@item 
bpo-27870@footnote{https://bugs.python.org/issue27870}: A left shift of zero by a large integer no longer attempts to
allocate large amounts of memory.

@item 
bpo-25402@footnote{https://bugs.python.org/issue25402}: In int-to-decimal-string conversion, improve the estimate of
the intermediate memory required, and remove an unnecessarily strict
overflow check. Patch by Serhiy Storchaka.

@item 
bpo-27214@footnote{https://bugs.python.org/issue27214}: In long_invert, be more careful about modifying object returned
by long_add, and remove an unnecessary check for small longs. Thanks Oren
Milman for analysis and patch.

@item 
bpo-27506@footnote{https://bugs.python.org/issue27506}: Support passing the bytes/bytearray.translate() "delete"
argument by keyword.

@item 
bpo-27812@footnote{https://bugs.python.org/issue27812}: Properly clear out a generator's frame's backreference to the
generator to prevent crashes in frame.clear().

@item 
bpo-27811@footnote{https://bugs.python.org/issue27811}: Fix a crash when a coroutine that has not been awaited is
finalized with warnings-as-errors enabled.

@item 
bpo-27587@footnote{https://bugs.python.org/issue27587}: Fix another issue found by PVS-Studio: Null pointer check after
use of 'def' in _PyState_AddModule(). Initial patch by Christian Heimes.

@item 
bpo-27792@footnote{https://bugs.python.org/issue27792}: The modulo operation applied to @code{bool} and other @code{int}
subclasses now always returns an @code{int}. Previously the return type
depended on the input values. Patch by Xiang Zhang.

@item 
bpo-26984@footnote{https://bugs.python.org/issue26984}: int() now always returns an instance of exact int.

@item 
bpo-25604@footnote{https://bugs.python.org/issue25604}: Fix a minor bug in integer true division; this bug could
potentially have caused off-by-one-ulp results on platforms with
unreliable ldexp implementations.

@item 
bpo-24254@footnote{https://bugs.python.org/issue24254}: Make class definition namespace ordered by default.

@item 
bpo-27662@footnote{https://bugs.python.org/issue27662}: Fix an overflow check in @code{List_New}: the original code was
checking against @code{Py_SIZE_MAX} instead of the correct upper bound of
@code{Py_SSIZE_T_MAX}. Patch by Xiang Zhang.

@item 
bpo-27782@footnote{https://bugs.python.org/issue27782}: Multi-phase extension module import now correctly allows the
@code{m_methods} field to be used to add module level functions to instances
of non-module types returned from @code{Py_create_mod}. Patch by Xiang Zhang.

@item 
bpo-27936@footnote{https://bugs.python.org/issue27936}: The round() function accepted a second None argument for some
types but not for others.  Fixed the inconsistency by accepting None for
all numeric types.

@item 
bpo-27487@footnote{https://bugs.python.org/issue27487}: Warn if a submodule argument to "python -m" or
runpy.run_module() is found in sys.modules after parent packages are
imported, but before the submodule is executed.

@item 
bpo-27157@footnote{https://bugs.python.org/issue27157}: Make only type() itself accept the one-argument form. Patch by
Eryk Sun and Emanuel Barry.

@item 
bpo-27558@footnote{https://bugs.python.org/issue27558}: Fix a SystemError in the implementation of "raise" statement.
In a brand new thread, raise a RuntimeError since there is no active
exception to reraise. Patch written by Xiang Zhang.

@item 
bpo-28008@footnote{https://bugs.python.org/issue28008}: Implement 
@geindex Python 提高建议; PEP 530
PEP 530@footnote{https://www.python.org/dev/peps/pep-0530} -- asynchronous comprehensions.

@item 
bpo-27942@footnote{https://bugs.python.org/issue27942}: Fix memory leak in codeobject.c
@end itemize

@node 库<44>,IDLE<36>,核心与内置<43>,Python 3 6 0 beta 1
@anchor{whatsnew/changelog id333}@anchor{10c9}
@subsubsection 库



@itemize -

@item 
bpo-28732@footnote{https://bugs.python.org/issue28732}: Fix crash in os.spawnv() with no elements in args

@item 
bpo-28485@footnote{https://bugs.python.org/issue28485}: Always raise ValueError for negative
compileall.compile_dir(workers=...) parameter, even when multithreading is
unavailable.

@item 
bpo-28037@footnote{https://bugs.python.org/issue28037}: Use sqlite3_get_autocommit() instead of setting
Connection->inTransaction manually.

@item 
bpo-25283@footnote{https://bugs.python.org/issue25283}: Attributes tm_gmtoff and tm_zone are now available on all
platforms in the return values of time.localtime() and time.gmtime().

@item 
bpo-24454@footnote{https://bugs.python.org/issue24454}: Regular expression match object groups are now accessible using
__getitem__. "mo[x]" is equivalent to "mo.group(x)".

@item 
bpo-10740@footnote{https://bugs.python.org/issue10740}: sqlite3 no longer implicitly commit an open transaction before
DDL statements.

@item 
bpo-17941@footnote{https://bugs.python.org/issue17941}: Add a @emph{module} parameter to collections.namedtuple().

@item 
bpo-22493@footnote{https://bugs.python.org/issue22493}: Inline flags now should be used only at the start of the
regular expression. Deprecation warning is emitted if uses them in the
middle of the regular expression.

@item 
bpo-26885@footnote{https://bugs.python.org/issue26885}: xmlrpc now supports unmarshalling additional data types used by
Apache XML-RPC implementation for numerics and None.

@item 
bpo-28070@footnote{https://bugs.python.org/issue28070}: Fixed parsing inline verbose flag in regular expressions.

@item 
bpo-19500@footnote{https://bugs.python.org/issue19500}: Add client-side SSL session resumption to the ssl module.

@item 
bpo-28022@footnote{https://bugs.python.org/issue28022}: Deprecate ssl-related arguments in favor of SSLContext. The
deprecation include manual creation of SSLSocket and certfile/keyfile (or
similar) in ftplib, httplib, imaplib, smtplib, poplib and urllib.

@item 
bpo-28043@footnote{https://bugs.python.org/issue28043}: SSLContext has improved default settings: OP_NO_SSLv2,
OP_NO_SSLv3, OP_NO_COMPRESSION, OP_CIPHER_SERVER_PREFERENCE,
OP_SINGLE_DH_USE, OP_SINGLE_ECDH_USE and HIGH ciphers without MD5.

@item 
bpo-24693@footnote{https://bugs.python.org/issue24693}: Changed some RuntimeError's in the zipfile module to more
appropriate types. Improved some error messages and debugging output.

@item 
bpo-17909@footnote{https://bugs.python.org/issue17909}: @code{json.load} and @code{json.loads} now support binary input
encoded as UTF-8, UTF-16 or UTF-32. Patch by Serhiy Storchaka.

@item 
bpo-27137@footnote{https://bugs.python.org/issue27137}: the pure Python fallback implementation of
@code{functools.partial} now matches the behaviour of its accelerated C
counterpart for subclassing, pickling and text representation purposes.
Patch by Emanuel Barry and Serhiy Storchaka.

@item 
Fix possible integer overflows and crashes in the mmap module with unusual
usage patterns.

@item 
bpo-1703178@footnote{https://bugs.python.org/issue1703178}: Fix the ability to pass the --link-objects option to the
distutils build_ext command.

@item 
bpo-28019@footnote{https://bugs.python.org/issue28019}: itertools.count() no longer rounds non-integer step in range
between 1.0 and 2.0 to 1.

@item 
bpo-18401@footnote{https://bugs.python.org/issue18401}: Pdb now supports the 'readrc' keyword argument to control
whether .pdbrc files should be read.  Patch by Martin Matusiak and Sam
Kimbrel.

@item 
bpo-25969@footnote{https://bugs.python.org/issue25969}: Update the lib2to3 grammar to handle the unpacking
generalizations added in 3.5.

@item 
bpo-14977@footnote{https://bugs.python.org/issue14977}: mailcap now respects the order of the lines in the mailcap
files ("first match"), as required by RFC 1542.  Patch by Michael Lazar.

@item 
bpo-28082@footnote{https://bugs.python.org/issue28082}: Convert re flag constants to IntFlag.

@item 
bpo-28025@footnote{https://bugs.python.org/issue28025}: Convert all ssl module constants to IntEnum and IntFlags.
SSLContext properties now return flags and enums.

@item 
bpo-23591@footnote{https://bugs.python.org/issue23591}: Add Flag, IntFlag, and auto() to enum module.

@item 
bpo-433028@footnote{https://bugs.python.org/issue433028}: Added support of modifier spans in regular expressions.

@item 
bpo-24594@footnote{https://bugs.python.org/issue24594}: Validates persist parameter when opening MSI database

@item 
bpo-17582@footnote{https://bugs.python.org/issue17582}: xml.etree.ElementTree nows preserves whitespaces in attributes
(Patch by Duane Griffin.  Reviewed and approved by Stefan Behnel.)

@item 
bpo-28047@footnote{https://bugs.python.org/issue28047}: Fixed calculation of line length used for the base64 CTE in the
new email policies.

@item 
bpo-27576@footnote{https://bugs.python.org/issue27576}: Fix call order in OrderedDict.__init__().

@item 
email.generator.DecodedGenerator now supports the policy keyword.

@item 
bpo-28027@footnote{https://bugs.python.org/issue28027}: Remove undocumented modules from @code{Lib/plat-*}: IN, CDROM,
DLFCN, TYPES, CDIO, and STROPTS.

@item 
bpo-27445@footnote{https://bugs.python.org/issue27445}: Don't pass str(_charset) to MIMEText.set_payload(). Patch by
Claude Paroz.

@item 
bpo-24277@footnote{https://bugs.python.org/issue24277}: The new email API is no longer provisional, and the docs have
been reorganized and rewritten to emphasize the new API.

@item 
bpo-22450@footnote{https://bugs.python.org/issue22450}: urllib now includes an @code{Accept: */*} header among the default
headers. This makes the results of REST API requests more consistent and
predictable especially when proxy servers are involved.

@item 
lib2to3.pgen3.driver.load_grammar() now creates a stable cache file
between runs given the same Grammar.txt input regardless of the hash
randomization setting.

@item 
bpo-28005@footnote{https://bugs.python.org/issue28005}: Allow ImportErrors in encoding implementation to propagate.

@item 
bpo-26667@footnote{https://bugs.python.org/issue26667}: Support path-like objects in importlib.util.

@item 
bpo-27570@footnote{https://bugs.python.org/issue27570}: Avoid zero-length memcpy() etc calls with null source pointers
in the "ctypes" and "array" modules.

@item 
bpo-22233@footnote{https://bugs.python.org/issue22233}: Break email header lines @emph{only} on the RFC specified CR and LF
characters, not on arbitrary unicode line breaks.  This also fixes a bug
in HTTP header parsing.

@item 
bpo-27331@footnote{https://bugs.python.org/issue27331}: The email.mime classes now all accept an optional policy
keyword.

@item 
bpo-27988@footnote{https://bugs.python.org/issue27988}: Fix email iter_attachments incorrect mutation of payload list.

@item 
bpo-16113@footnote{https://bugs.python.org/issue16113}: Add SHA-3 and SHAKE support to hashlib module.

@item 
Eliminate a tautological-pointer-compare warning in _scproxy.c.

@item 
bpo-27776@footnote{https://bugs.python.org/issue27776}: The @ref{4cb,,os.urandom()} function does now block on Linux 3.17
and newer until the system urandom entropy pool is initialized to increase
the security. This change is part of the 
@geindex Python 提高建议; PEP 524
PEP 524@footnote{https://www.python.org/dev/peps/pep-0524}.

@item 
bpo-27778@footnote{https://bugs.python.org/issue27778}: Expose the Linux @code{getrandom()} syscall as a new
@ref{564,,os.getrandom()} function. This change is part of the 
@geindex Python 提高建议; PEP 524
PEP 524@footnote{https://www.python.org/dev/peps/pep-0524}.

@item 
bpo-27691@footnote{https://bugs.python.org/issue27691}: Fix ssl module's parsing of GEN_RID subject alternative name
fields in X.509 certs.

@item 
bpo-18844@footnote{https://bugs.python.org/issue18844}: Add random.choices().

@item 
bpo-25761@footnote{https://bugs.python.org/issue25761}: Improved error reporting about truncated pickle data in C
implementation of unpickler.  UnpicklingError is now raised instead of
AttributeError and ValueError in some cases.

@item 
bpo-26798@footnote{https://bugs.python.org/issue26798}: Add BLAKE2 (blake2b and blake2s) to hashlib.

@item 
bpo-26032@footnote{https://bugs.python.org/issue26032}: Optimized globbing in pathlib by using os.scandir(); it is now
about 1.5--4 times faster.

@item 
bpo-25596@footnote{https://bugs.python.org/issue25596}: Optimized glob() and iglob() functions in the glob module; they
are now about 3--6 times faster.

@item 
bpo-27928@footnote{https://bugs.python.org/issue27928}: Add scrypt (password-based key derivation function) to hashlib
module (requires OpenSSL 1.1.0).

@item 
bpo-27850@footnote{https://bugs.python.org/issue27850}: Remove 3DES from ssl module's default cipher list to counter
measure sweet32 attack (CVE-2016-2183).

@item 
bpo-27766@footnote{https://bugs.python.org/issue27766}: Add ChaCha20 Poly1305 to ssl module's default cipher list.
(Required OpenSSL 1.1.0 or LibreSSL).

@item 
bpo-25387@footnote{https://bugs.python.org/issue25387}: Check return value of winsound.MessageBeep.

@item 
bpo-27866@footnote{https://bugs.python.org/issue27866}: Add SSLContext.get_ciphers() method to get a list of all
enabled ciphers.

@item 
bpo-27744@footnote{https://bugs.python.org/issue27744}: Add AF_ALG (Linux Kernel crypto) to socket module.

@item 
bpo-26470@footnote{https://bugs.python.org/issue26470}: Port ssl and hashlib module to OpenSSL 1.1.0.

@item 
bpo-11620@footnote{https://bugs.python.org/issue11620}: Fix support for SND_MEMORY in winsound.PlaySound.  Based on a
patch by Tim Lesher.

@item 
bpo-11734@footnote{https://bugs.python.org/issue11734}: Add support for IEEE 754 half-precision floats to the struct
module. Based on a patch by Eli Stevens.

@item 
bpo-27919@footnote{https://bugs.python.org/issue27919}: Deprecated @code{extra_path} distribution option in distutils
packaging.

@item 
bpo-23229@footnote{https://bugs.python.org/issue23229}: Add new @code{cmath} constants: @code{cmath.inf} and @code{cmath.nan} to
match @code{math.inf} and @code{math.nan}, and also @code{cmath.infj} and
@code{cmath.nanj} to match the format used by complex repr.

@item 
bpo-27842@footnote{https://bugs.python.org/issue27842}: The csv.DictReader now returns rows of type OrderedDict.
(Contributed by Steve Holden.)

@item 
Remove support for passing a file descriptor to os.access. It never worked
but previously didn't raise.

@item 
bpo-12885@footnote{https://bugs.python.org/issue12885}: Fix error when distutils encounters symlink.

@item 
bpo-27881@footnote{https://bugs.python.org/issue27881}: Fixed possible bugs when setting
sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

@item 
bpo-27861@footnote{https://bugs.python.org/issue27861}: Fixed a crash in sqlite3.Connection.cursor() when a factory
creates not a cursor.  Patch by Xiang Zhang.

@item 
bpo-19884@footnote{https://bugs.python.org/issue19884}: Avoid spurious output on OS X with Gnu Readline.

@item 
bpo-27706@footnote{https://bugs.python.org/issue27706}: Restore deterministic behavior of random.Random().seed() for
string seeds using seeding version 1.  Allows sequences of calls to
random() to exactly match those obtained in Python 2. Patch by Nofar
Schnider.

@item 
bpo-10513@footnote{https://bugs.python.org/issue10513}: Fix a regression in Connection.commit().  Statements should not
be reset after a commit.

@item 
bpo-12319@footnote{https://bugs.python.org/issue12319}: Chunked transfer encoding support added to
http.client.HTTPConnection requests.  The
urllib.request.AbstractHTTPHandler class does not enforce a Content-Length
header any more.  If a HTTP request has a file or iterable body, but no
Content-Length header, the library now falls back to use chunked
transfer-encoding.

@item 
A new version of typing.py from @indicateurl{https://github.com/python/typing}: -
Collection (only for 3.6) (bpo-27598@footnote{https://bugs.python.org/issue27598}) - Add FrozenSet to __all__
(upstream #261) - fix crash in _get_type_vars() (upstream #259) - Remove
the dict constraint in ForwardRef._eval_type (upstream #252)

@item 
bpo-27832@footnote{https://bugs.python.org/issue27832}: Make @code{_normalize} parameter to @code{Fraction} constructor
keyword-only, so that @code{Fraction(2, 3, 4)} now raises @code{TypeError}.

@item 
bpo-27539@footnote{https://bugs.python.org/issue27539}: Fix unnormalised @code{Fraction.__pow__} result in the case of
negative exponent and negative base.

@item 
bpo-21718@footnote{https://bugs.python.org/issue21718}: cursor.description is now available for queries using CTEs.

@item 
bpo-27819@footnote{https://bugs.python.org/issue27819}: In distutils sdists, simply produce the "gztar" (gzipped tar
format) distributions on all platforms unless "formats" is supplied.

@item 
bpo-2466@footnote{https://bugs.python.org/issue2466}: posixpath.ismount now correctly recognizes mount points which
the user does not have permission to access.

@item 
bpo-9998@footnote{https://bugs.python.org/issue9998}: On Linux, ctypes.util.find_library now looks in LD_LIBRARY_PATH
for shared libraries.

@item 
bpo-27573@footnote{https://bugs.python.org/issue27573}: exit message for code.interact is now configurable.

@item 
bpo-27930@footnote{https://bugs.python.org/issue27930}: Improved behaviour of logging.handlers.QueueListener. Thanks to
Paulo Andrade and Petr Viktorin for the analysis and patch.

@item 
bpo-6766@footnote{https://bugs.python.org/issue6766}: Distributed reference counting added to multiprocessing to
support nesting of shared values / proxy objects.

@item 
bpo-21201@footnote{https://bugs.python.org/issue21201}: Improves readability of multiprocessing error message.  Thanks
to Wojciech Walczak for patch.

@item 
asyncio: 在各Transport类中添加了 set_protocol / get_protocol 方法

@item 
bpo-27456@footnote{https://bugs.python.org/issue27456}: asyncio: Set TCP_NODELAY by default.
@end itemize

@node IDLE<36>,C API<26>,库<44>,Python 3 6 0 beta 1
@anchor{whatsnew/changelog id334}@anchor{10ca}
@subsubsection IDLE



@itemize -

@item 
bpo-15308@footnote{https://bugs.python.org/issue15308}: Add 'interrupt execution' (^C) to Shell menu. Patch by Roger
Serwy, updated by Bayard Randel.

@item 
bpo-27922@footnote{https://bugs.python.org/issue27922}: Stop IDLE tests from 'flashing' gui widgets on the screen.

@item 
bpo-27891@footnote{https://bugs.python.org/issue27891}: Consistently group and sort imports within idlelib modules.

@item 
bpo-17642@footnote{https://bugs.python.org/issue17642}: add larger font sizes for classroom projection.

@item 
在 IDLE 帮助窗口的标题中加入版本号

@item 
bpo-25564@footnote{https://bugs.python.org/issue25564}: In section on IDLE -- console differences, mention that using
exec means that __builtins__ is defined for each statement.

@item 
bpo-27821@footnote{https://bugs.python.org/issue27821}: Fix 3.6.0a3 regression that prevented custom key sets from
being selected when no custom theme was defined.
@end itemize

@node C API<26>,测试<34>,IDLE<36>,Python 3 6 0 beta 1
@anchor{whatsnew/changelog id335}@anchor{10cb}
@subsubsection C API



@itemize -

@item 
bpo-26900@footnote{https://bugs.python.org/issue26900}: Excluded underscored names and other private API from limited
API.

@item 
bpo-26027@footnote{https://bugs.python.org/issue26027}: Add support for path-like objects in PyUnicode_FSConverter() &
PyUnicode_FSDecoder().
@end itemize

@node 测试<34>,构建<36>,C API<26>,Python 3 6 0 beta 1
@anchor{whatsnew/changelog id336}@anchor{10cc}
@subsubsection 测试



@itemize -

@item 
bpo-27427@footnote{https://bugs.python.org/issue27427}: Additional tests for the math module. Patch by Francisco Couzo.

@item 
bpo-27953@footnote{https://bugs.python.org/issue27953}: Skip math and cmath tests that fail on OS X 10.4 due to a poor
libm implementation of tan.

@item 
bpo-26040@footnote{https://bugs.python.org/issue26040}: Improve test_math and test_cmath coverage and rigour. Patch by
Jeff Allen.

@item 
bpo-27787@footnote{https://bugs.python.org/issue27787}: Call gc.collect() before checking each test for "dangling
threads", since the dangling threads are weak references.
@end itemize

@node 构建<36>,工具/示例<24>,测试<34>,Python 3 6 0 beta 1
@anchor{whatsnew/changelog id337}@anchor{10cd}
@subsubsection 构建



@itemize -

@item 
bpo-27566@footnote{https://bugs.python.org/issue27566}: Fix clean target in freeze makefile (patch by Lisa Roach)

@item 
bpo-27705@footnote{https://bugs.python.org/issue27705}: Update message in validate_ucrtbase.py

@item 
bpo-27976@footnote{https://bugs.python.org/issue27976}: Deprecate building _ctypes with the bundled copy of libffi on
non-OSX UNIX platforms.

@item 
bpo-27983@footnote{https://bugs.python.org/issue27983}: Cause lack of llvm-profdata tool when using clang as required
for PGO linking to be a configure time error rather than make time when
@code{--with-optimizations} is enabled.  Also improve our ability to find the
llvm-profdata tool on MacOS and some Linuxes.

@item 
bpo-21590@footnote{https://bugs.python.org/issue21590}: Support for DTrace and SystemTap probes.

@item 
bpo-26307@footnote{https://bugs.python.org/issue26307}: The profile-opt build now applies PGO to the built-in modules.

@item 
bpo-26359@footnote{https://bugs.python.org/issue26359}: Add the --with-optimizations flag to turn on LTO and PGO build
support when available.

@item 
bpo-27917@footnote{https://bugs.python.org/issue27917}: Set platform triplets for Android builds.

@item 
bpo-25825@footnote{https://bugs.python.org/issue25825}: Update references to the $(LIBPL) installation path on AIX.
This path was changed in 3.2a4.

@item 
更新 OS X 安装包，使用SQLite 3.14.1 和 XZ 5.2.2版本。

@item 
bpo-21122@footnote{https://bugs.python.org/issue21122}: Fix LTO builds on OS X.

@item 
bpo-17128@footnote{https://bugs.python.org/issue17128}: Build OS X installer with a private copy of OpenSSL. Also
provide a sample Install Certificates command script to install a set of
root certificates from the third-party certifi module.
@end itemize

@node 工具/示例<24>,Windows<34>,构建<36>,Python 3 6 0 beta 1
@anchor{whatsnew/changelog id338}@anchor{10ce}
@subsubsection 工具/示例



@itemize -

@item 
bpo-27952@footnote{https://bugs.python.org/issue27952}: Get Tools/scripts/fixcid.py working with Python 3 and the
current "re" module, avoid invalid Python backslash escapes, and fix a bug
parsing escaped C quote signs.
@end itemize

@node Windows<34>,,工具/示例<24>,Python 3 6 0 beta 1
@anchor{whatsnew/changelog id339}@anchor{10cf}
@subsubsection Windows



@itemize -

@item 
bpo-28065@footnote{https://bugs.python.org/issue28065}: Update xz dependency to 5.2.2 and build it from source.

@item 
bpo-25144@footnote{https://bugs.python.org/issue25144}: Ensures TargetDir is set before continuing with custom install.

@item 
bpo-1602@footnote{https://bugs.python.org/issue1602}: Windows console doesn't input or print Unicode (PEP 528)

@item 
bpo-27781@footnote{https://bugs.python.org/issue27781}: Change file system encoding on Windows to UTF-8 (PEP 529)

@item 
bpo-27731@footnote{https://bugs.python.org/issue27731}: Opt-out of MAX_PATH on Windows 10

@item 
bpo-6135@footnote{https://bugs.python.org/issue6135}: Adds encoding and errors parameters to subprocess.

@item 
bpo-27959@footnote{https://bugs.python.org/issue27959}: Adds oem encoding, alias ansi to mbcs, move aliasmbcs to codec
lookup.

@item 
bpo-27982@footnote{https://bugs.python.org/issue27982}: The functions of the winsound module now accept keyword
arguments.

@item 
bpo-20366@footnote{https://bugs.python.org/issue20366}: Build full text search support into SQLite on Windows.

@item 
bpo-27756@footnote{https://bugs.python.org/issue27756}: Adds new icons for Python files and processes on Windows.
Designs by Cherry Wang.

@item 
bpo-27883@footnote{https://bugs.python.org/issue27883}: 在Windows上将sqlite更新到3.14.1.0
@end itemize

@node Python 3 6 0 alpha 4,Python 3 6 0 alpha 3,Python 3 6 0 beta 1,更新日志
@anchor{whatsnew/changelog python-3-6-0-alpha-4}@anchor{10d0}
@subsection Python 3.6.0 alpha 4


@emph{发布日期: 2016-08-15}

@menu
* 核心与内置: 核心与内置<44>. 
* 库: 库<45>. 
* IDLE: IDLE<37>. 
* 测试: 测试<35>. 
* Windows: Windows<35>. 
* 构建: 构建<37>. 

@end menu

@node 核心与内置<44>,库<45>,,Python 3 6 0 alpha 4
@anchor{whatsnew/changelog id340}@anchor{10d1}
@subsubsection 核心与内置



@itemize -

@item 
bpo-27704@footnote{https://bugs.python.org/issue27704}: Optimized creating bytes and bytearray from byte-like objects
and iterables. Speed up to 3 times for short objects.  Original patch by
Naoki Inada.

@item 
bpo-26823@footnote{https://bugs.python.org/issue26823}: Large sections of repeated lines in tracebacks are now
abbreviated as "[Previous line repeated @{count@} more times]" by the
builtin traceback rendering. Patch by Emanuel Barry.

@item 
bpo-27574@footnote{https://bugs.python.org/issue27574}: Decreased an overhead of parsing keyword arguments in functions
implemented with using Argument Clinic.

@item 
bpo-22557@footnote{https://bugs.python.org/issue22557}: Now importing already imported modules is up to 2.5 times
faster.

@item 
bpo-17596@footnote{https://bugs.python.org/issue17596}: Include <wincrypt.h> to help with Min GW building.

@item 
bpo-17599@footnote{https://bugs.python.org/issue17599}: On Windows, rename the privately defined REPARSE_DATA_BUFFER
structure to avoid conflicting with the definition from Min GW.

@item 
bpo-27507@footnote{https://bugs.python.org/issue27507}: Add integer overflow check in bytearray.extend().  Patch by
Xiang Zhang.

@item 
bpo-27581@footnote{https://bugs.python.org/issue27581}: Don't rely on wrapping for overflow check in
PySequence_Tuple().  Patch by Xiang Zhang.

@item 
bpo-1621@footnote{https://bugs.python.org/issue1621}: Avoid signed integer overflow in list and tuple operations.
Patch by Xiang Zhang.

@item 
bpo-27419@footnote{https://bugs.python.org/issue27419}: Standard __import__() no longer look up "__import__" in globals
or builtins for importing submodules or "from import".  Fixed a crash if
raise a warning about unabling to resolve package from __spec__ or
__package__.

@item 
bpo-27083@footnote{https://bugs.python.org/issue27083}: Respect the PYTHONCASEOK environment variable under Windows.

@item 
bpo-27514@footnote{https://bugs.python.org/issue27514}: Make having too many statically nested blocks a SyntaxError
instead of SystemError.

@item 
bpo-27366@footnote{https://bugs.python.org/issue27366}: Implemented 
@geindex Python 提高建议; PEP 487
PEP 487@footnote{https://www.python.org/dev/peps/pep-0487} (Simpler customization of class
creation). Upon subclassing, the __init_subclass__ classmethod is called
on the base class. Descriptors are initialized with __set_name__ after
class creation.
@end itemize

@node 库<45>,IDLE<37>,核心与内置<44>,Python 3 6 0 alpha 4
@anchor{whatsnew/changelog id341}@anchor{10d2}
@subsubsection 库



@itemize -

@item 
bpo-26027@footnote{https://bugs.python.org/issue26027}: Add 
@geindex Python 提高建议; PEP 519
PEP 519@footnote{https://www.python.org/dev/peps/pep-0519}/__fspath__() support to the os and os.path
modules. Includes code from Jelle Zijlstra. (See also: bpo-27524@footnote{https://bugs.python.org/issue27524})

@item 
bpo-27598@footnote{https://bugs.python.org/issue27598}: Add Collections to collections.abc. Patch by Ivan Levkivskyi,
docs by Neil Girdhar.

@item 
bpo-25958@footnote{https://bugs.python.org/issue25958}: Support "anti-registration" of special methods from various
ABCs, like __hash__, __iter__ or __len__.  All these (and several more)
can be set to None in an implementation class and the behavior will be as
if the method is not defined at all. (Previously, this mechanism existed
only for __hash__, to make mutable classes unhashable.)  Code contributed
by Andrew Barnert and Ivan Levkivskyi.

@item 
bpo-16764@footnote{https://bugs.python.org/issue16764}: Support keyword arguments to zlib.decompress().  Patch by Xiang
Zhang.

@item 
bpo-27736@footnote{https://bugs.python.org/issue27736}: Prevent segfault after interpreter re-initialization due to ref
count problem introduced in code for bpo-27038@footnote{https://bugs.python.org/issue27038} in 3.6.0a3. Patch by
Xiang Zhang.

@item 
bpo-25628@footnote{https://bugs.python.org/issue25628}: The @emph{verbose} and @emph{rename} parameters for
collections.namedtuple are now keyword-only.

@item 
bpo-12345@footnote{https://bugs.python.org/issue12345}: Add mathematical constant tau to math and cmath. See also
@geindex Python 提高建议; PEP 628
PEP 628@footnote{https://www.python.org/dev/peps/pep-0628}.

@item 
bpo-26823@footnote{https://bugs.python.org/issue26823}: traceback.StackSummary.format now abbreviates large sections of
repeated lines as "[Previous line repeated @{count@} more times]" (this
change then further affects other traceback display operations in the
module). Patch by Emanuel Barry.

@item 
bpo-27664@footnote{https://bugs.python.org/issue27664}: Add to concurrent.futures.thread.ThreadPoolExecutor() the
ability to specify a thread name prefix.

@item 
bpo-27181@footnote{https://bugs.python.org/issue27181}: Add geometric_mean and harmonic_mean to statistics module.

@item 
bpo-27573@footnote{https://bugs.python.org/issue27573}: code.interact now prints an message when exiting.

@item 
bpo-6422@footnote{https://bugs.python.org/issue6422}: Add autorange method to timeit.Timer objects.

@item 
bpo-27773@footnote{https://bugs.python.org/issue27773}: Correct some memory management errors server_hostname in
_ssl.wrap_socket().

@item 
bpo-26750@footnote{https://bugs.python.org/issue26750}: unittest.mock.create_autospec() now works properly for
subclasses of property() and other data descriptors.  Removes the never
publicly used, never documented unittest.mock.DescriptorTypes tuple.

@item 
bpo-26754@footnote{https://bugs.python.org/issue26754}: Undocumented support of general bytes-like objects as path in
compile() and similar functions is now deprecated.

@item 
bpo-26800@footnote{https://bugs.python.org/issue26800}: Undocumented support of general bytes-like objects as paths in
os functions is now deprecated.

@item 
bpo-26981@footnote{https://bugs.python.org/issue26981}: Add _order_ compatibility shim to enum.Enum for Python 2/3 code
bases.

@item 
bpo-27661@footnote{https://bugs.python.org/issue27661}: Added tzinfo keyword argument to datetime.combine.

@item 
In the curses module, raise an error if window.getstr() or window.instr()
is passed a negative value.

@item 
bpo-27783@footnote{https://bugs.python.org/issue27783}: Fix possible usage of uninitialized memory in
operator.methodcaller.

@item 
bpo-27774@footnote{https://bugs.python.org/issue27774}: Fix possible Py_DECREF on unowned object in _sre.

@item 
bpo-27760@footnote{https://bugs.python.org/issue27760}: Fix possible integer overflow in binascii.b2a_qp.

@item 
bpo-27758@footnote{https://bugs.python.org/issue27758}: Fix possible integer overflow in the _csv module for large
record lengths.

@item 
bpo-27568@footnote{https://bugs.python.org/issue27568}: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the
HTTP_PROXY variable when REQUEST_METHOD environment is set, which
indicates that the script is in CGI mode.

@item 
bpo-7063@footnote{https://bugs.python.org/issue7063}: Remove dead code from the "array" module's slice handling. Patch
by Chuck.

@item 
bpo-27656@footnote{https://bugs.python.org/issue27656}: Do not assume sched.h defines any SCHED_* constants.

@item 
bpo-27130@footnote{https://bugs.python.org/issue27130}: In the "zlib" module, fix handling of large buffers (typically
4 GiB) when compressing and decompressing.  Previously, inputs were
limited to 4 GiB, and compression and decompression operations did not
properly handle results of 4 GiB.

@item 
bpo-24773@footnote{https://bugs.python.org/issue24773}: Implemented 
@geindex Python 提高建议; PEP 495
PEP 495@footnote{https://www.python.org/dev/peps/pep-0495} (Local Time Disambiguation).

@item 
Expose the EPOLLEXCLUSIVE constant (when it is defined) in the select
module.

@item 
bpo-27567@footnote{https://bugs.python.org/issue27567}: Expose the EPOLLRDHUP and POLLRDHUP constants in the select
module.

@item 
bpo-1621@footnote{https://bugs.python.org/issue1621}: Avoid signed int negation overflow in the "audioop" module.

@item 
bpo-27533@footnote{https://bugs.python.org/issue27533}: Release GIL in nt._isdir

@item 
bpo-17711@footnote{https://bugs.python.org/issue17711}: Fixed unpickling by the persistent ID with protocol 0. Original
patch by Alexandre Vassalotti.

@item 
bpo-27522@footnote{https://bugs.python.org/issue27522}: Avoid an unintentional reference cycle in email.feedparser.

@item 
bpo-27512@footnote{https://bugs.python.org/issue27512}: Fix a segfault when os.fspath() called an __fspath__() method
that raised an exception. Patch by Xiang Zhang.
@end itemize

@node IDLE<37>,测试<35>,库<45>,Python 3 6 0 alpha 4
@anchor{whatsnew/changelog id342}@anchor{10d3}
@subsubsection IDLE



@itemize -

@item 
bpo-27714@footnote{https://bugs.python.org/issue27714}: text_textview and test_autocomplete now pass when re-run in the
same process.  This occurs when test_idle fails when run with the -w
option but without -jn.  Fix warning from test_config.

@item 
bpo-27621@footnote{https://bugs.python.org/issue27621}: Put query response validation error messages in the query box
itself instead of in a separate messagebox.  Redo tests to match. Add Mac
OSX refinements. Original patch by Mark Roseman.

@item 
bpo-27620@footnote{https://bugs.python.org/issue27620}: Escape key now closes Query box as cancelled.

@item 
bpo-27609@footnote{https://bugs.python.org/issue27609}: IDLE: tab after initial whitespace should tab, not
autocomplete. This fixes problem with writing docstrings at least twice
indented.

@item 
bpo-27609@footnote{https://bugs.python.org/issue27609}: Explicitly return None when there are also non-None returns. In
a few cases, reverse a condition and eliminate a return.

@item 
bpo-25507@footnote{https://bugs.python.org/issue25507}: IDLE no longer runs buggy code because of its tkinter imports.
Users must include the same imports required to run directly in Python.

@item 
bpo-27173@footnote{https://bugs.python.org/issue27173}: Add 'IDLE Modern Unix' to the built-in key sets. Make the
default key set depend on the platform. Add tests for the changes to the
config module.

@item 
bpo-27452@footnote{https://bugs.python.org/issue27452}: add line counter and crc to IDLE configHandler test dump.
@end itemize

@node 测试<35>,Windows<35>,IDLE<37>,Python 3 6 0 alpha 4
@anchor{whatsnew/changelog id343}@anchor{10d4}
@subsubsection 测试



@itemize -

@item 
bpo-25805@footnote{https://bugs.python.org/issue25805}: Skip a test in test_pkgutil as needed that doesn't work when
@code{__name__ == __main__}. Patch by SilentGhost.

@item 
bpo-27472@footnote{https://bugs.python.org/issue27472}: Add test.support.unix_shell as the path to the default shell.

@item 
bpo-27369@footnote{https://bugs.python.org/issue27369}: In test_pyexpat, avoid testing an error message detail that
changed in Expat 2.2.0.

@item 
bpo-27594@footnote{https://bugs.python.org/issue27594}: Prevent assertion error when running test_ast with coverage
enabled: ensure code object has a valid first line number. Patch suggested
by Ivan Levkivskyi.
@end itemize

@node Windows<35>,构建<37>,测试<35>,Python 3 6 0 alpha 4
@anchor{whatsnew/changelog id344}@anchor{10d5}
@subsubsection Windows



@itemize -

@item 
bpo-27647@footnote{https://bugs.python.org/issue27647}: Update bundled Tcl/Tk to 8.6.6.

@item 
bpo-27610@footnote{https://bugs.python.org/issue27610}: Adds 
@geindex Python 提高建议; PEP 514
PEP 514@footnote{https://www.python.org/dev/peps/pep-0514} metadata to Windows installer

@item 
bpo-27469@footnote{https://bugs.python.org/issue27469}: Adds a shell extension to the launcher so that drag and drop
works correctly.

@item 
bpo-27309@footnote{https://bugs.python.org/issue27309}: Enables proper Windows styles in python[w].exe manifest.
@end itemize

@node 构建<37>,,Windows<35>,Python 3 6 0 alpha 4
@anchor{whatsnew/changelog id345}@anchor{10d6}
@subsubsection 构建



@itemize -

@item 
bpo-27713@footnote{https://bugs.python.org/issue27713}: Suppress spurious build warnings when updating importlib's
bootstrap files. Patch by Xiang Zhang

@item 
bpo-25825@footnote{https://bugs.python.org/issue25825}: Correct the references to Modules/python.exp, which is required
on AIX.  The references were accidentally changed in 3.5.0a1.

@item 
bpo-27453@footnote{https://bugs.python.org/issue27453}: CPP invocation in configure must use CPPFLAGS. Patch by Chi
Hsuan Yen.

@item 
bpo-27641@footnote{https://bugs.python.org/issue27641}: The configure script now inserts comments into the makefile to
prevent the pgen and _freeze_importlib executables from being
cross-compiled.

@item 
bpo-26662@footnote{https://bugs.python.org/issue26662}: Set PYTHON_FOR_GEN in configure as the Python program to be
used for file generation during the build.

@item 
bpo-10910@footnote{https://bugs.python.org/issue10910}: Avoid C++ compilation errors on FreeBSD and OS X. Also update
FreedBSD version checks for the original ctype UTF-8 workaround.
@end itemize

@node Python 3 6 0 alpha 3,Python 3 6 0 alpha 2,Python 3 6 0 alpha 4,更新日志
@anchor{whatsnew/changelog python-3-6-0-alpha-3}@anchor{10d7}
@subsection Python 3.6.0 alpha 3


@emph{发布日期: 2016-07-11}

@menu
* 核心与内置: 核心与内置<45>. 
* 库: 库<46>. 
* 安全: 安全<23>. 
* 库: 库<47>. 
* 安全: 安全<24>. 
* 库: 库<48>. 
* IDLE: IDLE<38>. 
* C API: C API<27>. 
* 构建: 构建<38>. 
* 工具/示例: 工具/示例<25>. 
* 文档: 文档<35>. 
* 测试: 测试<36>. 

@end menu

@node 核心与内置<45>,库<46>,,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id346}@anchor{10d8}
@subsubsection 核心与内置



@itemize -

@item 
bpo-27473@footnote{https://bugs.python.org/issue27473}: Fixed possible integer overflow in bytes and bytearray
concatenations. Patch by Xiang Zhang.

@item 
bpo-23034@footnote{https://bugs.python.org/issue23034}: The output of a special Python build with defined COUNT_ALLOCS,
SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by  default.  It
can be re-enabled using the "-X showalloccount" option.  It now outputs to
stderr instead of stdout.

@item 
bpo-27443@footnote{https://bugs.python.org/issue27443}: __length_hint__() of bytearray iterators no longer return a
negative integer for a resized bytearray.

@item 
bpo-27007@footnote{https://bugs.python.org/issue27007}: The fromhex() class methods of bytes and bytearray subclasses
now return an instance of corresponding subclass.
@end itemize

@node 库<46>,安全<23>,核心与内置<45>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id347}@anchor{10d9}
@subsubsection 库



@itemize -

@item 
bpo-26844@footnote{https://bugs.python.org/issue26844}: Fix error message for imp.find_module() to refer to 'path'
instead of 'name'. Patch by Lev Maximov.

@item 
bpo-23804@footnote{https://bugs.python.org/issue23804}: Fix SSL zero-length recv() calls to not block and not raise an
error about unclean EOF.

@item 
bpo-27466@footnote{https://bugs.python.org/issue27466}: Change time format returned by http.cookie.time2netscape,
confirming the netscape cookie format and making it consistent with
documentation.

@item 
bpo-21708@footnote{https://bugs.python.org/issue21708}: Deprecated dbm.dumb behavior that differs from common dbm
behavior: creating a database in 'r' and 'w' modes and modifying a
database in 'r' mode.

@item 
bpo-26721@footnote{https://bugs.python.org/issue26721}: Change the socketserver.StreamRequestHandler.wfile attribute to
implement BufferedIOBase. In particular, the write() method no longer does
partial writes.

@item 
bpo-22115@footnote{https://bugs.python.org/issue22115}: Added methods trace_add, trace_remove and trace_info in the
tkinter.Variable class.  They replace old methods trace_variable, trace,
trace_vdelete and trace_vinfo that use obsolete Tcl commands and might not
work in future versions of Tcl.  Fixed old tracing methods:
trace_vdelete() with wrong mode no longer break tracing, trace_vinfo() now
always returns a list of pairs of strings, tracing in the "u" mode now
works.

@item 
bpo-26243@footnote{https://bugs.python.org/issue26243}: Only the level argument to zlib.compress() is keyword argument
now.  The first argument is positional-only.

@item 
bpo-27038@footnote{https://bugs.python.org/issue27038}: Expose the DirEntry type as os.DirEntry. Code patch by Jelle
Zijlstra.

@item 
bpo-27186@footnote{https://bugs.python.org/issue27186}: Update os.fspath()/PyOS_FSPath() to check the return value of
__fspath__() to be either str or bytes.

@item 
bpo-18726@footnote{https://bugs.python.org/issue18726}: All optional parameters of the dump(), dumps(), load() and
loads() functions and JSONEncoder and JSONDecoder class constructors in
the json module are now keyword-only.

@item 
bpo-27319@footnote{https://bugs.python.org/issue27319}: Methods selection_set(), selection_add(), selection_remove()
and selection_toggle() of ttk.TreeView now allow passing multiple items as
multiple arguments instead of passing them as a tuple.  Deprecated
undocumented ability of calling the selection() method with arguments.

@item 
bpo-27079@footnote{https://bugs.python.org/issue27079}: Fixed curses.ascii functions isblank(), iscntrl() and
ispunct().

@item 
bpo-27294@footnote{https://bugs.python.org/issue27294}: Numerical state in the repr for Tkinter event objects is now
represented as a combination of known flags.

@item 
bpo-27177@footnote{https://bugs.python.org/issue27177}: Match objects in the re module now support index-like objects
as group indices.  Based on patches by Jeroen Demeyer and Xiang Zhang.

@item 
bpo-26754@footnote{https://bugs.python.org/issue26754}: Some functions (compile() etc) accepted a filename argument
encoded as an iterable of integers. Now only strings and byte-like objects
are accepted.

@item 
bpo-26536@footnote{https://bugs.python.org/issue26536}: socket.ioctl now supports SIO_LOOPBACK_FAST_PATH. Patch by
Daniel Stokes.

@item 
bpo-27048@footnote{https://bugs.python.org/issue27048}: Prevents distutils failing on Windows when environment
variables contain non-ASCII characters

@item 
bpo-27330@footnote{https://bugs.python.org/issue27330}: Fixed possible leaks in the ctypes module.

@item 
bpo-27238@footnote{https://bugs.python.org/issue27238}: Got rid of bare excepts in the turtle module.  Original patch
by Jelle Zijlstra.

@item 
bpo-27122@footnote{https://bugs.python.org/issue27122}: When an exception is raised within the context being managed by
a contextlib.ExitStack() and one of the exit stack generators catches and
raises it in a chain, do not re-raise the original exception when exiting,
let the new chained one through.  This avoids the 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479} bug described
in issue25782.
@end itemize

@node 安全<23>,库<47>,库<46>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id348}@anchor{10da}
@subsubsection 安全



@itemize -

@item 
bpo-27278@footnote{https://bugs.python.org/issue27278}: Fix os.urandom() implementation using getrandom() on Linux.
Truncate size to INT_MAX and loop until we collected enough random bytes,
instead of casting a directly Py_ssize_t to int.
@end itemize

@node 库<47>,安全<24>,安全<23>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id349}@anchor{10db}
@subsubsection 库



@itemize -

@item 
bpo-16864@footnote{https://bugs.python.org/issue16864}: sqlite3.Cursor.lastrowid now supports REPLACE statement.
Initial patch by Alex LordThorsen.

@item 
bpo-26386@footnote{https://bugs.python.org/issue26386}: Fixed ttk.TreeView selection operations with item id's
containing spaces.

@item 
bpo-8637@footnote{https://bugs.python.org/issue8637}: Honor a pager set by the env var MANPAGER (in preference to one
set by the env var PAGER).
@end itemize

@node 安全<24>,库<48>,库<47>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id350}@anchor{10dc}
@subsubsection 安全



@itemize -

@item 
bpo-22636@footnote{https://bugs.python.org/issue22636}: Avoid shell injection problems with ctypes.util.find_library().
@end itemize

@node 库<48>,IDLE<38>,安全<24>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id351}@anchor{10dd}
@subsubsection 库



@itemize -

@item 
bpo-16182@footnote{https://bugs.python.org/issue16182}: Fix various functions in the "readline" module to use the
locale encoding, and fix get_begidx() and get_endidx() to return code
point indexes.

@item 
bpo-27392@footnote{https://bugs.python.org/issue27392}: Add loop.connect_accepted_socket(). Patch by Jim Fulton.
@end itemize

@node IDLE<38>,C API<27>,库<48>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id352}@anchor{10de}
@subsubsection IDLE



@itemize -

@item 
bpo-27477@footnote{https://bugs.python.org/issue27477}: IDLE search dialogs now use ttk widgets.

@item 
bpo-27173@footnote{https://bugs.python.org/issue27173}: Add 'IDLE Modern Unix' to the built-in key sets. Make the
default key set depend on the platform. Add tests for the changes to the
config module.

@item 
bpo-27452@footnote{https://bugs.python.org/issue27452}: make command line "idle-test> python test_help.py" work.
__file__ is relative when python is started in the file's directory.

@item 
bpo-27452@footnote{https://bugs.python.org/issue27452}: add line counter and crc to IDLE configHandler test dump.

@item 
bpo-27380@footnote{https://bugs.python.org/issue27380}: IDLE: add query.py with base Query dialog and ttk widgets.
Module had subclasses SectionName, ModuleName, and HelpSource, which are
used to get information from users by configdialog and file =>Load Module.
Each subclass has itw own validity checks.  Using ModuleName allows users
to edit bad module names instead of starting over. Add tests and delete
the two files combined into the new one.

@item 
bpo-27372@footnote{https://bugs.python.org/issue27372}: Test_idle no longer changes the locale.

@item 
bpo-27365@footnote{https://bugs.python.org/issue27365}: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.

@item 
bpo-27245@footnote{https://bugs.python.org/issue27245}: IDLE: Cleanly delete custom themes and key bindings.
Previously, when IDLE was started from a console or by import, a cascade
of warnings was emitted. Patch by Serhiy Storchaka.

@item 
bpo-24137@footnote{https://bugs.python.org/issue24137}: Run IDLE, test_idle, and htest with tkinter default root
disabled.  Fix code and tests that fail with this restriction.  Fix htests
to not create a second and redundant root and mainloop.

@item 
bpo-27310@footnote{https://bugs.python.org/issue27310}: Fix IDLE.app failure to launch on OS X due to vestigial import.
@end itemize

@node C API<27>,构建<38>,IDLE<38>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id353}@anchor{10df}
@subsubsection C API



@itemize -

@item 
bpo-26754@footnote{https://bugs.python.org/issue26754}: PyUnicode_FSDecoder() accepted a filename argument encoded as
an iterable of integers. Now only strings and byte-like objects are
accepted.
@end itemize

@node 构建<38>,工具/示例<25>,C API<27>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id354}@anchor{10e0}
@subsubsection 构建



@itemize -

@item 
bpo-28066@footnote{https://bugs.python.org/issue28066}: Fix the logic that searches build directories for generated
include files when building outside the source tree.

@item 
bpo-27442@footnote{https://bugs.python.org/issue27442}: Expose the Android API level that python was built against, in
sysconfig.get_config_vars() as 'ANDROID_API_LEVEL'.

@item 
bpo-27434@footnote{https://bugs.python.org/issue27434}: The interpreter that runs the cross-build, found in PATH, must
now be of the same feature version (e.g. 3.6) as the source being built.

@item 
bpo-26930@footnote{https://bugs.python.org/issue26930}: 更新Windows 构建以使用OpenSSL OpenSSL 1.0.2h.

@item 
bpo-23968@footnote{https://bugs.python.org/issue23968}: Rename the platform directory from plat-$(MACHDEP) to
plat-$(PLATFORM_TRIPLET). Rename the config directory (LIBPL) from
config-$(LDVERSION) to config-$(LDVERSION)-$(PLATFORM_TRIPLET). Install
the platform specific _sysconfigdata module into the platform directory
and rename it to include the ABIFLAGS.

@item 
在 GNU/Hurd 系统中不使用大文件支持。
@end itemize

@node 工具/示例<25>,文档<35>,构建<38>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id355}@anchor{10e1}
@subsubsection 工具/示例



@itemize -

@item 
bpo-27332@footnote{https://bugs.python.org/issue27332}: Fixed the type of the first argument of module-level functions
generated by Argument Clinic.  Patch by Petr Viktorin.

@item 
bpo-27418@footnote{https://bugs.python.org/issue27418}: Fixed Tools/importbench/importbench.py.
@end itemize

@node 文档<35>,测试<36>,工具/示例<25>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id356}@anchor{10e2}
@subsubsection 文档



@itemize -

@item 
bpo-19489@footnote{https://bugs.python.org/issue19489}: Moved the search box from the sidebar to the header and footer
of each page. Patch by Ammar Askar.

@item 
bpo-27285@footnote{https://bugs.python.org/issue27285}: Update documentation to reflect the deprecation of @code{pyvenv}
and normalize on the term "virtual environment". Patch by Steve Piercy.
@end itemize

@node 测试<36>,,文档<35>,Python 3 6 0 alpha 3
@anchor{whatsnew/changelog id357}@anchor{10e3}
@subsubsection 测试



@itemize -

@item 
bpo-27027@footnote{https://bugs.python.org/issue27027}: Added test.support.is_android that is True when this is an
Android build.
@end itemize

@node Python 3 6 0 alpha 2,Python 3 6 0 alpha 1,Python 3 6 0 alpha 3,更新日志
@anchor{whatsnew/changelog python-3-6-0-alpha-2}@anchor{10e4}
@subsection Python 3.6.0 alpha 2


@emph{发布日期: 2016-06-13}

@menu
* 核心与内置: 核心与内置<46>. 
* 库: 库<49>. 
* 安全: 安全<25>. 
* 库: 库<50>. 
* 安全: 安全<26>. 
* 库: 库<51>. 
* IDLE: IDLE<39>. 
* 文档: 文档<36>. 
* 测试: 测试<37>. 
* Windows: Windows<36>. 
* 构建: 构建<39>. 
* Windows: Windows<37>. 
* C API: C API<28>. 
* 工具/示例: 工具/示例<26>. 

@end menu

@node 核心与内置<46>,库<49>,,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id358}@anchor{10e5}
@subsubsection 核心与内置



@itemize -

@item 
bpo-27095@footnote{https://bugs.python.org/issue27095}: Simplified MAKE_FUNCTION and removed MAKE_CLOSURE opcodes.
Patch by Demur Rumed.

@item 
bpo-27190@footnote{https://bugs.python.org/issue27190}: Raise NotSupportedError if sqlite3 is older than 3.3.1. Patch
by Dave Sawyer.

@item 
bpo-27286@footnote{https://bugs.python.org/issue27286}: Fixed compiling BUILD_MAP_UNPACK_WITH_CALL opcode.  Calling
function with generalized unpacking (PEP 448) and conflicting keyword
names could cause undefined behavior.

@item 
bpo-27140@footnote{https://bugs.python.org/issue27140}: Added BUILD_CONST_KEY_MAP opcode.

@item 
bpo-27186@footnote{https://bugs.python.org/issue27186}: Add support for os.PathLike objects to open() (part of
@geindex Python 提高建议; PEP 519
PEP 519@footnote{https://www.python.org/dev/peps/pep-0519}).

@item 
bpo-27066@footnote{https://bugs.python.org/issue27066}: Fixed SystemError if a custom opener (for open()) returns a
negative number without setting an exception.

@item 
bpo-26983@footnote{https://bugs.python.org/issue26983}: float() now always return an instance of exact float. The
deprecation warning is emitted if __float__ returns an instance of a
strict subclass of float.  In a future versions of Python this can be an
error.

@item 
bpo-27097@footnote{https://bugs.python.org/issue27097}: Python interpreter is now about 7% faster due to optimized
instruction decoding.  Based on patch by Demur Rumed.

@item 
bpo-26647@footnote{https://bugs.python.org/issue26647}: Python interpreter now uses 16-bit wordcode instead of
bytecode. Patch by Demur Rumed.

@item 
bpo-23275@footnote{https://bugs.python.org/issue23275}: Allow assigning to an empty target list in round brackets: () =
iterable.

@item 
bpo-27243@footnote{https://bugs.python.org/issue27243}: Update the __aiter__ protocol: instead of returning an
awaitable that resolves to an asynchronous iterator, the asynchronous
iterator should be returned directly.  Doing the former will trigger a
PendingDeprecationWarning.
@end itemize

@node 库<49>,安全<25>,核心与内置<46>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id359}@anchor{10e6}
@subsubsection 库



@itemize -

@item 
Comment out socket (SO_REUSEPORT) and posix (O_SHLOCK, O_EXLOCK) constants
exposed on the API which are not implemented on GNU/Hurd. They would not
work at runtime anyway.

@item 
bpo-27025@footnote{https://bugs.python.org/issue27025}: Generated names for Tkinter widgets are now more meaningful and
recognizable.

@item 
bpo-25455@footnote{https://bugs.python.org/issue25455}: Fixed crashes in repr of recursive ElementTree.Element and
functools.partial objects.

@item 
bpo-27294@footnote{https://bugs.python.org/issue27294}: Improved repr for Tkinter event objects.

@item 
bpo-20508@footnote{https://bugs.python.org/issue20508}: Improve exception message of IPv@{4,6@}Network.__getitem__. Patch
by Gareth Rees.
@end itemize

@node 安全<25>,库<50>,库<49>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id360}@anchor{10e7}
@subsubsection 安全



@itemize -

@item 
bpo-26556@footnote{https://bugs.python.org/issue26556}: Update expat to 2.1.1, fixes CVE-2015-1283.

@item 
Fix TLS stripping vulnerability in smtplib, CVE-2016-0772. Reported by
Team Oststrom.
@end itemize

@node 库<50>,安全<26>,安全<25>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id361}@anchor{10e8}
@subsubsection 库



@itemize -

@item 
bpo-21386@footnote{https://bugs.python.org/issue21386}: Implement missing IPv4Address.is_global property.  It was
documented since 07a5610bae9d.  Initial patch by Roger Luethi.

@item 
bpo-27029@footnote{https://bugs.python.org/issue27029}: Removed deprecated support of universal newlines mode from
ZipFile.open().

@item 
bpo-27030@footnote{https://bugs.python.org/issue27030}: Unknown escapes consisting of @code{'\'} and an ASCII letter in
regular expressions now are errors.  The re.LOCALE flag now can be used
only with bytes patterns.

@item 
bpo-27186@footnote{https://bugs.python.org/issue27186}: Add os.PathLike support to DirEntry (part of 
@geindex Python 提高建议; PEP 519
PEP 519@footnote{https://www.python.org/dev/peps/pep-0519}).
Initial patch by Jelle Zijlstra.

@item 
bpo-20900@footnote{https://bugs.python.org/issue20900}: distutils register command now decodes HTTP responses
correctly.  Initial patch by ingrid.

@item 
bpo-27186@footnote{https://bugs.python.org/issue27186}: Add os.PathLike support to pathlib, removing its provisional
status (part of PEP 519). Initial patch by Dusty Phillips.

@item 
bpo-27186@footnote{https://bugs.python.org/issue27186}: Add support for os.PathLike objects to os.fsencode() and
os.fsdecode() (part of 
@geindex Python 提高建议; PEP 519
PEP 519@footnote{https://www.python.org/dev/peps/pep-0519}).

@item 
bpo-27186@footnote{https://bugs.python.org/issue27186}: Introduce os.PathLike and os.fspath() (part of 
@geindex Python 提高建议; PEP 519
PEP 519@footnote{https://www.python.org/dev/peps/pep-0519}).

@item 
A new version of typing.py provides several new classes and features:
@@overload outside stubs, Reversible, DefaultDict, Text, ContextManager,
Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some
of the new features are not yet implemented in mypy or other static
analyzers). Also classes for 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} (Awaitable, AsyncIterable,
AsyncIterator) have been added (in fact they made it into 3.5.1 but were
never mentioned).

@item 
bpo-25738@footnote{https://bugs.python.org/issue25738}: Stop http.server.BaseHTTPRequestHandler.send_error() from
sending a message body for 205 Reset Content.  Also, don't send Content
header fields in responses that don't have a body.  Patch by Susumu
Koshiba.

@item 
bpo-21313@footnote{https://bugs.python.org/issue21313}: Fix the "platform" module to tolerate when sys.version contains
truncated build information.
@end itemize

@node 安全<26>,库<51>,库<50>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id362}@anchor{10e9}
@subsubsection 安全



@itemize -

@item 
bpo-26839@footnote{https://bugs.python.org/issue26839}: On Linux, @ref{4cb,,os.urandom()} now calls @code{getrandom()} with
@code{GRND_NONBLOCK} to fall back on reading @code{/dev/urandom} if the urandom
entropy pool is not initialized yet. Patch written by Colm Buckley.
@end itemize

@node 库<51>,IDLE<39>,安全<26>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id363}@anchor{10ea}
@subsubsection 库



@itemize -

@item 
bpo-23883@footnote{https://bugs.python.org/issue23883}: Added missing APIs to __all__ to match the documented APIs for
the following modules: cgi, mailbox, mimetypes, plistlib and smtpd.
Patches by Jacek Kołodziej.

@item 
bpo-27164@footnote{https://bugs.python.org/issue27164}: In the zlib module, allow decompressing raw Deflate streams
with a predefined zdict.  Based on patch by Xiang Zhang.

@item 
bpo-24291@footnote{https://bugs.python.org/issue24291}: Fix wsgiref.simple_server.WSGIRequestHandler to completely
write data to the client.  Previously it could do partial writes and
truncate data.  Also, wsgiref.handler.ServerHandler can now handle stdout
doing partial writes, but this is deprecated.

@item 
bpo-21272@footnote{https://bugs.python.org/issue21272}: Use _sysconfigdata.py to initialize distutils.sysconfig.

@item 
bpo-19611@footnote{https://bugs.python.org/issue19611}: @ref{a0,,inspect} now reports the implicit @code{.0} parameters
generated by the compiler for comprehension and generator expression
scopes as if they were positional-only parameters called @code{implicit0}.
Patch by Jelle Zijlstra.

@item 
bpo-26809@footnote{https://bugs.python.org/issue26809}: Add @code{__all__} to @ref{f6,,string}.  Patch by Emanuel Barry.

@item 
bpo-26373@footnote{https://bugs.python.org/issue26373}: subprocess.Popen.communicate now correctly ignores
BrokenPipeError when the child process dies before .communicate() is
called in more/all circumstances.

@item 
signal, socket, and ssl module IntEnum constant name lookups now return a
consistent name for values having multiple names.  Ex: signal.Signals(6)
now refers to itself as signal.SIGALRM rather than flipping between that
and signal.SIGIOT based on the interpreter's hash randomization seed.

@item 
bpo-27167@footnote{https://bugs.python.org/issue27167}: Clarify the subprocess.CalledProcessError error message text
when the child process died due to a signal.

@item 
bpo-25931@footnote{https://bugs.python.org/issue25931}: Don't define socketserver.Forking* names on platforms such as
Windows that do not support os.fork().

@item 
bpo-21776@footnote{https://bugs.python.org/issue21776}: distutils.upload now correctly handles HTTPError. Initial patch
by Claudiu Popa.

@item 
bpo-26526@footnote{https://bugs.python.org/issue26526}: Replace custom parse tree validation in the parser module with
a simple DFA validator.

@item 
bpo-27114@footnote{https://bugs.python.org/issue27114}: Fix SSLContext._load_windows_store_certs fails with
PermissionError

@item 
bpo-18383@footnote{https://bugs.python.org/issue18383}: Avoid creating duplicate filters when using filterwarnings and
simplefilter. Based on patch by Alex Shkop.

@item 
bpo-23026@footnote{https://bugs.python.org/issue23026}: winreg.QueryValueEx() now return an integer for REG_QWORD type.

@item 
bpo-26741@footnote{https://bugs.python.org/issue26741}: subprocess.Popen destructor now emits a ResourceWarning warning
if the child process is still running.

@item 
bpo-27056@footnote{https://bugs.python.org/issue27056}: Optimize pickle.load() and pickle.loads(), up to 10% faster to
deserialize a lot of small objects.

@item 
bpo-21271@footnote{https://bugs.python.org/issue21271}: New keyword only parameters in reset_mock call.
@end itemize

@node IDLE<39>,文档<36>,库<51>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id364}@anchor{10eb}
@subsubsection IDLE



@itemize -

@item 
bpo-5124@footnote{https://bugs.python.org/issue5124}: Paste with text selected now replaces the selection on X11. This
matches how paste works on Windows, Mac, most modern Linux apps, and ttk
widgets. Original patch by Serhiy Storchaka.

@item 
bpo-24750@footnote{https://bugs.python.org/issue24750}: Switch all scrollbars in IDLE to ttk versions. Where needed,
minimal tests are added to cover changes.

@item 
bpo-24759@footnote{https://bugs.python.org/issue24759}: IDLE requires tk 8.5 and availability ttk widgets. Delete now
unneeded tk version tests and code for older versions. Add test for IDLE
syntax colorizer.

@item 
bpo-27239@footnote{https://bugs.python.org/issue27239}: idlelib.macosx.isXyzTk functions initialize as needed.

@item 
bpo-27262@footnote{https://bugs.python.org/issue27262}: move Aqua unbinding code, which enable context menus, to
macosx.

@item 
bpo-24759@footnote{https://bugs.python.org/issue24759}: Make clear in idlelib.idle_test.__init__ that the directory is
a private implementation of test.test_idle and tool for maintainers.

@item 
bpo-27196@footnote{https://bugs.python.org/issue27196}: Stop 'ThemeChanged' warnings when running IDLE tests. These
persisted after other warnings were suppressed in #20567. Apply Serhiy
Storchaka's update_idletasks solution to four test files. Record this
additional advice in idle_test/README.txt

@item 
bpo-20567@footnote{https://bugs.python.org/issue20567}: Revise idle_test/README.txt with advice about avoiding tk
warning messages from tests.  Apply advice to several IDLE tests.

@item 
bpo-24225@footnote{https://bugs.python.org/issue24225}: Update idlelib/README.txt with new file names and event
handlers.

@item 
bpo-27156@footnote{https://bugs.python.org/issue27156}: Remove obsolete code not used by IDLE.

@item 
bpo-27117@footnote{https://bugs.python.org/issue27117}: Make colorizer htest and turtledemo work with dark themes. Move
code for configuring text widget colors to a new function.

@item 
bpo-24225@footnote{https://bugs.python.org/issue24225}: Rename many @code{idlelib/*.py} and @code{idle_test/test_*.py} files.
Edit files to replace old names with new names when the old name referred
to the module rather than the class it contained. See the issue and IDLE
section in What's New in 3.6 for more.

@item 
bpo-26673@footnote{https://bugs.python.org/issue26673}: When tk reports font size as 0, change to size 10. Such fonts
on Linux prevented the configuration dialog from opening.

@item 
bpo-21939@footnote{https://bugs.python.org/issue21939}: Add test for IDLE's percolator. Original patch by Saimadhav
Heblikar.

@item 
bpo-21676@footnote{https://bugs.python.org/issue21676}: Add test for IDLE's replace dialog. Original patch by Saimadhav
Heblikar.

@item 
bpo-18410@footnote{https://bugs.python.org/issue18410}: Add test for IDLE's search dialog. Original patch by Westley
Martínez.

@item 
bpo-21703@footnote{https://bugs.python.org/issue21703}: Add test for undo delegator.  Patch mostly by Saimadhav
Heblikar .

@item 
bpo-27044@footnote{https://bugs.python.org/issue27044}: Add ConfigDialog.remove_var_callbacks to stop memory leaks.

@item 
bpo-23977@footnote{https://bugs.python.org/issue23977}: Add more asserts to test_delegator.
@end itemize

@node 文档<36>,测试<37>,IDLE<39>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id365}@anchor{10ec}
@subsubsection 文档



@itemize -

@item 
bpo-16484@footnote{https://bugs.python.org/issue16484}: Change the default PYTHONDOCS URL to "https:", and fix the
resulting links to use lowercase.  Patch by Sean Rodman, test by Kaushik
Nadikuditi.

@item 
bpo-24136@footnote{https://bugs.python.org/issue24136}: Document the new 
@geindex Python 提高建议; PEP 448
PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} unpacking syntax of 3.5.

@item 
bpo-22558@footnote{https://bugs.python.org/issue22558}: Add remaining doc links to source code for Python-coded
modules. Patch by Yoni Lavi.
@end itemize

@node 测试<37>,Windows<36>,文档<36>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id366}@anchor{10ed}
@subsubsection 测试



@itemize -

@item 
bpo-25285@footnote{https://bugs.python.org/issue25285}: regrtest now uses subprocesses when the -j1 command line option
is used: each test file runs in a fresh child process. Before, the -j1
option was ignored.

@item 
bpo-25285@footnote{https://bugs.python.org/issue25285}: Tools/buildbot/test.bat script now uses -j1 by default to run
each test file in fresh child process.
@end itemize

@node Windows<36>,构建<39>,测试<37>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id367}@anchor{10ee}
@subsubsection Windows



@itemize -

@item 
bpo-27064@footnote{https://bugs.python.org/issue27064}: The py.exe launcher now defaults to Python 3. The Windows
launcher @code{py.exe} no longer prefers an installed Python 2 version over
Python 3 by default when used interactively.
@end itemize

@node 构建<39>,Windows<37>,Windows<36>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id368}@anchor{10ef}
@subsubsection 构建



@itemize -

@item 
bpo-27229@footnote{https://bugs.python.org/issue27229}: Fix the cross-compiling pgen rule for in-tree builds.  Patch by
Xavier de Gaye.

@item 
bpo-26930@footnote{https://bugs.python.org/issue26930}: 更新OS X 10.5+（仅32位）安装程序以构建并链接OpenSSL 1.0.2h。
@end itemize

@node Windows<37>,C API<28>,构建<39>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id369}@anchor{10f0}
@subsubsection Windows



@itemize -

@item 
bpo-17500@footnote{https://bugs.python.org/issue17500}: Remove unused and outdated icons. (See also:
@indicateurl{https://github.com/python/pythondotorg/issues/945})
@end itemize

@node C API<28>,工具/示例<26>,Windows<37>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id370}@anchor{10f1}
@subsubsection C API



@itemize -

@item 
bpo-27186@footnote{https://bugs.python.org/issue27186}: Add the PyOS_FSPath() function (part of 
@geindex Python 提高建议; PEP 519
PEP 519@footnote{https://www.python.org/dev/peps/pep-0519}).

@item 
bpo-26282@footnote{https://bugs.python.org/issue26282}: PyArg_ParseTupleAndKeywords() now supports positional-only
parameters.
@end itemize

@node 工具/示例<26>,,C API<28>,Python 3 6 0 alpha 2
@anchor{whatsnew/changelog id371}@anchor{10f2}
@subsubsection 工具/示例



@itemize -

@item 
bpo-26282@footnote{https://bugs.python.org/issue26282}: Argument Clinic now supports positional-only and keyword
parameters in the same function.
@end itemize

@node Python 3 6 0 alpha 1,Python 3 5 5 正式版,Python 3 6 0 alpha 2,更新日志
@anchor{whatsnew/changelog python-3-6-0-alpha-1}@anchor{10f3}
@subsection Python 3.6.0 alpha 1


@emph{发布日期: 2016-05-16}

@menu
* 核心与内置: 核心与内置<47>. 
* 库: 库<52>. 
* 安全: 安全<27>. 
* 库: 库<53>. 
* 安全: 安全<28>. 
* 库: 库<54>. 
* 安全: 安全<29>. 
* 库: 库<55>. 
* IDLE: IDLE<40>. 
* 文档: 文档<37>. 
* 测试: 测试<38>. 
* 构建: 构建<40>. 
* Windows: Windows<38>. 
* 工具/示例: 工具/示例<27>. 
* C API: C API<29>. 

@end menu

@node 核心与内置<47>,库<52>,,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id372}@anchor{10f4}
@subsubsection 核心与内置



@itemize -

@item 
bpo-20041@footnote{https://bugs.python.org/issue20041}: Fixed TypeError when frame.f_trace is set to None. Patch by
Xavier de Gaye.

@item 
bpo-26168@footnote{https://bugs.python.org/issue26168}: Fixed possible refleaks in failing Py_BuildValue() with the "N"
format unit.

@item 
bpo-26991@footnote{https://bugs.python.org/issue26991}: Fix possible refleak when creating a function with annotations.

@item 
bpo-27039@footnote{https://bugs.python.org/issue27039}: Fixed bytearray.remove() for values greater than 127.  Based on
patch by Joe Jevnik.

@item 
bpo-23640@footnote{https://bugs.python.org/issue23640}: int.from_bytes() no longer bypasses constructors for
subclasses.

@item 
bpo-27005@footnote{https://bugs.python.org/issue27005}: Optimized the float.fromhex() class method for exact float. It
is now 2 times faster.

@item 
bpo-18531@footnote{https://bugs.python.org/issue18531}: Single var-keyword argument of dict subtype was passed
unscathed to the C-defined function.  Now it is converted to exact dict.

@item 
bpo-26811@footnote{https://bugs.python.org/issue26811}: gc.get_objects() no longer contains a broken tuple with NULL
pointer.

@item 
bpo-20120@footnote{https://bugs.python.org/issue20120}: Use RawConfigParser for .pypirc parsing, removing support for
interpolation unintentionally added with move to Python 3. Behavior no
longer does any interpolation in .pypirc files, matching behavior in
Python 2.7 and Setuptools 19.0.

@item 
bpo-26249@footnote{https://bugs.python.org/issue26249}: Memory functions of the @ref{4ff,,PyMem_Malloc()} domain
(@ref{503,,PYMEM_DOMAIN_MEM}) now use the @ref{5bc,,pymalloc allocator} rather than system @code{malloc()}. Applications calling
@ref{4ff,,PyMem_Malloc()} without holding the GIL can now crash: use
@code{PYTHONMALLOC=debug} environment variable to validate the usage of
memory allocators in your application.

@item 
bpo-26802@footnote{https://bugs.python.org/issue26802}: Optimize function calls only using unpacking like
@code{func(*tuple)} (no other positional argument, no keyword): avoid copying
the tuple. Patch written by Joe Jevnik.

@item 
bpo-26659@footnote{https://bugs.python.org/issue26659}: Make the builtin slice type support cycle collection.

@item 
bpo-26718@footnote{https://bugs.python.org/issue26718}: super.__init__ no longer leaks memory if called multiple times.
NOTE: A direct call of super.__init__ is not endorsed!

@item 
bpo-27138@footnote{https://bugs.python.org/issue27138}: Fix the doc comment for FileFinder.find_spec().

@item 
bpo-27147@footnote{https://bugs.python.org/issue27147}: Mention 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} in the importlib docs.

@item 
bpo-25339@footnote{https://bugs.python.org/issue25339}: PYTHONIOENCODING now has priority over locale in setting the
error handler for stdin and stdout.

@item 
bpo-26494@footnote{https://bugs.python.org/issue26494}: Fixed crash on iterating exhausting iterators. Affected classes
are generic sequence iterators, iterators of str, bytes, bytearray, list,
tuple, set, frozenset, dict, OrderedDict, corresponding views and
os.scandir() iterator.

@item 
bpo-26574@footnote{https://bugs.python.org/issue26574}: Optimize @code{bytes.replace(b'@w{'}, b'.')} and
@code{bytearray.replace(b'@w{'}, b'.')}. Patch written by Josh Snider.

@item 
bpo-26581@footnote{https://bugs.python.org/issue26581}: If coding cookie is specified multiple times on a line in
Python source code file, only the first one is taken to account.

@item 
bpo-19711@footnote{https://bugs.python.org/issue19711}: Add tests for reloading namespace packages.

@item 
bpo-21099@footnote{https://bugs.python.org/issue21099}: Switch applicable importlib tests to use 
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451} API.

@item 
bpo-26563@footnote{https://bugs.python.org/issue26563}: Debug hooks on Python memory allocators now raise a fatal error
if functions of the @ref{4ff,,PyMem_Malloc()} family are called without
holding the GIL.

@item 
bpo-26564@footnote{https://bugs.python.org/issue26564}: On error, the debug hooks on Python memory allocators now use
the @ref{114,,tracemalloc} module to get the traceback where a memory block
was allocated.

@item 
bpo-26558@footnote{https://bugs.python.org/issue26558}: The debug hooks on Python memory allocator
@ref{502,,PyObject_Malloc()} now detect when functions are called without
holding the GIL.

@item 
bpo-26516@footnote{https://bugs.python.org/issue26516}: Add 
@geindex PYTHONMALLOC
@geindex 环境变量; PYTHONMALLOC
@ref{4fd,,PYTHONMALLOC} environment variable to set the
Python memory allocators and/or install debug hooks.

@item 
bpo-26516@footnote{https://bugs.python.org/issue26516}: The @ref{504,,PyMem_SetupDebugHooks()} function can now also be
used on Python compiled in release mode.

@item 
bpo-26516@footnote{https://bugs.python.org/issue26516}: The 
@geindex PYTHONMALLOCSTATS
@geindex 环境变量; PYTHONMALLOCSTATS
@ref{10f5,,PYTHONMALLOCSTATS} environment variable can now
also be used on Python compiled in release mode. It now has no effect if
set to an empty string.

@item 
bpo-26516@footnote{https://bugs.python.org/issue26516}: In debug mode, debug hooks are now also installed on Python
memory allocators when Python is configured without pymalloc.

@item 
bpo-26464@footnote{https://bugs.python.org/issue26464}: Fix str.translate() when string is ASCII and first replacements
removes character, but next replacement uses a non-ASCII character or a
string longer than 1 character. Regression introduced in Python 3.5.0.

@item 
bpo-22836@footnote{https://bugs.python.org/issue22836}: Ensure exception reports from PyErr_Display() and
PyErr_WriteUnraisable() are sensible even when formatting them produces
secondary errors.  This affects the reports produced by
sys.__excepthook__() and when __del__() raises an exception.

@item 
bpo-26302@footnote{https://bugs.python.org/issue26302}: Correct behavior to reject comma as a legal character for
cookie names.

@item 
bpo-26136@footnote{https://bugs.python.org/issue26136}: Upgrade the warning when a generator raises StopIteration from
PendingDeprecationWarning to DeprecationWarning.  Patch by Anish Shah.

@item 
bpo-26204@footnote{https://bugs.python.org/issue26204}: The compiler now ignores all constant statements: bytes, str,
int, float, complex, name constants (None, False, True), Ellipsis and
ast.Constant; not only str and int. For example, @code{1.0} is now ignored in
@code{def f(): 1.0}.

@item 
bpo-4806@footnote{https://bugs.python.org/issue4806}: Avoid masking the original TypeError exception when using star
(@code{*}) unpacking in function calls.  Based on patch by Hagen Fürstenau
and Daniel Urban.

@item 
bpo-26146@footnote{https://bugs.python.org/issue26146}: Add a new kind of AST node: @code{ast.Constant}. It can be used by
external AST optimizers, but the compiler does not emit directly such
node.

@item 
bpo-23601@footnote{https://bugs.python.org/issue23601}: Sped-up allocation of dict key objects by using Python's small
object allocator.  (Contributed by Julian Taylor.)

@item 
bpo-18018@footnote{https://bugs.python.org/issue18018}: Import raises ImportError instead of SystemError if a relative
import is attempted without a known parent package.

@item 
bpo-25843@footnote{https://bugs.python.org/issue25843}: When compiling code, don't merge constants if they are equal
but have a different types. For example, @code{f1, f2 = lambda: 1, lambda:
1.0} is now correctly compiled to two different functions: @code{f1()}
returns @code{1} (@code{int}) and @code{f2()} returns @code{1.0} (@code{float}), even if
@code{1} and @code{1.0} are equal.

@item 
bpo-26107@footnote{https://bugs.python.org/issue26107}: The format of the @code{co_lnotab} attribute of code objects
changes to support negative line number delta.

@item 
bpo-26154@footnote{https://bugs.python.org/issue26154}: Add a new private _PyThreadState_UncheckedGet() function to get
the current Python thread state, but don't issue a fatal error if it is
NULL. This new function must be used instead of accessing directly the
_PyThreadState_Current variable.  The variable is no more exposed since
Python 3.5.1 to hide the exact implementation of atomic C types, to avoid
compiler issues.

@item 
bpo-25791@footnote{https://bugs.python.org/issue25791}: If __package__ != __spec__.parent or if neither __package__ or
__spec__ are defined then ImportWarning is raised.

@item 
bpo-22995@footnote{https://bugs.python.org/issue22995}: [UPDATE] Comment out the one of the pickleability tests in
_PyObject_GetState() due to regressions observed in Cython-based projects.

@item 
bpo-25961@footnote{https://bugs.python.org/issue25961}: Disallowed null characters in the type name.

@item 
bpo-25973@footnote{https://bugs.python.org/issue25973}: Fix segfault when an invalid nonlocal statement binds a name
starting with two underscores.

@item 
bpo-22995@footnote{https://bugs.python.org/issue22995}: Instances of extension types with a state that aren't
subclasses of list or dict and haven't implemented any pickle-related
methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or
__getstate__), can no longer be pickled.  Including memoryview.

@item 
bpo-20440@footnote{https://bugs.python.org/issue20440}: Massive replacing unsafe attribute setting code with special
macro Py_SETREF.

@item 
bpo-25766@footnote{https://bugs.python.org/issue25766}: Special method __bytes__() now works in str subclasses.

@item 
bpo-25421@footnote{https://bugs.python.org/issue25421}: __sizeof__ methods of builtin types now use dynamic basic size.
This allows sys.getsize() to work correctly with their subclasses with
__slots__ defined.

@item 
bpo-25709@footnote{https://bugs.python.org/issue25709}: Fixed problem with in-place string concatenation and utf-8
cache.

@item 
bpo-5319@footnote{https://bugs.python.org/issue5319}: New Py_FinalizeEx() API allowing Python to set an exit status of
120 on failure to flush buffered streams.

@item 
bpo-25485@footnote{https://bugs.python.org/issue25485}: telnetlib.Telnet is now a context manager.

@item 
bpo-24097@footnote{https://bugs.python.org/issue24097}: Fixed crash in object.__reduce__() if slot name is freed inside
__getattr__.

@item 
bpo-24731@footnote{https://bugs.python.org/issue24731}: Fixed crash on converting objects with special methods
__bytes__, __trunc__, and __float__ returning instances of subclasses of
bytes, int, and float to subclasses of bytes, int, and float
correspondingly.

@item 
bpo-25630@footnote{https://bugs.python.org/issue25630}: Fix a possible segfault during argument parsing in functions
that accept filesystem paths.

@item 
bpo-23564@footnote{https://bugs.python.org/issue23564}: Fixed a partially broken sanity check in the _posixsubprocess
internals regarding how fds_to_pass were passed to the child.  The bug had
no actual impact as subprocess.py already avoided it.

@item 
bpo-25388@footnote{https://bugs.python.org/issue25388}: Fixed tokenizer crash when processing undecodable source code
with a null byte.

@item 
bpo-25462@footnote{https://bugs.python.org/issue25462}: The hash of the key now is calculated only once in most
operations in C implementation of OrderedDict.

@item 
bpo-22995@footnote{https://bugs.python.org/issue22995}: Default implementation of __reduce__ and __reduce_ex__ now
rejects builtin types with not defined __new__.

@item 
bpo-24802@footnote{https://bugs.python.org/issue24802}: Avoid buffer overreads when int(), float(), compile(), exec()
and eval() are passed bytes-like objects.  These objects are not
necessarily terminated by a null byte, but the functions assumed they
were.

@item 
bpo-25555@footnote{https://bugs.python.org/issue25555}: Fix parser and AST: fill lineno and col_offset of "arg" node
when compiling AST from Python objects.

@item 
bpo-24726@footnote{https://bugs.python.org/issue24726}: Fixed a crash and leaking NULL in repr() of OrderedDict that
was mutated by direct calls of dict methods.

@item 
bpo-25449@footnote{https://bugs.python.org/issue25449}: Iterating OrderedDict with keys with unstable hash now raises
KeyError in C implementations as well as in Python implementation.

@item 
bpo-25395@footnote{https://bugs.python.org/issue25395}: Fixed crash when highly nested OrderedDict structures were
garbage collected.

@item 
bpo-25401@footnote{https://bugs.python.org/issue25401}: Optimize bytes.fromhex() and bytearray.fromhex(): they are now
between 2x and 3.5x faster.

@item 
bpo-25399@footnote{https://bugs.python.org/issue25399}: Optimize bytearray % args using the new private _PyBytesWriter
API. Formatting is now between 2.5 and 5 times faster.

@item 
bpo-25274@footnote{https://bugs.python.org/issue25274}: sys.setrecursionlimit() now raises a RecursionError if the new
recursion limit is too low depending at the current recursion depth.
Modify also the "lower-water mark" formula to make it monotonic. This mark
is used to decide when the overflowed flag of the thread state is reset.

@item 
bpo-24402@footnote{https://bugs.python.org/issue24402}: Fix input() to prompt to the redirected stdout when
sys.stdout.fileno() fails.

@item 
bpo-25349@footnote{https://bugs.python.org/issue25349}: Optimize bytes % args using the new private _PyBytesWriter API.
Formatting is now up to 2 times faster.

@item 
bpo-24806@footnote{https://bugs.python.org/issue24806}: Prevent builtin types that are not allowed to be subclassed
from being subclassed through multiple inheritance.

@item 
bpo-25301@footnote{https://bugs.python.org/issue25301}: The UTF-8 decoder is now up to 15 times as fast for error
handlers: @code{ignore}, @code{replace} and @code{surrogateescape}.

@item 
bpo-24848@footnote{https://bugs.python.org/issue24848}: Fixed a number of bugs in UTF-7 decoding of misformed data.

@item 
bpo-25267@footnote{https://bugs.python.org/issue25267}: The UTF-8 encoder is now up to 75 times as fast for error
handlers: @code{ignore}, @code{replace}, @code{surrogateescape}, @code{surrogatepass}.
Patch co-written with Serhiy Storchaka.

@item 
bpo-25280@footnote{https://bugs.python.org/issue25280}: Import trace messages emitted in verbose (-v) mode are no
longer formatted twice.

@item 
bpo-25227@footnote{https://bugs.python.org/issue25227}: Optimize ASCII and latin1 encoders with the @code{surrogateescape}
error handler: the encoders are now up to 3 times as fast. Initial patch
written by Serhiy Storchaka.

@item 
bpo-25003@footnote{https://bugs.python.org/issue25003}: On Solaris 11.3 or newer, os.urandom() now uses the getrandom()
function instead of the getentropy() function. The getentropy() function
is blocking to generate very good quality entropy, os.urandom() doesn't
need such high-quality entropy.

@item 
bpo-9232@footnote{https://bugs.python.org/issue9232}: Modify Python's grammar to allow trailing commas in the argument
list of a function declaration.  For example, "def f(*, a = 3,): pass" is
now legal. Patch from Mark Dickinson.

@item 
bpo-24965@footnote{https://bugs.python.org/issue24965}: Implement 
@geindex Python 提高建议; PEP 498
PEP 498@footnote{https://www.python.org/dev/peps/pep-0498} "Literal String Interpolation". This
allows you to embed expressions inside f-strings, which are converted to
normal strings at run time. Given x=3, then f'value=@{x@}' == 'value=3'.
Patch by Eric V. Smith.

@item 
bpo-26478@footnote{https://bugs.python.org/issue26478}: Fix semantic bugs when using binary operators with dictionary
views and tuples.

@item 
bpo-26171@footnote{https://bugs.python.org/issue26171}: Fix possible integer overflow and heap corruption in
zipimporter.get_data().

@item 
bpo-25660@footnote{https://bugs.python.org/issue25660}: Fix TAB key behaviour in REPL with readline.

@item 
bpo-26288@footnote{https://bugs.python.org/issue26288}: Optimize PyLong_AsDouble.

@item 
bpo-26289@footnote{https://bugs.python.org/issue26289}: Optimize floor and modulo division for single-digit longs.
Microbenchmarks show 2-2.5x improvement.  Built-in 'divmod' function is
now also ~10% faster. (See also: bpo-26315@footnote{https://bugs.python.org/issue26315})

@item 
bpo-25887@footnote{https://bugs.python.org/issue25887}: Raise a RuntimeError when a coroutine object is awaited more
than once.
@end itemize

@node 库<52>,安全<27>,核心与内置<47>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id373}@anchor{10f6}
@subsubsection 库



@itemize -

@item 
bpo-27057@footnote{https://bugs.python.org/issue27057}: Fix os.set_inheritable() on Android, ioctl() is blocked by
SELinux and fails with EACCESS. The function now falls back to fcntl().
Patch written by Michał Bednarski.

@item 
bpo-27014@footnote{https://bugs.python.org/issue27014}: Fix infinite recursion using typing.py.  Thanks to Kalle Tuure!

@item 
bpo-27031@footnote{https://bugs.python.org/issue27031}: Removed dummy methods in Tkinter widget classes: tk_menuBar()
and tk_bindForTraversal().

@item 
bpo-14132@footnote{https://bugs.python.org/issue14132}: Fix urllib.request redirect handling when the target only has a
query string.  Original fix by Ján Janech.

@item 
bpo-17214@footnote{https://bugs.python.org/issue17214}: The "urllib.request" module now percent-encodes non-ASCII bytes
found in redirect target URLs.  Some servers send Location header fields
with non-ASCII bytes, but "http.client" requires the request target to be
ASCII-encodable, otherwise a UnicodeEncodeError is raised.  Based on patch
by Christian Heimes.

@item 
bpo-27033@footnote{https://bugs.python.org/issue27033}: The default value of the decode_data parameter for
smtpd.SMTPChannel and smtpd.SMTPServer constructors is changed to False.

@item 
bpo-27034@footnote{https://bugs.python.org/issue27034}: Removed deprecated class asynchat.fifo.

@item 
bpo-26870@footnote{https://bugs.python.org/issue26870}: Added readline.set_auto_history(), which can stop entries being
automatically added to the history list.  Based on patch by Tyler
Crompton.

@item 
bpo-26039@footnote{https://bugs.python.org/issue26039}: zipfile.ZipFile.open() can now be used to write data into a ZIP
file, as well as for extracting data.  Patch by Thomas Kluyver.

@item 
bpo-26892@footnote{https://bugs.python.org/issue26892}: Honor debuglevel flag in urllib.request.HTTPHandler. Patch
contributed by Chi Hsuan Yen.

@item 
bpo-22274@footnote{https://bugs.python.org/issue22274}: In the subprocess module, allow stderr to be redirected to
stdout even when stdout is not redirected.  Patch by Akira Li.

@item 
bpo-26807@footnote{https://bugs.python.org/issue26807}: mock_open 'files' no longer error on readline at end of file.
Patch from Yolanda Robla.

@item 
bpo-25745@footnote{https://bugs.python.org/issue25745}: Fixed leaking a userptr in curses panel destructor.

@item 
bpo-26977@footnote{https://bugs.python.org/issue26977}: Removed unnecessary, and ignored, call to sum of squares helper
in statistics.pvariance.

@item 
bpo-26002@footnote{https://bugs.python.org/issue26002}: Use bisect in statistics.median instead of a linear search.
Patch by Upendra Kuma.

@item 
bpo-25974@footnote{https://bugs.python.org/issue25974}: Make use of new Decimal.as_integer_ratio() method in statistics
module. Patch by Stefan Krah.

@item 
bpo-26996@footnote{https://bugs.python.org/issue26996}: Add secrets module as described in 
@geindex Python 提高建议; PEP 506
PEP 506@footnote{https://www.python.org/dev/peps/pep-0506}.

@item 
bpo-26881@footnote{https://bugs.python.org/issue26881}: The modulefinder module now supports extended opcode arguments.

@item 
bpo-23815@footnote{https://bugs.python.org/issue23815}: Fixed crashes related to directly created instances of types in
_tkinter and curses.panel modules.

@item 
bpo-17765@footnote{https://bugs.python.org/issue17765}: weakref.ref() no longer silently ignores keyword arguments.
Patch by Georg Brandl.

@item 
bpo-26873@footnote{https://bugs.python.org/issue26873}: xmlrpc now raises ResponseError on unsupported type tags
instead of silently return incorrect result.

@item 
bpo-26915@footnote{https://bugs.python.org/issue26915}: The __contains__ methods in the collections ABCs now check for
identity before checking equality.  This better matches the behavior of
the concrete classes, allows sensible handling of NaNs, and makes it
easier to reason about container invariants.

@item 
bpo-26711@footnote{https://bugs.python.org/issue26711}: Fixed the comparison of plistlib.Data with other types.

@item 
bpo-24114@footnote{https://bugs.python.org/issue24114}: Fix an uninitialized variable in @code{ctypes.util}. The bug only
occurs on SunOS when the ctypes implementation searches for the @code{crle}
program.  Patch by Xiang Zhang.  Tested on SunOS by Kees Bos.

@item 
bpo-26864@footnote{https://bugs.python.org/issue26864}: In urllib.request, change the proxy bypass host checking
against no_proxy to be case-insensitive, and to not match unrelated host
names that happen to have a bypassed hostname as a suffix.  Patch by Xiang
Zhang.

@item 
bpo-24902@footnote{https://bugs.python.org/issue24902}: Print server URL on http.server startup.  Initial patch by
Felix Kaiser.

@item 
bpo-25788@footnote{https://bugs.python.org/issue25788}: fileinput.hook_encoded() now supports an "errors" argument for
passing to open.  Original patch by Joseph Hackman.

@item 
bpo-26634@footnote{https://bugs.python.org/issue26634}: recursive_repr() now sets __qualname__ of wrapper.  Patch by
Xiang Zhang.

@item 
bpo-26804@footnote{https://bugs.python.org/issue26804}: urllib.request will prefer lower_case proxy environment
variables over UPPER_CASE or Mixed_Case ones. Patch contributed by
Hans-Peter Jansen.

@item 
bpo-26837@footnote{https://bugs.python.org/issue26837}: assertSequenceEqual() now correctly outputs non-stringified
differing items (like bytes in the -b mode).  This affects
assertListEqual() and assertTupleEqual().

@item 
bpo-26041@footnote{https://bugs.python.org/issue26041}: Remove "will be removed in Python 3.7" from deprecation
messages of platform.dist() and platform.linux_distribution(). Patch by
Kumaripaba Miyurusara Athukorala.

@item 
bpo-26822@footnote{https://bugs.python.org/issue26822}: itemgetter, attrgetter and methodcaller objects no longer
silently ignore keyword arguments.

@item 
bpo-26733@footnote{https://bugs.python.org/issue26733}: Disassembling a class now disassembles class and static
methods. Patch by Xiang Zhang.

@item 
bpo-26801@footnote{https://bugs.python.org/issue26801}: Fix error handling in @ref{a45,,shutil.get_terminal_size()}, catch
@ref{393,,AttributeError} instead of @ref{d74,,NameError}. Patch written by
Emanuel Barry.

@item 
bpo-24838@footnote{https://bugs.python.org/issue24838}: tarfile's ustar and gnu formats now correctly calculate name
and link field limits for multibyte character encodings like utf-8.
@end itemize

@node 安全<27>,库<53>,库<52>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id374}@anchor{10f7}
@subsubsection 安全



@itemize -

@item 
bpo-26657@footnote{https://bugs.python.org/issue26657}: Fix directory traversal vulnerability with http.server on
Windows.  This fixes a regression that was introduced in 3.3.4rc1 and
3.4.0rc1.  Based on patch by Philipp Hagemeister.
@end itemize

@node 库<53>,安全<28>,安全<27>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id375}@anchor{10f8}
@subsubsection 库



@itemize -

@item 
bpo-26717@footnote{https://bugs.python.org/issue26717}: Stop encoding Latin-1-ized WSGI paths with UTF-8.  Patch by
Anthony Sottile.

@item 
bpo-26782@footnote{https://bugs.python.org/issue26782}: Add STARTUPINFO to subprocess.__all__ on Windows.

@item 
bpo-26404@footnote{https://bugs.python.org/issue26404}: Add context manager to socketserver.  Patch by Aviv Palivoda.

@item 
bpo-26735@footnote{https://bugs.python.org/issue26735}: Fix @ref{4cb,,os.urandom()} on Solaris 11.3 and newer when reading
more than 1,024 bytes: call @code{getrandom()} multiple times with a limit of
1024 bytes per call.

@item 
bpo-26585@footnote{https://bugs.python.org/issue26585}: Eliminate http.server._quote_html() and use
html.escape(quote=False).  Patch by Xiang Zhang.

@item 
bpo-26685@footnote{https://bugs.python.org/issue26685}: Raise OSError if closing a socket fails.

@item 
bpo-16329@footnote{https://bugs.python.org/issue16329}: Add .webm to mimetypes.types_map.  Patch by Giampaolo Rodola'.

@item 
bpo-13952@footnote{https://bugs.python.org/issue13952}: Add .csv to mimetypes.types_map.  Patch by Geoff Wilson.

@item 
bpo-26587@footnote{https://bugs.python.org/issue26587}: the site module now allows .pth files to specify files to be
added to sys.path (e.g. zip files).

@item 
bpo-25609@footnote{https://bugs.python.org/issue25609}: Introduce contextlib.AbstractContextManager and
typing.ContextManager.

@item 
bpo-26709@footnote{https://bugs.python.org/issue26709}: Fixed Y2038 problem in loading binary PLists.

@item 
bpo-23735@footnote{https://bugs.python.org/issue23735}: Handle terminal resizing with Readline 6.3+ by installing our
own SIGWINCH handler.  Patch by Eric Price.

@item 
bpo-25951@footnote{https://bugs.python.org/issue25951}: Change SSLSocket.sendall() to return None, as explicitly
documented for plain socket objects.  Patch by Aviv Palivoda.

@item 
bpo-26586@footnote{https://bugs.python.org/issue26586}: In http.server, respond with "413 Request header fields too
large" if there are too many header fields to parse, rather than killing
the connection and raising an unhandled exception.  Patch by Xiang Zhang.

@item 
bpo-26676@footnote{https://bugs.python.org/issue26676}: Added missing XMLPullParser to ElementTree.__all__.

@item 
bpo-22854@footnote{https://bugs.python.org/issue22854}: Change BufferedReader.writable() and BufferedWriter.readable()
to always return False.

@item 
bpo-26492@footnote{https://bugs.python.org/issue26492}: Exhausted iterator of array.array now conforms with the
behavior of iterators of other mutable sequences: it lefts exhausted even
if iterated array is extended.

@item 
bpo-26641@footnote{https://bugs.python.org/issue26641}: doctest.DocFileTest and doctest.testfile() now support packages
(module splitted into multiple directories) for the package parameter.

@item 
bpo-25195@footnote{https://bugs.python.org/issue25195}: Fix a regression in mock.MagicMock. _Call is a subclass of
tuple (changeset 3603bae63c13 only works for classes) so we need to
implement __ne__ ourselves.  Patch by Andrew Plummer.

@item 
bpo-26644@footnote{https://bugs.python.org/issue26644}: Raise ValueError rather than SystemError when a negative length
is passed to SSLSocket.recv() or read().

@item 
bpo-23804@footnote{https://bugs.python.org/issue23804}: Fix SSL recv(0) and read(0) methods to return zero bytes
instead of up to 1024.

@item 
bpo-26616@footnote{https://bugs.python.org/issue26616}: Fixed a bug in datetime.astimezone() method.

@item 
bpo-26637@footnote{https://bugs.python.org/issue26637}: The @ref{9b,,importlib} module now emits an @ref{32d,,ImportError}
rather than a @ref{192,,TypeError} if @ref{60b,,__import__()} is tried during the
Python shutdown process but @ref{482,,sys.path} is already cleared (set to
@code{None}).

@item 
bpo-21925@footnote{https://bugs.python.org/issue21925}: @ref{f83,,warnings.formatwarning()} now catches exceptions when
calling @ref{703,,linecache.getline()} and
@ref{10f9,,tracemalloc.get_object_traceback()} to be able to log
@ref{4ca,,ResourceWarning} emitted late during the Python shutdown process.

@item 
bpo-23848@footnote{https://bugs.python.org/issue23848}: On Windows, faulthandler.enable() now also installs an
exception handler to dump the traceback of all Python threads on any
Windows exception, not only on UNIX signals (SIGSEGV, SIGFPE, SIGABRT).

@item 
bpo-26530@footnote{https://bugs.python.org/issue26530}: Add C functions @code{_PyTraceMalloc_Track()} and
@code{_PyTraceMalloc_Untrack()} to track memory blocks using the
@ref{114,,tracemalloc} module. Add @code{_PyTraceMalloc_GetTraceback()} to
get the traceback of an object.

@item 
bpo-26588@footnote{https://bugs.python.org/issue26588}: The _tracemalloc now supports tracing memory allocations of
multiple address spaces (domains).

@item 
bpo-24266@footnote{https://bugs.python.org/issue24266}: Ctrl+C during Readline history search now cancels the search
mode when compiled with Readline 7.

@item 
bpo-26590@footnote{https://bugs.python.org/issue26590}: Implement a safe finalizer for the _socket.socket type. It now
releases the GIL to close the socket.

@item 
bpo-18787@footnote{https://bugs.python.org/issue18787}: spwd.getspnam() now raises a PermissionError if the user
doesn't have privileges.

@item 
bpo-26560@footnote{https://bugs.python.org/issue26560}: Avoid potential ValueError in BaseHandler.start_response.
Initial patch by Peter Inglesby.

@item 
bpo-26567@footnote{https://bugs.python.org/issue26567}: Add a new function @ref{5c7,,PyErr_ResourceWarning()} function to
pass the destroyed object. Add a @emph{source} attribute to
@code{warnings.WarningMessage}. Add warnings._showwarnmsg() which uses
tracemalloc to get the traceback where source object was allocated.
@end itemize

@node 安全<28>,库<54>,库<53>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id376}@anchor{10fa}
@subsubsection 安全



@itemize -

@item 
bpo-26313@footnote{https://bugs.python.org/issue26313}: ssl.py _load_windows_store_certs fails if windows cert store is
empty. Patch by Baji.
@end itemize

@node 库<54>,安全<29>,安全<28>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id377}@anchor{10fb}
@subsubsection 库



@itemize -

@item 
bpo-26569@footnote{https://bugs.python.org/issue26569}: Fix @ref{10fc,,pyclbr.readmodule()} and @ref{10fd,,pyclbr.readmodule_ex()}
to support importing packages.

@item 
bpo-26499@footnote{https://bugs.python.org/issue26499}: Account for remaining Content-Length in HTTPResponse.readline()
and read1(). Based on patch by Silent Ghost. Also document that
HTTPResponse now supports these methods.

@item 
bpo-25320@footnote{https://bugs.python.org/issue25320}: Handle sockets in directories unittest discovery is scanning.
Patch from Victor van den Elzen.

@item 
bpo-16181@footnote{https://bugs.python.org/issue16181}: cookiejar.http2time() now returns None if year is higher than
datetime.MAXYEAR.

@item 
bpo-26513@footnote{https://bugs.python.org/issue26513}: Fixes platform module detection of Windows Server

@item 
bpo-23718@footnote{https://bugs.python.org/issue23718}: Fixed parsing time in week 0 before Jan 1.  Original patch by
Tamás Bence Gedai.

@item 
bpo-26323@footnote{https://bugs.python.org/issue26323}: Add Mock.assert_called() and Mock.assert_called_once() methods
to unittest.mock. Patch written by Amit Saha.

@item 
bpo-20589@footnote{https://bugs.python.org/issue20589}: Invoking Path.owner() and Path.group() on Windows now raise
NotImplementedError instead of ImportError.

@item 
bpo-26177@footnote{https://bugs.python.org/issue26177}: Fixed the keys() method for Canvas and Scrollbar widgets.

@item 
bpo-15068@footnote{https://bugs.python.org/issue15068}: Got rid of excessive buffering in fileinput. The bufsize
parameter is now deprecated and ignored.

@item 
bpo-19475@footnote{https://bugs.python.org/issue19475}: Added an optional argument timespec to the datetime isoformat()
method to choose the precision of the time component.

@item 
bpo-2202@footnote{https://bugs.python.org/issue2202}: Fix UnboundLocalError in
AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu
Dupuy.

@item 
bpo-26167@footnote{https://bugs.python.org/issue26167}: Minimized overhead in copy.copy() and copy.deepcopy().
Optimized copying and deepcopying bytearrays, NotImplemented, slices,
short lists, tuples, dicts, sets.

@item 
bpo-25718@footnote{https://bugs.python.org/issue25718}: Fixed pickling and copying the accumulate() iterator with total
is None.

@item 
bpo-26475@footnote{https://bugs.python.org/issue26475}: Fixed debugging output for regular expressions with the (?x)
flag.

@item 
bpo-26482@footnote{https://bugs.python.org/issue26482}: Allowed pickling recursive dequeues.

@item 
bpo-26335@footnote{https://bugs.python.org/issue26335}: Make mmap.write() return the number of bytes written like other
write methods.  Patch by Jakub Stasiak.

@item 
bpo-26457@footnote{https://bugs.python.org/issue26457}: Fixed the subnets() methods in IP network classes for the case
when resulting prefix length is equal to maximal prefix length. Based on
patch by Xiang Zhang.

@item 
bpo-26385@footnote{https://bugs.python.org/issue26385}: Remove the file if the internal open() call in
NamedTemporaryFile() fails. Patch by Silent Ghost.

@item 
bpo-26402@footnote{https://bugs.python.org/issue26402}: Fix XML-RPC client to retry when the server shuts down a
persistent connection.  This was a regression related to the new
http.client.RemoteDisconnected exception in 3.5.0a4.

@item 
bpo-25913@footnote{https://bugs.python.org/issue25913}: Leading @code{<~} is optional now in base64.a85decode() with
adobe=True.  Patch by Swati Jaiswal.

@item 
bpo-26186@footnote{https://bugs.python.org/issue26186}: Remove an invalid type check in importlib.util.LazyLoader.

@item 
bpo-26367@footnote{https://bugs.python.org/issue26367}: importlib.__import__() raises ImportError like
builtins.__import__() when @code{level} is specified but without an
accompanying package specified.

@item 
bpo-26309@footnote{https://bugs.python.org/issue26309}: In the "socketserver" module, shut down the request (closing
the connected socket) when verify_request() returns false.  Patch by Aviv
Palivoda.

@item 
bpo-23430@footnote{https://bugs.python.org/issue23430}: Change the socketserver module to only catch exceptions raised
from a request handler that are derived from Exception (instead of
BaseException). Therefore SystemExit and KeyboardInterrupt no longer
trigger the handle_error() method, and will now to stop a single-threaded
server.
@end itemize

@node 安全<29>,库<55>,库<54>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id378}@anchor{10fe}
@subsubsection 安全



@itemize -

@item 
bpo-25939@footnote{https://bugs.python.org/issue25939}: On Windows open the cert store readonly in
ssl.enum_certificates.
@end itemize

@node 库<55>,IDLE<40>,安全<29>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id379}@anchor{10ff}
@subsubsection 库



@itemize -

@item 
bpo-25995@footnote{https://bugs.python.org/issue25995}: os.walk() no longer uses FDs proportional to the tree depth.

@item 
bpo-25994@footnote{https://bugs.python.org/issue25994}: Added the close() method and the support of the context manager
protocol for the os.scandir() iterator.

@item 
bpo-23992@footnote{https://bugs.python.org/issue23992}: multiprocessing: make MapResult not fail-fast upon exception.

@item 
bpo-26243@footnote{https://bugs.python.org/issue26243}: Support keyword arguments to zlib.compress().  Patch by Aviv
Palivoda.

@item 
bpo-26117@footnote{https://bugs.python.org/issue26117}: The os.scandir() iterator now closes file descriptor not only
when the iteration is finished, but when it was failed with error.

@item 
bpo-25949@footnote{https://bugs.python.org/issue25949}: __dict__ for an OrderedDict instance is now created only when
needed.

@item 
bpo-25911@footnote{https://bugs.python.org/issue25911}: Restored support of bytes paths in os.walk() on Windows.

@item 
bpo-26045@footnote{https://bugs.python.org/issue26045}: Add UTF-8 suggestion to error message when posting a
non-Latin-1 string with http.client.

@item 
bpo-26039@footnote{https://bugs.python.org/issue26039}: Added zipfile.ZipInfo.from_file() and zipinfo.ZipInfo.is_dir().
Patch by Thomas Kluyver.

@item 
bpo-12923@footnote{https://bugs.python.org/issue12923}: Reset FancyURLopener's redirect counter even if there is an
exception. Based on patches by Brian Brazil and Daniel Rocco.

@item 
bpo-25945@footnote{https://bugs.python.org/issue25945}: Fixed a crash when unpickle the functools.partial object with
wrong state. Fixed a leak in failed functools.partial constructor. "args"
and "keywords" attributes of functools.partial have now always types tuple
and dict correspondingly.

@item 
bpo-26202@footnote{https://bugs.python.org/issue26202}: copy.deepcopy() now correctly copies range() objects with
non-atomic attributes.

@item 
bpo-23076@footnote{https://bugs.python.org/issue23076}: Path.glob() now raises a ValueError if it's called with an
invalid pattern. Patch by Thomas Nyberg.

@item 
bpo-19883@footnote{https://bugs.python.org/issue19883}: Fixed possible integer overflows in zipimport.

@item 
bpo-26227@footnote{https://bugs.python.org/issue26227}: On Windows, getnameinfo(), gethostbyaddr() and
gethostbyname_ex() functions of the socket module now decode the hostname
from the ANSI code page rather than UTF-8.

@item 
bpo-26099@footnote{https://bugs.python.org/issue26099}: The site module now writes an error into stderr if
sitecustomize module can be imported but executing the module raise an
ImportError. Same change for usercustomize.

@item 
bpo-26147@footnote{https://bugs.python.org/issue26147}: xmlrpc now works with strings not encodable with used non-UTF-8
encoding.

@item 
bpo-25935@footnote{https://bugs.python.org/issue25935}: Garbage collector now breaks reference loops with OrderedDict.

@item 
bpo-16620@footnote{https://bugs.python.org/issue16620}: Fixed AttributeError in msilib.Directory.glob().

@item 
bpo-26013@footnote{https://bugs.python.org/issue26013}: Added compatibility with broken protocol 2 pickles created in
old Python 3 versions (3.4.3 and lower).

@item 
bpo-26129@footnote{https://bugs.python.org/issue26129}: Deprecated accepting non-integers in grp.getgrgid().

@item 
bpo-25850@footnote{https://bugs.python.org/issue25850}: Use cross-compilation by default for 64-bit Windows.

@item 
bpo-25822@footnote{https://bugs.python.org/issue25822}: Add docstrings to the fields of urllib.parse results. Patch
contributed by Swati Jaiswal.

@item 
bpo-22642@footnote{https://bugs.python.org/issue22642}: Convert trace module option parsing mechanism to argparse.
Patch contributed by SilentGhost.

@item 
bpo-24705@footnote{https://bugs.python.org/issue24705}: Fix sysconfig._parse_makefile not expanding $@{@} vars appearing
before $() vars.

@item 
bpo-26069@footnote{https://bugs.python.org/issue26069}: Remove the deprecated apis in the trace module.

@item 
bpo-22138@footnote{https://bugs.python.org/issue22138}: Fix mock.patch behavior when patching descriptors. Restore
original values after patching. Patch contributed by Sean McCully.

@item 
bpo-25672@footnote{https://bugs.python.org/issue25672}: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode
option if it is safe to do so.

@item 
bpo-26012@footnote{https://bugs.python.org/issue26012}: Don't traverse into symlinks for @code{**} pattern in
pathlib.Path.[r]glob().

@item 
bpo-24120@footnote{https://bugs.python.org/issue24120}: Ignore PermissionError when traversing a tree with
pathlib.Path.[r]glob(). Patch by Ulrich Petri.

@item 
bpo-21815@footnote{https://bugs.python.org/issue21815}: Accept ] characters in the data portion of imap responses, in
order to handle the flags with square brackets accepted and produced by
servers such as gmail.

@item 
bpo-25447@footnote{https://bugs.python.org/issue25447}: fileinput now uses sys.stdin as-is if it does not have a buffer
attribute (restores backward compatibility).

@item 
bpo-25971@footnote{https://bugs.python.org/issue25971}: Optimized creating Fractions from floats by 2 times and from
Decimals by 3 times.

@item 
bpo-25802@footnote{https://bugs.python.org/issue25802}: Document as deprecated the remaining implementations of
importlib.abc.Loader.load_module().

@item 
bpo-25928@footnote{https://bugs.python.org/issue25928}: Add Decimal.as_integer_ratio().

@item 
bpo-25447@footnote{https://bugs.python.org/issue25447}: Copying the lru_cache() wrapper object now always works,
independently from the type of the wrapped object (by returning the
original object unchanged).

@item 
bpo-25768@footnote{https://bugs.python.org/issue25768}: Have the functions in compileall return booleans instead of
ints and add proper documentation and tests for the return values.

@item 
bpo-24103@footnote{https://bugs.python.org/issue24103}: Fixed possible use after free in ElementTree.XMLPullParser.

@item 
bpo-25860@footnote{https://bugs.python.org/issue25860}: os.fwalk() no longer skips remaining directories when error
occurs. Original patch by Samson Lee.

@item 
bpo-25914@footnote{https://bugs.python.org/issue25914}: Fixed and simplified OrderedDict.__sizeof__.

@item 
bpo-25869@footnote{https://bugs.python.org/issue25869}: Optimized deepcopying ElementTree; it is now 20 times faster.

@item 
bpo-25873@footnote{https://bugs.python.org/issue25873}: Optimized iterating ElementTree.  Iterating elements
Element.iter() is now 40% faster, iterating text Element.itertext() is now
up to 2.5 times faster.

@item 
bpo-25902@footnote{https://bugs.python.org/issue25902}: Fixed various refcount issues in ElementTree iteration.

@item 
bpo-22227@footnote{https://bugs.python.org/issue22227}: The TarFile iterator is reimplemented using generator. This
implementation is simpler that using class.

@item 
bpo-25638@footnote{https://bugs.python.org/issue25638}: Optimized ElementTree.iterparse(); it is now 2x faster.
Optimized ElementTree parsing; it is now 10% faster.

@item 
bpo-25761@footnote{https://bugs.python.org/issue25761}: Improved detecting errors in broken pickle data.

@item 
bpo-25717@footnote{https://bugs.python.org/issue25717}: Restore the previous behaviour of tolerating most fstat()
errors when opening files.  This was a regression in 3.5a1, and stopped
anonymous temporary files from working in special cases.

@item 
bpo-24903@footnote{https://bugs.python.org/issue24903}: Fix regression in number of arguments compileall accepts when
'-d' is specified.  The check on the number of arguments has been dropped
completely as it never worked correctly anyway.

@item 
bpo-25764@footnote{https://bugs.python.org/issue25764}: In the subprocess module, preserve any exception caused by
fork() failure when preexec_fn is used.

@item 
bpo-25771@footnote{https://bugs.python.org/issue25771}: Tweak the exception message for importlib.util.resolve_name()
when 'package' isn't specified but necessary.

@item 
bpo-6478@footnote{https://bugs.python.org/issue6478}: _strptime's regexp cache now is reset after changing timezone
with time.tzset().

@item 
bpo-14285@footnote{https://bugs.python.org/issue14285}: When executing a package with the "python -m package" option,
and package initialization fails, a proper traceback is now reported.  The
"runpy" module now lets exceptions from package initialization pass back
to the caller, rather than raising ImportError.

@item 
bpo-19771@footnote{https://bugs.python.org/issue19771}: Also in runpy and the "-m" option, omit the irrelevant message
". . . is a package and cannot be directly executed" if the package could
not even be initialized (e.g. due to a bad @code{*.pyc} file).

@item 
bpo-25177@footnote{https://bugs.python.org/issue25177}: Fixed problem with the mean of very small and very large
numbers. As a side effect, statistics.mean and statistics.variance should
be significantly faster.

@item 
bpo-25718@footnote{https://bugs.python.org/issue25718}: Fixed copying object with state with boolean value is false.

@item 
bpo-10131@footnote{https://bugs.python.org/issue10131}: Fixed deep copying of minidom documents.  Based on patch by
Marian Ganisin.

@item 
bpo-7990@footnote{https://bugs.python.org/issue7990}: dir() on ElementTree.Element now lists properties: "tag",
"text", "tail" and "attrib".  Original patch by Santoso Wijaya.

@item 
bpo-25725@footnote{https://bugs.python.org/issue25725}: Fixed a reference leak in pickle.loads() when unpickling
invalid data including tuple instructions.

@item 
bpo-25663@footnote{https://bugs.python.org/issue25663}: In the Readline completer, avoid listing duplicate global
names, and search the global namespace before searching builtins.

@item 
bpo-25688@footnote{https://bugs.python.org/issue25688}: Fixed file leak in ElementTree.iterparse() raising an error.

@item 
bpo-23914@footnote{https://bugs.python.org/issue23914}: Fixed SystemError raised by unpickler on broken pickle data.

@item 
bpo-25691@footnote{https://bugs.python.org/issue25691}: Fixed crash on deleting ElementTree.Element attributes.

@item 
bpo-25624@footnote{https://bugs.python.org/issue25624}: ZipFile now always writes a ZIP_STORED header for directory
entries.  Patch by Dingyuan Wang.

@item 
bpo-25626@footnote{https://bugs.python.org/issue25626}: Change three zlib functions to accept sizes that fit in
Py_ssize_t, but internally cap those sizes to UINT_MAX.  This resolves a
regression in 3.5 where GzipFile.read() failed to read chunks larger than
2 or 4 GiB.  The change affects the zlib.Decompress.decompress()
max_length parameter, the zlib.decompress() bufsize parameter, and the
zlib.Decompress.flush() length parameter.

@item 
bpo-25583@footnote{https://bugs.python.org/issue25583}: Avoid incorrect errors raised by os.makedirs(exist_ok=True)
when the OS gives priority to errors such as EACCES over EEXIST.

@item 
bpo-25593@footnote{https://bugs.python.org/issue25593}: Change semantics of EventLoop.stop() in asyncio.

@item 
bpo-6973@footnote{https://bugs.python.org/issue6973}: When we know a subprocess.Popen process has died, do not allow
the send_signal(), terminate(), or kill() methods to do anything as they
could potentially signal a different process.

@item 
bpo-23883@footnote{https://bugs.python.org/issue23883}: Added missing APIs to __all__ to match the documented APIs for
the following modules: calendar, csv, enum, fileinput, ftplib, logging,
optparse, tarfile, threading and wave.  Also added a
test.support.check__all__() helper. Patches by Jacek Kołodziej, Mauro S.
M. Rodrigues and Joel Taddei.

@item 
bpo-25590@footnote{https://bugs.python.org/issue25590}: In the Readline completer, only call getattr() once per
attribute.  Also complete names of attributes such as properties and slots
which are listed by dir() but not yet created on an instance.

@item 
bpo-25498@footnote{https://bugs.python.org/issue25498}: Fix a crash when garbage-collecting ctypes objects created by
wrapping a memoryview.  This was a regression made in 3.5a1.  Based on
patch by Eryksun.

@item 
bpo-25584@footnote{https://bugs.python.org/issue25584}: Added "escape" to the __all__ list in the glob module.

@item 
bpo-25584@footnote{https://bugs.python.org/issue25584}: Fixed recursive glob() with patterns starting with @code{**}.

@item 
bpo-25446@footnote{https://bugs.python.org/issue25446}: Fix regression in smtplib's AUTH LOGIN support.

@item 
bpo-18010@footnote{https://bugs.python.org/issue18010}: Fix the pydoc web server's module search function to handle
exceptions from importing packages.

@item 
bpo-25554@footnote{https://bugs.python.org/issue25554}: Got rid of circular references in regular expression parsing.

@item 
bpo-18973@footnote{https://bugs.python.org/issue18973}: Command-line interface of the calendar module now uses argparse
instead of optparse.

@item 
bpo-25510@footnote{https://bugs.python.org/issue25510}: fileinput.FileInput.readline() now returns b'@w{'} instead of '@w{'} at
the end if the FileInput was opened with binary mode. Patch by Ryosuke
Ito.

@item 
bpo-25503@footnote{https://bugs.python.org/issue25503}: Fixed inspect.getdoc() for inherited docstrings of properties.
Original patch by John Mark Vandenberg.

@item 
bpo-25515@footnote{https://bugs.python.org/issue25515}: Always use os.urandom as a source of randomness in uuid.uuid4.

@item 
bpo-21827@footnote{https://bugs.python.org/issue21827}: Fixed textwrap.dedent() for the case when largest common
whitespace is a substring of smallest leading whitespace. Based on patch
by Robert Li.

@item 
bpo-25447@footnote{https://bugs.python.org/issue25447}: The lru_cache() wrapper objects now can be copied and pickled
(by returning the original object unchanged).

@item 
bpo-25390@footnote{https://bugs.python.org/issue25390}: typing: Don't crash on Union[str, Pattern].

@item 
bpo-25441@footnote{https://bugs.python.org/issue25441}: asyncio: Raise error from drain() when socket is closed.

@item 
bpo-25410@footnote{https://bugs.python.org/issue25410}: Cleaned up and fixed minor bugs in C implementation of
OrderedDict.

@item 
bpo-25411@footnote{https://bugs.python.org/issue25411}: Improved Unicode support in SMTPHandler through better use of
the email package. Thanks to user simon04 for the patch.

@item 
Move the imp module from a PendingDeprecationWarning to
DeprecationWarning.

@item 
bpo-25407@footnote{https://bugs.python.org/issue25407}: Remove mentions of the formatter module being removed in Python
3.6.

@item 
bpo-25406@footnote{https://bugs.python.org/issue25406}: Fixed a bug in C implementation of OrderedDict.move_to_end()
that caused segmentation fault or hang in iterating after moving several
items to the start of ordered dict.

@item 
bpo-25382@footnote{https://bugs.python.org/issue25382}: pickletools.dis() now outputs implicit memo index for the
MEMOIZE opcode.

@item 
bpo-25357@footnote{https://bugs.python.org/issue25357}: Add an optional newline parameter to binascii.b2a_base64().
base64.b64encode() uses it to avoid a memory copy.

@item 
bpo-24164@footnote{https://bugs.python.org/issue24164}: Objects that need calling @code{__new__} with keyword arguments,
can now be pickled using pickle protocols older than protocol version 4.

@item 
bpo-25364@footnote{https://bugs.python.org/issue25364}: zipfile now works in threads disabled builds.

@item 
bpo-25328@footnote{https://bugs.python.org/issue25328}: smtpd's SMTPChannel now correctly raises a ValueError if both
decode_data and enable_SMTPUTF8 are set to true.

@item 
bpo-16099@footnote{https://bugs.python.org/issue16099}: RobotFileParser now supports Crawl-delay and Request-rate
extensions.  Patch by Nikolay Bogoychev.

@item 
bpo-25316@footnote{https://bugs.python.org/issue25316}: distutils raises OSError instead of DistutilsPlatformError when
MSVC is not installed.

@item 
bpo-25380@footnote{https://bugs.python.org/issue25380}: Fixed protocol for the STACK_GLOBAL opcode in
pickletools.opcodes.

@item 
bpo-23972@footnote{https://bugs.python.org/issue23972}: Updates asyncio datagram create method allowing reuseport and
reuseaddr socket options to be set prior to binding the socket. Mirroring
the existing asyncio create_server method the reuseaddr option for
datagram sockets defaults to True if the O/S is 'posix' (except if the
platform is Cygwin). Patch by Chris Laws.

@item 
bpo-25304@footnote{https://bugs.python.org/issue25304}: Add asyncio.run_coroutine_threadsafe().  This lets you submit a
coroutine to a loop from another thread, returning a
concurrent.futures.Future.  By Vincent Michel.

@item 
bpo-25232@footnote{https://bugs.python.org/issue25232}: Fix CGIRequestHandler to split the query from the URL at the
first question mark (?) rather than the last. Patch from Xiang Zhang.

@item 
bpo-24657@footnote{https://bugs.python.org/issue24657}: Prevent CGIRequestHandler from collapsing slashes in the query
part of the URL as if it were a path. Patch from Xiang Zhang.

@item 
bpo-25287@footnote{https://bugs.python.org/issue25287}: Don't add crypt.METHOD_CRYPT to crypt.methods if it's not
supported. Check if it is supported, it may not be supported on OpenBSD
for example.

@item 
bpo-23600@footnote{https://bugs.python.org/issue23600}: Default implementation of tzinfo.fromutc() was returning wrong
results in some cases.

@item 
bpo-25203@footnote{https://bugs.python.org/issue25203}: Failed readline.set_completer_delims() no longer left the
module in inconsistent state.

@item 
bpo-25011@footnote{https://bugs.python.org/issue25011}: rlcompleter now omits private and special attribute names
unless the prefix starts with underscores.

@item 
bpo-25209@footnote{https://bugs.python.org/issue25209}: rlcompleter now can add a space or a colon after completed
keyword.

@item 
bpo-22241@footnote{https://bugs.python.org/issue22241}: timezone.utc name is now plain 'UTC', not 'UTC-00:00'.

@item 
bpo-23517@footnote{https://bugs.python.org/issue23517}: fromtimestamp() and utcfromtimestamp() methods of
datetime.datetime now round microseconds to nearest with ties going to
nearest even integer (ROUND_HALF_EVEN), as round(float), instead of
rounding towards -Infinity (ROUND_FLOOR).

@item 
bpo-23552@footnote{https://bugs.python.org/issue23552}: Timeit now warns when there is substantial (4x) variance
between best and worst times. Patch from Serhiy Storchaka.

@item 
bpo-24633@footnote{https://bugs.python.org/issue24633}: site-packages/README -> README.txt.

@item 
bpo-24879@footnote{https://bugs.python.org/issue24879}: help() and pydoc can now list named tuple fields in the order
they were defined rather than alphabetically.  The ordering is determined
by the _fields attribute if present.

@item 
bpo-24874@footnote{https://bugs.python.org/issue24874}: Improve speed of itertools.cycle() and make its pickle more
compact.

@item 
Fix crash in itertools.cycle.__setstate__() when the first argument wasn't
a list.

@item 
bpo-20059@footnote{https://bugs.python.org/issue20059}: urllib.parse raises ValueError on all invalid ports. Patch by
Martin Panter.

@item 
bpo-24360@footnote{https://bugs.python.org/issue24360}: Improve __repr__ of argparse.Namespace() for invalid
identifiers.  Patch by Matthias Bussonnier.

@item 
bpo-23426@footnote{https://bugs.python.org/issue23426}: run_setup was broken in distutils. Patch from Alexander
Belopolsky.

@item 
bpo-13938@footnote{https://bugs.python.org/issue13938}: 2to3 converts StringTypes to a tuple. Patch from Mark Hammond.

@item 
bpo-2091@footnote{https://bugs.python.org/issue2091}: open() accepted a 'U' mode string containing '+', but 'U' can
only be used with 'r'. Patch from Jeff Balogh and John O'Connor.

@item 
bpo-8585@footnote{https://bugs.python.org/issue8585}: improved tests for zipimporter2. Patch from Mark Lawrence.

@item 
bpo-18622@footnote{https://bugs.python.org/issue18622}: unittest.mock.mock_open().reset_mock would recurse infinitely.
Patch from Nicola Palumbo and Laurent De Buyst.

@item 
bpo-24426@footnote{https://bugs.python.org/issue24426}: Fast searching optimization in regular expressions now works
for patterns that starts with capturing groups.  Fast searching
optimization now can't be disabled at compile time.

@item 
bpo-23661@footnote{https://bugs.python.org/issue23661}: unittest.mock side_effects can now be exceptions again. This
was a regression vs Python 3.4. Patch from Ignacio Rossi

@item 
bpo-13248@footnote{https://bugs.python.org/issue13248}: Remove deprecated inspect.getmoduleinfo function.

@item 
bpo-25578@footnote{https://bugs.python.org/issue25578}: Fix (another) memory leak in SSLSocket.getpeercer().

@item 
bpo-25530@footnote{https://bugs.python.org/issue25530}: Disable the vulnerable SSLv3 protocol by default when creating
ssl.SSLContext.

@item 
bpo-25569@footnote{https://bugs.python.org/issue25569}: Fix memory leak in SSLSocket.getpeercert().

@item 
bpo-25471@footnote{https://bugs.python.org/issue25471}: Sockets returned from accept() shouldn't appear to be
nonblocking.

@item 
bpo-25319@footnote{https://bugs.python.org/issue25319}: When threading.Event is reinitialized, the underlying condition
should use a regular lock rather than a recursive lock.

@item 
Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu
Davis.

@item 
bpo-26050@footnote{https://bugs.python.org/issue26050}: Add asyncio.StreamReader.readuntil() method. Patch by Марк
Коренберг.

@item 
bpo-25924@footnote{https://bugs.python.org/issue25924}: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X
versions 10.5 or higher.  Original patch by A. Jesse Jiryu Davis.

@item 
bpo-26406@footnote{https://bugs.python.org/issue26406}: Avoid unnecessary serialization of getaddrinfo(3) calls on
current versions of OpenBSD and NetBSD.  Patch by A. Jesse Jiryu Davis.

@item 
bpo-26848@footnote{https://bugs.python.org/issue26848}: Fix asyncio/subprocess.communicate() to handle empty input.
Patch by Jack O'Connor.

@item 
bpo-27040@footnote{https://bugs.python.org/issue27040}: Add loop.get_exception_handler method

@item 
bpo-27041@footnote{https://bugs.python.org/issue27041}: asyncio: Add loop.create_future method
@end itemize

@node IDLE<40>,文档<37>,库<55>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id380}@anchor{1100}
@subsubsection IDLE



@itemize -

@item 
bpo-20640@footnote{https://bugs.python.org/issue20640}: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav
Heblikar.

@item 
In the 'IDLE-console differences' section of the IDLE doc, clarify how
running with IDLE affects sys.modules and the standard streams.

@item 
bpo-25507@footnote{https://bugs.python.org/issue25507}: fix incorrect change in IOBinding that prevented printing.
Augment IOBinding htest to include all major IOBinding functions.

@item 
bpo-25905@footnote{https://bugs.python.org/issue25905}: Revert unwanted conversion of ' to ’ RIGHT SINGLE QUOTATION
MARK in README.txt and open this and NEWS.txt with 'ascii'. Re-encode
CREDITS.txt to utf-8 and open it with 'utf-8'.

@item 
bpo-15348@footnote{https://bugs.python.org/issue15348}: Stop the debugger engine (normally in a user process) before
closing the debugger window (running in the IDLE process). This prevents
the RuntimeErrors that were being caught and ignored.

@item 
bpo-24455@footnote{https://bugs.python.org/issue24455}: Prevent IDLE from hanging when a) closing the shell while the
debugger is active (15347); b) closing the debugger with the [X] button
(15348); and c) activating the debugger when already active (24455). The
patch by Mark Roseman does this by making two changes. 1. Suspend and
resume the gui.interaction method with the tcl vwait mechanism intended
for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow
any existing interaction to terminate first.

@item 
Change 'The program' to 'Your program' in an IDLE 'kill program?' message
to make it clearer that the program referred to is the currently running
user program, not IDLE itself.

@item 
bpo-24750@footnote{https://bugs.python.org/issue24750}: Improve the appearance of the IDLE editor window status bar.
Patch by Mark Roseman.

@item 
bpo-25313@footnote{https://bugs.python.org/issue25313}: Change the handling of new built-in text color themes to better
address the compatibility problem introduced by the addition of IDLE Dark.
Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.

@item 
bpo-24782@footnote{https://bugs.python.org/issue24782}: Extension configuration is now a tab in the IDLE Preferences
dialog rather than a separate dialog.  The former tabs are now a sorted
list.  Patch by Mark Roseman.

@item 
bpo-22726@footnote{https://bugs.python.org/issue22726}: Re-activate the config dialog help button with some content
about the other buttons and the new IDLE Dark theme.

@item 
bpo-24820@footnote{https://bugs.python.org/issue24820}: IDLE now has an 'IDLE Dark' built-in text color theme. It is
more or less IDLE Classic inverted, with a cobalt blue background.
Strings, comments, keywords, ... are still green, red, orange, ... . To
use it with IDLEs released before November 2015, hit the 'Save as New
Custom Theme' button and enter a new name, such as 'Custom Dark'.  The
custom theme will work with any IDLE release, and can be modified.

@item 
bpo-25224@footnote{https://bugs.python.org/issue25224}: README.txt is now an idlelib index for IDLE developers and
curious users. The previous user content is now in the IDLE doc chapter.
'IDLE' now means 'Integrated Development and Learning Environment'.

@item 
bpo-24820@footnote{https://bugs.python.org/issue24820}: Users can now set breakpoint colors in Settings -> Custom
Highlighting. Original patch by Mark Roseman.

@item 
bpo-24972@footnote{https://bugs.python.org/issue24972}: Inactive selection background now matches active selection
background, as configured by users, on all systems.  Found items are now
always highlighted on Windows.  Initial patch by Mark Roseman.

@item 
bpo-24570@footnote{https://bugs.python.org/issue24570}: Idle: make calltip and completion boxes appear on Macs affected
by a tk regression.  Initial patch by Mark Roseman.

@item 
bpo-24988@footnote{https://bugs.python.org/issue24988}: Idle ScrolledList context menus (used in debugger) now work on
Mac Aqua. Patch by Mark Roseman.

@item 
bpo-24801@footnote{https://bugs.python.org/issue24801}: Make right-click for context menu work on Mac Aqua. Patch by
Mark Roseman.

@item 
bpo-25173@footnote{https://bugs.python.org/issue25173}: Associate tkinter messageboxes with a specific widget. For Mac
OSX, make them a 'sheet'.  Patch by Mark Roseman.

@item 
bpo-25198@footnote{https://bugs.python.org/issue25198}: Enhance the initial html viewer now used for Idle Help.
Properly indent fixed-pitch text (patch by Mark Roseman). Give code
snippet a very Sphinx-like light blueish-gray background. Re-use initial
width and height set by users for shell and editor. When the Table of
Contents (TOC) menu is used, put the section header at the top of the
screen.

@item 
bpo-25225@footnote{https://bugs.python.org/issue25225}: Condense and rewrite Idle doc section on text colors.

@item 
bpo-21995@footnote{https://bugs.python.org/issue21995}: Explain some differences between IDLE and console Python.

@item 
bpo-22820@footnote{https://bugs.python.org/issue22820}: Explain need for @emph{print} when running file from Idle editor.

@item 
bpo-25224@footnote{https://bugs.python.org/issue25224}: Doc: augment Idle feature list and no-subprocess section.

@item 
bpo-25219@footnote{https://bugs.python.org/issue25219}: Update doc for Idle command line options. Some were missing and
notes were not correct.

@item 
bpo-24861@footnote{https://bugs.python.org/issue24861}: Most of idlelib is private and subject to change. Use
idleib.idle.* to start Idle. See idlelib.__init__.__doc__.

@item 
bpo-25199@footnote{https://bugs.python.org/issue25199}: Idle: add synchronization comments for future maintainers.

@item 
bpo-16893@footnote{https://bugs.python.org/issue16893}: Replace help.txt with help.html for Idle doc display. The new
idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks
better than help.txt and will better document Idle as released. The
tkinter html viewer that works for this file was written by Rose Roseman.
The now unused EditorWindow.HelpDialog class and helt.txt file are
deprecated.

@item 
bpo-24199@footnote{https://bugs.python.org/issue24199}: Deprecate unused idlelib.idlever with possible removal in 3.6.

@item 
bpo-24790@footnote{https://bugs.python.org/issue24790}: Remove extraneous code (which also create 2 & 3 conflicts).
@end itemize

@node 文档<37>,测试<38>,IDLE<40>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id381}@anchor{1101}
@subsubsection 文档



@itemize -

@item 
bpo-26736@footnote{https://bugs.python.org/issue26736}: Used HTTPS for external links in the documentation if possible.

@item 
bpo-6953@footnote{https://bugs.python.org/issue6953}: Rework the Readline module documentation to group related
functions together, and add more details such as what underlying Readline
functions and variables are accessed.

@item 
bpo-23606@footnote{https://bugs.python.org/issue23606}: Adds note to ctypes documentation regarding cdll.msvcrt.

@item 
bpo-24952@footnote{https://bugs.python.org/issue24952}: Clarify the default size argument of stack_size() in the
"threading" and "_thread" modules. Patch from Mattip.

@item 
bpo-26014@footnote{https://bugs.python.org/issue26014}: Update 3.x packaging documentation: * "See also" links to the
new docs are now provided in the legacy pages * links to setuptools
documentation have been updated
@end itemize

@node 测试<38>,构建<40>,文档<37>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id382}@anchor{1102}
@subsubsection 测试



@itemize -

@item 
bpo-21916@footnote{https://bugs.python.org/issue21916}: Added tests for the turtle module.  Patch by ingrid, Gregory
Loyse and Jelle Zijlstra.

@item 
bpo-26295@footnote{https://bugs.python.org/issue26295}: When using "python3 -m test --testdir=TESTDIR", regrtest
doesn't add "test." prefix to test module names.

@item 
bpo-26523@footnote{https://bugs.python.org/issue26523}: The multiprocessing thread pool (multiprocessing.dummy.Pool)
was untested.

@item 
bpo-26015@footnote{https://bugs.python.org/issue26015}: Added new tests for pickling iterators of mutable sequences.

@item 
bpo-26325@footnote{https://bugs.python.org/issue26325}: Added test.support.check_no_resource_warning() to check that no
ResourceWarning is emitted.

@item 
bpo-25940@footnote{https://bugs.python.org/issue25940}: Changed test_ssl to use its internal local server more.  This
avoids relying on svn.python.org, which recently changed root certificate.

@item 
bpo-25616@footnote{https://bugs.python.org/issue25616}: Tests for OrderedDict are extracted from test_collections into
separate file test_ordered_dict.

@item 
bpo-25449@footnote{https://bugs.python.org/issue25449}: Added tests for OrderedDict subclasses.

@item 
bpo-25188@footnote{https://bugs.python.org/issue25188}: Add -P/--pgo to test.regrtest to suppress error output when
running the test suite for the purposes of a PGO build. Initial patch by
Alecsandru Patrascu.

@item 
bpo-22806@footnote{https://bugs.python.org/issue22806}: Add @code{python -m test --list-tests} command to list tests.

@item 
bpo-18174@footnote{https://bugs.python.org/issue18174}: @code{python -m test --huntrleaks ...} now also checks for leak of
file descriptors. Patch written by Richard Oudkerk.

@item 
bpo-25260@footnote{https://bugs.python.org/issue25260}: Fix @code{python -m test --coverage} on Windows. Remove the list
of ignored directories.

@item 
@code{PCbuild\rt.bat} now accepts an unlimited number of arguments to pass
along to regrtest.py.  Previously there was a limit of 9.

@item 
bpo-26583@footnote{https://bugs.python.org/issue26583}: Skip test_timestamp_overflow in test_import if bytecode files
cannot be written.
@end itemize

@node 构建<40>,Windows<38>,测试<38>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id383}@anchor{1103}
@subsubsection 构建



@itemize -

@item 
bpo-21277@footnote{https://bugs.python.org/issue21277}: Don't try to link _ctypes with a ffi_convenience library.

@item 
bpo-26884@footnote{https://bugs.python.org/issue26884}: Fix linking extension modules for cross builds. Patch by Xavier
de Gaye.

@item 
bpo-26932@footnote{https://bugs.python.org/issue26932}: Fixed support of RTLD_* constants defined as enum values, not
via macros (in particular on Android).  Patch by Chi Hsuan Yen.

@item 
bpo-22359@footnote{https://bugs.python.org/issue22359}: Disable the rules for running _freeze_importlib and pgen when
cross-compiling.  The output of these programs is normally saved with the
source code anyway, and is still regenerated when doing a native build.
Patch by Xavier de Gaye.

@item 
bpo-21668@footnote{https://bugs.python.org/issue21668}: Link audioop, _datetime, _ctypes_test modules to libm, except
on Mac OS X. Patch written by Chi Hsuan Yen.

@item 
bpo-25702@footnote{https://bugs.python.org/issue25702}: A --with-lto configure option has been added that will enable
link time optimizations at build time during a make profile-opt. Some
compilers and toolchains are known to not produce stable code when using
LTO, be sure to test things thoroughly before relying on it. It can
provide a few % speed up over profile-opt alone.

@item 
bpo-26624@footnote{https://bugs.python.org/issue26624}: Adds validation of ucrtbase[d].dll version with warning for old
versions.

@item 
bpo-17603@footnote{https://bugs.python.org/issue17603}: Avoid error about nonexistent fileblocks.o file by using a
lower-level check for st_blocks in struct stat.

@item 
bpo-26079@footnote{https://bugs.python.org/issue26079}: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern
Thiel.

@item 
bpo-26465@footnote{https://bugs.python.org/issue26465}: 更新Windows 构建OpenSSL 1.0.2g.

@item 
bpo-25348@footnote{https://bugs.python.org/issue25348}: Added @code{--pgo} and @code{--pgo-job} arguments to
@code{PCbuild\build.bat} for building with Profile-Guided Optimization.  The
old @code{PCbuild\build_pgo.bat} script is removed.

@item 
bpo-25827@footnote{https://bugs.python.org/issue25827}: Add support for building with ICC to @code{configure}, including a
new @code{--with-icc} flag.

@item 
bpo-25696@footnote{https://bugs.python.org/issue25696}: Fix installation of Python on UNIX with make -j9.

@item 
bpo-24986@footnote{https://bugs.python.org/issue24986}: It is now possible to build Python on Windows without errors
when external libraries are not available.

@item 
bpo-24421@footnote{https://bugs.python.org/issue24421}: Compile Modules/_math.c once, before building extensions.
Previously it could fail to compile properly if the math and cmath builds
were concurrent.

@item 
bpo-26465@footnote{https://bugs.python.org/issue26465}: 更新 OS X 10.5+（仅32位）安装程序以构建并链接 OpenSSL 1.0.2g.

@item 
bpo-26268@footnote{https://bugs.python.org/issue26268}: 更新Windows 构建OpenSSL 1.0.2f.

@item 
bpo-25136@footnote{https://bugs.python.org/issue25136}: Support Apple Xcode 7's new textual SDK stub libraries.

@item 
bpo-24324@footnote{https://bugs.python.org/issue24324}: Do not enable unreachable code warnings when using gcc as the
option does not work correctly in older versions of gcc and has been
silently removed as of gcc-4.5.
@end itemize

@node Windows<38>,工具/示例<27>,构建<40>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id384}@anchor{1104}
@subsubsection Windows



@itemize -

@item 
bpo-27053@footnote{https://bugs.python.org/issue27053}: Updates make_zip.py to correctly generate library ZIP file.

@item 
bpo-26268@footnote{https://bugs.python.org/issue26268}: Update the prepare_ssl.py script to handle OpenSSL releases
that don't include the contents of the include directory (that is, 1.0.2e
and later).

@item 
bpo-26071@footnote{https://bugs.python.org/issue26071}: bdist_wininst created binaries fail to start and find 32bit
Python

@item 
bpo-26073@footnote{https://bugs.python.org/issue26073}: Update the list of magic numbers in launcher

@item 
bpo-26065@footnote{https://bugs.python.org/issue26065}: Excludes venv from library when generating embeddable distro.

@item 
bpo-25022@footnote{https://bugs.python.org/issue25022}: Removed very outdated PC/example_nt/ directory.
@end itemize

@node 工具/示例<27>,C API<29>,Windows<38>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id385}@anchor{1105}
@subsubsection 工具/示例



@itemize -

@item 
bpo-26799@footnote{https://bugs.python.org/issue26799}: Fix python-gdb.py: don't get C types once when the Python code
is loaded, but get C types on demand. The C types can change if
python-gdb.py is loaded before the Python executable. Patch written by
Thomas Ilsche.

@item 
bpo-26271@footnote{https://bugs.python.org/issue26271}: Fix the Freeze tool to properly use flags passed through
configure. Patch by Daniel Shaulov.

@item 
bpo-26489@footnote{https://bugs.python.org/issue26489}: Add dictionary unpacking support to Tools/parser/unparse.py.
Patch by Guo Ci Teo.

@item 
bpo-26316@footnote{https://bugs.python.org/issue26316}: Fix variable name typo in Argument Clinic.

@item 
bpo-25440@footnote{https://bugs.python.org/issue25440}: Fix output of python-config --extension-suffix.

@item 
bpo-25154@footnote{https://bugs.python.org/issue25154}: The pyvenv script has been deprecated in favour of @code{python3 -m
venv}.
@end itemize

@node C API<29>,,工具/示例<27>,Python 3 6 0 alpha 1
@anchor{whatsnew/changelog id386}@anchor{1106}
@subsubsection C API



@itemize -

@item 
bpo-26312@footnote{https://bugs.python.org/issue26312}: SystemError is now raised in all programming bugs with using
PyArg_ParseTupleAndKeywords().  RuntimeError did raised before in some
programming bugs.

@item 
bpo-26198@footnote{https://bugs.python.org/issue26198}: ValueError is now raised instead of TypeError on buffer
overflow in parsing "es#" and "et#" format units.  SystemError is now
raised instead of TypeError on programmatical error in parsing format
string.
@end itemize

@node Python 3 5 5 正式版,Python 3 5 5 rc1,Python 3 6 0 alpha 1,更新日志
@anchor{whatsnew/changelog python-3-5-5-final}@anchor{1107}
@subsection Python 3.5.5 正式版


@emph{发布日期e: 2018-02-04}

在 3.5.5 版本中没有新的更改。

@node Python 3 5 5 rc1,Python 3 5 4 正式版,Python 3 5 5 正式版,更新日志
@anchor{whatsnew/changelog python-3-5-5-release-candidate-1}@anchor{1108}
@subsection Python 3.5.5 rc1


@emph{发布日期: 2018-01-23}

@menu
* 安全: 安全<30>. 
* 核心与内置: 核心与内置<48>. 
* 库: 库<56>. 

@end menu

@node 安全<30>,核心与内置<48>,,Python 3 5 5 rc1
@anchor{whatsnew/changelog id387}@anchor{1109}
@subsubsection 安全



@itemize -

@item 
bpo-32551@footnote{https://bugs.python.org/issue32551}: The @code{sys.path[0]} initialization change for bpo-29139@footnote{https://bugs.python.org/issue29139} caused
a regression by revealing an inconsistency in how sys.path is initialized
when executing @code{__main__} from a zipfile, directory, or other import
location. This is considered a potential security issue, as it may lead to
privileged processes unexpectedly loading code from user controlled
directories in situations where that was not previously the case. The
interpreter now consistently avoids ever adding the import location's
parent directory to @code{sys.path}, and ensures no other @code{sys.path}
entries are inadvertently modified when inserting the import location
named on the command line. (Originally reported as bpo-29723@footnote{https://bugs.python.org/issue29723} against
Python 3.6rc1, but it was missed at the time that the then upcoming Python
3.5.4 release would also be affected)

@item 
bpo-30657@footnote{https://bugs.python.org/issue30657}: Fixed possible integer overflow in PyBytes_DecodeEscape,
CVE-2017-1000158. Original patch by Jay Bosamiya; rebased to Python 3 by
Miro Hrončok.

@item 
bpo-30947@footnote{https://bugs.python.org/issue30947}: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to
get security fixes.
@end itemize

@node 核心与内置<48>,库<56>,安全<30>,Python 3 5 5 rc1
@anchor{whatsnew/changelog id388}@anchor{110a}
@subsubsection 核心与内置



@itemize -

@item 
bpo-31095@footnote{https://bugs.python.org/issue31095}: Fix potential crash during GC caused by @code{tp_dealloc} which
doesn't call @code{PyObject_GC_UnTrack()}.
@end itemize

@node 库<56>,,核心与内置<48>,Python 3 5 5 rc1
@anchor{whatsnew/changelog id389}@anchor{110b}
@subsubsection 库



@itemize -

@item 
bpo-32072@footnote{https://bugs.python.org/issue32072}: Fixed issues with binary plists: Fixed saving bytearrays.
Identical objects will be saved only once. Equal references will be load
as identical objects. Added support for saving and loading recursive data
structures.

@item 
bpo-31170@footnote{https://bugs.python.org/issue31170}: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of
partial characters for UTF-8 input (libexpat bug 115):
@indicateurl{https://github.com/libexpat/libexpat/issues/115}
@end itemize

@node Python 3 5 4 正式版,Python 3 5 4 rc1,Python 3 5 5 rc1,更新日志
@anchor{whatsnew/changelog python-3-5-4-final}@anchor{110c}
@subsection Python 3.5.4 正式版


@emph{发布日期: 2017-08-07}

@menu
* 库: 库<57>. 

@end menu

@node 库<57>,,,Python 3 5 4 正式版
@anchor{whatsnew/changelog id390}@anchor{110d}
@subsubsection 库



@itemize -

@item 
bpo-30119@footnote{https://bugs.python.org/issue30119}: ftplib.FTP.putline() now throws ValueError on commands that
contains CR or LF. Patch by Dong-hee Na.
@end itemize

@node Python 3 5 4 rc1,Python 3 5 3 正式版,Python 3 5 4 正式版,更新日志
@anchor{whatsnew/changelog python-3-5-4-release-candidate-1}@anchor{110e}
@subsection Python 3.5.4 rc1


@emph{发布日期: 2017-07-23}

@menu
* 安全: 安全<31>. 
* 核心与内置: 核心与内置<49>. 
* 库: 库<58>. 
* 文档: 文档<38>. 
* 测试: 测试<39>. 
* 构建: 构建<41>. 
* Windows: Windows<39>. 
* C API: C API<30>. 

@end menu

@node 安全<31>,核心与内置<49>,,Python 3 5 4 rc1
@anchor{whatsnew/changelog id391}@anchor{110f}
@subsubsection 安全



@itemize -

@item 
bpo-30730@footnote{https://bugs.python.org/issue30730}: Prevent environment variables injection in subprocess on
Windows.  Prevent passing other environment variables and command
arguments.

@item 
bpo-30694@footnote{https://bugs.python.org/issue30694}: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple
security vulnerabilities including: CVE-2017-9233 (External entity
infinite loop DoS), CVE-2016-9063 (Integer overflow, re-fix),
CVE-2016-0718 (Fix regression bugs from 2.2.0's fix to CVE-2016-0718) and
CVE-2012-0876 (Counter hash flooding with SipHash). Note: the
CVE-2016-5300 (Use os-specific entropy sources like getrandom) doesn't
impact Python, since Python already gets entropy from the OS to set the
expat secret using @code{XML_SetHashSalt()}.

@item 
bpo-30500@footnote{https://bugs.python.org/issue30500}: Fix urllib.parse.splithost() to correctly parse fragments. For
example, @code{splithost('//127.0.0.1#@@evil.com/')} now correctly returns the
@code{127.0.0.1} host, instead of treating @code{@@evil.com} as the host in an
authentication (@code{login@@host}).

@item 
bpo-29591@footnote{https://bugs.python.org/issue29591}: Update expat copy from 2.1.1 to 2.2.0 to get fixes of
CVE-2016-0718 and CVE-2016-4472. See
@indicateurl{https://sourceforge.net/p/expat/bugs/537/} for more information.
@end itemize

@node 核心与内置<49>,库<58>,安全<31>,Python 3 5 4 rc1
@anchor{whatsnew/changelog id392}@anchor{1110}
@subsubsection 核心与内置



@itemize -

@item 
bpo-30876@footnote{https://bugs.python.org/issue30876}: Relative import from unloaded package now reimports the package
instead of failing with SystemError.  Relative import from non-package now
fails with ImportError rather than SystemError.

@item 
bpo-30765@footnote{https://bugs.python.org/issue30765}: Avoid blocking in pthread_mutex_lock() when
PyThread_acquire_lock() is asked not to block.

@item 
bpo-27945@footnote{https://bugs.python.org/issue27945}: Fixed various segfaults with dict when input collections are
mutated during searching, inserting or comparing.  Based on patches by
Duane Griffin and Tim Mitchell.

@item 
bpo-25794@footnote{https://bugs.python.org/issue25794}: Fixed type.__setattr__() and type.__delattr__() for
non-interned attribute names.  Based on patch by Eryk Sun.

@item 
bpo-29935@footnote{https://bugs.python.org/issue29935}: Fixed error messages in the index() method of tuple, list and
deque when pass indices of wrong type.

@item 
bpo-28876@footnote{https://bugs.python.org/issue28876}: @code{bool(range)} works even if @code{len(range)} raises
@ref{95a,,OverflowError}.

@item 
bpo-29600@footnote{https://bugs.python.org/issue29600}: Fix wrapping coroutine return values in StopIteration.

@item 
bpo-29537@footnote{https://bugs.python.org/issue29537}: Restore runtime compatibility with bytecode files generated by
CPython 3.5.0 to 3.5.2, and adjust the eval loop to avoid the problems
that could be caused by the malformed variant of the
BUILD_MAP_UNPACK_WITH_CALL opcode that they may contain. Patch by Petr
Viktorin, Serhiy Storchaka, and Nick Coghlan.

@item 
bpo-28598@footnote{https://bugs.python.org/issue28598}: Support __rmod__ for subclasses of str being called before
str.__mod__. Patch by Martijn Pieters.

@item 
bpo-29602@footnote{https://bugs.python.org/issue29602}: Fix incorrect handling of signed zeros in complex constructor
for complex subclasses and for inputs having a __complex__ method. Patch
by Serhiy Storchaka.

@item 
bpo-29347@footnote{https://bugs.python.org/issue29347}: Fixed possibly dereferencing undefined pointers when creating
weakref objects.

@item 
bpo-29438@footnote{https://bugs.python.org/issue29438}: Fixed use-after-free problem in key sharing dict.

@item 
bpo-29319@footnote{https://bugs.python.org/issue29319}: Prevent RunMainFromImporter overwriting sys.path[0].

@item 
bpo-29337@footnote{https://bugs.python.org/issue29337}: Fixed possible BytesWarning when compare the code objects.
Warnings could be emitted at compile time.

@item 
bpo-29478@footnote{https://bugs.python.org/issue29478}: If max_line_length=None is specified while using the Compat32
policy, it is no longer ignored.  Patch by Mircea Cosbuc.
@end itemize

@node 库<58>,文档<38>,核心与内置<49>,Python 3 5 4 rc1
@anchor{whatsnew/changelog id393}@anchor{1111}
@subsubsection 库



@itemize -

@item 
bpo-29403@footnote{https://bugs.python.org/issue29403}: Fix @code{unittest.mock}'s autospec to not fail on method-bound
builtin functions.  Patch by Aaron Gallagher.

@item 
bpo-30961@footnote{https://bugs.python.org/issue30961}: Fix decrementing a borrowed reference in tracemalloc.

@item 
bpo-30886@footnote{https://bugs.python.org/issue30886}: Fix multiprocessing.Queue.join_thread(): it now waits until the
thread completes, even if the thread was started by the same process which
created the queue.

@item 
bpo-29854@footnote{https://bugs.python.org/issue29854}: Fix segfault in readline when using readline's history-size
option.  Patch by Nir Soffer.

@item 
bpo-30807@footnote{https://bugs.python.org/issue30807}: signal.setitimer() may disable the timer when passed a tiny
value. Tiny values (such as 1e-6) are valid non-zero values for
setitimer(), which is specified as taking microsecond-resolution
intervals. However, on some platform, our conversion routine could convert
1e-6 into a zero interval, therefore disabling the timer instead of
(re-)scheduling it.

@item 
bpo-30441@footnote{https://bugs.python.org/issue30441}: Fix bug when modifying os.environ while iterating over it

@item 
bpo-30532@footnote{https://bugs.python.org/issue30532}: Fix email header value parser dropping folding white space in
certain cases.

@item 
bpo-29169@footnote{https://bugs.python.org/issue29169}: Update zlib to 1.2.11.

@item 
bpo-30879@footnote{https://bugs.python.org/issue30879}: os.listdir() and os.scandir() now emit bytes names when called
with bytes-like argument.

@item 
bpo-30746@footnote{https://bugs.python.org/issue30746}: Prohibited the '=' character in environment variable names in
@code{os.putenv()} and @code{os.spawn*()}.

@item 
bpo-29755@footnote{https://bugs.python.org/issue29755}: Fixed the lgettext() family of functions in the gettext module.
They now always return bytes.

@item 
bpo-30645@footnote{https://bugs.python.org/issue30645}: Fix path calculation in imp.load_package(), fixing it for cases
when a package is only shipped with bytecodes. Patch by Alexandru
Ardelean.

@item 
bpo-23890@footnote{https://bugs.python.org/issue23890}: unittest.TestCase.assertRaises() now manually breaks a
reference cycle to not keep objects alive longer than expected.

@item 
bpo-30149@footnote{https://bugs.python.org/issue30149}: inspect.signature() now supports callables with
variable-argument parameters wrapped with partialmethod. Patch by Dong-hee
Na.

@item 
bpo-29931@footnote{https://bugs.python.org/issue29931}: Fixed comparison check for ipaddress.ip_interface objects.
Patch by Sanjay Sundaresan.

@item 
bpo-24484@footnote{https://bugs.python.org/issue24484}: Avoid race condition in multiprocessing cleanup.

@item 
bpo-28994@footnote{https://bugs.python.org/issue28994}: The traceback no longer displayed for SystemExit raised in a
callback registered by atexit.

@item 
bpo-30508@footnote{https://bugs.python.org/issue30508}: Don't log exceptions if Task/Future "cancel()" method was
called.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Updates to typing module: Add generic AsyncContextManager, add
support for ContextManager on all versions. Original PRs by Jelle Zijlstra
and Ivan Levkivskyi

@item 
bpo-29870@footnote{https://bugs.python.org/issue29870}: Fix ssl sockets leaks when connection is aborted in asyncio/ssl
implementation. Patch by Michaël Sghaïer.

@item 
bpo-29743@footnote{https://bugs.python.org/issue29743}: Closing transport during handshake process leaks open socket.
Patch by Nikolay Kim

@item 
bpo-27585@footnote{https://bugs.python.org/issue27585}: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu
Sornay.

@item 
bpo-30418@footnote{https://bugs.python.org/issue30418}: On Windows, subprocess.Popen.communicate() now also ignore
EINVAL on stdin.write() if the child process is still running but closed
the pipe.

@item 
bpo-30378@footnote{https://bugs.python.org/issue30378}: Fix the problem that logging.handlers.SysLogHandler cannot
handle IPv6 addresses.

@item 
bpo-29960@footnote{https://bugs.python.org/issue29960}: Preserve generator state when _random.Random.setstate() raises
an exception. Patch by Bryan Olson.

@item 
bpo-30414@footnote{https://bugs.python.org/issue30414}: multiprocessing.Queue._feed background running thread do not
break from main loop on exception.

@item 
bpo-30003@footnote{https://bugs.python.org/issue30003}: Fix handling escape characters in HZ codec.  Based on patch by
Ma Lin.

@item 
bpo-30301@footnote{https://bugs.python.org/issue30301}: Fix AttributeError when using SimpleQueue.empty() under @emph{spawn}
and @emph{forkserver} start methods.

@item 
bpo-30329@footnote{https://bugs.python.org/issue30329}: imaplib and poplib now catch the Windows socket WSAEINVAL error
(code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted.
This error occurs sometimes on SSL connections.

@item 
bpo-30375@footnote{https://bugs.python.org/issue30375}: Warnings emitted when compile a regular expression now always
point to the line in the user code.  Previously they could point into
inners of the re module if emitted from inside of groups or conditionals.

@item 
bpo-30048@footnote{https://bugs.python.org/issue30048}: Fixed @code{Task.cancel()} can be ignored when the task is running
coroutine and the coroutine returned without any more @code{await}.

@item 
bpo-29990@footnote{https://bugs.python.org/issue29990}: Fix range checking in GB18030 decoder.  Original patch by Ma
Lin.

@item 
bpo-26293@footnote{https://bugs.python.org/issue26293}: Change resulted because of zipfile breakage. (See also:
bpo-29094@footnote{https://bugs.python.org/issue29094})

@item 
bpo-30243@footnote{https://bugs.python.org/issue30243}: Removed the __init__ methods of _json's scanner and encoder.
Misusing them could cause memory leaks or crashes.  Now scanner and
encoder objects are completely initialized in the __new__ methods.

@item 
bpo-30185@footnote{https://bugs.python.org/issue30185}: Avoid KeyboardInterrupt tracebacks in forkserver helper process
when Ctrl-C is received.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Various updates to typing module: add typing.NoReturn type, use
WrapperDescriptorType, minor bug-fixes.  Original PRs by Jim
Fasarakis-Hilliard and Ivan Levkivskyi.

@item 
bpo-30205@footnote{https://bugs.python.org/issue30205}: Fix getsockname() for unbound AF_UNIX sockets on Linux.

@item 
bpo-30070@footnote{https://bugs.python.org/issue30070}: Fixed leaks and crashes in errors handling in the parser
module.

@item 
bpo-30061@footnote{https://bugs.python.org/issue30061}: Fixed crashes in IOBase methods __next__() and readlines() when
readline() or __next__() respectively return non-sizeable object. Fixed
possible other errors caused by not checking results of PyObject_Size(),
PySequence_Size(), or PyMapping_Size().

@item 
bpo-30068@footnote{https://bugs.python.org/issue30068}: _io._IOBase.readlines will check if it's closed first when hint
is present.

@item 
bpo-29694@footnote{https://bugs.python.org/issue29694}: Fixed race condition in pathlib mkdir with flags parents=True.
Patch by Armin Rigo.

@item 
bpo-29692@footnote{https://bugs.python.org/issue29692}: Fixed arbitrary unchaining of RuntimeError exceptions in
contextlib.contextmanager.  Patch by Siddharth Velankar.

@item 
bpo-29998@footnote{https://bugs.python.org/issue29998}: Pickling and copying ImportError now preserves name and path
attributes.

@item 
bpo-29942@footnote{https://bugs.python.org/issue29942}: Fix a crash in itertools.chain.from_iterable when encountering
long runs of empty iterables.

@item 
bpo-27863@footnote{https://bugs.python.org/issue27863}: Fixed multiple crashes in ElementTree caused by race conditions
and wrong types.

@item 
bpo-28699@footnote{https://bugs.python.org/issue28699}: Fixed a bug in pools in multiprocessing.pool that raising an
exception at the very first of an iterable may swallow the exception or
make the program hang. Patch by Davin Potts and Xiang Zhang.

@item 
bpo-25803@footnote{https://bugs.python.org/issue25803}: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when
the OS gives priority to errors such as EACCES over EEXIST.

@item 
bpo-29861@footnote{https://bugs.python.org/issue29861}: Release references to tasks, their arguments and their results
as soon as they are finished in multiprocessing.Pool.

@item 
bpo-29884@footnote{https://bugs.python.org/issue29884}: faulthandler: Restore the old sigaltstack during teardown.
Patch by Christophe Zeitouny.

@item 
bpo-25455@footnote{https://bugs.python.org/issue25455}: Fixed crashes in repr of recursive buffered file-like objects.

@item 
bpo-29800@footnote{https://bugs.python.org/issue29800}: Fix crashes in partial.__repr__ if the keys of partial.keywords
are not strings.  Patch by Michael Seifert.

@item 
bpo-29742@footnote{https://bugs.python.org/issue29742}: get_extra_info() raises exception if get called on closed ssl
transport. Patch by Nikolay Kim.

@item 
bpo-8256@footnote{https://bugs.python.org/issue8256}: Fixed possible failing or crashing input() if attributes
"encoding" or "errors" of sys.stdin or sys.stdout are not set or are not
strings.

@item 
bpo-28298@footnote{https://bugs.python.org/issue28298}: Fix a bug that prevented array 'Q', 'L' and 'I' from accepting
big intables (objects that have __int__) as elements.  Patch by Oren
Milman.

@item 
bpo-29615@footnote{https://bugs.python.org/issue29615}: SimpleXMLRPCDispatcher no longer chains KeyError (or any other
exception) to exception(s) raised in the dispatched methods. Patch by Petr
Motejlek.

@item 
bpo-29704@footnote{https://bugs.python.org/issue29704}: asyncio.subprocess.SubprocessStreamProtocol no longer closes
before all pipes are closed.

@item 
bpo-29703@footnote{https://bugs.python.org/issue29703}: Fix asyncio to support instantiation of new event loops in
child processes.

@item 
bpo-29376@footnote{https://bugs.python.org/issue29376}: Fix assertion error in threading._DummyThread.is_alive().

@item 
bpo-29110@footnote{https://bugs.python.org/issue29110}: Fix file object leak in aifc.open() when file is given as a
filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

@item 
bpo-28961@footnote{https://bugs.python.org/issue28961}: Fix unittest.mock._Call helper: don't ignore the name parameter
anymore. Patch written by Jiajun Huang.

@item 
bpo-29532@footnote{https://bugs.python.org/issue29532}: Altering a kwarg dictionary passed to functools.partial() no
longer affects a partial object after creation.

@item 
bpo-28556@footnote{https://bugs.python.org/issue28556}: Various updates to typing module: typing.Counter,
typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle
Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

@item 
bpo-29100@footnote{https://bugs.python.org/issue29100}: Fix datetime.fromtimestamp() regression introduced in Python
3.6.0: check minimum and maximum years.

@item 
bpo-29519@footnote{https://bugs.python.org/issue29519}: Fix weakref spewing exceptions during interpreter shutdown when
used with a rare combination of multiprocessing and custom codecs.

@item 
bpo-29416@footnote{https://bugs.python.org/issue29416}: Prevent infinite loop in pathlib.Path.mkdir

@item 
bpo-29444@footnote{https://bugs.python.org/issue29444}: Fixed out-of-bounds buffer access in the group() method of the
match object. Based on patch by WGH.

@item 
bpo-29335@footnote{https://bugs.python.org/issue29335}: Fix subprocess.Popen.wait() when the child process has exited
to a stopped instead of terminated state (ex: when under ptrace).

@item 
bpo-29290@footnote{https://bugs.python.org/issue29290}: Fix a regression in argparse that help messages would wrap at
non-breaking spaces.

@item 
bpo-28735@footnote{https://bugs.python.org/issue28735}: Fixed the comparison of mock.MagickMock with mock.ANY.

@item 
bpo-29011@footnote{https://bugs.python.org/issue29011}: Fix an important omission by adding Deque to the typing module.

@item 
bpo-29219@footnote{https://bugs.python.org/issue29219}: Fixed infinite recursion in the repr of uninitialized
ctypes.CDLL instances.

@item 
bpo-28969@footnote{https://bugs.python.org/issue28969}: Fixed race condition in C implementation of
functools.lru_cache. KeyError could be raised when cached function with
full cache was simultaneously called from different threads with the same
uncached arguments.

@item 
bpo-29142@footnote{https://bugs.python.org/issue29142}: In urllib.request, suffixes in no_proxy environment variable
with leading dots could match related hostnames again (e.g. .b.c matches
a.b.c). Patch by Milan Oberkirch.
@end itemize

@node 文档<38>,测试<39>,库<58>,Python 3 5 4 rc1
@anchor{whatsnew/changelog id394}@anchor{1112}
@subsubsection 文档



@itemize -

@item 
bpo-30176@footnote{https://bugs.python.org/issue30176}: Add missing attribute related constants in curses
documentation.

@item 
bpo-26985@footnote{https://bugs.python.org/issue26985}: Add missing info of code object in inspect documentation.

@item 
bpo-28929@footnote{https://bugs.python.org/issue28929}: Link the documentation to its source file on GitHub.

@item 
bpo-25008@footnote{https://bugs.python.org/issue25008}: Document smtpd.py as effectively deprecated and add a pointer
to aiosmtpd, a third-party asyncio-based replacement.

@item 
bpo-26355@footnote{https://bugs.python.org/issue26355}: Add canonical header link on each page to corresponding major
version of the documentation. Patch by Matthias Bussonnier.

@item 
bpo-29349@footnote{https://bugs.python.org/issue29349}: Fix Python 2 syntax in code for building the documentation.
@end itemize

@node 测试<39>,构建<41>,文档<38>,Python 3 5 4 rc1
@anchor{whatsnew/changelog id395}@anchor{1113}
@subsubsection 测试



@itemize -

@item 
bpo-30822@footnote{https://bugs.python.org/issue30822}: Fix regrtest command line parser to allow passing -u
extralargefile to run test_zipfile64.

@item 
bpo-30383@footnote{https://bugs.python.org/issue30383}: regrtest: Enhance regrtest and backport features from the
master branch. Add options: --coverage, --testdir, --list-tests (list test
files, don't run them), --list-cases (list test identifiers, don't run
them, bpo-30523@footnote{https://bugs.python.org/issue30523}), --matchfile (load a list of test filters from a
text file, bpo-30540@footnote{https://bugs.python.org/issue30540}), --slowest (alias to --slow). Enhance output:
add timestamp, test result, currently running tests, "Tests result: xxx"
summary with total duration, etc. Fix reference leak hunting in regrtest,
--huntrleaks: regrtest now warms up caches, create explicitly all internal
singletons which are created on demand to prevent false positives when
checking for reference leaks. (bpo-30675@footnote{https://bugs.python.org/issue30675}).

@item 
bpo-30357@footnote{https://bugs.python.org/issue30357}: test_thread: setUp() now uses support.threading_setup() and
support.threading_cleanup() to wait until threads complete to avoid random
side effects on following tests. Initial patch written by Grzegorz
Grzywacz.

@item 
bpo-28087@footnote{https://bugs.python.org/issue28087}: Skip test_asyncore and test_eintr poll failures on macOS. Skip
some tests of select.poll when running on macOS due to unresolved issues
with the underlying system poll function on some macOS versions.

@item 
bpo-30197@footnote{https://bugs.python.org/issue30197}: Enhanced functions swap_attr() and swap_item() in the
test.support module. They now work when delete replaced attribute or item
inside the with statement.  The old value of the attribute or item (or
None if it doesn't exist) now will be assigned to the target of the "as"
clause, if there is one.

@item 
bpo-29571@footnote{https://bugs.python.org/issue29571}: to match the behaviour of the @code{re.LOCALE} flag,
test_re.test_locale_flag now uses @code{locale.getpreferredencoding(False)}
to determine the candidate encoding for the test regex (allowing it to
correctly skip the test when the default locale encoding is a multi-byte
encoding)
@end itemize

@node 构建<41>,Windows<39>,测试<39>,Python 3 5 4 rc1
@anchor{whatsnew/changelog id396}@anchor{1114}
@subsubsection 构建



@itemize -

@item 
bpo-29243@footnote{https://bugs.python.org/issue29243}: Prevent unnecessary rebuilding of Python during @code{make test},
@code{make install} and some other make targets when configured with
@code{--enable-optimizations}.

@item 
bpo-23404@footnote{https://bugs.python.org/issue23404}: Don't regenerate generated files based on file modification
time anymore: the action is now explicit. Replace @code{make touch} with
@code{make regen-all}.

@item 
bpo-29643@footnote{https://bugs.python.org/issue29643}: Fix @code{--enable-optimization} didn't work.
@end itemize

@node Windows<39>,C API<30>,构建<41>,Python 3 5 4 rc1
@anchor{whatsnew/changelog id397}@anchor{1115}
@subsubsection Windows



@itemize -

@item 
bpo-30687@footnote{https://bugs.python.org/issue30687}: Locate msbuild.exe on Windows when building rather than
vcvarsall.bat

@item 
bpo-29392@footnote{https://bugs.python.org/issue29392}: Prevent crash when passing invalid arguments into msvcrt
module.
@end itemize

@node C API<30>,,Windows<39>,Python 3 5 4 rc1
@anchor{whatsnew/changelog id398}@anchor{1116}
@subsubsection C API



@itemize -

@item 
bpo-27867@footnote{https://bugs.python.org/issue27867}: Function PySlice_GetIndicesEx() is replaced with a macro if
Py_LIMITED_API is set to the value between 0x03050400 and 0x03060000 (not
including) or 0x03060100 or higher.

@item 
bpo-29083@footnote{https://bugs.python.org/issue29083}: Fixed the declaration of some public API functions.
PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in
limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and
Py_BuildValue() were not available in limited API of version < 3.3 when
PY_SSIZE_T_CLEAN is defined.
@end itemize

@node Python 3 5 3 正式版,Python 3 5 3 rc1,Python 3 5 4 rc1,更新日志
@anchor{whatsnew/changelog python-3-5-3-final}@anchor{1117}
@subsection Python 3.5.3 正式版


@emph{发布日期: 2017-01-17}

There were no code changes between 3.5.3rc1 and 3.5.3 final.

@node Python 3 5 3 rc1,Python 3 5 2 正式版,Python 3 5 3 正式版,更新日志
@anchor{whatsnew/changelog python-3-5-3-release-candidate-1}@anchor{1118}
@subsection Python 3.5.3 rc1


@emph{发布日期: 2017-01-02}

@menu
* 核心与内置: 核心与内置<50>. 
* 库: 库<59>. 
* 安全: 安全<32>. 
* 库: 库<60>. 
* 安全: 安全<33>. 
* 库: 库<61>. 
* IDLE: IDLE<41>. 
* C API: C API<31>. 
* 文档: 文档<39>. 
* 测试: 测试<40>. 
* 工具/示例: 工具/示例<28>. 
* Windows: Windows<40>. 
* 构建: 构建<42>. 

@end menu

@node 核心与内置<50>,库<59>,,Python 3 5 3 rc1
@anchor{whatsnew/changelog id399}@anchor{1119}
@subsubsection 核心与内置



@itemize -

@item 
bpo-29073@footnote{https://bugs.python.org/issue29073}: bytearray formatting no longer truncates on first null byte.

@item 
bpo-28932@footnote{https://bugs.python.org/issue28932}: Do not include <sys/random.h> if it does not exist.

@item 
bpo-28147@footnote{https://bugs.python.org/issue28147}: Fix a memory leak in split-table dictionaries: setattr() must
not convert combined table into split table.

@item 
bpo-25677@footnote{https://bugs.python.org/issue25677}: Correct the positioning of the syntax error caret for indented
blocks. Based on patch by Michael Layzell.

@item 
bpo-29000@footnote{https://bugs.python.org/issue29000}: Fixed bytes formatting of octals with zero padding in alternate
form.

@item 
bpo-28512@footnote{https://bugs.python.org/issue28512}: Fixed setting the offset attribute of SyntaxError by
PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

@item 
bpo-28991@footnote{https://bugs.python.org/issue28991}: functools.lru_cache() was susceptible to an obscure reentrancy
bug caused by a monkey-patched len() function.

@item 
bpo-28648@footnote{https://bugs.python.org/issue28648}: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X
when decode astral characters.  Patch by Xiang Zhang.

@item 
bpo-19398@footnote{https://bugs.python.org/issue19398}: Extra slash no longer added to sys.path components in case of
empty compile-time PYTHONPATH components.

@item 
bpo-28426@footnote{https://bugs.python.org/issue28426}: Fixed potential crash in PyUnicode_AsDecodedObject() in debug
build.

@item 
bpo-23782@footnote{https://bugs.python.org/issue23782}: Fixed possible memory leak in _PyTraceback_Add() and exception
loss in PyTraceBack_Here().

@item 
bpo-28379@footnote{https://bugs.python.org/issue28379}: Added sanity checks and tests for PyUnicode_CopyCharacters().
Patch by Xiang Zhang.

@item 
bpo-28376@footnote{https://bugs.python.org/issue28376}: The type of long range iterator is now registered as Iterator.
Patch by Oren Milman.

@item 
bpo-28376@footnote{https://bugs.python.org/issue28376}: The constructor of range_iterator now checks that step is not
0. Patch by Oren Milman.

@item 
bpo-26906@footnote{https://bugs.python.org/issue26906}: Resolving special methods of uninitialized type now causes
implicit initialization of the type instead of a fail.

@item 
bpo-18287@footnote{https://bugs.python.org/issue18287}: PyType_Ready() now checks that tp_name is not NULL. Original
patch by Niklas Koep.

@item 
bpo-24098@footnote{https://bugs.python.org/issue24098}: Fixed possible crash when AST is changed in process of
compiling it.

@item 
bpo-28350@footnote{https://bugs.python.org/issue28350}: String constants with null character no longer interned.

@item 
bpo-26617@footnote{https://bugs.python.org/issue26617}: Fix crash when GC runs during weakref callbacks.

@item 
bpo-27942@footnote{https://bugs.python.org/issue27942}: String constants now interned recursively in tuples and
frozensets.

@item 
bpo-21578@footnote{https://bugs.python.org/issue21578}: Fixed misleading error message when ImportError called with
invalid keyword args.

@item 
bpo-28203@footnote{https://bugs.python.org/issue28203}: Fix incorrect type in error message from @code{complex(1.0,
@{2:3@})}. Patch by Soumya Sharma.

@item 
bpo-27955@footnote{https://bugs.python.org/issue27955}: Fallback on reading /dev/urandom device when the getrandom()
syscall fails with EPERM, for example when blocked by SECCOMP.

@item 
bpo-28131@footnote{https://bugs.python.org/issue28131}: Fix a regression in zipimport's compile_source().  zipimport
should use the same optimization level as the interpreter.

@item 
bpo-25221@footnote{https://bugs.python.org/issue25221}: Fix corrupted result from PyLong_FromLong(0) when Python is
compiled with NSMALLPOSINTS = 0.

@item 
bpo-25758@footnote{https://bugs.python.org/issue25758}: Prevents zipimport from unnecessarily encoding a filename
(patch by Eryk Sun)

@item 
bpo-28189@footnote{https://bugs.python.org/issue28189}: dictitems_contains no longer swallows compare errors. (Patch by
Xiang Zhang)

@item 
bpo-27812@footnote{https://bugs.python.org/issue27812}: Properly clear out a generator's frame's backreference to the
generator to prevent crashes in frame.clear().

@item 
bpo-27811@footnote{https://bugs.python.org/issue27811}: Fix a crash when a coroutine that has not been awaited is
finalized with warnings-as-errors enabled.

@item 
bpo-27587@footnote{https://bugs.python.org/issue27587}: Fix another issue found by PVS-Studio: Null pointer check after
use of 'def' in _PyState_AddModule(). Initial patch by Christian Heimes.

@item 
bpo-26020@footnote{https://bugs.python.org/issue26020}: set literal evaluation order did not match documented
behaviour.

@item 
bpo-27782@footnote{https://bugs.python.org/issue27782}: Multi-phase extension module import now correctly allows the
@code{m_methods} field to be used to add module level functions to instances
of non-module types returned from @code{Py_create_mod}. Patch by Xiang Zhang.

@item 
bpo-27936@footnote{https://bugs.python.org/issue27936}: The round() function accepted a second None argument for some
types but not for others.  Fixed the inconsistency by accepting None for
all numeric types.

@item 
bpo-27487@footnote{https://bugs.python.org/issue27487}: Warn if a submodule argument to "python -m" or
runpy.run_module() is found in sys.modules after parent packages are
imported, but before the submodule is executed.

@item 
bpo-27558@footnote{https://bugs.python.org/issue27558}: Fix a SystemError in the implementation of "raise" statement.
In a brand new thread, raise a RuntimeError since there is no active
exception to reraise. Patch written by Xiang Zhang.

@item 
bpo-27419@footnote{https://bugs.python.org/issue27419}: Standard __import__() no longer look up "__import__" in globals
or builtins for importing submodules or "from import".  Fixed handling an
error of non-string package name.

@item 
bpo-27083@footnote{https://bugs.python.org/issue27083}: Respect the PYTHONCASEOK environment variable under Windows.

@item 
bpo-27514@footnote{https://bugs.python.org/issue27514}: Make having too many statically nested blocks a SyntaxError
instead of SystemError.

@item 
bpo-27473@footnote{https://bugs.python.org/issue27473}: Fixed possible integer overflow in bytes and bytearray
concatenations. Patch by Xiang Zhang.

@item 
bpo-27507@footnote{https://bugs.python.org/issue27507}: Add integer overflow check in bytearray.extend().  Patch by
Xiang Zhang.

@item 
bpo-27581@footnote{https://bugs.python.org/issue27581}: Don't rely on wrapping for overflow check in
PySequence_Tuple().  Patch by Xiang Zhang.

@item 
bpo-27443@footnote{https://bugs.python.org/issue27443}: __length_hint__() of bytearray iterators no longer return a
negative integer for a resized bytearray.

@item 
bpo-27942@footnote{https://bugs.python.org/issue27942}: Fix memory leak in codeobject.c
@end itemize

@node 库<59>,安全<32>,核心与内置<50>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id400}@anchor{111a}
@subsubsection 库



@itemize -

@item 
bpo-15812@footnote{https://bugs.python.org/issue15812}: inspect.getframeinfo() now correctly shows the first line of a
context. Patch by Sam Breese.

@item 
bpo-29094@footnote{https://bugs.python.org/issue29094}: Offsets in a ZIP file created with extern file object and modes
"w" and "x" now are relative to the start of the file.

@item 
bpo-13051@footnote{https://bugs.python.org/issue13051}: Fixed recursion errors in large or resized
curses.textpad.Textbox.  Based on patch by Tycho Andersen.

@item 
bpo-29119@footnote{https://bugs.python.org/issue29119}: Fix weakrefs in the pure python version of
collections.OrderedDict move_to_end() method. Contributed by Andra
Bogildea.

@item 
bpo-9770@footnote{https://bugs.python.org/issue9770}: curses.ascii predicates now work correctly with negative
integers.

@item 
bpo-28427@footnote{https://bugs.python.org/issue28427}: old keys should not remove new values from WeakValueDictionary
when collecting from another thread.

@item 
bpo-28923@footnote{https://bugs.python.org/issue28923}: Remove editor artifacts from Tix.py.

@item 
bpo-28871@footnote{https://bugs.python.org/issue28871}: Fixed a crash when deallocate deep ElementTree.

@item 
bpo-19542@footnote{https://bugs.python.org/issue19542}: Fix bugs in WeakValueDictionary.setdefault() and
WeakValueDictionary.pop() when a GC collection happens in another thread.

@item 
bpo-20191@footnote{https://bugs.python.org/issue20191}: Fixed a crash in resource.prlimit() when pass a sequence that
doesn't own its elements as limits.

@item 
bpo-28779@footnote{https://bugs.python.org/issue28779}: multiprocessing.set_forkserver_preload() would crash the
forkserver process if a preloaded module instantiated some multiprocessing
objects such as locks.

@item 
bpo-28847@footnote{https://bugs.python.org/issue28847}: dbm.dumb now supports reading read-only files and no longer
writes the index file when it is not changed.

@item 
bpo-25659@footnote{https://bugs.python.org/issue25659}: In ctypes, prevent a crash calling the from_buffer() and
from_buffer_copy() methods on abstract classes like Array.

@item 
bpo-28732@footnote{https://bugs.python.org/issue28732}: Fix crash in os.spawnv() with no elements in args

@item 
bpo-28485@footnote{https://bugs.python.org/issue28485}: Always raise ValueError for negative
compileall.compile_dir(workers=...) parameter, even when multithreading is
unavailable.

@item 
bpo-28387@footnote{https://bugs.python.org/issue28387}: Fixed possible crash in _io.TextIOWrapper deallocator when the
garbage collector is invoked in other thread.  Based on patch by Sebastian
Cufre.

@item 
bpo-27517@footnote{https://bugs.python.org/issue27517}: LZMA compressor and decompressor no longer raise exceptions if
given empty data twice.  Patch by Benjamin Fogle.

@item 
bpo-28549@footnote{https://bugs.python.org/issue28549}: Fixed segfault in curses's addch() with ncurses6.

@item 
bpo-28449@footnote{https://bugs.python.org/issue28449}: tarfile.open() with mode "r" or "r:" now tries to open a tar
file with compression before trying to open it without compression.
Otherwise it had 50% chance failed with ignore_zeros=True.

@item 
bpo-23262@footnote{https://bugs.python.org/issue23262}: The webbrowser module now supports Firefox 36+ and derived
browsers.  Based on patch by Oleg Broytman.

@item 
bpo-27939@footnote{https://bugs.python.org/issue27939}: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused
by representing the scale as float value internally in Tk.  tkinter.IntVar
now works if float value is set to underlying Tk variable.

@item 
bpo-28255@footnote{https://bugs.python.org/issue28255}: calendar.TextCalendar().prmonth() no longer prints a space at
the start of new line after printing a month's calendar.  Patch by Xiang
Zhang.

@item 
bpo-20491@footnote{https://bugs.python.org/issue20491}: The textwrap.TextWrapper class now honors non-breaking spaces.
Based on patch by Kaarle Ritvanen.

@item 
bpo-28353@footnote{https://bugs.python.org/issue28353}: os.fwalk() no longer fails on broken links.

@item 
bpo-25464@footnote{https://bugs.python.org/issue25464}: Fixed HList.header_exists() in tkinter.tix module by addin a
workaround to Tix library bug.

@item 
bpo-28488@footnote{https://bugs.python.org/issue28488}: shutil.make_archive() no longer add entry "./" to ZIP archive.

@item 
bpo-24452@footnote{https://bugs.python.org/issue24452}: Make webbrowser support Chrome on Mac OS X.

@item 
bpo-20766@footnote{https://bugs.python.org/issue20766}: Fix references leaked by pdb in the handling of SIGINT
handlers.

@item 
bpo-26293@footnote{https://bugs.python.org/issue26293}: Fixed writing ZIP files that starts not from the start of the
file.  Offsets in ZIP file now are relative to the start of the archive in
conforming to the specification.

@item 
bpo-28321@footnote{https://bugs.python.org/issue28321}: Fixed writing non-BMP characters with binary format in
plistlib.

@item 
bpo-28322@footnote{https://bugs.python.org/issue28322}: Fixed possible crashes when unpickle itertools objects from
incorrect pickle data.  Based on patch by John Leitch.

@item 
Fix possible integer overflows and crashes in the mmap module with unusual
usage patterns.

@item 
bpo-1703178@footnote{https://bugs.python.org/issue1703178}: Fix the ability to pass the --link-objects option to the
distutils build_ext command.

@item 
bpo-28253@footnote{https://bugs.python.org/issue28253}: Fixed calendar functions for extreme months: 0001-01 and
9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so
that they don't call itermonthdates() which can cause datetime.date
under/overflow.

@item 
bpo-28275@footnote{https://bugs.python.org/issue28275}: Fixed possible use after free in the decompress() methods of
the LZMADecompressor and BZ2Decompressor classes. Original patch by John
Leitch.

@item 
bpo-27897@footnote{https://bugs.python.org/issue27897}: Fixed possible crash in sqlite3.Connection.create_collation()
if pass invalid string-like object as a name.  Patch by Xiang Zhang.

@item 
bpo-18893@footnote{https://bugs.python.org/issue18893}: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py.
Patch by Madison May.

@item 
bpo-27611@footnote{https://bugs.python.org/issue27611}: Fixed support of default root window in the tkinter.tix module.

@item 
bpo-27348@footnote{https://bugs.python.org/issue27348}: In the traceback module, restore the formatting of exception
messages like "Exception: None".  This fixes a regression introduced in
3.5a2.

@item 
bpo-25651@footnote{https://bugs.python.org/issue25651}: Allow falsy values to be used for msg parameter of subTest().

@item 
bpo-27932@footnote{https://bugs.python.org/issue27932}: Prevent memory leak in win32_ver().

@item 
Fix UnboundLocalError in socket._sendfile_use_sendfile.

@item 
bpo-28075@footnote{https://bugs.python.org/issue28075}: Check for ERROR_ACCESS_DENIED in Windows implementation of
os.stat().  Patch by Eryk Sun.

@item 
bpo-25270@footnote{https://bugs.python.org/issue25270}: Prevent codecs.escape_encode() from raising SystemError when an
empty bytestring is passed.

@item 
bpo-28181@footnote{https://bugs.python.org/issue28181}: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

@item 
bpo-25895@footnote{https://bugs.python.org/issue25895}: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by
Gergely Imreh and Markus Holtermann.

@item 
bpo-27599@footnote{https://bugs.python.org/issue27599}: Fixed buffer overrun in binascii.b2a_qp() and
binascii.a2b_qp().

@item 
bpo-19003@footnote{https://bugs.python.org/issue19003}: m email.generator now replaces only @code{\r} and/or @code{\n} line
endings, per the RFC, instead of all unicode line endings.

@item 
bpo-28019@footnote{https://bugs.python.org/issue28019}: itertools.count() no longer rounds non-integer step in range
between 1.0 and 2.0 to 1.

@item 
bpo-25969@footnote{https://bugs.python.org/issue25969}: Update the lib2to3 grammar to handle the unpacking
generalizations added in 3.5.

@item 
bpo-14977@footnote{https://bugs.python.org/issue14977}: mailcap now respects the order of the lines in the mailcap
files ("first match"), as required by RFC 1542.  Patch by Michael Lazar.

@item 
bpo-24594@footnote{https://bugs.python.org/issue24594}: Validates persist parameter when opening MSI database

@item 
bpo-17582@footnote{https://bugs.python.org/issue17582}: xml.etree.ElementTree nows preserves whitespaces in attributes
(Patch by Duane Griffin.  Reviewed and approved by Stefan Behnel.)

@item 
bpo-28047@footnote{https://bugs.python.org/issue28047}: Fixed calculation of line length used for the base64 CTE in the
new email policies.

@item 
bpo-27445@footnote{https://bugs.python.org/issue27445}: Don't pass str(_charset) to MIMEText.set_payload(). Patch by
Claude Paroz.

@item 
bpo-22450@footnote{https://bugs.python.org/issue22450}: urllib now includes an @code{Accept: */*} header among the default
headers. This makes the results of REST API requests more consistent and
predictable especially when proxy servers are involved.

@item 
lib2to3.pgen3.driver.load_grammar() now creates a stable cache file
between runs given the same Grammar.txt input regardless of the hash
randomization setting.

@item 
bpo-27570@footnote{https://bugs.python.org/issue27570}: Avoid zero-length memcpy() etc calls with null source pointers
in the "ctypes" and "array" modules.

@item 
bpo-22233@footnote{https://bugs.python.org/issue22233}: Break email header lines @emph{only} on the RFC specified CR and LF
characters, not on arbitrary unicode line breaks.  This also fixes a bug
in HTTP header parsing.

@item 
bpo-27988@footnote{https://bugs.python.org/issue27988}: Fix email iter_attachments incorrect mutation of payload list.

@item 
bpo-27691@footnote{https://bugs.python.org/issue27691}: Fix ssl module's parsing of GEN_RID subject alternative name
fields in X.509 certs.

@item 
bpo-27850@footnote{https://bugs.python.org/issue27850}: Remove 3DES from ssl module's default cipher list to counter
measure sweet32 attack (CVE-2016-2183).

@item 
bpo-27766@footnote{https://bugs.python.org/issue27766}: Add ChaCha20 Poly1305 to ssl module's default cipher list.
(Required OpenSSL 1.1.0 or LibreSSL).

@item 
bpo-26470@footnote{https://bugs.python.org/issue26470}: Port ssl and hashlib module to OpenSSL 1.1.0.

@item 
Remove support for passing a file descriptor to os.access. It never worked
but previously didn't raise.

@item 
bpo-12885@footnote{https://bugs.python.org/issue12885}: Fix error when distutils encounters symlink.

@item 
bpo-27881@footnote{https://bugs.python.org/issue27881}: Fixed possible bugs when setting
sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

@item 
bpo-27861@footnote{https://bugs.python.org/issue27861}: Fixed a crash in sqlite3.Connection.cursor() when a factory
creates not a cursor.  Patch by Xiang Zhang.

@item 
bpo-19884@footnote{https://bugs.python.org/issue19884}: Avoid spurious output on OS X with Gnu Readline.

@item 
bpo-27706@footnote{https://bugs.python.org/issue27706}: Restore deterministic behavior of random.Random().seed() for
string seeds using seeding version 1.  Allows sequences of calls to
random() to exactly match those obtained in Python 2. Patch by Nofar
Schnider.

@item 
bpo-10513@footnote{https://bugs.python.org/issue10513}: Fix a regression in Connection.commit().  Statements should not
be reset after a commit.

@item 
A new version of typing.py from @indicateurl{https://github.com/python/typing}:
Collection (only for 3.6) (bpo-27598@footnote{https://bugs.python.org/issue27598}). Add FrozenSet to __all__
(upstream #261). Fix crash in _get_type_vars() (upstream #259). Remove the
dict constraint in ForwardRef._eval_type (upstream #252).

@item 
bpo-27539@footnote{https://bugs.python.org/issue27539}: Fix unnormalised @code{Fraction.__pow__} result in the case of
negative exponent and negative base.

@item 
bpo-21718@footnote{https://bugs.python.org/issue21718}: cursor.description is now available for queries using CTEs.

@item 
bpo-2466@footnote{https://bugs.python.org/issue2466}: posixpath.ismount now correctly recognizes mount points which
the user does not have permission to access.

@item 
bpo-27773@footnote{https://bugs.python.org/issue27773}: Correct some memory management errors server_hostname in
_ssl.wrap_socket().

@item 
bpo-26750@footnote{https://bugs.python.org/issue26750}: unittest.mock.create_autospec() now works properly for
subclasses of property() and other data descriptors.

@item 
In the curses module, raise an error if window.getstr() or window.instr()
is passed a negative value.

@item 
bpo-27783@footnote{https://bugs.python.org/issue27783}: Fix possible usage of uninitialized memory in
operator.methodcaller.

@item 
bpo-27774@footnote{https://bugs.python.org/issue27774}: Fix possible Py_DECREF on unowned object in _sre.

@item 
bpo-27760@footnote{https://bugs.python.org/issue27760}: Fix possible integer overflow in binascii.b2a_qp.

@item 
bpo-27758@footnote{https://bugs.python.org/issue27758}: Fix possible integer overflow in the _csv module for large
record lengths.

@item 
bpo-27568@footnote{https://bugs.python.org/issue27568}: Prevent HTTPoxy attack (CVE-2016-1000110). Ignore the
HTTP_PROXY variable when REQUEST_METHOD environment is set, which
indicates that the script is in CGI mode.

@item 
bpo-27656@footnote{https://bugs.python.org/issue27656}: Do not assume sched.h defines any SCHED_* constants.

@item 
bpo-27130@footnote{https://bugs.python.org/issue27130}: In the "zlib" module, fix handling of large buffers (typically
4 GiB) when compressing and decompressing.  Previously, inputs were
limited to 4 GiB, and compression and decompression operations did not
properly handle results of 4 GiB.

@item 
bpo-27533@footnote{https://bugs.python.org/issue27533}: Release GIL in nt._isdir

@item 
bpo-17711@footnote{https://bugs.python.org/issue17711}: Fixed unpickling by the persistent ID with protocol 0. Original
patch by Alexandre Vassalotti.

@item 
bpo-27522@footnote{https://bugs.python.org/issue27522}: Avoid an unintentional reference cycle in email.feedparser.

@item 
bpo-26844@footnote{https://bugs.python.org/issue26844}: Fix error message for imp.find_module() to refer to 'path'
instead of 'name'. Patch by Lev Maximov.

@item 
bpo-23804@footnote{https://bugs.python.org/issue23804}: Fix SSL zero-length recv() calls to not block and not raise an
error about unclean EOF.

@item 
bpo-27466@footnote{https://bugs.python.org/issue27466}: Change time format returned by http.cookie.time2netscape,
confirming the netscape cookie format and making it consistent with
documentation.

@item 
bpo-26664@footnote{https://bugs.python.org/issue26664}: Fix activate.fish by removing mis-use of @code{$}.

@item 
bpo-22115@footnote{https://bugs.python.org/issue22115}: Fixed tracing Tkinter variables: trace_vdelete() with wrong
mode no longer break tracing, trace_vinfo() now always returns a list of
pairs of strings, tracing in the "u" mode now works.

@item 
Fix a scoping issue in importlib.util.LazyLoader which triggered an
UnboundLocalError when lazy-loading a module that was already put into
sys.modules.

@item 
bpo-27079@footnote{https://bugs.python.org/issue27079}: Fixed curses.ascii functions isblank(), iscntrl() and
ispunct().

@item 
bpo-26754@footnote{https://bugs.python.org/issue26754}: Some functions (compile() etc) accepted a filename argument
encoded as an iterable of integers. Now only strings and byte-like objects
are accepted.

@item 
bpo-27048@footnote{https://bugs.python.org/issue27048}: Prevents distutils failing on Windows when environment
variables contain non-ASCII characters

@item 
bpo-27330@footnote{https://bugs.python.org/issue27330}: Fixed possible leaks in the ctypes module.

@item 
bpo-27238@footnote{https://bugs.python.org/issue27238}: Got rid of bare excepts in the turtle module.  Original patch
by Jelle Zijlstra.

@item 
bpo-27122@footnote{https://bugs.python.org/issue27122}: When an exception is raised within the context being managed by
a contextlib.ExitStack() and one of the exit stack generators catches and
raises it in a chain, do not re-raise the original exception when exiting,
let the new chained one through.  This avoids the 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479} bug described
in issue25782.
@end itemize

@node 安全<32>,库<60>,库<59>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id401}@anchor{111b}
@subsubsection 安全



@itemize -

@item 
bpo-27278@footnote{https://bugs.python.org/issue27278}: Fix os.urandom() implementation using getrandom() on Linux.
Truncate size to INT_MAX and loop until we collected enough random bytes,
instead of casting a directly Py_ssize_t to int.
@end itemize

@node 库<60>,安全<33>,安全<32>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id402}@anchor{111c}
@subsubsection 库



@itemize -

@item 
bpo-26386@footnote{https://bugs.python.org/issue26386}: Fixed ttk.TreeView selection operations with item id's
containing spaces.
@end itemize

@node 安全<33>,库<61>,库<60>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id403}@anchor{111d}
@subsubsection 安全



@itemize -

@item 
bpo-22636@footnote{https://bugs.python.org/issue22636}: Avoid shell injection problems with ctypes.util.find_library().
@end itemize

@node 库<61>,IDLE<41>,安全<33>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id404}@anchor{111e}
@subsubsection 库



@itemize -

@item 
bpo-16182@footnote{https://bugs.python.org/issue16182}: Fix various functions in the "readline" module to use the
locale encoding, and fix get_begidx() and get_endidx() to return code
point indexes.

@item 
bpo-27392@footnote{https://bugs.python.org/issue27392}: Add loop.connect_accepted_socket(). Patch by Jim Fulton.

@item 
bpo-27930@footnote{https://bugs.python.org/issue27930}: Improved behaviour of logging.handlers.QueueListener. Thanks to
Paulo Andrade and Petr Viktorin for the analysis and patch.

@item 
bpo-21201@footnote{https://bugs.python.org/issue21201}: Improves readability of multiprocessing error message.  Thanks
to Wojciech Walczak for patch.

@item 
bpo-27456@footnote{https://bugs.python.org/issue27456}: asyncio: Set TCP_NODELAY by default.

@item 
bpo-27906@footnote{https://bugs.python.org/issue27906}: Fix socket accept exhaustion during high TCP traffic. Patch by
Kevin Conway.

@item 
bpo-28174@footnote{https://bugs.python.org/issue28174}: Handle when SO_REUSEPORT isn't properly supported. Patch by
Seth Michael Larson.

@item 
bpo-26654@footnote{https://bugs.python.org/issue26654}: Inspect functools.partial in asyncio.Handle.__repr__. Patch by
iceboy.

@item 
bpo-26909@footnote{https://bugs.python.org/issue26909}: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

@item 
bpo-28176@footnote{https://bugs.python.org/issue28176}: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

@item 
bpo-27759@footnote{https://bugs.python.org/issue27759}: Fix selectors incorrectly retain invalid file descriptors.
Patch by Mark Williams.

@item 
bpo-28368@footnote{https://bugs.python.org/issue28368}: Refuse monitoring processes if the child watcher has no loop
attached. Patch by Vincent Michel.

@item 
bpo-28369@footnote{https://bugs.python.org/issue28369}: Raise RuntimeError when transport's FD is used with add_reader,
add_writer, etc.

@item 
bpo-28370@footnote{https://bugs.python.org/issue28370}: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг
Марк.

@item 
bpo-28371@footnote{https://bugs.python.org/issue28371}: Deprecate passing asyncio.Handles to run_in_executor.

@item 
bpo-28372@footnote{https://bugs.python.org/issue28372}: Fix asyncio to support formatting of non-python coroutines.

@item 
bpo-28399@footnote{https://bugs.python.org/issue28399}: Remove UNIX socket from FS before binding. Patch by Коренберг
Марк.

@item 
bpo-27972@footnote{https://bugs.python.org/issue27972}: Prohibit Tasks to await on themselves.

@item 
bpo-26923@footnote{https://bugs.python.org/issue26923}: Fix asyncio.Gather to refuse being cancelled once all children
are done. Patch by Johannes Ebke.

@item 
bpo-26796@footnote{https://bugs.python.org/issue26796}: Don't configure the number of workers for default threadpool
executor. Initial patch by Hans Lawrenz.

@item 
bpo-28600@footnote{https://bugs.python.org/issue28600}: Optimize loop.call_soon().

@item 
bpo-28613@footnote{https://bugs.python.org/issue28613}: Fix get_event_loop() return the current loop if called from
coroutines/callbacks.

@item 
bpo-28639@footnote{https://bugs.python.org/issue28639}: Fix inspect.isawaitable to always return bool Patch by Justin
Mayfield.

@item 
bpo-28652@footnote{https://bugs.python.org/issue28652}: Make loop methods reject socket kinds they do not support.

@item 
bpo-28653@footnote{https://bugs.python.org/issue28653}: Fix a refleak in functools.lru_cache.

@item 
bpo-28703@footnote{https://bugs.python.org/issue28703}: Fix asyncio.iscoroutinefunction to handle Mock objects.

@item 
bpo-24142@footnote{https://bugs.python.org/issue24142}: Reading a corrupt config file left the parser in an invalid
state.  Original patch by Florian Höch.

@item 
bpo-28990@footnote{https://bugs.python.org/issue28990}: Fix SSL hanging if connection is closed before handshake
completed. (Patch by HoHo-Ho)
@end itemize

@node IDLE<41>,C API<31>,库<61>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id405}@anchor{111f}
@subsubsection IDLE



@itemize -

@item 
bpo-15308@footnote{https://bugs.python.org/issue15308}: Add 'interrupt execution' (^C) to Shell menu. Patch by Roger
Serwy, updated by Bayard Randel.

@item 
bpo-27922@footnote{https://bugs.python.org/issue27922}: Stop IDLE tests from 'flashing' gui widgets on the screen.

@item 
在 IDLE 帮助窗口的标题中加入版本号

@item 
bpo-25564@footnote{https://bugs.python.org/issue25564}: In section on IDLE -- console differences, mention that using
exec means that __builtins__ is defined for each statement.

@item 
bpo-27714@footnote{https://bugs.python.org/issue27714}: text_textview and test_autocomplete now pass when re-run in the
same process.  This occurs when test_idle fails when run with the -w
option but without -jn.  Fix warning from test_config.

@item 
bpo-25507@footnote{https://bugs.python.org/issue25507}: IDLE no longer runs buggy code because of its tkinter imports.
Users must include the same imports required to run directly in Python.

@item 
bpo-27452@footnote{https://bugs.python.org/issue27452}: add line counter and crc to IDLE configHandler test dump.

@item 
bpo-27365@footnote{https://bugs.python.org/issue27365}: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.

@item 
bpo-27245@footnote{https://bugs.python.org/issue27245}: IDLE: Cleanly delete custom themes and key bindings.
Previously, when IDLE was started from a console or by import, a cascade
of warnings was emitted. Patch by Serhiy Storchaka.
@end itemize

@node C API<31>,文档<39>,IDLE<41>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id406}@anchor{1120}
@subsubsection C API



@itemize -

@item 
bpo-28808@footnote{https://bugs.python.org/issue28808}: PyUnicode_CompareWithASCIIString() now never raises exceptions.

@item 
bpo-26754@footnote{https://bugs.python.org/issue26754}: PyUnicode_FSDecoder() accepted a filename argument encoded as
an iterable of integers. Now only strings and bytes-like objects are
accepted.
@end itemize

@node 文档<39>,测试<40>,C API<31>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id407}@anchor{1121}
@subsubsection 文档



@itemize -

@item 
bpo-28513@footnote{https://bugs.python.org/issue28513}: Documented command-line interface of zipfile.
@end itemize

@node 测试<40>,工具/示例<28>,文档<39>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id408}@anchor{1122}
@subsubsection 测试



@itemize -

@item 
bpo-28950@footnote{https://bugs.python.org/issue28950}: Disallow -j0 to be combined with -T/-l/-M in regrtest command
line arguments.

@item 
bpo-28666@footnote{https://bugs.python.org/issue28666}: Now test.support.rmtree is able to remove unwritable or
unreadable directories.

@item 
bpo-23839@footnote{https://bugs.python.org/issue23839}: Various caches now are cleared before running every test file.

@item 
bpo-28409@footnote{https://bugs.python.org/issue28409}: regrtest: fix the parser of command line arguments.

@item 
bpo-27787@footnote{https://bugs.python.org/issue27787}: Call gc.collect() before checking each test for "dangling
threads", since the dangling threads are weak references.

@item 
bpo-27369@footnote{https://bugs.python.org/issue27369}: In test_pyexpat, avoid testing an error message detail that
changed in Expat 2.2.0.
@end itemize

@node 工具/示例<28>,Windows<40>,测试<40>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id409}@anchor{1123}
@subsubsection 工具/示例



@itemize -

@item 
bpo-27952@footnote{https://bugs.python.org/issue27952}: Get Tools/scripts/fixcid.py working with Python 3 and the
current "re" module, avoid invalid Python backslash escapes, and fix a bug
parsing escaped C quote signs.

@item 
bpo-27332@footnote{https://bugs.python.org/issue27332}: Fixed the type of the first argument of module-level functions
generated by Argument Clinic.  Patch by Petr Viktorin.

@item 
bpo-27418@footnote{https://bugs.python.org/issue27418}: Fixed Tools/importbench/importbench.py.
@end itemize

@node Windows<40>,构建<42>,工具/示例<28>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id410}@anchor{1124}
@subsubsection Windows



@itemize -

@item 
bpo-28251@footnote{https://bugs.python.org/issue28251}: Improvements to help manuals on Windows.

@item 
bpo-28110@footnote{https://bugs.python.org/issue28110}: launcher.msi has different product codes between 32-bit and
64-bit

@item 
bpo-25144@footnote{https://bugs.python.org/issue25144}: Ensures TargetDir is set before continuing with custom install.

@item 
bpo-27469@footnote{https://bugs.python.org/issue27469}: Adds a shell extension to the launcher so that drag and drop
works correctly.

@item 
bpo-27309@footnote{https://bugs.python.org/issue27309}: Enabled proper Windows styles in python[w].exe manifest.
@end itemize

@node 构建<42>,,Windows<40>,Python 3 5 3 rc1
@anchor{whatsnew/changelog id411}@anchor{1125}
@subsubsection 构建



@itemize -

@item 
bpo-29080@footnote{https://bugs.python.org/issue29080}: Removes hard dependency on hg.exe from PCBuild/build.bat

@item 
bpo-23903@footnote{https://bugs.python.org/issue23903}: Added missed names to PC/python3.def.

@item 
bpo-10656@footnote{https://bugs.python.org/issue10656}: Fix out-of-tree building on AIX.  Patch by Tristan Carel and
Michael Haubenwallner.

@item 
bpo-26359@footnote{https://bugs.python.org/issue26359}: Rename --with-optimiations to --enable-optimizations.

@item 
bpo-28444@footnote{https://bugs.python.org/issue28444}: Fix missing extensions modules when cross compiling.

@item 
bpo-28248@footnote{https://bugs.python.org/issue28248}: 更新Windows 构建和OS X安装程序以使用OpenSSL 1.0.2j.

@item 
bpo-28258@footnote{https://bugs.python.org/issue28258}: Fixed build with Estonian locale (python-config and distclean
targets in Makefile).  Patch by Arfrever Frehtes Taifersar Arahesis.

@item 
bpo-26661@footnote{https://bugs.python.org/issue26661}: setup.py now detects system libffi with multiarch wrapper.

@item 
bpo-28066@footnote{https://bugs.python.org/issue28066}: Fix the logic that searches build directories for generated
include files when building outside the source tree.

@item 
bpo-15819@footnote{https://bugs.python.org/issue15819}: Remove redundant include search directory option for building
outside the source tree.

@item 
bpo-27566@footnote{https://bugs.python.org/issue27566}: Fix clean target in freeze makefile (patch by Lisa Roach)

@item 
bpo-27705@footnote{https://bugs.python.org/issue27705}: Update message in validate_ucrtbase.py

@item 
bpo-27983@footnote{https://bugs.python.org/issue27983}: Cause lack of llvm-profdata tool when using clang as required
for PGO linking to be a configure time error rather than make time when
--with-optimizations is enabled.  Also improve our ability to find the
llvm-profdata tool on MacOS and some Linuxes.

@item 
bpo-26307@footnote{https://bugs.python.org/issue26307}: The profile-opt build now applies PGO to the built-in modules.

@item 
bpo-26359@footnote{https://bugs.python.org/issue26359}: Add the --with-optimizations configure flag.

@item 
bpo-27713@footnote{https://bugs.python.org/issue27713}: Suppress spurious build warnings when updating importlib's
bootstrap files. Patch by Xiang Zhang

@item 
bpo-25825@footnote{https://bugs.python.org/issue25825}: Correct the references to Modules/python.exp and ld_so_aix,
which are required on AIX.  This updates references to an installation
path that was changed in 3.2a4, and undoes changed references to the build
tree that were made in 3.5.0a1.

@item 
bpo-27453@footnote{https://bugs.python.org/issue27453}: CPP invocation in configure must use CPPFLAGS. Patch by Chi
Hsuan Yen.

@item 
bpo-27641@footnote{https://bugs.python.org/issue27641}: The configure script now inserts comments into the makefile to
prevent the pgen and _freeze_importlib executables from being
cross-compiled.

@item 
bpo-26662@footnote{https://bugs.python.org/issue26662}: Set PYTHON_FOR_GEN in configure as the Python program to be
used for file generation during the build.

@item 
bpo-10910@footnote{https://bugs.python.org/issue10910}: Avoid C++ compilation errors on FreeBSD and OS X. Also update
FreedBSD version checks for the original ctype UTF-8 workaround.

@item 
bpo-28676@footnote{https://bugs.python.org/issue28676}: Prevent missing 'getentropy' declaration warning on macOS.
Patch by Gareth Rees.
@end itemize

@node Python 3 5 2 正式版,Python 3 5 2 rc1,Python 3 5 3 rc1,更新日志
@anchor{whatsnew/changelog python-3-5-2-final}@anchor{1126}
@subsection Python 3.5.2 正式版


@emph{发布日期: 2016-06-26}

@menu
* 核心与内置: 核心与内置<51>. 
* 测试: 测试<41>. 
* IDLE: IDLE<42>. 

@end menu

@node 核心与内置<51>,测试<41>,,Python 3 5 2 正式版
@anchor{whatsnew/changelog id412}@anchor{1127}
@subsubsection 核心与内置



@itemize -

@item 
bpo-26930@footnote{https://bugs.python.org/issue26930}: 更新Windows 构建以使用OpenSSL OpenSSL 1.0.2h.
@end itemize

@node 测试<41>,IDLE<42>,核心与内置<51>,Python 3 5 2 正式版
@anchor{whatsnew/changelog id413}@anchor{1128}
@subsubsection 测试



@itemize -

@item 
bpo-26867@footnote{https://bugs.python.org/issue26867}: Ubuntu's openssl OP_NO_SSLv3 is forced on by default; fix test.
@end itemize

@node IDLE<42>,,测试<41>,Python 3 5 2 正式版
@anchor{whatsnew/changelog id414}@anchor{1129}
@subsubsection IDLE



@itemize -

@item 
bpo-27365@footnote{https://bugs.python.org/issue27365}: Allow non-ascii in idlelib/NEWS.txt - minimal part for 3.5.2.
@end itemize

@node Python 3 5 2 rc1,Python 3 5 1 正式版,Python 3 5 2 正式版,更新日志
@anchor{whatsnew/changelog python-3-5-2-release-candidate-1}@anchor{112a}
@subsection Python 3.5.2 rc1


@emph{发布日期: 2016-06-12}

@menu
* 核心与内置: 核心与内置<52>. 
* 安全: 安全<34>. 
* 库: 库<62>. 
* 安全: 安全<35>. 
* 库: 库<63>. 
* 安全: 安全<36>. 
* 库: 库<64>. 
* 安全: 安全<37>. 
* 库: 库<65>. 
* 安全: 安全<38>. 
* 库: 库<66>. 
* IDLE: IDLE<43>. 
* 文档: 文档<40>. 
* 测试: 测试<42>. 
* 构建: 构建<43>. 
* Windows: Windows<41>. 
* 工具/示例: 工具/示例<29>. 
* Windows: Windows<42>. 

@end menu

@node 核心与内置<52>,安全<34>,,Python 3 5 2 rc1
@anchor{whatsnew/changelog id415}@anchor{112b}
@subsubsection 核心与内置



@itemize -

@item 
bpo-27066@footnote{https://bugs.python.org/issue27066}: Fixed SystemError if a custom opener (for open()) returns a
negative number without setting an exception.

@item 
bpo-20041@footnote{https://bugs.python.org/issue20041}: Fixed TypeError when frame.f_trace is set to None. Patch by
Xavier de Gaye.

@item 
bpo-26168@footnote{https://bugs.python.org/issue26168}: Fixed possible refleaks in failing Py_BuildValue() with the "N"
format unit.

@item 
bpo-26991@footnote{https://bugs.python.org/issue26991}: Fix possible refleak when creating a function with annotations.

@item 
bpo-27039@footnote{https://bugs.python.org/issue27039}: Fixed bytearray.remove() for values greater than 127.  Patch by
Joe Jevnik.

@item 
bpo-23640@footnote{https://bugs.python.org/issue23640}: int.from_bytes() no longer bypasses constructors for
subclasses.

@item 
bpo-26811@footnote{https://bugs.python.org/issue26811}: gc.get_objects() no longer contains a broken tuple with NULL
pointer.

@item 
bpo-20120@footnote{https://bugs.python.org/issue20120}: Use RawConfigParser for .pypirc parsing, removing support for
interpolation unintentionally added with move to Python 3. Behavior no
longer does any interpolation in .pypirc files, matching behavior in
Python 2.7 and Setuptools 19.0.

@item 
bpo-26659@footnote{https://bugs.python.org/issue26659}: Make the builtin slice type support cycle collection.

@item 
bpo-26718@footnote{https://bugs.python.org/issue26718}: super.__init__ no longer leaks memory if called multiple times.
NOTE: A direct call of super.__init__ is not endorsed!

@item 
bpo-25339@footnote{https://bugs.python.org/issue25339}: PYTHONIOENCODING now has priority over locale in setting the
error handler for stdin and stdout.

@item 
bpo-26494@footnote{https://bugs.python.org/issue26494}: Fixed crash on iterating exhausting iterators. Affected classes
are generic sequence iterators, iterators of str, bytes, bytearray, list,
tuple, set, frozenset, dict, OrderedDict, corresponding views and
os.scandir() iterator.

@item 
bpo-26581@footnote{https://bugs.python.org/issue26581}: If coding cookie is specified multiple times on a line in
Python source code file, only the first one is taken to account.

@item 
bpo-26464@footnote{https://bugs.python.org/issue26464}: Fix str.translate() when string is ASCII and first replacements
removes character, but next replacement uses a non-ASCII character or a
string longer than 1 character. Regression introduced in Python 3.5.0.

@item 
bpo-22836@footnote{https://bugs.python.org/issue22836}: Ensure exception reports from PyErr_Display() and
PyErr_WriteUnraisable() are sensible even when formatting them produces
secondary errors.  This affects the reports produced by
sys.__excepthook__() and when __del__() raises an exception.

@item 
bpo-26302@footnote{https://bugs.python.org/issue26302}: Correct behavior to reject comma as a legal character for
cookie names.

@item 
bpo-4806@footnote{https://bugs.python.org/issue4806}: Avoid masking the original TypeError exception when using star
(@code{*}) unpacking in function calls.  Based on patch by Hagen Fürstenau
and Daniel Urban.

@item 
bpo-27138@footnote{https://bugs.python.org/issue27138}: Fix the doc comment for FileFinder.find_spec().

@item 
bpo-26154@footnote{https://bugs.python.org/issue26154}: Add a new private _PyThreadState_UncheckedGet() function to get
the current Python thread state, but don't issue a fatal error if it is
NULL. This new function must be used instead of accessing directly the
_PyThreadState_Current variable.  The variable is no more exposed since
Python 3.5.1 to hide the exact implementation of atomic C types, to avoid
compiler issues.

@item 
bpo-26194@footnote{https://bugs.python.org/issue26194}: Deque.insert() gave odd results for bounded deques that had
reached their maximum size.  Now an IndexError will be raised when
attempting to insert into a full deque.

@item 
bpo-25843@footnote{https://bugs.python.org/issue25843}: When compiling code, don't merge constants if they are equal
but have a different types. For example, @code{f1, f2 = lambda: 1, lambda:
1.0} is now correctly compiled to two different functions: @code{f1()}
returns @code{1} (@code{int}) and @code{f2()} returns @code{1.0} (@code{int}), even if
@code{1} and @code{1.0} are equal.

@item 
bpo-22995@footnote{https://bugs.python.org/issue22995}: [UPDATE] Comment out the one of the pickleability tests in
_PyObject_GetState() due to regressions observed in Cython-based projects.

@item 
bpo-25961@footnote{https://bugs.python.org/issue25961}: Disallowed null characters in the type name.

@item 
bpo-25973@footnote{https://bugs.python.org/issue25973}: Fix segfault when an invalid nonlocal statement binds a name
starting with two underscores.

@item 
bpo-22995@footnote{https://bugs.python.org/issue22995}: Instances of extension types with a state that aren't
subclasses of list or dict and haven't implemented any pickle-related
methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or
__getstate__), can no longer be pickled.  Including memoryview.

@item 
bpo-20440@footnote{https://bugs.python.org/issue20440}: Massive replacing unsafe attribute setting code with special
macro Py_SETREF.

@item 
bpo-25766@footnote{https://bugs.python.org/issue25766}: Special method __bytes__() now works in str subclasses.

@item 
bpo-25421@footnote{https://bugs.python.org/issue25421}: __sizeof__ methods of builtin types now use dynamic basic size.
This allows sys.getsize() to work correctly with their subclasses with
__slots__ defined.

@item 
bpo-25709@footnote{https://bugs.python.org/issue25709}: Fixed problem with in-place string concatenation and utf-8
cache.

@item 
bpo-27147@footnote{https://bugs.python.org/issue27147}: Mention 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} in the importlib docs.

@item 
bpo-24097@footnote{https://bugs.python.org/issue24097}: Fixed crash in object.__reduce__() if slot name is freed inside
__getattr__.

@item 
bpo-24731@footnote{https://bugs.python.org/issue24731}: Fixed crash on converting objects with special methods
__bytes__, __trunc__, and __float__ returning instances of subclasses of
bytes, int, and float to subclasses of bytes, int, and float
correspondingly.

@item 
bpo-26478@footnote{https://bugs.python.org/issue26478}: Fix semantic bugs when using binary operators with dictionary
views and tuples.

@item 
bpo-26171@footnote{https://bugs.python.org/issue26171}: Fix possible integer overflow and heap corruption in
zipimporter.get_data().

@item 
bpo-25660@footnote{https://bugs.python.org/issue25660}: Fix TAB key behaviour in REPL with readline.

@item 
bpo-25887@footnote{https://bugs.python.org/issue25887}: Raise a RuntimeError when a coroutine object is awaited more
than once.

@item 
bpo-27243@footnote{https://bugs.python.org/issue27243}: Update the __aiter__ protocol: instead of returning an
awaitable that resolves to an asynchronous iterator, the asynchronous
iterator should be returned directly.  Doing the former will trigger a
PendingDeprecationWarning.
@end itemize

@node 安全<34>,库<62>,核心与内置<52>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id416}@anchor{112c}
@subsubsection 安全



@itemize -

@item 
bpo-26556@footnote{https://bugs.python.org/issue26556}: Update expat to 2.1.1, fixes CVE-2015-1283.

@item 
Fix TLS stripping vulnerability in smtplib, CVE-2016-0772. Reported by
Team Oststrom
@end itemize

@node 库<62>,安全<35>,安全<34>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id417}@anchor{112d}
@subsubsection 库



@itemize -

@item 
bpo-21386@footnote{https://bugs.python.org/issue21386}: Implement missing IPv4Address.is_global property.  It was
documented since 07a5610bae9d.  Initial patch by Roger Luethi.

@item 
bpo-20900@footnote{https://bugs.python.org/issue20900}: distutils register command now decodes HTTP responses
correctly.  Initial patch by ingrid.

@item 
A new version of typing.py provides several new classes and features:
@@overload outside stubs, Reversible, DefaultDict, Text, ContextManager,
Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some
of the new features are not yet implemented in mypy or other static
analyzers). Also classes for 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} (Awaitable, AsyncIterable,
AsyncIterator) have been added (in fact they made it into 3.5.1 but were
never mentioned).

@item 
bpo-25738@footnote{https://bugs.python.org/issue25738}: Stop http.server.BaseHTTPRequestHandler.send_error() from
sending a message body for 205 Reset Content.  Also, don't send Content
header fields in responses that don't have a body.  Patch by Susumu
Koshiba.

@item 
bpo-21313@footnote{https://bugs.python.org/issue21313}: Fix the "platform" module to tolerate when sys.version contains
truncated build information.
@end itemize

@node 安全<35>,库<63>,库<62>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id418}@anchor{112e}
@subsubsection 安全



@itemize -

@item 
bpo-26839@footnote{https://bugs.python.org/issue26839}: On Linux, @ref{4cb,,os.urandom()} now calls @code{getrandom()} with
@code{GRND_NONBLOCK} to fall back on reading @code{/dev/urandom} if the urandom
entropy pool is not initialized yet. Patch written by Colm Buckley.
@end itemize

@node 库<63>,安全<36>,安全<35>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id419}@anchor{112f}
@subsubsection 库



@itemize -

@item 
bpo-27164@footnote{https://bugs.python.org/issue27164}: In the zlib module, allow decompressing raw Deflate streams
with a predefined zdict.  Based on patch by Xiang Zhang.

@item 
bpo-24291@footnote{https://bugs.python.org/issue24291}: Fix wsgiref.simple_server.WSGIRequestHandler to completely
write data to the client.  Previously it could do partial writes and
truncate data.  Also, wsgiref.handler.ServerHandler can now handle stdout
doing partial writes, but this is deprecated.

@item 
bpo-26809@footnote{https://bugs.python.org/issue26809}: Add @code{__all__} to @ref{f6,,string}.  Patch by Emanuel Barry.

@item 
bpo-26373@footnote{https://bugs.python.org/issue26373}: subprocess.Popen.communicate now correctly ignores
BrokenPipeError when the child process dies before .communicate() is
called in more/all circumstances.

@item 
bpo-21776@footnote{https://bugs.python.org/issue21776}: distutils.upload now correctly handles HTTPError. Initial patch
by Claudiu Popa.

@item 
bpo-27114@footnote{https://bugs.python.org/issue27114}: Fix SSLContext._load_windows_store_certs fails with
PermissionError

@item 
bpo-18383@footnote{https://bugs.python.org/issue18383}: Avoid creating duplicate filters when using filterwarnings and
simplefilter. Based on patch by Alex Shkop.

@item 
bpo-27057@footnote{https://bugs.python.org/issue27057}: Fix os.set_inheritable() on Android, ioctl() is blocked by
SELinux and fails with EACCESS. The function now falls back to fcntl().
Patch written by Michał Bednarski.

@item 
bpo-27014@footnote{https://bugs.python.org/issue27014}: Fix infinite recursion using typing.py.  Thanks to Kalle Tuure!

@item 
bpo-14132@footnote{https://bugs.python.org/issue14132}: Fix urllib.request redirect handling when the target only has a
query string.  Original fix by Ján Janech.

@item 
bpo-17214@footnote{https://bugs.python.org/issue17214}: The "urllib.request" module now percent-encodes non-ASCII bytes
found in redirect target URLs.  Some servers send Location header fields
with non-ASCII bytes, but "http.client" requires the request target to be
ASCII-encodable, otherwise a UnicodeEncodeError is raised.  Based on patch
by Christian Heimes.

@item 
bpo-26892@footnote{https://bugs.python.org/issue26892}: Honor debuglevel flag in urllib.request.HTTPHandler. Patch
contributed by Chi Hsuan Yen.

@item 
bpo-22274@footnote{https://bugs.python.org/issue22274}: In the subprocess module, allow stderr to be redirected to
stdout even when stdout is not redirected.  Patch by Akira Li.

@item 
bpo-26807@footnote{https://bugs.python.org/issue26807}: mock_open 'files' no longer error on readline at end of file.
Patch from Yolanda Robla.

@item 
bpo-25745@footnote{https://bugs.python.org/issue25745}: Fixed leaking a userptr in curses panel destructor.

@item 
bpo-26977@footnote{https://bugs.python.org/issue26977}: Removed unnecessary, and ignored, call to sum of squares helper
in statistics.pvariance.

@item 
bpo-26881@footnote{https://bugs.python.org/issue26881}: The modulefinder module now supports extended opcode arguments.

@item 
bpo-23815@footnote{https://bugs.python.org/issue23815}: Fixed crashes related to directly created instances of types in
_tkinter and curses.panel modules.

@item 
bpo-17765@footnote{https://bugs.python.org/issue17765}: weakref.ref() no longer silently ignores keyword arguments.
Patch by Georg Brandl.

@item 
bpo-26873@footnote{https://bugs.python.org/issue26873}: xmlrpc now raises ResponseError on unsupported type tags
instead of silently return incorrect result.

@item 
bpo-26711@footnote{https://bugs.python.org/issue26711}: Fixed the comparison of plistlib.Data with other types.

@item 
bpo-24114@footnote{https://bugs.python.org/issue24114}: Fix an uninitialized variable in @code{ctypes.util}. The bug only
occurs on SunOS when the ctypes implementation searches for the @code{crle}
program.  Patch by Xiang Zhang.  Tested on SunOS by Kees Bos.

@item 
bpo-26864@footnote{https://bugs.python.org/issue26864}: In urllib.request, change the proxy bypass host checking
against no_proxy to be case-insensitive, and to not match unrelated host
names that happen to have a bypassed hostname as a suffix.  Patch by Xiang
Zhang.

@item 
bpo-26634@footnote{https://bugs.python.org/issue26634}: recursive_repr() now sets __qualname__ of wrapper.  Patch by
Xiang Zhang.

@item 
bpo-26804@footnote{https://bugs.python.org/issue26804}: urllib.request will prefer lower_case proxy environment
variables over UPPER_CASE or Mixed_Case ones. Patch contributed by
Hans-Peter Jansen.

@item 
bpo-26837@footnote{https://bugs.python.org/issue26837}: assertSequenceEqual() now correctly outputs non-stringified
differing items (like bytes in the -b mode).  This affects
assertListEqual() and assertTupleEqual().

@item 
bpo-26041@footnote{https://bugs.python.org/issue26041}: Remove "will be removed in Python 3.7" from deprecation
messages of platform.dist() and platform.linux_distribution(). Patch by
Kumaripaba Miyurusara Athukorala.

@item 
bpo-26822@footnote{https://bugs.python.org/issue26822}: itemgetter, attrgetter and methodcaller objects no longer
silently ignore keyword arguments.

@item 
bpo-26733@footnote{https://bugs.python.org/issue26733}: Disassembling a class now disassembles class and static
methods. Patch by Xiang Zhang.

@item 
bpo-26801@footnote{https://bugs.python.org/issue26801}: Fix error handling in @ref{a45,,shutil.get_terminal_size()}, catch
@ref{393,,AttributeError} instead of @ref{d74,,NameError}. Patch written by
Emanuel Barry.

@item 
bpo-24838@footnote{https://bugs.python.org/issue24838}: tarfile's ustar and gnu formats now correctly calculate name
and link field limits for multibyte character encodings like utf-8.
@end itemize

@node 安全<36>,库<64>,库<63>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id420}@anchor{1130}
@subsubsection 安全



@itemize -

@item 
bpo-26657@footnote{https://bugs.python.org/issue26657}: Fix directory traversal vulnerability with http.server on
Windows.  This fixes a regression that was introduced in 3.3.4rc1 and
3.4.0rc1.  Based on patch by Philipp Hagemeister.
@end itemize

@node 库<64>,安全<37>,安全<36>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id421}@anchor{1131}
@subsubsection 库



@itemize -

@item 
bpo-26717@footnote{https://bugs.python.org/issue26717}: Stop encoding Latin-1-ized WSGI paths with UTF-8.  Patch by
Anthony Sottile.

@item 
bpo-26735@footnote{https://bugs.python.org/issue26735}: Fix @ref{4cb,,os.urandom()} on Solaris 11.3 and newer when reading
more than 1,024 bytes: call @code{getrandom()} multiple times with a limit of
1024 bytes per call.

@item 
bpo-16329@footnote{https://bugs.python.org/issue16329}: Add .webm to mimetypes.types_map.  Patch by Giampaolo Rodola'.

@item 
bpo-13952@footnote{https://bugs.python.org/issue13952}: Add .csv to mimetypes.types_map.  Patch by Geoff Wilson.

@item 
bpo-26709@footnote{https://bugs.python.org/issue26709}: Fixed Y2038 problem in loading binary PLists.

@item 
bpo-23735@footnote{https://bugs.python.org/issue23735}: Handle terminal resizing with Readline 6.3+ by installing our
own SIGWINCH handler.  Patch by Eric Price.

@item 
bpo-26586@footnote{https://bugs.python.org/issue26586}: In http.server, respond with "413 Request header fields too
large" if there are too many header fields to parse, rather than killing
the connection and raising an unhandled exception.  Patch by Xiang Zhang.

@item 
bpo-22854@footnote{https://bugs.python.org/issue22854}: Change BufferedReader.writable() and BufferedWriter.readable()
to always return False.

@item 
bpo-25195@footnote{https://bugs.python.org/issue25195}: Fix a regression in mock.MagicMock. _Call is a subclass of
tuple (changeset 3603bae63c13 only works for classes) so we need to
implement __ne__ ourselves.  Patch by Andrew Plummer.

@item 
bpo-26644@footnote{https://bugs.python.org/issue26644}: Raise ValueError rather than SystemError when a negative length
is passed to SSLSocket.recv() or read().

@item 
bpo-23804@footnote{https://bugs.python.org/issue23804}: Fix SSL recv(0) and read(0) methods to return zero bytes
instead of up to 1024.

@item 
bpo-26616@footnote{https://bugs.python.org/issue26616}: Fixed a bug in datetime.astimezone() method.

@item 
bpo-21925@footnote{https://bugs.python.org/issue21925}: @ref{f83,,warnings.formatwarning()} now catches exceptions on
@code{linecache.getline(...)} to be able to log @ref{4ca,,ResourceWarning}
emitted late during the Python shutdown process.

@item 
bpo-24266@footnote{https://bugs.python.org/issue24266}: Ctrl+C during Readline history search now cancels the search
mode when compiled with Readline 7.

@item 
bpo-26560@footnote{https://bugs.python.org/issue26560}: Avoid potential ValueError in BaseHandler.start_response.
Initial patch by Peter Inglesby.
@end itemize

@node 安全<37>,库<65>,库<64>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id422}@anchor{1132}
@subsubsection 安全



@itemize -

@item 
bpo-26313@footnote{https://bugs.python.org/issue26313}: ssl.py _load_windows_store_certs fails if windows cert store is
empty. Patch by Baji.
@end itemize

@node 库<65>,安全<38>,安全<37>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id423}@anchor{1133}
@subsubsection 库



@itemize -

@item 
bpo-26569@footnote{https://bugs.python.org/issue26569}: Fix @ref{10fc,,pyclbr.readmodule()} and @ref{10fd,,pyclbr.readmodule_ex()}
to support importing packages.

@item 
bpo-26499@footnote{https://bugs.python.org/issue26499}: Account for remaining Content-Length in HTTPResponse.readline()
and read1(). Based on patch by Silent Ghost. Also document that
HTTPResponse now supports these methods.

@item 
bpo-25320@footnote{https://bugs.python.org/issue25320}: Handle sockets in directories unittest discovery is scanning.
Patch from Victor van den Elzen.

@item 
bpo-16181@footnote{https://bugs.python.org/issue16181}: cookiejar.http2time() now returns None if year is higher than
datetime.MAXYEAR.

@item 
bpo-26513@footnote{https://bugs.python.org/issue26513}: Fixes platform module detection of Windows Server

@item 
bpo-23718@footnote{https://bugs.python.org/issue23718}: Fixed parsing time in week 0 before Jan 1.  Original patch by
Tamás Bence Gedai.

@item 
bpo-20589@footnote{https://bugs.python.org/issue20589}: Invoking Path.owner() and Path.group() on Windows now raise
NotImplementedError instead of ImportError.

@item 
bpo-26177@footnote{https://bugs.python.org/issue26177}: Fixed the keys() method for Canvas and Scrollbar widgets.

@item 
bpo-15068@footnote{https://bugs.python.org/issue15068}: Got rid of excessive buffering in the fileinput module. The
bufsize parameter is no longer used.

@item 
bpo-2202@footnote{https://bugs.python.org/issue2202}: Fix UnboundLocalError in
AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu
Dupuy.

@item 
bpo-25718@footnote{https://bugs.python.org/issue25718}: Fixed pickling and copying the accumulate() iterator with total
is None.

@item 
bpo-26475@footnote{https://bugs.python.org/issue26475}: Fixed debugging output for regular expressions with the (?x)
flag.

@item 
bpo-26457@footnote{https://bugs.python.org/issue26457}: Fixed the subnets() methods in IP network classes for the case
when resulting prefix length is equal to maximal prefix length. Based on
patch by Xiang Zhang.

@item 
bpo-26385@footnote{https://bugs.python.org/issue26385}: Remove the file if the internal open() call in
NamedTemporaryFile() fails. Patch by Silent Ghost.

@item 
bpo-26402@footnote{https://bugs.python.org/issue26402}: Fix XML-RPC client to retry when the server shuts down a
persistent connection.  This was a regression related to the new
http.client.RemoteDisconnected exception in 3.5.0a4.

@item 
bpo-25913@footnote{https://bugs.python.org/issue25913}: Leading @code{<~} is optional now in base64.a85decode() with
adobe=True.  Patch by Swati Jaiswal.

@item 
bpo-26186@footnote{https://bugs.python.org/issue26186}: Remove an invalid type check in importlib.util.LazyLoader.

@item 
bpo-26367@footnote{https://bugs.python.org/issue26367}: importlib.__import__() raises SystemError like
builtins.__import__() when @code{level} is specified but without an
accompanying package specified.

@item 
bpo-26309@footnote{https://bugs.python.org/issue26309}: In the "socketserver" module, shut down the request (closing
the connected socket) when verify_request() returns false.  Patch by Aviv
Palivoda.
@end itemize

@node 安全<38>,库<66>,库<65>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id424}@anchor{1134}
@subsubsection 安全



@itemize -

@item 
bpo-25939@footnote{https://bugs.python.org/issue25939}: On Windows open the cert store readonly in
ssl.enum_certificates.
@end itemize

@node 库<66>,IDLE<43>,安全<38>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id425}@anchor{1135}
@subsubsection 库



@itemize -

@item 
bpo-25995@footnote{https://bugs.python.org/issue25995}: os.walk() no longer uses FDs proportional to the tree depth.

@item 
bpo-26117@footnote{https://bugs.python.org/issue26117}: The os.scandir() iterator now closes file descriptor not only
when the iteration is finished, but when it was failed with error.

@item 
bpo-25911@footnote{https://bugs.python.org/issue25911}: Restored support of bytes paths in os.walk() on Windows.

@item 
bpo-26045@footnote{https://bugs.python.org/issue26045}: Add UTF-8 suggestion to error message when posting a
non-Latin-1 string with http.client.

@item 
bpo-12923@footnote{https://bugs.python.org/issue12923}: Reset FancyURLopener's redirect counter even if there is an
exception. Based on patches by Brian Brazil and Daniel Rocco.

@item 
bpo-25945@footnote{https://bugs.python.org/issue25945}: Fixed a crash when unpickle the functools.partial object with
wrong state. Fixed a leak in failed functools.partial constructor. "args"
and "keywords" attributes of functools.partial have now always types tuple
and dict correspondingly.

@item 
bpo-26202@footnote{https://bugs.python.org/issue26202}: copy.deepcopy() now correctly copies range() objects with
non-atomic attributes.

@item 
bpo-23076@footnote{https://bugs.python.org/issue23076}: Path.glob() now raises a ValueError if it's called with an
invalid pattern. Patch by Thomas Nyberg.

@item 
bpo-19883@footnote{https://bugs.python.org/issue19883}: Fixed possible integer overflows in zipimport.

@item 
bpo-26227@footnote{https://bugs.python.org/issue26227}: On Windows, getnameinfo(), gethostbyaddr() and
gethostbyname_ex() functions of the socket module now decode the hostname
from the ANSI code page rather than UTF-8.

@item 
bpo-26147@footnote{https://bugs.python.org/issue26147}: xmlrpc now works with strings not encodable with used non-UTF-8
encoding.

@item 
bpo-25935@footnote{https://bugs.python.org/issue25935}: Garbage collector now breaks reference loops with OrderedDict.

@item 
bpo-16620@footnote{https://bugs.python.org/issue16620}: Fixed AttributeError in msilib.Directory.glob().

@item 
bpo-26013@footnote{https://bugs.python.org/issue26013}: Added compatibility with broken protocol 2 pickles created in
old Python 3 versions (3.4.3 and lower).

@item 
bpo-25850@footnote{https://bugs.python.org/issue25850}: Use cross-compilation by default for 64-bit Windows.

@item 
bpo-17633@footnote{https://bugs.python.org/issue17633}: Improve zipimport's support for namespace packages.

@item 
bpo-24705@footnote{https://bugs.python.org/issue24705}: Fix sysconfig._parse_makefile not expanding $@{@} vars appearing
before $() vars.

@item 
bpo-22138@footnote{https://bugs.python.org/issue22138}: Fix mock.patch behavior when patching descriptors. Restore
original values after patching. Patch contributed by Sean McCully.

@item 
bpo-25672@footnote{https://bugs.python.org/issue25672}: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode
option if it is safe to do so.

@item 
bpo-26012@footnote{https://bugs.python.org/issue26012}: Don't traverse into symlinks for @code{**} pattern in
pathlib.Path.[r]glob().

@item 
bpo-24120@footnote{https://bugs.python.org/issue24120}: Ignore PermissionError when traversing a tree with
pathlib.Path.[r]glob(). Patch by Ulrich Petri.

@item 
bpo-25447@footnote{https://bugs.python.org/issue25447}: fileinput now uses sys.stdin as-is if it does not have a buffer
attribute (restores backward compatibility).

@item 
bpo-25447@footnote{https://bugs.python.org/issue25447}: Copying the lru_cache() wrapper object now always works,
independently from the type of the wrapped object (by returning the
original object unchanged).

@item 
bpo-24103@footnote{https://bugs.python.org/issue24103}: Fixed possible use after free in ElementTree.XMLPullParser.

@item 
bpo-25860@footnote{https://bugs.python.org/issue25860}: os.fwalk() no longer skips remaining directories when error
occurs. Original patch by Samson Lee.

@item 
bpo-25914@footnote{https://bugs.python.org/issue25914}: Fixed and simplified OrderedDict.__sizeof__.

@item 
bpo-25902@footnote{https://bugs.python.org/issue25902}: Fixed various refcount issues in ElementTree iteration.

@item 
bpo-25717@footnote{https://bugs.python.org/issue25717}: Restore the previous behaviour of tolerating most fstat()
errors when opening files.  This was a regression in 3.5a1, and stopped
anonymous temporary files from working in special cases.

@item 
bpo-24903@footnote{https://bugs.python.org/issue24903}: Fix regression in number of arguments compileall accepts when
'-d' is specified.  The check on the number of arguments has been dropped
completely as it never worked correctly anyway.

@item 
bpo-25764@footnote{https://bugs.python.org/issue25764}: In the subprocess module, preserve any exception caused by
fork() failure when preexec_fn is used.

@item 
bpo-6478@footnote{https://bugs.python.org/issue6478}: _strptime's regexp cache now is reset after changing timezone
with time.tzset().

@item 
bpo-14285@footnote{https://bugs.python.org/issue14285}: When executing a package with the "python -m package" option,
and package initialization fails, a proper traceback is now reported.  The
"runpy" module now lets exceptions from package initialization pass back
to the caller, rather than raising ImportError.

@item 
bpo-19771@footnote{https://bugs.python.org/issue19771}: Also in runpy and the "-m" option, omit the irrelevant message
". . . is a package and cannot be directly executed" if the package could
not even be initialized (e.g. due to a bad @code{*.pyc} file).

@item 
bpo-25177@footnote{https://bugs.python.org/issue25177}: Fixed problem with the mean of very small and very large
numbers. As a side effect, statistics.mean and statistics.variance should
be significantly faster.

@item 
bpo-25718@footnote{https://bugs.python.org/issue25718}: Fixed copying object with state with boolean value is false.

@item 
bpo-10131@footnote{https://bugs.python.org/issue10131}: Fixed deep copying of minidom documents.  Based on patch by
Marian Ganisin.

@item 
bpo-25725@footnote{https://bugs.python.org/issue25725}: Fixed a reference leak in pickle.loads() when unpickling
invalid data including tuple instructions.

@item 
bpo-25663@footnote{https://bugs.python.org/issue25663}: In the Readline completer, avoid listing duplicate global
names, and search the global namespace before searching builtins.

@item 
bpo-25688@footnote{https://bugs.python.org/issue25688}: Fixed file leak in ElementTree.iterparse() raising an error.

@item 
bpo-23914@footnote{https://bugs.python.org/issue23914}: Fixed SystemError raised by unpickler on broken pickle data.

@item 
bpo-25691@footnote{https://bugs.python.org/issue25691}: Fixed crash on deleting ElementTree.Element attributes.

@item 
bpo-25624@footnote{https://bugs.python.org/issue25624}: ZipFile now always writes a ZIP_STORED header for directory
entries.  Patch by Dingyuan Wang.

@item 
Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu
Davis.

@item 
bpo-26050@footnote{https://bugs.python.org/issue26050}: Add asyncio.StreamReader.readuntil() method. Patch by Марк
Коренберг.

@item 
bpo-25924@footnote{https://bugs.python.org/issue25924}: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X
versions 10.5 or higher.  Original patch by A. Jesse Jiryu Davis.

@item 
bpo-26406@footnote{https://bugs.python.org/issue26406}: Avoid unnecessary serialization of getaddrinfo(3) calls on
current versions of OpenBSD and NetBSD.  Patch by A. Jesse Jiryu Davis.

@item 
bpo-26848@footnote{https://bugs.python.org/issue26848}: Fix asyncio/subprocess.communicate() to handle empty input.
Patch by Jack O'Connor.

@item 
bpo-27040@footnote{https://bugs.python.org/issue27040}: Add loop.get_exception_handler method

@item 
bpo-27041@footnote{https://bugs.python.org/issue27041}: asyncio: Add loop.create_future method

@item 
bpo-27223@footnote{https://bugs.python.org/issue27223}: asyncio: Fix _read_ready and _write_ready to respect
_conn_lost. Patch by Łukasz Langa.

@item 
bpo-22970@footnote{https://bugs.python.org/issue22970}: asyncio: Fix inconsistency cancelling Condition.wait. Patch by
David Coles.
@end itemize

@node IDLE<43>,文档<40>,库<66>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id426}@anchor{1136}
@subsubsection IDLE



@itemize -

@item 
bpo-5124@footnote{https://bugs.python.org/issue5124}: Paste with text selected now replaces the selection on X11. This
matches how paste works on Windows, Mac, most modern Linux apps, and ttk
widgets. Original patch by Serhiy Storchaka.

@item 
bpo-24759@footnote{https://bugs.python.org/issue24759}: Make clear in idlelib.idle_test.__init__ that the directory is
a private implementation of test.test_idle and tool for maintainers.

@item 
bpo-27196@footnote{https://bugs.python.org/issue27196}: Stop 'ThemeChanged' warnings when running IDLE tests. These
persisted after other warnings were suppressed in #20567. Apply Serhiy
Storchaka's update_idletasks solution to four test files. Record this
additional advice in idle_test/README.txt

@item 
bpo-20567@footnote{https://bugs.python.org/issue20567}: Revise idle_test/README.txt with advice about avoiding tk
warning messages from tests.  Apply advice to several IDLE tests.

@item 
bpo-27117@footnote{https://bugs.python.org/issue27117}: Make colorizer htest and turtledemo work with dark themes. Move
code for configuring text widget colors to a new function.

@item 
bpo-26673@footnote{https://bugs.python.org/issue26673}: When tk reports font size as 0, change to size 10. Such fonts
on Linux prevented the configuration dialog from opening.

@item 
bpo-21939@footnote{https://bugs.python.org/issue21939}: Add test for IDLE's percolator. Original patch by Saimadhav
Heblikar.

@item 
bpo-21676@footnote{https://bugs.python.org/issue21676}: Add test for IDLE's replace dialog. Original patch by Saimadhav
Heblikar.

@item 
bpo-18410@footnote{https://bugs.python.org/issue18410}: Add test for IDLE's search dialog. Original patch by Westley
Martínez.

@item 
bpo-21703@footnote{https://bugs.python.org/issue21703}: Add test for IDLE's undo delegator. Original patch by Saimadhav
Heblikar .

@item 
bpo-27044@footnote{https://bugs.python.org/issue27044}: Add ConfigDialog.remove_var_callbacks to stop memory leaks.

@item 
bpo-23977@footnote{https://bugs.python.org/issue23977}: Add more asserts to test_delegator.

@item 
bpo-20640@footnote{https://bugs.python.org/issue20640}: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav
Heblikar.

@item 
In the 'IDLE-console differences' section of the IDLE doc, clarify how
running with IDLE affects sys.modules and the standard streams.

@item 
bpo-25507@footnote{https://bugs.python.org/issue25507}: fix incorrect change in IOBinding that prevented printing.
Augment IOBinding htest to include all major IOBinding functions.

@item 
bpo-25905@footnote{https://bugs.python.org/issue25905}: Revert unwanted conversion of ' to ’ RIGHT SINGLE QUOTATION
MARK in README.txt and open this and NEWS.txt with 'ascii'. Re-encode
CREDITS.txt to utf-8 and open it with 'utf-8'.
@end itemize

@node 文档<40>,测试<42>,IDLE<43>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id427}@anchor{1137}
@subsubsection 文档



@itemize -

@item 
bpo-19489@footnote{https://bugs.python.org/issue19489}: Moved the search box from the sidebar to the header and footer
of each page. Patch by Ammar Askar.

@item 
bpo-24136@footnote{https://bugs.python.org/issue24136}: Document the new 
@geindex Python 提高建议; PEP 448
PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} unpacking syntax of 3.5.

@item 
bpo-26736@footnote{https://bugs.python.org/issue26736}: Used HTTPS for external links in the documentation if possible.

@item 
bpo-6953@footnote{https://bugs.python.org/issue6953}: Rework the Readline module documentation to group related
functions together, and add more details such as what underlying Readline
functions and variables are accessed.

@item 
bpo-23606@footnote{https://bugs.python.org/issue23606}: Adds note to ctypes documentation regarding cdll.msvcrt.

@item 
bpo-25500@footnote{https://bugs.python.org/issue25500}: Fix documentation to not claim that __import__ is searched for
in the global scope.

@item 
bpo-26014@footnote{https://bugs.python.org/issue26014}: Update 3.x packaging documentation: * "See also" links to the
new docs are now provided in the legacy pages * links to setuptools
documentation have been updated
@end itemize

@node 测试<42>,构建<43>,文档<40>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id428}@anchor{1138}
@subsubsection 测试



@itemize -

@item 
bpo-21916@footnote{https://bugs.python.org/issue21916}: Added tests for the turtle module.  Patch by ingrid, Gregory
Loyse and Jelle Zijlstra.

@item 
bpo-26523@footnote{https://bugs.python.org/issue26523}: The multiprocessing thread pool (multiprocessing.dummy.Pool)
was untested.

@item 
bpo-26015@footnote{https://bugs.python.org/issue26015}: Added new tests for pickling iterators of mutable sequences.

@item 
bpo-26325@footnote{https://bugs.python.org/issue26325}: Added test.support.check_no_resource_warning() to check that no
ResourceWarning is emitted.

@item 
bpo-25940@footnote{https://bugs.python.org/issue25940}: Changed test_ssl to use self-signed.pythontest.net.  This
avoids relying on svn.python.org, which recently changed root certificate.

@item 
bpo-25616@footnote{https://bugs.python.org/issue25616}: Tests for OrderedDict are extracted from test_collections into
separate file test_ordered_dict.

@item 
bpo-26583@footnote{https://bugs.python.org/issue26583}: Skip test_timestamp_overflow in test_import if bytecode files
cannot be written.
@end itemize

@node 构建<43>,Windows<41>,测试<42>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id429}@anchor{1139}
@subsubsection 构建



@itemize -

@item 
bpo-26884@footnote{https://bugs.python.org/issue26884}: Fix linking extension modules for cross builds. Patch by Xavier
de Gaye.

@item 
bpo-22359@footnote{https://bugs.python.org/issue22359}: Disable the rules for running _freeze_importlib and pgen when
cross-compiling.  The output of these programs is normally saved with the
source code anyway, and is still regenerated when doing a native build.
Patch by Xavier de Gaye.

@item 
bpo-27229@footnote{https://bugs.python.org/issue27229}: Fix the cross-compiling pgen rule for in-tree builds.  Patch by
Xavier de Gaye.

@item 
bpo-21668@footnote{https://bugs.python.org/issue21668}: Link audioop, _datetime, _ctypes_test modules to libm, except
on Mac OS X. Patch written by Xavier de Gaye.

@item 
bpo-25702@footnote{https://bugs.python.org/issue25702}: A --with-lto configure option has been added that will enable
link time optimizations at build time during a make profile-opt. Some
compilers and toolchains are known to not produce stable code when using
LTO, be sure to test things thoroughly before relying on it. It can
provide a few % speed up over profile-opt alone.

@item 
bpo-26624@footnote{https://bugs.python.org/issue26624}: Adds validation of ucrtbase[d].dll version with warning for old
versions.

@item 
bpo-17603@footnote{https://bugs.python.org/issue17603}: Avoid error about nonexistent fileblocks.o file by using a
lower-level check for st_blocks in struct stat.

@item 
bpo-26079@footnote{https://bugs.python.org/issue26079}: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern
Thiel.

@item 
bpo-26465@footnote{https://bugs.python.org/issue26465}: 更新Windows 构建OpenSSL 1.0.2g.

@item 
bpo-24421@footnote{https://bugs.python.org/issue24421}: Compile Modules/_math.c once, before building extensions.
Previously it could fail to compile properly if the math and cmath builds
were concurrent.

@item 
bpo-25348@footnote{https://bugs.python.org/issue25348}: Added @code{--pgo} and @code{--pgo-job} arguments to
@code{PCbuild\build.bat} for building with Profile-Guided Optimization.  The
old @code{PCbuild\build_pgo.bat} script is now deprecated, and simply calls
@code{PCbuild\build.bat --pgo %*}.

@item 
bpo-25827@footnote{https://bugs.python.org/issue25827}: Add support for building with ICC to @code{configure}, including a
new @code{--with-icc} flag.

@item 
bpo-25696@footnote{https://bugs.python.org/issue25696}: Fix installation of Python on UNIX with make -j9.

@item 
bpo-26930@footnote{https://bugs.python.org/issue26930}: 更新OS X 10.5+（仅32位）安装程序以构建并链接OpenSSL 1.0.2h。

@item 
bpo-26268@footnote{https://bugs.python.org/issue26268}: 更新Windows 构建OpenSSL 1.0.2f.

@item 
bpo-25136@footnote{https://bugs.python.org/issue25136}: Support Apple Xcode 7's new textual SDK stub libraries.

@item 
bpo-24324@footnote{https://bugs.python.org/issue24324}: Do not enable unreachable code warnings when using gcc as the
option does not work correctly in older versions of gcc and has been
silently removed as of gcc-4.5.
@end itemize

@node Windows<41>,工具/示例<29>,构建<43>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id430}@anchor{113a}
@subsubsection Windows



@itemize -

@item 
bpo-27053@footnote{https://bugs.python.org/issue27053}: Updates make_zip.py to correctly generate library ZIP file.

@item 
bpo-26268@footnote{https://bugs.python.org/issue26268}: Update the prepare_ssl.py script to handle OpenSSL releases
that don't include the contents of the include directory (that is, 1.0.2e
and later).

@item 
bpo-26071@footnote{https://bugs.python.org/issue26071}: bdist_wininst created binaries fail to start and find 32bit
Python

@item 
bpo-26073@footnote{https://bugs.python.org/issue26073}: Update the list of magic numbers in launcher

@item 
bpo-26065@footnote{https://bugs.python.org/issue26065}: Excludes venv from library when generating embeddable distro.
@end itemize

@node 工具/示例<29>,Windows<42>,Windows<41>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id431}@anchor{113b}
@subsubsection 工具/示例



@itemize -

@item 
bpo-26799@footnote{https://bugs.python.org/issue26799}: Fix python-gdb.py: don't get C types once when the Python code
is loaded, but get C types on demand. The C types can change if
python-gdb.py is loaded before the Python executable. Patch written by
Thomas Ilsche.

@item 
bpo-26271@footnote{https://bugs.python.org/issue26271}: Fix the Freeze tool to properly use flags passed through
configure. Patch by Daniel Shaulov.

@item 
bpo-26489@footnote{https://bugs.python.org/issue26489}: Add dictionary unpacking support to Tools/parser/unparse.py.
Patch by Guo Ci Teo.

@item 
bpo-26316@footnote{https://bugs.python.org/issue26316}: Fix variable name typo in Argument Clinic.
@end itemize

@node Windows<42>,,工具/示例<29>,Python 3 5 2 rc1
@anchor{whatsnew/changelog id432}@anchor{113c}
@subsubsection Windows



@itemize -

@item 
bpo-17500@footnote{https://bugs.python.org/issue17500}: Remove unused and outdated icons. (See also:
@indicateurl{https://github.com/python/pythondotorg/issues/945})
@end itemize

@node Python 3 5 1 正式版,Python 3 5 1 rc1,Python 3 5 2 rc1,更新日志
@anchor{whatsnew/changelog python-3-5-1-final}@anchor{113d}
@subsection Python 3.5.1 正式版


@emph{发布日期: 2015-12-06}

@menu
* 核心与内置: 核心与内置<53>. 
* Windows: Windows<43>. 

@end menu

@node 核心与内置<53>,Windows<43>,,Python 3 5 1 正式版
@anchor{whatsnew/changelog id433}@anchor{113e}
@subsubsection 核心与内置



@itemize -

@item 
bpo-25709@footnote{https://bugs.python.org/issue25709}: Fixed problem with in-place string concatenation and utf-8
cache.
@end itemize

@node Windows<43>,,核心与内置<53>,Python 3 5 1 正式版
@anchor{whatsnew/changelog id434}@anchor{113f}
@subsubsection Windows



@itemize -

@item 
bpo-25715@footnote{https://bugs.python.org/issue25715}: Python 3.5.1 installer shows wrong upgrade path and incorrect
logic for launcher detection.
@end itemize

@node Python 3 5 1 rc1,Python 3 5 0 正式版,Python 3 5 1 正式版,更新日志
@anchor{whatsnew/changelog python-3-5-1-release-candidate-1}@anchor{1140}
@subsection Python 3.5.1 rc1


@emph{发布日期: 2015-11-22}

@menu
* 核心与内置: 核心与内置<54>. 
* 库: 库<67>. 
* IDLE: IDLE<44>. 
* 文档: 文档<41>. 
* 测试: 测试<43>. 
* 构建: 构建<44>. 
* Windows: Windows<44>. 
* 工具/示例: 工具/示例<30>. 

@end menu

@node 核心与内置<54>,库<67>,,Python 3 5 1 rc1
@anchor{whatsnew/changelog id435}@anchor{1141}
@subsubsection 核心与内置



@itemize -

@item 
bpo-25630@footnote{https://bugs.python.org/issue25630}: Fix a possible segfault during argument parsing in functions
that accept filesystem paths.

@item 
bpo-23564@footnote{https://bugs.python.org/issue23564}: Fixed a partially broken sanity check in the _posixsubprocess
internals regarding how fds_to_pass were passed to the child.  The bug had
no actual impact as subprocess.py already avoided it.

@item 
bpo-25388@footnote{https://bugs.python.org/issue25388}: Fixed tokenizer crash when processing undecodable source code
with a null byte.

@item 
bpo-25462@footnote{https://bugs.python.org/issue25462}: The hash of the key now is calculated only once in most
operations in C implementation of OrderedDict.

@item 
bpo-22995@footnote{https://bugs.python.org/issue22995}: Default implementation of __reduce__ and __reduce_ex__ now
rejects builtin types with not defined __new__.

@item 
bpo-25555@footnote{https://bugs.python.org/issue25555}: Fix parser and AST: fill lineno and col_offset of "arg" node
when compiling AST from Python objects.

@item 
bpo-24802@footnote{https://bugs.python.org/issue24802}: Avoid buffer overreads when int(), float(), compile(), exec()
and eval() are passed bytes-like objects.  These objects are not
necessarily terminated by a null byte, but the functions assumed they
were.

@item 
bpo-24726@footnote{https://bugs.python.org/issue24726}: Fixed a crash and leaking NULL in repr() of OrderedDict that
was mutated by direct calls of dict methods.

@item 
bpo-25449@footnote{https://bugs.python.org/issue25449}: Iterating OrderedDict with keys with unstable hash now raises
KeyError in C implementations as well as in Python implementation.

@item 
bpo-25395@footnote{https://bugs.python.org/issue25395}: Fixed crash when highly nested OrderedDict structures were
garbage collected.

@item 
bpo-25274@footnote{https://bugs.python.org/issue25274}: sys.setrecursionlimit() now raises a RecursionError if the new
recursion limit is too low depending at the current recursion depth.
Modify also the "lower-water mark" formula to make it monotonic. This mark
is used to decide when the overflowed flag of the thread state is reset.

@item 
bpo-24402@footnote{https://bugs.python.org/issue24402}: Fix input() to prompt to the redirected stdout when
sys.stdout.fileno() fails.

@item 
bpo-24806@footnote{https://bugs.python.org/issue24806}: Prevent builtin types that are not allowed to be subclassed
from being subclassed through multiple inheritance.

@item 
bpo-24848@footnote{https://bugs.python.org/issue24848}: Fixed a number of bugs in UTF-7 decoding of misformed data.

@item 
bpo-25280@footnote{https://bugs.python.org/issue25280}: Import trace messages emitted in verbose (-v) mode are no
longer formatted twice.

@item 
bpo-25003@footnote{https://bugs.python.org/issue25003}: On Solaris 11.3 or newer, os.urandom() now uses the getrandom()
function instead of the getentropy() function. The getentropy() function
is blocking to generate very good quality entropy, os.urandom() doesn't
need such high-quality entropy.

@item 
bpo-25182@footnote{https://bugs.python.org/issue25182}: The stdprinter (used as sys.stderr before the io module is
imported at startup) now uses the backslashreplace error handler.

@item 
bpo-25131@footnote{https://bugs.python.org/issue25131}: Make the line number and column offset of set/dict literals and
comprehensions correspond to the opening brace.

@item 
bpo-25150@footnote{https://bugs.python.org/issue25150}: Hide the private _Py_atomic_xxx symbols from the public
Python.h header to fix a compilation error with OpenMP.
PyThreadState_GET() becomes an alias to PyThreadState_Get() to avoid ABI
incompatibilities.
@end itemize

@node 库<67>,IDLE<44>,核心与内置<54>,Python 3 5 1 rc1
@anchor{whatsnew/changelog id436}@anchor{1142}
@subsubsection 库



@itemize -

@item 
bpo-25626@footnote{https://bugs.python.org/issue25626}: Change three zlib functions to accept sizes that fit in
Py_ssize_t, but internally cap those sizes to UINT_MAX.  This resolves a
regression in 3.5 where GzipFile.read() failed to read chunks larger than
2 or 4 GiB.  The change affects the zlib.Decompress.decompress()
max_length parameter, the zlib.decompress() bufsize parameter, and the
zlib.Decompress.flush() length parameter.

@item 
bpo-25583@footnote{https://bugs.python.org/issue25583}: Avoid incorrect errors raised by os.makedirs(exist_ok=True)
when the OS gives priority to errors such as EACCES over EEXIST.

@item 
bpo-25593@footnote{https://bugs.python.org/issue25593}: Change semantics of EventLoop.stop() in asyncio.

@item 
bpo-6973@footnote{https://bugs.python.org/issue6973}: When we know a subprocess.Popen process has died, do not allow
the send_signal(), terminate(), or kill() methods to do anything as they
could potentially signal a different process.

@item 
bpo-25590@footnote{https://bugs.python.org/issue25590}: In the Readline completer, only call getattr() once per
attribute.

@item 
bpo-25498@footnote{https://bugs.python.org/issue25498}: Fix a crash when garbage-collecting ctypes objects created by
wrapping a memoryview.  This was a regression made in 3.5a1.  Based on
patch by Eryksun.

@item 
bpo-25584@footnote{https://bugs.python.org/issue25584}: Added "escape" to the __all__ list in the glob module.

@item 
bpo-25584@footnote{https://bugs.python.org/issue25584}: Fixed recursive glob() with patterns starting with @code{**}.

@item 
bpo-25446@footnote{https://bugs.python.org/issue25446}: Fix regression in smtplib's AUTH LOGIN support.

@item 
bpo-18010@footnote{https://bugs.python.org/issue18010}: Fix the pydoc web server's module search function to handle
exceptions from importing packages.

@item 
bpo-25554@footnote{https://bugs.python.org/issue25554}: Got rid of circular references in regular expression parsing.

@item 
bpo-25510@footnote{https://bugs.python.org/issue25510}: fileinput.FileInput.readline() now returns b'@w{'} instead of '@w{'} at
the end if the FileInput was opened with binary mode. Patch by Ryosuke
Ito.

@item 
bpo-25503@footnote{https://bugs.python.org/issue25503}: Fixed inspect.getdoc() for inherited docstrings of properties.
Original patch by John Mark Vandenberg.

@item 
bpo-25515@footnote{https://bugs.python.org/issue25515}: Always use os.urandom as a source of randomness in uuid.uuid4.

@item 
bpo-21827@footnote{https://bugs.python.org/issue21827}: Fixed textwrap.dedent() for the case when largest common
whitespace is a substring of smallest leading whitespace. Based on patch
by Robert Li.

@item 
bpo-25447@footnote{https://bugs.python.org/issue25447}: The lru_cache() wrapper objects now can be copied and pickled
(by returning the original object unchanged).

@item 
bpo-25390@footnote{https://bugs.python.org/issue25390}: typing: Don't crash on Union[str, Pattern].

@item 
bpo-25441@footnote{https://bugs.python.org/issue25441}: asyncio: Raise error from drain() when socket is closed.

@item 
bpo-25410@footnote{https://bugs.python.org/issue25410}: Cleaned up and fixed minor bugs in C implementation of
OrderedDict.

@item 
bpo-25411@footnote{https://bugs.python.org/issue25411}: Improved Unicode support in SMTPHandler through better use of
the email package. Thanks to user simon04 for the patch.

@item 
bpo-25407@footnote{https://bugs.python.org/issue25407}: Remove mentions of the formatter module being removed in Python
3.6.

@item 
bpo-25406@footnote{https://bugs.python.org/issue25406}: Fixed a bug in C implementation of OrderedDict.move_to_end()
that caused segmentation fault or hang in iterating after moving several
items to the start of ordered dict.

@item 
bpo-25364@footnote{https://bugs.python.org/issue25364}: zipfile now works in threads disabled builds.

@item 
bpo-25328@footnote{https://bugs.python.org/issue25328}: smtpd's SMTPChannel now correctly raises a ValueError if both
decode_data and enable_SMTPUTF8 are set to true.

@item 
bpo-25316@footnote{https://bugs.python.org/issue25316}: distutils raises OSError instead of DistutilsPlatformError when
MSVC is not installed.

@item 
bpo-25380@footnote{https://bugs.python.org/issue25380}: Fixed protocol for the STACK_GLOBAL opcode in
pickletools.opcodes.

@item 
bpo-23972@footnote{https://bugs.python.org/issue23972}: Updates asyncio datagram create method allowing reuseport and
reuseaddr socket options to be set prior to binding the socket. Mirroring
the existing asyncio create_server method the reuseaddr option for
datagram sockets defaults to True if the O/S is 'posix' (except if the
platform is Cygwin). Patch by Chris Laws.

@item 
bpo-25304@footnote{https://bugs.python.org/issue25304}: Add asyncio.run_coroutine_threadsafe().  This lets you submit a
coroutine to a loop from another thread, returning a
concurrent.futures.Future.  By Vincent Michel.

@item 
bpo-25232@footnote{https://bugs.python.org/issue25232}: Fix CGIRequestHandler to split the query from the URL at the
first question mark (?) rather than the last. Patch from Xiang Zhang.

@item 
bpo-24657@footnote{https://bugs.python.org/issue24657}: Prevent CGIRequestHandler from collapsing slashes in the query
part of the URL as if it were a path. Patch from Xiang Zhang.

@item 
bpo-24483@footnote{https://bugs.python.org/issue24483}: C implementation of functools.lru_cache() now calculates key's
hash only once.

@item 
bpo-22958@footnote{https://bugs.python.org/issue22958}: Constructor and update method of weakref.WeakValueDictionary
now accept the self and the dict keyword arguments.

@item 
bpo-22609@footnote{https://bugs.python.org/issue22609}: Constructor of collections.UserDict now accepts the self
keyword argument.

@item 
bpo-25111@footnote{https://bugs.python.org/issue25111}: Fixed comparison of traceback.FrameSummary.

@item 
bpo-25262@footnote{https://bugs.python.org/issue25262}: Added support for BINBYTES8 opcode in Python implementation of
unpickler. Highest 32 bits of 64-bit size for BINUNICODE8 and BINBYTES8
opcodes no longer silently ignored on 32-bit platforms in C
implementation.

@item 
bpo-25034@footnote{https://bugs.python.org/issue25034}: Fix string.Formatter problem with auto-numbering and nested
format_specs. Patch by Anthon van der Neut.

@item 
bpo-25233@footnote{https://bugs.python.org/issue25233}: Rewrite the guts of asyncio.Queue and asyncio.Semaphore to be
more understandable and correct.

@item 
bpo-25203@footnote{https://bugs.python.org/issue25203}: Failed readline.set_completer_delims() no longer left the
module in inconsistent state.

@item 
bpo-23600@footnote{https://bugs.python.org/issue23600}: Default implementation of tzinfo.fromutc() was returning wrong
results in some cases.

@item 
bpo-23329@footnote{https://bugs.python.org/issue23329}: Allow the ssl module to be built with older versions of
LibreSSL.

@item 
Prevent overflow in _Unpickler_Read.

@item 
bpo-25047@footnote{https://bugs.python.org/issue25047}: The XML encoding declaration written by Element Tree now
respects the letter case given by the user. This restores the ability to
write encoding names in uppercase like "UTF-8", which worked in Python 2.

@item 
bpo-25135@footnote{https://bugs.python.org/issue25135}: Make deque_clear() safer by emptying the deque before clearing.
This helps avoid possible reentrancy issues.

@item 
bpo-19143@footnote{https://bugs.python.org/issue19143}: platform module now reads Windows version from kernel32.dll to
avoid compatibility shims.

@item 
bpo-25092@footnote{https://bugs.python.org/issue25092}: Fix datetime.strftime() failure when errno was already set to
EINVAL.

@item 
bpo-23517@footnote{https://bugs.python.org/issue23517}: Fix rounding in fromtimestamp() and utcfromtimestamp() methods
of datetime.datetime: microseconds are now rounded to nearest with ties
going to nearest even integer (ROUND_HALF_EVEN), instead of being rounding
towards minus infinity (ROUND_FLOOR). It's important that these methods
use the same rounding mode than datetime.timedelta to keep the property:
(datetime(1970,1,1) + timedelta(seconds=t)) ==
datetime.utcfromtimestamp(t). It also the rounding mode used by
round(float) for example.

@item 
bpo-25155@footnote{https://bugs.python.org/issue25155}: Fix datetime.datetime.now() and datetime.datetime.utcnow() on
Windows to support date after year 2038. It was a regression introduced in
Python 3.5.0.

@item 
bpo-25108@footnote{https://bugs.python.org/issue25108}: Omitted internal frames in traceback functions print_stack(),
format_stack(), and extract_stack() called without arguments.

@item 
bpo-25118@footnote{https://bugs.python.org/issue25118}: Fix a regression of Python 3.5.0 in os.waitpid() on Windows.

@item 
bpo-24684@footnote{https://bugs.python.org/issue24684}: socket.socket.getaddrinfo() now calls
PyUnicode_AsEncodedString() instead of calling the encode() method of the
host, to handle correctly custom string with an encode() method which
doesn't return a byte string. The encoder of the IDNA codec is now called
directly instead of calling the encode() method of the string.

@item 
bpo-25060@footnote{https://bugs.python.org/issue25060}: Correctly compute stack usage of the BUILD_MAP opcode.

@item 
bpo-24857@footnote{https://bugs.python.org/issue24857}: Comparing call_args to a long sequence now correctly returns a
boolean result instead of raising an exception.  Patch by A Kaptur.

@item 
bpo-23144@footnote{https://bugs.python.org/issue23144}: Make sure that HTMLParser.feed() returns all the data, even
when convert_charrefs is True.

@item 
bpo-24982@footnote{https://bugs.python.org/issue24982}: shutil.make_archive() with the "zip" format now adds entries
for directories (including empty directories) in ZIP file.

@item 
bpo-25019@footnote{https://bugs.python.org/issue25019}: Fixed a crash caused by setting non-string key of expat parser.
Based on patch by John Leitch.

@item 
bpo-16180@footnote{https://bugs.python.org/issue16180}: Exit pdb if file has syntax error, instead of trapping user in
an infinite loop.  Patch by Xavier de Gaye.

@item 
bpo-24891@footnote{https://bugs.python.org/issue24891}: Fix a race condition at Python startup if the file descriptor
of stdin (0), stdout (1) or stderr (2) is closed while Python is creating
sys.stdin, sys.stdout and sys.stderr objects. These attributes are now set
to None if the creation of the object failed, instead of raising an
OSError exception. Initial patch written by Marco Paolini.

@item 
bpo-24992@footnote{https://bugs.python.org/issue24992}: Fix error handling and a race condition (related to garbage
collection) in collections.OrderedDict constructor.

@item 
bpo-24881@footnote{https://bugs.python.org/issue24881}: Fixed setting binary mode in Python implementation of FileIO on
Windows and Cygwin.  Patch from Akira Li.

@item 
bpo-25578@footnote{https://bugs.python.org/issue25578}: Fix (another) memory leak in SSLSocket.getpeercer().

@item 
bpo-25530@footnote{https://bugs.python.org/issue25530}: Disable the vulnerable SSLv3 protocol by default when creating
ssl.SSLContext.

@item 
bpo-25569@footnote{https://bugs.python.org/issue25569}: Fix memory leak in SSLSocket.getpeercert().

@item 
bpo-25471@footnote{https://bugs.python.org/issue25471}: Sockets returned from accept() shouldn't appear to be
nonblocking.

@item 
bpo-25319@footnote{https://bugs.python.org/issue25319}: When threading.Event is reinitialized, the underlying condition
should use a regular lock rather than a recursive lock.

@item 
bpo-21112@footnote{https://bugs.python.org/issue21112}: Fix regression in unittest.expectedFailure on subclasses. Patch
from Berker Peksag.

@item 
bpo-24764@footnote{https://bugs.python.org/issue24764}: cgi.FieldStorage.read_multi() now ignores the Content-Length
header in part headers. Patch written by Peter Landry and reviewed by
Pierre Quentel.

@item 
bpo-24913@footnote{https://bugs.python.org/issue24913}: Fix overrun error in deque.index(). Found by John Leitch and
Bryce Darling.

@item 
bpo-24774@footnote{https://bugs.python.org/issue24774}: Fix docstring in http.server.test. Patch from Chiu-Hsiang Hsu.

@item 
bpo-21159@footnote{https://bugs.python.org/issue21159}: Improve message in
configparser.InterpolationMissingOptionError. Patch from Łukasz Langa.

@item 
bpo-20362@footnote{https://bugs.python.org/issue20362}: Honour TestCase.longMessage correctly in assertRegex. Patch
from Ilia Kurenkov.

@item 
bpo-23572@footnote{https://bugs.python.org/issue23572}: Fixed functools.singledispatch on classes with falsy
metaclasses.  Patch by Ethan Furman.

@item 
asyncio: ensure_future() now accepts awaitable objects.
@end itemize

@node IDLE<44>,文档<41>,库<67>,Python 3 5 1 rc1
@anchor{whatsnew/changelog id437}@anchor{1143}
@subsubsection IDLE



@itemize -

@item 
bpo-15348@footnote{https://bugs.python.org/issue15348}: Stop the debugger engine (normally in a user process) before
closing the debugger window (running in the IDLE process). This prevents
the RuntimeErrors that were being caught and ignored.

@item 
bpo-24455@footnote{https://bugs.python.org/issue24455}: Prevent IDLE from hanging when a) closing the shell while the
debugger is active (15347); b) closing the debugger with the [X] button
(15348); and c) activating the debugger when already active (24455). The
patch by Mark Roseman does this by making two changes. 1. Suspend and
resume the gui.interaction method with the tcl vwait mechanism intended
for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow
any existing interaction to terminate first.

@item 
Change 'The program' to 'Your program' in an IDLE 'kill program?' message
to make it clearer that the program referred to is the currently running
user program, not IDLE itself.

@item 
bpo-24750@footnote{https://bugs.python.org/issue24750}: Improve the appearance of the IDLE editor window status bar.
Patch by Mark Roseman.

@item 
bpo-25313@footnote{https://bugs.python.org/issue25313}: Change the handling of new built-in text color themes to better
address the compatibility problem introduced by the addition of IDLE Dark.
Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.

@item 
bpo-24782@footnote{https://bugs.python.org/issue24782}: Extension configuration is now a tab in the IDLE Preferences
dialog rather than a separate dialog.  The former tabs are now a sorted
list.  Patch by Mark Roseman.

@item 
bpo-22726@footnote{https://bugs.python.org/issue22726}: Re-activate the config dialog help button with some content
about the other buttons and the new IDLE Dark theme.

@item 
bpo-24820@footnote{https://bugs.python.org/issue24820}: IDLE now has an 'IDLE Dark' built-in text color theme. It is
more or less IDLE Classic inverted, with a cobalt blue background.
Strings, comments, keywords, ... are still green, red, orange, ... . To
use it with IDLEs released before November 2015, hit the 'Save as New
Custom Theme' button and enter a new name, such as 'Custom Dark'.  The
custom theme will work with any IDLE release, and can be modified.

@item 
bpo-25224@footnote{https://bugs.python.org/issue25224}: README.txt is now an idlelib index for IDLE developers and
curious users. The previous user content is now in the IDLE doc chapter.
'IDLE' now means 'Integrated Development and Learning Environment'.

@item 
bpo-24820@footnote{https://bugs.python.org/issue24820}: Users can now set breakpoint colors in Settings -> Custom
Highlighting. Original patch by Mark Roseman.

@item 
bpo-24972@footnote{https://bugs.python.org/issue24972}: Inactive selection background now matches active selection
background, as configured by users, on all systems.  Found items are now
always highlighted on Windows.  Initial patch by Mark Roseman.

@item 
bpo-24570@footnote{https://bugs.python.org/issue24570}: Idle: make calltip and completion boxes appear on Macs affected
by a tk regression.  Initial patch by Mark Roseman.

@item 
bpo-24988@footnote{https://bugs.python.org/issue24988}: Idle ScrolledList context menus (used in debugger) now work on
Mac Aqua. Patch by Mark Roseman.

@item 
bpo-24801@footnote{https://bugs.python.org/issue24801}: Make right-click for context menu work on Mac Aqua. Patch by
Mark Roseman.

@item 
bpo-25173@footnote{https://bugs.python.org/issue25173}: Associate tkinter messageboxes with a specific widget. For Mac
OSX, make them a 'sheet'.  Patch by Mark Roseman.

@item 
bpo-25198@footnote{https://bugs.python.org/issue25198}: Enhance the initial html viewer now used for Idle Help.
Properly indent fixed-pitch text (patch by Mark Roseman). Give code
snippet a very Sphinx-like light blueish-gray background. Re-use initial
width and height set by users for shell and editor. When the Table of
Contents (TOC) menu is used, put the section header at the top of the
screen.

@item 
bpo-25225@footnote{https://bugs.python.org/issue25225}: Condense and rewrite Idle doc section on text colors.

@item 
bpo-21995@footnote{https://bugs.python.org/issue21995}: Explain some differences between IDLE and console Python.

@item 
bpo-22820@footnote{https://bugs.python.org/issue22820}: Explain need for @emph{print} when running file from Idle editor.

@item 
bpo-25224@footnote{https://bugs.python.org/issue25224}: Doc: augment Idle feature list and no-subprocess section.

@item 
bpo-25219@footnote{https://bugs.python.org/issue25219}: Update doc for Idle command line options. Some were missing and
notes were not correct.

@item 
bpo-24861@footnote{https://bugs.python.org/issue24861}: Most of idlelib is private and subject to change. Use
idleib.idle.* to start Idle. See idlelib.__init__.__doc__.

@item 
bpo-25199@footnote{https://bugs.python.org/issue25199}: Idle: add synchronization comments for future maintainers.

@item 
bpo-16893@footnote{https://bugs.python.org/issue16893}: Replace help.txt with help.html for Idle doc display. The new
idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks
better than help.txt and will better document Idle as released. The
tkinter html viewer that works for this file was written by Mark Roseman.
The now unused EditorWindow.HelpDialog class and helt.txt file are
deprecated.

@item 
bpo-24199@footnote{https://bugs.python.org/issue24199}: Deprecate unused idlelib.idlever with possible removal in 3.6.

@item 
bpo-24790@footnote{https://bugs.python.org/issue24790}: Remove extraneous code (which also create 2 & 3 conflicts).
@end itemize

@node 文档<41>,测试<43>,IDLE<44>,Python 3 5 1 rc1
@anchor{whatsnew/changelog id438}@anchor{1144}
@subsubsection 文档



@itemize -

@item 
bpo-22558@footnote{https://bugs.python.org/issue22558}: Add remaining doc links to source code for Python-coded
modules. Patch by Yoni Lavi.

@item 
bpo-12067@footnote{https://bugs.python.org/issue12067}: Rewrite Comparisons section in the Expressions chapter of the
language reference. Some of the details of comparing mixed types were
incorrect or ambiguous. NotImplemented is only relevant at a lower level
than the Expressions chapter. Added details of comparing range() objects,
and default behaviour and consistency suggestions for user-defined
classes. Patch from Andy Maier.

@item 
bpo-24952@footnote{https://bugs.python.org/issue24952}: Clarify the default size argument of stack_size() in the
"threading" and "_thread" modules. Patch from Mattip.

@item 
bpo-23725@footnote{https://bugs.python.org/issue23725}: Overhaul tempfile docs. Note deprecated status of mktemp. Patch
from Zbigniew Jędrzejewski-Szmek.

@item 
bpo-24808@footnote{https://bugs.python.org/issue24808}: Update the types of some PyTypeObject fields.  Patch by Joseph
Weston.

@item 
bpo-22812@footnote{https://bugs.python.org/issue22812}: Fix unittest discovery examples. Patch from Pam McA'Nulty.
@end itemize

@node 测试<43>,构建<44>,文档<41>,Python 3 5 1 rc1
@anchor{whatsnew/changelog id439}@anchor{1145}
@subsubsection 测试



@itemize -

@item 
bpo-25449@footnote{https://bugs.python.org/issue25449}: Added tests for OrderedDict subclasses.

@item 
bpo-25099@footnote{https://bugs.python.org/issue25099}: Make test_compileall not fail when an entry on sys.path cannot
be written to (commonly seen in administrative installs on Windows).

@item 
bpo-23919@footnote{https://bugs.python.org/issue23919}: Prevents assert dialogs appearing in the test suite.

@item 
@code{PCbuild\rt.bat} now accepts an unlimited number of arguments to pass
along to regrtest.py.  Previously there was a limit of 9.
@end itemize

@node 构建<44>,Windows<44>,测试<43>,Python 3 5 1 rc1
@anchor{whatsnew/changelog id440}@anchor{1146}
@subsubsection 构建



@itemize -

@item 
bpo-24915@footnote{https://bugs.python.org/issue24915}: Add LLVM support for PGO builds and use the test suite to
generate the profile data. Initial patch by Alecsandru Patrascu of Intel.

@item 
bpo-24910@footnote{https://bugs.python.org/issue24910}: Windows MSIs now have unique display names.

@item 
bpo-24986@footnote{https://bugs.python.org/issue24986}: It is now possible to build Python on Windows without errors
when external libraries are not available.
@end itemize

@node Windows<44>,工具/示例<30>,构建<44>,Python 3 5 1 rc1
@anchor{whatsnew/changelog id441}@anchor{1147}
@subsubsection Windows



@itemize -

@item 
bpo-25450@footnote{https://bugs.python.org/issue25450}: Updates shortcuts to start Python in installation directory.

@item 
bpo-25164@footnote{https://bugs.python.org/issue25164}: Changes default all-users install directory to match per-user
directory.

@item 
bpo-25143@footnote{https://bugs.python.org/issue25143}: Improves installer error messages for unsupported platforms.

@item 
bpo-25163@footnote{https://bugs.python.org/issue25163}: Display correct directory in installer when using non-default
settings.

@item 
bpo-25361@footnote{https://bugs.python.org/issue25361}: Disables use of SSE2 instructions in Windows 32-bit build

@item 
bpo-25089@footnote{https://bugs.python.org/issue25089}: Adds logging to installer for case where launcher is not
selected on upgrade.

@item 
bpo-25165@footnote{https://bugs.python.org/issue25165}: Windows uninstallation should not remove launcher if other
versions remain

@item 
bpo-25112@footnote{https://bugs.python.org/issue25112}: py.exe launcher is missing icons

@item 
bpo-25102@footnote{https://bugs.python.org/issue25102}: Windows installer does not precompile for -O or -OO.

@item 
bpo-25081@footnote{https://bugs.python.org/issue25081}: Makes Back button in installer go back to upgrade page when
upgrading.

@item 
bpo-25091@footnote{https://bugs.python.org/issue25091}: Increases font size of the installer.

@item 
bpo-25126@footnote{https://bugs.python.org/issue25126}: Clarifies that the non-web installer will download some
components.

@item 
bpo-25213@footnote{https://bugs.python.org/issue25213}: Restores requestedExecutionLevel to manifest to disable UAC
virtualization.

@item 
bpo-25022@footnote{https://bugs.python.org/issue25022}: Removed very outdated PC/example_nt/ directory.
@end itemize

@node 工具/示例<30>,,Windows<44>,Python 3 5 1 rc1
@anchor{whatsnew/changelog id442}@anchor{1148}
@subsubsection 工具/示例



@itemize -

@item 
bpo-25440@footnote{https://bugs.python.org/issue25440}: Fix output of python-config --extension-suffix.
@end itemize

@node Python 3 5 0 正式版,Python 3 5 0 rc4,Python 3 5 1 rc1,更新日志
@anchor{whatsnew/changelog python-3-5-0-final}@anchor{1149}
@subsection Python 3.5.0 正式版


@emph{发布日期: 2015-09-13}

@menu
* 构建: 构建<45>. 

@end menu

@node 构建<45>,,,Python 3 5 0 正式版
@anchor{whatsnew/changelog id443}@anchor{114a}
@subsubsection 构建



@itemize -

@item 
bpo-25071@footnote{https://bugs.python.org/issue25071}: Windows installer should not require TargetDir parameter when
installing quietly.
@end itemize

@node Python 3 5 0 rc4,Python 3 5 0 rc3,Python 3 5 0 正式版,更新日志
@anchor{whatsnew/changelog python-3-5-0-release-candidate-4}@anchor{114b}
@subsection Python 3.5.0 rc4


@emph{发布日期: 2015-09-09}

@menu
* 库: 库<68>. 
* 构建: 构建<46>. 

@end menu

@node 库<68>,构建<46>,,Python 3 5 0 rc4
@anchor{whatsnew/changelog id444}@anchor{114c}
@subsubsection 库



@itemize -

@item 
bpo-25029@footnote{https://bugs.python.org/issue25029}: Fixes MemoryError in test_strptime.
@end itemize

@node 构建<46>,,库<68>,Python 3 5 0 rc4
@anchor{whatsnew/changelog id445}@anchor{114d}
@subsubsection 构建



@itemize -

@item 
bpo-25027@footnote{https://bugs.python.org/issue25027}: Reverts partial-static build options and adds vcruntime140.dll
to Windows installation.
@end itemize

@node Python 3 5 0 rc3,Python 3 5 0 rc2,Python 3 5 0 rc4,更新日志
@anchor{whatsnew/changelog python-3-5-0-release-candidate-3}@anchor{114e}
@subsection Python 3.5.0 rc3


@emph{发布日期: 2015-09-07}

@menu
* 核心与内置: 核心与内置<55>. 
* 库: 库<69>. 

@end menu

@node 核心与内置<55>,库<69>,,Python 3 5 0 rc3
@anchor{whatsnew/changelog id446}@anchor{114f}
@subsubsection 核心与内置



@itemize -

@item 
bpo-24305@footnote{https://bugs.python.org/issue24305}: Prevent import subsystem stack frames from being counted by the
warnings.warn(stacklevel=) parameter.

@item 
bpo-24912@footnote{https://bugs.python.org/issue24912}: Prevent __class__ assignment to immutable built-in objects.

@item 
bpo-24975@footnote{https://bugs.python.org/issue24975}: Fix AST compilation for 
@geindex Python 提高建议; PEP 448
PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} syntax.
@end itemize

@node 库<69>,,核心与内置<55>,Python 3 5 0 rc3
@anchor{whatsnew/changelog id447}@anchor{1150}
@subsubsection 库



@itemize -

@item 
bpo-24917@footnote{https://bugs.python.org/issue24917}: time_strftime() buffer over-read.

@item 
bpo-24748@footnote{https://bugs.python.org/issue24748}: To resolve a compatibility problem found with py2exe and
pywin32, imp.load_dynamic() once again ignores previously loaded modules
to support Python modules replacing themselves with extension modules.
Patch by Petr Viktorin.

@item 
bpo-24635@footnote{https://bugs.python.org/issue24635}: Fixed a bug in typing.py where isinstance([], typing.Iterable)
would return True once, then False on subsequent calls.

@item 
bpo-24989@footnote{https://bugs.python.org/issue24989}: Fixed buffer overread in BytesIO.readline() if a position is
set beyond size.  Based on patch by John Leitch.

@item 
bpo-24913@footnote{https://bugs.python.org/issue24913}: Fix overrun error in deque.index(). Found by John Leitch and
Bryce Darling.
@end itemize

@node Python 3 5 0 rc2,Python 3 5 0 rc1,Python 3 5 0 rc3,更新日志
@anchor{whatsnew/changelog python-3-5-0-release-candidate-2}@anchor{1151}
@subsection Python 3.5.0 rc2


@emph{发布日期: 2015-08-25}

@menu
* 核心与内置: 核心与内置<56>. 
* 库: 库<70>. 

@end menu

@node 核心与内置<56>,库<70>,,Python 3 5 0 rc2
@anchor{whatsnew/changelog id448}@anchor{1152}
@subsubsection 核心与内置



@itemize -

@item 
bpo-24769@footnote{https://bugs.python.org/issue24769}: Interpreter now starts properly when dynamic loading is
disabled.  Patch by Petr Viktorin.

@item 
bpo-21167@footnote{https://bugs.python.org/issue21167}: NAN operations are now handled correctly when python is
compiled with ICC even if -fp-model strict is not specified.

@item 
bpo-24492@footnote{https://bugs.python.org/issue24492}: A "package" lacking a __name__ attribute when trying to perform
a @code{from .. import ...} statement will trigger an ImportError instead of
an AttributeError.
@end itemize

@node 库<70>,,核心与内置<56>,Python 3 5 0 rc2
@anchor{whatsnew/changelog id449}@anchor{1153}
@subsubsection 库



@itemize -

@item 
bpo-24847@footnote{https://bugs.python.org/issue24847}: Removes vcruntime140.dll dependency from Tcl/Tk.

@item 
bpo-24839@footnote{https://bugs.python.org/issue24839}: platform._syscmd_ver raises DeprecationWarning

@item 
bpo-24867@footnote{https://bugs.python.org/issue24867}: Fix Task.get_stack() for 'async def' coroutines
@end itemize

@node Python 3 5 0 rc1,Python 3 5 0 beta 4,Python 3 5 0 rc2,更新日志
@anchor{whatsnew/changelog python-3-5-0-release-candidate-1}@anchor{1154}
@subsection Python 3.5.0 rc1


@emph{发布日期: 2015-08-09}

@menu
* 核心与内置: 核心与内置<57>. 
* 库: 库<71>. 
* IDLE: IDLE<45>. 
* 文档: 文档<42>. 
* 测试: 测试<44>. 

@end menu

@node 核心与内置<57>,库<71>,,Python 3 5 0 rc1
@anchor{whatsnew/changelog id450}@anchor{1155}
@subsubsection 核心与内置



@itemize -

@item 
bpo-24667@footnote{https://bugs.python.org/issue24667}: Resize odict in all cases that the underlying dict resizes.
@end itemize

@node 库<71>,IDLE<45>,核心与内置<57>,Python 3 5 0 rc1
@anchor{whatsnew/changelog id451}@anchor{1156}
@subsubsection 库



@itemize -

@item 
bpo-24824@footnote{https://bugs.python.org/issue24824}: Signatures of codecs.encode() and codecs.decode() now are
compatible with pydoc.

@item 
bpo-24634@footnote{https://bugs.python.org/issue24634}: Importing uuid should not try to load libc on Windows

@item 
bpo-24798@footnote{https://bugs.python.org/issue24798}: _msvccompiler.py doesn't properly support manifests

@item 
bpo-4395@footnote{https://bugs.python.org/issue4395}: Better testing and documentation of binary operators. Patch by
Martin Panter.

@item 
bpo-23973@footnote{https://bugs.python.org/issue23973}: Update typing.py from GitHub repo.

@item 
bpo-23004@footnote{https://bugs.python.org/issue23004}: mock_open() now reads binary data correctly when the type of
read_data is bytes.  Initial patch by Aaron Hill.

@item 
bpo-23888@footnote{https://bugs.python.org/issue23888}: Handle fractional time in cookie expiry. Patch by ssh.

@item 
bpo-23652@footnote{https://bugs.python.org/issue23652}: Make it possible to compile the select module against the libc
headers from the Linux Standard Base, which do not include some EPOLL
macros.  Patch by Matt Frank.

@item 
bpo-22932@footnote{https://bugs.python.org/issue22932}: Fix timezones in email.utils.formatdate. Patch from Dmitry
Shachnev.

@item 
bpo-23779@footnote{https://bugs.python.org/issue23779}: imaplib raises TypeError if authenticator tries to abort. Patch
from Craig Holmquist.

@item 
bpo-23319@footnote{https://bugs.python.org/issue23319}: Fix ctypes.BigEndianStructure, swap correctly bytes. Patch
written by Matthieu Gautier.

@item 
bpo-23254@footnote{https://bugs.python.org/issue23254}: Document how to close the TCPServer listening socket. Patch
from Martin Panter.

@item 
bpo-19450@footnote{https://bugs.python.org/issue19450}: 更新Windows和OS X安装程序以使用SQLite 3.8.11

@item 
bpo-17527@footnote{https://bugs.python.org/issue17527}: Add PATCH to wsgiref.validator. Patch from Luca Sbardella.

@item 
bpo-24791@footnote{https://bugs.python.org/issue24791}: Fix grammar regression for call syntax: 'g(*a or b)'.
@end itemize

@node IDLE<45>,文档<42>,库<71>,Python 3 5 0 rc1
@anchor{whatsnew/changelog id452}@anchor{1157}
@subsubsection IDLE



@itemize -

@item 
bpo-23672@footnote{https://bugs.python.org/issue23672}: Allow Idle to edit and run files with astral chars in name.
Patch by Mohd Sanad Zaki Rizvi.

@item 
bpo-24745@footnote{https://bugs.python.org/issue24745}: Idle editor default font. Switch from Courier to
platform-sensitive TkFixedFont.  This should not affect current customized
font selections.  If there is a problem, edit
$HOME/.idlerc/config-main.cfg and remove 'fontxxx' entries from [Editor
Window].  Patch by Mark Roseman.

@item 
bpo-21192@footnote{https://bugs.python.org/issue21192}: Idle editor. When a file is run, put its name in the restart
bar. Do not print false prompts. Original patch by Adnan Umer.

@item 
bpo-13884@footnote{https://bugs.python.org/issue13884}: Idle menus. Remove tearoff lines. Patch by Roger Serwy.
@end itemize

@node 文档<42>,测试<44>,IDLE<45>,Python 3 5 0 rc1
@anchor{whatsnew/changelog id453}@anchor{1158}
@subsubsection 文档



@itemize -

@item 
bpo-24129@footnote{https://bugs.python.org/issue24129}: Clarify the reference documentation for name resolution. This
includes removing the assumption that readers will be familiar with the
name resolution scheme Python used prior to the introduction of lexical
scoping for function namespaces. Patch by Ivan Levkivskyi.

@item 
bpo-20769@footnote{https://bugs.python.org/issue20769}: Improve reload() docs. Patch by Dorian Pula.

@item 
bpo-23589@footnote{https://bugs.python.org/issue23589}: Remove duplicate sentence from the FAQ.  Patch by Yongzhi Pan.

@item 
bpo-24729@footnote{https://bugs.python.org/issue24729}: Correct IO tutorial to match implementation regarding encoding
parameter to open function.
@end itemize

@node 测试<44>,,文档<42>,Python 3 5 0 rc1
@anchor{whatsnew/changelog id454}@anchor{1159}
@subsubsection 测试



@itemize -

@item 
bpo-24751@footnote{https://bugs.python.org/issue24751}: When running regrtest with the @code{-w} command line option, a
test run is no longer marked as a failure if all tests succeed when
re-run.
@end itemize

@node Python 3 5 0 beta 4,Python 3 5 0 beta 3,Python 3 5 0 rc1,更新日志
@anchor{whatsnew/changelog python-3-5-0-beta-4}@anchor{115a}
@subsection Python 3.5.0 beta 4


@emph{发布日期: 2015-07-26}

@menu
* 核心与内置: 核心与内置<58>. 
* 库: 库<72>. 
* 构建: 构建<47>. 

@end menu

@node 核心与内置<58>,库<72>,,Python 3 5 0 beta 4
@anchor{whatsnew/changelog id455}@anchor{115b}
@subsubsection 核心与内置



@itemize -

@item 
bpo-23573@footnote{https://bugs.python.org/issue23573}: Restored optimization of bytes.rfind() and bytearray.rfind()
for single-byte argument on Linux.

@item 
bpo-24569@footnote{https://bugs.python.org/issue24569}: Make 
@geindex Python 提高建议; PEP 448
PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} dictionary evaluation more consistent.

@item 
bpo-24583@footnote{https://bugs.python.org/issue24583}: Fix crash when set is mutated while being updated.

@item 
bpo-24407@footnote{https://bugs.python.org/issue24407}: Fix crash when dict is mutated while being updated.

@item 
bpo-24619@footnote{https://bugs.python.org/issue24619}: New approach for tokenizing async/await. As a consequence, it
is now possible to have one-line 'async def foo(): await ..' functions.

@item 
bpo-24687@footnote{https://bugs.python.org/issue24687}: Plug refleak on SyntaxError in function parameters annotations.

@item 
bpo-15944@footnote{https://bugs.python.org/issue15944}: memoryview: Allow arbitrary formats when casting to bytes.
Patch by Martin Panter.
@end itemize

@node 库<72>,构建<47>,核心与内置<58>,Python 3 5 0 beta 4
@anchor{whatsnew/changelog id456}@anchor{115c}
@subsubsection 库



@itemize -

@item 
bpo-23441@footnote{https://bugs.python.org/issue23441}: rcompleter now prints a tab character instead of displaying
possible completions for an empty word.  Initial patch by Martin Sekera.

@item 
bpo-24683@footnote{https://bugs.python.org/issue24683}: Fixed crashes in _json functions called with arguments of
inappropriate type.

@item 
bpo-21697@footnote{https://bugs.python.org/issue21697}: shutil.copytree() now correctly handles symbolic links that
point to directories.  Patch by Eduardo Seabra and Thomas Kluyver.

@item 
bpo-14373@footnote{https://bugs.python.org/issue14373}: Fixed segmentation fault when gc.collect() is called during
constructing lru_cache (C implementation).

@item 
bpo-24695@footnote{https://bugs.python.org/issue24695}: Fix a regression in traceback.print_exception().  If
exc_traceback is None we shouldn't print a traceback header like described
in the documentation.

@item 
bpo-24620@footnote{https://bugs.python.org/issue24620}: Random.setstate() now validates the value of state last
element.

@item 
bpo-22485@footnote{https://bugs.python.org/issue22485}: Fixed an issue that caused @ref{115d,,inspect.getsource} to return
incorrect results on nested functions.

@item 
bpo-22153@footnote{https://bugs.python.org/issue22153}: Improve unittest docs. Patch from Martin Panter and evilzero.

@item 
bpo-24580@footnote{https://bugs.python.org/issue24580}: Symbolic group references to open group in re patterns now are
explicitly forbidden as well as numeric group references.

@item 
bpo-24206@footnote{https://bugs.python.org/issue24206}: Fixed __eq__ and __ne__ methods of inspect classes.

@item 
bpo-24631@footnote{https://bugs.python.org/issue24631}: Fixed regression in the timeit module with multiline setup.

@item 
bpo-18622@footnote{https://bugs.python.org/issue18622}: unittest.mock.mock_open().reset_mock would recurse infinitely.
Patch from Nicola Palumbo and Laurent De Buyst.

@item 
bpo-23661@footnote{https://bugs.python.org/issue23661}: unittest.mock side_effects can now be exceptions again. This
was a regression vs Python 3.4. Patch from Ignacio Rossi

@item 
bpo-24608@footnote{https://bugs.python.org/issue24608}: chunk.Chunk.read() now always returns bytes, not str.

@item 
bpo-18684@footnote{https://bugs.python.org/issue18684}: Fixed reading out of the buffer in the re module.

@item 
bpo-24259@footnote{https://bugs.python.org/issue24259}: tarfile now raises a ReadError if an archive is truncated
inside a data segment.

@item 
bpo-15014@footnote{https://bugs.python.org/issue15014}: SMTP.auth() and SMTP.login() now support RFC 4954's optional
initial-response argument to the SMTP AUTH command.

@item 
bpo-24669@footnote{https://bugs.python.org/issue24669}: Fix inspect.getsource() for 'async def' functions. Patch by Kai
Groner.

@item 
bpo-24688@footnote{https://bugs.python.org/issue24688}: ast.get_docstring() for 'async def' functions.
@end itemize

@node 构建<47>,,库<72>,Python 3 5 0 beta 4
@anchor{whatsnew/changelog id457}@anchor{115e}
@subsubsection 构建



@itemize -

@item 
bpo-24603@footnote{https://bugs.python.org/issue24603}: 更新Windows 构建和OS X 10.5 安装程序以使用OpenSSL 1.0.2d.
@end itemize

@node Python 3 5 0 beta 3,Python 3 5 0 beta 2,Python 3 5 0 beta 4,更新日志
@anchor{whatsnew/changelog python-3-5-0-beta-3}@anchor{115f}
@subsection Python 3.5.0 beta 3


@emph{发布日期: 2015-07-05}

@menu
* 核心与内置: 核心与内置<59>. 
* 库: 库<73>. 
* 测试: 测试<45>. 
* 文档: 文档<43>. 
* 构建: 构建<48>. 

@end menu

@node 核心与内置<59>,库<73>,,Python 3 5 0 beta 3
@anchor{whatsnew/changelog id458}@anchor{1160}
@subsubsection 核心与内置



@itemize -

@item 
bpo-24467@footnote{https://bugs.python.org/issue24467}: Fixed possible buffer over-read in bytearray. The bytearray
object now always allocates place for trailing null byte and it's buffer
now is always null-terminated.

@item 
Upgrade to Unicode 8.0.0.

@item 
bpo-24345@footnote{https://bugs.python.org/issue24345}: Add Py_tp_finalize slot for the stable ABI.

@item 
bpo-24400@footnote{https://bugs.python.org/issue24400}: Introduce a distinct type for 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} coroutines; add
types.CoroutineType, inspect.getcoroutinestate,
inspect.getcoroutinelocals; coroutines no longer use CO_GENERATOR flag;
sys.set_coroutine_wrapper works only for 'async def' coroutines;
inspect.iscoroutine no longer uses collections.abc.Coroutine, it's
intended to test for pure 'async def' coroutines only; add new opcode:
GET_YIELD_FROM_ITER; fix generators wrapper used in types.coroutine to be
instance of collections.abc.Generator; collections.abc.Awaitable and
collections.abc.Coroutine can no longer be used to detect generator-based
coroutines--use inspect.isawaitable instead.

@item 
bpo-24450@footnote{https://bugs.python.org/issue24450}: Add gi_yieldfrom to generators and cr_await to coroutines.
Contributed by Benno Leslie and Yury Selivanov.

@item 
bpo-19235@footnote{https://bugs.python.org/issue19235}: Add new RecursionError exception. Patch by Georg Brandl.
@end itemize

@node 库<73>,测试<45>,核心与内置<59>,Python 3 5 0 beta 3
@anchor{whatsnew/changelog id459}@anchor{1161}
@subsubsection 库



@itemize -

@item 
bpo-21750@footnote{https://bugs.python.org/issue21750}: mock_open.read_data can now be read from each instance, as it
could in Python 3.3.

@item 
bpo-24552@footnote{https://bugs.python.org/issue24552}: Fix use after free in an error case of the _pickle module.

@item 
bpo-24514@footnote{https://bugs.python.org/issue24514}: tarfile now tolerates number fields consisting of only
whitespace.

@item 
bpo-19176@footnote{https://bugs.python.org/issue19176}: Fixed doctype() related bugs in C implementation of
ElementTree. A deprecation warning no longer issued by XMLParser subclass
with default doctype() method.  Direct call of doctype() now issues a
warning.  Parser's doctype() now is not called if target's doctype() is
called.  Based on patch by Martin Panter.

@item 
bpo-20387@footnote{https://bugs.python.org/issue20387}: Restore semantic round-trip correctness in tokenize/untokenize
for tab-indented blocks.

@item 
bpo-24456@footnote{https://bugs.python.org/issue24456}: Fixed possible buffer over-read in adpcm2lin() and lin2adpcm()
functions of the audioop module.

@item 
bpo-24336@footnote{https://bugs.python.org/issue24336}: The contextmanager decorator now works with functions with
keyword arguments called "func" and "self".  Patch by Martin Panter.

@item 
bpo-24522@footnote{https://bugs.python.org/issue24522}: Fix possible integer overflow in json accelerator module.

@item 
bpo-24489@footnote{https://bugs.python.org/issue24489}: ensure a previously set C errno doesn't disturb cmath.polar().

@item 
bpo-24408@footnote{https://bugs.python.org/issue24408}: Fixed AttributeError in measure() and metrics() methods of
tkinter.Font.

@item 
bpo-14373@footnote{https://bugs.python.org/issue14373}: C implementation of functools.lru_cache() now can be used with
methods.

@item 
bpo-24347@footnote{https://bugs.python.org/issue24347}: Set KeyError if PyDict_GetItemWithError returns NULL.

@item 
bpo-24348@footnote{https://bugs.python.org/issue24348}: Drop superfluous incref/decref.

@item 
bpo-24359@footnote{https://bugs.python.org/issue24359}: Check for changed OrderedDict size during iteration.

@item 
bpo-24368@footnote{https://bugs.python.org/issue24368}: Support keyword arguments in OrderedDict methods.

@item 
bpo-24362@footnote{https://bugs.python.org/issue24362}: Simplify the C OrderedDict fast nodes resize logic.

@item 
bpo-24377@footnote{https://bugs.python.org/issue24377}: Fix a ref leak in OrderedDict.__repr__.

@item 
bpo-24369@footnote{https://bugs.python.org/issue24369}: Defend against key-changes during iteration.
@end itemize

@node 测试<45>,文档<43>,库<73>,Python 3 5 0 beta 3
@anchor{whatsnew/changelog id460}@anchor{1162}
@subsubsection 测试



@itemize -

@item 
bpo-24373@footnote{https://bugs.python.org/issue24373}: _testmultiphase and xxlimited now use tp_traverse and
tp_finalize to avoid reference leaks encountered when combining tp_dealloc
with PyType_FromSpec (see bpo-16690@footnote{https://bugs.python.org/issue16690} for details)
@end itemize

@node 文档<43>,构建<48>,测试<45>,Python 3 5 0 beta 3
@anchor{whatsnew/changelog id461}@anchor{1163}
@subsubsection 文档



@itemize -

@item 
bpo-24458@footnote{https://bugs.python.org/issue24458}: Update documentation to cover multi-phase initialization for
extension modules (PEP 489). Patch by Petr Viktorin.

@item 
bpo-24351@footnote{https://bugs.python.org/issue24351}: Clarify what is meant by "identifier" in the context of
string.Template instances.
@end itemize

@node 构建<48>,,文档<43>,Python 3 5 0 beta 3
@anchor{whatsnew/changelog id462}@anchor{1164}
@subsubsection 构建



@itemize -

@item 
bpo-24432@footnote{https://bugs.python.org/issue24432}: 更新Windows 构建和OS X 10.5 安装程序以使用OpenSSL 1.0.2c.
@end itemize

@node Python 3 5 0 beta 2,Python 3 5 0 beta 1,Python 3 5 0 beta 3,更新日志
@anchor{whatsnew/changelog python-3-5-0-beta-2}@anchor{1165}
@subsection Python 3.5.0 beta 2


@emph{发布日期: 2015-05-31}

@menu
* 核心与内置: 核心与内置<60>. 
* 库: 库<74>. 

@end menu

@node 核心与内置<60>,库<74>,,Python 3 5 0 beta 2
@anchor{whatsnew/changelog id463}@anchor{1166}
@subsubsection 核心与内置



@itemize -

@item 
bpo-24284@footnote{https://bugs.python.org/issue24284}: The startswith and endswith methods of the str class no longer
return True when finding the empty string and the indexes are completely
out of range.

@item 
bpo-24115@footnote{https://bugs.python.org/issue24115}: Update uses of PyObject_IsTrue(), PyObject_Not(),
PyObject_IsInstance(), PyObject_RichCompareBool() and _PyDict_Contains()
to check for and handle errors correctly.

@item 
bpo-24328@footnote{https://bugs.python.org/issue24328}: Fix importing one character extension modules.

@item 
bpo-11205@footnote{https://bugs.python.org/issue11205}: In dictionary displays, evaluate the key before the value.

@item 
bpo-24285@footnote{https://bugs.python.org/issue24285}: Fixed regression that prevented importing extension modules
from inside packages. Patch by Petr Viktorin.
@end itemize

@node 库<74>,,核心与内置<60>,Python 3 5 0 beta 2
@anchor{whatsnew/changelog id464}@anchor{1167}
@subsubsection 库



@itemize -

@item 
bpo-23247@footnote{https://bugs.python.org/issue23247}: Fix a crash in the StreamWriter.reset() of CJK codecs.

@item 
bpo-24270@footnote{https://bugs.python.org/issue24270}: Add math.isclose() and cmath.isclose() functions as per
@geindex Python 提高建议; PEP 485
PEP 485@footnote{https://www.python.org/dev/peps/pep-0485}. Contributed by Chris Barker and Tal Einat.

@item 
bpo-5633@footnote{https://bugs.python.org/issue5633}: Fixed timeit when the statement is a string and the setup is
not.

@item 
bpo-24326@footnote{https://bugs.python.org/issue24326}: Fixed audioop.ratecv() with non-default weightB argument.
Original patch by David Moore.

@item 
bpo-16991@footnote{https://bugs.python.org/issue16991}: Add a C implementation of OrderedDict.

@item 
bpo-23934@footnote{https://bugs.python.org/issue23934}: Fix inspect.signature to fail correctly for builtin types
lacking signature information.  Initial patch by James Powell.
@end itemize

@node Python 3 5 0 beta 1,Python 3 5 0 alpha 4,Python 3 5 0 beta 2,更新日志
@anchor{whatsnew/changelog python-3-5-0-beta-1}@anchor{1168}
@subsection Python 3.5.0 beta 1


@emph{发布日期: 2015-05-24}

@menu
* 核心与内置: 核心与内置<61>. 
* 库: 库<75>. 
* IDLE: IDLE<46>. 
* 测试: 测试<46>. 
* 文档: 文档<44>. 
* 工具/示例: 工具/示例<31>. 

@end menu

@node 核心与内置<61>,库<75>,,Python 3 5 0 beta 1
@anchor{whatsnew/changelog id465}@anchor{1169}
@subsubsection 核心与内置



@itemize -

@item 
bpo-24276@footnote{https://bugs.python.org/issue24276}: Fixed optimization of property descriptor getter.

@item 
bpo-24268@footnote{https://bugs.python.org/issue24268}: PEP 489: Multi-phase extension module initialization. Patch by
Petr Viktorin.

@item 
bpo-23955@footnote{https://bugs.python.org/issue23955}: Add pyvenv.cfg option to suppress registry/environment lookup
for generating sys.path on Windows.

@item 
bpo-24257@footnote{https://bugs.python.org/issue24257}: Fixed system error in the comparison of faked
types.SimpleNamespace.

@item 
bpo-22939@footnote{https://bugs.python.org/issue22939}: Fixed integer overflow in iterator object.  Patch by Clement
Rouault.

@item 
bpo-23985@footnote{https://bugs.python.org/issue23985}: Fix a possible buffer overrun when deleting a slice from the
front of a bytearray and then appending some other bytes data.

@item 
bpo-24102@footnote{https://bugs.python.org/issue24102}: Fixed exception type checking in standard error handlers.

@item 
bpo-15027@footnote{https://bugs.python.org/issue15027}: The UTF-32 encoder is now 3x to 7x faster.

@item 
bpo-23290@footnote{https://bugs.python.org/issue23290}: Optimize set_merge() for cases where the target is empty.
(Contributed by Serhiy Storchaka.)

@item 
bpo-2292@footnote{https://bugs.python.org/issue2292}: PEP 448: Additional Unpacking Generalizations.

@item 
bpo-24096@footnote{https://bugs.python.org/issue24096}: Make warnings.warn_explicit more robust against mutation of the
warnings.filters list.

@item 
bpo-23996@footnote{https://bugs.python.org/issue23996}: Avoid a crash when a delegated generator raises an unnormalized
StopIteration exception.  Patch by Stefan Behnel.

@item 
bpo-23910@footnote{https://bugs.python.org/issue23910}: Optimize property() getter calls.  Patch by Joe Jevnik.

@item 
bpo-23911@footnote{https://bugs.python.org/issue23911}: Move path-based importlib bootstrap code to a separate frozen
module.

@item 
bpo-24192@footnote{https://bugs.python.org/issue24192}: Fix namespace package imports.

@item 
bpo-24022@footnote{https://bugs.python.org/issue24022}: Fix tokenizer crash when processing undecodable source code.

@item 
bpo-9951@footnote{https://bugs.python.org/issue9951}: Added a hex() method to bytes, bytearray, and memoryview.

@item 
bpo-22906@footnote{https://bugs.python.org/issue22906}: PEP 479: Change StopIteration handling inside generators.

@item 
bpo-24017@footnote{https://bugs.python.org/issue24017}: PEP 492: Coroutines with async and await syntax.
@end itemize

@node 库<75>,IDLE<46>,核心与内置<61>,Python 3 5 0 beta 1
@anchor{whatsnew/changelog id466}@anchor{116a}
@subsubsection 库



@itemize -

@item 
bpo-14373@footnote{https://bugs.python.org/issue14373}: Added C implementation of functools.lru_cache().  Based on
patches by Matt Joiner and Alexey Kachayev.

@item 
bpo-24230@footnote{https://bugs.python.org/issue24230}: The tempfile module now accepts bytes for prefix, suffix and
dir parameters and returns bytes in such situations (matching the os
module APIs).

@item 
bpo-22189@footnote{https://bugs.python.org/issue22189}: collections.UserString now supports __getnewargs__(),
__rmod__(), casefold(), format_map(), isprintable(), and maketrans().
Patch by Joe Jevnik.

@item 
bpo-24244@footnote{https://bugs.python.org/issue24244}: Prevents termination when an invalid format string is
encountered on Windows in strftime.

@item 
bpo-23973@footnote{https://bugs.python.org/issue23973}: PEP 484: Add the typing module.

@item 
bpo-23086@footnote{https://bugs.python.org/issue23086}: The collections.abc.Sequence() abstract base class added
@emph{start} and @emph{stop} parameters to the index() mixin. Patch by Devin
Jeanpierre.

@item 
bpo-20035@footnote{https://bugs.python.org/issue20035}: Replaced the @code{tkinter._fix} module used for setting up the
Tcl/Tk environment on Windows with a private function in the @code{_tkinter}
module that makes no permanent changes to the environment.

@item 
bpo-24257@footnote{https://bugs.python.org/issue24257}: Fixed segmentation fault in sqlite3.Row constructor with faked
cursor type.

@item 
bpo-15836@footnote{https://bugs.python.org/issue15836}: assertRaises(), assertRaisesRegex(), assertWarns() and
assertWarnsRegex() assertments now check the type of the first argument to
prevent possible user error.  Based on patch by Daniel Wagner-Hall.

@item 
bpo-9858@footnote{https://bugs.python.org/issue9858}: Add missing method stubs to _io.RawIOBase.  Patch by Laura
Rupprecht.

@item 
bpo-22955@footnote{https://bugs.python.org/issue22955}: attrgetter, itemgetter and methodcaller objects in the operator
module now support pickling.  Added readable and evaluable repr for these
objects. Based on patch by Josh Rosenberg.

@item 
bpo-22107@footnote{https://bugs.python.org/issue22107}: tempfile.gettempdir() and tempfile.mkdtemp() now try again when
a directory with the chosen name already exists on Windows as well as on
Unix. tempfile.mkstemp() now fails early if parent directory is not valid
(not exists or is a file) on Windows.

@item 
bpo-23780@footnote{https://bugs.python.org/issue23780}: Improved error message in os.path.join() with single argument.

@item 
bpo-6598@footnote{https://bugs.python.org/issue6598}: Increased time precision and random number range in
email.utils.make_msgid() to strengthen the uniqueness of the message ID.

@item 
bpo-24091@footnote{https://bugs.python.org/issue24091}: Fixed various crashes in corner cases in C implementation of
ElementTree.

@item 
bpo-21931@footnote{https://bugs.python.org/issue21931}: msilib.FCICreate() now raises TypeError in the case of a bad
argument instead of a ValueError with a bogus FCI error number. Patch by
Jeffrey Armstrong.

@item 
bpo-13866@footnote{https://bugs.python.org/issue13866}: @emph{quote_via} argument added to urllib.parse.urlencode.

@item 
bpo-20098@footnote{https://bugs.python.org/issue20098}: New mangle_from policy option for email, default True for
compat32, but False for all other policies.

@item 
bpo-24211@footnote{https://bugs.python.org/issue24211}: The email library now supports RFC 6532: it can generate
headers using utf-8 instead of encoded words.

@item 
bpo-16314@footnote{https://bugs.python.org/issue16314}: Added support for the LZMA compression in distutils.

@item 
bpo-21804@footnote{https://bugs.python.org/issue21804}: poplib now supports RFC 6856 (UTF8).

@item 
bpo-18682@footnote{https://bugs.python.org/issue18682}: Optimized pprint functions for builtin scalar types.

@item 
bpo-22027@footnote{https://bugs.python.org/issue22027}: smtplib now supports RFC 6531 (SMTPUTF8).

@item 
bpo-23488@footnote{https://bugs.python.org/issue23488}: Random generator objects now consume 2x less memory on 64-bit.

@item 
bpo-1322@footnote{https://bugs.python.org/issue1322}: platform.dist() and platform.linux_distribution() functions are
now deprecated.  Initial patch by Vajrasky Kok.

@item 
bpo-22486@footnote{https://bugs.python.org/issue22486}: Added the math.gcd() function.  The fractions.gcd() function
now is deprecated.  Based on patch by Mark Dickinson.

@item 
bpo-24064@footnote{https://bugs.python.org/issue24064}: Property() docstrings are now writeable. (Patch by Berker
Peksag.)

@item 
bpo-22681@footnote{https://bugs.python.org/issue22681}: Added support for the koi8_t encoding.

@item 
bpo-22682@footnote{https://bugs.python.org/issue22682}: Added support for the kz1048 encoding.

@item 
bpo-23796@footnote{https://bugs.python.org/issue23796}: peek and read1 methods of BufferedReader now raise ValueError
if they called on a closed object. Patch by John Hergenroeder.

@item 
bpo-21795@footnote{https://bugs.python.org/issue21795}: smtpd now supports the 8BITMIME extension whenever the new
@emph{decode_data} constructor argument is set to False.

@item 
bpo-24155@footnote{https://bugs.python.org/issue24155}: optimize heapq.heapify() for better cache performance when
heapifying large lists.

@item 
bpo-21800@footnote{https://bugs.python.org/issue21800}: imaplib now supports RFC 5161 (enable), RFC 6855
(utf8/internationalized email) and automatically encodes non-ASCII
usernames and passwords to UTF8.

@item 
bpo-20274@footnote{https://bugs.python.org/issue20274}: When calling a _sqlite.Connection, it now complains if passed
any keyword arguments.  Previously it silently ignored them.

@item 
bpo-20274@footnote{https://bugs.python.org/issue20274}: Remove ignored and erroneous "kwargs" parameters from three
METH_VARARGS methods on _sqlite.Connection.

@item 
bpo-24134@footnote{https://bugs.python.org/issue24134}: assertRaises(), assertRaisesRegex(), assertWarns() and
assertWarnsRegex() checks now emits a deprecation warning when callable is
None or keyword arguments except msg is passed in the context manager
mode.

@item 
bpo-24018@footnote{https://bugs.python.org/issue24018}: Add a collections.abc.Generator abstract base class.
Contributed by Stefan Behnel.

@item 
bpo-23880@footnote{https://bugs.python.org/issue23880}: Tkinter's getint() and getdouble() now support Tcl_Obj.
Tkinter's getdouble() now supports any numbers (in particular int).

@item 
bpo-22619@footnote{https://bugs.python.org/issue22619}: Added negative limit support in the traceback module. Based on
patch by Dmitry Kazakov.

@item 
bpo-24094@footnote{https://bugs.python.org/issue24094}: Fix possible crash in json.encode with poorly behaved dict
subclasses.

@item 
bpo-9246@footnote{https://bugs.python.org/issue9246}: On POSIX, os.getcwd() now supports paths longer than 1025 bytes.
Patch written by William Orr.

@item 
bpo-17445@footnote{https://bugs.python.org/issue17445}: add difflib.diff_bytes() to support comparison of byte strings
(fixes a regression from Python 2).

@item 
bpo-23917@footnote{https://bugs.python.org/issue23917}: Fall back to sequential compilation when ProcessPoolExecutor
doesn't exist. Patch by Claudiu Popa.

@item 
bpo-23008@footnote{https://bugs.python.org/issue23008}: Fixed resolving attributes with boolean value is False in
pydoc.

@item 
Fix asyncio issue 235: LifoQueue and PriorityQueue's put didn't increment
unfinished tasks (this bug was introduced when JoinableQueue was merged
with Queue).

@item 
bpo-23908@footnote{https://bugs.python.org/issue23908}: os functions now reject paths with embedded null character on
Windows instead of silently truncating them.

@item 
bpo-23728@footnote{https://bugs.python.org/issue23728}: binascii.crc_hqx() could return an integer outside of the range
0-0xffff for empty data.

@item 
bpo-23887@footnote{https://bugs.python.org/issue23887}: urllib.error.HTTPError now has a proper repr() representation.
Patch by Berker Peksag.

@item 
asyncio: New event loop APIs: set_task_factory() and get_task_factory().

@item 
asyncio: async() function is deprecated in favour of ensure_future().

@item 
bpo-24178@footnote{https://bugs.python.org/issue24178}: asyncio.Lock, Condition, Semaphore, and BoundedSemaphore
support new 'async with' syntax.  Contributed by Yury Selivanov.

@item 
bpo-24179@footnote{https://bugs.python.org/issue24179}: Support 'async for' for asyncio.StreamReader. Contributed by
Yury Selivanov.

@item 
bpo-24184@footnote{https://bugs.python.org/issue24184}: Add AsyncIterator and AsyncIterable ABCs to collections.abc.
Contributed by Yury Selivanov.

@item 
bpo-22547@footnote{https://bugs.python.org/issue22547}: Implement informative __repr__ for inspect.BoundArguments.
Contributed by Yury Selivanov.

@item 
bpo-24190@footnote{https://bugs.python.org/issue24190}: Implement inspect.BoundArgument.apply_defaults() method.
Contributed by Yury Selivanov.

@item 
bpo-20691@footnote{https://bugs.python.org/issue20691}: Add 'follow_wrapped' argument to
inspect.Signature.from_callable() and inspect.signature(). Contributed by
Yury Selivanov.

@item 
bpo-24248@footnote{https://bugs.python.org/issue24248}: Deprecate inspect.Signature.from_function() and
inspect.Signature.from_builtin().

@item 
bpo-23898@footnote{https://bugs.python.org/issue23898}: Fix inspect.classify_class_attrs() to support attributes with
overloaded __eq__ and __bool__.  Patch by Mike Bayer.

@item 
bpo-24298@footnote{https://bugs.python.org/issue24298}: Fix inspect.signature() to correctly unwrap wrappers around
bound methods.
@end itemize

@node IDLE<46>,测试<46>,库<75>,Python 3 5 0 beta 1
@anchor{whatsnew/changelog id467}@anchor{116b}
@subsubsection IDLE



@itemize -

@item 
bpo-23184@footnote{https://bugs.python.org/issue23184}: remove unused names and imports in idlelib. Initial patch by Al
Sweigart.
@end itemize

@node 测试<46>,文档<44>,IDLE<46>,Python 3 5 0 beta 1
@anchor{whatsnew/changelog id468}@anchor{116c}
@subsubsection 测试



@itemize -

@item 
bpo-21520@footnote{https://bugs.python.org/issue21520}: test_zipfile no longer fails if the word 'bad' appears anywhere
in the name of the current directory.

@item 
bpo-9517@footnote{https://bugs.python.org/issue9517}: Move script_helper into the support package. Patch by Christie
Wilson.
@end itemize

@node 文档<44>,工具/示例<31>,测试<46>,Python 3 5 0 beta 1
@anchor{whatsnew/changelog id469}@anchor{116d}
@subsubsection 文档



@itemize -

@item 
bpo-22155@footnote{https://bugs.python.org/issue22155}: Add File Handlers subsection with createfilehandler to tkinter
doc.  Remove obsolete example from FAQ.  Patch by Martin Panter.

@item 
bpo-24029@footnote{https://bugs.python.org/issue24029}: Document the name binding behavior for submodule imports.

@item 
bpo-24077@footnote{https://bugs.python.org/issue24077}: Fix typo in man page for -I command option: -s, not -S
@end itemize

@node 工具/示例<31>,,文档<44>,Python 3 5 0 beta 1
@anchor{whatsnew/changelog id470}@anchor{116e}
@subsubsection 工具/示例



@itemize -

@item 
bpo-24000@footnote{https://bugs.python.org/issue24000}: Improved Argument Clinic's mapping of converters to legacy
"format units". Updated the documentation to match.

@item 
bpo-24001@footnote{https://bugs.python.org/issue24001}: Argument Clinic converters now use accept=@{type@} instead of
types=@{'type'@} to specify the types the converter accepts.

@item 
bpo-23330@footnote{https://bugs.python.org/issue23330}: h2py now supports arbitrary filenames in #include.

@item 
bpo-24031@footnote{https://bugs.python.org/issue24031}: make patchcheck now supports git checkouts, too.
@end itemize

@node Python 3 5 0 alpha 4,Python 3 5 0 alpha 3,Python 3 5 0 beta 1,更新日志
@anchor{whatsnew/changelog python-3-5-0-alpha-4}@anchor{116f}
@subsection Python 3.5.0 alpha 4


@emph{发布日期: 2015-04-19}

@menu
* 核心与内置: 核心与内置<62>. 
* 库: 库<76>. 
* 构建: 构建<49>. 
* 测试: 测试<47>. 
* 工具/示例: 工具/示例<32>. 
* C API: C API<32>. 

@end menu

@node 核心与内置<62>,库<76>,,Python 3 5 0 alpha 4
@anchor{whatsnew/changelog id471}@anchor{1170}
@subsubsection 核心与内置



@itemize -

@item 
bpo-22980@footnote{https://bugs.python.org/issue22980}: Under Linux, GNU/KFreeBSD and the Hurd, C extensions now
include the architecture triplet in the extension name, to make it easy to
test builds for different ABIs in the same working tree.  Under OS X, the
extension name now includes 
@geindex Python 提高建议; PEP 3149
PEP 3149@footnote{https://www.python.org/dev/peps/pep-3149}-style information.

@item 
bpo-22631@footnote{https://bugs.python.org/issue22631}: Added Linux-specific socket constant CAN_RAW_FD_FRAMES. Patch
courtesy of Joe Jevnik.

@item 
bpo-23731@footnote{https://bugs.python.org/issue23731}: Implement 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488}: removal of .pyo files.

@item 
bpo-23726@footnote{https://bugs.python.org/issue23726}: Don't enable GC for user subclasses of non-GC types that don't
add any new fields.  Patch by Eugene Toder.

@item 
bpo-23309@footnote{https://bugs.python.org/issue23309}: Avoid a deadlock at shutdown if a daemon thread is aborted
while it is holding a lock to a buffered I/O object, and the main thread
tries to use the same I/O object (typically stdout or stderr).  A fatal
error is emitted instead.

@item 
bpo-22977@footnote{https://bugs.python.org/issue22977}: Fixed formatting Windows error messages on Wine. Patch by
Martin Panter.

@item 
bpo-23466@footnote{https://bugs.python.org/issue23466}: %c, %o, %x, and %X in bytes formatting now raise TypeError on
non-integer input.

@item 
bpo-24044@footnote{https://bugs.python.org/issue24044}: Fix possible null pointer dereference in list.sort in out of
memory conditions.

@item 
bpo-21354@footnote{https://bugs.python.org/issue21354}: PyCFunction_New function is exposed by python DLL again.
@end itemize

@node 库<76>,构建<49>,核心与内置<62>,Python 3 5 0 alpha 4
@anchor{whatsnew/changelog id472}@anchor{1171}
@subsubsection 库



@itemize -

@item 
bpo-23840@footnote{https://bugs.python.org/issue23840}: tokenize.open() now closes the temporary binary file on error
to fix a resource warning.

@item 
bpo-16914@footnote{https://bugs.python.org/issue16914}: new debuglevel 2 in smtplib adds timestamps to debug output.

@item 
bpo-7159@footnote{https://bugs.python.org/issue7159}: urllib.request now supports sending auth credentials
automatically after the first 401.  This enhancement is a superset of the
enhancement from bpo-19494@footnote{https://bugs.python.org/issue19494} and supersedes that change.

@item 
bpo-23703@footnote{https://bugs.python.org/issue23703}: Fix a regression in urljoin() introduced in 901e4e52b20a. Patch
by Demian Brecht.

@item 
bpo-4254@footnote{https://bugs.python.org/issue4254}: Adds _curses.update_lines_cols().  Patch by Arnon Yaari

@item 
bpo-19933@footnote{https://bugs.python.org/issue19933}: Provide default argument for ndigits in round. Patch by
Vajrasky Kok.

@item 
bpo-23193@footnote{https://bugs.python.org/issue23193}: Add a numeric_owner parameter to tarfile.TarFile.extract and
tarfile.TarFile.extractall. Patch by Michael Vogt and Eric Smith.

@item 
bpo-23342@footnote{https://bugs.python.org/issue23342}: Add a subprocess.run() function than returns a CalledProcess
instance for a more consistent API than the existing call* functions.

@item 
bpo-21217@footnote{https://bugs.python.org/issue21217}: inspect.getsourcelines() now tries to compute the start and end
lines from the code object, fixing an issue when a lambda function is used
as decorator argument. Patch by Thomas Ballinger and Allison Kaptur.

@item 
bpo-24521@footnote{https://bugs.python.org/issue24521}: Fix possible integer overflows in the pickle module.

@item 
bpo-22931@footnote{https://bugs.python.org/issue22931}: Allow '[' and ']' in cookie values.

@item 
The keywords attribute of functools.partial is now always a dictionary.

@item 
bpo-23811@footnote{https://bugs.python.org/issue23811}: Add missing newline to the PyCompileError error message. Patch
by Alex Shkop.

@item 
bpo-21116@footnote{https://bugs.python.org/issue21116}: Avoid blowing memory when allocating a multiprocessing shared
array that's larger than 50% of the available RAM.  Patch by Médéric
Boquien.

@item 
bpo-22982@footnote{https://bugs.python.org/issue22982}: Improve BOM handling when seeking to multiple positions of a
writable text file.

@item 
bpo-23464@footnote{https://bugs.python.org/issue23464}: Removed deprecated asyncio JoinableQueue.

@item 
bpo-23529@footnote{https://bugs.python.org/issue23529}: Limit the size of decompressed data when reading from GzipFile,
BZ2File or LZMAFile.  This defeats denial of service attacks using
compressed bombs (i.e. compressed payloads which decompress to a huge
size).  Patch by Martin Panter and Nikolaus Rath.

@item 
bpo-21859@footnote{https://bugs.python.org/issue21859}: Added Python implementation of io.FileIO.

@item 
bpo-23865@footnote{https://bugs.python.org/issue23865}: close() methods in multiple modules now are idempotent and more
robust at shutdown. If they need to release multiple resources, all are
released even if errors occur.

@item 
bpo-23400@footnote{https://bugs.python.org/issue23400}: Raise same exception on both Python 2 and 3 if sem_open is not
available. Patch by Davin Potts.

@item 
bpo-10838@footnote{https://bugs.python.org/issue10838}: The subprocess now module includes SubprocessError and
TimeoutError in its list of exported names for the users wild enough to
use @code{from subprocess import *}.

@item 
bpo-23411@footnote{https://bugs.python.org/issue23411}: Added DefragResult, ParseResult, SplitResult,
DefragResultBytes, ParseResultBytes, and SplitResultBytes to
urllib.parse.__all__. Patch by Martin Panter.

@item 
bpo-23881@footnote{https://bugs.python.org/issue23881}: urllib.request.ftpwrapper constructor now closes the socket if
the FTP connection failed to fix a ResourceWarning.

@item 
bpo-23853@footnote{https://bugs.python.org/issue23853}: @ref{675,,socket.socket.sendall()} does no more reset the socket
timeout each time data is sent successfully. The socket timeout is now the
maximum total duration to send all data.

@item 
bpo-22721@footnote{https://bugs.python.org/issue22721}: An order of multiline pprint output of set or dict containing
orderable and non-orderable elements no longer depends on iteration order
of set or dict.

@item 
bpo-15133@footnote{https://bugs.python.org/issue15133}: _tkinter.tkapp.getboolean() now supports Tcl_Obj and always
returns bool. tkinter.BooleanVar now validates input values (accepted
bool, int, str, and Tcl_Obj).  tkinter.BooleanVar.get() now always returns
bool.

@item 
bpo-10590@footnote{https://bugs.python.org/issue10590}: xml.sax.parseString() now supports string argument.

@item 
bpo-23338@footnote{https://bugs.python.org/issue23338}: Fixed formatting ctypes error messages on Cygwin. Patch by
Makoto Kato.

@item 
bpo-15582@footnote{https://bugs.python.org/issue15582}: inspect.getdoc() now follows inheritance chains.

@item 
bpo-2175@footnote{https://bugs.python.org/issue2175}: SAX parsers now support a character stream of InputSource
object.

@item 
bpo-16840@footnote{https://bugs.python.org/issue16840}: Tkinter now supports 64-bit integers added in Tcl 8.4 and
arbitrary precision integers added in Tcl 8.5.

@item 
bpo-23834@footnote{https://bugs.python.org/issue23834}: Fix socket.sendto(), use the C Py_ssize_t type to store the
result of sendto() instead of the C int type.

@item 
bpo-23618@footnote{https://bugs.python.org/issue23618}: @ref{670,,socket.socket.connect()} now waits until the connection
completes instead of raising @ref{653,,InterruptedError} if the connection is
interrupted by signals, signal handlers don't raise an exception and the
socket is blocking or has a timeout. @ref{670,,socket.socket.connect()} still
raise @ref{653,,InterruptedError} for non-blocking sockets.

@item 
bpo-21526@footnote{https://bugs.python.org/issue21526}: Tkinter now supports new boolean type in Tcl 8.5.

@item 
bpo-23836@footnote{https://bugs.python.org/issue23836}: Fix the faulthandler module to handle reentrant calls to its
signal handlers.

@item 
bpo-23838@footnote{https://bugs.python.org/issue23838}: linecache now clears the cache and returns an empty result on
MemoryError.

@item 
bpo-10395@footnote{https://bugs.python.org/issue10395}: Added os.path.commonpath(). Implemented in posixpath and
ntpath. Based on patch by Rafik Draoui.

@item 
bpo-23611@footnote{https://bugs.python.org/issue23611}: Serializing more "lookupable" objects (such as unbound methods
or nested classes) now are supported with pickle protocols < 4.

@item 
bpo-13583@footnote{https://bugs.python.org/issue13583}: sqlite3.Row now supports slice indexing.

@item 
bpo-18473@footnote{https://bugs.python.org/issue18473}: Fixed 2to3 and 3to2 compatible pickle mappings.  Fixed
ambiguous reverse mappings.  Added many new mappings.  Import mapping is
no longer applied to modules already mapped with full name mapping.

@item 
bpo-23485@footnote{https://bugs.python.org/issue23485}: select.select() is now retried automatically with the
recomputed timeout when interrupted by a signal, except if the signal
handler raises an exception. This change is part of the 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}.

@item 
bpo-23752@footnote{https://bugs.python.org/issue23752}: When built from an existing file descriptor, io.FileIO() now
only calls fstat() once. Before fstat() was called twice, which was not
necessary.

@item 
bpo-23704@footnote{https://bugs.python.org/issue23704}: collections.deque() objects now support __add__, __mul__, and
__imul__().

@item 
bpo-23171@footnote{https://bugs.python.org/issue23171}: csv.Writer.writerow() now supports arbitrary iterables.

@item 
bpo-23745@footnote{https://bugs.python.org/issue23745}: The new email header parser now handles duplicate MIME
parameter names without error, similar to how get_param behaves.

@item 
bpo-22117@footnote{https://bugs.python.org/issue22117}: Fix os.utime(), it now rounds the timestamp towards minus
infinity (-inf) instead of rounding towards zero.

@item 
bpo-23310@footnote{https://bugs.python.org/issue23310}: Fix MagicMock's initializer to work with __methods__, just like
configure_mock().  Patch by Kasia Jachim.
@end itemize

@node 构建<49>,测试<47>,库<76>,Python 3 5 0 alpha 4
@anchor{whatsnew/changelog id473}@anchor{1172}
@subsubsection 构建



@itemize -

@item 
bpo-23817@footnote{https://bugs.python.org/issue23817}: FreeBSD now uses "1.0" in the SOVERSION as other operating
systems, instead of just "1".

@item 
bpo-23501@footnote{https://bugs.python.org/issue23501}: Argument Clinic now generates code into separate files by
default.
@end itemize

@node 测试<47>,工具/示例<32>,构建<49>,Python 3 5 0 alpha 4
@anchor{whatsnew/changelog id474}@anchor{1173}
@subsubsection 测试



@itemize -

@item 
bpo-23799@footnote{https://bugs.python.org/issue23799}: Added test.support.start_threads() for running and cleaning up
multiple threads.

@item 
bpo-22390@footnote{https://bugs.python.org/issue22390}: test.regrtest now emits a warning if temporary files or
directories are left after running a test.
@end itemize

@node 工具/示例<32>,C API<32>,测试<47>,Python 3 5 0 alpha 4
@anchor{whatsnew/changelog id475}@anchor{1174}
@subsubsection 工具/示例



@itemize -

@item 
bpo-18128@footnote{https://bugs.python.org/issue18128}: pygettext now uses standard +NNNN format in the
POT-Creation-Date header.

@item 
bpo-23935@footnote{https://bugs.python.org/issue23935}: Argument Clinic's understanding of format units accepting
bytes, bytearrays, and buffers is now consistent with both the
documentation and the implementation.

@item 
bpo-23944@footnote{https://bugs.python.org/issue23944}: Argument Clinic now wraps long impl prototypes at column 78.

@item 
bpo-20586@footnote{https://bugs.python.org/issue20586}: Argument Clinic now ensures that functions without docstrings
have signatures.

@item 
bpo-23492@footnote{https://bugs.python.org/issue23492}: Argument Clinic now generates argument parsing code with
PyArg_Parse instead of PyArg_ParseTuple if possible.

@item 
bpo-23500@footnote{https://bugs.python.org/issue23500}: Argument Clinic is now smarter about generating the "#ifndef"
(empty) definition of the methoddef macro: it's only generated once, even
if Argument Clinic processes the same symbol multiple times, and it's
emitted at the end of all processing rather than immediately after the
first use.
@end itemize

@node C API<32>,,工具/示例<32>,Python 3 5 0 alpha 4
@anchor{whatsnew/changelog id476}@anchor{1175}
@subsubsection C API



@itemize -

@item 
bpo-23998@footnote{https://bugs.python.org/issue23998}: PyImport_ReInitLock() now checks for lock allocation error
@end itemize

@node Python 3 5 0 alpha 3,Python 3 5 0 alpha 2,Python 3 5 0 alpha 4,更新日志
@anchor{whatsnew/changelog python-3-5-0-alpha-3}@anchor{1176}
@subsection Python 3.5.0 alpha 3


@emph{发布日期: 2015-03-28}

@menu
* 核心与内置: 核心与内置<63>. 
* 库: 库<77>. 
* 构建: 构建<50>. 
* 测试: 测试<48>. 
* 工具/示例: 工具/示例<33>. 

@end menu

@node 核心与内置<63>,库<77>,,Python 3 5 0 alpha 3
@anchor{whatsnew/changelog id477}@anchor{1177}
@subsubsection 核心与内置



@itemize -

@item 
bpo-23573@footnote{https://bugs.python.org/issue23573}: Increased performance of string search operations (str.find,
str.index, str.count, the in operator, str.split, str.partition) with
arguments of different kinds (UCS1, UCS2, UCS4).

@item 
bpo-23753@footnote{https://bugs.python.org/issue23753}: Python doesn't support anymore platforms without stat() or
fstat(), these functions are always required.

@item 
bpo-23681@footnote{https://bugs.python.org/issue23681}: The -b option now affects comparisons of bytes with int.

@item 
bpo-23632@footnote{https://bugs.python.org/issue23632}: Memoryviews now allow tuple indexing (including for
multi-dimensional memoryviews).

@item 
bpo-23192@footnote{https://bugs.python.org/issue23192}: Fixed generator lambdas.  Patch by Bruno Cauet.

@item 
bpo-23629@footnote{https://bugs.python.org/issue23629}: Fix the default __sizeof__ implementation for variable-sized
objects.
@end itemize

@node 库<77>,构建<50>,核心与内置<63>,Python 3 5 0 alpha 3
@anchor{whatsnew/changelog id478}@anchor{1178}
@subsubsection 库



@itemize -

@item 
bpo-14260@footnote{https://bugs.python.org/issue14260}: The groupindex attribute of regular expression pattern object
now is non-modifiable mapping.

@item 
bpo-23792@footnote{https://bugs.python.org/issue23792}: Ignore KeyboardInterrupt when the pydoc pager is active. This
mimics the behavior of the standard unix pagers, and prevents pipepager
from shutting down while the pager itself is still running.

@item 
bpo-23775@footnote{https://bugs.python.org/issue23775}: pprint() of OrderedDict now outputs the same representation as
repr().

@item 
bpo-23765@footnote{https://bugs.python.org/issue23765}: Removed IsBadStringPtr calls in ctypes

@item 
bpo-22364@footnote{https://bugs.python.org/issue22364}: Improved some re error messages using regex for hints.

@item 
bpo-23742@footnote{https://bugs.python.org/issue23742}: ntpath.expandvars() no longer loses unbalanced single quotes.

@item 
bpo-21717@footnote{https://bugs.python.org/issue21717}: The zipfile.ZipFile.open function now supports 'x' (exclusive
creation) mode.

@item 
bpo-21802@footnote{https://bugs.python.org/issue21802}: The reader in BufferedRWPair now is closed even when closing
writer failed in BufferedRWPair.close().

@item 
bpo-23622@footnote{https://bugs.python.org/issue23622}: Unknown escapes in regular expressions that consist of @code{'\'}
and ASCII letter now raise a deprecation warning and will be forbidden in
Python 3.6.

@item 
bpo-23671@footnote{https://bugs.python.org/issue23671}: string.Template now allows specifying the "self" parameter as a
keyword argument.  string.Formatter now allows specifying the "self" and
the "format_string" parameters as keyword arguments.

@item 
bpo-23502@footnote{https://bugs.python.org/issue23502}: The pprint module now supports mapping proxies.

@item 
bpo-17530@footnote{https://bugs.python.org/issue17530}: pprint now wraps long bytes objects and bytearrays.

@item 
bpo-22687@footnote{https://bugs.python.org/issue22687}: Fixed some corner cases in breaking words in tetxtwrap. Got rid
of quadratic complexity in breaking long words.

@item 
bpo-4727@footnote{https://bugs.python.org/issue4727}: The copy module now uses pickle protocol 4 (PEP 3154) and
supports copying of instances of classes whose __new__ method takes
keyword-only arguments.

@item 
bpo-23491@footnote{https://bugs.python.org/issue23491}: Added a zipapp module to support creating executable zip file
archives of Python code. Registered ".pyz" and ".pyzw" extensions on
Windows for these archives (PEP 441).

@item 
bpo-23657@footnote{https://bugs.python.org/issue23657}: Avoid explicit checks for str in zipapp, adding support for
pathlib.Path objects as arguments.

@item 
bpo-23688@footnote{https://bugs.python.org/issue23688}: Added support of arbitrary bytes-like objects and avoided
unnecessary copying of memoryview in gzip.GzipFile.write(). Original patch
by Wolfgang Maier.

@item 
bpo-23252@footnote{https://bugs.python.org/issue23252}: Added support for writing ZIP files to unseekable streams.

@item 
bpo-23647@footnote{https://bugs.python.org/issue23647}: Increase imaplib's MAXLINE to accommodate modern mailbox sizes.

@item 
bpo-23539@footnote{https://bugs.python.org/issue23539}: If body is None, http.client.HTTPConnection.request now sets
Content-Length to 0 for PUT, POST, and PATCH headers to avoid 411 errors
from some web servers.

@item 
bpo-22351@footnote{https://bugs.python.org/issue22351}: The nntplib.NNTP constructor no longer leaves the connection
and socket open until the garbage collector cleans them up.  Patch by
Martin Panter.

@item 
bpo-23704@footnote{https://bugs.python.org/issue23704}: collections.deque() objects now support methods for index(),
insert(), and copy().  This allows deques to be registered as a
MutableSequence and it improves their substitutability for lists.

@item 
bpo-23715@footnote{https://bugs.python.org/issue23715}: @ref{679,,signal.sigwaitinfo()} and @ref{678,,signal.sigtimedwait()} are
now retried when interrupted by a signal not in the @emph{sigset} parameter, if
the signal handler does not raise an exception. signal.sigtimedwait()
recomputes the timeout with a monotonic clock when it is retried.

@item 
bpo-23001@footnote{https://bugs.python.org/issue23001}: Few functions in modules mmap, ossaudiodev, socket, ssl, and
codecs, that accepted only read-only bytes-like object now accept writable
bytes-like object too.

@item 
bpo-23646@footnote{https://bugs.python.org/issue23646}: If time.sleep() is interrupted by a signal, the sleep is now
retried with the recomputed delay, except if the signal handler raises an
exception (PEP 475).

@item 
bpo-23136@footnote{https://bugs.python.org/issue23136}: _strptime now uniformly handles all days in week 0, including
Dec 30 of previous year.  Based on patch by Jim Carroll.

@item 
bpo-23700@footnote{https://bugs.python.org/issue23700}: Iterator of NamedTemporaryFile now keeps a reference to
NamedTemporaryFile instance.  Patch by Bohuslav Kabrda.

@item 
bpo-22903@footnote{https://bugs.python.org/issue22903}: The fake test case created by unittest.loader when it fails
importing a test module is now picklable.

@item 
bpo-22181@footnote{https://bugs.python.org/issue22181}: On Linux, os.urandom() now uses the new getrandom() syscall if
available, syscall introduced in the Linux kernel 3.17. It is more
reliable and more secure, because it avoids the need of a file descriptor
and waits until the kernel has enough entropy.

@item 
bpo-2211@footnote{https://bugs.python.org/issue2211}: Updated the implementation of the http.cookies.Morsel class.
Setting attributes key, value and coded_value directly now is deprecated.
update() and setdefault() now transform and check keys.  Comparing for
equality now takes into account attributes key, value and coded_value.
copy() now returns a Morsel, not a dict.  repr() now contains all
attributes. Optimized checking keys and quoting values.  Added new tests.
Original patch by Demian Brecht.

@item 
bpo-18983@footnote{https://bugs.python.org/issue18983}: Allow selection of output units in timeit. Patch by Julian
Gindi.

@item 
bpo-23631@footnote{https://bugs.python.org/issue23631}: Fix traceback.format_list when a traceback has been mutated.

@item 
bpo-23568@footnote{https://bugs.python.org/issue23568}: Add rdivmod support to MagicMock() objects. Patch by Håkan
Lövdahl.

@item 
bpo-2052@footnote{https://bugs.python.org/issue2052}: Add charset parameter to HtmlDiff.make_file().

@item 
bpo-23668@footnote{https://bugs.python.org/issue23668}: Support os.truncate and os.ftruncate on Windows.

@item 
bpo-23138@footnote{https://bugs.python.org/issue23138}: Fixed parsing cookies with absent keys or values in cookiejar.
Patch by Demian Brecht.

@item 
bpo-23051@footnote{https://bugs.python.org/issue23051}: multiprocessing.Pool methods imap() and imap_unordered() now
handle exceptions raised by an iterator.  Patch by Alon Diamant and Davin
Potts.

@item 
bpo-23581@footnote{https://bugs.python.org/issue23581}: Add matmul support to MagicMock. Patch by Håkan Lövdahl.

@item 
bpo-23566@footnote{https://bugs.python.org/issue23566}: enable(), register(), dump_traceback() and
dump_traceback_later() functions of faulthandler now accept file
descriptors. Patch by Wei Wu.

@item 
bpo-22928@footnote{https://bugs.python.org/issue22928}: Disabled HTTP header injections in http.client. Original patch
by Demian Brecht.

@item 
bpo-23615@footnote{https://bugs.python.org/issue23615}: Modules bz2, tarfile and tokenize now can be reloaded with
imp.reload(). Patch by Thomas Kluyver.

@item 
bpo-23605@footnote{https://bugs.python.org/issue23605}: os.walk() now calls os.scandir() instead of os.listdir(). The
usage of os.scandir() reduces the number of calls to os.stat(). Initial
patch written by Ben Hoyt.
@end itemize

@node 构建<50>,测试<48>,库<77>,Python 3 5 0 alpha 3
@anchor{whatsnew/changelog id479}@anchor{1179}
@subsubsection 构建



@itemize -

@item 
bpo-23585@footnote{https://bugs.python.org/issue23585}: make patchcheck will ensure the interpreter is built.
@end itemize

@node 测试<48>,工具/示例<33>,构建<50>,Python 3 5 0 alpha 3
@anchor{whatsnew/changelog id480}@anchor{117a}
@subsubsection 测试



@itemize -

@item 
bpo-23583@footnote{https://bugs.python.org/issue23583}: Added tests for standard IO streams in IDLE.

@item 
bpo-22289@footnote{https://bugs.python.org/issue22289}: Prevent test_urllib2net failures due to ftp connection timeout.
@end itemize

@node 工具/示例<33>,,测试<48>,Python 3 5 0 alpha 3
@anchor{whatsnew/changelog id481}@anchor{117b}
@subsubsection 工具/示例



@itemize -

@item 
bpo-22826@footnote{https://bugs.python.org/issue22826}: The result of open() in Tools/freeze/bkfile.py is now better
compatible with regular files (in particular it now supports the context
management protocol).
@end itemize

@node Python 3 5 0 alpha 2,Python 3 5 0 alpha 1,Python 3 5 0 alpha 3,更新日志
@anchor{whatsnew/changelog python-3-5-0-alpha-2}@anchor{117c}
@subsection Python 3.5.0 alpha 2


@emph{发布日期: 2015-03-09}

@menu
* 核心与内置: 核心与内置<64>. 
* 库: 库<78>. 
* 构建: 构建<51>. 
* C API: C API<33>. 
* Windows: Windows<45>. 

@end menu

@node 核心与内置<64>,库<78>,,Python 3 5 0 alpha 2
@anchor{whatsnew/changelog id482}@anchor{117d}
@subsubsection 核心与内置



@itemize -

@item 
bpo-23571@footnote{https://bugs.python.org/issue23571}: PyObject_Call() and PyCFunction_Call() now raise a SystemError
if a function returns a result and raises an exception. The SystemError is
chained to the previous exception.
@end itemize

@node 库<78>,构建<51>,核心与内置<64>,Python 3 5 0 alpha 2
@anchor{whatsnew/changelog id483}@anchor{117e}
@subsubsection 库



@itemize -

@item 
bpo-22524@footnote{https://bugs.python.org/issue22524}: New os.scandir() function, part of the 
@geindex Python 提高建议; PEP 471
PEP 471@footnote{https://www.python.org/dev/peps/pep-0471}:
"os.scandir() function -- a better and faster directory iterator". Patch
written by Ben Hoyt.

@item 
bpo-23103@footnote{https://bugs.python.org/issue23103}: Reduced the memory consumption of IPv4Address and IPv6Address.

@item 
bpo-21793@footnote{https://bugs.python.org/issue21793}: BaseHTTPRequestHandler again logs response code as numeric, not
as stringified enum.  Patch by Demian Brecht.

@item 
bpo-23476@footnote{https://bugs.python.org/issue23476}: In the ssl module, enable OpenSSL's X509_V_FLAG_TRUSTED_FIRST
flag on certificate stores when it is available.

@item 
bpo-23576@footnote{https://bugs.python.org/issue23576}: Avoid stalling in SSL reads when EOF has been reached in the
SSL layer but the underlying connection hasn't been closed.

@item 
bpo-23504@footnote{https://bugs.python.org/issue23504}: Added an __all__ to the types module.

@item 
bpo-23563@footnote{https://bugs.python.org/issue23563}: Optimized utility functions in urllib.parse.

@item 
bpo-7830@footnote{https://bugs.python.org/issue7830}: Flatten nested functools.partial.

@item 
bpo-20204@footnote{https://bugs.python.org/issue20204}: Added the __module__ attribute to _tkinter classes.

@item 
bpo-19980@footnote{https://bugs.python.org/issue19980}: Improved help() for non-recognized strings.  help('@w{'}) now shows
the help on str.  help('help') now shows the help on help(). Original
patch by Mark Lawrence.

@item 
bpo-23521@footnote{https://bugs.python.org/issue23521}: Corrected pure python implementation of timedelta division.
Eliminated OverflowError from @code{timedelta * float} for some floats;
Corrected rounding in timedelta true division.

@item 
bpo-21619@footnote{https://bugs.python.org/issue21619}: Popen objects no longer leave a zombie after exit in the with
statement if the pipe was broken.  Patch by Martin Panter.

@item 
bpo-22936@footnote{https://bugs.python.org/issue22936}: Make it possible to show local variables in tracebacks for both
the traceback module and unittest.

@item 
bpo-15955@footnote{https://bugs.python.org/issue15955}: Add an option to limit the output size in bz2.decompress().
Patch by Nikolaus Rath.

@item 
bpo-6639@footnote{https://bugs.python.org/issue6639}: Module-level turtle functions no longer raise TclError after
closing the window.

@item 
bpo-814253@footnote{https://bugs.python.org/issue814253}: Group references and conditional group references now work in
lookbehind assertions in regular expressions. (See also: bpo-9179@footnote{https://bugs.python.org/issue9179})

@item 
bpo-23215@footnote{https://bugs.python.org/issue23215}: Multibyte codecs with custom error handlers that ignores errors
consumed too much memory and raised SystemError or MemoryError. Original
patch by Aleksi Torhamo.

@item 
bpo-5700@footnote{https://bugs.python.org/issue5700}: io.FileIO() called flush() after closing the file. flush() was
not called in close() if closefd=False.

@item 
bpo-23374@footnote{https://bugs.python.org/issue23374}: Fixed pydoc failure with non-ASCII files when stdout encoding
differs from file system encoding (e.g. on Mac OS).

@item 
bpo-23481@footnote{https://bugs.python.org/issue23481}: Remove RC4 from the SSL module's default cipher list.

@item 
bpo-21548@footnote{https://bugs.python.org/issue21548}: Fix pydoc.synopsis() and pydoc.apropos() on modules with empty
docstrings.

@item 
bpo-22885@footnote{https://bugs.python.org/issue22885}: Fixed arbitrary code execution vulnerability in the dbm.dumb
module. Original patch by Claudiu Popa.

@item 
bpo-23239@footnote{https://bugs.python.org/issue23239}: ssl.match_hostname() now supports matching of IP addresses.

@item 
bpo-23146@footnote{https://bugs.python.org/issue23146}: Fix mishandling of absolute Windows paths with forward slashes
in pathlib.

@item 
bpo-23096@footnote{https://bugs.python.org/issue23096}: Pickle representation of floats with protocol 0 now is the same
for both Python and C implementations.

@item 
bpo-19105@footnote{https://bugs.python.org/issue19105}: pprint now more efficiently uses free space at the right.

@item 
bpo-14910@footnote{https://bugs.python.org/issue14910}: Add allow_abbrev parameter to argparse.ArgumentParser. Patch by
Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson.

@item 
bpo-21717@footnote{https://bugs.python.org/issue21717}: tarfile.open() now supports 'x' (exclusive creation) mode.

@item 
bpo-23344@footnote{https://bugs.python.org/issue23344}: marshal.dumps() is now 20-25% faster on average.

@item 
bpo-20416@footnote{https://bugs.python.org/issue20416}: marshal.dumps() with protocols 3 and 4 is now 40-50% faster on
average.

@item 
bpo-23421@footnote{https://bugs.python.org/issue23421}: Fixed compression in tarfile CLI.  Patch by wdv4758h.

@item 
bpo-23367@footnote{https://bugs.python.org/issue23367}: Fix possible overflows in the unicodedata module.

@item 
bpo-23361@footnote{https://bugs.python.org/issue23361}: Fix possible overflow in Windows subprocess creation code.

@item 
logging.handlers.QueueListener now takes a respect_handler_level keyword
argument which, if set to True, will pass messages to handlers taking
handler levels into account.

@item 
bpo-19705@footnote{https://bugs.python.org/issue19705}: turtledemo now has a visual sorting algorithm demo.  Original
patch from Jason Yeo.

@item 
bpo-23801@footnote{https://bugs.python.org/issue23801}: Fix issue where cgi.FieldStorage did not always ignore the
entire preamble to a multipart body.
@end itemize

@node 构建<51>,C API<33>,库<78>,Python 3 5 0 alpha 2
@anchor{whatsnew/changelog id484}@anchor{117f}
@subsubsection 构建



@itemize -

@item 
bpo-23445@footnote{https://bugs.python.org/issue23445}: pydebug builds now use "gcc -Og" where possible, to make the
resulting executable faster.

@item 
bpo-23686@footnote{https://bugs.python.org/issue23686}: 更新OS X 10.5 安装程序以使用OpenSSL 1.0.2a.
@end itemize

@node C API<33>,Windows<45>,构建<51>,Python 3 5 0 alpha 2
@anchor{whatsnew/changelog id485}@anchor{1180}
@subsubsection C API



@itemize -

@item 
bpo-20204@footnote{https://bugs.python.org/issue20204}: Deprecation warning is now raised for builtin types without the
__module__ attribute.
@end itemize

@node Windows<45>,,C API<33>,Python 3 5 0 alpha 2
@anchor{whatsnew/changelog id486}@anchor{1181}
@subsubsection Windows



@itemize -

@item 
bpo-23465@footnote{https://bugs.python.org/issue23465}: Implement 
@geindex Python 提高建议; PEP 486
PEP 486@footnote{https://www.python.org/dev/peps/pep-0486} - Make the Python Launcher aware of
virtual environments. Patch by Paul Moore.

@item 
bpo-23437@footnote{https://bugs.python.org/issue23437}: Make user scripts directory versioned on Windows. Patch by Paul
Moore.
@end itemize

@node Python 3 5 0 alpha 1,,Python 3 5 0 alpha 2,更新日志
@anchor{whatsnew/changelog python-3-5-0-alpha-1}@anchor{1182}
@subsection Python 3.5.0 alpha 1


@emph{发布日期: 2015-02-08}

@menu
* 核心与内置: 核心与内置<65>. 
* 库: 库<79>. 
* IDLE: IDLE<47>. 
* 构建: 构建<52>. 
* C API: C API<34>. 
* 文档: 文档<45>. 
* 测试: 测试<49>. 
* 工具/示例: 工具/示例<34>. 
* Windows: Windows<46>. 

@end menu

@node 核心与内置<65>,库<79>,,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id487}@anchor{1183}
@subsubsection 核心与内置



@itemize -

@item 
bpo-23285@footnote{https://bugs.python.org/issue23285}: PEP 475 - EINTR handling.

@item 
bpo-22735@footnote{https://bugs.python.org/issue22735}: Fix many edge cases (including crashes) involving custom mro()
implementations.

@item 
bpo-22896@footnote{https://bugs.python.org/issue22896}: Avoid using PyObject_AsCharBuffer(), PyObject_AsReadBuffer()
and PyObject_AsWriteBuffer().

@item 
bpo-21295@footnote{https://bugs.python.org/issue21295}: Revert some changes (bpo-16795@footnote{https://bugs.python.org/issue16795}) to AST line numbers and
column offsets that constituted a regression.

@item 
bpo-22986@footnote{https://bugs.python.org/issue22986}: Allow changing an object's __class__ between a dynamic type and
static type in some cases.

@item 
bpo-15859@footnote{https://bugs.python.org/issue15859}: PyUnicode_EncodeFSDefault(), PyUnicode_EncodeMBCS() and
PyUnicode_EncodeCodePage() now raise an exception if the object is not a
Unicode object. For PyUnicode_EncodeFSDefault(), it was already the case
on platforms other than Windows. Patch written by Campbell Barton.

@item 
bpo-21408@footnote{https://bugs.python.org/issue21408}: The default __ne__() now returns NotImplemented if __eq__()
returned NotImplemented.  Original patch by Martin Panter.

@item 
bpo-23321@footnote{https://bugs.python.org/issue23321}: Fixed a crash in str.decode() when error handler returned
replacement string longer than malformed input data.

@item 
bpo-22286@footnote{https://bugs.python.org/issue22286}: The "backslashreplace" error handlers now works with decoding
and translating.

@item 
bpo-23253@footnote{https://bugs.python.org/issue23253}: Delay-load ShellExecute[AW] in os.startfile for reduced startup
overhead on Windows.

@item 
bpo-22038@footnote{https://bugs.python.org/issue22038}: pyatomic.h now uses stdatomic.h or GCC built-in functions for
atomic memory access if available. Patch written by Vitor de Lima and
Gustavo Temple.

@item 
bpo-20284@footnote{https://bugs.python.org/issue20284}: %-interpolation (aka printf) formatting added for bytes and
bytearray.

@item 
bpo-23048@footnote{https://bugs.python.org/issue23048}: Fix jumping out of an infinite while loop in the pdb.

@item 
bpo-20335@footnote{https://bugs.python.org/issue20335}: bytes constructor now raises TypeError when encoding or errors
is specified with non-string argument.  Based on patch by Renaud Blanch.

@item 
bpo-22834@footnote{https://bugs.python.org/issue22834}: If the current working directory ends up being set to a
non-existent directory then import will no longer raise FileNotFoundError.

@item 
bpo-22869@footnote{https://bugs.python.org/issue22869}: Move the interpreter startup & shutdown code to a new dedicated
pylifecycle.c module

@item 
bpo-22847@footnote{https://bugs.python.org/issue22847}: Improve method cache efficiency.

@item 
bpo-22335@footnote{https://bugs.python.org/issue22335}: Fix crash when trying to enlarge a bytearray to 0x7fffffff
bytes on a 32-bit platform.

@item 
bpo-22653@footnote{https://bugs.python.org/issue22653}: Fix an assertion failure in debug mode when doing a reentrant
dict insertion in debug mode.

@item 
bpo-22643@footnote{https://bugs.python.org/issue22643}: Fix integer overflow in Unicode case operations (upper, lower,
title, swapcase, casefold).

@item 
bpo-17636@footnote{https://bugs.python.org/issue17636}: Circular imports involving relative imports are now supported.

@item 
bpo-22604@footnote{https://bugs.python.org/issue22604}: Fix assertion error in debug mode when dividing a complex
number by (nan+0j).

@item 
bpo-21052@footnote{https://bugs.python.org/issue21052}: Do not raise ImportWarning when sys.path_hooks or sys.meta_path
are set to None.

@item 
bpo-16518@footnote{https://bugs.python.org/issue16518}: Use 'bytes-like object required' in error messages that
previously used the far more cryptic "'x' does not support the buffer
protocol.

@item 
bpo-22470@footnote{https://bugs.python.org/issue22470}: Fixed integer overflow issues in "backslashreplace",
"xmlcharrefreplace", and "surrogatepass" error handlers.

@item 
bpo-22540@footnote{https://bugs.python.org/issue22540}: speed up @code{PyObject_IsInstance} and @code{PyObject_IsSubclass} in the
common case that the second argument has metaclass @ref{603,,type}.

@item 
bpo-18711@footnote{https://bugs.python.org/issue18711}: Add a new @code{PyErr_FormatV} function, similar to @code{PyErr_Format}
but accepting a @code{va_list} argument.

@item 
bpo-22520@footnote{https://bugs.python.org/issue22520}: Fix overflow checking when generating the repr of a unicode
object.

@item 
bpo-22519@footnote{https://bugs.python.org/issue22519}: Fix overflow checking in PyBytes_Repr.

@item 
bpo-22518@footnote{https://bugs.python.org/issue22518}: Fix integer overflow issues in latin-1 encoding.

@item 
bpo-16324@footnote{https://bugs.python.org/issue16324}: _charset parameter of MIMEText now also accepts
email.charset.Charset instances. Initial patch by Claude Paroz.

@item 
bpo-1764286@footnote{https://bugs.python.org/issue1764286}: Fix inspect.getsource() to support decorated functions. Patch
by Claudiu Popa.

@item 
bpo-18554@footnote{https://bugs.python.org/issue18554}: os.__all__ includes posix functions.

@item 
bpo-21391@footnote{https://bugs.python.org/issue21391}: Use os.path.abspath in the shutil module.

@item 
bpo-11471@footnote{https://bugs.python.org/issue11471}: avoid generating a JUMP_FORWARD instruction at the end of an
if-block if there is no else-clause.  Original patch by Eugene Toder.

@item 
bpo-22215@footnote{https://bugs.python.org/issue22215}: Now ValueError is raised instead of TypeError when str or bytes
argument contains not permitted null character or byte.

@item 
bpo-22258@footnote{https://bugs.python.org/issue22258}: Fix the internal function set_inheritable() on Illumos. This
platform exposes the function @code{ioctl(FIOCLEX)}, but calling it fails
with errno is ENOTTY: "Inappropriate ioctl for device". set_inheritable()
now falls back to the slower @code{fcntl()} (@code{F_GETFD} and then
@code{F_SETFD}).

@item 
bpo-21389@footnote{https://bugs.python.org/issue21389}: Displaying the __qualname__ of the underlying function in the
repr of a bound method.

@item 
bpo-22206@footnote{https://bugs.python.org/issue22206}: Using pthread, PyThread_create_key() now sets errno to ENOMEM
and returns -1 (error) on integer overflow.

@item 
bpo-20184@footnote{https://bugs.python.org/issue20184}: Argument Clinic based signature introspection added for 30 of
the builtin functions.

@item 
bpo-22116@footnote{https://bugs.python.org/issue22116}: C functions and methods (of the 'builtin_function_or_method'
type) can now be weakref'ed.  Patch by Wei Wu.

@item 
bpo-22077@footnote{https://bugs.python.org/issue22077}: Improve index error messages for bytearrays, bytes, lists, and
tuples by adding 'or slices'. Added ', not <typename>' for bytearrays.
Original patch by Claudiu Popa.

@item 
bpo-20179@footnote{https://bugs.python.org/issue20179}: Apply Argument Clinic to bytes and bytearray. Patch by Tal
Einat.

@item 
bpo-22082@footnote{https://bugs.python.org/issue22082}: Clear interned strings in slotdefs.

@item 
升级 Unicode 数据库到 7.0.0 版本。

@item 
bpo-21897@footnote{https://bugs.python.org/issue21897}: Fix a crash with the f_locals attribute with closure variables
when frame.clear() has been called.

@item 
bpo-21205@footnote{https://bugs.python.org/issue21205}: Add a new @code{__qualname__} attribute to generator, the
qualified name, and use it in the representation of a generator
(@code{repr(gen)}). The default name of the generator (@code{__name__}
attribute) is now get from the function instead of the code. Use
@code{gen.gi_code.co_name} to get the name of the code.

@item 
bpo-21669@footnote{https://bugs.python.org/issue21669}: With the aid of heuristics in SyntaxError.__init__, the parser
now attempts to generate more meaningful (or at least more search engine
friendly) error messages when "exec" and "print" are used as statements.

@item 
bpo-21642@footnote{https://bugs.python.org/issue21642}: In the conditional if-else expression, allow an integer written
with no space between itself and the @code{else} keyword (e.g. @code{True if
42else False}) to be valid syntax.

@item 
bpo-21523@footnote{https://bugs.python.org/issue21523}: Fix over-pessimistic computation of the stack effect of some
opcodes in the compiler.  This also fixes a quadratic compilation time
issue noticeable when compiling code with a large number of "and" and "or"
operators.

@item 
bpo-21418@footnote{https://bugs.python.org/issue21418}: Fix a crash in the builtin function super() when called without
argument and without current frame (ex: embedded Python).

@item 
bpo-21425@footnote{https://bugs.python.org/issue21425}: Fix flushing of standard streams in the interactive
interpreter.

@item 
bpo-21435@footnote{https://bugs.python.org/issue21435}: In rare cases, when running finalizers on objects in cyclic
trash a bad pointer dereference could occur due to a subtle flaw in
internal iteration logic.

@item 
bpo-21377@footnote{https://bugs.python.org/issue21377}: PyBytes_Concat() now tries to concatenate in-place when the
first argument has a reference count of 1.  Patch by Nikolaus Rath.

@item 
bpo-20355@footnote{https://bugs.python.org/issue20355}: -W command line options now have higher priority than the
PYTHONWARNINGS environment variable.  Patch by Arfrever.

@item 
bpo-21274@footnote{https://bugs.python.org/issue21274}: Define PATH_MAX for GNU/Hurd in Python/pythonrun.c.

@item 
bpo-20904@footnote{https://bugs.python.org/issue20904}: Support setting FPU precision on m68k.

@item 
bpo-21209@footnote{https://bugs.python.org/issue21209}: Fix sending tuples to custom generator objects with the yield
from syntax.

@item 
bpo-21193@footnote{https://bugs.python.org/issue21193}: pow(a, b, c) now raises ValueError rather than TypeError when b
is negative. Patch by Josh Rosenberg.

@item 
bpo-21176@footnote{https://bugs.python.org/issue21176}: PEP 465: Add the '@@' operator for matrix multiplication.

@item 
bpo-21134@footnote{https://bugs.python.org/issue21134}: Fix segfault when str is called on an uninitialized
UnicodeEncodeError, UnicodeDecodeError, or UnicodeTranslateError object.

@item 
bpo-19537@footnote{https://bugs.python.org/issue19537}: Fix PyUnicode_DATA() alignment under m68k.  Patch by Andreas
Schwab.

@item 
bpo-20929@footnote{https://bugs.python.org/issue20929}: Add a type cast to avoid shifting a negative number.

@item 
bpo-20731@footnote{https://bugs.python.org/issue20731}: Properly position in source code files even if they are opened
in text mode. Patch by Serhiy Storchaka.

@item 
bpo-20637@footnote{https://bugs.python.org/issue20637}: Key-sharing now also works for instance dictionaries of
subclasses.  Patch by Peter Ingebretson.

@item 
bpo-8297@footnote{https://bugs.python.org/issue8297}: Attributes missing from modules now include the module name in
the error text.  Original patch by ysj.ray.

@item 
bpo-19995@footnote{https://bugs.python.org/issue19995}: %c, %o, %x, and %X now raise TypeError on non-integer input.

@item 
bpo-19655@footnote{https://bugs.python.org/issue19655}: The ASDL parser - used by the build process to generate code
for managing the Python AST in C - was rewritten. The new parser is self
contained and does not require to carry long the spark.py parser-generator
library; spark.py was removed from the source base.

@item 
bpo-12546@footnote{https://bugs.python.org/issue12546}: Allow @code{\x00} to be used as a fill character when using str,
int, float, and complex __format__ methods.

@item 
bpo-20480@footnote{https://bugs.python.org/issue20480}: Add ipaddress.reverse_pointer. Patch by Leon Weber.

@item 
bpo-13598@footnote{https://bugs.python.org/issue13598}: Modify string.Formatter to support auto-numbering of
replacement fields. It now matches the behavior of str.format() in this
regard. Patches by Phil Elson and Ramchandra Apte.

@item 
bpo-8931@footnote{https://bugs.python.org/issue8931}: Make alternate formatting ('#') for type 'c' raise an exception.
In versions prior to 3.5, '#' with 'c' had no effect. Now specifying it is
an error. Patch by Torsten Landschoff.

@item 
bpo-23165@footnote{https://bugs.python.org/issue23165}: Perform overflow checks before allocating memory in the
_Py_char2wchar function.
@end itemize

@node 库<79>,IDLE<47>,核心与内置<65>,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id488}@anchor{1184}
@subsubsection 库



@itemize -

@item 
bpo-23399@footnote{https://bugs.python.org/issue23399}: pyvenv creates relative symlinks where possible.

@item 
bpo-20289@footnote{https://bugs.python.org/issue20289}: cgi.FieldStorage() now supports the context management
protocol.

@item 
bpo-13128@footnote{https://bugs.python.org/issue13128}: Print response headers for CONNECT requests when debuglevel >
0. Patch by Demian Brecht.

@item 
bpo-15381@footnote{https://bugs.python.org/issue15381}: Optimized io.BytesIO to make less allocations and copyings.

@item 
bpo-22818@footnote{https://bugs.python.org/issue22818}: Splitting on a pattern that could match an empty string now
raises a warning.  Patterns that can only match empty strings are now
rejected.

@item 
bpo-23099@footnote{https://bugs.python.org/issue23099}: Closing io.BytesIO with exported buffer is rejected now to
prevent corrupting exported buffer.

@item 
bpo-23326@footnote{https://bugs.python.org/issue23326}: Removed __ne__ implementations.  Since fixing default __ne__
implementation in bpo-21408@footnote{https://bugs.python.org/issue21408} they are redundant.

@item 
bpo-23363@footnote{https://bugs.python.org/issue23363}: Fix possible overflow in itertools.permutations.

@item 
bpo-23364@footnote{https://bugs.python.org/issue23364}: Fix possible overflow in itertools.product.

@item 
bpo-23366@footnote{https://bugs.python.org/issue23366}: Fixed possible integer overflow in itertools.combinations.

@item 
bpo-23369@footnote{https://bugs.python.org/issue23369}: Fixed possible integer overflow in
_json.encode_basestring_ascii.

@item 
bpo-23353@footnote{https://bugs.python.org/issue23353}: Fix the exception handling of generators in
PyEval_EvalFrameEx(). At entry, save or swap the exception state even if
PyEval_EvalFrameEx() is called with throwflag=0. At exit, the exception
state is now always restored or swapped, not only if why is WHY_YIELD or
WHY_RETURN. Patch co-written with Antoine Pitrou.

@item 
bpo-14099@footnote{https://bugs.python.org/issue14099}: Restored support of writing ZIP files to tellable but
non-seekable streams.

@item 
bpo-14099@footnote{https://bugs.python.org/issue14099}: Writing to ZipFile and reading multiple ZipExtFiles is
threadsafe now.

@item 
bpo-19361@footnote{https://bugs.python.org/issue19361}: JSON decoder now raises JSONDecodeError instead of ValueError.

@item 
bpo-18518@footnote{https://bugs.python.org/issue18518}: timeit now rejects statements which can't be compiled outside a
function or a loop (e.g. "return" or "break").

@item 
bpo-23094@footnote{https://bugs.python.org/issue23094}: Fixed readline with frames in Python implementation of pickle.

@item 
bpo-23268@footnote{https://bugs.python.org/issue23268}: Fixed bugs in the comparison of ipaddress classes.

@item 
bpo-21408@footnote{https://bugs.python.org/issue21408}: Removed incorrect implementations of __ne__() which didn't
returned NotImplemented if __eq__() returned NotImplemented.  The default
__ne__() now works correctly.

@item 
bpo-19996@footnote{https://bugs.python.org/issue19996}: @code{email.feedparser.FeedParser} now handles (malformed)
headers with no key rather than assuming the body has started.

@item 
bpo-20188@footnote{https://bugs.python.org/issue20188}: Support Application-Layer Protocol Negotiation (ALPN) in the
ssl module.

@item 
bpo-23133@footnote{https://bugs.python.org/issue23133}: Pickling of ipaddress objects now produces more compact and
portable representation.

@item 
bpo-23248@footnote{https://bugs.python.org/issue23248}: 从最新的OpenSSL git master更新SSL错误代码。

@item 
bpo-23266@footnote{https://bugs.python.org/issue23266}: Much faster implementation of ipaddress.collapse_addresses()
when there are many non-consecutive addresses.

@item 
bpo-23098@footnote{https://bugs.python.org/issue23098}: 64-bit dev_t is now supported in the os module.

@item 
bpo-21817@footnote{https://bugs.python.org/issue21817}: When an exception is raised in a task submitted to a
ProcessPoolExecutor, the remote traceback is now displayed in the parent
process.  Patch by Claudiu Popa.

@item 
bpo-15955@footnote{https://bugs.python.org/issue15955}: Add an option to limit output size when decompressing LZMA
data.  Patch by Nikolaus Rath and Martin Panter.

@item 
bpo-23250@footnote{https://bugs.python.org/issue23250}: In the http.cookies module, capitalize "HttpOnly" and "Secure"
as they are written in the standard.

@item 
bpo-23063@footnote{https://bugs.python.org/issue23063}: In the distutils' check command, fix parsing of reST with code
or code-block directives.

@item 
bpo-23209@footnote{https://bugs.python.org/issue23209}: selectors.BaseSelector.get_key() now raises a RuntimeError if
the selector is closed. And selectors.BaseSelector.close() now clears its
internal reference to the selector mapping to break a reference cycle.
Initial patch written by Martin Richard. (See also: bpo-23225@footnote{https://bugs.python.org/issue23225})

@item 
bpo-17911@footnote{https://bugs.python.org/issue17911}: Provide a way to seed the linecache for a PEP-302 module
without actually loading the code.

@item 
bpo-17911@footnote{https://bugs.python.org/issue17911}: Provide a new object API for traceback, including the ability
to not lookup lines at all until the traceback is actually rendered,
without any trace of the original objects being kept alive.

@item 
bpo-19777@footnote{https://bugs.python.org/issue19777}: Provide a home() classmethod on Path objects.  Contributed by
Victor Salgado and Mayank Tripathi.

@item 
bpo-23206@footnote{https://bugs.python.org/issue23206}: Make @code{json.dumps(..., ensure_ascii=False)} as fast as the
default case of @code{ensure_ascii=True}.  Patch by Naoki Inada.

@item 
bpo-23185@footnote{https://bugs.python.org/issue23185}: Add math.inf and math.nan constants.

@item 
bpo-23186@footnote{https://bugs.python.org/issue23186}: Add ssl.SSLObject.shared_ciphers() and
ssl.SSLSocket.shared_ciphers() to fetch the client's list ciphers sent at
handshake.

@item 
bpo-23143@footnote{https://bugs.python.org/issue23143}: Remove compatibility with OpenSSLs older than 0.9.8.

@item 
bpo-23132@footnote{https://bugs.python.org/issue23132}: Improve performance and introspection support of comparison
methods created by functool.total_ordering.

@item 
bpo-19776@footnote{https://bugs.python.org/issue19776}: Add an expanduser() method on Path objects.

@item 
bpo-23112@footnote{https://bugs.python.org/issue23112}: Fix SimpleHTTPServer to correctly carry the query string and
fragment when it redirects to add a trailing slash.

@item 
bpo-21793@footnote{https://bugs.python.org/issue21793}: Added http.HTTPStatus enums (i.e. HTTPStatus.OK,
HTTPStatus.NOT_FOUND). Patch by Demian Brecht.

@item 
bpo-23093@footnote{https://bugs.python.org/issue23093}: In the io, module allow more operations to work on detached
streams.

@item 
bpo-23111@footnote{https://bugs.python.org/issue23111}: In the ftplib, make ssl.PROTOCOL_SSLv23 the default protocol
version.

@item 
bpo-22585@footnote{https://bugs.python.org/issue22585}: On OpenBSD 5.6 and newer, os.urandom() now calls getentropy(),
instead of reading /dev/urandom, to get pseudo-random bytes.

@item 
bpo-19104@footnote{https://bugs.python.org/issue19104}: pprint now produces evaluable output for wrapped strings.

@item 
bpo-23071@footnote{https://bugs.python.org/issue23071}: Added missing names to codecs.__all__.  Patch by Martin Panter.

@item 
bpo-22783@footnote{https://bugs.python.org/issue22783}: Pickling now uses the NEWOBJ opcode instead of the NEWOBJ_EX
opcode if possible.

@item 
bpo-15513@footnote{https://bugs.python.org/issue15513}: Added a __sizeof__ implementation for pickle classes.

@item 
bpo-19858@footnote{https://bugs.python.org/issue19858}: pickletools.optimize() now aware of the MEMOIZE opcode, can
produce more compact result and no longer produces invalid output if input
data contains MEMOIZE opcodes together with PUT or BINPUT opcodes.

@item 
bpo-22095@footnote{https://bugs.python.org/issue22095}: Fixed HTTPConnection.set_tunnel with default port.  The port
value in the host header was set to "None".  Patch by Demian Brecht.

@item 
bpo-23016@footnote{https://bugs.python.org/issue23016}: A warning no longer produces an AttributeError when the program
is run with pythonw.exe.

@item 
bpo-21775@footnote{https://bugs.python.org/issue21775}: shutil.copytree(): fix crash when copying to VFAT. An exception
handler assumed that OSError objects always have a 'winerror' attribute.
That is not the case, so the exception handler itself raised
AttributeError when run on Linux (and, presumably, any other non-Windows
OS). Patch by Greg Ward.

@item 
bpo-1218234@footnote{https://bugs.python.org/issue1218234}: Fix inspect.getsource() to load updated source of reloaded
module. Initial patch by Berker Peksag.

@item 
bpo-21740@footnote{https://bugs.python.org/issue21740}: Support wrapped callables in doctest. Patch by Claudiu Popa.

@item 
bpo-23009@footnote{https://bugs.python.org/issue23009}: Make sure selectors.EpollSelector.select() works when no FD is
registered.

@item 
bpo-22959@footnote{https://bugs.python.org/issue22959}: In the constructor of http.client.HTTPSConnection, prefer the
context's check_hostname attribute over the @emph{check_hostname} parameter.

@item 
bpo-22696@footnote{https://bugs.python.org/issue22696}: Add function @ref{75c,,sys.is_finalizing()} to know about
interpreter shutdown.

@item 
bpo-16043@footnote{https://bugs.python.org/issue16043}: Add a default limit for the amount of data
xmlrpclib.gzip_decode will return. This resolves CVE-2013-1753.

@item 
bpo-14099@footnote{https://bugs.python.org/issue14099}: ZipFile.open() no longer reopen the underlying file.  Objects
returned by ZipFile.open() can now operate independently of the ZipFile
even if the ZipFile was created by passing in a file-like object as the
first argument to the constructor.

@item 
bpo-22966@footnote{https://bugs.python.org/issue22966}: Fix __pycache__ pyc file name clobber when pyc_compile is asked
to compile a source file containing multiple dots in the source file name.

@item 
bpo-21971@footnote{https://bugs.python.org/issue21971}: Update turtledemo doc and add module to the index.

@item 
bpo-21032@footnote{https://bugs.python.org/issue21032}: Fixed socket leak if HTTPConnection.getresponse() fails.
Original patch by Martin Panter.

@item 
bpo-22407@footnote{https://bugs.python.org/issue22407}: Deprecated the use of re.LOCALE flag with str patterns or
re.ASCII. It was newer worked.

@item 
bpo-22902@footnote{https://bugs.python.org/issue22902}: The "ip" command is now used on Linux to determine MAC address
in uuid.getnode().  Pach by Bruno Cauet.

@item 
bpo-22960@footnote{https://bugs.python.org/issue22960}: Add a context argument to xmlrpclib.ServerProxy constructor.

@item 
bpo-22389@footnote{https://bugs.python.org/issue22389}: Add contextlib.redirect_stderr().

@item 
bpo-21356@footnote{https://bugs.python.org/issue21356}: Make ssl.RAND_egd() optional to support LibreSSL. The
availability of the function is checked during the compilation. Patch
written by Bernard Spil.

@item 
bpo-22915@footnote{https://bugs.python.org/issue22915}: SAX parser now supports files opened with file descriptor or
bytes path.

@item 
bpo-22609@footnote{https://bugs.python.org/issue22609}: Constructors and update methods of mapping classes in the
collections module now accept the self keyword argument.

@item 
bpo-22940@footnote{https://bugs.python.org/issue22940}: Add readline.append_history_file.

@item 
bpo-19676@footnote{https://bugs.python.org/issue19676}: Added the "namereplace" error handler.

@item 
bpo-22788@footnote{https://bugs.python.org/issue22788}: Add @emph{context} parameter to logging.handlers.HTTPHandler.

@item 
bpo-22921@footnote{https://bugs.python.org/issue22921}: Allow SSLContext to take the @emph{hostname} parameter even if
OpenSSL doesn't support SNI.

@item 
bpo-22894@footnote{https://bugs.python.org/issue22894}: TestCase.subTest() would cause the test suite to be stopped
when in failfast mode, even in the absence of failures.

@item 
bpo-22796@footnote{https://bugs.python.org/issue22796}: HTTP cookie parsing is now stricter, in order to protect
against potential injection attacks.

@item 
bpo-22370@footnote{https://bugs.python.org/issue22370}: Windows detection in pathlib is now more robust.

@item 
bpo-22841@footnote{https://bugs.python.org/issue22841}: Reject coroutines in asyncio add_signal_handler(). Patch by
Ludovic.Gasc.

@item 
bpo-19494@footnote{https://bugs.python.org/issue19494}: Added urllib.request.HTTPBasicPriorAuthHandler. Patch by Matej
Cepl.

@item 
bpo-22578@footnote{https://bugs.python.org/issue22578}: Added attributes to the re.error class.

@item 
bpo-22849@footnote{https://bugs.python.org/issue22849}: Fix possible double free in the io.TextIOWrapper constructor.

@item 
bpo-12728@footnote{https://bugs.python.org/issue12728}: Different Unicode characters having the same uppercase but
different lowercase are now matched in case-insensitive regular
expressions.

@item 
bpo-22821@footnote{https://bugs.python.org/issue22821}: Fixed fcntl() with integer argument on 64-bit big-endian
platforms.

@item 
bpo-21650@footnote{https://bugs.python.org/issue21650}: Add an @code{--sort-keys} option to json.tool CLI.

@item 
bpo-22824@footnote{https://bugs.python.org/issue22824}: Updated reprlib output format for sets to use set literals.
Patch contributed by Berker Peksag.

@item 
bpo-22824@footnote{https://bugs.python.org/issue22824}: Updated reprlib output format for arrays to display empty
arrays without an unnecessary empty list.  Suggested by Serhiy Storchaka.

@item 
bpo-22406@footnote{https://bugs.python.org/issue22406}: Fixed the uu_codec codec incorrectly ported to 3.x. Based on
patch by Martin Panter.

@item 
bpo-17293@footnote{https://bugs.python.org/issue17293}: uuid.getnode() now determines MAC address on AIX using netstat.
Based on patch by Aivars Kalvāns.

@item 
bpo-22769@footnote{https://bugs.python.org/issue22769}: Fixed ttk.Treeview.tag_has() when called without arguments.

@item 
bpo-22417@footnote{https://bugs.python.org/issue22417}: Verify certificates by default in httplib (PEP 476).

@item 
bpo-22775@footnote{https://bugs.python.org/issue22775}: Fixed unpickling of http.cookies.SimpleCookie with protocol 2
and above. Patch by Tim Graham.

@item 
bpo-22776@footnote{https://bugs.python.org/issue22776}: Brought excluded code into the scope of a try block in
SysLogHandler.emit().

@item 
bpo-22665@footnote{https://bugs.python.org/issue22665}: Add missing get_terminal_size and SameFileError to
shutil.__all__.

@item 
bpo-6623@footnote{https://bugs.python.org/issue6623}: Remove deprecated Netrc class in the ftplib module. Patch by
Matt Chaput.

@item 
bpo-17381@footnote{https://bugs.python.org/issue17381}: Fixed handling of case-insensitive ranges in regular
expressions.

@item 
bpo-22410@footnote{https://bugs.python.org/issue22410}: Module level functions in the re module now cache compiled
locale-dependent regular expressions taking into account the locale.

@item 
bpo-22759@footnote{https://bugs.python.org/issue22759}: Query methods on pathlib.Path() (exists(), is_dir(), etc.) now
return False when the underlying stat call raises NotADirectoryError.

@item 
bpo-8876@footnote{https://bugs.python.org/issue8876}: distutils now falls back to copying files when hard linking
doesn't work. This allows use with special filesystems such as VirtualBox
shared folders.

@item 
bpo-22217@footnote{https://bugs.python.org/issue22217}: Implemented reprs of classes in the zipfile module.

@item 
bpo-22457@footnote{https://bugs.python.org/issue22457}: Honour load_tests in the start_dir of discovery.

@item 
bpo-18216@footnote{https://bugs.python.org/issue18216}: gettext now raises an error when a .mo file has an unsupported
major version number.  Patch by Aaron Hill.

@item 
bpo-13918@footnote{https://bugs.python.org/issue13918}: Provide a locale.delocalize() function which can remove
locale-specific number formatting from a string representing a number,
without then converting it to a specific type.  Patch by Cédric Krier.

@item 
bpo-22676@footnote{https://bugs.python.org/issue22676}: Make the pickling of global objects which don't have a
__module__ attribute less slow.

@item 
bpo-18853@footnote{https://bugs.python.org/issue18853}: Fixed ResourceWarning in shlex.__nain__.

@item 
bpo-9351@footnote{https://bugs.python.org/issue9351}: Defaults set with set_defaults on an argparse subparser are no
longer ignored when also set on the parent parser.

@item 
bpo-7559@footnote{https://bugs.python.org/issue7559}: unittest test loading ImportErrors are reported as import errors
with their import exception rather than as attribute errors after the
import has already failed.

@item 
bpo-19746@footnote{https://bugs.python.org/issue19746}: Make it possible to examine the errors from unittest discovery
without executing the test suite. The new @code{errors} attribute on TestLoader
exposes these non-fatal errors encountered during discovery.

@item 
bpo-21991@footnote{https://bugs.python.org/issue21991}: Make email.headerregistry's header 'params' attributes be
read-only (MappingProxyType).  Previously the dictionary was modifiable
but a new one was created on each access of the attribute.

@item 
bpo-22638@footnote{https://bugs.python.org/issue22638}: SSLv3 is now disabled throughout the standard library. It can
still be enabled by instantiating a SSLContext manually.

@item 
bpo-22641@footnote{https://bugs.python.org/issue22641}: In asyncio, the default SSL context for client connections is
now created using ssl.create_default_context(), for stronger security.

@item 
bpo-17401@footnote{https://bugs.python.org/issue17401}: Include closefd in io.FileIO repr.

@item 
bpo-21338@footnote{https://bugs.python.org/issue21338}: Add silent mode for compileall. quiet parameters of
compile_@{dir, file, path@} functions now have a multilevel value. Also, -q
option of the CLI now have a multilevel value. Patch by Thomas Kluyver.

@item 
bpo-20152@footnote{https://bugs.python.org/issue20152}: Convert the array and cmath modules to Argument Clinic.

@item 
bpo-18643@footnote{https://bugs.python.org/issue18643}: Add socket.socketpair() on Windows.

@item 
bpo-22435@footnote{https://bugs.python.org/issue22435}: Fix a file descriptor leak when socketserver bind fails.

@item 
bpo-13096@footnote{https://bugs.python.org/issue13096}: Fixed segfault in CTypes POINTER handling of large values.

@item 
bpo-11694@footnote{https://bugs.python.org/issue11694}: Raise ConversionError in xdrlib as documented.  Patch by Filip
Gruszczyński and Claudiu Popa.

@item 
bpo-19380@footnote{https://bugs.python.org/issue19380}: Optimized parsing of regular expressions.

@item 
bpo-1519638@footnote{https://bugs.python.org/issue1519638}: Now unmatched groups are replaced with empty strings in
re.sub() and re.subn().

@item 
bpo-18615@footnote{https://bugs.python.org/issue18615}: sndhdr.what/whathdr now return a namedtuple.

@item 
bpo-22462@footnote{https://bugs.python.org/issue22462}: Fix pyexpat's creation of a dummy frame to make it appear in
exception tracebacks.

@item 
bpo-21965@footnote{https://bugs.python.org/issue21965}: Add support for in-memory SSL to the ssl module.  Patch by
Geert Jansen.

@item 
bpo-21173@footnote{https://bugs.python.org/issue21173}: Fix len() on a WeakKeyDictionary when .clear() was called with
an iterator alive.

@item 
bpo-11866@footnote{https://bugs.python.org/issue11866}: Eliminated race condition in the computation of names for new
threads.

@item 
bpo-21905@footnote{https://bugs.python.org/issue21905}: Avoid RuntimeError in pickle.whichmodule() when sys.modules is
mutated while iterating.  Patch by Olivier Grisel.

@item 
bpo-11271@footnote{https://bugs.python.org/issue11271}: concurrent.futures.Executor.map() now takes a @emph{chunksize}
argument to allow batching of tasks in child processes and improve
performance of ProcessPoolExecutor.  Patch by Dan O'Reilly.

@item 
bpo-21883@footnote{https://bugs.python.org/issue21883}: os.path.join() and os.path.relpath() now raise a TypeError with
more helpful error message for unsupported or mismatched types of
arguments.

@item 
bpo-22219@footnote{https://bugs.python.org/issue22219}: The zipfile module CLI now adds entries for directories
(including empty directories) in ZIP file.

@item 
bpo-22449@footnote{https://bugs.python.org/issue22449}: In the ssl.SSLContext.load_default_certs, consult the
environmental variables SSL_CERT_DIR and SSL_CERT_FILE on Windows.

@item 
bpo-22508@footnote{https://bugs.python.org/issue22508}: The email.__version__ variable has been removed; the email code
is no longer shipped separately from the stdlib, and __version__ hasn't
been updated in several releases.

@item 
bpo-20076@footnote{https://bugs.python.org/issue20076}: Added non derived UTF-8 aliases to locale aliases table.

@item 
bpo-20079@footnote{https://bugs.python.org/issue20079}: Added locales supported in glibc 2.18 to locale alias table.

@item 
bpo-20218@footnote{https://bugs.python.org/issue20218}: Added convenience methods read_text/write_text and read_bytes/
write_bytes to pathlib.Path objects.

@item 
bpo-22396@footnote{https://bugs.python.org/issue22396}: On 32-bit AIX platform, don't expose os.posix_fadvise() nor
os.posix_fallocate() because their prototypes in system headers are wrong.

@item 
bpo-22517@footnote{https://bugs.python.org/issue22517}: When an io.BufferedRWPair object is deallocated, clear its
weakrefs.

@item 
bpo-22437@footnote{https://bugs.python.org/issue22437}: Number of capturing groups in regular expression is no longer
limited by 100.

@item 
bpo-17442@footnote{https://bugs.python.org/issue17442}: InteractiveInterpreter now displays the full chained traceback
in its showtraceback method, to match the built in interactive
interpreter.

@item 
bpo-23392@footnote{https://bugs.python.org/issue23392}: Added tests for marshal C API that works with FILE*.

@item 
bpo-10510@footnote{https://bugs.python.org/issue10510}: distutils register and upload methods now use HTML standards
compliant CRLF line endings.

@item 
bpo-9850@footnote{https://bugs.python.org/issue9850}: Fixed macpath.join() for empty first component.  Patch by Oleg
Oshmyan.

@item 
bpo-5309@footnote{https://bugs.python.org/issue5309}: distutils' build and build_ext commands now accept a @code{-j}
option to enable parallel building of extension modules.

@item 
bpo-22448@footnote{https://bugs.python.org/issue22448}: Improve canceled timer handles cleanup to prevent unbound
memory usage. Patch by Joshua Moore-Oliva.

@item 
bpo-22427@footnote{https://bugs.python.org/issue22427}: TemporaryDirectory no longer attempts to clean up twice when
used in the with statement in generator.

@item 
bpo-22362@footnote{https://bugs.python.org/issue22362}: Forbidden ambiguous octal escapes out of range 0-0o377 in
regular expressions.

@item 
bpo-20912@footnote{https://bugs.python.org/issue20912}: Now directories added to ZIP file have correct Unix and MS-DOS
directory attributes.

@item 
bpo-21866@footnote{https://bugs.python.org/issue21866}: ZipFile.close() no longer writes ZIP64 central directory
records if allowZip64 is false.

@item 
bpo-22278@footnote{https://bugs.python.org/issue22278}: Fix urljoin problem with relative urls, a regression observed
after changes to issue22118 were submitted.

@item 
bpo-22415@footnote{https://bugs.python.org/issue22415}: Fixed debugging output of the GROUPREF_EXISTS opcode in the re
module. Removed trailing spaces in debugging output.

@item 
bpo-22423@footnote{https://bugs.python.org/issue22423}: Unhandled exception in thread no longer causes unhandled
AttributeError when sys.stderr is None.

@item 
bpo-21332@footnote{https://bugs.python.org/issue21332}: Ensure that @code{bufsize=1} in subprocess.Popen() selects line
buffering, rather than block buffering.  Patch by Akira Li.

@item 
bpo-21091@footnote{https://bugs.python.org/issue21091}: Fix API bug: email.message.EmailMessage.is_attachment is now a
method.

@item 
bpo-21079@footnote{https://bugs.python.org/issue21079}: Fix email.message.EmailMessage.is_attachment to return the
correct result when the header has parameters as well as a value.

@item 
bpo-22247@footnote{https://bugs.python.org/issue22247}: Add NNTPError to nntplib.__all__.

@item 
bpo-22366@footnote{https://bugs.python.org/issue22366}: urllib.request.urlopen will accept a context object
(SSLContext) as an argument which will then be used for HTTPS connection.
Patch by Alex Gaynor.

@item 
bpo-4180@footnote{https://bugs.python.org/issue4180}: The warnings registries are now reset when the filters are
modified.

@item 
bpo-22419@footnote{https://bugs.python.org/issue22419}: Limit the length of incoming HTTP request in wsgiref server to
65536 bytes and send a 414 error code for higher lengths. Patch
contributed by Devin Cook.

@item 
Lax cookie parsing in http.cookies could be a security issue when combined
with non-standard cookie handling in some Web browsers.  Reported by
Sergey Bobrov.

@item 
bpo-20537@footnote{https://bugs.python.org/issue20537}: logging methods now accept an exception instance as well as a
Boolean value or exception tuple. Thanks to Yury Selivanov for the patch.

@item 
bpo-22384@footnote{https://bugs.python.org/issue22384}: An exception in Tkinter callback no longer crashes the program
when it is run with pythonw.exe.

@item 
bpo-22168@footnote{https://bugs.python.org/issue22168}: Prevent turtle AttributeError with non-default Canvas on OS X.

@item 
bpo-21147@footnote{https://bugs.python.org/issue21147}: sqlite3 now raises an exception if the request contains a null
character instead of truncating it.  Based on patch by Victor Stinner.

@item 
bpo-13968@footnote{https://bugs.python.org/issue13968}: The glob module now supports recursive search in subdirectories
using the @code{**} pattern.

@item 
bpo-21951@footnote{https://bugs.python.org/issue21951}: Fixed a crash in Tkinter on AIX when called Tcl command with
empty string or tuple argument.

@item 
bpo-21951@footnote{https://bugs.python.org/issue21951}: Tkinter now most likely raises MemoryError instead of crash if
the memory allocation fails.

@item 
bpo-22338@footnote{https://bugs.python.org/issue22338}: Fix a crash in the json module on memory allocation failure.

@item 
bpo-12410@footnote{https://bugs.python.org/issue12410}: imaplib.IMAP4 now supports the context management protocol.
Original patch by Tarek Ziadé.

@item 
bpo-21270@footnote{https://bugs.python.org/issue21270}: We now override tuple methods in mock.call objects so that they
can be used as normal call attributes.

@item 
bpo-16662@footnote{https://bugs.python.org/issue16662}: load_tests() is now unconditionally run when it is present in a
package's __init__.py.  TestLoader.loadTestsFromModule() still accepts
use_load_tests, but it is deprecated and ignored.  A new keyword-only
attribute @code{pattern} is added and documented.  Patch given by Robert
Collins, tweaked by Barry Warsaw.

@item 
bpo-22226@footnote{https://bugs.python.org/issue22226}: First letter no longer is stripped from the "status" key in the
result of Treeview.heading().

@item 
bpo-19524@footnote{https://bugs.python.org/issue19524}: Fixed resource leak in the HTTP connection when an invalid
response is received.  Patch by Martin Panter.

@item 
bpo-20421@footnote{https://bugs.python.org/issue20421}: Add a .version() method to SSL sockets exposing the actual
protocol version in use.

@item 
bpo-19546@footnote{https://bugs.python.org/issue19546}: configparser exceptions no longer expose implementation
details. Chained KeyErrors are removed, which leads to cleaner tracebacks.
Patch by Claudiu Popa.

@item 
bpo-22051@footnote{https://bugs.python.org/issue22051}: turtledemo no longer reloads examples to re-run them.
Initialization of variables and gui setup should be done in main(), which
is called each time a demo is run, but not on import.

@item 
bpo-21933@footnote{https://bugs.python.org/issue21933}: Turtledemo users can change the code font size with a menu
selection or control(command) '-' or '+' or control-mousewheel. Original
patch by Lita Cho.

@item 
bpo-21597@footnote{https://bugs.python.org/issue21597}: The separator between the turtledemo text pane and the drawing
canvas can now be grabbed and dragged with a mouse.  The code text pane
can be widened to easily view or copy the full width of the text.  The
canvas can be widened on small screens.  Original patches by Jan Kanis and
Lita Cho.

@item 
bpo-18132@footnote{https://bugs.python.org/issue18132}: Turtledemo buttons no longer disappear when the window is
shrunk.  Original patches by Jan Kanis and Lita Cho.

@item 
bpo-22043@footnote{https://bugs.python.org/issue22043}: time.monotonic() is now always available.
@code{threading.Lock.acquire()}, @code{threading.RLock.acquire()} and socket
operations now use a monotonic clock, instead of the system clock, when a
timeout is used.

@item 
bpo-21527@footnote{https://bugs.python.org/issue21527}: Add a default number of workers to ThreadPoolExecutor equal to
5 times the number of CPUs.  Patch by Claudiu Popa.

@item 
bpo-22216@footnote{https://bugs.python.org/issue22216}: smtplib now resets its state more completely after a quit.  The
most obvious consequence of the previous behavior was a STARTTLS failure
during a connect/starttls/quit/connect/starttls sequence.

@item 
bpo-22098@footnote{https://bugs.python.org/issue22098}: ctypes' BigEndianStructure and LittleEndianStructure now define
an empty __slots__ so that subclasses don't always get an instance dict.
Patch by Claudiu Popa.

@item 
bpo-22185@footnote{https://bugs.python.org/issue22185}: Fix an occasional RuntimeError in threading.Condition.wait()
caused by mutation of the waiters queue without holding the lock.  Patch
by Doug Zongker.

@item 
bpo-22287@footnote{https://bugs.python.org/issue22287}: On UNIX, _PyTime_gettimeofday() now uses
clock_gettime(CLOCK_REALTIME) if available. As a side effect, Python now
depends on the librt library on Solaris and on Linux (only with glibc
older than 2.17).

@item 
bpo-22182@footnote{https://bugs.python.org/issue22182}: Use e.args to unpack exceptions correctly in
distutils.file_util.move_file. Patch by Claudiu Popa.

@item 
The webbrowser module now uses subprocess's start_new_session=True rather
than a potentially risky preexec_fn=os.setsid call.

@item 
bpo-22042@footnote{https://bugs.python.org/issue22042}: signal.set_wakeup_fd(fd) now raises an exception if the file
descriptor is in blocking mode.

@item 
bpo-16808@footnote{https://bugs.python.org/issue16808}: inspect.stack() now returns a named tuple instead of a tuple.
Patch by Daniel Shahaf.

@item 
bpo-22236@footnote{https://bugs.python.org/issue22236}: Fixed Tkinter images copying operations in NoDefaultRoot mode.

@item 
bpo-2527@footnote{https://bugs.python.org/issue2527}: Add a @emph{globals} argument to timeit functions, in order to
override the globals namespace in which the timed code is executed. Patch
by Ben Roberts.

@item 
bpo-22118@footnote{https://bugs.python.org/issue22118}: Switch urllib.parse to use RFC 3986 semantics for the
resolution of relative URLs, rather than RFCs 1808 and 2396. Patch by
Demian Brecht.

@item 
bpo-21549@footnote{https://bugs.python.org/issue21549}: Added the "members" parameter to TarFile.list().

@item 
bpo-19628@footnote{https://bugs.python.org/issue19628}: Allow compileall recursion depth to be specified with a -r
option.

@item 
bpo-15696@footnote{https://bugs.python.org/issue15696}: Add a __sizeof__ implementation for mmap objects on Windows.

@item 
bpo-22068@footnote{https://bugs.python.org/issue22068}: Avoided reference loops with Variables and Fonts in Tkinter.

@item 
bpo-22165@footnote{https://bugs.python.org/issue22165}: SimpleHTTPRequestHandler now supports undecodable file names.

@item 
bpo-15381@footnote{https://bugs.python.org/issue15381}: Optimized line reading in io.BytesIO.

@item 
bpo-8797@footnote{https://bugs.python.org/issue8797}: Raise HTTPError on failed Basic Authentication immediately.
Initial patch by Sam Bull.

@item 
bpo-20729@footnote{https://bugs.python.org/issue20729}: Restored the use of lazy iterkeys()/itervalues()/iteritems() in
the mailbox module.

@item 
bpo-21448@footnote{https://bugs.python.org/issue21448}: Changed FeedParser feed() to avoid O(N**2) behavior when
parsing long line. Original patch by Raymond Hettinger.

@item 
bpo-22184@footnote{https://bugs.python.org/issue22184}: The functools LRU Cache decorator factory now gives an earlier
and clearer error message when the user forgets the required parameters.

@item 
bpo-17923@footnote{https://bugs.python.org/issue17923}: glob() patterns ending with a slash no longer match non-dirs on
AIX.  Based on patch by Delhallt.

@item 
bpo-21725@footnote{https://bugs.python.org/issue21725}: Added support for RFC 6531 (SMTPUTF8) in smtpd.

@item 
bpo-22176@footnote{https://bugs.python.org/issue22176}: Update the ctypes module's libffi to v3.1.  This release adds
support for the Linux AArch64 and POWERPC ELF ABIv2 little endian
architectures.

@item 
bpo-5411@footnote{https://bugs.python.org/issue5411}: Added support for the "xztar" format in the shutil module.

@item 
bpo-21121@footnote{https://bugs.python.org/issue21121}: Don't force 3rd party C extensions to be built with
-Werror=declaration-after-statement.

@item 
bpo-21975@footnote{https://bugs.python.org/issue21975}: Fixed crash when using uninitialized sqlite3.Row (in particular
when unpickling pickled sqlite3.Row).  sqlite3.Row is now initialized in
the __new__() method.

@item 
bpo-20170@footnote{https://bugs.python.org/issue20170}: Convert posixmodule to use Argument Clinic.

@item 
bpo-21539@footnote{https://bugs.python.org/issue21539}: Add an @emph{exists_ok} argument to @code{Pathlib.mkdir()} to mimic
@code{mkdir -p} and @ref{3b5,,os.makedirs()} functionality.  When true, ignore
FileExistsErrors.  Patch by Berker Peksag.

@item 
bpo-22127@footnote{https://bugs.python.org/issue22127}: Bypass IDNA for pure-ASCII host names in the socket module (in
particular for numeric IPs).

@item 
bpo-21047@footnote{https://bugs.python.org/issue21047}: set the default value for the @emph{convert_charrefs} argument of
HTMLParser to True.  Patch by Berker Peksag.

@item 
在 html.entities 包中增加 __all__ 变量。

@item 
bpo-15114@footnote{https://bugs.python.org/issue15114}: the strict mode and argument of HTMLParser, HTMLParser.error,
and the HTMLParserError exception have been removed.

@item 
bpo-22085@footnote{https://bugs.python.org/issue22085}: 在 Tkinter 中删除了对 TK 8.3 的支持。

@item 
bpo-21580@footnote{https://bugs.python.org/issue21580}: Now Tkinter correctly handles bytes arguments passed to Tk. In
particular this allows initializing images from binary data.

@item 
bpo-22003@footnote{https://bugs.python.org/issue22003}: When initialized from a bytes object, io.BytesIO() now defers
making a copy until it is mutated, improving performance and memory use on
some use cases. Patch by David Wilson.

@item 
bpo-22018@footnote{https://bugs.python.org/issue22018}: On Windows, signal.set_wakeup_fd() now also supports sockets. A
side effect is that Python depends to the WinSock library.

@item 
bpo-22054@footnote{https://bugs.python.org/issue22054}: Add os.get_blocking() and os.set_blocking() functions to get
and set the blocking mode of a file descriptor (False if the O_NONBLOCK
flag is set, True otherwise). These functions are not available on
Windows.

@item 
bpo-17172@footnote{https://bugs.python.org/issue17172}: Make turtledemo start as active on OS X even when run with
subprocess. Patch by Lita Cho.

@item 
bpo-21704@footnote{https://bugs.python.org/issue21704}: Fix build error for _multiprocessing when semaphores are not
available. Patch by Arfrever Frehtes Taifersar Arahesis.

@item 
bpo-20173@footnote{https://bugs.python.org/issue20173}: Convert sha1, sha256, sha512 and md5 to ArgumentClinic. Patch
by Vajrasky Kok.

@item 
Fix repr(_socket.socket) on Windows 64-bit: don't fail with OverflowError
on closed socket. repr(socket.socket) already works fine.

@item 
bpo-22033@footnote{https://bugs.python.org/issue22033}: Reprs of most Python implemented classes now contain actual
class name instead of hardcoded one.

@item 
bpo-21947@footnote{https://bugs.python.org/issue21947}: The dis module can now disassemble generator-iterator objects
based on their gi_code attribute. Patch by Clement Rouault.

@item 
bpo-16133@footnote{https://bugs.python.org/issue16133}: The asynchat.async_chat.handle_read() method now ignores
BlockingIOError exceptions.

@item 
bpo-22044@footnote{https://bugs.python.org/issue22044}: Fixed premature DECREF in call_tzinfo_method. Patch by Tom
Flanagan.

@item 
bpo-19884@footnote{https://bugs.python.org/issue19884}: readline: Disable the meta modifier key if stdout is not a
terminal to not write the ANSI sequence @code{"\033[1034h"} into stdout. This
sequence is used on some terminal (ex: TERM=xterm-256color") to enable
support of 8 bit characters.

@item 
bpo-4350@footnote{https://bugs.python.org/issue4350}: Removed a number of out-of-dated and non-working for a long time
Tkinter methods.

@item 
bpo-6167@footnote{https://bugs.python.org/issue6167}: Scrollbar.activate() now returns the name of active element if
the argument is not specified.  Scrollbar.set() now always accepts only 2
arguments.

@item 
bpo-15275@footnote{https://bugs.python.org/issue15275}: Clean up and speed up the ntpath module.

@item 
bpo-21888@footnote{https://bugs.python.org/issue21888}: plistlib's load() and loads() now work if the fmt parameter is
specified.

@item 
bpo-22032@footnote{https://bugs.python.org/issue22032}: __qualname__ instead of __name__ is now always used to format
fully qualified class names of Python implemented classes.

@item 
bpo-22031@footnote{https://bugs.python.org/issue22031}: Reprs now always use hexadecimal format with the "0x" prefix
when contain an id in form " at 0x...".

@item 
bpo-22018@footnote{https://bugs.python.org/issue22018}: signal.set_wakeup_fd() now raises an OSError instead of a
ValueError on @code{fstat()} failure.

@item 
bpo-21044@footnote{https://bugs.python.org/issue21044}: tarfile.open() now handles fileobj with an integer 'name'
attribute.  Based on patch by Antoine Pietri.

@item 
bpo-21966@footnote{https://bugs.python.org/issue21966}: Respect -q command-line option when code module is ran.

@item 
bpo-19076@footnote{https://bugs.python.org/issue19076}: Don't pass the redundant 'file' argument to self.error().

@item 
bpo-16382@footnote{https://bugs.python.org/issue16382}: Improve exception message of warnings.warn() for bad category.
Initial patch by Phil Elson.

@item 
bpo-21932@footnote{https://bugs.python.org/issue21932}: os.read() now uses a @code{Py_ssize_t()} type instead of
@code{int} for the size to support reading more than 2 GB at once. On
Windows, the size is truncated to INT_MAX. As any call to os.read(), the
OS may read less bytes than the number of requested bytes.

@item 
bpo-21942@footnote{https://bugs.python.org/issue21942}: Fixed source file viewing in pydoc's server mode on Windows.

@item 
bpo-11259@footnote{https://bugs.python.org/issue11259}: asynchat.async_chat().set_terminator() now raises a ValueError
if the number of received bytes is negative.

@item 
bpo-12523@footnote{https://bugs.python.org/issue12523}: asynchat.async_chat.push() now raises a TypeError if it doesn't
get a bytes string

@item 
bpo-21707@footnote{https://bugs.python.org/issue21707}: Add missing kwonlyargcount argument to
ModuleFinder.replace_paths_in_code().

@item 
bpo-20639@footnote{https://bugs.python.org/issue20639}: calling Path.with_suffix('@w{'}) allows removing the suffix again.
Patch by July Tikhonov.

@item 
bpo-21714@footnote{https://bugs.python.org/issue21714}: Disallow the construction of invalid paths using
Path.with_name().  Original patch by Antony Lee.

@item 
bpo-15014@footnote{https://bugs.python.org/issue15014}: Added 'auth' method to smtplib to make implementing auth
mechanisms simpler, and used it internally in the login method.

@item 
bpo-21151@footnote{https://bugs.python.org/issue21151}: Fixed a segfault in the winreg module when @code{None} is passed
as a @code{REG_BINARY} value to SetValueEx.  Patch by John Ehresman.

@item 
bpo-21090@footnote{https://bugs.python.org/issue21090}: io.FileIO.readall() does not ignore I/O errors anymore. Before,
it ignored I/O errors if at least the first C call read() succeed.

@item 
bpo-5800@footnote{https://bugs.python.org/issue5800}: headers parameter of wsgiref.headers.Headers is now optional.
Initial patch by Pablo Torres Navarrete and SilentGhost.

@item 
bpo-21781@footnote{https://bugs.python.org/issue21781}: ssl.RAND_add() now supports strings longer than 2 GB.

@item 
bpo-21679@footnote{https://bugs.python.org/issue21679}: Prevent extraneous fstat() calls during open().  Patch by
Bohuslav Kabrda.

@item 
bpo-21863@footnote{https://bugs.python.org/issue21863}: cProfile now displays the module name of C extension functions,
in addition to their own name.

@item 
bpo-11453@footnote{https://bugs.python.org/issue11453}: asyncore: emit a ResourceWarning when an unclosed file_wrapper
object is destroyed. The destructor now closes the file if needed. The
close() method can now be called twice: the second call does nothing.

@item 
bpo-21858@footnote{https://bugs.python.org/issue21858}: Better handling of Python exceptions in the sqlite3 module.

@item 
bpo-21476@footnote{https://bugs.python.org/issue21476}: Make sure the email.parser.BytesParser TextIOWrapper is
discarded after parsing, so the input file isn't unexpectedly closed.

@item 
bpo-20295@footnote{https://bugs.python.org/issue20295}: imghdr now recognizes OpenEXR format images.

@item 
bpo-21729@footnote{https://bugs.python.org/issue21729}: Used the "with" statement in the dbm.dumb module to ensure
files closing. Patch by Claudiu Popa.

@item 
bpo-21491@footnote{https://bugs.python.org/issue21491}: socketserver: Fix a race condition in child processes reaping.

@item 
bpo-21719@footnote{https://bugs.python.org/issue21719}: Added the @code{st_file_attributes} field to os.stat_result on
Windows.

@item 
bpo-21832@footnote{https://bugs.python.org/issue21832}: Require named tuple inputs to be exact strings.

@item 
bpo-21722@footnote{https://bugs.python.org/issue21722}: The distutils "upload" command now exits with a non-zero return
code when uploading fails.  Patch by Martin Dengler.

@item 
bpo-21723@footnote{https://bugs.python.org/issue21723}: asyncio.Queue: support any type of number (ex: float) for the
maximum size. Patch written by Vajrasky Kok.

@item 
bpo-21711@footnote{https://bugs.python.org/issue21711}: support for "site-python" directories has now been removed from
the site module (it was deprecated in 3.4).

@item 
bpo-17552@footnote{https://bugs.python.org/issue17552}: new socket.sendfile() method allowing a file to be sent over a
socket by using high-performance os.sendfile() on UNIX. Patch by Giampaolo
Rodola'.

@item 
bpo-18039@footnote{https://bugs.python.org/issue18039}: dbm.dump.open() now always creates a new database when the flag
has the value 'n'.  Patch by Claudiu Popa.

@item 
bpo-21326@footnote{https://bugs.python.org/issue21326}: Add a new is_closed() method to asyncio.BaseEventLoop.
run_forever() and run_until_complete() methods of asyncio.BaseEventLoop
now raise an exception if the event loop was closed.

@item 
bpo-21766@footnote{https://bugs.python.org/issue21766}: Prevent a security hole in CGIHTTPServer by URL unquoting paths
before checking for a CGI script at that path.

@item 
bpo-21310@footnote{https://bugs.python.org/issue21310}: Fixed possible resource leak in failed open().

@item 
bpo-21256@footnote{https://bugs.python.org/issue21256}: Printout of keyword args should be in deterministic order in a
mock function call. This will help to write better doctests.

@item 
bpo-21677@footnote{https://bugs.python.org/issue21677}: Fixed chaining nonnormalized exceptions in io close() methods.

@item 
bpo-11709@footnote{https://bugs.python.org/issue11709}: Fix the pydoc.help function to not fail when sys.stdin is not a
valid file.

@item 
bpo-21515@footnote{https://bugs.python.org/issue21515}: tempfile.TemporaryFile now uses os.O_TMPFILE flag is available.

@item 
bpo-13223@footnote{https://bugs.python.org/issue13223}: Fix pydoc.writedoc so that the HTML documentation for methods
that use 'self' in the example code is generated correctly.

@item 
bpo-21463@footnote{https://bugs.python.org/issue21463}: In urllib.request, fix pruning of the FTP cache.

@item 
bpo-21618@footnote{https://bugs.python.org/issue21618}: The subprocess module could fail to close open fds that were
inherited by the calling process and already higher than POSIX resource
limits would otherwise allow.  On systems with a functioning /proc/self/fd
or /dev/fd interface the max is now ignored and all fds are closed.

@item 
bpo-20383@footnote{https://bugs.python.org/issue20383}: Introduce importlib.util.module_from_spec() as the preferred
way to create a new module.

@item 
bpo-21552@footnote{https://bugs.python.org/issue21552}: Fixed possible integer overflow of too long string lengths in
the tkinter module on 64-bit platforms.

@item 
bpo-14315@footnote{https://bugs.python.org/issue14315}: The zipfile module now ignores extra fields in the central
directory that are too short to be parsed instead of letting a
struct.unpack error bubble up as this "bad data" appears in many real
world zip files in the wild and is ignored by other zip tools.

@item 
bpo-13742@footnote{https://bugs.python.org/issue13742}: Added "key" and "reverse" parameters to heapq.merge(). (First
draft of patch contributed by Simon Sapin.)

@item 
bpo-21402@footnote{https://bugs.python.org/issue21402}: tkinter.ttk now works when default root window is not set.

@item 
bpo-3015@footnote{https://bugs.python.org/issue3015}: _tkinter.create() now creates tkapp object with wantobject=1 by
default.

@item 
bpo-10203@footnote{https://bugs.python.org/issue10203}: sqlite3.Row now truly supports sequence protocol.  In
particular it supports reverse() and negative indices.  Original patch by
Claudiu Popa.

@item 
bpo-18807@footnote{https://bugs.python.org/issue18807}: If copying (no symlinks) specified for a venv, then the python
interpreter aliases (python, python3) are now created by copying rather
than symlinking.

@item 
bpo-20197@footnote{https://bugs.python.org/issue20197}: Added support for the WebP image type in the imghdr module.
Patch by Fabrice Aneche and Claudiu Popa.

@item 
bpo-21513@footnote{https://bugs.python.org/issue21513}: Speedup some properties of IP addresses (IPv4Address,
IPv6Address) such as .is_private or .is_multicast.

@item 
bpo-21137@footnote{https://bugs.python.org/issue21137}: Improve the repr for threading.Lock() and its variants by
showing the "locked" or "unlocked" status.  Patch by Berker Peksag.

@item 
bpo-21538@footnote{https://bugs.python.org/issue21538}: The plistlib module now supports loading of binary plist files
when reference or offset size is not a power of two.

@item 
bpo-21455@footnote{https://bugs.python.org/issue21455}: Add a default backlog to socket.listen().

@item 
bpo-21525@footnote{https://bugs.python.org/issue21525}: Most Tkinter methods which accepted tuples now accept lists
too.

@item 
bpo-22166@footnote{https://bugs.python.org/issue22166}: With the assistance of a new internal _codecs._forget_codec
helping function, test_codecs now clears the encoding caches to avoid the
appearance of a reference leak

@item 
bpo-22236@footnote{https://bugs.python.org/issue22236}: Tkinter tests now don't reuse default root window.  New root
window is created for every test class.

@item 
bpo-10744@footnote{https://bugs.python.org/issue10744}: Fix 
@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} format strings on ctypes objects with a
nontrivial shape.

@item 
bpo-20826@footnote{https://bugs.python.org/issue20826}: Optimize ipaddress.collapse_addresses().

@item 
bpo-21487@footnote{https://bugs.python.org/issue21487}: Optimize ipaddress.summarize_address_range() and
ipaddress.@{IPv4Network,IPv6Network@}.subnets().

@item 
bpo-21486@footnote{https://bugs.python.org/issue21486}: Optimize parsing of netmasks in ipaddress.IPv4Network and
ipaddress.IPv6Network.

@item 
bpo-13916@footnote{https://bugs.python.org/issue13916}: Disallowed the surrogatepass error handler for non UTF-*
encodings.

@item 
bpo-20998@footnote{https://bugs.python.org/issue20998}: Fixed re.fullmatch() of repeated single character pattern with
ignore case. Original patch by Matthew Barnett.

@item 
bpo-21075@footnote{https://bugs.python.org/issue21075}: fileinput.FileInput now reads bytes from standard stream if
binary mode is specified.  Patch by Sam Kimbrel.

@item 
bpo-19775@footnote{https://bugs.python.org/issue19775}: Add a samefile() method to pathlib Path objects.  Initial patch
by Vajrasky Kok.

@item 
bpo-21226@footnote{https://bugs.python.org/issue21226}: Set up modules properly in PyImport_ExecCodeModuleObject (and
friends).

@item 
bpo-21398@footnote{https://bugs.python.org/issue21398}: Fix a unicode error in the pydoc pager when the documentation
contains characters not encodable to the stdout encoding.

@item 
bpo-16531@footnote{https://bugs.python.org/issue16531}: ipaddress.IPv4Network and ipaddress.IPv6Network now accept an
(address, netmask) tuple argument, so as to easily construct network
objects from existing addresses.

@item 
bpo-21156@footnote{https://bugs.python.org/issue21156}: importlib.abc.InspectLoader.source_to_code() is now a
staticmethod.

@item 
bpo-21424@footnote{https://bugs.python.org/issue21424}: Simplified and optimized heaqp.nlargest() and nmsmallest() to
make fewer tuple comparisons.

@item 
bpo-21396@footnote{https://bugs.python.org/issue21396}: Fix TextIOWrapper(..., write_through=True) to not force a
flush() on the underlying binary stream.  Patch by akira.

@item 
bpo-18314@footnote{https://bugs.python.org/issue18314}: Unlink now removes junctions on Windows. Patch by Kim Gräsman

@item 
bpo-21088@footnote{https://bugs.python.org/issue21088}: Bugfix for curses.window.addch() regression in 3.4.0. In
porting to Argument Clinic, the first two arguments were reversed.

@item 
bpo-21407@footnote{https://bugs.python.org/issue21407}: _decimal: The module now supports function signatures.

@item 
bpo-10650@footnote{https://bugs.python.org/issue10650}: Remove the non-standard 'watchexp' parameter from the
Decimal.quantize() method in the Python version.  It had never been
present in the C version.

@item 
bpo-21469@footnote{https://bugs.python.org/issue21469}: Reduced the risk of false positives in robotparser by checking
to make sure that robots.txt has been read or does not exist prior to
returning True in can_fetch().

@item 
bpo-19414@footnote{https://bugs.python.org/issue19414}: Have the OrderedDict mark deleted links as unusable. This gives
an early failure if the link is deleted during iteration.

@item 
bpo-21421@footnote{https://bugs.python.org/issue21421}: Add __slots__ to the MappingViews ABC. Patch by Josh Rosenberg.

@item 
bpo-21101@footnote{https://bugs.python.org/issue21101}: Eliminate double hashing in the C speed-up code for
collections.Counter().

@item 
bpo-21321@footnote{https://bugs.python.org/issue21321}: itertools.islice() now releases the reference to the source
iterator when the slice is exhausted.  Patch by Anton Afanasyev.

@item 
bpo-21057@footnote{https://bugs.python.org/issue21057}: TextIOWrapper now allows the underlying binary stream's read()
or read1() method to return an arbitrary bytes-like object (such as a
memoryview). Patch by Nikolaus Rath.

@item 
bpo-20951@footnote{https://bugs.python.org/issue20951}: SSLSocket.send() now raises either SSLWantReadError or
SSLWantWriteError on a non-blocking socket if the operation would block.
Previously, it would return 0.  Patch by Nikolaus Rath.

@item 
bpo-13248@footnote{https://bugs.python.org/issue13248}: removed previously deprecated asyncore.dispatcher __getattr__
cheap inheritance hack.

@item 
bpo-9815@footnote{https://bugs.python.org/issue9815}: assertRaises now tries to clear references to local variables in
the exception's traceback.

@item 
bpo-19940@footnote{https://bugs.python.org/issue19940}: ssl.cert_time_to_seconds() now interprets the given time string
in the UTC timezone (as specified in RFC 5280), not the local timezone.

@item 
bpo-13204@footnote{https://bugs.python.org/issue13204}: Calling sys.flags.__new__ would crash the interpreter, now it
raises a TypeError.

@item 
bpo-19385@footnote{https://bugs.python.org/issue19385}: Make operations on a closed dbm.dumb database always raise the
same exception.

@item 
bpo-21207@footnote{https://bugs.python.org/issue21207}: Detect when the os.urandom cached fd has been closed or
replaced, and open it anew.

@item 
bpo-21291@footnote{https://bugs.python.org/issue21291}: subprocess's Popen.wait() is now thread safe so that multiple
threads may be calling wait() or poll() on a Popen instance at the same
time without losing the Popen.returncode value.

@item 
bpo-21127@footnote{https://bugs.python.org/issue21127}: Path objects can now be instantiated from str subclass
instances (such as @code{numpy.str_}).

@item 
bpo-15002@footnote{https://bugs.python.org/issue15002}: urllib.response object to use _TemporaryFileWrapper (and
_TemporaryFileCloser) facility. Provides a better way to handle file
descriptor close. Patch contributed by Christian Theune.

@item 
bpo-12220@footnote{https://bugs.python.org/issue12220}: mindom now raises a custom ValueError indicating it doesn't
support spaces in URIs instead of letting a 'split' ValueError bubble up.

@item 
bpo-21068@footnote{https://bugs.python.org/issue21068}: The ssl.PROTOCOL* constants are now enum members.

@item 
bpo-21276@footnote{https://bugs.python.org/issue21276}: posixmodule: Don't define USE_XATTRS on KFreeBSD and the Hurd.

@item 
bpo-21262@footnote{https://bugs.python.org/issue21262}: New method assert_not_called for Mock. It raises AssertionError
if the mock has been called.

@item 
bpo-21238@footnote{https://bugs.python.org/issue21238}: New keyword argument @code{unsafe} to Mock. It raises
@ref{393,,AttributeError} incase of an attribute startswith assert or assret.

@item 
bpo-20896@footnote{https://bugs.python.org/issue20896}: ssl.get_server_certificate() now uses PROTOCOL_SSLv23, not
PROTOCOL_SSLv3, for maximum compatibility.

@item 
bpo-21239@footnote{https://bugs.python.org/issue21239}: patch.stopall() didn't work deterministically when the same
name was patched more than once.

@item 
bpo-21203@footnote{https://bugs.python.org/issue21203}: Updated fileConfig and dictConfig to remove inconsistencies.
Thanks to Jure Koren for the patch.

@item 
bpo-21222@footnote{https://bugs.python.org/issue21222}: Passing name keyword argument to mock.create_autospec now
works.

@item 
bpo-21197@footnote{https://bugs.python.org/issue21197}: Add lib64 -> lib symlink in venvs on 64-bit non-OS X POSIX.

@item 
bpo-17498@footnote{https://bugs.python.org/issue17498}: Some SMTP servers disconnect after certain errors, violating
strict RFC conformance.  Instead of losing the error code when we issue
the subsequent RSET, smtplib now returns the error code and defers raising
the SMTPServerDisconnected error until the next command is issued.

@item 
bpo-17826@footnote{https://bugs.python.org/issue17826}: setting an iterable side_effect on a mock function created by
create_autospec now works. Patch by Kushal Das.

@item 
bpo-7776@footnote{https://bugs.python.org/issue7776}: Fix @code{Host:} header and reconnection when using
http.client.HTTPConnection.set_tunnel(). Patch by Nikolaus Rath.

@item 
bpo-20968@footnote{https://bugs.python.org/issue20968}: unittest.mock.MagicMock now supports division. Patch by
Johannes Baiter.

@item 
bpo-21529@footnote{https://bugs.python.org/issue21529}: Fix arbitrary memory access in JSONDecoder.raw_decode with a
negative second parameter. Bug reported by Guido Vranken. (See also:
CVE-2014-4616)

@item 
bpo-21169@footnote{https://bugs.python.org/issue21169}: getpass now handles non-ascii characters that the input stream
encoding cannot encode by re-encoding using the replace error handler.

@item 
bpo-21171@footnote{https://bugs.python.org/issue21171}: Fixed undocumented filter API of the rot13 codec. Patch by
Berker Peksag.

@item 
bpo-20539@footnote{https://bugs.python.org/issue20539}: Improved math.factorial error message for large positive inputs
and changed exception type (OverflowError -> ValueError) for large
negative inputs.

@item 
bpo-21172@footnote{https://bugs.python.org/issue21172}: isinstance check relaxed from dict to collections.Mapping.

@item 
bpo-21155@footnote{https://bugs.python.org/issue21155}: asyncio.EventLoop.create_unix_server() now raises a ValueError
if path and sock are specified at the same time.

@item 
bpo-21136@footnote{https://bugs.python.org/issue21136}: Avoid unnecessary normalization of Fractions resulting from
power and other operations.  Patch by Raymond Hettinger.

@item 
bpo-17621@footnote{https://bugs.python.org/issue17621}: Introduce importlib.util.LazyLoader.

@item 
bpo-21076@footnote{https://bugs.python.org/issue21076}: signal module constants were turned into enums. Patch by
Giampaolo Rodola'.

@item 
bpo-20636@footnote{https://bugs.python.org/issue20636}: Improved the repr of Tkinter widgets.

@item 
bpo-19505@footnote{https://bugs.python.org/issue19505}: The items, keys, and values views of OrderedDict now support
reverse iteration using reversed().

@item 
bpo-21149@footnote{https://bugs.python.org/issue21149}: Improved thread-safety in logging cleanup during interpreter
shutdown. Thanks to Devin Jeanpierre for the patch.

@item 
bpo-21058@footnote{https://bugs.python.org/issue21058}: Fix a leak of file descriptor in
@ref{d42,,tempfile.NamedTemporaryFile()}, close the file descriptor if
@ref{654,,io.open()} fails

@item 
bpo-21200@footnote{https://bugs.python.org/issue21200}: Return None from pkgutil.get_loader() when __spec__ is missing.

@item 
bpo-21013@footnote{https://bugs.python.org/issue21013}: Enhance ssl.create_default_context() when used for server side
sockets to provide better security by default.

@item 
bpo-20145@footnote{https://bugs.python.org/issue20145}: @code{assertRaisesRegex} and @code{assertWarnsRegex} now raise a
TypeError if the second argument is not a string or compiled regex.

@item 
bpo-20633@footnote{https://bugs.python.org/issue20633}: Replace relative import by absolute import.

@item 
bpo-20980@footnote{https://bugs.python.org/issue20980}: Stop wrapping exception when using ThreadPool.

@item 
bpo-21082@footnote{https://bugs.python.org/issue21082}: In os.makedirs, do not set the process-wide umask. Note this
changes behavior of makedirs when exist_ok=True.

@item 
bpo-20990@footnote{https://bugs.python.org/issue20990}: Fix issues found by pyflakes for multiprocessing.

@item 
bpo-21015@footnote{https://bugs.python.org/issue21015}: SSL contexts will now automatically select an elliptic curve
for ECDH key exchange on OpenSSL 1.0.2 and later, and otherwise default to
"prime256v1".

@item 
bpo-21000@footnote{https://bugs.python.org/issue21000}: Improve the command-line interface of json.tool.

@item 
bpo-20995@footnote{https://bugs.python.org/issue20995}: Enhance default ciphers used by the ssl module to enable better
security and prioritize perfect forward secrecy.

@item 
bpo-20884@footnote{https://bugs.python.org/issue20884}: Don't assume that __file__ is defined on importlib.__init__.

@item 
bpo-21499@footnote{https://bugs.python.org/issue21499}: Ignore __builtins__ in several test_importlib.test_api tests.

@item 
bpo-20627@footnote{https://bugs.python.org/issue20627}: xmlrpc.client.ServerProxy is now a context manager.

@item 
bpo-19165@footnote{https://bugs.python.org/issue19165}: The formatter module now raises DeprecationWarning instead of
PendingDeprecationWarning.

@item 
bpo-13936@footnote{https://bugs.python.org/issue13936}: Remove the ability of datetime.time instances to be considered
false in boolean contexts.

@item 
bpo-18931@footnote{https://bugs.python.org/issue18931}: selectors module now supports /dev/poll on Solaris. Patch by
Giampaolo Rodola'.

@item 
bpo-19977@footnote{https://bugs.python.org/issue19977}: When the @code{LC_TYPE} locale is the POSIX locale (@code{C} locale),
@ref{306,,sys.stdin} and @ref{307,,sys.stdout} are now using the
@code{surrogateescape} error handler, instead of the @code{strict} error
handler.

@item 
bpo-20574@footnote{https://bugs.python.org/issue20574}: Implement incremental decoder for cp65001 code (Windows code
page 65001, Microsoft UTF-8).

@item 
bpo-20879@footnote{https://bugs.python.org/issue20879}: Delay the initialization of encoding and decoding tables for
base32, ascii85 and base85 codecs in the base64 module, and delay the
initialization of the unquote_to_bytes() table of the urllib.parse module,
to not waste memory if these modules are not used.

@item 
bpo-19157@footnote{https://bugs.python.org/issue19157}: Include the broadcast address in the usuable hosts for IPv6 in
ipaddress.

@item 
bpo-11599@footnote{https://bugs.python.org/issue11599}: When an external command (e.g. compiler) fails, distutils now
prints out the whole command line (instead of just the command name) if
the environment variable DISTUTILS_DEBUG is set.

@item 
bpo-4931@footnote{https://bugs.python.org/issue4931}: distutils should not produce unhelpful "error: None" messages
anymore. distutils.util.grok_environment_error is kept but doc-deprecated.

@item 
bpo-20875@footnote{https://bugs.python.org/issue20875}: Prevent possible gzip "'read' is not defined" NameError. Patch
by Claudiu Popa.

@item 
bpo-11558@footnote{https://bugs.python.org/issue11558}: @code{email.message.Message.attach} now returns a more useful
error message if @code{attach} is called on a message for which
@code{is_multipart} is False.

@item 
bpo-20283@footnote{https://bugs.python.org/issue20283}: RE pattern methods now accept the string keyword parameters as
documented. The pattern and source keyword parameters are left as
deprecated aliases.

@item 
bpo-20778@footnote{https://bugs.python.org/issue20778}: Fix modulefinder to work with bytecode-only modules.

@item 
bpo-20791@footnote{https://bugs.python.org/issue20791}: copy.copy() now doesn't make a copy when the input is a bytes
object. Initial patch by Peter Otten.

@item 
bpo-19748@footnote{https://bugs.python.org/issue19748}: On AIX, time.mktime() now raises an OverflowError for year
outsize range [1902; 2037].

@item 
bpo-19573@footnote{https://bugs.python.org/issue19573}: inspect.signature: Use enum for parameter kind constants.

@item 
bpo-20726@footnote{https://bugs.python.org/issue20726}: inspect.signature: Make Signature and Parameter picklable.

@item 
bpo-17373@footnote{https://bugs.python.org/issue17373}: Add inspect.Signature.from_callable method.

@item 
bpo-20378@footnote{https://bugs.python.org/issue20378}: Improve repr of inspect.Signature and inspect.Parameter.

@item 
bpo-20816@footnote{https://bugs.python.org/issue20816}: Fix inspect.getcallargs() to raise correct TypeError for
missing keyword-only arguments. Patch by Jeremiah Lowin.

@item 
bpo-20817@footnote{https://bugs.python.org/issue20817}: Fix inspect.getcallargs() to fail correctly if more than 3
arguments are missing. Patch by Jeremiah Lowin.

@item 
bpo-6676@footnote{https://bugs.python.org/issue6676}: Ensure a meaningful exception is raised when attempting to parse
more than one XML document per pyexpat xmlparser instance. (Original
patches by Hirokazu Yamamoto and Amaury Forgeot d'Arc, with suggested
wording by David Gutteridge)

@item 
bpo-21117@footnote{https://bugs.python.org/issue21117}: Fix inspect.signature to better support functools.partial. Due
to the specifics of functools.partial implementation,
positional-or-keyword arguments passed as keyword arguments become
keyword-only.

@item 
bpo-20334@footnote{https://bugs.python.org/issue20334}: inspect.Signature and inspect.Parameter are now hashable.
Thanks to Antony Lee for bug reports and suggestions.

@item 
bpo-15916@footnote{https://bugs.python.org/issue15916}: doctest.DocTestSuite returns an empty unittest.TestSuite
instead of raising ValueError if it finds no tests

@item 
bpo-21209@footnote{https://bugs.python.org/issue21209}: Fix asyncio.tasks.CoroWrapper to workaround a bug in yield-from
implementation in CPythons prior to 3.4.1.

@item 
asyncio: Add gi_@{frame,running,code@} properties to CoroWrapper (upstream
bpo-163@footnote{https://bugs.python.org/issue163}).

@item 
bpo-21311@footnote{https://bugs.python.org/issue21311}: Avoid exception in _osx_support with non-standard compiler
configurations. Patch by John Szakmeister.

@item 
bpo-11571@footnote{https://bugs.python.org/issue11571}: Ensure that the turtle window becomes the topmost window when
launched on OS X.

@item 
bpo-21801@footnote{https://bugs.python.org/issue21801}: Validate that __signature__ is None or an instance of
Signature.

@item 
bpo-21923@footnote{https://bugs.python.org/issue21923}: Prevent AttributeError in
distutils.sysconfig.customize_compiler due to possible uninitialized
_config_vars.

@item 
bpo-21323@footnote{https://bugs.python.org/issue21323}: Fix http.server to again handle scripts in CGI subdirectories,
broken by the fix for security bpo-19435@footnote{https://bugs.python.org/issue19435}.  Patch by Zach Byrne.

@item 
bpo-22733@footnote{https://bugs.python.org/issue22733}: Fix ffi_prep_args not zero-extending argument values correctly
on 64-bit Windows.

@item 
bpo-23302@footnote{https://bugs.python.org/issue23302}: Default to TCP_NODELAY=1 upon establishing an HTTPConnection.
Removed use of hard-coded MSS as it's an optimization that's no longer
needed with Nagle disabled.
@end itemize

@node IDLE<47>,构建<52>,库<79>,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id489}@anchor{1185}
@subsubsection IDLE



@itemize -

@item 
bpo-20577@footnote{https://bugs.python.org/issue20577}: Configuration of the max line length for the FormatParagraph
extension has been moved from the General tab of the Idle preferences
dialog to the FormatParagraph tab of the Config Extensions dialog. Patch
by Tal Einat.

@item 
bpo-16893@footnote{https://bugs.python.org/issue16893}: Update Idle doc chapter to match current Idle and add new
information.

@item 
bpo-3068@footnote{https://bugs.python.org/issue3068}: Add Idle extension configuration dialog to Options menu. Changes
are written to HOME/.idlerc/config-extensions.cfg. Original patch by Tal
Einat.

@item 
bpo-16233@footnote{https://bugs.python.org/issue16233}: A module browser (File : Class Browser, Alt+C) requires an
editor window with a filename.  When Class Browser is requested otherwise,
from a shell, output window, or 'Untitled' editor, Idle no longer displays
an error box. It now pops up an Open Module box (Alt+M). If a valid name
is entered and a module is opened, a corresponding browser is also opened.

@item 
bpo-4832@footnote{https://bugs.python.org/issue4832}: Save As to type Python files automatically adds .py to the name
you enter (even if your system does not display it).  Some systems
automatically add .txt when type is Text files.

@item 
bpo-21986@footnote{https://bugs.python.org/issue21986}: Code objects are not normally pickled by the pickle module. To
match this, they are no longer pickled when running under Idle.

@item 
bpo-17390@footnote{https://bugs.python.org/issue17390}: Adjust Editor window title; remove 'Python', move version to
end.

@item 
bpo-14105@footnote{https://bugs.python.org/issue14105}: Idle debugger breakpoints no longer disappear when inserting or
deleting lines.

@item 
bpo-17172@footnote{https://bugs.python.org/issue17172}: Turtledemo can now be run from Idle. Currently, the entry is on
the Help menu, but it may move to Run. Patch by Ramchandra Apt and Lita
Cho.

@item 
bpo-21765@footnote{https://bugs.python.org/issue21765}: Add support for non-ascii identifiers to HyperParser.

@item 
bpo-21940@footnote{https://bugs.python.org/issue21940}: Add unittest for WidgetRedirector. Initial patch by Saimadhav
Heblikar.

@item 
bpo-18592@footnote{https://bugs.python.org/issue18592}: Add unittest for SearchDialogBase. Patch by Phil Webster.

@item 
bpo-21694@footnote{https://bugs.python.org/issue21694}: Add unittest for ParenMatch. Patch by Saimadhav Heblikar.

@item 
bpo-21686@footnote{https://bugs.python.org/issue21686}: add unittest for HyperParser. Original patch by Saimadhav
Heblikar.

@item 
bpo-12387@footnote{https://bugs.python.org/issue12387}: Add missing upper(lower)case versions of default Windows key
bindings for Idle so Caps Lock does not disable them. Patch by Roger
Serwy.

@item 
bpo-21695@footnote{https://bugs.python.org/issue21695}: Closing a Find-in-files output window while the search is still
in progress no longer closes Idle.

@item 
bpo-18910@footnote{https://bugs.python.org/issue18910}: Add unittest for textView. Patch by Phil Webster.

@item 
bpo-18292@footnote{https://bugs.python.org/issue18292}: Add unittest for AutoExpand. Patch by Saihadhav Heblikar.

@item 
bpo-18409@footnote{https://bugs.python.org/issue18409}: Add unittest for AutoComplete. Patch by Phil Webster.

@item 
bpo-21477@footnote{https://bugs.python.org/issue21477}: htest.py - Improve framework, complete set of tests. Patches by
Saimadhav Heblikar

@item 
bpo-18104@footnote{https://bugs.python.org/issue18104}: Add idlelib/idle_test/htest.py with a few sample tests to begin
consolidating and improving human-validated tests of Idle. Change other
files as needed to work with htest.  Running the module as __main__ runs
all tests.

@item 
bpo-21139@footnote{https://bugs.python.org/issue21139}: Change default paragraph width to 72, the 
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008}
recommendation.

@item 
bpo-21284@footnote{https://bugs.python.org/issue21284}: Paragraph reformat test passes after user changes reformat
width.

@item 
bpo-17654@footnote{https://bugs.python.org/issue17654}: Ensure IDLE menus are customized properly on OS X for
non-framework builds and for all variants of Tk.

@item 
bpo-23180@footnote{https://bugs.python.org/issue23180}: Rename IDLE "Windows" menu item to "Window". Patch by Al
Sweigart.
@end itemize

@node 构建<52>,C API<34>,IDLE<47>,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id490}@anchor{1186}
@subsubsection 构建



@itemize -

@item 
bpo-15506@footnote{https://bugs.python.org/issue15506}: Use standard PKG_PROG_PKG_CONFIG autoconf macro in the
configure script.

@item 
bpo-22935@footnote{https://bugs.python.org/issue22935}: Allow the ssl module to be compiled if openssl doesn't support
SSL 3.

@item 
bpo-22592@footnote{https://bugs.python.org/issue22592}: 放弃对 Borland C 编译器构建Python的支持。distutils模块仍然支持它来构建扩展。

@item 
bpo-22591@footnote{https://bugs.python.org/issue22591}: 放弃对 MS-DOS 的支持，尤其是 DJGPP 编译器（GCC的MS-DOS端口）。

@item 
bpo-16537@footnote{https://bugs.python.org/issue16537}: Check whether self.extensions is empty in setup.py. Patch by
Jonathan Hosmer.

@item 
bpo-22359@footnote{https://bugs.python.org/issue22359}: Remove incorrect uses of recursive make.  Patch by Jonas
Wagner.

@item 
bpo-21958@footnote{https://bugs.python.org/issue21958}: Define HAVE_ROUND when building with Visual Studio 2013 and
above.  Patch by Zachary Turner.

@item 
bpo-18093@footnote{https://bugs.python.org/issue18093}: the programs that embed the CPython runtime are now in a
separate "Programs" directory, rather than being kept in the Modules
directory.

@item 
bpo-15759@footnote{https://bugs.python.org/issue15759}: "make suspicious", "make linkcheck" and "make doctest" in Doc/
now display special message when and only when there are failures.

@item 
bpo-21141@footnote{https://bugs.python.org/issue21141}: The Windows build process no longer attempts to find Perl,
instead relying on OpenSSL source being configured and ready to build.
The @code{PCbuild\build_ssl.py} script has been re-written and re-named to
@code{PCbuild\prepare_ssl.py}, and takes care of configuring OpenSSL source
for both 32 and 64 bit platforms.  OpenSSL sources obtained from
svn.python.org will always be pre-configured and ready to build.

@item 
bpo-21037@footnote{https://bugs.python.org/issue21037}: Add a build option to enable AddressSanitizer support.

@item 
bpo-19962@footnote{https://bugs.python.org/issue19962}: The Windows build process now creates "python.bat" in the root
of the source tree, which passes all arguments through to the most
recently built interpreter.

@item 
bpo-21285@footnote{https://bugs.python.org/issue21285}: Refactor and fix curses configure check to always search in a
ncursesw directory.

@item 
bpo-15234@footnote{https://bugs.python.org/issue15234}: For BerkelyDB and Sqlite, only add the found library and
include directories if they aren't already being searched. This avoids an
explicit runtime library dependency.

@item 
bpo-17861@footnote{https://bugs.python.org/issue17861}: Tools/scripts/generate_opcode_h.py automatically regenerates
Include/opcode.h from Lib/opcode.py if the latter gets any change.

@item 
bpo-20644@footnote{https://bugs.python.org/issue20644}: OS X installer build support for documentation build changes in
3.4.1: assume externally supplied sphinx-build is available in /usr/bin.

@item 
bpo-20022@footnote{https://bugs.python.org/issue20022}: Eliminate use of deprecated bundlebuilder in OS X builds.

@item 
bpo-15968@footnote{https://bugs.python.org/issue15968}: Incorporated Tcl, Tk, and Tix builds into the Windows build
solution.

@item 
bpo-17095@footnote{https://bugs.python.org/issue17095}: Fix Modules/Setup @emph{shared} support.

@item 
bpo-21811@footnote{https://bugs.python.org/issue21811}: Anticipated fixes to support OS X versions > 10.9.

@item 
bpo-21166@footnote{https://bugs.python.org/issue21166}: Prevent possible segfaults and other random failures of python
--generate-posix-vars in pybuilddir.txt build target.

@item 
bpo-18096@footnote{https://bugs.python.org/issue18096}: Fix library order returned by python-config.

@item 
bpo-17219@footnote{https://bugs.python.org/issue17219}: Add library build dir for Python extension cross-builds.

@item 
bpo-22919@footnote{https://bugs.python.org/issue22919}: Windows build updated to support VC 14.0 (Visual Studio 2015),
which will be used for the official release.

@item 
bpo-21236@footnote{https://bugs.python.org/issue21236}: Build _msi.pyd with cabinet.lib instead of fci.lib

@item 
bpo-17128@footnote{https://bugs.python.org/issue17128}: Use private version of OpenSSL for OS X 10.5+ installer.
@end itemize

@node C API<34>,文档<45>,构建<52>,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id491}@anchor{1187}
@subsubsection C API



@itemize -

@item 
bpo-14203@footnote{https://bugs.python.org/issue14203}: Remove obsolete support for view==NULL in PyBuffer_FillInfo(),
bytearray_getbuffer(), bytesiobuf_getbuffer() and array_buffer_getbuf().
All functions now raise BufferError in that case.

@item 
bpo-22445@footnote{https://bugs.python.org/issue22445}: PyBuffer_IsContiguous() now implements precise contiguity
tests, compatible with NumPy's NPY_RELAXED_STRIDES_CHECKING compilation
flag.  Previously the function reported false negatives for corner cases.

@item 
bpo-22079@footnote{https://bugs.python.org/issue22079}: PyType_Ready() now checks that statically allocated type has no
dynamically allocated bases.

@item 
bpo-22453@footnote{https://bugs.python.org/issue22453}: Removed non-documented macro PyObject_REPR().

@item 
bpo-18395@footnote{https://bugs.python.org/issue18395}: Rename @code{_Py_char2wchar()} to @ref{436,,Py_DecodeLocale()},
rename @code{_Py_wchar2char()} to @ref{437,,Py_EncodeLocale()}, and document
these functions.

@item 
bpo-21233@footnote{https://bugs.python.org/issue21233}: Add new C functions: PyMem_RawCalloc(), PyMem_Calloc(),
PyObject_Calloc(), _PyObject_GC_Calloc(). bytes(int) is now using
@code{calloc()} instead of @code{malloc()} for large objects which is faster and
use less memory.

@item 
bpo-20942@footnote{https://bugs.python.org/issue20942}: PyImport_ImportFrozenModuleObject() no longer sets __file__ to
match what importlib does; this affects _frozen_importlib as well as any
module loaded using imp.init_frozen().
@end itemize

@node 文档<45>,测试<49>,C API<34>,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id492}@anchor{1188}
@subsubsection 文档



@itemize -

@item 
bpo-19548@footnote{https://bugs.python.org/issue19548}: Update the codecs module documentation to better cover the
distinction between text encodings and other codecs, together with other
clarifications. Patch by Martin Panter.

@item 
bpo-22394@footnote{https://bugs.python.org/issue22394}: Doc/Makefile now supports @code{make venv PYTHON=../python} to
create a venv for generating the documentation, e.g., @code{make html
PYTHON=venv/bin/python3}.

@item 
bpo-21514@footnote{https://bugs.python.org/issue21514}: The documentation of the json module now refers to new JSON RFC
7159 instead of obsoleted RFC 4627.

@item 
bpo-21777@footnote{https://bugs.python.org/issue21777}: The binary sequence methods on bytes and bytearray are now
documented explicitly, rather than assuming users will be able to derive
the expected behaviour from the behaviour of the corresponding str
methods.

@item 
bpo-6916@footnote{https://bugs.python.org/issue6916}: undocument deprecated asynchat.fifo class.

@item 
bpo-17386@footnote{https://bugs.python.org/issue17386}: Expanded functionality of the @code{Doc/make.bat} script to make
it much more comparable to @code{Doc/Makefile}.

@item 
bpo-21312@footnote{https://bugs.python.org/issue21312}: Update the thread_foobar.h template file to include newer
threading APIs. Patch by Jack McCracken.

@item 
bpo-21043@footnote{https://bugs.python.org/issue21043}: Remove the recommendation for specific CA organizations and to
mention the ability to load the OS certificates.

@item 
bpo-20765@footnote{https://bugs.python.org/issue20765}: Add missing documentation for PurePath.with_name() and
PurePath.with_suffix().

@item 
bpo-19407@footnote{https://bugs.python.org/issue19407}: New package installation and distribution guides based on the
Python Packaging Authority tools. Existing guides have been retained as
legacy links from the distutils docs, as they still contain some required
reference material for tool developers that isn't recorded anywhere else.

@item 
bpo-19697@footnote{https://bugs.python.org/issue19697}: Document cases where __main__.__spec__ is None.
@end itemize

@node 测试<49>,工具/示例<34>,文档<45>,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id493}@anchor{1189}
@subsubsection 测试



@itemize -

@item 
bpo-18982@footnote{https://bugs.python.org/issue18982}: Add tests for CLI of the calendar module.

@item 
bpo-19548@footnote{https://bugs.python.org/issue19548}: Added some additional checks to test_codecs to ensure that
statements in the updated documentation remain accurate. Patch by Martin
Panter.

@item 
bpo-22838@footnote{https://bugs.python.org/issue22838}: All test_re tests now work with unittest test discovery.

@item 
bpo-22173@footnote{https://bugs.python.org/issue22173}: Update lib2to3 tests to use unittest test discovery.

@item 
bpo-16000@footnote{https://bugs.python.org/issue16000}: Convert test_curses to use unittest.

@item 
bpo-21456@footnote{https://bugs.python.org/issue21456}: Skip two tests in test_urllib2net.py if _ssl module not
present. Patch by Remi Pointel.

@item 
bpo-20746@footnote{https://bugs.python.org/issue20746}: Fix test_pdb to run in refleak mode (-R).  Patch by Xavier de
Gaye.

@item 
bpo-22060@footnote{https://bugs.python.org/issue22060}: test_ctypes has been somewhat cleaned up and simplified; it now
uses unittest test discovery to find its tests.

@item 
bpo-22104@footnote{https://bugs.python.org/issue22104}: regrtest.py no longer holds a reference to the suite of tests
loaded from test modules that don't define test_main().

@item 
bpo-22111@footnote{https://bugs.python.org/issue22111}: Assorted cleanups in test_imaplib.  Patch by Milan Oberkirch.

@item 
bpo-22002@footnote{https://bugs.python.org/issue22002}: Added @code{load_package_tests} function to test.support and used
it to implement/augment test discovery in test_asyncio, test_email,
test_importlib, test_json, and test_tools.

@item 
bpo-21976@footnote{https://bugs.python.org/issue21976}: Fix test_ssl to accept LibreSSL version strings.  Thanks to
William Orr.

@item 
bpo-21918@footnote{https://bugs.python.org/issue21918}: Converted test_tools from a module to a package containing
separate test files for each tested script.

@item 
bpo-9554@footnote{https://bugs.python.org/issue9554}: Use modern unittest features in test_argparse. Initial patch by
Denver Coneybeare and Radu Voicilas.

@item 
bpo-20155@footnote{https://bugs.python.org/issue20155}: Changed HTTP method names in failing tests in test_httpservers
so that packet filtering software (specifically Windows Base Filtering
Engine) does not interfere with the transaction semantics expected by the
tests.

@item 
bpo-19493@footnote{https://bugs.python.org/issue19493}: Refactored the ctypes test package to skip tests explicitly
rather than silently.

@item 
bpo-18492@footnote{https://bugs.python.org/issue18492}: All resources are now allowed when tests are not run by
regrtest.py.

@item 
bpo-21634@footnote{https://bugs.python.org/issue21634}: Fix pystone micro-benchmark: use floor division instead of true
division to benchmark integers instead of floating point numbers. Set
pystone version to 1.2. Patch written by Lennart Regebro.

@item 
bpo-21605@footnote{https://bugs.python.org/issue21605}: Added tests for Tkinter images.

@item 
bpo-21493@footnote{https://bugs.python.org/issue21493}: Added test for ntpath.expanduser().  Original patch by Claudiu
Popa.

@item 
bpo-19925@footnote{https://bugs.python.org/issue19925}: Added tests for the spwd module. Original patch by Vajrasky
Kok.

@item 
bpo-21522@footnote{https://bugs.python.org/issue21522}: Added Tkinter tests for Listbox.itemconfigure(),
PanedWindow.paneconfigure(), and Menu.entryconfigure().

@item 
bpo-17756@footnote{https://bugs.python.org/issue17756}: Fix test_code test when run from the installed location.

@item 
bpo-17752@footnote{https://bugs.python.org/issue17752}: Fix distutils tests when run from the installed location.

@item 
bpo-18604@footnote{https://bugs.python.org/issue18604}: Consolidated checks for GUI availability.  All platforms now at
least check whether Tk can be instantiated when the GUI resource is
requested.

@item 
bpo-21275@footnote{https://bugs.python.org/issue21275}: 修复KFreeBSD上的套接字测试。

@item 
bpo-21223@footnote{https://bugs.python.org/issue21223}: Pass test_site/test_startup_imports when some of the extensions
are built as builtins.

@item 
bpo-20635@footnote{https://bugs.python.org/issue20635}: 添加了针对Tk几何管理器的测试。

@item 
增加freeze包的测试用例。

@item 
bpo-20743@footnote{https://bugs.python.org/issue20743}: 修复test_tcl中的引用泄漏。

@item 
bpo-21097@footnote{https://bugs.python.org/issue21097}: 将test_namespace_pkgs 移至 test_importlib。

@item 
bpo-21503@footnote{https://bugs.python.org/issue21503}: Use test_both() consistently in test_importlib.

@item 
bpo-20939@footnote{https://bugs.python.org/issue20939}: Avoid various network test failures due to new redirect of
@indicateurl{http://www.python.org/} to @indicateurl{https://www.python.org}: use
@indicateurl{http://www.example.com} instead.

@item 
bpo-20668@footnote{https://bugs.python.org/issue20668}: asyncio tests no longer rely on tests.txt file. (Patch by
Vajrasky Kok)

@item 
bpo-21093@footnote{https://bugs.python.org/issue21093}: Prevent failures of ctypes test_macholib on OS X if a copy of
libz exists in $HOME/lib or /usr/local/lib.

@item 
bpo-22770@footnote{https://bugs.python.org/issue22770}: Prevent some Tk segfaults on OS X when running gui tests.

@item 
bpo-23211@footnote{https://bugs.python.org/issue23211}: Workaround test_logging failure on some OS X 10.6 systems.

@item 
bpo-23345@footnote{https://bugs.python.org/issue23345}: Prevent test_ssl failures with large OpenSSL patch level values
(like 0.9.8zc).
@end itemize

@node 工具/示例<34>,Windows<46>,测试<49>,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id494}@anchor{118a}
@subsubsection 工具/示例



@itemize -

@item 
bpo-22314@footnote{https://bugs.python.org/issue22314}: pydoc now works when the LINES environment variable is set.

@item 
bpo-22615@footnote{https://bugs.python.org/issue22615}: Argument Clinic now supports the "type" argument for the int
converter. This permits using the int converter with enums and typedefs.

@item 
bpo-20076@footnote{https://bugs.python.org/issue20076}: The makelocalealias.py script no longer ignores UTF-8 mapping.

@item 
bpo-20079@footnote{https://bugs.python.org/issue20079}: The makelocalealias.py script now can parse the SUPPORTED file
from glibc sources and supports command line options for source paths.

@item 
bpo-22201@footnote{https://bugs.python.org/issue22201}: Command-line interface of the zipfile module now correctly
extracts ZIP files with directory entries.  Patch by Ryan Wilson.

@item 
bpo-22120@footnote{https://bugs.python.org/issue22120}: For functions using an unsigned integer return converter,
Argument Clinic now generates a cast to that type for the comparison to -1
in the generated code.  (This suppresses a compilation warning.)

@item 
bpo-18974@footnote{https://bugs.python.org/issue18974}: Tools/scripts/diff.py now uses argparse instead of optparse.

@item 
bpo-21906@footnote{https://bugs.python.org/issue21906}: 让Tools/scripts/md5sum.py可以工作在Python 3。由Zachary Ware提供补丁。

@item 
bpo-21629@footnote{https://bugs.python.org/issue21629}: Fix Argument Clinic's "--converters" feature.

@item 
为2to3添加 @code{yield from} 的支持。

@item 
Add support for the 
@geindex Python 提高建议; PEP 465
PEP 465@footnote{https://www.python.org/dev/peps/pep-0465} matrix multiplication operator to 2to3.

@item 
bpo-16047@footnote{https://bugs.python.org/issue16047}: Fix module exception list and __file__ handling in freeze.
Patch by Meador Inge.

@item 
bpo-11824@footnote{https://bugs.python.org/issue11824}: Consider ABI tags in freeze. Patch by Meador Inge.

@item 
bpo-20535@footnote{https://bugs.python.org/issue20535}: PYTHONWARNING no longer affects the run_tests.py script. Patch
by Arfrever Frehtes Taifersar Arahesis.
@end itemize

@node Windows<46>,,工具/示例<34>,Python 3 5 0 alpha 1
@anchor{whatsnew/changelog id495}@anchor{118b}
@subsubsection Windows



@itemize -

@item 
bpo-23260@footnote{https://bugs.python.org/issue23260}: 更新Windows安装器

@item 
The bundled version of Tcl/Tk has been updated to 8.6.3.  The most visible
result of this change is the addition of new native file dialogs when
running on Windows Vista or newer.  See Tcl/Tk's TIP 432 for more
information.  Also, this version of Tcl/Tk includes support for Windows
10.

@item 
bpo-17896@footnote{https://bugs.python.org/issue17896}: The Windows build scripts now expect external library sources
to be in @code{PCbuild\..\externals} rather than @code{PCbuild\..\..}.

@item 
bpo-17717@footnote{https://bugs.python.org/issue17717}: The Windows build scripts now use a copy of NASM pulled from
svn.python.org to build OpenSSL.

@item 
bpo-21907@footnote{https://bugs.python.org/issue21907}: Improved the batch scripts provided for building Python.

@item 
bpo-22644@footnote{https://bugs.python.org/issue22644}: OpenSSL的捆绑版本已更新到1.0.1j。

@item 
bpo-10747@footnote{https://bugs.python.org/issue10747}: Use versioned labels in the Windows start menu. Patch by Olive
Kilburn.

@item 
bpo-22980@footnote{https://bugs.python.org/issue22980}: .pyd files with a version and platform tag (for example,
".cp35-win32.pyd") will now be loaded in preference to those without tags.
@end itemize

@strong{（有关旧版本的信息，请参阅HISTORY文件。)}

@node Python 教程,Python安装和使用,Python的新变化,Top
@anchor{tutorial/index doc}@anchor{118c}@anchor{tutorial/index the-python-tutorial}@anchor{118d}@anchor{tutorial/index tutorial-index}@anchor{118e}
@chapter Python 教程


Python 是一种易于学习又功能强大的编程语言。它提供了高效的高级数据结构，还能简单有效地面向对象编程。Python 优雅的语法和动态类型，以及解释型语言的本质，使它成为多数平台上写脚本和快速开发应用的理想语言。

Python 解释器及丰富的标准库，提供了适用于各个主要系统平台的源码或机器码，这些可以到 Python 官网 @indicateurl{https://www.python.org/} 免费获取，并可自由地分发。许多免费的第三方 Python 模块、程序、工具和它们的文档，也能在这个网站上找到对应内容或链接。

Python 解释器易于扩展，可以使用 C 或 C++（或者其他可以从 C 调用的语言）扩展新的功能和数据类型。Python 也可用作可定制化软件中的扩展程序语言。

这个教程非正式地介绍了 Python 语言和系统的基本概念和功能。最好在阅读的时候准备一个 Python 解释器进行练习。所有的例子都是相互独立的，所以这个教程也可以离线阅读。

有关标准的对象和模块，请参阅 @ref{118f,,Python 标准库}。@ref{1190,,Python语言参考} 提供了更正式的语言定义。想要编写 C 或者 C++ 扩展可以参考 @ref{1191,,扩展和嵌入 Python 解释器} 和 @ref{1192,,Python/C API 参考手册}。另外还有不少书籍深入讲解 Python。

这个教程并没有完整地介绍每一个功能，甚至可能没有涉及全部的常用功能。这个教程只介绍 Python 中最值得注意的功能，也会让你体会到这个语言的风格特色。学习完这个教程，你将可以阅读和编写 Python 模块和程序，也可以开始学习 @ref{118f,,Python 标准库}。

@ref{1193,,术语对照表} 也很值得一读。

@menu
* 课前甜点:: 
* 使用 Python 解释器:: 
* Python 的非正式介绍:: 
* 其他流程控制工具:: 
* 数据结构:: 
* 模块:: 
* 输入输出:: 
* 错误和异常:: 
* 类:: 
* 标准库简介:: 
* 标准库简介 —— 第二部分:: 
* 虚拟环境和包:: 
* 接下来？:: 
* 交互式编辑和编辑历史:: 
* 浮点算术：争议和限制:: 
* 附录:: 

@end menu

@node 课前甜点,使用 Python 解释器,,Python 教程
@anchor{tutorial/appetite doc}@anchor{1194}@anchor{tutorial/appetite tut-intro}@anchor{1195}@anchor{tutorial/appetite whetting-your-appetite}@anchor{1196}
@section 课前甜点


如果你经常在电脑上工作，总会有些任务会想让它自动化。比如，对一大堆文本文件进行查找替换，对很多照片文件按照比较复杂的规则重命名并放入不同的文件夹。也可能你想写一个小型的数据库应用，一个特定的图形界面应用，或者一个简单的游戏。

如果你是专业的软件开发人员，你可能需要编写一些 C/C++/Java 库，但总觉得通常的 编写、编译、测试、再次编译 流程太慢了。可能给这样的库写一组测试，就是很麻烦的工作了。或许你写了个软件，可以支持插件扩展语言，但你不想为了自己这一个应用，专门设计和实现一种新语言了。

那么，Python 正好能满足你的需要。

对于这些任务，你也可以写 Unix shell 脚本或者 Windows 批处理完成，但是 shell 脚本最擅长移动文件和替换文本，并不适合 GUI 界面或者游戏开发。你可以写一个 C/C++/Java 程序，但是可能初稿都要很长的开发时间。Python 的使用则更加简单，可以在 Windows，Mac OS X，以及 Unix 操作系统上使用，而且可以帮你更快地完成工作。

Python 很容易使用，但它是一种真正的编程语言，提供了很多数据结构，也支持大型程序，远超 shell 脚本或批处理文件的功能。Python 还提供比 C 语言更多的错误检查，而且作为一种 “超高级语言”，它有高级的内置数据类型，比如灵活的数组和字典。正因为这些更加通用的数据类型，Python 能够应付更多的问题，超过 Awk 甚至 Perl，而且很多东西在 Python 中至少和那些语言同样简单。

Python 允许你将程序划分为能在其他的 Python 程序中重复利用的模块。它内置了很多的标准模块，你可以在此基础上开发程序——也可以作为例子，开始学习 Python 编程。例如，一切内置模块提供诸如文件输入输出、系统调用、套接字、甚至图形界面接口工作包比如 Tk。

Python 是一种解释型语言，在程序开发阶段可以为你节省大量时间，因为不需要编译和链接。解释器可以交互式使用，这样就可以方便地尝试语言特性，写一些一次性的程序，或者在自底向上的程序开发中测试功能。它也是一个顺手的桌面计算器。

Python 程序的书写是紧凑而易读的。Python 代码通常比同样功能的 C，C++，Java 代码要短很多，有如下几个原因：


@itemize *

@item 
高级数据类型允许在一个表达式中表示复杂的操作；

@item 
代码块的划分是按照缩进而不是成对的花括号；

@item 
不需要预先定义变量或参数。
@end itemize

Python 是 “可扩展的”：如果你知道怎么写 C 语言程序，就能很容易地给解释器添加新的内置函数或模块，不论是让关键的操作以最高速度运行，还是把 Python 程序链接到只提供预编译程序的库（比如硬件相关的图形库）。一旦你真正链接上了，就能在 Python 解释器中扩展或者控制 C 语言编写的应用了。

顺便提一下，这种语言的名字（python 一词直译为 “蟒蛇”）得名自 BBC 节目 “Monty Python的飞行马戏团” ，而与爬行动物没有关系。在文档中用 Monty Python 来开玩笑不只是被允许的，还是被推荐的！

现在你已经对 Python 跃跃欲试了，想要深入了解一些细节了。因为学习语言的最佳方式是使用它，本教程邀请你一边阅读，一边在 Python 解释器中玩耍。

在下一章节，会讲解使用解释器的方法。看起来相当枯燥，但是对于尝试后续的例子来说，是非常关键的。

教程的其他部分将通过示例介绍 Python 语言和系统中的不同功能，开始是比较简单的表达式、语句和数据类型，然后是函数和模块，最终接触一些高级概念，比如异常、用户定义的类。

@node 使用 Python 解释器,Python 的非正式介绍,课前甜点,Python 教程
@anchor{tutorial/interpreter doc}@anchor{1197}@anchor{tutorial/interpreter tut-using}@anchor{1198}@anchor{tutorial/interpreter using-the-python-interpreter}@anchor{1199}
@section 使用 Python 解释器


@menu
* 调用解释器:: 
* 解释器的运行环境:: 

@end menu

@node 调用解释器,解释器的运行环境,,使用 Python 解释器
@anchor{tutorial/interpreter invoking-the-interpreter}@anchor{119a}@anchor{tutorial/interpreter tut-invoking}@anchor{119b}
@subsection 调用解释器


Python 解释器在其被使用的机器上通常安装为 @code{/usr/local/bin/python3.8}；将 @code{/usr/local/bin} 加入你的 Unix 终端的搜索路径就可以通过键入以下命令来启动它：

@example
python3.8
@end example

就能运行了 @footnote{@w{(1)} 
在Unix系统中，Python 3.x解释器默认安装后的执行文件并不叫作 @code{python}，这样才不会与同时安装的Python 2.x冲突。
} 。安装时可以选择安装目录，所以解释器也可能在别的地方；可以问问你身边的 Python 大牛，或者你的系统管理员。（比如 @code{/usr/local/python} 也是比较常用的备选路径）

在 Windows 机器上当你从 @ref{119c,,Microsoft Store} 安装 Python 之后，@code{python3.8} 命令将可使用。 如果你安装了 @ref{989,,py.exe 启动器}，你将可以使用 @code{py} 命令。 参阅 @ref{119d,,附录：设置环境变量} 了解其他启动 Python 的方式。

在主提示符中输入文件结束字符（在 Unix 系统中是 @code{Control-D}，Windows 系统中是 @code{Control-Z}）就退出解释器并返回退出状态为0。如果这样不管用，你还可以写这个命令退出：@code{quit()}。

解释器的行编辑功能在支持 GNU Readline@footnote{https://tiswww.case.edu/php/chet/readline/rltop.html} 库的系统中也包括交互式编辑，历史替换和代码补全等。 检测是否支持行编辑最快速的方式是在首次出现 Python 提示符时输入 @code{Control-P}。 如果听到“哔”提示音，就说明支持行编辑；请参阅附录 @ref{119e,,交互式编辑和编辑历史} 了解有关功能键的介绍。 如果什么都没发生，或是回显了 @code{^P}，说明不支持行编辑；你只能用退格键从当前行中删除字符。

解释器运行的时候有点像 Unix 命令行：在一个标准输入 tty 设备上调用，它能交互式地读取和执行命令；调用时提供文件名参数，或者有个文件重定向到标准输入的话，它就会读取和执行文件中的 @emph{脚本}。

另一种启动解释器的方式是 @code{python -c command [arg] ...}，其中 @emph{command} 要换成想执行的指令，就像命令行的 @ref{119f,,-c} 选项。由于 Python 代码中经常会包含对终端来说比较特殊的字符，通常情况下都建议用英文单引号把 @emph{command} 括起来。

有些 Python 模块也可以作为脚本使用。可以这样输入：@code{python -m module [arg] ...}，这会执行 @emph{module} 的源文件，就跟你在命令行把路径写全了一样。

在运行脚本的时候，有时可能也会需要在运行后进入交互模式。这种时候在文件参数前，加上选项 @ref{e18,,-i} 就可以了。

关于所有的命令行选项，请参考 @ref{f39,,命令行与环境}。

@menu
* 传入参数:: 
* 交互模式:: 

@end menu

@node 传入参数,交互模式,,调用解释器
@anchor{tutorial/interpreter argument-passing}@anchor{11a0}@anchor{tutorial/interpreter tut-argpassing}@anchor{11a1}
@subsubsection 传入参数


如果可能的话，解释器会读取命令行参数，转化为字符串列表存入 @code{sys} 模块中的 @code{argv} 变量中。执行命令 @code{import sys} 你可以导入这个模块并访问这个列表。这个列表最少也会有一个元素；如果没有给定输入参数，@code{sys.argv[0]} 就是个空字符串。如果脚本名是 @code{'-'`@w{`}（标准输入）时，`@w{`}sys.argv[0]} 就是 @code{'-'}。使用 @ref{119f,,-c} @emph{命令} 时，@code{sys.argv[0]} 就会是 @code{'-c'}。如果使用选项 @ref{330,,-m} @emph{module}，@code{sys.argv[0]} 就是包含目录的模块全名。在 @ref{119f,,-c} @emph{command} 或 @ref{330,,-m} @emph{module} 之后的选项不会被解释器处理，而会直接留在 @code{sys.argv} 中给命令或模块来处理。

@node 交互模式,,传入参数,调用解释器
@anchor{tutorial/interpreter interactive-mode}@anchor{11a2}@anchor{tutorial/interpreter tut-interactive}@anchor{8dd}
@subsubsection 交互模式


在终端（tty）输入并执行指令时，我们说解释器是运行在 @emph{交互模式（interactive mode）}。在这种模式中，它会显示 @emph{主提示符（primary prompt）}，提示输入下一条指令，通常用三个大于号（@code{>>>}）表示；连续输入行的时候，它会显示 @emph{次要提示符}，默认是三个点（@code{...}）。进入解释器时，它会先显示欢迎信息、版本信息、版权声明，然后就会出现提示符：

@example
$ python3.8
Python 3.8 (default, Sep 16 2015, 09:25:04)
[GCC 4.8.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
@end example

@c XXX update for new releases

多行指令需要在连续的多行中输入。比如，以 @ref{de0,,if} 为例：

@example
>>> the_world_is_flat = True
>>> if the_world_is_flat:
...     print("Be careful not to fall off!")
...
Be careful not to fall off!
@end example

有关交互模式的更多内容，请见 @ref{11a3,,交互模式}。

@node 解释器的运行环境,,调用解释器,使用 Python 解释器
@anchor{tutorial/interpreter the-interpreter-and-its-environment}@anchor{11a4}@anchor{tutorial/interpreter tut-interp}@anchor{11a5}
@subsection 解释器的运行环境


@menu
* 源文件的字符编码:: 

@end menu

@node 源文件的字符编码,,,解释器的运行环境
@anchor{tutorial/interpreter source-code-encoding}@anchor{11a6}@anchor{tutorial/interpreter tut-source-encoding}@anchor{11a7}
@subsubsection 源文件的字符编码


默认情况下，Python 源码文件以 UTF-8 编码方式处理。在这种编码方式中，世界上大多数语言的字符都可以同时用于字符串字面值、变量或函数名称以及注释中——尽管标准库中只用常规的 ASCII 字符作为变量或函数名，而且任何可移植的代码都应该遵守此约定。要正确显示这些字符，你的编辑器必须能识别 UTF-8 编码，而且必须使用能支持打开的文件中所有字符的字体。

如果不使用默认编码，要声明文件所使用的编码，文件的 @emph{第一} 行要写成特殊的注释。语法如下所示：

@example
# -*- coding: encoding -*-
@end example

其中 @emph{encoding} 可以是 Python 支持的任意一种 @ref{1c,,codecs}。

比如，要声明使用 Windows-1252 编码，你的源码文件要写成：

@example
# -*- coding: cp1252 -*-
@end example

关于 @emph{第一行} 规则的一种例外情况是，源码以 @ref{11a8,,UNIX "shebang" 行} 开头。这种情况下，编码声明就要写在文件的第二行。例如：

@example
#!/usr/bin/env python3
# -*- coding: cp1252 -*-
@end example

@subsubheading 备注


@node Python 的非正式介绍,其他流程控制工具,使用 Python 解释器,Python 教程
@anchor{tutorial/introduction doc}@anchor{11a9}@anchor{tutorial/introduction an-informal-introduction-to-python}@anchor{11aa}@anchor{tutorial/introduction tut-informal}@anchor{11ab}
@section Python 的非正式介绍


在下面的例子中，通过提示符 (@ref{11ac,,>>>} 与 @ref{11ad,,...}) 的出现与否来区分输入和输出：如果你想复现这些例子，当提示符出现后，你必须在提示符后键入例子中的每一个词；不以提示符开头的那些行是解释器的输出。注意例子中某行中出现第二个提示符意味着你必须键入一个空白行；这是用来结束多行命令的。

@geindex # (hash); comment

这个手册中的许多例子都包含注释，甚至交互性命令中也有。Python中的注释以井号 @code{#} 开头，并且一直延伸到该文本行结束为止。注释可以出现在一行的开头或者是空白和代码的后边，但是不能出现在字符串中间。字符串中的井号就是井号。因为注释是用来阐明代码的，不会被 Python 解释，所以在键入这些例子时，注释是可以被忽略的。

几个例子:

@example
# this is the first comment
spam = 1  # and this is the second comment
          # ... and now a third!
text = "# This is not a comment because it's inside quotes."
@end example

@menu
* Python 作为计算器使用:: 
* 走向编程的第一步:: 

@end menu

@node Python 作为计算器使用,走向编程的第一步,,Python 的非正式介绍
@anchor{tutorial/introduction tut-calculator}@anchor{11ae}@anchor{tutorial/introduction using-python-as-a-calculator}@anchor{11af}
@subsection Python 作为计算器使用


让我们尝试一些简单的 Python 命令。启动解释器，等待界面中的提示符，@code{>>>} （这应该花不了多少时间）。

@menu
* 数字:: 
* 字符串:: 
* 列表:: 

@end menu

@node 数字,字符串,,Python 作为计算器使用
@anchor{tutorial/introduction numbers}@anchor{11b0}@anchor{tutorial/introduction tut-numbers}@anchor{11b1}
@subsubsection 数字


解释器就像一个简单的计算器一样：你可以在里面输入一个表达式然后它会写出答案。 表达式的语法很直接：运算符 @code{+}、@code{-}、@code{*}、@code{/} 的用法和其他大部分语言一样（比如 Pascal 或者 C 语言）；括号 (@code{()}) 用来分组。比如:

@example
>>> 2 + 2
4
>>> 50 - 5*6
20
>>> (50 - 5*6) / 4
5.0
>>> 8 / 5  # division always returns a floating point number
1.6
@end example

整数（比如 @code{2}、@code{4}、@code{20} ）的类型是 @ref{184,,int}，有小数部分的（比如 @code{5.0}、@code{1.6} ）的类型是 @ref{187,,float}。 在这个手册的后半部分我们会看到更多的数字类型。

除法运算 (@code{/}) 永远返回浮点数类型。如果要做 @ref{11b2,,floor division} 得到一个整数结果（忽略小数部分）你可以使用 @code{//} 运算符；如果要计算余数，可以使用 @code{%}

@example
>>> 17 / 3  # classic division returns a float
5.666666666666667
>>>
>>> 17 // 3  # floor division discards the fractional part
5
>>> 17 % 3  # the % operator returns the remainder of the division
2
>>> 5 * 3 + 2  # result * divisor + remainder
17
@end example

在Python中，可以使用 @code{**} 运算符来计算乘方 @footnote{@w{(1)} 
因为 @code{**} 比 @code{-} 有更高的优先级, 所以 @code{-3**2} 会被解释成 @code{-(3**2)} ，因此结果是 @code{-9}.  为了避免这个并且得到结果 @code{9}, 你可以用这个式子 @code{(-3)**2}.
}

@example
>>> 5 ** 2  # 5 squared
25
>>> 2 ** 7  # 2 to the power of 7
128
@end example

等号 (@code{=}) 用于给一个变量赋值。然后在下一个交互提示符之前不会有结果显示出来:

@example
>>> width = 20
>>> height = 5 * 9
>>> width * height
900
@end example

如果一个变量未定义（未赋值），试图使用它时会向你提示错误:

@example
>>> n  # try to access an undefined variable
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'n' is not defined
@end example

Python中提供浮点数的完整支持；包含多种混合类型运算数的运算会把整数转换为浮点数:

@example
>>> 4 * 3.75 - 1
14.0
@end example

在交互模式下，上一次打印出来的表达式被赋值给变量 @code{_}。这意味着当你把Python用作桌面计算器时，继续计算会相对简单，比如:

@example
>>> tax = 12.5 / 100
>>> price = 100.50
>>> price * tax
12.5625
>>> price + _
113.0625
>>> round(_, 2)
113.06
@end example

这个变量应该被使用者当作是只读类型。不要向它显式地赋值——你会创建一个和它名字相同独立的本地变量，它会使用魔法行为屏蔽内部变量。

除了 @ref{184,,int} 和 @ref{187,,float}，Python也支持其他类型的数字，例如 @ref{188,,Decimal} 或者 @ref{185,,Fraction}。Python 也内置对 @ref{11b3,,复数} 的支持，使用后缀 @code{j} 或者 @code{J} 就可以表示虚数部分（例如 @code{3+5j} ）。

@node 字符串,列表,数字,Python 作为计算器使用
@anchor{tutorial/introduction strings}@anchor{11b4}@anchor{tutorial/introduction tut-strings}@anchor{11b5}
@subsubsection 字符串


除了数字，Python 也可以操作字符串。字符串有多种形式，可以使用单引号（@code{'...'}），双引号（@code{"..."}）都可以获得同样的结果 @footnote{@w{(2)} 
和其他语言不一样的是, 特殊字符比如说 @code{\n} 在单引号 (@code{'...'}) 和双引号 (@code{"..."}) 里有一样的意义. 这两种引号唯一的区别是，你不需要在单引号里转义双引号 @code{"} (但是你必须把单引号转义成 @code{\'}) ， 反之亦然.
}。反斜杠 @code{\} 可以用来转义:

@example
>>> 'spam eggs'  # single quotes
'spam eggs'
>>> 'doesn\'t'  # use \' to escape the single quote...
"doesn't"
>>> "doesn't"  # ...or use double quotes instead
"doesn't"
>>> '"Yes," they said.'
'"Yes," they said.'
>>> "\"Yes,\" they said."
'"Yes," they said.'
>>> '"Isn\'t," they said.'
'"Isn\'t," they said.'
@end example

在交互式解释器中，输出的字符串外面会加上引号，特殊字符会使用反斜杠来转义。 虽然有时这看起来会与输入不一样（外面所加的引号可能会改变），但两个字符串是相同的。 如果字符串中有单引号而没有双引号，该字符串外将加双引号来表示，否则就加单引号。 @ref{880,,print()} 函数会生成可读性更强的输出，即略去两边的引号，并且打印出经过转义的特殊字符:

@example
>>> '"Isn\'t," they said.'
'"Isn\'t," they said.'
>>> print('"Isn\'t," they said.')
"Isn't," they said.
>>> s = 'First line.\nSecond line.'  # \n means newline
>>> s  # without print(), \n is included in the output
'First line.\nSecond line.'
>>> print(s)  # with print(), \n produces a new line
First line.
Second line.
@end example

如果你不希望前置了 @code{\} 的字符转义成特殊字符，可以使用 @emph{原始字符串} 方式，在引号前添加 @code{r} 即可:

@example
>>> print('C:\some\name')  # here \n means newline!
C:\some
ame
>>> print(r'C:\some\name')  # note the r before the quote
C:\some\name
@end example

字符串字面值可以跨行连续输入。一种方式是用三重引号：@code{"""..."""} 或 @code{'@w{'}'...'@w{'}'}。字符串中的回车换行会自动包含到字符串中，如果不想包含，在行尾添加一个 @code{\} 即可。如下例:

@example
print("""\
Usage: thingy [OPTIONS]
     -h                        Display this usage message
     -H hostname               Hostname to connect to
""")
@end example

将产生如下输出（注意最开始的换行没有包括进来）:

@example
Usage: thingy [OPTIONS]
     -h                        Display this usage message
     -H hostname               Hostname to connect to
@end example

字符串可以用 @code{+} 进行连接（粘到一起），也可以用 @code{*} 进行重复:

@example
>>> # 3 times 'un', followed by 'ium'
>>> 3 * 'un' + 'ium'
'unununium'
@end example

相邻的两个或多个 @emph{字符串字面值} （引号引起来的字符）将会自动连接到一起.

@example
>>> 'Py' 'thon'
'Python'
@end example

把很长的字符串拆开分别输入的时候尤其有用:

@example
>>> text = ('Put several strings within parentheses '
...         'to have them joined together.')
>>> text
'Put several strings within parentheses to have them joined together.'
@end example

只能对两个字面值这样操作，变量或表达式不行:

@example
>>> prefix = 'Py'
>>> prefix 'thon'  # can't concatenate a variable and a string literal
  File "<stdin>", line 1
    prefix 'thon'
                ^
SyntaxError: invalid syntax
>>> ('un' * 3) 'ium'
  File "<stdin>", line 1
    ('un' * 3) 'ium'
                   ^
SyntaxError: invalid syntax
@end example

如果你想连接变量，或者连接变量和字面值，可以用 @code{+} 号:

@example
>>> prefix + 'thon'
'Python'
@end example

字符串是可以被 @emph{索引} （下标访问）的，第一个字符索引是 0。单个字符并没有特殊的类型，只是一个长度为一的字符串:

@example
>>> word = 'Python'
>>> word[0]  # character in position 0
'P'
>>> word[5]  # character in position 5
'n'
@end example

索引也可以用负数，这种会从右边开始数:

@example
>>> word[-1]  # last character
'n'
>>> word[-2]  # second-last character
'o'
>>> word[-6]
'P'
@end example

注意 -0 和 0 是一样的，所以负数索引从 -1 开始。

除了索引，字符串还支持 @emph{切片}。索引可以得到单个字符，而 @emph{切片} 可以获取子字符串:

@example
>>> word[0:2]  # characters from position 0 (included) to 2 (excluded)
'Py'
>>> word[2:5]  # characters from position 2 (included) to 5 (excluded)
'tho'
@end example

注意切片的开始总是被包括在结果中，而结束不被包括。这使得 @code{s[:i] + s[i:]} 总是等于 @code{s}

@example
>>> word[:2] + word[2:]
'Python'
>>> word[:4] + word[4:]
'Python'
@end example

切片的索引有默认值；省略开始索引时默认为0，省略结束索引时默认为到字符串的结束:

@example
>>> word[:2]   # character from the beginning to position 2 (excluded)
'Py'
>>> word[4:]   # characters from position 4 (included) to the end
'on'
>>> word[-2:]  # characters from the second-last (included) to the end
'on'
@end example

您也可以这么理解切片：将索引视作指向字符 @emph{之间} ，第一个字符的左侧标为0，最后一个字符的右侧标为 @emph{n} ，其中 @emph{n} 是字符串长度。例如:

@example
 +---+---+---+---+---+---+
 | P | y | t | h | o | n |
 +---+---+---+---+---+---+
 0   1   2   3   4   5   6
-6  -5  -4  -3  -2  -1
@end example

第一行数标注了字符串 0...6 的索引的位置，第二行标注了对应的负的索引。那么从 @emph{i} 到 @emph{j} 的切片就包括了标有 @emph{i} 和 @emph{j} 的位置之间的所有字符。

对于使用非负索引的切片，如果索引不越界，那么得到的切片长度就是起止索引之差。例如， @code{word[1:3]} 的长度为2。

试图使用过大的索引会产生一个错误:

@example
>>> word[42]  # the word only has 6 characters
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: string index out of range
@end example

但是，切片中的越界索引会被自动处理:

@example
>>> word[4:42]
'on'
>>> word[42:]
'@w{'}
@end example

Python 中的字符串不能被修改，它们是  @ref{11b6,,immutable} 的。因此，向字符串的某个索引位置赋值会产生一个错误:

@example
>>> word[0] = 'J'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment
>>> word[2:] = 'py'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment
@end example

如果需要一个不同的字符串，应当新建一个:

@example
>>> 'J' + word[1:]
'Jython'
>>> word[:2] + 'py'
'Pypy'
@end example

内建函数 @ref{150,,len()} 返回一个字符串的长度:

@example
>>> s = 'supercalifragilisticexpialidocious'
>>> len(s)
34
@end example


@subsubheading 参见



@table @asis

@item @ref{11b7,,文本序列类型 --- str}

字符串是一种 @emph{序列类型} ，因此也支持序列类型的各种操作。

@item @ref{11b8,,字符串的方法}

字符串支持许多变换和查找的方法。

@item @ref{15c,,格式化字符串字面值}

内嵌表达式的字符串字面值。

@item @ref{d13,,格式字符串语法}

使用 @ref{4d4,,str.format()} 进行字符串格式化。

@item @ref{11b9,,printf 风格的字符串格式化}

这里详述了使用 @code{%} 运算符进行字符串格式化。
@end table


@node 列表,,字符串,Python 作为计算器使用
@anchor{tutorial/introduction lists}@anchor{11ba}@anchor{tutorial/introduction tut-lists}@anchor{11bb}
@subsubsection 列表


Python 中可以通过组合一些值得到多种 @emph{复合} 数据类型。其中最常用的 @emph{列表} ，可以通过方括号括起、逗号分隔的一组值（元素）得到。一个 @emph{列表} 可以包含不同类型的元素，但通常使用时各个元素类型相同:

@example
>>> squares = [1, 4, 9, 16, 25]
>>> squares
[1, 4, 9, 16, 25]
@end example

和字符串（以及各种内置的 @ref{11bc,,sequence} 类型）一样，列表也支持索引和切片:

@example
>>> squares[0]  # indexing returns the item
1
>>> squares[-1]
25
>>> squares[-3:]  # slicing returns a new list
[9, 16, 25]
@end example

所有的切片操作都返回一个包含所请求元素的新列表。 这意味着以下切片操作会返回列表的一个 @ref{11bd,,浅拷贝}:

@example
>>> squares[:]
[1, 4, 9, 16, 25]
@end example

列表同样支持拼接操作:

@example
>>> squares + [36, 49, 64, 81, 100]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
@end example

与 @ref{11b6,,immutable} 的字符串不同, 列表是一个 @ref{11be,,mutable} 类型，就是说，它自己的内容可以改变:

@example
>>> cubes = [1, 8, 27, 65, 125]  # something's wrong here
>>> 4 ** 3  # the cube of 4 is 64, not 65!
64
>>> cubes[3] = 64  # replace the wrong value
>>> cubes
[1, 8, 27, 64, 125]
@end example

你也可以在列表末尾通过 @code{append()} @emph{方法} 来添加新元素（我们将在后面介绍有关方法的详情）:

@example
>>> cubes.append(216)  # add the cube of 6
>>> cubes.append(7 ** 3)  # and the cube of 7
>>> cubes
[1, 8, 27, 64, 125, 216, 343]
@end example

给切片赋值也是可以的，这样甚至可以改变列表大小，或者把列表整个清空:

@example
>>> letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> letters
['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> # replace some values
>>> letters[2:5] = ['C', 'D', 'E']
>>> letters
['a', 'b', 'C', 'D', 'E', 'f', 'g']
>>> # now remove them
>>> letters[2:5] = []
>>> letters
['a', 'b', 'f', 'g']
>>> # clear the list by replacing all the elements with an empty list
>>> letters[:] = []
>>> letters
[]
@end example

内置函数 @ref{150,,len()} 也可以作用到列表上:

@example
>>> letters = ['a', 'b', 'c', 'd']
>>> len(letters)
4
@end example

也可以嵌套列表 (创建包含其他列表的列表), 比如说:

@example
>>> a = ['a', 'b', 'c']
>>> n = [1, 2, 3]
>>> x = [a, n]
>>> x
[['a', 'b', 'c'], [1, 2, 3]]
>>> x[0]
['a', 'b', 'c']
>>> x[0][1]
'b'
@end example

@node 走向编程的第一步,,Python 作为计算器使用,Python 的非正式介绍
@anchor{tutorial/introduction first-steps-towards-programming}@anchor{11bf}@anchor{tutorial/introduction tut-firststeps}@anchor{11c0}
@subsection 走向编程的第一步


当然，我们可以将 Python 用于更复杂的任务，而不是仅仅两个和两个一起添加。 例如，我们可以编写 斐波那契数列@footnote{https://en.wikipedia.org/wiki/Fibonacci_number} 的初始子序列，如下所示:

@example
>>> # Fibonacci series:
... # the sum of two elements defines the next
... a, b = 0, 1
>>> while a < 10:
...     print(a)
...     a, b = b, a+b
...
0
1
1
2
3
5
8
@end example

这个例子引入了几个新的特性。


@itemize *

@item 
第一行含有一个 @emph{多重赋值}: 变量 @code{a} 和 @code{b} 同时得到了新值 0 和 1.  最后一行又用了一次多重赋值, 这展示出了右手边的表达式，在任何赋值发生之前就被求值了。右手边的表达式是从左到右被求值的。

@item 
@ref{11c1,,while} 循环只要它的条件（这里指： @code{a < 10}）保持为真就会一直执行。Python 和 C 一样，任何非零整数都为真；零为假。这个条件也可以是字符串或是列表的值，事实上任何序列都可以；长度非零就为真，空序列就为假。在这个例子里，判断条件是一个简单的比较。标准的比较操作符的写法和 C 语言里是一样： @code{<} （小于）、 @code{>} （大于）、 @code{==} （等于）、 @code{<=} （小于或等于)、 @code{>=} （大于或等于）以及 @code{!=} （不等于）。

@item 
@emph{循环体} 是 @emph{缩进的} ：缩进是 Python 组织语句的方式。在交互式命令行里，你得给每个缩进的行敲下 Tab 键或者（多个）空格键。实际上用文本编辑器的话，你要准备更复杂的输入方式；所有像样的文本编辑器都有自动缩进的设置。交互式命令行里，当一个组合的语句输入时, 需要在最后敲一个空白行表示完成（因为语法分析器猜不出来你什么时候打的是最后一行）。注意，在同一块语句中的每一行，都要缩进相同的长度。

@item 
@ref{880,,print()} 函数将所有传进来的参数值打印出来. 它和直接输入你要显示的表达式(比如我们之前在计算器的例子里做的)不一样， print() 能处理多个参数，包括浮点数，字符串。 字符串会打印不带引号的内容, 并且在参数项之间会插入一个空格, 这样你就可以很好的把东西格式化, 像这样:

@example
>>> i = 256*256
>>> print('The value of i is', i)
The value of i is 65536
@end example

关键字参数 @emph{end} 可以用来取消输出后面的换行, 或使用另外一个字符串来结尾:

@example
>>> a, b = 0, 1
>>> while a < 1000:
...     print(a, end=',')
...     a, b = b, a+b
...
0,1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,
@end example
@end itemize

@subsubheading 备注


@node 其他流程控制工具,数据结构,Python 的非正式介绍,Python 教程
@anchor{tutorial/controlflow doc}@anchor{11c2}@anchor{tutorial/controlflow more-control-flow-tools}@anchor{11c3}@anchor{tutorial/controlflow tut-morecontrol}@anchor{11c4}
@section 其他流程控制工具


除了刚刚介绍过的 @ref{11c1,,while} 语句，Python 中也会使用其他语言中常见的流程控制语句，只是稍有变化。

@menu
* if 语句:: 
* for 语句:: 
* range() 函数: range 函数. 
* break 和 continue 语句，以及循环中的 else 子句:: 
* pass 语句:: 
* 定义函数:: 
* 函数定义的更多形式:: 
* 小插曲：编码风格:: 

@end menu

@node if 语句,for 语句,,其他流程控制工具
@anchor{tutorial/controlflow if-statements}@anchor{11c5}@anchor{tutorial/controlflow tut-if}@anchor{11c6}
@subsection @code{if} 语句


可能最为人所熟知的编程语句就是 @ref{de0,,if} 语句了。例如

@example
>>> x = int(input("Please enter an integer: "))
Please enter an integer: 42
>>> if x < 0:
...     x = 0
...     print('Negative changed to zero')
... elif x == 0:
...     print('Zero')
... elif x == 1:
...     print('Single')
... else:
...     print('More')
...
More
@end example

可以有零个或多个 @ref{11c7,,elif} 部分，以及一个可选的 @ref{11c8,,else} 部分。 关键字 '@code{elif}' 是 'else if' 的缩写，适合用于避免过多的缩进。 一个 @code{if} ... @code{elif} ... @code{elif} ... 序列可以看作是其他语言中的 @code{switch} 或 @code{case} 语句的替代。

@node for 语句,range 函数,if 语句,其他流程控制工具
@anchor{tutorial/controlflow for-statements}@anchor{11c9}@anchor{tutorial/controlflow tut-for}@anchor{11ca}
@subsection @code{for} 语句


@geindex 语句; for

Python 中的 @ref{c29,,for} 语句与你在 C 或 Pascal 中所用到的有所不同。 Python 中的 @code{for} 语句并不总是对算术递增的数值进行迭代（如同 Pascal），或是给予用户定义迭代步骤和暂停条件的能力（如同 C），而是对任意序列进行迭代（例如列表或字符串），条目的迭代顺序与它们在序列中出现的顺序一致。 例如（此处英文为双关语）:

@c One suggestion was to give a real C example here, but that may only serve to
@c confuse non-C programmers.

@example
>>> # Measure some strings:
... words = ['cat', 'window', 'defenestrate']
>>> for w in words:
...     print(w, len(w))
...
cat 3
window 6
defenestrate 12
@end example

在遍历同一个集合时修改该集合的代码可能很难获得正确的结果。通常，更直接的做法是循环遍历该集合的副本或创建新集合：

@example
# Strategy:  Iterate over a copy
for user, status in users.copy().items():
    if status == 'inactive':
        del users[user]

# Strategy:  Create a new collection
active_users = @{@}
for user, status in users.items():
    if status == 'active':
        active_users[user] = status
@end example

@node range 函数,break 和 continue 语句，以及循环中的 else 子句,for 语句,其他流程控制工具
@anchor{tutorial/controlflow the-range-function}@anchor{11cb}@anchor{tutorial/controlflow tut-range}@anchor{11cc}
@subsection @code{range()} 函数


如果你确实需要遍历一个数字序列，内置函数 @ref{9b8,,range()}  会派上用场。它生成算术级数:

@example
>>> for i in range(5):
...     print(i)
...
0
1
2
3
4
@end example

给定的终止数值并不在要生成的序列里；@code{range(10)} 会生成10个值，并且是以合法的索引生成一个长度为10的序列。range也可以以另一个数字开头，或者以指定的幅度增加（甚至是负数；有时这也被叫做 '步进'）

@example
range(5, 10)
   5, 6, 7, 8, 9

range(0, 10, 3)
   0, 3, 6, 9

range(-10, -100, -30)
  -10, -40, -70
@end example

要以序列的索引来迭代，您可以将 @ref{9b8,,range()} 和 @ref{150,,len()} 组合如下:

@example
>>> a = ['Mary', 'had', 'a', 'little', 'lamb']
>>> for i in range(len(a)):
...     print(i, a[i])
...
0 Mary
1 had
2 a
3 little
4 lamb
@end example

然而，在大多数这类情况下，使用 @ref{ddc,,enumerate()} 函数比较方便，请参见 @ref{11cd,,循环的技巧} 。

如果你只打印 range，会出现奇怪的结果:

@example
>>> print(range(10))
range(0, 10)
@end example

@ref{9b8,,range()} 所返回的对象在许多方面表现得像一个列表，但实际上却并不是。此对象会在你迭代它时基于所希望的序列返回连续的项，但它没有真正生成列表，这样就能节省空间。

我们称这样对象为 @ref{ba5,,iterable}，也就是说，适合作为这样的目标对象：函数和结构期望从中获取连续的项直到所提供的项全部耗尽。 我们已经看到 @ref{c29,,for} 语句就是这样一种结构，而接受可迭代对象的函数的一个例子是 @ref{1e5,,sum()}:

@example
>>> sum(range(4))  # 0 + 1 + 2 + 3
6
@end example

稍后我们将看到更多返回可迭代对象以及将可迭代对象作为参数的函数。 最后，也许你会很好奇如何从一个指定范围内获取一个列表。 以下是解决方案：

@example
>>> list(range(4))
[0, 1, 2, 3]
@end example

在 @ref{11ce,,数据结构} 章节中，我们将讨论 @ref{262,,list()} 的更多细节。

@node break 和 continue 语句，以及循环中的 else 子句,pass 语句,range 函数,其他流程控制工具
@anchor{tutorial/controlflow break-and-continue-statements-and-else-clauses-on-loops}@anchor{11cf}@anchor{tutorial/controlflow tut-break}@anchor{11d0}
@subsection @code{break} 和 @code{continue} 语句，以及循环中的 @code{else} 子句


@ref{2db,,break} 语句，和 C 中的类似，用于跳出最近的 @ref{c29,,for} 或 @ref{11c1,,while} 循环.

循环语句可能带有 @code{else} 子句；它会在循环耗尽了可迭代对象 (使用 @ref{c29,,for}) 或循环条件变为假值 (使用 @ref{11c1,,while}) 时被执行，但不会在循环被 @ref{2db,,break} 语句终止时被执行。 以下搜索素数的循环就是这样的一个例子:

@example
>>> for n in range(2, 10):
...     for x in range(2, n):
...         if n % x == 0:
...             print(n, 'equals', x, '*', n//x)
...             break
...     else:
...         # loop fell through without finding a factor
...         print(n, 'is a prime number')
...
2 is a prime number
3 is a prime number
4 equals 2 * 2
5 is a prime number
6 equals 2 * 3
7 is a prime number
8 equals 2 * 4
9 equals 3 * 3
@end example

（是的，这是正确的代码。仔细看： @code{else} 子句属于 @ref{c29,,for} 循环， @strong{不属于} @ref{de0,,if} 语句。）

当和循环一起使用时，@code{else} 子句与 @ref{d6b,,try} 语句中的 @code{else} 子句的共同点多于 @ref{de0,,if} 语句中的同类子句: @ref{d6b,,try} 语句中的 @code{else} 子句会在未发生异常时执行，而循环中的 @code{else} 子句则会在未发生 @code{break} 时执行。 有关 @code{try} 语句和异常的更多信息，请参阅 @ref{11d1,,处理异常}。

@ref{181,,continue} 语句也是借鉴自 C 语言，表示继续循环中的下一次迭代:

@example
>>> for num in range(2, 10):
...     if num % 2 == 0:
...         print("Found an even number", num)
...         continue
...     print("Found a number", num)
Found an even number 2
Found a number 3
Found an even number 4
Found a number 5
Found an even number 6
Found a number 7
Found an even number 8
Found a number 9
@end example

@node pass 语句,定义函数,break 和 continue 语句，以及循环中的 else 子句,其他流程控制工具
@anchor{tutorial/controlflow pass-statements}@anchor{11d2}@anchor{tutorial/controlflow tut-pass}@anchor{11d3}
@subsection @code{pass} 语句


@ref{11d4,,pass} 语句什么也不做。当语法上需要一个语句，但程序需要什么动作也不做时，可以使用它。例如:

@example
>>> while True:
...     pass  # Busy-wait for keyboard interrupt (Ctrl+C)
...
@end example

这通常用于创建最小的类:

@example
>>> class MyEmptyClass:
...     pass
...
@end example

@ref{11d4,,pass} 的另一个可以使用的场合是在你编写新的代码时作为一个函数或条件子句体的占位符，允许你保持在更抽象的层次上进行思考。 @code{pass} 会被静默地忽略:

@example
>>> def initlog(*args):
...     pass   # Remember to implement this!
...
@end example

@node 定义函数,函数定义的更多形式,pass 语句,其他流程控制工具
@anchor{tutorial/controlflow defining-functions}@anchor{11d5}@anchor{tutorial/controlflow tut-functions}@anchor{11d6}
@subsection 定义函数


我们可以创建一个输出任意范围内 Fibonacci 数列的函数:

@example
>>> def fib(n):    # write Fibonacci series up to n
...     """Print a Fibonacci series up to n."""
...     a, b = 0, 1
...     while a < n:
...         print(a, end=' ')
...         a, b = b, a+b
...     print()
...
>>> # Now call the function we just defined:
... fib(2000)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597
@end example

@geindex documentation strings
@geindex docstrings
@geindex strings@comma{} documentation

关键字 @ref{db7,,def} 引入一个函数 @emph{定义}。它必须后跟函数名称和带括号的形式参数列表。构成函数体的语句从下一行开始，并且必须缩进。

函数体的第一个语句可以（可选的）是字符串文字；这个字符串文字是函数的文档字符串或 @emph{docstring} 。（有关文档字符串的更多信息，请参阅  @ref{11d7,,文档字符串} 部分）有些工具使用文档字符串自动生成在线或印刷文档，或者让用户以交互式的形式浏览代码；在你编写的代码中包含文档字符串是一种很好的做法，所以要养成习惯。

函数的 @emph{执行} 会引入一个用于函数局部变量的新符号表。 更确切地说，函数中所有的变量赋值都将存储在局部符号表中；而变量引用会首先在局部符号表中查找，然后是外层函数的局部符号表，再然后是全局符号表，最后是内置名称的符号表。 因此，全局变量和外层函数的变量不能在函数内部直接赋值（除非是在 @ref{11d8,,global} 语句中定义的全局变量，或者是在 @ref{c38,,nonlocal} 语句中定义的外层函数的变量），尽管它们可以被引用。

在函数被调用时，实际参数（实参）会被引入被调用函数的本地符号表中；因此，实参是通过 @emph{按值调用} 传递的（其中 @emph{值} 始终是对象 @emph{引用} 而不是对象的值）。@footnote{@w{(1)} 
实际上，@emph{通过对象引用调用} 会是一个更好的表述，因为如果传递的是可变对象，则调用者将看到被调用者对其做出的任何更改（插入到列表中的元素）。
} 当一个函数调用另外一个函数时，将会为该调用创建一个新的本地符号表。

函数定义会将函数名称与函数对象在当前符号表中进行关联。 解释器会将该名称所指向的对象识别为用户自定义函数。 其他名称也可指向同一个函数对象并可被用来访问访函数:

@example
>>> fib
<function fib at 10042ed0>
>>> f = fib
>>> f(100)
0 1 1 2 3 5 8 13 21 34 55 89
@end example

如果你学过其他语言，你可能会认为 @code{fib} 不是函数而是一个过程，因为它并不返回值。事实上，即使没有 @ref{190,,return} 语句的函数也会返回一个值，尽管它是一个相当无聊的值。这个值称为 @code{None} （它是内置名称）。一般来说解释器不会打印出单独的返回值 @code{None} ，如果你真想看到它，你可以使用 @ref{880,,print()}

@example
>>> fib(0)
>>> print(fib(0))
None
@end example

写一个返回斐波那契数列的列表（而不是把它打印出来）的函数，非常简单:

@example
>>> def fib2(n):  # return Fibonacci series up to n
...     """Return a list containing the Fibonacci series up to n."""
...     result = []
...     a, b = 0, 1
...     while a < n:
...         result.append(a)    # see below
...         a, b = b, a+b
...     return result
...
>>> f100 = fib2(100)    # call it
>>> f100                # write the result
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
@end example

此示例中，像往常一样，演示了一些新的 Python 功能:


@itemize *

@item 
@ref{190,,return} 语句会从函数内部返回一个值。 不带表达式参数的 @code{return} 会返回 @code{None}。 函数执行完毕退出也会返回 @code{None}。

@item 
@code{result.append(a)} 语句调用了列表对象 @code{result} 的 @emph{方法} 。方法是“属于”一个对象的函数，它被命名为 @code{obj.methodname} ，其中 @code{obj} 是某个对象（也可能是一个表达式）， @code{methodname} 是由对象类型中定义的方法的名称。不同的类型可以定义不同的方法。不同类型的方法可以有相同的名称而不会引起歧义。（可以使用 @emph{类} 定义自己的对象类型和方法，请参阅 @ref{11d9,,类} ）示例中的方法 @code{append()} 是为列表对象定义的；它会在列表的最后添加一个新的元素。在这个示例中它相当于 @code{result = result + [a]} ，但更高效。
@end itemize

@node 函数定义的更多形式,小插曲：编码风格,定义函数,其他流程控制工具
@anchor{tutorial/controlflow more-on-defining-functions}@anchor{11da}@anchor{tutorial/controlflow tut-defining}@anchor{11db}
@subsection 函数定义的更多形式


给函数定义有可变数目的参数也是可行的。这里有三种形式，可以组合使用。

@menu
* 参数默认值:: 
* 关键字参数:: 
* 特殊参数:: 
* 任意的参数列表:: 
* 解包参数列表:: 
* Lambda 表达式:: 
* 文档字符串:: 
* 函数标注:: 

@end menu

@node 参数默认值,关键字参数,,函数定义的更多形式
@anchor{tutorial/controlflow default-argument-values}@anchor{11dc}@anchor{tutorial/controlflow tut-defaultargs}@anchor{11dd}
@subsubsection 参数默认值


最有用的形式是对一个或多个参数指定一个默认值。这样创建的函数，可以用比定义时允许的更少的参数调用，比如:

@example
def ask_ok(prompt, retries=4, reminder='Please try again!'):
    while True:
        ok = input(prompt)
        if ok in ('y', 'ye', 'yes'):
            return True
        if ok in ('n', 'no', 'nop', 'nope'):
            return False
        retries = retries - 1
        if retries < 0:
            raise ValueError('invalid user response')
        print(reminder)
@end example

这个函数可以通过几种方式调用:


@itemize *

@item 
只给出必需的参数：@code{ask_ok('Do you really want to quit?')}

@item 
给出一个可选的参数：@code{ask_ok('OK to overwrite the file?', 2)}

@item 
或者给出所有的参数：@code{ask_ok('OK to overwrite the file?', 2, 'Come on, only yes or no!')}
@end itemize

这个示例还介绍了 @ref{79d,,in} 关键字。它可以测试一个序列是否包含某个值。

默认值是在 @emph{定义过程} 中在函数定义处计算的，所以

@example
i = 5

def f(arg=i):
    print(arg)

i = 6
f()
@end example

会打印 @code{5}。

@strong{重要警告：} 默认值只会执行一次。这条规则在默认值为可变对象（列表、字典以及大多数类实例）时很重要。比如，下面的函数会存储在后续调用中传递给它的参数:

@example
def f(a, L=[]):
    L.append(a)
    return L

print(f(1))
print(f(2))
print(f(3))
@end example

这将打印出

@example
[1]
[1, 2]
[1, 2, 3]
@end example

如果你不想要在后续调用之间共享默认值，你可以这样写这个函数:

@example
def f(a, L=None):
    if L is None:
        L = []
    L.append(a)
    return L
@end example

@node 关键字参数,特殊参数,参数默认值,函数定义的更多形式
@anchor{tutorial/controlflow keyword-arguments}@anchor{11de}@anchor{tutorial/controlflow tut-keywordargs}@anchor{11df}
@subsubsection 关键字参数


也可以使用形如 @code{kwarg=value} 的 @ref{5bf,,关键字参数} 来调用函数。例如下面的函数:

@example
def parrot(voltage, state='a stiff', action='voom', type='Norwegian Blue'):
    print("-- This parrot wouldn't", action, end=' ')
    print("if you put", voltage, "volts through it.")
    print("-- Lovely plumage, the", type)
    print("-- It's", state, "!")
@end example

接受一个必需的参数（@code{voltage}）和三个可选的参数（@code{state}, @code{action}，和 @code{type}）。这个函数可以通过下面的任何一种方式调用:

@example
parrot(1000)                                          # 1 positional argument
parrot(voltage=1000)                                  # 1 keyword argument
parrot(voltage=1000000, action='VOOOOOM')             # 2 keyword arguments
parrot(action='VOOOOOM', voltage=1000000)             # 2 keyword arguments
parrot('a million', 'bereft of life', 'jump')         # 3 positional arguments
parrot('a thousand', state='pushing up the daisies')  # 1 positional, 1 keyword
@end example

但下面的函数调用都是无效的:

@example
parrot()                     # required argument missing
parrot(voltage=5.0, 'dead')  # non-keyword argument after a keyword argument
parrot(110, voltage=220)     # duplicate value for the same argument
parrot(actor='John Cleese')  # unknown keyword argument
@end example

在函数调用中，关键字参数必须跟随在位置参数的后面。传递的所有关键字参数必须与函数接受的其中一个参数匹配（比如 @code{actor} 不是函数 @code{parrot} 的有效参数），它们的顺序并不重要。这也包括非可选参数，（比如 @code{parrot(voltage=1000)} 也是有效的）。不能对同一个参数多次赋值。下面是一个因为此限制而失败的例子:

@example
>>> def function(a):
...     pass
...
>>> function(0, a=0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: function() got multiple values for keyword argument 'a'
@end example

当存在一个形式为 @code{**name} 的最后一个形参时，它会接收一个字典 (参见 @ref{2f5,,映射类型 --- dict})，其中包含除了与已有形参相对应的关键字参数以外的所有关键字参数。 这可以与一个形式为 @code{*name}，接收一个包含除了已有形参列表以外的位置参数的 @ref{11e0,,元组} 的形参 (将在下一小节介绍) 组合使用 (@code{*name} 必须出现在 @code{**name} 之前。) 例如，如果我们这样定义一个函数:

@example
def cheeseshop(kind, *arguments, **keywords):
    print("-- Do you have any", kind, "?")
    print("-- I'm sorry, we're all out of", kind)
    for arg in arguments:
        print(arg)
    print("-" * 40)
    for kw in keywords:
        print(kw, ":", keywords[kw])
@end example

它可以像这样调用:

@example
cheeseshop("Limburger", "It's very runny, sir.",
           "It's really very, VERY runny, sir.",
           shopkeeper="Michael Palin",
           client="John Cleese",
           sketch="Cheese Shop Sketch")
@end example

当然它会打印:

@example
-- Do you have any Limburger ?
-- I'm sorry, we're all out of Limburger
It's very runny, sir.
It's really very, VERY runny, sir.
----------------------------------------
shopkeeper : Michael Palin
client : John Cleese
sketch : Cheese Shop Sketch
@end example

注意打印时关键字参数的顺序保证与调用函数时提供它们的顺序是相匹配的。

@node 特殊参数,任意的参数列表,关键字参数,函数定义的更多形式
@anchor{tutorial/controlflow special-parameters}@anchor{11e1}
@subsubsection 特殊参数


默认情况下，函数的参数传递形式可以是位置参数或是显式的关键字参数。 为了确保可读性和运行效率，限制允许的参数传递形式是有意义的，这样开发者只需查看函数定义即可确定参数项是仅按位置、按位置也按关键字，还是仅按关键字传递。

函数的定义看起来可以像是这样：

@example
def f(pos1, pos2, /, pos_or_kwd, *, kwd1, kwd2):
      -----------    ----------     ----------
        |             |                  |
        |        Positional or keyword   |
        |                                - Keyword only
         -- Positional only
@end example

在这里 @code{/} 和 @code{*} 是可选的。 如果使用这些符号则表明可以通过何种形参将参数值传递给函数：仅限位置、位置或关键字，以及仅限关键字。 关键字形参也被称为命名形参。

@menu
* 位置或关键字参数:: 
* 仅限位置参数:: 
* 仅限关键字参数:: 
* 函数示例:: 
* 概括:: 

@end menu

@node 位置或关键字参数,仅限位置参数,,特殊参数
@anchor{tutorial/controlflow positional-or-keyword-arguments}@anchor{11e2}
@subsubsection 位置或关键字参数


如果函数定义中未使用 @code{/} 和 @code{*}，则参数可以按位置或按关键字传递给函数。

@node 仅限位置参数,仅限关键字参数,位置或关键字参数,特殊参数
@anchor{tutorial/controlflow positional-only-parameters}@anchor{11e3}
@subsubsection 仅限位置参数


在这里还可以发现更多细节，特定形参可以被标记为 @emph{仅限位置}。 如果是 @emph{仅限位置} 的形参，则其位置是重要的，并且该形参不能作为关键字传入。 仅限位置形参要放在 @code{/} (正斜杠) 之前。 这个 @code{/} 被用来从逻辑上分隔仅限位置形参和其它形参。 如果函数定义中没有 @code{/}，则表示没有仅限位置形参。

在 @code{/} 之后的形参可以为 @emph{位置或关键字} 或 @emph{仅限关键字}。

@node 仅限关键字参数,函数示例,仅限位置参数,特殊参数
@anchor{tutorial/controlflow keyword-only-arguments}@anchor{11e4}
@subsubsection 仅限关键字参数


要将形参标记为 @emph{仅限关键字}，即指明该形参必须以关键字参数的形式传入，应在参数列表的第一个 @emph{仅限关键字} 形参之前放置一个 @code{*}。

@node 函数示例,概括,仅限关键字参数,特殊参数
@anchor{tutorial/controlflow function-examples}@anchor{11e5}
@subsubsection 函数示例


请考虑以下示例函数定义并特别注意 @code{/} 和 @code{*} 标记:

@example
>>> def standard_arg(arg):
...     print(arg)
...
>>> def pos_only_arg(arg, /):
...     print(arg)
...
>>> def kwd_only_arg(*, arg):
...     print(arg)
...
>>> def combined_example(pos_only, /, standard, *, kwd_only):
...     print(pos_only, standard, kwd_only)
@end example

第一个函数定义 @code{standard_arg} 是最常见的形式，对调用方式没有任何限制，参数可以按位置也可以按关键字传入:

@example
>>> standard_arg(2)
2

>>> standard_arg(arg=2)
2
@end example

第二个函数 @code{pos_only_arg} 在函数定义中带有 @code{/}，限制仅使用位置形参。:

@example
>>> pos_only_arg(1)
1

>>> pos_only_arg(arg=1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: pos_only_arg() got an unexpected keyword argument 'arg'
@end example

第三个函数 @code{kwd_only_args} 在函数定义中通过 @code{*} 指明仅允许关键字参数:

@example
>>> kwd_only_arg(3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: kwd_only_arg() takes 0 positional arguments but 1 was given

>>> kwd_only_arg(arg=3)
3
@end example

而最后一个则在同一函数定义中使用了全部三种调用方式:

@example
>>> combined_example(1, 2, 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: combined_example() takes 2 positional arguments but 3 were given

>>> combined_example(1, 2, kwd_only=3)
1 2 3

>>> combined_example(1, standard=2, kwd_only=3)
1 2 3

>>> combined_example(pos_only=1, standard=2, kwd_only=3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: combined_example() got an unexpected keyword argument 'pos_only'
@end example

最后，请考虑这个函数定义，它的位置参数 @code{name}  和 @code{**kwds} 之间由于存在关键字名称 @code{name} 而可能产生潜在冲突:

@example
def foo(name, **kwds):
    return 'name' in kwds
@end example

任何调用都不可能让它返回 @code{True}，因为关键字 @code{'name'} 将总是绑定到第一个形参。 例如:

@example
>>> foo(1, **@{'name': 2@})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo() got multiple values for argument 'name'
>>>
@end example

但使用 @code{/} (仅限位置参数) 就可能做到，因为它允许 @code{name} 作为位置参数，也允许 @code{'name'} 作为关键字参数的关键字名称:

@example
def foo(name, /, **kwds):
    return 'name' in kwds
>>> foo(1, **@{'name': 2@})
True
@end example

换句话说，仅限位置形参的名称可以在 @code{**kwds} 中使用而不产生歧义。

@node 概括,,函数示例,特殊参数
@anchor{tutorial/controlflow recap}@anchor{11e6}
@subsubsection 概括


用例将确定要在函数定义中使用的参数:

@example
def f(pos1, pos2, /, pos_or_kwd, *, kwd1, kwd2):
@end example

作为指导：


@itemize *

@item 
如果你希望形参名称对用户来说不可用，则使用仅限位置形参。 这适用于形参名称没有实际意义，以及当你希望强制规定调用时的参数顺序，或是需要同时收受一些位置形参和任意关键字形参等情况。

@item 
当形参名称有实际意义，以及显式指定形参名称可使函数定义更易理解，或者当你想要防止用户过于依赖传入参数的位置时，则使用仅限关键字形参。

@item 
对于 API 来说，使用仅限位置形参可以防止形参名称在未来被修改时造成破坏性的 API 变动。
@end itemize

@node 任意的参数列表,解包参数列表,特殊参数,函数定义的更多形式
@anchor{tutorial/controlflow arbitrary-argument-lists}@anchor{11e7}@anchor{tutorial/controlflow tut-arbitraryargs}@anchor{11e8}
@subsubsection 任意的参数列表


@geindex * (asterisk); in function calls

最后，最不常用的选项是可以使用任意数量的参数调用函数。这些参数会被包含在一个元组里（参见 @ref{11e0,,元组和序列} ）。在可变数量的参数之前，可能会出现零个或多个普通参数。:

@example
def write_multiple_items(file, separator, *args):
    file.write(separator.join(args))
@end example

一般来说，这些 @code{可变参数} 将在形式参数列表的末尾，因为它们收集传递给函数的所有剩余输入参数。出现在 @code{*args} 参数之后的任何形式参数都是 ‘仅限关键字参数’，也就是说它们只能作为关键字参数而不能是位置参数。:

@example
>>> def concat(*args, sep="/"):
...     return sep.join(args)
...
>>> concat("earth", "mars", "venus")
'earth/mars/venus'
>>> concat("earth", "mars", "venus", sep=".")
'earth.mars.venus'
@end example

@node 解包参数列表,Lambda 表达式,任意的参数列表,函数定义的更多形式
@anchor{tutorial/controlflow tut-unpacking-arguments}@anchor{11e9}@anchor{tutorial/controlflow unpacking-argument-lists}@anchor{11ea}
@subsubsection 解包参数列表


当参数已经在列表或元组中但要为需要单独位置参数的函数调用解包时，会发生相反的情况。例如，内置的 @ref{9b8,,range()} 函数需要单独的 @emph{start} 和 @emph{stop} 参数。如果它们不能单独使用，可以使用 @code{*} 操作符 来编写函数调用以便从列表或元组中解包参数:

@example
>>> list(range(3, 6))            # normal call with separate arguments
[3, 4, 5]
>>> args = [3, 6]
>>> list(range(*args))            # call with arguments unpacked from a list
[3, 4, 5]
@end example

@geindex **; in function calls

同样的方式，字典可使用 @code{**} 操作符 来提供关键字参数:

@example
>>> def parrot(voltage, state='a stiff', action='voom'):
...     print("-- This parrot wouldn't", action, end=' ')
...     print("if you put", voltage, "volts through it.", end=' ')
...     print("E's", state, "!")
...
>>> d = @{"voltage": "four million", "state": "bleedin' demised", "action": "VOOM"@}
>>> parrot(**d)
-- This parrot wouldn't VOOM if you put four million volts through it. E's bleedin' demised !
@end example

@node Lambda 表达式,文档字符串,解包参数列表,函数定义的更多形式
@anchor{tutorial/controlflow lambda-expressions}@anchor{11eb}@anchor{tutorial/controlflow tut-lambda}@anchor{11ec}
@subsubsection Lambda 表达式


可以用 @ref{c28,,lambda} 关键字来创建一个小的匿名函数。这个函数返回两个参数的和： @code{lambda a, b: a+b} 。Lambda函数可以在需要函数对象的任何地方使用。它们在语法上限于单个表达式。从语义上来说，它们只是正常函数定义的语法糖。与嵌套函数定义一样，lambda函数可以引用所包含域的变量:

@example
>>> def make_incrementor(n):
...     return lambda x: x + n
...
>>> f = make_incrementor(42)
>>> f(0)
42
>>> f(1)
43
@end example

上面的例子使用一个lambda表达式来返回一个函数。另一个用法是传递一个小函数作为参数:

@example
>>> pairs = [(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')]
>>> pairs.sort(key=lambda pair: pair[1])
>>> pairs
[(4, 'four'), (1, 'one'), (3, 'three'), (2, 'two')]
@end example

@node 文档字符串,函数标注,Lambda 表达式,函数定义的更多形式
@anchor{tutorial/controlflow documentation-strings}@anchor{11ed}@anchor{tutorial/controlflow tut-docstrings}@anchor{11d7}
@subsubsection 文档字符串


@geindex docstrings
@geindex documentation strings
@geindex strings@comma{} documentation

以下是有关文档字符串的内容和格式的一些约定。

第一行应该是对象目的的简要概述。为简洁起见，它不应显式声明对象的名称或类型，因为这些可通过其他方式获得（除非名称恰好是描述函数操作的动词）。这一行应以大写字母开头，以句点结尾。

如果文档字符串中有更多行，则第二行应为空白，从而在视觉上将摘要与其余描述分开。后面几行应该是一个或多个段落，描述对象的调用约定，它的副作用等。

Python 解析器不会从 Python 中删除多行字符串文字的缩进，因此处理文档的工具必须在需要时删除缩进。 这是使用以下约定完成的。 文档字符串第一行 @emph{之后} 的第一个非空行确定整个文档字符串的缩进量。（我们不能使用第一行，因为它通常与字符串的开头引号相邻，因此它的缩进在字符串文字中不明显。）然后从字符串的所有行的开头剥离与该缩进 "等效" 的空格。 缩进更少的行不应该出现，但是如果它们出现，则应该剥离它们的所有前导空格。 应在转化制表符为空格后测试空格的等效性（通常转化为8个空格）。

下面是一个多行文档字符串的例子:

@example
>>> def my_function():
...     """Do nothing, but document it.
...
...     No, really, it doesn't do anything.
...     """
...     pass
...
>>> print(my_function.__doc__)
Do nothing, but document it.

    No, really, it doesn't do anything.
@end example

@node 函数标注,,文档字符串,函数定义的更多形式
@anchor{tutorial/controlflow function-annotations}@anchor{11ee}@anchor{tutorial/controlflow tut-annotations}@anchor{11ef}
@subsubsection 函数标注


@geindex function; annotations
@geindex ->; function annotations
@geindex ; (colon); function annotations

@ref{11f0,,函数标注} 是关于用户自定义函数中使用的类型的完全可选元数据信息（有关详情请参阅 
@geindex Python 提高建议; PEP 3107
PEP 3107@footnote{https://www.python.org/dev/peps/pep-3107} 和 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} ）。

@ref{11f1,,函数标注} 以字典的形式存放在函数的 @code{__annotations__} 属性中，并且不会影响函数的任何其他部分。 形参标注的定义方式是在形参名称后加上冒号，后面跟一个表达式，该表达式会被求值为标注的值。 返回值标注的定义方式是加上一个组合符号 @code{->}，后面跟一个表达式，该标注位于形参列表和表示 @ref{db7,,def} 语句结束的冒号之间。 下面的示例有一个位置参数，一个关键字参数以及返回值带有相应标注:

@example
>>> def f(ham: str, eggs: str = 'eggs') -> str:
...     print("Annotations:", f.__annotations__)
...     print("Arguments:", ham, eggs)
...     return ham + ' and ' + eggs
...
>>> f('spam')
Annotations: @{'ham': <class 'str'>, 'return': <class 'str'>, 'eggs': <class 'str'>@}
Arguments: spam eggs
'spam and eggs'
@end example

@node 小插曲：编码风格,,函数定义的更多形式,其他流程控制工具
@anchor{tutorial/controlflow intermezzo-coding-style}@anchor{11f2}@anchor{tutorial/controlflow tut-codingstyle}@anchor{11f3}
@subsection 小插曲：编码风格


@geindex coding; style

现在你将要写更长，更复杂的 Python 代码，是时候讨论一下 @emph{代码风格} 了。 大多数语言都能以不同的风格被编写（或更准确地说，被格式化）；有些比其他的更具有可读性。 能让其他人轻松阅读你的代码总是一个好主意，采用一种好的编码风格对此有很大帮助。

对于Python，
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008} 已经成为大多数项目所遵循的风格指南；它促进了一种非常易读且令人赏心悦目的编码风格。每个Python开发人员都应该在某个时候阅读它；以下是为你提取的最重要的几个要点：


@itemize *

@item 
使用4个空格缩进，不要使用制表符。

4个空格是一个在小缩进（允许更大的嵌套深度）和大缩进（更容易阅读）的一种很好的折中方案。制表符会引入混乱，最好不要使用它。

@item 
换行，使一行不超过79个字符。

这有助于使用小型显示器的用户，并且可以在较大的显示器上并排放置多个代码文件。

@item 
使用空行分隔函数和类，以及函数内的较大的代码块。

@item 
如果可能，把注释放到单独的一行。

@item 
使用文档字符串。

@item 
在运算符前后和逗号后使用空格，但不能直接在括号内使用： @code{a = f(1, 2) + g(3, 4)}。

@item 
以一致的规则为你的类和函数命名；按照惯例应使用 @code{UpperCamelCase} 来命名类，而以 @code{lowercase_with_underscores} 来命名函数和方法。 始终应使用 @code{self} 来命名第一个方法参数 (有关类和方法的更多信息请参阅 @ref{11f4,,初探类})。

@item 
如果你的代码旨在用于国际环境，请不要使用花哨的编码。Python 默认的 UTF-8 或者纯 ASCII 在任何情况下都能有最好的表现。

@item 
同样，哪怕只有很小的可能，遇到说不同语言的人阅读或维护代码，也不要在标识符中使用非ASCII字符。
@end itemize

@subsubheading 备注


@node 数据结构,模块,其他流程控制工具,Python 教程
@anchor{tutorial/datastructures doc}@anchor{11f5}@anchor{tutorial/datastructures data-structures}@anchor{11f6}@anchor{tutorial/datastructures tut-structures}@anchor{11ce}
@section 数据结构


本章节将详细介绍一些您已经了解的内容，并添加了一些新内容。

@menu
* 列表的更多特性:: 
* del 语句:: 
* 元组和序列:: 
* 集合:: 
* 字典:: 
* 循环的技巧:: 
* 深入条件控制:: 
* 比较序列和其他类型:: 

@end menu

@node 列表的更多特性,del 语句,,数据结构
@anchor{tutorial/datastructures more-on-lists}@anchor{11f7}@anchor{tutorial/datastructures tut-morelists}@anchor{11f8}
@subsection 列表的更多特性


列表数据类型还有很多的方法。这里是列表对象方法的清单：


@deffn {方法} list.append (x)

在列表的末尾添加一个元素。相当于 @code{a[len(a):] = [x]} 。
@end deffn


@deffn {方法} list.extend (iterable)

使用可迭代对象中的所有元素来扩展列表。相当于  @code{a[len(a):] = iterable} 。
@end deffn


@deffn {方法} list.insert (i, x)

在给定的位置插入一个元素。第一个参数是要插入的元素的索引，所以 @code{a.insert(0, x)} 插入列表头部， @code{a.insert(len(a), x)} 等同于 @code{a.append(x)} 。
@end deffn


@deffn {方法} list.remove (x)

移除列表中第一个值为 @emph{x} 的元素。如果没有这样的元素，则抛出 @ref{1fb,,ValueError} 异常。
@end deffn


@deffn {方法} list.pop ([i])

删除列表中给定位置的元素并返回它。如果没有给定位置，@code{a.pop()} 将会删除并返回列表中的最后一个元素。（ 方法签名中 @emph{i} 两边的方括号表示这个参数是可选的，而不是要你输入方括号。你会在 Python 参考库中经常看到这种表示方法)。
@end deffn


@deffn {方法} list.clear ()

移除列表中的所有元素。等价于`@w{`}del a[:]`@w{`}
@end deffn


@deffn {方法} list.index (x[, start[, end]])

返回列表中第一个值为 @emph{x} 的元素的从零开始的索引。如果没有这样的元素将会抛出 @ref{1fb,,ValueError} 异常。

可选参数 @emph{start} 和 @emph{end} 是切片符号，用于将搜索限制为列表的特定子序列。返回的索引是相对于整个序列的开始计算的，而不是 @emph{start} 参数。
@end deffn


@deffn {方法} list.count (x)

返回元素 @emph{x} 在列表中出现的次数。
@end deffn


@deffn {方法} list.sort (key=None, reverse=False)

对列表中的元素进行排序（参数可用于自定义排序，解释请参见 @ref{43e,,sorted()}）。
@end deffn


@deffn {方法} list.reverse ()

翻转列表中的元素。
@end deffn


@deffn {方法} list.copy ()

返回列表的一个浅拷贝，等价于 @code{a[:]}。
@end deffn

多数列表方法示例：

@example
>>> fruits = ['orange', 'apple', 'pear', 'banana', 'kiwi', 'apple', 'banana']
>>> fruits.count('apple')
2
>>> fruits.count('tangerine')
0
>>> fruits.index('banana')
3
>>> fruits.index('banana', 4)  # Find next banana starting a position 4
6
>>> fruits.reverse()
>>> fruits
['banana', 'apple', 'kiwi', 'banana', 'pear', 'apple', 'orange']
>>> fruits.append('grape')
>>> fruits
['banana', 'apple', 'kiwi', 'banana', 'pear', 'apple', 'orange', 'grape']
>>> fruits.sort()
>>> fruits
['apple', 'apple', 'banana', 'banana', 'grape', 'kiwi', 'orange', 'pear']
>>> fruits.pop()
'pear'
@end example

你可能已经注意到，像 @code{insert} ，@code{remove} 或者 @code{sort} 方法，只修改列表，没有打印出返回值——它们返回默认值 @code{None} 。@footnote{@w{(1)} 
别的语言可能会返回一个可变对象，他们允许方法连续执行，例如 @code{d->insert("a")->remove("b")->sort();}。
} 这是Python中所有可变数据结构的设计原则。

你可能会注意到的另一件事是并非所有数据或可以排序或比较。 例如，@code{[None, 'hello', 10]} 就不可排序，因为整数不能与字符串比较，而 @emph{None} 不能与其他类型比较。 并且还存在一些没有定义顺序关系的类型。 例如，@code{3+4j < 5+7j} 就不是一个合法的比较。

@menu
* 列表作为栈使用:: 
* 列表作为队列使用:: 
* 列表推导式: 列表推导式<2>. 
* 嵌套的列表推导式:: 

@end menu

@node 列表作为栈使用,列表作为队列使用,,列表的更多特性
@anchor{tutorial/datastructures tut-lists-as-stacks}@anchor{11f9}@anchor{tutorial/datastructures using-lists-as-stacks}@anchor{11fa}
@subsubsection 列表作为栈使用


列表方法使得列表作为堆栈非常容易，最后一个插入，最先取出（“后进先出”）。要添加一个元素到堆栈的顶端，使用 @code{append()} 。要从堆栈顶部取出一个元素，使用 @code{pop()} ，不用指定索引。例如

@example
>>> stack = [3, 4, 5]
>>> stack.append(6)
>>> stack.append(7)
>>> stack
[3, 4, 5, 6, 7]
>>> stack.pop()
7
>>> stack
[3, 4, 5, 6]
>>> stack.pop()
6
>>> stack.pop()
5
>>> stack
[3, 4]
@end example

@node 列表作为队列使用,列表推导式<2>,列表作为栈使用,列表的更多特性
@anchor{tutorial/datastructures tut-lists-as-queues}@anchor{11fb}@anchor{tutorial/datastructures using-lists-as-queues}@anchor{11fc}
@subsubsection 列表作为队列使用


列表也可以用作队列，其中先添加的元素被最先取出 (“先进先出”)；然而列表用作这个目的相当低效。因为在列表的末尾添加和弹出元素非常快，但是在列表的开头插入或弹出元素却很慢 (因为所有的其他元素都必须移动一位)。

若要实现一个队列，可使用 @ref{52b,,collections.deque}，它被设计成可以快速地从两端添加或弹出元素。例如

@example
>>> from collections import deque
>>> queue = deque(["Eric", "John", "Michael"])
>>> queue.append("Terry")           # Terry arrives
>>> queue.append("Graham")          # Graham arrives
>>> queue.popleft()                 # The first to arrive now leaves
'Eric'
>>> queue.popleft()                 # The second to arrive now leaves
'John'
>>> queue                           # Remaining queue in order of arrival
deque(['Michael', 'Terry', 'Graham'])
@end example

@node 列表推导式<2>,嵌套的列表推导式,列表作为队列使用,列表的更多特性
@anchor{tutorial/datastructures list-comprehensions}@anchor{11fd}@anchor{tutorial/datastructures tut-listcomps}@anchor{11fe}
@subsubsection 列表推导式


列表推导式提供了一个更简单的创建列表的方法。常见的用法是把某种操作应用于序列或可迭代对象的每个元素上，然后使用其结果来创建列表，或者通过满足某些特定条件元素来创建子序列。

例如，假设我们想创建一个平方列表，像这样

@example
>>> squares = []
>>> for x in range(10):
...     squares.append(x**2)
...
>>> squares
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
@end example

注意这里创建（或被重写）的名为 @code{x} 的变量在for循环后仍然存在。我们可以计算平方列表的值而不会产生任何副作用

@example
squares = list(map(lambda x: x**2, range(10)))
@end example

或者，等价于

@example
squares = [x**2 for x in range(10)]
@end example

上面这种写法更加简洁易读。

列表推导式的结构是由一对方括号所包含的以下内容：一个表达式，后面跟一个 @code{for} 子句，然后是零个或多个 @code{for} 或 @code{if} 子句。 其结果将是一个新列表，由对表达式依据后面的 @code{for} 和 @code{if} 子句的内容进行求值计算而得出。 举例来说，以下列表推导式会将两个列表中不相等的元素组合起来:

@example
>>> [(x, y) for x in [1,2,3] for y in [3,1,4] if x != y]
[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]
@end example

而它等价于

@example
>>> combs = []
>>> for x in [1,2,3]:
...     for y in [3,1,4]:
...         if x != y:
...             combs.append((x, y))
...
>>> combs
[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]
@end example

注意在上面两个代码片段中， @ref{c29,,for} 和 @ref{de0,,if} 的顺序是相同的。

如果表达式是一个元组（例如上面的 @code{(x, y)}），那么就必须加上括号

@example
>>> vec = [-4, -2, 0, 2, 4]
>>> # create a new list with the values doubled
>>> [x*2 for x in vec]
[-8, -4, 0, 4, 8]
>>> # filter the list to exclude negative numbers
>>> [x for x in vec if x >= 0]
[0, 2, 4]
>>> # apply a function to all the elements
>>> [abs(x) for x in vec]
[4, 2, 0, 2, 4]
>>> # call a method on each element
>>> freshfruit = ['  banana', '  loganberry ', 'passion fruit  ']
>>> [weapon.strip() for weapon in freshfruit]
['banana', 'loganberry', 'passion fruit']
>>> # create a list of 2-tuples like (number, square)
>>> [(x, x**2) for x in range(6)]
[(0, 0), (1, 1), (2, 4), (3, 9), (4, 16), (5, 25)]
>>> # the tuple must be parenthesized, otherwise an error is raised
>>> [x, x**2 for x in range(6)]
  File "<stdin>", line 1, in <module>
    [x, x**2 for x in range(6)]
               ^
SyntaxError: invalid syntax
>>> # flatten a list using a listcomp with two 'for'
>>> vec = [[1,2,3], [4,5,6], [7,8,9]]
>>> [num for elem in vec for num in elem]
[1, 2, 3, 4, 5, 6, 7, 8, 9]
@end example

列表推导式可以使用复杂的表达式和嵌套函数

@example
>>> from math import pi
>>> [str(round(pi, i)) for i in range(1, 6)]
['3.1', '3.14', '3.142', '3.1416', '3.14159']
@end example

@node 嵌套的列表推导式,,列表推导式<2>,列表的更多特性
@anchor{tutorial/datastructures nested-list-comprehensions}@anchor{11ff}
@subsubsection 嵌套的列表推导式


列表推导式中的初始表达式可以是任何表达式，包括另一个列表推导式。

考虑下面这个 3x4的矩阵，它由3个长度为4的列表组成

@example
>>> matrix = [
...     [1, 2, 3, 4],
...     [5, 6, 7, 8],
...     [9, 10, 11, 12],
... ]
@end example

下面的列表推导式将交换其行和列

@example
>>> [[row[i] for row in matrix] for i in range(4)]
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]
@end example

如上节所示，嵌套的列表推导式是基于跟随其后的 @ref{c29,,for} 进行求值的，所以这个例子等价于:

@example
>>> transposed = []
>>> for i in range(4):
...     transposed.append([row[i] for row in matrix])
...
>>> transposed
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]
@end example

反过来说，也等价于

@example
>>> transposed = []
>>> for i in range(4):
...     # the following 3 lines implement the nested listcomp
...     transposed_row = []
...     for row in matrix:
...         transposed_row.append(row[i])
...     transposed.append(transposed_row)
...
>>> transposed
[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]
@end example

实际应用中，你应该会更喜欢使用内置函数去组成复杂的流程语句。 @ref{c2b,,zip()} 函数将会很好地处理这种情况

@example
>>> list(zip(*matrix))
[(1, 5, 9), (2, 6, 10), (3, 7, 11), (4, 8, 12)]
@end example

关于本行中星号的详细说明，参见 @ref{11e9,,解包参数列表}。

@node del 语句,元组和序列,列表的更多特性,数据结构
@anchor{tutorial/datastructures the-del-statement}@anchor{1200}@anchor{tutorial/datastructures tut-del}@anchor{1201}
@subsection @code{del} 语句


有一种方式可以从列表按照给定的索引而不是值来移除一个元素: 那就是 @ref{1202,,del} 语句。 它不同于会返回一个值的 @code{pop()} 方法。 @code{del} 语句也可以用来从列表中移除切片或者清空整个列表（我们之前用过的方式是将一个空列表赋值给指定的切片）。 例如:

@example
>>> a = [-1, 1, 66.25, 333, 333, 1234.5]
>>> del a[0]
>>> a
[1, 66.25, 333, 333, 1234.5]
>>> del a[2:4]
>>> a
[1, 66.25, 1234.5]
>>> del a[:]
>>> a
[]
@end example

@ref{1202,,del} 也可以删除整个变量

@example
>>> del a
@end example

此后再引用 @code{a} 时会报错（直到另一个值被赋给它）。我们会在后面了解到 @ref{1202,,del} 的其他用法。

@node 元组和序列,集合,del 语句,数据结构
@anchor{tutorial/datastructures tuples-and-sequences}@anchor{1203}@anchor{tutorial/datastructures tut-tuples}@anchor{11e0}
@subsection 元组和序列


我们看到列表和字符串有很多共同特性，例如索引和切片操作。他们是 @emph{序列} 数据类型（参见 @ref{1204,,序列类型 --- list@comma{} tuple@comma{} range}）中的两种。随着 Python 语言的发展，其他的序列类型也会被加入其中。这里介绍另一种标准序列类型: @emph{元组}。

一个元组由几个被逗号隔开的值组成，例如

@example
>>> t = 12345, 54321, 'hello!'
>>> t[0]
12345
>>> t
(12345, 54321, 'hello!')
>>> # Tuples may be nested:
... u = t, (1, 2, 3, 4, 5)
>>> u
((12345, 54321, 'hello!'), (1, 2, 3, 4, 5))
>>> # Tuples are immutable:
... t[0] = 88888
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>> # but they can contain mutable objects:
... v = ([1, 2, 3], [3, 2, 1])
>>> v
([1, 2, 3], [3, 2, 1])
@end example

如你所见，元组在输出时总是被圆括号包围的，以便正确表示嵌套元组。输入时圆括号可有可无，不过经常会是必须的（如果这个元组是一个更大的表达式的一部分）。给元组中的一个单独的元素赋值是不允许的，当然你可以创建包含可变对象的元组，例如列表。

虽然元组可能看起来与列表很像，但它们通常是在不同的场景被使用，并且有着不同的用途。元组是 @ref{11b6,,immutable} ，其序列通常包含不同种类的元素，并且通过解包（这一节下面会解释）或者索引来访问（如果是 @ref{1b6,,namedtuples} 的话甚至还可以通过属性访问）。列表是 @ref{11be,,mutable} ，并且列表中的元素一般是同种类型的，并且通过迭代访问。

一个特殊的问题是构造包含0个或1个元素的元组：为了适应这种情况，语法有一些额外的改变。空元组可以直接被一对空圆括号创建，含有一个元素的元组可以通过在这个元素后添加一个逗号来构建（圆括号里只有一个值的话不够明确）。丑陋，但是有效。例如

@example
>>> empty = ()
>>> singleton = 'hello',    # <-- note trailing comma
>>> len(empty)
0
>>> len(singleton)
1
>>> singleton
('hello',)
@end example

语句 @code{t = 12345, 54321, 'hello!'} 是 @emph{元组打包} 的一个例子：值 @code{12345}, @code{54321} 和 @code{'hello!'} 被打包进元组。其逆操作也是允许的

@example
>>> x, y, z = t
@end example

这被称为 @emph{序列解包}  也是很恰当的，因为解包操作的等号右侧可以是任何序列。序列解包要求等号左侧的变量数与右侧序列里所含的元素数相同。注意多重赋值其实也只是元组打包和序列解包的组合。

@node 集合,字典,元组和序列,数据结构
@anchor{tutorial/datastructures sets}@anchor{1205}@anchor{tutorial/datastructures tut-sets}@anchor{1206}
@subsection 集合


Python也包含有 @emph{集合} 类型。集合是由不重复元素组成的无序的集。它的基本用法包括成员检测和消除重复元素。集合对象也支持像 联合，交集，差集，对称差分等数学运算。

花括号或 @ref{b68,,set()} 函数可以用来创建集合。注意：要创建一个空集合你只能用 @code{set()} 而不能用 @code{@{@}}，因为后者是创建一个空字典，这种数据结构我们会在下一节进行讨论。

以下是一些简单的示例

@example
>>> basket = @{'apple', 'orange', 'apple', 'pear', 'orange', 'banana'@}
>>> print(basket)                      # show that duplicates have been removed
@{'orange', 'banana', 'pear', 'apple'@}
>>> 'orange' in basket                 # fast membership testing
True
>>> 'crabgrass' in basket
False

>>> # Demonstrate set operations on unique letters from two words
...
>>> a = set('abracadabra')
>>> b = set('alacazam')
>>> a                                  # unique letters in a
@{'a', 'r', 'b', 'c', 'd'@}
>>> a - b                              # letters in a but not in b
@{'r', 'd', 'b'@}
>>> a | b                              # letters in a or b or both
@{'a', 'c', 'r', 'd', 'b', 'm', 'z', 'l'@}
>>> a & b                              # letters in both a and b
@{'a', 'c'@}
>>> a ^ b                              # letters in a or b but not both
@{'r', 'd', 'b', 'm', 'z', 'l'@}
@end example

类似于 @ref{11fe,,列表推导式}，集合也支持推导式形式

@example
>>> a = @{x for x in 'abracadabra' if x not in 'abc'@}
>>> a
@{'r', 'd'@}
@end example

@node 字典,循环的技巧,集合,数据结构
@anchor{tutorial/datastructures dictionaries}@anchor{1207}@anchor{tutorial/datastructures tut-dictionaries}@anchor{1208}
@subsection 字典


另一个非常有用的 Python 內置数据类型是 @emph{字典} (参见 @ref{2f5,,映射类型 --- dict})。字典在其他语言里可能会被叫做 @emph{联合内存} 或 @emph{联合数组}。与以连续整数为索引的序列不同，字典是以 @emph{关键字} 为索引的，关键字可以是任意不可变类型，通常是字符串或数字。如果一个元组只包含字符串、数字或元组，那么这个元组也可以用作关键字。但如果元组直接或间接地包含了可变对象，那么它就不能用作关键字。列表不能用作关键字，因为列表可以通过索引、切片或 @code{append()} 和 @code{extend()} 之类的方法来改变。

理解字典的最好方式，就是将它看做是一个 @emph{键: 值} 对的集合，键必须是唯一的（在一个字典中）。一对花括号可以创建一个空字典：@code{@{@}} 。另一种初始化字典的方式是在一对花括号里放置一些以逗号分隔的键值对，而这也是字典输出的方式。

字典主要的操作是使用关键字存储和解析值。也可以用 @code{del} 来删除一个键值对。如果你使用了一个已经存在的关键字来存储值，那么之前与这个关键字关联的值就会被遗忘。用一个不存在的键来取值则会报错。

对一个字典执行 @code{list(d)} 将返回包含该字典中所有键的列表，按插入次序排列 (如需其他排序，则要使用 @code{sorted(d)})。要检查字典中是否存在一个特定键，可使用 @ref{79d,,in} 关键字。

以下是使用字典的一些简单示例

@example
>>> tel = @{'jack': 4098, 'sape': 4139@}
>>> tel['guido'] = 4127
>>> tel
@{'jack': 4098, 'sape': 4139, 'guido': 4127@}
>>> tel['jack']
4098
>>> del tel['sape']
>>> tel['irv'] = 4127
>>> tel
@{'jack': 4098, 'guido': 4127, 'irv': 4127@}
>>> list(tel)
['jack', 'guido', 'irv']
>>> sorted(tel)
['guido', 'irv', 'jack']
>>> 'guido' in tel
True
>>> 'jack' not in tel
False
@end example

@ref{1b8,,dict()} 构造函数可以直接从键值对序列里创建字典。

@example
>>> dict([('sape', 4139), ('guido', 4127), ('jack', 4098)])
@{'sape': 4139, 'guido': 4127, 'jack': 4098@}
@end example

此外，字典推导式可以从任意的键值表达式中创建字典

@example
>>> @{x: x**2 for x in (2, 4, 6)@}
@{2: 4, 4: 16, 6: 36@}
@end example

当关键字是简单字符串时，有时直接通过关键字参数来指定键值对更方便

@example
>>> dict(sape=4139, guido=4127, jack=4098)
@{'sape': 4139, 'guido': 4127, 'jack': 4098@}
@end example

@node 循环的技巧,深入条件控制,字典,数据结构
@anchor{tutorial/datastructures looping-techniques}@anchor{1209}@anchor{tutorial/datastructures tut-loopidioms}@anchor{11cd}
@subsection 循环的技巧


当在字典中循环时，用 @code{items()} 方法可将关键字和对应的值同时取出

@example
>>> knights = @{'gallahad': 'the pure', 'robin': 'the brave'@}
>>> for k, v in knights.items():
...     print(k, v)
...
gallahad the pure
robin the brave
@end example

当在序列中循环时，用 @ref{ddc,,enumerate()} 函数可以将索引位置和其对应的值同时取出

@example
>>> for i, v in enumerate(['tic', 'tac', 'toe']):
...     print(i, v)
...
0 tic
1 tac
2 toe
@end example

当同时在两个或更多序列中循环时，可以用 @ref{c2b,,zip()} 函数将其内元素一一匹配。

@example
>>> questions = ['name', 'quest', 'favorite color']
>>> answers = ['lancelot', 'the holy grail', 'blue']
>>> for q, a in zip(questions, answers):
...     print('What is your @{0@}?  It is @{1@}.'.format(q, a))
...
What is your name?  It is lancelot.
What is your quest?  It is the holy grail.
What is your favorite color?  It is blue.
@end example

如果要逆向循环一个序列，可以先正向定位序列，然后调用 @ref{18e,,reversed()} 函数

@example
>>> for i in reversed(range(1, 10, 2)):
...     print(i)
...
9
7
5
3
1
@end example

如果要按某个指定顺序循环一个序列，可以用 @ref{43e,,sorted()} 函数，它可以在不改动原序列的基础上返回一个新的排好序的序列

@example
>>> basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
>>> for f in sorted(set(basket)):
...     print(f)
...
apple
banana
orange
pear
@end example

有时可能会想在循环时修改列表内容，一般来说改为创建一个新列表是比较简单且安全的

@example
>>> import math
>>> raw_data = [56.2, float('NaN'), 51.7, 55.3, 52.5, float('NaN'), 47.8]
>>> filtered_data = []
>>> for value in raw_data:
...     if not math.isnan(value):
...         filtered_data.append(value)
...
>>> filtered_data
[56.2, 51.7, 55.3, 52.5, 47.8]
@end example

@node 深入条件控制,比较序列和其他类型,循环的技巧,数据结构
@anchor{tutorial/datastructures more-on-conditions}@anchor{120a}@anchor{tutorial/datastructures tut-conditions}@anchor{120b}
@subsection 深入条件控制


@code{while} 和 @code{if} 条件句中可以使用任意操作，而不仅仅是比较操作。

比较操作符 @code{in} 和 @code{not in} 校验一个值是否在（或不在）一个序列里。操作符 @code{is} 和 @code{is not} 比较两个对象是不是同一个对象，这只对像列表这样的可变对象比较重要。所有的比较操作符都有相同的优先级，且这个优先级比数值运算符低。

比较操作可以传递。例如 @code{a < b == c} 会校验是否 @code{a} 小于 @code{b} 并且 @code{b} 等于 @code{c}。

比较操作可以通过布尔运算符 @code{and} 和 @code{or} 来组合，并且比较操作（或其他任何布尔运算）的结果都可以用 @code{not} 来取反。这些操作符的优先级低于比较操作符；在它们之中，@code{not} 优先级最高， @code{or} 优先级最低，因此 @code{A and not B or C} 等价于 @code{(A and (not B)) or C}。和之前一样，你也可以在这种式子里使用圆括号。

布尔运算符 @code{and} 和 @code{or} 也被称为 @emph{短路} 运算符：它们的参数从左至右解析，一旦可以确定结果解析就会停止。例如，如果 @code{A} 和 @code{C} 为真而 @code{B} 为假，那么 @code{A and B and C} 不会解析 @code{C}。当用作普通值而非布尔值时，短路操作符的返回值通常是最后一个变量。

也可以把比较操作或者逻辑表达式的结果赋值给一个变量，例如

@example
>>> string1, string2, string3 = '@w{'}, 'Trondheim', 'Hammer Dance'
>>> non_null = string1 or string2 or string3
>>> non_null
'Trondheim'
@end example

请注意 Python 与 C 不同，在表达式内部赋值必须显式地使用 @ref{120c,,海象运算符} @code{:=} 来完成。 这避免了 C 程序中常见的一种问题：想要在表达式中写 @code{==} 时却写成了 @code{=}。

@node 比较序列和其他类型,,深入条件控制,数据结构
@anchor{tutorial/datastructures comparing-sequences-and-other-types}@anchor{120d}@anchor{tutorial/datastructures tut-comparing}@anchor{120e}
@subsection 比较序列和其他类型


序列对象通常可以与相同序列类型的其他对象比较。 这种比较使用 @emph{字典式} 顺序：首先比较开头的两个对应元素，如果两者不相等则比较结果就由此确定；如果两者相等则比较之后的两个元素，以此类推，直到有一个序列被耗尽。 如果要比较的两个元素本身又是相同类型的序列，则会递归地执行字典式顺序比较。 如果两个序列中所有的对应元素都相等，则两个序列也将被视为相等。 如果一个序列是另一个的初始子序列，则较短的序列就被视为较小（较少）。 对于字符串来说，字典式顺序是使用 Unicode 码位序号对单个字符排序。 下面是一些相同类型序列之间比较的例子:

@example
(1, 2, 3)              < (1, 2, 4)
[1, 2, 3]              < [1, 2, 4]
'ABC' < 'C' < 'Pascal' < 'Python'
(1, 2, 3, 4)           < (1, 2, 4)
(1, 2)                 < (1, 2, -1)
(1, 2, 3)             == (1.0, 2.0, 3.0)
(1, 2, ('aa', 'ab'))   < (1, 2, ('abc', 'a'), 4)
@end example

注意对不同类型对象来说，只要待比较对象提供了合适的比较方法，就可以使用 @code{<} 和 @code{>} 来比较。例如，混合数值类型是通过他们的数值进行比较的，所以 0 等于 0.0，等等。否则，解释器将抛出一个 @ref{192,,TypeError} 异常，而不是随便给出一个结果。

@subsubheading 备注


@node 模块,输入输出,数据结构,Python 教程
@anchor{tutorial/modules doc}@anchor{120f}@anchor{tutorial/modules modules}@anchor{1210}@anchor{tutorial/modules tut-modules}@anchor{1211}
@section 模块


如果你从Python解释器退出并再次进入，之前的定义（函数和变量）都会丢失。因此，如果你想编写一个稍长些的程序，最好使用文本编辑器为解释器准备输入并将该文件作为输入运行。这被称作编写 @emph{脚本} 。随着程序变得越来越长，你或许会想把它拆分成几个文件，以方便维护。你亦或想在不同的程序中使用一个便捷的函数， 而不必把这个函数复制到每一个程序中去。

为支持这些，Python有一种方法可以把定义放在一个文件里，并在脚本或解释器的交互式实例中使用它们。这样的文件被称作 @emph{模块} ；模块中的定义可以 @emph{导入} 到其它模块或者 @emph{主} 模块（你在顶级和计算器模式下执行的脚本中可以访问的变量集合）。

模块是一个包含Python定义和语句的文件。文件名就是模块名后跟文件后缀 @code{.py} 。在一个模块内部，模块名（作为一个字符串）可以通过全局变量 @code{__name__} 的值获得。例如，使用你最喜爱的文本编辑器在当前目录下创建一个名为 @code{fibo.py} 的文件， 文件中含有以下内容:

@example
# Fibonacci numbers module

def fib(n):    # write Fibonacci series up to n
    a, b = 0, 1
    while a < n:
        print(a, end=' ')
        a, b = b, a+b
    print()

def fib2(n):   # return Fibonacci series up to n
    result = []
    a, b = 0, 1
    while a < n:
        result.append(a)
        a, b = b, a+b
    return result
@end example

现在进入Python解释器，并用以下命令导入该模块:

@example
>>> import fibo
@end example

在当前的符号表中，这并不会直接进入到定义在 @code{fibo} 函数内的名称；它只是进入到模块名 @code{fibo} 中。你可以用模块名访问这些函数:

@example
>>> fibo.fib(1000)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987
>>> fibo.fib2(100)
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
>>> fibo.__name__
'fibo'
@end example

如果你想经常使用某个函数，你可以把它赋值给一个局部变量:

@example
>>> fib = fibo.fib
>>> fib(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
@end example

@menu
* 更多有关模块的信息:: 
* 标准模块:: 
* dir() 函数: dir 函数. 
* 包:: 

@end menu

@node 更多有关模块的信息,标准模块,,模块
@anchor{tutorial/modules more-on-modules}@anchor{1212}@anchor{tutorial/modules tut-moremodules}@anchor{1213}
@subsection 更多有关模块的信息


模块可以包含可执行的语句以及函数定义。这些语句用于初始化模块。它们仅在模块 @emph{第一次} 在 import 语句中被导入时才执行。 @footnote{@w{(1)} 
实际上，函数定义也是“被执行”的“语句”；模块级函数定义的执行在模块的全局符号表中输入该函数名。
} (当文件被当作脚本运行时，它们也会执行。)

每个模块都有它自己的私有符号表，该表用作模块中定义的所有函数的全局符号表。因此，模块的作者可以在模块内使用全局变量，而不必担心与用户的全局变量发生意外冲突。另一方面，如果你知道自己在做什么，则可以用跟访问模块内的函数的同样标记方法，去访问一个模块的全局变量，@code{modname.itemname}。

模块可以导入其它模块。习惯上但不要求把所有 @ref{c16,,import} 语句放在模块（或脚本）的开头。被导入的模块名存放在调入模块的全局符号表中。

@ref{c16,,import} 语句有一个变体，它可以把名字从一个被调模块内直接导入到现模块的符号表里。例如:

@example
>>> from fibo import fib, fib2
>>> fib(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
@end example

这并不会把被调模块名引入到局部变量表里（因此在这个例子里，@code{fibo} 是未被定义的）。

还有一个变体甚至可以导入模块内定义的所有名称:

@example
>>> from fibo import *
>>> fib(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
@end example

这会调入所有非以下划线（@code{_}）开头的名称。 在多数情况下，Python程序员都不会使用这个功能，因为它在解释器中引入了一组未知的名称，而它们很可能会覆盖一些你已经定义过的东西。

注意通常情况下从一个模块或者包内调入 @code{*} 的做法是不太被接受的， 因为这通常会导致代码的可读性很差。不过，在交互式编译器中为了节省打字可以这么用。

如果模块名称之后带有 @code{as}，则跟在 @code{as} 之后的名称将直接绑定到所导入的模块。

@example
>>> import fibo as fib
>>> fib.fib(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
@end example

这会和 @code{import fibo} 方式一样有效地调入模块， 唯一的区别是它以 @code{fib} 的名称存在的。

这种方式也可以在用到 @ref{c3e,,from} 的时候使用，并会有类似的效果:

@example
>>> from fibo import fib as fibonacci
>>> fibonacci(500)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
@end example

@cartouche
@quotation 注解 
出于效率的考虑，每个模块在每个解释器会话中只被导入一次。因此，如果你更改了你的模块，则必须重新启动解释器， 或者，如果它只是一个要交互式地测试的模块，请使用 @ref{391,,importlib.reload()}，例如 @code{import importlib; importlib.reload(modulename)}。
@end quotation
@end cartouche

@menu
* 以脚本的方式执行模块:: 
* 模块搜索路径:: 
* “编译过的”Python文件:: 

@end menu

@node 以脚本的方式执行模块,模块搜索路径,,更多有关模块的信息
@anchor{tutorial/modules executing-modules-as-scripts}@anchor{1214}@anchor{tutorial/modules tut-modulesasscripts}@anchor{1215}
@subsubsection 以脚本的方式执行模块


当你用下面方式运行一个Python模块:

@example
python fibo.py <arguments>
@end example

模块里的代码会被执行，就好像你导入了模块一样，但是 @code{__name__} 被赋值为 @code{"__main__"}。 这意味着通过在你的模块末尾添加这些代码:

@example
if __name__ == "__main__":
    import sys
    fib(int(sys.argv[1]))
@end example

你既可以把这个文件当作脚本又可当作一个可调入的模块来使用， 因为那段解析命令行的代码只有在当模块是以“main”文件的方式执行的时候才会运行:

@example
$ python fibo.py 50
0 1 1 2 3 5 8 13 21 34
@end example

如果模块是被导入的，那些代码是不运行的:

@example
>>> import fibo
>>>
@end example

这经常用于为模块提供一个方便的用户接口，或用于测试（以脚本的方式运行模块从而执行一些测试套件）。

@node 模块搜索路径,“编译过的”Python文件,以脚本的方式执行模块,更多有关模块的信息
@anchor{tutorial/modules the-module-search-path}@anchor{1216}@anchor{tutorial/modules tut-searchpath}@anchor{1217}
@subsubsection 模块搜索路径


@geindex module; search; path

当一个名为 @code{spam} 的模块被导入的时候，解释器首先寻找具有该名称的内置模块。如果没有找到，然后解释器从 @ref{482,,sys.path} 变量给出的目录列表里寻找名为 @code{spam.py} 的文件。@ref{482,,sys.path} 初始有这些目录地址:


@itemize *

@item 
包含输入脚本的目录（或者未指定文件时的当前目录）。

@item 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} （一个包含目录名称的列表，它和shell变量 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 有一样的语法）。

@item 
取决于安装的默认设置
@end itemize

@cartouche
@quotation 注解 
在支持符号链接的文件系统上，包含输入脚本的目录是在追加符号链接后才计算出来的。换句话说，包含符号链接的目录并 @strong{没有} 被添加到模块的搜索路径上。
@end quotation
@end cartouche

在初始化后，Python程序可以更改 @ref{482,,sys.path}。包含正在运行脚本的文件目录被放在搜索路径的开头处， 在标准库路径之前。这意味着将加载此目录里的脚本，而不是标准库中的同名模块。 除非有意更换，否则这是错误。更多信息请参阅 @ref{1218,,标准模块}。

@c %
@c Do we need stuff on zip files etc. ? DUBOIS

@node “编译过的”Python文件,,模块搜索路径,更多有关模块的信息
@anchor{tutorial/modules compiled-python-files}@anchor{1219}
@subsubsection “编译过的”Python文件


为了加速模块载入，Python在 @code{__pycache__} 目录里缓存了每个模块的编译后版本，名称为 @code{module.@emph{version}.pyc} ，其中名称中的版本字段对编译文件的格式进行编码； 它一般使用Python版本号。例如，在CPython版本3.3中，spam.py的编译版本将被缓存为 @code{__pycache__/spam.cpython-33.pyc}。此命名约定允许来自不同发行版和不同版本的Python的已编译模块共存。

Python根据编译版本检查源的修改日期，以查看它是否已过期并需要重新编译。这是一个完全自动化的过程。此外，编译的模块与平台无关，因此可以在具有不同体系结构的系统之间共享相同的库。

Python在两种情况下不会检查缓存。首先，对于从命令行直接载入的模块，它从来都是重新编译并且不存储编译结果；其次，如果没有源模块，它不会检查缓存。为了支持无源文件（仅编译）发行版本， 编译模块必须是在源目录下，并且绝对不能有源模块。

给专业人士的一些小建议:


@itemize *

@item 
你可以在Python命令中使用 @ref{685,,-O} 或者 @ref{686,,-OO} 开关， 以减小编译后模块的大小。 @code{-O} 开关去除断言语句，@code{-OO} 开关同时去除断言语句和 __doc__ 字符串。由于有些程序可能依赖于这些，你应当只在清楚自己在做什么时才使用这个选项。“优化过的”模块有一个 @code{opt-} 标签并且通常小些。将来的发行版本或许会更改优化的效果。

@item 
一个从 @code{.pyc} 文件读出的程序并不会比它从 @code{.py} 读出时运行的更快，@code{.pyc} 文件唯一快的地方在于载入速度。

@item 
@ref{21,,compileall} 模块可以为一个目录下的所有模块创建.pyc文件。

@item 
关于这个过程，
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} 中有更多细节，包括一个决策流程图。
@end itemize

@node 标准模块,dir 函数,更多有关模块的信息,模块
@anchor{tutorial/modules standard-modules}@anchor{121a}@anchor{tutorial/modules tut-standardmodules}@anchor{1218}
@subsection 标准模块


@geindex 模块; sys

Python附带了一个标准模块库，在单独的文档Python库参考（以下称为“库参考”）中进行了描述。一些模块内置于解释器中；它们提供对不属于语言核心但仍然内置的操作的访问，以提高效率或提供对系统调用等操作系统原语的访问。这些模块的集合是一个配置选项，它也取决于底层平台。例如，@ref{12a,,winreg} 模块只在Windows操作系统上提供。一个特别值得注意的模块 @ref{fd,,sys}，它被内嵌到每一个Python解释器中。变量 @code{sys.ps1} 和 @code{sys.ps2} 定义用作主要和辅助提示的字符串:

@example
>>> import sys
>>> sys.ps1
'>>> '
>>> sys.ps2
'... '
>>> sys.ps1 = 'C> '
C> print('Yuck!')
Yuck!
C>
@end example

这两个变量只有在编译器是交互模式下才被定义。

@code{sys.path} 变量是一个字符串列表，用于确定解释器的模块搜索路径。该变量被初始化为从环境变量 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 获取的默认路径，或者如果 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 未设置，则从内置默认路径初始化。你可以使用标准列表操作对其进行修改:

@example
>>> import sys
>>> sys.path.append('/ufs/guido/lib/python')
@end example

@node dir 函数,包,标准模块,模块
@anchor{tutorial/modules the-dir-function}@anchor{121b}@anchor{tutorial/modules tut-dir}@anchor{121c}
@subsection @code{dir()} 函数


内置函数 @ref{d2c,,dir()} 用于查找模块定义的名称。 它返回一个排序过的字符串列表:

@example
>>> import fibo, sys
>>> dir(fibo)
['__name__', 'fib', 'fib2']
>>> dir(sys)  
['__displayhook__', '__doc__', '__excepthook__', '__loader__', '__name__',
 '__package__', '__stderr__', '__stdin__', '__stdout__',
 '_clear_type_cache', '_current_frames', '_debugmallocstats', '_getframe',
 '_home', '_mercurial', '_xoptions', 'abiflags', 'api_version', 'argv',
 'base_exec_prefix', 'base_prefix', 'builtin_module_names', 'byteorder',
 'call_tracing', 'callstats', 'copyright', 'displayhook',
 'dont_write_bytecode', 'exc_info', 'excepthook', 'exec_prefix',
 'executable', 'exit', 'flags', 'float_info', 'float_repr_style',
 'getcheckinterval', 'getdefaultencoding', 'getdlopenflags',
 'getfilesystemencoding', 'getobjects', 'getprofile', 'getrecursionlimit',
 'getrefcount', 'getsizeof', 'getswitchinterval', 'gettotalrefcount',
 'gettrace', 'hash_info', 'hexversion', 'implementation', 'int_info',
 'intern', 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path',
 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'ps1',
 'setcheckinterval', 'setdlopenflags', 'setprofile', 'setrecursionlimit',
 'setswitchinterval', 'settrace', 'stderr', 'stdin', 'stdout',
 'thread_info', 'version', 'version_info', 'warnoptions']
@end example

如果没有参数，@ref{d2c,,dir()} 会列出你当前定义的名称:

@example
>>> a = [1, 2, 3, 4, 5]
>>> import fibo
>>> fib = fibo.fib
>>> dir()
['__builtins__', '__name__', 'a', 'fib', 'fibo', 'sys']
@end example

注意：它列出所有类型的名称：变量，模块，函数，等等。

@geindex 模块; builtins

@ref{d2c,,dir()} 不会列出内置函数和变量的名称。如果你想要这些，它们的定义是在标准模块 @ref{13,,builtins} 中:

@example
>>> import builtins
>>> dir(builtins)  
['ArithmeticError', 'AssertionError', 'AttributeError', 'BaseException',
 'BlockingIOError', 'BrokenPipeError', 'BufferError', 'BytesWarning',
 'ChildProcessError', 'ConnectionAbortedError', 'ConnectionError',
 'ConnectionRefusedError', 'ConnectionResetError', 'DeprecationWarning',
 'EOFError', 'Ellipsis', 'EnvironmentError', 'Exception', 'False',
 'FileExistsError', 'FileNotFoundError', 'FloatingPointError',
 'FutureWarning', 'GeneratorExit', 'IOError', 'ImportError',
 'ImportWarning', 'IndentationError', 'IndexError', 'InterruptedError',
 'IsADirectoryError', 'KeyError', 'KeyboardInterrupt', 'LookupError',
 'MemoryError', 'NameError', 'None', 'NotADirectoryError', 'NotImplemented',
 'NotImplementedError', 'OSError', 'OverflowError',
 'PendingDeprecationWarning', 'PermissionError', 'ProcessLookupError',
 'ReferenceError', 'ResourceWarning', 'RuntimeError', 'RuntimeWarning',
 'StopIteration', 'SyntaxError', 'SyntaxWarning', 'SystemError',
 'SystemExit', 'TabError', 'TimeoutError', 'True', 'TypeError',
 'UnboundLocalError', 'UnicodeDecodeError', 'UnicodeEncodeError',
 'UnicodeError', 'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning',
 'ValueError', 'Warning', 'ZeroDivisionError', '_', '__build_class__',
 '__debug__', '__doc__', '__import__', '__name__', '__package__', 'abs',
 'all', 'any', 'ascii', 'bin', 'bool', 'bytearray', 'bytes', 'callable',
 'chr', 'classmethod', 'compile', 'complex', 'copyright', 'credits',
 'delattr', 'dict', 'dir', 'divmod', 'enumerate', 'eval', 'exec', 'exit',
 'filter', 'float', 'format', 'frozenset', 'getattr', 'globals', 'hasattr',
 'hash', 'help', 'hex', 'id', 'input', 'int', 'isinstance', 'issubclass',
 'iter', 'len', 'license', 'list', 'locals', 'map', 'max', 'memoryview',
 'min', 'next', 'object', 'oct', 'open', 'ord', 'pow', 'print', 'property',
 'quit', 'range', 'repr', 'reversed', 'round', 'set', 'setattr', 'slice',
 'sorted', 'staticmethod', 'str', 'sum', 'super', 'tuple', 'type', 'vars',
 'zip']
@end example

@node 包,,dir 函数,模块
@anchor{tutorial/modules packages}@anchor{121d}@anchor{tutorial/modules tut-packages}@anchor{121e}
@subsection 包


包是一种通过用“带点号的模块名”来构造 Python 模块命名空间的方法。 例如，模块名 @code{A.B} 表示 @code{A} 包中名为 @code{B} 的子模块。正如模块的使用使得不同模块的作者不必担心彼此的全局变量名称一样，使用加点的模块名可以使得 NumPy 或 Pillow 等多模块软件包的作者不必担心彼此的模块名称一样。

假设你想为声音文件和声音数据的统一处理，设计一个模块集合（一个“包”）。由于存在很多不同的声音文件格式（通常由它们的扩展名来识别，例如：@code{.wav}， @code{.aiff}， @code{.au}），因此为了不同文件格式间的转换，你可能需要创建和维护一个不断增长的模块集合。 你可能还想对声音数据还做很多不同的处理（例如，混声，添加回声，使用均衡器功能，创造人工立体声效果）， 因此为了实现这些处理，你将另外写一个无穷尽的模块流。这是你的包的可能结构（以分层文件系统的形式表示）：

@example
sound/                          Top-level package
      __init__.py               Initialize the sound package
      formats/                  Subpackage for file format conversions
              __init__.py
              wavread.py
              wavwrite.py
              aiffread.py
              aiffwrite.py
              auread.py
              auwrite.py
              ...
      effects/                  Subpackage for sound effects
              __init__.py
              echo.py
              surround.py
              reverse.py
              ...
      filters/                  Subpackage for filters
              __init__.py
              equalizer.py
              vocoder.py
              karaoke.py
              ...
@end example

当导入这个包时，Python搜索 @code{sys.path} 里的目录，查找包的子目录。

必须要有 @code{__init__.py} 文件才能让 Python 将包含该文件的目录当作包。 这样可以防止具有通常名称例如 @code{string} 的目录在无意中隐藏稍后在模块搜索路径上出现的有效模块。 在最简单的情况下，@code{__init__.py} 可以只是一个空文件，但它也可以执行包的初始化代码或设置 @code{__all__} 变量，具体将在后文介绍。

包的用户可以从包中导入单个模块，例如:

@example
import sound.effects.echo
@end example

这会加载子模块 @code{sound.effects.echo} 。但引用它时必须使用它的全名。

@example
sound.effects.echo.echofilter(input, output, delay=0.7, atten=4)
@end example

导入子模块的另一种方法是

@example
from sound.effects import echo
@end example

这也会加载子模块 @code{echo} ，并使其在没有包前缀的情况下可用，因此可以按如下方式使用:

@example
echo.echofilter(input, output, delay=0.7, atten=4)
@end example

另一种形式是直接导入所需的函数或变量:

@example
from sound.effects.echo import echofilter
@end example

同样，这也会加载子模块 @code{echo}，但这会使其函数 @code{echofilter()} 直接可用:

@example
echofilter(input, output, delay=0.7, atten=4)
@end example

请注意，当使用 @code{from package import item} 时，item可以是包的子模块（或子包），也可以是包中定义的其他名称，如函数，类或变量。 @code{import} 语句首先测试是否在包中定义了item；如果没有，它假定它是一个模块并尝试加载它。如果找不到它，则引发 @ref{32d,,ImportError} 异常。

相反，当使用 @code{import item.subitem.subsubitem} 这样的语法时，除了最后一项之外的每一项都必须是一个包；最后一项可以是模块或包，但不能是前一项中定义的类或函数或变量。

@menu
* 从包中导入 *:: 
* 子包参考:: 
* 多个目录中的包:: 

@end menu

@node 从包中导入 *,子包参考,,包
@anchor{tutorial/modules importing-from-a-package}@anchor{121f}@anchor{tutorial/modules tut-pkg-import-star}@anchor{1220}
@subsubsection 从包中导入 *


@geindex __all__

当用户写 @code{from sound.effects import *} 会发生什么？理想情况下，人们希望这会以某种方式传递给文件系统，找到包中存在哪些子模块，并将它们全部导入。这可能需要很长时间，导入子模块可能会产生不必要的副作用，这种副作用只有在显式导入子模块时才会发生。

唯一的解决方案是让包作者提供一个包的显式索引。@ref{c16,,import} 语句使用下面的规范：如果一个包的 @code{__init__.py} 代码定义了一个名为 @code{__all__} 的列表，它会被视为在遇到 @code{from package import *} 时应该导入的模块名列表。在发布该包的新版本时，包作者可以决定是否让此列表保持更新。包作者如果认为从他们的包中导入 * 的操作没有必要被使用，也可以决定不支持此列表。例如，文件 @code{sound/effects/__init__.py} 可以包含以下代码:

@example
__all__ = ["echo", "surround", "reverse"]
@end example

这意味着 @code{from sound.effects import *} 将导入 @code{sound} 包的三个命名子模块。

如果没有定义 @code{__all__}，@code{from sound.effects import *} 语句 @emph{不} 会从包 @code{sound.effects} 中导入所有子模块到当前命名空间；它只确保导入了包 @code{sound.effects} （可能运行任何在 @code{__init__.py} 中的初始化代码），然后导入包中定义的任何名称。这包括 @code{__init__.py`} 定义的任何名称（以及显式加载的子模块）。它还包括由之前的 @ref{c16,,import} 语句显式加载的包的任何子模块。思考下面的代码:

@example
import sound.effects.echo
import sound.effects.surround
from sound.effects import *
@end example

在这个例子中， @code{echo} 和 @code{surround} 模块是在执行 @code{from...import} 语句时导入到当前命名空间中的，因为它们定义在 @code{sound.effects} 包中。（这在定义了 @code{__all__} 时也有效。）

虽然某些模块被设计为在使用 @code{import *} 时只导出遵循某些模式的名称，但在生产代码中它仍然被认为是不好的做法。

请记住，使用 @code{from package import specific_submodule} 没有任何问题！ 实际上，除非导入的模块需要使用来自不同包的同名子模块，否则这是推荐的表示法。

@node 子包参考,多个目录中的包,从包中导入 *,包
@anchor{tutorial/modules intra-package-references}@anchor{1221}
@subsubsection 子包参考


当包被构造成子包时（与示例中的 @code{sound} 包一样），你可以使用绝对导入来引用兄弟包的子模块。例如，如果模块 @code{sound.filters.vocoder} 需要在 @code{sound.effects} 包中使用 @code{echo} 模块，它可以使用 @code{from sound.effects import echo} 。

你还可以使用import语句的 @code{from module import name} 形式编写相对导入。这些导入使用前导点来指示相对导入中涉及的当前包和父包。例如，从 @code{surround} 模块，你可以使用:

@example
from . import echo
from .. import formats
from ..filters import equalizer
@end example

请注意，相对导入是基于当前模块的名称进行导入的。由于主模块的名称总是 @code{"__main__"} ，因此用作Python应用程序主模块的模块必须始终使用绝对导入。

@node 多个目录中的包,,子包参考,包
@anchor{tutorial/modules packages-in-multiple-directories}@anchor{1222}
@subsubsection 多个目录中的包


包支持另一个特殊属性， @ref{1223,,__path__} 。它被初始化为一个列表，其中包含在执行该文件中的代码之前保存包的文件 @code{__init__.py} 的目录的名称。这个变量可以修改；这样做会影响将来对包中包含的模块和子包的搜索。

虽然通常不需要此功能，但它可用于扩展程序包中的模块集。

@subsubheading 备注


@node 输入输出,错误和异常,模块,Python 教程
@anchor{tutorial/inputoutput doc}@anchor{1224}@anchor{tutorial/inputoutput input-and-output}@anchor{1225}@anchor{tutorial/inputoutput tut-io}@anchor{1226}
@section 输入输出


有几种方法可以显示程序的输出；数据可以以人类可读的形式打印出来，或者写入文件以供将来使用。本章将讨论一些可能性。

@menu
* 更漂亮的输出格式:: 
* 读写文件:: 

@end menu

@node 更漂亮的输出格式,读写文件,,输入输出
@anchor{tutorial/inputoutput fancier-output-formatting}@anchor{1227}@anchor{tutorial/inputoutput tut-formatting}@anchor{1228}
@subsection 更漂亮的输出格式


到目前为止，我们遇到了两种写入值的方法：@emph{表达式语句} 和 @ref{880,,print()} 函数。（第三种是使用文件对象的 @code{write()} 方法；标准输出文件可以作为 @code{sys.stdout} 引用。更多相关信息可参考标准库指南。）

通常，你需要更多地控制输出的格式，而不仅仅是打印空格分隔的值。有几种格式化输出的方法。


@itemize *

@item 
要使用 @ref{1229,,格式化字符串字面值} ，请在字符串的开始引号或三引号之前加上一个 @code{f} 或 @code{F} 。在此字符串中，你可以在 @code{@{} 和 @code{@}} 字符之间写可以引用的变量或字面值的 Python 表达式。

@example
>>> year = 2016
>>> event = 'Referendum'
>>> f'Results of the @{year@} @{event@}'
'Results of the 2016 Referendum'
@end example

@item 
字符串的 @ref{4d4,,str.format()} 方法需要更多的手动操作。你仍将使用 @code{@{} 和 @code{@}} 来标记变量将被替换的位置，并且可以提供详细的格式化指令，但你还需要提供要格式化的信息。

@example
>>> yes_votes = 42_572_654
>>> no_votes = 43_132_495
>>> percentage = yes_votes / (yes_votes + no_votes)
>>> '@{:-9@} YES votes  @{:2.2%@}'.format(yes_votes, percentage)
' 42572654 YES votes  49.67%'
@end example

@item 
最后，你可以使用字符串切片和连接操作自己完成所有的字符串处理，以创建你可以想象的任何布局。字符串类型有一些方法可以执行将字符串填充到给定列宽的有用操作。
@end itemize

当你不需要花哨的输出而只是想快速显示某些变量以进行调试时，可以使用 @ref{7c6,,repr()} or @ref{329,,str()} 函数将任何值转化为字符串。

@ref{329,,str()} 函数是用于返回人类可读的值的表示，而 @ref{7c6,,repr()} 是用于生成解释器可读的表示（如果没有等效的语法，则会强制执行 @ref{452,,SyntaxError}）对于没有人类可读性的表示的对象， @ref{329,,str()} 将返回和 @ref{7c6,,repr()} 一样的值。很多值使用任一函数都具有相同的表示，比如数字或类似列表和字典的结构。特殊的是字符串有两个不同的表示。

几个例子:

@example
>>> s = 'Hello, world.'
>>> str(s)
'Hello, world.'
>>> repr(s)
"'Hello, world.'"
>>> str(1/7)
'0.14285714285714285'
>>> x = 10 * 3.25
>>> y = 200 * 200
>>> s = 'The value of x is ' + repr(x) + ', and y is ' + repr(y) + '...'
>>> print(s)
The value of x is 32.5, and y is 40000...
>>> # The repr() of a string adds string quotes and backslashes:
... hello = 'hello, world\n'
>>> hellos = repr(hello)
>>> print(hellos)
'hello, world\n'
>>> # The argument to repr() may be any Python object:
... repr((x, y, ('spam', 'eggs')))
"(32.5, 40000, ('spam', 'eggs'))"
@end example

@ref{f6,,string} 模块包含一个 @ref{3e3,,Template} 类，它提供了另一种将值替换为字符串的方法，使用类似 @code{$x} 的占位符并用字典中的值替换它们，但对格式的控制要少的多。

@menu
* 格式化字符串文字:: 
* 字符串的 format() 方法: 字符串的 format 方法. 
* 手动格式化字符串:: 
* 旧的字符串格式化方法:: 

@end menu

@node 格式化字符串文字,字符串的 format 方法,,更漂亮的输出格式
@anchor{tutorial/inputoutput formatted-string-literals}@anchor{122a}@anchor{tutorial/inputoutput tut-f-strings}@anchor{1229}
@subsubsection 格式化字符串文字


@ref{15c,,格式化字符串字面值} （常简称为 f-字符串）能让你在字符串前加上 @code{f} 和 @code{F} 并将表达式写成 @code{@{expression@}} 来在字符串中包含 Python 表达式的值。

可选的格式说明符可以跟在表达式后面。这样可以更好地控制值的格式化方式。以下示例将pi舍入到小数点后三位:

@example
>>> import math
>>> print(f'The value of pi is approximately @{math.pi:.3f@}.')
The value of pi is approximately 3.142.
@end example

在 @code{':'} 后传递一个整数可以让该字段成为最小字符宽度。这在使列对齐时很有用。:

@example
>>> table = @{'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 7678@}
>>> for name, phone in table.items():
...     print(f'@{name:10@} ==> @{phone:10d@}')
...
Sjoerd     ==>       4127
Jack       ==>       4098
Dcab       ==>       7678
@end example

其他的修饰符可用于在格式化之前转化值。 @code{'!a'} 应用 @ref{d45,,ascii()} ，@code{'!s'} 应用 @ref{329,,str()}，还有 @code{'!r'} 应用 @ref{7c6,,repr()}:

@example
>>> animals = 'eels'
>>> print(f'My hovercraft is full of @{animals@}.')
My hovercraft is full of eels.
>>> print(f'My hovercraft is full of @{animals!r@}.')
My hovercraft is full of 'eels'.
@end example

有关这些格式规范的参考，请参阅参考指南 @ref{4d8,,格式规格迷你语言}。

@node 字符串的 format 方法,手动格式化字符串,格式化字符串文字,更漂亮的输出格式
@anchor{tutorial/inputoutput the-string-format-method}@anchor{122b}@anchor{tutorial/inputoutput tut-string-format}@anchor{122c}
@subsubsection 字符串的 format() 方法


@ref{4d4,,str.format()} 方法的基本用法如下所示:

@example
>>> print('We are the @{@} who say "@{@}!"'.format('knights', 'Ni'))
We are the knights who say "Ni!"
@end example

花括号和其中的字符（称为格式字段）将替换为传递给 @ref{4d4,,str.format()} 方法的对象。花括号中的数字可用来表示传递给 @ref{4d4,,str.format()} 方法的对象的位置。

@example
>>> print('@{0@} and @{1@}'.format('spam', 'eggs'))
spam and eggs
>>> print('@{1@} and @{0@}'.format('spam', 'eggs'))
eggs and spam
@end example

如果在 @ref{4d4,,str.format()} 方法中使用关键字参数，则使用参数的名称引用它们的值。:

@example
>>> print('This @{food@} is @{adjective@}.'.format(
...       food='spam', adjective='absolutely horrible'))
This spam is absolutely horrible.
@end example

位置和关键字参数可以任意组合:

@example
>>> print('The story of @{0@}, @{1@}, and @{other@}.'.format('Bill', 'Manfred',
                                                       other='Georg'))
The story of Bill, Manfred, and Georg.
@end example

如果你有一个非常长的格式字符串，你不想把它拆开，那么你最好是按名称而不是按位置引用变量来进行格式化。 这可以通过简单地传递字典并使用方括号 @code{'[]'} 访问键来完成。

@example
>>> table = @{'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678@}
>>> print('Jack: @{0[Jack]:d@}; Sjoerd: @{0[Sjoerd]:d@}; '
...       'Dcab: @{0[Dcab]:d@}'.format(table))
Jack: 4098; Sjoerd: 4127; Dcab: 8637678
@end example

这也可以通过使用 '**' 符号将 table 作为关键字参数传递。

@example
>>> table = @{'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678@}
>>> print('Jack: @{Jack:d@}; Sjoerd: @{Sjoerd:d@}; Dcab: @{Dcab:d@}'.format(**table))
Jack: 4098; Sjoerd: 4127; Dcab: 8637678
@end example

这在与内置函数 @ref{fca,,vars()} 结合使用时非常有用，它会返回包含所有局部变量的字典。

例如，下面几行代码生成一组整齐的列，其中包含给定的整数和它的平方以及立方:

@example
>>> for x in range(1, 11):
...     print('@{0:2d@} @{1:3d@} @{2:4d@}'.format(x, x*x, x*x*x))
...
 1   1    1
 2   4    8
 3   9   27
 4  16   64
 5  25  125
 6  36  216
 7  49  343
 8  64  512
 9  81  729
10 100 1000
@end example

关于使用 @ref{4d4,,str.format()} 进行字符串格式化的完整概述，请参阅 @ref{d13,,格式字符串语法} 。

@node 手动格式化字符串,旧的字符串格式化方法,字符串的 format 方法,更漂亮的输出格式
@anchor{tutorial/inputoutput manual-string-formatting}@anchor{122d}
@subsubsection 手动格式化字符串


这是同一个平方和立方的表，手动格式化的:

@example
>>> for x in range(1, 11):
...     print(repr(x).rjust(2), repr(x*x).rjust(3), end=' ')
...     # Note use of 'end' on previous line
...     print(repr(x*x*x).rjust(4))
...
 1   1    1
 2   4    8
 3   9   27
 4  16   64
 5  25  125
 6  36  216
 7  49  343
 8  64  512
 9  81  729
10 100 1000
@end example

（注意每列之间的一个空格是通过使用 @ref{880,,print()} 的方式添加的：它总是在其参数间添加空格。）

字符串对象的 @ref{122e,,str.rjust()} 方法通过在左侧填充空格来对给定宽度的字段中的字符串进行右对齐。类似的方法还有 @ref{122f,,str.ljust()} 和 @ref{1230,,str.center()} 。这些方法不会写入任何东西，它们只是返回一个新的字符串，如果输入的字符串太长，它们不会截断字符串，而是原样返回；这虽然会弄乱你的列布局，但这通常比另一种方法好，后者会在显示值时可能不准确（如果你真的想截断，你可以添加一个切片操作，例如 @code{x.ljust(n)[:n]} 。）

还有另外一个方法，@ref{1231,,str.zfill()} ，它会在数字字符串的左边填充零。它能识别正负号:

@example
>>> '12'.zfill(5)
'00012'
>>> '-3.14'.zfill(7)
'-003.14'
>>> '3.14159265359'.zfill(5)
'3.14159265359'
@end example

@node 旧的字符串格式化方法,,手动格式化字符串,更漂亮的输出格式
@anchor{tutorial/inputoutput old-string-formatting}@anchor{1232}
@subsubsection 旧的字符串格式化方法


% 运算符（求余）也可用于字符串格式化。 给定 @code{'string' % values}，则 @code{string} 中的 @code{%} 实例会以零个或多个 @code{values} 元素替换。 此操作通常被称为字符串插值。 例如:

@example
>>> import math
>>> print('The value of pi is approximately %5.3f.' % math.pi)
The value of pi is approximately 3.142.
@end example

可在 @ref{11b9,,printf 风格的字符串格式化} 部分找到更多信息。

@node 读写文件,,更漂亮的输出格式,输入输出
@anchor{tutorial/inputoutput reading-and-writing-files}@anchor{1233}@anchor{tutorial/inputoutput tut-files}@anchor{1234}
@subsection 读写文件


@geindex 內置函数; open
@geindex 对象; file

@ref{4ea,,open()} 返回一个 @ref{b3b,,file object}，最常用的有两个参数： @code{open(filename, mode)}。

@example
>>> f = open('workfile', 'w')
@end example

@c XXX str(f) is <io.TextIOWrapper object at 0x82e8dc4>
@c 
@c >>> print(f)
@c <open file 'workfile', mode 'w' at 80a0960>

第一个参数是包含文件名的字符串。第二个参数是另一个字符串，其中包含一些描述文件使用方式的字符。@emph{mode} 可以是 @code{'r'} ，表示文件只能读取，@code{'w'} 表示只能写入（已存在的同名文件会被删除），还有 @code{'a'} 表示打开文件以追加内容；任何写入的数据会自动添加到文件的末尾。@code{'r+'} 表示打开文件进行读写。@emph{mode} 参数是可选的；省略时默认为 @code{'r'}。

通常文件是以 @emph{text mode} 打开的，这意味着从文件中读取或写入字符串时，都会以指定的编码方式进行编码。如果未指定编码格式，默认值与平台相关 (参见 @ref{4ea,,open()})。在mode 中追加的 @code{'b'} 则以 @emph{binary mode} 打开文件：现在数据是以字节对象的形式进行读写的。这个模式应该用于所有不包含文本的文件。

在文本模式下读取时，默认会把平台特定的行结束符 (Unix 上的 @code{\n}, Windows 上的 @code{\r\n}) 转换为 @code{\n}。在文本模式下写入时，默认会把出现的 @code{\n} 转换回平台特定的结束符。这样在幕后修改文件数据对文本文件来说没有问题，但是会破坏二进制数据例如 @code{JPEG} 或 @code{EXE} 文件中的数据。请一定要注意在读写此类文件时应使用二进制模式。

在处理文件对象时，最好使用 @ref{6e3,,with} 关键字。 优点是当子句体结束后文件会正确关闭，即使在某个时刻引发了异常。 而且使用 @code{with} 相比等效的 @ref{d6b,,try}-@ref{182,,finally} 代码块要简短得多:

@example
>>> with open('workfile') as f:
...     read_data = f.read()

>>> # We can check that the file has been automatically closed.
>>> f.closed
True
@end example

如果你没有使用 @ref{6e3,,with} 关键字，那么你应该调用 @code{f.close()} 来关闭文件并立即释放它使用的所有系统资源。如果你没有显式地关闭文件，Python的垃圾回收器最终将销毁该对象并为你关闭打开的文件，但这个文件可能会保持打开状态一段时间。另外一个风险是不同的Python实现会在不同的时间进行清理。

通过 @ref{6e3,,with} 语句或者调用 @code{f.close()} 关闭文件对象后，尝试使用该文件对象将自动失败。:

@example
>>> f.close()
>>> f.read()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file.
@end example

@menu
* 文件对象的方法:: 
* 使用 json 保存结构化数据:: 

@end menu

@node 文件对象的方法,使用 json 保存结构化数据,,读写文件
@anchor{tutorial/inputoutput methods-of-file-objects}@anchor{1235}@anchor{tutorial/inputoutput tut-filemethods}@anchor{1236}
@subsubsection 文件对象的方法


本节中剩下的例子将假定你已创建名为 @code{f} 的文件对象。

要读取文件内容，请调用 @code{f.read(size)}，它会读取一些数据并将其作为字符串（在文本模式下）或字节串对象（在二进制模式下）返回。 @emph{size} 是一个可选的数值参数。 当 @emph{size} 被省略或者为负数时，将读取并返回整个文件的内容；如果文件的大小是你的机器内存的两倍就会出现问题。 当取其他值时，将读取并返回至多 @emph{size} 个字符（在文本模式下）或 @emph{size} 个字节（在二进制模式下）。 如果已到达文件末尾，@code{f.read()} 将返回一个空字符串 (@code{'@w{'}})。

@example
>>> f.read()
'This is the entire file.\n'
>>> f.read()
'@w{'}
@end example

@code{f.readline()} 从文件中读取一行；换行符（@code{\n}）留在字符串的末尾，如果文件不以换行符结尾，则在文件的最后一行省略。这使得返回值明确无误；如果 @code{f.readline()} 返回一个空的字符串，则表示已经到达了文件末尾，而空行使用 @code{'\n'} 表示，该字符串只包含一个换行符。:

@example
>>> f.readline()
'This is the first line of the file.\n'
>>> f.readline()
'Second line of the file\n'
>>> f.readline()
'@w{'}
@end example

要从文件中读取行，你可以循环遍历文件对象。这是内存高效，快速的，并简化代码:

@example
>>> for line in f:
...     print(line, end='@w{'})
...
This is the first line of the file.
Second line of the file
@end example

如果你想以列表的形式读取文件中的所有行，你也可以使用 @code{list(f)} 或 @code{f.readlines()}。

@code{f.write(string)} 会把 @emph{string} 的内容写入到文件中，并返回写入的字符数。:

@example
>>> f.write('This is a test\n')
15
@end example

在写入其他类型的对象之前，需要先把它们转化为字符串（在文本模式下）或者字节对象（在二进制模式下）:

@example
>>> value = ('the answer', 42)
>>> s = str(value)  # convert the tuple to string
>>> f.write(s)
18
@end example

@code{f.tell()} 返回一个整数，给出文件对象在文件中的当前位置，表示为二进制模式下时从文件开始的字节数，以及文本模式下的意义不明的数字。

要改变文件对象的位置，请使用 @code{f.seek(offset, whence)}。 通过向一个参考点添加 @emph{offset} 来计算位置；参考点由 @emph{whence} 参数指定。 @emph{whence} 的 0 值表示从文件开头起算，1 表示使用当前文件位置，2 表示使用文件末尾作为参考点。 @emph{whence} 如果省略则默认值为 0，即使用文件开头作为参考点。

@example
>>> f = open('workfile', 'rb+')
>>> f.write(b'0123456789abcdef')
16
>>> f.seek(5)      # Go to the 6th byte in the file
5
>>> f.read(1)
b'5'
>>> f.seek(-3, 2)  # Go to the 3rd byte before the end
13
>>> f.read(1)
b'd'
@end example

在文本文件（那些在模式字符串中没有 @code{b} 的打开的文件）中，只允许相对于文件开头搜索（使用 @code{seek(0, 2)} 搜索到文件末尾是个例外）并且唯一有效的 @emph{offset} 值是那些能从 @code{f.tell()} 中返回的或者是零。其他 @emph{offset} 值都会产生未定义的行为。

文件对象有一些额外的方法，例如 @code{isatty()} 和 @code{truncate()} ，它们使用频率较低；有关文件对象的完整指南请参阅库参考。

@node 使用 json 保存结构化数据,,文件对象的方法,读写文件
@anchor{tutorial/inputoutput saving-structured-data-with-json}@anchor{1237}@anchor{tutorial/inputoutput tut-json}@anchor{1238}
@subsubsection 使用 @code{json} 保存结构化数据


@geindex 模块; json

字符串可以很轻松地写入文件并从文件中读取出来。数字可能会费点劲，因为 @code{read()} 方法只能返回字符串，这些字符串必须传递给类似 @ref{184,,int()} 的函数，它会接受类似 @code{'123'} 这样的字符串并返回其数字值 123。当你想保存诸如嵌套列表和字典这样更复杂的数据类型时，手动解析和序列化会变得复杂。

Python 允许你使用称为  JSON (JavaScript Object Notation)@footnote{http://json.org} 的流行数据交换格式，而不是让用户不断的编写和调试代码以将复杂的数据类型保存到文件中。名为 @ref{a4,,json} 的标准模块可以采用 Python 数据层次结构，并将它们转化为字符串表示形式；这个过程称为 @emph{serializing} 。从字符串表示中重建数据称为 @emph{deserializing} 。在序列化和反序列化之间，表示对象的字符串可能已存储在文件或数据中，或通过网络连接发送到某个远程机器。

@cartouche
@quotation 注解 
JSON格式通常被现代应用程序用于允许数据交换。许多程序员已经熟悉它，这使其成为互操作性的良好选择。
@end quotation
@end cartouche

如果你有一个对象 @code{x} ，你可以用一行简单的代码来查看它的 JSON 字符串表示:

@example
>>> import json
>>> json.dumps([1, 'simple', 'list'])
'[1, "simple", "list"]'
@end example

@ref{600,,dumps()} 函数的另一个变体叫做 @ref{5ff,,dump()} ，它只是将对象序列化为 @ref{1239,,text file} 。因此，如果 @code{f} 是一个 @ref{1239,,text file} 对象，我们可以这样做:

@example
json.dump(x, f)
@end example

要再次解码对象，如果 @code{f} 是一个打开的以供阅读的 @ref{1239,,text file} 对象:

@example
x = json.load(f)
@end example

这种简单的序列化技术可以处理列表和字典，但是在JSON中序列化任意类的实例需要额外的努力。 @ref{a4,,json} 模块的参考包含对此的解释。


@subsubheading 参见


@ref{ca,,pickle} - 封存模块

与 @ref{1238,,JSON} 不同，@emph{pickle} 是一种允许对任意复杂 Python 对象进行序列化的协议。因此，它为 Python 所特有，不能用于与其他语言编写的应用程序通信。默认情况下它也是不安全的：如果数据是由熟练的攻击者精心设计的，则反序列化来自不受信任来源的 pickle 数据可以执行任意代码。


@node 错误和异常,类,输入输出,Python 教程
@anchor{tutorial/errors doc}@anchor{123a}@anchor{tutorial/errors errors-and-exceptions}@anchor{123b}@anchor{tutorial/errors tut-errors}@anchor{123c}
@section 错误和异常


到目前为止，我们还没有提到错误消息，但是如果你已经尝试过那些例子，你可能已经看过了一些错误消息。 目前（至少）有两种可区分的错误：@emph{语法错误} 和 @emph{异常}。

@menu
* 语法错误:: 
* 异常:: 
* 处理异常:: 
* 抛出异常:: 
* 用户自定义异常:: 
* 定义清理操作:: 
* 预定义的清理操作:: 

@end menu

@node 语法错误,异常,,错误和异常
@anchor{tutorial/errors syntax-errors}@anchor{123d}@anchor{tutorial/errors tut-syntaxerrors}@anchor{123e}
@subsection 语法错误


语法错误又称解析错误，可能是你在学习Python 时最容易遇到的错误:

@example
>>> while True print('Hello world')
  File "<stdin>", line 1
    while True print('Hello world')
                   ^
SyntaxError: invalid syntax
@end example

解析器会输出出现语法错误的那一行，并显示一个“箭头”，指向这行里面检测到第一个错误。 错误是由箭头指示的位置 @emph{上面} 的 token 引起的（或者至少是在这里被检测出的）：在示例中，在 @ref{880,,print()} 这个函数中检测到了错误，因为在它前面少了个冒号 (@code{':'}) 。文件名和行号也会被输出，以便输入来自脚本文件时你能知道去哪检查。

@node 异常,处理异常,语法错误,错误和异常
@anchor{tutorial/errors exceptions}@anchor{123f}@anchor{tutorial/errors tut-exceptions}@anchor{1240}
@subsection 异常


即使语句或表达式在语法上是正确的，但在尝试执行时，它仍可能会引发错误。 在执行时检测到的错误被称为 @emph{异常}，异常不一定会导致严重后果：你将很快学会如何在 Python 程序中处理它们。 但是，大多数异常并不会被程序处理，此时会显示如下所示的错误信息:

@example
>>> 10 * (1/0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ZeroDivisionError: division by zero
>>> 4 + spam*3
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'spam' is not defined
>>> '2' + 2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Can't convert 'int' object to str implicitly
@end example

错误信息的最后一行告诉我们程序遇到了什么类型的错误。异常有不同的类型，而其类型名称将会作为错误信息的一部分中打印出来：上述示例中的异常类型依次是：@ref{1241,,ZeroDivisionError}， @ref{d74,,NameError} 和 @ref{192,,TypeError}。作为异常类型打印的字符串是发生的内置异常的名称。对于所有内置异常都是如此，但对于用户定义的异常则不一定如此（虽然这是一个有用的规范）。标准的异常类型是内置的标识符（而不是保留关键字）。

这一行的剩下的部分根据异常类型及其原因提供详细信息。

错误信息的前一部分以堆栈回溯的形式显示发生异常时的上下文。通常它包含列出源代码行的堆栈回溯；但是它不会显示从标准输入中读取的行。

@ref{1242,,内置异常} 列出了内置异常和它们的含义。

@node 处理异常,抛出异常,异常,错误和异常
@anchor{tutorial/errors handling-exceptions}@anchor{1243}@anchor{tutorial/errors tut-handling}@anchor{11d1}
@subsection 处理异常


可以编写处理所选异常的程序。请看下面的例子，它会要求用户一直输入，直到输入的是一个有效的整数，但允许用户中断程序（使用 @code{Control-C} 或操作系统支持的其他操作）；请注意用户引起的中断可以通过引发 @ref{197,,KeyboardInterrupt} 异常来指示。:

@example
>>> while True:
...     try:
...         x = int(input("Please enter a number: "))
...         break
...     except ValueError:
...         print("Oops!  That was no valid number.  Try again...")
...
@end example

@ref{d6b,,try} 语句的工作原理如下。


@itemize *

@item 
首先，执行 @emph{try 子句} （@ref{d6b,,try} 和 @ref{b37,,except} 关键字之间的（多行）语句）。

@item 
如果没有异常发生，则跳过 @emph{except 子句} 并完成 @ref{d6b,,try} 语句的执行。

@item 
如果在执行try 子句时发生了异常，则跳过该子句中剩下的部分。然后，如果异常的类型和 @ref{b37,,except} 关键字后面的异常匹配，则执行 except 子句 ，然后继续执行 @ref{d6b,,try} 语句之后的代码。

@item 
如果发生的异常和 except 子句中指定的异常不匹配，则将其传递到外部的 @ref{d6b,,try} 语句中；如果没有找到处理程序，则它是一个 @emph{未处理异常}，执行将停止并显示如上所示的消息。
@end itemize

一个 @ref{d6b,,try} 语句可能有多个 except 子句，以指定不同异常的处理程序。 最多会执行一个处理程序。 处理程序只处理相应的 try 子句中发生的异常，而不处理同一 @code{try} 语句内其他处理程序中的异常。 一个 except 子句可以将多个异常命名为带括号的元组，例如:

@example
... except (RuntimeError, TypeError, NameError):
...     pass
@end example

如果发生的异常和 @ref{b37,,except} 子句中的类是同一个类或者是它的基类，则异常和 except 子句中的类是兼容的（但反过来则不成立 --- 列出派生类的 except 子句与基类不兼容）。 例如，下面的代码将依次打印 B, C, D

@example
class B(Exception):
    pass

class C(B):
    pass

class D(C):
    pass

for cls in [B, C, D]:
    try:
        raise cls()
    except D:
        print("D")
    except C:
        print("C")
    except B:
        print("B")
@end example

请注意如果 except 子句被颠倒（把 @code{except B} 放到第一个），它将打印 B，B，B --- 即第一个匹配的 except 子句被触发。

最后的 except 子句可以省略异常名，以用作通配符。但请谨慎使用，因为以这种方式很容易掩盖真正的编程错误！它还可用于打印错误消息，然后重新引发异常（同样允许调用者处理异常）:

@example
import sys

try:
    f = open('myfile.txt')
    s = f.readline()
    i = int(s.strip())
except OSError as err:
    print("OS error: @{0@}".format(err))
except ValueError:
    print("Could not convert data to an integer.")
except:
    print("Unexpected error:", sys.exc_info()[0])
    raise
@end example

@ref{d6b,,try} ... @ref{b37,,except} 语句有一个可选的 @emph{else 子句}，在使用时必须放在所有的 except 子句后面。对于在try 子句不引发异常时必须执行的代码来说很有用。例如:

@example
for arg in sys.argv[1:]:
    try:
        f = open(arg, 'r')
    except OSError:
        print('cannot open', arg)
    else:
        print(arg, 'has', len(f.readlines()), 'lines')
        f.close()
@end example

使用 @code{else} 子句比向 @ref{d6b,,try} 子句添加额外的代码要好，因为它避免了意外捕获由 @code{try} ... @code{except} 语句保护的代码未引发的异常。

发生异常时，它可能具有关联值，也称为异常 @emph{参数} 。参数的存在和类型取决于异常类型。

except 子句可以在异常名称后面指定一个变量。这个变量和一个异常实例绑定，它的参数存储在 @code{instance.args} 中。为了方便起见，异常实例定义了 @ref{e30,,__str__()} ，因此可以直接打印参数而无需引用 @code{.args} 。也可以在抛出之前首先实例化异常，并根据需要向其添加任何属性。:

@example
>>> try:
...     raise Exception('spam', 'eggs')
... except Exception as inst:
...     print(type(inst))    # the exception instance
...     print(inst.args)     # arguments stored in .args
...     print(inst)          # __str__ allows args to be printed directly,
...                          # but may be overridden in exception subclasses
...     x, y = inst.args     # unpack args
...     print('x =', x)
...     print('y =', y)
...
<class 'Exception'>
('spam', 'eggs')
('spam', 'eggs')
x = spam
y = eggs
@end example

如果异常有参数，则它们将作为未处理异常的消息的最后一部分（'详细信息'）打印。

异常处理程序不仅处理 try 子句中遇到的异常，还处理 try 子句中调用（即使是间接地）的函数内部发生的异常。例如:

@example
>>> def this_fails():
...     x = 1/0
...
>>> try:
...     this_fails()
... except ZeroDivisionError as err:
...     print('Handling run-time error:', err)
...
Handling run-time error: division by zero
@end example

@node 抛出异常,用户自定义异常,处理异常,错误和异常
@anchor{tutorial/errors raising-exceptions}@anchor{1244}@anchor{tutorial/errors tut-raising}@anchor{1245}
@subsection 抛出异常


@ref{c3b,,raise} 语句允许程序员强制发生指定的异常。例如:

@example
>>> raise NameError('HiThere')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: HiThere
@end example

@ref{c3b,,raise} 唯一的参数就是要抛出的异常。这个参数必须是一个异常实例或者是一个异常类（派生自 @ref{1a9,,Exception} 的类）。如果传递的是一个异常类，它将通过调用没有参数的构造函数来隐式实例化:

@example
raise ValueError  # shorthand for 'raise ValueError()'
@end example

如果你需要确定是否引发了异常但不打算处理它，则可以使用更简单的 @ref{c3b,,raise} 语句形式重新引发异常

@example
>>> try:
...     raise NameError('HiThere')
... except NameError:
...     print('An exception flew by!')
...     raise
...
An exception flew by!
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
NameError: HiThere
@end example

@node 用户自定义异常,定义清理操作,抛出异常,错误和异常
@anchor{tutorial/errors tut-userexceptions}@anchor{1246}@anchor{tutorial/errors user-defined-exceptions}@anchor{1247}
@subsection 用户自定义异常


程序可以通过创建新的异常类来命名它们自己的异常（有关Python 类的更多信息，请参阅 @ref{11d9,,类}）。异常通常应该直接或间接地从 @ref{1a9,,Exception} 类派生。

可以定义异常类，它可以执行任何其他类可以执行的任何操作，但通常保持简单，通常只提供许多属性，这些属性允许处理程序为异常提取有关错误的信息。在创建可能引发多个不同错误的模块时，通常的做法是为该模块定义的异常创建基类，并为不同错误条件创建特定异常类的子类:

@example
class Error(Exception):
    """Base class for exceptions in this module."""
    pass

class InputError(Error):
    """Exception raised for errors in the input.

    Attributes:
        expression -- input expression in which the error occurred
        message -- explanation of the error
    """

    def __init__(self, expression, message):
        self.expression = expression
        self.message = message

class TransitionError(Error):
    """Raised when an operation attempts a state transition that's not
    allowed.

    Attributes:
        previous -- state at beginning of transition
        next -- attempted new state
        message -- explanation of why the specific transition is not allowed
    """

    def __init__(self, previous, next, message):
        self.previous = previous
        self.next = next
        self.message = message
@end example

大多数异常都定义为名称以“Error”结尾，类似于标准异常的命名。

许多标准模块定义了它们自己的异常，以报告它们定义的函数中可能出现的错误。有关类的更多信息，请参见类 @ref{11d9,,类}。

@node 定义清理操作,预定义的清理操作,用户自定义异常,错误和异常
@anchor{tutorial/errors defining-clean-up-actions}@anchor{1248}@anchor{tutorial/errors tut-cleanup}@anchor{1249}
@subsection 定义清理操作


@ref{d6b,,try} 语句有另一个可选子句，用于定义必须在所有情况下执行的清理操作。例如:

@example
>>> try:
...     raise KeyboardInterrupt
... finally:
...     print('Goodbye, world!')
...
Goodbye, world!
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
KeyboardInterrupt
@end example

如果存在 @ref{182,,finally} 子句，则 @code{finally} 子句将作为 @ref{d6b,,try} 语句结束前的最后一项任务被执行。 @code{finally} 子句不论 @code{try} 语句是否产生了异常都会被执行。 以下几点讨论了当异常发生时一些更复杂的情况：


@itemize *

@item 
如果在执行 @code{try} 子句期间发生了异常，该异常可由一个 @ref{b37,,except} 子句进行处理。 如果异常没有被某个 @code{except} 子句所处理，则该异常会在 @code{finally} 子句执行之后被重新引发。

@item 
异常也可能在 @code{except} 或 @code{else} 子句执行期间发生。 同样地，该异常会在 @code{finally} 子句执行之后被重新引发。

@item 
如果在执行 @code{try} 语句时遇到一个 @ref{2db,,break}, @ref{181,,continue} 或 @ref{190,,return} 语句，则 @code{finally} 子句将在执行 @code{break}, @code{continue} 或 @code{return} 语句之前被执行。

@item 
如果 @code{finally} 子句中包含一个 @code{return} 语句，则返回值将来自 @code{finally} 子句的某个 @code{return} 语句的返回值，而非来自 @code{try} 子句的 @code{return} 语句的返回值。
@end itemize

例如

@example
>>> def bool_return():
...     try:
...         return True
...     finally:
...         return False
...
>>> bool_return()
False
@end example

一个更为复杂的例子:

@example
>>> def divide(x, y):
...     try:
...         result = x / y
...     except ZeroDivisionError:
...         print("division by zero!")
...     else:
...         print("result is", result)
...     finally:
...         print("executing finally clause")
...
>>> divide(2, 1)
result is 2.0
executing finally clause
>>> divide(2, 0)
division by zero!
executing finally clause
>>> divide("2", "1")
executing finally clause
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in divide
TypeError: unsupported operand type(s) for /: 'str' and 'str'
@end example

正如你所看到的，@ref{182,,finally} 子句在任何情况下都会被执行。 两个字符串相除所引发的 @ref{192,,TypeError} 不会由 @ref{b37,,except} 子句处理，因此会在 @code{finally} 子句执行后被重新引发。

在实际应用程序中，@ref{182,,finally} 子句对于释放外部资源（例如文件或者网络连接）非常有用，无论是否成功使用资源。

@node 预定义的清理操作,,定义清理操作,错误和异常
@anchor{tutorial/errors predefined-clean-up-actions}@anchor{124a}@anchor{tutorial/errors tut-cleanup-with}@anchor{124b}
@subsection 预定义的清理操作


某些对象定义了在不再需要该对象时要执行的标准清理操作，无论使用该对象的操作是成功还是失败。请查看下面的示例，它尝试打开一个文件并把其内容打印到屏幕上。:

@example
for line in open("myfile.txt"):
    print(line, end="")
@end example

这个代码的问题在于，它在这部分代码执行完后，会使文件在一段不确定的时间内处于打开状态。这在简单脚本中不是问题，但对于较大的应用程序来说可能是个问题。 @ref{6e3,,with} 语句允许像文件这样的对象能够以一种确保它们得到及时和正确的清理的方式使用。:

@example
with open("myfile.txt") as f:
    for line in f:
        print(line, end="")
@end example

执行完语句后，即使在处理行时遇到问题，文件 @emph{f} 也始终会被关闭。和文件一样，提供预定义清理操作的对象将在其文档中指出这一点。

@node 类,标准库简介,错误和异常,Python 教程
@anchor{tutorial/classes doc}@anchor{124c}@anchor{tutorial/classes classes}@anchor{124d}@anchor{tutorial/classes tut-classes}@anchor{11d9}
@section 类


类提供了一种组合数据和功能的方法。 创建一个新类意味着创建一个新的对象 @emph{类型}，从而允许创建一个该类型的新 @emph{实例} 。 每个类的实例可以拥有保存自己状态的属性。 一个类的实例也可以有改变自己状态的（定义在类中的）方法。

和其他编程语言相比，Python 用非常少的新语法和语义将类加入到语言中。它是 C++ 和 Modula-3 中类机制的结合。Python 的类提供了面向对象编程的所有标准特性：类继承机制允许多个基类，派生类可以覆盖它基类的任何方法，一个方法可以调用基类中相同名称的的方法。对象可以包含任意数量和类型的数据。和模块一样，类也拥有 Python 天然的动态特性：它们在运行时创建，可以在创建后修改。

在 C++ 术语中，通常类成员（包括数据成员）是 @emph{public} (例外见下文 @ref{124e,,私有变量})，所有成员函数都是 @emph{virtual}。 与在 Modula-3 中一样，没有用于从其方法引用对象成员的简写：方法函数使用表示对象的显式第一个参数声明，该参数由调用隐式提供。 与 Smalltalk 一样，类本身也是对象。 这为导入和重命名提供了语义。 与 C++ 和 Modula-3 不同，内置类型可以用作用户扩展的基类。 此外，与 C++ 一样，大多数具有特殊语法（算术运算符，下标等）的内置运算符都可以为类实例而重新定义。

（由于缺乏关于类的公认术语，我会偶尔使用 Smalltalk 和 C++ 的用辞。 我还会使用 Modula-3 的术语，因为其面向对象的语义比 C++ 更接近 Python，但我预计少有读者听说过它。）

@menu
* 名称和对象:: 
* Python 作用域和命名空间:: 
* 初探类:: 
* 补充说明:: 
* 继承:: 
* 私有变量:: 
* 杂项说明:: 
* 迭代器:: 
* 生成器:: 
* 生成器表达式:: 

@end menu

@node 名称和对象,Python 作用域和命名空间,,类
@anchor{tutorial/classes a-word-about-names-and-objects}@anchor{124f}@anchor{tutorial/classes tut-object}@anchor{1250}
@subsection 名称和对象


对象具有个性，多个名称（在多个作用域内）可以绑定到同一个对象。这在其他语言中称为别名。乍一看Python时通常不会理解这一点，在处理不可变的基本类型（数字，字符串，元组）时可以安全地忽略它。但是，别名对涉及可变对象，如列表，字典和大多数其他类型，的Python代码的语义可能会产生惊人的影响。这通常用于程序的好处，因为别名在某些方面表现得像指针。例如，传递一个对象很便宜，因为实现只传递一个指针；如果函数修改了作为参数传递的对象，调用者将看到更改 --- 这就不需要像 Pascal 中那样使用两个不同的参数传递机制。

@node Python 作用域和命名空间,初探类,名称和对象,类
@anchor{tutorial/classes python-scopes-and-namespaces}@anchor{1251}@anchor{tutorial/classes tut-scopes}@anchor{1252}
@subsection Python 作用域和命名空间


在介绍类之前，我首先要告诉你一些Python的作用域规则。类定义对命名空间有一些巧妙的技巧，你需要知道作用域和命名空间如何工作才能完全理解正在发生的事情。顺便说一下，关于这个主题的知识对任何高级Python程序员都很有用。

让我们从一些定义开始。

@emph{namespace} （命名空间）是一个从名字到对象的映射。 大部分命名空间当前都由 Python 字典实现，但一般情况下基本不会去关注它们（除了要面对性能问题时），而且也有可能在将来更改。 下面是几个命名空间的例子：存放内置函数的集合（包含 @ref{1253,,abs()} 这样的函数，和内建的异常等）；模块中的全局名称；函数调用中的局部名称。 从某种意义上说，对象的属性集合也是一种命名空间的形式。 关于命名空间的重要一点是，不同命名空间中的名称之间绝对没有关系；例如，两个不同的模块都可以定义一个 @code{maximize} 函数而不会产生混淆 --- 模块的用户必须在其前面加上模块名称。

顺便说明一下，我把任何跟在一个点号之后的名称都称为 @emph{属性} --- 例如，在表达式 @code{z.real} 中，@code{real} 是对象 @code{z} 的一个属性。按严格的说法，对模块中名称的引用属于属性引用：在表达式 @code{modname.funcname} 中，@code{modname} 是一个模块对象而 @code{funcname} 是它的一个属性。在此情况下在模块的属性和模块中定义的全局名称之间正好存在一个直观的映射：它们共享相同的命名空间！ @footnote{@w{(1)} 
存在一个例外。 模块对象有一个秘密的只读属性 @ref{4f6,,__dict__}，它返回用于实现模块命名空间的字典；@ref{4f6,,__dict__} 是属性但不是全局名称。 显然，使用这个将违反命名空间实现的抽象，应当仅被用于事后调试器之类的场合。
}

属性可以是只读或者可写的。如果为后者，那么对属性的赋值是可行的。模块属性是可以写，你可以写出 @code{modname.the_answer = 42} 。可写的属性同样可以用 @ref{1202,,del} 语句删除。例如， @code{del modname.the_answer} 将会从名为 @code{modname} 的对象中移除 @code{the_answer} 属性。

在不同时刻创建的命名空间拥有不同的生存期。包含内置名称的命名空间是在 Python 解释器启动时创建的，永远不会被删除。模块的全局命名空间在模块定义被读入时创建；通常，模块命名空间也会持续到解释器退出。被解释器的顶层调用执行的语句，从一个脚本文件读取或交互式地读取，被认为是 @ref{1,,__main__} 模块调用的一部分，因此它们拥有自己的全局命名空间。（内置名称实际上也存在于一个模块中；这个模块称作 @ref{13,,builtins} 。）

一个函数的本地命名空间在这个函数被调用时创建，并在函数返回或抛出一个不在函数内部处理的错误时被删除。（事实上，比起描述到底发生了什么，忘掉它更好。）当然，每次递归调用都会有它自己的本地命名空间。

一个 @emph{作用域} 是一个命名空间可直接访问的 Python 程序的文本区域。 这里的 “可直接访问” 意味着对名称的非限定引用会尝试在命名空间中查找名称。

虽然作用域是静态地确定的，但它们会被动态地使用。 在执行期间的任何时刻，会有 3 或 4 个个命名空间可被直接访问的嵌套作用域:


@itemize *

@item 
最先搜索的最内部作用域包含局部名称

@item 
从最近的封闭作用域开始搜索的任何封闭函数的作用域包含非局部名称，也包括非全局名称

@item 
倒数第二个作用域包含当前模块的全局名称

@item 
最外面的作用域（最后搜索）是包含内置名称的命名空间
@end itemize

如果一个名称被声明为全局变量，则所有引用和赋值将直接指向包含该模块的全局名称的中间作用域。 要重新绑定在最内层作用域以外找到的变量，可以使用 @ref{c38,,nonlocal} 语句声明为非本地变量。 如果没有被声明为非本地变量，这些变量将是只读的（尝试写入这样的变量只会在最内层作用域中创建一个 @emph{新的} 局部变量，而同名的外部变量保持不变）。

通常，当前局部作用域将（按字面文本）引用当前函数的局部名称。 在函数以外，局部作用域将引用与全局作用域相一致的命名空间：模块的命名空间。 类定义将在局部命名空间内再放置另一个命名空间。

重要的是应该意识到作用域是按字面文本来确定的：在一个模块内定义的函数的全局作用域就是该模块的命名空间，无论该函数从什么地方或以什么别名被调用。  另一方面，实际的名称搜索是在运行时动态完成的 --- 但是，Python 正在朝着“编译时静态名称解析”的方向发展，因此不要过于依赖动态名称解析！ （事实上，局部变量已经是被静态确定了。）

Python 的一个特殊规定是这样的 -- 如果不存在生效的 @ref{11d8,,global} 或 @ref{c38,,nonlocal} 语句 -- 则对名称的赋值总是会进入最内层作用域。 赋值不会复制数据 --- 它们只是将名称绑定到对象。 删除也是如此：语句 @code{del x} 会从局部作用域所引用的命名空间中移除对 @code{x} 的绑定。 事实上，所有引入新名称的操作都是使用局部作用域：特别地，@ref{c16,,import} 语句和函数定义会在局部作用域中绑定模块或函数名称。

@ref{11d8,,global} 语句可被用来表明特定变量生存于全局作用域并且应当在其中被重新绑定；@ref{c38,,nonlocal} 语句表明特定变量生存于外层作用域中并且应当在其中被重新绑定。

@menu
* 作用域和命名空间示例:: 

@end menu

@node 作用域和命名空间示例,,,Python 作用域和命名空间
@anchor{tutorial/classes scopes-and-namespaces-example}@anchor{1254}@anchor{tutorial/classes tut-scopeexample}@anchor{1255}
@subsubsection 作用域和命名空间示例


这个例子演示了如何引用不同作用域和名称空间，以及 @ref{11d8,,global} 和 @ref{c38,,nonlocal} 会如何影响变量绑定:

@example
def scope_test():
    def do_local():
        spam = "local spam"

    def do_nonlocal():
        nonlocal spam
        spam = "nonlocal spam"

    def do_global():
        global spam
        spam = "global spam"

    spam = "test spam"
    do_local()
    print("After local assignment:", spam)
    do_nonlocal()
    print("After nonlocal assignment:", spam)
    do_global()
    print("After global assignment:", spam)

scope_test()
print("In global scope:", spam)
@end example

示例代码的输出是：

@example
After local assignment: test spam
After nonlocal assignment: nonlocal spam
After global assignment: nonlocal spam
In global scope: global spam
@end example

请注意 @emph{局部} 赋值（这是默认状态）不会改变 @emph{scope_test} 对 @emph{spam} 的绑定。 @ref{c38,,nonlocal} 赋值会改变 @emph{scope_test} 对 @emph{spam} 的绑定，而 @ref{11d8,,global} 赋值会改变模块层级的绑定。

您还可以在 @ref{11d8,,global} 赋值之前看到之前没有 @emph{spam} 的绑定。

@node 初探类,补充说明,Python 作用域和命名空间,类
@anchor{tutorial/classes a-first-look-at-classes}@anchor{1256}@anchor{tutorial/classes tut-firstclasses}@anchor{11f4}
@subsection 初探类


类引入了一些新语法，三种新对象类型和一些新语义。

@menu
* 类定义语法:: 
* 类对象:: 
* 实例对象:: 
* 方法对象:: 
* 类和实例变量:: 

@end menu

@node 类定义语法,类对象,,初探类
@anchor{tutorial/classes class-definition-syntax}@anchor{1257}@anchor{tutorial/classes tut-classdefinition}@anchor{1258}
@subsubsection 类定义语法


最简单的类定义看起来像这样:

@example
class ClassName:
    <statement-1>
    .
    .
    .
    <statement-N>
@end example

类定义与函数定义 (@ref{db7,,def} 语句) 一样必须被执行才会起作用。 （你可以尝试将类定义放在 @ref{de0,,if} 语句的一个分支或是函数的内部。）

在实践中，类定义内的语句通常都是函数定义，但也允许有其他语句，有时还很有用 --- 我们会稍后再回来说明这个问题。 在类内部的函数定义通常具有一种特别形式的参数列表，这是方法调用的约定规范所指明的 --- 这个问题也将在稍后再说明。

当进入类定义时，将创建一个新的命名空间，并将其用作局部作用域 --- 因此，所有对局部变量的赋值都是在这个新命名空间之内。 特别的，函数定义会绑定到这里的新函数名称。

当（从结尾处）正常离开类定义时，将创建一个 @emph{类对象}。 这基本上是一个包围在类定义所创建命名空间内容周围的包装器；我们将在下一节了解有关类对象的更多信息。 原始的（在进入类定义之前起作用的）局部作用域将重新生效，类对象将在这里被绑定到类定义头所给出的类名称 (在这个示例中为 @code{ClassName})。

@node 类对象,实例对象,类定义语法,初探类
@anchor{tutorial/classes class-objects}@anchor{1259}@anchor{tutorial/classes tut-classobjects}@anchor{125a}
@subsubsection 类对象


类对象支持两种操作：属性引用和实例化。

@emph{属性引用} 使用 Python 中所有属性引用所使用的标准语法: @code{obj.name}。 有效的属性名称是类对象被创建时存在于类命名空间中的所有名称。 因此，如果类定义是这样的:

@example
class MyClass:
    """A simple example class"""
    i = 12345

    def f(self):
        return 'hello world'
@end example

那么 @code{MyClass.i} 和 @code{MyClass.f} 就是有效的属性引用，将分别返回一个整数和一个函数对象。 类属性也可以被赋值，因此可以通过赋值来更改 @code{MyClass.i} 的值。 @code{__doc__} 也是一个有效的属性，将返回所属类的文档字符串: @code{"A simple example class"}。

类的 @emph{实例化} 使用函数表示法。 可以把类对象视为是返回该类的一个新实例的不带参数的函数。 举例来说（假设使用上述的类）:

@example
x = MyClass()
@end example

创建类的新 @emph{实例} 并将此对象分配给局部变量 @code{x}。

实例化操作（“调用”类对象）会创建一个空对象。 许多类喜欢创建带有特定初始状态的自定义实例。 为此类定义可能包含一个名为 @ref{d57,,__init__()} 的特殊方法，就像这样:

@example
def __init__(self):
    self.data = []
@end example

当一个类定义了 @ref{d57,,__init__()} 方法时，类的实例化操作会自动为新创建的类实例发起调用 @ref{d57,,__init__()}。 因此在这个示例中，可以通过以下语句获得一个经初始化的新实例:

@example
x = MyClass()
@end example

当然，@ref{d57,,__init__()} 方法还可以有额外参数以实现更高灵活性。 在这种情况下，提供给类实例化运算符的参数将被传递给 @ref{d57,,__init__()}。 例如，:

@example
>>> class Complex:
...     def __init__(self, realpart, imagpart):
...         self.r = realpart
...         self.i = imagpart
...
>>> x = Complex(3.0, -4.5)
>>> x.r, x.i
(3.0, -4.5)
@end example

@node 实例对象,方法对象,类对象,初探类
@anchor{tutorial/classes instance-objects}@anchor{125b}@anchor{tutorial/classes tut-instanceobjects}@anchor{125c}
@subsubsection 实例对象


现在我们能用实例对象做什么？ 实例对象理解的唯一操作是属性引用。 有两种有效的属性名称：数据属性和方法。

@emph{数据属性} 对应于 Smalltalk 中的“实例变量”，以及 C++ 中的“数据成员”。 数据属性不需要声明；像局部变量一样，它们将在第一次被赋值时产生。 例如，如果 @code{x} 是上面创建的 @code{MyClass} 的实例，则以下代码段将打印数值 @code{16}，且不保留任何追踪信息:

@example
x.counter = 1
while x.counter < 10:
    x.counter = x.counter * 2
print(x.counter)
del x.counter
@end example

另一类实例属性引用称为 @emph{方法}。 方法是“从属于”对象的函数。 （在 Python 中，方法这个术语并不是类实例所特有的：其他对象也可以有方法。 例如，列表对象具有 append, insert, remove, sort 等方法。 然而，在以下讨论中，我们使用方法一词将专指类实例对象的方法，除非另外显式地说明。）

@geindex 对象; method

实例对象的有效方法名称依赖于其所属的类。 根据定义，一个类中所有是函数对象的属性都是定义了其实例的相应方法。 因此在我们的示例中，@code{x.f} 是有效的方法引用，因为 @code{MyClass.f} 是一个函数，而 @code{x.i} 不是方法，因为 @code{MyClass.i} 不是一个函数。 但是 @code{x.f} 与 @code{MyClass.f} 并不是一回事 --- 它是一个 @emph{方法对象}，不是函数对象。

@node 方法对象,类和实例变量,实例对象,初探类
@anchor{tutorial/classes method-objects}@anchor{125d}@anchor{tutorial/classes tut-methodobjects}@anchor{125e}
@subsubsection 方法对象


通常，方法在绑定后立即被调用:

@example
x.f()
@end example

在 @code{MyClass} 示例中，这将返回字符串 @code{'hello world'}。 但是，立即调用一个方法并不是必须的: @code{x.f} 是一个方法对象，它可以被保存起来以后再调用。 例如:

@example
xf = x.f
while True:
    print(xf())
@end example

将继续打印 @code{hello world}，直到结束。

当一个方法被调用时到底发生了什么？ 你可能已经注意到上面调用 @code{x.f()} 时并没有带参数，虽然 @code{f()} 的函数定义指定了一个参数。 这个参数发生了什么事？ 当不带参数地调用一个需要参数的函数时 Python 肯定会引发异常 --- 即使参数实际未被使用...

实际上，你可能已经猜到了答案：方法的特殊之处就在于实例对象会作为函数的第一个参数被传入。 在我们的示例中，调用 @code{x.f()} 其实就相当于 @code{MyClass.f(x)}。 总之，调用一个具有 @emph{n} 个参数的方法就相当于调用再多一个参数的对应函数，这个参数值为方法所属实例对象，位置在其他参数之前。

如果你仍然无法理解方法的运作原理，那么查看实现细节可能会澄清问题。 当一个实例的非数据属性被引用时，将搜索实例所属的类。 如果被引用的属性名称表示一个有效的类属性中的函数对象，会通过打包（指向）查找到的实例对象和函数对象到一个抽象对象的方式来创建方法对象：这个抽象对象就是方法对象。 当附带参数列表调用方法对象时，将基于实例对象和参数列表构建一个新的参数列表，并使用这个新参数列表调用相应的函数对象。

@node 类和实例变量,,方法对象,初探类
@anchor{tutorial/classes class-and-instance-variables}@anchor{125f}@anchor{tutorial/classes tut-class-and-instance-variables}@anchor{1260}
@subsubsection 类和实例变量


一般来说，实例变量用于每个实例的唯一数据，而类变量用于类的所有实例共享的属性和方法:

@example
class Dog:

    kind = 'canine'         # class variable shared by all instances

    def __init__(self, name):
        self.name = name    # instance variable unique to each instance

>>> d = Dog('Fido')
>>> e = Dog('Buddy')
>>> d.kind                  # shared by all dogs
'canine'
>>> e.kind                  # shared by all dogs
'canine'
>>> d.name                  # unique to d
'Fido'
>>> e.name                  # unique to e
'Buddy'
@end example

正如 @ref{1250,,名称和对象} 中已讨论过的，共享数据可能在涉及 @ref{11be,,mutable} 对象例如列表和字典的时候导致令人惊讶的结果。 例如以下代码中的 @emph{tricks} 列表不应该被用作类变量，因为所有的 @emph{Dog} 实例将只共享一个单独的列表:

@example
class Dog:

    tricks = []             # mistaken use of a class variable

    def __init__(self, name):
        self.name = name

    def add_trick(self, trick):
        self.tricks.append(trick)

>>> d = Dog('Fido')
>>> e = Dog('Buddy')
>>> d.add_trick('roll over')
>>> e.add_trick('play dead')
>>> d.tricks                # unexpectedly shared by all dogs
['roll over', 'play dead']
@end example

正确的类设计应该使用实例变量:

@example
class Dog:

    def __init__(self, name):
        self.name = name
        self.tricks = []    # creates a new empty list for each dog

    def add_trick(self, trick):
        self.tricks.append(trick)

>>> d = Dog('Fido')
>>> e = Dog('Buddy')
>>> d.add_trick('roll over')
>>> e.add_trick('play dead')
>>> d.tricks
['roll over']
>>> e.tricks
['play dead']
@end example

@node 补充说明,继承,初探类,类
@anchor{tutorial/classes random-remarks}@anchor{1261}@anchor{tutorial/classes tut-remarks}@anchor{1262}
@subsection 补充说明


@c These should perhaps be placed more carefully...

如果同样的属性名称同时出现在实例和类中，则属性查找会优先选择实例:

@example
>>> class Warehouse:
        purpose = 'storage'
        region = 'west'

>>> w1 = Warehouse()
>>> print(w1.purpose, w1.region)
storage west
>>> w2 = Warehouse()
>>> w2.region = 'east'
>>> print(w2.purpose, w2.region)
storage east
@end example

数据属性可以被方法以及一个对象的普通用户（“客户端”）所引用。 换句话说，类不能用于实现纯抽象数据类型。 实际上，在 Python 中没有任何东西能强制隐藏数据 --- 它是完全基于约定的。 （而在另一方面，用 C 语言编写的 Python 实现则可以完全隐藏实现细节，并在必要时控制对象的访问；此特性可以通过用 C 编写 Python 扩展来使用。）

客户端应当谨慎地使用数据属性 --- 客户端可能通过直接操作数据属性的方式破坏由方法所维护的固定变量。 请注意客户端可以向一个实例对象添加他们自己的数据属性而不会影响方法的可用性，只要保证避免名称冲突 --- 再次提醒，在此使用命名约定可以省去许多令人头痛的麻烦。

在方法内部引用数据属性（或其他方法！）并没有简便方式。 我发现这实际上提升了方法的可读性：当浏览一个方法代码时，不会存在混淆局部变量和实例变量的机会。

方法的第一个参数常常被命名为 @code{self}。 这也不过就是一个约定: @code{self} 这一名称在 Python 中绝对没有特殊含义。 但是要注意，不遵循此约定会使得你的代码对其他 Python 程序员来说缺乏可读性，而且也可以想像一个 @emph{类浏览器} 程序的编写可能会依赖于这样的约定。

任何一个作为类属性的函数都为该类的实例定义了一个相应方法。 函数定义的文本并非必须包含于类定义之内：将一个函数对象赋值给一个局部变量也是可以的。 例如:

@example
# Function defined outside the class
def f1(self, x, y):
    return min(x, x+y)

class C:
    f = f1

    def g(self):
        return 'hello world'

    h = g
@end example

现在 @code{f}, @code{g} 和 @code{h} 都是 @code{C} 类的引用函数对象的属性，因而它们就都是 @code{C} 的实例的方法 --- 其中 @code{h} 完全等同于 @code{g}。 但请注意，本示例的做法通常只会令程序的阅读者感到迷惑。

方法可以通过使用 @code{self} 参数的方法属性调用其他方法:

@example
class Bag:
    def __init__(self):
        self.data = []

    def add(self, x):
        self.data.append(x)

    def addtwice(self, x):
        self.add(x)
        self.add(x)
@end example

方法可以通过与普通函数相同的方式引用全局名称。 与方法相关联的全局作用域就是包含其定义的模块。 （类永远不会被作为全局作用域。） 虽然我们很少会有充分的理由在方法中使用全局作用域，但全局作用域存在许多合法的使用场景：举个例子，导入到全局作用域的函数和模块可以被方法所使用，在其中定义的函数和类也一样。 通常，包含该方法的类本身是在全局作用域中定义的，而在下一节中我们将会发现为何方法需要引用其所属类的很好的理由。

每个值都是一个对象，因此具有 @emph{类} （也称为 @emph{类型}），并存储为 @code{object.__class__} 。

@node 继承,私有变量,补充说明,类
@anchor{tutorial/classes inheritance}@anchor{1263}@anchor{tutorial/classes tut-inheritance}@anchor{1264}
@subsection 继承


当然，如果不支持继承，语言特性就不值得称为“类”。派生类定义的语法如下所示:

@example
class DerivedClassName(BaseClassName):
    <statement-1>
    .
    .
    .
    <statement-N>
@end example

名称 @code{BaseClassName} 必须定义于包含派生类定义的作用域中。 也允许用其他任意表达式代替基类名称所在的位置。 这有时也可能会用得上，例如，当基类定义在另一个模块中的时候:

@example
class DerivedClassName(modname.BaseClassName):
@end example

派生类定义的执行过程与基类相同。 当构造类对象时，基类会被记住。 此信息将被用来解析属性引用：如果请求的属性在类中找不到，搜索将转往基类中进行查找。 如果基类本身也派生自其他某个类，则此规则将被递归地应用。

派生类的实例化没有任何特殊之处: @code{DerivedClassName()} 会创建该类的一个新实例。 方法引用将按以下方式解析：搜索相应的类属性，如有必要将按基类继承链逐步向下查找，如果产生了一个函数对象则方法引用就生效。

派生类可能会重载其基类的方法。 因为方法在调用同一对象的其他方法时没有特殊权限，调用同一基类中定义的另一方法的基类方法最终可能会调用覆盖它的派生类的方法。 （对 C++ 程序员的提示：Python 中所有的方法实际上都是 @code{virtual} 方法。）

在派生类中的重载方法实际上可能想要扩展而非简单地替换同名的基类方法。 有一种方式可以简单地直接调用基类方法：即调用 @code{BaseClassName.methodname(self, arguments)}。 有时这对客户端来说也是有用的。 （请注意仅当此基类可在全局作用域中以 @code{BaseClassName} 的名称被访问时方可使用此方式。）

Python有两个内置函数可被用于继承机制：


@itemize *

@item 
使用 @ref{449,,isinstance()} 来检查一个实例的类型: @code{isinstance(obj, int)} 仅会在 @code{obj.__class__} 为 @ref{184,,int} 或某个派生自 @ref{184,,int} 的类时为 @code{True}。

@item 
使用 @ref{44a,,issubclass()} 来检查类的继承关系: @code{issubclass(bool, int)} 为 @code{True}，因为 @ref{183,,bool} 是 @ref{184,,int} 的子类。 但是，@code{issubclass(float, int)} 为 @code{False}，因为 @ref{187,,float} 不是 @ref{184,,int} 的子类。
@end itemize

@menu
* 多重继承:: 

@end menu

@node 多重继承,,,继承
@anchor{tutorial/classes multiple-inheritance}@anchor{1265}@anchor{tutorial/classes tut-multiple}@anchor{1266}
@subsubsection 多重继承


Python也支持一种多重继承。 带有多个基类的类定义语句如下所示:

@example
class DerivedClassName(Base1, Base2, Base3):
    <statement-1>
    .
    .
    .
    <statement-N>
@end example

对于多数应用来说，在最简单的情况下，你可以认为搜索从父类所继承属性的操作是深度优先、从左至右的，当层次结构中存在重叠时不会在同一个类中搜索两次。 因此，如果某一属性在 @code{DerivedClassName} 中未找到，则会到 @code{Base1} 中搜索它，然后（递归地）到 @code{Base1} 的基类中搜索，如果在那里未找到，再到 @code{Base2} 中搜索，依此类推。

真实情况比这个更复杂一些；方法解析顺序会动态改变以支持对 @ref{4dc,,super()} 的协同调用。 这种方式在某些其他多重继承型语言中被称为后续方法调用，它比单继承型语言中的 super 调用更强大。

动态改变顺序是有必要的，因为所有多重继承的情况都会显示出一个或更多的菱形关联（即至少有一个父类可通过多条路径被最底层类所访问）。 例如，所有类都是继承自 @ref{2b0,,object}，因此任何多重继承的情况都提供了一条以上的路径可以通向 @ref{2b0,,object}。 为了确保基类不会被访问一次以上，动态算法会用一种特殊方式将搜索顺序线性化， 保留每个类所指定的从左至右的顺序，只调用每个父类一次，并且保持单调（即一个类可以被子类化而不影响其父类的优先顺序）。 总而言之，这些特性使得设计具有多重继承的可靠且可扩展的类成为可能。 要了解更多细节，请参阅 @indicateurl{https://www.python.org/download/releases/2.3/mro/}。

@node 私有变量,杂项说明,继承,类
@anchor{tutorial/classes private-variables}@anchor{1267}@anchor{tutorial/classes tut-private}@anchor{124e}
@subsection 私有变量


那种仅限从一个对象内部访问的“私有”实例变量在 Python 中并不存在。 但是，大多数 Python 代码都遵循这样一个约定：带有一个下划线的名称 (例如 @code{_spam}) 应该被当作是 API 的非公有部分 (无论它是函数、方法或是数据成员)。 这应当被视为一个实现细节，可能不经通知即加以改变。

@geindex name; mangling

由于存在对于类私有成员的有效使用场景（例如避免名称与子类所定义的名称相冲突），因此存在对此种机制的有限支持，称为 @emph{名称改写}。 任何形式为 @code{__spam} 的标识符（至少带有两个前缀下划线，至多一个后缀下划线）的文本将被替换为 @code{_classname__spam}，其中 @code{classname} 为去除了前缀下划线的当前类名称。 这种改写不考虑标识符的句法位置，只要它出现在类定义内部就会进行。

名称改写有助于让子类重载方法而不破坏类内方法调用。例如:

@example
class Mapping:
    def __init__(self, iterable):
        self.items_list = []
        self.__update(iterable)

    def update(self, iterable):
        for item in iterable:
            self.items_list.append(item)

    __update = update   # private copy of original update() method

class MappingSubclass(Mapping):

    def update(self, keys, values):
        # provides new signature for update()
        # but does not break __init__()
        for item in zip(keys, values):
            self.items_list.append(item)
@end example

上面的示例即使在 @code{MappingSubclass} 引入了一个 @code{__update} 标识符的情况下也不会出错，因为它会在 @code{Mapping} 类中被替换为 @code{_Mapping__update} 而在 @code{MappingSubclass} 类中被替换为 @code{_MappingSubclass__update}。

请注意，改写规则的设计主要是为了避免意外冲突；访问或修改被视为私有的变量仍然是可能的。这在特殊情况下甚至会很有用，例如在调试器中。

请注意传递给 @code{exec()} 或 @code{eval()} 的代码不会将发起调用类的类名视作当前类；这类似于 @code{global} 语句的效果，因此这种效果仅限于同时经过字节码编译的代码。 同样的限制也适用于 @code{getattr()}, @code{setattr()} 和 @code{delattr()}，以及对于 @code{__dict__} 的直接引用。

@node 杂项说明,迭代器,私有变量,类
@anchor{tutorial/classes odds-and-ends}@anchor{1268}@anchor{tutorial/classes tut-odds}@anchor{1269}
@subsection 杂项说明


有时会需要使用类似于 Pascal 的“record”或 C 的“struct”这样的数据类型，将一些命名数据项捆绑在一起。 这种情况适合定义一个空类:

@example
class Employee:
    pass

john = Employee()  # Create an empty employee record

# Fill the fields of the record
john.name = 'John Doe'
john.dept = 'computer lab'
john.salary = 1000
@end example

一段需要特定抽象数据类型的 Python 代码往往可以被传入一个模拟了该数据类型的方法的类作为替代。 例如，如果你有一个基于文件对象来格式化某些数据的函数，你可以定义一个带有 @code{read()} 和 @code{readline()} 方法从字符串缓存获取数据的类，并将其作为参数传入。

@c (Unfortunately, this technique has its limitations: a class can't define
@c operations that are accessed by special syntax such as sequence subscripting
@c or arithmetic operators, and assigning such a "pseudo-file" to sys.stdin will
@c not cause the interpreter to read further input from it.)

实例方法对象也具有属性: @code{m.__self__} 就是带有 @code{m()} 方法的实例对象，而 @code{m.__func__} 则是该方法所对应的函数对象。

@node 迭代器,生成器,杂项说明,类
@anchor{tutorial/classes iterators}@anchor{126a}@anchor{tutorial/classes tut-iterators}@anchor{126b}
@subsection 迭代器


到目前为止，您可能已经注意到大多数容器对象都可以使用 @ref{c29,,for} 语句:

@example
for element in [1, 2, 3]:
    print(element)
for element in (1, 2, 3):
    print(element)
for key in @{'one':1, 'two':2@}:
    print(key)
for char in "123":
    print(char)
for line in open("myfile.txt"):
    print(line, end='@w{'})
@end example

这种访问风格清晰、简洁又方便。 迭代器的使用非常普遍并使得 Python 成为一个统一的整体。 在幕后，@ref{c29,,for} 语句会在容器对象上调用 @ref{d20,,iter()}。 该函数返回一个定义了 @ref{c5d,,__next__()} 方法的迭代器对象，此方法将逐一访问容器中的元素。 当元素用尽时，@ref{c5d,,__next__()} 将引发 @ref{480,,StopIteration} 异常来通知终止 @code{for} 循环。 你可以使用 @ref{67c,,next()} 内置函数来调用 @ref{c5d,,__next__()} 方法；这个例子显示了它的运作方式:

@example
>>> s = 'abc'
>>> it = iter(s)
>>> it
<iterator object at 0x00A1DB50>
>>> next(it)
'a'
>>> next(it)
'b'
>>> next(it)
'c'
>>> next(it)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    next(it)
StopIteration
@end example

看过迭代器协议的幕后机制，给你的类添加迭代器行为就很容易了。 定义一个 @ref{509,,__iter__()} 方法来返回一个带有 @ref{c5d,,__next__()} 方法的对象。 如果类已定义了 @code{__next__()}，则 @ref{509,,__iter__()} 可以简单地返回 @code{self}:

@example
class Reverse:
    """Iterator for looping over a sequence backwards."""
    def __init__(self, data):
        self.data = data
        self.index = len(data)

    def __iter__(self):
        return self

    def __next__(self):
        if self.index == 0:
            raise StopIteration
        self.index = self.index - 1
        return self.data[self.index]
@end example

@example
>>> rev = Reverse('spam')
>>> iter(rev)
<__main__.Reverse object at 0x00A1DB50>
>>> for char in rev:
...     print(char)
...
m
a
p
s
@end example

@node 生成器,生成器表达式,迭代器,类
@anchor{tutorial/classes generators}@anchor{126c}@anchor{tutorial/classes tut-generators}@anchor{126d}
@subsection 生成器


@ref{99c,,Generator} 是一个用于创建迭代器的简单而强大的工具。 它们的写法类似标准的函数，但当它们要返回数据时会使用 @ref{18f,,yield} 语句。 每次对生成器调用 @ref{67c,,next()} 时，它会从上次离开位置恢复执行（它会记住上次执行语句时的所有数据值）。 显示如何非常容易地创建生成器的示例如下:

@example
def reverse(data):
    for index in range(len(data)-1, -1, -1):
        yield data[index]
@end example

@example
>>> for char in reverse('golf'):
...     print(char)
...
f
l
o
g
@end example

可以用生成器来完成的操作同样可以用前一节所描述的基于类的迭代器来完成。 但生成器的写法更为紧凑，因为它会自动创建 @ref{509,,__iter__()} 和 @ref{126e,,__next__()} 方法。

另一个关键特性在于局部变量和执行状态会在每次调用之间自动保存。 这使得该函数相比使用 @code{self.index} 和 @code{self.data} 这种实例变量的方式更易编写且更为清晰。

除了会自动创建方法和保存程序状态，当生成器终结时，它们还会自动引发 @ref{480,,StopIteration}。 这些特性结合在一起，使得创建迭代器能与编写常规函数一样容易。

@node 生成器表达式,,生成器,类
@anchor{tutorial/classes generator-expressions}@anchor{126f}@anchor{tutorial/classes tut-genexps}@anchor{1270}
@subsection 生成器表达式


某些简单的生成器可以写成简洁的表达式代码，所用语法类似列表推导式，将外层为圆括号而非方括号。 这种表达式被设计用于生成器将立即被外层函数所使用的情况。 生成器表达式相比完整的生成器更紧凑但较不灵活，相比等效的列表推导式则更为节省内存。

示例:

@example
>>> sum(i*i for i in range(10))                 # sum of squares
285

>>> xvec = [10, 20, 30]
>>> yvec = [7, 5, 3]
>>> sum(x*y for x,y in zip(xvec, yvec))         # dot product
260

>>> unique_words = set(word for line in page  for word in line.split())

>>> valedictorian = max((student.gpa, student.name) for student in graduates)

>>> data = 'golf'
>>> list(data[i] for i in range(len(data)-1, -1, -1))
['f', 'l', 'o', 'g']
@end example

@subsubheading 备注


@node 标准库简介,标准库简介 —— 第二部分,类,Python 教程
@anchor{tutorial/stdlib doc}@anchor{1271}@anchor{tutorial/stdlib brief-tour-of-the-standard-library}@anchor{1272}@anchor{tutorial/stdlib tut-brieftour}@anchor{1273}
@section 标准库简介


@menu
* 操作系统接口:: 
* 文件通配符:: 
* 命令行参数:: 
* 错误输出重定向和程序终止:: 
* 字符串模式匹配:: 
* 数学:: 
* 互联网访问:: 
* 日期和时间:: 
* 数据压缩:: 
* 性能测量:: 
* 质量控制:: 
* 自带电池:: 

@end menu

@node 操作系统接口,文件通配符,,标准库简介
@anchor{tutorial/stdlib operating-system-interface}@anchor{1274}@anchor{tutorial/stdlib tut-os-interface}@anchor{1275}
@subsection 操作系统接口


@ref{c4,,os} 模块提供了许多与操作系统交互的函数:

@example
>>> import os
>>> os.getcwd()      # Return the current working directory
'C:\\Python38'
>>> os.chdir('/server/accesslogs')   # Change current working directory
>>> os.system('mkdir today')   # Run the command mkdir in the system shell
0
@end example

一定要使用 @code{import os} 而不是 @code{from os import *} 。这将避免内建的 @ref{4ea,,open()} 函数被 @ref{65f,,os.open()} 隐式替换掉，它们的使用方式大不相同。

@geindex 內置函数; help

内置的 @ref{d2c,,dir()} 和 @ref{56d,,help()} 函数可用作交互式辅助工具，用于处理大型模块，如 @ref{c4,,os}:

@example
>>> import os
>>> dir(os)
<returns a list of all module functions>
>>> help(os)
<returns an extensive manual page created from the module's docstrings>
@end example

对于日常文件和目录管理任务， @ref{e9,,shutil} 模块提供了更易于使用的更高级别的接口:

@example
>>> import shutil
>>> shutil.copyfile('data.db', 'archive.db')
'archive.db'
>>> shutil.move('/build/executables', 'installdir')
'installdir'
@end example

@node 文件通配符,命令行参数,操作系统接口,标准库简介
@anchor{tutorial/stdlib file-wildcards}@anchor{1276}@anchor{tutorial/stdlib tut-file-wildcards}@anchor{1277}
@subsection 文件通配符


@ref{8a,,glob} 模块提供了一个在目录中使用通配符搜索创建文件列表的函数:

@example
>>> import glob
>>> glob.glob('*.py')
['primes.py', 'random.py', 'quote.py']
@end example

@node 命令行参数,错误输出重定向和程序终止,文件通配符,标准库简介
@anchor{tutorial/stdlib command-line-arguments}@anchor{1278}@anchor{tutorial/stdlib tut-command-line-arguments}@anchor{1279}
@subsection 命令行参数


通用实用程序脚本通常需要处理命令行参数。这些参数作为列表存储在 @ref{fd,,sys} 模块的 @emph{argv} 属性中。例如，以下输出来自在命令行运行 @code{python demo.py one two three}

@example
>>> import sys
>>> print(sys.argv)
['demo.py', 'one', 'two', 'three']
@end example

@ref{6,,argparse} 模块提供了一种更复杂的机制来处理命令行参数。 以下脚本可提取一个或多个文件名，并可选择要显示的行数:

@example
import argparse

parser = argparse.ArgumentParser(prog = 'top',
    description = 'Show top lines from each file')
parser.add_argument('filenames', nargs='+')
parser.add_argument('-l', '--lines', type=int, default=10)
args = parser.parse_args()
print(args)
@end example

当在通过 @code{python top.py --lines=5 alpha.txt beta.txt} 在命令行运行时，该脚本会将 @code{args.lines} 设为 @code{5} 并将 @code{args.filenames} 设为 @code{['alpha.txt', 'beta.txt']}。

@node 错误输出重定向和程序终止,字符串模式匹配,命令行参数,标准库简介
@anchor{tutorial/stdlib error-output-redirection-and-program-termination}@anchor{127a}@anchor{tutorial/stdlib tut-stderr}@anchor{127b}
@subsection 错误输出重定向和程序终止


@ref{fd,,sys} 模块还具有 @emph{stdin} ， @emph{stdout} 和 @emph{stderr} 的属性。后者对于发出警告和错误消息非常有用，即使在 @emph{stdout} 被重定向后也可以看到它们:

@example
>>> sys.stderr.write('Warning, log file not found starting a new one\n')
Warning, log file not found starting a new one
@end example

终止脚本的最直接方法是使用 @code{sys.exit()} 。

@node 字符串模式匹配,数学,错误输出重定向和程序终止,标准库简介
@anchor{tutorial/stdlib string-pattern-matching}@anchor{127c}@anchor{tutorial/stdlib tut-string-pattern-matching}@anchor{127d}
@subsection 字符串模式匹配


@ref{dd,,re} 模块为高级字符串处理提供正则表达式工具。对于复杂的匹配和操作，正则表达式提供简洁，优化的解决方案:

@example
>>> import re
>>> re.findall(r'\bf[a-z]*', 'which foot or hand fell fastest')
['foot', 'fell', 'fastest']
>>> re.sub(r'(\b[a-z]+) \1', r'\1', 'cat in the the hat')
'cat in the hat'
@end example

当只需要简单的功能时，首选字符串方法因为它们更容易阅读和调试:

@example
>>> 'tea for too'.replace('too', 'two')
'tea for two'
@end example

@node 数学,互联网访问,字符串模式匹配,标准库简介
@anchor{tutorial/stdlib mathematics}@anchor{127e}@anchor{tutorial/stdlib tut-mathematics}@anchor{127f}
@subsection 数学


@ref{b1,,math} 模块提供对浮点数学的底层C库函数的访问:

@example
>>> import math
>>> math.cos(math.pi / 4)
0.70710678118654757
>>> math.log(1024, 2)
10.0
@end example

@ref{dc,,random} 模块提供了进行随机选择的工具:

@example
>>> import random
>>> random.choice(['apple', 'pear', 'banana'])
'apple'
>>> random.sample(range(100), 10)   # sampling without replacement
[30, 83, 16, 4, 8, 81, 41, 50, 18, 33]
>>> random.random()    # random float
0.17970987693706186
>>> random.randrange(6)    # random integer chosen from range(6)
4
@end example

@ref{f5,,statistics} 模块计算数值数据的基本统计属性（均值，中位数，方差等）:

@example
>>> import statistics
>>> data = [2.75, 1.75, 1.25, 0.25, 0.5, 1.25, 3.5]
>>> statistics.mean(data)
1.6071428571428572
>>> statistics.median(data)
1.25
>>> statistics.variance(data)
1.3720238095238095
@end example

SciPy项目 <@indicateurl{https://scipy.org}> 有许多其他模块用于数值计算。

@node 互联网访问,日期和时间,数学,标准库简介
@anchor{tutorial/stdlib internet-access}@anchor{1280}@anchor{tutorial/stdlib tut-internet-access}@anchor{1281}
@subsection 互联网访问


有许多模块可用于访问互联网和处理互联网协议。其中两个最简单的 @ref{120,,urllib.request} 用于从URL检索数据，以及 @ref{ed,,smtplib} 用于发送邮件:

@example
>>> from urllib.request import urlopen
>>> with urlopen('http://tycho.usno.navy.mil/cgi-bin/timer.pl') as response:
...     for line in response:
...         line = line.decode('utf-8')  # Decoding the binary data to text.
...         if 'EST' in line or 'EDT' in line:  # look for Eastern Time
...             print(line)

<BR>Nov. 25, 09:43:32 PM EST

>>> import smtplib
>>> server = smtplib.SMTP('localhost')
>>> server.sendmail('soothsayer@@example.org', 'jcaesar@@example.org',
... """To: jcaesar@@example.org
... From: soothsayer@@example.org
...
... Beware the Ides of March.
... """)
>>> server.quit()
@end example

（请注意，第二个示例需要在localhost上运行的邮件服务器。）

@node 日期和时间,数据压缩,互联网访问,标准库简介
@anchor{tutorial/stdlib dates-and-times}@anchor{1282}@anchor{tutorial/stdlib tut-dates-and-times}@anchor{1283}
@subsection 日期和时间


@ref{31,,datetime} 模块提供了以简单和复杂的方式操作日期和时间的类。虽然支持日期和时间算法，但实现的重点是有效的成员提取以进行输出格式化和操作。该模块还支持可感知时区的对象。

@example
>>> # dates are easily constructed and formatted
>>> from datetime import date
>>> now = date.today()
>>> now
datetime.date(2003, 12, 2)
>>> now.strftime("%m-%d-%y. %d %b %Y is a %A on the %d day of %B.")
'12-02-03. 02 Dec 2003 is a Tuesday on the 02 day of December.'

>>> # dates support calendar arithmetic
>>> birthday = date(1964, 7, 31)
>>> age = now - birthday
>>> age.days
14368
@end example

@node 数据压缩,性能测量,日期和时间,标准库简介
@anchor{tutorial/stdlib data-compression}@anchor{1284}@anchor{tutorial/stdlib tut-data-compression}@anchor{1285}
@subsection 数据压缩


常见的数据存档和压缩格式由模块直接支持，包括：@ref{144,,zlib}, @ref{8c,,gzip}, @ref{14,,bz2}, @ref{ad,,lzma}, @ref{142,,zipfile} 和 @ref{101,,tarfile}。:

@example
>>> import zlib
>>> s = b'witch which has which witches wrist watch'
>>> len(s)
41
>>> t = zlib.compress(s)
>>> len(t)
37
>>> zlib.decompress(t)
b'witch which has which witches wrist watch'
>>> zlib.crc32(s)
226805979
@end example

@node 性能测量,质量控制,数据压缩,标准库简介
@anchor{tutorial/stdlib performance-measurement}@anchor{1286}@anchor{tutorial/stdlib tut-performance-measurement}@anchor{1287}
@subsection 性能测量


一些Python用户对了解同一问题的不同方法的相对性能产生了浓厚的兴趣。 Python提供了一种可以立即回答这些问题的测量工具。

例如，元组封包和拆包功能相比传统的交换参数可能更具吸引力。@ref{10b,,timeit} 模块可以快速演示在运行效率方面一定的优势:

@example
>>> from timeit import Timer
>>> Timer('t=a; a=b; b=t', 'a=1; b=2').timeit()
0.57535828626024577
>>> Timer('a,b = b,a', 'a=1; b=2').timeit()
0.54962537085770791
@end example

与 @ref{10b,,timeit} 的精细粒度级别相反， @ref{d3,,profile} 和 @ref{d4,,pstats} 模块提供了用于在较大的代码块中识别时间关键部分的工具。

@node 质量控制,自带电池,性能测量,标准库简介
@anchor{tutorial/stdlib quality-control}@anchor{1288}@anchor{tutorial/stdlib tut-quality-control}@anchor{1289}
@subsection 质量控制


开发高质量软件的一种方法是在开发过程中为每个函数编写测试，并在开发过程中经常运行这些测试。

@ref{67,,doctest} 模块提供了一个工具，用于扫描模块并验证程序文档字符串中嵌入的测试。测试构造就像将典型调用及其结果剪切并粘贴到文档字符串一样简单。这通过向用户提供示例来改进文档，并且它允许doctest模块确保代码保持对文档的真实:

@example
def average(values):
    """Computes the arithmetic mean of a list of numbers.

    >>> print(average([20, 30, 70]))
    40.0
    """
    return sum(values) / len(values)

import doctest
doctest.testmod()   # automatically validate the embedded tests
@end example

@ref{11b,,unittest} 模块不像 @ref{67,,doctest} 模块那样易于使用，但它允许在一个单独的文件中维护更全面的测试集:

@example
import unittest

class TestStatisticalFunctions(unittest.TestCase):

    def test_average(self):
        self.assertEqual(average([20, 30, 70]), 40.0)
        self.assertEqual(round(average([1, 5, 7]), 1), 4.3)
        with self.assertRaises(ZeroDivisionError):
            average([])
        with self.assertRaises(TypeError):
            average(20, 30, 70)

unittest.main()  # Calling from the command line invokes all tests
@end example

@node 自带电池,,质量控制,标准库简介
@anchor{tutorial/stdlib batteries-included}@anchor{128a}@anchor{tutorial/stdlib tut-batteries-included}@anchor{128b}
@subsection 自带电池


Python有“自带电池”的理念。通过其包的复杂和强大功能可以最好地看到这一点。例如:


@itemize *

@item 
@ref{13f,,xmlrpc.client} 和 @ref{140,,xmlrpc.server} 模块使得实现远程过程调用变成了小菜一碟。 尽管存在于模块名称中，但用户不需要直接了解或处理 XML。

@item 
 @ref{69,,email} 包是一个用于管理电子邮件的库，包括MIME和其他符合 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html} 规范的邮件文档。与 @ref{ed,,smtplib} 和 @ref{d0,,poplib} 不同（它们实际上做的是发送和接收消息），电子邮件包提供完整的工具集，用于构建或解码复杂的消息结构（包括附件）以及实现互联网编码和标头协议。

@item 
 @ref{a4,,json} 包为解析这种流行的数据交换格式提供了强大的支持。 @ref{2a,,csv} 模块支持以逗号分隔值格式直接读取和写入文件，这种格式通常为数据库和电子表格所支持。 XML 处理由 @ref{137,,xml.etree.ElementTree} ， @ref{134,,xml.dom} 和 @ref{13b,,xml.sax} 包支持。这些模块和软件包共同大大简化了 Python 应用程序和其他工具之间的数据交换。

@item 
 @ref{f2,,sqlite3} 模块是 SQLite 数据库库的包装器，提供了一个可以使用稍微非标准的 SQL 语法更新和访问的持久数据库。

@item 
国际化由许多模块支持，包括 @ref{89,,gettext} ， @ref{a9,,locale} ，以及 @ref{1c,,codecs} 包。
@end itemize

@node 标准库简介 —— 第二部分,虚拟环境和包,标准库简介,Python 教程
@anchor{tutorial/stdlib2 doc}@anchor{128c}@anchor{tutorial/stdlib2 brief-tour-of-the-standard-library-part-ii}@anchor{128d}@anchor{tutorial/stdlib2 tut-brieftourtwo}@anchor{128e}
@section 标准库简介 —— 第二部分


第二部分涵盖了专业编程所需要的更高级的模块。这些模块很少用在小脚本中。

@menu
* 格式化输出:: 
* 模板:: 
* 使用二进制数据记录格式:: 
* 多线程: 多线程<2>. 
* 日志记录:: 
* 弱引用:: 
* 用于操作列表的工具:: 
* 十进制浮点运算:: 

@end menu

@node 格式化输出,模板,,标准库简介 —— 第二部分
@anchor{tutorial/stdlib2 output-formatting}@anchor{128f}@anchor{tutorial/stdlib2 tut-output-formatting}@anchor{1290}
@subsection 格式化输出


@ref{df,,reprlib} 模块提供了一个定制化版本的 @ref{7c6,,repr()} 函数，用于缩略显示大型或深层嵌套的容器对象:

@example
>>> import reprlib
>>> reprlib.repr(set('supercalifragilisticexpialidocious'))
"@{'a', 'c', 'd', 'e', 'f', 'g', ...@}"
@end example

@ref{d2,,pprint} 模块提供了更加复杂的打印控制，其输出的内置对象和用户自定义对象能够被解释器直接读取。当输出结果过长而需要折行时，“美化输出机制”会添加换行符和缩进，以更清楚地展示数据结构:

@example
>>> import pprint
>>> t = [[[['black', 'cyan'], 'white', ['green', 'red']], [['magenta',
...     'yellow'], 'blue']]]
...
>>> pprint.pprint(t, width=30)
[[[['black', 'cyan'],
   'white',
   ['green', 'red']],
  [['magenta', 'yellow'],
   'blue']]]
@end example

@ref{108,,textwrap} 模块能够格式化文本段落，以适应给定的屏幕宽度:

@example
>>> import textwrap
>>> doc = """The wrap() method is just like fill() except that it returns
... a list of strings instead of one big string with newlines to separate
... the wrapped lines."""
...
>>> print(textwrap.fill(doc, width=40))
The wrap() method is just like fill()
except that it returns a list of strings
instead of one big string with newlines
to separate the wrapped lines.
@end example

@ref{a9,,locale} 模块处理与特定地域文化相关的数据格式。locale 模块的 format 函数包含一个 grouping 属性，可直接将数字格式化为带有组分隔符的样式:

@example
>>> import locale
>>> locale.setlocale(locale.LC_ALL, 'English_United States.1252')
'English_United States.1252'
>>> conv = locale.localeconv()          # get a mapping of conventions
>>> x = 1234567.8
>>> locale.format("%d", x, grouping=True)
'1,234,567'
>>> locale.format_string("%s%.*f", (conv['currency_symbol'],
...                      conv['frac_digits'], x), grouping=True)
'$1,234,567.80'
@end example

@node 模板,使用二进制数据记录格式,格式化输出,标准库简介 —— 第二部分
@anchor{tutorial/stdlib2 templating}@anchor{1291}@anchor{tutorial/stdlib2 tut-templating}@anchor{1292}
@subsection 模板


@ref{f6,,string} 模块包含一个通用的 @ref{3e3,,Template} 类，具有适用于最终用户的简化语法。它允许用户在不更改应用逻辑的情况下定制自己的应用。

上述格式化操作是通过占位符实现的，占位符由 @code{$} 加上合法的 Python 标识符（只能包含字母、数字和下划线）构成。一旦使用花括号将占位符括起来，就可以在后面直接跟上更多的字母和数字而无需空格分割。@code{$$} 将被转义成单个字符 @code{$}:

@example
>>> from string import Template
>>> t = Template('$@{village@}folk send $$10 to $cause.')
>>> t.substitute(village='Nottingham', cause='the ditch fund')
'Nottinghamfolk send $10 to the ditch fund.'
@end example

如果在字典或关键字参数中未提供某个占位符的值，那么 @ref{1293,,substitute()} 方法将抛出 @ref{2c7,,KeyError}。对于邮件合并类型的应用，用户提供的数据有可能是不完整的，此时使用 @ref{1294,,safe_substitute()} 方法更加合适 —— 如果数据缺失，它会直接将占位符原样保留。

@example
>>> t = Template('Return the $item to $owner.')
>>> d = dict(item='unladen swallow')
>>> t.substitute(d)
Traceback (most recent call last):
  ...
KeyError: 'owner'
>>> t.safe_substitute(d)
'Return the unladen swallow to $owner.'
@end example

Template 的子类可以自定义定界符。例如，以下是某个照片浏览器的批量重命名功能，采用了百分号作为日期、照片序号和照片格式的占位符:

@example
>>> import time, os.path
>>> photofiles = ['img_1074.jpg', 'img_1076.jpg', 'img_1077.jpg']
>>> class BatchRename(Template):
...     delimiter = '%'
>>> fmt = input('Enter rename style (%d-date %n-seqnum %f-format):  ')
Enter rename style (%d-date %n-seqnum %f-format):  Ashley_%n%f

>>> t = BatchRename(fmt)
>>> date = time.strftime('%d%b%y')
>>> for i, filename in enumerate(photofiles):
...     base, ext = os.path.splitext(filename)
...     newname = t.substitute(d=date, n=i, f=ext)
...     print('@{0@} --> @{1@}'.format(filename, newname))

img_1074.jpg --> Ashley_0.jpg
img_1076.jpg --> Ashley_1.jpg
img_1077.jpg --> Ashley_2.jpg
@end example

模板的另一个应用是将程序逻辑与多样的格式化输出细节分离开来。这使得对 XML 文件、纯文本报表和 HTML 网络报表使用自定义模板成为可能。

@node 使用二进制数据记录格式,多线程<2>,模板,标准库简介 —— 第二部分
@anchor{tutorial/stdlib2 tut-binary-formats}@anchor{1295}@anchor{tutorial/stdlib2 working-with-binary-data-record-layouts}@anchor{1296}
@subsection 使用二进制数据记录格式


@ref{f8,,struct} 模块提供了 @ref{c04,,pack()} 和 @ref{1297,,unpack()} 函数，用于处理不定长度的二进制记录格式。下面的例子展示了在不使用 @ref{142,,zipfile} 模块的情况下，如何循环遍历一个 ZIP 文件的所有头信息。Pack 代码 @code{"H"} 和 @code{"I"} 分别代表两字节和四字节无符号整数。@code{"<"} 代表它们是标准尺寸的小尾型字节序:

@example
import struct

with open('myfile.zip', 'rb') as f:
    data = f.read()

start = 0
for i in range(3):                      # show the first 3 file headers
    start += 14
    fields = struct.unpack('<IIIHH', data[start:start+16])
    crc32, comp_size, uncomp_size, filenamesize, extra_size = fields

    start += 16
    filename = data[start:start+filenamesize]
    start += filenamesize
    extra = data[start:start+extra_size]
    print(filename, hex(crc32), comp_size, uncomp_size)

    start += extra_size + comp_size     # skip to the next header
@end example

@node 多线程<2>,日志记录,使用二进制数据记录格式,标准库简介 —— 第二部分
@anchor{tutorial/stdlib2 multi-threading}@anchor{1298}@anchor{tutorial/stdlib2 tut-multi-threading}@anchor{1299}
@subsection 多线程


线程是一种对于非顺序依赖的多个任务进行解耦的技术。多线程可以提高应用的响应效率，当接收用户输入的同时，保持其他任务在后台运行。一个有关的应用场景是，将 I/O 和计算运行在两个并行的线程中。

以下代码展示了高阶的 @ref{109,,threading} 模块如何在后台运行任务，且不影响主程序的继续运行:

@example
import threading, zipfile

class AsyncZip(threading.Thread):
    def __init__(self, infile, outfile):
        threading.Thread.__init__(self)
        self.infile = infile
        self.outfile = outfile

    def run(self):
        f = zipfile.ZipFile(self.outfile, 'w', zipfile.ZIP_DEFLATED)
        f.write(self.infile)
        f.close()
        print('Finished background zip of:', self.infile)

background = AsyncZip('mydata.txt', 'myarchive.zip')
background.start()
print('The main program continues to run in foreground.')

background.join()    # Wait for the background task to finish
print('Main program waited until background was done.')
@end example

多线程应用面临的主要挑战是，相互协调的多个线程之间需要共享数据或其他资源。为此，threading 模块提供了多个同步操作原语，包括线程锁、事件、条件变量和信号量。

尽管这些工具非常强大，但微小的设计错误却可以导致一些难以复现的问题。因此，实现多任务协作的首选方法是将对资源的所有请求集中到一个线程中，然后使用 @ref{da,,queue} 模块向该线程供应来自其他线程的请求。应用程序使用 @ref{d11,,Queue} 对象进行线程间通信和协调，更易于设计，更易读，更可靠。

@node 日志记录,弱引用,多线程<2>,标准库简介 —— 第二部分
@anchor{tutorial/stdlib2 logging}@anchor{129a}@anchor{tutorial/stdlib2 tut-logging}@anchor{129b}
@subsection 日志记录


@ref{aa,,logging} 模块提供功能齐全且灵活的日志记录系统。在最简单的情况下，日志消息被发送到文件或 @code{sys.stderr}

@example
import logging
logging.debug('Debugging information')
logging.info('Informational message')
logging.warning('Warning:config file %s not found', 'server.conf')
logging.error('Error occurred')
logging.critical('Critical error -- shutting down')
@end example

这会产生以下输出:

@example
WARNING:root:Warning:config file server.conf not found
ERROR:root:Error occurred
CRITICAL:root:Critical error -- shutting down
@end example

默认情况下，informational 和 debugging 消息被压制，输出会发送到标准错误流。其他输出选项包括将消息转发到电子邮件，数据报，套接字或 HTTP 服务器。新的过滤器可以根据消息优先级选择不同的路由方式：@code{DEBUG}，@code{INFO}，@code{WARNING}，@code{ERROR}，和 @code{CRITICAL}。

日志系统可以直接从 Python 配置，也可以从用户配置文件加载，以便自定义日志记录而无需更改应用程序。

@node 弱引用,用于操作列表的工具,日志记录,标准库简介 —— 第二部分
@anchor{tutorial/stdlib2 tut-weak-references}@anchor{129c}@anchor{tutorial/stdlib2 weak-references}@anchor{129d}
@subsection 弱引用


Python 会自动进行内存管理（对大多数对象进行引用计数并使用 @ref{129e,,garbage collection} 来清除循环引用）。 当某个对象的最后一个引用被移除后不久就会释放其所占用的内存。

此方式对大多数应用来说都适用，但偶尔也必须在对象持续被其他对象所使用时跟踪它们。 不幸的是，跟踪它们将创建一个会令其永久化的引用。 @ref{128,,weakref} 模块提供的工具可以不必创建引用就能跟踪对象。 当对象不再需要时，它将自动从一个弱引用表中被移除，并为弱引用对象触发一个回调。 典型应用包括对创建开销较大的对象进行缓存:

@example
>>> import weakref, gc
>>> class A:
...     def __init__(self, value):
...         self.value = value
...     def __repr__(self):
...         return str(self.value)
...
>>> a = A(10)                   # create a reference
>>> d = weakref.WeakValueDictionary()
>>> d['primary'] = a            # does not create a reference
>>> d['primary']                # fetch the object if it is still alive
10
>>> del a                       # remove the one reference
>>> gc.collect()                # run garbage collection right away
0
>>> d['primary']                # entry was automatically removed
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    d['primary']                # entry was automatically removed
  File "C:/python38/lib/weakref.py", line 46, in __getitem__
    o = self.data[key]()
KeyError: 'primary'
@end example

@node 用于操作列表的工具,十进制浮点运算,弱引用,标准库简介 —— 第二部分
@anchor{tutorial/stdlib2 tools-for-working-with-lists}@anchor{129f}@anchor{tutorial/stdlib2 tut-list-tools}@anchor{12a0}
@subsection 用于操作列表的工具


许多对于数据结构的需求可以通过内置列表类型来满足。 但是，有时也会需要具有不同效费比的替代实现。

@ref{7,,array} 模块提供了一种 @ref{44b,,array()} 对象，它类似于列表，但只能存储类型一致的数据且存储密集更高。 下面的例子演示了一个以两个字节为存储单元的无符号二进制数值的数组 (类型码为 @code{"H"})，而对于普通列表来说，每个条目存储为标准 Python 的 int 对象通常要占用16 个字节:

@example
>>> from array import array
>>> a = array('H', [4000, 10, 700, 22222])
>>> sum(a)
26932
>>> a[1:3]
array('H', [10, 700])
@end example

@ref{1e,,collections} 模块提供了一种 @ref{52b,,deque()} 对象，它类似于列表，但从左端添加和弹出的速度较快，而在中间查找的速度较慢。 此种对象适用于实现队列和广度优先树搜索:

@example
>>> from collections import deque
>>> d = deque(["task1", "task2", "task3"])
>>> d.append("task4")
>>> print("Handling", d.popleft())
Handling task1
@end example

@example
unsearched = deque([starting_node])
def breadth_first_search(unsearched):
    node = unsearched.popleft()
    for m in gen_moves(node):
        if is_goal(m):
            return m
        unsearched.append(m)
@end example

在替代的列表实现以外，标准库也提供了其他工具，例如 @ref{12,,bisect} 模块具有用于操作排序列表的函数:

@example
>>> import bisect
>>> scores = [(100, 'perl'), (200, 'tcl'), (400, 'lua'), (500, 'python')]
>>> bisect.insort(scores, (300, 'ruby'))
>>> scores
[(100, 'perl'), (200, 'tcl'), (300, 'ruby'), (400, 'lua'), (500, 'python')]
@end example

@ref{8e,,heapq} 模块提供了基于常规列表来实现堆的函数。 最小值的条目总是保持在位置零。 这对于需要重复访问最小元素而不希望运行完整列表排序的应用来说非常有用:

@example
>>> from heapq import heapify, heappop, heappush
>>> data = [1, 3, 5, 7, 9, 2, 4, 6, 8, 0]
>>> heapify(data)                      # rearrange the list into heap order
>>> heappush(data, -5)                 # add a new entry
>>> [heappop(data) for i in range(3)]  # fetch the three smallest entries
[-5, 0, 1]
@end example

@node 十进制浮点运算,,用于操作列表的工具,标准库简介 —— 第二部分
@anchor{tutorial/stdlib2 decimal-floating-point-arithmetic}@anchor{12a1}@anchor{tutorial/stdlib2 tut-decimal-fp}@anchor{12a2}
@subsection 十进制浮点运算


@ref{36,,decimal} 模块提供了一种 @ref{188,,Decimal} 数据类型用于十进制浮点运算。 相比内置的 @ref{187,,float} 二进制浮点实现，该类特别适用于


@itemize *

@item 
财务应用和其他需要精确十进制表示的用途，

@item 
控制精度，

@item 
控制四舍五入以满足法律或监管要求，

@item 
跟踪有效小数位，或

@item 
用户期望结果与手工完成的计算相匹配的应用程序。
@end itemize

例如，使用十进制浮点和二进制浮点数计算70美分手机和5％税的总费用，会产生的不同结果。如果结果四舍五入到最接近的分数差异会更大:

@example
>>> from decimal import *
>>> round(Decimal('0.70') * Decimal('1.05'), 2)
Decimal('0.74')
>>> round(.70 * 1.05, 2)
0.73
@end example

@ref{188,,Decimal} 表示的结果会保留尾部的零，并根据具有两个有效位的被乘数自动推出四个有效位。 Decimal 可以模拟手工运算来避免当二进制浮点数无法精确表示十进制数时会导致的问题。

精确表示特性使得 @ref{188,,Decimal} 类能够执行对于二进制浮点数来说不适用的模运算和相等性检测:

@example
>>> Decimal('1.00') % Decimal('.10')
Decimal('0.00')
>>> 1.00 % 0.10
0.09999999999999995

>>> sum([Decimal('0.1')]*10) == Decimal('1.0')
True
>>> sum([0.1]*10) == 1.0
False
@end example

@ref{36,,decimal} 模块提供了运算所需要的足够精度:

@example
>>> getcontext().prec = 36
>>> Decimal(1) / Decimal(7)
Decimal('0.142857142857142857142857142857142857')
@end example

@node 虚拟环境和包,接下来？,标准库简介 —— 第二部分,Python 教程
@anchor{tutorial/venv doc}@anchor{12a3}@anchor{tutorial/venv tut-venv}@anchor{12a4}@anchor{tutorial/venv virtual-environments-and-packages}@anchor{12a5}
@section 虚拟环境和包


@menu
* 概述: 概述<4>. 
* 创建虚拟环境:: 
* 使用pip管理包:: 

@end menu

@node 概述<4>,创建虚拟环境,,虚拟环境和包
@anchor{tutorial/venv introduction}@anchor{12a6}
@subsection 概述


Python应用程序通常会使用不在标准库内的软件包和模块。应用程序有时需要特定版本的库，因为应用程序可能需要修复特定的错误，或者可以使用库的过时版本的接口编写应用程序。

这意味着一个Python安装可能无法满足每个应用程序的要求。如果应用程序A需要特定模块的1.0版本但应用程序B需要2.0版本，则需求存在冲突，安装版本1.0或2.0将导致某一个应用程序无法运行。

这个问题的解决方案是创建一个 @ref{12a7,,virtual environment}，一个目录树，其中安装有特定Python版本，以及许多其他包。

然后，不同的应用将可以使用不同的虚拟环境。 要解决先前需求相冲突的例子，应用程序 A 可以拥有自己的 安装了 1.0 版本的虚拟环境，而应用程序 B 则拥有安装了 2.0 版本的另一个虚拟环境。 如果应用程序 B 要求将某个库升级到 3.0 版本，也不会影响应用程序 A 的环境。

@node 创建虚拟环境,使用pip管理包,概述<4>,虚拟环境和包
@anchor{tutorial/venv creating-virtual-environments}@anchor{12a8}
@subsection 创建虚拟环境


用于创建和管理虚拟环境的模块称为 @ref{125,,venv}。@ref{125,,venv} 通常会安装你可用的最新版本的 Python。如果您的系统上有多个版本的 Python，您可以通过运行 @code{python3} 或您想要的任何版本来选择特定的Python版本。

要创建虚拟环境，请确定要放置它的目录，并将 @ref{125,,venv} 模块作为脚本运行目录路径:

@example
python3 -m venv tutorial-env
@end example

如果它不存在，这将创建 @code{tutorial-env} 目录，并在其中创建包含Python解释器，标准库和各种支持文件的副本的目录。

虚拟环境的常用目录位置是 @code{.venv}。 这个名称通常会令该目录在你的终端中保持隐藏，从而避免需要对所在目录进行额外解释的一般名称。 它还能防止与某些工具所支持的 @code{.env} 环境变量定义文件发生冲突。

创建虚拟环境后，您可以激活它。

在Windows上，运行:

@example
tutorial-env\Scripts\activate.bat
@end example

在Unix或MacOS上，运行:

@example
source tutorial-env/bin/activate
@end example

（这个脚本是为bash shell编写的。如果你使用 @code{csh} 或 @code{fish} shell，你应该改用 @code{activate.csh} 或 @code{activate.fish} 脚本。）

激活虚拟环境将改变你所用终端的提示符，以显示你正在使用的虚拟环境，并修改环境以使 @code{python} 命令所运行的将是已安装的特定 Python 版本。 例如：

@example
$ source ~/envs/tutorial-env/bin/activate
(tutorial-env) $ python
Python 3.5.1 (default, May  6 2016, 10:59:36)
  ...
>>> import sys
>>> sys.path
['@w{'}, '/usr/local/lib/python35.zip', ...,
'~/envs/tutorial-env/lib/python3.5/site-packages']
>>>
@end example

@node 使用pip管理包,,创建虚拟环境,虚拟环境和包
@anchor{tutorial/venv managing-packages-with-pip}@anchor{12a9}
@subsection 使用pip管理包


你可以使用一个名为 @code{pip} 的程序来安装、升级和移除软件包。默认情况下 @code{pip} 将从 Python Package Index <@indicateurl{https://pypi.org}> 安装软件包。你可以在浏览器中访问 Python Package Index 或是使用 @code{pip} 受限的搜索功能:

@example
(tutorial-env) $ pip search astronomy
skyfield               - Elegant astronomy for Python
gary                   - Galactic astronomy and gravitational dynamics.
novas                  - The United States Naval Observatory NOVAS astronomy library
astroobs               - Provides astronomy ephemeris to plan telescope observations
PyAstronomy            - A collection of astronomy related tools for Python.
...
@end example

@code{pip} 有许多子命令：“search”、“install”、“uninstall”、“freeze”等等。（请参阅 @ref{7ef,,安装 Python 模块} 指南以了解  @code{pip} 的完整文档。）

您可以通过指定包的名称来安装最新版本的包：

@example
(tutorial-env) $ pip install novas
Collecting novas
  Downloading novas-3.1.1.3.tar.gz (136kB)
Installing collected packages: novas
  Running setup.py install for novas
Successfully installed novas-3.1.1.3
@end example

您还可以通过提供包名称后跟 @code{==} 和版本号来安装特定版本的包：

@example
(tutorial-env) $ pip install requests==2.6.0
Collecting requests==2.6.0
  Using cached requests-2.6.0-py2.py3-none-any.whl
Installing collected packages: requests
Successfully installed requests-2.6.0
@end example

如果你重新运行这个命令，@code{pip} 会注意到已经安装了所请求的版本并且什么都不做。您可以提供不同的版本号来获取该版本，或者您可以运行 @code{pip install --upgrade} 将软件包升级到最新版本：

@example
(tutorial-env) $ pip install --upgrade requests
Collecting requests
Installing collected packages: requests
  Found existing installation: requests 2.6.0
    Uninstalling requests-2.6.0:
      Successfully uninstalled requests-2.6.0
Successfully installed requests-2.7.0
@end example

@code{pip uninstall} 后跟一个或多个包名称将从虚拟环境中删除包。

@code{pip show} 将显示有关特定包的信息：

@example
(tutorial-env) $ pip show requests
---
Metadata-Version: 2.0
Name: requests
Version: 2.7.0
Summary: Python HTTP for Humans.
Home-page: http://python-requests.org
Author: Kenneth Reitz
Author-email: me@@kennethreitz.com
License: Apache 2.0
Location: /Users/akuchling/envs/tutorial-env/lib/python3.4/site-packages
Requires:
@end example

@code{pip list} 将显示虚拟环境中安装的所有软件包：

@example
(tutorial-env) $ pip list
novas (3.1.1.3)
numpy (1.9.2)
pip (7.0.3)
requests (2.7.0)
setuptools (16.0)
@end example

@cite{pip freeze`} 将生成一个类似的已安装包列表，但输出使用 @code{pip install} 期望的格式。一个常见的约定是将此列表放在 @code{requirements.txt} 文件中：

@example
(tutorial-env) $ pip freeze > requirements.txt
(tutorial-env) $ cat requirements.txt
novas==3.1.1.3
numpy==1.9.2
requests==2.7.0
@end example

然后可以将 @code{requirements.txt} 提交给版本控制并作为应用程序的一部分提供。然后用户可以使用 @code{install -r} 安装所有必需的包：

@example
(tutorial-env) $ pip install -r requirements.txt
Collecting novas==3.1.1.3 (from -r requirements.txt (line 1))
  ...
Collecting numpy==1.9.2 (from -r requirements.txt (line 2))
  ...
Collecting requests==2.7.0 (from -r requirements.txt (line 3))
  ...
Installing collected packages: novas, numpy, requests
  Running setup.py install for novas
Successfully installed novas-3.1.1.3 numpy-1.9.2 requests-2.7.0
@end example

@code{pip} 有更多选择。有关 @code{pip} 的完整文档，请参阅 @ref{7ef,,安装 Python 模块} 指南。当您编写一个包并希望在 Python 包索引中使它可用时，请参考 @ref{7f0,,分发 Python 模块} 指南。

@node 接下来？,交互式编辑和编辑历史,虚拟环境和包,Python 教程
@anchor{tutorial/whatnow doc}@anchor{12aa}@anchor{tutorial/whatnow tut-whatnow}@anchor{12ab}@anchor{tutorial/whatnow what-now}@anchor{12ac}
@section 接下来？


阅读本教程可能会增强您对使用Python的兴趣 - 您应该热衷于应用Python来解决您的实际问题。你应该去哪里了解更多？

本教程是Python文档集的一部分。其他文档：


@itemize *

@item 
@ref{118f,,Python 标准库}:

您应该浏览本手册，该手册提供了有关标准库中的类型，功能和模块的完整（尽管简洁）参考资料。标准的Python发行版包含 @emph{很多} 的附加代码。有些模块可以读取Unix邮箱，通过HTTP检索文档，生成随机数，解析命令行选项，编写CGI程序，压缩数据以及许多其他任务。浏览标准库参考可以了解更多可用的内容。

@item 
@ref{7ef,,安装 Python 模块} 解释了怎么安装由其他Python开发者编写的模块。

@item 
@ref{1190,,Python语言参考}: Python的语法和语义的详细解释。尽管阅读完非常繁重，但作为语言本身的完整指南是有用的。
@end itemize

更多Python资源：


@itemize *

@item 
@indicateurl{https://www.python.org} ：主要的Python网站。它包含代码，文档以及指向Web上与Python相关的页面的链接。该网站世界很多地区都有镜像，如欧洲，日本和澳大利亚；镜像可能比主站点更快，具体取决于您的地理位置。

@item 
@indicateurl{https://docs.python.org} ：快速访问Python的文档。

@item 
@indicateurl{https://pypi.org}: The Python Package Index，以前也被昵称为 Cheese Shop @footnote{@w{(1)} 
“Cheese Shop”是 Monty Python 的一个短剧：一位顾客来到一家奶酪商店，但无论他要哪种奶酪，店员都说没有货。
}，是可下载用户自制 Python 模块的索引。 当你要开始发布代码时，你可以在此处进行注册以便其他人能找到它。

@item 
@indicateurl{https://code.activestate.com/recipes/langs/python/} ：Python Cookbook是一个相当大的代码示例集，更多的模块和有用的脚本。特别值得注意的贡献收集在一本名为Python Cookbook（O'Reilly＆Associates，ISBN 0-596-00797-3）的书中。

@item 
@indicateurl{http://www.pyvideo.org} 从会议和用户组会议中收集与Python相关的视频的链接。

@item 
@indicateurl{https://scipy.org} ：Ecientific Python项目包括用于快速阵列计算和操作的模块，以及用于诸如线性代数，傅里叶变换，非线性求解器，随机数分布，统计分析等的一系列包。
@end itemize

对于与Python相关的问题和问题报告，您可以发布到新闻组 @code{comp.lang.python} ，或者将它们发送到邮件列表python-@email{list@@python.org}。新闻组和邮件列表是互通的，因此发布到一个地方将自动转发给另一个。每天有数百个帖子，询问（和回答）问题，建议新功能，以及宣布新模块。邮件列表档案可在 @indicateurl{https://mail.python.org/pipermail/} 上找到。

在发问之前，请务必查看以下列表 @ref{12ad,,常见问题} （或简写为 FAQ）。常见问题包含了很多一次又一次问到的问题及答案，并且可能已经包含了您的问题的解决方案。

@subsubheading 备注


@node 交互式编辑和编辑历史,浮点算术：争议和限制,接下来？,Python 教程
@anchor{tutorial/interactive doc}@anchor{12ae}@anchor{tutorial/interactive interactive-input-editing-and-history-substitution}@anchor{12af}@anchor{tutorial/interactive tut-interacting}@anchor{119e}
@section 交互式编辑和编辑历史


某些版本的 Python 解释器支持编辑当前输入行和编辑历史记录，类似 Korn shell 和 GNU Bash shell 的功能 。这个功能使用了 GNU Readline@footnote{https://tiswww.case.edu/php/chet/readline/rltop.html} 来实现，一个支持多种编辑方式的库。这个库有它自己的文档，在这里我们就不重复说明了。

@menu
* Tab 补全和编辑历史:: 
* 默认交互式解释器的替代品:: 

@end menu

@node Tab 补全和编辑历史,默认交互式解释器的替代品,,交互式编辑和编辑历史
@anchor{tutorial/interactive tab-completion-and-history-editing}@anchor{12b0}@anchor{tutorial/interactive tut-keybindings}@anchor{12b1}
@subsection Tab 补全和编辑历史


在解释器启动的时候，补全变量和模块名的功能将 @ref{8e0,,自动打开}，以便在按下 @code{Tab} 键的时候调用补全函数。它会查看 Python 语句名称，当前局部变量和可用的模块名称。处理像 @code{string.a} 的表达式，它会求值在最后一个 @code{'.'} 之前的表达式，接着根据求值结果对象的属性给出补全建议。如果拥有 @ref{313,,__getattr__()} 方法的对象是表达式的一部分，注意这可能会执行程序定义的代码。默认配置下会把编辑历史记录保存在用户目录下名为 @code{.python_history} 的文件。在下一次 Python 解释器会话期间，编辑历史记录仍旧可用。

@node 默认交互式解释器的替代品,,Tab 补全和编辑历史,交互式编辑和编辑历史
@anchor{tutorial/interactive alternatives-to-the-interactive-interpreter}@anchor{12b2}@anchor{tutorial/interactive tut-commentary}@anchor{12b3}
@subsection 默认交互式解释器的替代品


Python 解释器与早期版本的相比，向前迈进了一大步；无论怎样，还有些希望的功能：如果能在编辑连续行时建议缩进（解析器知道接下来是否需要缩进符号），那将很棒。补全机制可以使用解释器的符号表。有命令去检查（甚至建议）括号，引号以及其他符号是否匹配。

一个可选的增强型交互式解释器是 IPython@footnote{https://ipython.org/}，它已经存在了有一段时间，它具有 tab 补全，探索对象和高级历史记录管理功能。它还可以彻底定制并嵌入到其他应用程序中。另一个相似的增强型交互式环境是 bpython@footnote{https://www.bpython-interpreter.org/}。

@c import math

@node 浮点算术：争议和限制,附录,交互式编辑和编辑历史,Python 教程
@anchor{tutorial/floatingpoint doc}@anchor{12b4}@anchor{tutorial/floatingpoint bpython}@anchor{12b5}@anchor{tutorial/floatingpoint floating-point-arithmetic-issues-and-limitations}@anchor{12b6}@anchor{tutorial/floatingpoint tut-fp-issues}@anchor{12b7}
@section 浮点算术：争议和限制


浮点数在计算机硬件中表示为以 2 为基数（二进制）的小数。举例而言，十进制的小数

@example
0.125
@end example

等于 1/10 + 2/100 + 5/1000 ，同理，二进制的小数

@example
0.001
@end example

等于0/2 + 0/4 + 1/8。这两个小数具有相同的值，唯一真正的区别是第一个是以 10 为基数的小数表示法，第二个则是 2 为基数。

不幸的是，大多数的十进制小数都不能精确地表示为二进制小数。这导致在大多数情况下，你输入的十进制浮点数都只能近似地以二进制浮点数形式储存在计算机中。

用十进制来理解这个问题显得更加容易一些。考虑分数 1/3 。我们可以得到它在十进制下的一个近似值

@example
0.3
@end example

或者，更近似的，:

@example
0.33
@end example

或者，更近似的，:

@example
0.333
@end example

以此类推。结果是无论你写下多少的数字，它都永远不会等于 1/3 ，只是更加更加地接近 1/3 。

同样的道理，无论你使用多少位以 2 为基数的数码，十进制的 0.1 都无法精确地表示为一个以 2 为基数的小数。 在以 2 为基数的情况下， 1/10 是一个无限循环小数

@example
0.0001100110011001100110011001100110011001100110011...
@end example

在任何一个位置停下，你都只能得到一个近似值。因此，在今天的大部分架构上，浮点数都只能近似地使用二进制小数表示，对应分数的分子使用每 8 字节的前 53 位表示，分母则表示为 2 的幂次。在 1/10 这个例子中，相应的二进制分数是 @code{3602879701896397 / 2 ** 55} ，它很接近 1/10 ，但并不是 1/10 。

大部分用户都不会意识到这个差异的存在，因为 Python 只会打印计算机中存储的二进制值的十进制近似值。在大部分计算机中，如果 Python 想把 0.1 的二进制对应的精确十进制打印出来，将会变成这样

@example
>>> 0.1
0.1000000000000000055511151231257827021181583404541015625
@end example

这比大多数人认为有用的数字更多，因此Python通过显示舍入值来保持可管理的位数

@example
>>> 1 / 10
0.1
@end example

牢记，即使输出的结果看起来好像就是 1/10 的精确值，实际储存的值只是最接近 1/10 的计算机可表示的二进制分数。

有趣的是，有许多不同的十进制数共享相同的最接近的近似二进制小数。例如， @code{0.1} 、 @code{0.10000000000000001} 、 @code{0.1000000000000000055511151231257827021181583404541015625} 全都近似于 @code{3602879701896397 / 2 ** 55} 。由于所有这些十进制值都具有相同的近似值，因此可以显示其中任何一个，同时仍然保留不变的 @code{eval(repr(x)) == x} 。

在历史上，Python 提示符和内置的 @ref{7c6,,repr()} 函数会选择具有 17 位有效数字的来显示，即 @code{0.10000000000000001}。 从 Python 3.1 开始，Python（在大多数系统上）现在能够选择这些表示中最短的并简单地显示 @code{0.1} 。

请注意这种情况是二进制浮点数的本质特性：它不是 Python 的错误，也不是你代码中的错误。 你会在所有支持你的硬件中的浮点运算的语言中发现同样的情况（虽然某些语言在默认状态或所有输出模块下都不会 @emph{显示} 这种差异）。

想要更美观的输出，你可能会希望使用字符串格式化来产生限定长度的有效位数:

@example
>>> format(math.pi, '.12g')  # give 12 significant digits
'3.14159265359'

>>> format(math.pi, '.2f')   # give 2 digits after the point
'3.14'

>>> repr(math.pi)
'3.141592653589793'
@end example

必须重点了解的是，这在实际上只是一个假象：你只是将真正的机器码值进行了舍入操作再 @emph{显示} 而已。

一个假象还可能导致另一个假象。 例如，由于这个 0.1 并非真正的 1/10，将三个 0.1 的值相加也不一定能恰好得到 0.3:

@example
>>> .1 + .1 + .1 == .3
False
@end example

而且，由于这个 0.1 无法精确表示 1/10 的值而这个 0.3 也无法精确表示 3/10 的值，使用 @ref{c66,,round()} 函数进行预先舍入也是没用的:

@example
>>> round(.1, 1) + round(.1, 1) + round(.1, 1) == round(.3, 1)
False
@end example

虽然这些小数无法精确表示其所要代表的实际值，@ref{c66,,round()} 函数还是可以用来“事后舍入”，使得实际的结果值可以做相互比较:

@example
>>> round(.1 + .1 + .1, 10) == round(.3, 10)
True
@end example

二进制浮点运算会造成许多这样的“意外”。 有关 "0.1" 的问题会在下面的“表示性错误”一节中更详细地描述。 请参阅 浮点数的危险性@footnote{http://www.lahey.com/float.htm} 一文了解有关其他常见意外现象的更详细介绍。

正如那篇文章的结尾所言，“对此问题并无简单的答案。” 但是也不必过于担心浮点数的问题！ Python 浮点运算中的错误是从浮点运算硬件继承而来，而在大多数机器上每次浮点运算得到的 2**53 数码位都会被作为 1 个整体来处理。 这对大多数任务来说都已足够，但你确实需要记住它并非十进制算术，且每次浮点运算都可能会导致新的舍入错误。

虽然病态的情况确实存在，但对于大多数正常的浮点运算使用来说，你只需简单地将最终显示的结果舍入为你期望的十进制数值即可得到你期望的结果。 @ref{329,,str()} 通常已足够，对于更精度的控制可参看 @ref{d13,,格式字符串语法} 中 @ref{4d4,,str.format()} 方法的格式描述符。

对于需要精确十进制表示的使用场景，请尝试使用 @ref{36,,decimal} 模块，该模块实现了适合会计应用和高精度应用的十进制运算。

另一种形式的精确运算由 @ref{83,,fractions} 模块提供支持，该模块实现了基于有理数的算术运算（因此可以精确表示像 1/3 这样的数值）。

如果你是浮点运算的重度用户，你应该看一下数值运算 Python 包 NumPy 以及由 SciPy 项目所提供的许多其它数学和统计运算包。 参见 <@indicateurl{https://scipy.org}>。

Python 也提供了一些工具，可以在你真的 @emph{想要} 知道一个浮点数精确值的少数情况下提供帮助。 例如 @ref{12b8,,float.as_integer_ratio()} 方法会将浮点数表示为一个分数:

@example
>>> x = 3.14159
>>> x.as_integer_ratio()
(3537115888337719, 1125899906842624)
@end example

由于这是一个精确的比值，它可以被用来无损地重建原始值:

@example
>>> x == 3537115888337719 / 1125899906842624
True
@end example

@ref{12b9,,float.hex()} 方法会以十六进制（以 16 为基数）来表示浮点数，同样能给出保存在你的计算机中的精确值:

@example
>>> x.hex()
'0x1.921f9f01b866ep+1'
@end example

这种精确的十六进制表示法可被用来精确地重建浮点值:

@example
>>> x == float.fromhex('0x1.921f9f01b866ep+1')
True
@end example

由于这种表示法是精确的，它适用于跨越不同版本（平台无关）的 Python 移植数值，以及与支持相同格式的其他语言（例如 Java 和 C99）交换数据.

另一个有用的工具是 @ref{d37,,math.fsum()} 函数，它有助于减少求和过程中的精度损失。 它会在数值被添加到总计值的时候跟踪“丢失的位”。 这可以很好地保持总计值的精确度， 使得错误不会积累到能影响结果总数的程度:

@example
>>> sum([0.1] * 10) == 1.0
False
>>> math.fsum([0.1] * 10) == 1.0
True
@end example

@menu
* 表示性错误:: 

@end menu

@node 表示性错误,,,浮点算术：争议和限制
@anchor{tutorial/floatingpoint representation-error}@anchor{12ba}@anchor{tutorial/floatingpoint tut-fp-error}@anchor{12bb}
@subsection 表示性错误


本小节将详细解释 "0.1" 的例子，并说明你可以怎样亲自对此类情况进行精确分析。 假定前提是已基本熟悉二进制浮点表示法。

@emph{表示性错误} 是指某些（其实是大多数）十进制小数无法以二进制（以 2 为基数的计数制）精确表示这一事实造成的错误。 这就是为什么 Python（或者 Perl、C、C++、Java、Fortran 以及许多其他语言）经常不会显示你所期待的精确十进制数值的主要原因。

为什么会这样？ 1/10 是无法用二进制小数精确表示的。 目前（2000年11月）几乎所有使用 IEEE-754 浮点运算标准的机器以及几乎所有系统平台都会将 Python 浮点数映射为 IEEE-754 “双精度类型”。 754 双精度类型包含 53 位精度，因此在输入时，计算会尽量将 0.1 转换为以 @emph{J}/2**@emph{N} 形式所能表示的最接近分数，其中 @emph{J} 为恰好包含 53 个二进制位的整数。 重新将

@example
1 / 10 ~= J / (2**N)
@end example

写为

@example
J ~= 2**N / 10
@end example

并且由于 @emph{J} 恰好有 53 位 (即 @code{>= 2**52} 但 @code{< 2**53})，@emph{N} 的最佳值为 56:

@example
>>> 2**52 <=  2**56 // 10  < 2**53
True
@end example

也就是说，56 是唯一的 @emph{N} 值能令 @emph{J} 恰好有 53 位。 这样 @emph{J} 的最佳可能值就是经过舍入的商:

@example
>>> q, r = divmod(2**56, 10)
>>> r
6
@end example

由于余数超过 10 的一半，最佳近似值可通过四舍五入获得:

@example
>>> q+1
7205759403792794
@end example

这样在 754 双精度下 1/10 的最佳近似值为:

@example
7205759403792794 / 2 ** 56
@end example

分子和分母都除以二则结果小数为:

@example
3602879701896397 / 2 ** 55
@end example

请注意由于我们做了向上舍入，这个结果实际上略大于 1/10；如果我们没有向上舍入，则商将会略小于 1/10。 但无论如何它都不会是 @emph{精确的} 1/10！

因此计算永远不会“看到”1/10：它实际看到的就是上面所给出的小数，它所能达到的最佳 754 双精度近似值:

@example
>>> 0.1 * 2 ** 55
3602879701896397.0
@end example

如果我们将该小数乘以 10**55，我们可以看到该值输出为 55 位的十进制数:

@example
>>> 3602879701896397 * 10 ** 55 // 2 ** 55
1000000000000000055511151231257827021181583404541015625
@end example

这意味着存储在计算机中的确切数值等于十进制数值 0.1000000000000000055511151231257827021181583404541015625。 许多语言（包括较旧版本的 Python）都不会显示这个完整的十进制数值，而是将结果舍入为 17 位有效数字:

@example
>>> format(0.1, '.17f')
'0.10000000000000001'
@end example

@ref{83,,fractions} 和 @ref{36,,decimal} 模块可令进行此类计算更加容易:

@example
>>> from decimal import Decimal
>>> from fractions import Fraction

>>> Fraction.from_float(0.1)
Fraction(3602879701896397, 36028797018963968)

>>> (0.1).as_integer_ratio()
(3602879701896397, 36028797018963968)

>>> Decimal.from_float(0.1)
Decimal('0.1000000000000000055511151231257827021181583404541015625')

>>> format(Decimal.from_float(0.1), '.17')
'0.10000000000000001'
@end example

@node 附录,,浮点算术：争议和限制,Python 教程
@anchor{tutorial/appendix doc}@anchor{12bc}@anchor{tutorial/appendix appendix}@anchor{12bd}@anchor{tutorial/appendix tut-appendix}@anchor{12be}
@section 附录


@menu
* 交互模式: 交互模式<2>. 

@end menu

@node 交互模式<2>,,,附录
@anchor{tutorial/appendix interactive-mode}@anchor{12bf}@anchor{tutorial/appendix tut-interac}@anchor{11a3}
@subsection 交互模式


@menu
* 错误处理:: 
* 可执行的Python脚本:: 
* 交互式启动文件:: 
* 定制模块:: 

@end menu

@node 错误处理,可执行的Python脚本,,交互模式<2>
@anchor{tutorial/appendix error-handling}@anchor{12c0}@anchor{tutorial/appendix tut-error}@anchor{12c1}
@subsubsection 错误处理


当发生错误时，解释器会打印错误信息和错误堆栈。在交互模式下，将返回到主命令提示符；如果输入内容来自文件，在打印错误堆栈之后，程序会以非零状态退出。（这里所说的错误不包括 @ref{d6b,,try} 语句中由 @ref{b37,,except} 所捕获的异常。）有些错误是无条件致命的，会导致程序以非零状态退出；比如内部逻辑矛盾或内存耗尽。所有错误信息都会被写入标准错误流；而命令的正常输出则被写入标准输出流。

将中断字符（通常为 @code{Control-C} 或 @code{Delete} ）键入主要或辅助提示会取消输入并返回主提示符。 @footnote{@w{(1)} 
GNU Readline 包的问题可能会阻止这种情况。
} 在执行命令时键入中断引发的 @ref{197,,KeyboardInterrupt} 异常，可以由 @ref{d6b,,try} 语句处理。

@node 可执行的Python脚本,交互式启动文件,错误处理,交互模式<2>
@anchor{tutorial/appendix executable-python-scripts}@anchor{12c2}@anchor{tutorial/appendix tut-scripts}@anchor{11a8}
@subsubsection 可执行的Python脚本


在BSD等类Unix系统上，Python脚本可以直接执行，就像shell脚本一样，第一行添加:

@example
#!/usr/bin/env python3.5
@end example

（假设解释器位于用户的 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} ）脚本的开头，并将文件设置为可执行。 @code{#!} 必须是文件的前两个字符。在某些平台上，第一行必须以Unix样式的行结尾（@code{'\n'}）结束，而不是以Windows（@code{'\r\n'}）行结尾。请注意，散列或磅字符 @code{'#'} 在Python中代表注释开始。

可以使用 @code{chmod} 命令为脚本提供可执行模式或权限。

@example
$ chmod +x myscript.py
@end example

在Windows系统上，没有“可执行模式”的概念。 Python安装程序自动将 @code{.py} 文件与 @code{python.exe} 相关联，这样双击Python文件就会将其作为脚本运行。扩展也可以是 @code{.pyw} ，在这种情况下，会隐藏通常出现的控制台窗口。

@node 交互式启动文件,定制模块,可执行的Python脚本,交互模式<2>
@anchor{tutorial/appendix the-interactive-startup-file}@anchor{12c3}@anchor{tutorial/appendix tut-startup}@anchor{12c4}
@subsubsection 交互式启动文件


当您以交互方式使用Python时，每次启动解释器时都会执行一些标准命令，这通常很方便。您可以通过将名为 
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP} 的环境变量设置为包含启动命令的文件名来实现。这类似于Unix shell的 @code{.profile} 功能。

This file is only read in interactive sessions, not when Python reads commands
from a script, and not when @code{/dev/tty} is given as the explicit source of
commands (which otherwise behaves like an interactive session).  It is executed
in the same namespace where interactive commands are executed, so that objects
that it defines or imports can be used without qualification in the interactive
session. You can also change the prompts @code{sys.ps1} and @code{sys.ps2} in this
file.

如果你想从当前目录中读取一个额外的启动文件，你可以使用像 @code{if os.path.isfile('.pythonrc.py'): exec(open('.pythonrc.py').read())} 这样的代码在全局启动文件中对它进行编程。如果要在脚本中使用启动文件，则必须在脚本中显式执行此操作:

@example
import os
filename = os.environ.get('PYTHONSTARTUP')
if filename and os.path.isfile(filename):
    with open(filename) as fobj:
        startup_file = fobj.read()
    exec(startup_file)
@end example

@node 定制模块,,交互式启动文件,交互模式<2>
@anchor{tutorial/appendix the-customization-modules}@anchor{12c5}@anchor{tutorial/appendix tut-customize}@anchor{12c6}
@subsubsection 定制模块


Python提供了两个钩子来让你自定义它：@code{sitecustomize} 和 @code{usercustomize}。要查看其工作原理，首先需要找到用户site-packages目录的位置。启动Python并运行此代码:

@example
>>> import site
>>> site.getusersitepackages()
'/home/user/.local/lib/python3.5/site-packages'
@end example

现在，您可以在该目录中创建一个名为 @code{usercustomize.py} 的文件，并将所需内容放入其中。它会影响Python的每次启动，除非它以 @ref{d0e,,-s} 选项启动，以禁用自动导入。

@code{sitecustomize} 以相同的方式工作，但通常由计算机管理员在全局 site-packages 目录中创建，并在 @code{usercustomize} 之前被导入。有关详情请参阅 @ref{eb,,site} 模块的文档。

@subsubheading 备注


@node Python安装和使用,Python语言参考,Python 教程,Top
@anchor{using/index doc}@anchor{12c7}@anchor{using/index python-setup-and-usage}@anchor{12c8}@anchor{using/index using-index}@anchor{12c9}
@chapter Python安装和使用


这一部分文档专门介绍关于在不同平台上设置Python环境、调用解释器以及让使用Python更容易的一些事情的有用信息。

@c ATTENTION: You probably should update Misc/python.man, too, if you modify
@c this file.

@menu
* 命令行与环境:: 
* 在类Unix环境下使用Python:: 
* 在Windows上使用 Python:: 
* 在苹果系统上使用 Python:: 
* 编辑器和集成开发环境:: 

@end menu

@node 命令行与环境,在类Unix环境下使用Python,,Python安装和使用
@anchor{using/cmdline doc}@anchor{12ca}@anchor{using/cmdline command-line-and-environment}@anchor{12cb}@anchor{using/cmdline using-on-general}@anchor{f39}
@section 命令行与环境


CPython 解析器会扫描命令行与环境用于获取各种设置信息。

@strong{CPython implementation detail:} 其他实现的命令行方案可能有所不同。 更多相关资源请参阅 @ref{12cc,,其他实现}。

@menu
* 命令行:: 
* 环境变量:: 

@end menu

@node 命令行,环境变量,,命令行与环境
@anchor{using/cmdline command-line}@anchor{12cd}@anchor{using/cmdline using-on-cmdline}@anchor{925}
@subsection 命令行


对 Python 发起调用时，你可以指定以下的任意选项:

@example
python [-bBdEhiIOqsSuvVWx?] [-c command | -m module-name | script | - ] [args]
@end example

当然最常见的用例就是简单地启动执行一个脚本:

@example
python myscript.py
@end example

@menu
* 接口选项:: 
* 通用选项:: 
* 其他选项:: 
* 不应当使用的选项:: 

@end menu

@node 接口选项,通用选项,,命令行
@anchor{using/cmdline interface-options}@anchor{12ce}@anchor{using/cmdline using-on-interface-options}@anchor{12cf}
@subsubsection 接口选项


解释器接口类似于 UNIX shell，但提供了一些额外的发起调用方法:


@itemize *

@item 
当调用时附带连接到某个 tty 设备的标准输入时，它会提示输入命令并执行它们，直到读入一个 EOF（文件结束字符，其产生方式是在 UNIX 中按 @code{Ctrl-D} 或在 Windows 中按 @code{Ctrl-Z, Enter}。）

@item 
当调用时附带一个文件名参数或以一个文件作为标准输入时，它会从该文件读取并执行脚本程序。

@item 
当调用时附带一个目录名参数时，它会从该目录读取并执行具有适当名称的脚本程序。

@item 
当调用时附带 @code{-c command} 时，它会执行 @emph{command} 所给出的 Python 语句。 在这里 @emph{command} 可以包含以换行符分隔的多条语句。 请注意前导空格在 Python 语句中是有重要作用的！

@item 
当调用时附带 @code{-m module-name} 时，会在 Python 模块路径中查找指定的模块，并将其作为脚本程序执行。
@end itemize

在非交互模式下，会对全部输入先解析再执行。

一个接口选项会终结解释器所读入的选项列表，后续的所有参数将被放入 @ref{bf4,,sys.argv} -- 请注意其中首个元素即第零项 (@code{sys.argv[0]}) 会是一个表示程序源的字符串。

@geindex command line option; -c <command>
@anchor{using/cmdline cmdoption-c}@anchor{119f}
@deffn {程序选项} @w{-}c <command>

执行 @emph{command} 中的 Python 代码。 @emph{command} 可以为一条或以换行符分隔的多条语句，其中前导空格像在普通模块代码中一样具有作用。

如果给出此选项，@ref{bf4,,sys.argv} 的首个元素将为 @code{"-c"} 并且当前目录将被加入 @ref{482,,sys.path} 的开头（以允许该目录中的模块作为最高层级模块被导入）。

使用 @code{command} 参数会引发 @ref{12d0,,审计事件} @code{cpython.run_command} 。
@end deffn

@geindex command line option; -m <module-name>
@anchor{using/cmdline cmdoption-m}@anchor{330}
@deffn {程序选项} @w{-}m <module@w{-}name>

在 @ref{482,,sys.path} 中搜索指定名称的模块并将其内容作为 @ref{1,,__main__} 模块来执行。

由于该参数为 @emph{module} 名称，你不应给出文件扩展名 (@code{.py})。 模块名称应为绝对有效的 Python 模块名称，但具体实现可能并不总是强制要求这一点（例如它可能允许你使用包含连字符的名称）。

包名称（包括命名空间包）也允许使用。 当所提供的是包名称而非普通模块名称时，解释器将把 @code{<pkg>.__main__} 作为主模块来执行。 此行为特意被设计为与作为脚本参数传递给解释器的目录和 zip 文件的处理方式类似。

@cartouche
@quotation 注解 
此选项不适用于内置模块和以 C 编写的扩展模块，因为它们并没有对应的 Python 模块文件。 但是它仍然适用于预编译的模块，即使没有可用的初始源文件。
@end quotation
@end cartouche

如果给出此选项，@ref{bf4,,sys.argv} 的首个元素将为模块文件的完整路径 (在定位模块文件期间，首个元素将设为 @code{"-m"})。 与 @ref{119f,,-c} 选项一样，当前目录将被加入 @ref{482,,sys.path} 的开头。

@ref{f99,,-I} 选项可用来在隔离模式下运行脚本，此模式中 @ref{482,,sys.path} 既不包含当前目录也不包含用户的 site-packages 目录。 所有 
@geindex PYTHON*
@geindex 环境变量; PYTHON*
@code{PYTHON*} 环境变量也会被忽略。

许多标准库模块都包含作为脚本执行时会被发起调用的代码。 其中的一个例子是 @ref{10b,,timeit} 模块:

@example
python -m timeit -s 'setup here' 'benchmarked code here'
python -m timeit -h # for details
@end example

使用 @code{module-name} 参数会引发 @ref{12d0,,审计事件} @code{cpython.run_module} 。


@subsubheading 参见



@table @asis

@item @ref{12d1,,runpy.run_module()}

Python 代码可以直接使用的等效功能
@end table

@geindex Python 提高建议; PEP 338
PEP 338@footnote{https://www.python.org/dev/peps/pep-0338} -- 将模块作为脚本执行



在 3.1 版更改: 提供包名称来运行 @code{__main__} 子模块。



在 3.4 版更改: 同样支持命名空间包

@end deffn
@anchor{using/cmdline cmdarg-dash}@anchor{12d2}

@deffn {Describe} @w{-}

从标准输入 (@ref{306,,sys.stdin}) 读取命令。 如果标准输入为一个终端，则使用 @ref{e18,,-i}。

如果给出此选项，@ref{bf4,,sys.argv} 的首个元素将为 @code{"-"} 并且当前目录将被加入 @ref{482,,sys.path} 的开头。

没有参数会引发  @ref{12d0,,审计事件} @code{cpython.run_stdin} 。
@end deffn
@anchor{using/cmdline cmdarg-script}@anchor{12d3}

@deffn {Describe} <script>

执行 @emph{script} 中的 Python 代码，该参数应为一个（绝对或相对）文件系统路径，指向某个 Python 文件、包含 @code{__main__.py} 文件的目录，或包含 @code{__main__.py} 文件的 zip 文件。

如果给出此选项，@ref{bf4,,sys.argv} 的首个元素将为在命令行中指定的脚本名称。

如果脚本名称直接指向一个 Python 文件，则包含该文件的目录将被加入 @ref{482,,sys.path} 的开头，并且该文件会被作为 @ref{1,,__main__} 模块来执行。

如果脚本名称指向一个目录或 zip 文件，则脚本名称将被加入 @ref{482,,sys.path} 的开头，并且该位置中的 @code{__main__.py} 文件会被作为 @ref{1,,__main__} 模块来执行。

@ref{f99,,-I} 选项可用来在隔离模式下运行脚本，此模式中 @ref{482,,sys.path} 既不包含脚本所在目录也不包含用户的 site-packages 目录。 所有 
@geindex PYTHON*
@geindex 环境变量; PYTHON*
@code{PYTHON*} 环境变量也会被忽略。

使用 @code{filename} 参数会引发  @ref{12d0,,审计事件} @code{cpython.run_file} 。


@subsubheading 参见



@table @asis

@item @ref{caa,,runpy.run_path()}

Python 代码可以直接使用的等效功能
@end table

@end deffn

如果没有给出接口选项，则使用 @ref{e18,,-i}，@code{sys.argv[0]} 将为空字符串 (@code{""})，并且当前目录会被加入 @ref{482,,sys.path} 的开头。 此外，tab 补全和历史编辑会自动启用，如果你的系统平台支持此功能的话 (参见 @ref{8e0,,Readline configuration})。


@subsubheading 参见


@ref{119b,,调用解释器}



在 3.4 版更改: 自动启用 tab 补全和历史编辑。


@node 通用选项,其他选项,接口选项,命令行
@anchor{using/cmdline generic-options}@anchor{12d4}
@subsubsection 通用选项


@geindex command line option; -?
@geindex command line option; -h
@geindex command line option; --help
@anchor{using/cmdline cmdoption}@anchor{d85}
@deffn {程序选项} @w{-}?
@anchor{using/cmdline cmdoption-h}@anchor{12d5}
@deffnx {程序选项} @w{-}h
@anchor{using/cmdline cmdoption-help}@anchor{d84}
@deffnx {程序选项} @w{-}@w{-}help

打印全部命令行选项的简短描述。
@end deffn

@geindex command line option; -V
@geindex command line option; --version
@anchor{using/cmdline cmdoption-v}@anchor{5cd}
@deffn {程序选项} @w{-}V
@anchor{using/cmdline cmdoption-version}@anchor{5cc}
@deffnx {程序选项} @w{-}@w{-}version

打印 Python 版本号并退出。 示例输出信息如下:

@example
Python 3.8.0b2+
@end example

如果重复给出，则打印有关构建的更多信息，例如:

@example
Python 3.8.0b2+ (3.8:0c076caaa8, Apr 20 2019, 21:55:00)
[GCC 6.2.0 20161005]
@end example


3.6 新版功能: @code{-VV} 选项。

@end deffn

@node 其他选项,不应当使用的选项,通用选项,命令行
@anchor{using/cmdline miscellaneous-options}@anchor{12d6}@anchor{using/cmdline using-on-misc-options}@anchor{926}
@subsubsection 其他选项


@geindex command line option; -b
@anchor{using/cmdline cmdoption-b}@anchor{40d}
@deffn {程序选项} @w{-}b

在将 @ref{32a,,bytes} 或 @ref{32b,,bytearray} 与 @ref{329,,str} 或是将 @ref{32a,,bytes} 与 @ref{184,,int} 比较时发出警告。 如果重复给出该选项 (@code{-bb}) 则会引发错误。


在 3.5 版更改: 影响 @ref{32a,,bytes} 与 @ref{184,,int} 的比较。

@end deffn

@geindex command line option; -B
@anchor{using/cmdline id1}@anchor{d31}
@deffn {程序选项} @w{-}B

如果给出此选项，Python 将不会试图在导入源模块时写入 @code{.pyc} 文件。 另请参阅 
@geindex PYTHONDONTWRITEBYTECODE
@geindex 环境变量; PYTHONDONTWRITEBYTECODE
@ref{d32,,PYTHONDONTWRITEBYTECODE}。
@end deffn

@geindex command line option; --check-hash-based-pycs default|always|never
@anchor{using/cmdline cmdoption-check-hash-based-pycs}@anchor{12d7}
@deffn {程序选项} @w{-}@w{-}check@w{-}hash@w{-}based@w{-}pycs default|always|never

控制基于哈希值的 @code{.pyc} 文件的验证行为。 参见 @ref{322,,已缓存字节码的失效}。 当设为 @code{default} 时，已选定和未选定的基于哈希值的字节码缓存文件将根据其默认语义进行验证。 当设为 @code{always} 时，所有基于哈希值的 @code{.pyc} 文件，不论是已选定还是未选定的都将根据其对应的源文件进行验证。 当设为 @code{never} 时，基于哈希值的 @code{.pyc} 文件将不会根据其对应的源文件进行验证。

基于时间戳的 @code{.pyc} 文件的语义不会受此选项影响。
@end deffn

@geindex command line option; -d
@anchor{using/cmdline cmdoption-d}@anchor{12d8}
@deffn {程序选项} @w{-}d

开启解析器调试输出（限专家使用，依赖于编译选项）。 另请参阅 
@geindex PYTHONDEBUG
@geindex 环境变量; PYTHONDEBUG
@ref{12d9,,PYTHONDEBUG}。
@end deffn

@geindex command line option; -E
@anchor{using/cmdline cmdoption-e}@anchor{f9a}
@deffn {程序选项} @w{-}E

忽略所有 
@geindex PYTHON*
@geindex 环境变量; PYTHON*
@code{PYTHON*} 环境变量，例如可能已设置的 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 和 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME}。
@end deffn

@geindex command line option; -i
@anchor{using/cmdline cmdoption-i}@anchor{e18}
@deffn {程序选项} @w{-}i

当有脚本被作为首个参数传入或使用了 @ref{119f,,-c} 选项时，在执行脚本或命令之后进入交互模式，即使是在 @ref{306,,sys.stdin} 并不是一个终端的时候。 
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP} 文件不会被读取。

这一选项的用处是在脚本引发异常时检查全局变量或者栈跟踪。 另请参阅 
@geindex PYTHONINSPECT
@geindex 环境变量; PYTHONINSPECT
@ref{e17,,PYTHONINSPECT}。
@end deffn

@geindex command line option; -I
@anchor{using/cmdline id2}@anchor{f99}
@deffn {程序选项} @w{-}I

在隔离模式下运行 Python。 这将同时应用 -E 和 -s。 在隔离模式下 @ref{482,,sys.path} 既不包含脚本所在目录也不包含用户的 site-packages 目录。 所有 
@geindex PYTHON*
@geindex 环境变量; PYTHON*
@code{PYTHON*} 环境变量也会被忽略。 还可以施加更进一步的限制以防止用户注入恶意代码。


3.4 新版功能.

@end deffn

@geindex command line option; -O
@anchor{using/cmdline cmdoption-o}@anchor{685}
@deffn {程序选项} @w{-}O

移除 assert 语句以及任何以 @ref{f8d,,__debug__} 的值作为条件的代码。 通过在 @code{.pyc} 扩展名之前添加 @code{.opt-1} 来扩充已编译文件 (@ref{60f,,bytecode}) 的文件名  (参见 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488})。 另请参阅 
@geindex PYTHONOPTIMIZE
@geindex 环境变量; PYTHONOPTIMIZE
@ref{12da,,PYTHONOPTIMIZE}。


在 3.5 版更改: 依据 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} 修改 @code{.pyc} 文件名。

@end deffn

@geindex command line option; -OO
@anchor{using/cmdline cmdoption-oo}@anchor{686}
@deffn {程序选项} @w{-}OO

在启用 @ref{685,,-O} 的同时丢弃文档字符串。 通过在 @code{.pyc} 扩展名之前添加 @code{.opt-2} 来扩展已编译文件 (@ref{60f,,bytecode}) 的文件名 (参见 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488})。


在 3.5 版更改: 依据 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} 修改 @code{.pyc} 文件名。

@end deffn

@geindex command line option; -q
@anchor{using/cmdline cmdoption-q}@anchor{12db}
@deffn {程序选项} @w{-}q

即使在交互模式下也不显示版权和版本信息。


3.2 新版功能.

@end deffn

@geindex command line option; -R
@anchor{using/cmdline cmdoption-r}@anchor{1027}
@deffn {程序选项} @w{-}R

开启哈希随机化。 此选项权 
@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED} 环境变量设置为 @code{0} 时起作用，因为哈希随机化是默认启用的。

在Python的早期版本中，此选项启用哈希随机化，将 str 和 bytes 的对象 @ref{339,,__hash__()} 的值 "加盐" 为不可预测的随机值。虽然它们在单个Python进程中保持不变，但是在重复调用的Python进程之间它们是不可预测的。

哈希随机化旨在针对由精心选择的输入引起的拒绝服务攻击提供防护，这种输入利用了构造 dict 在最坏情况下的性能即 O(n^2) 复杂度。 详情请参阅 @indicateurl{http://www.ocert.org/advisories/ocert-2011-003.html}。

@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED} 允许你为哈希种子密码设置一个固定值。


在 3.7 版更改: 此选项不会再被忽略。



3.2.3 新版功能.

@end deffn

@geindex command line option; -s
@anchor{using/cmdline cmdoption-s}@anchor{d0e}
@deffn {程序选项} @w{-}s

不要将 @ref{12dc,,用户 site-packages 目录} 添加到 @ref{482,,sys.path}。


@subsubheading 参见


@geindex Python 提高建议; PEP 370
PEP 370@footnote{https://www.python.org/dev/peps/pep-0370} -- 分用户的 site-packages 目录

@end deffn

@geindex command line option; -S
@anchor{using/cmdline id3}@anchor{b1d}
@deffn {程序选项} @w{-}S

禁用 @ref{eb,,site} 的导入及其所附带的基于站点对 @ref{482,,sys.path} 的操作。 如果 @ref{eb,,site} 会在稍后被显式地导入也会禁用这些操作 (如果你希望触发它们则应调用 @ref{12dd,,site.main()})。
@end deffn

@geindex command line option; -u
@anchor{using/cmdline cmdoption-u}@anchor{12de}
@deffn {程序选项} @w{-}u

强制 stdout 和 stderr 流不使用缓冲。 此选项对 stdin 流无影响。

另请参阅 
@geindex PYTHONUNBUFFERED
@geindex 环境变量; PYTHONUNBUFFERED
@ref{12df,,PYTHONUNBUFFERED}。


在 3.7 版更改: stdout 和 stderr 流在文本层现在不使用缓冲。

@end deffn

@geindex command line option; -v
@anchor{using/cmdline id4}@anchor{d81}
@deffn {程序选项} @w{-}v

每当一个模块被初始化时打印一条信息，显示其加载位置（文件名或内置模块）。 当重复给出时 (@code{-vv})，为搜索模块时所检查的每个文件都打印一条消息。 此外还提供退出时有关模块清理的信息A。 另请参阅 
@geindex PYTHONVERBOSE
@geindex 环境变量; PYTHONVERBOSE
@ref{12e0,,PYTHONVERBOSE}。
@end deffn
@anchor{using/cmdline using-on-warnings}@anchor{12e1}
@geindex command line option; -W arg
@anchor{using/cmdline cmdoption-w}@anchor{40f}
@deffn {程序选项} @w{-}W arg

警告控制。 Python 的警告机制在默认情况下会向 @ref{308,,sys.stderr} 打印警告消息。 典型的警告消息具有如下形式：

@example
file:line: category: message
@end example

默认情况下，每个警告都对于其发生所在的每个源行都会打印一次。 此选项可控制警告打印的频繁程度。

可以给出多个 @ref{40f,,-W} 选项；当某个警告能与多个选项匹配时，将执行最后一个匹配选项的操作。 无效的 @ref{40f,,-W} 选项将被忽略（但是，在发出第一个警告时会打印有关无效选项的警告消息）。

警告也可以使用 
@geindex PYTHONWARNINGS
@geindex 环境变量; PYTHONWARNINGS
@ref{410,,PYTHONWARNINGS} 环境变量以及使用 @ref{126,,warnings} 模块在 Python 程序内部进行控制。

最简单的设置是将某个特定操作无条件地应用于进程所发出所有警告 (即使是在默认情况下会忽略的那些警告):

@example
-Wdefault  # Warn once per call location
-Werror    # Convert to exceptions
-Walways   # Warn every time
-Wmodule   # Warn once per calling module
-Wonce     # Warn once per Python process
-Wignore   # Never warn
@end example

操作名称可以根据需要进行缩写 (例如 @code{-Wi}, @code{-Wd}, @code{-Wa}, @code{-We})，解释器将会把它们解析为适当的操作名称。

请参阅 @ref{12e2,,The Warnings Filter} 和 @ref{12e3,,Describing Warning Filters} 了解更多细节。
@end deffn

@geindex command line option; -x
@anchor{using/cmdline cmdoption-x}@anchor{12e4}
@deffn {程序选项} @w{-}x

跳过源中第一行，以允许使用非 Unix 形式的 @code{#!cmd}。 这适用于 DOS 专属的破解操作。
@end deffn

@geindex command line option; -X
@anchor{using/cmdline id5}@anchor{155}
@deffn {程序选项} @w{-}X

保留用于各种具体实现专属的选项。 CPython 目前定义了下列可用的值：


@itemize *

@item 
@code{-X faulthandler} 启用 @ref{7d,,faulthandler}；

@item 
@code{-X showrefcount} 当程序结束或在交互解释器中的每条语句之后输出总引用计数和已使用内存块计数。 此选项仅在调试版本中有效。

@item 
@code{-X tracemalloc} 使用 @ref{114,,tracemalloc} 模块启动对 Python 内存分配的跟踪。 默认情况下，只有最近的帧会保存在跟踪的回溯信息中。 使用 @code{-X tracemalloc=NFRAME} 以启动限定回溯 @emph{NFRAME} 帧的跟踪。 请参阅 @ref{12e5,,tracemalloc.start()} 了解详情。

@item 
@code{-X showalloccount} 当程序结束时输出每种类型的已分配对象的总数。 此选项仅当 Python 在定义了 @code{COUNT_ALLOCS} 后构建时才会生效。

@item 
@code{-X importtime} 显示每次导入耗费的时间。 它会显示模块名称，累计时间（包括嵌套的导入）和自身时间（排除嵌套的导入）。 请注意它的输出在多线程应用程序中可能会出错。 典型用法如 @code{python3 -X importtime -c 'import asyncio'}。 另请参阅 
@geindex PYTHONPROFILEIMPORTTIME
@geindex 环境变量; PYTHONPROFILEIMPORTTIME
@ref{331,,PYTHONPROFILEIMPORTTIME}。

@item 
@code{-X dev}: 启用 CPython 的“开发模式”，引入额外的运行时检测，这些检测因开销过大而无法默认启用。 如果代码是正确的则它不会比默认输出更详细：新增警告只会在发现问题时才会发出。 开发模式的作用效果：


@itemize *

@item 
添加 @code{default} 警告过滤器，即 @ref{40f,,-W} @code{default}。

@item 
在内存分配器上安装调试钩子：参见 @ref{504,,PyMem_SetupDebugHooks()} C 函数。

@item 
启用 @ref{7d,,faulthandler} 模块以在发生崩溃时转储 Python 回溯信息。

@item 
启用 @ref{12e6,,asyncio 调试模式}。

@item 
将 @ref{b35,,sys.flags} 的 @code{dev_mode} 属性设为 @code{True}。

@item 
@ref{1db,,io.IOBase} 析构函数记录 @code{close()} 异常。
@end itemize

@item 
@code{-X utf8} 为操作系统接口启用 UTF-8 模式，覆盖默认的区域感知模式。 @code{-X utf8=0} 显式地禁用 UTF-8 模式（即使在它应当被自动激活的时候）。 请参阅 
@geindex PYTHONUTF8
@geindex 环境变量; PYTHONUTF8
@ref{30a,,PYTHONUTF8} 了解详情。

@item 
@code{-X pycache_prefix=PATH} 允许将 @code{.pyc} 文件写入以给定目录为根的并行树，而不是代码树。另见 
@geindex PYTHONPYCACHEPREFIX
@geindex 环境变量; PYTHONPYCACHEPREFIX
@ref{154,,PYTHONPYCACHEPREFIX} 。
@end itemize

它还允许传入任意值并通过 @ref{12e7,,sys._xoptions} 字典来提取这些值。


在 3.2 版更改: 增加了 @ref{155,,-X} 选项。



3.3 新版功能: @code{-X faulthandler} 选项。



3.4 新版功能: @code{-X showrefcount} 与 @code{-X tracemalloc} 选项。



3.6 新版功能: @code{-X showalloccount} 选项。



3.7 新版功能: @code{-X importtime}, @code{-X dev} 与 @code{-X utf8} 选项。



3.8 新版功能: @code{-X pycache_prefix} 选项。 @code{-X dev} 选项现在在 @ref{1db,,io.IOBase} 析构函数中记录 @code{close()} 异常。

@end deffn

@node 不应当使用的选项,,其他选项,命令行
@anchor{using/cmdline options-you-shouldn-t-use}@anchor{12e8}
@subsubsection 不应当使用的选项


@geindex command line option; -J
@anchor{using/cmdline cmdoption-j}@anchor{d30}
@deffn {程序选项} @w{-}J

保留给 Jython@footnote{http://www.jython.org/} 使用。
@end deffn

@node 环境变量,,命令行,命令行与环境
@anchor{using/cmdline environment-variables}@anchor{12e9}@anchor{using/cmdline using-on-envvars}@anchor{12ea}
@subsection 环境变量


这些环境变量会影响 Python 的行为，它们是在命令行开关之前被处理的，但 -E 或 -I 除外。 根据约定，当存在冲突时命令行开关会覆盖环境变量的设置。

@geindex 环境变量; PYTHONHOME
@anchor{using/cmdline envvar-PYTHONHOME}@anchor{4d0}
@deffn {环境变量} PYTHONHOME

更改标准 Python 库的位置。 默认情况下库是在 @code{@emph{prefix}/lib/python@emph{version}} 和 @code{@emph{exec_prefix}/lib/python@emph{version}} 中搜索，其中 @code{@emph{prefix}} 和 @code{@emph{exec_prefix}} 是由安装位置确定的目录，默认都位于 @code{/usr/local}。

当 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} 被设为单个目录时，它的值会同时替代 @code{@emph{prefix}} 和 @code{@emph{exec_prefix}}。 要为两者指定不同的值，请将 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} 设为 @code{@emph{prefix}:@emph{exec_prefix}}。
@end deffn

@geindex 环境变量; PYTHONPATH
@anchor{using/cmdline envvar-PYTHONPATH}@anchor{94d}
@deffn {环境变量} PYTHONPATH

增加模块文件默认搜索路径。 所用格式与终端的 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 相同：一个或多个由 @ref{12eb,,os.pathsep} 分隔的目录路径名称（例如 Unix 上用冒号而在 Windows 上用分号）。 默认忽略不存在的目录。

除了普通目录之外，单个 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 条目可以引用包含纯Python模块的zip文件（源代码或编译形式）。无法从zip文件导入扩展模块。

默认索引路径依赖于安装路径，但通常都是以 @code{@emph{prefix}/lib/python@emph{version}} 开始 (参见上文中的 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME})。 它 @emph{总是} 会被添加到 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH}。

有一个附加目录将被插入到索引路径的 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 之前，正如上文中 @ref{12cf,,接口选项} 所描述的。 搜索路径可以在 Python 程序内作为变量 @ref{482,,sys.path} 来进行操作。
@end deffn

@geindex 环境变量; PYTHONSTARTUP
@anchor{using/cmdline envvar-PYTHONSTARTUP}@anchor{8df}
@deffn {环境变量} PYTHONSTARTUP

这如果是一个可读文件的名称，该文件中的 Python 命令会在交互模式的首个提示符显示之前被执行。 该文件会在与交互式命令执行所在的同一命名空间中被执行，因此其中所定义或导入的对象可以在交互式会话中无限制地使用。 你还可以在这个文件中修改提示符 @ref{12ec,,sys.ps1} 和 @ref{12ed,,sys.ps2} 以及钩子 @ref{8de,,sys.__interactivehook__}。

使用 @code{filename} 参数会引发 @ref{12d0,,审计事件} @code{cpython.run_startup} 。
@end deffn

@geindex 环境变量; PYTHONOPTIMIZE
@anchor{using/cmdline envvar-PYTHONOPTIMIZE}@anchor{12da}
@deffn {环境变量} PYTHONOPTIMIZE

这如果被设为一个非空字符串，它就相当于指定 @ref{685,,-O} 选项。 如果设为一个整数，则它就相当于多次指定 @ref{685,,-O}。
@end deffn

@geindex 环境变量; PYTHONBREAKPOINT
@anchor{using/cmdline envvar-PYTHONBREAKPOINT}@anchor{30d}
@deffn {环境变量} PYTHONBREAKPOINT

此变量如果被设定，它会使用加点号的路径标记一个可调用对象。 包含该可调用对象的模块将被导入，随后该可调用对象将由 @ref{30c,,sys.breakpointhook()} 的默认实现来运行，后者自身将由内置的 @ref{2f2,,breakpoint()} 来调用。 如果未设定，或设定为空字符串，则它相当于值 "pdb.set_trace"。 将此变量设为字符串 "0" 会导致 @ref{30c,,sys.breakpointhook()} 的默认实现不做任何事而直接返回。


3.7 新版功能.

@end deffn

@geindex 环境变量; PYTHONDEBUG
@anchor{using/cmdline envvar-PYTHONDEBUG}@anchor{12d9}
@deffn {环境变量} PYTHONDEBUG

此变量如果被设为一个非空字符串，它就相当于指定 @ref{12d8,,-d} 选项。 如果设为一个整数，则它就相当于多次指定 @ref{12d8,,-d}。
@end deffn

@geindex 环境变量; PYTHONINSPECT
@anchor{using/cmdline envvar-PYTHONINSPECT}@anchor{e17}
@deffn {环境变量} PYTHONINSPECT

此变量如果被设为一个非空字符串，它就相当于指定 @ref{e18,,-i} 选项。

此变量也可由 Python 代码使用 @ref{b30,,os.environ} 来修改以在程序终结时强制检查模式。
@end deffn

@geindex 环境变量; PYTHONUNBUFFERED
@anchor{using/cmdline envvar-PYTHONUNBUFFERED}@anchor{12df}
@deffn {环境变量} PYTHONUNBUFFERED

此变量如果被设为一个非空字符串，它就相当于指定 @ref{12de,,-u} 选项。
@end deffn

@geindex 环境变量; PYTHONVERBOSE
@anchor{using/cmdline envvar-PYTHONVERBOSE}@anchor{12e0}
@deffn {环境变量} PYTHONVERBOSE

此变量如果被设为一个非空字符串，它就相当于指定 @ref{d81,,-v} 选项。 如果设为一个整数，则它就相当于多次指定 @ref{d81,,-v}。
@end deffn

@geindex 环境变量; PYTHONCASEOK
@anchor{using/cmdline envvar-PYTHONCASEOK}@anchor{e56}
@deffn {环境变量} PYTHONCASEOK

如果设置此变量，Python 将忽略 @ref{c16,,import} 语句中的大小写。 这仅在 Windows 和 OS X 上有效。
@end deffn

@geindex 环境变量; PYTHONDONTWRITEBYTECODE
@anchor{using/cmdline envvar-PYTHONDONTWRITEBYTECODE}@anchor{d32}
@deffn {环境变量} PYTHONDONTWRITEBYTECODE

此变量如果被设为一个非空字符串，Python 将不会尝试在导入源模块时写入 @code{.pyc} 文件。 这相当于指定 @ref{d31,,-B} 选项。
@end deffn

@geindex 环境变量; PYTHONPYCACHEPREFIX
@anchor{using/cmdline envvar-PYTHONPYCACHEPREFIX}@anchor{154}
@deffn {环境变量} PYTHONPYCACHEPREFIX

如果设置了此选项，Python将在镜像目录树中的此路径中写入 @code{.pyc} 文件，而不是源树中的 @code{__pycache__} 目录中。这相当于指定 @ref{155,,-X} @code{pycache_prefix=PATH} 选项。


3.8 新版功能.

@end deffn

@geindex 环境变量; PYTHONHASHSEED
@anchor{using/cmdline envvar-PYTHONHASHSEED}@anchor{9bf}
@deffn {环境变量} PYTHONHASHSEED

如果此变量未设置或设为 @code{random}，将使用一个随机值作为 str 和 bytes 对象哈希运算的种子。

如果 
@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED} 被设为一个整数值，它将被作为固定的种子数用来生成哈希随机化所涵盖的类型的 hash() 结果。

它的目的是允许可复现的哈希运算，例如用于解释器本身的自我检测，或允许一组 python 进程共享哈希值。

该整数必须为一个 [0,4294967295] 范围内的十进制数。 指定数值 0 将禁用哈希随机化。


3.2.3 新版功能.

@end deffn

@geindex 环境变量; PYTHONIOENCODING
@anchor{using/cmdline envvar-PYTHONIOENCODING}@anchor{929}
@deffn {环境变量} PYTHONIOENCODING

如果此变量在运行解释器之前被设置，它会覆盖通过 @code{encodingname:errorhandler} 语法设置的 stdin/stdout/stderr 所用编码。 @code{encodingname} 和 @code{:errorhandler} 部分都是可选项，与在 @ref{c30,,str.encode()} 中的含义相同。

对于 stderr，@code{:errorhandler} 部分会被忽略；处理程序将总是为 @code{'backslashreplace'}。


在 3.4 版更改: “encodingname” 部分现在是可选的。



在 3.6 版更改: 在 Windows 上，对于交互式控制台缓冲区会忽略此变量所指定的编码，除非还指定了 
@geindex PYTHONLEGACYWINDOWSSTDIO
@geindex 环境变量; PYTHONLEGACYWINDOWSSTDIO
@ref{4f4,,PYTHONLEGACYWINDOWSSTDIO}。 通过标准流重定向的文件和管道则不受其影响。

@end deffn

@geindex 环境变量; PYTHONNOUSERSITE
@anchor{using/cmdline envvar-PYTHONNOUSERSITE}@anchor{d0f}
@deffn {环境变量} PYTHONNOUSERSITE

如果设置了此变量，Python 将不会把 @ref{12dc,,用户 site-packages 目录} 添加到 @ref{482,,sys.path}。


@subsubheading 参见


@geindex Python 提高建议; PEP 370
PEP 370@footnote{https://www.python.org/dev/peps/pep-0370} -- 分用户的 site-packages 目录

@end deffn

@geindex 环境变量; PYTHONUSERBASE
@anchor{using/cmdline envvar-PYTHONUSERBASE}@anchor{d0d}
@deffn {环境变量} PYTHONUSERBASE

定义 @ref{12ee,,用户基准目录}，它会在执行 @code{python setup.py install --user} 时被用来计算 @ref{12dc,,用户 site-packages 目录} 的路径以及 @ref{12ef,,Distutils 安装路径}。


@subsubheading 参见


@geindex Python 提高建议; PEP 370
PEP 370@footnote{https://www.python.org/dev/peps/pep-0370} -- 分用户的 site-packages 目录

@end deffn

@geindex 环境变量; PYTHONEXECUTABLE
@anchor{using/cmdline envvar-PYTHONEXECUTABLE}@anchor{12f0}
@deffn {环境变量} PYTHONEXECUTABLE

如果设置了此环境变量，则 @code{sys.argv[0]} 将被设为此变量的值而不是通过 C 运行时所获得的值。 仅在 Mac OS X 上起作用。
@end deffn

@geindex 环境变量; PYTHONWARNINGS
@anchor{using/cmdline envvar-PYTHONWARNINGS}@anchor{410}
@deffn {环境变量} PYTHONWARNINGS

此变量等价于 @ref{40f,,-W} 选项。 如果被设为一个以逗号分隔的字符串，它就相当于多次指定 @ref{40f,,-W}，列表中后出现的过滤器优先级会高于列表中先出现的。

最简单的设置是将某个特定操作无条件地应用于进程所发出所有警告 (即使是在默认情况下会忽略的那些警告):

@example
PYTHONWARNINGS=default  # Warn once per call location
PYTHONWARNINGS=error    # Convert to exceptions
PYTHONWARNINGS=always   # Warn every time
PYTHONWARNINGS=module   # Warn once per calling module
PYTHONWARNINGS=once     # Warn once per Python process
PYTHONWARNINGS=ignore   # Never warn
@end example

请参阅 @ref{12e2,,The Warnings Filter} 和 @ref{12e3,,Describing Warning Filters} 了解更多细节。
@end deffn

@geindex 环境变量; PYTHONFAULTHANDLER
@anchor{using/cmdline envvar-PYTHONFAULTHANDLER}@anchor{9c2}
@deffn {环境变量} PYTHONFAULTHANDLER

如果此环境变量被设为一个非空字符串，@ref{543,,faulthandler.enable()} 会在启动时被调用：为 @code{SIGSEGV}, @code{SIGFPE}, @code{SIGABRT}, @code{SIGBUS} 和 @code{SIGILL} 等信号安装一个处理句柄以转储 Python 回溯信息。 此变量等价于 @ref{155,,-X} @code{faulthandler} 选项。


3.3 新版功能.

@end deffn

@geindex 环境变量; PYTHONTRACEMALLOC
@anchor{using/cmdline envvar-PYTHONTRACEMALLOC}@anchor{12f1}
@deffn {环境变量} PYTHONTRACEMALLOC

如果此环境变量被设为一个非空字符串，则会使用 @ref{114,,tracemalloc} 模块启动对 Python 内存分配的跟踪。 该变量的值是保存于跟踪的回溯信息中的最大帧数。 例如，@code{PYTHONTRACEMALLOC=1} 只保存最近的帧。 请参阅 @ref{12e5,,tracemalloc.start()} 了解详情。


3.4 新版功能.

@end deffn

@geindex 环境变量; PYTHONPROFILEIMPORTTIME
@anchor{using/cmdline envvar-PYTHONPROFILEIMPORTTIME}@anchor{331}
@deffn {环境变量} PYTHONPROFILEIMPORTTIME

如果此变量被设为一个非空字符串，Python 将显示每次导入花费了多长时间。 此变量完全等价于在命令行为设置 @code{-X importtime}。


3.7 新版功能.

@end deffn

@geindex 环境变量; PYTHONASYNCIODEBUG
@anchor{using/cmdline envvar-PYTHONASYNCIODEBUG}@anchor{12f2}
@deffn {环境变量} PYTHONASYNCIODEBUG

如果此变量被设为一个非空字符串，则会启用 @ref{a,,asyncio} 模块的 @ref{12e6,,调试模式}。


3.4 新版功能.

@end deffn

@geindex 环境变量; PYTHONMALLOC
@anchor{using/cmdline envvar-PYTHONMALLOC}@anchor{4fd}
@deffn {环境变量} PYTHONMALLOC

设置 Python 内存分配器和/或安装调试钩子。

设置 Python 所使用的内存分配器族群：


@itemize *

@item 
@code{default}: 使用 @ref{12f3,,默认内存分配器}。

@item 
@code{malloc}: 对所有域 (@ref{12f4,,PYMEM_DOMAIN_RAW}, @ref{503,,PYMEM_DOMAIN_MEM}, @ref{501,,PYMEM_DOMAIN_OBJ}) 使用 C 库的 @code{malloc()} 函数。

@item 
@code{pymalloc}: 对 @ref{503,,PYMEM_DOMAIN_MEM} 和 @ref{501,,PYMEM_DOMAIN_OBJ} 域使用 @ref{5bc,,pymalloc 分配器} 而对 @ref{12f4,,PYMEM_DOMAIN_RAW} 域使用 @code{malloc()} 函数。
@end itemize

安装调试钩子：


@itemize *

@item 
@code{debug}: 在 @ref{12f3,,默认内存分配器} 之上安装调试钩子。

@item 
@code{malloc_debug}: 与 @code{malloc} 相同但还会安装调试钩子。

@item 
@code{pymalloc_debug}: 与 @code{pymalloc} 相同但还会安装调试钩子。
@end itemize

请参阅 @ref{12f3,,默认内存分配器} 以及 @ref{504,,PyMem_SetupDebugHooks()} 函数（在 Python 内存分配器之上安装调试钩子）。


在 3.7 版更改: 增加了 @code{"default"} 分配器。



3.6 新版功能.

@end deffn

@geindex 环境变量; PYTHONMALLOCSTATS
@anchor{using/cmdline envvar-PYTHONMALLOCSTATS}@anchor{10f5}
@deffn {环境变量} PYTHONMALLOCSTATS

如果设为一个非空字符串，Python 将在每次创建新的 pymalloc 对象区域以及在关闭时打印 @ref{5bc,,pymalloc 内存分配器} 的统计信息。

如果 
@geindex PYTHONMALLOC
@geindex 环境变量; PYTHONMALLOC
@ref{4fd,,PYTHONMALLOC} 环境变量被用来强制开启 C 库的 @code{malloc()} 分配器，或者如果 Python 的配置不支持 @code{pymalloc}，则此变量将被忽略。


在 3.6 版更改: 此变量现在也可以被用于在发布模式下编译的 Python。 如果它被设置为一个空字符串则将没有任何效果。

@end deffn

@geindex 环境变量; PYTHONLEGACYWINDOWSFSENCODING
@anchor{using/cmdline envvar-PYTHONLEGACYWINDOWSFSENCODING}@anchor{4f1}
@deffn {环境变量} PYTHONLEGACYWINDOWSFSENCODING

如果设为一个非空字符串，则默认的文件系统编码和错误模式将分别恢复为它们在 3.6 版之前的值 'mbcs' 和 'replace'。 否则会使用新的默认值 'utf-8' 和 'surrogatepass'。

这也可以在运行时通过 @ref{4f2,,sys._enablelegacywindowsfsencoding()} 来启用。

@ref{12f5,,可用性}: Windows。


3.6 新版功能: 有关更多详细信息，请参阅 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529}。

@end deffn

@geindex 环境变量; PYTHONLEGACYWINDOWSSTDIO
@anchor{using/cmdline envvar-PYTHONLEGACYWINDOWSSTDIO}@anchor{4f4}
@deffn {环境变量} PYTHONLEGACYWINDOWSSTDIO

如果设为一个非空字符串，则不使用新的控制台读取器和写入器。 这意味着 Unicode 字符将根据活动控制台的代码页进行编码，而不是使用 utf-8。

如果标准流被重定向（到文件或管道）而不是指向控制台缓冲区则该变量会被忽略。

@ref{12f5,,可用性}: Windows。


3.6 新版功能.

@end deffn

@geindex 环境变量; PYTHONCOERCECLOCALE
@anchor{using/cmdline envvar-PYTHONCOERCECLOCALE}@anchor{305}
@deffn {环境变量} PYTHONCOERCECLOCALE

如果值设为 @code{0}，将导致主 Python 命令行应用跳过将传统的基于 ASCII 的 C 与 POSIX 区域设置强制转换为更强大的基于 UTF-8 的替代方案。

如果此变量 @emph{未被} 设置（或被设为 @code{0} 以外的值），则覆盖环境变量的 @code{LC_ALL} 区域选项也不会被设置，并且报告给 @code{LC_CTYPE} 类别的当前区域选项或者为默认的 @code{C} 区域，或者为显式指明的基于 ASCII 的 @code{POSIX} 区域，然后 Python CLI 将在加载解释器运行时之前尝试为 @code{LC_CTYPE} 类别按指定的顺序配置下列区域选项：


@itemize *

@item 
@code{C.UTF-8}

@item 
@code{C.utf8}

@item 
@code{UTF-8}
@end itemize

如果成功设置了以上区域类别中的一个，则初始化 Python 运行时之前也将在当前进程环境中相应地设置 @code{LC_CTYPE} 环境变量。 这会确保除了解释器本身和运行于同一进程中的其他可感知区域选项的组件 (例如 GNU @code{readline} 库) 之外，还能在子进程 (无论这些进程是否在运行 Python 解释器) 以及在查询环境而非当前 C 区域的操作 (例如 Python 自己的 @ref{12f6,,locale.getdefaultlocale()}) 中看到更新的设置。

(显式地或通过上述的隐式区域强制转换) 配置其中一个区域选项将自动为 @ref{306,,sys.stdin} 和 @ref{307,,sys.stdout} 启用 @code{surrogateescape} @ref{12f7,,错误处理句柄} (@ref{308,,sys.stderr} 会继续使用 @code{backslashreplace} 如同在任何其他区域选项中一样)。 这种流处理行为可以按通常方式使用 
@geindex PYTHONIOENCODING
@geindex 环境变量; PYTHONIOENCODING
@ref{929,,PYTHONIOENCODING} 来覆盖。

出于调试目的，如果激活了区域强制转换，或者如果当 Python 运行时被初始化时某个 @emph{应该} 触发强制转换的区域选项仍处于激活状态则设置 @code{PYTHONCOERCECLOCALE=warn} 将导致 Python 在 @code{stderr} 上发出警告消息。

还要注意，即使在区域转换转换被禁用，或者在其无法找到合适的目标区域时，默认 
@geindex PYTHONUTF8
@geindex 环境变量; PYTHONUTF8
@ref{30a,,PYTHONUTF8} 仍将在传统的基于 ASCII 的区域中被激活。 必须同时禁用这两项特性以强制解释器使用 @code{ASCII} 而不是 @code{UTF-8} 作为系统接口。

@ref{12f5,,可用性}: *nix。


3.7 新版功能: 请参阅 
@geindex Python 提高建议; PEP 538
PEP 538@footnote{https://www.python.org/dev/peps/pep-0538} 了解详情。

@end deffn

@geindex 环境变量; PYTHONDEVMODE
@anchor{using/cmdline envvar-PYTHONDEVMODE}@anchor{325}
@deffn {环境变量} PYTHONDEVMODE

如果此环境变量被设为一个非空字符串，则会启用 CPython “开发模式”。 参见 @ref{155,,-X} @code{dev} 选项。


3.7 新版功能.

@end deffn

@geindex 环境变量; PYTHONUTF8
@anchor{using/cmdline envvar-PYTHONUTF8}@anchor{30a}
@deffn {环境变量} PYTHONUTF8

如果设为 @code{1}，则会启用解释器的 UTF-8 模式，将 @code{UTF-8} 用作系统接口的文本编码，无论当前区域选项如何设置。

这意味着：

@quotation


@itemize *

@item 
@ref{4f0,,sys.getfilesystemencoding()} 将返回 @code{'UTF-8'} (本地编码会被忽略)。

@item 
@ref{39d,,locale.getpreferredencoding()} 将返回 @code{'UTF-8'} (本地编码会被忽略，并且该函数的 @code{do_setlocale} 参数不起作用)。

@item 
@ref{306,,sys.stdin}, @ref{307,,sys.stdout} 和 @ref{308,,sys.stderr} 都将 UTF-8 用作它们的文本编码，并且为 @ref{306,,sys.stdin} 和 @ref{307,,sys.stdout} 启用 @code{surrogateescape} @ref{12f7,,错误处理句柄} (@ref{308,,sys.stderr} 会继续使用 @code{backslashreplace} 如同在默认的局部感知模式下一样)
@end itemize
@end quotation

作为低层级 API 发生改变的结果，其他高层级 API 也会表现出不同的默认行为：

@quotation


@itemize *

@item 
命令行参数，环境变量和文件名会使用 UTF-8 编码来解码为文本。

@item 
@ref{4e8,,os.fsdecode()} 和 @ref{4e9,,os.fsencode()} 会使用 UTF-8 编码。

@item 
@ref{4ea,,open()}, @ref{654,,io.open()} 和 @ref{12f8,,codecs.open()} 默认会使用 UTF-8 编码。 但是，它们默认仍将使用严格错误处理句柄，因此试图在文本模式下打开二进制文件将可能引发异常，而不是生成无意义的数据。
@end itemize
@end quotation

请注意 UTF-8 模式下的标准流设置可以被 
@geindex PYTHONIOENCODING
@geindex 环境变量; PYTHONIOENCODING
@ref{929,,PYTHONIOENCODING} 所覆盖（在默认的区域感知模式下也同样如此）。

如果设置为“0”，则解释器以其默认的区域识别模式运行。

设置任何其他非空字符串会在解释器初始化期间导致错误。

如果根本未设置此环境变量，则解释器默认使用当前区域设置，@emph{除非} 当前区域被标识为基于 ASCII 的旧式区域设置（如 
@geindex PYTHONCOERCECLOCALE
@geindex 环境变量; PYTHONCOERCECLOCALE
@ref{305,,PYTHONCOERCECLOCALE} 所述），并且区域强制转换被禁用或失败。 在此类旧式区域设置中，解释器将默认启用 UTF-8 模式，除非显式地指定不这样做。

也可以使用 @ref{155,,-X} @code{utf8} 选项。


3.7 新版功能: 有关更多详细信息，请参阅 
@geindex Python 提高建议; PEP 540
PEP 540@footnote{https://www.python.org/dev/peps/pep-0540} 。

@end deffn

@menu
* 调试模式变量:: 

@end menu

@node 调试模式变量,,,环境变量
@anchor{using/cmdline debug-mode-variables}@anchor{12f9}
@subsubsection 调试模式变量


设置这些变量只会在Python的调试版本中产生影响。

@geindex 环境变量; PYTHONTHREADDEBUG
@anchor{using/cmdline envvar-PYTHONTHREADDEBUG}@anchor{12fa}
@deffn {环境变量} PYTHONTHREADDEBUG

如果设置，Python将打印线程调试信息。

需要使用 @code{--with-pydebug} 构建选项配置Python。
@end deffn

@geindex 环境变量; PYTHONDUMPREFS
@anchor{using/cmdline envvar-PYTHONDUMPREFS}@anchor{159}
@deffn {环境变量} PYTHONDUMPREFS

如果设置，Python在关闭解释器，及转储对象和引用计数后仍将保持活动。

需要使用 @code{--with-trace-refs} 构建选项配置Python。
@end deffn

@node 在类Unix环境下使用Python,在Windows上使用 Python,命令行与环境,Python安装和使用
@anchor{using/unix doc}@anchor{12fb}@anchor{using/unix using-on-unix}@anchor{12fc}@anchor{using/unix using-python-on-unix-platforms}@anchor{12fd}
@section 在类Unix环境下使用Python


@menu
* 获得并安装Python的最新版本:: 
* 构建Python:: 
* 与Python相关的路径和文件:: 
* 杂项:: 

@end menu

@node 获得并安装Python的最新版本,构建Python,,在类Unix环境下使用Python
@anchor{using/unix getting-and-installing-the-latest-version-of-python}@anchor{12fe}
@subsection 获得并安装Python的最新版本


@menu
* 在Linux中:: 
* 在FreeBSD和OpenBSD上:: 
* 在OpenSolaris系统上:: 

@end menu

@node 在Linux中,在FreeBSD和OpenBSD上,,获得并安装Python的最新版本
@anchor{using/unix on-linux}@anchor{12ff}
@subsubsection 在Linux中


Python预装在大多数Linux发行版上，并作为一个包提供给所有其他用户。 但是，您可能想要使用的某些功能在发行版提供的软件包中不可用。这时您可以从源代码轻松编译最新版本的Python。

如果Python没有预先安装并且不在发行版提供的库中，您可以轻松地为自己使用的发行版创建包。 参阅以下链接：


@subsubheading 参见



@table @asis

@item @indicateurl{https://www.debian.org/doc/manuals/maint-guide/first.en.html}

对于Debian用户

@item @indicateurl{https://en.opensuse.org/Portal:Packaging}

对于OpenSuse用户

@item @indicateurl{https://docs-old.fedoraproject.org/en-US/Fedora_Draft_Documentation/0.1/html/RPM_Guide/ch-creating-rpms.html}

对于Fedora用户

@item @indicateurl{http://www.slackbook.org/html/package-management-making-packages.html}

对于Slackware用户
@end table


@node 在FreeBSD和OpenBSD上,在OpenSolaris系统上,在Linux中,获得并安装Python的最新版本
@anchor{using/unix on-freebsd-and-openbsd}@anchor{1300}
@subsubsection 在FreeBSD和OpenBSD上



@itemize *

@item 
FreeBSD用户，使用以下命令添加包:

@example
pkg install python3
@end example

@item 
OpenBSD用户，使用以下命令添加包:

@example
pkg_add -r python

pkg_add ftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/<insert your architecture here>/python-<version>.tgz
@end example

例如：i386用户获取Python 2.5.1的可用版本:

@example
pkg_add ftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/i386/python-2.5.1p2.tgz
@end example
@end itemize

@node 在OpenSolaris系统上,,在FreeBSD和OpenBSD上,获得并安装Python的最新版本
@anchor{using/unix on-opensolaris}@anchor{1301}
@subsubsection 在OpenSolaris系统上


你可以从 OpenCSW@footnote{https://www.opencsw.org/} 获取、安装及使用各种版本的Python。比如 @code{pkgutil -i python27} 。

@node 构建Python,与Python相关的路径和文件,获得并安装Python的最新版本,在类Unix环境下使用Python
@anchor{using/unix building-python}@anchor{1302}@anchor{using/unix building-python-on-unix}@anchor{7ed}
@subsection 构建Python


如果你想自己编译CPython，首先要做的是获取 source@footnote{https://www.python.org/downloads/source/} 。您可以下载最新版本的源代码，也可以直接提取最新的 clone@footnote{https://devguide.python.org/setup/#getting-the-source-code} 。 （如果你想要制作补丁，则需要克隆代码。）

构建过程由常用命令组成：

@example
./configure
make
make install
@end example

特定Unix平台的配置选项和注意事项通常记录在Python源代码的根目录下的 README.rst@footnote{https://github.com/python/cpython/tree/3.8/README.rst} 文件中。

@cartouche
@quotation 警告 
@code{make install} 可以覆盖或伪装 @code{python3} 二进制文件。因此，建议使用 @code{make altinstall} 而不是 @code{make install} ，因为后者只安装了 @code{@emph{exec_prefix}/bin/python@emph{version}} 。
@end quotation
@end cartouche

@node 与Python相关的路径和文件,杂项,构建Python,在类Unix环境下使用Python
@anchor{using/unix python-related-paths-and-files}@anchor{1303}
@subsection 与Python相关的路径和文件


这取决于本地安装惯例； 
@geindex prefix
@geindex 环境变量; prefix
@code{prefix} （ @code{$@{prefix@}} ）和 
@geindex exec_prefix
@geindex 环境变量; exec_prefix
@code{exec_prefix} （ @code{$@{exec_prefix@}} ）  取决于安装，应解释为GNU软件；它们可能相同。

例如，在大多数Linux系统上，两者的默认值是 @code{/usr} 。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

文件/目录

@tab

含义

@item

@code{@emph{exec_prefix}/bin/python3}

@tab

解释器的推荐位置

@item

@code{@emph{prefix}/lib/python@emph{version}},
@code{@emph{exec_prefix}/lib/python@emph{version}}

@tab

包含标准模块的目录的推荐位置

@item

@code{@emph{prefix}/include/python@emph{version}},
@code{@emph{exec_prefix}/include/python@emph{version}}

@tab

包含开发Python扩展和嵌入解释器所需的include文件的目录的推荐位置

@end multitable


@node 杂项,,与Python相关的路径和文件,在类Unix环境下使用Python
@anchor{using/unix miscellaneous}@anchor{1304}
@subsection 杂项


要在Unix上使用Python脚本，需要添加可执行权限，例如：

@example
$ chmod +x script
@end example

并在脚本的顶部放置一个合适的Shebang线。一个很好的选择通常是:

@example
#!/usr/bin/env python3
@end example

将在整个 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 中搜索Python解释器。但是，某些Unix系统可能没有 @code{env} 命令，因此可能需要将 @code{/usr/bin/python3} 硬编码为解释器路径。

要在Python脚本中使用shell命令，请查看 @ref{f9,,subprocess} 模块。

@node 在Windows上使用 Python,在苹果系统上使用 Python,在类Unix环境下使用Python,Python安装和使用
@anchor{using/windows doc}@anchor{1305}@anchor{using/windows using-on-windows}@anchor{2d9}@anchor{using/windows using-python-on-windows}@anchor{1306}
@section 在Windows上使用 Python


本文档旨在概述在 Microsoft Windows 上使用 Python 时应了解的特定于 Windows 的行为。

与大多数UNIX系统和服务不同，Windows系统没有预安装Python。多年来CPython 团队已经编译了每一个 发行版@footnote{https://www.python.org/download/releases/} 的Windows安装程序（MSI 包），已便Windows 用户下载和安装。这些安装程序主要用于每个用户单独安装Python时，添加核心解释器和库。安装程序还可以为一台机器的所有用户安装，并且可以为应用程序本地分发提供单独的zip文件。

如 
@geindex Python 提高建议; PEP 11
PEP 11@footnote{https://www.python.org/dev/peps/pep-0011} 中所述，Python 仅支持微软产品支持生命周期内的Windows 版本。这意味着 Python 3.8 支持Windows Vista和更新版本。如果需要Windows XP支持，请安装Python 3.4。

Windows提供了许多不同的安装程序，每个安装程序都有一定的优点和缺点。

@ref{1307,,完整安装程序} 内含所有组件，对于使用Python 进行任何类型项目的开发人员而言，它是最佳选择。

@ref{119c,,Microsoft Store包} 是一个简单的Python 安装，适用于运行脚本和包，以及使用IDLE或其他开发环境。 它需要Windows 10，但可以安全地安装而不会破坏其他程序。 它还提供了许多方便的命令来启动Python及其工具。

@ref{1308,,nuget.org 安装包} 是用于持续集成系统的轻量级安装。它可用于构建Python包或运行脚本，但不可更新且没有用户界面工具。

@ref{1309,,可嵌入的包} 是Python的最小安装包，适合嵌入到更大的应用程序中。

@menu
* 完整安装程序:: 
* Microsoft Store包:: 
* nuget.org 安装包: nuget org 安装包. 
* 可嵌入的包:: 
* 替代捆绑包:: 
* 配置Python:: 
* UTF-8 模式:: 
* 适用于Windows的Python启动器:: 
* 查找模块:: 
* 附加模块:: 
* 在Windows上编译Python:: 
* 其他平台:: 

@end menu

@node 完整安装程序,Microsoft Store包,,在Windows上使用 Python
@anchor{using/windows the-full-installer}@anchor{130a}@anchor{using/windows windows-full}@anchor{1307}
@subsection 完整安装程序


@menu
* 安装步骤:: 
* 删除 MAX_PATH 限制:: 
* 无UI 安装:: 
* 免下载安装:: 
* 修改安装:: 

@end menu

@node 安装步骤,删除 MAX_PATH 限制,,完整安装程序
@anchor{using/windows installation-steps}@anchor{130b}
@subsubsection 安装步骤


四个 Python 3.8 安装程序可供下载 - 32位和64位版本的各有两个。 @emph{web installer} （网络安装包）是一个小的初始化工具，它将在安装过程中，根据需要自动下载所需的组件。 @emph{offline installer} （离线安装包）内含默认安装所需的组件，可选择功能仍需要Internet连接下载。请参阅 @ref{130c,,免下载安装} 以了解在安装过程中避免下载的其他方法。

启动安装程序后，可以选择以下两个选项之一：

@image{python-figures/win_installer,,,,png}

如果选择“Install Now（立即安装）”：


@itemize *

@item 
您 @emph{不} 需要成为管理员（除非需要对C运行库进行系统更新，或者为所有用户安装 @ref{989,,适用于Windows的Python启动器} ）

@item 
Python将安装到您的用户目录中

@item 
@ref{989,,适用于Windows的Python启动器} 将根据第一页底部的选项安装

@item 
将安装标准库，测试套件，启动器和pip

@item 
如果选择将安装目录将添加到 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH}

@item 
快捷方式仅对当前用户可见
@end itemize

选择“自定义安装”将允许您选择：要安装的功能、安装位置、其他选项或安装后的操作。如果要安装调试符号或二进制文件，您需要使用此选项。

如要为全部用户安装，应选择“自定义安装”。在这种情况下:


@itemize *

@item 
您可能需要提供管理凭据或批准

@item 
Python 将安装到Program Files目录中

@item 
@ref{989,,适用于Windows的Python启动器} 将安装到Windows目录中

@item 
安装期间可以选择可选功能

@item 
标准库可以预编译为字节码

@item 
如果选中，安装目录将添加到系统 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH}

@item 
快捷方式所有用户可用
@end itemize

@node 删除 MAX_PATH 限制,无UI 安装,安装步骤,完整安装程序
@anchor{using/windows max-path}@anchor{4cf}@anchor{using/windows removing-the-max-path-limitation}@anchor{130d}
@subsubsection 删除 MAX_PATH 限制


历史上Windows的路径长度限制为260个字符。这意味着长于此的路径将无法解决并导致错误。

在最新版本的Windows中，此限制可以扩展到大约32,000个字符。但需要管理员权限激活 “启用Win32长路径” 组策略，或将注册表值 @code{HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem@@LongPathsEnabled} 设置为 @code{1}。

这允许 @ref{4ea,,open()} 函数，@ref{c4,,os} 模块和大多数其他路径功能接受并返回长度超过 260 个字符的路径。

更改上述选项后，无需进一步配置。


在 3.6 版更改: Python中启用了对长路径的支持。


@node 无UI 安装,免下载安装,删除 MAX_PATH 限制,完整安装程序
@anchor{using/windows install-quiet-option}@anchor{130e}@anchor{using/windows installing-without-ui}@anchor{130f}
@subsubsection 无UI 安装


安装程序UI中的所有选项也可以从命令行指定，允许脚本安装程序在许多机器上复制安装，而无需用户交互。还可以在不禁用UI的情况下设置这些选项，以更改一些默认值。

要完全隐藏安装程序UI并静默安装Python，请使用 @code{/quiet} 选项。要跳过用户交互但仍然显示进度和错误，请使用 @code{/passive} 选项。可以通过 @code{/uninstall} 选项立即开始删除Python  - -   不会显示任何提示。

所有其他选项都传递为 @code{name=value} ，其中值通常是 @code{0} 来禁用某个特性， @code{1} 来启用某个特性或路径。可用选项的完整列表如下所示。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

名称

@tab

描述

@tab

默认值

@item

InstallAllUsers

@tab

为所有用户安装。

@tab

0

@item

TargetDir

@tab

安装目录

@tab

基于InstallAllUsers选择

@item

DefaultAllUsersTargetDir

@tab

为所有用户安装时的默认安装路径

@tab

@code{%ProgramFiles%\Python X.Y} 或 @code{%ProgramFiles(x86)%\Python X.Y}

@item

DefaultJustForMeTargetDir

@tab

仅为当前用户安装时的默认安装路径

@tab

@code{%LocalAppData%\Programs\PythonXY} 或 @code{%LocalAppData%\Programs\PythonXY-32} 或 @code{%LocalAppData%\Programs\PythonXY-64}

@item

DefaultCustomTargetDir

@tab

UI中显示的默认自定义安装目录

@tab

（空）

@item

AssociateFiles

@tab

如果还安装了启动器，则创建文件关联。

@tab

1

@item

CompileAll

@tab

将所有 @code{.py} 文件编译为 @code{.pyc} 。

@tab

0

@item

PrependPath

@tab

将install和Scripts目录添加到 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 以及将 @code{.PY} 添加到 
@geindex PATHEXT
@geindex 环境变量; PATHEXT
@code{PATHEXT}

@tab

0

@item

Shortcuts

@tab

如果已安装，为解释器，文档和IDLE创建快捷方式

@tab

1

@item

Include_doc

@tab

安装Python手册

@tab

1

@item

Include_debug

@tab

安装调试二进制文件

@tab

0

@item

Include_dev

@tab

安装开发人员头文件和库

@tab

1

@item

Include_exe

@tab

安装 @code{python.exe} 及相关文件

@tab

1

@item

Include_launcher

@tab

安装 @ref{989,,适用于Windows的Python启动器} .

@tab

1

@item

InstallLauncherAllUsers

@tab

为所有用户安装 @ref{989,,适用于Windows的Python启动器} 。

@tab

1

@item

Include_lib

@tab

安装标准库和扩展模块

@tab

1

@item

Include_pip

@tab

安装捆绑的pip和setuptools

@tab

1

@item

Include_symbols

@tab

安装调试符号(@cite{*}.pdb)

@tab

0

@item

Include_tcltk

@tab

安装Tcl/Tk 支持和IDLE

@tab

1

@item

Include_test

@tab

安装标准库测试套件

@tab

1

@item

Include_tools

@tab

安装实用程序脚本

@tab

1

@item

LauncherOnly

@tab

仅安装启动器。这将覆盖大多数其他选项。

@tab

0

@item

SimpleInstall

@tab

禁用大多数安装UI

@tab

0

@item

SimpleInstallDescription

@tab

使用简化安装UI时显示的自定义消息。

@tab

（空）

@end multitable


例如，要以静默方式全局安装默认的Python，您可以（在命令提示符>）使用以下命令:

@example
python-3.8.0.exe /quiet InstallAllUsers=1 PrependPath=1 Include_test=0
@end example

要允许用户在没有测试套件的情况下轻松安装Python的个人副本，可以使用以下命令提供快捷方式。这将显示一个简化的初始页面，不允许自定义:

@example
python-3.8.0.exe InstallAllUsers=0 Include_launcher=0 Include_test=0
    SimpleInstall=1 SimpleInstallDescription="Just for me, no test suite."
@end example

（请注意，省略启动器也会省略文件关联，并且仅在全局安装包含启动器时才建议用于每用户安装。）

上面列出的选项也可以在一个名为 @code{unattend.xml} 的文件中与可执行文件一起提供。此文件指定选项和值的列表。作为属性提供的值，（如果可能）它将转换为数字。作为文本提供的值，始终保留为字符串。此示例文件设置与上一示例采用相同的选项：

@example
<Options>
    <Option Name="InstallAllUsers" Value="no" />
    <Option Name="Include_launcher" Value="0" />
    <Option Name="Include_test" Value="no" />
    <Option Name="SimpleInstall" Value="yes" />
    <Option Name="SimpleInstallDescription">Just for me, no test suite</Option>
</Options>
@end example

@node 免下载安装,修改安装,无UI 安装,完整安装程序
@anchor{using/windows install-layout-option}@anchor{130c}@anchor{using/windows installing-without-downloading}@anchor{1310}
@subsubsection 免下载安装


由于下载的初始安装包中未包含Python的某些可选功能，如果选择安装这些功能可能需要Internet连接。为了避免这种需要，可以按需下载所有可能的组件，以创建一个完整的布局，该布局将不再需要internet连接，而不管所选择的特性是什么。请注意，此下载可能比要求的要大，但是如果要执行大量安装，则拥有本地缓存​​的副本非常有用。

从命令提示符执行以下命令以下载所有可能的必需文件。请记住将 @code{python-3.8.0.exe} 替换为安装程序的实际名称，并在自己的目录中创建布局，以避免同名的文件之间发生冲突。

@example
python-3.8.0.exe /layout [optional target directory]
@end example

您也可以指定 @code{/quiet} 选项来隐藏进度显示。

@node 修改安装,,免下载安装,完整安装程序
@anchor{using/windows modifying-an-install}@anchor{1311}
@subsubsection 修改安装


安装Python后，您可以通过Windows中的“程序和功能”工具添加或删除功能。选择Python条目并选择“卸载/更改”以在维护模式下打开安装程序。

“修改” 允许您通过修改复选框来添加或删除功能 - 未更改的复选框将不会安装或删除任何内容。在此模式下无法更改某些选项，例如安装目录；要修改这些，您需要完全删除然后重新安装Python。

“修复” 将使用当前设置验证应安装的所有文件，并替换已删除或修改的任何文件

“卸载” 将完全删除Python，但 @ref{989,,适用于Windows的Python启动器} 除外，它在“程序和功能”中有自己的条目。

@node Microsoft Store包,nuget org 安装包,完整安装程序,在Windows上使用 Python
@anchor{using/windows the-microsoft-store-package}@anchor{1312}@anchor{using/windows windows-store}@anchor{119c}
@subsection Microsoft Store包



3.7.2 新版功能.


Microsoft Store包是一个易于安装的Python解释器，主要用于交互式使用，例如，学生。

要安装软件包，请确保您拥有最新的Windows 10更新，并在Microsoft Store应用程序中搜索 "Python 3.8" 。确保您选择的应用程序由 Python Software Foundation 发布并安装。

@cartouche
@quotation 警告 
Python将始终在Microsoft Store上免费提供。如果要求您付款，则表示您没有选择正确的包。
@end quotation
@end cartouche

安装完成后，可以在开始菜单中找到它来启动 Python。或者可以在命令提示符或 PowerShell 会话中输入 @code{python} 来启动。此外可以输入 @code{pip} 或 @code{idle} 来使用 pip 和 IDLE。IDLE 也在开始菜单中。

所有这三个命令也可以使用版本号后缀，例如， @code{python3.exe} 和 @code{python3.x.exe} 以及 @code{python.exe} （其中 @code{3.x} 是您要启动的特定版本，例如 3.8 ）。在 @code{设置-->主页-->应用和功能} 页面中，点选 @code{管理可选功能} ，选择与每个命令关联的python版本。建议确保 @code{pip} 和 @code{idle} 与选择的 @code{python} 版本一致。

可以使用 @code{python -m venv} 创建虚拟环境并激活并正常使用。

如果你已经安装了另一个版本的Python并将它添加到你的 @code{PATH} 变量中，那么它将作为 @code{python.exe} 而不是来自Microsoft Store的那个。要访问新安装，请使用 @code{python3.exe} 或 @code{python3.x.exe} 。

@code{py.exe} 启动器将检测此 Python 安装版，但会优先使用来自传统安装器的安装版。

要删除Python，请打开“设置”并使用“应用程序和功能”，或者在“开始”中找到Python，然后右键单击以选择“卸载”。卸载将删除该已安装Python程序中的所有软件包，但不会删除任何虚拟环境

@menu
* 已知的问题:: 

@end menu

@node 已知的问题,,,Microsoft Store包
@anchor{using/windows known-issues}@anchor{1313}
@subsubsection 已知的问题


由于Microsoft Store应用程序的限制，Python脚本可能无法对共享位置（如 @code{TEMP} ）和注册表进行完全写入访问。相反，它将写入私人副本。如果脚本必须修改共享位置，则需要安装完整安装程序。

@node nuget org 安装包,可嵌入的包,Microsoft Store包,在Windows上使用 Python
@anchor{using/windows the-nuget-org-packages}@anchor{1314}@anchor{using/windows windows-nuget}@anchor{1308}
@subsection nuget.org 安装包



3.5.2 新版功能.


nuget.org是一个精简的Python环境，用于在没有全局安装Python的系统的持续集成和构建。虽然Nuget是“.NET的包管理器”，但是对于包含构建时工具的包来说，它也可以很好地工作。

访问 nuget.org@footnote{https://www.nuget.org/}  获取有关使用nuget的最新信息。下面的摘要对Python开发人员来说已经足够了。

 @code{nuget.exe} 命令行工具可以直接从 @code{https://aka.ms/nugetclidl} 下载，例如，使用curl或PowerShell。使用该工具安装64位或32位最新版本的Python:

@example
nuget.exe install python -ExcludeVersion -OutputDirectory .
nuget.exe install pythonx86 -ExcludeVersion -OutputDirectory .
@end example

要选择特定版本，请添加 @code{-Version 3.x.y} 。输出目录可以从 @code{.} 更改，包将安装到子目录中。默认情况下，子目录的名称与包的名称相同，如果没有 @code{-ExcludeVersion} 选项，则此名称将包含已安装的特定版本。子目录里面是一个包含Python安装的 @code{tools} 目录:

@example
# Without -ExcludeVersion
> .\python.3.5.2\tools\python.exe -V
Python 3.5.2

# With -ExcludeVersion
> .\python\tools\python.exe -V
Python 3.5.2
@end example

通常，nuget包不可升级，应该平行安装较新版本并使用完整路径引用。或者，手动删除程序包目录并再次安装。如果在构建之间不保留文件，许多CI系统将自动执行此操作。

除了 @code{tools} 目录外，还有一个 @code{build\native} 目录。它包含一个MSBuild属性文件 @code{python.props} ，可以在C++项目中使用该文件来引用Python安装。包含这些设置将自动在生成中使用标头和导入库。

nuget.org上的包信息页是 www.nuget.org/packages/python@footnote{https://www.nuget.org/packages/python}        对于64位版本和 www.nuget.org/packages/pythonx86@footnote{https://www.nuget.org/packages/pythonx86} 表示32位版本。

@node 可嵌入的包,替代捆绑包,nuget org 安装包,在Windows上使用 Python
@anchor{using/windows the-embeddable-package}@anchor{1315}@anchor{using/windows windows-embeddable}@anchor{1309}
@subsection 可嵌入的包



3.5 新版功能.


嵌入式发行版是一个包含最小Python环境的ZIP文件。它旨在作为另一个应用程序的一部分，而不是由最终用户直接访问。

解压缩后，嵌入式发行版（几乎）与用户系统完全隔离，包括环境变量、系统注册表设置和已安装的软件包。标准库作为预先编译和优化的 @code{.pyc} 文件包含在ZIP中，并提供了 @code{python3.dll} ， @code{python37.dll} ， @code{python.exe} 和 @code{pythonw.exe} 文件。不包括Tcl/tk（包括所有依赖项，如Idle），pip和Python文档。

@cartouche
@quotation 注解 
嵌入式发行版不包括 Microsoft C Runtime@footnote{https://www.microsoft.com/en-us/download/details.aspx?id=48145} ，应用程序安装程序负责提供此功能。运行时可能已经预先安装在用户的系统上或通过Windows Update自动安装，并且可以通过在系统目录中找到 @code{ucrtbase.dll} 来检测
@end quotation
@end cartouche

第三方软件包应该由应用程序与嵌入式发行版一起安装。这个发行版不支持像常规Python安装那样使用pip来管理依赖关系，不过可以小心地将pip包含进来并使用它进行自动更新。通常，第三方包应该作为应用程序的一部分(“打包”)处理，以便开发人员在向用户提供更新之前能够确保与新版本兼容。

下面描述了这个发行版的两个推荐用例。

@menu
* Python应用程序:: 
* 嵌入Python:: 

@end menu

@node Python应用程序,嵌入Python,,可嵌入的包
@anchor{using/windows python-application}@anchor{1316}
@subsubsection Python应用程序


用Python编写的应用程序并不一定要求用户了解这一事实。在这种情况下，可以使用嵌入式发行版在安装包中包含Python的私有版本。根据它应该有多透明(或者相反，它应该看起来有多专业)，有两个选项。

使用专门的可执行文件作为启动程序需要一些编码，但为用户提供了最透明的体验。使用定制的启动器，没有明显的迹象表明程序是在Python上运行的：图标可以定制，公司和版本信息可以指定，文件关联可以正常运行。在大多数情况下，自定义启动程序应该只需使用硬编码的命令行就能调用 @code{Py_Main}

更简单的方法是提供批处理文件或生成的快捷方式，使用所需的命令行参数直接调用 @code{python.exe} 或 @code{pythonw.exe} 。在这种情况下，应用程序将显示为Python而不是其实际名称，并且用户可能无法将其与其他正在运行的Python进程或文件关联区分开来。

对于后一种方法，包应该与Python可执行文件一起作为目录安装，以确保它们在路径上可用。使用专用的启动器，包可以位于其他位置，因为在启动应用程序之前有机会指定搜索路径。

@node 嵌入Python,,Python应用程序,可嵌入的包
@anchor{using/windows embedding-python}@anchor{1317}
@subsubsection 嵌入Python


用本地代码编写的应用程序通常需要某种形式的脚本语言，嵌入式Python发行版可以用于此目的。通常，应用程序的大部分都是本机代码，某些部分将调用 @code{python.exe} 或直接使用 @code{python3.dll} 。无论是哪种情况，将嵌入的发行版解压缩到应用程序安装的子目录中就足以提供可加载的Python解释器。

与应用程序使用一样，包可以安装到任何位置，因为在初始化解释器之前有机会指定搜索路径。否则，使用嵌入式发行版和常规安装之间没有根本区别。

@node 替代捆绑包,配置Python,可嵌入的包,在Windows上使用 Python
@anchor{using/windows alternative-bundles}@anchor{1318}
@subsection 替代捆绑包


除了标准的CPython发行版之外，还有一些包含附加功能的修改包。以下是热门版本及其主要功能的列表：


@table @asis

@item ActivePython@footnote{https://www.activestate.com/activepython/}

具有多平台兼容性的安装程序，文档，PyWin32

@item Anaconda@footnote{https://www.anaconda.com/download/}

流行的科学模块（如numpy，scipy和pandas）和 @code{conda} 包管理器。

@item Canopy@footnote{https://www.enthought.com/product/canopy/}

具有编辑器和其他开发工具的“全面的Python分析环境”。

@item WinPython@footnote{https://winpython.github.io/}

特定于Windows的发行版，包含用于构建包的预构建科学包和工具。
@end table

请注意，这些软件包可能不包含最新版本的Python或其他库，并且不由核心Python团队维护或支持。

@node 配置Python,UTF-8 模式,替代捆绑包,在Windows上使用 Python
@anchor{using/windows configuring-python}@anchor{1319}
@subsection 配置Python


要从命令提示符方便地运行Python，您可以考虑在Windows中更改一些默认环境变量。虽然安装程序提供了为您配置PATH和PATHEXT变量的选项，但这仅适用于单版本、全局安装。如果您经常使用多个版本的Python，请考虑使用 @ref{989,,适用于Windows的Python启动器} 。

@menu
* 附录：设置环境变量:: 
* 查找Python可执行文件:: 

@end menu

@node 附录：设置环境变量,查找Python可执行文件,,配置Python
@anchor{using/windows excursus-setting-environment-variables}@anchor{131a}@anchor{using/windows setting-envvars}@anchor{119d}
@subsubsection 附录：设置环境变量


Windows允许在用户级别和系统级别永久配置环境变量，或临时在命令提示符中配置环境变量。

要临时设置环境变量，请打开命令提示符并使用 @code{set} 命令：

@example
C:\>set PATH=C:\Program Files\Python 3.8;%PATH%
C:\>set PYTHONPATH=%PYTHONPATH%;C:\My_python_lib
C:\>python
@end example

这些环境变量的更改将应用​​于在该控制台中执行的任何其他命令，并且，由该控制台启动的任何应用程序都继承设这些设置。

在百分号中包含的变量名将被现有值替换，允许在开始或结束时添加新值。通过将包含 @code{python.exe} 的目录添加到开头来修改 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH}  是确保启动正确版本的Python的常用方法。

要永久修改默认环境变量，请单击“开始”并搜索“编辑环境变量”，或打开“系统属性” Advanced system settings ，然后单击 Environment Variables 按钮。在此对话框中，您可以添加或修改用户和系统变量。要更改系统变量，您需要对计算机进行无限制访问（即管理员权限）。

@cartouche
@quotation 注解 
Windows会将用户变量串联的系统变量 @emph{之后} ，这可能会在修改 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 时导致意外结果。

@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 变量被Python 2和Python 3的所有版本使用，因此除非它只包含与所有已安装的Python版本兼容的代码，否则不要永久配置此变量。
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@item @indicateurl{https://www.microsoft.com/en-us/wdsi/help/folder-variables}

Windows NT 的环境变量

@item @indicateurl{https://technet.microsoft.com/en-us/library/cc754250.aspx}

用于临时修改环境变量的SET命令

@item @indicateurl{https://technet.microsoft.com/en-us/library/cc755104.aspx}

用于永久修改环境变量的SETX命令

@item @indicateurl{https://support.microsoft.com/en-us/help/310519/how-to-manage-environment-variables-in-windows-xp}

如何在Windows XP中管理环境变量

@item @indicateurl{https://www.chem.gla.ac.uk/~louis/software/faq/q1.html}

设置环境变量（For Windows 2000/NT），Louis J. Farrugia
@end table


@node 查找Python可执行文件,,附录：设置环境变量,配置Python
@anchor{using/windows finding-the-python-executable}@anchor{131b}@anchor{using/windows windows-path-mod}@anchor{98a}
@subsubsection 查找Python可执行文件



在 3.5 版更改.


除了使用自动创建的Python解释器的开始菜单项之外，您可能还想在命令提示符下启动Python。安装程序有一个选项可以为您设置。

在安装程序的第一页上，可以选择标记为“将Python添加到环境变量”的选项，以使安装程序将安装位置添加到 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 。还添加了 @code{Scripts\} 文件夹的位置。这允许你输入 @code{python} 来运行解释器，并且 @code{pip} 用于包安装程序。因此，您还可以使用命令行选项执行脚本，请参阅 @ref{925,,命令行} 文档。

如果在安装时未启用此选项，则始终可以重新运行安装程序，选择“修改”并启用它。或者，您可以使用 @ref{119d,,附录：设置环境变量} 的方法手动修改 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 。您需要将Python安装目录添加到 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 环境变量中，该内容与其他条目用分号分隔。示例变量可能如下所示（假设前两个条目已经存在）:

@example
C:\WINDOWS\system32;C:\WINDOWS;C:\Program Files\Python 3.8
@end example

@node UTF-8 模式,适用于Windows的Python启动器,配置Python,在Windows上使用 Python
@anchor{using/windows utf-8-mode}@anchor{131c}@anchor{using/windows win-utf8-mode}@anchor{131d}
@subsection UTF-8 模式



3.7 新版功能.


Windows 仍然使用传统编码格式作为系统的编码格式（ANSI 代码页）。 Python 使用它作为文本文件默认的编码格式 (即 @ref{39d,,locale.getpreferredencoding()})。

这可能会造成问题，因为因特网和大多数 Unix 系统包括 WSL (Windows Subsystem for Linux) 广泛使用 UTF-8。

你可以使用 UTF-8 模式将默认的文本编码格式改为 UTF-8。 要启用 UTF-8 模式可以通过 @code{-X utf8} 命令行选项，或者 @code{PYTHONUTF8=1} 环境变量。 请参见 
@geindex PYTHONUTF8
@geindex 环境变量; PYTHONUTF8
@ref{30a,,PYTHONUTF8} 了解如何启用 UTF-8 模式，并参见 @ref{119d,,附录：设置环境变量} 了解如何修改环境变量。

当 UTF-8 模式被启用时：


@itemize *

@item 
@ref{39d,,locale.getpreferredencoding()} 将返回 @code{'UTF-8'} 而不是系统的编码格式。 此函数可用来在许多场合下获取默认的文本编码格式，包括 @ref{4ea,,open()}, @code{Popen}, @code{Path.read_text()} 等等。

@item 
@ref{306,,sys.stdin}, @ref{307,,sys.stdout} 和 @ref{308,,sys.stderr} 都将使用 UTF-8 作为其文本编码格式。

@item 
你仍然可以通过 "mbcs" 编解码器来使用系统的编码格式。
@end itemize

请注意添加 @code{PYTHONUTF8=1} 到默认环境变量将会影响你的系统中的所有 Python 3.7+ 应用。 如果你有任何 Python 3.7+ 应用仍然依赖于传统的系统编码格式，则推荐设置临时环境变量或使用 @code{-X utf8} 命令行选项。

@cartouche
@quotation 注解 
即使在不启用 UTF-8 模式时，Windows 版的 Python 也会在以下情况中默认使用 UTF-8：


@itemize *

@item 
控制台 I/O 包括标准 I/O (详情见 
@geindex Python 提高建议; PEP 528
PEP 528@footnote{https://www.python.org/dev/peps/pep-0528})。

@item 
文件系统编码格式 (详情见 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529})。
@end itemize
@end quotation
@end cartouche

@node 适用于Windows的Python启动器,查找模块,UTF-8 模式,在Windows上使用 Python
@anchor{using/windows launcher}@anchor{989}@anchor{using/windows python-launcher-for-windows}@anchor{131e}
@subsection 适用于Windows的Python启动器



3.3 新版功能.


用于Windows的Python启动器是一个实用程序，可帮助定位和执行不同的Python版本。它允许脚本（或命令行）指示特定Python版本的首选项，并将定位并执行该版本。

与 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 变量不同，启动器将正确选择最合适的Python版本。它更倾向于按用户安装而不是系统安装，并按语言版本排序，而不是使用最新安装的版本。

启动器最初是在 
@geindex Python 提高建议; PEP 397
PEP 397@footnote{https://www.python.org/dev/peps/pep-0397} 中指定的。

@menu
* 入门:: 
* Shebang Lines:: 
* shebang lines 的参数:: 
* 自定义:: 
* 诊断:: 

@end menu

@node 入门,Shebang Lines,,适用于Windows的Python启动器
@anchor{using/windows getting-started}@anchor{131f}
@subsubsection 入门


@menu
* 从命令行:: 
* 从虚拟环境:: 
* 从脚本:: 
* 从文件关联:: 

@end menu

@node 从命令行,从虚拟环境,,入门
@anchor{using/windows from-the-command-line}@anchor{1320}
@subsubsection 从命令行



在 3.6 版更改.


全局安装Python 3.3及更高版本将把启动器放在你的 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 上。启动程序与所有可用的Python版本兼容，因此安装哪个版本无关紧要。要检查启动程序是否可用，请在命令提示符中执行以下命令：

@example
py
@end example

您应该会发现已安装的最新版本的Python已启动 - 它可以正常退出，并且将指定的任何其他命令行参数直接发送到Python。

如果您安装了多个版本的Python（例如，2.7和 3.8 ），您会注意到Python 3.8 启动 - 如果要启动Python 2.7，尝试命令：

@example
py -2.7
@end example

如果您想使用 Python 2.x 的最新版本，请尝试以下命令：

@example
py -2
@end example

你会发现Python 2.x 的最新版本已启动。

如果您看到以下错误，则表明您没有安装启动器：

@example
'py' is not recognized as an internal or external command,
operable program or batch file.
@end example

除非在安装时选择了该选项，单个用户安装的Python不会将启动程序添加到 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 。

@node 从虚拟环境,从脚本,从命令行,入门
@anchor{using/windows virtual-environments}@anchor{1321}
@subsubsection 从虚拟环境



3.5 新版功能.


如果启动程序运行时没有明确的Python版本，并且虚拟环境（使用标准库创建 @ref{125,,venv} 模块或外部 @code{virtualenv} 工具）处于活动状态，则启动程序将运行虚拟环境的解释器而不是全局的。要运行全局解释器，请停用虚拟环境，或显式指定全局Python版本。

@node 从脚本,从文件关联,从虚拟环境,入门
@anchor{using/windows from-a-script}@anchor{1322}
@subsubsection 从脚本


让我们创建一个测试Python脚本 - 创建一个名为`@w{`}hello.py`@w{`}的文件，其中包含以下内容

@example
#! python
import sys
sys.stdout.write("hello from Python %s\n" % (sys.version,))
@end example

从hello.py所在的目录中，执行以下命令：

@example
py hello.py
@end example

您应该注意到最新的Python 2.x安装的版本号已打印出来。现在尝试将第一行更改为：

@example
#! python3
@end example

现在，重新执行该命令应该打印最新的Python 3.x信息。与上面的命令行示例一样，你可以更明确的指定版本限定符。假设您安装了Python 2.6，请尝试将第一行更改为 @code{#! python2.6} ，你会发现打印的2.6版本信息。

请注意，与交互式使用不同，裸“python”将使用您已安装的Python 2.x的最新版本。这是为了向后兼容及兼容Unix，其中命令 @code{python} 通常是指Python 2。

@node 从文件关联,,从脚本,入门
@anchor{using/windows from-file-associations}@anchor{1323}
@subsubsection 从文件关联


安装时应该将启动器与Python文件（即 @code{.py}, @code{.pyw}, @code{.pyc} 文件）相关联。这意味着当您从Windows资源管理器中双击其中一个文件时，将使用启动程序，因此您可以使用上述相同的工具让脚本指定应使用的版本。

这样做的主要好处是，单个启动程序可以同时支持多个Python版本，具体取决于第一行的内容。

@node Shebang Lines,shebang lines 的参数,入门,适用于Windows的Python启动器
@anchor{using/windows shebang-lines}@anchor{1324}
@subsubsection Shebang Lines


如果脚本文件的第一行以 @code{#!} 开头，则称为 "shebang" 行。Linux和其他类Unix操作系统都有对这些行的本机支持，它们通常在此类系统上用来指示应该如何执行脚本。这个启动器允许在Windows上对Python脚本使用相同的工具，上面的示例演示了它们的使用。

为了允许Python脚本中的shebang行在Unix和Windows之间移植，该启动器支持许多“虚拟”命令来指定要使用的解释器。支持的虚拟命令是：


@itemize *

@item 
@code{/usr/bin/env python}

@item 
@code{/usr/bin/python}

@item 
@code{/usr/local/bin/python}

@item 
@code{python}
@end itemize

例如，如果脚本开始的第一行

@example
#! /usr/bin/python
@end example

将找到并使用默认的Python。因为在Unix上编写的许多Python脚本已经有了这一行，你应该发现这些脚本可以由启动器使用而无需修改。如果您在Windows上编写一个新脚本，希望在Unix上有用，那么您应该使用以 @code{/usr} 开头的一个shebang行。

任何上述虚拟命令都可以显式指定版本（可以仅为主要版本，也可以为主要版本加次要版本）作为后缀。 此外，可以通过在次要版本之后添加 “-32” 来请求 32 位版本。 例如 @code{/usr/bin/python2.7-32} 将请求使用 32 位 python 2.7。


3.7 新版功能: 从python启动程序3.7开始，可以通过“-64”后缀调用64位版本。此外，可以指定没有次要的主要和架构（即 @code{/usr/bin/python3-64} ）。


shebang line的 @code{/usr/bin/env} 形式还有一个特殊属性。在寻找已安装的Python解释器之前，此表单将搜索可执行文件 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 以获取Python可执行文件。这对应于Unix中 @code{env} 程序的行为，该程序将在 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 执行搜索。

@node shebang lines 的参数,自定义,Shebang Lines,适用于Windows的Python启动器
@anchor{using/windows arguments-in-shebang-lines}@anchor{1325}
@subsubsection shebang lines 的参数


shebang lines 还可以指定要传递给Python解释器的其他选项。例如，如果你有一个shebang lines ：

@example
#! /usr/bin/python -v
@end example

然后Python将以 @code{-v} 选项启动

@node 自定义,诊断,shebang lines 的参数,适用于Windows的Python启动器
@anchor{using/windows customization}@anchor{1326}
@subsubsection 自定义


@menu
* 通过INI文件自定义:: 
* 自定义默认的Python版本:: 

@end menu

@node 通过INI文件自定义,自定义默认的Python版本,,自定义
@anchor{using/windows customization-via-ini-files}@anchor{1327}
@subsubsection 通过INI文件自定义


启动程序将搜索两个.ini文件 - 在当前用户的 "application data" 目录中搜索 @code{py.ini} （即通过使用 @code{CSIDL_LOCAL_APPDATA} 调用Windows函数 @code{SHGetFolderPath} 返回的目录）以及与启动器位于同一目录中的 @code{py.ini} 。相同的.ini文件既用于启动器的“控制台”版本（即 py.exe），也用于“windows”版本（即pyw.exe）

“应用程序目录”中指定的自定义优先于可执行文件旁边.ini文件的自定义，因此对启动程序旁边的.ini文件不具有写访问权限的用户可以覆盖该全局.ini文件中的命令。

@node 自定义默认的Python版本,,通过INI文件自定义,自定义
@anchor{using/windows customizing-default-python-versions}@anchor{1328}
@subsubsection 自定义默认的Python版本


在某些情况下，可以在命令中包含版本限定符，以指定命令将使用哪个Python版本。版本限定符以主版本号开头，可以选择后跟 ('.') 和次版本说明符。此外，可以通过添加 "-32" 或 “-64” 来指定是请求32位还是64位实现。

例如，一个shebang line 的 @code{#!python} 行没有版本限定符，而 @code{#!python3} 有一个版本限定符，它只指定一个主要版本。

如果在命令中找不到版本限定符，则可以设置环境变量 
@geindex PY_PYTHON
@geindex 环境变量; PY_PYTHON
@code{PY_PYTHON} 以指定默认版本限定符。 如果未设置，则默认为 "3"。 该变量可以指定能通过命令行传递的任何值，比如 "3", "3.7", "3.7-32" 或 "3.7-64"。 （请注意 "-64" 选项仅适用于 Python 3.7 或更高版本中包含的启动器。）

如果没有找到次要版本限定符，则可以设置环境变量 @code{PY_PYTHON@{major@}} （其中 @code{@{major@}} 是上面确定的当前主要版本限定符）以指定完整版本。如果没有找到这样的选项，启动器将枚举已安装的Python版本并使用为主要版本找到的最新次要版本，尽管不能保证，但该版本可能是该系列中最新安装的版本。

在安装了相同（major.minor）Python版本的32位和64位的64位Windows上，64位版本将始终是首选。对于启动程序的32位和64位实现都是如此 -- 这对于启动程序32位和64位都是正确的 -- 如果可用，32位启动程序将倾向于执行指定版本的64位Python安装。这样就可以预测启动器的行为，只知道PC上安装了哪些版本，而不考虑它们的安装顺序（即，不知道32位或64位版本的Python和相应的启动器是否是最后安装）。如上所述，可以在版本说明符上使用可选的“-32”或“-64”后缀来更改此行为。

示例：


@itemize *

@item 
如果没有设置相关选项，命令 @code{python} 和 @code{python2} 将使用安装的最新Python 2.x版本，命令 @code{python3} 将使用最新安装的Python 3.x.

@item 
命令 @code{python3.1} 和 @code{python2.7} 根本不会查阅任何选项，因为版本已完全指定。

@item 
如果 @code{PY_PYTHON=3} ，命令`@w{`}python`@w{`} 和 @code{python3} 都将使用最新安装的Python 3版本。

@item 
如果 @code{PY_PYTHON=3.1-32} ，命令 @code{python} 将使用3.1的32位实现，而命令 @code{python3} 将使用最新安装的Python（PY_PYTHON根本没有被视为指定了主要版本。）

@item 
如果 @code{PY_PYTHON=3} 且 @code{PY_PYTHON3=3.1}，命令 @code{python} 和 @code{python3} 都将特别使用3.1
@end itemize

除环境变量外，还可以在启动程序使用的.INI文件中配置相同的设置。 INI文件中的部分称为 @code{[defaults]} ，键名称将与没有前导 @code{PY_} 前缀的环境变量相同（并注意INI文件中的键名不区分大小写） 。）环境变量的内容将覆盖INI文件中指定的内容。

例如:


@itemize *

@item 
设置 @code{PY_PYTHON=3.1} 等同于包含以下内容的INI文件：
@end itemize

@example
[defaults]
python=3.1
@end example


@itemize *

@item 
设置 @code{PY_PYTHON=3} 和 @code{PY_PYTHON3=3.1} 相当于包含以下内容的INI文件：
@end itemize

@example
[defaults]
python=3
python3=3.1
@end example

@node 诊断,,自定义,适用于Windows的Python启动器
@anchor{using/windows diagnostics}@anchor{1329}
@subsubsection 诊断


如果设置了环境变量 @code{PYLAUNCH_DEBUG} （任何值），启动器将诊断信息打印到stderr（即：控制台）。虽然这些信息同时具有冗长 @emph{和} 简洁性，但它应该允许您查看Python的版本、选择特定版本的原因以及用于执行目标Python的确切命令行。

@node 查找模块,附加模块,适用于Windows的Python启动器,在Windows上使用 Python
@anchor{using/windows finding-modules}@anchor{4ab}@anchor{using/windows id1}@anchor{132a}
@subsection 查找模块


Python通常将其库（以及您的site-packages文件夹）存储在安装目录中。因此，如果您已将Python安装到 @code{C:\Python\} ，则默认库将驻留在 @code{C:\Python\Lib\} 中，第三方模块存储在 @code{C:\Python\Lib\site-packages\} 。

若要完全覆盖 @ref{482,,sys.path} ，请创建与DLL(@code{python37._pth})或可执行文件(“python._pth`”)同名的 @code{._pth} 文件，并为要添加的每个路径指定一行 @ref{482,,sys.path} 。基于DLL名称的文件覆盖基于可执行文件的文件，如果需要，可以为加载运行时的任何程序限制路径。

当文件存在时，将忽略所有注册表和环境变量，启用隔离模式，并且：除非文件中的一行指定 @code{import site} ，否则不会导入 @ref{eb,,site} 。以 @code{＃} 开头的空白路径和行将被忽略。每个路径可以是绝对的或相对于文件的位置。不允许使用除 @code{site} 以外的导入语句，并且不能指定任意代码。

请注意，当指定 @code{import site} 时， @code{.pth} 文件（没有前导下划线）将由 @ref{eb,,site} 模块正常处理。

当找不到 @code{._pth} 文件时， @ref{482,,sys.path} 是如何在Windows上填充的：


@itemize *

@item 
在开始时，添加一个空条目，该条目对应于当前目录。

@item 
如果环境变量 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 存在，如 @ref{12ea,,环境变量} 中所述，则接下来添加其条目。请注意，在Windows上，此变量中的路径必须用分号分隔，以区别于驱动器标识符中使用的冒号（ @code{C:\}  等）。

@item 
附加的 "application paths" 可以同时添加到注册表` @cite{HKEY_CURRENT_USER`} 和 @code{HKEY_LOCAL_MACHINE} 分支下的:samp:@cite{\SOFTWARE\Python\PythonCore\@{version@}\PythonPath}  中作为子键。以分号分隔的路径字符串作为默认值的子键将导致每个路径添加到 @ref{482,,sys.path} 。（请注意，所有已知的安装程序都只使用HKLM，因此HKCU通常为空。）

@item 
如果设置了环境变量 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME}  ，则将其假定为 “Python 主目录” 。否则，主Python可执行文件的路径用于定位 “landmark 文件” （ @code{Lib\os.py} 或 @code{pythonXY.zip} ）以推断 ”Python 主目录“ 。如果找到了Python主目录，则基于该文件夹将相关的子目录添加到 @ref{482,,sys.path} （@code{Lib} , @code{plat-win} 等）。否则，核心Python路径是从存储在注册表中的PythonPath构造的。

@item 
如果找不到Python Home，也没有指定 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 环境变量，并且找不到注册表项，则使用具有相对条目的默认路径（例如 @code{.\Lib; .\plat-win} 等等）。
@end itemize

如果在主可执行文件旁边或在可执行文件上一级的目录中找到 @code{pyvenv.cfg} 文件，则以下变体适用：


@itemize *

@item 
如果`@w{`}home`@w{`} 是一个绝对路径，并且 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} 未设置，则在推断起始位置时使用此路径而不是主可执行文件的路径
@end itemize

这一切的最终结果是：


@itemize *

@item 
运行 @code{python.exe} ，或主Python目录中的任何其他.exe（安装版本，或直接来自PCbuild目录）时，推导出核心路径，并忽略注册表中的核心路径。始终读取注册表中的其他“应用程序路径”。

@item 
当Python托管在另一个.exe（不同的目录，通过COM嵌入等）时，将不会推断出“Python Home”，因此使用了来自注册表的核心路径。始终读取注册表中的其他“应用程序路径”。

@item 
如果Python找不到它的主目录并且没有注册表值（冻结的.exe，一些非常奇怪的安装设置），那么你会得到一条带有一些默认但相对的路径的路径。
@end itemize

对于那些想要将Python捆绑到其应用程序或发行版中的人，以下建议将防止与其他安装冲突：


@itemize *

@item 
在您的可执行文件中包含一个 @code{._pth} 文件，其中包含目录。这将忽略注册表和环境变量中列出的路径，并忽略 @ref{eb,,site} ，除非列出 @code{import site} 。

@item 
如果你在自己的可执行文件中加载 @code{python3.dll} 或 @code{python37.dll} ，在 @ref{433,,Py_Initialize()} 之前，要显式调用 @ref{273,,Py_SetPath()}  或（至少） @ref{f18,,Py_SetProgramName()}

@item 
清除 和/或 覆盖 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 并在启动来自应用程序的 @code{python.exe} 之前设置 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} 。

@item 
如果您不能使用前面的建议（例如，您是一个允许人们直接运行：file:@cite{python.exe`的分发版），请确保安装目录中存在landmark 文件（:file:`Lib\os.py}）。（请注意，在zip文件中不会检测到该文件，但会检测到正确命名的zip文件。）
@end itemize

这些将确保系统范围安装中的文件不会优先于与应用程序捆绑在一起的标准库的副本。否则，用户可能会在使用您的应用程序时遇到问题请注意，第一个建议是最好的，因为其他建议可能仍然容易受到注册表和用户站点包中的非标准路径的影响。


@quotation
在 3.6 版更改: 

@itemize *

@item 
添加 @code{._pth} 文件支持并从 @code{pyvenv.cfg} 中删除 @code{applocal} 选项

@item 
当直接与可执行文件相邻时，添加 @code{pythonXX.zip} 作为潜在的 landmark 。
@end itemize
@end quotation



@quotation
3.6 版后已移除: 
在 @code{Modules} （不是 @code{PythonPath} ）下的注册表中指定的模块可以通过以下方式导入 @ref{5e0,,importlib.machinery.WindowsRegistryFinder} 。在Windows上，此查找程序在3.6.0及更早版本的可用，但可能需要在将来显式添加到 @ref{5e1,,sys.meta_path}
@end quotation


@node 附加模块,在Windows上编译Python,查找模块,在Windows上使用 Python
@anchor{using/windows additional-modules}@anchor{132b}
@subsection 附加模块


尽管Python的目标是在所有平台中都可移植，但是Windows有一些独特的特性。在标准库和外部都有一些模块和代码片段在使用这些特性。

特定于Windows的标准模块记录在 @ref{132c,,Windows系统相关模块} 中。

@menu
* PyWin32:: 
* cx_Freeze:: 
* WConio:: 

@end menu

@node PyWin32,cx_Freeze,,附加模块
@anchor{using/windows pywin32}@anchor{132d}
@subsubsection PyWin32


Mark Hammond 的 PyWin32@footnote{https://pypi.org/project/pywin32}  模块是一组用于高级Windows特定支持的模块。这包括以下实用程序：


@itemize *

@item 
组件对象模型@footnote{https://docs.microsoft.com/en-us/windows/desktop/com/component-object-model--com--portal} (COM)

@item 
Win32 API 调用

@item 
注册

@item 
事件日志

@item 
Microsoft Foundation Classes@footnote{https://msdn.microsoft.com/en-us/library/fe1cf721%28VS.80%29.aspx} (MFC) 用户界面
@end itemize

PythonWin@footnote{https://web.archive.org/web/20060524042422/https://www.python.org/windows/pythonwin/} 是PyWin32附带的一个示例MFC应用程序。它是一个内置调试器的可嵌入IDE。


@subsubheading 参见



@table @asis

@item Win32 How Do I...?@footnote{http://timgolden.me.uk/python/win32_how_do_i.html}

Tim Golden 著

@item Python and COM@footnote{http://www.boddie.org.uk/python/COM.html}

David 和 Paul Boddie 著
@end table


@node cx_Freeze,WConio,PyWin32,附加模块
@anchor{using/windows cx-freeze}@anchor{132e}
@subsubsection cx_Freeze


cx_Freeze@footnote{https://anthony-tuininga.github.io/cx_Freeze/} 是一个 @ref{39,,distutils} 的扩展（参见 @ref{132f,,扩展 Distutils} ），它将Python脚本包装成可执行的Windows程序（@code{@emph{*}.exe} 文件）。完成此操作后，您可以分发应用程序，而无需用户安装Python。

@node WConio,,cx_Freeze,附加模块
@anchor{using/windows wconio}@anchor{1330}
@subsubsection WConio


由于Python的高级终端处理层 @ref{2c,,curses} 仅限于类Unix系统，因此Windows还有一个独立的库：用于Python的Windows 控制台 I/O .

WConio@footnote{http://newcenturycomputers.net/projects/wconio.html} 是Turbo-C的 @code{CONIO.H} 装饰器,用于创建文本用户界面。

@node 在Windows上编译Python,其他平台,附加模块,在Windows上使用 Python
@anchor{using/windows compiling-python-on-windows}@anchor{1331}
@subsection 在Windows上编译Python


如果你想自己编译CPython，首先要做的是获取 source@footnote{https://www.python.org/downloads/source/}. 。您可以下载最新版本的源代码，也可以重新签出 checkout@footnote{https://devguide.python.org/setup/#getting-the-source-code}. 。

源代码树包含Microsoft Visual Studio 2015的构建解决方案和项目文件，它是用于构建官方Python版本的编译器。这些文件位于 @code{PCbuild} 目录中。

检查 @code{PCbuild/readme.txt} 以获取有关构建过程的一般信息。

有关扩展模块，请参阅 @ref{1332,,在Windows平台编译C和C++扩展} 。


@subsubheading 参见



@table @asis

@item Python + Windows + distutils + SWIG + gcc MinGW@footnote{http://sebsauvage.net/python/mingw.html}

或 "Creating Python extensions in C/C++ with SWIG and compiling them with MinGW gcc under Windows" 或 "Installing Python extension with distutils and without Microsoft Visual C++" by Sébastien Sauvage, 2003
@end table

MingW -- Python 扩展@footnote{http://www.mingw.org/wiki/FAQ#toc14}


@node 其他平台,,在Windows上编译Python,在Windows上使用 Python
@anchor{using/windows other-platforms}@anchor{1333}
@subsection 其他平台


随着Python的不断发展，不再支持以前曾经支持的一些平台（由于缺少用户或开发人员）。检查 
@geindex Python 提高建议; PEP 11
PEP 11@footnote{https://www.python.org/dev/peps/pep-0011} 了解所有不支持的平台的详细信息。


@itemize *

@item 
Windows CE@footnote{http://pythonce.sourceforge.net/} 仍然受支持。

@item 
Cygwin@footnote{https://cygwin.com/} 安装包也提供安装Python解释器 (cf. Cygwin package source@footnote{ftp://ftp.uni-erlangen.de/pub/pc/gnuwin32/cygwin/mirrors/cygnus/release/python}, Maintainer releases@footnote{http://www.tishler.net/jason/software/python/})
@end itemize

有关具有预编译安装程序平台的详细信息，请参阅 Python for Windows@footnote{https://www.python.org/downloads/windows/}

@node 在苹果系统上使用 Python,编辑器和集成开发环境,在Windows上使用 Python,Python安装和使用
@anchor{using/mac doc}@anchor{1334}@anchor{using/mac using-on-mac}@anchor{1335}@anchor{using/mac using-python-on-a-macintosh}@anchor{1336}
@section 在苹果系统上使用 Python


@*作者: 
Bob Savage <@email{bobsavage@@mac.com}>


运行 Mac OS X 的 Macintosh上 的 Python 原则上与任何其他 Unix 平台上的 Python 非常相似，但是还有一些额外的功能，例如 IDE 和包管理器，值得一提。

@menu
* 获取和安装 MacPython:: 
* IDE:: 
* 安装额外的 Python 包:: 
* Mac 上的图形界面编程:: 
* 在 Mac 上分发 Python 应用程序:: 
* 其他资源:: 

@end menu

@node 获取和安装 MacPython,IDE,,在苹果系统上使用 Python
@anchor{using/mac getting-and-installing-macpython}@anchor{1337}@anchor{using/mac getting-osx}@anchor{1338}
@subsection 获取和安装 MacPython


Mac OS X 10.8 附带 Apple 预安装的 Python 2.7 。 如果你愿意，可以从 Python 网站（ @indicateurl{https://www.python.org} ）安装最新版本的 Python 3 。  Python 的当前“通用二进制”版本可以在 Mac 的新 Intel 和传统 PPC CPU 上本地运行。

你安装后得到的东西有：


@itemize *

@item 
会有一个 @code{Python 3.8} 文件夹在你的 @code{Applications} 文件夹中。 在这里你可以找到 IDLE，它是作为官方 Python 发行版标准组成部分的开发环境；以及 PythonLauncher，它负责处理在 Finder 中双击 Python 脚本的操作。

@item 
框架 @code{/Library/Frameworks/Python.framework} ，包括 Python 可执行文件和库。安装程序将此位置添加到 shell 路径。 要卸载 MacPython ，你可以简单地移除这三个项目。 Python 可执行文件的符号链接放在 /usr/local/bin/ 中。
@end itemize

Apple 提供的 Python 版本分别安装在 @code{/System/Library/Frameworks/Python.framework} 和 @code{/usr/bin/python} 中。 你永远不应修改或删除这些内容，因为它们由 Apple 控制并由 Apple 或第三方软件使用。 请记住，如果你选择从 python.org 安装较新的 Python 版本，那么你的计算机上将安装两个不同但都有用的 Python ，因此你的路径和用法与你想要执行的操作一致非常重要。

IDLE 包含一个帮助菜单，允许你访问 Python 文档。 如果您是 Python 的新手，你应该开始阅读该文档中的教程介绍。

如果你熟悉其他 Unix 平台上的 Python ，那么你应该阅读有关从 Unix shell 运行 Python 脚本的部分。

@menu
* 如何运行 Python 脚本:: 
* 运行有图形界面的脚本:: 
* 配置:: 

@end menu

@node 如何运行 Python 脚本,运行有图形界面的脚本,,获取和安装 MacPython
@anchor{using/mac how-to-run-a-python-script}@anchor{1339}
@subsubsection 如何运行 Python 脚本


在 Mac OS X 上开始使用 Python 的最佳方法是通过 IDLE 集成开发环境，参见 @ref{133a,,IDE} 部分，并在 IDE 运行时使用“帮助”菜单。

如果要从终端窗口命令行或 Finder 运行 Python 脚本，首先需要一个编辑器来创建脚本。 Mac OS X 附带了许多标准的 Unix 命令行编辑器，如 @code{vim} 和 @code{emacs} 。 如果你想要一个更 Mac 化的编辑器，那么:program:@cite{BBEdit} 或来自 Bare Bones Software 的 @code{TextWrangler} （参见 @indicateurl{http://www.barebones.com/products/bbedit/index.html} ）是不错的选择 ，就如 @code{TextMate`（参见 https://macromates.com/ ）。 其他编辑器包括 :program:`Gvim} （ @indicateurl{http://macvim-dev.github.io/macvim/} ）和 @code{Aquamacs} （ @indicateurl{http://aquamacs.org/} ）。

要从终端窗口运行脚本，必须确保:file:@cite{/usr/local/bin} 位于 shell 搜索路径中。

要从 Finder 运行你的脚本，你有两个选择：


@itemize *

@item 
把脚本拖拽到 @code{PythonLauncher}

@item 
选择 @code{PythonLauncher} 作为通过 finder Info 窗口打开脚本（或任何 .py 脚本）的默认应用程序，然后双击脚本。 @code{PythonLauncher} 有各种首选项来控制脚本的启动方式。 拖拽方式允许你为一次调用更改这些选项，或使用其“首选项”菜单全局更改内容。
@end itemize

@node 运行有图形界面的脚本,配置,如何运行 Python 脚本,获取和安装 MacPython
@anchor{using/mac osx-gui-scripts}@anchor{133b}@anchor{using/mac running-scripts-with-a-gui}@anchor{133c}
@subsubsection 运行有图形界面的脚本


对于旧版本的 Python ，你需要注意一个 Mac OS X 的怪异之处：与 Aqua 窗口管理器通信的程序（换而言之，任何具有图形界面的程序）需要以特殊方式运行。 使用 @code{pythonw} 而不是 @code{python} 来启动这样的脚本。

对于Python 3.8，可以使用 @code{python} 或 @code{pythonw}

@node 配置,,运行有图形界面的脚本,获取和安装 MacPython
@anchor{using/mac configuration}@anchor{133d}
@subsubsection 配置


OS X 上的 Python 遵循所有标准的 Unix 环境变量，例如 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} ，但是为 Finder 启动的程序设置这些变量是非标准的，因为 Finder 在启动时不读取你的 @code{.profile} 或 @code{.cshrc} 。你需要创建一个文件 @code{~/.MacOSX/environment.plist} 。 有关详细信息，请参阅 Apple 的技术文档 QA1067 。

更多关于在 MacPython 中安装 Python 包的信息，参阅 @ref{133e,,安装额外的 Python 包} 部分。

@node IDE,安装额外的 Python 包,获取和安装 MacPython,在苹果系统上使用 Python
@anchor{using/mac ide}@anchor{133a}@anchor{using/mac the-ide}@anchor{133f}
@subsection IDE


MacPython 附带标准的 IDLE 开发环境。 有关使用 IDLE 的详细介绍，请访问 @indicateurl{http://www.hashcollision.org/hkn/python/idle_intro/index.html} 。

@node 安装额外的 Python 包,Mac 上的图形界面编程,IDE,在苹果系统上使用 Python
@anchor{using/mac installing-additional-python-packages}@anchor{1340}@anchor{using/mac mac-package-manager}@anchor{133e}
@subsection 安装额外的 Python 包


有几个方法可以安装额外的 Python 包：


@itemize *

@item 
可以通过标准的 Python distutils 模式（ @code{python setup.py install} ）安装软件包。

@item 
许多包也可以通过 @code{setuptools} 扩展或 @code{pip} 包装器安装，请参阅 @indicateurl{https://pip.pypa.io/} 。
@end itemize

@node Mac 上的图形界面编程,在 Mac 上分发 Python 应用程序,安装额外的 Python 包,在苹果系统上使用 Python
@anchor{using/mac gui-programming-on-the-mac}@anchor{1341}
@subsection Mac 上的图形界面编程


使用 Python 在 Mac 上构建 GUI 应用程序有多种选择。

@emph{PyObjC} 是一个 Python 到 Apple 的 Objective-C/Cocoa 框架的绑定，这是大多数现代 Mac 开发的基础。 有关 PyObjC 的信息，请访问 @indicateurl{https://pypi.org/project/pyobjc/}。

标准的 Python GUI 工具包是 @ref{10c,,tkinter} ，基于跨平台的 Tk 工具包（ @indicateurl{https://www.tcl.tk} ）。 Apple 的 OS X 捆绑了 Aqua 原生版本的 Tk ，最新版本可以从 @indicateurl{https://www.activestate.com} 下载和安装；它也可以从源代码构建。

@emph{wxPython} 是另一种流行的跨平台 GUI 工具包，可在 Mac OS X 上本机运行。软件包和文档可从 @indicateurl{https://www.wxpython.org} 获得。

@emph{PyQt} 是另一种流行的跨平台 GUI 工具包，可在 Mac OS X 上本机运行。更多信息可在 @indicateurl{https://riverbankcomputing.com/software/pyqt/intro} 上找到。

@node 在 Mac 上分发 Python 应用程序,其他资源,Mac 上的图形界面编程,在苹果系统上使用 Python
@anchor{using/mac distributing-python-applications-on-the-mac}@anchor{1342}
@subsection 在 Mac 上分发 Python 应用程序


在 Mac 上部署独立 Python 应用程序的标准工具是 @code{py2app} 。有关安装和使用 py2app 的更多信息，请访问 @indicateurl{http://undefined.org/python/#py2app} 。

@node 其他资源,,在 Mac 上分发 Python 应用程序,在苹果系统上使用 Python
@anchor{using/mac other-resources}@anchor{1343}
@subsection 其他资源


MacPython 邮件列表是 Mac 上 Python 用户和开发人员的优秀支持资源：

@indicateurl{https://www.python.org/community/sigs/current/pythonmac-sig/}

另一个有用的资源是 MacPython wiki ：

@indicateurl{https://wiki.python.org/moin/MacPython}

@node 编辑器和集成开发环境,,在苹果系统上使用 Python,Python安装和使用
@anchor{using/editors doc}@anchor{1344}@anchor{using/editors editors}@anchor{1345}@anchor{using/editors editors-and-ides}@anchor{1346}
@section 编辑器和集成开发环境


有很多支持Python编程语言的集成开发环境。大多数编辑器和集成开发环境支持语法高亮，调试工具和 
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008} 检查。

请访问 Python Editors@footnote{https://wiki.python.org/moin/PythonEditors} 和 Integrated Development Environments@footnote{https://wiki.python.org/moin/IntegratedDevelopmentEnvironments} 以获取完整列表。

@node Python语言参考,Python 标准库,Python安装和使用,Top
@anchor{reference/index doc}@anchor{1347}@anchor{reference/index reference-index}@anchor{1190}@anchor{reference/index the-python-language-reference}@anchor{1348}
@chapter Python语言参考


本参考手册描述了 Python 的语法和“核心语义”。本参考是简洁的，但试图做到准确和完整。 非必要的内建对象类型和内建函数、模块的语义描述在 @ref{118f,,Python 标准库} 中。有关该语言的非正式介绍，请参阅 @ref{118e,,Python 教程} 。对 C 或 C++ 程序员，还有两个额外的手册： @ref{1191,,扩展和嵌入 Python 解释器} 概述了如何编写一个 Python 扩展模块，@ref{1192,,Python/C API 参考手册} 详细介绍了 C/C++ 中可用的接口。

@menu
* 概述: 概述<5>. 
* 词法分析:: 
* 数据模型:: 
* 执行模型:: 
* 导入系统:: 
* 表达式:: 
* 简单语句:: 
* 复合语句:: 
* 最高层级组件:: 
* 完整的语法规范:: 

@end menu

@node 概述<5>,词法分析,,Python语言参考
@anchor{reference/introduction doc}@anchor{1349}@anchor{reference/introduction id1}@anchor{134a}@anchor{reference/introduction introduction}@anchor{134b}
@section 概述


本参考手册是对 Python 编程语言的描述。并不适宜作为教程使用。

我希望尽可能地保证内容精确无误，但还是选择使用自然词句进行描述，正式的规格定义仅用于句法和词法解析。这样应该能使文档对于普通人来说更易理解，但也可能导致一些歧义。因此，如果你是来自火星并且想凭借这份文档把 Python 重新实现一遍，也许有时需要自行猜测，实际上最终大概会得到一个十分不同的语言。而在另一方面，如果你正在使用 Python 并且想了解有关该语言特定领域的精确规则，你应该能够在这里找到它们。如果你希望查看对该语言更正式的定义，也许你可以花些时间自己写上一份 --- 或者发明一台克隆机器 :-)

在语言参考文档里加入过多的实现细节是很危险的 --- 具体实现可能发生改变，对同一语言的其他实现可能使用不同的方式。而在另一方面，CPython 是得到广泛使用的 Python 实现 (然而其他一些实现的拥护者也在增加)，其中的特殊细节有时也值得一提，特别是当其实现方式导致额外的限制时。因此，你会发现在正文里不时会跳出来一些简短的 "实现注释"。

每种 Python 实现都带有一些内置和标准的模块。相关的文档可参见 @ref{118f,,Python 标准库} 索引。少数内置模块也会在此提及，如果它们同语言描述存在明显的关联。

@menu
* 其他实现:: 
* 标注:: 

@end menu

@node 其他实现,标注,,概述<5>
@anchor{reference/introduction alternate-implementations}@anchor{134c}@anchor{reference/introduction implementations}@anchor{12cc}
@subsection 其他实现


虽然官方 Python 实现差不多得到最广泛的欢迎，但也有一些其他实现对特定领域的用户来说更具吸引力。

知名的实现包括:


@table @asis

@item CPython

这是最早出现并持续维护的 Python 实现，以 C 语言编写。新的语言特性通常在此率先添加。

@item Jython

以 Java 语言编写的 Python 实现。此实现可以作为 Java 应用的一个脚本语言，或者可以用来创建需要 Java 类库支持的应用。想了解更多信息可访问 Jython 网站@footnote{http://www.jython.org/}。

@item Python for .NET

此实现实际上使用了 CPython 实现，但是属于 .NET 托管应用并且可以引入 .NET 类库。它的创造者是 Brian Lloyd。想了解详情可访问 Python for .NET 主页@footnote{https://pythonnet.github.io/}。

@item IronPython

另一个 .NET 的 Python 实现，与 Python.NET 不同点在于它是生成 IL 的完全 Python 实现，并且将 Python 代码直接编译为 .NET 程序集。它的创造者就是当初创造 Jython 的 Jim Hugunin。想了解详情可访问 IronPython 网站@footnote{http://ironpython.net/}。

@item PyPy

完全使用 Python 语言编写的 Python 实现。它支持多个其他实现所没有的高级特性，例如非栈式支持和 JIT 编译器等。此项目的目标之一是通过允许方便地修改解释器 (因为它是用 Python 编写的)，鼓励该对语言本身进行试验。想了解详情可访问 PyPy 项目主页@footnote{http://pypy.org/}。
@end table

以上这些实现都可能在某些方面与此参考文档手册的描述有所差异，或是引入了超出标准 Python 文档范围的特定信息。请参考它们各自的专门文档，以确定你正在使用的这个实现有哪些你需要了解的东西。

@node 标注,,其他实现,概述<5>
@anchor{reference/introduction id2}@anchor{134d}@anchor{reference/introduction notation}@anchor{134e}
@subsection 标注


@geindex BNF
@geindex grammar
@geindex syntax
@geindex notation

句法和词法解析的描述采用经过改进的 BNF 语法标注。这包含以下定义样式:

@example
@anchor{reference/introduction grammar-token-name}@anchor{134f}name      ::= lc_letter (lc_letter | "_")*
@anchor{reference/introduction grammar-token-lc-letter}@anchor{1350}lc_letter ::= "a"..."z"
@end example

第一行表示 @code{name} 是一个 @code{lc_letter} 之后跟零个或多个 @code{lc_letter} 和下划线。而一个 @code{lc_letter} 则是任意单个 @code{'a'} 至 @code{'z'} 字符。(实际上在本文档中始终采用此规则来定义词法和语法规则的名称。)

每条规则的开头是一个名称 (即该规则所定义的名称) 加上 @code{::=}。竖线 (@code{|}) 被用来分隔可选项；它是此标注中最灵活的操作符。星号 (@code{*}) 表示前一项的零次或多次重复；类似地，加号 (@code{+}) 表示一次或多次重复，而由方括号括起的内容 (@code{[ ]}) 表示出现零次或一次 (或者说，这部分内容是可选的)。@code{*} 和 @code{+} 操作符的绑定是最紧密的；圆括号用于分组。固定字符串包含在引号内。空格的作用仅限于分隔形符。每条规则通常为一行；有许多个可选项的规则可能会以竖线为界分为多行。

@geindex lexical definitions
@geindex ASCII

在词法定义中 (如上述示例)，还额外使用了两个约定: 由三个点号分隔的两个字符字面值表示在指定 (闭) 区间范围内的任意单个 ASCII 字符。由尖括号 (@code{<...>}) 括起来的内容是对于所定义符号的非正式描述；即可以在必要时用来说明 '控制字符' 的意图。

虽然所用的标注方式几乎相同，但是词法定义和句法定义是存在很大区别的: 词法定义作用于输入源中单独的字符，而句法定义则作用于由词法分析所生成的形符流。在下一章节 ("词法分析") 中使用的 BNF 全部都是词法定义；在之后的章节中使用的则是句法定义。

@node 词法分析,数据模型,概述<5>,Python语言参考
@anchor{reference/lexical_analysis doc}@anchor{1351}@anchor{reference/lexical_analysis lexical}@anchor{1352}@anchor{reference/lexical_analysis lexical-analysis}@anchor{1353}
@section 词法分析


@geindex lexical analysis
@geindex parser
@geindex token

Python 程序由一个 @emph{解析器} 读取。输入到解析器的是一个由 @emph{词法分析器} 所生成的 @emph{形符} 流，本章将描述词法分析器是如何将一个文件拆分为一个个形符的。

Python 会将读取的程序文本转为 Unicode 码点；源文件的文本编码可由编码声明指定，默认为 UTF-8，详情见 
@geindex Python 提高建议; PEP 3120
PEP 3120@footnote{https://www.python.org/dev/peps/pep-3120}。如果源文件无法被解码，将会引发 @ref{452,,SyntaxError}。

@menu
* 行结构:: 
* 其他形符:: 
* 标识符和关键字:: 
* 字面值:: 
* 运算符:: 
* 分隔符:: 

@end menu

@node 行结构,其他形符,,词法分析
@anchor{reference/lexical_analysis id1}@anchor{1354}@anchor{reference/lexical_analysis line-structure}@anchor{1355}
@subsection 行结构


@geindex line structure

一个 Python 程序可分为许多 @emph{逻辑行}。

@menu
* 逻辑行:: 
* 物理行:: 
* 注释:: 
* 编码声明:: 
* 显式的行拼接:: 
* 隐式的行拼接:: 
* 空白行:: 
* 缩进:: 
* 形符之间的空白:: 

@end menu

@node 逻辑行,物理行,,行结构
@anchor{reference/lexical_analysis id2}@anchor{1356}@anchor{reference/lexical_analysis logical-lines}@anchor{1357}
@subsubsection 逻辑行


@geindex logical line
@geindex physical line
@geindex line joining
@geindex NEWLINE token

逻辑行的结束是以 NEWLINE 形符表示的。语句不能跨越逻辑行的边界，除非其语法允许包含 NEWLINE (例如复合语句可由多行子语句组成)。一个逻辑行可由一个或多个 @emph{物理行} 按照明确或隐含的 @emph{行拼接} 规则构成。

@node 物理行,注释,逻辑行,行结构
@anchor{reference/lexical_analysis id3}@anchor{1358}@anchor{reference/lexical_analysis physical-lines}@anchor{1359}
@subsubsection 物理行


物理行是以一个行终止序列结束的字符序列。在源文件和字符串中，可以使用任何标准平台上的行终止序列 - Unix 所用的 ASCII 字符 LF (换行), Windows 所用的 ASCII 字符序列 CR LF (回车加换行), 或者旧 Macintosh 所用的 ASCII 字符 CR (回车)。所有这些形式均可使用，无论具体平台。输入的结束也会被作为最后一个物理行的隐含终止标志。

当嵌入 Python 时，源码字符串传入 Python API 应使用标准 C 的传统换行符 (即 @code{\n}，表示 ASCII 字符 LF 作为行终止标志)。

@node 注释,编码声明,物理行,行结构
@anchor{reference/lexical_analysis comments}@anchor{135a}@anchor{reference/lexical_analysis id4}@anchor{135b}
@subsubsection 注释


@geindex comment
@geindex hash character
@geindex # (hash); comment

一条注释以不包含在字符串字面值内的井号 (@code{#}) 开头，并在物理行的末尾结束。 一条注释标志着逻辑行的结束，除非存在隐含的行拼接规则。 注释在语法分析中会被忽略。

@node 编码声明,显式的行拼接,注释,行结构
@anchor{reference/lexical_analysis encoding-declarations}@anchor{135c}@anchor{reference/lexical_analysis encodings}@anchor{135d}
@subsubsection 编码声明


@geindex source character set
@geindex encoding declarations (source file)
@geindex # (hash); source encoding declaration

如果一条注释位于 Python 脚本的第一或第二行，并且匹配正则表达式 @code{coding[=:]\s*([-\w.]+)}，这条注释会被作为编码声明来处理；上述表达式的第一组指定了源码文件的编码。编码声明必须独占一行。如果它是在第二行，则第一行也必须是注释。推荐的编码声明形式如下

@example
# -*- coding: <encoding-name> -*-
@end example

这也是 GNU Emacs 认可的形式，以及

@example
# vim:fileencoding=<encoding-name>
@end example

这是 Bram Moolenaar 的 VIM 认可的形式。

如果没有编码声明，则默认编码为 UTF-8。此外，如果文件的首字节为 UTF-8 字节顺序标志 (@code{b'\xef\xbb\xbf'})，文件编码也声明为 UTF-8 (这是 Microsoft 的 @code{notepad} 等软件支持的形式)。

编码声明指定的编码名称必须是 Python 所认可的编码。所有词法分析将使用此编码，包括语义字符串、注释和标识符。

@c XXX there should be a list of supported encodings.

@node 显式的行拼接,隐式的行拼接,编码声明,行结构
@anchor{reference/lexical_analysis explicit-joining}@anchor{135e}@anchor{reference/lexical_analysis explicit-line-joining}@anchor{135f}
@subsubsection 显式的行拼接


@geindex physical line
@geindex line joining
@geindex line continuation
@geindex backslash character

两个或更多个物理行可使用反斜杠字符 (@code{\}) 拼接为一个逻辑行，规则如下: 当一个物理行以一个不在字符串或注释内的反斜杠结尾时，它将与下一行拼接构成一个单独的逻辑行，反斜杠及其后的换行符会被删除。例如:

@example
if 1900 < year < 2100 and 1 <= month <= 12 \
   and 1 <= day <= 31 and 0 <= hour < 24 \
   and 0 <= minute < 60 and 0 <= second < 60:   # Looks like a valid date
        return 1
@end example

以反斜杠结束的行不能带有注释。反斜杠不能用来拼接注释。反斜杠不能用来拼接形符，字符串除外 (即原文字符串以外的形符不能用反斜杠分隔到两个物理行)。不允许有原文字符串以外的反斜杠存在于物理行的其他位置。

@node 隐式的行拼接,空白行,显式的行拼接,行结构
@anchor{reference/lexical_analysis implicit-joining}@anchor{1360}@anchor{reference/lexical_analysis implicit-line-joining}@anchor{1361}
@subsubsection 隐式的行拼接


圆括号、方括号或花括号以内的表达式允许分成多个物理行，无需使用反斜杠。例如:

@example
month_names = ['Januari', 'Februari', 'Maart',      # These are the
               'April',   'Mei',      'Juni',       # Dutch names
               'Juli',    'Augustus', 'September',  # for the months
               'Oktober', 'November', 'December']   # of the year
@end example

隐式的行拼接可以带有注释。后续行的缩进不影响程序结构。后续行也允许为空白行。隐式拼接的行之间不会有 NEWLINE 形符。隐式拼接的行也可以出现于三引号字符串中 (见下)；此情况下这些行不允许带有注释。

@node 空白行,缩进,隐式的行拼接,行结构
@anchor{reference/lexical_analysis blank-lines}@anchor{1362}@anchor{reference/lexical_analysis id5}@anchor{1363}
@subsubsection 空白行


@geindex blank line

一个只包含空格符，制表符，进纸符或者注释的逻辑行会被忽略 (即不生成 NEWLINE 形符)。在交互模式输入语句时，对空白行的处理可能会因读取-求值-打印循环的具体实现方式而存在差异。在标准交互模式解释器中，一个完全空白的逻辑行 (即连空格或注释都没有) 将会结束一条多行复合语句。

@node 缩进,形符之间的空白,空白行,行结构
@anchor{reference/lexical_analysis id6}@anchor{1364}@anchor{reference/lexical_analysis indentation}@anchor{1365}
@subsubsection 缩进


@geindex indentation
@geindex leading whitespace
@geindex space
@geindex tab
@geindex grouping
@geindex statement grouping

一个逻辑行开头处的空白 (空格符和制表符) 被用来计算该行的缩进等级，以决定语句段落的组织结构。

制表符会被 (从左至右) 替换为一至八个空格，这样缩进的空格总数为八的倍数 (这是为了与 Unix 所用的规则一致)。首个非空白字符之前的空格总数将确定该行的缩进层次。一个缩进不可使用反斜杠进行多行拼接；首个反斜杠之前的空格将确定缩进层次。

在一个源文件中如果混合使用制表符和空格符缩进，并使得确定缩进层次需要依赖于制表符对应的空格数量设置，则被视为不合规则；此情况将会引发 @ref{e70,,TabError}。

@strong{跨平台兼容性注释:} 由于非 UNIX 平台上文本编辑器本身的特性，在一个源文件中混合使用制表符和空格符是不明智的。另外也要注意不同平台还可能会显式地限制最大缩进层级。

行首有时可能会有一个进纸符；它在上述缩进层级计算中会被忽略。处于行首空格内其他位置的进纸符的效果未定义 (例如它可能导致空格计数重置为零)。

@geindex INDENT token
@geindex DEDENT token

多个连续行各自的缩进层级将会被放入一个堆栈用来生成 INDENT 和 DEDENT 形符，具体说明如下。

在读取文件的第一行之前，先向堆栈推入一个零值；它将不再被弹出。被推入栈的层级数值从底至顶持续增加。每个逻辑行开头的行缩进层级将与栈顶行比较。如果相同，则不做处理。如果新行层级较高，则会被推入栈顶，并生成一个 INDENT 形符。如果新行层级较低，则 @emph{应当} 是栈中的层级数值之一；栈中高于该层级的所有数值都将被弹出，每弹出一级数值生成一个 DEDENT 形符。在文件末尾，栈中剩余的每个大于零的数值生成一个 DEDENT 形符。

这是一个正确 (但令人迷惑) 的Python 代码缩进示例:

@example
def perm(l):
        # Compute the list of all permutations of l
    if len(l) <= 1:
                  return [l]
    r = []
    for i in range(len(l)):
             s = l[:i] + l[i+1:]
             p = perm(s)
             for x in p:
              r.append(l[i:i+1] + x)
    return r
@end example

以下示例显示了各种缩进错误:

@example
 def perm(l):                       # error: first line indented
for i in range(len(l)):             # error: not indented
    s = l[:i] + l[i+1:]
        p = perm(l[:i] + l[i+1:])   # error: unexpected indent
        for x in p:
                r.append(l[i:i+1] + x)
            return r                # error: inconsistent dedent
@end example

(实际上，前三个错误会被解析器发现；只有最后一个错误是由词法分析器发现的 --- @code{return r} 的缩进无法匹配弹出栈的缩进层级。)

@node 形符之间的空白,,缩进,行结构
@anchor{reference/lexical_analysis whitespace}@anchor{1366}@anchor{reference/lexical_analysis whitespace-between-tokens}@anchor{1367}
@subsubsection 形符之间的空白


除非是在逻辑行的开头或字符串内，空格符、制表符和进纸符等空白符都同样可以用来分隔形符。如果两个形符彼此相连会被解析为一个不同的形符，则需要使用空白来分隔 (例如 ab 是一个形符，而 a b 是两个形符)。

@node 其他形符,标识符和关键字,行结构,词法分析
@anchor{reference/lexical_analysis id7}@anchor{1368}@anchor{reference/lexical_analysis other-tokens}@anchor{1369}
@subsection 其他形符


除了 NEWLINE, INDENT 和 DEDENT，还存在以下类别的形符: @emph{标识符}, @emph{关键字}, @emph{字面值}, @emph{运算符} 以及 @emph{分隔符}。 空白字符 (之前讨论过的行终止符除外) 不属于形符，而是用来分隔形符。如果存在二义性，将从左至右读取尽可能长的合法字符串组成一个形符。

@node 标识符和关键字,字面值,其他形符,词法分析
@anchor{reference/lexical_analysis identifiers}@anchor{136a}@anchor{reference/lexical_analysis identifiers-and-keywords}@anchor{136b}
@subsection 标识符和关键字


@geindex identifier
@geindex name

标识符 (或者叫做 @emph{名称}) 由以下词法定义进行描述。

Python 中的标识符语法是基于 Unicode 标准附件 UAX-31，并加入了下文所定义的细化与修改；更多细节还可参见 
@geindex Python 提高建议; PEP 3131
PEP 3131@footnote{https://www.python.org/dev/peps/pep-3131} 。

在 ASCII 范围内 (U+0001..U+007F)，可用于标识符的字符与 Python 2.x 一致: 大写和小写字母 @code{A} 至 @code{Z}，下划线 @code{_} 以及数字 @code{0} 至 @code{9}，但不可以数字打头。

Python 3.0 引入了 ASCII 范围以外的额外字符 (见 
@geindex Python 提高建议; PEP 3131
PEP 3131@footnote{https://www.python.org/dev/peps/pep-3131})。这些字符的分类使用包含于 @ref{11a,,unicodedata} 模块中的 Unicode 字符数据库版本。

标识符的长度没有限制。对大小写敏感。

@example
@anchor{reference/lexical_analysis grammar-token-identifier}@anchor{136c}identifier   ::= xid_start xid_continue*
@anchor{reference/lexical_analysis grammar-token-id-start}@anchor{136d}id_start     ::= <all characters in general categories Lu, Ll, Lt, Lm, Lo, Nl, the underscore, and characters with the Other_ID_Start property>
@anchor{reference/lexical_analysis grammar-token-id-continue}@anchor{136e}id_continue  ::= <all characters in id_start, plus characters in the categories Mn, Mc, Nd, Pc and others with the Other_ID_Continue property>
@anchor{reference/lexical_analysis grammar-token-xid-start}@anchor{136f}xid_start    ::= <all characters in id_start whose NFKC normalization is in "id_start xid_continue*">
@anchor{reference/lexical_analysis grammar-token-xid-continue}@anchor{1370}xid_continue ::= <all characters in id_continue whose NFKC normalization is in "id_continue*">
@end example

上文所用 Unicode 类别码的含义:


@itemize *

@item 
@emph{Lu} - 大写字母

@item 
@emph{Ll} - 小写字母

@item 
@emph{Lt} - 词首大写字母

@item 
@emph{Lm} - 修饰字母

@item 
@emph{Lo} - 其他字母

@item 
@emph{Nl} - 字母数字

@item 
@emph{Mn} - 非空白标识

@item 
@emph{Mc} - 含空白标识

@item 
@emph{Nd} - 十进制数字

@item 
@emph{Pc} - 连接标点

@item 
@emph{Other_ID_Start} - 由 PropList.txt@footnote{http://www.unicode.org/Public/12.1.0/ucd/PropList.txt} 定义的显式字符列表，用来支持向下兼容

@item 
@emph{Other_ID_Continue} - 同上
@end itemize

所有标识符在解析时会被转换为规范形式 NFKC；标识符的比较都是基于 NFKC。

Unicode 4.1 中所有可用的标识符字符列表可参见以下非正式 HTML 文件 @indicateurl{https://www.unicode.org/Public/13.0.0/ucd/DerivedCoreProperties.txt}

@menu
* 关键字:: 
* 保留的标识符类:: 

@end menu

@node 关键字,保留的标识符类,,标识符和关键字
@anchor{reference/lexical_analysis id8}@anchor{1371}@anchor{reference/lexical_analysis keywords}@anchor{1372}
@subsubsection 关键字


@geindex keyword
@geindex reserved word

以下标识符被作为语言的保留字或称 @emph{关键字}，不可被用作普通标识符。关键字的拼写必须与这里列出的完全一致。

@example
False      await      else       import     pass
None       break      except     in         raise
True       class      finally    is         return
and        continue   for        lambda     try
as         def        from       nonlocal   while
assert     del        global     not        with
async      elif       if         or         yield
@end example

@geindex _@comma{} identifiers
@geindex __@comma{} identifiers

@node 保留的标识符类,,关键字,标识符和关键字
@anchor{reference/lexical_analysis id-classes}@anchor{1373}@anchor{reference/lexical_analysis reserved-classes-of-identifiers}@anchor{1374}
@subsubsection 保留的标识符类


某些标识符类 (除了关键字) 具有特殊的含义。这些标识符类的命名模式是以下划线字符打头和结尾:


@table @asis

@item @code{_*}

不会被 @code{from module import *} 导入。特殊标识符 @code{_} 在交互式解释器中被用来存放最近一次求值结果；它保存在 @ref{13,,builtins} 模块中。当不处于交互模式时，@code{_} 无特殊含义也没有预定义。参见 @ref{c16,,import 语句}。

@cartouche
@quotation 注解 
@code{_} 作为名称常用于连接国际化文本；请参看 @ref{89,,gettext} 模块文档了解有关此约定的详情。
@end quotation
@end cartouche

@item @code{__*__}

系统定义的名称，在非正式场合下被叫做 "dunder" 名称。 这些名称是由解释器及其实现（包括标准库）定义的。 现有系统定义名称相关的讨论请参见 @ref{508,,特殊方法名称} 等章节。 未来的 Python 版本中还将定义更多此类名称。 任何情况下 @emph{任何} 不遵循文档所显式指明的 @code{__*__} 名称使用方式都可能导致无警告的错误。

@item @code{__*}

类的私有名称。这种名称在类定义中使用时，会以一种混合形式重写以避免在基类及派生类的 "私有" 属性之间出现名称冲突。参见 @ref{1375,,标识符（名称）}。
@end table

@node 字面值,运算符,标识符和关键字,词法分析
@anchor{reference/lexical_analysis id9}@anchor{1376}@anchor{reference/lexical_analysis literals}@anchor{1377}
@subsection 字面值


@geindex literal
@geindex constant

字面值用于表示一些内置类型的常量。

@geindex string literal
@geindex bytes literal
@geindex ASCII
@geindex ' (single quote); string literal
@geindex " (double quote); string literal
@geindex u'; string literal
@geindex u"; string literal

@menu
* 字符串和字节串字面值:: 
* 字符串字面值拼接:: 
* 格式化字符串字面值:: 
* 数字字面值:: 
* 整型数字面值:: 
* 浮点数字面值:: 
* 虚数字面值:: 

@end menu

@node 字符串和字节串字面值,字符串字面值拼接,,字面值
@anchor{reference/lexical_analysis string-and-bytes-literals}@anchor{1378}@anchor{reference/lexical_analysis strings}@anchor{1379}
@subsubsection 字符串和字节串字面值


字符串字面值由以下词法定义进行描述:

@example
@anchor{reference/lexical_analysis grammar-token-stringliteral}@anchor{137a}stringliteral   ::= [stringprefix](shortstring | longstring)
@anchor{reference/lexical_analysis grammar-token-stringprefix}@anchor{137b}stringprefix    ::= "r" | "u" | "R" | "U" | "f" | "F"
                    | "fr" | "Fr" | "fR" | "FR" | "rf" | "rF" | "Rf" | "RF"
@anchor{reference/lexical_analysis grammar-token-shortstring}@anchor{137c}shortstring     ::= "'" shortstringitem* "'" | '"' shortstringitem* '"'
@anchor{reference/lexical_analysis grammar-token-longstring}@anchor{137d}longstring      ::= "'@w{'}'" longstringitem* "'@w{'}'" | '"""' longstringitem* '"""'
@anchor{reference/lexical_analysis grammar-token-shortstringitem}@anchor{137e}shortstringitem ::= shortstringchar | stringescapeseq
@anchor{reference/lexical_analysis grammar-token-longstringitem}@anchor{137f}longstringitem  ::= longstringchar | stringescapeseq
@anchor{reference/lexical_analysis grammar-token-shortstringchar}@anchor{1380}shortstringchar ::= <any source character except "\" or newline or the quote>
@anchor{reference/lexical_analysis grammar-token-longstringchar}@anchor{1381}longstringchar  ::= <any source character except "\">
@anchor{reference/lexical_analysis grammar-token-stringescapeseq}@anchor{1382}stringescapeseq ::= "\" <any source character>
@end example

@example
@anchor{reference/lexical_analysis grammar-token-bytesliteral}@anchor{1383}bytesliteral   ::= bytesprefix(shortbytes | longbytes)
@anchor{reference/lexical_analysis grammar-token-bytesprefix}@anchor{1384}bytesprefix    ::= "b" | "B" | "br" | "Br" | "bR" | "BR" | "rb" | "rB" | "Rb" | "RB"
@anchor{reference/lexical_analysis grammar-token-shortbytes}@anchor{1385}shortbytes     ::= "'" shortbytesitem* "'" | '"' shortbytesitem* '"'
@anchor{reference/lexical_analysis grammar-token-longbytes}@anchor{1386}longbytes      ::= "'@w{'}'" longbytesitem* "'@w{'}'" | '"""' longbytesitem* '"""'
@anchor{reference/lexical_analysis grammar-token-shortbytesitem}@anchor{1387}shortbytesitem ::= shortbyteschar | bytesescapeseq
@anchor{reference/lexical_analysis grammar-token-longbytesitem}@anchor{1388}longbytesitem  ::= longbyteschar | bytesescapeseq
@anchor{reference/lexical_analysis grammar-token-shortbyteschar}@anchor{1389}shortbyteschar ::= <any ASCII character except "\" or newline or the quote>
@anchor{reference/lexical_analysis grammar-token-longbyteschar}@anchor{138a}longbyteschar  ::= <any ASCII character except "\">
@anchor{reference/lexical_analysis grammar-token-bytesescapeseq}@anchor{138b}bytesescapeseq ::= "\" <any ASCII character>
@end example

这些条目中未提及的一个语法限制是 @ref{137b,,stringprefix} 或 @ref{1384,,bytesprefix} 与字面值的剩余部分之间不允许有空白。源字符集是由编码声明定义的；如果源文件中没有编码声明则默认为 UTF-8；参见 @ref{135d,,编码声明}。

@geindex triple-quoted string
@geindex Unicode Consortium
@geindex raw string
@geindex """; string literal
@geindex '@w{'}'; string literal

自然语言描述: 两种字面值都可以用成对单引号 (@code{'}) 或双引号 (@code{"}) 来标示首尾。它们也可以用成对的连续三个单引号或双引号来标示首尾 (这通常被称为 @emph{三引号字符串})。反斜杠 (@code{\}) 字符被用来对特殊含义的字符进行转义，例如换行，反斜杠本身或是引号等字符。

@geindex b'; bytes literal
@geindex b"; bytes literal

字节串字面值总是带有前缀 @code{'b'} 或 @code{'B'}；它们生成 @ref{32a,,bytes} 类型而非 @ref{329,,str} 类型的实例。它们只能包含 ASCII 字符；字节对应数值在128及以上必须以转义形式来表示。

@geindex r'; raw string literal
@geindex r"; raw string literal

字符串和字节串字面值都可以带有前缀 @code{'r'} 或 @code{'R'}；这种字符串被称为 @emph{原始字符串} 其中的反斜杠会被当作其本身的字面字符来处理。因此在原始字符串字面值中，@code{'\U'} 和 @code{'\u'} 转义形式不会被特殊对待。由于 Python 2.x 的原始统一码字面值的特性与 Python 3.x 不一致，@code{'ur'} 语法已不再被支持。


3.3 新版功能: 新加入了表示原始字节串的 @code{'rb'} 前缀，与 @code{'br'} 的意义相同。



3.3 新版功能: 对旧式统一码字面值 (@code{u'value'}) 的支持被重新引入以简化 Python 2.x 和 3.x 代码库的同步维护。详情见 
@geindex Python 提高建议; PEP 414
PEP 414@footnote{https://www.python.org/dev/peps/pep-0414}。


@geindex f'; formatted string literal
@geindex f"; formatted string literal

包含 @code{'f'} 或 @code{'F'} 前缀的字符串字面值称为 @emph{格式化字符串字面值}；参见 @ref{15c,,格式化字符串字面值}。@code{'f'} 可与 @code{'r'} 连用，但不能与 @code{'b'} 或 @code{'u'} 连用，因此存在原始格式化字符串，但不存在格式化字节串字面值。

在三引号字面值中，允许存在未经转义的换行和引号 (并原样保留)，除非是未经转义的连续三引号，这标示着字面值的结束。 ("引号" 是用来标示字面值的字符，即 @code{'} 或 @code{"}。)

@geindex physical line
@geindex escape sequence
@geindex Standard C
@geindex C
@geindex \ (backslash); escape sequence
@geindex \\; escape sequence
@geindex \a; escape sequence
@geindex \b; escape sequence
@geindex \f; escape sequence
@geindex \n; escape sequence
@geindex \r; escape sequence
@geindex \t; escape sequence
@geindex \v; escape sequence
@geindex \x; escape sequence
@geindex \N; escape sequence
@geindex \u; escape sequence
@geindex \U; escape sequence

除非带有 @code{'r'} 或 @code{'R'} 前缀，字符串和字节串字面值中的转义序列会基于类似标准 C 中的转义规则来解读。可用的转义序列如下:


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

转义序列

@tab

含义

@tab

注释

@item

@code{\newline}

@tab

反斜杠加换行全被忽略

@tab

@item

@code{\\}

@tab

反斜杠 (@code{\})

@tab

@item

@code{\'}

@tab

单引号 (@code{'})

@tab

@item

@code{\"}

@tab

双引号 (@code{"})

@tab

@item

@code{\a}

@tab

ASCII 响铃 (BEL)

@tab

@item

@code{\b}

@tab

ASCII 退格 (BS)

@tab

@item

@code{\f}

@tab

ASCII 进纸 (FF)

@tab

@item

@code{\n}

@tab

ASCII 换行 (LF)

@tab

@item

@code{\r}

@tab

ASCII 回车 (CR)

@tab

@item

@code{\t}

@tab

ASCII 水平制表 (TAB)

@tab

@item

@code{\v}

@tab

ASCII 垂直制表 (VT)

@tab

@item

@code{\ooo}

@tab

八进制数 @emph{ooo} 码位的字符

@tab

(1,3)

@item

@code{\xhh}

@tab

十六进制数 @emph{hh} 码位的字符

@tab

(2,3)

@end multitable


仅在字符串字面值中可用的转义序列如下:


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

转义序列

@tab

含义

@tab

注释

@item

@code{\N@{name@}}

@tab

Unicode 数据库中名称为 @emph{name} 的字符

@tab

(4)

@item

@code{\uxxxx}

@tab

16位十六进制数 @emph{xxxx} 码位的字符

@tab

(5)

@item

@code{\Uxxxxxxxx}

@tab

32位16进制数 @emph{xxxxxxxx} 码位的字符

@tab

(6)

@end multitable


注释:


@enumerate 

@item 
与标准 C 一致，接受最多三个八进制数码。

@item 
与标准 C 不同，要求必须为两个十六进制数码。

@item 
在字节串字面值中，十六进制数和八进制数转义码以相应数值代表每个字节。在字符串字面值中，这些转义码以相应数值代表每个 Unicode 字符。

@item 

在 3.3 版更改: 加入了对别名 @footnote{@w{(1)} 
@indicateurl{http://www.unicode.org/Public/11.0.0/ucd/NameAliases.txt}
} 的支持。


@item 
要求必须为四个十六进制数码。

@item 
此方式可用来表示任意 Unicode 字符。要求必须为八个十六进制数码。
@end enumerate

@geindex unrecognized escape sequence

与标准 C 不同，所有无法识别的转义序列将原样保留在字符串中，也就是说，@emph{反斜杠会在结果中保留}。(这种方式在调试时很有用: 如果输错了一个转义序列，更容易在输出结果中识别错误。) 另外要注意的一个关键点是：专用于字符串字面值中的转义序列如果在字节串字面值中出现，会被归类为无法识别的转义序列。

@quotation


在 3.6 版更改: 无法识别的转义序列将引发 @ref{278,,DeprecationWarning}。 在某个未来的 Python 版本中它们将引发 @ref{191,,SyntaxWarning} 并最终将改为引发 @ref{452,,SyntaxError}。

@end quotation

即使在原始字面值中，引号也可以加上反斜杠转义符，但反斜杠会保留在输出结果中；例如 @code{r"\""} 是一个有效的字符串字面值，包含两个字符: 一个反斜杠和一个双引号；而 @code{r"\"} 不是一个有效的字符串字面值 (即便是原始字符串也不能以奇数个反斜杠结束)。特别地，@emph{一个原始字面值不能以单个反斜杠结束} (因为此反斜杠会转义其后的引号字符)。还要注意一个反斜杠加一个换行在字面值中会被解释为两个字符，而 @emph{不是} 一个连续行。

@node 字符串字面值拼接,格式化字符串字面值,字符串和字节串字面值,字面值
@anchor{reference/lexical_analysis string-concatenation}@anchor{138c}@anchor{reference/lexical_analysis string-literal-concatenation}@anchor{138d}
@subsubsection 字符串字面值拼接


多个相邻的字符串或字节串字面值 (以空白符分隔)，所用的引号可以彼此不同，其含义等同于全部拼接为一体。因此， @code{"hello" 'world'} 等同于 @code{"helloworld"}。此特性可以减少反斜杠的使用，以方便地将很长的字符串分成多个物理行，甚至每部分字符串还可分别加注释，例如:

@example
re.compile("[A-Za-z_]"       # letter or underscore
           "[A-Za-z0-9_]*"   # letter, digit or underscore
          )
@end example

注意此特性是在句法层面定义的，但是在编译时实现。在运行时拼接字符串表达式必须使用 '+' 运算符。还要注意字面值拼接时每个部分可以使用不同的引号风格 (甚至混合使用原始字符串和三引号字符串)，格式化字符串字面值也可与普通字符串字面值拼接。

@geindex formatted string literal
@geindex interpolated string literal
@geindex string; formatted literal
@geindex string; interpolated literal
@geindex f-string
@geindex @{@} (curly brackets); in formatted string literal
@geindex ! (exclamation); in formatted string literal
@geindex ; (colon); in formatted string literal

@node 格式化字符串字面值,数字字面值,字符串字面值拼接,字面值
@anchor{reference/lexical_analysis f-strings}@anchor{15c}@anchor{reference/lexical_analysis formatted-string-literals}@anchor{138e}
@subsubsection 格式化字符串字面值



3.6 新版功能.


@emph{格式化字符串字面值} 或称 @emph{f-string} 是带有 @code{'f'} 或 @code{'F'} 前缀的字符串字面值。这种字符串可包含替换字段，即以 @code{@{@}} 标示的表达式。而其他字符串字面值总是一个常量，格式化字符串字面值实际上是会在运行时被求值的表达式。

转义序列会像在普通字符串字面值中一样被解码 (除非字面值还被标示为原始字符串)。解码之后，字符串内容所用的语法如下:

@example
@anchor{reference/lexical_analysis grammar-token-f-string}@anchor{138f}f_string          ::= (literal_char | "@{@{" | "@}@}" | replacement_field)*
@anchor{reference/lexical_analysis grammar-token-replacement-field}@anchor{1390}replacement_field ::= "@{" f_expression ["!" conversion] [":" format_spec] "@}"
@anchor{reference/lexical_analysis grammar-token-f-expression}@anchor{1391}f_expression      ::= (conditional_expression | "*" or_expr)
                        ("," conditional_expression | "," "*" or_expr)* [","]
                      | yield_expression
@anchor{reference/lexical_analysis grammar-token-conversion}@anchor{1392}conversion        ::= "s" | "r" | "a"
@anchor{reference/lexical_analysis grammar-token-format-spec}@anchor{1393}format_spec       ::= (literal_char | NULL | replacement_field)*
@anchor{reference/lexical_analysis grammar-token-literal-char}@anchor{1394}literal_char      ::= <any code point except "@{", "@}" or NULL>
@end example

字符串在花括号以外的部分按其字面值处理，除了双重花括号 @code{'@{@{'} 或 @code{'@}@}'} 会被替换为相应的单个花括号。单个左花括号 @code{'@{'} 标示一个替换字段，它以一个 Python 表达式打头，表达式之后可能有一个以叹号 @code{'!'} 标示的转换字段。之后还可能带有一个以冒号 @code{':'} 标示的格式说明符。替换字段以一个右花括号 @code{'@}'} 作为结束。

格式化字符串字面值中的表达式会被当作包含在圆括号中的普通 Python 表达式一样处理，但有少数例外。 空表达式不被允许，@ref{c28,,lambda} 和赋值表达式 @code{:=} 必须显式地加上圆括号。 替换表达式可以包含换行（例如在三重引号字符串中），但是不能包含注释。 每个表达式会在格式化字符串字面值所包含的位置按照从左至右的顺序被求值。


在 3.7 版更改: 在 Python 3.7 之前， @ref{1a3,,await} 表达式包含  @ref{2e3,,async for} 子句的推导式不允许在格式化字符串字面值表达式中使用，这是因为具体实现存在一个问题。


如果指定了转换符，表达式的求值结果会先转换再格式化。转换符 @code{'!s'} 即对结果调用 @ref{329,,str()}，@code{'!r'} 为调用 @ref{7c6,,repr()}，而 @code{'!a'} 为调用 @ref{d45,,ascii()}。

在此之后结果会使用 @ref{4d5,,format()} 协议进行格式化。格式说明符会被传入表达式或转换结果的 @ref{948,,__format__()} 方法。如果省略格式说明符则会传入一个空字符串。然后格式化结果会包含在整个字符串最终的值当中。

顶层的格式说明符可以包含有嵌套的替换字段。这些嵌套字段也可以包含有自己的转换字段和 @ref{4d8,,格式说明符}，但不可再包含更深层嵌套的替换字段。这里的 @ref{4d8,,格式说明符微型语言} 与字符串 .format() 方法所使用的相同。

格式化字符串字面值可以拼接，但是一个替换字段不能拆分到多个字面值。

一些格式化字符串字面值的示例:

@example
>>> name = "Fred"
>>> f"He said his name is @{name!r@}."
"He said his name is 'Fred'."
>>> f"He said his name is @{repr(name)@}."  # repr() is equivalent to !r
"He said his name is 'Fred'."
>>> width = 10
>>> precision = 4
>>> value = decimal.Decimal("12.34567")
>>> f"result: @{value:@{width@}.@{precision@}@}"  # nested fields
'result:      12.35'
>>> today = datetime(year=2017, month=1, day=27)
>>> f"@{today:%B %d, %Y@}"  # using date format specifier
'January 27, 2017'
>>> number = 1024
>>> f"@{number:#0x@}"  # using integer format specifier
'0x400'
@end example

与正常字符串字面值采用相同语法导致的一个结果就是替换字段中的字符不能与外部的格式化字符串字面值所用的引号相冲突:

@example
f"abc @{a["x"]@} def"    # error: outer string literal ended prematurely
f"abc @{a['x']@} def"    # workaround: use different quoting
@end example

格式表达式中不允许有反斜杠，这会引发错误:

@example
f"newline: @{ord('\n')@}"  # raises SyntaxError
@end example

想包含需要用反斜杠转义的值，可以创建一个临时变量。

@example
>>> newline = ord('\n')
>>> f"newline: @{newline@}"
'newline: 10'
@end example

格式化字符串字面值不可用作文档字符串，即便其中没有包含表达式。

@example
>>> def foo():
...     f"Not a docstring"
...
>>> foo.__doc__ is None
True
@end example

另请参见 
@geindex Python 提高建议; PEP 498
PEP 498@footnote{https://www.python.org/dev/peps/pep-0498} 了解加入格式化字符串字面值的提议，以及使用了相关的格式字符串机制的 @ref{4d4,,str.format()}。

@node 数字字面值,整型数字面值,格式化字符串字面值,字面值
@anchor{reference/lexical_analysis numbers}@anchor{1395}@anchor{reference/lexical_analysis numeric-literals}@anchor{1396}
@subsubsection 数字字面值


@geindex number
@geindex numeric literal
@geindex integer literal
@geindex floating point literal
@geindex hexadecimal literal
@geindex octal literal
@geindex binary literal
@geindex decimal literal
@geindex imaginary literal
@geindex complex literal

数字字面值有三种类型: 整型数、浮点数和虚数。没有专门的复数字面值 (复数可由一个实数加一个虚数合成)。

注意数字字面值并不包含正负号；@code{-1} 这样的负数实际上是由单目运算符 '@code{-}' 和字面值 @code{1} 合成的。

@geindex 0b; integer literal
@geindex 0o; integer literal
@geindex 0x; integer literal
@geindex _ (underscore); in numeric literal

@node 整型数字面值,浮点数字面值,数字字面值,字面值
@anchor{reference/lexical_analysis integer-literals}@anchor{1397}@anchor{reference/lexical_analysis integers}@anchor{1398}
@subsubsection 整型数字面值


整型数字面值由以下词法定义进行描述:

@example
@anchor{reference/lexical_analysis grammar-token-integer}@anchor{1399}integer      ::= decinteger | bininteger | octinteger | hexinteger
@anchor{reference/lexical_analysis grammar-token-decinteger}@anchor{139a}decinteger   ::= nonzerodigit (["_"] digit)* | "0"+ (["_"] "0")*
@anchor{reference/lexical_analysis grammar-token-bininteger}@anchor{139b}bininteger   ::= "0" ("b" | "B") (["_"] bindigit)+
@anchor{reference/lexical_analysis grammar-token-octinteger}@anchor{139c}octinteger   ::= "0" ("o" | "O") (["_"] octdigit)+
@anchor{reference/lexical_analysis grammar-token-hexinteger}@anchor{139d}hexinteger   ::= "0" ("x" | "X") (["_"] hexdigit)+
@anchor{reference/lexical_analysis grammar-token-nonzerodigit}@anchor{139e}nonzerodigit ::= "1"..."9"
@anchor{reference/lexical_analysis grammar-token-digit}@anchor{139f}digit        ::= "0"..."9"
@anchor{reference/lexical_analysis grammar-token-bindigit}@anchor{13a0}bindigit     ::= "0" | "1"
@anchor{reference/lexical_analysis grammar-token-octdigit}@anchor{13a1}octdigit     ::= "0"..."7"
@anchor{reference/lexical_analysis grammar-token-hexdigit}@anchor{13a2}hexdigit     ::= digit | "a"..."f" | "A"..."F"
@end example

整型数字面值的长度没有限制，能一直大到占满可用内存。

在确定数字大小时字面值中的下划线会被忽略。它们可用来将数码分组以提高可读性。一个下划线可放在数码之间，也可放在基数说明符例如 @code{0x} 之后。

注意非零的十进制数开头不允许有额外的零。这是为了避免与 Python 在版本 3.0 之前所使用的 C 风格八进制字面值相混淆。

一些整型数字面值的示例如下:

@example
7     2147483647                        0o177    0b100110111
3     79228162514264337593543950336     0o377    0xdeadbeef
      100_000_000_000                   0b_1110_0101
@end example


在 3.6 版更改: 允许在字面值中使用下划线进行分组。


@geindex . (dot); in numeric literal
@geindex e; in numeric literal
@geindex _ (underscore); in numeric literal

@node 浮点数字面值,虚数字面值,整型数字面值,字面值
@anchor{reference/lexical_analysis floating}@anchor{13a3}@anchor{reference/lexical_analysis floating-point-literals}@anchor{13a4}
@subsubsection 浮点数字面值


浮点数字面值由以下词法定义进行描述:

@example
@anchor{reference/lexical_analysis grammar-token-floatnumber}@anchor{13a5}floatnumber   ::= pointfloat | exponentfloat
@anchor{reference/lexical_analysis grammar-token-pointfloat}@anchor{13a6}pointfloat    ::= [digitpart] fraction | digitpart "."
@anchor{reference/lexical_analysis grammar-token-exponentfloat}@anchor{13a7}exponentfloat ::= (digitpart | pointfloat) exponent
@anchor{reference/lexical_analysis grammar-token-digitpart}@anchor{13a8}digitpart     ::= digit (["_"] digit)*
@anchor{reference/lexical_analysis grammar-token-fraction}@anchor{13a9}fraction      ::= "." digitpart
@anchor{reference/lexical_analysis grammar-token-exponent}@anchor{13aa}exponent      ::= ("e" | "E") ["+" | "-"] digitpart
@end example

注意整型数部分和指数部分在解析时总是以 10 为基数。例如，@code{077e010} 是合法的，且表示的数值与 @code{77e10} 相同。浮点数字面值允许的范围依赖于具体实现。对于整型数字面值，支持以下划线进行分组。

一些浮点数字面值的示例如下:

@example
3.14    10.    .001    1e100    3.14e-10    0e0    3.14_15_93
@end example


在 3.6 版更改: 允许在字面值中使用下划线进行分组。


@geindex j; in numeric literal

@node 虚数字面值,,浮点数字面值,字面值
@anchor{reference/lexical_analysis imaginary}@anchor{13ab}@anchor{reference/lexical_analysis imaginary-literals}@anchor{13ac}
@subsubsection 虚数字面值


虚数字面值由以下词法定义进行描述:

@example
@anchor{reference/lexical_analysis grammar-token-imagnumber}@anchor{13ad}imagnumber ::= (floatnumber | digitpart) ("j" | "J")
@end example

一个虚数字面值将生成一个实部为 0.0 的复数。复数是以一对浮点数来表示的，它们的取值范围相同。要创建一个实部不为零的复数，就加上一个浮点数，例如 @code{(3+4j)}。一些虚数字面值的示例如下:

@example
3.14j   10.j    10j     .001j   1e100j   3.14e-10j   3.14_15_93j
@end example

@node 运算符,分隔符,字面值,词法分析
@anchor{reference/lexical_analysis id11}@anchor{13ae}@anchor{reference/lexical_analysis operators}@anchor{13af}
@subsection 运算符


@geindex operators

以下形符属于运算符:

@example
+       -       *       **      /       //      %      @@
<<      >>      &       |       ^       ~       :=
<       >       <=      >=      ==      !=
@end example

@node 分隔符,,运算符,词法分析
@anchor{reference/lexical_analysis delimiters}@anchor{13b0}@anchor{reference/lexical_analysis id12}@anchor{13b1}
@subsection 分隔符


@geindex delimiters

以下形符在语法中归类为分隔符:

@example
(       )       [       ]       @{       @}
,       :       .       ;       @@       =       ->
+=      -=      *=      /=      //=     %=      @@=
&=      |=      ^=      >>=     <<=     **=
@end example

句点也可出现于浮点数和虚数字面值中。连续三个句点有表示一个省略符的特殊含义。以上列表的后半部分为增强赋值操作符，在词法中作为分隔符，但也起到运算作用。

以下可打印 ASCII 字符作为其他形符的组成部分时具有特殊含义，或是对词法分析器有重要意义:

@example
'       "       #       \
@end example

以下可打印 ASCII 字符不在 Python 词法中使用。如果出现于字符串字面值和注释之外将无条件地引发错误:

@example
$       ?       `
@end example

@subsubheading 备注


@node 数据模型,执行模型,词法分析,Python语言参考
@anchor{reference/datamodel doc}@anchor{13b2}@anchor{reference/datamodel data-model}@anchor{13b3}@anchor{reference/datamodel datamodel}@anchor{eba}
@section 数据模型


@menu
* 对象、值与类型:: 
* 标准类型层级结构:: 
* 特殊方法名称:: 
* 协程:: 

@end menu

@node 对象、值与类型,标准类型层级结构,,数据模型
@anchor{reference/datamodel objects}@anchor{13b4}@anchor{reference/datamodel objects-values-and-types}@anchor{13b5}
@subsection 对象、值与类型


@geindex object
@geindex data

@emph{对象} 是 Python 中对数据的抽象。 Python 程序中的所有数据都是由对象或对象间关系来表示的。 （从某种意义上说，按照冯·诺依曼的“存储程序计算机”模型，代码本身也是由对象来表示的。）

@geindex 內置函数; id
@geindex 內置函数; type
@geindex identity of an object
@geindex value of an object
@geindex type of an object
@geindex mutable object
@geindex immutable object

@c XXX it *is* now possible in some cases to change an object's
@c type, under certain controlled conditions

每个对象都有各自的编号、类型和值。一个对象被创建后，它的 @emph{编号} 就绝不会改变；你可以将其理解为该对象在内存中的地址。 '@ref{13b6,,is}' 运算符可以比较两个对象的编号是否相同；@ref{d7f,,id()} 函数能返回一个代表其编号的整型数。

@strong{CPython implementation detail:} 在 CPython 中，@code{id(x)} 就是存放 @code{x} 的内存的地址。

对象的类型决定该对象所支持的操作 (例如 "对象是否有长度属性？") 并且定义了该类型的对象可能的取值。@ref{603,,type()} 函数能返回一个对象的类型 (类型本身也是对象)。与编号一样，一个对象的 @emph{类型} 也是不可改变的。@footnote{@w{(1)} 
在某些情况下 @emph{有可能} 基于可控的条件改变一个对象的类型。 但这通常不是个好主意，因为如果处理不当会导致一些非常怪异的行为。
}

有些对象的 @emph{值} 可以改变。值可以改变的对象被称为 @emph{可变的}；值不可以改变的对象就被称为 @emph{不可变的}。(一个不可变容器对象如果包含对可变对象的引用，当后者的值改变时，前者的值也会改变；但是该容器仍属于不可变对象，因为它所包含的对象集是不会改变的。因此，不可变并不严格等同于值不能改变，实际含义要更微妙。) 一个对象的可变性是由其类型决定的；例如，数字、字符串和元组是不可变的，而字典和列表是可变的。

@geindex garbage collection
@geindex reference counting
@geindex unreachable object

对象绝不会被显式地销毁；然而，当无法访问时它们可能会被作为垃圾回收。允许具体的实现推迟垃圾回收或完全省略此机制 --- 如何实现垃圾回收是实现的质量问题，只要可访问的对象不会被回收即可。

@strong{CPython implementation detail:} CPython 目前使用带有 (可选) 延迟检测循环链接垃圾的引用计数方案，会在对象不可访问时立即回收其中的大部分，但不保证回收包含循环引用的垃圾。请查看 @ref{86,,gc} 模块的文档了解如何控制循环垃圾的收集相关信息。其他实现会有不同的行为方式，CPython 现有方式也可能改变。不要依赖不可访问对象的立即终结机制 (所以你应当总是显式地关闭文件)。

注意：使用实现的跟踪或调试功能可能令正常情况下会被回收的对象继续存活。还要注意通过 '@ref{d6b,,try}...@ref{b37,,except}' 语句捕捉异常也可能令对象保持存活。

有些对象包含对 "外部" 资源的引用，例如打开文件或窗口。当对象被作为垃圾回收时这些资源也应该会被释放，但由于垃圾回收并不确保发生，这些对象还提供了明确地释放外部资源的操作，通常为一个 @code{close()} 方法。强烈推荐在程序中显式关闭此类对象。'@ref{d6b,,try}...@ref{182,,finally}' 语句和 '@ref{6e3,,with}' 语句提供了进行此种操作的更便捷方式。

@geindex container

有些对象包含对其他对象的引用；它们被称为 @emph{容器}。容器的例子有元组、列表和字典等。这些引用是容器对象值的组成部分。在多数情况下，当谈论一个容器的值时，我们是指所包含对象的值而不是其编号；但是，当我们谈论一个容器的可变性时，则仅指其直接包含的对象的编号。因此，如果一个不可变容器 (例如元组) 包含对一个可变对象的引用，则当该可变对象被改变时容器的值也会改变。

类型会影响对象行为的几乎所有方面。甚至对象编号的重要性也在某种程度上受到影响: 对于不可变类型，会得出新值的运算实际上会返回对相同类型和取值的任一现有对象的引用，而对于可变类型来说这是不允许的。例如在 @code{a = 1; b = 1} 之后，@code{a} 和 @code{b} 可能会也可能不会指向同一个值为一的对象，这取决于具体实现，但是在 @code{c = []; d = []} 之后，@code{c} 和 @code{d} 保证会指向两个不同、单独的新建空列表。(请注意 @code{c = d = []} 则是将同一个对象赋值给 @code{c} 和 @code{d}。)

@node 标准类型层级结构,特殊方法名称,对象、值与类型,数据模型
@anchor{reference/datamodel the-standard-type-hierarchy}@anchor{13b7}@anchor{reference/datamodel types}@anchor{13b8}
@subsection 标准类型层级结构


@geindex type
@geindex data; type
@geindex type; hierarchy
@geindex extension; module
@geindex C; language

以下是 Python 内置类型的列表。扩展模块 (具体实现会以 C, Java 或其他语言编写) 可以定义更多的类型。未来版本的 Python 可能会加入更多的类型 (例如有理数、高效存储的整型数组等等)，不过新增类型往往都是通过标准库来提供的。

@geindex attribute
@geindex special; attribute
@geindex generic; special; attribute

以下部分类型的描述中包含有 '特殊属性列表' 段落。这些属性提供对具体实现的访问而非通常使用。它们的定义在未来可能会改变。


@table @asis

@item None

@geindex 对象; None

此类型只有一种取值。是一个具有此值的单独对象。此对象通过内置名称 @code{None} 访问。在许多情况下它被用来表示空值，例如未显式指明返回值的函数将返回 None。它的逻辑值为假。

@item NotImplemented

@geindex 对象; NotImplemented

此类型只有一种取值。是一个具有此值的单独对象。此对象通过内置名称 @code{NotImplemented} 访问。数值方法和丰富比较方法如未实现指定运算符表示的运算则应返回此值。(解释器会根据指定运算符继续尝试反向运算或其他回退操作)。它的逻辑值为真。

详情参见 @ref{13b9,,实现算数运算}。

@item Ellipsis

@geindex 对象; Ellipsis
@geindex ...; ellipsis literal

此类型只有一种取值。是一个具有此值的单独对象。此对象通过字面值 @code{...} 或内置名称 @code{Ellipsis} 访问。它的逻辑值为真。

@item @ref{13ba,,numbers.Number}

@geindex 对象; numeric

此类对象由数字字面值创建，并会被作为算术运算符和算术内置函数的返回结果。数字对象是不可变的；一旦创建其值就不再改变。Python 中的数字当然非常类似数学中的数字，但也受限于计算机中的数字表示方法。

Python 区分整型数、浮点型数和复数:


@table @asis

@item @ref{13bb,,numbers.Integral}

@geindex 对象; integer

此类对象表示数学中整数集合的成员 (包括正数和负数)。

整型数可细分为两种类型:

整型 (@ref{184,,int})

@quotation

此类对象表示任意大小的数字，仅受限于可用的内存 (包括虚拟内存)。在变换和掩码运算中会以二进制表示，负数会以 2 的补码表示，看起来像是符号位向左延伸补满空位。
@end quotation


@table @asis

@item 布尔型 (@ref{183,,bool})

@geindex 对象; Boolean
@geindex False
@geindex True

此类对象表示逻辑值 False 和 True。代表 @code{False} 和 @code{True} 值的两个对象是唯二的布尔对象。布尔类型是整型的子类型，两个布尔值在各种场合的行为分别类似于数值 0 和 1，例外情况只有在转换为字符串时分别返回字符串 @code{"False"} 或 @code{"True"}。
@end table

@geindex integer; representation

整型数表示规则的目的是在涉及负整型数的变换和掩码运算时提供最为合理的解释。

@item @ref{13bc,,numbers.Real} (@ref{187,,float})

@geindex 对象; floating point
@geindex floating point; number
@geindex C; language
@geindex Java; language

此类对象表示机器级的双精度浮点数。其所接受的取值范围和溢出处理将受制于底层的机器架构 (以及 C 或 Java 实现)。Python 不支持单精度浮点数；支持后者通常的理由是节省处理器和内存消耗，但这点节省相对于在 Python 中使用对象的开销来说太过微不足道，因此没有理由包含两种浮点数而令该语言变得复杂。

@item @ref{13bd,,numbers.Complex} (@ref{189,,complex})

@geindex 对象; complex
@geindex complex; number

此类对象以一对机器级的双精度浮点数来表示复数值。有关浮点数的附带规则对其同样有效。一个复数值 @code{z} 的实部和虚部可通过只读属性 @code{z.real} 和 @code{z.imag} 来获取。
@end table

@item 序列

@geindex 內置函数; len
@geindex 对象; sequence
@geindex index operation
@geindex item selection
@geindex subscription

此类对象表示以非负整数作为索引的有限有序集。内置函数 @ref{150,,len()} 可返回一个序列的条目数量。当一个序列的长度为 @emph{n} 时，索引集包含数字 0, 1, ..., @emph{n}-1。序列 @emph{a} 的条目 @emph{i} 可通过 @code{a[i]} 选择。

@geindex slicing

序列还支持切片: @code{a[i:j]} 选择索引号为 @emph{k} 的所有条目，@emph{i} @code{<=} @emph{k} @code{<} @emph{j}。当用作表达式时，序列的切片就是一个与序列类型相同的新序列。新序列的索引还是从 0 开始。

有些序列还支持带有第三个 "step" 形参的 "扩展切片": @code{a[i:j:k]} 选择 @emph{a} 中索引号为 @emph{x} 的所有条目，@code{x = i + n*k}, @emph{n} @code{>=} @code{0} 且 @emph{i} @code{<=} @emph{x} @code{<} @emph{j}。

序列可根据其可变性来加以区分:


@table @asis

@item 不可变序列

@geindex 对象; immutable sequence
@geindex 对象; immutable

不可变序列类型的对象一旦创建就不能再改变。(如果对象包含对其他对象的引用，其中的可变对象就是可以改变的；但是，一个不可变对象所直接引用的对象集是不能改变的。)

以下类型属于不可变对象:

@geindex string; immutable sequences


@table @asis

@item 字符串

@geindex 內置函数; chr
@geindex 內置函数; ord
@geindex character
@geindex integer
@geindex Unicode

字符串是由 Unicode 码位值组成的序列。范围在 @code{U+0000 - U+10FFFF} 之内的所有码位值都可在字符串中使用。Python 没有 @code{char} 类型；而是将字符串中的每个码位表示为一个长度为 @code{1} 的字符串对象。内置函数 @ref{13be,,ord()} 可将一个码位由字符串形式转换成一个范围在 @code{0 - 10FFFF} 之内的整型数；@ref{13bf,,chr()} 可将一个范围在 @code{0 - 10FFFF} 之内的整型数转换为长度为 @code{1} 的对应字符串对象。@ref{c30,,str.encode()} 可以使用指定的文本编码将 @ref{329,,str} 转换为 @ref{32a,,bytes}，而 @ref{c31,,bytes.decode()} 则可以实现反向的解码。

@item 元组

@geindex 对象; tuple
@geindex singleton; tuple
@geindex empty; tuple

一个元组中的条目可以是任意 Python 对象。包含两个或以上条目的元组由逗号分隔的表达式构成。只有一个条目的元组 ('单项元组') 可通过在表达式后加一个逗号来构成 (一个表达式本身不能创建为元组，因为圆括号要用来设置表达式分组)。一个空元组可通过一对内容为空的圆括号创建。

@item 字节串

@geindex bytes
@geindex byte

字节串对象是不可变的数组。其中每个条目都是一个 8 位字节，以取值范围 0 <= x < 256 的整型数表示。字节串字面值 (例如 @code{b'abc'}) 和内置的 @ref{32a,,bytes()} 构造器可被用来创建字节串对象。字节串对象还可以通过 @ref{c31,,decode()} 方法解码为字符串。
@end table

@item 可变序列

@geindex 对象; mutable sequence
@geindex 对象; mutable
@geindex assignment; statement
@geindex subscription
@geindex slicing

可变序列在被创建后仍可被改变。下标和切片标注可被用作赋值和 @ref{1202,,del} (删除) 语句的目标。

目前有两种内生可变序列类型:


@table @asis

@item 列表

@geindex 对象; list

列表中的条目可以是任意 Python 对象。列表由用方括号括起并由逗号分隔的多个表达式构成。(注意创建长度为 0 或 1 的列表无需使用特殊规则。)

@item 字节数组

@geindex bytearray

字节数组对象属于可变数组。可以通过内置的 @ref{32b,,bytearray()} 构造器来创建。除了是可变的 (因而也是不可哈希的)，在其他方面字节数组提供的接口和功能都于不可变的 @ref{32a,,bytes} 对象一致。
@end table

@geindex 模块; array

扩展模块 @ref{7,,array} 提供了一个额外的可变序列类型示例，@ref{1e,,collections} 模块也是如此。
@end table

@item 集合类型

@geindex 內置函数; len
@geindex 对象; set type

此类对象表示由不重复且不可变对象组成的无序且有限的集合。因此它们不能通过下标来索引。但是它们可被迭代，也可用内置函数 @ref{150,,len()} 返回集合中的条目数。集合常见的用处是快速成员检测，去除序列中的重复项，以及进行交、并、差和对称差等数学运算。

对于集合元素所采用的不可变规则与字典的键相同。注意数字类型遵循正常的数字比较规则: 如果两个数字相等 (例如 @code{1} 和 @code{1.0})，则同一集合中只能包含其中一个。

目前有两种内生集合类型:


@table @asis

@item 集合

@geindex 对象; set

此类对象表示可变集合。它们可通过内置的 @ref{b68,,set()} 构造器创建，并且创建之后可以通过方法进行修改，例如 @code{add()}。

@item 冻结集合

@geindex 对象; frozenset

此类对象表示不可变集合。它们可通过内置的 @ref{be7,,frozenset()} 构造器创建。由于 frozenset 对象不可变且 @ref{13c0,,hashable}，它可以被用作另一个集合的元素或是字典的键。
@end table

@item 映射

@geindex 內置函数; len
@geindex subscription
@geindex 对象; mapping

此类对象表示由任意索引集合所索引的对象的集合。通过下标 @code{a[k]} 可在映射 @code{a} 中选择索引为 @code{k} 的条目；这可以在表达式中使用，也可作为赋值或 @ref{1202,,del} 语句的目标。内置函数 @ref{150,,len()} 可返回一个映射中的条目数。

目前只有一种内生映射类型:


@table @asis

@item 字典

@geindex 对象; dictionary

此类对象表示由几乎任意值作为索引的有限个对象的集合。不可作为键的值类型只有包含列表或字典或其他可变类型，通过值而非对象编号进行比较的值，其原因在于高效的字典实现需要使用键的哈希值以保持一致性。用作键的数字类型遵循正常的数字比较规则: 如果两个数字相等 (例如 @code{1} 和 @code{1.0}) 则它们均可来用来索引同一个字典条目。

字典会保留插入顺序，这意味着键将以它们被添加的顺序在字典中依次产生。 替换某个现有的键不会改变其顺序，但是移除某个键再重新插入则会将其添加到末尾而不会保留其原有位置。

字典是可变的；它们可通过 @code{@{...@}} 标注来创建 (参见 @ref{648,,字典显示} 小节)。

@geindex 模块; dbm.ndbm
@geindex 模块; dbm.gnu

扩展模块 @ref{35,,dbm.ndbm} 和 @ref{34,,dbm.gnu} 提供了额外的映射类型示例，@ref{1e,,collections} 模块也是如此。


在 3.7 版更改: 在 Python 3.6 版之前字典不会保留插入顺序。 在 CPython 3.6 中插入顺序会被保留，但这在当时被当作是一个实现细节而非确定的语言特性。

@end table

@item 可调用类型

@geindex 对象; callable
@geindex function; call
@geindex invocation
@geindex function; argument

此类型可以被应用于函数调用操作 (参见 @ref{646,,调用} 小节):


@table @asis

@item 用户定义函数

@geindex user-defined; function
@geindex 对象; function
@geindex 对象; user-defined function

用户定义函数对象可通过函数定义来创建 (参见 @ref{11f0,,函数定义} 小节)。它被调用时应附带一个参数列表，其中包含的条目应与函数所定义的形参列表一致。

特殊属性:

@geindex __doc__ (function attribute)
@geindex __name__ (function attribute)
@geindex __module__ (function attribute)
@geindex __dict__ (function attribute)
@geindex __defaults__ (function attribute)
@geindex __closure__ (function attribute)
@geindex __code__ (function attribute)
@geindex __globals__ (function attribute)
@geindex __annotations__ (function attribute)
@geindex __kwdefaults__ (function attribute)
@geindex global; namespace


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx} 
@headitem

属性

@tab

含义

@tab

@item

@code{__doc__}

@tab

该函数的文档字符串，没有则为 @code{None}；不会被子类继承。

@tab

可写

@item

@ref{c60,,__name__}

@tab

该函数的名称。

@tab

可写

@item

@ref{13c1,,__qualname__}

@tab

该函数的 @ref{13c2,,qualified name}。


3.3 新版功能.


@tab

可写

@item

@code{__module__}

@tab

该函数所属模块的名称，没有则为 @code{None}。

@tab

可写

@item

@code{__defaults__}

@tab

由具有默认值的参数的默认参数值组成的元组，如无任何参数具有默认值则为 @code{None}。

@tab

可写

@item

@code{__code__}

@tab

表示编译后的函数体的代码对象。

@tab

可写

@item

@code{__globals__}

@tab

对存放该函数中全局变量的字典的引用 --- 函数所属模块的全局命名空间。

@tab

只读

@item

@ref{4f6,,__dict__}

@tab

命名空间支持的函数属性。

@tab

可写

@item

@code{__closure__}

@tab

@code{None} 或包含该函数可用变量的绑定的单元的元组。有关 @code{cell_contents} 属性的详情见下。

@tab

只读

@item

@code{__annotations__}

@tab

包含参数标注的字典。字典的键是参数名，如存在返回标注则为 @code{'return'}。

@tab

可写

@item

@code{__kwdefaults__}

@tab

仅包含关键字参数默认值的字典。

@tab

可写

@end multitable


大部分标有 "Writable" 的属性均会检查赋值的类型。

函数对象也支持获取和设置任意属性，例如这可以被用来给函数附加元数据。使用正规的属性点号标注获取和设置此类属性。@emph{注意当前实现仅支持用户定义函数属性。未来可能会增加支持内置函数属性。}

单元对象具有 @code{cell_contents} 属性。这可被用来获取以及设置单元的值。

有关函数定义的额外信息可以从其代码对象中提取；参见下文对内部类型的描述。 @ref{13c3,,cell} 类型可以在 @ref{118,,types} 模块中访问。

@item 实例方法

@geindex 对象; method
@geindex 对象; user-defined method
@geindex user-defined; method

实例方法用于结合类、类实例和任何可调用对象 (通常为用户定义函数)。

@geindex __func__ (method attribute)
@geindex __self__ (method attribute)
@geindex __doc__ (method attribute)
@geindex __name__ (method attribute)
@geindex __module__ (method attribute)

特殊的只读属性: @code{__self__} 为类实例对象本身，@code{__func__} 为函数对象；@code{__doc__} 为方法的文档 (与 @code{__func__.__doc__} 作用相同)；@ref{c60,,__name__} 为方法名称 (与 @code{__func__.__name__} 作用相同)；@code{__module__} 为方法所属模块的名称，没有则为 @code{None}。

方法还支持获取 (但不能设置) 下层函数对象的任意函数属性。

用户定义方法对象可在获取一个类的属性时被创建 (也可能通过该类的一个实例)，如果该属性为用户定义函数对象或类方法对象。

当通过从类实例获取一个用户定义函数对象的方式创建一个实例方法对象时，类实例对象的 @code{__self__} 属性即为该实例，并会绑定方法对象。该新建方法的 @code{__func__} 属性就是原来的函数对象。

当通过从类或实例获取一个类方法对象的方式创建一个实例对象时，实例对象的 @code{__self__} 属性为该类本身，其 @code{__func__} 属性为类方法对应的下层函数对象。

当一个实例方法对象被调用时，会调用对应的下层函数 (@code{__func__})，并将类实例 (@code{__self__}) 插入参数列表的开头。例如，当 @code{C} 是一个包含了 @code{f()} 函数定义的类，而 @code{x} 是 @code{C} 的一个实例，则调用 @code{x.f(1)} 就等同于调用 @code{C.f(x, 1)}。

当一个实例方法对象是衍生自一个类方法对象时，保存在 @code{__self__} 中的 "类实例" 实际上会是该类本身，因此无论是调用 @code{x.f(1)} 还是 @code{C.f(1)} 都等同于调用 @code{f(C,1)}，其中 @code{f} 为对应的下层函数。

请注意从函数对象到实例方法对象的变换会在每一次从实例获取属性时发生。在某些情况下，一种高效的优化方式是将属性赋值给一个本地变量并调用该本地变量。还要注意这样的变换只发生于用户定义函数；其他可调用对象 (以及所有不可调用对象) 在被获取时都不会发生变换。还有一个需要关注的要点是作为一个类实例属性的用户定义函数不会被转换为绑定方法；这样的变换 @emph{仅当} 函数是类属性时才会发生。

@item 生成器函数

@geindex generator; function
@geindex generator; iterator

一个使用 @ref{18f,,yield} 语句 （见 @ref{18f,,yield 语句} 章节）的函数或方法被称作一个 @emph{生成器函数}。 这样的函数在被调用时，总是返回一个可以执行函数体的迭代器对象：调用该迭代器的 @ref{c5d,,iterator.__next__()} 方法将会导致这个函数一直运行直到它使用 @code{yield} 语句提供了一个值为止。 当这个函数执行 @ref{190,,return} 语句或者执行到末尾时，将引发 @ref{480,,StopIteration} 异常并且这个迭代器将到达所返回的值集合的末尾。

@item 协程函数

@geindex coroutine; function

使用 @ref{284,,async def} 来定义的函数或方法就被称为 @emph{协程函数}。这样的函数在被调用时会返回一个 @ref{1a6,,coroutine} 对象。它可能包含 @ref{1a3,,await} 表达式以及 @ref{63d,,async with} 和 @ref{2e3,,async for} 语句。详情可参见 @ref{13c4,,协程对象} 一节。

@item 异步生成器函数

@geindex asynchronous generator; function
@geindex asynchronous generator; asynchronous iterator

使用 @ref{284,,async def} 来定义并包含 @ref{18f,,yield} 语句的函数或方法就被称为 @emph{异步生成器函数}。这样的函数在被调用时会返回一个异步迭代器对象，该对象可在 @ref{2e3,,async for} 语句中用来执行函数体。

调用异步迭代器的 @code{aiterator.__anext__()} 方法将会返回一个 @ref{513,,awaitable}，此对象会在被等待时执行直到使用 @ref{18f,,yield} 表达式输出一个值。当函数执行时到空的 @ref{190,,return} 语句或是最后一条语句时，将会引发 @ref{fa5,,StopAsyncIteration} 异常，异步迭代器也会到达要输出的值集合的末尾。

@item 内置函数

@geindex 对象; built-in function
@geindex 对象; function
@geindex C; language

内置函数对象是对于 C 函数的外部封装。内置函数的例子包括 @ref{150,,len()} 和 @ref{e08,,math.sin()}  (@ref{b1,,math} 是一个标准内置模块)。内置函数参数的数量和类型由 C 函数决定。特殊的只读属性: @code{__doc__} 是函数的文档字符串，如果没有则为 @code{None}; @ref{c60,,__name__} 是函数的名称; @code{__self__} 设定为 @code{None} (参见下一条目); @code{__module__} 是函数所属模块的名称，如果没有则为 @code{None}。

@item 内置方法

@geindex 对象; built-in method
@geindex 对象; method
@geindex built-in; method

此类型实际上是内置函数的另一种形式，只不过还包含了一个传入 C 函数的对象作为隐式的额外参数。内置方法的一个例子是 @code{alist.append()}，其中 @emph{alist} 为一个列表对象。在此示例中，特殊的只读属性 @code{__self__} 会被设为 @emph{alist} 所标记的对象。

@item 类

类是可调用的。此种对象通常是作为“工厂”来创建自身的实例，类也可以有重载 @ref{883,,__new__()} 的变体类型。调用的参数会传给 @ref{883,,__new__()}，而且通常也会传给 @ref{d57,,__init__()} 来初始化新的实例。

@item 类实例

任意类的实例通过在所属类中定义 @ref{13c5,,__call__()} 方法即能成为可调用的对象。
@end table

@item 模块

@geindex 语句; import
@geindex 对象; module

模块是 Python 代码的基本组织单元，由 @ref{13c6,,导入系统} 创建，由 @ref{c16,,import} 语句发起调用，或者通过 @ref{b0c,,importlib.import_module()} 和内置的 @ref{60b,,__import__()} 等函数发起调用。 模块对象具有由字典对象实现的命名空间（这是被模块中定义的函数的 @code{__globals__} 属性引用的字典）。 属性引用被转换为该字典中的查找，例如 @code{m.x} 相当于 @code{m.__dict__["x"]}。 模块对象不包含用于初始化模块的代码对象（因为初始化完成后不需要它）。

属性赋值会更新模块的命名空间字典，例如 @code{m.x = 1} 等同于 @code{m.__dict__["x"] = 1}。

@geindex __name__ (module attribute)
@geindex __doc__ (module attribute)
@geindex __file__ (module attribute)
@geindex __annotations__ (module attribute)
@geindex module; namespace

预定义的 (可写) 属性: @ref{d0b,,__name__} 为模块的名称; @code{__doc__} 为模块的文档字符串，如果没有则为 @code{None}; @code{__annotations__} (可选) 为一个包含 @ref{61a,,变量标注} 的字典，它是在模块体执行时获取的; @ref{13c7,,__file__} 是模块对应的被加载文件的路径名，如果它是加载自一个文件的话。某些类型的模块可能没有 @ref{13c7,,__file__} 属性，例如 C 模块是静态链接到解释器内部的; 对于从一个共享库动态加载的扩展模块来说该属性为该共享库文件的路径名。

@geindex __dict__ (module attribute)

特殊的只读属性: @ref{4f6,,__dict__} 为以字典对象表示的模块命名空间。

@strong{CPython implementation detail:} 由于 CPython 清理模块字典的设定，当模块离开作用域时模块字典将会被清理，即使该字典还有活动的引用。想避免此问题，可复制该字典或保持模块状态以直接使用其字典。

@item 自定义类

自定义类这种类型一般通过类定义来创建 (参见 @ref{c63,,类定义} 一节)。每个类都有通过一个字典对象实现的独立命名空间。类属性引用会被转化为在此字典中查找，例如 @code{C.x} 会被转化为 @code{C.__dict__["x"]} (不过也存在一些钩子对象以允许其他定位属性的方式)。当未在其中发现某个属性名称时，会继续在基类中查找。这种基类查找使用 C3 方法解析顺序，即使存在 '钻石形' 继承结构即有多条继承路径连到一个共同祖先也能保持正确的行为。有关 Python 使用的 C3 MRO 的详情可查看配合 2.3 版发布的文档 @indicateurl{https://www.python.org/download/releases/2.3/mro/}.

@c XXX: Could we add that MRO doc as an appendix to the language ref?

@geindex 对象; class
@geindex 对象; class instance
@geindex 对象; instance
@geindex class object; call
@geindex container
@geindex 对象; dictionary
@geindex class; attribute

当一个类属性引用 (假设类名为 @code{C}) 会产生一个类方法对象时，它将转化为一个 @code{__self__} 属性为 @code{C} 的实例方法对象。当其会产生一个静态方法对象时，它将转化为该静态方法对象所封装的对象。从类的 @ref{4f6,,__dict__} 所包含内容以外获取属性的其他方式请参看 @ref{4e3,,实现描述器} 一节。

@geindex class; attribute; assignment

类属性赋值会更新类的字典，但不会更新基类的字典。

@geindex class object; call

类对象可被调用 (见上文) 以产生一个类实例 (见下文)。

@geindex __name__ (class attribute)
@geindex __module__ (class attribute)
@geindex __dict__ (class attribute)
@geindex __bases__ (class attribute)
@geindex __doc__ (class attribute)
@geindex __annotations__ (class attribute)

特殊属性: @ref{c60,,__name__} 为类的名称; @code{__module__} 为类所在模块的名称; @ref{4f6,,__dict__} 为包含类命名空间的字典; @ref{e02,,__bases__} 为包含基类的元组，按其在基类列表中的出现顺序排列; @code{__doc__} 为类的文档字符串，如果没有则为 @code{None}; @code{__annotations__} (可选) 为一个包含 @ref{61a,,变量标注} 的字典，它是在类体执行时获取的。

@item 类实例

@geindex 对象; class instance
@geindex 对象; instance
@geindex class; instance
@geindex class instance; attribute

类实例可通过调用类对象来创建 (见上文)。每个类实例都有通过一个字典对象实现的独立命名空间，属性引用会首先在此字典中查找。当未在其中发现某个属性，而实例对应的类中有该属性时，会继续在类属性中查找。如果找到的类属性为一个用户定义函数对象，它会被转化为实例方法对象，其 @code{__self__} 属性即该实例。静态方法和类方法对象也会被转化；参见上文 "Classes" 一节。要了解其他通过类实例来获取相应类属性的方式可参见 @ref{4e3,,实现描述器} 一节，这样得到的属性可能与实际存放于类的 @ref{4f6,,__dict__} 中的对象不同。如果未找到类属性，而对象对应的类具有 @ref{313,,__getattr__()} 方法，则会调用该方法来满足查找要求。

@geindex class instance; attribute; assignment

属性赋值和删除会更新实例的字典，但不会更新对应类的字典。如果类具有 @ref{e25,,__setattr__()} 或 @ref{13c8,,__delattr__()} 方法，则将调用方法而不再直接更新实例的字典。

@geindex 对象; numeric
@geindex 对象; sequence
@geindex 对象; mapping

如果类实例具有某些特殊名称的方法，就可以伪装为数字、序列或映射。参见 @ref{508,,特殊方法名称} 一节。

@geindex __dict__ (instance attribute)
@geindex __class__ (instance attribute)

特殊属性: @ref{4f6,,__dict__} 为属性字典; @ref{e03,,__class__} 为实例对应的类。

@item I/O 对象 (或称文件对象)

@geindex 內置函数; open
@geindex 模块; io
@geindex popen() (in module os)
@geindex makefile() (socket method)
@geindex sys.stdin
@geindex sys.stdout
@geindex sys.stderr
@geindex stdio
@geindex stdin (in module sys)
@geindex stdout (in module sys)
@geindex stderr (in module sys)

@ref{b3b,,file object} 表示一个打开的文件。有多种快捷方式可用来创建文件对象: @ref{4ea,,open()} 内置函数，以及 @ref{2a9,,os.popen()}, @ref{13c9,,os.fdopen()} 和 socket 对象的 @ref{b12,,makefile()} 方法 (还可能使用某些扩展模块所提供的其他函数或方法)。

@code{sys.stdin}, @code{sys.stdout} 和 @code{sys.stderr} 会初始化为对应于解释器标准输入、输出和错误流的文件对象；它们都会以文本模式打开，因此都遵循 @ref{c32,,io.TextIOBase} 抽象类所定义的接口。

@item 内部类型

@geindex internal type
@geindex types@comma{} internal

某些由解释器内部使用的类型也被暴露给用户。它们的定义可能随未来解释器版本的更新而变化，为内容完整起见在此处一并介绍。

@geindex bytecode
@geindex object; code
@geindex code object


@table @asis

@item 代码对象

代码对象表示 @emph{编译为字节的} 可执行 Python 代码，或称 @ref{60f,,bytecode}。代码对象和函数对象的区别在于函数对象包含对函数全局对象 (函数所属的模块) 的显式引用，而代码对象不包含上下文；而且默认参数值会存放于函数对象而不是代码对象内 (因为它们表示在运行时算出的值)。与函数对象不同，代码对象不可变，也不包含对可变对象的引用 (不论是直接还是间接)。

@geindex co_argcount (code object attribute)
@geindex co_posonlyargcount (code object attribute)
@geindex co_kwonlyargcount (code object attribute)
@geindex co_code (code object attribute)
@geindex co_consts (code object attribute)
@geindex co_filename (code object attribute)
@geindex co_firstlineno (code object attribute)
@geindex co_flags (code object attribute)
@geindex co_lnotab (code object attribute)
@geindex co_name (code object attribute)
@geindex co_names (code object attribute)
@geindex co_nlocals (code object attribute)
@geindex co_stacksize (code object attribute)
@geindex co_varnames (code object attribute)
@geindex co_cellvars (code object attribute)
@geindex co_freevars (code object attribute)

特殊的只读属性: @code{co_name} 给出了函数名; @code{co_argcount} 为位置参数的总数量 (包括仅限位置参数和带有默认值的参数); @code{co_posonlyargcount} 为仅限位置参数的数量 (包括带有默认值的参数); @code{co_kwonlyargcount} 为仅限关键字参数的数量 (包括带有默认值的参数); @code{co_nlocals} 为函数使用的局部变量的数量 (包括参数); @code{co_varnames} 为一个包含局部变量名称的元组 (参数名排在最前面); @code{co_cellvars} 为一个包含被嵌套函数所引用的局部变量名称的元组; @code{co_freevars} 为一个包含自由变量名称的元组; @code{co_code} 为一个表示字节码指令序列的字符口中; @code{co_consts} 为一个包含字节码所使用的字面值的元组; @code{co_names} 为一个包含字节码所使用的名称的元组; @code{co_filename} 为被编码代码所在的文件名; @code{co_firstlineno} 为函数首行的行号; @code{co_lnotab} 为一个字符串，其中编码了从字节码偏移量到行号的映射 (详情参见解释器的源代码); @code{co_stacksize} 为要求的栈大小; @code{co_flags} 为一个整数，其中编码了解释器所用的多个旗标。

@geindex 对象; generator

以下是可用于 @code{co_flags} 的标志位定义：如果函数使用 @code{*arguments} 语法来接受任意数量的位置参数，则 @code{0x04} 位被设置；如果函数使用 @code{**keywords} 语法来接受任意数量的关键字参数，则 @code{0x08} 位被设置；如果函数是一个生成器，则 @code{0x20} 位被设置。

未来特性声明 (@code{from __future__ import division}) 也使用 @code{co_flags} 中的标志位来指明代码对象的编译是否启用特定的特性: 如果函数编译时启用未来除法特性则设置 @code{0x2000} 位; 在更早的 Python 版本中则使用 @code{0x10} 和 @code{0x1000} 位。

@code{co_flags} 中的其他位被保留为内部使用。

@geindex documentation string

如果代码对象表示一个函数，@code{co_consts} 中的第一项将是函数的文档字符串，如果未定义则为 @code{None}。
@end table
@anchor{reference/datamodel frame-objects}@anchor{13ca}

@table @asis

@item 帧对象

@geindex 对象; frame

帧对象表示执行帧。它们可能出现在回溯对象中 (见下文)，还会被传递给注册跟踪函数。

@geindex f_back (frame attribute)
@geindex f_code (frame attribute)
@geindex f_globals (frame attribute)
@geindex f_locals (frame attribute)
@geindex f_lasti (frame attribute)
@geindex f_builtins (frame attribute)

特殊的只读属性: @code{f_back} 为前一堆栈帧 (指向调用者)，如是最底层堆栈帧则为 @code{None}; @code{f_code} 为此帧中所执行的代码对象; @code{f_locals} 为用于查找本地变量的字典; @code{f_globals} 则用于查找全局变量; @code{f_builtins} 用于查找内置 (固有) 名称; @code{f_lasti} 给出精确指令 (这是代码对象的字节码字符串的一个索引)。

@geindex f_trace (frame attribute)
@geindex f_trace_lines (frame attribute)
@geindex f_trace_opcodes (frame attribute)
@geindex f_lineno (frame attribute)

特殊的可写属性: @code{f_trace}，如果不为 @code{None}，则是在代码执行期间调用各类事件的函数 (由调试器使用)。通常每个新源码行会触发一个事件 - 这可以通过将 @code{f_trace_lines} 设为 @ref{380,,False} 来禁用。

具体的实现 @emph{可能} 会通过将 @code{f_trace_opcodes} 设为 @ref{494,,True} 来允许按操作码请求事件。请注意如果跟踪函数引发的异常逃逸到被跟踪的函数中，这可能会导致未定义的解释器行为。

@code{f_lineno} 为帧的当前行号 --- 在这里写入从一个跟踪函数内部跳转的指定行 (仅用于最底层的帧)。调试器可以通过写入 f_lineno 实现一个 Jump 命令 (即设置下一语句)。

帧对象支持一个方法:

@geindex clear() (frame 方法)
@anchor{reference/datamodel frame clear}@anchor{805}
@deffn {方法} frame.clear ()

此方法清除该帧持有的全部对本地变量的引用。而且如果该帧属于一个生成器，生成器会被完成。这有助于打破包含帧对象的循环引用 (例如当捕获一个异常并保存其回溯在之后使用)。

如果该帧当前正在执行则会引发 @ref{2ba,,RuntimeError}。


3.4 新版功能.

@end deffn
@end table
@anchor{reference/datamodel traceback-objects}@anchor{32f}

@table @asis

@item 回溯对象

@geindex 对象; traceback
@geindex stack; trace
@geindex exception; handler
@geindex execution; stack
@geindex exc_info (in module sys)
@geindex last_traceback (in module sys)
@geindex sys.exc_info
@geindex sys.last_traceback

回溯对象表示一个异常的栈跟踪记录。当异常发生时会隐式地创建一个回溯对象，也可能通过调用 @ref{32e,,types.TracebackType} 显式地创建。

对于隐式地创建的回溯对象，当查找异常句柄使得执行栈展开时，会在每个展开层级的当前回溯之前插入一个回溯对象。当进入一个异常句柄时，栈跟踪将对程序启用。(参见 @ref{d6b,,try 语句} 一节。) 它可作为 @code{sys.exc_info()} 所返回的元组的第三项，以及所捕获异常的 @code{__traceback__} 属性被获取。

当程序不包含可用的句柄时，栈跟踪会 (以良好的格式) 写入标准错误流；如果解释器处于交互模式，它也可作为 @code{sys.last_traceback} 对用户启用。

对于显式创建的回溯对象，则由回溯对象的创建者来决定应该如何链接 @code{tb_next} 属性来构成完整的栈跟踪。

@geindex tb_frame (traceback attribute)
@geindex tb_lineno (traceback attribute)
@geindex tb_lasti (traceback attribute)
@geindex 语句; try

特殊的只读属性: @code{tb_frame} 指向当前层级的执行帧; @code{tb_lineno} 给出发生异常所在的行号; @code{tb_lasti} 标示具体指令。如果异常发生于没有匹配的 except 子句或有 finally 子句的 @ref{d6b,,try} 语句中，回溯对象中的行号和最后指令可能与相应帧对象中行号不同。

@geindex tb_next (traceback attribute)

特殊的可写属性: @code{tb_next} 为栈跟踪中的下一层级 (通往发生异常的帧)，如果没有下一层级则为 @code{None}。


在 3.7 版更改: 回溯对象现在可以使用 Python 代码显式地实例化，现有实例的 @code{tb_next} 属性可以被更新。


@item 切片对象

@geindex 內置函数; slice

切片对象用来表示 @ref{27f,,__getitem__()} 方法得到的切片。该对象也可使用内置的 @ref{dfd,,slice()} 函数来创建。

@geindex start (slice object attribute)
@geindex stop (slice object attribute)
@geindex step (slice object attribute)

特殊的只读属性: @code{start} 为下界; @code{stop} 为上界; @code{step} 为步长值; 各值如省略则为 @code{None}。这些属性可具有任意类型。

切片对象支持一个方法:

@geindex indices() (slice 方法)
@anchor{reference/datamodel slice indices}@anchor{959}
@deffn {方法} slice.indices (self, length)

此方法接受一个整型参数 @emph{length} 并计算在切片对象被应用到 @emph{length} 指定长度的条目序列时切片的相关信息应如何描述。其返回值为三个整型数组成的元组；这些数分别为切片的 @emph{start} 和 @emph{stop} 索引号以及 @emph{step} 步长值。索引号缺失或越界则按照正规连续切片的方式处理。
@end deffn

@item 静态方法对象

静态方法对象提供了一种避免上文所述将函数对象转换为方法对象的方式。静态方法对象为对任意其他对象的封装，通常用来封装用户定义方法对象。当从类或类实例获取一个静态方法对象时，实际返回的对象是封装的对象，它不会被进一步转换。静态方法对象自身不是可调用的，但它们所封装的对象通常都是可调用的。静态方法对象可通过内置的 @ref{1d9,,staticmethod()} 构造器来创建。

@item 类方法对象

类方法对象和静态方法一样是对其他对象的封装，会改变从类或类实例获取该对象的方式。类方法对象在此类获取操作中的行为已在上文  "用户定义方法" 一节中描述。类方法对象可通过内置的 @ref{1d8,,classmethod()} 构造器来创建。
@end table
@end table

@node 特殊方法名称,协程,标准类型层级结构,数据模型
@anchor{reference/datamodel special-method-names}@anchor{13cb}@anchor{reference/datamodel specialnames}@anchor{508}
@subsection 特殊方法名称


@geindex operator; overloading
@geindex __getitem__() (mapping object method)

一个类可以通过定义具有特殊名称的方法来实现由特殊语法所引发的特定操作 (例如算术运算或下标与切片)。这是 Python 实现 @emph{操作符重载} 的方式，允许每个类自行定义基于操作符的特定行为。例如，如果一个类定义了名为 @ref{27f,,__getitem__()} 的方法，并且 @code{x} 为该类的一个实例，则 @code{x[i]} 基本就等同于 @code{type(x).__getitem__(x, i)}。除非有说明例外情况，在没有定义适当方法的情况下尝试执行一种操作将引发一个异常 (通常为 @ref{393,,AttributeError} 或 @ref{192,,TypeError})。

将一个特殊方法设为 @code{None} 表示对应的操作不可用。例如，如果一个类将 @ref{509,,__iter__()} 设为 @code{None}，则该类就是不可迭代的，因此对其实例调用 @ref{d20,,iter()} 将引发一个 @ref{192,,TypeError} (而不会回退至 @ref{27f,,__getitem__()}). @footnote{@w{(2)} 
@ref{339,,__hash__()}, @ref{509,,__iter__()}, @ref{529,,__reversed__()} 以及 @ref{d21,,__contains__()} 方法对此有特殊处理；其他方法仍会引发 @ref{192,,TypeError}，但可能依靠 @code{None} 属于不可调用对象的行为来做到这一点。
}

在实现模拟任何内置类型的类时，很重要的一点是模拟的实现程度对于被模拟对象来说应当是有意义的。例如，提取单个元素的操作对于某些序列来说是适宜的，但提取切片可能就没有意义。(这种情况的一个实例是 W3C 的文档对象模型中的 @code{NodeList} 接口。)

@menu
* 基本定制:: 
* 自定义属性访问:: 
* 自定义类创建:: 
* 自定义实例及子类检查:: 
* 模拟泛型类型:: 
* 模拟可调用对象:: 
* 模拟容器类型:: 
* 模拟数字类型:: 
* with 语句上下文管理器:: 
* 特殊方法查找:: 

@end menu

@node 基本定制,自定义属性访问,,特殊方法名称
@anchor{reference/datamodel basic-customization}@anchor{13cc}@anchor{reference/datamodel customization}@anchor{13cd}
@subsubsection 基本定制


@geindex __new__() (object 方法)
@anchor{reference/datamodel object __new__}@anchor{883}
@deffn {方法} object.__new__ (cls[, ...])

@geindex subclassing; immutable types

调用以创建一个 @emph{cls} 类的新实例。@ref{883,,__new__()} 是一个静态方法 (因为是特例所以你不需要显式地声明)，它会将所请求实例所属的类作为第一个参数。其余的参数会被传递给对象构造器表达式 (对类的调用)。@ref{883,,__new__()} 的返回值应为新对象实例 (通常是 @emph{cls} 的实例)。

典型的实现会附带适宜的参数使用 @code{super().__new__(cls[, ...])}，通过超类的 @ref{883,,__new__()} 方法来创建一个类的新实例，然后根据需要修改新创建的实例再将其返回。

如果 @ref{883,,__new__()} 在构造对象期间被发起调用并且它返回了一个实例或 @emph{cls} 的子类，则新实例的 @ref{d57,,__init__()} 方法将以 @code{__init__(self[, ...])} 的形式被发起调用，其中 @emph{self} 为新实例而其余的参数与被传给对象构造器的参数相同。

如果 @ref{883,,__new__()} 未返回一个 @emph{cls} 的实例，则新实例的 @ref{d57,,__init__()} 方法就不会被执行。

@ref{883,,__new__()} 的目的主要是允许不可变类型的子类 (例如 int, str 或 tuple) 定制实例创建过程。它也常会在自定义元类中被重载以便定制类创建过程。
@end deffn

@geindex __init__() (object 方法)
@anchor{reference/datamodel object __init__}@anchor{d57}
@deffn {方法} object.__init__ (self[, ...])

@geindex class; constructor

在实例 (通过 @ref{883,,__new__()}) 被创建之后，返回调用者之前调用。其参数与传递给类构造器表达式的参数相同。一个基类如果有 @ref{d57,,__init__()} 方法，则其所派生的类如果也有 @ref{d57,,__init__()} 方法，就必须显式地调用它以确保实例基类部分的正确初始化；例如: @code{super().__init__([args...])}.

因为对象是由 @ref{883,,__new__()} 和 @ref{d57,,__init__()} 协作构造完成的 (由 @ref{883,,__new__()} 创建，并由 @ref{d57,,__init__()} 定制)，所以 @ref{d57,,__init__()} 返回的值只能是 @code{None}，否则会在运行时引发 @ref{192,,TypeError}。
@end deffn

@geindex __del__() (object 方法)
@anchor{reference/datamodel object __del__}@anchor{919}
@deffn {方法} object.__del__ (self)

@geindex destructor
@geindex finalizer
@geindex 语句; del

在实例将被销毁时调用。这还会调用终结器或析构器 (不适当)。如果一个基类具有 @ref{919,,__del__()} 方法，则其所派生的类如果也有 @ref{919,,__del__()} 方法，就必须显式地调用它以确保实例基类部分的正确清除。

@ref{919,,__del__()} 方法可以 (但不推荐!) 通过创建一个该实例的新引用来推迟其销毁。这被称为对象 @emph{重生}。@ref{919,,__del__()} 是否会在重生的对象将被销毁时再次被调用是由具体实现决定的 ；当前的 @ref{13ce,,CPython} 实现只会调用一次。

当解释器退出时不会确保为仍然存在的对象调用 @ref{919,,__del__()} 方法。

@cartouche
@quotation 注解 
@code{del x} 并不直接调用 @code{x.__del__()} --- 前者会将 @code{x} 的引用计数减一，而后者仅会在 @code{x} 的引用计数变为零时被调用。
@end quotation
@end cartouche

@strong{CPython implementation detail:} It is possible for a reference cycle to prevent the reference count
of an object from going to zero.  In this case, the cycle will be
later detected and deleted by the @ref{129e,,cyclic garbage collector}.  A common cause of reference cycles is when
an exception has been caught in a local variable.  The frame's
locals then reference the exception, which references its own
traceback, which references the locals of all frames caught in the
traceback.


@subsubheading 参见


@ref{86,,gc} 模块的文档。


@cartouche
@quotation 警告 
由于调用 @ref{919,,__del__()} 方法时周边状况已不确定，在其执行期间发生的异常将被忽略，改为打印一个警告到 @code{sys.stderr}。特别地：


@itemize *

@item 
@ref{919,,__del__()} 可在任意代码被执行时启用，包括来自任意线程的代码。如果 @ref{919,,__del__()} 需要接受锁或启用其他阻塞资源，可能会发生死锁，例如该资源已被为执行 @ref{919,,__del__()} 而中断的代码所获取。

@item 
@ref{919,,__del__()} 可以在解释器关闭阶段被执行。因此，它需要访问的全局变量（包含其他模块）可能已被删除或设为 @code{None}。Python 会保证先删除模块中名称以单个下划线打头的全局变量再删除其他全局变量；如果已不存在其他对此类全局变量的引用，这有助于确保导入的模块在 @ref{919,,__del__()} 方法被调用时仍然可用。
@end itemize
@end quotation
@end cartouche

@geindex repr() (built-in function); __repr__() (object method)
@end deffn

@geindex __repr__() (object 方法)
@anchor{reference/datamodel object __repr__}@anchor{337}
@deffn {方法} object.__repr__ (self)

由 @ref{7c6,,repr()} 内置函数调用以输出一个对象的“官方”字符串表示。如果可能，这应类似一个有效的 Python 表达式，能被用来重建具有相同取值的对象（只要有适当的环境）。如果这不可能，则应返回形式如 @code{<...some useful description...>} 的字符串。返回值必须是一个字符串对象。如果一个类定义了 @ref{337,,__repr__()} 但未定义 @ref{e30,,__str__()}，则在需要该类的实例的“非正式”字符串表示时也会使用 @ref{337,,__repr__()}。

此方法通常被用于调试，因此确保其表示的内容包含丰富信息且无歧义是很重要的。

@geindex string; __str__() (object method)
@geindex format() (built-in function); __str__() (object method)
@geindex print() (built-in function); __str__() (object method)
@end deffn

@geindex __str__() (object 方法)
@anchor{reference/datamodel object __str__}@anchor{e30}
@deffn {方法} object.__str__ (self)

通过 @ref{329,,str(object)} 以及内置函数 @ref{4d5,,format()} 和 @ref{880,,print()} 调用以生成一个对象的“非正式”或格式良好的字符串表示。返回值必须为一个 @ref{11b7,,字符串} 对象。

此方法与 @ref{337,,object.__repr__()} 的不同点在于 @ref{e30,,__str__()} 并不预期返回一个有效的 Python 表达式：可以使用更方便或更准确的描述信息。

内置类型 @ref{2b0,,object} 所定义的默认实现会调用 @ref{337,,object.__repr__()}。

@c XXX what about subclasses of string?
@end deffn

@geindex __bytes__() (object 方法)
@anchor{reference/datamodel object __bytes__}@anchor{13cf}
@deffn {方法} object.__bytes__ (self)

@geindex 內置函数; bytes

通过 @ref{1050,,bytes} 调用以生成一个对象的字节串表示。这应该返回一个 @ref{32a,,bytes} 对象。

@geindex string; __format__() (object method)
@geindex string; conversion
@geindex 內置函数; print
@end deffn

@geindex __format__() (object 方法)
@anchor{reference/datamodel object __format__}@anchor{948}
@deffn {方法} object.__format__ (self, format_spec)

通过 @ref{4d5,,format()} 内置函数、扩展、@ref{15c,,格式化字符串字面值} 的求值以及 @ref{4d4,,str.format()} 方法调用以生成一个对象的“格式化”字符串表示。 @emph{format_spec} 参数为包含所需格式选项描述的字符串。 @emph{format_spec} 参数的解读是由实现 @ref{948,,__format__()} 的类型决定的，不过大多数类或是将格式化委托给某个内置类型，或是使用相似的格式化选项语法。

请参看 @ref{4d8,,格式规格迷你语言} 了解标准格式化语法的描述。

返回值必须为一个字符串对象。


在 3.4 版更改: @code{object} 本身的 __format__ 方法如果被传入任何非空字符，将会引发一个 @ref{192,,TypeError}。



在 3.7 版更改: @code{object.__format__(x, '@w{'})} 现在等同于 @code{str(x)} 而不再是 @code{format(str(self), '@w{'})}。

@end deffn
@anchor{reference/datamodel richcmpfuncs}@anchor{13d0}
@geindex __lt__() (object 方法)
@geindex __le__() (object 方法)
@geindex __eq__() (object 方法)
@geindex __ne__() (object 方法)
@geindex __gt__() (object 方法)
@geindex __ge__() (object 方法)
@anchor{reference/datamodel object __lt__}@anchor{c2d}
@deffn {方法} object.__lt__ (self, other)
@anchor{reference/datamodel object __le__}@anchor{c99}
@deffnx {方法} object.__le__ (self, other)
@anchor{reference/datamodel object __eq__}@anchor{338}
@deffnx {方法} object.__eq__ (self, other)
@anchor{reference/datamodel object __ne__}@anchor{e4f}
@deffnx {方法} object.__ne__ (self, other)
@anchor{reference/datamodel object __gt__}@anchor{c9a}
@deffnx {方法} object.__gt__ (self, other)
@anchor{reference/datamodel object __ge__}@anchor{c9b}
@deffnx {方法} object.__ge__ (self, other)

@geindex comparisons

以上这些被称为“富比较”方法。运算符号与方法名称的对应关系如下：@code{x<y} 调用 @code{x.__lt__(y)}、@code{x<=y} 调用 @code{x.__le__(y)}、@code{x==y} 调用 @code{x.__eq__(y)}、@code{x!=y} 调用 @code{x.__ne__(y)}、@code{x>y} 调用 @code{x.__gt__(y)}、@code{x>=y} 调用 @code{x.__ge__(y)}。

如果指定的参数对没有相应的实现，富比较方法可能会返回单例对象 @code{NotImplemented}。按照惯例，成功的比较会返回 @code{False} 或 @code{True}。不过实际上这些方法可以返回任意值，因此如果比较运算符是要用于布尔值判断（例如作为 @code{if} 语句的条件），Python 会对返回值调用 @ref{183,,bool()} 以确定结果为真还是假。

在默认情况下 @ref{e4f,,__ne__()} 会委托给 @ref{338,,__eq__()} 并将结果取反，除非结果为 @code{NotImplemented}。比较运算符之间没有其他隐含关系，例如 @code{(x<y or x==y)} 为真并不意味着 @code{x<=y}。要根据单根运算自动生成排序操作，请参看 @ref{845,,functools.total_ordering()}。

请查看 @ref{339,,__hash__()} 的相关段落，了解创建可支持自定义比较运算并可用作字典键的 @ref{13c0,,hashable} 对象时要注意的一些事项。

这些方法并没有对调参数版本（在左边参数不支持该操作但右边参数支持时使用）；而是 @ref{c2d,,__lt__()} 和 @ref{c9a,,__gt__()} 互为对方的反射， @ref{c99,,__le__()} 和 @ref{c9b,,__ge__()} 互为对方的反射，而 @ref{338,,__eq__()} 和 @ref{e4f,,__ne__()} 则是它们自己的反射。如果两个操作数的类型不同，且右操作数类型是左操作数类型的直接或间接子类，则优先选择右操作数的反射方法，否则优先选择左操作数的方法。虚拟子类不会被考虑。
@end deffn

@geindex __hash__() (object 方法)
@anchor{reference/datamodel object __hash__}@anchor{339}
@deffn {方法} object.__hash__ (self)

@geindex 对象; dictionary
@geindex 內置函数; hash

通过内置函数 @ref{9be,,hash()} 调用以对哈希集的成员进行操作，属于哈希集的类型包括 @ref{b68,,set}、@ref{be7,,frozenset} 以及 @ref{1b8,,dict}。@ref{339,,__hash__()} 应该返回一个整数。对象比较结果相同所需的唯一特征属性是其具有相同的哈希值；建议的做法是把参与比较的对象全部组件的哈希值混在一起，即将它们打包为一个元组并对该元组做哈希运算。例如:

@example
def __hash__(self):
    return hash((self.name, self.nick, self.color))
@end example

@cartouche
@quotation 注解 
@ref{9be,,hash()} 会从一个对象自定义的 @ref{339,,__hash__()} 方法返回值中截断为 @code{Py_ssize_t} 的大小。通常对 64 位构建为 8 字节，对 32 位构建为 4 字节。如果一个对象的   @ref{339,,__hash__()} 必须在不同位大小的构建上进行互操作，请确保检查全部所支持构建的宽度。做到这一点的简单方法是使用 @code{python -c "import sys; print(sys.hash_info.width)"}。
@end quotation
@end cartouche

如果一个类没有定义 @ref{338,,__eq__()} 方法，那么也不应该定义 @ref{339,,__hash__()} 操作；如果它定义了 @ref{338,,__eq__()} 但没有定义 @ref{339,,__hash__()}，则其实例将不可被用作可哈希集的项。如果一个类定义了可变对象并实现了 @ref{338,,__eq__()} 方法，则不应该实现 @ref{339,,__hash__()}，因为可哈希集的实现要求键的哈希集是不可变的（如果对象的哈希值发生改变，它将处于错误的哈希桶中）。

用户定义的类默认带有 @ref{338,,__eq__()} 和 @ref{339,,__hash__()} 方法；使用它们与任何对象（自己除外）比较必定不相等，并且 @code{x.__hash__()} 会返回一个恰当的值以确保 @code{x == y} 同时意味着 @code{x is y} 且 @code{hash(x) == hash(y)}。

一个类如果重载了 @ref{338,,__eq__()} 且没有定义 @ref{339,,__hash__()} 则会将其 @ref{339,,__hash__()} 隐式地设为 @code{None}。当一个类的 @ref{339,,__hash__()} 方法为 @code{None} 时，该类的实例将在一个程序尝试获取其哈希值时正确地引发 @ref{192,,TypeError}，并会在检测 @code{isinstance(obj, collections.abc.Hashable)} 时被正确地识别为不可哈希对象。

如果一个重载了 @ref{338,,__eq__()} 的类需要保留来自父类的 @ref{339,,__hash__()} 实现，则必须通过设置 @code{__hash__ = <ParentClass>.__hash__} 来显式地告知解释器。

如果一个没有重载 @ref{338,,__eq__()} 的类需要去掉哈希支持，则应该在类定义中包含 @code{__hash__ = None}。一个自定义了 @ref{339,,__hash__()} 以显式地引发 @ref{192,,TypeError} 的类会被 @code{isinstance(obj, collections.abc.Hashable)} 调用错误地识别为可哈希对象。

@cartouche
@quotation 注解 
在默认情况下，str 和 bytes 对象的 @ref{339,,__hash__()} 值会使用一个不可预知的随机值“加盐”。 虽然它们在一个单独 Python 进程中会保持不变，但它们的值在重复运行的 Python 间是不可预测的。

这种做法是为了防止以下形式的拒绝服务攻击：通过仔细选择输入来利用字典插入操作在最坏情况下的执行效率即 O(n^2) 复杂度。详情见 @indicateurl{http://www.ocert.org/advisories/ocert-2011-003.html}

改变哈希值会影响集合的迭代次序。Python 也从不保证这个次序不会被改变（通常它在 32 位和 64 位构建上是不一致的）。

另见 
@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED}.
@end quotation
@end cartouche


在 3.3 版更改: 默认启用哈希随机化。

@end deffn

@geindex __bool__() (object 方法)
@anchor{reference/datamodel object __bool__}@anchor{c61}
@deffn {方法} object.__bool__ (self)

@geindex __len__() (mapping object method)

调用此方法以实现真值检测以及内置的 @code{bool()} 操作；应该返回 @code{False} 或 @code{True}。如果未定义此方法，则会查找并调用 @ref{dc4,,__len__()} 并在其返回非零值时视对象的逻辑值为真。如果一个类既未定义 @ref{dc4,,__len__()} 也未定义 @ref{c61,,__bool__()} 则视其所有实例的逻辑值为真。
@end deffn

@node 自定义属性访问,自定义类创建,基本定制,特殊方法名称
@anchor{reference/datamodel attribute-access}@anchor{13d1}@anchor{reference/datamodel customizing-attribute-access}@anchor{13d2}
@subsubsection 自定义属性访问


可以定义下列方法来自定义对类实例属性访问（@code{x.name} 的使用、赋值或删除）的具体含义.

@c XXX explain how descriptors interfere here!

@geindex __getattr__() (object 方法)
@anchor{reference/datamodel object __getattr__}@anchor{313}
@deffn {方法} object.__getattr__ (self, name)

当默认属性访问因引发 @ref{393,,AttributeError} 而失败时被调用 (可能是调用 @ref{441,,__getattribute__()} 时由于 @emph{name} 不是一个实例属性或 @code{self} 的类关系树中的属性而引发了 @ref{393,,AttributeError}；或者是对 @emph{name} 特性属性调用 @ref{13d3,,__get__()} 时引发了 @ref{393,,AttributeError})。此方法应当返回（找到的）属性值或是引发一个 @ref{393,,AttributeError} 异常。

请注意如果属性是通过正常机制找到的，@ref{313,,__getattr__()} 就不会被调用。（这是在 @ref{313,,__getattr__()} 和 @ref{e25,,__setattr__()} 之间故意设置的不对称性。）这既是出于效率理由也是因为不这样设置的话 @ref{313,,__getattr__()} 将无法访问实例的其他属性。要注意至少对于实例变量来说，你不必在实例属性字典中插入任何值（而是通过插入到其他对象）就可以模拟对它的完全控制。请参阅下面的 @ref{441,,__getattribute__()} 方法了解真正获取对属性访问的完全控制权的办法。
@end deffn

@geindex __getattribute__() (object 方法)
@anchor{reference/datamodel object __getattribute__}@anchor{441}
@deffn {方法} object.__getattribute__ (self, name)

此方法会无条件地被调用以实现对类实例属性的访问。如果类还定义了 @ref{313,,__getattr__()}，则后者不会被调用，除非 @ref{441,,__getattribute__()} 显式地调用它或是引发了 @ref{393,,AttributeError}。此方法应当返回（找到的）属性值或是引发一个 @ref{393,,AttributeError} 异常。为了避免此方法中的无限递归，其实现应该总是调用具有相同名称的基类方法来访问它所需要的任何属性，例如 @code{object.__getattribute__(self, name)}。

@cartouche
@quotation 注解 
此方法在作为通过特定语法或内置函数隐式地调用的结果的情况下查找特殊方法时仍可能会被跳过。参见 @ref{13d4,,特殊方法查找}。
@end quotation
@end cartouche
@end deffn

@geindex __setattr__() (object 方法)
@anchor{reference/datamodel object __setattr__}@anchor{e25}
@deffn {方法} object.__setattr__ (self, name, value)

此方法在一个属性被尝试赋值时被调用。这个调用会取代正常机制（即将值保存到实例字典）。 @emph{name} 为属性名称， @emph{value} 为要赋给属性的值。

如果 @ref{e25,,__setattr__()} 想要赋值给一个实例属性，它应该调用同名的基类方法，例如 @code{object.__setattr__(self, name, value)}。
@end deffn

@geindex __delattr__() (object 方法)
@anchor{reference/datamodel object __delattr__}@anchor{13c8}
@deffn {方法} object.__delattr__ (self, name)

类似于 @ref{e25,,__setattr__()} 但其作用为删除而非赋值。此方法应该仅在 @code{del obj.name} 对于该对象有意义时才被实现。
@end deffn

@geindex __dir__() (object 方法)
@anchor{reference/datamodel object __dir__}@anchor{314}
@deffn {方法} object.__dir__ (self)

此方法会在对相应对象调用 @ref{d2c,,dir()} 时被调用。返回值必须为一个序列。 @ref{d2c,,dir()} 会把返回的序列转换为列表并对其排序。
@end deffn

@menu
* 自定义模块属性访问:: 
* 实现描述器:: 
* 调用描述器:: 
* __slots__:: 

@end menu

@node 自定义模块属性访问,实现描述器,,自定义属性访问
@anchor{reference/datamodel customizing-module-attribute-access}@anchor{13d5}
@subsubsection 自定义模块属性访问


@geindex __getattr__ (module attribute)
@geindex __dir__ (module attribute)
@geindex __class__ (module attribute)

特殊名称 @code{__getattr__} 和 @code{__dir__} 还可被用来自定义对模块属性的访问。模块层级的 @code{__getattr__} 函数应当接受一个参数，其名称为一个属性名，并返回计算结果值或引发一个 @ref{393,,AttributeError}。如果通过正常查找即 @ref{441,,object.__getattribute__()} 未在模块对象中找到某个属性，则 @code{__getattr__} 会在模块的 @code{__dict__} 中查找，未找到时会引发一个 @ref{393,,AttributeError}。如果找到，它会以属性名被调用并返回结果值。

@code{__dir__} 函数应当不接受任何参数，并且返回一个表示模块中可访问名称的字符串序列。 此函数如果存在，将会重载一个模块中的标准 @ref{d2c,,dir()} 查找。

想要更细致地自定义模块的行为（设置属性和特性属性等待），可以将模块对象的 @code{__class__} 属性设置为一个 @ref{6eb,,types.ModuleType} 的子类。例如:

@example
import sys
from types import ModuleType

class VerboseModule(ModuleType):
    def __repr__(self):
        return f'Verbose @{self.__name__@}'

    def __setattr__(self, attr, value):
        print(f'Setting @{attr@}...')
        super().__setattr__(attr, value)

sys.modules[__name__].__class__ = VerboseModule
@end example

@cartouche
@quotation 注解 
定义模块的 @code{__getattr__} 和设置模块的 @code{__class__} 只会影响使用属性访问语法进行的查找 -- 直接访问模块全局变量（不论是通过模块内的代码还是通过对模块全局字典的引用）是不受影响的。
@end quotation
@end cartouche


在 3.5 版更改: @code{__class__} 模块属性改为可写。



3.7 新版功能: @code{__getattr__} 和 @code{__dir__} 模块属性。



@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 562

@item PEP 562@footnote{https://www.python.org/dev/peps/pep-0562} - 模块 __getattr__ 和 __dir__

描述用于模块的 @code{__getattr__} 和 @code{__dir__} 函数。
@end table


@node 实现描述器,调用描述器,自定义模块属性访问,自定义属性访问
@anchor{reference/datamodel descriptors}@anchor{4e3}@anchor{reference/datamodel implementing-descriptors}@anchor{13d6}
@subsubsection 实现描述器


以下方法仅当一个包含该方法的类（称为 @emph{描述器} 类）的实例出现于一个 @emph{所有者} 类中的时候才会起作用（该描述器必须在所有者类或其某个上级类的字典中）。在以下示例中，“属性”指的是名称为所有者类 @ref{4f6,,__dict__} 中的特征属性的键名的属性。

@geindex __get__() (object 方法)
@anchor{reference/datamodel object __get__}@anchor{13d3}
@deffn {方法} object.__get__ (self, instance, owner=None)

调用此方法以获取所有者类的属性（类属性访问）或该类的实例的属性（实例属性访问）。 可选的 @emph{owner} 参数是所有者类而 @emph{instance} 是被用来访问属性的实例，如果通过 @emph{owner} 来访问属性则返回 @code{None}。

此方法应当返回计算得到的属性值或是引发 @ref{393,,AttributeError} 异常。

@geindex Python 提高建议; PEP 252
PEP 252@footnote{https://www.python.org/dev/peps/pep-0252} 指明 @ref{13d3,,__get__()} 为带有一至二个参数的可调用对象。 Python 自身内置的描述器支持此规格定义；但是，某些第三方工具可能要求必须带两个参数。 Python 自身的 @ref{441,,__getattribute__()} 实现总是会传入两个参数，无论它们是否被要求提供。
@end deffn

@geindex __set__() (object 方法)
@anchor{reference/datamodel object __set__}@anchor{13d7}
@deffn {方法} object.__set__ (self, instance, value)

调用此方法以设置 @emph{instance} 指定的所有者类的实例的属性为新值 @emph{value}。

请注意，添加 @ref{13d7,,__set__()} 或 @ref{13d8,,__delete__()} 会将描述器变成“数据描述器”。 更多细节请参阅 @ref{13d9,,调用描述器}。
@end deffn

@geindex __delete__() (object 方法)
@anchor{reference/datamodel object __delete__}@anchor{13d8}
@deffn {方法} object.__delete__ (self, instance)

调用此方法以删除 @emph{instance} 指定的所有者类的实例的属性。
@end deffn

@geindex __set_name__() (object 方法)
@anchor{reference/datamodel object __set_name__}@anchor{4e2}
@deffn {方法} object.__set_name__ (self, owner, name)

在所有者类 @emph{owner} 创建时被调用。描述器会被赋值给 @emph{name}。

@cartouche
@quotation 注解 
@ref{4e2,,__set_name__()} 只是作为 @ref{603,,type} 构造器的一部分被隐式地调用，因此在某个类被初次创建之后又额外添加一个描述器时，那就需要显式地调用它并且附带适当的形参:

@example
class A:
   pass
descr = custom_descriptor()
A.attr = descr
descr.__set_name__(A, 'attr')
@end example

详情参见 @ref{4de,,创建类对象}。
@end quotation
@end cartouche


3.6 新版功能.

@end deffn

属性 @code{__objclass__} 会被 @ref{a0,,inspect} 模块解读为指定此对象定义所在的类（正确设置此属性有助于动态类属性的运行时内省）。对于可调用对象来说，它可以指明预期或要求提供一个特定类型（或子类）的实例作为第一个位置参数（例如，CPython 会为实现于 C 中的未绑定方法设置此属性）。

@node 调用描述器,__slots__,实现描述器,自定义属性访问
@anchor{reference/datamodel descriptor-invocation}@anchor{13d9}@anchor{reference/datamodel invoking-descriptors}@anchor{13da}
@subsubsection 调用描述器


总的说来，描述器就是具有“绑定行为”的对象属性，其属性访问已被描述器协议中的方法所重载，包括 @ref{13d3,,__get__()}, @ref{13d7,,__set__()} 和 @ref{13d8,,__delete__()}。如果一个对象定义了以上方法中的任意一个，它就被称为描述器。

属性访问的默认行为是从一个对象的字典中获取、设置或删除属性。例如，@code{a.x} 的查找顺序会从 @code{a.__dict__['x']} 开始，然后是 @code{type(a).__dict__['x']}，接下来依次查找 @code{type(a)} 的上级基类，不包括元类。

但是，如果找到的值是定义了某个描述器方法的对象，则 Python 可能会重载默认行为并转而发起调用描述器方法。这具体发生在优先级链的哪个环节则要根据所定义的描述器方法及其被调用的方式来决定。

描述器发起调用的开始点是一个绑定 @code{a.x}。参数的组合方式依 @code{a} 而定:


@table @asis

@item 直接调用

最简单但最不常见的调用方式是用户代码直接发起调用一个描述器方法:    @code{x.__get__(a)}。

@item 实例绑定

如果绑定到一个对象实例，@code{a.x} 会被转换为调用: @code{type(a).__dict__['x'].__get__(a, type(a))}。

@item 类绑定

如果绑定到一个类，@code{A.x} 会被转换为调用: @code{A.__dict__['x'].__get__(None, A)}。

@item 超绑定

如果 @code{a} 是 @ref{4dc,,super} 的一个实例，则绑定 @code{super(B, obj).m()} 会在 @code{obj.__class__.__mro__} 中搜索 @code{B} 的直接上级基类 @code{A} 然后通过以下调用发起调用描述器: @code{A.__dict__['m'].__get__(obj, obj.__class__)}。
@end table

对于实例绑定，发起描述器调用的优先级取决于定义了哪些描述器方法。一个描述器可以定义 @ref{13d3,,__get__()}、@ref{13d7,,__set__()} 和 @ref{13d8,,__delete__()} 的任意组合。如果它没有定义 @ref{13d3,,__get__()}，则访问属性会返回描述器对象自身，除非对象的实例字典中有相应属性值。如果描述器定义了 @ref{13d7,,__set__()} 和/或 @ref{13d8,,__delete__()}，则它是一个数据描述器；如果以上两个都未定义，则它是一个非数据描述器。通常，数据描述器会同时定义 @ref{13d3,,__get__()} 和 @ref{13d7,,__set__()}，而非数据描述器只有 @ref{13d3,,__get__()} 方法。定义了 @ref{13d7,,__set__()} 和 @ref{13d3,,__get__()} 的数据描述器总是会重载实例字典中的定义。与之相对的，非数据描述器可被实例所重载。

Python 方法 (包括 @ref{1d9,,staticmethod()} 和 @ref{1d8,,classmethod()}) 都是作为非描述器来实现的。因此实例可以重定义并重载方法。这允许单个实例获得与相同类的其他实例不一样的行为。

@ref{1d7,,property()} 函数是作为数据描述器来实现的。因此实例不能重载特性属性的行为。

@node __slots__,,调用描述器,自定义属性访问
@anchor{reference/datamodel id3}@anchor{13db}@anchor{reference/datamodel slots}@anchor{13dc}
@subsubsection __slots__


@emph{__slots__} 允许我们显式地声明数据成员（例如特征属性）并禁止创建 @emph{__dict__} 和 @emph{__weakref__} (除非是在 @emph{__slots__} 中显式地声明或是在父类中可用。)

相比使用 @emph{__dict__} 此方式可以显著地节省空间。 属性查找速度也可得到显著的提升。

@geindex object.__slots__ (內置变量)
@anchor{reference/datamodel object __slots__}@anchor{e26}
@deffn {数据} object.__slots__

这个类变量可赋值为字符串、可迭代对象或由实例使用的变量名构成的字符串序列。 @emph{__slots__} 会为已声明的变量保留空间，并阻止自动为每个实例创建 @emph{__dict__} 和 @emph{__weakref__}。
@end deffn

@menu
* 使用 __slots__ 的注意事项:: 

@end menu

@node 使用 __slots__ 的注意事项,,,__slots__
@anchor{reference/datamodel notes-on-using-slots}@anchor{13dd}
@subsubsection 使用 @emph{__slots__} 的注意事项



@itemize *

@item 
当继承自一个未定义 @emph{__slots__} 的类时，实例的 @emph{__dict__} 和 @emph{__weakref__} 属性将总是可访问。

@item 
没有 @emph{__dict__} 变量，实例就不能给未在 @emph{__slots__} 定义中列出的新变量赋值。尝试给一个未列出的变量名赋值将引发 @ref{393,,AttributeError}。新变量需要动态赋值，就要将 @code{'__dict__'} 加入到 @emph{__slots__} 声明的字符串序列中。

@item 
如果未给每个实例设置 @emph{__weakref__} 变量，定义了 @emph{__slots__} 的类就不支持对其实际的弱引用。如果需要弱引用支持，就要将 @code{'__weakref__'} 加入到 @emph{__slots__} 声明的字符串序列中。

@item 
@emph{__slots__} 是通过为每个变量名创建描述器 (@ref{4e3,,实现描述器}) 在类层级上实现的。因此，类属性不能被用来为通过 @emph{__slots__} 定义的实例变量设置默认值；否则，类属性就会覆盖描述器赋值。

@item 
@emph{__slots__} 声明的作用不只限于定义它的类。在父类中声明的 @emph{__slots__} 在其子类中同样可用。不过，子类将会获得 @emph{__dict__}  和 @emph{__weakref__} 除非它们也定义了 @emph{__slots__} (其中应该仅包含对任何 @emph{额外} 名称的声明位置)。

@item 
如果一个类定义的位置在某个基类中也有定义，则由基类位置定义的实例变量将不可访问（除非通过直接从基类获取其描述器的方式）。这会使得程序的含义变成未定义。未来可能会添加一个防止此情况的检查。

@item 
非空的 @emph{__slots__} 不适用于派生自“可变长度”内置类型例如 @ref{184,,int}、@ref{32a,,bytes} 和 @ref{478,,tuple} 的派生类。

@item 
任何非字符串可迭代对象都可以被赋值给 @emph{__slots__}。映射也可以被使用；不过，未来可能会分别赋给每个键具有特殊含义的值。

@item 
@emph{__class__} 赋值仅在两个类具有相同的 @emph{__slots__} 时才会起作用。

@item 
带有多个父类声明位置的多重继承也是可用的，但仅允许一个父类具有由声明位置创建的属性（其他基类必须具有空的位置布局） —— 违反规则将引发 @ref{192,,TypeError}。

@item 
如果为 @emph{__slots__} 使用了一个迭代器，则会为迭代器的每个值创建描述器。 但是 @emph{__slots__} 属性将为一个空迭代器。
@end itemize

@node 自定义类创建,自定义实例及子类检查,自定义属性访问,特殊方法名称
@anchor{reference/datamodel class-customization}@anchor{4df}@anchor{reference/datamodel customizing-class-creation}@anchor{13de}
@subsubsection 自定义类创建


当一个类继承其他类时，那个类的 @emph{__init_subclass__} 会被调用。这样就可以编写能够改变子类行为的类。这与类装饰器有紧密的关联，但是类装饰器是影响它们所应用的特定类，而 @code{__init_subclass__} 则只作用于定义了该方法的类所派生的子类。

@geindex __init_subclass__() (object 类方法)
@anchor{reference/datamodel object __init_subclass__}@anchor{4dd}
@deffn {方法} classmethod object.__init_subclass__ (cls)

当所在类派生子类时此方法就会被调用。@emph{cls} 将指向新的子类。如果定义为一个普通实例方法，此方法将被隐式地转换为类方法。

传入一个新类的关键字参数会被传给父类的 @code{__init_subclass__}。为了与其他使用 @code{__init_subclass__} 的类兼容，应当根据需要去掉部分关键字参数再将其余的传给基类，例如:

@example
class Philosopher:
    def __init_subclass__(cls, /, default_name, **kwargs):
        super().__init_subclass__(**kwargs)
        cls.default_name = default_name

class AustralianPhilosopher(Philosopher, default_name="Bruce"):
    pass
@end example

@code{object.__init_subclass__} 的默认实现什么都不做，只在带任意参数调用时引发一个错误。

@cartouche
@quotation 注解 
元类提示 @code{metaclass} 将被其它类型机制消耗掉，并不会被传给 @code{__init_subclass__} 的实现。实际的元类（而非显式的提示）可通过 @code{type(cls)} 访问。
@end quotation
@end cartouche


3.6 新版功能.

@end deffn

@menu
* 元类:: 
* 解析 MRO 条目:: 
* 确定适当的元类:: 
* 准备类命名空间:: 
* 执行类主体:: 
* 创建类对象:: 
* 元类的作用:: 

@end menu

@node 元类,解析 MRO 条目,,自定义类创建
@anchor{reference/datamodel id4}@anchor{13df}@anchor{reference/datamodel metaclasses}@anchor{13e0}
@subsubsection 元类


@geindex metaclass
@geindex 內置函数; type
@geindex = (equals); class definition

默认情况下，类是使用 @ref{603,,type()} 来构建的。类体会在一个新的命名空间内执行，类名会被局部绑定到 @code{type(name, bases, namespace)} 的结果。

类创建过程可通过在定义行传入 @code{metaclass} 关键字参数，或是通过继承一个包含此参数的现有类来进行定制。在以下示例中，@code{MyClass} 和 @code{MySubclass} 都是 @code{Meta} 的实例:

@example
class Meta(type):
    pass

class MyClass(metaclass=Meta):
    pass

class MySubclass(MyClass):
    pass
@end example

在类定义内指定的任何其他关键字参数都会在下面所描述的所有元类操作中进行传递。

当一个类定义被执行时，将发生以下步骤:


@itemize *

@item 
解析 MRO 条目；

@item 
确定适当的元类；

@item 
准备类命名空间；

@item 
执行类主体；

@item 
创建类对象。
@end itemize

@node 解析 MRO 条目,确定适当的元类,元类,自定义类创建
@anchor{reference/datamodel resolving-mro-entries}@anchor{13e1}
@subsubsection 解析 MRO 条目


如果在类定义中出现的基类不是 @ref{603,,type} 的实例，则使用 @code{__mro_entries__} 方法对其进行搜索，当找到结果时，它会以原始基类元组做参数进行调用。此方法必须返回类的元组以替代此基类被使用。元组可以为空，在此情况下原始基类将被忽略。


@subsubheading 参见


@geindex Python 提高建议; PEP 560
PEP 560@footnote{https://www.python.org/dev/peps/pep-0560} - 对 typing 模块和泛型类型的核心支持


@node 确定适当的元类,准备类命名空间,解析 MRO 条目,自定义类创建
@anchor{reference/datamodel determining-the-appropriate-metaclass}@anchor{13e2}
@subsubsection 确定适当的元类


@geindex metaclass hint

为一个类定义确定适当的元类是根据以下规则:


@itemize *

@item 
如果没有基类且没有显式指定元类，则使用 @ref{603,,type()}；

@item 
如果给出一个显式元类而且 @emph{不是} @ref{603,,type()} 的实例，则其会被直接用作元类；

@item 
如果给出一个 @ref{603,,type()} 的实例作为显式元类，或是定义了基类，则使用最近派生的元类。
@end itemize

最近派生的元类会从显式指定的元类（如果有）以及所有指定的基类的元类（即 @code{type(cls)}）中选取。最近派生的元类应为 @emph{所有} 这些候选元类的一个子类型。如果没有一个候选元类符合该条件，则类定义将失败并抛出 @code{TypeError}。

@node 准备类命名空间,执行类主体,确定适当的元类,自定义类创建
@anchor{reference/datamodel prepare}@anchor{4f7}@anchor{reference/datamodel preparing-the-class-namespace}@anchor{13e3}
@subsubsection 准备类命名空间


@geindex __prepare__ (metaclass method)

一旦确定了适当的元类，则将准备好类命名空间。 如果元类具有 @code{__prepare__} 属性，它会以 @code{namespace = metaclass.__prepare__(name, bases, **kwds)} 的形式被调用（其中如果有任何额外的关键字参数，则应当来自类定义）。 @code{__prepare__} 方法应该被实现为 @ref{1d8,,classmethod()}。 @code{__prepare__} 所返回的命名空间会被传入 @code{__new__}，但是当最终的类对象被创建时，该命名空间会被拷贝到一个新的 @code{dict} 中。

如果元类没有 @code{__prepare__} 属性，则类命名空间将初始化为一个空的有序映射。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3115

@item PEP 3115@footnote{https://www.python.org/dev/peps/pep-3115} - Python 3000 中的元类

引入 @code{__prepare__} 命名空间钩子
@end table


@node 执行类主体,创建类对象,准备类命名空间,自定义类创建
@anchor{reference/datamodel executing-the-class-body}@anchor{13e4}
@subsubsection 执行类主体


@geindex class; body

类主体会以（类似于） @code{exec(body, globals(), namespace)} 的形式被执行。普通调用与 @ref{c3d,,exec()} 的关键区别在于当类定义发生于函数内部时，词法作用域允许类主体（包括任何方法）引用来自当前和外部作用域的名称。

但是，即使当类定义发生于函数内部时，在类内部定义的方法仍然无法看到在类作用域层次上定义的名称。类变量必须通过实例的第一个形参或类方法来访问，或者是通过下一节中描述的隐式词法作用域的 @code{__class__} 引用。

@node 创建类对象,元类的作用,执行类主体,自定义类创建
@anchor{reference/datamodel class-object-creation}@anchor{4de}@anchor{reference/datamodel creating-the-class-object}@anchor{13e5}
@subsubsection 创建类对象


@geindex __class__ (method cell)
@geindex __classcell__ (class namespace entry)

一旦执行类主体完成填充类命名空间，将通过调用 @code{metaclass(name, bases, namespace, **kwds)} 创建类对象（此处的附加关键字参数与传入 @code{__prepare__} 的相同）。

如果类主体中有任何方法引用了 @code{__class__} 或 @code{super}，这个类对象会通过零参数形式的 @ref{4dc,,super()}. @code{__class__} 所引用，这是由编译器所创建的隐式闭包引用。这使用零参数形式的 @ref{4dc,,super()} 能够正确标识正在基于词法作用域来定义的类，而被用于进行当前调用的类或实例则是基于传递给方法的第一个参数来标识的。

@strong{CPython implementation detail:} 在 CPython 3.6 及之后的版本中，@code{__class__} 单元会作为类命名空间中的 @code{__classcell__} 条目被传给元类。 如果存在，它必须被向上传播给 @code{type.__new__} 调用，以便能正确地初始化该类。 如果不这样做，在 Python 3.8 中将引发 @ref{2ba,,RuntimeError}。

当使用默认的元类 @ref{603,,type} 或者任何最终会调用 @code{type.__new__} 的元类时，以下额外的自定义步骤将在创建类对象之后被发起调用:


@itemize *

@item 
首先，@code{type.__new__} 将收集类命名空间中所有定义了 @ref{4e2,,__set_name__()} 方法的描述器；

@item 
接下来，所有这些 @code{__set_name__} 方法将使用所定义的类和特定描述器所赋的名称进行调用；

@item 
最后，将在新类根据方法解析顺序所确定的直接父类上调用 @ref{4dd,,__init_subclass__()} 钩子。
@end itemize

在类对象创建之后，它会被传给包含在类定义中的类装饰器（如果有的话），得到的对象将作为已定义的类绑定到局部命名空间。

当通过 @code{type.__new__} 创建一个新类时，提供以作为命名空间形参的对象会被复制到一个新的有序映射并丢弃原对象。这个新副本包装于一个只读代理中，后者则成为类对象的 @ref{4f6,,__dict__} 属性。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3135

@item PEP 3135@footnote{https://www.python.org/dev/peps/pep-3135} - 新的超类型

描述隐式的 @code{__class__} 闭包引用
@end table


@node 元类的作用,,创建类对象,自定义类创建
@anchor{reference/datamodel uses-for-metaclasses}@anchor{13e6}
@subsubsection 元类的作用


元类的潜在作用非常广泛。已经过尝试的设想包括枚举、日志、接口检查、自动委托、自动特征属性创建、代理、框架以及自动资源锁定/同步等等。

@node 自定义实例及子类检查,模拟泛型类型,自定义类创建,特殊方法名称
@anchor{reference/datamodel customizing-instance-and-subclass-checks}@anchor{13e7}
@subsubsection 自定义实例及子类检查


以下方法被用来重载 @ref{449,,isinstance()} 和 @ref{44a,,issubclass()} 内置函数的默认行为。

特别地，元类 @ref{813,,abc.ABCMeta} 实现了这些方法以便允许将抽象基类（ABC）作为“虚拟基类”添加到任何类或类型（包括内置类型），包括其他 ABC 之中。

@geindex __instancecheck__() (class 方法)
@anchor{reference/datamodel class __instancecheck__}@anchor{13e8}
@deffn {方法} class.__instancecheck__ (self, instance)

如果 @emph{instance} 应被视为 @emph{class} 的一个（直接或间接）实例则返回真值。如果定义了此方法，则会被调用以实现 @code{isinstance(instance, class)}。
@end deffn

@geindex __subclasscheck__() (class 方法)
@anchor{reference/datamodel class __subclasscheck__}@anchor{13e9}
@deffn {方法} class.__subclasscheck__ (self, subclass)

Return true 如果 @emph{subclass} 应被视为 @emph{class} 的一个（直接或间接）子类则返回真值。如果定义了此方法，则会被调用以实现 @code{issubclass(subclass, class)}。
@end deffn

请注意这些方法的查找是基于类的类型（元类）。它们不能作为类方法在实际的类中被定义。这与基于实例被调用的特殊方法的查找是一致的，只有在此情况下实例本身被当作是类。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3119

@item PEP 3119@footnote{https://www.python.org/dev/peps/pep-3119} - 引入抽象基类

新增功能描述，通过 @ref{13e8,,__instancecheck__()} 和 @ref{13e9,,__subclasscheck__()} 来定制 @ref{449,,isinstance()} 和 @ref{44a,,issubclass()} 行为，加入此功能的动机是出于向该语言添加抽象基类的内容（参见 @ref{4,,abc} 模块）。
@end table


@node 模拟泛型类型,模拟可调用对象,自定义实例及子类检查,特殊方法名称
@anchor{reference/datamodel emulating-generic-types}@anchor{13ea}
@subsubsection 模拟泛型类型


通过定义一个特殊方法，可以实现由 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} 所规定的泛型类语法 (例如 @code{List[int]}):

@geindex __class_getitem__() (object 类方法)
@anchor{reference/datamodel object __class_getitem__}@anchor{320}
@deffn {方法} classmethod object.__class_getitem__ (cls, key)

按照 @emph{key} 参数指定的类型返回一个表示泛型类的专门化对象。
@end deffn

此方法的查找会基于对象自身，并且当定义于类体内部时，此方法将隐式地成为类方法。请注意，此机制主要是被保留用于静态类型提示，不鼓励在其他场合使用。


@subsubheading 参见


@geindex Python 提高建议; PEP 560
PEP 560@footnote{https://www.python.org/dev/peps/pep-0560} - 对 typing 模块和泛型类型的核心支持


@node 模拟可调用对象,模拟容器类型,模拟泛型类型,特殊方法名称
@anchor{reference/datamodel callable-types}@anchor{13eb}@anchor{reference/datamodel emulating-callable-objects}@anchor{13ec}
@subsubsection 模拟可调用对象


@geindex __call__() (object 方法)
@anchor{reference/datamodel object __call__}@anchor{13c5}
@deffn {方法} object.__call__ (self[, args...])

@geindex call; instance

此方法会在实例作为一个函数被“调用”时被调用；如果定义了此方法，则 @code{x(arg1, arg2, ...)} 就相当于 @code{x.__call__(arg1, arg2, ...)} 的快捷方式。
@end deffn

@node 模拟容器类型,模拟数字类型,模拟可调用对象,特殊方法名称
@anchor{reference/datamodel emulating-container-types}@anchor{13ed}@anchor{reference/datamodel sequence-types}@anchor{13ee}
@subsubsection 模拟容器类型


可以定义下列方法来实现容器对象。 容器通常属于序列（如列表或元组）或映射（如字典），但也存在其他形式的容器。 前几个方法集被用于模拟序列或是模拟映射；两者的不同之处在于序列允许的键应为整数 @emph{k} 且 @code{0 <= k < N} 其中 @emph{N} 是序列或定义指定区间的项的切片对象的长度。 此外还建议让映射提供 @code{keys()}, @code{values()}, @code{items()}, @code{get()}, @code{clear()}, @code{setdefault()}, @code{pop()}, @code{popitem()}, @code{copy()} 以及 @code{update()} 等方法，它们的行为应与 Python 标准字典对象的相应方法类似。 此外 @ref{1f,,collections.abc} 模块提供了一个 @ref{9e9,,MutableMapping} 抽象基类以便根据由 @ref{27f,,__getitem__()}, @ref{c5b,,__setitem__()}, @ref{c5c,,__delitem__()}, 和 @code{keys()} 组成的基本集来创建所需的方法。 可变序列还应像 Python 标准列表对象那样提供 @code{append()}, @code{count()}, @code{index()}, @code{extend()}, @code{insert()}, @code{pop()}, @code{remove()}, @code{reverse()} 和 @code{sort()} 等方法。 最后，序列类型还应通过定义下文描述的 @ref{13ef,,__add__()}, @ref{13f0,,__radd__()}, @ref{e68,,__iadd__()}, @ref{13f1,,__mul__()}, @ref{13f2,,__rmul__()} 和 @ref{13f3,,__imul__()} 等方法来实现加法（指拼接）和乘法（指重复）；它们不应定义其他数值运算符。 此外还建议映射和序列都实现 @ref{d21,,__contains__()} 方法以允许高效地使用 @code{in} 运算符；对于映射，@code{in} 应该搜索映射的键；对于序列，则应搜索其中的值。 另外还建议映射和序列都实现 @ref{509,,__iter__()} 方法以允许高效地迭代容器中的条目；对于映射，@ref{509,,__iter__()} 应当迭代对象的键；对于序列，则应当迭代其中的值。

@geindex __len__() (object 方法)
@anchor{reference/datamodel object __len__}@anchor{dc4}
@deffn {方法} object.__len__ (self)

@geindex 內置函数; len
@geindex __bool__() (object method)

调用此方法以实现内置函数 @ref{150,,len()}。应该返回对象的长度，以一个 @code{>=} 0 的整数表示。此外，如果一个对象未定义 @ref{c61,,__bool__()} 方法而其 @ref{dc4,,__len__()} 方法返回值为零，则在布尔运算中会被视为假值。

@strong{CPython implementation detail:} 在 CPython 中，要求长度最大为 @ref{b3c,,sys.maxsize}。如果长度大于 @code{sys.maxsize} 则某些特性 (例如 @ref{150,,len()}) 可能会引发 @ref{95a,,OverflowError}。要通过真值检测来防止引发 @code{OverflowError}，对象必须定义 @ref{c61,,__bool__()} 方法。
@end deffn

@geindex __length_hint__() (object 方法)
@anchor{reference/datamodel object __length_hint__}@anchor{806}
@deffn {方法} object.__length_hint__ (self)

调用此方法以实现 @ref{877,,operator.length_hint()}。 应该返回对象长度的估计值（可能大于或小于实际长度）。 此长度应为一个 @code{>=} 0 的整数。 返回值也可以为 @ref{846,,NotImplemented}，这会被视作与 @code{__length_hint__} 方法完全不存在时一样处理。 此方法纯粹是为了优化性能，并不要求正确无误。


3.4 新版功能.

@end deffn

@geindex 对象; slice

@cartouche
@quotation 注解 
切片是通过下述三个专门方法完成的。以下形式的调用

@example
a[1:2] = b
@end example

会为转写为

@example
a[slice(1, 2, None)] = b
@end example

其他形式以此类推。略去的切片项总是以 @code{None} 补全。
@end quotation
@end cartouche

@geindex __getitem__() (object 方法)
@anchor{reference/datamodel object __getitem__}@anchor{27f}
@deffn {方法} object.__getitem__ (self, key)

调用此方法以实现 @code{self[key]} 的求值。对于序列类型，接受的键应为整数和切片对象。请注意负数索引（如果类想要模拟序列类型）的特殊解读是取决于 @ref{27f,,__getitem__()} 方法。如果 @emph{key} 的类型不正确则会引发 @ref{192,,TypeError} 异常；如果为序列索引集范围以外的值（在进行任何负数索引的特殊解读之后）则应引发 @ref{e6e,,IndexError} 异常。对于映射类型，如果 @emph{key} 找不到（不在容器中）则应引发 @ref{2c7,,KeyError} 异常。

@cartouche
@quotation 注解 
@ref{c29,,for} 循环在有不合法索引时会期待捕获 @ref{e6e,,IndexError} 以便正确地检测到序列的结束。
@end quotation
@end cartouche
@end deffn

@geindex __setitem__() (object 方法)
@anchor{reference/datamodel object __setitem__}@anchor{c5b}
@deffn {方法} object.__setitem__ (self, key, value)

调用此方法以实现向 @code{self[key]} 赋值。注意事项与 @ref{27f,,__getitem__()} 相同。为对象实现此方法应该仅限于需要映射允许基于键修改值或添加键，或是序列允许元素被替换时。不正确的 @emph{key} 值所引发的异常应与 @ref{27f,,__getitem__()} 方法的情况相同。
@end deffn

@geindex __delitem__() (object 方法)
@anchor{reference/datamodel object __delitem__}@anchor{c5c}
@deffn {方法} object.__delitem__ (self, key)

调用此方法以实现 @code{self[key]} 的删除。注意事项与 @ref{27f,,__getitem__()} 相同。为对象实现此方法应该权限于需要映射允许移除键，或是序列允许移除元素时。不正确的 @emph{key} 值所引发的异常应与 @ref{27f,,__getitem__()} 方法的情况相同。
@end deffn

@geindex __missing__() (object 方法)
@anchor{reference/datamodel object __missing__}@anchor{b34}
@deffn {方法} object.__missing__ (self, key)

此方法由 @ref{1b8,,dict}.@ref{27f,,__getitem__()} 在找不到字典中的键时调用以实现 dict 子类的 @code{self[key]}。
@end deffn

@geindex __iter__() (object 方法)
@anchor{reference/datamodel object __iter__}@anchor{509}
@deffn {方法} object.__iter__ (self)

此方法在需要为容器创建迭代器时被调用。此方法应该返回一个新的迭代器对象，它能够逐个迭代容器中的所有对象。对于映射，它应该逐个迭代容器中的键。

迭代器对象也需要实现此方法；它们需要返回对象自身。有关迭代器对象的详情请参看 @ref{13f4,,迭代器类型} 一节。
@end deffn

@geindex __reversed__() (object 方法)
@anchor{reference/datamodel object __reversed__}@anchor{529}
@deffn {方法} object.__reversed__ (self)

此方法（如果存在）会被 @ref{18e,,reversed()} 内置函数调用以实现逆向迭代。它应当返回一个新的以逆序逐个迭代容器内所有对象的迭代器对象。

如果未提供 @ref{529,,__reversed__()} 方法，则 @ref{18e,,reversed()} 内置函数将回退到使用序列协议 (@ref{dc4,,__len__()} 和 @ref{27f,,__getitem__()})。支持序列协议的对象应当仅在能够提供比 @ref{18e,,reversed()} 所提供的实现更高效的实现时才提供 @ref{529,,__reversed__()} 方法。
@end deffn

成员检测运算符 (@ref{79d,,in} 和 @ref{13f5,,not in}) 通常以对容器进行逐个迭代的方式来实现。 不过，容器对象可以提供以下特殊方法并采用更有效率的实现，这样也不要求对象必须为可迭代对象。

@geindex __contains__() (object 方法)
@anchor{reference/datamodel object __contains__}@anchor{d21}
@deffn {方法} object.__contains__ (self, item)

调用此方法以实现成员检测运算符。如果 @emph{item} 是 @emph{self} 的成员则应返回真，否则返回假。对于映射类型，此检测应基于映射的键而不是值或者键值对。

对于未定义 @ref{d21,,__contains__()} 的对象，成员检测将首先尝试通过 @ref{509,,__iter__()} 进行迭代，然后再使用 @ref{27f,,__getitem__()} 的旧式序列迭代协议，参看 @ref{13f6,,语言参考中的相应部分}。
@end deffn

@node 模拟数字类型,with 语句上下文管理器,模拟容器类型,特殊方法名称
@anchor{reference/datamodel emulating-numeric-types}@anchor{13f7}@anchor{reference/datamodel numeric-types}@anchor{13f8}
@subsubsection 模拟数字类型


定义以下方法即可模拟数字类型。特定种类的数字不支持的运算（例如非整数不能进行位运算）所对应的方法应当保持未定义状态。

@geindex __add__() (object 方法)
@geindex __sub__() (object 方法)
@geindex __mul__() (object 方法)
@geindex __matmul__() (object 方法)
@geindex __truediv__() (object 方法)
@geindex __floordiv__() (object 方法)
@geindex __mod__() (object 方法)
@geindex __divmod__() (object 方法)
@geindex __pow__() (object 方法)
@geindex __lshift__() (object 方法)
@geindex __rshift__() (object 方法)
@geindex __and__() (object 方法)
@geindex __xor__() (object 方法)
@geindex __or__() (object 方法)
@anchor{reference/datamodel object __add__}@anchor{13ef}
@deffn {方法} object.__add__ (self, other)
@anchor{reference/datamodel object __sub__}@anchor{13f9}
@deffnx {方法} object.__sub__ (self, other)
@anchor{reference/datamodel object __mul__}@anchor{13f1}
@deffnx {方法} object.__mul__ (self, other)
@anchor{reference/datamodel object __matmul__}@anchor{642}
@deffnx {方法} object.__matmul__ (self, other)
@anchor{reference/datamodel object __truediv__}@anchor{780}
@deffnx {方法} object.__truediv__ (self, other)
@anchor{reference/datamodel object __floordiv__}@anchor{e2e}
@deffnx {方法} object.__floordiv__ (self, other)
@anchor{reference/datamodel object __mod__}@anchor{13fa}
@deffnx {方法} object.__mod__ (self, other)
@anchor{reference/datamodel object __divmod__}@anchor{781}
@deffnx {方法} object.__divmod__ (self, other)
@anchor{reference/datamodel object __pow__}@anchor{13fb}
@deffnx {方法} object.__pow__ (self, other[, modulo])
@anchor{reference/datamodel object __lshift__}@anchor{13fc}
@deffnx {方法} object.__lshift__ (self, other)
@anchor{reference/datamodel object __rshift__}@anchor{13fd}
@deffnx {方法} object.__rshift__ (self, other)
@anchor{reference/datamodel object __and__}@anchor{13fe}
@deffnx {方法} object.__and__ (self, other)
@anchor{reference/datamodel object __xor__}@anchor{13ff}
@deffnx {方法} object.__xor__ (self, other)
@anchor{reference/datamodel object __or__}@anchor{1400}
@deffnx {方法} object.__or__ (self, other)

@geindex 內置函数; divmod
@geindex 內置函数; pow
@geindex 內置函数; pow

调用这些方法来实现二进制算术运算 (@code{+}, @code{-}, @code{*}, @code{@@}, @code{/}, @code{//}, @code{%}, @ref{152,,divmod()}, @ref{19a,,pow()}, @code{**}, @code{<<}, @code{>>}, @code{&}, @code{^}, @code{|})。例如，求表达式 @code{x + y} 的值，其中 @emph{x} 是具有 @ref{13ef,,__add__()} 方法的类的一个实例，则会调用 @code{x.__add__(y)}。@ref{781,,__divmod__()} 方法应该等价于使用 @ref{e2e,,__floordiv__()} 和 @ref{13fa,,__mod__()}，它不应该被关联到 @ref{780,,__truediv__()}。请注意如果要支持三元版本的内置 @ref{19a,,pow()} 函数，则 @ref{13fb,,__pow__()} 的定义应该接受可选的第三个参数。

如果这些方法中的某一个不支持与所提供参数进行运算，它应该返回 @code{NotImplemented}。
@end deffn

@geindex __radd__() (object 方法)
@geindex __rsub__() (object 方法)
@geindex __rmul__() (object 方法)
@geindex __rmatmul__() (object 方法)
@geindex __rtruediv__() (object 方法)
@geindex __rfloordiv__() (object 方法)
@geindex __rmod__() (object 方法)
@geindex __rdivmod__() (object 方法)
@geindex __rpow__() (object 方法)
@geindex __rlshift__() (object 方法)
@geindex __rrshift__() (object 方法)
@geindex __rand__() (object 方法)
@geindex __rxor__() (object 方法)
@geindex __ror__() (object 方法)
@anchor{reference/datamodel object __radd__}@anchor{13f0}
@deffn {方法} object.__radd__ (self, other)
@anchor{reference/datamodel object __rsub__}@anchor{1401}
@deffnx {方法} object.__rsub__ (self, other)
@anchor{reference/datamodel object __rmul__}@anchor{13f2}
@deffnx {方法} object.__rmul__ (self, other)
@anchor{reference/datamodel object __rmatmul__}@anchor{643}
@deffnx {方法} object.__rmatmul__ (self, other)
@anchor{reference/datamodel object __rtruediv__}@anchor{1402}
@deffnx {方法} object.__rtruediv__ (self, other)
@anchor{reference/datamodel object __rfloordiv__}@anchor{1403}
@deffnx {方法} object.__rfloordiv__ (self, other)
@anchor{reference/datamodel object __rmod__}@anchor{6a9}
@deffnx {方法} object.__rmod__ (self, other)
@anchor{reference/datamodel object __rdivmod__}@anchor{1404}
@deffnx {方法} object.__rdivmod__ (self, other)
@anchor{reference/datamodel object __rpow__}@anchor{1405}
@deffnx {方法} object.__rpow__ (self, other[, modulo])
@anchor{reference/datamodel object __rlshift__}@anchor{1406}
@deffnx {方法} object.__rlshift__ (self, other)
@anchor{reference/datamodel object __rrshift__}@anchor{1407}
@deffnx {方法} object.__rrshift__ (self, other)
@anchor{reference/datamodel object __rand__}@anchor{1408}
@deffnx {方法} object.__rand__ (self, other)
@anchor{reference/datamodel object __rxor__}@anchor{1409}
@deffnx {方法} object.__rxor__ (self, other)
@anchor{reference/datamodel object __ror__}@anchor{140a}
@deffnx {方法} object.__ror__ (self, other)

@geindex 內置函数; divmod
@geindex 內置函数; pow

调用这些方法来实现具有反射（交换）操作数的二进制算术运算 (@code{+}, @code{-}, @code{*}, @code{@@}, @code{/}, @code{//}, @code{%}, @ref{152,,divmod()}, @ref{19a,,pow()}, @code{**}, @code{<<}, @code{>>}, @code{&}, @code{^}, @code{|})。这些成员函数仅会在左操作数不支持相应运算 @footnote{@w{(3)} 
这里的“不支持”是指该类无此方法，或方法返回 @code{NotImplemented}。 如果你想强制回退到右操作数的反射方法，请不要设置方法为 @code{None} — 那会造成显式地 @emph{阻塞} 此种回退的相反效果。
} 且两个操作数类型不同时被调用。@footnote{@w{(4)} 
对于相同类型的操作数，如果非反射方法 (例如 @ref{13ef,,__add__()}) 失败则会认为相应运算不被支持，这就是反射方法未被调用的原因。
} 例如，求表达式 @code{x - y} 的值，其中 @emph{y} 是具有 @ref{1401,,__rsub__()} 方法的类的一个实例，则当 @code{x.__sub__(y)} 返回 @emph{NotImplemented} 时会调用 @code{y.__rsub__(x)}。

@geindex 內置函数; pow

请注意三元版的 @ref{19a,,pow()} 并不会尝试调用 @ref{1405,,__rpow__()} (因为强制转换规则会太过复杂)。

@cartouche
@quotation 注解 
如果右操作数类型为左操作数类型的一个子类，且该子类提供了指定运算的反射方法，则此方法会先于左操作数的非反射方法被调用。此行为可允许子类重载其祖先类的运算符。
@end quotation
@end cartouche
@end deffn

@geindex __iadd__() (object 方法)
@geindex __isub__() (object 方法)
@geindex __imul__() (object 方法)
@geindex __imatmul__() (object 方法)
@geindex __itruediv__() (object 方法)
@geindex __ifloordiv__() (object 方法)
@geindex __imod__() (object 方法)
@geindex __ipow__() (object 方法)
@geindex __ilshift__() (object 方法)
@geindex __irshift__() (object 方法)
@geindex __iand__() (object 方法)
@geindex __ixor__() (object 方法)
@geindex __ior__() (object 方法)
@anchor{reference/datamodel object __iadd__}@anchor{e68}
@deffn {方法} object.__iadd__ (self, other)
@anchor{reference/datamodel object __isub__}@anchor{e69}
@deffnx {方法} object.__isub__ (self, other)
@anchor{reference/datamodel object __imul__}@anchor{13f3}
@deffnx {方法} object.__imul__ (self, other)
@anchor{reference/datamodel object __imatmul__}@anchor{644}
@deffnx {方法} object.__imatmul__ (self, other)
@anchor{reference/datamodel object __itruediv__}@anchor{140b}
@deffnx {方法} object.__itruediv__ (self, other)
@anchor{reference/datamodel object __ifloordiv__}@anchor{140c}
@deffnx {方法} object.__ifloordiv__ (self, other)
@anchor{reference/datamodel object __imod__}@anchor{140d}
@deffnx {方法} object.__imod__ (self, other)
@anchor{reference/datamodel object __ipow__}@anchor{140e}
@deffnx {方法} object.__ipow__ (self, other[, modulo])
@anchor{reference/datamodel object __ilshift__}@anchor{140f}
@deffnx {方法} object.__ilshift__ (self, other)
@anchor{reference/datamodel object __irshift__}@anchor{1410}
@deffnx {方法} object.__irshift__ (self, other)
@anchor{reference/datamodel object __iand__}@anchor{1411}
@deffnx {方法} object.__iand__ (self, other)
@anchor{reference/datamodel object __ixor__}@anchor{1412}
@deffnx {方法} object.__ixor__ (self, other)
@anchor{reference/datamodel object __ior__}@anchor{1413}
@deffnx {方法} object.__ior__ (self, other)

调用这些方法来实现扩展算术赋值 (@code{+=}, @code{-=}, @code{*=}, @code{@@=}, @code{/=}, @code{//=}, @code{%=}, @code{**=}, @code{<<=}, @code{>>=}, @code{&=}, @code{^=}, @code{|=})。这些方法应该尝试进行自身操作 (修改 @emph{self}) 并返回结果 (结果应该但并非必须为 @emph{self})。如果某个方法未被定义，相应的扩展算术赋值将回退到普通方法。例如，如果 @emph{x} 是具有 @ref{e68,,__iadd__()} 方法的类的一个实例，则 @code{x += y} 就等价于 @code{x = x.__iadd__(y)}。否则就如 @code{x + y} 的求值一样选择 @code{x.__add__(y)} 和 @code{y.__radd__(x)}。在某些情况下，扩展赋值可导致未预期的错误 (参见 @ref{1414,,为什么 a_tuple[i] += ['item'] 会在执行加法时引发异常？})，但此行为实际上是数据模型的一个组成部分。
@end deffn

@geindex __neg__() (object 方法)
@geindex __pos__() (object 方法)
@geindex __abs__() (object 方法)
@geindex __invert__() (object 方法)
@anchor{reference/datamodel object __neg__}@anchor{1415}
@deffn {方法} object.__neg__ (self)
@anchor{reference/datamodel object __pos__}@anchor{1416}
@deffnx {方法} object.__pos__ (self)
@anchor{reference/datamodel object __abs__}@anchor{1417}
@deffnx {方法} object.__abs__ (self)
@anchor{reference/datamodel object __invert__}@anchor{1418}
@deffnx {方法} object.__invert__ (self)

@geindex 內置函数; abs

调用此方法以实现一元算术运算 (@code{-}, @code{+}, @ref{1253,,abs()} 和 @code{~})。
@end deffn

@geindex __complex__() (object 方法)
@geindex __int__() (object 方法)
@geindex __float__() (object 方法)
@anchor{reference/datamodel object __complex__}@anchor{18d}
@deffn {方法} object.__complex__ (self)
@anchor{reference/datamodel object __int__}@anchor{18b}
@deffnx {方法} object.__int__ (self)
@anchor{reference/datamodel object __float__}@anchor{18c}
@deffnx {方法} object.__float__ (self)

@geindex 內置函数; complex
@geindex 內置函数; int
@geindex 內置函数; float

调用这些方法以实现内置函数 @ref{189,,complex()}, @ref{184,,int()} 和 @ref{187,,float()}。应当返回一个相应类型的值。
@end deffn

@geindex __index__() (object 方法)
@anchor{reference/datamodel object __index__}@anchor{18a}
@deffn {方法} object.__index__ (self)

调用此方法以实现 @ref{1419,,operator.index()} 以及 Python 需要无损地将数字对象转换为整数对象的场合（例如切片或是内置的 @ref{c39,,bin()}, @ref{c5f,,hex()} 和 @ref{c5e,,oct()} 函数)。 存在此方法表明数字对象属于整数类型。 必须返回一个整数。

如果未定义 @ref{18b,,__int__()}, @ref{18c,,__float__()} 和 @ref{18d,,__complex__()} 则相应的内置函数 @ref{184,,int()}, @ref{187,,float()} 和 @ref{189,,complex()} 将回退为 @ref{18a,,__index__()}。
@end deffn

@geindex __round__() (object 方法)
@geindex __trunc__() (object 方法)
@geindex __floor__() (object 方法)
@geindex __ceil__() (object 方法)
@anchor{reference/datamodel object __round__}@anchor{141a}
@deffn {方法} object.__round__ (self[, ndigits])
@anchor{reference/datamodel object __trunc__}@anchor{141b}
@deffnx {方法} object.__trunc__ (self)
@anchor{reference/datamodel object __floor__}@anchor{141c}
@deffnx {方法} object.__floor__ (self)
@anchor{reference/datamodel object __ceil__}@anchor{141d}
@deffnx {方法} object.__ceil__ (self)

@geindex 內置函数; round

调用这些方法以实现内置函数 @ref{c66,,round()} 以及 @ref{b1,,math} 函数 @ref{d27,,trunc()}, @ref{d25,,floor()} 和 @ref{d26,,ceil()}。 除了将 @emph{ndigits} 传给 @code{__round__()} 的情况之外这些方法的返回值都应当是原对象截断为 @ref{13bb,,Integral} (通常为 @ref{184,,int})。

如果未定义 @ref{18b,,__int__()} 则内置函数 @ref{184,,int()} 会回退到 @ref{141b,,__trunc__()}。
@end deffn

@node with 语句上下文管理器,特殊方法查找,模拟数字类型,特殊方法名称
@anchor{reference/datamodel context-managers}@anchor{141e}@anchor{reference/datamodel with-statement-context-managers}@anchor{141f}
@subsubsection with 语句上下文管理器


@emph{上下文管理器} 是一个对象，它定义了在执行 @ref{6e3,,with} 语句时要建立的运行时上下文。 上下文管理器处理进入和退出所需运行时上下文以执行代码块。 通常使用 @code{with} 语句（在 @ref{6e3,,with 语句} 中描述），但是也可以通过直接调用它们的方法来使用。

@geindex 语句; with
@geindex context manager

上下文管理器的典型用法包括保存和恢复各种全局状态，锁定和解锁资源，关闭打开的文件等等。

要了解上下文管理器的更多信息，请参阅 @ref{1420,,上下文管理器类型}。

@geindex __enter__() (object 方法)
@anchor{reference/datamodel object __enter__}@anchor{c8e}
@deffn {方法} object.__enter__ (self)

进入与此对象相关的运行时上下文。 @ref{6e3,,with} 语句将会绑定这个方法的返回值到 @code{as} 子句中指定的目标，如果有的话。
@end deffn

@geindex __exit__() (object 方法)
@anchor{reference/datamodel object __exit__}@anchor{c8f}
@deffn {方法} object.__exit__ (self, exc_type, exc_value, traceback)

退出关联到此对象的运行时上下文。 各个参数描述了导致上下文退出的异常。 如果上下文是无异常地退出的，三个参数都将为 @ref{157,,None}。

如果提供了异常，并且希望方法屏蔽此异常（即避免其被传播），则应当返回真值。 否则的话，异常将在退出此方法时按正常流程处理。

请注意 @ref{c8f,,__exit__()} 方法不应该重新引发被传入的异常，这是调用者的责任。
@end deffn


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 343

@item PEP 343@footnote{https://www.python.org/dev/peps/pep-0343} - "with" 语句

Python @ref{6e3,,with} 语句的规范描述、背景和示例。
@end table


@node 特殊方法查找,,with 语句上下文管理器,特殊方法名称
@anchor{reference/datamodel special-lookup}@anchor{13d4}@anchor{reference/datamodel special-method-lookup}@anchor{1421}
@subsubsection 特殊方法查找


对于自定义类来说，特殊方法的隐式发起调用仅保证在其定义于对象类型中时能正确地发挥作用，而不能定义在对象实例字典中。 该行为就是以下代码会引发异常的原因。:

@example
>>> class C:
...     pass
...
>>> c = C()
>>> c.__len__ = lambda: 5
>>> len(c)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: object of type 'C' has no len()
@end example

此行为背后的原理在于包括类型对象在内的所有对象都会实现的几个特殊方法，例如 @ref{339,,__hash__()} 和 @ref{337,,__repr__()}。 如果这些方法的隐式查找使用了传统的查找过程，它们会在对类型对象本身发起调用时失败:

@example
>>> 1 .__hash__() == hash(1)
True
>>> int.__hash__() == hash(int)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: descriptor '__hash__' of 'int' object needs an argument
@end example

以这种方式不正确地尝试发起调用一个类的未绑定方法有时被称为‘元类混淆’，可以通过在查找特殊方法时绕过实例的方式来避免:

@example
>>> type(1).__hash__(1) == hash(1)
True
>>> type(int).__hash__(int) == hash(int)
True
@end example

除了为了正确性而绕过任何实例属性之外，隐式特殊方法查找通常也会绕过 @ref{441,,__getattribute__()} 方法，甚至包括对象的元类:

@example
>>> class Meta(type):
...     def __getattribute__(*args):
...         print("Metaclass getattribute invoked")
...         return type.__getattribute__(*args)
...
>>> class C(object, metaclass=Meta):
...     def __len__(self):
...         return 10
...     def __getattribute__(*args):
...         print("Class getattribute invoked")
...         return object.__getattribute__(*args)
...
>>> c = C()
>>> c.__len__()                 # Explicit lookup via instance
Class getattribute invoked
10
>>> type(c).__len__(c)          # Explicit lookup via type
Metaclass getattribute invoked
10
>>> len(c)                      # Implicit lookup
10
@end example

以这种方式绕过 @ref{441,,__getattribute__()} 机制为解析器内部的速度优化提供了显著的空间，其代价则是牺牲了处理特殊方法时的一些灵活性（特殊方法 @emph{必须} 设置在类对象本身上以便始终一致地由解释器发起调用）。

@geindex coroutine

@node 协程,,特殊方法名称,数据模型
@anchor{reference/datamodel coroutines}@anchor{1422}
@subsection 协程


@menu
* 可等待对象:: 
* 协程对象:: 
* 异步迭代器:: 
* 异步上下文管理器:: 

@end menu

@node 可等待对象,协程对象,,协程
@anchor{reference/datamodel awaitable-objects}@anchor{1423}
@subsubsection 可等待对象


@ref{513,,awaitable} 对象主要实现了 @ref{63c,,__await__()} 方法。 从 @ref{284,,async def} 函数返回的 @ref{1a6,,Coroutine} 对象即属于可等待对象。

@cartouche
@quotation 注解 
从带有 @ref{776,,types.coroutine()} 或 @ref{282,,asyncio.coroutine()} 装饰器的生成器返回的 @ref{451,,generator iterator} 对象也属于可等待对象，但它们并未实现 @ref{63c,,__await__()}。
@end quotation
@end cartouche

@geindex __await__() (object 方法)
@anchor{reference/datamodel object __await__}@anchor{63c}
@deffn {方法} object.__await__ (self)

必须返回一个 @ref{fce,,iterator}。 应当被用来实现 @ref{513,,awaitable} 对象。 例如，@ref{43d,,asyncio.Future} 实现了此方法以与 @ref{1a3,,await} 表达式相兼容。
@end deffn


3.5 新版功能.



@subsubheading 参见


@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} 了解有关可等待对象的详细信息。


@node 协程对象,异步迭代器,可等待对象,协程
@anchor{reference/datamodel coroutine-objects}@anchor{13c4}@anchor{reference/datamodel id7}@anchor{1424}
@subsubsection 协程对象


@ref{1a6,,Coroutine} 对象属于 @ref{513,,awaitable} 对象。 协程的执行可通过调用 @ref{63c,,__await__()} 并迭代其结果来进行控制。 当协程结束执行并返回时，迭代器会引发 @ref{480,,StopIteration}，该异常的 @code{value} 属性将指向返回值。 如果协程引发了异常，它会被迭代器所传播。 协程不应该直接引发未处理的 @ref{480,,StopIteration} 异常。

协程也具有下面列出的方法，它们类似于生成器的对应方法 (参见 @ref{1425,,生成器-迭代器的方法})。 但是，与生成器不同，协程并不直接支持迭代。


在 3.5.2 版更改: 等待一个协程超过一次将引发 @ref{2ba,,RuntimeError}。


@geindex send() (coroutine 方法)
@anchor{reference/datamodel coroutine send}@anchor{1426}
@deffn {方法} coroutine.send (value)

开始或恢复协程的执行。 如果 @emph{value} 为 @code{None}，则这相当于前往 @ref{63c,,__await__()} 所返回迭代器的下一项。 如果 @emph{value} 不为 @code{None}，此方法将委托给导致协程挂起的迭代器的 @ref{1427,,send()} 方法。 其结果（返回值，@ref{480,,StopIteration} 或是其他异常）将与上述对 @ref{63c,,__await__()} 返回值进行迭代的结果相同。
@end deffn

@geindex throw() (coroutine 方法)
@anchor{reference/datamodel coroutine throw}@anchor{1428}
@deffn {方法} coroutine.throw (type[, value[, traceback]])

在协程内引发指定的异常。 此方法将委托给导致协程挂起的迭代器的 @ref{1429,,throw()} 方法，如果存在该方法。 否则的话，异常会在挂起点被引发。 其结果（返回值，@ref{480,,StopIteration} 或是其他异常）将与上述对 @ref{63c,,__await__()} 返回值进行迭代的结果相同。 如果异常未在协程内被捕获，则将回传给调用者。
@end deffn

@geindex close() (coroutine 方法)
@anchor{reference/datamodel coroutine close}@anchor{142a}
@deffn {方法} coroutine.close ()

此方法会使得协程清理自身并退出。 如果协程被挂起，此方法会先委托给导致协程挂起的迭代器的 @ref{142b,,close()} 方法，如果存在该方法。 然后它会在挂起点引发 @ref{d2b,,GeneratorExit}，使得协程立即清理自身。 最后，协程会被标记为已结束执行，即使它根本未被启动。

当协程对象将要被销毁时，会使用以上处理过程来自动关闭。
@end deffn

@node 异步迭代器,异步上下文管理器,协程对象,协程
@anchor{reference/datamodel async-iterators}@anchor{640}@anchor{reference/datamodel asynchronous-iterators}@anchor{142c}
@subsubsection 异步迭代器


@emph{异步迭代器} 可以在其 @code{__anext__} 方法中调用异步代码。

异步迭代器可在 @ref{2e3,,async for} 语句中使用。

@geindex __aiter__() (object 方法)
@anchor{reference/datamodel object __aiter__}@anchor{481}
@deffn {方法} object.__aiter__ (self)

必须返回一个 @emph{异步迭代器} 对象。
@end deffn

@geindex __anext__() (object 方法)
@anchor{reference/datamodel object __anext__}@anchor{142d}
@deffn {方法} object.__anext__ (self)

必须返回一个 @emph{可迭代对象} 输出迭代器的下一结果值。 当迭代结束时应该引发 @ref{fa5,,StopAsyncIteration} 错误。
@end deffn

异步可迭代对象的一个示例:

@example
class Reader:
    async def readline(self):
        ...

    def __aiter__(self):
        return self

    async def __anext__(self):
        val = await self.readline()
        if val == b'@w{'}:
            raise StopAsyncIteration
        return val
@end example


3.5 新版功能.



在 3.7 版更改: 在 Python 3.7 之前，@code{__aiter__} 可以返回一个 @emph{可迭代对象} 并解析为 @ref{63f,,异步迭代器}。

从 Python 3.7 开始，@code{__aiter__} 必须 返回一个异步迭代器对象。 返回任何其他对象都将导致 @ref{192,,TypeError} 错误。


@node 异步上下文管理器,,异步迭代器,协程
@anchor{reference/datamodel async-context-managers}@anchor{142e}@anchor{reference/datamodel asynchronous-context-managers}@anchor{142f}
@subsubsection 异步上下文管理器


@emph{异步上下文管理器} 是 @emph{上下文管理器} 的一种，它能够在其 @code{__aenter__} 和 @code{__aexit__} 方法中暂停执行。

异步上下文管理器可在 @ref{63d,,async with} 语句中使用。

@geindex __aenter__() (object 方法)
@anchor{reference/datamodel object __aenter__}@anchor{1430}
@deffn {方法} object.__aenter__ (self)

在语义上类似于 @ref{c8e,,__enter__()}，仅有的区别是它必须返回一个 @emph{可等待对象}。
@end deffn

@geindex __aexit__() (object 方法)
@anchor{reference/datamodel object __aexit__}@anchor{1431}
@deffn {方法} object.__aexit__ (self, exc_type, exc_value, traceback)

在语义上类似于 @ref{c8f,,__exit__()}，仅有的区别是它必须返回一个 @emph{可等待对象}。
@end deffn

异步上下文管理器类的一个示例:

@example
class AsyncContextManager:
    async def __aenter__(self):
        await log('entering context')

    async def __aexit__(self, exc_type, exc, tb):
        await log('exiting context')
@end example


3.5 新版功能.


@subsubheading 备注


@node 执行模型,导入系统,数据模型,Python语言参考
@anchor{reference/executionmodel doc}@anchor{1432}@anchor{reference/executionmodel execmodel}@anchor{1433}@anchor{reference/executionmodel execution-model}@anchor{1434}
@section 执行模型


@geindex execution model
@geindex code; block

@menu
* 程序的结构:: 
* 命名与绑定:: 
* 异常: 异常<2>. 

@end menu

@node 程序的结构,命名与绑定,,执行模型
@anchor{reference/executionmodel prog-structure}@anchor{1435}@anchor{reference/executionmodel structure-of-a-program}@anchor{1436}
@subsection 程序的结构


@geindex block

Python 程序是由代码块构成的。 @emph{代码块} 是被作为一个单元来执行的一段 Python 程序文本。 以下几个都是代码块：模块、函数体和类定义。 交互式输入的每条命令都是一个代码块。 一个脚本文件（作为标准输入发送给解释器或是作为命令行参数发送给解释器的文件）也是一个代码块。 一条脚本命令（通过 @ref{119f,,-c} 选项在解释器命令行中指定的命令）也是一个代码块。  传递给内置函数 @ref{b89,,eval()} 和 @ref{c3d,,exec()} 的字符串参数也是代码块。

@geindex execution; frame

代码块在 @emph{执行帧} 中被执行。 一个帧会包含某些管理信息（用于调试）并决定代码块执行完成后应前往何处以及如何继续执行。

@node 命名与绑定,异常<2>,程序的结构,执行模型
@anchor{reference/executionmodel naming}@anchor{1437}@anchor{reference/executionmodel naming-and-binding}@anchor{1438}
@subsection 命名与绑定


@geindex namespace
@geindex scope

@menu
* 名称的绑定:: 
* 名称的解析:: 
* 内置命名空间和受限的执行:: 
* 与动态特性的交互:: 

@end menu

@node 名称的绑定,名称的解析,,命名与绑定
@anchor{reference/executionmodel bind-names}@anchor{1439}@anchor{reference/executionmodel binding-of-names}@anchor{143a}
@subsubsection 名称的绑定


@geindex name
@geindex binding; name

@emph{名称} 用于指代对象。 名称是通过名称绑定操作来引入的。

@geindex from; import statement

以下构造会绑定名称：传给函数的正式形参，@ref{c16,,import} 语句，类与函数定义（这会在定义的代码块中绑定类或函数名称）以及发生以标识符为目标的赋值，@ref{c29,,for} 循环的开头，或 @ref{6e3,,with} 语句和 @ref{b37,,except} 子句的 @code{as} 之后。 @code{import} 语句的 @code{from ... import *} 形式会绑定在被导入模块中定义的所有名称，那些以下划线开头的除外。 这种形式仅在模块层级上被使用。

@ref{1202,,del} 语句的目标也被视作一种绑定（虽然其实际语义为解除名称绑定）。

每条赋值或导入语句均发生于类或函数内部定义的代码块中，或是发生于模块层级（即最高层级的代码块）。

@geindex free; variable

如果名称绑定在一个代码块中，则为该代码块的局部变量，除非声明为 @ref{c38,,nonlocal} 或 @ref{11d8,,global}。 如果名称绑定在模块层级，则为全局变量。 (模块代码块的变量既为局部变量又为全局变量。) 如果变量在一个代码块中被使用但不是在其中定义，则为 @emph{自由变量}。

每个在程序文本中出现的名称是指由以下名称解析规则所建立的对该名称的 @emph{绑定}。

@node 名称的解析,内置命名空间和受限的执行,名称的绑定,命名与绑定
@anchor{reference/executionmodel resolution-of-names}@anchor{143b}@anchor{reference/executionmodel resolve-names}@anchor{143c}
@subsubsection 名称的解析


@geindex scope

@emph{作用域} 定义了一个代码块中名称的可见性。 如果代码块中定义了一个局部变量，则其作用域包含该代码块。 如果定义发生于函数代码块中，则其作用域会扩展到该函数所包含的任何代码块，除非有某个被包含代码块引入了对该名称的不同绑定。

@geindex environment

当一个名称在代码块中被使用时，会由包含它的最近作用域来解析。 对一个代码块可见的所有这种作用域的集合称为该代码块的 @emph{环境}。

@geindex NameError (built-in exception)
@geindex UnboundLocalError

当一个名称完全找不到时，将会引发 @ref{d74,,NameError} 异常。 如果当前作用域为函数作用域，且该名称指向一个局部变量，而此变量在该名称被使用的时候尚未绑定到特定值，将会引发 @ref{e6f,,UnboundLocalError} 异常。 @ref{e6f,,UnboundLocalError} 为 @ref{d74,,NameError} 的一个子类。

如果一个代码块内的任何位置发生名称绑定操作，则代码块内所有对该名称的使用会被认为是对当前代码块的引用。 当一个名称在其被绑定前就在代码块内被使用时则会导致错误。 这个一个很微妙的规则。 Python 缺少声明语法，并允许名称绑定操作发生于代码块内的任何位置。 一个代码块的局部变量可通过在整个代码块文本中扫描名称绑定操作来确定。

如果 @ref{11d8,,global} 语句出现在一个代码块中，则所有对该语句所指定名称的使用都是在最高层级命名空间内对该名称绑定的引用。 名称在最高层级命名内的解析是通过全局命名空间，也就是包含该代码块的模块的命名空间，以及内置命名空间即 @ref{13,,builtins} 模块的命名空间。 全局命名空间会先被搜索。 如果未在其中找到指定名称，再搜索内置命名空间。  @code{global} 语句必须位于所有对其所指定名称的使用之前。

@ref{11d8,,global} 语句与同一代码块中名称绑定具有相同的作用域。 如果一个自由变量的最近包含作用域中有一条 global 语句，则该自由变量也会被当作是全局变量。

@c XXX say more about "nonlocal" semantics here

@ref{c38,,nonlocal} 语句会使得相应的名称指向之前在最近包含函数作用域中绑定的变量。 如果指定名称不存在于任何包含函数作用域中则将在编译时引发 @ref{452,,SyntaxError}。

@geindex 模块; __main__

模块的作用域会在模块第一次被导入时自动创建。 一个脚本的主模块总是被命名为 @ref{1,,__main__}。

类定义代码块以及传给 @ref{c3d,,exec()} 和 @ref{b89,,eval()} 的参数是名称解析上下文中的特殊情况。 类定义是可能使用并定义名称的可执行语句。 这些引用遵循正常的名称解析规则，例外之处在于未绑定的局部变量将会在全局命名空间中查找。 类定义的命名空间会成为该类的属性字典。 在类代码块中定义的名称的作用域会被限制在类代码块中；它不会扩展到方法的代码块中 -- 这也包括推导式和生成器表达式，因为它们都是使用函数作用域实现的。 这意味着以下代码将会失败:

@example
class A:
    a = 42
    b = list(a + i for i in range(10))
@end example

@node 内置命名空间和受限的执行,与动态特性的交互,名称的解析,命名与绑定
@anchor{reference/executionmodel builtins-and-restricted-execution}@anchor{143d}@anchor{reference/executionmodel restrict-exec}@anchor{143e}
@subsubsection 内置命名空间和受限的执行


@geindex restricted; execution

@strong{CPython implementation detail:} 用户不应该接触 @code{__builtins__}，严格说来它属于实现细节。 用户如果要重载内置命名空间中的值则应该 @ref{c16,,import} @ref{13,,builtins} 并相应地修改该模块中的属性。

与一个代码块的执行相关联的内置命名空间实际上是通过在其全局命名空间中搜索名称 @code{__builtins__} 来找到的；这应该是一个字典或一个模块（在后一种情况下会使用该模块的字典）。 默认情况下，当在 @ref{1,,__main__} 模块中时，@code{__builtins__} 就是内置模块 @ref{13,,builtins}；当在任何其他模块中时，@code{__builtins__} 则是 @ref{13,,builtins} 模块自身的字典的一个别名。

@node 与动态特性的交互,,内置命名空间和受限的执行,命名与绑定
@anchor{reference/executionmodel dynamic-features}@anchor{143f}@anchor{reference/executionmodel interaction-with-dynamic-features}@anchor{1440}
@subsubsection 与动态特性的交互


自由变量的名称解析发生于运行时而不是编译时。 这意味着以下代码将打印出 42:

@example
i = 10
def f():
    print(i)
i = 42
f()
@end example

@c XXX from * also invalid with relative imports (at least currently)

@ref{b89,,eval()} 和 @ref{c3d,,exec()} 函数没有对完整环境的访问权限来解析名称。 名称可以在调用者的局部和全局命名空间中被解析。 自由变量的解析不是在最近包含命名空间中，而是在全局命名空间中。 @footnote{@w{(1)} 
出现这样的限制是由于通过这些操作执行的代码在模块被编译的时候并不可用。
} @ref{c3d,,exec()} 和 @ref{b89,,eval()} 函数有可选参数用来重载全局和局部命名空间。 如果只指定一个命名空间，则它会同时作用于两者。

@node 异常<2>,,命名与绑定,执行模型
@anchor{reference/executionmodel exceptions}@anchor{1441}@anchor{reference/executionmodel id2}@anchor{1442}
@subsection 异常


@geindex exception

@geindex raise an exception
@geindex handle an exception
@geindex exception handler
@geindex errors
@geindex error handling

异常是中断代码块的正常控制流程以便处理错误或其他异常条件的一种方式。 异常会在错误被检测到的位置 @emph{引发}，它可以被当前包围代码块或是任何直接或间接发起调用发生错误的代码块的其他代码块所 @emph{处理}。

Python 解析器会在检测到运行时错误（例如零作为被除数）的时候引发异常。 Python 程序也可以通过 @ref{c3b,,raise} 语句显式地引发异常。 异常处理是通过 @ref{d6b,,try} ... @ref{b37,,except} 语句来指定的。 该语句的 @ref{182,,finally} 子句可被用来指定清理代码，它并不处理异常，而是无论之前的代码是否发生异常都会被执行。

@geindex termination model

Python 的错误处理采用的是“终止”模型：异常处理器可以找出发生了什么问题，并在外层继续执行，但它不能修复错误的根源并重试失败的操作（除非通过从顶层重新进入出错的代码片段）。

@geindex SystemExit (built-in exception)

当一个异常完全未被处理时，解释器会终止程序的执行，或者返回交互模式的主循环。 无论是哪种情况，它都会打印栈回溯信息，除非是当异常为 @ref{5f7,,SystemExit} 的时候。

异常是通过类实例来标识的。 @ref{b37,,except} 子句会依据实例的类来选择：它必须引用实例的类或是其所属的基类。 实例可通过处理器被接收，并可携带有关异常条件的附加信息。

@cartouche
@quotation 注解 
异常消息不是 Python API 的组成部分。 其内容可能在 Python 升级到新版本时不经警告地发生改变，不应该被需要在多版本解释器中运行的代码所依赖。
@end quotation
@end cartouche

另请参看  @ref{d6b,,try 语句} 小节中对 @ref{d6b,,try} 语句的描述以及 @ref{c3b,,raise 语句} 小节中对 @ref{c3b,,raise} 语句的描述。

@subsubheading 备注


@node 导入系统,表达式,执行模型,Python语言参考
@anchor{reference/import doc}@anchor{1443}@anchor{reference/import importsystem}@anchor{13c6}@anchor{reference/import the-import-system}@anchor{1444}
@section 导入系统


@geindex import machinery

一个 @ref{1445,,module} 内的 Python 代码通过 @ref{1446,,importing} 操作就能够访问另一个模块内的代码。 @ref{c16,,import} 语句是发起调用导入机制的最常用方式，但不是唯一的方式。 @ref{b0c,,importlib.import_module()} 以及内置的 @ref{60b,,__import__()} 等函数也可以被用来发起调用导入机制。

@ref{c16,,import} 语句结合了两个操作；它先搜索指定名称的模块，然后将搜索结果绑定到当前作用域中的名称。 @code{import} 语句的搜索操作定义为对 @ref{60b,,__import__()} 函数的调用并带有适当的参数。 @ref{60b,,__import__()} 的返回值会被用于执行 @code{import} 语句的名称绑定操作。 请参阅 @code{import} 语句了解名称绑定操作的更多细节。

对 @ref{60b,,__import__()} 的直接调用将仅执行模块搜索以及在找到时的模块创建操作。 不过也可能产生某些副作用，例如导入父包和更新各种缓存 (包括 @ref{eb5,,sys.modules})，只有 @ref{c16,,import} 语句会执行名称绑定操作。

当 @ref{c16,,import} 语句被执行时，标准的内置 @ref{60b,,__import__()} 函数会被调用。 其他发起调用导入系统的机制 (例如 @ref{b0c,,importlib.import_module()}) 可能会选择绕过 @ref{60b,,__import__()} 并使用它们自己的解决方案来实现导入机制。

当一个模块首次被导入时，Python 会搜索该模块，如果找到就创建一个 module 对象 @footnote{@w{(1)} 
参见 @ref{6eb,,types.ModuleType}。
} 并初始化它。 如果指定名称的模块未找到，则会引发 @ref{392,,ModuleNotFoundError}。 当发起调用导入机制时，Python 会实现多种策略来搜索指定名称的模块。 这些策略可以通过使用使用下文所描述的多种钩子来加以修改和扩展。


在 3.3 版更改: 导入系统已被更新以完全实现 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} 中的第二阶段要求。 不会再有任何隐式的导入机制 —— 整个导入系统都通过 @ref{5e1,,sys.meta_path} 暴露出来。 此外，对原生命名空间包的支持也已被实现 (参见 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420})。


@menu
* importlib: importlib<7>. 
* 包: 包<2>. 
* 搜索:: 
* 加载:: 
* 基于路径的查找器:: 
* 替换标准导入系统:: 
* 包相对导入:: 
* 有关 __main__ 的特殊事项:: 
* 开放问题项:: 
* 参考文献:: 

@end menu

@node importlib<7>,包<2>,,导入系统
@anchor{reference/import importlib}@anchor{1447}
@subsection @code{importlib}


@ref{9b,,importlib} 模块提供了一个丰富的 API 用来与导入系统进行交互。 例如 @ref{b0c,,importlib.import_module()} 提供了相比内置的 @ref{60b,,__import__()} 更推荐、更简单的 API 用来发起调用导入机制。 更多细节请参看 @ref{9b,,importlib} 库文档。

@node 包<2>,搜索,importlib<7>,导入系统
@anchor{reference/import packages}@anchor{1448}
@subsection 包


@geindex package

Python 只有一种模块对象类型，所有模块都属于该类型，无论模块是用 Python、C 还是别的语言实现。 为了帮助组织模块并提供名称层次结构，Python 还引入了 @ref{1449,,包} 的概念。

你可以把包看成是文件系统中的目录，并把模块看成是目录中的文件，但请不要对这个类似做过于字面的理解，因为包和模块不是必须来自于文件系统。 为了方便理解本文档，我们将继续使用这种目录和文件的类比。 与文件系统一样，包通过层次结构进行组织，在包之内除了一般的模块，还可以有子包。

要注意的一个重点概念是所有包都是模块，但并非所有模块都是包。 或者换句话说，包只是一种特殊的模块。 特别地，任何具有 @code{__path__} 属性的模块都会被当作是包。

所有模块都有自己的名字。 子包名与其父包名以点号分隔，与 Python 的标准属性访问语法一致。 例如你可能看到一个名为 @ref{fd,,sys} 的模块，以及一个名为 @ref{69,,email} 的包，这个包又有一个名为 @ref{73,,email.mime} 的子包和该子包中的名为 @code{email.mime.text} 的子包。

@menu
* 常规包:: 
* 命名空间包:: 

@end menu

@node 常规包,命名空间包,,包<2>
@anchor{reference/import regular-packages}@anchor{144a}
@subsubsection 常规包


@geindex package; regular

Python 定义了两种类型的包，@ref{144b,,常规包} 和 @ref{144c,,命名空间包}。 常规包是传统的包类型，它们在 Python 3.2 及之前就已存在。 常规包通常以一个包含 @code{__init__.py} 文件的目录形式实现。 当一个常规包被导入时，这个 @code{__init__.py} 文件会隐式地被执行，它所定义的对象会被绑定到该包命名空间中的名称。@code{__init__.py} 文件可以包含与任何其他模块中所包含的 Python 代码相似的代码，Python 将在模块被导入时为其添加额外的属性。

例如，以下文件系统布局定义了一个最高层级的 @code{parent} 包和三个子包:

@example
parent/
    __init__.py
    one/
        __init__.py
    two/
        __init__.py
    three/
        __init__.py
@end example

导入 @code{parent.one} 将隐式地执行 @code{parent/__init__.py} 和 @code{parent/one/__init__.py}。 后续导入 @code{parent.two} 或 @code{parent.three} 则将分别执行 @code{parent/two/__init__.py} 和 @code{parent/three/__init__.py}。

@node 命名空间包,,常规包,包<2>
@anchor{reference/import namespace-packages}@anchor{144d}
@subsubsection 命名空间包


@geindex package; namespace
@geindex package; portion

命名空间包是由多个 @ref{144e,,部分} 构成的，每个部分为父包增加一个子包。 各个部分可能处于文件系统的不同位置。 部分也可能处于 zip 文件中、网络上，或者 Python 在导入期间可以搜索的其他地方。 命名空间包并不一定会直接对应到文件系统中的对象；它们有可能是无实体表示的虚拟模块。

命名空间包的 @code{__path__} 属性不使用普通的列表。 而是使用定制的可迭代类型，如果其父包的路径 (或者最高层级包的 @ref{482,,sys.path}) 发生改变，这种对象会在该包内的下一次导入尝试时自动执行新的对包部分的搜索。

命名空间包没有 @code{parent/__init__.py} 文件。 实际上，在导入搜索期间可能找到多个 @code{parent} 目录，每个都由不同的部分所提供。 因此 @code{parent/one} 的物理位置不一定与 @code{parent/two} 相邻。 在这种情况下，Python 将为顶级的 @code{parent} 包创建一个命名空间包，无论是它本身还是它的某个子包被导入。

另请参阅 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} 了解对命名空间包的规格描述。

@node 搜索,加载,包<2>,导入系统
@anchor{reference/import searching}@anchor{144f}
@subsection 搜索


为了开始搜索，Python 需要被导入模块（或者包，对于当前讨论来说两者没有差别）的完整 @ref{13c2,,限定名称}。 此名称可以来自 @ref{c16,,import} 语句所带的各种参数，或者来自传给 @ref{b0c,,importlib.import_module()} 或 @ref{60b,,__import__()} 函数的形参。

此名称会在导入搜索的各个阶段被使用，它也可以是指向一个子模块的带点号路径，例如 @code{foo.bar.baz}。 在这种情况下，Python 会先尝试导入 @code{foo}，然后是 @code{foo.bar}，最后是 @code{foo.bar.baz}。 如果这些导入中的任何一个失败，都会引发 @ref{392,,ModuleNotFoundError}。

@menu
* 模块缓存:: 
* 查找器和加载器:: 
* 导入钩子:: 
* 元路径:: 

@end menu

@node 模块缓存,查找器和加载器,,搜索
@anchor{reference/import the-module-cache}@anchor{1450}
@subsubsection 模块缓存


@geindex sys.modules

在导入搜索期间首先会被检查的地方是 @ref{eb5,,sys.modules}。 这个映射起到缓存之前导入的所有模块的作用（包括其中间路径）。 因此如果之前导入过 @code{foo.bar.baz}，则 @ref{eb5,,sys.modules} 将包含 @code{foo}, @code{foo.bar} 和 @code{foo.bar.baz} 条目。 每个键的值就是相应的模块对象。

在导入期间，会在 @ref{eb5,,sys.modules} 查找模块名称，如存在则其关联的值就是需要导入的模块，导入过程完成。 然而，如果值为 @code{None}，则会引发 @ref{392,,ModuleNotFoundError}。 如果找不到指定模块名称，Python 将继续搜索该模块。

@ref{eb5,,sys.modules} 是可写的。删除键可能不会破坏关联的模块（因为其他模块可能会保留对它的引用），但它会使命名模块的缓存条目无效，导致 Python 在下次导入时重新搜索命名模块。键也可以赋值为 @code{None} ，强制下一次导入模块导致 @ref{392,,ModuleNotFoundError} 。

但是要小心，因为如果你还保有对某个模块对象的引用，同时停用其在 @ref{eb5,,sys.modules} 中的缓存条目，然后又再次导入该名称的模块，则前后两个模块对象将 @emph{不是} 同一个。 相反地，@ref{391,,importlib.reload()} 将重用 @emph{同一个} 模块对象，并简单地通过重新运行模块的代码来重新初始化模块内容。

@node 查找器和加载器,导入钩子,模块缓存,搜索
@anchor{reference/import finders-and-loaders}@anchor{1451}
@subsubsection 查找器和加载器


@geindex finder
@geindex loader
@geindex module spec

如果指定名称的模块在 @ref{eb5,,sys.modules} 找不到，则将发起调用 Python 的导入协议以查找和加载该模块。 此协议由两个概念性模块构成，即 @ref{1452,,查找器} 和 @ref{1453,,加载器}。 查找器的任务是确定是否能使用其所知的策略找到该名称的模块。 同时实现这两种接口的对象称为 @ref{1454,,导入器} —— 它们在确定能加载所需的模块时会返回其自身。

Python 包含了多个默认查找器和导入器。 第一个知道如何定位内置模块，第二个知道如何定位冻结模块。 第三个默认查找器会在 @ref{1455,,import path} 中搜索模块。 @ref{1455,,import path} 是一个由文件系统路径或 zip 文件组成的位置列表。 它还可以扩展为搜索任意可定位资源，例如由 URL 指定的资源。

导入机制是可扩展的，因此可以加入新的查找器以扩展模块搜索的范围和作用域。

查找器并不真正加载模块。 如果它们能找到指定名称的模块，会返回一个 @emph{模块规格说明}，这是对模块导入相关信息的封装，供后续导入机制用于在加载模块时使用。

以下各节描述了有关查找器和加载器协议的更多细节，包括你应该如何创建并注册新的此类对象来扩展导入机制。


在 3.4 版更改: 在之前的 Python 版本中，查找器会直接返回 @ref{1453,,加载器}，现在它们则返回模块规格说明，其中 @emph{包含} 加载器。 加载器仍然在导入期间被使用，但负担的任务有所减少。


@node 导入钩子,元路径,查找器和加载器,搜索
@anchor{reference/import import-hooks}@anchor{1456}
@subsubsection 导入钩子


@geindex import hooks
@geindex meta hooks
@geindex path hooks
@geindex hooks; import
@geindex hooks; meta
@geindex hooks; path

导入机制被设计为可扩展；其中的基本机制是 @emph{导入钩子}。 导入钩子有两种类型: @emph{元钩子} 和 @emph{导入路径钩子}。

元钩子在导入过程开始时被调用，此时任何其他导入过程尚未发生，但 @ref{eb5,,sys.modules} 缓存查找除外。 这允许元钩子重载 @ref{482,,sys.path} 过程、冻结模块甚至内置模块。 元钩子的注册是通过向 @ref{5e1,,sys.meta_path} 添加新的查找器对象，具体如下所述。

导入路径钩子是作为 @ref{482,,sys.path} (或 @code{package.__path__}) 过程的一部分，在遇到它们所关联的路径项的时候被调用。 导入路径钩子的注册是通过向 @ref{956,,sys.path_hooks} 添加新的可调用对象，具体如下所述。

@node 元路径,,导入钩子,搜索
@anchor{reference/import the-meta-path}@anchor{1457}
@subsubsection 元路径


@geindex sys.meta_path
@geindex finder; find_spec

当指定名称的模块在 @ref{eb5,,sys.modules} 中找不到时，Python 会接着搜索 @ref{5e1,,sys.meta_path}，其中包含元路径查找器对象列表。 这些查找器按顺序被查询以确定它们是否知道如何处理该名称的模块。 元路径查找器必须实现名为 @ref{45d,,find_spec()} 的方法，该方法接受三个参数：名称、导入路径和目标模块（可选）。 元路径查找器可使用任何策略来确定它是否能处理指定名称的模块。

如果元路径查找器知道如何处理指定名称的模块，它将返回一个说明对象。 如果它不能处理该名称的模块，则会返回 @code{None}。 如果 @ref{5e1,,sys.meta_path} 处理过程到达列表末尾仍未返回说明对象，则将引发 @ref{392,,ModuleNotFoundError}。 任何其他被引发异常将直接向上传播，并放弃导入过程。

元路径查找器的 @ref{45d,,find_spec()} 方法调用带有两到三个参数。 第一个是被导入模块的完整限定名称，例如 @code{foo.bar.baz}。 第二个参数是供模块搜索使用的路径条目。 对于最高层级模块，第二个参数为 @code{None}，但对于子模块或子包，第二个参数为父包 @code{__path__} 属性的值。 如果相应的 @code{__path__} 属性无法访问，将引发 @ref{392,,ModuleNotFoundError}。 第三个参数是一个将被作为稍后加载目标的现有模块对象。 导入系统仅会在重加载期间传入一个目标模块。

对于单个导入请求可以多次遍历元路径。 例如，假设所涉及的模块都尚未被缓存，则导入 @code{foo.bar.baz} 将首先执行顶级的导入，在每个元路径查找器 (@code{mpf}) 上调用 @code{mpf.find_spec("foo", None, None)}。 在导入 @code{foo} 之后，@code{foo.bar} 将通过第二次遍历元路径来导入，调用 @code{mpf.find_spec("foo.bar", foo.__path__, None)}。 一旦 @code{foo.bar} 完成导入，最后一次遍历将调用 @code{mpf.find_spec("foo.bar.baz", foo.bar.__path__, None)}。

有些元路径查找器只支持顶级导入。 当把 @code{None} 以外的对象作为第三个参数传入时，这些导入器将总是返回 @code{None}。

Python 的默认 @ref{5e1,,sys.meta_path} 具有三种元路径查找器，一种知道如何导入内置模块，一种知道如何导入冻结模块，还有一种知道如何导入来自 @ref{1455,,import path} 的模块 (即 @ref{1458,,path based finder})。


在 3.4 版更改: 元路径查找器的 @ref{45d,,find_spec()} 方法替代了 @ref{45c,,find_module()}，后者现已弃用，它将继续可用但不会再做改变，导入机制仅会在查找器未实现 @code{find_spec()} 时尝试使用它。


@node 加载,基于路径的查找器,搜索,导入系统
@anchor{reference/import loading}@anchor{1459}
@subsection 加载


当一个模块说明被找到时，导入机制将在加载该模块时使用它（及其所包含的加载器）。 下面是导入的加载部分所发生过程的简要说明:

@example
module = None
if spec.loader is not None and hasattr(spec.loader, 'create_module'):
    # It is assumed 'exec_module' will also be defined on the loader.
    module = spec.loader.create_module(spec)
if module is None:
    module = ModuleType(spec.name)
# The import-related module attributes get set here:
_init_module_attrs(spec, module)

if spec.loader is None:
    # unsupported
    raise ImportError
if spec.origin is None and spec.submodule_search_locations is not None:
    # namespace package
    sys.modules[spec.name] = module
elif not hasattr(spec.loader, 'exec_module'):
    module = spec.loader.load_module(spec.name)
    # Set __loader__ and __package__ if missing.
else:
    sys.modules[spec.name] = module
    try:
        spec.loader.exec_module(module)
    except BaseException:
        try:
            del sys.modules[spec.name]
        except KeyError:
            pass
        raise
return sys.modules[spec.name]
@end example

请注意以下细节:

@quotation


@itemize *

@item 
如果在 @ref{eb5,,sys.modules} 中存在指定名称的模块对象，导入操作会已经将其返回。

@item 
在加载器执行模块代码之前，该模块将存在于 @ref{eb5,,sys.modules} 中。 这一点很关键，因为该模块代码可能（直接或间接地）导入其自身；预先将其添加到 @ref{eb5,,sys.modules} 可防止在最坏情况下的无限递归和最好情况下的多次加载。

@item 
如果加载失败，则该模块 -- 只限加载失败的模块 -- 将从 @ref{eb5,,sys.modules} 中移除。 任何已存在于 @ref{eb5,,sys.modules} 缓存的模块，以及任何作为附带影响被成功加载的模块仍会保留在缓存中。 这与重新加载不同，后者会把即使加载失败的模块也保留在 @ref{eb5,,sys.modules} 中。

@item 
在模块创建完成但还未执行之前，导入机制会设置导入相关模块属性（在上面的示例伪代码中为 “_init_module_attrs”），详情参见 @ref{145a,,后续部分}。

@item 
模块执行是加载的关键时刻，在此期间将填充模块的命名空间。 执行会完全委托给加载器，由加载器决定要填充的内容和方式。

@item 
在加载过程中创建并传递给 exec_module() 的模块并不一定就是在导入结束时返回的模块 @footnote{@w{(2)} 
importlib 实现避免直接使用返回值。 而是通过在 @ref{eb5,,sys.modules} 中查找模块名称来获取模块对象。 这种方式的间接影响是被导入的模块可能在 @ref{eb5,,sys.modules} 中替换其自身。 这属于具体实现的特定行为，不保证能在其他 Python 实现中起作用。
}。
@end itemize
@end quotation


在 3.4 版更改: 导入系统已经接管了加载器建立样板的责任。 这些在以前是由 @ref{5de,,importlib.abc.Loader.load_module()} 方法来执行的。


@menu
* 加载器:: 
* 子模块:: 
* 模块规格说明:: 
* 导入相关的模块属性:: 
* module.__path__: module __path__. 
* 模块的 repr:: 
* 已缓存字节码的失效:: 

@end menu

@node 加载器,子模块,,加载
@anchor{reference/import loaders}@anchor{145b}
@subsubsection 加载器


模块加载器提供关键的加载功能：模块执行。 导入机制调用 @ref{5df,,importlib.abc.Loader.exec_module()} 方法并传入一个参数来执行模块对象。 从 @ref{5df,,exec_module()} 返回的任何值都将被忽略。

加载器必须满足下列要求:

@quotation


@itemize *

@item 
如果模块是一个 Python 模块（而非内置模块或动态加载的扩展），加载器应该在模块的全局命名空间 (@code{module.__dict__}) 中执行模块的代码。

@item 
如果加载器无法执行指定模块，它应该引发 @ref{32d,,ImportError}，不过在 @ref{5df,,exec_module()} 期间引发的任何其他异常也会被传播。
@end itemize
@end quotation

在许多情况下，查找器和加载器可以是同一对象；在此情况下 @ref{45d,,find_spec()} 方法将返回一个规格说明，其中加载器会被设为 @code{self}。

模块加载器可以选择通过实现 @ref{54f,,create_module()} 方法在加载期间创建模块对象。 它接受一个参数，即模块规格说明，并返回新的模块对象供加载期间使用。 @code{create_module()} 不需要在模块对象上设置任何属性。 如果模块返回 @code{None}，导入机制将自行创建新模块。


3.4 新版功能: 加载器的 @ref{54f,,create_module()} 方法。



在 3.4 版更改: @ref{5de,,load_module()} 方法被 @ref{5df,,exec_module()} 所替代，导入机制会对加载的所有样板责任作出假定。

为了与现有的加载器兼容，导入机制会使用导入器的 @code{load_module()} 方法，如果它存在且导入器也未实现 @code{exec_module()}。 但是，@code{load_module()} 现已弃用，加载器应该转而实现 @code{exec_module()}。

除了执行模块之外，@code{load_module()} 方法必须实现上文描述的所有样板加载功能。 所有相同的限制仍然适用，并带有一些附加规定:

@quotation


@itemize *

@item 
如果 @ref{eb5,,sys.modules} 中存在指定名称的模块对象，加载器必须使用已存在的模块。 （否则 @ref{391,,importlib.reload()} 将无法正确工作。） 如果该名称模块不存在于 @ref{eb5,,sys.modules} 中，加载器必须创建一个新的模块对象并将其加入 @ref{eb5,,sys.modules}。

@item 
在加载器执行模块代码之前，模块 @emph{必须} 存在于 @ref{eb5,,sys.modules} 之中，以防止无限递归或多次加载。

@item 
如果加载失败，加载器必须移除任何它已加入到 @ref{eb5,,sys.modules} 中的模块，但它必须 @strong{仅限} 移除加载失败的模块，且所移除的模块应为加载器自身显式加载的。
@end itemize
@end quotation



在 3.5 版更改: 当 @code{exec_module()} 已定义但 @code{create_module()} 未定义时将引发 @ref{278,,DeprecationWarning}。



在 3.6 版更改: 当 @code{exec_module()} 已定义但 @code{create_module()} 未定义时将引发 @ref{32d,,ImportError}。


@node 子模块,模块规格说明,加载器,加载
@anchor{reference/import submodules}@anchor{145c}
@subsubsection 子模块


当使用任意机制 (例如 @code{importlib} API, @code{import} 及 @code{import-from} 语句或者内置的 @code{__import__()}) 加载一个子模块时，父模块的命名空间中会添加一个对子模块对象的绑定。 例如，如果包 @code{spam} 有一个子模块 @code{foo}，则在导入 @code{spam.foo} 之后，@code{spam} 将具有一个 绑定到相应子模块的 @code{foo} 属性。 假如现在有如下的目录结构:

@example
spam/
    __init__.py
    foo.py
    bar.py
@end example

并且 @code{spam/__init__.py} 中有如下几行内容:

@example
from .foo import Foo
from .bar import Bar
@end example

则执行如下代码将在 @code{spam} 模块中添加对 @code{foo} 和 @code{bar} 的名称绑定:

@example
>>> import spam
>>> spam.foo
<module 'spam.foo' from '/tmp/imports/spam/foo.py'>
>>> spam.bar
<module 'spam.bar' from '/tmp/imports/spam/bar.py'>
@end example

按照通常的 Python 名称绑定规则，这看起来可能会令人惊讶，但它实际上是导入系统的一个基本特性。 保持不变的一点是如果你有 @code{sys.modules['spam']} 和 @code{sys.modules['spam.foo']} (例如在上述导入之后就是如此)，则后者必须显示为前者的 @code{foo} 属性。

@node 模块规格说明,导入相关的模块属性,子模块,加载
@anchor{reference/import module-spec}@anchor{145d}
@subsubsection 模块规格说明


导入机制在导入期间会使用有关每个模块的多种信息，特别是加载之前。 大多数信息都是所有模块通用的。 模块规格说明的目的是基于每个模块来封装这些导入相关信息。

在导入期间使用规格说明可允许状态在导入系统各组件之间传递，例如在创建模块规格说明的查找器和执行模块的加载器之间。 最重要的一点是，它允许导入机制执行加载的样板操作，在没有模块规格说明的情况下这是加载器的责任。

模块的规格说明会作为模块对象的 @code{__spec__} 属性对外公开。 有关模块规格的详细内容请参阅 @ref{145e,,ModuleSpec}。


3.4 新版功能.


@node 导入相关的模块属性,module __path__,模块规格说明,加载
@anchor{reference/import import-mod-attrs}@anchor{145a}@anchor{reference/import import-related-module-attributes}@anchor{145f}
@subsubsection 导入相关的模块属性


导入机制会在加载期间会根据模块的规格说明填充每个模块对象的这些属性，并在加载器执行模块之前完成。

@geindex __name__
@anchor{reference/import __name__}@anchor{d0b}
@deffn {属性} __name__

@code{__name__} 属性必须被设为模块的完整限定名称。 此名称被用来在导入系统中唯一地标识模块。
@end deffn

@geindex __loader__
@anchor{reference/import __loader__}@anchor{950}
@deffn {属性} __loader__

@code{__loader__} 属性必须被设为导入系统在加载模块时使用的加载器对象。 这主要是用于内省，但也可用于额外的加载器专用功能，例如获取关联到加载器的数据。
@end deffn

@geindex __package__
@anchor{reference/import __package__}@anchor{94f}
@deffn {属性} __package__

模块的 @code{__package__} 属性必须设定。 其取值必须为一个字符串，但可以与 @code{__name__} 取相同的值。 当模块是包时，其 @code{__package__} 值应该设为其 @code{__name__} 值。 当模块不是包时，对于最高层级模块 @code{__package__} 应该设为空字符串，对于子模块则应该设为其父包名。 更多详情可参阅 
@geindex Python 提高建议; PEP 366
PEP 366@footnote{https://www.python.org/dev/peps/pep-0366}。

该属性取代 @code{__name__} 被用来为主模块计算显式相对导入，相关定义见 
@geindex Python 提高建议; PEP 366
PEP 366@footnote{https://www.python.org/dev/peps/pep-0366}。 预期它与 @code{__spec__.parent} 具有相同的值。


在 3.6 版更改: @code{__package__} 预期与 @code{__spec__.parent} 具有相同的值。

@end deffn

@geindex __spec__
@anchor{reference/import __spec__}@anchor{1460}
@deffn {属性} __spec__

@code{__spec__} 属性必须设为在导入模块时要使用的模块规格说明。 对 @code{__spec__} 的正确设定将同时作用于 @ref{1461,,解释器启动期间初始化的模块}。 唯一的例外是 @code{__main__}，其中的 @code{__spec__} 会 @ref{1462,,在某些情况下设为 None}.

当 @code{__package__} 未定义时， @code{__spec__.parent} 会被用作回退项。


3.4 新版功能.



在 3.6 版更改: 当 @code{__package__} 未定义时，@code{__spec__.parent} 会被用作回退项。

@end deffn

@geindex __path__
@anchor{reference/import __path__}@anchor{1223}
@deffn {属性} __path__

如果模块为包（不论是正规包还是命名空间包），则必须设置模块对象的 @code{__path__} 属性。 属性值必须为可迭代对象，但如果 @code{__path__} 没有进一步的用处则可以为空。 如果 @code{__path__} 不为空，则在迭代时它应该产生字符串。 有关 @code{__path__} 语义的更多细节将在 @ref{1463,,下文} 中给出。

不是包的模块不应该具有 @code{__path__} 属性。
@end deffn

@geindex __file__
@anchor{reference/import __file__}@anchor{13c7}
@deffn {属性} __file__
@end deffn

@geindex __cached__
@anchor{reference/import __cached__}@anchor{b2b}
@deffn {属性} __cached__

@code{__file__} 是可选项。 如果设置，此属性的值必须为字符串。 导入系统可以选择在其没有语法意义时不设置 @code{__file__} (例如从数据库加载的模块)。

如果设置了 @code{__file__}，则也可以再设置 @code{__cached__} 属性，后者取值为编译版本代码（例如字节码文件）所在的路径。 设置此属性不要求文件已存在；该路径可以简单地指向应该存放编译文件的位置 (参见 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147})。

当未设置 @code{__file__} 时也可以设置 @code{__cached__}。 但是，那样的场景很不典型。 最终，加载器会使用 @code{__file__} 和/或 @code{__cached__}。 因此如果一个加载器可以从缓存加载模块但是不能从文件加载，那种非典型场景就是适当的。
@end deffn

@node module __path__,模块的 repr,导入相关的模块属性,加载
@anchor{reference/import module-path}@anchor{1464}@anchor{reference/import package-path-rules}@anchor{1463}
@subsubsection module.__path__


根据定义，如果一个模块具有 @code{__path__} 属性，它就是包。

包的 @code{__path__} 属性会在导入其子包期间被使用。 在导入机制内部，它的功能与 @ref{482,,sys.path} 基本相同，即在导入期间提供一个模块搜索位置列表。 但是，@code{__path__} 通常会比 @ref{482,,sys.path} 受到更多限制。

@code{__path__} 必须是由字符串组成的可迭代对象，但它也可以为空。 作用于 @ref{482,,sys.path} 的规则同样适用于包的 @code{__path__}，并且 @ref{956,,sys.path_hooks} (见下文) 会在遍历包的 @code{__path__} 时被查询。

包的 @code{__init__.py} 文件可以设置或更改包的 @code{__path__} 属性，而且这是在 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} 之前实现命名空间包的典型方式。 随着 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} 的引入，命名空间包不再需要提供仅包含 @code{__path__} 操控代码的 @code{__init__.py} 文件；导入机制会自动为命名空间包正确地设置 @code{__path__}。

@node 模块的 repr,已缓存字节码的失效,module __path__,加载
@anchor{reference/import module-reprs}@anchor{1465}
@subsubsection 模块的 repr


默认情况下，全部模块都具有一个可用的 repr，但是你可以依据上述的属性设置，在模块的规格说明中更为显式地控制模块对象的 repr。

如果模块具有 spec (@code{__spec__})，导入机制将尝试用它来生成一个 repr。 如果生成失败或找不到 spec，导入系统将使用模块中的各种可用信息来制作一个默认 repr。 它将尝试使用 @code{module.__name__}, @code{module.__file__} 以及 @code{module.__loader__} 作为 repr 的输入，并将任何丢失的信息赋为默认值。

以下是所使用的确切规则:

@quotation


@itemize *

@item 
如果模块具有 @code{__spec__} 属性，其中的规格信息会被用来生成 repr。 被查询的属性有 "name", "loader", "origin" 和 "has_location" 等等。

@item 
如果模块具有 @code{__file__} 属性，这会被用作模块 repr 的一部分。

@item 
如果模块没有 @code{__file__} 但是有 @code{__loader__} 且取值不为 @code{None}，则加载器的 repr 会被用作模块 repr 的一部分。

@item 
对于其他情况，仅在 repr 中使用模块的 @code{__name__}。
@end itemize
@end quotation


在 3.4 版更改: @ref{93b,,loader.module_repr()} 已弃用，导入机制现在使用模块规格说明来生成模块 repr。

为了向后兼容 Python 3.3，如果加载器定义了 @ref{93b,,module_repr()} 方法，则会在尝试上述两种方式之前先调用该方法来生成模块 repr。 但请注意此方法已弃用。


@node 已缓存字节码的失效,,模块的 repr,加载
@anchor{reference/import cached-bytecode-invalidation}@anchor{1466}@anchor{reference/import pyc-invalidation}@anchor{322}
@subsubsection 已缓存字节码的失效


在 Python 从 @code{.pyc} 文件加载已缓存字节码之前，它会检查缓存是否由最新的 @code{.py} 源文件所生成。 默认情况下，Python 通过在所写入缓存文件中保存源文件的最新修改时间戳和大小来实现这一点。 在运行时，导入系统会通过比对缓存文件中保存的元数据和源文件的元数据确定该缓存的有效性。

Python 也支持“基于哈希的”缓存文件，即保存源文件内容的哈希值而不是其元数据。 存在两种基于哈希的 @code{.pyc} 文件：检查型和非检查型。 对于检查型基于哈希的 @code{.pyc} 文件，Python 会通过求哈希源文件并将结果哈希值与缓存文件中的哈希值比对来确定缓存有效性。 如果检查型基于哈希的缓存文件被确定为失效，Python 会重新生成并写入一个新的检查型基于哈希的缓存文件。 对于非检查型 @code{.pyc} 文件，只要其存在 Python 就会直接认定缓存文件有效。 确定基于哈希的 @code{.pyc} 文件有效性的行为可通过 @ref{12d7,,--check-hash-based-pycs} 旗标来重载。


在 3.7 版更改: 增加了基于哈希的 @code{.pyc} 文件。在此之前，Python 只支持基于时间戳来确定字节码缓存的有效性。


@node 基于路径的查找器,替换标准导入系统,加载,导入系统
@anchor{reference/import the-path-based-finder}@anchor{1467}
@subsection 基于路径的查找器


@geindex path based finder

在之前已经提及，Python 带有几种默认的元路径查找器。 其中之一是 @ref{1458,,path based finder} (@ref{955,,PathFinder})，它会搜索包含一个 @ref{1468,,路径条目} 列表的 @ref{1455,,import path}。 每个路径条目指定一个用于搜索模块的位置。

基于路径的查找器自身并不知道如何进行导入。 它只是遍历单独的路径条目，将它们各自关联到某个知道如何处理特定类型路径的路径条目查找器。

默认的路径条目查找器集合实现了在文件系统中查找模块的所有语义，可处理多种特殊文件类型例如 Python 源码 (@code{.py} 文件)，Python 字节码 (@code{.pyc} 文件) 以及共享库 (例如 @code{.so} 文件)。 在标准库中 @ref{143,,zipimport} 模块的支持下，默认路径条目查找器还能处理所有来自 zip 文件的上述文件类型。

路径条目不必仅限于文件系统位置。 它们可以指向 URL、数据库查询或可以用字符串指定的任何其他位置。

基于路径的查找器还提供了额外的钩子和协议以便能扩展和定制可搜索路径条目的类型。 例如，如果你想要支持网络 URL 形式的路径条目，你可以编写一个实现 HTTP 语义在网络上查找模块的钩子。 这个钩子（可调用对象）应当返回一个支持下述协议的 @ref{9ac,,path entry finder}，以被用来获取一个专门针对来自网络的模块的加载器。

预先的警告：本节和上节都使用了 @emph{查找器} 这一术语，并通过 @ref{9ab,,meta path finder} 和 @ref{9ac,,path entry finder} 两个术语来明确区分它们。 这两种类型的查找器非常相似，支持相似的协议，且在导入过程中以相似的方式运作，但关键的一点是要记住它们是有微妙差异的。 特别地，元路径查找器作用于导入过程的开始，主要是启动 @ref{5e1,,sys.meta_path} 遍历。

相比之下，路径条目查找器在某种意义上说是基于路径的查找器的实现细节，实际上，如果需要从 @ref{5e1,,sys.meta_path} 移除基于路径的查找器，并不会有任何路径条目查找器被发起调用。

@menu
* 路径条目查找器:: 
* 路径条目查找器协议:: 

@end menu

@node 路径条目查找器,路径条目查找器协议,,基于路径的查找器
@anchor{reference/import path-entry-finders}@anchor{1469}
@subsubsection 路径条目查找器


@geindex sys.path
@geindex sys.path_hooks
@geindex sys.path_importer_cache
@geindex PYTHONPATH

@ref{1458,,path based finder} 会负责查找和加载通过 @ref{1468,,path entry} 字符串来指定位置的 Python 模块和包。 多数路径条目所指定的是文件系统中的位置，但它们并不必受限于此。

作为一种元路径查找器，@ref{1458,,path based finder} 实现了上文描述的 @ref{45d,,find_spec()} 协议，但是它还对外公开了一些附加钩子，可被用来定制模块如何从 @ref{1455,,import path} 查找和加载。

有三个变量由 @ref{1458,,path based finder}, @ref{482,,sys.path}, @ref{956,,sys.path_hooks} 和 @ref{498,,sys.path_importer_cache} 所使用。 包对象的 @code{__path__} 属性也会被使用。 它们提供了可用于定制导入机制的额外方式。

@ref{482,,sys.path} 包含一个提供模块和包搜索位置的字符串列表。 它初始化自 @code{PYTHONPATH} 环境变量以及多种其他特定安装和实现的默认设置。 @ref{482,,sys.path} 条目可指定的名称有文件系统中的目录、zip 文件和其他可用于搜索模块的潜在“位置”（参见 @ref{eb,,site} 模块），例如 URL 或数据库查询等。 在 @ref{482,,sys.path} 中只能出现字符串和字节串；所有其他数据类型都会被忽略。 字节串条目使用的编码由单独的 @ref{9ac,,路径条目查找器} 来确定。

@ref{1458,,path based finder} 是一种  @ref{9ab,,meta path finder}，因此导入机制会通过调用上文描述的基于路径的查找器的 @ref{934,,find_spec()} 方法来启动 @ref{1455,,import path} 搜索。 当要向 @ref{934,,find_spec()} 传入 @code{path} 参数时，它将是一个可遍历的字符串列表 —— 通常为用来在其内部进行导入的包的 @code{__path__} 属性。 如果 @code{path} 参数为 @code{None}，这表示最高层级的导入，将会使用 @ref{482,,sys.path}。

基于路径的查找器会迭代搜索路径中的每个条目，并且每次都查找与路径条目对应的 @ref{9ac,,path entry finder} (@ref{9ae,,PathEntryFinder})。 因为这种操作可能很耗费资源（例如搜索会有 @cite{stat()} 调用的开销），基于路径的查找器会维持一个缓存来将路径条目映射到路径条目查找器。 这个缓存放于 @ref{498,,sys.path_importer_cache} (尽管如此命名，但这个缓存实际存放的是查找器对象而非仅限于 @ref{1454,,importer} 对象)。 通过这种方式，对特定 @ref{1468,,path entry} 位置的 @ref{9ac,,path entry finder} 的高耗费搜索只需进行一次。 用户代码可以自由地从 @ref{498,,sys.path_importer_cache} 移除缓存条目，以强制基于路径的查找器再次执行路径条目搜索 @footnote{@w{(3)} 
在遗留代码中，有可能在 @ref{498,,sys.path_importer_cache} 中找到 @ref{9b5,,imp.NullImporter} 的实例。 建议将这些代码修改为使用 @code{None} 代替。 详情参见 @ref{b0b,,Porting Python code}。
}。

如果路径条目不存在于缓存中，基于路径的查找器会迭代 @ref{956,,sys.path_hooks} 中的每个可调用对象。 对此列表中的每个 @ref{146a,,路径条目钩子} 的调用会带有一个参数，即要搜索的路径条目。 每个可调用对象或是返回可处理路径条目的 @ref{9ac,,path entry finder}，或是引发 @ref{32d,,ImportError}。 基于路径的查找器使用 @ref{32d,,ImportError} 来表示钩子无法找到与 @ref{1468,,path entry} 相对应的 @ref{9ac,,path entry finder}。 该异常会被忽略并继续进行 @ref{1455,,import path} 的迭代。 每个钩子应该期待接收一个字符串或字节串对象；字节串对象的编码由钩子决定（例如可以是文件系统使用的编码  UTF-8 或其它编码），如果钩子无法解码参数，它应该引发 @ref{32d,,ImportError}。

如果 @ref{956,,sys.path_hooks} 迭代结束时没有返回 @ref{9ac,,path entry finder}，则基于路径的查找器 @ref{934,,find_spec()} 方法将在 @ref{498,,sys.path_importer_cache} 中存入 @code{None} (表示此路径条目没有对应的查找器) 并返回 @code{None}，表示此 @ref{9ab,,meta path finder} 无法找到该模块。

如果 @ref{956,,sys.path_hooks} 中的某个 @ref{146a,,path entry hook} 可调用对象的返回值 @emph{是} 一个 @ref{9ac,,path entry finder}，则以下协议会被用来向查找器请求一个模块的规格说明，并在加载该模块时被使用。

当前工作目录 -- 由一个空字符串表示 -- 的处理方式与 @ref{482,,sys.path} 中的其他条目略有不同。 首先，如果发现当前工作目录不存在，则 @ref{498,,sys.path_importer_cache} 中不会存放任何值。 其次，每个模块查找会对当前工作目录的值进行全新查找。 第三，由 @ref{498,,sys.path_importer_cache} 所使用并由 @ref{934,,importlib.machinery.PathFinder.find_spec()} 所返回的路径将是实际的当前工作目录而非空字符串。

@node 路径条目查找器协议,,路径条目查找器,基于路径的查找器
@anchor{reference/import path-entry-finder-protocol}@anchor{146b}
@subsubsection 路径条目查找器协议


为了支持模块和已初始化包的导入，也为了给命名空间包提供组成部分，路径条目查找器必须实现 @ref{45f,,find_spec()} 方法。

@ref{45f,,find_spec()} 接受两个参数，即要导入模块的完整限定名称，以及（可选的）目标模块。 @code{find_spec()} 返回模块的完全填充好的规格说明。 这个规格说明总是包含“加载器”集合（但有一个例外）。

为了向导入机制提示该规格说明代表一个命名空间的 @ref{144e,,portion}，路径条目查找器会将规格说明中的 "loader" 设为 @code{None} 并将 "submodule_search_locations" 设为一个包含该部分的列表。


在 3.4 版更改: @ref{45f,,find_spec()} 替代了 @ref{45e,,find_loader()} 和 @ref{935,,find_module()}，后两者现在都已弃用，但会在 @code{find_spec()} 未定义时被使用。

较旧的路径条目查找器可能会实现这两个已弃用的方法中的一个而没有实现 @code{find_spec()}。 为保持向后兼容，这两个方法仍会被接受。 但是，如果在路径条目查找器上实现了 @code{find_spec()}，这两个遗留方法就会被忽略。

@ref{45e,,find_loader()} 接受一个参数，即被导入模块的完整限定名称。 @code{find_loader()} 会返回一个二元组，其中第一项为加载器，第二项为一个命名空间 @ref{144e,,portion}。 当第一项（即加载器）为 @code{None} 时，这意味着路径条目查找器虽然没有指定名称模块的加载器，但它知道该路径条目为指定名称模块提供了一个命名空间部分。 这几乎总是表明一种情况，即 Python 被要求导入一个并不以文件系统中的实体形式存在的命名空间包。 当一个路径条目查找器返回的加载器为 @code{None} 时，该二元组返回值的第二项必须为一个序列，不过它也可以为空。

如果 @code{find_loader()} 所返回加载器的值不为 @code{None}，则该部分会被忽略，而该加载器会自基于路径的查找器返回，终止对路径条目的搜索。

为了向后兼容其他导入协议的实现，许多路径条目查找器也同样支持元路径查找器所支持的传统 @code{find_module()} 方法。 但是路径条目查找器 @code{find_module()} 方法的调用绝不会带有 @code{path} 参数（它们被期望记录来自对路径钩子初始调用的恰当路径信息）。

路径条目查找器的 @code{find_module()} 方法已弃用，因为它不允许路径条目查找器为命名空间包提供部分。 如果 @code{find_loader()} 和 @code{find_module()} 同时存在于一个路径条目查找器中，导入系统将总是调用 @code{find_loader()} 而不选择 @code{find_module()}。


@node 替换标准导入系统,包相对导入,基于路径的查找器,导入系统
@anchor{reference/import replacing-the-standard-import-system}@anchor{146c}
@subsection 替换标准导入系统


替换整个导入系统的最可靠机制是移除 @ref{5e1,,sys.meta_path} 的默认内容，,将其完全替换为自定义的元路径钩子。

一个可行的方式是仅改变导入语句的行为而不影响访问导入系统的其他 API，那么替换内置的 @ref{60b,,__import__()} 函数可能就够了。 这种技巧也可以在模块层级上运用，即只在某个模块内部改变导入语句的行为。

想要选择性地预先防止在元路径上从一个钩子导入某些模块（而不是完全禁用标准导入系统），只需直接从 @ref{45d,,find_spec()} 引发 @ref{392,,ModuleNotFoundError} 而非返回 @code{None} 就足够了。 返回后者表示元路径搜索应当继续，而引发异常则会立即终止搜索。

@node 包相对导入,有关 __main__ 的特殊事项,替换标准导入系统,导入系统
@anchor{reference/import package-relative-imports}@anchor{146d}@anchor{reference/import relativeimports}@anchor{146e}
@subsection 包相对导入


相对导入使用前缀点号。 一个前缀点号表示相对导入从当前包开始。 两个或更多前缀点号表示对当前包的上级包的相对导入，第一个点号之后的每个点号代表一级。 例如，给定以下的包布局结构:

@example
package/
    __init__.py
    subpackage1/
        __init__.py
        moduleX.py
        moduleY.py
    subpackage2/
        __init__.py
        moduleZ.py
    moduleA.py
@end example

不论是在 @code{subpackage1/moduleX.py} 还是 @code{subpackage1/__init__.py} 中，以下导入都是有效的:

@example
from .moduleY import spam
from .moduleY import spam as ham
from . import moduleY
from ..subpackage1 import moduleY
from ..subpackage2.moduleZ import eggs
from ..moduleA import foo
@end example

绝对导入可以使用 @code{import <>} 或 @code{from <> import <>} 语法，但相对导入只能使用第二种形式；其中的原因在于:

@example
import XXX.YYY.ZZZ
@end example

应当提供 @code{XXX.YYY.ZZZ} 作为可用表达式，但 .moduleY 不是一个有效的表达式。

@node 有关 __main__ 的特殊事项,开放问题项,包相对导入,导入系统
@anchor{reference/import special-considerations-for-main}@anchor{146f}
@subsection 有关 __main__ 的特殊事项


对于 Python 的导入系统来说 @ref{1,,__main__} 模块是一个特殊情况。 正如在 @ref{1461,,另一节} 中所述，@code{__main__} 模块是在解释器启动时直接初始化的，与 @ref{fd,,sys} 和 @ref{13,,builtins} 很类似。 但是，与那两者不同，它并不被严格归类为内置模块。 这是因为 @code{__main__} 被初始化的方式依赖于发起调用解释器所附带的旗标和其他选项。

@menu
* __main__.__spec__: __main__ __spec__. 

@end menu

@node __main__ __spec__,,,有关 __main__ 的特殊事项
@anchor{reference/import id4}@anchor{1470}@anchor{reference/import main-spec}@anchor{1462}
@subsubsection __main__.__spec__


根据 @ref{1,,__main__} 被初始化的方式，@code{__main__.__spec__} 会被设置相应值或是 @code{None}。

当 Python 附加 @ref{330,,-m} 选项启动时，@code{__spec__} 会被设为相应模块或包的模块规格说明。 @code{__spec__} 也会在 @code{__main__} 模块作为执行某个目录，zip 文件或其它 @ref{482,,sys.path} 条目的一部分加载时被填充。

在 @ref{12cf,,其余的情况} 下 @code{__main__.__spec__} 会被设为 @code{None}，因为用于填充 @ref{1,,__main__} 的代码不直接与可导入的模块相对应:


@itemize -

@item 
交互型提示

@item 
@ref{119f,,-c} 选项

@item 
从 stdin 运行

@item 
直接从源码或字节码文件运行
@end itemize

请注意在最后一种情况中 @code{__main__.__spec__} 总是为 @code{None}，@emph{即使} 文件从技术上说可以作为一个模块被导入。 如果想要让 @ref{1,,__main__} 中的元数据生效，请使用 @ref{330,,-m} 开关。

还要注意即使是在 @code{__main__} 对应于一个可导入模块且 @code{__main__.__spec__} 被相应地设定时，它们仍会被视为 @emph{不同的} 模块。 这是由于以下事实：使用 @code{if __name__ == "__main__":}  检测来保护的代码块仅会在模块被用来填充 @code{__main__} 命名空间时而非普通的导入时被执行。

@node 开放问题项,参考文献,有关 __main__ 的特殊事项,导入系统
@anchor{reference/import open-issues}@anchor{1471}
@subsection 开放问题项


XXX 最好是能增加一个图表。

XXX * (import_machinery.rst) 是否要专门增加一节来说明模块和包的属性，也许可以扩展或移植数据模型参考页中的相关条目？

XXX 库手册中的 runpy 和 pkgutil 等等应该都在页面顶端增加指向新的导入系统章节的“另请参阅”链接。

XXX 是否要增加关于初始化 @code{__main__} 的不同方式的更多解释？

XXX 增加更多有关 @code{__main__} 怪异/坑人特性的信息 (例如直接从 
@geindex Python 提高建议; PEP 395
PEP 395@footnote{https://www.python.org/dev/peps/pep-0395} 复制)。

@node 参考文献,,开放问题项,导入系统
@anchor{reference/import references}@anchor{1472}
@subsection 参考文献


导入机制自 Python 诞生之初至今已发生了很大的变化。 原始的 包规格说明@footnote{https://www.python.org/doc/essays/packages/} 仍然可以查阅，但在撰写该文档之后许多相关细节已被修改。

原始的 @ref{5e1,,sys.meta_path} 规格说明见 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}，后续的扩展说明见 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420}。

@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} 为 Python 3.3 引入了 @ref{144c,,命名空间包}。 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} 还引入了 @code{find_loader()} 协议作为 @code{find_module()} 的替代。

@geindex Python 提高建议; PEP 366
PEP 366@footnote{https://www.python.org/dev/peps/pep-0366} 描述了新增的 @code{__package__} 属性，用于在模块中的显式相对导入。

@geindex Python 提高建议; PEP 328
PEP 328@footnote{https://www.python.org/dev/peps/pep-0328} 引入了绝对和显式相对导入，并初次提出了 @code{__name__} 语义，最终由 
@geindex Python 提高建议; PEP 366
PEP 366@footnote{https://www.python.org/dev/peps/pep-0366} 为 @code{__package__} 加入规范描述。

@geindex Python 提高建议; PEP 338
PEP 338@footnote{https://www.python.org/dev/peps/pep-0338} 定义了将模块作为脚本执行。

@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451} 在 spec 对象中增加了对每个模块导入状态的封装。 它还将加载器的大部分样板责任移交回导入机制中。 这些改变允许弃用导入系统中的一些 API 并为查找器和加载器增加一些新的方法。

@subsubheading 备注


@node 表达式,简单语句,导入系统,Python语言参考
@anchor{reference/expressions doc}@anchor{1473}@anchor{reference/expressions expressions}@anchor{1474}@anchor{reference/expressions id1}@anchor{1475}
@section 表达式


@geindex expression
@geindex BNF

本章将解释 Python 中组成表达式的各种元素的的含义。

@strong{语法注释:} 在本章和后续章节中，会使用扩展 BNF 标注来描述语法而不是词法分析。 当（某种替代的）语法规则具有如下形式

@example
@anchor{reference/expressions grammar-token-name}@anchor{1476}name ::= othername
@end example

并且没有给出语义，则这种形式的 @code{name} 在语法上与 @code{othername} 相同。

@menu
* 算术转换:: 
* 原子:: 
* 原型:: 
* await 表达式:: 
* 幂运算符:: 
* 一元算术和位运算:: 
* 二元算术运算符:: 
* 移位运算:: 
* 二元位运算:: 
* 比较运算:: 
* 布尔运算:: 
* 赋值表达式: 赋值表达式<2>. 
* 条件表达式:: 
* lambda 表达式:: 
* 表达式列表:: 
* 求值顺序:: 
* 运算符优先级:: 

@end menu

@node 算术转换,原子,,表达式
@anchor{reference/expressions arithmetic-conversions}@anchor{1477}@anchor{reference/expressions conversions}@anchor{1478}
@subsection 算术转换


@geindex arithmetic; conversion

当对下述某个算术运算符的描述中使用了“数值参数被转换为普通类型”这样的说法，这意味着内置类型的运算符实现采用了如下运作方式:


@itemize *

@item 
如果任一参数为复数，另一参数会被转换为复数；

@item 
否则，如果任一参数为浮点数，另一参数会被转换为浮点数；

@item 
否则，两者应该都为整数，不需要进行转换。
@end itemize

某些附加规则会作用于特定运算符（例如，字符串作为 '%' 运算符的左运算参数）。 扩展必须定义它们自己的转换行为。

@node 原子,原型,算术转换,表达式
@anchor{reference/expressions atoms}@anchor{1479}@anchor{reference/expressions id2}@anchor{147a}
@subsection 原子


@geindex atom

“原子”指表达式的最基本构成元素。 最简单的原子是标识符和字面值。 以圆括号、方括号或花括号包括的形式在语法上也被归类为原子。 原子的句法为:

@example
@anchor{reference/expressions grammar-token-atom}@anchor{147b}atom      ::= identifier | literal | enclosure
@anchor{reference/expressions grammar-token-enclosure}@anchor{147c}enclosure ::= parenth_form | list_display | dict_display | set_display
              | generator_expression | yield_atom
@end example

@menu
* 标识符（名称）:: 
* 字面值: 字面值<2>. 
* 带圆括号的形式:: 
* 列表、集合与字典的显示:: 
* 列表显示:: 
* 集合显示:: 
* 字典显示:: 
* 生成器表达式: 生成器表达式<2>. 
* yield 表达式:: 

@end menu

@node 标识符（名称）,字面值<2>,,原子
@anchor{reference/expressions atom-identifiers}@anchor{1375}@anchor{reference/expressions identifiers-names}@anchor{147d}
@subsubsection 标识符（名称）


@geindex name
@geindex identifier

作为原子出现的标识符叫做名称。 请参看 @ref{136a,,标识符和关键字} 一节了解其词法定义，以及 @ref{1437,,命名与绑定} 获取有关命名与绑定的文档。

@geindex 例外; NameError

当名称被绑定到一个对象时，对该原子求值将返回相应对象。 当名称未被绑定时，尝试对其求值将引发 @ref{d74,,NameError} 异常。

@geindex name; mangling
@geindex private; names

@strong{私有名称转换:} 当以文本形式出现在类定义中的一个标识符以两个或更多下划线开头并且不以两个或更多下划线结尾，它会被视为该类的 @emph{私有名称}。 私有名称会在为其生成代码之前被转换为一种更长的形式。 转换时会插入类名，移除打头的下划线再在名称前增加一个下划线。 例如，出现在一个名为 @code{Ham} 的类中的标识符 @code{__spam} 会被转换为 @code{_Ham__spam}。 这种转换独立于标识符所使用的相关句法。 如果转换后的名称太长（超过 255 个字符），可能发生由具体实现定义的截断。 如果类名仅由下划线组成，则不会进行转换。

@node 字面值<2>,带圆括号的形式,标识符（名称）,原子
@anchor{reference/expressions atom-literals}@anchor{147e}@anchor{reference/expressions literals}@anchor{147f}
@subsubsection 字面值


@geindex literal

Python 支持字符串和字节串字面值，以及几种数字字面值:

@example
@anchor{reference/expressions grammar-token-literal}@anchor{1480}literal ::= stringliteral | bytesliteral
            | integer | floatnumber | imagnumber
@end example

对字面值求值将返回一个该值所对应类型的对象（字符串、字节串、整数、浮点数、复数）。 对于浮点数和虚数（复数）的情况，该值可能为近似值。 详情参见 @ref{1377,,字面值}。

@geindex immutable; data; type
@geindex immutable; object

所有字面值都对应与不可变数据类型，因此对象标识的重要性不如其实际值。 多次对具有相同值的字面值求值（不论是发生在程序文本的相同位置还是不同位置）可能得到相同对象或是具有相同值的不同对象。

@node 带圆括号的形式,列表、集合与字典的显示,字面值<2>,原子
@anchor{reference/expressions parenthesized}@anchor{1481}@anchor{reference/expressions parenthesized-forms}@anchor{1482}
@subsubsection 带圆括号的形式


@geindex parenthesized form
@geindex () (parentheses); tuple display

带圆括号的形式是包含在圆括号中的可选表达式列表。

@example
@anchor{reference/expressions grammar-token-parenth-form}@anchor{1483}parenth_form ::= "(" [starred_expression] ")"
@end example

带圆括号的表达式列表将返回该表达式列表所产生的任何东西：如果该列表包含至少一个逗号，它会产生一个元组；否则，它会产生该表达式列表所对应的单一表达式。

@geindex empty; tuple

一对内容为空的圆括号将产生一个空的元组对象。 由于元组是不可变对象，因此适用与字面值相同的规则（即两次出现的空元组产生的对象可能相同也可能不同）。

@geindex comma
@geindex @comma{} (comma)

请注意元组并不是由圆括号构建，实际起作用的是逗号操作符。 例外情况是空元组，这时圆括号 @emph{才是} 必须的 --- 允许在表达式中使用不带圆括号的 "空" 会导致歧义，并会造成常见输入错误无法被捕获。

@node 列表、集合与字典的显示,列表显示,带圆括号的形式,原子
@anchor{reference/expressions comprehensions}@anchor{1484}@anchor{reference/expressions displays-for-lists-sets-and-dictionaries}@anchor{1485}
@subsubsection 列表、集合与字典的显示


为了构建列表、集合或字典，Python 提供了名为“显示”的特殊句法，每个类型各有两种形式:


@itemize *

@item 
第一种是显式地列出容器内容

@item 
第二种是通过一组循环和筛选指令计算出来，称为 @emph{推导式}。
@end itemize

@geindex for; in comprehensions
@geindex if; in comprehensions
@geindex async for; in comprehensions

推导式的常用句法元素为:

@example
@anchor{reference/expressions grammar-token-comprehension}@anchor{1486}comprehension ::= assignment_expression comp_for
@anchor{reference/expressions grammar-token-comp-for}@anchor{1487}comp_for      ::= ["async"] "for" target_list "in" or_test [comp_iter]
@anchor{reference/expressions grammar-token-comp-iter}@anchor{1488}comp_iter     ::= comp_for | comp_if
@anchor{reference/expressions grammar-token-comp-if}@anchor{1489}comp_if       ::= "if" expression_nocond [comp_iter]
@end example

推导式的结构是一个单独表达式后面加至少一个 @code{for} 子句以及零个或更多个 @code{for} 或 @code{if} 子句。 在这种情况下，新容器的元素产生方式是将每个 @code{for} 或 @code{if} 子句视为一个代码块，按从左至右的顺序嵌套，然后每次到达最内层代码块时就对表达式进行求值以产生一个元素。

不过，除了最左边 @code{for} 子句中的可迭代表达式，推导式是在另一个隐式嵌套的作用域内执行的。 这能确保赋给目标列表的名称不会“泄露”到外层的作用域。

最左边的 @code{for} 子句中的可迭代对象表达式会直接在外层作用域中被求值，然后作为一个参数被传给隐式嵌套的作用域。 后续的 @code{for} 子句以及最左侧 @code{for} 子句中的任何筛选条件不能在外层作用域中被求值，因为它们可能依赖于从最左侧可迭代对象中获得的值。 例如: @code{[x*y for x in range(10) for y in range(x, x+10)]}。

为了确保推导式得出的结果总是一个类型正确的容器，在隐式嵌套作用域内禁止使用 @code{yield} 和 @code{yield from} 表达式。

@geindex await; in comprehensions

从 Python 3.6 开始，在 @ref{284,,async def} 函数中可以使用 @code{async for} 子句来迭代 @ref{63f,,asynchronous iterator}。 在 @code{async def} 函数中构建推导式可以通过在打头的表达式后加上 @code{for} 或 @code{async for} 子句，也可能包含额外的 @code{for} 或 @code{async for} 子句，还可能使用 @ref{1a3,,await} 表达式。 如果一个推导式包含 @code{async for} 子句或者 @code{await} 表达式，则被称为 @emph{异步推导式}。 异步推导式可以暂停执行它所在的协程函数。 另请参阅 
@geindex Python 提高建议; PEP 530
PEP 530@footnote{https://www.python.org/dev/peps/pep-0530}。


3.6 新版功能: 引入了异步推导式。



在 3.8 版更改: @code{yield} 和 @code{yield from} 在隐式嵌套的作用域中已被禁用。


@node 列表显示,集合显示,列表、集合与字典的显示,原子
@anchor{reference/expressions list-displays}@anchor{148a}@anchor{reference/expressions lists}@anchor{148b}
@subsubsection 列表显示


@geindex list; display
@geindex list; comprehensions
@geindex empty; list
@geindex 对象; list
@geindex [] (square brackets); list expression
@geindex @comma{} (comma); expression list

列表显示是一个用方括号括起来的可能为空的表达式系列:

@example
@anchor{reference/expressions grammar-token-list-display}@anchor{148c}list_display ::= "[" [starred_list | comprehension] "]"
@end example

列表显示会产生一个新的列表对象，其内容通过一系列表达式或一个推导式来指定。 当提供由逗号分隔的一系列表达式时，其元素会从左至右被求值并按此顺序放入列表对象。 当提供一个推导式时，列表会根据推导式所产生的结果元素进行构建。

@node 集合显示,字典显示,列表显示,原子
@anchor{reference/expressions set}@anchor{148d}@anchor{reference/expressions set-displays}@anchor{148e}
@subsubsection 集合显示


@geindex set; display
@geindex 对象; set
@geindex @{@} (curly brackets); set expression
@geindex @comma{} (comma); expression list

集合显示是用花括号标明的，与字典显示的区别在于没有冒号分隔的键和值:

@example
@anchor{reference/expressions grammar-token-set-display}@anchor{148f}set_display ::= "@{" (starred_list | comprehension) "@}"
@end example

集合显示会产生一个新的可变集合对象，其内容通过一系列表达式或一个推导式来指定。 当提供由逗号分隔的一系列表达式时，其元素会从左至右被求值并加入到集合对象。 当提供一个推导式时，集合会根据推导式所产生的结果元素进行构建。

空集合不能用 @code{@{@}} 来构建；该字面值所构建的是一个空字典。

@node 字典显示,生成器表达式<2>,集合显示,原子
@anchor{reference/expressions dict}@anchor{648}@anchor{reference/expressions dictionary-displays}@anchor{1490}
@subsubsection 字典显示


@geindex dictionary; display
@geindex key
@geindex datum
@geindex key/datum pair
@geindex 对象; dictionary
@geindex @{@} (curly brackets); dictionary expression
@geindex ; (colon); in dictionary expressions
@geindex @comma{} (comma); in dictionary displays

字典显示是一个用花括号括起来的可能为空的键/数据对系列:

@example
@anchor{reference/expressions grammar-token-dict-display}@anchor{1491}dict_display       ::= "@{" [key_datum_list | dict_comprehension] "@}"
@anchor{reference/expressions grammar-token-key-datum-list}@anchor{1492}key_datum_list     ::= key_datum ("," key_datum)* [","]
@anchor{reference/expressions grammar-token-key-datum}@anchor{1493}key_datum          ::= expression ":" expression | "**" or_expr
@anchor{reference/expressions grammar-token-dict-comprehension}@anchor{1494}dict_comprehension ::= expression ":" expression comp_for
@end example

字典显示会产生一个新的字典对象。

如果给出一个由逗号分隔的键/数据对序列，它们会从左至右被求值以定义字典的条目：每个键对象会被用作在字典中存放相应数据的键。 这意味着你可以在键/数据对序列中多次指定相同的键，最终字典的值将由最后一次给出的键决定。

@geindex unpacking; dictionary
@geindex **; in dictionary displays

双星号 @code{**} 表示 @emph{字典拆包}。 它的操作数必须是一个 @ref{b32,,mapping}。 每个映射项被会加入新的字典。 后续的值会替代先前的键/数据对和先前的字典拆包所设置的值。


3.5 新版功能: 拆包到字典显示，最初由 
@geindex Python 提高建议; PEP 448
PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} 提出。


字典推导式与列表和集合推导式有所不同，它需要以冒号分隔的两个表达式，后面带上标准的 "for" 和 "if" 子句。 当推导式被执行时，作为结果的键和值元素会按它们的产生顺序被加入新的字典。

@geindex immutable; object
@geindex hashable

对键取值类型的限制已列在之前的 @ref{13b8,,标准类型层级结构} 一节中。 (总的说来，键的类型应该为 @ref{13c0,,hashable}，这就把所有可变对象都排除在外。) 重复键之间的冲突不会被检测；指定键所保存的最后一个数据 (即在显示中排最右边的文本) 为最终有效数据。


在 3.8 版更改: 在 Python 3.8 之前的字典推导式中，并没有定义好键和值的求值顺序。 在 CPython 中，值会先于键被求值。 根据 
@geindex Python 提高建议; PEP 572
PEP 572@footnote{https://www.python.org/dev/peps/pep-0572} 的提议，从 3.8 开始，键会先于值被求值。


@node 生成器表达式<2>,yield 表达式,字典显示,原子
@anchor{reference/expressions generator-expressions}@anchor{1495}@anchor{reference/expressions genexpr}@anchor{1496}
@subsubsection 生成器表达式


@geindex generator; expression
@geindex 对象; generator
@geindex () (parentheses); generator expression

生成器表达式是用圆括号括起来的紧凑形式生成器标注。

@example
@anchor{reference/expressions grammar-token-generator-expression}@anchor{1497}generator_expression ::= "(" expression comp_for ")"
@end example

生成器表达式会产生一个新的生成器对象。 其句法与推导式相同，区别在于它是用圆括号而不是用方括号或花括号括起来的。

在生成器表达式中使用的变量会在为生成器对象调用 @ref{126e,,__next__()} 方法的时候以惰性方式被求值（即与普通生成器相同的方式）。 但是，最左侧 @code{for} 子句内的可迭代对象是会被立即求值的，因此它所造成的错误会在生成器表达式被定义时被检测到，而不是在获取第一个值时才出错。 后续的 @code{for} 子句以及最左侧 @code{for} 子句内的任何筛选条件无法在外层作用域内被求值，因为它们可能会依赖于从最左侧可迭代对象获取的值。 例如: @code{(x*y for x in range(10) for y in range(x, x+10))}.

圆括号在只附带一个参数的调用中可以被省略。 详情参见 @ref{646,,调用} 一节。

为了避免干扰到生成器表达式本身的预期操作，禁止在隐式定义的生成器中使用 @code{yield} 和 @code{yield from} 表达式。

如果生成器表达式包含 @code{async for} 子句或 @ref{1a3,,await} 表达式，则称为 @emph{异步生成器表达式}。 异步生成器表达式会返回一个新的异步生成器对象，此对象属于异步迭代器 (参见 @ref{640,,异步迭代器})。


3.6 新版功能: 引入了异步生成器表达式。



在 3.7 版更改: 在 Python 3.7 之前，异步生成器表达式只能在 @ref{284,,async def} 协和中出现。 从 3.7 开始，任何函数都可以使用异步生成器表达式。



在 3.8 版更改: @code{yield} 和 @code{yield from} 在隐式嵌套的作用域中已被禁用。


@node yield 表达式,,生成器表达式<2>,原子
@anchor{reference/expressions yield-expressions}@anchor{1498}@anchor{reference/expressions yieldexpr}@anchor{1499}
@subsubsection yield 表达式


@geindex 关键字; yield
@geindex 关键字; from
@geindex yield; expression
@geindex generator; function

@example
@anchor{reference/expressions grammar-token-yield-atom}@anchor{149a}yield_atom       ::= "(" yield_expression ")"
@anchor{reference/expressions grammar-token-yield-expression}@anchor{149b}yield_expression ::= "yield" [expression_list | "from" expression]
@end example

yield 表达式在定义 @ref{99c,,generator} 函数或是 @ref{149c,,asynchronous generator} 的时候才会用到。 因此只能在函数定义的内部使用yield表达式。 在一个函数体内使用 yield 表达式会使这个函数变成一个生成器，并且在一个 @ref{284,,async def} 定义的函数体内使用 yield 表达式会让协程函数变成异步的生成器。 比如说:

@example
def gen():  # defines a generator function
    yield 123

async def agen(): # defines an asynchronous generator function
    yield 123
@end example

由于它们会对外层作用域造成附带影响，@code{yield} 表达式不被允许作为用于实现推导式和生成器表达式的隐式定义作用域的一部分。


在 3.8 版更改: 禁止在实现推导式和生成器表达式的隐式嵌套作用域中使用 yield 表达式。


下面是对生成器函数的描述，异步生成器函数会在 @ref{149d,,异步生成器函数} 一节中单独介绍。

当一个生成器函数被调用的时候，它返回一个迭代器，称为生成器。然后这个生成器来控制生成器函数的执行。当这个生成器的某一个方法被调用的时候，生成器函数开始执行。这时会一直执行到第一个 yield 表达式，在此执行再次被挂起，给生成器的调用者返回  @ref{149e,,expression_list} 的值。挂起后，我们说所有局部状态都被保留下来，包括局部变量的当前绑定，指令指针，内部求值栈和任何异常处理的状态。通过调用生成器的某一个方法，生成器函数继续执行。此时函数的运行就和 yield 表达式只是一个外部函数调用的情况完全一致。恢复后 yield 表达式的值取决于调用的哪个方法来恢复执行。 如果用的是 @ref{126e,,__next__()} (通常通过语言内置的 @ref{c29,,for} 或是 @ref{67c,,next()} 来调用) 那么结果就是 @ref{157,,None}.  否则，如果用 @ref{1427,,send()}, 那么结果就是传递给send方法的值。

@geindex coroutine

所有这些使生成器函数与协程非常相似；它们 yield 多次，它们具有多个入口点，并且它们的执行可以被挂起。唯一的区别是生成器函数不能控制在它在 yield 后交给哪里继续执行；控制权总是转移到生成器的调用者。

在 @ref{d6b,,try} 结构中的任何位置都允许yield表达式。如果生成器在(因为引用计数到零或是因为被垃圾回收)销毁之前没有恢复执行，将调用生成器-迭代器的 @ref{142b,,close()} 方法. close 方法允许任何挂起的 @ref{182,,finally} 子句执行。

@geindex from; yield from expression

当使用 @code{yield from <expr>} 时，它会将所提供的表达式视为一个子迭代器。 这个子迭代器产生的所有值都直接被传递给当前生成器方法的调用者。 通过 @ref{1427,,send()} 传入的任何值以及通过 @ref{1429,,throw()} 传入的任何异常如果有适当的方法则会被传给下层迭代器。 如果不是这种情况，那么 @ref{1427,,send()} 将引发 @ref{393,,AttributeError} 或 @ref{192,,TypeError}，而 @ref{1429,,throw()} 将立即引发所传入的异常。

当下层迭代器完成时，被引发的 @ref{480,,StopIteration} 实例的 @code{value} 属性会成为 yield 表达式的值。 它可以在引发 @ref{480,,StopIteration} 时被显式地设置，也可以在子迭代器是一个生成器时自动地设置（通过从子生成器返回一个值）。

@quotation


在 3.3 版更改: 添加 @code{yield from <expr>} 以委托控制流给一个子迭代器。

@end quotation

当yield表达式是赋值语句右侧的唯一表达式时，括号可以省略。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 255

@item PEP 255@footnote{https://www.python.org/dev/peps/pep-0255} - 简单生成器

在 Python 中加入生成器和 @ref{18f,,yield} 语句的提议。

@geindex Python 提高建议; PEP 342

@item PEP 342@footnote{https://www.python.org/dev/peps/pep-0342} - 通过增强型生成器实现协程

增强生成器 API 和语法的提议，使其可以被用作简单的协程。

@geindex Python 提高建议; PEP 380

@item PEP 380@footnote{https://www.python.org/dev/peps/pep-0380} - 委托给子生成器的语法

引入 @code{yield_from} 语法以方便地委托给子生成器的提议。

@geindex Python 提高建议; PEP 525

@item PEP 525@footnote{https://www.python.org/dev/peps/pep-0525} - 异步生成器

通过给协程函数加入生成器功能对 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} 进行扩展的提议。
@end table


@geindex 对象; generator

@menu
* 生成器-迭代器的方法:: 
* 例子:: 
* 异步生成器函数:: 
* 异步生成器-迭代器方法:: 

@end menu

@node 生成器-迭代器的方法,例子,,yield 表达式
@anchor{reference/expressions generator-iterator-methods}@anchor{149f}@anchor{reference/expressions generator-methods}@anchor{1425}
@subsubsection 生成器-迭代器的方法


这个子小节描述了生成器迭代器的方法。 它们可被用于控制生成器函数的执行。

请注意在生成器已经在执行时调用以下任何方法都会引发 @ref{1fb,,ValueError} 异常。

@geindex 例外; StopIteration

@geindex __next__() (generator 方法)
@anchor{reference/expressions generator __next__}@anchor{126e}
@deffn {方法} generator.__next__ ()

开始一个生成器函数的执行或是从上次执行的 yield 表达式位置恢复执行。 当一个生成器函数通过 @ref{126e,,__next__()} 方法恢复执行时，当前的 yield 表达式总是取值为 @ref{157,,None}。 随后会继续执行到下一个 yield 表达式，其 @ref{149e,,expression_list} 的值会返回给 @ref{126e,,__next__()} 的调用者。 如果生成器没有产生下一个值就退出，则将引发 @ref{480,,StopIteration} 异常。

此方法通常是隐式地调用，例如通过 @ref{c29,,for} 循环或是内置的 @ref{67c,,next()} 函数。
@end deffn

@geindex send() (generator 方法)
@anchor{reference/expressions generator send}@anchor{1427}
@deffn {方法} generator.send (value)

恢复执行并向生成器函数“发送”一个值。 @emph{value} 参数将成为当前 yield 表达式的结果。 @ref{1427,,send()} 方法会返回生成器所产生的下一个值，或者如果生成器没有产生下一个值就退出则会引发 @ref{480,,StopIteration}。 当调用 @ref{1427,,send()} 来启动生成器时，它必须以 @ref{157,,None} 作为调用参数，因为这时没有可以接收值的 yield 表达式。
@end deffn

@geindex throw() (generator 方法)
@anchor{reference/expressions generator throw}@anchor{1429}
@deffn {方法} generator.throw (type[, value[, traceback]])

在生成器暂停的位置引发 @code{type} 类型的异常，并返回该生成器函数所产生的下一个值。 如果生成器没有产生下一个值就退出，则将引发 @ref{480,,StopIteration} 异常。 如果生成器函数没有捕获传入的异常，或引发了另一个异常，则该异常会被传播给调用者。
@end deffn

@geindex 例外; GeneratorExit

@geindex close() (generator 方法)
@anchor{reference/expressions generator close}@anchor{142b}
@deffn {方法} generator.close ()

在生成器函数暂停的位置引发 @ref{d2b,,GeneratorExit}。 如果之后生成器函数正常退出、关闭或引发 @ref{d2b,,GeneratorExit} (由于未捕获该异常) 则关闭并返回其调用者。 如果生成器产生了一个值，关闭会引发 @ref{2ba,,RuntimeError}。 如果生成器引发任何其他异常，它会被传播给调用者。 如果生成器已经由于异常或正常退出则 @ref{142b,,close()} 不会做任何事。
@end deffn

@geindex yield; examples

@node 例子,异步生成器函数,生成器-迭代器的方法,yield 表达式
@anchor{reference/expressions examples}@anchor{14a0}
@subsubsection 例子


这里是一个简单的例子，演示了生成器和生成器函数的行为:

@example
>>> def echo(value=None):
...     print("Execution starts when 'next()' is called for the first time.")
...     try:
...         while True:
...             try:
...                 value = (yield value)
...             except Exception as e:
...                 value = e
...     finally:
...         print("Don't forget to clean up when 'close()' is called.")
...
>>> generator = echo(1)
>>> print(next(generator))
Execution starts when 'next()' is called for the first time.
1
>>> print(next(generator))
None
>>> print(generator.send(2))
2
>>> generator.throw(TypeError, "spam")
TypeError('spam',)
>>> generator.close()
Don't forget to clean up when 'close()' is called.
@end example

对于 @code{yield from} 的例子, 参见“Python 有什么新变化”中的 @ref{972,,PEP 380; 委托给子生成器的语法}。

@node 异步生成器函数,异步生成器-迭代器方法,例子,yield 表达式
@anchor{reference/expressions asynchronous-generator-functions}@anchor{149d}@anchor{reference/expressions id3}@anchor{14a1}
@subsubsection 异步生成器函数


在一个使用 @ref{284,,async def} 定义的函数或方法中出现的 yield 表达式会进一步将该函数定义为一个 @ref{149c,,asynchronous generator} 函数。

当一个异步生成器函数被调用时，它会返回一个名为异步生成器对象的异步迭代器。 此对象将在之后控制该生成器函数的执行。 异步生成器对象通常被用在协程函数的 @ref{2e3,,async for} 语句中，类似于在 @ref{c29,,for} 语句中使用生成器对象。

调用异步生成器的方法之一将返回 @ref{513,,awaitable} 对象，执行会在此对象被等待时启动。 到那时，执行将前往第一个 yield 表达式，在那里它会再次暂停，将 @ref{149e,,expression_list} 的值返回给等待中的协程。 与生成器一样，挂起意味着局部的所有状态会被保留，包括局部变量的当前绑定、指令的指针、内部求值的堆栈以及任何异常处理的状态。 当执行在等待异步生成器的方法返回下一个对象后恢复时，该函数可以从原状态继续进行，就仿佛 yield 表达式只是另一个外部调用。 恢复执行之后 yield 表达式的值取决于恢复执行所用的方法。 如果使用 @ref{14a2,,__anext__()} 则结果为 @ref{157,,None}。 否则的话，如果使用 @ref{14a3,,asend()} 则结果将是传递给该方法的值。

在异步生成器函数中，yield 表达式允许出现在 @ref{d6b,,try} 结构的任何位置。 但是，如果一个异步生成器在其被终结（由于引用计数达到零或被作为垃圾回收）之前未被恢复，则then a yield expression within a @code{try} 结构中的 yield 表达式可能导致挂起的 @ref{182,,finally} 子句执行失败。 在此情况下，应由运行该异步生成器的事件循环或任务调度器来负责调用异步生成器-迭代器的 @ref{14a4,,aclose()} 方法并运行所返回的协程对象，从而允许任何挂起的 @code{finally} 子句得以执行。

为了能处理最终化，事件循环应该定义一个 @emph{终结器} 函数，它接受一个异步生成器-迭代器且可能调用 @ref{14a4,,aclose()} 并执行协程。 这个  @emph{终结器} 可能通过调用 @ref{eb8,,sys.set_asyncgen_hooks()} 来注册。 当首次迭代时，异步生成器-迭代器将保存已注册的 @emph{终结器} 以便在最终化时调用。 有关For a reference example of a @emph{终结器} 方法的参考示例请查看 Lib/asyncio/base_events.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/base_events.py} 中实现的 @code{asyncio.Loop.shutdown_asyncgens}。

@code{yield from <expr>} 表达式如果在异步生成器函数中使用会引发语法错误。

@geindex 对象; asynchronous-generator

@node 异步生成器-迭代器方法,,异步生成器函数,yield 表达式
@anchor{reference/expressions asynchronous-generator-iterator-methods}@anchor{14a5}@anchor{reference/expressions asynchronous-generator-methods}@anchor{14a6}
@subsubsection 异步生成器-迭代器方法


这个子小节描述了异步生成器迭代器的方法，它们可被用于控制生成器函数的执行。

@geindex 例外; StopAsyncIteration

@geindex __anext__() (agen 方法)
@anchor{reference/expressions agen __anext__}@anchor{14a2}
@deffn {方法} coroutine agen.__anext__ ()

返回一个可等待对象，它在运行时会开始执行该异步生成器或是从上次执行的 yield 表达式位置恢复执行。 当一个异步生成器函数通过 @ref{14a2,,__anext__()} 方法恢复执行时，当前的 yield 表达式所返回的可等待对象总是取值为 @ref{157,,None}，它在运行时将继续执行到下一个 yield 表达式。 该 yield 表达式的 @ref{149e,,expression_list} 的值会是完成的协程所引发的 @ref{480,,StopIteration} 异常的值。 如果异步生成器没有产生下一个值就退出，则该可等待对象将引发 @ref{fa5,,StopAsyncIteration} 异常，提示该异步迭代操作已完成。

此方法通常是通过 @ref{2e3,,async for} 循环隐式地调用。
@end deffn

@geindex asend() (agen 方法)
@anchor{reference/expressions agen asend}@anchor{14a3}
@deffn {方法} coroutine agen.asend (value)

返回一个可等待对象，它在运行时会恢复该异步生成器的执行。 与生成器的 @ref{1427,,send()} 方法一样，此方法会“发送”一个值给异步生成器函数，其 @emph{value} 参数会成为当前 yield 表达式的结果值。 @ref{14a3,,asend()} 方法所返回的可等待对象将返回生成器产生的下一个值，其值为所引发的 @ref{480,,StopIteration}，或者如果异步生成器没有产生下一个值就退出则引发 @ref{fa5,,StopAsyncIteration}。 当调用 @ref{14a3,,asend()} 来启动异步生成器时，它必须以 @ref{157,,None} 作为调用参数，因为这时没有可以接收值的 yield 表达式。
@end deffn

@geindex athrow() (agen 方法)
@anchor{reference/expressions agen athrow}@anchor{14a7}
@deffn {方法} coroutine agen.athrow (type[, value[, traceback]])

返回一个可等待对象，它会在异步生成器暂停的位置引发 @code{type} 类型的异常，并返回该生成器函数所产生的下一个值，其值为所引发的 @ref{480,,StopIteration} 异常。 如果异步生成器没有产生下一个值就退出，则将由该可等待对象引发 @ref{fa5,,StopAsyncIteration} 异步。 如果生成器函数没有捕获传入的异常，或引发了另一个异常，则当可等待对象运行时该异常会被传播给可等待对象的调用者。
@end deffn

@geindex 例外; GeneratorExit

@geindex aclose() (agen 方法)
@anchor{reference/expressions agen aclose}@anchor{14a4}
@deffn {方法} coroutine agen.aclose ()

返回一个可等待对象，它会在运行时向异步生成器函数暂停的位置抛入一个 @ref{d2b,,GeneratorExit}。 如果该异步生成器函数正常退出、关闭或引发 @ref{d2b,,GeneratorExit} (由于未捕获该异常) 则返回的可等待对象将引发 @ref{480,,StopIteration} 异常。 后续调用异步生成器所返回的任何其他可等待对象将引发 @ref{fa5,,StopAsyncIteration} 异常。 如果异步生成器产生了一个值，该可等待对象会引发 @ref{2ba,,RuntimeError}。 如果异步生成器引发任何其他异常，它会被传播给可等待对象的调用者。 如果异步生成器已经由于异常或正常退出则后续调用 @ref{14a4,,aclose()} 将返回一个不会做任何事的可等待对象。
@end deffn

@node 原型,await 表达式,原子,表达式
@anchor{reference/expressions id4}@anchor{14a8}@anchor{reference/expressions primaries}@anchor{14a9}
@subsection 原型


@geindex primary

原型代表编程语言中最紧密绑定的操作。 它们的句法如下:

@example
@anchor{reference/expressions grammar-token-primary}@anchor{14aa}primary ::= atom | attributeref | subscription | slicing | call
@end example

@menu
* 属性引用:: 
* 抽取:: 
* 切片:: 
* 调用:: 

@end menu

@node 属性引用,抽取,,原型
@anchor{reference/expressions attribute-references}@anchor{14ab}@anchor{reference/expressions id5}@anchor{14ac}
@subsubsection 属性引用


@geindex attribute; reference
@geindex . (dot); attribute reference

属性引用是后面带有一个句点加一个名称的原型:

@example
@anchor{reference/expressions grammar-token-attributeref}@anchor{14ad}attributeref ::= primary "." identifier
@end example

@geindex 例外; AttributeError
@geindex 对象; module
@geindex 对象; list

此原型必须求值为一个支持属性引用的类型的对象，多数对象都支持属性引用。 随后该对象会被要求产生以指定标识符为名称的属性。 这个产生过程可通过重载 @ref{313,,__getattr__()} 方法来自定义。 如果这个属性不可用，则将引发 @ref{393,,AttributeError} 异常。 否则的话，所产生对象的类型和值会根据该对象来确定。 对同一属性引用的多次求值可能产生不同的对象。

@node 抽取,切片,属性引用,原型
@anchor{reference/expressions id6}@anchor{14ae}@anchor{reference/expressions subscriptions}@anchor{14af}
@subsubsection 抽取


@geindex subscription
@geindex [] (square brackets); subscription

@geindex 对象; sequence
@geindex 对象; mapping
@geindex 对象; string
@geindex 对象; tuple
@geindex 对象; list
@geindex 对象; dictionary
@geindex sequence; item

抽取就是在序列（字符串、元组或列表）或映射（字典）对象中选择一项:

@example
@anchor{reference/expressions grammar-token-subscription}@anchor{14b0}subscription ::= primary "[" expression_list "]"
@end example

此原型必须求值为一个支持抽取操作的对象（例如列表或字典）。 用户定义的对象可通过定义 @ref{27f,,__getitem__()} 方法来支持抽取操作。

对于内置对象，有两种类型的对象支持抽取操作:

如果原型为映射，表达式列表必须求值为一个以该映射的键为值的对象，抽取操作会在映射中选出该键所对应的值。（表达式列表为一个元组，除非其中只有一项。）

如果原型为序列，表达式列表必须求值为一个整数或一个切片（详情见下节）。

正式句法规则并没有在序列中设置负标号的特殊保留条款；但是，内置序列所提供的 @ref{27f,,__getitem__()} 方法都可通过在索引中添加序列长度来解析负标号 (这样 @code{x[-1]} 会选出 @code{x} 中的最后一项)。 结果值必须为一个小于序列中项数的非负整数，抽取操作会选出标号为该值的项（从零开始数）。 由于对负标号和切片的支持存在于对象的 @ref{27f,,__getitem__()} 方法，重载此方法的子类需要显式地添加这种支持。

@geindex character
@geindex string; item

字符串的项是字符。 字符不是单独的数据类型而是仅有一个字符的字符串。

@node 切片,调用,抽取,原型
@anchor{reference/expressions id7}@anchor{14b1}@anchor{reference/expressions slicings}@anchor{14b2}
@subsubsection 切片


@geindex slicing
@geindex slice
@geindex ; (colon); slicing
@geindex @comma{} (comma); slicing

@geindex 对象; sequence
@geindex 对象; string
@geindex 对象; tuple
@geindex 对象; list

切片就是在序列对象（字符串、元组或列表）中选择某个范围内的项。 切片可被用作表达式以及赋值或 @ref{1202,,del} 语句的目标。 切片的句法如下:

@example
@anchor{reference/expressions grammar-token-slicing}@anchor{14b3}slicing      ::= primary "[" slice_list "]"
@anchor{reference/expressions grammar-token-slice-list}@anchor{14b4}slice_list   ::= slice_item ("," slice_item)* [","]
@anchor{reference/expressions grammar-token-slice-item}@anchor{14b5}slice_item   ::= expression | proper_slice
@anchor{reference/expressions grammar-token-proper-slice}@anchor{14b6}proper_slice ::= [lower_bound] ":" [upper_bound] [ ":" [stride] ]
@anchor{reference/expressions grammar-token-lower-bound}@anchor{14b7}lower_bound  ::= expression
@anchor{reference/expressions grammar-token-upper-bound}@anchor{14b8}upper_bound  ::= expression
@anchor{reference/expressions grammar-token-stride}@anchor{14b9}stride       ::= expression
@end example

此处的正式句法中存在一点歧义：任何形似表达式列表的东西同样也会形似切片列表，因此任何抽取操作也可以被解析为切片。 为了不使句法更加复杂，于是通过定义将此情况解析为抽取优先于解析为切片来消除这种歧义（切片列表未包含正确的切片就属于此情况）。

@geindex start (slice object attribute)
@geindex stop (slice object attribute)
@geindex step (slice object attribute)

切片的语义如下所述。 元型通过一个根据下面的切片列表来构造的键进行索引（与普通抽取一样使用 @ref{27f,,__getitem__()} 方法）。 如果切片列表包含至少一个逗号，则键将是一个包含切片项转换的元组；否则的话，键将是单个切片项的转换。 切片项如为一个表达式，则其转换就是该表达式。 一个正确切片的转换就是一个切片对象（参见 @ref{13b8,,标准类型层级结构} 一节），该对象的 @code{start}, @code{stop} 和 @code{step} 属性将分别为表达式所给出的下界、上界和步长值，省略的表达式将用 @code{None} 来替换。

@geindex 对象; callable
@geindex call
@geindex argument; call semantics
@geindex () (parentheses); call
@geindex @comma{} (comma); argument list
@geindex = (equals); in function calls

@node 调用,,切片,原型
@anchor{reference/expressions calls}@anchor{646}@anchor{reference/expressions id8}@anchor{14ba}
@subsubsection 调用


所谓调用就是附带可能为空的一系列 @ref{14bb,,参数} 来执行一个可调用对象 (例如 @ref{14bc,,function}):

@example
@anchor{reference/expressions grammar-token-call}@anchor{14bd}call                 ::= primary "(" [argument_list [","] | comprehension] ")"
@anchor{reference/expressions grammar-token-argument-list}@anchor{14be}argument_list        ::= positional_arguments ["," starred_and_keywords]
                           ["," keywords_arguments]
                         | starred_and_keywords ["," keywords_arguments]
                         | keywords_arguments
@anchor{reference/expressions grammar-token-positional-arguments}@anchor{14bf}positional_arguments ::= positional_item ("," positional_item)*
@anchor{reference/expressions grammar-token-positional-item}@anchor{14c0}positional_item      ::= assignment_expression | "*" expression
@anchor{reference/expressions grammar-token-starred-and-keywords}@anchor{14c1}starred_and_keywords ::= ("*" expression | keyword_item)
                         ("," "*" expression | "," keyword_item)*
@anchor{reference/expressions grammar-token-keywords-arguments}@anchor{14c2}keywords_arguments   ::= (keyword_item | "**" expression)
                         ("," keyword_item | "," "**" expression)*
@anchor{reference/expressions grammar-token-keyword-item}@anchor{14c3}keyword_item         ::= identifier "=" expression
@end example

一个可选项为在位置和关键字参数后加上逗号而不影响语义。

@geindex parameter; call semantics

此原型必须求值为一个可调用对象（用户定义的函数，内置函数，内置对象的方法，类对象，类实例的方法以及任何具有 @ref{13c5,,__call__()} 方法的对象都是可调用对象）。 所有参数表达式将在尝试调用前被求值。 请参阅 @ref{11f0,,函数定义} 一节了解正式的 @ref{14c4,,parameter} 列表句法。

@c XXX update with kwonly args PEP

如果存在关键字参数，它们会先通过以下操作被转换为位置参数。 首先，为正式参数创建一个未填充空位的列表. 如果有 N 个位置参数，则将它们放入前 N 个空位。 然后，对于每个关键字参数，使用标识符来确定其对应的空位（如果标识符与第一个正式参数名相同则使用第一个个空位，依此类推）。 如果空位已被填充，则会引发 @ref{192,,TypeError} 异常。 否则，将参数值放入空位进行填充（即使表达式为 @code{None} 也会填充空位）。 当所有参数处理完毕时，尚未填充的空位将用来自函数定义的相应默认值来填充。 （函数一旦定义其参数默认值就会被计算；因此，当列表或字典这类可变对象被用作默认值时，将会被所有未指定相应空位参数值的调用所共享；这种情况通常应当避免。） 如果任何一个未填充空位没有指定默认值，则会引发 @ref{192,,TypeError} 异常。 否则的话，已填充空位的列表会被作为调用的参数列表。

@strong{CPython implementation detail:} 某些实现可能提供位置参数没有名称的内置函数，即使它们在文档说明的场合下有“命名”，因此不能以关键字形式提供参数。 在 CPython 中，以 C 编写并使用 @ref{26a,,PyArg_ParseTuple()} 来解析其参数的函数实现就属于这种情况。

如果存在比正式参数空位多的位置参数，将会引发 @ref{192,,TypeError} 异常，除非有一个正式参数使用了 @code{*identifier} 句法；在此情况下，该正式参数将接受一个包含了多余位置参数的元组（如果没有多余位置参数则为一个空元组）。

如果任何关键字参数没有与之对应的正式参数名称，将会引发 @ref{192,,TypeError} 异常，除非有一个正式参数使用了 @code{**identifier} 句法，该正式参数将接受一个包含了多余关键字参数的字典（使用关键字作为键而参数值作为与键对应的值），如果没有多余关键字参数则为一个（新的）空字典。

@geindex * (asterisk); in function calls
@geindex unpacking; in function calls

如果函数调用中出现了 @code{*expression} 句法，@code{expression} 必须求值为一个 @ref{ba5,,iterable}。 来自该可迭代对象的元素会被当作是额外的位置参数。 对于 @code{f(x1, x2, *y, x3, x4)} 调用，如果 @emph{y} 求值为一个序列 @emph{y1}, ..., @emph{yM}，则它就等价于一个带有 M+4 个位置参数 @emph{x1}, @emph{x2}, @emph{y1}, ..., @emph{yM}, @emph{x3}, @emph{x4} 的调用。

这样做的一个后果是虽然 @code{*expression} 句法可能出现于显式的关键字参数 @emph{之后}，但它会在关键字参数（以及任何 @code{**expression} 参数 -- 见下文） @emph{之前} 被处理。 因此:

@example
>>> def f(a, b):
...     print(a, b)
...
>>> f(b=1, *(2,))
2 1
>>> f(a=1, *(2,))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: f() got multiple values for keyword argument 'a'
>>> f(1, *(2,))
1 2
@end example

在同一个调用中同时使用关键字参数和 @code{*expression} 句法并不常见，因此实际上这样的混淆不会发生。

@geindex **; in function calls

如果函数调用中出现了 @code{**expression} 句法，@code{expression} 必须求值为一个 @ref{b32,,mapping}，其内容会被当作是额外的关键字参数。 如果一个关键字已存在（作为显式关键字参数，或来自另一个拆包），则将引发 @ref{192,,TypeError} 异常。

使用 @code{*identifier} 或 @code{**identifier} 句法的正式参数不能被用作位置参数空位或关键字参数名称。


在 3.5 版更改: 函数调用接受任意数量的 @code{*} 和 @code{**} 拆包，位置参数可能跟在可迭代对象拆包 (@code{*}) 之后，而关键字参数可能跟在字典拆包 (@code{**}) 之后。 由 
@geindex Python 提高建议; PEP 448
PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} 发起最初提议。


除非引发了异常，调用总是会有返回值，返回值也可能为 @code{None}。 返回值的计算方式取决于可调用对象的类型。

如果类型为---


@table @asis

@item 用户自定义函数:

@geindex function; call
@geindex user-defined; function; call
@geindex 对象; user-defined function
@geindex 对象; function

函数的代码块会被执行，并向其传入参数列表。 代码块所做的第一件事是将正式形参绑定到对应参数；相关描述参见 @ref{11f0,,函数定义} 一节。 当代码块执行 @ref{190,,return} 语句时，由其指定函数调用的返回值。

@item 内置函数或方法:

@geindex function; call
@geindex built-in function; call
@geindex method; call
@geindex built-in method; call
@geindex 对象; built-in method
@geindex 对象; built-in function
@geindex 对象; method
@geindex 对象; function

具体结果依赖于解释器；有关内置函数和方法的描述参见 @ref{bec,,内置函数}。

@item 类对象:

@geindex 对象; class
@geindex class object; call

返回该类的一个新实例。

@item 类实例方法:

@geindex 对象; class instance
@geindex 对象; instance
@geindex class instance; call

调用相应的用户自定义函数，向其传入的参数列表会比调用的参数列表多一项：该实例将成为第一个参数。

@item 类实例:

@geindex instance; call
@geindex __call__() (object method)

该类必须定义有 @ref{13c5,,__call__()} 方法；作用效果将等价于调用该方法。
@end table

@geindex 关键字; await

@node await 表达式,幂运算符,原型,表达式
@anchor{reference/expressions await}@anchor{1a3}@anchor{reference/expressions await-expression}@anchor{14c5}
@subsection await 表达式


挂起 @ref{1a6,,coroutine} 的执行以等待一个 @ref{513,,awaitable} 对象。 只能在 @ref{639,,coroutine function} 内部使用。

@example
@anchor{reference/expressions grammar-token-await-expr}@anchor{14c6}await_expr ::= "await" primary
@end example


3.5 新版功能.


@node 幂运算符,一元算术和位运算,await 表达式,表达式
@anchor{reference/expressions power}@anchor{14c7}@anchor{reference/expressions the-power-operator}@anchor{14c8}
@subsection 幂运算符


@geindex power; operation
@geindex 运算符; **

幂运算符的绑定比在其左侧的一元运算符更紧密；但绑定紧密程度不及在其右侧的一元运算符。 句法如下:

@example
@anchor{reference/expressions grammar-token-power}@anchor{14c9}power ::= (await_expr | primary) ["**" u_expr]
@end example

因此，在一个未加圆括号的幂运算符和单目运算符序列中，运算符将从右向左求值（这不会限制操作数的求值顺序）: @code{-1**2} 结果将为 @code{-1}。

幂运算符与附带两个参数调用内置 @ref{19a,,pow()} 函数具有相同的语义：结果为对其左参数进行其右参数所指定幂次的乘方运算。 数值参数会先转换为相同类型，结果也为转换后的类型。

对于 int 类型的操作数，结果将具有与操作数相同的类型，除非第二个参数为负数；在那种情况下，所有参数会被转换为 float 类型并输出 float 类型的结果。 例如，@code{10**2} 返回 @code{100}，而 @code{10**-2} 返回 @code{0.01}。

对 @code{0.0} 进行负数幂次运算将导致 @ref{1241,,ZeroDivisionError}。 对负数进行分数幂次运算将返回 @ref{189,,complex} 数值。 （在早期版本中这将引发 @ref{1fb,,ValueError}。）

@node 一元算术和位运算,二元算术运算符,幂运算符,表达式
@anchor{reference/expressions unary}@anchor{14ca}@anchor{reference/expressions unary-arithmetic-and-bitwise-operations}@anchor{14cb}
@subsection 一元算术和位运算


@geindex unary; arithmetic; operation
@geindex unary; bitwise; operation

所有算术和位运算具有相同的优先级:

@example
@anchor{reference/expressions grammar-token-u-expr}@anchor{14cc}u_expr ::= power | "-" u_expr | "+" u_expr | "~" u_expr
@end example

@geindex negation
@geindex minus
@geindex operator; - (minus)
@geindex - (minus); unary operator

一元运算符 @code{-} (负) 会产生其数值参数的负值。

@geindex plus
@geindex operator; + (plus)
@geindex + (plus); unary operator

一元运算符 @code{+} (正) 会产生与其数值参数相同的值。

@geindex inversion
@geindex 运算符; ~ (tilde)

一元运算符 @code{~} (取反) 的结果是对其整数参数按位取反。 @code{x} 的按位取反被定义为 @code{-(x+1)}。 它只作用于整数。

@geindex 例外; TypeError

在所有三种情况下，如果参数的类型不正确，将引发 @ref{192,,TypeError} 异常。

@node 二元算术运算符,移位运算,一元算术和位运算,表达式
@anchor{reference/expressions binary}@anchor{14cd}@anchor{reference/expressions binary-arithmetic-operations}@anchor{14ce}
@subsection 二元算术运算符


@geindex binary; arithmetic; operation

二元算术运算符遵循传统的优先级。 请注意某些此类运算符也作用于特定的非数字类型。 除幂运算符以外只有两个优先级别，一个作用于乘法型运算符，另一个作用于加法型运算符:

@example
@anchor{reference/expressions grammar-token-m-expr}@anchor{14cf}m_expr ::= u_expr | m_expr "*" u_expr | m_expr "@@" m_expr |
           m_expr "//" u_expr | m_expr "/" u_expr |
           m_expr "%" u_expr
@anchor{reference/expressions grammar-token-a-expr}@anchor{14d0}a_expr ::= m_expr | a_expr "+" m_expr | a_expr "-" m_expr
@end example

@geindex multiplication
@geindex 运算符; * (asterisk)

运算符 @code{*} (乘) 将输出其参数的乘积。 两个参数或者必须都为数字，或者一个参数必须为整数而另一个参数必须为序列。 在前一种情况下，两个数字将被转换为相同类型然后相乘。 在后一种情况下，将执行序列的重复；重复因子为负数将输出空序列。

@geindex matrix multiplication
@geindex 运算符; @@ (at)

运算符 @code{@@} (at) 的目标是用于矩阵乘法。 没有内置 Python 类型实现此运算符。


3.5 新版功能.


@geindex 例外; ZeroDivisionError
@geindex division
@geindex 运算符; / (slash)
@geindex 运算符; //

运算符 @code{/} (除) 和 @code{//} (整除) 将输出其参数的商。 两个数字参数将先被转换为相同类型。 整数相除会输出一个 float 值，整数相整除的结果仍是整数；整除的结果就是使用 'floor' 函数进行算术除法的结果。 除以零的运算将引发 @ref{1241,,ZeroDivisionError} 异常。

@geindex modulo
@geindex 运算符; % (percent)

运算符 @code{%} (模) 将输出第一个参数除以第二个参数的余数。 两个数字参数将先被转换为相同类型。 右参数为零将引发 @ref{1241,,ZeroDivisionError} 异常。 参数可以为浮点数，例如 @code{3.14%0.7} 等于 @code{0.34} (因为 @code{3.14} 等于 @code{4*0.7 + 0.34})。 模运算符的结果的正负总是与第二个操作数一致（或是为零）；结果的绝对值一定小于第二个操作数的绝对值 @footnote{@w{(1)} 
虽然 @code{abs(x%y) < abs(y)} 在数学中必为真，但对于浮点数而言，由于舍入的存在，其在数值上未必为真。 例如，假设在某个平台上的 Python 浮点数为一个 IEEE 754 双精度数值，为了使 @code{-1e-100 % 1e100} 具有与 @code{1e100} 相同的正负性，计算结果将是 @code{-1e-100 + 1e100}，这在数值上正好等于 @code{1e100}。 函数 @ref{14d1,,math.fmod()} 返回的结果则会具有与第一个参数相同的正负性，因此在这种情况下将返回 @code{-1e-100}。 何种方式更适宜取决于具体的应用。
}。

整除与模运算符的联系可通过以下等式说明: @code{x == (x//y)*y + (x%y)}。 此外整除与模也可通过内置函数 @ref{152,,divmod()} 来同时进行: @code{divmod(x, y) == (x//y, x%y)}。 @footnote{@w{(2)} 
如果 x 恰好非常接近于 y 的整数倍，则由于舍入的存在 @code{x//y} 可能会比 @code{(x-x%y)//y} 大。 在这种情况下，Python 会返回后一个结果，以便保持令 @code{divmod(x,y)[0] * y + x % y} 尽量接近 @code{x}.
}。

除了对数字执行模运算，运算符 @code{%} 还被字符串对象重载用于执行旧式的字符串格式化（又称插值）。 字符串格式化句法的描述参见 Python 库参考的 @ref{11b9,,printf 风格的字符串格式化} 一节。

整除运算符，模运算符和 @ref{152,,divmod()} 函数未被定义用于复数。 如果有必要可以使用 @ref{1253,,abs()} 函数将其转换为浮点数。

@geindex addition
@geindex operator; + (plus)
@geindex + (plus); binary operator

运算符 @code{+} (addition) 将输出其参数的和。 两个参数或者必须都为数字，或者都为相同类型的序列。 在前一种情况下，两个数字将被转换为相同类型然后相加。 在后一种情况下，将执行序列拼接操作。

@geindex subtraction
@geindex operator; - (minus)
@geindex - (minus); binary operator

运算符 @code{-} (减) 将输出其参数的差。 两个数字参数将先被转换为相同类型。

@node 移位运算,二元位运算,二元算术运算符,表达式
@anchor{reference/expressions shifting}@anchor{14d2}@anchor{reference/expressions shifting-operations}@anchor{14d3}
@subsection 移位运算


@geindex shifting; operation
@geindex 运算符; <<
@geindex 运算符; >>

移位运算的优先级低于算术运算:

@example
@anchor{reference/expressions grammar-token-shift-expr}@anchor{14d4}shift_expr ::= a_expr | shift_expr ("<<" | ">>") a_expr
@end example

这些运算符接受整数参数。 它们会将第一个参数左移或右移第二个参数所指定的比特位数。

@geindex 例外; ValueError

右移 @emph{n} 位被定义为被 @code{pow(2,n)} 整除。 左移 @emph{n} 位被定义为乘以 @code{pow(2,n)}。

@node 二元位运算,比较运算,移位运算,表达式
@anchor{reference/expressions binary-bitwise-operations}@anchor{14d5}@anchor{reference/expressions bitwise}@anchor{14d6}
@subsection 二元位运算


@geindex binary; bitwise; operation

三种位运算具有各不相同的优先级:

@example
@anchor{reference/expressions grammar-token-and-expr}@anchor{14d7}and_expr ::= shift_expr | and_expr "&" shift_expr
@anchor{reference/expressions grammar-token-xor-expr}@anchor{14d8}xor_expr ::= and_expr | xor_expr "^" and_expr
@anchor{reference/expressions grammar-token-or-expr}@anchor{14d9}or_expr  ::= xor_expr | or_expr "|" xor_expr
@end example

@geindex bitwise; and
@geindex 运算符; & (ampersand)

运算符 @code{&} 对两个参数进行按位 AND (与) 运算，两个参数必须为整数。

@geindex bitwise; xor
@geindex exclusive; or
@geindex 运算符; ^ (caret)

运算符 @code{^} 对两个参数进行按位 XOR (异或) 运算，两个参数必须为整数。

@geindex bitwise; or
@geindex inclusive; or
@geindex 运算符; | (vertical bar)

运算符 @code{|} 对两个参数进行按位 OR (或) 运算，两个参数必须为整数。

@node 比较运算,布尔运算,二元位运算,表达式
@anchor{reference/expressions comparisons}@anchor{14da}@anchor{reference/expressions id11}@anchor{14db}
@subsection 比较运算


@geindex comparison
@geindex C; language
@geindex 运算符; < (less)
@geindex 运算符; > (greater)
@geindex 运算符; <=
@geindex 运算符; >=
@geindex 运算符; ==
@geindex 运算符; !=

与 C 不同，Python 中所有比较运算的优先级相同，低于任何算术、移位或位运算。 另一个与 C 不同之处在于 @code{a < b < c} 这样的表达式会按传统算术法则来解读:

@example
@anchor{reference/expressions grammar-token-comparison}@anchor{14dc}comparison    ::= or_expr (comp_operator or_expr)*
@anchor{reference/expressions grammar-token-comp-operator}@anchor{14dd}comp_operator ::= "<" | ">" | "==" | ">=" | "<=" | "!="
                  | "is" ["not"] | ["not"] "in"
@end example

比较运算将输出布尔值: @code{True} 或 @code{False}。

@geindex chaining; comparisons

比较运算可以任意串连，例如 @code{x < y <= z} 等价于 @code{x < y and y <= z}，除了 @code{y} 只被求值一次（但在两种写法下当 @code{x < y} 值为假时 @code{z} 都不会被求值）。

正式的说法是这样：如果 @emph{a}, @emph{b}, @emph{c}, ..., @emph{y}, @emph{z} 为表达式而 @emph{op1}, @emph{op2}, ..., @emph{opN} 为比较运算符，则 @code{a op1 b op2 c ... y opN z} 就等价于 @code{a op1 b and b op2 c and ... y opN z}，后者的不同之处只是每个表达式最多只被求值一次。

请注意 @code{a op1 b op2 c} 不意味着在 @emph{a} 和 @emph{c} 之间进行任何比较，因此，如 @code{x < y > z} 这样的写法是完全合法的（虽然也许不太好看）。

@menu
* 值比较:: 
* 成员检测运算:: 
* 标识号比较:: 

@end menu

@node 值比较,成员检测运算,,比较运算
@anchor{reference/expressions value-comparisons}@anchor{14de}
@subsubsection 值比较


运算符 @code{<}, @code{>}, @code{==}, @code{>=}, @code{<=} 和 @code{!=} 将比较两个对象的值。 两个对象不要求为相同类型。

@ref{13b4,,对象、值与类型} 一章已说明对象都有相应的值（还有类型和标识号）。 对象值在 Python 中是一个相当抽象的概念：例如，对象值并没有一个规范的访问方法。 而且，对象值并不要求具有特定的构建方式，例如由其全部数据属性组成等。 比较运算符实现了一个特定的对象值概念。 人们可以认为这是通过实现对象比较间接地定义了对象值。

由于所有类型都是 @ref{2b0,,object} 的（直接或间接）子类型，它们都从 @ref{2b0,,object} 继承了默认的比较行为。 类型可以通过实现 @emph{丰富比较方法} 例如 @ref{c2d,,__lt__()} 来定义自己的比较行为，详情参见 @ref{13cd,,基本定制}。

默认的一致性比较 (@code{==} 和 @code{!=}) 是基于对象的标识号。 因此，具有相同标识号的实例一致性比较结果为相等，具有不同标识号的实例一致性比较结果为不等。 规定这种默认行为的动机是希望所有对象都应该是自反射的 (即 @code{x is y} 就意味着 @code{x == y})。

次序比较 (@code{<}, @code{>}, @code{<=} 和 @code{>=}) 默认没有提供；如果尝试比较会引发 @ref{192,,TypeError}。 规定这种默认行为的原因是缺少与一致性比较类似的固定值。

按照默认的一致性比较行为，具有不同标识号的实例总是不相等，这可能不适合某些对象值需要有合理定义并有基于值的一致性的类型。 这样的类型需要定制自己的比较行为，实际上，许多内置类型都是这样做的。

以下列表描述了最主要内置类型的比较行为。


@itemize *

@item 
内置数值类型 (@ref{11b3,,数字类型 --- int@comma{} float@comma{} complex}) 以及标准库类型 @ref{185,,fractions.Fraction} 和 @ref{188,,decimal.Decimal} 可进行类型内部和跨类型的比较，例外限制是复数不支持次序比较。 在类型相关的限制以内，它们会按数学（算法）规则正确进行比较且不会有精度损失。

非数字值 @code{float('NaN')} 和 @code{decimal.Decimal('NaN')} 属于特例。 任何数字与非数字值的排序比较均返回假值。 还有一个反直觉的结果是非数字值不等于其自身。 举例来说，如果 @code{x = float('NaN')} 则 @code{3 < x}, @code{x < 3} 和 @code{x == x} 均为假值，而 @code{x != x} 则为真值。 此行为是遵循 IEEE 754 标准的。

@item 
@code{None} 和 @code{NotImplemented} 都是单例对象。 
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008} 建议单例对象的比较应当总是通过 @code{is} 或 @code{is not} 而不是等于运算符来进行。

@item 
二进制码序列 (@ref{32a,,bytes} 或 @ref{32b,,bytearray} 的实例) 可进行类型内部和跨类型的比较。 它们使用其元素的数字值按字典顺序进行比较。

@item 
字符串 (@ref{329,,str} 的实例) 使用其字符的 Unicode 码位数字值 (内置函数 @ref{13be,,ord()} 的结果) 按字典顺序进行比较。 @footnote{@w{(3)} 
Unicode 标准明确区分 @emph{码位} (例如 U+0041) 和 @emph{抽象字符} (例如 "大写拉丁字母 A")。 虽然 Unicode 中的大多数抽象字符都只用一个码位来代表，但也存在一些抽象字符可使用由多个码位组成的序列来表示。 例如，抽象字符 "带有下加符的大写拉丁字母 C" 可以用 U+00C7 码位上的单个 @emph{预设字符} 来表示，也可以用一个 U+0043 码位上的 @emph{基础字符} (大写拉丁字母 C) 加上一个 U+0327 码位上的 @emph{组合字符} (组合下加符) 组成的序列来表示。

对于字符串，比较运算符会按 Unicode 码位级别进行比较。 这可能会违反人类的直觉。 例如，@code{"\u00C7" == "\u0043\u0327"} 为 @code{False}，虽然两个字符串都代表同一个抽象字符 "带有下加符的大写拉丁字母 C"。

要按抽象字符级别（即对人类来说更直观的方式）对字符串进行比较，应使用 @ref{1042,,unicodedata.normalize()}。
}

字符串和二进制码序列不能直接比较。

@item 
序列 (@ref{478,,tuple}, @ref{262,,list} 或 @ref{9b8,,range} 的实例) 只可进行类型内部的比较，range 还有一个限制是不支持次序比较。 以上对象的跨类型一致性比较结果将是不相等，跨类型次序比较将引发 @ref{192,,TypeError}。

序列比较是按字典序对相应元素进行逐个比较。 内置容器通常设定同一对象与其自身是相等的。 这使得它们能跳过同一对象的相等性检测以提升运行效率并保持它们的内部不变性。

内置多项集间的字典序比较规则如下:


@itemize -

@item 
两个多项集若要相等，它们必须为相同类型、相同长度，并且每对相应的元素都必须相等（例如，@code{[1,2] == (1,2)} 为假值，因为类型不同）。

@item 
对于支持次序比较的多项集，排序与其第一个不相等元素的排序相同（例如 @code{[1,2,x] <= [1,2,y]} 的值与`@w{`}x <= y`@w{`} 相同）。 如果对应元素不存在，较短的多项集排序在前（例如 @code{[1,2] < [1,2,3]} 为真值）。
@end itemize

@item 
两个映射 (@ref{1b8,,dict} 的实例) 若要相等，必须当且仅当它们具有相同的 @cite{(键@comma{} 值)} 对。 键和值的一致性比较强制规定自反射性。

次序比较 (@code{<}, @code{>}, @code{<=} 和 @code{>=}) 将引发 @ref{192,,TypeError}。

@item 
集合 (@ref{b68,,set} 或 @ref{be7,,frozenset} 的实例) 可进行类型内部和跨类型的比较。

它们将比较运算符定义为子集和超集检测。 这类关系没有定义完全排序（例如 @code{@{1,2@}} 和 @code{@{2,3@}} 两个集合不相等，即不为彼此的子集，也不为彼此的超集。 相应地，集合不适宜作为依赖于完全排序的函数的参数（例如如果给出一个集合列表作为 @ref{803,,min()}, @ref{804,,max()} 和 @ref{43e,,sorted()} 的输入将产生未定义的结果）。

集合的比较强制规定其元素的自反射性。

@item 
大多数其他内置类型没有实现比较方法，因此它们会继承默认的比较行为。
@end itemize

在可能的情况下，用户定义类在定制其比较行为时应当遵循一些一致性规则:


@itemize *

@item 
相等比较应该是自反射的。 换句话说，相同的对象比较时应该相等:

@quotation

@code{x is y} 意味着 @code{x == y}
@end quotation

@item 
比较应该是对称的。 换句话说，下列表达式应该有相同的结果:

@quotation

@code{x == y} 和 @code{y == x}

@code{x != y} 和 @code{y != x}

@code{x < y} 和 @code{y > x}

@code{x <= y} 和 @code{y >= x}
@end quotation

@item 
比较应该是可传递的。 下列（简要的）例子显示了这一点:

@quotation

@code{x > y and y > z} 意味着 @code{x > z}

@code{x < y and y <= z} 意味着 @code{x < z}
@end quotation

@item 
反向比较应该导致布尔值取反。 换句话说，下列表达式应该有相同的结果:

@quotation

@code{x == y} 和 @code{not x != y}

@code{x < y} 和 @code{not x >= y} (对于完全排序)

@code{x > y} 和 @code{not x <= y} (对于完全排序)
@end quotation

最后两个表达式适用于完全排序的多项集（即序列而非集合或映射）。 另请参阅 @ref{845,,total_ordering()} 装饰器。

@item 
@ref{9be,,hash()} 的结果应该与是否相等一致。 相等的对象应该或者具有相同的哈希值，或者标记为不可哈希。
@end itemize

Python 并不强制要求这些一致性规则。 实际上，非数字值就是一个不遵循这些规则的例子。
@anchor{reference/expressions in}@anchor{79d}@anchor{reference/expressions not-in}@anchor{13f5}
@node 成员检测运算,标识号比较,值比较,比较运算
@anchor{reference/expressions membership-test-details}@anchor{13f6}@anchor{reference/expressions membership-test-operations}@anchor{14df}
@subsubsection 成员检测运算


运算符 @ref{79d,,in} 和 @ref{13f5,,not in} 用于成员检测。 如果 @emph{x} 是 @emph{s} 的成员则 @code{x in s} 求值为 @code{True}，否则为 @code{False}。 @code{x not in s} 返回 @code{x in s} 取反后的值。 所有内置序列和集合类型以及字典都支持此运算，对于字典来说 @code{in} 检测其是否有给定的键。 对于 list, tuple, set, frozenset, dict 或 collections.deque 这样的容器类型，表达式 @code{x in y} 等价于 @code{any(x is e or x == e for e in y)}。

对于字符串和字节串类型来说，当且仅当 @emph{x} 是 @emph{y} 的子串时 @code{x in y} 为 @code{True}。 一个等价的检测是 @code{y.find(x) != -1}。 空字符串总是被视为任何其他字符串的子串，因此 @code{"" in "abc"} 将返回 @code{True}。

对于定义了 @ref{d21,,__contains__()} 方法的用户自定义类来说，如果 @code{y.__contains__(x)} 返回真值则 @code{x in y} 返回 @code{True}，否则返回 @code{False}。

对于未定义 @ref{d21,,__contains__()} 但定义了 @ref{509,,__iter__()} 的用户自定义类来说，如果在对 @code{y} 进行迭代时产生了值 @code{z} 使得表达式 @code{x is z or x == z} 为真，则 @code{x in y} 为 @code{True}。 如果在迭代期间引发了异常，则等同于 @ref{79d,,in} 引发了该异常。

最后将会尝试旧式的迭代协议：如果一个类定义了 @ref{27f,,__getitem__()}，则当且仅当存在非负整数索引号 @emph{i} 使得 @code{x is y[i] or x == y[i]} 并且没有更小的索引号引发 @ref{e6e,,IndexError} 异常时 @code{x in y} 为 @code{True}。 （如果引发了任何其他异常，则等同于 @ref{79d,,in} 引发了该异常）。

@geindex 运算符; in
@geindex 运算符; not in
@geindex membership; test
@geindex 对象; sequence

运算符 @ref{13f5,,not in} 被定义为具有与 @ref{79d,,in} 相反的逻辑值。

@geindex 运算符; is
@geindex 运算符; is not
@geindex identity; test
@anchor{reference/expressions is}@anchor{13b6}
@node 标识号比较,,成员检测运算,比较运算
@anchor{reference/expressions identity-comparisons}@anchor{14e0}@anchor{reference/expressions is-not}@anchor{14e1}
@subsubsection 标识号比较


运算符 @ref{13b6,,is} 和 @ref{14e1,,is not} 用于检测对象的标识号：当且仅当 @emph{x} 和 @emph{y} 是同一对象时 @code{x is y} 为真。 一个对象的标识号可使用 @ref{d7f,,id()} 函数来确定。 @code{x is not y} 会产生相反的逻辑值。 @footnote{@w{(4)} 
由于存在自动垃圾收集、空闲列表以及描述器的动态特性，你可能会注意到在特定情况下使用 @ref{13b6,,is} 运算符会出现看似不正常的行为，例如涉及到实例方法或常量之间的比较时就是如此。 更多信息请查看有关它们的文档。
}
@anchor{reference/expressions booleans}@anchor{14e2}@anchor{reference/expressions and}@anchor{14e3}@anchor{reference/expressions or}@anchor{14e4}
@node 布尔运算,赋值表达式<2>,比较运算,表达式
@anchor{reference/expressions boolean-operations}@anchor{14e5}@anchor{reference/expressions not}@anchor{14e6}
@subsection 布尔运算


@geindex Conditional; expression
@geindex Boolean; operation

@example
@anchor{reference/expressions grammar-token-or-test}@anchor{14e7}or_test  ::= and_test | or_test "or" and_test
@anchor{reference/expressions grammar-token-and-test}@anchor{14e8}and_test ::= not_test | and_test "and" not_test
@anchor{reference/expressions grammar-token-not-test}@anchor{14e9}not_test ::= comparison | "not" not_test
@end example

在执行布尔运算的情况下，或是当表达式被用于流程控制语句时，以下值会被解析为假值: @code{False}, @code{None}, 所有类型的数字零，以及空字符串和空容器（包括字符串、元组、列表、字典、集合与冻结集合）。 所有其他值都会被解析为真值。 用户自定义对象可通过提供 @ref{c61,,__bool__()} 方法来定制其逻辑值。

@geindex 运算符; not

运算符 @ref{14e6,,not} 将在其参数为假值时产生 @code{True}，否则产生 @code{False}。

@geindex 运算符; and

表达式 @code{x and y} 首先对 @emph{x} 求值；如果 @emph{x} 为假则返回该值；否则对 @emph{y} 求值并返回其结果值。

@geindex 运算符; or

表达式 @code{x or y} 首先对 @emph{x} 求值；如果 @emph{x} 为真则返回该值；否则对 @emph{y} 求值并返回其结果值。

请注意 @ref{14e3,,and} 和 @ref{14e4,,or} 都不限制其返回的值和类型必须为 @code{False} 和 @code{True}，而是返回最终求值的参数。 此行为是有必要的，例如假设 @code{s} 为一个当其为空时应被替换为某个默认值的字符串，表达式 @code{s or 'foo'} 将产生希望的值。 由于 @ref{14e6,,not} 必须创建一个新值，不论其参数为何种类型它都会返回一个布尔值（例如，@code{not 'foo'} 结果为 @code{False} 而非 @code{'@w{'}}。）

@node 赋值表达式<2>,条件表达式,布尔运算,表达式
@anchor{reference/expressions assignment-expressions}@anchor{14ea}
@subsection 赋值表达式


@example
@anchor{reference/expressions grammar-token-assignment-expression}@anchor{14eb}assignment_expression ::= [identifier ":="] expression
@end example

@c TODO: BPO-39868

请参阅 
@geindex Python 提高建议; PEP 572
PEP 572@footnote{https://www.python.org/dev/peps/pep-0572} 了解有关赋值表达式的详情。

@node 条件表达式,lambda 表达式,赋值表达式<2>,表达式
@anchor{reference/expressions conditional-expressions}@anchor{14ec}@anchor{reference/expressions if-expr}@anchor{14ed}
@subsection 条件表达式


@geindex conditional; expression
@geindex ternary; operator
@geindex if; conditional expression
@geindex else; conditional expression

@example
@anchor{reference/expressions grammar-token-conditional-expression}@anchor{14ee}conditional_expression ::= or_test ["if" or_test "else" expression]
@anchor{reference/expressions grammar-token-expression}@anchor{14ef}expression             ::= conditional_expression | lambda_expr
@anchor{reference/expressions grammar-token-expression-nocond}@anchor{14f0}expression_nocond      ::= or_test | lambda_expr_nocond
@end example

条件表达式（有时称为“三元运算符”）在所有 Python 运算中具有最低的优先级。

表达式 @code{x if C else y} 首先是对条件 @emph{C} 而非 @emph{x} 求值。 如果 @emph{C} 为真，@emph{x} 将被求值并返回其值；否则将对 @emph{y} 求值并返回其值。

请参阅 
@geindex Python 提高建议; PEP 308
PEP 308@footnote{https://www.python.org/dev/peps/pep-0308} 了解有关条件表达式的详情。
@anchor{reference/expressions lambdas}@anchor{14f1}
@node lambda 表达式,表达式列表,条件表达式,表达式
@anchor{reference/expressions id14}@anchor{14f2}@anchor{reference/expressions lambda}@anchor{c28}
@subsection lambda 表达式


@geindex lambda; expression
@geindex lambda; form
@geindex anonymous; function
@geindex ; (colon); lambda expression

@example
@anchor{reference/expressions grammar-token-lambda-expr}@anchor{14f3}lambda_expr        ::= "lambda" [parameter_list] ":" expression
@anchor{reference/expressions grammar-token-lambda-expr-nocond}@anchor{14f4}lambda_expr_nocond ::= "lambda" [parameter_list] ":" expression_nocond
@end example

lambda 表达式（有时称为 lambda 构型）被用于创建匿名函数。 表达式 @code{lambda parameters: expression} 会产生一个函数对象 。 该未命名对象的行为类似于用以下方式定义的函数:

@example
def <lambda>(parameters):
    return expression
@end example

请参阅 @ref{11f0,,函数定义} 了解有关参数列表的句法。 请注意通过 lambda 表达式创建的函数不能包含语句或标注。

@node 表达式列表,求值顺序,lambda 表达式,表达式
@anchor{reference/expressions expression-lists}@anchor{14f5}@anchor{reference/expressions exprlists}@anchor{647}
@subsection 表达式列表


@geindex expression; list
@geindex @comma{} (comma); expression list

@example
@anchor{reference/expressions grammar-token-expression-list}@anchor{149e}expression_list    ::= expression ("," expression)* [","]
@anchor{reference/expressions grammar-token-starred-list}@anchor{14f6}starred_list       ::= starred_item ("," starred_item)* [","]
@anchor{reference/expressions grammar-token-starred-expression}@anchor{14f7}starred_expression ::= expression | (starred_item ",")* [starred_item]
@anchor{reference/expressions grammar-token-starred-item}@anchor{14f8}starred_item       ::= assignment_expression | "*" or_expr
@end example

@geindex 对象; tuple

除了作为列表或集合显示的一部分，包含至少一个逗号的表达式列表将生成一个元组。 元组的长度就是列表中表达式的数量。 表达式将从左至右被求值。

@geindex iterable; unpacking
@geindex * (asterisk); in expression lists

一个星号 @code{*} 表示 @emph{可迭代拆包}。 其操作数必须为一个 @ref{ba5,,iterable}。 该可迭代对象将被拆解为迭代项的序列，并被包含于在拆包位置上新建的元组、列表或集合之中。


3.5 新版功能: 表达式列表中的可迭代对象拆包，最初由 
@geindex Python 提高建议; PEP 448
PEP 448@footnote{https://www.python.org/dev/peps/pep-0448} 提出。


@geindex trailing; comma

末尾的逗号仅在创建单独元组 (或称 @emph{单例}) 时需要；在所有其他情况下都是可选项。 没有末尾逗号的单独表达式不会创建一个元组，而是产生该表达式的值。 （要创建一个空元组，应使用一对内容为空的圆括号: @code{()}。）

@node 求值顺序,运算符优先级,表达式列表,表达式
@anchor{reference/expressions evalorder}@anchor{14f9}@anchor{reference/expressions evaluation-order}@anchor{14fa}
@subsection 求值顺序


@geindex evaluation; order

Python 按从左至右的顺序对表达式求值。 但注意在对赋值操作求值时，右侧会先于左侧被求值。

在以下几行中，表达式将按其后缀的算术优先顺序被求值。:

@example
expr1, expr2, expr3, expr4
(expr1, expr2, expr3, expr4)
@{expr1: expr2, expr3: expr4@}
expr1 + expr2 * (expr3 - expr4)
expr1(expr2, expr3, *expr4, **expr5)
expr3, expr4 = expr1, expr2
@end example

@node 运算符优先级,,求值顺序,表达式
@anchor{reference/expressions operator-precedence}@anchor{14fb}@anchor{reference/expressions operator-summary}@anchor{14fc}
@subsection 运算符优先级


@geindex operator; precedence

下表对 Python 中运算符的优先顺序进行了总结，从最低优先级（最后绑定）到最高优先级（最先绑定）。 相同单元格内的运算符具有相同优先级。 除非句法显式地给出，否则运算符均指二元运算。 相同单元格内的运算符均从左至右分组（除了幂运算是从右至左分组）。

请注意比较、成员检测和标识号检测均为相同优先级，并具有如 @ref{14da,,比较运算} 一节所描述的从左至右串连特性。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算符

@tab

描述

@item

@code{:=}

@tab

赋值表达式

@item

@ref{c28,,lambda}

@tab

lambda 表达式

@item

@ref{14ed,,if} -- @code{else}

@tab

条件表达式

@item

@ref{14e4,,or}

@tab

布尔逻辑或 OR

@item

@ref{14e3,,and}

@tab

布尔逻辑与 AND

@item

@ref{14e6,,not} @code{x}

@tab

布尔逻辑非 NOT

@item

@ref{79d,,in}, @ref{13f5,,not in},
@ref{13b6,,is}, @ref{14e1,,is not}, @code{<},
@code{<=}, @code{>}, @code{>=}, @code{!=}, @code{==}

@tab

比较运算，包括成员检测和标识号检测

@item

@code{|}

@tab

按位或 OR

@item

@code{^}

@tab

按位异或 XOR

@item

@code{&}

@tab

按位与 AND

@item

@code{<<}, @code{>>}

@tab

移位

@item

@code{+}, @code{-}

@tab

加和减

@item

@code{*}, @code{@@}, @code{/}, @code{//}, @code{%}

@tab

乘，矩阵乘，除，整除，取余 @footnote{@w{(5)} 
@code{%} 运算符也被用于字符串格式化；在此场合下会使用同样的优先级。
}

@item

@code{+x}, @code{-x}, @code{~x}

@tab

正，负，按位非 NOT

@item

@code{**}

@tab

乘方 @footnote{@w{(6)} 
幂运算符 @code{**} 绑定的紧密程度低于在其右侧的算术或按位一元运算符，也就是说 @code{2**-1} 为 @code{0.5}。
}

@item

@ref{1a3,,await} @code{x}

@tab

await 表达式

@item

@code{x[index]}, @code{x[index:index]},
@code{x(arguments...)}, @code{x.attribute}

@tab

抽取，切片，调用，属性引用

@item

@code{(expressions...)},

@code{[expressions...]},
@code{@{key: value...@}},
@code{@{expressions...@}}

@tab

绑定或加圆括号的表达式，列表显示，字典显示，集合显示

@end multitable


@subsubheading 备注


@node 简单语句,复合语句,表达式,Python语言参考
@anchor{reference/simple_stmts doc}@anchor{14fd}@anchor{reference/simple_stmts simple}@anchor{14fe}@anchor{reference/simple_stmts simple-statements}@anchor{14ff}
@section 简单语句


@geindex simple; statement

简单语句由一个单独的逻辑行构成。 多条简单语句可以存在于同一行内并以分号分隔。 简单语句的句法为:

@example
@anchor{reference/simple_stmts grammar-token-simple-stmt}@anchor{1500}simple_stmt ::= expression_stmt
                | assert_stmt
                | assignment_stmt
                | augmented_assignment_stmt
                | annotated_assignment_stmt
                | pass_stmt
                | del_stmt
                | return_stmt
                | yield_stmt
                | raise_stmt
                | break_stmt
                | continue_stmt
                | import_stmt
                | future_stmt
                | global_stmt
                | nonlocal_stmt
@end example

@menu
* 表达式语句:: 
* 赋值语句:: 
* assert 语句:: 
* pass 语句: pass 语句<2>. 
* del 语句: del 语句<2>. 
* return 语句:: 
* yield 语句:: 
* raise 语句:: 
* break 语句:: 
* continue 语句:: 
* import 语句:: 
* global 语句:: 
* nonlocal 语句:: 

@end menu

@node 表达式语句,赋值语句,,简单语句
@anchor{reference/simple_stmts expression-statements}@anchor{1501}@anchor{reference/simple_stmts exprstmts}@anchor{1502}
@subsection 表达式语句


@geindex expression; statement
@geindex expression; list

@geindex expression; list

表达式语句用于计算和写入值（大多是在交互模式下），或者（通常情况）调用一个过程 (过程就是不返回有意义结果的函数；在 Python 中，过程的返回值为 @code{None})。 表达式语句的其他使用方式也是允许且有特定用处的。 表达式语句的句法为:

@example
@anchor{reference/simple_stmts grammar-token-expression-stmt}@anchor{1503}expression_stmt ::= starred_expression
@end example

表达式语句会对指定的表达式列表（也可能为单一表达式）进行求值。

@geindex 內置函数; repr
@geindex 对象; None
@geindex string; conversion
@geindex output
@geindex standard; output
@geindex writing; values
@geindex procedure; call

在交互模式下，如果结果值不为 @code{None}，它会通过内置的 @ref{7c6,,repr()} 函数转换为一个字符串，该结果字符串将以单独一行的形式写入标准输出（例外情况是如果结果为 @code{None}，则该过程调用不产生任何输出。）

@node 赋值语句,assert 语句,表达式语句,简单语句
@anchor{reference/simple_stmts assignment}@anchor{1504}@anchor{reference/simple_stmts assignment-statements}@anchor{1505}
@subsection 赋值语句


@geindex = (equals); assignment statement
@geindex assignment; statement
@geindex binding; name
@geindex rebinding; name
@geindex 对象; mutable
@geindex attribute; assignment

赋值语句用于将名称（重）绑定到特定值，以及修改属性或可变对象的成员项:

@example
@anchor{reference/simple_stmts grammar-token-assignment-stmt}@anchor{1506}assignment_stmt ::= (target_list "=")+ (starred_expression | yield_expression)
@anchor{reference/simple_stmts grammar-token-target-list}@anchor{1507}target_list     ::= target ("," target)* [","]
@anchor{reference/simple_stmts grammar-token-target}@anchor{1508}target          ::= identifier
                    | "(" [target_list] ")"
                    | "[" [target_list] "]"
                    | attributeref
                    | subscription
                    | slicing
                    | "*" target
@end example

(请参阅 @ref{14a9,,原型} 一节了解 @emph{属性引用}, @emph{抽取} 和 @emph{切片} 的句法定义。)

赋值语句会对指定的表达式列表进行求值（注意这可能为单一表达式或是由逗号分隔的列表，后者将产生一个元组）并将单一结果对象从左至右逐个赋值给目标列表。

@geindex target
@geindex target; list

赋值是根据目标（列表）的格式递归地定义的。 当目标为一个可变对象（属性引用、抽取或切片）的组成部分时，该可变对象必须最终执行赋值并决定其有效性，如果赋值操作不可接受也可能引发异常。 各种类型可用的规则和引发的异常通过对象类型的定义给出（参见 @ref{13b8,,标准类型层级结构} 一节）。

@geindex target; list; assignment
@geindex @comma{} (comma); in target list
@geindex * (asterisk); in assignment target list
@geindex [] (square brackets); in assignment target list
@geindex () (parentheses); in assignment target list

对象赋值的目标对象可以包含于圆括号或方括号内，具体操作按以下方式递归地定义。


@itemize *

@item 
如果目标列表为后面不带逗号、可以包含于圆括号内的单一目标，则将对象赋值给该目标。

@item 
否则：该对象必须为具有与目标列表相同项数的可迭代对象，这些项将按从左至右的顺序被赋值给对应的目标。


@itemize *

@item 
如果目标列表包含一个带有星号前缀的目标，这称为“加星”目标：则该对象至少必须为与目标列表项数减一相同项数的可迭代对象。 该可迭代对象前面的项将按从左至右的顺序被赋值给加星目标之前的目标。 该可迭代对象末尾的项将被赋值给加星目标之后的目标。 然后该可迭代对象中剩余项的列表将被赋值给加星目标（该列表可以为空）。

@item 
否则：该对象必须为具有与目标列表相同项数的可迭代对象，这些项将按从左至右的顺序被赋值给对应的目标。
@end itemize
@end itemize

对象赋值给单个目标的操作按以下方式递归地定义。


@itemize *

@item 
如果目标为标识符（名称）:


@itemize *

@item 
如果该名称未出现于当前代码块的 @ref{11d8,,global} 或 @ref{c38,,nonlocal} 语句中：该名称将被绑定到当前局部命名空间的对象。

@item 
否则：该名称将被分别绑定到全局命名空间或由 @ref{c38,,nonlocal} 所确定的外层命名空间的对象。
@end itemize

@geindex destructor

如果该名称已经被绑定则将被重新绑定。 这可能导致之前被绑定到该名称的对象的引用计数变为零，造成该对象进入释放过程并调用其析构器（如果存在）。

@geindex attribute; assignment

@item 
如果该对象为属性引用：引用中的原型表达式会被求值。 它应该产生一个具有可赋值属性的对象；否则将引发 @ref{192,,TypeError}。 该对象会被要求将可赋值对象赋值给指定的属性；如果它无法执行赋值，则会引发异常 (通常应为 @ref{393,,AttributeError} 但并不强制要求)。
@anchor{reference/simple_stmts attr-target-note}@anchor{1509}
注意：如果该对象为类实例并且属性引用在赋值运算符的两侧都出现，则右侧表达式 @code{a.x} 可以访问实例属性或（如果实例属性不存在）类属性。 左侧目标 @code{a.x} 将总是设定为实例属性，并在必要时创建该实例属性。 因此 @code{a.x} 的两次出现不一定指向相同的属性：如果右侧表达式指向一个类属性，则左侧会创建一个新的实例属性作为赋值的目标:

@example
class Cls:
    x = 3             # class variable
inst = Cls()
inst.x = inst.x + 1   # writes inst.x as 4 leaving Cls.x as 3
@end example

此描述不一定作用于描述器属性，例如通过 @ref{1d7,,property()} 创建的特征属性。

@geindex subscription; assignment
@geindex 对象; mutable

@item 
如果目标为一个抽取项：引用中的原型表达式会被求值。 它应当产生一个可变序列对象（例如列表）或一个映射对象（例如字典）。 接下来，该抽取表达式会被求值。

@geindex 对象; sequence
@geindex 对象; list

如果原型为一个可变序列对象（例如列表），抽取应产生一个整数。 如其为负值，则再加上序列长度。 结果值必须为一个小于序列长度的非负整数，序列将把被赋值对象赋值给该整数指定索引号的项。 如果索引超出范围，将会引发 @ref{e6e,,IndexError} (给被抽取序列赋值不能向列表添加新项)。

@geindex 对象; mapping
@geindex 对象; dictionary

如果原型为一个映射对象（例如字典），抽取必须具有与该映射的键类型相兼容的类型，然后映射中会创建一个将抽取映射到被赋值对象的键/值对。 这可以是替换一个现有键/值对并保持相同键值，也可以是插入一个新键/值对（如果具有相同值的键不存在）。

对于用户定义对象，会调用 @ref{c5b,,__setitem__()} 方法并附带适当的参数。

@geindex slicing; assignment

@item 
如果目标为一个切片：引用中的原型表达式会被求值。 它应当产生一个可变序列对象（例如列表）。 被赋值对象应当是一个相同类型的序列对象。 接下来，下界与上界表达式如果存在的话将被求值；默认值分别为零和序列长度。 上下边界值应当为整数。 如果某一边界为负值，则会加上序列长度。 求出的边界会被裁剪至介于零和序列长度的开区间中。 最后，将要求序列对象以被赋值序列的项替换该切片。 切片的长度可能与被赋值序列的长度不同，这会在目标序列允许的情况下改变目标序列的长度。
@end itemize

@strong{CPython implementation detail:} 在当前实现中，目标的句法被当作与表达式的句法相同，无效的句法会在代码生成阶段被拒绝，导致不太详细的错误信息。

虽然赋值的定义意味着左手边与右手边的重叠是“同时”进行的（例如 @code{a, b = b, a} 会交换两个变量的值），但在赋值给变量的多项集 @emph{之内} 的重叠是从左至右进行的，这有时会令人混淆。 例如，以下程序将会打印出 @code{[0, 2]}:

@example
x = [0, 1]
i = 0
i, x[i] = 1, 2         # i is updated, then x[i] is updated
print(x)
@end example


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3132

@item PEP 3132@footnote{https://www.python.org/dev/peps/pep-3132} - 扩展的可迭代对象拆包

对 @code{*target} 特性的规范说明。
@end table


@menu
* 增强赋值语句:: 
* 带标注的赋值语句:: 

@end menu

@node 增强赋值语句,带标注的赋值语句,,赋值语句
@anchor{reference/simple_stmts augassign}@anchor{150a}@anchor{reference/simple_stmts augmented-assignment-statements}@anchor{150b}
@subsubsection 增强赋值语句


@geindex augmented; assignment
@geindex statement; assignment@comma{} augmented
@geindex +=; augmented assignment
@geindex -=; augmented assignment
@geindex *=; augmented assignment
@geindex /=; augmented assignment
@geindex %=; augmented assignment
@geindex &=; augmented assignment
@geindex ^=; augmented assignment
@geindex |=; augmented assignment
@geindex **=; augmented assignment
@geindex //=; augmented assignment
@geindex >>=; augmented assignment
@geindex <<=; augmented assignment

增强赋值语句就是在单个语句中将二元运算和赋值语句合为一体:

@example
@anchor{reference/simple_stmts grammar-token-augmented-assignment-stmt}@anchor{150c}augmented_assignment_stmt ::= augtarget augop (expression_list | yield_expression)
@anchor{reference/simple_stmts grammar-token-augtarget}@anchor{150d}augtarget                 ::= identifier | attributeref | subscription | slicing
@anchor{reference/simple_stmts grammar-token-augop}@anchor{150e}augop                     ::= "+=" | "-=" | "*=" | "@@=" | "/=" | "//=" | "%=" | "**="
                              | ">>=" | "<<=" | "&=" | "^=" | "|="
@end example

（请参阅 @ref{14a9,,原型} 一节了解最后三种符号的句法定义。）

增强赋值语句将对目标和表达式列表求值（与普通赋值语句不同的是，前者不能为可迭代对象拆包），对两个操作数相应类型的赋值执行指定的二元运算，并将结果赋值给原始目标。 目标仅会被求值一次。

增强赋值语句例如 @code{x += 1} 可以改写为 @code{x = x + 1} 获得类似但并非完全等价的效果。 在增强赋值的版本中，@code{x} 仅会被求值一次。 而且，在可能的情况下，实际的运算是 @emph{原地} 执行的，也就是说并不是创建一个新对象并将其赋值给目标，而是直接修改原对象。

不同于普通赋值，增强赋值会在对右手边求值 @emph{之前} 对左手边求值。 例如，@code{a[i] += f(x)} 首先查找 @code{a[i]}，然后对 @code{f(x)} 求值并执行加法操作，最后将结果写回到 @code{a[i]}。

除了在单个语句中赋值给元组和多个目标的例外情况，增强赋值语句的赋值操作处理方式与普通赋值相同。 类似地，除了可能存在 @emph{原地} 操作行为的例外情况，增强赋值语句执行的二元运算也与普通二元运算相同。

对于属性引用类目标，针对常规赋值的 @ref{1509,,关于类和实例属性的警告} 也同样适用。

@node 带标注的赋值语句,,增强赋值语句,赋值语句
@anchor{reference/simple_stmts annassign}@anchor{150f}@anchor{reference/simple_stmts annotated-assignment-statements}@anchor{1510}
@subsubsection 带标注的赋值语句


@geindex annotated; assignment
@geindex statement; assignment@comma{} annotated
@geindex ; (colon); annotated variable

@ref{61a,,标注} 赋值就是在单个语句中将变量或属性标注和可选的赋值语句合为一体:

@example
@anchor{reference/simple_stmts grammar-token-annotated-assignment-stmt}@anchor{1511}annotated_assignment_stmt ::= augtarget ":" expression
                              ["=" (starred_expression | yield_expression)]
@end example

与普通 @ref{1504,,赋值语句} 的差别在于仅允许单个目标。

对于将简单名称作为赋值目标的情况，如果是在类或模块作用域中，标注会被求值并存入一个特殊的类或模块属性 @code{__annotations__} 中，这是一个将变量名称（如为私有会被移除）映射到被求值标注的字典。 此属性为可写并且在类或模块体开始执行时如果静态地发现标注就会自动创建。

对于将表达式作为赋值目标的情况，如果是在类或模块作用域中，标注会被求值，但不会保存。

如果一个名称在函数作用域内被标注，则该名称为该作用域的局部变量。 标注绝不会在函数作用域内被求值和保存。

如果存在右手边，带标注的赋值会在对标注求值之前（如果适用）执行实际的赋值。 如果用作表达式目标的右手边不存在，则解释器会对目标求值，但最后的 @ref{c5b,,__setitem__()} 或 @ref{e25,,__setattr__()} 调用除外。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 526

@item PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} - 变量标注的语法

该提议增加了标注变量（也包括类变量和实例变量）类型的语法，而不再是通过注释来进行表达。

@geindex Python 提高建议; PEP 484

@item PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} - 类型提示

该提议增加了 @ref{119,,typing} 模块以便为类型标注提供标准句法，可被静态分析工具和 IDE 所使用。
@end table



在 3.8 版更改: 现在带有标注的赋值允许在右边以同样的表达式作为常规赋值。 之前，某些表达式（例如未加圆括号的元组表达式）会导致语法错误。


@node assert 语句,pass 语句<2>,赋值语句,简单语句
@anchor{reference/simple_stmts assert}@anchor{dff}@anchor{reference/simple_stmts the-assert-statement}@anchor{1512}
@subsection @code{assert} 语句


@geindex 语句; assert
@geindex debugging; assertions
@geindex @comma{} (comma); expression list

assert 语句是在程序中插入调试性断言的简便方式:

@example
@anchor{reference/simple_stmts grammar-token-assert-stmt}@anchor{1513}assert_stmt ::= "assert" expression ["," expression]
@end example

简单形式 @code{assert expression} 等价于

@example
if __debug__:
    if not expression: raise AssertionError
@end example

扩展形式 @code{assert expression1, expression2} 等价于

@example
if __debug__:
    if not expression1: raise AssertionError(expression2)
@end example

@geindex __debug__
@geindex 例外; AssertionError

以上等价形式假定 @ref{f8d,,__debug__} 和 @ref{fc1,,AssertionError} 指向具有指定名称的内置变量。 在当前实现中，内置变量 @ref{f8d,,__debug__} 在正常情况下为 @code{True}，在请求优化时为 @code{False} (对应命令行选项为 @ref{685,,-O})。 如果在编译时请求优化，当前代码生成器不会为 assert 语句发出任何代码。 请注意不必在错误信息中包含失败表达式的源代码；它会被作为栈追踪的一部分被显示。

赋值给 @ref{f8d,,__debug__} 是非法的。 该内置变量的值会在解释器启动时确定。

@node pass 语句<2>,del 语句<2>,assert 语句,简单语句
@anchor{reference/simple_stmts pass}@anchor{11d4}@anchor{reference/simple_stmts the-pass-statement}@anchor{1514}
@subsection @code{pass} 语句


@geindex 语句; pass
@geindex null; operation
@geindex null; operation

@example
@anchor{reference/simple_stmts grammar-token-pass-stmt}@anchor{1515}pass_stmt ::= "pass"
@end example

@ref{11d4,,pass} 是一个空操作 --- 当它被执行时，什么都不发生。 它适合当语法上需要一条语句但并不需要执行任何代码时用来临时占位，例如:

@example
def f(arg): pass    # a function that does nothing (yet)

class C: pass       # a class with no methods (yet)
@end example

@node del 语句<2>,return 语句,pass 语句<2>,简单语句
@anchor{reference/simple_stmts del}@anchor{1202}@anchor{reference/simple_stmts the-del-statement}@anchor{1516}
@subsection @code{del} 语句


@geindex 语句; del
@geindex deletion; target
@geindex deletion; target; list

@example
@anchor{reference/simple_stmts grammar-token-del-stmt}@anchor{1517}del_stmt ::= "del" target_list
@end example

删除是递归定义的，与赋值的定义方式非常类似。 此处不再详细说明，只给出一些提示。

目标列表的删除将从左至右递归地删除每一个目标。

@geindex 语句; global
@geindex unbinding; name

名称的删除将从局部或全局命名空间中移除该名称的绑定，具体作用域的确定是看该名称是否有在同一代码块的 @ref{11d8,,global} 语句中出现。 如果该名称未被绑定，将会引发 @ref{d74,,NameError}。

@geindex attribute; deletion

属性引用、抽取和切片的删除会被传递给相应的原型对象；删除一个切片基本等价于赋值为一个右侧类型的空切片（但即便这一点也是由切片对象决定的）。


在 3.2 版更改: 在之前版本中，如果一个名称作为被嵌套代码块中的自由变量出现，则将其从局部命名空间中删除是非法的。


@node return 语句,yield 语句,del 语句<2>,简单语句
@anchor{reference/simple_stmts return}@anchor{190}@anchor{reference/simple_stmts the-return-statement}@anchor{1518}
@subsection @code{return} 语句


@geindex 语句; return
@geindex function; definition
@geindex class; definition

@example
@anchor{reference/simple_stmts grammar-token-return-stmt}@anchor{1519}return_stmt ::= "return" [expression_list]
@end example

@ref{190,,return} 在语法上只会出现于函数定义所嵌套的代码，不会出现于类定义所嵌套的代码。

如果提供了表达式列表，它将被求值，否则以 @code{None} 替代。

@ref{190,,return} 会离开当前函数调用，并以表达式列表 (或 @code{None}) 作为返回值。

@geindex 关键字; finally

当 @ref{190,,return} 将控制流传出一个带有 @ref{182,,finally} 子句的 @ref{d6b,,try} 语句时，该 @code{finally} 子句会先被执行然后再真正离开该函数。

在一个生成器函数中，@ref{190,,return} 语句表示生成器已完成并将导致 @ref{480,,StopIteration} 被引发。 返回值（如果有的话）会被当作一个参数用来构建 @ref{480,,StopIteration} 并成为 @code{StopIteration.value} 属性。

在一个异步生成器函数中，一个空的 @ref{190,,return} 语句表示异步生成器已完成并将导致 @ref{fa5,,StopAsyncIteration} 被引发。 一个非空的 @code{return} 语句在异步生成器函数中会导致语法错误。

@node yield 语句,raise 语句,return 语句,简单语句
@anchor{reference/simple_stmts the-yield-statement}@anchor{151a}@anchor{reference/simple_stmts yield}@anchor{18f}
@subsection @code{yield} 语句


@geindex 语句; yield
@geindex generator; function
@geindex generator; iterator
@geindex function; generator
@geindex 例外; StopIteration

@example
@anchor{reference/simple_stmts grammar-token-yield-stmt}@anchor{151b}yield_stmt ::= yield_expression
@end example

@ref{18f,,yield} 语句在语义上等同于 @ref{1499,,yield 表达式}。 yield 语句可用来省略在使用等效的 yield 表达式语句时所必须的圆括号。 例如，以下 yield 语句

@example
yield <expr>
yield from <expr>
@end example

等同于以下 yield 表达式语句

@example
(yield <expr>)
(yield from <expr>)
@end example

yield 表达式和语句仅在定义 @ref{99c,,generator} 函数时使用，并且仅被用于生成器函数的函数体内部。 在函数定义中使用 yield 就足以使得该定义创建的是生成器函数而非普通函数。

有关 @ref{18f,,yield} 语义的完整细节请参看 @ref{1499,,yield 表达式} 一节。

@node raise 语句,break 语句,yield 语句,简单语句
@anchor{reference/simple_stmts raise}@anchor{c3b}@anchor{reference/simple_stmts the-raise-statement}@anchor{151c}
@subsection @code{raise} 语句


@geindex 语句; raise
@geindex exception
@geindex raising; exception
@geindex __traceback__ (exception attribute)

@example
@anchor{reference/simple_stmts grammar-token-raise-stmt}@anchor{151d}raise_stmt ::= "raise" [expression ["from" expression]]
@end example

如果不带表达式，@ref{c3b,,raise} 会重新引发当前作用域内最后一个激活的异常。 如果当前作用域内没有激活的异常，将会引发 @ref{2ba,,RuntimeError} 来提示错误。

否则的话，@ref{c3b,,raise} 会将第一个表达式求值为异常对象。 它必须为 @ref{1a8,,BaseException} 的子类或实例。 如果它是一个类，当需要时会通过不带参数地实例化该类来获得异常的实例。

异常的 @emph{类型} 为异常实例的类，@emph{值} 为实例本身。

@geindex 对象; traceback

当异常被引发时通常会自动创建一个回溯对象并将其关联到可写的 @code{__traceback__} 属性。 你可以创建一个异常并同时使用 @code{with_traceback()} 异常方法（该方法将返回同一异常实例，并将回溯对象设为其参数）设置自己的回溯，就像这样:

@example
raise Exception("foo occurred").with_traceback(tracebackobj)
@end example

@geindex exception; chaining
@geindex __cause__ (exception attribute)
@geindex __context__ (exception attribute)

@code{from} 子句用于异常串连：如果有该子句，则第二个 @emph{表达式} 必须为另一个异常或实例，它将作为可写的 @code{__cause__} 属性被关联到所引发的异常。 如果引发的异常未被处理，两个异常都将被打印出来:

@example
>>> try:
...     print(1 / 0)
... except Exception as exc:
...     raise RuntimeError("Something bad happened") from exc
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
ZeroDivisionError: division by zero

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
RuntimeError: Something bad happened
@end example

如果一个异常在异常处理器或 @ref{182,,finally} clause: 中被引发，类似的机制会隐式地发挥作用，之前的异常将被关联到新异常的 @code{__context__} 属性:

@example
>>> try:
...     print(1 / 0)
... except:
...     raise RuntimeError("Something bad happened")
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
ZeroDivisionError: division by zero

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
RuntimeError: Something bad happened
@end example

异常串连可通过在 @code{from} 子句中指定 @ref{157,,None} 来显式地加以抑制:

@example
>>> try:
...     print(1 / 0)
... except:
...     raise RuntimeError("Something bad happened") from None
...
Traceback (most recent call last):
  File "<stdin>", line 4, in <module>
RuntimeError: Something bad happened
@end example

有关异常的更多信息可在 @ref{1441,,异常} 一节查看，有关处理异常的信息可在 @ref{d6b,,try 语句} 一节查看。


在 3.3 版更改: @ref{157,,None} 现在允许被用作 @code{raise X from Y} 中的 @code{Y}。



3.3 新版功能: 使用 @code{__suppress_context__} 属性来抑制异常上下文的自动显示。


@node break 语句,continue 语句,raise 语句,简单语句
@anchor{reference/simple_stmts break}@anchor{2db}@anchor{reference/simple_stmts the-break-statement}@anchor{151e}
@subsection @code{break} 语句


@geindex 语句; break
@geindex 语句; for
@geindex 语句; while
@geindex loop; statement

@example
@anchor{reference/simple_stmts grammar-token-break-stmt}@anchor{151f}break_stmt ::= "break"
@end example

@ref{2db,,break} 在语法上只会出现于 @ref{c29,,for} 或 @ref{11c1,,while} 循环所嵌套的代码，但不会出现于该循环内部的函数或类定义所嵌套的代码。

@geindex 关键字; else
@geindex loop control; target

它会终结最近的外层循环，如果循环有可选的 @code{else} 子句，也会跳过该子句。

如果一个 @ref{c29,,for} 循环被 @ref{2db,,break} 所终结，该循环的控制目标会保持其当前值。

@geindex 关键字; finally

当 @ref{2db,,break} 将控制流传出一个带有 @ref{182,,finally} 子句的 @ref{d6b,,try} 语句时，该 @code{finally} 子句会先被执行然后再真正离开该循环。

@node continue 语句,import 语句,break 语句,简单语句
@anchor{reference/simple_stmts continue}@anchor{181}@anchor{reference/simple_stmts the-continue-statement}@anchor{1520}
@subsection @code{continue} 语句


@geindex 语句; continue
@geindex 语句; for
@geindex 语句; while
@geindex loop; statement
@geindex 关键字; finally

@example
@anchor{reference/simple_stmts grammar-token-continue-stmt}@anchor{1521}continue_stmt ::= "continue"
@end example

@ref{181,,continue} 在语法上只会出现于 @ref{c29,,for} 或 @ref{11c1,,while} 循环所嵌套的代码中，但不会出现于该循环内部的函数或类定义中。 它会继续执行最近的外层循环的下一个轮次。

当 @ref{181,,continue} 将控制流传出一个带有 @ref{182,,finally} 子句的 @ref{d6b,,try} 语句时，该 @code{finally} 子句会先被执行然后再真正开始循环的下一个轮次。
@anchor{reference/simple_stmts import}@anchor{c16}
@node import 语句,global 语句,continue 语句,简单语句
@anchor{reference/simple_stmts from}@anchor{c3e}@anchor{reference/simple_stmts the-import-statement}@anchor{1522}
@subsection @code{import} 语句


@geindex 语句; import
@geindex module; importing
@geindex name; binding
@geindex 关键字; from
@geindex 关键字; as
@geindex 例外; ImportError
@geindex @comma{} (comma); import statement

@example
@anchor{reference/simple_stmts grammar-token-import-stmt}@anchor{1523}import_stmt     ::= "import" module ["as" identifier] ("," module ["as" identifier])*
                    | "from" relative_module "import" identifier ["as" identifier]
                    ("," identifier ["as" identifier])*
                    | "from" relative_module "import" "(" identifier ["as" identifier]
                    ("," identifier ["as" identifier])* [","] ")"
                    | "from" module "import" "*"
@anchor{reference/simple_stmts grammar-token-module}@anchor{1524}module          ::= (identifier ".")* identifier
@anchor{reference/simple_stmts grammar-token-relative-module}@anchor{1525}relative_module ::= "."* module | "."+
@end example

基本的 import 语句（不带 @ref{c3e,,from} 子句）会分两步执行:


@enumerate 

@item 
查找一个模块，如果有必要还会加载并初始化模块。

@item 
在局部命名空间中为 @ref{c16,,import} 语句发生位置所处的作用域定义一个或多个名称。
@end enumerate

当语句包含多个子句（由逗号分隔）时这两个步骤将对每个子句分别执行，如同这些子句被分成独立的 import 语句一样。

第一个步骤即查找和加载模块的详情 @ref{13c6,,导入系统} 一节中有更详细的描述，其中也描述了可被导入的多种类型的包和模块，以及可用于定制导入系统的所有钩子对象。 请注意这一步如果失败，则可能说明模块无法找到，@emph{或者} 是在初始化模块，包括执行模块代码期间发生了错误。

如果成功获取到请求的模块，则可以通过以下三种方式一之在局部命名空间中使用它:

@geindex as; import statement


@itemize *

@item 
如果模块名称之后带有 @code{as}，则跟在 @code{as} 之后的名称将直接绑定到所导入的模块。

@item 
如果没有指定其他名称，且被导入的模块为最高层级模块，则模块的名称将被绑定到局部命名空间作为对所导入模块的引用。

@item 
如果被导入的模块 @emph{不是} 最高层级模块，则包含该模块的最高层级包的名称将被绑定到局部命名空间作为对该最高层级包的引用。 所导入的模块必须使用其完整限定名称来访问而不能直接访问。
@end itemize

@geindex name; binding
@geindex from; import statement

@ref{c3e,,from} 形式使用的过程略微繁复一些:


@enumerate 

@item 
查找 @ref{c3e,,from} 子句中指定的模块，如有必要还会加载并初始化模块；

@item 
对于 @ref{c16,,import} 子句中指定的每个标识符：


@enumerate 

@item 
检查被导入模块是否有该名称的属性

@item 
如果没有，尝试导入具有该名称的子模块，然后再次检查被导入模块是否有该属性

@item 
如果未找到该属性，则引发 @ref{32d,,ImportError}。

@item 
否则的话，将对该值的引用存入局部命名空间，如果有 @code{as} 子句则使用其指定的名称，否则使用该属性的名称
@end enumerate
@end enumerate

示例:

@example
import foo                 # foo imported and bound locally
import foo.bar.baz         # foo.bar.baz imported, foo bound locally
import foo.bar.baz as fbb  # foo.bar.baz imported and bound as fbb
from foo.bar import baz    # foo.bar.baz imported and bound as baz
from foo import attr       # foo imported and foo.attr bound as attr
@end example

@geindex * (asterisk); import statement

如果标识符列表改为一个星号 (@code{'*'})，则在模块中定义的全部公有名称都将按 @ref{c16,,import} 语句所在的作用域被绑定到局部命名空间。

@geindex __all__ (optional module attribute)

一个模块所定义的 @emph{公有名称} 是由在模块的命名空间中检测一个名为 @code{__all__} 的变量来确定的；如果有定义，它必须是一个字符串列表，其中的项为该模块所定义或导入的名称。 在 @code{__all__} 中所给出的名称都会被视为公有并且应当存在。 如果 @code{__all__} 没有被定义，则公有名称的集合将包含在模块的命名空间中找到的所有不以下划线字符 (@code{'_'}) 打头的名称。 @code{__all__} 应当包括整个公有 API。 它的目标是避免意外地导出不属于 API 的一部分的项（例如在模块内部被导入和使用的库模块）。

通配符形式的导入 --- @code{from module import *} --- 仅在模块层级上被允许。 尝试在类或函数定义中使用它将引发 @ref{452,,SyntaxError}。

@geindex relative; import

当指定要导入哪个模块时，你不必指定模块的绝对名称。 当一个模块或包被包含在另一个包之中时，可以在同一个最高层级包中进行相对导入，而不必提及包名称。 通过在 @ref{c3e,,from} 之后指定的模块或包中使用前缀点号，你可以在不指定确切名称的情况下指明在当前包层级结构中要上溯多少级。 一个前缀点号表示是执行导入的模块所在的当前包，两个点号表示上溯一个包层级。 三个点号表示上溯两级，依此类推。 因此如果你执行 @code{from . import mod} 时所处位置为 @code{pkg} 包内的一个模块，则最终你将导入 @code{pkg.mod}。 如果你执行 @code{from ..subpkg2 import mod} 时所处位置为 @code{pkg.subpkg1} 则你将导入 @code{pkg.subpkg2.mod}。 有关相对导入的规范说明包含在 @ref{146e,,包相对导入} 一节中。

@ref{b0c,,importlib.import_module()} 被提供用来为动态地确定要导入模块的应用提供支持。

引发一个 @ref{12d0,,审计事件} @code{import} 附带参数 @code{module}, @code{filename}, @code{sys.path}, @code{sys.meta_path}, @code{sys.path_hooks}。

@menu
* future 语句:: 

@end menu

@node future 语句,,,import 语句
@anchor{reference/simple_stmts future}@anchor{1526}@anchor{reference/simple_stmts future-statements}@anchor{1527}
@subsubsection future 语句


@geindex future; statement
@geindex __future__; future statement

@emph{future 语句} 是一种针对编译器的指令，指明某个特定模块应当使用在特定的未来某个 Python 发行版中成为标准特性的语法或语义。

future 语句的目的是使得向在语言中引入了不兼容改变的 Python 未来版本的迁移更为容易。 它允许基于每个模块在某种新特性成为标准之前的发行版中使用该特性。

@example
@anchor{reference/simple_stmts grammar-token-future-stmt}@anchor{1528}future_stmt ::= "from" "__future__" "import" feature ["as" identifier]
                ("," feature ["as" identifier])*
                | "from" "__future__" "import" "(" feature ["as" identifier]
                ("," feature ["as" identifier])* [","] ")"
@anchor{reference/simple_stmts grammar-token-feature}@anchor{1529}feature     ::= identifier
@end example

future 语句必须在靠近模块开头的位置出现。 可以出现在 future 语句之前行只有:


@itemize *

@item 
模块的文档字符串（如果存在），

@item 
注释，

@item 
空行，以及

@item 
其他 future 语句。
@end itemize

在 Python 3.7 中唯一需要使用 future 语句的特性是 @code{标注}。

future 语句所启用的所有历史特性仍然为 Python 3 所认可。  其中包括 @code{absolute_import}, @code{division}, @code{generators}, @code{generator_stop}, @code{unicode_literals}, @code{print_function}, @code{nested_scopes} 和 @code{with_statement}。 它们都已成为冗余项，因为它们总是为已启用状态，保留它们只是为了向后兼容。

future 语句在编译时会被识别并做特殊对待：对核心构造语义的改变常常是通过生成不同的代码来实现。 新的特性甚至可能会引入新的不兼容语法（例如新的保留字），在这种情况下编译器可能需要以不同的方式来解析模块。 这样的决定不能推迟到运行时方才作出。

对于任何给定的发布版本，编译器要知道哪些特性名称已被定义，如果某个 future 语句包含未知的特性则会引发编译时错误。

直接运行时的语义与任何 import 语句相同：存在一个后文将详细说明的标准模块 @ref{0,,__future__}，它会在执行 future 语句时以通常的方式被导入。

相应的运行时语义取决于 future 语句所启用的指定特性。

请注意以下语句没有任何特别之处:

@example
import __future__ [as name]
@end example

这并非 future 语句；它只是一条没有特殊语义或语法限制的普通 import 语句。

在默认情况下，通过对Code compiled by calls to the 内置函数 @ref{c3d,,exec()} 和 @ref{1b4,,compile()} 的调用所编译的代码如果出现于一个包含有 future 语句的模块 @code{M} 之中，就会使用 future 语句所关联的语法和语义。 此行为可以通过 @ref{1b4,,compile()} 的可选参数加以控制 --- 请参阅该函数的文档以了解详情。

在交互式解释器提示符中键入的 future 语句将在解释器会话此后的交互中有效。 如果一个解释器的启动使用了 @ref{e18,,-i} 选项启动，并传入了一个脚本名称来执行，且该脚本包含 future 语句，它将在交互式会话开始执行脚本之后保持有效。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 236

@item PEP 236@footnote{https://www.python.org/dev/peps/pep-0236} - 回到 __future__

有关 __future__ 机制的最初提议。
@end table


@node global 语句,nonlocal 语句,import 语句,简单语句
@anchor{reference/simple_stmts global}@anchor{11d8}@anchor{reference/simple_stmts the-global-statement}@anchor{152a}
@subsection @code{global} 语句


@geindex 语句; global
@geindex global; name; binding
@geindex @comma{} (comma); identifier list

@example
@anchor{reference/simple_stmts grammar-token-global-stmt}@anchor{152b}global_stmt ::= "global" identifier ("," identifier)*
@end example

@ref{11d8,,global} 语句是作用于整个当前代码块的声明。 它意味着所列出的标识符将被解读为全局变量。 要给全局变量赋值不可能不用到 @code{global} 关键字，不过自由变量也可以指向全局变量而不必声明为全局变量。

在 @ref{11d8,,global} 语句中列出的名称不得在同一代码块内该 @code{global} 语句之前的位置中使用。

在 @ref{11d8,,global} 语句中列出的名称不得被定义为正式形参，不也得出现于 @ref{c29,,for} 循环的控制目标、@ref{c63,,class} 定义、函数定义、@ref{c16,,import} 语句或变量标注之中。

@strong{CPython implementation detail:} 当前的实现并未强制要求所有的上述限制，但程序不应当滥用这样的自由，因为未来的实现可能会改为强制要求，并静默地改变程序的含义。

@geindex 內置函数; exec
@geindex 內置函数; eval
@geindex 內置函数; compile

@strong{程序员注意事项:} @ref{11d8,,global} 是对解析器的指令。 它仅对与 @code{global} 语句同时被解析的代码起作用。 特别地，包含在提供给内置 @ref{c3d,,exec()} 函数字符串或代码对象中的 @code{global} 语句并不会影响 @emph{包含} 该函数调用的代码块，而包含在这种字符串中的代码也不会受到包含该函数调用的代码中的 @code{global} 语句影响。 这同样适用于 @ref{b89,,eval()} 和 @ref{1b4,,compile()} 函数。

@node nonlocal 语句,,global 语句,简单语句
@anchor{reference/simple_stmts nonlocal}@anchor{c38}@anchor{reference/simple_stmts the-nonlocal-statement}@anchor{152c}
@subsection @code{nonlocal} 语句


@geindex 语句; nonlocal
@geindex @comma{} (comma); identifier list

@example
@anchor{reference/simple_stmts grammar-token-nonlocal-stmt}@anchor{152d}nonlocal_stmt ::= "nonlocal" identifier ("," identifier)*
@end example

@c XXX add when implemented
@c : ["=" (`target_list` "=")+ starred_expression]
@c : | "nonlocal" identifier augop expression_list

@ref{c38,,nonlocal} 语句会使得所列出的名称指向之前在最近的包含作用域中绑定的除全局变量以外的变量。 这种功能很重要，因为绑定的默认行为是先搜索局部命名空间。 这个语句允许被封装的代码重新绑定局部作用域以外且非全局（模块）作用域当中的变量。

@c XXX not implemented
@c The :keyword:`nonlocal` statement may prepend an assignment or augmented
@c assignment, but not an expression.

与 @ref{11d8,,global} 语句中列出的名称不同，@ref{c38,,nonlocal} 语句中列出的名称必须指向之前存在于包含作用域之中的绑定（在这个应当用来创建新绑定的作用域不能被无歧义地确定）。

@ref{c38,,nonlocal} 语句中列出的名称不得与之前存在于局部作用域中的绑定相冲突。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3104

@item PEP 3104@footnote{https://www.python.org/dev/peps/pep-3104} - 访问外层作用域中的名称

有关 @ref{c38,,nonlocal} 语句的规范说明。
@end table


@node 复合语句,最高层级组件,简单语句,Python语言参考
@anchor{reference/compound_stmts doc}@anchor{152e}@anchor{reference/compound_stmts compound}@anchor{152f}@anchor{reference/compound_stmts compound-statements}@anchor{1530}
@section 复合语句


@geindex compound; statement

复合语句是包含其它语句（语句组）的语句；它们会以某种方式影响或控制所包含其它语句的执行。 通常，复合语句会跨越多行，虽然在某些简单形式下整个复合语句也可能包含于一行之内。

@ref{de0,,if}, @ref{11c1,,while} 和 @ref{c29,,for} 语句用来实现传统的控制流程构造。 @ref{d6b,,try} 语句为一组语句指定异常处理和/和清理代码，而 @ref{6e3,,with} 语句允许在一个代码块周围执行初始化和终结化代码。 函数和类定义在语法上也属于复合语句。

@geindex clause
@geindex suite
@geindex ; (semicolon)

一条复合语句由一个或多个‘子句’组成。 一个子句则包含一个句头和一个‘句体’。 特定复合语句的子句头都处于相同的缩进层级。 每个子句头以一个作为唯一标识的关键字开始并以一个冒号结束。 子句体是由一个子句控制的一组语句。 子句体可以是在子句头的冒号之后与其同处一行的一条或由分号分隔的多条简单语句，或者也可以是在其之后缩进的一行或多行语句。 只有后一种形式的子句体才能包含嵌套的复合语句；以下形式是不合法的，这主要是因为无法分清某个后续的 @ref{11c8,,else} 子句应该属于哪个 @ref{de0,,if} 子句:

@example
if test1: if test2: print(x)
@end example

还要注意的是在这种情形下分号的绑定比冒号更紧密，因此在以下示例中，所有 @ref{880,,print()} 调用或者都不执行，或者都执行:

@example
if x < y < z: print(x); print(y); print(z)
@end example

总结:

@example
@anchor{reference/compound_stmts grammar-token-compound-stmt}@anchor{1531}compound_stmt ::= if_stmt
                  | while_stmt
                  | for_stmt
                  | try_stmt
                  | with_stmt
                  | funcdef
                  | classdef
                  | async_with_stmt
                  | async_for_stmt
                  | async_funcdef
@anchor{reference/compound_stmts grammar-token-suite}@anchor{1532}suite         ::= stmt_list NEWLINE | NEWLINE INDENT statement+ DEDENT
@anchor{reference/compound_stmts grammar-token-statement}@anchor{1533}statement     ::= stmt_list NEWLINE | compound_stmt
@anchor{reference/compound_stmts grammar-token-stmt-list}@anchor{1534}stmt_list     ::= simple_stmt (";" simple_stmt)* [";"]
@end example

@geindex NEWLINE token
@geindex DEDENT token
@geindex dangling; else

请注意语句总是以 @code{NEWLINE} 结束，之后可能跟随一个 @code{DEDENT}。 还要注意可选的后续子句总是以一个不能作为语句开头的关键字作为开头，因此不会产生歧义（‘悬空的 @ref{11c8,,else}’问题在 Python 中是通过要求嵌套的 @ref{de0,,if} 语句必须缩进来解决的)。

为了保证清晰，以下各节中语法规则采用将每个子句都放在单独行中的格式。
@anchor{reference/compound_stmts if}@anchor{de0}@anchor{reference/compound_stmts elif}@anchor{11c7}
@menu
* if 语句: if 语句<2>. 
* while 语句:: 
* for 语句: for 语句<2>. 
* try 语句:: 
* with 语句:: 
* 函数定义:: 
* 类定义:: 
* 协程: 协程<2>. 

@end menu

@node if 语句<2>,while 语句,,复合语句
@anchor{reference/compound_stmts else}@anchor{11c8}@anchor{reference/compound_stmts the-if-statement}@anchor{1535}
@subsection @code{if} 语句


@geindex 语句; if
@geindex 关键字; elif
@geindex 关键字; else
@geindex ; (colon); compound statement

@ref{de0,,if} 语句用于有条件的执行:

@example
@anchor{reference/compound_stmts grammar-token-if-stmt}@anchor{1536}if_stmt ::= "if" assignment_expression ":" suite
            ("elif" assignment_expression ":" suite)*
            ["else" ":" suite]
@end example

它通过对表达式逐个求值直至找到一个真值（请参阅 @ref{14e2,,布尔运算} 了解真值与假值的定义）在子句体中选择唯一匹配的一个；然后执行该子句体（而且 @ref{de0,,if} 语句的其他部分不会被执行或求值）。 如果所有表达式均为假值，则如果 @ref{11c8,,else} 子句体如果存在就会被执行。

@node while 语句,for 语句<2>,if 语句<2>,复合语句
@anchor{reference/compound_stmts the-while-statement}@anchor{1537}@anchor{reference/compound_stmts while}@anchor{11c1}
@subsection @code{while} 语句


@geindex 语句; while
@geindex 关键字; else
@geindex loop; statement
@geindex ; (colon); compound statement

@ref{11c1,,while} 语句用于在表达式保持为真的情况下重复地执行:

@example
@anchor{reference/compound_stmts grammar-token-while-stmt}@anchor{1538}while_stmt ::= "while" assignment_expression ":" suite
               ["else" ":" suite]
@end example

这将重复地检验表达式，并且如果其值为真就执行第一个子句体；如果表达式值为假（这可能在第一次检验时就发生）则如果 @code{else} 子句体存在就会被执行并终止循环。

@geindex 语句; break
@geindex 语句; continue

第一个子句体中的 @ref{2db,,break} 语句在执行时将终止循环且不执行 @code{else} 子句体。 第一个子句体中的 @ref{181,,continue} 语句在执行时将跳过子句体中的剩余部分并返回检验表达式。

@node for 语句<2>,try 语句,while 语句,复合语句
@anchor{reference/compound_stmts for}@anchor{c29}@anchor{reference/compound_stmts the-for-statement}@anchor{1539}
@subsection @code{for} 语句


@geindex 语句; for
@geindex 关键字; in
@geindex 关键字; else
@geindex target; list
@geindex loop; statement
@geindex 对象; sequence
@geindex ; (colon); compound statement

@ref{c29,,for} 语句用于对序列（例如字符串、元组或列表）或其他可迭代对象中的元素进行迭代:

@example
@anchor{reference/compound_stmts grammar-token-for-stmt}@anchor{153a}for_stmt ::= "for" target_list "in" expression_list ":" suite
             ["else" ":" suite]
@end example

表达式列表会被求值一次；它应该产生一个可迭代对象。 系统将为 @code{expression_list} 的结果创建一个迭代器，然后将为迭代器所提供的每一项执行一次子句体，具体次序与迭代器的返回顺序一致。 每一项会按标准赋值规则 (参见 @ref{1504,,赋值语句}) 被依次赋值给目标列表，然后子句体将被执行。 当所有项被耗尽时 (这会在序列为空或迭代器引发 @ref{480,,StopIteration} 异常时立刻发生)，@code{else} 子句的子句体如果存在将会被执行，并终止循环。

@geindex 语句; break
@geindex 语句; continue

第一个子句体中的 @ref{2db,,break} 语句在执行时将终止循环且不执行 @code{else} 子句体。 第一个子句体中的 @ref{181,,continue} 语句在执行时将跳过子句体中的剩余部分并转往下一项继续执行，或者在没有下一项时转往 @code{else} 子句执行。

for 循环会对目标列表中的变量进行赋值。 这将覆盖之前对这些变量的所有赋值，包括在 for 循环体中的赋值:

@example
for i in range(10):
    print(i)
    i = 5             # this will not affect the for-loop
                      # because i will be overwritten with the next
                      # index in the range
@end example

@geindex 內置函数; range

目标列表中的名称在循环结束时不会被删除，但如果序列为空，则它们根本不会被循环所赋值。 提示：内置函数 @ref{9b8,,range()} 会返回一个可迭代的整数序列，适用于模拟 Pascal 中的 @code{for i := a to b do} 这种效果；例如 @code{list(range(3))} 会返回列表 @code{[0, 1, 2]}。

@cartouche
@quotation 注解 
@geindex loop; over mutable sequence
@geindex mutable sequence; loop over

当序列在循环中被修改时会有一个微妙的问题（这只可能发生于可变序列例如列表中）。 会有一个内部计数器被用来跟踪下一个要使用的项，每次迭代都会使计数器递增。 当计数器值达到序列长度时循环就会终止。 这意味着如果语句体从序列中删除了当前（或之前）的一项，下一项就会被跳过（因为其标号将变成已被处理的当前项的标号）。 类似地，如果语句体在序列当前项的前面插入一个新项，当前项会在循环的下一轮中再次被处理。 这会导致麻烦的程序错误，避免此问题的办法是对整个序列使用切片来创建一个临时副本，例如

@example
for x in a[:]:
    if x < 0: a.remove(x)
@end example
@end quotation
@end cartouche
@anchor{reference/compound_stmts try}@anchor{d6b}@anchor{reference/compound_stmts except}@anchor{b37}
@node try 语句,with 语句,for 语句<2>,复合语句
@anchor{reference/compound_stmts finally}@anchor{182}@anchor{reference/compound_stmts the-try-statement}@anchor{153b}
@subsection @code{try} 语句


@geindex 语句; try
@geindex 关键字; except
@geindex 关键字; finally
@geindex 关键字; else
@geindex 关键字; as
@geindex ; (colon); compound statement

@ref{d6b,,try} 语句可为一组语句指定异常处理器和/或清理代码:

@example
@anchor{reference/compound_stmts grammar-token-try-stmt}@anchor{153c}try_stmt  ::= try1_stmt | try2_stmt
@anchor{reference/compound_stmts grammar-token-try1-stmt}@anchor{153d}try1_stmt ::= "try" ":" suite
              ("except" [expression ["as" identifier]] ":" suite)+
              ["else" ":" suite]
              ["finally" ":" suite]
@anchor{reference/compound_stmts grammar-token-try2-stmt}@anchor{153e}try2_stmt ::= "try" ":" suite
              "finally" ":" suite
@end example

@ref{b37,,except} 子句指定一个或多个异常处理器。 当 @ref{d6b,,try} 子句中没有发生异常时，没有异常处理器会被执行。 当 @code{try} 子句中发生异常时，将启动对异常处理器的搜索。 此搜索会依次检查 except 子句，直至找到与该异常相匹配的子句。 如果存在无表达式的 except 子句，它必须是最后一个；它将匹配任何异常。 对于带有表达式的 except 子句，该表达式会被求值，如果结果对象与发生的异常“兼容”则该子句将匹配该异常。 一个对象如果是异常对象所属的类或基类，或者是包含有兼容该异常的项的元组则两者就是兼容的。

如果没有 except 子句与异常相匹配，则会在周边代码和发起调用栈上继续搜索异常处理器。 @footnote{@w{(1)} 
异常会被传播给发起调用栈，除非存在一个 @ref{182,,finally} 子句正好引发了另一个异常。 新引发的异常将导致旧异常的丢失。
}

如果在对 except 子句头中的表达式求值时引发了异常，则原来对处理器的搜索会被取消，并在周边代码和调用栈上启动对新异常的搜索（它会被视作是整个 @ref{d6b,,try} 语句所引发的异常）。

@geindex as; except clause

当找到一个匹配的 except 子句时，该异常将被赋值给该 except 子句在 @code{as} 关键字之后指定的目标，如果存在此关键字的话，并且该 except 子句体将被执行。 所有 except 子句都必须有可执行的子句体。 当到达子句体的末尾时，通常会转向整个 try 语句之后继续执行。 （这意味着如果对于同一异常存在有嵌套的两个处理器，而异常发生于内层处理器的 try 子句中，则外层处理器将不会处理该异常。）

当使用 @code{as} 将目标赋值为一个异常时，它将在 except 子句结束时被清除。 这就相当于

@example
except E as N:
    foo
@end example

被转写为

@example
except E as N:
    try:
        foo
    finally:
        del N
@end example

这意味着异常必须赋值给一个不同的名称才能在 except 子句之后引用它。 异常会被清除是因为在附加了回溯信息的情况下，它们会形成堆栈帧的循环引用，使得所有局部变量保持存活直到发生下一次垃圾回收。

@geindex 模块; sys
@geindex 对象; traceback

在一个 except 子句体被执行之前，有关异常的详细信息存放在 @ref{fd,,sys} 模块中，可通过 @ref{c58,,sys.exc_info()} 来访问。 @ref{c58,,sys.exc_info()} 返回一个 3 元组，由异常类、异常实例和回溯对象组成（参见 @ref{13b8,,标准类型层级结构} 一节），用于在程序中标识异常发生点。 当从处理异常的函数返回时 @ref{c58,,sys.exc_info()} 的值会恢复为（调用前的）原值。

@geindex 关键字; else
@geindex 语句; return
@geindex 语句; break
@geindex 语句; continue

如果控制流离开 @ref{d6b,,try} 子句体时没有引发异常，并且没有执行 @ref{190,,return}, @ref{181,,continue} 或 @ref{2db,,break} 语句，可选的 @code{else} 子句将被执行。  @code{else} 语句中的异常不会由之前的 @ref{b37,,except} 子句处理。

@geindex 关键字; finally

如果存在 @ref{182,,finally}，它将指定一个‘清理’处理程序。 @ref{d6b,,try} 子句会被执行，包括任何 @ref{b37,,except} 和 @code{else} 子句。 如果在这些子句中发生任何未处理的异常，该异常会被临时保存。 @code{finally} 子句将被执行。 如果存在被保存的异常，它会在 @code{finally} 子句的末尾被重新引发。 如果 @code{finally} 子句引发了另一个异常，被保存的异常会被设为新异常的上下文。 如果 @code{finally} 子句执行了 @ref{190,,return}, @ref{2db,,break} 或 @ref{181,,continue} 语句，则被保存的异常会被丢弃:

@example
>>> def f():
...     try:
...         1/0
...     finally:
...         return 42
...
>>> f()
42
@end example

在 @ref{182,,finally} 子句执行期间，程序不能获取异常信息。

@geindex 语句; return
@geindex 语句; break
@geindex 语句; continue

当 @ref{190,,return}, @ref{2db,,break} 或 @ref{181,,continue} 语句在一个 @code{try}...@code{finally} 语句的 @ref{d6b,,try} 子语句体中被执行时，@ref{182,,finally} 子语句也会‘在离开时’被执行。

函数的返回值是由最后被执行的 @ref{190,,return} 语句所决定的。 由于 @ref{182,,finally} 子句总是被执行，因此在 @code{finally} 子句中被执行的 @code{return} 语句总是最后被执行的:

@example
>>> def foo():
...     try:
...         return 'try'
...     finally:
...         return 'finally'
...
>>> foo()
'finally'
@end example

有关异常的更多信息可以在 @ref{1441,,异常} 一节找到，有关使用 @ref{c3b,,raise} 语句生成异常的信息可以在 @ref{c3b,,raise 语句} 一节找到。


在 3.8 版更改: 在 Python 3.8 之前，@ref{181,,continue} 语句不允许在 @ref{182,,finally} 子句中使用，这是因为具体实现存在一个问题。

@anchor{reference/compound_stmts with}@anchor{6e3}
@node with 语句,函数定义,try 语句,复合语句
@anchor{reference/compound_stmts as}@anchor{153f}@anchor{reference/compound_stmts the-with-statement}@anchor{1540}
@subsection @code{with} 语句


@geindex 语句; with
@geindex 关键字; as
@geindex as; with statement
@geindex @comma{} (comma); with statement
@geindex ; (colon); compound statement

@ref{6e3,,with} 语句用于包装带有使用上下文管理器 (参见 @ref{141e,,with 语句上下文管理器} 一节) 定义的方法的代码块的执行。 这允许对普通的 @ref{d6b,,try}...@ref{b37,,except}...@ref{182,,finally} 使用模式进行封装以方便地重用。

@example
@anchor{reference/compound_stmts grammar-token-with-stmt}@anchor{1541}with_stmt ::= "with" with_item ("," with_item)* ":" suite
@anchor{reference/compound_stmts grammar-token-with-item}@anchor{1542}with_item ::= expression ["as" target]
@end example

带有一个“项目”的 @ref{6e3,,with} 语句的执行过程如下:


@enumerate 

@item 
对上下文表达式 (在 @ref{1542,,with_item} 中给出的表达式) 求值以获得一个上下文管理器。

@item 
载入上下文管理器的 @ref{c8e,,__enter__()} 以便后续使用。

@item 
载入上下文管理器的 @ref{c8f,,__exit__()} 以便后续使用。

@item 
发起调用上下文管理器的 @ref{c8e,,__enter__()} 方法。

@item 
如果 @ref{6e3,,with} 语句中包含一个目标，来自 @ref{c8e,,__enter__()} 的返回值将被赋值给它。

@cartouche
@quotation 注解 
@ref{6e3,,with} 语句会保证如果 @ref{c8e,,__enter__()} 方法返回时未发生错误，则 @ref{c8f,,__exit__()} 将总是被调用。 因此，如果在对目标列表赋值期间发生错误，则会将其视为在语句体内部发生的错误。 参见下面的第 6 步。
@end quotation
@end cartouche

@item 
执行语句体。

@item 
发起调用上下文管理器的 @ref{c8f,,__exit__()} 方法。 如果语句体的退出是由异常导致的，则其类型、值和回溯信息将被作为参数传递给 @ref{c8f,,__exit__()}。 否则的话，将提供三个 @ref{157,,None} 参数。

如果语句体的退出是由异常导致的，并且来自 @ref{c8f,,__exit__()} 方法的返回值为假，则该异常会被重新引发。 如果返回值为真，则该异常会被抑制，并会继续执行 @ref{6e3,,with} 语句之后的语句。

如果语句体由于异常以外的任何原因退出，则来自 @ref{c8f,,__exit__()} 的返回值会被忽略，并会在该类退出正常的发生位置继续执行。
@end enumerate

以下代码:

@example
with EXPRESSION as TARGET:
    SUITE
@end example

在语义上等价于:

@example
manager = (EXPRESSION)
enter = type(manager).__enter__
exit = type(manager).__exit__
value = enter(manager)
hit_except = False

try:
    TARGET = value
    SUITE
except:
    hit_except = True
    if not exit(manager, *sys.exc_info()):
        raise
finally:
    if not hit_except:
        exit(manager, None, None, None)
@end example

如果有多个项目，则会视作存在多个 @ref{6e3,,with} 语句嵌套来处理多个上下文管理器:

@example
with A() as a, B() as b:
    SUITE
@end example

在语义上等价于:

@example
with A() as a:
    with B() as b:
        SUITE
@end example


在 3.1 版更改: 支持多个上下文表达式。



@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 343

@item PEP 343@footnote{https://www.python.org/dev/peps/pep-0343} - "with" 语句

Python @ref{6e3,,with} 语句的规范描述、背景和示例。
@end table


@geindex parameter; function definition
@anchor{reference/compound_stmts function}@anchor{11f0}
@node 函数定义,类定义,with 语句,复合语句
@anchor{reference/compound_stmts def}@anchor{db7}@anchor{reference/compound_stmts function-definitions}@anchor{1543}
@subsection 函数定义


@geindex 语句; def
@geindex function; definition
@geindex function; name
@geindex name; binding
@geindex 对象; user-defined function
@geindex 对象; function
@geindex function; name
@geindex name; binding
@geindex () (parentheses); function definition
@geindex @comma{} (comma); parameter list
@geindex ; (colon); compound statement

函数定义就是对用户自定义函数的定义（参见 @ref{13b8,,标准类型层级结构} 一节）:

@example
@anchor{reference/compound_stmts grammar-token-funcdef}@anchor{1544}funcdef                   ::= [decorators] "def" funcname "(" [parameter_list] ")"
                              ["->" expression] ":" suite
@anchor{reference/compound_stmts grammar-token-decorators}@anchor{1545}decorators                ::= decorator+
@anchor{reference/compound_stmts grammar-token-decorator}@anchor{1546}decorator                 ::= "@@" dotted_name ["(" [argument_list [","]] ")"] NEWLINE
@anchor{reference/compound_stmts grammar-token-dotted-name}@anchor{1547}dotted_name               ::= identifier ("." identifier)*
@anchor{reference/compound_stmts grammar-token-parameter-list}@anchor{1548}parameter_list            ::= defparameter ("," defparameter)* "," "/" ["," [parameter_list_no_posonly]]
                                | parameter_list_no_posonly
@anchor{reference/compound_stmts grammar-token-parameter-list-no-posonly}@anchor{1549}parameter_list_no_posonly ::= defparameter ("," defparameter)* ["," [parameter_list_starargs]]
                              | parameter_list_starargs
@anchor{reference/compound_stmts grammar-token-parameter-list-starargs}@anchor{154a}parameter_list_starargs   ::= "*" [parameter] ("," defparameter)* ["," ["**" parameter [","]]]
                              | "**" parameter [","]
@anchor{reference/compound_stmts grammar-token-parameter}@anchor{154b}parameter                 ::= identifier [":" expression]
@anchor{reference/compound_stmts grammar-token-defparameter}@anchor{154c}defparameter              ::= parameter ["=" expression]
@anchor{reference/compound_stmts grammar-token-funcname}@anchor{154d}funcname                  ::= identifier
@end example

函数定义是一条可执行语句。 它执行时会在当前局部命名空间中将函数名称绑定到一个函数对象（函数可执行代码的包装器）。 这个函数对象包含对当前全局命名空间的引用，作为函数被调用时所使用的全局命名空间。

函数定义并不会执行函数体；只有当函数被调用时才会执行此操作。 @footnote{@w{(2)} 
作为函数体的第一条语句出现的字符串字面值会被转换为函数的 @code{__doc__} 属性，也就是该函数的 @ref{154e,,docstring}。
}

@geindex @@ (at); function definition

一个函数定义可以被一个或多个 @ref{283,,decorator} 表达式所包装。 当函数被定义时将在包含该函数定义的作用域中对装饰器表达式求值。 求值结果必须是一个可调用对象，它会以该函数对象作为唯一参数被发起调用。 其返回值将被绑定到函数名称而非函数对象。 多个装饰器会以嵌套方式被应用。 例如以下代码

@example
@@f1(arg)
@@f2
def func(): pass
@end example

大致等价于

@example
def func(): pass
func = f1(arg)(f2(func))
@end example

不同之处在于原始函数并不会被临时绑定到名称 @code{func}。

@geindex default; parameter; value
@geindex argument; function definition
@geindex = (equals); function definition

当一个或多个 @ref{14c4,,形参} 具有 @emph{形参} @code{=} @emph{表达式} 这样的形式时，该函数就被称为具有“默认形参值”。 对于一个具有默认值的形参，其对应的 @ref{14bb,,argument} 可以在调用中被省略，在此情况下会用形参的默认值来替代。 如果一个形参具有默认值，后续所有在 "@code{*}" 之前的形参也必须具有默认值 --- 这个句法限制并未在语法中明确表达。

@strong{默认形参值会在执行函数定义时按从左至右的顺序被求值。} 这意味着当函数被定义时将对表达式求值一次，相同的“预计算”值将在每次调用时被使用。 这一点在默认形参为可变对象，例如列表或字典的时候尤其需要重点理解：如果函数修改了该对象（例如向列表添加了一项），则实际上默认值也会被修改。 这通常不是人们所预期的。 绕过此问题的一个方法是使用 @code{None} 作为默认值，并在函数体中显式地对其进行测试，例如:

@example
def whats_on_the_telly(penguin=None):
    if penguin is None:
        penguin = []
    penguin.append("property of the zoo")
    return penguin
@end example

@geindex * (asterisk); function definition
@geindex **; function definition

函数调用的语义在 @ref{646,,调用} 一节中有更详细的描述。 函数调用总是会给形参列表中列出的所有形参赋值，或用位置参数，或用关键字参数，或用默认值。 如果存在 "@code{*identifier}" 这样的形式，它会被初始化为一个元组来接收任何额外的位置参数，默认为空元组。 如果存在 "@code{**identifier}" 这样的形式，它会被初始化为一个新的有序映射来接收任何额外的关键字参数，默认为一个相同类型的空映射。 在 "@code{*}" 或 "@code{*identifier}" 之后的形参都是仅关键字形参，只能通过关键字参数传入值。

@geindex function; annotations
@geindex ->; function annotations
@geindex ; (colon); function annotations

形参可以带有 @ref{11f1,,标注}，其形式为在形参名称后加上 "@code{: expression}"。 任何形参都可以带有标注，甚至 @code{*identifier} 或 @code{**identifier} 这样的形参也可以。 函数可以带有“返回”标注，其形式为在形参列表后加上 "@code{-> expression}"。 这些标注可以是任何有效的 Python 表达式。 标注的存在不会改变函数的语义。 标注值可以作为函数对象的 @code{__annotations__} 属性中以对应形参名称为键的字典值被访问。 如果使用了 @code{annotations} import from @ref{0,,__future__} 的方式，则标注会在运行时保存为字符串以启用延迟求值特性。 否则，它们会在执行函数定义时被求值。 在这种情况下，标注的求值顺序可能与它们在源代码中出现的顺序不同。

@geindex lambda; expression

创建匿名函数（未绑定到一个名称的函数）以便立即在表达式中使用也是可能的。 这需要使用 lambda 表达式，具体描述见 @ref{c28,,lambda 表达式} 一节。 请注意 lambda 只是简单函数定义的一种简化写法；在 "@ref{db7,,def}" 语句中定义的函数也可以像用 lambda 表达式定义的函数一样被传递或赋值给其他名称。 "@code{def}" 形式实际上更为强大，因为它允许执行多条语句和使用标注。

@strong{程序员注意事项:} 函数属于一类对象。 在一个函数内部执行的 "@code{def}" 语句会定义一个局部函数并可被返回或传递。 在嵌套函数中使用的自由变量可以访问包含该 def 语句的函数的局部变量。 详情参见 @ref{1437,,命名与绑定} 一节。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3107

@item PEP 3107@footnote{https://www.python.org/dev/peps/pep-3107} - 函数标注

最初的函数标注规范说明。

@geindex Python 提高建议; PEP 484

@item PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} - 类型提示

标注的标准含意定义：类型提示。

@geindex Python 提高建议; PEP 526

@item PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} - 变量标注的语法

变量声明的类型提示功能，包括类变量和实例变量

@geindex Python 提高建议; PEP 563

@item PEP 563@footnote{https://www.python.org/dev/peps/pep-0563} - 延迟的标注求值

支持在运行时通过以字符串形式保存标注而非不是即求值来实现标注内部的向前引用。
@end table


@node 类定义,协程<2>,函数定义,复合语句
@anchor{reference/compound_stmts class}@anchor{c63}@anchor{reference/compound_stmts class-definitions}@anchor{154f}
@subsection 类定义


@geindex 对象; class
@geindex 语句; class
@geindex class; definition
@geindex class; name
@geindex name; binding
@geindex execution; frame
@geindex inheritance
@geindex docstring
@geindex () (parentheses); class definition
@geindex @comma{} (comma); expression list
@geindex ; (colon); compound statement

类定义就是对类对象的定义 (参见 @ref{13b8,,标准类型层级结构} 一节):

@example
@anchor{reference/compound_stmts grammar-token-classdef}@anchor{1550}classdef    ::= [decorators] "class" classname [inheritance] ":" suite
@anchor{reference/compound_stmts grammar-token-inheritance}@anchor{1551}inheritance ::= "(" [argument_list] ")"
@anchor{reference/compound_stmts grammar-token-classname}@anchor{1552}classname   ::= identifier
@end example

类定义是一条可执行语句。 其中继承列表通常给出基类的列表 (进阶用法请参见 @ref{13e0,,元类})，列表中的每一项都应当被求值为一个允许子类的类对象。 没有继承列表的类默认继承自基类 @ref{2b0,,object}；因此，:

@example
class Foo:
    pass
@end example

等价于

@example
class Foo(object):
    pass
@end example

随后类体将在一个新的执行帧 (参见 @ref{1437,,命名与绑定}) 中被执行，使用新创建的局部命名空间和原有的全局命名空间。 （通常，类体主要包含函数定义。） 当类体结束执行时，其执行帧将被丢弃而其局部命名空间会被保存。 @footnote{@w{(3)} 
作为类体的第一条语句出现的字符串字面值会被转换为命名空间的 @code{__doc__} 条目，也就是该类的 @ref{154e,,docstring}。
} 一个类对象随后会被创建，其基类使用给定的继承列表，属性字典使用保存的局部命名空间。 类名称将在原有的全局命名空间中绑定到该类对象。

在类体内定义的属性的顺序保存在新类的 @code{__dict__} 中。 请注意此顺序的可靠性只限于类刚被创建时，并且只适用于使用定义语法所定义的类。

类的创建可使用 @ref{13e0,,元类} 进行重度定制。

@geindex @@ (at); class definition

类也可以被装饰：就像装饰函数一样，:

@example
@@f1(arg)
@@f2
class Foo: pass
@end example

大致等价于

@example
class Foo: pass
Foo = f1(arg)(f2(Foo))
@end example

装饰器表达式的求值规则与函数装饰器相同。 结果随后会被绑定到类名称。

@strong{程序员注意事项:} 在类定义内定义的变量是类属性；它们将被类实例所共享。 实例属性可通过 @code{self.name = value} 在方法中设定。 类和实例属性均可通过 "@code{self.name}" 表示法来访问，当通过此方式访问时实例属性会隐藏同名的类属性。 类属性可被用作实例属性的默认值，但在此场景下使用可变值可能导致未预期的结果。 可以使用 @ref{4e3,,描述器} 来创建具有不同实现细节的实例变量。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3115

@item PEP 3115@footnote{https://www.python.org/dev/peps/pep-3115} - Python 3000 中的元类

将元类声明修改为当前语法的提议，以及关于如何构建带有元类的类的语义描述。

@geindex Python 提高建议; PEP 3129

@item PEP 3129@footnote{https://www.python.org/dev/peps/pep-3129} - 类装饰器

增加类装饰器的提议。 函数和方法装饰器是在 
@geindex Python 提高建议; PEP 318
PEP 318@footnote{https://www.python.org/dev/peps/pep-0318} 中被引入的。
@end table


@node 协程<2>,,类定义,复合语句
@anchor{reference/compound_stmts async}@anchor{1a2}@anchor{reference/compound_stmts coroutines}@anchor{1553}
@subsection 协程



3.5 新版功能.


@geindex 语句; async def

@menu
* 协程函数定义:: 
* async for 语句:: 
* async with 语句:: 

@end menu

@node 协程函数定义,async for 语句,,协程<2>
@anchor{reference/compound_stmts async-def}@anchor{284}@anchor{reference/compound_stmts coroutine-function-definition}@anchor{1554}
@subsubsection 协程函数定义


@example
@anchor{reference/compound_stmts grammar-token-async-funcdef}@anchor{1555}async_funcdef ::= [decorators] "async" "def" funcname "(" [parameter_list] ")"
                  ["->" expression] ":" suite
@end example

@geindex 关键字; async
@geindex 关键字; await

Python 协程可以在多个位置上挂起和恢复执行 (参见 @ref{1a6,,coroutine})。 在协程函数体内部，@code{await} 和 @code{async} 标识符已成为保留关键字；@ref{1a3,,await} 表达式，@ref{2e3,,async for} 以及 @ref{63d,,async with} 只能在协程函数体中使用。

使用 @code{async def} 语法定义的函数总是为协程函数，即使它们不包含 @code{await} 或 @code{async} 关键字。

在协程函数体中使用 @code{yield from} 表达式将引发 @ref{452,,SyntaxError}。

协程函数的例子:

@example
async def func(param1, param2):
    do_stuff()
    await some_coroutine()
@end example

@geindex 语句; async for

@node async for 语句,async with 语句,协程函数定义,协程<2>
@anchor{reference/compound_stmts async-for}@anchor{2e3}@anchor{reference/compound_stmts the-async-for-statement}@anchor{1556}
@subsubsection @code{async for} 语句


@example
@anchor{reference/compound_stmts grammar-token-async-for-stmt}@anchor{1557}async_for_stmt ::= "async" for_stmt
@end example

@ref{63a,,asynchronous iterable} 能够在其 @emph{iter} 实现中调用异步代码，而 @ref{63f,,asynchronous iterator} 可以在其 @emph{next} 方法中调用异步代码。

@code{async for} 语句允许方便地对异步迭代器进行迭代。

以下代码:

@example
async for TARGET in ITER:
    SUITE
else:
    SUITE2
@end example

在语义上等价于:

@example
iter = (ITER)
iter = type(iter).__aiter__(iter)
running = True

while running:
    try:
        TARGET = await type(iter).__anext__(iter)
    except StopAsyncIteration:
        running = False
    else:
        SUITE
else:
    SUITE2
@end example

另请参阅 @ref{481,,__aiter__()} 和 @ref{142d,,__anext__()} 了解详情。

在协程函数体之外使用 @code{async for} 语句将引发 @ref{452,,SyntaxError}。

@geindex 语句; async with

@node async with 语句,,async for 语句,协程<2>
@anchor{reference/compound_stmts async-with}@anchor{63d}@anchor{reference/compound_stmts the-async-with-statement}@anchor{1558}
@subsubsection @code{async with} 语句


@example
@anchor{reference/compound_stmts grammar-token-async-with-stmt}@anchor{1559}async_with_stmt ::= "async" with_stmt
@end example

@ref{63b,,asynchronous context manager} 是一种 @ref{563,,context manager}，能够在其 @emph{enter} 和 @emph{exit} 方法中暂停执行。

以下代码:

@example
async with EXPRESSION as TARGET:
    SUITE
@end example

在语义上等价于:

@example
manager = (EXPRESSION)
aexit = type(manager).__aexit__
aenter = type(manager).__aenter__
value = await aenter(manager)
hit_except = False

try:
    TARGET = value
    SUITE
except:
    hit_except = True
    if not await aexit(manager, *sys.exc_info()):
        raise
finally:
    if not hit_except:
        await aexit(manager, None, None, None)
@end example

另请参阅 @ref{1430,,__aenter__()} 和 @ref{1431,,__aexit__()} 了解详情。

在协程函数体之外使用 @code{async with} 语句将引发 @ref{452,,SyntaxError}。


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 492

@item PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} - 使用 async 和 await 语法实现协程

将协程作为 Python 中的一个正式的单独概念，并增加相应的支持语法。
@end table


@subsubheading 备注


@node 最高层级组件,完整的语法规范,复合语句,Python语言参考
@anchor{reference/toplevel_components doc}@anchor{155a}@anchor{reference/toplevel_components top-level}@anchor{155b}@anchor{reference/toplevel_components top-level-components}@anchor{155c}
@section 最高层级组件


@geindex interpreter

Python 解释器可以从多种源获得输入：作为标准输入或程序参数传入的脚本，以交互方式键入的语句，导入的模块源文件等等。 这一章将给出在这些情况下所用的语法。

@menu
* 完整的 Python 程序:: 
* 文件输入:: 
* 交互式输入:: 
* 表达式输入:: 

@end menu

@node 完整的 Python 程序,文件输入,,最高层级组件
@anchor{reference/toplevel_components complete-python-programs}@anchor{155d}@anchor{reference/toplevel_components programs}@anchor{1461}
@subsection 完整的 Python 程序


@geindex program

@geindex 模块; sys
@geindex 模块; __main__
@geindex 模块; builtins

虽然语言规范描述不必规定如何发起调用语言解释器，但对完整的 Python 程序加以说明还是很有用的。 一个完整的 Python 程序会在最小初始化环境中被执行：所有内置和标准模块均为可用，但均处于未初始化状态，只有 @ref{fd,,sys} (各种系统服务), @ref{13,,builtins} (内置函数、异常以及 @code{None}) 和 @ref{1,,__main__} 除外。 最后一个模块用于为完整程序的执行提供局部和全局命名空间。

适用于一个完整 Python 程序的语法即下节所描述的文件输入。

@geindex interactive mode
@geindex 模块; __main__

解释器也可以通过交互模式被发起调用；在此情况下，它并不读取和执行一个完整程序，而是每次读取和执行一条语句（可能为复合语句）。 此时的初始环境与一个完整程序的相同；每条语句会在 @ref{1,,__main__} 的命名空间中被执行。

@geindex UNIX
@geindex Windows
@geindex command line
@geindex standard input

一个完整程序可通过三种形式被传递给解释器：使用 @ref{119f,,-c} @emph{字符串} 命令行选项，使用一个文件作为第一个命令行参数，或者使用标准输入。 如果文件或标准输入是一个 tty 设置，解释器会进入交互模式；否则的话，它会将文件当作一个完整程序来执行。

@node 文件输入,交互式输入,完整的 Python 程序,最高层级组件
@anchor{reference/toplevel_components file-input}@anchor{155e}@anchor{reference/toplevel_components id1}@anchor{155f}
@subsection 文件输入


所有从非交互式文件读取的输入都具有相同的形式:

@example
@anchor{reference/toplevel_components grammar-token-file-input}@anchor{1560}file_input ::= (NEWLINE | statement)*
@end example

此语法用于下列几种情况:


@itemize *

@item 
解析一个完整 Python 程序时（从文件或字符串）；

@item 
解析一个模块时；

@item 
解析一个传递给 @ref{c3d,,exec()} 函数的字符串时；
@end itemize

@node 交互式输入,表达式输入,文件输入,最高层级组件
@anchor{reference/toplevel_components interactive}@anchor{1561}@anchor{reference/toplevel_components interactive-input}@anchor{1562}
@subsection 交互式输入


交互模式下的输入使用以下语法进行解析:

@example
@anchor{reference/toplevel_components grammar-token-interactive-input}@anchor{1563}interactive_input ::= [stmt_list] NEWLINE | compound_stmt NEWLINE
@end example

请注意在交互模式下一条（最高层级）复合语句必须带有一个空行；这对于帮助解析器确定输入的结束是必须的。

@node 表达式输入,,交互式输入,最高层级组件
@anchor{reference/toplevel_components expression-input}@anchor{1564}@anchor{reference/toplevel_components id2}@anchor{1565}
@subsection 表达式输入


@geindex input

@geindex 內置函数; eval

@ref{b89,,eval()} 被用于表达式输入。 它会忽略开头的空白。 传递给 @ref{b89,,eval()} 的字符串参数必须具有以下形式:

@example
@anchor{reference/toplevel_components grammar-token-eval-input}@anchor{1566}eval_input ::= expression_list NEWLINE*
@end example

@node 完整的语法规范,,最高层级组件,Python语言参考
@anchor{reference/grammar doc}@anchor{1567}@anchor{reference/grammar full-grammar-specification}@anchor{1568}
@section 完整的语法规范


这是完整的Python语法，它被送入解析器生成器，以生成解析Python源文件的解析器：

@example
# Grammar for Python

# NOTE WELL: You should also follow all the steps listed at
# https://devguide.python.org/grammar/

# Start symbols for the grammar:
#       single_input is a single interactive statement;
#       file_input is a module or sequence of commands read from an input file;
#       eval_input is the input for the eval() functions.
#       func_type_input is a PEP 484 Python 2 function type comment
# NB: compound_stmt in single_input is followed by extra NEWLINE!
# NB: due to the way TYPE_COMMENT is tokenized it will always be followed by a NEWLINE
single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
file_input: (NEWLINE | stmt)* ENDMARKER
eval_input: testlist NEWLINE* ENDMARKER

decorator: '@@' dotted_name [ '(' [arglist] ')' ] NEWLINE
decorators: decorator+
decorated: decorators (classdef | funcdef | async_funcdef)

async_funcdef: ASYNC funcdef
funcdef: 'def' NAME parameters ['->' test] ':' [TYPE_COMMENT] func_body_suite

parameters: '(' [typedargslist] ')'

# The following definition for typedarglist is equivalent to this set of rules:
#
#     arguments = argument (',' [TYPE_COMMENT] argument)*
#     argument = tfpdef ['=' test]
#     kwargs = '**' tfpdef [','] [TYPE_COMMENT]
#     args = '*' [tfpdef]
#     kwonly_kwargs = (',' [TYPE_COMMENT] argument)* (TYPE_COMMENT | [',' [TYPE_COMMENT] [kwargs]])
#     args_kwonly_kwargs = args kwonly_kwargs | kwargs
#     poskeyword_args_kwonly_kwargs = arguments ( TYPE_COMMENT | [',' [TYPE_COMMENT] [args_kwonly_kwargs]])
#     typedargslist_no_posonly  = poskeyword_args_kwonly_kwargs | args_kwonly_kwargs
#     typedarglist = (arguments ',' [TYPE_COMMENT] '/' [',' [[TYPE_COMMENT] typedargslist_no_posonly]])|(typedargslist_no_posonly)"
#
# It needs to be fully expanded to allow our LL(1) parser to work on it.

typedargslist: (
  (tfpdef ['=' test] (',' [TYPE_COMMENT] tfpdef ['=' test])* ',' [TYPE_COMMENT] '/' [',' [ [TYPE_COMMENT] tfpdef ['=' test] (
        ',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] [
        '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]])
      | '**' tfpdef [','] [TYPE_COMMENT]]])
  | '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]])
  | '**' tfpdef [','] [TYPE_COMMENT]]] )
|  (tfpdef ['=' test] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] [
   '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]])
  | '**' tfpdef [','] [TYPE_COMMENT]]])
  | '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]])
  | '**' tfpdef [','] [TYPE_COMMENT])
)
tfpdef: NAME [':' test]

# The following definition for varargslist is equivalent to this set of rules:
#
#     arguments = argument (',' argument )*
#     argument = vfpdef ['=' test]
#     kwargs = '**' vfpdef [',']
#     args = '*' [vfpdef]
#     kwonly_kwargs = (',' argument )* [',' [kwargs]]
#     args_kwonly_kwargs = args kwonly_kwargs | kwargs
#     poskeyword_args_kwonly_kwargs = arguments [',' [args_kwonly_kwargs]]
#     vararglist_no_posonly = poskeyword_args_kwonly_kwargs | args_kwonly_kwargs
#     varargslist = arguments ',' '/' [','[(vararglist_no_posonly)]] | (vararglist_no_posonly)
#
# It needs to be fully expanded to allow our LL(1) parser to work on it.

varargslist: vfpdef ['=' test ](',' vfpdef ['=' test])* ',' '/' [',' [ (vfpdef ['=' test] (',' vfpdef ['=' test])* [',' [
        '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
      | '**' vfpdef [',']]]
  | '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
  | '**' vfpdef [',']) ]] | (vfpdef ['=' test] (',' vfpdef ['=' test])* [',' [
        '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
      | '**' vfpdef [',']]]
  | '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
  | '**' vfpdef [',']
)
vfpdef: NAME

stmt: simple_stmt | compound_stmt
simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
small_stmt: (expr_stmt | del_stmt | pass_stmt | flow_stmt |
             import_stmt | global_stmt | nonlocal_stmt | assert_stmt)
expr_stmt: testlist_star_expr (annassign | augassign (yield_expr|testlist) |
                     [('=' (yield_expr|testlist_star_expr))+ [TYPE_COMMENT]] )
annassign: ':' test ['=' (yield_expr|testlist_star_expr)]
testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']
augassign: ('+=' | '-=' | '*=' | '@@=' | '/=' | '%=' | '&=' | '|=' | '^=' |
            '<<=' | '>>=' | '**=' | '//=')
# For normal and annotated assignments, additional restrictions enforced by the interpreter
del_stmt: 'del' exprlist
pass_stmt: 'pass'
flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt
break_stmt: 'break'
continue_stmt: 'continue'
return_stmt: 'return' [testlist_star_expr]
yield_stmt: yield_expr
raise_stmt: 'raise' [test ['from' test]]
import_stmt: import_name | import_from
import_name: 'import' dotted_as_names
# note below: the ('.' | '...') is necessary because '...' is tokenized as ELLIPSIS
import_from: ('from' (('.' | '...')* dotted_name | ('.' | '...')+)
              'import' ('*' | '(' import_as_names ')' | import_as_names))
import_as_name: NAME ['as' NAME]
dotted_as_name: dotted_name ['as' NAME]
import_as_names: import_as_name (',' import_as_name)* [',']
dotted_as_names: dotted_as_name (',' dotted_as_name)*
dotted_name: NAME ('.' NAME)*
global_stmt: 'global' NAME (',' NAME)*
nonlocal_stmt: 'nonlocal' NAME (',' NAME)*
assert_stmt: 'assert' test [',' test]

compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated | async_stmt
async_stmt: ASYNC (funcdef | with_stmt | for_stmt)
if_stmt: 'if' namedexpr_test ':' suite ('elif' namedexpr_test ':' suite)* ['else' ':' suite]
while_stmt: 'while' namedexpr_test ':' suite ['else' ':' suite]
for_stmt: 'for' exprlist 'in' testlist ':' [TYPE_COMMENT] suite ['else' ':' suite]
try_stmt: ('try' ':' suite
           ((except_clause ':' suite)+
            ['else' ':' suite]
            ['finally' ':' suite] |
           'finally' ':' suite))
with_stmt: 'with' with_item (',' with_item)*  ':' [TYPE_COMMENT] suite
with_item: test ['as' expr]
# NB compile.c makes sure that the default except clause is last
except_clause: 'except' [test ['as' NAME]]
suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT

namedexpr_test: test [':=' test]
test: or_test ['if' or_test 'else' test] | lambdef
test_nocond: or_test | lambdef_nocond
lambdef: 'lambda' [varargslist] ':' test
lambdef_nocond: 'lambda' [varargslist] ':' test_nocond
or_test: and_test ('or' and_test)*
and_test: not_test ('and' not_test)*
not_test: 'not' not_test | comparison
comparison: expr (comp_op expr)*
# <> isn't actually a valid comparison operator in Python. It's here for the
# sake of a __future__ import described in PEP 401 (which really works :-)
comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not'
star_expr: '*' expr
expr: xor_expr ('|' xor_expr)*
xor_expr: and_expr ('^' and_expr)*
and_expr: shift_expr ('&' shift_expr)*
shift_expr: arith_expr (('<<'|'>>') arith_expr)*
arith_expr: term (('+'|'-') term)*
term: factor (('*'|'@@'|'/'|'%'|'//') factor)*
factor: ('+'|'-'|'~') factor | power
power: atom_expr ['**' factor]
atom_expr: [AWAIT] atom trailer*
atom: ('(' [yield_expr|testlist_comp] ')' |
       '[' [testlist_comp] ']' |
       '@{' [dictorsetmaker] '@}' |
       NAME | NUMBER | STRING+ | '...' | 'None' | 'True' | 'False')
testlist_comp: (namedexpr_test|star_expr) ( comp_for | (',' (namedexpr_test|star_expr))* [','] )
trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
subscriptlist: subscript (',' subscript)* [',']
subscript: test | [test] ':' [test] [sliceop]
sliceop: ':' [test]
exprlist: (expr|star_expr) (',' (expr|star_expr))* [',']
testlist: test (',' test)* [',']
dictorsetmaker: ( ((test ':' test | '**' expr)
                   (comp_for | (',' (test ':' test | '**' expr))* [','])) |
                  ((test | star_expr)
                   (comp_for | (',' (test | star_expr))* [','])) )

classdef: 'class' NAME ['(' [arglist] ')'] ':' suite

arglist: argument (',' argument)*  [',']

# The reason that keywords are test nodes instead of NAME is that using NAME
# results in an ambiguity. ast.c makes sure it's a NAME.
# "test '=' test" is really "keyword '=' test", but we have no such token.
# These need to be in a single rule to avoid grammar that is ambiguous
# to our LL(1) parser. Even though 'test' includes '*expr' in star_expr,
# we explicitly match '*' here, too, to give it proper precedence.
# Illegal combinations and orderings are blocked in ast.c:
# multiple (test comp_for) arguments are blocked; keyword unpackings
# that precede iterable unpackings are blocked; etc.
argument: ( test [comp_for] |
            test ':=' test |
            test '=' test |
            '**' test |
            '*' test )

comp_iter: comp_for | comp_if
sync_comp_for: 'for' exprlist 'in' or_test [comp_iter]
comp_for: [ASYNC] sync_comp_for
comp_if: 'if' test_nocond [comp_iter]

# not used in grammar, but may appear in "node" passed from Parser to Compiler
encoding_decl: NAME

yield_expr: 'yield' [yield_arg]
yield_arg: 'from' test | testlist_star_expr

# the TYPE_COMMENT in suites is only parsed for funcdefs,
# but can't go elsewhere due to ambiguity
func_body_suite: simple_stmt | NEWLINE [TYPE_COMMENT NEWLINE] INDENT stmt+ DEDENT

func_type_input: func_type NEWLINE* ENDMARKER
func_type: '(' [typelist] ')' '->' test
# typelist is a modified typedargslist (see above)
typelist: (test (',' test)* [','
       ['*' [test] (',' test)* [',' '**' test] | '**' test]]
     |  '*' [test] (',' test)* [',' '**' test] | '**' test)
@end example

@node Python 标准库,扩展和嵌入 Python 解释器,Python语言参考,Top
@anchor{library/index doc}@anchor{1569}@anchor{library/index library-index}@anchor{118f}@anchor{library/index the-python-standard-library}@anchor{156a}
@chapter Python 标准库


@ref{1190,,Python语言参考} 描述了 Python 语言的具体语法和语义，这份库参考则介绍了与 Python 一同发行的标准库。它还描述了通常包含在 Python 发行版中的一些可选组件。

Python 标准库非常庞大，所提供的组件涉及范围十分广泛，正如以下内容目录所显示的。这个库包含了多个内置模块 (以 C 编写)，Python 程序员必须依靠它们来实现系统级功能，例如文件 I/O，此外还有大量以 Python 编写的模块，提供了日常编程中许多问题的标准解决方案。其中有些模块经过专门设计，通过将特定平台功能抽象化为平台中立的 API 来鼓励和加强 Python 程序的可移植性。

Windows 版本的 Python 安装程序通常包含整个标准库，往往还包含许多额外组件。对于类 Unix 操作系统，Python 通常会分成一系列的软件包，因此可能需要使用操作系统所提供的包管理工具来获取部分或全部可选组件。

在这个标准库以外还存在成千上万并且不断增加的其他组件 (从单独的程序、模块、软件包直到完整的应用开发框架)，访问 Python 包索引@footnote{https://pypi.org} 即可获取这些第三方包。

@c We don't use :numbered: option for the TOC below as it enforces
@c numbered sections for the entire stdlib docs.  If desired,
@c :numbered: can be enabled on a per-module basis.

@menu
* 概述: 概述<6>. 
* 内置函数:: 
* 内置常量:: 
* 内置类型:: 
* 内置异常:: 
* 文本处理服务:: 
* 二进制数据服务:: 
* 数据类型:: 
* 数字和数学模块:: 
* 函数式编程模块:: 
* 文件和目录访问:: 
* 数据持久化:: 
* 数据压缩和存档:: 
* 文件格式:: 
* 加密服务:: 
* 通用操作系统服务:: 
* 并发执行:: 
* contextvars: contextvars --- Context Variables. Context Variables
* 网络和进程间通信:: 
* 互联网数据处理:: 
* 结构化标记处理工具:: 
* 互联网协议和支持:: 
* 多媒体服务:: 
* 国际化:: 
* 程序框架:: 
* Tk图形用户界面(GUI): Tk图形用户界面 GUI. 
* 开发工具:: 
* 调试和分析:: 
* 软件打包和分发:: 
* Python运行时服务:: 
* 自定义 Python 解释器:: 
* 导入模块:: 
* Python 语言服务:: 
* 杂项服务:: 
* Windows系统相关模块:: 
* Unix 专有服务:: 
* 被取代的模块:: 
* 未创建文档的模块:: 

@end menu

@node 概述<6>,内置函数,,Python 标准库
@anchor{library/intro doc}@anchor{156b}@anchor{library/intro introduction}@anchor{156c}@anchor{library/intro library-intro}@anchor{156d}
@section 概述


"Python 库"中包含了几种不同的组件。

它包含通常被视为语言“核心”中的一部分的数据类型，例如数字和列表。对于这些类型，Python语言核心定义了文字的形式，并对它们的语义设置了一些约束，但没有完全定义语义。（另一方面，语言核心确实定义了语法属性，如操作符的拼写和优先级。）

这个库也包含了内置函数和异常 --- 不需要 @ref{c16,,import} 语句就可以在所有Python代码中使用的对象。有一些是由语言核心定义的，但是许多对于核心语义不是必需的，并且仅在这里描述。

不过这个库主要是由一系列的模块组成。这些模块集可以不同方式分类。有些模块是用 C 编写并内置于 Python 解释器中；另一些模块则是用 Python 编写并以源码形式导入。有些模块提供专用于 Python 的接口，例如打印栈追踪信息；有些模块提供专用于特定操作系统的接口，例如操作特定的硬件；另一些模块则提供针对特定应用领域的接口，例如万维网。有些模块在所有更新和移植版本的 Python 中可用；另一些模块仅在底层系统支持或要求时可用；还有些模块则仅当编译和安装 Python 时选择了特定配置选项时才可用。

本手册以 "从内到外" 的顺序组织：首先描述内置函数、数据类型和异常，最后是根据相关性进行分组的各种模块。

这意味着如果你从头开始阅读本手册，并在感到厌烦时跳到下一章，你仍能对 Python 库的可用模块和所支持的应用领域有个大致了解。当然，你并非 @emph{必须} 如同读小说一样从头读到尾 --- 你也可以先浏览内容目录 (在手册开头)，或在索引 (在手册末尾) 中查找某个特定函数、模块或条目。最后，如果你喜欢随意学习某个主题，你可以选择一个随机页码 (参见 @ref{dc,,random} 模块) 并读上一两小节。无论你想以怎样的顺序阅读本手册，还是建议先从 @ref{bec,,内置函数} 这一章开始，因为本手册的其余内容都需要你熟悉其中的基本概念。

让我们开始吧！

@menu
* 可用性注释:: 

@end menu

@node 可用性注释,,,概述<6>
@anchor{library/intro availability}@anchor{12f5}@anchor{library/intro notes-on-availability}@anchor{156e}
@subsection 可用性注释



@itemize *

@item 
如果出现“适用：Unix”注释，意味着相应函数通常存在于 Unix 系统中。 但这并不保证其存在于某个特定的操作系统中。

@item 
如果没有单独说明，所有注明 “适用：Unix” 的函数都支持基于 Unix 核心构建的 Mac OS X 系统。
@end itemize

@c XXX document all delegations to __special__ methods

@node 内置函数,内置常量,概述<6>,Python 标准库
@anchor{library/functions doc}@anchor{156f}@anchor{library/functions built-in-funcs}@anchor{bec}@anchor{library/functions built-in-functions}@anchor{1570}
@section 内置函数


Python 解释器内置了很多函数和类型，您可以在任何时候使用它们。以下按字母表顺序列出它们。


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} 
@headitem


@tab


@tab

内置函数

@tab


@tab


@item

@ref{1253,,abs()}

@tab

@ref{1571,,delattr()}

@tab

@ref{9be,,hash()}

@tab

@ref{1572,,memoryview()}

@tab

@ref{1573,,set()}

@item

@ref{d7e,,all()}

@tab

@ref{1574,,dict()}

@tab

@ref{56d,,help()}

@tab

@ref{803,,min()}

@tab

@ref{1575,,setattr()}

@item

@ref{d7d,,any()}

@tab

@ref{d2c,,dir()}

@tab

@ref{c5f,,hex()}

@tab

@ref{67c,,next()}

@tab

@ref{dfd,,slice()}

@item

@ref{d45,,ascii()}

@tab

@ref{152,,divmod()}

@tab

@ref{d7f,,id()}

@tab

@ref{2b0,,object()}

@tab

@ref{43e,,sorted()}

@item

@ref{c39,,bin()}

@tab

@ref{ddc,,enumerate()}

@tab

@ref{c64,,input()}

@tab

@ref{c5e,,oct()}

@tab

@ref{1d9,,staticmethod()}

@item

@ref{183,,bool()}

@tab

@ref{b89,,eval()}

@tab

@ref{184,,int()}

@tab

@ref{4ea,,open()}

@tab

@ref{1576,,str()}

@item

@ref{2f2,,breakpoint()}

@tab

@ref{c3d,,exec()}

@tab

@ref{449,,isinstance()}

@tab

@ref{13be,,ord()}

@tab

@ref{1e5,,sum()}

@item

@ref{1051,,bytearray()}

@tab

@ref{c27,,filter()}

@tab

@ref{44a,,issubclass()}

@tab

@ref{19a,,pow()}

@tab

@ref{4dc,,super()}

@item

@ref{1050,,bytes()}

@tab

@ref{187,,float()}

@tab

@ref{d20,,iter()}

@tab

@ref{880,,print()}

@tab

@ref{1577,,tuple()}

@item

@ref{b3d,,callable()}

@tab

@ref{4d5,,format()}

@tab

@ref{150,,len()}

@tab

@ref{1d7,,property()}

@tab

@ref{603,,type()}

@item

@ref{13bf,,chr()}

@tab

@ref{1578,,frozenset()}

@tab

@ref{1579,,list()}

@tab

@ref{157a,,range()}

@tab

@ref{fca,,vars()}

@item

@ref{1d8,,classmethod()}

@tab

@ref{443,,getattr()}

@tab

@ref{44f,,locals()}

@tab

@ref{7c6,,repr()}

@tab

@ref{c2b,,zip()}

@item

@ref{1b4,,compile()}

@tab

@ref{157b,,globals()}

@tab

@ref{c26,,map()}

@tab

@ref{18e,,reversed()}

@tab

@ref{60b,,__import__()}

@item

@ref{189,,complex()}

@tab

@ref{442,,hasattr()}

@tab

@ref{804,,max()}

@tab

@ref{c66,,round()}

@tab

@end multitable


@c using :func:`dict` would create a link to another page, so local targets are
@c used, with replacement texts to make the output in the table consistent

@geindex abs() (內置函数)
@anchor{library/functions abs}@anchor{1253}
@deffn {函数} abs (x)

返回一个数的绝对值。 参数可以是一个整数或浮点数。 如果参数是一个复数，则返回它的模。 如果 @emph{x} 定义了 @ref{1417,,__abs__()}，则 @code{abs(x)} 将返回 @code{x.__abs__()}。
@end deffn

@geindex all() (內置函数)
@anchor{library/functions all}@anchor{d7e}
@deffn {函数} all (iterable)

如果 @emph{iterable} 的所有元素均为真值（或可迭代对象为空）则返回 @code{True} 。 等价于:

@example
def all(iterable):
    for element in iterable:
        if not element:
            return False
    return True
@end example
@end deffn

@geindex any() (內置函数)
@anchor{library/functions any}@anchor{d7d}
@deffn {函数} any (iterable)

如果 @emph{iterable} 的任一元素为真值则返回 @code{True}。 如果可迭代对象为空，返回 @code{False}。 等价于:

@example
def any(iterable):
    for element in iterable:
        if element:
            return True
    return False
@end example
@end deffn

@geindex ascii() (內置函数)
@anchor{library/functions ascii}@anchor{d45}
@deffn {函数} ascii (object)

就像函数 @ref{7c6,,repr()}，返回一个对象可打印的字符串，但是 @ref{7c6,,repr()} 返回的字符串中非 ASCII 编码的字符，会使用 @code{\x}、@code{\u} 和 @code{\U} 来转义。生成的字符串和 Python 2 的 @ref{7c6,,repr()} 返回的结果相似。
@end deffn

@geindex bin() (內置函数)
@anchor{library/functions bin}@anchor{c39}
@deffn {函数} bin (x)

将一个整数转变为一个前缀为“0b”的二进制字符串。结果是一个合法的 Python 表达式。如果 @emph{x} 不是 Python 的 @ref{184,,int} 对象，那它需要定义 @ref{18a,,__index__()}  方法返回一个整数。一些例子：

@example
>>> bin(3)
'0b11'
>>> bin(-10)
'-0b1010'
@end example

如果不一定需要前缀“0b”，还可以使用如下的方法。

@example
>>> format(14, '#b'), format(14, 'b')
('0b1110', '1110')
>>> f'@{14:#b@}', f'@{14:b@}'
('0b1110', '1110')
@end example

另见 @ref{4d5,,format()} 获取更多信息。
@end deffn

@geindex bool (內置类)
@anchor{library/functions bool}@anchor{183}
@deffn {类} bool ([x])

返回一个布尔值，@code{True} 或者 @code{False}。 @emph{x} 使用标准的 @ref{157c,,真值测试过程} 来转换。如果 @emph{x} 是假的或者被省略，返回 @code{False}；其他情况返回 @code{True}。@ref{183,,bool} 类是 @ref{184,,int} 的子类（参见 @ref{11b3,,数字类型 --- int@comma{} float@comma{} complex}）。其他类不能继承自它。它只有 @code{False} 和 @code{True} 两个实例（参见 @ref{157d,,布尔值}）。

@geindex Boolean; type


在 3.7 版更改: @emph{x} 现在只能作为位置参数。

@end deffn

@geindex breakpoint() (內置函数)
@anchor{library/functions breakpoint}@anchor{2f2}
@deffn {函数} breakpoint (*args, **kws)

此函数会在调用时将你陷入调试器中。具体来说，它调用 @ref{30c,,sys.breakpointhook()} ，直接传递 @code{args} 和 @code{kws} 。默认情况下， @code{sys.breakpointhook()} 调用 @ref{3ba,,pdb.set_trace()} 且没有参数。在这种情况下，它纯粹是一个便利函数，因此您不必显式导入 @ref{c9,,pdb} 且键入尽可能少的代码即可进入调试器。但是， @ref{30c,,sys.breakpointhook()} 可以设置为其他一些函数并被 @ref{2f2,,breakpoint()} 自动调用，以允许进入你想用的调试器。

引发一个 @ref{12d0,,审计事件} @code{builtins.breakpoint} 并附带参数 @code{breakpointhook}。


3.7 新版功能.

@end deffn
@anchor{library/functions func-bytearray}@anchor{1051}

@deffn {类} bytearray ([source[, encoding[, errors]]])

返回一个新的 bytes 数组。 @ref{32b,,bytearray} 类是一个可变序列，包含范围为 0 <= x < 256 的整数。它有可变序列大部分常见的方法，见 @ref{157e,,可变序列类型} 的描述；同时有 @ref{32a,,bytes} 类型的大部分方法，参见 @ref{157f,,bytes 和 bytearray 操作}。

可选形参 @emph{source} 可以用不同的方式来初始化数组：


@itemize *

@item 
如果是一个 @emph{string}，您必须提供 @emph{encoding} 参数（@emph{errors} 参数仍是可选的）；@ref{32b,,bytearray()} 会使用 @ref{c30,,str.encode()} 方法来将 string 转变成 bytes。

@item 
如果是一个 @emph{integer}，会初始化大小为该数字的数组，并使用 null 字节填充。

@item 
如果是一个符合 @emph{buffer} 接口的对象，该对象的只读 buffer 会用来初始化字节数组。

@item 
如果是一个 @emph{iterable} 可迭代对象，它的元素的范围必须是 @code{0 <= x < 256} 的整数，它会被用作数组的初始内容。
@end itemize

如果没有实参，则创建大小为 0 的数组。

另见 @ref{1580,,二进制序列类型 --- bytes@comma{} bytearray@comma{} memoryview} 和 @ref{1581,,bytearray 对象}。
@end deffn
@anchor{library/functions func-bytes}@anchor{1050}

@deffn {类} bytes ([source[, encoding[, errors]]])

返回一个新的“bytes”对象， 是一个不可变序列，包含范围为 @code{0 <= x < 256} 的整数。@ref{32a,,bytes} 是 @ref{32b,,bytearray} 的不可变版本 - 它有其中不改变序列的方法和相同的索引、切片操作。

因此，构造函数的实参和 @ref{32b,,bytearray()} 相同。

字节对象还可以用字面值创建，参见 @ref{1379,,字符串和字节串字面值}。

另见 @ref{1580,,二进制序列类型 --- bytes@comma{} bytearray@comma{} memoryview}，@ref{1582,,bytes 对象} 和 @ref{157f,,bytes 和 bytearray 操作}。
@end deffn

@geindex callable() (內置函数)
@anchor{library/functions callable}@anchor{b3d}
@deffn {函数} callable (object)

如果参数 @emph{object} 是可调用的就返回 @ref{494,,True}，否则返回 @ref{380,,False}。 如果返回 @code{True}，调用仍可能失败，但如果返回 @code{False}，则调用 @emph{object} 将肯定不会成功。 请注意类是可调用的（调用类将返回一个新的实例）；如果实例所属的类有 @ref{13c5,,__call__()} 则它就是可调用的。


3.2 新版功能: 这个函数一开始在 Python 3.0 被移除了，但在 Python 3.2 被重新加入。

@end deffn

@geindex chr() (內置函数)
@anchor{library/functions chr}@anchor{13bf}
@deffn {函数} chr (i)

返回 Unicode 码位为整数 @emph{i} 的字符的字符串格式。例如，@code{chr(97)} 返回字符串 @code{'a'}，@code{chr(8364)} 返回字符串 @code{'€'}。这是 @ref{13be,,ord()} 的逆函数。

实参的合法范围是 0 到 1,114,111（16 进制表示是 0x10FFFF）。如果 @emph{i} 超过这个范围，会触发 @ref{1fb,,ValueError} 异常。
@end deffn

@geindex classmethod() (內置函数)
@anchor{library/functions classmethod}@anchor{1d8}
@deffn {函数} @@classmethod

把一个方法封装成类方法。

一个类方法把类自己作为第一个实参，就像一个实例方法把实例自己作为第一个实参。请用以下习惯来声明类方法:

@example
class C:
    @@classmethod
    def f(cls, arg1, arg2, ...): ...
@end example

@code{@@classmethod} 这样的形式称为函数的 @ref{283,,decorator} -- 详情参阅 @ref{11f0,,函数定义}。

类方法的调用可以在类上进行 (例如 @code{C.f()}) 也可以在实例上进行 (例如 @code{C().f()})。 其所属类以外的类实例会被忽略。 如果类方法在其所属类的派生类上调用，则该派生类对象会被作为隐含的第一个参数被传入。

类方法与 C++ 或 Java 中的静态方法不同。 如果你需要后者，请参阅 @ref{1d9,,staticmethod()}。

想了解更多有关类方法的信息，请参阅 @ref{13b8,,标准类型层级结构} 。
@end deffn

@geindex compile() (內置函数)
@anchor{library/functions compile}@anchor{1b4}
@deffn {函数} compile (source, filename, mode, flags=0, dont_inherit=False, optimize=-1)

将 @emph{source} 编译成代码或 AST 对象。代码对象可以被 @ref{c3d,,exec()} 或 @ref{b89,,eval()} 执行。@emph{source} 可以是常规的字符串、字节字符串，或者 AST 对象。参见 @ref{8,,ast} 模块的文档了解如何使用 AST 对象。

@emph{filename} 实参需要是代码读取的文件名；如果代码不需要从文件中读取，可以传入一些可辨识的值（经常会使用 @code{'<string>'}）。

@emph{mode} 实参指定了编译代码必须用的模式。如果 @emph{source} 是语句序列，可以是 @code{'exec'}；如果是单一表达式，可以是 @code{'eval'}；如果是单个交互式语句，可以是 @code{'single'}。（在最后一种情况下，如果表达式执行结果不是 @code{None} 将会被打印出来。）

可选参数 @emph{flags} 和 @emph{dont_inherit} 控制在编译 @emph{source} 时要用到哪个 @ref{1526,,future 语句}。 如果两者都未提供（或都为零）则会使用调用 @ref{1b4,,compile()} 的代码中有效的 future 语句来编译代码。 如果给出了 @emph{flags} 参数但没有 @emph{dont_inherit} (或是为零) 则 @emph{flags} 参数所指定的 以及那些无论如何都有效的 future 语句会被使用。 如果 @emph{dont_inherit} 为一个非零整数，则只使用 @emph{flags} 参数 -- 在调用外围有效的 future 语句将被忽略。

Future 语句使用比特位来指定，多个语句可以通过按位或来指定。具体特性的比特位可以通过 @ref{0,,__future__}  模块中的 @code{_Feature} 类的实例的 @code{compiler_flag} 属性来获得。

可选参数 @emph{flags} 还会控制是否允许编译的源码中包含最高层级 @code{await}, @code{async for} 和 @code{async with}。 当设定了比特位 @code{ast.PyCF_ALLOW_TOP_LEVEL_AWAIT} 时，所返回代码对象在 @code{co_code} 中设定了 @code{CO_COROUTINE}，并可通过 @code{await eval(code_object)} 交互式地执行。

@emph{optimize} 实参指定编译器的优化级别；默认值 @code{-1}  选择与解释器的 @ref{685,,-O} 选项相同的优化级别。显式级别为 @code{0} （没有优化；@code{__debug__}  为真）、@code{1} （断言被删除， @code{__debug__} 为假）或 @code{2} （文档字符串也被删除）。

如果编译的源码不合法，此函数会触发 @ref{452,,SyntaxError} 异常；如果源码包含 null 字节，则会触发 @ref{1fb,,ValueError} 异常。

如果您想分析 Python 代码的 AST 表示，请参阅 @ref{1a1,,ast.parse()}。

引发一个 @ref{12d0,,审计事件} @code{compile} 附带参数 @code{source}, @code{filename}。

@cartouche
@quotation 注解 
在 @code{'single'}  或 @code{'eval'} 模式编译多行代码字符串时，输入必须以至少一个换行符结尾。 这使 @ref{1b,,code} 模块更容易检测语句的完整性。
@end quotation
@end cartouche

@cartouche
@quotation 警告 
在将足够大或者足够复杂的字符串编译成 AST 对象时，Python 解释器有可能因为 Python AST 编译器的栈深度限制而崩溃。
@end quotation
@end cartouche


在 3.2 版更改: 允许使用 Windows 和 Mac 的换行符。在 @code{'exec'} 模式不再需要以换行符结尾。增加了  @emph{optimize} 形参。



在 3.5 版更改: 之前 @emph{source} 中包含 null 字节的话会触发 @ref{192,,TypeError} 异常。



3.8 新版功能: @code{ast.PyCF_ALLOW_TOP_LEVEL_AWAIT} 现在可在旗标中传入以启用对最高层级 @code{await}, @code{async for} 和 @code{async with} 的支持。

@end deffn

@geindex complex (內置类)
@anchor{library/functions complex}@anchor{189}
@deffn {类} complex ([real[, imag]])

返回值为 @emph{real} + @emph{imag}*1j 的复数，或将字符串或数字转换为复数。如果第一个形参是字符串，则它被解释为一个复数，并且函数调用时必须没有第二个形参。第二个形参不能是字符串。每个实参都可以是任意的数值类型（包括复数）。如果省略了 @emph{imag}，则默认值为零，构造函数会像 @ref{184,,int} 和 @ref{187,,float} 一样进行数值转换。如果两个实参都省略，则返回 @code{0j}。

对于一个普通 Python 对象 @code{x}，@code{complex(x)} 会委托给 @code{x.__complex__()}。  如果 @code{__complex__()} 未定义则将回退至 @ref{18c,,__float__()}。 如果 @code{__float__()} 未定义则将回退至 @ref{18a,,__index__()}。

@cartouche
@quotation 注解 
当从字符串转换时，字符串在 @code{+} 或 @code{-} 的周围必须不能有空格。例如 @code{complex('1+2j')} 是合法的，但 @code{complex('1 + 2j')} 会触发 @ref{1fb,,ValueError} 异常。
@end quotation
@end cartouche

@ref{11b3,,数字类型 --- int@comma{} float@comma{} complex} 描述了复数类型。


在 3.6 版更改: 您可以使用下划线将代码文字中的数字进行分组。



在 3.8 版更改: 如果 @ref{18d,,__complex__()} 和 @ref{18c,,__float__()} 未定义则回退至 @ref{18a,,__index__()}。

@end deffn

@geindex delattr() (內置函数)
@anchor{library/functions delattr}@anchor{1571}
@deffn {函数} delattr (object, name)

@ref{1575,,setattr()} 相关的函数。实参是一个对象和一个字符串。该字符串必须是对象的某个属性。如果对象允许，该函数将删除指定的属性。例如 @code{delattr(x, 'foobar')}  等价于 @code{del x.foobar} 。
@end deffn
@anchor{library/functions func-dict}@anchor{1574}

@deffn {类} dict (**kwarg)

@deffnx {类} dict (mapping, **kwarg)

@deffnx {类} dict (iterable, **kwarg)

创建一个新的字典。@ref{1b8,,dict} 对象是一个字典类。参见 @ref{1b8,,dict} 和 @ref{2f5,,映射类型 --- dict} 了解这个类。

其他容器类型，请参见内置的 @ref{262,,list}、@ref{b68,,set} 和 @ref{478,,tuple} 类，以及 @ref{1e,,collections} 模块。
@end deffn

@geindex dir() (內置函数)
@anchor{library/functions dir}@anchor{d2c}
@deffn {函数} dir ([object])

如果没有实参，则返回当前本地作用域中的名称列表。如果有实参，它会尝试返回该对象的有效属性列表。

如果对象有一个名为 @ref{314,,__dir__()} 的方法，那么该方法将被调用，并且必须返回一个属性列表。这允许实现自定义 @ref{313,,__getattr__()} 或 @ref{441,,__getattribute__()} 函数的对象能够自定义 @ref{d2c,,dir()} 来报告它们的属性。

如果对象不提供 @ref{314,,__dir__()}，这个函数会尝试从对象已定义的 @ref{4f6,,__dict__} 属性和类型对象收集信息。结果列表并不总是完整的，如果对象有自定义 @ref{313,,__getattr__()}，那结果可能不准确。

默认的 @ref{d2c,,dir()} 机制对不同类型的对象行为不同，它会试图返回最相关而不是最全的信息：


@itemize *

@item 
如果对象是模块对象，则列表包含模块的属性名称。

@item 
如果对象是类型或类对象，则列表包含它们的属性名称，并且递归查找所有基类的属性。

@item 
否则，列表包含对象的属性名称，它的类属性名称，并且递归查找它的类的所有基类的属性。
@end itemize

返回的列表按字母表排序。例如：

@example
>>> import struct
>>> dir()   # show the names in the module namespace  
['__builtins__', '__name__', 'struct']
>>> dir(struct)   # show the names in the struct module 
['Struct', '__all__', '__builtins__', '__cached__', '__doc__', '__file__',
 '__initializing__', '__loader__', '__name__', '__package__',
 '_clearcache', 'calcsize', 'error', 'pack', 'pack_into',
 'unpack', 'unpack_from']
>>> class Shape:
...     def __dir__(self):
...         return ['area', 'perimeter', 'location']
>>> s = Shape()
>>> dir(s)
['area', 'location', 'perimeter']
@end example

@cartouche
@quotation 注解 
因为 @ref{d2c,,dir()} 主要是为了便于在交互式时使用，所以它会试图返回人们感兴趣的名字集合，而不是试图保证结果的严格性或一致性，它具体的行为也可能在不同版本之间改变。例如，当实参是一个类时，metaclass 的属性不包含在结果列表中。
@end quotation
@end cartouche
@end deffn

@geindex divmod() (內置函数)
@anchor{library/functions divmod}@anchor{152}
@deffn {函数} divmod (a, b)

它将两个（非复数）数字作为实参，并在执行整数除法时返回一对商和余数。对于混合操作数类型，适用双目算术运算符的规则。对于整数，结果和 @code{(a // b, a % b)} 一致。对于浮点数，结果是 @code{(q, a % b)} ，@emph{q} 通常是 @code{math.floor(a / b)} 但可能会比 1 小。在任何情况下， @code{q * b + a % b} 和  @emph{a} 基本相等；如果 @code{a % b} 非零，它的符号和 @emph{b} 一样，并且 @code{0 <= abs(a % b) < abs(b)} 。
@end deffn

@geindex enumerate() (內置函数)
@anchor{library/functions enumerate}@anchor{ddc}
@deffn {函数} enumerate (iterable, start=0)

返回一个枚举对象。@emph{iterable} 必须是一个序列，或 @ref{fce,,iterator}，或其他支持迭代的对象。 @ref{ddc,,enumerate()} 返回的迭代器的 @ref{c5d,,__next__()} 方法返回一个元组，里面包含一个计数值（从 @emph{start} 开始，默认为 0）和通过迭代 @emph{iterable} 获得的值。

@example
>>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
>>> list(enumerate(seasons))
[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
>>> list(enumerate(seasons, start=1))
[(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]
@end example

等价于:

@example
def enumerate(sequence, start=0):
    n = start
    for elem in sequence:
        yield n, elem
        n += 1
@end example
@end deffn

@geindex eval() (內置函数)
@anchor{library/functions eval}@anchor{b89}
@deffn {函数} eval (expression[, globals[, locals]])

实参是一个字符串，以及可选的 globals 和 locals。@emph{globals} 实参必须是一个字典。@emph{locals} 可以是任何映射对象。

@emph{expression} 参数会作为一个 Python 表达式（从技术上说是一个条件列表）被解析并求值，并使用 @emph{globals} 和 @emph{locals} 字典作为全局和局部命名空间。 如果 @emph{globals} 字典存在且不包含以 @code{__builtins__} 为键的值，则会在解析 @emph{expression} 之前插入以此为键的对内置模块 @ref{13,,builtins} 的引用。 这意味着 @emph{expression} 通常具有对标准 @ref{13,,builtins} 模块的完全访问权限且受限的环境会被传播。 如果省略 @emph{locals} 字典则其默认值为 @emph{globals} 字典。 如果两个字典同时省略，则表达式执行时会使用 @ref{b89,,eval()} 被调用的环境中的 @emph{globals} 和 @emph{locals}。 请注意，@emph{eval()} 并没有对外围环境下的 (非局部) @ref{1583,,嵌套作用域} 的访问权限。

返回值就是表达式的求值结果。 语法错误将作为异常被报告。 例如：

@example
>>> x = 1
>>> eval('x+1')
2
@end example

这个函数也可以用来执行任何代码对象（如 @ref{1b4,,compile()}  创建的）。这种情况下，参数是代码对象，而不是字符串。如果编译该对象时的 @emph{mode} 实参是 @code{'exec'} 那么 @ref{b89,,eval()} 返回值为 @code{None} 。

提示： @ref{c3d,,exec()} 函数支持动态执行语句。 @ref{157b,,globals()} 和 @ref{44f,,locals()} 函数各自返回当前的全局和本地字典，因此您可以将它们传递给 @ref{b89,,eval()} 或 @ref{c3d,,exec()} 来使用。

另外可以参阅 @ref{4a0,,ast.literal_eval()}，该函数可以安全执行仅包含文字的表达式字符串。

引发一个 @ref{12d0,,审计事件} @code{exec} 附带参数 @code{code_object}。
@end deffn

@geindex 內置函数; exec

@geindex exec() (內置函数)
@anchor{library/functions exec}@anchor{c3d}
@deffn {函数} exec (object[, globals[, locals]])

这个函数支持动态执行 Python 代码。@emph{object} 必须是字符串或者代码对象。如果是字符串，那么该字符串将被解析为一系列 Python 语句并执行（除非发生语法错误）。@footnote{@w{(1)} 
解析器只接受 Unix 风格的行结束符。如果您从文件中读取代码，请确保用换行符转换模式转换 Windows 或 Mac 风格的换行符。
} 如果是代码对象，它将被直接执行。在任何情况下，被执行的代码都需要和文件输入一样是有效的（见参考手册中关于文件输入的章节）。请注意即使在传递给 @ref{c3d,,exec()} 函数的代码的上下文中，@ref{190,,return} 和 @ref{18f,,yield} 语句也不能在函数定义之外使用。该函数返回值是 @code{None} 。

无论哪种情况，如果省略了可选项，代码将在当前作用域内执行。 如果只提供了 @emph{globals}，则它必须是一个字典（不能是字典的子类），该字典将同时被用于全局和局部变量。 如果同时提供了 @emph{globals} 和 @emph{locals}，它们会分别被用于全局和局部变量。 如果提供了 @emph{locals}，则它可以是任何映射对象。 请记住在模块层级上，globals 和 locals 是同一个字典。 如果 exec 得到两个单独对象作为 @emph{globals} 和 @emph{locals}，则代码将如同嵌入类定义的情况一样执行。

如果 @emph{globals} 字典不包含 @code{__builtins__} 键值，则将为该键插入对内建 @ref{13,,builtins} 模块字典的引用。因此，在将执行的代码传递给 @ref{c3d,,exec()} 之前，可以通过将自己的 @code{__builtins__} 字典插入到 @emph{globals} 中来控制可以使用哪些内置代码。

引发一个 @ref{12d0,,审计事件} @code{exec} 附带参数 @code{code_object}。

@cartouche
@quotation 注解 
内置 @ref{157b,,globals()} 和 @ref{44f,,locals()} 函数各自返回当前的全局和本地字典，因此可以将它们传递给 @ref{c3d,,exec()} 的第二个和第三个实参。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
默认情况下，@emph{locals} 的行为如下面 @ref{44f,,locals()} 函数描述的一样：不要试图改变默认的 @emph{locals} 字典。如果您想在 @ref{c3d,,exec()} 函数返回时知道代码对 @emph{locals} 的变动，请明确地传递 @emph{locals} 字典。
@end quotation
@end cartouche
@end deffn

@geindex filter() (內置函数)
@anchor{library/functions filter}@anchor{c27}
@deffn {函数} filter (function, iterable)

用 @emph{iterable}  中函数 @emph{function} 返回真的那些元素，构建一个新的迭代器。@emph{iterable} 可以是一个序列，一个支持迭代的容器，或一个迭代器。如果 @emph{function} 是 @code{None} ，则会假设它是一个身份函数，即 @emph{iterable} 中所有返回假的元素会被移除。

请注意， @code{filter(function, iterable)} 相当于一个生成器表达式，当 function 不是 @code{None} 的时候为 @code{(item for item in iterable if function(item))}；function 是 @code{None} 的时候为 @code{(item for item in iterable if item)} 。

请参阅 @ref{1584,,itertools.filterfalse()} 了解，只有 @emph{function} 返回 false 时才选取 @emph{iterable} 中元素的补充函数。
@end deffn

@geindex float (內置类)
@anchor{library/functions float}@anchor{187}
@deffn {类} float ([x])

@geindex NaN
@geindex Infinity

返回从数字或字符串 @emph{x} 生成的浮点数。

如果实参是字符串，则它必须是包含十进制数字的字符串，字符串前面可以有符号，之前也可以有空格。可选的符号有 @code{'+'} 和 @code{'-'} ； @code{'+'} 对创建的值没有影响。实参也可以是 NaN（非数字）、正负无穷大的字符串。确切地说，除去首尾的空格后，输入必须遵循以下语法：

@example
@anchor{library/functions grammar-token-sign}@anchor{1585}sign           ::= "+" | "-"
@anchor{library/functions grammar-token-infinity}@anchor{1586}infinity       ::= "Infinity" | "inf"
@anchor{library/functions grammar-token-nan}@anchor{1587}nan            ::= "nan"
@anchor{library/functions grammar-token-numeric-value}@anchor{1588}numeric_value  ::= floatnumber | infinity | nan
@anchor{library/functions grammar-token-numeric-string}@anchor{1589}numeric_string ::= [sign] numeric_value
@end example

这里， @code{floatnumber} 是 Python 浮点数的字符串形式，详见 @ref{13a3,,浮点数字面值}。字母大小写都可以，例如，“inf”、“Inf”、“INFINITY”、“iNfINity” 都可以表示正无穷大。

另一方面，如果实参是整数或浮点数，则返回具有相同值（在 Python 浮点精度范围内）的浮点数。如果实参在 Python 浮点精度范围外，则会触发 @ref{95a,,OverflowError}。

对于一个普通 Python 对象 @code{x}，@code{float(x)} 会委托给 @code{x.__float__()}。 如果 @code{__float__()} 未定义则将回退至 @ref{18a,,__index__()}。

如果没有实参，则返回 @code{0.0} 。

示例:

@example
>>> float('+1.23')
1.23
>>> float('   -12345\n')
-12345.0
>>> float('1e-003')
0.001
>>> float('+1E6')
1000000.0
>>> float('-Infinity')
-inf
@end example

@ref{11b3,,数字类型 --- int@comma{} float@comma{} complex} 描述了浮点类型。


在 3.6 版更改: 您可以使用下划线将代码文字中的数字进行分组。



在 3.7 版更改: @emph{x} 现在只能作为位置参数。



在 3.8 版更改: 如果 @ref{18c,,__float__()} 未定义则回退至 @ref{18a,,__index__()}。

@end deffn

@geindex __format__
@geindex string; format() (built-in function)

@geindex format() (內置函数)
@anchor{library/functions format}@anchor{4d5}
@deffn {函数} format (value[, format_spec])

将 @emph{value} 转换为 @emph{format_spec} 控制的“格式化”表示。@emph{format_spec} 的解释取决于 @emph{value} 实参的类型，但是大多数内置类型使用标准格式化语法：@ref{4d8,,格式规格迷你语言}。

默认的 @emph{format_spec} 是一个空字符串，它通常和调用 @ref{329,,str(value)} 的结果相同。

调用 @code{format(value, format_spec)} 会转换成  @code{type(value).__format__(value, format_spec)} ，所以实例字典中的 @ref{948,,__format__()} 方法将不会调用。如果搜索到 @ref{2b0,,object} 有这个方法但  @emph{format_spec} 不为空，@emph{format_spec} 或返回值不是字符串，会触发 @ref{192,,TypeError} 异常。


在 3.4 版更改: 当 @emph{format_spec} 不是空字符串时， @code{object().__format__(format_spec)} 会触发  @ref{192,,TypeError}。

@end deffn
@anchor{library/functions func-frozenset}@anchor{1578}

@deffn {类} frozenset ([iterable])

返回一个新的 @ref{be7,,frozenset} 对象，它包含可选参数 @emph{iterable} 中的元素。 @code{frozenset} 是一个内置的类。有关此类的文档，请参阅 @ref{be7,,frozenset} 和 @ref{158a,,集合类型 --- set@comma{} frozenset}。

请参阅内建的 @ref{b68,,set}、@ref{262,,list}、@ref{478,,tuple} 和 @ref{1b8,,dict} 类，以及 @ref{1e,,collections} 模块来了解其它的容器。
@end deffn

@geindex getattr() (內置函数)
@anchor{library/functions getattr}@anchor{443}
@deffn {函数} getattr (object, name[, default])

返回对象命名属性的值。@emph{name} 必须是字符串。如果该字符串是对象的属性之一，则返回该属性的值。例如， @code{getattr(x, 'foobar')} 等同于 @code{x.foobar}。如果指定的属性不存在，且提供了 @emph{default} 值，则返回它，否则触发 @ref{393,,AttributeError}。
@end deffn

@geindex globals() (內置函数)
@anchor{library/functions globals}@anchor{157b}
@deffn {函数} globals ()

返回表示当前全局符号表的字典。这总是当前模块的字典（在函数或方法中，不是调用它的模块，而是定义它的模块）。
@end deffn

@geindex hasattr() (內置函数)
@anchor{library/functions hasattr}@anchor{442}
@deffn {函数} hasattr (object, name)

该实参是一个对象和一个字符串。如果字符串是对象的属性之一的名称，则返回 @code{True}，否则返回 @code{False}。（此功能是通过调用 @code{getattr(object, name)} 看是否有 @ref{393,,AttributeError} 异常来实现的。）
@end deffn

@geindex hash() (內置函数)
@anchor{library/functions hash}@anchor{9be}
@deffn {函数} hash (object)

返回该对象的哈希值（如果它有的话）。哈希值是整数。它们在字典查找元素时用来快速比较字典的键。相同大小的数字变量有相同的哈希值（即使它们类型不同，如 1 和 1.0）。

@cartouche
@quotation 注解 
如果对象实现了自己的 @ref{339,,__hash__()} 方法，请注意，@ref{9be,,hash()} 根据机器的字长来截断返回值。另请参阅 @ref{339,,__hash__()}。
@end quotation
@end cartouche
@end deffn

@geindex help() (內置函数)
@anchor{library/functions help}@anchor{56d}
@deffn {函数} help ([object])

启动内置的帮助系统（此函数主要在交互式中使用）。如果没有实参，解释器控制台里会启动交互式帮助系统。如果实参是一个字符串，则在模块、函数、类、方法、关键字或文档主题中搜索该字符串，并在控制台上打印帮助信息。如果实参是其他任意对象，则会生成该对象的帮助页。

请注意如果在函数的形参列表中出现了斜杠 (/)，则它在发起调用 @ref{56d,,help()} 的时候意味着斜杠之前的均为仅限位置形参。 更多相关信息，请参阅 @ref{158b,,有关仅限位置形参的 FAQ 条目}。

该函数通过 @ref{eb,,site} 模块加入到内置命名空间。


在 3.4 版更改: @ref{d9,,pydoc} 和 @ref{a0,,inspect} 的变更使得可调用对象的签名信息更加全面和一致。

@end deffn

@geindex hex() (內置函数)
@anchor{library/functions hex}@anchor{c5f}
@deffn {函数} hex (x)

将整数转换为以“0x”为前缀的小写十六进制字符串。如果 @emph{x} 不是 Python @ref{184,,int} 对象，则必须定义返回整数的 @ref{18a,,__index__()} 方法。一些例子：

@example
>>> hex(255)
'0xff'
>>> hex(-42)
'-0x2a'
@end example

如果要将整数转换为大写或小写的十六进制字符串，并可选择有无“0x”前缀，则可以使用如下方法：

@example
>>> '%#x' % 255, '%x' % 255, '%X' % 255
('0xff', 'ff', 'FF')
>>> format(255, '#x'), format(255, 'x'), format(255, 'X')
('0xff', 'ff', 'FF')
>>> f'@{255:#x@}', f'@{255:x@}', f'@{255:X@}'
('0xff', 'ff', 'FF')
@end example

另见 @ref{4d5,,format()} 获取更多信息。

另请参阅 @ref{184,,int()} 将十六进制字符串转换为以 16 为基数的整数。

@cartouche
@quotation 注解 
如果要获取浮点数的十六进制字符串形式，请使用 @ref{12b9,,float.hex()} 方法。
@end quotation
@end cartouche
@end deffn

@geindex id() (內置函数)
@anchor{library/functions id}@anchor{d7f}
@deffn {函数} id (object)

返回对象的“标识值”。该值是一个整数，在此对象的生命周期中保证是唯一且恒定的。两个生命期不重叠的对象可能具有相同的 @ref{d7f,,id()} 值。

@strong{CPython implementation detail:} This is the address of the object in memory.
@end deffn

@geindex input() (內置函数)
@anchor{library/functions input}@anchor{c64}
@deffn {函数} input ([prompt])

如果存在 @emph{prompt} 实参，则将其写入标准输出，末尾不带换行符。接下来，该函数从输入中读取一行，将其转换为字符串（除了末尾的换行符）并返回。当读取到 EOF 时，则触发 @ref{c65,,EOFError}。例如:

@example
>>> s = input('--> ')  
--> Monty Python's Flying Circus
>>> s  
"Monty Python's Flying Circus"
@end example

如果加载了 @ref{de,,readline} 模块，@ref{c64,,input()} 将使用它来提供复杂的行编辑和历史记录功能。

引发一个 @ref{12d0,,审计事件} @code{builtins.input} 附带参数 @code{prompt}。


在成功读取输入之后引发一个审计事件 @code{builtins.input/result} 附带结果。

@end deffn

@geindex int (內置类)
@anchor{library/functions int}@anchor{184}
@deffn {类} int ([x])

@deffnx {类} int (x, base=10)

返回一个基于数字或字符串 @emph{x} 构造的整数对象，或者在未给出参数时返回 @code{0}。 如果 @emph{x} 定义了 @ref{18b,,__int__()}，@code{int(x)} 将返回 @code{x.__int__()}。 如果 @emph{x} 定义了 @ref{18a,,__index__()}，它将返回 @code{x.__index__()}。 如果 @emph{x} 定义了 @ref{141b,,__trunc__()}，它将返回 @code{x.__trunc__()}。 对于浮点数，它将向零舍入。

如果 @emph{x} 不是数字，或者有 @emph{base} 参数，@emph{x} 必须是字符串、@ref{32a,,bytes}、表示进制为 @emph{base} 的 @ref{1398,,整数字面值} 的 @ref{32b,,bytearray} 实例。该文字前可以有 @code{+} 或 @code{-} （中间不能有空格），前后可以有空格。一个进制为 n 的数字包含 0 到 n-1 的数，其中 @code{a} 到 @code{z} （或 @code{A} 到 @code{Z} ）表示 10 到 35。默认的 @emph{base} 为 10 ，允许的进制有 0、2-36。2、8、16 进制的数字可以在代码中用 @code{0b}/@code{0B} 、 @code{0o}/@code{0O} 、 @code{0x}/@code{0X} 前缀来表示。进制为 0 将安照代码的字面量来精确解释，最后的结果会是 2、8、10、16 进制中的一个。所以 @code{int('010', 0)} 是非法的，但 @code{int('010')} 和 @code{int('010', 8)} 是合法的。

整数类型定义请参阅 @ref{11b3,,数字类型 --- int@comma{} float@comma{} complex} 。


在 3.4 版更改: 如果 @emph{base} 不是 @ref{184,,int} 的实例，但 @emph{base} 对象有 @ref{18a,,base.__index__} 方法，则会调用该方法来获取进制数。以前的版本使用 @ref{18b,,base.__int__} 而不是 @ref{18a,,base.__index__}。



在 3.6 版更改: 您可以使用下划线将代码文字中的数字进行分组。



在 3.7 版更改: @emph{x} 现在只能作为位置参数。



在 3.8 版更改: 如果 @ref{18b,,__int__()} 未定义则回退至 @ref{18a,,__index__()}。

@end deffn

@geindex isinstance() (內置函数)
@anchor{library/functions isinstance}@anchor{449}
@deffn {函数} isinstance (object, classinfo)

如果参数 @emph{object} 是参数 @emph{classinfo} 的实例或者是其 (直接、间接或 @ref{b2c,,虚拟}) 子类则返回 @code{True}。 如果 @emph{object} 不是给定类型的对象，函数将总是返回 @code{False}。 如果 @emph{classinfo} 是类型对象元组（或由其他此类元组递归组成的元组），那么如果 @emph{object} 是其中任何一个类型的实例就返回 @code{True}。 如果 @emph{classinfo} 既不是类型，也不是类型元组或类型元组的元组，则将引发 @ref{192,,TypeError} 异常。
@end deffn

@geindex issubclass() (內置函数)
@anchor{library/functions issubclass}@anchor{44a}
@deffn {函数} issubclass (class, classinfo)

如果 @emph{class} 是 @emph{classinfo} 的 (直接、间接或 @ref{b2c,,虚拟}) 子类则返回 @code{True}。 类会被视作其自身的子类。 @emph{classinfo} 也以是类对象的元组，在此情况下 @emph{classinfo} 中的每个条目都将被检查。 在任何其他情况下，都将引发 @ref{192,,TypeError} 异常。
@end deffn

@geindex iter() (內置函数)
@anchor{library/functions iter}@anchor{d20}
@deffn {函数} iter (object[, sentinel])

返回一个 @ref{fce,,iterator} 对象。根据是否存在第二个实参，第一个实参的解释是非常不同的。如果没有第二个实参，@emph{object} 必须是支持迭代协议（有 @ref{509,,__iter__()} 方法）的集合对象，或必须支持序列协议（有 @ref{27f,,__getitem__()} 方法，且数字参数从 @code{0} 开始）。如果它不支持这些协议，会触发 @ref{192,,TypeError}。如果有第二个实参 @emph{sentinel}，那么 @emph{object} 必须是可调用的对象。这种情况下生成的迭代器，每次迭代调用它的 @ref{c5d,,__next__()} 方法时都会不带实参地调用 @emph{object}；如果返回的结果是 @emph{sentinel} 则触发 @ref{480,,StopIteration}，否则返回调用结果。

另请参阅 @ref{13f4,,迭代器类型}。

适合 @ref{d20,,iter()} 的第二种形式的应用之一是构建块读取器。 例如，从二进制数据库文件中读取固定宽度的块，直至到达文件的末尾:

@example
from functools import partial
with open('mydata.db', 'rb') as f:
    for block in iter(partial(f.read, 64), b'@w{'}):
        process_block(block)
@end example
@end deffn

@geindex len() (內置函数)
@anchor{library/functions len}@anchor{150}
@deffn {函数} len (s)

返回对象的长度（元素个数）。实参可以是序列（如 string、bytes、tuple、list 或 range 等）或集合（如 dictionary、set 或 frozen set 等）。
@end deffn
@anchor{library/functions func-list}@anchor{1579}

@deffn {类} list ([iterable])

虽然被称为函数，@ref{262,,list} 实际上是一种可变序列类型，详情请参阅 @ref{158c,,列表} 和 @ref{1204,,序列类型 --- list@comma{} tuple@comma{} range}。
@end deffn

@geindex locals() (內置函数)
@anchor{library/functions locals}@anchor{44f}
@deffn {函数} locals ()

更新并返回表示当前本地符号表的字典。 在函数代码块但不是类代码块中调用 @ref{44f,,locals()} 时将返回自由变量。 请注意在模块层级上，@ref{44f,,locals()} 和 @ref{157b,,globals()} 是同一个字典。

@cartouche
@quotation 注解 
不要更改此字典的内容；更改不会影响解释器使用的局部变量或自由变量的值。
@end quotation
@end cartouche
@end deffn

@geindex map() (內置函数)
@anchor{library/functions map}@anchor{c26}
@deffn {函数} map (function, iterable, ...)

返回一个将 @emph{function} 应用于 @emph{iterable} 中每一项并输出其结果的迭代器。 如果传入了额外的 @emph{iterable} 参数，@emph{function} 必须接受相同个数的实参并被应用于从所有可迭代对象中并行获取的项。 当有多个可迭代对象时，最短的可迭代对象耗尽则整个迭代就将结束。 对于函数的输入已经是参数元组的情况，请参阅 @ref{a23,,itertools.starmap()}。
@end deffn

@geindex max() (內置函数)
@anchor{library/functions max}@anchor{804}
@deffn {函数} max (iterable, *[, key, default])

@deffnx {函数} max (arg1, arg2, *args[, key])

返回可迭代对象中最大的元素，或者返回两个及以上实参中最大的。

如果只提供了一个位置参数，它必须是非空 @ref{ba5,,iterable}，返回可迭代对象中最大的元素；如果提供了两个及以上的位置参数，则返回最大的位置参数。

有两个可选只能用关键字的实参。@emph{key} 实参指定排序函数用的参数，如传给 @ref{43f,,list.sort()} 的。@emph{default} 实参是当可迭代对象为空时返回的值。如果可迭代对象为空，并且没有给 @emph{default} ，则会触发 @ref{1fb,,ValueError}。

如果有多个最大元素，则此函数将返回第一个找到的。这和其他稳定排序工具如 @code{sorted(iterable, key=keyfunc, reverse=True)[0]} 和 @code{heapq.nlargest(1, iterable, key=keyfunc)} 保持一致。


3.4 新版功能: keyword-only 实参 @emph{default} 。



在 3.8 版更改: @emph{key} 可以为 @code{None}。

@end deffn
@anchor{library/functions func-memoryview}@anchor{1572}

@deffn {类} memoryview (obj)

返回由给定实参创建的“内存视图”对象。有关详细信息，请参阅 @ref{158d,,内存视图}。
@end deffn

@geindex min() (內置函数)
@anchor{library/functions min}@anchor{803}
@deffn {函数} min (iterable, *[, key, default])

@deffnx {函数} min (arg1, arg2, *args[, key])

返回可迭代对象中最小的元素，或者返回两个及以上实参中最小的。

如果只提供了一个位置参数，它必须是 @ref{ba5,,iterable}，返回可迭代对象中最小的元素；如果提供了两个及以上的位置参数，则返回最小的位置参数。

有两个可选只能用关键字的实参。@emph{key} 实参指定排序函数用的参数，如传给 @ref{43f,,list.sort()} 的。@emph{default} 实参是当可迭代对象为空时返回的值。如果可迭代对象为空，并且没有给 @emph{default} ，则会触发 @ref{1fb,,ValueError}。

如果有多个最小元素，则此函数将返回第一个找到的。这和其他稳定排序工具如 @code{sorted(iterable, key=keyfunc)[0]} 和 @code{heapq.nsmallest(1, iterable, key=keyfunc)} 保持一致。


3.4 新版功能: keyword-only 实参 @emph{default} 。



在 3.8 版更改: @emph{key} 可以为 @code{None}。

@end deffn

@geindex next() (內置函数)
@anchor{library/functions next}@anchor{67c}
@deffn {函数} next (iterator[, default])

通过调用 @emph{iterator} 的 @ref{c5d,,__next__()} 方法获取下一个元素。如果迭代器耗尽，则返回给定的 @emph{default}，如果没有默认值则触发 @ref{480,,StopIteration}。
@end deffn

@geindex object (內置类)
@anchor{library/functions object}@anchor{2b0}
@deffn {类} object

返回一个没有特征的新对象。@ref{2b0,,object} 是所有类的基类。它具有所有 Python 类实例的通用方法。这个函数不接受任何实参。

@cartouche
@quotation 注解 
由于 @ref{2b0,,object} 没有 @ref{4f6,,__dict__}，因此无法将任意属性赋给 @ref{2b0,,object} 的实例。
@end quotation
@end cartouche
@end deffn

@geindex oct() (內置函数)
@anchor{library/functions oct}@anchor{c5e}
@deffn {函数} oct (x)

将一个整数转变为一个前缀为“0o”的八进制字符串。结果是一个合法的 Python 表达式。如果 @emph{x} 不是 Python 的 @ref{184,,int} 对象，那它需要定义 @ref{18a,,__index__()}  方法返回一个整数。一些例子：

@example
>>> oct(8)
'0o10'
>>> oct(-56)
'-0o70'
@end example

如果要将整数转换为八进制字符串，并可选择有无“0o”前缀，则可以使用如下方法：

@example
>>> '%#o' % 10, '%o' % 10
('0o12', '12')
>>> format(10, '#o'), format(10, 'o')
('0o12', '12')
>>> f'@{10:#o@}', f'@{10:o@}'
('0o12', '12')
@end example

另见 @ref{4d5,,format()} 获取更多信息。

@quotation

@geindex file object; open() built-in function
@end quotation
@end deffn

@geindex open() (內置函数)
@anchor{library/functions open}@anchor{4ea}
@deffn {函数} open (file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

打开 @emph{file} 并返回对应的 @ref{b3b,,file object}。如果该文件不能打开，则触发 @ref{1d3,,OSError}。

@emph{file} 是一个 @ref{363,,path-like object}，表示将要打开的文件的路径（绝对路径或者当前工作目录的相对路径），也可以是要被封装的整数类型文件描述符。（如果是文件描述符，它会随着返回的 I/O 对象关闭而关闭，除非 @emph{closefd} 被设为 @code{False} 。）

@emph{mode} 是一个可选字符串，用于指定打开文件的模式。默认值是 @code{'r'}  ，这意味着它以文本模式打开并读取。其他常见模式有：写入 @code{'w'} （截断已经存在的文件）；排它性创建 @code{'x'} ；追加写 @code{'a'} （在 @emph{一些}  Unix 系统上，无论当前的文件指针在什么位置，@emph{所有} 写入都会追加到文件末尾）。在文本模式，如果 @emph{encoding} 没有指定，则根据平台来决定使用的编码：使用 @code{locale.getpreferredencoding(False)} 来获取本地编码。（要读取和写入原始字节，请使用二进制模式并不要指定 @emph{encoding}。）可用的模式有：
@anchor{library/functions filemodes}@anchor{158e}
@geindex file; modes


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

字符

@tab

含义

@item

@code{'r'}

@tab

读取（默认）

@item

@code{'w'}

@tab

写入，并先截断文件

@item

@code{'x'}

@tab

排它性创建，如果文件已存在则失败

@item

@code{'a'}

@tab

写入，如果文件存在则在末尾追加

@item

@code{'b'}

@tab

二进制模式

@item

@code{'t'}

@tab

文本模式（默认）

@item

@code{'+'}

@tab

打开用于更新（读取与写入）

@end multitable


默认模式为 @code{'r'} (打开用于读取文本，与 @code{'rt'} 同义)。 模式 @code{'w+'} 与 @code{'w+b'} 将打开文件并清空内容。 模式 @code{'r+'} 与 @code{'r+b'} 将打开文件并不清空内容。

正如在 @ref{158f,,概述} 中提到的，Python区分二进制和文本I/O。以二进制模式打开的文件（包括 @emph{mode} 参数中的 @code{'b'} ）返回的内容为 @code{bytes`对象，不进行任何解码。在文本模式下（默认情况下，或者在 *mode* 参数中包含 `}'t'` ）时，文件内容返回为 @ref{329,,str} ，首先使用指定的 @emph{encoding} （如果给定）或者使用平台默认的的字节编码解码。

此外还允许使用一个模式字符 @code{'U'}，该字符已不再具有任何效果，并被视为已弃用。 之前它会在文本模式中启用 @ref{5ef,,universal newlines}，这在 Python 3.0 中成为默认行为。 请参阅 @ref{1590,,newline} 形参的文档了解更多细节。

@cartouche
@quotation 注解 
Python不依赖于底层操作系统的文本文件概念;所有处理都由Python本身完成，因此与平台无关。
@end quotation
@end cartouche

@emph{buffering} 是一个可选的整数，用于设置缓冲策略。传递0以切换缓冲关闭（仅允许在二进制模式下），1选择行缓冲（仅在文本模式下可用），并且>1的整数以指示固定大小的块缓冲区的大小（以字节为单位）。如果没有给出 @emph{buffering} 参数，则默认缓冲策略的工作方式如下:


@itemize *

@item 
二进制文件以固定大小的块进行缓冲；使用启发式方法选择缓冲区的大小，尝试确定底层设备的“块大小”或使用 @ref{1591,,io.DEFAULT_BUFFER_SIZE}。在许多系统上，缓冲区的长度通常为4096或8192字节。

@item 
“交互式”文本文件（ @ref{1592,,isatty()} 返回 @code{True} 的文件）使用行缓冲。其他文本文件使用上述策略用于二进制文件。
@end itemize

@emph{encoding} 是用于解码或编码文件的编码的名称。这应该只在文本模式下使用。默认编码是依赖于平台的（不 管 @ref{39d,,locale.getpreferredencoding()} 返回何值），但可以使用任何Python支持的 @ref{1593,,text encoding} 。有关支持的编码列表，请参阅 @ref{1c,,codecs} 模块。

@emph{errors} 是一个可选的字符串参数，用于指定如何处理编码和解码错误 - 这不能在二进制模式下使用。可以使用各种标准错误处理程序（列在 @ref{12f7,,错误处理方案} ），但是使用 @ref{dee,,codecs.register_error()} 注册的任何错误处理名称也是有效的。标准名称包括:


@itemize *

@item 
如果存在编码错误，@code{'strict'} 会引发 @ref{1fb,,ValueError} 异常。 默认值 @code{None} 具有相同的效果。

@item 
@code{'ignore'} 忽略错误。请注意，忽略编码错误可能会导致数据丢失。

@item 
@code{'replace'} 会将替换标记（例如 @code{'?'} ）插入有错误数据的地方。

@item 
@code{'surrogateescape'} 将表示任何不正确的字节作为Unicode专用区中的代码点，范围从U+DC80到U+DCFF。当在写入数据时使用 @code{surrogateescape} 错误处理程序时，这些私有代码点将被转回到相同的字节中。这对于处理未知编码的文件很有用。

@item 
只有在写入文件时才支持 @code{'xmlcharrefreplace'}。编码不支持的字符将替换为相应的XML字符引用 @code{&#nnn;}。

@item 
@code{'backslashreplace'} 用Python的反向转义序列替换格式错误的数据。

@item 
@code{'namereplace'} （也只在编写时支持）用 @code{\N@{...@}} 转义序列替换不支持的字符。
@end itemize

@geindex universal newlines; open() built-in function
@anchor{library/functions open-newline-parameter}@anchor{1590}
@emph{newline} 控制 @ref{5ef,,universal newlines} 模式如何生效（它仅适用于文本模式）。它可以是 @code{None}，@code{'@w{'}}，@code{'\n'}，@code{'\r'} 和 @code{'\r\n'}。它的工作原理:


@itemize *

@item 
从流中读取输入时，如果 @emph{newline} 为 @code{None}，则启用通用换行模式。输入中的行可以以 @code{'\n'}，@code{'\r'} 或 @code{'\r\n'} 结尾，这些行被翻译成 @code{'\n'} 在返回呼叫者之前。如果它是 @code{'@w{'}}，则启用通用换行模式，但行结尾将返回给调用者未翻译。如果它具有任何其他合法值，则输入行仅由给定字符串终止，并且行结尾将返回给未调用的调用者。

@item 
将输出写入流时，如果 @emph{newline} 为 @code{None}，则写入的任何 @code{'\n'} 字符都将转换为系统默认行分隔符 @ref{1594,,os.linesep}。如果 @emph{newline} 是 @code{'@w{'}} 或 @code{'\n'}，则不进行翻译。如果 @emph{newline} 是任何其他合法值，则写入的任何 @code{'\n'} 字符将被转换为给定的字符串。
@end itemize

如果 @emph{closefd} 是 @code{False} 并且给出了文件描述符而不是文件名，那么当文件关闭时，底层文件描述符将保持打开状态。如果给出文件名则 @emph{closefd} 必须为 @code{True} （默认值），否则将引发错误。

可以通过传递可调用的 @emph{opener} 来使用自定义开启器。然后通过使用参数（ @emph{file}，@emph{flags} ）调用 @emph{opener} 获得文件对象的基础文件描述符。 @emph{opener} 必须返回一个打开的文件描述符（使用 @ref{65f,,os.open} as @emph{opener} 时与传递 @code{None} 的效果相同）。

新创建的文件是 @ref{7f4,,不可继承的}。

下面的示例使用 @ref{65f,,os.open()} 函数的 @ref{a2a,,dir_fd} 的形参，从给定的目录中用相对路径打开文件:

@example
>>> import os
>>> dir_fd = os.open('somedir', os.O_RDONLY)
>>> def opener(path, flags):
...     return os.open(path, flags, dir_fd=dir_fd)
...
>>> with open('spamspam.txt', 'w', opener=opener) as f:
...     print('This will be written to somedir/spamspam.txt', file=f)
...
>>> os.close(dir_fd)  # don't leak a file descriptor
@end example

@ref{4ea,,open()} 函数所返回的 @ref{b3b,,file object} 类型取决于所用模式。 当使用 @ref{4ea,,open()} 以文本模式 (@code{'w'}, @code{'r'}, @code{'wt'}, @code{'rt'} 等) 打开文件时，它将返回 @ref{c32,,io.TextIOBase} (特别是 @ref{5ee,,io.TextIOWrapper}) 的一个子类。 当使用缓冲以二进制模式打开文件时，返回的类是 @ref{583,,io.BufferedIOBase} 的一个子类。 具体的类会有多种：在只读的二进制模式下，它将返回 @ref{b83,,io.BufferedReader}；在写入二进制和追加二进制模式下，它将返回 @ref{1595,,io.BufferedWriter}，而在读/写模式下，它将返回 @ref{1596,,io.BufferedRandom}。 当禁用缓冲时，则会返回原始流，即 @ref{a0e,,io.RawIOBase} 的一个子类 @ref{c9d,,io.FileIO}。

@geindex line-buffered I/O
@geindex unbuffered I/O
@geindex buffer size@comma{} I/O
@geindex I/O control; buffering
@geindex binary mode
@geindex text mode
@geindex 模块; sys

另请参阅文件操作模块，例如 @ref{80,,fileinput}、@ref{a1,,io} （声明了 @ref{4ea,,open()}）、@ref{c4,,os}、@ref{c5,,os.path}、@ref{103,,tempfile} 和 @ref{e9,,shutil}。

引发一个 @ref{12d0,,审计事件} @code{open} 附带参数 @code{file}, @code{mode}, @code{flags}。

@code{mode} 与 @code{flags} 参数可以在原始调用的基础上被修改或传递。


@quotation
在 3.3 版更改: 

@itemize *

@item 
增加了 @emph{opener} 形参。

@item 
增加了 @code{'x'} 模式。

@item 
过去触发的 @ref{98c,,IOError}，现在是 @ref{1d3,,OSError} 的别名。

@item 
如果文件已存在但使用了排它性创建模式（ @code{'x'} ），现在会触发 @ref{952,,FileExistsError}。
@end itemize
@end quotation



@quotation
在 3.4 版更改: 

@itemize *

@item 
文件现在禁止继承。
@end itemize
@end quotation



Deprecated since version 3.4, will be removed in version 3.9: @code{'U'} 模式。



@quotation
在 3.5 版更改: 

@itemize *

@item 
如果系统调用被中断，但信号处理程序没有触发异常，此函数现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@item 
增加了 @code{'namereplace'} 错误处理接口。
@end itemize
@end quotation



@quotation
在 3.6 版更改: 

@itemize *

@item 
增加对实现了 @ref{4e5,,os.PathLike} 对象的支持。

@item 
在 Windows 上，打开一个控制台缓冲区将返回 @ref{a0e,,io.RawIOBase} 的子类，而不是 @ref{c9d,,io.FileIO}。
@end itemize
@end quotation

@end deffn

@geindex ord() (內置函数)
@anchor{library/functions ord}@anchor{13be}
@deffn {函数} ord (c)

对表示单个 Unicode 字符的字符串，返回代表它 Unicode 码点的整数。例如 @code{ord('a')} 返回整数 @code{97}， @code{ord('€')} （欧元符号）返回 @code{8364} 。这是 @ref{13bf,,chr()} 的逆函数。
@end deffn

@geindex pow() (內置函数)
@anchor{library/functions pow}@anchor{19a}
@deffn {函数} pow (base, exp[, mod])

返回 @emph{base} 的 @emph{exp} 次幂；如果 @emph{mod} 存在，则返回 @emph{base} 的 @emph{exp} 次幂对 @emph{mod} 取余（比 @code{pow(base, exp) % mod} 更高效）。 两参数形式 @code{pow(base, exp)} 等价于乘方运算符: @code{base**exp}。

参数必须具有数值类型。 对于混用的操作数类型，则将应用双目算术运算符的类型强制转换规则。 对于 @ref{184,,int} 操作数，结果具有与操作数相同的类型（强制转换后），除非第二个参数为负值；在这种情况下，所有参数将被转换为浮点数并输出浮点数结果。 例如，@code{10**2} 返回 @code{100}，但 @code{10**-2} 返回 @code{0.01}。

对于 @ref{184,,int} 操作数 @emph{base} 和 @emph{exp}，如果给出 @emph{mod}，则 @emph{mod} 必须为整数类型并且 @emph{mod} 必须不为零。 如果给出 @emph{mod} 并且 @emph{exp} 为负值，则 @emph{base} 必须相对于 @emph{mod} 不可整除。 在这种情况下，将会返回 @code{pow(inv_base, -exp, mod)}，其中 @emph{inv_base} 为 @emph{base} 的倒数对 @emph{mod} 取余。

下面的例子是 @code{38} 的倒数对 @code{97} 取余:

@example
>>> pow(38, -1, mod=97)
23
>>> 23 * 38 % 97 == 1
True
@end example


在 3.8 版更改: 对于 @ref{184,,int} 操作数，三参数形式的 @code{pow} 现在允许第二个参数为负值，即可以计算倒数的余数。



在 3.8 版更改: 允许关键字参数。 之前只支持位置参数。

@end deffn

@geindex print() (內置函数)
@anchor{library/functions print}@anchor{880}
@deffn {函数} print (*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

将 @emph{objects} 打印到 @emph{file} 指定的文本流，以 @emph{sep} 分隔并在末尾加上 @emph{end}。 @emph{sep}, @emph{end}, @emph{file} 和 @emph{flush} 如果存在，它们必须以关键字参数的形式给出。

所有非关键字参数都会被转换为字符串，就像是执行了 @ref{329,,str()} 一样，并会被写入到流，以 @emph{sep} 且在末尾加上 @emph{end}。 @emph{sep} 和 @emph{end} 都必须为字符串；它们也可以为 @code{None}，这意味着使用默认值。 如果没有给出 @emph{objects}，则 @ref{880,,print()} 将只写入 @emph{end}。

@emph{file} 参数必须是一个具有 @code{write(string)} 方法的对象；如果参数不存在或为 @code{None}，则将使用 @ref{307,,sys.stdout}。 由于要打印的参数会被转换为文本字符串，因此 @ref{880,,print()} 不能用于二进制模式的文件对象。 对于这些对象，应改用 @code{file.write(...)}。

输出是否被缓存通常决定于 @emph{file}，但如果 @emph{flush} 关键字参数为真值，流会被强制刷新。


在 3.3 版更改: 增加了 @emph{flush} 关键字参数。

@end deffn

@geindex property (內置类)
@anchor{library/functions property}@anchor{1d7}
@deffn {类} property (fget=None, fset=None, fdel=None, doc=None)

返回 property 属性。

@emph{fget} 是获取属性值的函数。 @emph{fset} 是用于设置属性值的函数。 @emph{fdel} 是用于删除属性值的函数。并且 @emph{doc} 为属性对象创建文档字符串。

一个典型的用法是定义一个托管属性 @code{x}:

@example
class C:
    def __init__(self):
        self._x = None

    def getx(self):
        return self._x

    def setx(self, value):
        self._x = value

    def delx(self):
        del self._x

    x = property(getx, setx, delx, "I'm the 'x' property.")
@end example

如果 @emph{c} 是 @emph{C} 的实例，@code{c.x} 将调用getter，@code{c.x = value} 将调用setter， @code{del c.x} 将调用deleter。

如果给出，@emph{doc} 将成为该 property 属性的文档字符串。 否则该 property 将拷贝 @emph{fget} 的文档字符串（如果存在）。 这令使用 @ref{1d7,,property()} 作为 @ref{283,,decorator} 来创建只读的特征属性可以很容易地实现:

@example
class Parrot:
    def __init__(self):
        self._voltage = 100000

    @@property
    def voltage(self):
        """Get the current voltage."""
        return self._voltage
@end example

以上 @code{@@property} 装饰器会将 @code{voltage()} 方法转化为一个具有相同名称的只读属性的 "getter"，并将 @emph{voltage} 的文档字符串设置为 "Get the current voltage."

特征属性对象具有 @code{getter}, @code{setter} 以及 @code{deleter} 方法，它们可用作装饰器来创建该特征属性的副本，并将相应的访问函数设为所装饰的函数。  这最好是用一个例子来解释:

@example
class C:
    def __init__(self):
        self._x = None

    @@property
    def x(self):
        """I'm the 'x' property."""
        return self._x

    @@x.setter
    def x(self, value):
        self._x = value

    @@x.deleter
    def x(self):
        del self._x
@end example

上述代码与第一个例子完全等价。 注意一定要给附加函数与原始的特征属性相同的名称 (在本例中为 @code{x}。)

返回的特征属性对象同样具有与构造器参数相对应的属性 @code{fget}, @code{fset} 和 @code{fdel}。


在 3.5 版更改: 特征属性对象的文档字符串现在是可写的。

@end deffn
@anchor{library/functions func-range}@anchor{157a}

@deffn {类} range (stop)

@deffnx {类} range (start, stop[, step])

虽然被称为函数，但 @ref{9b8,,range} 实际上是一个不可变的序列类型，参见在 @ref{1597,,range 对象} 与 @ref{1204,,序列类型 --- list@comma{} tuple@comma{} range} 中的文档说明。
@end deffn

@geindex repr() (內置函数)
@anchor{library/functions repr}@anchor{7c6}
@deffn {函数} repr (object)

返回包含一个对象的可打印表示形式的字符串。 对于许多类型来说，该函数会尝试返回的字符串将会与该对象被传递给 @ref{b89,,eval()} 时所生成的对象具有相同的值，在其他情况下表示形式会是一个括在尖括号中的字符串，其中包含对象类型的名称与通常包括对象名称和地址的附加信息。 类可以通过定义 @ref{337,,__repr__()} 方法来控制此函数为它的实例所返回的内容。
@end deffn

@geindex reversed() (內置函数)
@anchor{library/functions reversed}@anchor{18e}
@deffn {函数} reversed (seq)

返回一个反向的 @ref{fce,,iterator}。 @emph{seq} 必须是一个具有 @ref{529,,__reversed__()} 方法的对象或者是支持该序列协议（具有从 @code{0} 开始的整数类型参数的 @ref{dc4,,__len__()} 方法和 @ref{27f,,__getitem__()} 方法）。
@end deffn

@geindex round() (內置函数)
@anchor{library/functions round}@anchor{c66}
@deffn {函数} round (number[, ndigits])

返回 @emph{number} 舍入到小数点后 @emph{ndigits} 位精度的值。 如果 @emph{ndigits} 被省略或为 @code{None}，则返回最接近输入值的整数。

对于支持 @ref{c66,,round()} 的内置类型，值会被舍入到最接近的 10 的负 @emph{ndigits} 次幂的倍数；如果与两个倍数的距离相等，则选择偶数 (因此，@code{round(0.5)} 和 @code{round(-0.5)} 均为 @code{0} 而 @code{round(1.5)} 为 @code{2})。 任何整数值都可作为有效的 @emph{ndigits} (正数、零或负数)。 如果 @emph{ndigits} 被省略或为 @code{None} 则返回值将为整数。 否则返回值与 @emph{number} 的类型相同。

对于一般的 Python 对象 @code{number}, @code{round} 将委托给 @code{number.__round__}。

@cartouche
@quotation 注解 
对浮点数执行 @ref{c66,,round()} 的行为可能会令人惊讶：例如，@code{round(2.675, 2)} 将给出 @code{2.67} 而不是期望的 @code{2.68}。 这不算是程序错误：这一结果是由于大多数十进制小数实际上都不能以浮点数精确地表示。 请参阅 @ref{12b7,,浮点算术：争议和限制} 了解更多信息。
@end quotation
@end cartouche
@end deffn
@anchor{library/functions func-set}@anchor{1573}

@deffn {类} set ([iterable])

返回一个新的 @ref{b68,,set} 对象，可以选择带有从 @emph{iterable} 获取的元素。 @code{set} 是一个内置类型。 请查看 @ref{b68,,set} 和 @ref{158a,,集合类型 --- set@comma{} frozenset} 获取关于这个类的文档。

有关其他容器请参看内置的 @ref{be7,,frozenset}, @ref{262,,list}, @ref{478,,tuple} 和 @ref{1b8,,dict} 类，以及 @ref{1e,,collections} 模块。
@end deffn

@geindex setattr() (內置函数)
@anchor{library/functions setattr}@anchor{1575}
@deffn {函数} setattr (object, name, value)

此函数与 @ref{443,,getattr()} 两相对应。 其参数为一个对象、一个字符串和一个任意值。 字符串指定一个现有属性或者新增属性。 函数会将值赋给该属性，只要对象允许这种操作。 例如，@code{setattr(x, 'foobar', 123)} 等价于 @code{x.foobar = 123}。
@end deffn

@geindex slice (內置类)
@anchor{library/functions slice}@anchor{dfd}
@deffn {类} slice (stop)

@deffnx {类} slice (start, stop[, step])

@geindex Numerical Python

返回一个表示由 @code{range(start, stop, step)} 所指定索引集的 @ref{1598,,slice} 对象。 其中 @emph{start} 和 @emph{step} 参数默认为 @code{None}。 切片对象具有仅会返回对应参数值（或其默认值）的只读数据属性 @code{start}, @code{stop} 和 @code{step}。 它们没有其他的显式功能；不过它们会被 NumPy 以及其他第三方扩展所使用。 切片对象也会在使用扩展索引语法时被生成。 例如: @code{a[start:stop:step]} 或 @code{a[start:stop, i]}。 请参阅 @ref{39a,,itertools.islice()} 了解返回迭代器的一种替代版本。
@end deffn

@geindex sorted() (內置函数)
@anchor{library/functions sorted}@anchor{43e}
@deffn {函数} sorted (iterable, *, key=None, reverse=False)

根据 @emph{iterable} 中的项返回一个新的已排序列表。

具有两个可选参数，它们都必须指定为关键字参数。

@emph{key} 指定带有单个参数的函数，用于从 @emph{iterable} 的每个元素中提取用于比较的键 (例如 @code{key=str.lower})。 默认值为 @code{None} (直接比较元素)。

@emph{reverse} 为一个布尔值。 如果设为 @code{True}，则每个列表元素将按反向顺序比较进行排序。

使用 @ref{b4f,,functools.cmp_to_key()} 可将老式的 @emph{cmp} 函数转换为 @emph{key} 函数。

内置的 @ref{43e,,sorted()} 确保是稳定的。 如果一个排序确保不会改变比较结果相等的元素的相对顺序就称其为稳定的 --- 这有利于进行多重排序（例如先按部门、再按薪级排序）。

有关排序示例和简要排序教程，请参阅 @ref{1599,,排序指南} 。
@end deffn

@geindex staticmethod() (內置函数)
@anchor{library/functions staticmethod}@anchor{1d9}
@deffn {函数} @@staticmethod

将方法转换为静态方法。

静态方法不会接收隐式的第一个参数。要声明一个静态方法，请使用此语法

@example
class C:
    @@staticmethod
    def f(arg1, arg2, ...): ...
@end example

@code{@@staticmethod} 这样的形式称为函数的 @ref{283,,decorator} -- 详情参阅 @ref{11f0,,函数定义}。

静态方法的调用可以在类上进行 (例如 @code{C.f()}) 也可以在实例上进行 (例如 @code{C().f()})。

Python中的静态方法与Java或C ++中的静态方法类似。另请参阅 @ref{1d8,,classmethod()} ，用于创建备用类构造函数的变体。

像所有装饰器一样，也可以像常规函数一样调用 @code{staticmethod} ，并对其结果执行某些操作。比如某些情况下需要从类主体引用函数并且您希望避免自动转换为实例方法。对于这些情况，请使用此语法:

@example
class C:
    builtin_open = staticmethod(open)
@end example

想了解更多有关静态方法的信息，请参阅 @ref{13b8,,标准类型层级结构} 。
@end deffn

@geindex string; str() (built-in function)
@anchor{library/functions func-str}@anchor{1576}

@deffn {类} str (object='@w{'})

@deffnx {类} str (object=b'@w{'}, encoding='utf-8', errors='strict')

返回一个 @ref{329,,str} 版本的 @emph{object} 。有关详细信息，请参阅 @ref{329,,str()} 。

@code{str} 是内置字符串 @ref{159a,,class} 。更多关于字符串的信息查看 @ref{11b7,,文本序列类型 --- str}。
@end deffn

@geindex sum() (內置函数)
@anchor{library/functions sum}@anchor{1e5}
@deffn {函数} sum (iterable, /, start=0)

从 @emph{start} 开始自左向右对 @emph{iterable} 的项求和并返回总计值。 @emph{iterable} 的项通常为数字，而 start 值则不允许为字符串。

对某些用例来说，存在 @ref{1e5,,sum()} 的更好替代。 拼接字符串序列的更好更快方式是调用 @code{'@w{'}.join(sequence)}。 要以扩展精度对浮点值求和，请参阅 @ref{d37,,math.fsum()}。 要拼接一系列可迭代对象，请考虑使用 @ref{159b,,itertools.chain()}。


在 3.8 版更改: @emph{start} 形参可用关键字参数形式来指定。

@end deffn

@geindex super() (內置函数)
@anchor{library/functions super}@anchor{4dc}
@deffn {函数} super ([type[, object-or-type]])

返回一个代理对象，它会将方法调用委托给 @emph{type} 的父类或兄弟类。 这对于访问已在类中被重载的继承方法很有用。

@emph{object-or-type} 确定用于搜索的 @ref{159c,,method resolution order}。 搜索会从 @emph{type} 之后的类开始。

举例来说，如果 @emph{object-or-type} 的 @ref{159d,,__mro__} 为 @code{D -> B -> C -> A -> object} 并且 @emph{type} 的值为 @code{B}，则 @ref{4dc,,super()} 将会搜索 @code{C -> A -> object}。

@emph{object-or-type} 的 @ref{159d,,__mro__} 属性列出了 @ref{443,,getattr()} 和 @ref{4dc,,super()} 所共同使用的方法解析搜索顺序。 该属性是动态的，可以在任何继承层级结构发生更新的时候被改变。

如果省略第二个参数，则返回的超类对象是未绑定的。 如果第二个参数为一个对象，则 @code{isinstance(obj, type)} 必须为真值。 如果第二个参数为一个类型，则 @code{issubclass(type2, type)} 必须为真值（这适用于类方法）。

@emph{super} 有两个典型用例。 在具有单继承的类层级结构中，@emph{super} 可用来引用父类而不必显式地指定它们的名称，从而令代码更易维护。 这种用法与其他编程语言中 @emph{super} 的用法非常相似。

第二个用例是在动态执行环境中支持协作多重继承。 此用例为 Python 所独有，在静态编译语言或仅支持单继承的语言中是不存在的。 这使得实现“菱形图”成为可能，在这时会有多个基类实现相同的方法。 好的设计强制要求这种方法在每个情况下具有相同的调用签名（因为调用顺序是在运行时确定的，也因为该顺序要适应类层级结构的更改，还因为该顺序可能包含在运行时之前未知的兄弟类）。

对于以上两个用例，典型的超类调用看起来是这样的:

@example
class C(B):
    def method(self, arg):
        super().method(arg)    # This does the same thing as:
                               # super(C, self).method(arg)
@end example

除了方法查找之外，@ref{4dc,,super()} 也可用于属性查找。 一个可能的应用场合是在上级或同级类中调用 @ref{159e,,描述器}。

请注意 @ref{4dc,,super()} 是作为显式加点属性查找的绑定过程的一部分来实现的，例如 @code{super().__getitem__(name)}。 它做到这一点是通过实现自己的 @ref{441,,__getattribute__()} 方法，这样就能以可预测的顺序搜索类，并且支持协作多重继承。 对应地，@ref{4dc,,super()} 在像 @code{super()[name]} 这样使用语句或操作符进行隐式查找时则未被定义。

还要注意的是，除了零个参数的形式以外，@ref{4dc,,super()} 并不限于在方法内部使用。 两个参数的形式明确指定参数并进行相应的引用。 零个参数的形式仅适用于类定义内部，因为编译器需要填入必要的细节以正确地检索到被定义的类，还需要让普通方法访问当前实例。

对于有关如何使用 @ref{4dc,,super()} 来如何设计协作类的实用建议，请参阅 使用 super() 的指南@footnote{https://rhettinger.wordpress.com/2011/05/26/super-considered-super/}。
@end deffn
@anchor{library/functions func-tuple}@anchor{1577}

@deffn {类} tuple ([iterable])

虽然被称为函数，但 @ref{478,,tuple} 实际上是一个不可变的序列类型，参见在 @ref{159f,,元组} 与 @ref{1204,,序列类型 --- list@comma{} tuple@comma{} range} 中的文档说明。
@end deffn

@geindex type (內置类)
@anchor{library/functions type}@anchor{603}
@deffn {类} type (object)

@deffnx {类} type (name, bases, dict)

@geindex 对象; type

传入一个参数时，返回 @emph{object} 的类型。 返回值是一个 type 对象，通常与 @ref{e03,,object.__class__} 所返回的对象相同。

推荐使用 @ref{449,,isinstance()} 内置函数来检测对象的类型，因为它会考虑子类的情况。

传入三个参数时，返回一个新的 type 对象。 这在本质上是 @ref{c63,,class} 语句的一种动态形式。 @emph{name} 字符串即类名并且会成为 @ref{c60,,__name__} 属性；@emph{bases} 元组列出基类并且会成为 @ref{e02,,__bases__} 属性；而 @emph{dict} 字典为包含类主体定义的命名空间并且会被复制到一个标准字典成为 @ref{4f6,,__dict__} 属性。 例如，下面两条语句会创建相同的 @ref{603,,type} 对象:

@example
>>> class X:
...     a = 1
...
>>> X = type('X', (object,), dict(a=1))
@end example

另请参阅 @ref{15a0,,类型对象}。


在 3.6 版更改: @ref{603,,type} 的子类如果未重载 @code{type.__new__}，将不再能使用一个参数的形式来获取对象的类型。

@end deffn

@geindex vars() (內置函数)
@anchor{library/functions vars}@anchor{fca}
@deffn {函数} vars ([object])

返回模块、类、实例或任何其它具有 @ref{4f6,,__dict__} 属性的对象的 @ref{4f6,,__dict__} 属性。

模块和实例这样的对象具有可更新的 @ref{4f6,,__dict__} 属性；但是，其它对象的 @ref{4f6,,__dict__} 属性可能会设为限制写入（例如，类会使用 @ref{ab1,,types.MappingProxyType} 来防止直接更新字典）。

不带参数时，@ref{fca,,vars()} 的行为类似 @ref{44f,,locals()}。 请注意，locals 字典仅对于读取起作用，因为对 locals 字典的更新会被忽略。
@end deffn

@geindex zip() (內置函数)
@anchor{library/functions zip}@anchor{c2b}
@deffn {函数} zip (*iterables)

创建一个聚合了来自每个可迭代对象中的元素的迭代器。

返回一个元组的迭代器，其中的第 @emph{i} 个元组包含来自每个参数序列或可迭代对象的第 @emph{i} 个元素。 当所输入可迭代对象中最短的一个被耗尽时，迭代器将停止迭代。 当只有一个可迭代对象参数时，它将返回一个单元组的迭代器。 不带参数时，它将返回一个空迭代器。 相当于:

@example
def zip(*iterables):
    # zip('ABCD', 'xy') --> Ax By
    sentinel = object()
    iterators = [iter(it) for it in iterables]
    while iterators:
        result = []
        for it in iterators:
            elem = next(it, sentinel)
            if elem is sentinel:
                return
            result.append(elem)
        yield tuple(result)
@end example

函数会保证可迭代对象按从左至右的顺序被求值。 使得可以通过 @code{zip(*[iter(s)]*n)} 这样的惯用形式将一系列数据聚类为长度为 n 的分组。 这将重复 @emph{同样的} 迭代器 @code{n} 次，以便每个输出的元组具有第 @code{n} 次调用该迭代器的结果。 它的作用效果就是将输入拆分为长度为 n 的数据块。

当你不用关心较长可迭代对象末尾不匹配的值时，则 @ref{c2b,,zip()} 只须使用长度不相等的输入即可。 如果那些值很重要，则应改用 @ref{c2a,,itertools.zip_longest()}。

@ref{c2b,,zip()} 与 @code{*} 运算符相结合可以用来拆解一个列表:

@example
>>> x = [1, 2, 3]
>>> y = [4, 5, 6]
>>> zipped = zip(x, y)
>>> list(zipped)
[(1, 4), (2, 5), (3, 6)]
>>> x2, y2 = zip(*zip(x, y))
>>> x == list(x2) and y == list(y2)
True
@end example
@end deffn

@geindex __import__() (內置函数)
@anchor{library/functions __import__}@anchor{60b}
@deffn {函数} __import__ (name, globals=None, locals=None, fromlist=(), level=0)

@geindex 语句; import
@geindex 模块; imp

@cartouche
@quotation 注解 
与 @ref{b0c,,importlib.import_module()} 不同，这是一个日常 Python 编程中不需要用到的高级函数。
@end quotation
@end cartouche

此函数会由 @ref{c16,,import} 语句发起调用。 它可以被替换 (通过导入 @ref{13,,builtins} 模块并赋值给 @code{builtins.__import__}) 以便修改 @code{import} 语句的语义，但是 @strong{强烈} 不建议这样做，因为使用导入钩子 (参见 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}) 通常更容易实现同样的目标，并且不会导致代码问题，因为许多代码都会假定所用的是默认实现。 同样也不建议直接使用 @ref{60b,,__import__()} 而应该用 @ref{b0c,,importlib.import_module()}。

该函数会导入 @emph{name} 模块，有可能使用给定的 @emph{globals} 和 @emph{locals} 来确定如何在包的上下文中解读名称。 @emph{fromlist} 给出了应该从由 @emph{name} 指定的模块导入对象或子模块的名称。 标准实现完全不使用其 @emph{locals} 参数，而仅使用 @emph{globals} 参数来确定 @ref{c16,,import} 语句的包上下文。

@emph{level} 指定是使用绝对还是相对导入。 @code{0} (默认值) 意味着仅执行绝对导入。 @emph{level} 为正数值表示相对于模块调用 @ref{60b,,__import__()} 的目录，将要搜索的父目录层数 (详情参见 
@geindex Python 提高建议; PEP 328
PEP 328@footnote{https://www.python.org/dev/peps/pep-0328})。

当 @emph{name} 变量的形式为 @code{package.module} 时，通常将会返回最高层级的包（第一个点号之前的名称），而 @emph{不是} 以 @emph{name} 命名的模块。 但是，当给出了非空的 @emph{fromlist} 参数时，则将返回以 @emph{name} 命名的模块。

例如，语句 @code{import spam} 的结果将为与以下代码作用相同的字节码:

@example
spam = __import__('spam', globals(), locals(), [], 0)
@end example

语句 @code{import spam.ham} 的结果将为以下调用:

@example
spam = __import__('spam.ham', globals(), locals(), [], 0)
@end example

请注意在这里 @ref{60b,,__import__()} 是如何返回顶层模块的，因为这是通过 @ref{c16,,import} 语句被绑定到特定名称的对象。

另一方面，语句 @code{from spam.ham import eggs, sausage as saus} 的结果将为

@example
_temp = __import__('spam.ham', globals(), locals(), ['eggs', 'sausage'], 0)
eggs = _temp.eggs
saus = _temp.sausage
@end example

在这里， @code{spam.ham} 模块会由 @ref{60b,,__import__()} 返回。 要导入的对象将从此对象中提取并赋值给它们对应的名称。

如果您只想按名称导入模块（可能在包中），请使用 @ref{b0c,,importlib.import_module()}


在 3.3 版更改: Negative values for @emph{level} are no longer supported (which also changes
the default value to 0).

@end deffn

@subsubheading 备注


@node 内置常量,内置类型,内置函数,Python 标准库
@anchor{library/constants doc}@anchor{15a1}@anchor{library/constants built-in-constants}@anchor{15a2}@anchor{library/constants built-in-consts}@anchor{15a3}
@section 内置常量


有少数的常量存在于内置命名空间中。 它们是：

@geindex False (內置变量)
@anchor{library/constants False}@anchor{380}
@deffn {数据} False

@ref{183,,bool} 类型的假值。 给 @code{False} 赋值是非法的并会引发 @ref{452,,SyntaxError}。
@end deffn

@geindex True (內置变量)
@anchor{library/constants True}@anchor{494}
@deffn {数据} True

@ref{183,,bool} 类型的真值。 给 @code{True} 赋值是非法的并会引发 @ref{452,,SyntaxError}。
@end deffn

@geindex None (內置变量)
@anchor{library/constants None}@anchor{157}
@deffn {数据} None

@code{NoneType} 类型的唯一值。 @code{None} 经常用于表示缺少值，当因为默认参数未传递给函数时。 给 @code{None} 赋值是非法的并会引发 @ref{452,,SyntaxError}。
@end deffn

@geindex NotImplemented (內置变量)
@anchor{library/constants NotImplemented}@anchor{846}
@deffn {数据} NotImplemented

二进制特殊方法应返回的特殊值（例如，@ref{338,,__eq__()}、@ref{c2d,,__lt__()}、@code{__add __()}、@ref{1401,,__rsub__()} 等）表示操作没有针对其他类型实现；为了相同的目的，可以通过就地二进制特殊方法（例如，@code{__imul __()}、@code{__ rightnd__()} 等）返回。 它的逻辑值为真。

@cartouche
@quotation 注解 
当二进制（或就地）方法返回`@w{`}NotImplemented`@w{`}时，解释器将尝试对另一种类型（或其他一些回滚操作，取决于运算符）的反射操作。 如果所有尝试都返回`@w{`}NotImplemented`@w{`}，则解释器将引发适当的异常。 错误返回的`@w{`}NotImplemented`@w{`}将导致误导性错误消息或返回到Python代码中的`@w{`}NotImplemented`@w{`}值。

参见 @ref{13b9,,实现算数运算} 为例。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
@code{NotImplementedError} 和 @code{NotImplemented} 不可互换，即使它们有相似的名称和用途。 有关何时使用它的详细信息，请参阅 @ref{609,,NotImplementedError}。
@end quotation
@end cartouche
@end deffn

@geindex ...; ellipsis literal

@geindex Ellipsis (內置变量)
@anchor{library/constants Ellipsis}@anchor{15a4}
@deffn {数据} Ellipsis

与省略号文字字面 “@code{...}” 相同。 特殊值主要与用户定义的容器数据类型的扩展切片语法结合使用。
@end deffn

@geindex __debug__ (內置变量)
@anchor{library/constants __debug__}@anchor{f8d}
@deffn {数据} __debug__

如果 Python 没有以 @ref{685,,-O} 选项启动，则此常量为真值。 另请参见 @ref{dff,,assert} 语句。
@end deffn

@cartouche
@quotation 注解 
变量名 @ref{157,,None}，@ref{380,,False}，@ref{494,,True} 和 @code{__ debug__} 无法重新赋值（赋值给它们，即使是属性名，将引发 @ref{452,,SyntaxError} ），所以它们可以被认为是“真正的”常数。
@end quotation
@end cartouche

@menu
* 由 site 模块添加的常量:: 

@end menu

@node 由 site 模块添加的常量,,,内置常量
@anchor{library/constants constants-added-by-the-site-module}@anchor{15a5}
@subsection 由 @code{site} 模块添加的常量


@ref{eb,,site} 模块（在启动期间自动导入，除非给出 @ref{b1d,,-S} 命令行选项）将几个常量添加到内置命名空间。 它们对交互式解释器 shell 很有用，并且不应在程序中使用。

@geindex quit (內置变量)
@geindex exit (內置变量)
@anchor{library/constants quit}@anchor{15a6}
@deffn {数据} quit (code=None)
@anchor{library/constants exit}@anchor{15a7}
@deffnx {数据} exit (code=None)

当打印此对象时，会打印出一条消息，例如“Use quit() or Ctrl-D (i.e. EOF) to exit”，当调用此对象时，将使用指定的退出代码来引发 @ref{5f7,,SystemExit}。
@end deffn

@geindex copyright (內置变量)
@geindex credits (內置变量)
@anchor{library/constants copyright}@anchor{15a8}
@deffn {数据} copyright
@anchor{library/constants credits}@anchor{15a9}
@deffnx {数据} credits

打印或调用的对象分别打印版权或作者的文本。
@end deffn

@geindex license (內置变量)
@anchor{library/constants license}@anchor{15aa}
@deffn {数据} license

当打印此对象时，会打印出一条消息“Type license() to see the full license text”，当调用此对象时，将以分页形式显示完整的许可证文本（每次显示一屏）。
@end deffn

@c XXX: reference/datamodel and this have quite a few overlaps!

@node 内置类型,内置异常,内置常量,Python 标准库
@anchor{library/stdtypes doc}@anchor{15ab}@anchor{library/stdtypes bltin-types}@anchor{15ac}@anchor{library/stdtypes built-in-types}@anchor{15ad}
@section 内置类型


以下部分描述了解释器中内置的标准类型。

@geindex built-in; types

主要内置类型有数字、序列、映射、类、实例和异常。

有些多项集类是可变的。 它们用于添加、移除或重排其成员的方法将原地执行，并不返回特定的项，绝对不会返回多项集实例自身而是返回 @code{None}。

有些操作受多种对象类型的支持；特别地，实际上所有对象都可以比较是否相等、检测逻辑值，以及转换为字符串（使用 @ref{7c6,,repr()} 函数或略有差异的 @ref{329,,str()} 函数）。 后一个函数是在对象由 @ref{880,,print()} 函数输出时被隐式地调用的。

@menu
* 逻辑值检测:: 
* 布尔运算: 布尔运算 --- and or not. and, or, not
* 比较运算: 比较运算<2>. 
* 数字类型: 数字类型 --- int float complex. int, float, complex
* 迭代器类型:: 
* 序列类型: 序列类型 --- list tuple range. list, tuple, range
* 文本序列类型: 文本序列类型 --- str. str
* 二进制序列类型: 二进制序列类型 --- bytes bytearray memoryview. bytes, bytearray, memoryview
* 集合类型: 集合类型 --- set frozenset. set, frozenset
* 映射类型: 映射类型 --- dict. dict
* 上下文管理器类型:: 
* 其他内置类型:: 
* 特殊属性:: 

@end menu

@node 逻辑值检测,布尔运算 --- and or not,,内置类型
@anchor{library/stdtypes truth}@anchor{157c}@anchor{library/stdtypes truth-value-testing}@anchor{15ae}
@subsection 逻辑值检测


@geindex 语句; if
@geindex 语句; while
@geindex truth; value
@geindex Boolean; operations
@geindex false

任何对象都可以进行逻辑值的检测，以便在 @ref{de0,,if} 或 @ref{11c1,,while} 作为条件或是作为下文所述布尔运算的操作数来使用。

@geindex true

一个对象在默认情况下均被视为真值，除非当该对象被调用时其所属类定义了 @ref{c61,,__bool__()} 方法且返回 @code{False} 或是定义了 @ref{dc4,,__len__()} 方法且返回零。 @footnote{@w{(1)} 
有关这些特殊方法的额外信息可参看 Python 参考指南 (@ref{13cd,,基本定制})。
}  下面基本完整地列出了会被视为假值的内置对象:

@quotation

@geindex None (Built-in object)
@geindex False (Built-in object)
@end quotation


@itemize *

@item 
被定义为假值的常量: @code{None} 和 @code{False}。

@item 
任何数值类型的零: @code{0}, @code{0.0}, @code{0j}, @code{Decimal(0)}, @code{Fraction(0, 1)}

@item 
空的序列和多项集: @code{'@w{'}}, @code{()}, @code{[]}, @code{@{@}}, @code{set()}, @code{range(0)}
@end itemize

@geindex 运算符; or
@geindex 运算符; and
@geindex False
@geindex True

产生布尔值结果的运算和内置函数总是返回 @code{0} 或 @code{False} 作为假值，@code{1} 或 @code{True} 作为真值，除非另行说明。 （重要例外：布尔运算 @code{or} 和 @code{and} 总是返回其中一个操作数。）

@node 布尔运算 --- and or not,比较运算<2>,逻辑值检测,内置类型
@anchor{library/stdtypes boolean}@anchor{15af}@anchor{library/stdtypes boolean-operations-and-or-not}@anchor{15b0}
@subsection 布尔运算 --- @code{and}, @code{or}, @code{not}


@geindex Boolean; operations

这些属于布尔运算，按优先级升序排列:


@multitable {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

运算

@tab

结果：

@tab

注释

@item

@code{x or y}

@tab

if @emph{x} is false, then @emph{y}, else
@emph{x}

@tab

(1)

@item

@code{x and y}

@tab

if @emph{x} is false, then @emph{x}, else
@emph{y}

@tab

(2)

@item

@code{not x}

@tab

if @emph{x} is false, then @code{True},
else @code{False}

@tab

(3)

@end multitable


@geindex 运算符; and
@geindex 运算符; or
@geindex 运算符; not

注释:


@enumerate 

@item 
这是个短路运算符，因此只有在第一个参数为假值时才会对第二个参数求值。

@item 
这是个短路运算符，因此只有在第一个参数为真值时才会对第二个参数求值。

@item 
@code{not} 的优先级比非布尔运算符低，因此 @code{not a == b} 会被解读为 @code{not (a == b)} 而 @code{a == not b} 会引发语法错误。
@end enumerate

@node 比较运算<2>,数字类型 --- int float complex,布尔运算 --- and or not,内置类型
@anchor{library/stdtypes comparisons}@anchor{15b1}@anchor{library/stdtypes stdcomparisons}@anchor{15b2}
@subsection 比较运算


@geindex chaining; comparisons
@geindex operator; comparison
@geindex 运算符; ==
@geindex 运算符; < (less)
@geindex 运算符; <=
@geindex 运算符; > (greater)
@geindex 运算符; >=
@geindex 运算符; !=
@geindex 运算符; is
@geindex 运算符; is not

在 Python 中有八种比较运算符。 它们的优先级相同（比布尔运算的优先级高）。 比较运算可以任意串连；例如，@code{x < y <= z} 等价于 @code{x < y and y <= z}，前者的不同之处在于 @emph{y} 只被求值一次（但在两种情况下当 @code{x < y} 结果为假值时 @emph{z} 都不会被求值）。

此表格汇总了比较运算:


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

含义

@item

@code{<}

@tab

严格小于

@item

@code{<=}

@tab

小于或等于

@item

@code{>}

@tab

严格大于

@item

@code{>=}

@tab

大于或等于

@item

@code{==}

@tab

等于

@item

@code{!=}

@tab

不等于

@item

@code{is}

@tab

对象标识

@item

@code{is not}

@tab

否定的对象标识

@end multitable


@geindex object; numeric
@geindex objects; comparing

除不同的数字类型外，不同类型的对象不能进行相等比较。@code{==} 运算符总有定义，但对于某些对象类型（例如，类对象），它等于 @ref{13b6,,is} 。其他 @code{<}、@code{<=}、@code{>} 和 @code{>=} 运算符仅在有意义的地方定义。例如，当参与比较的参数之一为复数时，它们会抛出 @ref{192,,TypeError} 异常。

@geindex __eq__() (instance method)
@geindex __ne__() (instance method)
@geindex __lt__() (instance method)
@geindex __le__() (instance method)
@geindex __gt__() (instance method)
@geindex __ge__() (instance method)

具有不同标识的类的实例比较结果通常为不相等，除非类定义了 @ref{338,,__eq__()} 方法。

一个类实例不能与相同类或的其他实例或其他类型的对象进行排序，除非该类定义了足够多的方法，包括 @ref{c2d,,__lt__()}, @ref{c99,,__le__()}, @ref{c9a,,__gt__()} 以及 @ref{c9b,,__ge__()} (而如果你想实现常规意义上的比较操作，通常只要有 @ref{c2d,,__lt__()} 和 @ref{338,,__eq__()} 就可以了)。

@ref{13b6,,is} 和 @ref{14e1,,is not} 运算符无法自定义；并且它们可以被应用于任意两个对象而不会引发异常。

@geindex 运算符; in
@geindex 运算符; not in

还有两种具有相同语法优先级的运算 @ref{79d,,in} 和 @ref{13f5,,not in}，它们被 @ref{ba5,,iterable} 或实现了 @ref{d21,,__contains__()} 方法的类型所支持。

@node 数字类型 --- int float complex,迭代器类型,比较运算<2>,内置类型
@anchor{library/stdtypes numeric-types-int-float-complex}@anchor{15b3}@anchor{library/stdtypes typesnumeric}@anchor{11b3}
@subsection 数字类型 --- @code{int}, @code{float}, @code{complex}


@geindex 对象; numeric
@geindex 对象; Boolean
@geindex 对象; integer
@geindex 对象; floating point
@geindex 对象; complex number
@geindex C; language

存在三种不同的数字类型: @emph{整数}, @emph{浮点数} 和 @emph{复数}。 此外，布尔值属于整数的子类型。 整数具有无限的精度。 浮点数通常使用 C 中的 @code{double} 来实现；有关你的程序运行所在机器上浮点数的精度和内部表示法可在 @ref{f51,,sys.float_info} 中查看。 复数包含实部和虚部，分别以一个浮点数表示。 要从一个复数 @emph{z} 中提取这两个部分，可使用 @code{z.real} 和 @code{z.imag}。 （标准库包含附加的数字类型，如表示有理数的 @ref{185,,fractions.Fraction} 以及以用户定制精度表示浮点数的 @ref{188,,decimal.Decimal}。）

@geindex numeric; literals
@geindex integer; literals
@geindex floating point; literals
@geindex complex number; literals
@geindex hexadecimal; literals
@geindex octal; literals
@geindex binary; literals

数字是由数字字面值或内置函数与运算符的结果来创建的。 不带修饰的整数字面值（包括十六进制、八进制和二进制数）会生成整数。 包含小数点或幂运算符的数字字面值会生成浮点数。 在数字字面值末尾加上 @code{'j'} 或 @code{'J'} 会生成虚数（实部为零的复数），你可以将其与整数或浮点数相加来得到具有实部和虚部的复数。

@geindex arithmetic
@geindex 內置函数; int
@geindex 內置函数; float
@geindex 內置函数; complex
@geindex operator; + (plus)
@geindex + (plus); unary operator
@geindex + (plus); binary operator
@geindex operator; - (minus)
@geindex - (minus); unary operator
@geindex - (minus); binary operator
@geindex 运算符; * (asterisk)
@geindex 运算符; / (slash)
@geindex 运算符; //
@geindex 运算符; % (percent)
@geindex 运算符; **

Python fully supports mixed arithmetic: when a binary arithmetic operator has
operands of different numeric types, the operand with the "narrower" type is
widened to that of the other, where integer is narrower than floating point,
which is narrower than complex. A comparison between numbers of different types
behaves as though the exact values of those numbers were being compared. @footnote{@w{(2)} 
作为结果，列表 @code{[1, 2]} 与 @code{[1.0, 2.0]} 是相等的，元组的情况也类似。
}

The constructors @ref{184,,int()}, @ref{187,,float()}, and
@ref{189,,complex()} can be used to produce numbers of a specific type.

所有数字类型（复数除外）都支持下列运算（有关运算优先级，请参阅：@ref{14fc,,运算符优先级}）:


@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@tab

注释

@tab

完整文档

@item

@code{x + y}

@tab

@emph{x} 和 @emph{y} 的和

@tab

@tab

@item

@code{x - y}

@tab

@emph{x} 和 @emph{y} 的差

@tab

@tab

@item

@code{x * y}

@tab

@emph{x} 和 @emph{y} 的乘积

@tab

@tab

@item

@code{x / y}

@tab

@emph{x} 和 @emph{y} 的商

@tab

@tab

@item

@code{x // y}

@tab

@emph{x} 和 @emph{y} 的商数

@tab

(1)

@tab

@item

@code{x % y}

@tab

remainder of @code{x / y}

@tab

(2)

@tab

@item

@code{-x}

@tab

@emph{x} 取反

@tab

@tab

@item

@code{+x}

@tab

@emph{x} 不变

@tab

@tab

@item

@code{abs(x)}

@tab

@emph{x} 的绝对值或大小

@tab

@tab

@ref{1253,,abs()}

@item

@code{int(x)}

@tab

将 @emph{x} 转换为整数

@tab

(3)(6)

@tab

@ref{184,,int()}

@item

@code{float(x)}

@tab

将 @emph{x} 转换为浮点数

@tab

(4)(6)

@tab

@ref{187,,float()}

@item

@code{complex(re, im)}

@tab

一个带有实部 @emph{re} 和虚部 @emph{im} 的复数。@emph{im} 默认为0。

@tab

(6)

@tab

@ref{189,,complex()}

@item

@code{c.conjugate()}

@tab

复数 @emph{c} 的共轭

@tab

@tab

@item

@code{divmod(x, y)}

@tab

@code{(x // y, x % y)}

@tab

(2)

@tab

@ref{152,,divmod()}

@item

@code{pow(x, y)}

@tab

@emph{x} 的 @emph{y} 次幂

@tab

(5)

@tab

@ref{19a,,pow()}

@item

@code{x ** y}

@tab

@emph{x} 的 @emph{y} 次幂

@tab

(5)

@tab

@end multitable


@geindex operations on; numeric; types
@geindex conjugate() (complex number method)

注释:


@enumerate 

@item 
也称为整数除法。 结果值是一个整数，但结果的类型不一定是 int。 运算结果总是向负无穷的方向舍入: @code{1//2} 为 @code{0}, @code{(-1)//2} 为 @code{-1}, @code{1//(-2)} 为 @code{-1} 而 @code{(-1)//(-2)} 为 @code{0}。

@item 
不可用于复数。 而应在适当条件下使用 @ref{1253,,abs()} 转换为浮点数。

@item 
@geindex 模块; math
@geindex floor() (in module math)
@geindex ceil() (in module math)
@geindex trunc() (in module math)
@geindex numeric; conversions
@geindex C; language

从浮点数转换为整数会被舍入或是像在 C 语言中一样被截断；请参阅 @ref{d25,,math.floor()} 和 @ref{d26,,math.ceil()} 函数查看转换的完整定义。

@item 
float 也接受字符串 "nan" 和附带可选前缀 "+" 或 "-" 的 "inf" 分别表示非数字 (NaN) 以及正或负无穷。

@item 
Python 将 @code{pow(0, 0)} 和 @code{0 ** 0} 定义为 @code{1}，这是编程语言的普遍做法。

@item 
接受的数字字面值包括数码 @code{0} 到 @code{9} 或任何等效的 Unicode 字符（具有 @code{Nd} 特征属性的代码点）。

请参阅 @indicateurl{http://www.unicode.org/Public/12.1.0/ucd/extracted/DerivedNumericType.txt} 查看具有 @code{Nd} 特征属性的代码点的完整列表。
@end enumerate

所有 @ref{13bc,,numbers.Real} 类型 (@ref{184,,int} 和 @ref{187,,float}) 还包括下列运算:


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@item

@ref{d27,,math.trunc(x)}

@tab

@emph{x} 截断为 @ref{13bb,,Integral}

@item

@ref{c66,,round(x[@comma{} n])}

@tab

@emph{x} 舍入到 @emph{n} 位小数，半数值会舍入到偶数。 如果省略 @emph{n}，则默认为 0。

@item

@ref{d25,,math.floor(x)}

@tab

<= @emph{x} 的最大 @ref{13bb,,Integral}

@item

@ref{d26,,math.ceil(x)}

@tab

>= @emph{x} 的最小 @ref{13bb,,Integral}

@end multitable


有关更多的数字运算请参阅 @ref{b1,,math} 和 @ref{19,,cmath} 模块。

@c XXXJH exceptions: overflow (when? what operations?) zerodivision

@menu
* 整数类型的按位运算:: 
* 整数类型的附加方法:: 
* 浮点类型的附加方法:: 
* 数字类型的哈希运算:: 

@end menu

@node 整数类型的按位运算,整数类型的附加方法,,数字类型 --- int float complex
@anchor{library/stdtypes bitstring-ops}@anchor{15b4}@anchor{library/stdtypes bitwise-operations-on-integer-types}@anchor{15b5}
@subsubsection 整数类型的按位运算


@geindex operations on; integer; types
@geindex bitwise; operations
@geindex shifting; operations
@geindex masking; operations
@geindex 运算符; | (vertical bar)
@geindex 运算符; ^ (caret)
@geindex 运算符; & (ampersand)
@geindex 运算符; <<
@geindex 运算符; >>
@geindex 运算符; ~ (tilde)

按位运算只对整数有意义。 计算按位运算的结果，就相当于使用无穷多个二进制符号位对二的补码执行操作。

二进制按位运算的优先级全都低于数字运算，但又高于比较运算；一元运算 @code{~} 具有与其他一元算术运算 (@code{+} and @code{-}) 相同的优先级。

此表格是以优先级升序排序的按位运算列表:


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@tab

注释

@item

@code{x | y}

@tab

@emph{x} 和 @emph{y} 按位 @emph{或}

@tab

(4)

@item

@code{x ^ y}

@tab

@emph{x} 和 @emph{y} 按位 @emph{异或}

@tab

(4)

@item

@code{x & y}

@tab

@emph{x} 和 @emph{y} 按位 @emph{与}

@tab

(4)

@item

@code{x << n}

@tab

@emph{x} 左移 @emph{n} 位

@tab

(1)(2)

@item

@code{x >> n}

@tab

@emph{x} 右移 @emph{n} 位

@tab

(1)(3)

@item

@code{~x}

@tab

@emph{x} 逐位取反

@tab

@end multitable


注释:


@enumerate 

@item 
负的移位数是非法的，会导致引发 @ref{1fb,,ValueError}。

@item 
A left shift by @emph{n} bits is equivalent to multiplication by @code{pow(2, n)}.

@item 
A right shift by @emph{n} bits is equivalent to floor division by @code{pow(2, n)}.

@item 
使用带有至少一个额外符号扩展位的有限个二进制补码表示（有效位宽度为 @code{1 + max(x.bit_length(), y.bit_length())} 或以上）执行这些计算就足以获得相当于有无数个符号位时的同样结果。
@end enumerate

@node 整数类型的附加方法,浮点类型的附加方法,整数类型的按位运算,数字类型 --- int float complex
@anchor{library/stdtypes additional-methods-on-integer-types}@anchor{15b6}
@subsubsection 整数类型的附加方法


int 类型实现了 @ref{13bb,,numbers.Integral} @ref{b2c,,abstract base class}。 此外，它还提供了其他几个方法:

@geindex bit_length() (int 方法)
@anchor{library/stdtypes int bit_length}@anchor{15b7}
@deffn {方法} int.bit_length ()

返回以二进制表示一个整数所需要的位数，不包括符号位和前面的零:

@example
>>> n = -37
>>> bin(n)
'-0b100101'
>>> n.bit_length()
6
@end example

更准确地说，如果 @code{x} 非零，则 @code{x.bit_length()} 是使得 @code{2**(k-1) <= abs(x) < 2**k} 的唯一正整数 @code{k}。 同样地，当 @code{abs(x)} 小到足以具有正确的舍入对数时，则 @code{k = 1 + int(log(abs(x), 2))}。 如果 @code{x} 为零，则 @code{x.bit_length()} 返回 @code{0}。

等价于:

@example
def bit_length(self):
    s = bin(self)       # binary representation:  bin(-37) --> '-0b100101'
    s = s.lstrip('-0b') # remove leading zeros and minus sign
    return len(s)       # len('100101') --> 6
@end example


3.1 新版功能.

@end deffn

@geindex to_bytes() (int 方法)
@anchor{library/stdtypes int to_bytes}@anchor{15b8}
@deffn {方法} int.to_bytes (length, byteorder, *, signed=False)

返回表示一个整数的字节数组。

@example
>>> (1024).to_bytes(2, byteorder='big')
b'\x04\x00'
>>> (1024).to_bytes(10, byteorder='big')
b'\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00'
>>> (-1024).to_bytes(10, byteorder='big', signed=True)
b'\xff\xff\xff\xff\xff\xff\xff\xff\xfc\x00'
>>> x = 1000
>>> x.to_bytes((x.bit_length() + 7) // 8, byteorder='little')
b'\xe8\x03'
@end example

整数会使用 @emph{length} 个字节来表示。 如果整数不能用给定的字节数来表示则会引发 @ref{95a,,OverflowError}。

@emph{byteorder} 参数确定用于表示整数的字节顺序。 如果 @emph{byteorder} 为 @code{"big"}，则最高位字节放在字节数组的开头。 如果 @emph{byteorder} 为 @code{"little"}，则最高位字节放在字节数组的末尾。 要请求主机系统上的原生字节顺序，请使用 @ref{15b9,,sys.byteorder} 作为字节顺序值。

@emph{signed} 参数确定是否使用二的补码来表示整数。 如果 @emph{signed} 为 @code{False} 并且给出的是负整数，则会引发 @ref{95a,,OverflowError}。 @emph{signed} 的默认值为 @code{False}。


3.2 新版功能.

@end deffn

@geindex from_bytes() (int 类方法)
@anchor{library/stdtypes int from_bytes}@anchor{15ba}
@deffn {方法} classmethod int.from_bytes (bytes, byteorder, *, signed=False)

返回由给定字节数组所表示的整数。

@example
>>> int.from_bytes(b'\x00\x10', byteorder='big')
16
>>> int.from_bytes(b'\x00\x10', byteorder='little')
4096
>>> int.from_bytes(b'\xfc\x00', byteorder='big', signed=True)
-1024
>>> int.from_bytes(b'\xfc\x00', byteorder='big', signed=False)
64512
>>> int.from_bytes([255, 0, 0], byteorder='big')
16711680
@end example

@emph{bytes} 参数必须为一个 @ref{5e3,,bytes-like object} 或是生成字节的可迭代对象。

@emph{byteorder} 参数确定用于表示整数的字节顺序。 如果 @emph{byteorder} 为 @code{"big"}，则最高位字节放在字节数组的开头。 如果 @emph{byteorder} 为 @code{"little"}，则最高位字节放在字节数组的末尾。 要请求主机系统上的原生字节顺序，请使用 @ref{15b9,,sys.byteorder} 作为字节顺序值。

@emph{signed} 参数指明是否使用二的补码来表示整数。


3.2 新版功能.

@end deffn

@geindex as_integer_ratio() (int 方法)
@anchor{library/stdtypes int as_integer_ratio}@anchor{186}
@deffn {方法} int.as_integer_ratio ()

返回一对整数，其比率正好等于原整数并且分母为正数。 整数的比率总是用这个整数本身作为分子，@code{1} 作为分母。


3.8 新版功能.

@end deffn

@node 浮点类型的附加方法,数字类型的哈希运算,整数类型的附加方法,数字类型 --- int float complex
@anchor{library/stdtypes additional-methods-on-float}@anchor{15bb}
@subsubsection 浮点类型的附加方法


float 类型实现了 @ref{13bc,,numbers.Real} @ref{b2c,,abstract base class}。 float 还具有以下附加方法。

@geindex as_integer_ratio() (float 方法)
@anchor{library/stdtypes float as_integer_ratio}@anchor{12b8}
@deffn {方法} float.as_integer_ratio ()

返回一对整数，其比率正好等于原浮点数并且分母为正数。 无穷大会引发 @ref{95a,,OverflowError} 而 NaN 则会引发 @ref{1fb,,ValueError}。
@end deffn

@geindex is_integer() (float 方法)
@anchor{library/stdtypes float is_integer}@anchor{15bc}
@deffn {方法} float.is_integer ()

如果 float 实例可用有限位整数表示则返回 @code{True}，否则返回 @code{False}:

@example
>>> (-2.0).is_integer()
True
>>> (3.2).is_integer()
False
@end example
@end deffn

两个方法均支持与十六进制数字符串之间的转换。 由于 Python 浮点数在内部存储为二进制数，因此浮点数与 @emph{十进制数} 字符串之间的转换往往会导致微小的舍入错误。 而十六进制数字符串却允许精确地表示和描述浮点数。 这在进行调试和数值工作时非常有用。

@geindex hex() (float 方法)
@anchor{library/stdtypes float hex}@anchor{12b9}
@deffn {方法} float.hex ()

以十六进制字符串的形式返回一个浮点数表示。 对于有限浮点数，这种表示法将总是包含前导的 @code{0x} 和尾随的 @code{p} 加指数。
@end deffn

@geindex fromhex() (float 类方法)
@anchor{library/stdtypes float fromhex}@anchor{15bd}
@deffn {方法} classmethod float.fromhex (s)

返回以十六进制字符串 @emph{s} 表示的浮点数的类方法。 字符串 @emph{s} 可以带有前导和尾随的空格。
@end deffn

请注意 @ref{12b9,,float.hex()} 是实例方法，而 @ref{15bd,,float.fromhex()} 是类方法。

十六进制字符串采用的形式为:

@example
[sign] ['0x'] integer ['.' fraction] ['p' exponent]
@end example

可选的 @code{sign} 可以是 @code{+} 或 @code{-}，@code{integer} 和 @code{fraction} 是十六进制数码组成的字符串，@code{exponent} 是带有可选前导符的十进制整数。 大小写没有影响，在 integer 或 fraction 中必须至少有一个十六进制数码。 此语法类似于 C99 标准的 6.4.4.2 小节中所描述的语法，也是 Java 1.5 以上所使用的语法。 特别地，@ref{12b9,,float.hex()} 的输出可以用作 C 或 Java 代码中的十六进制浮点数字面值，而由 C 的 @code{%a} 格式字符或 Java 的 @code{Double.toHexString} 所生成的十六进制数字符串由为 @ref{15bd,,float.fromhex()} 所接受。

请注意 exponent 是十进制数而非十六进制数，它给出要与系数相乘的 2 的幂次。 例如，十六进制数字符串 @code{0x3.a7p10} 表示浮点数 @code{(3 + 10./16 + 7./16**2) * 2.0**10} 即 @code{3740.0}:

@example
>>> float.fromhex('0x3.a7p10')
3740.0
@end example

对 @code{3740.0} 应用反向转换会得到另一个代表相同数值的十六进制数字符串:

@example
>>> float.hex(3740.0)
'0x1.d380000000000p+11'
@end example

@node 数字类型的哈希运算,,浮点类型的附加方法,数字类型 --- int float complex
@anchor{library/stdtypes hashing-of-numeric-types}@anchor{15be}@anchor{library/stdtypes numeric-hash}@anchor{15bf}
@subsubsection 数字类型的哈希运算


对于可能为不同类型的数字 @code{x} 和 @code{y}，要求 @code{x == y} 时必定 @code{hash(x) == hash(y)} (详情参见 @ref{339,,__hash__()} 方法的文档)。 为了便于在各种数字类型 (包括 @ref{184,,int}, @ref{187,,float}, @ref{188,,decimal.Decimal} 和 @ref{185,,fractions.Fraction}) 上实现并保证效率，Python 对数字类型的哈希运算是基于为任意有理数定义统一的数学函数，因此该运算对 @ref{184,,int} 和 @ref{185,,fractions.Fraction} 的全部实例，以及 @ref{187,,float} 和 @ref{188,,decimal.Decimal} 的全部有限实例均可用。 从本质上说，此函数是通过以一个固定质数 @code{P} 进行 @code{P} 降模给出的。 @code{P} 的值在 Python 中可以 @ref{91b,,sys.hash_info} 的 @code{modulus} 属性的形式被访问。

@strong{CPython implementation detail:} 目前所用的质数设定，在 C long 为 32 位的机器上 @code{P = 2**31 - 1} 而在 C long 为 64 位的机器上 @code{P = 2**61 - 1}。

详细规则如下所述:


@itemize -

@item 
如果 @code{x = m / n} 是一个非负的有理数且 @code{n} 不可被 @code{P} 整除，则定义 @code{hash(x)} 为 @code{m * invmod(n, P) % P}，其中 @code{invmod(n, P)} 是对 @code{n} 模 @code{P} 取反。

@item 
如果 @code{x = m / n} 是一个非负的有理数且 @code{n} 可被 @code{P} 整除（但 @code{m} 不能）则 @code{n} 不能对 @code{P} 降模，以上规则不适用；在此情况下则定义 @code{hash(x)} 为常数值 @code{sys.hash_info.inf}。

@item 
如果 @code{x = m / n} 是一个负的有理数则定义 @code{hash(x)} 为 @code{-hash(-x)}。 如果结果哈希值为 @code{-1} 则将其替换为 @code{-2}。

@item 
特定值 @code{sys.hash_info.inf}, @code{-sys.hash_info.inf} 和 @code{sys.hash_info.nan} 被用作正无穷、负无穷和空值（所分别对应的）哈希值。 （所有可哈希的空值都具有相同的哈希值。）

@item 
对于一个 @ref{189,,complex} 值 @code{z}，会通过计算 @code{hash(z.real) + sys.hash_info.imag * hash(z.imag)} 将实部和虚部的哈希值结合起来，并进行降模 @code{2**sys.hash_info.width} 以使其处于 @code{range(-2**(sys.hash_info.width - 1), 2**(sys.hash_info.width - 1))} 范围之内。 同样地，如果结果为 @code{-1} 则将其替换为 @code{-2}。
@end itemize

为了阐明上述规则，这里有一些等价于内置哈希算法的 Python 代码示例，可用于计算有理数、@ref{187,,float} 或 @ref{189,,complex} 的哈希值:

@example
import sys, math

def hash_fraction(m, n):
    """Compute the hash of a rational number m / n.

    Assumes m and n are integers, with n positive.
    Equivalent to hash(fractions.Fraction(m, n)).

    """
    P = sys.hash_info.modulus
    # Remove common factors of P.  (Unnecessary if m and n already coprime.)
    while m % P == n % P == 0:
        m, n = m // P, n // P

    if n % P == 0:
        hash_value = sys.hash_info.inf
    else:
        # Fermat's Little Theorem: pow(n, P-1, P) is 1, so
        # pow(n, P-2, P) gives the inverse of n modulo P.
        hash_value = (abs(m) % P) * pow(n, P - 2, P) % P
    if m < 0:
        hash_value = -hash_value
    if hash_value == -1:
        hash_value = -2
    return hash_value

def hash_float(x):
    """Compute the hash of a float x."""

    if math.isnan(x):
        return sys.hash_info.nan
    elif math.isinf(x):
        return sys.hash_info.inf if x > 0 else -sys.hash_info.inf
    else:
        return hash_fraction(*x.as_integer_ratio())

def hash_complex(z):
    """Compute the hash of a complex number z."""

    hash_value = hash_float(z.real) + sys.hash_info.imag * hash_float(z.imag)
    # do a signed reduction modulo 2**sys.hash_info.width
    M = 2**(sys.hash_info.width - 1)
    hash_value = (hash_value & (M - 1)) - (hash_value & M)
    if hash_value == -1:
        hash_value = -2
    return hash_value
@end example

@node 迭代器类型,序列类型 --- list tuple range,数字类型 --- int float complex,内置类型
@anchor{library/stdtypes iterator-types}@anchor{15c0}@anchor{library/stdtypes typeiter}@anchor{13f4}
@subsection 迭代器类型


@geindex iterator protocol
@geindex protocol; iterator
@geindex sequence; iteration
@geindex container; iteration over

Python 支持在容器中进行迭代的概念。 这是通过使用两个单独方法来实现的；它们被用于允许用户自定义类对迭代的支持。 将在下文中详细描述的序列总是支持迭代方法。

容器对象要提供迭代支持，必须定义一个方法:

@c XXX duplicated in reference/datamodel!

@geindex __iter__() (container 方法)
@anchor{library/stdtypes container __iter__}@anchor{15c1}
@deffn {方法} container.__iter__ ()

返回一个迭代器对象。 该对象需要支持下文所述的迭代器协议。 如果容器支持不同的迭代类型，则可以提供额外的方法来专门地请求不同迭代类型的迭代器。 （支持多种迭代形式的对象的例子有同时支持广度优先和深度优先遍历的树结构。） 此方法对应于 Python/C API 中 Python 对象类型结构体的 @ref{e29,,tp_iter} 槽位。
@end deffn

迭代器对象自身需要支持以下两个方法，它们共同组成了 @emph{迭代器协议}:

@geindex __iter__() (iterator 方法)
@anchor{library/stdtypes iterator __iter__}@anchor{15c2}
@deffn {方法} iterator.__iter__ ()

返回迭代器对象本身。 这是同时允许容器和迭代器配合 @ref{c29,,for} 和 @ref{79d,,in} 语句使用所必须的。 此方法对应于 Python/C API 中 Python 对象类型结构体的 @ref{e29,,tp_iter} 槽位。
@end deffn

@geindex __next__() (iterator 方法)
@anchor{library/stdtypes iterator __next__}@anchor{c5d}
@deffn {方法} iterator.__next__ ()

从容器中返回下一项。 如果已经没有项可返回，则会引发 @ref{480,,StopIteration} 异常。 此方法对应于 Python/C API 中 Python 对象类型结构体的 @ref{e2a,,tp_iternext} 槽位。
@end deffn

Python 定义了几种迭代器对象以支持对一般和特定序列类型、字典和其他更特别的形式进行迭代。 除了迭代器协议的实现，特定类型的其他性质对迭代操作来说都不重要。

一旦迭代器的 @ref{c5d,,__next__()} 方法引发了 @ref{480,,StopIteration}，它必须一直对后续调用引发同样的异常。 不遵循此行为特性的实现将无法正常使用。

@menu
* 生成器类型:: 

@end menu

@node 生成器类型,,,迭代器类型
@anchor{library/stdtypes generator-types}@anchor{15c3}@anchor{library/stdtypes id3}@anchor{15c4}
@subsubsection 生成器类型


Python 的 @ref{99c,,generator} 提供了一种实现迭代器协议的便捷方式。 如果容器对象 @ref{509,,__iter__()} 方法被实现为一个生成器，它将自动返回一个迭代器对象（从技术上说是一个生成器对象），该对象提供 @ref{509,,__iter__()} 和 @ref{126e,,__next__()} 方法。 有关生成器的更多信息可以参阅 @ref{1499,,yield 表达式的文档}。

@node 序列类型 --- list tuple range,文本序列类型 --- str,迭代器类型,内置类型
@anchor{library/stdtypes sequence-types-list-tuple-range}@anchor{15c5}@anchor{library/stdtypes typesseq}@anchor{1204}
@subsection 序列类型 --- @code{list}, @code{tuple}, @code{range}


有三种基本序列类型：list, tuple 和 range 对象。 为处理 @ref{1580,,二进制数据} 和 @ref{11b7,,文本字符串} 而特别定制的附加序列类型会在专门的小节中描述。

@menu
* 通用序列操作:: 
* 不可变序列类型:: 
* 可变序列类型:: 
* 列表: 列表<2>. 
* 元组:: 
* range 对象:: 

@end menu

@node 通用序列操作,不可变序列类型,,序列类型 --- list tuple range
@anchor{library/stdtypes common-sequence-operations}@anchor{15c6}@anchor{library/stdtypes typesseq-common}@anchor{15c7}
@subsubsection 通用序列操作


@geindex 对象; sequence

大多数序列类型，包括可变类型和不可变类型都支持下表中的操作。 @ref{15c8,,collections.abc.Sequence} ABC 被提供用来更容易地在自定义序列类型上正确地实现这些操作。

此表按优先级升序列出了序列操作。 在表格中，@emph{s} 和 @emph{t} 是具有相同类型的序列，@emph{n}, @emph{i}, @emph{j} 和 @emph{k} 是整数而 @emph{x} 是任何满足 @emph{s} 所规定的类型和值限制的任意对象。

@code{in} 和 @code{not in} 操作具有与比较操作相同的优先级。 @code{+} (拼接) 和 @code{*} (重复) 操作具有与对应数值运算相同的优先级。 @footnote{@w{(3)} 
它们必须如此，因为解析器无法区分这些操作数的类型。
}

@geindex operations on; sequence; types
@geindex 內置函数; len
@geindex 內置函数; min
@geindex 內置函数; max
@geindex concatenation; operation
@geindex repetition; operation
@geindex subscript; operation
@geindex slice; operation
@geindex 运算符; in
@geindex 运算符; not in
@geindex count() (sequence method)
@geindex index() (sequence method)


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@tab

注释

@item

@code{x in s}

@tab

如果 @emph{s} 中的某项等于 @emph{x} 则结果为 @code{True}，否则为 @code{False}

@tab

(1)

@item

@code{x not in s}

@tab

如果 @emph{s} 中的某项等于 @emph{x} 则结果为 @code{False}，否则为 @code{True}

@tab

(1)

@item

@code{s + t}

@tab

@emph{s} 与 @emph{t} 相拼接

@tab

(6)(7)

@item

@code{s * n} 或 @code{n * s}

@tab

相当于 @emph{s} 与自身进行 @emph{n} 次拼接

@tab

(2)(7)

@item

@code{s[i]}

@tab

@emph{s} 的第 @emph{i} 项，起始为 0

@tab

(3)

@item

@code{s[i:j]}

@tab

@emph{s} 从 @emph{i} 到 @emph{j} 的切片

@tab

(3)(4)

@item

@code{s[i:j:k]}

@tab

@emph{s} 从 @emph{i} 到 @emph{j} 步长为 @emph{k} 的切片

@tab

(3)(5)

@item

@code{len(s)}

@tab

@emph{s} 的长度

@tab

@item

@code{min(s)}

@tab

@emph{s} 的最小项

@tab

@item

@code{max(s)}

@tab

@emph{s} 的最大项

@tab

@item

@code{s.index(x[, i[, j]])}

@tab

@emph{x} 在 @emph{s} 中首次出现项的索引号（索引号在 @emph{i} 或其后且在 @emph{j} 之前）

@tab

(8)

@item

@code{s.count(x)}

@tab

@emph{x} 在 @emph{s} 中出现的总次数

@tab

@end multitable


相同类型的序列也支持比较。 特别地，tuple 和 list 的比较是通过比较对应元素的字典顺序。 这意味着想要比较结果相等，则每个元素比较结果都必须相等，并且两个序列长度必须相同。 （完整细节请参阅语言参考的 @ref{14da,,比较运算} 部分。）

注释:


@enumerate 

@item 
虽然 @code{in} 和 @code{not in} 操作在通常情况下仅被用于简单的成员检测，某些专门化序列 (例如 @ref{329,,str}, @ref{32a,,bytes} 和 @ref{32b,,bytearray}) 也使用它们进行子序列检测:

@example
>>> "gg" in "eggs"
True
@end example

@item 
小于 @code{0} 的 @emph{n} 值会被当作 @code{0} 来处理 (生成一个与 @emph{s} 同类型的空序列)。 请注意序列 @emph{s} 中的项并不会被拷贝；它们会被多次引用。 这一点经常会令 Python 编程新手感到困扰；例如:

@example
>>> lists = [[]] * 3
>>> lists
[[], [], []]
>>> lists[0].append(3)
>>> lists
[[3], [3], [3]]
@end example

具体的原因在于 @code{[[]]} 是一个包含了一个空列表的单元素列表，所以 @code{[[]] * 3} 结果中的三个元素都是对这一个空列表的引用。 修改 @code{lists} 中的任何一个元素实际上都是对这一个空列表的修改。 你可以用以下方式创建以不同列表为元素的列表:

@example
>>> lists = [[] for i in range(3)]
>>> lists[0].append(3)
>>> lists[1].append(5)
>>> lists[2].append(7)
>>> lists
[[3], [5], [7]]
@end example

进一步的解释可以在 FAQ 条目 @ref{15c9,,如何创建多维列表？} 中查看。

@item 
如果 @emph{i} 或 @emph{j} 为负值，则索引顺序是相对于序列 @emph{s} 的末尾: 索引号会被替换为 @code{len(s) + i} 或 @code{len(s) + j}。 但要注意 @code{-0} 仍然为 @code{0}。

@item 
@emph{s} 从 @emph{i} 到 @emph{j} 的切片被定义为所有满足 @code{i <= k < j} 的索引号 @emph{k} 的项组成的序列。 如果 @emph{i} 或 @emph{j} 大于 @code{len(s)}，则使用 @code{len(s)}。 如果 @emph{i} 被省略或为 @code{None}，则使用 @code{0}。 如果 @emph{j} 被省略或为 @code{None}，则使用 @code{len(s)}。 如果 @emph{i} 大于等于 @emph{j}，则切片为空。

@item 
@emph{s} 从 @emph{i} 到 @emph{j} 步长为 @emph{k} 的切片被定义为所有满足 @code{0 <= n < (j-i)/k} 的索引号  @code{x = i + n*k} 的项组成的序列。 换句话说，索引号为 @code{i}, @code{i+k}, @code{i+2*k}, @code{i+3*k}，以此类推，当达到 @emph{j} 时停止 (但一定不包括 @emph{j})。 当 @emph{k} 为正值时，@emph{i} 和 @emph{j} 会被减至不大于 @code{len(s)}。 当 @emph{k} 为负值时，@emph{i} 和 @emph{j} 会被减至不大于 @code{len(s) - 1}。 如果 @emph{i} 或 @emph{j} 被省略或为 @code{None}，它们会成为“终止”值 (是哪一端的终止值则取决于 @emph{k} 的符号)。 请注意，@emph{k} 不可为零。 如果 @emph{k} 为 @code{None}，则当作 @code{1} 处理。

@item 
拼接不可变序列总是会生成新的对象。 这意味着通过重复拼接来构建序列的运行时开销将会基于序列总长度的乘方。 想要获得线性的运行时开销，你必须改用下列替代方案之一：


@itemize *

@item 
如果拼接 @ref{329,,str} 对象，你可以构建一个列表并在最后使用 @ref{15ca,,str.join()} 或是写入一个 @ref{827,,io.StringIO} 实例并在结束时获取它的值

@item 
如果拼接 @ref{32a,,bytes} 对象，你可以类似地使用 @ref{15cb,,bytes.join()} 或 @ref{795,,io.BytesIO}，或者你也可以使用 @ref{32b,,bytearray} 对象进行原地拼接。 @ref{32b,,bytearray} 对象是可变的，并且具有高效的重分配机制

@item 
如果拼接 @ref{478,,tuple} 对象，请改为扩展 @ref{262,,list} 类

@item 
对于其它类型，请查看相应的文档
@end itemize

@item 
某些序列类型 (例如 @ref{9b8,,range}) 仅支持遵循特定模式的项序列，因此并不支持序列拼接或重复。

@item 
当 @emph{x} 在 @emph{s} 中找不到时 @code{index} 会引发 @ref{1fb,,ValueError}。 不是所有实现都支持传入额外参数 @emph{i} 和 @emph{j}。 这两个参数允许高效地搜索序列的子序列。 传入这两个额外参数大致相当于使用 @code{s[i:j].index(x)}，但是不会复制任何数据，并且返回的索引是相对于序列的开头而非切片的开头。
@end enumerate

@node 不可变序列类型,可变序列类型,通用序列操作,序列类型 --- list tuple range
@anchor{library/stdtypes immutable-sequence-types}@anchor{15cc}@anchor{library/stdtypes typesseq-immutable}@anchor{15cd}
@subsubsection 不可变序列类型


@geindex immutable; sequence; types
@geindex 对象; tuple
@geindex 內置函数; hash

不可变序列类型普遍实现而可变序列类型未实现的唯一操作就是对 @ref{9be,,hash()} 内置函数的支持。

这种支持允许不可变类型，例如 @ref{478,,tuple} 实例被用作 @ref{1b8,,dict} 键，以及存储在 @ref{b68,,set} 和 @ref{be7,,frozenset} 实例中。

尝试对包含有不可哈希值的不可变序列进行哈希运算将会导致 @ref{192,,TypeError}。

@node 可变序列类型,列表<2>,不可变序列类型,序列类型 --- list tuple range
@anchor{library/stdtypes mutable-sequence-types}@anchor{15ce}@anchor{library/stdtypes typesseq-mutable}@anchor{157e}
@subsubsection 可变序列类型


@geindex mutable; sequence; types
@geindex 对象; list
@geindex 对象; bytearray

以下表格中的操作是在可变序列类型上定义的。 @ref{6a6,,collections.abc.MutableSequence} ABC 被提供用来更容易地在自定义序列类型上正确实现这些操作。

表格中的 @emph{s} 是可变序列类型的实例，@emph{t} 是任意可迭代对象，而 @emph{x} 是符合对 @emph{s} 所规定类型与值限制的任何对象 (例如，@ref{32b,,bytearray} 仅接受满足 @code{0 <= x <= 255} 值限制的整数)。

@geindex operations on; sequence; types
@geindex operations on; list; type
@geindex subscript; assignment
@geindex slice; assignment
@geindex 语句; del
@geindex append() (sequence method)
@geindex clear() (sequence method)
@geindex copy() (sequence method)
@geindex extend() (sequence method)
@geindex insert() (sequence method)
@geindex pop() (sequence method)
@geindex remove() (sequence method)
@geindex reverse() (sequence method)


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@tab

注释

@item

@code{s[i] = x}

@tab

将 @emph{s} 的第 @emph{i} 项替换为 @emph{x}

@tab

@item

@code{s[i:j] = t}

@tab

将 @emph{s} 从 @emph{i} 到 @emph{j} 的切片替换为可迭代对象 @emph{t} 的内容

@tab

@item

@code{del s[i:j]}

@tab

等同于 @code{s[i:j] = []}

@tab

@item

@code{s[i:j:k] = t}

@tab

将 @code{s[i:j:k]} 的元素替换为 @emph{t} 的元素

@tab

(1)

@item

@code{del s[i:j:k]}

@tab

从列表中移除 @code{s[i:j:k]} 的元素

@tab

@item

@code{s.append(x)}

@tab

将 @emph{x} 添加到序列的末尾 (等同于 @code{s[len(s):len(s)] = [x]})

@tab

@item

@code{s.clear()}

@tab

从 @emph{s} 中移除所有项 (等同于 @code{del s[:]})

@tab

(5)

@item

@code{s.copy()}

@tab

创建 @emph{s} 的浅拷贝 (等同于 @code{s[:]})

@tab

(5)

@item

@code{s.extend(t)} 或 @code{s += t}

@tab

用 @emph{t} 的内容扩展 @emph{s} (基本上等同于 @code{s[len(s):len(s)] = t})

@tab

@item

@code{s *= n}

@tab

使用 @emph{s} 的内容重复 @emph{n} 次来对其进行更新

@tab

(6)

@item

@code{s.insert(i, x)}

@tab

在由 @emph{i} 给出的索引位置将 @emph{x} 插入 @emph{s} (等同于 @code{s[i:i] = [x]})

@tab

@item

@code{s.pop([i])}

@tab

提取在 @emph{i} 位置上的项，并将其从 @emph{s} 中移除

@tab

(2)

@item

@code{s.remove(x)}

@tab

删除 @emph{s} 中第一个 @code{s[i]} 等于 @emph{x} 的项目。

@tab

(3)

@item

@code{s.reverse()}

@tab

就地将列表中的元素逆序。

@tab

(4)

@end multitable


注释:


@enumerate 

@item 
@emph{t} 必须与它所替换的切片具有相同的长度。

@item 
可选参数 @emph{i} 默认为 @code{-1}，因此在默认情况下会移除并返回最后一项。

@item 
当在 @emph{s} 中找不到 @emph{x} 时 @code{remove()} 操作会引发 @ref{1fb,,ValueError}。

@item 
当反转大尺寸序列时 @code{reverse()} 方法会原地修改该序列以保证空间经济性。 为提醒用户此操作是通过间接影响进行的，它并不会返回反转后的序列。

@item 
包括 @code{clear()} 和 @code{copy()} 是为了与不支持切片操作的可变容器 (例如 @ref{1b8,,dict} 和 @ref{b68,,set}) 的接口保持一致。 @code{copy()} 不是 @ref{6a6,,collections.abc.MutableSequence} ABC 的一部分，但大多数具体的可变序列类都提供了它。


3.3 新版功能: @code{clear()} 和 @code{copy()} 方法。


@item 
@emph{n} 值为一个整数，或是一个实现了 @ref{18a,,__index__()} 的对象。 @emph{n} 值为零或负数将清空序列。 序列中的项不会被拷贝；它们会被多次引用，正如 @ref{15c7,,通用序列操作} 中有关 @code{s * n} 的说明。
@end enumerate

@node 列表<2>,元组,可变序列类型,序列类型 --- list tuple range
@anchor{library/stdtypes lists}@anchor{15cf}@anchor{library/stdtypes typesseq-list}@anchor{158c}
@subsubsection 列表


@geindex 对象; list

列表是可变序列，通常用于存放同类项目的集合（其中精确的相似程度将根据应用而变化）。

@geindex list (內置类)
@anchor{library/stdtypes list}@anchor{262}
@deffn {类} list ([iterable])

可以用多种方式构建列表：


@itemize *

@item 
使用一对方括号来表示空列表: @code{[]}

@item 
使用方括号，其中的项以逗号分隔: @code{[a]}, @code{[a, b, c]}

@item 
使用列表推导式: @code{[x for x in iterable]}

@item 
使用类型的构造器: @code{list()} 或 @code{list(iterable)}
@end itemize

构造器将构造一个列表，其中的项与 @emph{iterable} 中的项具有相同的的值与顺序。 @emph{iterable} 可以是序列、支持迭代的容器或其它可迭代对象。 如果 @emph{iterable} 已经是一个列表，将创建并返回其副本，类似于 @code{iterable[:]}。 例如，@code{list('abc')} 返回 @code{['a', 'b', 'c']} 而 @code{list( (1, 2, 3) )} 返回 @code{[1, 2, 3]}。 如果没有给出参数，构造器将创建一个空列表 @code{[]}。

其它许多操作也会产生列表，包括 @ref{43e,,sorted()} 内置函数。

列表实现了所有 @ref{15c7,,一般} 和 @ref{157e,,可变} 序列的操作。 列表还额外提供了以下方法：

@geindex sort() (list 方法)
@anchor{library/stdtypes list sort}@anchor{43f}
@deffn {方法} sort (*, key=None, reverse=False)

此方法会对列表进行原地排序，只使用 @code{<} 来进行各项间比较。 异常不会被屏蔽 —— 如果有任何比较操作失败，整个排序操作将失败（而列表可能会处于被部分修改的状态）。

@ref{43f,,sort()} 接受两个仅限以关键字形式传入的参数 (@ref{2ac,,仅限关键字参数}):

@emph{key} 指定带有一个参数的函数，用于从每个列表元素中提取比较键 (例如 @code{key=str.lower})。 对应于列表中每一项的键会被计算一次，然后在整个排序过程中使用。 默认值 @code{None} 表示直接对列表项排序而不计算一个单独的键值。

可以使用 @ref{b4f,,functools.cmp_to_key()} 将 2.x 风格的 @emph{cmp} 函数转换为 @emph{key} 函数。

@emph{reverse} 为一个布尔值。 如果设为 @code{True}，则每个列表元素将按反向顺序比较进行排序。

当顺序大尺寸序列时此方法会原地修改该序列以保证空间经济性。 为提醒用户此操作是通过间接影响进行的，它并不会返回排序后的序列（请使用 @ref{43e,,sorted()} 显示地请求一个新的已排序列表实例）。

@ref{43f,,sort()} 方法确保是稳定的。 如果一个排序确保不会改变比较结果相等的元素的相对顺序就称其为稳定的 --- 这有利于进行多重排序（例如先按部门、再接薪级排序）。

有关排序示例和简要排序教程，请参阅 @ref{1599,,排序指南} 。

@strong{CPython implementation detail:} 在一个列表被排序期间，尝试改变甚至进行检测也会造成未定义的影响。 Python 的 C 实现会在排序期间将列表显示为空，如果发现列表在排序期间被改变将会引发 @ref{1fb,,ValueError}。
@end deffn
@end deffn

@node 元组,range 对象,列表<2>,序列类型 --- list tuple range
@anchor{library/stdtypes tuples}@anchor{15d0}@anchor{library/stdtypes typesseq-tuple}@anchor{159f}
@subsubsection 元组


@geindex 对象; tuple

元组是不可变序列，通常用于储存异构数据的多项集（例如由 @ref{ddc,,enumerate()} 内置函数所产生的二元组）。 元组也被用于需要同构数据的不可变序列的情况（例如允许存储到 @ref{b68,,set} 或 @ref{1b8,,dict} 的实例）。

@geindex tuple (內置类)
@anchor{library/stdtypes tuple}@anchor{478}
@deffn {类} tuple ([iterable])

可以用多种方式构建元组：


@itemize *

@item 
使用一对圆括号来表示空元组: @code{()}

@item 
使用一个后缀的逗号来表示单元组: @code{a,} 或 @code{(a,)}

@item 
使用以逗号分隔的多个项: @code{a, b, c} or @code{(a, b, c)}

@item 
使用内置的 @ref{478,,tuple()}: @code{tuple()} 或 @code{tuple(iterable)}
@end itemize

构造器将构造一个元组，其中的项与 @emph{iterable} 中的项具有相同的值与顺序。 @emph{iterable} 可以是序列、支持迭代的容器或其他可迭代对象。 如果 @emph{iterable} 已经是一个元组，会不加改变地将其返回。 例如，@code{tuple('abc')} 返回 @code{('a', 'b', 'c')} 而 @code{tuple( [1, 2, 3] )} 返回 @code{(1, 2, 3)}。 如果没有给出参数，构造器将创建一个空元组 @code{()}。

请注意决定生成元组的其实是逗号而不是圆括号。 圆括号只是可选的，生成空元组或需要避免语法歧义的情况除外。 例如，@code{f(a, b, c)} 是在调用函数时附带三个参数，而 @code{f((a, b, c))} 则是在调用函数时附带一个三元组。

元组实现了所有 @ref{15c7,,一般} 序列的操作。
@end deffn

对于通过名称访问相比通过索引访问更清晰的异构数据多项集，@ref{1b6,,collections.namedtuple()} 可能是比简单元组对象更为合适的选择。

@node range 对象,,元组,序列类型 --- list tuple range
@anchor{library/stdtypes ranges}@anchor{15d1}@anchor{library/stdtypes typesseq-range}@anchor{1597}
@subsubsection range 对象


@geindex 对象; range

@ref{9b8,,range} 类型表示不可变的数字序列，通常用于在 @ref{c29,,for} 循环中循环指定的次数。

@geindex range (內置类)
@anchor{library/stdtypes range}@anchor{9b8}
@deffn {类} range (stop)

@deffnx {类} range (start, stop[, step])

range 构造器的参数必须为整数（可以是内置的 @ref{184,,int} 或任何实现了 @code{__index__} 特殊方法的对象）。 如果省略 @emph{step} 参数，其默认值为 @code{1}。 如果省略 @emph{start} 参数，其默认值为 @code{0}，如果 @emph{step} 为零则会引发 @ref{1fb,,ValueError}。

如果 @emph{step} 为正值，确定 range @code{r} 内容的公式为 @code{r[i] = start + step*i} 其中 @code{i >= 0} 且 @code{r[i] < stop}。

如果 @emph{step} 为负值，确定 range 内容的公式仍然为 @code{r[i] = start + step*i}，但限制条件改为 @code{i >= 0} 且 @code{r[i] > stop}.

如果 @code{r[0]} 不符合值的限制条件，则该 range 对象为空。 range 对象确实支持负索引，但是会将其解读为从正索引所确定的序列的末尾开始索引。

元素绝对值大于 @ref{b3c,,sys.maxsize} 的 range 对象是被允许的，但某些特性 (例如 @ref{150,,len()}) 可能引发 @ref{95a,,OverflowError}。

一些 range 对象的例子:

@example
>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> list(range(1, 11))
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> list(range(0, 30, 5))
[0, 5, 10, 15, 20, 25]
>>> list(range(0, 10, 3))
[0, 3, 6, 9]
>>> list(range(0, -10, -1))
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
>>> list(range(0))
[]
>>> list(range(1, 0))
[]
@end example

range 对象实现了 @ref{15c7,,一般} 序列的所有操作，但拼接和重复除外（这是由于 range 对象只能表示符合严格模式的序列，而重复和拼接通常都会违反这样的模式）。

@geindex start (range 属性)
@anchor{library/stdtypes range start}@anchor{15d2}
@deffn {属性} start

@emph{start} 形参的值 (如果该形参未提供则为 @code{0})
@end deffn

@geindex stop (range 属性)
@anchor{library/stdtypes range stop}@anchor{15d3}
@deffn {属性} stop

@emph{stop} 形参的值
@end deffn

@geindex step (range 属性)
@anchor{library/stdtypes range step}@anchor{15d4}
@deffn {属性} step

@emph{step} 形参的值 (如果该形参未提供则为 @code{1})
@end deffn
@end deffn

@ref{9b8,,range} 类型相比常规 @ref{262,,list} 或 @ref{478,,tuple} 的优势在于一个 @ref{9b8,,range} 对象总是占用固定数量的（较小）内存，不论其所表示的范围有多大（因为它只保存了 @code{start}, @code{stop} 和 @code{step} 值，并会根据需要计算具体单项或子范围的值）。

range 对象实现了 @ref{15c8,,collections.abc.Sequence} ABC，提供如包含检测、元素索引查找、切片等特性，并支持负索引 (参见 @ref{1204,,序列类型 --- list@comma{} tuple@comma{} range}):

@example
>>> r = range(0, 20, 2)
>>> r
range(0, 20, 2)
>>> 11 in r
False
>>> 10 in r
True
>>> r.index(10)
5
>>> r[5]
10
>>> r[:5]
range(0, 10, 2)
>>> r[-1]
18
@end example

使用 @code{==} 和 @code{!=} 检测 range 对象是否相等是将其作为序列来比较。 也就是说，如果两个 range 对象表示相同的值序列就认为它们是相等的。 （请注意比较结果相等的两个 range 对象可能会具有不同的 @ref{15d2,,start}, @ref{15d3,,stop} 和 @ref{15d4,,step} 属性，例如 @code{range(0) == range(2, 1, 3)} 而 @code{range(0, 3, 2) == range(0, 4, 2)}。）


在 3.2 版更改: 实现 Sequence ABC。 支持切片和负数索引。 使用 @ref{184,,int} 对象在固定时间内进行成员检测，而不是逐一迭代所有项。



在 3.3 版更改: 定义 '==' 和 '!=' 以根据 range 对象所定义的值序列来进行比较（而不是根据对象的标识）。



3.3 新版功能: @ref{15d2,,start}, @ref{15d3,,stop} 和 @ref{15d4,,step} 属性。



@subsubheading 参见



@itemize *

@item 
linspace recipe@footnote{http://code.activestate.com/recipes/579000/} 演示了如何实现一个延迟求值版本的适合浮点数应用的 range 对象。
@end itemize


@geindex string; text sequence type
@geindex str (built-in class); (see also string)
@geindex 对象; string

@node 文本序列类型 --- str,二进制序列类型 --- bytes bytearray memoryview,序列类型 --- list tuple range,内置类型
@anchor{library/stdtypes text-sequence-type-str}@anchor{15d5}@anchor{library/stdtypes textseq}@anchor{11b7}
@subsection 文本序列类型 --- @code{str}


在 Python 中处理文本数据是使用 @ref{329,,str} 对象，也称为 @emph{字符串}。 字符串是由 Unicode 码位构成的不可变 @ref{1204,,序列}。 字符串字面值有多种不同的写法：


@itemize *

@item 
单引号: @code{'允许包含有 "双" 引号'}

@item 
双引号: @code{"允许包含有 '单' 引号"}。

@item 
三重引号: @code{'@w{'}'三重单引号'@w{'}'}, @code{"""三重双引号"""}
@end itemize

使用三重引号的字符串可以跨越多行 —— 其中所有的空白字符都将包含在该字符串字面值中。

作为单一表达式组成部分，之间只由空格分隔的多个字符串字面值会被隐式地转换为单个字符串字面值。 也就是说，@code{("spam " "eggs") == "spam eggs"}。

请参阅 @ref{1379,,字符串和字节串字面值} 有解有关不同字符串字面值的更多信息，包括所支持的转义序列，以及使用 @code{r} ("raw") 前缀来禁用大多数转义序列的处理。

字符串也可以通过使用 @ref{329,,str} 构造器从其他对象创建。

由于不存在单独的“字符”类型，对字符串做索引操作将产生一个长度为 1 的字符串。 也就是说，对于一个非空字符串 @emph{s}, @code{s[0] == s[0:1]}。

@geindex 对象; io.StringIO

不存在可变的字符串类型，但是 @ref{15ca,,str.join()} 或 @ref{827,,io.StringIO} 可以被被用来根据多个片段高效率地构建字符串。


在 3.3 版更改: 为了与 Python 2 系列的向下兼容，再次允许字符串字面值使用 @code{u} 前缀。 它对字符串字面值的含义没有影响，并且不能与 @code{r} 前缀同时出现。


@geindex string; str (built-in class)

@geindex str (內置类)
@anchor{library/stdtypes str}@anchor{329}
@deffn {类} str (object='@w{'})

@deffnx {类} str (object=b'@w{'}, encoding='utf-8', errors='strict')

返回 @emph{object} 的 @ref{11b7,,字符串} 版本。 如果未提供 @emph{object} 则返回空字符串。 在其他情况下 @code{str()} 的行为取决于 @emph{encoding} 或 @emph{errors} 是否有给出，具体见下。

如果 @emph{encoding} 或 @emph{errors} 均未给出，@code{str(object)} 返回 @ref{e30,,object.__str__()}，这是 @emph{object} 的“非正式”或格式良好的字符串表示。 对于字符串对象，这是该字符串本身。 如果 @emph{object} 没有 @ref{e30,,__str__()} 方法，则 @ref{329,,str()} 将回退为返回 @ref{7c6,,repr(object)}。

@geindex buffer protocol; str (built-in class)
@geindex bytes; str (built-in class)

如果 @emph{encoding} 或 @emph{errors} 至少给出其中之一，则 @emph{object} 应该是一个 @ref{5e3,,bytes-like object} (例如 @ref{32a,,bytes} 或 @ref{32b,,bytearray})。 在此情况下，如果 @emph{object} 是一个 @ref{32a,,bytes} (或 @ref{32b,,bytearray}) 对象，则 @code{str(bytes, encoding, errors)} 等价于 @ref{c31,,bytes.decode(encoding@comma{} errors)}。 否则的话，会在调用 @ref{c31,,bytes.decode()} 之前获取缓冲区对象下层的 bytes 对象。 请参阅 @ref{1580,,二进制序列类型 --- bytes@comma{} bytearray@comma{} memoryview} 与 @ref{15d6,,缓冲协议} 了解有关缓冲区对象的信息。

将一个 @ref{32a,,bytes} 对象传入 @ref{329,,str()} 而不给出 @emph{encoding} 或 @emph{errors} 参数的操作属于第一种情况， 将返回非正式的字符串表示（另请参阅 Python 的 @ref{40d,,-b} 命令行选项）。 例如:

@example
>>> str(b'Zoot!')
"b'Zoot!'"
@end example

有关 @code{str} 类及其方法的更多信息，请参阅下面的 @ref{11b7,,文本序列类型 --- str} 和 @ref{11b8,,字符串的方法} 小节。 要输出格式化字符串，请参阅 @ref{15c,,格式化字符串字面值} 和 @ref{d13,,格式字符串语法} 小节。 此外还可以参阅 @ref{15d7,,文本处理服务} 小节。
@end deffn

@geindex string; methods

@menu
* 字符串的方法: 字符串的方法<2>. 
* printf 风格的字符串格式化:: 

@end menu

@node 字符串的方法<2>,printf 风格的字符串格式化,,文本序列类型 --- str
@anchor{library/stdtypes id5}@anchor{15d8}@anchor{library/stdtypes string-methods}@anchor{11b8}
@subsubsection 字符串的方法


@geindex 模块; re

字符串实现了所有 @ref{15c7,,一般} 序列的操作，还额外提供了以下列出的一些附加方法。

字符串还支持两种字符串格式化样式，一种提供了很大程度的灵活性和可定制性 (参阅 @ref{4d4,,str.format()}, @ref{d13,,格式字符串语法} 和 @ref{15d9,,自定义字符串格式化}) 而另一种是基于 C @code{printf} 样式的格式化，它可处理的类型范围较窄，并且更难以正确使用，但对于它可处理的情况往往会更为快速 (@ref{11b9,,printf 风格的字符串格式化})。

标准库的 @ref{15da,,文本处理服务} 部分涵盖了许多其他模块，提供各种文本相关工具（例如包含于 @ref{dd,,re} 模块中的正则表达式支持）。

@geindex capitalize() (str 方法)
@anchor{library/stdtypes str capitalize}@anchor{15db}
@deffn {方法} str.capitalize ()

返回原字符串的副本，其首个字符大写，其余为小写。


在 3.8 版更改: 第一个字符现在被放入了 titlecase 而不是 uppercase。 这意味着复合字母类字符将只有首个字母改为大写，而再不是全部字符大写。

@end deffn

@geindex casefold() (str 方法)
@anchor{library/stdtypes str casefold}@anchor{6aa}
@deffn {方法} str.casefold ()

返回原字符串消除大小写的副本。 消除大小写的字符串可用于忽略大小写的匹配。

消除大小写类似于转为小写，但是更加彻底一些，因为它会移除字符串中的所有大小写变化形式。 例如，德语小写字母 @code{'ß'} 相当于 @code{"ss"}。 由于它已经是小写了，@ref{15dc,,lower()} 不会对 @code{'ß'} 做任何改变；而 @ref{6aa,,casefold()} 则会将其转换为 @code{"ss"}。

消除大小写算法的描述请参见 Unicode 标准的 3.13 节。


3.3 新版功能.

@end deffn

@geindex center() (str 方法)
@anchor{library/stdtypes str center}@anchor{1230}
@deffn {方法} str.center (width[, fillchar])

返回长度为 @emph{width} 的字符串，原字符串在其正中。 使用指定的 @emph{fillchar} 填充两边的空位（默认使用 ASCII 空格符）。 如果 @emph{width} 小于等于 @code{len(s)} 则返回原字符串的副本。
@end deffn

@geindex count() (str 方法)
@anchor{library/stdtypes str count}@anchor{15dd}
@deffn {方法} str.count (sub[, start[, end]])

反回子字符串 @emph{sub} 在 [@emph{start}, @emph{end}] 范围内非重叠出现的次数。 可选参数 @emph{start} 与 @emph{end} 会被解读为切片表示法。
@end deffn

@geindex encode() (str 方法)
@anchor{library/stdtypes str encode}@anchor{c30}
@deffn {方法} str.encode (encoding="utf-8", errors="strict")

返回原字符串编码为字节串对象的版本。 默认编码为 @code{'utf-8'}。 可以给出 @emph{errors} 来设置不同的错误处理方案。 @emph{errors} 的默认值为 @code{'strict'}，表示编码错误会引发 @ref{c34,,UnicodeError}。 其他可用的值为 @code{'ignore'}, @code{'replace'}, @code{'xmlcharrefreplace'}, @code{'backslashreplace'} 以及任何其他通过 @ref{dee,,codecs.register_error()} 注册的值，请参阅 @ref{12f7,,错误处理方案} 小节。 要查看可用的编码列表，请参阅 @ref{689,,标准编码} 小节。


在 3.1 版更改: 加入了对关键字参数的支持。

@end deffn

@geindex endswith() (str 方法)
@anchor{library/stdtypes str endswith}@anchor{7c1}
@deffn {方法} str.endswith (suffix[, start[, end]])

如果字符串以指定的 @emph{suffix} 结束返回 @code{True}，否则返回 @code{False}。 @emph{suffix} 也可以为由多个供查找的后缀构成的元组。 如果有可选项 @emph{start}，将从所指定位置开始检查。 如果有可选项 @emph{end}，将在所指定位置停止比较。
@end deffn

@geindex expandtabs() (str 方法)
@anchor{library/stdtypes str expandtabs}@anchor{15de}
@deffn {方法} str.expandtabs (tabsize=8)

返回字符串的副本，其中所有的制表符会由一个或多个空格替换，具体取决于当前列位置和给定的制表符宽度。 每 @emph{tabsize} 个字符设为一个制表位（默认值 8 时设定的制表位在列 0, 8, 16 依次类推）。 要展开字符串，当前列将被设为零并逐一检查字符串中的每个字符。 如果字符为制表符 (@code{\t})，则会在结果中插入一个或多个空格符，直到当前列等于下一个制表位。 （制表符本身不会被复制。） 如果字符为换行符 (@code{\n}) 或回车符 (@code{\r})，它会被复制并将当前列重设为零。 任何其他字符会被不加修改地复制并将当前列加一，不论该字符在被打印时会如何显示。

@example
>>> '01\t012\t0123\t01234'.expandtabs()
'01      012     0123    01234'
>>> '01\t012\t0123\t01234'.expandtabs(4)
'01  012 0123    01234'
@end example
@end deffn

@geindex find() (str 方法)
@anchor{library/stdtypes str find}@anchor{799}
@deffn {方法} str.find (sub[, start[, end]])

返回子字符串 @emph{sub} 在 @code{s[start:end]} 切片内被找到的最小索引。 可选参数 @emph{start} 与 @emph{end} 会被解读为切片表示法。 如果 @emph{sub} 未被找到则返回 @code{-1}。

@cartouche
@quotation 注解 
@ref{799,,find()} 方法应该只在你需要知道 @emph{sub} 所在位置时使用。 要检查 @emph{sub} 是否为子字符串，请使用 @ref{79d,,in} 操作符:

@example
>>> 'Py' in 'Python'
True
@end example
@end quotation
@end cartouche
@end deffn

@geindex format() (str 方法)
@anchor{library/stdtypes str format}@anchor{4d4}
@deffn {方法} str.format (*args, **kwargs)

执行字符串格式化操作。 调用此方法的字符串可以包含字符串字面值或者以花括号 @code{@{@}} 括起来的替换域。 每个替换域可以包含一个位置参数的数字索引，或者一个关键字参数的名称。 返回的字符串副本中每个替换域都会被替换为对应参数的字符串值。

@example
>>> "The sum of 1 + 2 is @{0@}".format(1+2)
'The sum of 1 + 2 is 3'
@end example

请参阅 @ref{d13,,格式字符串语法} 了解有关可以在格式字符串中指定的各种格式选项的说明。

@cartouche
@quotation 注解 
当使用 @code{n} 类型 (例如: @code{'@{:n@}'.format(1234)}) 来格式化数字 (@ref{184,,int}, @ref{187,,float}, @ref{189,,complex}, @ref{188,,decimal.Decimal} 及其子类) 的时候，该函数会临时性地将 @code{LC_CTYPE} 区域设置为 @code{LC_NUMERIC} 区域以解码  @code{localeconv()} 的 @code{decimal_point} 和 @code{thousands_sep} 字段，如果它们是非 ASCII 字符或长度超过 1 字节的话，并且 @code{LC_NUMERIC} 区域会与 @code{LC_CTYPE} 区域不一致。 这个临时更改会影响其他线程。
@end quotation
@end cartouche


在 3.7 版更改: 当使用 @code{n} 类型格式化数字时，该函数在某些情况下会临时性地将 @code{LC_CTYPE} 区域设置为 @code{LC_NUMERIC} 区域。

@end deffn

@geindex format_map() (str 方法)
@anchor{library/stdtypes str format_map}@anchor{6ab}
@deffn {方法} str.format_map (mapping)

类似于 @code{str.format(**mapping)}，不同之处在于 @code{mapping} 会被直接使用而不是复制到一个 @ref{1b8,,dict}。 适宜使用此方法的一个例子是当 @code{mapping} 为 dict 的子类的情况：

@example
>>> class Default(dict):
...     def __missing__(self, key):
...         return key
...
>>> '@{name@} was born in @{country@}'.format_map(Default(name='Guido'))
'Guido was born in country'
@end example


3.2 新版功能.

@end deffn

@geindex index() (str 方法)
@anchor{library/stdtypes str index}@anchor{15df}
@deffn {方法} str.index (sub[, start[, end]])

类似于 @ref{799,,find()}，但在找不到子类时会引发 @ref{1fb,,ValueError}。
@end deffn

@geindex isalnum() (str 方法)
@anchor{library/stdtypes str isalnum}@anchor{15e0}
@deffn {方法} str.isalnum ()

Return @code{True} if all characters in the string are alphanumeric and there is at
least one character, @code{False} otherwise.  A character @code{c} is alphanumeric if one
of the following returns @code{True}: @code{c.isalpha()}, @code{c.isdecimal()},
@code{c.isdigit()}, or @code{c.isnumeric()}.
@end deffn

@geindex isalpha() (str 方法)
@anchor{library/stdtypes str isalpha}@anchor{15e1}
@deffn {方法} str.isalpha ()

Return @code{True} if all characters in the string are alphabetic and there is at least
one character, @code{False} otherwise.  Alphabetic characters are those characters defined
in the Unicode character database as "Letter", i.e., those with general category
property being one of "Lm", "Lt", "Lu", "Ll", or "Lo".  Note that this is different
from the "Alphabetic" property defined in the Unicode Standard.
@end deffn

@geindex isascii() (str 方法)
@anchor{library/stdtypes str isascii}@anchor{32c}
@deffn {方法} str.isascii ()

Return @code{True} if the string is empty or all characters in the string are ASCII,
@code{False} otherwise.
ASCII characters have code points in the range U+0000-U+007F.


3.7 新版功能.

@end deffn

@geindex isdecimal() (str 方法)
@anchor{library/stdtypes str isdecimal}@anchor{15e2}
@deffn {方法} str.isdecimal ()

Return @code{True} if all characters in the string are decimal
characters and there is at least one character, @code{False}
otherwise. Decimal characters are those that can be used to form
numbers in base 10, e.g. U+0660, ARABIC-INDIC DIGIT
ZERO.  Formally a decimal character is a character in the Unicode
General Category "Nd".
@end deffn

@geindex isdigit() (str 方法)
@anchor{library/stdtypes str isdigit}@anchor{15e3}
@deffn {方法} str.isdigit ()

Return @code{True} if all characters in the string are digits and there is at least one
character, @code{False} otherwise.  Digits include decimal characters and digits that need
special handling, such as the compatibility superscript digits.
This covers digits which cannot be used to form numbers in base 10,
like the Kharosthi numbers.  Formally, a digit is a character that has the
property value Numeric_Type=Digit or Numeric_Type=Decimal.
@end deffn

@geindex isidentifier() (str 方法)
@anchor{library/stdtypes str isidentifier}@anchor{15e4}
@deffn {方法} str.isidentifier ()

Return @code{True} if the string is a valid identifier according to the language
definition, section @ref{136a,,标识符和关键字}.

调用 @ref{15e5,,keyword.iskeyword()} 来检测字符串 @code{s} 是否为保留标识符，例如 @ref{db7,,def} 和 @ref{c63,,class}。

示例：

@example
>>> from keyword import iskeyword

>>> 'hello'.isidentifier(), iskeyword('hello')
True, False
>>> 'def'.isidentifier(), iskeyword('def')
True, True
@end example
@end deffn

@geindex islower() (str 方法)
@anchor{library/stdtypes str islower}@anchor{15e6}
@deffn {方法} str.islower ()

Return @code{True} if all cased characters @footnote{@w{(4)} 
区分大小写的字符是指所属一般类别属性为 "Lu" (Letter, uppercase), "Ll" (Letter, lowercase) 或 "Lt" (Letter, titlecase) 之一的字符。
} in the string are lowercase and
there is at least one cased character, @code{False} otherwise.
@end deffn

@geindex isnumeric() (str 方法)
@anchor{library/stdtypes str isnumeric}@anchor{15e7}
@deffn {方法} str.isnumeric ()

Return @code{True} if all characters in the string are numeric
characters, and there is at least one character, @code{False}
otherwise. Numeric characters include digit characters, and all characters
that have the Unicode numeric value property, e.g. U+2155,
VULGAR FRACTION ONE FIFTH.  Formally, numeric characters are those with the property
value Numeric_Type=Digit, Numeric_Type=Decimal or Numeric_Type=Numeric.
@end deffn

@geindex isprintable() (str 方法)
@anchor{library/stdtypes str isprintable}@anchor{6ac}
@deffn {方法} str.isprintable ()

Return @code{True} if all characters in the string are printable or the string is
empty, @code{False} otherwise.  Nonprintable characters are those characters defined
in the Unicode character database as "Other" or "Separator", excepting the
ASCII space (0x20) which is considered printable.  (Note that printable
characters in this context are those which should not be escaped when
@ref{7c6,,repr()} is invoked on a string.  It has no bearing on the handling of
strings written to @ref{307,,sys.stdout} or @ref{308,,sys.stderr}.)
@end deffn

@geindex isspace() (str 方法)
@anchor{library/stdtypes str isspace}@anchor{15e8}
@deffn {方法} str.isspace ()

Return @code{True} if there are only whitespace characters in the string and there is
at least one character, @code{False} otherwise.

@emph{空白} 字符是指在 Unicode 字符数据库 (参见 @ref{11a,,unicodedata}) 中主要类别为 @code{Zs} ("Separator, space") 或所属双向类为 @code{WS}, @code{B} 或 @code{S} 的字符。
@end deffn

@geindex istitle() (str 方法)
@anchor{library/stdtypes str istitle}@anchor{15e9}
@deffn {方法} str.istitle ()

Return @code{True} if the string is a titlecased string and there is at least one
character, for example uppercase characters may only follow uncased characters
and lowercase characters only cased ones.  Return @code{False} otherwise.
@end deffn

@geindex isupper() (str 方法)
@anchor{library/stdtypes str isupper}@anchor{15ea}
@deffn {方法} str.isupper ()

Return @code{True} if all cased characters @footnote{@w{(4)} 
区分大小写的字符是指所属一般类别属性为 "Lu" (Letter, uppercase), "Ll" (Letter, lowercase) 或 "Lt" (Letter, titlecase) 之一的字符。
} in the string are uppercase and
there is at least one cased character, @code{False} otherwise.
@end deffn

@geindex join() (str 方法)
@anchor{library/stdtypes str join}@anchor{15ca}
@deffn {方法} str.join (iterable)

返回一个由 @emph{iterable} 中的字符串拼接而成的字符串。 如果 @emph{iterable} 中存在任何非字符串值包括 @ref{32a,,bytes} 对象则会引发 @ref{192,,TypeError}。 调用该方法的字符串将作为元素之间的分隔。
@end deffn

@geindex ljust() (str 方法)
@anchor{library/stdtypes str ljust}@anchor{122f}
@deffn {方法} str.ljust (width[, fillchar])

返回长度为 @emph{width} 的字符串，原字符串在其中靠左对齐。 使用指定的 @emph{fillchar} 填充空位 (默认使用 ASCII 空格符)。 如果 @emph{width} 小于等于 @code{len(s)} 则返回原字符串的副本。
@end deffn

@geindex lower() (str 方法)
@anchor{library/stdtypes str lower}@anchor{15dc}
@deffn {方法} str.lower ()

返回原字符串的副本，其所有区分大小写的字符 @footnote{@w{(4)} 
区分大小写的字符是指所属一般类别属性为 "Lu" (Letter, uppercase), "Ll" (Letter, lowercase) 或 "Lt" (Letter, titlecase) 之一的字符。
} 均转换为小写。

所用转换小写算法的描述请参见 Unicode 标准的 3.13 节。
@end deffn

@geindex lstrip() (str 方法)
@anchor{library/stdtypes str lstrip}@anchor{15eb}
@deffn {方法} str.lstrip ([chars])

返回原字符串的副本，移除其中的前导字符。 @emph{chars} 参数为指定要移除字符的字符串。 如果省略或为 @code{None}，则 @emph{chars} 参数默认移除空格符。 实际上 @emph{chars} 参数并非指定单个前缀；而是会移除参数值的所有组合:

@example
>>> '   spacious   '.lstrip()
'spacious   '
>>> 'www.example.com'.lstrip('cmowz.')
'example.com'
@end example
@end deffn

@geindex maketrans() (str 静态方法)
@anchor{library/stdtypes str maketrans}@anchor{6ad}
@deffn {方法} static str.maketrans (x[, y[, z]])

此静态方法返回一个可供 @ref{15ec,,str.translate()} 使用的转换对照表。

如果只有一个参数，则它必须是一个将 Unicode 码位序号（整数）或字符（长度为 1 的字符串）映射到 Unicode 码位序号、（任意长度的）字符串或 @code{None} 的字典。 字符键将会被转换为码位序号。

如果有两个参数，则它们必须是两个长度相等的字符串，并且在结果字典中，x 中每个字符将被映射到 y 中相同位置的字符。 如果有第三个参数，它必须是一个字符串，其中的字符将在结果中被映射到 @code{None}。
@end deffn

@geindex partition() (str 方法)
@anchor{library/stdtypes str partition}@anchor{79c}
@deffn {方法} str.partition (sep)

在 @emph{sep} 首次出现的位置拆分字符串，返回一个 3 元组，其中包含分隔符之前的部分、分隔符本身，以及分隔符之后的部分。 如果分隔符未找到，则返回的 3 元组中包含字符本身以及两个空字符串。
@end deffn

@geindex replace() (str 方法)
@anchor{library/stdtypes str replace}@anchor{15ed}
@deffn {方法} str.replace (old, new[, count])

返回字符串的副本，其中出现的所有子字符串 @emph{old} 都将被替换为 @emph{new}。 如果给出了可选参数 @emph{count}，则只替换前 @emph{count} 次出现。
@end deffn

@geindex rfind() (str 方法)
@anchor{library/stdtypes str rfind}@anchor{79a}
@deffn {方法} str.rfind (sub[, start[, end]])

返回子字符串 @emph{sub} 在字符串内被找到的最大（最右）索引，这样 @emph{sub} 将包含在 @code{s[start:end]} 当中。 可选参数 @emph{start} 与 @emph{end} 会被解读为切片表示法。 如果未找到则返回 @code{-1}。
@end deffn

@geindex rindex() (str 方法)
@anchor{library/stdtypes str rindex}@anchor{15ee}
@deffn {方法} str.rindex (sub[, start[, end]])

类似于 @ref{79a,,rfind()}，但在子字符串 @emph{sub} 未找到时会引发 @ref{1fb,,ValueError}。
@end deffn

@geindex rjust() (str 方法)
@anchor{library/stdtypes str rjust}@anchor{122e}
@deffn {方法} str.rjust (width[, fillchar])

返回长度为 @emph{width} 的字符串，原字符串在其中靠右对齐。 使用指定的 @emph{fillchar} 填充空位 (默认使用 ASCII 空格符)。 如果 @emph{width} 小于等于 @code{len(s)} 则返回原字符串的副本。
@end deffn

@geindex rpartition() (str 方法)
@anchor{library/stdtypes str rpartition}@anchor{15ef}
@deffn {方法} str.rpartition (sep)

在 @emph{sep} 最后一次出现的位置拆分字符串，返回一个 3 元组，其中包含分隔符之前的部分、分隔符本身，以及分隔符之后的部分。 如果分隔符未找到，则返回的 3 元组中包含两个空字符串以及字符串本身。
@end deffn

@geindex rsplit() (str 方法)
@anchor{library/stdtypes str rsplit}@anchor{15f0}
@deffn {方法} str.rsplit (sep=None, maxsplit=-1)

返回一个由字符串内单词组成的列表，使用 @emph{sep} 作为分隔字符串。 如果给出了 @emph{maxsplit}，则最多进行 @emph{maxsplit} 次拆分，从 @emph{最右边} 开始。 如果 @emph{sep} 未指定或为 @code{None}，任何空白字符串都会被作为分隔符。 除了从右边开始拆分，@ref{15f0,,rsplit()} 的其他行为都类似于下文所述的 @ref{79b,,split()}。
@end deffn

@geindex rstrip() (str 方法)
@anchor{library/stdtypes str rstrip}@anchor{15f1}
@deffn {方法} str.rstrip ([chars])

返回原字符串的副本，移除其中的末尾字符。 @emph{chars} 参数为指定要移除字符的字符串。 如果省略或为 @code{None}，则 @emph{chars} 参数默认移除空格符。 实际上 @emph{chars} 参数并非指定单个后缀；而是会移除参数值的所有组合:

@example
>>> '   spacious   '.rstrip()
'   spacious'
>>> 'mississippi'.rstrip('ipz')
'mississ'
@end example
@end deffn

@geindex split() (str 方法)
@anchor{library/stdtypes str split}@anchor{79b}
@deffn {方法} str.split (sep=None, maxsplit=-1)

返回一个由字符串内单词组成的列表，使用 @emph{sep} 作为分隔字符串。 如果给出了 @emph{maxsplit}，则最多进行 @emph{maxsplit} 次拆分（因此，列表最多会有 @code{maxsplit+1} 个元素）。 如果 @emph{maxsplit} 未指定或为 @code{-1}，则不限制拆分次数（进行所有可能的拆分）。

如果给出了 @emph{sep}，则连续的分隔符不会被组合在一起而是被视为分隔空字符串 (例如 @code{'1,,2'.split(',')} 将返回 @code{['1', '@w{'}, '2']})。 @emph{sep} 参数可能由多个字符组成 (例如 @code{'1<>2<>3'.split('<>')} 将返回 @code{['1', '2', '3']})。 使用指定的分隔符拆分空字符串将返回 @code{['@w{'}]}。

例如

@example
>>> '1,2,3'.split(',')
['1', '2', '3']
>>> '1,2,3'.split(',', maxsplit=1)
['1', '2,3']
>>> '1,2,,3,'.split(',')
['1', '2', '@w{'}, '3', '@w{'}]
@end example

如果 @emph{sep} 未指定或为 @code{None}，则会应用另一种拆分算法：连续的空格会被视为单个分隔符，其结果将不包含开头或末尾的空字符串，如果字符串包含前缀或后缀空格的话。 因此，使用 @code{None} 拆分空字符串或仅包含空格的字符串将返回 @code{[]}。

例如

@example
>>> '1 2 3'.split()
['1', '2', '3']
>>> '1 2 3'.split(maxsplit=1)
['1', '2 3']
>>> '   1   2   3   '.split()
['1', '2', '3']
@end example
@end deffn

@geindex universal newlines; str.splitlines method

@geindex splitlines() (str 方法)
@anchor{library/stdtypes str splitlines}@anchor{15f2}
@deffn {方法} str.splitlines ([keepends])

返回由原字符串中各行组成的列表，在行边界的位置拆分。 结果列表中不包含行边界，除非给出了 @emph{keepends} 且为真值。

此方法会以下列行边界进行拆分。 特别地，行边界是 @ref{5ef,,universal newlines} 的一个超集。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

表示符

@tab

描述

@item

@code{\n}

@tab

换行

@item

@code{\r}

@tab

回车

@item

@code{\r\n}

@tab

回车 + 换行

@item

@code{\v} 或 @code{\x0b}

@tab

行制表符

@item

@code{\f} 或 @code{\x0c}

@tab

换表单

@item

@code{\x1c}

@tab

文件分隔符

@item

@code{\x1d}

@tab

组分隔符

@item

@code{\x1e}

@tab

记录分隔符

@item

@code{\x85}

@tab

下一行 (C1 控制码)

@item

@code{\u2028}

@tab

行分隔符

@item

@code{\u2029}

@tab

段分隔符

@end multitable



在 3.2 版更改: @code{\v} 和 @code{\f} 被添加到行边界列表


例如

@example
>>> 'ab c\n\nde fg\rkl\r\n'.splitlines()
['ab c', '@w{'}, 'de fg', 'kl']
>>> 'ab c\n\nde fg\rkl\r\n'.splitlines(keepends=True)
['ab c\n', '\n', 'de fg\r', 'kl\r\n']
@end example

不同于 @ref{79b,,split()}，当给出了分隔字符串 @emph{sep} 时，对于空字符串此方法将返回一个空列表，而末尾的换行不会令结果中增加额外的行:

@example
>>> "".splitlines()
[]
>>> "One line\n".splitlines()
['One line']
@end example

作为比较，@code{split('\n')} 的结果为:

@example
>>> '@w{'}.split('\n')
['@w{'}]
>>> 'Two lines\n'.split('\n')
['Two lines', '@w{'}]
@end example
@end deffn

@geindex startswith() (str 方法)
@anchor{library/stdtypes str startswith}@anchor{7c0}
@deffn {方法} str.startswith (prefix[, start[, end]])

如果字符串以指定的 @emph{prefix} 开始则返回 @code{True}，否则返回 @code{False}。 @emph{prefix} 也可以为由多个供查找的前缀构成的元组。 如果有可选项 @emph{start}，将从所指定位置开始检查。 如果有可选项 @emph{end}，将在所指定位置停止比较。
@end deffn

@geindex strip() (str 方法)
@anchor{library/stdtypes str strip}@anchor{15f3}
@deffn {方法} str.strip ([chars])

返回原字符串的副本，移除其中的前导和末尾字符。 @emph{chars} 参数为指定要移除字符的字符串。 如果省略或为 @code{None}，则 @emph{chars} 参数默认移除空格符。 实际上 @emph{chars} 参数并非指定单个前缀或后缀；而是会移除参数值的所有组合:

@example
>>> '   spacious   '.strip()
'spacious'
>>> 'www.example.com'.strip('cmowz.')
'example'
@end example

最外侧的前导和末尾 @emph{chars} 参数值将从字符串中移除。 开头端的字符的移除将在遇到一个未包含于 @emph{chars} 所指定字符集的字符时停止。 类似的操作也将在结尾端发生。 例如:

@example
>>> comment_string = '#....... Section 3.2.1 Issue #32 .......'
>>> comment_string.strip('.#! ')
'Section 3.2.1 Issue #32'
@end example
@end deffn

@geindex swapcase() (str 方法)
@anchor{library/stdtypes str swapcase}@anchor{15f4}
@deffn {方法} str.swapcase ()

返回原字符串的副本，其中大写字符转换为小写，反之亦然。 请注意 @code{s.swapcase().swapcase() == s} 并不一定为真值。
@end deffn

@geindex title() (str 方法)
@anchor{library/stdtypes str title}@anchor{15f5}
@deffn {方法} str.title ()

返回原字符串的标题版本，其中每个单词第一个字母为大写，其余字母为小写。

例如

@example
>>> 'Hello world'.title()
'Hello World'
@end example

该算法使用一种简单的与语言无关的定义，将连续的字母组合视为单词。 该定义在多数情况下都很有效，但它也意味着代表缩写形式与所有格的撇号也会成为单词边界，这可能导致不希望的结果:

@example
>>> "they're bill's friends from the UK".title()
"They'Re Bill'S Friends From The Uk"
@end example

可以使用正则表达式来构建针对撇号的特别处理:

@example
>>> import re
>>> def titlecase(s):
...     return re.sub(r"[A-Za-z]+('[A-Za-z]+)?",
...                   lambda mo: mo.group(0).capitalize(),
...                   s)
...
>>> titlecase("they're bill's friends.")
"They're Bill's Friends."
@end example
@end deffn

@geindex translate() (str 方法)
@anchor{library/stdtypes str translate}@anchor{15ec}
@deffn {方法} str.translate (table)

返回原字符串的副本，其中每个字符按给定的转换表进行映射。 转换表必须是一个使用 @ref{27f,,__getitem__()} 来实现索引操作的对象，通常为 @ref{b32,,mapping} 或 @ref{11bc,,sequence}。 当以 Unicode 码位序号（整数）为索引时，转换表对象可以做以下任何一种操作：返回 Unicode 序号或字符串，将字符映射为一个或多个字符；返回 @code{None}，将字符从结果字符串中删除；或引发 @ref{15f6,,LookupError} 异常，将字符映射为其自身。

你可以使用 @ref{6ad,,str.maketrans()} 基于不同格式的字符到字符映射来创建一个转换映射表。

另请参阅 @ref{1c,,codecs} 模块以了解定制字符映射的更灵活方式。
@end deffn

@geindex upper() (str 方法)
@anchor{library/stdtypes str upper}@anchor{15f7}
@deffn {方法} str.upper ()

返回原字符串的副本，其中所有区分大小写的字符 @footnote{@w{(4)} 
区分大小写的字符是指所属一般类别属性为 "Lu" (Letter, uppercase), "Ll" (Letter, lowercase) 或 "Lt" (Letter, titlecase) 之一的字符。
} 均转换为大写。 请注意如果 @code{s} 包含不区分大小写的字符或者如果结果字符的 Unicode 类别不是 "Lu" (Letter, uppercase) 而是 "Lt" (Letter, titlecase) 则 @code{s.upper().isupper()} 有可能为 @code{False}。

所用转换大写算法的描述请参见 Unicode 标准的 3.13 节。
@end deffn

@geindex zfill() (str 方法)
@anchor{library/stdtypes str zfill}@anchor{1231}
@deffn {方法} str.zfill (width)

返回原字符串的副本，在左边填充 ASCII @code{'0'} 数码使其长度变为 @emph{width}。 正负值前缀 (@code{'+'}/@code{'-'}) 的处理方式是在正负符号 @emph{之后} 填充而非在之前。 如果 @emph{width} 小于等于 @code{len(s)} 则返回原字符串的副本。

例如

@example
>>> "42".zfill(5)
'00042'
>>> "-42".zfill(5)
'-0042'
@end example
@end deffn

@node printf 风格的字符串格式化,,字符串的方法<2>,文本序列类型 --- str
@anchor{library/stdtypes old-string-formatting}@anchor{11b9}@anchor{library/stdtypes printf-style-string-formatting}@anchor{15f8}
@subsubsection @code{printf} 风格的字符串格式化


@geindex formatting@comma{} string (%)
@geindex interpolation@comma{} string (%)
@geindex string; formatting@comma{} printf
@geindex string; interpolation@comma{} printf
@geindex printf-style formatting
@geindex sprintf-style formatting
@geindex % (percent); printf-style formatting

@cartouche
@quotation 注解 
此处介绍的格式化操作具有多种怪异特性，可能导致许多常见错误（例如无法正确显示元组和字典）。 使用较新的 @ref{15c,,格式化字符串字面值}，@ref{4d4,,str.format()} 接口或 @ref{15f9,,模板字符串} 有助于避免这样的错误。 这些替代方案中的每一种都更好地权衡并提供了简单、灵活以及可扩展性优势。
@end quotation
@end cartouche

字符串具有一种特殊的内置操作：使用 @code{%} (取模) 运算符。 这也被称为字符串的 @emph{格式化} 或 @emph{插值} 运算符。 对于 @code{format % values} (其中 @emph{format} 为一个字符串)，在 @emph{format} 中的 @code{%} 转换标记符将被替换为零个或多个 @emph{values} 条目。 其效果类似于在 C 语言中使用 @code{sprintf()}。

如果 @emph{format} 要求一个单独参数，则 @emph{values} 可以为一个非元组对象。 @footnote{@w{(5)} 
要格式化单独一个元组，那么你应当提供一个单例元组，其唯一的元素就是要被格式化的元组。
}  否则的话，@emph{values} 必须或者是一个包含项数与格式字符串中指定的转换符项数相同的元组，或者是一个单独映射对象（例如字典）。

@geindex () (parentheses); in printf-style formatting
@geindex * (asterisk); in printf-style formatting
@geindex . (dot); in printf-style formatting

转换标记符包含两个或更多字符并具有以下组成，且必须遵循此处规定的顺序：


@enumerate 

@item 
@code{'%'} 字符，用于标记转换符的起始。

@item 
映射键（可选），由加圆括号的字符序列组成 (例如 @code{(somename)})。

@item 
转换旗标（可选），用于影响某些转换类型的结果。

@item 
最小字段宽度（可选）。 如果指定为 @code{'*'} (星号)，则实际宽度会从 @emph{values} 元组的下一元素中读取，要转换的对象则为最小字段宽度和可选的精度之后的元素。

@item 
精度（可选），以在 @code{'.'} (点号) 之后加精度值的形式给出。 如果指定为 @code{'*'} (星号)，则实际精度会从 @emph{values} 元组的下一元素中读取，要转换的对象则为精度之后的元素。

@item 
长度修饰符（可选）。

@item 
转换类型。
@end enumerate

当右边的参数为一个字典（或其他映射类型）时，字符串中的格式 @emph{必须} 包含加圆括号的映射键，对应 @code{'%'} 字符之后字典中的每一项。 映射键将从映射中选取要格式化的值。 例如：

@example
>>> print('%(language)s has %(number)03d quote types.' %
...       @{'language': "Python", "number": 2@})
Python has 002 quote types.
@end example

在此情况下格式中不能出现 @code{*} 标记符（因其需要一个序列类的参数列表）。

转换旗标为：

@geindex # (hash); in printf-style formatting
@geindex - (minus); in printf-style formatting
@geindex + (plus); in printf-style formatting
@geindex space; in printf-style formatting


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Flag

@tab

含义

@item

@code{'#'}

@tab

值的转换将使用“替代形式”（具体定义见下文）。

@item

@code{'0'}

@tab

转换将为数字值填充零字符。

@item

@code{'-'}

@tab

转换值将靠左对齐（如果同时给出 @code{'0'} 转换，则会覆盖后者）。

@item

@code{' '}

@tab

(空格) 符号位转换产生的正数（或空字符串）前将留出一个空格。

@item

@code{'+'}

@tab

符号字符 (@code{'+'} 或 @code{'-'}) 将显示于转换结果的开头（会覆盖 "空格" 旗标）。

@end multitable


可以给出长度修饰符 (@code{h}, @code{l} 或 @code{L})，但会被忽略，因为对 Python 来说没有必要 -- 所以 @code{%ld} 等价于 @code{%d}。

转换类型为：


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

转换符

@tab

含义

@tab

注释

@item

@code{'d'}

@tab

有符号十进制整数。

@tab

@item

@code{'i'}

@tab

有符号十进制整数。

@tab

@item

@code{'o'}

@tab

有符号八进制数。

@tab

(1)

@item

@code{'u'}

@tab

过时类型 -- 等价于 @code{'d'}。

@tab

(6)

@item

@code{'x'}

@tab

有符号十六进制数（小写）。

@tab

(2)

@item

@code{'X'}

@tab

有符号十六进制数（大写）。

@tab

(2)

@item

@code{'e'}

@tab

浮点指数格式（小写）。

@tab

(3)

@item

@code{'E'}

@tab

浮点指数格式（大写）。

@tab

(3)

@item

@code{'f'}

@tab

浮点十进制格式。

@tab

(3)

@item

@code{'F'}

@tab

浮点十进制格式。

@tab

(3)

@item

@code{'g'}

@tab

浮点格式。 如果指数小于 -4 或不小于精度则使用小写指数格式，否则使用十进制格式。

@tab

(4)

@item

@code{'G'}

@tab

浮点格式。 如果指数小于 -4 或不小于精度则使用大写指数格式，否则使用十进制格式。

@tab

(4)

@item

@code{'c'}

@tab

单个字符（接受整数或单个字符的字符串）。

@tab

@item

@code{'r'}

@tab

字符串（使用 @ref{7c6,,repr()} 转换任何 Python 对象）。

@tab

(5)

@item

@code{'s'}

@tab

字符串（使用 @ref{329,,str()} 转换任何 Python 对象）。

@tab

(5)

@item

@code{'a'}

@tab

字符串（使用 @ref{d45,,ascii()} 转换任何 Python 对象）。

@tab

(5)

@item

@code{'%'}

@tab

不转换参数，在结果中输出一个 @code{'%'} 字符。

@tab

@end multitable


注释:


@enumerate 

@item 
此替代形式会在第一个数码之前插入标示八进制数的前缀 (@code{'0o'})。

@item 
此替代形式会在第一个数码之前插入 @code{'0x'} 或 @code{'0X'} 前缀（取决于是使用 @code{'x'} 还是 @code{'X'} 格式）。

@item 
此替代形式总是会在结果中包含一个小数点，即使其后并没有数码。

小数点后的数码位数由精度决定，默认为 6。

@item 
此替代形式总是会在结果中包含一个小数点，末尾各位的零不会如其他情况下那样被移除。

小数点前后的有效数码位数由精度决定，默认为 6。

@item 
如果精度为 @code{N}，输出将截短为 @code{N} 个字符。

@item 
参见 
@geindex Python 提高建议; PEP 237
PEP 237@footnote{https://www.python.org/dev/peps/pep-0237}。
@end enumerate

由于 Python 字符串显式指明长度，@code{%s} 转换不会将 @code{'\0'} 视为字符串的结束。

@c XXX Examples?


在 3.1 版更改: 绝对值超过 1e50 的 @code{%f} 转换不会再被替换为 @code{%g} 转换。


@geindex buffer protocol; binary sequence types

@node 二进制序列类型 --- bytes bytearray memoryview,集合类型 --- set frozenset,文本序列类型 --- str,内置类型
@anchor{library/stdtypes binary-sequence-types-bytes-bytearray-memoryview}@anchor{15fa}@anchor{library/stdtypes binaryseq}@anchor{1580}
@subsection 二进制序列类型 --- @code{bytes}, @code{bytearray}, @code{memoryview}


@geindex 对象; bytes
@geindex 对象; bytearray
@geindex 对象; memoryview
@geindex 模块; array

操作二进制数据的核心内置类型是 @ref{32a,,bytes} 和 @ref{32b,,bytearray}。 它们由 @ref{25c,,memoryview} 提供支持，该对象使用 @ref{15d6,,缓冲区协议} 来访问其他二进制对象所在内存，不需要创建对象的副本。

@ref{7,,array} 模块支持高效地存储基本数据类型，例如 32 位整数和 IEEE754 双精度浮点值。

@menu
* bytes 对象:: 
* bytearray 对象:: 
* bytes 和 bytearray 操作:: 
* printf 风格的字节串格式化:: 
* 内存视图:: 

@end menu

@node bytes 对象,bytearray 对象,,二进制序列类型 --- bytes bytearray memoryview
@anchor{library/stdtypes bytes-objects}@anchor{15fb}@anchor{library/stdtypes typebytes}@anchor{1582}
@subsubsection bytes 对象


@geindex 对象; bytes

bytes 对象是由单个字节构成的不可变序列。 由于许多主要二进制协议都基于 ASCII 文本编码，因此 bytes 对象提供了一些仅在处理 ASCII 兼容数据时可用，并且在许多特性上与字符串对象紧密相关的方法。

@geindex bytes (內置类)
@anchor{library/stdtypes bytes}@anchor{32a}
@deffn {类} bytes ([source[, encoding[, errors]]])

首先，表示 bytes 字面值的语法与字符串字面值的大致相同，只是添加了一个 @code{b} 前缀：


@itemize *

@item 
单引号: @code{b'同样允许嵌入 "双" 引号'}。

@item 
双引号: @code{b"同样允许嵌入 '单' 引号"}。

@item 
三重引号: @code{b'@w{'}'三重单引号'@w{'}'}, @code{b"""三重双引号"""}
@end itemize

bytes 字面值中只允许 ASCII 字符（无论源代码声明的编码为何）。 任何超出 127 的二进制值必须使用相应的转义序列形式加入 bytes 字面值。

像字符串字面值一样，bytes 字面值也可以使用 @code{r} 前缀来禁用转义序列处理。 请参阅 @ref{1379,,字符串和字节串字面值} 了解有关各种 bytes 字面值形式的详情，包括所支持的转义序列。

虽然 bytes 字面值和表示法是基于 ASCII 文本的，但 bytes 对象的行为实际上更像是不可变的整数序列，序列中的每个值的大小被限制为 @code{0 <= x < 256} (如果违反此限制将引发 @ref{1fb,,ValueError})。 这种限制是有意设计用以强调以下事实，虽然许多二进制格式都包含基于 ASCII 的元素，可以通过某些面向文本的算法进行有用的操作，但情况对于任意二进制数据来说通常却并非如此（盲目地将文本处理算法应用于不兼容 ASCII 的二进制数据格式往往将导致数据损坏）。

除了字面值形式，bytes 对象还可以通过其他几种方式来创建：


@itemize *

@item 
指定长度的以零值填充的 bytes 对象: @code{bytes(10)}

@item 
通过由整数组成的可迭代对象: @code{bytes(range(20))}

@item 
通过缓冲区协议复制现有的二进制数据:  @code{bytes(obj)}
@end itemize

另请参阅 @ref{1050,,bytes} 内置类型。

由于两个十六进制数码精确对应一个字节，因此十六进制数是描述二进制数据的常用格式。 相应地，bytes 类型具有从此种格式读取数据的附加类方法：

@geindex fromhex() (bytes 类方法)
@anchor{library/stdtypes bytes fromhex}@anchor{327}
@deffn {方法} classmethod fromhex (string)

此 @ref{32a,,bytes} 类方法返回一个解码给定字符串的 bytes 对象。 字符串必须由表示每个字节的两个十六进制数码构成，其中的 ASCII 空白符会被忽略。

@example
>>> bytes.fromhex('2Ef0 F1f2  ')
b'.\xf0\xf1\xf2'
@end example


在 3.7 版更改: @ref{327,,bytes.fromhex()} 现在会忽略所有 ASCII 空白符而不只是空格符。

@end deffn

存在一个反向转换函数，可以将 bytes 对象转换为对应的十六进制表示。

@geindex hex() (bytes 方法)
@anchor{library/stdtypes bytes hex}@anchor{62b}
@deffn {方法} hex ([sep[, bytes_per_sep]])

返回一个字符串对象，该对象包含实例中每个字节的两个十六进制数字。

@example
>>> b'\xf0\xf1\xf2'.hex()
'f0f1f2'
@end example

如果你希望令十六进制数字符串更易读，你可以指定单个字符分隔符作为 @emph{sep} 形参包含于输出中。 默认会放在每个字节之间。 第二个可选的 @emph{bytes_per_sep} 形参控制间距。 正值会从右开始计算分隔符的位置，负值则是从左开始。

@example
>>> value = b'\xf0\xf1\xf2'
>>> value.hex('-')
'f0-f1-f2'
>>> value.hex('_', 2)
'f0_f1f2'
>>> b'UUDDLRLRAB'.hex(' ', -4)
'55554444 4c524c52 4142'
@end example


3.5 新版功能.



在 3.8 版更改: @ref{62b,,bytes.hex()} 现在支持可选的 @emph{sep} 和 @emph{bytes_per_sep} 形参以在十六进制输出的字节之间插入分隔符。

@end deffn
@end deffn

由于 bytes 对象是由整数构成的序列（类似于元组），因此对于一个 bytes 对象 @emph{b}，@code{b[0]} 将为一个整数，而 @code{b[0:1]} 将为一个长度为 1 的 bytes 对象。 （这与文本字符串不同，索引和切片所产生的将都是一个长度为 1 的字符串）。

bytes 对象的表示使用字面值格式 (@code{b'...'})，因为它通常都要比像 @code{bytes([46, 46, 46])} 这样的格式更好用。 你总是可以使用 @code{list(b)} 将 bytes 对象转换为一个由整数构成的列表。

@cartouche
@quotation 注解 
针对 Python 2.x 用户的说明：在 Python 2.x 系列中，允许 8 位字符串（ 2.x 所提供的最接近内置二进制数据类型的对象）与 Unicode 字符串进行各种隐式转换。 这是为了实现向下兼容的变通做法，以适应 Python 最初只支持 8 位文本而 Unicode 文本是后来才被加入这一事实。 在 Python 3.x 中，这些隐式转换已被取消 —— 8 位二进制数据与 Unicode 文本间的转换必须显式地进行，bytes 与字符串对象的比较结果将总是不相等。
@end quotation
@end cartouche

@node bytearray 对象,bytes 和 bytearray 操作,bytes 对象,二进制序列类型 --- bytes bytearray memoryview
@anchor{library/stdtypes bytearray-objects}@anchor{15fc}@anchor{library/stdtypes typebytearray}@anchor{1581}
@subsubsection bytearray 对象


@geindex 对象; bytearray

@ref{32b,,bytearray} 对象是 @ref{32a,,bytes} 对象的可变对应物。

@geindex bytearray (內置类)
@anchor{library/stdtypes bytearray}@anchor{32b}
@deffn {类} bytearray ([source[, encoding[, errors]]])

bytearray 对象没有专属的字面值语法，它们总是通过调用构造器来创建：


@itemize *

@item 
创建一个空实例: @code{bytearray()}

@item 
创建一个指定长度的以零值填充的实例: @code{bytearray(10)}

@item 
通过由整数组成的可迭代对象: @code{bytearray(range(20))}

@item 
通过缓冲区协议复制现有的二进制数据:  @code{bytearray(b'Hi!')}
@end itemize

由于 bytearray 对象是可变的，该对象除了 @ref{157f,,bytes 和 bytearray 操作} 中所描述的 bytes 和 bytearray 共有操作之外，还支持 @ref{157e,,可变} 序列操作。

另请参见 @ref{1051,,bytearray} 内置类型。

由于两个十六进制数码精确对应一个字节，因此十六进制数是描述二进制数据的常用格式。 相应地，bytearray 类型具有从此种格式读取数据的附加类方法：

@geindex fromhex() (bytearray 类方法)
@anchor{library/stdtypes bytearray fromhex}@anchor{328}
@deffn {方法} classmethod fromhex (string)

@ref{32b,,bytearray} 类方法返回一个解码给定字符串的 bytearray 对象。 字符串必须由表示每个字节的两个十六进制数码构成，其中的 ASCII 空白符会被忽略。

@example
>>> bytearray.fromhex('2Ef0 F1f2  ')
bytearray(b'.\xf0\xf1\xf2')
@end example


在 3.7 版更改: @ref{328,,bytearray.fromhex()} 现在会忽略所有 ASCII 空白符而不只是空格符。

@end deffn

存在一个反向转换函数，可以将 bytearray 对象转换为对应的十六进制表示。

@geindex hex() (bytearray 方法)
@anchor{library/stdtypes bytearray hex}@anchor{62c}
@deffn {方法} hex ([sep[, bytes_per_sep]])

返回一个字符串对象，该对象包含实例中每个字节的两个十六进制数字。

@example
>>> bytearray(b'\xf0\xf1\xf2').hex()
'f0f1f2'
@end example


3.5 新版功能.



在 3.8 版更改: Similar to @ref{62b,,bytes.hex()}, @ref{62c,,bytearray.hex()} now supports
optional @emph{sep} and @emph{bytes_per_sep} parameters to insert separators
between bytes in the hex output.

@end deffn
@end deffn

由于 bytearray 对象是由整数构成的序列（类似于列表），因此对于一个 bytearray 对象 @emph{b}，@code{b[0]} 将为一个整数，而 @code{b[0:1]} 将为一个长度为 1 的 bytearray 对象。 （这与文本字符串不同，索引和切片所产生的将都是一个长度为 1 的字符串）。

bytearray 对象的表示使用 bytes 对象字面值格式 (@code{bytearray(b'...')})，因为它通常都要比 @code{bytearray([46, 46, 46])} 这样的格式更好用。 你总是可以使用 @code{list(b)} 将 bytearray 对象转换为一个由整数构成的列表。

@node bytes 和 bytearray 操作,printf 风格的字节串格式化,bytearray 对象,二进制序列类型 --- bytes bytearray memoryview
@anchor{library/stdtypes bytes-and-bytearray-operations}@anchor{15fd}@anchor{library/stdtypes bytes-methods}@anchor{157f}
@subsubsection bytes 和 bytearray 操作


@geindex bytes; methods
@geindex bytearray; methods

bytes 和 bytearray 对象都支持 @ref{15c7,,通用} 序列操作。 它们不仅能与相同类型的操作数，也能与任何 @ref{5e3,,bytes-like object} 进行互操作。 由于这样的灵活性，它们可以在操作中自由地混合而不会导致错误。 但是，操作结果的返回值类型可能取决于操作数的顺序。

@cartouche
@quotation 注解 
bytes 和 bytearray 对象的方法不接受字符串作为其参数，就像字符串的方法不接受 bytes 对象作为其参数一样。 例如，你必须使用以下写法:

@example
a = "abc"
b = a.replace("a", "f")
@end example

和:

@example
a = b"abc"
b = a.replace(b"a", b"f")
@end example
@end quotation
@end cartouche

某些 bytes 和 bytearray 操作假定使用兼容 ASCII 的二进制格式，因此在处理任意二进数数据时应当避免使用。 这些限制会在下文中说明。

@cartouche
@quotation 注解 
使用这些基于 ASCII 的操作来处理未以基于 ASCII 的格式存储的二进制数据可能会导致数据损坏。
@end quotation
@end cartouche

bytes 和 bytearray 对象的下列方法可以用于任意二进制数据。

@geindex count() (bytes 方法)
@geindex count() (bytearray 方法)
@anchor{library/stdtypes bytes count}@anchor{15fe}
@deffn {方法} bytes.count (sub[, start[, end]])
@anchor{library/stdtypes bytearray count}@anchor{15ff}
@deffnx {方法} bytearray.count (sub[, start[, end]])

返回子序列 @emph{sub} 在 [@emph{start}, @emph{end}] 范围内非重叠出现的次数。 可选参数 @emph{start} 与 @emph{end} 会被解读为切片表示法。

要搜索的子序列可以是任意 @ref{5e3,,bytes-like object} 或是 0 至 255 范围内的整数。


在 3.3 版更改: 也接受 0 至 255 范围内的整数作为子序列。

@end deffn

@geindex decode() (bytes 方法)
@geindex decode() (bytearray 方法)
@anchor{library/stdtypes bytes decode}@anchor{c31}
@deffn {方法} bytes.decode (encoding="utf-8", errors="strict")
@anchor{library/stdtypes bytearray decode}@anchor{1600}
@deffnx {方法} bytearray.decode (encoding="utf-8", errors="strict")

返回从给定 bytes 解码出来的字符串。 默认编码为 @code{'utf-8'}。 可以给出 @emph{errors} 来设置不同的错误处理方案。 @emph{errors} 的默认值为 @code{'strict'}，表示编码错误会引发 @ref{c34,,UnicodeError}。 其他可用的值为 @code{'ignore'}, @code{'replace'} 以及任何其他通过 @ref{dee,,codecs.register_error()} 注册的名称，请参阅 @ref{12f7,,错误处理方案} 小节。 要查看可用的编码列表，请参阅 @ref{689,,标准编码} 小节。

@cartouche
@quotation 注解 
将 @emph{encoding} 参数传给 @ref{329,,str} 允许直接解码任何 @ref{5e3,,bytes-like object}，无须创建临时的 bytes 或 bytearray 对象。
@end quotation
@end cartouche


在 3.1 版更改: 加入了对关键字参数的支持。

@end deffn

@geindex endswith() (bytes 方法)
@geindex endswith() (bytearray 方法)
@anchor{library/stdtypes bytes endswith}@anchor{1601}
@deffn {方法} bytes.endswith (suffix[, start[, end]])
@anchor{library/stdtypes bytearray endswith}@anchor{1602}
@deffnx {方法} bytearray.endswith (suffix[, start[, end]])

如果二进制数据以指定的 @emph{suffix} 结束则返回 @code{True}，否则返回 @code{False}。 @emph{suffix} 也可以为由多个供查找的后缀构成的元组。 如果有可选项 @emph{start}，将从所指定位置开始检查。 如果有可选项 @emph{end}，将在所指定位置停止比较。

要搜索的后缀可以是任意 @ref{5e3,,bytes-like object}。
@end deffn

@geindex find() (bytes 方法)
@geindex find() (bytearray 方法)
@anchor{library/stdtypes bytes find}@anchor{1603}
@deffn {方法} bytes.find (sub[, start[, end]])
@anchor{library/stdtypes bytearray find}@anchor{1604}
@deffnx {方法} bytearray.find (sub[, start[, end]])

返回子序列 @emph{sub} 在数据中被找到的最小索引，@emph{sub} 包含于切片 @code{s[start:end]} 之内。 可选参数 @emph{start} 与 @emph{end} 会被解读为切片表示法。 如果 @emph{sub} 未被找到则返回 @code{-1}。

要搜索的子序列可以是任意 @ref{5e3,,bytes-like object} 或是 0 至 255 范围内的整数。

@cartouche
@quotation 注解 
@ref{1603,,find()} 方法应该只在你需要知道 @emph{sub} 所在位置时使用。 要检查 @emph{sub} 是否为子串，请使用 @ref{79d,,in} 操作符:

@example
>>> b'Py' in b'Python'
True
@end example
@end quotation
@end cartouche


在 3.3 版更改: 也接受 0 至 255 范围内的整数作为子序列。

@end deffn

@geindex index() (bytes 方法)
@geindex index() (bytearray 方法)
@anchor{library/stdtypes bytes index}@anchor{1605}
@deffn {方法} bytes.index (sub[, start[, end]])
@anchor{library/stdtypes bytearray index}@anchor{1606}
@deffnx {方法} bytearray.index (sub[, start[, end]])

类似于 @ref{1603,,find()}，但在找不到子序列时会引发 @ref{1fb,,ValueError}。

要搜索的子序列可以是任意 @ref{5e3,,bytes-like object} 或是 0 至 255 范围内的整数。


在 3.3 版更改: 也接受 0 至 255 范围内的整数作为子序列。

@end deffn

@geindex join() (bytes 方法)
@geindex join() (bytearray 方法)
@anchor{library/stdtypes bytes join}@anchor{15cb}
@deffn {方法} bytes.join (iterable)
@anchor{library/stdtypes bytearray join}@anchor{1607}
@deffnx {方法} bytearray.join (iterable)

返回一个由 @emph{iterable} 中的二进制数据序列拼接而成的 bytes 或 bytearray 对象。 如果 @emph{iterable} 中存在任何非 @ref{5e3,,字节类对象} 包括存在 @ref{329,,str} 对象值则会引发 @ref{192,,TypeError}。 提供该方法的 bytes 或 bytearray 对象的内容将作为元素之间的分隔。
@end deffn

@geindex maketrans() (bytes 静态方法)
@geindex maketrans() (bytearray 静态方法)
@anchor{library/stdtypes bytes maketrans}@anchor{c02}
@deffn {方法} static bytes.maketrans (from, to)
@anchor{library/stdtypes bytearray maketrans}@anchor{c03}
@deffnx {方法} static bytearray.maketrans (from, to)

此静态方法返回一个可用于 @ref{1608,,bytes.translate()} 的转换对照表，它将把 @emph{from} 中的每个字符映射为 @emph{to} 中相同位置上的字符；@emph{from} 与 @emph{to} 必须都是 @ref{5e3,,字节类对象} 并且具有相同的长度。


3.1 新版功能.

@end deffn

@geindex partition() (bytes 方法)
@geindex partition() (bytearray 方法)
@anchor{library/stdtypes bytes partition}@anchor{1609}
@deffn {方法} bytes.partition (sep)
@anchor{library/stdtypes bytearray partition}@anchor{160a}
@deffnx {方法} bytearray.partition (sep)

在 @emph{sep} 首次出现的位置拆分序列，返回一个 3 元组，其中包含分隔符之前的部分、分隔符本身或其 bytearray 副本，以及分隔符之后的部分。 如果分隔符未找到，则返回的 3 元组中包含原序列以及两个空的 bytes 或 bytearray 对象。

要搜索的分隔符可以是任意 @ref{5e3,,bytes-like object}。
@end deffn

@geindex replace() (bytes 方法)
@geindex replace() (bytearray 方法)
@anchor{library/stdtypes bytes replace}@anchor{160b}
@deffn {方法} bytes.replace (old, new[, count])
@anchor{library/stdtypes bytearray replace}@anchor{160c}
@deffnx {方法} bytearray.replace (old, new[, count])

返回序列的副本，其中出现的所有子序列 @emph{old} 都将被替换为 @emph{new}。 如果给出了可选参数 @emph{count}，则只替换前 @emph{count} 次出现。

要搜索的子序列及其替换序列可以是任意 @ref{5e3,,bytes-like object}。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex rfind() (bytes 方法)
@geindex rfind() (bytearray 方法)
@anchor{library/stdtypes bytes rfind}@anchor{160d}
@deffn {方法} bytes.rfind (sub[, start[, end]])
@anchor{library/stdtypes bytearray rfind}@anchor{160e}
@deffnx {方法} bytearray.rfind (sub[, start[, end]])

返回子序列 @emph{sub} 在序列内被找到的最大（最右）索引，这样 @emph{sub} 将包含在 @code{s[start:end]} 当中。 可选参数 @emph{start} 与 @emph{end} 会被解读为切片表示法。 如果未找到则返回 @code{-1}。

要搜索的子序列可以是任意 @ref{5e3,,bytes-like object} 或是 0 至 255 范围内的整数。


在 3.3 版更改: 也接受 0 至 255 范围内的整数作为子序列。

@end deffn

@geindex rindex() (bytes 方法)
@geindex rindex() (bytearray 方法)
@anchor{library/stdtypes bytes rindex}@anchor{160f}
@deffn {方法} bytes.rindex (sub[, start[, end]])
@anchor{library/stdtypes bytearray rindex}@anchor{1610}
@deffnx {方法} bytearray.rindex (sub[, start[, end]])

类似于 @ref{160d,,rfind()}，但在子序列 @emph{sub} 未找到时会引发 @ref{1fb,,ValueError}。

要搜索的子序列可以是任意 @ref{5e3,,bytes-like object} 或是 0 至 255 范围内的整数。


在 3.3 版更改: 也接受 0 至 255 范围内的整数作为子序列。

@end deffn

@geindex rpartition() (bytes 方法)
@geindex rpartition() (bytearray 方法)
@anchor{library/stdtypes bytes rpartition}@anchor{1611}
@deffn {方法} bytes.rpartition (sep)
@anchor{library/stdtypes bytearray rpartition}@anchor{1612}
@deffnx {方法} bytearray.rpartition (sep)

在 @emph{sep} 最后一次出现的位置拆分序列，返回一个 3 元组，其中包含分隔符之前的部分，分隔符本身或其 bytearray 副本，以及分隔符之后的部分。 如果分隔符未找到，则返回的 3 元组中包含两个空的 bytes 或 bytearray 对象以及原序列的副本。

要搜索的分隔符可以是任意 @ref{5e3,,bytes-like object}。
@end deffn

@geindex startswith() (bytes 方法)
@geindex startswith() (bytearray 方法)
@anchor{library/stdtypes bytes startswith}@anchor{1613}
@deffn {方法} bytes.startswith (prefix[, start[, end]])
@anchor{library/stdtypes bytearray startswith}@anchor{1614}
@deffnx {方法} bytearray.startswith (prefix[, start[, end]])

如果二进制数据以指定的 @emph{prefix} 开头则返回 @code{True}，否则返回 @code{False}。 @emph{prefix} 也可以为由多个供查找的前缀构成的元组。 如果有可选项 @emph{start}，将从所指定位置开始检查。 如果有可选项 @emph{end}，将在所指定位置停止比较。

要搜索的前缀可以是任意 @ref{5e3,,bytes-like object}。
@end deffn

@geindex translate() (bytes 方法)
@geindex translate() (bytearray 方法)
@anchor{library/stdtypes bytes translate}@anchor{1608}
@deffn {方法} bytes.translate (table, /, delete=b'@w{'})
@anchor{library/stdtypes bytearray translate}@anchor{c8a}
@deffnx {方法} bytearray.translate (table, /, delete=b'@w{'})

返回原 bytes 或 bytearray 对象的副本，移除其中所有在可选参数 @emph{delete} 中出现的 bytes，其余 bytes 将通过给定的转换表进行映射，该转换表必须是长度为 256 的 bytes 对象。

你可以使用 @ref{c02,,bytes.maketrans()} 方法来创建转换表。

对于仅需移除字符的转换，请将 @emph{table} 参数设为 @code{None}:

@example
>>> b'read this short text'.translate(None, b'aeiou')
b'rd ths shrt txt'
@end example


在 3.6 版更改: 现在支持将 @emph{delete} 作为关键字参数。

@end deffn

以下 bytes 和 bytearray 对象的方法的默认行为会假定使用兼容 ASCII 的二进制格式，但通过传入适当的参数仍然可用于任意二进制数据。 请注意本小节中所有的 bytearray 方法都 @emph{不是} 原地执行操作，而是会产生新的对象。

@geindex center() (bytes 方法)
@geindex center() (bytearray 方法)
@anchor{library/stdtypes bytes center}@anchor{1615}
@deffn {方法} bytes.center (width[, fillbyte])
@anchor{library/stdtypes bytearray center}@anchor{1616}
@deffnx {方法} bytearray.center (width[, fillbyte])

返回原对象的副本，在长度为 @emph{width} 的序列内居中，使用指定的 @emph{fillbyte} 填充两边的空位（默认使用 ASCII 空格符）。 对于 @ref{32a,,bytes} 对象，如果 @emph{width} 小于等于 @code{len(s)} 则返回原序列的副本。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex ljust() (bytes 方法)
@geindex ljust() (bytearray 方法)
@anchor{library/stdtypes bytes ljust}@anchor{1617}
@deffn {方法} bytes.ljust (width[, fillbyte])
@anchor{library/stdtypes bytearray ljust}@anchor{1618}
@deffnx {方法} bytearray.ljust (width[, fillbyte])

反回原对象的副本，在长度为 @emph{width} 的序列中靠左对齐。 使用指定的 @emph{fillbyte} 填充空位（默认使用 ASCII 空格符）。 对于 @ref{32a,,bytes} 对象，如果 @emph{width} 小于等于 @code{len(s)} 则返回原序列的副本。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex lstrip() (bytes 方法)
@geindex lstrip() (bytearray 方法)
@anchor{library/stdtypes bytes lstrip}@anchor{1619}
@deffn {方法} bytes.lstrip ([chars])
@anchor{library/stdtypes bytearray lstrip}@anchor{161a}
@deffnx {方法} bytearray.lstrip ([chars])

返回原序列的副本，移除指定的前导字节。 @emph{chars} 参数为指定要移除字节值集合的二进制序列 —— 这个名称表明此方法通常是用于 ASCII 字符。 如果省略或为 @code{None}，则 @emph{chars} 参数默认移除 ASCII 空白符。 @emph{chars} 参数并非指定单个前缀；而是会移除参数值的所有组合:

@example
>>> b'   spacious   '.lstrip()
b'spacious   '
>>> b'www.example.com'.lstrip(b'cmowz.')
b'example.com'
@end example

要移除的字节值二进制序列可以是任意 @ref{5e3,,bytes-like object}。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex rjust() (bytes 方法)
@geindex rjust() (bytearray 方法)
@anchor{library/stdtypes bytes rjust}@anchor{161b}
@deffn {方法} bytes.rjust (width[, fillbyte])
@anchor{library/stdtypes bytearray rjust}@anchor{161c}
@deffnx {方法} bytearray.rjust (width[, fillbyte])

返回原对象的副本，在长度为 @emph{width} 的序列中靠右对齐。 使用指定的 @emph{fillbyte} 填充空位（默认使用 ASCII 空格符）。 对于 @ref{32a,,bytes} 对象，如果 @emph{width} 小于等于 @code{len(s)} 则返回原序列的副本。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex rsplit() (bytes 方法)
@geindex rsplit() (bytearray 方法)
@anchor{library/stdtypes bytes rsplit}@anchor{161d}
@deffn {方法} bytes.rsplit (sep=None, maxsplit=-1)
@anchor{library/stdtypes bytearray rsplit}@anchor{161e}
@deffnx {方法} bytearray.rsplit (sep=None, maxsplit=-1)

将二进制序列拆分为相同类型的子序列，使用 @emph{sep} 作为分隔符。 如果给出了 @emph{maxsplit}，则最多进行 @emph{maxsplit} 次拆分，从 @emph{最右边} 开始。 如果 @emph{sep} 未指定或为 @code{None}，任何只包含 ASCII 空白符的子序列都会被作为分隔符。 除了从右边开始拆分，@ref{161e,,rsplit()} 的其他行为都类似于下文所述的 @ref{161f,,split()}。
@end deffn

@geindex rstrip() (bytes 方法)
@geindex rstrip() (bytearray 方法)
@anchor{library/stdtypes bytes rstrip}@anchor{1620}
@deffn {方法} bytes.rstrip ([chars])
@anchor{library/stdtypes bytearray rstrip}@anchor{1621}
@deffnx {方法} bytearray.rstrip ([chars])

返回原序列的副本，移除指定的末尾字节。 @emph{chars} 参数为指定要移除字节值集合的二进制序列 —— 这个名称表明此方法通常是用于 ASCII 字符。 如果省略或为 @code{None}，则 @emph{chars} 参数默认移除 ASCII 空白符。 @emph{chars} 参数并非指定单个后缀；而是会移除参数值的所有组合:

@example
>>> b'   spacious   '.rstrip()
b'   spacious'
>>> b'mississippi'.rstrip(b'ipz')
b'mississ'
@end example

要移除的字节值二进制序列可以是任意 @ref{5e3,,bytes-like object}。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex split() (bytes 方法)
@geindex split() (bytearray 方法)
@anchor{library/stdtypes bytes split}@anchor{1622}
@deffn {方法} bytes.split (sep=None, maxsplit=-1)
@anchor{library/stdtypes bytearray split}@anchor{161f}
@deffnx {方法} bytearray.split (sep=None, maxsplit=-1)

将二进制序列拆分为相同类型的子序列，使用 @emph{sep} 作为分隔符。 如果给出了 @emph{maxsplit} 且非负值，则最多进行 @emph{maxsplit} 次拆分（因此，列表最多会有 @code{maxsplit+1} 个元素）。 如果 @emph{maxsplit} 未指定或为 @code{-1}，则不限制拆分次数（进行所有可能的拆分）。

如果给出了 @emph{sep}，则连续的分隔符不会被组合在一起而是被视为分隔空子序列 (例如 @code{b'1,,2'.split(b',')} 将返回 @code{[b'1', b'@w{'}, b'2']})。 @emph{sep} 参数可能为一个多字节序列 (例如 @code{b'1<>2<>3'.split(b'<>')} 将返回 @code{[b'1', b'2', b'3']})。 使用指定的分隔符拆分空序列将返回 @code{[b'@w{'}]} 或 @code{[bytearray(b'@w{'})]}，具体取决于被拆分对象的类型。 @emph{sep} 参数可以是任意 @ref{5e3,,bytes-like object}。

例如

@example
>>> b'1,2,3'.split(b',')
[b'1', b'2', b'3']
>>> b'1,2,3'.split(b',', maxsplit=1)
[b'1', b'2,3']
>>> b'1,2,,3,'.split(b',')
[b'1', b'2', b'@w{'}, b'3', b'@w{'}]
@end example

如果 @emph{sep} 未指定或为 @code{None}，则会应用另一种拆分算法：连续的 ASCII 空白符会被视为单个分隔符，其结果将不包含序列开头或末尾的空白符。 因此，在不指定分隔符的情况下对空序列或仅包含 ASCII 空白符的序列进行拆分将返回 @code{[]}。

例如

@example
>>> b'1 2 3'.split()
[b'1', b'2', b'3']
>>> b'1 2 3'.split(maxsplit=1)
[b'1', b'2 3']
>>> b'   1   2   3   '.split()
[b'1', b'2', b'3']
@end example
@end deffn

@geindex strip() (bytes 方法)
@geindex strip() (bytearray 方法)
@anchor{library/stdtypes bytes strip}@anchor{1623}
@deffn {方法} bytes.strip ([chars])
@anchor{library/stdtypes bytearray strip}@anchor{1624}
@deffnx {方法} bytearray.strip ([chars])

返回原序列的副本，移除指定的开头和末尾字节。 @emph{chars} 参数为指定要移除字节值集合的二进制序列 —— 这个名称表明此方法通常是用于 ASCII 字符。 如果省略或为 @code{None}，则 @emph{chars} 参数默认移除 ASCII 空白符。 @emph{chars} 参数并非指定单个前缀或后缀；而是会移除参数值的所有组合:

@example
>>> b'   spacious   '.strip()
b'spacious'
>>> b'www.example.com'.strip(b'cmowz.')
b'example'
@end example

要移除的字节值二进制序列可以是任意 @ref{5e3,,bytes-like object}。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

以下 bytes 和 bytearray 对象的方法会假定使用兼容 ASCII 的二进制格式，不应当被应用于任意二进制数据。 请注意本小节中所有的 bytearray 方法都 @emph{不是} 原地执行操作，而是会产生新的对象。

@geindex capitalize() (bytes 方法)
@geindex capitalize() (bytearray 方法)
@anchor{library/stdtypes bytes capitalize}@anchor{1625}
@deffn {方法} bytes.capitalize ()
@anchor{library/stdtypes bytearray capitalize}@anchor{1626}
@deffnx {方法} bytearray.capitalize ()

返回原序列的副本，其中每个字节将都将被解读为一个 ASCII 字符，并且第一个字节的字符大写而其余的小写。 非 ASCII 字节值将保持原样不变。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex expandtabs() (bytes 方法)
@geindex expandtabs() (bytearray 方法)
@anchor{library/stdtypes bytes expandtabs}@anchor{1627}
@deffn {方法} bytes.expandtabs (tabsize=8)
@anchor{library/stdtypes bytearray expandtabs}@anchor{1628}
@deffnx {方法} bytearray.expandtabs (tabsize=8)

返回序列的副本，其中所有的 ASCII 制表符会由一个或多个 ASCII 空格替换，具体取决于当前列位置和给定的制表符宽度。 每 @emph{tabsize} 个字节设为一个制表位（默认值 8 时设定的制表位在列 0, 8, 16 依次类推）。 要展开序列，当前列位置将被设为零并逐一检查序列中的每个字节。 如果字节为 ASCII 制表符 (@code{b'\t'})，则并在结果中插入一个或多个空格符，直到当前列等于下一个制表位。 （制表符本身不会被复制。） 如果当前字节为 ASCII 换行符 (@code{b'\n'}) 或回车符 (@code{b'\r'})，它会被复制并将当前列重设为零。 任何其他字节会被不加修改地复制并将当前列加一，不论该字节值在被打印时会如何显示:

@example
>>> b'01\t012\t0123\t01234'.expandtabs()
b'01      012     0123    01234'
>>> b'01\t012\t0123\t01234'.expandtabs(4)
b'01  012 0123    01234'
@end example

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex isalnum() (bytes 方法)
@geindex isalnum() (bytearray 方法)
@anchor{library/stdtypes bytes isalnum}@anchor{1629}
@deffn {方法} bytes.isalnum ()
@anchor{library/stdtypes bytearray isalnum}@anchor{162a}
@deffnx {方法} bytearray.isalnum ()

Return @code{True} if all bytes in the sequence are alphabetical ASCII characters
or ASCII decimal digits and the sequence is not empty, @code{False} otherwise.
Alphabetic ASCII characters are those byte values in the sequence
@code{b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'}. ASCII decimal
digits are those byte values in the sequence @code{b'0123456789'}.

例如

@example
>>> b'ABCabc1'.isalnum()
True
>>> b'ABC abc1'.isalnum()
False
@end example
@end deffn

@geindex isalpha() (bytes 方法)
@geindex isalpha() (bytearray 方法)
@anchor{library/stdtypes bytes isalpha}@anchor{162b}
@deffn {方法} bytes.isalpha ()
@anchor{library/stdtypes bytearray isalpha}@anchor{162c}
@deffnx {方法} bytearray.isalpha ()

Return @code{True} if all bytes in the sequence are alphabetic ASCII characters
and the sequence is not empty, @code{False} otherwise.  Alphabetic ASCII
characters are those byte values in the sequence
@code{b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'}.

例如

@example
>>> b'ABCabc'.isalpha()
True
>>> b'ABCabc1'.isalpha()
False
@end example
@end deffn

@geindex isascii() (bytes 方法)
@geindex isascii() (bytearray 方法)
@anchor{library/stdtypes bytes isascii}@anchor{162d}
@deffn {方法} bytes.isascii ()
@anchor{library/stdtypes bytearray isascii}@anchor{162e}
@deffnx {方法} bytearray.isascii ()

Return @code{True} if the sequence is empty or all bytes in the sequence are ASCII,
@code{False} otherwise.
ASCII bytes are in the range 0-0x7F.


3.7 新版功能.

@end deffn

@geindex isdigit() (bytes 方法)
@geindex isdigit() (bytearray 方法)
@anchor{library/stdtypes bytes isdigit}@anchor{162f}
@deffn {方法} bytes.isdigit ()
@anchor{library/stdtypes bytearray isdigit}@anchor{1630}
@deffnx {方法} bytearray.isdigit ()

Return @code{True} if all bytes in the sequence are ASCII decimal digits
and the sequence is not empty, @code{False} otherwise. ASCII decimal digits are
those byte values in the sequence @code{b'0123456789'}.

例如

@example
>>> b'1234'.isdigit()
True
>>> b'1.23'.isdigit()
False
@end example
@end deffn

@geindex islower() (bytes 方法)
@geindex islower() (bytearray 方法)
@anchor{library/stdtypes bytes islower}@anchor{1631}
@deffn {方法} bytes.islower ()
@anchor{library/stdtypes bytearray islower}@anchor{1632}
@deffnx {方法} bytearray.islower ()

Return @code{True} if there is at least one lowercase ASCII character
in the sequence and no uppercase ASCII characters, @code{False} otherwise.

例如

@example
>>> b'hello world'.islower()
True
>>> b'Hello world'.islower()
False
@end example

小写 ASCII 字符就是字节值包含在序列 @code{b'abcdefghijklmnopqrstuvwxyz'} 中的字符。 大写 ASCII 字符就是字节值包含在序列 @code{b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'} 中的字符。
@end deffn

@geindex isspace() (bytes 方法)
@geindex isspace() (bytearray 方法)
@anchor{library/stdtypes bytes isspace}@anchor{1633}
@deffn {方法} bytes.isspace ()
@anchor{library/stdtypes bytearray isspace}@anchor{1634}
@deffnx {方法} bytearray.isspace ()

Return @code{True} if all bytes in the sequence are ASCII whitespace and the
sequence is not empty, @code{False} otherwise.  ASCII whitespace characters are
those byte values in the sequence @code{b' \t\n\r\x0b\f'} (space, tab, newline,
carriage return, vertical tab, form feed).
@end deffn

@geindex istitle() (bytes 方法)
@geindex istitle() (bytearray 方法)
@anchor{library/stdtypes bytes istitle}@anchor{1635}
@deffn {方法} bytes.istitle ()
@anchor{library/stdtypes bytearray istitle}@anchor{1636}
@deffnx {方法} bytearray.istitle ()

Return @code{True} if the sequence is ASCII titlecase and the sequence is not
empty, @code{False} otherwise. See @ref{1637,,bytes.title()} for more details on the
definition of "titlecase".

例如

@example
>>> b'Hello World'.istitle()
True
>>> b'Hello world'.istitle()
False
@end example
@end deffn

@geindex isupper() (bytes 方法)
@geindex isupper() (bytearray 方法)
@anchor{library/stdtypes bytes isupper}@anchor{1638}
@deffn {方法} bytes.isupper ()
@anchor{library/stdtypes bytearray isupper}@anchor{1639}
@deffnx {方法} bytearray.isupper ()

Return @code{True} if there is at least one uppercase alphabetic ASCII character
in the sequence and no lowercase ASCII characters, @code{False} otherwise.

例如

@example
>>> b'HELLO WORLD'.isupper()
True
>>> b'Hello world'.isupper()
False
@end example

小写 ASCII 字符就是字节值包含在序列 @code{b'abcdefghijklmnopqrstuvwxyz'} 中的字符。 大写 ASCII 字符就是字节值包含在序列 @code{b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'} 中的字符。
@end deffn

@geindex lower() (bytes 方法)
@geindex lower() (bytearray 方法)
@anchor{library/stdtypes bytes lower}@anchor{163a}
@deffn {方法} bytes.lower ()
@anchor{library/stdtypes bytearray lower}@anchor{163b}
@deffnx {方法} bytearray.lower ()

返回原序列的副本，其所有大写 ASCII 字符均转换为对应的小写形式。

例如

@example
>>> b'Hello World'.lower()
b'hello world'
@end example

小写 ASCII 字符就是字节值包含在序列 @code{b'abcdefghijklmnopqrstuvwxyz'} 中的字符。 大写 ASCII 字符就是字节值包含在序列 @code{b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'} 中的字符。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex universal newlines; bytes.splitlines method
@geindex universal newlines; bytearray.splitlines method

@geindex splitlines() (bytes 方法)
@geindex splitlines() (bytearray 方法)
@anchor{library/stdtypes bytes splitlines}@anchor{163c}
@deffn {方法} bytes.splitlines (keepends=False)
@anchor{library/stdtypes bytearray splitlines}@anchor{163d}
@deffnx {方法} bytearray.splitlines (keepends=False)

返回由原二进制序列中各行组成的列表，在 ASCII 行边界符的位置拆分。 此方法使用 @ref{5ef,,universal newlines} 方式来分行。 结果列表中不包含换行符，除非给出了 @emph{keepends} 且为真值。

例如

@example
>>> b'ab c\n\nde fg\rkl\r\n'.splitlines()
[b'ab c', b'@w{'}, b'de fg', b'kl']
>>> b'ab c\n\nde fg\rkl\r\n'.splitlines(keepends=True)
[b'ab c\n', b'\n', b'de fg\r', b'kl\r\n']
@end example

不同于 @ref{1622,,split()}，当给出了分隔符 @emph{sep} 时，对于空字符串此方法将返回一个空列表，而末尾的换行不会令结果中增加额外的行:

@example
>>> b"".split(b'\n'), b"Two lines\n".split(b'\n')
([b'@w{'}], [b'Two lines', b'@w{'}])
>>> b"".splitlines(), b"One line\n".splitlines()
([], [b'One line'])
@end example
@end deffn

@geindex swapcase() (bytes 方法)
@geindex swapcase() (bytearray 方法)
@anchor{library/stdtypes bytes swapcase}@anchor{163e}
@deffn {方法} bytes.swapcase ()
@anchor{library/stdtypes bytearray swapcase}@anchor{163f}
@deffnx {方法} bytearray.swapcase ()

返回原序列的副本，其所有小写 ASCII 字符均转换为对应的大写形式，反之亦反。

例如

@example
>>> b'Hello World'.swapcase()
b'hELLO wORLD'
@end example

小写 ASCII 字符就是字节值包含在序列 @code{b'abcdefghijklmnopqrstuvwxyz'} 中的字符。 大写 ASCII 字符就是字节值包含在序列 @code{b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'} 中的字符。

不同于 @ref{15f4,,str.swapcase()}，在些二进制版本下 @code{bin.swapcase().swapcase() == bin} 总是成立。 大小写转换在 ASCII 中是对称的，即使其对于任意 Unicode 码位来说并不总是成立。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex title() (bytes 方法)
@geindex title() (bytearray 方法)
@anchor{library/stdtypes bytes title}@anchor{1637}
@deffn {方法} bytes.title ()
@anchor{library/stdtypes bytearray title}@anchor{1640}
@deffnx {方法} bytearray.title ()

返回原二进制序列的标题版本，其中每个单词以一个大写 ASCII 字符为开头，其余字母为小写。 不区别大小写的字节值将保持原样不变。

例如

@example
>>> b'Hello world'.title()
b'Hello World'
@end example

小写 ASCII 字符就是字节值包含在序列 @code{b'abcdefghijklmnopqrstuvwxyz'} 中的字符。 大写 ASCII 字符就是字节值包含在序列 @code{b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'} 中的字符。 所有其他字节值都不区分大小写。

该算法使用一种简单的与语言无关的定义，将连续的字母组合视为单词。 该定义在多数情况下都很有效，但它也意味着代表缩写形式与所有格的撇号也会成为单词边界，这可能导致不希望的结果:

@example
>>> b"they're bill's friends from the UK".title()
b"They'Re Bill'S Friends From The Uk"
@end example

可以使用正则表达式来构建针对撇号的特别处理:

@example
>>> import re
>>> def titlecase(s):
...     return re.sub(rb"[A-Za-z]+('[A-Za-z]+)?",
...                   lambda mo: mo.group(0)[0:1].upper() +
...                              mo.group(0)[1:].lower(),
...                   s)
...
>>> titlecase(b"they're bill's friends.")
b"They're Bill's Friends."
@end example

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex upper() (bytes 方法)
@geindex upper() (bytearray 方法)
@anchor{library/stdtypes bytes upper}@anchor{1641}
@deffn {方法} bytes.upper ()
@anchor{library/stdtypes bytearray upper}@anchor{1642}
@deffnx {方法} bytearray.upper ()

返回原序列的副本，其所有小写 ASCII 字符均转换为对应的大写形式。

例如

@example
>>> b'Hello World'.upper()
b'HELLO WORLD'
@end example

小写 ASCII 字符就是字节值包含在序列 @code{b'abcdefghijklmnopqrstuvwxyz'} 中的字符。 大写 ASCII 字符就是字节值包含在序列 @code{b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'} 中的字符。

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@geindex zfill() (bytes 方法)
@geindex zfill() (bytearray 方法)
@anchor{library/stdtypes bytes zfill}@anchor{1643}
@deffn {方法} bytes.zfill (width)
@anchor{library/stdtypes bytearray zfill}@anchor{1644}
@deffnx {方法} bytearray.zfill (width)

返回原序列的副本，在左边填充 @code{b'0'} 数码使序列长度为 @emph{width}。 正负值前缀 (@code{b'+'}/ @code{b'-'}) 的处理方式是在正负符号 @emph{之后} 填充而非在之前。 对于 @ref{32a,,bytes} 对象，如果 @emph{width} 小于等于 @code{len(seq)} 则返回原序列。

例如

@example
>>> b"42".zfill(5)
b'00042'
>>> b"-42".zfill(5)
b'-0042'
@end example

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche
@end deffn

@node printf 风格的字节串格式化,内存视图,bytes 和 bytearray 操作,二进制序列类型 --- bytes bytearray memoryview
@anchor{library/stdtypes bytes-formatting}@anchor{64a}@anchor{library/stdtypes printf-style-bytes-formatting}@anchor{1645}
@subsubsection @code{printf} 风格的字节串格式化


@geindex formatting; bytes (%)
@geindex formatting; bytearray (%)
@geindex interpolation; bytes (%)
@geindex interpolation; bytearray (%)
@geindex bytes; formatting
@geindex bytearray; formatting
@geindex bytes; interpolation
@geindex bytearray; interpolation
@geindex printf-style formatting
@geindex sprintf-style formatting
@geindex % (percent); printf-style formatting

@cartouche
@quotation 注解 
此处介绍的格式化操作具有多种怪异特性，可能导致许多常见错误（例如无法正确显示元组和字典）。 如果要打印的值可能为元组或字典，请将其放入一个元组中。
@end quotation
@end cartouche

字节串对象 (@code{bytes}/@code{bytearray}) 具有一种特殊的内置操作：使用 @code{%} (取模) 运算符。 这也被称为字节串的 @emph{格式化} 或 @emph{插值} 运算符。 对于 @code{format % values} (其中 @emph{format} 为一个字节串对象)，在 @emph{format} 中的 @code{%} 转换标记符将被替换为零个或多个 @emph{values} 条目。 其效果类似于在 C 语言中使用 @code{sprintf()}。

如果 @emph{format} 要求一个单独参数，则 @emph{values} 可以为一个非元组对象。 @footnote{@w{(5)} 
要格式化单独一个元组，那么你应当提供一个单例元组，其唯一的元素就是要被格式化的元组。
}  否则的话，@emph{values} 必须或是是一个包含项数与格式字节串对象中指定的转换符项数相同的元组，或者是一个单独的映射对象（例如元组）。

@geindex () (parentheses); in printf-style formatting
@geindex * (asterisk); in printf-style formatting
@geindex . (dot); in printf-style formatting

转换标记符包含两个或更多字符并具有以下组成，且必须遵循此处规定的顺序：


@enumerate 

@item 
@code{'%'} 字符，用于标记转换符的起始。

@item 
映射键（可选），由加圆括号的字符序列组成 (例如 @code{(somename)})。

@item 
转换旗标（可选），用于影响某些转换类型的结果。

@item 
最小字段宽度（可选）。 如果指定为 @code{'*'} (星号)，则实际宽度会从 @emph{values} 元组的下一元素中读取，要转换的对象则为最小字段宽度和可选的精度之后的元素。

@item 
精度（可选），以在 @code{'.'} (点号) 之后加精度值的形式给出。 如果指定为 @code{'*'} (星号)，则实际精度会从 @emph{values} 元组的下一元素中读取，要转换的对象则为精度之后的元素。

@item 
长度修饰符（可选）。

@item 
转换类型。
@end enumerate

当右边的参数为一个字典（或其他映射类型）时，字节串对象中的格式 @emph{必须} 包含加圆括号的映射键，对应 @code{'%'} 字符之后字典中的每一项。 映射键将从映射中选取要格式化的值。 例如：

@example
>>> print(b'%(language)s has %(number)03d quote types.' %
...       @{b'language': b"Python", b"number": 2@})
b'Python has 002 quote types.'
@end example

在此情况下格式中不能出现 @code{*} 标记符（因其需要一个序列类的参数列表）。

转换旗标为：

@geindex # (hash); in printf-style formatting
@geindex - (minus); in printf-style formatting
@geindex + (plus); in printf-style formatting
@geindex space; in printf-style formatting


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Flag

@tab

含义

@item

@code{'#'}

@tab

值的转换将使用“替代形式”（具体定义见下文）。

@item

@code{'0'}

@tab

转换将为数字值填充零字符。

@item

@code{'-'}

@tab

转换值将靠左对齐（如果同时给出 @code{'0'} 转换，则会覆盖后者）。

@item

@code{' '}

@tab

(空格) 符号位转换产生的正数（或空字符串）前将留出一个空格。

@item

@code{'+'}

@tab

符号字符 (@code{'+'} 或 @code{'-'}) 将显示于转换结果的开头（会覆盖 "空格" 旗标）。

@end multitable


可以给出长度修饰符 (@code{h}, @code{l} 或 @code{L})，但会被忽略，因为对 Python 来说没有必要 -- 所以 @code{%ld} 等价于 @code{%d}。

转换类型为：


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

转换符

@tab

含义

@tab

注释

@item

@code{'d'}

@tab

有符号十进制整数。

@tab

@item

@code{'i'}

@tab

有符号十进制整数。

@tab

@item

@code{'o'}

@tab

有符号八进制数。

@tab

(1)

@item

@code{'u'}

@tab

过时类型 -- 等价于 @code{'d'}。

@tab

(8)

@item

@code{'x'}

@tab

有符号十六进制数（小写）。

@tab

(2)

@item

@code{'X'}

@tab

有符号十六进制数（大写）。

@tab

(2)

@item

@code{'e'}

@tab

浮点指数格式（小写）。

@tab

(3)

@item

@code{'E'}

@tab

浮点指数格式（大写）。

@tab

(3)

@item

@code{'f'}

@tab

浮点十进制格式。

@tab

(3)

@item

@code{'F'}

@tab

浮点十进制格式。

@tab

(3)

@item

@code{'g'}

@tab

浮点格式。 如果指数小于 -4 或不小于精度则使用小写指数格式，否则使用十进制格式。

@tab

(4)

@item

@code{'G'}

@tab

浮点格式。 如果指数小于 -4 或不小于精度则使用大写指数格式，否则使用十进制格式。

@tab

(4)

@item

@code{'c'}

@tab

单个字节（接受整数或单个字节对象）。

@tab

@item

@code{'b'}

@tab

字节串（任何遵循 @ref{15d6,,缓冲区协议} 或是具有 @ref{13cf,,__bytes__()} 的对象）。

@tab

(5)

@item

@code{'s'}

@tab

@code{'s'} 是 @code{'b'} 的一个别名，只应当在基于 Python2/3 的代码中使用。

@tab

(6)

@item

@code{'a'}

@tab

字节串（使用 @code{repr(obj).encode('ascii','backslashreplace)} 转换任何 Python 对象）。

@tab

(5)

@item

@code{'r'}

@tab

@code{'r'} 是 @code{'a'} 的一个别名，只应当在基于 Python2/3 的代码中使用。

@tab

(7)

@item

@code{'%'}

@tab

不转换参数，在结果中输出一个 @code{'%'} 字符。

@tab

@end multitable


注释:


@enumerate 

@item 
此替代形式会在第一个数码之前插入标示八进制数的前缀 (@code{'0o'})。

@item 
此替代形式会在第一个数码之前插入 @code{'0x'} 或 @code{'0X'} 前缀（取决于是使用 @code{'x'} 还是 @code{'X'} 格式）。

@item 
此替代形式总是会在结果中包含一个小数点，即使其后并没有数码。

小数点后的数码位数由精度决定，默认为 6。

@item 
此替代形式总是会在结果中包含一个小数点，末尾各位的零不会如其他情况下那样被移除。

小数点前后的有效数码位数由精度决定，默认为 6。

@item 
如果精度为 @code{N}，输出将截短为 @code{N} 个字符。

@item 
@code{b'%s'} 已弃用，但在 3.x 系列中将不会被移除。

@item 
@code{b'%r'} 已弃用，但在 3.x 系列中将不会被移除。

@item 
参见 
@geindex Python 提高建议; PEP 237
PEP 237@footnote{https://www.python.org/dev/peps/pep-0237}。
@end enumerate

@cartouche
@quotation 注解 
此方法的 bytearray 版本 @emph{并非} 原地操作 —— 它总是产生一个新对象，即便没有做任何改变。
@end quotation
@end cartouche


@subsubheading 参见


@geindex Python 提高建议; PEP 461
PEP 461@footnote{https://www.python.org/dev/peps/pep-0461} - 为 bytes 和 bytearray 添加 % 格式化



3.5 新版功能.


@node 内存视图,,printf 风格的字节串格式化,二进制序列类型 --- bytes bytearray memoryview
@anchor{library/stdtypes memory-views}@anchor{1646}@anchor{library/stdtypes typememoryview}@anchor{158d}
@subsubsection 内存视图


@ref{25c,,memoryview} 对象允许 Python 代码访问一个对象的内部数据，只要该对象支持 @ref{15d6,,缓冲区协议} 而无需进行拷贝。

@geindex memoryview (內置类)
@anchor{library/stdtypes memoryview}@anchor{25c}
@deffn {类} memoryview (obj)

创建一个引用 @emph{obj} 的 @ref{25c,,memoryview}。 @emph{obj} 必须支持缓冲区协议。 支持缓冲区协议的内置对象包括 @ref{32a,,bytes} 和 @ref{32b,,bytearray}。

@ref{25c,,memoryview} 具有 @emph{元素} 的概念，即由原始对象 @emph{obj} 所处理的基本内存单元。 对于许多简单类型例如 @ref{32a,,bytes} 和 @ref{32b,,bytearray} 来说，一个元素就是一个字节，但是其他的类型例如 @ref{44b,,array.array} 可能有更大的元素。

@code{len(view)} 与 @ref{1647,,tolist} 的长度相等。 如果 @code{view.ndim = 0}，则其长度为 1。 如果 @code{view.ndim = 1}，则其长度等于 view 中元素的数量。 对于更高的维度，其长度等于表示 view 的嵌套列表的长度。 @ref{1648,,itemsize} 属性可向你给出单个元素所占的字节数。

@ref{25c,,memoryview} 支持通过切片和索引访问其元素。 一维切片的结果将是一个子视图:

@example
>>> v = memoryview(b'abcefg')
>>> v[1]
98
>>> v[-1]
103
>>> v[1:4]
<memory at 0x7f3ddc9f4350>
>>> bytes(v[1:4])
b'bce'
@end example

如果 @ref{1649,,format} 是一个来自于 @ref{f8,,struct} 模块的原生格式说明符，则也支持使用整数或由整数构成的元组进行索引，并返回具有正确类型的单个 @emph{元素}。 一维内存视图可以使用一个整数或由一个整数构成的元组进行索引。 多维内存视图可以使用由恰好 @emph{ndim} 个整数构成的元素进行索引，@emph{ndim} 即其维度。 零维内存视图可以使用空元组进行索引。

这里是一个使用非字节格式的例子:

@example
>>> import array
>>> a = array.array('l', [-11111111, 22222222, -33333333, 44444444])
>>> m = memoryview(a)
>>> m[0]
-11111111
>>> m[-1]
44444444
>>> m[::2].tolist()
[-11111111, -33333333]
@end example

如果下层对象是可写的，则内存视图支持一维切片赋值。 改变大小则不被允许:

@example
>>> data = bytearray(b'abcefg')
>>> v = memoryview(data)
>>> v.readonly
False
>>> v[0] = ord(b'z')
>>> data
bytearray(b'zbcefg')
>>> v[1:4] = b'123'
>>> data
bytearray(b'z123fg')
>>> v[2:3] = b'spam'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: memoryview assignment: lvalue and rvalue have different structures
>>> v[2:6] = b'spam'
>>> data
bytearray(b'z1spam')
@end example

由带有格式符号 'B', 'b' 或 'c' 的可哈希（只读）类型构成的一维内存视图同样是可哈希的。 哈希定义为 @code{hash(m) == hash(m.tobytes())}:

@example
>>> v = memoryview(b'abcefg')
>>> hash(v) == hash(b'abcefg')
True
>>> hash(v[2:4]) == hash(b'ce')
True
>>> hash(v[::-2]) == hash(b'abcefg'[::-2])
True
@end example


在 3.3 版更改: 一维内存视图现在可以被切片。 带有格式符号 'B', 'b' 或 'c' 的一维内存视图现在是可哈希的。



在 3.4 版更改: 内存视图现在会自动注册为 @ref{15c8,,collections.abc.Sequence}



在 3.5 版更改: 内存视图现在可使用整数元组进行索引。


@ref{25c,,memoryview} 具有以下一些方法：

@geindex __eq__() (memoryview 方法)
@anchor{library/stdtypes memoryview __eq__}@anchor{164a}
@deffn {方法} __eq__ (exporter)

memoryview 与 
@geindex Python 提高建议; PEP 3118
PEP 3118@footnote{https://www.python.org/dev/peps/pep-3118} 中的导出器这两者如果形状相同，并且如果当使用 @ref{f8,,struct} 语法解读操作数的相应格式代码时所有对应值都相同，则它们就是等价的。

对于 @ref{1647,,tolist()} 当前所支持的 @ref{f8,,struct} 格式字符串子集，如果 @code{v.tolist() == w.tolist()} 则 @code{v} 和 @code{w} 相等:

@example
>>> import array
>>> a = array.array('I', [1, 2, 3, 4, 5])
>>> b = array.array('d', [1.0, 2.0, 3.0, 4.0, 5.0])
>>> c = array.array('b', [5, 3, 1])
>>> x = memoryview(a)
>>> y = memoryview(b)
>>> x == a == y == b
True
>>> x.tolist() == a.tolist() == y.tolist() == b.tolist()
True
>>> z = y[::-2]
>>> z == c
True
>>> z.tolist() == c.tolist()
True
@end example

如果两边的格式字符串都不被 @ref{f8,,struct} 模块所支持，则两对象比较结果总是不相等（即使格式字符串和缓冲区内容相同）:

@example
>>> from ctypes import BigEndianStructure, c_long
>>> class BEPoint(BigEndianStructure):
...     _fields_ = [("x", c_long), ("y", c_long)]
...
>>> point = BEPoint(100, 200)
>>> a = memoryview(point)
>>> b = memoryview(point)
>>> a == point
False
>>> a == b
False
@end example

请注意，与浮点数的情况一样，对于内存视图对象来说，@code{v is w} 也 @emph{并不} 意味着 @code{v == w}。


在 3.3 版更改: 之前的版本比较原始内存时会忽略条目的格式与逻辑数组结构。

@end deffn

@geindex tobytes() (memoryview 方法)
@anchor{library/stdtypes memoryview tobytes}@anchor{164b}
@deffn {方法} tobytes (order=None)

将缓冲区中的数据作为字节串返回。 这相当于在内存视图上调用 @ref{32a,,bytes} 构造器。

@example
>>> m = memoryview(b"abc")
>>> m.tobytes()
b'abc'
>>> bytes(m)
b'abc'
@end example

对于非连续数组，结果等于平面化表示的列表，其中所有元素都转换为字节串。 @ref{164b,,tobytes()} 支持所有格式字符串，不符合 @ref{f8,,struct} 模块语法的那些也包括在内。


3.8 新版功能: @emph{order} 可以为 @{'C', 'F', 'A'@}。 当 @emph{order} 为 'C' 或 'F' 时，原始数组的数据会被转换至 C 或 Fortran 顺序。 对于连续视图，'A' 会返回物理内存的精确副本。 特别地，内存中的 Fortran 顺序会被保留。对于非连续视图，数据会先被转换为 C 形式。 @emph{order=None} 与 @emph{order='C'} 是相同的。

@end deffn

@geindex hex() (memoryview 方法)
@anchor{library/stdtypes memoryview hex}@anchor{62d}
@deffn {方法} hex ([sep[, bytes_per_sep]])

返回一个字符串对象，其中分别以两个十六进制数码表示缓冲区里的每个字节。

@example
>>> m = memoryview(b"abc")
>>> m.hex()
'616263'
@end example


3.5 新版功能.



在 3.8 版更改: Similar to @ref{62b,,bytes.hex()}, @ref{62d,,memoryview.hex()} now supports
optional @emph{sep} and @emph{bytes_per_sep} parameters to insert separators
between bytes in the hex output.

@end deffn

@geindex tolist() (memoryview 方法)
@anchor{library/stdtypes memoryview tolist}@anchor{1647}
@deffn {方法} tolist ()

将缓冲区内的数据以一个元素列表的形式返回。

@example
>>> memoryview(b'abc').tolist()
[97, 98, 99]
>>> import array
>>> a = array.array('d', [1.1, 2.2, 3.3])
>>> m = memoryview(a)
>>> m.tolist()
[1.1, 2.2, 3.3]
@end example


在 3.3 版更改: @ref{1647,,tolist()} 现在支持 @ref{f8,,struct} 模块语法中的所有单字符原生格式以及多维表示形式。

@end deffn

@geindex toreadonly() (memoryview 方法)
@anchor{library/stdtypes memoryview toreadonly}@anchor{164c}
@deffn {方法} toreadonly ()

返回 memoryview 对象的只读版本。 原始的 memoryview 对象不会被改变。

@example
>>> m = memoryview(bytearray(b'abc'))
>>> mm = m.toreadonly()
>>> mm.tolist()
[89, 98, 99]
>>> mm[0] = 42
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot modify read-only memory
>>> m[0] = 43
>>> mm.tolist()
[43, 98, 99]
@end example


3.8 新版功能.

@end deffn

@geindex release() (memoryview 方法)
@anchor{library/stdtypes memoryview release}@anchor{b36}
@deffn {方法} release ()

释放由内存视图对象所公开的底层缓冲区。 许多对象在被视图所获取时都会采取特殊动作（例如，@ref{32b,,bytearray} 将会暂时禁止调整大小）；因此，调用 release() 可以方便地尽早去除这些限制（并释放任何多余的资源）。

在此方法被调用后，任何对视图的进一步操作将引发 @ref{1fb,,ValueError} (@ref{b36,,release()} 本身除外，它可以被多次调用):

@example
>>> m = memoryview(b'abc')
>>> m.release()
>>> m[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: operation forbidden on released memoryview object
@end example

使用 @code{with} 语句，可以通过上下文管理协议达到类似的效果:

@example
>>> with memoryview(b'abc') as m:
...     m[0]
...
97
>>> m[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: operation forbidden on released memoryview object
@end example


3.2 新版功能.

@end deffn

@geindex cast() (memoryview 方法)
@anchor{library/stdtypes memoryview cast}@anchor{164d}
@deffn {方法} cast (format[, shape])

将内存视图转化为新的格式或形状。 @emph{shape} 默认为 @code{[byte_length//new_itemsize]}，这意味着结果视图将是一维的。 返回值是一个新的内存视图，但缓冲区本身不会被复制。 支持的转化有 1D -> C-@ref{164e,,contiguous} 和 C-contiguous -> 1D。

目标格式仅限于 @ref{f8,,struct} 语法中的单一元素原生格式。 其中一种格式必须为字节格式 ('B', 'b' 或 'c')。 结果的字节长度必须与原始长度相同。

将 1D/long 转换为 1D/unsigned bytes:

@example
>>> import array
>>> a = array.array('l', [1,2,3])
>>> x = memoryview(a)
>>> x.format
'l'
>>> x.itemsize
8
>>> len(x)
3
>>> x.nbytes
24
>>> y = x.cast('B')
>>> y.format
'B'
>>> y.itemsize
1
>>> len(y)
24
>>> y.nbytes
24
@end example

将 1D/unsigned bytes 转换为 1D/char:

@example
>>> b = bytearray(b'zyz')
>>> x = memoryview(b)
>>> x[0] = b'a'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: memoryview: invalid value for format "B"
>>> y = x.cast('c')
>>> y[0] = b'a'
>>> b
bytearray(b'ayz')
@end example

将 1D/bytes 转换为 3D/ints 再转换为 1D/signed char:

@example
>>> import struct
>>> buf = struct.pack("i"*12, *list(range(12)))
>>> x = memoryview(buf)
>>> y = x.cast('i', shape=[2,2,3])
>>> y.tolist()
[[[0, 1, 2], [3, 4, 5]], [[6, 7, 8], [9, 10, 11]]]
>>> y.format
'i'
>>> y.itemsize
4
>>> len(y)
2
>>> y.nbytes
48
>>> z = y.cast('b')
>>> z.format
'b'
>>> z.itemsize
1
>>> len(z)
48
>>> z.nbytes
48
@end example

将 1D/unsigned long 转换为 2D/unsigned long:

@example
>>> buf = struct.pack("L"*6, *list(range(6)))
>>> x = memoryview(buf)
>>> y = x.cast('L', shape=[2,3])
>>> len(y)
2
>>> y.nbytes
48
>>> y.tolist()
[[0, 1, 2], [3, 4, 5]]
@end example


3.3 新版功能.



在 3.5 版更改: 当转换为字节视图时，源格式将不再受限。

@end deffn

还存在一些可用的只读属性：

@geindex obj (memoryview 属性)
@anchor{library/stdtypes memoryview obj}@anchor{164f}
@deffn {属性} obj

内存视图的下层对象:

@example
>>> b  = bytearray(b'xyz')
>>> m = memoryview(b)
>>> m.obj is b
True
@end example


3.3 新版功能.

@end deffn

@geindex nbytes (memoryview 属性)
@anchor{library/stdtypes memoryview nbytes}@anchor{1650}
@deffn {属性} nbytes

@code{nbytes == product(shape) * itemsize == len(m.tobytes())}。 这是数组在连续表示时将会占用的空间总字节数。 它不一定等于 @code{len(m)}:

@example
>>> import array
>>> a = array.array('i', [1,2,3,4,5])
>>> m = memoryview(a)
>>> len(m)
5
>>> m.nbytes
20
>>> y = m[::2]
>>> len(y)
3
>>> y.nbytes
12
>>> len(y.tobytes())
12
@end example

多维数组:

@example
>>> import struct
>>> buf = struct.pack("d"*12, *[1.5*x for x in range(12)])
>>> x = memoryview(buf)
>>> y = x.cast('d', shape=[3,4])
>>> y.tolist()
[[0.0, 1.5, 3.0, 4.5], [6.0, 7.5, 9.0, 10.5], [12.0, 13.5, 15.0, 16.5]]
>>> len(y)
3
>>> y.nbytes
96
@end example


3.3 新版功能.

@end deffn

@geindex readonly (memoryview 属性)
@anchor{library/stdtypes memoryview readonly}@anchor{1651}
@deffn {属性} readonly

一个表明内存是否只读的布尔值。
@end deffn

@geindex format (memoryview 属性)
@anchor{library/stdtypes memoryview format}@anchor{1649}
@deffn {属性} format

一个字符串，包含视图中每个元素的格式（表示为 @ref{f8,,struct} 模块样式）。 内存视图可以从具有任意格式字符串的导出器创建，但某些方法 (例如 @ref{1647,,tolist()}) 仅限于原生的单元素格式。


在 3.3 版更改: 格式 @code{'B'} 现在会按照 struct 模块语法来处理。 这意味着 @code{memoryview(b'abc')[0] == b'abc'[0] == 97}。

@end deffn

@geindex itemsize (memoryview 属性)
@anchor{library/stdtypes memoryview itemsize}@anchor{1648}
@deffn {属性} itemsize

memoryview 中每个元素以字节表示的大小:

@example
>>> import array, struct
>>> m = memoryview(array.array('H', [32000, 32001, 32002]))
>>> m.itemsize
2
>>> m[0]
32000
>>> struct.calcsize('H') == m.itemsize
True
@end example
@end deffn

@geindex ndim (memoryview 属性)
@anchor{library/stdtypes memoryview ndim}@anchor{1652}
@deffn {属性} ndim

一个整数，表示内存所代表的多维数组具有多少个维度。
@end deffn

@geindex shape (memoryview 属性)
@anchor{library/stdtypes memoryview shape}@anchor{1653}
@deffn {属性} shape

一个整数元组，通过 @ref{1652,,ndim} 的长度值给出内存所代表的 N 维数组的形状。


在 3.3 版更改: 当 ndim = 0 时值为空元组而不再为 @code{None}。

@end deffn

@geindex strides (memoryview 属性)
@anchor{library/stdtypes memoryview strides}@anchor{1654}
@deffn {属性} strides

一个整数元组，通过 @ref{1652,,ndim} 的长度给出以字节表示的大小，以便访问数组中每个维度上的每个元素。


在 3.3 版更改: 当 ndim = 0 时值为空元组而不再为 @code{None}。

@end deffn

@geindex suboffsets (memoryview 属性)
@anchor{library/stdtypes memoryview suboffsets}@anchor{1655}
@deffn {属性} suboffsets

供 PIL 风格的数组内部使用。 该值仅作为参考信息。
@end deffn

@geindex c_contiguous (memoryview 属性)
@anchor{library/stdtypes memoryview c_contiguous}@anchor{1656}
@deffn {属性} c_contiguous

一个表明内存是否为 C-@ref{164e,,contiguous} 的布尔值。


3.3 新版功能.

@end deffn

@geindex f_contiguous (memoryview 属性)
@anchor{library/stdtypes memoryview f_contiguous}@anchor{1657}
@deffn {属性} f_contiguous

一个表明内存是否为 Fortran @ref{164e,,contiguous} 的布尔值。


3.3 新版功能.

@end deffn

@geindex contiguous (memoryview 属性)
@anchor{library/stdtypes memoryview contiguous}@anchor{1658}
@deffn {属性} contiguous

一个表明内存是否为 @ref{164e,,contiguous} 的布尔值。


3.3 新版功能.

@end deffn
@end deffn

@node 集合类型 --- set frozenset,映射类型 --- dict,二进制序列类型 --- bytes bytearray memoryview,内置类型
@anchor{library/stdtypes set-types-set-frozenset}@anchor{1659}@anchor{library/stdtypes types-set}@anchor{158a}
@subsection 集合类型 --- @code{set}, @code{frozenset}


@geindex 对象; set

@emph{set} 对象是由具有唯一性的 @ref{13c0,,hashable} 对象所组成的无序多项集。 常见的用途包括成员检测、从序列中去除重复项以及数学中的集合类计算，例如交集、并集、差集与对称差集等等。 （关于其他容器对象请参看 @ref{1b8,,dict}, @ref{262,,list} 与 @ref{478,,tuple} 等内置类，以及 @ref{1e,,collections} 模块。）

与其他多项集一样，集合也支持 @code{x in set}, @code{len(set)} 和 @code{for x in set}。 作为一种无序的多项集，集合并不记录元素位置或插入顺序。 相应地，集合不支持索引、切片或其他序列类的操作。

目前有两种内置集合类型，@ref{b68,,set} 和 @ref{be7,,frozenset}。 @ref{b68,,set} 类型是可变的 --- 其内容可以使用 @code{add()} 和 @code{remove()} 这样的方法来改变。 由于是可变类型，它没有哈希值，且不能被用作字典的键或其他集合的元素。 @ref{be7,,frozenset} 类型是不可变并且为 @ref{13c0,,hashable} --- 其内容在被创建后不能再改变；因此它可以被用作字典的键或其他集合的元素。

除了可以使用 @ref{b68,,set} 构造器，非空的 set (不是 frozenset) 还可以通过将以逗号分隔的元素列表包含于花括号之内来创建，例如: @code{@{'jack', 'sjoerd'@}}。

两个类的构造器具有相同的作用方式：

@geindex set (內置类)
@geindex frozenset (內置类)
@anchor{library/stdtypes set}@anchor{b68}
@deffn {类} set ([iterable])
@anchor{library/stdtypes frozenset}@anchor{be7}
@deffnx {类} frozenset ([iterable])

返回一个新的 set 或 frozenset 对象，其元素来自于 @emph{iterable}。 集合的元素必须为 @ref{13c0,,hashable}。 要表示由集合对象构成的集合，所有的内层集合必须为 @ref{be7,,frozenset} 对象。 如果未指定 @emph{iterable}，则将返回一个新的空集合。

@ref{b68,,set} 和 @ref{be7,,frozenset} 的实例提供以下操作：


@deffn {Describe} len(s)

返回集合 @emph{s} 中的元素数量（即 @emph{s} 的基数）。
@end deffn


@deffn {Describe} x in s

检测 @emph{x} 是否为 @emph{s} 中的成员。
@end deffn


@deffn {Describe} x not in s

检测 @emph{x} 是否非 @emph{s} 中的成员。
@end deffn

@geindex isdisjoint() (frozenset 方法)
@anchor{library/stdtypes frozenset isdisjoint}@anchor{165a}
@deffn {方法} isdisjoint (other)

如果集合中没有与 @emph{other} 共有的元素则返回 @code{True}。 当且仅当两个集合的交集为空集合时，两者为不相交集合。
@end deffn

@geindex issubset() (frozenset 方法)
@anchor{library/stdtypes frozenset issubset}@anchor{165b}
@deffn {方法} issubset (other)

@deffnx {方法} set <= other

检测是否集合中的每个元素都在 @emph{other} 之中。
@end deffn


@deffn {方法} set < other

检测集合是否为 @emph{other} 的真子集，即 @code{set <= other and set != other}。
@end deffn

@geindex issuperset() (frozenset 方法)
@anchor{library/stdtypes frozenset issuperset}@anchor{165c}
@deffn {方法} issuperset (other)

@deffnx {方法} set >= other

检测是否 @emph{other} 中的每个元素都在集合之中。
@end deffn


@deffn {方法} set > other

检测集合是否为 @emph{other} 的真超集，即 @code{set >= other and set != other}。
@end deffn

@geindex union() (frozenset 方法)
@anchor{library/stdtypes frozenset union}@anchor{165d}
@deffn {方法} union (*others)

@deffnx {方法} set | other | ...

返回一个新集合，其中包含来自原集合以及 others 指定的所有集合中的元素。
@end deffn

@geindex intersection() (frozenset 方法)
@anchor{library/stdtypes frozenset intersection}@anchor{165e}
@deffn {方法} intersection (*others)

@deffnx {方法} set & other & ...

返回一个新集合，其中包含原集合以及 others 指定的所有集合中共有的元素。
@end deffn

@geindex difference() (frozenset 方法)
@anchor{library/stdtypes frozenset difference}@anchor{165f}
@deffn {方法} difference (*others)

@deffnx {方法} set @w{-} other @w{-} ...

返回一个新集合，其中包含原集合中在 others 指定的其他集合中不存在的元素。
@end deffn

@geindex symmetric_difference() (frozenset 方法)
@anchor{library/stdtypes frozenset symmetric_difference}@anchor{1660}
@deffn {方法} symmetric_difference (other)

@deffnx {方法} set ^ other

返回一个新集合，其中的元素或属于原集合或属于 @emph{other} 指定的其他集合，但不能同时属于两者。
@end deffn

@geindex copy() (frozenset 方法)
@anchor{library/stdtypes frozenset copy}@anchor{1661}
@deffn {方法} copy ()

返回原集合的浅拷贝。
@end deffn

请注意，非运算符版本的 @ref{165d,,union()}, @ref{165e,,intersection()}, @ref{165f,,difference()}，以及 @ref{1660,,symmetric_difference()}, @ref{165b,,issubset()} 和 @ref{165c,,issuperset()} 方法会接受任意可迭代对象作为参数。 相比之下，它们所对应的运算符版本则要求其参数为集合。 这就排除了容易出错的构造形式例如 @code{set('abc') & 'cbs'}，而推荐可读性更强的 @code{set('abc').intersection('cbs')}。

@ref{b68,,set} 和 @ref{be7,,frozenset} 均支持集合与集合的比较。 两个集合当且仅当每个集合中的每个元素均包含于另一个集合之内（即各为对方的子集）时则相等。 一个集合当且仅当其为另一个集合的真子集（即为后者的子集但两者不相等）时则小于另一个集合。 一个集合当且仅当其为另一个集合的真超集（即为后者的超集但两者不相等）时则大于另一个集合。

@ref{b68,,set} 的实例与 @ref{be7,,frozenset} 的实例之间基于它们的成员进行比较。 例如 @code{set('abc') == frozenset('abc')} 返回 @code{True}，@code{set('abc') in set([frozenset('abc')])} 也一样。

子集与相等比较并不能推广为完全排序函数。 例如，任意两个非空且不相交的集合不相等且互不为对方的子集，因此以下 @emph{所有} 比较均返回 @code{False}: @code{a<b}, @code{a==b}, or @code{a>b}。

由于集合仅定义了部分排序（子集关系），因此由集合构成的列表 @ref{43f,,list.sort()} 方法的输出并无定义。

集合的元素，与字典的键类似，必须为 @ref{13c0,,hashable}。

混合了 @ref{b68,,set} 实例与 @ref{be7,,frozenset} 的二进制位运算将返回与第一个操作数相同的类型。例如: @code{frozenset('ab') | set('bc')} 将返回 @ref{be7,,frozenset} 的实例。

下表列出了可用于 @ref{b68,,set} 而不能用于不可变的 @ref{be7,,frozenset} 实例的操作：

@geindex update() (frozenset 方法)
@anchor{library/stdtypes frozenset update}@anchor{1662}
@deffn {方法} update (*others)

@deffnx {方法} set |= other | ...

更新集合，添加来自 others 中的所有元素。
@end deffn

@geindex intersection_update() (frozenset 方法)
@anchor{library/stdtypes frozenset intersection_update}@anchor{1663}
@deffn {方法} intersection_update (*others)

@deffnx {方法} set &= other & ...

更新集合，只保留其中在所有 others 中也存在的元素。
@end deffn

@geindex difference_update() (frozenset 方法)
@anchor{library/stdtypes frozenset difference_update}@anchor{1664}
@deffn {方法} difference_update (*others)

@deffnx {方法} set @w{-}= other | ...

更新集合，移除其中也存在于 others 中的元素。
@end deffn

@geindex symmetric_difference_update() (frozenset 方法)
@anchor{library/stdtypes frozenset symmetric_difference_update}@anchor{1665}
@deffn {方法} symmetric_difference_update (other)

@deffnx {方法} set ^= other

更新集合，只保留存在于集合的一方而非共同存在的元素。
@end deffn

@geindex add() (frozenset 方法)
@anchor{library/stdtypes frozenset add}@anchor{1666}
@deffn {方法} add (elem)

将元素 @emph{elem} 添加到集合中。
@end deffn

@geindex remove() (frozenset 方法)
@anchor{library/stdtypes frozenset remove}@anchor{1667}
@deffn {方法} remove (elem)

从集合中移除元素 @emph{elem}。 如果 @emph{elem} 不存在于集合中则会引发 @ref{2c7,,KeyError}。
@end deffn

@geindex discard() (frozenset 方法)
@anchor{library/stdtypes frozenset discard}@anchor{1668}
@deffn {方法} discard (elem)

如果元素 @emph{elem} 存在于集合中则将其移除。
@end deffn

@geindex pop() (frozenset 方法)
@anchor{library/stdtypes frozenset pop}@anchor{1669}
@deffn {方法} pop ()

从集合中移除并返回任意一个元素。 如果集合为空则会引发 @ref{2c7,,KeyError}。
@end deffn

@geindex clear() (frozenset 方法)
@anchor{library/stdtypes frozenset clear}@anchor{166a}
@deffn {方法} clear ()

从集合中移除所有元素。
@end deffn

请注意，非运算符版本的 @ref{1662,,update()}, @ref{1663,,intersection_update()}, @ref{1664,,difference_update()} 和 @ref{1665,,symmetric_difference_update()} 方法将接受任意可迭代对象作为参数。

请注意，@ref{d21,,__contains__()}, @ref{1667,,remove()} 和 @ref{1668,,discard()} 方法的 @emph{elem} 参数可能是一个 set。 为支持对一个等价的 frozenset 进行搜索，会根据 @emph{elem} 临时创建一个该类型对象。
@end deffn

@node 映射类型 --- dict,上下文管理器类型,集合类型 --- set frozenset,内置类型
@anchor{library/stdtypes mapping-types-dict}@anchor{166b}@anchor{library/stdtypes typesmapping}@anchor{2f5}
@subsection 映射类型 --- @code{dict}


@geindex 对象; mapping
@geindex 对象; dictionary
@geindex operations on; mapping; types
@geindex operations on; dictionary; type
@geindex 语句; del
@geindex 內置函数; len

@ref{b32,,mapping} 对象会将 @ref{13c0,,hashable} 值映射到任意对象。 映射属于可变对象。 目前仅有一种标准映射类型 @emph{字典}。 （关于其他容器对象请参看 @ref{262,,list}, @ref{b68,,set} 与 @ref{478,,tuple} 等内置类，以及 @ref{1e,,collections} 模块。）

字典的键 @emph{几乎} 可以是任何值。 非 @ref{13c0,,hashable} 的值，即包含列表、字典或其他可变类型的值（此类对象基于值而非对象标识进行比较）不可用作键。 数字类型用作键时遵循数字比较的一般规则：如果两个数值相等 (例如 @code{1} 和 @code{1.0}) 则两者可以被用来索引同一字典条目。 （但是请注意，由于计算机对于浮点数存储的只是近似值，因此将其用作字典键是不明智的。）

字典可以通过将以逗号分隔的 @code{键: 值} 对列表包含于花括号之内来创建，例如: @code{@{'jack': 4098, 'sjoerd': 4127@}} 或 @code{@{4098: 'jack', 4127: 'sjoerd'@}}，也可以通过 @ref{1b8,,dict} 构造器来创建。

@geindex dict (內置类)
@anchor{library/stdtypes dict}@anchor{1b8}
@deffn {类} dict (**kwarg)

@deffnx {类} dict (mapping, **kwarg)

@deffnx {类} dict (iterable, **kwarg)

返回一个新的字典，基于可选的位置参数和可能为空的关键字参数集来初始化。

如果没有给出位置参数，将创建一个空字典。 如果给出一个位置参数并且其属于映射对象，将创建一个具有与映射对象相同键值对的字典。 否则的话，位置参数必须为一个 @ref{ba5,,iterable} 对象。 该可迭代对象中的每一项本身必须为一个刚好包含两个元素的可迭代对象。 每一项中的第一个对象将成为新字典的一个键，第二个对象将成为其对应的值。 如果一个键出现一次以上，该键的最后一个值将成为其在新字典中对应的值。

如果给出了关键字参数，则关键字参数及其值会被加入到基于位置参数创建的字典。 如果要加入的键已存在，来自关键字参数的值将替代来自位置参数的值。

作为演示，以下示例返回的字典均等于 @code{@{"one": 1, "two": 2, "three": 3@}}:

@example
>>> a = dict(one=1, two=2, three=3)
>>> b = @{'one': 1, 'two': 2, 'three': 3@}
>>> c = dict(zip(['one', 'two', 'three'], [1, 2, 3]))
>>> d = dict([('two', 2), ('one', 1), ('three', 3)])
>>> e = dict(@{'three': 3, 'one': 1, 'two': 2@})
>>> a == b == c == d == e
True
@end example

像第一个例子那样提供关键字参数的方式只能使用有效的 Python 标识符作为键。 其他方式则可使用任何有效的键。

这些是字典所支持的操作（因而自定义的映射类型也应当支持）：


@deffn {Describe} list(d)

返回字典 @emph{d} 中使用的所有键的列表。
@end deffn


@deffn {Describe} len(d)

返回字典 @emph{d} 中的项数。
@end deffn


@deffn {Describe} d[key]

返回 @emph{d} 中以 @emph{key} 为键的项。 如果映射中不存在 @emph{key} 则会引发 @ref{2c7,,KeyError}。

@geindex __missing__()

如果字典的子类定义了方法 @ref{b34,,__missing__()} 并且 @emph{key} 不存在，则 @code{d[key]} 操作将调用该方法并附带键 @emph{key} 作为参数。 @code{d[key]} 随后将返回或引发 @code{__missing__(key)} 调用所返回或引发的任何对象或异常。 没有其他操作或方法会发起调用 @ref{b34,,__missing__()}。 如果未定义 @ref{b34,,__missing__()}，则会引发 @ref{2c7,,KeyError}。 @ref{b34,,__missing__()} 必须是一个方法；它不能是一个实例变量:

@example
>>> class Counter(dict):
...     def __missing__(self, key):
...         return 0
>>> c = Counter()
>>> c['red']
0
>>> c['red'] += 1
>>> c['red']
1
@end example

上面的例子显示了 @ref{9d4,,collections.Counter} 实现的部分代码。 还有另一个不同的 @code{__missing__} 方法是由 @ref{b33,,collections.defaultdict} 所使用的。
@end deffn


@deffn {Describe} d[key] = value

将 @code{d[key]} 设为 @emph{value}。
@end deffn


@deffn {Describe} del d[key]

将 @code{d[key]} 从 @emph{d} 中移除。 如果映射中不存在 @emph{key} 则会引发 @ref{2c7,,KeyError}。
@end deffn


@deffn {Describe} key in d

如果 @emph{d} 中存在键 @emph{key} 则返回 @code{True}，否则返回 @code{False}。
@end deffn


@deffn {Describe} key not in d

等价于 @code{not key in d}。
@end deffn


@deffn {Describe} iter(d)

返回以字典的键为元素的迭代器。 这是 @code{iter(d.keys())} 的快捷方式。
@end deffn

@geindex clear() (dict 方法)
@anchor{library/stdtypes dict clear}@anchor{166c}
@deffn {方法} clear ()

移除字典中的所有元素。
@end deffn

@geindex copy() (dict 方法)
@anchor{library/stdtypes dict copy}@anchor{440}
@deffn {方法} copy ()

返回原字典的浅拷贝。
@end deffn

@geindex fromkeys() (dict 类方法)
@anchor{library/stdtypes dict fromkeys}@anchor{166d}
@deffn {方法} classmethod fromkeys (iterable[, value])

使用来自 @emph{iterable} 的键创建一个新字典，并将键值设为 @emph{value}。

@ref{166d,,fromkeys()} 是一个返回新字典的类方法。 @emph{value} 默认为 @code{None}。 所有值都只引用一个单独的实例，因此让 @emph{value} 成为一个可变对象例如空列表通常是没有意义的。 要获取不同的值，请改用 @ref{648,,字典推导式}。
@end deffn

@geindex get() (dict 方法)
@anchor{library/stdtypes dict get}@anchor{166e}
@deffn {方法} get (key[, default])

如果 @emph{key} 存在于字典中则返回 @emph{key} 的值，否则返回 @emph{default}。 如果 @emph{default} 未给出则默认为 @code{None}，因而此方法绝不会引发 @ref{2c7,,KeyError}。
@end deffn

@geindex items() (dict 方法)
@anchor{library/stdtypes dict items}@anchor{c24}
@deffn {方法} items ()

返回由字典项 (@code{(键, 值)} 对) 组成的一个新视图。 参见 @ref{166f,,视图对象文档}。
@end deffn

@geindex keys() (dict 方法)
@anchor{library/stdtypes dict keys}@anchor{c23}
@deffn {方法} keys ()

返回由字典键组成的一个新视图。 参见 @ref{166f,,视图对象文档}。
@end deffn

@geindex pop() (dict 方法)
@anchor{library/stdtypes dict pop}@anchor{1670}
@deffn {方法} pop (key[, default])

如果 @emph{key} 存在于字典中则将其移除并返回其值，否则返回 @emph{default}。 如果 @emph{default} 未给出且 @emph{key} 不存在于字典中，则会引发 @ref{2c7,,KeyError}。
@end deffn

@geindex popitem() (dict 方法)
@anchor{library/stdtypes dict popitem}@anchor{1671}
@deffn {方法} popitem ()

从字典中移除并返回一个 @code{(键, 值)} 对。 键值对会按 @abbr{LIFO,后进先出} 的顺序被返回。

@ref{1671,,popitem()} 适用于对字典进行消耗性的迭代，这在集合算法中经常被使用。 如果字典为空，调用 @ref{1671,,popitem()} 将引发 @ref{2c7,,KeyError}。


在 3.7 版更改: 现在会确保采用 LIFO 顺序。 在之前的版本中，@ref{1671,,popitem()} 会返回一个任意的键/值对。

@end deffn


@deffn {Describe} reversed(d)

返回一个逆序获取字典键的迭代器。 这是 @code{reversed(d.keys())} 的快捷方式。


3.8 新版功能.

@end deffn

@geindex setdefault() (dict 方法)
@anchor{library/stdtypes dict setdefault}@anchor{9b9}
@deffn {方法} setdefault (key[, default])

如果字典存在键 @emph{key} ，返回它的值。如果不存在，插入值为 @emph{default} 的键 @emph{key} ，并返回 @emph{default} 。 @emph{default} 默认为 @code{None}。
@end deffn

@geindex update() (dict 方法)
@anchor{library/stdtypes dict update}@anchor{dc2}
@deffn {方法} update ([other])

使用来自 @emph{other} 的键/值对更新字典，覆盖原有的键。 返回 @code{None}。

@ref{dc2,,update()} 接受另一个字典对象，或者一个包含键/值对（以长度为二的元组或其他可迭代对象表示）的可迭代对象。 如果给出了关键字参数，则会以其所指定的键/值对更新字典: @code{d.update(red=1, blue=2)}。
@end deffn

@geindex values() (dict 方法)
@anchor{library/stdtypes dict values}@anchor{c25}
@deffn {方法} values ()

返回由字典值组成的一个新视图。 参见 @ref{166f,,视图对象文档}。

两个 @code{dict.values()} 视图之间的相等性比较将总是返回 @code{False}。 这在 @code{dict.values()} 与其自身比较时也同样适用:

@example
>>> d = @{'a': 1@}
>>> d.values() == d.values()
False
@end example
@end deffn

两个字典的比较当且仅当它们具有相同的 @code{(键, 值)} 对时才会相等（不考虑顺序）。 排序比较 ('<', '<=', '>=', '>') 会引发 @ref{192,,TypeError}。

字典会保留插入时的顺序。 请注意对键的更新不会影响顺序。 删除并再次添加的键将被插入到末尾。

@example
>>> d = @{"one": 1, "two": 2, "three": 3, "four": 4@}
>>> d
@{'one': 1, 'two': 2, 'three': 3, 'four': 4@}
>>> list(d)
['one', 'two', 'three', 'four']
>>> list(d.values())
[1, 2, 3, 4]
>>> d["one"] = 42
>>> d
@{'one': 42, 'two': 2, 'three': 3, 'four': 4@}
>>> del d["two"]
>>> d["two"] = None
>>> d
@{'one': 42, 'three': 3, 'four': 4, 'two': None@}
@end example


在 3.7 版更改: 字典顺序会确保为插入顺序。 此行为是自 3.6 版开始的 CPython 实现细节。


字典和字典视图都是可逆的。

@example
>>> d = @{"one": 1, "two": 2, "three": 3, "four": 4@}
>>> d
@{'one': 1, 'two': 2, 'three': 3, 'four': 4@}
>>> list(reversed(d))
['four', 'three', 'two', 'one']
>>> list(reversed(d.values()))
[4, 3, 2, 1]
>>> list(reversed(d.items()))
[('four', 4), ('three', 3), ('two', 2), ('one', 1)]
@end example


在 3.8 版更改: 字典现在是可逆的。

@end deffn


@subsubheading 参见


@ref{ab1,,types.MappingProxyType} 可被用来创建一个 @ref{1b8,,dict} 的只读视图。


@menu
* 字典视图对象:: 

@end menu

@node 字典视图对象,,,映射类型 --- dict
@anchor{library/stdtypes dict-views}@anchor{166f}@anchor{library/stdtypes dictionary-view-objects}@anchor{1672}
@subsubsection 字典视图对象


由 @ref{c23,,dict.keys()}, @ref{c25,,dict.values()} 和 @ref{c24,,dict.items()} 所返回的对象是 @emph{视图对象}。 该对象提供字典条目的一个动态视图，这意味着当字典改变时，视图也会相应改变。

字典视图可以被迭代以产生与其对应的数据，并支持成员检测：


@deffn {Describe} len(dictview)

返回字典中的条目数。
@end deffn


@deffn {Describe} iter(dictview)

返回字典中的键、值或项（以 @code{(键, 值)} 为元素的元组表示）的迭代器。

键和值是按插入时的顺序进行迭代的。 这样就允许使用 @ref{c2b,,zip()} 来创建 @code{(值, 键)} 对: @code{pairs = zip(d.values(), d.keys())}。 另一个创建相同列表的方式是 @code{pairs = [(v, k) for (k, v) in d.items()]}.

在添加或删除字典中的条目期间对视图进行迭代可能引发 @ref{2ba,,RuntimeError} 或者无法完全迭代所有条目。


在 3.7 版更改: 字典顺序会确保为插入顺序。

@end deffn


@deffn {Describe} x in dictview

如果 @emph{x} 是对应字典中存在的键、值或项（在最后一种情况下 @emph{x} 应为一个 @code{(键, 值)} 元组） 则返回 @code{True}。
@end deffn


@deffn {Describe} reversed(dictview)

返回一个逆序获取字典键、值或项的迭代器。 视图将按与插入时相反的顺序进行迭代。


在 3.8 版更改: 字典视图现在是可逆的。

@end deffn

键视图类似于集合，因为其条目不重复且可哈希。 如果所有值都是可哈希的，即 @code{(键, 值)} 对也是不重复且可哈希的，那么条目视图也会类似于集合。 （值视图则不被视为类似于集合，因其条目通常都是有重复的。） 对于类似于集合的视图，为抽象基类 @ref{1673,,collections.abc.Set} 所定义的全部操作都是有效的 (例如 @code{==}, @code{<} 或 @code{^})。

一个使用字典视图的示例:

@example
>>> dishes = @{'eggs': 2, 'sausage': 1, 'bacon': 1, 'spam': 500@}
>>> keys = dishes.keys()
>>> values = dishes.values()

>>> # iteration
>>> n = 0
>>> for val in values:
...     n += val
>>> print(n)
504

>>> # keys and values are iterated over in the same order (insertion order)
>>> list(keys)
['eggs', 'sausage', 'bacon', 'spam']
>>> list(values)
[2, 1, 1, 500]

>>> # view objects are dynamic and reflect dict changes
>>> del dishes['eggs']
>>> del dishes['sausage']
>>> list(keys)
['bacon', 'spam']

>>> # set operations
>>> keys & @{'eggs', 'bacon', 'salad'@}
@{'bacon'@}
>>> keys ^ @{'sausage', 'juice'@}
@{'juice', 'sausage', 'bacon', 'spam'@}
@end example

@node 上下文管理器类型,其他内置类型,映射类型 --- dict,内置类型
@anchor{library/stdtypes context-manager-types}@anchor{1674}@anchor{library/stdtypes typecontextmanager}@anchor{1420}
@subsection 上下文管理器类型


@geindex context manager
@geindex context management protocol
@geindex protocol; context management

Python 的 @ref{6e3,,with} 语句支持通过上下文管理器所定义的运行时上下文这一概念。 此对象的实现使用了一对专门方法，允许用户自定义类来定义运行时上下文，在语句体被执行前进入该上下文，并在语句执行完毕时退出该上下文：

@geindex __enter__() (contextmanager 方法)
@anchor{library/stdtypes contextmanager __enter__}@anchor{1675}
@deffn {方法} contextmanager.__enter__ ()

进入运行时上下文并返回此对象或关联到该运行时上下文的其他对象。 此方法的返回值会绑定到使用此上下文管理器的 @ref{6e3,,with} 语句的 @code{as} 子句中的标识符。

一个返回其自身的上下文管理器的例子是 @ref{b3b,,file object}。 文件对象会从 __enter__() 返回其自身，以允许 @ref{4ea,,open()} 被用作 @ref{6e3,,with} 语句中的上下文表达式。

一个返回关联对象的上下文管理器的例子是 @ref{1676,,decimal.localcontext()} 所返回的对象。 此种管理器会将活动的 decimal 上下文设为原始 decimal 上下文的一个副本并返回该副本。 这允许对 @ref{6e3,,with} 语句的语句体中的当前 decimal 上下文进行更改，而不会影响 @code{with} 语句以外的代码。
@end deffn

@geindex __exit__() (contextmanager 方法)
@anchor{library/stdtypes contextmanager __exit__}@anchor{1677}
@deffn {方法} contextmanager.__exit__ (exc_type, exc_val, exc_tb)

退出运行时上下文并返回一个布尔值旗标来表明所发生的任何异常是否应当被屏蔽。 如果在执行 @ref{6e3,,with} 语句的语句体期间发生了异常，则参数会包含异常的类型、值以及回溯信息。 在其他情况下三个参数均为 @code{None}。

自此方法返回一个真值将导致 @ref{6e3,,with} 语句屏蔽异常并继续执行紧随在 @code{with} 语句之后的语句。 否则异常将在此方法结束执行后继续传播。 在此方法执行期间发生的异常将会取代 @code{with} 语句的语句体中发生的任何异常。

传入的异常绝对不应当被显式地重新引发 —— 相反地，此方法应当返回一个假值以表明方法已成功完成并且不希望屏蔽被引发的异常。 这允许上下文管理代码方便地检测 @ref{1677,,__exit__()} 方法是否确实已失败。
@end deffn

Python 定义了一些上下文管理器来支持简易的线程同步、文件或其他对象的快速关闭，以及更方便地操作活动的十进制算术上下文。 除了实现上下文管理协议以外，不同类型不会被特殊处理。 请参阅 @ref{24,,contextlib} 模块查看相关的示例。

Python 的 @ref{99c,,generator} 和 @ref{b77,,contextlib.contextmanager} 装饰器提供了实现这些协议的便捷方式。 如果使用 @ref{b77,,contextlib.contextmanager} 装饰器来装饰一个生成器函数，它将返回一个实现了必要的 @ref{c8e,,__enter__()} and @ref{c8f,,__exit__()} 方法的上下文管理器，而不再是由未经装饰的生成器函数所产生的迭代器。

请注意，Python/C API 中 Python 对象的类型结构中并没有针对这些方法的专门槽位。 想要定义这些方法的扩展类型必须将它们作为普通的 Python 可访问方法来提供。 与设置运行时上下文的开销相比，单个类字典查找的开销可以忽略不计。

@node 其他内置类型,特殊属性,上下文管理器类型,内置类型
@anchor{library/stdtypes other-built-in-types}@anchor{1678}@anchor{library/stdtypes typesother}@anchor{1679}
@subsection 其他内置类型


解释器支持一些其他种类的对象。 这些对象大都仅支持一两种操作。

@menu
* 模块: 模块<2>. 
* 类与类实例:: 
* 函数:: 
* 方法:: 
* 代码对象:: 
* 类型对象:: 
* 空对象:: 
* 省略符对象:: 
* 未实现对象:: 
* 布尔值:: 
* 内部对象:: 

@end menu

@node 模块<2>,类与类实例,,其他内置类型
@anchor{library/stdtypes modules}@anchor{167a}@anchor{library/stdtypes typesmodules}@anchor{167b}
@subsubsection 模块


模块唯一的特殊操作是属性访问: @code{m.name}，这里 @emph{m} 为一个模块而 @emph{name} 访问定义在 @emph{m} 的符号表中的一个名称。 模块属性可以被赋值。 （请注意 @ref{c16,,import} 语句严格来说也是对模块对象的一种操作；@code{import foo} 不要求存在一个名为 @emph{foo} 的模块对象，而是要求存在一个对于名为 @emph{foo} 的模块的 (永久性) @emph{定义}。）

每个模块都有一个特殊属性 @ref{4f6,,__dict__}。 这是包含模块的符号表的字典。 修改此字典将实际改变模块的符号表，但是无法直接对 @ref{4f6,,__dict__} 赋值 (你可以写 @code{m.__dict__['a'] = 1}，这会将 @code{m.a} 定义为 @code{1}，但是你不能写 @code{m.__dict__ = @{@}})。 不建议直接修改 @ref{4f6,,__dict__}。

内置于解释器中的模块会写成这样: @code{<module 'sys' (built-in)>}。 如果是从一个文件加载，则会写成 @code{<module 'os' from '/usr/local/lib/pythonX.Y/os.pyc'>}。

@node 类与类实例,函数,模块<2>,其他内置类型
@anchor{library/stdtypes classes-and-class-instances}@anchor{167c}@anchor{library/stdtypes typesobjects}@anchor{167d}
@subsubsection 类与类实例


关于这些类型请参阅 @ref{13b4,,对象、值与类型} 和 @ref{c63,,类定义}。

@node 函数,方法,类与类实例,其他内置类型
@anchor{library/stdtypes functions}@anchor{167e}@anchor{library/stdtypes typesfunctions}@anchor{167f}
@subsubsection 函数


函数对象是通过函数定义创建的。 对函数对象的唯一操作是调用它: @code{func(argument-list)}。

实际上存在两种不同的函数对象：内置函数和用户自定义函数。 两者支持同样的操作（调用函数），但实现方式不同，因此对象类型也不同。

更多信息请参阅 @ref{11f0,,函数定义}。

@node 方法,代码对象,函数,其他内置类型
@anchor{library/stdtypes methods}@anchor{1680}@anchor{library/stdtypes typesmethods}@anchor{1681}
@subsubsection 方法


@geindex 对象; method

方法是使用属性表示法来调用的函数。 存在两种形式：内置方法（例如列表的 @code{append()} 方法）和类实例方法。 内置方法由支持它们的类型来描述。

如果你通过一个实例来访问方法（即定义在类命名空间内的函数），你会得到一个特殊对象: @emph{绑定方法} (或称 @emph{实例方法}) 对象。 当被调用时，它会将 @code{self} 参数添加到参数列表。 绑定方法具有两个特殊的只读属性: @code{m.__self__} 操作该方法的对象，而 @code{m.__func__} 是实现该方法的函数。 调用 @code{m(arg-1, arg-2, ..., arg-n)} 完全等价于调用 @code{m.__func__(m.__self__, arg-1, arg-2, ..., arg-n)}。

与函数对象类似，绑定方法对象也支持获取任意属性。 但是，由于方法属性实际上保存于下层的函数对象中 (@code{meth.__func__})，因此不允许设置绑定方法的方法属性。 尝试设置方法的属性将会导致引发 @ref{393,,AttributeError}。 想要设置方法属性，你必须在下层的函数对象中显式地对其进行设置:

@example
>>> class C:
...     def method(self):
...         pass
...
>>> c = C()
>>> c.method.whoami = 'my name is method'  # can't set on the method
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'method' object has no attribute 'whoami'
>>> c.method.__func__.whoami = 'my name is method'
>>> c.method.whoami
'my name is method'
@end example

更多信息请参阅 @ref{13b8,,标准类型层级结构}。

@geindex object; code
@geindex code object

@node 代码对象,类型对象,方法,其他内置类型
@anchor{library/stdtypes bltin-code-objects}@anchor{1682}@anchor{library/stdtypes code-objects}@anchor{1683}
@subsubsection 代码对象


@geindex 內置函数; compile
@geindex __code__ (function object attribute)

代码对象被具体实现用来表示“伪编译”的可执行 Python 代码，例如一个函数体。 它们不同于函数对象，因为它们不包含对其全局执行环境的引用。 代码对象由内置的 @ref{1b4,,compile()} 函数返回，并可通过从函数对象的 @code{__code__} 属性从中提取。 另请参阅 @ref{1b,,code} 模块。

@geindex 內置函数; exec
@geindex 內置函数; eval

可以通过将代码对象（而非源码字符串）传给 @ref{c3d,,exec()} 或 @ref{b89,,eval()} 内置函数来执行或求值。

更多信息请参阅 @ref{13b8,,标准类型层级结构}。

@node 类型对象,空对象,代码对象,其他内置类型
@anchor{library/stdtypes bltin-type-objects}@anchor{15a0}@anchor{library/stdtypes type-objects}@anchor{1684}
@subsubsection 类型对象


@geindex 內置函数; type
@geindex 模块; types

类型对象表示各种对象类型。 对象的类型可通过内置函数 @ref{603,,type()} 来获取。 类型没有特殊的操作。 标准库模块 @ref{118,,types} 定义了所有标准内置类型的名称。

类型以这样的写法来表示: @code{<class 'int'>}。

@node 空对象,省略符对象,类型对象,其他内置类型
@anchor{library/stdtypes bltin-null-object}@anchor{1685}@anchor{library/stdtypes the-null-object}@anchor{1686}
@subsubsection 空对象


此对象会由不显式地返回值的函数所返回。 它不支持任何特殊的操作。 空对象只有一种值 @code{None} (这是个内置名称)。 @code{type(None)()} 会生成同一个单例。

该对象的写法为 @code{None}。

@geindex ...; ellipsis literal

@node 省略符对象,未实现对象,空对象,其他内置类型
@anchor{library/stdtypes bltin-ellipsis-object}@anchor{1687}@anchor{library/stdtypes the-ellipsis-object}@anchor{1688}
@subsubsection 省略符对象


此对象常被用于切片 (参见 @ref{14b2,,切片})。 它不支持任何特殊的操作。 省略符对象只有一种值 @ref{15a4,,Ellipsis} (这是个内置名称)。 @code{type(Ellipsis)()} 会生成 @ref{15a4,,Ellipsis} 单例。

该对象的写法为 @code{Ellipsis} 或 @code{...}。

@node 未实现对象,布尔值,省略符对象,其他内置类型
@anchor{library/stdtypes bltin-notimplemented-object}@anchor{1689}@anchor{library/stdtypes the-notimplemented-object}@anchor{168a}
@subsubsection 未实现对象


此对象会被作为比较和二元运算被应用于它们所不支持的类型时的返回值。 请参阅 @ref{14da,,比较运算} 了解更多信息。 未实现对象只有一种值 @code{NotImplemented}。 @code{type(NotImplemented)()} 会生成这个单例。

该对象的写法为 @code{NotImplemented}。

@node 布尔值,内部对象,未实现对象,其他内置类型
@anchor{library/stdtypes bltin-boolean-values}@anchor{157d}@anchor{library/stdtypes boolean-values}@anchor{168b}
@subsubsection 布尔值


布尔值是两个常量对象 @code{False} 和 @code{True}。 它们被用来表示逻辑上的真假（不过其他值也可被当作真值或假值）。 在数字类的上下文中（例如被用作算术运算符的参数时），它们的行为分别类似于整数 0 和 1。 内置函数 @ref{183,,bool()} 可被用来将任意值转换为布尔值，只要该值可被解析为一个逻辑值（参见之前的 @ref{157c,,逻辑值检测} 部分）。

@geindex False
@geindex True
@geindex Boolean; values

该对象的写法分别为 @code{False} 和 @code{True}。

@node 内部对象,,布尔值,其他内置类型
@anchor{library/stdtypes internal-objects}@anchor{168c}@anchor{library/stdtypes typesinternal}@anchor{168d}
@subsubsection 内部对象


有关此对象的信息请参阅 @ref{13b8,,标准类型层级结构}。 其中描述了栈帧对象、回溯对象以及切片对象等等。

@node 特殊属性,,其他内置类型,内置类型
@anchor{library/stdtypes special-attributes}@anchor{168e}@anchor{library/stdtypes specialattrs}@anchor{168f}
@subsection 特殊属性


语言实现为部分对象类型添加了一些特殊的只读属性，它们具有各自的作用。 其中一些并不会被 @ref{d2c,,dir()} 内置函数所列出。

@geindex __dict__ (object 属性)
@anchor{library/stdtypes object __dict__}@anchor{4f6}
@deffn {属性} object.__dict__

一个字典或其他类型的映射对象，用于存储对象的（可写）属性。
@end deffn

@geindex __class__ (instance 属性)
@anchor{library/stdtypes instance __class__}@anchor{e03}
@deffn {属性} instance.__class__

类实例所属的类。
@end deffn

@geindex __bases__ (class 属性)
@anchor{library/stdtypes class __bases__}@anchor{e02}
@deffn {属性} class.__bases__

由类对象的基类所组成的元组。
@end deffn

@geindex __name__ (definition 属性)
@anchor{library/stdtypes definition __name__}@anchor{c60}
@deffn {属性} definition.__name__

类、函数、方法、描述器或生成器实例的名称。
@end deffn

@geindex __qualname__ (definition 属性)
@anchor{library/stdtypes definition __qualname__}@anchor{13c1}
@deffn {属性} definition.__qualname__

类、函数、方法、描述器或生成器实例的 @ref{13c2,,qualified name}。


3.3 新版功能.

@end deffn

@geindex __mro__ (class 属性)
@anchor{library/stdtypes class __mro__}@anchor{159d}
@deffn {属性} class.__mro__

此属性是由类组成的元组，在方法解析期间会基于它来查找基类。
@end deffn

@geindex mro() (class 方法)
@anchor{library/stdtypes class mro}@anchor{1690}
@deffn {方法} class.mro ()

此方法可被一个元类来重载，以为其实例定制方法解析顺序。 它会在类实例化时被调用，其结果存储于 @ref{159d,,__mro__} 之中。
@end deffn

@geindex __subclasses__() (class 方法)
@anchor{library/stdtypes class __subclasses__}@anchor{1691}
@deffn {方法} class.__subclasses__ ()

每个类会保存由对其直接子类的弱引用组成的列表。 此方法将返回一个由仍然存在的所有此类引用组成的列表。 例如:

@example
>>> int.__subclasses__()
[<class 'bool'>]
@end example
@end deffn

@subsubheading 备注


@node 内置异常,文本处理服务,内置类型,Python 标准库
@anchor{library/exceptions doc}@anchor{1692}@anchor{library/exceptions bltin-exceptions}@anchor{1242}@anchor{library/exceptions built-in-exceptions}@anchor{1693}
@section 内置异常


@geindex 语句; try
@geindex 语句; except

在 Python 中，所有异常必须为一个派生自 @ref{1a8,,BaseException} 的类的实例。 在带有提及一个特定类的 @ref{b37,,except} 子句的 @ref{d6b,,try} 语句中，该子句也会处理任何派生自该类的异常类（但不处理 @emph{它} 所派生出的异常类）。 通过子类化创建的两个不相关异常类永远是不等效的，既使它们具有相同的名称。

@geindex 语句; raise

下面列出的内置异常可通过解释器或内置函数来生成。除非另有说明，它们都会具有一个提示导致错误详细原因的“关联值”。 这可以是一个字符串或由多个信息项（例如一个错误码和一个解释错误的字符串）组成的元组。 关联值通常会作为参数被传递给异常类的构造器。

用户代码可以引发内置异常。 这可被用于测试异常处理程序或报告错误条件，“就像” 在解释器引发了相同异常的情况时一样；但是请注意，没有任何机制能防止用户代码引发不适当的错误。

内置异常类可以被子类化以定义新的异常；鼓励程序员从 @ref{1a9,,Exception} 类或它的某个子类而不是从 @ref{1a8,,BaseException} 来派生新的异常。 关于定义异常的更多信息可以在 Python 教程的 @ref{1246,,用户自定义异常} 部分查看。

当在 @ref{b37,,except} 或 @ref{182,,finally} 子句中引发（或重新引发）异常时，@code{__context__} 会被自动设为所捕获的最后一个异常；如果新的异常未被处理，则最终显示的回溯信息将包括原始的异常和最后的异常。

当引发一个新的异常（而不是简单地使用 @code{raise} 来重新引发当前在处理的异常）时，隐式的异常上下文可以通过使用带有 @ref{c3b,,raise} 的 @ref{c3e,,from} 来补充一个显式的原因:

@example
raise new_exc from original_exc
@end example

跟在 @ref{c3e,,from} 之后的表达式必须为一个异常或 @code{None}。 它将在所引发的异常上被设置为 @code{__cause__}。 设置 @code{__cause__} 还会隐式地将 @code{__suppress_context__} 属性设为 @code{True}，这样使用 @code{raise new_exc from None} 可以有效地将旧异常替换为新异常来显示其目的 (例如将 @ref{2c7,,KeyError} 转换为 @ref{393,,AttributeError})，同时让旧异常在 @code{__context__} 中保持可用状态以便在调试时进行内省。

除了异常本身的回溯以外，默认的回溯还会显示这些串连的异常。 @code{__cause__} 中的显式串连异常如果存在将总是显示。 @code{__context__} 中的隐式串连异常仅在 @code{__cause__} 为 @ref{157,,None} 并且 @code{__suppress_context__} 为假值时显示。

不论在哪种情况下，异常本身总会在任何串连异常之后显示，以便回溯的最后一行总是显示所引发的最后一个异常。

@menu
* 基类:: 
* 具体异常:: 
* 警告:: 
* 异常层次结构:: 

@end menu

@node 基类,具体异常,,内置异常
@anchor{library/exceptions base-classes}@anchor{1694}
@subsection 基类


下列异常主要被用作其他异常的基类。

@geindex BaseException
@anchor{library/exceptions BaseException}@anchor{1a8}
@deffn {例外} BaseException

所有内置异常的基类。 它不应该被用户自定义类直接继承 (这种情况请使用 @ref{1a9,,Exception})。 如果在此类的实例上调用 @ref{329,,str()}，则会返回实例的参数表示，或者当没有参数时返回空字符串。

@geindex args (BaseException 属性)
@anchor{library/exceptions BaseException args}@anchor{1695}
@deffn {属性} args

传给异常构造器的参数元组。 某些内置异常 (例如 @ref{1d3,,OSError}) 接受特定数量的参数并赋予此元组中的元素特殊的含义，而其他异常通常只接受一个给出错误信息的单独字符串。
@end deffn

@geindex with_traceback() (BaseException 方法)
@anchor{library/exceptions BaseException with_traceback}@anchor{1696}
@deffn {方法} with_traceback (tb)

此方法将 @emph{tb} 设为异常的新回溯信息并返回该异常对象。 它通常以如下的形式在异常处理程序中使用:

@example
try:
    ...
except SomeException:
    tb = sys.exc_info()[2]
    raise OtherException(...).with_traceback(tb)
@end example
@end deffn
@end deffn

@geindex Exception
@anchor{library/exceptions Exception}@anchor{1a9}
@deffn {例外} Exception

所有内置的非系统退出类异常都派生自此类。 所有用户自定义异常也应当派生自此类。
@end deffn

@geindex ArithmeticError
@anchor{library/exceptions ArithmeticError}@anchor{1697}
@deffn {例外} ArithmeticError

此基类用于派生针对各种算术类错误而引发的内置异常: @ref{95a,,OverflowError}, @ref{1241,,ZeroDivisionError}, @ref{1698,,FloatingPointError}。
@end deffn

@geindex BufferError
@anchor{library/exceptions BufferError}@anchor{1699}
@deffn {例外} BufferError

当与 @ref{15d6,,缓冲区} 相关的操作无法执行时将被引发。
@end deffn

@geindex LookupError
@anchor{library/exceptions LookupError}@anchor{15f6}
@deffn {例外} LookupError

此基类用于派生当映射或序列所使用的键或索引无效时引发的异常: @ref{e6e,,IndexError}, @ref{2c7,,KeyError}。 这可以通过 @ref{169a,,codecs.lookup()} 来直接引发。
@end deffn

@node 具体异常,警告,基类,内置异常
@anchor{library/exceptions concrete-exceptions}@anchor{169b}
@subsection 具体异常


以下异常属于经常被引发的异常。

@geindex AssertionError
@anchor{library/exceptions AssertionError}@anchor{fc1}
@deffn {例外} AssertionError

@geindex 语句; assert

当 @ref{dff,,assert} 语句失败时将被引发。
@end deffn

@geindex AttributeError
@anchor{library/exceptions AttributeError}@anchor{393}
@deffn {例外} AttributeError

当属性引用 (参见 @ref{14ab,,属性引用}) 或赋值失败时将被引发。 （当一个对象根本不支持属性引用或属性赋值时则将引发 @ref{192,,TypeError}。）
@end deffn

@geindex EOFError
@anchor{library/exceptions EOFError}@anchor{c65}
@deffn {例外} EOFError

当 @ref{c64,,input()} 函数未读取任何数据即达到文件结束条件 (EOF) 时将被引发。 （另外，@code{io.IOBase.read()} 和 @ref{169c,,io.IOBase.readline()} 方法在遇到 EOF 则将返回一个空字符串。）
@end deffn

@geindex FloatingPointError
@anchor{library/exceptions FloatingPointError}@anchor{1698}
@deffn {例外} FloatingPointError

目前未被使用。
@end deffn

@geindex GeneratorExit
@anchor{library/exceptions GeneratorExit}@anchor{d2b}
@deffn {例外} GeneratorExit

当一个 @ref{99c,,generator} 或 @ref{1a6,,coroutine} 被关闭时将被引发；参见 @ref{142b,,generator.close()} 和 @ref{142a,,coroutine.close()}。 它直接继承自 @ref{1a8,,BaseException} 而不是 @ref{1a9,,Exception}，因为从技术上来说它并不是一个错误。
@end deffn

@geindex ImportError
@anchor{library/exceptions ImportError}@anchor{32d}
@deffn {例外} ImportError

当 @ref{c16,,import} 语句尝试加载模块遇到麻烦时将被引发。 并且当 @code{from ... import} 中的 "from list" 存在无法找到的名称时也会被引发。

@code{name} 与 @code{path} 属性可通过对构造器使用仅关键字参数来设定。 设定后它们将分别表示被尝试导入的模块名称与触发异常的任意文件所在路径。


在 3.3 版更改: 添加了 @code{name} 与 @code{path} 属性。

@end deffn

@geindex ModuleNotFoundError
@anchor{library/exceptions ModuleNotFoundError}@anchor{392}
@deffn {例外} ModuleNotFoundError

@ref{32d,,ImportError} 的子类，当一个模块无法被定位时将由 @ref{c16,,import} 引发。 当在 @ref{eb5,,sys.modules} 中找到 @code{None} 时也会被引发。


3.6 新版功能.

@end deffn

@geindex IndexError
@anchor{library/exceptions IndexError}@anchor{e6e}
@deffn {例外} IndexError

当序列抽取超出范围时将被引发。 （切片索引会被静默截短到允许的范围；如果指定索引不是整数则 @ref{192,,TypeError} 会被引发。）

@c XXX xref to sequences
@end deffn

@geindex KeyError
@anchor{library/exceptions KeyError}@anchor{2c7}
@deffn {例外} KeyError

当在现有键集合中找不到指定的映射（字典）键时将被引发。

@c XXX xref to mapping objects?
@end deffn

@geindex KeyboardInterrupt
@anchor{library/exceptions KeyboardInterrupt}@anchor{197}
@deffn {例外} KeyboardInterrupt

当用户按下中断键 (通常为 @code{Control-C} 或 @code{Delete}) 时将被引发。 在执行期间，会定期检测中断信号。 该异常继承自 @ref{1a8,,BaseException} 以确保不会被处理 @ref{1a9,,Exception} 的代码意外捕获，这样可以避免退出解释器。
@end deffn

@geindex MemoryError
@anchor{library/exceptions MemoryError}@anchor{f9f}
@deffn {例外} MemoryError

当一个操作耗尽内存但情况仍可（通过删除一些对象）进行挽救时将被引发。 关联的值是一个字符串，指明是哪种（内部）操作耗尽了内存。 请注意由于底层的内存管理架构（C 的 @code{malloc()} 函数），解释器也许并不总是能够从这种情况下完全恢复；但它毕竟可以引发一个异常，这样就能打印出栈回溯信息，以便找出导致问题的失控程序。
@end deffn

@geindex NameError
@anchor{library/exceptions NameError}@anchor{d74}
@deffn {例外} NameError

当某个局部或全局名称未找到时将被引发。 此异常仅用于非限定名称。 关联的值是一条错误信息，其中包含未找到的名称。
@end deffn

@geindex NotImplementedError
@anchor{library/exceptions NotImplementedError}@anchor{609}
@deffn {例外} NotImplementedError

此异常派生自 @ref{2ba,,RuntimeError}。 在用户自定义的基类中，抽象方法应当在其要求所派生类重载该方法，或是在其要求所开发的类提示具体实现尚待添加时引发此异常。

@cartouche
@quotation 注解 
它不应当用来表示一个运算符或方法根本不能被支持 -- 在此情况下应当让特定运算符 / 方法保持未定义，或者在子类中将其设为 @ref{157,,None}。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
@code{NotImplementedError} 和 @code{NotImplemented} 不可互换，即使它们有相似的名称和用途。 请参阅 @ref{846,,NotImplemented} 了解有关何时使用它们的详细说明。
@end quotation
@end cartouche
@end deffn

@geindex OSError
@anchor{library/exceptions OSError}@anchor{1d3}
@deffn {例外} OSError ([arg])

@deffnx {例外} OSError (errno, strerror[, filename[, winerror[, filename2]]])

@geindex 模块; errno

此异常在一个系统函数返回系统相关的错误时将被引发，此类错误包括 I/O 操作失败例如 "文件未找到" 或 "磁盘已满" 等（不包括非法参数类型或其他偶然性错误）。

构造器的第二种形式可设置如下所述的相应属性。 如果未指定这些属性则默认为 @ref{157,,None}。 为了能向下兼容，如果传入了三个参数，则 @ref{1695,,args} 属性将仅包含由前两个构造器参数组成的 2 元组。

构造器实际返回的往往是 @ref{1d3,,OSError} 的某个子类，如下文 @ref{169d,,OS exceptions} 中所描述的。 具体的子类取决于最终的 @ref{169e,,errno} 值。 此行为仅在直接或通过别名来构造 @ref{1d3,,OSError} 时发生，并且在子类化时不会被继承。

@geindex errno (OSError 属性)
@anchor{library/exceptions OSError errno}@anchor{169e}
@deffn {属性} errno

来自于 C 变量 @code{errno} 的数字错误码。
@end deffn

@geindex winerror (OSError 属性)
@anchor{library/exceptions OSError winerror}@anchor{169f}
@deffn {属性} winerror

在 Windows 下，此参数将给出原生的 Windows 错误码。 而 @ref{169e,,errno} 属性将是该原生错误码在 POSIX 平台下的近似转换形式。

在 Windows 下，如果 @emph{winerror} 构造器参数是一个整数，则 @ref{169e,,errno} 属性会根据 Windows 错误码来确定，而 @emph{errno} 参数会被忽略。 在其他平台上，@emph{winerror} 参数会被忽略，并且 @ref{169f,,winerror} 属性将不存在。
@end deffn

@geindex strerror (OSError 属性)
@anchor{library/exceptions OSError strerror}@anchor{16a0}
@deffn {属性} strerror

操作系统所提供的相应错误信息。 它在 POSIX 平台中由 C 函数 @code{perror()} 来格式化，在 Windows 中则是由 @code{FormatMessage()}。
@end deffn

@geindex filename (OSError 属性)
@geindex filename2 (OSError 属性)
@anchor{library/exceptions OSError filename}@anchor{16a1}
@deffn {属性} filename
@anchor{library/exceptions OSError filename2}@anchor{16a2}
@deffnx {属性} filename2

对于与文件系统路径有关 (例如 @ref{4ea,,open()} 或 @ref{a37,,os.unlink()}) 的异常，@ref{16a1,,filename} 是传给函数的文件名。 对于涉及两个文件系统路径的函数 (例如 @ref{a33,,os.rename()})，@ref{16a2,,filename2} 将是传给函数的第二个文件名。
@end deffn


在 3.3 版更改: @ref{98d,,EnvironmentError}, @ref{98c,,IOError}, @ref{98e,,WindowsError}, @ref{98f,,socket.error}, @ref{990,,select.error} 与 @code{mmap.error} 已被合并到 @ref{1d3,,OSError}，构造器可能返回其中一个子类。



在 3.4 版更改: @ref{16a1,,filename} 属性现在将是传给函数的原始文件名，而不是经过编码或基于文件系统编码进行解码之后的名称。 此外还添加了 @emph{filename2} 构造器参数和属性。

@end deffn

@geindex OverflowError
@anchor{library/exceptions OverflowError}@anchor{95a}
@deffn {例外} OverflowError

当算术运算的结果大到无法表示时将被引发。 这对整数来说不可能发生（宁可引发 @ref{f9f,,MemoryError} 也不会放弃尝试）。 但是出于历史原因，有时也会在整数超出要求范围的情况下引发 OverflowError。 因为在 C 中缺少对浮点异常处理的标准化，大多数浮点运算都不会做检查。
@end deffn

@geindex RecursionError
@anchor{library/exceptions RecursionError}@anchor{62e}
@deffn {例外} RecursionError

此异常派生自 @ref{2ba,,RuntimeError}。 它会在解释器检测发现超过最大递归深度 (参见 @ref{e73,,sys.getrecursionlimit()}) 时被引发。


3.5 新版功能: 在此之前将只引发 @ref{2ba,,RuntimeError}。

@end deffn

@geindex ReferenceError
@anchor{library/exceptions ReferenceError}@anchor{e46}
@deffn {例外} ReferenceError

此异常将在使用 @ref{250,,weakref.proxy()} 函数所创建的弱引用来访问该引用的某个已被作为垃圾回收的属性时被引发。 有关弱引用的更多信息请参阅 @ref{128,,weakref} 模块。
@end deffn

@geindex RuntimeError
@anchor{library/exceptions RuntimeError}@anchor{2ba}
@deffn {例外} RuntimeError

当检测到一个不归属于任何其他类别的错误时将被引发。 关联的值是一个指明究竟发生了什么问题的字符串。
@end deffn

@geindex StopIteration
@anchor{library/exceptions StopIteration}@anchor{480}
@deffn {例外} StopIteration

由内置函数 @ref{67c,,next()} 和 @ref{fce,,iterator} 的 @ref{c5d,,__next__()} 方法所引发，用来表示该迭代器不能产生下一项。

该异常对象只有一个属性 @code{value}，它在构造该异常时作为参数给出，默认值为 @ref{157,,None}。

当一个 @ref{99c,,generator} 或 @ref{1a6,,coroutine} 函数返回时，将引发一个新的 @ref{480,,StopIteration} 实例，函数返回的值将被用作异常构造器的 @code{value} 形参。

如果某个生成器代码直接或间接地引发了 @ref{480,,StopIteration}，它会被转换为 @ref{2ba,,RuntimeError} (并将 @ref{480,,StopIteration} 保留为导致新异常的原因)。


在 3.3 版更改: 添加了 @code{value} 属性及其被生成器函数用作返回值的功能。



在 3.5 版更改: 引入了通过 @code{from __future__ import generator_stop} 来实现 RuntimeError 转换，参见 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479}。



在 3.7 版更改: 默认对所有代码启用 
@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479}: 在生成器中引发的 @ref{480,,StopIteration} 错误将被转换为 @ref{2ba,,RuntimeError}。

@end deffn

@geindex StopAsyncIteration
@anchor{library/exceptions StopAsyncIteration}@anchor{fa5}
@deffn {例外} StopAsyncIteration

必须由一个 @ref{63f,,asynchronous iterator} 对象的 @ref{142d,,__anext__()} 方法来引发以停止迭代操作。


3.5 新版功能.

@end deffn

@geindex SyntaxError
@anchor{library/exceptions SyntaxError}@anchor{452}
@deffn {例外} SyntaxError

当解析器遇到语法错误时将被引发。 这可以发生在 @ref{c16,,import} 语句，对内置函数 @ref{c3d,,exec()} 或 @ref{b89,,eval()} 的调用，或者读取原始脚本或标准输入（也包括交互模式）的时候。

该类的实例包含有属性 @code{filename}, @code{lineno}, @code{offset} 和 @code{text} 用于方便地访问相应的详细信息。 异常实例的 @ref{329,,str()} 仅返回消息文本。
@end deffn

@geindex IndentationError
@anchor{library/exceptions IndentationError}@anchor{e71}
@deffn {例外} IndentationError

与不正确的缩进相关的语法错误的基类。 这是 @ref{452,,SyntaxError} 的一个子类。
@end deffn

@geindex TabError
@anchor{library/exceptions TabError}@anchor{e70}
@deffn {例外} TabError

当缩进包含对制表符和空格符不一致的使用时将被引发。 这是 @ref{e71,,IndentationError} 的一个子类。
@end deffn

@geindex SystemError
@anchor{library/exceptions SystemError}@anchor{5f6}
@deffn {例外} SystemError

当解释器发现内部错误，但情况看起来尚未严重到要放弃所有希望时将被引发。 关联的值是一个指明发生了什么问题的字符串（表示为低层级的符号）。

你应当将此问题报告给你所用 Python 解释器的作者或维护人员。 请确认报告 Python 解释器的版本号 (@code{sys.version}; 它也会在交互式 Python 会话开始时被打印出来)，具体的错误消息（异常所关联的值）以及可能触发该错误的程序源码。
@end deffn

@geindex SystemExit
@anchor{library/exceptions SystemExit}@anchor{5f7}
@deffn {例外} SystemExit

此异常由 @ref{cdb,,sys.exit()} 函数引发。 它继承自 @ref{1a8,,BaseException} 而不是 @ref{1a9,,Exception} 以确保不会被处理 @ref{1a9,,Exception} 的代码意外捕获。 这允许此异常正确地向上传播并导致解释器退出。 如果它未被处理，则 Python 解释器就将退出；不会打印任何栈回溯信息。 构造器接受的可选参数与传递给 @ref{cdb,,sys.exit()} 的相同。 如果该值为一个整数，则它指明系统退出状态码（会传递给 C 的 @code{exit()} 函数）；如果该值为 @code{None}，则退出状态码为零；如果该值为其他类型（例如字符串），则会打印对象的值并将退出状态码设为一。

对 @ref{cdb,,sys.exit()} 的调用会被转换为一个异常以便能执行清理处理程序 (@ref{d6b,,try} 语句的 @ref{182,,finally} 子句)，并且使得调试器可以执行一段脚本而不必冒失去控制的风险。 如果绝对确实地需要立即退出（例如在调用 @ref{95b,,os.fork()} 之后的子进程中）则可使用 @ref{16a3,,os._exit()}.

@geindex code (SystemExit 属性)
@anchor{library/exceptions SystemExit code}@anchor{16a4}
@deffn {属性} code

传给构造器的退出状态码或错误信息（默认为 @code{None}。）
@end deffn
@end deffn

@geindex TypeError
@anchor{library/exceptions TypeError}@anchor{192}
@deffn {例外} TypeError

当一个操作或函数被应用于类型不适当的对象时将被引发。 关联的值是一个字符串，给出有关类型不匹配的详情。

此异常可以由用户代码引发，以表明尝试对某个对象进行的操作不受支持也不应当受支持。 如果某个对象应当支持给定的操作但尚未提供相应的实现，所要引发的适当异常应为 @ref{609,,NotImplementedError}。

传入参数的类型错误 (例如在要求 @ref{184,,int} 时却传入了 @ref{262,,list}) 应当导致 @ref{192,,TypeError}，但传入参数的值错误 (例如传入要求范围之外的数值) 则应当导致 @ref{1fb,,ValueError}。
@end deffn

@geindex UnboundLocalError
@anchor{library/exceptions UnboundLocalError}@anchor{e6f}
@deffn {例外} UnboundLocalError

当在函数或方法中对某个局部变量进行引用，但该变量并未绑定任何值时将被引发。 此异常是 @ref{d74,,NameError} 的一个子类。
@end deffn

@geindex UnicodeError
@anchor{library/exceptions UnicodeError}@anchor{c34}
@deffn {例外} UnicodeError

当发生与 Unicode 相关的编码或解码错误时将被引发。 此异常是 @ref{1fb,,ValueError} 的一个子类。

@ref{c34,,UnicodeError} 具有一些描述编码或解码错误的属性。 例如 @code{err.object[err.start:err.end]} 会给出导致编解码器失败的特定无效输入。

@geindex encoding (UnicodeError 属性)
@anchor{library/exceptions UnicodeError encoding}@anchor{16a5}
@deffn {属性} encoding

引发错误的编码名称。
@end deffn

@geindex reason (UnicodeError 属性)
@anchor{library/exceptions UnicodeError reason}@anchor{16a6}
@deffn {属性} reason

描述特定编解码器错误的字符串。
@end deffn

@geindex object (UnicodeError 属性)
@anchor{library/exceptions UnicodeError object}@anchor{16a7}
@deffn {属性} object

编解码器试图要编码或解码的对象。
@end deffn

@geindex start (UnicodeError 属性)
@anchor{library/exceptions UnicodeError start}@anchor{16a8}
@deffn {属性} start

@ref{2b0,,object} 中无效数据的开始位置索引。
@end deffn

@geindex end (UnicodeError 属性)
@anchor{library/exceptions UnicodeError end}@anchor{16a9}
@deffn {属性} end

@ref{2b0,,object} 中无效数据的末尾位置索引（不含）。
@end deffn
@end deffn

@geindex UnicodeEncodeError
@anchor{library/exceptions UnicodeEncodeError}@anchor{1fc}
@deffn {例外} UnicodeEncodeError

当在编码过程中发生与 Unicode 相关的错误时将被引发。 此异常是 @ref{c34,,UnicodeError} 的一个子类。
@end deffn

@geindex UnicodeDecodeError
@anchor{library/exceptions UnicodeDecodeError}@anchor{1fd}
@deffn {例外} UnicodeDecodeError

当在解码过程中发生与 Unicode 相关的错误时将被引发。 此异常是 @ref{c34,,UnicodeError} 的一个子类。
@end deffn

@geindex UnicodeTranslateError
@anchor{library/exceptions UnicodeTranslateError}@anchor{16aa}
@deffn {例外} UnicodeTranslateError

在转写过程中发生与 Unicode 相关的错误时将被引发。 此异常是 @ref{c34,,UnicodeError} 的一个子类。
@end deffn

@geindex ValueError
@anchor{library/exceptions ValueError}@anchor{1fb}
@deffn {例外} ValueError

当操作或函数接收到具有正确类型但值不适合的参数，并且情况不能用更精确的异常例如 @ref{e6e,,IndexError} 来描述时将被引发。
@end deffn

@geindex ZeroDivisionError
@anchor{library/exceptions ZeroDivisionError}@anchor{1241}
@deffn {例外} ZeroDivisionError

当除法或取余运算的第二个参数为零时将被引发。 关联的值是一个字符串，指明操作数和运算的类型。
@end deffn

下列异常被保留以与之前的版本相兼容；从 Python 3.3 开始，它们都是 @ref{1d3,,OSError} 的别名。

@geindex EnvironmentError
@anchor{library/exceptions EnvironmentError}@anchor{98d}
@deffn {例外} EnvironmentError
@end deffn

@geindex IOError
@anchor{library/exceptions IOError}@anchor{98c}
@deffn {例外} IOError
@end deffn

@geindex WindowsError
@anchor{library/exceptions WindowsError}@anchor{98e}
@deffn {例外} WindowsError

限在 Windows 中可用。
@end deffn

@menu
* OS 异常:: 

@end menu

@node OS 异常,,,具体异常
@anchor{library/exceptions os-exceptions}@anchor{169d}
@subsubsection OS 异常


下列异常均为 @ref{1d3,,OSError} 的子类，它们将根据系统错误代码被引发。

@geindex BlockingIOError
@anchor{library/exceptions BlockingIOError}@anchor{991}
@deffn {例外} BlockingIOError

当一个操作会被某个设置为非阻塞操作的对象（例如套接字）所阻塞时将被引发。 对应于 @code{errno} @code{EAGAIN}, @code{EALREADY}, @code{EWOULDBLOCK} 和 @code{EINPROGRESS}。

除了 @ref{1d3,,OSError} 已有的属性，@ref{991,,BlockingIOError} 还有一个额外属性：

@geindex characters_written (BlockingIOError 属性)
@anchor{library/exceptions BlockingIOError characters_written}@anchor{16ab}
@deffn {属性} characters_written

一个整数，表示在被阻塞前已写入到流的字符数。 当使用来自 @ref{a1,,io} 模块的带缓冲 I/O 类时此属性可用。
@end deffn
@end deffn

@geindex ChildProcessError
@anchor{library/exceptions ChildProcessError}@anchor{992}
@deffn {例外} ChildProcessError

当一个子进程上的操作失败时将被引发。 对应于 @code{errno} @code{ECHILD}。
@end deffn

@geindex ConnectionError
@anchor{library/exceptions ConnectionError}@anchor{6e0}
@deffn {例外} ConnectionError

与连接相关问题的基类。

其子类有 @ref{997,,BrokenPipeError}, @ref{998,,ConnectionAbortedError}, @ref{999,,ConnectionRefusedError} 和 @ref{99a,,ConnectionResetError}。
@end deffn

@geindex BrokenPipeError
@anchor{library/exceptions BrokenPipeError}@anchor{997}
@deffn {例外} BrokenPipeError

@ref{6e0,,ConnectionError} 的子类，当试图写入另一端已被关闭的管道，或是试图写入已关闭写入的套接字时将被引发。 对应于 @code{errno} @code{EPIPE} 和 @code{ESHUTDOWN}。
@end deffn

@geindex ConnectionAbortedError
@anchor{library/exceptions ConnectionAbortedError}@anchor{998}
@deffn {例外} ConnectionAbortedError

@ref{6e0,,ConnectionError} 的子类，当连接尝试被对端中止时将被引发。 对应于 @code{errno} @code{ECONNABORTED}。
@end deffn

@geindex ConnectionRefusedError
@anchor{library/exceptions ConnectionRefusedError}@anchor{999}
@deffn {例外} ConnectionRefusedError

@ref{6e0,,ConnectionError} 的子类，当连接尝试被对端拒绝时将被引发。 对应于 @code{errno} @code{ECONNREFUSED}。
@end deffn

@geindex ConnectionResetError
@anchor{library/exceptions ConnectionResetError}@anchor{99a}
@deffn {例外} ConnectionResetError

@ref{6e0,,ConnectionError} 的子类，当连接被对端重置时将被引发。 对应于 @code{errno} @code{ECONNRESET}。
@end deffn

@geindex FileExistsError
@anchor{library/exceptions FileExistsError}@anchor{952}
@deffn {例外} FileExistsError

当试图创建一个已存在的文件或目录时将被引发。 对应于 @code{errno} @code{EEXIST}。
@end deffn

@geindex FileNotFoundError
@anchor{library/exceptions FileNotFoundError}@anchor{7ba}
@deffn {例外} FileNotFoundError

当所请求的文件或目录不存在时将被引发。 对应于 @code{errno} @code{ENOENT}。
@end deffn

@geindex InterruptedError
@anchor{library/exceptions InterruptedError}@anchor{653}
@deffn {例外} InterruptedError

当系统调用被输入信号中断时将被引发。 对应于 @code{errno} @ref{652,,EINTR}。


在 3.5 版更改: 当系统调用被某个信号中断时，Python 现在会重试系统调用，除非该信号的处理程序引发了其它异常 (原理参见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}) 而不是引发 @ref{653,,InterruptedError}。

@end deffn

@geindex IsADirectoryError
@anchor{library/exceptions IsADirectoryError}@anchor{993}
@deffn {例外} IsADirectoryError

当请求对一个目录执行文件操作 (例如 @ref{a32,,os.remove()}) 将被引发。 对应于 @code{errno} @code{EISDIR}。
@end deffn

@geindex NotADirectoryError
@anchor{library/exceptions NotADirectoryError}@anchor{994}
@deffn {例外} NotADirectoryError

当请求对一个非目录对象执行目录操作 (例如 @ref{a3c,,os.listdir()}) 时将被引发。 对应于 @code{errno} @code{ENOTDIR}。
@end deffn

@geindex PermissionError
@anchor{library/exceptions PermissionError}@anchor{5fa}
@deffn {例外} PermissionError

当在没有足够操作权限的情况下试图执行某个操作时将被引发 —— 例如缺少文件系统权限。 对应于 @code{errno} @code{EACCES} 和 @code{EPERM}。
@end deffn

@geindex ProcessLookupError
@anchor{library/exceptions ProcessLookupError}@anchor{995}
@deffn {例外} ProcessLookupError

当给定的进程不存在时将被引发。 对应于 @code{errno} @code{ESRCH}。
@end deffn

@geindex TimeoutError
@anchor{library/exceptions TimeoutError}@anchor{996}
@deffn {例外} TimeoutError

当一个系统函数发生系统级超时的情况下将被引发。 对应于 @code{errno} @code{ETIMEDOUT}。
@end deffn


3.3 新版功能: 添加了以上所有 @ref{1d3,,OSError} 的子类。



@subsubheading 参见


@geindex Python 提高建议; PEP 3151
PEP 3151@footnote{https://www.python.org/dev/peps/pep-3151} - 重写 OS 和 IO 异常的层次结构


@node 警告,异常层次结构,具体异常,内置异常
@anchor{library/exceptions warning-categories-as-exceptions}@anchor{16ac}@anchor{library/exceptions warnings}@anchor{16ad}
@subsection 警告


下列异常被用作警告类别；请参阅 @ref{16ae,,警告类别} 文档了解详情。

@geindex Warning
@anchor{library/exceptions Warning}@anchor{16af}
@deffn {例外} Warning

警告类别的基类。
@end deffn

@geindex UserWarning
@anchor{library/exceptions UserWarning}@anchor{16b0}
@deffn {例外} UserWarning

用户代码所产生警告的基类。
@end deffn

@geindex DeprecationWarning
@anchor{library/exceptions DeprecationWarning}@anchor{278}
@deffn {例外} DeprecationWarning

如果所发出的警告是针对其他 Python 开发者的，则以此作为与已弃用特性相关警告的基类。
@end deffn

@geindex PendingDeprecationWarning
@anchor{library/exceptions PendingDeprecationWarning}@anchor{279}
@deffn {例外} PendingDeprecationWarning

对于已过时并预计在未来弃用，但目前尚未弃用的特性相关警告的基类。

这个类很少被使用，因为针对未来可能的弃用发出警告的做法并不常见，而针对当前已有的弃用则推荐使用 @ref{278,,DeprecationWarning}。
@end deffn

@geindex SyntaxWarning
@anchor{library/exceptions SyntaxWarning}@anchor{191}
@deffn {例外} SyntaxWarning

与模糊的语法相关的警告的基类。
@end deffn

@geindex RuntimeWarning
@anchor{library/exceptions RuntimeWarning}@anchor{2c0}
@deffn {例外} RuntimeWarning

与模糊的运行时行为相关的警告的基类。
@end deffn

@geindex FutureWarning
@anchor{library/exceptions FutureWarning}@anchor{31e}
@deffn {例外} FutureWarning

如果所发出的警告是针对以 Python 所编写应用的最终用户的，则以此作为与已弃用特性相关警告的基类。
@end deffn

@geindex ImportWarning
@anchor{library/exceptions ImportWarning}@anchor{5d3}
@deffn {例外} ImportWarning

与在模块导入中可能的错误相关的警告的基类。
@end deffn

@geindex UnicodeWarning
@anchor{library/exceptions UnicodeWarning}@anchor{d80}
@deffn {例外} UnicodeWarning

与 Unicode 相关的警告的基类。
@end deffn

@geindex BytesWarning
@anchor{library/exceptions BytesWarning}@anchor{4b0}
@deffn {例外} BytesWarning

与 @ref{32a,,bytes} 和 @ref{32b,,bytearray} 相关的警告的基类。
@end deffn

@geindex ResourceWarning
@anchor{library/exceptions ResourceWarning}@anchor{4ca}
@deffn {例外} ResourceWarning

与资源使用相关的警告的基类。 会被默认的警告过滤器忽略。


3.2 新版功能.

@end deffn

@node 异常层次结构,,警告,内置异常
@anchor{library/exceptions exception-hierarchy}@anchor{16b1}
@subsection 异常层次结构


内置异常的类层级结构如下：

@example
BaseException
 +-- SystemExit
 +-- KeyboardInterrupt
 +-- GeneratorExit
 +-- Exception
      +-- StopIteration
      +-- StopAsyncIteration
      +-- ArithmeticError
      |    +-- FloatingPointError
      |    +-- OverflowError
      |    +-- ZeroDivisionError
      +-- AssertionError
      +-- AttributeError
      +-- BufferError
      +-- EOFError
      +-- ImportError
      |    +-- ModuleNotFoundError
      +-- LookupError
      |    +-- IndexError
      |    +-- KeyError
      +-- MemoryError
      +-- NameError
      |    +-- UnboundLocalError
      +-- OSError
      |    +-- BlockingIOError
      |    +-- ChildProcessError
      |    +-- ConnectionError
      |    |    +-- BrokenPipeError
      |    |    +-- ConnectionAbortedError
      |    |    +-- ConnectionRefusedError
      |    |    +-- ConnectionResetError
      |    +-- FileExistsError
      |    +-- FileNotFoundError
      |    +-- InterruptedError
      |    +-- IsADirectoryError
      |    +-- NotADirectoryError
      |    +-- PermissionError
      |    +-- ProcessLookupError
      |    +-- TimeoutError
      +-- ReferenceError
      +-- RuntimeError
      |    +-- NotImplementedError
      |    +-- RecursionError
      +-- SyntaxError
      |    +-- IndentationError
      |         +-- TabError
      +-- SystemError
      +-- TypeError
      +-- ValueError
      |    +-- UnicodeError
      |         +-- UnicodeDecodeError
      |         +-- UnicodeEncodeError
      |         +-- UnicodeTranslateError
      +-- Warning
           +-- DeprecationWarning
           +-- PendingDeprecationWarning
           +-- RuntimeWarning
           +-- SyntaxWarning
           +-- UserWarning
           +-- FutureWarning
           +-- ImportWarning
           +-- UnicodeWarning
           +-- BytesWarning
           +-- ResourceWarning
@end example
@anchor{library/text stringservices}@anchor{15d7}
@node 文本处理服务,二进制数据服务,内置异常,Python 标准库
@anchor{library/text doc}@anchor{16b2}@anchor{library/text text-processing-services}@anchor{16b3}@anchor{library/text textservices}@anchor{15da}
@section 文本处理服务


本章介绍的模块提供了广泛的字符串操作和其他文本处理服务。

在 @ref{16b4,,二进制数据服务} 之下描述的  @ref{1c,,codecs} 模块也与文本处理高度相关。 此外也请参阅 Python 内置字符串类型的文档 @ref{11b7,,文本序列类型 --- str}。

@menu
* string: string --- 常见的字符串操作. 常见的字符串操作
* re: re --- 正则表达式操作. 正则表达式操作
* difflib: difflib --- 计算差异的辅助工具. 计算差异的辅助工具
* textwrap: textwrap --- 文本自动换行与填充. 文本自动换行与填充
* unicodedata: unicodedata --- Unicode 数据库. Unicode 数据库
* stringprep: stringprep --- 因特网字符串预备. 因特网字符串预备
* readline: readline --- GNU readline 接口. GNU readline 接口
* rlcompleter: rlcompleter --- GNU readline 的补全函数. GNU readline 的补全函数

@end menu

@node string --- 常见的字符串操作,re --- 正则表达式操作,,文本处理服务
@anchor{library/string doc}@anchor{16b5}@anchor{library/string module-string}@anchor{f6}@anchor{library/string string-common-string-operations}@anchor{16b6}
@subsection @code{string} --- 常见的字符串操作


@geindex string (模块)

@strong{源代码：} Lib/string.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/string.py}


__________________________________________________________________



@subsubheading 参见


@ref{11b7,,文本序列类型 --- str}

@ref{11b8,,字符串的方法}


@menu
* 字符串常量:: 
* 自定义字符串格式化:: 
* 格式字符串语法:: 
* 模板字符串:: 
* 辅助函数:: 

@end menu

@node 字符串常量,自定义字符串格式化,,string --- 常见的字符串操作
@anchor{library/string string-constants}@anchor{16b7}
@subsubsection 字符串常量


此模块中定义的常量为：

@geindex ascii_letters() (在 string 模块中)
@anchor{library/string string ascii_letters}@anchor{c55}
@deffn {数据} string.ascii_letters

下文所述 @ref{16b8,,ascii_lowercase} 和 @ref{16b9,,ascii_uppercase} 常量的拼连。 该值不依赖于语言区域。
@end deffn

@geindex ascii_lowercase() (在 string 模块中)
@anchor{library/string string ascii_lowercase}@anchor{16b8}
@deffn {数据} string.ascii_lowercase

小写字母 @code{'abcdefghijklmnopqrstuvwxyz'}。 该值不依赖于语言区域，不会发生改变。
@end deffn

@geindex ascii_uppercase() (在 string 模块中)
@anchor{library/string string ascii_uppercase}@anchor{16b9}
@deffn {数据} string.ascii_uppercase

大写字母 @code{'ABCDEFGHIJKLMNOPQRSTUVWXYZ'}。 该值不依赖于语言区域，不会发生改变。
@end deffn

@geindex digits() (在 string 模块中)
@anchor{library/string string digits}@anchor{16ba}
@deffn {数据} string.digits

字符串 @code{'0123456789'}。
@end deffn

@geindex hexdigits() (在 string 模块中)
@anchor{library/string string hexdigits}@anchor{16bb}
@deffn {数据} string.hexdigits

字符串 @code{'0123456789abcdefABCDEF'}。
@end deffn

@geindex octdigits() (在 string 模块中)
@anchor{library/string string octdigits}@anchor{16bc}
@deffn {数据} string.octdigits

字符串 @code{'01234567'}。
@end deffn

@geindex punctuation() (在 string 模块中)
@anchor{library/string string punctuation}@anchor{16bd}
@deffn {数据} string.punctuation

由在 @code{C} 区域设置中被视为标点符号的 ASCII 字符所组成的字符串: @code{!"#$%&'()*+,-./:;<=>?@@[\]^_`@{|@}~}.
@end deffn

@geindex printable() (在 string 模块中)
@anchor{library/string string printable}@anchor{16be}
@deffn {数据} string.printable

由被视为可打印符号的 ASCII 字符组成的字符串。 这是 @ref{16ba,,digits}, @ref{c55,,ascii_letters}, @ref{16bd,,punctuation} 和 @ref{16bf,,whitespace} 的总和。
@end deffn

@geindex whitespace() (在 string 模块中)
@anchor{library/string string whitespace}@anchor{16bf}
@deffn {数据} string.whitespace

由被视为空白符号的 ASCII 字符组成的字符串。 其中包括空格、制表、换行、回车、进纸和纵向制表符。
@end deffn

@node 自定义字符串格式化,格式字符串语法,字符串常量,string --- 常见的字符串操作
@anchor{library/string custom-string-formatting}@anchor{16c0}@anchor{library/string string-formatting}@anchor{15d9}
@subsubsection 自定义字符串格式化


内置的字符串类提供了通过使用 
@geindex Python 提高建议; PEP 3101
PEP 3101@footnote{https://www.python.org/dev/peps/pep-3101} 所描述的 @ref{4d4,,format()} 方法进行复杂变量替换和值格式化的能力。 @ref{f6,,string} 模块中的 @ref{7af,,Formatter} 类允许你使用与内置 @ref{4d4,,format()} 方法相同的实现来创建并定制你自己的字符串格式化行为。

@geindex Formatter (string 中的类)
@anchor{library/string string Formatter}@anchor{7af}
@deffn {类} string.Formatter

@ref{7af,,Formatter} 类包含下列公有方法：

@geindex format() (string.Formatter 方法)
@anchor{library/string string Formatter format}@anchor{486}
@deffn {方法} format (format_string, /, *args, **kwargs)

首要的 API 方法。 它接受一个格式字符串和任意一组位置和关键字参数。 它只是一个调用 @ref{16c1,,vformat()} 的包装器。


在 3.7 版更改: 格式字符串参数现在是 @ref{2a7,,仅限位置参数}。

@end deffn

@geindex vformat() (string.Formatter 方法)
@anchor{library/string string Formatter vformat}@anchor{16c1}
@deffn {方法} vformat (format_string, args, kwargs)

此函数执行实际的格式化操作。 它被公开为一个单独的函数，用于需要传入一个预定义字母作为参数，而不是使用 @code{*args} 和 @code{**kwargs} 语法将字典解包为多个单独参数并重打包的情况。 @ref{16c1,,vformat()} 完成将格式字符串分解为字符数据和替换字段的工作。 它会调用下文所述的几种不同方法。
@end deffn

此外，@ref{7af,,Formatter} 还定义了一些旨在被子类替换的方法：

@geindex parse() (string.Formatter 方法)
@anchor{library/string string Formatter parse}@anchor{16c2}
@deffn {方法} parse (format_string)

循环遍历 format_string 并返回一个由可迭代对象组成的元组 (@emph{literal_text}, @emph{field_name}, @emph{format_spec}, @emph{conversion})。 它会被 @ref{16c1,,vformat()} 用来将字符串分解为文本字面值或替换字段。

元组中的值在概念上表示一段字面文本加上一个替换字段。 如果没有字面文本（如果连续出现两个替换字段就会发生这种情况），则 @emph{literal_text} 将是一个长度为零的字符串。 如果没有替换字段，则 @emph{field_name}, @emph{format_spec} 和 @emph{conversion} 的值将为 @code{None}。
@end deffn

@geindex get_field() (string.Formatter 方法)
@anchor{library/string string Formatter get_field}@anchor{16c3}
@deffn {方法} get_field (field_name, args, kwargs)

给定 @emph{field_name} 作为 @ref{16c2,,parse()} (见上文) 的返回值，将其转换为要格式化的对象。 返回一个元组 (obj, used_key)。 默认版本接受在 
@geindex Python 提高建议; PEP 3101
PEP 3101@footnote{https://www.python.org/dev/peps/pep-3101} 所定义形式的字符串，例如 "0[name]" 或 "label.title"。 @emph{args} 和 @emph{kwargs} 与传给 @ref{16c1,,vformat()} 的一样。 返回值 @emph{used_key} 与 @ref{16c4,,get_value()} 的 @emph{key} 形参具有相同的含义。
@end deffn

@geindex get_value() (string.Formatter 方法)
@anchor{library/string string Formatter get_value}@anchor{16c4}
@deffn {方法} get_value (key, args, kwargs)

提取给定的字段值。 @emph{key} 参数将为整数或字符串。 如果是整数，它表示 @emph{args} 中位置参数的索引；如果是字符串，它表示 @emph{kwargs} 中的关键字参数名。

@emph{args} 形参会被设为 @ref{16c1,,vformat()} 的位置参数列表，而 @emph{kwargs} 形参会被设为由关键字参数组成的字典。

对于复合字段名称，仅会为字段名称的第一个组件调用这些函数；后续组件会通过普通属性和索引操作来进行处理。

因此举例来说，字段表达式 '0.name' 将导致调用 @ref{16c4,,get_value()} 时附带 @emph{key} 参数值 0。 在 @ref{16c4,,get_value()} 通过调用内置的 @ref{443,,getattr()} 函数返回后将会查找 @code{name} 属性。

如果索引或关键字引用了一个不存在的项，则将引发 @ref{e6e,,IndexError} 或 @ref{2c7,,KeyError}。
@end deffn

@geindex check_unused_args() (string.Formatter 方法)
@anchor{library/string string Formatter check_unused_args}@anchor{16c5}
@deffn {方法} check_unused_args (used_args, args, kwargs)

在必要时实现对未使用参数进行检测。 此函数的参数是是格式字符串中实际引用的所有参数键的集合（整数表示位置参数，字符串表示名称参数），以及被传给 vformat 的 @emph{args} 和 @emph{kwargs} 的引用。 未使用参数的集合可以根据这些形参计算出来。 如果检测失败则 @ref{16c5,,check_unused_args()} 应会引发一个异常。
@end deffn

@geindex format_field() (string.Formatter 方法)
@anchor{library/string string Formatter format_field}@anchor{16c6}
@deffn {方法} format_field (value, format_spec)

@ref{16c6,,format_field()} 会简单地调用内置全局函数 @ref{4d5,,format()}。 提供该方法是为了让子类能够重载它。
@end deffn

@geindex convert_field() (string.Formatter 方法)
@anchor{library/string string Formatter convert_field}@anchor{16c7}
@deffn {方法} convert_field (value, conversion)

使用给定的转换类型（来自 @ref{16c2,,parse()} 方法所返回的元组）来转换（由 @ref{16c3,,get_field()} 所返回的）值。 默认版本支持 's' (str), 'r' (repr) 和 'a' (ascii) 等转换类型。
@end deffn
@end deffn

@node 格式字符串语法,模板字符串,自定义字符串格式化,string --- 常见的字符串操作
@anchor{library/string format-string-syntax}@anchor{16c8}@anchor{library/string formatstrings}@anchor{d13}
@subsubsection 格式字符串语法


@ref{4d4,,str.format()} 方法和 @ref{7af,,Formatter} 类共享相同的格式字符串语法（虽然对于 @ref{7af,,Formatter} 来说，其子类可以定义它们自己的格式字符串语法）。 具体语法与 @ref{15c,,格式化字符串字面值} 相似，但也存在区别。

@geindex @{@} (curly brackets); in string formatting
@geindex . (dot); in string formatting
@geindex [] (square brackets); in string formatting
@geindex ! (exclamation); in string formatting
@geindex ; (colon); in string formatting

格式字符串包含有以花括号 @code{@{@}} 括起来的“替换字段”。 不在花括号之内的内容被视为字面文本，会不加修改地复制到输出中。 如果你需要在字面文本中包含花括号字符，可以通过重复来转义: @code{@{@{} and @code{@}@}}。

替换字段的语法如下：

@quotation

@example
@anchor{library/string grammar-token-replacement-field}@anchor{16c9}replacement_field ::= "@{" [field_name] ["!" conversion] [":" format_spec] "@}"
@anchor{library/string grammar-token-field-name}@anchor{16ca}field_name        ::= arg_name ("." attribute_name | "[" element_index "]")*
@anchor{library/string grammar-token-arg-name}@anchor{16cb}arg_name          ::= [identifier | digit+]
@anchor{library/string grammar-token-attribute-name}@anchor{16cc}attribute_name    ::= identifier
@anchor{library/string grammar-token-element-index}@anchor{16cd}element_index     ::= digit+ | index_string
@anchor{library/string grammar-token-index-string}@anchor{16ce}index_string      ::= <any source character except "]"> +
@anchor{library/string grammar-token-conversion}@anchor{16cf}conversion        ::= "r" | "s" | "a"
@anchor{library/string grammar-token-format-spec}@anchor{16d0}format_spec       ::= <described in the next section>
@end example
@end quotation

用不太正式的术语来描述，替换字段开头可以用一个 @emph{field_name} 指定要对值进行格式化并取代替换字符被插入到输出结果的对象。 @emph{field_name} 之后有可选的  @emph{conversion} 字段，它是一个感叹号 @code{'!'} 加一个 @emph{format_spec}，并以一个冒号 @code{':'} 打头。 这些指明了替换值的非默认格式。

另请参阅 @ref{4d8,,格式规格迷你语言} 一节。

@emph{field_name} 本身以一个数字或关键字 @emph{arg_name} 打头。 如果为数字，则它指向一个位置参数，而如果为关键字，则它指向一个命名关键字参数。 如果格式字符串中的数字 arg_names 为 0, 1, 2, ... 的序列，它们可以全部省略（而非部分省略），数字 0, 1, 2, ... 将会按顺序自动插入。 由于 @emph{arg_name} 不使用引号分隔，因此无法在格式字符串中指定任意的字典键 (例如字符串 @code{'10'} 或 @code{':-]'})。 @emph{arg_name} 之后可以带上任意数量的索引或属性表达式。 @code{'.name'} 形式的表达式会使用 @ref{443,,getattr()} 选择命名属性，而 @code{'[index]'} 形式的表达式会使用 @ref{27f,,__getitem__()} 执行索引查找。


在 3.1 版更改: 位置参数说明符对于 @ref{4d4,,str.format()} 可以省略，因此 @code{'@{@} @{@}'.format(a, b)} 等价于 @code{'@{0@} @{1@}'.format(a, b)}。



在 3.4 版更改: 位置参数说明符对于 @ref{7af,,Formatter} 可以省略。


一些简单的格式字符串示例

@example
"First, thou shalt count to @{0@}"  # References first positional argument
"Bring me a @{@}"                   # Implicitly references the first positional argument
"From @{@} to @{@}"                   # Same as "From @{0@} to @{1@}"
"My quest is @{name@}"              # References keyword argument 'name'
"Weight in tons @{0.weight@}"       # 'weight' attribute of first positional arg
"Units destroyed: @{players[0]@}"   # First element of keyword argument 'players'.
@end example

使用 @emph{conversion} 字段在格式化之前进行类型强制转换。 通常，格式化值的工作由值本身的 @ref{948,,__format__()} 方法来完成。 但是，在某些情况下最好强制将类型格式化为一个字符串，覆盖其本身的格式化定义。 通过在调用 @ref{948,,__format__()} 之前将值转换为字符串，可以绕过正常的格式化逻辑。

目前支持的转换旗标有三种: @code{'!s'} 会对值调用 @ref{329,,str()}，@code{'!r'} 调用 @ref{7c6,,repr()} 而 @code{'!a'} 则调用 @ref{d45,,ascii()}。

几个例子:

@example
"Harold's a clever @{0!s@}"        # Calls str() on the argument first
"Bring out the holy @{name!r@}"    # Calls repr() on the argument first
"More @{!a@}"                      # Calls ascii() on the argument first
@end example

@emph{format_spec} 字段包含值应如何呈现的规格描述，例如字段宽度、对齐、填充、小数精度等细节信息。 每种值类型可以定义自己的“格式化迷你语言”或对 @emph{format_spec} 的解读方式。

大多数内置类型都支持同样的格式化迷你语言，具体描述见下一节。

@emph{format_spec} 字段还可以在其内部包含嵌套的替换字段。 这些嵌套的替换字段可能包括字段名称、转换旗标和格式规格描述，但是不再允许更深层的嵌套。 format_spec 内部的替换字段会在解读 @emph{format_spec} 字符串之前先被解读。 这将允许动态地指定特定值的格式。

请参阅 @ref{16d1,,格式示例} 一节查看相关示例。

@menu
* 格式规格迷你语言:: 
* 格式示例:: 

@end menu

@node 格式规格迷你语言,格式示例,,格式字符串语法
@anchor{library/string format-specification-mini-language}@anchor{16d2}@anchor{library/string formatspec}@anchor{4d8}
@subsubsection 格式规格迷你语言


“格式规格”在格式字符串所包含的替换字段内部使用，用于定义单个值应如何呈现 (参见 @ref{d13,,格式字符串语法} 和 @ref{15c,,格式化字符串字面值})。 它们也可以被直接传给内置的 @ref{4d5,,format()} 函数。 每种可格式化的类型都可以自行定义如何对格式规格进行解读。

大多数内置类型都为格式规格实现了下列选项，不过某些格式化选项只被数值类型所支持。

一般约定空的格式描述将产生与在值上调用 @ref{329,,str()} 相同的结果。 非空格式描述通常会修改此结果。

@emph{标准格式说明符} 的一般形式如下：

@example
@anchor{library/string id1}@anchor{16d3}format_spec     ::= [[fill]align][sign][#][0][width][grouping_option][.precision][type]
@anchor{library/string grammar-token-fill}@anchor{16d4}fill            ::= <any character>
@anchor{library/string grammar-token-align}@anchor{16d5}align           ::= "<" | ">" | "=" | "^"
@anchor{library/string grammar-token-sign}@anchor{16d6}sign            ::= "+" | "-" | " "
@anchor{library/string grammar-token-width}@anchor{16d7}width           ::= digit+
@anchor{library/string grammar-token-grouping-option}@anchor{16d8}grouping_option ::= "_" | ","
@anchor{library/string grammar-token-precision}@anchor{16d9}precision       ::= digit+
@anchor{library/string grammar-token-type}@anchor{16da}type            ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
@end example

如果指定了一个有效的 @emph{align} 值，则可以在该值前面加一个 @emph{fill} 字符，它可以为任意字符，如果省略则默认为空格符。 在 @ref{15c,,格式化字符串字面值} 或在使用 @ref{4d4,,str.format()} 方法时是无法使用花括号字面值 ("@code{@{}" or "@code{@}}") 作为 @emph{fill} 字符的。 但是，通过嵌套替换字段插入花括号则是可以的。 这个限制不会影响 @ref{4d5,,format()} 函数。

各种对齐选项的含义如下：

@quotation

@geindex < (less); in string formatting
@geindex > (greater); in string formatting
@geindex = (equals); in string formatting
@geindex ^ (caret); in string formatting


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

含义

@item

@code{'<'}

@tab

强制字段在可用空间内左对齐（这是大多数对象的默认值）。

@item

@code{'>'}

@tab

强制字段在可用空间内右对齐（这是数字的默认值）。

@item

@code{'='}

@tab

强制将填充放置在符号（如果有）之后但在数字之前。这用于以“+000000120”形式打印字段。此对齐选项仅对数字类型有效。当'0'紧接在字段宽度之前时，它成为默认值。

@item

@code{'^'}

@tab

强制字段在可用空间内居中。

@end multitable

@end quotation

请注意，除非定义了最小字段宽度，否则字段宽度将始终与填充它的数据大小相同，因此在这种情况下，对齐选项没有意义。

@emph{sign} 选项仅对数字类型有效，可以是以下之一：

@quotation

@geindex + (plus); in string formatting
@geindex - (minus); in string formatting
@geindex space; in string formatting


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

含义

@item

@code{'+'}

@tab

表示标志应该用于正数和负数。

@item

@code{'-'}

@tab

表示标志应仅用于负数（这是默认行为）。

@item

space

@tab

表示应在正数上使用前导空格，在负数上使用减号。

@end multitable

@end quotation

@geindex # (hash); in string formatting

@code{'#'} 选项可以让“替代形式”被用于转换。 替代形式可针对不同类型分别定义。 此选项仅对整数、浮点、复数和 Decimal 类型有效。 对于整数类型，当使用二进制、八进制或十六进制输出时，此选项会为输出值添加相应的 @code{'0b'}, @code{'0o'} 或 @code{'0x'} 前缀。 对于浮点数、复数和 Decimal 类型，替代形式会使得转换结果总是包含小数点符号，即使其不带小数。 通常只有在带有小数的情况下，此类转换的结果中才会出现小数点符号。 此外，对于 @code{'g'} 和 @code{'G'} 转换，末尾的零不会从结果中被移除。

@geindex @comma{} (comma); in string formatting

@code{','} 选项表示使用逗号作为千位分隔符。 对于感应区域设置的分隔符，请改用 @code{'n'} 整数表示类型。


在 3.1 版更改: 添加了 @code{','} 选项 (另请参阅 
@geindex Python 提高建议; PEP 378
PEP 378@footnote{https://www.python.org/dev/peps/pep-0378})。


@geindex _ (underscore); in string formatting

@code{'_'} 选项表示对浮点表示类型和整数表示类型 @code{'d'} 使用下划线作为千位分隔符。 对于整数表示类型 @code{'b'}, @code{'o'}, @code{'x'} 和 @code{'X'}，将为每 4 个数位插入一个下划线。 对于其他表示类型指定此选项则将导致错误。


在 3.6 版更改: 添加了 @code{'_'} 选项 (另请参阅 
@geindex Python 提高建议; PEP 515
PEP 515@footnote{https://www.python.org/dev/peps/pep-0515})。


@emph{width} 是一个定义最小总字段宽度的十进制整数，包括任何前缀、分隔符和其他格式化字符。 如果未指定，则字段宽度将由内容确定。

当未显式给出对齐方式时，在 @emph{width} 字段前加一个零 (@code{'0'}) 字段将为数字类型启用感知正负号的零填充。 这相当于设置 @emph{fill} 字符为 @code{'0'} 且 @emph{alignment} 类型为 @code{'='}。

@emph{precision} 是一个十进制数字，表示对于以 @code{'f'} and @code{'F'} 格式化的浮点数值要在小数点后显示多少个数位，或者对于以 @code{'g'} 或 @code{'G'} 格式化的浮点数值要在小数点前后共显示多少个数位。 对于非数字类型，该字段表示最大字段大小 —— 换句话说就是要使用多少个来自字段内容的字符。 对于整数值则不允许使用 @emph{precision}。

最后，@emph{type} 确定了数据应如何呈现。

可用的字符串表示类型是：

@quotation


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

类型

@tab

含义

@item

@code{'s'}

@tab

字符串格式。这是字符串的默认类型，可以省略。

@item

None

@tab

和 @code{'s'} 一样。

@end multitable

@end quotation

可用的整数表示类型是：

@quotation


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

类型

@tab

含义

@item

@code{'b'}

@tab

二进制格式。 输出以 2 为基数的数字。

@item

@code{'c'}

@tab

字符。在打印之前将整数转换为相应的unicode字符。

@item

@code{'d'}

@tab

十进制整数。 输出以 10 为基数的数字。

@item

@code{'o'}

@tab

八进制格式。 输出以 8 为基数的数字。

@item

@code{'x'}

@tab

十六进制格式。 输出以 16 为基数的数字，使用小写字母表示 9 以上的数码。

@item

@code{'X'}

@tab

十六进制格式。 输出以 16 为基数的数字，使用大写字母表示 9 以上的数码。

@item

@code{'n'}

@tab

数字。 这与 @code{'d'} 相似，不同之处在于它会使用当前区域设置来插入适当的数字分隔字符。

@item

None

@tab

和 @code{'d'} 相同。

@end multitable

@end quotation

在上述的表示类型之外，整数还可以通过下列的浮点表示类型来格式化 (除了 @code{'n'} 和 @code{None})。 当这样做时，会在格式化之前使用 @ref{187,,float()} 将整数转换为浮点数。

浮点数和小数值可用的表示类型有：

@quotation


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

类型

@tab

含义

@item

@code{'e'}

@tab

指数表示。 以使用字母 'e' 来标示指数的科学计数法打印数字。 默认的精度为 @code{6}。

@item

@code{'E'}

@tab

指数表示。 与 @code{'e'} 相似，不同之处在于它使用大写字母 'E' 作为分隔字符。

@item

@code{'f'}

@tab

定点表示。 将数字显示为一个定点数。 默认的精确度为 @code{6}。

@item

@code{'F'}

@tab

定点表示。 与 @code{'f'} 相似，但会将 @code{nan} 转为  @code{NAN} 并将 @code{inf} 转为 @code{INF}。

@item

@code{'g'}

@tab

常规格式。 对于给定的精度 @code{p >= 1}，这会将数值舍入到 @code{p} 位有效数字，再将结果以定点格式或科学计数法进行格式化，具体取决于其值的大小。

准确的规则如下：假设使用表示类型 @code{'e'} 和精度 @code{p-1} 进行格式化的结果具有指数值 @code{exp}。 那么如果 @code{m <= exp < p}，其中 @code{m} 以 -4 表示浮点值而以 -6 表示 @ref{188,,Decimal} 值，该数字将使用类型 @code{'f'} 和精度 @code{p-1-exp} 进行格式化。 否则的话，该数字将使用表示类型 @code{'e'} 和精度 @code{p-1} 进行格式化。 在两种情况下，都会从有效数字中移除无意义的末尾零，如果小数点之后没有余下数字则小数点也会被移除，除非使用了 @code{'#'} 选项。

正负无穷，正负零和 nan 会分别被格式化为 @code{inf}, @code{-inf}, @code{0}, @code{-0} 和 @code{nan}，无论精度如何设定。

精度 @code{0} 会被视为等同于精度 @code{1}。 默认精度为 @code{6}。

@item

@code{'G'}

@tab

常规格式。 类似于 @code{'g'}，不同之处在于当数值非常大时会切换为 @code{'E'}。 无穷与 NaN 也会表示为大写形式。

@item

@code{'n'}

@tab

数字。 这与 @code{'g'} 相似，不同之处在于它会使用当前区域设置来插入适当的数字分隔字符。

@item

@code{'%'}

@tab

百分比。 将数字乘以 100 并显示为定点 (@code{'f'}) 格式，后面带一个百分号。

@item

None

@tab

类似于 @code{'g'}，不同之处在于当使用定点表示法时，小数点后将至少显示一位。 默认精度与表示给定值所需的精度一样。 整体效果为与其他格式修饰符所调整的 @ref{329,,str()} 输出保持一致。

@end multitable

@end quotation

@node 格式示例,,格式规格迷你语言,格式字符串语法
@anchor{library/string format-examples}@anchor{16db}@anchor{library/string formatexamples}@anchor{16d1}
@subsubsection 格式示例


本节包含 @ref{4d4,,str.format()} 语法的示例以及与旧式 @code{%} 格式化的比较。

该语法在大多数情况下与旧式的 @code{%} 格式化类似，只是增加了 @code{@{@}} 和 @code{:} 来取代 @code{%}。 例如，，@code{'%03.2f'} 可以被改写为 @code{'@{:03.2f@}'}。

新的格式语法还支持新增的不同选项，将在以下示例中说明。

按位置访问参数:

@example
>>> '@{0@}, @{1@}, @{2@}'.format('a', 'b', 'c')
'a, b, c'
>>> '@{@}, @{@}, @{@}'.format('a', 'b', 'c')  # 3.1+ only
'a, b, c'
>>> '@{2@}, @{1@}, @{0@}'.format('a', 'b', 'c')
'c, b, a'
>>> '@{2@}, @{1@}, @{0@}'.format(*'abc')      # unpacking argument sequence
'c, b, a'
>>> '@{0@}@{1@}@{0@}'.format('abra', 'cad')   # arguments' indices can be repeated
'abracadabra'
@end example

按名称访问参数:

@example
>>> 'Coordinates: @{latitude@}, @{longitude@}'.format(latitude='37.24N', longitude='-115.81W')
'Coordinates: 37.24N, -115.81W'
>>> coord = @{'latitude': '37.24N', 'longitude': '-115.81W'@}
>>> 'Coordinates: @{latitude@}, @{longitude@}'.format(**coord)
'Coordinates: 37.24N, -115.81W'
@end example

访问参数的属性:

@example
>>> c = 3-5j
>>> ('The complex number @{0@} is formed from the real part @{0.real@} '
...  'and the imaginary part @{0.imag@}.').format(c)
'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'
>>> class Point:
...     def __init__(self, x, y):
...         self.x, self.y = x, y
...     def __str__(self):
...         return 'Point(@{self.x@}, @{self.y@})'.format(self=self)
...
>>> str(Point(4, 2))
'Point(4, 2)'
@end example

访问参数的项:

@example
>>> coord = (3, 5)
>>> 'X: @{0[0]@};  Y: @{0[1]@}'.format(coord)
'X: 3;  Y: 5'
@end example

替代 @code{%s} 和 @code{%r}:

@example
>>> "repr() shows quotes: @{!r@}; str() doesn't: @{!s@}".format('test1', 'test2')
"repr() shows quotes: 'test1'; str() doesn't: test2"
@end example

对齐文本以及指定宽度:

@example
>>> '@{:<30@}'.format('left aligned')
'left aligned                  '
>>> '@{:>30@}'.format('right aligned')
'                 right aligned'
>>> '@{:^30@}'.format('centered')
'           centered           '
>>> '@{:*^30@}'.format('centered')  # use '*' as a fill char
'***********centered***********'
@end example

替代 @code{%+f}, @code{%-f} 和 @code{% f} 以及指定正负号:

@example
>>> '@{:+f@}; @{:+f@}'.format(3.14, -3.14)  # show it always
'+3.140000; -3.140000'
>>> '@{: f@}; @{: f@}'.format(3.14, -3.14)  # show a space for positive numbers
' 3.140000; -3.140000'
>>> '@{:-f@}; @{:-f@}'.format(3.14, -3.14)  # show only the minus -- same as '@{:f@}; @{:f@}'
'3.140000; -3.140000'
@end example

替代 @code{%x} 和 @code{%o} 以及转换基于不同进位制的值:

@example
>>> # format also supports binary numbers
>>> "int: @{0:d@};  hex: @{0:x@};  oct: @{0:o@};  bin: @{0:b@}".format(42)
'int: 42;  hex: 2a;  oct: 52;  bin: 101010'
>>> # with 0x, 0o, or 0b as prefix:
>>> "int: @{0:d@};  hex: @{0:#x@};  oct: @{0:#o@};  bin: @{0:#b@}".format(42)
'int: 42;  hex: 0x2a;  oct: 0o52;  bin: 0b101010'
@end example

使用逗号作为千位分隔符:

@example
>>> '@{:,@}'.format(1234567890)
'1,234,567,890'
@end example

表示为百分数:

@example
>>> points = 19
>>> total = 22
>>> 'Correct answers: @{:.2%@}'.format(points/total)
'Correct answers: 86.36%'
@end example

使用特定类型的专属格式化:

@example
>>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '@{:%Y-%m-%d %H:%M:%S@}'.format(d)
'2010-07-04 12:15:58'
@end example

嵌套参数以及更复杂的示例:

@example
>>> for align, text in zip('<^>', ['left', 'center', 'right']):
...     '@{0:@{fill@}@{align@}16@}'.format(text, fill=align, align=align)
...
'left<<<<<<<<<<<<'
'^^^^^center^^^^^'
'>>>>>>>>>>>right'
>>>
>>> octets = [192, 168, 0, 1]
>>> '@{:02X@}@{:02X@}@{:02X@}@{:02X@}'.format(*octets)
'C0A80001'
>>> int(_, 16)
3232235521
>>>
>>> width = 5
>>> for num in range(5,12): 
...     for base in 'dXob':
...         print('@{0:@{width@}@{base@}@}'.format(num, base=base, width=width), end=' ')
...     print()
...
    5     5     5   101
    6     6     6   110
    7     7     7   111
    8     8    10  1000
    9     9    11  1001
   10     A    12  1010
   11     B    13  1011
@end example

@node 模板字符串,辅助函数,格式字符串语法,string --- 常见的字符串操作
@anchor{library/string id2}@anchor{16dc}@anchor{library/string template-strings}@anchor{15f9}
@subsubsection 模板字符串


模板字符串提供了由 
@geindex Python 提高建议; PEP 292
PEP 292@footnote{https://www.python.org/dev/peps/pep-0292} 所描述的更简便的字符串替换方式。 模板字符串的一个主要用例是文本国际化 (i18n)，因为在此场景下，更简单的语法和功能使得文本翻译过程比使用 Python 的其他内置字符串格式化工具更为方便。 作为基于模板字符串构建以实现 i18n 的库的一个示例，请参看 flufl.i18n@footnote{http://flufli18n.readthedocs.io/en/latest/} 包。

@geindex $ (dollar); in template strings

模板字符串支持基于 @code{$} 的替换，使用以下规则：


@itemize *

@item 
@code{$$} 为转义符号；它会被替换为单个的 @code{$}。

@item 
@code{$identifier} 为替换占位符，它会匹配一个名为 @code{"identifier"} 的映射键。 在默认情况下，@code{"identifier"} 限制为任意 ASCII 字母数字（包括下划线）组成的字符串，不区分大小写，以下划线或 ASCII 字母开头。 在 @code{$} 字符之后的第一个非标识符字符将表明占位符的终结。

@item 
@code{$@{identifier@}} 等价于 @code{$identifier}。 当占位符之后紧跟着有效的但又不是占位符一部分的标识符字符时需要使用，例如 @code{"$@{noun@}ification"}。
@end itemize

在字符串的其他位置出现 @code{$} 将导致引发 @ref{1fb,,ValueError}。

@ref{f6,,string} 模块提供了实现这些规则的 @ref{3e3,,Template} 类。 @ref{3e3,,Template} 有下列方法：

@geindex Template (string 中的类)
@anchor{library/string string Template}@anchor{3e3}
@deffn {类} string.Template (template)

该构造器接受一个参数作为模板字符串。

@geindex substitute() (string.Template 方法)
@anchor{library/string string Template substitute}@anchor{1293}
@deffn {方法} substitute (mapping=@{@}, /, **kwds)

执行模板替换，返回一个新字符串。 @emph{mapping} 为任意字典类对象，其中的键将匹配模板中的占位符。 或者你也可以提供一组关键字参数，其中的关键字即对应占位符。 当同时给出 @emph{mapping} 和 @emph{kwds} 并且存在重复时，则以 @emph{kwds} 中的占位符为优先。
@end deffn

@geindex safe_substitute() (string.Template 方法)
@anchor{library/string string Template safe_substitute}@anchor{1294}
@deffn {方法} safe_substitute (mapping=@{@}, /, **kwds)

类似于 @ref{1293,,substitute()}，不同之处是如果有占位符未在 @emph{mapping} 和 @emph{kwds} 中找到，不是引发 @ref{2c7,,KeyError} 异常，而是将原始占位符不加修改地显示在结果字符串中。 另一个与 @ref{1293,,substitute()} 的差异是任何在其他情况下出现的 @code{$} 将简单地返回 @code{$} 而不是引发 @ref{1fb,,ValueError}。

此方法被认为“安全”，因为虽然仍有可能发生其他异常，但它总是尝试返回可用的字符串而不是引发一个异常。 从另一方面来说，@ref{1294,,safe_substitute()} 也可能根本算不上安全，因为它将静默地忽略错误格式的模板，例如包含多余的分隔符、不成对的花括号或不是合法 Python 标识符的占位符等等。
@end deffn

@ref{3e3,,Template} 的实例还提供一个公有数据属性：

@geindex template (string.Template 属性)
@anchor{library/string string Template template}@anchor{16dd}
@deffn {属性} template

这是作为构造器的 @emph{template} 参数被传入的对象。 一般来说，你不应该修改它，但并不强制要求只读访问。
@end deffn
@end deffn

以下是一个如何使用模版的示例：

@example
>>> from string import Template
>>> s = Template('$who likes $what')
>>> s.substitute(who='tim', what='kung pao')
'tim likes kung pao'
>>> d = dict(who='tim')
>>> Template('Give $who $100').substitute(d)
Traceback (most recent call last):
...
ValueError: Invalid placeholder in string: line 1, col 11
>>> Template('$who likes $what').substitute(d)
Traceback (most recent call last):
...
KeyError: 'what'
>>> Template('$who likes $what').safe_substitute(d)
'tim likes $what'
@end example

进阶用法：你可以派生 @ref{3e3,,Template} 的子类来自定义占位符语法、分隔符，或用于解析模板字符串的整个正则表达式。 为此目的，你可以重载这些类属性：


@itemize *

@item 
@emph{delimiter} -- 这是用来表示占位符的起始的分隔符的字符串字面值。 默认值为 @code{$}。 请注意此参数 @emph{不能} 为正则表达式，因为其实现将在必要时对此字符串调用 @ref{490,,re.escape()}。 还要注意你不能在创建类之后改变此分隔符（例如在子类的类命名空间中必须设置不同的分隔符）。

@item 
@emph{idpattern} -- 这是用来描述不带花括号的占位符的模式的正则表达式。 默认值为正则表达式 @code{(?a:[_a-z][_a-z0-9]*)}。 如果给出了此属性并且 @emph{braceidpattern} 为 @code{None} 则此模式也将作用于带花括号的占位符。

@cartouche
@quotation 注解 
由于默认的 @emph{flags} 为 @code{re.IGNORECASE}，模式 @code{[a-z]} 可以匹配某些非 ASCII 字符。 因此我们在这里使用了局部旗标 @code{a}。
@end quotation
@end cartouche


在 3.7 版更改: @emph{braceidpattern} 可被用来定义对花括号内部和外部进行区分的模式。


@item 
@emph{braceidpattern} -- 此属性类似于 @emph{idpattern} 但是用来描述带花括号的占位符的模式。 默认值 @code{None} 意味着回退到 @emph{idpattern} (即在花括号内部和外部使用相同的模式)。 如果给出此属性，这将允许你为带花括号和不带花括号的占位符定义不同的模式。


3.7 新版功能.


@item 
@emph{flags} -- 将在编译用于识别替换内容的正则表达式被应用的正则表达式旗标。 默认值为 @code{re.IGNORECASE}。 请注意 @code{re.VERBOSE} 总是会被加为旗标，因此自定义的 @emph{idpattern} 必须遵循详细正则表达式的约定。


3.2 新版功能.

@end itemize

作为另一种选项，你可以通过重载类属性 @emph{pattern} 来提供整个正则表达式模式。 如果你这样做，该值必须为一个具有四个命名捕获组的正则表达式对象。 这些捕获组对应于上面已经给出的规则，以及无效占位符的规则：


@itemize *

@item 
@emph{escaped} -- 这个组匹配转义序列，在默认模式中即 @code{$$}。

@item 
@emph{named} -- 这个组匹配不带花括号的占位符名称；它不应当包含捕获组中的分隔符。

@item 
@emph{braced} -- 这个组匹配带有花括号的占位符名称；它不应当包含捕获组中的分隔符或者花括号。

@item 
@emph{invalid} -- 这个组匹配任何其他分隔符模式（通常为单个分隔符），并且它应当出现在正则表达式的末尾。
@end itemize

@node 辅助函数,,模板字符串,string --- 常见的字符串操作
@anchor{library/string helper-functions}@anchor{16de}
@subsubsection 辅助函数


@geindex capwords() (在 string 模块中)
@anchor{library/string string capwords}@anchor{16df}
@deffn {函数} string.capwords (s, sep=None)

使用 @ref{79b,,str.split()} 将参数拆分为单词，使用 @ref{15db,,str.capitalize()} 将单词转为大写形式，使用 @ref{15ca,,str.join()} 将大写的单词进行拼接。 如果可选的第二个参数 @emph{sep} 被省略或为 @code{None}，则连续的空白字符会被替换为单个空格符并且开头和末尾的空白字符会被移除，否则 @emph{sep} 会被用来拆分和拼接单词。
@end deffn

@node re --- 正则表达式操作,difflib --- 计算差异的辅助工具,string --- 常见的字符串操作,文本处理服务
@anchor{library/re doc}@anchor{16e0}@anchor{library/re module-re}@anchor{dd}@anchor{library/re re-regular-expression-operations}@anchor{16e1}
@subsection @code{re} --- 正则表达式操作


@geindex re (模块)

@strong{源代码:} Lib/re.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/re.py}


__________________________________________________________________


这个模块提供了与 Perl 语言类似的正则表达式匹配操作。

模式和被搜索的字符串既可以是 Unicode 字符串 (@ref{329,,str}) ，也可以是8位字节串 (@ref{32a,,bytes})。 但是，Unicode 字符串与8位字节串不能混用：也就是说，你不能用一个字节串模式去匹配 Unicode 字符串，反之亦然；类似地，当进行替换操作时，替换字符串的类型也必须与所用的模式和搜索字符串的类型一致。

正则表达式使用反斜杠字符 (@code{'\'}) 来表示特殊形式或是允许在使用特殊字符时不引发它们的特殊含义。 这会与 Python 的字符串字面值中对相同字符出于相同目的的用法产生冲突；例如，要匹配一个反斜杠字面值，用户可能必须写成 @code{'\\\\'} 来作为模式字符串，因为正则表达式必须为 @code{\\}，而每个反斜杠在普通 Python 字符串字面值中又必须表示为 @code{\\}。 而且还要注意，在 Python 的字符串字面值中使用的反斜杠如果有任何无效的转义序列，现在将会产生 @ref{278,,DeprecationWarning} 并将在未来改为 @ref{452,,SyntaxError}。 此行为即使对于正则表达式来说有效的转义字符同样会发生。

解决办法是对于正则表达式样式使用 Python 的原始字符串表示法；在带有 @code{'r'} 前缀的字符串字面值中，反斜杠不必做任何特殊处理。 因此 @code{r"\n"} 表示包含 @code{'\'} 和 @code{'n'} 两个字符的字符串，而 @code{"\n"} 则表示只包含一个换行符的字符串。 样式在 Python 代码中通常都会使用这种原始字符串表示法来表示。

绝大部分正则表达式操作都提供为模块函数和方法，在 @ref{896,,编译正则表达式}.  这些函数是一个捷径，不需要先编译一个正则对象，但是损失了一些优化参数。


@subsubheading 参见


第三方模块 regex@footnote{https://pypi.org/project/regex/} , 提供了与标准库 @ref{dd,,re} 模块兼容的API接口, 同时还提供了额外的功能和更全面的Unicode支持。


@menu
* 正则表达式语法:: 
* 模块内容:: 
* 正则表达式对象 （正则对象）:: 
* 匹配对象:: 
* 正则表达式例子:: 

@end menu

@node 正则表达式语法,模块内容,,re --- 正则表达式操作
@anchor{library/re re-syntax}@anchor{16e2}@anchor{library/re regular-expression-syntax}@anchor{16e3}
@subsubsection 正则表达式语法


一个正则表达式（或RE）指定了一集与之匹配的字符串；模块内的函数可以让你检查某个字符串是否跟给定的正则表达式匹配（或者一个正则表达式是否匹配到一个字符串，这两种说法含义相同）。

正则表达式可以拼接； 如果 @emph{A} 和 @emph{B} 都是正则表达式， 那么 @emph{AB} 也是正则表达式。 通常， 如果字符串 @emph{p} 匹配 @emph{A} 并且另一个字符串 @emph{q} 匹配 @emph{B}, 那么 @emph{pq} 可以匹配 AB。除非 @emph{A} 或者 @emph{B} 包含低优先级操作，@emph{A} 和 @emph{B} 存在边界条件；或者命名组引用。所以，复杂表达式可以很容易的从这里描述的简单源语表达式构建。 了解更多正则表达式理论和实现，参考the Friedl book @ref{16e4,,[Frie09]} ，或者其他编译器构建的书籍。

以下是正则表达式格式的简要说明。更详细的信息和演示，参考  @ref{16e5,,正则表达式HOWTO}。

正则表达式可以包含普通或者特殊字符。绝大部分普通字符，比如 @code{'A'}, @code{'a'}, 或者 @code{'0'}，都是最简单的正则表达式。它们就匹配自身。你可以拼接普通字符，所以 @code{last} 匹配字符串 @code{'last'}.  （在这一节的其他部分，我们将用 @code{this special style} 这种方式表示正则表达式，通常不带引号，要匹配的字符串用 @code{'in single quotes'} ，单引号形式。）

有些字符，比如 @code{'|'} 或者 @code{'('}，属于特殊字符。 特殊字符既可以表示它的普通含义， 也可以影响它旁边的正则表达式的解释。

重复修饰符 (@code{*}, @code{+}, @code{?}, @code{@{m,n@}}, 等) 不能直接嵌套。这样避免了非贪婪后缀 @code{?} 修饰符，和其他实现中的修饰符产生的多义性。要应用一个内层重复嵌套，可以使用括号。 比如，表达式 @code{(?:a@{6@})*} 匹配6个 @code{'a'} 字符重复任意次数。

特殊字符有：

@geindex . (dot); in regular expressions


@table @asis

@item @code{.}

(点) 在默认模式，匹配除了换行的任意字符。如果指定了标签 @ref{16e6,,DOTALL} ，它将匹配包括换行符的任意字符。
@end table

@geindex ^ (caret); in regular expressions


@table @asis

@item @code{^}

(插入符号)  匹配字符串的开头， 并且在 @ref{16e7,,MULTILINE} 模式也匹配换行后的首个符号。
@end table

@geindex $ (dollar); in regular expressions


@table @asis

@item @code{$}

匹配字符串尾或者换行符的前一个字符，在 @ref{16e7,,MULTILINE} 模式匹配换行符的前一个字符。  @code{foo} 匹配 @code{'foo'} 和 @code{'foobar'} , 但正则 @code{foo$} 只匹配 @code{'foo'}。更有趣的是， 在 @code{'foo1\nfoo2\n'} 搜索 @code{foo.$} ，通常匹配  @code{'foo2'} ，但在 @ref{16e7,,MULTILINE} 模式 ，可以匹配到 @code{'foo1'} ；在 @code{'foo\n'} 搜索 @code{$} 会找到两个空串：一个在换行前，一个在字符串最后。
@end table

@geindex * (asterisk); in regular expressions


@table @asis

@item @code{*}

对它前面的正则式匹配0到任意次重复， 尽量多的匹配字符串。  @code{ab*} 会匹配 @code{'a'}， @code{'ab'}， 或者 @code{'a'`@w{`}后面跟随任意个 `@w{`}'b'}。
@end table

@geindex + (plus); in regular expressions


@table @asis

@item @code{+}

对它前面的正则式匹配1到任意次重复。 @code{ab+} 会匹配 @code{'a'} 后面跟随1个以上到任意个 @code{'b'}，它不会匹配 @code{'a'}。
@end table

@geindex ? (question mark); in regular expressions


@table @asis

@item @code{?}

对它前面的正则式匹配0到1次重复。 @code{ab?} 会匹配 @code{'a'} 或者 @code{'ab'}。
@end table

@geindex *?; in regular expressions
@geindex +?; in regular expressions
@geindex ??; in regular expressions


@table @asis

@item @code{*?}, @code{+?}, @code{??}

@code{'*'}, @code{'+'}，和 @code{'?'} 修饰符都是 @emph{贪婪的}；它们在字符串进行尽可能多的匹配。有时候并不需要这种行为。如果正则式 @code{<.*>} 希望找到 @code{'<a> b <c>'}，它将会匹配整个字符串，而不仅是 @code{'<a>'}。在修饰符之后添加 @code{?} 将使样式以 @emph{非贪婪`方式或者 :dfn:`最小} 方式进行匹配； 尽量 @emph{少} 的字符将会被匹配。 使用正则式 @code{<.*?>} 将会仅仅匹配 @code{'<a>'}。
@end table

@geindex @{@} (curly brackets); in regular expressions


@table @asis

@item @code{@{m@}}

对其之前的正则式指定匹配 @emph{m} 个重复；少于 @emph{m} 的话就会导致匹配失败。比如， @code{a@{6@}} 将匹配6个 @code{'a'} , 但是不能是5个。

@item @code{@{m,n@}}

对正则式进行 @emph{m} 到 @emph{n} 次匹配，在 @emph{m} 和 @emph{n} 之间取尽量多。 比如，@code{a@{3,5@}} 将匹配 3 到 5个 @code{'a'}。忽略 @emph{m} 意为指定下界为0，忽略 @emph{n} 指定上界为无限次。 比如 @code{a@{4,@}b} 将匹配 @code{'aaaab'} 或者1000个 @code{'a'} 尾随一个 @code{'b'}，但不能匹配 @code{'aaab'}。逗号不能省略，否则无法辨别修饰符应该忽略哪个边界。

@item @code{@{m,n@}?}

前一个修饰符的非贪婪模式，只匹配尽量少的字符次数。比如，对于 @code{'aaaaaa'}， @code{a@{3,5@}} 匹配 5个 @code{'a'} ，而 @code{a@{3,5@}?} 只匹配3个 @code{'a'}。
@end table

@geindex \ (backslash); in regular expressions


@table @asis

@item @code{\}

转义特殊字符（允许你匹配 @code{'*'}, @code{'?'}, 或者此类其他），或者表示一个特殊序列；特殊序列之后进行讨论。

如果你没有使用原始字符串（ @code{r'raw'} ）来表达样式，要牢记Python也使用反斜杠作为转义序列；如果转义序列不被Python的分析器识别，反斜杠和字符才能出现在字符串中。如果Python可以识别这个序列，那么反斜杠就应该重复两次。这将导致理解障碍，所以高度推荐，就算是最简单的表达式，也要使用原始字符串。
@end table

@geindex [] (square brackets); in regular expressions


@table @asis

@item @code{[]}

用于表示一个字符集合。在一个集合中：


@itemize *

@item 
字符可以单独列出，比如 @code{[amk]} 匹配 @code{'a'}， @code{'m'}， 或者 @code{'k'}。
@end itemize

@geindex - (minus); in regular expressions


@itemize *

@item 
可以表示字符范围，通过用 @code{'-'} 将两个字符连起来。比如 @code{[a-z]} 将匹配任何小写ASCII字符， @code{[0-5][0-9]} 将匹配从 @code{00} 到 @code{59} 的两位数字， @code{[0-9A-Fa-f]} 将匹配任何十六进制数位。 如果 @code{-} 进行了转义 （比如 @code{[a\-z]}）或者它的位置在首位或者末尾（如 @code{[-a]} 或 @code{[a-]}），它就只表示普通字符 @code{'-'}。

@item 
特殊字符在集合中，失去它的特殊含义。比如 @code{[(+*)]} 只会匹配这几个文法字符 @code{'('}, @code{'+'}, @code{'*'}, or @code{')'}。
@end itemize

@geindex \ (backslash); in regular expressions


@itemize *

@item 
字符类如 @code{\w} 或者 @code{\S} (如下定义) 在集合内可以接受，它们可以匹配的字符由 @ref{3c0,,ASCII} 或者 @ref{3c1,,LOCALE} 模式决定。
@end itemize

@geindex ^ (caret); in regular expressions


@itemize *

@item 
不在集合范围内的字符可以通过 @emph{取反} 来进行匹配。如果集合首字符是 @code{'^'} ，所有 @emph{不} 在集合内的字符将会被匹配，比如 @code{[^5]} 将匹配所有字符，除了 @code{'5'}， @code{[^^]} 将匹配所有字符，除了 @code{'^'}.  @code{^} 如果不在集合首位，就没有特殊含义。

@item 
在集合内要匹配一个字符 @code{']'}，有两种方法，要么就在它之前加上反斜杠，要么就把它放到集合首位。比如， @code{[()[\]@{@}]} 和 @code{[]()[@{@}]} 都可以匹配括号。
@end itemize

@c .. index:: single: --; in regular expressions

@c .. index:: single: &&; in regular expressions

@c .. index:: single: ~~; in regular expressions

@c .. index:: single: ||; in regular expressions


@itemize *

@item 
Unicode Technical Standard #18@footnote{https://unicode.org/reports/tr18/} 里的嵌套集合和集合操作支持可能在未来添加。这将会改变语法，所以为了帮助这个改变，一个 @ref{31e,,FutureWarning} 将会在有多义的情况里被 @code{raise}，包含以下几种情况，集合由 @code{'['} 开始，或者包含下列字符序列  @code{'--'}, @code{'&&'}, @code{'~~'}, 和 @code{'||'}。为了避免警告，需要将它们用反斜杠转义。
@end itemize


在 3.7 版更改: 如果一个字符串构建的语义在未来会改变的话，一个 @ref{31e,,FutureWarning} 会 @code{raise} 。

@end table

@geindex | (vertical bar); in regular expressions


@table @asis

@item @code{|}

@code{A|B}， @emph{A} 和 @emph{B} 可以是任意正则表达式，创建一个正则表达式，匹配 @emph{A} 或者 @emph{B}.  任意个正则表达式可以用 @code{'|'} 连接。它也可以在组合（见下列）内使用。扫描目标字符串时， @code{'|'} 分隔开的正则样式从左到右进行匹配。当一个样式完全匹配时，这个分支就被接受。意思就是，一旦 @emph{A} 匹配成功， @emph{B} 就不再进行匹配，即便它能产生一个更好的匹配。或者说，@code{'|'} 操作符绝不贪婪。  如果要匹配 @code{'|'} 字符，使用 @code{\|}， 或者把它包含在字符集里，比如 @code{[|]}.
@end table

@geindex () (parentheses); in regular expressions


@table @asis

@item @code{(...)}

（组合），匹配括号内的任意正则表达式，并标识出组合的开始和结尾。匹配完成后，组合的内容可以被获取，并可以在之后用  @code{\number} 转义序列进行再次匹配，之后进行详细说明。要匹配字符 @code{'('} 或者 @code{')'}, 用 @code{\(} 或 @code{\)}, 或者把它们包含在字符集合里: @code{[(]}, @code{[)]}.
@end table

@geindex (?; in regular expressions


@table @asis

@item @code{(?…)}

这是个扩展标记法 （一个 @code{'?'} 跟随 @code{'('} 并无含义）。  @code{'?'} 后面的第一个字符决定了这个构建采用什么样的语法。这种扩展通常并不创建新的组合； @code{(?P<name>...)} 是唯一的例外。 以下是目前支持的扩展。

@item @code{(?aiLmsux)}

( @code{'a'}, @code{'i'}, @code{'L'}, @code{'m'}, @code{'s'}, @code{'u'}, @code{'x'} 中的一个或多个) 这个组合匹配一个空字符串；这些字符对正则表达式设置以下标记 @ref{16e8,,re.A} (只匹配ASCII字符), @ref{16e9,,re.I} (忽略大小写), @ref{16ea,,re.L} (语言依赖), @ref{16eb,,re.M} (多行模式), @ref{16ec,,re.S} (点dot匹配全部字符), @code{re.U} (Unicode匹配), and @ref{16ed,,re.X} (冗长模式)。 (这些标记在 @ref{16ee,,模块内容} 中描述) 如果你想将这些标记包含在正则表达式中，这个方法就很有用，免去了在 @ref{444,,re.compile()} 中传递 @emph{flag} 参数。标记应该在表达式字符串首位表示。
@end table

@geindex (?;; in regular expressions


@table @asis

@item @code{(?:…)}

正则括号的非捕获版本。 匹配在括号内的任何正则表达式，但该分组所匹配的子字符串 @emph{不能} 在执行匹配后被获取或是之后在模式中被引用。

@item @code{(?aiLmsux-imsx:…)}

(@code{'a'}, @code{'i'}, @code{'L'}, @code{'m'}, @code{'s'}, @code{'u'}, @code{'x'} 中的0或者多个， 之后可选跟随 @code{'-'} 在后面跟随 @code{'i'} , @code{'m'} , @code{'s'} , @code{'x'} 中的一到多个 .) 这些字符为表达式的其中一部分 @emph{设置} 或者 @emph{去除} 相应标记 @ref{16e8,,re.A} (只匹配ASCII), @ref{16e9,,re.I} (忽略大小写), @ref{16ea,,re.L} (语言依赖), @ref{16eb,,re.M} (多行), @ref{16ec,,re.S} (点匹配所有字符), @code{re.U} (Unicode匹配), and @ref{16ed,,re.X} (冗长模式)。(标记描述在 @ref{16ee,,模块内容} .)

@code{'a'}, @code{'L'} and @code{'u'} 作为内联标记是相互排斥的， 所以它们不能结合在一起，或者跟随 @code{'-'} 。 当他们中的某个出现在内联组中，它就覆盖了括号组内的匹配模式。在Unicode样式中， @code{(?a:...)} 切换为 只匹配ASCII， @code{(?u:...)} 切换为Unicode匹配 (默认).  在byte样式中 @code{(?L:...)} 切换为语言依赖模式， @code{(?a:...)} 切换为 只匹配ASCII (默认)。这种方式只覆盖组合内匹配，括号外的匹配模式不受影响。


3.6 新版功能.



在 3.7 版更改: 符号 @code{'a'}, @code{'L'} 和 @code{'u'} 同样可以用在一个组合内。

@end table

@geindex (?P<; in regular expressions


@table @asis

@item @code{(?P<name>…)}

（命名组合）类似正则组合，但是匹配到的子串组在外部是通过定义的 @emph{name} 来获取的。组合名必须是有效的Python标识符，并且每个组合名只能用一个正则表达式定义，只能定义一次。一个符号组合同样是一个数字组合，就像这个组合没有被命名一样。

命名组合可以在三种上下文中引用。如果样式是 @code{(?P<quote>['"]).*?(?P=quote)} （也就是说，匹配单引号或者双引号括起来的字符串)：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

引用组合 "quote" 的上下文

@tab

引用方法

@item

在正则式自身内

@tab


@itemize *

@item 
@code{(?P=quote)} (如示)

@item 
@code{\1}
@end itemize

@item

处理匹配对象 @emph{m}

@tab


@itemize *

@item 
@code{m.group('quote')}

@item 
@code{m.end('quote')} (等)
@end itemize

@item

传递到 @code{re.sub()} 里的 @emph{repl} 参数中

@tab


@itemize *

@item 
@code{\g<quote>}

@item 
@code{\g<1>}

@item 
@code{\1}
@end itemize

@end multitable

@end table

@geindex (?P=; in regular expressions


@table @asis

@item @code{(?P=name)}

反向引用一个命名组合；它匹配前面那个叫 @emph{name} 的命名组中匹配到的串同样的字串。
@end table

@geindex (?#; in regular expressions


@table @asis

@item @code{(?#…)}

注释；里面的内容会被忽略。
@end table

@geindex (?=; in regular expressions


@table @asis

@item @code{(?=…)}

匹配 @code{…} 的内容，但是并不消费样式的内容。这个叫做 @emph{lookahead assertion}。比如， @code{Isaac (?=Asimov)} 匹配 @code{'Isaac '} 只有在后面是  @code{'Asimov'} 的时候。
@end table

@geindex (?!; in regular expressions


@table @asis

@item @code{(?!…)}

匹配 @code{…} 不符合的情况。这个叫 @emph{negative lookahead assertion} （前视取反）。比如说， @code{Isaac (?!Asimov)} 只有后面 @emph{不} 是 @code{'Asimov'} 的时候才匹配 @code{'Isaac '} 。
@end table

@geindex (?<=; in regular expressions


@table @asis

@item @code{(?<=…)}

匹配字符串的当前位置，它的前面匹配 @code{…} 的内容到当前位置。这叫:dfn:@cite{positive lookbehind assertion} （正向后视断定）。 @code{(?<=abc)def} 会在 @code{'abcdef'} 中找到一个匹配，因为后视会往后看3个字符并检查是否包含匹配的样式。包含的匹配样式必须是定长的，意思就是 @code{abc} 或 @code{a|b} 是允许的，但是 @code{a*} 和 @code{a@{3,4@}} 不可以。注意以 positive lookbehind assertions 开始的样式，如 @code{(?<=abc)def} ，并不是从 a 开始搜索，而是从 d 往回看的。你可能更加愿意使用 @ref{bab,,search()} 函数，而不是 @ref{bac,,match()} 函数：

@example
>>> import re
>>> m = re.search('(?<=abc)def', 'abcdef')
>>> m.group(0)
'def'
@end example

这个例子搜索一个跟随在连字符后的单词：

@example
>>> m = re.search(r'(?<=-)\w+', 'spam-egg')
>>> m.group(0)
'egg'
@end example


在 3.5 版更改: 添加定长组合引用的支持。

@end table

@geindex (?<!; in regular expressions


@table @asis

@item @code{(?<!…)}

匹配当前位置之前不是 @code{...} 的样式。这个叫 @emph{negative lookbehind assertion} （后视断定取非）。类似正向后视断定，包含的样式匹配必须是定长的。由 negative lookbehind assertion 开始的样式可以从字符串搜索开始的位置进行匹配。

@item @code{(?(id/name)yes-pattern|no-pattern)}

如果给定的  @emph{id} 或 @emph{name} 存在，将会尝试匹配 @code{yes-pattern} ，否则就尝试匹配 @code{no-pattern}，@code{no-pattern} 可选，也可以被忽略。比如， @code{(<)?(\w+@@\w+(?:\.\w+)+)(?(1)>|$)} 是一个email样式匹配，将匹配 @code{'<user@@host.com>'} 或 @code{'user@@host.com'} ，但不会匹配 @code{'<user@@host.com'} ，也不会匹配 @code{'user@@host.com>'}。
@end table

由 @code{'\'} 和一个字符组成的特殊序列在以下列出。 如果普通字符不是ASCII数位或者ASCII字母，那么正则样式将匹配第二个字符。比如，@code{\$} 匹配字符 @code{'$'}.

@geindex \ (backslash); in regular expressions


@table @asis

@item @code{\number}

匹配数字代表的组合。每个括号是一个组合，组合从1开始编号。比如 @code{(.+) \1} 匹配 @code{'the the'} 或者 @code{'55 55'}, 但不会匹配 @code{'thethe'} (注意组合后面的空格)。这个特殊序列只能用于匹配前面99个组合。如果  @emph{number} 的第一个数位是0， 或者 @emph{number} 是三个八进制数，它将不会被看作是一个组合，而是八进制的数字值。在 @code{'['} 和 @code{']'} 字符集合内，任何数字转义都被看作是字符。
@end table

@geindex \A; in regular expressions


@table @asis

@item @code{\A}

只匹配字符串开始。
@end table

@geindex \b; in regular expressions


@table @asis

@item @code{\b}

匹配空字符串，但只在单词开始或结尾的位置。一个单词被定义为一个单词字符的序列。注意，通常 @code{\b} 定义为 @code{\w} 和 @code{\W} 字符之间，或者 @code{\w} 和字符串开始/结尾的边界， 意思就是 @code{r'\bfoo\b'} 匹配 @code{'foo'}, @code{'foo.'}, @code{'(foo)'}, @code{'bar foo baz'} 但不匹配 @code{'foobar'} 或者 @code{'foo3'}。

默认情况下，Unicode字母和数字是在Unicode样式中使用的，但是可以用  @ref{3c0,,ASCII} 标记来更改。如果 @ref{3c1,,LOCALE} 标记被设置的话，词的边界是由当前语言区域设置决定的，@code{\b} 表示退格字符，以便与Python字符串文本兼容。
@end table

@geindex \B; in regular expressions


@table @asis

@item @code{\B}

匹配空字符串，但 @emph{不} 能在词的开头或者结尾。意思就是 @code{r'py\B'} 匹配 @code{'python'}, @code{'py3'}, @code{'py2'}, 但不匹配 @code{'py'}, @code{'py.'}, 或者 @code{'py!'}. @code{\B} 是 @code{\b} 的取非，所以Unicode样式的词语是由Unicode字母，数字或下划线构成的，虽然可以用 @ref{3c0,,ASCII} 标志来改变。如果使用了 @ref{3c1,,LOCALE} 标志，则词的边界由当前语言区域设置。
@end table

@geindex \d; in regular expressions


@table @asis

@item @code{\d}


@table @asis

@item 对于 Unicode (str) 样式：

匹配任何Unicode十进制数（就是在Unicode字符目录[Nd]里的字符）。这包括了 @code{[0-9]} ，和很多其他的数字字符。如果设置了 @ref{3c0,,ASCII} 标志，就只匹配 @code{[0-9]} 。

@item 对于8位(bytes)样式：

匹配任何十进制数，就是 @code{[0-9]}。
@end table
@end table

@geindex \D; in regular expressions


@table @asis

@item @code{\D}

匹配任何非十进制数字的字符。就是 @code{\d} 取非。 如果设置了 @ref{3c0,,ASCII} 标志，就相当于 @code{[^0-9]} 。
@end table

@geindex \s; in regular expressions


@table @asis

@item @code{\s}


@table @asis

@item 对于 Unicode (str) 样式：

匹配任何Unicode空白字符（包括 @code{[ \t\n\r\f\v]} ，还有很多其他字符，比如不同语言排版规则约定的不换行空格）。如果 @ref{3c0,,ASCII} 被设置，就只匹配 @code{[ \t\n\r\f\v]} 。

@item 对于8位(bytes)样式：

匹配ASCII中的空白字符，就是 @code{[ \t\n\r\f\v]} 。
@end table
@end table

@geindex \S; in regular expressions


@table @asis

@item @code{\S}

匹配任何非空白字符。就是 @code{\s} 取非。如果设置了 @ref{3c0,,ASCII} 标志，就相当于 @code{[^ \t\n\r\f\v]} 。
@end table

@geindex \w; in regular expressions


@table @asis

@item @code{\w}


@table @asis

@item 对于 Unicode (str) 样式：

匹配Unicode词语的字符，包含了可以构成词语的绝大部分字符，也包括数字和下划线。如果设置了 @ref{3c0,,ASCII} 标志，就只匹配 @code{[a-zA-Z0-9_]} 。

@item 对于8位(bytes)样式：

匹配ASCII字符中的数字和字母和下划线，就是 @code{[a-zA-Z0-9_]} 。如果设置了 @ref{3c1,,LOCALE} 标记，就匹配当前语言区域的数字和字母和下划线。
@end table
@end table

@geindex \W; in regular expressions


@table @asis

@item @code{\W}

匹配非单词字符的字符。这与 @code{\w} 正相反。如果使用了 @ref{3c0,,ASCII} 旗标，这就等价于 @code{[^a-zA-Z0-9_]}。如果使用了 @ref{3c1,,LOCALE} 旗标，则会匹配当前区域中既非字母数字也非下划线的字符。
@end table

@geindex \Z; in regular expressions


@table @asis

@item @code{\Z}

只匹配字符串尾。
@end table

@geindex \a; in regular expressions
@geindex \b; in regular expressions
@geindex \f; in regular expressions
@geindex \n; in regular expressions
@geindex \N; in regular expressions
@geindex \r; in regular expressions
@geindex \t; in regular expressions
@geindex \u; in regular expressions
@geindex \U; in regular expressions
@geindex \v; in regular expressions
@geindex \x; in regular expressions
@geindex \\; in regular expressions

绝大部分Python的标准转义字符也被正则表达式分析器支持。:

@example
\a      \b      \f      \n
\N      \r      \t      \u
\U      \v      \x      \\
@end example

（注意 @code{\b} 被用于表示词语的边界，它只在字符集合内表示退格，比如 @code{[\b]} 。）

@code{'\u'}, @code{'\U'} 和 @code{'\N'} 转义序列只在 Unicode 模式中可被识别。 在 bytes 模式中它们会导致错误。 未知的 ASCII 字母转义序列保留在未来使用，会被当作错误来处理。

八进制转义包含为一个有限形式。如果首位数字是 0， 或者有三个八进制数位，那么就认为它是八进制转义。其他的情况，就看作是组引用。对于字符串文本，八进制转义最多有三个数位长。


在 3.3 版更改: 增加了 @code{'\u'} 和 @code{'\U'} 转义序列。



在 3.6 版更改: 由 @code{'\'} 和一个ASCII字符组成的未知转义会被看成错误。



在 3.8 版更改: 添加了 @code{'\N@{name@}'} 转义序列。 与在字符串字面值中一样，它扩展了命名 Unicode 字符 (例如 @code{'\N@{EM DASH@}'})。


@node 模块内容,正则表达式对象 （正则对象）,正则表达式语法,re --- 正则表达式操作
@anchor{library/re contents-of-module-re}@anchor{16ee}@anchor{library/re module-contents}@anchor{16ef}
@subsubsection 模块内容


模块定义了几个函数，常量，和一个例外。有些函数是编译后的正则表达式方法的简化版本（少了一些特性）。绝大部分重要的应用，总是会先将正则表达式编译，之后在进行操作。


在 3.6 版更改: 标志常量现在是 @code{RegexFlag} 类的实例，这个类是 @ref{16f0,,enum.IntFlag} 的子类。


@geindex compile() (在 re 模块中)
@anchor{library/re re compile}@anchor{444}
@deffn {函数} re.compile (pattern, flags=0)

将正则表达式的样式编译为一个 @ref{896,,正则表达式对象}  （正则对象），可以用于匹配，通过这个对象的方法  @ref{16f1,,match()}, @ref{16f2,,search()} 以及其他如下描述。

这个表达式的行为可以通过指定 @emph{标记} 的值来改变。值可以是以下任意变量，可以通过位的OR操作来结合（ @code{|} 操作符）。

序列

@example
prog = re.compile(pattern)
result = prog.match(string)
@end example

等价于

@example
result = re.match(pattern, string)
@end example

如果需要多次使用这个正则表达式的话，使用 @ref{444,,re.compile()} 和保存这个正则对象以便复用，可以让程序更加高效。

@cartouche
@quotation 注解 
通过 @ref{444,,re.compile()} 编译后的样式，和模块级的函数会被缓存， 所以少数的正则表达式使用无需考虑编译的问题。
@end quotation
@end cartouche
@end deffn

@geindex A() (在 re 模块中)
@geindex ASCII() (在 re 模块中)
@anchor{library/re re A}@anchor{16e8}
@deffn {数据} re.A
@anchor{library/re re ASCII}@anchor{3c0}
@deffnx {数据} re.ASCII

让 @code{\w}, @code{\W}, @code{\b}, @code{\B}, @code{\d}, @code{\D}, @code{\s} 和 @code{\S} 只匹配ASCII，而不是Unicode。这只对Unicode样式有效，会被byte样式忽略。相当于前面语法中的内联标志 @code{(?a)} 。

注意，为了保持向后兼容， @code{re.U} 标记依然存在（还有他的同义  @code{re.UNICODE} 和嵌入形式 @code{(?u)} ) ， 但是这些在 Python 3 是冗余的，因为默认字符串已经是Unicode了（并且Unicode匹配不允许byte出现)。
@end deffn

@geindex DEBUG() (在 re 模块中)
@anchor{library/re re DEBUG}@anchor{16f3}
@deffn {数据} re.DEBUG

显示编译时的debug信息，没有内联标记。
@end deffn

@geindex I() (在 re 模块中)
@geindex IGNORECASE() (在 re 模块中)
@anchor{library/re re I}@anchor{16e9}
@deffn {数据} re.I
@anchor{library/re re IGNORECASE}@anchor{16f4}
@deffnx {数据} re.IGNORECASE

进行忽略大小写匹配；表达式如 @code{[A-Z]} 也会匹配小写字符。Unicode匹配（比如 @code{Ü} 匹配 @code{ü}）同样有用，除非设置了 @ref{3c0,,re.ASCII} 标记来禁用非ASCII匹配。当前语言区域不会改变这个标记，除非设置了 @ref{3c1,,re.LOCALE} 标记。这个相当于内联标记 @code{(?i)} 。

注意，当设置了 @ref{16f4,,IGNORECASE} 标记，搜索Unicode样式 @code{[a-z]} 或 @code{[A-Z]} 的结合时，它将会匹配52个ASCII字符和4个额外的非ASCII字符： 'İ' (U+0130, 拉丁大写的 I 带个点在上面), 'ı' (U+0131, 拉丁小写没有点的 I ), 'ſ' (U+017F, 拉丁小写长 s) and 'K' (U+212A, 开尔文符号).如果使用 @ref{3c0,,ASCII} 标记，就只匹配 'a' 到 'z' 和 'A' 到 'Z' 。
@end deffn

@geindex L() (在 re 模块中)
@geindex LOCALE() (在 re 模块中)
@anchor{library/re re L}@anchor{16ea}
@deffn {数据} re.L
@anchor{library/re re LOCALE}@anchor{3c1}
@deffnx {数据} re.LOCALE

由当前语言区域决定 @code{\w}, @code{\W}, @code{\b}, @code{\B} 和大小写敏感匹配。这个标记只能对byte样式有效。这个标记不推荐使用，因为语言区域机制很不可靠，它一次只能处理一个 "习惯”，而且只对8位字节有效。Unicode匹配在Python 3 里默认启用，并可以处理不同语言。 这个对应内联标记 @code{(?L)} 。


在 3.6 版更改: @ref{3c1,,re.LOCALE} 只能用于byte样式，而且不能和 @ref{3c0,,re.ASCII} 一起用。



在 3.7 版更改: 设置了 @ref{3c1,,re.LOCALE} 标记的编译正则对象不再在编译时依赖语言区域设置。语言区域设置只在匹配的时候影响其结果。

@end deffn

@geindex M() (在 re 模块中)
@geindex MULTILINE() (在 re 模块中)
@anchor{library/re re M}@anchor{16eb}
@deffn {数据} re.M
@anchor{library/re re MULTILINE}@anchor{16e7}
@deffnx {数据} re.MULTILINE

设置以后，样式字符 @code{'^'} 匹配字符串的开始，和每一行的开始（换行符后面紧跟的符号）；样式字符 @code{'$'} 匹配字符串尾，和每一行的结尾（换行符前面那个符号）。默认情况下，@code{’^’} 匹配字符串头，@code{'$'} 匹配字符串尾。对应内联标记 @code{(?m)} 。
@end deffn

@geindex S() (在 re 模块中)
@geindex DOTALL() (在 re 模块中)
@anchor{library/re re S}@anchor{16ec}
@deffn {数据} re.S
@anchor{library/re re DOTALL}@anchor{16e6}
@deffnx {数据} re.DOTALL

让 @code{'.'} 特殊字符匹配任何字符，包括换行符；如果没有这个标记，@code{'.'} 就匹配 @emph{除了} 换行符的其他任意字符。对应内联标记 @code{(?s)} 。
@end deffn

@geindex X() (在 re 模块中)
@geindex VERBOSE() (在 re 模块中)
@anchor{library/re re X}@anchor{16ed}
@deffn {数据} re.X
@anchor{library/re re VERBOSE}@anchor{16f5}
@deffnx {数据} re.VERBOSE

@geindex # (hash); in regular expressions

这个标记允许你编写更具可读性更友好的正则表达式。通过分段和添加注释。空白符号会被忽略，除非在一个字符集合当中或者由反斜杠转义，或者在 @code{*?}, @code{(?:} or @code{(?P<…>} 分组之内。当一个行内有 @code{#} 不在字符集和转义序列，那么它之后的所有字符都是注释。

意思就是下面两个正则表达式等价地匹配一个十进制数字：

@example
a = re.compile(r"""\d +  # the integral part
                   \.    # the decimal point
                   \d *  # some fractional digits""", re.X)
b = re.compile(r"\d+\.\d*")
@end example

对应内联标记 @code{(?x)} 。
@end deffn

@geindex search() (在 re 模块中)
@anchor{library/re re search}@anchor{bab}
@deffn {函数} re.search (pattern, string, flags=0)

扫描整个 @emph{字符串} 找到匹配样式的第一个位置，并返回一个相应的 @ref{897,,匹配对象}。如果没有匹配，就返回一个 @code{None} ； 注意这和找到一个零长度匹配是不同的。
@end deffn

@geindex match() (在 re 模块中)
@anchor{library/re re match}@anchor{bac}
@deffn {函数} re.match (pattern, string, flags=0)

如果 @emph{string} 开始的0或者多个字符匹配到了正则表达式样式，就返回一个相应的 @ref{897,,匹配对象} 。 如果没有匹配，就返回 @code{None} ；注意它跟零长度匹配是不同的。

注意即便是 @ref{16e7,,MULTILINE} 多行模式， @ref{bac,,re.match()} 也只匹配字符串的开始位置，而不匹配每行开始。

如果你想定位 @emph{string} 的任何位置，使用 @ref{bab,,search()} 来替代（也可参考 @ref{16f6,,search() vs. match()} ）
@end deffn

@geindex fullmatch() (在 re 模块中)
@anchor{library/re re fullmatch}@anchor{895}
@deffn {函数} re.fullmatch (pattern, string, flags=0)

如果整个 @emph{string} 匹配到正则表达式样式，就返回一个相应的 @ref{897,,匹配对象} 。 否则就返回一个 @code{None} ；注意这跟零长度匹配是不同的。


3.4 新版功能.

@end deffn

@geindex split() (在 re 模块中)
@anchor{library/re re split}@anchor{3c2}
@deffn {函数} re.split (pattern, string, maxsplit=0, flags=0)

用 @emph{pattern} 分开  @emph{string} 。 如果在 @emph{pattern} 中捕获到括号，那么所有的组里的文字也会包含在列表里。如果 @emph{maxsplit} 非零， 最多进行 @emph{maxsplit} 次分隔， 剩下的字符全部返回到列表的最后一个元素。

@example
>>> re.split(r'\W+', 'Words, words, words.')
['Words', 'words', 'words', '@w{'}]
>>> re.split(r'(\W+)', 'Words, words, words.')
['Words', ', ', 'words', ', ', 'words', '.', '@w{'}]
>>> re.split(r'\W+', 'Words, words, words.', 1)
['Words', 'words, words.']
>>> re.split('[a-f]+', '0a3B9', flags=re.IGNORECASE)
['0', '3', '9']
@end example

如果分隔符里有捕获组合，并且匹配到字符串的开始，那么结果将会以一个空字符串开始。对于结尾也是一样

@example
>>> re.split(r'(\W+)', '...words, words...')
['@w{'}, '...', 'words', ', ', 'words', '...', '@w{'}]
@end example

这样的话，分隔组将会出现在结果列表中同样的位置。

样式的空匹配将分开字符串，但只在不相临的状况生效。

@example
>>> re.split(r'\b', 'Words, words, words.')
['@w{'}, 'Words', ', ', 'words', ', ', 'words', '.']
>>> re.split(r'\W*', '...words...')
['@w{'}, '@w{'}, 'w', 'o', 'r', 'd', 's', '@w{'}, '@w{'}]
>>> re.split(r'(\W*)', '...words...')
['@w{'}, '...', '@w{'}, '@w{'}, 'w', '@w{'}, 'o', '@w{'}, 'r', '@w{'}, 'd', '@w{'}, 's', '...', '@w{'}, '@w{'}, '@w{'}]
@end example


在 3.1 版更改: 增加了可选标记参数。



在 3.7 版更改: 增加了空字符串的样式分隔。

@end deffn

@geindex findall() (在 re 模块中)
@anchor{library/re re findall}@anchor{95d}
@deffn {函数} re.findall (pattern, string, flags=0)

对 @emph{string} 返回一个不重复的 @emph{pattern} 的匹配列表， @emph{string} 从左到右进行扫描，匹配按找到的顺序返回。如果样式里存在一到多个组，就返回一个组合列表；就是一个元组的列表（如果样式里有超过一个组合的话）。空匹配也会包含在结果里。


在 3.7 版更改: 非空匹配现在可以在前一个空匹配之后出现了。

@end deffn

@geindex finditer() (在 re 模块中)
@anchor{library/re re finditer}@anchor{16f7}
@deffn {函数} re.finditer (pattern, string, flags=0)

@emph{pattern} 在 @emph{string} 里所有的非重复匹配，返回为一个迭代器  @ref{fce,,iterator} 保存了  @ref{897,,匹配对象} 。 @emph{string} 从左到右扫描，匹配按顺序排列。空匹配也包含在结果里。


在 3.7 版更改: 非空匹配现在可以在前一个空匹配之后出现了。

@end deffn

@geindex sub() (在 re 模块中)
@anchor{library/re re sub}@anchor{475}
@deffn {函数} re.sub (pattern, repl, string, count=0, flags=0)

返回通过使用 @emph{repl} 替换在 @emph{string} 最左边非重叠出现的 @emph{pattern} 而获得的字符串。 如果样式没有找到，则不加改变地返回 @emph{string}。 @emph{repl} 可以是字符串或函数；如为字符串，则其中任何反斜杠转义序列都会被处理。 也就是说，@code{\n} 会被转换为一个换行符，@code{\r} 会被转换为一个回车附，依此类推。 未知的 ASCII 字符转义序列保留在未来使用，会被当作错误来处理。 其他未知转义序列例如 @code{\&} 会保持原样。 向后引用像是 @code{\6} 会用样式中第 6 组所匹配到的子字符串来替换。 例如:

@example
>>> re.sub(r'def\s+([a-zA-Z_][a-zA-Z_0-9]*)\s*\(\s*\):',
...        r'static PyObject*\npy_\1(void)\n@{',
...        'def myfunc():')
'static PyObject*\npy_myfunc(void)\n@{'
@end example

如果 @emph{repl} 是一个函数，那它会对每个非重复的 @emph{pattern} 的情况调用。这个函数只能有一个 @ref{897,,匹配对象} 参数，并返回一个替换后的字符串。比如

@example
>>> def dashrepl(matchobj):
...     if matchobj.group(0) == '-': return ' '
...     else: return '-'
>>> re.sub('-@{1,2@}', dashrepl, 'pro----gram-files')
'pro--gram files'
>>> re.sub(r'\sAND\s', ' & ', 'Baked Beans And Spam', flags=re.IGNORECASE)
'Baked Beans & Spam'
@end example

样式可以是一个字符串或者一个 @ref{896,,样式对象} 。

可选参数 @emph{count} 是要替换的最大次数；@emph{count} 必须是非负整数。如果忽略这个参数，或者设置为0，所有的匹配都会被替换。空匹配只在不相临连续的情况被更替，所以  @code{sub('x*', '-', 'abxd')} 返回 @code{'-a-b--d-'} 。

@geindex \g; in regular expressions

在字符串类型的 @emph{repl} 参数里，如上所述的转义和向后引用中，@code{\g<name>} 会使用命名组合 @code{name}，（在  @code{(?P<name>…)} 语法中定义） @code{\g<number>} 会使用数字组；@code{\g<2>} 就是 @code{\2}，但它避免了二义性，如 @code{\g<2>0}。 @code{\20} 就会被解释为组20，而不是组2后面跟随一个字符 @code{'0'}。向后引用 @code{\g<0>} 把 @emph{pattern} 作为一整个组进行引用。


在 3.1 版更改: 增加了可选标记参数。



在 3.5 版更改: 不匹配的组合替换为空字符串。



在 3.6 版更改: @emph{pattern} 中的未知转义（由 @code{'\'} 和一个 ASCII 字符组成）被视为错误。



在 3.7 版更改: @emph{repl} 中的未知转义（由 @code{'\'} 和一个 ASCII 字符组成）被视为错误。



在 3.7 版更改: 样式中的空匹配相邻接时会被替换。

@end deffn

@geindex subn() (在 re 模块中)
@anchor{library/re re subn}@anchor{72e}
@deffn {函数} re.subn (pattern, repl, string, count=0, flags=0)

行为与 @ref{475,,sub()} 相同，但是返回一个元组 @code{(字符串, 替换次数)}.


在 3.1 版更改: 增加了可选标记参数。



在 3.5 版更改: 不匹配的组合替换为空字符串。

@end deffn

@geindex escape() (在 re 模块中)
@anchor{library/re re escape}@anchor{490}
@deffn {函数} re.escape (pattern)

转义 @emph{pattern} 中的特殊字符。如果你想对任意可能包含正则表达式元字符的文本字符串进行匹配，它就是有用的。比如

@example
>>> print(re.escape('http://www.python.org'))
http://www\.python\.org

>>> legal_chars = string.ascii_lowercase + string.digits + "!#$%&'*+-.^_`|~:"
>>> print('[%s]+' % re.escape(legal_chars))
[abcdefghijklmnopqrstuvwxyz0123456789!\#\$%\&'\*\+\-\.\^_`\|\~:]+

>>> operators = ['+', '-', '*', '/', '**']
>>> print('|'.join(map(re.escape, sorted(operators, reverse=True))))
/|\-|\+|\*\*|\*
@end example

这个函数不能被用于 @ref{475,,sub()} 和 @ref{72e,,subn()} 的替换字符串，只有反斜杠应该被转义。 例如:

@example
>>> digits_re = r'\d+'
>>> sample = '/usr/sbin/sendmail - 0 errors, 12 warnings'
>>> print(re.sub(digits_re, digits_re.replace('\\', r'\\'), sample))
/usr/sbin/sendmail - \d+ errors, \d+ warnings
@end example


在 3.3 版更改: @code{'_'} 不再被转义。



在 3.7 版更改: 只有在正则表达式中具有特殊含义的字符才会被转义。 因此， @code{'!'}, @code{'"'}, @code{'%'}, @code{"'"}, @code{','}, @code{'/'}, @code{':'}, @code{';'}, @code{'<'}, @code{'='}, @code{'>'}, @code{'@@'} 和 @code{"`"} 将不再会被转义。

@end deffn

@geindex purge() (在 re 模块中)
@anchor{library/re re purge}@anchor{16f8}
@deffn {函数} re.purge ()

清除正则表达式的缓存。
@end deffn

@geindex error
@anchor{library/re re error}@anchor{72f}
@deffn {例外} re.error (msg, pattern=None, pos=None)

@code{raise} 一个例外。当传递到函数的字符串不是一个有效正则表达式的时候（比如，包含一个不匹配的括号）或者其他错误在编译时或匹配时产生。如果字符串不包含样式匹配，是不会被视为错误的。错误实例有以下附加属性：

@geindex msg (re.error 属性)
@anchor{library/re re error msg}@anchor{730}
@deffn {属性} msg

未格式化的错误消息。
@end deffn

@geindex pattern (re.error 属性)
@anchor{library/re re error pattern}@anchor{731}
@deffn {属性} pattern

正则表达式的模式串。
@end deffn

@geindex pos (re.error 属性)
@anchor{library/re re error pos}@anchor{732}
@deffn {属性} pos

编译失败的 @emph{pattern} 的位置索引（可以是 @code{None} ）。
@end deffn

@geindex lineno (re.error 属性)
@anchor{library/re re error lineno}@anchor{733}
@deffn {属性} lineno

对应 @emph{pos} (可以是 @code{None}) 的行号。
@end deffn

@geindex colno (re.error 属性)
@anchor{library/re re error colno}@anchor{734}
@deffn {属性} colno

对应 @emph{pos} (可以是 @code{None}) 的列号。
@end deffn


在 3.5 版更改: 增加了额外的属性。

@end deffn

@node 正则表达式对象 （正则对象）,匹配对象,模块内容,re --- 正则表达式操作
@anchor{library/re re-objects}@anchor{896}@anchor{library/re regular-expression-objects}@anchor{16f9}
@subsubsection 正则表达式对象 （正则对象）


编译后的正则表达式对象支持以下方法和属性：

@geindex search() (re.Pattern 方法)
@anchor{library/re re Pattern search}@anchor{16f2}
@deffn {方法} Pattern.search (string[, pos[, endpos]])

扫描整个 @emph{string} 寻找第一个匹配的位置， 并返回一个相应的 @ref{897,,匹配对象}。如果没有匹配，就返回 @code{None} ；注意它和零长度匹配是不同的。

可选的第二个参数 @emph{pos} 给出了字符串中开始搜索的位置索引；默认为 @code{0}，它不完全等价于字符串切片； @code{'^'} 样式字符匹配字符串真正的开头，和换行符后面的第一个字符，但不会匹配索引规定开始的位置。

可选参数 @emph{endpos} 限定了字符串搜索的结束；它假定字符串长度到 @emph{endpos} ， 所以只有从 @code{pos} 到 @code{endpos - 1} 的字符会被匹配。如果 @emph{endpos} 小于 @emph{pos}，就不会有匹配产生；另外，如果 @emph{rx} 是一个编译后的正则对象， @code{rx.search(string, 0, 50)} 等价于 @code{rx.search(string[:50], 0)}。

@example
>>> pattern = re.compile("d")
>>> pattern.search("dog")     # Match at index 0
<re.Match object; span=(0, 1), match='d'>
>>> pattern.search("dog", 1)  # No match; search doesn't include the "d"
@end example
@end deffn

@geindex match() (re.Pattern 方法)
@anchor{library/re re Pattern match}@anchor{16f1}
@deffn {方法} Pattern.match (string[, pos[, endpos]])

如果 @emph{string} 的 @emph{开始位置} 能够找到这个正则样式的任意个匹配，就返回一个相应的 @ref{897,,匹配对象}。如果不匹配，就返回 @code{None} ；注意它与零长度匹配是不同的。

可选参数 @emph{pos} 和 @emph{endpos} 与 @ref{16f2,,search()} 含义相同。

@example
>>> pattern = re.compile("o")
>>> pattern.match("dog")      # No match as "o" is not at the start of "dog".
>>> pattern.match("dog", 1)   # Match as "o" is the 2nd character of "dog".
<re.Match object; span=(1, 2), match='o'>
@end example

如果你想定位匹配在 @emph{string} 中的位置，使用 @ref{16f2,,search()} 来替代（另参考  @ref{16f6,,search() vs. match()}）。
@end deffn

@geindex fullmatch() (re.Pattern 方法)
@anchor{library/re re Pattern fullmatch}@anchor{16fa}
@deffn {方法} Pattern.fullmatch (string[, pos[, endpos]])

如果整个 @emph{string} 匹配这个正则表达式，就返回一个相应的 @ref{897,,匹配对象} 。 否则就返回 @code{None} ； 注意跟零长度匹配是不同的。

可选参数 @emph{pos} 和 @emph{endpos} 与 @ref{16f2,,search()} 含义相同。

@example
>>> pattern = re.compile("o[gh]")
>>> pattern.fullmatch("dog")      # No match as "o" is not at the start of "dog".
>>> pattern.fullmatch("ogre")     # No match as not the full string matches.
>>> pattern.fullmatch("doggie", 1, 3)   # Matches within given limits.
<re.Match object; span=(1, 3), match='og'>
@end example


3.4 新版功能.

@end deffn

@geindex split() (re.Pattern 方法)
@anchor{library/re re Pattern split}@anchor{16fb}
@deffn {方法} Pattern.split (string, maxsplit=0)

等价于 @ref{3c2,,split()} 函数，使用了编译后的样式。
@end deffn

@geindex findall() (re.Pattern 方法)
@anchor{library/re re Pattern findall}@anchor{16fc}
@deffn {方法} Pattern.findall (string[, pos[, endpos]])

类似函数 @ref{95d,,findall()} ， 使用了编译后样式，但也可以接收可选参数 @emph{pos} 和 @emph{endpos} ，限制搜索范围，就像 @ref{bab,,search()}。
@end deffn

@geindex finditer() (re.Pattern 方法)
@anchor{library/re re Pattern finditer}@anchor{16fd}
@deffn {方法} Pattern.finditer (string[, pos[, endpos]])

类似函数 @code{finiter()} ， 使用了编译后样式，但也可以接收可选参数 @emph{pos} 和 @emph{endpos} ，限制搜索范围，就像 @ref{bab,,search()}。
@end deffn

@geindex sub() (re.Pattern 方法)
@anchor{library/re re Pattern sub}@anchor{16fe}
@deffn {方法} Pattern.sub (repl, string, count=0)

等价于 @ref{475,,sub()} 函数，使用了编译后的样式。
@end deffn

@geindex subn() (re.Pattern 方法)
@anchor{library/re re Pattern subn}@anchor{16ff}
@deffn {方法} Pattern.subn (repl, string, count=0)

等价于 @ref{72e,,subn()} 函数，使用了编译后的样式。
@end deffn

@geindex flags (re.Pattern 属性)
@anchor{library/re re Pattern flags}@anchor{1700}
@deffn {属性} Pattern.flags

正则匹配标记。这是可以传递给 @ref{444,,compile()} 的参数，任何 @code{(?…)} 内联标记，隐性标记比如 @code{UNICODE} 的结合。
@end deffn

@geindex groups (re.Pattern 属性)
@anchor{library/re re Pattern groups}@anchor{1701}
@deffn {属性} Pattern.groups

捕获到的模式串中组的数量。
@end deffn

@geindex groupindex (re.Pattern 属性)
@anchor{library/re re Pattern groupindex}@anchor{1702}
@deffn {属性} Pattern.groupindex

映射由 @code{(?P<id>)} 定义的命名符号组合和数字组合的字典。如果没有符号组，那字典就是空的。
@end deffn

@geindex pattern (re.Pattern 属性)
@anchor{library/re re Pattern pattern}@anchor{1703}
@deffn {属性} Pattern.pattern

编译对象的原始样式字符串。
@end deffn


在 3.7 版更改: 添加 @ref{3c3,,copy.copy()} 和 @ref{3c4,,copy.deepcopy()} 函数的支持。编译后的正则表达式对象被认为是原子性的。


@node 匹配对象,正则表达式例子,正则表达式对象 （正则对象）,re --- 正则表达式操作
@anchor{library/re id2}@anchor{1704}@anchor{library/re match-objects}@anchor{897}
@subsubsection 匹配对象


匹配对象总是有一个布尔值 @code{True}。如果没有匹配的话 @ref{16f1,,match()} 和 @ref{16f2,,search()} 返回 @code{None} 所以你可以简单的用 @code{if} 语句来判断是否匹配

@example
match = re.search(pattern, string)
if match:
    process(match)
@end example

匹配对象支持以下方法和属性：

@geindex expand() (re.Match 方法)
@anchor{library/re re Match expand}@anchor{1705}
@deffn {方法} Match.expand (template)

对 @emph{template} 进行反斜杠转义替换并且返回，就像 @ref{16fe,,sub()} 方法中一样。转义如同 @code{\n} 被转换成合适的字符，数字引用(@code{\1}, @code{\2})和命名组合(@code{\g<1>}, @code{\g<name>}) 替换为相应组合的内容。


在 3.5 版更改: 不匹配的组合替换为空字符串。

@end deffn

@geindex group() (re.Match 方法)
@anchor{library/re re Match group}@anchor{1706}
@deffn {方法} Match.group ([group1, ...])

返回一个或者多个匹配的子组。如果只有一个参数，结果就是一个字符串，如果有多个参数，结果就是一个元组（每个参数对应一个项），如果没有参数，组1默认到0（整个匹配都被返回）。 如果一个组N 参数值为 0，相应的返回值就是整个匹配字符串；如果它是一个范围 [1..99]，结果就是相应的括号组字符串。如果一个组号是负数，或者大于样式中定义的组数，一个 @ref{e6e,,IndexError} 索引错误就 @code{raise}。如果一个组包含在样式的一部分，并被匹配多次，就返回最后一个匹配。:

@example
>>> m = re.match(r"(\w+) (\w+)", "Isaac Newton, physicist")
>>> m.group(0)       # The entire match
'Isaac Newton'
>>> m.group(1)       # The first parenthesized subgroup.
'Isaac'
>>> m.group(2)       # The second parenthesized subgroup.
'Newton'
>>> m.group(1, 2)    # Multiple arguments give us a tuple.
('Isaac', 'Newton')
@end example

如果正则表达式使用了 @code{(?P<name>…)} 语法， @emph{groupN} 参数就也可能是命名组合的名字。如果一个字符串参数在样式中未定义为组合名，一个 @ref{e6e,,IndexError} 就 @code{raise}。

一个相对复杂的例子

@example
>>> m = re.match(r"(?P<first_name>\w+) (?P<last_name>\w+)", "Malcolm Reynolds")
>>> m.group('first_name')
'Malcolm'
>>> m.group('last_name')
'Reynolds'
@end example

命名组合同样可以通过索引值引用

@example
>>> m.group(1)
'Malcolm'
>>> m.group(2)
'Reynolds'
@end example

如果一个组匹配成功多次，就只返回最后一个匹配

@example
>>> m = re.match(r"(..)+", "a1b2c3")  # Matches 3 times.
>>> m.group(1)                        # Returns only the last match.
'c3'
@end example
@end deffn

@geindex __getitem__() (re.Match 方法)
@anchor{library/re re Match __getitem__}@anchor{1707}
@deffn {方法} Match.__getitem__ (g)

这个等价于 @code{m.group(g)}。这允许更方便的引用一个匹配

@example
>>> m = re.match(r"(\w+) (\w+)", "Isaac Newton, physicist")
>>> m[0]       # The entire match
'Isaac Newton'
>>> m[1]       # The first parenthesized subgroup.
'Isaac'
>>> m[2]       # The second parenthesized subgroup.
'Newton'
@end example


3.6 新版功能.

@end deffn

@geindex groups() (re.Match 方法)
@anchor{library/re re Match groups}@anchor{1708}
@deffn {方法} Match.groups (default=None)

返回一个元组，包含所有匹配的子组，在样式中出现的从1到任意多的组合。 @emph{default} 参数用于不参与匹配的情况，默认为 @code{None}。

例如

@example
>>> m = re.match(r"(\d+)\.(\d+)", "24.1632")
>>> m.groups()
('24', '1632')
@end example

如果我们使小数点可选，那么不是所有的组都会参与到匹配当中。这些组合默认会返回一个 @code{None} ，除非指定了 @emph{default} 参数。

@example
>>> m = re.match(r"(\d+)\.?(\d+)?", "24")
>>> m.groups()      # Second group defaults to None.
('24', None)
>>> m.groups('0')   # Now, the second group defaults to '0'.
('24', '0')
@end example
@end deffn

@geindex groupdict() (re.Match 方法)
@anchor{library/re re Match groupdict}@anchor{1709}
@deffn {方法} Match.groupdict (default=None)

返回一个字典，包含了所有的 @emph{命名} 子组。key就是组名。 @emph{default} 参数用于不参与匹配的组合；默认为 @code{None}。 例如

@example
>>> m = re.match(r"(?P<first_name>\w+) (?P<last_name>\w+)", "Malcolm Reynolds")
>>> m.groupdict()
@{'first_name': 'Malcolm', 'last_name': 'Reynolds'@}
@end example
@end deffn

@geindex start() (re.Match 方法)
@geindex end() (re.Match 方法)
@anchor{library/re re Match start}@anchor{170a}
@deffn {方法} Match.start ([group])
@anchor{library/re re Match end}@anchor{170b}
@deffnx {方法} Match.end ([group])

返回 @emph{group} 匹配到的字串的开始和结束标号。@emph{group} 默认为0（意思是整个匹配的子串）。如果  @emph{group} 存在，但未产生匹配，就返回 @code{-1} 。对于一个匹配对象 @emph{m}， 和一个未参与匹配的组 @emph{g} ，组 @emph{g} (等价于 @code{m.group(g)})产生的匹配是

@example
m.string[m.start(g):m.end(g)]
@end example

注意 @code{m.start(group)} 将会等于 @code{m.end(group)} ，如果 @emph{group} 匹配一个空字符串的话。比如，在 @code{m = re.search('b(c?)', 'cba')} 之后，@code{m.start(0)} 为 1, @code{m.end(0)} 为 2, @code{m.start(1)} 和 @code{m.end(1)} 都是 2, @code{m.start(2)} raise 一个 @ref{e6e,,IndexError} 例外。

这个例子会从email地址中移除掉 @emph{remove_this}

@example
>>> email = "tony@@tiremove_thisger.net"
>>> m = re.search("remove_this", email)
>>> email[:m.start()] + email[m.end():]
'tony@@tiger.net'
@end example
@end deffn

@geindex span() (re.Match 方法)
@anchor{library/re re Match span}@anchor{170c}
@deffn {方法} Match.span ([group])

对于一个匹配 @emph{m} ， 返回一个二元组 @code{(m.start(group), m.end(group))} 。 注意如果 @emph{group} 没有在这个匹配中，就返回 @code{(-1, -1)} 。@emph{group} 默认为0，就是整个匹配。
@end deffn

@geindex pos (re.Match 属性)
@anchor{library/re re Match pos}@anchor{170d}
@deffn {属性} Match.pos

@emph{pos} 的值，会传递给 @ref{16f2,,search()} 或 @ref{16f1,,match()} 的方法 a @ref{896,,正则对象} 。这个是正则引擎开始在字符串搜索一个匹配的索引位置。
@end deffn

@geindex endpos (re.Match 属性)
@anchor{library/re re Match endpos}@anchor{170e}
@deffn {属性} Match.endpos

@emph{endpos} 的值，会传递给 @ref{16f2,,search()} 或 @ref{16f1,,match()} 的方法 a @ref{896,,正则对象} 。这个是正则引擎停止在字符串搜索一个匹配的索引位置。
@end deffn

@geindex lastindex (re.Match 属性)
@anchor{library/re re Match lastindex}@anchor{170f}
@deffn {属性} Match.lastindex

捕获组的最后一个匹配的整数索引值，或者 @code{None} 如果没有匹配产生的话。比如，对于字符串 @code{'ab'}，表达式 @code{(a)b}, @code{((a)(b))}, 和 @code{((ab))} 将得到 @code{lastindex == 1} ， 而 @code{(a)(b)} 会得到 @code{lastindex == 2} 。
@end deffn

@geindex lastgroup (re.Match 属性)
@anchor{library/re re Match lastgroup}@anchor{1710}
@deffn {属性} Match.lastgroup

最后一个匹配的命名组名字，或者 @code{None} 如果没有产生匹配的话。
@end deffn

@geindex re (re.Match 属性)
@anchor{library/re re Match re}@anchor{1711}
@deffn {属性} Match.re

返回产生这个实例的 @ref{896,,正则对象} ， 这个实例是由 正则对象的 @ref{16f1,,match()} 或 @ref{16f2,,search()} 方法产生的。
@end deffn

@geindex string (re.Match 属性)
@anchor{library/re re Match string}@anchor{1712}
@deffn {属性} Match.string

传递到 @ref{16f1,,match()} 或 @ref{16f2,,search()} 的字符串。
@end deffn


在 3.7 版更改: 添加了对 @ref{3c3,,copy.copy()} 和 @ref{3c4,,copy.deepcopy()} 的支持。匹配对象被看作是原子性的。


@node 正则表达式例子,,匹配对象,re --- 正则表达式操作
@anchor{library/re re-examples}@anchor{bed}@anchor{library/re regular-expression-examples}@anchor{1713}
@subsubsection 正则表达式例子


@menu
* 检查对子:: 
* 模拟 scanf(): 模拟 scanf. 
* search() vs. match(): search vs match. 
* 制作一个电话本:: 
* 文字整理:: 
* 查找所有副词:: 
* 查找所有的副词及其位置:: 
* 原始字符串标记:: 
* 写一个词法分析器:: 

@end menu

@node 检查对子,模拟 scanf,,正则表达式例子
@anchor{library/re checking-for-a-pair}@anchor{1714}
@subsubsection 检查对子


在这个例子里，我们使用以下辅助函数来更好地显示匹配对象:

@example
def displaymatch(match):
    if match is None:
        return None
    return '<Match: %r, groups=%r>' % (match.group(), match.groups())
@end example

假设你在写一个扑克程序，一个玩家的一手牌为五个字符的串，每个字符表示一张牌，"a" 就是 A, "k"  K， "q"  Q, "j" J, "t" 为 10, "2" 到 "9" 表示2 到 9。

要看给定的字符串是否有效，我们可以按照以下步骤

@example
>>> valid = re.compile(r"^[a2-9tjqk]@{5@}$")
>>> displaymatch(valid.match("akt5q"))  # Valid.
"<Match: 'akt5q', groups=()>"
>>> displaymatch(valid.match("akt5e"))  # Invalid.
>>> displaymatch(valid.match("akt"))    # Invalid.
>>> displaymatch(valid.match("727ak"))  # Valid.
"<Match: '727ak', groups=()>"
@end example

最后一手牌，@code{"727ak"} ，包含了一个对子，或者两张同样数值的牌。要用正则表达式匹配它，应该使用向后引用如下

@example
>>> pair = re.compile(r".*(.).*\1")
>>> displaymatch(pair.match("717ak"))     # Pair of 7s.
"<Match: '717', groups=('7',)>"
>>> displaymatch(pair.match("718ak"))     # No pairs.
>>> displaymatch(pair.match("354aa"))     # Pair of aces.
"<Match: '354aa', groups=('a',)>"
@end example

要找出对子由什么牌组成，开发者可以按照下面的方式来使用匹配对象的 @ref{1706,,group()} 方法:

@example
>>> pair = re.compile(r".*(.).*\1")
>>> pair.match("717ak").group(1)
'7'

# Error because re.match() returns None, which doesn't have a group() method:
>>> pair.match("718ak").group(1)
Traceback (most recent call last):
  File "<pyshell#23>", line 1, in <module>
    re.match(r".*(.).*\1", "718ak").group(1)
AttributeError: 'NoneType' object has no attribute 'group'

>>> pair.match("354aa").group(1)
'a'
@end example

@node 模拟 scanf,search vs match,检查对子,正则表达式例子
@anchor{library/re simulating-scanf}@anchor{1715}
@subsubsection 模拟 scanf()


@geindex scanf()

Python 目前没有一个类似c函数 @code{scanf()} 的替代品。正则表达式通常比 @code{scanf()} 格式字符串要更强大一些，但也带来更多复杂性。下面的表格提供了 @code{scanf()} 格式符和正则表达式大致相同的映射。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

@code{scanf()} 格式符

@tab

正则表达式

@item

@code{%c}

@tab

@code{.}

@item

@code{%5c}

@tab

@code{.@{5@}}

@item

@code{%d}

@tab

@code{[-+]?\d+}

@item

@code{%e}, @code{%E}, @code{%f}, @code{%g}

@tab

@code{[-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?}

@item

@code{%i}

@tab

@code{[-+]?(0[xX][\dA-Fa-f]+|0[0-7]*|\d+)}

@item

@code{%o}

@tab

@code{[-+]?[0-7]+}

@item

@code{%s}

@tab

@code{\S+}

@item

@code{%u}

@tab

@code{\d+}

@item

@code{%x}, @code{%X}

@tab

@code{[-+]?(0[xX])?[\dA-Fa-f]+}

@end multitable


从文件名和数字提取字符串

@example
/usr/sbin/sendmail - 0 errors, 4 warnings
@end example

你可以使用 @code{scanf()} 格式化

@example
%s - %d errors, %d warnings
@end example

等价的正则表达式是：

@example
(\S+) - (\d+) errors, (\d+) warnings
@end example

@node search vs match,制作一个电话本,模拟 scanf,正则表达式例子
@anchor{library/re id3}@anchor{1716}@anchor{library/re search-vs-match}@anchor{16f6}
@subsubsection search() vs. match()


Python 提供了两种不同的操作：基于 @ref{bac,,re.match()} 检查字符串开头，或者 @ref{bab,,re.search()} 检查字符串的任意位置（默认Perl中的行为）。

例如

@example
>>> re.match("c", "abcdef")    # No match
>>> re.search("c", "abcdef")   # Match
<re.Match object; span=(2, 3), match='c'>
@end example

在 @ref{bab,,search()} 中，可以用 @code{'^'} 作为开始来限制匹配到字符串的首位

@example
>>> re.match("c", "abcdef")    # No match
>>> re.search("^c", "abcdef")  # No match
>>> re.search("^a", "abcdef")  # Match
<re.Match object; span=(0, 1), match='a'>
@end example

注意 @ref{16e7,,MULTILINE} 多行模式中函数 @ref{bac,,match()} 只匹配字符串的开始，但使用 @ref{bab,,search()} 和以 @code{'^'} 开始的正则表达式会匹配每行的开始

@example
>>> re.match('X', 'A\nB\nX', re.MULTILINE)  # No match
>>> re.search('^X', 'A\nB\nX', re.MULTILINE)  # Match
<re.Match object; span=(4, 5), match='X'>
@end example

@node 制作一个电话本,文字整理,search vs match,正则表达式例子
@anchor{library/re making-a-phonebook}@anchor{1717}
@subsubsection 制作一个电话本


@ref{3c2,,split()} 将字符串用参数传递的样式分隔开。这个方法对于转换文本数据到易读而且容易修改的数据结构，是很有用的，如下面的例子证明。

首先，这里是输入。 它通常来自一个文件，这里我们使用三重引号字符串语法

@example
>>> text = """Ross McFluff: 834.345.1254 155 Elm Street
...
... Ronald Heathmore: 892.345.3428 436 Finley Avenue
... Frank Burger: 925.541.7625 662 South Dogwood Way
...
...
... Heather Albrecht: 548.326.4584 919 Park Place"""
@end example

条目用一个或者多个换行符分开。现在我们将字符串转换为一个列表，每个非空行都有一个条目:

@example
>>> entries = re.split("\n+", text)
>>> entries
['Ross McFluff: 834.345.1254 155 Elm Street',
'Ronald Heathmore: 892.345.3428 436 Finley Avenue',
'Frank Burger: 925.541.7625 662 South Dogwood Way',
'Heather Albrecht: 548.326.4584 919 Park Place']
@end example

最终，将每个条目分割为一个由名字、姓氏、电话号码和地址组成的列表。我们为 @ref{3c2,,split()} 使用了 @code{maxsplit} 形参，因为地址中包含有被我们作为分割模式的空格符:

@example
>>> [re.split(":? ", entry, 3) for entry in entries]
[['Ross', 'McFluff', '834.345.1254', '155 Elm Street'],
['Ronald', 'Heathmore', '892.345.3428', '436 Finley Avenue'],
['Frank', 'Burger', '925.541.7625', '662 South Dogwood Way'],
['Heather', 'Albrecht', '548.326.4584', '919 Park Place']]
@end example

@code{:?} 样式匹配姓后面的冒号，因此它不出现在结果列表中。如果 @code{maxsplit} 设置为 @code{4} ，我们还可以从地址中获取到房间号:

@example
>>> [re.split(":? ", entry, 4) for entry in entries]
[['Ross', 'McFluff', '834.345.1254', '155', 'Elm Street'],
['Ronald', 'Heathmore', '892.345.3428', '436', 'Finley Avenue'],
['Frank', 'Burger', '925.541.7625', '662', 'South Dogwood Way'],
['Heather', 'Albrecht', '548.326.4584', '919', 'Park Place']]
@end example

@node 文字整理,查找所有副词,制作一个电话本,正则表达式例子
@anchor{library/re text-munging}@anchor{1718}
@subsubsection 文字整理


@ref{475,,sub()} 替换字符串中出现的样式的每一个实例。这个例子证明了使用  @ref{475,,sub()} 来整理文字，或者随机化每个字符的位置，除了首位和末尾字符

@example
>>> def repl(m):
...     inner_word = list(m.group(2))
...     random.shuffle(inner_word)
...     return m.group(1) + "".join(inner_word) + m.group(3)
>>> text = "Professor Abdolmalek, please report your absences promptly."
>>> re.sub(r"(\w)(\w+)(\w)", repl, text)
'Poefsrosr Aealmlobdk, pslaee reorpt your abnseces plmrptoy.'
>>> re.sub(r"(\w)(\w+)(\w)", repl, text)
'Pofsroser Aodlambelk, plasee reoprt yuor asnebces potlmrpy.'
@end example

@node 查找所有副词,查找所有的副词及其位置,文字整理,正则表达式例子
@anchor{library/re finding-all-adverbs}@anchor{1719}
@subsubsection 查找所有副词


@ref{95d,,findall()} 匹配样式 @emph{所有} 的出现，不仅是像 @ref{bab,,search()} 中的第一个匹配。比如，如果一个作者希望找到文字中的所有副词，他可能会按照以下方法用 @ref{95d,,findall()}

@example
>>> text = "He was carefully disguised but captured quickly by police."
>>> re.findall(r"\w+ly", text)
['carefully', 'quickly']
@end example

@node 查找所有的副词及其位置,原始字符串标记,查找所有副词,正则表达式例子
@anchor{library/re finding-all-adverbs-and-their-positions}@anchor{171a}
@subsubsection 查找所有的副词及其位置


如果需要匹配样式的更多信息， @ref{16f7,,finditer()} 可以起到作用，它提供了 @ref{897,,匹配对象} 作为返回值，而不是字符串。继续上面的例子，如果一个作者希望找到所有副词和它的位置，可以按照下面方法使用 @ref{16f7,,finditer()}

@example
>>> text = "He was carefully disguised but captured quickly by police."
>>> for m in re.finditer(r"\w+ly", text):
...     print('%02d-%02d: %s' % (m.start(), m.end(), m.group(0)))
07-16: carefully
40-47: quickly
@end example

@node 原始字符串标记,写一个词法分析器,查找所有的副词及其位置,正则表达式例子
@anchor{library/re raw-string-notation}@anchor{171b}
@subsubsection 原始字符串标记


原始字符串记法 (@code{r"text"}) 保持正则表达式正常。否则，每个正则式里的反斜杠(@code{'\'}) 都必须前缀一个反斜杠来转义。比如，下面两行代码功能就是完全一致的

@example
>>> re.match(r"\W(.)\1\W", " ff ")
<re.Match object; span=(0, 4), match=' ff '>
>>> re.match("\\W(.)\\1\\W", " ff ")
<re.Match object; span=(0, 4), match=' ff '>
@end example

当需要匹配一个字符反斜杠，它必须在正则表达式中转义。在原始字符串记法，就是 @code{r"\\"}。否则就必须用 @code{"\\\\"}，来表示同样的意思

@example
>>> re.match(r"\\", r"\\")
<re.Match object; span=(0, 1), match='\\'>
>>> re.match("\\\\", r"\\")
<re.Match object; span=(0, 1), match='\\'>
@end example

@node 写一个词法分析器,,原始字符串标记,正则表达式例子
@anchor{library/re writing-a-tokenizer}@anchor{171c}
@subsubsection 写一个词法分析器


一个 词法器或词法分析器@footnote{https://en.wikipedia.org/wiki/Lexical_analysis} 分析字符串，并分类成目录组。 这是写一个编译器或解释器的第一步。

文字目录是由正则表达式指定的。这个技术是通过将这些样式合并为一个主正则式，并且循环匹配来实现的

@example
from typing import NamedTuple
import re

class Token(NamedTuple):
    type: str
    value: str
    line: int
    column: int

def tokenize(code):
    keywords = @{'IF', 'THEN', 'ENDIF', 'FOR', 'NEXT', 'GOSUB', 'RETURN'@}
    token_specification = [
        ('NUMBER',   r'\d+(\.\d*)?'),  # Integer or decimal number
        ('ASSIGN',   r':='),           # Assignment operator
        ('END',      r';'),            # Statement terminator
        ('ID',       r'[A-Za-z]+'),    # Identifiers
        ('OP',       r'[+\-*/]'),      # Arithmetic operators
        ('NEWLINE',  r'\n'),           # Line endings
        ('SKIP',     r'[ \t]+'),       # Skip over spaces and tabs
        ('MISMATCH', r'.'),            # Any other character
    ]
    tok_regex = '|'.join('(?P<%s>%s)' % pair for pair in token_specification)
    line_num = 1
    line_start = 0
    for mo in re.finditer(tok_regex, code):
        kind = mo.lastgroup
        value = mo.group()
        column = mo.start() - line_start
        if kind == 'NUMBER':
            value = float(value) if '.' in value else int(value)
        elif kind == 'ID' and value in keywords:
            kind = value
        elif kind == 'NEWLINE':
            line_start = mo.end()
            line_num += 1
            continue
        elif kind == 'SKIP':
            continue
        elif kind == 'MISMATCH':
            raise RuntimeError(f'@{value!r@} unexpected on line @{line_num@}')
        yield Token(kind, value, line_num, column)

statements = '@w{'}'
    IF quantity THEN
        total := total + price * quantity;
        tax := price * 0.05;
    ENDIF;
'@w{'}'

for token in tokenize(statements):
    print(token)
@end example

该词法器产生以下的输出

@example
Token(type='IF', value='IF', line=2, column=4)
Token(type='ID', value='quantity', line=2, column=7)
Token(type='THEN', value='THEN', line=2, column=16)
Token(type='ID', value='total', line=3, column=8)
Token(type='ASSIGN', value=':=', line=3, column=14)
Token(type='ID', value='total', line=3, column=17)
Token(type='OP', value='+', line=3, column=23)
Token(type='ID', value='price', line=3, column=25)
Token(type='OP', value='*', line=3, column=31)
Token(type='ID', value='quantity', line=3, column=33)
Token(type='END', value=';', line=3, column=41)
Token(type='ID', value='tax', line=4, column=8)
Token(type='ASSIGN', value=':=', line=4, column=12)
Token(type='ID', value='price', line=4, column=15)
Token(type='OP', value='*', line=4, column=21)
Token(type='NUMBER', value=0.05, line=4, column=23)
Token(type='END', value=';', line=4, column=27)
Token(type='ENDIF', value='ENDIF', line=5, column=4)
Token(type='END', value=';', line=5, column=9)
@end example

@anchor{library/re frie09}@anchor{16e4}@w{(Frie09)} 
Friedl, Jeffrey. Mastering Regular Expressions. 3rd ed., O'Reilly Media, 2009. 该书的第三版不再包含 Python，但第一版极详细地覆盖了正则表达式模式串的编写。

@node difflib --- 计算差异的辅助工具,textwrap --- 文本自动换行与填充,re --- 正则表达式操作,文本处理服务
@anchor{library/difflib doc}@anchor{171d}@anchor{library/difflib difflib-helpers-for-computing-deltas}@anchor{171e}@anchor{library/difflib module-difflib}@anchor{37}
@subsection @code{difflib} --- 计算差异的辅助工具


@geindex difflib (模块)

@c Markup by Fred L. Drake, Jr. <fdrake@acm.org>

@strong{源代码:} Lib/difflib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/difflib.py}

@c import sys
@c from difflib import *


__________________________________________________________________


此模块提供用于比较序列的类和函数。 例如，它可以用于比较文件，并可以产生各种格式的不同信息，包括 HTML 和上下文以及统一格式的差异点。 有关目录和文件的比较，请参见 @ref{7f,,filecmp} 模块。

@geindex SequenceMatcher (difflib 中的类)
@anchor{library/difflib difflib SequenceMatcher}@anchor{949}
@deffn {类} difflib.SequenceMatcher

这是一个灵活的类，可用于比较任何类型的序列对，只要序列元素为 @ref{13c0,,hashable} 对象。 其基本算法要早于由 Ratcliff 和 Obershelp 于 1980 年代末期发表并以“格式塔模式匹配”的夸张名称命名的算法，并且更加有趣一些。 其思路是找到不包含“垃圾”元素的最长连续匹配子序列；所谓“垃圾”元素是指其在某种意义上没有价值，例如空白行或空白符。 （处理垃圾元素是对 Ratcliff 和 Obershelp 算法的一个扩展。） 然后同样的思路将递归地应用于匹配序列的左右序列片段。 这并不能产生最小编辑序列，但确实能产生在人们看来“正确”的匹配。

@strong{耗时:} 基本 Ratcliff-Obershelp 算法在最坏情况下为立方时间而在一般情况下为平方时间。 @ref{949,,SequenceMatcher} 在最坏情况下为平方时间而在一般情况下的行为受到序列中有多少相同元素这一因素的微妙影响；在最佳情况下则为线性时间。

@strong{自动垃圾启发式计算:} @ref{949,,SequenceMatcher} 支持使用启发式计算来自动将特定序列项视为垃圾。 这种启发式计算会统计每个单独项在序列中出现的次数。 如果某一项（在第一项之后）的重复次数超过序列长度的 1% 并且序列长度至少有 200 项，该项会被标记为“热门”并被视为序列匹配中的垃圾。 这种启发式计算可以通过在创建 @ref{949,,SequenceMatcher} 时将 @code{autojunk} 参数设为 @code{False} 来关闭。


3.2 新版功能: @emph{autojunk} 形参。

@end deffn

@geindex Differ (difflib 中的类)
@anchor{library/difflib difflib Differ}@anchor{171f}
@deffn {类} difflib.Differ

这个类的作用是比较由文本行组成的序列，并产生可供人阅读的差异或增量信息。 Differ 统一使用 @ref{949,,SequenceMatcher} 来完成行序列的比较以及相似（接近匹配）行内部字符序列的比较。

@ref{171f,,Differ} 增量的每一行均以双字母代码打头：


@multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

双字母代码

@tab

含义

@item

@code{'- '}

@tab

行为序列 1 所独有

@item

@code{'+ '}

@tab

行为序列 2 所独有

@item

@code{'  '}

@tab

行在两序列中相同

@item

@code{'? '}

@tab

行不存在于任一输入序列

@end multitable


以 '@code{?}' 打头的行尝试将视线引至行以外而不存在于任一输入序列的差异。 如果序列包含制表符则这些行可能会令人感到迷惑。
@end deffn

@geindex HtmlDiff (difflib 中的类)
@anchor{library/difflib difflib HtmlDiff}@anchor{1720}
@deffn {类} difflib.HtmlDiff

这个类可用于创建 HTML 表格（或包含表格的完整 HTML 文件）以并排地逐行显示文本比较，行间与行外的更改将突出显示。 此表格可以基于完全或上下文差异模式来生成。

这个类的构造函数：

@geindex __init__() (difflib.HtmlDiff 方法)
@anchor{library/difflib difflib HtmlDiff __init__}@anchor{1721}
@deffn {方法} __init__ (tabsize=8, wrapcolumn=None, linejunk=None, charjunk=IS_CHARACTER_JUNK)

初始化 @ref{1720,,HtmlDiff} 的实例。

@emph{tabsize} 是一个可选关键字参数，指定制表位的间隔，默认值为 @code{8}。

@emph{wrapcolumn} 是一个可选关键字参数，指定行文本自动打断并换行的列位置，默认值为 @code{None} 表示不自动换行。

@emph{linejunk} 和 @emph{charjunk} 均是可选关键字参数，会传入 @ref{1722,,ndiff()} (被 @ref{1720,,HtmlDiff} 用来生成并排显示的 HTML 差异)。 请参阅 @ref{1722,,ndiff()} 文档了解参数默认值及其说明。
@end deffn

下列是公开的方法

@geindex make_file() (difflib.HtmlDiff 方法)
@anchor{library/difflib difflib HtmlDiff make_file}@anchor{6c3}
@deffn {方法} make_file (fromlines, tolines, fromdesc='@w{'}, todesc='@w{'}, context=False, numlines=5, *, charset='utf-8')

比较 @emph{fromlines} 和 @emph{tolines} (字符串列表) 并返回一个字符串，表示一个完整 HTML 文件，其中包含各行差异的表格，行间与行外的更改将突出显示。

@emph{fromdesc} 和 @emph{todesc} 均是可选关键字参数，指定来源/目标文件的列标题字符串（默认均为空白字符串）。

@emph{context} 和 @emph{numlines} 均是可选关键字参数。 当只要显示上下文差异时就将 @emph{context} 设为 @code{True}，否则默认值 @code{False} 为显示完整文件。 @emph{numlines} 默认为 @code{5}。 当 @emph{context} 为 @code{True} 时 @emph{numlines} 将控制围绕突出显示差异部分的上下文行数。 当 @emph{context} 为 @code{False} 时 @emph{numlines} 将控制在使用 "next" 超链接时突出显示差异部分之前所显示的行数（设为零则会导致 "next" 超链接将下一个突出显示差异部分放在浏览器顶端，不添加任何前导上下文）。

@cartouche
@quotation 注解 
@emph{fromdesc} 和 @emph{todesc} 会被当作未转义的 HTML 来解读，当接收不可信来源的输入时应该适当地进行转义。
@end quotation
@end cartouche


在 3.5 版更改: 增加了 @emph{charset} 关键字参数。 HTML 文档的默认字符集从 @code{'ISO-8859-1'} 更改为 @code{'utf-8'}。

@end deffn

@geindex make_table() (difflib.HtmlDiff 方法)
@anchor{library/difflib difflib HtmlDiff make_table}@anchor{1723}
@deffn {方法} make_table (fromlines, tolines, fromdesc='@w{'}, todesc='@w{'}, context=False, numlines=5)

比较 @emph{fromlines} 和 @emph{tolines} (字符串列表) 并返回一个字符串，表示一个包含各行差异的完整 HTML 表格，行间与行外的更改将突出显示。

此方法的参数与 @ref{6c3,,make_file()} 方法的相同。
@end deffn

@code{Tools/scripts/diff.py} 是这个类的命令行前端，其中包含一个很好的使用示例。
@end deffn

@geindex context_diff() (在 difflib 模块中)
@anchor{library/difflib difflib context_diff}@anchor{1724}
@deffn {函数} difflib.context_diff (a, b, fromfile='@w{'}, tofile='@w{'}, fromfiledate='@w{'}, tofiledate='@w{'}, n=3, lineterm='\n')

比较 @emph{a} 和 @emph{b} (字符串列表)；返回上下文差异格式的增量信息 (一个产生增量行的 @ref{99c,,generator})。

所谓上下文差异是一种只显示有更改的行再加几个上下文行的紧凑形式。 更改被显示为之前/之后的样式。 上下文行数由 @emph{n} 设定，默认为三行。

默认情况下，差异控制行（以 @code{***} or @code{---} 表示）是通过末尾换行符来创建的。 这样做的好处是从 @ref{1725,,io.IOBase.readlines()} 创建的输入将得到适用于 @ref{1726,,io.IOBase.writelines()} 的差异信息，因为输入和输出都带有末尾换行符。

对于没有末尾换行符的输入，应将 @emph{lineterm} 参数设为 @code{""}，这样输出内容将统一不带换行符。

上下文差异格式通常带有一个记录文件名和修改时间的标头。 这些信息的部分或全部可以使用字符串 @emph{fromfile}, @emph{tofile}, @emph{fromfiledate} 和 @emph{tofiledate} 来指定。 修改时间通常以 ISO 8601 格式表示。 如果未指定，这些字符串默认为空。

@example
>>> s1 = ['bacon\n', 'eggs\n', 'ham\n', 'guido\n']
>>> s2 = ['python\n', 'eggy\n', 'hamster\n', 'guido\n']
>>> sys.stdout.writelines(context_diff(s1, s2, fromfile='before.py', tofile='after.py'))
*** before.py
--- after.py
***************
*** 1,4 ****
! bacon
! eggs
! ham
  guido
--- 1,4 ----
! python
! eggy
! hamster
  guido
@end example

请参阅 @ref{1727,,difflib 的命令行接口} 获取更详细的示例。
@end deffn

@geindex get_close_matches() (在 difflib 模块中)
@anchor{library/difflib difflib get_close_matches}@anchor{1728}
@deffn {函数} difflib.get_close_matches (word, possibilities, n=3, cutoff=0.6)

返回由最佳“近似”匹配构成的列表。 @emph{word} 为一个指定目标近似匹配的序列（通常为字符串），@emph{possibilities} 为一个由用于匹配 @emph{word} 的序列构成的列表（通常为字符串列表）。

可选参数 @emph{n} (默认为 @code{3}) 指定最多返回多少个近似匹配； @emph{n} 必须大于 @code{0}.

可选参数 @emph{cutoff} (默认为 @code{0.6}) 是一个 [0, 1] 范围内的浮点数。 与 @emph{word} 相似度得分未达到该值的候选匹配将被忽略。

候选匹配中（不超过 @emph{n} 个）的最佳匹配将以列表形式返回，按相似度得分排序，最相似的排在最前面。

@example
>>> get_close_matches('appel', ['ape', 'apple', 'peach', 'puppy'])
['apple', 'ape']
>>> import keyword
>>> get_close_matches('wheel', keyword.kwlist)
['while']
>>> get_close_matches('pineapple', keyword.kwlist)
[]
>>> get_close_matches('accept', keyword.kwlist)
['except']
@end example
@end deffn

@geindex ndiff() (在 difflib 模块中)
@anchor{library/difflib difflib ndiff}@anchor{1722}
@deffn {函数} difflib.ndiff (a, b, linejunk=None, charjunk=IS_CHARACTER_JUNK)

比较 @emph{a} 和 @emph{b} (字符串列表)；返回 @ref{171f,,Differ} 形式的增量信息 (一个产生增量行的 @ref{99c,,generator})。

可选关键字形参 @emph{linejunk} 和 @emph{charjunk} 均为过滤函数 (或为 @code{None})：

@emph{linejunk}: 此函数接受单个字符串参数，如果其为垃圾字符串则返回真值，否则返回假值。 默认为 @code{None}。 此外还有一个模块层级的函数 @ref{1729,,IS_LINE_JUNK()}，它会过滤掉没有可见字符的行，除非该行添加了至多一个井号符 (@code{'#'}) -- 但是下层的 @ref{949,,SequenceMatcher} 类会动态分析哪些行的重复频繁到足以形成噪音，这通常会比使用此函数的效果更好。

@emph{charjunk}: 此函数接受一个字符（长度为 1 的字符串)，如果其为垃圾字符则返回真值，否则返回假值。 默认为模块层级的函数 @ref{172a,,IS_CHARACTER_JUNK()}，它会过滤掉空白字符（空格符或制表符；但包含换行符可不是个好主意！）。

@code{Tools/scripts/ndiff.py} 是这个函数的命令行前端。

@example
>>> diff = ndiff('one\ntwo\nthree\n'.splitlines(keepends=True),
...              'ore\ntree\nemu\n'.splitlines(keepends=True))
>>> print('@w{'}.join(diff), end="")
- one
?  ^
+ ore
?  ^
- two
- three
?  -
+ tree
+ emu
@end example
@end deffn

@geindex restore() (在 difflib 模块中)
@anchor{library/difflib difflib restore}@anchor{172b}
@deffn {函数} difflib.restore (sequence, which)

返回两个序列中产生增量的那一个。

给出一个由 @ref{172c,,Differ.compare()} 或 @ref{1722,,ndiff()} 产生的 @emph{序列}，提取出来自文件 1 或 2 (@emph{which} 形参) 的行，去除行前缀。

示例:

@example
>>> diff = ndiff('one\ntwo\nthree\n'.splitlines(keepends=True),
...              'ore\ntree\nemu\n'.splitlines(keepends=True))
>>> diff = list(diff) # materialize the generated delta into a list
>>> print('@w{'}.join(restore(diff, 1)), end="")
one
two
three
>>> print('@w{'}.join(restore(diff, 2)), end="")
ore
tree
emu
@end example
@end deffn

@geindex unified_diff() (在 difflib 模块中)
@anchor{library/difflib difflib unified_diff}@anchor{172d}
@deffn {函数} difflib.unified_diff (a, b, fromfile='@w{'}, tofile='@w{'}, fromfiledate='@w{'}, tofiledate='@w{'}, n=3, lineterm='\n')

比较 @emph{a} 和 @emph{b} (字符串列表)；返回统一差异格式的增量信息 (一个产生增量行的 @ref{99c,,generator})。

所以统一差异是一种只显示有更改的行再加几个上下文行的紧凑形式。 更改被显示为内联的样式（而不是分开的之前/之后文本块）。 上下文行数由 @emph{n} 设定，默认为三行。

默认情况下，差异控制行 (以 @code{---}, @code{+++} 或 @code{@@@@} 表示) 是通过末尾换行符来创建的。 这样做的好处是从 @ref{1725,,io.IOBase.readlines()} 创建的输入将得到适用于 @ref{1726,,io.IOBase.writelines()} 的差异信息，因为输入和输出都带有末尾换行符。

对于没有末尾换行符的输入，应将 @emph{lineterm} 参数设为 @code{""}，这样输出内容将统一不带换行符。

上下文差异格式通常带有一个记录文件名和修改时间的标头。 这些信息的部分或全部可以使用字符串 @emph{fromfile}, @emph{tofile}, @emph{fromfiledate} 和 @emph{tofiledate} 来指定。 修改时间通常以 ISO 8601 格式表示。 如果未指定，这些字符串默认为空。

@example
>>> s1 = ['bacon\n', 'eggs\n', 'ham\n', 'guido\n']
>>> s2 = ['python\n', 'eggy\n', 'hamster\n', 'guido\n']
>>> sys.stdout.writelines(unified_diff(s1, s2, fromfile='before.py', tofile='after.py'))
--- before.py
+++ after.py
@@@@ -1,4 +1,4 @@@@
-bacon
-eggs
-ham
+python
+eggy
+hamster
 guido
@end example

请参阅 @ref{1727,,difflib 的命令行接口} 获取更详细的示例。
@end deffn

@geindex diff_bytes() (在 difflib 模块中)
@anchor{library/difflib difflib diff_bytes}@anchor{6c4}
@deffn {函数} difflib.diff_bytes (dfunc, a, b, fromfile=b'@w{'}, tofile=b'@w{'}, fromfiledate=b'@w{'}, tofiledate=b'@w{'}, n=3, lineterm=b'\n')

使用 @emph{dfunc} 比较 @emph{a} 和 @emph{b} (字节串对象列表)；产生以 @emph{dfunc} 所返回格式表示的差异行列表（也是字节串）。 @emph{dfunc} 必须是可调用对象，通常为 @ref{172d,,unified_diff()} 或 @ref{1724,,context_diff()}。

允许你比较编码未知或不一致的数据。 除 @emph{n} 之外的所有输入都必须为字节串对象而非字符串。 作用方式为无损地将所有输入 (除 @emph{n} 之外) 转换为字符串，并调用 @code{dfunc(a, b, fromfile, tofile, fromfiledate, tofiledate, n, lineterm)}。 @emph{dfunc} 的输出会被随即转换回字节串，这样你所得到的增量行将具有与 @emph{a} 和 @emph{b} 相同的未知/不一致编码。


3.5 新版功能.

@end deffn

@geindex IS_LINE_JUNK() (在 difflib 模块中)
@anchor{library/difflib difflib IS_LINE_JUNK}@anchor{1729}
@deffn {函数} difflib.IS_LINE_JUNK (line)

对于可忽略的行返回 @code{True}。 如果 @emph{line} 为空行或只包含单个 @code{'#'} 则 @emph{line} 行就是可忽略的，否则就是不可忽略的。 此函数被用作较旧版本 @ref{1722,,ndiff()} 中 @emph{linejunk} 形参的默认值。
@end deffn

@geindex IS_CHARACTER_JUNK() (在 difflib 模块中)
@anchor{library/difflib difflib IS_CHARACTER_JUNK}@anchor{172a}
@deffn {函数} difflib.IS_CHARACTER_JUNK (ch)

对于可忽略的字符返回 @code{True}。 字符 @emph{ch} 如果为空格符或制表符则 @emph{ch} 就是可忽略的，否则就是不可忽略的。 此函数被用作 @ref{1722,,ndiff()} 中 @emph{charjunk} 形参的默认值。
@end deffn


@subsubheading 参见



@table @asis

@item 模式匹配：格式塔方法@footnote{http://www.drdobbs.com/database/pattern-matching-the-gestalt-approach/184407970}

John W. Ratcliff 和 D. E. Metzener 对于一种类似算法的讨论。 此文于 1988 年 7 月发表于 Dr. Dobb's Journal@footnote{http://www.drdobbs.com/}。
@end table


@menu
* SequenceMatcher 对象:: 
* SequenceMatcher 的示例:: 
* Differ 对象:: 
* Differ 示例:: 
* difflib 的命令行接口:: 

@end menu

@node SequenceMatcher 对象,SequenceMatcher 的示例,,difflib --- 计算差异的辅助工具
@anchor{library/difflib sequence-matcher}@anchor{172e}@anchor{library/difflib sequencematcher-objects}@anchor{172f}
@subsubsection SequenceMatcher 对象


@ref{949,,SequenceMatcher} 类具有这样的构造器：

@geindex SequenceMatcher (difflib 中的类)

@deffn {类} difflib.SequenceMatcher (isjunk=None, a='@w{'}, b='@w{'}, autojunk=True)

可选参数 @emph{isjunk} 必须为 @code{None} (默认值) 或为接受一个序列元素并当且仅当其为应忽略的“垃圾”元素时返回真值的单参数函数。 传入 @code{None} 作为 @emph{isjunk} 的值就相当于传入 @code{lambda x: False}；也就是说不忽略任何值。 例如，传入:

@example
lambda x: x in " \t"
@end example

如果你以字符序列的形式对行进行比较，并且不希望区分空格符或硬制表符。

可选参数 @emph{a} 和 @emph{b} 为要比较的序列；两者默认为空字符串。 两个序列的元素都必须为 @ref{13c0,,hashable}。

可选参数 @emph{autojunk} 可用于启用自动垃圾启发式计算。


3.2 新版功能: @emph{autojunk} 形参。


SequenceMatcher 对象接受三个数据属性: @emph{bjunk} 是 @emph{b} 当中 @emph{isjunk} 为 @code{True} 的元素集合；@emph{bpopular} 是被启发式计算（如果其未被禁用）视为热门候选的非垃圾元素集合；@emph{b2j} 是将 @emph{b} 当中剩余元素映射到一个它们出现位置列表的字典。 所有三个数据属性将在 @emph{b} 通过 @ref{1730,,set_seqs()} 或 @ref{1731,,set_seq2()} 重置时被重置。


3.2 新版功能: @emph{bjunk} 和 @emph{bpopular} 属性。


@ref{949,,SequenceMatcher} 对象具有以下方法：

@geindex set_seqs() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher set_seqs}@anchor{1730}
@deffn {方法} set_seqs (a, b)

设置要比较的两个序列。
@end deffn

@ref{949,,SequenceMatcher} 计算并缓存有关第二个序列的详细信息，这样如果你想要将一个序列与多个序列进行比较，可使用 @ref{1731,,set_seq2()} 一次性地设置该常用序列并重复地对每个其他序列各调用一次 @ref{1732,,set_seq1()}。

@geindex set_seq1() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher set_seq1}@anchor{1732}
@deffn {方法} set_seq1 (a)

设置要比较的第一个序列。 要比较的第二个序列不会改变。
@end deffn

@geindex set_seq2() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher set_seq2}@anchor{1731}
@deffn {方法} set_seq2 (b)

设置要比较的第二个序列。 要比较的第一个序列不会改变。
@end deffn

@geindex find_longest_match() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher find_longest_match}@anchor{1733}
@deffn {方法} find_longest_match (alo, ahi, blo, bhi)

找出 @code{a[alo:ahi]} 和 @code{b[blo:bhi]} 中的最长匹配块。

如果 @emph{isjunk} 被省略或为 @code{None}，@ref{1733,,find_longest_match()} 将返回 @code{(i, j, k)} 使得 @code{a[i:i+k]} 等于 @code{b[j:j+k]}，其中 @code{alo <= i <= i+k <= ahi} 并且 @code{blo <= j <= j+k <= bhi}。 对于所有满足这些条件的 @code{(i', j', k')}，如果 @code{i == i'}, @code{j <= j'} 也被满足，则附加条件 @code{k >= k'}, @code{i <= i'}。 换句话说，对于所有最长匹配块，返回在 @emph{a} 当中最先出现的一个，而对于在 @emph{a} 当中最先出现的所有最长匹配块，则返回在 @emph{b} 当中最先出现的一个。

@example
>>> s = SequenceMatcher(None, " abcd", "abcd abcd")
>>> s.find_longest_match(0, 5, 0, 9)
Match(a=0, b=4, size=5)
@end example

如果提供了 @emph{isjunk}，将按上述规则确定第一个最长匹配块，但额外附加不允许块内出现垃圾元素的限制。 然后将通过（仅）匹配两边的垃圾元素来尽可能地扩展该块。 这样结果块绝对不会匹配垃圾元素，除非同样的垃圾元素正好与有意义的匹配相邻。

这是与之前相同的例子，但是将空格符视为垃圾。 这将防止 @code{' abcd'} 直接与第二个序列末尾的 @code{' abcd'} 相匹配。 而只可以匹配 @code{'abcd'}，并且是匹配第二个序列最左边的 @code{'abcd'}：

@example
>>> s = SequenceMatcher(lambda x: x==" ", " abcd", "abcd abcd")
>>> s.find_longest_match(0, 5, 0, 9)
Match(a=1, b=0, size=4)
@end example

如果未找到匹配块，此方法将返回 @code{(alo, blo, 0)}。

此方法将返回一个 @ref{a9e,,named tuple} @code{Match(a, b, size)}。
@end deffn

@geindex get_matching_blocks() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher get_matching_blocks}@anchor{1734}
@deffn {方法} get_matching_blocks ()

返回描述非重叠匹配子序列的三元组列表。 每个三元组的形式为 @code{(i, j, n)}，其含义为 @code{a[i:i+n] == b[j:j+n]}。 这些三元组按 @emph{i} 和 @emph{j} 单调递增排列。

最后一个三元组用于占位，其值为 @code{(len(a), len(b), 0)}。 它是唯一 @code{n == 0} 的三元组。 如果 @code{(i, j, n)} 和 @code{(i', j', n')} 是在列表中相邻的三元组，且后者不是列表中的最后一个三元组，则 @code{i+n < i'} 或 @code{j+n < j'}；换句话说，相邻的三元组总是描述非相邻的相等块。

@c XXX Explain why a dummy is used!

@example
>>> s = SequenceMatcher(None, "abxcd", "abcd")
>>> s.get_matching_blocks()
[Match(a=0, b=0, size=2), Match(a=3, b=2, size=2), Match(a=5, b=4, size=0)]
@end example
@end deffn

@geindex get_opcodes() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher get_opcodes}@anchor{1735}
@deffn {方法} get_opcodes ()

返回描述如何将 @emph{a} 变为 @emph{b} 的 5 元组列表，每个元组的形式为 @code{(tag, i1, i2, j1, j2)}。 在第一个元组中 @code{i1 == j1 == 0}，而在其余的元组中 @emph{i1} 等于前一个元组的 @emph{i2}，并且 @emph{j1} 也等于前一个元组的 @emph{j2}。

@emph{tag} 值为字符串，其含义如下：


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

含义

@item

@code{'replace'}

@tab

@code{a[i1:i2]} 应由 @code{b[j1:j2]} 替换。

@item

@code{'delete'}

@tab

@code{a[i1:i2]} 应被删除。 请注意在此情况下 @code{j1 == j2}。

@item

@code{'insert'}

@tab

@code{b[j1:j2]} 应插入到 @code{a[i1:i1]}。 请注意在此情况下 @code{i1 == i2}。

@item

@code{'equal'}

@tab

@code{a[i1:i2] == b[j1:j2]} (两个子序列相同)。

@end multitable


例如

@example
>>> a = "qabxcd"
>>> b = "abycdf"
>>> s = SequenceMatcher(None, a, b)
>>> for tag, i1, i2, j1, j2 in s.get_opcodes():
...     print('@{:7@}   a[@{@}:@{@}] --> b[@{@}:@{@}] @{!r:>8@} --> @{!r@}'.format(
...         tag, i1, i2, j1, j2, a[i1:i2], b[j1:j2]))
delete    a[0:1] --> b[0:0]      'q' --> '@w{'}
equal     a[1:3] --> b[0:2]     'ab' --> 'ab'
replace   a[3:4] --> b[2:3]      'x' --> 'y'
equal     a[4:6] --> b[3:5]     'cd' --> 'cd'
insert    a[6:6] --> b[5:6]       '@w{'} --> 'f'
@end example
@end deffn

@geindex get_grouped_opcodes() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher get_grouped_opcodes}@anchor{1736}
@deffn {方法} get_grouped_opcodes (n=3)

返回一个带有最多 @emph{n} 行上下文的分组的 @ref{99c,,generator}。

从 @ref{1735,,get_opcodes()} 所返回的组开始，此方法会拆分出较小的更改簇并消除没有更改的间隔区域。

这些分组以与 @ref{1735,,get_opcodes()} 相同的格式返回。
@end deffn

@geindex ratio() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher ratio}@anchor{1737}
@deffn {方法} ratio ()

返回一个取值范围 [0, 1] 的浮点数作为序列相似性度量。

其中 T 是两个序列中元素的总数量，M 是匹配的数量，即 2.0*M / T。 请注意如果两个序列完全相同则该值为 @code{1.0}，如果两者完全不同则为 @code{0.0}。

如果 @ref{1734,,get_matching_blocks()} 或 @ref{1735,,get_opcodes()} 尚未被调用则此方法运算消耗较大，在此情况下你可能需要先调用 @ref{1738,,quick_ratio()} 或 @ref{1739,,real_quick_ratio()} 来获取一个上界。

@cartouche
@quotation 注解 
注意: @ref{1737,,ratio()} 调用的结果可能会取决于参数的顺序。 例如:

@example
>>> SequenceMatcher(None, 'tide', 'diet').ratio()
0.25
>>> SequenceMatcher(None, 'diet', 'tide').ratio()
0.5
@end example
@end quotation
@end cartouche
@end deffn

@geindex quick_ratio() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher quick_ratio}@anchor{1738}
@deffn {方法} quick_ratio ()

相对快速地返回一个 @ref{1737,,ratio()} 的上界。
@end deffn

@geindex real_quick_ratio() (difflib.SequenceMatcher 方法)
@anchor{library/difflib difflib SequenceMatcher real_quick_ratio}@anchor{1739}
@deffn {方法} real_quick_ratio ()

非常快速地返回一个 @ref{1737,,ratio()} 的上界。
@end deffn
@end deffn

这三个返回匹配部分占字符总数的比率的方法可能由于不同的近似级别而给出不一样的结果，但是 @code{quick_ratio()} 和 @code{real_quick_ratio()} 总是会至少与 @code{ratio()} 一样大：

@example
>>> s = SequenceMatcher(None, "abcd", "bcde")
>>> s.ratio()
0.75
>>> s.quick_ratio()
0.75
>>> s.real_quick_ratio()
1.0
@end example

@node SequenceMatcher 的示例,Differ 对象,SequenceMatcher 对象,difflib --- 计算差异的辅助工具
@anchor{library/difflib id1}@anchor{173a}@anchor{library/difflib sequencematcher-examples}@anchor{173b}
@subsubsection SequenceMatcher 的示例


以下示例比较两个字符串，并将空格视为“垃圾”：

@example
>>> s = SequenceMatcher(lambda x: x == " ",
...                     "private Thread currentThread;",
...                     "private volatile Thread currentThread;")
@end example

@code{ratio()} 返回一个 [0, 1] 范围内的整数作为两个序列相似性的度量。 根据经验，@code{ratio()} 值超过 0.6 就意味着两个序列是近似匹配的：

@example
>>> print(round(s.ratio(), 3))
0.866
@end example

如果你只对两个序列相匹配的位置感兴趣，则 @code{get_matching_blocks()} 就很方便：

@example
>>> for block in s.get_matching_blocks():
...     print("a[%d] and b[%d] match for %d elements" % block)
a[0] and b[0] match for 8 elements
a[8] and b[17] match for 21 elements
a[29] and b[38] match for 0 elements
@end example

请注意 @code{get_matching_blocks()} 返回的最后一个元组总是只用于占位的 @code{(len(a), len(b), 0)}，这也是元组末尾元素（匹配的元素数量）为 @code{0} 的唯一情况。

如果你想要知道如何将第一个序列转成第二个序列，可以使用 @code{get_opcodes()}:

@example
>>> for opcode in s.get_opcodes():
...     print("%6s a[%d:%d] b[%d:%d]" % opcode)
 equal a[0:8] b[0:8]
insert a[8:8] b[8:17]
 equal a[8:29] b[17:38]
@end example


@subsubheading 参见



@itemize *

@item 
此模块中的 @ref{1728,,get_close_matches()} 函数显示了如何基于 @ref{949,,SequenceMatcher} 构建简单的代码来执行有用的功能。

@item 
使用 @ref{949,,SequenceMatcher} 构建小型应用的 简易版本控制方案@footnote{https://code.activestate.com/recipes/576729/}。
@end itemize


@node Differ 对象,Differ 示例,SequenceMatcher 的示例,difflib --- 计算差异的辅助工具
@anchor{library/difflib differ-objects}@anchor{173c}@anchor{library/difflib id2}@anchor{173d}
@subsubsection Differ 对象


请注意 @ref{171f,,Differ} 所生成的增量并不保证是 @strong{最小} 差异。 相反，最小差异往往是违反直觉的，因为它们会同步任何可能的地方，有时甚至意外产生相距 100 页的匹配。 将同步点限制为连续匹配保留了一些局部性概念，这偶尔会带来产生更长差异的代价。

@ref{171f,,Differ} 类具有这样的构造器：

@geindex Differ (difflib 中的类)

@deffn {类} difflib.Differ (linejunk=None, charjunk=None)

可选关键字形参 @emph{linejunk} 和 @emph{charjunk} 均为过滤函数 (或为 @code{None})：

@emph{linejunk}: 接受单个字符串作为参数的函数，如果其为垃圾字符串则返回真值。 默认值为 @code{None}，意味着没有任何行会被视为垃圾行。

@emph{charjunk}: 接受单个字符（长度为 1 的字符串）作为参数的函数，如果其为垃圾字符则返回真值。 默认值为 @code{None}，意味着没有任何字符会被视为垃圾字符。

这些垃圾过滤函数可加快查找差异的匹配速度，并且不会导致任何差异行或字符被忽略。 请阅读 @ref{1733,,find_longest_match()} 方法的 @emph{isjunk} 形参的描述了解详情。

@ref{171f,,Differ} 对象是通过一个单独方法来使用（生成增量）的：

@geindex compare() (difflib.Differ 方法)
@anchor{library/difflib difflib Differ compare}@anchor{172c}
@deffn {方法} compare (a, b)

比较两个由行组成的序列，并生成增量（一个由行组成的序列）。

每个序列必须包含一个以换行符结尾的单行字符串。 这样的序列可以通过文件类对象的 @ref{1725,,readlines()} 方法来获取。 所生成的增量同样由以换行符结尾的字符串构成，可以通过文件类对象的 @ref{1726,,writelines()} 方法原样打印出来。
@end deffn
@end deffn

@node Differ 示例,difflib 的命令行接口,Differ 对象,difflib --- 计算差异的辅助工具
@anchor{library/difflib differ-example}@anchor{173e}@anchor{library/difflib differ-examples}@anchor{173f}
@subsubsection Differ 示例


此示例比较两段文本。 首先我们设置文本为以换行符结尾的单行字符串构成的序列（这样的序列也可以通过文件类对象的 @code{readlines()} 方法来获取）：

@example
>>> text1 = '@w{'}'  1. Beautiful is better than ugly.
...   2. Explicit is better than implicit.
...   3. Simple is better than complex.
...   4. Complex is better than complicated.
... '@w{'}'.splitlines(keepends=True)
>>> len(text1)
4
>>> text1[0][-1]
'\n'
>>> text2 = '@w{'}'  1. Beautiful is better than ugly.
...   3.   Simple is better than complex.
...   4. Complicated is better than complex.
...   5. Flat is better than nested.
... '@w{'}'.splitlines(keepends=True)
@end example

接下来我们实例化一个 Differ 对象：

@example
>>> d = Differ()
@end example

请注意在实例化 @ref{171f,,Differ} 对象时我们可以传入函数来过滤掉“垃圾”行和字符。 详情参见 @ref{171f,,Differ()} 构造器说明。

最后，我们比较两个序列：

@example
>>> result = list(d.compare(text1, text2))
@end example

@code{result} 是一个字符串列表，让我们将其美化打印出来：

@example
>>> from pprint import pprint
>>> pprint(result)
['    1. Beautiful is better than ugly.\n',
 '-   2. Explicit is better than implicit.\n',
 '-   3. Simple is better than complex.\n',
 '+   3.   Simple is better than complex.\n',
 '?     ++\n',
 '-   4. Complex is better than complicated.\n',
 '?            ^                     ---- ^\n',
 '+   4. Complicated is better than complex.\n',
 '?           ++++ ^                      ^\n',
 '+   5. Flat is better than nested.\n']
@end example

作为单独的多行字符串显示出来则是这样：

@example
>>> import sys
>>> sys.stdout.writelines(result)
    1. Beautiful is better than ugly.
-   2. Explicit is better than implicit.
-   3. Simple is better than complex.
+   3.   Simple is better than complex.
?     ++
-   4. Complex is better than complicated.
?            ^                     ---- ^
+   4. Complicated is better than complex.
?           ++++ ^                      ^
+   5. Flat is better than nested.
@end example

@node difflib 的命令行接口,,Differ 示例,difflib --- 计算差异的辅助工具
@anchor{library/difflib a-command-line-interface-to-difflib}@anchor{1740}@anchor{library/difflib difflib-interface}@anchor{1727}
@subsubsection difflib 的命令行接口


这个实例演示了如何使用 difflib 来创建一个类似于 @code{diff} 的工具。 它同样包含在 Python 源码发布包中，文件名为 @code{Tools/scripts/diff.py}。

@example
#!/usr/bin/env python3
""" Command line interface to difflib.py providing diffs in four formats:

* ndiff:    lists every line and highlights interline changes.
* context:  highlights clusters of changes in a before/after format.
* unified:  highlights clusters of changes in an inline format.
* html:     generates side by side comparison with change highlights.

"""

import sys, os, difflib, argparse
from datetime import datetime, timezone

def file_mtime(path):
    t = datetime.fromtimestamp(os.stat(path).st_mtime,
                               timezone.utc)
    return t.astimezone().isoformat()

def main():

    parser = argparse.ArgumentParser()
    parser.add_argument('-c', action='store_true', default=False,
                        help='Produce a context format diff (default)')
    parser.add_argument('-u', action='store_true', default=False,
                        help='Produce a unified format diff')
    parser.add_argument('-m', action='store_true', default=False,
                        help='Produce HTML side by side diff '
                             '(can use -c and -l in conjunction)')
    parser.add_argument('-n', action='store_true', default=False,
                        help='Produce a ndiff format diff')
    parser.add_argument('-l', '--lines', type=int, default=3,
                        help='Set number of context lines (default 3)')
    parser.add_argument('fromfile')
    parser.add_argument('tofile')
    options = parser.parse_args()

    n = options.lines
    fromfile = options.fromfile
    tofile = options.tofile

    fromdate = file_mtime(fromfile)
    todate = file_mtime(tofile)
    with open(fromfile) as ff:
        fromlines = ff.readlines()
    with open(tofile) as tf:
        tolines = tf.readlines()

    if options.u:
        diff = difflib.unified_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)
    elif options.n:
        diff = difflib.ndiff(fromlines, tolines)
    elif options.m:
        diff = difflib.HtmlDiff().make_file(fromlines,tolines,fromfile,tofile,context=options.c,numlines=n)
    else:
        diff = difflib.context_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)

    sys.stdout.writelines(diff)

if __name__ == '__main__':
    main()
@end example

@node textwrap --- 文本自动换行与填充,unicodedata --- Unicode 数据库,difflib --- 计算差异的辅助工具,文本处理服务
@anchor{library/textwrap doc}@anchor{1741}@anchor{library/textwrap module-textwrap}@anchor{108}@anchor{library/textwrap textwrap-text-wrapping-and-filling}@anchor{1742}
@subsection @code{textwrap} --- 文本自动换行与填充


@geindex textwrap (模块)

@strong{源代码:} Lib/textwrap.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/textwrap.py}


__________________________________________________________________


@ref{108,,textwrap} 模块提供了一些快捷函数，以及可以完成所有工作的类 @ref{8e4,,TextWrapper}。 如果你只是要对一两个文本字符串进行自动换行或填充，快捷函数应该就够用了；否则的话，你应该使用 @ref{8e4,,TextWrapper} 的实例来提高效率。

@geindex wrap() (在 textwrap 模块中)
@anchor{library/textwrap textwrap wrap}@anchor{1743}
@deffn {函数} textwrap.wrap (text, width=70, **kwargs)

对 @emph{text} (字符串) 中的单独段落自动换行以使每行长度最多为 @emph{width} 个字符。 返回由输出行组成的列表，行尾不带换行符。

可选的关键字参数对应于 @ref{8e4,,TextWrapper} 的实例属性，具体文档见下。 @emph{width} 默认为 @code{70}。

请参阅 @ref{1744,,TextWrapper.wrap()} 方法了解有关 @ref{1743,,wrap()} 行为的详细信息。
@end deffn

@geindex fill() (在 textwrap 模块中)
@anchor{library/textwrap textwrap fill}@anchor{1745}
@deffn {函数} textwrap.fill (text, width=70, **kwargs)

对 @emph{text} 中的单独段落自动换行，并返回一个包含被自动换行段落的单独字符串。 @ref{1745,,fill()} 是以下语句的快捷方式

@example
"\n".join(wrap(text, ...))
@end example

特别要说明的是，@ref{1745,,fill()} 接受与 @ref{1743,,wrap()} 完全相同的关键字参数。
@end deffn

@geindex shorten() (在 textwrap 模块中)
@anchor{library/textwrap textwrap shorten}@anchor{8e7}
@deffn {函数} textwrap.shorten (text, width, **kwargs)

折叠并截短给定的 @emph{text} 以符合给定的 @emph{width}。

首先将折叠 @emph{text} 中的空格（所有连续空格替换为单个空格）。 如果结果能适合 @emph{width} 则将其返回。 否则将丢弃足够数量的末尾单词以使得剩余单词加 @code{placeholder} 能适合 @code{width}:

@example
>>> textwrap.shorten("Hello  world!", width=12)
'Hello world!'
>>> textwrap.shorten("Hello  world!", width=11)
'Hello [...]'
>>> textwrap.shorten("Hello world", width=10, placeholder="...")
'Hello...'
@end example

可选的关键字参数对应于 @ref{8e4,,TextWrapper} 的实际属性，具体见下文。 请注意文本在被传入 @ref{8e4,,TextWrapper} 的 @ref{1745,,fill()} 函数之前会被折叠，因此改变 @ref{1746,,tabsize}, @ref{1747,,expand_tabs}, @ref{1748,,drop_whitespace} 和 @ref{1749,,replace_whitespace} 的值将没有任何效果。


3.4 新版功能.

@end deffn

@geindex dedent() (在 textwrap 模块中)
@anchor{library/textwrap textwrap dedent}@anchor{174a}
@deffn {函数} textwrap.dedent (text)

移除 @emph{text} 中每一行的任何相同前缀空白符。

这可以用来清除三重引号字符串行左侧空格，而仍然在源码中显示为缩进格式。

请注意制表符和空格符都被视为是空白符，但它们并不相等：以下两行 @code{"  hello"} 和 @code{"\thello"} 不会被视为具有相同的前缀空白符。

只包含空白符的行会在输入时被忽略并在输出时被标准化为单个换行符。

例如

@example
def test():
    # end first line with \ to avoid the empty line!
    s = '@w{'}'\
    hello
      world
    '@w{'}'
    print(repr(s))          # prints '    hello\n      world\n    '
    print(repr(dedent(s)))  # prints 'hello\n  world\n'
@end example
@end deffn

@geindex indent() (在 textwrap 模块中)
@anchor{library/textwrap textwrap indent}@anchor{aa3}
@deffn {函数} textwrap.indent (text, prefix, predicate=None)

将 @emph{prefix} 添加到 @emph{text} 中选定行的开头。

通过调用 @code{text.splitlines(True)} 来对行进行拆分。

默认情况下，@emph{prefix} 会被添加到所有不是只由空白符（包括任何行结束符）组成的行。

例如

@example
>>> s = 'hello\n\n \nworld'
>>> indent(s, '  ')
'  hello\n\n \n  world'
@end example

可选的 @emph{predicate} 参数可用来控制哪些行要缩进。 例如，可以很容易地为空行或只有空白符的行添加 @emph{prefix}:

@example
>>> print(indent(s, '+ ', lambda line: True))
+ hello
+
+
+ world
@end example


3.3 新版功能.

@end deffn

@ref{1743,,wrap()}, @ref{1745,,fill()} 和 @ref{8e7,,shorten()} 的作用方式为创建一个 @ref{8e4,,TextWrapper} 实例并在其上调用单个方法。 该实例不会被重用，因此对于要使用 @ref{1743,,wrap()} 和/或 @ref{1745,,fill()} 来处理许多文本字符串的应用来说，创建你自己的 @ref{8e4,,TextWrapper} 对象可能会更有效率。

文本最好在空白符位置自动换行，包括带连字符单词的连字符之后；长单词仅在必要时会被拆分，除非 @ref{174b,,TextWrapper.break_long_words} 被设为假值。

@geindex TextWrapper (textwrap 中的类)
@anchor{library/textwrap textwrap TextWrapper}@anchor{8e4}
@deffn {类} textwrap.TextWrapper (**kwargs)

@ref{8e4,,TextWrapper} 构造器接受多个可选的关键字参数。 每个关键字参数对应一个实例属性，比如说

@example
wrapper = TextWrapper(initial_indent="* ")
@end example

就相当于

@example
wrapper = TextWrapper()
wrapper.initial_indent = "* "
@end example

你可以多次重用相同的 @ref{8e4,,TextWrapper} 对象，并且你也可以在使用期间通过直接向实例属性赋值来修改它的任何选项。

@ref{8e4,,TextWrapper} 的实例属性（以及构造器的关键字参数）如下所示：

@geindex width (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper width}@anchor{174c}
@deffn {属性} width

(默认: @code{70}) 自动换行的最大行长度。 只要输入文本中没有长于 @ref{174c,,width} 的单个单词，@ref{8e4,,TextWrapper} 就能保证没有长于 @ref{174c,,width} 个字符的输出行。
@end deffn

@geindex expand_tabs (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper expand_tabs}@anchor{1747}
@deffn {属性} expand_tabs

(默认: @code{True}) 如果为真值，则 @emph{text} 中所有的制表符将使用 @emph{text} 的 @code{expandtabs()} 方法扩展为空格符。
@end deffn

@geindex tabsize (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper tabsize}@anchor{1746}
@deffn {属性} tabsize

(默认: @code{8}) 如果 @ref{1747,,expand_tabs} 为真值，则 @emph{text} 中所有的制表符将扩展为零个或多个空格，具体取决于当前列位置和给定的制表宽度。


3.3 新版功能.

@end deffn

@geindex replace_whitespace (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper replace_whitespace}@anchor{1749}
@deffn {属性} replace_whitespace

(default: @code{True}) 如果为真值，在制表符扩展之后、自动换行之前，@ref{1743,,wrap()} 方法将把每个空白字符都替换为单个空格。 会被替换的空白字符如下：制表，换行，垂直制表，进纸和回车 (@code{'\t\n\v\f\r'})。

@cartouche
@quotation 注解 
如果 @ref{1747,,expand_tabs} 为假值且 @ref{1749,,replace_whitespace} 为真值，每个制表符将被替换为单个空格，这与制表符扩展是 @emph{不} 一样的。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
如果 @ref{1749,,replace_whitespace} 为假值，在一行的中间有可能出现换行符并导致怪异的输出。 因此，文本应当（使用 @ref{15f2,,str.splitlines()} 或类似方法）拆分为段落并分别进行自动换行。
@end quotation
@end cartouche
@end deffn

@geindex drop_whitespace (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper drop_whitespace}@anchor{1748}
@deffn {属性} drop_whitespace

(默认: @code{True}) 如果为真值，每一行开头和末尾的空白字符（在包装之后、缩进之前）会被丢弃。 但是段落开头的空白字符如果后面不带任何非空白字符则不会被丢弃。 如果被丢弃的空白字符占据了一个整行，则该整行将被丢弃。
@end deffn

@geindex initial_indent (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper initial_indent}@anchor{174d}
@deffn {属性} initial_indent

(默认: @code{'@w{'}}) 将被添加到被自动换行输出内容的第一行的字符串。 其长度会被计入第一行的长度。 空字符串不会被缩进。
@end deffn

@geindex subsequent_indent (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper subsequent_indent}@anchor{174e}
@deffn {属性} subsequent_indent

(default: @code{'@w{'}}) 将被添加到被自动换行输出内容除第一行外的所有行的字符串。 其长度会被计入除行一行外的所有行的长度。
@end deffn

@geindex fix_sentence_endings (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper fix_sentence_endings}@anchor{174f}
@deffn {属性} fix_sentence_endings

(默认: @code{False}) 如果为真值，@ref{8e4,,TextWrapper} 将尝试检测句子结尾并确保句子间总是以恰好两个空格符分隔。 对于使用等宽字体的文本来说通常都需要这样。 但是，句子检测算法并不完美：它假定句子结尾是一个小写字母加字符 @code{'.'}, @code{'!'} 或 @code{'?'} 中的一个，并可能带有字符 @code{'"'} 或 @code{"'"}，最后以一个空格结束。 此算法的问题之一是它无法区分以下文本中的 "Dr."

@example
[...] Dr. Frankenstein's monster [...]
@end example

和以下文本中的 "Spot."

@example
[...] See Spot. See Spot run [...]
@end example

@ref{174f,,fix_sentence_endings} 默认为假值。

由于句子检测算法依赖于 @code{string.lowercase} 来确定“小写字母”，以及约定在句点后使用两个空格来分隔处于同一行的句子，因此只适用于英语文本。
@end deffn

@geindex break_long_words (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper break_long_words}@anchor{174b}
@deffn {属性} break_long_words

(默认: @code{True}) 如果为真值，则长度超过 @ref{174c,,width} 的单词将被分开以保证行的长度不会超过 @ref{174c,,width}。 如果为假值，超长单词不会被分开，因而某些行的长度可能会超过 @ref{174c,,width}。 （超长单词将被单独作为一行，以尽量减少超出 @ref{174c,,width} 的情况。）
@end deffn

@geindex break_on_hyphens (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper break_on_hyphens}@anchor{1750}
@deffn {属性} break_on_hyphens

(默认: @code{True}) 如果为真值，将根据英语的惯例首选在空白符和复合词的连字符之后自动换行。 如果为假值，则只有空白符会被视为合适的潜在断行位置，但如果你确实不希望出现分开的单词则你必须将 @ref{174b,,break_long_words} 设为假值。 之前版本的默认行为总是允许分开带有连字符的单词。
@end deffn

@geindex max_lines (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper max_lines}@anchor{8e5}
@deffn {属性} max_lines

(默认: @code{None}) 如果不为 @code{None}，则输出内容将最多包含 @emph{max_lines} 行，并使 @emph{placeholder} 出现在输出内容的末尾。


3.4 新版功能.

@end deffn

@geindex ...; placeholder

@geindex placeholder (textwrap.TextWrapper 属性)
@anchor{library/textwrap textwrap TextWrapper placeholder}@anchor{8e6}
@deffn {属性} placeholder

(默认: @code{' [...]'}) 该文本将在输出文本被截短时出现在文本末尾。


3.4 新版功能.

@end deffn

@ref{8e4,,TextWrapper} 还提供了一些公有方法，类似于模块层级的便捷函数：

@geindex wrap() (textwrap.TextWrapper 方法)
@anchor{library/textwrap textwrap TextWrapper wrap}@anchor{1744}
@deffn {方法} wrap (text)

对 @emph{text} (字符串) 中的单独段落自动换行以使每行长度最多为 @ref{174c,,width} 个字符。 所有自动换行选项均获取自 @ref{8e4,,TextWrapper} 实例的实例属性。 返回由输出行组成的列表，行尾不带换行符。 如果自动换行输出结果没有任何内容，则返回空列表。
@end deffn

@geindex fill() (textwrap.TextWrapper 方法)
@anchor{library/textwrap textwrap TextWrapper fill}@anchor{1751}
@deffn {方法} fill (text)

对 @emph{text} 中的单独段落自动换行并返回包含被自动换行段落的单独字符串。
@end deffn
@end deffn

@node unicodedata --- Unicode 数据库,stringprep --- 因特网字符串预备,textwrap --- 文本自动换行与填充,文本处理服务
@anchor{library/unicodedata doc}@anchor{1752}@anchor{library/unicodedata module-unicodedata}@anchor{11a}@anchor{library/unicodedata unicodedata-unicode-database}@anchor{1753}
@subsection @code{unicodedata} --- Unicode 数据库


@geindex unicodedata (模块)

@geindex Unicode
@geindex character
@geindex Unicode; database


__________________________________________________________________


此模块提供了对 Unicode Character Database (UCD) 的访问，其中定义了所有 Unicode 字符的字符属性。 此数据库中包含的数据编译自 UCD 版本 12.1.0@footnote{http://www.unicode.org/Public/12.1.0/ucd}。

该模块使用与 Unicode 标准附件 #44 “Unicode 字符数据库”@footnote{https://www.unicode.org/reports/tr44/} 中所定义的相同名称和符号。 它定义了以下函数：

@geindex lookup() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata lookup}@anchor{9b7}
@deffn {函数} unicodedata.lookup (name)

按名称查找字符。如果找到具有给定名称的字符，则返回相应的字符。 如果没有找到，则 @ref{2c7,,KeyError} 被引发。


在 3.3 版更改: 已添加对名称别名 @footnote{@w{(1)} 
@indicateurl{http://www.unicode.org/Public/12.1.0/ucd/NameAliases.txt}
} 和命名序列 @footnote{@w{(2)} 
@indicateurl{http://www.unicode.org/Public/12.1.0/ucd/NamedSequences.txt}
} 的支持。

@end deffn

@geindex name() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata name}@anchor{1754}
@deffn {函数} unicodedata.name (chr[, default])

返回分配给字符 @emph{chr} 的名称作为字符串。如果没有定义名称，则返回 @emph{default} ，如果没有给出，则 @ref{1fb,,ValueError} 被引发。
@end deffn

@geindex decimal() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata decimal}@anchor{1755}
@deffn {函数} unicodedata.decimal (chr[, default])

返回分配给字符 @emph{chr} 的十进制值作为整数。 如果没有定义这样的值，则返回 @emph{default} ，如果没有给出，则 @ref{1fb,,ValueError} 被引发。
@end deffn

@geindex digit() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata digit}@anchor{1756}
@deffn {函数} unicodedata.digit (chr[, default])

返回分配给字符 @emph{chr} 的数字值作为整数。 如果没有定义这样的值，则返回 @emph{default} ，如果没有给出，则 @ref{1fb,,ValueError} 被引发。
@end deffn

@geindex numeric() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata numeric}@anchor{bf2}
@deffn {函数} unicodedata.numeric (chr[, default])

返回分配给字符 @emph{chr} 的数值作为浮点数。 如果没有定义这样的值，则返回 @emph{default} ，如果没有给出，则 @ref{1fb,,ValueError} 被引发。
@end deffn

@geindex category() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata category}@anchor{1757}
@deffn {函数} unicodedata.category (chr)

返回分配给字符 @emph{chr} 的常规类别为字符串。
@end deffn

@geindex bidirectional() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata bidirectional}@anchor{1758}
@deffn {函数} unicodedata.bidirectional (chr)

返回分配给字符 @emph{chr} 的双向类作为字符串。如果未定义此类值，则返回空字符串。
@end deffn

@geindex combining() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata combining}@anchor{1759}
@deffn {函数} unicodedata.combining (chr)

返回分配给字符 @emph{chr} 的规范组合类作为整数。如果没有定义组合类，则返回 @code{0} 。
@end deffn

@geindex east_asian_width() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata east_asian_width}@anchor{175a}
@deffn {函数} unicodedata.east_asian_width (chr)

返回分配给字符 @emph{chr} 的东亚宽度作为字符串。
@end deffn

@geindex mirrored() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata mirrored}@anchor{175b}
@deffn {函数} unicodedata.mirrored (chr)

返回分配给字符 @emph{chr} 的镜像属性为整数。如果字符在双向文本中被识别为“镜像”字符，则返回 @code{1} ，否则返回 @code{0} 。
@end deffn

@geindex decomposition() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata decomposition}@anchor{175c}
@deffn {函数} unicodedata.decomposition (chr)

返回分配给字符 @emph{chr} 的字符分解映射作为字符串。如果未定义此类映射，则返回空字符串。
@end deffn

@geindex normalize() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata normalize}@anchor{1042}
@deffn {函数} unicodedata.normalize (form, unistr)

返回 Unicode 字符串 @emph{unistr} 的正常形式 @emph{form} 。 @emph{form} 的有效值为 'NFC' 、 'NFKC' 、 'NFD' 和 'NFKD' 。

Unicode 标准基于规范等价和兼容性等效的定义定义了 Unicode 字符串的各种规范化形式。在 Unicode 中，可以以各种方式表示多个字符。 例如，字符 U+00C7 （带有 CEDILLA 的 LATIN CAPITAL LETTER C ）也可以表示为序列 U+0043（ LATIN CAPITAL LETTER C ）U+0327（ COMBINING CEDILLA ）。

对于每个字符，有两种正规形式：正规形式 C 和正规形式 D 。正规形式D（NFD）也称为规范分解，并将每个字符转换为其分解形式。 正规形式C（NFC）首先应用规范分解，然后再次组合预组合字符。

除了这两种形式之外，还有两种基于兼容性等效的其他常规形式。 在 Unicode 中，支持某些字符，这些字符通常与其他字符统一。 例如， U+2160（ROMAN NUMERAL ONE）与 U+0049（LATIN CAPITAL LETTER I）完全相同。 但是， Unicode 支持它与现有字符集（例如 gb2312 ）的兼容性。

正规形式KD（NFKD）将应用兼容性分解，即用其等价项替换所有兼容性字符。 正规形式KC（NFKC）首先应用兼容性分解，然后是规范组合。

即使两个 unicode 字符串被规范化并且人类读者看起来相同，如果一个具有组合字符而另一个没有，则它们可能无法相等。
@end deffn

@geindex is_normalized() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata is_normalized}@anchor{246}
@deffn {函数} unicodedata.is_normalized (form, unistr)

判断 Unicode 字符串 @emph{unistr} 是否为正规形式 @emph{form}。 @emph{form} 的有效值为 'NFC', 'NFKC', 'NFD' 和 'NFKD'。


3.8 新版功能.

@end deffn

此外，该模块暴露了以下常量：

@geindex unidata_version() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata unidata_version}@anchor{175d}
@deffn {数据} unicodedata.unidata_version

此模块中使用的 Unicode 数据库的版本。
@end deffn

@geindex ucd_3_2_0() (在 unicodedata 模块中)
@anchor{library/unicodedata unicodedata ucd_3_2_0}@anchor{d95}
@deffn {数据} unicodedata.ucd_3_2_0

这是一个与整个模块具有相同方法的对象，但对于需要此特定版本的 Unicode 数据库（如 IDNA ）的应用程序，则使用 Unicode 数据库版本 3.2 。
@end deffn

示例：

@example
>>> import unicodedata
>>> unicodedata.lookup('LEFT CURLY BRACKET')
'@{'
>>> unicodedata.name('/')
'SOLIDUS'
>>> unicodedata.decimal('9')
9
>>> unicodedata.decimal('a')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: not a decimal
>>> unicodedata.category('A')  # 'L'etter, 'u'ppercase
'Lu'
>>> unicodedata.bidirectional('\u0660') # 'A'rabic, 'N'umber
'AN'
@end example

@subsubheading 备注


@node stringprep --- 因特网字符串预备,readline --- GNU readline 接口,unicodedata --- Unicode 数据库,文本处理服务
@anchor{library/stringprep doc}@anchor{175e}@anchor{library/stringprep module-stringprep}@anchor{f7}@anchor{library/stringprep stringprep-internet-string-preparation}@anchor{175f}
@subsection @code{stringprep} --- 因特网字符串预备


@geindex stringprep (模块)

@strong{源代码:} Lib/stringprep.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/stringprep.py}


__________________________________________________________________


在标识因特网上的事物（例如主机名），经常需要比较这些标识是否（相等）。 这种比较的具体执行可能会取决于应用域的不同，例如是否要区分大小写等等。 有时也可能需要限制允许的标识为仅由“可打印”字符组成。

@geindex RFC; RFC 3454
RFC 3454@footnote{https://tools.ietf.org/html/rfc3454.html} 定义了在因特网协议中 Unicode 字符串的“预备”过程。 在将字符串连线传输之前，它们会先使用预备过程进行处理，之后它们将具有特定的标准形式。 该 RFC 定义了一系列表格，它们可以被组合为选项配置。 每个配置必须定义所使用的表格，@code{stringprep} 过程的其他可选项也是配置的组成部分。 @code{stringprep} 配置的一个例子是 @code{nameprep}，它被用于国际化域名。

模块 @ref{f7,,stringprep} 仅公开了来自 
@geindex RFC; RFC 3454
RFC 3454@footnote{https://tools.ietf.org/html/rfc3454.html} 的表格。 由于这些如果表格如果表示为字典或列表将会非常庞大，该模块在内部使用 Unicode 字符数据库。 该模块本身的源代码是使用 @code{mkstringprep.py} 工具生成的。

因此，这些表格以函数而非数据结构的形式公开。 在 RFC 中有两种表格：集合与映射。 对于集合，@ref{f7,,stringprep} 提供了“特征函数”，即如果形参是集合的一部分则返回值为 @code{True} 的函数。 对于映射，它提供了映射函数：它会根据给定的键返回所关联的值。 以下是模块中所有可用函数的列表。

@geindex in_table_a1() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_a1}@anchor{1760}
@deffn {函数} stringprep.in_table_a1 (code)

确定 @emph{code} 是否属于 tableA.1 (Unicode 3.2 中的未分配码位)。
@end deffn

@geindex in_table_b1() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_b1}@anchor{1761}
@deffn {函数} stringprep.in_table_b1 (code)

确定 @emph{code} 是否属于 tableB.1 (通常映射为空值)。
@end deffn

@geindex map_table_b2() (在 stringprep 模块中)
@anchor{library/stringprep stringprep map_table_b2}@anchor{1762}
@deffn {函数} stringprep.map_table_b2 (code)

返回 @emph{code} 依据 tableB.2 (配合 NFKC 使用的大小写转换映射) 所映射的值。
@end deffn

@geindex map_table_b3() (在 stringprep 模块中)
@anchor{library/stringprep stringprep map_table_b3}@anchor{1763}
@deffn {函数} stringprep.map_table_b3 (code)

返回 @emph{code} 依据 tableB.3 (不附带正规化的大小写折叠映射) 所映射的值。
@end deffn

@geindex in_table_c11() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c11}@anchor{1764}
@deffn {函数} stringprep.in_table_c11 (code)

确定 @emph{code} 是否属于 tableC.1.1  (ASCII 空白字符)。
@end deffn

@geindex in_table_c12() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c12}@anchor{1765}
@deffn {函数} stringprep.in_table_c12 (code)

确定 @emph{code} 是否属于 tableC.1.2  (非 ASCII 空白字符)。
@end deffn

@geindex in_table_c11_c12() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c11_c12}@anchor{1766}
@deffn {函数} stringprep.in_table_c11_c12 (code)

确定 @emph{code} 是否属于 tableC.1  (空白字符，C.1.1 和 C.1.2 的并集)。
@end deffn

@geindex in_table_c21() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c21}@anchor{1767}
@deffn {函数} stringprep.in_table_c21 (code)

确定 @emph{code} 是否属于 tableC.2.1  (ASCII 控制字符)。
@end deffn

@geindex in_table_c22() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c22}@anchor{1768}
@deffn {函数} stringprep.in_table_c22 (code)

确定 @emph{code} 是否属于 tableC.2.2  (非 ASCII 控制字符)。
@end deffn

@geindex in_table_c21_c22() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c21_c22}@anchor{1769}
@deffn {函数} stringprep.in_table_c21_c22 (code)

确定 @emph{code} 是否属于 tableC.2  (控制字符，C.2.1 和 C.2.2 的并集)。
@end deffn

@geindex in_table_c3() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c3}@anchor{176a}
@deffn {函数} stringprep.in_table_c3 (code)

确定 @emph{code} 是否属于 tableC.3  (私有使用)。
@end deffn

@geindex in_table_c4() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c4}@anchor{176b}
@deffn {函数} stringprep.in_table_c4 (code)

确定 @emph{code} 是否属于 tableC.4  (非字符码位)。
@end deffn

@geindex in_table_c5() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c5}@anchor{176c}
@deffn {函数} stringprep.in_table_c5 (code)

确定 @emph{code} 是否属于 tableC.5  (替代码)。
@end deffn

@geindex in_table_c6() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c6}@anchor{176d}
@deffn {函数} stringprep.in_table_c6 (code)

确定 @emph{code} 是否属于 tableC.6  (不适用于纯文本)。
@end deffn

@geindex in_table_c7() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c7}@anchor{176e}
@deffn {函数} stringprep.in_table_c7 (code)

确定 @emph{code} 是否属于 tableC.7  (不适用于规范表示)。
@end deffn

@geindex in_table_c8() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c8}@anchor{176f}
@deffn {函数} stringprep.in_table_c8 (code)

确定 @emph{code} 是否属于 tableC.8  (改变显示属性或已弃用)。
@end deffn

@geindex in_table_c9() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_c9}@anchor{1770}
@deffn {函数} stringprep.in_table_c9 (code)

确定 @emph{code} 是否属于 tableC.9  (标记字符)。
@end deffn

@geindex in_table_d1() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_d1}@anchor{1771}
@deffn {函数} stringprep.in_table_d1 (code)

确定 @emph{code} 是否属于 tableD.1  (带有双向属性 "R" 或 "AL" 的字符)。
@end deffn

@geindex in_table_d2() (在 stringprep 模块中)
@anchor{library/stringprep stringprep in_table_d2}@anchor{1772}
@deffn {函数} stringprep.in_table_d2 (code)

确定 @emph{code} 是否属于 tableD.2  (带有双向属性 "L" 的字符)。
@end deffn

@node readline --- GNU readline 接口,rlcompleter --- GNU readline 的补全函数,stringprep --- 因特网字符串预备,文本处理服务
@anchor{library/readline doc}@anchor{1773}@anchor{library/readline module-readline}@anchor{de}@anchor{library/readline readline-gnu-readline-interface}@anchor{1774}
@subsection @code{readline} --- GNU readline 接口


@geindex readline (模块)


__________________________________________________________________


@ref{de,,readline} 模块定义了许多方便从 Python 解释器完成和读取/写入历史文件的函数。 此模块可以直接使用，或通过支持在交互提示符下完成 Python 标识符的 @ref{e1,,rlcompleter} 模块使用。 使用此模块进行的设置会同时影响解释器的交互提示符以及内置 @ref{c64,,input()} 函数提供的提示符。

Readline keybindings may be configured via an initialization file, typically
@code{.inputrc} in your home directory.  See Readline Init File@footnote{https://tiswww.cwru.edu/php/chet/readline/rluserman.html#SEC9}
in the GNU Readline manual for information about the format and
allowable constructs of that file, and the capabilities of the
Readline library in general.

@cartouche
@quotation 注解 
底层的 Readline 库 API 可能使用 @code{libedit} 库来实现而不是 GNU readline。 在 macOS 上 @ref{de,,readline} 模块会在运行时检测所使用的是哪个库。

@code{libedit} 所用的配置文件与 GNU readline 的不同。 如果你要在程序中载入配置字符串你可以在 @code{readline.__doc__} 中检测文本 "libedit" 来区分 GNU readline 和 libedit。

如果你是在 macOS 上使用 @emph{editline}/@code{libedit} readline 模拟，则位于你的主目录中的初始化文件名称为 @code{.editrc}。 例如，@code{~/.editrc} 中的以下内容将开启 @emph{vi} 按键绑定以及 TAB 补全:

@example
python:bind -v
python:bind ^I rl_complete
@end example
@end quotation
@end cartouche

@menu
* 初始化文件:: 
* 行缓冲区:: 
* 历史文件:: 
* 历史列表:: 
* 启动钩子:: 
* Completion:: 
* 示例:: 

@end menu

@node 初始化文件,行缓冲区,,readline --- GNU readline 接口
@anchor{library/readline init-file}@anchor{1775}
@subsubsection 初始化文件


下列函数与初始化文件和用户配置有关：

@geindex parse_and_bind() (在 readline 模块中)
@anchor{library/readline readline parse_and_bind}@anchor{1776}
@deffn {函数} readline.parse_and_bind (string)

执行在 @emph{string} 参数中提供的初始化行。 此函数会调用底层库中的 @code{rl_parse_and_bind()}。
@end deffn

@geindex read_init_file() (在 readline 模块中)
@anchor{library/readline readline read_init_file}@anchor{1777}
@deffn {函数} readline.read_init_file ([filename])

执行一个 readline 初始化文件。 默认文件名为最近所使用的文件名。 此函数会调用底层库中的 @code{rl_read_init_file()}。
@end deffn

@node 行缓冲区,历史文件,初始化文件,readline --- GNU readline 接口
@anchor{library/readline line-buffer}@anchor{1778}
@subsubsection 行缓冲区


下列函数会在行缓冲区上操作。

@geindex get_line_buffer() (在 readline 模块中)
@anchor{library/readline readline get_line_buffer}@anchor{1779}
@deffn {函数} readline.get_line_buffer ()

返回行缓冲区的当前内容 (底层库中的 @code{rl_line_buffer})。
@end deffn

@geindex insert_text() (在 readline 模块中)
@anchor{library/readline readline insert_text}@anchor{177a}
@deffn {函数} readline.insert_text (string)

将文本插入行缓冲区的当前游标位置。 该函数会调用底层库中的 @code{rl_insert_text()}，但会忽略其返回值。
@end deffn

@geindex redisplay() (在 readline 模块中)
@anchor{library/readline readline redisplay}@anchor{177b}
@deffn {函数} readline.redisplay ()

改变屏幕的显示以反映行缓冲区的当前内容。 该函数会调用底层库中的 @code{rl_redisplay()}。
@end deffn

@node 历史文件,历史列表,行缓冲区,readline --- GNU readline 接口
@anchor{library/readline history-file}@anchor{177c}
@subsubsection 历史文件


下列函数会在历史文件上操作：

@geindex read_history_file() (在 readline 模块中)
@anchor{library/readline readline read_history_file}@anchor{177d}
@deffn {函数} readline.read_history_file ([filename])

载入一个 readline 历史文件，并将其添加到历史列表。 默认文件名为 @code{~/.history}。 此函数会调用底层库中的 @code{read_history()}。
@end deffn

@geindex write_history_file() (在 readline 模块中)
@anchor{library/readline readline write_history_file}@anchor{177e}
@deffn {函数} readline.write_history_file ([filename])

将历史列表保存为 readline 历史文件，覆盖任何现有文件。 默认文件名为 @code{~/.history}。 此函数会调用底层库中的 @code{write_history()}。
@end deffn

@geindex append_history_file() (在 readline 模块中)
@anchor{library/readline readline append_history_file}@anchor{736}
@deffn {函数} readline.append_history_file (nelements[, filename])

将历史列表的最后 @emph{nelements} 项添加到历史文件。 默认文件名为 @code{~/.history}。 文件必须已存在。 此函数会调用底层库中的 @code{append_history()}。 此函数仅当 Python 编译包带有支持此功能的库版本时才会存在。


3.5 新版功能.

@end deffn

@geindex get_history_length() (在 readline 模块中)
@geindex set_history_length() (在 readline 模块中)
@anchor{library/readline readline get_history_length}@anchor{177f}
@deffn {函数} readline.get_history_length ()
@anchor{library/readline readline set_history_length}@anchor{1780}
@deffnx {函数} readline.set_history_length (length)

设置或返回需要保存到历史文件的行数。 @ref{177e,,write_history_file()} 函数会通过调用底层库中的 @code{history_truncate_file()} 以使用该值来截取历史文件。 负值意味着不限制历史文件的大小。
@end deffn

@node 历史列表,启动钩子,历史文件,readline --- GNU readline 接口
@anchor{library/readline history-list}@anchor{1781}
@subsubsection 历史列表


以下函数会在全局历史列表上操作：

@geindex clear_history() (在 readline 模块中)
@anchor{library/readline readline clear_history}@anchor{1782}
@deffn {函数} readline.clear_history ()

清除当前历史。 此函数会调用底层库的 @code{clear_history()}。 此 Python 函数仅当 Python 编译包带有支持此功能的库版本时才会存在。
@end deffn

@geindex get_current_history_length() (在 readline 模块中)
@anchor{library/readline readline get_current_history_length}@anchor{1783}
@deffn {函数} readline.get_current_history_length ()

返回历史列表的当前项数。 （此函数不同于 @ref{177f,,get_history_length()}，后者是返回将被写入历史文件的最大行数。）
@end deffn

@geindex get_history_item() (在 readline 模块中)
@anchor{library/readline readline get_history_item}@anchor{1784}
@deffn {函数} readline.get_history_item (index)

返回序号为 @emph{index} 的历史条目的当前内容。 条目序号从一开始。 此函数会调用底层库中的 @code{history_get()}。
@end deffn

@geindex remove_history_item() (在 readline 模块中)
@anchor{library/readline readline remove_history_item}@anchor{1785}
@deffn {函数} readline.remove_history_item (pos)

从历史列表中移除指定位置上的历史条目。 条目位置从零开始。 此函数会调用底层库中的 @code{remove_history()}。
@end deffn

@geindex replace_history_item() (在 readline 模块中)
@anchor{library/readline readline replace_history_item}@anchor{1786}
@deffn {函数} readline.replace_history_item (pos, line)

将指定位置上的历史条目替换为 @emph{line}。 条目位置从零开始。 此函数会调用底层库中的 @code{replace_history_entry()}。
@end deffn

@geindex add_history() (在 readline 模块中)
@anchor{library/readline readline add_history}@anchor{1787}
@deffn {函数} readline.add_history (line)

将 @emph{line} 添加到历史缓冲区，相当于是最近输入的一行。 此函数会调用底层库中的 @code{add_history()}。
@end deffn

@geindex set_auto_history() (在 readline 模块中)
@anchor{library/readline readline set_auto_history}@anchor{572}
@deffn {函数} readline.set_auto_history (enabled)

启用或禁用当通过 readline 读取输入时自动调用 @code{add_history()}。 @emph{enabled} 参数应为一个布尔值，当其为真值时启用自动历史，当其为假值时禁用自动历史。


3.6 新版功能.


@strong{CPython implementation detail:} Auto history is enabled by default, and changes to this do not persist
across multiple sessions.
@end deffn

@node 启动钩子,Completion,历史列表,readline --- GNU readline 接口
@anchor{library/readline startup-hooks}@anchor{1788}
@subsubsection 启动钩子


@geindex set_startup_hook() (在 readline 模块中)
@anchor{library/readline readline set_startup_hook}@anchor{1789}
@deffn {函数} readline.set_startup_hook ([function])

设置或移除底层库的 @code{rl_startup_hook} 回调所发起调用的函数。 如果指定了 @emph{function}，它将被用作新的钩子函数；如果省略或为 @code{None}，任何已安装的函数将被移除。 钩子函数将在 readline 打印第一个提示信息之前不带参数地被调用。
@end deffn

@geindex set_pre_input_hook() (在 readline 模块中)
@anchor{library/readline readline set_pre_input_hook}@anchor{178a}
@deffn {函数} readline.set_pre_input_hook ([function])

设置或移除底层库的 @code{rl_pre_input_hook} 回调所发起调用的函数。 如果指定了 @emph{function}，它将被用作新的钩子函数；如果省略或为 @code{None}，任何已安装的函数将被移除。 钩子函数将在打印第一个提示信息之后、readline 开始读取输入字符之前不带参数地被调用。 此函数仅当 Python 编译包带有支持此功能的库版本时才会存在。
@end deffn

@node Completion,示例,启动钩子,readline --- GNU readline 接口
@anchor{library/readline completion}@anchor{178b}
@subsubsection Completion


以下函数与自定义单词补全函数的实现有关。 这通常使用 Tab 键进行操作，能够提示并自动补全正在输入的单词。 默认情况下，Readline 设置为由 @ref{e1,,rlcompleter} 来补全交互模式解释器的 Python 标识符。 如果 @ref{de,,readline} 模块要配合自定义的补全函数来使用，则需要设置不同的单词分隔符。

@geindex set_completer() (在 readline 模块中)
@anchor{library/readline readline set_completer}@anchor{178c}
@deffn {函数} readline.set_completer ([function])

设置或移除补全函数。 如果指定了 @emph{function}，它将被用作新的补全函数；如果省略或为 @code{None}，任何已安装的补全函数将被移除。 补全函数的调用形式为 @code{function(text, state)}，其中 @emph{state} 为 @code{0}, @code{1}, @code{2}, ..., 直至其返回一个非字符串值。 它应当返回下一个以 @emph{text} 开头的候选补全内容。

已安装的补全函数将由传递给底层库中 @code{rl_completion_matches()} 的 @emph{entry_func} 回调函数来发起调用。 @emph{text} 字符串来自于底层库中 @code{rl_attempted_completion_function} 回调函数的第一个形参。
@end deffn

@geindex get_completer() (在 readline 模块中)
@anchor{library/readline readline get_completer}@anchor{178d}
@deffn {函数} readline.get_completer ()

获取补全函数，如果没有设置补全函数则返回 @code{None}。
@end deffn

@geindex get_completion_type() (在 readline 模块中)
@anchor{library/readline readline get_completion_type}@anchor{178e}
@deffn {函数} readline.get_completion_type ()

获取正在尝试的补全类型。 此函数会将底层库中的 @code{rl_completion_type} 变量作为一个整数返回。
@end deffn

@geindex get_begidx() (在 readline 模块中)
@geindex get_endidx() (在 readline 模块中)
@anchor{library/readline readline get_begidx}@anchor{178f}
@deffn {函数} readline.get_begidx ()
@anchor{library/readline readline get_endidx}@anchor{1790}
@deffnx {函数} readline.get_endidx ()

获取补全域的开始和结束序号。 这些序号就是传给底层库中 @code{rl_attempted_completion_function} 回调函数的 @emph{start} 和 @emph{end} 参数。
@end deffn

@geindex set_completer_delims() (在 readline 模块中)
@geindex get_completer_delims() (在 readline 模块中)
@anchor{library/readline readline set_completer_delims}@anchor{1791}
@deffn {函数} readline.set_completer_delims (string)
@anchor{library/readline readline get_completer_delims}@anchor{1792}
@deffnx {函数} readline.get_completer_delims ()

设置或获取补全的单词分隔符。 此分隔符确定了要考虑补全的单词的开始和结束位置（补全域）。 这些函数会访问底层库的 @code{rl_completer_word_break_characters} 变量。
@end deffn

@geindex set_completion_display_matches_hook() (在 readline 模块中)
@anchor{library/readline readline set_completion_display_matches_hook}@anchor{1793}
@deffn {函数} readline.set_completion_display_matches_hook ([function])

设置或移除补全显示函数。 如果指定了 @emph{function}，它将被用作新的补全显示函数；如果省略或为 @code{None}，任何已安装的补全显示函数将被移除。 此函数会设置或清除底层库的 @code{rl_completion_display_matches_hook} 回调函数。 补全显示函数会在每次需要显示匹配项时以 @code{function(substitution, [matches], longest_match_length)} 的形式被调用。
@end deffn

@node 示例,,Completion,readline --- GNU readline 接口
@anchor{library/readline example}@anchor{1794}@anchor{library/readline readline-example}@anchor{1795}
@subsubsection 示例


以下示例演示了如何使用 @ref{de,,readline} 模块的历史读取或写入函数来自动加载和保存用户主目录下名为 @code{.python_history} 的历史文件。 以下代码通常应当在交互会话期间从用户的 
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP} 文件自动执行。

@example
import atexit
import os
import readline

histfile = os.path.join(os.path.expanduser("~"), ".python_history")
try:
    readline.read_history_file(histfile)
    # default history len is -1 (infinite), which may grow unruly
    readline.set_history_length(1000)
except FileNotFoundError:
    pass

atexit.register(readline.write_history_file, histfile)
@end example

此代码实际上会在 Python 运行于 @ref{8dd,,交互模式} 时自动运行 (参见 @ref{8e0,,Readline configuration})。

以下示例实现了同样的目标，但是通过只添加新历史的方式来支持并发的交互会话。

@example
import atexit
import os
import readline
histfile = os.path.join(os.path.expanduser("~"), ".python_history")

try:
    readline.read_history_file(histfile)
    h_len = readline.get_current_history_length()
except FileNotFoundError:
    open(histfile, 'wb').close()
    h_len = 0

def save(prev_h_len, histfile):
    new_h_len = readline.get_current_history_length()
    readline.set_history_length(1000)
    readline.append_history_file(new_h_len - prev_h_len, histfile)
atexit.register(save, h_len, histfile)
@end example

以下示例扩展了 @ref{1796,,code.InteractiveConsole} 类以支持历史保存/恢复。

@example
import atexit
import code
import os
import readline

class HistoryConsole(code.InteractiveConsole):
    def __init__(self, locals=None, filename="<console>",
                 histfile=os.path.expanduser("~/.console-history")):
        code.InteractiveConsole.__init__(self, locals, filename)
        self.init_history(histfile)

    def init_history(self, histfile):
        readline.parse_and_bind("tab: complete")
        if hasattr(readline, "read_history_file"):
            try:
                readline.read_history_file(histfile)
            except FileNotFoundError:
                pass
            atexit.register(self.save_history, histfile)

    def save_history(self, histfile):
        readline.set_history_length(1000)
        readline.write_history_file(histfile)
@end example

@node rlcompleter --- GNU readline 的补全函数,,readline --- GNU readline 接口,文本处理服务
@anchor{library/rlcompleter doc}@anchor{1797}@anchor{library/rlcompleter module-rlcompleter}@anchor{e1}@anchor{library/rlcompleter rlcompleter-completion-function-for-gnu-readline}@anchor{1798}
@subsection @code{rlcompleter} --- GNU readline 的补全函数


@geindex rlcompleter (模块)

@strong{源代码:} Lib/rlcompleter.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/rlcompleter.py}


__________________________________________________________________


@code{rlcompeleter} 通过补全有效的 Python 标识符和关键字定义了一个适用于 @ref{de,,readline} 模块的补全函数。

当此模块在具有可用的 @ref{de,,readline} 模块的 Unix 平台被导入, 一个 @code{Completer} 实例将被自动创建并且它的 @code{complete()} 方法将设置为 @ref{de,,readline} 的补全器.

示例:

@example
>>> import rlcompleter
>>> import readline
>>> readline.parse_and_bind("tab: complete")
>>> readline. <TAB PRESSED>
readline.__doc__          readline.get_line_buffer(  readline.read_init_file(
readline.__file__         readline.insert_text(      readline.set_completer(
readline.__name__         readline.parse_and_bind(
>>> readline.
@end example

@ref{e1,,rlcompleter} 模块是为了使用 Python 的 @ref{8dd,,交互模式} 而设计的。 除非 Python 是通过 @ref{b1d,,-S} 选项运行, 这个模块总是自动地被导入且配置 (参见 @ref{8e0,,Readline configuration})。

在没有 @ref{de,,readline} 的平台, 此模块定义的 @code{Completer} 类仍然可以用于自定义行为.

@menu
* Completer 对象:: 

@end menu

@node Completer 对象,,,rlcompleter --- GNU readline 的补全函数
@anchor{library/rlcompleter completer-objects}@anchor{1799}@anchor{library/rlcompleter id1}@anchor{179a}
@subsubsection Completer 对象


Completer 对象具有以下方法：

@geindex complete() (rlcompleter.Completer 方法)
@anchor{library/rlcompleter rlcompleter Completer complete}@anchor{179b}
@deffn {方法} Completer.complete (text, state)

为 @emph{text} 返回第 @emph{state} 项补全。

如果指定的 @emph{text} 不包含句点字符 (@code{'.'})，它将根据当前 @ref{1,,__main__}, @ref{13,,builtins} 和保留关键字（定义于 @ref{a6,,keyword} 模块）所定义的名称进行补全。

如果为带有句点的名称执行调用，它将尝试尽量求值直到最后一部分为止而不产生附带影响（函数不会被求值，但它可以生成对 @ref{313,,__getattr__()} 的调用），并通过 @ref{d2c,,dir()} 函数来匹配剩余部分。 在对表达式求值期间引发的任何异常都会被捕获、静默处理并返回 @ref{157,,None}。
@end deffn

@node 二进制数据服务,数据类型,文本处理服务,Python 标准库
@anchor{library/binary doc}@anchor{179c}@anchor{library/binary binary-data-services}@anchor{179d}@anchor{library/binary binaryservices}@anchor{16b4}
@section 二进制数据服务


本章介绍的模块提供了一些操作二进制数据的基本服务操作。 有关二进制数据的其他操作，特别是与文件格式和网络协议有关的操作，将在相关章节中介绍。

下面描述的一些库 @ref{15da,,文本处理服务} 也可以使用 ASCII 兼容的二进制格式（例如 @ref{dd,,re} ）或所有二进制数据（例如 @ref{37,,difflib} ）。

另外，请参阅 Python 的内置二进制数据类型的文档 @ref{1580,,二进制序列类型 --- bytes@comma{} bytearray@comma{} memoryview} 。

@menu
* struct: struct --- 将字节串解读为打包的二进制数据. 将字节串解读为打包的二进制数据
* codecs: codecs --- 编解码器注册和相关基类. 编解码器注册和相关基类

@end menu

@node struct --- 将字节串解读为打包的二进制数据,codecs --- 编解码器注册和相关基类,,二进制数据服务
@anchor{library/struct doc}@anchor{179e}@anchor{library/struct module-struct}@anchor{f8}@anchor{library/struct struct-interpret-bytes-as-packed-binary-data}@anchor{179f}
@subsection @code{struct} --- 将字节串解读为打包的二进制数据


@geindex struct (模块)

@strong{源代码：} Lib/struct.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/struct.py}

@geindex C; structures
@geindex packing; binary; data


__________________________________________________________________


此模块可以执行 Python 值和以 Python @ref{32a,,bytes} 对象表示的 C 结构之间的转换。 这可以被用来处理存储在文件中或是从网络连接等其他来源获取的二进制数据。 它使用 @ref{17a0,,格式字符串} 作为 C 结构布局的精简描述以及与 Python 值的双向转换。

@cartouche
@quotation 注解 
默认情况下，打包给定 C 结构的结果会包含填充字节以使得所涉及的 C 类型保持正确的对齐；类似地，对齐在解包时也会被纳入考虑。 选择此种行为的目的是使得被打包结构的字节能与相应 C 结构在内存中的布局完全一致。 要处理平台独立的数据格式或省略隐式的填充字节，请使用 @code{standard} 大小和对齐而不是 @code{native} 大小和对齐：详情参见 @ref{17a1,,字节顺序，大小和对齐方式}。
@end quotation
@end cartouche

某些 @ref{f8,,struct} 的函数（以及 @ref{17a2,,Struct} 的方法）接受一个 @emph{buffer} 参数。 这将指向实现了 @ref{15d6,,缓冲协议} 并提供只读或是可读写缓冲的对象。 用于此目的的最常见类型为 @ref{32a,,bytes} 和 @ref{32b,,bytearray}，但许多其他可被视为字节数组的类型也实现了缓冲协议，因此它们无需额外从 @ref{32a,,bytes} 对象复制即可被读取或填充。

@menu
* 函数和异常:: 
* 格式字符串:: 
* 类: 类<2>. 

@end menu

@node 函数和异常,格式字符串,,struct --- 将字节串解读为打包的二进制数据
@anchor{library/struct functions-and-exceptions}@anchor{17a3}
@subsubsection 函数和异常


此模块定义了下列异常和函数：

@geindex error
@anchor{library/struct struct error}@anchor{cad}
@deffn {例外} struct.error

会在多种场合下被引发的异常；其参数为一个描述错误信息的字符串。
@end deffn

@geindex pack() (在 struct 模块中)
@anchor{library/struct struct pack}@anchor{c04}
@deffn {函数} struct.pack (format, v1, v2, ...)

返回一个 bytes 对象，其中包含根据格式字符串 @emph{format} 打包的值 @emph{v1}, @emph{v2}, ... 参数个数必须与格式字符串所要求的值完全匹配。
@end deffn

@geindex pack_into() (在 struct 模块中)
@anchor{library/struct struct pack_into}@anchor{17a4}
@deffn {函数} struct.pack_into (format, buffer, offset, v1, v2, ...)

根据格式字符串 @emph{format} 打包 @emph{v1}, @emph{v2}, ... 等值并将打包的字节串写入可写缓冲区 @emph{buffer} 从 @emph{offset} 开始的位置。 请注意 @emph{offset} 是必需的参数。
@end deffn

@geindex unpack() (在 struct 模块中)
@anchor{library/struct struct unpack}@anchor{1297}
@deffn {函数} struct.unpack (format, buffer)

根据格式字符串 @emph{format} 从缓冲区 @emph{buffer} 解包（假定是由 @code{pack(format, ...)} 打包）。 结果为一个元组，即使其只包含一个条目。 缓冲区的字节大小必须匹配格式所要求的大小，如 @ref{17a5,,calcsize()} 所示。
@end deffn

@geindex unpack_from() (在 struct 模块中)
@anchor{library/struct struct unpack_from}@anchor{17a6}
@deffn {函数} struct.unpack_from (format, buffer, offset=0)

对 @emph{buffer} 从位置 @emph{offset} 开始根据格式字符串 @emph{format} 进行解包。 结果为一个元组，即使其中只包含一个条目。 缓冲区的字节大小从位置 @emph{offset} 开始必须至少为 @ref{17a5,,calcsize()} 显示的格式所要求的大小。
@end deffn

@geindex iter_unpack() (在 struct 模块中)
@anchor{library/struct struct iter_unpack}@anchor{8d2}
@deffn {函数} struct.iter_unpack (format, buffer)

根据格式字符串 @emph{format} 以迭代方式从缓冲区 @emph{buffer} 解包。 此函数返回一个迭代器，它将从缓冲区读取相同大小的块直至其内容全部耗尽。 缓冲区的字节大小必须整数倍于格式所要求的大小，如 @ref{17a5,,calcsize()} 所示。

每次迭代将产生一个如格式字符串所指定的元组。


3.4 新版功能.

@end deffn

@geindex calcsize() (在 struct 模块中)
@anchor{library/struct struct calcsize}@anchor{17a5}
@deffn {函数} struct.calcsize (format)

返回与格式字符串 @emph{format} 相对应的结构的大小（亦即 @code{pack(format, ...)} 所产生的字节串对象的大小）。
@end deffn

@node 格式字符串,类<2>,函数和异常,struct --- 将字节串解读为打包的二进制数据
@anchor{library/struct format-strings}@anchor{17a7}@anchor{library/struct struct-format-strings}@anchor{17a0}
@subsubsection 格式字符串


格式字符串是用来在打包和解包数据时指定预期布局的机制。 它们使用指定被打包/解包数据类型的 @ref{17a8,,格式字符} 进行构建。 此外，还有一些特殊字符用来控制 @ref{17a1,,字节顺序，大小和对齐方式}。

@menu
* 字节顺序，大小和对齐方式:: 
* 格式字符:: 
* 例子: 例子<2>. 

@end menu

@node 字节顺序，大小和对齐方式,格式字符,,格式字符串
@anchor{library/struct byte-order-size-and-alignment}@anchor{17a9}@anchor{library/struct struct-alignment}@anchor{17a1}
@subsubsection 字节顺序，大小和对齐方式


默认情况下，C类型以机器的本机格式和字节顺序表示，并在必要时通过跳过填充字节进行正确对齐（根据C编译器使用的规则）。

@geindex @@ (at); in struct format strings
@geindex = (equals); in struct format strings
@geindex < (less); in struct format strings
@geindex > (greater); in struct format strings
@geindex ! (exclamation); in struct format strings

或者，根据下表，格式字符串的第一个字符可用于指示打包数据的字节顺序，大小和对齐方式：


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx} {xxxxxxxxxxxxx} 
@headitem

字符

@tab

字节顺序

@tab

大小

@tab

对齐方式

@item

@code{@@}

@tab

按原字节

@tab

按原字节

@tab

按原字节

@item

@code{=}

@tab

按原字节

@tab

标准

@tab

无

@item

@code{<}

@tab

小端

@tab

标准

@tab

无

@item

@code{>}

@tab

大端

@tab

标准

@tab

无

@item

@code{!}

@tab

网络（=大端）

@tab

标准

@tab

无

@end multitable


如果第一个字符不是其中之一，则假定为 @code{'@@'} 。

本机字节顺序可能为大端或是小端，取决于主机系统的不同。 例如， Intel x86 和 AMD64 (x86-64) 是小端的；Motorola 68000 和 PowerPC G5 是大端的；ARM 和 Intel Itanium 具有可切换的字节顺序（双端）。 请使用 @code{sys.byteorder} 来检查你的系统字节顺序。

本机大小和对齐方式是使用 C 编译器的 @code{sizeof} 表达式来确定的。 这总是会与本机字节顺序相绑定。

标准大小仅取决于格式字符；请参阅 @ref{17a8,,格式字符} 部分中的表格。

请注意 @code{'@@'} 和 @code{'='} 之间的区别：两个都使用本机字节顺序，但后者的大小和对齐方式是标准化的。

格式 @code{'!'} 适合给那些宣称他们记不得网络字节顺序是大端还是小端的可怜人使用。

没有什么方式能指定非本机字节顺序（强制字节对调）；请正确选择使用 @code{'<'} 或 @code{'>'}。

注释:


@enumerate 

@item 
填充只会在连续结构成员之间自动添加。 填充不会添加到已编码结构的开头和末尾。

@item 
当使用非本机大小和对齐方式即 '<', '>', '=', and '!' 时不会添加任何填充。

@item 
要将结构的末尾对齐到符合特定类型的对齐要求，请以该类型代码加重复计数的零作为格式结束。 参见 @ref{17aa,,例子}。
@end enumerate

@node 格式字符,例子<2>,字节顺序，大小和对齐方式,格式字符串
@anchor{library/struct format-characters}@anchor{17a8}@anchor{library/struct id1}@anchor{17ab}
@subsubsection 格式字符


格式字符具有以下含义；C 和 Python 值之间的按其指定类型的转换应当是相当明显的。 ‘标准大小’列是指当使用标准大小时以字节表示的已打包值大小；也就是当格式字符串以 @code{'<'}, @code{'>'}, @code{'!'} 或 @code{'='} 之一开头的情况。 当使用本机大小时，已打包值的大小取决于具体的平台。


@multitable {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} 
@headitem

格式

@tab

C 类型

@tab

Python 类型

@tab

标准大小

@tab

注释

@item

@code{x}

@tab

填充字节

@tab

无

@tab

@tab

@item

@code{c}

@tab

@code{char}

@tab

长度为 1 的字节串

@tab

1

@tab

@item

@code{b}

@tab

@code{signed char}

@tab

整数

@tab

1

@tab

(1), (2)

@item

@code{B}

@tab

@code{unsigned char}

@tab

整数

@tab

1

@tab

(2)

@item

@code{?}

@tab

@code{_Bool}

@tab

bool

@tab

1

@tab

(1)

@item

@code{h}

@tab

@code{short}

@tab

整数

@tab

2

@tab

(2)

@item

@code{H}

@tab

@code{unsigned short}

@tab

整数

@tab

2

@tab

(2)

@item

@code{i}

@tab

@code{int}

@tab

整数

@tab

4

@tab

(2)

@item

@code{I}

@tab

@code{unsigned int}

@tab

整数

@tab

4

@tab

(2)

@item

@code{l}

@tab

@code{long}

@tab

整数

@tab

4

@tab

(2)

@item

@code{L}

@tab

@code{unsigned long}

@tab

整数

@tab

4

@tab

(2)

@item

@code{q}

@tab

@code{long long}

@tab

整数

@tab

8

@tab

(2)

@item

@code{Q}

@tab

@code{unsigned long
long}

@tab

整数

@tab

8

@tab

(2)

@item

@code{n}

@tab

@code{ssize_t}

@tab

整数

@tab

@tab

(3)

@item

@code{N}

@tab

@code{size_t}

@tab

整数

@tab

@tab

(3)

@item

@code{e}

@tab

(6)

@tab

float

@tab

2

@tab

(4)

@item

@code{f}

@tab

@code{float}

@tab

float

@tab

4

@tab

(4)

@item

@code{d}

@tab

@code{double}

@tab

float

@tab

8

@tab

(4)

@item

@code{s}

@tab

@code{char[]}

@tab

字节串

@tab

@tab

@item

@code{p}

@tab

@code{char[]}

@tab

字节串

@tab

@tab

@item

@code{P}

@tab

@code{void *}

@tab

整数

@tab

@tab

(5)

@end multitable



在 3.3 版更改: 增加了对 @code{'n'} 和 @code{'N'} 格式的支持



在 3.6 版更改: 添加了对 @code{'e'} 格式的支持。


注释:


@enumerate 

@item 
@geindex ? (question mark); in struct format strings

@code{'?'} 转换码对应于 C99 定义的 @code{_Bool} 类型。 如果此类型不可用，则使用 @code{char} 来模拟。 在标准模式下，它总是以一个字节表示。

@item 
当尝试使用任何整数转换码打包一个非整数时，如果该非整数具有 @ref{18a,,__index__()} 方法，则会在打包之前调用该方法将参数转换为一个整数。


在 3.2 版更改: 为非整数使用 @ref{18a,,__index__()} 方法是 3.2 版的新增特性。


@item 
@code{'n'} 和 @code{'N'} 转换码仅对本机大小可用（选择为默认或使用 @code{'@@'} 字节顺序字符）。 对于标准大小，你可以使用适合你的应用的任何其他整数格式。

@item 
对于 @code{'f'}, @code{'d'} 和 @code{'e'} 转换码，打包表示形式将使用 IEEE 754 binary32, binary64 或 binary16 格式 (分别对应于 @code{'f'}, @code{'d'} 或 @code{'e'})，无论平台使用何种浮点格式。

@item 
@code{'P'} 格式字符仅对本机字节顺序可用（选择为默认或使用 @code{'@@'} 字节顺序字符）。 字节顺序字符 @code{'='} 选择使用基于主机系统的小端或大端排序。 struct 模块不会将其解读为本机排序，因此 @code{'P'} 格式将不可用。

@item 
IEEE 754 binary16 "半精度" 类型是在 IEEE 754 标准@footnote{https://en.wikipedia.org/wiki/IEEE_floating_point#IEEE_754-2008} 的 2008 修订版中引入的。 它包含一个符号位，5 个指数位和 11 个精度位（明确存储 10 位），可以完全精确地表示大致范围在 @code{6.1e-05} 和 @code{6.5e+04} 之间的数字。 此类型并不被 C 编译器广泛支持：在一台典型的机器上，可以使用 unsigned short 进行存储，但不会被用于数学运算。 请参阅维基百科页面 half-precision floating-point format@footnote{https://en.wikipedia.org/wiki/Half-precision_floating-point_format} 了解详情。
@end enumerate

格式字符之前可以带有整数重复计数。 例如，格式字符串 @code{'4h'} 的含义与 @code{'hhhh'} 完全相同。

格式之间的空白字符会被忽略；但是计数及其格式字符中不可有空白字符。

对于 @code{'s'} 格式字符，计数会被解析为字节的长度，而不是像其他格式字符那样的重复计数；例如，@code{'10s'} 表示一个 10 字节的字节串，而 @code{'10c'} 表示 10 个字符。 如果未给出计数，则默认值为 1。 对于打包操作，字节串会被适当地截断或填充空字节以符合要求。 对于解包操作，结果字节对象总是恰好具有指定数量的字节。 作为特殊情况，@code{'0s'} 表示一个空字符串（而 @code{'0c'} 表示 0 个字符）。

当使用某一种整数格式 (@code{'b'}, @code{'B'}, @code{'h'}, @code{'H'}, @code{'i'}, @code{'I'}, @code{'l'}, @code{'L'}, @code{'q'}, @code{'Q'}) 打包值 @code{x} 时，如果 @code{x} 在该格式的有效范围之外则将引发 @ref{cad,,struct.error}。


在 3.1 版更改: 在 3.0 中，某些包装了超范围值的整数格式会引发 @ref{278,,DeprecationWarning} 而不是 @ref{cad,,struct.error}。


@code{'p'} 格式字符用于编码“Pascal 字符串”，即存储在由计数指定的 @emph{固定长度字节} 中的可变长度短字符串。 所存储的第一个字节为字符串长度或 255 中的较小值。 之后是字符串对应的字节。 如果传入 @ref{c04,,pack()} 的字符串过长（超过计数值减 1），则只有字符串前 @code{count-1} 个字节会被存储。 如果字符串短于 @code{count-1}，则会填充空字节以使得恰好使用了 count 个字节。 请注意对于 @ref{1297,,unpack()}，@code{'p'} 格式字符会消耗 @code{count} 个字节，但返回的字符串永远不会包含超过 255 个字节。

@geindex ? (question mark); in struct format strings

对于 @code{'?'} 格式字符，返回值为 @ref{494,,True} 或 @ref{380,,False}。 在打包时将会使用参数对象的逻辑值。 以本机或标准 bool 类型表示的 0 或 1 将被打包，任何非零值在解包时将为 @code{True}。

@node 例子<2>,,格式字符,格式字符串
@anchor{library/struct examples}@anchor{17ac}@anchor{library/struct struct-examples}@anchor{17aa}
@subsubsection 例子


@cartouche
@quotation 注解 
所有示例都假定使用一台大端机器的本机字节顺序、大小和对齐方式。
@end quotation
@end cartouche

打包/解包三个整数的基础示例:

@example
>>> from struct import *
>>> pack('hhl', 1, 2, 3)
b'\x00\x01\x00\x02\x00\x00\x00\x03'
>>> unpack('hhl', b'\x00\x01\x00\x02\x00\x00\x00\x03')
(1, 2, 3)
>>> calcsize('hhl')
8
@end example

解包的字段可通过将它们赋值给变量或将结果包装为一个具名元组来命名:

@example
>>> record = b'raymond   \x32\x12\x08\x01\x08'
>>> name, serialnum, school, gradelevel = unpack('<10sHHb', record)

>>> from collections import namedtuple
>>> Student = namedtuple('Student', 'name serialnum school gradelevel')
>>> Student._make(unpack('<10sHHb', record))
Student(name=b'raymond   ', serialnum=4658, school=264, gradelevel=8)
@end example

格式字符的顺序可能对大小产生影响，因为满足对齐要求所需的填充是不同的:

@example
>>> pack('ci', b'*', 0x12131415)
b'*\x00\x00\x00\x12\x13\x14\x15'
>>> pack('ic', 0x12131415, b'*')
b'\x12\x13\x14\x15*'
>>> calcsize('ci')
8
>>> calcsize('ic')
5
@end example

以下格式 @code{'llh0l'} 指定在末尾有两个填充字节，假定 long 类型按 4 个字节的边界对齐:

@example
>>> pack('llh0l', 1, 2, 3)
b'\x00\x00\x00\x01\x00\x00\x00\x02\x00\x03\x00\x00'
@end example

这仅当本机大小和对齐方式生效时才会起作用；标准大小和对齐方式并不会强制进行任何对齐。


@subsubheading 参见



@table @asis

@item 模块 @ref{7,,array}

被打包为二进制存储的同质数据。

@item 模块 @ref{132,,xdrlib}

打包和解包 XDR 数据。
@end table


@node 类<2>,,格式字符串,struct --- 将字节串解读为打包的二进制数据
@anchor{library/struct classes}@anchor{17ad}@anchor{library/struct struct-objects}@anchor{17ae}
@subsubsection 类


@ref{f8,,struct} 模块还定义了以下类型：

@geindex Struct (struct 中的类)
@anchor{library/struct struct Struct}@anchor{17a2}
@deffn {类} struct.Struct (format)

返回一个新的 Struct 对象，它会根据格式字符串 @emph{format} 来写入和读取二进制数据。 一次性地创建 Struct 对象并调用其方法相比使用同样的格式调用 @ref{f8,,struct} 函数更为高效，因为这样格式字符串只需被编译一次。

@cartouche
@quotation 注解 
传递给 @ref{17a2,,Struct} 和模块层级函数的已编译版最新格式字符串会被缓存，因此只使用少量格式字符串的程序无需担心重用单独的 @ref{17a2,,Struct} 实例。
@end quotation
@end cartouche

已编译的 Struct 对象支持以下方法和属性：

@geindex pack() (struct.Struct 方法)
@anchor{library/struct struct Struct pack}@anchor{17af}
@deffn {方法} pack (v1, v2, ...)

等价于 @ref{c04,,pack()} 函数，使用了已编译的格式。 (@code{len(result)} 将等于 @ref{17b0,,size}。)
@end deffn

@geindex pack_into() (struct.Struct 方法)
@anchor{library/struct struct Struct pack_into}@anchor{17b1}
@deffn {方法} pack_into (buffer, offset, v1, v2, ...)

等价于 @ref{17a4,,pack_into()} 函数，使用了已编译的格式。
@end deffn

@geindex unpack() (struct.Struct 方法)
@anchor{library/struct struct Struct unpack}@anchor{17b2}
@deffn {方法} unpack (buffer)

等价于 @ref{1297,,unpack()} 函数，使用了已编译的格式。 缓冲区的字节大小必须等于 @ref{17b0,,size}。
@end deffn

@geindex unpack_from() (struct.Struct 方法)
@anchor{library/struct struct Struct unpack_from}@anchor{17b3}
@deffn {方法} unpack_from (buffer, offset=0)

等价于 @ref{17a6,,unpack_from()} 函数，使用了已编译的格式。 缓冲区的字节大小从位置 @emph{offset} 开始必须至少为 @ref{17b0,,size}。
@end deffn

@geindex iter_unpack() (struct.Struct 方法)
@anchor{library/struct struct Struct iter_unpack}@anchor{8d3}
@deffn {方法} iter_unpack (buffer)

等价于 @ref{8d2,,iter_unpack()} 函数，使用了已编译的格式。 缓冲区的大小必须为 @ref{17b0,,size} 的整数倍。


3.4 新版功能.

@end deffn

@geindex format (struct.Struct 属性)
@anchor{library/struct struct Struct format}@anchor{48c}
@deffn {属性} format

用于构造此 Struct 对象的格式字符串。


在 3.7 版更改: 格式字符串类型现在是 @ref{329,,str} 而不再是 @ref{32a,,bytes}。

@end deffn

@geindex size (struct.Struct 属性)
@anchor{library/struct struct Struct size}@anchor{17b0}
@deffn {属性} size

计算出对应于 @ref{4d5,,format} 的结构大小（亦即 @ref{c04,,pack()} 方法所产生的字节串对象的大小）。
@end deffn
@end deffn

@node codecs --- 编解码器注册和相关基类,,struct --- 将字节串解读为打包的二进制数据,二进制数据服务
@anchor{library/codecs doc}@anchor{17b4}@anchor{library/codecs codecs-codec-registry-and-base-classes}@anchor{17b5}@anchor{library/codecs ieee-754-standard}@anchor{17b6}@anchor{library/codecs module-codecs}@anchor{1c}
@subsection @code{codecs} --- 编解码器注册和相关基类


@geindex codecs (模块)

@strong{源代码：} Lib/codecs.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/codecs.py}

@geindex Unicode
@geindex Codecs
@geindex Codecs; encode
@geindex Codecs; decode
@geindex streams
@geindex stackable; streams


__________________________________________________________________


这个模块定义了标准 Python 编解码器（编码器和解码器）的基类，并提供接口用来访问内部的 Python 编解码器注册表，该注册表负责管理编解码器和错误处理的查找过程。 大多数标准编解码器都属于 @ref{1593,,文本编码}，它们可将文本编码为字节串，但也提供了一些编解码器可将文本编码为文本，以及字节串编码为字节串。 自定义编解码器可以在任意类型间进行编码和解码，但某些模块特性仅适用于 @ref{1593,,文本编码} 或将数据编码为 @code{字节串} 的编解码器。

该模块定义了以下用于使用任何编解码器进行编码和解码的函数:

@geindex encode() (在 codecs 模块中)
@anchor{library/codecs codecs encode}@anchor{7fc}
@deffn {函数} codecs.encode (obj, encoding='utf-8', errors='strict')

使用为 @emph{encoding} 注册的编解码器对 @emph{obj} 进行编码。

可以给定 @emph{Errors} 以设置所需要的错误处理方案。 默认的错误处理方案 @code{'strict'} 表示编码错误将引发 @ref{1fb,,ValueError} (或更特定编解码器相关的子类，例如 @ref{1fc,,UnicodeEncodeError})。 请参阅 @ref{17b7,,编解码器基类} 了解有关编解码器错误处理的更多信息。
@end deffn

@geindex decode() (在 codecs 模块中)
@anchor{library/codecs codecs decode}@anchor{7fd}
@deffn {函数} codecs.decode (obj, encoding='utf-8', errors='strict')

使用为 @emph{encoding} 注册的编解码器对 @emph{obj} 进行解码。

可以给定 @emph{Errors} 以设置所需要的错误处理方案。 默认的错误处理方案 @code{'strict'} 表示编码错误将引发 @ref{1fb,,ValueError} (或更特定编解码器相关的子类，例如 @ref{1fd,,UnicodeDecodeError})。 请参阅 @ref{17b7,,编解码器基类} 了解有关编解码器错误处理的更多信息。
@end deffn

每种编解码器的完整细节也可以直接查找获取：

@geindex lookup() (在 codecs 模块中)
@anchor{library/codecs codecs lookup}@anchor{169a}
@deffn {函数} codecs.lookup (encoding)

在 Python 编解码器注册表中查找编解码器信息，并返回一个 @ref{17b8,,CodecInfo} 对象，其定义见下文。

首先将会在注册表缓存中查找编码，如果未找到，则会扫描注册的搜索函数列表。 如果没有找到 @ref{17b8,,CodecInfo} 对象，则将引发 @ref{15f6,,LookupError}。 否则，@ref{17b8,,CodecInfo} 对象将被存入缓存并返回给调用者。
@end deffn

@geindex CodecInfo (codecs 中的类)
@anchor{library/codecs codecs CodecInfo}@anchor{17b8}
@deffn {类} codecs.CodecInfo (encode, decode, streamreader=None, streamwriter=None, incrementalencoder=None, incrementaldecoder=None, name=None)

查找编解码器注册表所得到的编解码器细节信息。 构造器参数将保存为同名的属性：

@geindex name (codecs.CodecInfo 属性)
@anchor{library/codecs codecs CodecInfo name}@anchor{17b9}
@deffn {属性} name

编码名称
@end deffn

@geindex encode (codecs.CodecInfo 属性)
@geindex decode (codecs.CodecInfo 属性)
@anchor{library/codecs codecs CodecInfo encode}@anchor{17ba}
@deffn {属性} encode
@anchor{library/codecs codecs CodecInfo decode}@anchor{17bb}
@deffnx {属性} decode

无状态的编码和解码函数。 它们必须是具有与 Codec 的 @ref{17bc,,encode()} 和 @ref{17bd,,decode()} 方法相同接口的函数或方法 (参见 @ref{17be,,Codec 接口})。 这些函数或方法应当工作于无状态的模式。
@end deffn

@geindex incrementalencoder (codecs.CodecInfo 属性)
@geindex incrementaldecoder (codecs.CodecInfo 属性)
@anchor{library/codecs codecs CodecInfo incrementalencoder}@anchor{17bf}
@deffn {属性} incrementalencoder
@anchor{library/codecs codecs CodecInfo incrementaldecoder}@anchor{17c0}
@deffnx {属性} incrementaldecoder

增量式的编码器和解码器类或工厂函数。 这些函数必须分别提供由基类 @ref{17c1,,IncrementalEncoder} 和 @ref{17c2,,IncrementalDecoder} 所定义的接口。 增量式编解码器可以保持状态。
@end deffn

@geindex streamwriter (codecs.CodecInfo 属性)
@geindex streamreader (codecs.CodecInfo 属性)
@anchor{library/codecs codecs CodecInfo streamwriter}@anchor{17c3}
@deffn {属性} streamwriter
@anchor{library/codecs codecs CodecInfo streamreader}@anchor{17c4}
@deffnx {属性} streamreader

流式写入器和读取器类或工厂函数。 这些函数必须分别提供由基类 @ref{17c5,,StreamWriter} 和 @ref{17c6,,StreamReader} 所定义的接口。 流式编解码器可以保持状态。
@end deffn
@end deffn

为了简化对各种编解码器组件的访问，本模块提供了以下附加函数，它们使用 @ref{169a,,lookup()} 来执行编解码器查找：

@geindex getencoder() (在 codecs 模块中)
@anchor{library/codecs codecs getencoder}@anchor{17c7}
@deffn {函数} codecs.getencoder (encoding)

查找给定编码的编解码器并返回其编码器函数。

在编码无法找到时将引发 @ref{15f6,,LookupError}。
@end deffn

@geindex getdecoder() (在 codecs 模块中)
@anchor{library/codecs codecs getdecoder}@anchor{17c8}
@deffn {函数} codecs.getdecoder (encoding)

查找给定编码的编解码器并返回其解码器函数。

在编码无法找到时将引发 @ref{15f6,,LookupError}。
@end deffn

@geindex getincrementalencoder() (在 codecs 模块中)
@anchor{library/codecs codecs getincrementalencoder}@anchor{17c9}
@deffn {函数} codecs.getincrementalencoder (encoding)

查找给定编码的编解码器并返回其增量式编码器类或工厂函数。

在编码无法找到或编解码器不支持增量式编码器时将引发 @ref{15f6,,LookupError}。
@end deffn

@geindex getincrementaldecoder() (在 codecs 模块中)
@anchor{library/codecs codecs getincrementaldecoder}@anchor{17ca}
@deffn {函数} codecs.getincrementaldecoder (encoding)

查找给定编码的编解码器并返回其增量式解码器类或工厂函数。

在编码无法找到或编解码器不支持增量式解码器时将引发 @ref{15f6,,LookupError}。
@end deffn

@geindex getreader() (在 codecs 模块中)
@anchor{library/codecs codecs getreader}@anchor{17cb}
@deffn {函数} codecs.getreader (encoding)

查找给定编码的编解码器并返回其 @ref{17c6,,StreamReader} 类或工厂函数。

在编码无法找到时将引发 @ref{15f6,,LookupError}。
@end deffn

@geindex getwriter() (在 codecs 模块中)
@anchor{library/codecs codecs getwriter}@anchor{17cc}
@deffn {函数} codecs.getwriter (encoding)

查找给定编码的编解码器并返回其 @ref{17c5,,StreamWriter} 类或工厂函数。

在编码无法找到时将引发 @ref{15f6,,LookupError}。
@end deffn

自定义编解码器的启用是通过注册适当的编解码器搜索函数：

@geindex register() (在 codecs 模块中)
@anchor{library/codecs codecs register}@anchor{17cd}
@deffn {函数} codecs.register (search_function)

注册一个编解码器搜索函数。 搜索函数预期接收一个参数，即全部以小写字母表示的编码名称，并返回一个 @ref{17b8,,CodecInfo} 对象。 在搜索函数无法找到给定编码的情况下，它应当返回 @code{None}。

@cartouche
@quotation 注解 
搜索函数的注册目前是不可逆的，这在某些情况下可能导致问题，例如单元测试或模块重载等。
@end quotation
@end cartouche
@end deffn

虽然内置的 @ref{4ea,,open()} 和相关联的 @ref{a1,,io} 模块是操作已编码文本文件的推荐方式，但本模块也提供了额外的工具函数和类，允许在操作二进制文件时使用更多各类的编解码器：

@geindex open() (在 codecs 模块中)
@anchor{library/codecs codecs open}@anchor{12f8}
@deffn {函数} codecs.open (filename, mode='r', encoding=None, errors='strict', buffering=-1)

使用给定的 @emph{mode} 打开已编码的文件并返回一个 @ref{17ce,,StreamReaderWriter} 的实例，提供透明的编码/解码。 默认的文件模式为 @code{'r'}，表示以读取模式打开文件。

@cartouche
@quotation 注解 
下层的已编码文件总是以二进制模式打开。 在读取和写入时不会自动执行 @code{'\n'} 的转换。 @emph{mode} 参数可以是内置 @ref{4ea,,open()} 函数所接受的任意二进制模式；@code{'b'} 会被自动添加。
@end quotation
@end cartouche

@emph{encoding} 指定文件所要使用的编码格式。 允许任何编码为字节串或从字节串解码的编码格式，而文件方法所支持的数据类型则取决于所使用的编解码器。

可以指定 @emph{errors} 来定义错误处理方案。 默认值 @code{'strict'} 表示在出现编码错误时引发 @ref{1fb,,ValueError}。

@emph{buffering} 的含义与内置 @ref{4ea,,open()} 函数中的相同。 默认值 -1 表示将使用默认的缓冲区大小。
@end deffn

@geindex EncodedFile() (在 codecs 模块中)
@anchor{library/codecs codecs EncodedFile}@anchor{17cf}
@deffn {函数} codecs.EncodedFile (file, data_encoding, file_encoding=None, errors='strict')

返回一个 @ref{f5d,,StreamRecoder} 实例，它提供了 @emph{file} 的透明转码包装版本。 当包装版本被关闭时原始文件也会被关闭。

写入已包装文件的数据会根据给定的 @emph{data_encoding} 解码，然后以使用 @emph{file_encoding} 的字节形式写入原始文件。 从原始文件读取的字节串将根据 @emph{file_encoding} 解码，其结果将使用 @emph{data_encoding} 进行编码。

如果 @emph{file_encoding} 未给定，则默认为 @emph{data_encoding}。

可以指定 @emph{errors} 来定义错误处理方案。 默认值 @code{'strict'} 表示在出现编码错误时引发 @ref{1fb,,ValueError}。
@end deffn

@geindex iterencode() (在 codecs 模块中)
@anchor{library/codecs codecs iterencode}@anchor{17d0}
@deffn {函数} codecs.iterencode (iterator, encoding, errors='strict', **kwargs)

使用增量式编码器通过迭代来编码由 @emph{iterator} 所提供的输入。 此函数属于 @ref{99c,,generator}。 @emph{errors} 参数（以及任何其他关键字参数）会被传递给增量式编码器。

此函数要求编解码器接受 @ref{329,,str} 对象形式的文本进行编码。 因此它不支持字节到字节的编码器，例如 @code{base64_codec}。
@end deffn

@geindex iterdecode() (在 codecs 模块中)
@anchor{library/codecs codecs iterdecode}@anchor{17d1}
@deffn {函数} codecs.iterdecode (iterator, encoding, errors='strict', **kwargs)

使用增量式解码器通过迭代来解码由 @emph{iterator} 所提供的输入。 此函数属于 @ref{99c,,generator}。 @emph{errors} 参数（以及任何其他关键字参数）会被传递给增量式解码器。

此函数要求编解码器接受 @ref{32a,,bytes} 对象进行解码。 因此它不支持文本到文本的编码器，例如 @code{rot_13}，但是 @code{rot_13} 可以通过同样效果的 @ref{17d0,,iterencode()} 来使用。
@end deffn

本模块还提供了以下常量，适用于读取和写入依赖于平台的文件：

@geindex BOM() (在 codecs 模块中)
@geindex BOM_BE() (在 codecs 模块中)
@geindex BOM_LE() (在 codecs 模块中)
@geindex BOM_UTF8() (在 codecs 模块中)
@geindex BOM_UTF16() (在 codecs 模块中)
@geindex BOM_UTF16_BE() (在 codecs 模块中)
@geindex BOM_UTF16_LE() (在 codecs 模块中)
@geindex BOM_UTF32() (在 codecs 模块中)
@geindex BOM_UTF32_BE() (在 codecs 模块中)
@geindex BOM_UTF32_LE() (在 codecs 模块中)
@anchor{library/codecs codecs BOM}@anchor{17d2}
@deffn {数据} codecs.BOM
@anchor{library/codecs codecs BOM_BE}@anchor{17d3}
@deffnx {数据} codecs.BOM_BE
@anchor{library/codecs codecs BOM_LE}@anchor{17d4}
@deffnx {数据} codecs.BOM_LE
@anchor{library/codecs codecs BOM_UTF8}@anchor{17d5}
@deffnx {数据} codecs.BOM_UTF8
@anchor{library/codecs codecs BOM_UTF16}@anchor{17d6}
@deffnx {数据} codecs.BOM_UTF16
@anchor{library/codecs codecs BOM_UTF16_BE}@anchor{17d7}
@deffnx {数据} codecs.BOM_UTF16_BE
@anchor{library/codecs codecs BOM_UTF16_LE}@anchor{17d8}
@deffnx {数据} codecs.BOM_UTF16_LE
@anchor{library/codecs codecs BOM_UTF32}@anchor{17d9}
@deffnx {数据} codecs.BOM_UTF32
@anchor{library/codecs codecs BOM_UTF32_BE}@anchor{17da}
@deffnx {数据} codecs.BOM_UTF32_BE
@anchor{library/codecs codecs BOM_UTF32_LE}@anchor{17db}
@deffnx {数据} codecs.BOM_UTF32_LE

这些常量定义了多种字节序列，即一些编码格式的 Unicode 字节顺序标记（BOM）。 它们在 UTF-16 和 UTF-32 数据流中被用以指明所使用的字节顺序，并在 UTF-8 中被用作 Unicode 签名。 @ref{17d6,,BOM_UTF16} 是 @ref{17d7,,BOM_UTF16_BE} 或 @ref{17d8,,BOM_UTF16_LE}，具体取决于平台的本机字节顺序，@ref{17d2,,BOM} 是 @ref{17d6,,BOM_UTF16} 的别名, @ref{17d4,,BOM_LE} 是 @ref{17d8,,BOM_UTF16_LE} 的别名，@ref{17d3,,BOM_BE} 是 @ref{17d7,,BOM_UTF16_BE} 的别名。 其他序列则表示 UTF-8 和 UTF-32 编码格式中的 BOM。
@end deffn

@menu
* 编解码器基类:: 
* 编码格式与 Unicode:: 
* 标准编码:: 
* Python 专属的编码格式:: 
* encodings.idna: encodings idna --- 应用程序中的国际化域名. 应用程序中的国际化域名
* encodings.mbcs: encodings mbcs --- Windows ANSI代码页. Windows ANSI代码页
* encodings.utf_8_sig: encodings utf_8_sig --- 带BOM签名的UTF-8编解码器. 带BOM签名的UTF-8编解码器

@end menu

@node 编解码器基类,编码格式与 Unicode,,codecs --- 编解码器注册和相关基类
@anchor{library/codecs codec-base-classes}@anchor{17b7}@anchor{library/codecs id1}@anchor{17dc}
@subsubsection 编解码器基类


@ref{1c,,codecs} 模块定义了一系列基类用来定义配合编解码器对象进行工作的接口，并且也可用作定制编解码器实现的基础。

每种编解码器必须定义四个接口以便用作 Python 中的编解码器：无状态编码器、无状态解码器、流读取器和流写入器。 流读取器和写入器通常会重用无状态编码器/解码器来实现文件协议。 编解码器作者还需要定义编解码器将如何处理编码和解码错误。
@anchor{library/codecs surrogateescape}@anchor{17dd}
@menu
* 错误处理方案:: 
* 无状态的编码和解码:: 
* 增量式的编码和解码:: 
* 流式的编码和解码:: 

@end menu

@node 错误处理方案,无状态的编码和解码,,编解码器基类
@anchor{library/codecs error-handlers}@anchor{12f7}@anchor{library/codecs id2}@anchor{17de}
@subsubsection 错误处理方案


为了简化和标准化错误处理，编解码器可以通过接受 @emph{errors} 字符串参数来实现不同的错误处理方案。 所有标准的 Python 编解码器都定义并实现了以下字符串值：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

含义

@item

@code{'strict'}

@tab

引发 @ref{c34,,UnicodeError} (或其子类)；这是默认的方案。 在 @ref{17df,,strict_errors()} 中实现。

@item

@code{'ignore'}

@tab

忽略错误格式的数据并且不加进一步通知就继续执行。 在 @ref{17e0,,ignore_errors()} 中实现。

@end multitable


以下错误处理方案仅适用于 @ref{1593,,文本编码}:

@geindex ? (question mark); replacement character
@geindex \ (backslash); escape sequence
@geindex \x; escape sequence
@geindex \u; escape sequence
@geindex \U; escape sequence
@geindex \N; escape sequence


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

含义

@item

@code{'replace'}

@tab

使用适当的替换标记进行替换；Python 内置编解码器将在解码时使用官方 @code{U+FFFD} 替换字符，而在编码时使用 '?' 。 在 @ref{17e1,,replace_errors()} 中实现。

@item

@code{'xmlcharrefreplace'}

@tab

使用适当的 XML 字符引用进行替换（仅在编码时）。 在 @ref{17e2,,xmlcharrefreplace_errors()} 中实现。

@item

@code{'backslashreplace'}

@tab

使用带反斜杠的转义序列进行替换。 在 @ref{17e3,,backslashreplace_errors()} 中实现。

@item

@code{'namereplace'}

@tab

使用 @code{\N@{...@}} 转义序列进行替换（仅在编码时）。 在 @ref{17e4,,namereplace_errors()} 中实现。

@item

@code{'surrogateescape'}

@tab

在解码时，将字节替换为 @code{U+DC80} 至 @code{U+DCFF} 范围内的单个代理代码。 当在编码数据时使用 @code{'surrogateescape'} 错误处理方案时，此代理将被转换回相同的字节。 （请参阅 
@geindex Python 提高建议; PEP 383
PEP 383@footnote{https://www.python.org/dev/peps/pep-0383} 了解详情。）

@end multitable


此外，以下错误处理方案被专门用于指定的编解码器：


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

编解码器

@tab

含义

@item

@code{'surrogatepass'}

@tab

utf-8, utf-16, utf-32,
utf-16-be, utf-16-le,
utf-32-be, utf-32-le

@tab

允许编码和解码代理代码。 这些编解码器通常会将出现的代理代码视为错误。

@end multitable



3.1 新版功能: @code{'surrogateescape'} 和 @code{'surrogatepass'} 错误处理方案。



在 3.4 版更改: @code{'surrogatepass'} 错误处理方案现在适用于 utf-16* 和 utf-32* 编解码器。



3.5 新版功能: @code{'namereplace'} 错误处理方案。



在 3.5 版更改: @code{'backslashreplace'} 错误处理方案现在适用于解码和转换。


允许的值集合可以通过注册新命名的错误处理方案来扩展：

@geindex register_error() (在 codecs 模块中)
@anchor{library/codecs codecs register_error}@anchor{dee}
@deffn {函数} codecs.register_error (name, error_handler)

在名称 @emph{name} 之下注册错误处理函数 @emph{error_handler}。 当 @emph{name} 被指定为错误形参时，@emph{error_handler} 参数所指定的对象将在编码和解码期间发生错误的情况下被调用，

对于编码操作，将会调用 @emph{error_handler} 并传入一个 @ref{1fc,,UnicodeEncodeError} 实例，其中包含有关错误位置的信息。 错误处理程序必须引发此异常或别的异常，或者也可以返回一个元组，其中包含输入的不可编码部分的替换对象，以及应当继续进行编码的位置。 替换对象可以为 @ref{329,,str} 或 @ref{32a,,bytes} 类型。 如果替换对象为字节串，编码器将简单地将其复制到输出缓冲区。 如果替换对象为字符串，编码器将对替换对象进行编码。 对原始输入的编码操作会在指定位置继续进行。 负的位置值将被视为相对于输入字符串的末尾。 如果结果位置超出范围则将引发 @ref{e6e,,IndexError}。

解码和转换的做法很相似，不同之处在于将把 @ref{1fd,,UnicodeDecodeError} 或 @ref{16aa,,UnicodeTranslateError} 传给处理程序，并且来自错误处理程序的替换对象将被直接放入输出。
@end deffn

之前注册的错误处理方案（包括标准错误处理方案）可通过名称进行查找：

@geindex lookup_error() (在 codecs 模块中)
@anchor{library/codecs codecs lookup_error}@anchor{def}
@deffn {函数} codecs.lookup_error (name)

返回之前在名称 @emph{name} 之下注册的错误处理方案。

在处理方案无法找到时将引发 @ref{15f6,,LookupError}。
@end deffn

以下标准错误处理方案也可通过模块层级函数的方式来使用：

@geindex strict_errors() (在 codecs 模块中)
@anchor{library/codecs codecs strict_errors}@anchor{17df}
@deffn {函数} codecs.strict_errors (exception)

实现 @code{'strict'} 错误处理方案：每个编码或解码错误都会引发 @ref{c34,,UnicodeError}。
@end deffn

@geindex replace_errors() (在 codecs 模块中)
@anchor{library/codecs codecs replace_errors}@anchor{17e1}
@deffn {函数} codecs.replace_errors (exception)

实现 @code{'replace'} 错误处理方案 (仅用于 @ref{1593,,文本编码})：编码错误替换为 @code{'?'} (并由编解码器编码)，解码错误替换为 @code{'\ufffd'} (Unicode 替换字符)。
@end deffn

@geindex ignore_errors() (在 codecs 模块中)
@anchor{library/codecs codecs ignore_errors}@anchor{17e0}
@deffn {函数} codecs.ignore_errors (exception)

实现 @code{'ignore'} 错误处理方案：忽略错误格式的数据并且不加进一步通知就继续执行。
@end deffn

@geindex xmlcharrefreplace_errors() (在 codecs 模块中)
@anchor{library/codecs codecs xmlcharrefreplace_errors}@anchor{17e2}
@deffn {函数} codecs.xmlcharrefreplace_errors (exception)

实现 @code{'xmlcharrefreplace'} 错误处理方案 (仅用于 @ref{1593,,文本编码} 的编码过程)：不可编码的字符将以适当的 XML 字符引用进行替换。
@end deffn

@geindex backslashreplace_errors() (在 codecs 模块中)
@anchor{library/codecs codecs backslashreplace_errors}@anchor{17e3}
@deffn {函数} codecs.backslashreplace_errors (exception)

实现 @code{'backslashreplace'} 错误处理方案 (仅用于 @ref{1593,,文本编码})：错误格式的数据将以带反斜杠的转义序列进行替换。
@end deffn

@geindex namereplace_errors() (在 codecs 模块中)
@anchor{library/codecs codecs namereplace_errors}@anchor{17e4}
@deffn {函数} codecs.namereplace_errors (exception)

实现 @code{'namereplace'} 错误处理方案 (仅用于 @ref{1593,,文本编码} 的编码过程)：不可编码的字符将以 @code{\N@{...@}} 转义序列进行替换。


3.5 新版功能.

@end deffn

@node 无状态的编码和解码,增量式的编码和解码,错误处理方案,编解码器基类
@anchor{library/codecs codec-objects}@anchor{17be}@anchor{library/codecs stateless-encoding-and-decoding}@anchor{17e5}
@subsubsection 无状态的编码和解码


基本 @code{Codec} 类定义了这些方法，同时还定义了无状态编码器和解码器的函数接口：

@geindex encode() (codecs.Codec 方法)
@anchor{library/codecs codecs Codec encode}@anchor{17bc}
@deffn {方法} Codec.encode (input[, errors])

编码 @emph{input} 对象并返回一个元组 (输出对象, 消耗长度)。 例如，@ref{1593,,text encoding} 会使用特定的字符集编码格式 (例如 @code{cp1252} 或 @code{iso-8859-1}) 将字符串转换为字节串对象。

@emph{errors} 参数定义了要应用的错误处理方案。 默认为 @code{'strict'} 处理方案。

此方法不一定会在 @code{Codec} 实例中保存状态。 可使用必须保存状态的 @ref{17c5,,StreamWriter} 作为编解码器以便高效地进行编码。

编码器必须能够处理零长度的输入并在此情况下返回输出对象类型的空对象。
@end deffn

@geindex decode() (codecs.Codec 方法)
@anchor{library/codecs codecs Codec decode}@anchor{17bd}
@deffn {方法} Codec.decode (input[, errors])

解码 @emph{input} 对象并返回一个元组 (输出对象, 消耗长度)。 例如，@ref{1593,,text encoding} 的解码操作会使用特定的字符集编码格式将字节串对象转换为字符串对象。

对于文本编码格式和字节到字节编解码器，@emph{input} 必须为一个字节串对象或提供了只读缓冲区接口的对象 -- 例如，缓冲区对象和映射到内存的文件。

@emph{errors} 参数定义了要应用的错误处理方案。 默认为 @code{'strict'} 处理方案。

此方法不一定会在 @code{Codec} 实例中保存状态。 可使用必须保存状态的 @ref{17c6,,StreamReader} 作为编解码器以便高效地进行解码。

解码器必须能够处理零长度的输入并在此情况下返回输出对象类型的空对象。
@end deffn

@node 增量式的编码和解码,流式的编码和解码,无状态的编码和解码,编解码器基类
@anchor{library/codecs incremental-encoding-and-decoding}@anchor{17e6}
@subsubsection 增量式的编码和解码


@ref{17c1,,IncrementalEncoder} 和 @ref{17c2,,IncrementalDecoder} 类提供了增量式编码和解码的基本接口。 对输入的编码/解码不是通过对无状态编码器/解码器的一次调用，而是通过对增量式编码器/解码器的 @ref{17e7,,encode()}/@ref{17e8,,decode()} 方法的多次调用。 增量式编码器/解码器会在方法调用期间跟踪编码/解码过程。

调用 @ref{17e7,,encode()}/@ref{17e8,,decode()} 方法后的全部输出相当于将所有通过无状态编码器/解码器进行编码/解码的单个输入连接在一起所得到的输出。

@menu
* IncrementalEncoder 对象:: 
* IncrementalDecoder 对象:: 

@end menu

@node IncrementalEncoder 对象,IncrementalDecoder 对象,,增量式的编码和解码
@anchor{library/codecs incremental-encoder-objects}@anchor{17e9}@anchor{library/codecs incrementalencoder-objects}@anchor{17ea}
@subsubsection IncrementalEncoder 对象


@ref{17c1,,IncrementalEncoder} 类用来对一个输入进行分步编码。 它定义了以下方法，每个增量式编码器都必须定义这些方法以便与 Python 编解码器注册表相兼容。

@geindex IncrementalEncoder (codecs 中的类)
@anchor{library/codecs codecs IncrementalEncoder}@anchor{17c1}
@deffn {类} codecs.IncrementalEncoder (errors='strict')

@ref{17c1,,IncrementalEncoder} 实例的构造器。

所有增量式编码器必须提供此构造器接口。 它们可以自由地添加额外的关键字参数，但只有在这里定义的参数才会被 Python 编解码器注册表所使用。

@ref{17c1,,IncrementalEncoder} 可以通过提供 @emph{errors} 关键字参数来实现不同的错误处理方案。 可用的值请参阅 @ref{12f7,,错误处理方案}。

@emph{errors} 参数将被赋值给一个同名的属性。 通过对此属性赋值就可以在 @ref{17c1,,IncrementalEncoder} 对象的生命期内在不同的错误处理策略之间进行切换。

@geindex encode() (codecs.IncrementalEncoder 方法)
@anchor{library/codecs codecs IncrementalEncoder encode}@anchor{17e7}
@deffn {方法} encode (object[, final])

编码 @emph{object} (会将编码器的当前状态纳入考虑) 并返回已编码的结果对象。 如果这是对 @ref{7fc,,encode()} 的最终调用则 @emph{final} 必须为真值（默认为假值）。
@end deffn

@geindex reset() (codecs.IncrementalEncoder 方法)
@anchor{library/codecs codecs IncrementalEncoder reset}@anchor{17eb}
@deffn {方法} reset ()

将编码器重置为初始状态。 输出将被丢弃：调用 @code{.encode(object, final=True)}，在必要时传入一个空字节串或字符串，重置编码器并得到输出。
@end deffn

@geindex getstate() (codecs.IncrementalEncoder 方法)
@anchor{library/codecs codecs IncrementalEncoder getstate}@anchor{17ec}
@deffn {方法} getstate ()

返回编码器的当前状态，该值必须为一个整数。 实现应当确保 @code{0} 是最常见的状态。 （比整数更复杂的状态表示可以通过编组/选择状态并将结果字符串的字节数据编码为整数来转换为一个整数值）。
@end deffn

@geindex setstate() (codecs.IncrementalEncoder 方法)
@anchor{library/codecs codecs IncrementalEncoder setstate}@anchor{17ed}
@deffn {方法} setstate (state)

将编码器的状态设为 @emph{state}。 @emph{state} 必须为 @ref{17ec,,getstate()} 所返回的一个编码器状态。
@end deffn
@end deffn

@node IncrementalDecoder 对象,,IncrementalEncoder 对象,增量式的编码和解码
@anchor{library/codecs incremental-decoder-objects}@anchor{17ee}@anchor{library/codecs incrementaldecoder-objects}@anchor{17ef}
@subsubsection IncrementalDecoder 对象


@ref{17c2,,IncrementalDecoder} 类用来对一个输入进行分步解码。 它定义了以下方法，每个增量式解码器都必须定义这些方法以便与 Python 编解码器注册表相兼容。

@geindex IncrementalDecoder (codecs 中的类)
@anchor{library/codecs codecs IncrementalDecoder}@anchor{17c2}
@deffn {类} codecs.IncrementalDecoder (errors='strict')

@ref{17c2,,IncrementalDecoder} 实例的构造器。

所有增量式解码器必须提供此构造器接口。 它们可以自由地添加额外的关键字参数，但只有在这里定义的参数才会被 Python 编解码器注册表所使用。

@ref{17c2,,IncrementalDecoder} 可以通过提供 @emph{errors} 关键字参数来实现不同的错误处理方案。 可用的值请参阅 @ref{12f7,,错误处理方案}。

@emph{errors} 参数将被赋值给一个同名的属性。 通过对此属性赋值就可以在 @ref{17c2,,IncrementalDecoder} 对象的生命期内在不同的错误处理策略之间进行切换。

@geindex decode() (codecs.IncrementalDecoder 方法)
@anchor{library/codecs codecs IncrementalDecoder decode}@anchor{17e8}
@deffn {方法} decode (object[, final])

解码 @emph{object} (会将解码器的当前状态纳入考虑) 并返回已解码的结果对象。 如果这是对 @ref{7fd,,decode()} 的最终调用则 @emph{final} 必须为真值（默认为假值）。 如果 @emph{final} 为真值则解码器必须对输入进行完全解码并且必须 刷新所有缓冲区。 如果这无法做到（例如由于在输入结束时字节串序列不完整）则它必须像在无状态的情况下那样初始化错误处理（这可能引发一个异常）。
@end deffn

@geindex reset() (codecs.IncrementalDecoder 方法)
@anchor{library/codecs codecs IncrementalDecoder reset}@anchor{17f0}
@deffn {方法} reset ()

将解码器重置为初始状态。
@end deffn

@geindex getstate() (codecs.IncrementalDecoder 方法)
@anchor{library/codecs codecs IncrementalDecoder getstate}@anchor{17f1}
@deffn {方法} getstate ()

返回解码器的当前状态。 这必须为一个二元组，第一项必须是包含尚未解码的输入的缓冲区。 第二项必须为一个整数，可以表示附加状态信息。 （实现应当确保 @code{0} 是最常见的附加状态信息。） 如果此附加状态信息为 @code{0} 则必须可以将解码器设为没有已缓冲输入并且以 @code{0} 作为附加状态信息，以便将先前已缓冲的输入馈送到解码器使其返回到先前的状态而不产生任何输出。 （比整数更复杂的附加状态信息可以通过编组/选择状态信息并将结果字符串的字节数据编码为整数来转换为一个整数值。）
@end deffn

@geindex setstate() (codecs.IncrementalDecoder 方法)
@anchor{library/codecs codecs IncrementalDecoder setstate}@anchor{17f2}
@deffn {方法} setstate (state)

将解码器的状态设为 @emph{state}。 @emph{state} 必须为 @ref{17f1,,getstate()} 所返回的一个解码器状态。
@end deffn
@end deffn

@node 流式的编码和解码,,增量式的编码和解码,编解码器基类
@anchor{library/codecs stream-encoding-and-decoding}@anchor{17f3}
@subsubsection 流式的编码和解码


@ref{17c5,,StreamWriter} 和 @ref{17c6,,StreamReader} 类提供了一些泛用工作接口，可被用来非常方便地实现新的编码格式子模块。 请参阅 @code{encodings.utf_8} 中的示例了解如何做到这一点。

@menu
* StreamWriter 对象:: 
* StreamReader 对象:: 
* StreamReaderWriter 对象:: 
* StreamRecoder 对象:: 

@end menu

@node StreamWriter 对象,StreamReader 对象,,流式的编码和解码
@anchor{library/codecs stream-writer-objects}@anchor{17f4}@anchor{library/codecs streamwriter-objects}@anchor{17f5}
@subsubsection StreamWriter 对象


@ref{17c5,,StreamWriter} 类是 @code{Codec} 的子类，它定义了以下方法，每个流式写入器都必须定义这些方法以便与 Python 编解码器注册表相兼容。

@geindex StreamWriter (codecs 中的类)
@anchor{library/codecs codecs StreamWriter}@anchor{17c5}
@deffn {类} codecs.StreamWriter (stream, errors='strict')

@ref{17c5,,StreamWriter} 实例的构造器。

所有流式写入器必须提供此构造器接口。 它们可以自由地添加额外的关键字参数，但只有在这里定义的参数才会被 Python 编解码器注册表所使用。

@emph{stream} 参数必须为一个基于特定编解码器打开用于写入文本或二进制数据的文件类对象。

@ref{17c5,,StreamWriter} 可以通过提供 @emph{errors} 关键字参数来实现不同的错误处理方案。 请参阅 @ref{12f7,,错误处理方案} 了解下层的流式编解码器可支持的标准错误处理方案。

@emph{errors} 参数将被赋值给一个同名的属性。 通过对此属性赋值就可以在 @ref{17c5,,StreamWriter} 对象的生命期内在不同的错误处理策略之间进行切换。

@geindex write() (codecs.StreamWriter 方法)
@anchor{library/codecs codecs StreamWriter write}@anchor{17f6}
@deffn {方法} write (object)

将编码后的对象内容写入到流。
@end deffn

@geindex writelines() (codecs.StreamWriter 方法)
@anchor{library/codecs codecs StreamWriter writelines}@anchor{17f7}
@deffn {方法} writelines (list)

将拼接后的字符串列表写入到流（可能通过重用 @ref{17f6,,write()} 方法）。 标准的字节到字节编解码器不支持此方法。
@end deffn

@geindex reset() (codecs.StreamWriter 方法)
@anchor{library/codecs codecs StreamWriter reset}@anchor{17f8}
@deffn {方法} reset ()

刷新并重置用于保持状态的编解码器缓冲区。

调用此方法应当确保在干净的状态下放入输出数据，以允许直接添加新的干净数据而无须重新扫描整个流来恢复状态。
@end deffn
@end deffn

除了上述的方法，@ref{17c5,,StreamWriter} 还必须继承来自下层流的所有其他方法和属性。

@node StreamReader 对象,StreamReaderWriter 对象,StreamWriter 对象,流式的编码和解码
@anchor{library/codecs stream-reader-objects}@anchor{17f9}@anchor{library/codecs streamreader-objects}@anchor{17fa}
@subsubsection StreamReader 对象


@ref{17c6,,StreamReader} 类是 @code{Codec} 的子类，它定义了以下方法，每个流式读取器都必须定义这些方法以便与 Python 编解码器注册表相兼容。

@geindex StreamReader (codecs 中的类)
@anchor{library/codecs codecs StreamReader}@anchor{17c6}
@deffn {类} codecs.StreamReader (stream, errors='strict')

@ref{17c6,,StreamReader} 实例的构造器。

所有流式读取器必须提供此构造器接口。 它们可以自由地添加额外的关键字参数，但只有在这里定义的参数才会被 Python 编解码器注册表所使用。

@emph{stream} 参数必须为一个基于特定编解码器打开用于读取文本或二进制数据的文件类对象。

@ref{17c6,,StreamReader} 可以通过提供 @emph{errors} 关键字参数来实现不同的错误处理方案。 请参阅 @ref{12f7,,错误处理方案} 了解下层的流式编解码器可支持的标准错误处理方案。

@emph{errors} 参数将被赋值给一个同名的属性。 通过对此属性赋值就可以在 @ref{17c6,,StreamReader} 对象的生命期内在不同的错误处理策略之间进行切换。

@emph{errors} 参数所允许的值集合可以使用 @ref{dee,,register_error()} 来扩展。

@geindex read() (codecs.StreamReader 方法)
@anchor{library/codecs codecs StreamReader read}@anchor{17fb}
@deffn {方法} read ([size[, chars[, firstline]]])

解码来自流的数据并返回结果对象。

@emph{chars} 参数指明要返回的解码后码位或字节数量。 @ref{17fb,,read()} 方法绝不会返回超出请求数量的数据，但如果可用数量不足，它可能返回少于请求数量的数据。

@emph{size} 参数指明要读取并解码的已编码字节或码位的最大数量近似值。 解码器可以适当地修改此设置。 默认值 -1 表示尽可能多地读取并解码。 此形参的目的是防止一次性解码过于巨大的文件。

@emph{firstline} 旗标指明如果在后续行发生解码错误，则仅返回第一行就足够了。

此方法应当使用“贪婪”读取策略，这意味着它应当在编码格式定义和给定大小所允许的情况下尽可能多地读取数据，例如，如果在流上存在可选的编码结束或状态标记，这些内容也应当被读取。
@end deffn

@geindex readline() (codecs.StreamReader 方法)
@anchor{library/codecs codecs StreamReader readline}@anchor{17fc}
@deffn {方法} readline ([size[, keepends]])

从输入流读取一行并返回解码后的数据。

如果给定了 @emph{size}，则将其作为 size 参数传递给流的 @ref{17fb,,read()} 方法。

如果 @emph{keepends} 为假值，则行结束符将从返回的行中去除。
@end deffn

@geindex readlines() (codecs.StreamReader 方法)
@anchor{library/codecs codecs StreamReader readlines}@anchor{17fd}
@deffn {方法} readlines ([sizehint[, keepends]])

从输入流读取所有行并将其作为一个行列表返回。

行结束符会使用编解码器的 @ref{7fd,,decode()} 方法来实现，并且如果 @emph{keepends} 为真值则会将其包含在列表条目中。

如果给定了 @emph{sizehint}，则将其作为 @emph{size} 参数传递给流的 @ref{17fb,,read()} 方法。
@end deffn

@geindex reset() (codecs.StreamReader 方法)
@anchor{library/codecs codecs StreamReader reset}@anchor{17fe}
@deffn {方法} reset ()

重置用于保持状态的编解码器缓冲区。

请注意不应当对流进行重定位。 使用此方法的主要目的是为了能够从解码错误中恢复。
@end deffn
@end deffn

除了上述的方法，@ref{17c6,,StreamReader} 还必须继承来自下层流的所有其他方法和属性。

@node StreamReaderWriter 对象,StreamRecoder 对象,StreamReader 对象,流式的编码和解码
@anchor{library/codecs stream-reader-writer}@anchor{17ff}@anchor{library/codecs streamreaderwriter-objects}@anchor{1800}
@subsubsection StreamReaderWriter 对象


@ref{17ce,,StreamReaderWriter} 是一个方便的类，允许对同时工作于读取和写入模式的流进行包装。

其设计使得开发者可以使用 @ref{169a,,lookup()} 函数所返回的工厂函数来构造实例。

@geindex StreamReaderWriter (codecs 中的类)
@anchor{library/codecs codecs StreamReaderWriter}@anchor{17ce}
@deffn {类} codecs.StreamReaderWriter (stream, Reader, Writer, errors='strict')

创建一个 @ref{17ce,,StreamReaderWriter} 实例。 @emph{stream} 必须为一个文件类对象。 @emph{Reader} 和 @emph{Writer} 必须为分别提供了 @ref{17c6,,StreamReader} 和 @ref{17c5,,StreamWriter} 接口的工厂函数或类。 错误处理通过与流式读取器和写入器所定义的相同方式来完成。
@end deffn

@ref{17ce,,StreamReaderWriter} 实例定义了 @ref{17c6,,StreamReader} 和 @ref{17c5,,StreamWriter} 类的组合接口。 它们还继承了来自下层流的所有其他方法和属性。

@node StreamRecoder 对象,,StreamReaderWriter 对象,流式的编码和解码
@anchor{library/codecs stream-recoder-objects}@anchor{1801}@anchor{library/codecs streamrecoder-objects}@anchor{1802}
@subsubsection StreamRecoder 对象


@ref{f5d,,StreamRecoder} 将数据从一种编码格式转换为另一种，这对于处理不同编码环境的情况有时会很有用。

其设计使得开发者可以使用 @ref{169a,,lookup()} 函数所返回的工厂函数来构造实例。

@geindex StreamRecoder (codecs 中的类)
@anchor{library/codecs codecs StreamRecoder}@anchor{f5d}
@deffn {类} codecs.StreamRecoder (stream, encode, decode, Reader, Writer, errors='strict')

创建一个实现了双向转换的 @ref{f5d,,StreamRecoder} 实例: @emph{encode} 和 @emph{decode} 工作于前端 — 对代码可见的数据调用 @code{read()} 和 @code{write()}，而 @emph{Reader} 和 @emph{Writer} 工作于后端 —  @emph{stream} 中的数据。

你可以使用这些对象来进行透明转码，例如从 Latin-1 转为 UTF-8 以及反向转换。

@emph{stream} 参数必须为一个文件类对象。

@emph{encode} 和 @emph{decode} 参数必须遵循 @code{Codec} 接口。 @emph{Reader} 和 @emph{Writer} 必须为分别提供了 @ref{17c6,,StreamReader} 和 @ref{17c5,,StreamWriter} 接口对象的工厂函数或类。

错误处理通过与流式读取器和写入器所定义的相同方式来完成。
@end deffn

@ref{f5d,,StreamRecoder} 实例定义了 @ref{17c6,,StreamReader} 和 @ref{17c5,,StreamWriter} 类的组合接口。 它们还继承了来自下层流的所有其他方法和属性。

@node 编码格式与 Unicode,标准编码,编解码器基类,codecs --- 编解码器注册和相关基类
@anchor{library/codecs encodings-and-unicode}@anchor{1803}@anchor{library/codecs encodings-overview}@anchor{1804}
@subsubsection 编码格式与 Unicode


字符串在系统内部存储为 @code{0x0}--@code{0x10FFFF} 范围内的码位序列。 （请参阅 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393} 了解有关实现的详情。） 一旦字符串对象要在 CPU 和内存以外使用，字节的大小端顺序和字节数组的存储方式就成为一个关键问题。 如同使用其他编解码器一样，将字符串序列化为字节序列被称为 @emph{编码}，而从字节序列重建字符串被称为 @emph{解码}。 存在许多不同的文本序列化编解码器，它们被统称为 @ref{1593,,文本编码}。

最简单的文本编码格式 (称为 @code{'latin-1'} 或 @code{'iso-8859-1'}) 将码位 0--255 映射为字节值 @code{0x0}--@code{0xff}，这意味着包含 @code{U+00FF} 以上码位的字符串对象无法使用此编解码器进行编码。 这样做将引发 @ref{1fc,,UnicodeEncodeError}，其形式类似下面这样（不过详细的错误信息可能会有所不同）: @code{UnicodeEncodeError: 'latin-1' codec can't encode character '\u1234' in position 3: ordinal not in range(256)}。

还有另外一组编码格式（所谓的字符映射编码）会选择全部 Unicode 码位的不同子集并设定如何将这些码位映射为字节值 @code{0x0}--@code{0xff}。 要查看这是如何实现的，只需简单地打开相应源码例如 @code{encodings/cp1252.py} (这是一个主要在 Windows 上使用的编码格式)。 其中会有一个包含 256 个字符的字符串常量，指明每个字符所映射的字节值。

所有这些编码格式只能对 Unicode 所定义的 1114112 个码位中的 256 个进行编码。 一种能够存储每个 Unicode 码位的简单而直接的办法就是将每个码位存储为四个连续的字节。 存在两种不同的可能性：以大端序存储或以小端序存储。 这两种编码格式分别被称为 @code{UTF-32-BE} 和 @code{UTF-32-LE}。 它们的缺点可以举例说明：如果你在一台小端序的机器上使用 @code{UTF-32-BE} 则你将必须在编码和解码时翻转字节。 @code{UTF-32} 避免了这个问题：字节的排列将总是使用自然顺序。 当这些字节被具有不同字节顺序的 CPU 读取时，则必须进行字节翻转。 为了能够检测 @code{UTF-16} 或 @code{UTF-32} 字节序列的大小端序，可以使用所谓的 BOM ("字节顺序标记")。 这对应于 Unicode 字符 @code{U+FEFF}。 此字符可添加到每个 @code{UTF-16} 或 @code{UTF-32} 字节序列的开头。 此字符的字节翻转版本 (@code{0xFFFE}) 是一个不可出现于 Unicode 文本中的非法字符。 因此当发现一个 @code{UTF-16} 或 @code{UTF-32} 字节序列的首个字符是 @code{U+FFFE} 时，就必须在解码时进行字节翻转。 不幸的是字符 @code{U+FEFF} 还有第二个含义 @code{ZERO WIDTH NO-BREAK SPACE}: 即宽度为零并且不允许用来拆分单词的字符。 它可以被用来为语言分析算法提供提示。 在 Unicode 4.0 中用 @code{U+FEFF} 表示 @code{ZERO WIDTH NO-BREAK SPACE} 已被弃用（改用 @code{U+2060} (@code{WORD JOINER}) 负责此任务）。  然而 Unicode 软件仍然必须能够处理 @code{U+FEFF} 的两个含义：作为 BOM 它被用来确定已编码字节的存储布局，并在字节序列被解码为字符串后将其去除；作为 @code{ZERO WIDTH NO-BREAK SPACE} 它是一个普通字符，将像其他字符一样被解码。

还有另一种编码格式能够对所有的 Unicode 字符进行编码：UTF-8。 UTF-8 是一种 8 位编码，这意味着在 UTF-8 中没有字节顺序问题。 UTF-8 字节序列中的每个字节由两部分组成：标志位（最重要的位）和内容位。 标志位是由零至四个值为 @code{1} 的二进制位加一个值为 @code{0} 的二进制位构成的序列。 Unicode 字符会按以下形式进行编码（其中 x 为内容位，当拼接为一体时将给出对应的 Unicode 字符）：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

范围

@tab

编码

@item

@code{U-00000000} ... @code{U-0000007F}

@tab

0xxxxxxx

@item

@code{U-00000080} ... @code{U-000007FF}

@tab

110xxxxx 10xxxxxx

@item

@code{U-00000800} ... @code{U-0000FFFF}

@tab

1110xxxx 10xxxxxx 10xxxxxx

@item

@code{U-00010000} ... @code{U-0010FFFF}

@tab

11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

@end multitable


Unicode 字符最不重要的一个位就是最右侧的二进制位 x。

由于 UTF-8 是一种 8 位编码格式，因此 BOM 是不必要的，并且已编码字符串中的任何 @code{U+FEFF} 字符（即使是作为第一个字符）都会被视为是 @code{ZERO WIDTH NO-BREAK SPACE}。

在没有外部信息的情况下，就不可能毫无疑义地确定一个字符串使用了何种编码格式。 每种字符映射编码格式都可以解码任意的随机字节序列。 然而对 UTF-8 来说这却是不可能的，因为 UTF-8 字节序列具有不允许任意字节序列的特别结构。 为了提升 UTF-8 编码检测的可靠性，Microsoft 发明了一种 UTF-8 变体形式 (Python 2.5 称之为 @code{"utf-8-sig"}) 专门用于其 Notepad 程序：在任何 Unicode 字符在被写入文件之前，会先写入一个 UTF-8 编码的 BOM (它看起来是这样一个字节序列: @code{0xef}, @code{0xbb}, @code{0xbf})。 由于任何字符映射编码后的文件都不大可能以这些字节值开头（例如它们会映射为

@quotation


@display
LATIN SMALL LETTER I WITH DIAERESIS@w{ }
RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK@w{ }
INVERTED QUESTION MARK@w{ }
@end display


@end quotation

对于 iso-8859-1 编码格式来说），这提升了根据字节序列来正确猜测 @code{utf-8-sig} 编码格式的成功率。 所以在这里 BOM 的作用并不是帮助确定生成字节序列所使用的字节顺序，而是作为帮助猜测编码格式的记号。 在进行编码时 utf-8-sig 编解码器将把 @code{0xef}, @code{0xbb}, @code{0xbf} 作为头三个字节写入文件。 在进行解码时 @code{utf-8-sig} 将跳过这三个字节，如果它们作为文件的头三个字节出现的话。 在 UTF-8 中并不推荐使用 BOM，通常应当避免它们的出现。

@node 标准编码,Python 专属的编码格式,编码格式与 Unicode,codecs --- 编解码器注册和相关基类
@anchor{library/codecs id3}@anchor{1805}@anchor{library/codecs standard-encodings}@anchor{689}
@subsubsection 标准编码


Python 自带了许多内置的编解码器，它们的实现或者是通过 C 函数，或者是通过映射表。 以下表格是按名称排序的编解码器列表，并提供了一些常见别名以及编码格式通常针对的语言。 别名和语言列表都不是详尽无遗的。 请注意仅有大小写区别或使用连字符替代下划线的拼写形式也都是有效的别名；因此，@code{'utf-8'} 是 @code{'utf_8'} 编解码器的有效别名。

@strong{CPython implementation detail:} 有些常见编码格式可以绕过编解码器查找机制来提升性能。 这些优化机会对于 CPython 来说仅能通过一组有限的别名（大小写不敏感）来识别：utf-8, utf8, latin-1, latin1, iso-8859-1, iso8859-1, mbcs (Windows 专属), ascii, us-ascii, utf-16, utf16, utf-32, utf32, 也包括使用下划线替代连字符的的形式。 使用这些编码格式的其他别名可能会导致更慢的执行速度。


在 3.6 版更改: 可识别针对 us-ascii 的优化机会。


许多字符集都支持相同的语言。 它们在个别字符（例如是否支持 EURO SIGN 等）以及给字符所分配的码位方面存在差异。 特别是对于欧洲语言来说，通常存在以下几种变体：


@itemize *

@item 
某个 ISO 8859 编码集

@item 
某个 Microsoft Windows 编码页，通常是派生自某个 8859 编码集，但会用附加的图形字符来替换控制字符。

@item 
某个 IBM EBCDIC 编码页

@item 
某个 IBM PC 编码页，通常会兼容 ASCII
@end itemize


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

编码

@tab

别名

@tab

语言

@item

ascii

@tab

646, us-ascii

@tab

英语

@item

big5

@tab

big5-tw, csbig5

@tab

繁体中文

@item

big5hkscs

@tab

big5-hkscs, hkscs

@tab

繁体中文

@item

cp037

@tab

IBM037, IBM039

@tab

英语

@item

cp273

@tab

273, IBM273, csIBM273

@tab

德语


3.4 新版功能.


@item

cp424

@tab

EBCDIC-CP-HE, IBM424

@tab

希伯来语

@item

cp437

@tab

437, IBM437

@tab

英语

@item

cp500

@tab

EBCDIC-CP-BE, EBCDIC-CP-CH,
IBM500

@tab

西欧

@item

cp720

@tab

@tab

阿拉伯语

@item

cp737

@tab

@tab

希腊语

@item

cp775

@tab

IBM775

@tab

波罗的海语言

@item

cp850

@tab

850, IBM850

@tab

西欧

@item

cp852

@tab

852, IBM852

@tab

中欧和东欧

@item

cp855

@tab

855, IBM855

@tab

保加利亚语，白俄罗斯语，马其顿语，俄语，塞尔维亚语

@item

cp856

@tab

@tab

希伯来语

@item

cp857

@tab

857, IBM857

@tab

土耳其语

@item

cp858

@tab

858, IBM858

@tab

西欧

@item

cp860

@tab

860, IBM860

@tab

葡萄牙语

@item

cp861

@tab

861, CP-IS, IBM861

@tab

冰岛语

@item

cp862

@tab

862, IBM862

@tab

希伯来语

@item

cp863

@tab

863, IBM863

@tab

加拿大语

@item

cp864

@tab

IBM864

@tab

阿拉伯语

@item

cp865

@tab

865, IBM865

@tab

丹麦语/挪威语

@item

cp866

@tab

866, IBM866

@tab

俄语

@item

cp869

@tab

869, CP-GR, IBM869

@tab

希腊语

@item

cp874

@tab

@tab

泰语

@item

cp875

@tab

@tab

希腊语

@item

cp932

@tab

932, ms932, mskanji, ms-kanji

@tab

日语

@item

cp949

@tab

949, ms949, uhc

@tab

韩语

@item

cp950

@tab

950, ms950

@tab

繁体中文

@item

cp1006

@tab

@tab

乌尔都语

@item

cp1026

@tab

ibm1026

@tab

土耳其语

@item

cp1125

@tab

1125, ibm1125, cp866u, ruscii

@tab

乌克兰语


3.4 新版功能.


@item

cp1140

@tab

ibm1140

@tab

西欧

@item

cp1250

@tab

windows-1250

@tab

中欧和东欧

@item

cp1251

@tab

windows-1251

@tab

保加利亚语，白俄罗斯语，马其顿语，俄语，塞尔维亚语

@item

cp1252

@tab

windows-1252

@tab

西欧

@item

cp1253

@tab

windows-1253

@tab

希腊语

@item

cp1254

@tab

windows-1254

@tab

土耳其语

@item

cp1255

@tab

windows-1255

@tab

希伯来语

@item

cp1256

@tab

windows-1256

@tab

阿拉伯语

@item

cp1257

@tab

windows-1257

@tab

波罗的海语言

@item

cp1258

@tab

windows-1258

@tab

越南语

@item

euc_jp

@tab

eucjp, ujis, u-jis

@tab

日语

@item

euc_jis_2004

@tab

jisx0213, eucjis2004

@tab

日语

@item

euc_jisx0213

@tab

eucjisx0213

@tab

日语

@item

euc_kr

@tab

euckr, korean, ksc5601,
ks_c-5601, ks_c-5601-1987,
ksx1001, ks_x-1001

@tab

韩语

@item

gb2312

@tab

chinese, csiso58gb231280,
euc-cn, euccn, eucgb2312-cn,
gb2312-1980, gb2312-80,
iso-ir-58

@tab

简体中文

@item

gbk

@tab

936, cp936, ms936

@tab

统一汉语

@item

gb18030

@tab

gb18030-2000

@tab

统一汉语

@item

hz

@tab

hzgb, hz-gb, hz-gb-2312

@tab

简体中文

@item

iso2022_jp

@tab

csiso2022jp, iso2022jp,
iso-2022-jp

@tab

日语

@item

iso2022_jp_1

@tab

iso2022jp-1, iso-2022-jp-1

@tab

日语

@item

iso2022_jp_2

@tab

iso2022jp-2, iso-2022-jp-2

@tab

日语，韩语，简体中文，西欧，希腊语

@item

iso2022_jp_2004

@tab

iso2022jp-2004,
iso-2022-jp-2004

@tab

日语

@item

iso2022_jp_3

@tab

iso2022jp-3, iso-2022-jp-3

@tab

日语

@item

iso2022_jp_ext

@tab

iso2022jp-ext, iso-2022-jp-ext

@tab

日语

@item

iso2022_kr

@tab

csiso2022kr, iso2022kr,
iso-2022-kr

@tab

韩语

@item

latin_1

@tab

iso-8859-1, iso8859-1, 8859,
cp819, latin, latin1, L1

@tab

西欧

@item

iso8859_2

@tab

iso-8859-2, latin2, L2

@tab

中欧和东欧

@item

iso8859_3

@tab

iso-8859-3, latin3, L3

@tab

世界语，马耳他语

@item

iso8859_4

@tab

iso-8859-4, latin4, L4

@tab

波罗的海语言

@item

iso8859_5

@tab

iso-8859-5, cyrillic

@tab

保加利亚语，白俄罗斯语，马其顿语，俄语，塞尔维亚语

@item

iso8859_6

@tab

iso-8859-6, arabic

@tab

阿拉伯语

@item

iso8859_7

@tab

iso-8859-7, greek, greek8

@tab

希腊语

@item

iso8859_8

@tab

iso-8859-8, hebrew

@tab

希伯来语

@item

iso8859_9

@tab

iso-8859-9, latin5, L5

@tab

土耳其语

@item

iso8859_10

@tab

iso-8859-10, latin6, L6

@tab

北欧语言

@item

iso8859_11

@tab

iso-8859-11, thai

@tab

泰语

@item

iso8859_13

@tab

iso-8859-13, latin7, L7

@tab

波罗的海语言

@item

iso8859_14

@tab

iso-8859-14, latin8, L8

@tab

凯尔特语

@item

iso8859_15

@tab

iso-8859-15, latin9, L9

@tab

西欧

@item

iso8859_16

@tab

iso-8859-16, latin10, L10

@tab

东南欧

@item

johab

@tab

cp1361, ms1361

@tab

韩语

@item

koi8_r

@tab

@tab

俄语

@item

koi8_t

@tab

@tab

塔吉克


3.5 新版功能.


@item

koi8_u

@tab

@tab

乌克兰语

@item

kz1048

@tab

kz_1048, strk1048_2002, rk1048

@tab

哈萨克语


3.5 新版功能.


@item

mac_cyrillic

@tab

maccyrillic

@tab

保加利亚语，白俄罗斯语，马其顿语，俄语，塞尔维亚语

@item

mac_greek

@tab

macgreek

@tab

希腊语

@item

mac_iceland

@tab

maciceland

@tab

冰岛语

@item

mac_latin2

@tab

maclatin2, maccentraleurope

@tab

中欧和东欧

@item

mac_roman

@tab

macroman, macintosh

@tab

西欧

@item

mac_turkish

@tab

macturkish

@tab

土耳其语

@item

ptcp154

@tab

csptcp154, pt154, cp154,
cyrillic-asian

@tab

哈萨克语

@item

shift_jis

@tab

csshiftjis, shiftjis, sjis,
s_jis

@tab

日语

@item

shift_jis_2004

@tab

shiftjis2004, sjis_2004,
sjis2004

@tab

日语

@item

shift_jisx0213

@tab

shiftjisx0213, sjisx0213,
s_jisx0213

@tab

日语

@item

utf_32

@tab

U32, utf32

@tab

所有语言

@item

utf_32_be

@tab

UTF-32BE

@tab

所有语言

@item

utf_32_le

@tab

UTF-32LE

@tab

所有语言

@item

utf_16

@tab

U16, utf16

@tab

所有语言

@item

utf_16_be

@tab

UTF-16BE

@tab

所有语言

@item

utf_16_le

@tab

UTF-16LE

@tab

所有语言

@item

utf_7

@tab

U7, unicode-1-1-utf-7

@tab

所有语言

@item

utf_8

@tab

U8, UTF, utf8, cp65001

@tab

所有语言

@item

utf_8_sig

@tab

@tab

所有语言

@end multitable



在 3.4 版更改: utf-16* 和 utf-32* 编码器将不再允许编码代理码位 (@code{U+D800}--@code{U+DFFF})。 utf-32* 解码器将不再解码与代理码位相对应的字节序列。



在 3.8 版更改: @code{cp65001} 现在是 @code{utf_8} 的一个别名。


@node Python 专属的编码格式,encodings idna --- 应用程序中的国际化域名,标准编码,codecs --- 编解码器注册和相关基类
@anchor{library/codecs python-specific-encodings}@anchor{1806}
@subsubsection Python 专属的编码格式


有一些预定义编解码器是 Python 专属的，因此它们在 Python 之外没有意义。 这些编解码器按其所预期的输入和输出类型在下表中列出（请注意虽然文本编码是编解码器最常见的使用场景，但下层的编解码器架构支持任意数据转换而不仅是文本编码）。 对于非对称编解码器，该列描述的含义是编码方向。

@menu
* 文字编码:: 
* 二进制转换:: 
* 文字转换:: 

@end menu

@node 文字编码,二进制转换,,Python 专属的编码格式
@anchor{library/codecs text-encodings}@anchor{1807}
@subsubsection 文字编码


以下编解码器提供了 @ref{329,,str} 到 @ref{32a,,bytes} 的编码和 @ref{5e3,,bytes-like object} 到 @ref{329,,str} 的解码，类似于 Unicode 文本编码。


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

编码

@tab

别名

@tab

含义

@item

idna

@tab

@tab

实现 
@geindex RFC; RFC 3490
RFC 3490@footnote{https://tools.ietf.org/html/rfc3490.html}，另请参阅 @ref{77,,encodings.idna} 。仅支持 @code{errors='strict'} 。

@item

mbcs

@tab

ansi,
dbcs

@tab

Windows 专属：根据 ANSI 代码页（CP_ACP）对操作数进行编码。

@item

oem

@tab

@tab

Windows 专属：根据 OEM 代码页（CP_OEMCP）对操作数进行编码。


3.6 新版功能.


@item

palmos

@tab

@tab

PalmOS 3.5 的编码格式

@item

punycode

@tab

@tab

实现 
@geindex RFC; RFC 3492
RFC 3492@footnote{https://tools.ietf.org/html/rfc3492.html}。 不支持有状态编解码器。

@item

raw_unicode_escape

@tab

@tab

Latin-1 编码格式附带对其他码位以 @code{\uXXXX} 和 @code{\UXXXXXXXX} 进行编码。 现有反斜杠不会以任何方式转义。 它被用于 Python 的 pickle 协议。

@item

undefined

@tab

@tab

所有转换都将引发异常，甚至对空字符串也不例外。 错误处理方案会被忽略。

@item

unicode_escape

@tab

@tab

适合用于以 ASCII 编码的 Python 源代码中的 Unicode 字面值内容的编码格式，但引号不会被转义。 对 Latin-1 源代码进行解码。 请注意 Python 源代码实际上默认使用 UTF-8。

@end multitable



在 3.8 版更改: "unicode_internal" 编解码器已被移除。


@node 二进制转换,文字转换,文字编码,Python 专属的编码格式
@anchor{library/codecs binary-transforms}@anchor{7fe}@anchor{library/codecs id4}@anchor{1808}
@subsubsection 二进制转换


以下编解码器提供了二进制转换: @ref{5e3,,bytes-like object} 到 @ref{32a,,bytes} 的映射。 它们不被 @ref{c31,,bytes.decode()} 所支持（该方法只生成 @ref{329,,str} 类型的输出）。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

编码

@tab

别名

@tab

含义

@tab

编码器/解码器

@item

base64_codec @footnote{@w{(1)} 
除了 @ref{5e3,,字节类对象}，@code{'base64_codec'} 也接受仅包含 ASCII 的 @ref{329,,str} 实例用于解码
}

@tab

base64, base_64

@tab

将操作数转换为多行 MIME base64 (结果总是包含一个末尾的 @code{'\n'})


在 3.4 版更改: 接受任意 @ref{5e3,,bytes-like object} 作为输入用于编码和解码


@tab

@ref{1809,,base64.encodebytes()} /
@ref{180a,,base64.decodebytes()}

@item

bz2_codec

@tab

bz2

@tab

使用bz2压缩操作数

@tab

@ref{180b,,bz2.compress()} /
@ref{9d1,,bz2.decompress()}

@item

hex_codec

@tab

hex

@tab

将操作数转换为十六进制表示，每个字节有两位数

@tab

@ref{180c,,binascii.b2a_hex()} /
@ref{180d,,binascii.a2b_hex()}

@item

quopri_codec

@tab

quopri,
quotedprintable,
quoted_printable

@tab

将操作数转换为 MIME 带引号的可打印数据

@tab

@ref{180e,,quopri.encode()} 且 @code{quotetabs=True} / @ref{180f,,quopri.decode()}

@item

uu_codec

@tab

uu

@tab

使用uuencode转换操作数

@tab

@ref{407,,uu.encode()} /
@ref{1810,,uu.decode()}

@item

zlib_codec

@tab

zip, zlib

@tab

使用gzip压缩操作数

@tab

@ref{5b9,,zlib.compress()} /
@ref{5ba,,zlib.decompress()}

@end multitable



3.2 新版功能: 恢复二进制转换。



在 3.4 版更改: 恢复二进制转换的别名。


@node 文字转换,,二进制转换,Python 专属的编码格式
@anchor{library/codecs id6}@anchor{1811}@anchor{library/codecs text-transforms}@anchor{7ff}
@subsubsection 文字转换


以下编解码器提供了文本转换: @ref{329,,str} 到 @ref{329,,str} 的映射。 它不被 @ref{c30,,str.encode()} 所支持（该方法只生成 @ref{32a,,bytes} 类型的输出）。


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

编码

@tab

别名

@tab

含义

@item

rot_13

@tab

rot13

@tab

返回操作数的凯撒密码加密结果

@end multitable



3.2 新版功能: 恢复 @code{rot_13} 文本转换。



在 3.4 版更改: 恢复 @code{rot13} 别名。


@node encodings idna --- 应用程序中的国际化域名,encodings mbcs --- Windows ANSI代码页,Python 专属的编码格式,codecs --- 编解码器注册和相关基类
@anchor{library/codecs encodings-idna-internationalized-domain-names-in-applications}@anchor{1812}@anchor{library/codecs module-encodings idna}@anchor{77}
@subsubsection @code{encodings.idna} --- 应用程序中的国际化域名


@geindex encodings.idna (模块)

此模块实现了 
@geindex RFC; RFC 3490
RFC 3490@footnote{https://tools.ietf.org/html/rfc3490.html} (应用程序中的国际化域名) 和 
@geindex RFC; RFC 3492
RFC 3492@footnote{https://tools.ietf.org/html/rfc3492.html} (Nameprep: 用于国际化域名 (IDN) 的 Stringprep 配置文件)。 它是在 @code{punycode} 编码格式和 @ref{f7,,stringprep} 的基础上构建的。

这些 RFC 共同定义了一个在域名中支持非 ASCII 字符的协议。 一个包含非 ASCII 字符的域名 (例如 @code{www.Alliancefrançaise.nu}) 会被转换为兼容 ASCII 的编码格式 (简称 ACE，例如 @code{www.xn--alliancefranaise-npb.nu})。 随后此域名的 ACE 形式可以用于所有由于特定协议而不允许使用任意字符的场合，例如 DNS 查询，HTTP @code{Host} 字段等等。 此转换是在应用中进行的；如有可能将对用户可见：应用应当透明地将 Unicode 域名标签转换为线上的 IDNA，并在 ACE 标签被呈现给用户之前将其转换回 Unicode。

Python 以多种方式支持这种转换:  @code{idna} 编解码器执行 Unicode 和 ACE 之间的转换，基于在 
@geindex RFC; RFC 3490#section-3.1
section 3.1 of RFC 3490@footnote{https://tools.ietf.org/html/rfc3490.html#section-3.1} 中定义的分隔字符将输入字符串拆分为标签，再根据需要将每个标签转换为 ACE，相反地又会基于 @code{.} 分隔符将输入字节串拆分为标签，再将找到的任何 ACE 标签转换为 Unicode。 此外，@ref{ef,,socket} 模块可透明地将 Unicode 主机名转换为 ACE，以便应用在将它们传给 socket 模块时无须自行转换主机名。 除此之外，许多包含以主机名作为函数参数的模块例如 @ref{94,,http.client} 和 @ref{84,,ftplib} 都接受 Unicode 主机名（并且 @ref{94,,http.client} 也会在 @code{Host} 字段中透明地发送 IDNA 主机名，如果它需要发送该字段的话）。

当从线路接收主机名时（例如反向名称查找），到 Unicode 的转换不会自动被执行：希望向用户提供此种主机名的应用应当将它们解码为 Unicode。

@ref{77,,encodings.idna} 模块还实现了 nameprep 过程，该过程会对主机名执行特定的规范化操作，以实现国际域名的大小写不敏感特性与合并相似的字符。 如果有需要可以直接使用 nameprep 函数。

@geindex nameprep() (在 encodings.idna 模块中)
@anchor{library/codecs encodings idna nameprep}@anchor{1813}
@deffn {函数} encodings.idna.nameprep (label)

返回 @emph{label} 经过名称处理操作的版本。 该实现目前基于查询字符串，因此 @code{AllowUnassigned} 为真值。
@end deffn

@geindex ToASCII() (在 encodings.idna 模块中)
@anchor{library/codecs encodings idna ToASCII}@anchor{1814}
@deffn {函数} encodings.idna.ToASCII (label)

将标签转换为 ASCII，规则定义见 
@geindex RFC; RFC 3490
RFC 3490@footnote{https://tools.ietf.org/html/rfc3490.html}。 @code{UseSTD3ASCIIRules} 预设为假值。
@end deffn

@geindex ToUnicode() (在 encodings.idna 模块中)
@anchor{library/codecs encodings idna ToUnicode}@anchor{1815}
@deffn {函数} encodings.idna.ToUnicode (label)

将标签转换为 Unicode，规则定义见 
@geindex RFC; RFC 3490
RFC 3490@footnote{https://tools.ietf.org/html/rfc3490.html}。
@end deffn

@node encodings mbcs --- Windows ANSI代码页,encodings utf_8_sig --- 带BOM签名的UTF-8编解码器,encodings idna --- 应用程序中的国际化域名,codecs --- 编解码器注册和相关基类
@anchor{library/codecs encodings-mbcs-windows-ansi-codepage}@anchor{1816}@anchor{library/codecs module-encodings mbcs}@anchor{78}
@subsubsection @code{encodings.mbcs} --- Windows ANSI代码页


@geindex encodings.mbcs (模块)

此模块实现ANSI代码页（CP_ACP）。

@ref{12f5,,Availability}: 仅Windows可用


在 3.3 版更改: 支持任何错误处理



在 3.2 版更改: 在 3.2 版之前， @emph{errors} 参数会被忽略；总是会使用 @code{'replace'} 进行编码，并使用 @code{'ignore'} 进行解码。


@node encodings utf_8_sig --- 带BOM签名的UTF-8编解码器,,encodings mbcs --- Windows ANSI代码页,codecs --- 编解码器注册和相关基类
@anchor{library/codecs encodings-utf-8-sig-utf-8-codec-with-bom-signature}@anchor{1817}@anchor{library/codecs module-encodings utf_8_sig}@anchor{79}
@subsubsection @code{encodings.utf_8_sig} --- 带BOM签名的UTF-8编解码器


@geindex encodings.utf_8_sig (模块)

此模块实现了 UTF-8 编解码器的一个变种：在编码时将把 UTF-8 已编码 BOM 添加到 UTF-8 编码字节数据的开头。 对于有状态编码器此操作只执行一次（当首次写入字节流时）。 在解码时将跳过数据开头作为可选项的 UTF-8 已编码 BOM。

@node 数据类型,数字和数学模块,二进制数据服务,Python 标准库
@anchor{library/datatypes doc}@anchor{1818}@anchor{library/datatypes data-types}@anchor{1819}@anchor{library/datatypes datatypes}@anchor{181a}
@section 数据类型


本章所描述的模块提供了许多专门的数据类型，如日期和时间、固定类型的数组、堆队列、双端队列、以及枚举。

Python也提供一些内置数据类型，特别是，@ref{1b8,,dict}、 @ref{262,,list}、@ref{b68,,set}、@ref{be7,,frozenset}、以及 @ref{478,,tuple}。@ref{329,,str} 这个类是用来存储Unicode字符串的，而 @ref{32a,,bytes} 和 @ref{32b,,bytearray} 这两个类是用来存储二进制数据的。

本章包含以下模块的文档：

@menu
* datetime: datetime --- 基本的日期和时间类型. 基本的日期和时间类型
* calendar: calendar --- 日历相关函数. 日历相关函数
* collections: collections --- 容器数据类型. 容器数据类型
* collections.abc: collections abc --- 容器的抽象基类. 容器的抽象基类
* heapq: heapq --- 堆队列算法. 堆队列算法
* bisect: bisect --- 数组二分查找算法. 数组二分查找算法
* array: array --- 高效的数值数组. 高效的数值数组
* weakref: weakref --- 弱引用. 弱引用
* types: types --- 动态类型创建和内置类型名称. 动态类型创建和内置类型名称
* copy: copy --- 浅层 shallow 和深层 deep 复制操作. 浅层 (shallow) 和深层 (deep) 复制操作
* pprint: pprint --- 数据美化输出. 数据美化输出
* reprlib: reprlib --- 另一种 repr 实现. 另一种 repr() 实现
* enum: enum --- 对枚举的支持. 对枚举的支持

@end menu

@node datetime --- 基本的日期和时间类型,calendar --- 日历相关函数,,数据类型
@anchor{library/datetime doc}@anchor{181b}@anchor{library/datetime datetime-basic-date-and-time-types}@anchor{181c}@anchor{library/datetime module-datetime}@anchor{31}
@subsection @code{datetime} --- 基本的日期和时间类型


@geindex datetime (模块)

@strong{源代码：} Lib/datetime.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/datetime.py}


__________________________________________________________________


@c XXX what order should the types be discussed in?

@ref{31,,datetime} 模块提供用于处理日期和时间的类。

在支持日期时间数学运算的同时，实现的关注点更着重于如何能够更有效地解析其属性用于格式化输出和数据操作。


@subsubheading 参见



@table @asis

@item 模块 @ref{15,,calendar}

通用日历相关函数

@item 模块 @ref{10a,,time}

时间的访问和转换

@item dateutil@footnote{https://dateutil.readthedocs.io/en/stable/} 包

具有扩展时区和解析支持的第三方库。
@end table


@menu
* 感知型对象和简单型对象:: 
* 常量:: 
* 有效的类型:: 
* timedelta 类对象:: 
* date 对象:: 
* datetime 对象:: 
* time 对象:: 
* tzinfo 对象:: 
* timezone 对象:: 
* strftime() 和 strptime() 的行为: strftime 和 strptime 的行为. 

@end menu

@node 感知型对象和简单型对象,常量,,datetime --- 基本的日期和时间类型
@anchor{library/datetime aware-and-naive-objects}@anchor{181d}@anchor{library/datetime datetime-naive-aware}@anchor{181e}
@subsubsection 感知型对象和简单型对象


日期和时间对象可以根据它们是否包含时区信息而分为“感知型”和“简单型”两类。

充分掌握应用性算法和政治性时间调整信息例如时区和夏令时的情况下，一个 @strong{感知型} 对象就能相对于其他感知型对象来精确定位自身时间点。 感知型对象是用来表示一个没有解释空间的固定时间点。 @footnote{@w{(1)} 
就是说如果我们忽略相对论效应的话。
}

@strong{简单型} 对象没有包含足够多的信息来无歧义地相对于其他 date/time 对象来定位自身时间点。 不论一个简单型对象所代表的是世界标准时间（UTC）、当地时间还是某个其他时区的时间完全取决于具体程序，就像一个特定数字所代表的是米、英里还是质量完全取决于具体程序一样。 简单型对象更易于理解和使用，代价则是忽略了某些现实性考量。

对于要求感知型对象的应用，@ref{194,,datetime} 和 @ref{4ed,,time} 对象具有一个可选的时区信息属性 @code{tzinfo}，它可被设为抽象类 @ref{378,,tzinfo} 的子类的一个实例。 这些 @ref{378,,tzinfo} 对象会捕获与 UTC 时间的差值、时区名称以及夏令时是否生效等信息。

@ref{31,,datetime} 模块只提供了一个具体的 @ref{378,,tzinfo} 类，即 @ref{9fb,,timezone} 类。 @ref{9fb,,timezone} 类可以表示具有相对于 UTC 的固定时差的简单时区，例如 UTC 本身或北美的 EST 和 EDT 时区等。 支持时间的详细程度取决于具体的应用。 世界各地的时间调整规则往往是政治性多于合理性，经常会发生变化，除了 UTC 之外并没有一个能适合所有应用的标准。

@node 常量,有效的类型,感知型对象和简单型对象,datetime --- 基本的日期和时间类型
@anchor{library/datetime constants}@anchor{181f}
@subsubsection 常量


The @ref{31,,datetime} module exports the following constants:

@geindex MINYEAR() (在 datetime 模块中)
@anchor{library/datetime datetime MINYEAR}@anchor{1820}
@deffn {数据} datetime.MINYEAR

@ref{193,,date} 或者 @ref{194,,datetime} 对象允许的最小年份。 常量 @ref{1820,,MINYEAR} 是 @code{1} 。
@end deffn

@geindex MAXYEAR() (在 datetime 模块中)
@anchor{library/datetime datetime MAXYEAR}@anchor{1821}
@deffn {数据} datetime.MAXYEAR

@ref{193,,date} 或 @ref{194,,datetime} 对象允许最大的年份。常量 @ref{1821,,MAXYEAR} 是 @code{9999} 。
@end deffn

@node 有效的类型,timedelta 类对象,常量,datetime --- 基本的日期和时间类型
@anchor{library/datetime available-types}@anchor{1822}
@subsubsection 有效的类型



@deffn {类} datetime.date

一个理想化的简单型日期，它假设当今的公历在过去和未来永远有效。 属性: @ref{1823,,year}, @ref{1824,,month}, and @ref{1825,,day}。
@end deffn


@deffn {类} datetime.time

一个独立于任何特定日期的理想化时间，它假设每一天都恰好等于 24*60*60 秒。 （这里没有“闰秒”的概念。） 包含属性: @ref{1826,,hour}, @ref{1827,,minute}, @ref{1828,,second}, @ref{1829,,microsecond} 和 @ref{182a,,tzinfo}。
@end deffn


@deffn {类} datetime.datetime

日期和时间的结合。属性：@ref{182b,,year}, @ref{182c,,month}, @ref{182d,,day}, @ref{182e,,hour}, @ref{182f,,minute}, @ref{1830,,second}, @ref{1831,,microsecond}, and @ref{1832,,tzinfo}.
@end deffn


@deffn {类} datetime.timedelta

表示两个 @ref{193,,date} 对象或者 @ref{4ed,,time} 对象,或者 @ref{194,,datetime} 对象之间的时间间隔，精确到微秒。
@end deffn


@deffn {类} datetime.tzinfo

一个描述时区信息对象的抽象基类。 用来给 @ref{194,,datetime} 和 @ref{4ed,,time} 类提供自定义的时间调整概念（例如处理时区和/或夏令时）。
@end deffn


@deffn {类} datetime.timezone

一个实现了 @ref{378,,tzinfo} 抽象基类的子类，用于表示相对于 世界标准时间（UTC）的偏移量。


3.2 新版功能.

@end deffn

这些类型的对象都是不可变的。

子类关系

@example
object
    timedelta
    tzinfo
        timezone
    time
    date
        datetime
@end example

@menu
* 通用的特征属性:: 
* 确定一个对象是感知型还是简单型:: 

@end menu

@node 通用的特征属性,确定一个对象是感知型还是简单型,,有效的类型
@anchor{library/datetime common-properties}@anchor{1833}
@subsubsection 通用的特征属性


@ref{193,,date}, @ref{194,,datetime}, @ref{4ed,,time} 和 @ref{9fb,,timezone} 类型共享这些通用特性:


@itemize -

@item 
这些类型的对象都是不可变的。

@item 
这些类型的对象是可哈希的，这意味着它们可被作为字典的键。

@item 
这些类型的对象支持通过 @ref{ca,,pickle} 模块进行高效的封存。
@end itemize

@node 确定一个对象是感知型还是简单型,,通用的特征属性,有效的类型
@anchor{library/datetime determining-if-an-object-is-aware-or-naive}@anchor{1834}
@subsubsection 确定一个对象是感知型还是简单型


@ref{193,,date}  类型的对象都是简单型的。

@ref{4ed,,time} 或 @ref{194,,datetime} 类型的对象可以是感知型或者简单型。

一个 @ref{194,,datetime} 对象 @emph{d} 在以下条件同时成立时将是感知型的：


@enumerate 

@item 
@code{d.tzinfo} 不为 @code{None}

@item 
@code{d.tzinfo.utcoffset(d)} 不返回 @code{None}
@end enumerate

在其他情况下，@emph{d} 将是简单型的。

一个 @ref{4ed,,time} 对象 @emph{t} 在以下条件同时成立时将是感知型的：


@enumerate 

@item 
@code{t.tzinfo} 不为 @code{None}

@item 
@code{t.tzinfo.utcoffset(None)} 不返回 @code{None}。
@end enumerate

在其他情况下，@emph{t} 将是简单型的。

感知型和简单型之间的区别不适用于 @ref{195,,timedelta} 对象。

@node timedelta 类对象,date 对象,有效的类型,datetime --- 基本的日期和时间类型
@anchor{library/datetime datetime-timedelta}@anchor{1835}@anchor{library/datetime timedelta-objects}@anchor{1836}
@subsubsection @code{timedelta} 类对象


@ref{195,,timedelta} 对象表示两个 date 或者 time 的时间间隔。

@geindex timedelta (datetime 中的类)
@anchor{library/datetime datetime timedelta}@anchor{195}
@deffn {类} datetime.timedelta (days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)

所有参数都是可选的并且默认为 @code{0}。 这些参数可以是整数或者浮点数，也可以是正数或者负数。

只有 @emph{days}, @emph{seconds} 和 @emph{microseconds} 会存储在内部。 参数单位的换算规则如下：


@itemize *

@item 
1毫秒会转换成1000微秒。

@item 
1分钟会转换成60秒。

@item 
1小时会转换成3600秒。

@item 
1星期会转换成7天。
@end itemize

并且 days, seconds, microseconds 会经标准化处理以保证表达方式的唯一性，即：


@itemize *

@item 
@code{0 <= microseconds < 1000000}

@item 
@code{0 <= seconds < 3600*24} (一天的秒数)

@item 
@code{-999999999 <= days <= 999999999}
@end itemize

下面的例子演示了如何对 @emph{days}, @emph{seconds} 和 @emph{microseconds} 以外的任意参数执行“合并”操作并标准化为以上三个结果属性:

@example
>>> from datetime import timedelta
>>> delta = timedelta(
...     days=50,
...     seconds=27,
...     microseconds=10,
...     milliseconds=29000,
...     minutes=5,
...     hours=8,
...     weeks=2
... )
>>> # Only days, seconds, and microseconds remain
>>> delta
datetime.timedelta(days=64, seconds=29156, microseconds=10)
@end example

在有任何参数为浮点型并且 microseconds 值为小数的情况下，从所有参数中余下的微秒数将被合并，并使用四舍五入偶不入奇的规则将总计值舍入到最接近的整数微秒值。 如果没有任何参数为浮点型的情况下，则转换和标准化过程将是完全精确的（不会丢失信息）。

如果标准化后的 days 数值超过了指定范围，将会抛出 @ref{95a,,OverflowError} 异常。

请注意对负数值进行标准化的结果可能会令人感到惊讶。 例如:

@example
>>> from datetime import timedelta
>>> d = timedelta(microseconds=-1)
>>> (d.days, d.seconds, d.microseconds)
(-1, 86399, 999999)
@end example
@end deffn

类属性：

@geindex min (datetime.timedelta 属性)
@anchor{library/datetime datetime timedelta min}@anchor{1837}
@deffn {属性} timedelta.min

The most negative @ref{195,,timedelta} object, @code{timedelta(-999999999)}.
@end deffn

@geindex max (datetime.timedelta 属性)
@anchor{library/datetime datetime timedelta max}@anchor{1838}
@deffn {属性} timedelta.max

The most positive @ref{195,,timedelta} object, @code{timedelta(days=999999999,
hours=23, minutes=59, seconds=59, microseconds=999999)}.
@end deffn

@geindex resolution (datetime.timedelta 属性)
@anchor{library/datetime datetime timedelta resolution}@anchor{1839}
@deffn {属性} timedelta.resolution

两个不相等的 @ref{195,,timedelta} 类对象最小的间隔为 @code{timedelta(microseconds=1)}。
@end deffn

需要注意的是，因为标准化的缘故，@code{timedelta.max} > @code{-timedelta.min}，@code{-timedelta.max} 不可以表示一个 @ref{195,,timedelta} 类对象。

实例属性（只读）：


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性

@tab

值

@item

@code{days}

@tab

-999999999 至 999999999 ，含999999999

@item

@code{seconds}

@tab

0 至 86399，包含86399

@item

@code{microseconds}

@tab

0 至 999999，包含999999

@end multitable


支持的运算：

@c XXX this table is too wide!


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@item

@code{t1 = t2 + t3}

@tab

@emph{t2} 和 @emph{t3} 的和。 运算后 @emph{t1}-@emph{t2} == @emph{t3} and @emph{t1}-@emph{t3} == @emph{t2} 必为真值。(1)

@item

@code{t1 = t2 - t3}

@tab

@emph{t2} 减 @emph{t3} 的差。 运算后 @emph{t1} == @emph{t2} - @emph{t3} and @emph{t2} == @emph{t1} + @emph{t3} 必为真值。 (1)(6)

@item

@code{t1 = t2 * i or t1 = i * t2}

@tab

乘以一个整数。运算后假如 @code{i != 0} 则 @emph{t1} // i == @emph{t2} 必为真值。

@item

@tab

In general, @emph{t1} * i == @emph{t1} * (i-1) + @emph{t1}
is true. (1)

@item

@code{t1 = t2 * f or t1 = f * t2}

@tab

乘以一个浮点数，结果会被舍入到 timedelta 最接近的整数倍。 精度使用四舍五偶入奇不入规则。

@item

@code{f = t2 / t3}

@tab

总时间 @emph{t2} 除以间隔单位 @emph{t3} (3)。 返回一个 @ref{187,,float} 对象。

@item

@code{t1 = t2 / f or t1 = t2 / i}

@tab

除以一个浮点数或整数。 结果会被舍入到 timedelta 最接近的整数倍。 精度使用四舍五偶入奇不入规则。

@item

@code{t1 = t2 // i} or
@code{t1 = t2 // t3}

@tab

计算底数，其余部分（如果有）将被丢弃。在第二种情况下，将返回整数。 （3）

@item

@code{t1 = t2 % t3}

@tab

余数为一个 @ref{195,,timedelta} 对象。(3)

@item

@code{q, r = divmod(t1, t2)}

@tab

通过 : @code{q = t1 // t2} (3) and @code{r = t1 % t2} 计算出商和余数。q是一个整数，r是一个 @ref{195,,timedelta} 对象。

@item

@code{+t1}

@tab

返回一个相同数值的 @ref{195,,timedelta} 对象。

@item

@code{-t1}

@tab

等价于 @ref{195,,timedelta}(-@emph{t1.days}, -@emph{t1.seconds}, -@emph{t1.microseconds}), 和 @emph{t1}* -1. (1)(4)

@item

@code{abs(t)}

@tab

当 @code{t.days >= 0`@w{`}时等于 +\ *t*, 当 `@w{`}t.days < 0} 时 -@emph{t} 。 (2)

@item

@code{str(t)}

@tab

返回一个形如 @code{[D day[s], ][H]H:MM:SS[.UUUUUU]} 的字符串，当 @code{t} 为负数的时候，  D 也为负数。 (5)

@item

@code{repr(t)}

@tab

返回一个 @ref{195,,timedelta} 对象的字符串表示形式，作为附带正规属性值的构造器调用。

@end multitable


注释:


@enumerate 

@item 
结果正确，但可能会溢出。

@item 
结果正确，不会溢出。

@item 
除以0将会抛出异常  @ref{1241,,ZeroDivisionError} 。

@item 
-@emph{timedelta.max} 不是一个 @ref{195,,timedelta} 类对象。

@item 
@ref{195,,timedelta} 对象的字符串表示形式类似于其内部表示形式被规范化。对于负时间增量，这会导致一些不寻常的结果。例如:

@example
>>> timedelta(hours=-5)
datetime.timedelta(days=-1, seconds=68400)
>>> print(_)
-1 day, 19:00:00
@end example

@item 
表达式 @code{t2 - t3} 通常与 @code{t2 + (-t3)} 是等价的，除非 t3 等于 @code{timedelta.max}; 在这种情况下前者会返回结果，而后者则会溢出。
@end enumerate

除了上面列举的操作以外，@ref{195,,timedelta} 对象还支持与 @ref{193,,date} 和 @ref{194,,datetime} 对象进行特定的相加和相减运算（见下文）。


在 3.2 版更改: 现在已支持 @ref{195,,timedelta} 对象与另一个 @ref{195,,timedelta} 对象相整除或相除，包括求余运算和 @ref{152,,divmod()} 函数。 现在也支持 @ref{195,,timedelta} 对象加上或乘以一个 @ref{187,,float} 对象。


支持 @ref{195,,timedelta} 对象之间进行比较，但其中有一些注意事项。

@code{==} 或 @code{!=} 比较 @emph{总是} 返回一个 @ref{183,,bool} 对象，无论被比较的对象是什么类型:

@example
>>> from datetime import timedelta
>>> delta1 = timedelta(seconds=57)
>>> delta2 = timedelta(hours=25, seconds=2)
>>> delta2 != delta1
True
>>> delta2 == 5
False
@end example

对于所有其他比较 (例如 @code{<} 和 @code{>})，当一个 @ref{195,,timedelta} 对象与其他类型的对象比较时，将引发 @ref{192,,TypeError}:

@example
>>> delta2 > delta1
True
>>> delta2 > 5
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '>' not supported between instances of 'datetime.timedelta' and 'int'
@end example

在布尔运算中，@ref{195,,timedelta} 对象当且仅当其不等于 @code{timedelta(0)} 时则会被视为真值。

实例方法：

@geindex total_seconds() (datetime.timedelta 方法)
@anchor{library/datetime datetime timedelta total_seconds}@anchor{c95}
@deffn {方法} timedelta.total_seconds ()

返回时间间隔包含了多少秒。造价于 @code{td / timedelta(seconds=1)}。对于其它单位可以直接使用除法的形式 (例如  @code{td / timedelta(microseconds=1)})。

需要注意的是，时间间隔较大时，这个方法的结果中的微秒将会失真（大多数平台上大于270年视为一个较大的时间间隔）。


3.2 新版功能.

@end deffn

@menu
* class;timedelta 用法示例: class timedelta 用法示例. 

@end menu

@node class timedelta 用法示例,,,timedelta 类对象
@anchor{library/datetime examples-of-usage-timedelta}@anchor{183a}
@subsubsection class:@cite{timedelta} 用法示例


一个标准化的附加示例:

@example
>>> # Components of another_year add up to exactly 365 days
>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> another_year = timedelta(weeks=40, days=84, hours=23,
...                          minutes=50, seconds=600)
>>> year == another_year
True
>>> year.total_seconds()
31536000.0
@end example

@ref{195,,timedelta} 算术运算的示例:

@example
>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> ten_years = 10 * year
>>> ten_years
datetime.timedelta(days=3650)
>>> ten_years.days // 365
10
>>> nine_years = ten_years - year
>>> nine_years
datetime.timedelta(days=3285)
>>> three_years = nine_years // 3
>>> three_years, three_years.days // 365
(datetime.timedelta(days=1095), 3)
@end example

@node date 对象,datetime 对象,timedelta 类对象,datetime --- 基本的日期和时间类型
@anchor{library/datetime date-objects}@anchor{183b}@anchor{library/datetime datetime-date}@anchor{183c}
@subsubsection @code{date} 对象


@ref{193,,date} 对象代表一个理想化历法中的日期（年、月和日），即当今的格列高利历向前后两个方向无限延伸。

公元 1 年 1 月 1日是第 1 日，公元 1 年 1 月 2 日是第 2 日，依此类推。 @footnote{@w{(2)} 
这与 Dershowitz 和 Reingold 所著 @emph{Calendrical Calculations} 中“预期格列高利”历法的定义一致，它是适用于该书中所有运算的基础历法。 请参阅该书了解在预期格利高利历序列与许多其他历法系统之间进行转换的算法。
}

@geindex date (datetime 中的类)
@anchor{library/datetime datetime date}@anchor{193}
@deffn {类} datetime.date (year, month, day)

所有参数都是必要的。 参数必须是在下面范围内的整数：


@itemize *

@item 
@code{MINYEAR <= year <= MAXYEAR}

@item 
@code{1 <= month <= 12}

@item 
@code{1 <= 日期 <= 给定年月对应的天数}
@end itemize

如果参数不在这些范围内，则抛出 @ref{1fb,,ValueError} 异常。
@end deffn

其它构造器，所有的类方法：

@geindex today() (datetime.date 类方法)
@anchor{library/datetime datetime date today}@anchor{183d}
@deffn {方法} classmethod date.today ()

返回当前的本地日期。

这等价于 @code{date.fromtimestamp(time.time())}。
@end deffn

@geindex fromtimestamp() (datetime.date 类方法)
@anchor{library/datetime datetime date fromtimestamp}@anchor{183e}
@deffn {方法} classmethod date.fromtimestamp (timestamp)

返回对应于 POSIX 时间戳的当地时间，例如 @ref{316,,time.time()} 返回的就是时间戳。

这可能引发 @ref{95a,,OverflowError}，如果时间戳数值超出所在平台 C @code{localtime()} 函数的支持范围的话，并且会在 @code{localtime()} 出错时引发 @ref{1d3,,OSError}。 通常该数值会被限制在 1970 年至 2038 年之间。 请注意在时间戳概念包含闰秒的非 POSIX 系统上，闰秒会被 @ref{183e,,fromtimestamp()} 所忽略。


在 3.3 版更改: 引发 @ref{95a,,OverflowError} 而不是 @ref{1fb,,ValueError}，如果时间戳数值超出所在平台 C @code{localtime()} 函数的支持范围的话，并会在 @code{localtime()} 出错时引发 @ref{1d3,,OSError} 而不是 @ref{1fb,,ValueError}。

@end deffn

@geindex fromordinal() (datetime.date 类方法)
@anchor{library/datetime datetime date fromordinal}@anchor{183f}
@deffn {方法} classmethod date.fromordinal (ordinal)

返回对应于预期格列高利历序号的日期，其中公元 1 年 1 月 1 晶的序号为 1。

除非 @code{1 <= ordinal <= date.max.toordinal()} 否则会引发 @ref{1fb,,ValueError}。对于任意日期 @emph{d}，@code{date.fromordinal(d.toordinal()) == d}。
@end deffn

@geindex fromisoformat() (datetime.date 类方法)
@anchor{library/datetime datetime date fromisoformat}@anchor{102a}
@deffn {方法} classmethod date.fromisoformat (date_string)

返回一个对应于以 @code{YYYY-MM-DD} 格式给出的 @emph{date_string} 的 @ref{193,,date} 对象:

@example
>>> from datetime import date
>>> date.fromisoformat('2019-12-04')
datetime.date(2019, 12, 4)
@end example

这是 @ref{1840,,date.isoformat()} 的逆操作。 它只支持 @code{YYYY-MM-DD} 格式。


3.7 新版功能.

@end deffn

@geindex fromisocalendar() (datetime.date 类方法)
@anchor{library/datetime datetime date fromisocalendar}@anchor{1c4}
@deffn {方法} classmethod date.fromisocalendar (year, week, day)

返回指定 year, week 和 day 所对应 ISO 历法日期的 @ref{193,,date}。 这是函数 @ref{1841,,date.isocalendar()} 的逆操作。


3.8 新版功能.

@end deffn

类属性：

@geindex min (datetime.date 属性)
@anchor{library/datetime datetime date min}@anchor{1842}
@deffn {属性} date.min

最小的日期 @code{date(MINYEAR, 1, 1)} 。
@end deffn

@geindex max (datetime.date 属性)
@anchor{library/datetime datetime date max}@anchor{1843}
@deffn {属性} date.max

最大的日期 ，@code{date(MAXYEAR, 12, 31)}。
@end deffn

@geindex resolution (datetime.date 属性)
@anchor{library/datetime datetime date resolution}@anchor{1844}
@deffn {属性} date.resolution

两个日期对象的最小间隔，@code{timedelta(days=1)}。
@end deffn

实例属性（只读）：

@geindex year (datetime.date 属性)
@anchor{library/datetime datetime date year}@anchor{1823}
@deffn {属性} date.year

在 @ref{1820,,MINYEAR} 和 @ref{1821,,MAXYEAR} 之间，包含边界。
@end deffn

@geindex month (datetime.date 属性)
@anchor{library/datetime datetime date month}@anchor{1824}
@deffn {属性} date.month

1 至 12（含）
@end deffn

@geindex day (datetime.date 属性)
@anchor{library/datetime datetime date day}@anchor{1825}
@deffn {属性} date.day

返回1到指定年月的天数间的数字。
@end deffn

支持的运算：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@item

@code{date2 = date1 + timedelta}

@tab

@emph{date2} 等于从 @emph{date1} 减去 @code{timedelta.days} 天。 (1)

@item

@code{date2 = date1 - timedelta}

@tab

计算 @emph{date2} 的值使得 @code{date2 + timedelta == date1}。 (2)

@item

@code{timedelta = date1 - date2}

@tab

(3)

@item

@code{date1 < date2}

@tab

如果 @emph{date1} 的时间在 @emph{date2} 之前则认为 @emph{date1} 小于 @emph{date2} 。 (4)

@end multitable


注释:


@enumerate 

@item 
如果 @code{timedelta.days > 0} 则 @emph{date2} 将在时间线上前进，如果 @code{timedelta.days < 0} 则将后退。 操作完成后 @code{date2 - date1 == timedelta.days}。 @code{timedelta.seconds} 和 @code{timedelta.microseconds} 会被忽略。 如果 @code{date2.year} 将小于 @ref{1820,,MINYEAR} 或大于 @ref{1821,,MAXYEAR} 则会引发 @ref{95a,,OverflowError}。

@item 
@code{timedelta.seconds} 和 @code{timedelta.microseconds} 会被忽略。

@item 
此值完全精确且不会溢出。 操作完成后 timedelta.seconds 和 timedelta.microseconds 均为 0，并且 date2 + timedelta == date1。

@item 
换句话说，当且仅当 @code{date1.toordinal() < date2.toordinal()} 时 @code{date1 < date2}。 日期比较会引发 @ref{192,,TypeError}，如果比较目标不为 @ref{193,,date} 对象的话。 不过也可能会返回 @code{NotImplemented}，如果比较目标具有 @code{timetuple()} 属性的话。 这个钩子给予其他日期对象类型实现混合类型比较的机会。 否则，当 @ref{193,,date} 对象与不同类型的对象比较时将会引发 @ref{192,,TypeError}，除非是 @code{==} 或 @code{!=} 比较。 后两种情况将分别返回 @ref{380,,False} 或 @ref{494,,True}。
@end enumerate

在布尔运算中，所有 @ref{193,,date} 对象都会被视为真值。

实例方法：

@geindex replace() (datetime.date 方法)
@anchor{library/datetime datetime date replace}@anchor{1845}
@deffn {方法} date.replace (year=self.year, month=self.month, day=self.day)

返回一个具有同样值的日期，除非通过任何关键字参数给出了某些形参的新值。

示例:

@example
>>> from datetime import date
>>> d = date(2002, 12, 31)
>>> d.replace(day=26)
datetime.date(2002, 12, 26)
@end example
@end deffn

@geindex timetuple() (datetime.date 方法)
@anchor{library/datetime datetime date timetuple}@anchor{1846}
@deffn {方法} date.timetuple ()

返回一个 @ref{594,,time.struct_time}，即 @ref{edc,,time.localtime()} 所返回的类型。

hours, minutes 和 seconds 值均为 0，且 DST 旗标值为 -1。

@code{d.timetuple()} 等价于:

@example
time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1))
@end example

其中 @code{yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1} 是当前年份中的日期序号，1 月 1 日的序号为 @code{1}。
@end deffn

@geindex toordinal() (datetime.date 方法)
@anchor{library/datetime datetime date toordinal}@anchor{1847}
@deffn {方法} date.toordinal ()

返回日期的预期格列高利历序号，其中公元 1 年 1 月 1 日的序号为 1。 对于任意 @ref{193,,date} 对象 @emph{d}，@code{date.fromordinal(d.toordinal()) == d}。
@end deffn

@geindex weekday() (datetime.date 方法)
@anchor{library/datetime datetime date weekday}@anchor{1848}
@deffn {方法} date.weekday ()

返回一个整数代表星期几，星期一为0，星期天为6。例如， @code{date(2002, 12, 4).weekday() == 2}，表示的是星期三。参阅 @ref{1849,,isoweekday()}。
@end deffn

@geindex isoweekday() (datetime.date 方法)
@anchor{library/datetime datetime date isoweekday}@anchor{1849}
@deffn {方法} date.isoweekday ()

返回一个整数代表星期几，星期一为1，星期天为7。例如：@code{date(2002, 12, 4).isoweekday() == 3},表示星期三。参见 @ref{1848,,weekday()}, @ref{1841,,isocalendar()}。
@end deffn

@geindex isocalendar() (datetime.date 方法)
@anchor{library/datetime datetime date isocalendar}@anchor{1841}
@deffn {方法} date.isocalendar ()

返回一个三元元组，(ISO year, ISO week number, ISO weekday) 。

ISO 历法是一种被广泛使用的格列高利历。 @footnote{@w{(3)} 
请参阅 R. H. van Gent 所著 ` ISO 8601 历法的数学指导 <@indicateurl{https://www.staff.science.uu.nl/~gent0113/calendar/isocalendar.htm}>`_ 以获取更完整的说明。
}

ISO 年由 52 或 53 个完整星期构成，每个星期开始于星期一结束于星期日。 一个 ISO 年的第一个星期就是（格列高利）历法的一年中第一个包含星期四的星期。 这被称为 1 号星期，这个星期四所在的 ISO 年与其所在的格列高利年相同。

例如，2004 年的第一天是星期四，因此 ISO 2004 年的第一个星期开始于 2003 年 12 月 29 日星期一，结束于 2004 年 1 月 4 日星期日:

@example
>>> from datetime import date
>>> date(2003, 12, 29).isocalendar()
(2004, 1, 1)
>>> date(2004, 1, 4).isocalendar()
(2004, 1, 7)
@end example
@end deffn

@geindex isoformat() (datetime.date 方法)
@anchor{library/datetime datetime date isoformat}@anchor{1840}
@deffn {方法} date.isoformat ()

返回一个以 ISO 8601 格式 @code{YYYY-MM-DD} 来表示日期的字符串:

@example
>>> from datetime import date
>>> date(2002, 12, 4).isoformat()
'2002-12-04'
@end example

这是 @ref{102a,,date.fromisoformat()} 的逆操作。
@end deffn

@geindex __str__() (datetime.date 方法)
@anchor{library/datetime datetime date __str__}@anchor{184a}
@deffn {方法} date.__str__ ()

对于日期对象 @emph{d}, @code{str(d)} 等价于 @code{d.isoformat()} 。
@end deffn

@geindex ctime() (datetime.date 方法)
@anchor{library/datetime datetime date ctime}@anchor{184b}
@deffn {方法} date.ctime ()

返回一个表示日期的字符串:

@example
>>> from datetime import date
>>> date(2002, 12, 4).ctime()
'Wed Dec  4 00:00:00 2002'
@end example

@code{d.ctime()} 等效于:

@example
time.ctime(time.mktime(d.timetuple()))
@end example

在原生 C @code{ctime()} 函数 (@ref{184c,,time.ctime()} 会发起调用该函数，但 @ref{184b,,date.ctime()} 则不会) 遵循 C 标准的平台上。
@end deffn

@geindex strftime() (datetime.date 方法)
@anchor{library/datetime datetime date strftime}@anchor{532}
@deffn {方法} date.strftime (format)

返回一个由显式格式字符串所指明的代表日期的字符串。 表示时、分或秒的格式代码值将为 0。 要获取格式指令的完整列表请参阅 @ref{184d,,strftime() 和 strptime() 的行为}。
@end deffn

@geindex __format__() (datetime.date 方法)
@anchor{library/datetime datetime date __format__}@anchor{184e}
@deffn {方法} date.__format__ (format)

与 @ref{532,,date.strftime()} 相同。 此方法使得为 @ref{193,,date} 对象指定以 @ref{15c,,格式化字符串字面值} 表示的格式化字符串以及使用 @ref{4d4,,str.format()} 进行格式化成为可能。 要获取格式指令的完整列表，请参阅 @ref{184d,,strftime() 和 strptime() 的行为}。
@end deffn

@menu
* class;date 用法示例: class date 用法示例. 

@end menu

@node class date 用法示例,,,date 对象
@anchor{library/datetime examples-of-usage-date}@anchor{184f}
@subsubsection class:@cite{date} 用法示例


计算距离特定事件天数的例子:

@example
>>> import time
>>> from datetime import date
>>> today = date.today()
>>> today
datetime.date(2007, 12, 5)
>>> today == date.fromtimestamp(time.time())
True
>>> my_birthday = date(today.year, 6, 24)
>>> if my_birthday < today:
...     my_birthday = my_birthday.replace(year=today.year + 1)
>>> my_birthday
datetime.date(2008, 6, 24)
>>> time_to_birthday = abs(my_birthday - today)
>>> time_to_birthday.days
202
@end example

使用 @ref{193,,date} 的更多例子：

@example
>>> from datetime import date
>>> d = date.fromordinal(730920) # 730920th day after 1. 1. 0001
>>> d
datetime.date(2002, 3, 11)

>>> # Methods related to formatting string output
>>> d.isoformat()
'2002-03-11'
>>> d.strftime("%d/%m/%y")
'11/03/02'
>>> d.strftime("%A %d. %B %Y")
'Monday 11. March 2002'
>>> d.ctime()
'Mon Mar 11 00:00:00 2002'
>>> 'The @{1@} is @{0:%d@}, the @{2@} is @{0:%B@}.'.format(d, "day", "month")
'The day is 11, the month is March.'

>>> # Methods for to extracting 'components' under different calendars
>>> t = d.timetuple()
>>> for i in t:     
...     print(i)
2002                # year
3                   # month
11                  # day
0
0
0
0                   # weekday (0 = Monday)
70                  # 70th day in the year
-1
>>> ic = d.isocalendar()
>>> for i in ic:    
...     print(i)
2002                # ISO year
11                  # ISO week number
1                   # ISO day number ( 1 = Monday )

>>> # A date object is immutable; all operations produce a new object
>>> d.replace(year=2005)
datetime.date(2005, 3, 11)
@end example

@node datetime 对象,time 对象,date 对象,datetime --- 基本的日期和时间类型
@anchor{library/datetime datetime-datetime}@anchor{1850}@anchor{library/datetime datetime-objects}@anchor{1851}
@subsubsection @code{datetime} 对象


@ref{194,,datetime} 对象是包含来自 @ref{193,,date} 对象和 @ref{4ed,,time} 对象的所有信息的单一对象。

与 @ref{193,,date} 对象一样，@ref{194,,datetime} 假定当前的格列高利历向前后两个方向无限延伸；与 @ref{4ed,,time} 对象一样，@ref{194,,datetime} 假定每一天恰好有 3600*24 秒。

构造器 ：

@geindex datetime (datetime 中的类)
@anchor{library/datetime datetime datetime}@anchor{194}
@deffn {类} datetime.datetime (year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

@emph{year}, @emph{month} 和 @emph{day} 参数是必须的。 @emph{tzinfo} 可以是 @code{None} 或者是一个 @ref{378,,tzinfo} 子类的实例。 其余的参数必须是在下面范围内的整数：


@itemize *

@item 
@code{MINYEAR <= year <= MAXYEAR},

@item 
@code{1 <= month <= 12},

@item 
@code{1 <= day <= 指定年月的天数},

@item 
@code{0 <= hour < 24},

@item 
@code{0 <= minute < 60},

@item 
@code{0 <= second < 60},

@item 
@code{0 <= microsecond < 1000000},

@item 
@code{fold in [0, 1]}.
@end itemize

如果参数不在这些范围内，则抛出 @ref{1fb,,ValueError} 异常。


3.6 新版功能: 增加了 @code{fold} 参数。

@end deffn

其它构造器，所有的类方法：

@geindex today() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime today}@anchor{1852}
@deffn {方法} classmethod datetime.today ()

返回表示当前地方时的 datetime 对象，其中 @ref{1832,,tzinfo} 为 @code{None}。

等价于:

@example
datetime.fromtimestamp(time.time())
@end example

另请参阅 @ref{f91,,now()}, @ref{101e,,fromtimestamp()}。

此方法的功能等价于 @ref{f91,,now()}，但是不带 @code{tz} 形参。
@end deffn

@geindex now() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime now}@anchor{f91}
@deffn {方法} classmethod datetime.now (tz=None)

返回表示当前地方时的 date 和 time 对象。

如果可选参数 @emph{tz} 为 @code{None} 或未指定，这就类似于 @ref{1852,,today()}，但该方法会在可能的情况下提供比通过 @ref{316,,time.time()} 时间戳所获时间值更高的精度（例如，在提供了 C @code{gettimeofday()} 函数的平台上就可以做到这一点）。

如果 @emph{tz} 不为 @code{None}，它必须是 @ref{378,,tzinfo} 子类的一个实例，并且当前日期和时间将被转换到 @emph{tz} 时区。

此函数可以替代 @ref{1852,,today()} 和 @ref{1853,,utcnow()}。
@end deffn

@geindex utcnow() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime utcnow}@anchor{1853}
@deffn {方法} classmethod datetime.utcnow ()

返回表示当前 UTC 时间的 date 和 time，其中 @ref{1832,,tzinfo} 为 @code{None}。

这类似于 @ref{f91,,now()}，但返回的是当前 UTC 日期和时间，类型为简单型 @ref{194,,datetime} 对象。 感知型的当前 UTC 日期时间可通过调用 @code{datetime.now(timezone.utc)} 来获得。 另请参阅 @ref{f91,,now()}。

@cartouche
@quotation 警告 
由于简单型 @code{datetime} 对象会被许多 @code{datetime} 方法当作本地时间来处理，最好是使用感知型日期时间对象来表示 UTC 时间。 因此，创建表示当前 UTC 时间的对象的推荐方式是通过调用 @code{datetime.now(timezone.utc)}。
@end quotation
@end cartouche
@end deffn

@geindex fromtimestamp() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime fromtimestamp}@anchor{101e}
@deffn {方法} classmethod datetime.fromtimestamp (timestamp, tz=None)

返回对应于 POSIX 时间戳例如 @ref{316,,time.time()} 的返回值的本地日期和时间。 如果可选参数 @emph{tz} 为 @code{None} 或未指定，时间戳会被转换为所在平台的本地日期和时间，返回的 @ref{194,,datetime} 对象将为天真型。

如果 @emph{tz} 不为 @code{None}，它必须是 @ref{378,,tzinfo} 子类的一个实例，并且时间戳将被转换到 @emph{tz} 指定的时区。

@ref{101e,,fromtimestamp()} 可能会引发 @ref{95a,,OverflowError}，如果时间戳数值超出所在平台 C @code{localtime()} 或 @code{gmtime()} 函数的支持范围的话，并会在 @code{localtime()} 或 @code{gmtime()} 报错时引发 @ref{1d3,,OSError}。 通常该数值会被限制在 1970 年至 2038 年之间。 请注意在时间戳概念包含闰秒的非 POSIX 系统上，闰秒会被 @ref{101e,,fromtimestamp()} 所忽略，结果可能导致两个相差一秒的时间戳产生相同的 @ref{194,,datetime} 对象。 相比 @ref{1854,,utcfromtimestamp()} 更推荐使用此方法。


在 3.3 版更改: 引发 @ref{95a,,OverflowError} 而不是 @ref{1fb,,ValueError}，如果时间戳数值超出所在平台 C @code{localtime()} 或 @code{gmtime()} 函数的支持范围的话。 并会在 @code{localtime()} 或 @code{gmtime()} 出错时引发 @ref{1d3,,OSError} 而不是 @ref{1fb,,ValueError}。



在 3.6 版更改: @ref{101e,,fromtimestamp()} 可能返回 @ref{4ee,,fold} 值设为 1 的实例。

@end deffn

@geindex utcfromtimestamp() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime utcfromtimestamp}@anchor{1854}
@deffn {方法} classmethod datetime.utcfromtimestamp (timestamp)

返回对应于 POSIX 时间戳的 UTC @ref{194,,datetime}，其中 @ref{1832,,tzinfo} 值为 @code{None}。 （结果为简单型对象。）

这可能引发 @ref{95a,,OverflowError}，如果时间戳数值超出所在平台 C @code{gmtime()} 函数的支持范围的话，并会在 @code{gmtime()} 报错时引发 @ref{1d3,,OSError}。 通常该数值会被限制在 1970 至 2038 年之间。

要得到一个感知型 @ref{194,,datetime} 对象，应调用 @ref{101e,,fromtimestamp()}:

@example
datetime.fromtimestamp(timestamp, timezone.utc)
@end example

在 POSIX 兼容的平台上，它等价于以下表达式:

@example
datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp)
@end example

不同之处在于后一种形式总是支持完整年份范围：从 @ref{1820,,MINYEAR} 到 @ref{1821,,MAXYEAR} 的开区间。

@cartouche
@quotation 警告 
由于简单型 @code{datetime} 对象会被许多 @code{datetime} 方法当作本地时间来处理，最好是使用感知型日期时间对象来表示 UTC 时间。 因此，创建表示特定 UTC 时间戳的日期时间对象的推荐方式是通过调用 @code{datetime.fromtimestamp(timestamp, tz=timezone.utc)}。
@end quotation
@end cartouche


在 3.3 版更改: 引发 @ref{95a,,OverflowError} 而不是 @ref{1fb,,ValueError}，如果时间戳数值超出所在平台 C @code{gmtime()} 函数的支持范围的话。 并会在 @code{gmtime()} 出错时引发 @ref{1d3,,OSError} 而不是 @ref{1fb,,ValueError}。

@end deffn

@geindex fromordinal() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime fromordinal}@anchor{1855}
@deffn {方法} classmethod datetime.fromordinal (ordinal)

返回对应于预期格列高利历序号的 @ref{194,,datetime}，其中公元 1 年 1 月 1 日的序号为 1。 除非 @code{1 <= ordinal <= datetime.max.toordinal()} 否则会引发 @ref{1fb,,ValueError}。 结果的 hour, minute, second 和 microsecond 值均为 0，并且 @ref{1832,,tzinfo} 值为 @code{None}。
@end deffn

@geindex combine() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime combine}@anchor{534}
@deffn {方法} classmethod datetime.combine (date, time, tzinfo=self.tzinfo)

返回一个新的 @ref{194,,datetime} 对象，对象的日期部分等于给定的 @ref{193,,date} 对象的值，而其时间部分等于给定的 @ref{4ed,,time} 对象的值。 如果提供了 @emph{tzinfo} 参数，其值会被用来设置结果的 @ref{1832,,tzinfo} 属性，否则将使用 @emph{time} 参数的 @ref{182a,,tzinfo} 属性。

对于任意 @ref{194,,datetime} 对象 @emph{d}，@code{d == datetime.combine(d.date(), d.time(), d.tzinfo)}。 如果 date 是一个 @ref{194,,datetime} 对象，它的时间部分和 @ref{1832,,tzinfo} 属性会被忽略。


在 3.6 版更改: 增加了 @emph{tzinfo} 参数。

@end deffn

@geindex fromisoformat() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime fromisoformat}@anchor{377}
@deffn {方法} classmethod datetime.fromisoformat (date_string)

返回一个对应于 @ref{1840,,date.isoformat()} 和 @ref{533,,datetime.isoformat()} 所提供的某一种 @emph{date_string} 的 @ref{194,,datetime} 对象。

特别地，此函数支持以下格式的字符串：

@example
YYYY-MM-DD[*HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]]
@end example

其中 @code{*} 可以匹配任意的单个字符。

@cartouche
@quotation 警告 
此函数 @emph{并不} 支持解析任意 ISO 8601 字符串 —— 它的目的只是作为 @ref{533,,datetime.isoformat()} 的逆操作。 在第三方包 dateutil@footnote{https://dateutil.readthedocs.io/en/stable/parser.html#dateutil.parser.isoparse} 中提供了一个更完善的 ISO 8601 解析器 @code{dateutil.parser.isoparse}。
@end quotation
@end cartouche

示例:

@example
>>> from datetime import datetime
>>> datetime.fromisoformat('2011-11-04')
datetime.datetime(2011, 11, 4, 0, 0)
>>> datetime.fromisoformat('2011-11-04T00:05:23')
datetime.datetime(2011, 11, 4, 0, 5, 23)
>>> datetime.fromisoformat('2011-11-04 00:05:23.283')
datetime.datetime(2011, 11, 4, 0, 5, 23, 283000)
>>> datetime.fromisoformat('2011-11-04 00:05:23.283+00:00')
datetime.datetime(2011, 11, 4, 0, 5, 23, 283000, tzinfo=datetime.timezone.utc)
>>> datetime.fromisoformat('2011-11-04T00:05:23+04:00')   
datetime.datetime(2011, 11, 4, 0, 5, 23,
    tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
@end example


3.7 新版功能.

@end deffn

@geindex fromisocalendar() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime fromisocalendar}@anchor{1c5}
@deffn {方法} classmethod datetime.fromisocalendar (year, week, day)

返回以 year, week 和 day 值指明的 ISO 历法日期所对应的 @ref{194,,datetime}。 该datetime 对象的非日期部分将使用其标准默认值来填充。 这是函数 @ref{1856,,datetime.isocalendar()} 的逆操作。


3.8 新版功能.

@end deffn

@geindex strptime() (datetime.datetime 类方法)
@anchor{library/datetime datetime datetime strptime}@anchor{f3f}
@deffn {方法} classmethod datetime.strptime (date_string, format)

返回一个对应于 @emph{date_string}，根据 @emph{format} 进行解析得到的 @ref{194,,datetime} 对象。

这相当于:

@example
datetime(*(time.strptime(date_string, format)[0:6]))
@end example

如果 date_string 和 format 无法被 @ref{d8a,,time.strptime()} 解析或它返回一个不是时间元组的值，则将引发 @ref{1fb,,ValueError}。 要获取格式化指令的完整列表，请参阅 @ref{184d,,strftime() 和 strptime() 的行为}。
@end deffn

类属性：

@geindex min (datetime.datetime 属性)
@anchor{library/datetime datetime datetime min}@anchor{1857}
@deffn {属性} datetime.min

最早的可表示 @ref{194,,datetime}，@code{datetime(MINYEAR, 1, 1, tzinfo=None)}。
@end deffn

@geindex max (datetime.datetime 属性)
@anchor{library/datetime datetime datetime max}@anchor{1858}
@deffn {属性} datetime.max

最晚的可表示 @ref{194,,datetime}，@code{datetime(MAXYEAR, 12, 31, 23, 59, 59, 999999, tzinfo=None)}。
@end deffn

@geindex resolution (datetime.datetime 属性)
@anchor{library/datetime datetime datetime resolution}@anchor{1859}
@deffn {属性} datetime.resolution

两个不相等的 @ref{194,,datetime} 对象之间可能的最小间隔，@code{timedelta(microseconds=1)}。
@end deffn

实例属性（只读）：

@geindex year (datetime.datetime 属性)
@anchor{library/datetime datetime datetime year}@anchor{182b}
@deffn {属性} datetime.year

在 @ref{1820,,MINYEAR} 和 @ref{1821,,MAXYEAR} 之间，包含边界。
@end deffn

@geindex month (datetime.datetime 属性)
@anchor{library/datetime datetime datetime month}@anchor{182c}
@deffn {属性} datetime.month

1 至 12（含）
@end deffn

@geindex day (datetime.datetime 属性)
@anchor{library/datetime datetime datetime day}@anchor{182d}
@deffn {属性} datetime.day

返回1到指定年月的天数间的数字。
@end deffn

@geindex hour (datetime.datetime 属性)
@anchor{library/datetime datetime datetime hour}@anchor{182e}
@deffn {属性} datetime.hour

取值范围是 @code{range(24)}。
@end deffn

@geindex minute (datetime.datetime 属性)
@anchor{library/datetime datetime datetime minute}@anchor{182f}
@deffn {属性} datetime.minute

取值范围是 @code{range(60)}。
@end deffn

@geindex second (datetime.datetime 属性)
@anchor{library/datetime datetime datetime second}@anchor{1830}
@deffn {属性} datetime.second

取值范围是 @code{range(60)}。
@end deffn

@geindex microsecond (datetime.datetime 属性)
@anchor{library/datetime datetime datetime microsecond}@anchor{1831}
@deffn {属性} datetime.microsecond

取值范围是 @code{range(1000000)}。
@end deffn

@geindex tzinfo (datetime.datetime 属性)
@anchor{library/datetime datetime datetime tzinfo}@anchor{1832}
@deffn {属性} datetime.tzinfo

作为 @emph{tzinfo} 参数被传给 @ref{194,,datetime} 构造器的对象，如果没有传入值则为 @code{None}。
@end deffn

@geindex fold (datetime.datetime 属性)
@anchor{library/datetime datetime datetime fold}@anchor{4ee}
@deffn {属性} datetime.fold

取值范围是 @code{[0, 1]}。 用于在重复的时间段中消除边界时间歧义。 （当夏令时结束时回拨时钟或由于政治原因导致当明时区的 UTC 时差减少就会出现重复的时间段。） 取值 0 (1) 表示两个时刻早于（晚于）所代表的同一边界时间。


3.6 新版功能.

@end deffn

支持的运算：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

结果：

@item

@code{datetime2 = datetime1 + timedelta}

@tab

(1)

@item

@code{datetime2 = datetime1 - timedelta}

@tab

(2)

@item

@code{timedelta = datetime1 - datetime2}

@tab

(3)

@item

@code{datetime1 < datetime2}

@tab

比较 @ref{194,,datetime} 与 @ref{194,,datetime}。 (4)

@end multitable



@enumerate 

@item 
datetime2 是从 datetime1 去掉了一段 timedelta 的结果，如果 @code{timedelta.days} > 0 则是在时间线上前进，如果 @code{timedelta.days} < 0 则是在时间线上后退。 该结果具有与输入的 datetime 相同的 @ref{1832,,tzinfo} 属性，并且操作完成后 datetime2 - datetime1 == timedelta。 如果 datetime2.year 将要小于 @ref{1820,,MINYEAR} 或大于 @ref{1821,,MAXYEAR} 则会引发 @ref{95a,,OverflowError}。 请注意即使输入的是一个感知型对象，该方法也不会进行时区调整。

@item 
计算 datetime2 使得 datetime2 + timedelta == datetime1。 与相加操作一样，结果具有与输入的 datetime 相同的 @ref{1832,,tzinfo} 属性，即使输入的是一个感知型对象，该方法也不会进行时区调整。

@item 
从一个 @ref{194,,datetime} 减去一个 @ref{194,,datetime} 仅对两个操作数均为简单型或均为感知型时有定义。 如果一个是感知型而另一个是简单型，则会引发 @ref{192,,TypeError}。

如果两个操作数都是简单型，或都是感知型并且具有相同的 @ref{1832,,tzinfo} 属性，则 @ref{1832,,tzinfo} 属性会被忽略，并且结果会是一个使得 @code{datetime2 + t == datetime1} 的 @ref{195,,timedelta} 对象 @emph{t}。 在此情况下不会进行时区调整。

如果两个操作数都是感知型且具有不同的 @ref{1832,,tzinfo} 属性，@code{a-b} 操作的效果就如同 @emph{a} 和 @emph{b} 首先被转换为简单型 UTC 日期时间。 结果将是 @code{(a.replace(tzinfo=None) - a.utcoffset()) - (b.replace(tzinfo=None) - b.utcoffset())}，除非具体实现绝对不溢出。

@item 
当 @emph{datetime1} 的时间在 @emph{datetime2} 之前则认为 @emph{datetime1} 小于 @emph{datetime2}。

如果比较的一方是简单型而另一方是感知型，则如果尝试进行顺序比较将引发 @ref{192,,TypeError}。 对于相等比较，简单型实例将永远不等于感知型实例。

如果两个比较方都是感知型，且具有相同的 @ref{1832,,tzinfo} 属性，则相同的 @ref{1832,,tzinfo} 属性会被忽略并对基本日期时间值进行比较。 如果两个比较方都是感知型且具有不同的 @ref{1832,,tzinfo} 属性，则两个比较方将首先通过减去它们的 UTC 差值（使用 @code{self.utcoffset()} 获取）来进行调整。


在 3.3 版更改: 感知型和简单型 @ref{194,,datetime} 实例之间的相等比较不会引发 @ref{192,,TypeError}。


@cartouche
@quotation 注解 
为了防止比较操作回退为默认的对象地址比较方式，datetime 比较通常会引发 @ref{192,,TypeError}，如果比较目标不同样为 @ref{194,,datetime} 对象的话。 不过也可能会返回 @code{NotImplemented}，如果比较目标具有 @code{timetuple()} 属性的话。 这个钩子给予其他种类的日期对象实现混合类型比较的机会。 如果未实现，则当 @ref{194,,datetime} 对象与不同类型比较时将会引发 @ref{192,,TypeError}，除非是 @code{==} 或 @code{!=} 比较。 后两种情况将分别返回 @ref{380,,False} 或 @ref{494,,True}。
@end quotation
@end cartouche
@end enumerate

实例方法：

@geindex date() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime date}@anchor{185a}
@deffn {方法} datetime.date ()

返回具有同样 year, month 和 day 值的 @ref{193,,date} 对象。
@end deffn

@geindex time() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime time}@anchor{185b}
@deffn {方法} datetime.time ()

返回具有同样 hour, minute, second, microsecond 和 fold 值的 @ref{4ed,,time} 对象。 @ref{1832,,tzinfo} 值为 @code{None}。 另请参见 @ref{185c,,timetz()} 方法。


在 3.6 版更改: fold 值会被复制给返回的 @ref{4ed,,time} 对象。

@end deffn

@geindex timetz() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime timetz}@anchor{185c}
@deffn {方法} datetime.timetz ()

返回具有同样 hour, minute, second, microsecond, fold 和 tzinfo 属性性的 @ref{4ed,,time} 对象。 另请参见 @ref{10a,,time()} 方法。


在 3.6 版更改: fold 值会被复制给返回的 @ref{4ed,,time} 对象。

@end deffn

@geindex replace() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime replace}@anchor{185d}
@deffn {方法} datetime.replace (year=self.year, month=self.month, day=self.day, hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, * fold=0)

返回一个具有同样属性值的 datetime，除非通过任何关键字参数为某些属性指定了新值。 请注意可以通过指定 @code{tzinfo=None} 来从一个感知型 datetime 创建一个简单型 datetime 而不必转换日期和时间数据。


3.6 新版功能: 增加了 @code{fold} 参数。

@end deffn

@geindex astimezone() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime astimezone}@anchor{196}
@deffn {方法} datetime.astimezone (tz=None)

返回一个具有新的 @ref{1832,,tzinfo} 属性 @emph{tz} 的 @ref{194,,datetime} 对象，并会调整日期和时间数据使得结果对应的 UTC 时间与 @emph{self} 相同，但为 @emph{tz} 时区的本地时间。

如果给出了 @emph{tz}，则它必须是一个 @ref{378,,tzinfo} 子类的实例，并且其 @ref{185e,,utcoffset()} 和 @ref{185f,,dst()} 方法不可返回 @code{None}。 如果 @emph{self} 为简单型，它会被假定为基于系统时区表示的时间。

如果调用时不传入参数 (或传入 @code{tz=None}) 则将假定目标时区为系统的本地时区。 转换后 datetime 实例的 @code{.tzinfo} 属性将被设为一个 @ref{9fb,,timezone} 实例，时区名称和时差值将从 OS 获取。

如果 @code{self.tzinfo} 为 @emph{tz}，@code{self.astimezone(tz)} 等于 @emph{self}: 不会对日期或时间数据进行调整。 否则结果为 @emph{tz} 时区的本地时间，代表的 UTC 时间与 @emph{self} 相同：在 @code{astz = dt.astimezone(tz)} 之后，@code{astz - astz.utcoffset()} 将具有与 @code{dt - dt.utcoffset()} 相同的日期和时间数据。

如果你只是想要附加一个时区对象 @emph{tz} 到一个 datetime 对象 @emph{dt} 而不调整日期和时间数据，请使用 @code{dt.replace(tzinfo=tz)}。 如果你只想从一个感知型 datetime 对象 @emph{dt} 移除时区对象，请使用 @code{dt.replace(tzinfo=None)}。

请注意默认的 @ref{1860,,tzinfo.fromutc()} 方法在 @ref{378,,tzinfo} 的子类中可以被重载，从而影响 @ref{196,,astimezone()} 的返回结果。 如果忽略出错的情况，@ref{196,,astimezone()} 的行为就类似于:

@example
def astimezone(self, tz):
    if self.tzinfo is tz:
        return self
    # Convert self to UTC, and attach the new time zone object.
    utc = (self - self.utcoffset()).replace(tzinfo=tz)
    # Convert from UTC to tz's local time.
    return tz.fromutc(utc)
@end example


在 3.3 版更改: @emph{tz} 现在可以被省略。



在 3.6 版更改: @ref{196,,astimezone()} 方法可以由简单型实例调用，这将假定其表示本地时间。

@end deffn

@geindex utcoffset() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime utcoffset}@anchor{185e}
@deffn {方法} datetime.utcoffset ()

如果 @ref{1832,,tzinfo} 为 @code{None}，则返回 @code{None}，否则返回 @code{self.tzinfo.utcoffset(self)}，并且在后者不返回 @code{None} 或者一个幅度小于一天的 @ref{195,,timedelta} 对象时将引发异常。


在 3.7 版更改: UTC 时差不再限制为一个整数分钟值。

@end deffn

@geindex dst() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime dst}@anchor{185f}
@deffn {方法} datetime.dst ()

如果 @ref{1832,,tzinfo} 为 @code{None}，则返回 @code{None}，否则返回 @code{self.tzinfo.dst(self)}，并且在后者不返回 @code{None} 或者一个幅度小于一天的 @ref{195,,timedelta} 对象时将引发异常。


在 3.7 版更改: DST 差值不再限制为一个整数分钟值。

@end deffn

@geindex tzname() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime tzname}@anchor{1861}
@deffn {方法} datetime.tzname ()

如果 @ref{1832,,tzinfo} 为 @code{None}，则返回 @code{None}，否则返回 @code{self.tzinfo.tzname(self)}，如果后者不返回 @code{None} 或者一个字符串对象则将引发异常。
@end deffn

@geindex timetuple() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime timetuple}@anchor{1862}
@deffn {方法} datetime.timetuple ()

返回一个 @ref{594,,time.struct_time}，即 @ref{edc,,time.localtime()} 所返回的类型。

@code{d.timetuple()} 等价于:

@example
time.struct_time((d.year, d.month, d.day,
                  d.hour, d.minute, d.second,
                  d.weekday(), yday, dst))
@end example

其中 @code{yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1} 是日期在当前年份中的序号，起始序号 @code{1} 表示 1 月 1 日。 结果的 @code{tm_isdst} 旗标的设定会依据 @ref{185f,,dst()} 方法：如果 @ref{1832,,tzinfo} 为 @code{None} 或 @ref{185f,,dst()} 返回 @code{None}，则 @code{tm_isdst} 将设为 @code{-1}；否则如果 @ref{185f,,dst()} 返回一个非零值，则 @code{tm_isdst} 将设为 @code{1}；在其他情况下 @code{tm_isdst} 将设为 @code{0}。
@end deffn

@geindex utctimetuple() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime utctimetuple}@anchor{1863}
@deffn {方法} datetime.utctimetuple ()

如果 @ref{194,,datetime} 实例 @emph{d} 为简单型，这类似于 @code{d.timetuple()}，不同之处在于 @code{tm_isdst} 会强制设为 0，无论 @code{d.dst()} 返回什么结果。 DST 对于 UTC 时间永远无效。

如果 @emph{d} 为感知型， @emph{d} 会通过减去 @code{d.utcoffset()} 来标准化为 UTC 时间，并返回该标准化时间所对应的 @ref{594,,time.struct_time}。 @code{tm_isdst} 会强制设为 0。 请注意如果 @emph{d}.year 为 @code{MINYEAR} 或 @code{MAXYEAR} 并且 UTC 调整超出一年的边界则可能引发 @ref{95a,,OverflowError}。

@cartouche
@quotation 警告 
由于简单型 @code{datetime} 对象会被许多 @code{datetime} 方法当作本地时间来处理，最好是使用感知型日期时间来表示 UTC 时间；因此，使用 @code{utcfromtimetuple} 可能会给出误导性的结果。 如果你有一个表示 UTC 的简单型 @code{datetime}，请使用 @code{datetime.replace(tzinfo=timezone.utc)} 将其改为感知型，这样你才能使用 @ref{1862,,datetime.timetuple()}。
@end quotation
@end cartouche
@end deffn

@geindex toordinal() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime toordinal}@anchor{1864}
@deffn {方法} datetime.toordinal ()

返回日期的预期格列高利历序号。 与 @code{self.date().toordinal()} 相同。
@end deffn

@geindex timestamp() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime timestamp}@anchor{9dc}
@deffn {方法} datetime.timestamp ()

返回对应于 @ref{194,,datetime} 实例的 POSIX 时间戳。 此返回值是与 @ref{316,,time.time()} 返回值类似的 @ref{187,,float} 对象。

简单型 @ref{194,,datetime} 实例会假定为代表本地时间，并且此方法依赖于平台的 C @code{mktime()} 函数来执行转换。 由于在许多平台上 @ref{194,,datetime} 支持的范围比 @code{mktime()} 更广，对于极其遥远的过去或未来此方法可能引发 @ref{95a,,OverflowError}。

对于感知型 @ref{194,,datetime} 实例，返回值的计算方式为:

@example
(dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds()
@end example


3.3 新版功能.



在 3.6 版更改: @ref{9dc,,timestamp()} 方法使用 @ref{4ee,,fold} 属性来消除重复间隔中的时间歧义。


@cartouche
@quotation 注解 
没有一个方法能直接从表示 UTC 时间的简单型 @ref{194,,datetime} 实例获取 POSIX 时间戳。 如果你的应用程序使用此惯例并且你的系统时区不是设为 UTC，你可以通过提供 @code{tzinfo=timezone.utc} 来获取 POSIX 时间戳:

@example
timestamp = dt.replace(tzinfo=timezone.utc).timestamp()
@end example

或者通过直接计算时间戳:

@example
timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)
@end example
@end quotation
@end cartouche
@end deffn

@geindex weekday() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime weekday}@anchor{1865}
@deffn {方法} datetime.weekday ()

返回一个整数代表星期几，星期一为 0，星期天为 6。 相当于 @code{self.date().weekday()}。 另请参阅 @ref{1866,,isoweekday()}。
@end deffn

@geindex isoweekday() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime isoweekday}@anchor{1866}
@deffn {方法} datetime.isoweekday ()

返回一个整数代表星期几，星期一为 1，星期天为 7。 相当于 @code{self.date().isoweekday()}。 另请参阅 @ref{1865,,weekday()}, @ref{1856,,isocalendar()}。
@end deffn

@geindex isocalendar() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime isocalendar}@anchor{1856}
@deffn {方法} datetime.isocalendar ()

返回一个 3 元组 (ISO 年份, ISO 周序号, ISO 周日期)。 等同于 @code{self.date().isocalendar()}。
@end deffn

@geindex isoformat() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime isoformat}@anchor{533}
@deffn {方法} datetime.isoformat (sep='T', timespec='auto')

返回一个以 ISO 8601 格式表示的日期和时间字符串：


@itemize -

@item 
@code{YYYY-MM-DDTHH:MM:SS.ffffff}，如果 @ref{1831,,microsecond} 不为 0

@item 
@code{YYYY-MM-DDTHH:MM:SS}，如果 @ref{1831,,microsecond} 为 0
@end itemize

如果 @ref{185e,,utcoffset()} 返回值不为 @code{None}，则添加一个字符串来给出 UTC 时差：


@itemize -

@item 
@code{YYYY-MM-DDTHH:MM:SS.ffffff+HH:MM[:SS[.ffffff]]}，如果 @ref{1831,,microsecond} 不为 0

@item 
@code{YYYY-MM-DDTHH:MM:SS+HH:MM[:SS[.ffffff]]}，如果 @ref{1831,,microsecond} 为 0
@end itemize

示例:

@example
>>> from datetime import datetime, timezone
>>> datetime(2019, 5, 18, 15, 17, 8, 132263).isoformat()
'2019-05-18T15:17:08.132263'
>>> datetime(2019, 5, 18, 15, 17, tzinfo=timezone.utc).isoformat()
'2019-05-18T15:17:00+00:00'
@end example

可选参数 @emph{sep} (默认为 @code{'T'}) 为单个分隔字符，会被放在结果的日期和时间两部分之间。 例如:

@example
>>> from datetime import tzinfo, timedelta, datetime
>>> class TZ(tzinfo):
...     """A time zone with an arbitrary, constant -06:39 offset."""
...     def utcoffset(self, dt):
...         return timedelta(hours=-6, minutes=-39)
...
>>> datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
'2002-12-25 00:00:00-06:39'
>>> datetime(2009, 11, 27, microsecond=100, tzinfo=TZ()).isoformat()
'2009-11-27T00:00:00.000100-06:39'
@end example

可选参数 @emph{timespec} 要包含的额外时间组件值 (默认为 @code{'auto'})。它可以是以下值之一：


@itemize -

@item 
@code{'auto'}: 如果 @ref{1831,,microsecond} 为 0 则与 @code{'seconds'} 相同，否则与 @code{'microseconds'} 相同。

@item 
@code{'hours'}: 以两个数码的 @code{HH} 格式 包含 @ref{182e,,hour}。

@item 
@code{'minutes'}: 以 @code{HH:MM} 格式包含 @ref{182e,,hour} 和 @ref{182f,,minute}。

@item 
@code{'seconds'}: 以 @code{HH:MM:SS} 格式包含 @ref{182e,,hour}, @ref{182f,,minute} 和 @ref{1830,,second}。

@item 
@code{'milliseconds'}: 包含完整时间，但将秒值的小数部分截断至微秒。 格式为 @code{HH:MM:SS.sss}

@item 
@code{'microseconds'}: 以 @code{HH:MM:SS.ffffff} 格式包含完整时间。
@end itemize

@cartouche
@quotation 注解 
排除掉的时间部分将被截断，而不是被舍入。
@end quotation
@end cartouche

对于无效的 @emph{timespec} 参数将引发 @ref{1fb,,ValueError}:

@example
>>> from datetime import datetime
>>> datetime.now().isoformat(timespec='minutes')   
'2002-12-25T00:00'
>>> dt = datetime(2015, 1, 1, 12, 30, 59, 0)
>>> dt.isoformat(timespec='microseconds')
'2015-01-01T12:30:59.000000'
@end example


3.6 新版功能: 增加了 @emph{timespec} 参数。

@end deffn

@geindex __str__() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime __str__}@anchor{1867}
@deffn {方法} datetime.__str__ ()

对于 @ref{194,,datetime} 实例 @emph{d}，@code{str(d)} 等价于 @code{d.isoformat(' ')}。
@end deffn

@geindex ctime() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime ctime}@anchor{1868}
@deffn {方法} datetime.ctime ()

返回一个表示日期和时间的字符串:

@example
>>> from datetime import datetime
>>> datetime(2002, 12, 4, 20, 30, 40).ctime()
'Wed Dec  4 20:30:40 2002'
@end example

输出字符串将 @emph{并不} 包括时区信息，无论输入的是感知型还是简单型。

@code{d.ctime()} 等效于:

@example
time.ctime(time.mktime(d.timetuple()))
@end example

在原生 C @code{ctime()} 函数 (@ref{184c,,time.ctime()} 会发起调用该函数，但 @ref{1868,,datetime.ctime()} 则不会) 遵循 C 标准的平台上。
@end deffn

@geindex strftime() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime strftime}@anchor{531}
@deffn {方法} datetime.strftime (format)

返回一个由显式格式字符串所指明的代表日期和时间的字符串，要获取格式指令的完整列表，请参阅 @ref{184d,,strftime() 和 strptime() 的行为}。
@end deffn

@geindex __format__() (datetime.datetime 方法)
@anchor{library/datetime datetime datetime __format__}@anchor{1869}
@deffn {方法} datetime.__format__ (format)

与 @ref{531,,datetime.strftime()} 相同。 此方法使得为 @ref{194,,datetime} 对象指定以 @ref{15c,,格式化字符串字面值} 表示的格式化字符串以及使用 @ref{4d4,,str.format()} 进行格式化成为可能。 要获取格式指令的完整列表，请参阅 @ref{184d,,strftime() 和 strptime() 的行为}。
@end deffn

@menu
* 用法示例; datetime: 用法示例 datetime. 

@end menu

@node 用法示例 datetime,,,datetime 对象
@anchor{library/datetime examples-of-usage-datetime}@anchor{186a}
@subsubsection 用法示例: @code{datetime}


使用 @ref{194,,datetime} 对象的例子：

@example
>>> from datetime import datetime, date, time, timezone

>>> # Using datetime.combine()
>>> d = date(2005, 7, 14)
>>> t = time(12, 30)
>>> datetime.combine(d, t)
datetime.datetime(2005, 7, 14, 12, 30)

>>> # Using datetime.now()
>>> datetime.now()   
datetime.datetime(2007, 12, 6, 16, 29, 43, 79043)   # GMT +1
>>> datetime.now(timezone.utc)   
datetime.datetime(2007, 12, 6, 15, 29, 43, 79060, tzinfo=datetime.timezone.utc)

>>> # Using datetime.strptime()
>>> dt = datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M")
>>> dt
datetime.datetime(2006, 11, 21, 16, 30)

>>> # Using datetime.timetuple() to get tuple of all attributes
>>> tt = dt.timetuple()
>>> for it in tt:   
...     print(it)
...
2006    # year
11      # month
21      # day
16      # hour
30      # minute
0       # second
1       # weekday (0 = Monday)
325     # number of days since 1st January
-1      # dst - method tzinfo.dst() returned None

>>> # Date in ISO format
>>> ic = dt.isocalendar()
>>> for it in ic:   
...     print(it)
...
2006    # ISO year
47      # ISO week
2       # ISO weekday

>>> # Formatting a datetime
>>> dt.strftime("%A, %d. %B %Y %I:%M%p")
'Tuesday, 21. November 2006 04:30PM'
>>> 'The @{1@} is @{0:%d@}, the @{2@} is @{0:%B@}, the @{3@} is @{0:%I:%M%p@}.'.format(dt, "day", "month", "time")
'The day is 21, the month is November, the time is 04:30PM.'
@end example

以下示例定义了一个 @ref{378,,tzinfo} 子类，它捕获 Kabul, Afghanistan 时区的信息，该时区使用 +4 UTC 直到 1945 年，之后则使用 +4:30 UTC:

@example
from datetime import timedelta, datetime, tzinfo, timezone

class KabulTz(tzinfo):
    # Kabul used +4 until 1945, when they moved to +4:30
    UTC_MOVE_DATE = datetime(1944, 12, 31, 20, tzinfo=timezone.utc)

    def utcoffset(self, dt):
        if dt.year < 1945:
            return timedelta(hours=4)
        elif (1945, 1, 1, 0, 0) <= dt.timetuple()[:5] < (1945, 1, 1, 0, 30):
            # An ambiguous ("imaginary") half-hour range representing
            # a 'fold' in time due to the shift from +4 to +4:30.
            # If dt falls in the imaginary range, use fold to decide how
            # to resolve. See PEP495.
            return timedelta(hours=4, minutes=(30 if dt.fold else 0))
        else:
            return timedelta(hours=4, minutes=30)

    def fromutc(self, dt):
        # Follow same validations as in datetime.tzinfo
        if not isinstance(dt, datetime):
            raise TypeError("fromutc() requires a datetime argument")
        if dt.tzinfo is not self:
            raise ValueError("dt.tzinfo is not self")

        # A custom implementation is required for fromutc as
        # the input to this function is a datetime with utc values
        # but with a tzinfo set to self.
        # See datetime.astimezone or fromtimestamp.
        if dt.replace(tzinfo=timezone.utc) >= self.UTC_MOVE_DATE:
            return dt + timedelta(hours=4, minutes=30)
        else:
            return dt + timedelta(hours=4)

    def dst(self, dt):
        # Kabul does not observe daylight saving time.
        return timedelta(0)

    def tzname(self, dt):
        if dt >= self.UTC_MOVE_DATE:
            return "+04:30"
        return "+04"
@end example

上述 @code{KabulTz} 的用法:

@example
>>> tz1 = KabulTz()

>>> # Datetime before the change
>>> dt1 = datetime(1900, 11, 21, 16, 30, tzinfo=tz1)
>>> print(dt1.utcoffset())
4:00:00

>>> # Datetime after the change
>>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=tz1)
>>> print(dt2.utcoffset())
4:30:00

>>> # Convert datetime to another time zone
>>> dt3 = dt2.astimezone(timezone.utc)
>>> dt3
datetime.datetime(2006, 6, 14, 8, 30, tzinfo=datetime.timezone.utc)
>>> dt2
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=KabulTz())
>>> dt2 == dt3
True
@end example

@node time 对象,tzinfo 对象,datetime 对象,datetime --- 基本的日期和时间类型
@anchor{library/datetime datetime-time}@anchor{186b}@anchor{library/datetime time-objects}@anchor{186c}
@subsubsection @code{time} 对象


一个 @ref{10a,,time} 对象代表某日的（本地）时间，它独立于任何特定日期，并可通过 @ref{378,,tzinfo} 对象来调整。

@geindex time (datetime 中的类)
@anchor{library/datetime datetime time}@anchor{4ed}
@deffn {类} datetime.time (hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

所有参数都是可选的。 @emph{tzinfo} 可以是 @code{None}，或者是一个 @ref{378,,tzinfo} 子类的实例。 其余的参数必须是在下面范围内的整数：


@itemize *

@item 
@code{0 <= hour < 24},

@item 
@code{0 <= minute < 60},

@item 
@code{0 <= second < 60},

@item 
@code{0 <= microsecond < 1000000},

@item 
@code{fold in [0, 1]}.
@end itemize

如果给出一个此范围以外的参数，则会引发 @ref{1fb,,ValueError}。 所有参数值默认为 @code{0}，只有 @emph{tzinfo} 默认为 @ref{157,,None}。
@end deffn

类属性：

@geindex min (datetime.time 属性)
@anchor{library/datetime datetime time min}@anchor{186d}
@deffn {属性} time.min

早最的可表示 @ref{4ed,,time}, @code{time(0, 0, 0, 0)}。
@end deffn

@geindex max (datetime.time 属性)
@anchor{library/datetime datetime time max}@anchor{186e}
@deffn {属性} time.max

最晚的可表示 @ref{4ed,,time}, @code{time(23, 59, 59, 999999)}。
@end deffn

@geindex resolution (datetime.time 属性)
@anchor{library/datetime datetime time resolution}@anchor{186f}
@deffn {属性} time.resolution

两个不相等的 @ref{4ed,,time} 对象之间可能的最小间隔，@code{timedelta(microseconds=1)}，但是请注意 @ref{4ed,,time} 对象并不支持算术运算。
@end deffn

实例属性（只读）：

@geindex hour (datetime.time 属性)
@anchor{library/datetime datetime time hour}@anchor{1826}
@deffn {属性} time.hour

取值范围是 @code{range(24)}。
@end deffn

@geindex minute (datetime.time 属性)
@anchor{library/datetime datetime time minute}@anchor{1827}
@deffn {属性} time.minute

取值范围是 @code{range(60)}。
@end deffn

@geindex second (datetime.time 属性)
@anchor{library/datetime datetime time second}@anchor{1828}
@deffn {属性} time.second

取值范围是 @code{range(60)}。
@end deffn

@geindex microsecond (datetime.time 属性)
@anchor{library/datetime datetime time microsecond}@anchor{1829}
@deffn {属性} time.microsecond

取值范围是 @code{range(1000000)}。
@end deffn

@geindex tzinfo (datetime.time 属性)
@anchor{library/datetime datetime time tzinfo}@anchor{182a}
@deffn {属性} time.tzinfo

作为 tzinfo 参数被传给 @ref{4ed,,time} 构造器的对象，如果没有传入值则为 @code{None}。
@end deffn

@geindex fold (datetime.time 属性)
@anchor{library/datetime datetime time fold}@anchor{1870}
@deffn {属性} time.fold

取值范围是 @code{[0, 1]}。 用于在重复的时间段中消除边界时间歧义。 （当夏令时结束时回拨时钟或由于政治原因导致当明时区的 UTC 时差减少就会出现重复的时间段。） 取值 0 (1) 表示两个时刻早于（晚于）所代表的同一边界时间。


3.6 新版功能.

@end deffn

@ref{4ed,,time} 对象支持 @ref{4ed,,time} 与 @ref{4ed,,time} 的比较，当 @emph{a} 时间在 @emph{b} 之前时，则认为 @emph{a} 小于 @emph{b}。 如果比较的一方是简单型而另一方是感知型，则如果尝试进行顺序比较将引发 @ref{192,,TypeError}。 对于相等比较，简单型实例将永远不等于感知型实例。

如果两个比较方都是感知型，且具有相同的 @ref{182a,,tzinfo} 属性，相同的 @ref{182a,,tzinfo} 属性会被忽略并对基本时间值进行比较。 如果两个比较方都是感知型且具有不同的 @ref{182a,,tzinfo} 属性，两个比较方将首先通过减去它们的 UTC 时差（从 @code{self.utcoffset()} 获取）来进行调整。 为了防止将混合类型比较回退为基于对象地址的默认比较，当 @ref{4ed,,time} 对象与不同类型的对象比较时，将会引发 @ref{192,,TypeError}，除非比较运算符是 @code{==} 或 @code{!=}。 在后两种情况下将分别返回 @ref{380,,False} 或 @ref{494,,True}。


在 3.3 版更改: 感知型和简单型 @ref{4ed,,time} 实例之间的相等比较不会引发 @ref{192,,TypeError}。


在布尔运算时，@ref{4ed,,time} 对象总是被视为真值。


在 3.5 版更改: 在 Python 3.5 之前，如果一个 @ref{4ed,,time} 对象代表 UTC 午夜零时则会被视为假值。 此行为被认为容易引发困惑和错误，因此从 Python 3.5 起已被去除。 详情参见 bpo-13936@footnote{https://bugs.python.org/issue13936}。


其他构造方法：

@geindex fromisoformat() (datetime.time 类方法)
@anchor{library/datetime datetime time fromisoformat}@anchor{1029}
@deffn {方法} classmethod time.fromisoformat (time_string)

返回对应于 @ref{1871,,time.isoformat()} 所提供的某种 @emph{time_string} 格式的 @ref{4ed,,time}。 特别地，此函数支持以下格式的字符串：

@example
HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]
@end example

@cartouche
@quotation 警告 
此方法 @emph{并不} 支持解析任意 ISO 8601 字符串。 它的目的只是作为 @ref{1871,,time.isoformat()} 的逆操作。
@end quotation
@end cartouche

示例:

@example
>>> from datetime import time
>>> time.fromisoformat('04:23:01')
datetime.time(4, 23, 1)
>>> time.fromisoformat('04:23:01.000384')
datetime.time(4, 23, 1, 384)
>>> time.fromisoformat('04:23:01+04:00')
datetime.time(4, 23, 1, tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
@end example


3.7 新版功能.

@end deffn

实例方法：

@geindex replace() (datetime.time 方法)
@anchor{library/datetime datetime time replace}@anchor{1872}
@deffn {方法} time.replace (hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, * fold=0)

返回一个具有同样属性值的 @ref{4ed,,time}，除非通过任何关键字参数指定了某些属性值。 请注意可以通过指定 @code{tzinfo=None} 从一个感知型 @ref{4ed,,time} 创建一个简单型 @ref{4ed,,time}，而不必转换时间数据。


3.6 新版功能: 增加了 @code{fold} 参数。

@end deffn

@geindex isoformat() (datetime.time 方法)
@anchor{library/datetime datetime time isoformat}@anchor{1871}
@deffn {方法} time.isoformat (timespec='auto')

返回表示为下列 ISO 8601 格式之一的时间字符串：


@itemize -

@item 
@code{HH:MM:SS.ffffff}，如果 @ref{1829,,microsecond} 不为 0

@item 
@code{HH:MM:SS}，如果 @ref{1829,,microsecond} 为 0

@item 
@code{HH:MM:SS.ffffff+HH:MM[:SS[.ffffff]]}，如果 @ref{1873,,utcoffset()} 不返回 @code{None}

@item 
@code{HH:MM:SS+HH:MM[:SS[.ffffff]]}，如果 @ref{1829,,microsecond} 为 0 并且 @ref{1873,,utcoffset()} 不返回 @code{None}
@end itemize

可选参数 @emph{timespec} 要包含的额外时间组件值 (默认为 @code{'auto'})。它可以是以下值之一：


@itemize -

@item 
@code{'auto'}: 如果 @ref{1829,,microsecond} 为 0 则与 @code{'seconds'} 相同，否则与 @code{'microseconds'} 相同。

@item 
@code{'hours'}: 以两个数码的 @code{HH} 格式 包含 @ref{1826,,hour}。

@item 
@code{'minutes'}: 以 @code{HH:MM} 格式包含 @ref{1826,,hour} 和 @ref{1827,,minute}。

@item 
@code{'seconds'}: 以 @code{HH:MM:SS} 格式包含 @ref{1826,,hour}, @ref{1827,,minute} 和 @ref{1828,,second}。

@item 
@code{'milliseconds'}: 包含完整时间，但将秒值的小数部分截断至微秒。 格式为 @code{HH:MM:SS.sss}

@item 
@code{'microseconds'}: 以 @code{HH:MM:SS.ffffff} 格式包含完整时间。
@end itemize

@cartouche
@quotation 注解 
排除掉的时间部分将被截断，而不是被舍入。
@end quotation
@end cartouche

对于无效的 @emph{timespec} 参数将引发 @ref{1fb,,ValueError}。

示例:

@example
>>> from datetime import time
>>> time(hour=12, minute=34, second=56, microsecond=123456).isoformat(timespec='minutes')
'12:34'
>>> dt = time(hour=12, minute=34, second=56, microsecond=0)
>>> dt.isoformat(timespec='microseconds')
'12:34:56.000000'
>>> dt.isoformat(timespec='auto')
'12:34:56'
@end example


3.6 新版功能: 增加了 @emph{timespec} 参数。

@end deffn

@geindex __str__() (datetime.time 方法)
@anchor{library/datetime datetime time __str__}@anchor{1874}
@deffn {方法} time.__str__ ()

对于时间对象 @emph{t}, @code{str(t)} 等价于 @code{t.isoformat()}。
@end deffn

@geindex strftime() (datetime.time 方法)
@anchor{library/datetime datetime time strftime}@anchor{1875}
@deffn {方法} time.strftime (format)

返回一个由显式格式字符串所指明的代表时间的字符串。 要获取格式指令的完整列表，请参阅 @ref{184d,,strftime() 和 strptime() 的行为}。
@end deffn

@geindex __format__() (datetime.time 方法)
@anchor{library/datetime datetime time __format__}@anchor{1876}
@deffn {方法} time.__format__ (format)

与 @ref{1875,,time.strftime()} 相同。 此方法使得为 @ref{4ed,,time} 对象指定以 @ref{15c,,格式化字符串字面值} 表示的格式化字符串以及使用 @ref{4d4,,str.format()} 进行格式化成为可能。 要获取格式指令的完整列表，请参阅 @ref{184d,,strftime() 和 strptime() 的行为}。
@end deffn

@geindex utcoffset() (datetime.time 方法)
@anchor{library/datetime datetime time utcoffset}@anchor{1873}
@deffn {方法} time.utcoffset ()

如果 @ref{182a,,tzinfo} 为 @code{None}，则返回 @code{None}，否则返回 @code{self.tzinfo.utcoffset(None)}，并且在后者不返回 @code{None} 或一个幅度小于一天的 a @ref{195,,timedelta} 对象时将引发异常。


在 3.7 版更改: UTC 时差不再限制为一个整数分钟值。

@end deffn

@geindex dst() (datetime.time 方法)
@anchor{library/datetime datetime time dst}@anchor{1877}
@deffn {方法} time.dst ()

如果 @ref{182a,,tzinfo} 为 @code{None}，则返回 @code{None}，否则返回 @code{self.tzinfo.dst(None)}，并且在后者不返回 @code{None} 或者一个幅度小于一天的 @ref{195,,timedelta} 对象时将引发异常。


在 3.7 版更改: DST 差值不再限制为一个整数分钟值。

@end deffn

@geindex tzname() (datetime.time 方法)
@anchor{library/datetime datetime time tzname}@anchor{1878}
@deffn {方法} time.tzname ()

如果 @ref{182a,,tzinfo} 为 @code{None}，则返回 @code{None}，否则返回 @code{self.tzinfo.tzname(None)}，如果后者不返回 @code{None} 或者一个字符串对象则将引发异常。
@end deffn

@menu
* 用法示例; time: 用法示例 time. 

@end menu

@node 用法示例 time,,,time 对象
@anchor{library/datetime examples-of-usage-time}@anchor{1879}
@subsubsection 用法示例: @code{time}


使用 @ref{4ed,,time} 对象的例子:

@example
>>> from datetime import time, tzinfo, timedelta
>>> class TZ1(tzinfo):
...     def utcoffset(self, dt):
...         return timedelta(hours=1)
...     def dst(self, dt):
...         return timedelta(0)
...     def tzname(self,dt):
...         return "+01:00"
...     def  __repr__(self):
...         return f"@{self.__class__.__name__@}()"
...
>>> t = time(12, 10, 30, tzinfo=TZ1())
>>> t
datetime.time(12, 10, 30, tzinfo=TZ1())
>>> t.isoformat()
'12:10:30+01:00'
>>> t.dst()
datetime.timedelta(0)
>>> t.tzname()
'+01:00'
>>> t.strftime("%H:%M:%S %Z")
'12:10:30 +01:00'
>>> 'The @{@} is @{:%H:%M@}.'.format("time", t)
'The time is 12:10.'
@end example

@node tzinfo 对象,timezone 对象,time 对象,datetime --- 基本的日期和时间类型
@anchor{library/datetime datetime-tzinfo}@anchor{187a}@anchor{library/datetime tzinfo-objects}@anchor{187b}
@subsubsection @code{tzinfo} 对象


@geindex tzinfo (datetime 中的类)
@anchor{library/datetime datetime tzinfo}@anchor{378}
@deffn {类} datetime.tzinfo

这是一个抽象基类，也就是说该类不应被直接实例化。 请定义 @ref{378,,tzinfo} 的子类来捕获有关特定时区的信息。

@ref{378,,tzinfo} 的（某个实体子类）的实例可以被传给 @ref{194,,datetime} 和 @ref{4ed,,time} 对象的构造器。 这些对象会将它们的属性视为对应于本地时间，并且 @ref{378,,tzinfo} 对象支持展示本地时间与 UTC 的差值、时区名称以及 DST 差值的方法，都是与传给它们的日期或时间对象的相对值。

你需要派生一个实体子类，并且（至少）提供你使用 @ref{194,,datetime} 方法所需要的标准 @ref{378,,tzinfo} 方法的实现。 @ref{31,,datetime} 模块提供了 @ref{9fb,,timezone}，这是 @ref{378,,tzinfo} 的一个简单实体子类，它能以与 UTC 的固定差值来表示不同的时区，例如 UTC 本身或北美的 EST 和 EDT。

对于封存操作的特殊要求：一个 @ref{378,,tzinfo} 子类必须具有可不带参数调用的 @ref{d57,,__init__()} 方法，否则它虽然可以被封存，但可能无法再次解封。 这是个技术性要求，在未来可能会被取消。

一个 @ref{378,,tzinfo} 的实体子类可能需要实现以下方法。 具体需要实现的方法取决于感知型 @ref{31,,datetime} 对象如何使用它。 如果有疑问，可以简单地全都实现。
@end deffn

@geindex utcoffset() (datetime.tzinfo 方法)
@anchor{library/datetime datetime tzinfo utcoffset}@anchor{187c}
@deffn {方法} tzinfo.utcoffset (dt)

将本地时间与 UTC 时差返回为一个 @ref{195,,timedelta} 对象，如果本地时区在 UTC 以东则为正值。 如果本地时区在 UTC 以西则为负值。

这表示与 UTC 的 @emph{总计} 时差；举例来说，如果一个 @ref{378,,tzinfo} 对象同时代表时区和 DST 调整，则 @ref{187c,,utcoffset()} 应当返回两者的和。 如果 UTC 时差不确定则返回 @code{None}。 在其他情况下返回值必须为一个 @ref{195,,timedelta} 对象，其取值严格限制于 @code{-timedelta(hours=24)} 和 @code{timedelta(hours=24)} 之间（差值的幅度必须小于一天）。 大多数 @ref{187c,,utcoffset()} 的实现看起来可能像是以下两者之一:

@example
return CONSTANT                 # fixed-offset class
return CONSTANT + self.dst(dt)  # daylight-aware class
@end example

如果 @ref{187c,,utcoffset()} 返回值不为 @code{None}，则 @ref{187d,,dst()} 也不应返回 @code{None}。

默认的 @ref{187c,,utcoffset()} 实现会引发 @ref{609,,NotImplementedError}。


在 3.7 版更改: UTC 时差不再限制为一个整数分钟值。

@end deffn

@geindex dst() (datetime.tzinfo 方法)
@anchor{library/datetime datetime tzinfo dst}@anchor{187d}
@deffn {方法} tzinfo.dst (dt)

将夏令时（DST）调整返回为一个 @ref{195,,timedelta} 对象，如果 DST 信息未知则返回 @code{None}。

如果 DST 未启用则返回 @code{timedelta(0)}。 如果 DST 已启用则将差值作为一个 @ref{195,,timedelta} 对象返回（参见 @ref{187c,,utcoffset()} 了解详情）。 请注意 DST 差值如果可用，就会直接被加入 @ref{187c,,utcoffset()} 所返回的 UTC 时差，因此无需额外查询 @ref{187d,,dst()} 除非你希望单独获取 DST 信息。 例如，@ref{1862,,datetime.timetuple()} 会调用其 @ref{1832,,tzinfo} 属性的 @ref{187d,,dst()} 方法来确定应该如何设置 @code{tm_isdst} 旗标，而 @ref{1860,,tzinfo.fromutc()} 会调用 @ref{187d,,dst()} 来在跨越时区时处理 DST 的改变。

一个可以同时处理标准时和夏令时的 @ref{378,,tzinfo} 子类的实例 @emph{tz} 必须在此情形中保持一致：

@code{tz.utcoffset(dt) - tz.dst(dt)}

必须为具有同样的 @ref{378,,tzinfo} 子类实例且 @code{dt.tzinfo == tz} 的每个 @ref{194,,datetime} 对象 @emph{dt} 返回同样的结果，此表达式会产生时区的“标准时差”，它不应取决于具体日期或时间，只取决于地理位置。 @ref{196,,datetime.astimezone()} 的实现依赖此方法，但无法检测违反规则的情况；确保符合规则是程序员的责任。 如果一个 @ref{378,,tzinfo} 子类不能保证这一点，也许可以重载 @ref{1860,,tzinfo.fromutc()} 的默认实现以便在任何情况下与 @code{astimezone()} 正确配合。

大多数 @ref{187d,,dst()} 的实现可能会如以下两者之一:

@example
def dst(self, dt):
    # a fixed-offset class:  doesn't account for DST
    return timedelta(0)
@end example

或者：

@example
def dst(self, dt):
    # Code to set dston and dstoff to the time zone's DST
    # transition times based on the input dt.year, and expressed
    # in standard local time.

    if dston <= dt.replace(tzinfo=None) < dstoff:
        return timedelta(hours=1)
    else:
        return timedelta(0)
@end example

默认的 @ref{187d,,dst()} 实现会引发 @ref{609,,NotImplementedError}。


在 3.7 版更改: DST 差值不再限制为一个整数分钟值。

@end deffn

@geindex tzname() (datetime.tzinfo 方法)
@anchor{library/datetime datetime tzinfo tzname}@anchor{187e}
@deffn {方法} tzinfo.tzname (dt)

将对应于 @ref{194,,datetime} 对象 @emph{dt} 的时区名称作为字符串返回。 @ref{31,,datetime} 模块没有定义任何字符串名称相关内容，也不要求名称有任何特定含义。 例如 "GMT", "UTC", "-500", "-5:00", "EDT", "US/Eastern", "America/New York" 都是有效的返回值。 如果字符串名称未知则返回 @code{None}。 请注意这是一个方法而不是一个固定的字符串，这主要是因为某些 @ref{378,,tzinfo} 子类可能需要根据所传入的特定 @emph{dt} 值返回不同的名称，特别是当 @ref{378,,tzinfo} 类要负责处理夏令时的时候。

默认的 @ref{187e,,tzname()} 实现会引发 @ref{609,,NotImplementedError}。
@end deffn

这些方法会被 @ref{194,,datetime} 或 @ref{4ed,,time} 对象调用，用来与它们的同名方法相对应。 @ref{194,,datetime} 对象会将自身作为传入参数，而 @ref{4ed,,time} 对象会将 @code{None} 作为传入参数。 这样 @ref{378,,tzinfo} 子类的方法应当准备好接受 @emph{dt} 参数值为 @code{None} 或是 @ref{194,,datetime} 类的实例。

当传入 @code{None} 时，应当由类的设计者来决定最佳回应方式。 例如，返回 @code{None} 适用于希望该类提示时间对象不参与 @ref{378,,tzinfo} 协议处理。 让 @code{utcoffset(None)} 返回标准 UTC 时差也许会更有用处，因为并没有其他可用于发现标准时差的约定惯例。

当传入一个 @ref{194,,datetime} 对象来回应 @ref{194,,datetime} 方法时，@code{dt.tzinfo} 与 @emph{self} 是同一对象。 @ref{378,,tzinfo} 方法可以依赖这一点，除非用户代码直接调用了 @ref{378,,tzinfo} 方法。 此行为的目的是使得 @ref{378,,tzinfo} 方法将 @emph{dt} 解读为本地时间，而不需要担心其他时区的相关对象。

还有一个额外的 @ref{378,,tzinfo} 方法，某个子类可能会希望重载它：

@geindex fromutc() (datetime.tzinfo 方法)
@anchor{library/datetime datetime tzinfo fromutc}@anchor{1860}
@deffn {方法} tzinfo.fromutc (dt)

此方法会由默认的 @ref{196,,datetime.astimezone()} 实现来调用。 当被其调用时，@code{dt.tzinfo} 为 @emph{self}，并且 @emph{dt} 的日期和时间数据会被视为表示 UTC 时间，@ref{1860,,fromutc()} 的目标是调整日期和时间数据，返回一个等价的 datetime 来表示 @emph{self} 的本地时间。

大多数 @ref{378,,tzinfo} 子类应该能够毫无问题地继承默认的 @ref{1860,,fromutc()} 实现。 它的健壮性足以处理固定差值的时区以及同时负责标准时和夏令时的时区，对于后者甚至还能处理 DST 转换时间在各个年份有变化的情况。 一个默认 @ref{1860,,fromutc()} 实现可能无法在所有情况下正确处理的例子是（与 UTC 的）标准时差取决于所经过的特定日期和时间，这种情况可能由于政治原因而出现。 默认的 @code{astimezone()} 和 @ref{1860,,fromutc()} 实现可能无法生成你希望的结果，如果这个结果恰好是跨越了标准时差发生改变的时刻当中的某个小时值的话。

忽略针对错误情况的代码，默认 @ref{1860,,fromutc()} 实现的行为方式如下:

@example
def fromutc(self, dt):
    # raise ValueError error if dt.tzinfo is not self
    dtoff = dt.utcoffset()
    dtdst = dt.dst()
    # raise ValueError if dtoff is None or dtdst is None
    delta = dtoff - dtdst  # this is self's standard offset
    if delta:
        dt += delta   # convert to standard local time
        dtdst = dt.dst()
        # raise ValueError if dtdst is None
    if dtdst:
        return dt + dtdst
    else:
        return dt
@end example
@end deffn

在以下 @code{tzinfo_examples.py} 文件中有一些 @ref{378,,tzinfo} 类的例子：

@example
from datetime import tzinfo, timedelta, datetime

ZERO = timedelta(0)
HOUR = timedelta(hours=1)
SECOND = timedelta(seconds=1)

# A class capturing the platform's idea of local time.
# (May result in wrong values on historical times in
#  timezones where UTC offset and/or the DST rules had
#  changed in the past.)
import time as _time

STDOFFSET = timedelta(seconds = -_time.timezone)
if _time.daylight:
    DSTOFFSET = timedelta(seconds = -_time.altzone)
else:
    DSTOFFSET = STDOFFSET

DSTDIFF = DSTOFFSET - STDOFFSET

class LocalTimezone(tzinfo):

    def fromutc(self, dt):
        assert dt.tzinfo is self
        stamp = (dt - datetime(1970, 1, 1, tzinfo=self)) // SECOND
        args = _time.localtime(stamp)[:6]
        dst_diff = DSTDIFF // SECOND
        # Detect fold
        fold = (args == _time.localtime(stamp - dst_diff))
        return datetime(*args, microsecond=dt.microsecond,
                        tzinfo=self, fold=fold)

    def utcoffset(self, dt):
        if self._isdst(dt):
            return DSTOFFSET
        else:
            return STDOFFSET

    def dst(self, dt):
        if self._isdst(dt):
            return DSTDIFF
        else:
            return ZERO

    def tzname(self, dt):
        return _time.tzname[self._isdst(dt)]

    def _isdst(self, dt):
        tt = (dt.year, dt.month, dt.day,
              dt.hour, dt.minute, dt.second,
              dt.weekday(), 0, 0)
        stamp = _time.mktime(tt)
        tt = _time.localtime(stamp)
        return tt.tm_isdst > 0

Local = LocalTimezone()


# A complete implementation of current DST rules for major US time zones.

def first_sunday_on_or_after(dt):
    days_to_go = 6 - dt.weekday()
    if days_to_go:
        dt += timedelta(days_to_go)
    return dt


# US DST Rules
#
# This is a simplified (i.e., wrong for a few cases) set of rules for US
# DST start and end times. For a complete and up-to-date set of DST rules
# and timezone definitions, visit the Olson Database (or try pytz):
# http://www.twinsun.com/tz/tz-link.htm
# http://sourceforge.net/projects/pytz/ (might not be up-to-date)
#
# In the US, since 2007, DST starts at 2am (standard time) on the second
# Sunday in March, which is the first Sunday on or after Mar 8.
DSTSTART_2007 = datetime(1, 3, 8, 2)
# and ends at 2am (DST time) on the first Sunday of Nov.
DSTEND_2007 = datetime(1, 11, 1, 2)
# From 1987 to 2006, DST used to start at 2am (standard time) on the first
# Sunday in April and to end at 2am (DST time) on the last
# Sunday of October, which is the first Sunday on or after Oct 25.
DSTSTART_1987_2006 = datetime(1, 4, 1, 2)
DSTEND_1987_2006 = datetime(1, 10, 25, 2)
# From 1967 to 1986, DST used to start at 2am (standard time) on the last
# Sunday in April (the one on or after April 24) and to end at 2am (DST time)
# on the last Sunday of October, which is the first Sunday
# on or after Oct 25.
DSTSTART_1967_1986 = datetime(1, 4, 24, 2)
DSTEND_1967_1986 = DSTEND_1987_2006

def us_dst_range(year):
    # Find start and end times for US DST. For years before 1967, return
    # start = end for no DST.
    if 2006 < year:
        dststart, dstend = DSTSTART_2007, DSTEND_2007
    elif 1986 < year < 2007:
        dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006
    elif 1966 < year < 1987:
        dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986
    else:
        return (datetime(year, 1, 1), ) * 2

    start = first_sunday_on_or_after(dststart.replace(year=year))
    end = first_sunday_on_or_after(dstend.replace(year=year))
    return start, end


class USTimeZone(tzinfo):

    def __init__(self, hours, reprname, stdname, dstname):
        self.stdoffset = timedelta(hours=hours)
        self.reprname = reprname
        self.stdname = stdname
        self.dstname = dstname

    def __repr__(self):
        return self.reprname

    def tzname(self, dt):
        if self.dst(dt):
            return self.dstname
        else:
            return self.stdname

    def utcoffset(self, dt):
        return self.stdoffset + self.dst(dt)

    def dst(self, dt):
        if dt is None or dt.tzinfo is None:
            # An exception may be sensible here, in one or both cases.
            # It depends on how you want to treat them.  The default
            # fromutc() implementation (called by the default astimezone()
            # implementation) passes a datetime with dt.tzinfo is self.
            return ZERO
        assert dt.tzinfo is self
        start, end = us_dst_range(dt.year)
        # Can't compare naive to aware objects, so strip the timezone from
        # dt first.
        dt = dt.replace(tzinfo=None)
        if start + HOUR <= dt < end - HOUR:
            # DST is in effect.
            return HOUR
        if end - HOUR <= dt < end:
            # Fold (an ambiguous hour): use dt.fold to disambiguate.
            return ZERO if dt.fold else HOUR
        if start <= dt < start + HOUR:
            # Gap (a non-existent hour): reverse the fold rule.
            return HOUR if dt.fold else ZERO
        # DST is off.
        return ZERO

    def fromutc(self, dt):
        assert dt.tzinfo is self
        start, end = us_dst_range(dt.year)
        start = start.replace(tzinfo=self)
        end = end.replace(tzinfo=self)
        std_time = dt + self.stdoffset
        dst_time = std_time + HOUR
        if end <= dst_time < end + HOUR:
            # Repeated hour
            return std_time.replace(fold=1)
        if std_time < start or dst_time >= end:
            # Standard time
            return std_time
        if start <= std_time < end - HOUR:
            # Daylight saving time
            return dst_time


Eastern  = USTimeZone(-5, "Eastern",  "EST", "EDT")
Central  = USTimeZone(-6, "Central",  "CST", "CDT")
Mountain = USTimeZone(-7, "Mountain", "MST", "MDT")
Pacific  = USTimeZone(-8, "Pacific",  "PST", "PDT")
@end example

请注意同时负责标准时和夏令时的 @ref{378,,tzinfo} 子类在每年两次的 DST 转换点上会出现不可避免的微妙问题。具体而言，考虑美国东部时区 (UTC -0500)，它的 EDT 从三月的第二个星期天 1:59 (EST) 之后一分钟开始，并在十一月的第一天星期天 1:59 (EDT) 之后一分钟结束:

@example
  UTC   3:MM  4:MM  5:MM  6:MM  7:MM  8:MM
  EST  22:MM 23:MM  0:MM  1:MM  2:MM  3:MM
  EDT  23:MM  0:MM  1:MM  2:MM  3:MM  4:MM

start  22:MM 23:MM  0:MM  1:MM  3:MM  4:MM

  end  23:MM  0:MM  1:MM  1:MM  2:MM  3:MM
@end example

当 DST 开始时（即 "start" 行），本地时钟从 1:59 跳到 3:00。 形式为 2:MM 的时间值在那一天是没有意义的，因此在 DST 开始那一天 @code{astimezone(Eastern)} 不会输出包含 @code{hour == 2} 的结果。 例如，在 2016 年春季时钟向前调整时，我们得到:

@example
>>> from datetime import datetime, timezone
>>> from tzinfo_examples import HOUR, Eastern
>>> u0 = datetime(2016, 3, 13, 5, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname())
...
05:00:00 UTC = 00:00:00 EST
06:00:00 UTC = 01:00:00 EST
07:00:00 UTC = 03:00:00 EDT
08:00:00 UTC = 04:00:00 EDT
@end example

当 DST 结束时（见 "end" 行），会有更糟糕的潜在问题：本地时间值中有一个小时是不可能没有歧义的：夏令时的最后一小时。 即以北美东部时间表示当天夏令时结束时的形式为 5:MM UTC 的时间。 本地时钟从 1:59 (夏令时) 再次跳回到 1:00 (标准时)。 形式为 1:MM 的本地时间就是有歧义的。 此时 @code{astimezone()} 是通过将两个相邻的 UTC 小时映射到两个相同的本地小时来模仿本地时钟的行为。 在这个北美东部时间的示例中，形式为 5:MM 和 6:MM 的 UTC 时间在转换为北美东部时间时都将被映射到 1:MM，但前一个时间会将 @ref{4ee,,fold} 属性设为 0 而后一个时间会将其设为 1。 例如，在 2016 年秋季时钟往回调整时，我们得到:

@example
>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0
@end example

请注意不同的 @ref{194,,datetime} 实例仅通过 @ref{4ee,,fold} 属性值来加以区分，它们在比较时会被视为相等。

不允许时间显示存在歧义的应用需要显式地检查 @ref{4ee,,fold} 属性的值，或者避免使用混合式的 @ref{378,,tzinfo} 子类；当使用 @ref{9fb,,timezone} 或者任何其他固定差值的 @ref{378,,tzinfo} 子类例如仅表示 EST（固定差值 -5 小时）或仅表示 EDT（固定差值 -4 小时）的类时是不会有歧义的。


@subsubheading 参见



@table @asis

@item dateutil.tz@footnote{https://dateutil.readthedocs.io/en/stable/tz.html}

@ref{31,,datetime} 模块有一个基本 @ref{9fb,,timezone} 类（用来处理任意与 UTC 的固定时差）及其 @ref{187f,,timezone.utc} 属性（一个 UTC 时区实例）。

@emph{dateutil.tz} 库将 @emph{IANA 时区数据库} (又名 Olson 数据库) 引入 Python 并推荐使用。

@item IANA 时区数据库@footnote{https://www.iana.org/time-zones}

该时区数据库 (通常称为 tz, tzdata 或 zoneinfo) 包含大量代码和数据用来表示全球许多有代表性的地点的本地时间的历史信息。 它会定期进行更新以反映各政治实体对时区边界、UTC 差值和夏令时规则的更改。
@end table


@node timezone 对象,strftime 和 strptime 的行为,tzinfo 对象,datetime --- 基本的日期和时间类型
@anchor{library/datetime datetime-timezone}@anchor{1880}@anchor{library/datetime timezone-objects}@anchor{1881}
@subsubsection @code{timezone} 对象


@ref{9fb,,timezone} 类是 @ref{378,,tzinfo} 的子类，它的每个实例都代表一个以与 UTC 的固定时差来定义的时区。

此类的对象不可被用于代表某些特殊地点的时区信息，这些地点在一年的不同日期会使用不同的时差，或是在历史上对民用时间进行过调整。

@geindex timezone (datetime 中的类)
@anchor{library/datetime datetime timezone}@anchor{9fb}
@deffn {类} datetime.timezone (offset, name=None)

@emph{offset} 参数必须指定为一个 @ref{195,,timedelta} 对象，表示本地时间与 UTC 的时差。 它必须严格限制于 @code{-timedelta(hours=24)} 和 @code{timedelta(hours=24)} 之间，否则会引发 @ref{1fb,,ValueError}。

@emph{name} 参数是可选的。 如果指定则必须为一个字符串，它将被用作 @ref{1861,,datetime.tzname()} 方法的返回值。


3.2 新版功能.



在 3.7 版更改: UTC 时差不再限制为一个整数分钟值。

@end deffn

@geindex utcoffset() (datetime.timezone 方法)
@anchor{library/datetime datetime timezone utcoffset}@anchor{1882}
@deffn {方法} timezone.utcoffset (dt)

返回当 @ref{9fb,,timezone} 实例被构造时指定的固定值。

@emph{dt} 参数会被忽略。 返回值是一个 @ref{195,,timedelta} 实例，其值等于本地时间与 UTC 之间的时差。


在 3.7 版更改: UTC 时差不再限制为一个整数分钟值。

@end deffn

@geindex tzname() (datetime.timezone 方法)
@anchor{library/datetime datetime timezone tzname}@anchor{1883}
@deffn {方法} timezone.tzname (dt)

返回当 @ref{9fb,,timezone} 实例被构造时指定的固定值。

如果没有在构造器中提供 @emph{name}，则 @code{tzname(dt)} 所返回的名称将根据 @code{offset} 值按以下规则生成。 如果 @emph{offset} 为 @code{timedelta(0)}，则名称为“UTC”，否则为字符串 @code{UTC±HH:MM}，其中 ± 为 @code{offset} 的正负符号，HH 和 MM 分别为表示 @code{offset.hours} 和 @code{offset.minutes} 的两个数码。


在 3.6 版更改: 由 @code{offset=timedelta(0)} 生成的名称现在为简单的 @cite{'UTC'} 而不再是 @code{'UTC+00:00'}。

@end deffn

@geindex dst() (datetime.timezone 方法)
@anchor{library/datetime datetime timezone dst}@anchor{1884}
@deffn {方法} timezone.dst (dt)

总是返回 @code{None}。
@end deffn

@geindex fromutc() (datetime.timezone 方法)
@anchor{library/datetime datetime timezone fromutc}@anchor{1885}
@deffn {方法} timezone.fromutc (dt)

返回 @code{dt + offset}。 @emph{dt} 参数必须为一个感知型 @ref{194,,datetime} 实例，其中 @code{tzinfo} 值设为 @code{self}。
@end deffn

类属性：

@geindex utc (datetime.timezone 属性)
@anchor{library/datetime datetime timezone utc}@anchor{187f}
@deffn {属性} timezone.utc

UTC 时区，@code{timezone(timedelta(0))}。
@end deffn

@geindex % (percent); datetime format

@node strftime 和 strptime 的行为,,timezone 对象,datetime --- 基本的日期和时间类型
@anchor{library/datetime strftime-and-strptime-behavior}@anchor{1886}@anchor{library/datetime strftime-strptime-behavior}@anchor{184d}
@subsubsection @code{strftime()} 和 @code{strptime()} 的行为


@ref{193,,date}, @ref{194,,datetime} 和 @ref{4ed,,time} 对象都支持 @code{strftime(format)} 方法，可用来创建由一个显式格式字符串所控制的表示时间的字符串。

相反地，@ref{f3f,,datetime.strptime()} 类会根据表示日期和时间的字符串和相应的格式字符串来创建一个 @ref{194,,datetime} 对象。

下表提供了 @code{strftime()} 与 @code{strptime()} 的高层级比较：


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

@tab

@code{strftime}

@tab

@code{strptime}

@item

用法

@tab

根据给定的格式将对象转换为字符串

@tab

将字符串解析为给定相应格式的 @ref{194,,datetime} 对象

@item

方法类型

@tab

实例方法

@tab

类方法

@item

方法

@tab

@ref{193,,date}; @ref{194,,datetime}; @ref{4ed,,time}

@tab

@ref{194,,datetime}

@item

签名

@tab

@code{strftime(format)}

@tab

@code{strptime(date_string, format)}

@end multitable


@menu
* strftime() 和 strptime() Format Codes: strftime 和 strptime Format Codes. 
* 技术细节:: 

@end menu

@node strftime 和 strptime Format Codes,技术细节,,strftime 和 strptime 的行为
@anchor{library/datetime strftime-and-strptime-format-codes}@anchor{1887}
@subsubsection @code{strftime()} 和 @code{strptime()} Format Codes


以下列表显示了 1989 版 C 标准所要求的全部格式代码，它们在带有标准 C 实现的所有平台上均可用。


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

指令

@tab

含义

@tab

示例

@tab

注释

@item

@code{%a}

@tab

当地工作日的缩写。

@tab


@display
Sun, Mon, ..., Sat (en_US);@w{ }
So, Mo, ..., Sa (de_DE)@w{ }
@end display



@tab

(1)

@item

@code{%A}

@tab

本地化的星期中每日的完整名称。

@tab


@display
Sunday, Monday, ..., Saturday (en_US);@w{ }
Sonntag, Montag, ..., Samstag (de_DE)@w{ }
@end display



@tab

(1)

@item

@code{%w}

@tab

以十进制数显示的工作日，其中0表示星期日，6表示星期六。

@tab

0, 1, ..., 6

@tab

@item

@code{%d}

@tab

补零后，以十进制数显示的月份中的一天。

@tab

01, 02, ..., 31

@tab

(9)

@item

@code{%b}

@tab

当地月份的缩写。

@tab


@display
Jan, Feb, ..., Dec (en_US);@w{ }
Jan, Feb, ..., Dez (de_DE)@w{ }
@end display



@tab

(1)

@item

@code{%B}

@tab

本地化的月份全名。

@tab


@display
January, February, ..., December (en_US);@w{ }
Januar, Februar, ..., Dezember (de_DE)@w{ }
@end display



@tab

(1)

@item

@code{%m}

@tab

补零后，以十进制数显示的月份。

@tab

01, 02, ..., 12

@tab

(9)

@item

@code{%y}

@tab

补零后，以十进制数表示的，不带世纪的年份。

@tab

00, 01, ..., 99

@tab

(9)

@item

@code{%Y}

@tab

十进制数表示的带世纪的年份。

@tab

0001, 0002, ..., 2013,
2014, ..., 9998, 9999

@tab

(2)

@item

@code{%H}

@tab

以补零后的十进制数表示的小时（24 小时制）。

@tab

00, 01, ..., 23

@tab

(9)

@item

@code{%I}

@tab

以补零后的十进制数表示的小时（12 小时制）。

@tab

01, 02, ..., 12

@tab

(9)

@item

@code{%p}

@tab

本地化的 AM 或 PM 。

@tab


@display
AM, PM (en_US);@w{ }
am, pm (de_DE)@w{ }
@end display



@tab

(1),
(3)

@item

@code{%M}

@tab

补零后，以十进制数显示的分钟。

@tab

00, 01, ..., 59

@tab

(9)

@item

@code{%S}

@tab

补零后，以十进制数显示的秒。

@tab

00, 01, ..., 59

@tab

(4),
(9)

@item

@code{%f}

@tab

以十进制数表示的微秒，在左侧补零。

@tab

000000, 000001, ...,
999999

@tab

(5)

@item

@code{%z}

@tab

UTC 偏移量，格式为 @code{±HHMM[SS[.ffffff]]} （如果是简单型对象则为空字符串）。

@tab

(空), +0000, -0400, +1030, +063415, -030712.345216

@tab

(6)

@item

@code{%Z}

@tab

时区名称（如果对象为简单型则为空字符串）。

@tab

(空), UTC, EST, CST

@tab

@item

@code{%j}

@tab

以补零后的十进制数表示的一年中的日序号。

@tab

001, 002, ..., 366

@tab

(9)

@item

@code{%U}

@tab

以补零后的十进制数表示的一年中的周序号（星期日作为每周的第一天）。 在新的一年中第一个星期日之前的所有日子都被视为是在第 0 周。

@tab

00, 01, ..., 53

@tab

(7),
(9)

@item

@code{%W}

@tab

以十进制数表示的一年中的周序号（星期一作为每周的第一天）。 在新的一年中第一个第期一之前的所有日子都被视为是在第 0 周。

@tab

00, 01, ..., 53

@tab

(7),
(9)

@item

@code{%c}

@tab

本地化的适当日期和时间表示。

@tab


@display
Tue Aug 16 21:30:00 1988 (en_US);@w{ }
Di 16 Aug 21:30:00 1988 (de_DE)@w{ }
@end display



@tab

(1)

@item

@code{%x}

@tab

本地化的适当日期表示。

@tab


@display
08/16/88 (None);@w{ }
08/16/1988 (en_US);@w{ }
16.08.1988 (de_DE)@w{ }
@end display



@tab

(1)

@item

@code{%X}

@tab

本地化的适当时间表示。

@tab


@display
21:30:00 (en_US);@w{ }
21:30:00 (de_DE)@w{ }
@end display



@tab

(1)

@item

@code{%%}

@tab

字面的 @code{'%'} 字符。

@tab

%

@tab

@end multitable


为了方便起见，还包括了C89标准不需要的其他一些指令。这些参数都对应于ISO 8601日期值。


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

指令

@tab

含义

@tab

示例

@tab

注释

@item

@code{%G}

@tab

带有世纪的 ISO 8601 年份，表示包含大部分 ISO 星期 (@code{%V}) 的年份。

@tab

0001, 0002, ..., 2013,
2014, ..., 9998, 9999

@tab

(8)

@item

@code{%u}

@tab

以十进制数显示的 ISO 8601 星期中的日序号，其中 1 表示星期一。

@tab

1, 2, ..., 7

@tab

@item

@code{%V}

@tab

以十进制数显示的 ISO 8601 星期，以星期一作为每周的第一天。 第 01 周为包含 1 月 4 日的星期。

@tab

01, 02, ..., 53

@tab

(8),
(9)

@end multitable


这些代码可能不是在所有平台上都可与 @code{strftime()} 方法配合使用。 ISO 8601 年份和 ISO 8601 星期指令并不能与上面的年份和星期序号指令相互替代。 调用 @code{strptime()} 时传入不完整或有歧义的 ISO 8601 指令将引发 @ref{1fb,,ValueError}。

对完整格式代码集的支持在不同平台上有所差异，因为 Python 要调用所在平台的 C 库的 @code{strftime()} 函数，而不同平台的差异是很常见的。 要查看你所用平台所支持的完整格式代码集，请参阅 @code{strftime(3)} 文档。


3.6 新版功能: 增加了 @code{%G},  @code{%u}  和 @code{%V}。


@node 技术细节,,strftime 和 strptime Format Codes,strftime 和 strptime 的行为
@anchor{library/datetime technical-detail}@anchor{1888}
@subsubsection 技术细节


总体而言，@code{d.strftime(fmt)} 类似于 @ref{10a,,time} 模块的 @code{time.strftime(fmt, d.timetuple())}，但是并非所有对象都支持 @code{timetuple()} 方法。

对于 @ref{f3f,,datetime.strptime()} 类方法，默认值为 @code{1900-01-01T00:00:00.000}: 任何未在格式字符串中指定的部分都将从默认值中提取。 @footnote{@w{(4)} 
传入 @code{datetime.strptime('Feb 29', '%b %d')} 将导致错误，因为 @code{1900} 不是闰年。
}

使用 @code{datetime.strptime(date_string, format)} 等价于:

@example
datetime(*(time.strptime(date_string, format)[0:6]))
@end example

除非格式中包含秒以下的部分或时区差值信息，它们在 @code{datetime.strptime} 中受支持但会被 @code{time.strptime} 所丢弃。

对于 @ref{4ed,,time} 对象，年、月、日的格式代码不应被使用，因为 @ref{10a,,time} 对象没有这些值。 如果它们被使用，则年份将被替换为 @code{1900}，而月和日将被替换为 @code{1}。

对于 @ref{193,,date} 对象，时、分、秒和微秒的格式代码不应被使用，因为 @ref{193,,date} 对象没有这些值。 如果它们被使用，则它们都将被替换为 @code{0}。

出于相同的原因，对于包含当前区域设置字符集所无法表示的 Unicode 码位的格式字符串的处理方式也取决于具体平台。 在某些平台上这样的码位会不加修改地原样输出，而在其他平台上 @code{strftime} 则可能引发 @ref{c34,,UnicodeError} 或只返回一个空字符串。

注释:


@enumerate 

@item 
由于此格式依赖于当前区域设置，因此对具体输出值应当保持谨慎预期。 字段顺序会发生改变（例如 "month/day/year" 与 "day/month/year"），并且输出可能包含使用区域设置所指定的默认编码格式的 Unicode 字符（例如如果当前区域为 @code{ja_JP}，则默认编码格式可能为 @code{eucJP}, @code{SJIS} 或 @code{utf-8} 中的一个；使用 @ref{1889,,locale.getlocale()} 可确定当前区域设置的编码格式）。

@item 
@code{strptime()} 方法能够解析整个 [1, 9999] 范围内的年份，但 < 1000 的年份必须加零填充为 4 位数字宽度。


在 3.2 版更改: 在之前的版本中，@code{strftime()} 方法只限于 >= 1900 的年份。



在 3.3 版更改: 在版本3.2中，@code{strftime()} 方法只限于 years >= 1000。


@item 
当与 @code{strptime()} 方法一起使用时，如果使用 @code{%I} 指令来解析小时，@code{%p} 指令只影响输出小时字段。

@item 
与 @ref{10a,,time} 模块不同的是， @ref{31,,datetime} 模块不支持闰秒。

@item 
当与 @code{strptime()} 方法一起使用时，@code{%f} 指令可接受一至六个数码及左边的零填充。 @code{%f} 是对 C 标准中格式字符集的扩展（但单独在 datetime 对象中实现，因此它总是可用）。

@item 
对于简单型对象，@code{%z} and @code{%Z} 格式代码会被替换为空字符串。

对于一个感知型对象而言：


@table @asis

@item @code{%z}

@code{utcoffset()} 会被转换为 @code{±HHMM[SS[.ffffff]]} 形式的字符串，其中 @code{HH} 为给出 UTC 时差的小时部分的 2 位数码字符串，@code{MM} 为给出 UTC 时差的分钟部分的 2 位数码字符串，@code{SS} 为给出 UTC 时差的秒部分的 2 位数码字符串，而 @code{ffffff} 为给出 UTC 时差的微秒部分的 6 位数码字符串。 当时差为整数秒时 @code{ffffff} 部分将被省略，而当时差为整数分钟时 @code{ffffff} 和 @code{SS} 部分都将被省略。 例如，如果 @code{utcoffset()} 返回 @code{timedelta(hours=-3, minutes=-30)}，则 @code{%z} 会被替换为字符串 @code{'-0330'}。
@end table


在 3.7 版更改: UTC 时差不再限制为一个整数分钟值。



在 3.7 版更改: 当提供 @code{%z} 指令给 @code{strptime()} 方法时，UTC 差值可以在时、分和秒之间使用冒号分隔符。 例如，@code{'+01:00:00'} 将被解读为一小时的差值。 此外，提供 @code{'Z'} 就相当于 @code{'+00:00'}。



@table @asis

@item @code{%Z}

如果 @code{tzname()} 返回 @code{None}，@code{%Z} 会被替换为一个空字符串。 在其他情况下 @code{%Z} 会被替换为返回值，这必须为一个字符串。
@end table


在 3.2 版更改: 当提供 @code{%z} 指令给 @code{strptime()} 方法时，将产生一个感知型 @ref{194,,datetime} 对象。 结果的 @code{tzinfo} 将被设为一个 @ref{9fb,,timezone} 实例。


@item 
当与 @code{strptime()} 方法一起使用时，@code{%U} 和 @code{%W} 仅用于指定星期几和日历年份 (@code{%Y}) 的计算。

@item 
类似于 @code{%U} 和 @code{%W}，@code{%V} 仅用于在 @code{strptime()} 格式字符串中指定星期几和 ISO 年份 (@code{%G}) 的计算。 还要注意 @code{%G} 和 @code{%Y} 是不可交换的。

@item 
当于 @code{strptime()} 方法一起使用时，前导的零在格式 @code{%d}, @code{%m}, @code{%H}, @code{%I}, @code{%M}, @code{%S}, @code{%J}, @code{%U}, @code{%W} 和 @code{%V} 中是可选的。 格式 @code{%y} 不要求有前导的零。
@end enumerate

@subsubheading 备注


@node calendar --- 日历相关函数,collections --- 容器数据类型,datetime --- 基本的日期和时间类型,数据类型
@anchor{library/calendar doc}@anchor{188a}@anchor{library/calendar calendar-general-calendar-related-functions}@anchor{188b}@anchor{library/calendar module-calendar}@anchor{15}
@subsection @code{calendar} --- 日历相关函数


@geindex calendar (模块)

@strong{源代码：} Lib/calendar.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/calendar.py}


__________________________________________________________________


这个模块让你可以输出像 Unix @code{cal} 那样的日历，它还提供了其它与日历相关的实用函数。 默认情况下，这些日历把星期一当作一周的第一天，星期天为一周的最后一天（按照欧洲惯例）。 可以使用 @ref{188c,,setfirstweekday()} 方法设置一周的第一天为星期天 (6) 或者其它任意一天。 使用整数作为指定日期的参数。 更多相关的函数，参见 @ref{31,,datetime} 和 @ref{10a,,time} 模块。

在这个模块中定义的函数和类都基于一个理想化的日历，现行公历向过去和未来两个方向无限扩展。这与 Dershowitz 和 Reingold 的书 "历法计算" 中所有计算的基本日历 -- "proleptic Gregorian" 日历的定义相符合。 ISO 8601标准还规定了 0 和 负数年份。0年指公元前1年， -1年指公元前2年，依此类推。

@geindex Calendar (calendar 中的类)
@anchor{library/calendar calendar Calendar}@anchor{188d}
@deffn {类} calendar.Calendar (firstweekday=0)

创建一个 @ref{188d,,Calendar} 对象。 @emph{firstweekday} 是一个整数，用于指定一周的第一天。 @code{0} 是星期一（默认值），@code{6} 是星期天。

@ref{188d,,Calendar} 对象提供了一些可被用于准备日历数据格式化的方法。 这个类本身不执行任何格式化操作。 这部分任务应由子类来完成。

@ref{188d,,Calendar} 类的实例有下列方法：

@geindex iterweekdays() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar iterweekdays}@anchor{188e}
@deffn {方法} iterweekdays ()

返回一个迭代器，迭代器的内容为一星期的数字。迭代器的第一个值与 @ref{188f,,firstweekday} 属性的值一至。
@end deffn

@geindex itermonthdates() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar itermonthdates}@anchor{4a1}
@deffn {方法} itermonthdates (year, month)

返回一个迭代器，迭代器的内容为 @emph{year} 年 @emph{month} 月(1-12)的日期。这个迭代器返回当月的所有日期 ( @ref{193,,datetime.date}  对象)，日期包含了本月头尾用于组成完整一周的日期。
@end deffn

@geindex itermonthdays() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar itermonthdays}@anchor{1890}
@deffn {方法} itermonthdays (year, month)

返回一个迭代器，迭代器的内容与 @ref{4a1,,itermonthdates()} 类似，为 @emph{year} 年 @emph{month} 月的日期，但不受 @ref{193,,datetime.date} 范围限制。返回的日期为当月每一天的日期对应的天数。对于不在当月的日期，显示为 @code{0}。
@end deffn

@geindex itermonthdays2() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar itermonthdays2}@anchor{1891}
@deffn {方法} itermonthdays2 (year, month)

返回一个迭代器，迭代器的内容与 @ref{4a1,,itermonthdates()} 类似为 @emph{year} 年 @emph{month} 月的日期，但不受 @ref{193,,datetime.date} 范围的限制。迭代器中的元素为一个由日期和代表星期几的数字组成的的元组。
@end deffn

@geindex itermonthdays3() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar itermonthdays3}@anchor{4a2}
@deffn {方法} itermonthdays3 (year, month)

返回一个迭代器，迭代器的内容与 @ref{4a1,,itermonthdates()} 类似为 @emph{year} 年 @emph{month} 月的日期，但不受 @ref{193,,datetime.date} 范围的限制。迭代器的元素为一个由年，月，日组成的元组。


3.7 新版功能.

@end deffn

@geindex itermonthdays4() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar itermonthdays4}@anchor{4a3}
@deffn {方法} itermonthdays4 (year, month)

返回一个迭代器，迭代器的内容与 @ref{4a1,,itermonthdates()} 类似为 @emph{year} 年 @emph{month} 月的日期，但不受 @ref{193,,datetime.date} 范围的限制。迭代器的元素为一个由年，月，日和代表星期几的数字组成的元组。


3.7 新版功能.

@end deffn

@geindex monthdatescalendar() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar monthdatescalendar}@anchor{1892}
@deffn {方法} monthdatescalendar (year, month)

返回一个表示指定年月的周列表。周列表由七个  @ref{193,,datetime.date} 对象组成。
@end deffn

@geindex monthdays2calendar() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar monthdays2calendar}@anchor{1893}
@deffn {方法} monthdays2calendar (year, month)

返回一个表示指定年月的周列表。周列表由七个代表日期的数字和代表周几的数字组成的二元元组。
@end deffn

@geindex monthdayscalendar() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar monthdayscalendar}@anchor{1894}
@deffn {方法} monthdayscalendar (year, month)

返回一个表示指定年月的周列表。周列表由七个代表日期的数字组成。
@end deffn

@geindex yeardatescalendar() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar yeardatescalendar}@anchor{1895}
@deffn {方法} yeardatescalendar (year, width=3)

返回可以用来格式化的指定年月的数据。返回的值是一个列表，列表是月份组成的行。每一行包含了最多 @emph{width} 个月(默认为3)。每个月包含了4到6周，每周包含1--7天。每一天使用 @ref{193,,datetime.date} 对象。
@end deffn

@geindex yeardays2calendar() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar yeardays2calendar}@anchor{1896}
@deffn {方法} yeardays2calendar (year, width=3)

返回可以用来模式化的指定年月的数据(与 @ref{1895,,yeardatescalendar()} 类似)。周列表的元素是由表示日期的数字和表示星期几的数字组成的元组。不在这个月的日子为0。
@end deffn

@geindex yeardayscalendar() (calendar.Calendar 方法)
@anchor{library/calendar calendar Calendar yeardayscalendar}@anchor{1897}
@deffn {方法} yeardayscalendar (year, width=3)

返回可以用来模式化的指定年月的数据(与 @ref{1895,,yeardatescalendar()} 类似)。周列表的元素是表示日期的数字。不在这个月的日子为0。
@end deffn
@end deffn

@geindex TextCalendar (calendar 中的类)
@anchor{library/calendar calendar TextCalendar}@anchor{1898}
@deffn {类} calendar.TextCalendar (firstweekday=0)

可以使用这个类生成纯文本日历。

@ref{1898,,TextCalendar} 实例有以下方法：

@geindex formatmonth() (calendar.TextCalendar 方法)
@anchor{library/calendar calendar TextCalendar formatmonth}@anchor{1899}
@deffn {方法} formatmonth (theyear, themonth, w=0, l=0)

返回一个多行字符串来表示指定年月的日历。@emph{w} 为日期的宽度，但始终保持日期居中。@emph{l} 指定了每星期占用的行数。以上这些还依赖于构造器或者 @ref{188c,,setfirstweekday()} 方法指定的周的第一天是哪一天。
@end deffn

@geindex prmonth() (calendar.TextCalendar 方法)
@anchor{library/calendar calendar TextCalendar prmonth}@anchor{189a}
@deffn {方法} prmonth (theyear, themonth, w=0, l=0)

与 @ref{1899,,formatmonth()} 方法一样，返回一个月的日历。
@end deffn

@geindex formatyear() (calendar.TextCalendar 方法)
@anchor{library/calendar calendar TextCalendar formatyear}@anchor{189b}
@deffn {方法} formatyear (theyear, w=2, l=1, c=6, m=3)

返回一个多行字符串，这个字符串为一个 @emph{m} 列日历。可选参数 @emph{w}, @emph{l}, 和 @emph{c} 分别表示日期列数， 周的行数， 和月之间的间隔。同样，以上这些还依赖于构造器或者 @ref{188c,,setfirstweekday()} 指定哪一天为一周的第一天。日历的第一年由平台依赖于使用的平台。
@end deffn

@geindex pryear() (calendar.TextCalendar 方法)
@anchor{library/calendar calendar TextCalendar pryear}@anchor{189c}
@deffn {方法} pryear (theyear, w=2, l=1, c=6, m=3)

与 @ref{189b,,formatyear()} 方法一样，返回一整年的日历。
@end deffn
@end deffn

@geindex HTMLCalendar (calendar 中的类)
@anchor{library/calendar calendar HTMLCalendar}@anchor{368}
@deffn {类} calendar.HTMLCalendar (firstweekday=0)

可以使用这个类生成 HTML 日历。

@code{HTMLCalendar} 实例有以下方法：

@geindex formatmonth() (calendar.HTMLCalendar 方法)
@anchor{library/calendar calendar HTMLCalendar formatmonth}@anchor{189d}
@deffn {方法} formatmonth (theyear, themonth, withyear=True)

返回一个 HTML 表格作为指定年月的日历。 @emph{withyear} 为真，则年份将会包含在表头，否则只显示月份。
@end deffn

@geindex formatyear() (calendar.HTMLCalendar 方法)
@anchor{library/calendar calendar HTMLCalendar formatyear}@anchor{189e}
@deffn {方法} formatyear (theyear, width=3)

返回一个 HTML 表格作为指定年份的日历。 @emph{width} (默认为3) 用于规定每一行显示月份的数量。
@end deffn

@geindex formatyearpage() (calendar.HTMLCalendar 方法)
@anchor{library/calendar calendar HTMLCalendar formatyearpage}@anchor{189f}
@deffn {方法} formatyearpage (theyear, width=3, css='calendar.css', encoding=None)

返回一个完整的 HTML 页面作为指定年份的日历。 @emph{width*(默认为3) 用于规定每一行显示的月份数量。 *css} 为层叠样式表的名字。如果不使用任何层叠样式表，可以使用 @ref{157,,None} 。 @emph{encoding} 为输出页面的编码 (默认为系统的默认编码)。
@end deffn

@code{HTMLCalendar} 有以下属性，你可以重载它们来自定义应用日历的样式。

@geindex cssclasses (calendar.HTMLCalendar 属性)
@anchor{library/calendar calendar HTMLCalendar cssclasses}@anchor{18a0}
@deffn {属性} cssclasses

一个对应星期一到星期天的 CSS class 列表。默认列表为

@example
cssclasses = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"]
@end example

可以向每天加入其它样式

@example
cssclasses = ["mon text-bold", "tue", "wed", "thu", "fri", "sat", "sun red"]
@end example

需要注意的是，列表的长度必须为7。
@end deffn

@geindex cssclass_noday (calendar.HTMLCalendar 属性)
@anchor{library/calendar calendar HTMLCalendar cssclass_noday}@anchor{18a1}
@deffn {属性} cssclass_noday

工作日的 CSS 类在上个月或下个月发生。


3.7 新版功能.

@end deffn

@geindex cssclasses_weekday_head (calendar.HTMLCalendar 属性)
@anchor{library/calendar calendar HTMLCalendar cssclasses_weekday_head}@anchor{18a2}
@deffn {属性} cssclasses_weekday_head

用于标题行中的工作日名称的 CSS 类 列表。默认值与 @ref{18a0,,cssclasses} 相同。


3.7 新版功能.

@end deffn

@geindex cssclass_month_head (calendar.HTMLCalendar 属性)
@anchor{library/calendar calendar HTMLCalendar cssclass_month_head}@anchor{18a3}
@deffn {属性} cssclass_month_head

月份的头 CSS 类（由 @code{formatmonthname()} 使用）。默认值为 @code{"month"} 。


3.7 新版功能.

@end deffn

@geindex cssclass_month (calendar.HTMLCalendar 属性)
@anchor{library/calendar calendar HTMLCalendar cssclass_month}@anchor{18a4}
@deffn {属性} cssclass_month

某个月的月历的 CSS 类（由 @ref{189d,,formatmonth()} 使用）。默认值为 @code{"month"} 。


3.7 新版功能.

@end deffn

@geindex cssclass_year (calendar.HTMLCalendar 属性)
@anchor{library/calendar calendar HTMLCalendar cssclass_year}@anchor{18a5}
@deffn {属性} cssclass_year

某年的年历的 CSS 类（由 @ref{189e,,formatyear()} 使用）。默认值为 @code{"year"} 。


3.7 新版功能.

@end deffn

@geindex cssclass_year_head (calendar.HTMLCalendar 属性)
@anchor{library/calendar calendar HTMLCalendar cssclass_year_head}@anchor{18a6}
@deffn {属性} cssclass_year_head

年历的·表头 CSS 类（由 @ref{189e,,formatyear()} 使用）。默认值为 @code{"year"} 。


3.7 新版功能.

@end deffn

需要注意的是，尽管上面命名的样式类都是单独出现的(如： @code{cssclass_month} @code{cssclass_noday}), 但我们可以使用空格将样式类列表中的多个元素分隔开，例如：

@example
"text-bold text-red"
@end example

下面是一个如何自定义  @code{HTMLCalendar} 的示例

@example
class CustomHTMLCal(calendar.HTMLCalendar):
    cssclasses = [style + " text-nowrap" for style in
                  calendar.HTMLCalendar.cssclasses]
    cssclass_month_head = "text-center month-head"
    cssclass_month = "text-center month"
    cssclass_year = "text-italic lead"
@end example
@end deffn

@geindex LocaleTextCalendar (calendar 中的类)
@anchor{library/calendar calendar LocaleTextCalendar}@anchor{18a7}
@deffn {类} calendar.LocaleTextCalendar (firstweekday=0, locale=None)

这个子类 @ref{1898,,TextCalendar} 可以在构造函数中传递一个语言环境名称，并且返回月份和星期几的名称在特定语言环境中。如果此语言环境包含编码，则包含月份和工作日名称的所有字符串将作为 unicode 返回。
@end deffn

@geindex LocaleHTMLCalendar (calendar 中的类)
@anchor{library/calendar calendar LocaleHTMLCalendar}@anchor{18a8}
@deffn {类} calendar.LocaleHTMLCalendar (firstweekday=0, locale=None)

This subclass of @ref{368,,HTMLCalendar} can be passed a locale name in the
constructor and will return month and weekday names in the specified
locale. If this locale includes an encoding all strings containing month and
weekday names will be returned as unicode.
@end deffn

@cartouche
@quotation 注解 
这两个类的 @code{formatweekday()} 和 @code{formatmonthname()} 方法临时更改dang当前区域至给定 @emph{locale} 。由于当前的区域设置是进程范围的设置，因此它们不是线程安全的。
@end quotation
@end cartouche

对于简单的文本日历，这个模块提供了以下方法。

@geindex setfirstweekday() (在 calendar 模块中)
@anchor{library/calendar calendar setfirstweekday}@anchor{188c}
@deffn {函数} calendar.setfirstweekday (weekday)

设置每一周的开始(@code{0} 表示星期一，@code{6} 表示星期天)。calendar还提供了  @code{MONDAY}, @code{TUESDAY}, @code{WEDNESDAY}, @code{THURSDAY}, @code{FRIDAY}, @code{SATURDAY} 和 @code{SUNDAY} 几个常量方便使用。例如，设置每周的第一天为星期天

@example
import calendar
calendar.setfirstweekday(calendar.SUNDAY)
@end example
@end deffn

@geindex firstweekday() (在 calendar 模块中)
@anchor{library/calendar calendar firstweekday}@anchor{188f}
@deffn {函数} calendar.firstweekday ()

返回当前设置的每星期的第一天的数值。
@end deffn

@geindex isleap() (在 calendar 模块中)
@anchor{library/calendar calendar isleap}@anchor{18a9}
@deffn {函数} calendar.isleap (year)

如果 @emph{year} 是闰年则返回  @ref{494,,True} ,否则返回 @ref{380,,False}。
@end deffn

@geindex leapdays() (在 calendar 模块中)
@anchor{library/calendar calendar leapdays}@anchor{18aa}
@deffn {函数} calendar.leapdays (y1, y2)

返回在范围 @emph{y1} 至 @emph{y2} （包含 y1 和 y2 ）之间的闰年的年数，其中 @emph{y1} 和 @emph{y2} 是年份。

此函数适用于跨越一个世纪变化的范围。
@end deffn

@geindex weekday() (在 calendar 模块中)
@anchor{library/calendar calendar weekday}@anchor{18ab}
@deffn {函数} calendar.weekday (year, month, day)

返回某年（ @code{1970} -- ...），某月（ @code{1} -- @code{12} ），某日（ @code{1} -- @code{31} ）是星期几（ @code{0} 是星期一）。
@end deffn

@geindex weekheader() (在 calendar 模块中)
@anchor{library/calendar calendar weekheader}@anchor{18ac}
@deffn {函数} calendar.weekheader (n)

返回一个包含星期几的缩写名的头。 @emph{n} 指定星期几缩写的字符宽度。
@end deffn

@geindex monthrange() (在 calendar 模块中)
@anchor{library/calendar calendar monthrange}@anchor{18ad}
@deffn {函数} calendar.monthrange (year, month)

返回指定 @emph{年份} 的指定 @emph{月份} 的第一天是星期几和这个月的天数。
@end deffn

@geindex monthcalendar() (在 calendar 模块中)
@anchor{library/calendar calendar monthcalendar}@anchor{18ae}
@deffn {函数} calendar.monthcalendar (year, month)

返回表示一个月的日历的矩阵。 每一行代表一周；此月份外的日子由零表示。 每周从周一开始，除非使用 @ref{188c,,setfirstweekday()} 改变设置。
@end deffn

@geindex prmonth() (在 calendar 模块中)
@anchor{library/calendar calendar prmonth}@anchor{18af}
@deffn {函数} calendar.prmonth (theyear, themonth, w=0, l=0)

打印由 @ref{18b0,,month()} 返回的一个月的日历。
@end deffn

@geindex month() (在 calendar 模块中)
@anchor{library/calendar calendar month}@anchor{18b0}
@deffn {函数} calendar.month (theyear, themonth, w=0, l=0)

使用 @ref{1898,,TextCalendar} 类的 @code{formatmonth()} 以多行字符串形式返回月份日历。
@end deffn

@geindex prcal() (在 calendar 模块中)
@anchor{library/calendar calendar prcal}@anchor{18b1}
@deffn {函数} calendar.prcal (year, w=0, l=0, c=6, m=3)

打印由 @ref{15,,calendar()} 返回的整年的日历。
@end deffn

@geindex calendar() (在 calendar 模块中)
@anchor{library/calendar calendar calendar}@anchor{18b2}
@deffn {函数} calendar.calendar (year, w=2, l=1, c=6, m=3)

使用 @ref{1898,,TextCalendar} 类的 @code{formatyear()} 返回整年的3列的日历以多行字符串的形式。
@end deffn

@geindex timegm() (在 calendar 模块中)
@anchor{library/calendar calendar timegm}@anchor{18b3}
@deffn {函数} calendar.timegm (tuple)

一个不相关但很好用的函数，它接受一个时间元组例如 @ref{10a,,time} 模块中的 @ref{b38,,gmtime()} 函数的返回并返回相应的 Unix 时间戳值，假定 1970 年开始计数， POSIX 编码。实际上， @ref{b38,,time.gmtime()} 和 @ref{18b3,,timegm()} 是彼此相反的。
@end deffn

@ref{15,,calendar} 模块导出以下数据属性：

@geindex day_name() (在 calendar 模块中)
@anchor{library/calendar calendar day_name}@anchor{18b4}
@deffn {数据} calendar.day_name

在当前语言环境下表示星期几的数组。
@end deffn

@geindex day_abbr() (在 calendar 模块中)
@anchor{library/calendar calendar day_abbr}@anchor{18b5}
@deffn {数据} calendar.day_abbr

在当前语言环境下表示星期几缩写的数组。
@end deffn

@geindex month_name() (在 calendar 模块中)
@anchor{library/calendar calendar month_name}@anchor{18b6}
@deffn {数据} calendar.month_name

在当前语言环境下表示一年中月份的数组。这遵循一月的月号为 1 的通常惯例，所以它的长度为 13 且 @code{month_name[0]} 是空字符串。
@end deffn

@geindex month_abbr() (在 calendar 模块中)
@anchor{library/calendar calendar month_abbr}@anchor{18b7}
@deffn {数据} calendar.month_abbr

在当前语言环境下表示月份简写的数组。这遵循一月的月号为 1 的通常惯例，所以它的长度为 13 且 @code{month_abbr[0]} 是空字符串。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{31,,datetime}

为日期和时间提供与 @ref{10a,,time} 模块相似功能的面向对象接口。

@item 模块 @ref{10a,,time}

底层时间相关函数。
@end table


@node collections --- 容器数据类型,collections abc --- 容器的抽象基类,calendar --- 日历相关函数,数据类型
@anchor{library/collections doc}@anchor{18b8}@anchor{library/collections collections-container-datatypes}@anchor{18b9}@anchor{library/collections module-collections}@anchor{1e}
@subsection @code{collections} --- 容器数据类型


@geindex collections (模块)

@strong{Source code:} Lib/collections/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/collections/__init__.py}

@c from collections import *
@c import itertools
@c __name__ = '<doctest>'


__________________________________________________________________


这个模块实现了特定目标的容器，以提供Python标准内建容器  @ref{1b8,,dict} , @ref{262,,list} , @ref{b68,,set} , 和 @ref{478,,tuple} 的替代选择。


@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{1b6,,namedtuple()}

@tab

创建命名元组子类的工厂函数

@item

@ref{52b,,deque}

@tab

类似列表(list)的容器，实现了在两端快速添加(append)和弹出(pop)

@item

@ref{4a4,,ChainMap}

@tab

类似字典(dict)的容器类，将多个映射集合到一个视图里面

@item

@ref{9d4,,Counter}

@tab

字典的子类，提供了可哈希对象的计数功能

@item

@ref{1b9,,OrderedDict}

@tab

字典的子类，保存了他们被添加的顺序

@item

@ref{b33,,defaultdict}

@tab

字典的子类，提供了一个工厂函数，为字典查询提供一个默认值

@item

@ref{18ba,,UserDict}

@tab

封装了字典对象，简化了字典子类化

@item

@ref{18bb,,UserList}

@tab

封装了列表对象，简化了列表子类化

@item

@ref{6a7,,UserString}

@tab

封装了列表对象，简化了字符串子类化

@end multitable



Deprecated since version 3.3, will be removed in version 3.10: 已将 @ref{18bc,,容器抽象基类} 移至 @ref{1f,,collections.abc} 模块。 为了保持向下兼容性，它们在 Python 3.9 版的这个模块中仍然存在。


@menu
* ChainMap 对象:: 
* Counter 对象:: 
* deque 对象:: 
* defaultdict 对象:: 
* namedtuple() 命名元组的工厂函数: namedtuple 命名元组的工厂函数. 
* OrderedDict 对象:: 
* UserDict 对象:: 
* UserList 对象:: 
* UserString 对象:: 

@end menu

@node ChainMap 对象,Counter 对象,,collections --- 容器数据类型
@anchor{library/collections chainmap-objects}@anchor{18bd}
@subsubsection @code{ChainMap} 对象



3.3 新版功能.


一个 @ref{4a4,,ChainMap} 类是为了将多个映射快速的链接到一起，这样它们就可以作为一个单元处理。它通常比创建一个新字典和多次调用 @ref{dc2,,update()} 要快很多。

这个类可以用于模拟嵌套作用域，并且在模版化的时候比较有用。

@geindex ChainMap (collections 中的类)
@anchor{library/collections collections ChainMap}@anchor{4a4}
@deffn {类} collections.ChainMap (*maps)

一个 @ref{4a4,,ChainMap} 将多个字典或者其他映射组合在一起，创建一个单独的可更新的视图。  如果没有 @emph{maps} 被指定，就提供一个默认的空字典，这样一个新链至少有一个映射。

底层映射被存储在一个列表中。这个列表是公开的，可以通过 @emph{maps} 属性存取和更新。没有其他的状态。

搜索查询底层映射，直到一个键被找到。不同的是，写，更新和删除只操作第一个映射。

一个 @ref{4a4,,ChainMap} 通过引用合并底层映射。 所以，如果一个底层映射更新了，这些更改会反映到 @ref{4a4,,ChainMap} 。

支持所有常用字典方法。另外还有一个  @emph{maps} 属性(attribute)，一个创建子上下文的方法(method)， 一个存取它们首个映射的属性(property):

@geindex maps (collections.ChainMap 属性)
@anchor{library/collections collections ChainMap maps}@anchor{18be}
@deffn {属性} maps

一个可以更新的映射列表。这个列表是按照第一次搜索到最后一次搜索的顺序组织的。它是仅有的存储状态，可以被修改。列表最少包含一个映射。
@end deffn

@geindex new_child() (collections.ChainMap 方法)
@anchor{library/collections collections ChainMap new_child}@anchor{823}
@deffn {方法} new_child (m=None)

返回一个新的 @ref{4a4,,ChainMap} 类，包含了一个新映射(map)，后面跟随当前实例的全部映射(map)。如果 @code{m} 被指定，它就成为不同新的实例，就是在所有映射前加上 m，如果没有指定，就加上一个空字典，这样的话一个 @code{d.new_child()} 调用等价于 @code{ChainMap(@{@}, *d.maps)} 。这个方法用于创建子上下文，不改变任何父映射的值。


在 3.4 版更改: 添加了 @code{m}  可选参数。

@end deffn

@geindex parents (collections.ChainMap 属性)
@anchor{library/collections collections ChainMap parents}@anchor{18bf}
@deffn {属性} parents

属性返回一个新的 @ref{4a4,,ChainMap} 包含所有的当前实例的映射，除了第一个。这样可以在搜索的时候跳过第一个映射。 使用的场景类似在 @ref{1583,,nested scopes} 嵌套作用域中使用 @ref{c38,,nonlocal} 关键词。用例也可以类比内建函数  @ref{4dc,,super()} 。一个 @code{d.parents} 的引用等价于 @code{ChainMap(*d.maps[1:])} 。
@end deffn

注意，一个 @ref{4a4,,ChainMap()} 的迭代顺序是通过扫描最后的映射来确定的:

@example
>>> baseline = @{'music': 'bach', 'art': 'rembrandt'@}
>>> adjustments = @{'art': 'van gogh', 'opera': 'carmen'@}
>>> list(ChainMap(adjustments, baseline))
['music', 'art', 'opera']
@end example

这给出了与 @ref{dc2,,dict.update()} 调用序列相同的顺序，从最后一个映射开始:

@example
>>> combined = baseline.copy()
>>> combined.update(adjustments)
>>> list(combined)
['music', 'art', 'opera']
@end example
@end deffn


@subsubheading 参见



@itemize *

@item 
MultiContext class@footnote{https://github.com/enthought/codetools/blob/4.0.0/codetools/contexts/multi_context.py} 在 Enthought CodeTools package@footnote{https://github.com/enthought/codetools} 有支持写映射的选项。

@item 
Django 的 Context class@footnote{https://github.com/django/django/blob/master/django/template/context.py} 模版是只读映射。它的上下文的push和pop特性也类似于 @ref{823,,new_child()} 方法 @ref{18bf,,parents} 属性。

@item 
Nested Contexts recipe@footnote{https://code.activestate.com/recipes/577434/} 提供了是否对第一个映射或其他映射进行写和其他修改的选项。

@item 
一个 极简的只读版 Chainmap@footnote{https://code.activestate.com/recipes/305268/}.
@end itemize


@menu
* ChainMap 例子和方法:: 

@end menu

@node ChainMap 例子和方法,,,ChainMap 对象
@anchor{library/collections chainmap-examples-and-recipes}@anchor{18c0}
@subsubsection @code{ChainMap} 例子和方法


这一节提供了多个使用链映射的案例。

模拟Python内部lookup链的例子

@example
import builtins
pylookup = ChainMap(locals(), globals(), vars(builtins))
@end example

让用户指定的命令行参数优先于环境变量，优先于默认值的例子

@example
import os, argparse

defaults = @{'color': 'red', 'user': 'guest'@}

parser = argparse.ArgumentParser()
parser.add_argument('-u', '--user')
parser.add_argument('-c', '--color')
namespace = parser.parse_args()
command_line_args = @{k: v for k, v in vars(namespace).items() if v is not None@}

combined = ChainMap(command_line_args, os.environ, defaults)
print(combined['color'])
print(combined['user'])
@end example

用 @ref{4a4,,ChainMap} 类模拟嵌套上下文的例子

@example
c = ChainMap()        # Create root context
d = c.new_child()     # Create nested child context
e = c.new_child()     # Child of c, independent from d
e.maps[0]             # Current context dictionary -- like Python's locals()
e.maps[-1]            # Root context -- like Python's globals()
e.parents             # Enclosing context chain -- like Python's nonlocals

d['x'] = 1            # Set value in current context
d['x']                # Get first key in the chain of contexts
del d['x']            # Delete from current context
list(d)               # All nested values
k in d                # Check all nested values
len(d)                # Number of nested values
d.items()             # All nested items
dict(d)               # Flatten into a regular dictionary
@end example

@ref{4a4,,ChainMap} 类只更新链中的第一个映射，但lookup会搜索整个链。 然而，如果需要深度写和删除，也可以很容易的通过定义一个子类来实现它

@example
class DeepChainMap(ChainMap):
    'Variant of ChainMap that allows direct updates to inner scopes'

    def __setitem__(self, key, value):
        for mapping in self.maps:
            if key in mapping:
                mapping[key] = value
                return
        self.maps[0][key] = value

    def __delitem__(self, key):
        for mapping in self.maps:
            if key in mapping:
                del mapping[key]
                return
        raise KeyError(key)

>>> d = DeepChainMap(@{'zebra': 'black'@}, @{'elephant': 'blue'@}, @{'lion': 'yellow'@})
>>> d['lion'] = 'orange'         # update an existing key two levels down
>>> d['snake'] = 'red'           # new keys get added to the topmost dict
>>> del d['elephant']            # remove an existing key one level down
>>> d                            # display result
DeepChainMap(@{'zebra': 'black', 'snake': 'red'@}, @{@}, @{'lion': 'orange'@})
@end example

@node Counter 对象,deque 对象,ChainMap 对象,collections --- 容器数据类型
@anchor{library/collections counter-objects}@anchor{18c1}
@subsubsection @code{Counter} 对象


一个计数器工具提供快速和方便的计数。比如

@example
>>> # Tally occurrences of words in a list
>>> cnt = Counter()
>>> for word in ['red', 'blue', 'red', 'green', 'blue', 'blue']:
...     cnt[word] += 1
>>> cnt
Counter(@{'blue': 3, 'red': 2, 'green': 1@})

>>> # Find the ten most common words in Hamlet
>>> import re
>>> words = re.findall(r'\w+', open('hamlet.txt').read().lower())
>>> Counter(words).most_common(10)
[('the', 1143), ('and', 966), ('to', 762), ('of', 669), ('i', 631),
 ('you', 554),  ('a', 546), ('my', 514), ('hamlet', 471), ('in', 451)]
@end example

@geindex Counter (collections 中的类)
@anchor{library/collections collections Counter}@anchor{9d4}
@deffn {类} collections.Counter ([iterable-or-mapping])

一个 @ref{9d4,,Counter} 是一个 @ref{1b8,,dict} 的子类，用于计数可哈希对象。它是一个集合，元素像字典键(key)一样存储，它们的计数存储为值。计数可以是任何整数值，包括0和负数。 @ref{9d4,,Counter} 类有点像其他语言中的 bags或multisets。

元素从一个 @emph{iterable} 被计数或从其他的 @emph{mapping} (or counter)初始化：

@example
>>> c = Counter()                           # a new, empty counter
>>> c = Counter('gallahad')                 # a new counter from an iterable
>>> c = Counter(@{'red': 4, 'blue': 2@})      # a new counter from a mapping
>>> c = Counter(cats=4, dogs=8)             # a new counter from keyword args
@end example

Counter对象有一个字典接口，如果引用的键没有任何记录，就返回一个0，而不是弹出一个 @ref{2c7,,KeyError} :

@example
>>> c = Counter(['eggs', 'ham'])
>>> c['bacon']                              # count of a missing element is zero
0
@end example

设置一个计数为0不会从计数器中移去一个元素。使用 @code{del} 来删除它:

@example
>>> c['sausage'] = 0                        # counter entry with a zero count
>>> del c['sausage']                        # del actually removes the entry
@end example


3.1 新版功能.



在 3.7 版更改: 作为 @ref{1b8,,dict} 的子类，@ref{9d4,,Counter} 继承了记住插入顺序的功能。 @emph{Counter} 对象进行数学运算时同样会保持顺序。 结果会先按每个元素在运算符左边的出现时间排序，然后再按其在运算符右边的出现时间排序。


计数器对象除了字典方法以外，还提供了三个其他的方法：

@geindex elements() (collections.Counter 方法)
@anchor{library/collections collections Counter elements}@anchor{c93}
@deffn {方法} elements ()

返回一个迭代器，其中每个元素将重复出现计数值所指定次。 元素会按首次出现的顺序返回。 如果一个元素的计数值小于一，@ref{c93,,elements()} 将会忽略它。

@example
>>> c = Counter(a=4, b=2, c=0, d=-2)
>>> sorted(c.elements())
['a', 'a', 'a', 'a', 'b', 'b']
@end example
@end deffn

@geindex most_common() (collections.Counter 方法)
@anchor{library/collections collections Counter most_common}@anchor{c92}
@deffn {方法} most_common ([n])

返回一个列表，其中包含 @emph{n} 个最常见的元素及出现次数，按常见程度由高到低排序。 如果 @emph{n} 被省略或为 @code{None}，@ref{c92,,most_common()} 将返回计数器中的 @emph{所有} 元素。 计数值相等的元素按首次出现的顺序排序：

@example
>>> Counter('abracadabra').most_common(3)
[('a', 5), ('b', 2), ('r', 2)]
@end example
@end deffn

@geindex subtract() (collections.Counter 方法)
@anchor{library/collections collections Counter subtract}@anchor{b53}
@deffn {方法} subtract ([iterable-or-mapping])

从 @emph{迭代对象} 或 @emph{映射对象} 减去元素。像 @ref{dc2,,dict.update()} 但是是减去，而不是替换。输入和输出都可以是0或者负数。

@example
>>> c = Counter(a=4, b=2, c=0, d=-2)
>>> d = Counter(a=1, b=2, c=3, d=4)
>>> c.subtract(d)
>>> c
Counter(@{'a': 3, 'b': 0, 'c': -3, 'd': -6@})
@end example


3.2 新版功能.

@end deffn

通常字典方法都可用于 @ref{9d4,,Counter} 对象，除了有两个方法工作方式与字典并不相同。

@geindex fromkeys() (collections.Counter 方法)
@anchor{library/collections collections Counter fromkeys}@anchor{18c2}
@deffn {方法} fromkeys (iterable)

这个类方法没有在 @ref{9d4,,Counter} 中实现。
@end deffn

@geindex update() (collections.Counter 方法)
@anchor{library/collections collections Counter update}@anchor{18c3}
@deffn {方法} update ([iterable-or-mapping])

从 @emph{迭代对象} 计数元素或者 从另一个 @emph{映射对象} (或计数器) 添加。 像 @ref{dc2,,dict.update()} 但是是加上，而不是替换。另外，@emph{迭代对象} 应该是序列元素，而不是一个 @code{(key, value)} 对。
@end deffn
@end deffn

@ref{9d4,,Counter} 对象的常用案例

@example
sum(c.values())                 # total of all counts
c.clear()                       # reset all counts
list(c)                         # list unique elements
set(c)                          # convert to a set
dict(c)                         # convert to a regular dictionary
c.items()                       # convert to a list of (elem, cnt) pairs
Counter(dict(list_of_pairs))    # convert from a list of (elem, cnt) pairs
c.most_common()[:-n-1:-1]       # n least common elements
+c                              # remove zero and negative counts
@end example

提供了几个数学操作，可以结合  @ref{9d4,,Counter} 对象，以生产 multisets (计数器中大于0的元素）。 加和减，结合计数器，通过加上或者减去元素的相应计数。交集和并集返回相应计数的最小或最大值。每种操作都可以接受带符号的计数，但是输出会忽略掉结果为零或者小于零的计数。

@example
>>> c = Counter(a=3, b=1)
>>> d = Counter(a=1, b=2)
>>> c + d                       # add two counters together:  c[x] + d[x]
Counter(@{'a': 4, 'b': 3@})
>>> c - d                       # subtract (keeping only positive counts)
Counter(@{'a': 2@})
>>> c & d                       # intersection:  min(c[x], d[x]) 
Counter(@{'a': 1, 'b': 1@})
>>> c | d                       # union:  max(c[x], d[x])
Counter(@{'a': 3, 'b': 2@})
@end example

单目加和减（一元操作符）意思是从空计数器加或者减去。

@example
>>> c = Counter(a=2, b=-4)
>>> +c
Counter(@{'a': 2@})
>>> -c
Counter(@{'b': 4@})
@end example


3.3 新版功能: 添加了对一元加，一元减和位置集合操作的支持。


@cartouche
@quotation 注解 
计数器主要是为了表达运行的正的计数而设计；但是，小心不要预先排除负数或者其他类型。为了帮助这些用例，这一节记录了最小范围和类型限制。


@itemize *

@item 
@ref{9d4,,Counter} 类是一个字典的子类，不限制键和值。值用于表示计数，但你实际上 @emph{可以} 存储任何其他值。

@item 
@ref{c92,,most_common()} 方法在值需要排序的时候用。

@item 
原地操作比如 @code{c[key] += 1} ， 值类型只需要支持加和减。 所以分数，小数，和十进制都可以用，负值也可以支持。这两个方法 @ref{18c3,,update()} 和 @ref{b53,,subtract()} 的输入和输出也一样支持负数和0。

@item 
Multiset多集合方法只为正值的使用情况设计。输入可以是负数或者0，但只输出计数为正的值。没有类型限制，但值类型需要支持加，减和比较操作。

@item 
@ref{c93,,elements()} 方法要求正整数计数。忽略0和负数计数。
@end itemize
@end quotation
@end cartouche


@subsubheading 参见



@itemize *

@item 
Bag class@footnote{https://www.gnu.org/software/smalltalk/manual-base/html_node/Bag.html} 在 Smalltalk。

@item 
Wikipedia 链接 Multisets@footnote{https://en.wikipedia.org/wiki/Multiset}.

@item 
C++ multisets@footnote{http://www.java2s.com/Tutorial/Cpp/0380__set-multiset/Catalog0380__set-multiset.htm} 教程和例子。

@item 
数学操作和多集合用例，参考 @emph{Knuth, Donald. The Art of Computer Programming Volume II, Section 4.6.3, Exercise 19} 。

@item 
在给定数量和集合元素枚举所有不同的多集合，参考 @ref{c12,,itertools.combinations_with_replacement()}

@example
map(Counter, combinations_with_replacement('ABC', 2)) # --> AA AB AC BB BC CC
@end example
@end itemize


@node deque 对象,defaultdict 对象,Counter 对象,collections --- 容器数据类型
@anchor{library/collections deque-objects}@anchor{18c4}
@subsubsection @code{deque} 对象


@geindex deque (collections 中的类)
@anchor{library/collections collections deque}@anchor{52b}
@deffn {类} collections.deque ([iterable[, maxlen]])

返回一个新的双向队列对象，从左到右初始化(用方法 @ref{18c5,,append()}) ，从 @emph{iterable} （迭代对象) 数据创建。如果 @emph{iterable} 没有指定，新队列为空。

Deque队列是由栈或者queue队列生成的（发音是 “deck”，”double-ended queue”的简称）。Deque 支持线程安全，内存高效添加(append)和弹出(pop)，从两端都可以，两个方向的大概开销都是 O(1) 复杂度。

虽然 @ref{262,,list} 对象也支持类似操作，不过这里优化了定长操作和 @code{pop(0)} 和 @code{insert(0, v)} 的开销。它们引起 O(n) 内存移动的操作，改变底层数据表达的大小和位置。

如果 @emph{maxlen} 没有指定或者是 @code{None} ，deques 可以增长到任意长度。否则，deque就限定到指定最大长度。一旦限定长度的deque满了，当新项加入时，同样数量的项就从另一端弹出。限定长度deque提供类似Unix filter @code{tail} 的功能。它们同样可以用与追踪最近的交换和其他数据池活动。

双向队列(deque)对象支持以下方法：

@geindex append() (collections.deque 方法)
@anchor{library/collections collections deque append}@anchor{18c5}
@deffn {方法} append (x)

添加 @emph{x} 到右端。
@end deffn

@geindex appendleft() (collections.deque 方法)
@anchor{library/collections collections deque appendleft}@anchor{18c6}
@deffn {方法} appendleft (x)

添加 @emph{x} 到左端。
@end deffn

@geindex clear() (collections.deque 方法)
@anchor{library/collections collections deque clear}@anchor{18c7}
@deffn {方法} clear ()

移除所有元素，使其长度为0.
@end deffn

@geindex copy() (collections.deque 方法)
@anchor{library/collections collections deque copy}@anchor{6a5}
@deffn {方法} copy ()

创建一份浅拷贝。


3.5 新版功能.

@end deffn

@geindex count() (collections.deque 方法)
@anchor{library/collections collections deque count}@anchor{b55}
@deffn {方法} count (x)

计算 deque 中元素等于 @emph{x} 的个数。


3.2 新版功能.

@end deffn

@geindex extend() (collections.deque 方法)
@anchor{library/collections collections deque extend}@anchor{18c8}
@deffn {方法} extend (iterable)

扩展deque的右侧，通过添加iterable参数中的元素。
@end deffn

@geindex extendleft() (collections.deque 方法)
@anchor{library/collections collections deque extendleft}@anchor{18c9}
@deffn {方法} extendleft (iterable)

扩展deque的左侧，通过添加iterable参数中的元素。注意，左添加时，在结果中iterable参数中的顺序将被反过来添加。
@end deffn

@geindex index() (collections.deque 方法)
@anchor{library/collections collections deque index}@anchor{6a3}
@deffn {方法} index (x[, start[, stop]])

返回 @emph{x} 在 deque 中的位置（在索引 @emph{start} 之后，索引 @emph{stop} 之前）。 返回第一个匹配项，如果未找到则引发 @ref{1fb,,ValueError}。


3.5 新版功能.

@end deffn

@geindex insert() (collections.deque 方法)
@anchor{library/collections collections deque insert}@anchor{6a4}
@deffn {方法} insert (i, x)

在位置 @emph{i} 插入 @emph{x} 。

如果插入会导致一个限长 deque 超出长度 @emph{maxlen} 的话，就引发一个 @ref{e6e,,IndexError}。


3.5 新版功能.

@end deffn

@geindex pop() (collections.deque 方法)
@anchor{library/collections collections deque pop}@anchor{18ca}
@deffn {方法} pop ()

移去并且返回一个元素，deque 最右侧的那一个。 如果没有元素的话，就引发一个 @ref{e6e,,IndexError}。
@end deffn

@geindex popleft() (collections.deque 方法)
@anchor{library/collections collections deque popleft}@anchor{18cb}
@deffn {方法} popleft ()

移去并且返回一个元素，deque 最左侧的那一个。 如果没有元素的话，就引发 @ref{e6e,,IndexError}。
@end deffn

@geindex remove() (collections.deque 方法)
@anchor{library/collections collections deque remove}@anchor{18cc}
@deffn {方法} remove (value)

移除找到的第一个 @emph{value}。 如果没有的话就引发 @ref{1fb,,ValueError}。
@end deffn

@geindex reverse() (collections.deque 方法)
@anchor{library/collections collections deque reverse}@anchor{b56}
@deffn {方法} reverse ()

将deque逆序排列。返回 @code{None} 。


3.2 新版功能.

@end deffn

@geindex rotate() (collections.deque 方法)
@anchor{library/collections collections deque rotate}@anchor{18cd}
@deffn {方法} rotate (n=1)

向右循环移动 @emph{n} 步。 如果 @emph{n} 是负数，就向左循环。

如果deque不是空的，向右循环移动一步就等价于 @code{d.appendleft(d.pop())} ， 向左循环一步就等价于 @code{d.append(d.popleft())} 。
@end deffn

Deque对象同样提供了一个只读属性:

@geindex maxlen (collections.deque 属性)
@anchor{library/collections collections deque maxlen}@anchor{c94}
@deffn {属性} maxlen

Deque的最大尺寸，如果没有限定的话就是 @code{None} 。


3.1 新版功能.

@end deffn
@end deffn

除了以上操作，deque 还支持迭代、封存、@code{len(d)}、@code{reversed(d)}、@code{copy.copy(d)}、@code{copy.deepcopy(d)}、成员检测运算符 @ref{79d,,in} 以及下标引用例如通过 @code{d[0]} 访问首个元素等。 索引访问在两端的复杂度均为 O(1) 但在中间则会低至 O(n)。 如需快速随机访问，请改用列表。

Deque从版本3.5开始支持 @code{__add__()}, @code{__mul__()}, 和 @code{__imul__()} 。

示例:

@example
>>> from collections import deque
>>> d = deque('ghi')                 # make a new deque with three items
>>> for elem in d:                   # iterate over the deque's elements
...     print(elem.upper())
G
H
I

>>> d.append('j')                    # add a new entry to the right side
>>> d.appendleft('f')                # add a new entry to the left side
>>> d                                # show the representation of the deque
deque(['f', 'g', 'h', 'i', 'j'])

>>> d.pop()                          # return and remove the rightmost item
'j'
>>> d.popleft()                      # return and remove the leftmost item
'f'
>>> list(d)                          # list the contents of the deque
['g', 'h', 'i']
>>> d[0]                             # peek at leftmost item
'g'
>>> d[-1]                            # peek at rightmost item
'i'

>>> list(reversed(d))                # list the contents of a deque in reverse
['i', 'h', 'g']
>>> 'h' in d                         # search the deque
True
>>> d.extend('jkl')                  # add multiple elements at once
>>> d
deque(['g', 'h', 'i', 'j', 'k', 'l'])
>>> d.rotate(1)                      # right rotation
>>> d
deque(['l', 'g', 'h', 'i', 'j', 'k'])
>>> d.rotate(-1)                     # left rotation
>>> d
deque(['g', 'h', 'i', 'j', 'k', 'l'])

>>> deque(reversed(d))               # make a new deque in reverse order
deque(['l', 'k', 'j', 'i', 'h', 'g'])
>>> d.clear()                        # empty the deque
>>> d.pop()                          # cannot pop from an empty deque
Traceback (most recent call last):
    File "<pyshell#6>", line 1, in -toplevel-
        d.pop()
IndexError: pop from an empty deque

>>> d.extendleft('abc')              # extendleft() reverses the input order
>>> d
deque(['c', 'b', 'a'])
@end example

@menu
* deque 用法:: 

@end menu

@node deque 用法,,,deque 对象
@anchor{library/collections deque-recipes}@anchor{18ce}
@subsubsection @code{deque} 用法


这一节展示了deque的多种用法。

限长deque提供了类似Unix @code{tail} 过滤功能

@example
def tail(filename, n=10):
    'Return the last n lines of a file'
    with open(filename) as f:
        return deque(f, n)
@end example

另一个用法是维护一个近期添加元素的序列，通过从右边添加和从左边弹出

@example
def moving_average(iterable, n=3):
    # moving_average([40, 30, 50, 46, 39, 44]) --> 40.0 42.0 45.0 43.0
    # http://en.wikipedia.org/wiki/Moving_average
    it = iter(iterable)
    d = deque(itertools.islice(it, n-1))
    d.appendleft(0)
    s = sum(d)
    for elem in it:
        s += elem - d.popleft()
        d.append(elem)
        yield s / n
@end example

一个 轮询调度器@footnote{https://en.wikipedia.org/wiki/Round-robin_scheduling} 可以通过在 @ref{52b,,deque} 中放入迭代器来实现。值从当前迭代器的位置0被取出并暂存(yield)。 如果这个迭代器消耗完毕，就用 @ref{18cb,,popleft()} 将其从对列中移去；否则，就通过  @ref{18cd,,rotate()} 将它移到队列的末尾

@example
def roundrobin(*iterables):
    "roundrobin('ABC', 'D', 'EF') --> A D E B F C"
    iterators = deque(map(iter, iterables))
    while iterators:
        try:
            while True:
                yield next(iterators[0])
                iterators.rotate(-1)
        except StopIteration:
            # Remove an exhausted iterator.
            iterators.popleft()
@end example

@ref{18cd,,rotate()} 方法提供了一种方式来实现 @ref{52b,,deque} 切片和删除。 例如， 一个纯的Python @code{del d[n]} 实现依赖于 @code{rotate()} 来定位要弹出的元素

@example
def delete_nth(d, n):
    d.rotate(-n)
    d.popleft()
    d.rotate(n)
@end example

要实现 @ref{52b,,deque} 切片， 使用一个类似的方法，应用 @ref{18cd,,rotate()} 将目标元素放到左边。通过 @ref{18cb,,popleft()} 移去老的条目（entries），通过 @ref{18c8,,extend()} 添加新的条目， 然后反向 rotate。这个方法可以最小代价实现命令式的栈操作，诸如 @code{dup}, @code{drop}, @code{swap}, @code{over}, @code{pick}, @code{rot}, 和 @code{roll} 。

@node defaultdict 对象,namedtuple 命名元组的工厂函数,deque 对象,collections --- 容器数据类型
@anchor{library/collections defaultdict-objects}@anchor{18cf}
@subsubsection @code{defaultdict} 对象


@geindex defaultdict (collections 中的类)
@anchor{library/collections collections defaultdict}@anchor{b33}
@deffn {类} collections.defaultdict ([default_factory[, ...]])

返回一个新的类似字典的对象。 @ref{b33,,defaultdict} 是内置 @ref{1b8,,dict} 类的子类。它重载了一个方法并添加了一个可写的实例变量。其余的功能与 @ref{1b8,,dict} 类相同，此处不再重复说明。

本对象包含一个名为 @ref{18d0,,default_factory} 的属性，构造时，第一个参数用于为该属性提供初始值，默认为 @code{None}。所有其他参数（包括关键字参数）都相当于传递给 @ref{1b8,,dict} 的构造函数。

@ref{b33,,defaultdict} 对象除了支持标准 @ref{1b8,,dict} 的操作，还支持以下方法作为扩展：

@geindex __missing__() (collections.defaultdict 方法)
@anchor{library/collections collections defaultdict __missing__}@anchor{18d1}
@deffn {方法} __missing__ (key)

如果 @ref{18d0,,default_factory} 属性为 @code{None}，则调用本方法会抛出 @ref{2c7,,KeyError} 异常，附带参数 @emph{key}。

如果 @ref{18d0,,default_factory} 不为 @code{None}，则它会被（不带参数地）调用来为 @emph{key} 提供一个默认值，这个值和 @emph{key} 作为一对键值对被插入到字典中，并作为本方法的返回值返回。

如果调用 @ref{18d0,,default_factory} 时抛出了异常，这个异常会原封不动地向外层传递。

在无法找到所需键值时，本方法会被 @ref{1b8,,dict} 中的 @ref{27f,,__getitem__()} 方法调用。无论本方法返回了值还是抛出了异常，都会被 @ref{27f,,__getitem__()} 传递。

注意，@ref{18d1,,__missing__()} @emph{不会} 被 @ref{27f,,__getitem__()} 以外的其他方法调用。意味着 @code{get()} 会像正常的 dict 那样返回 @code{None}，而不是使用 @ref{18d0,,default_factory}。
@end deffn

@ref{b33,,defaultdict} 对象支持以下实例变量：

@geindex default_factory (collections.defaultdict 属性)
@anchor{library/collections collections defaultdict default_factory}@anchor{18d0}
@deffn {属性} default_factory

本属性由 @ref{18d1,,__missing__()} 方法来调用。如果构造对象时提供了第一个参数，则本属性会被初始化成那个参数，如果未提供第一个参数，则本属性为 @code{None}。
@end deffn
@end deffn

@menu
* defaultdict 例子:: 

@end menu

@node defaultdict 例子,,,defaultdict 对象
@anchor{library/collections defaultdict-examples}@anchor{18d2}
@subsubsection @code{defaultdict} 例子


使用 @ref{262,,list} 作为 @ref{18d0,,default_factory}，很轻松地将（键-值对组成的）序列转换为（键-列表组成的）字典：

@example
>>> s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
>>> d = defaultdict(list)
>>> for k, v in s:
...     d[k].append(v)
...
>>> sorted(d.items())
[('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])]
@end example

当每个键第一次遇见时，它还没有在字典里面，所以自动创建该条目，即调用 @ref{18d0,,default_factory} 方法，返回一个空的 @ref{262,,list}。 @code{list.append()} 操作添加值到这个新的列表里。当再次存取该键时，就正常操作，@code{list.append()} 添加另一个值到列表中。这个计数比它的等价方法 @ref{9b9,,dict.setdefault()} 要快速和简单：

@example
>>> d = @{@}
>>> for k, v in s:
...     d.setdefault(k, []).append(v)
...
>>> sorted(d.items())
[('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])]
@end example

设置 @ref{18d0,,default_factory} 为 @ref{184,,int}，使 @ref{b33,,defaultdict} 用于计数（类似其他语言中的 bag 或 multiset）：

@example
>>> s = 'mississippi'
>>> d = defaultdict(int)
>>> for k in s:
...     d[k] += 1
...
>>> sorted(d.items())
[('i', 4), ('m', 1), ('p', 2), ('s', 4)]
@end example

当一个字母首次遇到时，它会查询失败，则 @ref{18d0,,default_factory} 会调用 @ref{184,,int()} 来提供一个整数 0 作为默认值。后续的自增操作建立起对每个字母的计数。

函数 @ref{184,,int()} 总是返回 0，这是常数函数的特殊情况。一个更快和灵活的方法是使用 lambda 函数，可以提供任何常量值（不只是0）：

@example
>>> def constant_factory(value):
...     return lambda: value
>>> d = defaultdict(constant_factory('<missing>'))
>>> d.update(name='John', action='ran')
>>> '%(name)s %(action)s to %(object)s' % d
'John ran to <missing>'
@end example

设置 @ref{18d0,,default_factory} 为 @ref{b68,,set} 使 @ref{b33,,defaultdict} 用于构建 set 集合：

@example
>>> s = [('red', 1), ('blue', 2), ('red', 3), ('blue', 4), ('red', 1), ('blue', 4)]
>>> d = defaultdict(set)
>>> for k, v in s:
...     d[k].add(v)
...
>>> sorted(d.items())
[('blue', @{2, 4@}), ('red', @{1, 3@})]
@end example

@node namedtuple 命名元组的工厂函数,OrderedDict 对象,defaultdict 对象,collections --- 容器数据类型
@anchor{library/collections namedtuple-factory-function-for-tuples-with-named-fields}@anchor{18d3}
@subsubsection @code{namedtuple()} 命名元组的工厂函数


命名元组赋予每个位置一个含义，提供可读性和自文档性。它们可以用于任何普通元组，并添加了通过名字获取值的能力，通过索引值也是可以的。

@geindex namedtuple() (在 collections 模块中)
@anchor{library/collections collections namedtuple}@anchor{1b6}
@deffn {函数} collections.namedtuple (typename, field_names, *, rename=False, defaults=None, module=None)

返回一个新的元组子类，名为 @emph{typename} 。这个新的子类用于创建类元组的对象，可以通过字段名来获取属性值，同样也可以通过索引和迭代获取值。子类实例同样有文档字符串（类名和字段名）另外一个有用的 @ref{337,,__repr__()} 方法，以 @code{name=value} 格式列明了元组内容。

@emph{field_names} 是一个像 @code{[‘x’, ‘y’]} 一样的字符串序列。另外 @emph{field_names} 可以是一个纯字符串，用空白或逗号分隔开元素名，比如 @code{'x y'} 或者 @code{'x, y'} 。

任何有效的Python 标识符都可以作为字段名，除了下划线开头的那些。有效标识符由字母，数字，下划线组成，但首字母不能是数字或下划线，另外不能是关键词 @ref{a6,,keyword} 比如 @emph{class}, @emph{for}, @emph{return}, @emph{global}, @emph{pass}, 或 @emph{raise} 。

如果 @emph{rename} 为真， 无效字段名会自动转换成位置名。比如 @code{['abc', 'def', 'ghi', 'abc']} 转换成 @code{['abc', '_1', 'ghi', '_3']} ， 消除关键词 @code{def}  和重复字段名 @code{abc} 。

@emph{defaults} 可以为 @code{None} 或者是一个默认值的 @ref{ba5,,iterable} 。如果一个默认值域必须跟其他没有默认值的域在一起出现，@emph{defaults} 就应用到最右边的参数。比如如果域名 @code{['x', 'y', 'z']} 和默认值 @code{(1, 2)} ，那么 @code{x} 就必须指定一个参数值 ，@code{y} 默认值 @code{1} ， @code{z} 默认值 @code{2} 。

如果 @emph{module} 值有定义，命名元组的 @code{__module__} 属性值就被设置。

命名元组实例没有字典，所以它们要更轻量，并且占用更小内存。


在 3.1 版更改: 添加了对 @emph{rename} 的支持。



在 3.6 版更改: @emph{verbose} 和 @emph{rename} 参数成为 @ref{2ac,,仅限关键字参数}.



在 3.6 版更改: 添加了 @emph{module} 参数。



在 3.7 版更改: 移除了 @emph{verbose} 形参和 @code{_source} 属性。



在 3.7 版更改: 添加了 @emph{defaults} 参数和 @code{_field_defaults} 属性。

@end deffn

@example
>>> # Basic example
>>> Point = namedtuple('Point', ['x', 'y'])
>>> p = Point(11, y=22)     # instantiate with positional or keyword arguments
>>> p[0] + p[1]             # indexable like the plain tuple (11, 22)
33
>>> x, y = p                # unpack like a regular tuple
>>> x, y
(11, 22)
>>> p.x + p.y               # fields also accessible by name
33
>>> p                       # readable __repr__ with a name=value style
Point(x=11, y=22)
@end example

命名元组尤其有用于赋值 @ref{2a,,csv}  @ref{f2,,sqlite3} 模块返回的元组

@example
EmployeeRecord = namedtuple('EmployeeRecord', 'name, age, title, department, paygrade')

import csv
for emp in map(EmployeeRecord._make, csv.reader(open("employees.csv", "rb"))):
    print(emp.name, emp.title)

import sqlite3
conn = sqlite3.connect('/companydata')
cursor = conn.cursor()
cursor.execute('SELECT name, age, title, department, paygrade FROM employees')
for emp in map(EmployeeRecord._make, cursor.fetchall()):
    print(emp.name, emp.title)
@end example

除了继承元组的方法，命名元组还支持三个额外的方法和两个属性。为了防止字段名冲突，方法和属性以下划线开始。

@geindex _make() (collections.somenamedtuple 类方法)
@anchor{library/collections collections somenamedtuple _make}@anchor{18d4}
@deffn {方法} classmethod somenamedtuple._make (iterable)

类方法从存在的序列或迭代实例创建一个新实例。

@example
>>> t = [11, 22]
>>> Point._make(t)
Point(x=11, y=22)
@end example
@end deffn

@geindex _asdict() (collections.somenamedtuple 方法)
@anchor{library/collections collections somenamedtuple _asdict}@anchor{1b7}
@deffn {方法} somenamedtuple._asdict ()

返回一个新的 @ref{1b8,,dict} ，它将字段名称映射到它们对应的值：

@example
>>> p = Point(x=11, y=22)
>>> p._asdict()
@{'x': 11, 'y': 22@}
@end example


在 3.1 版更改: 返回一个 @ref{1b9,,OrderedDict} 而不是  @ref{1b8,,dict} 。



在 3.8 版更改: 返回一个常规 @ref{1b8,,dict} 而不是 @ref{1b9,,OrderedDict}。 因为自 Python 3.7 起，常规字典已经保证有序。 如果需要 @ref{1b9,,OrderedDict} 的额外特性，推荐的解决方案是将结果转换为需要的类型: @code{OrderedDict(nt._asdict())}。

@end deffn

@geindex _replace() (collections.somenamedtuple 方法)
@anchor{library/collections collections somenamedtuple _replace}@anchor{18d5}
@deffn {方法} somenamedtuple._replace (**kwargs)

返回一个新的命名元组实例，并将指定域替换为新的值

@example
>>> p = Point(x=11, y=22)
>>> p._replace(x=33)
Point(x=33, y=22)

>>> for partnum, record in inventory.items():
...     inventory[partnum] = record._replace(price=newprices[partnum], timestamp=time.now())
@end example
@end deffn

@geindex _fields (collections.somenamedtuple 属性)
@anchor{library/collections collections somenamedtuple _fields}@anchor{18d6}
@deffn {属性} somenamedtuple._fields

字符串元组列出了字段名。用于提醒和从现有元组创建一个新的命名元组类型。

@example
>>> p._fields            # view the field names
('x', 'y')

>>> Color = namedtuple('Color', 'red green blue')
>>> Pixel = namedtuple('Pixel', Point._fields + Color._fields)
>>> Pixel(11, 22, 128, 255, 0)
Pixel(x=11, y=22, red=128, green=255, blue=0)
@end example
@end deffn

@geindex _field_defaults (collections.somenamedtuple 属性)
@anchor{library/collections collections somenamedtuple _field_defaults}@anchor{18d7}
@deffn {属性} somenamedtuple._field_defaults

字典将字段名称映射到默认值。

@example
>>> Account = namedtuple('Account', ['type', 'balance'], defaults=[0])
>>> Account._field_defaults
@{'balance': 0@}
>>> Account('premium')
Account(type='premium', balance=0)
@end example
@end deffn

要获取这个名字域的值，使用 @ref{443,,getattr()} 函数 :

@example
>>> getattr(p, 'x')
11
@end example

转换一个字典到命名元组，使用 ** 两星操作符 (所述如 @ref{11e9,,解包参数列表}):

@example
>>> d = @{'x': 11, 'y': 22@}
>>> Point(**d)
Point(x=11, y=22)
@end example

因为一个命名元组是一个正常的Python类，它可以很容易的通过子类更改功能。这里是如何添加一个计算域和定宽输出打印格式:

@example
>>> class Point(namedtuple('Point', ['x', 'y'])):
...     __slots__ = ()
...     @@property
...     def hypot(self):
...         return (self.x ** 2 + self.y ** 2) ** 0.5
...     def __str__(self):
...         return 'Point: x=%6.3f  y=%6.3f  hypot=%6.3f' % (self.x, self.y, self.hypot)

>>> for p in Point(3, 4), Point(14, 5/7):
...     print(p)
Point: x= 3.000  y= 4.000  hypot= 5.000
Point: x=14.000  y= 0.714  hypot=14.018
@end example

上面的子类设置 @code{__slots__} 为一个空元组。通过阻止创建实例字典保持了较低的内存开销。

子类化对于添加和存储新的名字域是无效的。应当通过 @ref{18d6,,_fields} 创建一个新的命名元组来实现它:

@example
>>> Point3D = namedtuple('Point3D', Point._fields + ('z',))
@end example

文档字符串可以自定义，通过直接赋值给 @code{__doc__} 属性:

@example
>>> Book = namedtuple('Book', ['id', 'title', 'authors'])
>>> Book.__doc__ += ': Hardcover book in active collection'
>>> Book.id.__doc__ = '13-digit ISBN'
>>> Book.title.__doc__ = 'Title of first printing'
>>> Book.authors.__doc__ = 'List of authors sorted by last name'
@end example


在 3.5 版更改: 文档字符串属性变成可写。



@subsubheading 参见



@itemize *

@item 
请参阅 @ref{280,,typing.NamedTuple} ，以获取为命名元组添加类型提示的方法。 它还使用 @ref{c63,,class} 关键字提供了一种优雅的符号:

@example
class Component(NamedTuple):
    part_number: int
    weight: float
    description: Optional[str] = None
@end example

@item 
对于以字典为底层的可变域名， 参考 @ref{9a6,,types.SimpleNamespace()} 。

@item 
@ref{30,,dataclasses} 模块提供了一个装饰器和一些函数，用于自动将生成的特殊方法添加到用户定义的类中。
@end itemize


@node OrderedDict 对象,UserDict 对象,namedtuple 命名元组的工厂函数,collections --- 容器数据类型
@anchor{library/collections ordereddict-objects}@anchor{18d8}
@subsubsection @code{OrderedDict} 对象


有序词典就像常规词典一样，但有一些与排序操作相关的额外功能。由于内置的 @ref{1b8,,dict} 类获得了记住插入顺序的能力（在 Python 3.7 中保证了这种新行为），它们变得不那么重要了。

一些与 @ref{1b8,,dict} 的不同仍然存在：


@itemize *

@item 
常规的 @ref{1b8,,dict} 被设计为非常擅长映射操作。 跟踪插入顺序是次要的。

@item 
@ref{1b9,,OrderedDict} 旨在擅长重新排序操作。 空间效率、迭代速度和更新操作的性能是次要的。

@item 
算法上， @ref{1b9,,OrderedDict} 可以比 @ref{1b8,,dict} 更好地处理频繁的重新排序操作。 这使其适用于跟踪最近的访问（例如在 LRU cache@footnote{https://medium.com/@@krishankantsinghal/my-first-blog-on-medium-583159139237} 中）。

@item 
对于 @ref{1b9,,OrderedDict} ，相等操作检查匹配顺序。

@item 
@ref{1b9,,OrderedDict} 类的 @code{popitem()} 方法有不同的签名。它接受一个可选参数来指定弹出哪个元素。

@item 
@ref{1b9,,OrderedDict} 类有一个 @code{move_to_end()} 方法，可以有效地将元素移动到任一端。

@item 
Python 3.8之前， @ref{1b8,,dict} 缺少 @ref{529,,__reversed__()} 方法。
@end itemize

@geindex OrderedDict (collections 中的类)
@anchor{library/collections collections OrderedDict}@anchor{1b9}
@deffn {类} collections.OrderedDict ([items])

返回一个 @ref{1b8,,dict} 子类的实例，它具有专门用于重新排列字典顺序的方法。


3.1 新版功能.


@geindex popitem() (collections.OrderedDict 方法)
@anchor{library/collections collections OrderedDict popitem}@anchor{c7d}
@deffn {方法} popitem (last=True)

有序字典的 @ref{c7d,,popitem()} 方法移除并返回一个 (key, value) 键值对。 如果 @emph{last} 值为真，则按 @abbr{LIFO} 后进先出的顺序返回键值对，否则就按 @abbr{FIFO} 先进先出的顺序返回键值对。
@end deffn

@geindex move_to_end() (collections.OrderedDict 方法)
@anchor{library/collections collections OrderedDict move_to_end}@anchor{b54}
@deffn {方法} move_to_end (key, last=True)

将现有 @emph{key} 移动到有序字典的任一端。 如果 @emph{last} 为真值（默认）则将元素移至末尾；如果  @emph{last} 为假值则将元素移至开头。如果 @emph{key} 不存在则会触发 @ref{2c7,,KeyError}:

@example
>>> d = OrderedDict.fromkeys('abcde')
>>> d.move_to_end('b')
>>> '@w{'}.join(d.keys())
'acdeb'
>>> d.move_to_end('b', last=False)
>>> '@w{'}.join(d.keys())
'bacde'
@end example


3.2 新版功能.

@end deffn
@end deffn

相对于通常的映射方法，有序字典还另外提供了逆序迭代的支持，通过 @ref{18e,,reversed()} 。

@ref{1b9,,OrderedDict} 之间的相等测试是顺序敏感的，实现为 @code{list(od1.items())==list(od2.items())} 。 @ref{1b9,,OrderedDict} 对象和其他的  @ref{18d9,,Mapping} 的相等测试，是顺序敏感的字典测试。这允许 @ref{1b9,,OrderedDict} 替换为任何字典可以使用的场所。


在 3.5 版更改: @ref{1b9,,OrderedDict} 的项(item)，键(key)和值(value) @ref{18da,,视图} 现在支持逆序迭代，通过 @ref{18e,,reversed()} 。



在 3.6 版更改: 
@geindex Python 提高建议; PEP 468
PEP 468@footnote{https://www.python.org/dev/peps/pep-0468} 赞成将关键词参数的顺序保留， 通过传递给 @ref{1b9,,OrderedDict} 构造器和它的 @code{update()} 方法。


@menu
* OrderedDict 例子和用法:: 

@end menu

@node OrderedDict 例子和用法,,,OrderedDict 对象
@anchor{library/collections ordereddict-examples-and-recipes}@anchor{18db}
@subsubsection @code{OrderedDict} 例子和用法


创建记住键值 @emph{最后} 插入顺序的有序字典变体很简单。 如果新条目覆盖现有条目，则原始插入位置将更改并移至末尾:

@example
class LastUpdatedOrderedDict(OrderedDict):
    'Store items in the order the keys were last added'

    def __setitem__(self, key, value):
        super().__setitem__(key, value)
        self.move_to_end(key)
@end example

一个 @ref{1b9,,OrderedDict} 对于实现 @ref{1c7,,functools.lru_cache()} 的变体也很有用:

@example
class LRU(OrderedDict):
    'Limit size, evicting the least recently looked-up key when full'

    def __init__(self, maxsize=128, /, *args, **kwds):
        self.maxsize = maxsize
        super().__init__(*args, **kwds)

    def __getitem__(self, key):
        value = super().__getitem__(key)
        self.move_to_end(key)
        return value

    def __setitem__(self, key, value):
        if key in self:
            self.move_to_end(key)
        super().__setitem__(key, value)
        if len(self) > self.maxsize:
            oldest = next(iter(self))
            del self[oldest]
@end example

@node UserDict 对象,UserList 对象,OrderedDict 对象,collections --- 容器数据类型
@anchor{library/collections userdict-objects}@anchor{18dc}
@subsubsection @code{UserDict} 对象


@ref{18ba,,UserDict} 类是用作字典对象的外包装。对这个类的需求已部分由直接创建 @ref{1b8,,dict} 的子类的功能所替代；不过，这个类处理起来更容易，因为底层的字典可以作为属性来访问。

@geindex UserDict (collections 中的类)
@anchor{library/collections collections UserDict}@anchor{18ba}
@deffn {类} collections.UserDict ([initialdata])

模拟一个字典类。这个实例的内容保存为一个正常字典， 可以通过 @ref{18ba,,UserDict} 实例的 @ref{18dd,,data} 属性存取。如果提供了 @emph{initialdata} 值， @ref{18dd,,data} 就被初始化为它的内容；注意一个 @emph{initialdata} 的引用不会被保留作为其他用途。

@ref{18ba,,UserDict} 实例提供了以下属性作为扩展方法和操作的支持:

@geindex data (collections.UserDict 属性)
@anchor{library/collections collections UserDict data}@anchor{18dd}
@deffn {属性} data

一个真实的字典，用于保存 @ref{18ba,,UserDict} 类的内容。
@end deffn
@end deffn

@node UserList 对象,UserString 对象,UserDict 对象,collections --- 容器数据类型
@anchor{library/collections userlist-objects}@anchor{18de}
@subsubsection @code{UserList} 对象


这个类封装了列表对象。它是一个有用的基础类，对于你想自定义的类似列表的类，可以继承和覆盖现有的方法，也可以添加新的方法。这样我们可以对列表添加新的行为。

对这个类的需求已部分由直接创建 @ref{262,,list} 的子类的功能所替代；不过，这个类处理起来更容易，因为底层的列表可以作为属性来访问。

@geindex UserList (collections 中的类)
@anchor{library/collections collections UserList}@anchor{18bb}
@deffn {类} collections.UserList ([list])

模拟一个列表。这个实例的内容被保存为一个正常列表，通过 @ref{18bb,,UserList} 的 @ref{18df,,data} 属性存取。实例内容被初始化为一个 @emph{list} 的copy，默认为 @code{[]} 空列表。 @emph{list} 可以是迭代对象，比如一个Python列表，或者一个  @ref{18bb,,UserList} 对象。

@ref{18bb,,UserList} 提供了以下属性作为可变序列的方法和操作的扩展:

@geindex data (collections.UserList 属性)
@anchor{library/collections collections UserList data}@anchor{18df}
@deffn {属性} data

一个 @ref{262,,list} 对象用于存储 @ref{18bb,,UserList} 的内容。
@end deffn
@end deffn

@strong{子类化的要求:} @ref{18bb,,UserList} 的子类需要提供一个构造器，可以无参数调用，或者一个参数调用。返回一个新序列的列表操作需要创建一个实现类的实例。它假定了构造器可以以一个参数进行调用，这个参数是一个序列对象，作为数据源。

如果一个分离的类不希望依照这个需求，所有的特殊方法就必须重写；请参照源代码进行修改。

@node UserString 对象,,UserList 对象,collections --- 容器数据类型
@anchor{library/collections userstring-objects}@anchor{18e0}
@subsubsection @code{UserString} 对象


@ref{6a7,,UserString} 类是用作字符串对象的外包装。对这个类的需求已部分由直接创建 @ref{329,,str} 的子类的功能所替代；不过，这个类处理起来更容易，因为底层的字符串可以作为属性来访问。

@geindex UserString (collections 中的类)
@anchor{library/collections collections UserString}@anchor{6a7}
@deffn {类} collections.UserString (seq)

模拟一个字符串对象。这个实例对象的内容保存为一个正常字符串，通过 @ref{6a7,,UserString} 的 @ref{18e1,,data} 属性存取。实例内容初始化设置为 @emph{seq} 的copy。@emph{seq} 参数可以是任何可通过内建 @ref{329,,str()} 函数转换为字符串的对象。

@ref{6a7,,UserString} 提供了以下属性作为字符串方法和操作的额外支持：

@geindex data (collections.UserString 属性)
@anchor{library/collections collections UserString data}@anchor{18e1}
@deffn {属性} data

一个真正的 @ref{329,,str} 对象用来存放 @ref{6a7,,UserString} 类的内容。
@end deffn


在 3.5 版更改: 新方法 @code{__getnewargs__}, @code{__rmod__}, @code{casefold}, @code{format_map}, @code{isprintable}, 和 @code{maketrans}。

@end deffn

@node collections abc --- 容器的抽象基类,heapq --- 堆队列算法,collections --- 容器数据类型,数据类型
@anchor{library/collections abc doc}@anchor{18e2}@anchor{library/collections abc collections-abc-abstract-base-classes-for-containers}@anchor{18e3}@anchor{library/collections abc module-collections abc}@anchor{1f}
@subsection @code{collections.abc} --- 容器的抽象基类


@geindex collections.abc (模块)


3.3 新版功能: 该模块曾是 @ref{1e,,collections} 模块的组成部分。


@strong{源代码：} Lib/_collections_abc.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/_collections_abc.py}

@c from collections import *
@c import itertools
@c __name__ = '<doctest>'


__________________________________________________________________


该模块定义了一些 @ref{b2c,,抽象基类}，它们可用于判断一个具体类是否具有某一特定的接口；例如，这个类是否可哈希，或其是否为映射类。

@menu
* 容器抽象基类:: 

@end menu

@node 容器抽象基类,,,collections abc --- 容器的抽象基类
@anchor{library/collections abc collections-abstract-base-classes}@anchor{18bc}@anchor{library/collections abc id1}@anchor{18e4}
@subsubsection 容器抽象基类


这个容器模块提供了以下 @ref{b2c,,ABCs}:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

抽象基类

@tab

继承自

@tab

抽象方法

@tab

Mixin 方法

@item

@ref{18e5,,Container}

@tab

@tab

@code{__contains__}

@tab

@item

@ref{18e6,,Hashable}

@tab

@tab

@code{__hash__}

@tab

@item

@ref{18e7,,Iterable}

@tab

@tab

@code{__iter__}

@tab

@item

@ref{18e8,,Iterator}

@tab

@ref{18e7,,Iterable}

@tab

@code{__next__}

@tab

@code{__iter__}

@item

@ref{528,,Reversible}

@tab

@ref{18e7,,Iterable}

@tab

@code{__reversed__}

@tab

@item

@ref{6af,,Generator}

@tab

@ref{18e8,,Iterator}

@tab

@code{send}, @code{throw}

@tab

@code{close}, @code{__iter__}, @code{__next__}

@item

@ref{18e9,,Sized}

@tab

@tab

@code{__len__}

@tab

@item

@ref{18ea,,Callable}

@tab

@tab

@code{__call__}

@tab

@item

@ref{527,,Collection}

@tab

@ref{18e9,,Sized},
@ref{18e7,,Iterable},
@ref{18e5,,Container}

@tab

@code{__contains__},
@code{__iter__},
@code{__len__}

@tab

@item

@ref{15c8,,Sequence}

@tab

@ref{528,,Reversible},
@ref{527,,Collection}

@tab

@code{__getitem__},
@code{__len__}

@tab

@code{__contains__}, @code{__iter__}, @code{__reversed__},
@code{index}, and @code{count}

@item

@ref{6a6,,MutableSequence}

@tab

@ref{15c8,,Sequence}

@tab

@code{__getitem__},
@code{__setitem__},
@code{__delitem__},
@code{__len__},
@code{insert}

@tab

继承自 @ref{15c8,,Sequence} 的方法，以及 @code{append}, @code{reverse}, @code{extend}, @code{pop}, @code{remove}，和 @code{__iadd__}

@item

@ref{18eb,,ByteString}

@tab

@ref{15c8,,Sequence}

@tab

@code{__getitem__},
@code{__len__}

@tab

继承自 @ref{15c8,,Sequence} 的方法

@item

@ref{1673,,Set}

@tab

@ref{527,,Collection}

@tab

@code{__contains__},
@code{__iter__},
@code{__len__}

@tab

@code{__le__}, @code{__lt__}, @code{__eq__}, @code{__ne__},
@code{__gt__}, @code{__ge__}, @code{__and__}, @code{__or__},
@code{__sub__}, @code{__xor__}, and @code{isdisjoint}

@item

@ref{18ec,,MutableSet}

@tab

@ref{1673,,Set}

@tab

@code{__contains__},
@code{__iter__},
@code{__len__},
@code{add},
@code{discard}

@tab

继承自 @ref{1673,,Set} 的方法以及 @code{clear}, @code{pop}, @code{remove}, @code{__ior__}, @code{__iand__}, @code{__ixor__}，和  @code{__isub__}

@item

@ref{18d9,,Mapping}

@tab

@ref{527,,Collection}

@tab

@code{__getitem__},
@code{__iter__},
@code{__len__}

@tab

@code{__contains__}, @code{keys}, @code{items}, @code{values},
@code{get}, @code{__eq__}, and @code{__ne__}

@item

@ref{9e9,,MutableMapping}

@tab

@ref{18d9,,Mapping}

@tab

@code{__getitem__},
@code{__setitem__},
@code{__delitem__},
@code{__iter__},
@code{__len__}

@tab

继承自 @ref{18d9,,Mapping} 的方法以及 @code{pop}, @code{popitem}, @code{clear}, @code{update}，和 @code{setdefault}

@item

@ref{18ed,,MappingView}

@tab

@ref{18e9,,Sized}

@tab

@tab

@code{__len__}

@item

@ref{18ee,,ItemsView}

@tab

@ref{18ed,,MappingView},
@ref{1673,,Set}

@tab

@tab

@code{__contains__},
@code{__iter__}

@item

@ref{18ef,,KeysView}

@tab

@ref{18ed,,MappingView},
@ref{1673,,Set}

@tab

@tab

@code{__contains__},
@code{__iter__}

@item

@ref{18f0,,ValuesView}

@tab

@ref{18ed,,MappingView},
@ref{527,,Collection}

@tab

@tab

@code{__contains__}, @code{__iter__}

@item

@ref{6b0,,Awaitable}

@tab

@tab

@code{__await__}

@tab

@item

@ref{6b1,,Coroutine}

@tab

@ref{6b0,,Awaitable}

@tab

@code{send}, @code{throw}

@tab

@code{close}

@item

@ref{6b3,,AsyncIterable}

@tab

@tab

@code{__aiter__}

@tab

@item

@ref{6b2,,AsyncIterator}

@tab

@ref{6b3,,AsyncIterable}

@tab

@code{__anext__}

@tab

@code{__aiter__}

@item

@ref{52a,,AsyncGenerator}

@tab

@ref{6b2,,AsyncIterator}

@tab

@code{asend}, @code{athrow}

@tab

@code{aclose}, @code{__aiter__}, @code{__anext__}

@end multitable


@geindex Container (collections.abc 中的类)
@geindex Hashable (collections.abc 中的类)
@geindex Sized (collections.abc 中的类)
@geindex Callable (collections.abc 中的类)
@anchor{library/collections abc collections abc Container}@anchor{18e5}
@deffn {类} collections.abc.Container
@anchor{library/collections abc collections abc Hashable}@anchor{18e6}
@deffnx {类} collections.abc.Hashable
@anchor{library/collections abc collections abc Sized}@anchor{18e9}
@deffnx {类} collections.abc.Sized
@anchor{library/collections abc collections abc Callable}@anchor{18ea}
@deffnx {类} collections.abc.Callable

分别提供了 @ref{d21,,__contains__()}, @ref{339,,__hash__()}, @ref{dc4,,__len__()} 和 @ref{13c5,,__call__()} 方法的抽象基类。
@end deffn

@geindex Iterable (collections.abc 中的类)
@anchor{library/collections abc collections abc Iterable}@anchor{18e7}
@deffn {类} collections.abc.Iterable

提供了 @ref{509,,__iter__()} 方法的抽象基类。

使用 @code{isinstance(obj, Iterable)} 可以检测一个类是否已经注册到了 @ref{18e7,,Iterable} 或者实现了 @ref{509,,__iter__()} 函数，但是无法检测这个类是否能够使用 @ref{27f,,__getitem__()} 方法进行迭代。检测一个对象是否是 @ref{ba5,,iterable} 的唯一可信赖的方法是调用 @code{iter(obj)}。
@end deffn

@geindex Collection (collections.abc 中的类)
@anchor{library/collections abc collections abc Collection}@anchor{527}
@deffn {类} collections.abc.Collection

集合了 Sized 和 Iterable 类的抽象基类。


3.6 新版功能.

@end deffn

@geindex Iterator (collections.abc 中的类)
@anchor{library/collections abc collections abc Iterator}@anchor{18e8}
@deffn {类} collections.abc.Iterator

提供了 @ref{15c2,,__iter__()} 和 @ref{c5d,,__next__()} 方法的抽象基类。参见 @ref{fce,,iterator} 的定义。
@end deffn

@geindex Reversible (collections.abc 中的类)
@anchor{library/collections abc collections abc Reversible}@anchor{528}
@deffn {类} collections.abc.Reversible

为可迭代类提供了 @ref{529,,__reversed__()} 方法的抽象基类。


3.6 新版功能.

@end deffn

@geindex Generator (collections.abc 中的类)
@anchor{library/collections abc collections abc Generator}@anchor{6af}
@deffn {类} collections.abc.Generator

生成器类，实现了 
@geindex Python 提高建议; PEP 342
PEP 342@footnote{https://www.python.org/dev/peps/pep-0342} 中定义的协议，继承并扩展了迭代器，提供了 @ref{1427,,send()}, @ref{1429,,throw()} 和 @ref{142b,,close()} 方法。参见 @ref{99c,,generator} 的定义。


3.5 新版功能.

@end deffn

@geindex Sequence (collections.abc 中的类)
@geindex MutableSequence (collections.abc 中的类)
@geindex ByteString (collections.abc 中的类)
@anchor{library/collections abc collections abc Sequence}@anchor{15c8}
@deffn {类} collections.abc.Sequence
@anchor{library/collections abc collections abc MutableSequence}@anchor{6a6}
@deffnx {类} collections.abc.MutableSequence
@anchor{library/collections abc collections abc ByteString}@anchor{18eb}
@deffnx {类} collections.abc.ByteString

只读且可变的序列 @ref{11bc,,sequences} 的抽象基类。

实现笔记：一些混入（Maxin）方法比如 @ref{509,,__iter__()}, @ref{529,,__reversed__()} 和 @code{index()} 会重复调用底层的 @ref{27f,,__getitem__()} 方法。因此，如果实现的 @ref{27f,,__getitem__()} 是常数级访问速度，那么相应的混入方法会有一个线性的表现；然而，如果底层方法是线性实现（例如链表），那么混入方法将会是平方级的表现，这也许就需要被重构了。


在 3.5 版更改: index() 方法支持 @emph{stop} 和 @emph{start} 参数。

@end deffn

@geindex Set (collections.abc 中的类)
@geindex MutableSet (collections.abc 中的类)
@anchor{library/collections abc collections abc Set}@anchor{1673}
@deffn {类} collections.abc.Set
@anchor{library/collections abc collections abc MutableSet}@anchor{18ec}
@deffnx {类} collections.abc.MutableSet

只读且可变的集合的抽象基类。
@end deffn

@geindex Mapping (collections.abc 中的类)
@geindex MutableMapping (collections.abc 中的类)
@anchor{library/collections abc collections abc Mapping}@anchor{18d9}
@deffn {类} collections.abc.Mapping
@anchor{library/collections abc collections abc MutableMapping}@anchor{9e9}
@deffnx {类} collections.abc.MutableMapping

只读且可变的映射 @ref{b32,,mappings} 的抽象基类。
@end deffn

@geindex MappingView (collections.abc 中的类)
@geindex ItemsView (collections.abc 中的类)
@geindex KeysView (collections.abc 中的类)
@geindex ValuesView (collections.abc 中的类)
@anchor{library/collections abc collections abc MappingView}@anchor{18ed}
@deffn {类} collections.abc.MappingView
@anchor{library/collections abc collections abc ItemsView}@anchor{18ee}
@deffnx {类} collections.abc.ItemsView
@anchor{library/collections abc collections abc KeysView}@anchor{18ef}
@deffnx {类} collections.abc.KeysView
@anchor{library/collections abc collections abc ValuesView}@anchor{18f0}
@deffnx {类} collections.abc.ValuesView

映射及其键和值的视图 @ref{18da,,views} 的抽象基类。
@end deffn

@geindex Awaitable (collections.abc 中的类)
@anchor{library/collections abc collections abc Awaitable}@anchor{6b0}
@deffn {类} collections.abc.Awaitable

为可等待对象 @ref{513,,awaitable} 提供的类，可以被用于 @ref{1a3,,await} 表达式中。习惯上必须实现 @ref{63c,,__await__()} 方法。

协程对象 @ref{1a6,,Coroutine} 和 @ref{6b1,,Coroutine} 抽象基类的实例都是这个抽象基类的实例。

@cartouche
@quotation 注解 
在 CPython 里，基于生成器的协程（使用 @ref{776,,types.coroutine()} 或 @ref{282,,asyncio.coroutine()} 包装的生成器）都是 @emph{可等待对象}，即使他们不含有 @ref{63c,,__await__()} 方法。使用 @code{isinstance(gencoro, Awaitable)} 来检测他们会返回 @code{False}。要使用 @ref{6f3,,inspect.isawaitable()} 来检测他们。
@end quotation
@end cartouche


3.5 新版功能.

@end deffn

@geindex Coroutine (collections.abc 中的类)
@anchor{library/collections abc collections abc Coroutine}@anchor{6b1}
@deffn {类} collections.abc.Coroutine

用于协程兼容类的抽象基类。实现了如下定义在 @ref{13c4,,协程对象}: 里的方法： @ref{1426,,send()}，@ref{1428,,throw()} 和 @ref{142a,,close()}。通常的实现里还需要实现 @ref{63c,,__await__()} 方法。所有的 @ref{6b1,,Coroutine} 实例都必须是 @ref{6b0,,Awaitable} 实例。参见 @ref{1a6,,coroutine} 的定义。

@cartouche
@quotation 注解 
在 CPython 里，基于生成器的协程（使用 @ref{776,,types.coroutine()} 或 @ref{282,,asyncio.coroutine()} 包装的生成器）都是 @emph{可等待对象}，即使他们不含有 @ref{63c,,__await__()} 方法。使用 @code{isinstance(gencoro, Coroutine)} 来检测他们会返回 @code{False}。要使用 @ref{6f3,,inspect.isawaitable()} 来检测他们。
@end quotation
@end cartouche


3.5 新版功能.

@end deffn

@geindex AsyncIterable (collections.abc 中的类)
@anchor{library/collections abc collections abc AsyncIterable}@anchor{6b3}
@deffn {类} collections.abc.AsyncIterable

提供了 @code{__aiter__} 方法的抽象基类。参见 @ref{63a,,asynchronous iterable} 的定义。


3.5 新版功能.

@end deffn

@geindex AsyncIterator (collections.abc 中的类)
@anchor{library/collections abc collections abc AsyncIterator}@anchor{6b2}
@deffn {类} collections.abc.AsyncIterator

提供了 @code{__aiter__} 和 @code{__anext__} 方法的抽象基类。参见 @ref{63f,,asynchronous iterator} 的定义。


3.5 新版功能.

@end deffn

@geindex AsyncGenerator (collections.abc 中的类)
@anchor{library/collections abc collections abc AsyncGenerator}@anchor{52a}
@deffn {类} collections.abc.AsyncGenerator

为异步生成器类提供的抽象基类，这些类实现了定义在 
@geindex Python 提高建议; PEP 525
PEP 525@footnote{https://www.python.org/dev/peps/pep-0525} 和 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} 里的协议。


3.6 新版功能.

@end deffn

这些抽象基类让我们可以确定类和示例拥有某些特定的函数，例如：

@example
size = None
if isinstance(myvar, collections.abc.Sized):
    size = len(myvar)
@end example

有些抽象基类也可以用作混入类（mixin），这可以更容易地开发支持容器 API 的类。例如，要写一个支持完整 @ref{1673,,Set} API 的类，只需要提供下面这三个方法： @ref{d21,,__contains__()}, @ref{509,,__iter__()} 和 @ref{dc4,,__len__()}。抽象基类会补充上其余的方法，比如 @ref{13fe,,__and__()} 和 @code{isdisjoint()}:

@example
class ListBasedSet(collections.abc.Set):
    '@w{'}' Alternate set implementation favoring space over speed
        and not requiring the set elements to be hashable. '@w{'}'
    def __init__(self, iterable):
        self.elements = lst = []
        for value in iterable:
            if value not in lst:
                lst.append(value)

    def __iter__(self):
        return iter(self.elements)

    def __contains__(self, value):
        return value in self.elements

    def __len__(self):
        return len(self.elements)

s1 = ListBasedSet('abcdef')
s2 = ListBasedSet('defghi')
overlap = s1 & s2            # The __and__() method is supported automatically
@end example

当把 @ref{1673,,Set} 和 @ref{18ec,,MutableSet} 用作混入类时需注意：


@enumerate 

@item 
由于某些集合操作会创建新集合，默认的混入方法需要一种从可迭代对象里创建新实例的方法。假如其类构造函数签名形如 @code{ClassName(iterable)} ，则其会调用一个内部的类方法 @code{_from_iterable()}，其中调用了 @code{cls(iterable)} 来生成一个新集合。如果这个 @ref{1673,,Set} 混入类在类中被使用，但其构造函数的签名却是不同的形式，那么你就需要重载 @code{_from_iterable()} 方法，将其编写成一个类方法，并且它能够从可迭代对象参数中构造一个新实例。

@item 
重载比较符时时（想必是为了速度，因为其语义都是固定的），只需要重定义 @ref{c99,,__le__()} 和 @ref{c9b,,__ge__()} 函数，然后其他的操作会自动跟进。

@item 
混入集合类 @ref{1673,,Set} 提供了一个 @code{_hash()} 方法为集合计算哈希值，然而， @ref{339,,__hash__()} 函数却没有被定义，因为并不是所有集合都是可哈希并且不可变的。为了使用混入类为集合添加哈希能力，可以同时继承 @ref{1673,,Set()} 和 @ref{18e6,,Hashable()} 类，然后定义 @code{__hash__ = Set._hash}。
@end enumerate


@subsubheading 参见



@itemize *

@item 
OrderedSet recipe@footnote{https://code.activestate.com/recipes/576694/} 是基于 @ref{18ec,,MutableSet} 构建的一个示例。

@item 
对于抽象基类，参见 @ref{4,,abc} 模块和 
@geindex Python 提高建议; PEP 3119
PEP 3119@footnote{https://www.python.org/dev/peps/pep-3119}。
@end itemize


@node heapq --- 堆队列算法,bisect --- 数组二分查找算法,collections abc --- 容器的抽象基类,数据类型
@anchor{library/heapq doc}@anchor{18f1}@anchor{library/heapq heapq-heap-queue-algorithm}@anchor{18f2}@anchor{library/heapq module-heapq}@anchor{8e}
@subsection @code{heapq} --- 堆队列算法


@geindex heapq (模块)

@strong{源码：}Lib/heapq.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/heapq.py}


__________________________________________________________________


这个模块提供了堆队列算法的实现，也称为优先队列算法。

堆是一个二叉树，它的每个父节点的值都只会小于或大于所有孩子节点（的值）。它使用了数组来实现：从零开始计数，对于所有的 @emph{k} ，都有 @code{heap[k] <= heap[2*k+1]} 和 @code{heap[k] <= heap[2*k+2]}。 为了便于比较，不存在的元素被认为是无限大。 堆最有趣的特性在于最小的元素总是在根结点：@code{heap[0]}。

这个API与教材的堆算法实现有所不同，具体区别有两方面：（a）我们使用了从零开始的索引。这使得节点和其孩子节点索引之间的关系不太直观但更加适合，因为 Python 使用从零开始的索引。 （b）我们的 pop 方法返回最小的项而不是最大的项（这在教材中称为“最小堆”；而“最大堆”在教材中更为常见，因为它更适用于原地排序）。

基于这两方面，把堆看作原生的Python list也没什么奇怪的： @code{heap[0]} 表示最小的元素，同时 @code{heap.sort()} 维护了堆的不变性！

要创建一个堆，可以使用list来初始化为 @code{[]} ，或者你可以通过一个函数 @ref{18f3,,heapify()} ，来把一个list转换成堆。

定义了以下函数：

@geindex heappush() (在 heapq 模块中)
@anchor{library/heapq heapq heappush}@anchor{18f4}
@deffn {函数} heapq.heappush (heap, item)

将 @emph{item} 的值加入 @emph{heap} 中，保持堆的不变性。
@end deffn

@geindex heappop() (在 heapq 模块中)
@anchor{library/heapq heapq heappop}@anchor{18f5}
@deffn {函数} heapq.heappop (heap)

弹出并返回 @emph{heap} 的最小的元素，保持堆的不变性。如果堆为空，抛出 @ref{e6e,,IndexError} 。使用 @code{heap[0]} ，可以只访问最小的元素而不弹出它。
@end deffn

@geindex heappushpop() (在 heapq 模块中)
@anchor{library/heapq heapq heappushpop}@anchor{18f6}
@deffn {函数} heapq.heappushpop (heap, item)

将 @emph{item} 放入堆中，然后弹出并返回 @emph{heap} 的最小元素。该组合操作比先调用 @ref{18f4,,heappush()} 再调用 @ref{18f5,,heappop()} 运行起来更有效率。
@end deffn

@geindex heapify() (在 heapq 模块中)
@anchor{library/heapq heapq heapify}@anchor{18f3}
@deffn {函数} heapq.heapify (x)

将list @emph{x} 转换成堆，原地，线性时间内。
@end deffn

@geindex heapreplace() (在 heapq 模块中)
@anchor{library/heapq heapq heapreplace}@anchor{18f7}
@deffn {函数} heapq.heapreplace (heap, item)

弹出并返回 @emph{heap} 中最小的一项，同时推入新的 @emph{item}。 堆的大小不变。 如果堆为空则引发 @ref{e6e,,IndexError}。

这个单步骤操作比 @ref{18f5,,heappop()} 加 @ref{18f4,,heappush()} 更高效，并且在使用固定大小的堆时更为适宜。 pop/push 组合总是会从堆中返回一个元素并将其替换为 @emph{item}。

返回的值可能会比添加的 @emph{item} 更大。 如果不希望如此，可考虑改用 @ref{18f6,,heappushpop()}。 它的 push/pop 组合会返回两个值中较小的一个，将较大的值留在堆中。
@end deffn

该模块还提供了三个基于堆的通用功能函数。

@geindex merge() (在 heapq 模块中)
@anchor{library/heapq heapq merge}@anchor{6d9}
@deffn {函数} heapq.merge (*iterables, key=None, reverse=False)

将多个已排序的输入合并为一个已排序的输出（例如，合并来自多个日志文件的带时间戳的条目）。 返回已排序值的 @ref{fce,,iterator}。

类似于 @code{sorted(itertools.chain(*iterables))} 但返回一个可迭代对象，不会一次性地将数据全部放入内存，并假定每个输入流都是已排序的（从小到大）。

具有两个可选参数，它们都必须指定为关键字参数。

@emph{key} 指定带有单个参数的 @ref{6da,,key function}，用于从每个输入元素中提取比较键。 默认值为 @code{None} (直接比较元素)。

@emph{reverse} 为一个布尔值。 如果设为 @code{True}，则输入元素将按比较结果逆序进行合并。 要达成与 @code{sorted(itertools.chain(*iterables), reverse=True)} 类似的行为，所有可迭代对象必须是已从大到小排序的。


在 3.5 版更改: 添加了可选的 @emph{key} 和 @emph{reverse} 形参。

@end deffn

@geindex nlargest() (在 heapq 模块中)
@anchor{library/heapq heapq nlargest}@anchor{18f8}
@deffn {函数} heapq.nlargest (n, iterable, key=None)

从 @emph{iterable} 所定义的数据集中返回前 @emph{n} 个最大元素组成的列表。 如果提供了 @emph{key} 则其应指定一个单参数的函数，用于从 @emph{iterable} 的每个元素中提取比较键 (例如 @code{key=str.lower})。 等价于:  @code{sorted(iterable, key=key, reverse=True)[:n]}。
@end deffn

@geindex nsmallest() (在 heapq 模块中)
@anchor{library/heapq heapq nsmallest}@anchor{18f9}
@deffn {函数} heapq.nsmallest (n, iterable, key=None)

从 @emph{iterable} 所定义的数据集中返回前 @emph{n} 个最小元素组成的列表。 如果提供了 @emph{key} 则其应指定一个单参数的函数，用于从 @emph{iterable} 的每个元素中提取比较键 (例如 @code{key=str.lower})。 等价于: @code{sorted(iterable, key=key)[:n]}。
@end deffn

后两个函数在 @emph{n} 值较小时性能最好。 对于更大的值，使用 @ref{43e,,sorted()} 函数会更有效率。 此外，当 @code{n==1} 时，使用内置的 @ref{803,,min()} 和 @ref{804,,max()} 函数会更有效率。 如果需要重复使用这些函数，请考虑将可迭代对象转为真正的堆。

@menu
* 基本示例:: 
* 优先队列实现说明:: 
* 理论:: 

@end menu

@node 基本示例,优先队列实现说明,,heapq --- 堆队列算法
@anchor{library/heapq basic-examples}@anchor{18fa}
@subsubsection 基本示例


堆排序@footnote{https://en.wikipedia.org/wiki/Heapsort} 可以通过将所有值推入堆中然后每次弹出一个最小值项来实现。

@example
>>> def heapsort(iterable):
...     h = []
...     for value in iterable:
...         heappush(h, value)
...     return [heappop(h) for i in range(len(h))]
...
>>> heapsort([1, 3, 5, 7, 9, 2, 4, 6, 8, 0])
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
@end example

这类似于 @code{sorted(iterable)}，但与 @ref{43e,,sorted()} 不同的是这个实现是不稳定的。

堆元素可以为元组。 这适用于将比较值（例如任务优先级）与跟踪的主记录进行赋值的场合:

@example
>>> h = []
>>> heappush(h, (5, 'write code'))
>>> heappush(h, (7, 'release product'))
>>> heappush(h, (1, 'write spec'))
>>> heappush(h, (3, 'create tests'))
>>> heappop(h)
(1, 'write spec')
@end example

@node 优先队列实现说明,理论,基本示例,heapq --- 堆队列算法
@anchor{library/heapq priority-queue-implementation-notes}@anchor{18fb}
@subsubsection 优先队列实现说明


优先队列@footnote{https://en.wikipedia.org/wiki/Priority_queue} 是堆的常用场合，并且它的实现包含了多个挑战：


@itemize *

@item 
排序稳定性：你该如何令相同优先级的两个任务按它们最初被加入时的顺序返回？

@item 
如果优先级相同且任务没有默认比较顺序，则 (priority, task) 对的元组比较将会中断。

@item 
如果任务优先级发生改变，你该如何将其移至堆中的新位置？

@item 
或者如果一个挂起的任务需要被删除，你该如何找到它并将其移出队列？
@end itemize

针对前两项挑战的一种解决方案是将条目保存为包含优先级、条目计数和任务对象 3 个元素的列表。 条目计数可用来打破平局，这样具有相同优先级的任务将按它们的添加顺序返回。 并且由于没有哪两个条目计数是相同的，元组比较将永远不会直接比较两个任务。

不可比较任务问题的另一种解决方案是创建一个忽略任务条目并且只比较优先级字段的包装器类:

@example
from dataclasses import dataclass, field
from typing import Any

@@dataclass(order=True)
class PrioritizedItem:
    priority: int
    item: Any=field(compare=False)
@end example

其余的挑战主要包括找到挂起的任务并修改其优先级或将其完全移除。 找到一个任务可使用一个指向队列中条目的字典来实现。

移除条目或改变其优先级的操作实现起来更为困难，因为它会破坏堆结构不变量。 因此，一种可能的解决方案是将条目标记为已移除，再添加一个改变了优先级的新条目:

@example
pq = []                         # list of entries arranged in a heap
entry_finder = @{@}               # mapping of tasks to entries
REMOVED = '<removed-task>'      # placeholder for a removed task
counter = itertools.count()     # unique sequence count

def add_task(task, priority=0):
    'Add a new task or update the priority of an existing task'
    if task in entry_finder:
        remove_task(task)
    count = next(counter)
    entry = [priority, count, task]
    entry_finder[task] = entry
    heappush(pq, entry)

def remove_task(task):
    'Mark an existing task as REMOVED.  Raise KeyError if not found.'
    entry = entry_finder.pop(task)
    entry[-1] = REMOVED

def pop_task():
    'Remove and return the lowest priority task. Raise KeyError if empty.'
    while pq:
        priority, count, task = heappop(pq)
        if task is not REMOVED:
            del entry_finder[task]
            return task
    raise KeyError('pop from an empty priority queue')
@end example

@node 理论,,优先队列实现说明,heapq --- 堆队列算法
@anchor{library/heapq theory}@anchor{18fc}
@subsubsection 理论


堆是通过数组来实现的，其中的元素从 0 开始计数，对于所有的 @emph{k} 都有 @code{a[k] <= a[2*k+1]} 且 @code{a[k] <= a[2*k+2]}。 为了便于比较，不存在的元素被视为无穷大。 堆最有趣的特性在于 @code{a[0]} 总是其中最小的元素。

上面的特殊不变量是用来作为一场锦标赛的高效内存表示。 下面的数字是 @emph{k} 而不是 @code{a[k]}:

@example
                               0

              1                                 2

      3               4                5               6

  7       8       9       10      11      12      13      14

15 16   17 18   19 20   21 22   23 24   25 26   27 28   29 30
@end example

在上面的树中，每个 @emph{k} 单元都位于 @code{2*k+1} 和 @code{2*k+2} 之上。 体育运动中我们经常见到二元锦标赛模式，每个胜者单元都位于另两个单元之上，并且我们可以沿着树形图向下追溯胜者所遇到的所有对手。 但是，在许多采用这种锦标赛模式的计算机应用程序中，我们并不需要追溯胜者的历史。 为了获得更高的内存利用效率，当一个胜者晋级时，我们会用较低层级的另一条目来替代它，因此规则变为一个单元和它之下的两个单元包含三个不同条目，上方单元“胜过”了两个下方单元。

如果此堆的不变量始终受到保护，则序号 0 显然是最后的赢家。 删除它并找出“下一个”赢家的最简单算法方式是家某个输家（让我们假定是上图中的 30 号单元）移至 0 号位置，然后将这个新的 0 号沿树下行，不断进行值的交换，直到不变量重新建立。 这显然会是树中条目总数的对数。 通过迭代所有条目，你将得到一个 O(n log n) 复杂度的排序。

此排序有一个很好的特性就是你可以在排序进行期间高效地插入新条目，前提是插入的条目不比你最近取出的 0 号元素“更好”。 这在模拟上下文时特别有用，在这种情况下树保存的是所有传入事件，“胜出”条件是最小调度时间。 当一个事件将其他事件排入执行计划时，它们的调试时间向未来方向延长，这样它们可方便地入堆。 因此，堆结构很适宜用来实现调度器，我的 MIDI 音序器就是用的这个 :-)。

用于实现调度器的各种结构都得到了充分的研究，堆是非常适宜的一种，因为它们的速度相当快，并且几乎是恒定的，最坏的情况与平均情况没有太大差别。 虽然还存在其他总体而言更高效的实现方式，但其最坏的情况却可能非常糟糕。

堆在大磁盘排序中也非常有用。 你应该已经了解大规模排序会有多个“运行轮次”（即预排序的序列，其大小通常与 CPU 内存容量相关），随后这些轮次会进入合并通道，轮次合并的组织往往非常巧妙 @footnote{@w{(1)} 
当前时代的磁盘平衡算法与其说是巧妙，不如说是麻烦，这是由磁盘的寻址能力导致的结果。 在无法寻址的设备例如大型磁带机上，情况则相当不同，开发者必须非常聪明地（极为提前地）确保每次磁带转动都尽可能地高效（就是说能够最好地加入到合并“进程”中）。 有些磁带甚至能够反向读取，这也被用来避免倒带的耗时。 请相信我，真正优秀的磁带机排序看起来是极其壮观的，排序从来都是一门伟大的艺术！ :-)
}。 非常重要的一点是初始排序应产生尽可能长的运行轮次。 锦标赛模式是达成此目标的好办法。 如果你使用全部有用内存来进行锦标赛，替换和安排恰好适合当前运行轮次的条目，你将可以对于随机输入生成两倍于内存大小的运行轮次，对于模糊排序的输入还会有更好的效果。

另外，如果你输出磁盘上的第 0 个条目并获得一个可能不适合当前锦标赛的输入（因为其值要“胜过”上一个输出值），它无法被放入堆中，因此堆的尺寸将缩小。 被释放的内存可以被巧妙地立即重用以逐步构建第二个堆，其增长速度与第一个堆的缩减速度正好相同。 当第一个堆完全消失时，你可以切换新堆并启动新的运行轮次。 这样做既聪明又高效！

总之，堆是值得了解的有用内存结构。 我在一些应用中用到了它们，并且认为保留一个 'heap' 模块是很有意义的。 :-)

@subsubheading 备注


@node bisect --- 数组二分查找算法,array --- 高效的数值数组,heapq --- 堆队列算法,数据类型
@anchor{library/bisect doc}@anchor{18fd}@anchor{library/bisect bisect-array-bisection-algorithm}@anchor{18fe}@anchor{library/bisect module-bisect}@anchor{12}
@subsection @code{bisect} --- 数组二分查找算法


@geindex bisect (模块)

@c example based on the PyModules FAQ entry by Aaron Watters <arw@pythonpros.com>

@strong{源代码：} Lib/bisect.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/bisect.py}


__________________________________________________________________


这个模块对有序列表提供了支持，使得他们可以在插入新数据仍然保持有序。对于长列表，如果其包含元素的比较操作十分昂贵的话，这可以是对更常见方法的改进。这个模块叫做 @ref{12,,bisect} 因为其使用了基本的二分（bisection）算法。源代码也可以作为很棒的算法示例（边界判断也做好啦！）

定义了以下函数：

@geindex bisect_left() (在 bisect 模块中)
@anchor{library/bisect bisect bisect_left}@anchor{18ff}
@deffn {函数} bisect.bisect_left (a, x, lo=0, hi=len(a))

在 @emph{a} 中找到 @emph{x} 合适的插入点以维持有序。参数 @emph{lo} 和 @emph{hi} 可以被用于确定需要考虑的子集；默认情况下整个列表都会被使用。如果 @emph{x} 已经在 @emph{a} 里存在，那么插入点会在已存在元素之前（也就是左边）。如果 @emph{a} 是列表（list）的话，返回值是可以被放在 @code{list.insert()} 的第一个参数的。

返回的插入点 @emph{i} 可以将数组 @emph{a} 分成两部分。左侧是 @code{all(val < x for val in a[lo:i])} ，右侧是 @code{all(val >= x for val in a[i:hi])} 。
@end deffn

@geindex bisect_right() (在 bisect 模块中)
@geindex bisect() (在 bisect 模块中)
@anchor{library/bisect bisect bisect_right}@anchor{1900}
@deffn {函数} bisect.bisect_right (a, x, lo=0, hi=len(a))
@anchor{library/bisect bisect bisect}@anchor{1901}
@deffnx {函数} bisect.bisect (a, x, lo=0, hi=len(a))

类似于 @ref{18ff,,bisect_left()}，但是返回的插入点是 @emph{a} 中已存在元素 @emph{x} 的右侧。

返回的插入点 @emph{i} 可以将数组 @emph{a} 分成两部分。左侧是 @code{all(val <= x for val in a[lo:i])}，右侧是 @code{all(val > x for val in a[i:hi])} for the right side。
@end deffn

@geindex insort_left() (在 bisect 模块中)
@anchor{library/bisect bisect insort_left}@anchor{1902}
@deffn {函数} bisect.insort_left (a, x, lo=0, hi=len(a))

将 @emph{x} 插入到一个有序序列 @emph{a} 里，并维持其有序。如果 @emph{a} 有序的话，这相当于 @code{a.insert(bisect.bisect_left(a, x, lo, hi), x)}。要注意搜索是 O(log n) 的，插入却是 O(n) 的。
@end deffn

@geindex insort_right() (在 bisect 模块中)
@geindex insort() (在 bisect 模块中)
@anchor{library/bisect bisect insort_right}@anchor{1903}
@deffn {函数} bisect.insort_right (a, x, lo=0, hi=len(a))
@anchor{library/bisect bisect insort}@anchor{1904}
@deffnx {函数} bisect.insort (a, x, lo=0, hi=len(a))

类似于 @ref{1902,,insort_left()}，但是把 @emph{x} 插入到 @emph{a} 中已存在元素 @emph{x} 的右侧。
@end deffn


@subsubheading 参见


SortedCollection recipe@footnote{https://code.activestate.com/recipes/577197-sortedcollection/} 使用 bisect 构造了一个功能完整的集合类，提供了直接的搜索方法和对用于搜索的 key 方法的支持。所有用于搜索的键都是预先计算的，以避免在搜索时对 key 方法的不必要调用。


@menu
* 搜索有序列表:: 
* 其他示例:: 

@end menu

@node 搜索有序列表,其他示例,,bisect --- 数组二分查找算法
@anchor{library/bisect searching-sorted-lists}@anchor{1905}
@subsubsection 搜索有序列表


上面的 @ref{12,,bisect()} 函数对于找到插入点是有用的，但在一般的搜索任务中可能会有点尴尬。下面 5 个函数展示了如何将其转变成有序列表中的标准查找函数

@example
def index(a, x):
    'Locate the leftmost value exactly equal to x'
    i = bisect_left(a, x)
    if i != len(a) and a[i] == x:
        return i
    raise ValueError

def find_lt(a, x):
    'Find rightmost value less than x'
    i = bisect_left(a, x)
    if i:
        return a[i-1]
    raise ValueError

def find_le(a, x):
    'Find rightmost value less than or equal to x'
    i = bisect_right(a, x)
    if i:
        return a[i-1]
    raise ValueError

def find_gt(a, x):
    'Find leftmost value greater than x'
    i = bisect_right(a, x)
    if i != len(a):
        return a[i]
    raise ValueError

def find_ge(a, x):
    'Find leftmost item greater than or equal to x'
    i = bisect_left(a, x)
    if i != len(a):
        return a[i]
    raise ValueError
@end example

@node 其他示例,,搜索有序列表,bisect --- 数组二分查找算法
@anchor{library/bisect other-examples}@anchor{1906}
@subsubsection 其他示例

@anchor{library/bisect bisect-example}@anchor{1907}
函数 @ref{12,,bisect()} 还可以用于数字表查询。这个例子是使用 @ref{12,,bisect()} 从一个给定的考试成绩集合里，通过一个有序数字表，查出其对应的字母等级：90 分及以上是 'A'，80 到 89 是 'B'，以此类推

@example
>>> def grade(score, breakpoints=[60, 70, 80, 90], grades='FDCBA'):
...     i = bisect(breakpoints, score)
...     return grades[i]
...
>>> [grade(score) for score in [33, 99, 77, 70, 89, 90, 100]]
['F', 'A', 'C', 'C', 'B', 'A', 'A']
@end example

与 @ref{43e,,sorted()} 函数不同，对于 @ref{12,,bisect()} 函数来说，@emph{key} 或者 @emph{reversed} 参数并没有什么意义。因为这会导致设计效率低下（连续调用 bisect 函数时，是不会 "记住" 过去查找过的键的）。

正相反，最好去搜索预先计算好的键列表，来查找相关记录的索引。

@example
>>> data = [('red', 5), ('blue', 1), ('yellow', 8), ('black', 0)]
>>> data.sort(key=lambda r: r[1])
>>> keys = [r[1] for r in data]         # precomputed list of keys
>>> data[bisect_left(keys, 0)]
('black', 0)
>>> data[bisect_left(keys, 1)]
('blue', 1)
>>> data[bisect_left(keys, 5)]
('red', 5)
>>> data[bisect_left(keys, 8)]
('yellow', 8)
@end example

@node array --- 高效的数值数组,weakref --- 弱引用,bisect --- 数组二分查找算法,数据类型
@anchor{library/array doc}@anchor{1908}@anchor{library/array array-efficient-arrays-of-numeric-values}@anchor{1909}@anchor{library/array module-array}@anchor{7}
@subsection @code{array} --- 高效的数值数组


@geindex array (模块)

@geindex arrays


__________________________________________________________________


此模块定义了一种对象类型，可以紧凑地表示基本类型值的数组：字符、整数、浮点数等。 数组属于序列类型，其行为与列表非常相似，不同之处在于其中存储的对象类型是受限的。 类型在对象创建时使用单个字符的 @emph{类型码} 来指定。 已定义的类型码如下：


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

类型码

@tab

C 类型

@tab

Python 类型

@tab

以字节表示的最小尺寸

@tab

注释

@item

@code{'b'}

@tab

signed char

@tab

int

@tab

1

@tab

@item

@code{'B'}

@tab

unsigned char

@tab

int

@tab

1

@tab

@item

@code{'u'}

@tab

Py_UNICODE

@tab

Unicode 字符

@tab

2

@tab

(1)

@item

@code{'h'}

@tab

signed short

@tab

int

@tab

2

@tab

@item

@code{'H'}

@tab

unsigned short

@tab

int

@tab

2

@tab

@item

@code{'i'}

@tab

signed int

@tab

int

@tab

2

@tab

@item

@code{'I'}

@tab

unsigned int

@tab

int

@tab

2

@tab

@item

@code{'l'}

@tab

signed long

@tab

int

@tab

4

@tab

@item

@code{'L'}

@tab

unsigned long

@tab

int

@tab

4

@tab

@item

@code{'q'}

@tab

signed long long

@tab

int

@tab

8

@tab

@item

@code{'Q'}

@tab

unsigned long long

@tab

int

@tab

8

@tab

@item

@code{'f'}

@tab

float

@tab

float

@tab

4

@tab

@item

@code{'d'}

@tab

double

@tab

float

@tab

8

@tab

@end multitable


注释:


@enumerate 

@item 
@code{'u'} 类型码对应于 Python 中已过时的 unicode 字符 (@ref{ae9,,Py_UNICODE} 即 @code{wchar_t})。 根据系统平台的不同，它可能是 16 位或 32 位。

@code{'u'} 将与其它的 @ref{ae9,,Py_UNICODE} API 一起被移除。


Deprecated since version 3.3, will be removed in version 4.0.

@end enumerate

值的实际表示会由机器的架构决定（严格地说是由 C 实现决定）。 实际大小可通过 @code{itemsize} 属性来获取。

这个模块定义了以下类型：

@geindex array (array 中的类)
@anchor{library/array array array}@anchor{44b}
@deffn {类} array.array (typecode[, initializer])

一个包含由 @emph{typecode} 限制类型的条目的新数组，并由可选的 @emph{initializer} 值进行初始化，该值必须为一个列表、@ref{5e3,,bytes-like object} 或包含正确类型元素的可迭代对象。

如果给定一个列表或字符串，该 initializer 会被传给新数组的 @ref{190a,,fromlist()}, @ref{190b,,frombytes()} 或 @ref{190c,,fromunicode()} 方法（见下文）以将初始条目添加到数组中。 否则会将可迭代对象作为 initializer 传给 @ref{190d,,extend()} 方法。

引发一个 @ref{12d0,,审计事件} @code{array.__new__} 附带参数 @code{typecode}, @code{initializer}。
@end deffn

@geindex typecodes() (在 array 模块中)
@anchor{library/array array typecodes}@anchor{190e}
@deffn {数据} array.typecodes

一个包含所有可用类型码的字符串。
@end deffn

数组对象支持普通的序列操作如索引、切片、拼接和重复等。 当使用切片赋值时，所赋的值必须为具有相同类型码的数组对象；所有其他情况都将引发 @ref{192,,TypeError}。 数组对象也实现了缓冲区接口，可以用于所有支持 @ref{5e3,,字节类对象} 的场合。

以下数据项和方法也受到支持：

@geindex typecode (array.array 属性)
@anchor{library/array array array typecode}@anchor{190f}
@deffn {属性} array.typecode

用于创建数组的类型码字符。
@end deffn

@geindex itemsize (array.array 属性)
@anchor{library/array array array itemsize}@anchor{1910}
@deffn {属性} array.itemsize

在内部表示中一个数组项的字节长度。
@end deffn

@geindex append() (array.array 方法)
@anchor{library/array array array append}@anchor{1911}
@deffn {方法} array.append (x)

添加一个值为 @emph{x} 的新项到数组末尾。
@end deffn

@geindex buffer_info() (array.array 方法)
@anchor{library/array array array buffer_info}@anchor{1912}
@deffn {方法} array.buffer_info ()

返回一个元组 @code{(address, length)} 以给出用于存放数组内容的缓冲区元素的当前内存地址和长度。 以字节表示的内存缓冲区大小可通过 @code{array.buffer_info()[1] * array.itemsize} 来计算。 这在使用需要内存地址的低层级（因此不够安全） I/O 接口时会很有用，例如某些 @code{ioctl()} 操作。 只要数组存在并且没有应用改变长度的操作，返回数值就是有效的。

@cartouche
@quotation 注解 
当在 C 或 C++ 编写的代码中使用数组对象时（这是有效使用此类信息的唯一方式），使用数组对象所支持的缓冲区接口更为适宜。 此方法仅保留用作向下兼容，应避免在新代码中使用。 缓冲区接口的文档参见 @ref{15d6,,缓冲协议}。
@end quotation
@end cartouche
@end deffn

@geindex byteswap() (array.array 方法)
@anchor{library/array array array byteswap}@anchor{1913}
@deffn {方法} array.byteswap ()

“字节对调”所有数组项。 此方法只支持大小为 1, 2, 4 或 8 字节的值；对于其他值类型将引发 @ref{2ba,,RuntimeError}。 它适用于从不同字节序机器所生成的文件中读取数据的情况。
@end deffn

@geindex count() (array.array 方法)
@anchor{library/array array array count}@anchor{1914}
@deffn {方法} array.count (x)

返回 @emph{x} 在数组中的出现次数。
@end deffn

@geindex extend() (array.array 方法)
@anchor{library/array array array extend}@anchor{190d}
@deffn {方法} array.extend (iterable)

将来自 @emph{iterable} 的项添加到数组末尾。 如果 @emph{iterable} 是另一个数组，它必须具有 @emph{完全} 相同的类型码；否则将引发 @ref{192,,TypeError}。 如果 @emph{iterable} 不是一个数组，则它必须为可迭代对象并且其元素必须为可添加到数组的适当类型。
@end deffn

@geindex frombytes() (array.array 方法)
@anchor{library/array array array frombytes}@anchor{190b}
@deffn {方法} array.frombytes (s)

添加来自字符串的项，将字符串解读为机器值的数组（相当于使用 @ref{1915,,fromfile()} 方法从文件中读取数据）。


3.2 新版功能: @ref{1916,,fromstring()} 重命名为 @ref{190b,,frombytes()} 以使其含义更清晰。

@end deffn

@geindex fromfile() (array.array 方法)
@anchor{library/array array array fromfile}@anchor{1915}
@deffn {方法} array.fromfile (f, n)

从 @ref{b3b,,file object} @emph{f} 中读取 @emph{n} 项（解读为机器值）并将它们添加到数组末尾。 如果可读取数据少于 @emph{n} 项则将引发 @ref{c65,,EOFError}，但有效的项仍然会被插入数组。 @emph{f} 必须为一个真实的内置文件对象；不支持带有 @code{read()} 方法的其它对象。
@end deffn

@geindex fromlist() (array.array 方法)
@anchor{library/array array array fromlist}@anchor{190a}
@deffn {方法} array.fromlist (list)

添加来自 list 的项。 这等价于 @code{for x in list: a.append(x)}，区别在于如果发生类型错误，数组将不会被改变。
@end deffn

@geindex fromstring() (array.array 方法)
@anchor{library/array array array fromstring}@anchor{1916}
@deffn {方法} array.fromstring ()

@ref{190b,,frombytes()} 的已弃用别名。


Deprecated since version 3.2, will be removed in version 3.9.

@end deffn

@geindex fromunicode() (array.array 方法)
@anchor{library/array array array fromunicode}@anchor{190c}
@deffn {方法} array.fromunicode (s)

使用来自给定 Unicode 字符串的数组扩展数组。 数组必须是类型为 @code{'u'} 的数组；否则将引发 @ref{1fb,,ValueError}。 请使用 @code{array.frombytes(unicodestring.encode(enc))} 来将 Unicode 数据添加到其他类型的数组。
@end deffn

@geindex index() (array.array 方法)
@anchor{library/array array array index}@anchor{e9a}
@deffn {方法} array.index (x)

返回最小的 @emph{i} 使得 @emph{i} 为 @emph{x} 在数组中首次出现的序号。
@end deffn

@geindex insert() (array.array 方法)
@anchor{library/array array array insert}@anchor{1917}
@deffn {方法} array.insert (i, x)

将值 @emph{x} 作为新项插入数组的 @emph{i} 位置之前。 负值将被视为相对于数组末尾的位置。
@end deffn

@geindex pop() (array.array 方法)
@anchor{library/array array array pop}@anchor{1918}
@deffn {方法} array.pop ([i])

从数组中移除序号为 @emph{i} 的项并将其返回。 可选参数值默认为 @code{-1}，因此默认将移除并返回末尾项。
@end deffn

@geindex remove() (array.array 方法)
@anchor{library/array array array remove}@anchor{1919}
@deffn {方法} array.remove (x)

从数组中移除首次出现的 @emph{x}。
@end deffn

@geindex reverse() (array.array 方法)
@anchor{library/array array array reverse}@anchor{191a}
@deffn {方法} array.reverse ()

反转数组中各项的顺序。
@end deffn

@geindex tobytes() (array.array 方法)
@anchor{library/array array array tobytes}@anchor{191b}
@deffn {方法} array.tobytes ()

将数组转换为一个机器值数组并返回其字节表示（即相当与通过 @ref{191c,,tofile()} 方法写入到文件的字节序列。）


3.2 新版功能: @ref{191d,,tostring()} 被重命名为 @ref{191b,,tobytes()} 以使其含义更清晰。

@end deffn

@geindex tofile() (array.array 方法)
@anchor{library/array array array tofile}@anchor{191c}
@deffn {方法} array.tofile (f)

将所有项（作为机器值）写入到 @ref{b3b,,file object} @emph{f}。
@end deffn

@geindex tolist() (array.array 方法)
@anchor{library/array array array tolist}@anchor{191e}
@deffn {方法} array.tolist ()

将数组转换为包含相同项的普通列表。
@end deffn

@geindex tostring() (array.array 方法)
@anchor{library/array array array tostring}@anchor{191d}
@deffn {方法} array.tostring ()

@ref{191b,,tobytes()} 的已弃用别名。


Deprecated since version 3.2, will be removed in version 3.9.

@end deffn

@geindex tounicode() (array.array 方法)
@anchor{library/array array array tounicode}@anchor{191f}
@deffn {方法} array.tounicode ()

将数组转换为一个 Unicode 字符串。 数组必须是类型为 @code{'u'} 的数组；否则将引发 @ref{1fb,,ValueError}。 请使用 @code{array.tobytes().decode(enc)} 来从其他类型的数组生成 Unicode 字符串。
@end deffn

当一个数组对象被打印或转换为字符串时，它会表示为 @code{array(typecode, initializer)}。 如果数组为空则 @emph{initializer} 会被省略，否则如果 @emph{typecode} 为 @code{'u'} 则它是一个字符串，否则它是一个数字列表。 使用 @ref{b89,,eval()} 保证能将字符串转换回具有相同类型和值的数组，只要 @ref{44b,,array} 类已通过 @code{from array import array} 被引入。 例如:

@example
array('l')
array('u', 'hello \u2641')
array('l', [1, 2, 3, 4, 5])
array('d', [1.0, 2.0, 3.14])
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{f8,,struct}

打包和解包异构二进制数据。

@item 模块 @ref{132,,xdrlib}

打包和解包用于某些远程过程调用系统的 External Data Representation (XDR) 数据。

@item Numerical Python 文档@footnote{https://docs.scipy.org/doc/}

Numeric Python 扩展 (NumPy) 定义了另一种数组类型；请访问 @indicateurl{http://www.numpy.org/} 了解有关 Numerical Python 的更多信息。
@end table


@node weakref --- 弱引用,types --- 动态类型创建和内置类型名称,array --- 高效的数值数组,数据类型
@anchor{library/weakref doc}@anchor{1920}@anchor{library/weakref module-weakref}@anchor{128}@anchor{library/weakref weakref-weak-references}@anchor{1921}
@subsection @code{weakref} --- 弱引用


@geindex weakref (模块)

@strong{源码：} Lib/weakref.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/weakref.py}


__________________________________________________________________


@ref{128,,weakref} 模块允许Python程序员创建对象的 @emph{weak references} 。

@c When making changes to the examples in this file, be sure to update
@c Lib/test/test_weakref.py::libreftest too!

在下文中，术语 @emph{referent} 表示由弱引用引用的对象。

对对象的弱引用不能保证对象存活：当对像的引用只剩弱引用时， @ref{129e,,garbage collection} 可以销毁引用并将其内存重用于其他内容。但是，在实际销毁对象之前，即使没有强引用，弱引用也一直能返回该对象。

弱引用的主要用途是实现保存大对象的高速缓存或映射，但又并希望大对象仅仅因为它出现在高速缓存或映射中而保持存活。

例如，如果您有许多大型二进制图像对象，则可能希望将名称与每个对象关联起来。如果您使用Python字典将名称映射到图像，或将图像映射到名称，则图像对象将保持活动状态，因为它们在字典中显示为值或键。 @ref{128,,weakref} 模块提供的 @ref{1922,,WeakKeyDictionary} 和 @ref{1923,,WeakValueDictionary} 类可以替代Python字典，使用弱引用来构造映射，这些映射不会仅仅因为它们出现在映射对象中而使对象保持存活。例如，如果一个图像对象是 @ref{1923,,WeakValueDictionary} 中的值，那么当对该图像对象的剩余引用是弱映射对象所持有的弱引用时，垃圾回收可以回收该对象并将其在弱映射对象中相应的条目删除。

@ref{1922,,WeakKeyDictionary} 和 @ref{1923,,WeakValueDictionary} 在它们的实现中使用弱引用，在弱引用上设置回调函数，当键或值被垃圾回收回收时通知弱字典。 @ref{cb1,,WeakSet} 实现了 @ref{b68,,set} 接口，但像 @ref{1922,,WeakKeyDictionary} 一样，只持有其元素的弱引用。`

@ref{29d,,finalize} 提供了注册一个对象被垃圾收集时要调用的清理函数的方式。这比在原始弱引用上设置回调函数更简单，因为模块会自动确保对象被回收前终结器一直保持存活。

这些弱容器类型之一或者 @ref{29d,,finalize} 就是大多数程序所需要的 - 通常不需要直接创建自己的弱引用。@ref{128,,weakref} 模块暴露了低级机制，以便于高级用途。

并非所有对象都可以被弱引用；可以被弱引用的对象包括类实例，用 Python（而不是用 C）编写的函数，实例方法、集合、冻结集合，某些 @ref{b3b,,文件对象}，@ref{99c,,生成器}，类型对象，套接字，数组，双端队列，正则表达式模式对象以及代码对象等。


在 3.2 版更改: 添加了对thread.lock，threading.Lock和代码对象的支持。


几个内建类型如 @ref{262,,list} 和 @ref{1b8,,dict} 不直接支持弱引用，但可以通过子类化添加支持:

@example
class Dict(dict):
    pass

obj = Dict(red=1, green=2, blue=3)   # this object is weak referenceable
@end example

@strong{CPython implementation detail:} 其他内置类型例如 @ref{478,,tuple} 和 @ref{184,,int} 不支持弱引用，即使通过子类化也不支持。

Extension types can easily be made to support weak references; see
@ref{1924,,Weak Reference Support}.

@geindex ref (weakref 中的类)
@anchor{library/weakref weakref ref}@anchor{90a}
@deffn {类} weakref.ref (object[, callback])

返回对 @emph{对象} 的弱引用。如果原始对象仍然存活，则可以通过调用引用对象来检索原始对象；如果引用的原始对象不再存在，则调用引用对象将得到 @ref{157,,None} 。如果提供了 @emph{回调} 而且值不是 @ref{157,,None} ，并且返回的弱引用对象仍然存活，则在对象即将终结时将调用回调;弱引用对象将作为回调的唯一参数传递；指示物将不再可用。

许多弱引用也允许针对相同对象来构建。 为每个弱引用注册的回调将按从最近注册的回调到最早注册的回调的顺序被调用。

回调所引发的异常将记录于标准错误输出，但无法被传播；它们会按与对象的 @ref{919,,__del__()} 方法所引发的异常相同的方式被处理。

如果 @emph{object} 可哈希，则弱引用也为 @ref{13c0,,hashable}。 即使在 @emph{object} 被删除之后它们仍将保持其哈希值。 如果 @ref{9be,,hash()} 在 @emph{object} 被删除之后才首次被调用，则该调用将引发 @ref{192,,TypeError}。

弱引用支持相等检测，但不支持排序比较。 如果被引用对象仍然存在，两个引用具有与它们的被引用对象一致的相等关系（无论 @emph{callback} 是否相同）。 如果删除了任一被引用对象，则仅在两个引用对象为同一对象时两者才相等。

这是一个可子类化的类型而非一个工厂函数。

@geindex __callback__ (weakref.ref 属性)
@anchor{library/weakref weakref ref __callback__}@anchor{90b}
@deffn {属性} __callback__

这个只读属性会返回当前关联到弱引用的回调。 如果回调不存在或弱引用的被引用对象已不存在，则此属性的值为 @code{None}。
@end deffn


在 3.4 版更改: 添加了 @ref{90b,,__callback__} 属性。

@end deffn

@geindex proxy() (在 weakref 模块中)
@anchor{library/weakref weakref proxy}@anchor{250}
@deffn {函数} weakref.proxy (object[, callback])

返回 @emph{object} 的一个使用弱引用的代理。 此函数支持在大多数上下文中使用代理，而不要求显式地对所使用的弱引用对象解除引用。 返回的对象类型将为 @code{ProxyType} 或 @code{CallableProxyType}，具体取决于 @emph{object} 是否可调用。 Proxy 对象不是 @ref{13c0,,hashable} 对象，无论被引用对象是否可哈希；这可避免与它们的基本可变性质相关的多种问题，并可防止它们被用作字典键。 @emph{callback} 与 @ref{90a,,ref()} 函数的同名形参含义相同。


在 3.8 版更改: 扩展代理对象所支持的运算符，包括矩阵乘法运算符 @code{@@} 和 @code{@@=}。

@end deffn

@geindex getweakrefcount() (在 weakref 模块中)
@anchor{library/weakref weakref getweakrefcount}@anchor{1925}
@deffn {函数} weakref.getweakrefcount (object)

返回指向 @emph{object} 的弱引用和代理的数量。
@end deffn

@geindex getweakrefs() (在 weakref 模块中)
@anchor{library/weakref weakref getweakrefs}@anchor{1926}
@deffn {函数} weakref.getweakrefs (object)

返回由指向 @emph{object} 的所有弱引用和代理构成的列表。
@end deffn

@geindex WeakKeyDictionary (weakref 中的类)
@anchor{library/weakref weakref WeakKeyDictionary}@anchor{1922}
@deffn {类} weakref.WeakKeyDictionary ([dict])

弱引用键的映射类。 当不再有对键的强引用时字典中的条目将被丢弃。 这可被用来将额外数据关联到一个应用中其他部分所拥有的对象而无需在那些对象中添加属性。 这对于重载了属性访问的对象来说特别有用。
@end deffn

@ref{1922,,WeakKeyDictionary} 对象具有一个额外方法可以直接公开内部引用。 这些引用不保证在它们被使用时仍然保持“存活”，因此这些引用的调用结果需要在使用前进行检测。 此方法可用于避免创建会导致垃圾回收器将保留键超出实际需要时长的引用。

@geindex keyrefs() (weakref.WeakKeyDictionary 方法)
@anchor{library/weakref weakref WeakKeyDictionary keyrefs}@anchor{1927}
@deffn {方法} WeakKeyDictionary.keyrefs ()

返回包含对键的弱引用的可迭代对象。
@end deffn

@geindex WeakValueDictionary (weakref 中的类)
@anchor{library/weakref weakref WeakValueDictionary}@anchor{1923}
@deffn {类} weakref.WeakValueDictionary ([dict])

弱引用值的映射类。 当不再有对键的强引用时字典中的条目将被丢弃。
@end deffn

@ref{1923,,WeakValueDictionary} 对象具有一个额外方法，此方法存在与 @ref{1922,,WeakKeyDictionary} 对象的 @code{keyrefs()} 方法相同的问题。

@geindex valuerefs() (weakref.WeakValueDictionary 方法)
@anchor{library/weakref weakref WeakValueDictionary valuerefs}@anchor{1928}
@deffn {方法} WeakValueDictionary.valuerefs ()

返回包含对值的弱引用的可迭代对象。
@end deffn

@geindex WeakSet (weakref 中的类)
@anchor{library/weakref weakref WeakSet}@anchor{cb1}
@deffn {类} weakref.WeakSet ([elements])

保持对其元素弱引用的集合类。 当不再有对某个元素的强引用时元素将被丢弃。
@end deffn

@geindex WeakMethod (weakref 中的类)
@anchor{library/weakref weakref WeakMethod}@anchor{909}
@deffn {类} weakref.WeakMethod (method)

一个模拟对绑定方法（即在类中定义并在实例中查找的方法）进行弱引用的自定义 @ref{90a,,ref} 子类。 由于绑定方法是临时性的，标准弱引用无法保持它。 @ref{909,,WeakMethod} 包含特别代码用来重新创建绑定方法，直到对象或初始函数被销毁:

@example
>>> class C:
...     def method(self):
...         print("method called!")
...
>>> c = C()
>>> r = weakref.ref(c.method)
>>> r()
>>> r = weakref.WeakMethod(c.method)
>>> r()
<bound method C.method of <__main__.C object at 0x7fc859830220>>
>>> r()()
method called!
>>> del c
>>> gc.collect()
0
>>> r()
>>>
@end example


3.4 新版功能.

@end deffn

@geindex finalize (weakref 中的类)
@anchor{library/weakref weakref finalize}@anchor{29d}
@deffn {类} weakref.finalize (obj, func, *args, **kwargs)

返回一个可调用的终结器对象，该对象将在 @emph{obj} 作为垃圾回收时被调用。 与普通的弱引用不同，终结器将总是存活，直到引用对象被回收，这极大地简化了生存期管理。

终结器总是被视为 @emph{存活} 直到它被调用（显式调用或在垃圾回收时隐式调用），调用之后它将 @emph{死亡}。 调用存活的终结器将返回 @code{func(*arg, **kwargs)} 的求值结果，而调用死亡的终结器将返回 @ref{157,,None}。

在垃圾收集期间由终结器回调所引发异常将显示于标准错误输出，但无法被传播。 它们会按与对象的 @ref{919,,__del__()} 方法或弱引用的回调所引发异常相同的方式被处理。

当程序退出时，剩余的存活终结器会被调用，除非它们的 @ref{c,,atexit} 属性已被设为假值。 它们会按与创建时相反的顺序被调用。

终结器在 @ref{75d,,interpreter shutdown} 的后期绝不会发起调用其回调函数，此时模块全局变量很可能已被替换为 @ref{157,,None}。

@geindex __call__() (weakref.finalize 方法)
@anchor{library/weakref weakref finalize __call__}@anchor{1929}
@deffn {方法} __call__ ()

如果 @emph{self} 为存活状态则将其标记为已死亡，并返回调用 @code{func(*args, **kwargs)} 的结果。 如果 @emph{self} 已死亡则返回 @ref{157,,None}。
@end deffn

@geindex detach() (weakref.finalize 方法)
@anchor{library/weakref weakref finalize detach}@anchor{192a}
@deffn {方法} detach ()

如果 @emph{self} 为存活状态则将其标记为已死亡，并返回元组 @code{(obj, func, args, kwargs)}。 如果 @emph{self} 已死亡则返 @ref{157,,None}。
@end deffn

@geindex peek() (weakref.finalize 方法)
@anchor{library/weakref weakref finalize peek}@anchor{192b}
@deffn {方法} peek ()

如果 @emph{self} 为存活状态则返回元组 @code{(obj, func, args, kwargs)}。 如果 @emph{self} 已死亡则返回 @ref{157,,None}。
@end deffn

@geindex alive (weakref.finalize 属性)
@anchor{library/weakref weakref finalize alive}@anchor{192c}
@deffn {属性} alive

如果终结器为存活状态则该特征属性为真值，否则为假值。
@end deffn

@geindex atexit (weakref.finalize 属性)
@anchor{library/weakref weakref finalize atexit}@anchor{192d}
@deffn {属性} atexit

一个可写的布尔型特征属性，默认为真值。 当程序退出时，它会调用所有 @ref{192d,,atexit} 为真值的剩余存活终结器。 它们会按与创建时相反的顺序被调用。
@end deffn

@cartouche
@quotation 注解 
很重要的一点是确保 @emph{func}, @emph{args} 和 @emph{kwargs} 不拥有任何对 @emph{obj} 的引用，无论是直接的或是间接的，否则的话 @emph{obj} 将永远不会被作为垃圾回收。 特别地，@emph{func} 不应当是 @emph{obj} 的一个绑定方法。
@end quotation
@end cartouche


3.4 新版功能.

@end deffn

@geindex ReferenceType() (在 weakref 模块中)
@anchor{library/weakref weakref ReferenceType}@anchor{192e}
@deffn {数据} weakref.ReferenceType

弱引用对象的类型对象。
@end deffn

@geindex ProxyType() (在 weakref 模块中)
@anchor{library/weakref weakref ProxyType}@anchor{192f}
@deffn {数据} weakref.ProxyType

不可调用对象的代理的类型对象。
@end deffn

@geindex CallableProxyType() (在 weakref 模块中)
@anchor{library/weakref weakref CallableProxyType}@anchor{1930}
@deffn {数据} weakref.CallableProxyType

可调用对象的代理的类型对象。
@end deffn

@geindex ProxyTypes() (在 weakref 模块中)
@anchor{library/weakref weakref ProxyTypes}@anchor{1931}
@deffn {数据} weakref.ProxyTypes

包含所有代理的类型对象的序列。 这可以用于更方便地检测一个对象是否是代理，而不必依赖于两种代理对象的名称。
@end deffn


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 205

@item PEP 205@footnote{https://www.python.org/dev/peps/pep-0205} - 弱引用

此特性的提议和理由，包括早期实现的链接和其他语言中类似特性的相关信息。
@end table


@menu
* 弱引用对象:: 
* 示例: 示例<2>. 
* 终结器对象:: 
* 比较终结器与 __del__() 方法: 比较终结器与 __del__ 方法. 

@end menu

@node 弱引用对象,示例<2>,,weakref --- 弱引用
@anchor{library/weakref weak-reference-objects}@anchor{1932}@anchor{library/weakref weakref-objects}@anchor{1933}
@subsubsection 弱引用对象


弱引用对象没有 @ref{90b,,ref.__callback__} 以外的方法和属性。 一个弱引用对象如果存在，就允许通过调用它来获取引用:

@example
>>> import weakref
>>> class Object:
...     pass
...
>>> o = Object()
>>> r = weakref.ref(o)
>>> o2 = r()
>>> o is o2
True
@end example

如果引用已不存在，则调用引用对象将返回 @ref{157,,None}:

@example
>>> del o, o2
>>> print(r())
None
@end example

检测一个弱引用对象是否仍然存在应该使用表达式 @code{ref() is not None}。 通常，需要使用引用对象的应用代码应当遵循这样的模式:

@example
# r is a weak reference object
o = r()
if o is None:
    # referent has been garbage collected
    print("Object has been deallocated; can't frobnicate.")
else:
    print("Object is still live!")
    o.do_something_useful()
@end example

使用单独的“存活”测试会在多线程应用中制造竞争条件；其他线程可能导致某个弱引用在该弱引用被调用前就失效；上述的写法在多线程应用和单线程应用中都是安全的。

特别版本的 @ref{90a,,ref} 对象可以通过子类化来创建。 在 @ref{1923,,WeakValueDictionary} 的实现中就使用了这种方式来减少映射中每个条目的内存开销。 这对于将附加信息关联到引用的情况最为适用，但也可以被用于在调用中插入额外处理来提取引用。

这个例子演示了如何将 @ref{90a,,ref} 的一个子类用于存储有关对象的附加信息并在引用被访问时影响其所返回的值:

@example
import weakref

class ExtendedRef(weakref.ref):
    def __init__(self, ob, callback=None, /, **annotations):
        super(ExtendedRef, self).__init__(ob, callback)
        self.__counter = 0
        for k, v in annotations.items():
            setattr(self, k, v)

    def __call__(self):
        """Return a pair containing the referent and the number of
        times the reference has been called.
        """
        ob = super(ExtendedRef, self).__call__()
        if ob is not None:
            self.__counter += 1
            ob = (ob, self.__counter)
        return ob
@end example

@node 示例<2>,终结器对象,弱引用对象,weakref --- 弱引用
@anchor{library/weakref example}@anchor{1934}@anchor{library/weakref weakref-example}@anchor{1935}
@subsubsection 示例


这个简单的例子演示了一个应用如何使用对象 ID 来提取之前出现过的对象。 然后对象的 ID 可以在其它数据结构中使用，而无须强制对象保持存活，但处于存活状态的对象也仍然可以通过 ID 来提取。

@c Example contributed by Tim Peters.

@example
import weakref

_id2obj_dict = weakref.WeakValueDictionary()

def remember(obj):
    oid = id(obj)
    _id2obj_dict[oid] = obj
    return oid

def id2obj(oid):
    return _id2obj_dict[oid]
@end example

@node 终结器对象,比较终结器与 __del__ 方法,示例<2>,weakref --- 弱引用
@anchor{library/weakref finalize-examples}@anchor{1936}@anchor{library/weakref finalizer-objects}@anchor{1937}
@subsubsection 终结器对象


使用 @ref{29d,,finalize} 的主要好处在于它能更简便地注册回调函数，而无须保留所返回的终结器对象。 例如

@example
>>> import weakref
>>> class Object:
...     pass
...
>>> kenny = Object()
>>> weakref.finalize(kenny, print, "You killed Kenny!")  
<finalize object at ...; for 'Object' at ...>
>>> del kenny
You killed Kenny!
@end example

终结器也可以被直接调用。 但是终结器最多只能对回调函数发起一次调用。

@example
>>> def callback(x, y, z):
...     print("CALLBACK")
...     return x + y + z
...
>>> obj = Object()
>>> f = weakref.finalize(obj, callback, 1, 2, z=3)
>>> assert f.alive
>>> assert f() == 6
CALLBACK
>>> assert not f.alive
>>> f()                     # callback not called because finalizer dead
>>> del obj                 # callback not called because finalizer dead
@end example

你可以使用 @ref{192a,,detach()} 方法来注销一个终结器。 该方法将销毁终结器并返回其被创建时传给构造器的参数。

@example
>>> obj = Object()
>>> f = weakref.finalize(obj, callback, 1, 2, z=3)
>>> f.detach()                                           
(<...Object object ...>, <function callback ...>, (1, 2), @{'z': 3@})
>>> newobj, func, args, kwargs = _
>>> assert not f.alive
>>> assert newobj is obj
>>> assert func(*args, **kwargs) == 6
CALLBACK
@end example

除非你将 @ref{192d,,atexit} 属性设为 @ref{380,,False}，否则终结器在程序退出时如果仍然存活就将被调用。 例如

@example
>>> obj = Object()
>>> weakref.finalize(obj, print, "obj dead or exiting")
<finalize object at ...; for 'Object' at ...>
>>> exit()
obj dead or exiting
@end example

@node 比较终结器与 __del__ 方法,,终结器对象,weakref --- 弱引用
@anchor{library/weakref comparing-finalizers-with-del-methods}@anchor{1938}
@subsubsection 比较终结器与 @code{__del__()} 方法


假设我们想创建一个类，用它的实例来代表临时目录。 当以下事件中的某一个发生时，这个目录应当与其内容一起被删除：


@itemize *

@item 
对象被作为垃圾回收，

@item 
对象的 @code{remove()} 方法被调用，或

@item 
程序退出。
@end itemize

我们可以尝试使用 @ref{919,,__del__()} 方法来实现这个类，如下所示:

@example
class TempDir:
    def __init__(self):
        self.name = tempfile.mkdtemp()

    def remove(self):
        if self.name is not None:
            shutil.rmtree(self.name)
            self.name = None

    @@property
    def removed(self):
        return self.name is None

    def __del__(self):
        self.remove()
@end example

从 Python 3.4 开始，@ref{919,,__del__()} 方法不会再阻止循环引用被作为垃圾回收，并且模块全局变量在 @ref{75d,,interpreter shutdown} 期间不会被强制设为 @ref{157,,None}。 因此这段代码在 CPython 上应该会正常运行而不会出现任何问题。

然而，@ref{919,,__del__()} 方法的处理会严重地受到具体实现的影响，因为它依赖于解释器垃圾回收实现方式的内部细节。

更健壮的替代方式可以是定义一个终结器，只引用它所需要的特定函数和对象，而不是获取对整个对象状态的访问权:

@example
class TempDir:
    def __init__(self):
        self.name = tempfile.mkdtemp()
        self._finalizer = weakref.finalize(self, shutil.rmtree, self.name)

    def remove(self):
        self._finalizer()

    @@property
    def removed(self):
        return not self._finalizer.alive
@end example

像这样定义后，我们的终结器将只接受一个对其完成正确清理目录任务所需细节的引用。 如果对象一直未被作为垃圾回收，终结器仍会在退出时被调用。

基于弱引用的终结器还具有另一项优势，就是它们可被用来为定义由第三方控制的类注册终结器，例如当一个模块被卸载时运行特定代码:

@example
import weakref, sys
def unloading_module():
    # implicit reference to the module globals from the function body
weakref.finalize(sys.modules[__name__], unloading_module)
@end example

@cartouche
@quotation 注解 
如果当程序退出时你恰好在守护线程中创建终结器对象，则有可能该终结器不会在退出时被调用。 但是，在一个守护线程中 @ref{e7e,,atexit.register()}, @code{try: ... finally: ...} 和 @code{with: ...} 同样不能保证执行清理。
@end quotation
@end cartouche

@node types --- 动态类型创建和内置类型名称,copy --- 浅层 shallow 和深层 deep 复制操作,weakref --- 弱引用,数据类型
@anchor{library/types doc}@anchor{1939}@anchor{library/types module-types}@anchor{118}@anchor{library/types types-dynamic-type-creation-and-names-for-built-in-types}@anchor{193a}
@subsection @code{types} --- 动态类型创建和内置类型名称


@geindex types (模块)

@strong{源代码:} Lib/types.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/types.py}


__________________________________________________________________


此模块定义了一些工具函数，用于协助动态创建新的类型。

它还为某些对象类型定义了名称，这些名称由标准 Python 解释器所使用，但并不像内置的 @ref{184,,int} 或 @ref{329,,str} 那样对外公开。

最后，它还额外提供了一些类型相关但重要程度不足以作为内置对象的工具类和函数。

@menu
* 动态类型创建:: 
* 标准解释器类型:: 
* 附加工具类和函数:: 
* 协程工具函数:: 

@end menu

@node 动态类型创建,标准解释器类型,,types --- 动态类型创建和内置类型名称
@anchor{library/types dynamic-type-creation}@anchor{193b}
@subsubsection 动态类型创建


@geindex new_class() (在 types 模块中)
@anchor{library/types types new_class}@anchor{ab2}
@deffn {函数} types.new_class (name, bases=(), kwds=None, exec_body=None)

使用适当的元类动态地创建一个类对象。

前三个参数是组成类定义头的部件：类名称，基类 (有序排列)，关键字参数 (例如 @code{metaclass})。

@emph{exec_body} 参数是一个回调函数，用于填充新创建类的命名空间。 它应当接受类命名空间作为其唯一的参数并使用类内容直接更新命名空间。 如果未提供回调函数，则它就等效于传入 @code{lambda ns: ns}。


3.3 新版功能.

@end deffn

@geindex prepare_class() (在 types 模块中)
@anchor{library/types types prepare_class}@anchor{ab3}
@deffn {函数} types.prepare_class (name, bases=(), kwds=None)

计算适当的元类并创建类命名空间。

参数是组成类定义头的部件：类名称，基类 (有序排列) 以及关键字参数 (例如 @code{metaclass})。

返回值是一个 3 元组: @code{metaclass, namespace, kwds}

@emph{metaclass} 是适当的元类，@emph{namespace} 是预备好的类命名空间而 @emph{kwds} 是所传入 @emph{kwds} 参数移除每个 @code{'metaclass'} 条目后的已更新副本。 如果未传入 @emph{kwds} 参数，这将为一个空字典。


3.3 新版功能.



在 3.6 版更改: 所返回元组中 @code{namespace} 元素的默认值已被改变。 现在当元类没有 @code{__prepare__} 方法时将会使用一个保留插入顺序的映射。

@end deffn


@subsubheading 参见



@table @asis

@item @ref{13e0,,元类}

这些函数所支持的类创建过程的完整细节

@geindex Python 提高建议; PEP 3115

@item PEP 3115@footnote{https://www.python.org/dev/peps/pep-3115} - Python 3000 中的元类

引入 @code{__prepare__} 命名空间钩子
@end table


@geindex resolve_bases() (在 types 模块中)
@anchor{library/types types resolve_bases}@anchor{3fe}
@deffn {函数} types.resolve_bases (bases)

动态地解析 MRO 条目，具体描述见 
@geindex Python 提高建议; PEP 560
PEP 560@footnote{https://www.python.org/dev/peps/pep-0560}。

此函数会在 @emph{bases} 中查找不是 @ref{603,,type} 的实例的项，并返回一个元组，其中每个具有 @code{__mro_entries__} 方法的此种对象对象将被替换为调用该方法解包后的结果。 如果一个 @emph{bases} 项是 @ref{603,,type} 的实例，或它不具有 @code{__mro_entries__} 方法，则它将不加改变地被包含在返回的元组中。


3.7 新版功能.

@end deffn


@subsubheading 参见


@geindex Python 提高建议; PEP 560
PEP 560@footnote{https://www.python.org/dev/peps/pep-0560} - 对 typing 模块和泛型类型的核心支持


@node 标准解释器类型,附加工具类和函数,动态类型创建,types --- 动态类型创建和内置类型名称
@anchor{library/types standard-interpreter-types}@anchor{193c}
@subsubsection 标准解释器类型


此模块为许多类型提供了实现 Python 解释器所要求的名称。 它刻意地避免了包含某些仅在处理过程中偶然出现的类型，例如 @code{listiterator} 类型。

此种名称的典型应用如 @ref{449,,isinstance()} 或 @ref{44a,,issubclass()} 检测。

如果你要实例化这些类型中的任何一种，请注意其签名在不同 Python 版本之间可能出现变化。

以下类型有相应的标准名称定义：

@geindex FunctionType() (在 types 模块中)
@geindex LambdaType() (在 types 模块中)
@anchor{library/types types FunctionType}@anchor{193d}
@deffn {数据} types.FunctionType
@anchor{library/types types LambdaType}@anchor{193e}
@deffnx {数据} types.LambdaType

用户自定义函数以及由 @ref{c28,,lambda}  表达式所创建函数的类型。
@end deffn

@geindex GeneratorType() (在 types 模块中)
@anchor{library/types types GeneratorType}@anchor{193f}
@deffn {数据} types.GeneratorType

@ref{99c,,generator} 迭代器对象的类型，由生成器函数创建。
@end deffn

@geindex CoroutineType() (在 types 模块中)
@anchor{library/types types CoroutineType}@anchor{777}
@deffn {数据} types.CoroutineType

@ref{1a6,,coroutine} 对象的类型，由 @ref{284,,async def} 函数创建。


3.5 新版功能.

@end deffn

@geindex AsyncGeneratorType() (在 types 模块中)
@anchor{library/types types AsyncGeneratorType}@anchor{1940}
@deffn {数据} types.AsyncGeneratorType

@ref{149c,,asynchronous generator} 迭代器对象的类型，由异步生成器函数创建。


3.6 新版功能.

@end deffn

@geindex CodeType (types 中的类)
@anchor{library/types types CodeType}@anchor{198}
@deffn {类} types.CodeType (**kwargs)

@geindex 內置函数; compile

代码对象的类型，例如 @ref{1b4,,compile()} 的返回值。

引发 @ref{12d0,,审计事件} @code{code.__new__} 附带参数 @code{code}, @code{filename}, @code{name}, @code{argcount}, @code{posonlyargcount}, @code{kwonlyargcount}, @code{nlocals}, @code{stacksize}, @code{flags}。

请注意被审核参数可能不匹配初始化器所要求的名称或位置。

@geindex replace() (types.CodeType 方法)
@anchor{library/types types CodeType replace}@anchor{1941}
@deffn {方法} replace (**kwargs)

返回代码对象的一个副本，使用指定的新字段值。


3.8 新版功能.

@end deffn
@end deffn

@geindex CellType() (在 types 模块中)
@anchor{library/types types CellType}@anchor{13c3}
@deffn {数据} types.CellType

单元对象的类型：这种对象被用作函数中自由变量的容器。


3.8 新版功能.

@end deffn

@geindex MethodType() (在 types 模块中)
@anchor{library/types types MethodType}@anchor{1942}
@deffn {数据} types.MethodType

用户自定义类实例方法的类型。
@end deffn

@geindex BuiltinFunctionType() (在 types 模块中)
@geindex BuiltinMethodType() (在 types 模块中)
@anchor{library/types types BuiltinFunctionType}@anchor{1943}
@deffn {数据} types.BuiltinFunctionType
@anchor{library/types types BuiltinMethodType}@anchor{1944}
@deffnx {数据} types.BuiltinMethodType

内置函数例如 @ref{150,,len()} 或 @ref{cdb,,sys.exit()} 以及内置类方法的类型。 （这里所说的“内置”是指“以 C 语言编写”。）
@end deffn

@geindex WrapperDescriptorType() (在 types 模块中)
@anchor{library/types types WrapperDescriptorType}@anchor{3fa}
@deffn {数据} types.WrapperDescriptorType

某些内置数据类型和基类的方法的类型，例如 @ref{d57,,object.__init__()} 或 @ref{c2d,,object.__lt__()}。


3.7 新版功能.

@end deffn

@geindex MethodWrapperType() (在 types 模块中)
@anchor{library/types types MethodWrapperType}@anchor{3fb}
@deffn {数据} types.MethodWrapperType

某些内置数据类型和基类的 @emph{绑定} 方法的类型。 例如 @code{object().__str__} 所属的类型。


3.7 新版功能.

@end deffn

@geindex MethodDescriptorType() (在 types 模块中)
@anchor{library/types types MethodDescriptorType}@anchor{3fc}
@deffn {数据} types.MethodDescriptorType

某些内置数据类型方法例如 @ref{15ca,,str.join()} 的类型。


3.7 新版功能.

@end deffn

@geindex ClassMethodDescriptorType() (在 types 模块中)
@anchor{library/types types ClassMethodDescriptorType}@anchor{3fd}
@deffn {数据} types.ClassMethodDescriptorType

某些内置数据类型 @emph{非绑定} 类方法例如 @code{dict.__dict__['fromkeys']} 的类型。


3.7 新版功能.

@end deffn

@geindex ModuleType (types 中的类)
@anchor{library/types types ModuleType}@anchor{6eb}
@deffn {类} types.ModuleType (name, doc=None)

@ref{1445,,模块} 的类型。 构造器接受待创建模块的名称及其作为可选项 @ref{154e,,docstring}。

@cartouche
@quotation 注解 
如果你希望设置各种由导入控制的属性，请使用 @ref{6ea,,importlib.util.module_from_spec()} 来创建一个新模块。
@end quotation
@end cartouche

@geindex __doc__ (types.ModuleType 属性)
@anchor{library/types types ModuleType __doc__}@anchor{1945}
@deffn {属性} __doc__

模块的 @ref{154e,,docstring}。 默认为 @code{None}。
@end deffn

@geindex __loader__ (types.ModuleType 属性)
@anchor{library/types types ModuleType __loader__}@anchor{1946}
@deffn {属性} __loader__

用于加载模块的 @ref{1453,,loader}。 默认为 @code{None}。


在 3.4 版更改: 默认为 @code{None}。 之前该属性为可选项。

@end deffn

@geindex __name__ (types.ModuleType 属性)
@anchor{library/types types ModuleType __name__}@anchor{1947}
@deffn {属性} __name__

模块的名字
@end deffn

@geindex __package__ (types.ModuleType 属性)
@anchor{library/types types ModuleType __package__}@anchor{1948}
@deffn {属性} __package__

一个模块所属的 @ref{1449,,package}。 如果模块为最高层级的（即不是任何特定包的组成部分）则该属性应设为 @code{'@w{'}}，否则它应设为特定包的名称 (如果模块本身也是一个包则名称可以为 @ref{d0b,,__name__})。 默认为 @code{None}。


在 3.4 版更改: 默认为 @code{None}。 之前该属性为可选项。

@end deffn
@end deffn

@geindex TracebackType (types 中的类)
@anchor{library/types types TracebackType}@anchor{32e}
@deffn {类} types.TracebackType (tb_next, tb_frame, tb_lasti, tb_lineno)

回溯对象的类型，例如 @code{sys.exc_info()[2]} 中的对象。

请查看 @ref{32f,,语言参考} 了解可用属性和操作的细节，以及动态地创建回溯对象的指南。
@end deffn

@geindex FrameType() (在 types 模块中)
@anchor{library/types types FrameType}@anchor{1949}
@deffn {数据} types.FrameType

帧对象的类型，例如 @code{tb.tb_frame} 中的对象，其中 @code{tb} 是一个回溯对象。

请查看 @ref{13ca,,语言参考} 了解可用属性和操作的细节。
@end deffn

@geindex GetSetDescriptorType() (在 types 模块中)
@anchor{library/types types GetSetDescriptorType}@anchor{194a}
@deffn {数据} types.GetSetDescriptorType

使用 @code{PyGetSetDef} 在扩展模块中定义的对象的类型，例如 @code{FrameType.f_locals} 或 @code{array.array.typecode}。 此类型被用作对象属性的描述器；它的目的与 @ref{1d7,,property} 类型相同，但专门针对在扩展模块中定义的类。
@end deffn

@geindex MemberDescriptorType() (在 types 模块中)
@anchor{library/types types MemberDescriptorType}@anchor{194b}
@deffn {数据} types.MemberDescriptorType

使用 @code{PyMemberDef} 在扩展模块中定义的对象的类型，例如 @code{datetime.timedelta.days}。 此类型被用作使用标准转换函数的简单 C 数据成员的描述器；它的目的与 @ref{1d7,,property} 类型相同，但专门针对在扩展模块中定义的类。

@strong{CPython implementation detail:} 在 Python 的其它实现中，此类型可能与 @code{GetSetDescriptorType} 完全相同。
@end deffn

@geindex MappingProxyType (types 中的类)
@anchor{library/types types MappingProxyType}@anchor{ab1}
@deffn {类} types.MappingProxyType (mapping)

一个映射的只读代理。 它提供了对映射条目的动态视图，这意味着当映射发生改变时，视图会反映这些改变。


3.3 新版功能.



@deffn {Describe} key in proxy

如果下层的映射中存在键 @emph{key} 则返回 @code{True}，否则返回 @code{False}。
@end deffn


@deffn {Describe} proxy[key]

返回下层的映射中以 @emph{key} 为键的项。 如果下层的映射中不存在键 @emph{key} 则引发 @ref{2c7,,KeyError}。
@end deffn


@deffn {Describe} iter(proxy)

返回由下层映射的键为元素的迭代器。 这是 @code{iter(proxy.keys())} 的快捷方式。
@end deffn


@deffn {Describe} len(proxy)

返回下层映射中的项数。
@end deffn

@geindex copy() (types.MappingProxyType 方法)
@anchor{library/types types MappingProxyType copy}@anchor{194c}
@deffn {方法} copy ()

返回下层映射的浅拷贝。
@end deffn

@geindex get() (types.MappingProxyType 方法)
@anchor{library/types types MappingProxyType get}@anchor{194d}
@deffn {方法} get (key[, default])

如果 @emph{key} 存在于下层映射中则返回 @emph{key} 的值，否则返回 @emph{default}。 如果 @emph{default} 未给出则默认为 @code{None}，因而此方法绝不会引发 @ref{2c7,,KeyError}。
@end deffn

@geindex items() (types.MappingProxyType 方法)
@anchor{library/types types MappingProxyType items}@anchor{194e}
@deffn {方法} items ()

返回由下层映射的项 (@code{(键, 值)} 对) 组成的一个新视图。
@end deffn

@geindex keys() (types.MappingProxyType 方法)
@anchor{library/types types MappingProxyType keys}@anchor{194f}
@deffn {方法} keys ()

返回由下层映射的键组成的一个新视图。
@end deffn

@geindex values() (types.MappingProxyType 方法)
@anchor{library/types types MappingProxyType values}@anchor{1950}
@deffn {方法} values ()

返回由下层映射的值组成的一个新视图。
@end deffn
@end deffn

@node 附加工具类和函数,协程工具函数,标准解释器类型,types --- 动态类型创建和内置类型名称
@anchor{library/types additional-utility-classes-and-functions}@anchor{1951}
@subsubsection 附加工具类和函数


@geindex SimpleNamespace (types 中的类)
@anchor{library/types types SimpleNamespace}@anchor{9a6}
@deffn {类} types.SimpleNamespace

一个简单的 @ref{2b0,,object} 子类，提供了访问其命名空间的属性，以及一个有意义的 repr。

不同于 @ref{2b0,,object}，对于 @code{SimpleNamespace} 你可以添加和移除属性。 如果一个 @code{SimpleNamespace} 对象使用关键字参数进行初始化，这些参数会被直接加入下层命名空间。

此类型大致等价于以下代码:

@example
class SimpleNamespace:
    def __init__(self, /, **kwargs):
        self.__dict__.update(kwargs)

    def __repr__(self):
        keys = sorted(self.__dict__)
        items = ("@{@}=@{!r@}".format(k, self.__dict__[k]) for k in keys)
        return "@{@}(@{@})".format(type(self).__name__, ", ".join(items))

    def __eq__(self, other):
        return self.__dict__ == other.__dict__
@end example

@code{SimpleNamespace} 可被用于替代 @code{class NS: pass}。 但是，对于结构化记录类型则应改用 @ref{1b6,,namedtuple()}。


3.3 新版功能.

@end deffn

@geindex DynamicClassAttribute() (在 types 模块中)
@anchor{library/types types DynamicClassAttribute}@anchor{8ed}
@deffn {函数} types.DynamicClassAttribute (fget=None, fset=None, fdel=None, doc=None)

在类上访问 __getattr__ 的路由属性。

这是一个描述器，用于定义通过实例与通过类访问时具有不同行为的属性。 当实例访问时保持正常行为，但当类访问属性时将被路由至类的 __getattr__ 方法；这是通过引发 AttributeError 来完成的。

这样就允许有在实例上激活的特征属性，同时又有在类上的同名虚拟属性（一个这样的例子是 Enum）。


3.4 新版功能.

@end deffn

@node 协程工具函数,,附加工具类和函数,types --- 动态类型创建和内置类型名称
@anchor{library/types coroutine-utility-functions}@anchor{1952}
@subsubsection 协程工具函数


@geindex coroutine() (在 types 模块中)
@anchor{library/types types coroutine}@anchor{776}
@deffn {函数} types.coroutine (gen_func)

此函数可将 @ref{99c,,generator} 函数转换为返回基于生成器的协程的 @ref{639,,coroutine function}。 基于生成器的协程仍然属于 @ref{451,,generator iterator}，但同时又可被视为 @ref{1a6,,coroutine} 对象兼 @ref{513,,awaitable}。 不过，它没有必要实现 @ref{63c,,__await__()} 方法。

如果 @emph{gen_func} 是一个生成器函数，它将被原地修改。

如果 @emph{gen_func} 不是一个生成器函数，则它会被包装。 如果它返回一个 @ref{6af,,collections.abc.Generator} 的实例，该实例将被包装在一个 @emph{awaitable} 代理对象中。 所有其他对象类型将被原样返回。


3.5 新版功能.

@end deffn

@node copy --- 浅层 shallow 和深层 deep 复制操作,pprint --- 数据美化输出,types --- 动态类型创建和内置类型名称,数据类型
@anchor{library/copy doc}@anchor{1953}@anchor{library/copy copy-shallow-and-deep-copy-operations}@anchor{1954}@anchor{library/copy module-copy}@anchor{26}
@subsection @code{copy} --- 浅层 (shallow) 和深层 (deep) 复制操作


@geindex copy (模块)

@strong{源代码:} Lib/copy.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/copy.py}


__________________________________________________________________


Python 中赋值语句不复制对象，而是在目标和对象之间创建绑定 (bindings) 关系。对于自身可变或者包含可变项的集合对象，开发者有时会需要生成其副本用于改变操作，进而避免改变原对象。本模块提供了通用的浅层复制和深层复制操作（如下所述）。

接口摘要：

@geindex copy() (在 copy 模块中)
@anchor{library/copy copy copy}@anchor{3c3}
@deffn {函数} copy.copy (x)

返回 @emph{x} 的浅层复制。
@end deffn

@geindex deepcopy() (在 copy 模块中)
@anchor{library/copy copy deepcopy}@anchor{3c4}
@deffn {函数} copy.deepcopy (x[, memo])

返回 @emph{x} 的深层复制。
@end deffn

@geindex error
@anchor{library/copy copy error}@anchor{1955}
@deffn {例外} copy.error

针对模块特定错误引发。
@end deffn
@anchor{library/copy shallow-vs-deep-copy}@anchor{11bd}
浅层复制和深层复制之间的区别仅与复合对象 (即包含其他对象的对象，如列表或类的实例) 相关:


@itemize *

@item 
一个 @emph{浅层复制} 会构造一个新的复合对象，然后（在可能的范围内）将原对象中找到的 @emph{引用} 插入其中。

@item 
一个 @emph{深层复制} 会构造一个新的复合对象，然后递归地将原始对象中所找到的对象的 @emph{副本} 插入。
@end itemize

深度复制操作通常存在两个问题, 而浅层复制操作并不存在这些问题：


@itemize *

@item 
递归对象 (直接或间接包含对自身引用的复合对象) 可能会导致递归循环。

@item 
由于深层复制会复制所有内容，因此可能会过多复制（例如本应该在副本之间共享的数据）。
@end itemize

The @ref{3c4,,deepcopy()} function avoids these problems by:


@itemize *

@item 
保留在当前复制过程中已复制的对象的 "备忘录" （@code{memo}） 字典；以及

@item 
允许用户定义的类重载复制操作或复制的组件集合。
@end itemize

该模块不复制模块、方法、栈追踪（stack trace）、栈帧（stack frame）、文件、套接字、窗口、数组以及任何类似的类型。它通过不改变地返回原始对象来（浅层或深层地）“复制”函数和类；这与 @ref{ca,,pickle} 模块处理这类问题的方式是相似的。

制作字典的浅层复制可以使用 @ref{440,,dict.copy()} 方法，而制作列表的浅层复制可以通过赋值整个列表的切片完成，例如，@code{copied_list = original_list[:]}。

@geindex 模块; pickle

类可以使用与控制序列化（pickling）操作相同的接口来控制复制操作，关于这些方法的描述信息请参考 @ref{ca,,pickle} 模块。实际上，@ref{26,,copy} 模块使用的正是从 @ref{27,,copyreg} 模块中注册的 pickle 函数。

@geindex __copy__() (copy protocol)
@geindex __deepcopy__() (copy protocol)

想要给一个类定义它自己的拷贝操作实现，可以通过定义特殊方法 @code{__copy__()} 和 @code{__deepcopy__()}。 调用前者以实现浅层拷贝操作，该方法不用传入额外参数。 调用后者以实现深层拷贝操作；它应传入一个参数即 @code{memo} 字典。 如果 @code{__deepcopy__()} 实现需要创建一个组件的深层拷贝，它应当调用 @ref{3c4,,deepcopy()} 函数并以该组件作为第一个参数，而将 memo 字典作为第二个参数。


@subsubheading 参见



@table @asis

@item 模块 @ref{ca,,pickle}

讨论了支持对象状态检索和恢复的特殊方法。
@end table


@node pprint --- 数据美化输出,reprlib --- 另一种 repr 实现,copy --- 浅层 shallow 和深层 deep 复制操作,数据类型
@anchor{library/pprint doc}@anchor{1956}@anchor{library/pprint module-pprint}@anchor{d2}@anchor{library/pprint pprint-data-pretty-printer}@anchor{1957}
@subsection @code{pprint} --- 数据美化输出


@geindex pprint (模块)

@strong{源代码：} Lib/pprint.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pprint.py}


__________________________________________________________________


@ref{d2,,pprint} 模块提供了“美化打印”任意 Python 数据结构的功能，这种美化形式可用作对解释器的输入。 如果经格式化的结构包含非基本 Python 类型的对象，则其美化形式可能无法被加载。 包含文件、套接字或类对象，以及许多其他不能用 Python 字面值来表示的对象都有可能导致这样的结果。

格式化后的形式会在可能的情况下以单行来表示对象，并在无法在允许宽度内容纳对象的情况下将其分为多行。 如果你需要调整宽度限制则应显式地构造 @ref{88f,,PrettyPrinter} 对象。

字典在计算其显示形式前会先根据键来排序。

@ref{d2,,pprint} 模块定义了一个类：

@c First the implementation class:

@geindex ...; placeholder

@geindex PrettyPrinter (pprint 中的类)
@anchor{library/pprint pprint PrettyPrinter}@anchor{88f}
@deffn {类} pprint.PrettyPrinter (indent=1, width=80, depth=None, stream=None, *, compact=False, sort_dicts=True)

构造一个 @ref{88f,,PrettyPrinter} 实例。 此构造器接受几个关键字形参。 使用 @emph{stream} 关键字可设置输出流；流对象使用的唯一方法是文件协议的 @code{write()} 方法。 如果未指定此关键字，则 @ref{88f,,PrettyPrinter} 会选择 @code{sys.stdout}。 每个递归层次的缩进量由 @emph{indent} 指定；默认值为一。 其他值可导致输出看起来有些怪异，，但可使得嵌套结构更易区分。 可被打印的层级数量由 @emph{depth} 控制；如果数据结构的层级被打印得过深，其所包含的下一层级会被替换为 @code{...}。 在默认情况下，对被格式化对象的层级深度没有限制。 希望的输出宽度可使用 @emph{width} 形参来限制；默认值为 80 个字符。 如果一个结构无法在限定宽度内被格式化，则将做到尽可能接近。 如果 @emph{compact} 为假值（默认）则长序列的每一项将被格式化为单独的行。 如果 @emph{compact} 为真值，则将在 @emph{width} 可容纳的的情况下把尽可能多的项放入每个输出行。 如果 @emph{sort_dicts} 为真值（默认），字典将被格式化为按键排序，否则将按插入顺序显示。


在 3.4 版更改: 增加了 @emph{compact} 形参。



在 3.8 版更改: 增加了 @emph{sort_dicts} 形参。

@example
>>> import pprint
>>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni']
>>> stuff.insert(0, stuff[:])
>>> pp = pprint.PrettyPrinter(indent=4)
>>> pp.pprint(stuff)
[   ['spam', 'eggs', 'lumberjack', 'knights', 'ni'],
    'spam',
    'eggs',
    'lumberjack',
    'knights',
    'ni']
>>> pp = pprint.PrettyPrinter(width=41, compact=True)
>>> pp.pprint(stuff)
[['spam', 'eggs', 'lumberjack',
  'knights', 'ni'],
 'spam', 'eggs', 'lumberjack', 'knights',
 'ni']
>>> tup = ('spam', ('eggs', ('lumberjack', ('knights', ('ni', ('dead',
... ('parrot', ('fresh fruit',))))))))
>>> pp = pprint.PrettyPrinter(depth=6)
>>> pp.pprint(tup)
('spam', ('eggs', ('lumberjack', ('knights', ('ni', ('dead', (...)))))))
@end example

@end deffn

@ref{d2,,pprint} 模块还提供了一些快捷函数：

@geindex pformat() (在 pprint 模块中)
@anchor{library/pprint pprint pformat}@anchor{890}
@deffn {函数} pprint.pformat (object, indent=1, width=80, depth=None, *, compact=False, sort_dicts=True)

@emph{object} 的格式化表示作为字符串返回。 @emph{indent}, @emph{width}, @emph{depth}, @emph{compact} 和 @emph{sort_dicts} 将作为格式化形参被传入 @ref{88f,,PrettyPrinter} 构造器。


在 3.4 版更改: 增加了 @emph{compact} 形参。



在 3.8 版更改: 增加了 @emph{sort_dicts} 形参。

@end deffn

@geindex pp() (在 pprint 模块中)
@anchor{library/pprint pprint pp}@anchor{212}
@deffn {函数} pprint.pp (object, *args, sort_dicts=False, **kwargs)

打印 @emph{object} 的格式化表示并附带一个换行符。 如果 @emph{sort_dicts} 为假值（默认），字典将按键的插入顺序显示，否则将按字典键排序。 @emph{args} 和 @emph{kwargs} 将作为格式化形参被传给 @ref{d2,,pprint()}。


3.8 新版功能.

@end deffn

@geindex pprint() (在 pprint 模块中)
@anchor{library/pprint pprint pprint}@anchor{213}
@deffn {函数} pprint.pprint (object, stream=None, indent=1, width=80, depth=None, *, compact=False, sort_dicts=True)

在 @emph{stream} 上打打印 @emph{object} 的格式化表示，并附带一个换行符。 如果 @emph{stream} 为 @code{None}，则使用 @code{sys.stdout}。 这可以替代 @ref{880,,print()} 函数在交互式解释器中使用以查看值（你甚至可以执行重新赋值 @code{print = pprint.pprint} 以在特定作用域中使用）。 @emph{indent}, @emph{width}, @emph{depth}, @emph{compact} 和 @emph{sort_dicts} 将作为格式化形参被传给 @ref{88f,,PrettyPrinter} 构造器。


在 3.4 版更改: 增加了 @emph{compact} 形参。



在 3.8 版更改: 增加了 @emph{sort_dicts} 形参。

@example
>>> import pprint
>>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni']
>>> stuff.insert(0, stuff)
>>> pprint.pprint(stuff)
[<Recursion on list with id=...>,
 'spam',
 'eggs',
 'lumberjack',
 'knights',
 'ni']
@end example

@end deffn

@geindex isreadable() (在 pprint 模块中)
@anchor{library/pprint pprint isreadable}@anchor{1958}
@deffn {函数} pprint.isreadable (object)

@geindex 內置函数; eval

确定 @emph{object} 的格式化表示是否“可读”，或是否可被用来通过 @ref{b89,,eval()} 重新构建对象的值。 此函数对于递归对象总是返回 @code{False}。

@example
>>> pprint.isreadable(stuff)
False
@end example
@end deffn

@geindex isrecursive() (在 pprint 模块中)
@anchor{library/pprint pprint isrecursive}@anchor{1959}
@deffn {函数} pprint.isrecursive (object)

确定 @emph{object} 是否需要递归表示。
@end deffn

此外还定义了一个支持函数：

@geindex saferepr() (在 pprint 模块中)
@anchor{library/pprint pprint saferepr}@anchor{195a}
@deffn {函数} pprint.saferepr (object)

返回 @emph{object} 的字符串表示，并为递归数据结构提供保护。 如果 @emph{object} 的表示形式公开了一个递归条目，该递归引用会被表示为 @code{<Recursion on typename with id=number>}。 该表示因而不会进行其它格式化。

@example
>>> pprint.saferepr(stuff)
"[<Recursion on list with id=...>, 'spam', 'eggs', 'lumberjack', 'knights', 'ni']"
@end example
@end deffn

@menu
* PrettyPrinter 对象:: 
* 示例: 示例<3>. 

@end menu

@node PrettyPrinter 对象,示例<3>,,pprint --- 数据美化输出
@anchor{library/pprint id1}@anchor{195b}@anchor{library/pprint prettyprinter-objects}@anchor{195c}
@subsubsection PrettyPrinter 对象


@ref{88f,,PrettyPrinter} 的实例具有下列方法：

@geindex pformat() (pprint.PrettyPrinter 方法)
@anchor{library/pprint pprint PrettyPrinter pformat}@anchor{195d}
@deffn {方法} PrettyPrinter.pformat (object)

返回 @emph{object} 格式化表示。 这会将传给 @ref{88f,,PrettyPrinter} 构造器的选项纳入考虑。
@end deffn

@geindex pprint() (pprint.PrettyPrinter 方法)
@anchor{library/pprint pprint PrettyPrinter pprint}@anchor{195e}
@deffn {方法} PrettyPrinter.pprint (object)

在所配置的流上打印 @emph{object} 的格式化表示，并附加一个换行符。
@end deffn

下列方法提供了与同名函数相对应的实现。 在实例上使用这些方法效率会更高一些，因为不需要创建新的 @ref{88f,,PrettyPrinter} 对象。

@geindex isreadable() (pprint.PrettyPrinter 方法)
@anchor{library/pprint pprint PrettyPrinter isreadable}@anchor{195f}
@deffn {方法} PrettyPrinter.isreadable (object)

@geindex 內置函数; eval

确定对象的格式化表示是否“可读”，或者是否可使用 @ref{b89,,eval()} 重建对象值。 请注意此方法对于递归对象将返回 @code{False}。 如果设置了 @ref{88f,,PrettyPrinter} 的 @emph{depth} 形参并且对象深度超出允许范围，此方法将返回 @code{False}。
@end deffn

@geindex isrecursive() (pprint.PrettyPrinter 方法)
@anchor{library/pprint pprint PrettyPrinter isrecursive}@anchor{1960}
@deffn {方法} PrettyPrinter.isrecursive (object)

确定对象是否需要递归表示。
@end deffn

此方法作为一个钩子提供，允许子类修改将对象转换为字符串的方式。 默认实现使用 @ref{195a,,saferepr()} 实现的内部方式。

@geindex format() (pprint.PrettyPrinter 方法)
@anchor{library/pprint pprint PrettyPrinter format}@anchor{1961}
@deffn {方法} PrettyPrinter.format (object, context, maxlevels, level)

返回三个值：字符串形式的 @emph{object} 已格式化版本，指明结果是否可读的旗标，以及指明是否检测到递归的旗标。 第一个参数是要表示的对象。 第二个是以对象 @ref{d7f,,id()} 为键的字典，这些对象是当前表示上下文的一部分（影响 @emph{object} 表示的直接和间接容器）；如果需要呈现一个已经在 @emph{context} 中表示的对象，则第三个返回值应当为 @code{True}。 对 @ref{1961,,format()} 方法的递归调用应当将容器的附加条目添加到此字典中。 第三个参数 @emph{maxlevels} 给出了对递归的请求限制；如果没有请求限制则其值将为 @code{0}。 此参数应当不加修改地传给递归调用。 第四个参数 @emph{level} 给出于当前层级；传给递归调用的参数值应当小于当前调用的值。
@end deffn

@node 示例<3>,,PrettyPrinter 对象,pprint --- 数据美化输出
@anchor{library/pprint example}@anchor{1962}@anchor{library/pprint pprint-example}@anchor{1963}
@subsubsection 示例


为了演示 @ref{d2,,pprint()} 函数及其形参的几种用法，让我们从 PyPI@footnote{https://pypi.org} 获取关于某个项目的信息:

@example
>>> import json
>>> import pprint
>>> from urllib.request import urlopen
>>> with urlopen('https://pypi.org/pypi/sampleproject/json') as resp:
...     project_info = json.load(resp)['info']
@end example

@ref{d2,,pprint()} 以其基本形式显示了整个对象:

@example
>>> pprint.pprint(project_info)
@{'author': 'The Python Packaging Authority',
 'author_email': 'pypa-dev@@googlegroups.com',
 'bugtrack_url': None,
 'classifiers': ['Development Status :: 3 - Alpha',
                 'Intended Audience :: Developers',
                 'License :: OSI Approved :: MIT License',
                 'Programming Language :: Python :: 2',
                 'Programming Language :: Python :: 2.6',
                 'Programming Language :: Python :: 2.7',
                 'Programming Language :: Python :: 3',
                 'Programming Language :: Python :: 3.2',
                 'Programming Language :: Python :: 3.3',
                 'Programming Language :: Python :: 3.4',
                 'Topic :: Software Development :: Build Tools'],
 'description': 'A sample Python project\n'
                '=======================\n'
                '\n'
                'This is the description file for the project.\n'
                '\n'
                'The file should use UTF-8 encoding and be written using '
                'ReStructured Text. It\n'
                'will be used to generate the project webpage on PyPI, and '
                'should be written for\n'
                'that purpose.\n'
                '\n'
                'Typical contents for this file would include an overview of '
                'the project, basic\n'
                'usage examples, etc. Generally, including the project '
                'changelog in here is not\n'
                'a good idea, although a simple "What\'s New" section for the '
                'most recent version\n'
                'may be appropriate.',
 'description_content_type': None,
 'docs_url': None,
 'download_url': 'UNKNOWN',
 'downloads': @{'last_day': -1, 'last_month': -1, 'last_week': -1@},
 'home_page': 'https://github.com/pypa/sampleproject',
 'keywords': 'sample setuptools development',
 'license': 'MIT',
 'maintainer': None,
 'maintainer_email': None,
 'name': 'sampleproject',
 'package_url': 'https://pypi.org/project/sampleproject/',
 'platform': 'UNKNOWN',
 'project_url': 'https://pypi.org/project/sampleproject/',
 'project_urls': @{'Download': 'UNKNOWN',
                  'Homepage': 'https://github.com/pypa/sampleproject'@},
 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
 'requires_dist': None,
 'requires_python': None,
 'summary': 'A sample Python project',
 'version': '1.2.0'@}
@end example

结果可以被限制到特定的 @emph{depth} (更深层的内容将使用省略号):

@example
>>> pprint.pprint(project_info, depth=1)
@{'author': 'The Python Packaging Authority',
 'author_email': 'pypa-dev@@googlegroups.com',
 'bugtrack_url': None,
 'classifiers': [...],
 'description': 'A sample Python project\n'
                '=======================\n'
                '\n'
                'This is the description file for the project.\n'
                '\n'
                'The file should use UTF-8 encoding and be written using '
                'ReStructured Text. It\n'
                'will be used to generate the project webpage on PyPI, and '
                'should be written for\n'
                'that purpose.\n'
                '\n'
                'Typical contents for this file would include an overview of '
                'the project, basic\n'
                'usage examples, etc. Generally, including the project '
                'changelog in here is not\n'
                'a good idea, although a simple "What\'s New" section for the '
                'most recent version\n'
                'may be appropriate.',
 'description_content_type': None,
 'docs_url': None,
 'download_url': 'UNKNOWN',
 'downloads': @{...@},
 'home_page': 'https://github.com/pypa/sampleproject',
 'keywords': 'sample setuptools development',
 'license': 'MIT',
 'maintainer': None,
 'maintainer_email': None,
 'name': 'sampleproject',
 'package_url': 'https://pypi.org/project/sampleproject/',
 'platform': 'UNKNOWN',
 'project_url': 'https://pypi.org/project/sampleproject/',
 'project_urls': @{...@},
 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
 'requires_dist': None,
 'requires_python': None,
 'summary': 'A sample Python project',
 'version': '1.2.0'@}
@end example

此外，还可以设置建议的最大字符 @emph{width}。 如果一个对象无法被拆分，则将超出指定宽度:

@example
>>> pprint.pprint(project_info, depth=1, width=60)
@{'author': 'The Python Packaging Authority',
 'author_email': 'pypa-dev@@googlegroups.com',
 'bugtrack_url': None,
 'classifiers': [...],
 'description': 'A sample Python project\n'
                '=======================\n'
                '\n'
                'This is the description file for the '
                'project.\n'
                '\n'
                'The file should use UTF-8 encoding and be '
                'written using ReStructured Text. It\n'
                'will be used to generate the project '
                'webpage on PyPI, and should be written '
                'for\n'
                'that purpose.\n'
                '\n'
                'Typical contents for this file would '
                'include an overview of the project, '
                'basic\n'
                'usage examples, etc. Generally, including '
                'the project changelog in here is not\n'
                'a good idea, although a simple "What\'s '
                'New" section for the most recent version\n'
                'may be appropriate.',
 'description_content_type': None,
 'docs_url': None,
 'download_url': 'UNKNOWN',
 'downloads': @{...@},
 'home_page': 'https://github.com/pypa/sampleproject',
 'keywords': 'sample setuptools development',
 'license': 'MIT',
 'maintainer': None,
 'maintainer_email': None,
 'name': 'sampleproject',
 'package_url': 'https://pypi.org/project/sampleproject/',
 'platform': 'UNKNOWN',
 'project_url': 'https://pypi.org/project/sampleproject/',
 'project_urls': @{...@},
 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
 'requires_dist': None,
 'requires_python': None,
 'summary': 'A sample Python project',
 'version': '1.2.0'@}
@end example

@node reprlib --- 另一种 repr 实现,enum --- 对枚举的支持,pprint --- 数据美化输出,数据类型
@anchor{library/reprlib doc}@anchor{1964}@anchor{library/reprlib module-reprlib}@anchor{df}@anchor{library/reprlib reprlib-alternate-repr-implementation}@anchor{1965}
@subsection @code{reprlib} --- 另一种 @code{repr()} 实现


@geindex reprlib (模块)

@strong{源代码:} Lib/reprlib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/reprlib.py}


__________________________________________________________________


@ref{df,,reprlib} 模块提供了一种对象表示的产生方式，它会对结果字符串的大小进行限制。 该方式被用于 Python 调试器，也适用于某些其他场景。

此模块提供了一个类、一个实例和一个函数：

@geindex Repr (reprlib 中的类)
@anchor{library/reprlib reprlib Repr}@anchor{1966}
@deffn {类} reprlib.Repr

该类提供了格式化服务 适用于实现与内置 @ref{7c6,,repr()} 相似的方法；其中附加了针对不同对象类型的大小限制，以避免生成超长的表示。
@end deffn

@geindex aRepr() (在 reprlib 模块中)
@anchor{library/reprlib reprlib aRepr}@anchor{1967}
@deffn {数据} reprlib.aRepr

这是 @ref{1966,,Repr} 的一个实例，用于提供如下所述的 @ref{1968,,repr()} 函数。 改变此对象的属性将会影响 @ref{1968,,repr()} 和 Python 调试器所使用的大小限制。
@end deffn

@geindex repr() (在 reprlib 模块中)
@anchor{library/reprlib reprlib repr}@anchor{1968}
@deffn {函数} reprlib.repr (obj)

这是 @code{aRepr} 的 @ref{1969,,repr()} 方法。 它会返回与同名内置函数所返回字符串相似的字符串，区别在于附带了对多数类型的大小限制。
@end deffn

在大小限制工具以外，此模块还提供了一个装饰器，用于检测对 @ref{337,,__repr__()} 的递归调用并改用一个占位符来替换。

@geindex ...; placeholder

@geindex recursive_repr() (在 reprlib 模块中)
@anchor{library/reprlib reprlib recursive_repr}@anchor{b69}
@deffn {函数} @@reprlib.recursive_repr (fillvalue="...")

用于为 @ref{337,,__repr__()} 方法检测同一线程内部递归调用的装饰器。 如果执行了递归调用，则会返回 @emph{fillvalue}，否则执行正常的 @ref{337,,__repr__()} 调用。 例如：

@example
>>> from reprlib import recursive_repr
>>> class MyList(list):
...     @@recursive_repr()
...     def __repr__(self):
...         return '<' + '|'.join(map(repr, self)) + '>'
...
>>> m = MyList('abc')
>>> m.append(m)
>>> m.append('x')
>>> print(m)
<'a'|'b'|'c'|...|'x'>
@end example


3.2 新版功能.

@end deffn

@menu
* Repr 对象:: 
* 子类化 Repr 对象:: 

@end menu

@node Repr 对象,子类化 Repr 对象,,reprlib --- 另一种 repr 实现
@anchor{library/reprlib id1}@anchor{196a}@anchor{library/reprlib repr-objects}@anchor{196b}
@subsubsection Repr 对象


@ref{1966,,Repr} 实例对象包含一些属性可以用于为不同对象类型的表示提供大小限制，还包含一些方法可以格式化特定的对象类型。

@geindex maxlevel (reprlib.Repr 属性)
@anchor{library/reprlib reprlib Repr maxlevel}@anchor{196c}
@deffn {属性} Repr.maxlevel

创建递归表示形式的深度限制。 默认为 @code{6}。
@end deffn

@geindex maxdict (reprlib.Repr 属性)
@geindex maxlist (reprlib.Repr 属性)
@geindex maxtuple (reprlib.Repr 属性)
@geindex maxset (reprlib.Repr 属性)
@geindex maxfrozenset (reprlib.Repr 属性)
@geindex maxdeque (reprlib.Repr 属性)
@geindex maxarray (reprlib.Repr 属性)
@anchor{library/reprlib reprlib Repr maxdict}@anchor{196d}
@deffn {属性} Repr.maxdict
@anchor{library/reprlib reprlib Repr maxlist}@anchor{196e}
@deffnx {属性} Repr.maxlist
@anchor{library/reprlib reprlib Repr maxtuple}@anchor{196f}
@deffnx {属性} Repr.maxtuple
@anchor{library/reprlib reprlib Repr maxset}@anchor{1970}
@deffnx {属性} Repr.maxset
@anchor{library/reprlib reprlib Repr maxfrozenset}@anchor{1971}
@deffnx {属性} Repr.maxfrozenset
@anchor{library/reprlib reprlib Repr maxdeque}@anchor{1972}
@deffnx {属性} Repr.maxdeque
@anchor{library/reprlib reprlib Repr maxarray}@anchor{1973}
@deffnx {属性} Repr.maxarray

表示命名对象类型的条目数量限制。 对于 @ref{196d,,maxdict} 的默认值为 @code{4}，对于 @ref{1973,,maxarray} 为 @code{5}，对于其他则为  @code{6}。
@end deffn

@geindex maxlong (reprlib.Repr 属性)
@anchor{library/reprlib reprlib Repr maxlong}@anchor{1974}
@deffn {属性} Repr.maxlong

表示整数的最大字符数量。 数码会从中间被丢弃。 默认值为 @code{40}。
@end deffn

@geindex maxstring (reprlib.Repr 属性)
@anchor{library/reprlib reprlib Repr maxstring}@anchor{1975}
@deffn {属性} Repr.maxstring

表示字符串的字符数量限制。 请注意字符源会使用字符串的“正常”表示形式：如果表示中需要用到转义序列，在缩短表示时它们可能会被破坏。 默认值为 @code{30}。
@end deffn

@geindex maxother (reprlib.Repr 属性)
@anchor{library/reprlib reprlib Repr maxother}@anchor{1976}
@deffn {属性} Repr.maxother

此限制用于控制在 @ref{1966,,Repr} 对象上没有特定的格式化方法可用的对象类型的大小。 它会以类似 @ref{1975,,maxstring} 的方式被应用。 默认值为 @code{20}。
@end deffn

@geindex repr() (reprlib.Repr 方法)
@anchor{library/reprlib reprlib Repr repr}@anchor{1969}
@deffn {方法} Repr.repr (obj)

内置 @ref{7c6,,repr()} 的等价形式，它使用实例专属的格式化。
@end deffn

@geindex repr1() (reprlib.Repr 方法)
@anchor{library/reprlib reprlib Repr repr1}@anchor{1977}
@deffn {方法} Repr.repr1 (obj, level)

供 @ref{1969,,repr()} 使用的递归实现。 此方法使用 @emph{obj} 的类型来确定要调用哪个格式化方法，并传入 @emph{obj} 和 @emph{level}。 类型专属的方法应当调用 @ref{1977,,repr1()} 来执行递归格式化，在递归调用中使用 @code{level - 1} 作为 @emph{level} 的值。
@end deffn


@deffn {方法} Repr.repr_TYPE (obj, level)

特定类型的格式化方法会被实现为基于类型名称来命名的方法。 在方法名称中，@strong{TYPE} 会被替换为 @code{'_'.join(type(obj).__name__.split())}。 对这些方法的分派会由 @ref{1977,,repr1()} 来处理。 需要对值进行递归格式化的类型专属方法应当调用 @code{self.repr1(subobj, level - 1)}。
@end deffn

@node 子类化 Repr 对象,,Repr 对象,reprlib --- 另一种 repr 实现
@anchor{library/reprlib subclassing-repr-objects}@anchor{1978}@anchor{library/reprlib subclassing-reprs}@anchor{1979}
@subsubsection 子类化 Repr 对象


通过 @ref{1977,,Repr.repr1()} 使用动态分派允许 @ref{1966,,Repr} 的子类添加对额外内置对象类型的支持，或是修改对已支持类型的处理。 这个例子演示了如何添加对文件对象的特殊支持:

@example
import reprlib
import sys

class MyRepr(reprlib.Repr):

    def repr_TextIOWrapper(self, obj, level):
        if obj.name in @{'<stdin>', '<stdout>', '<stderr>'@}:
            return obj.name
        return repr(obj)

aRepr = MyRepr()
print(aRepr.repr(sys.stdin))         # prints '<stdin>'
@end example

@node enum --- 对枚举的支持,,reprlib --- 另一种 repr 实现,数据类型
@anchor{library/enum doc}@anchor{197a}@anchor{library/enum enum-support-for-enumerations}@anchor{197b}@anchor{library/enum module-enum}@anchor{7b}
@subsection @code{enum} --- 对枚举的支持


@geindex enum (模块)


3.4 新版功能.


@strong{源代码：} Lib/enum.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/enum.py}


__________________________________________________________________


枚举是一组符号名称（枚举成员）的集合，枚举成员应该是唯一的、不可变的。在枚举中，可以对成员进行恒等比较，并且枚举本身是可迭代的。

@menu
* 模块内容: 模块内容<2>. 
* 创建一个 Enum:: 
* 对枚举成员及其属性的程序化访问:: 
* 复制枚举成员和值:: 
* 确保唯一的枚举值:: 
* 使用自动设定的值:: 
* 迭代:: 
* 比较运算: 比较运算<3>. 
* 允许的枚举成员和属性:: 
* 受限的 Enum 子类化:: 
* 封存:: 
* 功能性 API:: 
* 派生的枚举:: 
* 何时使用 __new__() 与 __init__(): 何时使用 __new__ 与 __init__. 
* 有趣的示例:: 
* 各种枚举有何区别？:: 

@end menu

@node 模块内容<2>,创建一个 Enum,,enum --- 对枚举的支持
@anchor{library/enum module-contents}@anchor{197c}
@subsubsection 模块内容


此模块定义了四个枚举类，它们可被用来定义名称和值的不重复集合: @ref{37f,,Enum}, @ref{588,,IntEnum}, @ref{540,,Flag} 和 @ref{16f0,,IntFlag}。 此外还定义了一个装饰器 @ref{197d,,unique()} 和一个辅助类 @ref{541,,auto}。

@geindex Enum (enum 中的类)
@anchor{library/enum enum Enum}@anchor{37f}
@deffn {类} enum.Enum

此基类用于创建枚举常量。 请参阅 @ref{197e,,Functional API} 小节了解另一种替代性的构建语法。
@end deffn

@geindex IntEnum (enum 中的类)
@anchor{library/enum enum IntEnum}@anchor{588}
@deffn {类} enum.IntEnum

此基类用于创建属于 @ref{184,,int} 的子类的枚举常量。
@end deffn

@geindex IntFlag (enum 中的类)
@anchor{library/enum enum IntFlag}@anchor{16f0}
@deffn {类} enum.IntFlag

此基类用于创建可使用按位运算符进行组合而不会丢失其 @ref{16f0,,IntFlag} 成员资格的枚举常量。 @ref{16f0,,IntFlag} 成员同样也是 @ref{184,,int} 的子类。
@end deffn

@geindex Flag (enum 中的类)
@anchor{library/enum enum Flag}@anchor{540}
@deffn {类} enum.Flag

此基类用于创建枚举常量 可使用按位运算符进行组合而不会丢失其 @ref{540,,Flag} 成员资格的枚举常量。
@end deffn

@geindex unique() (在 enum 模块中)
@anchor{library/enum enum unique}@anchor{197d}
@deffn {函数} enum.unique ()

此 Enum 类装饰器可确保只将一个名称绑定到任意一个值。
@end deffn

@geindex auto (enum 中的类)
@anchor{library/enum enum auto}@anchor{541}
@deffn {类} enum.auto

实例会被替换为一个可作为 Enum 成员的适当的值。 初始值从 1 开始。
@end deffn


3.6 新版功能: @code{Flag}, @code{IntFlag}, @code{auto}


@node 创建一个 Enum,对枚举成员及其属性的程序化访问,模块内容<2>,enum --- 对枚举的支持
@anchor{library/enum creating-an-enum}@anchor{197f}
@subsubsection 创建一个 Enum


枚举是使用 @ref{c63,,class} 语法来创建的，这使得它们易于读写。 另一种替代创建方法的描述见 @ref{197e,,Functional API}。 要定义一个枚举，可以对 @ref{37f,,Enum} 进行如下的子类化:

@example
>>> from enum import Enum
>>> class Color(Enum):
...     RED = 1
...     GREEN = 2
...     BLUE = 3
...
@end example

@cartouche
@quotation 注解 
Enum 的成员值

成员值可以为任意类型: @ref{184,,int}, @ref{329,,str} 等等。 如果具体的值不重要，你可以使用 @ref{541,,auto} 实例，将为你选择适当的值。 但如果你混用 @ref{541,,auto} 与其他值则需要小心谨慎。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
命名法


@itemize -

@item 
类 @code{Color} 是一个 @emph{枚举} (或称 @emph{enum})

@item 
属性 @code{Color.RED}, @code{Color.GREEN} 等等是 @emph{枚举成员} (或称 @emph{enum 成员}) 并且被用作常量。

@item 
枚举成员具有 @emph{名称} 和 @emph{值} (@code{Color.RED} 的名称为 @code{RED}，@code{Color.BLUE} 的值为 @code{3} 等等。)
@end itemize
@end quotation
@end cartouche

@cartouche
@quotation 注解 
虽然我们使用 @ref{c63,,class} 语法来创建 Enum，但 Enum 并不是普通的 Python 类。 更多细节请参阅 @ref{1980,,How are Enums different?}。
@end quotation
@end cartouche

枚举成员具有适合人类阅读的表示形式:

@example
>>> print(Color.RED)
Color.RED
@end example

...而它们的 @code{repr} 包含更多信息:

@example
>>> print(repr(Color.RED))
<Color.RED: 1>
@end example

一个枚举成员的 @emph{type} 就是它所从属的枚举:

@example
>>> type(Color.RED)
<enum 'Color'>
>>> isinstance(Color.GREEN, Color)
True
>>>
@end example

Enum 的成员还有一个包含其条目名称的特征属性:

@example
>>> print(Color.RED.name)
RED
@end example

枚举支持按照定义顺序进行迭代:

@example
>>> class Shake(Enum):
...     VANILLA = 7
...     CHOCOLATE = 4
...     COOKIES = 9
...     MINT = 3
...
>>> for shake in Shake:
...     print(shake)
...
Shake.VANILLA
Shake.CHOCOLATE
Shake.COOKIES
Shake.MINT
@end example

枚举成员是可哈希的，因此它们可在字典和集合中可用:

@example
>>> apples = @{@}
>>> apples[Color.RED] = 'red delicious'
>>> apples[Color.GREEN] = 'granny smith'
>>> apples == @{Color.RED: 'red delicious', Color.GREEN: 'granny smith'@}
True
@end example

@node 对枚举成员及其属性的程序化访问,复制枚举成员和值,创建一个 Enum,enum --- 对枚举的支持
@anchor{library/enum programmatic-access-to-enumeration-members-and-their-attributes}@anchor{1981}
@subsubsection 对枚举成员及其属性的程序化访问


有时对枚举中的成员进行程序化访问是很有用的（例如在某些场合不能使用 @code{Color.RED} 因为在编程时并不知道要指定的确切颜色）。  @code{Enum} 允许这样的访问:

@example
>>> Color(1)
<Color.RED: 1>
>>> Color(3)
<Color.BLUE: 3>
@end example

如果你希望通过 @emph{name} 来访问枚举成员，可使用条目访问:

@example
>>> Color['RED']
<Color.RED: 1>
>>> Color['GREEN']
<Color.GREEN: 2>
@end example

如果你有一个枚举成员并且需要它的 @code{name} 或 @code{value}:

@example
>>> member = Color.RED
>>> member.name
'RED'
>>> member.value
1
@end example

@node 复制枚举成员和值,确保唯一的枚举值,对枚举成员及其属性的程序化访问,enum --- 对枚举的支持
@anchor{library/enum duplicating-enum-members-and-values}@anchor{1982}
@subsubsection 复制枚举成员和值


不允许有同名的枚举成员:

@example
>>> class Shape(Enum):
...     SQUARE = 2
...     SQUARE = 3
...
Traceback (most recent call last):
...
TypeError: Attempted to reuse key: 'SQUARE'
@end example

但是，允许两个枚举成员有相同的值。 假定两个成员 A 和 B 有相同的值（且 A 先被定义），则 B 就是 A 的一个别名。 按值查找 A 和 B 的值将返回 A。 按名称查找 B 也将返回 A:

@example
>>> class Shape(Enum):
...     SQUARE = 2
...     DIAMOND = 1
...     CIRCLE = 3
...     ALIAS_FOR_SQUARE = 2
...
>>> Shape.SQUARE
<Shape.SQUARE: 2>
>>> Shape.ALIAS_FOR_SQUARE
<Shape.SQUARE: 2>
>>> Shape(2)
<Shape.SQUARE: 2>
@end example

@cartouche
@quotation 注解 
试图创建具有与某个已定义的属性（另一个成员或方法等）相同名称的成员或者试图创建具有相同名称的属性也是不允许的。
@end quotation
@end cartouche

@node 确保唯一的枚举值,使用自动设定的值,复制枚举成员和值,enum --- 对枚举的支持
@anchor{library/enum ensuring-unique-enumeration-values}@anchor{1983}
@subsubsection 确保唯一的枚举值


默认情况下，枚举允许有多个名称作为某个相同值的别名。 如果不想要这样的行为，可以使用以下装饰器来确保每个值在枚举中只被使用一次:

@geindex unique() (在 enum 模块中)

@deffn {函数} @@enum.unique
@end deffn

专用于枚举的 @ref{c63,,class} 装饰器。 它会搜索一个枚举的 @code{__members__} 并收集所找到的任何别名；只要找到任何别名就会引发 @ref{1fb,,ValueError} 并附带相关细节信息:

@example
>>> from enum import Enum, unique
>>> @@unique
... class Mistake(Enum):
...     ONE = 1
...     TWO = 2
...     THREE = 3
...     FOUR = 3
...
Traceback (most recent call last):
...
ValueError: duplicate values found in <enum 'Mistake'>: FOUR -> THREE
@end example

@node 使用自动设定的值,迭代,确保唯一的枚举值,enum --- 对枚举的支持
@anchor{library/enum using-automatic-values}@anchor{1984}
@subsubsection 使用自动设定的值


如果确切的值不重要，你可以使用 @ref{541,,auto}:

@example
>>> from enum import Enum, auto
>>> class Color(Enum):
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...
>>> list(Color)
[<Color.RED: 1>, <Color.BLUE: 2>, <Color.GREEN: 3>]
@end example

值将由 @code{_generate_next_value_()} 来选择，该函数可以被重载:

@example
>>> class AutoName(Enum):
...     def _generate_next_value_(name, start, count, last_values):
...         return name
...
>>> class Ordinal(AutoName):
...     NORTH = auto()
...     SOUTH = auto()
...     EAST = auto()
...     WEST = auto()
...
>>> list(Ordinal)
[<Ordinal.NORTH: 'NORTH'>, <Ordinal.SOUTH: 'SOUTH'>, <Ordinal.EAST: 'EAST'>, <Ordinal.WEST: 'WEST'>]
@end example

@cartouche
@quotation 注解 
默认 @code{_generate_next_value_()} 方法的目标是提供所给出的最后一个 @ref{184,,int} 所在序列的下一个 @ref{184,,int}，但这种行为方式属于实现细节并且可能发生改变。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
@code{_generate_next_value_()} 方法定义必须在任何其他成员之前。
@end quotation
@end cartouche

@node 迭代,比较运算<3>,使用自动设定的值,enum --- 对枚举的支持
@anchor{library/enum iteration}@anchor{1985}
@subsubsection 迭代


对枚举成员的迭代不会给出别名:

@example
>>> list(Shape)
[<Shape.SQUARE: 2>, <Shape.DIAMOND: 1>, <Shape.CIRCLE: 3>]
@end example

特殊属性 @code{__members__} 是一个从名称到成员的只读有序映射。 它包含枚举中定义的所有名称，包括别名:

@example
>>> for name, member in Shape.__members__.items():
...     name, member
...
('SQUARE', <Shape.SQUARE: 2>)
('DIAMOND', <Shape.DIAMOND: 1>)
('CIRCLE', <Shape.CIRCLE: 3>)
('ALIAS_FOR_SQUARE', <Shape.SQUARE: 2>)
@end example

@code{__members__} 属性可被用于对枚举成员进行详细的程序化访问。 例如，找出所有别名:

@example
>>> [name for name, member in Shape.__members__.items() if member.name != name]
['ALIAS_FOR_SQUARE']
@end example

@node 比较运算<3>,允许的枚举成员和属性,迭代,enum --- 对枚举的支持
@anchor{library/enum comparisons}@anchor{1986}
@subsubsection 比较运算


枚举成员是按标识号进行比较的:

@example
>>> Color.RED is Color.RED
True
>>> Color.RED is Color.BLUE
False
>>> Color.RED is not Color.BLUE
True
@end example

枚举值之间的排序比较 @emph{不被} 支持。 Enum 成员不属于整数 (另请参阅下文的 @ref{1987,,IntEnum}):

@example
>>> Color.RED < Color.BLUE
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '<' not supported between instances of 'Color' and 'Color'
@end example

相等比较的定义如下:

@example
>>> Color.BLUE == Color.RED
False
>>> Color.BLUE != Color.RED
True
>>> Color.BLUE == Color.BLUE
True
@end example

与非枚举值的比较将总是不相等（同样地，@ref{588,,IntEnum} 被显式设计成不同的行为，参见下文）:

@example
>>> Color.BLUE == 2
False
@end example

@node 允许的枚举成员和属性,受限的 Enum 子类化,比较运算<3>,enum --- 对枚举的支持
@anchor{library/enum allowed-members-and-attributes-of-enumerations}@anchor{1988}
@subsubsection 允许的枚举成员和属性


以上示例使用整数作为枚举值。 使用整数相当简洁方便（并由 @ref{197e,,Functional API} 默认提供），但并不强制要求使用。 在大部分用例中，开发者都关心枚举的实际值是什么。 但如果值 @emph{确实} 重要，则枚举可以使用任意的值。

枚举属于 Python 的类，并可具有普通方法和特殊方法。 如果我们有这样一个枚举:

@example
>>> class Mood(Enum):
...     FUNKY = 1
...     HAPPY = 3
...
...     def describe(self):
...         # self is the member here
...         return self.name, self.value
...
...     def __str__(self):
...         return 'my custom str! @{0@}'.format(self.value)
...
...     @@classmethod
...     def favorite_mood(cls):
...         # cls here is the enumeration
...         return cls.HAPPY
...
@end example

那么:

@example
>>> Mood.favorite_mood()
<Mood.HAPPY: 3>
>>> Mood.HAPPY.describe()
('HAPPY', 3)
>>> str(Mood.FUNKY)
'my custom str! 1'
@end example

对于允许内容的规则如下：以单下划线开头和结尾的名称是由枚举保留而不可使用；在枚举中定义的所有其他属性将成为该枚举的成员，例外项则包括特殊方法成员 (@ref{e30,,__str__()}, @ref{13ef,,__add__()} 等)，描述符 (方法也属于描述符) 以及在 @code{_ignore_} 中列出的变量名。

注意：如果你的枚举定义了 @ref{883,,__new__()} 和/或 @ref{d57,,__init__()} 那么指定给枚举成员的任何值都会被传入这些方法。 请参阅示例 @ref{1989,,Planet}。

@node 受限的 Enum 子类化,封存,允许的枚举成员和属性,enum --- 对枚举的支持
@anchor{library/enum restricted-enum-subclassing}@anchor{198a}
@subsubsection 受限的 Enum 子类化


一个新的 @ref{37f,,Enum} 类必须基于一个 Enum 类，至多一个实体数据类型以及出于实际需要的任意多个基于 @ref{2b0,,object} 的 mixin 类。 这些基类的顺序为:

@example
class EnumName([mix-in, ...,] [data-type,] base-enum):
    pass
@end example

另外，仅当一个枚举未定义任何成员时才允许子类化该枚举。 因此禁止这样的写法:

@example
>>> class MoreColor(Color):
...     PINK = 17
...
Traceback (most recent call last):
...
TypeError: Cannot extend enumerations
@end example

但是允许这样的写法:

@example
>>> class Foo(Enum):
...     def some_behavior(self):
...         pass
...
>>> class Bar(Foo):
...     HAPPY = 1
...     SAD = 2
...
@end example

允许子类化定义了成员的枚举将会导致违反类型与实例的某些重要的不可变规则。 在另一方面，允许在一组枚举之间共享某些通用行为也是有意义的。 （请参阅示例 @ref{198b,,OrderedEnum} 。）

@node 封存,功能性 API,受限的 Enum 子类化,enum --- 对枚举的支持
@anchor{library/enum pickling}@anchor{198c}
@subsubsection 封存


枚举可以被封存与解封:

@example
>>> from test.test_enum import Fruit
>>> from pickle import dumps, loads
>>> Fruit.TOMATO is loads(dumps(Fruit.TOMATO))
True
@end example

封存的常规限制同样适用：可封存枚举必须在模块的最高层级中定义，因为解封操作要求它们可以从该模块导入。

@cartouche
@quotation 注解 
使用 pickle 协议版本 4 可以方便地封存嵌套在其他类中的枚举。
@end quotation
@end cartouche

通过在枚举类中定义 @ref{198d,,__reduce_ex__()} 可以对 Enum 成员的封存/解封方式进行修改。

@node 功能性 API,派生的枚举,封存,enum --- 对枚举的支持
@anchor{library/enum functional-api}@anchor{197e}
@subsubsection 功能性 API


@ref{37f,,Enum} 类属于可调用对象，它提供了以下功能性 API:

@example
>>> Animal = Enum('Animal', 'ANT BEE CAT DOG')
>>> Animal
<enum 'Animal'>
>>> Animal.ANT
<Animal.ANT: 1>
>>> Animal.ANT.value
1
>>> list(Animal)
[<Animal.ANT: 1>, <Animal.BEE: 2>, <Animal.CAT: 3>, <Animal.DOG: 4>]
@end example

该 API 的主义类似于 @ref{1b6,,namedtuple}。 调用 @ref{37f,,Enum} 的第一个参数是枚举的名称。

第二个参数是枚举成员名称的 @emph{来源}。 它可以是一个用空格分隔的名称字符串、名称序列、键/值对 2 元组的序列，或者名称到值的映射（例如字典）。 最后两种选项使得可以为枚举任意赋值；其他选项会自动以从 1 开始递增的整数赋值（使用 @code{start} 形参可指定不同的起始值）。 返回值是一个派生自 @ref{37f,,Enum} 的新类。 换句话说，以上对 @code{Animal} 的赋值就等价于:

@example
>>> class Animal(Enum):
...     ANT = 1
...     BEE = 2
...     CAT = 3
...     DOG = 4
...
@end example

默认以 @code{1} 而以 @code{0} 作为起始数值的原因在于 @code{0} 的布尔值为 @code{False}，但所有枚举成员都应被求值为 @code{True}。

对使用功能性 API 创建的枚举执行封存可能会很麻烦，因为要使用帧堆栈的实现细节来尝试并找出枚举是在哪个模块中创建的（例如当你使用了另一个模块中的工具函数就可能失败，在 IronPython 或 Jython 上也可能无效）。 解决办法是显式地指定模块名称，如下所示:

@example
>>> Animal = Enum('Animal', 'ANT BEE CAT DOG', module=__name__)
@end example

@cartouche
@quotation 警告 
如果未提供 @code{module}，且 Enum 无法确定是哪个模块，新的 Enum 成员将不可被解封；为了让错误尽量靠近源头，封存将被禁用。
@end quotation
@end cartouche

新的 pickle 协议版本 4 在某些情况下同样依赖于 @ref{13c1,,__qualname__} 被设为特定位置以便 pickle 能够找到相应的类。 例如，类是否存在于全局作用域的 SomeData 类中:

@example
>>> Animal = Enum('Animal', 'ANT BEE CAT DOG', qualname='SomeData.Animal')
@end example

完整的签名为:

@example
Enum(value='NewEnumName', names=<...>, *, module='...', qualname='...', type=<mixed-in class>, start=1)
@end example

@*值: 
将被新 Enum 类将记录为其名称的数据。


@*names: 
Enum 的成员。 这可以是一个空格或逗号分隔的字符串 (起始值将为 1，除非另行指定):

@example
'RED GREEN BLUE' | 'RED,GREEN,BLUE' | 'RED, GREEN, BLUE'
@end example

或是一个名称的迭代器:

@example
['RED', 'GREEN', 'BLUE']
@end example

或是一个 (名称, 值) 对的迭代器:

@example
[('CYAN', 4), ('MAGENTA', 5), ('YELLOW', 6)]
@end example

或是一个映射:

@example
@{'CHARTREUSE': 7, 'SEA_GREEN': 11, 'ROSEMARY': 42@}
@end example


@*module: 
新 Enum 类所在模块的名称。


@*qualname: 
新 Enum 类在模块中的具体位置。


@*type: 
要加入新 Enum 类的类型。


@*start: 
当只传入名称时要使用的起始数值。



在 3.5 版更改: 增加了 @emph{start} 形参。


@node 派生的枚举,何时使用 __new__ 与 __init__,功能性 API,enum --- 对枚举的支持
@anchor{library/enum derived-enumerations}@anchor{198e}
@subsubsection 派生的枚举


@menu
* IntEnum:: 
* IntFlag:: 
* Flag:: 
* 其他事项:: 

@end menu

@node IntEnum,IntFlag,,派生的枚举
@anchor{library/enum intenum}@anchor{1987}
@subsubsection IntEnum


所提供的第一个变种 @ref{37f,,Enum} 同时也是 @ref{184,,int} 的一个子类。 @ref{588,,IntEnum} 的成员可与整数进行比较；通过扩展，不同类型的整数枚举也可以相互进行比较:

@example
>>> from enum import IntEnum
>>> class Shape(IntEnum):
...     CIRCLE = 1
...     SQUARE = 2
...
>>> class Request(IntEnum):
...     POST = 1
...     GET = 2
...
>>> Shape == 1
False
>>> Shape.CIRCLE == 1
True
>>> Shape.CIRCLE == Request.POST
True
@end example

不过，它们仍然不可与标准 @ref{37f,,Enum} 枚举进行比较:

@example
>>> class Shape(IntEnum):
...     CIRCLE = 1
...     SQUARE = 2
...
>>> class Color(Enum):
...     RED = 1
...     GREEN = 2
...
>>> Shape.CIRCLE == Color.RED
False
@end example

@ref{588,,IntEnum} 值在其他方面的行为都如你预期的一样类似于整数:

@example
>>> int(Shape.CIRCLE)
1
>>> ['a', 'b', 'c'][Shape.CIRCLE]
'b'
>>> [i for i in range(Shape.SQUARE)]
[0, 1]
@end example

@node IntFlag,Flag,IntEnum,派生的枚举
@anchor{library/enum intflag}@anchor{198f}
@subsubsection IntFlag


所提供的下一个 @ref{37f,,Enum} 的变种 @ref{16f0,,IntFlag} 同样是基于 @ref{184,,int} 的，不同之处在于 @ref{16f0,,IntFlag} 成员可使用按位运算符 (&, |, ^, ~) 进行组合且结果仍然为 @ref{16f0,,IntFlag} 成员。 如果，正如名称所表明的，@ref{16f0,,IntFlag} 成员同时也是 @ref{184,,int} 的子类，并能在任何使用 @ref{184,,int} 的场合被使用。 @ref{16f0,,IntFlag} 成员进行除按位运算以外的其他运算都将导致失去 @ref{16f0,,IntFlag} 成员资格。


3.6 新版功能.


示例 @ref{16f0,,IntFlag} 类:

@example
>>> from enum import IntFlag
>>> class Perm(IntFlag):
...     R = 4
...     W = 2
...     X = 1
...
>>> Perm.R | Perm.W
<Perm.R|W: 6>
>>> Perm.R + Perm.W
6
>>> RW = Perm.R | Perm.W
>>> Perm.R in RW
True
@end example

对于组合同样可以进行命名:

@example
>>> class Perm(IntFlag):
...     R = 4
...     W = 2
...     X = 1
...     RWX = 7
>>> Perm.RWX
<Perm.RWX: 7>
>>> ~Perm.RWX
<Perm.-8: -8>
@end example

@ref{16f0,,IntFlag} 和 @ref{37f,,Enum} 的另一个重要区别在于如果没有设置任何旗标（值为 0），则其布尔值为 @ref{380,,False}:

@example
>>> Perm.R & Perm.X
<Perm.0: 0>
>>> bool(Perm.R & Perm.X)
False
@end example

由于 @ref{16f0,,IntFlag} 成员同时也是 @ref{184,,int} 的子类，因此它们可以相互组合:

@example
>>> Perm.X | 8
<Perm.8|X: 9>
@end example

@node Flag,其他事项,IntFlag,派生的枚举
@anchor{library/enum flag}@anchor{1990}
@subsubsection Flag


最后一个变种是 @ref{540,,Flag}。 与 @ref{16f0,,IntFlag} 类似，@ref{540,,Flag} 成员可使用按位运算符 (&, |, ^, ~) 进行组合，与 @ref{16f0,,IntFlag} 不同的是它们不可与任何其它 @ref{540,,Flag} 枚举或 @ref{184,,int} 进行组合或比较。 虽然可以直接指定值，但推荐使用 @ref{541,,auto} 作为值以便让 @ref{540,,Flag} 选择适当的值。


3.6 新版功能.


与 @ref{16f0,,IntFlag} 类似，如果 @ref{540,,Flag} 成员的某种组合导致没有设置任何旗标，则其布尔值为 @ref{380,,False}:

@example
>>> from enum import Flag, auto
>>> class Color(Flag):
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...
>>> Color.RED & Color.GREEN
<Color.0: 0>
>>> bool(Color.RED & Color.GREEN)
False
@end example

单个旗标的值应当为二的乘方 (1, 2, 4, 8, ...)，旗标的组合则无此限制:

@example
>>> class Color(Flag):
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...     WHITE = RED | BLUE | GREEN
...
>>> Color.WHITE
<Color.WHITE: 7>
@end example

对 "no flags set" 条件指定一个名称并不会改变其布尔值:

@example
>>> class Color(Flag):
...     BLACK = 0
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...
>>> Color.BLACK
<Color.BLACK: 0>
>>> bool(Color.BLACK)
False
@end example

@cartouche
@quotation 注解 
对于大多数新代码，强烈推荐使用 @ref{37f,,Enum} 和 @ref{540,,Flag}，因为 @ref{588,,IntEnum} 和 @ref{16f0,,IntFlag} 打破了枚举的某些语义约定（例如可以同整数进行比较，并因而导致此行为被传递给其他无关的枚举）。 @ref{588,,IntEnum} 和 @ref{16f0,,IntFlag} 的使用应当仅限于 @ref{37f,,Enum} 和 @ref{540,,Flag} 无法使用的场合；例如，当使用枚举替代整数常量时，或是与其他系统进行交互操作时。
@end quotation
@end cartouche

@node 其他事项,,Flag,派生的枚举
@anchor{library/enum others}@anchor{1991}
@subsubsection 其他事项


虽然 @ref{588,,IntEnum} 是 @ref{7b,,enum} 模块的一部分，但要独立实现也应该相当容易:

@example
class IntEnum(int, Enum):
    pass
@end example

这里演示了如何定义类似的派生枚举；例如一个混合了 @ref{329,,str} 而不是 @ref{184,,int} 的 @code{StrEnum}。

几条规则：


@enumerate 

@item 
当子类化 @ref{37f,,Enum} 时，在基类序列中的混合类型必须出现于 @ref{37f,,Enum} 本身之前，如以上 @ref{588,,IntEnum} 的例子所示。

@item 
虽然 @ref{37f,,Enum} 可以拥有任意类型的成员，不过一旦你混合了附加类型，则所有成员必须为相应类型的值，如在上面的例子中即为 @ref{184,,int}。 此限制不适用于仅添加方法而未指定另一数据类型如 @ref{184,,int} 或 @ref{329,,str} 的混合类。

@item 
当混合了另一数据类型时，@code{value} 属性会 @emph{不同于} 枚举成员自身，但它们仍保持等价且比较结果也相等。

@item 
%-style formatting:  @cite{%s} 和 @cite{%r} 会分别调用 @ref{37f,,Enum} 类的 @ref{e30,,__str__()} 和 @ref{337,,__repr__()}；其他代码 (例如表示 IntEnum 的 @cite{%i} 或 @cite{%h}) 会将枚举成员视为对应的混合类型。

@item 
@ref{15c,,格式化字符串字面值}, @ref{4d4,,str.format()} 和 @ref{4d5,,format()} 将使用混合类型的 @ref{948,,__format__()}。 如果需要 @ref{37f,,Enum} 类的 @ref{329,,str()} 或 @ref{7c6,,repr()}，请使用 @cite{!s} 或 @cite{!r} 格式代码。
@end enumerate

@node 何时使用 __new__ 与 __init__,有趣的示例,派生的枚举,enum --- 对枚举的支持
@anchor{library/enum when-to-use-new-vs-init}@anchor{1992}
@subsubsection 何时使用 @code{__new__()} 与 @code{__init__()}


当你想要定制 @ref{37f,,Enum} 成员的实际值时必须使用 @ref{883,,__new__()}。 任何其他修改可以用 @ref{883,,__new__()} 也可以用 @ref{d57,,__init__()}，应优先使用 @ref{d57,,__init__()}。

举例来说，如果你要向构造器传入多个条目，但只希望将其中一个作为值:

@example
>>> class Coordinate(bytes, Enum):
...     """
...     Coordinate with binary codes that can be indexed by the int code.
...     """
...     def __new__(cls, value, label, unit):
...         obj = bytes.__new__(cls, [value])
...         obj._value_ = value
...         obj.label = label
...         obj.unit = unit
...         return obj
...     PX = (0, 'P.X', 'km')
...     PY = (1, 'P.Y', 'km')
...     VX = (2, 'V.X', 'km/s')
...     VY = (3, 'V.Y', 'km/s')
...

>>> print(Coordinate['PY'])
Coordinate.PY

>>> print(Coordinate(3))
Coordinate.VY
@end example

@node 有趣的示例,各种枚举有何区别？,何时使用 __new__ 与 __init__,enum --- 对枚举的支持
@anchor{library/enum interesting-examples}@anchor{1993}
@subsubsection 有趣的示例


虽然 @ref{37f,,Enum}, @ref{588,,IntEnum}, @ref{16f0,,IntFlag} 和 @ref{540,,Flag} 预期可覆盖大多数应用场景，但它们无法覆盖全部。 这里有一些不同类型枚举的方案，它们可以被直接使用，或是作为自行创建的参考示例。

@menu
* 省略值:: 
* OrderedEnum:: 
* DuplicateFreeEnum:: 
* Planet:: 
* TimePeriod:: 

@end menu

@node 省略值,OrderedEnum,,有趣的示例
@anchor{library/enum omitting-values}@anchor{1994}
@subsubsection 省略值


在许多应用场景中人们都不关心枚举的实际值是什么。 有几个方式可以定义此种类型的简单枚举：


@itemize -

@item 
使用 @ref{541,,auto} 的实例作为值

@item 
使用 @ref{2b0,,object} 的实例作为值

@item 
使用描述性的字符串作为值

@item 
使用元组作为值并用自定义的 @ref{883,,__new__()} 以一个 @ref{184,,int} 值来替代该元组
@end itemize

使用以上任何一种方法均可向用户指明值并不重要，并且使人能够添加、移除或重排序成员而不必改变其余成员的数值。

无论你选择何种方法，你都应当提供一个 @ref{7c6,,repr()} 并且它也需要隐藏（不重要的）值:

@example
>>> class NoValue(Enum):
...     def __repr__(self):
...         return '<%s.%s>' % (self.__class__.__name__, self.name)
...
@end example

@menu
* 使用 auto:: 
* 使用 object:: 
* 使用描述性字符串:: 
* 使用自定义的 __new__(): 使用自定义的 __new__. 

@end menu

@node 使用 auto,使用 object,,省略值
@anchor{library/enum using-auto}@anchor{1995}
@subsubsection 使用 @code{auto}


使用 @ref{541,,auto} 的形式如下:

@example
>>> class Color(NoValue):
...     RED = auto()
...     BLUE = auto()
...     GREEN = auto()
...
>>> Color.GREEN
<Color.GREEN>
@end example

@node 使用 object,使用描述性字符串,使用 auto,省略值
@anchor{library/enum using-object}@anchor{1996}
@subsubsection 使用 @code{object}


使用 @ref{2b0,,object} 的形式如下:

@example
>>> class Color(NoValue):
...     RED = object()
...     GREEN = object()
...     BLUE = object()
...
>>> Color.GREEN
<Color.GREEN>
@end example

@node 使用描述性字符串,使用自定义的 __new__,使用 object,省略值
@anchor{library/enum using-a-descriptive-string}@anchor{1997}
@subsubsection 使用描述性字符串


使用字符串作为值的形式如下:

@example
>>> class Color(NoValue):
...     RED = 'stop'
...     GREEN = 'go'
...     BLUE = 'too fast!'
...
>>> Color.GREEN
<Color.GREEN>
>>> Color.GREEN.value
'go'
@end example

@node 使用自定义的 __new__,,使用描述性字符串,省略值
@anchor{library/enum using-a-custom-new}@anchor{1998}
@subsubsection 使用自定义的 @code{__new__()}


使用自动编号 @ref{883,,__new__()} 的形式如下:

@example
>>> class AutoNumber(NoValue):
...     def __new__(cls):
...         value = len(cls.__members__) + 1
...         obj = object.__new__(cls)
...         obj._value_ = value
...         return obj
...
>>> class Color(AutoNumber):
...     RED = ()
...     GREEN = ()
...     BLUE = ()
...
>>> Color.GREEN
<Color.GREEN>
>>> Color.GREEN.value
2
@end example

@cartouche
@quotation 注解 
如果定义了 @ref{883,,__new__()} 则它会在创建 Enum 成员期间被使用；随后它将被 Enum 的 @ref{883,,__new__()} 所替换，该方法会在类创建后被用来查找现有成员。
@end quotation
@end cartouche

@node OrderedEnum,DuplicateFreeEnum,省略值,有趣的示例
@anchor{library/enum orderedenum}@anchor{198b}
@subsubsection OrderedEnum


一个有序枚举，它不是基于 @ref{588,,IntEnum}，因此保持了正常的 @ref{37f,,Enum} 不变特性（例如不可与其他枚举进行比较）:

@example
>>> class OrderedEnum(Enum):
...     def __ge__(self, other):
...         if self.__class__ is other.__class__:
...             return self.value >= other.value
...         return NotImplemented
...     def __gt__(self, other):
...         if self.__class__ is other.__class__:
...             return self.value > other.value
...         return NotImplemented
...     def __le__(self, other):
...         if self.__class__ is other.__class__:
...             return self.value <= other.value
...         return NotImplemented
...     def __lt__(self, other):
...         if self.__class__ is other.__class__:
...             return self.value < other.value
...         return NotImplemented
...
>>> class Grade(OrderedEnum):
...     A = 5
...     B = 4
...     C = 3
...     D = 2
...     F = 1
...
>>> Grade.C < Grade.A
True
@end example

@node DuplicateFreeEnum,Planet,OrderedEnum,有趣的示例
@anchor{library/enum duplicatefreeenum}@anchor{1999}
@subsubsection DuplicateFreeEnum


如果发现重复的成员名称则将引发错误而不是创建别名:

@example
>>> class DuplicateFreeEnum(Enum):
...     def __init__(self, *args):
...         cls = self.__class__
...         if any(self.value == e.value for e in cls):
...             a = self.name
...             e = cls(self.value).name
...             raise ValueError(
...                 "aliases not allowed in DuplicateFreeEnum:  %r --> %r"
...                 % (a, e))
...
>>> class Color(DuplicateFreeEnum):
...     RED = 1
...     GREEN = 2
...     BLUE = 3
...     GRENE = 2
...
Traceback (most recent call last):
...
ValueError: aliases not allowed in DuplicateFreeEnum:  'GRENE' --> 'GREEN'
@end example

@cartouche
@quotation 注解 
这个例子适用于子类化 Enum 来添加或改变禁用别名以及其他行为。 如果需要的改变只是禁用别名，也可以选择使用 @ref{197d,,unique()} 装饰器。
@end quotation
@end cartouche

@node Planet,TimePeriod,DuplicateFreeEnum,有趣的示例
@anchor{library/enum planet}@anchor{1989}
@subsubsection Planet


如果定义了 @ref{883,,__new__()} 或 @ref{d57,,__init__()} 则枚举成员的值将被传给这些方法:

@example
>>> class Planet(Enum):
...     MERCURY = (3.303e+23, 2.4397e6)
...     VENUS   = (4.869e+24, 6.0518e6)
...     EARTH   = (5.976e+24, 6.37814e6)
...     MARS    = (6.421e+23, 3.3972e6)
...     JUPITER = (1.9e+27,   7.1492e7)
...     SATURN  = (5.688e+26, 6.0268e7)
...     URANUS  = (8.686e+25, 2.5559e7)
...     NEPTUNE = (1.024e+26, 2.4746e7)
...     def __init__(self, mass, radius):
...         self.mass = mass       # in kilograms
...         self.radius = radius   # in meters
...     @@property
...     def surface_gravity(self):
...         # universal gravitational constant  (m3 kg-1 s-2)
...         G = 6.67300E-11
...         return G * self.mass / (self.radius * self.radius)
...
>>> Planet.EARTH.value
(5.976e+24, 6378140.0)
>>> Planet.EARTH.surface_gravity
9.802652743337129
@end example

@node TimePeriod,,Planet,有趣的示例
@anchor{library/enum timeperiod}@anchor{199a}
@subsubsection TimePeriod


一个演示如何使用 @code{_ignore_} 属性的例子:

@example
>>> from datetime import timedelta
>>> class Period(timedelta, Enum):
...     "different lengths of time"
...     _ignore_ = 'Period i'
...     Period = vars()
...     for i in range(367):
...         Period['day_%d' % i] = i
...
>>> list(Period)[:2]
[<Period.day_0: datetime.timedelta(0)>, <Period.day_1: datetime.timedelta(days=1)>]
>>> list(Period)[-2:]
[<Period.day_365: datetime.timedelta(days=365)>, <Period.day_366: datetime.timedelta(days=366)>]
@end example

@node 各种枚举有何区别？,,有趣的示例,enum --- 对枚举的支持
@anchor{library/enum how-are-enums-different}@anchor{1980}
@subsubsection 各种枚举有何区别？


枚举具有自定义的元类，它会影响所派生枚举类及其实例（成员）的各个方面。

@menu
* 枚举类:: 
* 枚举成员（即实例）:: 
* 细节要点:: 

@end menu

@node 枚举类,枚举成员（即实例）,,各种枚举有何区别？
@anchor{library/enum enum-classes}@anchor{199b}
@subsubsection 枚举类


@code{EnumMeta} 元类负责提供 @ref{d21,,__contains__()}, @ref{314,,__dir__()}, @ref{509,,__iter__()} 及其他方法以允许用户通过 @ref{37f,,Enum} 类来完成一般类做不到的事情，例如 @cite{list(Color)} 或 @cite{some_enum_var in Color}。 @code{EnumMeta} 会负责确保最终 @ref{37f,,Enum} 类中的各种其他方法是正确的 (例如 @ref{883,,__new__()}, @ref{6a8,,__getnewargs__()}, @ref{e30,,__str__()} 和 @ref{337,,__repr__()})。

@node 枚举成员（即实例）,细节要点,枚举类,各种枚举有何区别？
@anchor{library/enum enum-members-aka-instances}@anchor{199c}
@subsubsection 枚举成员（即实例）


有关枚举成员最有趣的特点是它们都是单例对象。 @code{EnumMeta} 会在创建 @ref{37f,,Enum} 类本身时将它们全部创建完成，然后准备好一个自定义的 @ref{883,,__new__()}，通过只返回现有的成员实例来确保不会再实例化新的对象。

@node 细节要点,,枚举成员（即实例）,各种枚举有何区别？
@anchor{library/enum finer-points}@anchor{199d}
@subsubsection 细节要点


@menu
* 支持的 __dunder__ 名称:: 
* 支持的 _sunder_ 名称:: 
* Enum 成员类型:: 
* Enum 类和成员的布尔值:: 
* 带有方法的 Enum 类:: 
* 组合 Flag 的成员:: 

@end menu

@node 支持的 __dunder__ 名称,支持的 _sunder_ 名称,,细节要点
@anchor{library/enum supported-dunder-names}@anchor{199e}
@subsubsection 支持的 @code{__dunder__} 名称


@code{__members__} 是一个 @code{member_name}:@code{member} 条目的只读有序映射。 它只在类上可用。

如果指定了 @ref{883,,__new__()}，它必须创建并返回枚举成员；相应地设定成员的 @code{_value_} 也是一个很好的主意。 一旦所有成员都创建完成它就不会再被使用。

@node 支持的 _sunder_ 名称,Enum 成员类型,支持的 __dunder__ 名称,细节要点
@anchor{library/enum supported-sunder-names}@anchor{199f}
@subsubsection 支持的 @code{_sunder_} 名称



@itemize -

@item 
@code{_name_} -- 成员的名称

@item 
@code{_value_} -- 成员的值；可以在 @code{__new__} 中设置 / 修改

@item 
@code{_missing_} -- 当未发现某个值时所使用的查找函数；可被重载

@item 
@code{_ignore_} -- 一个名称列表，可以为 @ref{262,,list()} 或 @ref{329,,str()}，它将不会被转化为成员，并会从最终类中被移除

@item 
@code{_order_} -- 用于 Python 2/3 代码以确保成员顺序一致（类属性，在类创建期间会被移除）

@item 
@code{_generate_next_value_} -- 用于 @ref{197e,,Functional API} 并通过 @ref{541,,auto} 为枚举成员获取适当的值；可被重载
@end itemize


3.6 新版功能: @code{_missing_}, @code{_order_}, @code{_generate_next_value_}



3.7 新版功能: @code{_ignore_}


用来帮助 Python 2 / Python 3 代码保持同步提供 @code{_order_} 属性。 它将与枚举的实际顺序进行对照检查，如果两者不匹配则会引发错误:

@example
>>> class Color(Enum):
...     _order_ = 'RED GREEN BLUE'
...     RED = 1
...     BLUE = 3
...     GREEN = 2
...
Traceback (most recent call last):
...
TypeError: member order does not match _order_
@end example

@cartouche
@quotation 注解 
在 Python 2 代码中 @code{_order_} 属性是必须的，因为定义顺序在被记录之前就会丢失。
@end quotation
@end cartouche

@node Enum 成员类型,Enum 类和成员的布尔值,支持的 _sunder_ 名称,细节要点
@anchor{library/enum enum-member-type}@anchor{19a0}
@subsubsection @code{Enum} 成员类型


@ref{37f,,Enum} 成员是其 @ref{37f,,Enum} 类的实例，一般通过 @code{EnumClass.member} 的形式来访问。 在特定情况下它们也可通过 @code{EnumClass.member.member} 的形式来访问，但你绝对不应这样做，因为查找可能失败，或者更糟糕地返回你所查找的 @ref{37f,,Enum} 成员以外的对象（这也是成员应使用全大写名称的另一个好理由）:

@example
>>> class FieldTypes(Enum):
...     name = 0
...     value = 1
...     size = 2
...
>>> FieldTypes.value.size
<FieldTypes.size: 2>
>>> FieldTypes.size.value
2
@end example


在 3.5 版更改.


@node Enum 类和成员的布尔值,带有方法的 Enum 类,Enum 成员类型,细节要点
@anchor{library/enum boolean-value-of-enum-classes-and-members}@anchor{19a1}
@subsubsection @code{Enum} 类和成员的布尔值


混合了非 @ref{37f,,Enum} 类型（例如 @ref{184,,int}, @ref{329,,str} 等）的 @ref{37f,,Enum} 成员会按所混合类型的规则被求值；在其他情况下，所有成员都将被求值为 @ref{494,,True}。 要使你的自定义 Enum 的布尔值取决于成员的值，请在你的类中添加以下代码:

@example
def __bool__(self):
    return bool(self.value)
@end example

@ref{37f,,Enum} 类总是会被求值为 @ref{494,,True}。

@node 带有方法的 Enum 类,组合 Flag 的成员,Enum 类和成员的布尔值,细节要点
@anchor{library/enum enum-classes-with-methods}@anchor{19a2}
@subsubsection 带有方法的 @code{Enum} 类


如果你为你的 @ref{37f,,Enum} 子类添加了额外的方法，如同上述的 @ref{1989,,Planet} 类一样，这些方法将在对成员执行 @ref{d2c,,dir()} 时显示出来，但对类执行时则不会显示:

@example
>>> dir(Planet)
['EARTH', 'JUPITER', 'MARS', 'MERCURY', 'NEPTUNE', 'SATURN', 'URANUS', 'VENUS', '__class__', '__doc__', '__members__', '__module__']
>>> dir(Planet.EARTH)
['__class__', '__doc__', '__module__', 'name', 'surface_gravity', 'value']
@end example

@node 组合 Flag 的成员,,带有方法的 Enum 类,细节要点
@anchor{library/enum combining-members-of-flag}@anchor{19a3}
@subsubsection 组合 @code{Flag} 的成员


如果 Flag 成员的某种组合未被命名，则 @ref{7c6,,repr()} 将包含所有已命名的旗标和值中所有已命名的旗标组合:

@example
>>> class Color(Flag):
...     RED = auto()
...     GREEN = auto()
...     BLUE = auto()
...     MAGENTA = RED | BLUE
...     YELLOW = RED | GREEN
...     CYAN = GREEN | BLUE
...
>>> Color(3)  # named combination
<Color.YELLOW: 3>
>>> Color(7)      # not named combination
<Color.CYAN|MAGENTA|BLUE|YELLOW|GREEN|RED: 7>
@end example

@node 数字和数学模块,函数式编程模块,数据类型,Python 标准库
@anchor{library/numeric doc}@anchor{19a4}@anchor{library/numeric numeric}@anchor{19a5}@anchor{library/numeric numeric-and-mathematical-modules}@anchor{19a6}
@section 数字和数学模块


本章介绍的模块提供与数字和数学相关的函数和数据类型。 @ref{c1,,numbers} 模块定义了数字类型的抽象层次结构。 @ref{b1,,math} 和 @ref{19,,cmath} 模块包含浮点数和复数的各种数学函数。 @ref{36,,decimal} 模块支持使用任意精度算术的十进制数的精确表示。

本章包含以下模块的文档：

@menu
* numbers: numbers --- 数字的抽象基类. 数字的抽象基类
* math: math --- 数学函数. 数学函数
* cmath: cmath --- 关于复数的数学函数. 关于复数的数学函数
* decimal: decimal --- 十进制定点和浮点运算. 十进制定点和浮点运算
* fractions: fractions --- 分数. 分数
* random: random --- 生成伪随机数. 生成伪随机数
* statistics: statistics --- 数学统计函数. 数学统计函数

@end menu

@node numbers --- 数字的抽象基类,math --- 数学函数,,数字和数学模块
@anchor{library/numbers doc}@anchor{19a7}@anchor{library/numbers module-numbers}@anchor{c1}@anchor{library/numbers numbers-numeric-abstract-base-classes}@anchor{19a8}
@subsection @code{numbers} --- 数字的抽象基类


@geindex numbers (模块)

@strong{源代码：} Lib/numbers.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/numbers.py}


__________________________________________________________________


@ref{c1,,numbers} 模块 (
@geindex Python 提高建议; PEP 3141
PEP 3141@footnote{https://www.python.org/dev/peps/pep-3141}) 定义了数字 @ref{b2c,,抽象基类} 的层次结构，其中逐级定义了更多操作。 此模块中所定义的类型都不可被实例化。

@geindex Number (numbers 中的类)
@anchor{library/numbers numbers Number}@anchor{13ba}
@deffn {类} numbers.Number

数字的层次结构的基础。如果你只想确认参数 @emph{x} 是不是数字而不关心其类型，则使用`@w{`}isinstance(x, Number)`@w{`}。
@end deffn

@menu
* 数字的层次:: 
* 类型接口注释。:: 

@end menu

@node 数字的层次,类型接口注释。,,numbers --- 数字的抽象基类
@anchor{library/numbers the-numeric-tower}@anchor{19a9}
@subsubsection 数字的层次


@geindex Complex (numbers 中的类)
@anchor{library/numbers numbers Complex}@anchor{13bd}
@deffn {类} numbers.Complex

内置在类型 @ref{189,,complex} 里的子类描述了复数和它的运算操作。这些操作有：转化至  @ref{189,,complex} 和 @ref{183,,bool}， @ref{19aa,,real}、 @ref{19ab,,imag}、@code{+}、@code{-}、@code{*}、@code{/}、 @ref{1253,,abs()}、 @ref{19ac,,conjugate()}、 @code{==} 和 @code{!=}。 所有的异常，@code{-} 和 @code{!=} ，都是抽象的。

@geindex real (numbers.Complex 属性)
@anchor{library/numbers numbers Complex real}@anchor{19aa}
@deffn {属性} real

抽象的。得到该数字的实数部分。
@end deffn

@geindex imag (numbers.Complex 属性)
@anchor{library/numbers numbers Complex imag}@anchor{19ab}
@deffn {属性} imag

抽象的。得到该数字的虚数部分。
@end deffn

@geindex conjugate() (numbers.Complex 方法)
@anchor{library/numbers numbers Complex conjugate}@anchor{19ac}
@deffn {方法} abstractmethod conjugate ()

抽象的。返回共轭复数。例如 @code{(1+3j).conjugate() == (1-3j)}。
@end deffn
@end deffn

@geindex Real (numbers 中的类)
@anchor{library/numbers numbers Real}@anchor{13bc}
@deffn {类} numbers.Real

相对于 @ref{13bd,,Complex}，@ref{13bc,,Real} 加入了只有实数才能进行的操作。

简单的说，它们是：转化至 @ref{187,,float}，@ref{d27,,math.trunc()}、 @ref{c66,,round()}、 @ref{d25,,math.floor()}、 @ref{d26,,math.ceil()}、 @ref{152,,divmod()}、 @code{//}、 @code{%}、 @code{<}、 @code{<=}、 @code{>}、 和 @code{>=}。

实数同样默认支持 @ref{189,,complex()}、 @ref{19aa,,real}、 @ref{19ab,,imag} 和 @ref{19ac,,conjugate()}。
@end deffn

@geindex Rational (numbers 中的类)
@anchor{library/numbers numbers Rational}@anchor{c51}
@deffn {类} numbers.Rational

子类型 @ref{13bc,,Real} 并加入 @ref{19ad,,numerator} 和 @ref{19ae,,denominator} 两种属性，这两种属性应该属于最低的级别。加入后，这默认支持 @ref{187,,float()}。

@geindex numerator (numbers.Rational 属性)
@anchor{library/numbers numbers Rational numerator}@anchor{19ad}
@deffn {属性} numerator

摘要。
@end deffn

@geindex denominator (numbers.Rational 属性)
@anchor{library/numbers numbers Rational denominator}@anchor{19ae}
@deffn {属性} denominator

摘要。
@end deffn
@end deffn

@geindex Integral (numbers 中的类)
@anchor{library/numbers numbers Integral}@anchor{13bb}
@deffn {类} numbers.Integral

子类型 @ref{c51,,Rational} 加上转化至 @ref{184,,int}。 默认支持 @ref{187,,float()}、 @ref{19ad,,numerator} 和 @ref{19ae,,denominator}。 在 @code{**} 中加入抽象方法和比特字符串的操作： @code{<<}、 @code{>>}、 @code{&}、 @code{^}、 @code{|}、 @code{~}。
@end deffn

@node 类型接口注释。,,数字的层次,numbers --- 数字的抽象基类
@anchor{library/numbers notes-for-type-implementors}@anchor{19af}
@subsubsection 类型接口注释。


实现者需要注意使相等的数字相等并拥有同样的值。当这两个数使用不同的扩展模块时，这其中的差异是很微妙的。例如，用 @ref{185,,fractions.Fraction} 实现 @ref{9be,,hash()} 如下:

@example
def __hash__(self):
    if self.denominator == 1:
        # Get integers right.
        return hash(self.numerator)
    # Expensive check, but definitely correct.
    if self == float(self):
        return hash(float(self))
    else:
        # Use tuple's hash to avoid a high collision rate on
        # simple fractions.
        return hash((self.numerator, self.denominator))
@end example

@menu
* 加入更多数字的ABC:: 
* 实现算数运算:: 

@end menu

@node 加入更多数字的ABC,实现算数运算,,类型接口注释。
@anchor{library/numbers adding-more-numeric-abcs}@anchor{19b0}
@subsubsection 加入更多数字的ABC


当然，这里有更多支持数字的ABC，如果不加入这些，就将缺少层次感。你可以用如下方法在 @ref{13bd,,Complex} 和 @ref{13bc,,Real} 中加入`@w{`}MyFoo`@w{`}：

@example
class MyFoo(Complex): ...
MyFoo.register(Real)
@end example

@node 实现算数运算,,加入更多数字的ABC,类型接口注释。
@anchor{library/numbers id1}@anchor{19b1}@anchor{library/numbers implementing-the-arithmetic-operations}@anchor{13b9}
@subsubsection 实现算数运算


我们希望实现计算，因此，混合模式操作要么调用一个作者知道参数类型的实现，要么转变成为最接近的内置类型并对这个执行操作。对于子类 @ref{13bb,,Integral}，这意味着 @ref{13ef,,__add__()} 和 @ref{13f0,,__radd__()} 必须用如下方式定义：

@example
class MyIntegral(Integral):

    def __add__(self, other):
        if isinstance(other, MyIntegral):
            return do_my_adding_stuff(self, other)
        elif isinstance(other, OtherTypeIKnowAbout):
            return do_my_other_adding_stuff(self, other)
        else:
            return NotImplemented

    def __radd__(self, other):
        if isinstance(other, MyIntegral):
            return do_my_adding_stuff(other, self)
        elif isinstance(other, OtherTypeIKnowAbout):
            return do_my_other_adding_stuff(other, self)
        elif isinstance(other, Integral):
            return int(other) + int(self)
        elif isinstance(other, Real):
            return float(other) + float(self)
        elif isinstance(other, Complex):
            return complex(other) + complex(self)
        else:
            return NotImplemented
@end example

There are 5 different cases for a mixed-type operation on subclasses
of @ref{13bd,,Complex}. I'll refer to all of the above code that doesn't
refer to @code{MyIntegral} and @code{OtherTypeIKnowAbout} as
"boilerplate". @code{a} will be an instance of @code{A}, which is a subtype
of @ref{13bd,,Complex} (@code{a : A <: Complex}), and @code{b : B <:
Complex}. I'll consider @code{a + b}:

@quotation


@enumerate 

@item 
如果 @code{A} 被定义成一个承认`@w{`}b`@w{`} 的 @ref{13ef,,__add__()}，一切都没有问题。

@item 
如果 @code{A} 转回成“模板”失败，它将返回一个属于 @ref{13ef,,__add__()} 的值，我们需要避免 @code{B} 定义了一个更加智能的 @ref{13f0,,__radd__()}，因此模板需要返回一个属于 @ref{13ef,,__add__()} 的 @ref{846,,NotImplemented} 。（或者 @code{A} 可能完全不实现 @ref{13ef,,__add__()} 。）

@item 
接着看 @code{B} 的 @ref{13f0,,__radd__()} 。如果它承认 @code{a} ，一切都没有问题。

@item 
如果没有成功回退到模板，就没有更多的方法可以去尝试，因此这里将使用默认的实现。

@item 
如果 @code{B <: A} ， Python 在 @code{A.__add__} 之前尝试 @code{B.__radd__} 。 这是可行的，是通过对 @code{A} 的认识实现的，因此这可以在交给 @ref{13bd,,Complex} 处理之前处理这些实例。
@end enumerate
@end quotation

如果 @code{A <: Complex} 和 @code{B <: Real} 没有共享任何资源，那么适当的共享操作涉及内置的 @ref{189,,complex} ，并且分别获得 @ref{13f0,,__radd__()} ，因此 @code{a+b == b+a}。

由于对任何一直类型的大部分操作是十分相似的，可以定义一个帮助函数，即一个生成后续或相反的实例的生成器。例如，使用 @ref{185,,fractions.Fraction} 如下：

@example
def _operator_fallbacks(monomorphic_operator, fallback_operator):
    def forward(a, b):
        if isinstance(b, (int, Fraction)):
            return monomorphic_operator(a, b)
        elif isinstance(b, float):
            return fallback_operator(float(a), b)
        elif isinstance(b, complex):
            return fallback_operator(complex(a), b)
        else:
            return NotImplemented
    forward.__name__ = '__' + fallback_operator.__name__ + '__'
    forward.__doc__ = monomorphic_operator.__doc__

    def reverse(b, a):
        if isinstance(a, Rational):
            # Includes ints.
            return monomorphic_operator(a, b)
        elif isinstance(a, numbers.Real):
            return fallback_operator(float(a), float(b))
        elif isinstance(a, numbers.Complex):
            return fallback_operator(complex(a), complex(b))
        else:
            return NotImplemented
    reverse.__name__ = '__r' + fallback_operator.__name__ + '__'
    reverse.__doc__ = monomorphic_operator.__doc__

    return forward, reverse

def _add(a, b):
    """a + b"""
    return Fraction(a.numerator * b.denominator +
                    b.numerator * a.denominator,
                    a.denominator * b.denominator)

__add__, __radd__ = _operator_fallbacks(_add, operator.add)

# ...
@end example

@node math --- 数学函数,cmath --- 关于复数的数学函数,numbers --- 数字的抽象基类,数字和数学模块
@anchor{library/math doc}@anchor{19b2}@anchor{library/math math-mathematical-functions}@anchor{19b3}@anchor{library/math module-math}@anchor{b1}
@subsection @code{math} --- 数学函数


@geindex math (模块)

@c from math import fsum


__________________________________________________________________


该模块提供了对C标准定义的数学函数的访问。

这些函数不适用于复数；如果你需要计算复数，请使用 @ref{19,,cmath} 模块中的同名函数。将支持计算复数的函数区分开的目的，来自于大多数开发者并不愿意像数学家一样需要学习复数的概念。得到一个异常而不是一个复数结果使得开发者能够更早地监测到传递给这些函数的参数中包含复数，进而调查其产生的原因。

该模块提供了以下函数。除非另有明确说明，否则所有返回值均为浮点数。

@menu
* 数论与表示函数:: 
* 幂函数与对数函数:: 
* 三角函数:: 
* 角度转换:: 
* 双曲函数:: 
* 特殊函数:: 
* 常量: 常量<2>. 

@end menu

@node 数论与表示函数,幂函数与对数函数,,math --- 数学函数
@anchor{library/math number-theoretic-and-representation-functions}@anchor{19b4}
@subsubsection 数论与表示函数


@geindex ceil() (在 math 模块中)
@anchor{library/math math ceil}@anchor{d26}
@deffn {函数} math.ceil (x)

返回 @emph{x} 的上限，即大于或者等于 @emph{x} 的最小整数。如果 @emph{x} 不是一个浮点数，则委托  @code{x.__ceil__()}, 返回一个 @ref{13bb,,Integral} 类的值。
@end deffn

@geindex comb() (在 math 模块中)
@anchor{library/math math comb}@anchor{1e7}
@deffn {函数} math.comb (n, k)

返回不重复且无顺序地从 @emph{n} 项中选择 @emph{k} 项的方式总数。

当 @code{k <= n} 时取值为 @code{n! / (k! * (n - k)!)}；当 @code{k > n} 时取值为零。

也称为二项式系数，因为它等价于表达式 @code{(1 + x) ** n} 的多项式展开中第 k 项的系数。

如果任一参数不为整数则会引发 @ref{192,,TypeError}。 如果任一参数为负数则会引发 @ref{1fb,,ValueError}。


3.8 新版功能.

@end deffn

@geindex copysign() (在 math 模块中)
@anchor{library/math math copysign}@anchor{d36}
@deffn {函数} math.copysign (x, y)

返回一个基于 @emph{x} 的绝对值和 @emph{y} 的符号的浮点数。在支持带符号零的平台上，@code{copysign(1.0, -0.0)} 返回 @emph{-1.0}.
@end deffn

@geindex fabs() (在 math 模块中)
@anchor{library/math math fabs}@anchor{19b5}
@deffn {函数} math.fabs (x)

返回 @emph{x} 的绝对值。
@end deffn

@geindex factorial() (在 math 模块中)
@anchor{library/math math factorial}@anchor{1ea}
@deffn {函数} math.factorial (x)

以一个整数返回 @emph{x} 的阶乘。 如果 @emph{x} 不是整数或为负数时则将引发 @ref{1fb,,ValueError}。
@end deffn

@geindex floor() (在 math 模块中)
@anchor{library/math math floor}@anchor{d25}
@deffn {函数} math.floor (x)

返回 @emph{x} 的向下取整，小于或等于 @emph{x} 的最大整数。如果 @emph{x} 不是浮点数，则委托 @code{x.__floor__()} ，它应返回 @ref{13bb,,Integral} 值。
@end deffn

@geindex fmod() (在 math 模块中)
@anchor{library/math math fmod}@anchor{14d1}
@deffn {函数} math.fmod (x, y)

返回 @code{fmod(x, y)} ，由平台C库定义。请注意，Python表达式 @code{x % y} 可能不会返回相同的结果。C标准的目的是 @code{fmod(x, y)} 完全（数学上；到无限精度）等于 @code{x - n*y} 对于某个整数 @emph{n} ，使得结果具有 与 @emph{x} 相同的符号和小于 @code{abs(y)} 的幅度。Python的 @code{x % y} 返回带有 @emph{y} 符号的结果，并且可能不能完全计算浮点参数。 例如， @code{fmod(-1e-100, 1e100)} 是 @code{-1e-100} ，但Python的 @code{-1e-100 % 1e100} 的结果是 @code{1e100-1e-100} ，它不能完全表示为浮点数，并且取整为令人惊讶的 @code{1e100} 。 出于这个原因，函数 @ref{14d1,,fmod()} 在使用浮点数时通常是首选，而Python的 @code{x % y} 在使用整数时是首选。
@end deffn

@geindex frexp() (在 math 模块中)
@anchor{library/math math frexp}@anchor{19b6}
@deffn {函数} math.frexp (x)

返回 @emph{x} 的尾数和指数作为对`@w{`}(m, e)`@w{`}。 @emph{m} 是一个浮点数， @emph{e} 是一个整数，正好是 @code{x == m * 2**e} 。 如果 @emph{x} 为零，则返回 @code{(0.0, 0)} ，否则返回 @code{0.5 <= abs(m) < 1} 。这用于以可移植方式“分离”浮点数的内部表示。
@end deffn

@geindex fsum() (在 math 模块中)
@anchor{library/math math fsum}@anchor{d37}
@deffn {函数} math.fsum (iterable)

返回迭代中的精确浮点值。通过跟踪多个中间部分和来避免精度损失:

@example
>>> sum([.1, .1, .1, .1, .1, .1, .1, .1, .1, .1])
0.9999999999999999
>>> fsum([.1, .1, .1, .1, .1, .1, .1, .1, .1, .1])
1.0
@end example

该算法的准确性取决于IEEE-754算术保证和舍入模式为半偶的典型情况。在某些非Windows版本中，底层C库使用扩展精度添加，并且有时可能会使中间和加倍，导致它在最低有效位中关闭。

有关待进一步讨论和两种替代方法，参见 ASPN cookbook recipes for accurate floating point summation@footnote{https://code.activestate.com/recipes/393090/}。
@end deffn

@geindex gcd() (在 math 模块中)
@anchor{library/math math gcd}@anchor{710}
@deffn {函数} math.gcd (a, b)

返回整数 @emph{a} 和 @emph{b} 的最大公约数。如果 @emph{a} 或 @emph{b} 之一非零，则 @code{gcd(a, b)} 的值是能同时整除 @emph{a} 和 @emph{b} 的最大正整数。@code{gcd(0, 0)} 返回 @code{0}。


3.5 新版功能.

@end deffn

@geindex isclose() (在 math 模块中)
@anchor{library/math math isclose}@anchor{680}
@deffn {函数} math.isclose (a, b, *, rel_tol=1e-09, abs_tol=0.0)

若 @emph{a} 和 @emph{b} 的值比较接近则返回 @code{True}，否则返回 @code{False}。

根据给定的绝对和相对容差确定两个值是否被认为是接近的。

@emph{rel_tol} 是相对容差 —— 它是 @emph{a} 和 @emph{b} 之间允许的最大差值，相对于 @emph{a} 或 @emph{b} 的较大绝对值。例如，要设置5％的容差，请传递 @code{rel_tol=0.05} 。默认容差为 @code{1e-09}，确保两个值在大约9位十进制数字内相同。 @emph{rel_tol} 必须大于零。

@emph{abs_tol} 是最小绝对容差 —— 对于接近零的比较很有用。 @emph{abs_tol} 必须至少为零。

如果没有错误发生，结果将是： @code{abs(a-b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)} 。

IEEE 754特殊值 @code{NaN} ， @code{inf} 和 @code{-inf} 将根据IEEE规则处理。具体来说， @code{NaN} 不被认为接近任何其他值，包括 @code{NaN} 。 @code{inf} 和 @code{-inf} 只被认为接近自己。


3.5 新版功能.



@subsubheading 参见


@geindex Python 提高建议; PEP 485
PEP 485@footnote{https://www.python.org/dev/peps/pep-0485} —— 用于测试近似相等的函数

@end deffn

@geindex isfinite() (在 math 模块中)
@anchor{library/math math isfinite}@anchor{b60}
@deffn {函数} math.isfinite (x)

如果 @emph{x} 既不是无穷大也不是NaN，则返回 @code{True} ，否则返回 @code{False} 。 （注意 @code{0.0} 被认为 @emph{是} 有限的。）


3.2 新版功能.

@end deffn

@geindex isinf() (在 math 模块中)
@anchor{library/math math isinf}@anchor{d34}
@deffn {函数} math.isinf (x)

如果 @emph{x} 是正或负无穷大，则返回 @code{True} ，否则返回 @code{False} 。
@end deffn

@geindex isnan() (在 math 模块中)
@anchor{library/math math isnan}@anchor{d35}
@deffn {函数} math.isnan (x)

如果 @emph{x} 是 NaN（不是数字），则返回 @code{True} ，否则返回 @code{False} 。
@end deffn

@geindex isqrt() (在 math 模块中)
@anchor{library/math math isqrt}@anchor{1e8}
@deffn {函数} math.isqrt (n)

返回非负整数 @emph{n} 的整数平方根。 这就是对 @emph{n} 的实际平方根向下取整，或者相当于使得 @emph{a}² ≤ @emph{n} 的最大整数 @emph{a}。

对于某些应用来说，可以更适合取值为使得 @emph{n} ≤ @emph{a}² 的最小整数 @emph{a} ，或者换句话说就是 @emph{n} 的实际平方根向上取整。 对于正数 @emph{n}，这可以使用 @code{a = 1 + isqrt(n - 1)} 来计算。


3.8 新版功能.

@end deffn

@geindex ldexp() (在 math 模块中)
@anchor{library/math math ldexp}@anchor{19b7}
@deffn {函数} math.ldexp (x, i)

返回 @code{x * (2**i)} 。 这基本上是函数  @ref{19b6,,frexp()}  的反函数。
@end deffn

@geindex modf() (在 math 模块中)
@anchor{library/math math modf}@anchor{19b8}
@deffn {函数} math.modf (x)

返回 @emph{x} 的小数和整数部分。两个结果都带有 @emph{x} 的符号并且是浮点数。
@end deffn

@geindex perm() (在 math 模块中)
@anchor{library/math math perm}@anchor{1e6}
@deffn {函数} math.perm (n, k=None)

返回不重复且有顺序地从 @emph{n} 项中选择 @emph{k} 项的方式总数。

当 @code{k <= n} 时取值为 @code{n! / (n - k)!}；当 @code{k > n} 时取值为零。

如果 @emph{k} 未指定或为 None，则 @emph{k} 默认值为 @emph{n} 并且函数将返回 @code{n!}。

如果任一参数不为整数则会引发 @ref{192,,TypeError}。 如果任一参数为负数则会引发 @ref{1fb,,ValueError}。


3.8 新版功能.

@end deffn

@geindex prod() (在 math 模块中)
@anchor{library/math math prod}@anchor{1e4}
@deffn {函数} math.prod (iterable, *, start=1)

计算输入的 @emph{iterable} 中所有元素的积。 积的默认 @emph{start} 值为 @code{1}。

当可迭代对象为空时，返回起始值。 此函数特别针对数字值使用，并会拒绝非数字类型。


3.8 新版功能.

@end deffn

@geindex remainder() (在 math 模块中)
@anchor{library/math math remainder}@anchor{3a3}
@deffn {函数} math.remainder (x, y)

返回 IEEE 754 风格的 @emph{x} 相对于 @emph{y} 的余数。对于有限 @emph{x} 和有限非零 @emph{y} ，这是差异 @code{x - n*y} ，其中 @code{n} 是与商 @code{x / y} 的精确值最接近的整数。如果 @code{x / y} 恰好位于两个连续整数之间，则最近的 * even* 整数用于 @code{n} 。 余数 @code{r = remainder(x, y)} 因此总是满足 @code{abs(r) <= 0.5 * abs(y)} 。

特殊情况遵循IEEE 754：特别是 @code{remainder(x, math.inf)} 对于任何有限 @emph{x} 都是 @emph{x} ，而 @code{remainder(x, 0)} 和 @code{remainder(math.inf, x)} 引发  @ref{1fb,,ValueError} 适用于任何非NaN的 @emph{x} 。如果余数运算的结果为零，则该零将具有与 @emph{x} 相同的符号。

在使用IEEE 754二进制浮点的平台上，此操作的结果始终可以完全表示：不会引入舍入错误。


3.7 新版功能.

@end deffn

@geindex trunc() (在 math 模块中)
@anchor{library/math math trunc}@anchor{d27}
@deffn {函数} math.trunc (x)

返回 @ref{13bc,,Real} 值 @emph{x} 截断为 @ref{13bb,,Integral} （通常是整数）。 委托给 @ref{141b,,x.__trunc__()}。
@end deffn

注意 @ref{19b6,,frexp()} 和 @ref{19b8,,modf()} 具有与它们的C等价函数不同的调用/返回模式：它们采用单个参数并返回一对值，而不是通过 '输出形参' 返回它们的第二个返回参数（Python中没有这样的东西）。

对于 @ref{d26,,ceil()} ， @ref{d25,,floor()} 和 @ref{19b8,,modf()} 函数，请注意 @emph{所有} 足够大的浮点数都是精确整数。Python浮点数通常不超过53位的精度（与平台C double类型相同），在这种情况下，任何浮点 @emph{x} 与 @code{abs(x) >= 2**52} 必然没有小数位。

@node 幂函数与对数函数,三角函数,数论与表示函数,math --- 数学函数
@anchor{library/math power-and-logarithmic-functions}@anchor{19b9}
@subsubsection 幂函数与对数函数


@geindex exp() (在 math 模块中)
@anchor{library/math math exp}@anchor{ca2}
@deffn {函数} math.exp (x)

返回 @emph{e} 次 @emph{x} 幂，其中 @emph{e} = 2.718281... 是自然对数的基数。这通常比 @code{math.e ** x} 或 @code{pow(math.e, x)} 更精确。
@end deffn

@geindex expm1() (在 math 模块中)
@anchor{library/math math expm1}@anchor{b61}
@deffn {函数} math.expm1 (x)

返回 @emph{e} 的 @emph{x} 次幂，减1。这里 @emph{e} 是自然对数的基数。对于小浮点数 @emph{x} ， @code{exp(x) - 1} 中的减法可能导致 significant loss of precision@footnote{https://en.wikipedia.org/wiki/Loss_of_significance}； @ref{b61,,expm1()} 函数提供了一种将此数量计算为全精度的方法:

@example
>>> from math import exp, expm1
>>> exp(1e-5) - 1  # gives result accurate to 11 places
1.0000050000069649e-05
>>> expm1(1e-5)    # result accurate to full precision
1.0000050000166668e-05
@end example


3.2 新版功能.

@end deffn

@geindex log() (在 math 模块中)
@anchor{library/math math log}@anchor{e0a}
@deffn {函数} math.log (x[, base])

使用一个参数，返回 @emph{x} 的自然对数（底为 @emph{e} ）。

使用两个参数，返回给定的 @emph{base} 的对数 @emph{x} ，计算为 @code{log(x)/log(base)} 。
@end deffn

@geindex log1p() (在 math 模块中)
@anchor{library/math math log1p}@anchor{d3b}
@deffn {函数} math.log1p (x)

返回 @emph{1+x} (base @emph{e}) 的自然对数。以对于接近零的 @emph{x} 精确的方式计算结果。
@end deffn

@geindex log2() (在 math 模块中)
@anchor{library/math math log2}@anchor{a1b}
@deffn {函数} math.log2 (x)

返回 @emph{x} 以2为底的对数。这通常比 @code{log(x, 2)} 更准确。


3.3 新版功能.



@subsubheading 参见


@ref{15b7,,int.bit_length()} 返回表示二进制整数所需的位数，不包括符号和前导零。

@end deffn

@geindex log10() (在 math 模块中)
@anchor{library/math math log10}@anchor{19ba}
@deffn {函数} math.log10 (x)

返回 @emph{x} 底为10的对数。这通常比 @code{log(x, 10)} 更准确。
@end deffn

@geindex pow() (在 math 模块中)
@anchor{library/math math pow}@anchor{19bb}
@deffn {函数} math.pow (x, y)

将返回 @code{x} 的 @code{y} 次幂。特殊情况尽可能遵循C99标准的附录'F'。特别是， @code{pow(1.0, x)} 和 @code{pow(x, 0.0)} 总是返回 @code{1.0} ，即使 @code{x} 是零或NaN。 如果 @code{x} 和 @code{y} 都是有限的， @code{x} 是负数， @code{y} 不是整数那么 @code{pow(x, y)} 是未定义的，并且引发 @ref{1fb,,ValueError} 。

与内置的 @code{**} 运算符不同， @ref{19bb,,math.pow()} 将其参数转换为 @ref{187,,float} 类型。使用 @code{**} 或内置的 @ref{19a,,pow()} 函数来计算精确的整数幂。
@end deffn

@geindex sqrt() (在 math 模块中)
@anchor{library/math math sqrt}@anchor{1e9}
@deffn {函数} math.sqrt (x)

返回 @emph{x} 的平方根。
@end deffn

@node 三角函数,角度转换,幂函数与对数函数,math --- 数学函数
@anchor{library/math trigonometric-functions}@anchor{19bc}
@subsubsection 三角函数


@geindex acos() (在 math 模块中)
@anchor{library/math math acos}@anchor{19bd}
@deffn {函数} math.acos (x)

以弧度为单位返回 @emph{x} 的反余弦值。
@end deffn

@geindex asin() (在 math 模块中)
@anchor{library/math math asin}@anchor{19be}
@deffn {函数} math.asin (x)

以弧度为单位返回 @emph{x} 的反正弦值。
@end deffn

@geindex atan() (在 math 模块中)
@anchor{library/math math atan}@anchor{19bf}
@deffn {函数} math.atan (x)

以弧度为单位返回 @emph{x} 的反正切值。
@end deffn

@geindex atan2() (在 math 模块中)
@anchor{library/math math atan2}@anchor{19c0}
@deffn {函数} math.atan2 (y, x)

以弧度为单位返回 @code{atan(y / x)} 。结果是在 @code{-pi} 和 @code{pi} 之间。从原点到点 @code{(x, y)}  的平面矢量使该角度与正X轴成正比。 @ref{19c0,,atan2()} 的点的两个输入的符号都是已知的，因此它可以计算角度的正确象限。 例如， @code{atan(1)} 和 @code{atan2(1, 1)}  都是 @code{pi/4} ，但 @code{atan2(-1, -1)} 是 @code{-3*pi/4} 。
@end deffn

@geindex cos() (在 math 模块中)
@anchor{library/math math cos}@anchor{e09}
@deffn {函数} math.cos (x)

返回 @emph{x} 弧度的余弦值。
@end deffn

@geindex dist() (在 math 模块中)
@anchor{library/math math dist}@anchor{1e2}
@deffn {函数} math.dist (p, q)

返回 @emph{p} 与 @emph{q} 两点之间的欧几里得距离，以一个坐标序列（或可迭代对象）的形式给出。 两个点必须具有相同的维度。

大致相当于：

@example
sqrt(sum((px - qx) ** 2.0 for px, qx in zip(p, q)))
@end example


3.8 新版功能.

@end deffn

@geindex hypot() (在 math 模块中)
@anchor{library/math math hypot}@anchor{1e3}
@deffn {函数} math.hypot (*coordinates)

返回欧几里得范数，@code{sqrt(sum(x**2 for x in coordinates))}。 这是从原点到坐标给定点的向量长度。

对于一个二维点 @code{(x, y)}，这等价于使用毕达哥拉斯定义 @code{sqrt(x*x + y*y)} 计算一个直角三角形的斜边。


在 3.8 版更改: 添加了对 n 维点的支持。 之前的版本只支持二维点。

@end deffn

@geindex sin() (在 math 模块中)
@anchor{library/math math sin}@anchor{e08}
@deffn {函数} math.sin (x)

返回 @emph{x} 弧度的正弦值。
@end deffn

@geindex tan() (在 math 模块中)
@anchor{library/math math tan}@anchor{19c1}
@deffn {函数} math.tan (x)

返回 @emph{x} 弧度的正切值。
@end deffn

@node 角度转换,双曲函数,三角函数,math --- 数学函数
@anchor{library/math angular-conversion}@anchor{19c2}
@subsubsection 角度转换


@geindex degrees() (在 math 模块中)
@anchor{library/math math degrees}@anchor{19c3}
@deffn {函数} math.degrees (x)

将角度 @emph{x} 从弧度转换为度数。
@end deffn

@geindex radians() (在 math 模块中)
@anchor{library/math math radians}@anchor{19c4}
@deffn {函数} math.radians (x)

将角度 @emph{x} 从度数转换为弧度。
@end deffn

@node 双曲函数,特殊函数,角度转换,math --- 数学函数
@anchor{library/math hyperbolic-functions}@anchor{19c5}
@subsubsection 双曲函数


双曲函数@footnote{https://en.wikipedia.org/wiki/Hyperbolic_function} 是基于双曲线而非圆来对三角函数进行模拟。

@geindex acosh() (在 math 模块中)
@anchor{library/math math acosh}@anchor{d38}
@deffn {函数} math.acosh (x)

返回 @emph{x} 的反双曲余弦值。
@end deffn

@geindex asinh() (在 math 模块中)
@anchor{library/math math asinh}@anchor{d39}
@deffn {函数} math.asinh (x)

返回 @emph{x} 的反双曲正弦值。
@end deffn

@geindex atanh() (在 math 模块中)
@anchor{library/math math atanh}@anchor{d3a}
@deffn {函数} math.atanh (x)

返回 @emph{x} 的反双曲正切值。
@end deffn

@geindex cosh() (在 math 模块中)
@anchor{library/math math cosh}@anchor{19c6}
@deffn {函数} math.cosh (x)

返回 @emph{x} 的双曲余弦值。
@end deffn

@geindex sinh() (在 math 模块中)
@anchor{library/math math sinh}@anchor{19c7}
@deffn {函数} math.sinh (x)

返回 @emph{x} 的双曲正弦值。
@end deffn

@geindex tanh() (在 math 模块中)
@anchor{library/math math tanh}@anchor{19c8}
@deffn {函数} math.tanh (x)

返回 @emph{x} 的双曲正切值。
@end deffn

@node 特殊函数,常量<2>,双曲函数,math --- 数学函数
@anchor{library/math special-functions}@anchor{19c9}
@subsubsection 特殊函数


@geindex erf() (在 math 模块中)
@anchor{library/math math erf}@anchor{44c}
@deffn {函数} math.erf (x)

返回 @emph{x} 处的 error function@footnote{https://en.wikipedia.org/wiki/Error_function} 。

@ref{44c,,erf()} 函数可用于计算传统的统计函数，如 累积标准正态分布@footnote{https://en.wikipedia.org/wiki/Normal_distribution#Cumulative_distribution_function}

@example
def phi(x):
    'Cumulative distribution function for the standard normal distribution'
    return (1.0 + erf(x / sqrt(2.0))) / 2.0
@end example


3.2 新版功能.

@end deffn

@geindex erfc() (在 math 模块中)
@anchor{library/math math erfc}@anchor{44d}
@deffn {函数} math.erfc (x)

返回 @emph{x} 处的互补误差函数。 互补错误函数@footnote{https://en.wikipedia.org/wiki/Error_function} 定义为 @code{1.0 - erf(x)}。 它用于 @emph{x} 的大值，从其中减去一个会导致 有效位数损失@footnote{https://en.wikipedia.org/wiki/Loss_of_significance}。


3.2 新版功能.

@end deffn

@geindex gamma() (在 math 模块中)
@anchor{library/math math gamma}@anchor{b62}
@deffn {函数} math.gamma (x)

返回 @emph{x} 处的 伽马函数@footnote{https://en.wikipedia.org/wiki/Gamma_function} 值。


3.2 新版功能.

@end deffn

@geindex lgamma() (在 math 模块中)
@anchor{library/math math lgamma}@anchor{b63}
@deffn {函数} math.lgamma (x)

返回Gamma函数在 @emph{x} 绝对值的自然对数。


3.2 新版功能.

@end deffn

@node 常量<2>,,特殊函数,math --- 数学函数
@anchor{library/math constants}@anchor{19ca}
@subsubsection 常量


@geindex pi() (在 math 模块中)
@anchor{library/math math pi}@anchor{19cb}
@deffn {数据} math.pi

数学常数 @emph{π} = 3.141592...，精确到可用精度。
@end deffn

@geindex e() (在 math 模块中)
@anchor{library/math math e}@anchor{19cc}
@deffn {数据} math.e

数学常数 @emph{e} = 2.718281...，精确到可用精度。
@end deffn

@geindex tau() (在 math 模块中)
@anchor{library/math math tau}@anchor{19cd}
@deffn {数据} math.tau

数学常数 @emph{τ} = 6.283185...，精确到可用精度。Tau 是一个圆周常数，等于 2@emph{π}，圆的周长与半径之比。更多关于 Tau 的信息可参考 Vi Hart 的视频 Pi is (still) Wrong@footnote{https://www.youtube.com/watch?v=jG7vhMMXagQ}。吃两倍多的派来庆祝 Tau 日@footnote{https://tauday.com/} 吧！


3.6 新版功能.

@end deffn

@geindex inf() (在 math 模块中)
@anchor{library/math math inf}@anchor{522}
@deffn {数据} math.inf

浮点正无穷大。 （对于负无穷大，使用 @code{-math.inf} 。）相当于 @code{float('inf')} 的输出。


3.5 新版功能.

@end deffn

@geindex nan() (在 math 模块中)
@anchor{library/math math nan}@anchor{523}
@deffn {数据} math.nan

浮点“非数字”（NaN）值。 相当于 @code{float('nan')} 的输出。


3.5 新版功能.

@end deffn

@strong{CPython implementation detail:} @ref{b1,,math} 模块主要包含围绕平台C数学库函数的简单包装器。特殊情况下的行为在适当情况下遵循C99标准的附录F。当前的实现将引发 @ref{1fb,,ValueError} 用于无效操作，如 @code{sqrt(-1.0)} 或 @code{log(0.0)} （其中C99附件F建议发出无效操作信号或被零除）， 和 @ref{95a,,OverflowError} 用于溢出的结果（例如， @code{exp(1000.0)} ）。除非一个或多个输入参数是NaN，否则不会从上述任何函数返回NaN；在这种情况下，大多数函数将返回一个NaN，但是（再次遵循C99附件F）这个规则有一些例外，例如 @code{pow(float('nan'), 0.0)} 或 @code{hypot(float('nan'), float('inf'))} 。

请注意，Python不会将显式NaN与静默NaN区分开来，并且显式NaN的行为仍未明确。典型的行为是将所有NaN视为静默的。


@subsubheading 参见



@table @asis

@item @ref{19,,cmath} 模块

这里很多函数的复数版本。
@end table


@node cmath --- 关于复数的数学函数,decimal --- 十进制定点和浮点运算,math --- 数学函数,数字和数学模块
@anchor{library/cmath doc}@anchor{19ce}@anchor{library/cmath cmath-mathematical-functions-for-complex-numbers}@anchor{19cf}@anchor{library/cmath module-cmath}@anchor{19}
@subsection @code{cmath} --- 关于复数的数学函数


@geindex cmath (模块)


__________________________________________________________________


这一模块提供了一些关于复数的数学函数。 该模块的函数的参数为整数、浮点数或复数。 这些函数的参数也可为一个拥有 @ref{18d,,__complex__()} 或 @ref{18c,,__float__()} 方法的 Python 对象，这些方法分别用于将对象转换为复数和浮点数，这些函数作用于转换后的结果。

@cartouche
@quotation 注解 
在具有对于有符号零的硬件和系统级支持的平台上，涉及分歧点的函数在分歧点的 @emph{两侧} 都是连续的：零的符号可用来区别分歧点的一侧和另一侧。 在不支持有符号零的平台上，连续性的规则见下文。
@end quotation
@end cartouche

@menu
* 到极坐标和从极坐标的转换:: 
* 幂函数与对数函数: 幂函数与对数函数<2>. 
* 三角函数: 三角函数<2>. 
* 双曲函数: 双曲函数<2>. 
* 分类函数:: 
* 常量: 常量<3>. 

@end menu

@node 到极坐标和从极坐标的转换,幂函数与对数函数<2>,,cmath --- 关于复数的数学函数
@anchor{library/cmath conversions-to-and-from-polar-coordinates}@anchor{19d0}
@subsubsection 到极坐标和从极坐标的转换


使用 @emph{矩形坐标} 或 @emph{笛卡尔坐标} 在内部存储 Python 复数 @code{z}。 这完全取决于它的 @emph{实部} @code{z.real} 和 @emph{虚部} @code{z.imag}。 换句话说:

@example
z == z.real + z.imag*1j
@end example

@emph{极坐标} 提供了另一种复数的表示方法。在极坐标中，一个复数 @emph{z} 由模量 @emph{r} 和相位角 @emph{phi} 来定义。模量 @emph{r} 是从 @emph{z} 到坐标原点的距离，而相位角 @emph{phi} 是以弧度为单位的，逆时针的，从正X轴到连接原点和 @emph{z} 的线段间夹角的角度。

下面的函数可用于原生直角坐标与极坐标的相互转换。

@geindex phase() (在 cmath 模块中)
@anchor{library/cmath cmath phase}@anchor{19d1}
@deffn {函数} cmath.phase (x)

将 @emph{x} 的相位 (也称为 @emph{x} 的 @emph{参数}) 返回为一个浮点数。@code{phase(x)} 相当于 @code{math.atan2(x.imag, x.real)}。 结果处于 [-@emph{π}, @emph{π}] 之间，以及这个操作的分支切断处于负实轴上，从上方连续。 在支持有符号零的系统上（这包涵大多数当前的常用系统），这意味着结果的符号与 @code{x.imag} 的符号相同，即使 @code{x.imag} 的值是 0:

@example
>>> phase(complex(-1.0, 0.0))
3.141592653589793
>>> phase(complex(-1.0, -0.0))
-3.141592653589793
@end example
@end deffn

@cartouche
@quotation 注解 
一个复数 @emph{x} 的模数（绝对值）可以通过内置函数 @ref{1253,,abs()} 计算。没有单独的 @ref{19,,cmath} 模块函数用于这个操作。
@end quotation
@end cartouche

@geindex polar() (在 cmath 模块中)
@anchor{library/cmath cmath polar}@anchor{19d2}
@deffn {函数} cmath.polar (x)

在极坐标中返回 @emph{x} 的表达方式。返回一个数对 @code{(r, phi)}，@emph{r} 是 @emph{x} 的模数，@emph{phi} 是 @emph{x} 的相位角。 @code{polar(x)} 相当于 @code{(abs(x), phase(x))}。
@end deffn

@geindex rect() (在 cmath 模块中)
@anchor{library/cmath cmath rect}@anchor{19d3}
@deffn {函数} cmath.rect (r, phi)

通过极坐标的 @emph{r} 和 @emph{phi} 返回复数 @emph{x}。相当于 @code{r * (math.cos(phi) + math.sin(phi)*1j)}。
@end deffn

@node 幂函数与对数函数<2>,三角函数<2>,到极坐标和从极坐标的转换,cmath --- 关于复数的数学函数
@anchor{library/cmath power-and-logarithmic-functions}@anchor{19d4}
@subsubsection 幂函数与对数函数


@geindex exp() (在 cmath 模块中)
@anchor{library/cmath cmath exp}@anchor{19d5}
@deffn {函数} cmath.exp (x)

返回 @emph{e} 的 @emph{x} 次方，@emph{e} 是自然对数的底数。
@end deffn

@geindex log() (在 cmath 模块中)
@anchor{library/cmath cmath log}@anchor{19d6}
@deffn {函数} cmath.log (x[, base])

返回给定 @emph{base} 的 @emph{x} 的对数。如果没有给定 @emph{base}，返回 @emph{x} 的自然对数。 从 0 到 -∞ 存在一个分歧点，沿负实轴之上连续。
@end deffn

@geindex log10() (在 cmath 模块中)
@anchor{library/cmath cmath log10}@anchor{19d7}
@deffn {函数} cmath.log10 (x)

返回底数为 10 的 @emph{x} 的对数。它具有与 @ref{19d6,,log()} 相同的分歧点。
@end deffn

@geindex sqrt() (在 cmath 模块中)
@anchor{library/cmath cmath sqrt}@anchor{19d8}
@deffn {函数} cmath.sqrt (x)

返回 @emph{x} 的平方根。 它具有与 @ref{19d6,,log()} 相同的分歧点。
@end deffn

@node 三角函数<2>,双曲函数<2>,幂函数与对数函数<2>,cmath --- 关于复数的数学函数
@anchor{library/cmath trigonometric-functions}@anchor{19d9}
@subsubsection 三角函数


@geindex acos() (在 cmath 模块中)
@anchor{library/cmath cmath acos}@anchor{19da}
@deffn {函数} cmath.acos (x)

返回 @emph{x} 的反余弦。这里有两个分歧点：一个沿着实轴从 1 向右延伸到 ∞，从下面连续延伸。另外一个沿着实轴从 -1 向左延伸到 -∞，从上面连续延伸。
@end deffn

@geindex asin() (在 cmath 模块中)
@anchor{library/cmath cmath asin}@anchor{19db}
@deffn {函数} cmath.asin (x)

返回 @emph{x} 的反正弦。它与 @ref{19da,,acos()} 有相同的分歧点。
@end deffn

@geindex atan() (在 cmath 模块中)
@anchor{library/cmath cmath atan}@anchor{19dc}
@deffn {函数} cmath.atan (x)

返回 @emph{x} 的反正切。它具有两个分歧点：一个沿着虚轴从 @code{1j}  延伸到 @code{∞j}，向右持续延伸。另一个是沿着虚轴从 @code{-1j} 延伸到 @code{-∞j} ，向左持续延伸。
@end deffn

@geindex cos() (在 cmath 模块中)
@anchor{library/cmath cmath cos}@anchor{19dd}
@deffn {函数} cmath.cos (x)

返回 @emph{x} 的余弦。
@end deffn

@geindex sin() (在 cmath 模块中)
@anchor{library/cmath cmath sin}@anchor{19de}
@deffn {函数} cmath.sin (x)

返回 @emph{x} 的正弦。
@end deffn

@geindex tan() (在 cmath 模块中)
@anchor{library/cmath cmath tan}@anchor{19df}
@deffn {函数} cmath.tan (x)

返回 @emph{x} 的正切。
@end deffn

@node 双曲函数<2>,分类函数,三角函数<2>,cmath --- 关于复数的数学函数
@anchor{library/cmath hyperbolic-functions}@anchor{19e0}
@subsubsection 双曲函数


@geindex acosh() (在 cmath 模块中)
@anchor{library/cmath cmath acosh}@anchor{19e1}
@deffn {函数} cmath.acosh (x)

返回 @emph{x} 的反双曲余弦。它有一个分歧点沿着实轴从 1 到  -∞ 向左延伸，从上方持续延伸。
@end deffn

@geindex asinh() (在 cmath 模块中)
@anchor{library/cmath cmath asinh}@anchor{19e2}
@deffn {函数} cmath.asinh (x)

返回 @emph{x} 的反双曲正弦。它有两个分歧点：一个沿着虚轴从 @code{1j} 向右持续延伸到 @code{∞j}。另一个是沿着虚轴从 @code{-1j} 向左持续延伸到 @code{-∞j}。
@end deffn

@geindex atanh() (在 cmath 模块中)
@anchor{library/cmath cmath atanh}@anchor{19e3}
@deffn {函数} cmath.atanh (x)

返回 @emph{x} 的反双曲正切。它有两个分歧点：一个是沿着实轴从 @code{1} 延展到 @code{∞}，从下面持续延展。另一个是沿着实轴从 @code{-1} 延展到 @code{-∞}，从上面持续延展。
@end deffn

@geindex cosh() (在 cmath 模块中)
@anchor{library/cmath cmath cosh}@anchor{19e4}
@deffn {函数} cmath.cosh (x)

返回 @emph{x} 的双曲余弦值。
@end deffn

@geindex sinh() (在 cmath 模块中)
@anchor{library/cmath cmath sinh}@anchor{19e5}
@deffn {函数} cmath.sinh (x)

返回 @emph{x} 的双曲正弦值。
@end deffn

@geindex tanh() (在 cmath 模块中)
@anchor{library/cmath cmath tanh}@anchor{19e6}
@deffn {函数} cmath.tanh (x)

返回 @emph{x} 的双曲正切值。
@end deffn

@node 分类函数,常量<3>,双曲函数<2>,cmath --- 关于复数的数学函数
@anchor{library/cmath classification-functions}@anchor{19e7}
@subsubsection 分类函数


@geindex isfinite() (在 cmath 模块中)
@anchor{library/cmath cmath isfinite}@anchor{19e8}
@deffn {函数} cmath.isfinite (x)

如果 @emph{x} 的实部和虚部都是有限的，则返回 @code{True}，否则返回 @code{False}。


3.2 新版功能.

@end deffn

@geindex isinf() (在 cmath 模块中)
@anchor{library/cmath cmath isinf}@anchor{19e9}
@deffn {函数} cmath.isinf (x)

如果 @emph{x} 的实部或者虚部是无穷大的，则返回 @code{True}，否则返回 @code{False}。
@end deffn

@geindex isnan() (在 cmath 模块中)
@anchor{library/cmath cmath isnan}@anchor{19ea}
@deffn {函数} cmath.isnan (x)

如果 @emph{x} 的实部或者虚部是 NaN，则返回 @code{True} ，否则返回 @code{False}。
@end deffn

@geindex isclose() (在 cmath 模块中)
@anchor{library/cmath cmath isclose}@anchor{681}
@deffn {函数} cmath.isclose (a, b, *, rel_tol=1e-09, abs_tol=0.0)

若 @emph{a} 和 @emph{b} 的值比较接近则返回 @code{True}，否则返回 @code{False}。

根据给定的绝对和相对容差确定两个值是否被认为是接近的。

@emph{rel_tol} 是相对容差 —— 它是 @emph{a} 和 @emph{b} 之间允许的最大差值，相对于 @emph{a} 或 @emph{b} 的较大绝对值。例如，要设置5％的容差，请传递 @code{rel_tol=0.05} 。默认容差为 @code{1e-09}，确保两个值在大约9位十进制数字内相同。 @emph{rel_tol} 必须大于零。

@emph{abs_tol} 是最小绝对容差 —— 对于接近零的比较很有用。 @emph{abs_tol} 必须至少为零。

如果没有错误发生，结果将是： @code{abs(a-b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)} 。

IEEE 754特殊值 @code{NaN} ， @code{inf} 和 @code{-inf} 将根据IEEE规则处理。具体来说， @code{NaN} 不被认为接近任何其他值，包括 @code{NaN} 。 @code{inf} 和 @code{-inf} 只被认为接近自己。


3.5 新版功能.



@subsubheading 参见


@geindex Python 提高建议; PEP 485
PEP 485@footnote{https://www.python.org/dev/peps/pep-0485} —— 用于测试近似相等的函数

@end deffn

@node 常量<3>,,分类函数,cmath --- 关于复数的数学函数
@anchor{library/cmath constants}@anchor{19eb}
@subsubsection 常量


@geindex pi() (在 cmath 模块中)
@anchor{library/cmath cmath pi}@anchor{19ec}
@deffn {数据} cmath.pi

数学常数 @emph{π} ，作为一个浮点数。
@end deffn

@geindex e() (在 cmath 模块中)
@anchor{library/cmath cmath e}@anchor{19ed}
@deffn {数据} cmath.e

数学常数 @emph{e} ，作为一个浮点数。
@end deffn

@geindex tau() (在 cmath 模块中)
@anchor{library/cmath cmath tau}@anchor{51f}
@deffn {数据} cmath.tau

数学常数 @emph{τ} ，作为一个浮点数。


3.6 新版功能.

@end deffn

@geindex inf() (在 cmath 模块中)
@anchor{library/cmath cmath inf}@anchor{520}
@deffn {数据} cmath.inf

浮点正无穷大。相当于 @code{float('inf')}。


3.6 新版功能.

@end deffn

@geindex infj() (在 cmath 模块中)
@anchor{library/cmath cmath infj}@anchor{524}
@deffn {数据} cmath.infj

具有零实部和正无穷虚部的复数。相当于 @code{complex(0.0, float('inf'))}。


3.6 新版功能.

@end deffn

@geindex nan() (在 cmath 模块中)
@anchor{library/cmath cmath nan}@anchor{521}
@deffn {数据} cmath.nan

浮点“非数字”（NaN）值。相当于 @code{float('nan')}。


3.6 新版功能.

@end deffn

@geindex nanj() (在 cmath 模块中)
@anchor{library/cmath cmath nanj}@anchor{525}
@deffn {数据} cmath.nanj

具有零实部和 NaN 虚部的复数。相当于 @code{complex(0.0, float('nan'))}。


3.6 新版功能.

@end deffn

@geindex 模块; math

请注意，函数的选择与模块 @ref{b1,,math} 中的函数选择相似，但不完全相同。 拥有两个模块的原因是因为有些用户对复数不感兴趣，甚至根本不知道它们是什么。它们宁愿 @code{math.sqrt(-1)} 引发异常，也不想返回一个复数。 另请注意，被 @ref{19,,cmath} 定义的函数始终会返回一个复数，尽管答案可以表示为一个实数（在这种情况下，复数的虚数部分为零）。

关于分歧点的注释：它们是沿着给定函数无法连续的曲线。它们是许多复杂函数的必要特征。假设您需要使用复杂函数进行计算，您将了解分歧点。请参阅几乎所有关于复杂变量的（不太基本）的书来进行启发。关于分歧点数值目的的正确选择信息，应提供以下良好参考：


@subsubheading 参见


Kahan, W: Branch cuts for complex elementary functions; or, Much ado about nothing's sign bit. In Iserles, A., and Powell, M. (eds.), The state of the art in numerical analysis. Clarendon Press (1987) pp165--211.


@node decimal --- 十进制定点和浮点运算,fractions --- 分数,cmath --- 关于复数的数学函数,数字和数学模块
@anchor{library/decimal doc}@anchor{19ee}@anchor{library/decimal decimal-decimal-fixed-point-and-floating-point-arithmetic}@anchor{19ef}@anchor{library/decimal module-decimal}@anchor{36}
@subsection @code{decimal} --- 十进制定点和浮点运算


@geindex decimal (模块)

@strong{源码：} Lib/decimal.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/decimal.py}

@c import modules for testing inline doctests with the Sphinx doctest builder

@c import decimal
@c import math
@c from decimal import *
@c # make sure each group gets a fresh context
@c setcontext(Context())

@c # make sure other tests (outside this file) get a fresh context
@c setcontext(Context())


__________________________________________________________________


@ref{36,,decimal} 模块为快速正确舍入的十进制浮点运算提供支持。 与 @ref{187,,float} 数据类型相比，它具有以下几个优点：


@itemize *

@item 
Decimal 类型的“设计是基于考虑人类习惯的浮点数模型，并且因此具有以下最高指导原则 —— 计算机必须提供与人们在学校所学习的算术相一致的算术。” —— 摘自 decimal 算术规范描述。

@item 
Decimal 数字的表示是完全精确的。 相比之下，@code{1.1} 和 @code{2.2} 这样的数字在二进制浮点中没有精确的表示。 最终用户通常不希望 @code{1.1 + 2.2} 如二进制浮点数表示那样被显示为 @code{3.3000000000000003}。

@item 
精确性会延续到算术类操作中。 对于 decimal 浮点数，@code{0.1 + 0.1 + 0.1 - 0.3} 会精确地等于零。 而对于二进制浮点数，结果则为 @code{5.5511151231257827e-017} 。 虽然接近于零，但其中的误差将妨碍可靠的相等性检验，并且误差还会不断累积。 因此，decimal 更适合具有严格相等不变性要求的会计类应用。

@item 
十进制模块包含有效位的概念，因此 @code{1.30 + 1.20} 的结果是 @code{2.50} 。 保留尾随零以表示有效位。 这是货币的惯用表示方法。乘法则沿用 “教科书“ 中：保留被乘数中的所有数字的方法。 例如， @code{1.3 * 1.2} 结果是 @code{1.56} 而 @code{1.30 * 1.20} 结果是 @code{1.5600} 。

@item 
与基于硬件的二进制浮点不同，十进制模块具有用户可更改的精度（默认为28位），可以与给定问题所需的一样大：

@example
>>> from decimal import *
>>> getcontext().prec = 6
>>> Decimal(1) / Decimal(7)
Decimal('0.142857')
>>> getcontext().prec = 28
>>> Decimal(1) / Decimal(7)
Decimal('0.1428571428571428571428571429')
@end example

@item 
二进制和 decimal 浮点数都是根据已发布的标准实现的。 虽然内置浮点类型只公开其功能的一小部分，但 decimal 模块公开了标准的所有必需部分。 在需要时，程序员可以完全控制舍入和信号处理。 这包括通过使用异常来阻止任何不精确操作来强制执行精确算术的选项。

@item 
decimal 模块旨在支持“无偏差，精确无舍入的十进制算术（有时称为定点数算术）和有舍入的浮点数算术”。 —— 摘自 decimal 算术规范说明。
@end itemize

该模块的设计以三个概念为中心：decimal 数值，算术上下文和信号。

decimal 数值是不可变对象。 它由符号，系数和指数位组成。 为了保持有效位，系数位不会截去末尾零。 decimal 数值也包括特殊值例如 @code{Infinity} ，@code{-Infinity} 和 @code{NaN} 。 该标准还区分 @code{-0} 和 @code{+0} 。

算术的上下文是指定精度、舍入规则、指数限制、指示操作结果的标志以及确定符号是否被视为异常的陷阱启用器的环境。 舍入选项包括 @ref{19f0,,ROUND_CEILING} 、 @ref{19f1,,ROUND_DOWN} 、 @ref{19f2,,ROUND_FLOOR} 、 @ref{19f3,,ROUND_HALF_DOWN}, @ref{19f4,,ROUND_HALF_EVEN} 、 @ref{19f5,,ROUND_HALF_UP} 、 @ref{19f6,,ROUND_UP} 以及 @ref{19f7,,ROUND_05UP}.

信号是在计算过程中出现的异常条件组。 根据应用程序的需要，信号可能会被忽略，被视为信息，或被视为异常。 十进制模块中的信号有：@ref{19f8,,Clamped} 、 @ref{9e5,,InvalidOperation} 、 @ref{19f9,,DivisionByZero} 、 @ref{19fa,,Inexact} 、 @ref{19fb,,Rounded} 、 @ref{19fc,,Subnormal} 、 @ref{19fd,,Overflow} 、 @ref{19fe,,Underflow} 以及 @ref{9df,,FloatOperation} 。

对于每个信号，都有一个标志和一个陷阱启动器。 遇到信号时，其标志设置为 1 ，然后，如果陷阱启用器设置为 1 ，则引发异常。 标志是粘性的，因此用户需要在监控计算之前重置它们。


@subsubheading 参见



@itemize *

@item 
IBM 的通用十进制算术规范描述 The General Decimal Arithmetic Specification@footnote{http://speleotrove.com/decimal/decarith.html}。
@end itemize


@c %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

@menu
* 快速入门教程:: 
* Decimal 对象:: 
* 上下文对象:: 
* 常量: 常量<4>. 
* 舍入模式:: 
* 信号:: 
* 浮点数说明:: 
* 使用线程:: 
* 例程:: 
* Decimal 常见问题:: 

@end menu

@node 快速入门教程,Decimal 对象,,decimal --- 十进制定点和浮点运算
@anchor{library/decimal decimal-tutorial}@anchor{19ff}@anchor{library/decimal quick-start-tutorial}@anchor{1a00}
@subsubsection 快速入门教程


通常使用 decimal 的方式是先导入该模块，通过 @ref{1a01,,getcontext()} 查看当前上下文，并在必要时为精度、舍入或启用的陷阱设置新值:

@example
>>> from decimal import *
>>> getcontext()
Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,
        capitals=1, clamp=0, flags=[], traps=[Overflow, DivisionByZero,
        InvalidOperation])

>>> getcontext().prec = 7       # Set a new precision
@end example

可以基于整数、字符串、浮点数或元组构造 Decimal 实例。 基于整数或浮点数构造将执行该整数或浮点值的精确转换。 Decimal 数字包括特殊值例如 @code{NaN} 表示“非数字”，正的和负的 @code{Infinity} 和 @code{-0}

@example
>>> getcontext().prec = 28
>>> Decimal(10)
Decimal('10')
>>> Decimal('3.14')
Decimal('3.14')
>>> Decimal(3.14)
Decimal('3.140000000000000124344978758017532527446746826171875')
>>> Decimal((0, (3, 1, 4), -2))
Decimal('3.14')
>>> Decimal(str(2.0 ** 0.5))
Decimal('1.4142135623730951')
>>> Decimal(2) ** Decimal('0.5')
Decimal('1.414213562373095048801688724')
>>> Decimal('NaN')
Decimal('NaN')
>>> Decimal('-Infinity')
Decimal('-Infinity')
@end example

如果 @ref{9df,,FloatOperation} 信号被捕获，构造函数中的小数和浮点数的意外混合或排序比较会引发异常

@example
>>> c = getcontext()
>>> c.traps[FloatOperation] = True
>>> Decimal(3.14)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
decimal.FloatOperation: [<class 'decimal.FloatOperation'>]
>>> Decimal('3.5') < 3.7
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
decimal.FloatOperation: [<class 'decimal.FloatOperation'>]
>>> Decimal('3.5') == 3.5
True
@end example


3.3 新版功能.


新 Decimal 的重要性仅由输入的位数决定。 上下文精度和舍入仅在算术运算期间发挥作用。

@example
>>> getcontext().prec = 6
>>> Decimal('3.0')
Decimal('3.0')
>>> Decimal('3.1415926535')
Decimal('3.1415926535')
>>> Decimal('3.1415926535') + Decimal('2.7182818285')
Decimal('5.85987')
>>> getcontext().rounding = ROUND_UP
>>> Decimal('3.1415926535') + Decimal('2.7182818285')
Decimal('5.85988')
@end example

如果超出了 C 版本的内部限制，则构造一个 decimal 将引发 @ref{9e5,,InvalidOperation}

@example
>>> Decimal("1e9999999999999999999")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
decimal.InvalidOperation: [<class 'decimal.InvalidOperation'>]
@end example


在 3.3 版更改.


Decimal 数字能很好地与 Python 的其余部分交互。 以下是一个小小的 decimal 浮点数飞行马戏团：

@example
>>> data = list(map(Decimal, '1.34 1.87 3.45 2.35 1.00 0.03 9.25'.split()))
>>> max(data)
Decimal('9.25')
>>> min(data)
Decimal('0.03')
>>> sorted(data)
[Decimal('0.03'), Decimal('1.00'), Decimal('1.34'), Decimal('1.87'),
 Decimal('2.35'), Decimal('3.45'), Decimal('9.25')]
>>> sum(data)
Decimal('19.29')
>>> a,b,c = data[:3]
>>> str(a)
'1.34'
>>> float(a)
1.34
>>> round(a, 1)
Decimal('1.3')
>>> int(a)
1
>>> a * 5
Decimal('6.70')
>>> a * b
Decimal('2.5058')
>>> c % a
Decimal('0.77')
@end example

Decimal 也可以使用一些数学函数：

@example
>>> getcontext().prec = 28
>>> Decimal(2).sqrt()
Decimal('1.414213562373095048801688724')
>>> Decimal(1).exp()
Decimal('2.718281828459045235360287471')
>>> Decimal('10').ln()
Decimal('2.302585092994045684017991455')
>>> Decimal('10').log10()
Decimal('1')
@end example

@code{quantize()} 方法将数字舍入为固定指数。 此方法对于将结果舍入到固定的位置的货币应用程序非常有用：

@example
>>> Decimal('7.325').quantize(Decimal('.01'), rounding=ROUND_DOWN)
Decimal('7.32')
>>> Decimal('7.325').quantize(Decimal('1.'), rounding=ROUND_UP)
Decimal('8')
@end example

如上所示，@ref{1a01,,getcontext()} 函数访问当前上下文并允许更改设置。 这种方法满足大多数应用程序的需求。

对于更高级的工作，使用 Context() 构造函数创建备用上下文可能很有用。 要使用备用活动，请使用 @ref{1a02,,setcontext()} 函数。

根据标准，@ref{36,,decimal} 模块提供了两个现成的标准上下文 @ref{9e3,,BasicContext} 和 @ref{9e4,,ExtendedContext} 。 前者对调试特别有用，因为许多陷阱都已启用：

@example
>>> myothercontext = Context(prec=60, rounding=ROUND_HALF_DOWN)
>>> setcontext(myothercontext)
>>> Decimal(1) / Decimal(7)
Decimal('0.142857142857142857142857142857142857142857142857142857142857')

>>> ExtendedContext
Context(prec=9, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,
        capitals=1, clamp=0, flags=[], traps=[])
>>> setcontext(ExtendedContext)
>>> Decimal(1) / Decimal(7)
Decimal('0.142857143')
>>> Decimal(42) / Decimal(0)
Decimal('Infinity')

>>> setcontext(BasicContext)
>>> Decimal(42) / Decimal(0)
Traceback (most recent call last):
  File "<pyshell#143>", line 1, in -toplevel-
    Decimal(42) / Decimal(0)
DivisionByZero: x / 0
@end example

上下文还具有用于监视计算期间遇到的异常情况的信号标志。 标志保持设置直到明确清除，因此最好通过使用 @code{clear_flags()} 方法清除每组受监控计算之前的标志。:

@example
>>> setcontext(ExtendedContext)
>>> getcontext().clear_flags()
>>> Decimal(355) / Decimal(113)
Decimal('3.14159292')
>>> getcontext()
Context(prec=9, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,
        capitals=1, clamp=0, flags=[Inexact, Rounded], traps=[])
@end example

@emph{flags} 条目显示对 @code{Pi} 的有理逼近被舍入（超出上下文精度的数字被抛弃）并且结果是不精确的（一些丢弃的数字不为零）。

使用上下文的 @code{traps} 字段中的字典设置单个陷阱：

@example
>>> setcontext(ExtendedContext)
>>> Decimal(1) / Decimal(0)
Decimal('Infinity')
>>> getcontext().traps[DivisionByZero] = 1
>>> Decimal(1) / Decimal(0)
Traceback (most recent call last):
  File "<pyshell#112>", line 1, in -toplevel-
    Decimal(1) / Decimal(0)
DivisionByZero: x / 0
@end example

大多数程序仅在程序开始时调整当前上下文一次。 并且，在许多应用程序中，数据在循环内单个强制转换为 @ref{188,,Decimal} 。 通过创建上下文集和小数，程序的大部分操作数据与其他 Python 数字类型没有区别。

@c %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

@node Decimal 对象,上下文对象,快速入门教程,decimal --- 十进制定点和浮点运算
@anchor{library/decimal decimal-decimal}@anchor{1a03}@anchor{library/decimal decimal-objects}@anchor{1a04}
@subsubsection Decimal 对象


@geindex Decimal (decimal 中的类)
@anchor{library/decimal decimal Decimal}@anchor{188}
@deffn {类} decimal.Decimal (value="0", context=None)

根据 @emph{value} 构造一个新的 @ref{188,,Decimal} 对象。

@emph{value} 可以是整数，字符串，元组，@ref{187,,float} ，或另一个 @ref{188,,Decimal} 对象。 如果没有给出 @emph{value}，则返回 @code{Decimal('0')}。 如果 @emph{value} 是一个字符串，它应该在前导和尾随空格字符以及下划线被删除之后符合十进制数字字符串语法:

@example
sign           ::=  '+' | '-'
digit          ::=  '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
indicator      ::=  'e' | 'E'
digits         ::=  digit [digit]...
decimal-part   ::=  digits '.' [digits] | ['.'] digits
exponent-part  ::=  indicator [sign] digits
infinity       ::=  'Infinity' | 'Inf'
nan            ::=  'NaN' [digits] | 'sNaN' [digits]
numeric-value  ::=  decimal-part [exponent-part] | infinity
numeric-string ::=  [sign] numeric-value | [sign] nan
@end example

当上面出现 @code{digit} 时也允许其他十进制数码。 其中包括来自各种其他语言系统的十进制数码（例如阿拉伯-印地语和天城文的数码）以及全宽数码 @code{'\uff10'} 到 @code{'\uff19'}。

如果 @emph{value} 是一个 @ref{478,,tuple} ，它应该有三个组件，一个符号（ @code{0} 表示正数或 @code{1} 表示负数），一个数字的 @ref{478,,tuple} 和整数指数。 例如， @code{Decimal((0, (1, 4, 1, 4), -3))} 返回 @code{Decimal('1.414')}。

如果 @emph{value} 是 @ref{187,,float} ，则二进制浮点值无损地转换为其精确的十进制等效值。 此转换通常需要53位或更多位数的精度。 例如， @code{Decimal(float('1.1'))} 转换为`@w{`}Decimal('1.100000000000000088817841970012523233890533447265625')`@w{`}。

@emph{context} 精度不会影响存储的位数。 这完全由 @emph{value} 中的位数决定。 例如，@code{Decimal('3.00000')} 记录所有五个零，即使上下文精度只有三。

@emph{context} 参数的目的是确定 @emph{value} 是格式错误的字符串时该怎么做。 如果上下文陷阱 @ref{9e5,,InvalidOperation}，则引发异常；否则，构造函数返回一个新的 Decimal，其值为 @code{NaN}。

构造完成后， @ref{188,,Decimal} 对象是不可变的。


在 3.2 版更改: 现在允许构造函数的参数为 @ref{187,,float} 实例。



在 3.3 版更改: @ref{187,,float} 参数在设置 @ref{9df,,FloatOperation} 陷阱时引发异常。 默认情况下，陷阱已关闭。



在 3.6 版更改: 允许下划线进行分组，就像代码中的整数和浮点文字一样。


十进制浮点对象与其他内置数值类型共享许多属性，例如 @ref{187,,float} 和 @ref{184,,int} 。 所有常用的数学运算和特殊方法都适用。 同样，十进制对象可以复制、pickle、打印、用作字典键、用作集合元素、比较、排序和强制转换为另一种类型（例如 @ref{187,,float} 或 @ref{184,,int} ）。

算术对十进制对象和算术对整数和浮点数有一些小的差别。 当余数运算符 @code{%} 应用于Decimal对象时，结果的符号是 @emph{被除数} 的符号，而不是除数的符号:

@example
>>> (-7) % 4
1
>>> Decimal(-7) % Decimal(4)
Decimal('-3')
@end example

整数除法运算符 @code{//} 的行为类似，返回真商的整数部分（截断为零）而不是它的向下取整，以便保留通常的标识 @code{x == (x // y) * y + x % y}:

@example
>>> -7 // 4
-2
>>> Decimal(-7) // Decimal(4)
Decimal('-1')
@end example

@code{%} 和 @code{//} 运算符实现了 @code{remainder} 和 @code{divide-integer} 操作（分别），如规范中所述。

十进制对象通常不能与浮点数或 @ref{185,,fractions.Fraction} 实例在算术运算中结合使用：例如,尝试将 @ref{188,,Decimal} 加到 @ref{187,,float} ，将引发 @ref{192,,TypeError}。 但是，可以使用 Python 的比较运算符来比较 @ref{188,,Decimal} 实例 @code{x} 和另一个数字 @code{y} 。 这样可以避免在对不同类型的数字进行相等比较时混淆结果。


在 3.2 版更改: 现在完全支持 @ref{188,,Decimal} 实例和其他数字类型之间的混合类型比较。


除了标准的数字属性，十进制浮点对象还有许多专门的方法：

@geindex adjusted() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal adjusted}@anchor{1a05}
@deffn {方法} adjusted ()

在移出系数最右边的数字之后返回调整后的指数，直到只剩下前导数字：@code{Decimal('321e+5').adjusted()} 返回 7 。 用于确定最高有效位相对于小数点的位置。
@end deffn

@geindex as_integer_ratio() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal as_integer_ratio}@anchor{536}
@deffn {方法} as_integer_ratio ()

返回一对 @code{(n, d)} 整数，表示给定的 @ref{188,,Decimal} 实例作为分数、最简形式项并带有正分母:

@example
>>> Decimal('-3.14').as_integer_ratio()
(-157, 50)
@end example

转换是精确的。 在 Infinity 上引发 OverflowError ，在 NaN 上引起 ValueError 。
@end deffn


3.6 新版功能.


@geindex as_tuple() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal as_tuple}@anchor{1a06}
@deffn {方法} as_tuple ()

返回一个 @ref{a9e,,named tuple} 表示的数字： @code{DecimalTuple(sign, digits, exponent)}。
@end deffn

@geindex canonical() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal canonical}@anchor{1a07}
@deffn {方法} canonical ()

返回参数的规范编码。 目前，一个 @ref{188,,Decimal} 实例的编码始终是规范的，因此该操作返回其参数不变。
@end deffn

@geindex compare() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal compare}@anchor{1a08}
@deffn {方法} compare (other, context=None)

比较两个 Decimal 实例的值。 @ref{1a08,,compare()} 返回一个 Decimal 实例，如果任一操作数是 NaN ，那么结果是 NaN

@example
a or b is a NaN  ==> Decimal('NaN')
a < b            ==> Decimal('-1')
a == b           ==> Decimal('0')
a > b            ==> Decimal('1')
@end example
@end deffn

@geindex compare_signal() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal compare_signal}@anchor{1a09}
@deffn {方法} compare_signal (other, context=None)

除了所有 NaN 信号之外，此操作与 @ref{1a08,,compare()} 方法相同。 也就是说，如果两个操作数都不是信令NaN，那么任何静默的 NaN 操作数都被视为信令NaN。
@end deffn

@geindex compare_total() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal compare_total}@anchor{1a0a}
@deffn {方法} compare_total (other, context=None)

使用它们的抽象表示而不是它们的数值来比较两个操作数。 类似于 @ref{1a08,,compare()} 方法，但结果给出了一个总排序 @ref{188,,Decimal} 实例。 两个 @ref{188,,Decimal} 实例具有相同的数值但不同的表示形式在此排序中比较不相等：

@example
>>> Decimal('12.0').compare_total(Decimal('12'))
Decimal('-1')
@end example

静默和发出信号的 NaN 也包括在总排序中。 这个函数的结果是 @code{Decimal('0')} 如果两个操作数具有相同的表示，或是 @code{Decimal('-1')} 如果第一个操作数的总顺序低于第二个操作数，或是 @code{Decimal('1')} 如果第一个操作数在总顺序中高于第二个操作数。 有关总排序的详细信息，请参阅规范。

此操作不受上下文影响且静默：不更改任何标志且不执行舍入。 作为例外，如果无法准确转换第二个操作数，则C版本可能会引发InvalidOperation。
@end deffn

@geindex compare_total_mag() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal compare_total_mag}@anchor{1a0b}
@deffn {方法} compare_total_mag (other, context=None)

比较两个操作数使用它们的抽象表示而不是它们的值，如 @ref{1a0a,,compare_total()}，但忽略每个操作数的符号。 @code{x.compare_total_mag(y)} 相当于 @code{x.copy_abs().compare_total(y.copy_abs())}。

此操作不受上下文影响且静默：不更改任何标志且不执行舍入。 作为例外，如果无法准确转换第二个操作数，则C版本可能会引发InvalidOperation。
@end deffn

@geindex conjugate() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal conjugate}@anchor{1a0c}
@deffn {方法} conjugate ()

只返回self，这种方法只符合 Decimal 规范。
@end deffn

@geindex copy_abs() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal copy_abs}@anchor{1a0d}
@deffn {方法} copy_abs ()

返回参数的绝对值。 此操作不受上下文影响并且是静默的：没有更改标志且不执行舍入。
@end deffn

@geindex copy_negate() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal copy_negate}@anchor{1a0e}
@deffn {方法} copy_negate ()

回到参数的否定。 此操作不受上下文影响并且是静默的：没有标志更改且不执行舍入。
@end deffn

@geindex copy_sign() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal copy_sign}@anchor{1a0f}
@deffn {方法} copy_sign (other, context=None)

返回第一个操作数的副本，其符号设置为与第二个操作数的符号相同。 例如：

@example
>>> Decimal('2.3').copy_sign(Decimal('-1.5'))
Decimal('-2.3')
@end example

此操作不受上下文影响且静默：不更改任何标志且不执行舍入。 作为例外，如果无法准确转换第二个操作数，则C版本可能会引发InvalidOperation。
@end deffn

@geindex exp() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal exp}@anchor{9e7}
@deffn {方法} exp (context=None)

返回给定数字的（自然）指数函数`@w{`}e**x`@w{`}的值。结果使用 @ref{19f4,,ROUND_HALF_EVEN} 舍入模式正确舍入。

@example
>>> Decimal(1).exp()
Decimal('2.718281828459045235360287471')
>>> Decimal(321).exp()
Decimal('2.561702493119680037517373933E+139')
@end example
@end deffn

@geindex from_float() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal from_float}@anchor{b79}
@deffn {方法} from_float (f)

将浮点数转换为十进制数的类方法。

注意， @cite{Decimal.from_float(0.1)} 与 @cite{Decimal('0.1')} 不同。 由于 0.1 在二进制浮点中不能精确表示，因此该值存储为最接近的可表示值，即 @cite{0x1.999999999999ap-4} 。 十进制的等效值是`0.1000000000000000055511151231257827021181583404541015625`。

@cartouche
@quotation 注解 
从 Python 3.2 开始，@ref{188,,Decimal} 实例也可以直接从 @ref{187,,float} 构造。
@end quotation
@end cartouche

@example
>>> Decimal.from_float(0.1)
Decimal('0.1000000000000000055511151231257827021181583404541015625')
>>> Decimal.from_float(float('nan'))
Decimal('NaN')
>>> Decimal.from_float(float('inf'))
Decimal('Infinity')
>>> Decimal.from_float(float('-inf'))
Decimal('-Infinity')
@end example


3.1 新版功能.

@end deffn

@geindex fma() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal fma}@anchor{1a10}
@deffn {方法} fma (other, third, context=None)

混合乘法加法。 返回 self*other+third ，中间乘积 self*other 没有舍入。

@example
>>> Decimal(2).fma(3, 5)
Decimal('11')
@end example
@end deffn

@geindex is_canonical() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_canonical}@anchor{1a11}
@deffn {方法} is_canonical ()

如果参数是规范的，则为返回 @ref{494,,True}，否则为 @ref{380,,False} 。 目前，@ref{188,,Decimal} 实例总是规范的，所以这个操作总是返回 @ref{494,,True} 。
@end deffn

@geindex is_finite() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_finite}@anchor{1a12}
@deffn {方法} is_finite ()

如果参数是一个有限的数，则返回为 @ref{494,,True} ；如果参数为无穷大或 NaN ，则返回为 @ref{380,,False}。
@end deffn

@geindex is_infinite() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_infinite}@anchor{1a13}
@deffn {方法} is_infinite ()

如果参数为正负无穷大，则返回为 @ref{494,,True} ，否则为 @ref{380,,False} 。
@end deffn

@geindex is_nan() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_nan}@anchor{1a14}
@deffn {方法} is_nan ()

如果参数为 NaN （无论是否静默），则返回为 @ref{494,,True} ，否则为 @ref{380,,False} 。
@end deffn

@geindex is_normal() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_normal}@anchor{1a15}
@deffn {方法} is_normal (context=None)

如果参数是一个 @emph{标准的} 有限数则返回 @ref{494,,True}。 如果参数为零、次标准数、无穷大或 NaN 则返回 @ref{380,,False}。
@end deffn

@geindex is_qnan() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_qnan}@anchor{1a16}
@deffn {方法} is_qnan ()

如果参数为静默 NaN，返回 @ref{494,,True}，否则返回 @ref{380,,False}。
@end deffn

@geindex is_signed() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_signed}@anchor{1a17}
@deffn {方法} is_signed ()

如果参数带有负号，则返回为 @ref{494,,True}，否则返回 @ref{380,,False}。注意，0 和 NaN 都可带有符号。
@end deffn

@geindex is_snan() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_snan}@anchor{1a18}
@deffn {方法} is_snan ()

如果参数为显式 NaN，则返回 @ref{494,,True}，否则返回 @ref{380,,False}。
@end deffn

@geindex is_subnormal() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_subnormal}@anchor{1a19}
@deffn {方法} is_subnormal (context=None)

如果参数为次标准数，则返回 @ref{494,,True}，否则返回 @ref{380,,False}。
@end deffn

@geindex is_zero() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal is_zero}@anchor{1a1a}
@deffn {方法} is_zero ()

如果参数是0（正负皆可），则返回 @ref{494,,True}，否则返回 @ref{380,,False}。
@end deffn

@geindex ln() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal ln}@anchor{9e8}
@deffn {方法} ln (context=None)

返回操作数的自然对数（以 e 为底）。结果是使用 @ref{19f4,,ROUND_HALF_EVEN} 舍入模式正确舍入的。
@end deffn

@geindex log10() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal log10}@anchor{1a1b}
@deffn {方法} log10 (context=None)

返回操作数的以十为底的对数。结果是使用 @ref{19f4,,ROUND_HALF_EVEN} 舍入模式正确舍入的。
@end deffn

@geindex logb() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal logb}@anchor{1a1c}
@deffn {方法} logb (context=None)

对于一个非零数，返回其运算数的调整后指数作为一个 @ref{188,,Decimal} 实例。 如果运算数为零将返回 @code{Decimal('-Infinity')} 并且产生 the @ref{19f9,,DivisionByZero} 标志。如果运算数是无限大则返回 @code{Decimal('Infinity')} 。
@end deffn

@geindex logical_and() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal logical_and}@anchor{1a1d}
@deffn {方法} logical_and (other, context=None)

@ref{1a1d,,logical_and()} 是需要两个 @emph{逻辑运算数} 的逻辑运算（参考 @ref{1a1e,,逻辑操作数} ）。按位输出两运算数的 @code{and} 运算的结果。
@end deffn

@geindex logical_invert() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal logical_invert}@anchor{1a1f}
@deffn {方法} logical_invert (context=None)

@ref{1a1f,,logical_invert()} 是一个逻辑运算。结果是操作数的按位求反。
@end deffn

@geindex logical_or() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal logical_or}@anchor{1a20}
@deffn {方法} logical_or (other, context=None)

@ref{1a20,,logical_or()} 是需要两个 @emph{logical operands} 的逻辑运算（请参阅 @ref{1a1e,,逻辑操作数} ）。结果是两个运算数的按位的 @code{or} 运算。
@end deffn

@geindex logical_xor() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal logical_xor}@anchor{1a21}
@deffn {方法} logical_xor (other, context=None)

@ref{1a21,,logical_xor()} 是需要两个 @emph{逻辑运算数} 的逻辑运算（参考 @ref{1a1e,,逻辑操作数} ）。结果是按位输出的两运算数的异或运算。
@end deffn

@geindex max() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal max}@anchor{1a22}
@deffn {方法} max (other, context=None)

像 @code{max(self, other)} 一样，除了在返回之前应用上下文舍入规则并且用信号通知或忽略 @code{NaN} 值（取决于上下文以及它们是发信号还是安静）。
@end deffn

@geindex max_mag() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal max_mag}@anchor{1a23}
@deffn {方法} max_mag (other, context=None)

与 @ref{1a22,,max()} 方法相似，但是操作数使用绝对值完成比较。
@end deffn

@geindex min() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal min}@anchor{1a24}
@deffn {方法} min (other, context=None)

像 @code{min(self, other)} 一样，除了在返回之前应用上下文舍入规则并且用信号通知或忽略 @code{NaN} 值（取决于上下文以及它们是发信号还是安静）。
@end deffn

@geindex min_mag() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal min_mag}@anchor{1a25}
@deffn {方法} min_mag (other, context=None)

与 @ref{1a24,,min()} 方法相似，但是操作数使用绝对值完成比较。
@end deffn

@geindex next_minus() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal next_minus}@anchor{1a26}
@deffn {方法} next_minus (context=None)

返回小于给定操作数的上下文中可表示的最大数字（或者当前线程的上下文中的可表示的最大数字如果没有给定上下文）。
@end deffn

@geindex next_plus() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal next_plus}@anchor{1a27}
@deffn {方法} next_plus (context=None)

返回大于给定操作数的上下文中可表示的最小数字（或者当前线程的上下文中的可表示的最小数字如果没有给定上下文）。
@end deffn

@geindex next_toward() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal next_toward}@anchor{1a28}
@deffn {方法} next_toward (other, context=None)

如果两运算数不相等，返回在第二个操作数的方向上最接近第一个操作数的数。如果两操作数数值上相等，返回将符号设置为与第二个运算数相同的第一个运算数的拷贝。
@end deffn

@geindex normalize() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal normalize}@anchor{1a29}
@deffn {方法} normalize (context=None)

通过去除尾随的零并将所有结果等于 @code{Decimal('0')} 的转化为 @code{Decimal('0e0')} 来标准化数字。用于为等效类的属性生成规范值。比如， @code{Decimal('32.100')} 和 @code{Decimal('0.321000e+2')} 都被标准化为相同的值 @code{Decimal('32.1')}。
@end deffn

@geindex number_class() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal number_class}@anchor{1a2a}
@deffn {方法} number_class (context=None)

返回一个字符串描述运算数的 @emph{class} 。返回值是以下十个字符串中的一个。


@itemize *

@item 
@code{"-Infinity"} ，指示运算数为负无穷大。

@item 
@code{"-Normal"} ，指示该运算数是负正常数字。

@item 
@code{"-Subnormal"} ，指示该运算数是负的次标准数。

@item 
@code{"-Zero"} ，指示该运算数是负零。

@item 
@code{"-Zero"} ，指示该运算数是正零。

@item 
@code{"+Subnormal"} ，指示该运算数是正的次标准数。

@item 
@code{"+Normal"} ，指示该运算数是正的标准数。

@item 
@code{"+Infinity"} ，指示该运算数是正无穷。

@item 
@code{"NaN"} ，指示该运算数是肃静 NaN （非数字）。

@item 
@code{"sNaN"} ，指示该运算数是信号 NaN 。
@end itemize
@end deffn

@geindex quantize() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal quantize}@anchor{9eb}
@deffn {方法} quantize (exp, rounding=None, context=None)

返回的值等于舍入后的第一个运算数并且具有第二个操作数的指数。

@example
>>> Decimal('1.41421356').quantize(Decimal('1.000'))
Decimal('1.414')
@end example

与其他运算不同，如果量化运算后的系数长度大于精度，那么会发出一个 @ref{9e5,,InvalidOperation} 信号。这保证了除非有一个错误情况，量化指数恒等于右手运算数的指数。

与其他运算不同，量化永不信号下溢，即使结果不正常且不精确。

如果第二个运算数的指数大于第一个运算数的指数那或许需要舍入。在这种情况下，舍入模式由给定 @code{rounding} 参数决定，其余的由给定 @code{context} 参数决定；如果参数都未给定，使用当前线程上下文的舍入模式。

每当结果的指数大于 @code{Emax} 或小于 @code{Etiny} 就会返回错误。
@end deffn

@geindex radix() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal radix}@anchor{1a2b}
@deffn {方法} radix ()

返回 @code{Decimal(10)}，即 @ref{188,,Decimal} 类进行所有算术运算所用的数制（基数）。 这是为保持与规范描述的兼容性而加入的。
@end deffn

@geindex remainder_near() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal remainder_near}@anchor{1a2c}
@deffn {方法} remainder_near (other, context=None)

返回 @emph{self} 除以 @emph{other} 的余数。 这与 @code{self % other} 的区别在于所选择的余数要使其绝对值最小化。 更准确地说，返回值为 @code{self - n * other} 其中 @code{n} 是最接近 @code{self / other} 的实际值的整数，并且如果两个整数与实际值的差相等则会选择其中的偶数。

如果结果为零则其符号将为 @emph{self} 的符号。

@example
>>> Decimal(18).remainder_near(Decimal(10))
Decimal('-2')
>>> Decimal(25).remainder_near(Decimal(10))
Decimal('5')
>>> Decimal(35).remainder_near(Decimal(10))
Decimal('-5')
@end example
@end deffn

@geindex rotate() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal rotate}@anchor{1a2d}
@deffn {方法} rotate (other, context=None)

返回对第一个操作数的数码按第二个操作数所指定的数量进行轮转的结果。 第二个操作数必须为 -precision 至 precision 精度范围内的整数。 第二个操作数的绝对值给出要轮转的位数。 如果第二个操作数为正值则向左轮转；否则向右轮转。 如有必要第一个操作数的系数会在左侧填充零以达到 precision 所指定的长度。 第一个操作数的符号和指数保持不变。
@end deffn

@geindex same_quantum() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal same_quantum}@anchor{1a2e}
@deffn {方法} same_quantum (other, context=None)

检测自身与 other 是否具有相同的指数或是否均为 @code{NaN}。

此操作不受上下文影响且静默：不更改任何标志且不执行舍入。 作为例外，如果无法准确转换第二个操作数，则C版本可能会引发InvalidOperation。
@end deffn

@geindex scaleb() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal scaleb}@anchor{1a2f}
@deffn {方法} scaleb (other, context=None)

返回第一个操作数使用第二个操作数对指数进行调整的结果。 等价于返回第一个操作数乘以 @code{10**other} 的结果。 第二个操作数必须为整数。
@end deffn

@geindex shift() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal shift}@anchor{1a30}
@deffn {方法} shift (other, context=None)

返回第一个操作数的数码按第二个操作数所指定的数量进行移位的结果。 第二个操作数必须为 -precision 至 precision 范围内的整数。 第二个操作数的绝对值给出要移动的位数。 如果第二个操作数为正值则向左移位；否则向右移位。 移入系数的数码为零。 第一个操作数的符号和指数保持不变。
@end deffn

@geindex sqrt() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal sqrt}@anchor{1a31}
@deffn {方法} sqrt (context=None)

返回参数的平方根精确到完整精度。
@end deffn

@geindex to_eng_string() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal to_eng_string}@anchor{1a32}
@deffn {方法} to_eng_string (context=None)

转换为字符串，如果需要指数则会使用工程标注法。

工程标注法的指数是 3 的倍数。 这会在十进制位的左边保留至多 3 个数码，并可能要求添加一至两个末尾零。

例如，此方法会将 @code{Decimal('123E+1')} 转换为 @code{Decimal('1.23E+3')}。
@end deffn

@geindex to_integral() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal to_integral}@anchor{1a33}
@deffn {方法} to_integral (rounding=None, context=None)

与 @ref{1a34,,to_integral_value()} 方法相同。 保留 @code{to_integral} 名称是为了与旧版本兼容。
@end deffn

@geindex to_integral_exact() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal to_integral_exact}@anchor{1a35}
@deffn {方法} to_integral_exact (rounding=None, context=None)

舍入到最接近的整数，发出信号 @ref{19fa,,Inexact} 或者如果发生舍入则相应地发出信号 @ref{19fb,,Rounded}。 如果给出 @code{rounding} 形参则由其确定舍入模式，否则由给定的 @code{context} 来确定。 如果没有给定任何形参则会使用当前上下文的舍入模式。
@end deffn

@geindex to_integral_value() (decimal.Decimal 方法)
@anchor{library/decimal decimal Decimal to_integral_value}@anchor{1a34}
@deffn {方法} to_integral_value (rounding=None, context=None)

舍入到最接近的整数而不发出 @ref{19fa,,Inexact} 或 @ref{19fb,,Rounded} 信号。 如果给出 @emph{rounding} 则会应用其所指定的舍入模式；否则使用所提供的 @emph{context} 或当前上下文的舍入方法。
@end deffn
@end deffn

@menu
* 逻辑操作数:: 

@end menu

@node 逻辑操作数,,,Decimal 对象
@anchor{library/decimal logical-operands}@anchor{1a36}@anchor{library/decimal logical-operands-label}@anchor{1a1e}
@subsubsection 逻辑操作数


@code{logical_and()}, @code{logical_invert()}, @code{logical_or()} 和 @code{logical_xor()} 方法期望其参数为 @emph{逻辑操作数}。 @emph{逻辑操作数} 是指数位与符号位均为零的 @ref{188,,Decimal} 实例，并且其数字位均为 @code{0} 或 @code{1}。

@c %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

@node 上下文对象,常量<4>,Decimal 对象,decimal --- 十进制定点和浮点运算
@anchor{library/decimal context-objects}@anchor{1a37}@anchor{library/decimal decimal-context}@anchor{1a38}
@subsubsection 上下文对象


上下文是算术运算所在的环境。 它们管理精度、设置舍入规则、确定将哪些信号视为异常，并限制指数的范围。

每个线程都有自己的当前上下文，可使用 @ref{1a01,,getcontext()} 和 @ref{1a02,,setcontext()} 函数来读取或修改：

@geindex getcontext() (在 decimal 模块中)
@anchor{library/decimal decimal getcontext}@anchor{1a01}
@deffn {函数} decimal.getcontext ()

返回活动线程的当前上下文。
@end deffn

@geindex setcontext() (在 decimal 模块中)
@anchor{library/decimal decimal setcontext}@anchor{1a02}
@deffn {函数} decimal.setcontext (c)

将活动线程的当前上下文设为 @emph{c}。
@end deffn

你也可以使用 @ref{6e3,,with} 语句和 @ref{1676,,localcontext()} 函数来临时改变活动上下文。

@geindex localcontext() (在 decimal 模块中)
@anchor{library/decimal decimal localcontext}@anchor{1676}
@deffn {函数} decimal.localcontext (ctx=None)

返回一个上下文管理器，它将在进入 with 语句时将活动线程的当前上下文设为 @emph{ctx} 的一个副本并在退出 with 语句时恢复之前的上下文。 如果未指定上下文，则会使用当前上下文的一个副本。

例如，以下代码会将当前 decimal 精度设为 42 位，执行一个运算，然后自动恢复之前的上下文:

@example
from decimal import localcontext

with localcontext() as ctx:
    ctx.prec = 42   # Perform a high precision calculation
    s = calculate_something()
s = +s  # Round the final result back to the default precision
@end example
@end deffn

新的上下文也可使用下述的 @ref{9ea,,Context} 构造器来创建。 此外，模块还提供了三种预设的上下文:

@geindex BasicContext (decimal 中的类)
@anchor{library/decimal decimal BasicContext}@anchor{9e3}
@deffn {类} decimal.BasicContext

这是由通用十进制算术规范描述所定义的标准上下文。 精度设为九。 舍入设为 @ref{19f5,,ROUND_HALF_UP}。 清除所有旗标。 启用所有陷阱（视为异常），但 @ref{19fa,,Inexact}, @ref{19fb,,Rounded} 和 @ref{19fc,,Subnormal} 除外。

由于启用了许多陷阱，此上下文适用于进行调试。
@end deffn

@geindex ExtendedContext (decimal 中的类)
@anchor{library/decimal decimal ExtendedContext}@anchor{9e4}
@deffn {类} decimal.ExtendedContext

这是由通用十进制算术规范描述所定义的标准上下文。 精度设为九。 舍入设为 @ref{19f4,,ROUND_HALF_EVEN}。 清除所有旗标。 不启用任何陷阱（因此在计算期间不会引发异常）。

由于禁用了陷阱，此上下文适用于希望结果值为 @code{NaN} 或 @code{Infinity} 而不是引发异常的应用。 这允许应用在出现当其他情况下会中止程序的条件时仍能完成运行。
@end deffn

@geindex DefaultContext (decimal 中的类)
@anchor{library/decimal decimal DefaultContext}@anchor{9e2}
@deffn {类} decimal.DefaultContext

此上下文被 @ref{9ea,,Context} 构造器用作新上下文的原型。 改变一个字段（例如精度）的效果将是改变 @ref{9ea,,Context} 构造器所创建的新上下文的默认值。

此上下文最适用于多线程环境。 在线程开始前改变一个字段具有设置全系统默认值的效果。 不推荐在线程开始后改变字段，因为这会要求线程同步避免竞争条件。

在单线程环境中，最好完全不使用此上下文。 而是简单地电显式创建上下文，具体如下所述。

默认值为 @code{prec}=@code{28}, @code{rounding}=@ref{19f4,,ROUND_HALF_EVEN}，并为 @ref{19fd,,Overflow}, @ref{9e5,,InvalidOperation} 和 @ref{19f9,,DivisionByZero} 启用陷阱。
@end deffn

在已提供的三种上下文之外，还可以使用 @ref{9ea,,Context} 构造器创建新的上下文。

@geindex Context (decimal 中的类)
@anchor{library/decimal decimal Context}@anchor{9ea}
@deffn {类} decimal.Context (prec=None, rounding=None, Emin=None, Emax=None, capitals=None, clamp=None, flags=None, traps=None)

创建一个新上下文。 如果某个字段未指定或为 @ref{157,,None}，则从 @ref{9e2,,DefaultContext} 拷贝默认值。 如果 @emph{flags} 字段未指定或为 @ref{157,,None}，则清空所有旗标。

@emph{prec} 为一个 [@code{1}, @ref{1a39,,MAX_PREC}] 范围内的整数，用于设置该上下文中算术运算的精度。

@emph{rounding} 选项应为 @ref{1a3a,,Rounding Modes} 小节中列出的常量之一。

@emph{traps} 和 @emph{flags} 字段列出要设置的任何信号。 通常，新上下文应当只设置 traps 而让 flags 为空。

@emph{Emin} 和 @emph{Emax} 字段给定指数所允许的外部上限。 @emph{Emin} 必须在 [@ref{1a3b,,MIN_EMIN}, @code{0}] 范围内，@emph{Emax} 在 [@code{0}, @ref{1a3c,,MAX_EMAX}] 范围内。

@emph{capitals} 字段为 @code{0} 或 @code{1} (默认值)。 如果设为 @code{1}，指数将附带打印大写的 @code{E}；其他情况则将使用小写的 @code{e}: @code{Decimal('6.02e+23')}。

@emph{clamp} 字段为 @code{0} (默认值) 或 @code{1}。 如果设为 @code{1}，则 @ref{188,,Decimal} 实例的指数 @code{e} 的表示范围在此上下文中将严格限制为 @code{Emin - prec + 1 <= e <= Emax - prec + 1}。 如果 @emph{clamp} 为 @code{0} 则将适用较弱的条件: @ref{188,,Decimal} 实例调整后的指数最大值为 @code{Emax}。 当 @emph{clamp} 为 @code{1} 时，一个较大的普通数值将在可能的情况下减小其指数并为其系统添加相应数量的零，以便符合指数值限制；这可以保持数字值但会丢失有效末尾零的信息。 例如:

@example
>>> Context(prec=6, Emax=999, clamp=1).create_decimal('1.23e999')
Decimal('1.23000E+999')
@end example

@emph{clamp} 值为 @code{1} 时即允许与在 IEEE 754 中描述的固定宽度十进制交换格式保持兼容性。

@ref{9ea,,Context} 类定义了几种通用方法以及大量直接在给定上下文中进行算术运算的方法。 此外，对于上述的每种 @ref{188,,Decimal} 方法（不包括 @code{adjusted()} 和 @code{as_tuple()} 方法）都有一个相应的 @ref{9ea,,Context} 方法。 例如，对于一个 @ref{9ea,,Context} 的实例 @code{C} 和 @ref{188,,Decimal} 的实例 @code{x}，@code{C.exp(x)} 就等价于 @code{x.exp(context=C)}。 每个 @ref{9ea,,Context} 方法都接受一个 Python 整数（即 @ref{184,,int} 的实例）在任何接受 Decimal 的实例的地方使用。

@geindex clear_flags() (decimal.Context 方法)
@anchor{library/decimal decimal Context clear_flags}@anchor{1a3d}
@deffn {方法} clear_flags ()

将所有旗标重置为 @code{0}。
@end deffn

@geindex clear_traps() (decimal.Context 方法)
@anchor{library/decimal decimal Context clear_traps}@anchor{1a3e}
@deffn {方法} clear_traps ()

将所有陷阱重置为零 @code{0}。


3.3 新版功能.

@end deffn

@geindex copy() (decimal.Context 方法)
@anchor{library/decimal decimal Context copy}@anchor{1a3f}
@deffn {方法} copy ()

返回上下文的一个副本。
@end deffn

@geindex copy_decimal() (decimal.Context 方法)
@anchor{library/decimal decimal Context copy_decimal}@anchor{1a40}
@deffn {方法} copy_decimal (num)

返回 Decimal 实例 num 的一个副本。
@end deffn

@geindex create_decimal() (decimal.Context 方法)
@anchor{library/decimal decimal Context create_decimal}@anchor{9e6}
@deffn {方法} create_decimal (num)

基于 @emph{num} 创建一个新 Decimal 实例但使用 @emph{self} 作为上下文。 与 @ref{188,,Decimal} 构造器不同，该上下文的精度、舍入方法、旗标和陷阱会被应用于转换过程。

此方法很有用处，因为常量往往被给予高于应用所需的精度。 另一个好处在于立即执行舍入可以消除超出当前精度的数位所导致的意外效果。 在下面的示例中，使用未舍入的输入意味着在总和中添加零会改变结果：

@example
>>> getcontext().prec = 3
>>> Decimal('3.4445') + Decimal('1.0023')
Decimal('4.45')
>>> Decimal('3.4445') + Decimal(0) + Decimal('1.0023')
Decimal('4.44')
@end example

此方法实现了 IBM 规格描述中的转换为数字操作。 如果参数为字符串，则不允许有开头或末尾的空格或下划线。
@end deffn

@geindex create_decimal_from_float() (decimal.Context 方法)
@anchor{library/decimal decimal Context create_decimal_from_float}@anchor{1a41}
@deffn {方法} create_decimal_from_float (f)

基于浮点数 @emph{f} 创建一个新的 Decimal 实例，但会使用 @emph{self} 作为上下文来执行舍入。 与 @ref{b79,,Decimal.from_float()} 类方法不同，上下文的精度、舍入方法、旗标和陷阱会应用到转换中。

@example
>>> context = Context(prec=5, rounding=ROUND_DOWN)
>>> context.create_decimal_from_float(math.pi)
Decimal('3.1415')
>>> context = Context(prec=5, traps=[Inexact])
>>> context.create_decimal_from_float(math.pi)
Traceback (most recent call last):
    ...
decimal.Inexact: None
@end example


3.1 新版功能.

@end deffn

@geindex Etiny() (decimal.Context 方法)
@anchor{library/decimal decimal Context Etiny}@anchor{1a42}
@deffn {方法} Etiny ()

返回一个等于 @code{Emin - prec + 1} 的值即次标准化结果中的最小指数值。 当发生向下溢出时，指数会设为 @ref{1a42,,Etiny}。
@end deffn

@geindex Etop() (decimal.Context 方法)
@anchor{library/decimal decimal Context Etop}@anchor{1a43}
@deffn {方法} Etop ()

返回一个等于 @code{Emax - prec + 1} 的值。
@end deffn

使用 decimal 的通常方式是创建 @ref{188,,Decimal} 实例然后对其应用算术运算,这些运算发生在活动线程的当前上下文中。 一种替代方式则是使用上下文的方法在特定上下文中进行计算。 这些方法类似于 @ref{188,,Decimal} 类的方法，在此仅简单地重新列出。

@geindex abs() (decimal.Context 方法)
@anchor{library/decimal decimal Context abs}@anchor{1a44}
@deffn {方法} abs (x)

返回 @emph{x} 的绝对值。
@end deffn

@geindex add() (decimal.Context 方法)
@anchor{library/decimal decimal Context add}@anchor{1a45}
@deffn {方法} add (x, y)

返回 @emph{x} 与 @emph{y} 的和。
@end deffn

@geindex canonical() (decimal.Context 方法)
@anchor{library/decimal decimal Context canonical}@anchor{c96}
@deffn {方法} canonical (x)

返回相同的 Decimal 对象 @emph{x}。
@end deffn

@geindex compare() (decimal.Context 方法)
@anchor{library/decimal decimal Context compare}@anchor{1a46}
@deffn {方法} compare (x, y)

对 @emph{x} 与 @emph{y} 进行数值比较。
@end deffn

@geindex compare_signal() (decimal.Context 方法)
@anchor{library/decimal decimal Context compare_signal}@anchor{1a47}
@deffn {方法} compare_signal (x, y)

对两个操作数进行数值比较。
@end deffn

@geindex compare_total() (decimal.Context 方法)
@anchor{library/decimal decimal Context compare_total}@anchor{1a48}
@deffn {方法} compare_total (x, y)

对两个操作数使用其抽象表示进行比较。
@end deffn

@geindex compare_total_mag() (decimal.Context 方法)
@anchor{library/decimal decimal Context compare_total_mag}@anchor{1a49}
@deffn {方法} compare_total_mag (x, y)

对两个操作数使用其抽象表示进行比较，忽略符号。
@end deffn

@geindex copy_abs() (decimal.Context 方法)
@anchor{library/decimal decimal Context copy_abs}@anchor{1a4a}
@deffn {方法} copy_abs (x)

返回 @emph{x} 的副本，符号设为 0。
@end deffn

@geindex copy_negate() (decimal.Context 方法)
@anchor{library/decimal decimal Context copy_negate}@anchor{1a4b}
@deffn {方法} copy_negate (x)

返回 @emph{x} 的副本，符号取反。
@end deffn

@geindex copy_sign() (decimal.Context 方法)
@anchor{library/decimal decimal Context copy_sign}@anchor{1a4c}
@deffn {方法} copy_sign (x, y)

从 @emph{y} 拷贝符号至 @emph{x}。
@end deffn

@geindex divide() (decimal.Context 方法)
@anchor{library/decimal decimal Context divide}@anchor{1a4d}
@deffn {方法} divide (x, y)

返回 @emph{x} 除以 @emph{y} 的结果。
@end deffn

@geindex divide_int() (decimal.Context 方法)
@anchor{library/decimal decimal Context divide_int}@anchor{1a4e}
@deffn {方法} divide_int (x, y)

返回 @emph{x} 除以 @emph{y} 的结果，截短为整数。
@end deffn

@geindex divmod() (decimal.Context 方法)
@anchor{library/decimal decimal Context divmod}@anchor{1a4f}
@deffn {方法} divmod (x, y)

两个数字相除并返回结果的整数部分。
@end deffn

@geindex exp() (decimal.Context 方法)
@anchor{library/decimal decimal Context exp}@anchor{1a50}
@deffn {方法} exp (x)

返回 @cite{e ** x}。
@end deffn

@geindex fma() (decimal.Context 方法)
@anchor{library/decimal decimal Context fma}@anchor{1a51}
@deffn {方法} fma (x, y, z)

返回 @emph{x} 乘以 @emph{y} 再加 @emph{z} 的结果。
@end deffn

@geindex is_canonical() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_canonical}@anchor{c97}
@deffn {方法} is_canonical (x)

如果 @emph{x} 是规范的则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex is_finite() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_finite}@anchor{1a52}
@deffn {方法} is_finite (x)

如果 @emph{x} 为有限的则返回`@w{`}True`@w{`}；否则返回 @code{False}。
@end deffn

@geindex is_infinite() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_infinite}@anchor{1a53}
@deffn {方法} is_infinite (x)

如果 @emph{x} 是无限的则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex is_nan() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_nan}@anchor{1a54}
@deffn {方法} is_nan (x)

如果 @emph{x} 是 qNaN 或 sNaN 则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex is_normal() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_normal}@anchor{1a55}
@deffn {方法} is_normal (x)

如果 @emph{x} 是标准数则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex is_qnan() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_qnan}@anchor{1a56}
@deffn {方法} is_qnan (x)

如果 @emph{x} 是静默 NaN 则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex is_signed() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_signed}@anchor{1a57}
@deffn {方法} is_signed (x)

@emph{x} 是负数则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex is_snan() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_snan}@anchor{1a58}
@deffn {方法} is_snan (x)

如果 @emph{x} 是显式 NaN 则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex is_subnormal() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_subnormal}@anchor{1a59}
@deffn {方法} is_subnormal (x)

如果 @emph{x} 是次标准数则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex is_zero() (decimal.Context 方法)
@anchor{library/decimal decimal Context is_zero}@anchor{1a5a}
@deffn {方法} is_zero (x)

如果 @emph{x} 为零则返回 @code{True}；否则返回 @code{False}。
@end deffn

@geindex ln() (decimal.Context 方法)
@anchor{library/decimal decimal Context ln}@anchor{1a5b}
@deffn {方法} ln (x)

返回 @emph{x} 的自然对数（以 e 为底）。
@end deffn

@geindex log10() (decimal.Context 方法)
@anchor{library/decimal decimal Context log10}@anchor{1a5c}
@deffn {方法} log10 (x)

返回 @emph{x} 的以 10 为底的对数。
@end deffn

@geindex logb() (decimal.Context 方法)
@anchor{library/decimal decimal Context logb}@anchor{1a5d}
@deffn {方法} logb (x)

返回操作数的 MSD 等级的指数。
@end deffn

@geindex logical_and() (decimal.Context 方法)
@anchor{library/decimal decimal Context logical_and}@anchor{1a5e}
@deffn {方法} logical_and (x, y)

在操作数的每个数位间应用逻辑运算 @emph{and}。
@end deffn

@geindex logical_invert() (decimal.Context 方法)
@anchor{library/decimal decimal Context logical_invert}@anchor{1a5f}
@deffn {方法} logical_invert (x)

反转 @emph{x} 中的所有数位。
@end deffn

@geindex logical_or() (decimal.Context 方法)
@anchor{library/decimal decimal Context logical_or}@anchor{1a60}
@deffn {方法} logical_or (x, y)

在操作数的每个数位间应用逻辑运算 @emph{or}。
@end deffn

@geindex logical_xor() (decimal.Context 方法)
@anchor{library/decimal decimal Context logical_xor}@anchor{1a61}
@deffn {方法} logical_xor (x, y)

在操作数的每个数位间应用逻辑运算 @emph{xor}。
@end deffn

@geindex max() (decimal.Context 方法)
@anchor{library/decimal decimal Context max}@anchor{1a62}
@deffn {方法} max (x, y)

对两个值执行数字比较并返回其中的最大值。
@end deffn

@geindex max_mag() (decimal.Context 方法)
@anchor{library/decimal decimal Context max_mag}@anchor{1a63}
@deffn {方法} max_mag (x, y)

对两个值执行忽略正负号的数字比较。
@end deffn

@geindex min() (decimal.Context 方法)
@anchor{library/decimal decimal Context min}@anchor{1a64}
@deffn {方法} min (x, y)

对两个值执行数字比较并返回其中的最小值。
@end deffn

@geindex min_mag() (decimal.Context 方法)
@anchor{library/decimal decimal Context min_mag}@anchor{1a65}
@deffn {方法} min_mag (x, y)

对两个值执行忽略正负号的数字比较。
@end deffn

@geindex minus() (decimal.Context 方法)
@anchor{library/decimal decimal Context minus}@anchor{1a66}
@deffn {方法} minus (x)

对应于 Python 中的单目前缀取负运算符执行取负操作。
@end deffn

@geindex multiply() (decimal.Context 方法)
@anchor{library/decimal decimal Context multiply}@anchor{1a67}
@deffn {方法} multiply (x, y)

返回 @emph{x} 和 @emph{y} 的积。
@end deffn

@geindex next_minus() (decimal.Context 方法)
@anchor{library/decimal decimal Context next_minus}@anchor{1a68}
@deffn {方法} next_minus (x)

返回小于 @emph{x} 的最大数字表示形式。
@end deffn

@geindex next_plus() (decimal.Context 方法)
@anchor{library/decimal decimal Context next_plus}@anchor{1a69}
@deffn {方法} next_plus (x)

返回大于 @emph{x} 的最小数字表示形式。
@end deffn

@geindex next_toward() (decimal.Context 方法)
@anchor{library/decimal decimal Context next_toward}@anchor{1a6a}
@deffn {方法} next_toward (x, y)

返回 @emph{x} 趋向于 @emph{y} 的最接近的数字。
@end deffn

@geindex normalize() (decimal.Context 方法)
@anchor{library/decimal decimal Context normalize}@anchor{1a6b}
@deffn {方法} normalize (x)

将 @emph{x} 改写为最简形式。
@end deffn

@geindex number_class() (decimal.Context 方法)
@anchor{library/decimal decimal Context number_class}@anchor{1a6c}
@deffn {方法} number_class (x)

返回 @emph{x} 的类的表示。
@end deffn

@geindex plus() (decimal.Context 方法)
@anchor{library/decimal decimal Context plus}@anchor{1a6d}
@deffn {方法} plus (x)

对应于 Python 中的单目前缀取正运算符执行取正操作。 此操作将应用上下文精度和舍入，因此它 @emph{不是} 标识运算。
@end deffn

@geindex power() (decimal.Context 方法)
@anchor{library/decimal decimal Context power}@anchor{1a6e}
@deffn {方法} power (x, y, modulo=None)

返回 @code{x} 的 @code{y} 次方，如果给出了模数 @code{modulo} 则取其余数。

如为两个参数则计算 @code{x**y}。 如果 @code{x} 为负值则 @code{y} 必须为整数。 除非 @code{y} 为整数且结果为有限值并可在 'precision' 位内精确表示否则结果将是不精确的。 上下文的舍入模式将被使用。 结果在 Python 版中总是会被正确地舍入。

@code{Decimal(0) ** Decimal(0)} results in @code{InvalidOperation}, and if @code{InvalidOperation}
is not trapped, then results in @code{Decimal('NaN')}.


在 3.3 版更改: C 模块计算 @ref{1a6e,,power()} 时会使用已正确舍入的 @ref{1a50,,exp()} 和 @ref{1a5b,,ln()} 函数。 结果是经过良好定义的，但仅限于“几乎总是正确地舍入”。


带有三个参数时，计算 @code{(x**y) % modulo}。 对于三个参数的形式，参数将会应用以下限制：

@quotation


@itemize -

@item 
三个参数必须都是整数

@item 
@code{y} 必须是非负数

@item 
@code{x} 或 @code{y} 至少有一个不为零

@item 
@code{modulo} 必须不为零且至多有 'precision' 位
@end itemize
@end quotation

来自 @code{Context.power(x, y, modulo)} 的结果值等于使用无限精度计算 @code{(x**y) % modulo} 所得到的值，但其计算过程更高效。 结果的指数为零，无论 @code{x}, @code{y} 和 @code{modulo} 的指数是多少。 结果值总是完全精确的。
@end deffn

@geindex quantize() (decimal.Context 方法)
@anchor{library/decimal decimal Context quantize}@anchor{1a6f}
@deffn {方法} quantize (x, y)

返回的值等于 @emph{x} (舍入后)，并且指数为 @emph{y}。
@end deffn

@geindex radix() (decimal.Context 方法)
@anchor{library/decimal decimal Context radix}@anchor{1a70}
@deffn {方法} radix ()

恰好返回 10，因为这是 Decimal 对象 :)
@end deffn

@geindex remainder() (decimal.Context 方法)
@anchor{library/decimal decimal Context remainder}@anchor{1a71}
@deffn {方法} remainder (x, y)

返回整除所得到的余数。

结果的符号，如果不为零，则与原始除数的符号相同。
@end deffn

@geindex remainder_near() (decimal.Context 方法)
@anchor{library/decimal decimal Context remainder_near}@anchor{1a72}
@deffn {方法} remainder_near (x, y)

返回 @code{x - y * n}，其中 @emph{n} 为最接近 @code{x / y} 实际值的整数（如结果为 0 则其符号将与 @emph{x} 的符号相同）。
@end deffn

@geindex rotate() (decimal.Context 方法)
@anchor{library/decimal decimal Context rotate}@anchor{1a73}
@deffn {方法} rotate (x, y)

返回 @emph{x} 翻转 @emph{y} 次的副本。
@end deffn

@geindex same_quantum() (decimal.Context 方法)
@anchor{library/decimal decimal Context same_quantum}@anchor{1a74}
@deffn {方法} same_quantum (x, y)

如果两个操作数具有相同的指数则返回 @code{True}。
@end deffn

@geindex scaleb() (decimal.Context 方法)
@anchor{library/decimal decimal Context scaleb}@anchor{1a75}
@deffn {方法} scaleb (x, y)

返回第一个操作数添加第二个值的指数后的结果。
@end deffn

@geindex shift() (decimal.Context 方法)
@anchor{library/decimal decimal Context shift}@anchor{1a76}
@deffn {方法} shift (x, y)

返回 @emph{x} 变换 @emph{y} 次的副本。
@end deffn

@geindex sqrt() (decimal.Context 方法)
@anchor{library/decimal decimal Context sqrt}@anchor{1a77}
@deffn {方法} sqrt (x)

非负数基于上下文精度的平方根。
@end deffn

@geindex subtract() (decimal.Context 方法)
@anchor{library/decimal decimal Context subtract}@anchor{1a78}
@deffn {方法} subtract (x, y)

返回 @emph{x} 和 @emph{y} 的差。
@end deffn

@geindex to_eng_string() (decimal.Context 方法)
@anchor{library/decimal decimal Context to_eng_string}@anchor{1a79}
@deffn {方法} to_eng_string (x)

转换为字符串，如果需要指数则会使用工程标注法。

工程标注法的指数是 3 的倍数。 这会在十进制位的左边保留至多 3 个数码，并可能要求添加一至两个末尾零。
@end deffn

@geindex to_integral_exact() (decimal.Context 方法)
@anchor{library/decimal decimal Context to_integral_exact}@anchor{1a7a}
@deffn {方法} to_integral_exact (x)

舍入到一个整数。
@end deffn

@geindex to_sci_string() (decimal.Context 方法)
@anchor{library/decimal decimal Context to_sci_string}@anchor{1a7b}
@deffn {方法} to_sci_string (x)

使用科学计数法将一个数字转换为字符串。
@end deffn
@end deffn

@c %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

@node 常量<4>,舍入模式,上下文对象,decimal --- 十进制定点和浮点运算
@anchor{library/decimal constants}@anchor{1a7c}@anchor{library/decimal decimal-rounding-modes}@anchor{1a7d}
@subsubsection 常量


本节中的常量仅与 C 模块相关。 它们也被包含在纯 Python 版本以保持兼容性。


@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

@tab

32位

@tab

64位

@item

@geindex MAX_PREC() (在 decimal 模块中)
@anchor{library/decimal decimal MAX_PREC}@anchor{1a39}
@deffn {数据} decimal.MAX_PREC
@end deffn

@tab

@code{425000000}

@tab

@code{999999999999999999}

@item

@geindex MAX_EMAX() (在 decimal 模块中)
@anchor{library/decimal decimal MAX_EMAX}@anchor{1a3c}
@deffn {数据} decimal.MAX_EMAX
@end deffn

@tab

@code{425000000}

@tab

@code{999999999999999999}

@item

@geindex MIN_EMIN() (在 decimal 模块中)
@anchor{library/decimal decimal MIN_EMIN}@anchor{1a3b}
@deffn {数据} decimal.MIN_EMIN
@end deffn

@tab

@code{-425000000}

@tab

@code{-999999999999999999}

@item

@geindex MIN_ETINY() (在 decimal 模块中)
@anchor{library/decimal decimal MIN_ETINY}@anchor{1a7e}
@deffn {数据} decimal.MIN_ETINY
@end deffn

@tab

@code{-849999999}

@tab

@code{-1999999999999999997}

@end multitable


@geindex HAVE_THREADS() (在 decimal 模块中)
@anchor{library/decimal decimal HAVE_THREADS}@anchor{9e0}
@deffn {数据} decimal.HAVE_THREADS

该值为 @code{True}。 已弃用，因为 Python 现在总是启用线程。
@end deffn


3.9 版后已移除.


@geindex HAVE_CONTEXTVAR() (在 decimal 模块中)
@anchor{library/decimal decimal HAVE_CONTEXTVAR}@anchor{1a7f}
@deffn {数据} decimal.HAVE_CONTEXTVAR

默认值为 @code{True}。 如果 Python 的编译带有 @code{--without-decimal-contextvar} 选项，则 C 版本会使用线程局部而不是协程局部上下文并且该值为 @code{False}。 这在某些嵌套上下文场景中将稍快一些。
@end deffn


3.9 新版功能: 向下移植到 3.7 和 3.8


@node 舍入模式,信号,常量<4>,decimal --- 十进制定点和浮点运算
@anchor{library/decimal rounding-modes}@anchor{1a3a}
@subsubsection 舍入模式


@geindex ROUND_CEILING() (在 decimal 模块中)
@anchor{library/decimal decimal ROUND_CEILING}@anchor{19f0}
@deffn {数据} decimal.ROUND_CEILING

舍入方向为 @code{Infinity}。
@end deffn

@geindex ROUND_DOWN() (在 decimal 模块中)
@anchor{library/decimal decimal ROUND_DOWN}@anchor{19f1}
@deffn {数据} decimal.ROUND_DOWN

舍入方向为零。
@end deffn

@geindex ROUND_FLOOR() (在 decimal 模块中)
@anchor{library/decimal decimal ROUND_FLOOR}@anchor{19f2}
@deffn {数据} decimal.ROUND_FLOOR

舍入方向为 @code{-Infinity}。
@end deffn

@geindex ROUND_HALF_DOWN() (在 decimal 模块中)
@anchor{library/decimal decimal ROUND_HALF_DOWN}@anchor{19f3}
@deffn {数据} decimal.ROUND_HALF_DOWN

舍入到最接近的数，同样接近则舍入方向为零。
@end deffn

@geindex ROUND_HALF_EVEN() (在 decimal 模块中)
@anchor{library/decimal decimal ROUND_HALF_EVEN}@anchor{19f4}
@deffn {数据} decimal.ROUND_HALF_EVEN

舍入到最接近的数，同样接近则舍入到最接近的偶数。
@end deffn

@geindex ROUND_HALF_UP() (在 decimal 模块中)
@anchor{library/decimal decimal ROUND_HALF_UP}@anchor{19f5}
@deffn {数据} decimal.ROUND_HALF_UP

舍入到最接近的数，同样接近则舍入到零的反方向。
@end deffn

@geindex ROUND_UP() (在 decimal 模块中)
@anchor{library/decimal decimal ROUND_UP}@anchor{19f6}
@deffn {数据} decimal.ROUND_UP

舍入到零的反方向。
@end deffn

@geindex ROUND_05UP() (在 decimal 模块中)
@anchor{library/decimal decimal ROUND_05UP}@anchor{19f7}
@deffn {数据} decimal.ROUND_05UP

如果最后一位朝零的方向舍入后为 0 或 5 则舍入到零的反方向；否则舍入方向为零。
@end deffn

@node 信号,浮点数说明,舍入模式,decimal --- 十进制定点和浮点运算
@anchor{library/decimal decimal-signals}@anchor{1a80}@anchor{library/decimal signals}@anchor{1a81}
@subsubsection 信号


信号代表在计算期间引发的条件。 每个信号对应于一个上下文旗标和一个上下文陷阱启用器。

上下文旗标将在遇到特定条件时被设定。 在完成计算之后，将为了获得信息而检测旗标（例如确定计算是否精确）。 在检测旗标后，请确保在开始下一次计算之前清除所有旗标。

如果为信号设定了上下文的陷阱启用器，则条件会导致特定的 Python 异常被引发。 举例来说，如果设定了 @ref{19f9,,DivisionByZero} 陷阱，则当遇到此条件时就将引发 @ref{19f9,,DivisionByZero} 异常。

@geindex Clamped (decimal 中的类)
@anchor{library/decimal decimal Clamped}@anchor{19f8}
@deffn {类} decimal.Clamped

修改一个指数以符合表示限制。

通常，限位将在一个指数超出上下文的 @code{Emin} 和 @code{Emax} 限制时发生。 在可能的情况下，会通过给系数添加零来将指数缩减至符合限制。
@end deffn

@geindex DecimalException (decimal 中的类)
@anchor{library/decimal decimal DecimalException}@anchor{1a82}
@deffn {类} decimal.DecimalException

其他信号的基类，并且也是 @ref{1697,,ArithmeticError} 的一个子类。
@end deffn

@geindex DivisionByZero (decimal 中的类)
@anchor{library/decimal decimal DivisionByZero}@anchor{19f9}
@deffn {类} decimal.DivisionByZero

非无限数被零除的信号。

可在除法、取余队法或对一个数求负数次幂时发生。 如果此信号未被陷阱捕获，则返回 @code{Infinity} 或 @code{-Infinity} 并且由对计算的输入来确定正负符号。
@end deffn

@geindex Inexact (decimal 中的类)
@anchor{library/decimal decimal Inexact}@anchor{19fa}
@deffn {类} decimal.Inexact

表明发生了舍入且结果是不精确的。

有非零数位在舍入期间被丢弃的信号。 舍入结果将被返回。 此信号旗标或陷阱被用于检测结果不精确的情况。
@end deffn

@geindex InvalidOperation (decimal 中的类)
@anchor{library/decimal decimal InvalidOperation}@anchor{9e5}
@deffn {类} decimal.InvalidOperation

执行了一个无效的操作。

表明请求了一个无意义的操作。 如未被陷阱捕获则返回 @code{NaN}。 可能的原因包括:

@example
Infinity - Infinity
0 * Infinity
Infinity / Infinity
x % 0
Infinity % x
sqrt(-x) and x > 0
0 ** 0
x ** (non-integer)
x ** Infinity
@end example
@end deffn

@geindex Overflow (decimal 中的类)
@anchor{library/decimal decimal Overflow}@anchor{19fd}
@deffn {类} decimal.Overflow

数值的溢出。

表明在发生舍入之后的指数大于 @code{Emax}。 如果未被陷阱捕获，则结果将取决于舍入模式，或者向下舍入为最大的可表示有限数，或者向上舍入为 @code{Infinity}。 无论哪种情况，都将引发 @ref{19fa,,Inexact} 和 @ref{19fb,,Rounded} 信号。
@end deffn

@geindex Rounded (decimal 中的类)
@anchor{library/decimal decimal Rounded}@anchor{19fb}
@deffn {类} decimal.Rounded

发生了舍入，但或许并没有信息丢失。

一旦舍入丢弃了数位就会发出此信号；即使被丢弃的数位是零 (例如将 @code{5.00} 舍入为 @code{5.0})。 如果未被陷阱捕获，则不经修改地返回结果。 此信号用于检测有效位数的丢弃。
@end deffn

@geindex Subnormal (decimal 中的类)
@anchor{library/decimal decimal Subnormal}@anchor{19fc}
@deffn {类} decimal.Subnormal

在舍入之前指数低于 @code{Emin}。

当操作结果是次标准数（即指数过小）时就会发出此信号。 如果未被陷阱捕获，则不经修改过返回结果。
@end deffn

@geindex Underflow (decimal 中的类)
@anchor{library/decimal decimal Underflow}@anchor{19fe}
@deffn {类} decimal.Underflow

数字向下溢出导致结果舍入到零。

当一个次标准数结果通过舍入转为零时就会发出此信号。 同时还将引发 @ref{19fa,,Inexact} 和 @ref{19fc,,Subnormal} 信号。
@end deffn

@geindex FloatOperation (decimal 中的类)
@anchor{library/decimal decimal FloatOperation}@anchor{9df}
@deffn {类} decimal.FloatOperation

为 float 和 Decimal 的混合启用更严格的语义。

如果信号未被捕获（默认），则在 @ref{188,,Decimal} 构造器、@ref{9e6,,create_decimal()} 和所有比较运算中允许 float 和 Decimal 的混合。 转换和比较都是完全精确的。 发生的任何混合运算都将通过在上下文旗标中设置 @ref{9df,,FloatOperation} 来静默地记录。 通过 @ref{b79,,from_float()} 或 @ref{1a41,,create_decimal_from_float()} 进行显式转换则不会设置旗标。

在其他情况下（即信号被捕获），则只静默执行相等性比较和显式转换。 所有其他混合运算都将引发 @ref{9df,,FloatOperation}。
@end deffn

以下表格总结了信号的层级结构:

@example
exceptions.ArithmeticError(exceptions.Exception)
    DecimalException
        Clamped
        DivisionByZero(DecimalException, exceptions.ZeroDivisionError)
        Inexact
            Overflow(Inexact, Rounded)
            Underflow(Inexact, Rounded, Subnormal)
        InvalidOperation
        Rounded
        Subnormal
        FloatOperation(DecimalException, exceptions.TypeError)
@end example

@c %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

@node 浮点数说明,使用线程,信号,decimal --- 十进制定点和浮点运算
@anchor{library/decimal decimal-notes}@anchor{1a83}@anchor{library/decimal floating-point-notes}@anchor{1a84}
@subsubsection 浮点数说明


@menu
* 通过提升精度来解决舍入错误:: 
* 特殊的值:: 

@end menu

@node 通过提升精度来解决舍入错误,特殊的值,,浮点数说明
@anchor{library/decimal mitigating-round-off-error-with-increased-precision}@anchor{1a85}
@subsubsection 通过提升精度来解决舍入错误


使用十进制浮点数可以消除十进制表示错误（即能够完全精确地表示 @code{0.1} 这样的数）；然而，某些运算在非零数位超出给定的精度时仍然可能导致舍入错误。

舍入错误的影响可能因接近相互抵销的加减运算被放大从而导致丢失有效位。 Knuth 提供了两个指导性示例，其中出现了精度不足的浮点算术舍入，导致加法的交换律和分配律被打破：

@example
# Examples from Seminumerical Algorithms, Section 4.2.2.
>>> from decimal import Decimal, getcontext
>>> getcontext().prec = 8

>>> u, v, w = Decimal(11111113), Decimal(-11111111), Decimal('7.51111111')
>>> (u + v) + w
Decimal('9.5111111')
>>> u + (v + w)
Decimal('10')

>>> u, v, w = Decimal(20000), Decimal(-6), Decimal('6.0000003')
>>> (u*v) + (u*w)
Decimal('0.01')
>>> u * (v+w)
Decimal('0.0060000')
@end example

@ref{36,,decimal} 模块则可以通过充分地扩展精度来避免有效位的丢失：

@example
>>> getcontext().prec = 20
>>> u, v, w = Decimal(11111113), Decimal(-11111111), Decimal('7.51111111')
>>> (u + v) + w
Decimal('9.51111111')
>>> u + (v + w)
Decimal('9.51111111')
>>>
>>> u, v, w = Decimal(20000), Decimal(-6), Decimal('6.0000003')
>>> (u*v) + (u*w)
Decimal('0.0060000')
>>> u * (v+w)
Decimal('0.0060000')
@end example

@node 特殊的值,,通过提升精度来解决舍入错误,浮点数说明
@anchor{library/decimal special-values}@anchor{1a86}
@subsubsection 特殊的值


@ref{36,,decimal} 模块的数字系统提供了一些特殊的值，包括 @code{NaN}, @code{sNaN}, @code{-Infinity}, @code{Infinity} 以及两种零值 @code{+0} 和 @code{-0}。

无穷大可以使用 @code{Decimal('Infinity')} 来构建。 它们也可以在不捕获 @ref{19f9,,DivisionByZero} 信号捕获时通过除以零来产生。 类似地，当不捕获 @ref{19fd,,Overflow} 信号时，也可以通过舍入到超出最大可表示数字限制的方式产生无穷大的结果。

无穷大是有符号的（仿射）并可用于算术运算，它们会被当作极其巨大的不确定数字来处理。 例如，无穷大加一个常量结果也将为无穷大。

某些不存在有效结果的运算将会返回 @code{NaN}，或者如果捕获了 @ref{9e5,,InvalidOperation} 信号则会引发一个异常。 例如，@code{0/0} 会返回 @code{NaN} 表示结果“不是一个数字”。 这样的 @code{NaN} 是静默产生的，并且在产生之后参与其它计算时总是会得到 @code{NaN} 的结果。 这种行为对于偶而缺少输入的各类计算都很有用处 --- 它允许在将特定结果标记为无效的同时让计算继续运行。

另一种变体形式是 @code{sNaN}，它在每次运算后会发出信号而不是保持静默。 当对于无效结果需要中断计算进行特别处理时，这是一个很有用的返回值。

Python 中比较运算符的行为在涉及 @code{NaN} 时可能会令人有点惊讶。 相等性检测在操作数中有静默型或信号型 @code{NaN} 时总是会返回 @ref{380,,False} (即使是执行 @code{Decimal('NaN')==Decimal('NaN')})，而不等性检测总是会返回 @ref{494,,True}。 当尝试使用 @code{<}, @code{<=}, @code{>} 或 @code{>=} 运算符中的任何一个来比较两个 Decimal 值时，如果运算数中有 @code{NaN} 则将引发 @ref{9e5,,InvalidOperation} 信号，如果此信号未被捕获则将返回 @ref{380,,False}。 请注意通用十进制算术规范并未规定直接比较行为；这些涉及 @code{NaN} 的比较规则来自于 IEEE 854 标准 (见第 5.7 节表 3)。 要确保严格符合标准，请改用 @code{compare()} 和 @code{compare-signal()} 方法。

有符号零值可以由向下溢出的运算产生。 它们保留符号是为了让运算结果能以更高的精度传递。 由于它们的大小为零，正零和负零会被视为相等，且它们的符号具有信息。

在这两个不相同但却相等的有符号零之外，还存在几种零的不同表示形式，它们的精度不同但值也都相等。 这需要一些时间来逐渐适应。 对于习惯了标准浮点表示形式的眼睛来说，以下运算返回等于零的值并不是显而易见的：

@example
>>> 1 / Decimal('Infinity')
Decimal('0E-1000026')
@end example

@c %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

@node 使用线程,例程,浮点数说明,decimal --- 十进制定点和浮点运算
@anchor{library/decimal decimal-threads}@anchor{1a87}@anchor{library/decimal working-with-threads}@anchor{1a88}
@subsubsection 使用线程


@ref{1a01,,getcontext()} 函数会为每个线程访问不同的 @ref{9ea,,Context} 对象。 具有单独线程上下文意味着线程可以修改上下文 (例如 @code{getcontext().prec=10}) 而不影响其他线程。

类似的 @ref{1a02,,setcontext()} 会为当前上下文的目标自动赋值。

如果在调用 @ref{1a02,,setcontext()} 之前调用了 @ref{1a01,,getcontext()}，则 @ref{1a01,,getcontext()} 将自动创建一个新的上下文在当前线程中使用。

新的上下文拷贝自一个名为 @emph{DefaultContext} 的原型上下文。 要控制默认值以便每个线程在应用运行期间都使用相同的值，可以直接修改 @emph{DefaultContext} 对象。 这应当在任何线程启动 @emph{之前} 完成以使得调用 @ref{1a01,,getcontext()} 的线程之间不会产生竞争条件。 例如:

@example
# Set applicationwide defaults for all threads about to be launched
DefaultContext.prec = 12
DefaultContext.rounding = ROUND_DOWN
DefaultContext.traps = ExtendedContext.traps.copy()
DefaultContext.traps[InvalidOperation] = 1
setcontext(DefaultContext)

# Afterwards, the threads can be started
t1.start()
t2.start()
t3.start()
 . . .
@end example

@c %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

@node 例程,Decimal 常见问题,使用线程,decimal --- 十进制定点和浮点运算
@anchor{library/decimal decimal-recipes}@anchor{1a89}@anchor{library/decimal recipes}@anchor{1a8a}
@subsubsection 例程


以下是一些用作工具函数的例程，它们演示了使用 @ref{188,,Decimal} 类的各种方式:

@example
def moneyfmt(value, places=2, curr='@w{'}, sep=',', dp='.',
             pos='@w{'}, neg='-', trailneg='@w{'}):
    """Convert Decimal to a money formatted string.

    places:  required number of places after the decimal point
    curr:    optional currency symbol before the sign (may be blank)
    sep:     optional grouping separator (comma, period, space, or blank)
    dp:      decimal point indicator (comma or period)
             only specify as blank when places is zero
    pos:     optional sign for positive numbers: '+', space or blank
    neg:     optional sign for negative numbers: '-', '(', space or blank
    trailneg:optional trailing minus indicator:  '-', ')', space or blank

    >>> d = Decimal('-1234567.8901')
    >>> moneyfmt(d, curr='$')
    '-$1,234,567.89'
    >>> moneyfmt(d, places=0, sep='.', dp='@w{'}, neg='@w{'}, trailneg='-')
    '1.234.568-'
    >>> moneyfmt(d, curr='$', neg='(', trailneg=')')
    '($1,234,567.89)'
    >>> moneyfmt(Decimal(123456789), sep=' ')
    '123 456 789.00'
    >>> moneyfmt(Decimal('-0.02'), neg='<', trailneg='>')
    '<0.02>'

    """
    q = Decimal(10) ** -places      # 2 places --> '0.01'
    sign, digits, exp = value.quantize(q).as_tuple()
    result = []
    digits = list(map(str, digits))
    build, next = result.append, digits.pop
    if sign:
        build(trailneg)
    for i in range(places):
        build(next() if digits else '0')
    if places:
        build(dp)
    if not digits:
        build('0')
    i = 0
    while digits:
        build(next())
        i += 1
        if i == 3 and digits:
            i = 0
            build(sep)
    build(curr)
    build(neg if sign else pos)
    return '@w{'}.join(reversed(result))

def pi():
    """Compute Pi to the current precision.

    >>> print(pi())
    3.141592653589793238462643383

    """
    getcontext().prec += 2  # extra digits for intermediate steps
    three = Decimal(3)      # substitute "three=3.0" for regular floats
    lasts, t, s, n, na, d, da = 0, three, 3, 1, 0, 0, 24
    while s != lasts:
        lasts = s
        n, na = n+na, na+8
        d, da = d+da, da+32
        t = (t * n) / d
        s += t
    getcontext().prec -= 2
    return +s               # unary plus applies the new precision

def exp(x):
    """Return e raised to the power of x.  Result type matches input type.

    >>> print(exp(Decimal(1)))
    2.718281828459045235360287471
    >>> print(exp(Decimal(2)))
    7.389056098930650227230427461
    >>> print(exp(2.0))
    7.38905609893
    >>> print(exp(2+0j))
    (7.38905609893+0j)

    """
    getcontext().prec += 2
    i, lasts, s, fact, num = 0, 0, 1, 1, 1
    while s != lasts:
        lasts = s
        i += 1
        fact *= i
        num *= x
        s += num / fact
    getcontext().prec -= 2
    return +s

def cos(x):
    """Return the cosine of x as measured in radians.

    The Taylor series approximation works best for a small value of x.
    For larger values, first compute x = x % (2 * pi).

    >>> print(cos(Decimal('0.5')))
    0.8775825618903727161162815826
    >>> print(cos(0.5))
    0.87758256189
    >>> print(cos(0.5+0j))
    (0.87758256189+0j)

    """
    getcontext().prec += 2
    i, lasts, s, fact, num, sign = 0, 0, 1, 1, 1, 1
    while s != lasts:
        lasts = s
        i += 2
        fact *= i * (i-1)
        num *= x * x
        sign *= -1
        s += num / fact * sign
    getcontext().prec -= 2
    return +s

def sin(x):
    """Return the sine of x as measured in radians.

    The Taylor series approximation works best for a small value of x.
    For larger values, first compute x = x % (2 * pi).

    >>> print(sin(Decimal('0.5')))
    0.4794255386042030002732879352
    >>> print(sin(0.5))
    0.479425538604
    >>> print(sin(0.5+0j))
    (0.479425538604+0j)

    """
    getcontext().prec += 2
    i, lasts, s, fact, num, sign = 1, 0, x, 1, x, 1
    while s != lasts:
        lasts = s
        i += 2
        fact *= i * (i-1)
        num *= x * x
        sign *= -1
        s += num / fact * sign
    getcontext().prec -= 2
    return +s
@end example

@c %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

@node Decimal 常见问题,,例程,decimal --- 十进制定点和浮点运算
@anchor{library/decimal decimal-faq}@anchor{1a8b}@anchor{library/decimal id1}@anchor{1a8c}
@subsubsection Decimal 常见问题


Q. 总是输入 @code{decimal.Decimal('1234.5')} 是否过于笨拙。 在使用交互解释器时有没有最小化输入量的方式？

A. 有些用户会将构造器简写为一个字母：

@example
>>> D = decimal.Decimal
>>> D('1.23') + D('3.45')
Decimal('4.68')
@end example

Q. 在带有两个十进制位的定点数应用中，有些输入值具有许多位，需要被舍入。 另一些数则不应具有多余位，需要验证有效性。 这种情况应该用什么方法？

A. 用 @code{quantize()} 方法舍入到固定数量的十进制位。 如果设置了 @ref{19fa,,Inexact} 陷阱，它也适用于验证有效性：

@example
>>> TWOPLACES = Decimal(10) ** -2       # same as Decimal('0.01')
@end example

@example
>>> # Round to two places
>>> Decimal('3.214').quantize(TWOPLACES)
Decimal('3.21')
@end example

@example
>>> # Validate that a number does not exceed two places
>>> Decimal('3.21').quantize(TWOPLACES, context=Context(traps=[Inexact]))
Decimal('3.21')
@end example

@example
>>> Decimal('3.214').quantize(TWOPLACES, context=Context(traps=[Inexact]))
Traceback (most recent call last):
   ...
Inexact: None
@end example

Q. 当我使用两个有效位的输入时，我要如何在一个应用中保持有效位不变？

A. 某些运算例如与整数相加、相减和相乘将会自动保留固定的小数位数。 其他运算，例如相除和非整数相乘则将会改变小数位数，需要再加上 @code{quantize()} 处理步骤：

@example
>>> a = Decimal('102.72')           # Initial fixed-point values
>>> b = Decimal('3.17')
>>> a + b                           # Addition preserves fixed-point
Decimal('105.89')
>>> a - b
Decimal('99.55')
>>> a * 42                          # So does integer multiplication
Decimal('4314.24')
>>> (a * b).quantize(TWOPLACES)     # Must quantize non-integer multiplication
Decimal('325.62')
>>> (b / a).quantize(TWOPLACES)     # And quantize division
Decimal('0.03')
@end example

在开发定点数应用时，更方便的做法是定义处理 @code{quantize()} 步骤的函数：

@example
>>> def mul(x, y, fp=TWOPLACES):
...     return (x * y).quantize(fp)
>>> def div(x, y, fp=TWOPLACES):
...     return (x / y).quantize(fp)
@end example

@example
>>> mul(a, b)                       # Automatically preserve fixed-point
Decimal('325.62')
>>> div(b, a)
Decimal('0.03')
@end example

Q. 表示同一个值有许多方式。 数字 @code{200}, @code{200.000}, @code{2E2} 和 @code{02E+4} 的值都相同但有精度不同。 是否有办法将它们转换为一个可识别的规范值？

A. @code{normalize()} 方法可将所有相同的值映射为统一表示形式：

@example
>>> values = map(Decimal, '200 200.000 2E2 .02E+4'.split())
>>> [v.normalize() for v in values]
[Decimal('2E+2'), Decimal('2E+2'), Decimal('2E+2'), Decimal('2E+2')]
@end example

Q. 有些十进制值总是被打印为指数表示形式。 是否有办法得到一个非指数表示形式？

A. 对于某些值来说，指数表示形式是表示系数中有效位的唯一办法。 例如，将 @code{5.0E+3} 表示为 @code{5000} 可以让值保持恒定，但是无法显示原本的两位有效数字。

如果一个应用不必关心追踪有效位，则可以很容易地移除指数和末尾的零，丢弃有效位但让值保持不变：

@example
>>> def remove_exponent(d):
...     return d.quantize(Decimal(1)) if d == d.to_integral() else d.normalize()
@end example

@example
>>> remove_exponent(Decimal('5E+3'))
Decimal('5000')
@end example

Q. 是否有办法将一个普通浮点数转换为 @ref{188,,Decimal}？

A. 是的，任何二进制浮点数都可以精确地表示为 Decimal 值，但完全精确的转换可能需要比平常感觉更高的精度：

@example
>>> Decimal(math.pi)
Decimal('3.141592653589793115997963468544185161590576171875')
@end example

Q. 在一个复杂的计算中，我怎样才能保证不会得到由精度不足和舍入异常所导致的虚假结果。

A. 使用 decimal 模块可以很容易地检测结果。 最好的做法是使用更高的精度和不同的舍入模式重新进行计算。 明显不同的结果表明存在精度不足、舍入模式问题、不符合条件的输入或是结果不稳定的算法。

Q. 我发现上下文精度的应用只针对运算结果而不针对输入。在混合使用不同精度的值时有什么需要注意的吗？

A. 是的。 原则上所有值都会被视为精确值，在这些值上进行的算术运算也是如此。 只有结果会被舍入。 对于输入来说其好处是“所输入即所得”。 而其缺点则是如果你忘记了输入没有被舍入，结果看起来可能会很奇怪：

@example
>>> getcontext().prec = 3
>>> Decimal('3.104') + Decimal('2.104')
Decimal('5.21')
>>> Decimal('3.104') + Decimal('0.000') + Decimal('2.104')
Decimal('5.20')
@end example

解决办法是提高精度或使用单目加法运算对输入执行强制舍入：

@example
>>> getcontext().prec = 3
>>> +Decimal('1.23456789')      # unary plus triggers rounding
Decimal('1.23')
@end example

此外，还可以使用 @ref{9e6,,Context.create_decimal()} 方法在创建输入时执行舍入：

@example
>>> Context(prec=5, rounding=ROUND_DOWN).create_decimal('1.2345678')
Decimal('1.2345')
@end example

Q. CPython 实现对于巨大数字是否足够快速？

A. 是的，在 CPython 和 PyPy3 实现中，decimal 模块的 C/CFFI 版本集成了高速 libmpdec@footnote{https://www.bytereef.org/mpdecimal/doc/libmpdec/index.html} 库用于实现任意精度正确舍入的十进制浮点算术。 @code{libmpdec} 会对中等的数字使用 Karatsuba 乘法@footnote{https://en.wikipedia.org/wiki/Karatsuba_algorithm} 而对非常巨大的数字使用 数字原理变换@footnote{https://en.wikipedia.org/wiki/Discrete_Fourier_transform_(general)#Number-theoretic_transform} 。 但是，想要实现这种性能提升，需要对未舍入的运算设置上下文。

@example
>>> c = getcontext()
>>> c.prec = MAX_PREC
>>> c.Emax = MAX_EMAX
>>> c.Emin = MIN_EMIN
@end example


3.3 新版功能.


@node fractions --- 分数,random --- 生成伪随机数,decimal --- 十进制定点和浮点运算,数字和数学模块
@anchor{library/fractions doc}@anchor{1a8d}@anchor{library/fractions fractions-rational-numbers}@anchor{1a8e}@anchor{library/fractions module-fractions}@anchor{83}
@subsection @code{fractions} --- 分数


@geindex fractions (模块)

@strong{源代码} Lib/fractions.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/fractions.py}


__________________________________________________________________


@ref{83,,fractions} 模块支持分数运算。

分数实例可以由一对整数，一个分数，或者一个字符串构建而成。

@geindex Fraction (fractions 中的类)
@anchor{library/fractions fractions Fraction}@anchor{185}
@deffn {类} fractions.Fraction (numerator=0, denominator=1)

@deffnx {类} fractions.Fraction (other_fraction)

@deffnx {类} fractions.Fraction (float)

@deffnx {类} fractions.Fraction (decimal)

@deffnx {类} fractions.Fraction (string)

第一个版本要求 @emph{numerator} 和 @emph{denominator} 是 @ref{c51,,numbers.Rational} 的实例，并返回一个新的 @ref{185,,Fraction} 实例，其值为 @code{numerator/denominator}。 如果 @emph{denominator} 为 @code{0} 将会引发 @ref{1241,,ZeroDivisionError}。 第二个版本要求 @emph{other_fraction} 是 @ref{c51,,numbers.Rational} 的实例，并返回一个 @ref{185,,Fraction} 实例且与传入值相等。 下两个版本接受 @ref{187,,float} 或 @ref{188,,decimal.Decimal} 的实例，并返回一个 @ref{185,,Fraction} 实例且与传入值完全相等。 请注意由于二进制浮点数通常存在的问题 (参见 @ref{12b7,,浮点算术：争议和限制})，@code{Fraction(1.1)} 的参数并不会精确等于 11/10，因此 @code{Fraction(1.1)} 也 @emph{不会} 返回用户所期望的 @code{Fraction(11, 10)}。 （请参阅下文中 @ref{1a8f,,limit_denominator()} 方法的文档。） 构造器的最后一个版本接受一个字符串或 unicode 实例。 此实例的通常形式为:

@example
[sign] numerator ['/' denominator]
@end example

其中的可选项 @code{sign} 可以为 '+' 或 '-' 并且 @code{numerator} 和 @code{denominator} (如果存在) 是十进制数码的字符串。 此外，@ref{187,,float} 构造器所接受的任何表示一个有限值的字符串也都为 @ref{185,,Fraction} 构造器所接受。 不论哪种形式的输入字符串也都可以带有前缀和/或后缀的空格符。 这里是一些示例:

@example
>>> from fractions import Fraction
>>> Fraction(16, -10)
Fraction(-8, 5)
>>> Fraction(123)
Fraction(123, 1)
>>> Fraction()
Fraction(0, 1)
>>> Fraction('3/7')
Fraction(3, 7)
>>> Fraction(' -3/7 ')
Fraction(-3, 7)
>>> Fraction('1.414213 \t\n')
Fraction(1414213, 1000000)
>>> Fraction('-.125')
Fraction(-1, 8)
>>> Fraction('7e-6')
Fraction(7, 1000000)
>>> Fraction(2.25)
Fraction(9, 4)
>>> Fraction(1.1)
Fraction(2476979795053773, 2251799813685248)
>>> from decimal import Decimal
>>> Fraction(Decimal('1.1'))
Fraction(11, 10)
@end example

@ref{185,,Fraction} 类继承自抽象基类 @ref{c51,,numbers.Rational}，并实现了该类的所有方法和操作。 @ref{185,,Fraction} 实例是可哈希的，并应当被视为不可变对象。 此外，@ref{185,,Fraction} 还具有以下属性和方法：


在 3.2 版更改: @ref{185,,Fraction} 构造器现在接受 @ref{187,,float} 和 @ref{188,,decimal.Decimal} 实例。


@geindex numerator (fractions.Fraction 属性)
@anchor{library/fractions fractions Fraction numerator}@anchor{1a90}
@deffn {属性} numerator

最简分数形式的分子。
@end deffn

@geindex denominator (fractions.Fraction 属性)
@anchor{library/fractions fractions Fraction denominator}@anchor{1a91}
@deffn {属性} denominator

最简分数形式的分母。
@end deffn

@geindex as_integer_ratio() (fractions.Fraction 方法)
@anchor{library/fractions fractions Fraction as_integer_ratio}@anchor{1a92}
@deffn {方法} as_integer_ratio ()

返回由两个整数组成的元组，两数之比等于该分数的值且其分母为正数。


3.8 新版功能.

@end deffn

@geindex from_float() (fractions.Fraction 方法)
@anchor{library/fractions fractions Fraction from_float}@anchor{b7a}
@deffn {方法} from_float (flt)

此类方法可构造一个 @ref{185,,Fraction} 来表示 @emph{flt} 的精确值，该参数必须是一个 @ref{187,,float}。 请注意 @code{Fraction.from_float(0.3)} 的值并不等于 @code{Fraction(3, 10)}。

@cartouche
@quotation 注解 
从 Python 3.2 开始，在构造 @ref{185,,Fraction} 实例时可以直接使用 @ref{187,,float}。
@end quotation
@end cartouche
@end deffn

@geindex from_decimal() (fractions.Fraction 方法)
@anchor{library/fractions fractions Fraction from_decimal}@anchor{b7b}
@deffn {方法} from_decimal (dec)

此类方法可构造一个 @ref{185,,Fraction} 来表示 @emph{dec} 的精确值，该参数必须是一个 @ref{188,,decimal.Decimal} 实例。

@cartouche
@quotation 注解 
从 Python 3.2 开始，在构造 @ref{185,,Fraction} 实例时可以直接使用 @ref{188,,decimal.Decimal} 实例。
@end quotation
@end cartouche
@end deffn

@geindex limit_denominator() (fractions.Fraction 方法)
@anchor{library/fractions fractions Fraction limit_denominator}@anchor{1a8f}
@deffn {方法} limit_denominator (max_denominator=1000000)

找到并返回一个 @ref{185,,Fraction} 使得其值最接近 @code{self} 并且分母不大于 max_denominator。 此方法适用于找出给定浮点数的有理数近似值：

@example
>>> from fractions import Fraction
>>> Fraction('3.1415926535897932').limit_denominator(1000)
Fraction(355, 113)
@end example

或是用来恢复被表示为一个浮点数的有理数：

@example
>>> from math import pi, cos
>>> Fraction(cos(pi/3))
Fraction(4503599627370497, 9007199254740992)
>>> Fraction(cos(pi/3)).limit_denominator()
Fraction(1, 2)
>>> Fraction(1.1).limit_denominator()
Fraction(11, 10)
@end example
@end deffn

@geindex __floor__() (fractions.Fraction 方法)
@anchor{library/fractions fractions Fraction __floor__}@anchor{1a93}
@deffn {方法} __floor__ ()

返回最大的 @ref{184,,int} @code{<= self}。 此方法也可通过 @ref{d25,,math.floor()} 函数来使用：

@example
>>> from math import floor
>>> floor(Fraction(355, 113))
3
@end example
@end deffn

@geindex __ceil__() (fractions.Fraction 方法)
@anchor{library/fractions fractions Fraction __ceil__}@anchor{1a94}
@deffn {方法} __ceil__ ()

返回最小的 @ref{184,,int} @code{>= self}。 此方法也可通过 @ref{d26,,math.ceil()} 函数来使用。
@end deffn

@geindex __round__() (fractions.Fraction 方法)
@anchor{library/fractions fractions Fraction __round__}@anchor{1a95}
@deffn {方法} __round__ ()

@deffnx {方法} __round__ (ndigits)

第一个版本返回一个 @ref{184,,int} 使得其值最接近 @code{self}，位值为二分之一时只对偶数舍入。第二个版本会将 @code{self} 舍入到最接近 @code{Fraction(1, 10**ndigits)} 的倍数（如果 @code{ndigits} 为负值则为逻辑运算），位值为二分之一时同样只对偶数舍入。 此方法也可通过 @ref{c66,,round()} 函数来使用。
@end deffn
@end deffn

@geindex gcd() (在 fractions 模块中)
@anchor{library/fractions fractions gcd}@anchor{711}
@deffn {函数} fractions.gcd (a, b)

返回整数 @emph{a} 和 @emph{b} 的最大公约数。如果 @emph{a} 或 @emph{b} 之一非零，则 @code{gcd(a, b)} 的绝对值是能同时整除 @emph{a} 和 @emph{b} 的最大整数。若 @emph{b} 非零，则 @code{gcd(a,b)} 与 @emph{b} 同号；否则返回值与 @emph{a} 同号。@code{gcd(0, 0)} 返回 @code{0}。


3.5 版后已移除: 由 @ref{710,,math.gcd()} 取代.

@end deffn


@subsubheading 参见



@table @asis

@item @ref{c1,,numbers} 模块

构成数字塔的所有抽象基类。
@end table


@node random --- 生成伪随机数,statistics --- 数学统计函数,fractions --- 分数,数字和数学模块
@anchor{library/random doc}@anchor{1a96}@anchor{library/random module-random}@anchor{dc}@anchor{library/random random-generate-pseudo-random-numbers}@anchor{1a97}
@subsection @code{random} --- 生成伪随机数


@geindex random (模块)

@strong{源码：} Lib/random.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/random.py}


__________________________________________________________________


该模块实现了各种分布的伪随机数生成器。

对于整数，从范围中有统一的选择。 对于序列，存在随机元素的统一选择、用于生成列表的随机排列的函数、以及用于随机抽样而无需替换的函数。

在实数轴上，有计算均匀、正态（高斯）、对数正态、负指数、伽马和贝塔分布的函数。 为了生成角度分布，可以使用 von Mises 分布。

几乎所有模块函数都依赖于基本函数 @ref{1a98,,random()} ，它在半开放区间 [0.0,1.0) 内均匀生成随机浮点数。 Python 使用 Mersenne Twister 作为核心生成器。 它产生 53 位精度浮点数，周期为 2**19937-1 ，其在 C 中的底层实现既快又线程安全。 Mersenne Twister 是现存最广泛测试的随机数发生器之一。 但是，因为完全确定性，它不适用于所有目的，并且完全不适合加密目的。

这个模块提供的函数实际上是 @ref{1a99,,random.Random} 类的隐藏实例的绑定方法。 你可以实例化自己的 @ref{1a99,,Random} 类实例以获取不共享状态的生成器。

如果你想使用自己设计的不同基础生成器，类 @ref{1a99,,Random} 也可以作为子类：在这种情况下，重载 @code{random()} 、 @code{seed()} 、 @code{getstate()} 以及 @code{setstate()} 方法。可选地，新生成器可以提供 @code{getrandbits()} 方法——这允许 @ref{bb4,,randrange()} 在任意大的范围内产生选择。

@ref{dc,,random} 模块还提供 @ref{1a9a,,SystemRandom} 类，它使用系统函数 @ref{4cb,,os.urandom()} 从操作系统提供的源生成随机数。

@cartouche
@quotation 警告 
不应将此模块的伪随机生成器用于安全目的。 有关安全性或加密用途，请参阅 @ref{e4,,secrets} 模块。
@end quotation
@end cartouche


@subsubheading 参见


M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-dimensionally
equidistributed uniform pseudorandom number generator", ACM Transactions on
Modeling and Computer Simulation Vol. 8, No. 1, January pp.3--30 1998.

Complementary-Multiply-with-Carry recipe@footnote{https://code.activestate.com/recipes/576707/} 用于兼容的替代随机数发生器，具有长周期和相对简单的更新操作。


@menu
* 簿记功能:: 
* 整数用函数:: 
* 序列用函数:: 
* 实值分布:: 
* 替代生成器:: 
* 关于再现性的说明:: 
* 例子和配方:: 

@end menu

@node 簿记功能,整数用函数,,random --- 生成伪随机数
@anchor{library/random bookkeeping-functions}@anchor{1a9b}
@subsubsection 簿记功能


@geindex seed() (在 random 模块中)
@anchor{library/random random seed}@anchor{c01}
@deffn {函数} random.seed (a=None, version=2)

初始化随机数生成器。

如果 @emph{a} 被省略或为 @code{None} ，则使用当前系统时间。 如果操作系统提供随机源，则使用它们而不是系统时间（有关可用性的详细信息，请参阅 @ref{4cb,,os.urandom()} 函数）。

如果 @emph{a} 是 int 类型，则直接使用。

对于版本2（默认的），@ref{329,,str} 、 @ref{32a,,bytes} 或 @ref{32b,,bytearray} 对象转换为 @ref{184,,int} 并使用它的所有位。

对于版本1（用于从旧版本的Python再现随机序列），用于 @ref{329,,str} 和 @ref{32a,,bytes} 的算法生成更窄的种子范围。


在 3.2 版更改: 已移至版本2方案，该方案使用字符串种子中的所有位。

@end deffn

@geindex getstate() (在 random 模块中)
@anchor{library/random random getstate}@anchor{1a9c}
@deffn {函数} random.getstate ()

返回捕获生成器当前内部状态的对象。 这个对象可以传递给 @ref{1a9d,,setstate()} 来恢复状态。
@end deffn

@geindex setstate() (在 random 模块中)
@anchor{library/random random setstate}@anchor{1a9d}
@deffn {函数} random.setstate (state)

@emph{state} 应该是从之前调用 @ref{1a9c,,getstate()} 获得的，并且 @ref{1a9d,,setstate()} 将生成器的内部状态恢复到 @ref{1a9c,,getstate()} 被调用时的状态。
@end deffn

@geindex getrandbits() (在 random 模块中)
@anchor{library/random random getrandbits}@anchor{92d}
@deffn {函数} random.getrandbits (k)

返回具有 @emph{k} 个随机比特位的 Python 整数。 此方法随  Mersenne Twister 生成器一起提供，其他一些生成器也可能将其作为 API 的可选部分提供。 在可能的情况下，@ref{92d,,getrandbits()} 会启用 @ref{bb4,,randrange()} 来处理任意大的区间。
@end deffn

@node 整数用函数,序列用函数,簿记功能,random --- 生成伪随机数
@anchor{library/random functions-for-integers}@anchor{1a9e}
@subsubsection 整数用函数


@geindex randrange() (在 random 模块中)
@anchor{library/random random randrange}@anchor{bb4}
@deffn {函数} random.randrange (stop)

@deffnx {函数} random.randrange (start, stop[, step])

从 @code{range(start, stop, step)} 返回一个随机选择的元素。 这相当于 @code{choice(range(start, stop, step))} ，但实际上并没有构建一个 range 对象。

位置参数模式匹配 @ref{9b8,,range()} 。不应使用关键字参数，因为该函数可能以意外的方式使用它们。


在 3.2 版更改: @ref{bb4,,randrange()} 在生成均匀分布的值方面更为复杂。 以前它使用了像`@w{`}int(random()*n)`@w{`}这样的形式，它可以产生稍微不均匀的分布。

@end deffn

@geindex randint() (在 random 模块中)
@anchor{library/random random randint}@anchor{bb5}
@deffn {函数} random.randint (a, b)

返回随机整数 @emph{N} 满足 @code{a <= N <= b}。相当于 @code{randrange(a, b+1)}。
@end deffn

@node 序列用函数,实值分布,整数用函数,random --- 生成伪随机数
@anchor{library/random functions-for-sequences}@anchor{1a9f}
@subsubsection 序列用函数


@geindex choice() (在 random 模块中)
@anchor{library/random random choice}@anchor{bb6}
@deffn {函数} random.choice (seq)

从非空序列 @emph{seq} 返回一个随机元素。 如果 @emph{seq} 为空，则引发 @ref{e6e,,IndexError}。
@end deffn

@geindex choices() (在 random 模块中)
@anchor{library/random random choices}@anchor{56f}
@deffn {函数} random.choices (population, weights=None, *, cum_weights=None, k=1)

从*population*中选择替换，返回大小为 @emph{k} 的元素列表。 如果 @emph{population} 为空，则引发 @ref{e6e,,IndexError}。

如果指定了 @emph{weight} 序列，则根据相对权重进行选择。 或者，如果给出 @emph{cum_weights} 序列，则根据累积权重（可能使用 @ref{1dd,,itertools.accumulate()} 计算）进行选择。 例如，相对权重`@w{`}[10, 5, 30, 5]`@w{`}相当于累积权重`@w{`}[10, 15, 45, 50]`@w{`}。 在内部，相对权重在进行选择之前会转换为累积权重，因此提供累积权重可以节省工作量。

如果既未指定 @emph{weight} 也未指定 @emph{cum_weights} ，则以相等的概率进行选择。 如果提供了权重序列，则它必须与 @emph{population} 序列的长度相同。 一个 @ref{192,,TypeError} 指定了 @emph{weights} 和*cum_weights*。

@emph{weights} 或 @emph{cum_weights} 可以使用任何与 @ref{dc,,random()} 所返回的 @ref{187,,float} 值互操作的数值类型（包括整数、浮点数和分数但不包括十进制小数）。 权重假定为非负数。

对于给定的种子，具有相等加权的 @ref{56f,,choices()} 函数通常产生与重复调用 @ref{bb6,,choice()} 不同的序列。 @ref{56f,,choices()} 使用的算法使用浮点运算来实现内部一致性和速度。 @ref{bb6,,choice()}  使用的算法默认为重复选择的整数运算，以避免因舍入误差引起的小偏差。


3.6 新版功能.

@end deffn

@geindex shuffle() (在 random 模块中)
@anchor{library/random random shuffle}@anchor{bb7}
@deffn {函数} random.shuffle (x[, random])

将序列 @emph{x} 随机打乱位置。

可选参数 @emph{random} 是一个0参数函数，在 [0.0, 1.0) 中返回随机浮点数；默认情况下，这是函数 @ref{1a98,,random()} 。

要改变一个不可变的序列并返回一个新的打乱列表，请使用`@w{`}sample(x, k=len(x))`@w{`}。

请注意，即使对于小的 @code{len(x)}，@emph{x} 的排列总数也可以快速增长，大于大多数随机数生成器的周期。 这意味着长序列的大多数排列永远不会产生。 例如，长度为2080的序列是可以在 Mersenne Twister 随机数生成器的周期内拟合的最大序列。
@end deffn

@geindex sample() (在 random 模块中)
@anchor{library/random random sample}@anchor{bb8}
@deffn {函数} random.sample (population, k)

返回从总体序列或集合中选择的唯一元素的 @emph{k} 长度列表。 用于无重复的随机抽样。

返回包含来自总体的元素的新列表，同时保持原始总体不变。 结果列表按选择顺序排列，因此所有子切片也将是有效的随机样本。 这允许抽奖获奖者（样本）被划分为大奖和第二名获胜者（子切片）。

总体成员不必是 @ref{13c0,,hashable} 或 unique 。 如果总体包含重复，则每次出现都是样本中可能的选择。

要从一系列整数中选择样本，请使用 @ref{9b8,,range()} 对象作为参数。 对于从大量人群中采样，这种方法特别快速且节省空间：@code{sample(range(10000000), k=60)} 。

如果样本大小大于总体大小，则引发 @ref{1fb,,ValueError} 。
@end deffn

@node 实值分布,替代生成器,序列用函数,random --- 生成伪随机数
@anchor{library/random real-valued-distributions}@anchor{1aa0}
@subsubsection 实值分布


以下函数生成特定的实值分布。如常用数学实践中所使用的那样, 函数参数以分布方程中的相应变量命名;大多数这些方程都可以在任何统计学教材中找到。

@geindex random() (在 random 模块中)
@anchor{library/random random random}@anchor{1a98}
@deffn {函数} random.random ()

返回 [0.0, 1.0) 范围内的下一个随机浮点数。
@end deffn

@geindex uniform() (在 random 模块中)
@anchor{library/random random uniform}@anchor{1aa1}
@deffn {函数} random.uniform (a, b)

返回一个随机浮点数 @emph{N} ，当 @code{a <= b} 时 @code{a <= N <= b} ，当 @code{b < a} 时 @code{b <= N <= a} 。

取决于等式 @code{a + (b-a) * random()} 中的浮点舍入，终点 @code{b} 可以包括或不包括在该范围内。
@end deffn

@geindex triangular() (在 random 模块中)
@anchor{library/random random triangular}@anchor{1aa2}
@deffn {函数} random.triangular (low, high, mode)

返回一个随机浮点数 @emph{N} ，使得 @code{low <= N <= high} 并在这些边界之间使用指定的 @emph{mode} 。 @emph{low} 和 @emph{high} 边界默认为零和一。 @emph{mode} 参数默认为边界之间的中点，给出对称分布。
@end deffn

@geindex betavariate() (在 random 模块中)
@anchor{library/random random betavariate}@anchor{1aa3}
@deffn {函数} random.betavariate (alpha, beta)

Beta 分布。 参数的条件是 @code{alpha > 0} 和 @code{beta > 0}。 返回值的范围介于 0 和 1 之间。
@end deffn

@geindex expovariate() (在 random 模块中)
@anchor{library/random random expovariate}@anchor{1aa4}
@deffn {函数} random.expovariate (lambd)

指数分布。 @emph{lambd} 是 1.0 除以所需的平均值，它应该是非零的。 （该参数本应命名为 “lambda” ，但这是 Python 中的保留字。）如果 @emph{lambd} 为正，则返回值的范围为 0 到正无穷大；如果 @emph{lambd} 为负，则返回值从负无穷大到 0。
@end deffn

@geindex gammavariate() (在 random 模块中)
@anchor{library/random random gammavariate}@anchor{1aa5}
@deffn {函数} random.gammavariate (alpha, beta)

Gamma 分布。 （ @emph{不是} gamma 函数！ ） 参数的条件是 @code{alpha > 0} 和 @code{beta > 0}。

概率分布函数是:

@example
          x ** (alpha - 1) * math.exp(-x / beta)
pdf(x) =  --------------------------------------
            math.gamma(alpha) * beta ** alpha
@end example
@end deffn

@geindex gauss() (在 random 模块中)
@anchor{library/random random gauss}@anchor{1aa6}
@deffn {函数} random.gauss (mu, sigma)

高斯分布。 @emph{mu} 是平均值，@emph{sigma} 是标准差。 这比下面定义的 @ref{1aa7,,normalvariate()} 函数略快。
@end deffn

@geindex lognormvariate() (在 random 模块中)
@anchor{library/random random lognormvariate}@anchor{1aa8}
@deffn {函数} random.lognormvariate (mu, sigma)

对数正态分布。 如果你采用这个分布的自然对数，你将得到一个正态分布，平均值为 @emph{mu} 和标准差为 @emph{sigma} 。 @emph{mu} 可以是任何值，@emph{sigma} 必须大于零。
@end deffn

@geindex normalvariate() (在 random 模块中)
@anchor{library/random random normalvariate}@anchor{1aa7}
@deffn {函数} random.normalvariate (mu, sigma)

正态分布。 @emph{mu} 是平均值，@emph{sigma} 是标准差。
@end deffn

@geindex vonmisesvariate() (在 random 模块中)
@anchor{library/random random vonmisesvariate}@anchor{1aa9}
@deffn {函数} random.vonmisesvariate (mu, kappa)

冯·米塞斯（von Mises）分布。 @emph{mu} 是平均角度，以弧度表示，介于0和 2*@emph{pi} 之间，@emph{kappa} 是浓度参数，必须大于或等于零。 如果 @emph{kappa} 等于零，则该分布在 0 到 2*@emph{pi} 的范围内减小到均匀的随机角度。
@end deffn

@geindex paretovariate() (在 random 模块中)
@anchor{library/random random paretovariate}@anchor{1aaa}
@deffn {函数} random.paretovariate (alpha)

帕累托分布。 @emph{alpha} 是形状参数。
@end deffn

@geindex weibullvariate() (在 random 模块中)
@anchor{library/random random weibullvariate}@anchor{1aab}
@deffn {函数} random.weibullvariate (alpha, beta)

威布尔分布。 @emph{alpha} 是比例参数，@emph{beta} 是形状参数。
@end deffn

@node 替代生成器,关于再现性的说明,实值分布,random --- 生成伪随机数
@anchor{library/random alternative-generator}@anchor{1aac}
@subsubsection 替代生成器


@geindex Random (random 中的类)
@anchor{library/random random Random}@anchor{1a99}
@deffn {类} random.Random ([seed])

。该类实现了 @ref{dc,,random} 模块所用的默认伪随机数生成器。
@end deffn

@geindex SystemRandom (random 中的类)
@anchor{library/random random SystemRandom}@anchor{1a9a}
@deffn {类} random.SystemRandom ([seed])

使用 @ref{4cb,,os.urandom()} 函数的类，用从操作系统提供的源生成随机数。 这并非适用于所有系统。 也不依赖于软件状态，序列不可重现。 因此，@ref{c01,,seed()} 方法没有效果而被忽略。 @ref{1a9c,,getstate()} 和 @ref{1a9d,,setstate()} 方法如果被调用则引发 @ref{609,,NotImplementedError}。
@end deffn

@node 关于再现性的说明,例子和配方,替代生成器,random --- 生成伪随机数
@anchor{library/random notes-on-reproducibility}@anchor{1aad}
@subsubsection 关于再现性的说明


有时能够重现伪随机数生成器给出的序列是有用的。 通过重新使用种子值，只要多个线程没有运行，相同的序列就可以在两次不同运行之间重现。

大多数随机模块的算法和种子函数都会在 Python 版本中发生变化，但保证两个方面不会改变：


@itemize *

@item 
如果添加了新的播种方法，则将提供向后兼容的播种机。

@item 
当兼容的播种机被赋予相同的种子时，生成器的 @code{random()} 方法将继续产生相同的序列。
@end itemize

@node 例子和配方,,关于再现性的说明,random --- 生成伪随机数
@anchor{library/random examples-and-recipes}@anchor{1aae}@anchor{library/random random-examples}@anchor{b51}
@subsubsection 例子和配方


基本示例:

@example
>>> random()                             # Random float:  0.0 <= x < 1.0
0.37444887175646646

>>> uniform(2.5, 10.0)                   # Random float:  2.5 <= x < 10.0
3.1800146073117523

>>> expovariate(1 / 5)                   # Interval between arrivals averaging 5 seconds
5.148957571865031

>>> randrange(10)                        # Integer from 0 to 9 inclusive
7

>>> randrange(0, 101, 2)                 # Even integer from 0 to 100 inclusive
26

>>> choice(['win', 'lose', 'draw'])      # Single random element from a sequence
'draw'

>>> deck = 'ace two three four'.split()
>>> shuffle(deck)                        # Shuffle a list
>>> deck
['four', 'two', 'ace', 'three']

>>> sample([10, 20, 30, 40, 50], k=4)    # Four samples without replacement
[40, 10, 50, 30]
@end example

模拟:

@example
>>> # Six roulette wheel spins (weighted sampling with replacement)
>>> choices(['red', 'black', 'green'], [18, 18, 2], k=6)
['red', 'green', 'black', 'black', 'red', 'black']

>>> # Deal 20 cards without replacement from a deck of 52 playing cards
>>> # and determine the proportion of cards with a ten-value
>>> # (a ten, jack, queen, or king).
>>> deck = collections.Counter(tens=16, low_cards=36)
>>> seen = sample(list(deck.elements()), k=20)
>>> seen.count('tens') / 20
0.15

>>> # Estimate the probability of getting 5 or more heads from 7 spins
>>> # of a biased coin that settles on heads 60% of the time.
>>> def trial():
...     return choices('HT', cum_weights=(0.60, 1.00), k=7).count('H') >= 5
...
>>> sum(trial() for i in range(10_000)) / 10_000
0.4169

>>> # Probability of the median of 5 samples being in middle two quartiles
>>> def trial():
...     return 2_500 <= sorted(choices(range(10_000), k=5))[2] < 7_500
...
>>> sum(trial() for i in range(10_000)) / 10_000
0.7958
@end example

statistical bootstrapping@footnote{https://en.wikipedia.org/wiki/Bootstrapping_(statistics)} 的示例，使用重新采样和替换来估计一个样本的均值的置信区间:

@example
# http://statistics.about.com/od/Applications/a/Example-Of-Bootstrapping.htm
from statistics import fmean as mean
from random import choices

data = [41, 50, 29, 37, 81, 30, 73, 63, 20, 35, 68, 22, 60, 31, 95]
means = sorted(mean(choices(data, k=len(data))) for i in range(100))
print(f'The sample mean of @{mean(data):.1f@} has a 90% confidence '
      f'interval from @{means[5]:.1f@} to @{means[94]:.1f@}')
@end example

使用 重新采样排列测试@footnote{https://en.wikipedia.org/wiki/Resampling_(statistics)#Permutation_tests} 来确定统计学显著性或者使用  p-值@footnote{https://en.wikipedia.org/wiki/P-value} 来观察药物与安慰剂的作用之间差异的示例:

@example
# Example from "Statistics is Easy" by Dennis Shasha and Manda Wilson
from statistics import fmean as mean
from random import shuffle

drug = [54, 73, 53, 70, 73, 68, 52, 65, 65]
placebo = [54, 51, 58, 44, 55, 52, 42, 47, 58, 46]
observed_diff = mean(drug) - mean(placebo)

n = 10_000
count = 0
combined = drug + placebo
for i in range(n):
    shuffle(combined)
    new_diff = mean(combined[:len(drug)]) - mean(combined[len(drug):])
    count += (new_diff >= observed_diff)

print(f'@{n@} label reshufflings produced only @{count@} instances with a difference')
print(f'at least as extreme as the observed difference of @{observed_diff:.1f@}.')
print(f'The one-sided p-value of @{count / n:.4f@} leads us to reject the null')
print(f'hypothesis that there is no difference between the drug and the placebo.')
@end example

多服务器队列的到达时间和服务交付模拟:

@example
from heapq import heappush, heappop
from random import expovariate, gauss
from statistics import mean, median, stdev

average_arrival_interval = 5.6
average_service_time = 15.0
stdev_service_time = 3.5
num_servers = 3

waits = []
arrival_time = 0.0
servers = [0.0] * num_servers  # time when each server becomes available
for i in range(100_000):
    arrival_time += expovariate(1.0 / average_arrival_interval)
    next_server_available = heappop(servers)
    wait = max(0.0, next_server_available - arrival_time)
    waits.append(wait)
    service_duration = gauss(average_service_time, stdev_service_time)
    service_completed = arrival_time + wait + service_duration
    heappush(servers, service_completed)

print(f'Mean wait: @{mean(waits):.1f@}.  Stdev wait: @{stdev(waits):.1f@}.')
print(f'Median wait: @{median(waits):.1f@}.  Max wait: @{max(waits):.1f@}.')
@end example


@subsubheading 参见


Statistics for Hackers@footnote{https://www.youtube.com/watch?v=Iq9DzN6mvYA} Jake Vanderplas@footnote{https://us.pycon.org/2016/speaker/profile/295/} 撰写的视频教程，使用一些基本概念进行统计分析，包括模拟、抽样、改组和交叉验证。

Economics Simulation@footnote{http://nbviewer.jupyter.org/url/norvig.com/ipython/Economics.ipynb} Peter Norvig@footnote{http://norvig.com/bio.html} 编写的市场模拟，显示了该模块提供的许多工具和分布的有效使用（高斯、均匀、样本、beta变量、选择、三角和随机范围等）。

A Concrete Introduction to Probability (using Python)@footnote{http://nbviewer.jupyter.org/url/norvig.com/ipython/Probability.ipynb} Peter Norvig@footnote{http://norvig.com/bio.html} 撰写的教程，涵盖了概率论基础知识，如何编写模拟，以及如何使用 Python 进行数据分析。


@node statistics --- 数学统计函数,,random --- 生成伪随机数,数字和数学模块
@anchor{library/statistics doc}@anchor{1aaf}@anchor{library/statistics module-statistics}@anchor{f5}@anchor{library/statistics statistics-mathematical-statistics-functions}@anchor{1ab0}
@subsection @code{statistics} --- 数学统计函数


@geindex statistics (模块)


3.4 新版功能.


@strong{源代码:} Lib/statistics.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/statistics.py}

@c from statistics import *
@c __name__ = '<doctest>'


__________________________________________________________________


该模块提供了用于计算数字 (@ref{13bc,,Real}-valued) 数据的数理统计量的函数。

此模块并不是诸如 NumPy@footnote{https://numpy.org} ， SciPy@footnote{https://www.scipy.org/} 等第三方库或者诸如 Minitab ， SAS ， Matlab 等针对专业统计学家的专有全功能统计软件包的竟品。此模块针对图形和科学计算器的水平。

除非明确注释，这些函数支持 @ref{184,,int} ， @ref{187,,float} ， @ref{188,,Decimal} 和 @ref{185,,Fraction} 。当前不支持同其他类型（是否在数字塔中）的行为。混合类型的集合也是未定义的，并且依赖于实现。如果你输入的数据由混合类型组成，你应该能够使用 @ref{c26,,map()} 来确保一个一致的结果，比如： @code{map(float, input_data)} 。

@menu
* 平均值以及对中心位置的评估:: 
* 对分散程度的评估:: 
* 函数细节:: 
* 异常: 异常<3>. 
* NormalDist 对象:: 

@end menu

@node 平均值以及对中心位置的评估,对分散程度的评估,,statistics --- 数学统计函数
@anchor{library/statistics averages-and-measures-of-central-location}@anchor{1ab1}
@subsubsection 平均值以及对中心位置的评估


这些函数用于计算一个总体或样本的平均值或者典型值。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{199,,mean()}

@tab

数据的算术平均数（“平均数”）。

@item

@ref{227,,fmean()}

@tab

快速的，浮点算数平均数。

@item

@ref{228,,geometric_mean()}

@tab

数据的几何平均数

@item

@ref{58a,,harmonic_mean()}

@tab

数据的调和均值

@item

@ref{1ab2,,median()}

@tab

数据的中位数（中间值）

@item

@ref{1ab3,,median_low()}

@tab

数据的低中位数

@item

@ref{1ab4,,median_high()}

@tab

数据的高中位数

@item

@ref{1ab5,,median_grouped()}

@tab

分组数据的中位数，即第50个百分点。

@item

@ref{2bb,,mode()}

@tab

离散的或标称的数据的单个众数（出现最多的值）。

@item

@ref{229,,multimode()}

@tab

离散的或标称的数据的众数列表（出现最多的值）。

@item

@ref{22a,,quantiles()}

@tab

将数据以相等的概率分为多个间隔。

@end multitable


@node 对分散程度的评估,函数细节,平均值以及对中心位置的评估,statistics --- 数学统计函数
@anchor{library/statistics measures-of-spread}@anchor{1ab6}
@subsubsection 对分散程度的评估


这些函数用于计算总体或样本与典型值或平均值的偏离程度。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{1ab7,,pstdev()}

@tab

数据的总体标准差

@item

@ref{1ab8,,pvariance()}

@tab

数据的总体方差

@item

@ref{1ab9,,stdev()}

@tab

数据的样本标准差

@item

@ref{1aba,,variance()}

@tab

数据的样本方差

@end multitable


@node 函数细节,异常<3>,对分散程度的评估,statistics --- 数学统计函数
@anchor{library/statistics function-details}@anchor{1abb}
@subsubsection 函数细节


注释：这些函数不需要对提供给它们的数据进行排序。但是，为了方便阅读，大多数例子展示的是已排序的序列。

@geindex mean() (在 statistics 模块中)
@anchor{library/statistics statistics mean}@anchor{199}
@deffn {函数} statistics.mean (data)

返回 @emph{data} 的样本算术平均数，形式为序列或迭代器。

算术平均数是数据之和与数据点个数的商。通常称作“平均数”，尽管它指示诸多数学平均数之一。它是数据的中心位置的度量。

若 @emph{data} 为空，将会引发 @ref{1abc,,StatisticsError}。

一些用法示例：

@example
>>> mean([1, 2, 3, 4, 4])
2.8
>>> mean([-1.0, 2.5, 3.25, 5.75])
2.625

>>> from fractions import Fraction as F
>>> mean([F(3, 7), F(1, 21), F(5, 3), F(1, 3)])
Fraction(13, 21)

>>> from decimal import Decimal as D
>>> mean([D("0.5"), D("0.75"), D("0.625"), D("0.375")])
Decimal('0.5625')
@end example

@cartouche
@quotation 注解 
均值非常受异常值的影响并且这不是中心位置的可靠估计：均值不一定是数据点的典型示例。如需要更可靠的的估计，请参考 @ref{1ab2,,median()} 和 @ref{2bb,,mode()} 。

样本均值给出了一个无偏向的真实总体均值的估计，因此当平均抽取所有可能的样本， @code{mean(sample)} 收敛于整个总体的真实均值。如果 @emph{data} 代表整个总体而不是样本，那么 @code{mean(data)} 等同于计算真实整体均值 μ 。
@end quotation
@end cartouche
@end deffn

@geindex fmean() (在 statistics 模块中)
@anchor{library/statistics statistics fmean}@anchor{227}
@deffn {函数} statistics.fmean (data)

将 @emph{data} 转换成浮点数并且计算算术平均数。

此函数的运行速度比 @ref{199,,mean()} 函数快并且它总是返回一个 @ref{187,,float}。 @emph{data} 可以为序列或可迭代对象。 如果输入数据集为空，则会引发 @ref{1abc,,StatisticsError}。

@example
>>> fmean([3.5, 4.0, 5.25])
4.25
@end example


3.8 新版功能.

@end deffn

@geindex geometric_mean() (在 statistics 模块中)
@anchor{library/statistics statistics geometric_mean}@anchor{228}
@deffn {函数} statistics.geometric_mean (data)

将 @emph{data} 转换成浮点数并且计算几何平均数。

几何平均值使用值的乘积表示 @emph{数据} 的中心趋势或典型值（与使用它们的总和的算术平均值相反）。

如果输入数据集为空、包含零或包含负值则将引发 @ref{1abc,,StatisticsError}。 @emph{data} 可以是序列或可迭代对象。

无需做出特殊努力即可获得准确的结果。（但是，将来或许会修改。）

@example
>>> round(geometric_mean([54, 24, 36]), 1)
36.0
@end example


3.8 新版功能.

@end deffn

@geindex harmonic_mean() (在 statistics 模块中)
@anchor{library/statistics statistics harmonic_mean}@anchor{58a}
@deffn {函数} statistics.harmonic_mean (data)

返回 @emph{data} 调和均值，该参数可以是序列或包含实数值的可迭代对象。

调和均值,也叫次相反均值，所有数据的倒数的算术平均数 @ref{199,,mean()} 的倒数。比如说，数据 @emph{a} ， @emph{b} ， @emph{c} 的调和均值等于 @code{3/(1/a + 1/b + 1/c)} 。如果其中一个值为零，结果为零。

调和均值是一种均值类型，是数据中心位置的度量。它通常适合于求比率和比例的平均值，比如速率。

假设一辆车在 40 km/hr 的速度下行驶了 10 km ，然后又以 60 km/hr 的速度行驶了 10 km 。车辆的平均速率是多少？

@example
>>> harmonic_mean([40, 60])
48.0
@end example

假设一名投资者在三家公司各购买了等价值的股票，以 2.5， 3 ， 10 的 P/E (价格/收益) 率。投资者投资组合的平均市盈率是多少？

@example
>>> harmonic_mean([2.5, 3, 10])  # For an equal investment portfolio.
3.6
@end example

如果 @emph{data} 为空或者 任何一个元素的值小于零，会引发 @ref{1abc,,StatisticsError} 。

当前算法在输入中遇到零时会提前退出。这意味着不会测试后续输入的有效性。（此行为将来可能会更改。）


3.6 新版功能.

@end deffn

@geindex median() (在 statistics 模块中)
@anchor{library/statistics statistics median}@anchor{1ab2}
@deffn {函数} statistics.median (data)

使用普通的“取中间两数平均值”方法返回数值数据的中位数（中间值）。 如果 @emph{data} 为空，则将引发 @ref{1abc,,StatisticsError}。 @emph{data} 可以是序列或可迭代对象。

中位数是衡量中间位置的可靠方式，并且较少受到极端值的影响。 当数据点的总数为奇数时，将返回中间数据点：

@example
>>> median([1, 3, 5])
3
@end example

当数据点的总数为偶数时，中位数将通过对两个中间值求平均进行插值得出：

@example
>>> median([1, 3, 5, 7])
4.0
@end example

这适用于当你的数据是离散的，并且你不介意中位数不是实际数据点的情况。

如果数据是有序的（支持排序操作）但不是数字（不支持加法），请考虑改用 @ref{1ab3,,median_low()} 或 @ref{1ab4,,median_high()}。
@end deffn

@geindex median_low() (在 statistics 模块中)
@anchor{library/statistics statistics median_low}@anchor{1ab3}
@deffn {函数} statistics.median_low (data)

返回数值数据的低中位数。 如果 @emph{data} 为空则将引发 @ref{1abc,,StatisticsError}。 @emph{data} 可以是序列或可迭代对象。

低中位数一定是数据集的成员。 当数据点总数为奇数时，将返回中间值。 当其为偶数时，将返回两个中间值中较小的那个。

@example
>>> median_low([1, 3, 5])
3
>>> median_low([1, 3, 5, 7])
3
@end example

当你的数据是离散的，并且你希望中位数是一个实际数据点而非插值结果时可以使用低中位数。
@end deffn

@geindex median_high() (在 statistics 模块中)
@anchor{library/statistics statistics median_high}@anchor{1ab4}
@deffn {函数} statistics.median_high (data)

返回数据的高中位数。 如果 @emph{data} 为空则将引发 @ref{1abc,,StatisticsError}。 @emph{data} 可以是序列或可迭代对象。

高中位数一定是数据集的成员。 当数据点总数为奇数时，将返回中间值。 当其为偶数时，将返回两个中间值中较大的那个。

@example
>>> median_high([1, 3, 5])
3
>>> median_high([1, 3, 5, 7])
5
@end example

当你的数据是离散的，并且你希望中位数是一个实际数据点而非插值结果时可以使用高中位数。
@end deffn

@geindex median_grouped() (在 statistics 模块中)
@anchor{library/statistics statistics median_grouped}@anchor{1ab5}
@deffn {函数} statistics.median_grouped (data, interval=1)

返回分组的连续数据的中位数，根据第 50 个百分点的位置使用插值来计算。 如果 @emph{data} 为空则将引发 @ref{1abc,,StatisticsError}。 @emph{data} 可以是序列或可迭代对象。

@example
>>> median_grouped([52, 52, 53, 54])
52.5
@end example

在下面的示例中，数据已经过舍入，这样每个值都代表数据分类的中间点，例如 1 是 0.5--1.5 分类的中间点，2 是 1.5--2.5 分类的中间点，3 是 2.5--3.5 的中间点等待。 根据给定的数据，中间值应落在 3.5--4.5 分类之内，并可使用插值法来进行估算：

@example
>>> median_grouped([1, 2, 2, 3, 4, 4, 4, 4, 4, 5])
3.7
@end example

可选参数 @emph{interval} 表示分类间隔，默认值为 1。 改变分类间隔自然会改变插件结果：

@example
>>> median_grouped([1, 3, 3, 5, 7], interval=1)
3.25
>>> median_grouped([1, 3, 3, 5, 7], interval=2)
3.5
@end example

此函数不会检查数据点之间是否至少相隔 @emph{interval} 的距离。

@strong{CPython implementation detail:} 在某些情况下，@ref{1ab5,,median_grouped()} 可以会将数据点强制转换为浮点数。 此行为在未来有可能会发生改变。


@subsubheading 参见



@itemize *

@item 
"Statistics for the Behavioral Sciences", Frederick J Gravetter and
Larry B Wallnau (8th Edition).

@item 
Gnome Gnumeric 电子表格中的 SSMEDIAN@footnote{https://help.gnome.org/users/gnumeric/stable/gnumeric.html#gnumeric-function-SSMEDIAN} 函数，包括 这篇讨论@footnote{https://mail.gnome.org/archives/gnumeric-list/2011-April/msg00018.html}。
@end itemize

@end deffn

@geindex mode() (在 statistics 模块中)
@anchor{library/statistics statistics mode}@anchor{2bb}
@deffn {函数} statistics.mode (data)

从离散或标称的 @emph{data} 返回单个出现最多的数据点。 此众数（如果存在）是最典型的值，并可用来度量中心的位置。

如果存在具有相同频率的多个众数，则返回在 @emph{data} 中遇到的第一个。 如果想要其中最小或最大的一个，请使用 @code{min(multimode(data))} 或 @code{max(multimode(data))}。 如果输入的 @emph{data} 为空，则会引发 @ref{1abc,,StatisticsError}。

@code{mode} 将假定是离散数据并返回一个单一的值。 这是通常的学校教学中标准的处理方式：

@example
>>> mode([1, 1, 2, 3, 3, 3, 3, 4])
3
@end example

此众数的独特之处在于它是这个包中唯一还可应用于标称（非数字）数据的统计信息：

@example
>>> mode(["red", "blue", "blue", "red", "green", "red", "red"])
'red'
@end example


在 3.8 版更改: 现在会通过返回所遇到的第一个众数来处理多模数据集。 之前它会在遇到超过一个的众数时引发 @ref{1abc,,StatisticsError}。

@end deffn

@geindex multimode() (在 statistics 模块中)
@anchor{library/statistics statistics multimode}@anchor{229}
@deffn {函数} statistics.multimode (data)

返回最频繁出现的值的列表，并按它们在 @emph{data} 中首次出现的位置排序。 如果存在多个众数则将返回一个以上的众数，或者如果 @emph{data} 为空则将返回空列表：

@example
>>> multimode('aabbbbccddddeeffffgg')
['b', 'd', 'f']
>>> multimode('@w{'})
[]
@end example


3.8 新版功能.

@end deffn

@geindex pstdev() (在 statistics 模块中)
@anchor{library/statistics statistics pstdev}@anchor{1ab7}
@deffn {函数} statistics.pstdev (data, mu=None)

返回总体标准差（总体方差的平方根）。 请参阅 @ref{1ab8,,pvariance()} 了解参数和其他细节。

@example
>>> pstdev([1.5, 2.5, 2.5, 2.75, 3.25, 4.75])
0.986893273527251
@end example
@end deffn

@geindex pvariance() (在 statistics 模块中)
@anchor{library/statistics statistics pvariance}@anchor{1ab8}
@deffn {函数} statistics.pvariance (data, mu=None)

返回非空序列或包含实数值的可迭代对象 @emph{data} 的总体方差。 方差或称相对于均值的二阶距，是对数据变化幅度（延展度或分散度）的度量。 方差值较大表明数据的散布范围较大；方差值较小表明它紧密聚集于均值附近。

如果给出了可选的第二个参数 @emph{mu}，它通常是 @emph{data} 的均值。 它也可以被用来计算相对于一个非均值点的二阶距。 如果该参数省略或为 @code{None} (默认值)，则会自动进行算术均值的计算。

使用此函数可根据所有数值来计算方差。 要根据一个样本来估算方差，通常 @ref{1aba,,variance()} 函数是更好的选择。

如果 @emph{data} 为空则会引发 @ref{1abc,,StatisticsError}。

示例：

@example
>>> data = [0.0, 0.25, 0.25, 1.25, 1.5, 1.75, 2.75, 3.25]
>>> pvariance(data)
1.25
@end example

如果你已经计算过数据的平均值，你可以将其作为可选的第二个参数 @emph{mu} 传入以避免重复计算：

@example
>>> mu = mean(data)
>>> pvariance(data, mu)
1.25
@end example

同样也支持使用 Decimal 和 Fraction 值：

@example
>>> from decimal import Decimal as D
>>> pvariance([D("27.5"), D("30.25"), D("30.25"), D("34.5"), D("41.75")])
Decimal('24.815')

>>> from fractions import Fraction as F
>>> pvariance([F(1, 4), F(5, 4), F(1, 2)])
Fraction(13, 72)
@end example

@cartouche
@quotation 注解 
当调用时附带完整的总体数据时，这将给出总体方差 σ²。 而当调用时只附带一个样本时，这将给出偏置样本方差 s²，也被称为带有 N 个自由度的方差。

如果你通过某种方式知道了真实的总体平均值 μ，则可以使用此函数来计算一个样本的方差，并将已知的总体平均值作为第二个参数。 假设数据点是总体的一个随机样本，则结果将为总体方差的无偏估计值。
@end quotation
@end cartouche
@end deffn

@geindex stdev() (在 statistics 模块中)
@anchor{library/statistics statistics stdev}@anchor{1ab9}
@deffn {函数} statistics.stdev (data, xbar=None)

返回样本标准差（样本方差的平方根）。 请参阅 @ref{1aba,,variance()} 了解参数和其他细节。

@example
>>> stdev([1.5, 2.5, 2.5, 2.75, 3.25, 4.75])
1.0810874155219827
@end example
@end deffn

@geindex variance() (在 statistics 模块中)
@anchor{library/statistics statistics variance}@anchor{1aba}
@deffn {函数} statistics.variance (data, xbar=None)

返回包含至少两个实数值的可迭代对象 @emph{data} 的样本方差。 方差或称相对于均值的二阶矩，是对数据变化幅度（延展度或分散度）的度量。 方差值较大表明数据的散布范围较大；方差值较小表明它紧密聚集于均值附近。

如果给出了可选的第二个参数 @emph{xbar}，它应当是 @emph{data} 的均值。 如果该参数省略或为 @code{None} (默认值)，则会自动进行均值的计算。

当你的数据是总体数据的样本时请使用此函数。 要根据整个总体数据来计算方差，请参见 @ref{1ab8,,pvariance()}。

如果 @emph{data} 包含的值少于两个则会引发 @ref{1abc,,StatisticsError}。

示例：

@example
>>> data = [2.75, 1.75, 1.25, 0.25, 0.5, 1.25, 3.5]
>>> variance(data)
1.3720238095238095
@end example

如果你已经计算过数据的平均值，你可以将其作为可选的第二个参数 @emph{xbar} 传入以避免重复计算：

@example
>>> m = mean(data)
>>> variance(data, m)
1.3720238095238095
@end example

此函数不会试图检查你所传入的 @emph{xbar} 是否为真实的平均值。 使用任意值作为 @emph{xbar} 可能导致无效或不可能的结果。

同样也支持使用 Decimal 和 Fraction 值：

@example
>>> from decimal import Decimal as D
>>> variance([D("27.5"), D("30.25"), D("30.25"), D("34.5"), D("41.75")])
Decimal('31.01875')

>>> from fractions import Fraction as F
>>> variance([F(1, 6), F(1, 2), F(5, 3)])
Fraction(67, 108)
@end example

@cartouche
@quotation 注解 
这是附带贝塞尔校正的样本方差 s²，也称为具有 N-1 自由度的方差。 假设数据点具有代表性（即为独立且均匀的分布），则结果应当是对总体方差的无偏估计。

如果你通过某种方式知道了真实的总体平均值 μ 则应当调用 @ref{1ab8,,pvariance()} 函数并将该值作为 @emph{mu} 形参传入以得到一个样本的方差。
@end quotation
@end cartouche
@end deffn

@geindex quantiles() (在 statistics 模块中)
@anchor{library/statistics statistics quantiles}@anchor{22a}
@deffn {函数} statistics.quantiles (data, *, n=4, method='exclusive')

将 @emph{data} 分隔为具有相等概率的 @emph{n} 个连续区间。 返回分隔这些区间的 @code{n - 1} 个分隔点的列表。

将 @emph{n} 设为 4 以使用四分位（默认值）。 将 @emph{n} 设为 10 以使用十分位。 将 @emph{n} 设为 100 以使用百分位，即给出 99 个分隔点来将 @emph{data} 分隔为 100 个大小相等的组。 如果 @emph{n} 小于 1 则将引发 @ref{1abc,,StatisticsError}。

@emph{data} 可以是包含样本数据的任意可迭代对象。 为了获得有意义的结果，@emph{data} 中数据点的数量应当大于 @emph{n}。 如果数据点的数量小于两个则将引发 @ref{1abc,,StatisticsError}。

分隔点是通过对两个最接近的数据点进行线性插值得到的。 例如，如果一个分隔点落在两个样本值 @code{100} 和 @code{112} 之间距离三分之一的位置，则分隔点的取值将为 @code{104}。

@emph{method} 用于计算分位值，它会由于 @emph{data} 是包含还是排除总体的最低和最高可能值而有所不同。

默认 @emph{method} 是 “唯一的” 并且被用于在总体中数据采样这样可以有比样本中找到的更多的极端值。落在 @emph{m} 个排序数据点的第 @emph{i-th} 个以下的总体部分被计算为 @code{i / (m + 1)} 。给定九个样本值，方法排序它们并且分配一下的百分位： 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% 。

将 @emph{method} 设为 "inclusive" 可用于描述总体数据或已明确知道包含有总体数据中最极端值的样本。 @emph{data} 中的最小值会被作为第 0 个百分位而最大值会被作为第 100 个百分位。 总体数据里处于 @emph{m} 个已排序数据点中 @emph{第 i 个} 以下的部分会以 @code{(i - 1) / (m - 1)} 来计算。 给定 11 个样本值，该方法会对它们进行排序并赋予以下百分位: 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%。

@example
# Decile cut points for empirically sampled data
>>> data = [105, 129, 87, 86, 111, 111, 89, 81, 108, 92, 110,
...         100, 75, 105, 103, 109, 76, 119, 99, 91, 103, 129,
...         106, 101, 84, 111, 74, 87, 86, 103, 103, 106, 86,
...         111, 75, 87, 102, 121, 111, 88, 89, 101, 106, 95,
...         103, 107, 101, 81, 109, 104]
>>> [round(q, 1) for q in quantiles(data, n=10)]
[81.0, 86.2, 89.0, 99.4, 102.5, 103.6, 106.0, 109.8, 111.0]
@end example


3.8 新版功能.

@end deffn

@node 异常<3>,NormalDist 对象,函数细节,statistics --- 数学统计函数
@anchor{library/statistics exceptions}@anchor{1abd}
@subsubsection 异常


只定义了一个异常：

@geindex StatisticsError
@anchor{library/statistics statistics StatisticsError}@anchor{1abc}
@deffn {例外} statistics.StatisticsError

@ref{1fb,,ValueError} 的子类，表示统计相关的异常。
@end deffn

@node NormalDist 对象,,异常<3>,statistics --- 数学统计函数
@anchor{library/statistics normaldist-objects}@anchor{1abe}
@subsubsection @code{NormalDist} 对象


@ref{22b,,NormalDist} 工具可用于创建和操纵 随机变量@footnote{http://www.stat.yale.edu/Courses/1997-98/101/ranvar.htm} 的正态分布。 这个类将数据度量值的平均值和标准差作为单一实体来处理。

正态分布的概念来自于 中央极限定理@footnote{https://en.wikipedia.org/wiki/Central_limit_theorem} 并且在统计学中有广泛的应用。

@geindex NormalDist (statistics 中的类)
@anchor{library/statistics statistics NormalDist}@anchor{22b}
@deffn {类} statistics.NormalDist (mu=0.0, sigma=1.0)

返回一个新的 @emph{NormalDist} 对象，其中 @emph{mu} 代表 算术平均值@footnote{https://en.wikipedia.org/wiki/Arithmetic_mean} 而 @emph{sigma} 代表 标准差@footnote{https://en.wikipedia.org/wiki/Standard_deviation}。

若 @emph{sigma} 为负数，将会引发 @ref{1abc,,StatisticsError}。

@geindex mean (statistics.NormalDist 属性)
@anchor{library/statistics statistics NormalDist mean}@anchor{1abf}
@deffn {属性} mean

一个只读特征属性，表示特定正态分布的 算术平均值@footnote{https://en.wikipedia.org/wiki/Arithmetic_mean}。
@end deffn

@geindex median (statistics.NormalDist 属性)
@anchor{library/statistics statistics NormalDist median}@anchor{1ac0}
@deffn {属性} median

一个只读特征属性，表示特定正态分布的 中位数@footnote{https://en.wikipedia.org/wiki/Median}。
@end deffn

@geindex mode (statistics.NormalDist 属性)
@anchor{library/statistics statistics NormalDist mode}@anchor{1ac1}
@deffn {属性} mode

一个只读特征属性，表示特定正态分布的 众数@footnote{https://en.wikipedia.org/wiki/Mode_(statistics)}。
@end deffn

@geindex stdev (statistics.NormalDist 属性)
@anchor{library/statistics statistics NormalDist stdev}@anchor{1ac2}
@deffn {属性} stdev

一个只读特征属性，表示特定正态分布的 标准差@footnote{https://en.wikipedia.org/wiki/Standard_deviation}。
@end deffn

@geindex variance (statistics.NormalDist 属性)
@anchor{library/statistics statistics NormalDist variance}@anchor{1ac3}
@deffn {属性} variance

一个只读特征属性，表示特定正态分布的 方差@footnote{https://en.wikipedia.org/wiki/Variance}。 等于标准差的平方。
@end deffn

@geindex from_samples() (statistics.NormalDist 类方法)
@anchor{library/statistics statistics NormalDist from_samples}@anchor{1ac4}
@deffn {方法} classmethod from_samples (data)

传入使用 @ref{227,,fmean()} 和 @ref{1ab9,,stdev()} 基于 @emph{data} 估算出的 @emph{mu} 和 @emph{sigma} 形参创建一个正态分布实例。

@emph{data} 可以是任何 @ref{ba5,,iterable} 并且应当包含能被转换为 @ref{187,,float} 类型的值。 如果 @emph{data} 不包含至少两个元素，则会引发 @ref{1abc,,StatisticsError}，因为估算中心值至少需要一个点而估算分散度至少需要两个点。
@end deffn

@geindex samples() (statistics.NormalDist 方法)
@anchor{library/statistics statistics NormalDist samples}@anchor{1ac5}
@deffn {方法} samples (n, *, seed=None)

对于给定的平均值和标准差生成 @emph{n} 个随机样本。 返回一个由 @ref{187,,float} 值组成的 @ref{262,,list}。

当给定 @emph{seed} 时，创建一个新的底层随机数生成器实例。 这适用于创建可重现的结果，即使对于多线程上下文也有效。
@end deffn

@geindex pdf() (statistics.NormalDist 方法)
@anchor{library/statistics statistics NormalDist pdf}@anchor{1ac6}
@deffn {方法} pdf (x)

使用 概率密度函数 (pdf)@footnote{https://en.wikipedia.org/wiki/Probability_density_function}，计算一个随机变量 @emph{X} 趋向于给定值 @emph{x} 的相对可能性。 在数学意义上，它是当 @emph{dx} 趋向于零时比率 @code{P(x <= X < x+dx) / dx} 的极限。

相对可能性的计算方法是用一个狭窄区间内某个样本出现的概率除以区间的宽度（因此使用“密度”一词）。 由于可能性是相对于其他点的，它的值可以大于 @cite{1.0}。
@end deffn

@geindex cdf() (statistics.NormalDist 方法)
@anchor{library/statistics statistics NormalDist cdf}@anchor{1ac7}
@deffn {方法} cdf (x)

使用 累积分布函数 (cdf)@footnote{https://en.wikipedia.org/wiki/Cumulative_distribution_function}，计算一个随机变量 @emph{X} 小于等于 @emph{x} 的概率。 在数学上，它表示为 @code{P(X <= x)}。
@end deffn

@geindex inv_cdf() (statistics.NormalDist 方法)
@anchor{library/statistics statistics NormalDist inv_cdf}@anchor{1ac8}
@deffn {方法} inv_cdf (p)

计算反向累积分布函数，也称为 分位数函数@footnote{https://en.wikipedia.org/wiki/Quantile_function} 或 百分点@footnote{https://www.statisticshowto.datasciencecentral.com/inverse-distribution-function/} 函数。 在数学上，它表示为 @code{x : P(X <= x) = p}。

找出随机变量 @emph{X} 的值 @emph{x} 使得该变量小于等于该值的概率等于给定的概率 @emph{p}。
@end deffn

@geindex overlap() (statistics.NormalDist 方法)
@anchor{library/statistics statistics NormalDist overlap}@anchor{1ac9}
@deffn {方法} overlap (other)

测量两个正态概率分布之间的一致性。 返回介于 0.0 和 1.0 之间的值，给出 两个概率密度函数的重叠区域@footnote{https://www.rasch.org/rmt/rmt101r.htm}。
@end deffn

@geindex quantiles() (statistics.NormalDist 方法)
@anchor{library/statistics statistics NormalDist quantiles}@anchor{1aca}
@deffn {方法} quantiles (n=4)

将指定正态分布划分为 @emph{n} 个相等概率的连续分隔区。 返回这些分隔区对应的 (n - 1) 个分隔点的列表。

将 @emph{n} 设为 4 以使用四分位（默认值）。 将 @emph{n} 设为 10 以使用十分位。将 @emph{n} 设为 100 以使用百分位，即给出 99 个分隔点来将正态分布分隔为 100 个大小相等的组。
@end deffn

@ref{22b,,NormalDist} 的实例支持加上、减去、乘以或除以一个常量。 这些运算被用于转换和缩放。 例如：

@example
>>> temperature_february = NormalDist(5, 2.5)             # Celsius
>>> temperature_february * (9/5) + 32                     # Fahrenheit
NormalDist(mu=41.0, sigma=4.5)
@end example

不允许一个常量除以 @ref{22b,,NormalDist} 的实例，因为结果将不是正态分布。

由于正态分布是由独立变量的累加效应产生的，因此允许表示为 @ref{22b,,NormalDist} 实例的 两组独立正态分布的随机变量相加和相减@footnote{https://en.wikipedia.org/wiki/Sum_of_normally_distributed_random_variables}。 例如：

@example
>>> birth_weights = NormalDist.from_samples([2.5, 3.1, 2.1, 2.4, 2.7, 3.5])
>>> drug_effects = NormalDist(0.4, 0.15)
>>> combined = birth_weights + drug_effects
>>> round(combined.mean, 1)
3.1
>>> round(combined.stdev, 1)
0.5
@end example


3.8 新版功能.

@end deffn

@menu
* NormalDist 示例和用法:: 

@end menu

@node NormalDist 示例和用法,,,NormalDist 对象
@anchor{library/statistics normaldist-examples-and-recipes}@anchor{1acb}
@subsubsection @code{NormalDist} 示例和用法


@ref{22b,,NormalDist} 适合用来解决经典概率问题。

举例来说，如果 SAT 考试的历史数据@footnote{https://nces.ed.gov/programs/digest/d17/tables/dt17_226.40.asp} 显示分数呈平均值为 1060 且标准差为 195 的正态分布，则可以确定考试分数处于 1100 和 1200 之间的学生的百分比舍入到最接近的整数应为：

@example
>>> sat = NormalDist(1060, 195)
>>> fraction = sat.cdf(1200 + 0.5) - sat.cdf(1100 - 0.5)
>>> round(fraction * 100.0, 1)
18.4
@end example

求 SAT 分数的 四分位@footnote{https://en.wikipedia.org/wiki/Quartile} 和 十分位@footnote{https://en.wikipedia.org/wiki/Decile}：

@example
>>> list(map(round, sat.quantiles()))
[928, 1060, 1192]
>>> list(map(round, sat.quantiles(n=10)))
[810, 896, 958, 1011, 1060, 1109, 1162, 1224, 1310]
@end example

为了估算一个不易解析的模型分布，@ref{22b,,NormalDist} 可以生成用于 蒙特卡洛模拟@footnote{https://en.wikipedia.org/wiki/Monte_Carlo_method} 的输入样本：

@example
>>> def model(x, y, z):
...     return (3*x + 7*x*y - 5*y) / (11 * z)
...
>>> n = 100_000
>>> X = NormalDist(10, 2.5).samples(n, seed=3652260728)
>>> Y = NormalDist(15, 1.75).samples(n, seed=4582495471)
>>> Z = NormalDist(50, 1.25).samples(n, seed=6582483453)
>>> quantiles(map(model, X, Y, Z))       
[1.4591308524824727, 1.8035946855390597, 2.175091447274739]
@end example

当样本量较大并且成功试验的可能性接近 50% 时，正态分布可以被用来模拟 二项分布@footnote{http://mathworld.wolfram.com/BinomialDistribution.html}。

例如，一次开源会议有 750 名与会者和两个可分别容纳 500 人的会议厅。 会上有一场关于 Python 的演讲和一场关于 Ruby 的演讲。 在往届会议中，65% 的与会者更愿意去听关于 Python 的演讲。 假定人群的偏好没有发生改变，那么 Python 演讲的会议厅不超出其容量上限的可能性是多少？

@example
>>> n = 750             # Sample size
>>> p = 0.65            # Preference for Python
>>> q = 1.0 - p         # Preference for Ruby
>>> k = 500             # Room capacity

>>> # Approximation using the cumulative normal distribution
>>> from math import sqrt
>>> round(NormalDist(mu=n*p, sigma=sqrt(n*p*q)).cdf(k + 0.5), 4)
0.8402

>>> # Solution using the cumulative binomial distribution
>>> from math import comb, fsum
>>> round(fsum(comb(n, r) * p**r * q**(n-r) for r in range(k+1)), 4)
0.8402

>>> # Approximation using a simulation
>>> from random import seed, choices
>>> seed(8675309)
>>> def trial():
...     return choices(('Python', 'Ruby'), (p, q), k=n).count('Python')
>>> mean(trial() <= k for i in range(10_000))
0.8398
@end example

在机器学习问题中也经常会出现正态分布。

Wikipedia 上有一个 朴素贝叶斯分类器的好例子@footnote{https://en.wikipedia.org/wiki/Naive_Bayes_classifier#Sex_classification}。 挑战的问题是根据对多个正态分布的特征测量值包括身高、体重和足部尺码来预测一个人的性别。

我们得到了由八个人的测量值组成的训练数据集。 假定这些测量值是正态分布的，因此我们用 @ref{22b,,NormalDist} 来总结数据：

@example
>>> height_male = NormalDist.from_samples([6, 5.92, 5.58, 5.92])
>>> height_female = NormalDist.from_samples([5, 5.5, 5.42, 5.75])
>>> weight_male = NormalDist.from_samples([180, 190, 170, 165])
>>> weight_female = NormalDist.from_samples([100, 150, 130, 150])
>>> foot_size_male = NormalDist.from_samples([12, 11, 12, 10])
>>> foot_size_female = NormalDist.from_samples([6, 8, 7, 9])
@end example

接下来，我们遇到一个特征测量值已知但性别未知的新人：

@example
>>> ht = 6.0        # height
>>> wt = 130        # weight
>>> fs = 8          # foot size
@end example

从是男是女各 50% 的 先验概率@footnote{https://en.wikipedia.org/wiki/Prior_probability} 出发，我们通过将该先验概率乘以给定性别的特征度量值的可能性累积值来计算后验概率：

@example
>>> prior_male = 0.5
>>> prior_female = 0.5
>>> posterior_male = (prior_male * height_male.pdf(ht) *
...                   weight_male.pdf(wt) * foot_size_male.pdf(fs))

>>> posterior_female = (prior_female * height_female.pdf(ht) *
...                     weight_female.pdf(wt) * foot_size_female.pdf(fs))
@end example

最终预测值应为最大后验概率值。 这种算法被称为 maximum a posteriori@footnote{https://en.wikipedia.org/wiki/Maximum_a_posteriori_estimation} 或 MAP：

@example
>>> 'male' if posterior_male > posterior_female else 'female'
'female'
@end example

@c # This modelines must appear within the last ten lines of the file.
@c kate: indent-width 3; remove-trailing-space on; replace-tabs on; encoding utf-8;

@node 函数式编程模块,文件和目录访问,数字和数学模块,Python 标准库
@anchor{library/functional doc}@anchor{1acc}@anchor{library/functional functional-programming-modules}@anchor{1acd}
@section 函数式编程模块


本章里描述的模块提供了函数和类，以支持函数式编程风格和在可调用对象上的通用操作。

本章包含以下模块的文档：

@menu
* itertools: itertools --- 为高效循环而创建迭代器的函数. 为高效循环而创建迭代器的函数
* functools: functools --- 高阶函数和可调用对象上的操作. 高阶函数和可调用对象上的操作
* operator: operator --- 标准运算符替代函数. 标准运算符替代函数

@end menu

@node itertools --- 为高效循环而创建迭代器的函数,functools --- 高阶函数和可调用对象上的操作,,函数式编程模块
@anchor{library/itertools doc}@anchor{1ace}@anchor{library/itertools itertools-functions-creating-iterators-for-efficient-looping}@anchor{1acf}@anchor{library/itertools module-itertools}@anchor{a3}
@subsection @code{itertools} --- 为高效循环而创建迭代器的函数


@geindex itertools (模块)

@c from itertools import *


__________________________________________________________________


本模块实现一系列 @ref{fce,,iterator} ，这些迭代器受到APL，Haskell和SML的启发。为了适用于Python，它们都被重新写过。

本模块标准化了一个快速、高效利用内存的核心工具集，这些工具本身或组合都很有用。它们一起形成了“迭代器代数”，这使得在纯Python中有可能创建简洁又高效的专用工具。

例如，SML有一个制表工具： @code{tabulate(f)}，它可产生一个序列 @code{f(0), f(1), ...}。在Python中可以组合 @ref{c26,,map()} 和 @ref{c14,,count()} 实现： @code{map(f, count())}。

这些内置工具同时也能很好地与 @ref{c2,,operator} 模块中的高效函数配合使用。例如，我们可以将两个向量的点积映射到乘法运算符： @code{sum(map(operator.mul, vector1, vector2))} 。

@strong{无穷迭代器：}


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

迭代器

@tab

实参

@tab

结果

@tab

示例

@item

@ref{c14,,count()}

@tab

start, [step]

@tab

start, start+step, start+2*step, ...

@tab

@code{count(10) --> 10 11 12 13 14 ...}

@item

@ref{1ad0,,cycle()}

@tab

p

@tab

p0, p1, ... plast, p0, p1, ...

@tab

@code{cycle('ABCD') --> A B C D A B C D ...}

@item

@ref{1045,,repeat()}

@tab

elem [,n]

@tab

elem, elem, elem, ... 重复无限次或n次

@tab

@code{repeat(10, 3) --> 10 10 10}

@end multitable


@strong{根据最短输入序列长度停止的迭代器：}


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

迭代器

@tab

实参

@tab

结果

@tab

示例

@item

@ref{1dd,,accumulate()}

@tab

p [,func]

@tab

p0, p0+p1, p0+p1+p2, ...

@tab

@code{accumulate([1,2,3,4,5]) --> 1 3 6 10 15}

@item

@ref{159b,,chain()}

@tab

p, q, ...

@tab

p0, p1, ... plast, q0, q1, ...

@tab

@code{chain('ABC', 'DEF') --> A B C D E F}

@item

@ref{1ad1,,chain.from_iterable()}

@tab

iterable -- 可迭代对象

@tab

p0, p1, ... plast, q0, q1, ...

@tab

@code{chain.from_iterable(['ABC', 'DEF']) --> A B C D E F}

@item

@ref{c13,,compress()}

@tab

data, selectors

@tab

(d[0] if s[0]), (d[1] if s[1]), ...

@tab

@code{compress('ABCDEF', [1,0,1,0,1,1]) --> A C E F}

@item

@ref{1ad2,,dropwhile()}

@tab

pred, seq

@tab

seq[n], seq[n+1], ... 从pred首次真值测试失败开始

@tab

@code{dropwhile(lambda x: x<5, [1,4,6,4,1]) --> 6 4 1}

@item

@ref{1584,,filterfalse()}

@tab

pred, seq

@tab

seq中pred(x)为假值的元素，x是seq中的元素。

@tab

@code{filterfalse(lambda x: x%2, range(10)) --> 0 2 4 6 8}

@item

@ref{1ad3,,groupby()}

@tab

iterable[, key]

@tab

根据key(v)值分组的迭代器

@tab

@item

@ref{39a,,islice()}

@tab

seq, [start,] stop [, step]

@tab

seq[start:stop:step]中的元素

@tab

@code{islice('ABCDEFG', 2, None) --> C D E F G}

@item

@ref{a23,,starmap()}

@tab

func, seq

@tab

func(*seq[0]), func(*seq[1]), ...

@tab

@code{starmap(pow, [(2,5), (3,2), (10,3)]) --> 32 9 1000}

@item

@ref{1ad4,,takewhile()}

@tab

pred, seq

@tab

seq[0], seq[1], ..., 直到pred真值测试失败

@tab

@code{takewhile(lambda x: x<5, [1,4,6,4,1]) --> 1 4}

@item

@ref{1ad5,,tee()}

@tab

it, n

@tab

it1, it2, ... itn 将一个迭代器拆分为n个迭代器

@tab

@item

@ref{c2a,,zip_longest()}

@tab

p, q, ...

@tab

(p[0], q[0]), (p[1], q[1]), ...

@tab

@code{zip_longest('ABCD', 'xy', fillvalue='-') --> Ax By C- D-}

@end multitable


@strong{排列组合迭代器：}


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

迭代器

@tab

实参

@tab

结果

@item

@ref{ca0,,product()}

@tab

p, q, ... [repeat=1]

@tab

笛卡尔积，相当于嵌套的for循环

@item

@ref{1ad6,,permutations()}

@tab

p[, r]

@tab

长度r元组，所有可能的排列，无重复元素

@item

@ref{c9f,,combinations()}

@tab

p, r

@tab

长度r元组，有序，无重复元素

@item

@ref{c12,,combinations_with_replacement()}

@tab

p, r

@tab

长度r元组，有序，元素可重复

@end multitable



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

例子

@tab

结果

@item

@code{product('ABCD', repeat=2)}

@tab

@code{AA AB AC AD BA BB BC BD CA CB CC CD DA DB DC DD}

@item

@code{permutations('ABCD', 2)}

@tab

@code{AB AC AD BA BC BD CA CB CD DA DB DC}

@item

@code{combinations('ABCD', 2)}

@tab

@code{AB AC AD BC BD CD}

@item

@code{combinations_with_replacement('ABCD', 2)}

@tab

@code{AA AB AC AD BB BC BD CC CD DD}

@end multitable


@menu
* Itertool函数:: 
* itertools 配方:: 

@end menu

@node Itertool函数,itertools 配方,,itertools --- 为高效循环而创建迭代器的函数
@anchor{library/itertools itertool-functions}@anchor{1ad7}@anchor{library/itertools itertools-functions}@anchor{1ad8}
@subsubsection Itertool函数


下列模块函数均创建并返回迭代器。有些迭代器不限制输出流长度，所以它们只应在能截断输出流的函数或循环中使用。

@geindex accumulate() (在 itertools 模块中)
@anchor{library/itertools itertools accumulate}@anchor{1dd}
@deffn {函数} itertools.accumulate (iterable[, func, *, initial=None])

创建一个迭代器，返回累积汇总值或其他双目运算函数的累积结果值（通过可选的 @emph{func} 参数指定）。

如果提供了 @emph{func}，它应当为带有两个参数的函数。 输入 @emph{iterable} 的元素可以是能被 @emph{func} 接受为参数的任意类型。 （例如，对于默认的加法运算，元素可以是任何可相加的类型包括 @ref{188,,Decimal} 或 @ref{185,,Fraction}。）

通常，输出的元素数量与输入的可迭代对象是一致的。 但是，如果提供了关键字参数 @emph{initial}，则累加会以 @emph{initial} 值开始，这样输出就比输入的可迭代对象多一个元素。

大致相当于：

@example
def accumulate(iterable, func=operator.add, *, initial=None):
    'Return running totals'
    # accumulate([1,2,3,4,5]) --> 1 3 6 10 15
    # accumulate([1,2,3,4,5], initial=100) --> 100 101 103 106 110 115
    # accumulate([1,2,3,4,5], operator.mul) --> 1 2 6 24 120
    it = iter(iterable)
    total = initial
    if initial is None:
        try:
            total = next(it)
        except StopIteration:
            return
    yield total
    for element in it:
        total = func(total, element)
        yield total
@end example

@emph{func} 参数有几种用法。它可以被设为 @ref{803,,min()} 最终得到一个最小值，或者设为 @ref{804,,max()} 最终得到一个最大值，或设为 @ref{1ad9,,operator.mul()} 最终得到一个乘积。摊销表可通过累加利息和支付款项得到。给iterable设置初始值并只将参数 @emph{func} 设为累加总数可以对一阶 递归关系@footnote{https://en.wikipedia.org/wiki/Recurrence_relation} 建模。

@example
>>> data = [3, 4, 6, 2, 1, 9, 0, 7, 5, 8]
>>> list(accumulate(data, operator.mul))     # running product
[3, 12, 72, 144, 144, 1296, 0, 0, 0, 0]
>>> list(accumulate(data, max))              # running maximum
[3, 4, 6, 6, 6, 9, 9, 9, 9, 9]

# Amortize a 5% loan of 1000 with 4 annual payments of 90
>>> cashflows = [1000, -90, -90, -90, -90]
>>> list(accumulate(cashflows, lambda bal, pmt: bal*1.05 + pmt))
[1000, 960.0, 918.0, 873.9000000000001, 827.5950000000001]

# Chaotic recurrence relation https://en.wikipedia.org/wiki/Logistic_map
>>> logistic_map = lambda x, _:  r * x * (1 - x)
>>> r = 3.8
>>> x0 = 0.4
>>> inputs = repeat(x0, 36)     # only the initial value is used
>>> [format(x, '.2f') for x in accumulate(inputs, logistic_map)]
['0.40', '0.91', '0.30', '0.81', '0.60', '0.92', '0.29', '0.79', '0.63',
 '0.88', '0.39', '0.90', '0.33', '0.84', '0.52', '0.95', '0.18', '0.57',
 '0.93', '0.25', '0.71', '0.79', '0.63', '0.88', '0.39', '0.91', '0.32',
 '0.83', '0.54', '0.95', '0.20', '0.60', '0.91', '0.30', '0.80', '0.60']
@end example

参考一个类似函数  @ref{c68,,functools.reduce()}  ，它只返回一个最终累积值。


3.2 新版功能.



在 3.3 版更改: 增加可选参数 @emph{func} 。



在 3.8 版更改: 添加了可选的 @emph{initial} 形参。

@end deffn

@geindex chain() (在 itertools 模块中)
@anchor{library/itertools itertools chain}@anchor{159b}
@deffn {函数} itertools.chain (*iterables)

创建一个迭代器，它首先返回第一个可迭代对象中所有元素，接着返回下一个可迭代对象中所有元素，直到耗尽所有可迭代对象中的元素。可将多个序列处理为单个序列。大致相当于：

@example
def chain(*iterables):
    # chain('ABC', 'DEF') --> A B C D E F
    for it in iterables:
        for element in it:
            yield element
@end example
@end deffn

@geindex from_iterable() (itertools.chain 类方法)
@anchor{library/itertools itertools chain from_iterable}@anchor{1ad1}
@deffn {方法} classmethod chain.from_iterable (iterable)

构建类似 @ref{159b,,chain()} 迭代器的另一个选择。从一个单独的可迭代参数中得到链式输入，该参数是延迟计算的。大致相当于：

@example
def from_iterable(iterables):
    # chain.from_iterable(['ABC', 'DEF']) --> A B C D E F
    for it in iterables:
        for element in it:
            yield element
@end example
@end deffn

@geindex combinations() (在 itertools 模块中)
@anchor{library/itertools itertools combinations}@anchor{c9f}
@deffn {函数} itertools.combinations (iterable, r)

返回由输入 @emph{iterable} 中元素组成长度为 @emph{r} 的子序列。

组合元组会以字典顺序根据所输入 @emph{iterable} 的顺序发出。 因此，如果所输入 @emph{iterable} 是已排序的，组合元组也将按已排序的顺序生成。

即使元素的值相同，不同位置的元素也被认为是不同的。如果元素各自不同，那么每个组合中没有重复元素。

大致相当于：

@example
def combinations(iterable, r):
    # combinations('ABCD', 2) --> AB AC AD BC BD CD
    # combinations(range(4), 3) --> 012 013 023 123
    pool = tuple(iterable)
    n = len(pool)
    if r > n:
        return
    indices = list(range(r))
    yield tuple(pool[i] for i in indices)
    while True:
        for i in reversed(range(r)):
            if indices[i] != i + n - r:
                break
        else:
            return
        indices[i] += 1
        for j in range(i+1, r):
            indices[j] = indices[j-1] + 1
        yield tuple(pool[i] for i in indices)
@end example

@ref{c9f,,combinations()} 的代码可被改写为 @ref{1ad6,,permutations()} 过滤后的子序列，（相对于元素在输入中的位置）元素不是有序的。

@example
def combinations(iterable, r):
    pool = tuple(iterable)
    n = len(pool)
    for indices in permutations(range(n), r):
        if sorted(indices) == list(indices):
            yield tuple(pool[i] for i in indices)
@end example

当 @code{0 <= r <= n} 时，返回项的个数是 @code{n! / r! / (n-r)!}；当 @code{r > n} 时，返回项个数为0。
@end deffn

@geindex combinations_with_replacement() (在 itertools 模块中)
@anchor{library/itertools itertools combinations_with_replacement}@anchor{c12}
@deffn {函数} itertools.combinations_with_replacement (iterable, r)

返回由输入 @emph{iterable} 中元素组成的长度为 @emph{r} 的子序列，允许每个元素可重复出现。

组合元组会以字典顺序根据所输入 @emph{iterable} 的顺序发出。 因此，如果所输入 @emph{iterable} 是已排序的，组合元组也将按已排序的顺序生成。

不同位置的元素是不同的，即使它们的值相同。因此如果输入中的元素都是不同的话，返回的组合中元素也都会不同。

大致相当于：

@example
def combinations_with_replacement(iterable, r):
    # combinations_with_replacement('ABC', 2) --> AA AB AC BB BC CC
    pool = tuple(iterable)
    n = len(pool)
    if not n and r:
        return
    indices = [0] * r
    yield tuple(pool[i] for i in indices)
    while True:
        for i in reversed(range(r)):
            if indices[i] != n - 1:
                break
        else:
            return
        indices[i:] = [indices[i] + 1] * (r - i)
        yield tuple(pool[i] for i in indices)
@end example

@ref{c12,,combinations_with_replacement()} 的代码可被改写为 @code{production()} 过滤后的子序列，（相对于元素在输入中的位置）元素不是有序的。

@example
def combinations_with_replacement(iterable, r):
    pool = tuple(iterable)
    n = len(pool)
    for indices in product(range(n), repeat=r):
        if sorted(indices) == list(indices):
            yield tuple(pool[i] for i in indices)
@end example

当 @code{n > 0} 时，返回项个数为 @code{(n+r-1)! / r! / (n-1)!}.


3.1 新版功能.

@end deffn

@geindex compress() (在 itertools 模块中)
@anchor{library/itertools itertools compress}@anchor{c13}
@deffn {函数} itertools.compress (data, selectors)

创建一个迭代器，它返回 @emph{data} 中经 @emph{selectors} 真值测试为 @code{True} 的元素。迭代器在两者较短的长度处停止。大致相当于：

@example
def compress(data, selectors):
    # compress('ABCDEF', [1,0,1,0,1,1]) --> A C E F
    return (d for d, s in zip(data, selectors) if s)
@end example


3.1 新版功能.

@end deffn

@geindex count() (在 itertools 模块中)
@anchor{library/itertools itertools count}@anchor{c14}
@deffn {函数} itertools.count (start=0, step=1)

创建一个迭代器，它从 @emph{start} 值开始，返回均匀间隔的值。常用于 @ref{c26,,map()} 中的实参来生成连续的数据点。此外，还用于 @ref{c2b,,zip()} 来添加序列号。大致相当于：

@example
def count(start=0, step=1):
    # count(10) --> 10 11 12 13 14 ...
    # count(2.5, 0.5) -> 2.5 3.0 3.5 ...
    n = start
    while True:
        yield n
        n += step
@end example

当对浮点数计数时，替换为乘法代码有时精度会更好，例如： @code{(start + step * i for i in count())} 。


在 3.1 版更改: 增加参数 @emph{step} ，允许非整型。

@end deffn

@geindex cycle() (在 itertools 模块中)
@anchor{library/itertools itertools cycle}@anchor{1ad0}
@deffn {函数} itertools.cycle (iterable)

创建一个迭代器，返回 @emph{iterable} 中所有元素并保存一个副本。当取完 @emph{iterable} 中所有元素，返回副本中的所有元素。无限重复。大致相当于：

@example
def cycle(iterable):
    # cycle('ABCD') --> A B C D A B C D A B C D ...
    saved = []
    for element in iterable:
        yield element
        saved.append(element)
    while saved:
        for element in saved:
              yield element
@end example

注意，该函数可能需要相当大的辅助空间（取决于 @emph{iterable} 的长度）。
@end deffn

@geindex dropwhile() (在 itertools 模块中)
@anchor{library/itertools itertools dropwhile}@anchor{1ad2}
@deffn {函数} itertools.dropwhile (predicate, iterable)

创建一个迭代器，如果 @emph{predicate} 为true，迭代器丢弃这些元素，然后返回其他元素。注意，迭代器在 @emph{predicate} 首次为false之前不会产生任何输出，所以可能需要一定长度的启动时间。大致相当于：

@example
def dropwhile(predicate, iterable):
    # dropwhile(lambda x: x<5, [1,4,6,4,1]) --> 6 4 1
    iterable = iter(iterable)
    for x in iterable:
        if not predicate(x):
            yield x
            break
    for x in iterable:
        yield x
@end example
@end deffn

@geindex filterfalse() (在 itertools 模块中)
@anchor{library/itertools itertools filterfalse}@anchor{1584}
@deffn {函数} itertools.filterfalse (predicate, iterable)

创建一个迭代器，只返回 @emph{iterable} 中 @emph{predicate} 为 @code{False} 的元素。如果 @emph{predicate} 是 @code{None}，返回真值测试为false的元素。大致相当于：

@example
def filterfalse(predicate, iterable):
    # filterfalse(lambda x: x%2, range(10)) --> 0 2 4 6 8
    if predicate is None:
        predicate = bool
    for x in iterable:
        if not predicate(x):
            yield x
@end example
@end deffn

@geindex groupby() (在 itertools 模块中)
@anchor{library/itertools itertools groupby}@anchor{1ad3}
@deffn {函数} itertools.groupby (iterable, key=None)

创建一个迭代器，返回 @emph{iterable} 中连续的键和组。@emph{key} 是一个计算元素键值函数。如果未指定或为 @code{None}，@emph{key} 缺省为恒等函数（identity function），返回元素不变。一般来说，@emph{iterable} 需用同一个键值函数预先排序。

@ref{1ad3,,groupby()} 操作类似于Unix中的 @code{uniq}。当每次 @emph{key} 函数产生的键值改变时，迭代器会分组或生成一个新组（这就是为什么通常需要使用同一个键值函数先对数据进行排序）。这种行为与SQL的GROUP BY操作不同，SQL的操作会忽略输入的顺序将相同键值的元素分在同组中。

返回的组本身也是一个迭代器，它与 @ref{1ad3,,groupby()} 共享底层的可迭代对象。因为源是共享的，当 @ref{1ad3,,groupby()} 对象向后迭代时，前一个组将消失。因此如果稍后还需要返回结果，可保存为列表：

@example
groups = []
uniquekeys = []
data = sorted(data, key=keyfunc)
for k, g in groupby(data, keyfunc):
    groups.append(list(g))      # Store group iterator as a list
    uniquekeys.append(k)
@end example

@ref{1ad3,,groupby()} 大致相当于：

@example
class groupby:
    # [k for k, g in groupby('AAAABBBCCDAABBB')] --> A B C D A B
    # [list(g) for k, g in groupby('AAAABBBCCD')] --> AAAA BBB CC D
    def __init__(self, iterable, key=None):
        if key is None:
            key = lambda x: x
        self.keyfunc = key
        self.it = iter(iterable)
        self.tgtkey = self.currkey = self.currvalue = object()
    def __iter__(self):
        return self
    def __next__(self):
        self.id = object()
        while self.currkey == self.tgtkey:
            self.currvalue = next(self.it)    # Exit on StopIteration
            self.currkey = self.keyfunc(self.currvalue)
        self.tgtkey = self.currkey
        return (self.currkey, self._grouper(self.tgtkey, self.id))
    def _grouper(self, tgtkey, id):
        while self.id is id and self.currkey == tgtkey:
            yield self.currvalue
            try:
                self.currvalue = next(self.it)
            except StopIteration:
                return
            self.currkey = self.keyfunc(self.currvalue)
@end example
@end deffn

@geindex islice() (在 itertools 模块中)
@anchor{library/itertools itertools islice}@anchor{39a}
@deffn {函数} itertools.islice (iterable, stop)

@deffnx {函数} itertools.islice (iterable, start, stop[, step])

创建一个迭代器，返回从 @emph{iterable} 里选中的元素。如果 @emph{start} 不是0，跳过 @emph{iterable} 中的元素，直到到达 @emph{start} 这个位置。之后迭代器连续返回元素，除非 @emph{step} 设置的值很高导致被跳过。如果 @emph{stop} 为 @code{None}，迭代器耗光为止；否则，在指定的位置停止。与普通的切片不同，@ref{39a,,islice()} 不支持将 @emph{start} ， @emph{stop} ，或 @emph{step} 设为负值。可用来从内部数据结构被压平的数据中提取相关字段（例如一个多行报告，它的名称字段出现在每三行上）。大致相当于：

@example
def islice(iterable, *args):
    # islice('ABCDEFG', 2) --> A B
    # islice('ABCDEFG', 2, 4) --> C D
    # islice('ABCDEFG', 2, None) --> C D E F G
    # islice('ABCDEFG', 0, None, 2) --> A C E G
    s = slice(*args)
    start, stop, step = s.start or 0, s.stop or sys.maxsize, s.step or 1
    it = iter(range(start, stop, step))
    try:
        nexti = next(it)
    except StopIteration:
        # Consume *iterable* up to the *start* position.
        for i, element in zip(range(start), iterable):
            pass
        return
    try:
        for i, element in enumerate(iterable):
            if i == nexti:
                yield element
                nexti = next(it)
    except StopIteration:
        # Consume to *stop*.
        for i, element in zip(range(i + 1, stop), iterable):
            pass
@end example

如果 @emph{start} 为 @code{None}，迭代从0开始。如果 @emph{step} 为 @code{None} ，步长缺省为1。
@end deffn

@geindex permutations() (在 itertools 模块中)
@anchor{library/itertools itertools permutations}@anchor{1ad6}
@deffn {函数} itertools.permutations (iterable, r=None)

连续返回由 @emph{iterable} 元素生成长度为 @emph{r} 的排列。

如果 @emph{r} 未指定或为 @code{None} ，@emph{r} 默认设置为 @emph{iterable} 的长度，这种情况下，生成所有全长排列。

排列元组会以字典顺序根据所输入 @emph{iterable} 的顺序发出。 因此，如果所输入 @emph{iterable} 是已排序的，组合元组也将按已排序的顺序生成。

即使元素的值相同，不同位置的元素也被认为是不同的。如果元素值都不同，每个排列中的元素值不会重复。

大致相当于：

@example
def permutations(iterable, r=None):
    # permutations('ABCD', 2) --> AB AC AD BA BC BD CA CB CD DA DB DC
    # permutations(range(3)) --> 012 021 102 120 201 210
    pool = tuple(iterable)
    n = len(pool)
    r = n if r is None else r
    if r > n:
        return
    indices = list(range(n))
    cycles = list(range(n, n-r, -1))
    yield tuple(pool[i] for i in indices[:r])
    while n:
        for i in reversed(range(r)):
            cycles[i] -= 1
            if cycles[i] == 0:
                indices[i:] = indices[i+1:] + indices[i:i+1]
                cycles[i] = n - i
            else:
                j = cycles[i]
                indices[i], indices[-j] = indices[-j], indices[i]
                yield tuple(pool[i] for i in indices[:r])
                break
        else:
            return
@end example

@ref{1ad6,,permutations()} 的代码也可被改写为 @ref{ca0,,product()} 的子序列，只要将含有重复元素（来自输入中同一位置的）的项排除。

@example
def permutations(iterable, r=None):
    pool = tuple(iterable)
    n = len(pool)
    r = n if r is None else r
    for indices in product(range(n), repeat=r):
        if len(set(indices)) == r:
            yield tuple(pool[i] for i in indices)
@end example

当 @code{0 <= r <= n} ，返回项个数为 @code{n! / (n-r)!} ；当 @code{r > n} ，返回项个数为0。
@end deffn

@geindex product() (在 itertools 模块中)
@anchor{library/itertools itertools product}@anchor{ca0}
@deffn {函数} itertools.product (*iterables, repeat=1)

可迭代对象输入的笛卡儿积。

大致相当于生成器表达式中的嵌套循环。例如， @code{product(A, B)} 和 @code{((x,y) for x in A for y in B)} 返回结果一样。

嵌套循环像里程表那样循环变动，每次迭代时将最右侧的元素向后迭代。这种模式形成了一种字典序，因此如果输入的可迭代对象是已排序的，笛卡尔积元组依次序发出。

要计算可迭代对象自身的笛卡尔积，将可选参数 @emph{repeat} 设定为要重复的次数。例如，@code{product(A, repeat=4)} 和 @code{product(A, A, A, A)} 是一样的。

该函数大致相当于下面的代码，只不过实际实现方案不会在内存中创建中间结果。

@example
def product(*args, repeat=1):
    # product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy
    # product(range(2), repeat=3) --> 000 001 010 011 100 101 110 111
    pools = [tuple(pool) for pool in args] * repeat
    result = [[]]
    for pool in pools:
        result = [x+[y] for x in result for y in pool]
    for prod in result:
        yield tuple(prod)
@end example
@end deffn

@geindex repeat() (在 itertools 模块中)
@anchor{library/itertools itertools repeat}@anchor{1045}
@deffn {函数} itertools.repeat (object[, times])

创建一个迭代器，不断重复 @emph{object} 。除非设定参数 @emph{times} ，否则将无限重复。可用于 @ref{c26,,map()} 函数中的参数，被调用函数可得到一个不变参数。也可用于 @ref{c2b,,zip()} 的参数以在元组记录中创建一个不变的部分。

大致相当于：

@example
def repeat(object, times=None):
    # repeat(10, 3) --> 10 10 10
    if times is None:
        while True:
            yield object
    else:
        for i in range(times):
            yield object
@end example

@emph{repeat} 最常见的用途就是在 @emph{map} 或 @emph{zip} 提供一个常量流：

@example
>>> list(map(pow, range(10), repeat(2)))
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
@end example
@end deffn

@geindex starmap() (在 itertools 模块中)
@anchor{library/itertools itertools starmap}@anchor{a23}
@deffn {函数} itertools.starmap (function, iterable)

创建一个迭代器，使用从可迭代对象中获取的参数来计算该函数。当参数对应的形参已从一个单独可迭代对象组合为元组时（数据已被“预组对”）可用此函数代替 @ref{c26,,map()}。@ref{c26,,map()} 与 @ref{a23,,starmap()} 之间的区别可以类比 @code{function(a,b)} 与 @code{function(*c)} 的区别。大致相当于:

@example
def starmap(function, iterable):
    # starmap(pow, [(2,5), (3,2), (10,3)]) --> 32 9 1000
    for args in iterable:
        yield function(*args)
@end example
@end deffn

@geindex takewhile() (在 itertools 模块中)
@anchor{library/itertools itertools takewhile}@anchor{1ad4}
@deffn {函数} itertools.takewhile (predicate, iterable)

创建一个迭代器，只要 predicate 为真就从可迭代对象中返回元素。大致相当于:

@example
def takewhile(predicate, iterable):
    # takewhile(lambda x: x<5, [1,4,6,4,1]) --> 1 4
    for x in iterable:
        if predicate(x):
            yield x
        else:
            break
@end example
@end deffn

@geindex tee() (在 itertools 模块中)
@anchor{library/itertools itertools tee}@anchor{1ad5}
@deffn {函数} itertools.tee (iterable, n=2)

从一个可迭代对象中返回 @emph{n} 个独立的迭代器。

下面的Python代码能帮助解释 @emph{tee} 做了什么（尽管实际的实现更复杂，而且仅使用了一个底层的 @abbr{FIFO} 队列）。

大致相当于：

@example
def tee(iterable, n=2):
    it = iter(iterable)
    deques = [collections.deque() for i in range(n)]
    def gen(mydeque):
        while True:
            if not mydeque:             # when the local deque is empty
                try:
                    newval = next(it)   # fetch a new value and
                except StopIteration:
                    return
                for d in deques:        # load it to all the deques
                    d.append(newval)
            yield mydeque.popleft()
    return tuple(gen(d) for d in deques)
@end example

一旦 @ref{1ad5,,tee()} 实施了一次分裂，原有的 @emph{iterable} 不应再被使用；否则tee对象无法得知 @emph{iterable} 可能已向后迭代。

@code{tee} 迭代器不是线程安全的。当同时使用由同一个 @ref{1ad5,,tee()} 调用所返回的迭代器时可能引发 @ref{2ba,,RuntimeError}，即使原本的 @emph{iterable} 是线程安全的。

该迭代工具可能需要相当大的辅助存储空间（这取决于要保存多少临时数据）。通常，如果一个迭代器在另一个迭代器开始之前就要使用大部份或全部数据，使用 @ref{262,,list()} 会比 @ref{1ad5,,tee()} 更快。
@end deffn

@geindex zip_longest() (在 itertools 模块中)
@anchor{library/itertools itertools zip_longest}@anchor{c2a}
@deffn {函数} itertools.zip_longest (*iterables, fillvalue=None)

创建一个迭代器，从每个可迭代对象中收集元素。如果可迭代对象的长度未对齐，将根据 @emph{fillvalue} 填充缺失值。迭代持续到耗光最长的可迭代对象。大致相当于：

@example
def zip_longest(*args, fillvalue=None):
    # zip_longest('ABCD', 'xy', fillvalue='-') --> Ax By C- D-
    iterators = [iter(it) for it in args]
    num_active = len(iterators)
    if not num_active:
        return
    while True:
        values = []
        for i, it in enumerate(iterators):
            try:
                value = next(it)
            except StopIteration:
                num_active -= 1
                if not num_active:
                    return
                iterators[i] = repeat(fillvalue)
                value = fillvalue
            values.append(value)
        yield tuple(values)
@end example

如果其中一个可迭代对象有无限长度，@ref{c2a,,zip_longest()} 函数应封装在限制调用次数的场景中（例如 @ref{39a,,islice()} 或 @ref{1ad4,,takewhile()}）。除非指定， @emph{fillvalue} 默认为 @code{None} 。
@end deffn

@node itertools 配方,,Itertool函数,itertools --- 为高效循环而创建迭代器的函数
@anchor{library/itertools id1}@anchor{1ada}@anchor{library/itertools itertools-recipes}@anchor{bee}
@subsubsection itertools 配方


本节将展示如何使用现有的 itertools 作为基础构件来创建扩展的工具集。

基本上所有这些西方和许许多多其他的配方都可以通过 Python Package Index 上的 more-itertools 项目@footnote{https://pypi.org/project/more-itertools/} 来安装:

@example
pip install more-itertools
@end example

扩展的工具提供了与底层工具集相同的高性能。保持了超棒的内存利用率，因为一次只处理一个元素，而不是将整个可迭代对象加载到内存。代码量保持得很小，以函数式风格将这些工具连接在一起，有助于消除临时变量。速度依然很快，因为倾向于使用“矢量化”构件来取代解释器开销大的 for 循环和 @ref{99c,,generator} 。

@example
def take(n, iterable):
    "Return first n items of the iterable as a list"
    return list(islice(iterable, n))

def prepend(value, iterator):
    "Prepend a single value in front of an iterator"
    # prepend(1, [2, 3, 4]) -> 1 2 3 4
    return chain([value], iterator)

def tabulate(function, start=0):
    "Return function(0), function(1), ..."
    return map(function, count(start))

def tail(n, iterable):
    "Return an iterator over the last n items"
    # tail(3, 'ABCDEFG') --> E F G
    return iter(collections.deque(iterable, maxlen=n))

def consume(iterator, n=None):
    "Advance the iterator n-steps ahead. If n is None, consume entirely."
    # Use functions that consume iterators at C speed.
    if n is None:
        # feed the entire iterator into a zero-length deque
        collections.deque(iterator, maxlen=0)
    else:
        # advance to the empty slice starting at position n
        next(islice(iterator, n, n), None)

def nth(iterable, n, default=None):
    "Returns the nth item or a default value"
    return next(islice(iterable, n, None), default)

def all_equal(iterable):
    "Returns True if all the elements are equal to each other"
    g = groupby(iterable)
    return next(g, True) and not next(g, False)

def quantify(iterable, pred=bool):
    "Count how many times the predicate is true"
    return sum(map(pred, iterable))

def padnone(iterable):
    """Returns the sequence elements and then returns None indefinitely.

    Useful for emulating the behavior of the built-in map() function.
    """
    return chain(iterable, repeat(None))

def ncycles(iterable, n):
    "Returns the sequence elements n times"
    return chain.from_iterable(repeat(tuple(iterable), n))

def dotproduct(vec1, vec2):
    return sum(map(operator.mul, vec1, vec2))

def flatten(list_of_lists):
    "Flatten one level of nesting"
    return chain.from_iterable(list_of_lists)

def repeatfunc(func, times=None, *args):
    """Repeat calls to func with specified arguments.

    Example:  repeatfunc(random.random)
    """
    if times is None:
        return starmap(func, repeat(args))
    return starmap(func, repeat(args, times))

def pairwise(iterable):
    "s -> (s0,s1), (s1,s2), (s2, s3), ..."
    a, b = tee(iterable)
    next(b, None)
    return zip(a, b)

def grouper(iterable, n, fillvalue=None):
    "Collect data into fixed-length chunks or blocks"
    # grouper('ABCDEFG', 3, 'x') --> ABC DEF Gxx"
    args = [iter(iterable)] * n
    return zip_longest(*args, fillvalue=fillvalue)

def roundrobin(*iterables):
    "roundrobin('ABC', 'D', 'EF') --> A D E B F C"
    # Recipe credited to George Sakkis
    num_active = len(iterables)
    nexts = cycle(iter(it).__next__ for it in iterables)
    while num_active:
        try:
            for next in nexts:
                yield next()
        except StopIteration:
            # Remove the iterator we just exhausted from the cycle.
            num_active -= 1
            nexts = cycle(islice(nexts, num_active))

def partition(pred, iterable):
    'Use a predicate to partition entries into false entries and true entries'
    # partition(is_odd, range(10)) --> 0 2 4 6 8   and  1 3 5 7 9
    t1, t2 = tee(iterable)
    return filterfalse(pred, t1), filter(pred, t2)

def powerset(iterable):
    "powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
    s = list(iterable)
    return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))

def unique_everseen(iterable, key=None):
    "List unique elements, preserving order. Remember all elements ever seen."
    # unique_everseen('AAAABBBCCDAABBB') --> A B C D
    # unique_everseen('ABBCcAD', str.lower) --> A B C D
    seen = set()
    seen_add = seen.add
    if key is None:
        for element in filterfalse(seen.__contains__, iterable):
            seen_add(element)
            yield element
    else:
        for element in iterable:
            k = key(element)
            if k not in seen:
                seen_add(k)
                yield element

def unique_justseen(iterable, key=None):
    "List unique elements, preserving order. Remember only the element just seen."
    # unique_justseen('AAAABBBCCDAABBB') --> A B C D A B
    # unique_justseen('ABBCcAD', str.lower) --> A B C A D
    return map(next, map(operator.itemgetter(1), groupby(iterable, key)))

def iter_except(func, exception, first=None):
    """ Call a function repeatedly until an exception is raised.

    Converts a call-until-exception interface to an iterator interface.
    Like builtins.iter(func, sentinel) but uses an exception instead
    of a sentinel to end the loop.

    Examples:
        iter_except(functools.partial(heappop, h), IndexError)   # priority queue iterator
        iter_except(d.popitem, KeyError)                         # non-blocking dict iterator
        iter_except(d.popleft, IndexError)                       # non-blocking deque iterator
        iter_except(q.get_nowait, Queue.Empty)                   # loop over a producer Queue
        iter_except(s.pop, KeyError)                             # non-blocking set iterator

    """
    try:
        if first is not None:
            yield first()            # For database APIs needing an initial cast to db.first()
        while True:
            yield func()
    except exception:
        pass

def first_true(iterable, default=False, pred=None):
    """Returns the first true value in the iterable.

    If no true value is found, returns *default*

    If *pred* is not None, returns the first item
    for which pred(item) is true.

    """
    # first_true([a,b,c], x) --> a or b or c or x
    # first_true([a,b], x, f) --> a if f(a) else b if f(b) else x
    return next(filter(pred, iterable), default)

def random_product(*args, repeat=1):
    "Random selection from itertools.product(*args, **kwds)"
    pools = [tuple(pool) for pool in args] * repeat
    return tuple(random.choice(pool) for pool in pools)

def random_permutation(iterable, r=None):
    "Random selection from itertools.permutations(iterable, r)"
    pool = tuple(iterable)
    r = len(pool) if r is None else r
    return tuple(random.sample(pool, r))

def random_combination(iterable, r):
    "Random selection from itertools.combinations(iterable, r)"
    pool = tuple(iterable)
    n = len(pool)
    indices = sorted(random.sample(range(n), r))
    return tuple(pool[i] for i in indices)

def random_combination_with_replacement(iterable, r):
    "Random selection from itertools.combinations_with_replacement(iterable, r)"
    pool = tuple(iterable)
    n = len(pool)
    indices = sorted(random.randrange(n) for i in range(r))
    return tuple(pool[i] for i in indices)

def nth_combination(iterable, r, index):
    'Equivalent to list(combinations(iterable, r))[index]'
    pool = tuple(iterable)
    n = len(pool)
    if r < 0 or r > n:
        raise ValueError
    c = 1
    k = min(r, n-r)
    for i in range(1, k+1):
        c = c * (n - k + i) // i
    if index < 0:
        index += c
    if index < 0 or index >= c:
        raise IndexError
    result = []
    while r:
        c, n, r = c*r//n, n-1, r-1
        while index >= c:
            index -= c
            c, n = c*(n-r)//n, n-1
        result.append(pool[-1-n])
    return tuple(result)
@end example

@node functools --- 高阶函数和可调用对象上的操作,operator --- 标准运算符替代函数,itertools --- 为高效循环而创建迭代器的函数,函数式编程模块
@anchor{library/functools doc}@anchor{1adb}@anchor{library/functools functools-higher-order-functions-and-operations-on-callable-objects}@anchor{1adc}@anchor{library/functools module-functools}@anchor{85}
@subsection @code{functools} --- 高阶函数和可调用对象上的操作


@geindex functools (模块)

@strong{源代码:} Lib/functools.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/functools.py}


__________________________________________________________________


@ref{85,,functools} 模块应用于高阶函数，即参数或（和）返回值为其他函数的函数。 通常来说，此模块的功能适用于所有可调用对象。

@ref{85,,functools} 模块定义了以下函数:

@geindex cached_property() (在 functools 模块中)
@anchor{library/functools functools cached_property}@anchor{1c8}
@deffn {函数} @@functools.cached_property (func)

将一个类方法转换为特征属性，一次性计算该特征属性的值，然后将其缓存为实例生命周期内的普通属性。 类似于 @ref{1d7,,property()} 但增加了缓存功能。 对于在其他情况下实际不可变的高计算资源消耗的实例特征属性来说该函数非常有用。

示例:

@example
class DataSet:
    def __init__(self, sequence_of_numbers):
        self._data = sequence_of_numbers

    @@cached_property
    def stdev(self):
        return statistics.stdev(self._data)

    @@cached_property
    def variance(self):
        return statistics.variance(self._data)
@end example


3.8 新版功能.


@cartouche
@quotation 注解 
此装饰器要求每个实例上的 @code{__dict__} 属性是可变的映射。 这意味着它将不适用于某些类型，例如元类（因为类型实例上的 @code{__dict__} 属性是类命名空间的只读代理），以及那些指定了 @code{__slots__} 但未包含 @code{__dict__} 作为所定义的空位之一的类（因为这样的类根本没有提供 @code{__dict__} 属性）。
@end quotation
@end cartouche
@end deffn

@geindex cmp_to_key() (在 functools 模块中)
@anchor{library/functools functools cmp_to_key}@anchor{b4f}
@deffn {函数} functools.cmp_to_key (func)

将(旧式的)比较函数转换为新式的 @ref{6da,,key function} .  在类似于 @ref{43e,,sorted()} ， @ref{803,,min()} ， @ref{804,,max()} ， @ref{18f8,,heapq.nlargest()} ， @ref{18f9,,heapq.nsmallest()} ， @ref{1ad3,,itertools.groupby()} 等函数的 @cite{key} 参数中使用。此函数主要用作将 Python 2 程序转换至新版的转换工具，以保持对比较函数的兼容。

比较函数意为一个可调用对象，该对象接受两个参数并比较它们，结果为小于则返回一个负数，相等则返回零，大于则返回一个正数。key function则是一个接受一个参数，并返回另一个用以排序的值的可调用对象。

示例:

@example
sorted(iterable, key=cmp_to_key(locale.strcoll))  # locale-aware sort order
@end example

有关排序示例和简要排序教程，请参阅 @ref{1599,,排序指南} 。


3.2 新版功能.

@end deffn

@geindex lru_cache() (在 functools 模块中)
@anchor{library/functools functools lru_cache}@anchor{1c7}
@deffn {函数} @@functools.lru_cache (user_function)

@deffnx {函数} @@functools.lru_cache (maxsize=128, typed=False)

一个为函数提供缓存功能的装饰器，缓存 @emph{maxsize} 组传入参数，在下次以相同参数调用时直接返回上一次的结果。用以节约高开销或I/O函数的调用时间。

由于使用了字典存储缓存，所以该函数的固定参数和关键字参数必须是可哈希的。

不同模式的参数可能被视为不同从而产生多个缓存项，例如, @cite{f(a=1@comma{} b=2)} 和 @cite{f(b=2@comma{} a=1)} 因其参数顺序不同，可能会被缓存两次。

如果指定了 @emph{user_function}，它必须是一个可调用对象。 这允许 @emph{lru_cache} 装饰器被直接应用于一个用户自定义函数，让 @emph{maxsize} 保持其默认值 128:

@example
@@lru_cache
def count_vowels(sentence):
    sentence = sentence.casefold()
    return sum(sentence.count(vowel) for vowel in 'aeiou')
@end example

如果 @emph{maxsize} 设为 @code{None}，LRU 特性将被禁用且缓存可无限增长。

如果 @emph{typed} 设置为true，不同类型的函数参数将被分别缓存。例如， @code{f(3)} 和 @code{f(3.0)} 将被视为不同而分别缓存。

为了衡量缓存的有效性以便调整 @emph{maxsize} 形参，被装饰的函数带有一个 @code{cache_info()} 函数。当调用 @code{cache_info()} 函数时，返回一个具名元组，包含命中次数 @emph{hits}，未命中次数 @emph{misses} ，最大缓存数量 @emph{maxsize} 和 当前缓存大小 @emph{currsize}。在多线程环境中，命中数与未命中数是不完全准确的。

该装饰器也提供了一个用于清理/使缓存失效的函数 @code{cache_clear()} 。

原始的未经装饰的函数可以通过 @code{__wrapped__} 属性访问。它可以用于检查、绕过缓存，或使用不同的缓存再次装饰原始函数。

“最久未使用算法”（LRU）缓存@footnote{https://en.wikipedia.org/wiki/Cache_algorithms#Examples} 在“最近的调用是即将到来的调用的最佳预测因子”时性能最好（比如，新闻服务器上最受欢迎的文章倾向于每天更改）。 “缓存大小限制”参数保证缓存不会在长时间运行的进程比如说网站服务器上无限制的增加自身的大小。

一般来说，LRU缓存只在当你想要重用之前计算的结果时使用。因此，用它缓存具有副作用的函数、需要在每次调用时创建不同、易变的对象的函数或者诸如time（）或random（）之类的不纯函数是没有意义的。

静态 Web 内容的 LRU 缓存示例:

@example
@@lru_cache(maxsize=32)
def get_pep(num):
    'Retrieve text of a Python Enhancement Proposal'
    resource = 'http://www.python.org/dev/peps/pep-%04d/' % num
    try:
        with urllib.request.urlopen(resource) as s:
            return s.read()
    except urllib.error.HTTPError:
        return 'Not Found'

>>> for n in 8, 290, 308, 320, 8, 218, 320, 279, 289, 320, 9991:
...     pep = get_pep(n)
...     print(n, len(pep))

>>> get_pep.cache_info()
CacheInfo(hits=3, misses=8, maxsize=32, currsize=8)
@end example

以下是使用缓存通过 动态规划@footnote{https://zh.wikipedia.org/wiki/动态规划}  计算 斐波那契数列@footnote{https://zh.wikipedia.org/wiki/斐波那契数列}  的例子。

@example
@@lru_cache(maxsize=None)
def fib(n):
    if n < 2:
        return n
    return fib(n-1) + fib(n-2)

>>> [fib(n) for n in range(16)]
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610]

>>> fib.cache_info()
CacheInfo(hits=28, misses=16, maxsize=None, currsize=16)
@end example


3.2 新版功能.



在 3.3 版更改: 添加 @emph{typed} 选项。



在 3.8 版更改: 添加了 @emph{user_function} 选项。

@end deffn

@geindex total_ordering() (在 functools 模块中)
@anchor{library/functools functools total_ordering}@anchor{845}
@deffn {函数} @@functools.total_ordering

给定一个声明一个或多个全比较排序方法的类，这个类装饰器实现剩余的方法。这减轻了指定所有可能的全比较操作的工作。

此类必须包含以下方法之一：@ref{c2d,,__lt__()} 、@ref{c99,,__le__()}、@ref{c9a,,__gt__()} 或 @ref{c9b,,__ge__()}。另外，此类必须支持 @ref{338,,__eq__()} 方法。

例如

@example
@@total_ordering
class Student:
    def _is_valid_operand(self, other):
        return (hasattr(other, "lastname") and
                hasattr(other, "firstname"))
    def __eq__(self, other):
        if not self._is_valid_operand(other):
            return NotImplemented
        return ((self.lastname.lower(), self.firstname.lower()) ==
                (other.lastname.lower(), other.firstname.lower()))
    def __lt__(self, other):
        if not self._is_valid_operand(other):
            return NotImplemented
        return ((self.lastname.lower(), self.firstname.lower()) <
                (other.lastname.lower(), other.firstname.lower()))
@end example

@cartouche
@quotation 注解 
虽然此装饰器使得创建具有良好行为的完全有序类型变得非常容易，但它 @emph{确实} 是以执行速度更缓慢和派生比较方法的堆栈回溯更复杂为代价的。 如果性能基准测试表明这是特定应用的瓶颈所在，则改为实现全部六个富比较方法应该会轻松提升速度。
@end quotation
@end cartouche


3.2 新版功能.



在 3.4 版更改: 现在已支持从未识别类型的下层比较函数返回 NotImplemented 异常。

@end deffn

@geindex partial() (在 functools 模块中)
@anchor{library/functools functools partial}@anchor{7c2}
@deffn {函数} functools.partial (func, /, *args, **keywords)

返回一个新的 @ref{1add,,部分对象}，当被调用时其行为类似于 @emph{func} 附带位置参数 @emph{args} 和关键字参数 @emph{keywords} 被调用。 如果为调用提供了更多的参数，它们会被附加到 @emph{args}。 如果提供了额外的关键字参数，它们会扩展并重载 @emph{keywords}。 大致等价于:

@example
def partial(func, /, *args, **keywords):
    def newfunc(*fargs, **fkeywords):
        newkeywords = @{**keywords, **fkeywords@}
        return func(*args, *fargs, **newkeywords)
    newfunc.func = func
    newfunc.args = args
    newfunc.keywords = keywords
    return newfunc
@end example

@ref{7c2,,partial()} 会被“冻结了”一部分函数参数和/或关键字的部分函数应用所使用，从而得到一个具有简化签名的新对象。 例如，@ref{7c2,,partial()} 可用来创建一个行为类似于 @ref{184,,int()} 函数的可调用对象，其中 @emph{base} 参数默认为二：

@example
>>> from functools import partial
>>> basetwo = partial(int, base=2)
>>> basetwo.__doc__ = 'Convert base 2 string to an int.'
>>> basetwo('10010')
18
@end example
@end deffn

@geindex partialmethod (functools 中的类)
@anchor{library/functools functools partialmethod}@anchor{29c}
@deffn {类} functools.partialmethod (func, /, *args, **keywords)

返回一个新的 @ref{29c,,partialmethod} 描述器，其行为类似 @ref{7c2,,partial} 但它被设计用作方法定义而非直接用作可调用对象。

@emph{func} 必须是一个 @ref{159e,,descriptor} 或可调用对象（同属两者的对象例如普通函数会被当作描述器来处理）。

当 @emph{func} 是一个描述器（例如普通 Python 函数, @ref{1d8,,classmethod()}, @ref{1d9,,staticmethod()}, @code{abstractmethod()} 或其他 @ref{29c,,partialmethod} 的实例）时, 对 @code{__get__} 的调用会被委托给底层的描述器，并会返回一个适当的 @ref{1add,,部分对象} 作为结果。

当 @emph{func} 是一个非描述器类可调用对象时，则会动态创建一个适当的绑定方法。 当用作方法时其行为类似普通 Python 函数：将会插入 @emph{self} 参数作为第一个位置参数，其位置甚至会处于提供给 @ref{29c,,partialmethod} 构造器的 @emph{args} 和 @emph{keywords} 之前。

示例:

@example
>>> class Cell(object):
...     def __init__(self):
...         self._alive = False
...     @@property
...     def alive(self):
...         return self._alive
...     def set_state(self, state):
...         self._alive = bool(state)
...     set_alive = partialmethod(set_state, True)
...     set_dead = partialmethod(set_state, False)
...
>>> c = Cell()
>>> c.alive
False
>>> c.set_alive()
>>> c.alive
True
@end example


3.4 新版功能.

@end deffn

@geindex reduce() (在 functools 模块中)
@anchor{library/functools functools reduce}@anchor{c68}
@deffn {函数} functools.reduce (function, iterable[, initializer])

将两个参数的 @emph{function} 从左至右积累地应用到 @emph{iterable} 的条目，以便将该可迭代对象缩减为单一的值。 例如，@code{reduce(lambda x, y: x+y, [1, 2, 3, 4, 5])} 是计算 @code{((((1+2)+3)+4)+5)} 的值。 左边的参数 @emph{x} 是积累值而右边的参数 @emph{y} 则是来自 @emph{iterable} 的更新值。 如果存在可选项 @emph{initializer}，它会被放在参与计算的可迭代对象的条目之前，并在可迭代对象为空时作为默认值。 如果没有给出 @emph{initializer} 并且 @emph{iterable} 仅包含一个条目，则将返回第一项。

大致相当于：

@example
def reduce(function, iterable, initializer=None):
    it = iter(iterable)
    if initializer is None:
        value = next(it)
    else:
        value = initializer
    for element in it:
        value = function(value, element)
    return value
@end example

请参阅 @ref{1dd,,itertools.accumulate()} 了解有关可产生所有中间值的迭代器。
@end deffn

@geindex singledispatch() (在 functools 模块中)
@anchor{library/functools functools singledispatch}@anchor{382}
@deffn {函数} @@functools.singledispatch

将一个函数转换为 @ref{1ca,,单分派} @ref{1cb,,generic function}。

要定义一个泛型函数，应使用 @code{@@singledispatch} 装饰器进行装饰。 请注意分派是作用于第一个参数的类型，要相应地创建你的函数:

@example
>>> from functools import singledispatch
>>> @@singledispatch
... def fun(arg, verbose=False):
...     if verbose:
...         print("Let me just say,", end=" ")
...     print(arg)
@end example

要将重载的实现添加到函数中，请使用泛型函数的 @code{register()} 属性。 它是一个装饰器。 对于带有类型标注的函数，该装饰器将自动推断第一个参数的类型:

@example
>>> @@fun.register
... def _(arg: int, verbose=False):
...     if verbose:
...         print("Strength in numbers, eh?", end=" ")
...     print(arg)
...
>>> @@fun.register
... def _(arg: list, verbose=False):
...     if verbose:
...         print("Enumerate this:")
...     for i, elem in enumerate(arg):
...         print(i, elem)
@end example

对于不使用类型标注的代码，可以将适当的类型参数显式地传给装饰器本身:

@example
>>> @@fun.register(complex)
... def _(arg, verbose=False):
...     if verbose:
...         print("Better than complicated.", end=" ")
...     print(arg.real, arg.imag)
...
@end example

要启用注册 lambda 和现有函数，可以使用函数形式的 @code{register()} 属性:

@example
>>> def nothing(arg, verbose=False):
...     print("Nothing.")
...
>>> fun.register(type(None), nothing)
@end example

@code{register()} 属性将返回启用了装饰器堆栈、封存的未装饰函数，并会为每个变量单独创建单元测试:

@example
>>> @@fun.register(float)
... @@fun.register(Decimal)
... def fun_num(arg, verbose=False):
...     if verbose:
...         print("Half of your number:", end=" ")
...     print(arg / 2)
...
>>> fun_num is fun
False
@end example

在调用时，泛型函数会根据第一个参数的类型进行分派:

@example
>>> fun("Hello, world.")
Hello, world.
>>> fun("test.", verbose=True)
Let me just say, test.
>>> fun(42, verbose=True)
Strength in numbers, eh? 42
>>> fun(['spam', 'spam', 'eggs', 'spam'], verbose=True)
Enumerate this:
0 spam
1 spam
2 eggs
3 spam
>>> fun(None)
Nothing.
>>> fun(1.23)
0.615
@end example

在没有用于特定类型的已注册实现的情况下，则会使用其方法解析顺序来查找更通用的实现。 以 @code{@@singledispatch} 装饰的原始函数将为最基本的 @code{object} 类型进行注册，这意味着它将在找不到更好的实现时被使用。

要检查泛型函数将为给定类型选择哪个实现，请使用 @code{dispatch()} 属性:

@example
>>> fun.dispatch(float)
<function fun_num at 0x1035a2840>
>>> fun.dispatch(dict)    # note: default implementation
<function fun at 0x103fe0000>
@end example

要访问所有忆注册实现，请使用只读的 @code{registry} 属性:

@example
>>> fun.registry.keys()
dict_keys([<class 'NoneType'>, <class 'int'>, <class 'object'>,
          <class 'decimal.Decimal'>, <class 'list'>,
          <class 'float'>])
>>> fun.registry[float]
<function fun_num at 0x1035a2840>
>>> fun.registry[object]
<function fun at 0x103fe0000>
@end example


3.4 新版功能.



在 3.7 版更改: @code{register()} 属性支持使用类型标注。

@end deffn

@geindex singledispatchmethod (functools 中的类)
@anchor{library/functools functools singledispatchmethod}@anchor{1c9}
@deffn {类} functools.singledispatchmethod (func)

将一个方法转换为 @ref{1ca,,单分派} @ref{1cb,,generic function}。

要定义一个泛型方法，应使用 @code{@@singledispatchmethod} 装饰器进行装饰。 请注意分派是作用于第一个非 self 或非 cls 参数的类型，要相应地创建你的函数:

@example
class Negator:
    @@singledispatchmethod
    def neg(self, arg):
        raise NotImplementedError("Cannot negate a")

    @@neg.register
    def _(self, arg: int):
        return -arg

    @@neg.register
    def _(self, arg: bool):
        return not arg
@end example

@code{@@singledispatchmethod} 支持与其他装饰器如 @code{@@classmethod} 相嵌套。 请注意如果要允许 @code{dispatcher.register}，则 @code{singledispatchmethod} 必须是 @emph{最外层} 的装饰器。 下面的示例定义了 @code{Negator} 类，其中包含绑定到类的 @code{neg} 方法:

@example
class Negator:
    @@singledispatchmethod
    @@classmethod
    def neg(cls, arg):
        raise NotImplementedError("Cannot negate a")

    @@neg.register
    @@classmethod
    def _(cls, arg: int):
        return -arg

    @@neg.register
    @@classmethod
    def _(cls, arg: bool):
        return not arg
@end example

同样的模式也被用于其他类似的装饰器: @code{staticmethod}, @code{abstractmethod} 等等。


3.8 新版功能.

@end deffn

@geindex update_wrapper() (在 functools 模块中)
@anchor{library/functools functools update_wrapper}@anchor{954}
@deffn {函数} functools.update_wrapper (wrapper, wrapped, assigned=WRAPPER_ASSIGNMENTS, updated=WRAPPER_UPDATES)

更新一个 @emph{wrapper} 函数以使其类似于 @emph{wrapped} 函数。 可选参数为指明原函数的哪些属性要直接被赋值给 wrapper 函数的匹配属性的元组，并且这些 wrapper 函数的属性将使用原函数的对应属性来更新。 这些参数的默认值是模块级常量 @code{WRAPPER_ASSIGNMENTS} (它将被赋值给 wrapper 函数的 @code{__module__}, @code{__name__}, @code{__qualname__}, @code{__annotations__} 和 @code{__doc__} 即文档字符串) 以及 @code{WRAPPER_UPDATES} (它将更新 wrapper 函数的 @code{__dict__} 即实例字典)。

为了允许出于内省和其他目的访问原始函数（例如绕过 @ref{1c7,,lru_cache()} 之类的缓存装饰器），此函数会自动为 wrapper 添加一个指向被包装函数的 @code{__wrapped__} 属性。

此函数的主要目的是在 @ref{283,,decorator} 函数中用来包装被装饰的函数并返回包装器。 如果包装器函数未被更新，则被返回函数的元数据将反映包装器定义而不是原始函数定义，这通常没有什么用处。

@ref{954,,update_wrapper()} 可以与函数之外的可调用对象一同使用。 在 @emph{assigned} 或 @emph{updated} 中命名的任何属性如果不存在于被包装对象则会被忽略（即该函数将不会尝试在包装器函数上设置它们）。 如果包装器函数自身缺少在 @emph{updated} 中命名的任何属性则仍将引发 @ref{393,,AttributeError}。


3.2 新版功能: 自动添加 @code{__wrapped__} 属性。



3.2 新版功能: 默认拷贝 @code{__annotations__} 属性。



在 3.2 版更改: 不存在的属性将不再触发 @ref{393,,AttributeError}。



在 3.4 版更改: @code{__wrapped__} 属性现在总是指向被包装的函数，即使该函数定义了 @code{__wrapped__} 属性。 (参见 bpo-17482@footnote{https://bugs.python.org/issue17482})

@end deffn

@geindex wraps() (在 functools 模块中)
@anchor{library/functools functools wraps}@anchor{864}
@deffn {函数} @@functools.wraps (wrapped, assigned=WRAPPER_ASSIGNMENTS, updated=WRAPPER_UPDATES)

这是一个便捷函数，用于在定义包装器函数时发起调用 @ref{954,,update_wrapper()} 作为函数装饰器。 它等价于 @code{partial(update_wrapper, wrapped=wrapped, assigned=assigned, updated=updated)}。 例如:

@example
>>> from functools import wraps
>>> def my_decorator(f):
...     @@wraps(f)
...     def wrapper(*args, **kwds):
...         print('Calling decorated function')
...         return f(*args, **kwds)
...     return wrapper
...
>>> @@my_decorator
... def example():
...     """Docstring"""
...     print('Called example function')
...
>>> example()
Calling decorated function
Called example function
>>> example.__name__
'example'
>>> example.__doc__
'Docstring'
@end example

如果不使用这个装饰器工厂函数，则 example 函数的名称将变为 @code{'wrapper'}，并且 @code{example()} 原本的文档字符串将会丢失。
@end deffn

@menu
* partial 对象:: 

@end menu

@node partial 对象,,,functools --- 高阶函数和可调用对象上的操作
@anchor{library/functools id1}@anchor{1ade}@anchor{library/functools partial-objects}@anchor{1add}
@subsubsection @code{partial} 对象


@ref{7c2,,partial} 对象是由 @ref{7c2,,partial()} 创建的可调用对象。 它们具有三个只读属性：

@geindex func (functools.partial 属性)
@anchor{library/functools functools partial func}@anchor{1adf}
@deffn {属性} partial.func

一个可调用对象或函数。 对 @ref{7c2,,partial} 对象的调用将被转发给 @ref{1adf,,func} 并附带新的参数和关键字。
@end deffn

@geindex args (functools.partial 属性)
@anchor{library/functools functools partial args}@anchor{1ae0}
@deffn {属性} partial.args

最左边的位置参数将放置在提供给 @ref{7c2,,partial} 对象调用的位置参数之前。
@end deffn

@geindex keywords (functools.partial 属性)
@anchor{library/functools functools partial keywords}@anchor{1ae1}
@deffn {属性} partial.keywords

当调用 @ref{7c2,,partial} 对象时将要提供的关键字参数。
@end deffn

@ref{7c2,,partial} 对象与 @code{function} 对象的类似之处在于它们都是可调用、可弱引用的对象并可拥有属性。 但两者也存在一些重要的区别。 例如前者不会自动创建 @ref{c60,,__name__} 和 @code{__doc__} 属性。 而且，在类中定义的 @ref{7c2,,partial} 对象的行为类似于静态方法，并且不会在实例属性查找期间转换为绑定方法。

@node operator --- 标准运算符替代函数,,functools --- 高阶函数和可调用对象上的操作,函数式编程模块
@anchor{library/operator doc}@anchor{1ae2}@anchor{library/operator module-operator}@anchor{c2}@anchor{library/operator operator-standard-operators-as-functions}@anchor{1ae3}
@subsection @code{operator} --- 标准运算符替代函数


@geindex operator (模块)

@strong{源代码:} Lib/operator.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/operator.py}

@c import operator
@c from operator import itemgetter, iadd


__________________________________________________________________


@ref{c2,,operator} 模块提供了一套与Python的内置运算符对应的高效率函数。例如，@code{operator.add(x, y)} 与表达式 @code{x+y} 相同。 许多函数名与特殊方法名相同，只是没有双下划线。为了向后兼容性，也保留了许多包含双下划线的函数。为了表述清楚，建议使用没有双下划线的函数。

函数包含的种类有：对象的比较运算、逻辑运算、数学运算以及序列运算。

对象比较函数适用于所有的对象，函数名根据它们对应的比较运算符命名。

@geindex lt() (在 operator 模块中)
@geindex le() (在 operator 模块中)
@geindex eq() (在 operator 模块中)
@geindex ne() (在 operator 模块中)
@geindex ge() (在 operator 模块中)
@geindex gt() (在 operator 模块中)
@geindex __lt__() (在 operator 模块中)
@geindex __le__() (在 operator 模块中)
@geindex __eq__() (在 operator 模块中)
@geindex __ne__() (在 operator 模块中)
@geindex __ge__() (在 operator 模块中)
@geindex __gt__() (在 operator 模块中)
@anchor{library/operator operator lt}@anchor{1ae4}
@deffn {函数} operator.lt (a, b)
@anchor{library/operator operator le}@anchor{1ae5}
@deffnx {函数} operator.le (a, b)
@anchor{library/operator operator eq}@anchor{1ae6}
@deffnx {函数} operator.eq (a, b)
@anchor{library/operator operator ne}@anchor{1ae7}
@deffnx {函数} operator.ne (a, b)
@anchor{library/operator operator ge}@anchor{1ae8}
@deffnx {函数} operator.ge (a, b)
@anchor{library/operator operator gt}@anchor{1ae9}
@deffnx {函数} operator.gt (a, b)
@anchor{library/operator operator __lt__}@anchor{1aea}
@deffnx {函数} operator.__lt__ (a, b)
@anchor{library/operator operator __le__}@anchor{1aeb}
@deffnx {函数} operator.__le__ (a, b)
@anchor{library/operator operator __eq__}@anchor{1aec}
@deffnx {函数} operator.__eq__ (a, b)
@anchor{library/operator operator __ne__}@anchor{1aed}
@deffnx {函数} operator.__ne__ (a, b)
@anchor{library/operator operator __ge__}@anchor{1aee}
@deffnx {函数} operator.__ge__ (a, b)
@anchor{library/operator operator __gt__}@anchor{1aef}
@deffnx {函数} operator.__gt__ (a, b)

在 @emph{a} 和 @emph{b} 之间进行全比较。具体的，@code{lt(a, b)} 与 @code{a < b} 相同， @code{le(a, b)} 与 @code{a <= b} 相同，@code{eq(a, b)} 与 @code{a == b} 相同，@code{ne(a, b)} 与 @code{a != b} 相同，@code{gt(a, b)} 与 @code{a > b} 相同，@code{ge(a, b)`@w{`}与 `@w{`}a >= b} 相同。注意这些函数可以返回任何值，无论它是否可当作布尔值。关于全比较的更多信息请参考 @ref{14da,,比较运算} 。
@end deffn

逻辑运算通常也适用于所有对象，并且支持真值检测、标识检测和布尔运算：

@geindex not_() (在 operator 模块中)
@geindex __not__() (在 operator 模块中)
@anchor{library/operator operator not_}@anchor{1af0}
@deffn {函数} operator.not_ (obj)
@anchor{library/operator operator __not__}@anchor{1af1}
@deffnx {函数} operator.__not__ (obj)

返回 @ref{14e6,,not} @emph{obj} 的结果。 （请注意对象实例并没有 @ref{1af1,,__not__()} 方法；只有解释器核心可定义此操作。 结果会受 @ref{c61,,__bool__()} 和 @ref{dc4,,__len__()} 方法影响。）
@end deffn

@geindex truth() (在 operator 模块中)
@anchor{library/operator operator truth}@anchor{1af2}
@deffn {函数} operator.truth (obj)

如果 @emph{obj} 为真值则返回 @ref{494,,True}，否则返回 @ref{380,,False}。 这等价于使用 @ref{183,,bool} 构造器。
@end deffn

@geindex is_() (在 operator 模块中)
@anchor{library/operator operator is_}@anchor{1af3}
@deffn {函数} operator.is_ (a, b)

返回 @code{a is b}。 检测对象标识。
@end deffn

@geindex is_not() (在 operator 模块中)
@anchor{library/operator operator is_not}@anchor{1af4}
@deffn {函数} operator.is_not (a, b)

返回 @code{a is not b}。 检测对象标识。
@end deffn

数学和按位运算的种类是最多的：

@geindex abs() (在 operator 模块中)
@geindex __abs__() (在 operator 模块中)
@anchor{library/operator operator abs}@anchor{1af5}
@deffn {函数} operator.abs (obj)
@anchor{library/operator operator __abs__}@anchor{1af6}
@deffnx {函数} operator.__abs__ (obj)

返回 @emph{obj} 的绝对值。
@end deffn

@geindex add() (在 operator 模块中)
@geindex __add__() (在 operator 模块中)
@anchor{library/operator operator add}@anchor{1af7}
@deffn {函数} operator.add (a, b)
@anchor{library/operator operator __add__}@anchor{1af8}
@deffnx {函数} operator.__add__ (a, b)

对于数字 @emph{a} 和 @emph{b}，返回 @code{a + b}。
@end deffn

@geindex and_() (在 operator 模块中)
@geindex __and__() (在 operator 模块中)
@anchor{library/operator operator and_}@anchor{1af9}
@deffn {函数} operator.and_ (a, b)
@anchor{library/operator operator __and__}@anchor{1afa}
@deffnx {函数} operator.__and__ (a, b)

返回 @emph{x} 和 @emph{y} 按位与的结果。
@end deffn

@geindex floordiv() (在 operator 模块中)
@geindex __floordiv__() (在 operator 模块中)
@anchor{library/operator operator floordiv}@anchor{1afb}
@deffn {函数} operator.floordiv (a, b)
@anchor{library/operator operator __floordiv__}@anchor{1afc}
@deffnx {函数} operator.__floordiv__ (a, b)

返回 @code{a // b}。
@end deffn

@geindex index() (在 operator 模块中)
@geindex __index__() (在 operator 模块中)
@anchor{library/operator operator index}@anchor{1419}
@deffn {函数} operator.index (a)
@anchor{library/operator operator __index__}@anchor{1afd}
@deffnx {函数} operator.__index__ (a)

返回 @emph{a} 转换为整数的结果。 等价于 @code{a.__index__()}。
@end deffn

@geindex inv() (在 operator 模块中)
@geindex invert() (在 operator 模块中)
@geindex __inv__() (在 operator 模块中)
@geindex __invert__() (在 operator 模块中)
@anchor{library/operator operator inv}@anchor{1afe}
@deffn {函数} operator.inv (obj)
@anchor{library/operator operator invert}@anchor{1aff}
@deffnx {函数} operator.invert (obj)
@anchor{library/operator operator __inv__}@anchor{1b00}
@deffnx {函数} operator.__inv__ (obj)
@anchor{library/operator operator __invert__}@anchor{1b01}
@deffnx {函数} operator.__invert__ (obj)

返回数字 @emph{obj} 按位取反的结果。 这等价于 @code{~obj}。
@end deffn

@geindex lshift() (在 operator 模块中)
@geindex __lshift__() (在 operator 模块中)
@anchor{library/operator operator lshift}@anchor{1b02}
@deffn {函数} operator.lshift (a, b)
@anchor{library/operator operator __lshift__}@anchor{1b03}
@deffnx {函数} operator.__lshift__ (a, b)

返回 @emph{a} 左移 @emph{b} 位的结果。
@end deffn

@geindex mod() (在 operator 模块中)
@geindex __mod__() (在 operator 模块中)
@anchor{library/operator operator mod}@anchor{1b04}
@deffn {函数} operator.mod (a, b)
@anchor{library/operator operator __mod__}@anchor{1b05}
@deffnx {函数} operator.__mod__ (a, b)

返回 @code{a % b}。
@end deffn

@geindex mul() (在 operator 模块中)
@geindex __mul__() (在 operator 模块中)
@anchor{library/operator operator mul}@anchor{1ad9}
@deffn {函数} operator.mul (a, b)
@anchor{library/operator operator __mul__}@anchor{1b06}
@deffnx {函数} operator.__mul__ (a, b)

对于数字 @emph{a} 和 @emph{b}，返回 @code{a * b}。
@end deffn

@geindex matmul() (在 operator 模块中)
@geindex __matmul__() (在 operator 模块中)
@anchor{library/operator operator matmul}@anchor{717}
@deffn {函数} operator.matmul (a, b)
@anchor{library/operator operator __matmul__}@anchor{1b07}
@deffnx {函数} operator.__matmul__ (a, b)

返回 @code{a @@ b}。


3.5 新版功能.

@end deffn

@geindex neg() (在 operator 模块中)
@geindex __neg__() (在 operator 模块中)
@anchor{library/operator operator neg}@anchor{1b08}
@deffn {函数} operator.neg (obj)
@anchor{library/operator operator __neg__}@anchor{1b09}
@deffnx {函数} operator.__neg__ (obj)

返回 @emph{obj} 取负的结果 (@code{-obj})。
@end deffn

@geindex or_() (在 operator 模块中)
@geindex __or__() (在 operator 模块中)
@anchor{library/operator operator or_}@anchor{1b0a}
@deffn {函数} operator.or_ (a, b)
@anchor{library/operator operator __or__}@anchor{1b0b}
@deffnx {函数} operator.__or__ (a, b)

返回 @emph{a} 和 @emph{b} 按位或的结果。
@end deffn

@geindex pos() (在 operator 模块中)
@geindex __pos__() (在 operator 模块中)
@anchor{library/operator operator pos}@anchor{1b0c}
@deffn {函数} operator.pos (obj)
@anchor{library/operator operator __pos__}@anchor{1b0d}
@deffnx {函数} operator.__pos__ (obj)

返回 @emph{obj} 取正的结果 (@code{+obj})。
@end deffn

@geindex pow() (在 operator 模块中)
@geindex __pow__() (在 operator 模块中)
@anchor{library/operator operator pow}@anchor{1b0e}
@deffn {函数} operator.pow (a, b)
@anchor{library/operator operator __pow__}@anchor{1b0f}
@deffnx {函数} operator.__pow__ (a, b)

对于数字 @emph{a} 和 @emph{b}，返回 @code{a ** b}。
@end deffn

@geindex rshift() (在 operator 模块中)
@geindex __rshift__() (在 operator 模块中)
@anchor{library/operator operator rshift}@anchor{1b10}
@deffn {函数} operator.rshift (a, b)
@anchor{library/operator operator __rshift__}@anchor{1b11}
@deffnx {函数} operator.__rshift__ (a, b)

返回 @emph{a} 右移 @emph{b} 位的结果。
@end deffn

@geindex sub() (在 operator 模块中)
@geindex __sub__() (在 operator 模块中)
@anchor{library/operator operator sub}@anchor{1b12}
@deffn {函数} operator.sub (a, b)
@anchor{library/operator operator __sub__}@anchor{1b13}
@deffnx {函数} operator.__sub__ (a, b)

返回 @code{a - b}。
@end deffn

@geindex truediv() (在 operator 模块中)
@geindex __truediv__() (在 operator 模块中)
@anchor{library/operator operator truediv}@anchor{1b14}
@deffn {函数} operator.truediv (a, b)
@anchor{library/operator operator __truediv__}@anchor{1b15}
@deffnx {函数} operator.__truediv__ (a, b)

返回 @code{a / b} 例如 2/3 将等于 .66 而不是 0。 这也被称为“真”除法。
@end deffn

@geindex xor() (在 operator 模块中)
@geindex __xor__() (在 operator 模块中)
@anchor{library/operator operator xor}@anchor{1b16}
@deffn {函数} operator.xor (a, b)
@anchor{library/operator operator __xor__}@anchor{1b17}
@deffnx {函数} operator.__xor__ (a, b)

返回 @emph{a} 和 @emph{b} 按位异或的结果。
@end deffn

适用于序列的操作（其中一些也适用于映射）包括：

@geindex concat() (在 operator 模块中)
@geindex __concat__() (在 operator 模块中)
@anchor{library/operator operator concat}@anchor{1b18}
@deffn {函数} operator.concat (a, b)
@anchor{library/operator operator __concat__}@anchor{1b19}
@deffnx {函数} operator.__concat__ (a, b)

对于序列 @emph{a} 和 @emph{b}，返回 @code{a + b}。
@end deffn

@geindex contains() (在 operator 模块中)
@geindex __contains__() (在 operator 模块中)
@anchor{library/operator operator contains}@anchor{e92}
@deffn {函数} operator.contains (a, b)
@anchor{library/operator operator __contains__}@anchor{1b1a}
@deffnx {函数} operator.__contains__ (a, b)

返回 @code{b in a} 检测的结果。 请注意操作数是反序的。
@end deffn

@geindex countOf() (在 operator 模块中)
@anchor{library/operator operator countOf}@anchor{e94}
@deffn {函数} operator.countOf (a, b)

返回 @emph{b} 在 @emph{a} 中的出现次数。
@end deffn

@geindex delitem() (在 operator 模块中)
@geindex __delitem__() (在 operator 模块中)
@anchor{library/operator operator delitem}@anchor{1b1b}
@deffn {函数} operator.delitem (a, b)
@anchor{library/operator operator __delitem__}@anchor{1b1c}
@deffnx {函数} operator.__delitem__ (a, b)

移除索引号 @emph{b} 上的值 @emph{a}。
@end deffn

@geindex getitem() (在 operator 模块中)
@geindex __getitem__() (在 operator 模块中)
@anchor{library/operator operator getitem}@anchor{1b1d}
@deffn {函数} operator.getitem (a, b)
@anchor{library/operator operator __getitem__}@anchor{1b1e}
@deffnx {函数} operator.__getitem__ (a, b)

返回索引号 @emph{b} 上的值 @emph{a}。
@end deffn

@geindex indexOf() (在 operator 模块中)
@anchor{library/operator operator indexOf}@anchor{e93}
@deffn {函数} operator.indexOf (a, b)

返回 @emph{b} 在 @emph{a} 中首次出现所在的索引号。
@end deffn

@geindex setitem() (在 operator 模块中)
@geindex __setitem__() (在 operator 模块中)
@anchor{library/operator operator setitem}@anchor{1b1f}
@deffn {函数} operator.setitem (a, b, c)
@anchor{library/operator operator __setitem__}@anchor{1b20}
@deffnx {函数} operator.__setitem__ (a, b, c)

将索引号 @emph{b} 上的值 @emph{a} 设为 @emph{c}。
@end deffn

@geindex length_hint() (在 operator 模块中)
@anchor{library/operator operator length_hint}@anchor{877}
@deffn {函数} operator.length_hint (obj, default=0)

返回对象 @emph{o} 的估计长度。 首先尝试返回其实际长度，再使用 @ref{806,,object.__length_hint__()} 得出估计值，最后返回默认值。


3.4 新版功能.

@end deffn

@ref{c2,,operator} 模块还定义了一些用于常规属性和条目查找的工具。 这些工具适合用来编写快速字段提取器作为 @ref{c26,,map()}, @ref{43e,,sorted()}, @ref{1ad3,,itertools.groupby()} 或其他需要相应函数参数的函数的参数。

@geindex attrgetter() (在 operator 模块中)
@anchor{library/operator operator attrgetter}@anchor{715}
@deffn {函数} operator.attrgetter (attr)

@deffnx {函数} operator.attrgetter (*attrs)

返回一个可从操作数中获取 @emph{attr} 的可调用对象。 如果请求了一个以上的属性，则返回一个属性元组。 属性名称还可包含点号。 例如：


@itemize *

@item 
在 @code{f = attrgetter('name')} 之后，调用 @code{f(b)} 将返回 @code{b.name}。

@item 
在 @code{f = attrgetter('name', 'date')} 之后，调用 @code{f(b)} 将返回 @code{(b.name, b.date)}。

@item 
在 @code{f = attrgetter('name.first', 'name.last')} 之后，调用 @code{f(b)} 将返回 @code{(b.name.first, b.name.last)}。
@end itemize

等价于:

@example
def attrgetter(*items):
    if any(not isinstance(item, str) for item in items):
        raise TypeError('attribute name must be a string')
    if len(items) == 1:
        attr = items[0]
        def g(obj):
            return resolve_attr(obj, attr)
    else:
        def g(obj):
            return tuple(resolve_attr(obj, attr) for attr in items)
    return g

def resolve_attr(obj, attr):
    for name in attr.split("."):
        obj = getattr(obj, name)
    return obj
@end example
@end deffn

@geindex itemgetter() (在 operator 模块中)
@anchor{library/operator operator itemgetter}@anchor{261}
@deffn {函数} operator.itemgetter (item)

@deffnx {函数} operator.itemgetter (*items)

返回一个使用操作数的 @ref{1b1e,,__getitem__()} 方法从操作数中获取 @emph{item} 的可调用对象。 如果指定了多个条目，则返回一个查找值的元组。 例如：


@itemize *

@item 
在 @code{f = itemgetter(2)} 之后，调用 @code{f(r)} 将返回 @code{r[2]}。

@item 
在 @code{g = itemgetter(2, 5, 3)} 之后，调用 @code{g(r)} 将返回 @code{(r[2], r[5], r[3])}。
@end itemize

等价于:

@example
def itemgetter(*items):
    if len(items) == 1:
        item = items[0]
        def g(obj):
            return obj[item]
    else:
        def g(obj):
            return tuple(obj[item] for item in items)
    return g
@end example

传入的条目可以为操作数的 @ref{1b1e,,__getitem__()} 所接受的任何类型。 字典接受任意可哈希的值。 列表、元组和字符串接受 index 或 slice 对象：

@example
>>> itemgetter('name')(@{'name': 'tu', 'age': 18@})
'tu'
>>> itemgetter(1)('ABCDEFG')
'B'
>>> itemgetter(1,3,5)('ABCDEFG')
('B', 'D', 'F')
>>> itemgetter(slice(2,None))('ABCDEFG')
'CDEFG'
@end example

@example
>>> soldier = dict(rank='captain', name='dotterbart')
>>> itemgetter('rank')(soldier)
'captain'
@end example

使用 @ref{261,,itemgetter()} 从元组的记录中提取特定字段的例子：

@example
>>> inventory = [('apple', 3), ('banana', 2), ('pear', 5), ('orange', 1)]
>>> getcount = itemgetter(1)
>>> list(map(getcount, inventory))
[3, 2, 5, 1]
>>> sorted(inventory, key=getcount)
[('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)]
@end example
@end deffn

@geindex methodcaller() (在 operator 模块中)
@anchor{library/operator operator methodcaller}@anchor{716}
@deffn {函数} operator.methodcaller (name, /, *args, **kwargs)

返回一个在操作数上调用 @emph{name} 方法的可调用对象。 如果给出额外的参数和/或关键字参数，它们也将被传给该方法。 例如：


@itemize *

@item 
在 @code{f = methodcaller('name')} 之后，调用 @code{f(b)} 将返回 @code{b.name()}。

@item 
在 @code{f = methodcaller('name', 'foo', bar=1)} 之后，调用 @code{f(b)} 将返回 @code{b.name('foo', bar=1)}。
@end itemize

等价于:

@example
def methodcaller(name, /, *args, **kwargs):
    def caller(obj):
        return getattr(obj, name)(*args, **kwargs)
    return caller
@end example
@end deffn

@menu
* 将运算符映射到函数:: 
* 原地运算符:: 

@end menu

@node 将运算符映射到函数,原地运算符,,operator --- 标准运算符替代函数
@anchor{library/operator mapping-operators-to-functions}@anchor{1b21}@anchor{library/operator operator-map}@anchor{1b22}
@subsubsection 将运算符映射到函数


以下表格显示了抽象运算是如何对应于 Python 语法中的运算符和 @ref{c2,,operator} 模块中的函数的。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

运算

@tab

语法

@tab

函数

@item

加法

@tab

@code{a + b}

@tab

@code{add(a, b)}

@item

字符串拼接

@tab

@code{seq1 + seq2}

@tab

@code{concat(seq1, seq2)}

@item

包含测试

@tab

@code{obj in seq}

@tab

@code{contains(seq, obj)}

@item

除法

@tab

@code{a / b}

@tab

@code{truediv(a, b)}

@item

除法

@tab

@code{a // b}

@tab

@code{floordiv(a, b)}

@item

按位与

@tab

@code{a & b}

@tab

@code{and_(a, b)}

@item

按位异或

@tab

@code{a ^ b}

@tab

@code{xor(a, b)}

@item

按位取反

@tab

@code{~ a}

@tab

@code{invert(a)}

@item

按位或

@tab

@code{a | b}

@tab

@code{or_(a, b)}

@item

取幂

@tab

@code{a ** b}

@tab

@code{pow(a, b)}

@item

标识

@tab

@code{a is b}

@tab

@code{is_(a, b)}

@item

标识

@tab

@code{a is not b}

@tab

@code{is_not(a, b)}

@item

索引赋值

@tab

@code{obj[k] = v}

@tab

@code{setitem(obj, k, v)}

@item

索引删除

@tab

@code{del obj[k]}

@tab

@code{delitem(obj, k)}

@item

索引取值

@tab

@code{obj[k]}

@tab

@code{getitem(obj, k)}

@item

左移

@tab

@code{a << b}

@tab

@code{lshift(a, b)}

@item

取模

@tab

@code{a % b}

@tab

@code{mod(a, b)}

@item

乘法

@tab

@code{a * b}

@tab

@code{mul(a, b)}

@item

矩阵乘法

@tab

@code{a @@ b}

@tab

@code{matmul(a, b)}

@item

取反（算术）

@tab

@code{- a}

@tab

@code{neg(a)}

@item

取反（逻辑）

@tab

@code{not a}

@tab

@code{not_(a)}

@item

正数

@tab

@code{+ a}

@tab

@code{pos(a)}

@item

右移

@tab

@code{a >> b}

@tab

@code{rshift(a, b)}

@item

切片赋值

@tab

@code{seq[i:j] = values}

@tab

@code{setitem(seq, slice(i, j), values)}

@item

切片删除

@tab

@code{del seq[i:j]}

@tab

@code{delitem(seq, slice(i, j))}

@item

切片取值

@tab

@code{seq[i:j]}

@tab

@code{getitem(seq, slice(i, j))}

@item

字符串格式化

@tab

@code{s % obj}

@tab

@code{mod(s, obj)}

@item

减法

@tab

@code{a - b}

@tab

@code{sub(a, b)}

@item

真值测试

@tab

@code{obj}

@tab

@code{truth(obj)}

@item

比较

@tab

@code{a < b}

@tab

@code{lt(a, b)}

@item

比较

@tab

@code{a <= b}

@tab

@code{le(a, b)}

@item

相等

@tab

@code{a == b}

@tab

@code{eq(a, b)}

@item

不等

@tab

@code{a != b}

@tab

@code{ne(a, b)}

@item

比较

@tab

@code{a >= b}

@tab

@code{ge(a, b)}

@item

比较

@tab

@code{a > b}

@tab

@code{gt(a, b)}

@end multitable


@node 原地运算符,,将运算符映射到函数,operator --- 标准运算符替代函数
@anchor{library/operator in-place-operators}@anchor{1b23}
@subsubsection 原地运算符


许多运算都有“原地”版本。 以下列出的是提供对原地运算符相比通常语法更底层访问的函数，例如 @ref{1b24,,statement} @code{x += y} 相当于 @code{x = operator.iadd(x, y)}。 换一种方式来讲就是 @code{z = operator.iadd(x, y)} 等价于语句块 @code{z = x; z += y}。

在这些例子中，请注意当调用一个原地方法时，运算和赋值是分成两个步骤来执行的。 下面列出的原地函数只执行第一步即调用原地方法。 第二步赋值则不加处理。

对于不可变的目标例如字符串、数字和元组，更新的值会被计算，但不会被再被赋值给输入变量：

@example
>>> a = 'hello'
>>> iadd(a, ' world')
'hello world'
>>> a
'hello'
@end example

对于可变的目标例如列表和字典，原地方法将执行更新，因此不需要后续赋值操作：

@example
>>> s = ['h', 'e', 'l', 'l', 'o']
>>> iadd(s, [' ', 'w', 'o', 'r', 'l', 'd'])
['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']
>>> s
['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']
@end example

@geindex iadd() (在 operator 模块中)
@geindex __iadd__() (在 operator 模块中)
@anchor{library/operator operator iadd}@anchor{1b25}
@deffn {函数} operator.iadd (a, b)
@anchor{library/operator operator __iadd__}@anchor{1b26}
@deffnx {函数} operator.__iadd__ (a, b)

@code{a = iadd(a, b)} 等价于 @code{a += b}。
@end deffn

@geindex iand() (在 operator 模块中)
@geindex __iand__() (在 operator 模块中)
@anchor{library/operator operator iand}@anchor{1b27}
@deffn {函数} operator.iand (a, b)
@anchor{library/operator operator __iand__}@anchor{1b28}
@deffnx {函数} operator.__iand__ (a, b)

@code{a = iand(a, b)} 等价于 @code{a &= b}。
@end deffn

@geindex iconcat() (在 operator 模块中)
@geindex __iconcat__() (在 operator 模块中)
@anchor{library/operator operator iconcat}@anchor{1b29}
@deffn {函数} operator.iconcat (a, b)
@anchor{library/operator operator __iconcat__}@anchor{1b2a}
@deffnx {函数} operator.__iconcat__ (a, b)

@code{a = iconcat(a, b)} 等价于 @code{a += b} 其中 @emph{a} 和 @emph{b} 为序列。
@end deffn

@geindex ifloordiv() (在 operator 模块中)
@geindex __ifloordiv__() (在 operator 模块中)
@anchor{library/operator operator ifloordiv}@anchor{1b2b}
@deffn {函数} operator.ifloordiv (a, b)
@anchor{library/operator operator __ifloordiv__}@anchor{1b2c}
@deffnx {函数} operator.__ifloordiv__ (a, b)

@code{a = ifloordiv(a, b)} 等价于 @code{a //= b}。
@end deffn

@geindex ilshift() (在 operator 模块中)
@geindex __ilshift__() (在 operator 模块中)
@anchor{library/operator operator ilshift}@anchor{1b2d}
@deffn {函数} operator.ilshift (a, b)
@anchor{library/operator operator __ilshift__}@anchor{1b2e}
@deffnx {函数} operator.__ilshift__ (a, b)

@code{a = ilshift(a, b)} 等价于 @code{a <<= b}。
@end deffn

@geindex imod() (在 operator 模块中)
@geindex __imod__() (在 operator 模块中)
@anchor{library/operator operator imod}@anchor{1b2f}
@deffn {函数} operator.imod (a, b)
@anchor{library/operator operator __imod__}@anchor{1b30}
@deffnx {函数} operator.__imod__ (a, b)

@code{a = imod(a, b)} 等价于 @code{a %= b}。
@end deffn

@geindex imul() (在 operator 模块中)
@geindex __imul__() (在 operator 模块中)
@anchor{library/operator operator imul}@anchor{1b31}
@deffn {函数} operator.imul (a, b)
@anchor{library/operator operator __imul__}@anchor{1b32}
@deffnx {函数} operator.__imul__ (a, b)

@code{a = imul(a, b)} 等价于 @code{a *= b}。
@end deffn

@geindex imatmul() (在 operator 模块中)
@geindex __imatmul__() (在 operator 模块中)
@anchor{library/operator operator imatmul}@anchor{718}
@deffn {函数} operator.imatmul (a, b)
@anchor{library/operator operator __imatmul__}@anchor{1b33}
@deffnx {函数} operator.__imatmul__ (a, b)

@code{a = imatmul(a, b)} 等价于 @code{a @@= b}。


3.5 新版功能.

@end deffn

@geindex ior() (在 operator 模块中)
@geindex __ior__() (在 operator 模块中)
@anchor{library/operator operator ior}@anchor{1b34}
@deffn {函数} operator.ior (a, b)
@anchor{library/operator operator __ior__}@anchor{1b35}
@deffnx {函数} operator.__ior__ (a, b)

@code{a = ior(a, b)} 等价于 @code{a |= b}。
@end deffn

@geindex ipow() (在 operator 模块中)
@geindex __ipow__() (在 operator 模块中)
@anchor{library/operator operator ipow}@anchor{1b36}
@deffn {函数} operator.ipow (a, b)
@anchor{library/operator operator __ipow__}@anchor{1b37}
@deffnx {函数} operator.__ipow__ (a, b)

@code{a = ipow(a, b)} 等价于 @code{a **= b}。
@end deffn

@geindex irshift() (在 operator 模块中)
@geindex __irshift__() (在 operator 模块中)
@anchor{library/operator operator irshift}@anchor{1b38}
@deffn {函数} operator.irshift (a, b)
@anchor{library/operator operator __irshift__}@anchor{1b39}
@deffnx {函数} operator.__irshift__ (a, b)

@code{a = irshift(a, b)} 等价于 @code{a >>= b}。
@end deffn

@geindex isub() (在 operator 模块中)
@geindex __isub__() (在 operator 模块中)
@anchor{library/operator operator isub}@anchor{1b3a}
@deffn {函数} operator.isub (a, b)
@anchor{library/operator operator __isub__}@anchor{1b3b}
@deffnx {函数} operator.__isub__ (a, b)

@code{a = isub(a, b)} 等价于 @code{a -= b}。
@end deffn

@geindex itruediv() (在 operator 模块中)
@geindex __itruediv__() (在 operator 模块中)
@anchor{library/operator operator itruediv}@anchor{1b3c}
@deffn {函数} operator.itruediv (a, b)
@anchor{library/operator operator __itruediv__}@anchor{1b3d}
@deffnx {函数} operator.__itruediv__ (a, b)

@code{a = itruediv(a, b)} 等价于 @code{a /= b}。
@end deffn

@geindex ixor() (在 operator 模块中)
@geindex __ixor__() (在 operator 模块中)
@anchor{library/operator operator ixor}@anchor{1b3e}
@deffn {函数} operator.ixor (a, b)
@anchor{library/operator operator __ixor__}@anchor{1b3f}
@deffnx {函数} operator.__ixor__ (a, b)

@code{a = ixor(a, b)} 等价于 @code{a ^= b}。
@end deffn

@node 文件和目录访问,数据持久化,函数式编程模块,Python 标准库
@anchor{library/filesys doc}@anchor{1b40}@anchor{library/filesys file-and-directory-access}@anchor{1b41}@anchor{library/filesys filesys}@anchor{1b42}
@section 文件和目录访问


本章中描述的模块处理磁盘文件和目录。 例如，有一些模块用于读取文件的属性，以可移植的方式操作路径以及创建临时文件。 本章的完整模块列表如下：

@menu
* pathlib: pathlib --- 面向对象的文件系统路径. 面向对象的文件系统路径
* os.path: os path --- 常用路径操作. 常用路径操作
* fileinput: fileinput --- 迭代来自多个输入流的行. 迭代来自多个输入流的行
* stat: stat --- 解析 stat 结果. 解析 stat() 结果
* filecmp: filecmp --- 文件及目录的比较. 文件及目录的比较
* tempfile: tempfile --- 生成临时文件和目录. 生成临时文件和目录
* glob: glob --- Unix 风格路径名模式扩展. Unix 风格路径名模式扩展
* fnmatch: fnmatch --- Unix 文件名模式匹配. Unix 文件名模式匹配
* linecache: linecache --- 随机读写文本行. 随机读写文本行
* shutil: shutil --- 高阶文件操作. 高阶文件操作

@end menu

@node pathlib --- 面向对象的文件系统路径,os path --- 常用路径操作,,文件和目录访问
@anchor{library/pathlib doc}@anchor{1b43}@anchor{library/pathlib module-pathlib}@anchor{c8}@anchor{library/pathlib pathlib-object-oriented-filesystem-paths}@anchor{1b44}
@subsection @code{pathlib} --- 面向对象的文件系统路径


@geindex pathlib (模块)


3.4 新版功能.


@strong{源代码} Lib/pathlib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pathlib.py}

@geindex path; operations


__________________________________________________________________


该模块提供表示文件系统路径的类，其语义适用于不同的操作系统。路径类被分为提供纯计算操作而没有 I/O 的 @ref{1b45,,纯路径}，以及从纯路径继承而来但提供 I/O 操作的 @ref{1b46,,具体路径}。

@image{python-figures/pathlib-inheritance,,,,png}

如果你以前从未使用过此模块或者不确定在项目中使用哪一个类是正确的，则 @ref{201,,Path} 总是你需要的。它在运行代码的平台上实例化为一个 @ref{1b46,,具体路径}。

在一些用例中纯路径很有用，例如：


@enumerate 

@item 
如果你想要在 Unix 设备上操作 Windows 路径（或者相反）。你不应在 Unix 上实例化一个 @ref{1b47,,WindowsPath}，但是你可以实例化 @ref{1b48,,PureWindowsPath}。

@item 
你只想操作路径但不想实际访问操作系统。在这种情况下，实例化一个纯路径是有用的，因为它们没有任何访问操作系统的操作。
@end enumerate


@subsubheading 参见


@geindex Python 提高建议; PEP 428
PEP 428@footnote{https://www.python.org/dev/peps/pep-0428}：pathlib 模块 -- 面向对象的的文件系统路径。



@subsubheading 参见


对于底层的路径字符串操作，你也可以使用 @ref{c5,,os.path} 模块。


@menu
* 基础使用:: 
* 纯路径:: 
* 具体路径:: 
* 对应的 os 模块的工具:: 

@end menu

@node 基础使用,纯路径,,pathlib --- 面向对象的文件系统路径
@anchor{library/pathlib basic-use}@anchor{1b49}
@subsubsection 基础使用


导入主类:

@example
>>> from pathlib import Path
@end example

列出子目录:

@example
>>> p = Path('.')
>>> [x for x in p.iterdir() if x.is_dir()]
[PosixPath('.hg'), PosixPath('docs'), PosixPath('dist'),
 PosixPath('__pycache__'), PosixPath('build')]
@end example

列出当前目录树下的所有 Python 源代码文件:

@example
>>> list(p.glob('**/*.py'))
[PosixPath('test_pathlib.py'), PosixPath('setup.py'),
 PosixPath('pathlib.py'), PosixPath('docs/conf.py'),
 PosixPath('build/lib/pathlib.py')]
@end example

在目录树中移动:

@example
>>> p = Path('/etc')
>>> q = p / 'init.d' / 'reboot'
>>> q
PosixPath('/etc/init.d/reboot')
>>> q.resolve()
PosixPath('/etc/rc.d/init.d/halt')
@end example

查询路径的属性:

@example
>>> q.exists()
True
>>> q.is_dir()
False
@end example

打开一个文件:

@example
>>> with q.open() as f: f.readline()
...
'#!/bin/bash\n'
@end example

@node 纯路径,具体路径,基础使用,pathlib --- 面向对象的文件系统路径
@anchor{library/pathlib id1}@anchor{1b4a}@anchor{library/pathlib pure-paths}@anchor{1b45}
@subsubsection 纯路径


纯路径对象提供了不实际访问文件系统的路径处理操作。有三种方式来访问这些类，也是不同的风格：

@geindex PurePath (pathlib 中的类)
@anchor{library/pathlib pathlib PurePath}@anchor{fd4}
@deffn {类} pathlib.PurePath (*pathsegments)

一个通用的类，代表当前系统的路径风格（实例化为 @ref{1b4b,,PurePosixPath} 或者 @ref{1b48,,PureWindowsPath}）:

@example
>>> PurePath('setup.py')      # Running on a Unix machine
PurePosixPath('setup.py')
@end example

每一个 @emph{pathsegments} 的元素可能是一个代表路径片段的字符串，一个返回字符串的实现了 @ref{4e5,,os.PathLike} 接口的对象，或者另一个路径对象:

@example
>>> PurePath('foo', 'some/path', 'bar')
PurePosixPath('foo/some/path/bar')
>>> PurePath(Path('foo'), Path('bar'))
PurePosixPath('foo/bar')
@end example

当 @emph{pathsegments} 为空的时候，假定为当前目录:

@example
>>> PurePath()
PurePosixPath('.')
@end example

当给出一些绝对路径，最后一位将被当作锚（模仿 @ref{eeb,,os.path.join()} 的行为）:

@example
>>> PurePath('/etc', '/usr', 'lib64')
PurePosixPath('/usr/lib64')
>>> PureWindowsPath('c:/Windows', 'd:bar')
PureWindowsPath('d:bar')
@end example

但是，在 Windows 路径中，改变本地根目录并不会丢弃之前盘符的设置:

@example
>>> PureWindowsPath('c:/Windows', '/Program Files')
PureWindowsPath('c:/Program Files')
@end example

假斜线和单独的点都会被消除，但是双点 （@code{‘..’}） 不会，以防改变符号链接的含义。

@example
>>> PurePath('foo//bar')
PurePosixPath('foo/bar')
>>> PurePath('foo/./bar')
PurePosixPath('foo/bar')
>>> PurePath('foo/../bar')
PurePosixPath('foo/../bar')
@end example

（如果你想让 @code{PurePosixPath('foo/../bar')} 等同于 @code{PurePosixPath('bar')}，那么 you are too young, too simple, sometimes naive!  如果 @code{foo} 是一个指向其他其他目录的符号链接，那就出毛病啦。）

纯路径对象实现了 @ref{4e5,,os.PathLike} 接口，允许它们在任何接受此接口的地方使用。


在 3.6 版更改: 添加了 @ref{4e5,,os.PathLike} 接口支持。

@end deffn

@geindex PurePosixPath (pathlib 中的类)
@anchor{library/pathlib pathlib PurePosixPath}@anchor{1b4b}
@deffn {类} pathlib.PurePosixPath (*pathsegments)

一个 @ref{fd4,,PurePath} 的子类，路径风格不同于 Windows 文件系统:

@example
>>> PurePosixPath('/etc')
PurePosixPath('/etc')
@end example

@emph{pathsegments} 参数的指定和 @ref{fd4,,PurePath} 相同。
@end deffn

@geindex PureWindowsPath (pathlib 中的类)
@anchor{library/pathlib pathlib PureWindowsPath}@anchor{1b48}
@deffn {类} pathlib.PureWindowsPath (*pathsegments)

@ref{fd4,,PurePath} 的一个子类，路径风格为 Windows 文件系统路径:

@example
>>> PureWindowsPath('c:/Program Files/')
PureWindowsPath('c:/Program Files')
@end example

@emph{pathsegments} 参数的指定和 @ref{fd4,,PurePath} 相同。
@end deffn

无论你正运行什么系统，你都可以实例化这些类，因为它们提供的操作不做任何系统调用。

@menu
* 通用性质:: 
* 运算符: 运算符<2>. 
* 访问个别部分:: 
* 方法和特征属性:: 

@end menu

@node 通用性质,运算符<2>,,纯路径
@anchor{library/pathlib general-properties}@anchor{1b4c}
@subsubsection 通用性质


路径是不可变并可哈希的。相同风格的路径可以排序与比较。这些性质尊重对应风格的大小写转换语义:

@example
>>> PurePosixPath('foo') == PurePosixPath('FOO')
False
>>> PureWindowsPath('foo') == PureWindowsPath('FOO')
True
>>> PureWindowsPath('FOO') in @{ PureWindowsPath('foo') @}
True
>>> PureWindowsPath('C:') < PureWindowsPath('d:')
True
@end example

不同风格的路径比较得到不等的结果并且无法被排序:

@example
>>> PureWindowsPath('foo') == PurePosixPath('foo')
False
>>> PureWindowsPath('foo') < PurePosixPath('foo')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '<' not supported between instances of 'PureWindowsPath' and 'PurePosixPath'
@end example

@node 运算符<2>,访问个别部分,通用性质,纯路径
@anchor{library/pathlib operators}@anchor{1b4d}
@subsubsection 运算符


斜杠 @code{/} 操作符有助于创建子路径，就像 @ref{eeb,,os.path.join()} 一样:

@example
>>> p = PurePath('/etc')
>>> p
PurePosixPath('/etc')
>>> p / 'init.d' / 'apache2'
PurePosixPath('/etc/init.d/apache2')
>>> q = PurePath('bin')
>>> '/usr' / q
PurePosixPath('/usr/bin')
@end example

文件对象可用于任何接受 @ref{4e5,,os.PathLike} 接口实现的地方。

@example
>>> import os
>>> p = PurePath('/etc')
>>> os.fspath(p)
'/etc'
@end example

路径的字符串表示法为它自己原始的文件系统路径（以原生形式，例如在 Windows 下使用反斜杠）。你可以传递给任何需要字符串形式路径的函数。

@example
>>> p = PurePath('/etc')
>>> str(p)
'/etc'
>>> p = PureWindowsPath('c:/Program Files')
>>> str(p)
'c:\\Program Files'
@end example

类似地，在路径上调用 @ref{32a,,bytes} 将原始文件系统路径作为字节对象给出，就像被 @ref{4e9,,os.fsencode()} 编码一样:

@example
>>> bytes(p)
b'/etc'
@end example

@cartouche
@quotation 注解 
只推荐在 Unix 下调用 @ref{32a,,bytes}。在 Windows， unicode 形式是文件系统路径的规范表示法。
@end quotation
@end cartouche

@node 访问个别部分,方法和特征属性,运算符<2>,纯路径
@anchor{library/pathlib accessing-individual-parts}@anchor{1b4e}
@subsubsection 访问个别部分


为了访问路径独立的部分 （组件），使用以下特征属性：

@geindex PurePath.parts() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath parts}@anchor{1b4f}
@deffn {数据} PurePath.parts

一个元组，可以访问路径的多个组件:

@example
>>> p = PurePath('/usr/bin/python3')
>>> p.parts
('/', 'usr', 'bin', 'python3')

>>> p = PureWindowsPath('c:/Program Files/PSF')
>>> p.parts
('c:\\', 'Program Files', 'PSF')
@end example

（注意盘符和本地根目录是如何重组的）
@end deffn

@node 方法和特征属性,,访问个别部分,纯路径
@anchor{library/pathlib methods-and-properties}@anchor{1b50}
@subsubsection 方法和特征属性


@c from pathlib import PurePosixPath, PureWindowsPath

纯路径提供以下方法和特征属性：

@geindex PurePath.drive() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath drive}@anchor{1b51}
@deffn {数据} PurePath.drive

一个表示驱动器盘符或命名的字符串，如果存在:

@example
>>> PureWindowsPath('c:/Program Files/').drive
'c:'
>>> PureWindowsPath('/Program Files/').drive
'@w{'}
>>> PurePosixPath('/etc').drive
'@w{'}
@end example

UNC 分享也被认作驱动器:

@example
>>> PureWindowsPath('//host/share/foo.txt').drive
'\\\\host\\share'
@end example
@end deffn

@geindex PurePath.root() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath root}@anchor{1b52}
@deffn {数据} PurePath.root

一个表示（本地或全局）根的字符串，如果存在:

@example
>>> PureWindowsPath('c:/Program Files/').root
'\\'
>>> PureWindowsPath('c:Program Files/').root
'@w{'}
>>> PurePosixPath('/etc').root
'/'
@end example

UNC 分享一样拥有根:

@example
>>> PureWindowsPath('//host/share').root
'\\'
@end example
@end deffn

@geindex PurePath.anchor() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath anchor}@anchor{1b53}
@deffn {数据} PurePath.anchor

驱动器和根的联合:

@example
>>> PureWindowsPath('c:/Program Files/').anchor
'c:\\'
>>> PureWindowsPath('c:Program Files/').anchor
'c:'
>>> PurePosixPath('/etc').anchor
'/'
>>> PureWindowsPath('//host/share').anchor
'\\\\host\\share\\'
@end example
@end deffn

@geindex PurePath.parents() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath parents}@anchor{1b54}
@deffn {数据} PurePath.parents

An immutable sequence providing access to the logical ancestors of
the path:

@example
>>> p = PureWindowsPath('c:/foo/bar/setup.py')
>>> p.parents[0]
PureWindowsPath('c:/foo/bar')
>>> p.parents[1]
PureWindowsPath('c:/foo')
>>> p.parents[2]
PureWindowsPath('c:/')
@end example
@end deffn

@geindex PurePath.parent() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath parent}@anchor{1b55}
@deffn {数据} PurePath.parent

此路径的逻辑父路径:

@example
>>> p = PurePosixPath('/a/b/c/d')
>>> p.parent
PurePosixPath('/a/b/c')
@end example

你不能超过一个 anchor 或空路径:

@example
>>> p = PurePosixPath('/')
>>> p.parent
PurePosixPath('/')
>>> p = PurePosixPath('.')
>>> p.parent
PurePosixPath('.')
@end example

@cartouche
@quotation 注解 
这是一个单纯的词法操作，因此有以下行为:

@example
>>> p = PurePosixPath('foo/..')
>>> p.parent
PurePosixPath('foo')
@end example

如果你想要向上移动任意文件系统路径，推荐先使用 @ref{1b56,,Path.resolve()} 来解析符号链接以及消除 @code{".."} 组件。
@end quotation
@end cartouche
@end deffn

@geindex PurePath.name() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath name}@anchor{1b57}
@deffn {数据} PurePath.name

一个表示最后路径组件的字符串，排除了驱动器与根目录，如果存在的话:

@example
>>> PurePosixPath('my/library/setup.py').name
'setup.py'
@end example

UNC 驱动器名不被考虑:

@example
>>> PureWindowsPath('//some/share/setup.py').name
'setup.py'
>>> PureWindowsPath('//some/share').name
'@w{'}
@end example
@end deffn

@geindex PurePath.suffix() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath suffix}@anchor{1b58}
@deffn {数据} PurePath.suffix

最后一个组件的文件扩展名，如果存在:

@example
>>> PurePosixPath('my/library/setup.py').suffix
'.py'
>>> PurePosixPath('my/library.tar.gz').suffix
'.gz'
>>> PurePosixPath('my/library').suffix
'@w{'}
@end example
@end deffn

@geindex PurePath.suffixes() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath suffixes}@anchor{1b59}
@deffn {数据} PurePath.suffixes

路径的文件扩展名列表:

@example
>>> PurePosixPath('my/library.tar.gar').suffixes
['.tar', '.gar']
>>> PurePosixPath('my/library.tar.gz').suffixes
['.tar', '.gz']
>>> PurePosixPath('my/library').suffixes
[]
@end example
@end deffn

@geindex PurePath.stem() (在 pathlib 模块中)
@anchor{library/pathlib pathlib PurePath stem}@anchor{1b5a}
@deffn {数据} PurePath.stem

最后一个路径组件，除去后缀:

@example
>>> PurePosixPath('my/library.tar.gz').stem
'library.tar'
>>> PurePosixPath('my/library.tar').stem
'library'
>>> PurePosixPath('my/library').stem
'library'
@end example
@end deffn

@geindex as_posix() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath as_posix}@anchor{1b5b}
@deffn {方法} PurePath.as_posix ()

返回使用正斜杠（@code{/}）的路径字符串:

@example
>>> p = PureWindowsPath('c:\\windows')
>>> str(p)
'c:\\windows'
>>> p.as_posix()
'c:/windows'
@end example
@end deffn

@geindex as_uri() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath as_uri}@anchor{1b5c}
@deffn {方法} PurePath.as_uri ()

将路径表示为 @code{file} URL。如果并非绝对路径，抛出 @ref{1fb,,ValueError}。

@example
>>> p = PurePosixPath('/etc/passwd')
>>> p.as_uri()
'file:///etc/passwd'
>>> p = PureWindowsPath('c:/Windows')
>>> p.as_uri()
'file:///c:/Windows'
@end example
@end deffn

@geindex is_absolute() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath is_absolute}@anchor{1b5d}
@deffn {方法} PurePath.is_absolute ()

返回此路径是否为绝对路径。如果路径同时拥有驱动器符与根路径（如果风格允许）则将被认作绝对路径。

@example
>>> PurePosixPath('/a/b').is_absolute()
True
>>> PurePosixPath('a/b').is_absolute()
False

>>> PureWindowsPath('c:/a/b').is_absolute()
True
>>> PureWindowsPath('/a/b').is_absolute()
False
>>> PureWindowsPath('c:').is_absolute()
False
>>> PureWindowsPath('//some/share').is_absolute()
True
@end example
@end deffn

@geindex is_reserved() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath is_reserved}@anchor{1b5e}
@deffn {方法} PurePath.is_reserved ()

在 @ref{1b48,,PureWindowsPath}，如果路径是被 Windows 保留的则返回 @code{True}，否则 @code{False}。在 @ref{1b4b,,PurePosixPath}，总是返回 @code{False}。

@example
>>> PureWindowsPath('nul').is_reserved()
True
>>> PurePosixPath('nul').is_reserved()
False
@end example

当保留路径上的文件系统被调用，则可能出现玄学失败或者意料之外的效应。
@end deffn

@geindex joinpath() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath joinpath}@anchor{1b5f}
@deffn {方法} PurePath.joinpath (*other)

调用此方法等同于将每个 @emph{other} 参数中的项目连接在一起:

@example
>>> PurePosixPath('/etc').joinpath('passwd')
PurePosixPath('/etc/passwd')
>>> PurePosixPath('/etc').joinpath(PurePosixPath('passwd'))
PurePosixPath('/etc/passwd')
>>> PurePosixPath('/etc').joinpath('init.d', 'apache2')
PurePosixPath('/etc/init.d/apache2')
>>> PureWindowsPath('c:').joinpath('/Program Files')
PureWindowsPath('c:/Program Files')
@end example
@end deffn

@geindex match() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath match}@anchor{1b60}
@deffn {方法} PurePath.match (pattern)

将此路径与提供的通配符风格的模式匹配。如果匹配成功则返回 @code{True}，否则返回 @code{False}。

如果 @emph{pattern} 是相对的，则路径可以是相对路径或绝对路径，并且匹配是从右侧完成的：

@example
>>> PurePath('a/b.py').match('*.py')
True
>>> PurePath('/a/b/c.py').match('b/*.py')
True
>>> PurePath('/a/b/c.py').match('a/*.py')
False
@end example

如果 @emph{pattern} 是绝对的，则路径必须是绝对的，并且路径必须完全匹配:

@example
>>> PurePath('/a.py').match('/*.py')
True
>>> PurePath('a/b.py').match('/*.py')
False
@end example

与其他方法一样，是否大小写敏感遵循平台的默认规则:

@example
>>> PurePosixPath('b.py').match('*.PY')
False
>>> PureWindowsPath('b.py').match('*.PY')
True
@end example
@end deffn

@geindex relative_to() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath relative_to}@anchor{1b61}
@deffn {方法} PurePath.relative_to (*other)

计算此路径相对 @emph{other} 表示路径的版本。如果不可计算，则抛出 ValueError:

@example
>>> p = PurePosixPath('/etc/passwd')
>>> p.relative_to('/')
PurePosixPath('etc/passwd')
>>> p.relative_to('/etc')
PurePosixPath('passwd')
>>> p.relative_to('/usr')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pathlib.py", line 694, in relative_to
    .format(str(self), str(formatted)))
ValueError: '/etc/passwd' does not start with '/usr'
@end example
@end deffn

@geindex with_name() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath with_name}@anchor{1b62}
@deffn {方法} PurePath.with_name (name)

返回一个新的路径并修改 @ref{1b57,,name}。如果原本路径没有 name，ValueError 被抛出:

@example
>>> p = PureWindowsPath('c:/Downloads/pathlib.tar.gz')
>>> p.with_name('setup.py')
PureWindowsPath('c:/Downloads/setup.py')
>>> p = PureWindowsPath('c:/')
>>> p.with_name('setup.py')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/antoine/cpython/default/Lib/pathlib.py", line 751, in with_name
    raise ValueError("%r has an empty name" % (self,))
ValueError: PureWindowsPath('c:/') has an empty name
@end example
@end deffn

@geindex with_suffix() (pathlib.PurePath 方法)
@anchor{library/pathlib pathlib PurePath with_suffix}@anchor{fc3}
@deffn {方法} PurePath.with_suffix (suffix)

返回一个新的路径并修改 @ref{1b58,,suffix}。如果原本的路径没有后缀，新的 @emph{suffix} 则被追加以代替。如果 @emph{suffix} 是空字符串，则原本的后缀被移除:

@example
>>> p = PureWindowsPath('c:/Downloads/pathlib.tar.gz')
>>> p.with_suffix('.bz2')
PureWindowsPath('c:/Downloads/pathlib.tar.bz2')
>>> p = PureWindowsPath('README')
>>> p.with_suffix('.txt')
PureWindowsPath('README.txt')
>>> p = PureWindowsPath('README.txt')
>>> p.with_suffix('@w{'})
PureWindowsPath('README')
@end example
@end deffn

@node 具体路径,对应的 os 模块的工具,纯路径,pathlib --- 面向对象的文件系统路径
@anchor{library/pathlib concrete-paths}@anchor{1b46}@anchor{library/pathlib id2}@anchor{1b63}
@subsubsection 具体路径


具体路径是纯路径的子类。除了后者提供的操作之外，它们还提供了对路径对象进行系统调用的方法。有三种方法可以实例化具体路径:

@geindex Path (pathlib 中的类)
@anchor{library/pathlib pathlib Path}@anchor{201}
@deffn {类} pathlib.Path (*pathsegments)

一个 @ref{fd4,,PurePath} 的子类，此类以当前系统的路径风格表示路径（实例化为 @ref{1b64,,PosixPath} 或 @ref{1b47,,WindowsPath}）:

@example
>>> Path('setup.py')
PosixPath('setup.py')
@end example

@emph{pathsegments} 参数的指定和 @ref{fd4,,PurePath} 相同。
@end deffn

@geindex PosixPath (pathlib 中的类)
@anchor{library/pathlib pathlib PosixPath}@anchor{1b64}
@deffn {类} pathlib.PosixPath (*pathsegments)

一个 @ref{201,,Path} 和 @ref{1b4b,,PurePosixPath} 的子类，此类表示一个非 Windows 文件系统的具体路径:

@example
>>> PosixPath('/etc')
PosixPath('/etc')
@end example

@emph{pathsegments} 参数的指定和 @ref{fd4,,PurePath} 相同。
@end deffn

@geindex WindowsPath (pathlib 中的类)
@anchor{library/pathlib pathlib WindowsPath}@anchor{1b47}
@deffn {类} pathlib.WindowsPath (*pathsegments)

@ref{201,,Path} 和 @ref{1b48,,PureWindowsPath} 的子类，从类表示一个 Windows 文件系统的具体路径:

@example
>>> WindowsPath('c:/Program Files/')
WindowsPath('c:/Program Files')
@end example

@emph{pathsegments} 参数的指定和 @ref{fd4,,PurePath} 相同。
@end deffn

你只能实例化与当前系统风格相同的类（允许系统调用作用于不兼容的路径风格可能在应用程序中导致缺陷或失败）:

@example
>>> import os
>>> os.name
'posix'
>>> Path('setup.py')
PosixPath('setup.py')
>>> PosixPath('setup.py')
PosixPath('setup.py')
>>> WindowsPath('setup.py')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pathlib.py", line 798, in __new__
    % (cls.__name__,))
NotImplementedError: cannot instantiate 'WindowsPath' on your system
@end example

@menu
* 方法: 方法<2>. 

@end menu

@node 方法<2>,,,具体路径
@anchor{library/pathlib methods}@anchor{1b65}
@subsubsection 方法


除纯路径方法外，实体路径还提供以下方法。 如果系统调用失败（例如因为路径不存在）这些方法中许多都会引发 @ref{1d3,,OSError}。


在 3.8 版更改: 对于包含 OS 层级无法表示字符的路径，@ref{202,,exists()}, @ref{203,,is_dir()}, @ref{204,,is_file()}, @ref{205,,is_mount()}, @ref{206,,is_symlink()}, @ref{207,,is_block_device()}, @ref{208,,is_char_device()}, @ref{209,,is_fifo()}, @ref{20a,,is_socket()} 现在将返回 @code{False} 而不是引发异常。


@geindex cwd() (pathlib.Path 类方法)
@anchor{library/pathlib pathlib Path cwd}@anchor{1b66}
@deffn {方法} classmethod Path.cwd ()

返回一个新的表示当前目录的路径对象（和 @ref{f6f,,os.getcwd()} 返回的相同）:

@example
>>> Path.cwd()
PosixPath('/home/antoine/pathlib')
@end example
@end deffn

@geindex home() (pathlib.Path 类方法)
@anchor{library/pathlib pathlib Path home}@anchor{725}
@deffn {方法} classmethod Path.home ()

返回一个表示当前用户家目录的新路径对象（和 @ref{1fe,,os.path.expanduser()} 构造含 @code{~} 路径返回的相同）:

@example
>>> Path.home()
PosixPath('/home/antoine')
@end example


3.5 新版功能.

@end deffn

@geindex stat() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path stat}@anchor{1b67}
@deffn {方法} Path.stat ()

返回一个 @ref{101d,,os.stat_result} 对象，其中包含有关此路径的信息，例如 @ref{1f1,,os.stat()}。 结果会在每次调用此方法时重新搜索。

@example
>>> p = Path('setup.py')
>>> p.stat().st_size
956
>>> p.stat().st_mtime
1327883547.852554
@end example
@end deffn

@geindex chmod() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path chmod}@anchor{1b68}
@deffn {方法} Path.chmod (mode)

改变文件的模式和权限，和 @ref{a2e,,os.chmod()} 一样:

@example
>>> p = Path('setup.py')
>>> p.stat().st_mode
33277
>>> p.chmod(0o444)
>>> p.stat().st_mode
33060
@end example
@end deffn

@geindex exists() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path exists}@anchor{202}
@deffn {方法} Path.exists ()

此路径是否指向一个已存在的文件或目录:

@example
>>> Path('.').exists()
True
>>> Path('setup.py').exists()
True
>>> Path('/etc').exists()
True
>>> Path('nonexistentfile').exists()
False
@end example

@cartouche
@quotation 注解 
如果路径指向一个符号链接， @ref{202,,exists()} 返回此符号链接是否指向存在的文件或目录。
@end quotation
@end cartouche
@end deffn

@geindex expanduser() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path expanduser}@anchor{724}
@deffn {方法} Path.expanduser ()

返回展开了包含 @code{~} 和 @code{~user} 的构造，就和 @ref{1fe,,os.path.expanduser()} 一样:

@example
>>> p = PosixPath('~/films/Monty Python')
>>> p.expanduser()
PosixPath('/home/eric/films/Monty Python')
@end example


3.5 新版功能.

@end deffn

@geindex glob() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path glob}@anchor{1b69}
@deffn {方法} Path.glob (pattern)

解析相对于此路径的通配符 @emph{pattern}，产生所有匹配的文件:

@example
>>> sorted(Path('.').glob('*.py'))
[PosixPath('pathlib.py'), PosixPath('setup.py'), PosixPath('test_pathlib.py')]
>>> sorted(Path('.').glob('*/*.py'))
[PosixPath('docs/conf.py')]
@end example

"@code{**}" 模式表示 “此目录以及所有子目录，递归”。换句话说，它启用递归通配:

@example
>>> sorted(Path('.').glob('**/*.py'))
[PosixPath('build/lib/pathlib.py'),
 PosixPath('docs/conf.py'),
 PosixPath('pathlib.py'),
 PosixPath('setup.py'),
 PosixPath('test_pathlib.py')]
@end example

@cartouche
@quotation 注解 
在一个较大的目录树中使用 "@code{**}" 模式可能会消耗非常多的时间。
@end quotation
@end cartouche
@end deffn

@geindex group() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path group}@anchor{1b6a}
@deffn {方法} Path.group ()

返回拥有此文件的用户组。如果文件的 GID 无法在系统数据库中找到，将抛出 @ref{2c7,,KeyError} 。
@end deffn

@geindex is_dir() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path is_dir}@anchor{203}
@deffn {方法} Path.is_dir ()

如果路径指向一个目录（或者一个指向目录的符号链接）则返回 @code{True}，如果指向其他类型的文件则返回 @code{False}。

当路径不存在或者是一个破损的符号链接时也会返回 @code{False}；其他错误（例如权限错误）被传播。
@end deffn

@geindex is_file() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path is_file}@anchor{204}
@deffn {方法} Path.is_file ()

如果路径指向一个正常的文件（或者一个指向正常文件的符号链接）则返回 @code{True}，如果指向其他类型的文件则返回 @code{False}。

当路径不存在或者是一个破损的符号链接时也会返回 @code{False}；其他错误（例如权限错误）被传播。
@end deffn

@geindex is_mount() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path is_mount}@anchor{205}
@deffn {方法} Path.is_mount ()

如果路径是一个 @emph{挂载点 <mount point>}：在文件系统中被其他不同的文件系统挂载的地点。在 POSIX 系统，此函数检查 @emph{path} 的父级 —— @code{path/..} 是否处于一个和 @emph{path} 不同的设备中，或者 file:@cite{path/..} 和 @emph{path} 是否指向相同设备的相同 i-node —— 这能检测所有 Unix 以及 POSIX 变种上的挂载点。 Windows 上未实现。


3.7 新版功能.

@end deffn

@geindex is_symlink() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path is_symlink}@anchor{206}
@deffn {方法} Path.is_symlink ()

如果路径指向符号链接则返回 @code{True}， 否则 @code{False}。

如果路径不存在也返回 @code{False}；其他错误（例如权限错误）被传播。
@end deffn

@geindex is_socket() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path is_socket}@anchor{20a}
@deffn {方法} Path.is_socket ()

如果路径指向一个 Unix socket 文件（或者指向 Unix socket 文件的符号链接）则返回 @code{True}，如果指向其他类型的文件则返回 @code{False}。

当路径不存在或者是一个破损的符号链接时也会返回 @code{False}；其他错误（例如权限错误）被传播。
@end deffn

@geindex is_fifo() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path is_fifo}@anchor{209}
@deffn {方法} Path.is_fifo ()

如果路径指向一个先进先出存储（或者指向先进先出存储的符号链接）则返回 @code{True} ，指向其他类型的文件则返回 @code{False}。

当路径不存在或者是一个破损的符号链接时也会返回 @code{False}；其他错误（例如权限错误）被传播。
@end deffn

@geindex is_block_device() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path is_block_device}@anchor{207}
@deffn {方法} Path.is_block_device ()

如果文件指向一个块设备（或者指向块设备的符号链接）则返回 @code{True}，指向其他类型的文件则返回 @code{False}。

当路径不存在或者是一个破损的符号链接时也会返回 @code{False}；其他错误（例如权限错误）被传播。
@end deffn

@geindex is_char_device() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path is_char_device}@anchor{208}
@deffn {方法} Path.is_char_device ()

如果路径指向一个字符设备（或指向字符设备的符号链接）则返回 @code{True}，指向其他类型的文件则返回 @code{False}。

当路径不存在或者是一个破损的符号链接时也会返回 @code{False}；其他错误（例如权限错误）被传播。
@end deffn

@geindex iterdir() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path iterdir}@anchor{1b6b}
@deffn {方法} Path.iterdir ()

当路径指向一个目录时，产生该路径下的对象的路径:

@example
>>> p = Path('docs')
>>> for child in p.iterdir(): child
...
PosixPath('docs/conf.py')
PosixPath('docs/_templates')
PosixPath('docs/make.bat')
PosixPath('docs/index.rst')
PosixPath('docs/_build')
PosixPath('docs/_static')
PosixPath('docs/Makefile')
@end example
@end deffn

@geindex lchmod() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path lchmod}@anchor{1b6c}
@deffn {方法} Path.lchmod (mode)

就像 @ref{1b68,,Path.chmod()} 但是如果路径指向符号链接则是修改符号链接的模式，而不是修改符号链接的目标。
@end deffn

@geindex lstat() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path lstat}@anchor{1b6d}
@deffn {方法} Path.lstat ()

就和 @ref{1b67,,Path.stat()} 一样，但是如果路径指向符号链接，则是返回符号链接而不是目标的信息。
@end deffn

@geindex mkdir() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path mkdir}@anchor{723}
@deffn {方法} Path.mkdir (mode=0o777, parents=False, exist_ok=False)

新建给定路径的目录。如果给出了 @emph{mode} ，它将与当前进程的 @code{umask} 值合并来决定文件模式和访问标志。如果路径已经存在，则抛出 @ref{952,,FileExistsError}。

如果 @emph{parents} 为 true，任何找不到的父目录都会伴随着此路径被创建；它们会以默认权限被创建，而不考虑 @emph{mode} 设置（模仿 POSIX 的 @code{mkdir -p} 命令）。

如果 @emph{parents} 为 false（默认），则找不到的父级目录会导致 @ref{7ba,,FileNotFoundError} 被抛出。

如果 @emph{exist_ok} 为 false（默认），则在目标已存在的情况下抛出 @ref{952,,FileExistsError}。

如果 @emph{exist_ok} 为 true， 则 @ref{952,,FileExistsError} 异常将被忽略（和 POSIX @code{mkdir -p} 命令行为相同），但是只有在最后一个路径组件不是现存的非目录文件时才生效。


在 3.5 版更改: @emph{exist_ok} 形参被加入。

@end deffn

@geindex open() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path open}@anchor{1b6e}
@deffn {方法} Path.open (mode='r', buffering=-1, encoding=None, errors=None, newline=None)

打开路径指向的文件，就像内置的 @ref{4ea,,open()} 函数所做的一样:

@example
>>> p = Path('setup.py')
>>> with p.open() as f:
...     f.readline()
...
'#!/usr/bin/env python3\n'
@end example
@end deffn

@geindex owner() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path owner}@anchor{1b6f}
@deffn {方法} Path.owner ()

返回拥有此文件的用户名。如果文件的 UID 无法在系统数据库中找到，则抛出 @ref{2c7,,KeyError}。
@end deffn

@geindex read_bytes() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path read_bytes}@anchor{729}
@deffn {方法} Path.read_bytes ()

以字节对象的形式返回路径指向的文件的二进制内容:

@example
>>> p = Path('my_binary_file')
>>> p.write_bytes(b'Binary file contents')
20
>>> p.read_bytes()
b'Binary file contents'
@end example


3.5 新版功能.

@end deffn

@geindex read_text() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path read_text}@anchor{727}
@deffn {方法} Path.read_text (encoding=None, errors=None)

以字符串形式返回路径指向的文件的解码后文本内容。

@example
>>> p = Path('my_text_file')
>>> p.write_text('Text file contents')
18
>>> p.read_text()
'Text file contents'
@end example

文件先被打开然后关闭。有和 @ref{4ea,,open()} 一样的可选形参。


3.5 新版功能.

@end deffn

@geindex rename() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path rename}@anchor{1b70}
@deffn {方法} Path.rename (target)

将文件或目录重命名为给定的 @emph{target}，并返回一个新的指向 @emph{target} 的 Path 实例。 在 Unix 上，如果 @emph{target} 存在且为一个文件，如果用户有足够权限，则它将被静默地替换。 @emph{target} 可以是一个字符串或者另一个路径对象:

@example
>>> p = Path('foo')
>>> p.open('w').write('some text')
9
>>> target = Path('bar')
>>> p.rename(target)
PosixPath('bar')
>>> target.open().read()
'some text'
@end example


在 3.8 版更改: 添加了返回值，返回新的 Path 实例。

@end deffn

@geindex replace() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path replace}@anchor{1b71}
@deffn {方法} Path.replace (target)

将文件名目录重命名为给定的 @emph{target}，并返回一个新的指向 @emph{target} 的 Path 实例。 如果 @emph{target} 指向一个现有文件或目录，则它将被无条件地替换。


在 3.8 版更改: 添加了返回值，返回新的 Path 实例。

@end deffn

@geindex resolve() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path resolve}@anchor{1b56}
@deffn {方法} Path.resolve (strict=False)

将路径绝对化，解析任何符号链接。返回新的路径对象:

@example
>>> p = Path()
>>> p
PosixPath('.')
>>> p.resolve()
PosixPath('/home/antoine/pathlib')
@end example

"@code{..}" 组件也将被消除（只有这一种方法这么做）:

@example
>>> p = Path('docs/../setup.py')
>>> p.resolve()
PosixPath('/home/antoine/pathlib/setup.py')
@end example

如果路径不存在并且 @emph{strict} 设为 @code{True}，则抛出 @ref{7ba,,FileNotFoundError}。如果 @emph{strict} 为 @code{False}，则路径将被尽可能地解析并且任何剩余部分都会被不检查是否存在地追加。如果在解析路径上发生无限循环，则抛出 @ref{2ba,,RuntimeError}。


3.6 新版功能: 加入*strict* 参数（3.6之前的版本相当于strict值为True）

@end deffn

@geindex rglob() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path rglob}@anchor{1b72}
@deffn {方法} Path.rglob (pattern)

这就像调用 @code{Path.glob`时在给定的相对 *pattern* 前面添加了"`@w{`}**/`()}"

@example
>>> sorted(Path().rglob("*.py"))
[PosixPath('build/lib/pathlib.py'),
 PosixPath('docs/conf.py'),
 PosixPath('pathlib.py'),
 PosixPath('setup.py'),
 PosixPath('test_pathlib.py')]
@end example
@end deffn

@geindex rmdir() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path rmdir}@anchor{1b73}
@deffn {方法} Path.rmdir ()

移除此目录。此目录必须为空的。
@end deffn

@geindex samefile() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path samefile}@anchor{722}
@deffn {方法} Path.samefile (other_path)

返回此目录是否指向与可能是字符串或者另一个路径对象的 @emph{other_path} 相同的文件。语义类似于 @ref{87c,,os.path.samefile()} 与 @ref{87b,,os.path.samestat()}。

如果两者都以同一原因无法访问，则抛出 @ref{1d3,,OSError}。

@example
>>> p = Path('spam')
>>> q = Path('eggs')
>>> p.samefile(q)
False
>>> p.samefile('spam')
True
@end example


3.5 新版功能.

@end deffn

@geindex symlink_to() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path symlink_to}@anchor{1b74}
@deffn {方法} Path.symlink_to (target, target_is_directory=False)

将此路径创建为指向 @emph{target} 的符号链接。在 Windows 下，如果链接的目标是一个目录则 @emph{target_is_directory} 必须为 true （默认为 @code{False}）。在 POSIX 下， @emph{target_is_directory} 的值将被忽略。

@example
>>> p = Path('mylink')
>>> p.symlink_to('setup.py')
>>> p.resolve()
PosixPath('/home/antoine/pathlib/setup.py')
>>> p.stat().st_size
956
>>> p.lstat().st_size
8
@end example

@cartouche
@quotation 注解 
参数的顺序（link, target) 和 @ref{a36,,os.symlink()} 是相反的。
@end quotation
@end cartouche
@end deffn

@geindex touch() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path touch}@anchor{1b75}
@deffn {方法} Path.touch (mode=0o666, exist_ok=True)

将给定的路径创建为文件。如果给出了 @emph{mode} 它将与当前进程的 @code{umask} 值合并以确定文件的模式和访问标志。如果文件已经存在，则当 @emph{exist_ok} 为 true 则函数仍会成功（并且将它的修改事件更新为当前事件），否则抛出 @ref{952,,FileExistsError}。
@end deffn

@geindex unlink() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path unlink}@anchor{f5e}
@deffn {方法} Path.unlink (missing_ok=False)

移除此文件或符号链接。如果路径指向目录，则用 @ref{1b73,,Path.rmdir()} 代替。

如果 @emph{missing_ok} 为假值（默认），则如果路径不存在将会引发 @ref{7ba,,FileNotFoundError}。

如果 @emph{missing_ok} 为真值，则 @ref{7ba,,FileNotFoundError} 异常将被忽略（和 POSIX @code{rm -f} 命令的行为相同）。


在 3.8 版更改: 增加了 @emph{missing_ok} 形参。

@end deffn

@geindex link_to() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path link_to}@anchor{20b}
@deffn {方法} Path.link_to (target)

创建一个指向名为 @emph{target} 的路径的硬链接。


在 3.8 版更改.

@end deffn

@geindex write_bytes() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path write_bytes}@anchor{728}
@deffn {方法} Path.write_bytes (data)

将文件以二进制模式打开，写入 @emph{data} 并关闭:

@example
>>> p = Path('my_binary_file')
>>> p.write_bytes(b'Binary file contents')
20
>>> p.read_bytes()
b'Binary file contents'
@end example

一个同名的现存文件将被覆盖。


3.5 新版功能.

@end deffn

@geindex write_text() (pathlib.Path 方法)
@anchor{library/pathlib pathlib Path write_text}@anchor{726}
@deffn {方法} Path.write_text (data, encoding=None, errors=None)

将文件以文本模式打开，写入 @emph{data} 并关闭:

@example
>>> p = Path('my_text_file')
>>> p.write_text('Text file contents')
18
>>> p.read_text()
'Text file contents'
@end example

同名的现有文件会被覆盖。 可选形参的含义与 @ref{4ea,,open()} 的相同。


3.5 新版功能.

@end deffn

@node 对应的 os 模块的工具,,具体路径,pathlib --- 面向对象的文件系统路径
@anchor{library/pathlib correspondence-to-tools-in-the-os-module}@anchor{1b76}
@subsubsection 对应的 @code{os} 模块的工具


以下是一个映射了 @ref{c4,,os} 与 @ref{fd4,,PurePath}/@ref{201,,Path} 对应相同的函数的表。

@cartouche
@quotation 注解 
尽管 @ref{1b77,,os.path.relpath()} 和 @ref{1b61,,PurePath.relative_to()} 拥有相同的重叠的用例，但是它们语义相差很大，不能认为它们等价。
@end quotation
@end cartouche


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

os 和 os.path

@tab

pathlib

@item

@ref{ca9,,os.path.abspath()}

@tab

@ref{1b56,,Path.resolve()}

@item

@ref{a2e,,os.chmod()}

@tab

@ref{1b68,,Path.chmod()}

@item

@ref{a31,,os.mkdir()}

@tab

@ref{723,,Path.mkdir()}

@item

@ref{a33,,os.rename()}

@tab

@ref{1b70,,Path.rename()}

@item

@ref{a34,,os.replace()}

@tab

@ref{1b71,,Path.replace()}

@item

@ref{a35,,os.rmdir()}

@tab

@ref{1b73,,Path.rmdir()}

@item

@ref{a32,,os.remove()}, @ref{a37,,os.unlink()}

@tab

@ref{f5e,,Path.unlink()}

@item

@ref{f6f,,os.getcwd()}

@tab

@ref{1b66,,Path.cwd()}

@item

@ref{1f6,,os.path.exists()}

@tab

@ref{202,,Path.exists()}

@item

@ref{1fe,,os.path.expanduser()}

@tab

@ref{724,,Path.expanduser()} 和 @ref{725,,Path.home()}

@item

@ref{1f8,,os.path.isdir()}

@tab

@ref{203,,Path.is_dir()}

@item

@ref{1f9,,os.path.isfile()}

@tab

@ref{204,,Path.is_file()}

@item

@ref{1f4,,os.path.islink()}

@tab

@ref{206,,Path.is_symlink()}

@item

@ref{1f1,,os.stat()}

@tab

@ref{1b67,,Path.stat()},
@ref{1b6f,,Path.owner()},
@ref{1b6a,,Path.group()}

@item

@ref{1b78,,os.path.isabs()}

@tab

@ref{1b5d,,PurePath.is_absolute()}

@item

@ref{eeb,,os.path.join()}

@tab

@ref{1b5f,,PurePath.joinpath()}

@item

@ref{1b79,,os.path.basename()}

@tab

@ref{1b57,,PurePath.name}

@item

@ref{1b7a,,os.path.dirname()}

@tab

@ref{1b55,,PurePath.parent}

@item

@ref{87c,,os.path.samefile()}

@tab

@ref{722,,Path.samefile()}

@item

@ref{1b7b,,os.path.splitext()}

@tab

@ref{1b58,,PurePath.suffix}

@end multitable


@node os path --- 常用路径操作,fileinput --- 迭代来自多个输入流的行,pathlib --- 面向对象的文件系统路径,文件和目录访问
@anchor{library/os path doc}@anchor{1b7c}@anchor{library/os path module-os path}@anchor{c5}@anchor{library/os path os-path-common-pathname-manipulations}@anchor{1b7d}
@subsection @code{os.path} --- 常用路径操作


@geindex os.path (模块)

@strong{源代码：} Lib/posixpath.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/posixpath.py} （用于 POSIX）和 Lib/ntpath.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/ntpath.py} （用于 Windows NT）

@geindex path; operations


__________________________________________________________________


该模块在路径名上实现了一些有用的功能：如需读取或写入文件，请参见 @ref{4ea,,open()} ；有关访问文件系统的信息，请参见 @ref{c4,,os} 模块。路径参数可以字符串或字节形式传递。我们鼓励应用程序将文件名表示为（Unicode）字符串。不幸的是，某些文件名在Unix上可能无法用字符串表示，因此在Unix上平台上需要支持任意文件名的应用程序，应使用字节对象来表示路径名。反之亦然，在Windows平台上仅使用字节对象，不能表示的所有文件名（以标准 @code{mbcs} 编码），因此Windows应用程序应使用字符串对象来访问所有文件。

与unix shell不同，Python不执行任何 @emph{自动} 路径扩展。当应用程序需要类似shell的路径扩展时，可以显式调用诸如 @ref{1fe,,expanduser()} 和 @ref{d3d,,expandvars()} 之类的函数。 （另请参见 @ref{8a,,glob} 模块。）


@subsubheading 参见


@ref{c8,,pathlib} 模块提供高级路径对象。


@cartouche
@quotation 注解 
所有这些函数都仅接受字节或字符串对象作为其参数。如果返回路径或文件名，则结果是相同类型的对象。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
由于不同的操作系统具有不同的路径名称约定，因此标准库中有此模块的几个版本。@ref{c5,,os.path} 模块始终是适合 Python 运行的操作系统的路径模块，因此可用于本地路径。但是，如果操作的路径 @emph{总是} 以一种不同的格式显示，那么也可以分别导入和使用各个模块。它们都具有相同的接口：


@itemize *

@item 
@code{posixpath} 用于Unix 样式的路径

@item 
@code{ntpath} 用于 Windows 路径
@end itemize
@end quotation
@end cartouche


在 3.8 版更改: @ref{1f6,,exists()}、@ref{1f7,,lexists()}、@ref{1f8,,isdir()}、@ref{1f9,,isfile()}、@ref{1f4,,islink()} 和 @ref{1fa,,ismount()} 现在遇到系统层面上不可表示的字符或字节的路径时，会返回 @code{False}，而不是抛出异常。


@geindex abspath() (在 os.path 模块中)
@anchor{library/os path os path abspath}@anchor{ca9}
@deffn {函数} os.path.abspath (path)

返回路径 @emph{path} 的绝对路径（标准化的）。在大多数平台上，这等同于用 @code{normpath(join(os.getcwd(), path))} 的方式调用 @ref{ca8,,normpath()} 函数。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex basename() (在 os.path 模块中)
@anchor{library/os path os path basename}@anchor{1b79}
@deffn {函数} os.path.basename (path)

返回路径 @emph{path} 的基本名称。这是将 @emph{path} 传入函数 @ref{1b7e,,split()} 之后，返回的一对值中的第二个元素。请注意，此函数的结果与Unix @code{basename} 程序不同。@code{basename} 在 @code{'/foo/bar/'} 上返回 @code{'bar'}，而 @ref{1b79,,basename()} 函数返回一个空字符串 (@code{'@w{'}})。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex commonpath() (在 os.path 模块中)
@anchor{library/os path os path commonpath}@anchor{71f}
@deffn {函数} os.path.commonpath (paths)

接受包含多个路径的序列 @emph{paths}，返回 @emph{paths} 的最长公共子路径。如果 @emph{paths} 同时包含绝对路径和相对路径，或 @emph{paths} 在不同的驱动器上，或 @emph{paths} 为空，则抛出 @ref{1fb,,ValueError} 异常。与 @ref{720,,commonprefix()} 不同，本方法返回有效路径。

@ref{12f5,,可用性}: Unix, Windows。


3.5 新版功能.



在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 序列。

@end deffn

@geindex commonprefix() (在 os.path 模块中)
@anchor{library/os path os path commonprefix}@anchor{720}
@deffn {函数} os.path.commonprefix (list)

接受包含多个路径的 @emph{列表}，返回所有路径的最长公共前缀（逐字符比较）。如果 @emph{列表} 为空，则返回空字符串 (@code{'@w{'}})。

@cartouche
@quotation 注解 
此函数是逐字符比较，因此可能返回无效路径。要获取有效路径，参见 @ref{71f,,commonpath()}。

@example
>>> os.path.commonprefix(['/usr/lib', '/usr/local/lib'])
'/usr/l'

>>> os.path.commonpath(['/usr/lib', '/usr/local/lib'])
'/usr'
@end example
@end quotation
@end cartouche


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex dirname() (在 os.path 模块中)
@anchor{library/os path os path dirname}@anchor{1b7a}
@deffn {函数} os.path.dirname (path)

返回路径 @emph{path} 的目录名称。这是将 @emph{path} 传入函数 @ref{1b7e,,split()} 之后，返回的一对值中的第一个元素。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex exists() (在 os.path 模块中)
@anchor{library/os path os path exists}@anchor{1f6}
@deffn {函数} os.path.exists (path)

如果 @emph{path} 指向一个已存在的路径或已打开的文件描述符，返回 @code{True}。对于失效的符号链接，返回 @code{False}。在某些平台上，如果使用 @ref{1f1,,os.stat()} 查询到目标文件没有执行权限，即使 @emph{path} 确实存在，本函数也可能返回 @code{False}。


在 3.3 版更改: @emph{path} 现在可以是一个整数：如果该整数是一个已打开的文件描述符，返回 @code{True}，否则返回 @code{False}。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex lexists() (在 os.path 模块中)
@anchor{library/os path os path lexists}@anchor{1f7}
@deffn {函数} os.path.lexists (path)

如果 @emph{path} 指向一个已存在的路径，返回 @code{True}。对于失效的符号链接，也返回 @code{True}。在缺失 @ref{1f2,,os.lstat()} 的平台上等同于 @ref{1f6,,exists()}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex ~ (tilde); home directory expansion

@geindex expanduser() (在 os.path 模块中)
@anchor{library/os path os path expanduser}@anchor{1fe}
@deffn {函数} os.path.expanduser (path)

在 Unix 和 Windows 上，将参数中开头部分的 @code{~} 或 @code{~user} 替换为当前 @emph{用户} 的家目录并返回。

@geindex 模块; pwd

在 Unix 上，开头的 @code{~} 会被环境变量 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME} 代替，如果变量未设置，则通过内置模块 @ref{d6,,pwd} 在 password 目录中查找当前用户的主目录。以 @code{~user} 开头则直接在 password 目录中查找。

在 Windows 上，如果设置了 
@geindex USERPROFILE
@geindex 环境变量; USERPROFILE
@code{USERPROFILE}，就使用这个变量，否则会将 
@geindex HOMEPATH
@geindex 环境变量; HOMEPATH
@code{HOMEPATH} 和 
@geindex HOMEDRIVE
@geindex 环境变量; HOMEDRIVE
@code{HOMEDRIVE} 结合在一起使用。以 @code{~user} 开头则将上述方法生成路径的最后一截目录替换成 user。

如果展开路径失败，或者路径不是以波浪号开头，则路径将保持不变。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。



在 3.8 版更改: Windows 不再使用 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME}。

@end deffn

@geindex $ (dollar); environment variables expansion
@geindex % (percent); environment variables expansion (Windows)

@geindex expandvars() (在 os.path 模块中)
@anchor{library/os path os path expandvars}@anchor{d3d}
@deffn {函数} os.path.expandvars (path)

输入带有环境变量的路径作为参数，返回展开变量以后的路径。@code{$name} 或 @code{$@{name@}} 形式的子字符串被环境变量 @emph{name} 的值替换。格式错误的变量名称和对不存在变量的引用保持不变。

在 Windows 上，除了 @code{$name} 和 @code{$@{name@}} 外，还可以展开 @code{%name%}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex getatime() (在 os.path 模块中)
@anchor{library/os path os path getatime}@anchor{1b7f}
@deffn {函数} os.path.getatime (path)

返回 @emph{path} 的最后访问时间。返回值是一个浮点数，为纪元秒数（参见 @ref{10a,,time} 模块）。如果该文件不存在或不可访问，则抛出 @ref{1d3,,OSError} 异常。
@end deffn

@geindex getmtime() (在 os.path 模块中)
@anchor{library/os path os path getmtime}@anchor{1b80}
@deffn {函数} os.path.getmtime (path)

返回 @emph{path} 的最后修改时间。返回值是一个浮点数，为纪元秒数（参见 @ref{10a,,time} 模块）。如果该文件不存在或不可访问，则抛出 @ref{1d3,,OSError} 异常。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex getctime() (在 os.path 模块中)
@anchor{library/os path os path getctime}@anchor{1b81}
@deffn {函数} os.path.getctime (path)

返回 @emph{path} 在系统中的 ctime，在有些系统（比如 Unix）上，它是元数据的最后修改时间，其他系统（比如 Windows）上，它是 @emph{path} 的创建时间。返回值是一个数，为纪元秒数（参见 @ref{10a,,time} 模块）。如果该文件不存在或不可访问，则抛出 @ref{1d3,,OSError} 异常。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex getsize() (在 os.path 模块中)
@anchor{library/os path os path getsize}@anchor{1b82}
@deffn {函数} os.path.getsize (path)

返回 @emph{path} 的大小，以字节为单位。如果该文件不存在或不可访问，则抛出 @ref{1d3,,OSError} 异常。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex isabs() (在 os.path 模块中)
@anchor{library/os path os path isabs}@anchor{1b78}
@deffn {函数} os.path.isabs (path)

如果 @emph{path} 是一个绝对路径，则返回 @code{True}。在 Unix 上，它就是以斜杠开头，而在 Windows 上，它可以是去掉驱动器号后以斜杠（或反斜杠）开头。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex isfile() (在 os.path 模块中)
@anchor{library/os path os path isfile}@anchor{1f9}
@deffn {函数} os.path.isfile (path)

如果 @emph{path} 是 @ref{1f6,,现有的} 常规文件，则返回 @code{True}。本方法会跟踪符号链接，因此，对于同一路径，@ref{1f4,,islink()} 和 @ref{1f9,,isfile()} 都可能为 @code{True}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex isdir() (在 os.path 模块中)
@anchor{library/os path os path isdir}@anchor{1f8}
@deffn {函数} os.path.isdir (path)

如果 @emph{path} 是 @ref{1f6,,现有的} 目录，则返回 @code{True}。本方法会跟踪符号链接，因此，对于同一路径，@ref{1f4,,islink()} 和 @ref{1f8,,isdir()} 都可能为 @code{True}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex islink() (在 os.path 模块中)
@anchor{library/os path os path islink}@anchor{1f4}
@deffn {函数} os.path.islink (path)

如果 @emph{path} 指向的 @ref{1f6,,现有} 目录条目是一个符号链接，则返回 @code{True}。如果 Python 运行时不支持符号链接，则总是返回 @code{False}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex ismount() (在 os.path 模块中)
@anchor{library/os path os path ismount}@anchor{1fa}
@deffn {函数} os.path.ismount (path)

如果路径 @emph{path} 是 @emph{挂载点} （文件系统中挂载其他文件系统的点），则返回 @code{True}。在 POSIX 上，该函数检查 @emph{path} 的父目录 @code{@emph{path}/..} 是否在与 @emph{path} 不同的设备上，或者 @code{@emph{path}/..} 和 @emph{path} 是否指向同一设备上的同一 inode（这一检测挂载点的方法适用于所有 Unix 和 POSIX 变体）。本方法不能可靠地检测同一文件系统上的绑定挂载 (bind mount)。在 Windows 上，盘符和共享 UNC 始终是挂载点，对于任何其他路径，将调用 @code{GetVolumePathName} 来查看它是否与输入的路径不同。


3.4 新版功能: 支持在 Windows 上检测非根挂载点。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex join() (在 os.path 模块中)
@anchor{library/os path os path join}@anchor{eeb}
@deffn {函数} os.path.join (path, *paths)

合理地拼接一个或多个路径部分。返回值是 @emph{path} 和 @emph{*paths} 所有值的连接，每个非空部分后面都紧跟一个目录分隔符 (@code{os.sep})，除了最后一部分。这意味着如果最后一部分为空，则结果将以分隔符结尾。如果参数中某个部分是绝对路径，则绝对路径前的路径都将被丢弃，并从绝对路径部分开始连接。

在 Windows 上，遇到绝对路径部分（例如 @code{r'\foo'}）时，不会重置盘符。如果某部分路径包含盘符，则会丢弃所有先前的部分，并重置盘符。请注意，由于每个驱动器都有一个“当前目录”，所以 @code{os.path.join("c:", "foo")} 表示驱动器 @code{C:} 上当前目录的相对路径 (@code{c:foo})，而不是 @code{c:\foo}。


在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 用于 @emph{path} 和 @emph{paths} 。

@end deffn

@geindex normcase() (在 os.path 模块中)
@anchor{library/os path os path normcase}@anchor{1b83}
@deffn {函数} os.path.normcase (path)

规范路径的大小写。在 Windows 上，将路径中的所有字符都转换为小写，并将正斜杠转换为反斜杠。在其他操作系统上返回原路径。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex normpath() (在 os.path 模块中)
@anchor{library/os path os path normpath}@anchor{ca8}
@deffn {函数} os.path.normpath (path)

通过折叠多余的分隔符和对上级目录的引用来标准化路径名，所以 @code{A//B}、@code{A/B/}、@code{A/./B} 和 @code{A/foo/../B} 都会转换成 @code{A/B}。这个字符串操作可能会改变带有符号链接的路径的含义。在 Windows 上，本方法将正斜杠转换为反斜杠。要规范大小写，请使用 @ref{1b83,,normcase()}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex realpath() (在 os.path 模块中)
@anchor{library/os path os path realpath}@anchor{1ff}
@deffn {函数} os.path.realpath (path)

返回指定文件的规范路径，消除路径中存在的任何符号链接（如果操作系统支持）。

@cartouche
@quotation 注解 
当发生符号链接循环时，返回的路径将是该循环的某个组成部分，但不能保证是哪个部分。
@end quotation
@end cartouche


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。



在 3.8 版更改: 在 Windows 上现在可以正确解析符号链接和交接点 (junction point)。

@end deffn

@geindex relpath() (在 os.path 模块中)
@anchor{library/os path os path relpath}@anchor{1b77}
@deffn {函数} os.path.relpath (path, start=os.curdir)

返回从当前目录或 @emph{start} 目录（可选）到达 @emph{path} 之间要经过的相对路径。这仅仅是对路径的计算，不会访问文件系统来确认 @emph{path} 或 @emph{start} 的存在性或属性。

@emph{start} 默认为 @ref{1b84,,os.curdir}。

@ref{12f5,,可用性}: Unix, Windows。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex samefile() (在 os.path 模块中)
@anchor{library/os path os path samefile}@anchor{87c}
@deffn {函数} os.path.samefile (path1, path2)

如果两个路径都指向相同的文件或目录，则返回 @code{True}。这由设备号和 inode 号确定，在任一路径上调用 @ref{1f1,,os.stat()} 失败则抛出异常。

@ref{12f5,,可用性}: Unix, Windows。


在 3.2 版更改: 添加了对 Windows 的支持。



在 3.4 版更改: Windows现在使用与其他所有平台相同的实现。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex sameopenfile() (在 os.path 模块中)
@anchor{library/os path os path sameopenfile}@anchor{1b85}
@deffn {函数} os.path.sameopenfile (fp1, fp2)

如果文件描述符 @emph{fp1} 和 @emph{fp2} 指向相同文件，则返回 @code{True}。

@ref{12f5,,可用性}: Unix, Windows。


在 3.2 版更改: 添加了对 Windows 的支持。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex samestat() (在 os.path 模块中)
@anchor{library/os path os path samestat}@anchor{87b}
@deffn {函数} os.path.samestat (stat1, stat2)

如果 stat 元组 @emph{stat1} 和 @emph{stat2} 指向相同文件，则返回 @code{True}。这些 stat 元组可能是由 @ref{659,,os.fstat()}、@ref{1f2,,os.lstat()} 或 @ref{1f1,,os.stat()} 返回的。本函数实现了 @ref{87c,,samefile()} 和 @ref{1b85,,sameopenfile()} 底层所使用的比较过程。

@ref{12f5,,可用性}: Unix, Windows。


在 3.4 版更改: 添加了对 Windows 的支持。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex split() (在 os.path 模块中)
@anchor{library/os path os path split}@anchor{1b7e}
@deffn {函数} os.path.split (path)

将路径 @emph{path} 拆分为一对，即 @code{(head, tail)}，其中，@emph{tail} 是路径的最后一部分，而 @emph{head} 里是除最后部分外的所有内容。@emph{tail} 部分不会包含斜杠，如果 @emph{path} 以斜杠结尾，则 @emph{tail} 将为空。如果 @emph{path} 中没有斜杠，@emph{head} 将为空。如果 @emph{path} 为空，则 @emph{head} 和 @emph{tail} 均为空。@emph{head} 末尾的斜杠会被去掉，除非它是根目录（即它仅包含一个或多个斜杠）。在所有情况下，@code{join(head, tail)} 指向的位置都与 @emph{path} 相同（但字符串可能不同）。另请参见函数 @ref{1b7a,,dirname()} 和 @ref{1b79,,basename()}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex splitdrive() (在 os.path 模块中)
@anchor{library/os path os path splitdrive}@anchor{477}
@deffn {函数} os.path.splitdrive (path)

将路径 @emph{path} 拆分为一对，即 @code{(drive, tail)}，其中 @emph{drive} 是挂载点或空字符串。在没有驱动器概念的系统上，@emph{drive} 将始终为空字符串。在所有情况下，@code{drive + tail} 都与 @emph{path} 相同。

在 Windows 上，本方法将路径拆分为驱动器/UNC 根节点和相对路径。

如果路径 path 包含盘符，则 drive 将包含冒号及冒号前面的所有内容。例如 @code{splitdrive("c:/dir")} 返回 @code{("c:", "/dir")}。

如果 path 是一个 UNC 路径，则 drive 将包含主机名和共享点，但不包括第四个分隔符。例如 @code{splitdrive("//host/computer/dir")} 返回 @code{("//host/computer", "/dir")}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex splitext() (在 os.path 模块中)
@anchor{library/os path os path splitext}@anchor{1b7b}
@deffn {函数} os.path.splitext (path)

将路径 @emph{path} 拆分为一对，即 @code{(root, ext)}，使 @code{root + ext == path}，其中 @emph{ext} 为空或以英文句点开头，且最多包含一个句点。路径前的句点将被忽略，例如 @code{splitext('.cshrc')} 返回 @code{('.cshrc', '@w{'})}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex supports_unicode_filenames() (在 os.path 模块中)
@anchor{library/os path os path supports_unicode_filenames}@anchor{de6}
@deffn {数据} os.path.supports_unicode_filenames

如果（在文件系统限制下）允许将任意 Unicode 字符串用作文件名，则为 @code{True}。
@end deffn

@node fileinput --- 迭代来自多个输入流的行,stat --- 解析 stat 结果,os path --- 常用路径操作,文件和目录访问
@anchor{library/fileinput doc}@anchor{1b86}@anchor{library/fileinput fileinput-iterate-over-lines-from-multiple-input-streams}@anchor{1b87}@anchor{library/fileinput module-fileinput}@anchor{80}
@subsection @code{fileinput} --- 迭代来自多个输入流的行


@geindex fileinput (模块)

@strong{源代码:} Lib/fileinput.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/fileinput.py}


__________________________________________________________________


此模块实现了一个辅助类和一些函数用来快速编写访问标准输入或文件列表的循环。 如果你只想要读写一个文件请参阅 @ref{4ea,,open()}。

典型用法为:

@example
import fileinput
for line in fileinput.input():
    process(line)
@end example

此程序会迭代 @code{sys.argv[1:]} 中列出的所有文件内的行，如果列表为空则会使用 @code{sys.stdin}。 如果有一个文件名为 @code{'-'}，它也会被替换为 @code{sys.stdin} 并且可选参数 @emph{mode} 和 @emph{openhook} 会被忽略。 要指定替代文件列表，请将其作为第一个参数传给 @ref{2ad,,input()}。 也允许使用单个文件。

所有文件都默认以文本模式打开，但你可以通过在调用 @ref{2ad,,input()} 或 @ref{27e,,FileInput} 时指定 @emph{mode} 形参来重载此行为。 如果在打开或读取文件时发生了 I/O 错误，将会引发 @ref{1d3,,OSError}。


在 3.3 版更改: 原来会引发 @ref{98c,,IOError}；现在它是 @ref{1d3,,OSError} 的别名。


如果 @code{sys.stdin} 被使用超过一次，则第二次之后的使用将不返回任何行，除非是被交互式的使用，或都是被显式地重置 (例如使用 @code{sys.stdin.seek(0)})。

空文件打开后将立即被关闭；它们在文件列表中会被注意到的唯一情况只有当最后打开的文件为空的时候。

反回的行不会对换行符做任何处理，这意味着文件中的最后一行可能不带换行符。

想要控制文件的打开方式，你可以通过将 @emph{openhook} 形参传给 @ref{2ad,,fileinput.input()} 或 @ref{27e,,FileInput()} 来提供一个打开钩子。 此钩子必须为一个函数，它接受两个参数，@emph{filename} 和 @emph{mode}，并返回一个以相应模式打开的文件类对象。 此模块已经提供了两个有用的钩子。

以下函数是此模块的初始接口：

@geindex input() (在 fileinput 模块中)
@anchor{library/fileinput fileinput input}@anchor{2ad}
@deffn {函数} fileinput.input (files=None, inplace=False, backup='@w{'}, *, mode='r', openhook=None)

创建一个 @ref{27e,,FileInput} 类的实例。 该实例将被用作此模块中函数的全局状态，并且还将在迭代期间被返回使用。 此函数的形参将被继续传递给 @ref{27e,,FileInput} 类的构造器。

@ref{27e,,FileInput} 实例可以在 @ref{6e3,,with} 语句中被用作上下文管理器。 在这个例子中，@emph{input} 在 @code{with} 语句结束后将会被关闭，即使发生了异常也是如此:

@example
with fileinput.input(files=('spam.txt', 'eggs.txt')) as f:
    for line in f:
        process(line)
@end example


在 3.2 版更改: 可以被用作上下文管理器。



在 3.8 版更改: 关键字形参 @emph{mode} 和 @emph{openhook} 现在是仅限关键字形参。

@end deffn

下列函数会使用 @ref{2ad,,fileinput.input()} 所创建的全局状态；如果没有活动的状态，则会引发 @ref{2ba,,RuntimeError}。

@geindex filename() (在 fileinput 模块中)
@anchor{library/fileinput fileinput filename}@anchor{1b88}
@deffn {函数} fileinput.filename ()

返回当前被读取的文件名。 在第一行被读取之前，返回 @code{None}。
@end deffn

@geindex fileno() (在 fileinput 模块中)
@anchor{library/fileinput fileinput fileno}@anchor{1b89}
@deffn {函数} fileinput.fileno ()

返回以整数表示的当前文件“文件描述符”。 当未打开文件时（处在第一行和文件之间），返回 @code{-1}。
@end deffn

@geindex lineno() (在 fileinput 模块中)
@anchor{library/fileinput fileinput lineno}@anchor{1b8a}
@deffn {函数} fileinput.lineno ()

返回已被读取的累计行号。 在第一行被读取之前，返回 @code{0}。 在最后一个文件的最后一行被读取之后，返回该行的行号。
@end deffn

@geindex filelineno() (在 fileinput 模块中)
@anchor{library/fileinput fileinput filelineno}@anchor{1b8b}
@deffn {函数} fileinput.filelineno ()

返回当前文件中的行号。 在第一行被读取之前，返回 @code{0}。 在最后一个文件的最后一行被读取之后，返回此文件中该行的行号。
@end deffn

@geindex isfirstline() (在 fileinput 模块中)
@anchor{library/fileinput fileinput isfirstline}@anchor{1b8c}
@deffn {函数} fileinput.isfirstline ()

如果刚读取的行是其所在文件的第一行则返回 @code{True}，否则返回 @code{False}。
@end deffn

@geindex isstdin() (在 fileinput 模块中)
@anchor{library/fileinput fileinput isstdin}@anchor{1b8d}
@deffn {函数} fileinput.isstdin ()

如果最后读取的行来自 @code{sys.stdin} 则返回 @code{True}，否则返回 @code{False}。
@end deffn

@geindex nextfile() (在 fileinput 模块中)
@anchor{library/fileinput fileinput nextfile}@anchor{1b8e}
@deffn {函数} fileinput.nextfile ()

关闭当前文件以使下次迭代将从下一个文件（如果存在）读取第一行；不是从该文件读取的行将不会被计入累计行数。 直到下一个文件的第一行被读取之后文件名才会改变。 在第一行被读取之前，此函数将不会生效；它不能被用来跳过第一个文件。 在最后一个文件的最后一行被读取之后，此函数将不再生效。
@end deffn

@geindex close() (在 fileinput 模块中)
@anchor{library/fileinput fileinput close}@anchor{1b8f}
@deffn {函数} fileinput.close ()

关闭序列。
@end deffn

此模块所提供的实现了序列行为的类同样也可用于子类化：

@geindex FileInput (fileinput 中的类)
@anchor{library/fileinput fileinput FileInput}@anchor{27e}
@deffn {类} fileinput.FileInput (files=None, inplace=False, backup='@w{'}, *, mode='r', openhook=None)

类 @ref{27e,,FileInput} 是一个实现；它的方法 @ref{1b88,,filename()}, @ref{1b89,,fileno()}, @ref{1b8a,,lineno()}, @ref{1b8b,,filelineno()}, @ref{1b8c,,isfirstline()}, @ref{1b8d,,isstdin()}, @ref{1b8e,,nextfile()} 和 @ref{1b8f,,close()} 对应于此模块中具有相同名称的函数。 此外它还有一个 @ref{1b90,,readline()} 方法可返回下一个输入行，以及一个 @ref{27f,,__getitem__()} 方法，该方法实现了序列行为。 这种序列必须以严格的序列顺序来读写；随机读写和 @ref{1b90,,readline()} 不可以被混用。

通过 @emph{mode} 你可以指定要传给 @ref{4ea,,open()} 的文件模式。 它必须为 @code{'r'}, @code{'rU'}, @code{'U'} 和 @code{'rb'} 中的一个。

@emph{openhook} 如果给出则必须为一个函数，它接受两个参数 @emph{filename} 和 @emph{mode}，并相应地返回一个打开的文件类对象。 你不能同时使用 @emph{inplace} 和 @emph{openhook}。

@ref{27e,,FileInput} 实例可以在 @ref{6e3,,with} 语句中被用作上下文管理器。 在这个例子中，@emph{input} 在 @code{with} 语句结束后将会被关闭，即使发生了异常也是如此:

@example
with FileInput(files=('spam.txt', 'eggs.txt')) as input:
    process(input)
@end example


在 3.2 版更改: 可以被用作上下文管理器。



3.4 版后已移除: @code{'rU'} 和 @code{'U'} 模式。



3.8 版后已移除: 对 @ref{27f,,__getitem__()} 方法的支持已弃用。



在 3.8 版更改: 关键字形参 @emph{mode} 和 @emph{openhook} 现在是仅限关键字形参。

@end deffn

@strong{可选的原地过滤:} 如果传递了关键字参数 @code{inplace=True} 给 @ref{2ad,,fileinput.input()} 或 @ref{27e,,FileInput} 构造器，则文件会被移至备份文件并将标准输出定向到输入文件（如果已存在与备份文件同名的文件，它将被静默地替换）。 这使得编写一个能够原地重写其输入文件的过滤器成为可能。 如果给出了 @emph{backup} 形参 (通常形式为 @code{backup='.<some extension>'})，它将指定备份文件的扩展名，并且备份文件会被保留；默认情况下扩展名为 @code{'.bak'} 并且它会在输出文件关闭时被删除。 在读取标准输入时原地过滤会被禁用。

此模块提供了以下两种打开文件钩子：

@geindex hook_compressed() (在 fileinput 模块中)
@anchor{library/fileinput fileinput hook_compressed}@anchor{1b91}
@deffn {函数} fileinput.hook_compressed (filename, mode)

使用 @ref{8c,,gzip} 和 @ref{14,,bz2} 模块透明地打开 gzip 和 bzip2 压缩的文件（通过扩展名 @code{'.gz'} 和 @code{'.bz2'} 来识别）。 如果文件扩展名不是 @code{'.gz'} 或 @code{'.bz2'}，文件会以正常方式打开（即使用 @ref{4ea,,open()} 并且不带任何解压操作）。

使用示例:  @code{fi = fileinput.FileInput(openhook=fileinput.hook_compressed)}
@end deffn

@geindex hook_encoded() (在 fileinput 模块中)
@anchor{library/fileinput fileinput hook_encoded}@anchor{545}
@deffn {函数} fileinput.hook_encoded (encoding, errors=None)

返回一个通过 @ref{4ea,,open()} 打开每个文件的钩子，使用给定的 @emph{encoding} 和 @emph{errors} 来读取文件。

使用示例: @code{fi = fileinput.FileInput(openhook=fileinput.hook_encoded("utf-8", "surrogateescape"))}


在 3.6 版更改: 添加了可选的 @emph{errors} 形参。

@end deffn

@node stat --- 解析 stat 结果,filecmp --- 文件及目录的比较,fileinput --- 迭代来自多个输入流的行,文件和目录访问
@anchor{library/stat doc}@anchor{1b92}@anchor{library/stat module-stat}@anchor{f4}@anchor{library/stat stat-interpreting-stat-results}@anchor{1b93}
@subsection @code{stat} --- 解析 @code{stat()} 结果


@geindex stat (模块)

@strong{源代码：} Lib/stat.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/stat.py}


__________________________________________________________________


@ref{f4,,stat} 模块定义了一些用于解析 @ref{1f1,,os.stat()}, @ref{659,,os.fstat()} 和 @ref{1f2,,os.lstat()} (如果它们存在) 输出结果的常量和函数。 有关 @code{stat()}, @code{fstat()} 和 @code{lstat()} 调用的完整细节，请参阅你的系统文档。


在 3.4 版更改: stat 模块是通过 C 实现来支持的。


@ref{f4,,stat} 模块定义了以下函数来检测特定文件类型：

@geindex S_ISDIR() (在 stat 模块中)
@anchor{library/stat stat S_ISDIR}@anchor{1b94}
@deffn {函数} stat.S_ISDIR (mode)

如果 mode 来自一个目录则返回非零值。
@end deffn

@geindex S_ISCHR() (在 stat 模块中)
@anchor{library/stat stat S_ISCHR}@anchor{1b95}
@deffn {函数} stat.S_ISCHR (mode)

如果 mode 来自一个字符特殊设备文件则返回非零值。
@end deffn

@geindex S_ISBLK() (在 stat 模块中)
@anchor{library/stat stat S_ISBLK}@anchor{1b96}
@deffn {函数} stat.S_ISBLK (mode)

如果 mode 来自一个块特殊设备文件则返回非零值。
@end deffn

@geindex S_ISREG() (在 stat 模块中)
@anchor{library/stat stat S_ISREG}@anchor{1b97}
@deffn {函数} stat.S_ISREG (mode)

如果 mode 来自一个常规文件则返回非零值。
@end deffn

@geindex S_ISFIFO() (在 stat 模块中)
@anchor{library/stat stat S_ISFIFO}@anchor{1b98}
@deffn {函数} stat.S_ISFIFO (mode)

如果 mode 来自一个 FIFO (命名管道) 则返回非零值。
@end deffn

@geindex S_ISLNK() (在 stat 模块中)
@anchor{library/stat stat S_ISLNK}@anchor{1b99}
@deffn {函数} stat.S_ISLNK (mode)

如果 mode 来自一个符号链接则返回非零值。
@end deffn

@geindex S_ISSOCK() (在 stat 模块中)
@anchor{library/stat stat S_ISSOCK}@anchor{1b9a}
@deffn {函数} stat.S_ISSOCK (mode)

如果 mode 来自一个套接字则返回非零值。
@end deffn

@geindex S_ISDOOR() (在 stat 模块中)
@anchor{library/stat stat S_ISDOOR}@anchor{ef9}
@deffn {函数} stat.S_ISDOOR (mode)

如果 mode 来自一个门则返回非零值。


3.4 新版功能.

@end deffn

@geindex S_ISPORT() (在 stat 模块中)
@anchor{library/stat stat S_ISPORT}@anchor{efa}
@deffn {函数} stat.S_ISPORT (mode)

如果 mode 来自一个事件端口则返回非零值。


3.4 新版功能.

@end deffn

@geindex S_ISWHT() (在 stat 模块中)
@anchor{library/stat stat S_ISWHT}@anchor{efb}
@deffn {函数} stat.S_ISWHT (mode)

如果 mode 来自一个白输出则返回非零值。


3.4 新版功能.

@end deffn

定义了两个附加函数用于对文件模式进行更一般化的操作：

@geindex S_IMODE() (在 stat 模块中)
@anchor{library/stat stat S_IMODE}@anchor{1b9b}
@deffn {函数} stat.S_IMODE (mode)

返回文件模式中可由 @ref{a2e,,os.chmod()} 进行设置的部分 --- 即文件的 permission 位，加上 sticky 位、set-group-id 以及 set-user-id 位（在支持这些部分的系统上）。
@end deffn

@geindex S_IFMT() (在 stat 模块中)
@anchor{library/stat stat S_IFMT}@anchor{1b9c}
@deffn {函数} stat.S_IFMT (mode)

返回文件模式中描述文件类型的部分（供上面的 @code{S_IS*()} 函数使用）。
@end deffn

通常，你应当使用 @code{os.path.is*()} 函数来检测文件的类型；这里提供的函数则适用于当你要对同一文件执行多项检测并且希望避免每项检测的 @code{stat()} 系统调用开销的情况。 这些函数也适用于检测有关未被 @ref{c5,,os.path} 处理的信息，例如检测块和字符设备等。

示例:

@example
import os, sys
from stat import *

def walktree(top, callback):
    '@w{'}'recursively descend the directory tree rooted at top,
       calling the callback function for each regular file'@w{'}'

    for f in os.listdir(top):
        pathname = os.path.join(top, f)
        mode = os.stat(pathname).st_mode
        if S_ISDIR(mode):
            # It's a directory, recurse into it
            walktree(pathname, callback)
        elif S_ISREG(mode):
            # It's a file, call the callback function
            callback(pathname)
        else:
            # Unknown file type, print a message
            print('Skipping %s' % pathname)

def visitfile(file):
    print('visiting', file)

if __name__ == '__main__':
    walktree(sys.argv[1], visitfile)
@end example

另外还提供了一个附加的辅助函数用来将文件模式转换为人类易读的字符串：

@geindex filemode() (在 stat 模块中)
@anchor{library/stat stat filemode}@anchor{a98}
@deffn {函数} stat.filemode (mode)

将文件模式转换为 '-rwxrwxrwx' 形式的字符串。


3.3 新版功能.



在 3.4 版更改: 此函数支持 @ref{8ce,,S_IFDOOR}, @ref{8cf,,S_IFPORT} and @ref{8d0,,S_IFWHT}。

@end deffn

以下所有变量是一些简单的符号索引，用于访问 @ref{1f1,,os.stat()}, @ref{659,,os.fstat()} 或 @ref{1f2,,os.lstat()} 所返回的 10 条目元组。

@geindex ST_MODE() (在 stat 模块中)
@anchor{library/stat stat ST_MODE}@anchor{8cd}
@deffn {数据} stat.ST_MODE

inode 保护模式。
@end deffn

@geindex ST_INO() (在 stat 模块中)
@anchor{library/stat stat ST_INO}@anchor{1b9d}
@deffn {数据} stat.ST_INO

Inode 号
@end deffn

@geindex ST_DEV() (在 stat 模块中)
@anchor{library/stat stat ST_DEV}@anchor{1b9e}
@deffn {数据} stat.ST_DEV

Inode 所在的设备。
@end deffn

@geindex ST_NLINK() (在 stat 模块中)
@anchor{library/stat stat ST_NLINK}@anchor{1b9f}
@deffn {数据} stat.ST_NLINK

Inode 拥有的链接数量。
@end deffn

@geindex ST_UID() (在 stat 模块中)
@anchor{library/stat stat ST_UID}@anchor{1ba0}
@deffn {数据} stat.ST_UID

所有者的用户 ID。
@end deffn

@geindex ST_GID() (在 stat 模块中)
@anchor{library/stat stat ST_GID}@anchor{1ba1}
@deffn {数据} stat.ST_GID

所有者的用户组ID。
@end deffn

@geindex ST_SIZE() (在 stat 模块中)
@anchor{library/stat stat ST_SIZE}@anchor{1ba2}
@deffn {数据} stat.ST_SIZE

以字节为单位的普通文件大小；对于某些特殊文件则是所等待的数据量。
@end deffn

@geindex ST_ATIME() (在 stat 模块中)
@anchor{library/stat stat ST_ATIME}@anchor{1ba3}
@deffn {数据} stat.ST_ATIME

上次访问的时间。
@end deffn

@geindex ST_MTIME() (在 stat 模块中)
@anchor{library/stat stat ST_MTIME}@anchor{1ba4}
@deffn {数据} stat.ST_MTIME

上次修改的时间。
@end deffn

@geindex ST_CTIME() (在 stat 模块中)
@anchor{library/stat stat ST_CTIME}@anchor{1ba5}
@deffn {数据} stat.ST_CTIME

操作系统所报告的 "ctime"。 在某些系统上（例如 Unix）是元数据的最后修改时间，而在其他系统上（例如 Windows）则是创建时间（请参阅系统平台的文档了解相关细节）。
@end deffn

对于“文件大小”的解析可因文件类型的不同而变化。 对于普通文件就是文件的字节数。 对于大部分种类的 Unix（特别包括 Linux）的 FIFO 和套接字来说，“大小”则是指在调用 @ref{1f1,,os.stat()}, @ref{659,,os.fstat()} 或 @ref{1f2,,os.lstat()} 时等待读取的字节数；这在某些时候很有用处，特别是在一个非阻塞的打开后轮询这些特殊文件中的一个时。 其他字符和块设备的文件大小字段的含义还会有更多变化，具体取决于底层系统调用的实现方式。

以下变量定义了在 @ref{8cd,,ST_MODE} 字段中使用的旗标。

使用上面的函数会比使用第一组旗标更容易移植：

@geindex S_IFSOCK() (在 stat 模块中)
@anchor{library/stat stat S_IFSOCK}@anchor{1ba6}
@deffn {数据} stat.S_IFSOCK

套接字。
@end deffn

@geindex S_IFLNK() (在 stat 模块中)
@anchor{library/stat stat S_IFLNK}@anchor{1ba7}
@deffn {数据} stat.S_IFLNK

符号链接。
@end deffn

@geindex S_IFREG() (在 stat 模块中)
@anchor{library/stat stat S_IFREG}@anchor{1ba8}
@deffn {数据} stat.S_IFREG

普通文件。
@end deffn

@geindex S_IFBLK() (在 stat 模块中)
@anchor{library/stat stat S_IFBLK}@anchor{1ba9}
@deffn {数据} stat.S_IFBLK

块设备。
@end deffn

@geindex S_IFDIR() (在 stat 模块中)
@anchor{library/stat stat S_IFDIR}@anchor{1baa}
@deffn {数据} stat.S_IFDIR

目录。
@end deffn

@geindex S_IFCHR() (在 stat 模块中)
@anchor{library/stat stat S_IFCHR}@anchor{1bab}
@deffn {数据} stat.S_IFCHR

字符设备。
@end deffn

@geindex S_IFIFO() (在 stat 模块中)
@anchor{library/stat stat S_IFIFO}@anchor{1bac}
@deffn {数据} stat.S_IFIFO

先进先出。
@end deffn

@geindex S_IFDOOR() (在 stat 模块中)
@anchor{library/stat stat S_IFDOOR}@anchor{8ce}
@deffn {数据} stat.S_IFDOOR

门。


3.4 新版功能.

@end deffn

@geindex S_IFPORT() (在 stat 模块中)
@anchor{library/stat stat S_IFPORT}@anchor{8cf}
@deffn {数据} stat.S_IFPORT

事件端口。


3.4 新版功能.

@end deffn

@geindex S_IFWHT() (在 stat 模块中)
@anchor{library/stat stat S_IFWHT}@anchor{8d0}
@deffn {数据} stat.S_IFWHT

白输出。


3.4 新版功能.

@end deffn

@cartouche
@quotation 注解 
@ref{8ce,,S_IFDOOR}, @ref{8cf,,S_IFPORT} or @ref{8d0,,S_IFWHT} 等文件类型在不受系统平台支持时会被定义为 0。
@end quotation
@end cartouche

以下旗标还可以 @ref{a2e,,os.chmod()} 的在 @emph{mode} 参数中使用：

@geindex S_ISUID() (在 stat 模块中)
@anchor{library/stat stat S_ISUID}@anchor{1bad}
@deffn {数据} stat.S_ISUID

设置 UID 位。
@end deffn

@geindex S_ISGID() (在 stat 模块中)
@anchor{library/stat stat S_ISGID}@anchor{1bae}
@deffn {数据} stat.S_ISGID

设置分组 ID 位。 这个位有几种特殊用途。 对于目录它表示该目录将使用 BSD 语义：在其中创建的文件将从目录继承其分组 ID，而不是从创建进程的有效分组 ID 继承，并且在其中创建的目录也将设置 @ref{1bae,,S_ISGID} 位。 对于没有设置分组执行位 (@ref{1baf,,S_IXGRP}) 的文件，设置分组 ID 位表示强制性文件/记录锁定 (另请参见 @ref{1bb0,,S_ENFMT})。
@end deffn

@geindex S_ISVTX() (在 stat 模块中)
@anchor{library/stat stat S_ISVTX}@anchor{1bb1}
@deffn {数据} stat.S_ISVTX

固定位。 当对目录设置该位时则意味着此目录中的文件只能由文件所有者、目录所有者或特权进程来重命名或删除。
@end deffn

@geindex S_IRWXU() (在 stat 模块中)
@anchor{library/stat stat S_IRWXU}@anchor{1bb2}
@deffn {数据} stat.S_IRWXU

文件所有者权限的掩码。
@end deffn

@geindex S_IRUSR() (在 stat 模块中)
@anchor{library/stat stat S_IRUSR}@anchor{1bb3}
@deffn {数据} stat.S_IRUSR

所有者具有读取权限。
@end deffn

@geindex S_IWUSR() (在 stat 模块中)
@anchor{library/stat stat S_IWUSR}@anchor{1bb4}
@deffn {数据} stat.S_IWUSR

所有者具有写入权限。
@end deffn

@geindex S_IXUSR() (在 stat 模块中)
@anchor{library/stat stat S_IXUSR}@anchor{1bb5}
@deffn {数据} stat.S_IXUSR

所有者具有执行权限。
@end deffn

@geindex S_IRWXG() (在 stat 模块中)
@anchor{library/stat stat S_IRWXG}@anchor{1bb6}
@deffn {数据} stat.S_IRWXG

组权限的掩码。
@end deffn

@geindex S_IRGRP() (在 stat 模块中)
@anchor{library/stat stat S_IRGRP}@anchor{1bb7}
@deffn {数据} stat.S_IRGRP

组具有读取权限。
@end deffn

@geindex S_IWGRP() (在 stat 模块中)
@anchor{library/stat stat S_IWGRP}@anchor{1bb8}
@deffn {数据} stat.S_IWGRP

组具有写入权限。
@end deffn

@geindex S_IXGRP() (在 stat 模块中)
@anchor{library/stat stat S_IXGRP}@anchor{1baf}
@deffn {数据} stat.S_IXGRP

组具有执行权限。
@end deffn

@geindex S_IRWXO() (在 stat 模块中)
@anchor{library/stat stat S_IRWXO}@anchor{1bb9}
@deffn {数据} stat.S_IRWXO

其他人（不在组中）的权限掩码。
@end deffn

@geindex S_IROTH() (在 stat 模块中)
@anchor{library/stat stat S_IROTH}@anchor{1bba}
@deffn {数据} stat.S_IROTH

其他人具有读取权限。
@end deffn

@geindex S_IWOTH() (在 stat 模块中)
@anchor{library/stat stat S_IWOTH}@anchor{1bbb}
@deffn {数据} stat.S_IWOTH

其他人具有写入权限。
@end deffn

@geindex S_IXOTH() (在 stat 模块中)
@anchor{library/stat stat S_IXOTH}@anchor{1bbc}
@deffn {数据} stat.S_IXOTH

其他人具有执行权限。
@end deffn

@geindex S_ENFMT() (在 stat 模块中)
@anchor{library/stat stat S_ENFMT}@anchor{1bb0}
@deffn {数据} stat.S_ENFMT

System V 执行文件锁定。 此旗标是与 @ref{1bae,,S_ISGID} 共享的：文件/记录锁定会针对未设置分组执行位 (@ref{1baf,,S_IXGRP}) 的文件强制执行。
@end deffn

@geindex S_IREAD() (在 stat 模块中)
@anchor{library/stat stat S_IREAD}@anchor{1bbd}
@deffn {数据} stat.S_IREAD

Unix V7 中 @ref{1bb3,,S_IRUSR} 的同义词。
@end deffn

@geindex S_IWRITE() (在 stat 模块中)
@anchor{library/stat stat S_IWRITE}@anchor{1bbe}
@deffn {数据} stat.S_IWRITE

Unix V7 中 @ref{1bb4,,S_IWUSR} 的同义词。
@end deffn

@geindex S_IEXEC() (在 stat 模块中)
@anchor{library/stat stat S_IEXEC}@anchor{1bbf}
@deffn {数据} stat.S_IEXEC

Unix V7 中 @ref{1bb5,,S_IXUSR} 的同义词。
@end deffn

以下旗标可以在 @ref{a2d,,os.chflags()} 的 @emph{flags} 参数中使用：

@geindex UF_NODUMP() (在 stat 模块中)
@anchor{library/stat stat UF_NODUMP}@anchor{1bc0}
@deffn {数据} stat.UF_NODUMP

不要转储文件。
@end deffn

@geindex UF_IMMUTABLE() (在 stat 模块中)
@anchor{library/stat stat UF_IMMUTABLE}@anchor{1bc1}
@deffn {数据} stat.UF_IMMUTABLE

文件不能被更改。
@end deffn

@geindex UF_APPEND() (在 stat 模块中)
@anchor{library/stat stat UF_APPEND}@anchor{1bc2}
@deffn {数据} stat.UF_APPEND

文件只能被附加。
@end deffn

@geindex UF_OPAQUE() (在 stat 模块中)
@anchor{library/stat stat UF_OPAQUE}@anchor{1bc3}
@deffn {数据} stat.UF_OPAQUE

当通过联合堆栈查看时，目录是不透明的。
@end deffn

@geindex UF_NOUNLINK() (在 stat 模块中)
@anchor{library/stat stat UF_NOUNLINK}@anchor{1bc4}
@deffn {数据} stat.UF_NOUNLINK

文件不能重命名或删除。
@end deffn

@geindex UF_COMPRESSED() (在 stat 模块中)
@anchor{library/stat stat UF_COMPRESSED}@anchor{1bc5}
@deffn {数据} stat.UF_COMPRESSED

文件是压缩存储的（Mac OS X 10.6+）。
@end deffn

@geindex UF_HIDDEN() (在 stat 模块中)
@anchor{library/stat stat UF_HIDDEN}@anchor{1bc6}
@deffn {数据} stat.UF_HIDDEN

文件不能显示在GUI 中（Mac OS X 10.5+）。
@end deffn

@geindex SF_ARCHIVED() (在 stat 模块中)
@anchor{library/stat stat SF_ARCHIVED}@anchor{1bc7}
@deffn {数据} stat.SF_ARCHIVED

文件可能已存档。
@end deffn

@geindex SF_IMMUTABLE() (在 stat 模块中)
@anchor{library/stat stat SF_IMMUTABLE}@anchor{1bc8}
@deffn {数据} stat.SF_IMMUTABLE

文件不能被更改。
@end deffn

@geindex SF_APPEND() (在 stat 模块中)
@anchor{library/stat stat SF_APPEND}@anchor{1bc9}
@deffn {数据} stat.SF_APPEND

文件只能被附加。
@end deffn

@geindex SF_NOUNLINK() (在 stat 模块中)
@anchor{library/stat stat SF_NOUNLINK}@anchor{1bca}
@deffn {数据} stat.SF_NOUNLINK

文件不能重命名或删除。
@end deffn

@geindex SF_SNAPSHOT() (在 stat 模块中)
@anchor{library/stat stat SF_SNAPSHOT}@anchor{1bcb}
@deffn {数据} stat.SF_SNAPSHOT

文件有一个快照文件
@end deffn

请参阅 *BSD 或 Mac OS 系统的指南页 @code{chflags(2)} 了解详情。

在 Windows 上，以下文件属性常量可被用来检测 @ref{1f1,,os.stat()} 所返回的 @code{st_file_attributes} 成员中的位。 请参阅 Windows API 文档@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/gg258117.aspx} 了解有关这些常量含义的详情。

@geindex FILE_ATTRIBUTE_ARCHIVE() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_COMPRESSED() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_DEVICE() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_DIRECTORY() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_ENCRYPTED() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_HIDDEN() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_INTEGRITY_STREAM() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_NORMAL() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_NOT_CONTENT_INDEXED() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_NO_SCRUB_DATA() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_OFFLINE() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_READONLY() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_REPARSE_POINT() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_SPARSE_FILE() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_SYSTEM() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_TEMPORARY() (在 stat 模块中)
@geindex FILE_ATTRIBUTE_VIRTUAL() (在 stat 模块中)
@anchor{library/stat stat FILE_ATTRIBUTE_ARCHIVE}@anchor{1bcc}
@deffn {数据} stat.FILE_ATTRIBUTE_ARCHIVE
@anchor{library/stat stat FILE_ATTRIBUTE_COMPRESSED}@anchor{1bcd}
@deffnx {数据} stat.FILE_ATTRIBUTE_COMPRESSED
@anchor{library/stat stat FILE_ATTRIBUTE_DEVICE}@anchor{1bce}
@deffnx {数据} stat.FILE_ATTRIBUTE_DEVICE
@anchor{library/stat stat FILE_ATTRIBUTE_DIRECTORY}@anchor{1bcf}
@deffnx {数据} stat.FILE_ATTRIBUTE_DIRECTORY
@anchor{library/stat stat FILE_ATTRIBUTE_ENCRYPTED}@anchor{1bd0}
@deffnx {数据} stat.FILE_ATTRIBUTE_ENCRYPTED
@anchor{library/stat stat FILE_ATTRIBUTE_HIDDEN}@anchor{1bd1}
@deffnx {数据} stat.FILE_ATTRIBUTE_HIDDEN
@anchor{library/stat stat FILE_ATTRIBUTE_INTEGRITY_STREAM}@anchor{1bd2}
@deffnx {数据} stat.FILE_ATTRIBUTE_INTEGRITY_STREAM
@anchor{library/stat stat FILE_ATTRIBUTE_NORMAL}@anchor{1bd3}
@deffnx {数据} stat.FILE_ATTRIBUTE_NORMAL
@anchor{library/stat stat FILE_ATTRIBUTE_NOT_CONTENT_INDEXED}@anchor{1bd4}
@deffnx {数据} stat.FILE_ATTRIBUTE_NOT_CONTENT_INDEXED
@anchor{library/stat stat FILE_ATTRIBUTE_NO_SCRUB_DATA}@anchor{1bd5}
@deffnx {数据} stat.FILE_ATTRIBUTE_NO_SCRUB_DATA
@anchor{library/stat stat FILE_ATTRIBUTE_OFFLINE}@anchor{1bd6}
@deffnx {数据} stat.FILE_ATTRIBUTE_OFFLINE
@anchor{library/stat stat FILE_ATTRIBUTE_READONLY}@anchor{1bd7}
@deffnx {数据} stat.FILE_ATTRIBUTE_READONLY
@anchor{library/stat stat FILE_ATTRIBUTE_REPARSE_POINT}@anchor{1bd8}
@deffnx {数据} stat.FILE_ATTRIBUTE_REPARSE_POINT
@anchor{library/stat stat FILE_ATTRIBUTE_SPARSE_FILE}@anchor{1bd9}
@deffnx {数据} stat.FILE_ATTRIBUTE_SPARSE_FILE
@anchor{library/stat stat FILE_ATTRIBUTE_SYSTEM}@anchor{1bda}
@deffnx {数据} stat.FILE_ATTRIBUTE_SYSTEM
@anchor{library/stat stat FILE_ATTRIBUTE_TEMPORARY}@anchor{1bdb}
@deffnx {数据} stat.FILE_ATTRIBUTE_TEMPORARY
@anchor{library/stat stat FILE_ATTRIBUTE_VIRTUAL}@anchor{1bdc}
@deffnx {数据} stat.FILE_ATTRIBUTE_VIRTUAL


3.5 新版功能.

@end deffn

在 Windows 上，以下常量可被用来与 @ref{1f2,,os.lstat()} 所返回的 @code{st_reparse_tag} 成员进行比较。 这些是最主要的常量，而不是详尽的清单。

@geindex IO_REPARSE_TAG_SYMLINK() (在 stat 模块中)
@geindex IO_REPARSE_TAG_MOUNT_POINT() (在 stat 模块中)
@geindex IO_REPARSE_TAG_APPEXECLINK() (在 stat 模块中)
@anchor{library/stat stat IO_REPARSE_TAG_SYMLINK}@anchor{1bdd}
@deffn {数据} stat.IO_REPARSE_TAG_SYMLINK
@anchor{library/stat stat IO_REPARSE_TAG_MOUNT_POINT}@anchor{1bde}
@deffnx {数据} stat.IO_REPARSE_TAG_MOUNT_POINT
@anchor{library/stat stat IO_REPARSE_TAG_APPEXECLINK}@anchor{1bdf}
@deffnx {数据} stat.IO_REPARSE_TAG_APPEXECLINK


3.8 新版功能.

@end deffn

@node filecmp --- 文件及目录的比较,tempfile --- 生成临时文件和目录,stat --- 解析 stat 结果,文件和目录访问
@anchor{library/filecmp doc}@anchor{1be0}@anchor{library/filecmp filecmp-file-and-directory-comparisons}@anchor{1be1}@anchor{library/filecmp module-filecmp}@anchor{7f}
@subsection @code{filecmp} --- 文件及目录的比较


@geindex filecmp (模块)

@strong{源代码:} Lib/filecmp.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/filecmp.py}


__________________________________________________________________


@ref{7f,,filecmp} 模块定义了用于比较文件及目录的函数，并且可以选取多种关于时间和准确性的折衷方案。对于文件的比较，另见 @ref{37,,difflib} 模块。

@ref{7f,,filecmp}  模块定义了如下函数：

@geindex cmp() (在 filecmp 模块中)
@anchor{library/filecmp filecmp cmp}@anchor{1be2}
@deffn {函数} filecmp.cmp (f1, f2, shallow=True)

比较名为 @emph{f1} 和 @emph{f2} 的文件，如果它们似乎相等则返回 @code{True} ，否则返回 @code{False} 。

如果 @emph{shallow} 为真，那么具有相同 @ref{1f1,,os.stat()} 签名的文件将会被认为是相等的。否则，将比较文件的内容。

需要注意，没有外部程序被该函数调用，这赋予了该函数可移植性与效率。

该函数会缓存过去的比较及其结果，且在文件的 @ref{1f1,,os.stat()} 信息变化后缓存条目失效。所有的缓存可以通过使用  @ref{841,,clear_cache()} 来清除。
@end deffn

@geindex cmpfiles() (在 filecmp 模块中)
@anchor{library/filecmp filecmp cmpfiles}@anchor{1be3}
@deffn {函数} filecmp.cmpfiles (dir1, dir2, common, shallow=True)

比较在两个目录 @emph{dir1} 和 @emph{dir2} 中，由 @emph{common} 所确定名称的文件。

返回三组文件名列表： @emph{match}, @emph{mismatch}, @emph{errors} 。 @emph{match} 含有相匹配的文件， @emph{mismatch} 含有那些不匹配的，然后 @emph{errors} 列出那些未被比较文件的名称。如果文件不存在于两目录中的任一个，或者用户缺少读取它们的权限，又或者因为其他的一些原因而无法比较，那么这些文件将会被列在 @emph{errors} 中。

参数 @emph{shallow} 具有同 @ref{1be2,,filecmp.cmp()} 一致的含义与默认值。

例如， @code{cmpfiles('a', 'b', ['c', 'd/e'])} 将会比较 @code{a/c} 与 @code{b/c} 以及 @code{a/d/e} 与 @code{b/d/e} 。 @code{'c'} 和 @code{'d/e'} 将会各自出现在返回的三个列表里的某一个列表中。
@end deffn

@geindex clear_cache() (在 filecmp 模块中)
@anchor{library/filecmp filecmp clear_cache}@anchor{841}
@deffn {函数} filecmp.clear_cache ()

清除 filecmp 缓存。如果一个文件过快地修改，以至于超过底层文件系统记录修改时间的精度，那么该函数可能有助于比较该类文件。


3.4 新版功能.

@end deffn

@menu
* dircmp 类:: 

@end menu

@node dircmp 类,,,filecmp --- 文件及目录的比较
@anchor{library/filecmp dircmp-objects}@anchor{1be4}@anchor{library/filecmp the-dircmp-class}@anchor{1be5}
@subsubsection @code{dircmp} 类


@geindex dircmp (filecmp 中的类)
@anchor{library/filecmp filecmp dircmp}@anchor{843}
@deffn {类} filecmp.dircmp (a, b, ignore=None, hide=None)

创建一个用于比较目录 @emph{a} 和 @emph{b} 的新的目录比较对象。 @emph{ignore} 是需要忽略的文件名列表，且默认为  @ref{842,,filecmp.DEFAULT_IGNORES} 。 @emph{hide} 是需要隐藏的文件名列表，且默认为 @code{[os.curdir, os.pardir]} 。

@ref{843,,dircmp} 类如 @ref{1be2,,filecmp.cmp()} 中所描述的那样对文件进行 @emph{shallow} 比较。

@ref{843,,dircmp} 类提供以下方法：

@geindex report() (filecmp.dircmp 方法)
@anchor{library/filecmp filecmp dircmp report}@anchor{1be6}
@deffn {方法} report ()

将 @emph{a} 与 @emph{b} 之间的比较结果打印（到  @ref{307,,sys.stdout} ）。
@end deffn

@geindex report_partial_closure() (filecmp.dircmp 方法)
@anchor{library/filecmp filecmp dircmp report_partial_closure}@anchor{1be7}
@deffn {方法} report_partial_closure ()

打印 @emph{a} 与 @emph{b}  及共同直接子目录的比较结果。
@end deffn

@geindex report_full_closure() (filecmp.dircmp 方法)
@anchor{library/filecmp filecmp dircmp report_full_closure}@anchor{1be8}
@deffn {方法} report_full_closure ()

打印 @emph{a} 与 @emph{b} 及共同子目录比较结果（递归地）。
@end deffn

@ref{843,,dircmp} 类提供了一些有趣的属性，用以得到关于参与比较的目录树的各种信息。

需要注意，通过 @ref{313,,__getattr__()}  钩子，所有的属性将会惰性求值，因此如果只使用那些计算简便的属性，将不会有速度损失。

@geindex left (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp left}@anchor{1be9}
@deffn {属性} left

目录 @emph{a} 。
@end deffn

@geindex right (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp right}@anchor{1bea}
@deffn {属性} right

目录 @emph{b} 。
@end deffn

@geindex left_list (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp left_list}@anchor{1beb}
@deffn {属性} left_list

经 @emph{hide} 和 @emph{ignore} 过滤，目录 @emph{a} 中的文件与子目录。
@end deffn

@geindex right_list (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp right_list}@anchor{1bec}
@deffn {属性} right_list

经 @emph{hide} 和 @emph{ignore} 过滤，目录 @emph{b} 中的文件与子目录。
@end deffn

@geindex common (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp common}@anchor{1bed}
@deffn {属性} common

同时存在于目录 @emph{a} 和 @emph{b} 中的文件和子目录。
@end deffn

@geindex left_only (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp left_only}@anchor{1bee}
@deffn {属性} left_only

仅在目录 @emph{a} 中的文件和子目录。
@end deffn

@geindex right_only (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp right_only}@anchor{1bef}
@deffn {属性} right_only

仅在目录 @emph{b} 中的文件和子目录。
@end deffn

@geindex common_dirs (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp common_dirs}@anchor{1bf0}
@deffn {属性} common_dirs

同时存在于目录 @emph{a} 和 @emph{b} 中的子目录。
@end deffn

@geindex common_files (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp common_files}@anchor{1bf1}
@deffn {属性} common_files

同时存在于目录 @emph{a} 和 @emph{b} 中的文件。
@end deffn

@geindex common_funny (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp common_funny}@anchor{1bf2}
@deffn {属性} common_funny

在目录 @emph{a} 和 @emph{b} 中类型不同的名字，或者那些 @ref{1f1,,os.stat()} 报告错误的名字。
@end deffn

@geindex same_files (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp same_files}@anchor{1bf3}
@deffn {属性} same_files

在目录 @emph{a} 和 @emph{b} 中，使用类的文件比较操作符判定相等的文件。
@end deffn

@geindex diff_files (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp diff_files}@anchor{1bf4}
@deffn {属性} diff_files

在目录 @emph{a} 和 @emph{b} 中，根据类的文件比较操作符判定内容不等的文件。
@end deffn

@geindex funny_files (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp funny_files}@anchor{1bf5}
@deffn {属性} funny_files

在目录 @emph{a} 和 @emph{b} 中无法比较的文件。
@end deffn

@geindex subdirs (filecmp.dircmp 属性)
@anchor{library/filecmp filecmp dircmp subdirs}@anchor{1bf6}
@deffn {属性} subdirs

一个将 @ref{1bf0,,common_dirs} 中名称映射为 @ref{843,,dircmp} 对象的字典。
@end deffn
@end deffn

@geindex DEFAULT_IGNORES() (在 filecmp 模块中)
@anchor{library/filecmp filecmp DEFAULT_IGNORES}@anchor{842}
@deffn {属性} filecmp.DEFAULT_IGNORES


3.4 新版功能.


默认被 @ref{843,,dircmp} 忽略的目录列表。
@end deffn

下面是一个简单的例子，使用 @code{subdirs} 属性递归搜索两个目录以显示公共差异文件：

@example
>>> from filecmp import dircmp
>>> def print_diff_files(dcmp):
...     for name in dcmp.diff_files:
...         print("diff_file %s found in %s and %s" % (name, dcmp.left,
...               dcmp.right))
...     for sub_dcmp in dcmp.subdirs.values():
...         print_diff_files(sub_dcmp)
...
>>> dcmp = dircmp('dir1', 'dir2') 
>>> print_diff_files(dcmp) 
@end example

@node tempfile --- 生成临时文件和目录,glob --- Unix 风格路径名模式扩展,filecmp --- 文件及目录的比较,文件和目录访问
@anchor{library/tempfile doc}@anchor{1bf7}@anchor{library/tempfile module-tempfile}@anchor{103}@anchor{library/tempfile tempfile-generate-temporary-files-and-directories}@anchor{1bf8}
@subsection @code{tempfile} --- 生成临时文件和目录


@geindex tempfile (模块)

@strong{源代码：} Lib/tempfile.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tempfile.py}

@geindex temporary; file name
@geindex temporary; file


__________________________________________________________________


该模块用于创建临时文件和目录，它可以跨平台使用。@ref{1bf9,,TemporaryFile}、@ref{d42,,NamedTemporaryFile}、@ref{bc1,,TemporaryDirectory} 和 @ref{aa1,,SpooledTemporaryFile} 是带有自动清理功能的高级接口，可用作上下文管理器。@ref{1bfa,,mkstemp()} 和 @ref{1bfb,,mkdtemp()} 是低级函数，使用完毕需手动清理。

所有由用户调用的函数和构造函数都带有参数，这些参数可以设置临时文件和临时目录的路径和名称。该模块生成的文件名包括一串随机字符，在公共的临时目录中，这些字符可以让创建文件更加安全。为了保持向后兼容性，参数的顺序有些奇怪。所以为了代码清晰，建议使用关键字参数。

这个模块定义了以下内容供用户调用：

@geindex TemporaryFile() (在 tempfile 模块中)
@anchor{library/tempfile tempfile TemporaryFile}@anchor{1bf9}
@deffn {函数} tempfile.TemporaryFile (mode='w+b', buffering=None, encoding=None, newline=None, suffix=None, prefix=None, dir=None, *, errors=None)

返回一个 @ref{1bfc,,file-like object} （文件类对象）作为临时存储区域。创建该文件使用了与 @ref{1bfa,,mkstemp()} 相同的安全规则。它将在关闭后立即销毁（包括垃圾回收机制关闭该对象时）。在 Unix 下，该文件在目录中的条目根本不创建，或者创建文件后立即就被删除了，其他平台不支持此功能。您的代码不应依赖使用此功能创建的临时文件名称，因为它在文件系统中的名称可能是可见的，也可能是不可见的。

生成的对象可以用作上下文管理器（参见 @ref{1bfd,,例子}）。完成上下文或销毁临时文件对象后，临时文件将从文件系统中删除。

@emph{mode} 参数默认值为 @code{'w+b'}，所以创建的文件不用关闭，就可以读取或写入。因为用的是二进制模式，所以无论存的是什么数据，它在所有平台上都表现一致。@emph{buffering}、@emph{encoding}、@emph{errors} 和 @emph{newline} 的含义与 @ref{4ea,,open()} 中的相同。

参数 @emph{dir}、@emph{prefix} 和 @emph{suffix} 的含义和默认值都与它们在 @ref{1bfa,,mkstemp()} 中的相同。

在 POSIX 平台上，它返回的对象是真实的文件对象。在其他平台上，它是一个文件类对象 (file-like object)，它的 @code{file} 属性是底层的真实文件对象。

如果可用，则使用 @ref{87e,,os.O_TMPFILE} 标志（仅限于 Linux，需要 3.11 及更高版本的内核）。

引发一个 @code{tempfile.mkstemp} @ref{12d0,,审计事件}，附带参数 @code{fullpath}。


在 3.5 版更改: 如果可用，现在用的是 @ref{87e,,os.O_TMPFILE} 标志。



在 3.8 版更改: 添加了 @emph{errors} 参数。

@end deffn

@geindex NamedTemporaryFile() (在 tempfile 模块中)
@anchor{library/tempfile tempfile NamedTemporaryFile}@anchor{d42}
@deffn {函数} tempfile.NamedTemporaryFile (mode='w+b', buffering=None, encoding=None, newline=None, suffix=None, prefix=None, dir=None, delete=True, *, errors=None)

此函数执行的操作与 @ref{1bf9,,TemporaryFile()} 完全相同，但确保了该临时文件在文件系统中具有可见的名称（在 Unix 上表现为目录条目不取消链接）。从返回的文件类对象的 @code{name} 属性中可以检索到文件名。在临时文件仍打开时，是否允许用文件名第二次打开文件，在各个平台上是不同的（在 Unix 上可以，但在 Windows NT 或更高版本上不行）。如果 @emph{delete} 为 true（默认值），则文件会在关闭后立即被删除。该函数返回的对象始终是文件类对象 (file-like object)，它的 @code{file} 属性是底层的真实文件对象。文件类对象可以像普通文件一样在 @ref{6e3,,with} 语句中使用。

引发一个 @code{tempfile.mkstemp} @ref{12d0,,审计事件}，附带参数 @code{fullpath}。


在 3.8 版更改: 添加了 @emph{errors} 参数。

@end deffn

@geindex SpooledTemporaryFile() (在 tempfile 模块中)
@anchor{library/tempfile tempfile SpooledTemporaryFile}@anchor{aa1}
@deffn {函数} tempfile.SpooledTemporaryFile (max_size=0, mode='w+b', buffering=None, encoding=None, newline=None, suffix=None, prefix=None, dir=None, *, errors=None)

此函数执行的操作与 @ref{1bf9,,TemporaryFile()} 完全相同，但会将数据缓存在内存中，直到文件大小超过 @emph{max_size}，或调用文件的 @code{fileno()} 方法为止，此时数据会被写入磁盘，并且写入操作与 @ref{1bf9,,TemporaryFile()} 相同。

此函数生成的文件对象有一个额外的方法——@code{rollover()}，可以忽略文件大小，让文件立即写入磁盘。

返回的对象是文件类对象 (file-like object)，它的 @code{_file} 属性是 @ref{795,,io.BytesIO} 或 @ref{5ee,,io.TextIOWrapper} 对象（取决于指定的是二进制模式还是文本模式）或真实的文件对象（取决于是否已调用 @code{rollover()}）。文件类对象可以像普通文件一样在 @ref{6e3,,with} 语句中使用。


在 3.3 版更改: 现在，文件的 truncate 方法可接受一个 @code{size} 参数。



在 3.8 版更改: 添加了 @emph{errors} 参数。

@end deffn

@geindex TemporaryDirectory() (在 tempfile 模块中)
@anchor{library/tempfile tempfile TemporaryDirectory}@anchor{bc1}
@deffn {函数} tempfile.TemporaryDirectory (suffix=None, prefix=None, dir=None)

此函数会安全地创建一个临时目录，且使用与 @ref{1bfb,,mkdtemp()} 相同的规则。此函数返回的对象可用作上下文管理器（参见 @ref{1bfd,,例子}）。完成上下文或销毁临时目录对象后，新创建的临时目录及其所有内容将从文件系统中删除。

可以从返回对象的 @code{name} 属性中找到临时目录的名称。当返回的对象用作上下文管理器时，这个 @code{name} 会作为 @ref{6e3,,with} 语句中 @code{as} 子句的目标（如果有 as 的话）。

可以调用 @code{cleanup()} 方法来手动清理目录。

引发一个 @code{tempfile.mkdtemp} @ref{12d0,,审计事件}，附带参数 @code{fullpath}。


3.2 新版功能.

@end deffn

@geindex mkstemp() (在 tempfile 模块中)
@anchor{library/tempfile tempfile mkstemp}@anchor{1bfa}
@deffn {函数} tempfile.mkstemp (suffix=None, prefix=None, dir=None, text=False)

以最安全的方式创建一个临时文件。假设所在平台正确实现了 @ref{65f,,os.open()} 的 @ref{1bfe,,os.O_EXCL} 标志，则创建文件时不会有竞争的情况。该文件只能由创建者读写，如果所在平台用权限位来标记文件是否可执行，那么没有人有执行权。文件描述符不会过继给子进程。

与 @ref{1bf9,,TemporaryFile()} 不同，@ref{1bfa,,mkstemp()} 用户用完临时文件后需要自行将其删除。

如果 @emph{suffix} 不是 @code{None} 则文件名将以该后缀结尾，是 @code{None} 则没有后缀。@ref{1bfa,,mkstemp()} 不会在文件名和后缀之间加点，如果需要加一个点号，请将其放在 @emph{suffix} 的开头。

如果 @emph{prefix} 不是 @code{None}，则文件名将以该前缀开头，是 @code{None}      则使用默认前缀。默认前缀是 @ref{1bff,,gettempprefix()} 或 @ref{1c00,,gettempprefixb()} 函数的返回值（自动调用合适的函数）。

如果 @emph{dir} 不为 @code{None}，则在指定的目录创建文件，是 @code{None} 则使用默认目录。默认目录是从一个列表中选择出来的，这个列表不同平台不一样，但是用户可以设置 @emph{TMPDIR}、@emph{TEMP} 或 @emph{TMP} 环境变量来设置目录的位置。因此，不能保证生成的临时文件路径很规范，比如，通过 @code{os.popen()} 将路径传递给外部命令时仍需要加引号。

如果 @emph{suffix}、@emph{prefix} 和 @emph{dir} 中的任何一个不是 @code{None}，就要保证它们是同一数据类型。如果它们是 bytes，则返回的名称的类型就是 bytes 而不是 str。如果确实要用默认参数，但又想要返回值是 bytes 类型，请传入 @code{suffix=b'@w{'}}。

如果指定了 @emph{text} 参数，它表示的是以二进制模式（默认）还是文本模式打开文件。在某些平台上，两种模式没有区别。

@ref{1bfa,,mkstemp()} 返回一个元组，元组中第一个元素是句柄，它是一个系统级句柄，指向一个打开的文件（等同于 @ref{65f,,os.open()} 的返回值），第二元素是该文件的绝对路径。

引发一个 @code{tempfile.mkstemp} @ref{12d0,,审计事件}，附带参数 @code{fullpath}。


在 3.5 版更改: 现在，@emph{suffix}、@emph{prefix} 和 @emph{dir} 可以以 bytes 类型按顺序提供，以获得 bytes 类型的返回值。之前只允许使用 str。@emph{suffix} 和 @emph{prefix} 现在可以接受 @code{None}，并且默认为 @code{None} 以使用合适的默认值。



在 3.6 版更改: @emph{dir} 参数现在可接受一个路径类对象 (@ref{363,,path-like object})。

@end deffn

@geindex mkdtemp() (在 tempfile 模块中)
@anchor{library/tempfile tempfile mkdtemp}@anchor{1bfb}
@deffn {函数} tempfile.mkdtemp (suffix=None, prefix=None, dir=None)

以最安全的方式创建一个临时目录，创建该目录时不会有竞争的情况。该目录只能由创建者读取、写入和搜索。

@ref{1bfb,,mkdtemp()} 用户用完临时目录后需要自行将其删除。

@emph{prefix}、@emph{suffix} 和 @emph{dir} 的含义与它们在 @ref{1bfa,,mkstemp()} 中的相同。

@ref{1bfb,,mkdtemp()} 返回新目录的绝对路径。

引发一个 @code{tempfile.mkdtemp} @ref{12d0,,审计事件}，附带参数 @code{fullpath}。


在 3.5 版更改: 现在，@emph{suffix}、@emph{prefix} 和 @emph{dir} 可以以 bytes 类型按顺序提供，以获得 bytes 类型的返回值。之前只允许使用 str。@emph{suffix} 和 @emph{prefix} 现在可以接受 @code{None}，并且默认为 @code{None} 以使用合适的默认值。



在 3.6 版更改: @emph{dir} 参数现在可接受一个路径类对象 (@ref{363,,path-like object})。

@end deffn

@geindex gettempdir() (在 tempfile 模块中)
@anchor{library/tempfile tempfile gettempdir}@anchor{1c01}
@deffn {函数} tempfile.gettempdir ()

返回放置临时文件的目录的名称。这个方法的返回值就是本模块所有函数的 @emph{dir} 参数的默认值。

Python 搜索标准目录列表，以找到调用者可以在其中创建文件的目录。这个列表是：


@enumerate 

@item 
@geindex TMPDIR
@geindex 环境变量; TMPDIR
@code{TMPDIR} 环境变量指向的目录。

@item 
@geindex TEMP
@geindex 环境变量; TEMP
@code{TEMP} 环境变量指向的目录。

@item 
@geindex TMP
@geindex 环境变量; TMP
@code{TMP} 环境变量指向的目录。

@item 
与平台相关的位置：


@itemize *

@item 
在 Windows 上，依次为 @code{C:\TEMP}、@code{C:\TMP}、@code{\TEMP} 和 @code{\TMP}。

@item 
在所有其他平台上，依次为 @code{/tmp}、@code{/var/tmp} 和 @code{/usr/tmp}。
@end itemize

@item 
不得已时，使用当前工作目录。
@end enumerate

搜索的结果会缓存起来，参见下面 @ref{1c02,,tempdir} 的描述。
@end deffn

@geindex gettempdirb() (在 tempfile 模块中)
@anchor{library/tempfile tempfile gettempdirb}@anchor{1c03}
@deffn {函数} tempfile.gettempdirb ()

与 @ref{1c01,,gettempdir()} 相同，但返回值为字节类型。


3.5 新版功能.

@end deffn

@geindex gettempprefix() (在 tempfile 模块中)
@anchor{library/tempfile tempfile gettempprefix}@anchor{1bff}
@deffn {函数} tempfile.gettempprefix ()

返回用于创建临时文件的文件名前缀，它不包含目录部分。
@end deffn

@geindex gettempprefixb() (在 tempfile 模块中)
@anchor{library/tempfile tempfile gettempprefixb}@anchor{1c00}
@deffn {函数} tempfile.gettempprefixb ()

与 @ref{1bff,,gettempprefix()} 相同，但返回值为字节类型。


3.5 新版功能.

@end deffn

本模块使用一个全局变量来存储由 @ref{1c01,,gettempdir()} 返回的临时文件目录路径。可以直接给它赋值，这样可以覆盖自动选择的路径，但是不建议这样做。本模块中的所有函数都带有一个 @emph{dir} 参数，该参数可用于指定目录，这是推荐的方法。

@geindex tempdir() (在 tempfile 模块中)
@anchor{library/tempfile tempfile tempdir}@anchor{1c02}
@deffn {数据} tempfile.tempdir

当设置为 @code{None} 以外的其他值时，此变量将决定本模块所有函数的 @emph{dir} 参数的默认值。

如果在调用除 @ref{1bff,,gettempprefix()} 外的上述任何函数时 @code{tempdir} 为 @code{None} (默认值) 则它会按照 @ref{1c01,,gettempdir()} 中所描述的算法来初始化。
@end deffn

@menu
* 例子: 例子<3>. 
* 已弃用的函数和变量:: 

@end menu

@node 例子<3>,已弃用的函数和变量,,tempfile --- 生成临时文件和目录
@anchor{library/tempfile examples}@anchor{1c04}@anchor{library/tempfile tempfile-examples}@anchor{1bfd}
@subsubsection 例子


以下是 @ref{103,,tempfile} 模块典型用法的一些示例:

@example
>>> import tempfile

# create a temporary file and write some data to it
>>> fp = tempfile.TemporaryFile()
>>> fp.write(b'Hello world!')
# read data from file
>>> fp.seek(0)
>>> fp.read()
b'Hello world!'
# close the file, it will be removed
>>> fp.close()

# create a temporary file using a context manager
>>> with tempfile.TemporaryFile() as fp:
...     fp.write(b'Hello world!')
...     fp.seek(0)
...     fp.read()
b'Hello world!'
>>>
# file is now closed and removed

# create a temporary directory using the context manager
>>> with tempfile.TemporaryDirectory() as tmpdirname:
...     print('created temporary directory', tmpdirname)
>>>
# directory and contents have been removed
@end example

@node 已弃用的函数和变量,,例子<3>,tempfile --- 生成临时文件和目录
@anchor{library/tempfile deprecated-functions-and-variables}@anchor{1c05}
@subsubsection 已弃用的函数和变量


创建临时文件有一种历史方法，首先使用 @ref{1c06,,mktemp()} 函数生成一个文件名，然后使用该文件名创建文件。不幸的是，这是不安全的，因为在调用 @ref{1c06,,mktemp()} 与随后尝试创建文件的进程之间的时间里，其他进程可能会使用该名称创建文件。解决方案是将两个步骤结合起来，立即创建文件。这个方案目前被 @ref{1bfa,,mkstemp()} 和上述其他函数所采用。

@geindex mktemp() (在 tempfile 模块中)
@anchor{library/tempfile tempfile mktemp}@anchor{1c06}
@deffn {函数} tempfile.mktemp (suffix='@w{'}, prefix='tmp', dir=None)


2.3 版后已移除: 使用 @ref{1bfa,,mkstemp()} 来代替。


返回一个绝对路径，这个路径指向的文件在调用本方法时不存在。@emph{prefix}、@emph{suffix} 和 @emph{dir} 参数与 @ref{1bfa,,mkstemp()} 中的同名参数类似，不同之处在于不支持字节类型的文件名，不支持 @code{suffix=None} 和 @code{prefix=None}。

@cartouche
@quotation 警告 
使用此功能可能会在程序中引入安全漏洞。当你开始使用本方法返回的文件执行任何操作时，可能有人已经捷足先登了。@ref{1c06,,mktemp()} 的功能可以很轻松地用 @ref{d42,,NamedTemporaryFile()} 代替，当然需要传递 @code{delete=False} 参数:

@example
>>> f = NamedTemporaryFile(delete=False)
>>> f.name
'/tmp/tmptjujjt'
>>> f.write(b"Hello World!\n")
13
>>> f.close()
>>> os.unlink(f.name)
>>> os.path.exists(f.name)
False
@end example
@end quotation
@end cartouche
@end deffn

@node glob --- Unix 风格路径名模式扩展,fnmatch --- Unix 文件名模式匹配,tempfile --- 生成临时文件和目录,文件和目录访问
@anchor{library/glob doc}@anchor{1c07}@anchor{library/glob glob-unix-style-pathname-pattern-expansion}@anchor{1c08}@anchor{library/glob module-glob}@anchor{8a}
@subsection @code{glob} --- Unix 风格路径名模式扩展


@geindex glob (模块)

@strong{源代码:} Lib/glob.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/glob.py}

@geindex filenames; pathname expansion


__________________________________________________________________


@geindex * (asterisk); in glob-style wildcards
@geindex ? (question mark); in glob-style wildcards
@geindex [] (square brackets); in glob-style wildcards
@geindex ! (exclamation); in glob-style wildcards
@geindex - (minus); in glob-style wildcards
@geindex . (dot); in glob-style wildcards

@ref{8a,,glob} 模块可根据 Unix 终端所用规则找出所有匹配特定模式的路径名，但会按不确定的顺序返回结果。 波浪号扩展不会生效，但 @code{*}, @code{?} 以及表示为 @code{[]} 的字符范围将被正确地匹配。 这是通过配合使用 @ref{25f,,os.scandir()} 和 @ref{1c09,,fnmatch.fnmatch()} 函数来实现的，而不是通过实际发起调用子终端。 请注意不同于 @ref{1c09,,fnmatch.fnmatch()}，@ref{8a,,glob} 会将以点号 (@code{.}) 开头的文件名作为特殊情况来处理。 （对于波浪号和终端变量扩展，请使用 @ref{1fe,,os.path.expanduser()} 和 @ref{d3d,,os.path.expandvars()}。）

对于字面值匹配，请将原字符用方括号括起来。 例如，@code{'[?]'} 将匹配字符 @code{'?'}。


@subsubheading 参见


@ref{c8,,pathlib} 模块提供高级路径对象。


@geindex glob() (在 glob 模块中)
@anchor{library/glob glob glob}@anchor{5c1}
@deffn {函数} glob.glob (pathname, *, recursive=False)

返回匹配 @emph{pathname} 的可能为空的路径名列表，其中的元素必须为包含一个路径信息的字符串。 @emph{pathname} 可以是绝对路径 (如 @code{/usr/src/Python-1.5/Makefile}) 或相对路径 (如 @code{../../Tools/*/*.gif})，并且可包含 shell 风格的通配符。 结果也将包含无效的符号链接 (与在 shell 中一致)。 结果是否排序取决于具体文件系统。

@geindex **; in glob-style wildcards

如果 @emph{recursive} 为真值，则模式 "@code{**}" 将匹配目录中的任何文件以及零个或多个目录、子目录和符号链接。 如果模式加了一个 @ref{1c0a,,os.sep} 或 @ref{1c0b,,os.altsep} 则将不匹配文件。

引发一个 @ref{12d0,,审计事件} @code{glob.glob} 附带参数 @code{pathname}, @code{recursive}。

@cartouche
@quotation 注解 
在一个较大的目录树中使用 "@code{**}" 模式可能会消耗非常多的时间。
@end quotation
@end cartouche


在 3.5 版更改: 支持使用 "@code{**}" 的递归 glob。

@end deffn

@geindex iglob() (在 glob 模块中)
@anchor{library/glob glob iglob}@anchor{5c2}
@deffn {函数} glob.iglob (pathname, *, recursive=False)

返回一个 @ref{fce,,iterator}，它会产生与 @ref{8a,,glob()} 相同的结果，但不会实际地同时保存它们。

引发一个 @ref{12d0,,审计事件} @code{glob.glob} 附带参数 @code{pathname}, @code{recursive}。
@end deffn

@geindex escape() (在 glob 模块中)
@anchor{library/glob glob escape}@anchor{84a}
@deffn {函数} glob.escape (pathname)

转义所有特殊字符 (@code{'?'}, @code{'*'} 和 @code{'['})。 这适用于当你想要匹配可能带有特殊字符的任意字符串字面值的情况。 在 drive/UNC 共享点中的特殊字符不会被转义，例如在 Windows 上 @code{escape('//?/c:/Quo vadis?.txt')} 将返回 @code{'//?/c:/Quo vadis[?].txt'}。


3.4 新版功能.

@end deffn

例如，考虑一个包含以下内容的目录：文件 @code{1.gif}, @code{2.txt}, @code{card.gif} 以及一个子目录 @code{sub} 其中只包含一个文件 @code{3.txt}.  @ref{8a,,glob()} 将产生如下结果。 请注意路径的任何开头部分都将被保留。:

@example
>>> import glob
>>> glob.glob('./[0-9].*')
['./1.gif', './2.txt']
>>> glob.glob('*.gif')
['1.gif', 'card.gif']
>>> glob.glob('?.gif')
['1.gif']
>>> glob.glob('**/*.txt', recursive=True)
['2.txt', 'sub/3.txt']
>>> glob.glob('./**/', recursive=True)
['./', './sub/']
@end example

如果目录包含以 @code{.} 打头的文件，它们默认将不会被匹配。 例如，考虑一个包含 @code{card.gif} 和 @code{.card.gif} 的目录:

@example
>>> import glob
>>> glob.glob('*.gif')
['card.gif']
>>> glob.glob('.c*')
['.card.gif']
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{81,,fnmatch}

Shell 风格文件名（而非路径）扩展
@end table


@node fnmatch --- Unix 文件名模式匹配,linecache --- 随机读写文本行,glob --- Unix 风格路径名模式扩展,文件和目录访问
@anchor{library/fnmatch doc}@anchor{1c0c}@anchor{library/fnmatch fnmatch-unix-filename-pattern-matching}@anchor{1c0d}@anchor{library/fnmatch module-fnmatch}@anchor{81}
@subsection @code{fnmatch} --- Unix 文件名模式匹配


@geindex fnmatch (模块)

@strong{源代码:} Lib/fnmatch.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/fnmatch.py}

@geindex filenames; wildcard expansion

@geindex 模块; re


__________________________________________________________________


此模块提供了 Unix shell 风格的通配符，它们 @emph{并不} 等同于正则表达式（关于后者的文档参见 @ref{dd,,re} 模块）。 shell 风格通配符所使用的特殊字符如下：

@geindex * (asterisk); in glob-style wildcards
@geindex ? (question mark); in glob-style wildcards
@geindex [] (square brackets); in glob-style wildcards
@geindex ! (exclamation); in glob-style wildcards
@geindex - (minus); in glob-style wildcards


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

模式

@tab

含义

@item

@code{*}

@tab

匹配所有

@item

@code{?}

@tab

匹配任何单个字符

@item

@code{[seq]}

@tab

匹配 @emph{seq} 中的任何字符

@item

@code{[!seq]}

@tab

匹配任何不在 @emph{seq} 中的字符

@end multitable


对于字面值匹配，请将原字符用方括号括起来。 例如，@code{'[?]'} 将匹配字符 @code{'?'}。

@geindex 模块; glob

注意文件名分隔符 (Unix 上为 @code{'/'}) @emph{不是} 此模块所特有的。 请参见 @ref{8a,,glob} 模块了解文件名扩展 (@ref{8a,,glob} 使用 @ref{1c0e,,filter()} 来匹配文件名的各个部分)。 类似地，以一个句点打头的文件名也不是此模块所特有的，可以通过 @code{*} 和 @code{?} 模式来匹配。

@geindex fnmatch() (在 fnmatch 模块中)
@anchor{library/fnmatch fnmatch fnmatch}@anchor{1c09}
@deffn {函数} fnmatch.fnmatch (filename, pattern)

检测 @emph{filename} 字符串是否匹配 @emph{pattern} 字符串，返回 @ref{494,,True} 或 @ref{380,,False}。 两个形参都会使用 @ref{1b83,,os.path.normcase()} 进行大小写正规化。 @ref{1c0f,,fnmatchcase()} 可被用于执行大小写敏感的比较，无论这是否为所在操作系统的标准。

这个例子将打印当前目录下带有扩展名 @code{.txt} 的所有文件名:

@example
import fnmatch
import os

for file in os.listdir('.'):
    if fnmatch.fnmatch(file, '*.txt'):
        print(file)
@end example
@end deffn

@geindex fnmatchcase() (在 fnmatch 模块中)
@anchor{library/fnmatch fnmatch fnmatchcase}@anchor{1c0f}
@deffn {函数} fnmatch.fnmatchcase (filename, pattern)

检测 @emph{filename} 是否匹配 @emph{pattern}，返回 @ref{494,,True} 或 @ref{380,,False}；此比较是大小写敏感的，并且不会应用 @ref{1b83,,os.path.normcase()}。
@end deffn

@geindex filter() (在 fnmatch 模块中)
@anchor{library/fnmatch fnmatch filter}@anchor{1c0e}
@deffn {函数} fnmatch.filter (names, pattern)

返回 @emph{names} 列表中匹配 @emph{pattern} 的子集。 它等价于 @code{[n for n in names if fnmatch(n, pattern)]}，但其实现更为高效。
@end deffn

@geindex translate() (在 fnmatch 模块中)
@anchor{library/fnmatch fnmatch translate}@anchor{fd0}
@deffn {函数} fnmatch.translate (pattern)

返回 shell 风格 @emph{pattern} 转换成的正则表达式以便用于 @ref{bac,,re.match()}。

示例:

@example
>>> import fnmatch, re
>>>
>>> regex = fnmatch.translate('*.txt')
>>> regex
'(?s:.*\\.txt)\\Z'
>>> reobj = re.compile(regex)
>>> reobj.match('foobar.txt')
<re.Match object; span=(0, 10), match='foobar.txt'>
@end example
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{8a,,glob}

Unix shell 风格路径扩展。
@end table


@node linecache --- 随机读写文本行,shutil --- 高阶文件操作,fnmatch --- Unix 文件名模式匹配,文件和目录访问
@anchor{library/linecache doc}@anchor{1c10}@anchor{library/linecache linecache-random-access-to-text-lines}@anchor{1c11}@anchor{library/linecache module-linecache}@anchor{a8}
@subsection @code{linecache} --- 随机读写文本行


@geindex linecache (模块)

@strong{源代码:} Lib/linecache.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/linecache.py}


__________________________________________________________________


@ref{a8,,linecache} 模块允许从一个 Python 源文件中获取任意的行，并会尝试使用缓存进行内部优化，常应用于从单个文件读取多行的场合。 此模块被 @ref{113,,traceback} 模块用来提取源码行以便包含在格式化的回溯中。

@ref{1c12,,tokenize.open()} 函数被用于打开文件。 此函数使用 @ref{1c13,,tokenize.detect_encoding()} 来获取文件的编码格式；如果未指明编码格式，则默认编码为 UTF-8。

@ref{a8,,linecache} 模块定义了下列函数：

@geindex getline() (在 linecache 模块中)
@anchor{library/linecache linecache getline}@anchor{703}
@deffn {函数} linecache.getline (filename, lineno, module_globals=None)

从名为 @emph{filename} 的文件中获取 @emph{lineno} 行，此函数绝不会引发异常 --- 出现错误时它将返回 @code{'@w{'}} (所有找到的行都将包含换行符作为结束)。

@geindex module; search; path

如果找不到名为 @emph{filename} 的文件，此函数会先在 @emph{module_globals} 中检查 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} @code{__loader__}。 如果存在这样的加载器并且它定义了 @code{get_source} 方法，则由该方法来确定源行 (如果 @code{get_source()} 返回 @code{None}，则该函数返回 @code{'@w{'}})。 最后，如果 @emph{filename} 是一个相对路径文件名，则它会在模块搜索路径 @code{sys.path} 中按条目的相对位置进行查找。
@end deffn

@geindex clearcache() (在 linecache 模块中)
@anchor{library/linecache linecache clearcache}@anchor{1c14}
@deffn {函数} linecache.clearcache ()

清空缓存。 如果你不再需要之前使用 @ref{703,,getline()} 从文件读取的行即可使用此函数。
@end deffn

@geindex checkcache() (在 linecache 模块中)
@anchor{library/linecache linecache checkcache}@anchor{1c15}
@deffn {函数} linecache.checkcache (filename=None)

检查缓存有效性。 如果缓存中的文件在磁盘上发生了改变，而你需要更新后的版本即可使用此函数。 如果省略了 @emph{filename}，它会检查缓存中的所有条目。
@end deffn

@geindex lazycache() (在 linecache 模块中)
@anchor{library/linecache linecache lazycache}@anchor{702}
@deffn {函数} linecache.lazycache (filename, module_globals)

捕获有关某个非基于文件的模块的足够细节信息，以允许稍后再通过 @ref{703,,getline()} 来获取其中的行，即使当稍后调用时 @emph{module_globals} 为 @code{None}。 这可以避免在实际需要读取行之前执行 I/O，也不必始终保持模块全局变量。


3.5 新版功能.

@end deffn

示例:

@example
>>> import linecache
>>> linecache.getline(linecache.__file__, 8)
'import sys\n'
@end example

@node shutil --- 高阶文件操作,,linecache --- 随机读写文本行,文件和目录访问
@anchor{library/shutil doc}@anchor{1c16}@anchor{library/shutil module-shutil}@anchor{e9}@anchor{library/shutil shutil-high-level-file-operations}@anchor{1c17}
@subsection @code{shutil} --- 高阶文件操作


@geindex shutil (模块)

@c partly based on the docstrings

@strong{源代码：} Lib/shutil.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/shutil.py}

@geindex file; copying
@geindex copying files


__________________________________________________________________


@ref{e9,,shutil} 模块提供了一系列对文件和文件集合的高阶操作。 特别是提供了一些支持文件拷贝和删除的函数。 对于单个文件的操作，请参阅 @ref{c4,,os} 模块。

@cartouche
@quotation 警告 
即便是高阶文件拷贝函数 (@ref{259,,shutil.copy()}, @ref{25a,,shutil.copy2()}) 也无法拷贝所有的文件元数据。

在 POSIX 平台上，这意味着将丢失文件所有者和组以及 ACL 数据。 在 Mac OS 上，资源钩子和其他元数据不被使用。 这意味着将丢失这些资源并且文件类型和创建者代码将不正确。 在 Windows 上，将不会拷贝文件所有者、ACL 和替代数据流。
@end quotation
@end cartouche

@menu
* 目录和文件操作:: 
* 归档操作:: 
* 查询输出终端的尺寸:: 

@end menu

@node 目录和文件操作,归档操作,,shutil --- 高阶文件操作
@anchor{library/shutil directory-and-files-operations}@anchor{1c18}@anchor{library/shutil file-operations}@anchor{1c19}
@subsubsection 目录和文件操作


@geindex copyfileobj() (在 shutil 模块中)
@anchor{library/shutil shutil copyfileobj}@anchor{25d}
@deffn {函数} shutil.copyfileobj (fsrc, fdst[, length])

将文件类对象 @emph{fsrc} 的内容拷贝到文件类对象 @emph{fdst}。 整数值 @emph{length} 如果给出则为缓冲区大小。 特别地， @emph{length} 为负值表示拷贝数据时不对源数据进行分块循环处理；默认情况下会分块读取数据以避免不受控制的内存消耗。 请注意如果 @emph{fsrc} 对象的当前文件位置不为 0，则只有从当前文件位置到文件末尾的内容会被拷贝。
@end deffn

@geindex copyfile() (在 shutil 模块中)
@anchor{library/shutil shutil copyfile}@anchor{258}
@deffn {函数} shutil.copyfile (src, dst, *, follow_symlinks=True)

将名为 @emph{src} 的文件的内容（不包括元数据）拷贝到名为 @emph{dst} 的文件并以尽可能高效的方式返回 @emph{dst}。 @emph{src} 和 @emph{dst} 均为路径类对象或以字符串形式给出的路径名。

@emph{dst} 必须是完整的目标文件名；对于接受目标目录路径的拷贝请参见 @ref{259,,copy()}。 如果 @emph{src} 和 @emph{dst} 指定了同一个文件，则将引发 @ref{8ad,,SameFileError}。

目标位置必须是可写的；否则将引发 @ref{1d3,,OSError} 异常。 如果 @emph{dst} 已经存在，它将被替换。 特殊文件如字符或块设备以及管道无法用此函数来拷贝。

如果 @emph{follow_symlinks} 为假值且 @emph{src} 为符号链接，则将创建一个新的符号链接而不是拷贝 @emph{src} 所指向的文件。

引发一个 @ref{12d0,,审计事件} @code{shutil.copyfile} 附带参数 @code{src}, @code{dst}。


在 3.3 版更改: 曾经是引发 @ref{98c,,IOError} 而不是 @ref{1d3,,OSError}。 增加了 @emph{follow_symlinks} 参数。 现在是返回 @emph{dst}。



在 3.4 版更改: 引发 @ref{8ad,,SameFileError} 而不是 @ref{8ac,,Error}。 由于前者是后者的子类，此改变是向后兼容的。



在 3.8 版更改: 可能会在内部使用平台专属的快速拷贝系统调用以更高效地拷贝文件。 参见 @ref{25e,,依赖于具体平台的高效拷贝操作} 一节。

@end deffn

@geindex SameFileError
@anchor{library/shutil shutil SameFileError}@anchor{8ad}
@deffn {例外} shutil.SameFileError

此异常会在 @ref{258,,copyfile()} 中的源和目标为同一文件时被引发。


3.4 新版功能.

@end deffn

@geindex copymode() (在 shutil 模块中)
@anchor{library/shutil shutil copymode}@anchor{1c1a}
@deffn {函数} shutil.copymode (src, dst, *, follow_symlinks=True)

从 @emph{src} 拷贝权限位到 @emph{dst}。 文件的内容、所有者和分组将不受影响。 @emph{src} 和 @emph{dst} 均为路径类对象或字符串形式的路径名。 如果 @emph{follow_symlinks} 为假值，并且 @emph{src} 和 @emph{dst} 均为符号链接，@ref{1c1a,,copymode()} 将尝试修改 @emph{dst} 本身的模式（而非它所指向的文件）。 此功能并不是在所有平台上均可用；请参阅 @ref{a72,,copystat()} 了解详情。 如果 @ref{1c1a,,copymode()} 无法修改本机平台上的符号链接，而它被要求这样做，它将不做任何操作即返回。

引发一个 @ref{12d0,,审计事件} @code{shutil.copymode} 附带参数 @code{src}, @code{dst}。


在 3.3 版更改: 加入 @emph{follow_symlinks} 参数。

@end deffn

@geindex copystat() (在 shutil 模块中)
@anchor{library/shutil shutil copystat}@anchor{a72}
@deffn {函数} shutil.copystat (src, dst, *, follow_symlinks=True)

从 @emph{src} 拷贝权限位、最近访问时间、最近修改时间以及旗标到 @emph{dst}。 在 Linux上，@ref{a72,,copystat()} 还会在可能的情况下拷贝“扩展属性”。 文件的内容、所有者和分组将不受影响。 @emph{src} 和 @emph{dst} 均为路径类对象或字符串形式的路径名。

如果 @emph{follow_symlinks} 为假值，并且 @emph{src} 和 @emph{dst} 均指向符号链接，@ref{a72,,copystat()} 将作用于符号链接本身而非该符号链接所指向的文件 — 从 @emph{src} 符号链接读取信息，并将信息写入 @emph{dst} 符号链接。

@cartouche
@quotation 注解 
并非所有平台者提供检查和修改符号链接的功能。 Python 本身可以告诉你哪些功能是在本机上可用的。


@itemize *

@item 
如果 @code{os.chmod in os.supports_follow_symlinks} 为 @code{True}，则 @ref{a72,,copystat()} 可以修改符号链接的权限位。

@item 
如果 @code{os.utime in os.supports_follow_symlinks} 为 @code{True}，则 @ref{a72,,copystat()} 可以修改符号链接的最近访问和修改时间。

@item 
如果 @code{os.chflags in os.supports_follow_symlinks} 为 @code{True}，则 @ref{a72,,copystat()} 可以修改符号链接的旗标。 (@code{os.chflags} 不是在所有平台上均可用。)
@end itemize

在此功能部分或全部不可用的平台上，当被要求修改一个符号链接时，@ref{a72,,copystat()} 将尽量拷贝所有内容。 @ref{a72,,copystat()} 一定不会返回失败信息。

更多信息请参阅 @ref{1c1b,,os.supports_follow_symlinks}。
@end quotation
@end cartouche

引发一个 @ref{12d0,,审计事件} @code{shutil.copystat} 附带参数 @code{src}, @code{dst}。


在 3.3 版更改: 添加了 @emph{follow_symlinks} 参数并且支持 Linux 扩展属性。

@end deffn

@geindex copy() (在 shutil 模块中)
@anchor{library/shutil shutil copy}@anchor{259}
@deffn {函数} shutil.copy (src, dst, *, follow_symlinks=True)

将文件 @emph{src} 拷贝到文件或目录 @emph{dst}。 @emph{src} 和 @emph{dst} 应为字符串。 如果 @emph{dst} 指定了一个目录，文件将使用 @emph{src} 中的基准文件名拷贝到 @emph{dst}。 返回新创建文件的路径。

如果 @emph{follow_symlinks} 为假值且 @emph{src} 为符号链接，则 @emph{dst} 也将被创建为符号链接。 如果 @emph{follow_symlinks} 为真值且 @emph{src} 为符号链接，@emph{dst} 将成为 @emph{src} 所指向的文件的一个副本。

@ref{259,,copy()} 会拷贝文件数据和文件的权限模式 (参见 @ref{a2e,,os.chmod()})。 其他元数据，例如文件的创建和修改时间不会被保留。 要保留所有原有的元数据，请改用 @ref{25a,,copy2()} 。

引发一个 @ref{12d0,,审计事件} @code{shutil.copyfile} 附带参数 @code{src}, @code{dst}。

引发一个 @ref{12d0,,审计事件} @code{shutil.copymode} 附带参数 @code{src}, @code{dst}。


在 3.3 版更改: 添加了 @emph{follow_symlinks} 参数。 现在会返回新创建文件的路径。



在 3.8 版更改: 可能会在内部使用平台专属的快速拷贝系统调用以更高效地拷贝文件。 参见 @ref{25e,,依赖于具体平台的高效拷贝操作} 一节。

@end deffn

@geindex copy2() (在 shutil 模块中)
@anchor{library/shutil shutil copy2}@anchor{25a}
@deffn {函数} shutil.copy2 (src, dst, *, follow_symlinks=True)

类似于 @ref{259,,copy()}，区别在于 @ref{25a,,copy2()} 还会尝试保留文件的元数据。

当 @emph{follow_symlinks} 为假值且 @emph{src} 为符号链接时，@ref{25a,,copy2()} 会尝试将来自 @emph{src} 符号链接的所有元数据拷贝到新创建的 @emph{dst} 符号链接。 但是，此功能不是在所有平台上均可用。 在此功能部分或全部不可用的平台上，@ref{25a,,copy2()} 将尽量保留所有元数据；@ref{25a,,copy2()} 一定不会由于无法保留文件元数据而引发异常。

@ref{25a,,copy2()} 会使用 @ref{a72,,copystat()} 来拷贝文件元数据。 请参阅 @ref{a72,,copystat()} 了解有关修改符号链接元数据的平台支持的更多信息。

引发一个 @ref{12d0,,审计事件} @code{shutil.copyfile} 附带参数 @code{src}, @code{dst}。

引发一个 @ref{12d0,,审计事件} @code{shutil.copystat} 附带参数 @code{src}, @code{dst}。


在 3.3 版更改: 添加了 @emph{follow_symlinks} 参数，还会尝试拷贝扩展文件系统属性（目前仅限 Linux）。 现在会返回新创建文件的路径。



在 3.8 版更改: 可能会在内部使用平台专属的快速拷贝系统调用以更高效地拷贝文件。 参见 @ref{25e,,依赖于具体平台的高效拷贝操作} 一节。

@end deffn

@geindex ignore_patterns() (在 shutil 模块中)
@anchor{library/shutil shutil ignore_patterns}@anchor{1c1c}
@deffn {函数} shutil.ignore_patterns (*patterns)

这个工厂函数会创建一个函数，它可被用作 @ref{21a,,copytree()} 的 @emph{ignore} 可调用对象参数，以忽略那些匹配所提供的 glob 风格的 @emph{patterns} 之一的文件和目录。 参见以下示例。
@end deffn

@geindex copytree() (在 shutil 模块中)
@anchor{library/shutil shutil copytree}@anchor{21a}
@deffn {函数} shutil.copytree (src, dst, symlinks=False, ignore=None, copy_function=copy2, ignore_dangling_symlinks=False, dirs_exist_ok=False)

将以 @emph{src} 为根起点的整个目录树拷贝到名为 @emph{dst} 的目录并返回目标目录。 @emph{dirs_exist_ok} 指明是否要在 @emph{dst} 或任何丢失的父目录已存在的情况下引发异常。

目录的权限和时间会通过 @ref{a72,,copystat()} 来拷贝，单个文件则会使用 @ref{25a,,copy2()} 来拷贝。

如果 @emph{symlinks} 为真值，源目录树中的符号链接会在新目录树中表示为符号链接，并且原链接的元数据在平台允许的情况下也会被拷贝；如果为假值或省略，则会将被链接文件的内容和元数据拷贝到新目录树。

当 @emph{symlinks} 为假值时，如果符号链接所指向的文件不存在，则会在拷贝进程的末尾将一个异常添加到 @ref{8ac,,Error} 异常中的错误列表。 如果你希望屏蔽此异常那就将可选的 @emph{ignore_dangling_symlinks} 旗标设为真值。 请注意此选项在不支持 @ref{a36,,os.symlink()} 的平台上将不起作用。

如果给出了 @emph{ignore}，它必须是一个可调用对象，该对象将接受 @ref{21a,,copytree()} 所访问的目录以及 @ref{a3c,,os.listdir()} 所返回的目录内容列表作为其参数。 由于 @ref{21a,,copytree()} 是递归地被调用的，@emph{ignore} 可调用对象对于每个被拷贝目录都将被调用一次。 该可调用对象必须返回一个相对于当前目录的目录和文件名序列（即其第二个参数的子集）；随后这些名称将在拷贝进程中被忽略。 @ref{1c1c,,ignore_patterns()} 可被用于创建这种基于 glob 风格模式来忽略特定名称的可调用对象。

如果发生了（一个或多个）异常，将引发一个附带原因列表的 @ref{8ac,,Error}。

如果给出了 @emph{copy_function}，它必须是一个将被用来拷贝每个文件的可调用对象。 它在被调用时会将源路径和目标路径作为参数传入。 默认情况下，@ref{25a,,copy2()} 将被使用，但任何支持同样签名（与 @ref{259,,copy()} 一致）都可以使用。

引发一个 @ref{12d0,,审计事件} @code{shutil.copytree} 附带参数 @code{src}, @code{dst}。


在 3.3 版更改: 当 @emph{symlinks} 为假值时拷贝元数据。 现在会返回 @emph{dst}。



在 3.2 版更改: 添加了 @emph{copy_function} 参数以允许提供定制的拷贝函数。 添加了 @emph{ignore_dangling_symlinks} 参数以便在 @emph{symlinks} 为假值时屏蔽符号链接错误。



在 3.8 版更改: 可能会在内部使用平台专属的快速拷贝系统调用以更高效地拷贝文件。 参见 @ref{25e,,依赖于具体平台的高效拷贝操作} 一节。



3.8 新版功能: @emph{dirs_exist_ok} 形参。

@end deffn

@geindex rmtree() (在 shutil 模块中)
@anchor{library/shutil shutil rmtree}@anchor{21c}
@deffn {函数} shutil.rmtree (path, ignore_errors=False, onerror=None)

@geindex directory; deleting

删除一个完整的目录树；@emph{path} 必须指向一个目录（但不能是一个目录的符号链接）。 如果 @emph{ignore_errors} 为真值，删除失败导致的错误将被忽略；如果为假值或是省略，此类错误将通过调用由 @emph{onerror} 所指定的处理程序来处理，或者如果此参数被省略则将引发一个异常。

@cartouche
@quotation 注解 
在支持必要的基于 fd 的函数的平台上，默认会使用 @ref{21c,,rmtree()} 的可防御符号链接攻击的版本。 在其他平台上，@ref{21c,,rmtree()} 较易遭受符号链接攻击：给定适当的时间和环境，攻击者可以操纵文件系统中的符号链接来删除他们在其他情况下无法访问的文件。 应用程序可以使用 @ref{1c1d,,rmtree.avoids_symlink_attacks} 函数属性来确定此类情况具体是哪一些。
@end quotation
@end cartouche

如果提供了 @emph{onerror}，它必须为接受三个形参的可调用对象: @emph{function}, @emph{path} 和 @emph{excinfo}。

第一个形参 @emph{function} 是引发异常的函数；它依赖于具体的平台和实现。 第二个形参 @emph{path} 将是传递给 @emph{function} 的路径名。 第三个形参 @emph{excinfo} 将是由 @ref{c58,,sys.exc_info()} 所返回的异常信息。 由 @emph{onerror} 所引发的异常将不会被捕获。

引发一个 @ref{12d0,,审计事件} @code{shutil.rmtree} 附带参数 @code{path}。


在 3.3 版更改: 添加了一个防御符号链接攻击的版本，如果平台支持基于 fd 的函数就会被使用。



在 3.8 版更改: 在 Windows 上将不会再在移除连接之前删除目录连接中的内容。


@geindex avoids_symlink_attacks (shutil.rmtree 属性)
@anchor{library/shutil shutil rmtree avoids_symlink_attacks}@anchor{1c1d}
@deffn {属性} rmtree.avoids_symlink_attacks

指明当前平台和实现是否提供防御符号链接攻击的 @ref{21c,,rmtree()} 版本。 目前它仅在平台支持基于 fd 的目录访问函数时才返回真值。


3.3 新版功能.

@end deffn
@end deffn

@geindex move() (在 shutil 模块中)
@anchor{library/shutil shutil move}@anchor{25b}
@deffn {函数} shutil.move (src, dst, copy_function=copy2)

递归地将一个文件或目录 (@emph{src}) 移至另一位置 (@emph{dst}) 并返回目标位置。

如果目标是已存在的目录，则 @emph{src} 会被移至该目录下。 如果目标已存在但不是目录，它可能会被覆盖，具体取决于 @ref{a33,,os.rename()} 的语义。

如果目标是在当前文件系统中，则会使用 @ref{a33,,os.rename()}。 在其他情况下，@emph{src} 将被拷贝至 @emph{dst}，使用的函数为 @emph{copy_function}，然后目标会被移除。 对于符号链接，则将在 @emph{dst} 之下或以其本身为名称创建一个指向 @emph{src} 目标的新符号链接，并且 @emph{src} 将被移除。

如果给出了 @emph{copy_function}，则它必须为接受两个参数 @emph{src} 和 @emph{dst} 的可调用对象，并会在 @ref{a33,,os.rename()} 无法使用时被用来将 @emph{src} 拷贝到 @emph{dest}。 如果源位置是一个目录，则会调用 @ref{21a,,copytree()}，并向它传入 @code{copy_function()}。 默认的 @emph{copy_function} 是 @ref{25a,,copy2()}。 使用 @ref{259,,copy()} 作为 @emph{copy_function} 允许在无法附带拷贝元数据时让移动操作成功执行，但其代价是不拷贝任何元数据。

引发一个 @ref{12d0,,审计事件} @code{shutil.move} 附带参数 @code{src}, @code{dst}。


在 3.3 版更改: 为异类文件系统添加了显式的符号链接处理，以便使它适应 GNU 的 @code{mv} 的行为。 现在会返回 @emph{dst}。



在 3.5 版更改: 增加了 @emph{copy_function} 关键字参数。



在 3.8 版更改: 可能会在内部使用平台专属的快速拷贝系统调用以更高效地拷贝文件。 参见 @ref{25e,,依赖于具体平台的高效拷贝操作} 一节。

@end deffn

@geindex disk_usage() (在 shutil 模块中)
@anchor{library/shutil shutil disk_usage}@anchor{a70}
@deffn {函数} shutil.disk_usage (path)

返回给定路径的磁盘使用统计数据，形式为一个 @ref{a9e,,named tuple}，其中包含 @emph{total}, @emph{used} 和 @emph{free} 属性，分别表示总计、已使用和未使用空间的字节数。 @emph{path} 可以是一个文件或是一个目录。


3.3 新版功能.



在 3.8 版更改: 在 Windows 上，@emph{path} 现在可以是一个文件或目录。


@ref{12f5,,可用性}: Unix, Windows。
@end deffn

@geindex chown() (在 shutil 模块中)
@anchor{library/shutil shutil chown}@anchor{a71}
@deffn {函数} shutil.chown (path, user=None, group=None)

修改给定 @emph{path} 的所有者 @emph{user} 和/或 @emph{group}。

@emph{user} 可以是一个系统用户名或 uid；@emph{group} 同样如此。 要求至少有一个参数。

另请参阅下层的函数 @ref{a2f,,os.chown()}。

引发一个 @ref{12d0,,审计事件} @code{shutil.chown} 附带参数 @code{path}, @code{user}, @code{group}。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex which() (在 shutil 模块中)
@anchor{library/shutil shutil which}@anchor{f6c}
@deffn {函数} shutil.which (cmd, mode=os.F_OK | os.X_OK, path=None)

返回当给定的 @emph{cmd} 被调用时将要运行的可执行文件的路径。 如果没有 @emph{cmd} 会被调用则返回 @code{None}。

@emph{mode} 是一个传递给 @ref{a2c,,os.access()} 的权限掩码，在默认情况下将确定文件是否存在并且为可执行文件。

当未指定 @emph{path} 时，将会使用 @ref{b30,,os.environ()} 的结果，返回 "PATH" 的值或回退为 @ref{f70,,os.defpath}。

在 Windows 上当前目录总是会被添加为 @emph{path} 的第一项，无论你是否使用默认值或提供你自己的路径，这是命令行终端在查找可执行文件时所采用的行为方式。 此外，当在 @emph{path} 中查找 @emph{cmd} 时，还会检查 @code{PATHEXT} 环境变量。 例如，如果你调用 @code{shutil.which("python")}，@ref{f6c,,which()} 将搜索 @code{PATHEXT} 来确定它要在 @emph{path} 目录中查找 @code{python.exe}。 例如，在 Windows 上:

@example
>>> shutil.which("python")
'C:\\Python33\\python.EXE'
@end example


3.3 新版功能.



在 3.8 版更改: 现在可以接受 @ref{32a,,bytes} 类型。 如果 @emph{cmd} 的类型为 @ref{32a,,bytes}，结果的类型也将为 @ref{32a,,bytes}。

@end deffn

@geindex Error
@anchor{library/shutil shutil Error}@anchor{8ac}
@deffn {例外} shutil.Error

此异常会收集在多文件操作期间所引发的异常。 对于 @ref{21a,,copytree()}，此异常参数将是一个由三元组 (@emph{srcname}, @emph{dstname}, @emph{exception}) 构成的列表。
@end deffn

@menu
* 依赖于具体平台的高效拷贝操作:: 
* copytree 示例:: 
* rmtree 示例:: 

@end menu

@node 依赖于具体平台的高效拷贝操作,copytree 示例,,目录和文件操作
@anchor{library/shutil platform-dependent-efficient-copy-operations}@anchor{1c1e}@anchor{library/shutil shutil-platform-dependent-efficient-copy-operations}@anchor{25e}
@subsubsection 依赖于具体平台的高效拷贝操作


从 Python 3.8 开始，所有涉及文件拷贝的函数 (@ref{258,,copyfile()}, @ref{26,,copy()}, @ref{25a,,copy2()}, @ref{21a,,copytree()}, 以及 @ref{25b,,move()}) 将会使用平台专属的 "fast-copy" 系统调用以便更高效地拷贝文件 (参见 bpo-33671@footnote{https://bugs.python.org/issue33671})。 "fast-copy" 意味着拷贝操作将发生于内核之中，避免像在 "@code{outfd.write(infd.read())}" 中那样使用用户空间的缓冲区。

在 macOS 上将会使用 fcopyfile@footnote{http://www.manpagez.com/man/3/copyfile/} 来拷贝文件内容（不含元数据）。

在 Linux 上将会使用 @ref{352,,os.sendfile()}。

在 Windows 上 @ref{258,,shutil.copyfile()} 将会使用更大的默认缓冲区（1 MiB 而非 64 KiB）并且会使用基于 @ref{25c,,memoryview()} 的 @ref{25d,,shutil.copyfileobj()} 变种形式。

如果快速拷贝操作失败并且没有数据被写入目标文件，则 shutil 将在内部静默地回退到使用效率较低的 @ref{25d,,copyfileobj()} 函数。


在 3.8 版更改.


@node copytree 示例,rmtree 示例,依赖于具体平台的高效拷贝操作,目录和文件操作
@anchor{library/shutil copytree-example}@anchor{1c1f}@anchor{library/shutil shutil-copytree-example}@anchor{1c20}
@subsubsection copytree 示例


这个示例就是上面所描述的 @ref{21a,,copytree()} 函数的实现，其中省略了文档字符串。 它还展示了此模块所提供的许多其他函数。

@example
def copytree(src, dst, symlinks=False):
    names = os.listdir(src)
    os.makedirs(dst)
    errors = []
    for name in names:
        srcname = os.path.join(src, name)
        dstname = os.path.join(dst, name)
        try:
            if symlinks and os.path.islink(srcname):
                linkto = os.readlink(srcname)
                os.symlink(linkto, dstname)
            elif os.path.isdir(srcname):
                copytree(srcname, dstname, symlinks)
            else:
                copy2(srcname, dstname)
            # XXX What about devices, sockets etc.?
        except OSError as why:
            errors.append((srcname, dstname, str(why)))
        # catch the Error from the recursive copytree so that we can
        # continue with other files
        except Error as err:
            errors.extend(err.args[0])
    try:
        copystat(src, dst)
    except OSError as why:
        # can't copy file access times on Windows
        if why.winerror is None:
            errors.extend((src, dst, str(why)))
    if errors:
        raise Error(errors)
@end example

另一个使用 @ref{1c1c,,ignore_patterns()} 辅助函数的例子:

@example
from shutil import copytree, ignore_patterns

copytree(source, destination, ignore=ignore_patterns('*.pyc', 'tmp*'))
@end example

这将会拷贝除 @code{.pyc} 文件和以 @code{tmp} 打头的文件或目录以外的所有条目.

另一个使用 @emph{ignore} 参数来添加记录调用的例子:

@example
from shutil import copytree
import logging

def _logpath(path, names):
    logging.info('Working in %s', path)
    return []   # nothing will be ignored

copytree(source, destination, ignore=_logpath)
@end example

@node rmtree 示例,,copytree 示例,目录和文件操作
@anchor{library/shutil rmtree-example}@anchor{1c21}@anchor{library/shutil shutil-rmtree-example}@anchor{1c22}
@subsubsection rmtree 示例


这个例子演示了如何在 Windows 上删除一个目录树，其中部分文件设置了只读属性位。 它会使用 onerror 回调函数来清除只读属性位并再次尝试删除。 任何后续的失败都将被传播。

@example
import os, stat
import shutil

def remove_readonly(func, path, _):
    "Clear the readonly bit and reattempt the removal"
    os.chmod(path, stat.S_IWRITE)
    func(path)

shutil.rmtree(directory, onerror=remove_readonly)
@end example

@node 归档操作,查询输出终端的尺寸,目录和文件操作,shutil --- 高阶文件操作
@anchor{library/shutil archiving-operations}@anchor{b8f}@anchor{library/shutil id1}@anchor{1c23}
@subsubsection 归档操作



3.2 新版功能.



在 3.5 版更改: 添加了对 @emph{xztar} 格式的支持。


本模块也提供了用于创建和读取压缩和归档文件的高层级工具。 它们依赖于 @ref{142,,zipfile} 和 @ref{101,,tarfile} 模块。

@geindex make_archive() (在 shutil 模块中)
@anchor{library/shutil shutil make_archive}@anchor{21b}
@deffn {函数} shutil.make_archive (base_name, format[, root_dir[, base_dir[, verbose[, dry_run[, owner[, group[, logger]]]]]]])

创建一个归档文件（例如 zip 或 tar）并返回其名称。

@emph{base_name} 是要创建的文件名称，包括路径，去除任何特定格式的扩展名。 @emph{format} 是归档格式：为 "zip" (如果 @ref{144,,zlib} 模块可用), "tar", "gztar" (如果 @ref{144,,zlib} 模块可用), "bztar" (如果 @ref{14,,bz2} 模块可用) 或 "xztar" (如果 @ref{ad,,lzma} 模块可用) 中的一个。

@emph{root_dir} 是一个目录，它将作为归档文件的根目录，归档中的所有路径都将是它的相对路径；例如，我们通常会在创建归档之前用 chdir 命令切换到 @emph{root_dir}。

@emph{base_dir} 是我们要执行归档的起始目录；也就是说 @emph{base_dir} 将成为归档中所有文件和目录共有的路径前缀。 @emph{base_dir} 必须相对于 @emph{root_dir} 给出。 请参阅 @ref{1c24,,使用 base_dir 的归档程序示例} 了解如何同时使用 @emph{base_dir} 和 @emph{root_dir}。

@emph{root_dir} 和 @emph{base_dir} 默认均为当前目录。

如果 @emph{dry_run} 为真值，则不会创建归档文件，但将要被执行的操作会被记录到 @emph{logger}。

@emph{owner} 和 @emph{group} 将在创建 tar 归档文件时被使用。 默认会使用当前的所有者和分组。

@emph{logger} 必须是一个兼容 
@geindex Python 提高建议; PEP 282
PEP 282@footnote{https://www.python.org/dev/peps/pep-0282} 的对象，通常为 @ref{39f,,logging.Logger} 的实例。

@emph{verbose} 参数已不再使用并进入弃用状态。

引发一个 @ref{12d0,,审计事件} @code{shutil.make_archive} 并附带参数 @code{base_name}, @code{format}, @code{root_dir}, @code{base_dir}。


在 3.8 版更改: 现在对于通过 @code{format="tar"} 创建的归档文件将使用新式的 pax (POSIX.1-2001) 格式而非旧式的 GNU 格式。

@end deffn

@geindex get_archive_formats() (在 shutil 模块中)
@anchor{library/shutil shutil get_archive_formats}@anchor{1c25}
@deffn {函数} shutil.get_archive_formats ()

返回支持的归档格式列表。 所返回序列中的每个元素为一个元组 @code{(name, description)}。

默认情况下 @ref{e9,,shutil} 提供以下格式:


@itemize -

@item 
@emph{zip}: ZIP 文件（如果 @ref{144,,zlib} 模块可用）。

@item 
@emph{tar}: 未压缩的 tar 文件。 对于新归档文件将使用 POSIX.1-2001 pax 格式。

@item 
@emph{gztar}: gzip 压缩的 tar 文件（如果 @ref{144,,zlib} 模块可用）。

@item 
@emph{bztar}: bzip2 压缩的 tar 文件（如果 @ref{14,,bz2} 模块可用）。

@item 
@emph{xztar}: xz 压缩的 tar 文件（如果 @ref{ad,,lzma} 模块可用）。
@end itemize

你可以通过使用 @ref{1c26,,register_archive_format()} 注册新的格式或为任何现有格式提供你自己的归档器。
@end deffn

@geindex register_archive_format() (在 shutil 模块中)
@anchor{library/shutil shutil register_archive_format}@anchor{1c26}
@deffn {函数} shutil.register_archive_format (name, function[, extra_args[, description]])

为 @emph{name} 格式注册一个归档器。

@emph{function} 是将被用来解包归档文件的可调用对象。 该可调用对象将接收要创建文件的 @emph{base_name}，再加上要归档内容的 @emph{base_dir} (其默认值为 @ref{1b84,,os.curdir})。 更多参数会被作为关键字参数传入: @emph{owner}, @emph{group}, @emph{dry_run} 和 @emph{logger} (与向 @ref{21b,,make_archive()} 传入的参数一致)。

如果给出了 @emph{extra_args}，则其应为一个 @code{(name, value)} 对的序列，将在归档器可调用对象被使用时作为附加的关键字参数。

@emph{description} 由 @ref{1c25,,get_archive_formats()} 使用，它将返回归档器的列表。 默认值为一个空字符串。
@end deffn

@geindex unregister_archive_format() (在 shutil 模块中)
@anchor{library/shutil shutil unregister_archive_format}@anchor{1c27}
@deffn {函数} shutil.unregister_archive_format (name)

从支持的格式中移除归档格式 @emph{name}。
@end deffn

@geindex unpack_archive() (在 shutil 模块中)
@anchor{library/shutil shutil unpack_archive}@anchor{b90}
@deffn {函数} shutil.unpack_archive (filename[, extract_dir[, format]])

解包一个归档文件。 @emph{filename} 是归档文件的完整路径。

@emph{extract_dir} 是归档文件解包的目标目录名称。 如果未提供，则将使用当前工作目录。

@emph{format} 是归档格式：应为 "zip", "tar", "gztar", "bztar" 或 "xztar" 之一。 或者任何通过 @ref{1c28,,register_unpack_format()} 注册的其他格式。 如果未提供，@ref{b90,,unpack_archive()} 将使用归档文件的扩展名来检查是否注册了对应于该扩展名的解包器。 在未找到任何解包器的情况下，将引发 @ref{1fb,,ValueError}。

引发一个 @ref{12d0,,审计事件} @code{shutil.unpack_archive} 附带参数 @code{filename}, @code{extract_dir}, @code{format}。


在 3.7 版更改: 接受一个 @ref{363,,path-like object} 作为 @emph{filename} 和 @emph{extract_dir}。

@end deffn

@geindex register_unpack_format() (在 shutil 模块中)
@anchor{library/shutil shutil register_unpack_format}@anchor{1c28}
@deffn {函数} shutil.register_unpack_format (name, extensions, function[, extra_args[, description]])

注册一个解包格式。 @emph{name} 为格式名称而 @emph{extensions} 为对应于该格式的扩展名列表，例如 Zip 文件的扩展名为 @code{.zip}。

@emph{function} 是将被用来解包归档文件的可调用对象。 该可调用对象将接受归档文件的路径，加上该归档文件要被解包的目标目录。

如果提供了 @emph{extra_args}，则其应为一个 @code{(name, value)} 元组的序列，将被作为关键字参数传递给该可调用对象。

可以提供 @emph{description} 来描述该格式，它将被 @ref{1c29,,get_unpack_formats()} 返回。
@end deffn

@geindex unregister_unpack_format() (在 shutil 模块中)
@anchor{library/shutil shutil unregister_unpack_format}@anchor{1c2a}
@deffn {函数} shutil.unregister_unpack_format (name)

撤销注册一个解包格式。 @emph{name} 为格式的名称。
@end deffn

@geindex get_unpack_formats() (在 shutil 模块中)
@anchor{library/shutil shutil get_unpack_formats}@anchor{1c29}
@deffn {函数} shutil.get_unpack_formats ()

返回所有已注册的解包格式列表。 所返回序列中的每个元素为一个元组 @code{(name, extensions, description)}。

默认情况下 @ref{e9,,shutil} 提供以下格式:


@itemize -

@item 
@emph{zip}: ZIP 文件（只有在相应模块可用时才能解包压缩文件）。

@item 
@emph{tar}: 未压缩的 tar 文件。

@item 
@emph{gztar}: gzip 压缩的 tar 文件（如果 @ref{144,,zlib} 模块可用）。

@item 
@emph{bztar}: bzip2 压缩的 tar 文件（如果 @ref{14,,bz2} 模块可用）。

@item 
@emph{xztar}: xz 压缩的 tar 文件（如果 @ref{ad,,lzma} 模块可用）。
@end itemize

你可以通过使用 @ref{1c28,,register_unpack_format()} 注册新的格式或为任何现有格式提供你自己的解包器。
@end deffn

@menu
* 归档程序示例:: 
* 使用 base_dir 的归档程序示例:: 

@end menu

@node 归档程序示例,使用 base_dir 的归档程序示例,,归档操作
@anchor{library/shutil archiving-example}@anchor{1c2b}@anchor{library/shutil shutil-archiving-example}@anchor{1c2c}
@subsubsection 归档程序示例


在这个示例中，我们创建了一个 gzip 压缩的 tar 归档文件，其中包含用户的 @code{.ssh} 目录下的所有文件:

@example
>>> from shutil import make_archive
>>> import os
>>> archive_name = os.path.expanduser(os.path.join('~', 'myarchive'))
>>> root_dir = os.path.expanduser(os.path.join('~', '.ssh'))
>>> make_archive(archive_name, 'gztar', root_dir)
'/Users/tarek/myarchive.tar.gz'
@end example

结果归档文件中包含有:

@example
$ tar -tzvf /Users/tarek/myarchive.tar.gz
drwx------ tarek/staff       0 2010-02-01 16:23:40 ./
-rw-r--r-- tarek/staff     609 2008-06-09 13:26:54 ./authorized_keys
-rwxr-xr-x tarek/staff      65 2008-06-09 13:26:54 ./config
-rwx------ tarek/staff     668 2008-06-09 13:26:54 ./id_dsa
-rwxr-xr-x tarek/staff     609 2008-06-09 13:26:54 ./id_dsa.pub
-rw------- tarek/staff    1675 2008-06-09 13:26:54 ./id_rsa
-rw-r--r-- tarek/staff     397 2008-06-09 13:26:54 ./id_rsa.pub
-rw-r--r-- tarek/staff   37192 2010-02-06 18:23:10 ./known_hosts
@end example

@node 使用 base_dir 的归档程序示例,,归档程序示例,归档操作
@anchor{library/shutil archiving-example-with-base-dir}@anchor{1c2d}@anchor{library/shutil shutil-archiving-example-with-basedir}@anchor{1c24}
@subsubsection 使用 @emph{base_dir} 的归档程序示例


在这个例子中，与 @ref{1c2c,,上面的例子} 类似，我们演示了如何使用 @ref{21b,,make_archive()}，但这次是使用 @emph{base_dir}。 我们现在具有如下的目录结构:

@example
$ tree tmp
tmp
└── root
    └── structure
        ├── content
            └── please_add.txt
        └── do_not_add.txt
@end example

在最终的归档中，应当会包括 @code{please_add.txt}，但不应当包括 @code{do_not_add.txt}。 因此我们使用以下代码:

@example
>>> from shutil import make_archive
>>> import os
>>> archive_name = os.path.expanduser(os.path.join('~', 'myarchive'))
>>> make_archive(
...     archive_name,
...     'tar',
...     root_dir='tmp/root',
...     base_dir='structure/content',
... )
'/Users/tarek/my_archive.tar'
@end example

列出结果归档中的文件我们将会得到:

@example
$ python -m tarfile -l /Users/tarek/myarchive.tar
structure/content/
structure/content/please_add.txt
@end example

@node 查询输出终端的尺寸,,归档操作,shutil --- 高阶文件操作
@anchor{library/shutil querying-the-size-of-the-output-terminal}@anchor{1c2e}
@subsubsection 查询输出终端的尺寸


@geindex get_terminal_size() (在 shutil 模块中)
@anchor{library/shutil shutil get_terminal_size}@anchor{a45}
@deffn {函数} shutil.get_terminal_size (fallback=(columns, lines))

获取终端窗口的尺寸。

对于两个维度中的每一个，会分别检查环境变量 @code{COLUMNS} 和 @code{LINES}。 如果定义了这些变量并且其值为正整数，则将使用这些值。

如果未定义 @code{COLUMNS} 或 @code{LINES}，这是通常的情况，则连接到 @ref{1c2f,,sys.__stdout__} 的终端将通过发起调用 @ref{a44,,os.get_terminal_size()} 被查询。

如果由于系统不支持查询，或是由于我们未连接到某个终端而导致查询终端尺寸不成功，则会使用在 @code{fallback} 形参中给出的值。 @code{fallback} 默认为 @code{(80, 24)}，这是许多终端模拟器所使用的默认尺寸。

返回的值是一个 @ref{1c30,,os.terminal_size} 类型的具名元组。

另请参阅: The Single UNIX Specification, Version 2, Other Environment Variables@footnote{http://pubs.opengroup.org/onlinepubs/7908799/xbd/envvar.html#tag_002_003}.


3.3 新版功能.

@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{c4,,os}

操作系统接口，包括处理比 Python @ref{b3b,,文件对象} 更低级别文件的功能。

@item 模块 @ref{a1,,io}

Python的内置 I/O 库，包括抽象类和一些具体的类，如文件 I/O 。

@item 内置函数 @ref{4ea,,open()}

使用 Python 打开文件进行读写的标准方法。
@end table


@node 数据持久化,数据压缩和存档,文件和目录访问,Python 标准库
@anchor{library/persistence doc}@anchor{1c31}@anchor{library/persistence data-persistence}@anchor{1c32}@anchor{library/persistence other-environment-variables}@anchor{1c33}@anchor{library/persistence persistence}@anchor{1c34}
@section 数据持久化


本章中描述的模块支持在磁盘上以持久形式存储 Python 数据。 @ref{ca,,pickle} 和 @ref{b0,,marshal} 模块可以将许多 Python 数据类型转换为字节流，然后从字节中重新创建对象。 各种与 DBM 相关的模块支持一系列基于散列的文件格式，这些格式存储字符串到其他字符串的映射。

本章中描述的模块列表是：

@menu
* pickle: pickle --- Python 对象序列化. Python 对象序列化
* copyreg: copyreg --- 注册配合 pickle 模块使用的函数. 注册配合 pickle 模块使用的函数
* shelve: shelve --- Python 对象持久化. Python 对象持久化
* marshal: marshal --- 内部 Python 对象序列化. 内部 Python 对象序列化
* dbm: dbm --- Unix "数据库" 接口. Unix "数据库" 接口
* sqlite3: sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块. SQLite 数据库 DB-API 2.0 接口模块

@end menu

@node pickle --- Python 对象序列化,copyreg --- 注册配合 pickle 模块使用的函数,,数据持久化
@anchor{library/pickle doc}@anchor{1c35}@anchor{library/pickle module-pickle}@anchor{ca}@anchor{library/pickle pickle-python-object-serialization}@anchor{1c36}
@subsection @code{pickle} --- Python 对象序列化


@geindex pickle (模块)

@strong{源代码：} Lib/pickle.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pickle.py}

@geindex persistence
@geindex persistent; objects
@geindex serializing; objects
@geindex marshalling; objects
@geindex flattening; objects
@geindex pickling; objects


__________________________________________________________________


模块 @ref{ca,,pickle} 实现了对一个 Python 对象结构的二进制序列化和反序列化。 @emph{"pickling"} 是将 Python 对象及其所拥有的层次结构转化为一个字节流的过程，而 @emph{"unpickling"} 是相反的操作，会将（来自一个 @ref{1c37,,binary file} 或者 @ref{5e3,,bytes-like object} 的）字节流转化回一个对象层次结构。 pickling（和 unpickling）也被称为“序列化”, “编组” @footnote{@w{(1)} 
不要把它与 @ref{b0,,marshal} 模块混淆。
} 或者 “平面化”。而为了避免混乱，此处采用术语 “封存 (pickling)” 和 “解封 (unpickling)”。

@cartouche
@quotation 警告 
@code{pickle} 模块**并不安全**。你只应该对你信任的数据进行unpickle操作。

构建恶意的 pickle 数据来**在解封时执行任意代码**是可能的。绝对不要对不信任来源的数据和可能被篡改过的数据进行解封。

请考虑使用 @ref{8f,,hmac} 来对数据进行签名，确保数据没有被篡改。

在你处理不信任数据时，更安全的序列化格式如 @ref{a4,,json} 可能更为适合。参见  @ref{1c38,,与 json 模块的比较} 。
@end quotation
@end cartouche

@menu
* 与其他 Python 模块间的关系:: 
* 数据流格式:: 
* 模块接口:: 
* 可以被封存/解封的对象:: 
* 封存类实例:: 
* 类型，函数和其他对象的自定义归约:: 
* 外部缓冲区:: 
* 限制全局变量:: 
* 性能: 性能<2>. 
* 例子: 例子<4>. 

@end menu

@node 与其他 Python 模块间的关系,数据流格式,,pickle --- Python 对象序列化
@anchor{library/pickle relationship-to-other-python-modules}@anchor{1c39}
@subsubsection 与其他 Python 模块间的关系


@menu
* 与 marshal 间的关系:: 
* 与 json 模块的比较:: 

@end menu

@node 与 marshal 间的关系,与 json 模块的比较,,与其他 Python 模块间的关系
@anchor{library/pickle comparison-with-marshal}@anchor{1c3a}
@subsubsection 与 @code{marshal} 间的关系


Python 有一个更原始的序列化模块称为 @ref{b0,,marshal}，但一般地 @ref{ca,,pickle} 应该是序列化 Python 对象时的首选。@ref{b0,,marshal} 存在主要是为了支持 Python 的 @code{.pyc} 文件.

@ref{ca,,pickle} 模块与 @ref{b0,,marshal} 在如下几方面显著地不同：


@itemize *

@item 
@ref{ca,,pickle} 模块会跟踪已被序列化的对象，所以该对象之后再次被引用时不会再次被序列化。@ref{b0,,marshal} 不会这么做。

这隐含了递归对象和共享对象。递归对象指包含对自己的引用的对象。这种对象并不会被 marshal 接受，并且实际上尝试 marshal 递归对象会让你的 Python 解释器崩溃。对象共享发生在对象层级中存在多处引用同一对象时。@ref{ca,,pickle} 只会存储这些对象一次，并确保其他的引用指向同一个主副本。共享对象将保持共享，这可能对可变对象非常重要。

@item 
@ref{b0,,marshal} 不能被用于序列化用户定义类及其实例。@ref{ca,,pickle} 能够透明地存储并保存类实例，然而此时类定义必须能够从与被存储时相同的模块被引入。

@item 
同样用于序列化的 @ref{b0,,marshal} 格式不保证数据能移植到不同的 Python 版本中。因为它的主要任务是支持 @code{.pyc} 文件，必要时会以破坏向后兼容的方式更改这种序列化格式，为此 Python 的实现者保留了更改格式的权利。@ref{ca,,pickle} 序列化格式可以在不同版本的 Python 中实现向后兼容，前提是选择了合适的 pickle 协议。如果你的数据要在 Python 2 与 Python 3 之间跨越传递，封存和解封的代码在 2 和 3 之间也是不同的。
@end itemize

@node 与 json 模块的比较,,与 marshal 间的关系,与其他 Python 模块间的关系
@anchor{library/pickle comparison-with-json}@anchor{1c38}@anchor{library/pickle id2}@anchor{1c3b}
@subsubsection 与 @code{json} 模块的比较


Pickle 协议和 JSON (JavaScript Object Notation)@footnote{http://json.org} 间有着本质的不同：


@itemize *

@item 
JSON 是一个文本序列化格式（它输出 unicode 文本，尽管在大多数时候它会接着以 @code{utf-8} 编码），而 pickle 是一个二进制序列化格式；

@item 
JSON 是我们可以直观阅读的，而 pickle 不是；

@item 
JSON是可互操作的，在Python系统之外广泛使用，而pickle则是Python专用的；

@item 
默认情况下，JSON 只能表示 Python 内置类型的子集，不能表示自定义的类；但 pickle 可以表示大量的 Python 数据类型（可以合理使用 Python 的对象内省功能自动地表示大多数类型，复杂情况可以通过实现 @ref{1c3c,,specific object APIs} 来解决）。

@item 
不像pickle，对一个不信任的JSON进行反序列化的操作本身不会造成任意代码执行漏洞。
@end itemize


@subsubheading 参见


@ref{a4,,json} 模块:一个允许JSON序列化和反序列化的标准库模块


@node 数据流格式,模块接口,与其他 Python 模块间的关系,pickle --- Python 对象序列化
@anchor{library/pickle data-stream-format}@anchor{1c3d}@anchor{library/pickle pickle-protocols}@anchor{569}
@subsubsection 数据流格式


@geindex External Data Representation

@ref{ca,,pickle} 所使用的数据格式仅可用于 Python。这样做的好处是没有外部标准给该格式强加限制，比如 JSON 或 XDR（不能表示共享指针）标准；但这也意味着非 Python 程序可能无法重新读取 pickle 封存的 Python 对象。

默认情况下，@ref{ca,,pickle} 格式使用相对紧凑的二进制来存储。如果需要让文件更小，可以高效地 @ref{1c3e,,压缩} 由 pickle 封存的数据。

@ref{cb,,pickletools} 模块包含了相应的工具用于分析 @ref{ca,,pickle} 生成的数据流。@ref{cb,,pickletools} 源码中包含了对 pickle 协议使用的操作码的大量注释。

当前共有 6 种不同的协议可用于封存操作。 使用的协议版本越高，读取所生成 pickle 对象所需的 Python 版本就要越新。


@itemize *

@item 
v0 版协议是原始的“人类可读”协议，并且向后兼容早期版本的 Python。

@item 
v1 版协议是较早的二进制格式，它也与早期版本的 Python 兼容。

@item 
v2 版协议是在 Python 2.3 中引入的。它为存储 @ref{1c3f,,new-style class} 提供了更高效的机制。欲了解有关第 2 版协议带来的改进，请参阅 
@geindex Python 提高建议; PEP 307
PEP 307@footnote{https://www.python.org/dev/peps/pep-0307}。

@item 
v3 版协议是在 Python 3.0 中引入的。 它显式地支持 @ref{32a,,bytes} 字节对象，不能使用 Python 2.x 解封。这是 Python 3.0-3.7 的默认协议。

@item 
v4 版协议添加于 Python 3.4。它支持存储非常大的对象，能存储更多种类的对象，还包括一些针对数据格式的优化。它是Python 3.8使用的默认协议。有关第 4 版协议带来改进的信息，请参阅 
@geindex Python 提高建议; PEP 3154
PEP 3154@footnote{https://www.python.org/dev/peps/pep-3154}。

@item 
第 5 版协议是在 Python 3.8 中加入的。 它增加了对带外数据的支持，并可加速带内数据处理。 请参阅 
@geindex Python 提高建议; PEP 574
PEP 574@footnote{https://www.python.org/dev/peps/pep-0574} 了解第 5 版协议所带来的改进的详情。
@end itemize

@cartouche
@quotation 注解 
序列化是一种比持久化更底层的概念，虽然 @ref{ca,,pickle} 读取和写入的是文件对象，但它不处理持久对象的命名问题，也不处理对持久对象的并发访问（甚至更复杂）的问题。@ref{ca,,pickle} 模块可以将复杂对象转换为字节流，也可以将字节流转换为具有相同内部结构的对象。处理这些字节流最常见的做法是将它们写入文件，但它们也可以通过网络发送或存储在数据库中。@ref{e7,,shelve} 模块提供了一个简单的接口，用于在 DBM 类型的数据库文件上封存和解封对象。
@end quotation
@end cartouche

@node 模块接口,可以被封存/解封的对象,数据流格式,pickle --- Python 对象序列化
@anchor{library/pickle module-interface}@anchor{1c40}
@subsubsection 模块接口


要序列化某个包含层次结构的对象，只需调用 @ref{df8,,dumps()} 函数即可。同样，要反序列化数据流，可以调用 @ref{5be,,loads()} 函数。但是，如果要对序列化和反序列化加以更多的控制，可以分别创建 @ref{20d,,Pickler} 或 @ref{1c41,,Unpickler} 对象。

@ref{ca,,pickle} 模块包含了以下常量：

@geindex HIGHEST_PROTOCOL() (在 pickle 模块中)
@anchor{library/pickle pickle HIGHEST_PROTOCOL}@anchor{df9}
@deffn {数据} pickle.HIGHEST_PROTOCOL

整数，可用的最高 @ref{569,,协议版本}。此值可以作为 @emph{协议} 值传递给 @ref{1c42,,dump()} 和 @ref{df8,,dumps()} 函数，以及 @ref{20d,,Pickler} 的构造函数。
@end deffn

@geindex DEFAULT_PROTOCOL() (在 pickle 模块中)
@anchor{library/pickle pickle DEFAULT_PROTOCOL}@anchor{1c43}
@deffn {数据} pickle.DEFAULT_PROTOCOL

整数，用于 pickle 数据的默认 @ref{569,,协议版本}。它可能小于 @ref{df9,,HIGHEST_PROTOCOL}。当前默认协议是 v4，它在 Python 3.4 中首次引入，与之前的版本不兼容。


在 3.0 版更改: 默认协议版本是 3。



在 3.8 版更改: 默认协议版本是 4。

@end deffn

@ref{ca,,pickle} 模块提供了以下方法，让封存过程更加方便：

@geindex dump() (在 pickle 模块中)
@anchor{library/pickle pickle dump}@anchor{1c42}
@deffn {函数} pickle.dump (obj, file, protocol=None, *, fix_imports=True, buffer_callback=None)

将对象 @emph{obj} 封存以后的对象写入已打开的 @ref{b3b,,file object} @emph{file}。它等同于 @code{Pickler(file, protocol).dump(obj)}。

参数 @emph{file}、@emph{protocol}、@emph{fix_imports} 和 @emph{buffer_callback} 的含义与它们在 @ref{20d,,Pickler} 的构造函数中的含义相同。


在 3.8 版更改: 加入了 @emph{buffer_callback} 参数。

@end deffn

@geindex dumps() (在 pickle 模块中)
@anchor{library/pickle pickle dumps}@anchor{df8}
@deffn {函数} pickle.dumps (obj, protocol=None, *, fix_imports=True, buffer_callback=None)

将 @emph{obj} 封存以后的对象作为 @ref{32a,,bytes} 类型直接返回，而不是将其写入到文件。

参数 @emph{protocol}、@emph{fix_imports} 和 @emph{buffer_callback} 的含义与它们在 @ref{20d,,Pickler} 的构造函数中的含义相同。


在 3.8 版更改: 加入了 @emph{buffer_callback} 参数。

@end deffn

@geindex load() (在 pickle 模块中)
@anchor{library/pickle pickle load}@anchor{5bd}
@deffn {函数} pickle.load (file, *, fix_imports=True, encoding="ASCII", errors="strict", buffers=None)

从已打开的 @ref{b3b,,file object} @emph{文件} 中读取封存后的对象，重建其中特定对象的层次结构并返回。它相当于 @code{Unpickler(file).load()}。

Pickle 协议版本是自动检测出来的，所以不需要参数来指定协议。封存对象以外的其他字节将被忽略。

参数 @emph{file}、@emph{fix_imports}、@emph{encoding}、@emph{errors}、@emph{strict} 和 @emph{buffers} 的含义与它们在 @ref{1c41,,Unpickler} 的构造函数中的含义相同。


在 3.8 版更改: 加入了 @emph{buffers} 参数。

@end deffn

@geindex loads() (在 pickle 模块中)
@anchor{library/pickle pickle loads}@anchor{5be}
@deffn {函数} pickle.loads (data, *, fix_imports=True, encoding="ASCII", errors="strict", buffers=None)

重建并返回一个对象的封存表示形式 @emph{data} 的对象层级结构。 @emph{data} 必须为 @ref{5e3,,bytes-like object}。

Pickle 协议版本是自动检测出来的，所以不需要参数来指定协议。封存对象以外的其他字节将被忽略。

参数 @emph{file}、@emph{fix_imports}、@emph{encoding}、@emph{errors}、@emph{strict} 和 @emph{buffers} 的含义与它们在 @ref{1c41,,Unpickler} 的构造函数中的含义相同。


在 3.8 版更改: 加入了 @emph{buffers} 参数。

@end deffn

@ref{ca,,pickle} 模块定义了以下 3 个异常：

@geindex PickleError
@anchor{library/pickle pickle PickleError}@anchor{1c44}
@deffn {例外} pickle.PickleError

其他 pickle 异常的基类。它是 @ref{1a9,,Exception} 的一个子类。
@end deffn

@geindex PicklingError
@anchor{library/pickle pickle PicklingError}@anchor{1c45}
@deffn {例外} pickle.PicklingError

当 @ref{20d,,Pickler} 遇到无法解封的对象时抛出此错误。它是 @ref{1c44,,PickleError} 的子类。

参考 @ref{1c46,,可以被封存/解封的对象} 来了解哪些对象可以被封存。
@end deffn

@geindex UnpicklingError
@anchor{library/pickle pickle UnpicklingError}@anchor{1c47}
@deffn {例外} pickle.UnpicklingError

当解封出错时抛出此异常，例如数据损坏或对象不安全。它是 @ref{1c44,,PickleError} 的子类。

注意，解封时可能还会抛出其他异常，包括（但不限于） AttributeError、EOFError、ImportError 和 IndexError。
@end deffn

@ref{ca,,pickle} 模块包含了 3 个类，@ref{20d,,Pickler}、@ref{1c41,,Unpickler} 和 @ref{1c48,,PickleBuffer}：

@geindex Pickler (pickle 中的类)
@anchor{library/pickle pickle Pickler}@anchor{20d}
@deffn {类} pickle.Pickler (file, protocol=None, *, fix_imports=True, buffer_callback=None)

它接受一个二进制文件用于写入 pickle 数据流。

可选参数 @emph{protocol} 是一个整数，告知 pickler 使用指定的协议，可选择的协议范围从 0 到 @ref{df9,,HIGHEST_PROTOCOL}。如果没有指定，这一参数默认值为 @ref{1c43,,DEFAULT_PROTOCOL}。指定一个负数就相当于指定 @ref{df9,,HIGHEST_PROTOCOL}。

参数 @emph{file} 必须有一个 write() 方法，该 write() 方法要能接收字节作为其唯一参数。因此，它可以是一个打开的磁盘文件（用于写入二进制内容），也可以是一个 @ref{795,,io.BytesIO} 实例，也可以是满足这一接口的其他任何自定义对象。

如果 @emph{fix_imports} 为 True 且 @emph{protocol} 小于 3，pickle 将尝试将 Python 3 中的新名称映射到 Python 2 中的旧模块名称，因此 Python 2 也可以读取封存的数据流。

如果 @emph{buffer_callback} 为 None（默认情况），缓冲区视图（buffer view）将会作为 pickle 流的一部分被序列化到 @emph{file} 中。

如果 @emph{buffer_callback} 不为 None，那它可以用缓冲区视图调用任意次。如果某次调用返回了 False 值（例如 None），则给定的缓冲区是 @ref{1c49,,带外的}，否则缓冲区是带内的（例如保存在了 pickle 流里面）。

如果 @emph{buffer_callback} 不是 None 且 @emph{protocol} 是 None 或小于 5，就会出错。


在 3.8 版更改: 加入了 @emph{buffer_callback} 参数。


@geindex dump() (pickle.Pickler 方法)
@anchor{library/pickle pickle Pickler dump}@anchor{fcf}
@deffn {方法} dump (obj)

将 @emph{obj} 封存后的内容写入已打开的文件对象，该文件对象已经在构造函数中指定。
@end deffn

@geindex persistent_id() (pickle.Pickler 方法)
@anchor{library/pickle pickle Pickler persistent_id}@anchor{1c4a}
@deffn {方法} persistent_id (obj)

默认无动作，子类继承重载时使用。

如果 @ref{1c4a,,persistent_id()} 返回 @code{None}，@emph{obj} 会被照常 pickle。如果返回其他值，@ref{20d,,Pickler} 会将这个函数的返回值作为 @emph{obj} 的持久化 ID（Pickler 本应得到序列化数据流并将其写入文件，若此函数有返回值，则得到此函数的返回值并写入文件）。这个持久化 ID 的解释应当定义在 @ref{1c4b,,Unpickler.persistent_load()} 中（该方法定义还原对象的过程，并返回得到的对象）。注意，@ref{1c4a,,persistent_id()} 的返回值本身不能拥有持久化 ID。

参阅 @ref{1c4c,,持久化外部对象} 获取详情和使用示例。
@end deffn

@geindex dispatch_table (pickle.Pickler 属性)
@anchor{library/pickle pickle Pickler dispatch_table}@anchor{a64}
@deffn {属性} dispatch_table

Pickler 对象的 dispatch 表是 @ref{1c4d,,copyreg.pickle()} 中用到的 @emph{reduction 函数} 的注册。dispatch 表本身是一个 class 到其 reduction 函数的映射键值对。一个 reduction 函数只接受一个参数，就是其关联的 class，函数行为应当遵守 @ref{19b,,__reduce__()} 接口规范。

Pickler 对象默认并没有 @ref{a64,,dispatch_table} 属性，该对象默认使用 @ref{27,,copyreg} 模块中定义的全局 dispatch 表。如果要为特定 Pickler 对象自定义序列化过程，可以将 @ref{a64,,dispatch_table} 属性设置为类字典对象（dict-like object）。另外，如果 @ref{20d,,Pickler} 的子类设置了 @ref{a64,,dispatch_table} 属性，则该子类的实例会使用这个表作为默认的 dispatch 表。

参阅 @ref{1c4e,,Dispatch 表} 获取使用示例。


3.3 新版功能.

@end deffn

@geindex reducer_override() (pickle.Pickler 方法)
@anchor{library/pickle pickle Pickler reducer_override}@anchor{20e}
@deffn {方法} reducer_override (self, obj)

可以在 @ref{20d,,Pickler} 的子类中定义的特殊 reducer。此方法的优先级高于 @ref{a64,,dispatch_table} 中的任何 reducer。它应该与 @ref{19b,,__reduce__()} 方法遵循相同的接口，它也可以返回 @code{NotImplemented}，这将使用 @ref{a64,,dispatch_table} 里注册的 reducer 来封存 @code{obj}。

参阅 @ref{1c4f,,类型，函数和其他对象的自定义归约} 获取详细的示例。


3.8 新版功能.

@end deffn

@geindex fast (pickle.Pickler 属性)
@anchor{library/pickle pickle Pickler fast}@anchor{1c50}
@deffn {属性} fast

已弃用。设为 True 则启用快速模式。快速模式禁用了“备忘录” (memo) 的使用，即不生成多余的 PUT 操作码来加快封存过程。不应将其与自指 (self-referential) 对象一起使用，否则将导致 @ref{20d,,Pickler} 无限递归。

如果需要进一步提高 pickle 的压缩率，请使用 @ref{1c51,,pickletools.optimize()}。
@end deffn
@end deffn

@geindex Unpickler (pickle 中的类)
@anchor{library/pickle pickle Unpickler}@anchor{1c41}
@deffn {类} pickle.Unpickler (file, *, fix_imports=True, encoding="ASCII", errors="strict", buffers=None)

它接受一个二进制文件用于读取 pickle 数据流。

Pickle 协议版本是自动检测出来的，所以不需要参数来指定协议。

参数 @emph{file} 必须有三个方法，read() 方法接受一个整数参数，readinto() 方法接受一个缓冲区作为参数，readline() 方法不需要参数，这与 @ref{583,,io.BufferedIOBase} 里定义的接口是相同的。因此 @emph{file} 可以是一个磁盘上用于二进制读取的文件，也可以是一个 @ref{795,,io.BytesIO} 实例，也可以是满足这一接口的其他任何自定义对象。

可选的参数是 @emph{fix_imports}, @emph{encoding} 和 @emph{errors}，用于控制由Python 2 生成的 pickle 流的兼容性。如果 @emph{fix_imports} 为 True，则 pickle 将尝试将旧的 Python 2 名称映射到 Python 3 中对应的新名称。@emph{encoding} 和 @emph{errors} 参数告诉 pickle 如何解码 Python 2 存储的 8 位字符串实例；这两个参数默认分别为 'ASCII' 和 'strict'。@emph{encoding} 参数可置为 'bytes' 来将这些 8 位字符串实例读取为字节对象。读取 NumPy array 和 Python 2 存储的 @ref{194,,datetime}、@ref{193,,date} 和 @ref{4ed,,time} 实例时，请使用 @code{encoding='latin1'}。

如果 @emph{buffers} 为 None（默认值），则反序列化所需的所有数据都必须包含在 pickle 流中。这意味着在实例化 @ref{20d,,Pickler} 时（或调用 @ref{1c42,,dump()} 或 @ref{df8,,dumps()} 时），参数 @emph{buffer_callback} 为 None。

如果 @emph{buffers} 不为 None，则每次 pickle 流引用 @ref{1c49,,带外} 缓冲区视图时，消耗的对象都应该是可迭代的启用缓冲区的对象。这样的缓冲区应该按顺序地提供给 Pickler 对象的 @emph{buffer_callback} 方法。


在 3.8 版更改: 加入了 @emph{buffers} 参数。


@geindex load() (pickle.Unpickler 方法)
@anchor{library/pickle pickle Unpickler load}@anchor{1c52}
@deffn {方法} load ()

从构造函数中指定的文件对象里读取封存好的对象，重建其中特定对象的层次结构并返回。封存对象以外的其他字节将被忽略。
@end deffn

@geindex persistent_load() (pickle.Unpickler 方法)
@anchor{library/pickle pickle Unpickler persistent_load}@anchor{1c4b}
@deffn {方法} persistent_load (pid)

默认抛出 @ref{1c47,,UnpicklingError} 异常。

如果定义了此方法，@ref{1c4b,,persistent_load()} 应当返回持久化 ID @emph{pid} 所指定的对象。 如果遇到无效的持久化 ID，则应当引发 @ref{1c47,,UnpicklingError}。

参阅 @ref{1c4c,,持久化外部对象} 获取详情和使用示例。
@end deffn

@geindex find_class() (pickle.Unpickler 方法)
@anchor{library/pickle pickle Unpickler find_class}@anchor{1c53}
@deffn {方法} find_class (module, name)

如有必要，导入 @emph{module} 模块并返回其中名叫 @emph{name} 的对象，其中 @emph{module} 和 @emph{name} 参数都是 @ref{329,,str} 对象。注意，不要被这个函数的名字迷惑， @ref{1c53,,find_class()} 同样可以用来导入函数。

子类可以重载此方法，来控制加载对象的类型和加载对象的方式，从而尽可能降低安全风险。参阅 @ref{1c54,,限制全局变量} 获取更详细的信息。

引发一个 @ref{12d0,,审计事件} @code{pickle.find_class} 附带参数 @code{module}、@code{name}。
@end deffn
@end deffn

@geindex PickleBuffer (pickle 中的类)
@anchor{library/pickle pickle PickleBuffer}@anchor{1c48}
@deffn {类} pickle.PickleBuffer (buffer)

缓冲区的包装器 (wrapper)，缓冲区中包含着可封存的数据。@emph{buffer} 必须是一个 @ref{15d6,,buffer-providing} 对象，比如 @ref{5e3,,bytes-like object} 或多维数组。

@ref{1c48,,PickleBuffer} 本身就可以生成缓冲区对象，因此可以将其传递给需要缓冲区生成器的其他 API，比如 @ref{25c,,memoryview}。

@ref{1c48,,PickleBuffer} 对象只能用 pickle 版本 5 及以上协议进行序列化。它们符合 @ref{1c49,,带外序列化} 的条件。


3.8 新版功能.


@geindex raw() (pickle.PickleBuffer 方法)
@anchor{library/pickle pickle PickleBuffer raw}@anchor{1c55}
@deffn {方法} raw ()

返回该缓冲区底层内存区域的 @ref{25c,,memoryview}。 返回的对象是一维的、C 连续布局的 memoryview，格式为 @code{B} (无符号字节)。 如果缓冲区既不是 C 连续布局也不是 Fortran 连续布局的，则抛出 @ref{1699,,BufferError} 异常。
@end deffn

@geindex release() (pickle.PickleBuffer 方法)
@anchor{library/pickle pickle PickleBuffer release}@anchor{1c56}
@deffn {方法} release ()

释放由 PickleBuffer 占用的底层缓冲区。
@end deffn
@end deffn

@node 可以被封存/解封的对象,封存类实例,模块接口,pickle --- Python 对象序列化
@anchor{library/pickle pickle-picklable}@anchor{1c46}@anchor{library/pickle what-can-be-pickled-and-unpickled}@anchor{1c57}
@subsubsection 可以被封存/解封的对象


下列类型可以被封存：


@itemize *

@item 
@code{None}、@code{True} 和 @code{False}

@item 
整数、浮点数、复数

@item 
str、byte、bytearray

@item 
只包含可封存对象的集合，包括 tuple、list、set 和 dict

@item 
定义在模块最外层的函数（使用 @ref{db7,,def} 定义，@ref{c28,,lambda} 函数则不可以）

@item 
定义在模块最外层的内置函数

@item 
定义在模块最外层的类

@item 
某些类实例，这些类的 @ref{4f6,,__dict__} 属性值或 @ref{dfa,,__getstate__()} 函数的返回值可以被封存（详情参阅 @ref{1c3c,,封存类实例} 这一段）。
@end itemize

尝试封存不能被封存的对象会抛出 @ref{1c45,,PicklingError} 异常，异常发生时，可能有部分字节已经被写入指定文件中。尝试封存递归层级很深的对象时，可能会超出最大递归层级限制，此时会抛出 @ref{62e,,RecursionError} 异常，可以通过 @ref{e74,,sys.setrecursionlimit()} 调整递归层级，不过请谨慎使用这个函数，因为可能会导致解释器崩溃。

注意，函数（内置函数或用户自定义函数）在被封存时，引用的是函数全名。@footnote{@w{(2)} 
这就是为什么 @ref{c28,,lambda} 函数不可以被封存：所有的匿名函数都有同一个名字：@code{<lambda>}。
} 这意味着只有函数所在的模块名，与函数名会被封存，函数体及其属性不会被封存。因此，在解封的环境中，函数所属的模块必须是可以被导入的，而且模块必须包含这个函数被封存时的名称，否则会抛出异常。@footnote{@w{(3)} 
抛出的异常有可能是 @ref{32d,,ImportError} 或 @ref{393,,AttributeError}，也可能是其他异常。
}

同样的，类也只封存名称，所以在解封环境中也有和函数相同的限制。注意，类体及其数据不会被封存，所以在下面的例子中类属性 @code{attr} 不会存在于解封后的环境中：

@example
class Foo:
    attr = 'A class attribute'

picklestring = pickle.dumps(Foo)
@end example

这些限制决定了为什么必须在一个模块的最外层定义可封存的函数和类。

类似的，在封存类的实例时，其类体和类数据不会跟着实例一起被封存，只有实例数据会被封存。这样设计是有目的的，在将来修复类中的错误、给类增加方法之后，仍然可以载入原来版本类实例的封存数据来还原该实例。如果你准备长期使用一个对象，可能会同时存在较多版本的类体，可以为对象添加版本号，这样就可以通过类的 @ref{19c,,__setstate__()} 方法将老版本转换成新版本。

@node 封存类实例,类型，函数和其他对象的自定义归约,可以被封存/解封的对象,pickle --- Python 对象序列化
@anchor{library/pickle pickle-inst}@anchor{1c3c}@anchor{library/pickle pickling-class-instances}@anchor{1c58}
@subsubsection 封存类实例


在本节中，我们描述了可用于定义、自定义和控制如何封存和解封类实例的通用流程。

通常，使一个实例可被封存不需要附加任何代码。Pickle 默认会通过 Python 的内省机制获得实例的类及属性。而当实例解封时，它的 @ref{d57,,__init__()} 方法通常 @emph{不会} 被调用。其默认动作是：先创建一个未初始化的实例，然后还原其属性，下面的代码展示了这种行为的实现机制：

@example
def save(obj):
    return (obj.__class__, obj.__dict__)

def load(cls, attributes):
    obj = cls.__new__(cls)
    obj.__dict__.update(attributes)
    return obj
@end example

类可以改变默认行为，只需定义以下一种或几种特殊方法：

@geindex __getnewargs_ex__() (object 方法)
@anchor{library/pickle object __getnewargs_ex__}@anchor{1c59}
@deffn {方法} object.__getnewargs_ex__ ()

对于使用第 2 版或更高版协议的 pickle，实现了 @ref{1c59,,__getnewargs_ex__()} 方法的类可以控制在解封时传给 @ref{883,,__new__()} 方法的参数。本方法必须返回一对 @code{(args, kwargs)} 用于构建对象，其中 @emph{args} 是表示位置参数的 tuple，而 @emph{kwargs} 是表示命名参数的 dict。它们会在解封时传递给 @ref{883,,__new__()} 方法。

如果类的 @ref{883,,__new__()} 方法只接受关键字参数，则应当实现这个方法。否则，为了兼容性，更推荐实现 @ref{6a8,,__getnewargs__()} 方法。


在 3.6 版更改: @ref{1c59,,__getnewargs_ex__()} 现在可用于第 2 和第 3 版协议。

@end deffn

@geindex __getnewargs__() (object 方法)
@anchor{library/pickle object __getnewargs__}@anchor{6a8}
@deffn {方法} object.__getnewargs__ ()

这个方法与上一个 @ref{1c59,,__getnewargs_ex__()} 方法类似，但仅支持位置参数。它要求返回一个 tuple 类型的 @code{args}，用于解封时传递给 @ref{883,,__new__()} 方法。

如果定义了 @ref{1c59,,__getnewargs_ex__()}，那么 @ref{6a8,,__getnewargs__()} 就不会被调用。


在 3.6 版更改: 在 Python 3.6 前，第 2、3 版协议会调用 @ref{6a8,,__getnewargs__()}，更高版本协议会调用 @ref{1c59,,__getnewargs_ex__()}。

@end deffn

@geindex __getstate__() (object 方法)
@anchor{library/pickle object __getstate__}@anchor{dfa}
@deffn {方法} object.__getstate__ ()

类还可以进一步控制其实例的封存过程。如果类定义了 @ref{dfa,,__getstate__()}，它就会被调用，其返回的对象是被当做实例内容来封存的，否则封存的是实例的 __dict__。如果 @ref{dfa,,__getstate__()} 未定义，实例的 @ref{4f6,,__dict__} 会被照常封存。
@end deffn

@geindex __setstate__() (object 方法)
@anchor{library/pickle object __setstate__}@anchor{19c}
@deffn {方法} object.__setstate__ (state)

当解封时，如果类定义了 @ref{19c,,__setstate__()}，就会在已解封状态下调用它。此时不要求实例的 state 对象必须是 dict。没有定义此方法的话，先前封存的 state 对象必须是 dict，且该 dict 内容会在解封时赋给新实例的 __dict__。

@cartouche
@quotation 注解 
如果 @ref{dfa,,__getstate__()} 返回 False，那么在解封时就不会调用 @ref{19c,,__setstate__()} 方法。
@end quotation
@end cartouche
@end deffn

参考 @ref{1c5a,,处理有状态的对象} 一段获取如何使用 @ref{dfa,,__getstate__()} 和 @ref{19c,,__setstate__()} 方法的更多信息。

@cartouche
@quotation 注解 
在解封时，实例的某些方法例如 @ref{313,,__getattr__()}, @ref{441,,__getattribute__()} 或 @ref{e25,,__setattr__()} 可能会被调用。 由于这些方法可能要求某些内部不变量为真值，因此该类型应当实现 @ref{883,,__new__()} 以建立这样的不变量，因为当解封一个实例时 @ref{d57,,__init__()} 并不会被调用。
@end quotation
@end cartouche

@geindex copy; protocol

可以看出，其实 pickle 并不直接调用上面的几个函数。事实上，这几个函数是复制协议的一部分，它们实现了 @ref{19b,,__reduce__()} 这一特殊接口。复制协议提供了统一的接口，用于在封存或复制对象的过程中取得所需数据。@footnote{@w{(4)} 
@ref{26,,copy} 模块使用这一协议实现浅层 (shallow) 和深层 (deep) 复制操作。
}

尽管这个协议功能很强，但是直接在类中实现 @ref{19b,,__reduce__()} 接口容易产生错误。因此，设计类时应当尽可能的使用高级接口（比如 @ref{1c59,,__getnewargs_ex__()}、@ref{dfa,,__getstate__()} 和 @ref{19c,,__setstate__()}）。后面仍然可以看到直接实现 @ref{19b,,__reduce__()} 接口的状况，可能别无他法，可能为了获得更好的性能，或者两者皆有之。

@geindex __reduce__() (object 方法)
@anchor{library/pickle object __reduce__}@anchor{19b}
@deffn {方法} object.__reduce__ ()

该接口当前定义如下。@ref{19b,,__reduce__()} 方法不带任何参数，并且应返回字符串或最好返回一个元组（返回的对象通常称为“reduce 值”）。

如果返回字符串，该字符串会被当做一个全局变量的名称。它应该是对象相对于其模块的本地名称，pickle 模块会搜索模块命名空间来确定对象所属的模块。这种行为常在单例模式使用。

如果返回的是元组，则应当包含 2 到 6 个元素，可选元素可以省略或设置为 @code{None}。每个元素代表的意义如下：

@c XXX Mention __newobj__ special-case?


@itemize *

@item 
一个可调用对象，该对象会在创建对象的最初版本时调用。

@item 
可调用对象的参数，是一个元组。如果可调用对象不接受参数，必须提供一个空元组。

@item 
可选元素，用于表示对象的状态，将被传给前述的 @ref{19c,,__setstate__()} 方法。 如果对象没有此方法，则这个元素必须是字典类型，并会被添加至 @ref{4f6,,__dict__} 属性中。

@item 
可选元素，一个返回连续项的迭代器（而不是序列）。这些项会被 @code{obj.append(item)} 逐个加入对象，或被 @code{obj.extend(list_of_items)} 批量加入对象。这个元素主要用于 list 的子类，也可以用于那些正确实现了 @code{append()} 和 @code{extend()} 方法的类。（具体是使用 @code{append()} 还是 @code{extend()} 取决于 pickle 协议版本以及待插入元素的项数，所以这两个方法必须同时被类支持。）

@item 
可选元素，一个返回连续键值对的迭代器（而不是序列）。这些键值对将会以 @code{obj[key] = value} 的方式存储于对象中。该元素主要用于 dict 子类，也可以用于那些实现了 @ref{c5b,,__setitem__()} 的类。

@item 
可选元素，一个带有 @code{(obj, state)} 签名的可调用对象。该可调用对象允许用户以编程方式控制特定对象的状态更新行为，而不是使用 @code{obj} 的静态 @ref{19c,,__setstate__()} 方法。如果此处不是 @code{None}，则此可调用对象的优先级高于 @code{obj} 的 @ref{19c,,__setstate__()}。


3.8 新版功能: 新增了元组的第 6 项，可选元素 @code{(obj, state)}。

@end itemize
@end deffn

@geindex __reduce_ex__() (object 方法)
@anchor{library/pickle object __reduce_ex__}@anchor{198d}
@deffn {方法} object.__reduce_ex__ (protocol)

作为替代选项，也可以实现 @ref{198d,,__reduce_ex__()} 方法。 此方法的唯一不同之处在于它应接受一个整型参数用于指定协议版本。 如果定义了这个函数，则会覆盖 @ref{19b,,__reduce__()} 的行为。 此外，@ref{19b,,__reduce__()} 方法会自动成为扩展版方法的同义词。 这个函数主要用于为以前的 Python 版本提供向后兼容的 reduce 值。
@end deffn

@menu
* 持久化外部对象:: 
* Dispatch 表:: 
* 处理有状态的对象:: 

@end menu

@node 持久化外部对象,Dispatch 表,,封存类实例
@anchor{library/pickle persistence-of-external-objects}@anchor{1c5b}@anchor{library/pickle pickle-persistent}@anchor{1c4c}
@subsubsection 持久化外部对象


@geindex persistent_id (pickle protocol)
@geindex persistent_load (pickle protocol)

为了获取对象持久化的利益， @ref{ca,,pickle} 模块支持引用已封存数据流之外的对象。 这样的对象是通过一个持久化 ID 来引用的，它应当是一个由字母数字类字符组成的字符串 (对于第 0 版协议) @footnote{@w{(5)} 
对字母数字类字符的限制是由于持久化 ID 在协议版本 0 中是由分行符来分隔的。 因此如果持久化 ID 中出现任何形式的分行符，封存结果就将变得无法读取。
} 或是一个任意对象 (用于任意新版协议)。

@ref{ca,,pickle} 模块不提供对持久化 ID 的解析工作，它将解析工作分配给用户定义的方法，分别是 pickler 中的 @ref{1c4a,,persistent_id()} 方法和 unpickler 中的 @ref{1c4b,,persistent_load()} 方法。

要通过持久化 ID 将外部对象封存，必须在 pickler 中实现 @ref{1c4a,,persistent_id()} 方法，该方法接受需要被封存的对象作为参数，返回一个 @code{None} 或返回该对象的持久化 ID。如果返回 @code{None}，该对象会被按照默认方式封存为数据流。如果返回字符串形式的持久化 ID，则会封存这个字符串并加上一个标记，这样 unpickler 才能将其识别为持久化 ID。

要解封外部对象，Unpickler 必须实现 @ref{1c4b,,persistent_load()} 方法，接受一个持久化 ID 对象作为参数并返回一个引用的对象。

下面是一个全面的例子，展示了如何使用持久化 ID 来封存外部对象。

@example
# Simple example presenting how persistent ID can be used to pickle
# external objects by reference.

import pickle
import sqlite3
from collections import namedtuple

# Simple class representing a record in our database.
MemoRecord = namedtuple("MemoRecord", "key, task")

class DBPickler(pickle.Pickler):

    def persistent_id(self, obj):
        # Instead of pickling MemoRecord as a regular class instance, we emit a
        # persistent ID.
        if isinstance(obj, MemoRecord):
            # Here, our persistent ID is simply a tuple, containing a tag and a
            # key, which refers to a specific record in the database.
            return ("MemoRecord", obj.key)
        else:
            # If obj does not have a persistent ID, return None. This means obj
            # needs to be pickled as usual.
            return None


class DBUnpickler(pickle.Unpickler):

    def __init__(self, file, connection):
        super().__init__(file)
        self.connection = connection

    def persistent_load(self, pid):
        # This method is invoked whenever a persistent ID is encountered.
        # Here, pid is the tuple returned by DBPickler.
        cursor = self.connection.cursor()
        type_tag, key_id = pid
        if type_tag == "MemoRecord":
            # Fetch the referenced record from the database and return it.
            cursor.execute("SELECT * FROM memos WHERE key=?", (str(key_id),))
            key, task = cursor.fetchone()
            return MemoRecord(key, task)
        else:
            # Always raises an error if you cannot return the correct object.
            # Otherwise, the unpickler will think None is the object referenced
            # by the persistent ID.
            raise pickle.UnpicklingError("unsupported persistent object")


def main():
    import io
    import pprint

    # Initialize and populate our database.
    conn = sqlite3.connect(":memory:")
    cursor = conn.cursor()
    cursor.execute("CREATE TABLE memos(key INTEGER PRIMARY KEY, task TEXT)")
    tasks = (
        'give food to fish',
        'prepare group meeting',
        'fight with a zebra',
        )
    for task in tasks:
        cursor.execute("INSERT INTO memos VALUES(NULL, ?)", (task,))

    # Fetch the records to be pickled.
    cursor.execute("SELECT * FROM memos")
    memos = [MemoRecord(key, task) for key, task in cursor]
    # Save the records using our custom DBPickler.
    file = io.BytesIO()
    DBPickler(file).dump(memos)

    print("Pickled records:")
    pprint.pprint(memos)

    # Update a record, just for good measure.
    cursor.execute("UPDATE memos SET task='learn italian' WHERE key=1")

    # Load the records from the pickle data stream.
    file.seek(0)
    memos = DBUnpickler(file, conn).load()

    print("Unpickled records:")
    pprint.pprint(memos)


if __name__ == '__main__':
    main()
@end example

@node Dispatch 表,处理有状态的对象,持久化外部对象,封存类实例
@anchor{library/pickle dispatch-tables}@anchor{1c5c}@anchor{library/pickle pickle-dispatch}@anchor{1c4e}
@subsubsection Dispatch 表


如果想对某些类进行自定义封存，而又不想在类中增加用于封存的代码，就可以创建带有特殊 dispatch 表的 pickler。

在 @ref{27,,copyreg} 模块的 @code{copyreg.dispatch_table} 中定义了全局 dispatch 表。因此，可以使用 @code{copyreg.dispatch_table} 修改后的副本作为自有 dispatch 表。

例如

@example
f = io.BytesIO()
p = pickle.Pickler(f)
p.dispatch_table = copyreg.dispatch_table.copy()
p.dispatch_table[SomeClass] = reduce_SomeClass
@end example

创建了一个带有自有 dispatch 表的 @ref{20d,,pickle.Pickler} 实例，它可以对 @code{SomeClass} 类进行特殊处理。另外，下列代码

@example
class MyPickler(pickle.Pickler):
    dispatch_table = copyreg.dispatch_table.copy()
    dispatch_table[SomeClass] = reduce_SomeClass
f = io.BytesIO()
p = MyPickler(f)
@end example

完成了相同的操作，但所有 @code{MyPickler} 的实例都会共用同一份 dispatch 表。使用 @ref{27,,copyreg} 模块实现的等效代码是

@example
copyreg.pickle(SomeClass, reduce_SomeClass)
f = io.BytesIO()
p = pickle.Pickler(f)
@end example

@node 处理有状态的对象,,Dispatch 表,封存类实例
@anchor{library/pickle handling-stateful-objects}@anchor{1c5d}@anchor{library/pickle pickle-state}@anchor{1c5a}
@subsubsection 处理有状态的对象


@geindex __getstate__() (copy protocol)
@geindex __setstate__() (copy protocol)

下面的示例展示了如何修改类在封存时的行为。其中 @code{TextReader} 类打开了一个文本文件，每次调用其 @code{readline()} 方法则返回行号和该行的字符。 在封存这个 @code{TextReader} 的实例时，@emph{除了} 文件对象，其他属性都会被保存。 当解封实例时，需要重新打开文件，然后从上次的位置开始继续读取。实现这些功能需要实现 @ref{19c,,__setstate__()} 和 @ref{dfa,,__getstate__()} 方法。

@example
class TextReader:
    """Print and number lines in a text file."""

    def __init__(self, filename):
        self.filename = filename
        self.file = open(filename)
        self.lineno = 0

    def readline(self):
        self.lineno += 1
        line = self.file.readline()
        if not line:
            return None
        if line.endswith('\n'):
            line = line[:-1]
        return "%i: %s" % (self.lineno, line)

    def __getstate__(self):
        # Copy the object's state from self.__dict__ which contains
        # all our instance attributes. Always use the dict.copy()
        # method to avoid modifying the original state.
        state = self.__dict__.copy()
        # Remove the unpicklable entries.
        del state['file']
        return state

    def __setstate__(self, state):
        # Restore instance attributes (i.e., filename and lineno).
        self.__dict__.update(state)
        # Restore the previously opened file's state. To do so, we need to
        # reopen it and read from it until the line count is restored.
        file = open(self.filename)
        for _ in range(self.lineno):
            file.readline()
        # Finally, save the file.
        self.file = file
@end example

使用方法如下所示：

@example
>>> reader = TextReader("hello.txt")
>>> reader.readline()
'1: Hello world!'
>>> reader.readline()
'2: I am line number two.'
>>> new_reader = pickle.loads(pickle.dumps(reader))
>>> new_reader.readline()
'3: Goodbye!'
@end example

@node 类型，函数和其他对象的自定义归约,外部缓冲区,封存类实例,pickle --- Python 对象序列化
@anchor{library/pickle custom-reduction-for-types-functions-and-other-objects}@anchor{1c5e}@anchor{library/pickle reducer-override}@anchor{1c4f}
@subsubsection 类型，函数和其他对象的自定义归约



3.8 新版功能.


有时，@ref{a64,,dispatch_table} 可能不够灵活。 特别是当我们想要基于对象类型以外的其他规则来对封存进行定制，或是当我们想要对函数和类的封存进行定制的时候。

对于那些情况，可能要基于 @ref{20d,,Pickler} 类进行子类化并实现 @ref{20e,,reducer_override()} 方法。 此方法可返回任意的归约元组 (参见 @ref{19b,,__reduce__()})。 它也可以选择返回 @code{NotImplemented} 来回退到传统行为。

如果同时定义了 @ref{a64,,dispatch_table} 和 @ref{20e,,reducer_override()}，则 @ref{20e,,reducer_override()} 方法具有优先权。

@cartouche
@quotation 注解 
出于性能理由，可能不会为以下对象调用 @ref{20e,,reducer_override()}: @code{None}, @code{True}, @code{False}, 以及 @ref{184,,int}, @ref{187,,float}, @ref{32a,,bytes}, @ref{329,,str}, @ref{1b8,,dict}, @ref{b68,,set}, @ref{be7,,frozenset}, @ref{262,,list} 和 @ref{478,,tuple} 的具体实例。
@end quotation
@end cartouche

以下是一个简单的例子，其中我们允许封存并重新构建一个给定的类:

@example
import io
import pickle

class MyClass:
    my_attribute = 1

class MyPickler(pickle.Pickler):
    def reducer_override(self, obj):
        """Custom reducer for MyClass."""
        if getattr(obj, "__name__", None) == "MyClass":
            return type, (obj.__name__, obj.__bases__,
                          @{'my_attribute': obj.my_attribute@})
        else:
            # For any other object, fallback to usual reduction
            return NotImplemented

f = io.BytesIO()
p = MyPickler(f)
p.dump(MyClass)

del MyClass

unpickled_class = pickle.loads(f.getvalue())

assert isinstance(unpickled_class, type)
assert unpickled_class.__name__ == "MyClass"
assert unpickled_class.my_attribute == 1
@end example

@node 外部缓冲区,限制全局变量,类型，函数和其他对象的自定义归约,pickle --- Python 对象序列化
@anchor{library/pickle out-of-band-buffers}@anchor{1c5f}@anchor{library/pickle pickle-oob}@anchor{1c49}
@subsubsection 外部缓冲区



3.8 新版功能.


在某些场景中，@ref{ca,,pickle} 模块会被用来传输海量的数据。 因此，最小化内存复制次数以保证性能和节省资源是很重要的。 但是 @ref{ca,,pickle} 模块的正常运作会将图类对象结构转换为字节序列流，因此在本质上就要从封存流中来回复制数据。

如果 @emph{provider} (待传输对象类型的实现) 和 @emph{consumer} (通信系统的实现) 都支持 pickle 第 5 版或更高版本所提供的外部传输功能，则此约束可以被撤销。

@menu
* 提供方 API:: 
* 使用方 API:: 
* 示例: 示例<4>. 

@end menu

@node 提供方 API,使用方 API,,外部缓冲区
@anchor{library/pickle provider-api}@anchor{1c60}
@subsubsection 提供方 API


大的待封存数据对象必须实现协议 5 及以上版本专属的 @ref{198d,,__reduce_ex__()} 方法，该方法将为任意大的数据返回一个 @ref{1c48,,PickleBuffer} 实例（而不是 @ref{32a,,bytes} 对象等）。

@ref{1c48,,PickleBuffer} 对象会 @emph{表明} 底层缓冲区可被用于外部数据传输。 那些对象仍将保持与 @ref{ca,,pickle} 模块的正常用法兼容。 但是，使用方也可以选择告知 @ref{ca,,pickle} 它们将自行处理那些缓冲区。

@node 使用方 API,示例<4>,提供方 API,外部缓冲区
@anchor{library/pickle consumer-api}@anchor{1c61}
@subsubsection 使用方 API


当序列化一个对象图时，通信系统可以启用对所生成 @ref{1c48,,PickleBuffer} 对象的定制处理。

发送端需要传递 @emph{buffer_callback} 参数到 @ref{20d,,Pickler} (或是到 @ref{1c42,,dump()} 或 @ref{df8,,dumps()} 函数)，该回调函数将在封存对象图时附带每个所生成的 @ref{1c48,,PickleBuffer} 被调用。 由 @emph{buffer_callback} 所累积的缓冲区的数据将不会被拷贝到 pickle 流，而是仅插入一个简单的标记。

接收端需要传递 @emph{buffers} 参数到 @ref{1c41,,Unpickler} (或是到 @ref{5bd,,load()} 或 @ref{5be,,loads()} 函数)，其值是一个由缓冲区组成的可迭代对象，它会被传递给 @emph{buffer_callback}。 该可迭代对象应当按其被传递给 @emph{buffer_callback} 时的顺序产生缓冲区。 这些缓冲区将提供对象重构造器所期望的数据，对这些数据的封存产生了原本的 @ref{1c48,,PickleBuffer} 对象。

在发送端和接受端之间，通信系统可以自由地实现它自己用于外部缓冲区的传输机制。 潜在的优化包括使用共享内存或基于特定数据类型的压缩等。

@node 示例<4>,,使用方 API,外部缓冲区
@anchor{library/pickle example}@anchor{1c62}
@subsubsection 示例


下面是一个小例子，在其中我们实现了一个 @ref{32b,,bytearray} 的子类，能够用于外部缓冲区封存:

@example
class ZeroCopyByteArray(bytearray):

    def __reduce_ex__(self, protocol):
        if protocol >= 5:
            return type(self)._reconstruct, (PickleBuffer(self),), None
        else:
            # PickleBuffer is forbidden with pickle protocols <= 4.
            return type(self)._reconstruct, (bytearray(self),)

    @@classmethod
    def _reconstruct(cls, obj):
        with memoryview(obj) as m:
            # Get a handle over the original buffer object
            obj = m.obj
            if type(obj) is cls:
                # Original buffer object is a ZeroCopyByteArray, return it
                # as-is.
                return obj
            else:
                return cls(obj)
@end example

重构造器 (@code{_reconstruct} 类方法) 会在缓冲区的提供对象具有正确类型时返回该对象。 在此小示例中这是模拟零拷贝行为的便捷方式。

在使用方，我们可以按通常方式封存那些对象，它们在反序列化时将提供原始对象的一个副本:

@example
b = ZeroCopyByteArray(b"abc")
data = pickle.dumps(b, protocol=5)
new_b = pickle.loads(data)
print(b == new_b)  # True
print(b is new_b)  # False: a copy was made
@end example

但是如果我们传入 @emph{buffer_callback} 然后在反序列化时给回累积的缓冲区，我们就能够取回原始对象:

@example
b = ZeroCopyByteArray(b"abc")
buffers = []
data = pickle.dumps(b, protocol=5, buffer_callback=buffers.append)
new_b = pickle.loads(data, buffers=buffers)
print(b == new_b)  # True
print(b is new_b)  # True: no copy was made
@end example

这个例子受限于 @ref{32b,,bytearray} 会自行分配内存这一事实：你无法基于另一个对象的内存创建 @ref{32b,,bytearray} 的实例。 但是，第三方数据类型例如 NumPy 数组则没有这种限制，允许在单独进程或系统间传输时使用零拷贝的封存（或是尽可能少地拷贝） 。


@subsubheading 参见


@geindex Python 提高建议; PEP 574
PEP 574@footnote{https://www.python.org/dev/peps/pep-0574} -- 带有外部数据缓冲区的 pickle 协议 5


@node 限制全局变量,性能<2>,外部缓冲区,pickle --- Python 对象序列化
@anchor{library/pickle pickle-restrict}@anchor{1c54}@anchor{library/pickle restricting-globals}@anchor{1c63}
@subsubsection 限制全局变量


@geindex find_class() (pickle protocol)

默认情况下，解封将会导入在 pickle 数据中找到的任何类或函数。 对于许多应用来说，此行为是不可接受的，因为它会允许解封器导入并发起调用任意代码。 只须考虑当这个手工构建的 pickle 数据流被加载时会做什么:

@example
>>> import pickle
>>> pickle.loads(b"cos\nsystem\n(S'echo hello world'\ntR.")
hello world
0
@end example

在这个例子里，解封器导入 @ref{dba,,os.system()} 函数然后应用字符串参数 "echo hello world"。 虽然这个例子不具攻击性，但是不难想象别人能够通过此方式对你的系统造成损害。

出于这样的理由，你可能会希望通过定制 @ref{1c53,,Unpickler.find_class()} 来控制要解封的对象。 与其名称所提示的不同，@ref{1c53,,Unpickler.find_class()} 会在执行对任何全局对象（例如一个类或一个函数）的请求时被调用。 因此可以完全禁止全局对象或是将它们限制在一个安全的子集中。

下面的例子是一个解封器，它只允许某一些安全的来自 @ref{13,,builtins} 模块的类被加载:

@example
import builtins
import io
import pickle

safe_builtins = @{
    'range',
    'complex',
    'set',
    'frozenset',
    'slice',
@}

class RestrictedUnpickler(pickle.Unpickler):

    def find_class(self, module, name):
        # Only allow safe classes from builtins.
        if module == "builtins" and name in safe_builtins:
            return getattr(builtins, name)
        # Forbid everything else.
        raise pickle.UnpicklingError("global '%s.%s' is forbidden" %
                                     (module, name))

def restricted_loads(s):
    """Helper function analogous to pickle.loads()."""
    return RestrictedUnpickler(io.BytesIO(s)).load()
@end example

我们这个解封器的一个示例用法所达成的目标:

@example
>>> restricted_loads(pickle.dumps([1, 2, range(15)]))
[1, 2, range(0, 15)]
>>> restricted_loads(b"cos\nsystem\n(S'echo hello world'\ntR.")
Traceback (most recent call last):
  ...
pickle.UnpicklingError: global 'os.system' is forbidden
>>> restricted_loads(b'cbuiltins\neval\n'
...                  b'(S\'getattr(__import__("os"), "system")'
...                  b'("echo hello world")\'\ntR.')
Traceback (most recent call last):
  ...
pickle.UnpicklingError: global 'builtins.eval' is forbidden
@end example

@c XXX Add note about how extension codes could evade our protection
@c mechanism (e.g. cached classes do not invokes find_class()).

正如我们这个例子所显示的，对于允许解封的对象你必须要保持谨慎。 因此如果要保证安全，你可以考虑其他选择例如 @ref{13f,,xmlrpc.client} 中的编组 API 或是第三方解决方案。

@node 性能<2>,例子<4>,限制全局变量,pickle --- Python 对象序列化
@anchor{library/pickle performance}@anchor{1c64}
@subsubsection 性能


较新版本的 pickle 协议（第 2 版或更高）具有针对某些常见特性和内置类型的高效二进制编码格式。 此外，@ref{ca,,pickle} 模块还拥有一个以 C 编写的透明优化器。

@node 例子<4>,,性能<2>,pickle --- Python 对象序列化
@anchor{library/pickle examples}@anchor{1c65}@anchor{library/pickle pickle-example}@anchor{1c66}
@subsubsection 例子


对于最简单的代码，请使用 @ref{1c42,,dump()} 和 @ref{5bd,,load()} 函数。

@example
import pickle

# An arbitrary collection of objects supported by pickle.
data = @{
    'a': [1, 2.0, 3, 4+6j],
    'b': ("character string", b"byte string"),
    'c': @{None, True, False@}
@}

with open('data.pickle', 'wb') as f:
    # Pickle the 'data' dictionary using the highest protocol available.
    pickle.dump(data, f, pickle.HIGHEST_PROTOCOL)
@end example

以下示例读取之前封存的数据。

@example
import pickle

with open('data.pickle', 'rb') as f:
    # The protocol version used is detected automatically, so we do not
    # have to specify it.
    data = pickle.load(f)
@end example

@c XXX: Add examples showing how to optimize pickles for size (like using

@c pickletools.optimize() or the gzip module).


@subsubheading 参见



@table @asis

@item 模块 @ref{27,,copyreg}

为扩展类型提供 pickle 接口所需的构造函数。

@item 模块 @ref{cb,,pickletools}

用于处理和分析已封存数据的工具。

@item 模块 @ref{e7,,shelve}

带索引的数据库，用于存放对象，使用了 @ref{ca,,pickle} 模块。

@item 模块 @ref{26,,copy}

浅层 (shallow) 和深层 (deep) 复制对象操作

@item 模块 @ref{b0,,marshal}

高效地序列化内置类型的数据。
@end table


@subsubheading 备注


@node copyreg --- 注册配合 pickle 模块使用的函数,shelve --- Python 对象持久化,pickle --- Python 对象序列化,数据持久化
@anchor{library/copyreg doc}@anchor{1c67}@anchor{library/copyreg copyreg-register-pickle-support-functions}@anchor{1c68}@anchor{library/copyreg module-copyreg}@anchor{27}
@subsection @code{copyreg} --- 注册配合 @code{pickle} 模块使用的函数


@geindex copyreg (模块)

@strong{源代码:} Lib/copyreg.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/copyreg.py}

@geindex 模块; pickle
@geindex 模块; copy


__________________________________________________________________


@ref{27,,copyreg} 模块提供了可在封存特定对象时使用的一种定义函数方式。 @ref{ca,,pickle} 和 @ref{26,,copy} 模块会在封存/拷贝特定对象时使用这些函数。 此模块提供了非类对象构造器的相关配置信息。 这样的构造器可以是工厂函数或类实例。

@geindex constructor() (在 copyreg 模块中)
@anchor{library/copyreg copyreg constructor}@anchor{1c69}
@deffn {函数} copyreg.constructor (object)

将 @emph{object} 声明为一个有效的构造器。 如果 @emph{object} 是不可调用的（因而不是一个有效的构造器）则会引发 @ref{192,,TypeError}。
@end deffn

@geindex pickle() (在 copyreg 模块中)
@anchor{library/copyreg copyreg pickle}@anchor{1c4d}
@deffn {函数} copyreg.pickle (type, function, constructor=None)

声明该 @emph{function} 应当被用作 @emph{type} 类型对象的“归约函数”。 @emph{function} 应当返回字符串或包含两到三个元素的元组。

如果提供了可选的 @emph{constructor} 形参，它应当是一个可用来重建相应对象的可调用对象，在调用该对象时应传入由 @emph{function} 所返回的参数元组。 如果 @emph{object} 是一个类或 @emph{constructor} 是不可调用的则将引发 @ref{192,,TypeError}。

请查看 @ref{ca,,pickle} 模块了解 @emph{function} 和 @emph{constructor} 所要求的接口的详情。 请注意一个 pickler 对象或 @ref{20d,,pickle.Pickler} 的子类的 @ref{a64,,dispatch_table} 属性也可以被用来声明归约函数。
@end deffn

@menu
* 示例: 示例<5>. 

@end menu

@node 示例<5>,,,copyreg --- 注册配合 pickle 模块使用的函数
@anchor{library/copyreg example}@anchor{1c6a}
@subsubsection 示例


以下示例将会显示如何注册一个封存函数，以及如何来使用它：

@example
>>> import copyreg, copy, pickle
>>> class C(object):
...     def __init__(self, a):
...         self.a = a
...
>>> def pickle_c(c):
...     print("pickling a C instance...")
...     return C, (c.a,)
...
>>> copyreg.pickle(C, pickle_c)
>>> c = C(1)
>>> d = copy.copy(c)  
pickling a C instance...
>>> p = pickle.dumps(c)  
pickling a C instance...
@end example

@node shelve --- Python 对象持久化,marshal --- 内部 Python 对象序列化,copyreg --- 注册配合 pickle 模块使用的函数,数据持久化
@anchor{library/shelve doc}@anchor{1c6b}@anchor{library/shelve module-shelve}@anchor{e7}@anchor{library/shelve shelve-python-object-persistence}@anchor{1c6c}
@subsection @code{shelve} --- Python 对象持久化


@geindex shelve (模块)

@strong{源代码:} Lib/shelve.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/shelve.py}

@geindex 模块; pickle


__________________________________________________________________


"Shelf" 是一种持久化的类似字典的对象。 与 "dbm" 数据库的区别在于 Shelf 中的值（不是键！）实际上可以为任意 Python 对象 --- 即 @ref{ca,,pickle} 模块能够处理的任何东西。 这包括大部分类实例、递归数据类型，以及包含大量共享子对象的对象。 键则为普通的字符串。

@geindex open() (在 shelve 模块中)
@anchor{library/shelve shelve open}@anchor{1c6d}
@deffn {函数} shelve.open (filename, flag='c', protocol=None, writeback=False)

打开一个持久化字典。 filename 指定下层数据库的基准文件名。 作为附带效果，会为 filename 添加一个扩展名并且可能创建更多的文件。 默认情况下，下层数据库会以读写模式打开。 可选的 @emph{flag} 形参具有与 @ref{82a,,dbm.open()} @emph{flag} 形参相同的含义。

默认会使用第 3 版 pickle 协议来序列化值。  pickle 协议版本可通过 @emph{protocol} 形参来指定。

由于 Python 语义的限制，Shelf 对象无法确定一个可变的持久化字典条目在何时被修改。 默认情况下 @emph{只有} 在被修改对象再赋值给 shelf 时才会写入该对象 (参见 @ref{1c6e,,示例})。 如果可选的 @emph{writeback} 形参设为 @code{True}，则所有被访问的条目都将在内存中被缓存，并会在 @ref{1c6f,,sync()} 和 @ref{1c70,,close()} 时被写入；这可以使得对持久化字典中可变条目的修改更方便，但是如果访问的条目很多，这会消耗大量内存作为缓存，并会使得关闭操作变得非常缓慢，因为所有被访问的条目都需要写回到字典（无法确定被访问的条目中哪个是可变的，也无法确定哪个被实际修改了）。

@cartouche
@quotation 注解 
请不要依赖于 Shelf 的自动关闭功能；当你不再需要时应当总是显式地调用 @ref{1c70,,close()}，或者使用 @ref{1c6d,,shelve.open()} 作为上下文管理器:

@example
with shelve.open('spam') as db:
    db['eggs'] = 'eggs'
@end example
@end quotation
@end cartouche
@end deffn

@cartouche
@quotation 警告 
由于 @ref{e7,,shelve} 模块需要 @ref{ca,,pickle} 的支持，因此从不可靠的来源载入 shelf 是不安全的。 与 pickle 一样，载入 Shelf 时可以执行任意代码。
@end quotation
@end cartouche

字典所支持的所有方法都被 Shelf 对象所支持。 因此很容易将基于字典的代码转换为需要持久化存储的代码。

额外支持的两个方法：

@geindex sync() (shelve.Shelf 方法)
@anchor{library/shelve shelve Shelf sync}@anchor{1c6f}
@deffn {方法} Shelf.sync ()

如果 Shelf 打开时将 @emph{writeback} 设为 @ref{494,,True} 则写回缓存中的所有条目。 如果可行还会清空缓存并将持久化字典同步到磁盘。 此方法会在使用 @ref{1c70,,close()} 关闭 Shelf 时自动被调用。
@end deffn

@geindex close() (shelve.Shelf 方法)
@anchor{library/shelve shelve Shelf close}@anchor{1c70}
@deffn {方法} Shelf.close ()

同步并关闭持久化 @emph{dict} 对象。 对已关闭 Shelf 的操作将失败并引发 @ref{1fb,,ValueError}。
@end deffn


@subsubheading 参见


持久化字典方案@footnote{https://code.activestate.com/recipes/576642/}，使用了广泛支持的存储格式并具有原生字典的速度。


@menu
* 限制:: 
* 示例: 示例<6>. 

@end menu

@node 限制,示例<6>,,shelve --- Python 对象持久化
@anchor{library/shelve restrictions}@anchor{1c71}
@subsubsection 限制


@quotation

@geindex 模块; dbm.ndbm
@geindex 模块; dbm.gnu
@end quotation


@itemize *

@item 
可选择使用哪种数据库包 (例如 @ref{35,,dbm.ndbm} 或 @ref{34,,dbm.gnu}) 取决于支持哪种接口。 因此使用 @ref{32,,dbm} 直接打开数据库是不安全的。 如果使用了 @ref{32,,dbm}，数据库同样会（不幸地）受限于它 --- 这意味着存储在数据库中的（封存形式的）对象尺寸应当较小，并且在少数情况下键冲突有可能导致数据库拒绝更新。

@item 
@ref{e7,,shelve} 模块不支持对 Shelf 对象的 @emph{并发} 读/写访问。 （多个同时读取访问则是安全的。） 当一个程序打开一个 shelve 对象来写入时，不应再有其他程序同时打开它来读取或写入。 Unix 文件锁定可被用来解决此问题，但这在不同 Unix 版本上会存在差异，并且需要有关所用数据库实现的细节知识。
@end itemize

@geindex Shelf (shelve 中的类)
@anchor{library/shelve shelve Shelf}@anchor{8aa}
@deffn {类} shelve.Shelf (dict, protocol=None, writeback=False, keyencoding='utf-8')

@ref{9e9,,collections.abc.MutableMapping} 的一个子类，它会将封存的值保存在 @emph{dict} 对象中。

默认会使用第 3 版 pickle 协议来序列化值。 pickle 协议版本可通过 @emph{protocol} 形参来指定。 请参阅 @ref{ca,,pickle} 文档来查看 pickle 协议的相关讨论。

如果 @emph{writeback} 形参为 @code{True}，对象将为所有访问过的条目保留缓存并在同步和关闭时将它们写回到 @emph{dict}。 这允许对可变的条目执行自然操作，但是会消耗更多内存并让同步和关闭花费更长时间。

@emph{keyencoding} 形参是在下层字典被使用之前用于编码键的编码格式。

@ref{8aa,,Shelf} 对象还可以被用作上下文管理器，在这种情况下它将在 @ref{6e3,,with} 语句块结束时自动被关闭。


在 3.2 版更改: 添加了 @emph{keyencoding} 形参；之前，键总是使用 UTF-8 编码。



在 3.4 版更改: 添加了上下文管理器支持。

@end deffn

@geindex BsdDbShelf (shelve 中的类)
@anchor{library/shelve shelve BsdDbShelf}@anchor{1c72}
@deffn {类} shelve.BsdDbShelf (dict, protocol=None, writeback=False, keyencoding='utf-8')

@ref{8aa,,Shelf} 的一个子类，将 @code{first()}, @code{next()}, @code{previous()}, @code{last()} 和 @code{set_location()} 对外公开，在来自 pybsddb@footnote{https://www.jcea.es/programacion/pybsddb.htm} 的第三方 @code{bsddb} 模块中可用，但在其他数据库模块中不可用。 传给构造器的 @emph{dict} 对象必须支持这些方法。 这通常是通过调用 @code{bsddb.hashopen()}, @code{bsddb.btopen()} 或 @code{bsddb.rnopen()} 之一来完成的。  可选的 @emph{protocol}, @emph{writeback} 和 @emph{keyencoding} 形参具有与 @ref{8aa,,Shelf} 类相同的含义。
@end deffn

@geindex DbfilenameShelf (shelve 中的类)
@anchor{library/shelve shelve DbfilenameShelf}@anchor{1c73}
@deffn {类} shelve.DbfilenameShelf (filename, flag='c', protocol=None, writeback=False)

@ref{8aa,,Shelf} 的一个子类，它接受一个 @emph{filename} 而非字典类对象。 下层文件将使用 @ref{82a,,dbm.open()} 来打开。 默认情况下，文件将以读写模式打开。 可选的 @emph{flag} 形参具有与 @ref{1c6d,,open()} 函数相同的含义。 可选的 @emph{protocol} 和 @emph{writeback} 形参具有与 @ref{8aa,,Shelf} 类相同的含义。
@end deffn

@node 示例<6>,,限制,shelve --- Python 对象持久化
@anchor{library/shelve example}@anchor{1c74}@anchor{library/shelve shelve-example}@anchor{1c6e}
@subsubsection 示例


对接口的总结如下 (@code{key} 为字符串，@code{data} 为任意对象):

@example
import shelve

d = shelve.open(filename)  # open -- file may get suffix added by low-level
                           # library

d[key] = data              # store data at key (overwrites old data if
                           # using an existing key)
data = d[key]              # retrieve a COPY of data at key (raise KeyError
                           # if no such key)
del d[key]                 # delete data stored at key (raises KeyError
                           # if no such key)

flag = key in d            # true if the key exists
klist = list(d.keys())     # a list of all existing keys (slow!)

# as d was opened WITHOUT writeback=True, beware:
d['xx'] = [0, 1, 2]        # this works as expected, but...
d['xx'].append(3)          # *this doesn't!* -- d['xx'] is STILL [0, 1, 2]!

# having opened d without writeback=True, you need to code carefully:
temp = d['xx']             # extracts the copy
temp.append(5)             # mutates the copy
d['xx'] = temp             # stores the copy right back, to persist it

# or, d=shelve.open(filename,writeback=True) would let you just code
# d['xx'].append(5) and have it work as expected, BUT it would also
# consume more memory and make the d.close() operation slower.

d.close()                  # close it
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{32,,dbm}

@code{dbm} 风格数据库的泛型接口。

@item 模块 @ref{ca,,pickle}

@ref{e7,,shelve} 所使用的对象序列化。
@end table


@node marshal --- 内部 Python 对象序列化,dbm --- Unix "数据库" 接口,shelve --- Python 对象持久化,数据持久化
@anchor{library/marshal doc}@anchor{1c75}@anchor{library/marshal marshal-internal-python-object-serialization}@anchor{1c76}@anchor{library/marshal module-marshal}@anchor{b0}
@subsection @code{marshal} --- 内部 Python 对象序列化


@geindex marshal (模块)


__________________________________________________________________


此模块包含一此能以二进制格式来读写 Python 值的函数。 这种格式是 Python 专属的，但是独立于特定的机器架构（即你可以在一台 PC 上写入某个 Python 值，将文件传到一台 Sun 上并在那里读取它）。 这种格式的细节有意不带文档说明；它可能在不同 Python 版本中发生改变（但这种情况极少发生）。 @footnote{@w{(1)} 
此模块的名称来源于 Modula-3 (及其他语言) 的设计者所使用的术语，他们使用术语 "marshal" 来表示以自包含的形式传输数据。 严格地说，将数据从内部形式转换为外部形式 (例如用于 RPC 缓冲区) 称为 "marshal" 而其逆过程则称为 "unmarshal"。
}

@geindex 模块; pickle
@geindex 模块; shelve

这不是一个通用的“持久化”模块。 对于通用的持久化以及通过 RPC 调用传递 Python 对象，请参阅 @ref{ca,,pickle} 和 @ref{e7,,shelve} 等模块。 @ref{b0,,marshal} 模块主要是为了支持读写 @code{.pyc} 文件形式“伪编译”代码的 Python 模块。 因此，Python 维护者保留在必要时以不向下兼容的方式修改 marshal 格式的权利。 如果你要序列化和反序列化 Python 对象，请改用 @ref{ca,,pickle} 模块 -- 其执行效率相当，版本独立性有保证，并且 pickle 还支持比 marshal 更多样的对象类型。

@cartouche
@quotation 警告 
@ref{b0,,marshal} 模块对于错误或恶意构建的数据来说是不安全的。 永远不要 unmarshal 来自不受信任的或未经验证的来源的数据。
@end quotation
@end cartouche

@geindex object; code
@geindex code object

不是所有 Python 对象类型都受支持；一般来说，此模块只能写入和读取不依赖于特定 Python 调用的对象。 下列类型是受支持的：布尔值、整数、浮点数、复数、字符串、字节串、字节数组、元组、列表、集合、冻结集合、字典和代码对象，需要了解的一点是元组、列表、集合、冻结集合和字典只在其所包含的值也是这些值时才受支持。 单例对象 @ref{157,,None}, @ref{15a4,,Ellipsis} and @ref{480,,StopIteration} 也可以被 marshal 和 unmarshal。 对于 @emph{version} 低于 3 的格式，递归列表、集合和字典无法被写入（见下文）。

有些函数可以读/写文件，还有些函数可以操作字节类对象。

这个模块定义了以下函数：

@geindex dump() (在 marshal 模块中)
@anchor{library/marshal marshal dump}@anchor{1c77}
@deffn {函数} marshal.dump (value, file[, version])

向打开的文件写入值。 值必须为受支持的类型。 文件必须为可写的 @ref{1c37,,binary file}。

如果值具有（或所包含的对象具有）不受支持的类型，则会引发 @ref{1fb,,ValueError} --- 但是将向文件写入垃圾数据。 对象也将不能正确地通过 @ref{f81,,load()} 重新读取。

@emph{version} 参数指明 @code{dump} 应当使用的数据格式（见下文）。
@end deffn

@geindex load() (在 marshal 模块中)
@anchor{library/marshal marshal load}@anchor{f81}
@deffn {函数} marshal.load (file)

从打开的文件读取一个值并返回。 如果读不到有效的值（例如由于数据为不同 Python 版本的不兼容 marshal 格式），则会引发 @ref{c65,,EOFError}, @ref{1fb,,ValueError} 或 @ref{192,,TypeError}。 文件必须为可读的 @ref{1c37,,binary file}。

@cartouche
@quotation 注解 
如果通过 @ref{1c77,,dump()} marshal 了一个包含不受支持类型的对象，@ref{f81,,load()} 将为不可 marshal 的类型替换 @code{None}。
@end quotation
@end cartouche
@end deffn

@geindex dumps() (在 marshal 模块中)
@anchor{library/marshal marshal dumps}@anchor{796}
@deffn {函数} marshal.dumps (value[, version])

返回将通过 @code{dump(value, file)} 被写入一个文件的字节串对象。 值必须属于受支持的类型。 如果值属于（或包含的对象属于）不受支持的类型则会引发 @ref{1fb,,ValueError}。

@emph{version} 参数指明 @code{dumps} 应当使用的数据类型（见下文）。
@end deffn

@geindex loads() (在 marshal 模块中)
@anchor{library/marshal marshal loads}@anchor{1c78}
@deffn {函数} marshal.loads (bytes)

将 @ref{5e3,,bytes-like object} 转换为一个值。 如果找不到有效的值，则会引发 @ref{c65,,EOFError}, @ref{1fb,,ValueError} 或 @ref{192,,TypeError}。 输入的额外字节串会被忽略。
@end deffn

此外，还定义了以下常量：

@geindex version() (在 marshal 模块中)
@anchor{library/marshal marshal version}@anchor{1c79}
@deffn {数据} marshal.version

指明模块所使用的格式。 第 0 版为历史格式，第 1 版为共享固化的字符串，第 2 版对浮点数使用二进制格式。 第 3 版添加了对于对象实例化和递归的支持。 目前使用的为第 4 版。
@end deffn

@subsubheading 备注


@node dbm --- Unix "数据库" 接口,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块,marshal --- 内部 Python 对象序列化,数据持久化
@anchor{library/dbm doc}@anchor{1c7a}@anchor{library/dbm dbm-interfaces-to-unix-databases}@anchor{1c7b}@anchor{library/dbm module-dbm}@anchor{32}
@subsection @code{dbm} --- Unix "数据库" 接口


@geindex dbm (模块)

@strong{源代码:} Lib/dbm/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/dbm/__init__.py}


__________________________________________________________________


@ref{32,,dbm} 是一种泛用接口，针对各种 DBM 数据库 --- 包括 @ref{34,,dbm.gnu} 或 @ref{35,,dbm.ndbm}。 如果未安装这些模块中的任何一种，则将使用 @ref{33,,dbm.dumb} 模块中慢速但简单的实现。 还有一个适用于 Oracle Berkeley DB 的 第三方接口@footnote{https://www.jcea.es/programacion/pybsddb.htm}。

@geindex error
@anchor{library/dbm dbm error}@anchor{1c7c}
@deffn {例外} dbm.error

一个元组，其中包含每个受支持的模块可引发的异常，另外还有一个名为 @ref{1c7c,,dbm.error} 的特殊异常作为第一项 --- 后者最在引发 @ref{1c7c,,dbm.error} 时被使用。
@end deffn

@geindex whichdb() (在 dbm 模块中)
@anchor{library/dbm dbm whichdb}@anchor{1c7d}
@deffn {函数} dbm.whichdb (filename)

此函数会猜测各种简单数据库模块中的哪一个是可用的 --- @ref{34,,dbm.gnu}, @ref{35,,dbm.ndbm} 还是 @ref{33,,dbm.dumb} --- 应该被用来打开给定的文件。

返回下列值中的一个：如果文件由于不可读或不存在而无法打开则返回 @code{None}；如果文件的格式无法猜测则返回空字符串 (@code{'@w{'}})；或是包含所需模块名称的字符串，例如 @code{'dbm.ndbm'} 或 @code{'dbm.gnu'}。
@end deffn

@geindex open() (在 dbm 模块中)
@anchor{library/dbm dbm open}@anchor{82a}
@deffn {函数} dbm.open (file, flag='r', mode=0o666)

打开数据库文件 @emph{file} 并返回一个相应的对象。

如果数据库文件已存在，则使用 @ref{1c7d,,whichdb()} 函数来确定其类型和要使用的适当模块；如果文件不存在，则会使用上述可导入模块中的第一个。

可选的 @emph{flag} 参数可以是：


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

含义

@item

@code{'r'}

@tab

以只读方式打开现有数据库（默认）

@item

@code{'w'}

@tab

以读写方式打开现有数据库

@item

@code{'c'}

@tab

以读写方式打开数据库，如果不存在则创建它

@item

@code{'n'}

@tab

始终创建一个新的空数据库，以读写方式打开

@end multitable


可选的 @emph{mode} 参数是文件的 Unix 模式，仅在要创建数据库时才会被使用。 其默认值为八进制数 @code{0o666} (并将被当前的 umask 所修改)。
@end deffn

@ref{82a,,open()} 所返回的对象支持与字典相同的基本功能；可以存储、获取和删除键及其对应的值，并可使用 @ref{79d,,in} 运算符和 @code{keys()} 方法，以及 @code{get()} 和 @code{setdefault()}。


在 3.2 版更改: 现在 @code{get()} 和 @code{setdefault()} 在所有数据库模块中均可用。



在 3.8 版更改: 从只读数据库中删除键将引发数据库模块专属的错误而不是 @ref{2c7,,KeyError}。


键和值总是被存储为字节串。 这意味着当使用字符串时它们会在被存储之前隐式地转换至默认编码格式。

这些对象也支持在 @ref{6e3,,with} 语句中使用，当语句结束时将自动关闭它们。


在 3.4 版更改: 向 @ref{82a,,open()} 所返回的对象添加了上下文管理协议的原生支持。


以下示例记录了一些主机名和对应的标题，随后将数据库的内容打印出来。:

@example
import dbm

# Open database, creating it if necessary.
with dbm.open('cache', 'c') as db:

    # Record some values
    db[b'hello'] = b'there'
    db['www.python.org'] = 'Python Website'
    db['www.cnn.com'] = 'Cable News Network'

    # Note that the keys are considered bytes now.
    assert db[b'www.python.org'] == b'Python Website'
    # Notice how the value is now in bytes.
    assert db['www.cnn.com'] == b'Cable News Network'

    # Often-used methods of the dict interface work too.
    print(db.get('python.org', b'not present'))

    # Storing a non-string key or value will raise an exception (most
    # likely a TypeError).
    db['www.yahoo.com'] = 4

# db is automatically closed when leaving the with statement.
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{e7,,shelve}

存储非字符串数据的持久化模块。
@end table


以下部分描述了各个单独的子模块。

@menu
* dbm.gnu: dbm gnu --- GNU 对 dbm 的重解析. GNU 对 dbm 的重解析
* dbm.ndbm: dbm ndbm --- 基于 ndbm 的接口. 基于 ndbm 的接口
* dbm.dumb: dbm dumb --- 便携式 DBM 实现. 便携式 DBM 实现

@end menu

@node dbm gnu --- GNU 对 dbm 的重解析,dbm ndbm --- 基于 ndbm 的接口,,dbm --- Unix "数据库" 接口
@anchor{library/dbm dbm-gnu-gnu-s-reinterpretation-of-dbm}@anchor{1c7e}@anchor{library/dbm module-dbm gnu}@anchor{34}
@subsubsection @code{dbm.gnu} --- GNU 对 dbm 的重解析


@geindex dbm.gnu (模块)

@strong{源代码:} Lib/dbm/gnu.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/dbm/gnu.py}


__________________________________________________________________


此模块与 @ref{32,,dbm} 模块很相似，但是改用 GNU 库 @code{gdbm} 来提供某些附加功能。 请注意由 @ref{34,,dbm.gnu} 与 @ref{35,,dbm.ndbm} 所创建的文件格式是不兼容的。

@ref{34,,dbm.gnu} 模块提供了对 GNU DBM 库的接口。 @code{dbm.gnu.gdbm} 对象的行为类似于映射（字典），区别在于其键和值总是会在存储之前被转换为字节串。 打印 @code{gdbm} 对象不会打印出键和值，并且 @code{items()} 和 @code{values()} 等方法也不受支持。

@geindex error
@anchor{library/dbm dbm gnu error}@anchor{2c5}
@deffn {例外} dbm.gnu.error

针对 @ref{34,,dbm.gnu} 专属错误例如 I/O 错误引发。 @ref{2c7,,KeyError} 的引发则针对一般映射错误例如指定了不正确的键。
@end deffn

@geindex open() (在 dbm.gnu 模块中)
@anchor{library/dbm dbm gnu open}@anchor{fc4}
@deffn {函数} dbm.gnu.open (filename[, flag[, mode]])

打开一个 @code{gdbm} 数据库并返回 @code{gdbm} 对象。 @emph{filename} 参数为数据库文件名称。

可选的 @emph{flag} 参数可以是：


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

含义

@item

@code{'r'}

@tab

以只读方式打开现有数据库（默认）

@item

@code{'w'}

@tab

以读写方式打开现有数据库

@item

@code{'c'}

@tab

以读写方式打开数据库，如果不存在则创建它

@item

@code{'n'}

@tab

始终创建一个新的空数据库，以读写方式打开

@end multitable


下列附加字符可被添加至旗标以控制数据库的打开方式：


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

含义

@item

@code{'f'}

@tab

以快速模式打开数据库。写入数据库将不会同步。

@item

@code{'s'}

@tab

同步模式。这将导致数据库的更改立即写入文件。

@item

@code{'u'}

@tab

不要锁定数据库。

@end multitable


不是所有旗标都可用于所有版本的 @code{gdbm}。 模块常量 @code{open_flags} 为包含受支持旗标字符的字符串。 如果指定了无效的旗标则会引发 @ref{2c5,,error}。

可选的 @emph{mode} 参数是文件的 Unix 模式，仅在要创建数据库时才会被使用。 其默认值为八进制数 @code{0o666}。

除了与字典类似的方法，@code{gdbm} 对象还有以下方法：

@geindex firstkey() (dbm.gnu.gdbm 方法)
@anchor{library/dbm dbm gnu gdbm firstkey}@anchor{1c7f}
@deffn {方法} gdbm.firstkey ()

使用此方法和 @ref{1c80,,nextkey()} 方法可以循环遍历数据库中的每个键。 遍历的顺序是按照 @code{gdbm} 的内部哈希值，而不会根据键的值排序。 此方法将返回起始键。
@end deffn

@geindex nextkey() (dbm.gnu.gdbm 方法)
@anchor{library/dbm dbm gnu gdbm nextkey}@anchor{1c80}
@deffn {方法} gdbm.nextkey (key)

在遍历中返回 @emph{key} 之后的的下一个键。 以下代码将打印数据库 @code{db} 中的每个键，而不会在内存中创建一个包含所有键的列表:

@example
k = db.firstkey()
while k != None:
    print(k)
    k = db.nextkey(k)
@end example
@end deffn

@geindex reorganize() (dbm.gnu.gdbm 方法)
@anchor{library/dbm dbm gnu gdbm reorganize}@anchor{1c81}
@deffn {方法} gdbm.reorganize ()

如果你进行了大量删除操作并且想要缩减 @code{gdbm} 文件所使用的空间，此例程将可重新组织数据库。 除非使用此重组功能否则 @code{gdbm} 对象不会缩减数据库文件大小；在其他情况下，被删除的文件空间将会保留并在添加新的 (键, 值) 对时被重用。
@end deffn

@geindex sync() (dbm.gnu.gdbm 方法)
@anchor{library/dbm dbm gnu gdbm sync}@anchor{1c82}
@deffn {方法} gdbm.sync ()

当以快速模式打开数据库时，此方法会将任何未写入数据强制写入磁盘。
@end deffn

@geindex close() (dbm.gnu.gdbm 方法)
@anchor{library/dbm dbm gnu gdbm close}@anchor{1c83}
@deffn {方法} gdbm.close ()

关闭 @code{gdbm} 数据库。
@end deffn
@end deffn

@node dbm ndbm --- 基于 ndbm 的接口,dbm dumb --- 便携式 DBM 实现,dbm gnu --- GNU 对 dbm 的重解析,dbm --- Unix "数据库" 接口
@anchor{library/dbm dbm-ndbm-interface-based-on-ndbm}@anchor{1c84}@anchor{library/dbm module-dbm ndbm}@anchor{35}
@subsubsection @code{dbm.ndbm} --- 基于 ndbm 的接口


@geindex dbm.ndbm (模块)

@strong{源代码:} Lib/dbm/ndbm.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/dbm/ndbm.py}


__________________________________________________________________


@ref{35,,dbm.ndbm} 模块提供了对 Unix "(n)dbm" 库的接口。 Dbm 对象的行为类似于映射（字典），区别在于其键和值总是被存储为字节串。 打印 @code{dbm} 对象不会打印出键和值，并且 @code{items()} 和 @code{values()} 等方法也不受支持。

此模块可与 "经典classic" ndbm 接口或 GNU GDBM 兼容接口一同使用。 在 Unix 上，@code{configure} 脚本将尝试定位适当的头文件来简化此模块的构建。

@geindex error
@anchor{library/dbm dbm ndbm error}@anchor{2c6}
@deffn {例外} dbm.ndbm.error

针对 @ref{35,,dbm.ndbm} 专属错误例如 I/O 错误引发。 @ref{2c7,,KeyError} 的引发则针对一般映射错误例如指定了不正确的键。
@end deffn

@geindex library() (在 dbm.ndbm 模块中)
@anchor{library/dbm dbm ndbm library}@anchor{1c85}
@deffn {数据} dbm.ndbm.library

所使用的 @code{ndbm} 实现库的名称。
@end deffn

@geindex open() (在 dbm.ndbm 模块中)
@anchor{library/dbm dbm ndbm open}@anchor{fc5}
@deffn {函数} dbm.ndbm.open (filename[, flag[, mode]])

打开一个 dbm 数据库并返回 @code{ndbm} 对象。 @emph{filename} 参数为数据库文件名称（不带 @code{.dir} 或 @code{.pag} 扩展名）。

可选的 @emph{flag} 参数必须是下列值之一：


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

含义

@item

@code{'r'}

@tab

以只读方式打开现有数据库（默认）

@item

@code{'w'}

@tab

以读写方式打开现有数据库

@item

@code{'c'}

@tab

以读写方式打开数据库，如果不存在则创建它

@item

@code{'n'}

@tab

始终创建一个新的空数据库，以读写方式打开

@end multitable


可选的 @emph{mode} 参数是文件的 Unix 模式，仅在要创建数据库时才会被使用。 其默认值为八进制数 @code{0o666} (并将被当前的 umask 所修改)。

除了与字典类似的方法，@code{ndbm} 对象还有以下方法：

@geindex close() (dbm.ndbm.ndbm 方法)
@anchor{library/dbm dbm ndbm ndbm close}@anchor{1c86}
@deffn {方法} ndbm.close ()

关闭 @code{ndbm} 数据库。
@end deffn
@end deffn

@node dbm dumb --- 便携式 DBM 实现,,dbm ndbm --- 基于 ndbm 的接口,dbm --- Unix "数据库" 接口
@anchor{library/dbm dbm-dumb-portable-dbm-implementation}@anchor{1c87}@anchor{library/dbm module-dbm dumb}@anchor{33}
@subsubsection @code{dbm.dumb} --- 便携式 DBM 实现


@geindex dbm.dumb (模块)

@strong{源代码:} Lib/dbm/dumb.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/dbm/dumb.py}

@geindex databases

@cartouche
@quotation 注解 
@ref{33,,dbm.dumb} 模块的目的是在更健壮的模块不可用时作为 @ref{32,,dbm} 模块的最终回退项。 @ref{33,,dbm.dumb} 不是为高速运行而编写的，也不像其他数据库模块一样被经常使用。
@end quotation
@end cartouche


__________________________________________________________________


@ref{33,,dbm.dumb} 模块提供了一个完全以 Python 编写的持久化字典类接口。 不同于 @ref{34,,dbm.gnu} 等其他模块，它不需要外部库。 与其他持久化映射一样，它的键和值也总是被存储为字节串。

该模块定义以下内容：

@geindex error
@anchor{library/dbm dbm dumb error}@anchor{2c4}
@deffn {例外} dbm.dumb.error

针对 @ref{33,,dbm.dumb} 专属错误例如 I/O 错误引发。  @ref{2c7,,KeyError} 的引发则针对一般映射例如指定了不正确的键。
@end deffn

@geindex open() (在 dbm.dumb 模块中)
@anchor{library/dbm dbm dumb open}@anchor{2bf}
@deffn {函数} dbm.dumb.open (filename[, flag[, mode]])

打开一个 @code{dumbdbm} 数据库并返回 dumbdbm 对象。 @emph{filename} 参数为数据库文件的主名称（不带任何特定扩展名）。 创建一个 dumbdbm 数据库时将创建多个带有 @code{.dat} 和 @code{.dir} 扩展名的文件。

可选的 @emph{flag} 参数可以是：


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

含义

@item

@code{'r'}

@tab

以只读方式打开现有数据库（默认）

@item

@code{'w'}

@tab

以读写方式打开现有数据库

@item

@code{'c'}

@tab

以读写方式打开数据库，如果不存在则创建它

@item

@code{'n'}

@tab

始终创建一个新的空数据库，以读写方式打开

@end multitable


可选的 @emph{mode} 参数是文件的 Unix 模式，仅在要创建数据库时才会被使用。 其默认值为八进制数 @code{0o666} (并将被当前的 umask 所修改)。

@cartouche
@quotation 警告 
当载入包含足够巨大/复杂条目的数据库时有可能导致 Python 解释器的崩溃，这是由于 Python AST 编译器有栈深度限制。
@end quotation
@end cartouche


在 3.5 版更改: @ref{2bf,,open()} 在 flag 值为 @code{'n'} 时将总是创建一个新的数据库。



在 3.8 版更改: 附带 @code{'r'} 旗标打开的数据库现在将是只读的。 附带 @code{'r'} 和 @code{'w'} 旗标的打开操作不会再创建数据库。


除了 @ref{9e9,,collections.abc.MutableMapping} 类所提供的方法，@code{dumbdbm} 对象还提供了以下方法：

@geindex sync() (dbm.dumb.dumbdbm 方法)
@anchor{library/dbm dbm dumb dumbdbm sync}@anchor{1c88}
@deffn {方法} dumbdbm.sync ()

同步磁盘上的目录和数据文件。 此方法会由 @code{Shelve.sync()} 方法来调用。
@end deffn

@geindex close() (dbm.dumb.dumbdbm 方法)
@anchor{library/dbm dbm dumb dumbdbm close}@anchor{1c89}
@deffn {方法} dumbdbm.close ()

关闭 @code{dumbdbm} 数据库。
@end deffn
@end deffn

@node sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块,,dbm --- Unix "数据库" 接口,数据持久化
@anchor{library/sqlite3 doc}@anchor{1c8a}@anchor{library/sqlite3 module-sqlite3}@anchor{f2}@anchor{library/sqlite3 sqlite3-db-api-2-0-interface-for-sqlite-databases}@anchor{1c8b}
@subsection @code{sqlite3} --- SQLite 数据库 DB-API 2.0 接口模块


@geindex sqlite3 (模块)

@strong{源代码：} Lib/sqlite3/@footnote{https://github.com/python/cpython/tree/3.8/Lib/sqlite3/}


__________________________________________________________________


SQLite 是一个C语言库，它可以提供一种轻量级的基于磁盘的数据库，这种数据库不需要独立的服务器进程，也允许需要使用一种非标准的 SQL 查询语言来访问它。一些应用程序可以使用 SQLite 作为内部数据存储。可以用它来创建一个应用程序原型，然后再迁移到更大的数据库，比如 PostgreSQL 或 Oracle。

sqlite3 模块由  Gerhard Häring 编写。它提供了符合 DB-API 2.0 规范的接口，这个规范是 
@geindex Python 提高建议; PEP 249
PEP 249@footnote{https://www.python.org/dev/peps/pep-0249}。

要使用这个模块，必须先创建一个  @ref{3d0,,Connection} 对象，它代表数据库。下面例子中，数据将存储在 @code{example.db} 文件中：

@example
import sqlite3
conn = sqlite3.connect('example.db')
@end example

你也可以使用 @code{:memory:} 来创建一个内存中的数据库

当有了 @ref{3d0,,Connection} 对象后，你可以创建一个 @ref{1c8c,,Cursor} 游标对象，然后调用它的 @ref{1c8d,,execute()} 方法来执行 SQL 语句：

@example
c = conn.cursor()

# Create table
c.execute('@w{'}'CREATE TABLE stocks
             (date text, trans text, symbol text, qty real, price real)'@w{'}')

# Insert a row of data
c.execute("INSERT INTO stocks VALUES ('2006-01-05','BUY','RHAT',100,35.14)")

# Save (commit) the changes
conn.commit()

# We can also close the connection if we are done with it.
# Just be sure any changes have been committed or they will be lost.
conn.close()
@end example

这些数据被持久化保存了，而且可以在之后的会话中使用它们：

@example
import sqlite3
conn = sqlite3.connect('example.db')
c = conn.cursor()
@end example

通常你的 SQL 操作需要使用一些 Python 变量的值。你不应该使用 Python 的字符串操作来创建你的查询语句，因为那样做不安全；它会使你的程序容易受到 SQL 注入攻击（在 @indicateurl{https://xkcd.com/327/} 上有一个搞笑的例子，看看有什么后果）

推荐另外一种方法：使用 DB-API 的参数替换。在你的 SQL 语句中，使用 @code{?} 占位符来代替值，然后把对应的值组成的元组做为 @ref{1c8d,,execute()} 方法的第二个参数。（其他数据库可能会使用不同的占位符，比如 @code{%s} 或者 @code{:1}）例如：

@example
# Never do this -- insecure!
symbol = 'RHAT'
c.execute("SELECT * FROM stocks WHERE symbol = '%s'" % symbol)

# Do this instead
t = ('RHAT',)
c.execute('SELECT * FROM stocks WHERE symbol=?', t)
print(c.fetchone())

# Larger example that inserts many records at a time
purchases = [('2006-03-28', 'BUY', 'IBM', 1000, 45.00),
             ('2006-04-05', 'BUY', 'MSFT', 1000, 72.00),
             ('2006-04-06', 'SELL', 'IBM', 500, 53.00),
            ]
c.executemany('INSERT INTO stocks VALUES (?,?,?,?,?)', purchases)
@end example

要在执行 SELECT 语句后获取数据，你可以把游标作为 @ref{fce,,iterator}，然后调用它的 @ref{1c8e,,fetchone()} 方法来获取一条匹配的行，也可以调用 @ref{1c8f,,fetchall()} 来得到包含多个匹配行的列表。

下面是一个使用迭代器形式的例子：

@example
>>> for row in c.execute('SELECT * FROM stocks ORDER BY price'):
        print(row)

('2006-01-05', 'BUY', 'RHAT', 100, 35.14)
('2006-03-28', 'BUY', 'IBM', 1000, 45.0)
('2006-04-06', 'SELL', 'IBM', 500, 53.0)
('2006-04-05', 'BUY', 'MSFT', 1000, 72.0)
@end example


@subsubheading 参见



@table @asis

@item @indicateurl{https://github.com/ghaering/pysqlite}

pysqlite的主页 -- sqlite3 在外部使用 “pysqlite” 名字进行开发。

@item @indicateurl{https://www.sqlite.org}

SQLite的主页；它的文档详细描述了它所支持的 SQL 方言的语法和可用的数据类型。

@item @indicateurl{https://www.w3schools.com/sql/}

学习 SQL 语法的教程、参考和例子。

@geindex Python 提高建议; PEP 249

@item PEP 249@footnote{https://www.python.org/dev/peps/pep-0249} - DB-API 2.0 规范

PEP 由 Marc-André Lemburg 撰写。
@end table


@menu
* 模块函数和常量:: 
* 连接对象（Connection）:: 
* Cursor 对象:: 
* 行对象:: 
* 异常: 异常<4>. 
* SQLite 与 Python 类型:: 
* 控制事务:: 
* 有效使用 sqlite3:: 
* 常见问题:: 

@end menu

@node 模块函数和常量,连接对象（Connection）,,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 module-functions-and-constants}@anchor{1c90}@anchor{library/sqlite3 sqlite3-module-contents}@anchor{1c91}
@subsubsection 模块函数和常量


@geindex version() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 version}@anchor{1c92}
@deffn {数据} sqlite3.version

这个模块的版本号，是一个字符串。不是 SQLite 库的版本号。
@end deffn

@geindex version_info() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 version_info}@anchor{1c93}
@deffn {数据} sqlite3.version_info

这个模块的版本号，是一个由整数组成的元组。不是 SQLite 库的版本号。
@end deffn

@geindex sqlite_version() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 sqlite_version}@anchor{1c94}
@deffn {数据} sqlite3.sqlite_version

使用中的 SQLite 库的版本号，是一个字符串。
@end deffn

@geindex sqlite_version_info() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 sqlite_version_info}@anchor{1c95}
@deffn {数据} sqlite3.sqlite_version_info

使用中的 SQLite 库的版本号，是一个整数组成的元组。
@end deffn

@geindex PARSE_DECLTYPES() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 PARSE_DECLTYPES}@anchor{1c96}
@deffn {数据} sqlite3.PARSE_DECLTYPES

这个常量可以作为 @ref{3d2,,connect()} 函数的 @emph{detect_types} 参数。

设置这个参数后，@ref{f2,,sqlite3} 模块将解析它返回的每一列申明的类型。它会申明的类型的第一个单词，比如“integer primary key”，它会解析出“integer”，再比如“number(10)”，它会解析出“number”。然后，它会在转换器字典里查找那个类型注册的转换器函数，并调用它。
@end deffn

@geindex PARSE_COLNAMES() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 PARSE_COLNAMES}@anchor{1c97}
@deffn {数据} sqlite3.PARSE_COLNAMES

这个常量可以作为 @ref{3d2,,connect()} 函数的 @emph{detect_types} 参数。

设置此参数可使得 SQLite 接口解析它所返回的每一列的列名。 它将在其中查找形式为 [mytype] 的字符串，然后将 'mytype' 确定为列的类型。 它将尝试在转换器字典中查找 'mytype' 条目，然后用找到的转换器函数来返回值。 在 @ref{1c98,,Cursor.description} 中找到的列名并不包括类型，举例来说，如果你在你的 SQL 中使用了像 @code{'as "Expiration date [datetime]"'} 这样的写法，那么我们将解析出在第一个 then we will parse out everything until the first @code{'['} 之前的所有内容并去除前导空格作为列名：即列名将为 "Expiration date"。
@end deffn

@geindex connect() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 connect}@anchor{3d2}
@deffn {函数} sqlite3.connect (database[, timeout, detect_types, isolation_level, check_same_thread, factory, cached_statements, uri])

连接 SQLite 数据库 @emph{database}。默认返回 @ref{3d0,,Connection} 对象，除非使用了自定义的 @emph{factory} 参数。

@emph{database} 是准备打开的数据库文件的路径（绝对路径或相对于当前目录的相对路径），它是 @ref{363,,path-like object}。你也可以用 @code{":memory:"} 在内存中打开一个数据库。

当一个数据库被多个连接访问的时候，如果其中一个进程修改这个数据库，在这个事务提交之前，这个 SQLite 数据库将会被一直锁定。@emph{timeout} 参数指定了这个连接等待锁释放的超时时间，超时之后会引发一个异常。这个超时时间默认是 5.0（5秒）。

@emph{isolation_level} 参数，请查看 @ref{3d0,,Connection} 对象的 @ref{1c99,,isolation_level} 属性。

SQLite 原生只支持5种类型：TEXT，INTEGER，REAL，BLOB 和 NULL。如果你想用其它类型，你必须自己添加相应的支持。使用 @emph{detect_types} 参数和模块级别的 @ref{1c9a,,register_converter()} 函数注册**转换器** 可以简单的实现。

@emph{detect_types} 默认为0（即关闭，没有类型检测）。你也可以组合 @ref{1c96,,PARSE_DECLTYPES} 和 @ref{1c97,,PARSE_COLNAMES} 来开启类型检测。

默认情况下，@emph{check_same_thread} 为 @ref{494,,True}，只有当前的线程可以使用该连接。 如果设置为 @ref{380,,False}，则多个线程可以共享返回的连接。 当多个线程使用同一个连接的时候，用户应该把写操作进行序列化，以避免数据损坏。

默认情况下，当调用 connect 方法的时候，@ref{f2,,sqlite3} 模块使用了它的 @ref{3d0,,Connection} 类。当然，你也可以创建 @ref{3d0,,Connection} 类的子类，然后创建提供了 @emph{factory} 参数的 @ref{3d2,,connect()} 方法。

详情请查阅当前手册的 @ref{1c9b,,SQLite 与 Python 类型} 部分。

@ref{f2,,sqlite3} 模块在内部使用语句缓存来避免 SQL 解析开销。 如果要显式设置当前连接可以缓存的语句数，可以设置 @emph{cached_statements} 参数。 当前实现的默认值是缓存100条语句。

如果 @emph{uri} 为真，则 @emph{database} 被解释为 URI。 它允许您指定选项。 例如，以只读模式打开数据库：

@example
db = sqlite3.connect('file:path/to/database?mode=ro', uri=True)
@end example

有关此功能的更多信息，包括已知选项的列表，可以在 ` SQLite URI 文档 <@indicateurl{https://www.sqlite.org/uri.html}>`_ 中找到。

引发一个 @ref{12d0,,审计事件} @code{sqlite3.connect}，附带参数 @code{database}。


在 3.4 版更改: 增加了 @emph{uri} 参数。



在 3.7 版更改: @emph{database} 现在可以是一个 @ref{363,,path-like object} 对象了，不仅仅是字符串。

@end deffn

@geindex register_converter() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 register_converter}@anchor{1c9a}
@deffn {函数} sqlite3.register_converter (typename, callable)

注册一个回调对象 @emph{callable}, 用来转换数据库中的字节串为自定的 Python 类型。所有类型为 @emph{typename} 的数据库的值在转换时，都会调用这个回调对象。通过指定 @ref{3d2,,connect()} 函数的 @emph{detect-types} 参数来设置类型检测的方式。注意，@emph{typename} 与查询语句中的类型名进行匹配时不区分大小写。
@end deffn

@geindex register_adapter() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 register_adapter}@anchor{1c9c}
@deffn {函数} sqlite3.register_adapter (type, callable)

注册一个回调对象 @emph{callable}，用来转换自定义Python类型为一个 SQLite 支持的类型。 这个回调对象 @emph{callable} 仅接受一个 Python 值作为参数，而且必须返回以下某个类型的值：int，float，str 或 bytes。
@end deffn

@geindex complete_statement() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 complete_statement}@anchor{1c9d}
@deffn {函数} sqlite3.complete_statement (sql)

如果字符串 @emph{sql} 包含一个或多个完整的 SQL 语句（以分号结束）则返回 @ref{494,,True}。它不会验证 SQL 语法是否正确，仅会验证字符串字面上是否完整，以及是否以分号结束。

它可以用来构建一个 SQLite shell，下面是一个例子：

@example
# A minimal SQLite shell for experiments

import sqlite3

con = sqlite3.connect(":memory:")
con.isolation_level = None
cur = con.cursor()

buffer = ""

print("Enter your SQL commands to execute in sqlite3.")
print("Enter a blank line to exit.")

while True:
    line = input()
    if line == "":
        break
    buffer += line
    if sqlite3.complete_statement(buffer):
        try:
            buffer = buffer.strip()
            cur.execute(buffer)

            if buffer.lstrip().upper().startswith("SELECT"):
                print(cur.fetchall())
        except sqlite3.Error as e:
            print("An error occurred:", e.args[0])
        buffer = ""

con.close()
@end example
@end deffn

@geindex enable_callback_tracebacks() (在 sqlite3 模块中)
@anchor{library/sqlite3 sqlite3 enable_callback_tracebacks}@anchor{1c9e}
@deffn {函数} sqlite3.enable_callback_tracebacks (flag)

默认情况下，您不会获得任何用户定义函数中的回溯消息，比如聚合，转换器，授权器回调等。如果要调试它们，可以设置 @emph{flag} 参数为 @code{True} 并调用此函数。 之后，回调中的回溯信息将会输出到 @code{sys.stderr}。 再次使用 @ref{380,,False} 来禁用该功能。
@end deffn

@node 连接对象（Connection）,Cursor 对象,模块函数和常量,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 connection-objects}@anchor{1c9f}@anchor{library/sqlite3 sqlite3-connection-objects}@anchor{1ca0}
@subsubsection 连接对象（Connection）


@geindex Connection (sqlite3 中的类)
@anchor{library/sqlite3 sqlite3 Connection}@anchor{3d0}
@deffn {类} sqlite3.Connection

SQLite 数据库连接对象有如下的属性和方法：

@geindex isolation_level (sqlite3.Connection 属性)
@anchor{library/sqlite3 sqlite3 Connection isolation_level}@anchor{1c99}
@deffn {属性} isolation_level

获取或设置当前默认的隔离级别。 表示自动提交模式的 @ref{157,,None} 以及 "DEFERRED", "IMMEDIATE" 或 "EXCLUSIVE" 其中之一。 详细描述请参阅 @ref{1ca1,,控制事务}。
@end deffn

@geindex in_transaction (sqlite3.Connection 属性)
@anchor{library/sqlite3 sqlite3 Connection in_transaction}@anchor{1ca2}
@deffn {属性} in_transaction

如果是在活动事务中（还没有提交改变），返回 @ref{494,,True}，否则，返回 @ref{380,,False}。它是一个只读属性。


3.2 新版功能.

@end deffn

@geindex cursor() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection cursor}@anchor{1ca3}
@deffn {方法} cursor (factory=Cursor)

这个方法接受一个可选参数 @emph{factory}，如果要指定这个参数，它必须是一个可调用对象，而且必须返回 @ref{1c8c,,Cursor} 类的一个实例或者子类。
@end deffn

@geindex commit() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection commit}@anchor{1ca4}
@deffn {方法} commit ()

这个方法提交当前事务。如果没有调用这个方法，那么从上一次提交 @code{commit()} 以来所有的变化在其他数据库连接上都是不可见的。如果你往数据库里写了数据，但是又查询不到，请检查是否忘记了调用这个方法。
@end deffn

@geindex rollback() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection rollback}@anchor{1ca5}
@deffn {方法} rollback ()

这个方法回滚从上一次调用 @ref{1ca4,,commit()} 以来所有数据库的改变。
@end deffn

@geindex close() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection close}@anchor{1ca6}
@deffn {方法} close ()

关闭数据库连接。注意，它不会自动调用 @ref{1ca4,,commit()} 方法。如果在关闭数据库连接之前没有调用 @ref{1ca4,,commit()}，那么你的修改将会丢失！
@end deffn

@geindex execute() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection execute}@anchor{1ca7}
@deffn {方法} execute (sql[, parameters])

这是一个非标准的快捷方法，它会调用 @ref{1ca3,,cursor()} 方法来创建一个游标对象，并使用给定的 @emph{parameters} 参数来调用游标对象的 @ref{1c8d,,execute()} 方法，最后返回这个游标对象。
@end deffn

@geindex executemany() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection executemany}@anchor{1ca8}
@deffn {方法} executemany (sql[, parameters])

这是一个非标准的快捷方法，它会调用 @ref{1ca3,,cursor()} 方法来创建一个游标对象，并使用给定的 @emph{parameters} 参数来调用游标对象的 @ref{1ca9,,executemany()} 方法，最后返回这个游标对象。
@end deffn

@geindex executescript() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection executescript}@anchor{1caa}
@deffn {方法} executescript (sql_script)

这是一个非标准的快捷方法，它会调用 @ref{1ca3,,cursor()} 方法来创建一个游标对象，并使用给定的 @emph{sql_script} 参数来调用游标对象的 @ref{1cab,,executescript()} 方法，最后返回这个游标对象。
@end deffn

@geindex create_function() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection create_function}@anchor{f2d}
@deffn {方法} create_function (name, num_params, func, *, deterministic=False)

创建一个可以在 SQL 语句中使用的用户自定义函数，函数名为 @emph{name}。 @emph{num_params} 为该函数所接受的形参个数（如果 @emph{num_params} 为 -1，则该函数可接受任意数量的参数）， @emph{func} 是一个 Python 可调用对象，它将作为 SQL 函数被调用。 如果 @emph{deterministic} 为真值，则所创建的函数将被标记为 deterministic@footnote{https://sqlite.org/deterministic.html}，这允许 SQLite 执行额外的优化。 此旗标在 SQLite 3.8.3 或更高版本中受到支持，如果在旧版本中使用将引发 @ref{1cac,,NotSupportedError}。

此函数可返回任何 SQLite 所支持的类型: bytes, str, int, float 和 @code{None}。


在 3.8 版更改: 增加了 @emph{deterministic} 形参。


示例:

@example
import sqlite3
import hashlib

def md5sum(t):
    return hashlib.md5(t).hexdigest()

con = sqlite3.connect(":memory:")
con.create_function("md5", 1, md5sum)
cur = con.cursor()
cur.execute("select md5(?)", (b"foo",))
print(cur.fetchone()[0])

con.close()
@end example
@end deffn

@geindex create_aggregate() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection create_aggregate}@anchor{f2c}
@deffn {方法} create_aggregate (name, num_params, aggregate_class)

创建一个自定义的聚合函数。

参数中 @emph{aggregate_class} 类必须实现两个方法：@code{step} 和 @code{finalize}。@code{step} 方法接受 @emph{num_params} 个参数（如果 @emph{num_params} 为 -1，那么这个函数可以接受任意数量的参数）；@code{finalize} 方法返回最终的聚合结果。

@code{finalize} 方法可以返回任何 SQLite 支持的类型：bytes，str，int，float 和 @code{None}。

示例:

@example
import sqlite3

class MySum:
    def __init__(self):
        self.count = 0

    def step(self, value):
        self.count += value

    def finalize(self):
        return self.count

con = sqlite3.connect(":memory:")
con.create_aggregate("mysum", 1, MySum)
cur = con.cursor()
cur.execute("create table test(i)")
cur.execute("insert into test(i) values (1)")
cur.execute("insert into test(i) values (2)")
cur.execute("select mysum(i) from test")
print(cur.fetchone()[0])

con.close()
@end example
@end deffn

@geindex create_collation() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection create_collation}@anchor{1cad}
@deffn {方法} create_collation (name, callable)

使用 @emph{name} 和 @emph{callable} 创建排序规则。这个 @emph{callable} 接受两个字符串对象，如果第一个小于第二个则返回 -1， 如果两个相等则返回 0，如果第一个大于第二个则返回 1。注意，这是用来控制排序的（SQL 中的 ORDER BY），所以它不会影响其它的 SQL 操作。

注意，这个 @emph{callable} 可调用对象会把它的参数作为 Python 字节串，通常会以 UTF-8 编码格式对它进行编码。

以下示例显示了使用“错误方式”进行排序的自定义排序规则：

@example
import sqlite3

def collate_reverse(string1, string2):
    if string1 == string2:
        return 0
    elif string1 < string2:
        return 1
    else:
        return -1

con = sqlite3.connect(":memory:")
con.create_collation("reverse", collate_reverse)

cur = con.cursor()
cur.execute("create table test(x)")
cur.executemany("insert into test(x) values (?)", [("a",), ("b",)])
cur.execute("select x from test order by x collate reverse")
for row in cur:
    print(row)
con.close()
@end example

要移除一个排序规则，需要调用 @code{create_collation} 并设置 callable 参数为 @code{None}。

@example
con.create_collation("reverse", None)
@end example
@end deffn

@geindex interrupt() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection interrupt}@anchor{1cae}
@deffn {方法} interrupt ()

可以从不同的线程调用这个方法来终止所有查询操作，这些查询操作可能正在连接上执行。此方法调用之后， 查询将会终止，而且查询的调用者会获得一个异常。
@end deffn

@geindex set_authorizer() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection set_authorizer}@anchor{f2e}
@deffn {方法} set_authorizer (authorizer_callback)

此方法注册一个授权回调对象。每次在访问数据库中某个表的某一列的时候，这个回调对象将会被调用。如果要允许访问，则返回 @code{SQLITE_OK}，如果要终止整个 SQL 语句，则返回 @code{SQLITE_DENY}，如果这一列需要当做 NULL 值处理，则返回 @code{SQLITE_IGNORE}。这些常量可以在  @ref{f2,,sqlite3} 模块中找到。

回调的第一个参数表示要授权的操作类型。 第二个和第三个参数将是参数或 @ref{157,,None}，具体取决于第一个参数的值。 第 4 个参数是数据库的名称（“main”，“temp”等），如果需要的话。 第 5 个参数是负责访问尝试的最内层触发器或视图的名称，或者如果此访问尝试直接来自输入 SQL 代码，则为 @ref{157,,None}。

请参阅 SQLite 文档，了解第一个参数的可能值以及第二个和第三个参数的含义，具体取决于第一个参数。 所有必需的常量都可以在 @ref{f2,,sqlite3} 模块中找到。
@end deffn

@geindex set_progress_handler() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection set_progress_handler}@anchor{f2f}
@deffn {方法} set_progress_handler (handler, n)

此例程注册回调。 对SQLite虚拟机的每个多指令调用回调。 如果要在长时间运行的操作期间从SQLite调用（例如更新用户界面），这非常有用。

如果要清除以前安装的任何进度处理程序，调用该方法时请将 @emph{handler} 参数设置为 @ref{157,,None}。

从处理函数返回非零值将终止当前正在执行的查询并导致它引发 @ref{1caf,,OperationalError} 异常。
@end deffn

@geindex set_trace_callback() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection set_trace_callback}@anchor{a88}
@deffn {方法} set_trace_callback (trace_callback)

为每个 SQLite 后端实际执行的 SQL 语句注册要调用的 @emph{trace_callback}。

传递给回调的唯一参数是正在执行的语句（作为字符串）。 回调的返回值将被忽略。 请注意，后端不仅运行传递给 @ref{1c8d,,Cursor.execute()} 方法的语句。 其他来源包括 Python 模块的事务管理和当前数据库中定义的触发器的执行。

将传入的 @emph{trace_callback} 设为 @ref{157,,None} 将禁用跟踪回调。


3.3 新版功能.

@end deffn

@geindex enable_load_extension() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection enable_load_extension}@anchor{b92}
@deffn {方法} enable_load_extension (enabled)

此例程允许/禁止SQLite引擎从共享库加载SQLite扩展。 SQLite扩展可以定义新功能，聚合或全新的虚拟表实现。 一个众所周知的扩展是与SQLite一起分发的全文搜索扩展。

默认情况下禁用可加载扩展。 见 @footnote{@w{(1)} 
sqlite3 模块默认没有构建可加载扩展支持，因为有一些平台带有不支持这个特性的 SQLite 库（特别是 Mac OS X）。要获得可加载扩展的支持，那么在编译配置的时候必须指定 --enable-loadable-sqlite-extensions 选项。
}.


3.2 新版功能.


@example
import sqlite3

con = sqlite3.connect(":memory:")

# enable extension loading
con.enable_load_extension(True)

# Load the fulltext search extension
con.execute("select load_extension('./fts3.so')")

# alternatively you can load the extension using an API call:
# con.load_extension("./fts3.so")

# disable extension loading again
con.enable_load_extension(False)

# example from SQLite wiki
con.execute("create virtual table recipe using fts3(name, ingredients)")
con.executescript("""
    insert into recipe (name, ingredients) values ('broccoli stew', 'broccoli peppers cheese tomatoes');
    insert into recipe (name, ingredients) values ('pumpkin stew', 'pumpkin onions garlic celery');
    insert into recipe (name, ingredients) values ('broccoli pie', 'broccoli cheese onions flour');
    insert into recipe (name, ingredients) values ('pumpkin pie', 'pumpkin sugar flour butter');
    """)
for row in con.execute("select rowid, name, ingredients from recipe where name match 'pie'"):
    print(row)

con.close()
@end example
@end deffn

@geindex load_extension() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection load_extension}@anchor{b93}
@deffn {方法} load_extension (path)

此例程从共享库加载SQLite扩展。 在使用此例程之前，必须使用 @ref{b92,,enable_load_extension()} 启用扩展加载。

默认情况下禁用可加载扩展。 见 @footnote{@w{(1)} 
sqlite3 模块默认没有构建可加载扩展支持，因为有一些平台带有不支持这个特性的 SQLite 库（特别是 Mac OS X）。要获得可加载扩展的支持，那么在编译配置的时候必须指定 --enable-loadable-sqlite-extensions 选项。
}.


3.2 新版功能.

@end deffn

@geindex row_factory (sqlite3.Connection 属性)
@anchor{library/sqlite3 sqlite3 Connection row_factory}@anchor{1cb0}
@deffn {属性} row_factory

您可以将此属性更改为可接受游标和原始行作为元组的可调用对象，并将返回实际结果行。 这样，您可以实现更高级的返回结果的方法，例如返回一个可以按名称访问列的对象。

示例:

@example
import sqlite3

def dict_factory(cursor, row):
    d = @{@}
    for idx, col in enumerate(cursor.description):
        d[col[0]] = row[idx]
    return d

con = sqlite3.connect(":memory:")
con.row_factory = dict_factory
cur = con.cursor()
cur.execute("select 1 as a")
print(cur.fetchone()["a"])

con.close()
@end example

如果返回一个元组是不够的，并且你想要对列进行基于名称的访问，你应该考虑将 @ref{1cb0,,row_factory} 设置为高度优化的 @ref{758,,sqlite3.Row} 类型。 @ref{758,,Row} 提供基于索引和不区分大小写的基于名称的访问，几乎没有内存开销。 它可能比您自己的基于字典的自定义方法甚至基于 db_row 的解决方案更好。

@c XXX what's a db_row-based solution?
@end deffn

@geindex text_factory (sqlite3.Connection 属性)
@anchor{library/sqlite3 sqlite3 Connection text_factory}@anchor{1cb1}
@deffn {属性} text_factory

使用此属性可以控制为 @code{TEXT} 数据类型返回的对象。 默认情况下，此属性设置为 @ref{329,,str} 和 @ref{f2,,sqlite3} 模块将返回 @code{TEXT} 的 Unicode 对象。 如果要返回字节串，可以将其设置为 @ref{32a,,bytes}。

您还可以将其设置为接受单个 bytestring 参数的任何其他可调用对象，并返回结果对象。

请参阅以下示例代码以进行说明：

@example
import sqlite3

con = sqlite3.connect(":memory:")
cur = con.cursor()

AUSTRIA = "\xd6sterreich"

# by default, rows are returned as Unicode
cur.execute("select ?", (AUSTRIA,))
row = cur.fetchone()
assert row[0] == AUSTRIA

# but we can make sqlite3 always return bytestrings ...
con.text_factory = bytes
cur.execute("select ?", (AUSTRIA,))
row = cur.fetchone()
assert type(row[0]) is bytes
# the bytestrings will be encoded in UTF-8, unless you stored garbage in the
# database ...
assert row[0] == AUSTRIA.encode("utf-8")

# we can also implement a custom text_factory ...
# here we implement one that appends "foo" to all strings
con.text_factory = lambda x: x.decode("utf-8") + "foo"
cur.execute("select ?", ("bar",))
row = cur.fetchone()
assert row[0] == "barfoo"

con.close()
@end example
@end deffn

@geindex total_changes (sqlite3.Connection 属性)
@anchor{library/sqlite3 sqlite3 Connection total_changes}@anchor{1cb2}
@deffn {属性} total_changes

返回自打开数据库连接以来已修改，插入或删除的数据库行的总数。
@end deffn

@geindex iterdump() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection iterdump}@anchor{1cb3}
@deffn {方法} iterdump ()

返回以SQL文本格式转储数据库的迭代器。 保存内存数据库以便以后恢复时很有用。 此函数提供与 @code{sqlite3} shell 中的 @code{.dump} 命令相同的功能。

示例:

@example
# Convert file existing_db.db to SQL dump file dump.sql
import sqlite3

con = sqlite3.connect('existing_db.db')
with open('dump.sql', 'w') as f:
    for line in con.iterdump():
        f.write('%s\n' % line)
con.close()
@end example
@end deffn

@geindex backup() (sqlite3.Connection 方法)
@anchor{library/sqlite3 sqlite3 Connection backup}@anchor{3d1}
@deffn {方法} backup (target, *, pages=0, progress=None, name="main", sleep=0.250)

即使在 SQLite 数据库被其他客户端访问时，或者同时由同一连接访问，该方法也会对其进行备份。 该副本将写入强制参数 @emph{target}，该参数必须是另一个 @ref{3d0,,Connection} 实例。

默认情况下，或者当 @emph{pages} 为 @code{0} 或负整数时，整个数据库将在一个步骤中复制；否则该方法一次循环复制 @emph{pages} 规定数量的页面。

如果指定了 @emph{progress}，则它必须为 @code{None} 或一个将在每次迭代时附带三个整数参数执行的可调用对象，这三个参数分别是前一次迭代的状态 @emph{status}，将要拷贝的剩余页数 @emph{remaining} 以及总页数 @emph{total}。

@emph{name} 参数指定将被拷贝的数据库名称：它必须是一个字符串，其内容为表示主数据库的默认值 @code{"main"}，表示临时数据库的 @code{"temp"} 或是在 @code{ATTACH DATABASE} 语句的 @code{AS} 关键字之后指定表示附加数据库的名称。

@emph{sleep} 参数指定在备份剩余页的连续尝试之间要休眠的秒数，可以指定为一个整数或一个浮点数值。

示例一，将现有数据库复制到另一个数据库中：

@example
import sqlite3

def progress(status, remaining, total):
    print(f'Copied @{total-remaining@} of @{total@} pages...')

con = sqlite3.connect('existing_db.db')
bck = sqlite3.connect('backup.db')
with bck:
    con.backup(bck, pages=1, progress=progress)
bck.close()
con.close()
@end example

示例二，将现有数据库复制到临时副本中：

@example
import sqlite3

source = sqlite3.connect('existing_db.db')
dest = sqlite3.connect(':memory:')
source.backup(dest)
@end example

可用性：SQLite 3.6.11 或以上版本


3.7 新版功能.

@end deffn
@end deffn

@node Cursor 对象,行对象,连接对象（Connection）,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 cursor-objects}@anchor{1cb4}@anchor{library/sqlite3 sqlite3-cursor-objects}@anchor{1cb5}
@subsubsection Cursor 对象


@geindex Cursor (sqlite3 中的类)
@anchor{library/sqlite3 sqlite3 Cursor}@anchor{1c8c}
@deffn {类} sqlite3.Cursor

@ref{1c8c,,Cursor} 游标实例具有以下属性和方法。

@geindex ? (question mark); in SQL statements

@geindex ; (colon); in SQL statements

@geindex execute() (sqlite3.Cursor 方法)
@anchor{library/sqlite3 sqlite3 Cursor execute}@anchor{1c8d}
@deffn {方法} execute (sql[, parameters])

执行SQL语句。 可以是参数化 SQL 语句（即，在 SQL 语句中使用占位符）。@ref{f2,,sqlite3} 模块支持两种占位符：问号（qmark风格）和命名占位符（命名风格）。

以下是两种风格的示例：

@example
import sqlite3

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute("create table people (name_last, age)")

who = "Yeltsin"
age = 72

# This is the qmark style:
cur.execute("insert into people values (?, ?)", (who, age))

# And this is the named style:
cur.execute("select * from people where name_last=:who and age=:age", @{"who": who, "age": age@})

print(cur.fetchone())

con.close()
@end example

@ref{1c8d,,execute()} 将只执行一条单独的 SQL 语句。 如果你尝试用它执行超过一条语句，将会引发 @ref{1cb6,,Warning}。 如果你想要用一次调用执行多条 SQL 语句请使用 @ref{1cab,,executescript()}。
@end deffn

@geindex executemany() (sqlite3.Cursor 方法)
@anchor{library/sqlite3 sqlite3 Cursor executemany}@anchor{1ca9}
@deffn {方法} executemany (sql, seq_of_parameters)

基于在序列 @emph{seq_of_parameters} 中找到的所有形参序列或映射执行一条 SQL 命令。 @ref{f2,,sqlite3} 模块还允许使用 @ref{fce,,iterator} 代替序列来产生形参。

@example
import sqlite3

class IterChars:
    def __init__(self):
        self.count = ord('a')

    def __iter__(self):
        return self

    def __next__(self):
        if self.count > ord('z'):
            raise StopIteration
        self.count += 1
        return (chr(self.count - 1),) # this is a 1-tuple

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute("create table characters(c)")

theIter = IterChars()
cur.executemany("insert into characters(c) values (?)", theIter)

cur.execute("select c from characters")
print(cur.fetchall())

con.close()
@end example

这是一个使用生成器 @ref{99c,,generator} 的简短示例：

@example
import sqlite3
import string

def char_generator():
    for c in string.ascii_lowercase:
        yield (c,)

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute("create table characters(c)")

cur.executemany("insert into characters(c) values (?)", char_generator())

cur.execute("select c from characters")
print(cur.fetchall())

con.close()
@end example
@end deffn

@geindex executescript() (sqlite3.Cursor 方法)
@anchor{library/sqlite3 sqlite3 Cursor executescript}@anchor{1cab}
@deffn {方法} executescript (sql_script)

这是一个非标准的便捷方法，可用于一次执行多条 SQL 语句。 它会首先执行一条 @code{COMMIT} 语句，再执行以形参方式获取的 SQL 脚本。

@emph{sql_script} 可以是一个 @ref{329,,str} 类的实例。

示例:

@example
import sqlite3

con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.executescript("""
    create table person(
        firstname,
        lastname,
        age
    );

    create table book(
        title,
        author,
        published
    );

    insert into book(title, author, published)
    values (
        'Dirk Gently'@w{'}s Holistic Detective Agency',
        'Douglas Adams',
        1987
    );
    """)
con.close()
@end example
@end deffn

@geindex fetchone() (sqlite3.Cursor 方法)
@anchor{library/sqlite3 sqlite3 Cursor fetchone}@anchor{1c8e}
@deffn {方法} fetchone ()

获取一个查询结果集的下一行，返回一个单独序列，或是在没有更多可用数据时返回 @ref{157,,None}。
@end deffn

@geindex fetchmany() (sqlite3.Cursor 方法)
@anchor{library/sqlite3 sqlite3 Cursor fetchmany}@anchor{1cb7}
@deffn {方法} fetchmany (size=cursor.arraysize)

获取下一个多行查询结果集，返回一个列表。 当没有更多可用行时将返回一个空列表。

每次调用获取的行数由 @emph{size} 形参指定。 如果没有给出该形参，则由 cursor 的 arraysize 决定要获取的行数。 此方法将基于 size 形参值尝试获取指定数量的行。 如果获取不到指定的行数，则可能返回较少的行。

请注意 @emph{size} 形参会涉及到性能方面的考虑。为了获得优化的性能，通常最好是使用 arraysize 属性。 如果使用 @emph{size} 形参，则最好在从一个 @ref{1cb7,,fetchmany()} 调用到下一个调用之间保持相同的值。
@end deffn

@geindex fetchall() (sqlite3.Cursor 方法)
@anchor{library/sqlite3 sqlite3 Cursor fetchall}@anchor{1c8f}
@deffn {方法} fetchall ()

获取一个查询结果的所有（剩余）行，返回一个列表。 请注意 cursor 的 arraysize 属性会影响此操作的执行效率。 当没有可用行时将返回一个空列表。
@end deffn

@geindex close() (sqlite3.Cursor 方法)
@anchor{library/sqlite3 sqlite3 Cursor close}@anchor{1cb8}
@deffn {方法} close ()

立即关闭 cursor（而不是在当 @code{__del__} 被调用的时候）。

从这一时刻起该 cursor 将不再可用，如果再尝试用该 cursor 执行任何操作将引发 @ref{1cb9,,ProgrammingError} 异常。
@end deffn

@geindex rowcount (sqlite3.Cursor 属性)
@anchor{library/sqlite3 sqlite3 Cursor rowcount}@anchor{1cba}
@deffn {属性} rowcount

虽然 @ref{f2,,sqlite3} 模块的 @ref{1c8c,,Cursor} 类实现了此属性，但数据库引擎本身对于确定 "受影响行"/"已选择行" 的支持并不完善。

对于 @ref{1ca9,,executemany()} 语句，修改行数会被汇总至 @ref{1cba,,rowcount}。

根据 Python DB API 规格描述的要求，@ref{1cba,,rowcount} 属性 "当未在 cursor 上执行 @code{executeXX()} 或者上一次操作的 rowcount 不是由接口确定时为 -1"。 这包括 @code{SELECT} 语句，因为我们无法确定一次查询将产生的行计数，而要等获取了所有行时才会知道。

在 SQLite 的 3.6.5 版之前，如果你执行 @code{DELETE FROM table} 时不附带任何条件，则 @ref{1cba,,rowcount} 将被设为 0。
@end deffn

@geindex lastrowid (sqlite3.Cursor 属性)
@anchor{library/sqlite3 sqlite3 Cursor lastrowid}@anchor{579}
@deffn {属性} lastrowid

这个只读属性会提供最近修改行的 rowid。 它只在你使用 @ref{1c8d,,execute()} 方法执行 @code{INSERT} 或 @code{REPLACE} 语句时会被设置。 对于 @code{INSERT} 或 @code{REPLACE} 以外的操作或者当 @ref{1ca9,,executemany()} 被调用时，@ref{579,,lastrowid} 会被设为 @ref{157,,None}。

如果 @code{INSERT} 或 @code{REPLACE} 语句操作失败则将返回上一次成功操作的 rowid。


在 3.6 版更改: 增加了 @code{REPLACE} 语句的支持。

@end deffn

@geindex arraysize (sqlite3.Cursor 属性)
@anchor{library/sqlite3 sqlite3 Cursor arraysize}@anchor{1cbb}
@deffn {属性} arraysize

用于控制 @ref{1cb7,,fetchmany()} 返回行数的可读取/写入属性。 该属性的默认值为 1，表示每次调用将获取单独一行。
@end deffn

@geindex description (sqlite3.Cursor 属性)
@anchor{library/sqlite3 sqlite3 Cursor description}@anchor{1c98}
@deffn {属性} description

这个只读属性将提供上一次查询的列名称。 为了与 Python DB API 保持兼容，它会为每个列返回一个 7 元组，每个元组的最后六个条目均为 @ref{157,,None}。

对于没有任何匹配行的 @code{SELECT} 语句同样会设置该属性。
@end deffn

@geindex connection (sqlite3.Cursor 属性)
@anchor{library/sqlite3 sqlite3 Cursor connection}@anchor{1cbc}
@deffn {属性} connection

这个只读属性将提供 @ref{1c8c,,Cursor} 对象所使用的 SQLite 数据库 @ref{3d0,,Connection}。 通过调用 @ref{1ca3,,con.cursor()} 创建的 @ref{1c8c,,Cursor} 对象所包含的 @ref{1cbc,,connection} 属性将指向 @emph{con}:

@example
>>> con = sqlite3.connect(":memory:")
>>> cur = con.cursor()
>>> cur.connection == con
True
@end example
@end deffn
@end deffn

@node 行对象,异常<4>,Cursor 对象,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 row-objects}@anchor{1cbd}@anchor{library/sqlite3 sqlite3-row-objects}@anchor{1cbe}
@subsubsection 行对象


@geindex Row (sqlite3 中的类)
@anchor{library/sqlite3 sqlite3 Row}@anchor{758}
@deffn {类} sqlite3.Row

一个 @ref{758,,Row} 实例，该实例将作为用于 @ref{3d0,,Connection} 对象的高度优化的 @ref{1cb0,,row_factory}。 它的大部分行为都会模仿元组的特性。

它支持使用列名称的映射访问以及索引、迭代、文本表示、相等检测和 @ref{150,,len()} 等操作。

如果两个 @ref{758,,Row} 对象具有完全相同的列并且其成员均相等，则它们的比较结果为相等。

@geindex keys() (sqlite3.Row 方法)
@anchor{library/sqlite3 sqlite3 Row keys}@anchor{1cbf}
@deffn {方法} keys ()

此方法会在一次查询之后立即返回一个列名称的列表，它是 @ref{1c98,,Cursor.description} 中每个元组的第一个成员。
@end deffn


在 3.5 版更改: 添加了对切片操作的支持。

@end deffn

让我们假设我们如上面的例子所示初始化一个表:

@example
conn = sqlite3.connect(":memory:")
c = conn.cursor()
c.execute('@w{'}'create table stocks
(date text, trans text, symbol text,
 qty real, price real)'@w{'}')
c.execute("""insert into stocks
          values ('2006-01-05','BUY','RHAT',100,35.14)""")
conn.commit()
c.close()
@end example

现在我们将 @ref{758,,Row} 插入:

@example
>>> conn.row_factory = sqlite3.Row
>>> c = conn.cursor()
>>> c.execute('select * from stocks')
<sqlite3.Cursor object at 0x7f4e7dd8fa80>
>>> r = c.fetchone()
>>> type(r)
<class 'sqlite3.Row'>
>>> tuple(r)
('2006-01-05', 'BUY', 'RHAT', 100.0, 35.14)
>>> len(r)
5
>>> r[2]
'RHAT'
>>> r.keys()
['date', 'trans', 'symbol', 'qty', 'price']
>>> r['qty']
100.0
>>> for member in r:
...     print(member)
...
2006-01-05
BUY
RHAT
100.0
35.14
@end example

@node 异常<4>,SQLite 与 Python 类型,行对象,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 exceptions}@anchor{1cc0}@anchor{library/sqlite3 sqlite3-exceptions}@anchor{1cc1}
@subsubsection 异常


@geindex Warning
@anchor{library/sqlite3 sqlite3 Warning}@anchor{1cb6}
@deffn {例外} sqlite3.Warning

@ref{1a9,,Exception} 的一个子类。
@end deffn

@geindex Error
@anchor{library/sqlite3 sqlite3 Error}@anchor{1cc2}
@deffn {例外} sqlite3.Error

此模块中其他异常的基类。 它是 @ref{1a9,,Exception} 的一个子类。
@end deffn

@geindex DatabaseError
@anchor{library/sqlite3 sqlite3 DatabaseError}@anchor{1cc3}
@deffn {例外} sqlite3.DatabaseError

针对数据库相关错误引发的异常。
@end deffn

@geindex IntegrityError
@anchor{library/sqlite3 sqlite3 IntegrityError}@anchor{1cc4}
@deffn {例外} sqlite3.IntegrityError

当数据库的关系一致性受到影响时引发的异常。 例如外键检查失败等。 它是 @ref{1cc3,,DatabaseError} 的子类。
@end deffn

@geindex ProgrammingError
@anchor{library/sqlite3 sqlite3 ProgrammingError}@anchor{1cb9}
@deffn {例外} sqlite3.ProgrammingError

编程错误引发的异常，例如表未找到或已存在，SQL 语句存在语法错误，指定的形参数量错误等。 它是 @ref{1cc3,,DatabaseError} 的子类。
@end deffn

@geindex OperationalError
@anchor{library/sqlite3 sqlite3 OperationalError}@anchor{1caf}
@deffn {例外} sqlite3.OperationalError

与数据库操作相关而不一定能受程序员掌控的错误引发的异常，例如发生非预期的连接中断，数据源名称未找到，事务无法被执行等。 它是 @ref{1cc3,,DatabaseError} 的子类。
@end deffn

@geindex NotSupportedError
@anchor{library/sqlite3 sqlite3 NotSupportedError}@anchor{1cac}
@deffn {例外} sqlite3.NotSupportedError

在使用了某个数据库不支持的方法或数据库 API 时引发的异常，例如在一个不支持事务或禁用了事务的连接上调用 @ref{1ca5,,rollback()} 方法等。 它是 @ref{1cc3,,DatabaseError} 的子类。
@end deffn

@node SQLite 与 Python 类型,控制事务,异常<4>,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 sqlite-and-python-types}@anchor{1cc5}@anchor{library/sqlite3 sqlite3-types}@anchor{1c9b}
@subsubsection SQLite 与 Python 类型


@menu
* 概述: 概述<7>. 
* 使用适配器将额外的 Python 类型保存在 SQLite 数据库中。:: 
* 将SQLite 值转换为自定义Python 类型:: 
* 默认适配器和转换器:: 

@end menu

@node 概述<7>,使用适配器将额外的 Python 类型保存在 SQLite 数据库中。,,SQLite 与 Python 类型
@anchor{library/sqlite3 introduction}@anchor{1cc6}
@subsubsection 概述


SQLite 原生支持如下的类型： @code{NULL}，@code{INTEGER}，@code{REAL}，@code{TEXT}，@code{BLOB}。

因此可以将以下Python类型发送到SQLite而不会出现任何问题：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} 
@headitem

Python 类型

@tab

SQLite 类型

@item

@ref{157,,None}

@tab

@code{NULL}

@item

@ref{184,,int}

@tab

@code{INTEGER}

@item

@ref{187,,float}

@tab

@code{REAL}

@item

@ref{329,,str}

@tab

@code{TEXT}

@item

@ref{32a,,bytes}

@tab

@code{BLOB}

@end multitable


这是SQLite类型默认转换为Python类型的方式：


@multitable {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

SQLite 类型

@tab

Python 类型

@item

@code{NULL}

@tab

@ref{157,,None}

@item

@code{INTEGER}

@tab

@ref{184,,int}

@item

@code{REAL}

@tab

@ref{187,,float}

@item

@code{TEXT}

@tab

取决于 @ref{1cb1,,text_factory} , 默认为 @ref{329,,str}

@item

@code{BLOB}

@tab

@ref{32a,,bytes}

@end multitable


@ref{f2,,sqlite3} 模块的类型系统可通过两种方式来扩展：你可以通过对象适配将额外的 Python 类型保存在 SQLite 数据库中，你也可以让 @ref{f2,,sqlite3} 模块通过转换器将 SQLite 类型转换为不同的 Python 类型。

@node 使用适配器将额外的 Python 类型保存在 SQLite 数据库中。,将SQLite 值转换为自定义Python 类型,概述<7>,SQLite 与 Python 类型
@anchor{library/sqlite3 using-adapters-to-store-additional-python-types-in-sqlite-databases}@anchor{1cc7}
@subsubsection 使用适配器将额外的 Python 类型保存在 SQLite 数据库中。


如上文所述，SQLite 只包含对有限类型集的原生支持。 要让 SQLite 能使用其他 Python 类型，你必须将它们 @strong{适配} 至 sqlite3 模块所支持的 SQLite 类型中的一种：NoneType, int, float, str, bytes。

有两种方式能让 @ref{f2,,sqlite3} 模块将某个定制的 Python 类型适配为受支持的类型。

@menu
* 让对象自行适配:: 
* 注册可调用的适配器:: 

@end menu

@node 让对象自行适配,注册可调用的适配器,,使用适配器将额外的 Python 类型保存在 SQLite 数据库中。
@anchor{library/sqlite3 letting-your-object-adapt-itself}@anchor{1cc8}
@subsubsection 让对象自行适配


如果类是你自己编写的，这将是一个很好的方式。 假设你有这样一个类:

@example
class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y
@end example

现在你想将这种点对象保存在一个 SQLite 列中。 首先你必须选择一种受支持的类型用来表示点对象。 让我们就用 str 并使用一个分号来分隔坐标值。 然后你需要给你的类加一个方法 @code{__conform__(self, protocol)}，它必须返回转换后的值。 形参 @emph{protocol} 将为 @code{PrepareProtocol}。

@example
import sqlite3

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

    def __conform__(self, protocol):
        if protocol is sqlite3.PrepareProtocol:
            return "%f;%f" % (self.x, self.y)

con = sqlite3.connect(":memory:")
cur = con.cursor()

p = Point(4.0, -3.2)
cur.execute("select ?", (p,))
print(cur.fetchone()[0])

con.close()
@end example

@node 注册可调用的适配器,,让对象自行适配,使用适配器将额外的 Python 类型保存在 SQLite 数据库中。
@anchor{library/sqlite3 registering-an-adapter-callable}@anchor{1cc9}
@subsubsection 注册可调用的适配器


另一种可能的做法是创建一个将该类型转换为字符串表示的函数并使用 @ref{1c9c,,register_adapter()} 注册该函数。

@example
import sqlite3

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

def adapt_point(point):
    return "%f;%f" % (point.x, point.y)

sqlite3.register_adapter(Point, adapt_point)

con = sqlite3.connect(":memory:")
cur = con.cursor()

p = Point(4.0, -3.2)
cur.execute("select ?", (p,))
print(cur.fetchone()[0])

con.close()
@end example

@ref{f2,,sqlite3} 模块有两个适配器可用于 Python 的内置 @ref{193,,datetime.date} 和 @ref{194,,datetime.datetime} 类型。 现在假设我们想要存储 @ref{194,,datetime.datetime} 对象，但不是表示为 ISO 格式，而是表示为 Unix 时间戳。

@example
import sqlite3
import datetime
import time

def adapt_datetime(ts):
    return time.mktime(ts.timetuple())

sqlite3.register_adapter(datetime.datetime, adapt_datetime)

con = sqlite3.connect(":memory:")
cur = con.cursor()

now = datetime.datetime.now()
cur.execute("select ?", (now,))
print(cur.fetchone()[0])

con.close()
@end example

@node 将SQLite 值转换为自定义Python 类型,默认适配器和转换器,使用适配器将额外的 Python 类型保存在 SQLite 数据库中。,SQLite 与 Python 类型
@anchor{library/sqlite3 converting-sqlite-values-to-custom-python-types}@anchor{1cca}
@subsubsection 将SQLite 值转换为自定义Python 类型


编写适配器让你可以将定制的 Python 类型发送给 SQLite。 但要令它真正有用，我们需要实现从 Python 到 SQLite 再回到 Python 的双向转换。

输入转换器。

让我们回到 @code{Point} 类。 我们以字符串形式在 SQLite 中存储了 x 和 y 坐标值。

首先，我们将定义一个转换器函数，它接受这样的字符串作为形参并根据该参数构造一个 @code{Point} 对象。

@cartouche
@quotation 注解 
转换器函数在调用时 @strong{总是} 会附带一个 @ref{32a,,bytes} 对象，无论你将何种数据类型的值发给 SQLite。
@end quotation
@end cartouche

@example
def convert_point(s):
    x, y = map(float, s.split(b";"))
    return Point(x, y)
@end example

现在你需要让 @ref{f2,,sqlite3} 模块知道你从数据库中选取的其实是一个点对象。 有两种方式都可以做到这件事：


@itemize *

@item 
隐式的声明类型

@item 
显式的通过列名
@end itemize

这两种方式会在 @ref{1c91,,模块函数和常量} 一节中描述，相应条目为 @ref{1c96,,PARSE_DECLTYPES} 和 @ref{1c97,,PARSE_COLNAMES} 常量。

下面的示例说明了这两种方法。

@example
import sqlite3

class Point:
    def __init__(self, x, y):
        self.x, self.y = x, y

    def __repr__(self):
        return "(%f;%f)" % (self.x, self.y)

def adapt_point(point):
    return ("%f;%f" % (point.x, point.y)).encode('ascii')

def convert_point(s):
    x, y = list(map(float, s.split(b";")))
    return Point(x, y)

# Register the adapter
sqlite3.register_adapter(Point, adapt_point)

# Register the converter
sqlite3.register_converter("point", convert_point)

p = Point(4.0, -3.2)

#########################
# 1) Using declared types
con = sqlite3.connect(":memory:", detect_types=sqlite3.PARSE_DECLTYPES)
cur = con.cursor()
cur.execute("create table test(p point)")

cur.execute("insert into test(p) values (?)", (p,))
cur.execute("select p from test")
print("with declared types:", cur.fetchone()[0])
cur.close()
con.close()

#######################
# 1) Using column names
con = sqlite3.connect(":memory:", detect_types=sqlite3.PARSE_COLNAMES)
cur = con.cursor()
cur.execute("create table test(p)")

cur.execute("insert into test(p) values (?)", (p,))
cur.execute('select p as "p [point]" from test')
print("with column names:", cur.fetchone()[0])
cur.close()
con.close()
@end example

@node 默认适配器和转换器,,将SQLite 值转换为自定义Python 类型,SQLite 与 Python 类型
@anchor{library/sqlite3 default-adapters-and-converters}@anchor{1ccb}
@subsubsection 默认适配器和转换器


对于 datetime 模块中的 date 和 datetime 类型已提供了默认的适配器。 它们将会以 ISO 日期/ISO 时间戳的形式发给 SQLite。

默认转换器使用的注册名称是针对 @ref{193,,datetime.date} 的 "date" 和针对 @ref{194,,datetime.datetime} 的 "timestamp"。

通过这种方式，你可以在大多数情况下使用 Python 的 date/timestamp 对象而无须任何额外处理。 适配器的格式还与实验性的 SQLite date/time 函数兼容。

下面的示例演示了这一点。

@example
import sqlite3
import datetime

con = sqlite3.connect(":memory:", detect_types=sqlite3.PARSE_DECLTYPES|sqlite3.PARSE_COLNAMES)
cur = con.cursor()
cur.execute("create table test(d date, ts timestamp)")

today = datetime.date.today()
now = datetime.datetime.now()

cur.execute("insert into test(d, ts) values (?, ?)", (today, now))
cur.execute("select d, ts from test")
row = cur.fetchone()
print(today, "=>", row[0], type(row[0]))
print(now, "=>", row[1], type(row[1]))

cur.execute('select current_date as "d [date]", current_timestamp as "ts [timestamp]"')
row = cur.fetchone()
print("current_date", row[0], type(row[0]))
print("current_timestamp", row[1], type(row[1]))

con.close()
@end example

如果存储在 SQLite 中的时间戳的小数位多于 6 个数字，则时间戳转换器会将该值截断至微秒精度。

@node 控制事务,有效使用 sqlite3,SQLite 与 Python 类型,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 controlling-transactions}@anchor{1ccc}@anchor{library/sqlite3 sqlite3-controlling-transactions}@anchor{1ca1}
@subsubsection 控制事务


底层的 @code{sqlite3} 库默认会以 @code{autocommit} 模式运行，但 Python 的 @ref{f2,,sqlite3} 模块默认则不使用此模式。

@code{autocommit} 模式意味着修改数据库的操作会立即生效。 @code{BEGIN} 或 @code{SAVEPOINT} 语句会禁用 @code{autocommit} 模式，而用于结束外层事务的 @code{COMMIT}, @code{ROLLBACK} 或 @code{RELEASE} 则会恢复 @code{autocommit} 模式。

Python 的 @ref{f2,,sqlite3} 模块默认会在数据修改语言 (DML) 类语句 (即 @code{INSERT}/@code{UPDATE}/@code{DELETE}/@code{REPLACE}) 之前隐式地执行一条 @code{BEGIN} 语句。

你可以控制 @ref{f2,,sqlite3} 隐式执行的 @code{BEGIN} 语句的种类，具体做法是通过将 @emph{isolation_level} 形参传给 @ref{3d2,,connect()} 调用，或者通过指定连接的 @code{isolation_level} 属性。 如果你没有指定 @emph{isolation_level}，将使用基本的 @code{BEGIN}，它等价于指定 @code{DEFERRED}。 其他可能的值为 @code{IMMEDIATE} 和 @code{EXCLUSIVE}。

你可以禁用 @ref{f2,,sqlite3} 模块的隐式事务管理，具体做法是将 @code{isolation_level} 设为 @code{None}。 这将使得下层的 @code{sqlite3} 库采用 @code{autocommit} 模式。 随后你可以通过在代码中显式地使用 @code{BEGIN}, @code{ROLLBACK}, @code{SAVEPOINT} 和 @code{RELEASE} 语句来完全控制事务状态。


在 3.6 版更改: 以前 @ref{f2,,sqlite3} 会在 DDL 语句之前隐式地提交未完成事务。 现在则不会再这样做。


@node 有效使用 sqlite3,常见问题,控制事务,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 using-sqlite3-efficiently}@anchor{1ccd}
@subsubsection 有效使用 @code{sqlite3}


@menu
* 使用快捷方式:: 
* 通过名称而不是索引访问索引:: 
* 使用连接作为上下文管理器:: 

@end menu

@node 使用快捷方式,通过名称而不是索引访问索引,,有效使用 sqlite3
@anchor{library/sqlite3 using-shortcut-methods}@anchor{1cce}
@subsubsection 使用快捷方式


使用 @ref{3d0,,Connection} 对象的非标准 @code{execute()}, @code{executemany()} 和 @code{executescript()} 方法，可以更简洁地编写代码，因为不必显式创建（通常是多余的） @ref{1c8c,,Cursor} 对象。相反， @ref{1c8c,,Cursor} 对象是隐式创建的，这些快捷方法返回游标对象。这样，只需对 @ref{3d0,,Connection} 对象调用一次，就能直接执行 @code{SELECT} 语句并遍历对象。

@example
import sqlite3

persons = [
    ("Hugo", "Boss"),
    ("Calvin", "Klein")
    ]

con = sqlite3.connect(":memory:")

# Create the table
con.execute("create table person(firstname, lastname)")

# Fill the table
con.executemany("insert into person(firstname, lastname) values (?, ?)", persons)

# Print the table contents
for row in con.execute("select firstname, lastname from person"):
    print(row)

print("I just deleted", con.execute("delete from person").rowcount, "rows")

# close is not a shortcut method and it's not called automatically,
# so the connection object should be closed manually
con.close()
@end example

@node 通过名称而不是索引访问索引,使用连接作为上下文管理器,使用快捷方式,有效使用 sqlite3
@anchor{library/sqlite3 accessing-columns-by-name-instead-of-by-index}@anchor{1ccf}
@subsubsection 通过名称而不是索引访问索引


@ref{f2,,sqlite3} 模块的一个有用功能是内置的 @ref{758,,sqlite3.Row} 类，它被设计用作行对象的工厂。

该类的行装饰器可以用索引（如元组）和不区分大小写的名称访问：

@example
import sqlite3

con = sqlite3.connect(":memory:")
con.row_factory = sqlite3.Row

cur = con.cursor()
cur.execute("select 'John' as name, 42 as age")
for row in cur:
    assert row[0] == row["name"]
    assert row["name"] == row["nAmE"]
    assert row[1] == row["age"]
    assert row[1] == row["AgE"]

con.close()
@end example

@node 使用连接作为上下文管理器,,通过名称而不是索引访问索引,有效使用 sqlite3
@anchor{library/sqlite3 using-the-connection-as-a-context-manager}@anchor{1cd0}
@subsubsection 使用连接作为上下文管理器


连接对象可以用来作为上下文管理器，它可以自动提交或者回滚事务。如果出现异常，事务会被回滚；否则，事务会被提交。

@example
import sqlite3

con = sqlite3.connect(":memory:")
con.execute("create table person (id integer primary key, firstname varchar unique)")

# Successful, con.commit() is called automatically afterwards
with con:
    con.execute("insert into person(firstname) values (?)", ("Joe",))

# con.rollback() is called after the with block finishes with an exception, the
# exception is still raised and must be caught
try:
    with con:
        con.execute("insert into person(firstname) values (?)", ("Joe",))
except sqlite3.IntegrityError:
    print("couldn't add Joe twice")

# Connection object used as context manager only commits or rollbacks transactions,
# so the connection object should be closed manually
con.close()
@end example

@node 常见问题,,有效使用 sqlite3,sqlite3 --- SQLite 数据库 DB-API 2 0 接口模块
@anchor{library/sqlite3 common-issues}@anchor{1cd1}
@subsubsection 常见问题


@menu
* 多线程: 多线程<3>. 

@end menu

@node 多线程<3>,,,常见问题
@anchor{library/sqlite3 multithreading}@anchor{1cd2}
@subsubsection 多线程


较老版本的 SQLite 在共享线程之间存在连接问题。这就是Python模块不允许线程之间共享连接和游标的原因。如果仍然尝试这样做，则在运行时会出现异常。

唯一的例外是调用 @ref{1cae,,interrupt()} 方法，该方法仅在从其他线程进行调用时才有意义。

@subsubheading 备注


@node 数据压缩和存档,文件格式,数据持久化,Python 标准库
@anchor{library/archiving doc}@anchor{1c3e}@anchor{library/archiving archiving}@anchor{1cd3}@anchor{library/archiving data-compression-and-archiving}@anchor{1cd4}
@section 数据压缩和存档


本章中描述的模块支持 zlib、gzip、bzip2 和 lzma 数据压缩算法，以及创建 ZIP 和 tar 格式的归档文件。参见由 @ref{e9,,shutil} 模块提供的 @ref{b8f,,归档操作} 。

@menu
* zlib: zlib --- 与 gzip 兼容的压缩. 与 gzip 兼容的压缩
* gzip: gzip --- 对 gzip 格式的支持. 对 gzip 格式的支持
* bz2: bz2 --- 对 bzip2 压缩算法的支持. 对 bzip2 压缩算法的支持
* lzma: lzma --- 用 LZMA 算法压缩. 用 LZMA 算法压缩
* zipfile: zipfile --- 使用ZIP存档. 使用ZIP存档
* tarfile: tarfile --- 读写tar归档文件. 读写tar归档文件

@end menu

@node zlib --- 与 gzip 兼容的压缩,gzip --- 对 gzip 格式的支持,,数据压缩和存档
@anchor{library/zlib doc}@anchor{1cd5}@anchor{library/zlib module-zlib}@anchor{144}@anchor{library/zlib zlib-compression-compatible-with-gzip}@anchor{1cd6}
@subsection @code{zlib} --- 与 @code{gzip} 兼容的压缩


@geindex zlib (模块)


__________________________________________________________________


此模块为需要数据压缩的程序提供了一系列函数，用于压缩和解压缩。这些函数使用了 zlib 库。zlib 库的项目主页是 @indicateurl{http://www.zlib.net}. 版本低于 1.1.3 的 zlib 与此 Python 模块之间存在已知的不兼容。1.1.3 版本的 zlib 存在一个安全漏洞，我们推荐使用 1.1.4 或更新的版本。

zlib 的函数有很多选项，一般需要按特定顺序使用。本文档没有覆盖全部的用法。更多详细信息请于 @indicateurl{http://www.zlib.net/manual.html} 参阅官方手册。

要读写 @code{.gz} 格式的文件，请参考 @ref{8c,,gzip} 模块。

此模块中可用的异常和函数如下：

@geindex error
@anchor{library/zlib zlib error}@anchor{1cd7}
@deffn {例外} zlib.error

在压缩或解压缩过程中发生错误时的异常。
@end deffn

@geindex adler32() (在 zlib 模块中)
@anchor{library/zlib zlib adler32}@anchor{1cd8}
@deffn {函数} zlib.adler32 (data[, value])

计算 @emph{data} 的 Adler-32 校验值。(Adler-32 校验的可靠性与 CRC32 基本相当，但比计算 CRC32 更高效。) 计算的结果是一个 32 位的整数。参数 @emph{value} 是校验时的起始值，其默认值为 1。借助参数 @emph{value} 可为分段的输入计算校验值。此算法没有加密强度，不应用于身份验证和数字签名。此算法的目的仅为验证数据的正确性，不适合作为通用散列算法。


在 3.0 版更改: 返回值永远是无符号数。要在所有的 Python 版本和平台上获得相同的值，请使用 @code{adler32(data) & 0xffffffff}。

@end deffn

@geindex compress() (在 zlib 模块中)
@anchor{library/zlib zlib compress}@anchor{5b9}
@deffn {函数} zlib.compress (data, level=-1)

压缩 @emph{data} 中的字节，返回含有已压缩内容的 bytes 对象。参数 @emph{level} 为整数，可取值为 @code{0} 到 @code{9} 或 @code{-1}，用于指定压缩等级。@code{1} (Z_BEST_SPEED) 表示最快速度和最低压缩率，@code{9} (Z_BEST_COMPRESSION) 表示最慢速度和最高压缩率。@code{0} (Z_NO_COMPRESSION) 表示不压缩。参数默认值为 @code{-1} (Z_DEFAULT_COMPRESSION)。Z_DEFAULT_COMPRESSION 是速度和压缩率之间的平衡 (一般相当于设压缩等级为 6)。函数发生错误时抛出 @ref{1cd7,,error} 异常。


在 3.6 版更改: 现在，@emph{level} 可作为关键字参数。

@end deffn

@geindex compressobj() (在 zlib 模块中)
@anchor{library/zlib zlib compressobj}@anchor{1cd9}
@deffn {函数} zlib.compressobj (level=-1, method=DEFLATED, wbits=MAX_WBITS, memLevel=DEF_MEM_LEVEL, strategy=Z_DEFAULT_STRATEGY[, zdict])

返回一个 压缩对象，用来压缩内存中难以容下的数据流。

参数 @emph{level} 为压缩等级，是整数，可取值为 @code{0} 到 @code{9} 或 @code{-1}。@code{1} (Z_BEST_SPEED) 表示最快速度和最低压缩率，@code{9} (Z_BEST_COMPRESSION) 表示最慢速度和最高压缩率。@code{0} (Z_NO_COMPRESSION) 表示不压缩。参数默认值为 @code{-1} (Z_DEFAULT_COMPRESSION)。Z_DEFAULT_COMPRESSION 是速度和压缩率之间的平衡 (一般相当于设压缩等级为 6)。

@emph{method} 表示压缩算法。现在只支持 @code{DEFLATED} 这个算法。

参数 @emph{wbits} 指定压缩数据时所使用的历史缓冲区的大小 (窗口大小)，并指定压缩输出是否包含头部或尾部。参数的默认值是 @code{15} (MAX_WBITS)。参数的值分为几个范围：


@itemize *

@item 
+9 至 +15：窗口大小以二为底的对数。 即这些值对应着 512 至 32768 的窗口大小。 更大的值会提供更好的压缩，同时内存开销也会更大。 压缩输出会包含 zlib 特定格式的头部和尾部。

@item 
−9 至 −15：绝对值为窗口大小以二为底的对数。 压缩输出仅包含压缩数据，没有头部和尾部。

@item 
+25 至 +31 = 16 + (9 至 15)：后 4 个比特位为窗口大小以二为底的对数。 压缩输出包含一个基本的 @code{gzip} 头部，并以校验和为尾部。
@end itemize

参数 @emph{memLevel} 指定内部压缩操作时所占用内存大小。参数取 @code{1} 到 @code{9}。更大的值占用更多的内存，同时速度也更快输出也更小。

参数 @emph{strategy} 用于调节压缩算法。可取值为  @code{Z_DEFAULT_STRATEGY}、@code{Z_FILTERED}、@code{Z_HUFFMAN_ONLY}、@code{Z_RLE} (zlib 1.2.0.1) 或 @code{Z_FIXED} (zlib 1.2.2.2)。

参数 @emph{zdict} 指定预定义的压缩字典。它是一个字节序列 (如 @ref{32a,,bytes} 对象)，其中包含用户认为要压缩的数据中可能频繁出现的子序列。频率高的子序列应当放在字典的尾部。


在 3.3 版更改: 添加关键字参数 @emph{zdict}。

@end deffn

@geindex crc32() (在 zlib 模块中)
@anchor{library/zlib zlib crc32}@anchor{1cda}
@deffn {函数} zlib.crc32 (data[, value])

@geindex Cyclic Redundancy Check
@geindex checksum; Cyclic Redundancy Check

计算 @emph{data} 的 CRC (循环冗余校验) 值。计算的结果是一个 32 位的整数。参数 @emph{value} 是校验时的起始值，其默认值为 0。借助参数 @emph{value} 可为分段的输入计算校验值。此算法没有加密强度，不应用于身份验证和数字签名。此算法的目的仅为验证数据的正确性，不适合作为通用散列算法。


在 3.0 版更改: 返回值永远是无符号数。要在所有的 Python 版本和平台上获得相同的值，请使用 @code{crc32(data) & 0xffffffff}。

@end deffn

@geindex decompress() (在 zlib 模块中)
@anchor{library/zlib zlib decompress}@anchor{5ba}
@deffn {函数} zlib.decompress (data, wbits=MAX_WBITS, bufsize=DEF_BUF_SIZE)

解压 @emph{data} 中的字节，返回含有已解压内容的 bytes 对象。参数 @emph{wbits} 取决于 @emph{data} 的格式，具体参见下边的说明。@emph{bufsize} 为输出缓冲区的起始大小。函数发生错误时抛出 @ref{1cd7,,error} 异常。
@anchor{library/zlib decompress-wbits}@anchor{1cdb}
@emph{wbits} 形参控制历史缓冲区的大小（或称“窗口大小”）以及所期望的头部和尾部格式。 它类似于 @ref{1cd9,,compressobj()} 的形参，但可接受更大范围的值：


@itemize *

@item 
+8 至 +15：窗口尺寸以二为底的对数。 输入必须包含 zlib 头部和尾部。

@item 
0：根据 zlib 头部自动确定窗口大小。 只从 zlib 1.2.3.5 版起受支持。

@item 
−8 至 −15：使用 @emph{wbits} 的绝对值作为窗口大小以二为底的对数。 输入必须为原始数据流，没有头部和尾部。

@item 
+24 至 +31 = 16 + (8 至 15)：使用后 4 个比特位作为窗口大小以二为底的对数。 输入必须包括 gzip 头部和尾部。

@item 
+40 至 +47 = 32 + (8 至 15)：使用后 4 个比特位作为窗口大小以二为底的对数，并且自动接受 zlib 或 gzip 格式。
@end itemize

当解压缩一个数据流时，窗口大小必须不小于用于压缩数据流的原始窗口大小；使用太小的值可能导致 @ref{1cd7,,error} 异常。 默认 @emph{wbits} 值对应于最大的窗口大小并且要求包括 zlib 头部和尾部。

@emph{bufsize} 是用于存放解压数据的缓冲区初始大小。 如果需要更大空间，缓冲区大小将按需增加，因此你不需要让这个值完全精确；对其进行调整仅会节省一点对 @code{malloc()} 的调用次数。


在 3.6 版更改: @emph{wbits} 和 @emph{bufsize} 可用作关键字参数。

@end deffn

@geindex decompressobj() (在 zlib 模块中)
@anchor{library/zlib zlib decompressobj}@anchor{1cdc}
@deffn {函数} zlib.decompressobj (wbits=MAX_WBITS[, zdict])

返回一个解压对象，用来解压无法被一次性放入内存的数据流。

@emph{wbits} 形参控制历史缓冲区的大小（或称“窗口大小”）以及所期望的头部和尾部格式。 它的含义与 @ref{1cdb,,对 decompress() 的描述} 相同。

@emph{zdict} 形参指定指定一个预定义的压缩字典。 如果提供了此形参，它必须与产生将解压数据的压缩器所使用的字典相同。

@cartouche
@quotation 注解 
如果 @emph{zdict} 是一个可变对象 (例如 @ref{32b,,bytearray})，则你不可在对 @ref{1cdc,,decompressobj()} 的调用和对解压器的 @code{decompress()} 方法的调用之间修改其内容。
@end quotation
@end cartouche


在 3.3 版更改: 增加了 @emph{zdict} 形参。

@end deffn

压缩对象支持以下方法：

@geindex compress() (zlib.Compress 方法)
@anchor{library/zlib zlib Compress compress}@anchor{1cdd}
@deffn {方法} Compress.compress (data)

压缩 @emph{data} 并返回 bytes 对象，这个对象含有 @emph{data} 的部分或全部内容的已压缩数据。所得的对象必须拼接在上一次调用 @ref{5b9,,compress()} 方法所得数据的后面。缓冲区中可能留存部分输入以供下一次调用。
@end deffn

@geindex flush() (zlib.Compress 方法)
@anchor{library/zlib zlib Compress flush}@anchor{1cde}
@deffn {方法} Compress.flush ([mode])

压缩所有缓冲区的数据并返回已压缩的数据。参数 @emph{mode} 可以传入的常量为：@code{Z_NO_FLUSH}、@code{Z_PARTIAL_FLUSH}、@code{Z_SYNC_FLUSH}、@code{Z_FULL_FLUSH}、@code{Z_BLOCK} (zlib 1.2.3.4) 或 @code{Z_FINISH}。默认值为 @code{Z_FINISH}。@code{Z_FINISH} 关闭已压缩数据流并不允许再压缩其他数据，@code{Z_FINISH}  以外的值皆允许这个对象继续压缩数据。调用 @ref{1cde,,flush()} 方法并将 @emph{mode} 设为 @code{Z_FINISH} 后会无法再次调用 @ref{5b9,,compress()}，此时只能删除这个对象。
@end deffn

@geindex copy() (zlib.Compress 方法)
@anchor{library/zlib zlib Compress copy}@anchor{1cdf}
@deffn {方法} Compress.copy ()

返回此压缩对象的一个拷贝。它可以用来高效压缩一系列拥有相同前缀的数据。
@end deffn


在 3.8 版更改: 添加了对压缩对象执行 @ref{3c3,,copy.copy()} 和 @ref{3c4,,copy.deepcopy()} 的支持。


解压缩对象支持以下方法：

@geindex unused_data (zlib.Decompress 属性)
@anchor{library/zlib zlib Decompress unused_data}@anchor{1ce0}
@deffn {属性} Decompress.unused_data

一个 bytes 对象，其中包含压缩数据结束之后的任何字节数据。 也就是说，它将为 @code{b""} 直到包含压缩数据的末尾字节可用。 如果整个结果字节串都包含压缩数据，它将为一个空的 bytes 对象 @code{b""}。
@end deffn

@geindex unconsumed_tail (zlib.Decompress 属性)
@anchor{library/zlib zlib Decompress unconsumed_tail}@anchor{1ce1}
@deffn {属性} Decompress.unconsumed_tail

一个 bytes 对象，其中包含未被上一次 @ref{5ba,,decompress()} 调用所消耗的任何数据。 此数据不能被 zlib 机制看到，因此你必须将其送回（可能要附带额外的数据拼接）到后续的 @ref{5ba,,decompress()} 方法调用以获得正确的输出。
@end deffn

@geindex eof (zlib.Decompress 属性)
@anchor{library/zlib zlib Decompress eof}@anchor{ac1}
@deffn {属性} Decompress.eof

一个布尔值，指明是否已到达压缩数据流的末尾。

这使得区分正确构造的压缩数据流和不完整或被截断的压缩数据流成为可能。


3.3 新版功能.

@end deffn

@geindex decompress() (zlib.Decompress 方法)
@anchor{library/zlib zlib Decompress decompress}@anchor{1ce2}
@deffn {方法} Decompress.decompress (data, max_length=0)

解压缩 @emph{data} 并返回 bytes 对象，其中包含对应于 @emph{string} 中至少一部分数据的解压缩数据。 此数据应当被拼接到之前任何对 @ref{5ba,,decompress()} 方法的调用所产生的输出。 部分输入数据可能会被保留在内部缓冲区以供后续处理。

如果可选的形参 @emph{max_length} 非零则返回值将不会长于 @emph{max_length}。 这可能意味着不是所有已压缩输入都能被处理；并且未被消耗的数据将被保存在 @ref{1ce1,,unconsumed_tail} 属性中。 如果要继续解压缩则这个字节串必须被传给对 @ref{5ba,,decompress()} 的后续调用。 如果 @emph{max_length} 为零则整个输入都会被解压缩，并且 @ref{1ce1,,unconsumed_tail} 将为空。


在 3.6 版更改: @emph{max_length} 可用作关键字参数。

@end deffn

@geindex flush() (zlib.Decompress 方法)
@anchor{library/zlib zlib Decompress flush}@anchor{1ce3}
@deffn {方法} Decompress.flush ([length])

所有挂起的输入会被处理，并且返回包含剩余未压缩输出的 bytes 对象。 在调用 @ref{1ce3,,flush()} 之后，@ref{5ba,,decompress()} 方法将无法被再次调用；唯一可行的操作是删除该对象。

可选的形参 @emph{length} 设置输出缓冲区的初始大小。
@end deffn

@geindex copy() (zlib.Decompress 方法)
@anchor{library/zlib zlib Decompress copy}@anchor{1ce4}
@deffn {方法} Decompress.copy ()

返回解压缩对象的一个拷贝。 它可以用来在数据流的中途保存解压缩器的状态以便加快随机查找数据流后续位置的速度。
@end deffn


在 3.8 版更改: 添加了对解压缩对象执行 @ref{3c3,,copy.copy()} 和 @ref{3c4,,copy.deepcopy()} 的支持。


通过下列常量可获取模块所使用的 zlib 库的版本信息：

@geindex ZLIB_VERSION() (在 zlib 模块中)
@anchor{library/zlib zlib ZLIB_VERSION}@anchor{1ce5}
@deffn {数据} zlib.ZLIB_VERSION

构建此模块时所用的 zlib 库的版本字符串。它的值可能与运行时所加载的 zlib 不同。运行时加载的 zlib 库的版本字符串为 @ref{ac2,,ZLIB_RUNTIME_VERSION}。
@end deffn

@geindex ZLIB_RUNTIME_VERSION() (在 zlib 模块中)
@anchor{library/zlib zlib ZLIB_RUNTIME_VERSION}@anchor{ac2}
@deffn {数据} zlib.ZLIB_RUNTIME_VERSION

解释器所加载的 zlib 库的版本字符串。


3.3 新版功能.

@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{8c,,gzip}

读写 @code{gzip} 格式的文件。

@item @indicateurl{http://www.zlib.net}

zlib 库项目主页。

@item @indicateurl{http://www.zlib.net/manual.html}

zlib 库用户手册。提供了库的许多功能的解释和用法。
@end table


@node gzip --- 对 gzip 格式的支持,bz2 --- 对 bzip2 压缩算法的支持,zlib --- 与 gzip 兼容的压缩,数据压缩和存档
@anchor{library/gzip doc}@anchor{1ce6}@anchor{library/gzip gzip-support-for-gzip-files}@anchor{1ce7}@anchor{library/gzip module-gzip}@anchor{8c}
@subsection @code{gzip} --- 对 @code{gzip} 格式的支持


@geindex gzip (模块)

@strong{源代码：} Lib/gzip.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/gzip.py}


__________________________________________________________________


此模块提供的简单接口帮助用户压缩和解压缩文件，功能类似于 GNU 应用程序 @code{gzip} 和 @code{gunzip}。

数据压缩由 @ref{144,,zlib} 模块提供。

@ref{8c,,gzip} 模块提供 @ref{6d7,,GzipFile} 类和 @ref{1ce8,,open()}、@ref{1d1,,compress()}、@ref{b82,,decompress()} 几个便利的函数。@ref{6d7,,GzipFile} 类可以读写 @code{gzip} 格式的文件，还能自动压缩和解压缩数据，这让操作压缩文件如同操作普通的 @ref{b3b,,file object} 一样方便。

注意，此模块不支持部分可以被 @code{gzip} 和 @code{gunzip} 解压的格式，如利用 @code{compress} 或 @code{pack} 压缩所得的文件。

这个模块定义了以下内容：

@geindex open() (在 gzip 模块中)
@anchor{library/gzip gzip open}@anchor{1ce8}
@deffn {函数} gzip.open (filename, mode='rb', compresslevel=9, encoding=None, errors=None, newline=None)

以二进制方式或者文本方式打开一个 gzip 格式的压缩文件，返回一个 @ref{b3b,,file object}。

@emph{filename} 参数可以是一个实际的文件名(一个a @ref{329,,str} 对象或者 @ref{32a,,bytes} 对象), 或者是一个用来读写的已存在的文件对象。

@emph{mode} 参数可以是二进制模式： @code{'r'}, @code{'rb'}, @code{'a'}, @code{'ab'}, @code{'w'}, @code{'wb'}, @code{'x'} or @code{'xb'} , 或者是文本模式 @code{'rt'}, @code{'at'}, @code{'wt'}, or @code{'xt'}。默认值是 @code{'rb'}。

The @emph{compresslevel} argument is an integer from 0 to 9, as for the
@ref{6d7,,GzipFile} constructor.

对于二进制模式，这个函数等价于 @ref{6d7,,GzipFile} 构造器：@code{GzipFile(filename, mode, compresslevel)}。在这个例子中，@emph{encoding}, @emph{errors} 和 @emph{newline} 三个参数一定不要设置。

对于文本模式，将会创建一个 @ref{6d7,,GzipFile} 对象，并将它封装到一个 @ref{5ee,,io.TextIOWrapper} 实例中， 这个实例默认了指定编码，错误抓获行为和行。


在 3.3 版更改: 支持 @emph{filename} 为一个文件对象，支持文本模式和 @emph{encoding}, @emph{errors} 和 @emph{newline} 参数。



在 3.4 版更改: 支持 @code{'x'}, @code{'xb'} 和`@w{`}'xt'`@w{`} 三种模式。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex BadGzipFile
@anchor{library/gzip gzip BadGzipFile}@anchor{1d2}
@deffn {例外} gzip.BadGzipFile

针对无效 gzip 文件引发的异常。 它继承自 @ref{1d3,,OSError}。 针对无效 gzip 文件也可能引发 @ref{c65,,EOFError} 和 @ref{1cd7,,zlib.error}。


3.8 新版功能.

@end deffn

@geindex GzipFile (gzip 中的类)
@anchor{library/gzip gzip GzipFile}@anchor{6d7}
@deffn {类} gzip.GzipFile (filename=None, mode=None, compresslevel=9, fileobj=None, mtime=None)

@ref{6d7,,GzipFile} 类的构造器支持 @code{truncate()} 的异常，与 @ref{b3b,,file object} 的大多数方法非常相似。@emph{fileobj} 和 @emph{filename} 至少有一个不为空。

新的实例基于  @emph{fileobj}，它可以是一个普通文件，一个 @ref{795,,io.BytesIO} 对象，或者任何一个与文件相似的对象。当 @emph{filename} 是一个文件对象时，它的默认值是 @code{None}。

当  @emph{fileobj} 为 @code{None} 时， @emph{filename} 参数只用于  @code{gzip} 文件头中，这个文件有可能包含未压缩文件的源文件名。如果文件可以被识别，默认 @emph{fileobj} 的文件名；否则默认为空字符串，在这种情况下文件头将不包含源文件名。

@emph{mode} 可以是`@w{`}'r'@code{, `@w{`}'rb'}, @code{'a'}, @code{'ab'}, @code{'w'}, @code{'wb'}, @code{'x'}, 或者 @code{'xb'}，选择哪个取决于是读文件还是写文件。如果可以分辨是，默认的模式是 @emph{fileobj}，否则为 @code{'rb'}。

需要注意的是，文件默认使用二进制模式打开。如果要以文本模式打开文件一个压缩文件，请使用 @ref{1ce8,,open()} 方法(或者使用 @ref{5ee,,io.TextIOWrapper} 包装 @ref{6d7,,GzipFile} )。

@emph{compresslevel} 参数是一个从 @code{0} 到 @code{9} 的整数，用于控制压缩等级；@code{1} 最快但压缩比例最小，@code{9} 最慢但压缩比例最大。 @code{0} 不压缩。默认为 @code{9}。

@emph{mtime} 参数是一个可选的数字时间戳用于写入流的最后修改字段，。@emph{mtime} 只在压缩模式中使用。如果省略或者值为 @code{None}，则使用当前时间。更多细节，详见 @ref{1ce9,,mtime} 属性。

调用 @ref{6d7,,GzipFile} 的 @code{close()} 方法不会关闭 @emph{fileobj}，因为你可以希望增加其它内容到已经压缩的数中。你可以将一个 @ref{795,,io.BytesIO} 对象作为 @emph{fileobj}，也可以使用 @ref{795,,io.BytesIO} 的 @ref{1cea,,getvalue()} 方法从内存缓存中恢复数据。

@ref{6d7,,GzipFile} 支持 @ref{583,,io.BufferedIOBase} 类的接口, 包括迭代和 @ref{6e3,,with} 语句。只有 @code{truncate()} 方法没有实现。

@ref{6d7,,GzipFile} 还提供了以下的方法和属性:

@geindex peek() (gzip.GzipFile 方法)
@anchor{library/gzip gzip GzipFile peek}@anchor{b81}
@deffn {方法} peek (n)

在不移动文件指针的情况下读取  @emph{n} 个未压缩字节。最多只有一个单独的读取流来服务这个方法调用。返回的字节数不一定刚好等于要求的数量。

@cartouche
@quotation 注解 
调用 @ref{b81,,peek()} 并没有改变 @ref{6d7,,GzipFile} 的文件指针，它可能改变潜在文件对象(例如： @ref{6d7,,GzipFile} 使用 @emph{fileobj} 参数进行初始化)。
@end quotation
@end cartouche


3.2 新版功能.

@end deffn

@geindex mtime (gzip.GzipFile 属性)
@anchor{library/gzip gzip GzipFile mtime}@anchor{1ce9}
@deffn {属性} mtime

在解压的过程中，最后修改时间字段的值可能来自于这个属性，以整数的形式出现。在读取任何文件头信息前，初始值为 @code{None}。

所有 @code{gzip} 东方压缩流中必须包含时间戳这个字段。以便于像 @code{gunzip}这样的程序可以使用时间戳。格式与 @ref{316,,time.time()} 的返回值和  @ref{1f1,,os.stat()} 对象的 @ref{1ceb,,st_mtime} 属性值一样。
@end deffn


在 3.1 版更改: 支持 @ref{6e3,,with} 语句，构造器参数 @emph{mtime} 和  @ref{1ce9,,mtime} 属性。



在 3.2 版更改: 添加了对零填充和不可搜索文件的支持。



在 3.3 版更改: 实现 @ref{1cec,,io.BufferedIOBase.read1()}  方法。



在 3.4 版更改: 支持 @code{'x'} and @code{'xb'} 两种模式。



在 3.5 版更改: 支持写入任意 @ref{5e3,,bytes-like objects}。@ref{1ced,,read()} 方法可以接受`@w{`}None`@w{`}为参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex compress() (在 gzip 模块中)
@anchor{library/gzip gzip compress}@anchor{1d1}
@deffn {函数} gzip.compress (data, compresslevel=9, *, mtime=None)

压缩 @emph{data}，返回一个包含压缩数据的 @ref{32a,,bytes} 对象。 @emph{compresslevel} 和 @emph{mtime} 的含义与上文中 @ref{6d7,,GzipFile} 构造器的相同。


3.2 新版功能.



在 3.8 版更改: 添加了 @emph{mtime} 形参用于可重复的输出。

@end deffn

@geindex decompress() (在 gzip 模块中)
@anchor{library/gzip gzip decompress}@anchor{b82}
@deffn {函数} gzip.decompress (data)

解压缩 @emph{data}，返回一个包含未压缩数据的 @ref{32a,,bytes} 对象。


3.2 新版功能.

@end deffn

@menu
* 用法示例:: 
* 命令行界面:: 

@end menu

@node 用法示例,命令行界面,,gzip --- 对 gzip 格式的支持
@anchor{library/gzip examples-of-usage}@anchor{1cee}@anchor{library/gzip gzip-usage-examples}@anchor{1cef}
@subsubsection 用法示例


读取压缩文件示例：

@example
import gzip
with gzip.open('/home/joe/file.txt.gz', 'rb') as f:
    file_content = f.read()
@end example

创建GZIP 文件示例：

@example
import gzip
content = b"Lots of content here"
with gzip.open('/home/joe/file.txt.gz', 'wb') as f:
    f.write(content)
@end example

使用 GZIP 压缩已有的文件示例：

@example
import gzip
import shutil
with open('/home/joe/file.txt', 'rb') as f_in:
    with gzip.open('/home/joe/file.txt.gz', 'wb') as f_out:
        shutil.copyfileobj(f_in, f_out)
@end example

使用 GZIP 压缩二进制字符串示例：

@example
import gzip
s_in = b"Lots of content here"
s_out = gzip.compress(s_in)
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{144,,zlib}

支持 @code{gzip} 格式所需要的基本压缩模块。
@end table


@node 命令行界面,,用法示例,gzip --- 对 gzip 格式的支持
@anchor{library/gzip command-line-interface}@anchor{1cf0}
@subsubsection 命令行界面


@ref{8c,,gzip} 模块提供了简单的命令行界面用于压缩和解压缩文件。

在执行后 @ref{8c,,gzip} 模块会保留输入文件。


在 3.8 版更改: 添加一个带有用法说明的新命令行界面命令。 默认情况下，当你要执行 CLI 时，默认压缩等级为 6。


@menu
* 命令行选项:: 

@end menu

@node 命令行选项,,,命令行界面
@anchor{library/gzip command-line-options}@anchor{1cf1}
@subsubsection 命令行选项


@geindex gzip command line option; file
@anchor{library/gzip cmdoption-gzip-arg-file}@anchor{1cf2}
@deffn {程序选项} file

如果 @emph{file} 未指定，则从 @ref{306,,sys.stdin} 读取。
@end deffn

@geindex gzip command line option; --fast
@anchor{library/gzip cmdoption-gzip-fast}@anchor{1cf3}
@deffn {程序选项} @w{-}@w{-}fast

指明最快速的压缩方法（较低压缩率）。
@end deffn

@geindex gzip command line option; --best
@anchor{library/gzip cmdoption-gzip-best}@anchor{1cf4}
@deffn {程序选项} @w{-}@w{-}best

指明最慢速的压缩方法（最高压缩率）。
@end deffn

@geindex gzip command line option; -d
@geindex gzip command line option; --decompress
@anchor{library/gzip cmdoption-gzip-d}@anchor{1cf5}
@deffn {程序选项} @w{-}d, @w{-}@w{-}decompress

解压缩给定的文件。
@end deffn

@geindex gzip command line option; -h
@geindex gzip command line option; --help
@anchor{library/gzip cmdoption-gzip-h}@anchor{1cf6}
@deffn {程序选项} @w{-}h, @w{-}@w{-}help

显示帮助消息。
@end deffn

@node bz2 --- 对 bzip2 压缩算法的支持,lzma --- 用 LZMA 算法压缩,gzip --- 对 gzip 格式的支持,数据压缩和存档
@anchor{library/bz2 doc}@anchor{1cf7}@anchor{library/bz2 bz2-support-for-bzip2-compression}@anchor{1cf8}@anchor{library/bz2 module-bz2}@anchor{14}
@subsection @code{bz2} --- 对 @code{bzip2} 压缩算法的支持


@geindex bz2 (模块)

@strong{源代码：} Lib/bz2.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/bz2.py}


__________________________________________________________________


此模块提供了使用 bzip2 压缩算法压缩和解压数据的一套完整的接口。

@ref{14,,bz2} 模块包含：


@itemize *

@item 
用于读写压缩文件的 @ref{9d0,,open()} 函数和 @ref{92b,,BZ2File} 类。

@item 
用于增量压缩和解压的 @ref{1cf9,,BZ2Compressor} 和 @ref{1cfa,,BZ2Decompressor} 类。

@item 
用于一次性压缩和解压的 @ref{180b,,compress()} 和 @ref{9d1,,decompress()} 函数。
@end itemize

此模块中的所有类都能安全地从多个线程访问。

@menu
* 文件压缩和解压:: 
* 增量压缩和解压:: 
* 一次性压缩或解压缩:: 
* 用法示例: 用法示例<2>. 

@end menu

@node 文件压缩和解压,增量压缩和解压,,bz2 --- 对 bzip2 压缩算法的支持
@anchor{library/bz2 de-compression-of-files}@anchor{1cfb}
@subsubsection 文件压缩和解压


@geindex open() (在 bz2 模块中)
@anchor{library/bz2 bz2 open}@anchor{9d0}
@deffn {函数} bz2.open (filename, mode='r', compresslevel=9, encoding=None, errors=None, newline=None)

以二进制或文本模式打开 bzip2 压缩文件，返回一个 @ref{b3b,,file object}。

和 @ref{92b,,BZ2File} 的构造函数类似，@emph{filename} 参数可以是一个实际的文件名（@ref{329,,str} 或 @ref{32a,,bytes} 对象），或是已有的可供读取或写入的文件对象。

@emph{mode} 参数可设为二进制模式的 @code{'r'}、@code{'rb'}、@code{'w'}、@code{'wb'}、@code{'x'}、@code{'xb'}、@code{'a'} 或 @code{'ab'}，或者文本模式的 @code{'rt'}、@code{'wt'}、@code{'xt'} 或 @code{'at'}。默认是 @code{'rb'}。

@emph{compresslevel} 参数是 1 到 9 的整数，和 @ref{92b,,BZ2File} 的构造函数一样。

对于二进制模式，这个函数等价于 @ref{92b,,BZ2File} 构造器: @code{BZ2File(filename, mode, compresslevel=compresslevel)}。 在这种情况下，不可提供 @emph{encoding}, @emph{errors} 和 @emph{newline} 参数。

对于文本模式，将会创建一个 @ref{92b,,BZ2File} 对象，并将它包装到一个 @ref{5ee,,io.TextIOWrapper} 实例中，此实例带有指定的编码格式、错误处理行为和行结束符。


3.3 新版功能.



在 3.4 版更改: 添加了 @code{'x'} (单独创建) 模式。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex BZ2File (bz2 中的类)
@anchor{library/bz2 bz2 BZ2File}@anchor{92b}
@deffn {类} bz2.BZ2File (filename, mode='r', buffering=None, compresslevel=9)

用二进制模式打开 bzip2 压缩文件。

如果 @emph{filename} 是一个 @ref{329,,str} 或 @ref{32a,,bytes} 对象，则打开名称对应的文件目录。 否则的话，@emph{filename} 应当是一个 @ref{b3b,,file object}，它将被用来读取或写入压缩数据。

@emph{mode} 参数可以是表示读取的 @code{'r'} (默认值)，表示覆写的 @code{'w'}，表示单独创建的 @code{'x'}，或表示添加的 @code{'a'}。 这些模式还可分别以 @code{'rb'}, @code{'wb'}, @code{'xb'} 和 @code{'ab'} 的等价形式给出。

如果 @emph{filename} 是一个文件对象（而不是实际的文件名），则 @code{'w'} 模式并不会截断文件，而是会等价于 @code{'a'}。

@emph{buffering} 参数会被忽略。 从 Python 3.0 开始它已被弃用。

如果 @emph{mode} 为 @code{'w'} 或 @code{'a'}，则 @emph{compresslevel} 可以是 @code{1} 到 @code{9} 之间的整数，用于指定压缩等级: @code{1} 产生最低压缩率，而 @code{9} (默认值) 产生最高压缩率。

如果 @emph{mode} 为 @code{'r'}，则输入文件可以为多个压缩流的拼接。

@ref{92b,,BZ2File} 提供了 @ref{583,,io.BufferedIOBase} 所指定的所有成员，但 @code{detach()} 和 @code{truncate()} 除外。 并支持迭代和 @ref{6e3,,with} 语句。

@ref{92b,,BZ2File} 还提供了以下方法：

@geindex peek() (bz2.BZ2File 方法)
@anchor{library/bz2 bz2 BZ2File peek}@anchor{1cfc}
@deffn {方法} peek ([n])

返回缓冲的数据而不前移文件位置。 至少将返回一个字节的数据（除非为 EOF）。 实际返回的字节数不确定。

@cartouche
@quotation 注解 
虽然调用 @ref{1cfc,,peek()} 不会改变 @ref{92b,,BZ2File} 的文件位置，但它可能改变下层文件对象的位置（举例来说如果 @ref{92b,,BZ2File} 是通过传入一个文件对象作为 @emph{filename} 的话）。
@end quotation
@end cartouche


3.3 新版功能.

@end deffn


3.0 版后已移除: 关键字参数 @emph{buffering} 已弃用，现在会被忽略。



在 3.1 版更改: 添加了对 @ref{6e3,,with} 语句的支持。



在 3.3 版更改: 添加了 @code{fileno()}, @code{readable()}, @code{seekable()}, @code{writable()}, @code{read1()} 和 @code{readinto()} 方法。



在 3.3 版更改: 添加了对 @emph{filename} 使用 @ref{b3b,,file object} 而非实际文件名的支持。



在 3.3 版更改: 添加了 @code{'a'} (append) 模式，以及对读取多数据流文件的支持。



在 3.4 版更改: 添加了 @code{'x'} (单独创建) 模式。



在 3.5 版更改: @ref{1ced,,read()} 方法现在接受 @code{None} 作为参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@node 增量压缩和解压,一次性压缩或解压缩,文件压缩和解压,bz2 --- 对 bzip2 压缩算法的支持
@anchor{library/bz2 incremental-de-compression}@anchor{1cfd}
@subsubsection 增量压缩和解压


@geindex BZ2Compressor (bz2 中的类)
@anchor{library/bz2 bz2 BZ2Compressor}@anchor{1cf9}
@deffn {类} bz2.BZ2Compressor (compresslevel=9)

创建一个新的压缩器对象。 此对象可被用来执行增量数据压缩。 对于一次性压缩，请改用 @ref{180b,,compress()} 函数。

如果给定 @emph{compresslevel}，它必须为 @code{1} 至 @code{9} 之间的整数。 默认值为 @code{9}。

@geindex compress() (bz2.BZ2Compressor 方法)
@anchor{library/bz2 bz2 BZ2Compressor compress}@anchor{1cfe}
@deffn {方法} compress (data)

向压缩器对象提供数据。 在可能的情况下返回一段已压缩数据，否则返回空字节串。

当你已结束向压缩器提供数据时，请调用 @ref{1cff,,flush()} 方法来完成压缩进程。
@end deffn

@geindex flush() (bz2.BZ2Compressor 方法)
@anchor{library/bz2 bz2 BZ2Compressor flush}@anchor{1cff}
@deffn {方法} flush ()

结束压缩进程，返回内部缓冲中剩余的压缩完成的数据。

调用此方法之后压缩器对象将不可再被使用。
@end deffn
@end deffn

@geindex BZ2Decompressor (bz2 中的类)
@anchor{library/bz2 bz2 BZ2Decompressor}@anchor{1cfa}
@deffn {类} bz2.BZ2Decompressor

创建一个新的解压缩器对象。 此对象可被用来执行增量数据解压缩。 对于一次性解压缩，请改用 @ref{9d1,,decompress()} 函数。

@cartouche
@quotation 注解 
这个类不会透明地处理包含多个已压缩数据流的输入，这不同于 @ref{9d1,,decompress()} 和 @ref{92b,,BZ2File}。 如果你需要通过 @ref{1cfa,,BZ2Decompressor} 来解压缩多个数据流输入，你必须为每个数据流都使用新的解压缩器。
@end quotation
@end cartouche

@geindex decompress() (bz2.BZ2Decompressor 方法)
@anchor{library/bz2 bz2 BZ2Decompressor decompress}@anchor{69d}
@deffn {方法} decompress (data, max_length=-1)

解压缩 @emph{data} (一个 @ref{5e3,,bytes-like object})，返回字节串形式的解压缩数据。 某些 @emph{data} 可以在内部被缓冲，以便用于后续的 @ref{9d1,,decompress()} 调用。 返回的数据应当与之前任何 @ref{9d1,,decompress()} 调用的输出进行拼接。

如果 @emph{max_length} 为非负数，将返回至多 @emph{max_length} 个字节的解压缩数据。 如果达到此限制并且可以产生后续输出，则 @ref{1d00,,needs_input} 属性将被设为 @code{False}。 在这种情况下，下一次 @ref{69d,,decompress()} 调用提供的 @emph{data} 可以为 @code{b'@w{'}} 以获取更多的输出。

如果所有输入数据都已被解压缩并返回（或是因为它少于 @emph{max_length} 个字节，或是因为 @emph{max_length} 为负数），则 @ref{1d00,,needs_input} 属性将被设为 @code{True}。

在到达数据流末尾之后再尝试解压缩数据会引发 @cite{EOFError}。 在数据流末尾之后获取的任何数据都会被忽略并存储至 @ref{1d01,,unused_data} 属性。


在 3.5 版更改: 添加了 @emph{max_length} 形参。

@end deffn

@geindex eof (bz2.BZ2Decompressor 属性)
@anchor{library/bz2 bz2 BZ2Decompressor eof}@anchor{1d02}
@deffn {属性} eof

若达到了数据流的末尾标记则为 @code{True}。


3.3 新版功能.

@end deffn

@geindex unused_data (bz2.BZ2Decompressor 属性)
@anchor{library/bz2 bz2 BZ2Decompressor unused_data}@anchor{1d01}
@deffn {属性} unused_data

在压缩数据流的末尾之后获取的数据。

如果在达到数据流末尾之前访问此属性，其值将为 @code{b'@w{'}}。
@end deffn

@geindex needs_input (bz2.BZ2Decompressor 属性)
@anchor{library/bz2 bz2 BZ2Decompressor needs_input}@anchor{1d00}
@deffn {属性} needs_input

如果在要求新的未解压缩输入之前 @ref{69d,,decompress()} 方法可以提供更多的解压缩数据则为 @code{False}。


3.5 新版功能.

@end deffn
@end deffn

@node 一次性压缩或解压缩,用法示例<2>,增量压缩和解压,bz2 --- 对 bzip2 压缩算法的支持
@anchor{library/bz2 one-shot-de-compression}@anchor{1d03}
@subsubsection 一次性压缩或解压缩


@geindex compress() (在 bz2 模块中)
@anchor{library/bz2 bz2 compress}@anchor{180b}
@deffn {函数} bz2.compress (data, compresslevel=9)

压缩 @emph{data}，此参数为一个 @ref{5e3,,字节类对象}。

如果给定 @emph{compresslevel}，它必须为 @code{1} 至 @code{9} 之间的整数。 默认值为 @code{9}。

对于增量压缩，请改用 @ref{1cf9,,BZ2Compressor}。
@end deffn

@geindex decompress() (在 bz2 模块中)
@anchor{library/bz2 bz2 decompress}@anchor{9d1}
@deffn {函数} bz2.decompress (data)

解压缩 @emph{data}，此参数为一个 @ref{5e3,,字节类对象}。

如果 @emph{data} 是多个压缩数据流的拼接，则解压缩所有数据流。

对于增量解压缩，请改用 @ref{1cfa,,BZ2Decompressor}。


在 3.3 版更改: 支持了多数据流的输入。

@end deffn

@node 用法示例<2>,,一次性压缩或解压缩,bz2 --- 对 bzip2 压缩算法的支持
@anchor{library/bz2 bz2-usage-examples}@anchor{1d04}@anchor{library/bz2 examples-of-usage}@anchor{1d05}
@subsubsection 用法示例


以下是 @ref{14,,bz2} 模块典型用法的一些示例。

使用 @ref{180b,,compress()} 和 @ref{9d1,,decompress()} 来显示往复式的压缩：

@example
>>> import bz2
@end example

@example
>>> data = b"""\
... Donec rhoncus quis sapien sit amet molestie. Fusce scelerisque vel augue
... nec ullamcorper. Nam rutrum pretium placerat. Aliquam vel tristique lorem,
... sit amet cursus ante. In interdum laoreet mi, sit amet ultrices purus
... pulvinar a. Nam gravida euismod magna, non varius justo tincidunt feugiat.
... Aliquam pharetra lacus non risus vehicula rutrum. Maecenas aliquam leo
... felis. Pellentesque semper nunc sit amet nibh ullamcorper, ac elementum
... dolor luctus. Curabitur lacinia mi ornare consectetur vestibulum."""
@end example

@example
>>> c = bz2.compress(data)
>>> len(data) / len(c)  # Data compression ratio
1.513595166163142
@end example

@example
>>> d = bz2.decompress(c)
>>> data == d  # Check equality to original object after round-trip
True
@end example

使用 @ref{1cf9,,BZ2Compressor} 进行增量压缩：

@example
>>> import bz2
@end example

@example
>>> def gen_data(chunks=10, chunksize=1000):
...     """Yield incremental blocks of chunksize bytes."""
...     for _ in range(chunks):
...         yield b"z" * chunksize
...
>>> comp = bz2.BZ2Compressor()
>>> out = b""
>>> for chunk in gen_data():
...     # Provide data to the compressor object
...     out = out + comp.compress(chunk)
...
>>> # Finish the compression process.  Call this once you have
>>> # finished providing data to the compressor.
>>> out = out + comp.flush()
@end example

上面的示例使用了十分“非随机”的数据流（即 @cite{b"z"} 块数据流）。 随机数据的压缩率通常很差，而有序、重复的数据通常会产生很高的压缩率。

用二进制模式写入和读取 bzip2 压缩文件：

@example
>>> import bz2
@end example

@example
>>> data = b"""\
... Donec rhoncus quis sapien sit amet molestie. Fusce scelerisque vel augue
... nec ullamcorper. Nam rutrum pretium placerat. Aliquam vel tristique lorem,
... sit amet cursus ante. In interdum laoreet mi, sit amet ultrices purus
... pulvinar a. Nam gravida euismod magna, non varius justo tincidunt feugiat.
... Aliquam pharetra lacus non risus vehicula rutrum. Maecenas aliquam leo
... felis. Pellentesque semper nunc sit amet nibh ullamcorper, ac elementum
... dolor luctus. Curabitur lacinia mi ornare consectetur vestibulum."""
@end example

@example
>>> with bz2.open("myfile.bz2", "wb") as f:
...     # Write compressed data to file
...     unused = f.write(data)
@end example

@example
>>> with bz2.open("myfile.bz2", "rb") as f:
...     # Decompress data from file
...     content = f.read()
@end example

@example
>>> content == data  # Check equality to original object after round-trip
True
@end example

@node lzma --- 用 LZMA 算法压缩,zipfile --- 使用ZIP存档,bz2 --- 对 bzip2 压缩算法的支持,数据压缩和存档
@anchor{library/lzma doc}@anchor{1d06}@anchor{library/lzma lzma-compression-using-the-lzma-algorithm}@anchor{1d07}@anchor{library/lzma module-lzma}@anchor{ad}
@subsection @code{lzma} --- 用 LZMA 算法压缩


@geindex lzma (模块)


3.3 新版功能.


@strong{源代码：} Lib/lzma.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/lzma.py}


__________________________________________________________________


此模块提供了可以压缩和解压缩使用 LZMA 压缩算法的数据的类和便携函数。 其中还包含支持 @code{xz} 工具所使用的 @code{.xz} 和旧式 @code{.lzma} 文件格式的文件接口，以及相应的原始压缩数据流。

此模块所提供的接口与 @ref{14,,bz2} 模块的非常类似。 但是，请注意 @ref{92c,,LZMAFile} @emph{不是} 线程安全的，这与 @ref{92b,,bz2.BZ2File} 不同，因此如果你需要在多个线程中使用单个 @ref{92c,,LZMAFile} 实例，则需要通过锁来保护它。

@geindex LZMAError
@anchor{library/lzma lzma LZMAError}@anchor{1d08}
@deffn {例外} lzma.LZMAError

当在压缩或解压缩期间或是在初始化压缩器/解压缩器的状态期间发生错误时此异常会被引发。
@end deffn

@menu
* 读写压缩文件:: 
* 在内存中压缩和解压缩数据:: 
* 杂项: 杂项<2>. 
* 指定自定义的过滤器链:: 
* 例子: 例子<5>. 

@end menu

@node 读写压缩文件,在内存中压缩和解压缩数据,,lzma --- 用 LZMA 算法压缩
@anchor{library/lzma reading-and-writing-compressed-files}@anchor{1d09}
@subsubsection 读写压缩文件


@geindex open() (在 lzma 模块中)
@anchor{library/lzma lzma open}@anchor{1d0a}
@deffn {函数} lzma.open (filename, mode="rb", *, format=None, check=-1, preset=None, filters=None, encoding=None, errors=None, newline=None)

以二进制或文本模式打开 LZMA 压缩文件，返回一个 @ref{b3b,,file object}。

@emph{filename} 参数可以是一个实际的文件名（以 @ref{329,,str}, @ref{32a,,bytes} 或 @ref{363,,路径类} 对象的形式给出），在此情况下会打开指定名称的文件，或者可以是一个用于读写的现有文件对象。

@emph{mode} 参数可以是二进制模式的 @code{"r"}, @code{"rb"}, @code{"w"}, @code{"wb"}, @code{"x"}, @code{"xb"}, @code{"a"} 或 @code{"ab"}，或者文本模式的 @code{"rt"}, @code{"wt"}, @code{"xt"} 或 @code{"at"}。 默认值为 @code{"rb"}。

当打开一个文件用于读取时，@emph{format} 和 @emph{filters} 参数具有与 @ref{1d0b,,LZMADecompressor} 的参数相同的含义。 在此情况下，@emph{check} 和 @emph{preset} 参数不应被使用。

当打开一个文件用于写入的，@emph{format}, @emph{check}, @emph{preset} 和 @emph{filters} 参数具有与 @ref{1d0c,,LZMACompressor} 的参数相同的含义。

对于二进制模式，这个函数等价于 @ref{92c,,LZMAFile} 构造器: @code{LZMAFile(filename, mode, ...)}。 在这种情况下，不可提供 @emph{encoding}, @emph{errors} 和 @emph{newline} 参数。

对于文本模式，将会创建一个 @ref{92c,,LZMAFile} 对象，并将它包装到一个 @ref{5ee,,io.TextIOWrapper} 实例中，此实例带有指定的编码格式、错误处理行为和行结束符。


在 3.4 版更改: 增加了对 @code{"x"}, @code{"xb"} 和 @code{"xt"} 模式的支持。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex LZMAFile (lzma 中的类)
@anchor{library/lzma lzma LZMAFile}@anchor{92c}
@deffn {类} lzma.LZMAFile (filename=None, mode="r", *, format=None, check=-1, preset=None, filters=None)

以二进制模式打开一个 LZMA 压缩文件。

@ref{92c,,LZMAFile} 可以包装在一个已打开的 @ref{b3b,,file object} 中，或者是在给定名称的文件上直接操作。 @emph{filename} 参数指定所包装的文件对象，或是要打开的文件名称（类型为 @ref{329,,str}, @ref{32a,,bytes} 或 @ref{363,,路径类} 对象）。 如果是包装现有的文件对象，被包装的文件在 @ref{92c,,LZMAFile} 被关闭时将不会被关闭。

@emph{mode} 参数可以是表示读取的 @code{"r"} (默认值)，表示覆写的 @code{"w"}，表示单独创建的 @code{"x"}，或表示添加的 @code{"a"}。 这些模式还可以分别以 @code{"rb"}, @code{"wb"}, @code{"xb"} 和 @code{"ab"} 的等价形式给出。

如果 @emph{filename} 是一个文件对象（而不是实际的文件名），则 @code{"w"} 模式并不会截断文件，而会等价于 @code{"a"}。

当打开一个文件用于读取时，输入文件可以为多个独立压缩流的拼接。 它们会被作为单个逻辑流被透明地解码。

当打开一个文件用于读取时，@emph{format} 和 @emph{filters} 参数具有与 @ref{1d0b,,LZMADecompressor} 的参数相同的含义。 在此情况下，@emph{check} 和 @emph{preset} 参数不应被使用。

当打开一个文件用于写入的，@emph{format}, @emph{check}, @emph{preset} 和 @emph{filters} 参数具有与 @ref{1d0c,,LZMACompressor} 的参数相同的含义。

@ref{92c,,LZMAFile} 支持 @ref{583,,io.BufferedIOBase} 所指定的所有成员，但 @code{detach()} 和 @code{truncate()} 除外。 并支持迭代和 @ref{6e3,,with} 语句。

也提供以下方法：

@geindex peek() (lzma.LZMAFile 方法)
@anchor{library/lzma lzma LZMAFile peek}@anchor{1d0d}
@deffn {方法} peek (size=-1)

返回缓冲的数据而不前移文件位置。 至少将返回一个字节的数据，除非已经到达 EOF。 实际返回的字节数不确定（会忽略 @emph{size} 参数）。

@cartouche
@quotation 注解 
虽然调用 @ref{1d0d,,peek()} 不会改变 @ref{92c,,LZMAFile} 的文件位置，但它可能改变下层文件对象的位置（举例来说如果 @ref{92c,,LZMAFile} 是通过传入一个文件对象作为 @emph{filename} 的话）。
@end quotation
@end cartouche
@end deffn


在 3.4 版更改: 增加了对 @code{"x"} 和 @code{"xb"} 模式的支持。



在 3.5 版更改: @ref{1ced,,read()} 方法现在接受 @code{None} 作为参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@node 在内存中压缩和解压缩数据,杂项<2>,读写压缩文件,lzma --- 用 LZMA 算法压缩
@anchor{library/lzma compressing-and-decompressing-data-in-memory}@anchor{1d0e}
@subsubsection 在内存中压缩和解压缩数据


@geindex LZMACompressor (lzma 中的类)
@anchor{library/lzma lzma LZMACompressor}@anchor{1d0c}
@deffn {类} lzma.LZMACompressor (format=FORMAT_XZ, check=-1, preset=None, filters=None)

创建一个压缩器对象，此对象可被用来执行增量压缩。

压缩单个数据块的更便捷方式请参阅 @ref{1d0f,,compress()}。

@emph{format} 参数指定应当使用哪种容器格式。 可能的值有：


@itemize *

@item 

@table @asis

@item @code{FORMAT_XZ}: @code{.xz} 容器格式。

这是默认格式。
@end table

@item 

@table @asis

@item @code{FORMAT_ALONE}: 传统的 @code{.lzma} 容器格式。

这种格式相比 @code{.xz} 更为受限 -- 它不支持一致性检查或多重过滤器。
@end table

@item 

@table @asis

@item @code{FORMAT_RAW}: 原始数据流，不使用任何容器格式。

这个格式描述器不支持一致性检查，并且要求你必须指定一个自定义的过滤器链（用于压缩和解压缩）。 此外，以这种方式压缩的数据不可使用 @code{FORMAT_AUTO} 来解压缩 (参见 @ref{1d0b,,LZMADecompressor})。
@end table
@end itemize

@emph{check} 参数指定要包含在压缩数据中的一致性检查类型。 这种检查在解压缩时使用，以确保数据没有被破坏。 可能的值是：


@itemize *

@item 
@code{CHECK_NONE}: 没有一致性检查。 这是 @code{FORMAT_ALONE} 和 @code{FORMAT_RAW} 的默认值（也是唯一可接受的值）。

@item 
@code{CHECK_CRC32}: 32 位循环冗余检查。

@item 
@code{CHECK_CRC64}: 64 位循环冗余检查。 这是 @code{FORMAT_XZ} 的默认值。

@item 
@code{CHECK_SHA256}: 256 位安全哈希算法。
@end itemize

如果指定的检查不受支持，则会引发 @ref{1d08,,LZMAError}。

压缩设置可被指定为一个预设的压缩等级（通过 @emph{preset} 参数）或以自定义过滤器链来详细设置（通过 @emph{filters} 参数）。

@emph{preset} 参数（如果提供）应当为一个 @code{0} 到 @code{9} (包括边界) 之间的整数，可以选择与常数 @code{PRESET_EXTREME} 进行 OR 运算。 如果 @emph{preset} 和 @emph{filters} 均未给出，则默认行为是使用 @code{PRESET_DEFAULT} (预设等级 @code{6})。 更高的预设等级会产生更小的输出，但会使得压缩过程更缓慢。

@cartouche
@quotation 注解 
除了更加 CPU 密集，使用更高的预设等级来压缩还需要更多的内存（并产生需要更多内存来解压缩的输出）。 例如使用预设等级 @code{9} 时，一个 @ref{1d0c,,LZMACompressor} 对象的开销可以高达 800 MiB。 出于这样的原因，通常最好是保持使用默认预设等级。
@end quotation
@end cartouche

@emph{filters} 参数（如果提供）应当指定一个过滤器链。 详情参见 @ref{1d10,,指定自定义的过滤器链}。

@geindex compress() (lzma.LZMACompressor 方法)
@anchor{library/lzma lzma LZMACompressor compress}@anchor{1d11}
@deffn {方法} compress (data)

压缩 @emph{data} (一个 @ref{32a,,bytes} object)，返回包含针对输入的至少一部分已压缩数据的 @ref{32a,,bytes} 对象。 一部 @emph{data} 可能会被放入内部缓冲区，以便用于后续的 @ref{1d0f,,compress()} 和 @ref{1d12,,flush()} 调用。 返回的数据应当与之前任何 @ref{1d0f,,compress()} 调用的输出进行拼接。
@end deffn

@geindex flush() (lzma.LZMACompressor 方法)
@anchor{library/lzma lzma LZMACompressor flush}@anchor{1d12}
@deffn {方法} flush ()

结束压缩进程，返回包含保存在压缩器的内部缓冲区中的任意数据的 @ref{32a,,bytes} 对象。

调用此方法之后压缩器将不可再被使用。
@end deffn
@end deffn

@geindex LZMADecompressor (lzma 中的类)
@anchor{library/lzma lzma LZMADecompressor}@anchor{1d0b}
@deffn {类} lzma.LZMADecompressor (format=FORMAT_AUTO, memlimit=None, filters=None)

创建一个压缩器对象，此对象可被用来执行增量解压缩。

一次性解压缩整个压缩数据流的更便捷方式请参阅 @ref{1d13,,decompress()}。

@emph{format} 参数指定应当被使用的容器格式。 默认值为 @code{FORMAT_AUTO}，它可以解压缩 @code{.xz} 和 @code{.lzma} 文件。 其他可能的值为 @code{FORMAT_XZ}, @code{FORMAT_ALONE} 和 @code{FORMAT_RAW}。

@emph{memlimit} 参数指定解压缩器可以使用的内存上限（字节数）。 当使用此参数时，如果不可能在给定内存上限之内解压缩输入数据则解压缩将失败并引发 @ref{1d08,,LZMAError}。

@emph{filters} 参数指定用于创建被解压缩数据流的过滤器链。 此参数在 @emph{format} 为 @code{FORMAT_RAW} 时要求提供，但对于其他格式不应使用。 有关过滤器链的更多信息请参阅 @ref{1d10,,指定自定义的过滤器链}。

@cartouche
@quotation 注解 
这个类不会透明地处理包含多个已压缩数据流的输入，这不同于 @ref{1d13,,decompress()} 和 @ref{92c,,LZMAFile}。 要通过 @ref{1d0b,,LZMADecompressor} 来解压缩多个数据流输入，你必须为每个数据流都创建一个新的解压缩器。
@end quotation
@end cartouche

@geindex decompress() (lzma.LZMADecompressor 方法)
@anchor{library/lzma lzma LZMADecompressor decompress}@anchor{70e}
@deffn {方法} decompress (data, max_length=-1)

解压缩 @emph{data} (一个 @ref{5e3,,bytes-like object})，返回字节串形式的解压缩数据。 某些 @emph{data} 可以在内部被缓冲，以便用于后续的 @ref{1d13,,decompress()} 调用。 返回的数据应当与之前任何 @ref{1d13,,decompress()} 调用的输出进行拼接。

如果 @emph{max_length} 为非负数，将返回至多 @emph{max_length} 个字节的解压缩数据。 如果达到此限制并且可以产生后续输出，则 @ref{1d14,,needs_input} 属性将被设为 @code{False}。 在这种情况下，下一次 @ref{70e,,decompress()} 调用提供的 @emph{data} 可以为 @code{b'@w{'}} 以获取更多的输出。

如果所有输入数据都已被解压缩并返回（或是因为它少于 @emph{max_length} 个字节，或是因为 @emph{max_length} 为负数），则 @ref{1d14,,needs_input} 属性将被设为 @code{True}。

在到达数据流末尾之后再尝试解压缩数据会引发 @cite{EOFError}。 在数据流末尾之后获取的任何数据都会被忽略并存储至 @ref{1d15,,unused_data} 属性。


在 3.5 版更改: 添加了 @emph{max_length} 形参。

@end deffn

@geindex check (lzma.LZMADecompressor 属性)
@anchor{library/lzma lzma LZMADecompressor check}@anchor{1d16}
@deffn {属性} check

输入流使用的一致性检查的 ID。 这可能为 @code{CHECK_UNKNOWN} 直到已解压了足够的输入数据来确定它所使用的一致性检查。
@end deffn

@geindex eof (lzma.LZMADecompressor 属性)
@anchor{library/lzma lzma LZMADecompressor eof}@anchor{1d17}
@deffn {属性} eof

若达到了数据流的末尾标记则为 @code{True}。
@end deffn

@geindex unused_data (lzma.LZMADecompressor 属性)
@anchor{library/lzma lzma LZMADecompressor unused_data}@anchor{1d15}
@deffn {属性} unused_data

在压缩数据流的末尾之后获取的数据。

在达到数据流末尾之前，这个值将为 @code{b""}。
@end deffn

@geindex needs_input (lzma.LZMADecompressor 属性)
@anchor{library/lzma lzma LZMADecompressor needs_input}@anchor{1d14}
@deffn {属性} needs_input

如果在要求新的未解压缩输入之前 @ref{70e,,decompress()} 方法可以提供更多的解压缩数据则为 @code{False}。


3.5 新版功能.

@end deffn
@end deffn

@geindex compress() (在 lzma 模块中)
@anchor{library/lzma lzma compress}@anchor{1d0f}
@deffn {函数} lzma.compress (data, format=FORMAT_XZ, check=-1, preset=None, filters=None)

压缩 @emph{data} (一个 @ref{32a,,bytes} 对象)，返回包含压缩数据的 @ref{32a,,bytes} 对象。

参见上文的 @ref{1d0c,,LZMACompressor} 了解有关 @emph{format}, @emph{check}, @emph{preset} 和 @emph{filters} 参数的说明。
@end deffn

@geindex decompress() (在 lzma 模块中)
@anchor{library/lzma lzma decompress}@anchor{1d13}
@deffn {函数} lzma.decompress (data, format=FORMAT_AUTO, memlimit=None, filters=None)

解压缩 @emph{data} (一个 @ref{32a,,bytes} 对象)，返回包含解压缩数据的 @ref{32a,,bytes} 对象。

如果 @emph{data} 是多个单独压缩数据流的拼接，则解压缩所有相应数据流，并返回结果的拼接。

参见上文的 @ref{1d0b,,LZMADecompressor} 了解有关 @emph{format}, @emph{memlimit} 和 @emph{filters} 参数的说明。
@end deffn

@node 杂项<2>,指定自定义的过滤器链,在内存中压缩和解压缩数据,lzma --- 用 LZMA 算法压缩
@anchor{library/lzma miscellaneous}@anchor{1d18}
@subsubsection 杂项


@geindex is_check_supported() (在 lzma 模块中)
@anchor{library/lzma lzma is_check_supported}@anchor{1d19}
@deffn {函数} lzma.is_check_supported (check)

如果本系统支持给定的一致性检查则返回 @code{True}。

@code{CHECK_NONE} 和 @code{CHECK_CRC32} 总是受支持。 @code{CHECK_CRC64} 和 @code{CHECK_SHA256} 或许不可用，如果你正在使用基于受限制特性集编译的 @code{liblzma} 版本的话。
@end deffn

@node 指定自定义的过滤器链,例子<5>,杂项<2>,lzma --- 用 LZMA 算法压缩
@anchor{library/lzma filter-chain-specs}@anchor{1d10}@anchor{library/lzma specifying-custom-filter-chains}@anchor{1d1a}
@subsubsection 指定自定义的过滤器链


过滤器链描述符是由字典组成的序列，其中每个字典包含单个过滤器的 ID 和选项。 每个字典必须包含键 @code{"id"}，并可能包含额外的键用来指定基于过滤器的选项。 有效的过滤器 ID 如下：


@itemize *

@item 

@table @asis

@item 压缩过滤器：


@itemize *

@item 
@code{FILTER_LZMA1} (配合 @code{FORMAT_ALONE} 使用)

@item 
@code{FILTER_LZMA2} (配合 @code{FORMAT_XZ} 和 @code{FORMAT_RAW} 使用)
@end itemize
@end table

@item 

@table @asis

@item Delta 过滤器：


@itemize *

@item 
@code{FILTER_DELTA}
@end itemize
@end table

@item 

@table @asis

@item Branch-Call-Jump (BCJ) 过滤器：


@itemize *

@item 
@code{FILTER_X86}

@item 
@code{FILTER_IA64}

@item 
@code{FILTER_ARM}

@item 
@code{FILTER_ARMTHUMB}

@item 
@code{FILTER_POWERPC}

@item 
@code{FILTER_SPARC}
@end itemize
@end table
@end itemize

一个过滤器链最多可由 4 个过滤器组成，并且不能为空。 过滤器链中的最后一个过滤器必须为压缩过滤器，其他过滤器必须为 Delta 或 BCJ 过滤器。

压缩过滤器支持下列选项（指定为表示过滤器的字典中的附加条目）：

@quotation


@itemize *

@item 
@code{preset}: 压缩预设选项，用于作为未显式指定的选项的默认值的来源。

@item 
@code{dict_size}: 以字节表示的字典大小。 这应当在 4 KiB 和 1.5 GiB 之间（包含边界）。

@item 
@code{lc}: 字面值上下文的比特数。

@item 
@code{lp}: 字面值位置的比特数。 总计值 @code{lc + lp} 必须不大于 4。

@item 
@code{pb}: 位置的比特数；必须不大于 4。

@item 
@code{mode}: @code{MODE_FAST} 或 @code{MODE_NORMAL}。

@item 
@code{nice_len}: 对于一个匹配应当被视为“适宜长度”的值。 这应当小于或等于 273。

@item 
@code{mf}: 要使用的匹配查找器 -- @code{MF_HC3}, @code{MF_HC4}, @code{MF_BT2}, @code{MF_BT3} 或 @code{MF_BT4}。

@item 
@code{depth}: 匹配查找器使用的最大查找深度。 0 (默认值) 表示基于其他过滤器选项自动选择。
@end itemize
@end quotation

Delta 过滤器保存字节数据之间的差值，在特定环境下可产生更具重复性的输入。 它支持一个 @code{dist} 选项，指明要减去的字节之间的差值大小。 默认值为 1，即相邻字节之间的差值。

BCJ 过滤器主要作用于机器码。 它们会转换机器码内的相对分支、调用和跳转以使用绝对寻址，其目标是提升冗余度以供压缩器利用。 这些过滤器支持一个 @code{start_offset} 选项，指明应当被映射到输入数据开头的地址。 默认值为 0。

@node 例子<5>,,指定自定义的过滤器链,lzma --- 用 LZMA 算法压缩
@anchor{library/lzma examples}@anchor{1d1b}
@subsubsection 例子


在已压缩的数据中读取:

@example
import lzma
with lzma.open("file.xz") as f:
    file_content = f.read()
@end example

创建一个压缩文件:

@example
import lzma
data = b"Insert Data Here"
with lzma.open("file.xz", "w") as f:
    f.write(data)
@end example

在内存中压缩文件:

@example
import lzma
data_in = b"Insert Data Here"
data_out = lzma.compress(data_in)
@end example

增量压缩:

@example
import lzma
lzc = lzma.LZMACompressor()
out1 = lzc.compress(b"Some data\n")
out2 = lzc.compress(b"Another piece of data\n")
out3 = lzc.compress(b"Even more data\n")
out4 = lzc.flush()
# Concatenate all the partial results:
result = b"".join([out1, out2, out3, out4])
@end example

写入已压缩数据到已打开的文件:

@example
import lzma
with open("file.xz", "wb") as f:
    f.write(b"This data will not be compressed\n")
    with lzma.open(f, "w") as lzf:
        lzf.write(b"This *will* be compressed\n")
    f.write(b"Not compressed\n")
@end example

使用自定义过滤器链创建一个已压缩文件:

@example
import lzma
my_filters = [
    @{"id": lzma.FILTER_DELTA, "dist": 5@},
    @{"id": lzma.FILTER_LZMA2, "preset": 7 | lzma.PRESET_EXTREME@},
]
with lzma.open("file.xz", "w", filters=my_filters) as f:
    f.write(b"blah blah blah")
@end example

@node zipfile --- 使用ZIP存档,tarfile --- 读写tar归档文件,lzma --- 用 LZMA 算法压缩,数据压缩和存档
@anchor{library/zipfile doc}@anchor{1d1c}@anchor{library/zipfile module-zipfile}@anchor{142}@anchor{library/zipfile zipfile-work-with-zip-archives}@anchor{1d1d}
@subsection @code{zipfile} --- 使用ZIP存档


@geindex zipfile (模块)

@strong{源代码：} Lib/zipfile.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/zipfile.py}


__________________________________________________________________


ZIP 文件格式是一个常用的归档与压缩标准。 这个模块提供了创建、读取、写入、添加及列出 ZIP 文件的工具。 任何对此模块的进阶使用都将需要理解此格式，其定义参见 PKZIP 应用程序笔记@footnote{https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT}。

此模块目前不能处理分卷 ZIP 文件。它可以处理使用 ZIP64 扩展（超过 4 GB 的 ZIP 文件）的 ZIP 文件。它支持解密 ZIP 归档中的加密文件，但是目前不能创建一个加密的文件。解密非常慢，因为它是使用原生 Python 而不是 C 实现的。

这个模块定义了以下内容：

@geindex BadZipFile
@anchor{library/zipfile zipfile BadZipFile}@anchor{1d1e}
@deffn {例外} zipfile.BadZipFile

为损坏的 ZIP 文件抛出的错误。


3.2 新版功能.

@end deffn

@geindex BadZipfile
@anchor{library/zipfile zipfile BadZipfile}@anchor{1d1f}
@deffn {例外} zipfile.BadZipfile

@ref{1d1e,,BadZipFile} 的别名，与旧版本 Python 保持兼容性。


3.2 版后已移除.

@end deffn

@geindex LargeZipFile
@anchor{library/zipfile zipfile LargeZipFile}@anchor{1d20}
@deffn {例外} zipfile.LargeZipFile

当 ZIP 文件需要 ZIP64 功能但是未启用时会抛出此错误。
@end deffn


@deffn {类} zipfile.ZipFile

用于读写 ZIP 文件的类。 欲了解构造函数的描述，参阅段落 @ref{1d21,,ZipFile 对象}。
@end deffn


@deffn {类} zipfile.Path

用于 zip 文件的兼容 pathlib 的包装器。 详情参见 @ref{1d22,,Path 对象}。


3.8 新版功能.

@end deffn


@deffn {类} zipfile.PyZipFile

用于创建包含 Python 库的 ZIP 归档的类。
@end deffn

@geindex ZipInfo (zipfile 中的类)
@anchor{library/zipfile zipfile ZipInfo}@anchor{5b5}
@deffn {类} zipfile.ZipInfo (filename='NoName', date_time=(1980, 1, 1, 0, 0, 0))

用于表示档案内一个成员信息的类。 此类的实例会由 @ref{417,,ZipFile} 对象的 @ref{1d23,,getinfo()} 和 @ref{1d24,,infolist()} 方法返回。 大多数 @ref{142,,zipfile} 模块的用户都不必创建它们，只需使用此模块所创建的实例。 @emph{filename} 应当是档案成员的全名，@emph{date_time} 应当是包含六个字段的描述最近修改时间的元组；这些字段的描述请参阅 @ref{1d25,,ZipInfo 对象}。
@end deffn

@geindex is_zipfile() (在 zipfile 模块中)
@anchor{library/zipfile zipfile is_zipfile}@anchor{cb3}
@deffn {函数} zipfile.is_zipfile (filename)

根据文件的 Magic Number，如果 @emph{filename} 是一个有效的 ZIP 文件则返回 @code{True}，否则返回 @code{False}。 @emph{filename} 也可能是一个文件或类文件对象。


在 3.1 版更改: 支持文件或类文件对象。

@end deffn

@geindex ZIP_STORED() (在 zipfile 模块中)
@anchor{library/zipfile zipfile ZIP_STORED}@anchor{1d26}
@deffn {数据} zipfile.ZIP_STORED

未被压缩的归档成员的数字常数。
@end deffn

@geindex ZIP_DEFLATED() (在 zipfile 模块中)
@anchor{library/zipfile zipfile ZIP_DEFLATED}@anchor{1d27}
@deffn {数据} zipfile.ZIP_DEFLATED

常用的 ZIP 压缩方法的数字常数。需要 @ref{144,,zlib} 模块。
@end deffn

@geindex ZIP_BZIP2() (在 zipfile 模块中)
@anchor{library/zipfile zipfile ZIP_BZIP2}@anchor{1d28}
@deffn {数据} zipfile.ZIP_BZIP2

BZIP2 压缩方法的数字常数。需要 @ref{14,,bz2} 模块。


3.3 新版功能.

@end deffn

@geindex ZIP_LZMA() (在 zipfile 模块中)
@anchor{library/zipfile zipfile ZIP_LZMA}@anchor{1d29}
@deffn {数据} zipfile.ZIP_LZMA

LZMA 压缩方法的数字常数。需要 @ref{ad,,lzma} 模块。


3.3 新版功能.


@cartouche
@quotation 注解 
ZIP 文件格式规范包括自 2001 年以来对 bzip2 压缩的支持，以及自 2006 年以来对 LZMA 压缩的支持。但是，一些工具（包括较旧的 Python 版本）不支持这些压缩方法，并且可能拒绝完全处理 ZIP 文件，或者无法提取单个文件。
@end quotation
@end cartouche
@end deffn


@subsubheading 参见



@table @asis

@item PKZIP 应用程序笔记@footnote{https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT}

Phil Katz 编写的 ZIP 文件格式文档，此格式和使用的算法的创建者。

@item Info-ZIP 主页@footnote{http://www.info-zip.org/}

有关 Info-ZIP 项目的 ZIP 存档程序和开发库的信息。
@end table


@menu
* ZipFile 对象:: 
* Path 对象:: 
* PyZipFile 对象:: 
* ZipInfo 对象:: 
* 命令行界面: 命令行界面<2>. 
* 解压缩的障碍:: 

@end menu

@node ZipFile 对象,Path 对象,,zipfile --- 使用ZIP存档
@anchor{library/zipfile id1}@anchor{1d2a}@anchor{library/zipfile zipfile-objects}@anchor{1d21}
@subsubsection ZipFile 对象


@geindex ZipFile (zipfile 中的类)
@anchor{library/zipfile zipfile ZipFile}@anchor{417}
@deffn {类} zipfile.ZipFile (file, mode='r', compression=ZIP_STORED, allowZip64=True, compresslevel=None, *, strict_timestamps=True)

打开一个 ZIP 文件，@emph{file} 为一个指向文件的路径（字符串），一个类文件对象或者一个 @ref{363,,path-like object}。

形参 @emph{mode} 应当为 @code{'r'} 来读取一个存在的文件，@code{'w'} 来截断并写入新的文件， @code{'a'} 来添加到一个存在的文件，或者 @code{'x'} 来仅新建并写入新的文件。如果 @emph{mode} 为 @code{'x'} 并且 @emph{file} 指向已经存在的文件，则抛出 @ref{952,,FileExistsError}。如果 @emph{mode} 为 @code{'a'} 且 @emph{file} 为已存在的文件，则格外的文件将被加入。如果 @emph{file} 不指向 ZIP 文件，之后一个新的 ZIP 归档将被追加为此文件。这是为了将 ZIP 归档添加到另一个文件（例如 @code{python.exe}）。如果 @emph{mode} 为 @code{'a'} 并且文件不存在， 则会新建。如果 @emph{mode} 为 @code{'r'} 或 @code{'a'}， 则文件应当可定位。

@emph{compression} 是在写入归档时要使用的 ZIP 压缩方法，应为 @ref{1d26,,ZIP_STORED}, @ref{1d27,,ZIP_DEFLATED}, @ref{1d28,,ZIP_BZIP2} 或 @ref{1d29,,ZIP_LZMA}；不可识别的值将导致引发 @ref{609,,NotImplementedError}。 如果指定了 @ref{1d27,,ZIP_DEFLATED}, @ref{1d28,,ZIP_BZIP2} 或 @ref{1d29,,ZIP_LZMA} 但相应的模块 (@ref{144,,zlib}, @ref{14,,bz2} 或 @ref{ad,,lzma}) 不可用，则会引发 @ref{2ba,,RuntimeError}。 默认值为 @ref{1d26,,ZIP_STORED}。

如果 @emph{allowZip64} 为 @code{True} (默认值) 则当 zipfile 大于 4 GiB 时 zipfile 将创建使用 ZIP64 扩展的 ZIP 文件。 如果该参数为 @code{false} 则当 ZIP 文件需要 ZIP64 扩展时 @ref{142,,zipfile} 将引发异常。

@emph{compresslevel} 形参控制在将文件写入归档时要使用的压缩等级。 当使用 @ref{1d26,,ZIP_STORED} 或 @ref{1d29,,ZIP_LZMA} 时无压缩效果。 当使用 @ref{1d27,,ZIP_DEFLATED} 时接受整数 @code{0} 至 @code{9} (更多信息参见 @ref{1cd9,,zlib})。 当使用 @ref{1d28,,ZIP_BZIP2} 时接受整数 @code{1} 至 @code{9} (更多信息参见 @ref{92b,,bz2})。

@emph{strict_timestamps} 参数在设为 @code{False} 时允许压缩早于 1980-01-01 的文件，代价时会将时间戳设为 1980-01-01。 类似的行为也会对晚于 2107-12-31 的文件发生，时间戳也会被设为该上限值。

如果创建文件时使用 @code{'w'}, @code{'x'} 或 @code{'a'} 模式并且未向归档添加任何文件就执行了 @ref{1d2b,,closed}，则会将适当的空归档 ZIP 结构写入文件。

ZipFile 也是一个上下文管理器，因此支持 @ref{6e3,,with} 语句。 在这个示例中，@emph{myzip} 将在 @code{with} 语句块执行完成之后被关闭 --- 即使是发生了异常:

@example
with ZipFile('spam.zip', 'w') as myzip:
    myzip.write('eggs.txt')
@end example


3.2 新版功能: 添加了将 @ref{417,,ZipFile} 用作上下文管理员的功能。



在 3.3 版更改: 添加了对 @ref{14,,bzip2} 和 @ref{ad,,lzma} 压缩的支持。



在 3.4 版更改: 默认启用 ZIP64 扩展。



在 3.5 版更改: 添加了对不可查找数据流的支持。 并添加了对 @code{'x'} 模式的支持。



在 3.6 版更改: 在此之前，对于不可识别的压缩值将引发普通的 @ref{2ba,,RuntimeError}。



在 3.6.2 版更改: @emph{file} 形参接受一个 @ref{363,,path-like object}。



在 3.7 版更改: 添加了 @emph{compresslevel} 形参。



3.8 新版功能: @emph{strict_timestamps} 仅限关键字参数

@end deffn

@geindex close() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile close}@anchor{1d2b}
@deffn {方法} ZipFile.close ()

关闭归档文件。 你必须在退出程序之前调用 @ref{1d2b,,close()} 否则将不会写入关键记录数据。
@end deffn

@geindex getinfo() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile getinfo}@anchor{1d23}
@deffn {方法} ZipFile.getinfo (name)

返回一个 @ref{5b5,,ZipInfo} 对象，其中包含有关归档成员 @emph{name} 的信息。 针对一个目前并不包含于归档中的名称调用 @ref{1d23,,getinfo()} 将会引发 @ref{2c7,,KeyError}。
@end deffn

@geindex infolist() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile infolist}@anchor{1d24}
@deffn {方法} ZipFile.infolist ()

返回一个列表，其中包含每个归档成员的 @ref{5b5,,ZipInfo} 对象。 如果是打开一个现有归档则这些对象的排列顺序与它们对应条目在磁盘上的实际 ZIP 文件中的顺序一致。
@end deffn

@geindex namelist() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile namelist}@anchor{1d2c}
@deffn {方法} ZipFile.namelist ()

返回按名称排序的归档成员列表。
@end deffn

@geindex open() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile open}@anchor{5b7}
@deffn {方法} ZipFile.open (name, mode='r', pwd=None, *, force_zip64=False)

以二进制文件类对象的形式访问一个归档成员。 @emph{name} 可以是归档内某个文件的名称也可以是某个 @ref{5b5,,ZipInfo} 对象。 如果包含了 @emph{mode} 形参，则它必须为 @code{'r'} (默认值) 或 @code{'w'}。  @emph{pwd} 为用于解密已加密 ZIP 文件的密码。

@ref{5b7,,open()} 也是一个上下文管理器，因此支持 @ref{6e3,,with} 语句:

@example
with ZipFile('spam.zip') as myzip:
    with myzip.open('eggs.txt') as myfile:
        print(myfile.read())
@end example

如果 @emph{mode} 为 @code{'r'} 则文件类对象 (@code{ZipExtFile}) 将为只读并且提供下列方法: @ref{1ced,,read()}, @ref{169c,,readline()}, @ref{1725,,readlines()}, @ref{1d2d,,seek()}, @ref{1d2e,,tell()}, @ref{509,,__iter__()}, @ref{c5d,,__next__()}。 这些对象可独立于 ZipFile 进行操作。

如果 @code{mode='w'} 则返回一个可写入的文件句柄，它将支持 @ref{584,,write()} 方法。 当一个可写入的文件句柄被打开时，尝试读写 ZIP 文件中的其他文件将会引发 @ref{1fb,,ValueError}。

当写入一个文件时，如果文件大小不能预先确定但是可能超过 2 GiB，可传入 @code{force_zip64=True} 以确保标头格式能够支持超大文件。 如果文件大小可以预先确定，则在构造 @ref{5b5,,ZipInfo} 对象时应设置 @ref{1d2f,,file_size}，并将其用作 @emph{name} 形参。

@cartouche
@quotation 注解 
@ref{5b7,,open()}, @ref{cb2,,read()} 和 @ref{1d30,,extract()} 方法可接受文件名或 @ref{5b5,,ZipInfo} 对象。 当尝试读取一个包含重复名称成员的 ZIP 文件时你将发现此功能很有好处。
@end quotation
@end cartouche


在 3.6 版更改: 移除了对 @code{mode='U'} 的支持。 请使用 @ref{5ee,,io.TextIOWrapper} 以在 @ref{5ef,,universal newlines} 模式中读取已压缩的文本文件。



在 3.6 版更改: @ref{4ea,,open()} 现在可以被用来配合 @code{mode='w'} 选项来将文件写入归档。



在 3.6 版更改: 在已关闭的 ZipFile 上调用 @ref{5b7,,open()} 将引发 @ref{1fb,,ValueError}。 在之前的版本中则会引发 @ref{2ba,,RuntimeError}。

@end deffn

@geindex extract() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile extract}@anchor{1d30}
@deffn {方法} ZipFile.extract (member, path=None, pwd=None)

从归档中提取出一个成员放入当前工作目录；@emph{member} 必须为成员的完整名称或 @ref{5b5,,ZipInfo} 对象。 成员的文件信息会尽可能精确地被提取。 @emph{path} 指定一个要提取到的不同目录。 @emph{member} 可以是一个文件名或 @ref{5b5,,ZipInfo} 对象。 @emph{pwd} 是用于解密文件的密码。

返回所创建的经正规化的路径（对应于目录或新文件）。

@cartouche
@quotation 注解 
如果一个成员文件名为绝对路径，则将去掉驱动器/UNC共享点和前导的（反）斜杠，例如: @code{///foo/bar} 在 Unix 上将变为 @code{foo/bar}，而 @code{C:\foo\bar} 在 Windows 上将变为 @code{foo\bar}。 并且一个成员文件名中的所有 @code{".."} 都将被移除，例如: @code{../../foo../../ba..r} 将变为 @code{foo../ba..r}。 在 Windows 上非法字符 (@code{:}, @code{<}, @code{>}, @code{|}, @code{"}, @code{?}, and @code{*}) 会被替换为下划线 (@code{_})。
@end quotation
@end cartouche


在 3.6 版更改: 在已关闭的 ZipFile 上调用 @ref{1d30,,extract()} 将引发 @ref{1fb,,ValueError}。 在之前的版本中则将引发 @ref{2ba,,RuntimeError}。



在 3.6.2 版更改: @emph{path} 形参接受一个 @ref{363,,path-like object}。

@end deffn

@geindex extractall() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile extractall}@anchor{1d31}
@deffn {方法} ZipFile.extractall (path=None, members=None, pwd=None)

从归档中提取出所有成员放入当前工作目录。 @emph{path} 指定一个要提取到的不同目录。 @emph{members} 为可选项且必须为 @ref{1d2c,,namelist()} 所返回列表的一个子集。 @emph{pwd} 是用于解密文件的密码。

@cartouche
@quotation 警告 
绝不要未经预先检验就从不可靠的源中提取归档文件。 这样有可能在 @emph{path} 之外创建文件，例如某些成员具有以 @code{"/"} 开始的文件名或带有两个点号 @code{".."} 的文件名。 此模块会尝试防止这种情况。 参见 @ref{1d30,,extract()} 的注释。
@end quotation
@end cartouche


在 3.6 版更改: 在已关闭的 ZipFile 上调用 @ref{1d31,,extractall()} 将引发 @ref{1fb,,ValueError}。 在之前的版本中则将引发 @ref{2ba,,RuntimeError}。



在 3.6.2 版更改: @emph{path} 形参接受一个 @ref{363,,path-like object}。

@end deffn

@geindex printdir() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile printdir}@anchor{1d32}
@deffn {方法} ZipFile.printdir ()

将归档的目录表打印到 @code{sys.stdout}。
@end deffn

@geindex setpassword() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile setpassword}@anchor{1d33}
@deffn {方法} ZipFile.setpassword (pwd)

设置 @emph{pwd} 为用于提取已加密文件的默认密码。
@end deffn

@geindex read() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile read}@anchor{cb2}
@deffn {方法} ZipFile.read (name, pwd=None)

返回归档中文件 @emph{name} 的字节数据。 @emph{name} 是归档中文件的名称，或是一个 @ref{5b5,,ZipInfo} 对象。 归档必须以读取或追加方式打开。 @emph{pwd} 为用于已加密文件的密码，并且如果指定该参数则它将覆盖通过 @ref{1d33,,setpassword()} 设置的默认密码。  on a ZipFile that uses a compression method 在使用 @ref{1d26,,ZIP_STORED} , @ref{1d27,,ZIP_DEFLATED}, @ref{1d28,,ZIP_BZIP2} 或 @ref{1d29,,ZIP_LZMA} 以外的压缩方法的 ZipFile 上调用 @ref{cb2,,read()} 将引发 @ref{609,,NotImplementedError}。 如果相应的压缩模块不可用也会引发错误。


在 3.6 版更改: 在已关闭的 ZipFile 上调用 @ref{cb2,,read()} 将引发 @ref{1fb,,ValueError}。 在之前的版本中则会引发 @ref{2ba,,RuntimeError}。

@end deffn

@geindex testzip() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile testzip}@anchor{1d34}
@deffn {方法} ZipFile.testzip ()

读取归档中的所有文件并检查它们的 CRC 和文件头。 返回第一个已损坏文件的名称，在其他情况下则返回 @code{None}。


在 3.6 版更改: 在已关闭的 ZipFile 上调用 @ref{1d34,,testzip()} 将引发 @ref{1fb,,ValueError}。 在之前的版本中则将引发 @ref{2ba,,RuntimeError}。

@end deffn

@geindex write() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile write}@anchor{60a}
@deffn {方法} ZipFile.write (filename, arcname=None, compress_type=None, compresslevel=None)

将名为 @emph{filename} 的文件写入归档，给予的归档名为 @emph{arcname} (默认情况下将与 @emph{filename} 一致，但是不带驱动器盘符并会移除开头的路径分隔符)。 @emph{compress_type} 如果给出，它将覆盖作为构造器 @emph{compression} 形参对于新条目所给出的值。 类似地，@emph{compresslevel} 如果给出也将覆盖构造器。 归档必须使用 @code{'w'}, @code{'x'} 或 @code{'a'} 模式打开。

@cartouche
@quotation 注解 
归档名称应当是基于归档根目录的相对路径，也就是说，它们不应以路径分隔符开头。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
如果 @code{arcname} (或 @code{filename}，如果 @code{arcname} 未给出) 包含一个空字节，则归档中该文件的名称将在空字节位置被截断。
@end quotation
@end cartouche


在 3.6 版更改: 在使用 @code{'r'} 模式创建的 ZipFile 或已关闭的 ZipFile 上调用 @ref{60a,,write()} 将引发 @ref{1fb,,ValueError}。 在之前的版本中则会引发 @ref{2ba,,RuntimeError}。

@end deffn

@geindex writestr() (zipfile.ZipFile 方法)
@anchor{library/zipfile zipfile ZipFile writestr}@anchor{cb4}
@deffn {方法} ZipFile.writestr (zinfo_or_arcname, data, compress_type=None, compresslevel=None)

将一个文件写入归档。 内容为 @emph{data}，它可以是一个 @ref{329,,str} 或 @ref{32a,,bytes} 的实例；如果是 @ref{329,,str}，则会先使用 UTF-8 进行编码。 @emph{zinfo_or_arcname} 可以是它在归档中将被给予的名称，或者是 @ref{5b5,,ZipInfo} 的实例。 如果它是一个实例，则至少必须给定文件名、日期和时间。 如果它是一个名称，则日期和时间会被设为当前日期和时间。 归档必须以 @code{'w'}, @code{'x'} 或 @code{'a'} 模式打开。

如果给定了 @emph{compress_type}，它将会覆盖作为新条目构造器的 @emph{compression} 形参或在 @emph{zinfo_or_arcname} (如果是一个 @ref{5b5,,ZipInfo} 实例) 中所给出的值。 类似地，如果给定了 @emph{compresslevel}，它将会覆盖构造器。

@cartouche
@quotation 注解 
当传入一个 @ref{5b5,,ZipInfo} 实例作为 @emph{zinfo_or_arcname} 形参时，所使用的压缩方法将为在给定的 @ref{5b5,,ZipInfo} 实例的 @emph{compress_type} 成员中指定的方法。 默认情况下，@ref{5b5,,ZipInfo} 构造器将将此成员设为 @ref{1d26,,ZIP_STORED}。
@end quotation
@end cartouche


在 3.2 版更改: @emph{compress_type} 参数。



在 3.6 版更改: 在使用 @code{'r'} 模式创建的 ZipFile 或已关闭的 ZipFile 上调用 @ref{cb4,,writestr()} 将引发 @ref{1fb,,ValueError}。 在之前的版本中则会引发 @ref{2ba,,RuntimeError}。

@end deffn

以下数据属性也是可用的:

@geindex filename (zipfile.ZipFile 属性)
@anchor{library/zipfile zipfile ZipFile filename}@anchor{1d35}
@deffn {属性} ZipFile.filename

ZIP 文件的名称。
@end deffn

@geindex debug (zipfile.ZipFile 属性)
@anchor{library/zipfile zipfile ZipFile debug}@anchor{1d36}
@deffn {属性} ZipFile.debug

要使用的调试输出等级。 这可以设为从 @code{0} (默认无输出) 到 @code{3} (最多输出) 的值。 调试信息会被写入 @code{sys.stdout}。
@end deffn

@geindex comment (zipfile.ZipFile 属性)
@anchor{library/zipfile zipfile ZipFile comment}@anchor{1d37}
@deffn {属性} ZipFile.comment

关联到 ZIP 文件的 @ref{32a,,bytes} 对象形式的说明。 如果将说明赋给以 @code{'w'}, @code{'x'} 或 @code{'a'} 模式创建的 @ref{417,,ZipFile} 实例，它的长度不应超过 65535 字节。 超过此长度的说明将被截断。
@end deffn

@node Path 对象,PyZipFile 对象,ZipFile 对象,zipfile --- 使用ZIP存档
@anchor{library/zipfile id2}@anchor{1d38}@anchor{library/zipfile path-objects}@anchor{1d22}
@subsubsection Path 对象


@geindex Path (zipfile 中的类)
@anchor{library/zipfile zipfile Path}@anchor{e98}
@deffn {类} zipfile.Path (root, at='@w{'})

根据 @code{root} zipfile (它可以是一个 @ref{417,,ZipFile} 实例或适合传给 @ref{417,,ZipFile} 构造器的 @code{file}) 构造一个 Path 对象。

@code{at} 指定此 Path 在 zipfile 中的位置，例如 'dir/file.txt', 'dir/' 或 '@w{'}。 默认为空字符串，即指定跟目录。
@end deffn

Path 对象会公开 @ref{201,,pathlib.Path} 对象的下列特性:

Path 对象可以使用 @code{/} 操作符进行遍历。

@geindex name (zipfile.Path 属性)
@anchor{library/zipfile zipfile Path name}@anchor{1d39}
@deffn {属性} Path.name

最终的路径组成部分。
@end deffn

@geindex open() (zipfile.Path 方法)
@anchor{library/zipfile zipfile Path open}@anchor{1d3a}
@deffn {方法} Path.open (*, **)

在当前路径上发起调用 @ref{5b7,,ZipFile.open()}。 接受与 @ref{5b7,,ZipFile.open()} 相同的参数。

@cartouche
@quotation 警告 
此函数的签名在 Python 3.9 版进行了不兼容的改变。 想要编写对未来版本兼容的程序，请考虑使用第三方的 zipp.Path 包（3.0 或更新的版本）。
@end quotation
@end cartouche
@end deffn

@geindex iterdir() (zipfile.Path 方法)
@anchor{library/zipfile zipfile Path iterdir}@anchor{1d3b}
@deffn {方法} Path.iterdir ()

枚举当前目录的子目录。
@end deffn

@geindex is_dir() (zipfile.Path 方法)
@anchor{library/zipfile zipfile Path is_dir}@anchor{1d3c}
@deffn {方法} Path.is_dir ()

如果当前上下文引用了一个目录则返回 @code{True}。
@end deffn

@geindex is_file() (zipfile.Path 方法)
@anchor{library/zipfile zipfile Path is_file}@anchor{1d3d}
@deffn {方法} Path.is_file ()

如果当前上下文引用了一个文件则返回 @code{True}。
@end deffn

@geindex exists() (zipfile.Path 方法)
@anchor{library/zipfile zipfile Path exists}@anchor{1d3e}
@deffn {方法} Path.exists ()

如果当前上下文引用了 zip 文件内的一个文件或目录则返回 @code{True}。
@end deffn

@geindex read_text() (zipfile.Path 方法)
@anchor{library/zipfile zipfile Path read_text}@anchor{1d3f}
@deffn {方法} Path.read_text (*, **)

读取当前文件为 unicode 文本。 位置和关键字参数会被传递给 @ref{5ee,,io.TextIOWrapper} (@code{buffer} 除外，它将由上下文确定)。
@end deffn

@geindex read_bytes() (zipfile.Path 方法)
@anchor{library/zipfile zipfile Path read_bytes}@anchor{1d40}
@deffn {方法} Path.read_bytes ()

读取当前文件为字节串。
@end deffn

@node PyZipFile 对象,ZipInfo 对象,Path 对象,zipfile --- 使用ZIP存档
@anchor{library/zipfile id3}@anchor{1d41}@anchor{library/zipfile pyzipfile-objects}@anchor{1d42}
@subsubsection PyZipFile 对象


@ref{915,,PyZipFile} 构造器接受与 @ref{417,,ZipFile} 构造器相同的形参，以及一个额外的形参 @emph{optimize}。

@geindex PyZipFile (zipfile 中的类)
@anchor{library/zipfile zipfile PyZipFile}@anchor{915}
@deffn {类} zipfile.PyZipFile (file, mode='r', compression=ZIP_STORED, allowZip64=True, optimize=-1)


3.2 新版功能: @emph{optimize} 形参。



在 3.4 版更改: 默认启用 ZIP64 扩展。


实例在 @ref{417,,ZipFile} 对象所具有的方法以外还附加了一个方法:

@geindex writepy() (zipfile.PyZipFile 方法)
@anchor{library/zipfile zipfile PyZipFile writepy}@anchor{914}
@deffn {方法} writepy (pathname, basename='@w{'}, filterfunc=None)

查找 @code{*.py} 文件并将相应的文件添加到归档。

如果 @ref{915,,PyZipFile} 的 @emph{optimize} 形参未给定或为 @code{-1}，则相应的文件为 @code{*.pyc} 文件，并在必要时进行编译。

如果 @ref{915,,PyZipFile} 的 @emph{optimize} 形参为 @code{0}, @code{1} 或 @code{2}，则限具有相应优化级别 (参见 @ref{1b4,,compile()}) 的文件会被添加到归档，并在必要时进行编译。

如果 @emph{pathname} 是文件，则文件名必须以 @code{.py} 为后缀，并且只有 (相应的 @code{*.pyc}) 文件会被添加到最高层级（不带路径信息）。 如果 @emph{pathname} 不是以 @code{.py} 为后缀的文件，则将引发 @ref{2ba,,RuntimeError}。 如果它是目录，并且该目录不是一个包目录，则所有的 @code{*.pyc} 文件会被添加到最高层级。 如果目录是一个包目录，则所有的 @code{*.pyc} 会被添加到包名所表示的文件路径下，并且如果有任何子目录为包目录，则会以排好的顺序递归地添加这些目录。

@emph{basename} 仅限在内部使用。

如果给定 @emph{filterfunc}，则它必须是一个接受单个字符串参数的函数。 在将其添加到归档之前它将被传入每个路径（包括每个单独的完整路径）。 如果 @emph{filterfunc} 返回假值，则路径将不会被添加，而如果它是一个目录则其内容将被忽略。 例如，如果我们的测试文件全都位于 @code{test} 目录或以字符串 @code{test_} 打头，则我们可以使用一个 @emph{filterfunc} 来排除它们:

@example
>>> zf = PyZipFile('myprog.zip')
>>> def notests(s):
...     fn = os.path.basename(s)
...     return (not (fn == 'test' or fn.startswith('test_')))
>>> zf.writepy('myprog', filterfunc=notests)
@end example

@ref{914,,writepy()} 方法会产生带有这样一些文件名的归档:

@example
string.pyc                   # Top level name
test/__init__.pyc            # Package directory
test/testall.pyc             # Module test.testall
test/bogus/__init__.pyc      # Subpackage directory
test/bogus/myfile.pyc        # Submodule test.bogus.myfile
@end example


3.4 新版功能: @emph{filterfunc} 形参。



在 3.6.2 版更改: @emph{pathname} 形参接受一个 @ref{363,,path-like object}。



在 3.7 版更改: 递归排序目录条目。

@end deffn
@end deffn

@node ZipInfo 对象,命令行界面<2>,PyZipFile 对象,zipfile --- 使用ZIP存档
@anchor{library/zipfile id4}@anchor{1d43}@anchor{library/zipfile zipinfo-objects}@anchor{1d25}
@subsubsection ZipInfo 对象


@ref{5b5,,ZipInfo} 类的实例会通过 @ref{1d23,,getinfo()} 和 @ref{417,,ZipFile} 对象的 @ref{1d24,,infolist()} 方法返回。 每个对象将存储关于 ZIP 归档的一个成员的信息。

有一个类方法可以为文件系统文件创建 @ref{5b5,,ZipInfo} 实例:

@geindex from_file() (zipfile.ZipInfo 类方法)
@anchor{library/zipfile zipfile ZipInfo from_file}@anchor{5b4}
@deffn {方法} classmethod ZipInfo.from_file (filename, arcname=None, *, strict_timestamps=True)

为文件系统中的文件构造一个 @ref{5b5,,ZipInfo} 实例，并准备将其添加到一个 zip 文件。

@emph{filename} 应为文件系统中某个文件或目录的路径。

如果指定了 @emph{arcname}，它会被用作归档中的名称。 如果未指定 @emph{arcname}，则所用名称与 @emph{filename} 相同，但将去除任何驱动器盘符和打头的路径分隔符。

@emph{strict_timestamps} 参数在设为 @code{False} 时允许压缩早于 1980-01-01 的文件，代价时会将时间戳设为 1980-01-01。 类似的行为也会对晚于 2107-12-31 的文件发生，时间戳也会被设为该上限值。


3.6 新版功能.



在 3.6.2 版更改: @emph{filename} 形参接受一个 @ref{363,,path-like object}。



3.8 新版功能: @emph{strict_timestamps} 仅限关键字参数

@end deffn

实例具有下列方法和属性:

@geindex is_dir() (zipfile.ZipInfo 方法)
@anchor{library/zipfile zipfile ZipInfo is_dir}@anchor{5b6}
@deffn {方法} ZipInfo.is_dir ()

如果此归档成员是一个目录则返回 @code{True}。

这会使用条目的名称：目录应当总是以 @code{/} 结尾。


3.6 新版功能.

@end deffn

@geindex filename (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo filename}@anchor{1d44}
@deffn {属性} ZipInfo.filename

归档中的文件名称。
@end deffn

@geindex date_time (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo date_time}@anchor{1d45}
@deffn {属性} ZipInfo.date_time

上次修改存档成员的时间和日期。这是六个值的元组：


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

值

@item

@code{0}

@tab

Year (>= 1980)

@item

@code{1}

@tab

月（1为基数）

@item

@code{2}

@tab

月份中的日期（1为基数）

@item

@code{3}

@tab

小时（0为基数）

@item

@code{4}

@tab

分钟（0为基数）

@item

@code{5}

@tab

秒（0为基数）

@end multitable


@cartouche
@quotation 注解 
ZIP文件格式不支持1980年以前的时间戳。
@end quotation
@end cartouche
@end deffn

@geindex compress_type (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo compress_type}@anchor{1d46}
@deffn {属性} ZipInfo.compress_type

归档成员的压缩类型。
@end deffn

@geindex comment (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo comment}@anchor{1d47}
@deffn {属性} ZipInfo.comment

@ref{32a,,bytes} 对象形式的单个归档成员的注释。
@end deffn

@geindex extra (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo extra}@anchor{1d48}
@deffn {属性} ZipInfo.extra

扩展字段数据。 PKZIP Application Note@footnote{https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT} 包含一些保存于该 @ref{32a,,bytes} 对象中的内部结构的注释。
@end deffn

@geindex create_system (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo create_system}@anchor{1d49}
@deffn {属性} ZipInfo.create_system

创建 ZIP 归档所用的系统。
@end deffn

@geindex create_version (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo create_version}@anchor{1d4a}
@deffn {属性} ZipInfo.create_version

创建 ZIP 归档所用的 PKZIP 版本。
@end deffn

@geindex extract_version (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo extract_version}@anchor{1d4b}
@deffn {属性} ZipInfo.extract_version

需要用来提取归档的 PKZIP 版本。
@end deffn

@geindex reserved (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo reserved}@anchor{1d4c}
@deffn {属性} ZipInfo.reserved

必须为零。
@end deffn

@geindex flag_bits (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo flag_bits}@anchor{1d4d}
@deffn {属性} ZipInfo.flag_bits

ZIP 标志位。
@end deffn

@geindex volume (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo volume}@anchor{1d4e}
@deffn {属性} ZipInfo.volume

文件头的分卷号。
@end deffn

@geindex internal_attr (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo internal_attr}@anchor{1d4f}
@deffn {属性} ZipInfo.internal_attr

内部属性。
@end deffn

@geindex external_attr (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo external_attr}@anchor{1d50}
@deffn {属性} ZipInfo.external_attr

外部文件属性。
@end deffn

@geindex header_offset (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo header_offset}@anchor{1d51}
@deffn {属性} ZipInfo.header_offset

文件头的字节偏移量。
@end deffn

@geindex CRC (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo CRC}@anchor{1d52}
@deffn {属性} ZipInfo.CRC

未压缩文件的 CRC-32。
@end deffn

@geindex compress_size (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo compress_size}@anchor{1d53}
@deffn {属性} ZipInfo.compress_size

已压缩数据的大小。
@end deffn

@geindex file_size (zipfile.ZipInfo 属性)
@anchor{library/zipfile zipfile ZipInfo file_size}@anchor{1d2f}
@deffn {属性} ZipInfo.file_size

未压缩文件的大小。
@end deffn

@node 命令行界面<2>,解压缩的障碍,ZipInfo 对象,zipfile --- 使用ZIP存档
@anchor{library/zipfile command-line-interface}@anchor{1d54}@anchor{library/zipfile zipfile-commandline}@anchor{1d55}
@subsubsection 命令行界面


@ref{142,,zipfile} 模块提供了简单的命令行接口用于与 ZIP 归档的交互。

如果你想要创建一个新的 ZIP 归档，请在 @ref{1d56,,-c} 选项后指定其名称然后列出应当被包含的文件名:

@example
$ python -m zipfile -c monty.zip spam.txt eggs.txt
@end example

传入一个字典也是可接受的:

@example
$ python -m zipfile -c monty.zip life-of-brian_1979/
@end example

如果你想要将一个 ZIP 归档提取到指定的目录，请使用 @ref{1d57,,-e} 选项:

@example
$ python -m zipfile -e monty.zip target-dir/
@end example

要获取一个 ZIP 归档中的文件列表，请使用 @ref{1d58,,-l} 选项:

@example
$ python -m zipfile -l monty.zip
@end example

@menu
* 命令行选项: 命令行选项<2>. 

@end menu

@node 命令行选项<2>,,,命令行界面<2>
@anchor{library/zipfile command-line-options}@anchor{1d59}
@subsubsection 命令行选项


@geindex zipfile command line option; -l <zipfile>
@geindex zipfile command line option; --list <zipfile>
@anchor{library/zipfile cmdoption-zipfile-l}@anchor{1d58}
@deffn {程序选项} @w{-}l <zipfile>
@anchor{library/zipfile cmdoption-zipfile-list}@anchor{1d5a}
@deffnx {程序选项} @w{-}@w{-}list <zipfile>

列出一个 zipfile 中的文件名。
@end deffn

@geindex zipfile command line option; -c <zipfile> <source1> ... <sourceN>
@geindex zipfile command line option; --create <zipfile> <source1> ... <sourceN>
@anchor{library/zipfile cmdoption-zipfile-c}@anchor{1d56}
@deffn {程序选项} @w{-}c <zipfile> <source1> ... <sourceN>
@anchor{library/zipfile cmdoption-zipfile-create}@anchor{1d5b}
@deffnx {程序选项} @w{-}@w{-}create <zipfile> <source1> ... <sourceN>

基于源文件创建 zipfile。
@end deffn

@geindex zipfile command line option; -e <zipfile> <output_dir>
@geindex zipfile command line option; --extract <zipfile> <output_dir>
@anchor{library/zipfile cmdoption-zipfile-e}@anchor{1d57}
@deffn {程序选项} @w{-}e <zipfile> <output_dir>
@anchor{library/zipfile cmdoption-zipfile-extract}@anchor{1d5c}
@deffnx {程序选项} @w{-}@w{-}extract <zipfile> <output_dir>

将 zipfile 提取到目标目录中。
@end deffn

@geindex zipfile command line option; -t <zipfile>
@geindex zipfile command line option; --test <zipfile>
@anchor{library/zipfile cmdoption-zipfile-t}@anchor{1d5d}
@deffn {程序选项} @w{-}t <zipfile>
@anchor{library/zipfile cmdoption-zipfile-test}@anchor{1d5e}
@deffnx {程序选项} @w{-}@w{-}test <zipfile>

检测 zipfile 是否有效。
@end deffn

@node 解压缩的障碍,,命令行界面<2>,zipfile --- 使用ZIP存档
@anchor{library/zipfile decompression-pitfalls}@anchor{1d5f}
@subsubsection 解压缩的障碍


zipfile 模块的提取操作可能会由于下面列出的障碍而失败。

@menu
* 由于文件本身:: 
* 文件系统限制:: 
* 资源限制:: 
* 中断:: 
* 提取的默认行为:: 

@end menu

@node 由于文件本身,文件系统限制,,解压缩的障碍
@anchor{library/zipfile from-file-itself}@anchor{1d60}
@subsubsection 由于文件本身


解压缩可能由于不正确的密码 / CRC 校验和 / ZIP 格式或不受支持的压缩 / 解密方法而失败。

@node 文件系统限制,资源限制,由于文件本身,解压缩的障碍
@anchor{library/zipfile file-system-limitations}@anchor{1d61}
@subsubsection 文件系统限制


超出特定文件系统上的限制可能会导致解压缩失败。 例如目录条目所允许的字符、文件名的长度、路径名的长度、单个文件的大小以及文件的数量等等。

@node 资源限制,中断,文件系统限制,解压缩的障碍
@anchor{library/zipfile resources-limitations}@anchor{1d62}
@subsubsection 资源限制


缺乏内存或磁盘空间将会导致解压缩失败。 例如，作用于 zipfile 库的解压缩炸弹 (即 ZIP bomb@footnote{https://en.wikipedia.org/wiki/Zip_bomb}) 就可能造成磁盘空间耗尽。

@node 中断,提取的默认行为,资源限制,解压缩的障碍
@anchor{library/zipfile interruption}@anchor{1d63}
@subsubsection 中断


在解压缩期间中断执行，例如按下 ctrl-C 或杀死解压缩进程可能会导致归档文件的解压缩不完整。

@node 提取的默认行为,,中断,解压缩的障碍
@anchor{library/zipfile default-behaviors-of-extraction}@anchor{1d64}
@subsubsection 提取的默认行为


不了解提取的默认行为可能导致不符合期望的解压缩结果。 例如，当提取相同归档两次时，它会不经询问地覆盖文件。

@node tarfile --- 读写tar归档文件,,zipfile --- 使用ZIP存档,数据压缩和存档
@anchor{library/tarfile doc}@anchor{1d65}@anchor{library/tarfile module-tarfile}@anchor{101}@anchor{library/tarfile pkzip-application-note}@anchor{1d66}@anchor{library/tarfile tarfile-read-and-write-tar-archive-files}@anchor{1d67}
@subsection @code{tarfile} --- 读写tar归档文件


@geindex tarfile (模块)

@strong{源代码:} Lib/tarfile.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tarfile.py}


__________________________________________________________________


@ref{101,,tarfile} 模块可以用来读写 tar 归档，包括使用 gzip, bz2 和 lzma 压缩的归档。 请使用 @ref{142,,zipfile} 模块来读写 @code{.zip} 文件，或者使用 @ref{b8f,,shutil} 的高层级函数。

一些事实和数字:


@itemize *

@item 
读写 @ref{8c,,gzip}, @ref{14,,bz2} 和 @ref{ad,,lzma} 解压的归档要求相应的模块可用。

@item 
支持读取 / 写入 POSIX.1-1988 (ustar) 格式。

@item 
对 GNU tar 格式的读/写支持，包括 @emph{longname} 和 @emph{longlink} 扩展，对所有种类 @emph{sparse} 扩展的只读支持，包括 sparse 文件的恢复。

@item 
对 POSIX.1-2001 (pax) 格式的读/写支持。

@item 
处理目录、正常文件、硬链接、符号链接、fifo 管道、字符设备和块设备，并且能够获取和恢复文件信息例如时间戳、访问权限和所有者等。
@end itemize


在 3.3 版更改: 添加了对 @ref{ad,,lzma} 压缩的支持。


@geindex open() (在 tarfile 模块中)
@anchor{library/tarfile tarfile open}@anchor{760}
@deffn {函数} tarfile.open (name=None, mode='r', fileobj=None, bufsize=10240, **kwargs)

针对路径名 @emph{name} 返回 @ref{b85,,TarFile} 对象。 有关 @ref{b85,,TarFile} 对象以及所允许的关键字参数的详细信息请参阅 @ref{1d68,,TarFile 对象}。

@emph{mode} 必须是 @code{'filemode[:compression]'} 形式的字符串，其默认值为 @code{'r'}。 以下是模式组合的完整列表:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

模式

@tab

action

@item

@code{'r' or 'r:*'}

@tab

打开和读取使用透明压缩（推荐）。

@item

@code{'r:'}

@tab

打开和读取不使用压缩。

@item

@code{'r:gz'}

@tab

打开和读取使用gzip 压缩。

@item

@code{'r:bz2'}

@tab

打开和读取使用bzip2 压缩。

@item

@code{'r:xz'}

@tab

打开和读取使用lzma 压缩。

@item

@code{'x'} 或 @code{'x:'}

@tab

创建tarfile不进行压缩。如果文件已经存在，则抛出 @ref{952,,FileExistsError} 异常。

@item

@code{'x:gz'}

@tab

使用gzip压缩创建tarfile。如果文件已经存在，则抛出 @ref{952,,FileExistsError} 异常。

@item

@code{'x:bz2'}

@tab

使用bzip2 压缩创建tarfile。如果文件已经存在，则抛出 @ref{952,,FileExistsError} 异常。

@item

@code{'x:xz'}

@tab

使用lzma 压缩创建tarfile。如果文件已经存在，则抛出 @ref{952,,FileExistsError} 异常。

@item

@code{'a' or 'a:'}

@tab

打开以便在没有压缩的情况下追加。如果文件不存在，则创建该文件。

@item

@code{'w' or 'w:'}

@tab

打开用于未压缩的写入。

@item

@code{'w:gz'}

@tab

打开用于 gzip 压缩的写入。

@item

@code{'w:bz2'}

@tab

打开用于 bzip2 压缩的写入。

@item

@code{'w:xz'}

@tab

打开用于 lzma 压缩的写入。

@end multitable


请注意 @code{'a:gz'}, @code{'a:bz2'} 或 @code{'a:xz'} 是不可能的组合。 如果 @emph{mode} 不适用于打开特定（压缩的）文件用于读取，则会引发 @ref{1d69,,ReadError}。 请使用 @emph{mode} @code{'r'} 来避免这种情况。 如果某种压缩方法不受支持，则会引发 @ref{1d6a,,CompressionError}。

如果指定了 @emph{fileobj}，它会被用作对应于 @emph{name} 的以二进制模式打开的 @ref{b3b,,file object} 的替代。 它会被设定为处在位置 0。

对于 @code{'w:gz'}, @code{'r:gz'}, @code{'w:bz2'}, @code{'r:bz2'}, @code{'x:gz'}, @code{'x:bz2'} 等模式，@ref{760,,tarfile.open()} 接受关键字参数 @emph{compresslevel} (默认值为 @code{9}) 来指定文件的压缩等级。

针对特殊的目的，还存在第二种 @emph{mode} 格式: @code{'filemode|[compression]'}。 @ref{760,,tarfile.open()} 将返回一个将其数据作为数据块流来处理的 @ref{b85,,TarFile} 对象。 对此文件将不能执行随机查找。 如果给定了 @emph{fileobj}，它可以是任何具有 @code{read()} 或 @code{write()} 方法 (由 @emph{mode} 确定) 的对象。 @emph{bufsize} 指定块大小，默认值为 @code{20 * 512} 字节。 可与此格式组合使用的有 @code{sys.stdin}, 套接字 @ref{b3b,,file object} 或磁带设备等。 但是，对于这样的 @ref{b85,,TarFile} 对象存在不允许随机访问的限制，参见 @ref{1d6b,,例子}。 目前可用的模式如下:


@multitable {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

模式

@tab

动作

@item

@code{'r|*'}

@tab

打开 tar 块的 @emph{流} 以进行透明压缩读取。

@item

@code{'r|'}

@tab

打开一个未压缩的 tar 块的 @emph{stream} 用于读取。

@item

@code{'r|gz'}

@tab

打开一个 gzip 压缩的 @emph{stream} 用于读取。

@item

@code{'r|bz2'}

@tab

打开一个 bzip2 压缩的 @emph{stream} 用于读取。

@item

@code{'r|xz'}

@tab

打开一个 lzma 压缩 @emph{stream} 用于读取。

@item

@code{'w|'}

@tab

打开一个未压缩的 @emph{stream} 用于写入。

@item

@code{'w|gz'}

@tab

打开一个 gzip 压缩的 @emph{stream} 用于写入。

@item

@code{'w|bz2'}

@tab

打开一个 bzip2 压缩的 @emph{stream} 用于写入。

@item

@code{'w|xz'}

@tab

打开一个 lzma 压缩的 @emph{stream} 用于写入。

@end multitable



在 3.5 版更改: 添加了 @code{'x'} (单独创建) 模式。



在 3.6 版更改: @emph{name} 形参接受一个 @ref{363,,path-like object}。

@end deffn

@geindex TarFile (tarfile 中的类)
@anchor{library/tarfile tarfile TarFile}@anchor{b85}
@deffn {类} tarfile.TarFile

用于读取和写入 tar 归档的类。 请不要直接使用这个类：而要使用 @ref{760,,tarfile.open()}。 参见 @ref{1d68,,TarFile 对象}。
@end deffn

@geindex is_tarfile() (在 tarfile 模块中)
@anchor{library/tarfile tarfile is_tarfile}@anchor{1d6c}
@deffn {函数} tarfile.is_tarfile (name)

如果 @emph{name} 是一个 @ref{101,,tarfile} 模块能读取的 tar 归档文件则返回 @ref{494,,True}。
@end deffn

@ref{101,,tarfile} 模块定义了以下异常:

@geindex TarError
@anchor{library/tarfile tarfile TarError}@anchor{1d6d}
@deffn {例外} tarfile.TarError

所有 @ref{101,,tarfile} 异常的基类。
@end deffn

@geindex ReadError
@anchor{library/tarfile tarfile ReadError}@anchor{1d69}
@deffn {例外} tarfile.ReadError

当一个不能被 @ref{101,,tarfile} 模块处理或者因某种原因而无效的 tar 归档被打开时将被引发。
@end deffn

@geindex CompressionError
@anchor{library/tarfile tarfile CompressionError}@anchor{1d6a}
@deffn {例外} tarfile.CompressionError

当一个压缩方法不受支持或者当数据无法被正确解码时将被引发。
@end deffn

@geindex StreamError
@anchor{library/tarfile tarfile StreamError}@anchor{1d6e}
@deffn {例外} tarfile.StreamError

当达到流式 @ref{b85,,TarFile} 对象的典型限制时将被引发。
@end deffn

@geindex ExtractError
@anchor{library/tarfile tarfile ExtractError}@anchor{1d6f}
@deffn {例外} tarfile.ExtractError

当使用 @ref{762,,TarFile.extract()} 时针对 @emph{non-fatal} 所引发的异常，但是仅限 @code{TarFile.errorlevel}@code{== 2}。
@end deffn

@geindex HeaderError
@anchor{library/tarfile tarfile HeaderError}@anchor{1d70}
@deffn {例外} tarfile.HeaderError

如果获取的缓冲区无效则会由 @ref{1d71,,TarInfo.frombuf()} 引发的异常。
@end deffn

以下常量在模块层级上可用:

@geindex ENCODING() (在 tarfile 模块中)
@anchor{library/tarfile tarfile ENCODING}@anchor{1d72}
@deffn {数据} tarfile.ENCODING

默认的字符编码格式：在 Windows 上为 @code{'utf-8'}，其他系统上则为 @ref{4f0,,sys.getfilesystemencoding()} 所返回的值。
@end deffn

以下常量各自定义了一个 @ref{101,,tarfile} 模块能够创建的 tar 归档格式。 相关细节请参阅 @ref{1d73,,受支持的 tar 格式} 小节。

@geindex USTAR_FORMAT() (在 tarfile 模块中)
@anchor{library/tarfile tarfile USTAR_FORMAT}@anchor{1d74}
@deffn {数据} tarfile.USTAR_FORMAT

POSIX.1-1988 (ustar) 格式。
@end deffn

@geindex GNU_FORMAT() (在 tarfile 模块中)
@anchor{library/tarfile tarfile GNU_FORMAT}@anchor{1d75}
@deffn {数据} tarfile.GNU_FORMAT

GNU tar 格式。
@end deffn

@geindex PAX_FORMAT() (在 tarfile 模块中)
@anchor{library/tarfile tarfile PAX_FORMAT}@anchor{1d76}
@deffn {数据} tarfile.PAX_FORMAT

POSIX.1-2001 (pax) 格式。
@end deffn

@geindex DEFAULT_FORMAT() (在 tarfile 模块中)
@anchor{library/tarfile tarfile DEFAULT_FORMAT}@anchor{1d77}
@deffn {数据} tarfile.DEFAULT_FORMAT

用于创建归档的默认格式。 目前为 @ref{1d76,,PAX_FORMAT}。


在 3.8 版更改: 新归档的默认格式已更改为 @ref{1d76,,PAX_FORMAT} 而不再是 @ref{1d75,,GNU_FORMAT}。

@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{142,,zipfile}

@ref{142,,zipfile} 标准模块的文档。

@item @ref{b8f,,归档操作}

标准 @ref{e9,,shutil} 模块所提供的高层级归档工具的文档。

@item GNU tar manual@comma{} Basic Tar Format@footnote{https://www.gnu.org/software/tar/manual/html_node/Standard.html}

针对 tar 归档文件的文档，包含 GNU tar 扩展。
@end table


@menu
* TarFile 对象:: 
* TarInfo 对象:: 
* 命令行界面: 命令行界面<3>. 
* 例子: 例子<6>. 
* 受支持的 tar 格式:: 
* Unicode 问题:: 

@end menu

@node TarFile 对象,TarInfo 对象,,tarfile --- 读写tar归档文件
@anchor{library/tarfile id1}@anchor{1d78}@anchor{library/tarfile tarfile-objects}@anchor{1d68}
@subsubsection TarFile 对象


@ref{b85,,TarFile} 对象提供了一个 tar 归档的接口。 一个 tar 归档就是数据块的序列。 一个归档成员（被保存文件）是由一个标头块加多个数据块组成的。 一个文件可以在一个 tar 归档中多次被保存。 每个归档成员都由一个 @ref{b86,,TarInfo} 对象来代表，详情参见 @ref{1d79,,TarInfo 对象}。

@ref{b85,,TarFile} 对象可在 @ref{6e3,,with} 语句中作为上下文管理器使用。 当语句块结束时它将自动被关闭。 请注意在发生异常事件时被打开用于写入的归档将不会被终结；只有内部使用的文件对象将被关闭。 相关用例请参见 @ref{1d6b,,例子}。


3.2 新版功能: 添加了对上下文管理器协议的支持。


@geindex TarFile (tarfile 中的类)

@deffn {类} tarfile.TarFile (name=None, mode='r', fileobj=None, format=DEFAULT_FORMAT, tarinfo=TarInfo, dereference=False, ignore_zeros=False, encoding=ENCODING, errors='surrogateescape', pax_headers=None, debug=0, errorlevel=0)

下列所有参数都是可选项并且也可作为实例属性来访问。

@emph{name} 是归档的路径名称。 @emph{name} 可以是一个 @ref{363,,path-like object}。 如果给定了 @emph{fileobj} 则它可以被省略。 在此情况下，如果对象的 @code{name} 属性存在则它会被使用。

@emph{mode} 可以为 @code{'r'} 表示从现有归档读取，@code{'a'} 表示将数据追加到现有文件，@code{'w'} 表示创建新文件覆盖现有文件，或者 @code{'x'} 表示仅在文件不存在时创建新文件。

如果给定了 @emph{fileobj}，它会被用于读取或写入数据。 如果可以被确定，则 @emph{mode} 会被 @emph{fileobj} 的模式所覆盖。 @emph{fileobj} 的使用将从位置 0 开始。

@cartouche
@quotation 注解 
当 @ref{b85,,TarFile} 被关闭时，@emph{fileobj} 不会被关闭。
@end quotation
@end cartouche

@emph{format} 控制用于写入的归档格式。 它必须为在模块层级定义的常量 @ref{1d74,,USTAR_FORMAT}, @ref{1d75,,GNU_FORMAT} 或 @ref{1d76,,PAX_FORMAT} 中的一个。 当读取时，格式将被自动检测，即使单个归档中存在不同的格式。

@emph{tarinfo} 参数可以被用来将默认的 @ref{b86,,TarInfo} 类替换为另一个。

如果 @emph{dereference} 为 @ref{380,,False}，则会将符号链接和硬链接添加到归档中。 如果为 @ref{494,,True}，则会将目标文件的内容添加到归档中。 在不支持符号链接的系统上参数将不起作用。

如果 @emph{ignore_zeros} 为 @ref{380,,False}，则会将空的数据块当作归档的末尾来处理。 如果为 @ref{494,,True}，则会跳过空的（和无效的）数据块并尝试获取尽可能多的成员。 此参数仅适用于读取拼接的或损坏的归档。

@emph{debug} 可设为从 @code{0} (无调试消息) 到 @code{3} (全部调试消息)。 消息会被写入到 @code{sys.stderr}。

如果 @emph{errorlevel} 为 @code{0}，则当使用 @ref{762,,TarFile.extract()} 时会忽略所有错误。 无论何种情况，当启用调试时它们都将被显示为调试输出的错误消息。 如果为 @code{1}，则所有 @emph{fatal} 错误会被作为 @ref{1d3,,OSError} 异常被引发。 如果为 @code{2}，则所有 @emph{non-fatal} 错误也会被作为 @ref{1d6d,,TarError} 异常被引发。

@emph{encoding} 和 @emph{errors} 参数定义了读取或写入归档所使用的字符编码格式以及要如何处理转换错误。 默认设置将适用于大多数用户。 要深入了解详情可参阅 @ref{1d7a,,Unicode 问题} 小节。

可选的 @emph{pax_headers} 参数是字符串的字典，如果 @emph{format} 为 @ref{1d76,,PAX_FORMAT} 它将被作为 pax 全局标头被添加。


在 3.2 版更改: 使用 @code{'surrogateescape'} 作为 @emph{errors} 参数的默认值。



在 3.5 版更改: 添加了 @code{'x'} (单独创建) 模式。



在 3.6 版更改: @emph{name} 形参接受一个 @ref{363,,path-like object}。

@end deffn

@geindex open() (tarfile.TarFile 类方法)
@anchor{library/tarfile tarfile TarFile open}@anchor{1d7b}
@deffn {方法} classmethod TarFile.open (...)

作为替代的构造器。 @ref{760,,tarfile.open()} 函数实际上是这个类方法的快捷方式。
@end deffn

@geindex getmember() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile getmember}@anchor{1d7c}
@deffn {方法} TarFile.getmember (name)

返回成员 @emph{name} 的 @ref{b86,,TarInfo} 对象。 如果 @emph{name} 在归档中找不到，则会引发 @ref{2c7,,KeyError}。

@cartouche
@quotation 注解 
如果一个成员在归档中出现超过一次，它的最后一次出现会被视为是最新的版本。
@end quotation
@end cartouche
@end deffn

@geindex getmembers() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile getmembers}@anchor{764}
@deffn {方法} TarFile.getmembers ()

以 @ref{b86,,TarInfo} 对象列表的形式返回归档的成员。 列表的顺序与归档中成员的顺序一致。
@end deffn

@geindex getnames() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile getnames}@anchor{1d7d}
@deffn {方法} TarFile.getnames ()

以名称列表的形式返回成员。 它的顺序与 @ref{764,,getmembers()} 所返回列表的顺序一致。
@end deffn

@geindex list() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile list}@anchor{763}
@deffn {方法} TarFile.list (verbose=True, *, members=None)

将内容清单打印到 @code{sys.stdout}。 如果 @emph{verbose} 为 @ref{380,,False}，则将只打印成员名称。 如果为 @ref{494,,True}，则输出将类似于 @code{ls -l} 的输出效果。 如果给定了可选的 @emph{members}，它必须为 @ref{764,,getmembers()} 所返回的列表的一个子集。


在 3.5 版更改: 添加了 @emph{members} 形参。

@end deffn

@geindex next() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile next}@anchor{1d7e}
@deffn {方法} TarFile.next ()

当 @ref{b85,,TarFile} 被打开用于读取时，以 @ref{b86,,TarInfo} 对象的形式返回归档的下一个成员。 如果不再有可用对象则返回 @ref{157,,None}。
@end deffn

@geindex extractall() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile extractall}@anchor{761}
@deffn {方法} TarFile.extractall (path=".", members=None, *, numeric_owner=False)

将归档中的所有成员提取到当前工作目录或 @emph{path} 目录。 如果给定了可选的 @emph{members}，则它必须为 @ref{764,,getmembers()} 所返回的列表的一个子集。 字典信息例如所有者、修改时间和权限会在所有成员提取完毕后被设置。 这样做是为了避免两个问题：目录的修改时间会在每当在其中创建文件时被重置。 并且如果目录的权限不允许写入，提取文件到目录的操作将失败。

如果 @emph{numeric_owner} 为 @ref{494,,True}，则将使用来自 tarfile 的 uid 和 gid 数值来设置被提取文件的所有者/用户组。 在其他情况下，则会使用来自 tarfile 的名称值。

@cartouche
@quotation 警告 
绝不要未经预先检验就从不可靠的源中提取归档文件。 这样有可能在 @emph{path} 之外创建文件，例如某些成员具有以 @code{"/"} 开始的绝对路径文件名或带有两个点号 @code{".."} 的文件名。
@end quotation
@end cartouche


在 3.5 版更改: 添加了 @emph{numeric_owner} 形参。



在 3.6 版更改: @emph{path} 形参接受一个 @ref{363,,path-like object}。

@end deffn

@geindex extract() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile extract}@anchor{762}
@deffn {方法} TarFile.extract (member, path="", set_attrs=True, *, numeric_owner=False)

从归档中提取出一个成员放入当前工作目录，将使用其完整名称。 成员的文件信息会尽可能精确地被提取。 @emph{member} 可以是一个文件名或 @ref{b86,,TarInfo} 对象。 你可以使用 @emph{path} 指定一个不同的目录。 @emph{path} 可以是一个 @ref{363,,path-like object}。 将会设置文件属性 (owner, mtime, mode) 除非 @emph{set_attrs} 为假值。

如果 @emph{numeric_owner} 为 @ref{494,,True}，则将使用来自 tarfile 的 uid 和 gid 数值来设置被提取文件的所有者/用户组。 在其他情况下，则会使用来自 tarfile 的名称值。

@cartouche
@quotation 注解 
@ref{762,,extract()} 方法不会处理某些提取问题。 在大多数情况下你应当考虑使用 @ref{761,,extractall()} 方法。
@end quotation
@end cartouche

@cartouche
@quotation 警告 
查看 @ref{761,,extractall()} 的警告信息。
@end quotation
@end cartouche


在 3.2 版更改: 添加了 @emph{set_attrs} 形参。



在 3.5 版更改: 添加了 @emph{numeric_owner} 形参。



在 3.6 版更改: @emph{path} 形参接受一个 @ref{363,,path-like object}。

@end deffn

@geindex extractfile() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile extractfile}@anchor{1d7f}
@deffn {方法} TarFile.extractfile (member)

将归档中的一个成员提取为文件对象。 @emph{member} 可以是一个文件名或 @ref{b86,,TarInfo} 对象。 如果 @emph{member} 是一个常规文件或链接，则会返回一个 @ref{b83,,io.BufferedReader} 对象。 在其他情况下将返回 @ref{157,,None}。


在 3.3 版更改: 返回一个 @ref{b83,,io.BufferedReader} 对象。

@end deffn

@geindex add() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile add}@anchor{476}
@deffn {方法} TarFile.add (name, arcname=None, recursive=True, *, filter=None)

将文件 @emph{name} 添加到归档。 @emph{name} 可以为任意类型的文件（目录、fifo、符号链接等等）。 如果给出 @emph{arcname} 则它将为归档中的文件指定一个替代名称。 默认情况下会递归地添加目录。 这可以通过将 @emph{recursive} 设为 @ref{380,,False} 来避免。 递归操作会按排序顺序添加条目。 如果给定了 @emph{filter}，它应当为一个接受 @ref{b86,,TarInfo} 对象并返回已修改 @ref{b86,,TarInfo} 对象的函数。 如果它返回 @ref{157,,None} 则 @ref{b86,,TarInfo} 对象将从归档中被排除。 具体示例参见 @ref{1d6b,,例子}。


在 3.2 版更改: 添加了 @emph{filter} 形参。



在 3.7 版更改: 递归操作按排序顺序添加条目。

@end deffn

@geindex addfile() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile addfile}@anchor{1d80}
@deffn {方法} TarFile.addfile (tarinfo, fileobj=None)

将 @ref{b86,,TarInfo} 对象 @emph{tarinfo} 添加到归档。 如果给定了 @emph{fileobj}，它应当是一个 @ref{1c37,,binary file}，并会从中读取 @code{tarinfo.size} 个字节添加到归档。 你可以直接创建 @ref{b86,,TarInfo} 对象，或是使用 @ref{1d81,,gettarinfo()} 来创建。
@end deffn

@geindex gettarinfo() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile gettarinfo}@anchor{1d81}
@deffn {方法} TarFile.gettarinfo (name=None, arcname=None, fileobj=None)

基于 @ref{1f1,,os.stat()} 的结果或者现有文件的相同数据创建一个 @ref{b86,,TarInfo}。 文件或者是命名为 @emph{name}，或者是使用文件描述符指定为一个 @ref{b3b,,file object} @emph{fileobj}。 @emph{name} 可以是一个 @ref{363,,path-like object}。 如果给定了 @emph{arcname}，则它将为归档中的文件指定一个替代名称，在其他情况下，名称将从 @emph{fileobj} 的 @ref{1d82,,name} 属性或 @emph{name} 参数获取。 名称应当是一个文本字符串。

你可以在使用 @ref{1d80,,addfile()} 添加 @ref{b86,,TarInfo} 的某些属性之前修改它们。 如果文件对象不是从文件开头进行定位的普通文件对象，@ref{1d83,,size} 之类的属性就可能需要修改。 例如 @ref{6d7,,GzipFile} 之类的文件就属于这种情况。  @ref{1d84,,name} 也可以被修改，在这种情况下 @emph{arcname} 可以是一个占位字符串。


在 3.6 版更改: @emph{name} 形参接受一个 @ref{363,,path-like object}。

@end deffn

@geindex close() (tarfile.TarFile 方法)
@anchor{library/tarfile tarfile TarFile close}@anchor{1d85}
@deffn {方法} TarFile.close ()

关闭 @ref{b85,,TarFile}。 在写入模式下，会向归档添加两个表示结束的零数据块。
@end deffn

@geindex pax_headers (tarfile.TarFile 属性)
@anchor{library/tarfile tarfile TarFile pax_headers}@anchor{1d86}
@deffn {属性} TarFile.pax_headers

一个包含 pax 全局标头的键值对的字典。
@end deffn

@node TarInfo 对象,命令行界面<3>,TarFile 对象,tarfile --- 读写tar归档文件
@anchor{library/tarfile id2}@anchor{1d87}@anchor{library/tarfile tarinfo-objects}@anchor{1d79}
@subsubsection TarInfo 对象


@ref{b86,,TarInfo} 对象代表 @ref{b85,,TarFile} 中的一个文件。 除了会存储所有必要的文件属性（例如文件类型、大小、时间、权限、所有者等），它还提供了一些确定文件类型的有用方法。 此对象 @emph{并不} 包含文件数据本身。

@ref{b86,,TarInfo} 对象可通过 @ref{b85,,TarFile} 的方法 @code{getmember()}, @code{getmembers()} 和 @code{gettarinfo()} 返回。

@geindex TarInfo (tarfile 中的类)
@anchor{library/tarfile tarfile TarInfo}@anchor{b86}
@deffn {类} tarfile.TarInfo (name="")

创建一个 @ref{b86,,TarInfo} 对象。
@end deffn

@geindex frombuf() (tarfile.TarInfo 类方法)
@anchor{library/tarfile tarfile TarInfo frombuf}@anchor{1d71}
@deffn {方法} classmethod TarInfo.frombuf (buf, encoding, errors)

基于字符串缓冲区 @emph{buf} 创建并返回一个 @ref{b86,,TarInfo} 对象。

如果缓冲区无效则会引发 @ref{1d70,,HeaderError}。
@end deffn

@geindex fromtarfile() (tarfile.TarInfo 类方法)
@anchor{library/tarfile tarfile TarInfo fromtarfile}@anchor{1d88}
@deffn {方法} classmethod TarInfo.fromtarfile (tarfile)

从 @ref{b85,,TarFile} 对象 @emph{tarfile} 读取下一个成员并将其作为 @ref{b86,,TarInfo} 对象返回。
@end deffn

@geindex tobuf() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo tobuf}@anchor{1d89}
@deffn {方法} TarInfo.tobuf (format=DEFAULT_FORMAT, encoding=ENCODING, errors='surrogateescape')

基于 @ref{b86,,TarInfo} 对象创建一个字符串缓冲区。 有关参数的信息请参见 @ref{b85,,TarFile} 类的构造器。


在 3.2 版更改: 使用 @code{'surrogateescape'} 作为 @emph{errors} 参数的默认值。

@end deffn

@code{TarInfo} 对象具有以下公有数据属性:

@geindex name (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo name}@anchor{1d84}
@deffn {属性} TarInfo.name

归档成员的名称。
@end deffn

@geindex size (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo size}@anchor{1d83}
@deffn {属性} TarInfo.size

以字节表示的大小。
@end deffn

@geindex mtime (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo mtime}@anchor{1d8a}
@deffn {属性} TarInfo.mtime

上次修改的时间。
@end deffn

@geindex mode (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo mode}@anchor{1d8b}
@deffn {属性} TarInfo.mode

权限位。
@end deffn

@geindex type (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo type}@anchor{1d8c}
@deffn {属性} TarInfo.type

文件类型。 @emph{type} 通常为以下常量之一: @code{REGTYPE}, @code{AREGTYPE}, @code{LNKTYPE}, @code{SYMTYPE}, @code{DIRTYPE}, @code{FIFOTYPE}, @code{CONTTYPE}, @code{CHRTYPE}, @code{BLKTYPE}, @code{GNUTYPE_SPARSE}。 要更方便地确定一个 @ref{b86,,TarInfo} 对象的类型，请使用下述的 @code{is*()} 方法。
@end deffn

@geindex linkname (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo linkname}@anchor{1d8d}
@deffn {属性} TarInfo.linkname

目标文件名的名称，该属性仅在类型为 @code{LNKTYPE} 和 @code{SYMTYPE} 的 @ref{b86,,TarInfo} 对象中存在。
@end deffn

@geindex uid (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo uid}@anchor{1d8e}
@deffn {属性} TarInfo.uid

最初保存该成员的用户的用户 ID。
@end deffn

@geindex gid (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo gid}@anchor{1d8f}
@deffn {属性} TarInfo.gid

最初保存该成员的用户的分组 ID。
@end deffn

@geindex uname (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo uname}@anchor{1d90}
@deffn {属性} TarInfo.uname

用户名。
@end deffn

@geindex gname (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo gname}@anchor{1d91}
@deffn {属性} TarInfo.gname

分组名。
@end deffn

@geindex pax_headers (tarfile.TarInfo 属性)
@anchor{library/tarfile tarfile TarInfo pax_headers}@anchor{1d92}
@deffn {属性} TarInfo.pax_headers

一个包含所关联的 pax 扩展标头的键值对的字典。
@end deffn

@ref{b86,,TarInfo} 对象还提供了一些便捷查询方法:

@geindex isfile() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo isfile}@anchor{1d93}
@deffn {方法} TarInfo.isfile ()

如果 @code{Tarinfo} 对象为普通文件则返回 @ref{494,,True}。
@end deffn

@geindex isreg() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo isreg}@anchor{1d94}
@deffn {方法} TarInfo.isreg ()

与 @ref{1d93,,isfile()} 相同。
@end deffn

@geindex isdir() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo isdir}@anchor{1d95}
@deffn {方法} TarInfo.isdir ()

如果为目录则返回 @ref{494,,True}。
@end deffn

@geindex issym() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo issym}@anchor{1d96}
@deffn {方法} TarInfo.issym ()

如果为符号链接则返回 @ref{494,,True}。
@end deffn

@geindex islnk() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo islnk}@anchor{1d97}
@deffn {方法} TarInfo.islnk ()

如果为硬链接则返回 @ref{494,,True}。
@end deffn

@geindex ischr() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo ischr}@anchor{1d98}
@deffn {方法} TarInfo.ischr ()

如果为字符设备则返回 @ref{494,,True}。
@end deffn

@geindex isblk() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo isblk}@anchor{1d99}
@deffn {方法} TarInfo.isblk ()

如果为块设备则返回 @ref{494,,True}。
@end deffn

@geindex isfifo() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo isfifo}@anchor{1d9a}
@deffn {方法} TarInfo.isfifo ()

如果为 FIFO 则返回 @ref{494,,True}。.
@end deffn

@geindex isdev() (tarfile.TarInfo 方法)
@anchor{library/tarfile tarfile TarInfo isdev}@anchor{1d9b}
@deffn {方法} TarInfo.isdev ()

如果为字符设备、块设备或 FIFO 之一则返回 @ref{494,,True}。
@end deffn

@node 命令行界面<3>,例子<6>,TarInfo 对象,tarfile --- 读写tar归档文件
@anchor{library/tarfile command-line-interface}@anchor{1d9c}@anchor{library/tarfile tarfile-commandline}@anchor{8e2}
@subsubsection 命令行界面



3.4 新版功能.


@ref{101,,tarfile} 模块提供了简单的命令行接口以便与 tar 归档进行交互。

如果你想要创建一个新的 tar 归档，请在 @ref{1d9d,,-c} 选项后指定其名称然后列出应当被包含的文件名:

@example
$ python -m tarfile -c monty.tar  spam.txt eggs.txt
@end example

传入一个字典也是可接受的:

@example
$ python -m tarfile -c monty.tar life-of-brian_1979/
@end example

如果你想要将一个 tar 归档提取到指定的目录，请使用 @ref{1d9e,,-e} 选项:

@example
$ python -m tarfile -e monty.tar
@end example

你也可以通过传入目录名称将一个 tar 归档提取到不同的目录:

@example
$ python -m tarfile -e monty.tar  other-dir/
@end example

要获取一个 tar 归档中文件的列表，请使用 @ref{1d9f,,-l} 选项:

@example
$ python -m tarfile -l monty.tar
@end example

@menu
* 命令行选项: 命令行选项<3>. 

@end menu

@node 命令行选项<3>,,,命令行界面<3>
@anchor{library/tarfile command-line-options}@anchor{1da0}
@subsubsection 命令行选项


@geindex tarfile command line option; -l <tarfile>
@geindex tarfile command line option; --list <tarfile>
@anchor{library/tarfile cmdoption-tarfile-l}@anchor{1d9f}
@deffn {程序选项} @w{-}l <tarfile>
@anchor{library/tarfile cmdoption-tarfile-list}@anchor{1da1}
@deffnx {程序选项} @w{-}@w{-}list <tarfile>

列出一个 tarfile 中的文件名。
@end deffn

@geindex tarfile command line option; -c <tarfile> <source1> ... <sourceN>
@geindex tarfile command line option; --create <tarfile> <source1> ... <sourceN>
@anchor{library/tarfile cmdoption-tarfile-c}@anchor{1d9d}
@deffn {程序选项} @w{-}c <tarfile> <source1> ... <sourceN>
@anchor{library/tarfile cmdoption-tarfile-create}@anchor{1da2}
@deffnx {程序选项} @w{-}@w{-}create <tarfile> <source1> ... <sourceN>

基于源文件创建 tarfile。
@end deffn

@geindex tarfile command line option; -e <tarfile> [<output_dir>]
@geindex tarfile command line option; --extract <tarfile> [<output_dir>]
@anchor{library/tarfile cmdoption-tarfile-e}@anchor{1d9e}
@deffn {程序选项} @w{-}e <tarfile> [<output_dir>]
@anchor{library/tarfile cmdoption-tarfile-extract}@anchor{1da3}
@deffnx {程序选项} @w{-}@w{-}extract <tarfile> [<output_dir>]

如果未指定 @emph{output_dir} 则会将 tarfile 提取到当前目录。
@end deffn

@geindex tarfile command line option; -t <tarfile>
@geindex tarfile command line option; --test <tarfile>
@anchor{library/tarfile cmdoption-tarfile-t}@anchor{1da4}
@deffn {程序选项} @w{-}t <tarfile>
@anchor{library/tarfile cmdoption-tarfile-test}@anchor{1da5}
@deffnx {程序选项} @w{-}@w{-}test <tarfile>

检测 tarfile 是否有效。
@end deffn

@geindex tarfile command line option; -v
@geindex tarfile command line option; --verbose
@anchor{library/tarfile cmdoption-tarfile-v}@anchor{1da6}
@deffn {程序选项} @w{-}v, @w{-}@w{-}verbose

更详细地输出结果。
@end deffn

@node 例子<6>,受支持的 tar 格式,命令行界面<3>,tarfile --- 读写tar归档文件
@anchor{library/tarfile examples}@anchor{1da7}@anchor{library/tarfile tar-examples}@anchor{1d6b}
@subsubsection 例子


如何将整个 tar 归档提取到当前工作目录:

@example
import tarfile
tar = tarfile.open("sample.tar.gz")
tar.extractall()
tar.close()
@end example

如何通过 @ref{761,,TarFile.extractall()} 使用生成器函数而非列表来提取一个 tar 归档的子集:

@example
import os
import tarfile

def py_files(members):
    for tarinfo in members:
        if os.path.splitext(tarinfo.name)[1] == ".py":
            yield tarinfo

tar = tarfile.open("sample.tar.gz")
tar.extractall(members=py_files(tar))
tar.close()
@end example

如何基于一个文件名列表创建未压缩的 tar 归档:

@example
import tarfile
tar = tarfile.open("sample.tar", "w")
for name in ["foo", "bar", "quux"]:
    tar.add(name)
tar.close()
@end example

使用 @ref{6e3,,with} 语句的同一个示例:

@example
import tarfile
with tarfile.open("sample.tar", "w") as tar:
    for name in ["foo", "bar", "quux"]:
        tar.add(name)
@end example

如何读取一个 gzip 压缩的 tar 归档并显示一些成员信息:

@example
import tarfile
tar = tarfile.open("sample.tar.gz", "r:gz")
for tarinfo in tar:
    print(tarinfo.name, "is", tarinfo.size, "bytes in size and is ", end="")
    if tarinfo.isreg():
        print("a regular file.")
    elif tarinfo.isdir():
        print("a directory.")
    else:
        print("something else.")
tar.close()
@end example

如何创建一个归档并使用 @ref{476,,TarFile.add()} 中的 @emph{filter} 形参来重置用户信息:

@example
import tarfile
def reset(tarinfo):
    tarinfo.uid = tarinfo.gid = 0
    tarinfo.uname = tarinfo.gname = "root"
    return tarinfo
tar = tarfile.open("sample.tar.gz", "w:gz")
tar.add("foo", filter=reset)
tar.close()
@end example

@node 受支持的 tar 格式,Unicode 问题,例子<6>,tarfile --- 读写tar归档文件
@anchor{library/tarfile supported-tar-formats}@anchor{1da8}@anchor{library/tarfile tar-formats}@anchor{1d73}
@subsubsection 受支持的 tar 格式


通过 @ref{101,,tarfile} 模块可以创建三种 tar 格式:


@itemize *

@item 
The POSIX.1-1988 ustar 格式 (@ref{1d74,,USTAR_FORMAT})。 它支持最多 256 个字符的文件名长度和最多 100 个字符的链接名长度。 文件大小上限为 8 GiB。 这是一种老旧但广受支持的格式。

@item 
GNU tar 格式 (@ref{1d75,,GNU_FORMAT})。 它支持长文件名和链接名、大于 8 GiB 的文件以及稀疏文件。 它是 GNU/Linux 系统上的事实标准。 @ref{101,,tarfile} 完全支持针对长名称的 GNU tar 扩展，稀疏文件支持则限制为只读。

@item 
POSIX.1-2001 pax 格式 (@ref{1d76,,PAX_FORMAT})。 它是几乎无限制的最灵活格式。 它支持长文件名和链接名，大文件以及使用便捷方式存储路径名。 现代的 tar 实现，包括 GNU tar, bsdtar/libarchive 和 star，完全支持扩展 @emph{pax} 特性；某些老旧或不维护的库可能不受支持，但应当会将 @emph{pax} 归档视为广受支持的 @emph{ustar} 格式。 这是目前新建归档的默认格式。

它扩展了现有的 @emph{ustar} 格式，包括用于无法以其他方式存储的附加标头。 存在两种形式的 pax 标头：扩展标头只影响后续的文件标头，全局标头则适用于完整归档并会影响所有后续的文件。 为了便于移植，在 pax 标头中的所有数据均以 @emph{UTF-8} 编码。
@end itemize

还有一些 tar 格式的其他变种，它们可以被读取但不能被创建:


@itemize *

@item 
古老的 V7 格式。 这是来自 Unix 第七版的第一个 tar 格式，它只存储常规文件和目录。 名称长度不能超过 100 个字符，并且没有用户/分组名信息。 某些归档在带有非 ASCII 字符字段的情况下会产生计算错误的标头校验和。

@item 
SunOS tar 扩展格式。 此格式是 POSIX.1-2001 pax 格式的一个变种，但并不保持兼容。
@end itemize

@node Unicode 问题,,受支持的 tar 格式,tarfile --- 读写tar归档文件
@anchor{library/tarfile tar-unicode}@anchor{1d7a}@anchor{library/tarfile unicode-issues}@anchor{1da9}
@subsubsection Unicode 问题


最初 tar 格式被设计用来在磁带机上生成备份，主要关注于保存文件系统信息。 现在 tar 归档通常用于文件分发和在网络上交换归档。 最初格式（它是所有其他格式的基础）的一个问题是它没有支持不同字符编码格式的概念。 例如，一个在 @emph{UTF-8} 系统上创建的普通 tar 归档如果包含非 @emph{ASCII} 字符则将无法在 @emph{Latin-1} 系统上被正确读取。 文本元数据（例如文件名，链接名，用户/分组名）将变为损坏状态。 不幸的是，没有什么办法能够自动检测一个归档的编码格式。 pax 格式被设计用来解决这个问题。 它使用通用字符编码格式 @emph{UTF-8} 来存储非 ASCII 元数据。

在 @ref{101,,tarfile} 中字符转换的细节由 @ref{b85,,TarFile} 类的 @emph{encoding} 和 @emph{errors} 关键字参数控制。

@emph{encoding} 定义了用于归档中元数据的字符编码格式。 默认值为 @ref{4f0,,sys.getfilesystemencoding()} 或是回退选项 @code{'ascii'}。 根据归档是被读取还是被写入，元数据必须被解码或编码。 如果没有正确设置 @emph{encoding}，转换可能会失败。

@emph{errors} 参数定义了不能被转换的字符将如何处理。 可能的取值在 @ref{12f7,,错误处理方案} 小节列出。 默认方案为 @code{'surrogateescape'}，它也被 Python 用于文件系统调用，参见 @ref{1daa,,文件名，命令行参数，以及环境变量。}。

对于 @ref{1d76,,PAX_FORMAT} 归档（默认格式），@emph{encoding} 通常是不必要的，因为所有元数据都使用 @emph{UTF-8} 来存储。 @emph{encoding} 仅在解码二进制 pax 标头或存储带有替代字符的字符串等少数场景下会被使用。

@node 文件格式,加密服务,数据压缩和存档,Python 标准库
@anchor{library/fileformats doc}@anchor{1dab}@anchor{library/fileformats file-formats}@anchor{1dac}@anchor{library/fileformats fileformats}@anchor{1dad}
@section 文件格式


本章中描述的模块解析各种不是标记语言且与电子邮件无关的杂项文件格式。

@menu
* csv: csv --- CSV 文件读写. CSV 文件读写
* configparser: configparser --- 配置文件解析器. 配置文件解析器
* netrc: netrc --- netrc 文件处理. netrc 文件处理
* xdrlib: xdrlib --- 编码与解码 XDR 数据. 编码与解码 XDR 数据
* plistlib: plistlib --- 生成与解析 Mac OS X plist 文件. 生成与解析 Mac OS X .plist 文件

@end menu

@node csv --- CSV 文件读写,configparser --- 配置文件解析器,,文件格式
@anchor{library/csv doc}@anchor{1dae}@anchor{library/csv csv-csv-file-reading-and-writing}@anchor{1daf}@anchor{library/csv module-csv}@anchor{2a}
@subsection @code{csv} --- CSV 文件读写


@geindex csv (模块)

@strong{源代码：} Lib/csv.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/csv.py}

@geindex csv
@geindex data; tabular


__________________________________________________________________


CSV (Comma Separated Vaules) 格式是电子表格和数据库中最常见的输入、输出文件格式。在 
@geindex RFC; RFC 4180
RFC 4180@footnote{https://tools.ietf.org/html/rfc4180.html} 规范推出的很多年前，CSV 格式就已经被开始使用了，由于当时并没有合理的标准，不同应用程序读写的数据会存在细微的差别。这种差别让处理多个来源的 CSV 文件变得困难。但尽管分隔符会变化，此类文件的大致格式是相似的，所以编写一个单独的模块以高效处理此类数据，将程序员从读写数据的繁琐细节中解放出来是有可能的。

@ref{2a,,csv} 模块实现了 CSV 格式表单数据的读写。其提供了诸如“以兼容 Excel 的方式输出数据文件”或“读取 Excel 程序输出的数据文件”的功能，程序员无需知道 Excel 所采用 CSV 格式的细节。此模块同样可以用于定义其他应用程序可用的 CSV 格式或定义特定需求的 CSV 格式。

@ref{2a,,csv} 模块中的 @ref{1db0,,reader} 类和 @ref{df5,,writer} 类可用于读写序列化的数据。也可使用 @ref{1bd,,DictReader} 类和 @ref{b73,,DictWriter} 类以字典的形式读写数据。


@subsubheading 参见



@table @asis

@item 该实现在“Python 增强提议” - PEP @cite{305} (CSV 文件 API)  中被提出

《Python 增强提议》提出了对 Python 的这一补充。
@end table


@menu
* 模块内容: 模块内容<3>. 
* 变种与格式参数:: 
* Reader 对象:: 
* Writer 对象:: 
* 例子: 例子<7>. 

@end menu

@node 模块内容<3>,变种与格式参数,,csv --- CSV 文件读写
@anchor{library/csv csv-contents}@anchor{1db1}@anchor{library/csv module-contents}@anchor{1db2}
@subsubsection 模块内容


@ref{2a,,csv} 模块定义了以下函数：

@geindex universal newlines; csv.reader function

@geindex reader() (在 csv 模块中)
@anchor{library/csv csv reader}@anchor{1db0}
@deffn {函数} csv.reader (csvfile, dialect='excel', **fmtparams)

返回一个 reader 对象，该对象将逐行遍历 @emph{csvfile}。@emph{csvfile} 可以是任何对象，只要这个对象支持 @ref{fce,,iterator} 协议并在每次调用 @code{__next__()} 方法时都返回字符串，@ref{b3b,,文件对象} 和列表对象均适用。如果 @emph{csvfile} 是文件对象，则打开它时应使用 @code{newline='@w{'}}。 @footnote{@w{(1)} 
如果没有指定 @code{newline='@w{'}}，则嵌入引号中的换行符将无法正确解析，并且在写入时，使用 @code{\r\n} 换行的平台会有多余的 @code{\r} 写入。由于 csv 模块会执行自己的（@ref{5ef,,通用}）换行符处理，因此指定 @code{newline='@w{'}} 应该总是安全的。
} 可选参数 @emph{dialect} 是用于不同的 CSV 变种的特定参数组。它可以是 @ref{1db3,,Dialect} 类的子类的实例，也可以是 @ref{1db4,,list_dialects()} 函数返回的字符串之一。另一个可选关键字参数 @emph{fmtparams} 可以覆写当前变种格式中的单个格式设置。有关变种和格式设置参数的完整详细信息，请参见 @ref{1db5,,变种与格式参数} 部分。

csv 文件的每一行都读取为一个由字符串组成的列表。除非指定了 @code{QUOTE_NONNUMERIC} 格式选项（在这种情况下，未加引号的字段会转换为浮点数），否则不会执行自动数据类型转换。

一个简短的用法示例:

@example
>>> import csv
>>> with open('eggs.csv', newline='@w{'}) as csvfile:
...     spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
...     for row in spamreader:
...         print(', '.join(row))
Spam, Spam, Spam, Spam, Spam, Baked Beans
Spam, Lovely Spam, Wonderful Spam
@end example
@end deffn

@geindex writer() (在 csv 模块中)
@anchor{library/csv csv writer}@anchor{df5}
@deffn {函数} csv.writer (csvfile, dialect='excel', **fmtparams)

返回一个 writer 对象，该对象负责将用户的数据在给定的文件类对象上转换为带分隔符的字符串。@emph{csvfile} 可以是具有 @code{write()} 方法的任何对象。如果 @emph{csvfile} 是文件对象，则打开它时应使用 @code{newline='@w{'}}。 @footnote{@w{(1)} 
如果没有指定 @code{newline='@w{'}}，则嵌入引号中的换行符将无法正确解析，并且在写入时，使用 @code{\r\n} 换行的平台会有多余的 @code{\r} 写入。由于 csv 模块会执行自己的（@ref{5ef,,通用}）换行符处理，因此指定 @code{newline='@w{'}} 应该总是安全的。
} 可选参数 @emph{dialect} 是用于不同的 CSV 变种的特定参数组。它可以是 @ref{1db3,,Dialect} 类的子类的实例，也可以是 @ref{1db4,,list_dialects()} 函数返回的字符串之一。另一个可选关键字参数 @emph{fmtparams} 可以覆写当前变种格式中的单个格式设置。有关变种和格式设置参数的完整详细信息，请参见 @ref{1db5,,变种与格式参数} 部分。为了尽量简化与数据库 API 模块之间的对接，@ref{157,,None} 值会写入为空字符串。虽然这个转换是不可逆的，但它让 SQL 空数据值转储到 CSV 文件更容易，而无需预处理从 @code{cursor.fetch*} 调用返回的数据。写入前，所有非字符串数据都先用 @ref{329,,str()} 转化为字符串再写入。

一个简短的用法示例:

@example
import csv
with open('eggs.csv', 'w', newline='@w{'}) as csvfile:
    spamwriter = csv.writer(csvfile, delimiter=' ',
                            quotechar='|', quoting=csv.QUOTE_MINIMAL)
    spamwriter.writerow(['Spam'] * 5 + ['Baked Beans'])
    spamwriter.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])
@end example
@end deffn

@geindex register_dialect() (在 csv 模块中)
@anchor{library/csv csv register_dialect}@anchor{1db6}
@deffn {函数} csv.register_dialect (name[, dialect[, **fmtparams]])

将 @emph{name} 与 @emph{dialect} 关联起来。@emph{name} 必须是字符串。要指定变种 (dialect)，可以给出 @ref{1db3,,Dialect} 的子类，或给出 @emph{fmtparams} 关键字参数，或两者都给出（此时关键字参数会覆盖 @emph{dialect} 参数）。 有关变种和格式设置参数的完整详细信息，请参见 @ref{1db5,,变种与格式参数} 部分。
@end deffn

@geindex unregister_dialect() (在 csv 模块中)
@anchor{library/csv csv unregister_dialect}@anchor{1db7}
@deffn {函数} csv.unregister_dialect (name)

从变种注册表中删除 @emph{name} 对应的变种。如果 @emph{name} 不是已注册的变种名称，则抛出 @ref{1db8,,Error} 异常。
@end deffn

@geindex get_dialect() (在 csv 模块中)
@anchor{library/csv csv get_dialect}@anchor{1db9}
@deffn {函数} csv.get_dialect (name)

返回 @emph{name} 对应的变种。如果 @emph{name} 不是已注册的变种名称，则抛出 @ref{1db8,,Error} 异常。该函数返回的是不可变的 @ref{1db3,,Dialect} 对象。
@end deffn

@geindex list_dialects() (在 csv 模块中)
@anchor{library/csv csv list_dialects}@anchor{1db4}
@deffn {函数} csv.list_dialects ()

返回所有已注册变种的名称。
@end deffn

@geindex field_size_limit() (在 csv 模块中)
@anchor{library/csv csv field_size_limit}@anchor{1dba}
@deffn {函数} csv.field_size_limit ([new_limit])

返回解析器当前允许的最大字段大小。如果指定了 @emph{new_limit}，则它将成为新的最大字段大小。
@end deffn

@ref{2a,,csv} 模块定义了以下类：

@geindex DictReader (csv 中的类)
@anchor{library/csv csv DictReader}@anchor{1bd}
@deffn {类} csv.DictReader (f, fieldnames=None, restkey=None, restval=None, dialect='excel', *args, **kwds)

创建一个对象，该对象在操作上类似于常规 reader，但是将每行中的信息映射到一个 @ref{1b8,,dict}，该 dict 的键由 @emph{fieldnames} 可选参数给出。

@emph{fieldnames} 参数是一个 @ref{11bc,,sequence}。如果省略 @emph{fieldnames}，则文件 @emph{f} 第一行中的值将用作字段名。无论字段名是如何确定的，字典都将保留其原始顺序。

如果某一行中的字段多于字段名，则剩余数据会被放入一个列表，并与 @emph{restkey} 所指定的字段名 (默认为 @code{None}) 一起保存。 如果某个非空白行的字段少于字段名，则缺失的值会使用 @emph{restval} 的值来填充 (默认为 @code{None})。

所有其他可选或关键字参数都传递给底层的 @ref{1db0,,reader} 实例。


在 3.6 版更改: 返回的行现在的类型是 @code{OrderedDict}。



在 3.8 版更改: 现在，返回的行是 @ref{1b8,,dict} 类型。


一个简短的用法示例:

@example
>>> import csv
>>> with open('names.csv', newline='@w{'}) as csvfile:
...     reader = csv.DictReader(csvfile)
...     for row in reader:
...         print(row['first_name'], row['last_name'])
...
Eric Idle
John Cleese

>>> print(row)
@{'first_name': 'John', 'last_name': 'Cleese'@}
@end example
@end deffn

@geindex DictWriter (csv 中的类)
@anchor{library/csv csv DictWriter}@anchor{b73}
@deffn {类} csv.DictWriter (f, fieldnames, restval='@w{'}, extrasaction='raise', dialect='excel', *args, **kwds)

创建一个对象，该对象在操作上类似常规 writer，但会将字典映射到输出行。 @emph{fieldnames} 参数是由键组成的 @ref{1f,,序列}，它指定字典中值的顺序，这些值会按指定顺序传递给 @code{writerow()} 方法并写入文件 @emph{f}。 如果字典缺少 @emph{fieldnames} 中的键，则可选参数 @emph{restval} 用于指定要写入的值。 如果传递给 @code{writerow()} 方法的字典的某些键在 @emph{fieldnames} 中找不到，则可选参数 @emph{extrasaction} 用于指定要执行的操作。 如果将其设置为默认值 @code{'raise'}，则会引发 @ref{1fb,,ValueError}。 如果将其设置为 @code{'ignore'}，则字典中的其他键值将被忽略。 所有其他可选或关键字参数都传递给底层的 @ref{df5,,writer} 实例。

注意，与 @ref{1bd,,DictReader} 类不同，@ref{b73,,DictWriter} 类的 @emph{fieldnames} 参数不是可选参数。

一个简短的用法示例:

@example
import csv

with open('names.csv', 'w', newline='@w{'}) as csvfile:
    fieldnames = ['first_name', 'last_name']
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)

    writer.writeheader()
    writer.writerow(@{'first_name': 'Baked', 'last_name': 'Beans'@})
    writer.writerow(@{'first_name': 'Lovely', 'last_name': 'Spam'@})
    writer.writerow(@{'first_name': 'Wonderful', 'last_name': 'Spam'@})
@end example
@end deffn

@geindex Dialect (csv 中的类)
@anchor{library/csv csv Dialect}@anchor{1db3}
@deffn {类} csv.Dialect

@ref{1db3,,Dialect} 类是主要依赖于其属性的容器类，用于将定义好的参数传递给特定的 @ref{1db0,,reader} 或 @ref{df5,,writer} 实例。
@end deffn

@geindex excel (csv 中的类)
@anchor{library/csv csv excel}@anchor{1dbb}
@deffn {类} csv.excel

@ref{1dbb,,excel} 类定义了 Excel 生成的 CSV 文件的常规属性。它在变种注册表中的名称是 @code{'excel'}。
@end deffn

@geindex excel_tab (csv 中的类)
@anchor{library/csv csv excel_tab}@anchor{1dbc}
@deffn {类} csv.excel_tab

@ref{1dbc,,excel_tab} 类定义了 Excel 生成的、制表符分隔的 CSV 文件的常规属性。它在变种注册表中的名称是 @code{'excel-tab'}。
@end deffn

@geindex unix_dialect (csv 中的类)
@anchor{library/csv csv unix_dialect}@anchor{b72}
@deffn {类} csv.unix_dialect

@ref{b72,,unix_dialect} 类定义了在 UNIX 系统上生成的 CSV 文件的常规属性，即使用 @code{'\n'} 作为换行符，且所有字段都有引号包围。它在变种注册表中的名称是 @code{'unix'}。


3.2 新版功能.

@end deffn

@geindex Sniffer (csv 中的类)
@anchor{library/csv csv Sniffer}@anchor{1dbd}
@deffn {类} csv.Sniffer

@ref{1dbd,,Sniffer} 类用于推断 CSV 文件的格式。

@ref{1dbd,,Sniffer} 类提供了两个方法：

@geindex sniff() (csv.Sniffer 方法)
@anchor{library/csv csv Sniffer sniff}@anchor{1dbe}
@deffn {方法} sniff (sample, delimiters=None)

分析给定的 @emph{sample} 并返回一个 @ref{1db3,,Dialect} 子类，该子类中包含了分析出的格式参数。如果给出可选的 @emph{delimiters} 参数，则该参数会被解释为字符串，该字符串包含了可能的有效定界符。
@end deffn

@geindex has_header() (csv.Sniffer 方法)
@anchor{library/csv csv Sniffer has_header}@anchor{1dbf}
@deffn {方法} has_header (sample)

分析示例文本（假定为 CSV 格式），如果第一行很可能是一系列列标题，则返回 @ref{494,,True}。
@end deffn
@end deffn

使用 @ref{1dbd,,Sniffer} 的示例：

@example
with open('example.csv', newline='@w{'}) as csvfile:
    dialect = csv.Sniffer().sniff(csvfile.read(1024))
    csvfile.seek(0)
    reader = csv.reader(csvfile, dialect)
    # ... process CSV file contents here ...
@end example

@ref{2a,,csv} 模块定义了以下常量：

@geindex QUOTE_ALL() (在 csv 模块中)
@anchor{library/csv csv QUOTE_ALL}@anchor{1dc0}
@deffn {数据} csv.QUOTE_ALL

指示 @ref{df5,,writer} 对象给所有字段加上引号。
@end deffn

@geindex QUOTE_MINIMAL() (在 csv 模块中)
@anchor{library/csv csv QUOTE_MINIMAL}@anchor{1dc1}
@deffn {数据} csv.QUOTE_MINIMAL

指示 @ref{df5,,writer} 对象仅为包含特殊字符（例如 @emph{定界符}、@emph{引号字符} 或 @emph{行结束符} 中的任何字符）的字段加上引号。
@end deffn

@geindex QUOTE_NONNUMERIC() (在 csv 模块中)
@anchor{library/csv csv QUOTE_NONNUMERIC}@anchor{1dc2}
@deffn {数据} csv.QUOTE_NONNUMERIC

指示 @ref{df5,,writer} 对象为所有非数字字段加上引号。

指示 reader 将所有未用引号引出的字段转换为 @emph{float} 类型。
@end deffn

@geindex QUOTE_NONE() (在 csv 模块中)
@anchor{library/csv csv QUOTE_NONE}@anchor{1dc3}
@deffn {数据} csv.QUOTE_NONE

指示 @ref{df5,,writer} 对象不使用引号引出字段。当 @emph{定界符} 出现在输出数据中时，其前面应该有 @emph{转义符}。如果未设置 @emph{转义符}，则遇到任何需要转义的字符时，writer 都会抛出 @ref{1db8,,Error} 异常。

指示 @ref{1db0,,reader} 不对引号字符进行特殊处理。
@end deffn

@ref{2a,,csv} 模块定义了以下异常：

@geindex Error
@anchor{library/csv csv Error}@anchor{1db8}
@deffn {例外} csv.Error

该异常可能由任何发生错误的函数抛出。
@end deffn

@node 变种与格式参数,Reader 对象,模块内容<3>,csv --- CSV 文件读写
@anchor{library/csv csv-fmt-params}@anchor{1db5}@anchor{library/csv dialects-and-formatting-parameters}@anchor{1dc4}
@subsubsection 变种与格式参数


为了更容易指定输入和输出记录的格式，特定的一组格式参数组合为一个 dialect（变种）。一个 dialect 是一个 @ref{1db3,,Dialect} 类的子类，它具有一组特定的方法和一个 @code{validate()} 方法。创建 @ref{1db0,,reader} 或 @ref{df5,,writer} 对象时，程序员可以将某个字符串或 @ref{1db3,,Dialect} 类的子类指定为 dialect 参数。要想补充或覆盖 @emph{dialect} 参数，程序员还可以单独指定某些格式参数，这些参数的名称与下面 @ref{1db3,,Dialect} 类定义的属性相同。

Dialect 类支持以下属性：

@geindex delimiter (csv.Dialect 属性)
@anchor{library/csv csv Dialect delimiter}@anchor{1dc5}
@deffn {属性} Dialect.delimiter

一个用于分隔字段的单字符，默认为 @code{','}。
@end deffn

@geindex doublequote (csv.Dialect 属性)
@anchor{library/csv csv Dialect doublequote}@anchor{1dc6}
@deffn {属性} Dialect.doublequote

控制出现在字段中的 @emph{引号字符} 本身应如何被引出。当该属性为 @ref{494,,True} 时，双写引号字符。如果该属性为 @ref{380,,False}，则在 @emph{引号字符} 的前面放置 @emph{转义符}。默认值为 @ref{494,,True}。

在输出时，如果 @emph{doublequote} 是 @ref{380,,False}，且 @emph{转义符} 未指定，且在字段中发现 @emph{引号字符} 时，会抛出 @ref{1db8,,Error} 异常。
@end deffn

@geindex escapechar (csv.Dialect 属性)
@anchor{library/csv csv Dialect escapechar}@anchor{1dc7}
@deffn {属性} Dialect.escapechar

一个用于 writer 的单字符，用来在 @emph{quoting} 设置为 @ref{1dc3,,QUOTE_NONE} 的情况下转义 @emph{定界符}，在 @emph{doublequote} 设置为 @ref{380,,False} 的情况下转义 @emph{引号字符}。在读取时，@emph{escapechar} 去除了其后所跟字符的任何特殊含义。该属性默认为 @ref{157,,None}，表示禁用转义。
@end deffn

@geindex lineterminator (csv.Dialect 属性)
@anchor{library/csv csv Dialect lineterminator}@anchor{1dc8}
@deffn {属性} Dialect.lineterminator

放在 @ref{df5,,writer} 产生的行的结尾，默认为 @code{'\r\n'}。

@cartouche
@quotation 注解 
@ref{1db0,,reader} 经过硬编码，会识别 @code{'\r'} 或 @code{'\n'} 作为行尾，并忽略 @emph{lineterminator}。未来可能会更改这一行为。
@end quotation
@end cartouche
@end deffn

@geindex quotechar (csv.Dialect 属性)
@anchor{library/csv csv Dialect quotechar}@anchor{1dc9}
@deffn {属性} Dialect.quotechar

一个单字符，用于包住含有特殊字符的字段，特殊字符如 @emph{定界符} 或 @emph{引号字符} 或换行符。默认为 @code{'"'}。
@end deffn

@geindex quoting (csv.Dialect 属性)
@anchor{library/csv csv Dialect quoting}@anchor{1dca}
@deffn {属性} Dialect.quoting

控制 writer 何时生成引号，以及 reader 何时识别引号。该属性可以等于任何 @code{QUOTE_*} 常量（参见 @ref{1db1,,模块内容} 段落），默认为 @ref{1dc1,,QUOTE_MINIMAL}。
@end deffn

@geindex skipinitialspace (csv.Dialect 属性)
@anchor{library/csv csv Dialect skipinitialspace}@anchor{1dcb}
@deffn {属性} Dialect.skipinitialspace

如果为 @ref{494,,True}，则忽略 @emph{定界符} 之后的空格。默认值为 @ref{380,,False}。
@end deffn

@geindex strict (csv.Dialect 属性)
@anchor{library/csv csv Dialect strict}@anchor{1dcc}
@deffn {属性} Dialect.strict

如果为 @code{True}，则在输入错误的 CSV 时抛出 @ref{1db8,,Error} 异常。默认值为 @code{False}。
@end deffn

@node Reader 对象,Writer 对象,变种与格式参数,csv --- CSV 文件读写
@anchor{library/csv reader-objects}@anchor{1dcd}
@subsubsection Reader 对象


Reader 对象（@ref{1bd,,DictReader} 实例和 @ref{1db0,,reader()} 函数返回的对象）具有以下公开方法：

@geindex __next__() (csv.csvreader 方法)
@anchor{library/csv csv csvreader __next__}@anchor{1dce}
@deffn {方法} csvreader.__next__ ()

返回 reader 的可迭代对象的下一行，返回值可能是列表（由 @ref{1db0,,reader()} 返回的对象）或字典（由 @ref{1bd,,DictReader} 返回的对象），解析是根据当前设置的变种进行的。通常应该这样调用它：@code{next(reader)}。
@end deffn

Reader 对象具有以下公开属性：

@geindex dialect (csv.csvreader 属性)
@anchor{library/csv csv csvreader dialect}@anchor{1dcf}
@deffn {属性} csvreader.dialect

变种描述，只读，供解析器使用。
@end deffn

@geindex line_num (csv.csvreader 属性)
@anchor{library/csv csv csvreader line_num}@anchor{1dd0}
@deffn {属性} csvreader.line_num

源迭代器已经读取了的行数。它与返回的记录数不同，因为记录可能跨越多行。
@end deffn

DictReader 对象具有以下公开属性：

@geindex fieldnames (csv.csvreader 属性)
@anchor{library/csv csv csvreader fieldnames}@anchor{1dd1}
@deffn {属性} csvreader.fieldnames

字段名称。如果在创建对象时未传入字段名称，则首次访问时或从文件中读取第一条记录时会初始化此属性。
@end deffn

@node Writer 对象,例子<7>,Reader 对象,csv --- CSV 文件读写
@anchor{library/csv writer-objects}@anchor{1dd2}
@subsubsection Writer 对象


@code{Writer} 对象（@ref{b73,,DictWriter} 实例和 @ref{df5,,writer()} 函数返回的对象）具有下面的公开方法。对于 @code{Writer} 对象，@emph{行} 必须是（一组可迭代的）字符串或数字。对于 @ref{b73,,DictWriter} 对象，@emph{行} 必须是一个字典，这个字典将字段名映射为字符串或数字（数字要先经过 @ref{329,,str()} 转换类型）。请注意，输出的复数会有括号包围。这样其他程序读取 CSV 文件时可能会有一些问题（假设它们完全支持复数）。

@geindex writerow() (csv.csvwriter 方法)
@anchor{library/csv csv csvwriter writerow}@anchor{6be}
@deffn {方法} csvwriter.writerow (row)

将参数 @emph{row} 写入 writer 的文件对象，并根据当前设置的变种进行格式化。本方法的返回值就是底层文件对象 @emph{write} 方法的返回值。


在 3.5 版更改: 开始支持任意类型的迭代器。

@end deffn

@geindex writerows() (csv.csvwriter 方法)
@anchor{library/csv csv csvwriter writerows}@anchor{1dd3}
@deffn {方法} csvwriter.writerows (rows)

将 @emph{rows*（即能迭代出多个上述 *row} 对象的迭代器）中的所有元素写入 writer 的文件对象，并根据当前设置的变种进行格式化。
@end deffn

Writer 对象具有以下公开属性：

@geindex dialect (csv.csvwriter 属性)
@anchor{library/csv csv csvwriter dialect}@anchor{1dd4}
@deffn {属性} csvwriter.dialect

变种描述，只读，供 writer 使用。
@end deffn

DictWriter 对象具有以下公开方法：

@geindex writeheader() (csv.DictWriter 方法)
@anchor{library/csv csv DictWriter writeheader}@anchor{b74}
@deffn {方法} DictWriter.writeheader ()

在 writer 的文件对象中，写入一行字段名称（字段名称在构造函数中指定），并根据当前设置的变种进行格式化。本方法的返回值就是内部使用的 @ref{6be,,csvwriter.writerow()} 方法的返回值。


3.2 新版功能.



在 3.8 版更改: 现在 @ref{b74,,writeheader()} 也返回其内部使用的 @ref{6be,,csvwriter.writerow()} 方法的返回值。

@end deffn

@node 例子<7>,,Writer 对象,csv --- CSV 文件读写
@anchor{library/csv csv-examples}@anchor{1dd5}@anchor{library/csv examples}@anchor{1dd6}
@subsubsection 例子


读取 CSV 文件最简单的一个例子:

@example
import csv
with open('some.csv', newline='@w{'}) as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)
@end example

读取其他格式的文件:

@example
import csv
with open('passwd', newline='@w{'}) as f:
    reader = csv.reader(f, delimiter=':', quoting=csv.QUOTE_NONE)
    for row in reader:
        print(row)
@end example

相应最简单的写入示例是:

@example
import csv
with open('some.csv', 'w', newline='@w{'}) as f:
    writer = csv.writer(f)
    writer.writerows(someiterable)
@end example

由于使用 @ref{4ea,,open()} 来读取 CSV 文件，因此默认情况下，将使用系统默认编码来解码文件并转换为 unicode（请参阅 @ref{39d,,locale.getpreferredencoding()}）。要使用其他编码来解码文件，请使用 open 的 @code{encoding} 参数:

@example
import csv
with open('some.csv', newline='@w{'}, encoding='utf-8') as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)
@end example

这同样适用于写入非系统默认编码的内容：打开输出文件时，指定 encoding 参数。

注册一个新的变种:

@example
import csv
csv.register_dialect('unixpwd', delimiter=':', quoting=csv.QUOTE_NONE)
with open('passwd', newline='@w{'}) as f:
    reader = csv.reader(f, 'unixpwd')
@end example

Reader 的更高级用法——捕获并报告错误:

@example
import csv, sys
filename = 'some.csv'
with open(filename, newline='@w{'}) as f:
    reader = csv.reader(f)
    try:
        for row in reader:
            print(row)
    except csv.Error as e:
        sys.exit('file @{@}, line @{@}: @{@}'.format(filename, reader.line_num, e))
@end example

尽管该模块不直接支持解析字符串，但仍可如下轻松完成:

@example
import csv
for row in csv.reader(['one,two,three']):
    print(row)
@end example

@subsubheading 备注


@node configparser --- 配置文件解析器,netrc --- netrc 文件处理,csv --- CSV 文件读写,文件格式
@anchor{library/configparser doc}@anchor{1dd7}@anchor{library/configparser configparser-configuration-file-parser}@anchor{1dd8}@anchor{library/configparser module-configparser}@anchor{23}
@subsection @code{configparser} --- 配置文件解析器


@geindex configparser (模块)

@strong{源代码:} Lib/configparser.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/configparser.py}

@geindex .ini; file
@geindex configuration; file
@geindex ini file
@geindex Windows ini file


__________________________________________________________________


此模块提供了它实现一种基本配置语言 @ref{4a5,,ConfigParser} 类，这种语言所提供的结构与 Microsoft Windows INI 文件的类似。 你可以使用这种语言来编写能够由最终用户来自定义的 Python 程序。

@cartouche
@quotation 注解 
这个库 @emph{并不} 能够解析或写入在 Windows Registry 扩展版本 INI 语法中所使用的值-类型前缀。
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@item 模块 @ref{e8,,shlex}

支持创建可被用作应用配置文件的替代的 Unix 终端式微语言。

@item 模块 @ref{a4,,json}

json 模块实现了一个 JavaScript 语法的子集，它也可被用于这种目的。
@end table


@c import configparser

@menu
* 快速起步:: 
* 支持的数据类型:: 
* 回退值:: 
* 受支持的 INI 文件结构:: 
* 值的插值:: 
* 映射协议访问:: 
* 定制解析器行为:: 
* 旧式 API 示例:: 
* ConfigParser 对象:: 
* RawConfigParser 对象:: 
* 异常: 异常<5>. 

@end menu

@node 快速起步,支持的数据类型,,configparser --- 配置文件解析器
@anchor{library/configparser quick-start}@anchor{1dd9}
@subsubsection 快速起步


让我们准备一个非常基本的配置文件，它看起来是这样的:

@example
[DEFAULT]
ServerAliveInterval = 45
Compression = yes
CompressionLevel = 9
ForwardX11 = yes

[bitbucket.org]
User = hg

[topsecret.server.com]
Port = 50022
ForwardX11 = no
@end example

INI 文件的结构描述见 @ref{1dda,,以下章节}。 总的来说，这种文件由多个节组成，每个节包含多个带有值的键。 @ref{23,,configparser} 类可以读取和写入这种文件。 让我们先通过程序方式来创建上述的配置文件。

@example
>>> import configparser
>>> config = configparser.ConfigParser()
>>> config['DEFAULT'] = @{'ServerAliveInterval': '45',
...                      'Compression': 'yes',
...                      'CompressionLevel': '9'@}
>>> config['bitbucket.org'] = @{@}
>>> config['bitbucket.org']['User'] = 'hg'
>>> config['topsecret.server.com'] = @{@}
>>> topsecret = config['topsecret.server.com']
>>> topsecret['Port'] = '50022'     # mutates the parser
>>> topsecret['ForwardX11'] = 'no'  # same here
>>> config['DEFAULT']['ForwardX11'] = 'yes'
>>> with open('example.ini', 'w') as configfile:
...   config.write(configfile)
...
@end example

如你所见，我们可以把配置解析器当作一个字典来处理。 两者确实存在差异，@ref{1ddb,,将在后文说明}，但是其行为非常接近于字典所具有一般行为。

现在我们已经创建并保存了一个配置文件，让我们再将它读取出来并探究其中包含的数据。

@example
>>> config = configparser.ConfigParser()
>>> config.sections()
[]
>>> config.read('example.ini')
['example.ini']
>>> config.sections()
['bitbucket.org', 'topsecret.server.com']
>>> 'bitbucket.org' in config
True
>>> 'bytebong.com' in config
False
>>> config['bitbucket.org']['User']
'hg'
>>> config['DEFAULT']['Compression']
'yes'
>>> topsecret = config['topsecret.server.com']
>>> topsecret['ForwardX11']
'no'
>>> topsecret['Port']
'50022'
>>> for key in config['bitbucket.org']:  
...     print(key)
user
compressionlevel
serveraliveinterval
compression
forwardx11
>>> config['bitbucket.org']['ForwardX11']
'yes'
@end example

正如我们在上面所看到的，相关的 API 相当直观。 唯一有些神奇的地方是 @code{DEFAULT} 小节，它为所有其他小节提供了默认值 @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
}。 还要注意小节中的键大小写不敏感并且会存储为小写形式 @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
}。

@node 支持的数据类型,回退值,快速起步,configparser --- 配置文件解析器
@anchor{library/configparser supported-datatypes}@anchor{1ddd}
@subsubsection 支持的数据类型


配置解析器并不会猜测配置文件中值的类型，而总是将它们在内部存储为字符串。 这意味着如果你需要其他数据类型，你应当自己来转换:

@example
>>> int(topsecret['Port'])
50022
>>> float(topsecret['CompressionLevel'])
9.0
@end example

由于这种任务十分常用，配置解析器提供了一系列便捷的获取方法来处理整数、浮点数和布尔值。 最后一个类型的处理最为有趣，因为简单地将值传给 @code{bool()} 是没有用的，@code{bool('False')} 仍然会是 @code{True}。 为解决这个问题配置解析器还提供了 @ref{1dde,,getboolean()}。 这个方法对大小写不敏感并可识别 @code{'yes'}/@code{'no'}, @code{'on'}/@code{'off'}, @code{'true'}/@code{'false'} 和 @code{'1'}/@code{'0'} @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
} 等布尔值。 例如:

@example
>>> topsecret.getboolean('ForwardX11')
False
>>> config['bitbucket.org'].getboolean('ForwardX11')
True
>>> config.getboolean('bitbucket.org', 'Compression')
True
@end example

除了 @ref{1dde,,getboolean()}，配置解析器还提供了同类的 @ref{1ddf,,getint()} 和 @ref{1de0,,getfloat()} 方法。 你可以注册你自己的转换器并或是定制已提供的转换器。 @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
}

@node 回退值,受支持的 INI 文件结构,支持的数据类型,configparser --- 配置文件解析器
@anchor{library/configparser fallback-values}@anchor{1de1}
@subsubsection 回退值


与字典类似，你可以使用某个小节的 @code{get()} 方法来提供回退值:

@example
>>> topsecret.get('Port')
'50022'
>>> topsecret.get('CompressionLevel')
'9'
>>> topsecret.get('Cipher')
>>> topsecret.get('Cipher', '3des-cbc')
'3des-cbc'
@end example

请注意默认值会优先于回退值。 例如，在我们的示例中 @code{'CompressionLevel'} 键仅在 @code{'DEFAULT'} 小节被指定。 如果你尝试在 @code{'topsecret.server.com'} 小节获取它，我们将总是获取到默认值，即使我们指定了一个回退值:

@example
>>> topsecret.get('CompressionLevel', '3')
'9'
@end example

还需要注意的一点是解析器层级的 @code{get()} 方法提供了自定义的更复杂接口，它被维护用于向下兼容。 当使用此方法时，回退值可以通过 @code{fallback} 仅限关键字参数来提供:

@example
>>> config.get('bitbucket.org', 'monster',
...            fallback='No such things as monsters')
'No such things as monsters'
@end example

同样的 @code{fallback} 参数也可在 @ref{1ddf,,getint()}, @ref{1de0,,getfloat()} 和 @ref{1dde,,getboolean()} 方法中使用，例如:

@example
>>> 'BatchMode' in topsecret
False
>>> topsecret.getboolean('BatchMode', fallback=True)
True
>>> config['DEFAULT']['BatchMode'] = 'no'
>>> topsecret.getboolean('BatchMode', fallback=True)
False
@end example

@node 受支持的 INI 文件结构,值的插值,回退值,configparser --- 配置文件解析器
@anchor{library/configparser supported-ini-file-structure}@anchor{1dda}
@subsubsection 受支持的 INI 文件结构


配置文件是由小节组成的，每个小节都有一个 @code{[section]} 标头，加上多个由特定字符串 (默认为 @code{=} 或 @code{:} @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
}) 分隔的键/值条目。 默认情况下小节名对大小写敏感而键对大小写不敏感 @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
}。 键和值开头和末尾的空格会被移除。 值可以被省略，在此情况下键/值分隔符也可以被省略。 值还可以跨越多行，只要其他行带有比值的第一行更深的缩进。 依据解析器的具体模式，空白行可能被视为多行值的组成部分也可能被忽略。

配置文件可以包含注释，要带有指定字符前缀 (默认为 @code{#} 和 @code{;} @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
})。 注释可以单独出现于原本的空白行，并可使用缩进。 @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
}

例如:

@example
[Simple Values]
key=value
spaces in keys=allowed
spaces in values=allowed as well
spaces around the delimiter = obviously
you can also use : to delimit keys from values

[All Values Are Strings]
values like this: 1000000
or this: 3.14159265359
are they treated as numbers? : no
integers, floats and booleans are held as: strings
can use the API to get converted values directly: true

[Multiline Values]
chorus: I'm a lumberjack, and I'm okay
    I sleep all night and I work all day

[No Values]
key_without_value
empty string value here =

[You can use comments]
# like this
; or this

# By default only in an empty line.
# Inline comments can be harmful because they prevent users
# from using the delimiting characters as parts of values.
# That being said, this can be customized.

    [Sections Can Be Indented]
        can_values_be_as_well = True
        does_that_mean_anything_special = False
        purpose = formatting for readability
        multiline_values = are
            handled just fine as
            long as they are indented
            deeper than the first line
            of a value
        # Did I mention we can indent comments, too?
@end example

@node 值的插值,映射协议访问,受支持的 INI 文件结构,configparser --- 配置文件解析器
@anchor{library/configparser interpolation-of-values}@anchor{1de2}
@subsubsection 值的插值


在核心功能之上，@ref{4a5,,ConfigParser} 还支持插值。 这意味着值可以在被 @code{get()} 调用返回之前进行预处理。

@geindex % (percent); interpolation in configuration files

@geindex BasicInterpolation (configparser 中的类)
@anchor{library/configparser configparser BasicInterpolation}@anchor{1de3}
@deffn {类} configparser.BasicInterpolation

默认实现由 @ref{4a5,,ConfigParser} 来使用。 它允许值包含引用了相同小节中其他值或者特殊的默认小节中的值的格式字符串 @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
}。 额外的默认值可以在初始化时提供。

例如:

@example
[Paths]
home_dir: /Users
my_dir: %(home_dir)s/lumberjack
my_pictures: %(my_dir)s/Pictures

[Escape]
gain: 80%%  # use a %% to escape the % sign (% is the only character that needs to be escaped)
@end example

在上面的例子里，@ref{4a5,,ConfigParser} 的 @emph{interpolation} 设为 @code{BasicInterpolation()}，这会将 @code{%(home_dir)s} 求解为 @code{home_dir} 的值 (在这里是 @code{/Users})。 @code{%(my_dir)s} 的将被实际求解为 @code{/Users/lumberjack}。 所有插值都是按需进行的，这样引用链中使用的键不必以任何特定顺序在配置文件中指明。

当 @code{interpolation} 设为 @code{None} 时，解析器会简单地返回 @code{%(my_dir)s/Pictures} 作为 @code{my_pictures} 的值，并返回 @code{%(home_dir)s/lumberjack} 作为 @code{my_dir} 的值。
@end deffn

@geindex $ (dollar); interpolation in configuration files

@geindex ExtendedInterpolation (configparser 中的类)
@anchor{library/configparser configparser ExtendedInterpolation}@anchor{bd5}
@deffn {类} configparser.ExtendedInterpolation

一个用于插值的替代处理程序实现了更高级的语法，它被用于 @code{zc.buildout} 中的实例。 扩展插值使用 @code{$@{section:option@}} 来表示来自外部小节的值。 插值可以跨越多个层级。 为了方便使用，@code{section:} 部分可被省略，插值会默认作用于当前小节（可能会从特殊小节获取默认值）。

例如，上面使用基本插值描述的配置，使用扩展插值将是这个样子:

@example
[Paths]
home_dir: /Users
my_dir: $@{home_dir@}/lumberjack
my_pictures: $@{my_dir@}/Pictures

[Escape]
cost: $$80  # use a $$ to escape the $ sign ($ is the only character that needs to be escaped)
@end example

来自其他小节的值也可以被获取:

@example
[Common]
home_dir: /Users
library_dir: /Library
system_dir: /System
macports_dir: /opt/local

[Frameworks]
Python: 3.2
path: $@{Common:system_dir@}/Library/Frameworks/

[Arthur]
nickname: Two Sheds
last_name: Jackson
my_dir: $@{Common:home_dir@}/twosheds
my_pictures: $@{my_dir@}/Pictures
python_dir: $@{Frameworks:path@}/Python/Versions/$@{Frameworks:Python@}
@end example
@end deffn

@node 映射协议访问,定制解析器行为,值的插值,configparser --- 配置文件解析器
@anchor{library/configparser mapping-protocol-access}@anchor{1ddb}
@subsubsection 映射协议访问



3.2 新版功能.


映射协议访问这个通用名称是指允许以字典的方式来使用自定义对象的功能。 在 @ref{23,,configparser} 中，映射接口的实现使用了 @code{parser['section']['option']} 标记法。

@code{parser['section']} 专门为解析器中的小节数据返回一个代理。 这意味着其中的值不会被拷贝，而是在需要时从原始解析器中获取。 更为重要的是，当值在小节代理上被修改时，它们其实是在原始解析器中发生了改变。

@ref{23,,configparser} 对象的行为会尽可能地接近真正的字典。 映射接口是完整而且遵循 @ref{9e9,,MutableMapping} ABC 规范的。 但是，还是有一些差异应当被纳入考虑:


@itemize *

@item 
默认情况下，小节中的所有键是以大小写不敏感的方式来访问的 @footnote{@w{(1)} 
配置解析器允许重度定制。 如果你有兴趣改变脚注说明中所介绍的行为，请参阅 @ref{1ddc,,Customizing Parser Behaviour} 一节。
}。 例如 @code{for option in parser["section"]} 只会产生 @code{optionxform} 形式的选项键名称。 也就是说默认使用小写字母键名。 与此同时，对于一个包含键 @code{'a'} 的小节，以下两个表达式均将返回 @code{True}:

@example
"a" in parser["section"]
"A" in parser["section"]
@end example

@item 
所有小节也包括 @code{DEFAULTSECT}，这意味着对一个小节执行 @code{.clear()} 可能无法使得该小节显示为空。 这是因为默认值是无法从小节中被删除的（因为从技术上说它们并不在那里）。 如果它们在小节中被覆盖，删除将导致默认值重新变为可见。 尝试删除默认值将会引发 @ref{2c7,,KeyError}。

@item 
@code{DEFAULTSECT} 无法从解析器中被移除:


@itemize *

@item 
尝试删除将引发 @ref{1fb,,ValueError}，

@item 
@code{parser.clear()} 会保留其原状，

@item 
@code{parser.popitem()} 绝不会将其返回。
@end itemize

@item 
@code{parser.get(section, option, **kwargs)} - 第二个参数 @strong{并非} 回退值。 但是请注意小节层级的 @code{get()} 方法可同时兼容映射协议和经典配置解析器 API。

@item 
@code{parser.items()} 兼容映射协议（返回 @emph{section_name}, @emph{section_proxy} 对的列表，包括 DEFAULTSECT）。 但是，此方法也可以带参数发起调用: @code{parser.items(section, raw, vars)}。 这种调用形式返回指定 @code{section} 的 @emph{option}, @emph{value} 对的列表，将展开所有插值（除非提供了 @code{raw=True} 选项）。
@end itemize

映射协议是在现有的传统 API 之上实现的，以便重载原始接口的子类仍然具有符合预期的有效映射。

@node 定制解析器行为,旧式 API 示例,映射协议访问,configparser --- 配置文件解析器
@anchor{library/configparser customizing-parser-behaviour}@anchor{1ddc}
@subsubsection 定制解析器行为


INI 格式的变种数量几乎和使用此格式的应用一样多。 @ref{23,,configparser} 花费了很大力气来为尽量大范围的可用 INI 样式提供支持。 默认的可用功能主要由历史状况来确定，你很可能会想要定制某些特性。

改变特定配置解析器行为的最常见方式是使用 @ref{d57,,__init__()} 选项:


@itemize *

@item 
@emph{defaults}，默认值: @code{None}

此选项接受一个键值对的字典，它将被首先放入 @code{DEFAULT} 小节。 这实现了一种优雅的方式来支持简洁的配置文件，它不必指定与已记录的默认值相同的值。

提示：如果你想要为特定的小节指定默认的值，请在读取实际文件之前使用 @code{read_dict()}。

@item 
@emph{dict_type}，默认值: @ref{1b8,,dict}

此选项主要影响映射协议的行为和写入配置文件的外观。 使用标准字典时，每个小节是按照它们被加入解析器的顺序保存的。 在小节内的选项也是如此。

还有其他替换的字典类型可以使用，例如在写回数据时对小节和选项进行排序。

请注意：存在其他方式只用一次操作来添加键值对的集合。 当你在这些操作中使用一个常规字典时，键将按顺序进行排列。 例如:

@example
>>> parser = configparser.ConfigParser()
>>> parser.read_dict(@{'section1': @{'key1': 'value1',
...                                'key2': 'value2',
...                                'key3': 'value3'@},
...                   'section2': @{'keyA': 'valueA',
...                                'keyB': 'valueB',
...                                'keyC': 'valueC'@},
...                   'section3': @{'foo': 'x',
...                                'bar': 'y',
...                                'baz': 'z'@}
... @})
>>> parser.sections()
['section1', 'section2', 'section3']
>>> [option for option in parser['section3']]
['foo', 'bar', 'baz']
@end example

@item 
@emph{allow_no_value}，默认值: @code{False}

已知某些配置文件会包括不带值的设置，但其在其他方面均符合 @ref{23,,configparser} 所支持的语法。 构造器的 @emph{allow_no_value} 形参可用于指明应当接受这样的值:

@example
>>> import configparser

>>> sample_config = """
... [mysqld]
...   user = mysql
...   pid-file = /var/run/mysqld/mysqld.pid
...   skip-external-locking
...   old_passwords = 1
...   skip-bdb
...   # we don't need ACID today
...   skip-innodb
... """
>>> config = configparser.ConfigParser(allow_no_value=True)
>>> config.read_string(sample_config)

>>> # Settings with values are treated as before:
>>> config["mysqld"]["user"]
'mysql'

>>> # Settings without values provide None:
>>> config["mysqld"]["skip-bdb"]

>>> # Settings which aren't specified still raise an error:
>>> config["mysqld"]["does-not-exist"]
Traceback (most recent call last):
  ...
KeyError: 'does-not-exist'
@end example

@item 
@emph{delimiters}，默认值: @code{('=', ':')}

分隔符是用于在小节内分隔键和值的子字符串。 在一行中首次出现的分隔子字符串会被视为一个分隔符。 这意味着值可以包含分隔符（但键不可以）。

另请参见 @ref{1de4,,ConfigParser.write()} 的 @emph{space_around_delimiters} 参数。

@item 
@emph{comment_prefixes}，默认值: @code{('#', ';')}

@item 
@emph{inline_comment_prefixes}，默认值: @code{None}

注释前缀是配置文件中用于标示一条有效注释的开头的字符串。 @emph{comment_prefixes} 仅用在被视为空白的行（可以缩进）之前而 @emph{inline_comment_prefixes} 可用在每个有效值之后（例如小节名称、选项以及空白的行）。 默认情况下禁用行内注释，并且 @code{'#'} 和 @code{';'} 都被用作完整行注释的前缀。


在 3.2 版更改: 在之前的 @ref{23,,configparser} 版本中行为匹配 @code{comment_prefixes=('#',';')} 和 @code{inline_comment_prefixes=(';',)}。


请注意配置解析器不支持对注释前缀的转义，因此使用 @emph{inline_comment_prefixes} 可能妨碍用户将被用作注释前缀的字符指定为可选值。 当有疑问时，请避免设置 @emph{inline_comment_prefixes}。 在许多情况下，在多行值的一行开头存储注释前缀字符的唯一方式是进行前缀插值，例如:

@example
>>> from configparser import ConfigParser, ExtendedInterpolation
>>> parser = ConfigParser(interpolation=ExtendedInterpolation())
>>> # the default BasicInterpolation could be used as well
>>> parser.read_string("""
... [DEFAULT]
... hash = #
...
... [hashes]
... shebang =
...   $@{hash@}!/usr/bin/env python
...   $@{hash@} -*- coding: utf-8 -*-
...
... extensions =
...   enabled_extension
...   another_extension
...   #disabled_by_comment
...   yet_another_extension
...
... interpolation not necessary = if # is not at line start
... even in multiline values = line #1
...   line #2
...   line #3
... """)
>>> print(parser['hashes']['shebang'])

#!/usr/bin/env python
# -*- coding: utf-8 -*-
>>> print(parser['hashes']['extensions'])

enabled_extension
another_extension
yet_another_extension
>>> print(parser['hashes']['interpolation not necessary'])
if # is not at line start
>>> print(parser['hashes']['even in multiline values'])
line #1
line #2
line #3
@end example

@item 
@emph{strict}，默认值: @code{True}

当设为 @code{True} 时，解析器在从单一源读取 (使用 @code{read_file()}, @code{read_string()} 或 @code{read_dict()}) 期间将不允许任何小节或选项出现重复。 推荐在新的应用中使用严格解析器。


在 3.2 版更改: 在之前的 @ref{23,,configparser} 版本中行为匹配 @code{strict=False}。


@item 
@emph{empty_lines_in_values}，默认值: @code{True}

在配置解析器中，值可以包含多行，只要它们的缩进级别低于它们所对应的键。 默认情况下解析器还会将空行视为值的一部分。 于此同时，键本身也可以任意缩进以提升可读性。 因此，当配置文件变得非常庞大而复杂时，用户很容易失去对文件结构的掌控。 例如:

@example
[Section]
key = multiline
  value with a gotcha

 this = is still a part of the multiline value of 'key'
@end example

在用户查看时这可能会特别有问题，如果她是使用比例字体来编辑文件的话。 这就是为什么当你的应用不需要带有空行的值时，你应该考虑禁用它们。 这将使得空行每次都会作为键之间的分隔。 在上面的示例中，空行产生了两个键，@code{key} 和 @code{this}。

@item 
@emph{default_section}，默认值: @code{configparser.DEFAULTSECT} (即: @code{"DEFAULT"})

允许设置一个保存默认值的特殊节在其他节或插值等目的中使用的惯例是这个库所拥有的一个强大概念，使得用户能够创建复杂的声明性配置。 这种特殊节通常称为 @code{"DEFAULT"} 但也可以被定制为指向任何其他有效的节名称。 一些典型的值包括: @code{"general"} 或 @code{"common"}。 所提供的名称在从任意节读取的时候被用于识别默认的节，而且也会在将配置写回文件时被使用。 它的当前值可以使用 @code{parser_instance.default_section} 属性来获取，并且可以在运行时被修改（即将文件从一种格式转换为另一种格式）。

@item 
@emph{interpolation}，默认值: @code{configparser.BasicInterpolation}

插值行为可以用通过提供 @emph{interpolation} 参数提供自定义处理程序的方式来定制。 @code{None} 可用来完全禁用插值，@code{ExtendedInterpolation()} 提供了一种更高级的变体形式，它的设计受到了 @code{zc.buildout} 的启发。 有关该主题的更多信息请参见 @ref{1de2,,专门的文档章节}。 @ref{86b,,RawConfigParser} 具有默认的值 @code{None}。

@item 
@emph{converters}，默认值: 不设置

配置解析器提供了可选的值获取方法用来执行类型转换。 默认实现包括 @ref{1ddf,,getint()}, @ref{1de0,,getfloat()} 以及 @ref{1dde,,getboolean()}。 如果还需要其他获取方法，用户可以在子类中定义它们，或者传入一个字典，其中每个键都是一个转换器的名称而每个值都是一个实现了特定转换的可调用对象。 例如，传入 @code{@{'decimal': decimal.Decimal@}} 将对解释器对象和所有节代理添加 @code{getdecimal()}。 换句话说，可以同时编写 @code{parser_instance.getdecimal('section', 'key', fallback=0)} 和 @code{parser_instance['section'].getdecimal('key', 0)}。

如果转换器需要访问解析器的状态，可以在配置解析器子类上作为一个方法来实现。 如果该方法的名称是以 @code{get} 打头的，它将在所有节代理上以兼容字典的形式提供（参见上面的 @code{getdecimal()} 示例）。
@end itemize

更多高级定制选项可通过重载这些解析器属性的默认值来达成。 默认值是在类中定义的，因此它们可以通过子类或属性赋值来重载。

@geindex BOOLEAN_STATES (configparser.ConfigParser 属性)
@anchor{library/configparser configparser ConfigParser BOOLEAN_STATES}@anchor{1de5}
@deffn {属性} ConfigParser.BOOLEAN_STATES

默认情况下当使用 @ref{1dde,,getboolean()} 时，配置解析器会将下列值视为 @code{True}: @code{'1'}, @code{'yes'}, @code{'true'}, @code{'on'} 而将下列值视为 @code{False}: @code{'0'}, @code{'no'}, @code{'false'}, @code{'off'}。 你可以通过指定一个自定义的字符串键及其对应的布尔值字典来重载此行为。 例如:

@example
>>> custom = configparser.ConfigParser()
>>> custom['section1'] = @{'funky': 'nope'@}
>>> custom['section1'].getboolean('funky')
Traceback (most recent call last):
...
ValueError: Not a boolean: nope
>>> custom.BOOLEAN_STATES = @{'sure': True, 'nope': False@}
>>> custom['section1'].getboolean('funky')
False
@end example

其他典型的布尔值对包括 @code{accept}/@code{reject} 或 @code{enabled}/@code{disabled}。
@end deffn

@geindex optionxform() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser optionxform}@anchor{1de6}
@deffn {方法} ConfigParser.optionxform (option)

这个方法会转换每次 read, get, 或 set 操作的选项名称。 默认会将名称转换为小写形式。 这也意味着当一个配置文件被写入时，所有键都将为小写形式。 如果此行为不合适则要重载此方法。 例如:

@example
>>> config = """
... [Section1]
... Key = Value
...
... [Section2]
... AnotherKey = Value
... """
>>> typical = configparser.ConfigParser()
>>> typical.read_string(config)
>>> list(typical['Section1'].keys())
['key']
>>> list(typical['Section2'].keys())
['anotherkey']
>>> custom = configparser.RawConfigParser()
>>> custom.optionxform = lambda option: option
>>> custom.read_string(config)
>>> list(custom['Section1'].keys())
['Key']
>>> list(custom['Section2'].keys())
['AnotherKey']
@end example

@cartouche
@quotation 注解 
optionxform 函数会将选项名称转换为规范形式。 这应该是一个幂等函数：如果名称已经为规范形式，则应不加修改地将其返回。
@end quotation
@end cartouche
@end deffn

@geindex SECTCRE (configparser.ConfigParser 属性)
@anchor{library/configparser configparser ConfigParser SECTCRE}@anchor{1de7}
@deffn {属性} ConfigParser.SECTCRE

一个已编译正则表达式会被用来解析节标头。 默认将 @code{[section]} 匹配到名称 @code{"section"}。 空格会被视为节名称的一部分，因此 @code{[  larch  ]} 将被读取为一个名称为 @code{"  larch  "} 的节。 如果此行为不合适则要重载此属性。 例如:

@example
>>> import re
>>> config = """
... [Section 1]
... option = value
...
... [  Section 2  ]
... another = val
... """
>>> typical = configparser.ConfigParser()
>>> typical.read_string(config)
>>> typical.sections()
['Section 1', '  Section 2  ']
>>> custom = configparser.ConfigParser()
>>> custom.SECTCRE = re.compile(r"\[ *(?P<header>[^]]+?) *\]")
>>> custom.read_string(config)
>>> custom.sections()
['Section 1', 'Section 2']
@end example

@cartouche
@quotation 注解 
虽然 ConfigParser 对象也使用 @code{OPTCRE} 属性来识别选项行，但并不推荐重载它，因为这会与构造器选项 @emph{allow_no_value} 和 @emph{delimiters} 产生冲突。
@end quotation
@end cartouche
@end deffn

@node 旧式 API 示例,ConfigParser 对象,定制解析器行为,configparser --- 配置文件解析器
@anchor{library/configparser legacy-api-examples}@anchor{1de8}
@subsubsection 旧式 API 示例


主要出于向下兼容性的考虑，@ref{23,,configparser} 还提供了一种采用显式 @code{get}/@code{set} 方法的旧式 API。 虽然以下介绍的方法存在有效的用例，但对于新项目仍建议采用映射协议访问。 旧式 API 在多数时候都更复杂、更底层并且完全违反直觉。

一个写入配置文件的示例:

@example
import configparser

config = configparser.RawConfigParser()

# Please note that using RawConfigParser's set functions, you can assign
# non-string values to keys internally, but will receive an error when
# attempting to write to a file or when you get it in non-raw mode. Setting
# values using the mapping protocol or ConfigParser's set() does not allow
# such assignments to take place.
config.add_section('Section1')
config.set('Section1', 'an_int', '15')
config.set('Section1', 'a_bool', 'true')
config.set('Section1', 'a_float', '3.1415')
config.set('Section1', 'baz', 'fun')
config.set('Section1', 'bar', 'Python')
config.set('Section1', 'foo', '%(bar)s is %(baz)s!')

# Writing our configuration file to 'example.cfg'
with open('example.cfg', 'w') as configfile:
    config.write(configfile)
@end example

一个再次读取配置文件的示例:

@example
import configparser

config = configparser.RawConfigParser()
config.read('example.cfg')

# getfloat() raises an exception if the value is not a float
# getint() and getboolean() also do this for their respective types
a_float = config.getfloat('Section1', 'a_float')
an_int = config.getint('Section1', 'an_int')
print(a_float + an_int)

# Notice that the next output does not interpolate '%(bar)s' or '%(baz)s'.
# This is because we are using a RawConfigParser().
if config.getboolean('Section1', 'a_bool'):
    print(config.get('Section1', 'foo'))
@end example

要获取插值，请使用 @ref{4a5,,ConfigParser}:

@example
import configparser

cfg = configparser.ConfigParser()
cfg.read('example.cfg')

# Set the optional *raw* argument of get() to True if you wish to disable
# interpolation in a single get operation.
print(cfg.get('Section1', 'foo', raw=False))  # -> "Python is fun!"
print(cfg.get('Section1', 'foo', raw=True))   # -> "%(bar)s is %(baz)s!"

# The optional *vars* argument is a dict with members that will take
# precedence in interpolation.
print(cfg.get('Section1', 'foo', vars=@{'bar': 'Documentation',
                                       'baz': 'evil'@}))

# The optional *fallback* argument can be used to provide a fallback value
print(cfg.get('Section1', 'foo'))
      # -> "Python is fun!"

print(cfg.get('Section1', 'foo', fallback='Monty is not.'))
      # -> "Python is fun!"

print(cfg.get('Section1', 'monster', fallback='No such things as monsters.'))
      # -> "No such things as monsters."

# A bare print(cfg.get('Section1', 'monster')) would raise NoOptionError
# but we can also use:

print(cfg.get('Section1', 'monster', fallback=None))
      # -> None
@end example

默认值在两种类型的 ConfigParser 中均可用。 它们将在当某个选项未在别处定义时被用于插值。

@example
import configparser

# New instance with 'bar' and 'baz' defaulting to 'Life' and 'hard' each
config = configparser.ConfigParser(@{'bar': 'Life', 'baz': 'hard'@})
config.read('example.cfg')

print(config.get('Section1', 'foo'))     # -> "Python is fun!"
config.remove_option('Section1', 'bar')
config.remove_option('Section1', 'baz')
print(config.get('Section1', 'foo'))     # -> "Life is hard!"
@end example

@node ConfigParser 对象,RawConfigParser 对象,旧式 API 示例,configparser --- 配置文件解析器
@anchor{library/configparser configparser-objects}@anchor{1de9}@anchor{library/configparser id11}@anchor{1dea}
@subsubsection ConfigParser 对象


@geindex ConfigParser (configparser 中的类)
@anchor{library/configparser configparser ConfigParser}@anchor{4a5}
@deffn {类} configparser.ConfigParser (defaults=None, dict_type=dict, allow_no_value=False, delimiters=('=', ':'), comment_prefixes=('#', ';'), inline_comment_prefixes=None, strict=True, empty_lines_in_values=True, default_section=configparser.DEFAULTSECT, interpolation=BasicInterpolation(), converters=@{@})

主配置解析器。 当给定 @emph{defaults} 时，它会被初始化为包含固有默认值的字典。 当给定 @emph{dict_type} 时，它将被用来创建包含节、节中的选项以及默认值的字典。

当给定 @emph{delimiters} 时，它会被用作分隔键与值的子字符串的集合。 当给定 @emph{comment_prefixes} 时，它将被用作在否则为空行的注释的前缀子字符串的集合。 注释可以被缩进。 当给定 @emph{inline_comment_prefixes} 时，它将被用作非空行的注释的前缀子字符串的集合。

当 @emph{strict} 为 @code{True} (默认值) 时，解析器在从单个源（文件、字符串或字典）读取时将不允许任何节或选项出现重复，否则会引发 @ref{bfe,,DuplicateSectionError} 或 @ref{bff,,DuplicateOptionError}。 当 @emph{empty_lines_in_values} 为 @code{False} (默认值: @code{True}) 时，每个空行均表示一个选项的结束。 在其他情况下，一个多行选项内部的空行会被保留为值的一部分。 当 @emph{allow_no_value} 为 @code{True} (默认值: @code{False}) 时，将接受没有值的选项；此种选项的值将为 @code{None} 并且它们会以不带末尾分隔符的形式被序列化。

当给定 @emph{default_section} 时，它将指定存放其他节的默认值和用于插值的特殊节的名称 (通常命名为 @code{"DEFAULT"})。 该值可通过使用 @code{default_section} 实例属性在运行时被读取或修改。

插值行为可通过给出 @emph{interpolation} 参数提供自定义处理程序的方式来定制。 @code{None} 可用来完全禁用插值，@code{ExtendedInterpolation()} 提供了一种更高级的变体形式，它的设计受到了 @code{zc.buildout} 的启发。 有关该主题的更多信息请参见 @ref{1de2,,专门的文档章节}。

插值中使用的所有选项名称将像任何其他选项名称引用一样通过 @ref{1de6,,optionxform()} 方法来传递。 例如，使用 @ref{1de6,,optionxform()} 的默认实现（它会将选项名称转换为小写形式）时，值 @code{foo %(bar)s} 和 @code{foo %(BAR)s} 是等价的。

当给定 @emph{converters} 时，它应当为一个字典，其中每个键代表一个类型转换器的名称而每个值则为实现从字符串到目标数据类型的转换的可调用对象。 每个转换器会获得其在解析器对象和节代理上对应的 @code{get*()} 方法。


在 3.1 版更改: 默认的 @emph{dict_type} 为 @ref{1b9,,collections.OrderedDict}。



在 3.2 版更改: 添加了 @emph{allow_no_value}, @emph{delimiters}, @emph{comment_prefixes}, @emph{strict}, @emph{empty_lines_in_values}, @emph{default_section} 以及 @emph{interpolation}。



在 3.5 版更改: 添加了 @emph{converters} 参数。



在 3.7 版更改: @emph{defaults} 参数会通过 @ref{1deb,,read_dict()} 来读取，提供全解析器范围内一致的行为：非字符串类型的键和值会被隐式地转换为字符串。



在 3.8 版更改: 默认的 @emph{dict_type} 为 @ref{1b8,,dict}，因为它现在会保留插入顺序。


@geindex defaults() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser defaults}@anchor{1dec}
@deffn {方法} defaults ()

返回包含实例范围内默认值的字典。
@end deffn

@geindex sections() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser sections}@anchor{1ded}
@deffn {方法} sections ()

返回可用节的列表；@emph{default section} 不包括在该列表中。
@end deffn

@geindex add_section() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser add_section}@anchor{bfd}
@deffn {方法} add_section (section)

向实例添加一个名为 @emph{section} 的节。 如果给定名称的节已存在，将会引发 @ref{bfe,,DuplicateSectionError}。 如果传入了 @emph{default section} 名称，则会引发 @ref{1fb,,ValueError}。 节名称必须为字符串；如果不是则会引发 @ref{192,,TypeError}。


在 3.2 版更改: 非字符串的节名称将引发 @ref{192,,TypeError}。

@end deffn

@geindex has_section() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser has_section}@anchor{1dee}
@deffn {方法} has_section (section)

指明相应名称的 @emph{section} 是否存在于配置中。 @emph{default section} 不包含在内。
@end deffn

@geindex options() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser options}@anchor{1def}
@deffn {方法} options (section)

返回指定 @emph{section} 中可用选项的列表。
@end deffn

@geindex has_option() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser has_option}@anchor{1df0}
@deffn {方法} has_option (section, option)

如果给定的 @emph{section} 存在并且包含给定的 @emph{option} 则返回 @ref{494,,True}；否则返回 @ref{380,,False}。 如果指定的 @emph{section} 为 @ref{157,,None} 或空字符串，则会使用 DEFAULT。
@end deffn

@geindex read() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser read}@anchor{1037}
@deffn {方法} read (filenames, encoding=None)

尝试读取并解析一个包含文件名的可迭代对象，返回一个被成功解析的文件名列表。

如果 @emph{filenames} 为字符串、@ref{32a,,bytes} 对象或 @ref{363,,path-like object}，它会被当作单个文件来处理。 如果 @emph{filenames} 中名称对应的某个文件无法被打开，该文件将被忽略。 这样的设计使得你可以指定包含多个潜在配置文件位置的可迭代对象（例如当前目录、用户家目录以及某个系统级目录），存在于该可迭代对象中的所有配置文件都将被读取。

如果名称对应的文件全都不存在，则 @ref{4a5,,ConfigParser} 实例将包含一个空数据集。 一个要求从文件加载初始值的应用应当在调用 @ref{1037,,read()} 来获取任何可选文件之前使用 @ref{1df1,,read_file()} 来加载所要求的一个或多个文件:

@example
import configparser, os

config = configparser.ConfigParser()
config.read_file(open('defaults.cfg'))
config.read(['site.cfg', os.path.expanduser('~/.myapp.cfg')],
            encoding='cp1250')
@end example


3.2 新版功能: @emph{encoding} 形参。 在之前的版本中，所有文件都将使用 @ref{4ea,,open()} 的默认编码格式来读取。



3.6.1 新版功能: @emph{filenames} 形参接受一个 @ref{363,,path-like object}。



3.7 新版功能: @emph{filenames} 形参接受一个 @ref{32a,,bytes} 对象。

@end deffn

@geindex read_file() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser read_file}@anchor{1df1}
@deffn {方法} read_file (f, source=None)

从 @emph{f} 读取并解析配置数据，它必须是一个产生 Unicode 字符串的可迭代对象（例如以文本模式打开的文件）。

可选参数 @emph{source} 指定要读取的文件名称。 如果未给出并且 @emph{f} 具有 @code{name} 属性，则该属性会被用作 @emph{source}；默认值为 @code{'<???>'}。


3.2 新版功能: 替代 @ref{1df2,,readfp()}。

@end deffn

@geindex read_string() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser read_string}@anchor{1df3}
@deffn {方法} read_string (string, source='<string>')

从字符串中解析配置数据。

可选参数 @emph{source} 指定一个所传入字符串的上下文专属名称。 如果未给出，则会使用 @code{'<string>'}。 这通常应为一个文件系统路径或 URL。


3.2 新版功能.

@end deffn

@geindex read_dict() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser read_dict}@anchor{1deb}
@deffn {方法} read_dict (dictionary, source='<dict>')

从任意一个提供了类似于字典的 @code{items()} 方法的对象加载配置。 键为节名称，值为包含节中所出现的键和值的字典。 如果所用的字典类型会保留顺序，则节和其中的键将按顺序加入。 值会被自动转换为字符串。

可选参数 @emph{source} 指定一个所传入字曲的上下文专属名称。 如果未给出，则会使用 @code{<dict>}。

此方法可被用于在解析器之间拷贝状态。


3.2 新版功能.

@end deffn

@geindex get() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser get}@anchor{bfb}
@deffn {方法} get (section, option, *, raw=False, vars=None[, fallback])

获取指定名称的 @emph{section} 的一个 @emph{option} 的值。 如果提供了 @emph{vars}，则它必须为一个字典。 @emph{option} 的查找顺序为 @emph{vars*（如果有提供）、*section} 以及 @emph{DEFAULTSECT}。 如果未找到该键并且提供了 @emph{fallback}，则它会被用作回退值。 可以提供 @code{None} 作为 @emph{fallback} 值。

所有 @code{'%'} 插值会在返回值中被展开，除非 @emph{raw} 参数为真值。 插值键所使用的值会按与选项相同的方式来查找。


在 3.2 版更改: @emph{raw}, @emph{vars} 和 @emph{fallback} 都是仅限关键字参数，以防止用户试图使用第三个参数作业为 @emph{fallback} 回退值（特别是在使用映射 协议的时候）。

@end deffn

@geindex getint() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser getint}@anchor{1ddf}
@deffn {方法} getint (section, option, *, raw=False, vars=None[, fallback])

将在指定 @emph{section} 中的 @emph{option} 强制转换为整数的便捷方法。 参见 @ref{bfb,,get()} 获取对于 @emph{raw}, @emph{vars} 和 @emph{fallback} 的解释。
@end deffn

@geindex getfloat() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser getfloat}@anchor{1de0}
@deffn {方法} getfloat (section, option, *, raw=False, vars=None[, fallback])

将在指定 @emph{section} 中的 @emph{option} 强制转换为浮点数的便捷方法。 参见 @ref{bfb,,get()} 获取对于 @emph{raw}, @emph{vars} 和 @emph{fallback} 的解释。
@end deffn

@geindex getboolean() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser getboolean}@anchor{1dde}
@deffn {方法} getboolean (section, option, *, raw=False, vars=None[, fallback])

将在指定 @emph{section} 中的 @emph{option} 强制转换为布尔值的便捷方法。 请注意选项所接受的值为 @code{'1'}, @code{'yes'}, @code{'true'} 和 @code{'on'}，它们会使得此方法返回 @code{True}，以及 @code{'0'}, @code{'no'}, @code{'false'} 和 @code{'off'}，它们会使得此方法返回 @code{False}。 这些字符串值会以对大小写不敏感的方式被检测。 任何其他值都将导致引发 @ref{1fb,,ValueError}。 参见 @ref{bfb,,get()} 获取对于 @emph{raw}, @emph{vars} 和 @emph{fallback} 的解释。
@end deffn

@geindex items() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser items}@anchor{1df4}
@deffn {方法} items (raw=False, vars=None)

@deffnx {方法} items (section, raw=False, vars=None)

当未给出 @emph{section} 时，将返回由 @emph{section_name}, @emph{section_proxy} 对组成的列表，包括 DEFAULTSECT。

在其他情况下，将返回给定的 @emph{section} 中的 option 的 @emph{name}, @emph{value} 对组成的列表。 可选参数具有与 @ref{bfb,,get()} 方法的参数相同的含义。


在 3.8 版更改: @emph{vars} 中的条目将不在结果中出现。 之前的行为混淆了实际的解析器选项和为插值提供的变量。

@end deffn

@geindex set() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser set}@anchor{bfc}
@deffn {方法} set (section, option, value)

如果给定的节存在，则将所给出的选项设为指定的值；在其他情况下将引发 @ref{1df5,,NoSectionError}。 @emph{option} 和 @emph{value} 必须为字符串；如果不是则将引发 @ref{192,,TypeError}。
@end deffn

@geindex write() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser write}@anchor{1de4}
@deffn {方法} write (fileobject, space_around_delimiters=True)

将配置的表示形式写入指定的 @ref{b3b,,file object}，该对象必须以文本模式打开（接受字符串）。 此表示形式可由将来的 @ref{1037,,read()} 调用进行解析。 如果 @emph{space_around_delimiters} 为真值，键和值之前的分隔符两边将加上空格。
@end deffn

@geindex remove_option() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser remove_option}@anchor{1df6}
@deffn {方法} remove_option (section, option)

将指定的 @emph{option} 从指定的 @emph{section} 中移除。 如果指定的节不存在则会引发 @ref{1df5,,NoSectionError}。 如果要移除的选项存在则返回 @ref{494,,True}；在其他情况下将返回 @ref{380,,False}。
@end deffn

@geindex remove_section() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser remove_section}@anchor{1df7}
@deffn {方法} remove_section (section)

从配置中移除指定的 @emph{section}。 如果指定的节确实存在则返回 @code{True}。 在其他情况下将返回 @code{False}。
@end deffn

@geindex optionxform() (configparser.ConfigParser 方法)

@deffn {方法} optionxform (option)

将选项名 @emph{option} 转换为输入文件中的形式或客户端代码所传入的应当在内部结构中使用的形式。 默认实现将返回 @emph{option} 的小写形式版本；子类可以重载此行为，或者客户端代码也可以在实例上设置一个具有此名称的属性来影响此行为。

你不需要子类化解析器来使用此方法，你也可以在一个实例上设置它，或使用一个接受字符串参数并返回字符串的函数。 例如将它设为 @code{str} 将使得选项名称变得大小写敏感:

@example
cfgparser = ConfigParser()
cfgparser.optionxform = str
@end example

请注意当读取配置文件时，选项名称两边的空格将在调用 @ref{1de6,,optionxform()} 之前被去除。
@end deffn

@geindex readfp() (configparser.ConfigParser 方法)
@anchor{library/configparser configparser ConfigParser readfp}@anchor{1df2}
@deffn {方法} readfp (fp, filename=None)


3.2 版后已移除: 使用 @ref{1df1,,read_file()} 来代替。



在 3.2 版更改: @ref{1df2,,readfp()} 现在将在 @emph{fp} 上执行迭代而不是调用 @code{fp.readline()}。


对于调用 @ref{1df2,,readfp()} 时传入不支持迭代的参数的现有代码，可以在文件类对象外使用以下生成器作为包装器:

@example
def readline_generator(fp):
    line = fp.readline()
    while line:
        yield line
        line = fp.readline()
@end example

不再使用 @code{parser.readfp(fp)} 而是改用 @code{parser.read_file(readline_generator(fp))}。
@end deffn
@end deffn

@geindex MAX_INTERPOLATION_DEPTH() (在 configparser 模块中)
@anchor{library/configparser configparser MAX_INTERPOLATION_DEPTH}@anchor{1df8}
@deffn {数据} configparser.MAX_INTERPOLATION_DEPTH

当 @emph{raw} 形参为假值时 @code{get()} 所采用的递归插值的最大深度。 这只在使用默认的 @emph{interpolation} 时会起作用。
@end deffn

@node RawConfigParser 对象,异常<5>,ConfigParser 对象,configparser --- 配置文件解析器
@anchor{library/configparser id13}@anchor{1df9}@anchor{library/configparser rawconfigparser-objects}@anchor{1dfa}
@subsubsection RawConfigParser 对象


@geindex RawConfigParser (configparser 中的类)
@anchor{library/configparser configparser RawConfigParser}@anchor{86b}
@deffn {类} configparser.RawConfigParser (defaults=None, dict_type=dict, allow_no_value=False, *, delimiters=('=', ':'), comment_prefixes=('#', ';'), inline_comment_prefixes=None, strict=True, empty_lines_in_values=True, default_section=configparser.DEFAULTSECT[, interpolation])

旧式 @ref{4a5,,ConfigParser}。 它默认禁用插值并且允许通过不安全的 @code{add_section} 和 @code{set} 方法以及旧式 @code{defaults=} 关键字参数处理来设置非字符串的节名、选项名和值。


在 3.8 版更改: 默认的 @emph{dict_type} 为 @ref{1b8,,dict}，因为它现在会保留插入顺序。


@cartouche
@quotation 注解 
考虑改用 @ref{4a5,,ConfigParser}，它会检查内部保存的值的类型。 如果你不想要插值，你可以使用 @code{ConfigParser(interpolation=None)}。
@end quotation
@end cartouche

@geindex add_section() (configparser.RawConfigParser 方法)
@anchor{library/configparser configparser RawConfigParser add_section}@anchor{1dfb}
@deffn {方法} add_section (section)

向实例添加一个名为 @emph{section} 的节。 如果给定名称的节已存在，将会引发 @ref{bfe,,DuplicateSectionError}。 如果传入了 @emph{default section} 名称，则会引发 @ref{1fb,,ValueError}。

不检查 @emph{section} 以允许用户创建以非字符串命名的节。 此行为已不受支持并可能导致内部错误。
@end deffn

@geindex set() (configparser.RawConfigParser 方法)
@anchor{library/configparser configparser RawConfigParser set}@anchor{1dfc}
@deffn {方法} set (section, option, value)

如果给定的节存在，则将给定的选项设为指定的值；在其他情况下将引发 @ref{1df5,,NoSectionError}。 虽然可能使用 @ref{86b,,RawConfigParser} (或使用 @ref{4a5,,ConfigParser} 并将 @emph{raw} 形参设为真值) 以便实现非字符串值的 @emph{internal} 存储，但是完整功能（包括插值和输出到文件）只能使用字符串值来实现。

此方法允许用户在内部将非字符串值赋给键。 此行为已不受支持并会在尝试写入到文件或在非原始模式下获取数据时导致错误。 @strong{请使用映射协议 API}，它不允许出现这样的赋值。
@end deffn
@end deffn

@node 异常<5>,,RawConfigParser 对象,configparser --- 配置文件解析器
@anchor{library/configparser exceptions}@anchor{1dfd}
@subsubsection 异常


@geindex Error
@anchor{library/configparser configparser Error}@anchor{1dfe}
@deffn {例外} configparser.Error

所有其他 @ref{23,,configparser} 异常的基类。
@end deffn

@geindex NoSectionError
@anchor{library/configparser configparser NoSectionError}@anchor{1df5}
@deffn {例外} configparser.NoSectionError

当找不到指定节时引发的异常。
@end deffn

@geindex DuplicateSectionError
@anchor{library/configparser configparser DuplicateSectionError}@anchor{bfe}
@deffn {例外} configparser.DuplicateSectionError

当调用 @code{add_section()} 时传入已存在的节名称，或者在严格解析器中当单个输入文件、字符串或字典内出现重复的节时引发的异常。


3.2 新版功能: 将可选的 @code{source} 和 @code{lineno} 属性和参数添加到 @ref{d57,,__init__()}。

@end deffn

@geindex DuplicateOptionError
@anchor{library/configparser configparser DuplicateOptionError}@anchor{bff}
@deffn {例外} configparser.DuplicateOptionError

当单个选项在从单个文件、字符串或字典读取时出现两次时引发的异常。 这会捕获拼写错误和大小写敏感相关的错误，例如一个字典可能包含两个键分别代表同一个大小写不敏感的配置键。
@end deffn

@geindex NoOptionError
@anchor{library/configparser configparser NoOptionError}@anchor{1dff}
@deffn {例外} configparser.NoOptionError

当指定的选项未在指定的节中被找到时引发的异常。
@end deffn

@geindex InterpolationError
@anchor{library/configparser configparser InterpolationError}@anchor{1e00}
@deffn {例外} configparser.InterpolationError

当执行字符串插值发生问题时所引发的异常的基类。
@end deffn

@geindex InterpolationDepthError
@anchor{library/configparser configparser InterpolationDepthError}@anchor{1e01}
@deffn {例外} configparser.InterpolationDepthError

当字符串插值由于迭代次数超出 @ref{1df8,,MAX_INTERPOLATION_DEPTH} 而无法完成所引发的异常。 为 @ref{1e00,,InterpolationError} 的子类。
@end deffn

@geindex InterpolationMissingOptionError
@anchor{library/configparser configparser InterpolationMissingOptionError}@anchor{1e02}
@deffn {例外} configparser.InterpolationMissingOptionError

当从某个值引用的选项并不存在时引发的异常。 为 @ref{1e00,,InterpolationError} 的子类。
@end deffn

@geindex InterpolationSyntaxError
@anchor{library/configparser configparser InterpolationSyntaxError}@anchor{1e03}
@deffn {例外} configparser.InterpolationSyntaxError

当将要执行替换的源文本不符合要求的语法时引发的异常。 为 @ref{1e00,,InterpolationError} 的子类。
@end deffn

@geindex MissingSectionHeaderError
@anchor{library/configparser configparser MissingSectionHeaderError}@anchor{1e04}
@deffn {例外} configparser.MissingSectionHeaderError

当尝试解析一个不带节标头的文件时引发的异常。
@end deffn

@geindex ParsingError
@anchor{library/configparser configparser ParsingError}@anchor{1e05}
@deffn {例外} configparser.ParsingError

当尝试解析一个文件而发生错误时引发的异常。


在 3.2 版更改: @code{filename} 属性和 @ref{d57,,__init__()} 参数被重命名为 @code{source} 以保持一致性。

@end deffn

@subsubheading 备注


@node netrc --- netrc 文件处理,xdrlib --- 编码与解码 XDR 数据,configparser --- 配置文件解析器,文件格式
@anchor{library/netrc doc}@anchor{1e06}@anchor{library/netrc module-netrc}@anchor{be}@anchor{library/netrc netrc-netrc-file-processing}@anchor{1e07}
@subsection @code{netrc} --- netrc 文件处理


@geindex netrc (模块)

@strong{源代码:} Lib/netrc.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/netrc.py}


__________________________________________________________________


@ref{1033,,netrc} 类解析并封装了 Unix 的 @code{ftp} 程序和其他 FTP 客户端所使用的 netrc 文件格式。

@geindex netrc (netrc 中的类)
@anchor{library/netrc netrc netrc}@anchor{1033}
@deffn {类} netrc.netrc ([file])

@ref{1033,,netrc} 的实例或其子类的实例会被用来封装来自 netrc 文件的数据。 如果有初始化参数，它将指明要解析的文件。 如果未给出参数，则位于用户家目录的 @code{.netrc} 文件 -- 即 @ref{1fe,,os.path.expanduser()} 所确定的文件 -- 将会被读取。 在其他情况下，则将引发 @ref{7ba,,FileNotFoundError} 异常。 解析错误将引发 @ref{1e08,,NetrcParseError} 并附带诊断信息，包括文件名、行号以及终止令牌。 如果在 POSIX 系统上未指明参数，则当 @code{.netrc} 文件中有密码时，如果文件归属或权限不安全（归属的用户不是运行进程的用户，或者可供任何其他用户读取或写入）将引发 @ref{1e08,,NetrcParseError}。 这实现了与 ftp 和其他使用 @code{.netrc} 的程序同等的安全行为。


在 3.4 版更改: 添加了 POSIX 权限检查。



在 3.7 版更改: 当未将 @emph{file} 作为参数传入时会使用 @ref{1fe,,os.path.expanduser()} 来查找 @code{.netrc} 文件的位置。

@end deffn

@geindex NetrcParseError
@anchor{library/netrc netrc NetrcParseError}@anchor{1e08}
@deffn {例外} netrc.NetrcParseError

当在源文本中遇到语法错误时由 @ref{1033,,netrc} 类引发的异常。 此异常的实例提供了三个有用属性:  @code{msg} 为错误的文本说明，@code{filename} 为源文件的名称，而 @code{lineno} 给出了错误所在的行号。
@end deffn

@menu
* netrc 对象:: 

@end menu

@node netrc 对象,,,netrc --- netrc 文件处理
@anchor{library/netrc id1}@anchor{1e09}@anchor{library/netrc netrc-objects}@anchor{1e0a}
@subsubsection netrc 对象


@ref{1033,,netrc} 实例具有下列方法:

@geindex authenticators() (netrc.netrc 方法)
@anchor{library/netrc netrc netrc authenticators}@anchor{1e0b}
@deffn {方法} netrc.authenticators (host)

针对 @emph{host} 的身份验证者返回一个 3 元组 @code{(login, account, password)}。 如果 netrc 文件不包含针对给定主机的条目，则返回关联到 'default' 条目的元组。 如果匹配的主机或默认条目均不可用，则返回 @code{None}。
@end deffn

@geindex __repr__() (netrc.netrc 方法)
@anchor{library/netrc netrc netrc __repr__}@anchor{1e0c}
@deffn {方法} netrc.__repr__ ()

将类数据以 netrc 文件的格式转储为一个字符串。 （这会丢弃注释并可能重排条目顺序。）
@end deffn

@ref{1033,,netrc} 的实例具有一些公共实例变量:

@geindex hosts (netrc.netrc 属性)
@anchor{library/netrc netrc netrc hosts}@anchor{1e0d}
@deffn {属性} netrc.hosts

将主机名映射到 @code{(login, account, password)} 元组的字典。 如果存在 'default' 条目，则会表示为使用该名称的伪主机。
@end deffn

@geindex macros (netrc.netrc 属性)
@anchor{library/netrc netrc netrc macros}@anchor{1e0e}
@deffn {属性} netrc.macros

将宏名称映射到字符串列表的字典。
@end deffn

@cartouche
@quotation 注解 
密码会被限制为 ASCII 字符集的一个子集。 所有 ASCII 标点符号均可用作密码，但是要注意空白符和非打印字符不允许用作密码。 这是 .netrc 文件解析方式带来的限制，在未来可能会被解除。
@end quotation
@end cartouche

@node xdrlib --- 编码与解码 XDR 数据,plistlib --- 生成与解析 Mac OS X plist 文件,netrc --- netrc 文件处理,文件格式
@anchor{library/xdrlib doc}@anchor{1e0f}@anchor{library/xdrlib module-xdrlib}@anchor{132}@anchor{library/xdrlib xdrlib-encode-and-decode-xdr-data}@anchor{1e10}
@subsection @code{xdrlib} --- 编码与解码 XDR 数据


@geindex xdrlib (模块)

@strong{源代码:} Lib/xdrlib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xdrlib.py}

@geindex XDR
@geindex External Data Representation


__________________________________________________________________


@ref{132,,xdrlib} 模块为外部数据表示标准提供支持，该标准的描述见 
@geindex RFC; RFC 1014
RFC 1014@footnote{https://tools.ietf.org/html/rfc1014.html}，由 Sun Microsystems, Inc. 在 1987 年 6 月撰写。 它支持该 RFC 中描述的大部分数据类型。

@ref{132,,xdrlib} 模块定义了两个类，一个用于将变量打包为 XDR 表示形式，另一个用于从 XDR 表示形式解包。 此外还有两个异常类。

@geindex Packer (xdrlib 中的类)
@anchor{library/xdrlib xdrlib Packer}@anchor{1e11}
@deffn {类} xdrlib.Packer

@ref{1e11,,Packer} 是用于将数据打包为 XDR 表示形式的类。 @ref{1e11,,Packer} 类的实例化不附带参数。
@end deffn

@geindex Unpacker (xdrlib 中的类)
@anchor{library/xdrlib xdrlib Unpacker}@anchor{1e12}
@deffn {类} xdrlib.Unpacker (data)

@code{Unpacker} 是用于相应地从字符串缓冲区解包 XDR 数据值的类。 输入缓冲区将作为 @emph{data} 给出。
@end deffn


@subsubheading 参见



@table @asis

@geindex RFC; RFC 1014

@item RFC 1014@footnote{https://tools.ietf.org/html/rfc1014.html} - XDR: 外部数据表示标准

这个 RFC 定义了最初编写此模块时 XDR 所用的数据编码格式。 显然它已被 
@geindex RFC; RFC 1832
RFC 1832@footnote{https://tools.ietf.org/html/rfc1832.html} 所淘汰。

@geindex RFC; RFC 1832

@item RFC 1832@footnote{https://tools.ietf.org/html/rfc1832.html} - XDR: 外部数据表示标准

更新的 RFC，它提供了经修订的 XDR 定义。
@end table


@menu
* Packer 对象:: 
* Unpacker 对象:: 
* 异常: 异常<6>. 

@end menu

@node Packer 对象,Unpacker 对象,,xdrlib --- 编码与解码 XDR 数据
@anchor{library/xdrlib packer-objects}@anchor{1e13}@anchor{library/xdrlib xdr-packer-objects}@anchor{1e14}
@subsubsection Packer 对象


@ref{1e11,,Packer} 实例具有下列方法:

@geindex get_buffer() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer get_buffer}@anchor{1e15}
@deffn {方法} Packer.get_buffer ()

将当前打包缓冲区以字符串的形式返回。
@end deffn

@geindex reset() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer reset}@anchor{1e16}
@deffn {方法} Packer.reset ()

将打包缓冲区重置为空字符串。
@end deffn

总体来说，你可以通过调用适当的 @code{pack_type()} 方法来打包任何最常见的 XDR 数据类型。 每个方法都是接受单个参数，即要打包的值。 受支持的简单数据类型打包方法如下: @code{pack_uint()}, @code{pack_int()}, @code{pack_enum()}, @code{pack_bool()}, @code{pack_uhyper()} 以及 @code{pack_hyper()}。

@geindex pack_float() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_float}@anchor{1e17}
@deffn {方法} Packer.pack_float (value)

打包单精度浮点数 @emph{value}。
@end deffn

@geindex pack_double() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_double}@anchor{1e18}
@deffn {方法} Packer.pack_double (value)

打包双精度浮点数 @emph{value}。
@end deffn

以下方法支持打包字符串、字节串以及不透明数据。

@geindex pack_fstring() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_fstring}@anchor{1e19}
@deffn {方法} Packer.pack_fstring (n, s)

打包固定长度字符串 @emph{s}。 @emph{n} 为字符串的长度，但它 @emph{不会} 被打包进数据缓冲区。 如有必要字符串会以空字节串填充以保证 4 字节对齐。
@end deffn

@geindex pack_fopaque() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_fopaque}@anchor{1e1a}
@deffn {方法} Packer.pack_fopaque (n, data)

打包固定长度不透明数据流，类似于 @ref{1e19,,pack_fstring()}。
@end deffn

@geindex pack_string() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_string}@anchor{1e1b}
@deffn {方法} Packer.pack_string (s)

打包可变长度字符串 @emph{s}。 先将字符串的长度打包为无符号整数，再用 @ref{1e19,,pack_fstring()} 来打包字符串数据。
@end deffn

@geindex pack_opaque() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_opaque}@anchor{1e1c}
@deffn {方法} Packer.pack_opaque (data)

打包可变长度不透明数据流，类似于 @ref{1e1b,,pack_string()}。
@end deffn

@geindex pack_bytes() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_bytes}@anchor{1e1d}
@deffn {方法} Packer.pack_bytes (bytes)

打包可变长度字节流，类似于 @ref{1e1b,,pack_string()}。
@end deffn

下列方法支持打包数组和列表:

@geindex pack_list() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_list}@anchor{1e1e}
@deffn {方法} Packer.pack_list (list, pack_item)

打包由同质条目构成的 @emph{list}。 此方法适用于不确定长度的列表；即其长度无法在遍历整个列表之前获知。 对于列表中的每个条目，先打包一个无符号整数 @code{1}，再添加列表中数据的值。 @emph{pack_item} 是在打包单个条目时要调用的函数。 在列表的末尾，会再打包一个无符号整数 @code{0}。

例如，要打包一个整数列表，代码看起来会是这样:

@example
import xdrlib
p = xdrlib.Packer()
p.pack_list([1, 2, 3], p.pack_int)
@end example
@end deffn

@geindex pack_farray() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_farray}@anchor{1e1f}
@deffn {方法} Packer.pack_farray (n, array, pack_item)

打包由同质条目构成的固定长度列表 (@emph{array})。 @emph{n} 为列表长度；它 @emph{不会} 被打包到缓冲区，但是如果 @code{len(array)} 不等于 @emph{n} 则会引发 @ref{1fb,,ValueError}。 如上所述，@emph{pack_item} 是在打包每个元素时要使用的函数。
@end deffn

@geindex pack_array() (xdrlib.Packer 方法)
@anchor{library/xdrlib xdrlib Packer pack_array}@anchor{1e20}
@deffn {方法} Packer.pack_array (list, pack_item)

打包由同质条目构成的可变长度 @emph{list}。 先将列表的长度打包为无符号整数，再像上面的 @ref{1e1f,,pack_farray()} 一样打包每个元素。
@end deffn

@node Unpacker 对象,异常<6>,Packer 对象,xdrlib --- 编码与解码 XDR 数据
@anchor{library/xdrlib unpacker-objects}@anchor{1e21}@anchor{library/xdrlib xdr-unpacker-objects}@anchor{1e22}
@subsubsection Unpacker 对象


@ref{1e12,,Unpacker} 类提供以下方法:

@geindex reset() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker reset}@anchor{1e23}
@deffn {方法} Unpacker.reset (data)

使用给定的 @emph{data} 重置字符串缓冲区。
@end deffn

@geindex get_position() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker get_position}@anchor{1e24}
@deffn {方法} Unpacker.get_position ()

返回数据缓冲区中的当前解包位置。
@end deffn

@geindex set_position() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker set_position}@anchor{1e25}
@deffn {方法} Unpacker.set_position (position)

将数据缓冲区的解包位置设为 @emph{position}。 你应当小心使用 @ref{1e24,,get_position()} 和 @ref{1e25,,set_position()}。
@end deffn

@geindex get_buffer() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker get_buffer}@anchor{1e26}
@deffn {方法} Unpacker.get_buffer ()

将当前解包数据缓冲区以字符串的形式返回。
@end deffn

@geindex done() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker done}@anchor{1e27}
@deffn {方法} Unpacker.done ()

表明解包完成。 如果数据没有全部完成解包则会引发 @ref{1e28,,Error} 异常。
@end deffn

此外，每种可通过 @ref{1e11,,Packer} 打包的数据类型都可通过 @ref{1e12,,Unpacker} 来解包。 解包方法的形式为 @code{unpack_type()}，并且不接受任何参数。 该方法将返回解包后的对象。

@geindex unpack_float() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_float}@anchor{1e29}
@deffn {方法} Unpacker.unpack_float ()

解包单精度浮点数。
@end deffn

@geindex unpack_double() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_double}@anchor{1e2a}
@deffn {方法} Unpacker.unpack_double ()

解包双精度浮点数，类似于 @ref{1e29,,unpack_float()}。
@end deffn

此外，以下方法可用来解包字符串、字节串以及不透明数据:

@geindex unpack_fstring() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_fstring}@anchor{1e2b}
@deffn {方法} Unpacker.unpack_fstring (n)

解包并返回固定长度字符串。 @emph{n} 为期望的字符数量。 会预设以空字节串填充以保证 4 字节对齐。
@end deffn

@geindex unpack_fopaque() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_fopaque}@anchor{1e2c}
@deffn {方法} Unpacker.unpack_fopaque (n)

解包并返回固定长度数据流，类似于 @ref{1e2b,,unpack_fstring()}。
@end deffn

@geindex unpack_string() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_string}@anchor{1e2d}
@deffn {方法} Unpacker.unpack_string ()

解包并返回可变长度字符串。 先将字符串的长度解包为无符号整数，再用 @ref{1e2b,,unpack_fstring()} 来解包字符串数据。
@end deffn

@geindex unpack_opaque() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_opaque}@anchor{1e2e}
@deffn {方法} Unpacker.unpack_opaque ()

解包并返回可变长度不透明数据流，类似于 @ref{1e2d,,unpack_string()}。
@end deffn

@geindex unpack_bytes() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_bytes}@anchor{1e2f}
@deffn {方法} Unpacker.unpack_bytes ()

解包并返回可变长度字节流，类似于 @ref{1e2d,,unpack_string()}。
@end deffn

下列方法支持解包数组和列表:

@geindex unpack_list() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_list}@anchor{1e30}
@deffn {方法} Unpacker.unpack_list (unpack_item)

解包并返回同质条目的列表。 该列表每次解包一个元素，先解包一个无符号整数旗标。 如果旗标为 @code{1}，则解包条目并将其添加到列表。 旗标为 @code{0} 表明列表结束。 @emph{unpack_item} 为在解包条目时调用的函数。
@end deffn

@geindex unpack_farray() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_farray}@anchor{1e31}
@deffn {方法} Unpacker.unpack_farray (n, unpack_item)

解包并（以列表形式）返回由同质条目构成的固定长度数组。 @emph{n} 为期望的缓冲区内列表元素数量。 如上所述，@emph{unpack_item} 是解包每个元素时要使用的函数。
@end deffn

@geindex unpack_array() (xdrlib.Unpacker 方法)
@anchor{library/xdrlib xdrlib Unpacker unpack_array}@anchor{1e32}
@deffn {方法} Unpacker.unpack_array (unpack_item)

解包并返回由同质条目构成的可变长度 @emph{list}。 先将列表的长度解包为无符号整数，再像上面的 @ref{1e31,,unpack_farray()} 一样解包每个元素。
@end deffn

@node 异常<6>,,Unpacker 对象,xdrlib --- 编码与解码 XDR 数据
@anchor{library/xdrlib exceptions}@anchor{1e33}@anchor{library/xdrlib xdr-exceptions}@anchor{1e34}
@subsubsection 异常


此模块中的异常会表示为类实例代码:

@geindex Error
@anchor{library/xdrlib xdrlib Error}@anchor{1e28}
@deffn {例外} xdrlib.Error

基本异常类。 @ref{1e28,,Error} 具有一个公共属性 @code{msg}，其中包含对错误的描述。
@end deffn

@geindex ConversionError
@anchor{library/xdrlib xdrlib ConversionError}@anchor{1e35}
@deffn {例外} xdrlib.ConversionError

从 @ref{1e28,,Error} 所派生的类。 不包含额外的实例变量。
@end deffn

以下是一个应该如何捕获这些异常的示例:

@example
import xdrlib
p = xdrlib.Packer()
try:
    p.pack_double(8.01)
except xdrlib.ConversionError as instance:
    print('packing the double failed:', instance.msg)
@end example

@node plistlib --- 生成与解析 Mac OS X plist 文件,,xdrlib --- 编码与解码 XDR 数据,文件格式
@anchor{library/plistlib doc}@anchor{1e36}@anchor{library/plistlib module-plistlib}@anchor{cf}@anchor{library/plistlib plistlib-generate-and-parse-mac-os-x-plist-files}@anchor{1e37}
@subsection @code{plistlib} --- 生成与解析 Mac OS X @code{.plist} 文件


@geindex plistlib (模块)

@c (harvested from docstrings in the original file)

@strong{源代码:} Lib/plistlib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/plistlib.py}

@geindex plist; file
@geindex property list


__________________________________________________________________


此模块提供了读写主要用于 Mac OS X 的 "property list" 文件的接口，并同时支持二进制和 XML plist 文件。

property list (@code{.plist}) 文件格式是一种简单的序列化格式，它支持一些基本对象类型，例如字典、列表、数字和字符串等。 通常使用一个字典作为最高层级对象。

要写入和解析 plist 文件，请使用 @ref{886,,dump()} 和 @ref{885,,load()} 函数。

要以字节串对象形式操作 plist 数据，请使用 @ref{888,,dumps()} 和 @ref{887,,loads()}。

值可以为字符串、整数、浮点数、布尔值、元组、列表、字典（但只允许用字符串作为键）、@ref{941,,Data}、@ref{32a,,bytes}、@code{bytesarray} 或 @ref{194,,datetime.datetime} 对象。


在 3.4 版更改: 新版 API，旧版 API 已被弃用。 添加了对二进制 plist 格式的支持。



在 3.8 版更改: 添加了在二进制 plist 中读写 @ref{210,,UID} 令牌的支持，例如用于 NSKeyedArchiver 和 NSKeyedUnarchiver。



@subsubheading 参见



@table @asis

@item PList 指南页面@footnote{https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/PropertyLists/}

针对该文件格式的 Apple 文档。
@end table


这个模块定义了以下函数：

@geindex load() (在 plistlib 模块中)
@anchor{library/plistlib plistlib load}@anchor{885}
@deffn {函数} plistlib.load (fp, *, fmt=None, use_builtin_types=True, dict_type=dict)

读取 plist 文件。 @emph{fp} 应当可读并且为二进制文件对象。 返回已解包的根对象（通常是一个字典）。

@emph{fmt} 为文件的格式，有效的值如下:


@itemize *

@item 
@ref{157,,None}: 自动检测文件格式

@item 
@ref{889,,FMT_XML}: XML 文件格式

@item 
@ref{88a,,FMT_BINARY}: 二进制 plist 格式
@end itemize

如果 @emph{use_builtin_types} 为真值（默认）则将以 @ref{32a,,bytes} 实例的形式返回二进制数据，否则将以 @ref{941,,Data} 实例的形式返回。

@emph{dict_type} 为字典用来从 plist 文件读取的类型。

@ref{889,,FMT_XML} 格式的 XML 数据 会使用来自 @ref{138,,xml.parsers.expat} 的 Expat 解析器 -- 请参阅其文档了解错误格式 XML 可能引发的异常。 未知元素将被 plist 解析器直接略过。

当文件无法被解析时二进制格式的解析器将引发 @code{InvalidFileException}。


3.4 新版功能.

@end deffn

@geindex loads() (在 plistlib 模块中)
@anchor{library/plistlib plistlib loads}@anchor{887}
@deffn {函数} plistlib.loads (data, *, fmt=None, use_builtin_types=True, dict_type=dict)

从一个 bytes 对象加载 plist。 参阅 @ref{885,,load()} 获取相应关键字参数的说明。


3.4 新版功能.

@end deffn

@geindex dump() (在 plistlib 模块中)
@anchor{library/plistlib plistlib dump}@anchor{886}
@deffn {函数} plistlib.dump (value, fp, *, fmt=FMT_XML, sort_keys=True, skipkeys=False)

将 @emph{value} 写入 plist 文件。 @emph{Fp} 应当可写并且为二进制文件对象。

@emph{fmt} 参数指定 plist 文件的格式，可以是以下值之一:


@itemize *

@item 
@ref{889,,FMT_XML}: XML 格式的 plist 文件

@item 
@ref{88a,,FMT_BINARY}: 二进制格式的 plist 文件
@end itemize

当 @emph{sort_keys} 为真值（默认）时字典的键将经过排序再写入 plist，否则将按字典的迭代顺序写入。

当 @emph{skipkeys} 为假值（默认）时该函数将在字典的键不为字符串时引发 @ref{192,,TypeError}，否则将跳过这样的键。

如果对象是不受支持的类型或者是包含不受支持类型的对象的容器则将引发 @ref{192,,TypeError}。

对于无法在（二进制）plist 文件中表示的整数值，将会引发 @ref{95a,,OverflowError}。


3.4 新版功能.

@end deffn

@geindex dumps() (在 plistlib 模块中)
@anchor{library/plistlib plistlib dumps}@anchor{888}
@deffn {函数} plistlib.dumps (value, *, fmt=FMT_XML, sort_keys=True, skipkeys=False)

将 @emph{value} 以 plist 格式字节串对象的形式返回。 参阅 @ref{886,,dump()} 的文档获取此函数的关键字参数的说明。


3.4 新版功能.

@end deffn

以下函数已被弃用:

@geindex readPlist() (在 plistlib 模块中)
@anchor{library/plistlib plistlib readPlist}@anchor{479}
@deffn {函数} plistlib.readPlist (pathOrFile)

读取 plist 文件。 @emph{pathOrFile} 可以是文件名或（可读并且为二进制的）文件对象。 返回已解包的根对象（通常是一个字典）。

此函数会调用 @ref{885,,load()} 来完成实际操作，请参阅 @ref{885,,该函数} 的文档获取相应关键字参数的说明。


3.4 版后已移除: 使用 @ref{885,,load()} 来代替。



在 3.7 版更改: 结果中的字典值现在是普通字典。 你不能再使用属性引用形式来访问这些字典中的项。

@end deffn

@geindex writePlist() (在 plistlib 模块中)
@anchor{library/plistlib plistlib writePlist}@anchor{93f}
@deffn {函数} plistlib.writePlist (rootObject, pathOrFile)

将 @emph{rootObject} 写入 XML plist 文件。 @emph{pathOrFile} 可以是文件名或（可写并且为二进制的）文件对象。


3.4 版后已移除: 使用 @ref{886,,dump()} 来代替。

@end deffn

@geindex readPlistFromBytes() (在 plistlib 模块中)
@anchor{library/plistlib plistlib readPlistFromBytes}@anchor{47a}
@deffn {函数} plistlib.readPlistFromBytes (data)

从字节串对象读取 plist 数据。 返回根对象。

参阅 @ref{885,,load()} 获取相应关键字参数的说明。


3.4 版后已移除: 使用 @ref{887,,loads()} 来代替。



在 3.7 版更改: 结果中的字典值现在是普通字典。 你不能再使用属性引用形式来访问这些字典中的项。

@end deffn

@geindex writePlistToBytes() (在 plistlib 模块中)
@anchor{library/plistlib plistlib writePlistToBytes}@anchor{940}
@deffn {函数} plistlib.writePlistToBytes (rootObject)

将 @emph{rootObject} 作为 XML plist 格式的字节串对象返回。


3.4 版后已移除: 使用 @ref{888,,dumps()} 来代替。

@end deffn

可以使用以下的类:

@geindex Data (plistlib 中的类)
@anchor{library/plistlib plistlib Data}@anchor{941}
@deffn {类} plistlib.Data (data)

返回一个包含字节串对象 @emph{data} 的 "data" 包装器对象。 该类将在对 plist 进行双向转换的函数中被用来代表 plist 中可用的 @code{<data>} 类型。

它具有一个属性 @code{data}，可被用来提取其中所保存的 Python 字节串对象。


3.4 版后已移除: 使用 @ref{32a,,bytes} 对象来代替。

@end deffn

@geindex UID (plistlib 中的类)
@anchor{library/plistlib plistlib UID}@anchor{210}
@deffn {类} plistlib.UID (data)

包装一个 @ref{184,,int}。 该类将在读取或写入 NSKeyedArchiver 编码的数据时被使用，其中包含 UID（参见 PList 指南）。

它具有一个属性 @code{data}，可被用来提取 UID 的 int 值。 @code{data} 的取值范围必须为 @cite{0 <= data < 2**64}。


3.8 新版功能.

@end deffn

可以使用以下的常量:

@geindex FMT_XML() (在 plistlib 模块中)
@anchor{library/plistlib plistlib FMT_XML}@anchor{889}
@deffn {数据} plistlib.FMT_XML

用于 plist 文件的 XML 格式。


3.4 新版功能.

@end deffn

@geindex FMT_BINARY() (在 plistlib 模块中)
@anchor{library/plistlib plistlib FMT_BINARY}@anchor{88a}
@deffn {数据} plistlib.FMT_BINARY

用于 plist 文件的二进制格式。


3.4 新版功能.

@end deffn

@menu
* 例子: 例子<8>. 

@end menu

@node 例子<8>,,,plistlib --- 生成与解析 Mac OS X plist 文件
@anchor{library/plistlib examples}@anchor{1e38}
@subsubsection 例子


生成一个 plist:

@example
pl = dict(
    aString = "Doodah",
    aList = ["A", "B", 12, 32.1, [1, 2, 3]],
    aFloat = 0.1,
    anInt = 728,
    aDict = dict(
        anotherString = "<hello & hi there!>",
        aThirdString = "M\xe4ssig, Ma\xdf",
        aTrueValue = True,
        aFalseValue = False,
    ),
    someData = b"<binary gunk>",
    someMoreData = b"<lots of binary gunk>" * 10,
    aDate = datetime.datetime.fromtimestamp(time.mktime(time.gmtime())),
)
with open(fileName, 'wb') as fp:
    dump(pl, fp)
@end example

解析一个 plist:

@example
with open(fileName, 'rb') as fp:
    pl = load(fp)
print(pl["aKey"])
@end example

@node 加密服务,通用操作系统服务,文件格式,Python 标准库
@anchor{library/crypto doc}@anchor{1e39}@anchor{library/crypto crypto}@anchor{1e3a}@anchor{library/crypto cryptographic-services}@anchor{1e3b}
@section 加密服务


@geindex cryptography

本章中描述的模块实现了加密性质的各种算法。 它们可以在安装时自行选择。 在 Unix 系统上，@ref{29,,crypt} 模块也可以使用。 以下是为内容概要：

@menu
* hashlib: hashlib --- 安全哈希与消息摘要. 安全哈希与消息摘要
* hmac: hmac --- 基于密钥的消息验证. 基于密钥的消息验证
* secrets: secrets --- 生成安全随机数字用于管理密码. 生成安全随机数字用于管理密码

@end menu

@node hashlib --- 安全哈希与消息摘要,hmac --- 基于密钥的消息验证,,加密服务
@anchor{library/hashlib doc}@anchor{1e3c}@anchor{library/hashlib hashlib-secure-hashes-and-message-digests}@anchor{1e3d}@anchor{library/hashlib module-hashlib}@anchor{8d}
@subsection @code{hashlib} --- 安全哈希与消息摘要


@geindex hashlib (模块)

@strong{源码：} Lib/hashlib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/hashlib.py}

@geindex message digest@comma{} MD5
@geindex secure hash algorithm@comma{} SHA1@comma{} SHA224@comma{} SHA256@comma{} SHA384@comma{} SHA512

@c import hashlib


__________________________________________________________________


这个模块针对不同的安全哈希和消息摘要算法实现了一个通用的接口。包括 FIPS 的 SHA1, SHA224, SHA256, SHA384, and SHA512 (定义于 FIPS 180-2) 算法，以及 RSA 的 MD5 算法( 定义于 Internet 
@geindex RFC; RFC 1321
RFC 1321@footnote{https://tools.ietf.org/html/rfc1321.html})。术语“安全哈希”和“消息摘要”是可互换的，较旧的算法被称为消息摘要，现代术语是安全哈希。

@cartouche
@quotation 注解 
如果你想找到 adler32 或 crc32 哈希函数，它们在 @ref{144,,zlib} 模块中。
@end quotation
@end cartouche

@cartouche
@quotation 警告 
有些算法已知存在哈希碰撞弱点，请参考最后的“另请参阅”段。
@end quotation
@end cartouche

@menu
* 哈希算法:: 
* SHAKE 可变长度摘要:: 
* 密钥派生:: 
* BLAKE2:: 

@end menu

@node 哈希算法,SHAKE 可变长度摘要,,hashlib --- 安全哈希与消息摘要
@anchor{library/hashlib hash-algorithms}@anchor{1e3e}@anchor{library/hashlib id1}@anchor{1e3f}
@subsubsection 哈希算法


每种类型的 @emph{hash} 都有一个构造器方法。 它们都返回一个具有相同的简单接口的 hash 对象。 例如，使用 use @code{sha256()} 创建一个 SHA-256 hash 对象。 你可以使用 @code{update()} 方法向这个对象输入 @ref{5e3,,字节类对象} (通常是 @ref{32a,,bytes})。 在任何时候你都可以使用 @code{digest()} 或 @code{hexdigest()} 方法获得到目前为止输入这个对象的拼接数据的 @emph{digest}。

@cartouche
@quotation 注解 
为了更好的多线程性能，在对象创建或者更新时，若数据大于2047字节则 Python 的 @ref{be3,,GIL} 会被释放。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
向 @code{update()} 输入字符串对象是不被支持的，因为哈希基于字节而非字符。
@end quotation
@end cartouche

@geindex OpenSSL; (use in module hashlib)

此模块中总是可用的哈希算法构造器有 @code{sha1()}, @code{sha224()}, @code{sha256()}, @code{sha384()}, @code{sha512()}, @ref{547,,blake2b()} 和 @ref{548,,blake2s()}。 @code{md5()} 通常也是可用的，但如果你在使用少见的 "FIPS 兼容" 的 Python 编译版本则可能会找不到它。 此外还可能有一些附加的算法，具体取决于你的平台上的 Python 所使用的 OpenSSL 库。 在大部分平台上可用的还有 @code{sha3_224()}, @code{sha3_256()}, @code{sha3_384()}, @code{sha3_512()}, @code{shake_128()}, @code{shake_256()} 等等。


3.6 新版功能: SHA3 (Keccak) 和 SHAKE 构造器 @code{sha3_224()}, @code{sha3_256()}, @code{sha3_384()}, @code{sha3_512()}, @code{shake_128()}, @code{shake_256()}.



3.6 新版功能: 添加了 @ref{547,,blake2b()} 和 @ref{548,,blake2s()} 。


例如，如果想获取字节串 @code{b'Nobody inspects the spammish repetition'} 的摘要:

@example
>>> import hashlib
>>> m = hashlib.sha256()
>>> m.update(b"Nobody inspects")
>>> m.update(b" the spammish repetition")
>>> m.digest()
b'\x03\x1e\xdd@}Ae\x15\x93\xc5\xfe\\\x00o\xa5u+7\xfd\xdf\xf7\xbcN\x84:\xa6\xaf\x0c\x95\x0fK\x94\x06'
>>> m.digest_size
32
>>> m.block_size
64
@end example

更简要的写法：

@example
>>> hashlib.sha224(b"Nobody inspects the spammish repetition").hexdigest()
'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'
@end example

@geindex new() (在 hashlib 模块中)
@anchor{library/hashlib hashlib new}@anchor{1e40}
@deffn {函数} hashlib.new (name[, data])

一个接受所希望的算法对应的字符串 @emph{name} 作为第一个形参的通用构造器。 它还允许访问上面列出的哈希算法以及你的 OpenSSL 库可能提供的任何其他算法。 同名的构造器要比 @ref{1e40,,new()} 更快所以应当优先使用。
@end deffn

使用 @ref{1e40,,new()} 并附带由 OpenSSL 所提供了算法:

@example
>>> h = hashlib.new('ripemd160')
>>> h.update(b"Nobody inspects the spammish repetition")
>>> h.hexdigest()
'cc4a5ce1b3df48aec5d22d1f16b894a0b894eccc'
@end example

Hashlib 提供下列常量属性：

@geindex algorithms_guaranteed() (在 hashlib 模块中)
@anchor{library/hashlib hashlib algorithms_guaranteed}@anchor{cf5}
@deffn {数据} hashlib.algorithms_guaranteed

一个集合，其中包含此模块在所有平台上都保证支持的哈希算法的名称。 请注意 'md5' 也在此清单中，虽然某些上游厂商提供了一个怪异的排除了此算法的 "FIPS 兼容" Python 编译版本。


3.2 新版功能.

@end deffn

@geindex algorithms_available() (在 hashlib 模块中)
@anchor{library/hashlib hashlib algorithms_available}@anchor{cf6}
@deffn {数据} hashlib.algorithms_available

一个集合，其中包含在所运行的 Python 解释器上可用的哈希算法的名称。 将这些名称传给 @ref{1e40,,new()} 时将可被识别。 @ref{cf5,,algorithms_guaranteed} 将总是它的一个子集。 同样的算法在此集合中可能以不同的名称出现多次（这是 OpenSSL 的原因）。


3.2 新版功能.

@end deffn

下列值会以构造器所返回的哈希对象的常量属性的形式被提供:

@geindex hash.digest_size() (在 hashlib 模块中)
@anchor{library/hashlib hashlib hash digest_size}@anchor{1e41}
@deffn {数据} hash.digest_size

以字节表示的结果哈希对象的大小。
@end deffn

@geindex hash.block_size() (在 hashlib 模块中)
@anchor{library/hashlib hashlib hash block_size}@anchor{1e42}
@deffn {数据} hash.block_size

以字节表示的哈希算法的内部块大小。
@end deffn

hash 对象具有以下属性：

@geindex name (hashlib.hash 属性)
@anchor{library/hashlib hashlib hash name}@anchor{84c}
@deffn {属性} hash.name

此哈希对象的规范名称，总是为小写形式并且总是可以作为 @ref{1e40,,new()} 的形参用来创建另一个此类型的哈希对象。


在 3.4 版更改: 该属性名称自被引入起即存在于 CPython 中，但在 Python 3.4 之前并未正式指明，因此可能不存在于某些平台上。

@end deffn

哈希对象具有下列方法:

@geindex update() (hashlib.hash 方法)
@anchor{library/hashlib hashlib hash update}@anchor{1e43}
@deffn {方法} hash.update (data)

用 @ref{5e3,,bytes-like object} 来更新哈希对象。 重复调用相当于单次调用并传入所有参数的拼接结果: @code{m.update(a); m.update(b)} 等价于 @code{m.update(a+b)}。


在 3.1 版更改: 当使用 OpenSSL 提供的哈希算法在大于 2047 字节的数据上执行哈希更新时 Python GIL 会被释放以允许其他线程运行。

@end deffn

@geindex digest() (hashlib.hash 方法)
@anchor{library/hashlib hashlib hash digest}@anchor{1e44}
@deffn {方法} hash.digest ()

返回当前已传给 @ref{1e43,,update()} 方法的数据摘要。 这是一个大小为 @ref{1e41,,digest_size} 的字节串对象，字节串中可包含 0 至 255 的完整取值范围。
@end deffn

@geindex hexdigest() (hashlib.hash 方法)
@anchor{library/hashlib hashlib hash hexdigest}@anchor{1e45}
@deffn {方法} hash.hexdigest ()

类似于 @ref{1e44,,digest()} 但摘要会以两倍长度字符串对象的形式返回，其中仅包含十六进制数码。 这可以被用于在电子邮件或其他非二进制环境中安全地交换数据值。
@end deffn

@geindex copy() (hashlib.hash 方法)
@anchor{library/hashlib hashlib hash copy}@anchor{1e46}
@deffn {方法} hash.copy ()

返回哈希对象的副本（“克隆”）。 这可被用来高效地计算共享相同初始子串的数据的摘要。
@end deffn

@node SHAKE 可变长度摘要,密钥派生,哈希算法,hashlib --- 安全哈希与消息摘要
@anchor{library/hashlib shake-variable-length-digests}@anchor{1e47}
@subsubsection SHAKE 可变长度摘要


@code{shake_128()} 和 @code{shake_256()} 算法提供安全的 length_in_bits//2 至 128 或 256 位可变长度摘要。 为此，它们的摘要需指定一个长度。 SHAKE 算法不限制最大长度。

@geindex digest() (hashlib.shake 方法)
@anchor{library/hashlib hashlib shake digest}@anchor{fb8}
@deffn {方法} shake.digest (length)

返回当前已传给 @code{update()} 方法的数据摘要。 这是一个大小为 @emph{length} 的字节串对象，字节串中可包含 0 to 255 的完整取值范围。
@end deffn

@geindex hexdigest() (hashlib.shake 方法)
@anchor{library/hashlib hashlib shake hexdigest}@anchor{fb9}
@deffn {方法} shake.hexdigest (length)

类似于 @ref{fb8,,digest()} 但摘要会以两倍长度字符串对象的形式返回，其中仅包含十六进制数码。 这可以被用于在电子邮件或其他非二进制环境中安全地交换数据值。
@end deffn

@node 密钥派生,BLAKE2,SHAKE 可变长度摘要,hashlib --- 安全哈希与消息摘要
@anchor{library/hashlib key-derivation}@anchor{1e48}
@subsubsection 密钥派生


密钥派生和密钥延展算法被设计用于安全密码哈希。 @code{sha1(password)} 这样的简单算法无法防御暴力攻击。 好的密码哈希函数必须可以微调、放慢步调，并且包含 加盐@footnote{https://en.wikipedia.org/wiki/Salt_%28cryptography%29}。

@geindex pbkdf2_hmac() (在 hashlib 模块中)
@anchor{library/hashlib hashlib pbkdf2_hmac}@anchor{7e0}
@deffn {函数} hashlib.pbkdf2_hmac (hash_name, password, salt, iterations, dklen=None)

此函数提供 PKCS#5 基于密码的密钥派生函数 2。 它使用 HMAC 作为伪随机函数。

字符串 @emph{hash_name} 是要求用于 HMAC 的哈希摘要算法的名称，例如 'sha1' 或 'sha256'。 @emph{password} 和 @emph{salt} 会以字节串缓冲区的形式被解析。 应用和库应当将 @emph{password} 限制在合理长度 (例如 1024)。 @emph{salt} 应当为适当来源例如 @ref{4cb,,os.urandom()} 的大约 16 个或更多的字节串数据。

@emph{iterations} 数值应当基于哈希算法和算力来选择。 在 2013 年时，建议至少为 100,000 次 SHA-256 迭代。

@emph{dklen} 为派生密钥的长度。 如果 @emph{dklen} 为 @code{None} 则会使用哈希算法 @emph{hash_name} 的摘要大小，例如 SHA-512 为 64。

@example
>>> import hashlib
>>> dk = hashlib.pbkdf2_hmac('sha256', b'password', b'salt', 100000)
>>> dk.hex()
'0394a2ede332c9a13eb82e9b24631604c31df978b4e2f0fbd2c549944f9d79a5'
@end example


3.4 新版功能.


@cartouche
@quotation 注解 
随同 OpenSSL 提供了一个快速的 @emph{pbkdf2_hmac} 实现。 Python 实现是使用 @ref{8f,,hmac} 的内联版本。 它的速度大约要慢上三倍并且不会释放 GIL。
@end quotation
@end cartouche
@end deffn

@geindex scrypt() (在 hashlib 模块中)
@anchor{library/hashlib hashlib scrypt}@anchor{4cc}
@deffn {函数} hashlib.scrypt (password, *, salt, n, r, p, maxmem=0, dklen=64)

此函数提供基于密码加密的密钥派生函数，其定义参见 
@geindex RFC; RFC 7914
RFC 7914@footnote{https://tools.ietf.org/html/rfc7914.html}。

@emph{password} 和 @emph{salt} 必须为 @ref{5e3,,字节类对象}。 应用和库应当将 @emph{password} 限制在合理长度 (例如 1024)。 @emph{salt} 应当为适当来源例如 @ref{4cb,,os.urandom()} 的大约 16 个或更多的字节串数据。

@emph{n} 为 CPU/内存开销因子，@emph{r} 为块大小，@emph{p} 为并行化因子，@emph{maxmem} 为内存限制 (OpenSSL 1.1.0 默认为 32 MiB)。 @emph{dklen} 为派生密钥的长度。

@ref{12f5,,可用性}: OpenSSL 1.1+。


3.6 新版功能.

@end deffn

@node BLAKE2,,密钥派生,hashlib --- 安全哈希与消息摘要
@anchor{library/hashlib blake2}@anchor{1e49}
@subsubsection BLAKE2


@geindex blake2b@comma{} blake2s

BLAKE2@footnote{https://blake2.net} 是在 
@geindex RFC; RFC 7693
RFC 7693@footnote{https://tools.ietf.org/html/rfc7693.html} 中定义的加密哈希函数，它有两种形式:


@itemize *

@item 
@strong{BLAKE2b}，针对 64 位平台进行优化，并会生成长度介于 1 和 64 字节之间任意大小的摘要。

@item 
@strong{BLAKE2s}，针对 8 至 32 位平台进行优化，并会生成长度介于 1 和 32 字节之间任意大小的摘要。
@end itemize

BLAKE2 支持 @strong{keyed mode} (HMAC@footnote{https://en.wikipedia.org/wiki/Hash-based_message_authentication_code} 的更快速更简单的替代), @strong{salted hashing}, @strong{personalization} 和 @strong{tree hashing}.

此模块的哈希对象遵循标准库 @ref{8d,,hashlib} 对象的 API。

@menu
* 创建哈希对象:: 
* 常量: 常量<5>. 
* 例子: 例子<9>. 
* 开发人员:: 

@end menu

@node 创建哈希对象,常量<5>,,BLAKE2
@anchor{library/hashlib creating-hash-objects}@anchor{1e4a}
@subsubsection 创建哈希对象


新哈希对象可通过调用构造器函数来创建:

@geindex blake2b() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2b}@anchor{547}
@deffn {函数} hashlib.blake2b (data=b'@w{'}, *, digest_size=64, key=b'@w{'}, salt=b'@w{'}, person=b'@w{'}, fanout=1, depth=1, leaf_size=0, node_offset=0, node_depth=0, inner_size=0, last_node=False)
@end deffn

@geindex blake2s() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2s}@anchor{548}
@deffn {函数} hashlib.blake2s (data=b'@w{'}, *, digest_size=32, key=b'@w{'}, salt=b'@w{'}, person=b'@w{'}, fanout=1, depth=1, leaf_size=0, node_offset=0, node_depth=0, inner_size=0, last_node=False)
@end deffn

这些函数返回用于计算 BLAKE2b 或 BLAKE2s 的相应的哈希对象。 它们接受下列可选通用形参:


@itemize *

@item 
@emph{data}: 要哈希的初始数据块，它必须为 @ref{5e3,,bytes-like object}。 它只能作为位置参数传入。

@item 
@emph{digest_size}: 以字节数表示的输出摘要大小。

@item 
@emph{key}: 用于密钥哈希的密钥（对于 BLAKE2b 最长 64 字节，对于 BLAKE2s 最长 32 字节）。

@item 
@emph{salt}: 用于随机哈希的盐值（对于 BLAKE2b 最长 16 字节，对于 BLAKE2s 最长 8 字节）。

@item 
@emph{person}: 个性化字符串（对于 BLAKE2b 最长 16 字节，对于 BLAKE2s 最长 8 字节）。
@end itemize

下表显示了常规参数的限制（以字节为单位）：


@multitable {xxxxxxxxx} {xxxxxxxxxxxxx} {xxxxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxx} 
@headitem

Hash

@tab

目标长度

@tab

长度（键）

@tab

长度（盐）

@tab

长度（个人）

@item

BLAKE2b

@tab

64

@tab

64

@tab

16

@tab

16

@item

BLAKE2s

@tab

32

@tab

32

@tab

8

@tab

8

@end multitable


@cartouche
@quotation 注解 
BLAKE2 规格描述为盐值和个性化形参定义了固定的长度，但是为了方便起见，此实现接受指定在长度以内的任意大小的字节串。 如果形参长度小于指定值，它将以零值进行填充，因此举例来说，@code{b'salt'} 和 @code{b'salt\x00'} 为相同的值 (@emph{key} 的情况则并非如此。)
@end quotation
@end cartouche

如下面的模块 @ref{1e4b,,constants} 所描述，这些是可用的大小取值。

构造器函数还接受下列树形哈希形参:


@itemize *

@item 
@emph{fanout}: 扇出值 (0 至 255，如无限制即为 0，连续模式下为 1)。

@item 
@emph{depth}: 树的最大深度 (1 至 255，如无限制则为 255，连续模式下为 1)。

@item 
@emph{leaf_size}: 叶子的最大字节长度 (0 至 2**32-1，如无限制或在连续模式下则为 0)。

@item 
@emph{node_offset}: 节点偏移量 (对于 BLAKE2b 为 0 至 2**64-1，对于 BLAKE2s 为 0 至 2**48-1，对于最左边第一个叶子或在连续模式下则为 0)。

@item 
@emph{node_depth}: 节点深度 (0 至 255，对于叶子或在连续模式下则为 0)。

@item 
@emph{inner_size}: 内部摘要大小 (对于 BLAKE2b 为 0 至 64，对于 BLAKE2s 为 0 至 32，连续模式下则为 0)。

@item 
@emph{last_node}: 一个布尔值，指明所处理的节点是否为最后一个 (连续模式下则为 @cite{False})。
@end itemize


@float Figure

@image{python-figures/hashlib-blake2-tree,,,Explanation of tree mode parameters.,png}

@end float


请参阅 BLAKE2 规格描述@footnote{https://blake2.net/blake2_20130129.pdf} 第 2.10 节获取有关树形哈希的完整说明。

@node 常量<5>,例子<9>,创建哈希对象,BLAKE2
@anchor{library/hashlib constants}@anchor{1e4b}
@subsubsection 常量


@geindex blake2b.SALT_SIZE() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2b SALT_SIZE}@anchor{1e4c}
@deffn {数据} blake2b.SALT_SIZE
@end deffn

@geindex blake2s.SALT_SIZE() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2s SALT_SIZE}@anchor{1e4d}
@deffn {数据} blake2s.SALT_SIZE
@end deffn

盐值长度（构造器所接受的最大长度）。

@geindex blake2b.PERSON_SIZE() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2b PERSON_SIZE}@anchor{1e4e}
@deffn {数据} blake2b.PERSON_SIZE
@end deffn

@geindex blake2s.PERSON_SIZE() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2s PERSON_SIZE}@anchor{1e4f}
@deffn {数据} blake2s.PERSON_SIZE
@end deffn

个性化字符串长度（构造器所接受的最大长度）。

@geindex blake2b.MAX_KEY_SIZE() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2b MAX_KEY_SIZE}@anchor{1e50}
@deffn {数据} blake2b.MAX_KEY_SIZE
@end deffn

@geindex blake2s.MAX_KEY_SIZE() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2s MAX_KEY_SIZE}@anchor{1e51}
@deffn {数据} blake2s.MAX_KEY_SIZE
@end deffn

最大密钥长度。

@geindex blake2b.MAX_DIGEST_SIZE() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2b MAX_DIGEST_SIZE}@anchor{1e52}
@deffn {数据} blake2b.MAX_DIGEST_SIZE
@end deffn

@geindex blake2s.MAX_DIGEST_SIZE() (在 hashlib 模块中)
@anchor{library/hashlib hashlib blake2s MAX_DIGEST_SIZE}@anchor{1e53}
@deffn {数据} blake2s.MAX_DIGEST_SIZE
@end deffn

哈希函数可输出的最大摘要长度。

@node 例子<9>,开发人员,常量<5>,BLAKE2
@anchor{library/hashlib examples}@anchor{1e54}
@subsubsection 例子


@menu
* 简单哈希:: 
* 使用不同的摘要大小:: 
* 密钥哈希:: 
* 随机哈希:: 
* 个性化:: 
* 树形模式:: 

@end menu

@node 简单哈希,使用不同的摘要大小,,例子<9>
@anchor{library/hashlib simple-hashing}@anchor{1e55}
@subsubsection 简单哈希


要计算某个数据的哈希值，你应该首先通过调用适当的构造器函数 (@ref{547,,blake2b()} 或 @ref{548,,blake2s()}) 来构造一个哈希对象，然后通过在该对象上调用 @code{update()} 来更新目标数据，最后通过调用 @code{digest()} (或针对十六进制编码字符串的 @code{hexdigest()}) 来获取该对象的摘要。

@example
>>> from hashlib import blake2b
>>> h = blake2b()
>>> h.update(b'Hello world')
>>> h.hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'
@end example

作为快捷方式，你可以直接以位置参数的形式向构造器传入第一个数据块来直接更新:

@example
>>> from hashlib import blake2b
>>> blake2b(b'Hello world').hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'
@end example

你可以多次调用 @ref{1e43,,hash.update()} 至你所想要的任意次数以迭代地更新哈希值:

@example
>>> from hashlib import blake2b
>>> items = [b'Hello', b' ', b'world']
>>> h = blake2b()
>>> for item in items:
...     h.update(item)
>>> h.hexdigest()
'6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183'
@end example

@node 使用不同的摘要大小,密钥哈希,简单哈希,例子<9>
@anchor{library/hashlib using-different-digest-sizes}@anchor{1e56}
@subsubsection 使用不同的摘要大小


BLAKE2 具有可配置的摘要大小，对于 BLAKE2b 最多 64 字节，对于 BLAKE2s 最多 32 字节。 例如，要使用 BLAKE2b 来替代 SHA-1 而不改变输出大小，我们可以让 BLAKE2b 产生 20 个字节的摘要:

@example
>>> from hashlib import blake2b
>>> h = blake2b(digest_size=20)
>>> h.update(b'Replacing SHA1 with the more secure function')
>>> h.hexdigest()
'd24f26cf8de66472d58d4e1b1774b4c9158b1f4c'
>>> h.digest_size
20
>>> len(h.digest())
20
@end example

不同摘要大小的哈希对象具有完全不同的输出（较短哈希值 @emph{并非} 较长哈希值的前缀）；即使输出长度相同，BLAKE2b 和 BLAKE2s 也会产生不同的输出:

@example
>>> from hashlib import blake2b, blake2s
>>> blake2b(digest_size=10).hexdigest()
'6fa1d8fcfd719046d762'
>>> blake2b(digest_size=11).hexdigest()
'eb6ec15daf9546254f0809'
>>> blake2s(digest_size=10).hexdigest()
'1bf21a98c78a1c376ae9'
>>> blake2s(digest_size=11).hexdigest()
'567004bf96e4a25773ebf4'
@end example

@node 密钥哈希,随机哈希,使用不同的摘要大小,例子<9>
@anchor{library/hashlib keyed-hashing}@anchor{1e57}
@subsubsection 密钥哈希


密钥哈希可被用于身份验证，作为 基于哈希的消息验证代码@footnote{https://en.wikipedia.org/wiki/Hash-based_message_authentication_code} (HMAC) 的一种更快速更简单的替代。 BLAKE2 可在前缀 MAC 模式下安全地使用，这是由于它从 BLAKE 所继承的不可区分特性。

这个例子演示了如何使用密钥 @code{b'pseudorandom key'} 来为 @code{b'message data'} 获取一个（十六进制编码的）128 位验证代码:

@example
>>> from hashlib import blake2b
>>> h = blake2b(key=b'pseudorandom key', digest_size=16)
>>> h.update(b'message data')
>>> h.hexdigest()
'3d363ff7401e02026f4a4687d4863ced'
@end example

作为实际的例子，一个 Web 应用可为发送给用户的 cookies 进行对称签名，并在之后对其进行验证以确保它们没有被篡改:

@example
>>> from hashlib import blake2b
>>> from hmac import compare_digest
>>>
>>> SECRET_KEY = b'pseudorandomly generated server secret key'
>>> AUTH_SIZE = 16
>>>
>>> def sign(cookie):
...     h = blake2b(digest_size=AUTH_SIZE, key=SECRET_KEY)
...     h.update(cookie)
...     return h.hexdigest().encode('utf-8')
>>>
>>> def verify(cookie, sig):
...     good_sig = sign(cookie)
...     return compare_digest(good_sig, sig)
>>>
>>> cookie = b'user-alice'
>>> sig = sign(cookie)
>>> print("@{0@},@{1@}".format(cookie.decode('utf-8'), sig))
user-alice,b'43b3c982cf697e0c5ab22172d1ca7421'
>>> verify(cookie, sig)
True
>>> verify(b'user-bob', sig)
False
>>> verify(cookie, b'0102030405060708090a0b0c0d0e0f00')
False
@end example

即使存在原生的密钥哈希模式，BLAKE2 也同样可在 @ref{8f,,hmac} 模块的 HMAC 构造过程中使用:

@example
>>> import hmac, hashlib
>>> m = hmac.new(b'secret key', digestmod=hashlib.blake2s)
>>> m.update(b'message')
>>> m.hexdigest()
'e3c8102868d28b5ff85fc35dda07329970d1a01e273c37481326fe0c861c8142'
@end example

@node 随机哈希,个性化,密钥哈希,例子<9>
@anchor{library/hashlib randomized-hashing}@anchor{1e58}
@subsubsection 随机哈希


用户可通过设置 @emph{salt} 形参来为哈希函数引入随机化。 随机哈希适用于防止对数字签名中使用的哈希函数进行碰撞攻击。

@quotation

随机哈希被设计用来处理当一方（消息准备者）要生成由另一方（消息签名者）进行签名的全部或部分消息的情况。 如果消息准备者能够找到加密哈希函数的碰撞现象（即两条消息产生相同的哈希值），则他们就可以准备将产生相同哈希值和数字签名但却具有不同结果的有意义的消息版本（例如向某个账户转入 $1,000,000 而不是 $10）。 加密哈希函数的设计都是以防碰撞性能为其主要目标之一的，但是当前针对加密哈希函数的集中攻击可能导致特定加密哈希函数所提供的防碰撞性能低于预期。 随机哈希为签名者提供了额外的保护，可以降低准备者在数字签名生成过程中使得两条或更多条消息最终产生相同哈希值的可能性 --- 即使为特定哈希函数找到碰撞现象是可行的。 但是，当消息的所有部分均由签名者准备时，使用随机哈希可能降低数字签名所提供的安全性。

(NIST SP-800-106 "数字签名的随机哈希"@footnote{https://csrc.nist.gov/publications/detail/sp/800-106/final})
@end quotation

在 BLAKE2 中，盐值会在初始化期间作为对哈希函数的一次性输入而不是对每个压缩函数的输入来处理。

@cartouche
@quotation 警告 
使用 BLAKE2 或任何其他通用加密哈希函数例如 SHA-256 进行 @emph{加盐哈希} (或纯哈希) 并不适用于哈希密码。 请参阅 BLAKE2 FAQ@footnote{https://blake2.net/#qa} 了解更多信息。
@end quotation
@end cartouche


@example
>>> import os
>>> from hashlib import blake2b
>>> msg = b'some message'
>>> # Calculate the first hash with a random salt.
>>> salt1 = os.urandom(blake2b.SALT_SIZE)
>>> h1 = blake2b(salt=salt1)
>>> h1.update(msg)
>>> # Calculate the second hash with a different random salt.
>>> salt2 = os.urandom(blake2b.SALT_SIZE)
>>> h2 = blake2b(salt=salt2)
>>> h2.update(msg)
>>> # The digests are different.
>>> h1.digest() != h2.digest()
True
@end example

@node 个性化,树形模式,随机哈希,例子<9>
@anchor{library/hashlib personalization}@anchor{1e59}
@subsubsection 个性化


出于不同的目的强制让哈希函数为相同的输入生成不同的摘要有时也是有用的。 正如 Skein 哈希函数的作者所言:

@quotation

我们建议所有应用设计者慎重考虑这种做法；我们已看到有许多协议在协议的某一部分中计算出来的哈希值在另一个完全不同的部分中也可以被使用，因为两次哈希计算是针对类似或相关的数据进行的，这样攻击者可以强制应用为相同的输入生成哈希值。 个性化协议中所使用的每个哈希函数将有效地阻止这种类型的攻击。

(Skein 哈希函数族@footnote{http://www.skein-hash.info/sites/default/files/skein1.3.pdf}, p. 21)
@end quotation

BLAKE2 可通过向 @emph{person} 参数传入字节串来进行个性化:

@example
>>> from hashlib import blake2b
>>> FILES_HASH_PERSON = b'MyApp Files Hash'
>>> BLOCK_HASH_PERSON = b'MyApp Block Hash'
>>> h = blake2b(digest_size=32, person=FILES_HASH_PERSON)
>>> h.update(b'the same content')
>>> h.hexdigest()
'20d9cd024d4fb086aae819a1432dd2466de12947831b75c5a30cf2676095d3b4'
>>> h = blake2b(digest_size=32, person=BLOCK_HASH_PERSON)
>>> h.update(b'the same content')
>>> h.hexdigest()
'cf68fb5761b9c44e7878bfb2c4c9aea52264a80b75005e65619778de59f383a3'
@end example

个性化配合密钥模式也可被用来从单个密钥派生出多个不同密钥。

@example
>>> from hashlib import blake2s
>>> from base64 import b64decode, b64encode
>>> orig_key = b64decode(b'Rm5EPJai72qcK3RGBpW3vPNfZy5OZothY+kHY6h21KM=')
>>> enc_key = blake2s(key=orig_key, person=b'kEncrypt').digest()
>>> mac_key = blake2s(key=orig_key, person=b'kMAC').digest()
>>> print(b64encode(enc_key).decode('utf-8'))
rbPb15S/Z9t+agffno5wuhB77VbRi6F9Iv2qIxU7WHw=
>>> print(b64encode(mac_key).decode('utf-8'))
G9GtHFE1YluXY1zWPlYk1e/nWfu0WSEb0KRcjhDeP/o=
@end example

@node 树形模式,,个性化,例子<9>
@anchor{library/hashlib tree-mode}@anchor{1e5a}
@subsubsection 树形模式


以下是对包含两个叶子节点的最小树进行哈希的例子:

@example
  10
 /  \
00  01
@end example

这个例子使用 64 字节内部摘要，返回 32 字节最终摘要:

@example
>>> from hashlib import blake2b
>>>
>>> FANOUT = 2
>>> DEPTH = 2
>>> LEAF_SIZE = 4096
>>> INNER_SIZE = 64
>>>
>>> buf = bytearray(6000)
>>>
>>> # Left leaf
... h00 = blake2b(buf[0:LEAF_SIZE], fanout=FANOUT, depth=DEPTH,
...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
...               node_offset=0, node_depth=0, last_node=False)
>>> # Right leaf
... h01 = blake2b(buf[LEAF_SIZE:], fanout=FANOUT, depth=DEPTH,
...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
...               node_offset=1, node_depth=0, last_node=True)
>>> # Root node
... h10 = blake2b(digest_size=32, fanout=FANOUT, depth=DEPTH,
...               leaf_size=LEAF_SIZE, inner_size=INNER_SIZE,
...               node_offset=0, node_depth=1, last_node=True)
>>> h10.update(h00.digest())
>>> h10.update(h01.digest())
>>> h10.hexdigest()
'3ad2a9b37c6070e374c7a8c508fe20ca86b6ed54e286e93a0318e95e881db5aa'
@end example

@node 开发人员,,例子<9>,BLAKE2
@anchor{library/hashlib credits}@anchor{1e5b}
@subsubsection 开发人员


BLAKE2@footnote{https://blake2.net} 是由 @emph{Jean-Philippe Aumasson}, @emph{Samuel Neves}, @emph{Zooko Wilcox-O'Hearn} 和 @emph{Christian Winnerlein} 基于 @emph{Jean-Philippe Aumasson}, @emph{Luca Henzen}, @emph{Willi Meier} 和 @emph{Raphael C.-W. Phan} 所创造的 SHA-3@footnote{https://en.wikipedia.org/wiki/NIST_hash_function_competition} 入围方案 BLAKE@footnote{https://131002.net/blake/} 进行设计的。

它使用的核心算法来自由 @emph{Daniel J. Bernstein} 所设计的 ChaCha@footnote{https://cr.yp.to/chacha.html} 加密。

stdlib 实现是基于 pyblake2@footnote{https://pythonhosted.org/pyblake2/} 模块的。 它由 @emph{Dmitry Chestnykh} 在 @emph{Samuel Neves} 所编写的 C 实现的基础上编写。 此文档拷贝自 pyblake2@footnote{https://pythonhosted.org/pyblake2/} 并由 @emph{Dmitry Chestnykh} 撰写。

C 代码由 @emph{Christian Heimes} 针对 Python 进行了部分的重写。

以下公共领域贡献同时适用于 C 哈希函数实现、扩展代码和本文档:

@quotation

在法律许可的范围内，作者已将此软件的全部版权以及关联和邻接权利贡献到全球公共领域。 此软件的发布不附带任何担保。

你应该已收到此软件附带的 CC0 公共领域专属证书的副本。 如果没有，请参阅 @indicateurl{https://creativecommons.org/publicdomain/zero/1.0/}。
@end quotation

根据创意分享公共领域贡献 1.0 通用规范，下列人士为此项目的开发提供了帮助或对公共领域的修改作出了贡献:


@itemize *

@item 
@emph{Alexandr Sokolovskiy}
@end itemize


@subsubheading 参见



@table @asis

@item 模块 @ref{8f,,hmac}

使用哈希运算来生成消息验证代码的模块。

@item 模块 @ref{e,,base64}

针对非二进制环境对二进制哈希值进行编辑的另一种方式。

@item @indicateurl{https://blake2.net}

BLAKE2 官方网站

@item @indicateurl{https://csrc.nist.gov/csrc/media/publications/fips/180/2/archive/2002-08-01/documents/fips180-2.pdf}

有关安全哈希算法的 FIPS 180-2 出版物。

@item @indicateurl{https://en.wikipedia.org/wiki/Cryptographic_hash_function#Cryptographic_hash_algorithms}

包含关于哪些算法存在已知问题以及对其使用所造成的影响的信息的 Wikipedia 文章。

@item @indicateurl{https://www.ietf.org/rfc/rfc2898.txt}

PKCS #5: 基于密码的加密规范描述 2.0 版
@end table


@node hmac --- 基于密钥的消息验证,secrets --- 生成安全随机数字用于管理密码,hashlib --- 安全哈希与消息摘要,加密服务
@anchor{library/hmac doc}@anchor{1e5c}@anchor{library/hmac hmac-keyed-hashing-for-message-authentication}@anchor{1e5d}@anchor{library/hmac module-hmac}@anchor{8f}
@subsection @code{hmac} --- 基于密钥的消息验证


@geindex hmac (模块)

@strong{源代码:} Lib/hmac.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/hmac.py}


__________________________________________________________________


此模块实现了 HMAC 算法，算法的描述参见 
@geindex RFC; RFC 2104
RFC 2104@footnote{https://tools.ietf.org/html/rfc2104.html}。

@geindex new() (在 hmac 模块中)
@anchor{library/hmac hmac new}@anchor{84e}
@deffn {函数} hmac.new (key, msg=None, digestmod='@w{'})

返回一个新的 hmac 对象。 @emph{key} 是一个指定密钥的 bytes 或 bytearray 对象。 如果提供了 @emph{msg}，将会调用 @code{update(msg)} 方法。 @emph{digestmod} 为 HMAC 对象所用的摘要名称、摘要构造器或模块。 它可以是适用于 @ref{1e40,,hashlib.new()} 的任何名称。 虽然该参数位置靠后，但它却是必须的。


在 3.4 版更改: 形参 @emph{key} 可以为 bytes 或 bytearray 对象。 形参 @emph{msg} 可以为 @ref{8d,,hashlib} 所支持的任意类型。 形参 @emph{digestmod} 可以为某种哈希算法的名称。



Deprecated since version 3.4, removed in version 3.8: MD5 作为 @emph{digestmod} 的隐式默认摘要已被弃用。 digestmod 形参现在是必须的。 请将其作为关键字参数传入以避免当你没有初始 msg 时将导致的麻烦。

@end deffn

@geindex digest() (在 hmac 模块中)
@anchor{library/hmac hmac digest}@anchor{388}
@deffn {函数} hmac.digest (key, msg, digest)

基于给定密钥 @emph{key} 和 @emph{digest} 返回 @emph{msg} 的摘要。 此函数等价于 @code{HMAC(key, msg, digest).digest()}，但使用了优化的 C 或内联实现，对放入内存的消息能处理得更快。 形参 @emph{key}, @emph{msg} 和 @emph{digest} 具有与 @ref{84e,,new()} 中相同的含义。

作为 CPython 的实现细节，优化的 C 实现仅当 @emph{digest} 为字符串并且是一个 OpenSSL 所支持的摘要算法的名称时才会被使用。


3.7 新版功能.

@end deffn

HMAC 对象具有下列方法:

@geindex update() (hmac.HMAC 方法)
@anchor{library/hmac hmac HMAC update}@anchor{84f}
@deffn {方法} HMAC.update (msg)

用 @emph{msg} 来更新 hmac 对象。 重复调用相当于单次调用并传入所有参数的拼接结果: @code{m.update(a); m.update(b)} 等价于 @code{m.update(a + b)}。


在 3.4 版更改: 形参 @emph{msg} 可以为 @ref{8d,,hashlib} 所支持的任何类型。

@end deffn

@geindex digest() (hmac.HMAC 方法)
@anchor{library/hmac hmac HMAC digest}@anchor{1e5e}
@deffn {方法} HMAC.digest ()

返回当前已传给 @ref{84f,,update()} 方法的字节串数据的摘要。 这个字节串数据的长度将与传给构造器的摘要的长度 @emph{digest_size} 相同。 它可以包含非 ASCII 的字节，包括 NUL 字节。

@cartouche
@quotation 警告 
在验证例程运行期间将 @ref{388,,digest()} 的输出与外部提供的摘要进行比较时，建议使用 @ref{a07,,compare_digest()} 函数而不是 @code{==} 运算符以减少定时攻击防御力的不足。
@end quotation
@end cartouche
@end deffn

@geindex hexdigest() (hmac.HMAC 方法)
@anchor{library/hmac hmac HMAC hexdigest}@anchor{1e5f}
@deffn {方法} HMAC.hexdigest ()

类似于 @ref{388,,digest()} 但摘要会以两倍长度字符串的形式返回，其中仅包含十六进制数码。 这可以被用于在电子邮件或其他非二进制环境中安全地交换数据值。

@cartouche
@quotation 警告 
在验证例程运行期间将 @ref{1e5f,,hexdigest()} 的输出与外部提供的摘要进行比较时，建议使用 @ref{a07,,compare_digest()} 函数而不是 @code{==} 运算符以减少定时攻击防御力的不足。
@end quotation
@end cartouche
@end deffn

@geindex copy() (hmac.HMAC 方法)
@anchor{library/hmac hmac HMAC copy}@anchor{1e60}
@deffn {方法} HMAC.copy ()

返回 hmac 对象的副本（“克隆）。 这可被用来高效地计算共享相同初始子串的数据的摘要。
@end deffn

hash 对象具有以下属性：

@geindex digest_size (hmac.HMAC 属性)
@anchor{library/hmac hmac HMAC digest_size}@anchor{852}
@deffn {属性} HMAC.digest_size

以字节表示的结果 HMAC 摘要的大小。
@end deffn

@geindex block_size (hmac.HMAC 属性)
@anchor{library/hmac hmac HMAC block_size}@anchor{850}
@deffn {属性} HMAC.block_size

以字节表示的哈希算法的内部块大小。


3.4 新版功能.

@end deffn

@geindex name (hmac.HMAC 属性)
@anchor{library/hmac hmac HMAC name}@anchor{851}
@deffn {属性} HMAC.name

HMAC 的规范名称，总是为小写形式，例如 @code{hmac-md5}。


3.4 新版功能.

@end deffn

这个模块还提供了下列辅助函数:

@geindex compare_digest() (在 hmac 模块中)
@anchor{library/hmac hmac compare_digest}@anchor{a07}
@deffn {函数} hmac.compare_digest (a, b)

返回 @code{a == b}。 此函数使用一种经专门设计的方式通过避免基于内容的短路行为来防止定时分析，使得它适合处理密码。 @emph{a} 和 @emph{b} 必须为相同的类型：或者是 @ref{329,,str} (仅限 ASCII 字符，如 @ref{1e5f,,HMAC.hexdigest()} 的返回值)，或者是 @ref{5e3,,bytes-like object}。

@cartouche
@quotation 注解 
如果 @emph{a} 和 @emph{b} 具有不同的长度，或者如果发生了错误，定时攻击在理论上可以获取有关 @emph{a} 和 @emph{b} 的类型和长度信息 — 但不能获取它们的值。
@end quotation
@end cartouche


3.3 新版功能.

@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{8d,,hashlib}

提供安全哈希函数的 Python 模块。
@end table


@node secrets --- 生成安全随机数字用于管理密码,,hmac --- 基于密钥的消息验证,加密服务
@anchor{library/secrets doc}@anchor{1e61}@anchor{library/secrets module-secrets}@anchor{e4}@anchor{library/secrets secrets-generate-secure-random-numbers-for-managing-secrets}@anchor{1e62}
@subsection @code{secrets} --- 生成安全随机数字用于管理密码


@geindex secrets (模块)


3.6 新版功能.


@c from secrets import *
@c __name__ = '<doctest>'

@strong{源代码:} Lib/secrets.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/secrets.py}


__________________________________________________________________


@ref{e4,,secrets} 模块可用于生成高加密强度的随机数，适应管理密码、账户验证、安全凭据和相关机密数据管理的需要。

特别地，应当优先使用 @ref{e4,,secrets} 来替代 @ref{dc,,random} 模块中默认的伪随机数生成器，后者被设计用于建模和仿真，而不适用于安全和加密。


@subsubheading 参见


@geindex Python 提高建议; PEP 506
PEP 506@footnote{https://www.python.org/dev/peps/pep-0506}


@menu
* 随机数:: 
* 生成凭据:: 
* 其他功能:: 
* 应用技巧与最佳实践:: 

@end menu

@node 随机数,生成凭据,,secrets --- 生成安全随机数字用于管理密码
@anchor{library/secrets random-numbers}@anchor{1e63}
@subsubsection 随机数


通过 @ref{e4,,secrets} 模块可以访问你的操作系统所能提供的最安全的随机性来源。

@geindex SystemRandom (secrets 中的类)
@anchor{library/secrets secrets SystemRandom}@anchor{1e64}
@deffn {类} secrets.SystemRandom

使用操作系统所提供的最高质量源来生成随机数的类。 请参阅 @ref{1a9a,,random.SystemRandom} 了解更多细节。
@end deffn

@geindex choice() (在 secrets 模块中)
@anchor{library/secrets secrets choice}@anchor{1e65}
@deffn {函数} secrets.choice (sequence)

返回从一个非空序列中随机选取的元素。
@end deffn

@geindex randbelow() (在 secrets 模块中)
@anchor{library/secrets secrets randbelow}@anchor{1e66}
@deffn {函数} secrets.randbelow (n)

返回一个 [0, @emph{n}) 范围之内的随机整数。
@end deffn

@geindex randbits() (在 secrets 模块中)
@anchor{library/secrets secrets randbits}@anchor{1e67}
@deffn {函数} secrets.randbits (k)

返回一个具有 @emph{k} 个随机比特位的整数。
@end deffn

@node 生成凭据,其他功能,随机数,secrets --- 生成安全随机数字用于管理密码
@anchor{library/secrets generating-tokens}@anchor{1e68}
@subsubsection 生成凭据


@ref{e4,,secrets} 模块提供了一些生成安全凭据的函数，适用于诸如密码重置、难以猜测的 URL 之类的应用场景。

@geindex token_bytes() (在 secrets 模块中)
@anchor{library/secrets secrets token_bytes}@anchor{1e69}
@deffn {函数} secrets.token_bytes ([nbytes=None])

返回一个包含 @emph{nbytes} 个字节的随机字节串。 如果 @emph{nbytes} 为 @code{None} 或未提供，则会使用一个合理的默认值。

@example
>>> token_bytes(16)  
b'\xebr\x17D*t\xae\xd4\xe3S\xb6\xe2\xebP1\x8b'
@end example
@end deffn

@geindex token_hex() (在 secrets 模块中)
@anchor{library/secrets secrets token_hex}@anchor{1e6a}
@deffn {函数} secrets.token_hex ([nbytes=None])

返回一个十六进制数码形式的随机字符串。 字符串具有 @emph{nbytes} 个随机字节，每个字节转换为两个十六进制数码。 如果 @emph{nbytes} 为 @code{None} 或未提供，则会使用一个合理的默认值。

@example
>>> token_hex(16)  
'f9bf78b9a18ce6d46a0cd2b0b86df9da'
@end example
@end deffn

@geindex token_urlsafe() (在 secrets 模块中)
@anchor{library/secrets secrets token_urlsafe}@anchor{1e6b}
@deffn {函数} secrets.token_urlsafe ([nbytes=None])

返回一个 URL 安全的随机字符串，包含 @emph{nbytes} 个随机字节。 文本将使用 Base64 编码，因此平均来说每个字节将对应 1.3 个结果字符。 如果 @emph{nbytes} 为 @code{None} 或未提供，则会使用一个合理的默认值。

@example
>>> token_urlsafe(16)  
'Drmhze6EPcv0fN_81Bj-nA'
@end example
@end deffn

@menu
* 凭据应当使用多少个字节？:: 

@end menu

@node 凭据应当使用多少个字节？,,,生成凭据
@anchor{library/secrets how-many-bytes-should-tokens-use}@anchor{1e6c}
@subsubsection 凭据应当使用多少个字节？


为了在面对 暴力攻击@footnote{https://en.wikipedia.org/wiki/Brute-force_attack} 时保证安全，凭据必须具有足够的随机性。 不幸的是，对随机性是否足够的标准会随着计算机越来越强大并能够在更短时间内进行更多猜测而不断提高。 在 2015 年时，人们认为 32 字节（256 位）的随机性对于 @ref{e4,,secrets} 模块所适合的典型用例来说是足够的。

作为想要自行管理凭据长度的用户，你可以通过为各种 @code{token_*} 函数指定一个 @ref{184,,int} 参数来显式地指定凭据要使用多大的随机性。 该参数以字节数来表示要使用的随机性大小。

在其他情况下，如果未提供参数，或者如果参数为 @code{None}，则 @code{token_*} 函数将改用一个合理的默认值。

@cartouche
@quotation 注解 
该默认值可能在任何时候被改变，包括在维护版本更新的时候。
@end quotation
@end cartouche

@node 其他功能,应用技巧与最佳实践,生成凭据,secrets --- 生成安全随机数字用于管理密码
@anchor{library/secrets other-functions}@anchor{1e6d}
@subsubsection 其他功能


@geindex compare_digest() (在 secrets 模块中)
@anchor{library/secrets secrets compare_digest}@anchor{1e6e}
@deffn {函数} secrets.compare_digest (a, b)

如果字符串 @emph{a} 与 @emph{b} 相等则返回 @code{True}，否则返回 @code{False}，该处理方式可降低 定时攻击@footnote{https://codahale.com/a-lesson-in-timing-attacks/} 的风险。 请参阅 @ref{a07,,hmac.compare_digest()} 了解更多细节。
@end deffn

@node 应用技巧与最佳实践,,其他功能,secrets --- 生成安全随机数字用于管理密码
@anchor{library/secrets recipes-and-best-practices}@anchor{1e6f}
@subsubsection 应用技巧与最佳实践


本节展示了一些使用 @ref{e4,,secrets} 来管理基本安全级别的应用技巧和最佳实践。

生成长度为八个字符的字母数字密码:

@example
import string
import secrets
alphabet = string.ascii_letters + string.digits
password = '@w{'}.join(secrets.choice(alphabet) for i in range(8))
@end example

@cartouche
@quotation 注解 
应用程序不能 以可恢复的格式存储密码@footnote{http://cwe.mitre.org/data/definitions/257.html}，无论是用纯文本还是加密。 它们应当使用高加密强度的单向（不可恢复）哈希函数来加盐并生成哈希值。
@end quotation
@end cartouche

生成长度为十个字符的字母数字密码，其中包含至少一个小写字母，至少一个大写字母以及至少三个数字:

@example
import string
import secrets
alphabet = string.ascii_letters + string.digits
while True:
    password = '@w{'}.join(secrets.choice(alphabet) for i in range(10))
    if (any(c.islower() for c in password)
            and any(c.isupper() for c in password)
            and sum(c.isdigit() for c in password) >= 3):
        break
@end example

生成 XKCD 风格的密码串@footnote{https://xkcd.com/936/}:

@example
import secrets
# On standard Linux systems, use a convenient dictionary file.
# Other platforms may need to provide their own word-list.
with open('/usr/share/dict/words') as f:
    words = [word.strip() for word in f]
    password = ' '.join(secrets.choice(words) for i in range(4))
@end example

生成难以猜测的临时 URL，其中包含适合密码恢复应用的安全凭据:

@example
import secrets
url = 'https://mydomain.com/reset=' + secrets.token_urlsafe()
@end example

@c # This modeline must appear within the last ten lines of the file.
@c kate: indent-width 3; remove-trailing-space on; replace-tabs on; encoding utf-8;

@node 通用操作系统服务,并发执行,加密服务,Python 标准库
@anchor{library/allos doc}@anchor{1e70}@anchor{library/allos allos}@anchor{1e71}@anchor{library/allos generic-operating-system-services}@anchor{1e72}
@section 通用操作系统服务


本章中描述的各模块提供了在（几乎）所有的操作系统上可用的操作系统特性的接口，例如文件和时钟。这些接口通常以 Unix 或 C 接口为参考对象，不过在大多数其他系统上也可用。这里有一个概述：

@menu
* os: os --- 多种操作系统接口. 多种操作系统接口
* io: io --- 处理流的核心工具. 处理流的核心工具
* time: time --- 时间的访问和转换. 时间的访问和转换
* argparse: argparse --- 命令行选项、参数和子命令解析器. 命令行选项、参数和子命令解析器
* getopt: getopt --- C 风格的命令行选项解析器. C 风格的命令行选项解析器
* logging: logging --- Python 的日志记录工具. Python 的日志记录工具
* logging.config: logging config --- 日志记录配置. 日志记录配置
* logging.handlers: logging handlers --- 日志处理. 日志处理
* getpass: getpass --- 便携式密码输入工具. 便携式密码输入工具
* curses: curses --- 终端字符单元显示的处理. 终端字符单元显示的处理
* curses.textpad: curses textpad --- Text input widget for curses programs. Text input widget for curses programs
* curses.ascii: curses ascii --- Utilities for ASCII characters. Utilities for ASCII characters
* curses.panel: curses panel --- A panel stack extension for curses. A panel stack extension for curses
* platform: platform --- 获取底层平台的标识数据. 获取底层平台的标识数据
* errno: errno --- 标准 errno 系统符号. 标准 errno 系统符号
* ctypes: ctypes --- Python 的外部函数库. Python 的外部函数库

@end menu

@node os --- 多种操作系统接口,io --- 处理流的核心工具,,通用操作系统服务
@anchor{library/os doc}@anchor{1e73}@anchor{library/os module-os}@anchor{c4}@anchor{library/os os-miscellaneous-operating-system-interfaces}@anchor{1e74}
@subsection @code{os} --- 多种操作系统接口


@geindex os (模块)

@strong{源代码：} Lib/os.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/os.py}


__________________________________________________________________


本模块提供了一种使用与操作系统相关的功能的便捷式途径。 如果你只是想读写一个文件，请参阅 @ref{4ea,,open()}，如果你想操作文件路径，请参阅 @ref{c5,,os.path} 模块，如果你想读取通过命令行给出的所有文件中的所有行，请参阅 @ref{80,,fileinput} 模块。 为了创建临时文件和目录，请参阅 @ref{103,,tempfile} 模块，对于高级文件和目录处理，请参阅 @ref{e9,,shutil} 模块。

关于这些函数的适用性的说明：


@itemize *

@item 
Python中所有依赖于操作系统的内置模块的设计都是这样，只要不同的操作系统某一相同的功能可用，它就使用相同的接口。例如，函数 @code{os.stat(path)} 以相同的格式返回关于 @emph{path} 的状态信息（该格式源于 POSIX 接口）。

@item 
特定于某一操作系统的扩展通过操作 @ref{c4,,os} 模块也是可用的，但是使用它们当然是对可移植性的一种威胁。

@item 
所有接受路径或文件名的函数都同时支持字节串和字符串对象，并在返回路径或文件名时使用相应类型的对象作为结果。

@item 
在 VxWorks 系统上，os.fork, os.execv 和 os.spawn*p* 不被支持。
@end itemize

@cartouche
@quotation 注解 
如果使用无效或无法访问的文件名与路径，或者其他类型正确但操作系统不接受的参数，此模块的所有函数都抛出 @ref{1d3,,OSError} （或者它的子类）。
@end quotation
@end cartouche

@geindex error
@anchor{library/os os error}@anchor{1e75}
@deffn {例外} os.error

内建的 @ref{1d3,,OSError} 异常的一个别名。
@end deffn

@geindex name() (在 os 模块中)
@anchor{library/os os name}@anchor{1e76}
@deffn {数据} os.name

导入的依赖特定操作系统的模块的名称。以下名称目前已注册: @code{'posix'}, @code{'nt'}, @code{'java'}.


@subsubheading 参见


@ref{2b1,,sys.platform} 有更详细的描述. @ref{a58,,os.uname()} 只给出系统提供的版本信息。

@ref{ce,,platform} 模块对系统的标识有更详细的检查。

@end deffn
@anchor{library/os os-filenames}@anchor{1daa}
@menu
* 文件名，命令行参数，以及环境变量。:: 
* 进程参数:: 
* 创建文件对象:: 
* 文件描述符操作:: 
* 文件和目录:: 
* 进程管理:: 
* 调度器接口:: 
* 其他系统信息:: 
* 随机数: 随机数<2>. 

@end menu

@node 文件名，命令行参数，以及环境变量。,进程参数,,os --- 多种操作系统接口
@anchor{library/os file-names-command-line-arguments-and-environment-variables}@anchor{1e77}@anchor{library/os filesystem-encoding}@anchor{1e78}
@subsubsection 文件名，命令行参数，以及环境变量。


在 Python 中，使用字符串类型表示文件名、命令行参数和环境变量。 在某些系统上，在将这些字符串传递给操作系统之前，必须将这些字符串解码为字节。 Python 使用文件系统编码来执行此转换（请参阅 @ref{4f0,,sys.getfilesystemencoding()} ）。


在 3.1 版更改: 在某些系统上，使用文件系统编码进行转换可能会失败。 在这种情况下，Python 会使用 @ref{17dd,,代理转义编码错误处理器}，这意味着在解码时，不可解码的字节被 Unicode 字符 U+DCxx 替换，并且这些字节在编码时再次转换为原始字节。


文件系统编码必须保证成功解码小于 128 的所有字节。如果文件系统编码无法提供此保证， API 函数可能会引发 UnicodeErrors 。

@node 进程参数,创建文件对象,文件名，命令行参数，以及环境变量。,os --- 多种操作系统接口
@anchor{library/os os-procinfo}@anchor{1e79}@anchor{library/os process-parameters}@anchor{1e7a}
@subsubsection 进程参数


这些函数和数据项提供了操作当前进程和用户的信息。

@geindex ctermid() (在 os 模块中)
@anchor{library/os os ctermid}@anchor{1e7b}
@deffn {函数} os.ctermid ()

返回与进程控制终端对应的文件名。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex environ() (在 os 模块中)
@anchor{library/os os environ}@anchor{b30}
@deffn {数据} os.environ

一个表示字符串环境的 @ref{b32,,mapping} 对象。 例如，@code{environ['HOME']} 是你的主目录（在某些平台上）的路径名，相当于 C 中的 @code{getenv("HOME")}。

这个映射是在第一次导入 @ref{c4,,os} 模块时捕获的，通常作为 Python 启动时处理 @code{site.py} 的一部分。除了通过直接修改 @code{os.environ} 之外，在此之后对环境所做的更改不会反映在 @code{os.environ} 中。

如果平台支持 @ref{1e7c,,putenv()} 函数，这个映射除了可以用于查询环境外还能用于修改环境。 当这个映射被修改时，@ref{1e7c,,putenv()} 将被自动调用。

在Unix系统上，键和值会使用 @ref{4f0,,sys.getfilesystemencoding()} 和 @code{'surrogateescape'} 的错误处理。如果你想使用其他的编码，使用 @ref{b8d,,environb}。

@cartouche
@quotation 注解 
直接调用 @ref{1e7c,,putenv()} 并不会影响  @code{os.environ}，所以推荐直接修改 @code{os.environ}。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
在某些平台上，包括 FreeBSD 和 Mac OS X，设置 @code{environ} 可能导致内存泄露。参阅 @code{putenv()} 的系统文档。
@end quotation
@end cartouche

如果平台没有提供 @ref{1e7c,,putenv()}, 为了使启动的子进程使用修改后的环境，一份修改后的映射会被传给合适的进程创建函数。

如果平台支持 @ref{d3c,,unsetenv()} 函数，你可以通过删除映射中元素的方式来删除对应的环境变量。当一个元素被从 @code{os.environ} 删除时，以及 @code{pop()} 或 @code{clear()} 被调用时， @ref{d3c,,unsetenv()} 会被自动调用。
@end deffn

@geindex environb() (在 os 模块中)
@anchor{library/os os environb}@anchor{b8d}
@deffn {数据} os.environb

字节版本的 @ref{b30,,environ}: 一个以字节串表示环境的 @ref{b32,,mapping} 对象。 @ref{b30,,environ} 和 @ref{b8d,,environb} 是同步的（修改 @ref{b8d,,environb} 会更新 @ref{b30,,environ}，反之亦然）。

只有在 @ref{b8b,,supports_bytes_environ} 为 @code{True} 的时候 @ref{b8d,,environb} 才是可用的。


3.2 新版功能.

@end deffn


@deffn {函数} os.chdir (path)

@deffnx {函数} os.fchdir (fd)

@deffnx {函数} os.getcwd ()

以上函数请参阅 @ref{1e7d,,文件和目录} 。
@end deffn

@geindex fsencode() (在 os 模块中)
@anchor{library/os os fsencode}@anchor{4e9}
@deffn {函数} os.fsencode (filename)

编码 @ref{363,,路径类} @emph{文件名} 为文件系统接受的形式，使用 @code{'surrogateescape'} 代理转义编码错误处理器，在Windows系统上会使用 @code{'strict'} ；返回 @ref{32a,,bytes} 字节类型不变。

@ref{4e8,,fsdecode()} 是此函数的逆向函数。


3.2 新版功能.



在 3.6 版更改: 增加对实现了 @ref{4e5,,os.PathLike} 接口的对象的支持。

@end deffn

@geindex fsdecode() (在 os 模块中)
@anchor{library/os os fsdecode}@anchor{4e8}
@deffn {函数} os.fsdecode (filename)

从文件系统编码方式解码为 @ref{363,,路径类} 文件名，使用 @code{'surrogateescape'} 代理转义编码错误处理器，在Windows系统上会使用 @code{'strict'} ；返回 @ref{329,,str} 字符串不变。

@ref{4e9,,fsencode()} 是此函数的逆向函数。


3.2 新版功能.



在 3.6 版更改: 增加对实现了 @ref{4e5,,os.PathLike} 接口的对象的支持。

@end deffn

@geindex fspath() (在 os 模块中)
@anchor{library/os os fspath}@anchor{4e7}
@deffn {函数} os.fspath (path)

返回路径的文件系统表示。

如果传入的是 @ref{329,,str} 或 @ref{32a,,bytes} 类型的字符串，将原样返回。否则 @ref{4e6,,__fspath__()} 将被调用，如果得到的是一个 @ref{329,,str} 或 @ref{32a,,bytes} 类型的对象，那就返回这个值。其他所有情况则会抛出 @ref{192,,TypeError}  异常。


3.6 新版功能.

@end deffn

@geindex PathLike (os 中的类)
@anchor{library/os os PathLike}@anchor{4e5}
@deffn {类} os.PathLike

某些对象用于表示文件系统中的路径（如 @ref{fd4,,pathlib.PurePath} 对象），本类是这些对象的 @ref{b2c,,抽象基类}。


3.6 新版功能.


@geindex __fspath__() (os.PathLike 方法)
@anchor{library/os os PathLike __fspath__}@anchor{4e6}
@deffn {方法} abstractmethod __fspath__ ()

返回当前对象的文件系统表示。

这个方法只应该返回一个 @ref{329,,str} 字符串或 @ref{32a,,bytes} 字节串，请优先选择 @ref{329,,str} 字符串。
@end deffn
@end deffn

@geindex getenv() (在 os 模块中)
@anchor{library/os os getenv}@anchor{1e7e}
@deffn {函数} os.getenv (key, default=None)

如果存在，返回环境变量 @emph{key} 的值，否则返回 @emph{default}。 @emph{key} ， @emph{default} 和返回值均为 str 字符串类型。

在Unix系统上，键和值会使用 @ref{4f0,,sys.getfilesystemencoding()} 和`@w{`}'surrogateescape'`@w{`} 错误处理进行解码。如果你想使用其他的编码，使用 @ref{b8c,,os.getenvb()}。

@ref{12f5,,可用性}: 大部分的Unix系统，Windows。
@end deffn

@geindex getenvb() (在 os 模块中)
@anchor{library/os os getenvb}@anchor{b8c}
@deffn {函数} os.getenvb (key, default=None)

如果存在环境变量 @emph{key} 那么返回其值，否则返回 @emph{default}。 @emph{key} ， @emph{default} 和返回值均为bytes字节串类型。

@ref{b8c,,getenvb()} 仅在 @ref{b8b,,supports_bytes_environ} 为 @code{True} 时可用。

@ref{12f5,,可用性}: 大部分的Unix系统。


3.2 新版功能.

@end deffn

@geindex get_exec_path() (在 os 模块中)
@anchor{library/os os get_exec_path}@anchor{1e7f}
@deffn {函数} os.get_exec_path (env=None)

返回将用于搜索可执行文件的目录列表，与在外壳程序中启动一个进程时相似。指定的 @emph{env} 应为用于搜索 PATH 的环境变量字典。默认情况下，当 @emph{env} 为 @code{None} 时，将会使用 @ref{b30,,environ} 。


3.2 新版功能.

@end deffn

@geindex getegid() (在 os 模块中)
@anchor{library/os os getegid}@anchor{1e80}
@deffn {函数} os.getegid ()

返回当前进程的有效组ID。对应当前进程执行文件的 "set id" 位。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex geteuid() (在 os 模块中)
@anchor{library/os os geteuid}@anchor{1e81}
@deffn {函数} os.geteuid ()

@geindex user; effective id

返回当前进程的有效用户ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex getgid() (在 os 模块中)
@anchor{library/os os getgid}@anchor{1e82}
@deffn {函数} os.getgid ()

@geindex process; group

返回当前进程的实际组ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex getgrouplist() (在 os 模块中)
@anchor{library/os os getgrouplist}@anchor{a56}
@deffn {函数} os.getgrouplist (user, group)

返回该用户所在的组 ID 列表。可能 @emph{group} 参数没有在返回的列表中，实际上用户应该也是属于该 @emph{group}。@emph{group} 参数一般可以从储存账户信息的密码记录文件中找到。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex getgroups() (在 os 模块中)
@anchor{library/os os getgroups}@anchor{1e83}
@deffn {函数} os.getgroups ()

返回当前进程关联的附加组ID列表

@ref{12f5,,可用性}: Unix。

@cartouche
@quotation 注解 
在Mac OS X系统中，@ref{1e83,,getgroups()} 会和其他 Unix 平台有些不同。如果 Python 解释器是在 @code{10.5} 或更早版本中部署，@ref{1e83,,getgroups()} 返回当前用户进程相关的有效组ID列表。 该列表长度由于系统预设的接口限制，最长为 16。 而且在适当的权限下，返回结果还会因 @ref{1e83,,getgroups()} 而发生变化；如果 Python 解释器是在 @code{10.5} 以上版本中部署，@ref{1e83,,getgroups()} 返回进程所属有效用户 ID 所对应的用户的组 ID 列表，组用户列表可能因为进程的生存周期而发生变动，而且也不会因为 @ref{1e84,,setgroups()} 的调用而发生，返回的组用户列表长度也没有长度 16 的限制。在部署中，Python 解释器用到的变量 @code{MACOSX_DEPLOYMENT_TARGET} 可以用 @ref{95e,,sysconfig.get_config_var()}。
@end quotation
@end cartouche
@end deffn

@geindex getlogin() (在 os 模块中)
@anchor{library/os os getlogin}@anchor{1e85}
@deffn {函数} os.getlogin ()

返回通过控制终端进程进行登录的用户名。在多数情况下，使用 @ref{1e86,,getpass.getuser()} 会更有效，因为后者会通过检查环境变量 
@geindex LOGNAME
@geindex 环境变量; LOGNAME
@code{LOGNAME} 或 
@geindex USERNAME
@geindex 环境变量; USERNAME
@code{USERNAME} 来查找用户，再由 @code{pwd.getpwuid(os.getuid())[0]} 来获取当前用户 ID 的登录名。

@ref{12f5,,可用性}: Unix, Windows。
@end deffn

@geindex getpgid() (在 os 模块中)
@anchor{library/os os getpgid}@anchor{1e87}
@deffn {函数} os.getpgid (pid)

根据进程id @emph{pid} 返回进程的组 ID 列表。如果 @emph{pid} 为 0，则返回当前进程的进程组 ID 列表

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex getpgrp() (在 os 模块中)
@anchor{library/os os getpgrp}@anchor{1e88}
@deffn {函数} os.getpgrp ()

@geindex process; group

返回当时进程组的ID

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex getpid() (在 os 模块中)
@anchor{library/os os getpid}@anchor{1e89}
@deffn {函数} os.getpid ()

@geindex process; id

返回当前进程ID
@end deffn

@geindex getppid() (在 os 模块中)
@anchor{library/os os getppid}@anchor{1e8a}
@deffn {函数} os.getppid ()

@geindex process; id of parent

返回父进程ID。当父进程已经结束，在Unix中返回的ID是初始进程(1)中的一个，在Windows中仍然是同一个进程ID，该进程ID有可能已经被进行进程所占用。

@ref{12f5,,可用性}: Unix, Windows。


在 3.2 版更改: 添加WIndows的支持。

@end deffn

@geindex getpriority() (在 os 模块中)
@anchor{library/os os getpriority}@anchor{a41}
@deffn {函数} os.getpriority (which, who)

@geindex process; scheduling priority

获取程序调度优先级。@emph{which} 参数值可以是 @ref{1e8b,,PRIO_PROCESS}，@ref{1e8c,,PRIO_PGRP}，或 @ref{1e8d,,PRIO_USER} 中的一个，@emph{who} 是相对于 @emph{which} (@ref{1e8b,,PRIO_PROCESS} 的进程标识符，@ref{1e8c,,PRIO_PGRP} 的进程组标识符和 @ref{1e8d,,PRIO_USER} 的用户ID)。当 @emph{who} 为 0 时（分别）表示调用的进程，调用进程的进程组或调用进程所属的真实用户 ID。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex PRIO_PROCESS() (在 os 模块中)
@geindex PRIO_PGRP() (在 os 模块中)
@geindex PRIO_USER() (在 os 模块中)
@anchor{library/os os PRIO_PROCESS}@anchor{1e8b}
@deffn {数据} os.PRIO_PROCESS
@anchor{library/os os PRIO_PGRP}@anchor{1e8c}
@deffnx {数据} os.PRIO_PGRP
@anchor{library/os os PRIO_USER}@anchor{1e8d}
@deffnx {数据} os.PRIO_USER

函数 @ref{a41,,getpriority()} 和 @ref{a42,,setpriority()} 的参数。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex getresuid() (在 os 模块中)
@anchor{library/os os getresuid}@anchor{ca4}
@deffn {函数} os.getresuid ()

返回一个由 (ruid, euid, suid) 所组成的元组，分别表示当前进程的真实用户ID，有效用户ID和暂存用户ID。

@ref{12f5,,可用性}: Unix。


3.2 新版功能.

@end deffn

@geindex getresgid() (在 os 模块中)
@anchor{library/os os getresgid}@anchor{ca3}
@deffn {函数} os.getresgid ()

返回一个由 (rgid, egid, sgid) 所组成的元组，分别表示当前进程的真实组ID，有效组ID和暂存组ID。

@ref{12f5,,可用性}: Unix。


3.2 新版功能.

@end deffn

@geindex getuid() (在 os 模块中)
@anchor{library/os os getuid}@anchor{1e8e}
@deffn {函数} os.getuid ()

@geindex user; id

返回当前进程的真实用户ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex initgroups() (在 os 模块中)
@anchor{library/os os initgroups}@anchor{ca7}
@deffn {函数} os.initgroups (username, gid)

调用系统 initgroups()，使用指定用户所在的所有值来初始化组访问列表，包括指定的组ID。

@ref{12f5,,可用性}: Unix。


3.2 新版功能.

@end deffn

@geindex putenv() (在 os 模块中)
@anchor{library/os os putenv}@anchor{1e7c}
@deffn {函数} os.putenv (key, value)

@geindex environment variables; setting

将名为 @emph{key} 的环境变量值设置为 @emph{value}。该变量名修改会影响由 @ref{dba,,os.system()}， @ref{2a9,,popen()} ，@ref{95b,,fork()} 和 @ref{1e8f,,execv()} 发起的子进程。

@ref{12f5,,可用性}: 大部分的Unix系统，Windows。

@cartouche
@quotation 注解 
在一些平台，包括 FreeBSD 和 Mac OS X，设置 @code{environ} 可能导致内存泄露。详情参考 putenv 相关系统文档。
@end quotation
@end cartouche

当系统支持 @ref{1e7c,,putenv()} 时，@code{os.environ} 中的参数赋值会自动转换为对 @ref{1e7c,,putenv()} 的调用。不过 @ref{1e7c,,putenv()} 的调用不会更新 @code{os.environ}，因此最好使用 @code{os.environ} 对变量赋值。

引发一个 @ref{12d0,,审计事件} @code{os.putenv}，附带参数 @code{key}, @code{value}。
@end deffn

@geindex setegid() (在 os 模块中)
@anchor{library/os os setegid}@anchor{1e90}
@deffn {函数} os.setegid (egid)

设置当前进程的有效组ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex seteuid() (在 os 模块中)
@anchor{library/os os seteuid}@anchor{1e91}
@deffn {函数} os.seteuid (euid)

设置当前进程的有效用户ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex setgid() (在 os 模块中)
@anchor{library/os os setgid}@anchor{1e92}
@deffn {函数} os.setgid (gid)

设置当前进程的组ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex setgroups() (在 os 模块中)
@anchor{library/os os setgroups}@anchor{1e84}
@deffn {函数} os.setgroups (groups)

将 @emph{group} 参数值设置为与当进程相关联的附加组ID列表。@emph{group} 参数必须为一个序列，每个元素应为每个组的数字ID。该操作通常只适用于超级用户。

@ref{12f5,,可用性}: Unix。

@cartouche
@quotation 注解 
在 Mac OS X 中，@emph{groups} 的长度不能超过系统定义的最大有效组 ID 个数，一般为 16。 如果它没有返回与调用 setgroups() 所设置的相同的组列表，请参阅 @ref{1e83,,getgroups()} 的文档。
@end quotation
@end cartouche
@end deffn

@geindex setpgrp() (在 os 模块中)
@anchor{library/os os setpgrp}@anchor{1e93}
@deffn {函数} os.setpgrp ()

根据已实现的版本（如果有）来调用系统 @code{setpgrp()} 或 @code{setpgrp(0, 0)} 。相关说明，请参考 Unix 手册。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex setpgid() (在 os 模块中)
@anchor{library/os os setpgid}@anchor{1e94}
@deffn {函数} os.setpgid (pid, pgrp)

使用系统调用 @code{setpgid()}，将 @emph{pid} 对应进程的组ID设置为 @emph{pgrp}。相关说明，请参考 Unix 手册。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex setpriority() (在 os 模块中)
@anchor{library/os os setpriority}@anchor{a42}
@deffn {函数} os.setpriority (which, who, priority)

@geindex process; scheduling priority

设置程序调度优先级。 @emph{which} 的值为 @ref{1e8b,,PRIO_PROCESS}, @ref{1e8c,,PRIO_PGRP} 或 @ref{1e8d,,PRIO_USER} 之一，而 @emph{who} 会相对于 @emph{which} (@ref{1e8b,,PRIO_PROCESS} 的进程标识符, @ref{1e8c,,PRIO_PGRP} 的进程组标识符和 @ref{1e8d,,PRIO_USER} 的用户 ID) 被解析。 @emph{who} 值为零 (分别) 表示调用进程，调用进程的进程组或调用进程的真实用户 ID。 @emph{priority} 是范围在 -20 至 19 的值。 默认优先级为 0；较小的优先级数值会更优先被调度。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex setregid() (在 os 模块中)
@anchor{library/os os setregid}@anchor{1e95}
@deffn {函数} os.setregid (rgid, egid)

设置当前进程的真实和有效组ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex setresgid() (在 os 模块中)
@anchor{library/os os setresgid}@anchor{ca5}
@deffn {函数} os.setresgid (rgid, egid, sgid)

设置当前进程的真实，有效和暂存组ID。

@ref{12f5,,可用性}: Unix。


3.2 新版功能.

@end deffn

@geindex setresuid() (在 os 模块中)
@anchor{library/os os setresuid}@anchor{ca6}
@deffn {函数} os.setresuid (ruid, euid, suid)

设置当前进程的真实，有效和暂存用户ID。

@ref{12f5,,可用性}: Unix。


3.2 新版功能.

@end deffn

@geindex setreuid() (在 os 模块中)
@anchor{library/os os setreuid}@anchor{1e96}
@deffn {函数} os.setreuid (ruid, euid)

设置当前进程的真实和有效用户ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex getsid() (在 os 模块中)
@anchor{library/os os getsid}@anchor{1e97}
@deffn {函数} os.getsid (pid)

调用系统调用 @code{getsid()}。相关说明，请参考 Unix 手册。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex setsid() (在 os 模块中)
@anchor{library/os os setsid}@anchor{ebd}
@deffn {函数} os.setsid ()

使用系统调用 @code{getsid()}。相关说明，请参考 Unix 手册。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex setuid() (在 os 模块中)
@anchor{library/os os setuid}@anchor{1e98}
@deffn {函数} os.setuid (uid)

@geindex user; id@comma{} setting

设置当前进程的用户ID。

@ref{12f5,,可用性}: Unix。
@end deffn

@c placed in this section since it relates to errno.... a little weak

@geindex strerror() (在 os 模块中)
@anchor{library/os os strerror}@anchor{1e99}
@deffn {函数} os.strerror (code)

根据 @emph{code} 中的错误码返回错误消息。 在某些平台上当给出未知错误码时 @code{strerror()} 将返回 @code{NULL} 并会引发 @ref{1fb,,ValueError}。
@end deffn

@geindex supports_bytes_environ() (在 os 模块中)
@anchor{library/os os supports_bytes_environ}@anchor{b8b}
@deffn {数据} os.supports_bytes_environ

如果操作系统上原生环境类型是字节型则为 @code{True} (例如在 Windows 上为 @code{False})。


3.2 新版功能.

@end deffn

@geindex umask() (在 os 模块中)
@anchor{library/os os umask}@anchor{1e9a}
@deffn {函数} os.umask (mask)

设定当前数值掩码并返回之前的掩码。
@end deffn

@geindex uname() (在 os 模块中)
@anchor{library/os os uname}@anchor{a58}
@deffn {函数} os.uname ()

@geindex gethostname() (in module socket)
@geindex gethostbyaddr() (in module socket)

返回当前操作系统的识别信息。返回值是一个有5个属性的对象：


@itemize *

@item 
@code{sysname} - 操作系统名

@item 
@code{nodename} - 机器在网络上的名称（需要先设定）

@item 
@code{release} - 操作系统发行信息

@item 
@code{version} - 操作系统版本信息

@item 
@code{machine} - 硬件标识符
@end itemize

为了向后兼容，该对象也是可迭代的，像是一个按照 @code{sysname}，@code{nodename}，@code{release}，@code{version}，和 @code{machine} 顺序组成的元组。

有些系统会将 @code{nodename} 截短为 8 个字符或截短至前缀部分；获取主机名的一个更好方式是 @ref{1e9b,,socket.gethostname()}  或甚至可以用 @code{socket.gethostbyaddr(socket.gethostname())}。

@ref{12f5,,可用性}: 较新的 Unix 版本。


在 3.3 版更改: 返回结果的类型由元组变成一个类似元组的对象，同时具有命名的属性。

@end deffn

@geindex unsetenv() (在 os 模块中)
@anchor{library/os os unsetenv}@anchor{d3c}
@deffn {函数} os.unsetenv (key)

@geindex environment variables; deleting

取消设置（删除）名为 @emph{key} 的环境变量。变量名的改变会影响由 @ref{dba,,os.system()}，@ref{2a9,,popen()}，@ref{95b,,fork()} 和 @ref{1e8f,,execv()} 触发的子进程。

当系统支持 @ref{d3c,,unsetenv()} ，删除在 @code{os.environ} 中的变量会自动转换为对 @ref{d3c,,unsetenv()} 的调用。但是 @ref{d3c,,unsetenv()} 不能更新 @code{os.environ}，因此最好直接删除 @code{os.environ} 中的变量。

引发一个 @ref{12d0,,审计事件} @code{os.unsetenv}，附带参数 @code{key}。

@ref{12f5,,可用性}: 大部分的Unix系统。
@end deffn

@node 创建文件对象,文件描述符操作,进程参数,os --- 多种操作系统接口
@anchor{library/os file-object-creation}@anchor{1e9c}@anchor{library/os os-newstreams}@anchor{1e9d}
@subsubsection 创建文件对象


这些函数创建新的 @ref{b3b,,file objects} 。（参见 @ref{65f,,open()} 以获取打开文件描述符的相关信息。）

@geindex fdopen() (在 os 模块中)
@anchor{library/os os fdopen}@anchor{13c9}
@deffn {函数} os.fdopen (fd, *args, **kwargs)

返回打开文件描述符 @emph{fd} 对应文件的对象。类似内建 @ref{4ea,,open()} 函数，二者接受同样的参数。不同之处在于 @ref{13c9,,fdopen()} 第一个参数应该为整数。
@end deffn

@node 文件描述符操作,文件和目录,创建文件对象,os --- 多种操作系统接口
@anchor{library/os file-descriptor-operations}@anchor{1e9e}@anchor{library/os os-fd-ops}@anchor{1e9f}
@subsubsection 文件描述符操作


这些函数对文件描述符所引用的 I/O 流进行操作。

文件描述符是一些小的整数，对应于当前进程所打开的文件。例如，标准输入的文件描述符通常是0，标准输出是1，标准错误是2。之后被进程打开的文件的文件描述符会被依次指定为3，4，5等。“文件描述符”这个词有点误导性，在 Unix 平台中套接字和管道也被文件描述符所引用。

当需要时，可以用 @ref{1ea0,,fileno()} 可以获得 @ref{b3b,,file object} 所对应的文件描述符。需要注意的是，直接使用文件描述符会绕过文件对象的方法，会忽略如数据内部缓冲等情况。

@geindex close() (在 os 模块中)
@anchor{library/os os close}@anchor{3ca}
@deffn {函数} os.close (fd)

关闭文件描述符 @emph{fd}。

@cartouche
@quotation 注解 
该功能适用于低级 I/O 操作，必须用于 @ref{65f,,os.open()} 或 @ref{1ea1,,pipe()} 返回的文件描述符。若要关闭由内建函数 @ref{4ea,,open()}、@ref{2a9,,popen()} 或 @ref{13c9,,fdopen()} 返回的 "文件对象"，则应使用其相应的 @ref{fa0,,close()} 方法。
@end quotation
@end cartouche
@end deffn

@geindex closerange() (在 os 模块中)
@anchor{library/os os closerange}@anchor{1ea2}
@deffn {函数} os.closerange (fd_low, fd_high)

关闭从 @emph{fd_low} （包括）到 @emph{fd_high} （排除）间的文件描述符，并忽略错误。类似（但快于）:

@example
for fd in range(fd_low, fd_high):
    try:
        os.close(fd)
    except OSError:
        pass
@end example
@end deffn

@geindex copy_file_range() (在 os 模块中)
@anchor{library/os os copy_file_range}@anchor{1ea3}
@deffn {函数} os.copy_file_range (src, dst, count, offset_src=None, offset_dst=None)

从文件描述符 @emph{src} 复制 @emph{count} 字节，从偏移量 @emph{offset_src} 开始读取，到文件描述符 @emph{dst}，从偏移量 @emph{offset_dst} 开始写入。如果 @emph{offset_src} 为 None，则 @emph{src} 将从当前位置开始读取；@emph{offset_dst} 同理。@emph{src} 和 @emph{dst} 指向的文件必须处于相同的文件系统，否则将会抛出一个 @ref{169e,,errno} 被设为 @ref{1ea4,,errno.EXDEV} 的 @ref{1d3,,OSError} 。

此复制的完成没有额外的从内核到用户空间再回到内核的数据转移花费。另外，一些文件系统可能实现额外的优化。完成复制就如同打开两个二进制文件一样。

返回值是复制的字节的数目。这可能低于需求的数目。

@ref{12f5,,Availability}: Linux kernel >= 4.5 或 glibc >= 2.27。


3.8 新版功能.

@end deffn

@geindex device_encoding() (在 os 模块中)
@anchor{library/os os device_encoding}@anchor{1ea5}
@deffn {函数} os.device_encoding (fd)

如果连接到终端，则返回一个与 @emph{fd} 关联的设备描述字符，否则返回 @ref{157,,None}。
@end deffn

@geindex dup() (在 os 模块中)
@anchor{library/os os dup}@anchor{f23}
@deffn {函数} os.dup (fd)

返回一个文件描述符 @emph{fd} 的副本。该文件描述符的副本是 @ref{7f4,,不可继承的}。

在 Windows 中，当复制一个标准流（0: stdin, 1: stdout, 2: stderr）时，新的文件描述符是 @ref{7f4,,可继承的}。


在 3.4 版更改: 新的文件描述符现在是不可继承的。

@end deffn

@geindex dup2() (在 os 模块中)
@anchor{library/os os dup2}@anchor{3b6}
@deffn {函数} os.dup2 (fd, fd2, inheritable=True)

把文件描述符 @emph{fd} 复制为 @emph{fd2}，必要时先关闭后者。返回 @emph{fd2}。新的文件描述符默认是 @ref{7f4,,可继承的}，除非在 @emph{inheritable} 为 @code{False} 时，是不可继承的。


在 3.4 版更改: 添加可选参数 @emph{inheritable}。



在 3.7 版更改: 成功时返回 @emph{fd2}，以过去的版本中，总是返回 @code{None}。

@end deffn

@geindex fchmod() (在 os 模块中)
@anchor{library/os os fchmod}@anchor{656}
@deffn {函数} os.fchmod (fd, mode)

将 @emph{fd} 指定文件的权限状态修改为 @emph{mode}。可以参考 @ref{a2e,,chmod()} 中列出 @emph{mode} 的可用值。从Python 3.3开始，这相当于 @code{os.chmod(fd, mode)}。

引发一个 @ref{12d0,,审计事件} @code{os.chmod}，附带参数 @code{path}、@code{mode}、@code{dir_fd}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex fchown() (在 os 模块中)
@anchor{library/os os fchown}@anchor{657}
@deffn {函数} os.fchown (fd, uid, gid)

分别将 @emph{fd} 指定文件的所有者和组 ID 修改为 @emph{uid} 和 @emph{gid} 的值。若不想变更其中的某个 ID，可将相应值设为 -1。参考  @ref{a2f,,chown()}。从 Python 3.3 开始，这相当于 @code{os.chown(fd, uid, gid)}。

引发一个 @ref{12d0,,审计事件} @code{os.chown}，附带参数 @code{path}、@code{uid}、@code{gid}、@code{dir_fd}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex fdatasync() (在 os 模块中)
@anchor{library/os os fdatasync}@anchor{658}
@deffn {函数} os.fdatasync (fd)

强制将文件描述符 @emph{fd} 指定文件写入磁盘。不强制更新元数据。

@ref{12f5,,可用性}: Unix。

@cartouche
@quotation 注解 
该功能在 MacOS 中不可用。
@end quotation
@end cartouche
@end deffn

@geindex fpathconf() (在 os 模块中)
@anchor{library/os os fpathconf}@anchor{1ea6}
@deffn {函数} os.fpathconf (fd, name)

返回与打开的文件有关的系统配置信息。@emph{name} 指定要查找的配置名称，它可以是字符串，是一个系统已定义的名称，这些名称定义在不同标准（POSIX.1，Unix 95，Unix 98 等）中。一些平台还定义了额外的其他名称。当前操作系统已定义的名称在 @code{pathconf_names} 字典中给出。对于未包含在该映射中的配置名称，也可以传递一个整数作为 @emph{name}。

如果 @emph{name} 是一个字符串且不是已定义的名称，将抛出 @ref{1fb,,ValueError} 异常。如果当前系统不支持 @emph{name} 指定的配置名称，即使该名称存在于 @code{pathconf_names}，也会抛出 @ref{1d3,,OSError} 异常，错误码为 @ref{f59,,errno.EINVAL}。

从 Python 3.3 起，此功能等价于 @code{os.pathconf(fd, name)}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex fstat() (在 os 模块中)
@anchor{library/os os fstat}@anchor{659}
@deffn {函数} os.fstat (fd)

获取文件描述符 @emph{fd} 的状态. 返回一个 @ref{101d,,stat_result} 对象。

从 Python 3.3 起，此功能等价于 @code{os.stat(fd)}。


@subsubheading 参见


@ref{1f1,,stat()} 函数。

@end deffn

@geindex fstatvfs() (在 os 模块中)
@anchor{library/os os fstatvfs}@anchor{65a}
@deffn {函数} os.fstatvfs (fd)

返回文件系统的信息，该文件系统是文件描述符 @emph{fd} 指向的文件所在的文件系统，与 @ref{a3e,,statvfs()} 一样。从 Python 3.3 开始，它等效于 @code{os.statvfs(fd)}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex fsync() (在 os 模块中)
@anchor{library/os os fsync}@anchor{65b}
@deffn {函数} os.fsync (fd)

强制将文件描述符 @emph{fd} 指向的文件写入磁盘。在 Unix，这将调用原生 @code{fsync()} 函数；在 Windows，则是 MS @code{_commit()} 函数。

如果要写入的是缓冲区内的 Python @ref{b3b,,文件对象} @emph{f}，请先执行 @code{f.flush()}，然后执行 @code{os.fsync(f.fileno())}，以确保与 @emph{f} 关联的所有内部缓冲区都写入磁盘。

@ref{12f5,,可用性}: Unix, Windows。
@end deffn

@geindex ftruncate() (在 os 模块中)
@anchor{library/os os ftruncate}@anchor{65c}
@deffn {函数} os.ftruncate (fd, length)

截断文件描述符 @emph{fd} 指向的文件，以使其最大为 @emph{length} 字节。从 Python 3.3 开始，它等效于 @code{os.truncate(fd, length)}。

引发一个 @ref{12d0,,审计事件} @code{os.truncate}，附带参数 @code{fd}, @code{length}。

@ref{12f5,,可用性}: Unix, Windows。


在 3.5 版更改: 添加了 Windows 支持

@end deffn

@geindex get_blocking() (在 os 模块中)
@anchor{library/os os get_blocking}@anchor{71b}
@deffn {函数} os.get_blocking (fd)

获取文件描述符的阻塞模式：如果设置了 @ref{71d,,O_NONBLOCK} 标志位，返回 @code{False}，如果该标志位被清除，返回 @code{True}。

参见 @ref{71c,,set_blocking()} 和 @ref{1ea7,,socket.socket.setblocking()}。

@ref{12f5,,可用性}: Unix。


3.5 新版功能.

@end deffn

@geindex isatty() (在 os 模块中)
@anchor{library/os os isatty}@anchor{1ea8}
@deffn {函数} os.isatty (fd)

如果文件描述符 @emph{fd} 打开且已连接至 tty 设备（或类 tty 设备），返回 @code{True}，否则返回 @code{False}。
@end deffn

@geindex lockf() (在 os 模块中)
@anchor{library/os os lockf}@anchor{a55}
@deffn {函数} os.lockf (fd, cmd, len)

在打开的文件描述符上，使用、测试或删除 POSIX 锁。@emph{fd} 是一个打开的文件描述符。@emph{cmd} 指定要进行的操作，它们是 @ref{1ea9,,F_LOCK}、@ref{1eaa,,F_TLOCK}、@ref{1eab,,F_ULOCK} 或 @ref{1eac,,F_TEST} 中的一个。@emph{len} 指定哪部分文件需要锁定。

引发一个 @ref{12d0,,审计事件} @code{os.lockf}，附带参数 @code{fd}、@code{cmd}、@code{len}。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex F_LOCK() (在 os 模块中)
@geindex F_TLOCK() (在 os 模块中)
@geindex F_ULOCK() (在 os 模块中)
@geindex F_TEST() (在 os 模块中)
@anchor{library/os os F_LOCK}@anchor{1ea9}
@deffn {数据} os.F_LOCK
@anchor{library/os os F_TLOCK}@anchor{1eaa}
@deffnx {数据} os.F_TLOCK
@anchor{library/os os F_ULOCK}@anchor{1eab}
@deffnx {数据} os.F_ULOCK
@anchor{library/os os F_TEST}@anchor{1eac}
@deffnx {数据} os.F_TEST

标志位，用于指定 @ref{a55,,lockf()} 进行哪一种操作。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex lseek() (在 os 模块中)
@anchor{library/os os lseek}@anchor{a59}
@deffn {函数} os.lseek (fd, pos, how)

将文件描述符 @emph{fd} 的当前位置设置为 @emph{pos}，位置的计算方式 @emph{how} 如下：设置为 @ref{d8d,,SEEK_SET} 或 @code{0} 表示从文件开头计算，设置为 @ref{d8e,,SEEK_CUR} 或 @code{1} 表示从文件当前位置计算，设置为 @ref{d8f,,SEEK_END} 或 @code{2} 表示文件末尾计算。返回新指针位置，这个位置是从文件开头计算的，单位是字节。
@end deffn

@geindex SEEK_SET() (在 os 模块中)
@geindex SEEK_CUR() (在 os 模块中)
@geindex SEEK_END() (在 os 模块中)
@anchor{library/os os SEEK_SET}@anchor{d8d}
@deffn {数据} os.SEEK_SET
@anchor{library/os os SEEK_CUR}@anchor{d8e}
@deffnx {数据} os.SEEK_CUR
@anchor{library/os os SEEK_END}@anchor{d8f}
@deffnx {数据} os.SEEK_END

@ref{a59,,lseek()} 函数的参数，它们的值分别为 0、1 和 2。


3.3 新版功能: 某些操作系统可能支持其他值，例如 @code{os.SEEK_HOLE} 或 @code{os.SEEK_DATA}。

@end deffn

@geindex open() (在 os 模块中)
@anchor{library/os os open}@anchor{65f}
@deffn {函数} os.open (path, flags, mode=0o777, *, dir_fd=None)

打开文件 @emph{path}，根据 @emph{flags} 设置各种标志位，并根据 @emph{mode} 设置其权限状态。当计算 @emph{mode} 时，会首先根据当前 umask 值将部分权限去除。本方法返回新文件的描述符。新的文件描述符是 @ref{7f4,,不可继承} 的。

有关 flag 和 mode 取值的说明，请参见 C 运行时文档。标志位常量（如 @ref{1ead,,O_RDONLY} 和 @ref{1eae,,O_WRONLY}）在 @ref{c4,,os} 模块中定义。特别地，在 Windows 上需要添加 @ref{1eaf,,O_BINARY} 才能以二进制模式打开文件。

本函数带有 @emph{dir_fd} 参数，支持 @ref{a2a,,基于目录描述符的相对路径}。

@code{open} 附带参数 @code{path}、@code{mode}、@code{flags} 会引发 @ref{12d0,,审计事件}。


在 3.4 版更改: 新的文件描述符现在是不可继承的。


@cartouche
@quotation 注解 
本函数适用于底层的 I/O。常规用途请使用内置函数 @ref{4ea,,open()}，该函数的 @code{read()} 和 @code{write()} 方法（及其他方法）会返回 @ref{b3b,,文件对象}。要将文件描述符包装在文件对象中，请使用 @ref{13c9,,fdopen()}。
@end quotation
@end cartouche


3.3 新版功能: @emph{dir_fd} 参数。



在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此函数现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

以下常量是 @ref{65f,,open()} 函数 @emph{flags} 参数的选项。可以用按位或运算符 @code{|} 将它们组合使用。部分常量并非在所有平台上都可用。有关其可用性和用法的说明，请参阅 @code{open(2)} 手册（Unix 上）或 MSDN@footnote{https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx} （Windows 上）。

@geindex O_RDONLY() (在 os 模块中)
@geindex O_WRONLY() (在 os 模块中)
@geindex O_RDWR() (在 os 模块中)
@geindex O_APPEND() (在 os 模块中)
@geindex O_CREAT() (在 os 模块中)
@geindex O_EXCL() (在 os 模块中)
@geindex O_TRUNC() (在 os 模块中)
@anchor{library/os os O_RDONLY}@anchor{1ead}
@deffn {数据} os.O_RDONLY
@anchor{library/os os O_WRONLY}@anchor{1eae}
@deffnx {数据} os.O_WRONLY
@anchor{library/os os O_RDWR}@anchor{1eb0}
@deffnx {数据} os.O_RDWR
@anchor{library/os os O_APPEND}@anchor{1eb1}
@deffnx {数据} os.O_APPEND
@anchor{library/os os O_CREAT}@anchor{1eb2}
@deffnx {数据} os.O_CREAT
@anchor{library/os os O_EXCL}@anchor{1bfe}
@deffnx {数据} os.O_EXCL
@anchor{library/os os O_TRUNC}@anchor{1eb3}
@deffnx {数据} os.O_TRUNC

上述常量在 Unix 和 Windows 上均可用。
@end deffn

@geindex O_DSYNC() (在 os 模块中)
@geindex O_RSYNC() (在 os 模块中)
@geindex O_SYNC() (在 os 模块中)
@geindex O_NDELAY() (在 os 模块中)
@geindex O_NONBLOCK() (在 os 模块中)
@geindex O_NOCTTY() (在 os 模块中)
@geindex O_CLOEXEC() (在 os 模块中)
@anchor{library/os os O_DSYNC}@anchor{1eb4}
@deffn {数据} os.O_DSYNC
@anchor{library/os os O_RSYNC}@anchor{1eb5}
@deffnx {数据} os.O_RSYNC
@anchor{library/os os O_SYNC}@anchor{1eb6}
@deffnx {数据} os.O_SYNC
@anchor{library/os os O_NDELAY}@anchor{1eb7}
@deffnx {数据} os.O_NDELAY
@anchor{library/os os O_NONBLOCK}@anchor{71d}
@deffnx {数据} os.O_NONBLOCK
@anchor{library/os os O_NOCTTY}@anchor{1eb8}
@deffnx {数据} os.O_NOCTTY
@anchor{library/os os O_CLOEXEC}@anchor{9bd}
@deffnx {数据} os.O_CLOEXEC

这个常数仅在 Unix 系统中可用。


在 3.3 版更改: 增加 @ref{9bd,,O_CLOEXEC} 常量。

@end deffn

@geindex O_BINARY() (在 os 模块中)
@geindex O_NOINHERIT() (在 os 模块中)
@geindex O_SHORT_LIVED() (在 os 模块中)
@geindex O_TEMPORARY() (在 os 模块中)
@geindex O_RANDOM() (在 os 模块中)
@geindex O_SEQUENTIAL() (在 os 模块中)
@geindex O_TEXT() (在 os 模块中)
@anchor{library/os os O_BINARY}@anchor{1eaf}
@deffn {数据} os.O_BINARY
@anchor{library/os os O_NOINHERIT}@anchor{1eb9}
@deffnx {数据} os.O_NOINHERIT
@anchor{library/os os O_SHORT_LIVED}@anchor{1eba}
@deffnx {数据} os.O_SHORT_LIVED
@anchor{library/os os O_TEMPORARY}@anchor{1ebb}
@deffnx {数据} os.O_TEMPORARY
@anchor{library/os os O_RANDOM}@anchor{1ebc}
@deffnx {数据} os.O_RANDOM
@anchor{library/os os O_SEQUENTIAL}@anchor{1ebd}
@deffnx {数据} os.O_SEQUENTIAL
@anchor{library/os os O_TEXT}@anchor{1ebe}
@deffnx {数据} os.O_TEXT

这个常数仅在 Windows 系统中可用。
@end deffn

@geindex O_ASYNC() (在 os 模块中)
@geindex O_DIRECT() (在 os 模块中)
@geindex O_DIRECTORY() (在 os 模块中)
@geindex O_NOFOLLOW() (在 os 模块中)
@geindex O_NOATIME() (在 os 模块中)
@geindex O_PATH() (在 os 模块中)
@geindex O_TMPFILE() (在 os 模块中)
@geindex O_SHLOCK() (在 os 模块中)
@geindex O_EXLOCK() (在 os 模块中)
@anchor{library/os os O_ASYNC}@anchor{1ebf}
@deffn {数据} os.O_ASYNC
@anchor{library/os os O_DIRECT}@anchor{1ec0}
@deffnx {数据} os.O_DIRECT
@anchor{library/os os O_DIRECTORY}@anchor{1ec1}
@deffnx {数据} os.O_DIRECTORY
@anchor{library/os os O_NOFOLLOW}@anchor{1ec2}
@deffnx {数据} os.O_NOFOLLOW
@anchor{library/os os O_NOATIME}@anchor{1ec3}
@deffnx {数据} os.O_NOATIME
@anchor{library/os os O_PATH}@anchor{87d}
@deffnx {数据} os.O_PATH
@anchor{library/os os O_TMPFILE}@anchor{87e}
@deffnx {数据} os.O_TMPFILE
@anchor{library/os os O_SHLOCK}@anchor{d90}
@deffnx {数据} os.O_SHLOCK
@anchor{library/os os O_EXLOCK}@anchor{d91}
@deffnx {数据} os.O_EXLOCK

上述常量是扩展常量，如果 C 库未定义它们，则不存在。


在 3.4 版更改: 在支持的系统上增加 @ref{87d,,O_PATH}。增加 @ref{87e,,O_TMPFILE}，仅在 Linux Kernel 3.11 或更高版本可用。

@end deffn

@geindex openpty() (在 os 模块中)
@anchor{library/os os openpty}@anchor{1ec4}
@deffn {函数} os.openpty ()

@geindex 模块; pty

打开一对新的伪终端，返回一对文件描述符 @code{（主，从）}，分别为 pty 和 tty。新的文件描述符是 @ref{7f4,,不可继承} 的。对于（稍微）轻量一些的方法，请使用 @ref{d5,,pty} 模块。

@ref{12f5,,可用性}: 某些 Unix。


在 3.4 版更改: 新的文件描述符不再可继承。

@end deffn

@geindex pipe() (在 os 模块中)
@anchor{library/os os pipe}@anchor{1ea1}
@deffn {函数} os.pipe ()

创建一个管道，返回一对分别用于读取和写入的文件描述符 @code{(r, w)}。新的文件描述符是 @ref{7f4,,不可继承} 的。

@ref{12f5,,可用性}: Unix, Windows。


在 3.4 版更改: 新的文件描述符不再可继承。

@end deffn

@geindex pipe2() (在 os 模块中)
@anchor{library/os os pipe2}@anchor{a29}
@deffn {函数} os.pipe2 (flags)

创建带有 @emph{flags} 标志位的管道。可通过对以下一个或多个值进行“或”运算来构造这些 @emph{flags}：@ref{71d,,O_NONBLOCK}、@ref{9bd,,O_CLOEXEC}。返回一对分别用于读取和写入的文件描述符 @code{(r, w)}。

@ref{12f5,,可用性}: 某些 Unix。


3.3 新版功能.

@end deffn

@geindex posix_fallocate() (在 os 模块中)
@anchor{library/os os posix_fallocate}@anchor{661}
@deffn {函数} os.posix_fallocate (fd, offset, len)

确保为 @emph{fd} 指向的文件分配了足够的磁盘空间，该空间从偏移量 @emph{offset} 开始，到 @emph{len} 字节为止。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex posix_fadvise() (在 os 模块中)
@anchor{library/os os posix_fadvise}@anchor{660}
@deffn {函数} os.posix_fadvise (fd, offset, len, advice)

声明即将以特定模式访问数据，使内核可以提前进行优化。数据范围是从 @emph{fd} 所指向文件的 @emph{offset} 开始，持续 @emph{len} 个字节。@emph{advice} 的取值是如下之一：@ref{1ec5,,POSIX_FADV_NORMAL}, @ref{1ec6,,POSIX_FADV_SEQUENTIAL}, @ref{1ec7,,POSIX_FADV_RANDOM}, @ref{1ec8,,POSIX_FADV_NOREUSE}, @ref{1ec9,,POSIX_FADV_WILLNEED} 或 @ref{1eca,,POSIX_FADV_DONTNEED}。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex POSIX_FADV_NORMAL() (在 os 模块中)
@geindex POSIX_FADV_SEQUENTIAL() (在 os 模块中)
@geindex POSIX_FADV_RANDOM() (在 os 模块中)
@geindex POSIX_FADV_NOREUSE() (在 os 模块中)
@geindex POSIX_FADV_WILLNEED() (在 os 模块中)
@geindex POSIX_FADV_DONTNEED() (在 os 模块中)
@anchor{library/os os POSIX_FADV_NORMAL}@anchor{1ec5}
@deffn {数据} os.POSIX_FADV_NORMAL
@anchor{library/os os POSIX_FADV_SEQUENTIAL}@anchor{1ec6}
@deffnx {数据} os.POSIX_FADV_SEQUENTIAL
@anchor{library/os os POSIX_FADV_RANDOM}@anchor{1ec7}
@deffnx {数据} os.POSIX_FADV_RANDOM
@anchor{library/os os POSIX_FADV_NOREUSE}@anchor{1ec8}
@deffnx {数据} os.POSIX_FADV_NOREUSE
@anchor{library/os os POSIX_FADV_WILLNEED}@anchor{1ec9}
@deffnx {数据} os.POSIX_FADV_WILLNEED
@anchor{library/os os POSIX_FADV_DONTNEED}@anchor{1eca}
@deffnx {数据} os.POSIX_FADV_DONTNEED

用于 @ref{660,,posix_fadvise()} 的 @emph{advice} 参数的标志位，指定可能使用的访问模式。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex pread() (在 os 模块中)
@anchor{library/os os pread}@anchor{3b1}
@deffn {函数} os.pread (fd, n, offset)

从文件描述符 @emph{fd} 所指向文件的偏移位置 @emph{offset} 开始，读取至多 @emph{n} 个字节，而保持文件偏移量不变。

返回所读取字节的字节串 (bytestring)。如果到达了 @emph{fd} 指向的文件末尾，则返回空字节对象。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex preadv() (在 os 模块中)
@anchor{library/os os preadv}@anchor{3af}
@deffn {函数} os.preadv (fd, buffers, offset, flags=0)

从文件描述符 @emph{fd} 所指向文件的偏移位置 @emph{offset} 开始，将数据读取至可变 @ref{5e3,,字节类对象} 缓冲区 @emph{buffers} 中，保持文件偏移量不变。将数据依次存放到每个缓冲区中，填满一个后继续存放到序列中的下一个缓冲区，来保存其余数据。

flags 参数可以由零个或多个标志位进行按位或运算来得到：


@itemize -

@item 
@ref{1ecb,,RWF_HIPRI}

@item 
@ref{1ecc,,RWF_NOWAIT}
@end itemize

返回实际读取的字节总数，该总数可以小于所有对象的总容量。

操作系统可能对允许使用的缓冲区数量有限制（使用 @ref{1ecd,,sysconf()} 获取 @code{'SC_IOV_MAX'} 值）。

本方法结合了 @ref{3b0,,os.readv()} 和 @ref{3b1,,os.pread()} 的功能。

@ref{12f5,,可用性}：Linux 2.6.30 或更高版本，FreeBSD 6.0 或更高版本，OpenBSD 2.7 或更高版本。使用标志位需要 Linux 4.6 或更高版本。


3.7 新版功能.

@end deffn

@geindex RWF_NOWAIT() (在 os 模块中)
@anchor{library/os os RWF_NOWAIT}@anchor{1ecc}
@deffn {数据} os.RWF_NOWAIT

不要等待无法立即获得的数据。如果指定了此标志，那么当需要从后备存储器中读取数据，或等待文件锁时，系统调用将立即返回。

如果成功读取数据，则返回读取的字节数。如果未读取到数据，则返回 @code{-1}，并将错误码 errno 置为 @ref{1ece,,errno.EAGAIN}。

@ref{12f5,,可用性}：Linux 4.14 或更高版本。


3.7 新版功能.

@end deffn

@geindex RWF_HIPRI() (在 os 模块中)
@anchor{library/os os RWF_HIPRI}@anchor{1ecb}
@deffn {数据} os.RWF_HIPRI

高优先级读/写。允许基于块的文件系统对设备进行轮询，这样可以降低延迟，但可能会占用更多资源。

目前在 Linux 上，此功能仅在使用 @ref{1ec0,,O_DIRECT} 标志打开的文件描述符上可用。

@ref{12f5,,可用性}：Linux 4.6 或更高版本。


3.7 新版功能.

@end deffn

@geindex pwrite() (在 os 模块中)
@anchor{library/os os pwrite}@anchor{3b4}
@deffn {函数} os.pwrite (fd, str, offset)

将 @emph{str} 中的字节串 (bytestring) 写入文件描述符 @emph{fd} 的偏移位置 @emph{offset} 处，保持文件偏移量不变。

返回实际写入的字节数。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex pwritev() (在 os 模块中)
@anchor{library/os os pwritev}@anchor{3b2}
@deffn {函数} os.pwritev (fd, buffers, offset, flags=0)

将缓冲区 @emph{buffers} 的内容写入文件描述符 @emph{fd} 的偏移位置 @emph{offset} 处，保持文件偏移量不变。缓冲区 @emph{buffers} 必须是由 @ref{5e3,,字节类对象} 组成的序列。缓冲区以数组顺序处理。先写入第一个缓冲区的全部内容，再写入第二个缓冲区，照此继续。

flags 参数可以由零个或多个标志位进行按位或运算来得到：


@itemize -

@item 
@ref{1ecf,,RWF_DSYNC}

@item 
@ref{1ed0,,RWF_SYNC}
@end itemize

返回实际写入的字节总数。

操作系统可能对允许使用的缓冲区数量有限制（使用 @ref{1ecd,,sysconf()} 获取 @code{'SC_IOV_MAX'} 值）。

本方法结合了 @ref{3b3,,os.writev()} 和 @ref{3b4,,os.pwrite()} 的功能。

@ref{12f5,,可用性}：Linux 2.6.30 或更高版本，FreeBSD 6.0 或更高版本，OpenBSD 2.7 或更高版本。使用标志位需要 Linux 4.7 或更高版本。


3.7 新版功能.

@end deffn

@geindex RWF_DSYNC() (在 os 模块中)
@anchor{library/os os RWF_DSYNC}@anchor{1ecf}
@deffn {数据} os.RWF_DSYNC

提供立即写入功能，等效于 @ref{1eb4,,O_DSYNC} @code{open(2)} 标志。该标志仅作用于系统调用写入的数据。

@ref{12f5,,可用性}：Linux 4.7 或更高版本。


3.7 新版功能.

@end deffn

@geindex RWF_SYNC() (在 os 模块中)
@anchor{library/os os RWF_SYNC}@anchor{1ed0}
@deffn {数据} os.RWF_SYNC

提供立即写入功能，等效于 @ref{1eb6,,O_SYNC} @code{open(2)} 标志。该标志仅作用于系统调用写入的数据。

@ref{12f5,,可用性}：Linux 4.7 或更高版本。


3.7 新版功能.

@end deffn

@geindex read() (在 os 模块中)
@anchor{library/os os read}@anchor{662}
@deffn {函数} os.read (fd, n)

从文件描述符 @emph{fd} 中读取至多 @emph{n} 个字节。

返回所读取字节的字节串 (bytestring)。如果到达了 @emph{fd} 指向的文件末尾，则返回空字节对象。

@cartouche
@quotation 注解 
该功能适用于低级 I/O 操作，必须用于 @ref{65f,,os.open()} 或 @ref{1ea1,,pipe()} 返回的文件描述符。若要读取由内建函数 @ref{4ea,,open()}、@ref{2a9,,popen()}、@ref{13c9,,fdopen()} 或 @ref{306,,sys.stdin} 返回的 "文件对象"，则应使用其相应的 @code{read()} 或 @code{readline()} 方法。
@end quotation
@end cartouche


在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此函数现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex sendfile() (在 os 模块中)
@anchor{library/os os sendfile}@anchor{352}
@deffn {函数} os.sendfile (out, in, offset, count)

@deffnx {函数} os.sendfile (out, in, offset, count[, headers][, trailers], flags=0)

将文件描述符 @emph{in} 中的 @emph{count} 字节复制到文件描述符 @emph{out} 的偏移位置 @emph{offset} 处。返回复制的字节数，如果到达 EOF，返回 0。

定义了 @ref{352,,sendfile()} 的所有平台均支持第一种函数用法。

在 Linux 上，将 @emph{offset} 设置为 @code{None}，则从 @emph{in} 的当前位置开始读取，并更新 @emph{in} 的位置。

第二种函数用法可以在 Mac OS X 和 FreeBSD 上使用，其中，@emph{headers} 和 @emph{trailers} 是任意的缓冲区序列，它们分别在写入 @emph{in} 的数据前、后被写入。返回值与第一种用法相同。

在 Mac OS X 和 FreeBSD 上，将 @emph{count} 设为 0 表示持续复制直到 @emph{in} 的结尾。

所有平台都支持将套接字作为 @emph{out} 文件描述符，有些平台也支持其他类型（如常规文件或管道）。

跨平台应用程序不应使用 @emph{headers}、@emph{trailers} 和 @emph{flags} 参数。

@ref{12f5,,可用性}: Unix。

@cartouche
@quotation 注解 
有关 @ref{352,,sendfile()} 的高级封装，参见 @ref{744,,socket.socket.sendfile()}。
@end quotation
@end cartouche


3.3 新版功能.

@end deffn

@geindex set_blocking() (在 os 模块中)
@anchor{library/os os set_blocking}@anchor{71c}
@deffn {函数} os.set_blocking (fd, blocking)

设置指定文件描述符的阻塞模式：如果 blocking 为 @code{False}，则为该描述符设置 @ref{71d,,O_NONBLOCK} 标志位，反之则清除该标志位。

参见 @ref{71b,,get_blocking()} 和 @ref{1ea7,,socket.socket.setblocking()}。

@ref{12f5,,可用性}: Unix。


3.5 新版功能.

@end deffn

@geindex SF_NODISKIO() (在 os 模块中)
@geindex SF_MNOWAIT() (在 os 模块中)
@geindex SF_SYNC() (在 os 模块中)
@anchor{library/os os SF_NODISKIO}@anchor{1ed1}
@deffn {数据} os.SF_NODISKIO
@anchor{library/os os SF_MNOWAIT}@anchor{1ed2}
@deffnx {数据} os.SF_MNOWAIT
@anchor{library/os os SF_SYNC}@anchor{1ed3}
@deffnx {数据} os.SF_SYNC

@ref{352,,sendfile()} 函数的参数（假设当前实现支持这些参数）。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex readv() (在 os 模块中)
@anchor{library/os os readv}@anchor{3b0}
@deffn {函数} os.readv (fd, buffers)

从文件描述符 @emph{fd} 将数据读取至多个可变的 @ref{5e3,,字节类对象} 缓冲区 @emph{buffers} 中。将数据依次存放到每个缓冲区中，填满一个后继续存放到序列中的下一个缓冲区，来保存其余数据。

返回实际读取的字节总数，该总数可以小于所有对象的总容量。

操作系统可能对允许使用的缓冲区数量有限制（使用 @ref{1ecd,,sysconf()} 获取 @code{'SC_IOV_MAX'} 值）。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex tcgetpgrp() (在 os 模块中)
@anchor{library/os os tcgetpgrp}@anchor{1ed4}
@deffn {函数} os.tcgetpgrp (fd)

返回与 @emph{fd} 指定的终端相关联的进程组（@emph{fd} 是由 @ref{65f,,os.open()} 返回的已打开的文件描述符）。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex tcsetpgrp() (在 os 模块中)
@anchor{library/os os tcsetpgrp}@anchor{1ed5}
@deffn {函数} os.tcsetpgrp (fd, pg)

设置与 @emph{fd} 指定的终端相关联的进程组为 @emph{pg*（*fd} 是由 @ref{65f,,os.open()} 返回的已打开的文件描述符）。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex ttyname() (在 os 模块中)
@anchor{library/os os ttyname}@anchor{1ed6}
@deffn {函数} os.ttyname (fd)

返回一个字符串，该字符串表示与文件描述符 @emph{fd} 关联的终端。如果 @emph{fd} 没有与终端关联，则抛出异常。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex write() (在 os 模块中)
@anchor{library/os os write}@anchor{668}
@deffn {函数} os.write (fd, str)

将 @emph{str} 中的字节串 (bytestring) 写入文件描述符 @emph{fd}。

返回实际写入的字节数。

@cartouche
@quotation 注解 
该功能适用于低级 I/O 操作，必须用于 @ref{65f,,os.open()} 或 @ref{1ea1,,pipe()} 返回的文件描述符。若要写入由内建函数 @ref{4ea,,open()}、@ref{2a9,,popen()}、@ref{13c9,,fdopen()}、@ref{307,,sys.stdout} 或 @ref{308,,sys.stderr} 返回的 "文件对象"，则应使用其相应的 @code{write()} 方法。
@end quotation
@end cartouche


在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此函数现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex writev() (在 os 模块中)
@anchor{library/os os writev}@anchor{3b3}
@deffn {函数} os.writev (fd, buffers)

将缓冲区 @emph{buffers} 的内容写入文件描述符 @emph{fd}。缓冲区 @emph{buffers} 必须是由 @ref{5e3,,字节类对象} 组成的序列。缓冲区以数组顺序处理。先写入第一个缓冲区的全部内容，再写入第二个缓冲区，照此继续。

返回实际写入的字节总数。

操作系统可能对允许使用的缓冲区数量有限制（使用 @ref{1ecd,,sysconf()} 获取 @code{'SC_IOV_MAX'} 值）。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@menu
* 查询终端的尺寸:: 
* 文件描述符的继承:: 

@end menu

@node 查询终端的尺寸,文件描述符的继承,,文件描述符操作
@anchor{library/os querying-the-size-of-a-terminal}@anchor{1ed7}@anchor{library/os terminal-size}@anchor{1ed8}
@subsubsection 查询终端的尺寸



3.3 新版功能.


@geindex get_terminal_size() (在 os 模块中)
@anchor{library/os os get_terminal_size}@anchor{a44}
@deffn {函数} os.get_terminal_size (fd=STDOUT_FILENO)

返回终端窗口的尺寸，格式为 @code{(columns, lines)}，它是类型为 @ref{1c30,,terminal_size} 的元组。

可选参数 @code{fd} （默认为 @code{STDOUT_FILENO} 或标准输出）指定应查询的文件描述符。

如果文件描述符未连接到终端，则抛出 @ref{1d3,,OSError} 异常。

@ref{a45,,shutil.get_terminal_size()} 是供常规使用的高阶函数，@code{os.get_terminal_size} 是其底层的实现。

@ref{12f5,,可用性}: Unix, Windows。
@end deffn

@geindex terminal_size (os 中的类)
@anchor{library/os os terminal_size}@anchor{1c30}
@deffn {类} os.terminal_size

元组的子类，存储终端窗口尺寸 @code{(columns, lines)}。

@geindex columns (os.terminal_size 属性)
@anchor{library/os os terminal_size columns}@anchor{1ed9}
@deffn {属性} columns

终端窗口的宽度，单位为字符。
@end deffn

@geindex lines (os.terminal_size 属性)
@anchor{library/os os terminal_size lines}@anchor{1eda}
@deffn {属性} lines

终端窗口的高度，单位为字符。
@end deffn
@end deffn

@node 文件描述符的继承,,查询终端的尺寸,文件描述符操作
@anchor{library/os fd-inheritance}@anchor{7f4}@anchor{library/os inheritance-of-file-descriptors}@anchor{1edb}
@subsubsection 文件描述符的继承



3.4 新版功能.


每个文件描述符都有一个 "inheritable"（可继承）标志位，该标志位控制了文件描述符是否可以由子进程继承。从 Python 3.4 开始，由 Python 创建的文件描述符默认是不可继承的。

在 UNIX 上，执行新程序时，不可继承的文件描述符在子进程中是关闭的，其他文件描述符将被继承。

在 Windows 上，不可继承的句柄和文件描述符在子进程中是关闭的，但标准流（文件描述符 0、1 和 2 即标准输入、标准输出和标准错误）是始终继承的。如果使用 @ref{1edc,,spawn*} 函数，所有可继承的句柄和文件描述符都将被继承。如果使用 @ref{f9,,subprocess} 模块，将关闭除标准流以外的所有文件描述符，并且仅当 @emph{close_fds} 参数为 @code{False} 时才继承可继承的句柄。

@geindex get_inheritable() (在 os 模块中)
@anchor{library/os os get_inheritable}@anchor{7f5}
@deffn {函数} os.get_inheritable (fd)

获取指定文件描述符的“可继承”标志位（为布尔值）。
@end deffn

@geindex set_inheritable() (在 os 模块中)
@anchor{library/os os set_inheritable}@anchor{7f6}
@deffn {函数} os.set_inheritable (fd, inheritable)

设置指定文件描述符的“可继承”标志位。
@end deffn

@geindex get_handle_inheritable() (在 os 模块中)
@anchor{library/os os get_handle_inheritable}@anchor{7f7}
@deffn {函数} os.get_handle_inheritable (handle)

获取指定句柄的“可继承”标志位（为布尔值）。

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex set_handle_inheritable() (在 os 模块中)
@anchor{library/os os set_handle_inheritable}@anchor{7f8}
@deffn {函数} os.set_handle_inheritable (handle, inheritable)

设置指定句柄的“可继承”标志位。

@ref{12f5,,可用性}: Windows。
@end deffn

@node 文件和目录,进程管理,文件描述符操作,os --- 多种操作系统接口
@anchor{library/os files-and-directories}@anchor{1edd}@anchor{library/os os-file-dir}@anchor{1e7d}
@subsubsection 文件和目录


在某些 Unix 平台上，许多函数支持以下一项或多项功能：
@anchor{library/os path-fd}@anchor{3ad}

@itemize *

@item 
@strong{指定文件描述符为参数：} 通常在 @ref{c4,,os} 模块中提供给函数的 @emph{path} 参数必须是表示文件路径的字符串，但是，某些函数现在可以接受其 @emph{path} 参数为打开文件描述符，该函数将对描述符指向的文件进行操作。（对于 POSIX 系统，Python 将调用以 @code{f} 开头的函数变体（如调用 @code{fchdir} 而不是 @code{chdir}）。）

可以用 @ref{a3f,,os.supports_fd} 检查某个函数在你的平台上是否支持将 @emph{path} 参数指定为文件描述符。如果不支持，使用该功能将抛出 @ref{609,,NotImplementedError} 异常。

如果该函数还支持 @emph{dir_fd} 或 @emph{follow_symlinks} 参数，那么用文件描述符作为 @emph{path} 后就不能再指定上述参数了。
@end itemize
@anchor{library/os dir-fd}@anchor{a2a}

@itemize *

@item 
@strong{基于目录描述符的相对路径：} 如果 @emph{dir_fd} 不是 @code{None}，它就应该是一个指向目录的文件描述符，这时待操作的 path 应该是相对路径，相对路径是相对于前述目录的。如果 path 是绝对路径，则 @emph{dir_fd} 将被忽略。（对于 POSIX 系统，Python 将调用该函数的变体，变体以 @code{at} 结尾，可能以 @code{f} 开头（如调用 @code{faccessat} 而不是 @code{access}）。

可以用 @ref{a39,,os.supports_dir_fd} 检查某个函数在你的平台上是否支持 @emph{dir_fd}。如果不支持，使用该功能将抛出 @ref{609,,NotImplementedError} 异常。
@end itemize
@anchor{library/os follow-symlinks}@anchor{a2b}

@itemize *

@item 
@strong{不跟踪符号链接：} 如果 @emph{follow_symlinks} 为 @code{False}，并且待操作路径的最后一个元素是符号链接，则该函数将在符号链接本身而不是链接所指向的文件上操作。（对于 POSIX 系统，Python 将调用该函数的 @code{l...} 变体。）

可以用 @ref{1c1b,,os.supports_follow_symlinks} 检查某个函数在你的平台上是否支持 @emph{follow_symlinks}。如果不支持，使用该功能将抛出 @ref{609,,NotImplementedError} 异常。
@end itemize

@geindex access() (在 os 模块中)
@anchor{library/os os access}@anchor{a2c}
@deffn {函数} os.access (path, mode, *, dir_fd=None, effective_ids=False, follow_symlinks=True)

使用 实际用户ID/用户组ID 测试对 @emph{path} 的访问。请注意，大多数测试操作将使用 有效用户ID/用户组ID，因此可以在 suid/sgid 环境中运用此例程，来测试调用用户是否具有对 @emph{path} 的指定访问权限。@emph{mode} 为 @ref{1ede,,F_OK} 时用于测试 @emph{path} 是否存在，也可以对 @ref{1edf,,R_OK}、@ref{1ee0,,W_OK} 和 @ref{1ee1,,X_OK} 中的一个或多个进行“或”运算来测试指定权限。允许访问则返回 @ref{494,,True}，否则返回 @ref{380,,False}。更多信息请参见 Unix 手册页 @code{access(2)}。

本函数支持指定 @ref{a2a,,基于目录描述符的相对路径} 和 @ref{a2b,,不跟踪符号链接}。

如果 @emph{effective_ids} 为 @code{True}，@ref{a2c,,access()} 将使用 有效用户ID/用户组ID 而非 实际用户ID/用户组ID 进行访问检查。您的平台可能不支持 @emph{effective_ids}，您可以使用 @ref{a40,,os.supports_effective_ids} 检查它是否可用。如果不可用，使用它时会抛出 @ref{609,,NotImplementedError} 异常。

@cartouche
@quotation 注解 
使用 @ref{a2c,,access()} 来检查用户是否具有某项权限（如打开文件的权限），然后再使用 @ref{4ea,,open()} 打开文件，这样做存在一个安全漏洞，因为用户可能会在检查和打开文件之间的时间里做其他操作。推荐使用 @ref{1ee2,,EAFP} 技术。如:

@example
if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"
@end example

最好写成:

@example
try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()
@end example
@end quotation
@end cartouche

@cartouche
@quotation 注解 
即使 @ref{a2c,,access()} 指示 I/O 操作会成功，但实际操作仍可能失败，尤其是对网络文件系统的操作，其权限语义可能超出常规的 POSIX 权限位模型。
@end quotation
@end cartouche


在 3.3 版更改: 添加 @emph{dir_fd}、@emph{effective_ids} 和 @emph{follow_symlinks} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex F_OK() (在 os 模块中)
@geindex R_OK() (在 os 模块中)
@geindex W_OK() (在 os 模块中)
@geindex X_OK() (在 os 模块中)
@anchor{library/os os F_OK}@anchor{1ede}
@deffn {数据} os.F_OK
@anchor{library/os os R_OK}@anchor{1edf}
@deffnx {数据} os.R_OK
@anchor{library/os os W_OK}@anchor{1ee0}
@deffnx {数据} os.W_OK
@anchor{library/os os X_OK}@anchor{1ee1}
@deffnx {数据} os.X_OK

作为 @ref{a2c,,access()} 的 @emph{mode} 参数的可选值，分别测试 @emph{path} 的存在性、可读性、可写性和可执行性。
@end deffn

@geindex chdir() (在 os 模块中)
@anchor{library/os os chdir}@anchor{a3a}
@deffn {函数} os.chdir (path)

@geindex directory; changing

将当前工作目录更改为 @emph{path}。

本函数支持 @ref{3ad,,指定文件描述符为参数}。其中，描述符必须指向打开的目录，不能是打开的文件。

本函数可以抛出 @ref{1d3,,OSError} 及其子类的异常，如 @ref{7ba,,FileNotFoundError}、@ref{5fa,,PermissionError} 和 @ref{994,,NotADirectoryError} 异常。

引发一个 @ref{12d0,,审计事件} @code{os.chdir}，附带参数 @code{path}。


3.3 新版功能: 在某些平台上新增支持将 @emph{path} 参数指定为文件描述符。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex chflags() (在 os 模块中)
@anchor{library/os os chflags}@anchor{a2d}
@deffn {函数} os.chflags (path, flags, *, follow_symlinks=True)

将 @emph{path} 的 flags 设置为其他由数字表示的 @emph{flags}。@emph{flags} 可以用以下值按位或组合起来（以下值在 @ref{f4,,stat} 模块中定义）：


@itemize *

@item 
@ref{1bc0,,stat.UF_NODUMP}

@item 
@ref{1bc1,,stat.UF_IMMUTABLE}

@item 
@ref{1bc2,,stat.UF_APPEND}

@item 
@ref{1bc3,,stat.UF_OPAQUE}

@item 
@ref{1bc4,,stat.UF_NOUNLINK}

@item 
@ref{1bc5,,stat.UF_COMPRESSED}

@item 
@ref{1bc6,,stat.UF_HIDDEN}

@item 
@ref{1bc7,,stat.SF_ARCHIVED}

@item 
@ref{1bc8,,stat.SF_IMMUTABLE}

@item 
@ref{1bc9,,stat.SF_APPEND}

@item 
@ref{1bca,,stat.SF_NOUNLINK}

@item 
@ref{1bcb,,stat.SF_SNAPSHOT}
@end itemize

本函数支持 @ref{a2b,,不跟踪符号链接}。

引发一个 @ref{12d0,,审计事件} @code{os.chflags}，附带参数 @code{path}、@code{flags}。

@ref{12f5,,可用性}: Unix。


3.3 新版功能: @emph{follow_symlinks} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex chmod() (在 os 模块中)
@anchor{library/os os chmod}@anchor{a2e}
@deffn {函数} os.chmod (path, mode, *, dir_fd=None, follow_symlinks=True)

将 @emph{path} 的 mode 更改为其他由数字表示的 @emph{mode}。@emph{mode} 可以用以下值之一，也可以将它们按位或组合起来（以下值在 @ref{f4,,stat} 模块中定义）：


@itemize *

@item 
@ref{1bad,,stat.S_ISUID}

@item 
@ref{1bae,,stat.S_ISGID}

@item 
@ref{1bb0,,stat.S_ENFMT}

@item 
@ref{1bb1,,stat.S_ISVTX}

@item 
@ref{1bbd,,stat.S_IREAD}

@item 
@ref{1bbe,,stat.S_IWRITE}

@item 
@ref{1bbf,,stat.S_IEXEC}

@item 
@ref{1bb2,,stat.S_IRWXU}

@item 
@ref{1bb3,,stat.S_IRUSR}

@item 
@ref{1bb4,,stat.S_IWUSR}

@item 
@ref{1bb5,,stat.S_IXUSR}

@item 
@ref{1bb6,,stat.S_IRWXG}

@item 
@ref{1bb7,,stat.S_IRGRP}

@item 
@ref{1bb8,,stat.S_IWGRP}

@item 
@ref{1baf,,stat.S_IXGRP}

@item 
@ref{1bb9,,stat.S_IRWXO}

@item 
@ref{1bba,,stat.S_IROTH}

@item 
@ref{1bbb,,stat.S_IWOTH}

@item 
@ref{1bbc,,stat.S_IXOTH}
@end itemize

本函数支持 @ref{3ad,,指定文件描述符}、@ref{a2a,,指定基于目录描述符的相对路径} 和 @ref{a2b,,不跟踪符号链接}。

@cartouche
@quotation 注解 
尽管 Windows 支持 @ref{a2e,,chmod()}，但只能用它设置文件的只读标志（@code{stat.S_IWRITE} 和 @code{stat.S_IREAD} 常量或对应的整数值）。所有其他标志位都会被忽略。
@end quotation
@end cartouche

引发一个 @ref{12d0,,审计事件} @code{os.chmod}，附带参数 @code{path}、@code{mode}、@code{dir_fd}。


3.3 新版功能: 添加了指定 @emph{path} 为文件描述符的支持，以及 @emph{dir_fd} 和 @emph{follow_symlinks} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex chown() (在 os 模块中)
@anchor{library/os os chown}@anchor{a2f}
@deffn {函数} os.chown (path, uid, gid, *, dir_fd=None, follow_symlinks=True)

将 @emph{path} 的用户和组 ID 分别修改为数字形式的 @emph{uid} 和 @emph{gid}。若要使其中某个 ID 保持不变，请将其置为 -1。

本函数支持 @ref{3ad,,指定文件描述符}、@ref{a2a,,指定基于目录描述符的相对路径} 和 @ref{a2b,,不跟踪符号链接}。

参见更高阶的函数 @ref{a71,,shutil.chown()}，除了数字 ID 之外，它也接受名称。

引发一个 @ref{12d0,,审计事件} @code{os.chown}，附带参数 @code{path}、@code{uid}、@code{gid}、@code{dir_fd}。

@ref{12f5,,可用性}: Unix。


3.3 新版功能: 添加了指定 @emph{path} 为文件描述符的支持，以及 @emph{dir_fd} 和 @emph{follow_symlinks} 参数。



在 3.6 版更改: 支持 @ref{363,,类路径对象}。

@end deffn

@geindex chroot() (在 os 模块中)
@anchor{library/os os chroot}@anchor{ed0}
@deffn {函数} os.chroot (path)

将当前进程的根目录更改为 @emph{path}。

@ref{12f5,,可用性}: Unix。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex fchdir() (在 os 模块中)
@anchor{library/os os fchdir}@anchor{655}
@deffn {函数} os.fchdir (fd)

将当前工作目录更改为文件描述符 @emph{fd} 指向的目录。fd 必须指向打开的目录而非文件。从 Python 3.3 开始，它等效于 @code{os.chdir(fd)}。

引发一个 @ref{12d0,,审计事件} @code{os.chdir}，附带参数 @code{path}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex getcwd() (在 os 模块中)
@anchor{library/os os getcwd}@anchor{f6f}
@deffn {函数} os.getcwd ()

返回表示当前工作目录的字符串。
@end deffn

@geindex getcwdb() (在 os 模块中)
@anchor{library/os os getcwdb}@anchor{2b8}
@deffn {函数} os.getcwdb ()

返回表示当前工作目录的字节串 (bytestring)。


在 3.8 版更改: 在 Windows 上，本函数现在会使用 UTF-8 编码格式而不是 ANSI 代码页：请参看 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529} 了解具体原因。 该函数在 Windows 上不再被弃用。

@end deffn

@geindex lchflags() (在 os 模块中)
@anchor{library/os os lchflags}@anchor{1ee3}
@deffn {函数} os.lchflags (path, flags)

将 @emph{path} 的 flags 设置为其他由数字表示的 @emph{flags}，与 @ref{a2d,,chflags()} 类似，但不跟踪符号链接。从 Python 3.3 开始，它等效于 @code{os.chflags(path, flags, follow_symlinks=False)}。

引发一个 @ref{12d0,,审计事件} @code{os.chflags}，附带参数 @code{path}、@code{flags}。

@ref{12f5,,可用性}: Unix。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex lchmod() (在 os 模块中)
@anchor{library/os os lchmod}@anchor{fbc}
@deffn {函数} os.lchmod (path, mode)

将 @emph{path} 的权限状态修改为 @emph{mode}。如果 path 是符号链接，则影响符号链接本身而非链接目标。可以参考 @ref{a2e,,chmod()} 中列出 @emph{mode} 的可用值。从 Python 3.3 开始，它等效于 @code{os.chmod(path, mode, follow_symlinks=False)}。

引发一个 @ref{12d0,,审计事件} @code{os.chmod}，附带参数 @code{path}、@code{mode}、@code{dir_fd}。

@ref{12f5,,可用性}: Unix。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex lchown() (在 os 模块中)
@anchor{library/os os lchown}@anchor{1ee4}
@deffn {函数} os.lchown (path, uid, gid)

将 @emph{path} 的用户和组 ID 分别修改为数字形式的 @emph{uid} 和 @emph{gid}，本函数不跟踪符号链接。从 Python 3.3 开始，它等效于 @code{os.chown(path, uid, gid, follow_symlinks=False)}。

引发一个 @ref{12d0,,审计事件} @code{os.chown}，附带参数 @code{path}、@code{uid}、@code{gid}、@code{dir_fd}。

@ref{12f5,,可用性}: Unix。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex link() (在 os 模块中)
@anchor{library/os os link}@anchor{a30}
@deffn {函数} os.link (src, dst, *, src_dir_fd=None, dst_dir_fd=None, follow_symlinks=True)

创建一个指向 @emph{src} 的硬链接，名为 @emph{dst}。

本函数支持将 @emph{src_dir_fd} 和 @emph{dst_dir_fd} 中的一个或两个指定为 @ref{a2a,,基于目录描述符的相对路径}，支持 @ref{a2b,,不跟踪符号链接}。

引发一个 @ref{12d0,,审计事件} @code{os.link} 附带参数 @code{src}、@code{dst}、@code{src_dir_fd}、@code{dst_dir_fd}。

@ref{12f5,,可用性}: Unix, Windows。


在 3.2 版更改: 添加了对 Windows 的支持。



3.3 新版功能: 添加 @emph{src_dir_fd}、@emph{dst_dir_fd} 和 @emph{follow_symlinks} 参数。



在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{src} 和 @emph{dst}。

@end deffn

@geindex listdir() (在 os 模块中)
@anchor{library/os os listdir}@anchor{a3c}
@deffn {函数} os.listdir (path='.')

返回一个列表，该列表包含了 @emph{path} 中所有文件与目录的名称。该列表按任意顺序排列，并且不包含特殊条目 @code{'.'} 和 @code{'..'}，即使它们确实在目录中存在。

@emph{path} 可以是 @ref{363,,类路径对象}。如果 @emph{path} 是（直接传入或通过 @ref{4e5,,PathLike} 接口间接传入） @code{bytes} 类型，则返回的文件名也将是 @code{bytes} 类型，其他情况下是 @code{str} 类型。

本函数也支持 @ref{3ad,,指定文件描述符为参数}，其中描述符必须指向目录。

引发一个 @ref{12d0,,审计事件} @code{os.listdir}，附带参数 @code{path}。

@cartouche
@quotation 注解 
要将 @code{str} 类型的文件名编码为 @code{bytes}，请使用 @ref{4e9,,fsencode()}。
@end quotation
@end cartouche


@subsubheading 参见


@ref{25f,,scandir()} 函数返回目录内文件名的同时，也返回文件属性信息，它在某些具体情况下能提供更好的性能。



在 3.2 版更改: @emph{path} 变为可选参数。



3.3 新版功能: 新增支持将 @emph{path} 参数指定为打开的文件描述符。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex lstat() (在 os 模块中)
@anchor{library/os os lstat}@anchor{1f2}
@deffn {函数} os.lstat (path, *, dir_fd=None)

在给定路径上执行本函数，其操作相当于 @code{lstat()} 系统调用，类似于 @ref{1f1,,stat()} 但不跟踪符号链接。返回值是 @ref{101d,,stat_result} 对象。

在不支持符号链接的平台上，本函数是 @ref{1f1,,stat()} 的别名。

从 Python 3.3 起，此功能等价于 @code{os.stat(path, dir_fd=dir_fd, follow_symlinks=False)}。

本函数支持 @ref{a2a,,基于目录描述符的相对路径}。


@subsubheading 参见


@ref{1f1,,stat()} 函数。



在 3.2 版更改: 添加对 Windows 6.0 (Vista) 符号链接的支持。



在 3.3 版更改: 添加了 @emph{dir_fd} 参数。



在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{src} 和 @emph{dst}。



在 3.8 版更改: 目前在 Windows 上，遇到表示另一个路径的重解析点（即名称代理，包括符号链接和目录结点），本函数将打开它。其他种类的重解析点由 @ref{1f1,,stat()} 交由操作系统解析。

@end deffn

@geindex mkdir() (在 os 模块中)
@anchor{library/os os mkdir}@anchor{a31}
@deffn {函数} os.mkdir (path, mode=0o777, *, dir_fd=None)

创建一个名为 @emph{path} 的目录，应用以数字表示的权限模式 @emph{mode}。

如果目录已存在，则抛出 @ref{952,,FileExistsError} 异常。
@anchor{library/os mkdir-modebits}@anchor{1ee5}
某些系统会忽略 @emph{mode}。如果没有忽略它，那么将首先从它中减去当前的 umask 值。如果除最后 9 位（即 @emph{mode} 八进制的最后 3 位）之外，还设置了其他位，则其他位的含义取决于各个平台。在某些平台上，它们会被忽略，应显式调用 @ref{a2e,,chmod()} 进行设置。

本函数支持 @ref{a2a,,基于目录描述符的相对路径}。

如果需要创建临时目录，请参阅 @ref{103,,tempfile} 模块中的 @ref{1bfb,,tempfile.mkdtemp()} 函数。

引发一个 @ref{12d0,,审计事件} @code{os.mkdir}，附带参数 @code{path}、@code{mode}、@code{dir_fd}。


3.3 新版功能: @emph{dir_fd} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex makedirs() (在 os 模块中)
@anchor{library/os os makedirs}@anchor{3b5}
@deffn {函数} os.makedirs (name, mode=0o777, exist_ok=False)

@geindex directory; creating
@geindex UNC paths; and os.makedirs()

递归目录创建函数。与 @ref{a31,,mkdir()} 类似，但会自动创建到达最后一级目录所需要的中间目录。

@emph{mode} 参数会传递给 @ref{a31,,mkdir()}，用来创建最后一级目录，对于该参数的解释，请参阅 @ref{1ee5,,mkdir() 中的描述}。要设置某些新建的父目录的权限，可以在调用 @ref{3b5,,makedirs()} 之前设置 umask。现有父目录的权限不会更改。

如果 @emph{exist_ok} 为 @code{False} (默认值)，则如果目标目录已存在将引发 @ref{952,,FileExistsError}。

@cartouche
@quotation 注解 
如果要创建的路径元素包含 @ref{1ee6,,pardir} (如 UNIX 系统中的 "..") @ref{3b5,,makedirs()} 将无法明确目标。
@end quotation
@end cartouche

本函数能正确处理 UNC 路径。

引发一个 @ref{12d0,,审计事件} @code{os.mkdir}，附带参数 @code{path}、@code{mode}、@code{dir_fd}。


3.2 新版功能: @emph{exist_ok} 参数。



在 3.4.1 版更改: 在 Python 3.4.1 以前，如果 @emph{exist_ok} 为 @code{True}，且目录已存在，且 @emph{mode} 与现有目录的权限不匹配，@ref{3b5,,makedirs()} 仍会抛出错误。由于无法安全地实现此行为，因此在 Python 3.4.1 中将该行为删除。请参阅 bpo-21082@footnote{https://bugs.python.org/issue21082}。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。



在 3.7 版更改: @emph{mode} 参数不再影响新创建的中间目录的权限。

@end deffn

@geindex mkfifo() (在 os 模块中)
@anchor{library/os os mkfifo}@anchor{65d}
@deffn {函数} os.mkfifo (path, mode=0o666, *, dir_fd=None)

创建一个名为 @emph{path} 的 FIFO（命名管道，一种先进先出队列），具有以数字表示的权限状态 @emph{mode}。将从 mode 中首先减去当前的 umask 值。

本函数支持 @ref{a2a,,基于目录描述符的相对路径}。

FIFO 是可以像常规文件一样访问的管道。FIFO 如果没有被删除（如使用 @ref{a37,,os.unlink()}），会一直存在。通常，FIFO 用作“客户端”和“服务器”进程之间的汇合点：服务器打开 FIFO 进行读取，而客户端打开 FIFO 进行写入。请注意，@ref{65d,,mkfifo()} 不会打开 FIFO --- 它只是创建汇合点。

@ref{12f5,,可用性}: Unix。


3.3 新版功能: @emph{dir_fd} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex mknod() (在 os 模块中)
@anchor{library/os os mknod}@anchor{65e}
@deffn {函数} os.mknod (path, mode=0o600, device=0, *, dir_fd=None)

创建一个名为 @emph{path} 的文件系统节点（文件，设备专用文件或命名管道）。@emph{mode} 指定权限和节点类型，方法是将权限与下列节点类型 @code{stat.S_IFREG}、@code{stat.S_IFCHR}、@code{stat.S_IFBLK} 和 @code{stat.S_IFIFO} 之一（按位或）组合（这些常量可以在 @ref{f4,,stat} 模块中找到）。对于 @code{stat.S_IFCHR} 和 @code{stat.S_IFBLK}，@emph{device} 参数指定了新创建的设备专用文件（可能会用到 @ref{1ee7,,os.makedev()}），否则该参数将被忽略。

本函数支持 @ref{a2a,,基于目录描述符的相对路径}。

@ref{12f5,,可用性}: Unix。


3.3 新版功能: @emph{dir_fd} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex major() (在 os 模块中)
@anchor{library/os os major}@anchor{1ee8}
@deffn {函数} os.major (device)

提取主设备号，提取自原始设备号（通常是 @code{stat} 中的 @code{st_dev} 或 @code{st_rdev} 字段）。
@end deffn

@geindex minor() (在 os 模块中)
@anchor{library/os os minor}@anchor{1ee9}
@deffn {函数} os.minor (device)

提取次设备号，提取自原始设备号（通常是 @code{stat} 中的 @code{st_dev} 或 @code{st_rdev} 字段）。
@end deffn

@geindex makedev() (在 os 模块中)
@anchor{library/os os makedev}@anchor{1ee7}
@deffn {函数} os.makedev (major, minor)

将主设备号和次设备号组合成原始设备号。
@end deffn

@geindex pathconf() (在 os 模块中)
@anchor{library/os os pathconf}@anchor{a3d}
@deffn {函数} os.pathconf (path, name)

返回所给名称的文件有关的系统配置信息。@emph{name} 指定要查找的配置名称，它可以是字符串，是一个系统已定义的名称，这些名称定义在不同标准（POSIX.1，Unix 95，Unix 98 等）中。一些平台还定义了额外的其他名称。当前操作系统已定义的名称在 @code{pathconf_names} 字典中给出。对于未包含在该映射中的配置名称，也可以传递一个整数作为 @emph{name}。

如果 @emph{name} 是一个字符串且不是已定义的名称，将抛出 @ref{1fb,,ValueError} 异常。如果当前系统不支持 @emph{name} 指定的配置名称，即使该名称存在于 @code{pathconf_names}，也会抛出 @ref{1d3,,OSError} 异常，错误码为 @ref{f59,,errno.EINVAL}。

本函数支持 @ref{3ad,,指定文件描述符为参数}。

@ref{12f5,,可用性}: Unix。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex pathconf_names() (在 os 模块中)
@anchor{library/os os pathconf_names}@anchor{1eea}
@deffn {数据} os.pathconf_names

字典，表示映射关系，为 @ref{a3d,,pathconf()} 和 @ref{1ea6,,fpathconf()} 可接受名称与操作系统为这些名称定义的整数值之间的映射。这可用于判断系统已定义了哪些名称。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex readlink() (在 os 模块中)
@anchor{library/os os readlink}@anchor{1f3}
@deffn {函数} os.readlink (path, *, dir_fd=None)

返回一个字符串，为符号链接指向的实际路径。其结果可以是绝对或相对路径。如果是相对路径，则可用 @code{os.path.join(os.path.dirname(path), result)} 转换为绝对路径。

如果 @emph{path} 是字符串对象（直接传入或通过 @ref{4e5,,PathLike} 接口间接传入），则结果也将是字符串对象，且此类调用可能会引发 UnicodeDecodeError。如果 @emph{path} 是字节对象（直接传入或间接传入），则结果将会是字节对象。

本函数支持 @ref{a2a,,基于目录描述符的相对路径}。

当尝试解析的路径可能含有链接时，请改用 @ref{1ff,,realpath()} 以正确处理递归和平台差异。

@ref{12f5,,可用性}: Unix, Windows。


在 3.2 版更改: 添加对 Windows 6.0 (Vista) 符号链接的支持。



3.3 新版功能: @emph{dir_fd} 参数。



在 3.6 版更改: 在 Unix 上可以接受一个 @ref{363,,类路径对象}。



在 3.8 版更改: 在 Windows 上接受 @ref{363,,类路径对象} 和字节对象。



在 3.8 版更改: 增加了对目录链接的支持，且返回值改为了“替换路径”的形式（通常带有 @code{\\?\} 前缀），而不是先前那样返回可选的 "print name" 字段。

@end deffn

@geindex remove() (在 os 模块中)
@anchor{library/os os remove}@anchor{a32}
@deffn {函数} os.remove (path, *, dir_fd=None)

移除（删除）文件 @emph{path}。如果 @emph{path} 是目录，则抛出 @ref{993,,IsADirectoryError} 异常。请使用 @ref{a35,,rmdir()} 删除目录。

本函数支持 @ref{a2a,,基于目录描述符的相对路径}。

在 Windows 上，尝试删除正在使用的文件会抛出异常。而在 Unix 上，虽然该文件的条目会被删除，但分配给文件的存储空间仍然不可用，直到原始文件不再使用为止。

本函数在语义上与 @ref{a37,,unlink()} 相同。

引发一个 @ref{12d0,,审计事件} @code{os.remove}，附带参数 @code{path}、@code{dir_fd}。


3.3 新版功能: @emph{dir_fd} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex removedirs() (在 os 模块中)
@anchor{library/os os removedirs}@anchor{1eeb}
@deffn {函数} os.removedirs (name)

@geindex directory; deleting

递归删除目录。工作方式类似于 @ref{a35,,rmdir()}，不同之处在于，如果成功删除了末尾一级目录，@ref{1eeb,,removedirs()} 会尝试依次删除 @emph{path} 中提到的每个父目录，直到抛出错误为止（但该错误会被忽略，因为这通常表示父目录不是空目录）。例如，@code{os.removedirs('foo/bar/baz')} 将首先删除目录 @code{'foo/bar/baz'}，然后如果 @code{'foo/bar'} 和 @code{'foo'} 为空，则继续删除它们。如果无法成功删除末尾一级目录，则抛出 @ref{1d3,,OSError} 异常。

引发一个 @ref{12d0,,审计事件} @code{os.remove}，附带参数 @code{path}、@code{dir_fd}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex rename() (在 os 模块中)
@anchor{library/os os rename}@anchor{a33}
@deffn {函数} os.rename (src, dst, *, src_dir_fd=None, dst_dir_fd=None)

将文件或目录 @emph{src} 重命名为 @emph{dst}。如果 @emph{dst} 已存在，则下列情况下将会操作失败，并抛出 @ref{1d3,,OSError} 的子类：

在 Windows 上，如果 @emph{dst} 已存在，则抛出 @ref{952,,FileExistsError} 异常。

在 Unix 上，如果 @emph{src} 是文件而 @emph{dst} 是目录，将抛出 @ref{993,,IsADirectoryError} 异常，反之则抛出 @ref{994,,NotADirectoryError} 异常。如果两者都是目录且 @emph{dst} 为空，则 @emph{dst} 将被静默替换。如果 @emph{dst} 是非空目录，则抛出 @ref{1d3,,OSError} 异常。如果两者都是文件，则在用户具有权限的情况下，将对 @emph{dst} 进行静默替换。如果 @emph{src} 和 @emph{dst} 在不同的文件系统上，则本操作在某些 Unix 分支上可能会失败。如果成功，重命名操作将是一个原子操作（这是 POSIX 的要求）。

本函数支持将 @emph{src_dir_fd} 和 @emph{dst_dir_fd} 中的一个或两个指定为 @ref{a2a,,基于目录描述符的相对路径}。

如果需要在不同平台上都能替换目标，请使用 @ref{a34,,replace()}。

引发一个 @ref{12d0,,审计事件} @code{os.rename} 附带参数 @code{src}、@code{dst}、@code{src_dir_fd}、@code{dst_dir_fd}。


3.3 新版功能: @emph{src_dir_fd} 和 @emph{dst_dir_fd} 参数。



在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{src} 和 @emph{dst}。

@end deffn

@geindex renames() (在 os 模块中)
@anchor{library/os os renames}@anchor{1eec}
@deffn {函数} os.renames (old, new)

递归重命名目录或文件。工作方式类似 @ref{a33,,rename()}，除了会首先创建新路径所需的中间目录。重命名后，将调用 @ref{1eeb,,removedirs()} 删除旧路径中不需要的目录。

@cartouche
@quotation 注解 
如果用户没有权限删除末级的目录或文件，则本函数可能会无法建立新的目录结构。
@end quotation
@end cartouche

引发一个 @ref{12d0,,审计事件} @code{os.rename} 附带参数 @code{src}、@code{dst}、@code{src_dir_fd}、@code{dst_dir_fd}。


在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{old} 和 @emph{new}。

@end deffn

@geindex replace() (在 os 模块中)
@anchor{library/os os replace}@anchor{a34}
@deffn {函数} os.replace (src, dst, *, src_dir_fd=None, dst_dir_fd=None)

将文件或目录 @emph{src} 重命名为 @emph{dst}。如果 @emph{dst} 是目录，将抛出 @ref{1d3,,OSError} 异常。如果 @emph{dst} 已存在且为文件，则在用户具有权限的情况下，将对其进行静默替换。如果 @emph{src} 和 @emph{dst} 在不同的文件系统上，本操作可能会失败。如果成功，重命名操作将是一个原子操作（这是 POSIX 的要求）。

本函数支持将 @emph{src_dir_fd} 和 @emph{dst_dir_fd} 中的一个或两个指定为 @ref{a2a,,基于目录描述符的相对路径}。

引发一个 @ref{12d0,,审计事件} @code{os.rename} 附带参数 @code{src}、@code{dst}、@code{src_dir_fd}、@code{dst_dir_fd}。


3.3 新版功能.



在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{src} 和 @emph{dst}。

@end deffn

@geindex rmdir() (在 os 模块中)
@anchor{library/os os rmdir}@anchor{a35}
@deffn {函数} os.rmdir (path, *, dir_fd=None)

移除（删除）目录 @emph{path}。如果目录不存在或不为空，则会分别抛出 @ref{7ba,,FileNotFoundError} 或 @ref{1d3,,OSError} 异常。要删除整个目录树，可以使用 @ref{21c,,shutil.rmtree()}。

本函数支持 @ref{a2a,,基于目录描述符的相对路径}。

引发一个 @ref{12d0,,审计事件} @code{os.rmdir}，附带参数 @code{path}、@code{dir_fd}。


3.3 新版功能: @emph{dir_fd} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex scandir() (在 os 模块中)
@anchor{library/os os scandir}@anchor{25f}
@deffn {函数} os.scandir (path='.')

返回一个迭代出 @ref{4eb,,os.DirEntry} 对象的迭代器，这些对象对应于 @emph{path} 目录中的条目。条目的生成顺序是任意的，特殊条目 @code{'.'} 和 @code{'..'} 不包括在内。

如果需要文件类型或文件属性信息，使用 @ref{25f,,scandir()} 代替 @ref{a3c,,listdir()} 可以大大提高这部分代码的性能，因为如果操作系统在扫描目录时返回的是 @ref{4eb,,os.DirEntry} 对象，则该对象包含了这些信息。所有 @ref{4eb,,os.DirEntry} 的方法都可能执行一次系统调用，但是 @ref{1eed,,is_dir()} 和 @ref{64f,,is_file()} 通常只在有符号链接时才执行一次系统调用。@ref{1eee,,os.DirEntry.stat()} 在 Unix 上始终需要一次系统调用，而在 Windows 上只在有符号链接时才需要。

@emph{path} 可以是 @ref{363,,类路径对象}。如果 @emph{path} 是（直接传入或通过 @ref{4e5,,PathLike} 接口间接传入的） @code{bytes} 类型，那么每个 @ref{4eb,,os.DirEntry} 的 @ref{1eef,,name} 和 @ref{1ef0,,path} 属性将是 @code{bytes} 类型，其他情况下是 @code{str} 类型。

本函数也支持 @ref{3ad,,指定文件描述符为参数}，其中描述符必须指向目录。

引发一个 @ref{12d0,,审计事件} @code{os.scandir}，附带参数 @code{path}。

@ref{25f,,scandir()} 迭代器支持 @ref{563,,上下文管理} 协议，并具有以下方法：

@geindex close() (os.scandir 方法)
@anchor{library/os os scandir close}@anchor{562}
@deffn {方法} scandir.close ()

关闭迭代器并释放占用的资源。

当迭代器迭代完毕，或垃圾回收，或迭代过程出错时，将自动调用本方法。但仍建议显式调用它或使用 @ref{6e3,,with} 语句。


3.6 新版功能.

@end deffn

下面的例子演示了 @ref{25f,,scandir()} 的简单用法，用来显示给定 @emph{path} 中所有不以 @code{'.'} 开头的文件（不包括目录）。@code{entry.is_file()} 通常不会增加一次额外的系统调用:

@example
with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)
@end example

@cartouche
@quotation 注解 
在基于 Unix 的系统上，@ref{25f,,scandir()} 使用系统的 opendir()@footnote{http://pubs.opengroup.org/onlinepubs/009695399/functions/opendir.html} 和 readdir()@footnote{http://pubs.opengroup.org/onlinepubs/009695399/functions/readdir_r.html} 函数。在 Windows 上，它使用 Win32 FindFirstFileW@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa364418(v=vs.85).aspx} 和 FindNextFileW@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa364428(v=vs.85).aspx} 函数。
@end quotation
@end cartouche


3.5 新版功能.



3.6 新版功能: 添加了对 @ref{563,,上下文管理} 协议和 @ref{562,,close()} 方法的支持。如果 @ref{25f,,scandir()} 迭代器没有迭代完毕且没有显式关闭，其析构函数将发出 @ref{4ca,,ResourceWarning} 警告。

本函数接受一个 @ref{363,,类路径对象}。



在 3.7 版更改: 在 Unix 上新增支持 @ref{3ad,,指定文件描述符为参数}。

@end deffn

@geindex DirEntry (os 中的类)
@anchor{library/os os DirEntry}@anchor{4eb}
@deffn {类} os.DirEntry

由 @ref{25f,,scandir()} 生成的对象，用于显示目录内某个条目的文件路径和其他文件属性。

@ref{25f,,scandir()} 将在不进行额外系统调用的情况下，提供尽可能多的此类信息。每次进行 @code{stat()} 或 @code{lstat()} 系统调用时，@code{os.DirEntry} 对象会将结果缓存下来。

@code{os.DirEntry} 实例不适合存储在长期存在的数据结构中，如果你知道文件元数据已更改，或者自调用 @ref{25f,,scandir()} 以来已经经过了很长时间，请调用 @code{os.stat(entry.path)} 来获取最新信息。

因为 @code{os.DirEntry} 方法可以进行系统调用，所以它也可能抛出 @ref{1d3,,OSError} 异常。如需精确定位错误，可以逐个调用 @code{os.DirEntry} 中的方法来捕获 @ref{1d3,,OSError}，并适当处理。

为了能直接用作 @ref{363,,类路径对象}，@code{os.DirEntry} 实现了 @ref{4e5,,PathLike} 接口。

@code{os.DirEntry} 实例所包含的属性和方法如下：

@geindex name (os.DirEntry 属性)
@anchor{library/os os DirEntry name}@anchor{1eef}
@deffn {属性} name

本条目的基本文件名，是根据 @ref{25f,,scandir()} 的 @emph{path} 参数得出的相对路径。

如果 @ref{25f,,scandir()} 的 @emph{path} 参数是 @code{bytes} 类型，则 @ref{1e76,,name} 属性也是 @code{bytes} 类型，否则为 @code{str}。使用 @ref{4e8,,fsdecode()} 解码 byte 类型的文件名。
@end deffn

@geindex path (os.DirEntry 属性)
@anchor{library/os os DirEntry path}@anchor{1ef0}
@deffn {属性} path

本条目的完整路径：等效于 @code{os.path.join(scandir_path, entry.name)}，其中 @emph{scandir_path} 就是 @ref{25f,,scandir()} 的 @emph{path} 参数。仅当 @ref{25f,,scandir()} 的 @emph{path} 参数为绝对路径时，本路径才是绝对路径。如果 @ref{25f,,scandir()} 的 @emph{path} 参数是 @ref{3ad,,文件描述符}，则 @ref{c5,,path} 属性与上述 @ref{1e76,,name} 属性相同。

如果 @ref{25f,,scandir()} 的 @emph{path} 参数是 @code{bytes} 类型，则 @ref{c5,,path} 属性也是 @code{bytes} 类型，否则为 @code{str}。使用 @ref{4e8,,fsdecode()} 解码 byte 类型的文件名。
@end deffn

@geindex inode() (os.DirEntry 方法)
@anchor{library/os os DirEntry inode}@anchor{1ef1}
@deffn {方法} inode ()

返回本条目的索引节点号 (inode number)。

这一结果是缓存在 @code{os.DirEntry} 对象中的，请调用 @code{os.stat(entry.path, follow_symlinks=False).st_ino} 来获取最新信息。

一开始没有缓存时，在 Windows 上需要一次系统调用，但在 Unix 上不需要。
@end deffn

@geindex is_dir() (os.DirEntry 方法)
@anchor{library/os os DirEntry is_dir}@anchor{1eed}
@deffn {方法} is_dir (*, follow_symlinks=True)

如果本条目是目录，或是指向目录的符号链接，则返回 @code{True}。如果本条目是文件，或指向任何其他类型的文件，或该目录不再存在，则返回 @code{False}。

如果 @emph{follow_symlinks} 是 @code{False}，那么仅当本条目为目录时返回 @code{True} （不跟踪符号链接），如果本条目是任何类型的文件，或该文件不再存在，则返回 @code{False}。

这一结果是缓存在 @code{os.DirEntry} 对象中的，且 @emph{follow_symlinks} 为 @code{True} 和 @code{False} 时的缓存是分开的。请调用 @ref{1f1,,os.stat()} 和 @ref{1b94,,stat.S_ISDIR()} 来获取最新信息。

一开始没有缓存时，大多数情况下不需要系统调用。特别是对于非符号链接，Windows 和 Unix 都不需要系统调用，除非某些 Unix 文件系统（如网络文件系统）返回了 @code{dirent.d_type == DT_UNKNOWN}。如果本条目是符号链接，则需要一次系统调用来跟踪它（除非 @emph{follow_symlinks} 为 @code{False}）。

本方法可能抛出 @ref{1d3,,OSError} 异常，如 @ref{5fa,,PermissionError} 异常，但 @ref{7ba,,FileNotFoundError} 异常会被内部捕获且不会抛出。
@end deffn

@geindex is_file() (os.DirEntry 方法)
@anchor{library/os os DirEntry is_file}@anchor{64f}
@deffn {方法} is_file (*, follow_symlinks=True)

如果本条目是文件，或是指向文件的符号链接，则返回 @code{True}。如果本条目是目录，或指向目录，或指向其他非文件条目，或该文件不再存在，则返回 @code{False}。

如果 @emph{follow_symlinks} 是 @code{False}，那么仅当本条目为文件时返回 @code{True} （不跟踪符号链接），如果本条目是目录或其他非文件条目，或该文件不再存在，则返回 @code{False}。

这一结果是缓存在 @code{os.DirEntry} 对象中的。缓存、系统调用、异常抛出都与 @ref{1eed,,is_dir()} 一致。
@end deffn

@geindex is_symlink() (os.DirEntry 方法)
@anchor{library/os os DirEntry is_symlink}@anchor{1ef2}
@deffn {方法} is_symlink ()

如果本条目是符号链接（即使是断开的链接），返回 @code{True}。如果是目录或任何类型的文件，或本条目不再存在，返回 @code{False}。

这一结果是缓存在 @code{os.DirEntry} 对象中的，请调用 @ref{1f4,,os.path.islink()} 来获取最新信息。

一开始没有缓存时，大多数情况下不需要系统调用。其实 Windows 和 Unix 都不需要系统调用，除非某些 Unix 文件系统（如网络文件系统）返回了 @code{dirent.d_type == DT_UNKNOWN}。

本方法可能抛出 @ref{1d3,,OSError} 异常，如 @ref{5fa,,PermissionError} 异常，但 @ref{7ba,,FileNotFoundError} 异常会被内部捕获且不会抛出。
@end deffn

@geindex stat() (os.DirEntry 方法)
@anchor{library/os os DirEntry stat}@anchor{1eee}
@deffn {方法} stat (*, follow_symlinks=True)

返回本条目对应的 @ref{101d,,stat_result} 对象。本方法默认会跟踪符号链接，要获取符号链接本身的 stat，请添加 @code{follow_symlinks=False} 参数。

在 Unix 上，本方法需要一次系统调用。在 Windows 上，仅在 @emph{follow_symlinks} 为 @code{True} 且该条目是一个重解析点（如符号链接或目录结点）时，才需要一次系统调用。

在 Windows 上，@ref{101d,,stat_result} 的 @code{st_ino}、@code{st_dev} 和 @code{st_nlink} 属性总是为零。请调用 @ref{1f1,,os.stat()} 以获得这些属性。

这一结果是缓存在 @code{os.DirEntry} 对象中的，且 @emph{follow_symlinks} 为 @code{True} 和 @code{False} 时的缓存是分开的。请调用 @ref{1f1,,os.stat()} 来获取最新信息。
@end deffn

注意，@code{os.DirEntry} 和 @ref{201,,pathlib.Path} 的几个属性和方法之间存在很好的对应关系。具体来说是 @code{name} 属性，以及 @code{is_dir()}、@code{is_file()}、@code{is_symlink()} 和 @code{stat()} 方法，在两个类中具有相同的含义。


3.5 新版功能.



在 3.6 版更改: 添加了对 @ref{4e5,,PathLike} 接口的支持。在 Windows 上添加了对 @ref{32a,,bytes} 类型路径的支持。

@end deffn

@geindex stat() (在 os 模块中)
@anchor{library/os os stat}@anchor{1f1}
@deffn {函数} os.stat (path, *, dir_fd=None, follow_symlinks=True)

获取文件或文件描述符的状态。在所给路径上执行等效于 @code{stat()} 系统调用的操作。@emph{path} 可以是字符串类型，或（直接传入或通过 @ref{4e5,,PathLike} 接口间接传入的） bytes 类型，或打开的文件描述符。返回一个 @ref{101d,,stat_result} 对象。

本函数默认会跟踪符号链接，要获取符号链接本身的 stat，请添加 @code{follow_symlinks=False} 参数，或使用 @ref{1f2,,lstat()}。

本函数支持 @ref{3ad,,指定文件描述符为参数} 和 @ref{a2b,,不跟踪符号链接}。

在 Windows 上，传入 @code{follow_symlinks=False} 将禁用所有名称代理重解析点，其中包括符号链接和目录结点。其他类型的重解析点将直接打开，比如不像链接的或系统无法跟踪的重解析点。当多个链接形成一个链时，本方法可能会返回原始链接的 stat，无法完整遍历到非链接的对象。在这种情况下，要获取最终路径的 stat，请使用 @ref{1ff,,os.path.realpath()} 函数尽可能地解析路径，并在解析结果上调用 @ref{1f2,,lstat()}。这不适用于空链接或交接点，否则会抛出异常。

@geindex 模块; stat

示例:

@example
>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264
@end example


@subsubheading 参见


@ref{659,,fstat()} 和 @ref{1f2,,lstat()} 函数。



3.3 新版功能: 增加 @emph{dir_fd} 和 @emph{follow_symlinks} 参数，可指定文件描述符代替路径。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。



在 3.8 版更改: 在 Windows 上，本方法将跟踪系统能解析的所有重解析点，并且传入 @code{follow_symlinks=False} 会停止跟踪所有名称代理重解析点。现在，如果操作系统遇到无法跟踪的重解析点，@emph{stat} 将返回原始路径的信息，就像已指定 @code{follow_symlinks=False} 一样，而不会抛出异常。

@end deffn

@geindex stat_result (os 中的类)
@anchor{library/os os stat_result}@anchor{101d}
@deffn {类} os.stat_result

本对象的属性大致对应于 @code{stat} 结构体成员，主要作为 @ref{1f1,,os.stat()}、@ref{659,,os.fstat()} 和 @ref{1f2,,os.lstat()} 的返回值。

属性：

@geindex st_mode (os.stat_result 属性)
@anchor{library/os os stat_result st_mode}@anchor{1ef3}
@deffn {属性} st_mode

文件模式：包括文件类型和文件模式位（即权限位）。
@end deffn

@geindex st_ino (os.stat_result 属性)
@anchor{library/os os stat_result st_ino}@anchor{1ef4}
@deffn {属性} st_ino

与平台有关，但如果不为零，则根据 @code{st_dev} 值唯一地标识文件。通常：


@itemize *

@item 
在 Unix 上该值表示索引节点号 (inode number)。

@item 
在 Windows 上该值表示 文件索引号@footnote{https://msdn.microsoft.com/en-us/library/aa363788} 。
@end itemize
@end deffn

@geindex st_dev (os.stat_result 属性)
@anchor{library/os os stat_result st_dev}@anchor{1ef5}
@deffn {属性} st_dev

该文件所在设备的标识符。
@end deffn

@geindex st_nlink (os.stat_result 属性)
@anchor{library/os os stat_result st_nlink}@anchor{1ef6}
@deffn {属性} st_nlink

硬链接的数量。
@end deffn

@geindex st_uid (os.stat_result 属性)
@anchor{library/os os stat_result st_uid}@anchor{1ef7}
@deffn {属性} st_uid

文件所有者的用户 ID。
@end deffn

@geindex st_gid (os.stat_result 属性)
@anchor{library/os os stat_result st_gid}@anchor{1ef8}
@deffn {属性} st_gid

文件所有者的用户组 ID。
@end deffn

@geindex st_size (os.stat_result 属性)
@anchor{library/os os stat_result st_size}@anchor{1ef9}
@deffn {属性} st_size

文件大小（以字节为单位），文件可以是常规文件或符号链接。符号链接的大小是它包含的路径的长度，不包括末尾的空字节。
@end deffn

时间戳：

@geindex st_atime (os.stat_result 属性)
@anchor{library/os os stat_result st_atime}@anchor{1efa}
@deffn {属性} st_atime

最近的访问时间，以秒为单位。
@end deffn

@geindex st_mtime (os.stat_result 属性)
@anchor{library/os os stat_result st_mtime}@anchor{1ceb}
@deffn {属性} st_mtime

最近的修改时间，以秒为单位。
@end deffn

@geindex st_ctime (os.stat_result 属性)
@anchor{library/os os stat_result st_ctime}@anchor{1efb}
@deffn {属性} st_ctime

取决于平台：


@itemize *

@item 
在 Unix 上表示最近的元数据更改时间，

@item 
在 Windows 上表示创建时间，以秒为单位。
@end itemize
@end deffn

@geindex st_atime_ns (os.stat_result 属性)
@anchor{library/os os stat_result st_atime_ns}@anchor{1efc}
@deffn {属性} st_atime_ns

最近的访问时间，以纳秒表示，为整数。
@end deffn

@geindex st_mtime_ns (os.stat_result 属性)
@anchor{library/os os stat_result st_mtime_ns}@anchor{1efd}
@deffn {属性} st_mtime_ns

最近的修改时间，以纳秒表示，为整数。
@end deffn

@geindex st_ctime_ns (os.stat_result 属性)
@anchor{library/os os stat_result st_ctime_ns}@anchor{1efe}
@deffn {属性} st_ctime_ns

取决于平台：


@itemize *

@item 
在 Unix 上表示最近的元数据更改时间，

@item 
在 Windows 上表示创建时间，以纳秒表示，为整数。
@end itemize
@end deffn

@cartouche
@quotation 注解 
@ref{1efa,,st_atime}、@ref{1ceb,,st_mtime} 和 @ref{1efb,,st_ctime} 属性的确切含义和分辨率取决于操作系统和文件系统。例如，在使用 FAT 或 FAT32 文件系统的 Windows 上，@ref{1ceb,,st_mtime} 有 2 秒的分辨率，而 @ref{1efa,,st_atime} 仅有 1 天的分辨率。详细信息请参阅操作系统文档。

类似地，尽管 @ref{1efc,,st_atime_ns}、@ref{1efd,,st_mtime_ns} 和 @ref{1efe,,st_ctime_ns} 始终以纳秒表示，但许多系统并不提供纳秒精度。在确实提供纳秒精度的系统上，用于存储 @ref{1efa,,st_atime}、@ref{1ceb,,st_mtime} 和 @ref{1efb,,st_ctime} 的浮点对象无法保留所有精度，因此不够精确。如果需要确切的时间戳，则应始终使用 @ref{1efc,,st_atime_ns}、@ref{1efd,,st_mtime_ns} 和 @ref{1efe,,st_ctime_ns}。
@end quotation
@end cartouche

在某些 Unix 系统上（如 Linux 上），以下属性可能也可用：

@geindex st_blocks (os.stat_result 属性)
@anchor{library/os os stat_result st_blocks}@anchor{1eff}
@deffn {属性} st_blocks

为文件分配的字节块数，每块 512 字节。文件是稀疏文件时，它可能小于 @ref{1ef9,,st_size}/512。
@end deffn

@geindex st_blksize (os.stat_result 属性)
@anchor{library/os os stat_result st_blksize}@anchor{1f00}
@deffn {属性} st_blksize

“首选的” 块大小，用于提高文件系统 I/O 效率。写入文件时块大小太小可能会导致读取-修改-重写效率低下。
@end deffn

@geindex st_rdev (os.stat_result 属性)
@anchor{library/os os stat_result st_rdev}@anchor{1f01}
@deffn {属性} st_rdev

设备类型（如果是 inode 设备）。
@end deffn

@geindex st_flags (os.stat_result 属性)
@anchor{library/os os stat_result st_flags}@anchor{1f02}
@deffn {属性} st_flags

用户定义的文件标志位。
@end deffn

在其他 Unix 系统上（如 FreeBSD 上），以下属性可能可用（但仅当 root 使用它们时才被填充）：

@geindex st_gen (os.stat_result 属性)
@anchor{library/os os stat_result st_gen}@anchor{1f03}
@deffn {属性} st_gen

文件生成号。
@end deffn

@geindex st_birthtime (os.stat_result 属性)
@anchor{library/os os stat_result st_birthtime}@anchor{1f04}
@deffn {属性} st_birthtime

文件创建时间。
@end deffn

在 Solaris 及其衍生版本上，以下属性可能也可用：

@geindex st_fstype (os.stat_result 属性)
@anchor{library/os os stat_result st_fstype}@anchor{3b7}
@deffn {属性} st_fstype

文件所在文件系统的类型的唯一标识，为字符串。
@end deffn

在 Mac OS 系统上，以下属性可能也可用：

@geindex st_rsize (os.stat_result 属性)
@anchor{library/os os stat_result st_rsize}@anchor{1f05}
@deffn {属性} st_rsize

文件的实际大小。
@end deffn

@geindex st_creator (os.stat_result 属性)
@anchor{library/os os stat_result st_creator}@anchor{1f06}
@deffn {属性} st_creator

文件的创建者。
@end deffn

@geindex st_type (os.stat_result 属性)
@anchor{library/os os stat_result st_type}@anchor{1f07}
@deffn {属性} st_type

文件类型。
@end deffn

在 Windows 系统上，以下属性也可用：

@geindex st_file_attributes (os.stat_result 属性)
@anchor{library/os os stat_result st_file_attributes}@anchor{71a}
@deffn {属性} st_file_attributes

Windows 文件属性：@code{dwFileAttributes}，由 @code{GetFileInformationByHandle()} 返回的 @code{BY_HANDLE_FILE_INFORMATION} 结构体的成员之一。请参阅 @ref{f4,,stat} 模块中的 @code{FILE_ATTRIBUTE_*} 常量。
@end deffn

@geindex st_reparse_tag (os.stat_result 属性)
@anchor{library/os os stat_result st_reparse_tag}@anchor{1f08}
@deffn {属性} st_reparse_tag

当 @ref{71a,,st_file_attributes} 存在 @code{FILE_ATTRIBUTE_REPARSE_POINT} 集合时，本字段包含重解析点类型标记。请参阅 @ref{f4,,stat} 模块中的 @code{IO_REPARSE_TAG_*} 常量。
@end deffn

标准模块 @ref{f4,,stat} 中定义了函数和常量，这些函数和常量可用于从 @code{stat} 结构体中提取信息。（在 Windows 上，某些项填充的是虚值。）

为了向后兼容，一个 @ref{101d,,stat_result} 实例还可以作为至少包含 10 个整数的元组访问，以提供 @code{stat} 结构中最重要（和可移植）的成员，整数顺序为 @ref{1ef3,,st_mode}, @ref{1ef4,,st_ino}, @ref{1ef5,,st_dev}, @ref{1ef6,,st_nlink}, @ref{1ef7,,st_uid}, @ref{1ef8,,st_gid}, @ref{1ef9,,st_size}, @ref{1efa,,st_atime}, @ref{1ceb,,st_mtime}, @ref{1efb,,st_ctime}。某些实现可能在末尾还有更多项。为了与旧版 Python 兼容，以元组形式访问 @ref{101d,,stat_result} 始终返回整数。


3.3 新版功能: 添加了 @ref{1efc,,st_atime_ns}、@ref{1efd,,st_mtime_ns} 和 @ref{1efe,,st_ctime_ns} 成员。



3.5 新版功能: 在 Windows 上添加了 @ref{71a,,st_file_attributes} 成员。



在 3.5 版更改: 在 Windows 上，如果可用，会返回文件索引作为 @ref{1ef4,,st_ino} 的值。



3.7 新版功能: 在 Solaris 及其衍生版本上添加了 @ref{3b7,,st_fstype} 成员。



3.8 新版功能: 在 Windows 上添加了 @ref{1f08,,st_reparse_tag} 成员。



在 3.8 版更改: 在 Windows 上，@ref{1ef3,,st_mode} 成员现在可以根据需要将特殊文件标识为 @code{S_IFCHR}、@code{S_IFIFO} 或 @code{S_IFBLK}。

@end deffn

@geindex statvfs() (在 os 模块中)
@anchor{library/os os statvfs}@anchor{a3e}
@deffn {函数} os.statvfs (path)

在所给的路径上执行 @code{statvfs()} 系统调用。返回值是一个对象，其属性描述了所给路径上的文件系统，并且与 @code{statvfs} 结构体的成员相对应，即：@code{f_bsize}, @code{f_frsize}, @code{f_blocks}, @code{f_bfree}, @code{f_bavail}, @code{f_files}, @code{f_ffree}, @code{f_favail}, @code{f_flag}, @code{f_namemax}, @code{f_fsid}。

为 @code{f_flag} 属性位定义了两个模块级常量：如果存在 @code{ST_RDONLY} 位，则文件系统以只读挂载；如果存在 @code{ST_NOSUID} 位，则文件系统禁用或不支持 setuid/setgid 位。

为基于 GNU/glibc 的系统还定义了额外的模块级常量。它们是 @code{ST_NODEV} （禁止访问设备专用文件），@code{ST_NOEXEC} （禁止执行程序），@code{ST_SYNCHRONOUS} （写入后立即同步），@code{ST_MANDLOCK} （允许文件系统上的强制锁定），@code{ST_WRITE} （写入文件/目录/符号链接），@code{ST_APPEND} （仅追加文件），@code{ST_IMMUTABLE} （不可变文件），@code{ST_NOATIME} （不更新访问时间），@code{ST_NODIRATIME} （不更新目录访问时间），@code{ST_RELATIME} （相对于 mtime/ctime 更新访问时间）。

本函数支持 @ref{3ad,,指定文件描述符为参数}。

@ref{12f5,,可用性}: Unix。


在 3.2 版更改: 添加了 @code{ST_RDONLY} 和 @code{ST_NOSUID} 常量。



3.3 新版功能: 新增支持将 @emph{path} 参数指定为打开的文件描述符。



在 3.4 版更改: 添加了 @code{ST_NODEV}、@code{ST_NOEXEC}、@code{ST_SYNCHRONOUS}、@code{ST_MANDLOCK}、@code{ST_WRITE}、@code{ST_APPEND}、@code{ST_IMMUTABLE}、@code{ST_NOATIME}、@code{ST_NODIRATIME} 和 @code{ST_RELATIME} 常量。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。



3.7 新版功能: 添加了 @code{f_fsid}。

@end deffn

@geindex supports_dir_fd() (在 os 模块中)
@anchor{library/os os supports_dir_fd}@anchor{a39}
@deffn {数据} os.supports_dir_fd

一个 @ref{b68,,set} 对象，指示 @ref{c4,,os} 模块中的哪些函数接受一个打开的文件描述符作为 @emph{dir_fd} 参数。不同平台提供的功能不同，且 Python 用于实现 @emph{dir_fd} 参数的底层函数并非在 Python 支持的所有平台上都可用。考虑到一致性，支持 @emph{dir_fd} 的函数始终允许指定描述符，但如果在底层不支持时调用了该函数，则会抛出异常。（在所有平台上始终支持将 @emph{dir_fd} 指定为 @code{None}。）

要检查某个函数是否接受打开的文件描述符作为 @emph{dir_fd} 参数，请在 @code{supports_dir_fd} 前使用 @code{in} 运算符。例如，如果 @ref{1f1,,os.stat()} 在当前平台上接受打开的文件描述符作为 @emph{dir_fd} 参数，则此表达式的计算结果为 @code{True}:

@example
os.stat in os.supports_dir_fd
@end example

目前 @emph{dir_fd} 参数仅在 Unix 平台上有效，在 Windows 上均无效。


3.3 新版功能.

@end deffn

@geindex supports_effective_ids() (在 os 模块中)
@anchor{library/os os supports_effective_ids}@anchor{a40}
@deffn {数据} os.supports_effective_ids

一个 @ref{b68,,set} 对象，指示 @ref{a2c,,os.access()} 是否允许在当前平台上将其 @emph{effective_ids} 参数指定为 @code{True}。（所有平台都支持将 @emph{effective_ids} 指定为 @code{False}。）如果当前平台支持，则集合将包含 @ref{a2c,,os.access()}，否则集合为空。

如果当前平台上的 @ref{a2c,,os.access()} 支持 @code{effective_ids=True}，则此表达式的计算结果为 @code{True}:

@example
os.access in os.supports_effective_ids
@end example

目前仅 Unix 平台支持 @emph{effective_ids}，Windows 不支持。


3.3 新版功能.

@end deffn

@geindex supports_fd() (在 os 模块中)
@anchor{library/os os supports_fd}@anchor{a3f}
@deffn {数据} os.supports_fd

一个 @ref{b68,,set} 对象，指示在当前平台上 @ref{c4,,os} 模块中的哪些函数接受一个打开的文件描述符作为 @emph{path} 参数。不同平台提供的功能不同，且 Python 所使用到的底层函数（用于实现接受描述符作为 @emph{path}）并非在 Python 支持的所有平台上都可用。

要判断某个函数是否接受打开的文件描述符作为 @emph{path} 参数，请在 @code{supports_fd} 前使用 @code{in} 运算符。例如，如果 @ref{a3a,,os.chdir()} 在当前平台上接受打开的文件描述符作为 @emph{path} 参数，则此表达式的计算结果为 @code{True}:

@example
os.chdir in os.supports_fd
@end example


3.3 新版功能.

@end deffn

@geindex supports_follow_symlinks() (在 os 模块中)
@anchor{library/os os supports_follow_symlinks}@anchor{1c1b}
@deffn {数据} os.supports_follow_symlinks

一个 @ref{b68,,set} 对象，指示在当前平台上 @ref{c4,,os} 模块中的哪些函数的 @emph{follow_symlinks} 参数可指定为 @code{False}。不同平台提供的功能不同，且 Python 用于实现 @emph{follow_symlinks} 的底层函数并非在 Python 支持的所有平台上都可用。考虑到一致性，支持 @emph{follow_symlinks} 的函数始终允许将其指定为 @code{False}，但如果在底层不支持时调用了该函数，则会抛出异常。（在所有平台上始终支持将 @emph{follow_symlinks} 指定为 @code{True}。）

要检查某个函数的 @emph{follow_symlinks} 参数是否可以指定为 @code{False}，请在 @code{supports_follow_symlinks} 前使用 @code{in} 运算符。例如，如果在当前平台上调用 @ref{1f1,,os.stat()} 时可以指定 @code{follow_symlinks=False}，则此表达式的计算结果为 @code{True}:

@example
os.stat in os.supports_follow_symlinks
@end example


3.3 新版功能.

@end deffn

@geindex symlink() (在 os 模块中)
@anchor{library/os os symlink}@anchor{a36}
@deffn {函数} os.symlink (src, dst, target_is_directory=False, *, dir_fd=None)

创建一个指向 @emph{src} 的符号链接，名为 @emph{dst}。

在 Windows 上，符号链接可以表示文件或目录两种类型，并且不会动态改变类型。如果目标存在，则新建链接的类型将与目标一致。否则，如果 @emph{target_is_directory} 为 @code{True}，则符号链接将创建为目录链接，为 @code{False} （默认）将创建为文件链接。在非 Windows 平台上，@emph{target_is_directory} 被忽略。

本函数支持 @ref{a2a,,基于目录描述符的相对路径}。

@cartouche
@quotation 注解 
在 Windows 10 或更高版本上，如果启用了开发人员模式，非特权帐户可以创建符号链接。如果开发人员模式不可用/未启用，则需要 @emph{SeCreateSymbolicLinkPrivilege} 权限，或者该进程必须以管理员身份运行。

当本函数由非特权账户调用时，抛出 @ref{1d3,,OSError} 异常。
@end quotation
@end cartouche

引发一个 @ref{12d0,,审计事件} @code{os.symlink}，附带参数 @code{src}、@code{dst}、@code{dir_fd}。

@ref{12f5,,可用性}: Unix, Windows。


在 3.2 版更改: 添加对 Windows 6.0 (Vista) 符号链接的支持。



3.3 新版功能: 添加了 @emph{dir_fd} 参数，现在在非 Windows 平台上允许 @emph{target_is_directory} 参数。



在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{src} 和 @emph{dst}。



在 3.8 版更改: 针对启用了开发人员模式的 Windows，添加了非特权账户创建符号链接的支持。

@end deffn

@geindex sync() (在 os 模块中)
@anchor{library/os os sync}@anchor{a54}
@deffn {函数} os.sync ()

强制将所有内容写入磁盘。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex truncate() (在 os 模块中)
@anchor{library/os os truncate}@anchor{71e}
@deffn {函数} os.truncate (path, length)

截断 @emph{path} 对应的文件，以使其最大为 @emph{length} 字节。

本函数支持 @ref{3ad,,指定文件描述符为参数}。

引发一个 @ref{12d0,,审计事件} @code{os.truncate}，附带参数 @code{path}, @code{length}。

@ref{12f5,,可用性}: Unix, Windows。


3.3 新版功能.



在 3.5 版更改: 添加了 Windows 支持



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex unlink() (在 os 模块中)
@anchor{library/os os unlink}@anchor{a37}
@deffn {函数} os.unlink (path, *, dir_fd=None)

移除（删除）文件 @emph{path}。该函数在语义上与 @ref{a32,,remove()} 相同，@code{unlink} 是其传统的 Unix 名称。请参阅 @ref{a32,,remove()} 的文档以获取更多信息。

引发一个 @ref{12d0,,审计事件} @code{os.remove}，附带参数 @code{path}、@code{dir_fd}。


3.3 新版功能: @emph{dir_fd} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex utime() (在 os 模块中)
@anchor{library/os os utime}@anchor{a38}
@deffn {函数} os.utime (path, times=None, *[, ns], dir_fd=None, follow_symlinks=True)

设置文件 @emph{path} 的访问时间和修改时间。

@ref{a38,,utime()} 有 @emph{times} 和 @emph{ns} 两个可选参数，它们指定了设置给 @emph{path} 的时间，用法如下：


@itemize -

@item 
如果指定 @emph{ns}，它必须是一个 @code{(atime_ns, mtime_ns)} 形式的二元组，其中每个成员都是一个表示纳秒的整数。

@item 
如果 @emph{times} 不为 @code{None}，则它必须是 @code{(atime, mtime)} 形式的二元组，其中每个成员都是一个表示秒的 int 或 float。

@item 
如果 @emph{times} 为 @code{None} 且未指定 @emph{ns}，则相当于指定 @code{ns=(atime_ns, mtime_ns)}，其中两个时间均为当前时间。
@end itemize

同时为 @emph{times} 和 @emph{ns} 指定元组会出错。

注意，根据操作系统记录访问时间和修改时间的分辨率，后续的 @ref{1f1,,stat()} 调用可能不会返回此处设置的确切时间。请参阅 @ref{1f1,,stat()}。保留精确时间的最佳方法是使用 @ref{1f1,,os.stat()} 结果对象中的 @emph{st_atime_ns} 和 @emph{st_mtime_ns} 字段，并将 @emph{ns} 参数设置为 @cite{utime}。

本函数支持 @ref{3ad,,指定文件描述符}、@ref{a2a,,指定基于目录描述符的相对路径} 和 @ref{a2b,,不跟踪符号链接}。

引发一个 @ref{12d0,,审计事件} @code{os.utime}，附带参数 @code{path}、@code{times}、@code{ns}、@code{dir_fd}。


3.3 新版功能: 新增支持将 @emph{path} 参数指定为打开的文件描述符，以及支持 @emph{dir_fd}、@emph{follow_symlinks} 和 @emph{ns} 参数。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex walk() (在 os 模块中)
@anchor{library/os os walk}@anchor{64e}
@deffn {函数} os.walk (top, topdown=True, onerror=None, followlinks=False)

@geindex directory; walking
@geindex directory; traversal

生成目录树中的文件名，方式是按上->下或下->上顺序浏览目录树。对于以 @emph{top} 为根的目录树中的每个目录（包括 @emph{top} 本身），它都会生成一个三元组 @code{(dirpath, dirnames, filenames)}。

@emph{dirpath} 是一个字符串，表示目录的路径。@emph{dirnames} 是一个列表，内含 @emph{dirpath} 中子目录的名称（不包括 @code{'.'} 和 @code{'..'} ）。@emph{filenames} 也是列表，内含 @emph{dirpath} 中文件（非目录）的名称。注意，列表中的名称不包含路径部分。要获取 @emph{dirpath} 中文件或目录的完整路径（从 @emph{top} 起始），请执行 @code{os.path.join(dirpath, name)}。

如果可选参数 @emph{topdown} 为 @code{True} 或未指定，则在所有子目录的三元组之前生成父目录的三元组（目录是自上而下生成的）。如果 @emph{topdown} 为 @code{False}，则在所有子目录的三元组生成之后再生成父目录的三元组（目录是自下而上生成的）。无论 @emph{topdown} 为何值，在生成目录及其子目录的元组之前，都将检索全部子目录列表。

当 @emph{topdown} 为 @code{True} 时，调用者可以就地修改 @emph{dirnames} 列表（也许用到了 @ref{1202,,del} 或切片），而 @ref{64e,,walk()} 将仅仅递归到仍保留在 @emph{dirnames} 中的子目录内。这可用于减少搜索、加入特定的访问顺序，甚至可在继续 @ref{64e,,walk()} 之前告知 @ref{64e,,walk()} 由调用者新建或重命名的目录的信息。当 @emph{topdown} 为 @code{False} 时，修改 @emph{dirnames} 对 walk 的行为没有影响，因为在自下而上模式中，@emph{dirnames} 中的目录是在 @emph{dirpath} 本身之前生成的。

默认将忽略 @ref{25f,,scandir()} 调用中的错误。如果指定了可选参数 @emph{onerror}，它应该是一个函数。出错时它会被调用，参数是一个 @ref{1d3,,OSError} 实例。它可以报告错误然后继续遍历，或者抛出异常然后中止遍历。注意，可以从异常对象的 @code{filename} 属性中获取出错的文件名。

@ref{64e,,walk()} 默认不会递归进指向目录的符号链接。可以在支持符号链接的系统上将 @emph{followlinks} 设置为 @code{True}，以访问符号链接指向的目录。

@cartouche
@quotation 注解 
注意，如果链接指向自身的父目录，则将 @emph{followlinks} 设置为 @code{True} 可能导致无限递归。@ref{64e,,walk()} 不会记录它已经访问过的目录。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
如果传入的是相对路径，请不要在恢复 @ref{64e,,walk()} 之间更改当前工作目录。@ref{64e,,walk()} 不会更改当前目录，并假定其调用者也不会更改当前目录。
@end quotation
@end cartouche

下面的示例遍历起始目录内所有子目录，打印每个目录内的文件占用的字节数，CVS 子目录不会被遍历:

@example
import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories
@end example

在下一个示例（@ref{21c,,shutil.rmtree()} 的简单实现）中，必须使树自下而上遍历，因为 @ref{a35,,rmdir()} 只允许在目录为空时删除目录:

@example
# Delete everything reachable from the directory named in "top",
# assuming there are no symbolic links.
# CAUTION:  This is dangerous!  For example, if top == '/', it
# could delete all your disk files.
import os
for root, dirs, files in os.walk(top, topdown=False):
    for name in files:
        os.remove(os.path.join(root, name))
    for name in dirs:
        os.rmdir(os.path.join(root, name))
@end example


在 3.5 版更改: 现在，本函数调用的是 @ref{25f,,os.scandir()} 而不是 @ref{a3c,,os.listdir()}，从而减少了调用 @ref{1f1,,os.stat()} 的次数而变得更快。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex fwalk() (在 os 模块中)
@anchor{library/os os fwalk}@anchor{3ac}
@deffn {函数} os.fwalk (top='.', topdown=True, onerror=None, *, follow_symlinks=False, dir_fd=None)

@geindex directory; walking
@geindex directory; traversal

本方法的行为与 @ref{64e,,walk()} 完全一样，除了它产生的是 4 元组 @code{(dirpath, dirnames, filenames, dirfd)}，并且它支持 @code{dir_fd}。

@emph{dirpath}、@emph{dirnames} 和 @emph{filenames} 与 @ref{64e,,walk()} 输出的相同，@emph{dirfd} 是指向目录 @emph{dirpath} 的文件描述符。

本函数始终支持 @ref{a2a,,基于目录描述符的相对路径} 和 @ref{a2b,,不跟踪符号链接}。但是请注意，与其他函数不同，@ref{3ac,,fwalk()} 的 @emph{follow_symlinks} 的默认值为 @code{False}。

@cartouche
@quotation 注解 
由于 @ref{3ac,,fwalk()} 会生成文件描述符，而它们仅在下一个迭代步骤前有效，因此如果要将描述符保留更久，则应复制它们（比如使用 @ref{f23,,dup()}）。
@end quotation
@end cartouche

下面的示例遍历起始目录内所有子目录，打印每个目录内的文件占用的字节数，CVS 子目录不会被遍历:

@example
import os
for root, dirs, files, rootfd in os.fwalk('python/Lib/email'):
    print(root, "consumes", end="")
    print(sum([os.stat(name, dir_fd=rootfd).st_size for name in files]),
          end="")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories
@end example

在下一个示例中，必须使树自下而上遍历，因为 @ref{a35,,rmdir()} 只允许在目录为空时删除目录:

@example
# Delete everything reachable from the directory named in "top",
# assuming there are no symbolic links.
# CAUTION:  This is dangerous!  For example, if top == '/', it
# could delete all your disk files.
import os
for root, dirs, files, rootfd in os.fwalk(top, topdown=False):
    for name in files:
        os.unlink(name, dir_fd=rootfd)
    for name in dirs:
        os.rmdir(name, dir_fd=rootfd)
@end example

@ref{12f5,,可用性}: Unix。


3.3 新版功能.



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。



在 3.7 版更改: 添加了对 @ref{32a,,bytes} 类型路径的支持。

@end deffn

@geindex memfd_create() (在 os 模块中)
@anchor{library/os os memfd_create}@anchor{1f0}
@deffn {函数} os.memfd_create (name[, flags=os.MFD_CLOEXEC])

创建一个匿名文件，返回指向该文件的文件描述符。@emph{flags} 必须是系统上可用的 @code{os.MFD_*} 常量之一（或将它们按位“或”组合起来）。新文件描述符默认是 @ref{7f4,,不可继承的}。

@emph{name} 提供的名称会被用作文件名，并且 @code{/proc/self/fd/} 目录中相应符号链接的目标将显示为该名称。显示的名称始终以 @code{memfd:} 为前缀，并且仅用于调试目的。名称不会影响文件描述符的行为，因此多个文件可以有相同的名称，不会有副作用。

@ref{12f5,,可用性}：Linux 3.17 或更高版本，且装有 glibc 2.27 或更高版本。


3.8 新版功能.

@end deffn

@geindex MFD_CLOEXEC() (在 os 模块中)
@geindex MFD_ALLOW_SEALING() (在 os 模块中)
@geindex MFD_HUGETLB() (在 os 模块中)
@geindex MFD_HUGE_SHIFT() (在 os 模块中)
@geindex MFD_HUGE_MASK() (在 os 模块中)
@geindex MFD_HUGE_64KB() (在 os 模块中)
@geindex MFD_HUGE_512KB() (在 os 模块中)
@geindex MFD_HUGE_1MB() (在 os 模块中)
@geindex MFD_HUGE_2MB() (在 os 模块中)
@geindex MFD_HUGE_8MB() (在 os 模块中)
@geindex MFD_HUGE_16MB() (在 os 模块中)
@geindex MFD_HUGE_32MB() (在 os 模块中)
@geindex MFD_HUGE_256MB() (在 os 模块中)
@geindex MFD_HUGE_512MB() (在 os 模块中)
@geindex MFD_HUGE_1GB() (在 os 模块中)
@geindex MFD_HUGE_2GB() (在 os 模块中)
@geindex MFD_HUGE_16GB() (在 os 模块中)
@anchor{library/os os MFD_CLOEXEC}@anchor{1f09}
@deffn {数据} os.MFD_CLOEXEC
@anchor{library/os os MFD_ALLOW_SEALING}@anchor{1f0a}
@deffnx {数据} os.MFD_ALLOW_SEALING
@anchor{library/os os MFD_HUGETLB}@anchor{1f0b}
@deffnx {数据} os.MFD_HUGETLB
@anchor{library/os os MFD_HUGE_SHIFT}@anchor{1f0c}
@deffnx {数据} os.MFD_HUGE_SHIFT
@anchor{library/os os MFD_HUGE_MASK}@anchor{1f0d}
@deffnx {数据} os.MFD_HUGE_MASK
@anchor{library/os os MFD_HUGE_64KB}@anchor{1f0e}
@deffnx {数据} os.MFD_HUGE_64KB
@anchor{library/os os MFD_HUGE_512KB}@anchor{1f0f}
@deffnx {数据} os.MFD_HUGE_512KB
@anchor{library/os os MFD_HUGE_1MB}@anchor{1f10}
@deffnx {数据} os.MFD_HUGE_1MB
@anchor{library/os os MFD_HUGE_2MB}@anchor{1f11}
@deffnx {数据} os.MFD_HUGE_2MB
@anchor{library/os os MFD_HUGE_8MB}@anchor{1f12}
@deffnx {数据} os.MFD_HUGE_8MB
@anchor{library/os os MFD_HUGE_16MB}@anchor{1f13}
@deffnx {数据} os.MFD_HUGE_16MB
@anchor{library/os os MFD_HUGE_32MB}@anchor{1f14}
@deffnx {数据} os.MFD_HUGE_32MB
@anchor{library/os os MFD_HUGE_256MB}@anchor{1f15}
@deffnx {数据} os.MFD_HUGE_256MB
@anchor{library/os os MFD_HUGE_512MB}@anchor{1f16}
@deffnx {数据} os.MFD_HUGE_512MB
@anchor{library/os os MFD_HUGE_1GB}@anchor{1f17}
@deffnx {数据} os.MFD_HUGE_1GB
@anchor{library/os os MFD_HUGE_2GB}@anchor{1f18}
@deffnx {数据} os.MFD_HUGE_2GB
@anchor{library/os os MFD_HUGE_16GB}@anchor{1f19}
@deffnx {数据} os.MFD_HUGE_16GB

以上标志位可以传递给 @ref{1f0,,memfd_create()}。

@ref{12f5,,可用性}：Linux 3.17 或更高版本，且装有 glibc 2.27 或更高版本。@code{MFD_HUGE*} 标志仅在 Linux 4.14 及以上可用。


3.8 新版功能.

@end deffn

@menu
* Linux 扩展属性:: 

@end menu

@node Linux 扩展属性,,,文件和目录
@anchor{library/os linux-extended-attributes}@anchor{1f1a}
@subsubsection Linux 扩展属性



3.3 新版功能.


这些函数仅在 Linux 上可用。

@geindex getxattr() (在 os 模块中)
@anchor{library/os os getxattr}@anchor{a46}
@deffn {函数} os.getxattr (path, attribute, *, follow_symlinks=True)

返回 @emph{path} 的扩展文件系统属性 @emph{attribute} 的值。@emph{attribute} 可以是 bytes 或 str （直接传入或通过 @ref{4e5,,PathLike} 接口间接传入）。如果是 str，则使用文件系统编码来编码字符串。

本函数支持 @ref{3ad,,指定文件描述符为参数} 和 @ref{a2b,,不跟踪符号链接}。

引发一个 @ref{12d0,,审计事件} @code{os.getxattr}，附带参数 @code{path}、@code{attribute}。


在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{path} 和 @emph{attribute}。

@end deffn

@geindex listxattr() (在 os 模块中)
@anchor{library/os os listxattr}@anchor{a47}
@deffn {函数} os.listxattr (path=None, *, follow_symlinks=True)

返回一个列表，包含 @emph{path} 的所有扩展文件系统属性。列表中的属性都表示为字符串，它们是根据文件系统编码解码出来的。如果 @emph{path} 为 @code{None}，则 @ref{a47,,listxattr()} 将检查当前目录。

本函数支持 @ref{3ad,,指定文件描述符为参数} 和 @ref{a2b,,不跟踪符号链接}。

引发一个 @ref{12d0,,审计事件} @code{os.listxattr}，附带参数 @code{path}。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex removexattr() (在 os 模块中)
@anchor{library/os os removexattr}@anchor{a48}
@deffn {函数} os.removexattr (path, attribute, *, follow_symlinks=True)

从 @emph{path} 中删除扩展文件系统属性 @emph{attribute}。@emph{attribute} 应该是 bytes 或 str （直接传入或通过 @ref{4e5,,PathLike} 接口间接传入）。如果是 str，则使用文件系统编码来编码字符串。

本函数支持 @ref{3ad,,指定文件描述符为参数} 和 @ref{a2b,,不跟踪符号链接}。

引发一个 @ref{12d0,,审计事件} @code{os.removexattr}，附带参数 @code{path}、@code{attribute}。


在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{path} 和 @emph{attribute}。

@end deffn

@geindex setxattr() (在 os 模块中)
@anchor{library/os os setxattr}@anchor{a49}
@deffn {函数} os.setxattr (path, attribute, value, flags=0, *, follow_symlinks=True)

将 @emph{path} 的扩展文件系统属性 @emph{attribute} 设置为 @emph{value}。@emph{attribute} 必须是没有空字符的 bytes 或 str （直接传入或通过 @ref{4e5,,PathLike} 接口间接传入）。如果是 str，则应使用文件系统编码进行编码。@emph{flags} 可以是 @ref{1f1b,,XATTR_REPLACE} 或 @ref{1f1c,,XATTR_CREATE}。如果指定 @ref{1f1b,,XATTR_REPLACE} 而该属性不存在，则抛出 @code{EEXISTS} 异常。如果指定 @ref{1f1c,,XATTR_CREATE} 而该属性已经存在，则不会创建该属性，抛出 @code{ENODATA} 异常。

本函数支持 @ref{3ad,,指定文件描述符为参数} 和 @ref{a2b,,不跟踪符号链接}。

@cartouche
@quotation 注解 
Linux kernel 2.6.39 以下版本的一个 bug 导致在某些文件系统上，flags 参数会被忽略。
@end quotation
@end cartouche

引发一个 @ref{12d0,,审计事件} @code{os.setxattr}，附带参数 @code{path}、@code{attribute}、@code{value}、@code{flags}。


在 3.6 版更改: 接受一个 @ref{363,,类路径对象} 作为 @emph{path} 和 @emph{attribute}。

@end deffn

@geindex XATTR_SIZE_MAX() (在 os 模块中)
@anchor{library/os os XATTR_SIZE_MAX}@anchor{1f1d}
@deffn {数据} os.XATTR_SIZE_MAX

一条扩展属性的值的最大大小。在当前的 Linux 上是 64 KiB。
@end deffn

@geindex XATTR_CREATE() (在 os 模块中)
@anchor{library/os os XATTR_CREATE}@anchor{1f1c}
@deffn {数据} os.XATTR_CREATE

这是 @ref{a49,,setxattr()} 的 flags 参数的可取值，它表示该操作必须创建一个属性。
@end deffn

@geindex XATTR_REPLACE() (在 os 模块中)
@anchor{library/os os XATTR_REPLACE}@anchor{1f1b}
@deffn {数据} os.XATTR_REPLACE

这是 @ref{a49,,setxattr()} 的 flags 参数的可取值，它表示该操作必须替换现有属性。
@end deffn

@node 进程管理,调度器接口,文件和目录,os --- 多种操作系统接口
@anchor{library/os os-process}@anchor{1f1e}@anchor{library/os process-management}@anchor{1f1f}
@subsubsection 进程管理


下列函数可用于创建和管理进程。

所有 @ref{1f20,,exec*} 函数都接受一个参数列表，用来给新程序加载到它的进程中。在所有情况下，传递给新程序的第一个参数是程序本身的名称，而不是用户在命令行上输入的参数。对于 C 程序员来说，这就是传递给 @code{main()} 函数的 @code{argv[0]}。例如，@code{os.execv('/bin/echo', ['foo', 'bar'])} 只会在标准输出上打印 @code{bar}，而 @code{foo} 会被忽略。

@geindex abort() (在 os 模块中)
@anchor{library/os os abort}@anchor{1f21}
@deffn {函数} os.abort ()

发送 @code{SIGABRT} 信号到当前进程。在 Unix 上，默认行为是生成一个核心转储。在 Windows 上，该进程立即返回退出代码 @code{3}。请注意，使用 @ref{a78,,signal.signal()} 可以为 @code{SIGABRT} 注册 Python 信号处理程序，而调用本函数将不会调用按前述方法注册的程序。
@end deffn

@geindex add_dll_directory() (在 os 模块中)
@anchor{library/os os add_dll_directory}@anchor{1c2}
@deffn {函数} os.add_dll_directory (path)

将路径添加到 DLL 搜索路径。

当需要解析扩展模块的依赖时（扩展模块本身通过 sys.path 解析），会使用该搜索路径，@ref{2b,,ctypes} 也会使用该搜索路径。

要移除目录，可以在返回的对象上调用 @strong{close()}，也可以在 @ref{6e3,,with} 语句内使用本方法。

参阅 Microsoft 文档@footnote{https://msdn.microsoft.com/44228cf2-6306-466c-8f16-f513cd3ba8b5} 获取如何加载 DLL 的信息。

引发一个 @ref{12d0,,审计事件} @code{os.add_dll_directory}，附带参数 @code{path}。

@ref{12f5,,可用性}: Windows。


3.8 新版功能: 早期版本的 CPython 解析 DLL 时用的是当前进程的默认行为。这会导致不一致，比如不是每次都会去搜索 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 和当前工作目录，且系统函数（如 @code{AddDllDirectory} ）失效。

在 3.8 中，DLL 的两种主要加载方式现在可以显式覆盖进程的行为，以确保一致性。请参阅 @ref{2ca,,移植说明} 了解如何更新你的库。

@end deffn

@geindex execl() (在 os 模块中)
@geindex execle() (在 os 模块中)
@geindex execlp() (在 os 模块中)
@geindex execlpe() (在 os 模块中)
@geindex execv() (在 os 模块中)
@geindex execve() (在 os 模块中)
@geindex execvp() (在 os 模块中)
@geindex execvpe() (在 os 模块中)
@anchor{library/os os execl}@anchor{1f20}
@deffn {函数} os.execl (path, arg0, arg1, ...)
@anchor{library/os os execle}@anchor{1f22}
@deffnx {函数} os.execle (path, arg0, arg1, ..., env)
@anchor{library/os os execlp}@anchor{1f23}
@deffnx {函数} os.execlp (file, arg0, arg1, ...)
@anchor{library/os os execlpe}@anchor{1f24}
@deffnx {函数} os.execlpe (file, arg0, arg1, ..., env)
@anchor{library/os os execv}@anchor{1e8f}
@deffnx {函数} os.execv (path, args)
@anchor{library/os os execve}@anchor{a3b}
@deffnx {函数} os.execve (path, args, env)
@anchor{library/os os execvp}@anchor{1f25}
@deffnx {函数} os.execvp (file, args)
@anchor{library/os os execvpe}@anchor{1f26}
@deffnx {函数} os.execvpe (file, args, env)

这些函数都将执行一个新程序，以替换当前进程。它们没有返回值。在 Unix 上，新程序会加载到当前进程中，且进程号与调用者相同。过程中的错误会被报告为 @ref{1d3,,OSError} 异常。

当前进程会被立即替换。打开的文件对象和描述符都不会刷新，因此如果这些文件上可能缓冲了数据，则应在调用 @ref{1f20,,exec*} 函数之前使用 @code{sys.stdout.flush()} 或 @ref{65b,,os.fsync()} 刷新它们。

@ref{1f20,,exec*} 函数的 "l" 和 "v" 变体不同在于命令行参数的传递方式。如果在编码时固定了参数数量，则 "l" 变体可能是最方便的，各参数作为 @code{execl*()} 函数的附加参数传入即可。当参数数量可变时，"v" 变体更方便，参数以列表或元组的形式作为 @emph{args} 参数传递。在这两种情况下，子进程的第一个参数都应该是即将运行的命令名称，但这不是强制性的。

结尾包含 "p" 的变体（@ref{1f23,,execlp()}、@ref{1f24,,execlpe()}、@ref{1f25,,execvp()} 和 @ref{1f26,,execvpe()} ）将使用 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 环境变量来查找程序 @emph{file}。当环境被替换时（使用下一段讨论的 @ref{1f20,,exec*e} 变体之一），
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 变量将来自于新环境。其他变体 @ref{1f20,,execl()}、@ref{1f22,,execle()}、@ref{1e8f,,execv()} 和 @ref{a3b,,execve()} 不使用 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 变量来查找程序，因此 @emph{path} 必须包含正确的绝对或相对路径。

对于 @ref{1f22,,execle()}、@ref{1f24,,execlpe()}、@ref{a3b,,execve()} 和 @ref{1f26,,execvpe()} （都以 "e" 结尾），@emph{env} 参数是一个映射，用于定义新进程的环境变量（代替当前进程的环境变量）。而函数 @ref{1f20,,execl()}、@ref{1f23,,execlp()}、@ref{1e8f,,execv()} 和 @ref{1f25,,execvp()} 会将当前进程的环境变量过继给新进程。

某些平台上的 @ref{a3b,,execve()} 可以将 @emph{path} 指定为打开的文件描述符。当前平台可能不支持此功能，可以使用 @ref{a3f,,os.supports_fd} 检查它是否支持。如果不可用，则使用它会抛出 @ref{609,,NotImplementedError} 异常。

引发一个 @ref{12d0,,审计事件} @code{os.exec}，附带参数 @code{path}、@code{args}、@code{env}。

@ref{12f5,,可用性}: Unix, Windows。


3.3 新版功能: 新增支持将 @ref{a3b,,execve()} 的 @emph{path} 参数指定为打开的文件描述符。



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex _exit() (在 os 模块中)
@anchor{library/os os _exit}@anchor{16a3}
@deffn {函数} os._exit (n)

以状态码 @emph{n} 退出进程，不会调用清理处理程序，不会刷新 stdio，等等。

@cartouche
@quotation 注解 
退出的标准方法是使用 @code{sys.exit(n)}。而 @ref{16a3,,_exit()} 通常只应在 @ref{95b,,fork()} 出的子进程中使用。
@end quotation
@end cartouche
@end deffn

以下是已定义的退出代码，可以用于 @ref{16a3,,_exit()}，尽管它们不是必需的。这些退出代码通常用于 Python 编写的系统程序，例如邮件服务器的外部命令传递程序。

@cartouche
@quotation 注解 
其中部分退出代码在部分 Unix 平台上可能不可用，因为平台间存在差异。如果底层平台定义了这些常量，那上层也会定义。
@end quotation
@end cartouche

@geindex EX_OK() (在 os 模块中)
@anchor{library/os os EX_OK}@anchor{1f27}
@deffn {数据} os.EX_OK

退出代码，表示未发生任何错误。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_USAGE() (在 os 模块中)
@anchor{library/os os EX_USAGE}@anchor{1f28}
@deffn {数据} os.EX_USAGE

退出代码，表示命令使用不正确，如给出的参数数量有误。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_DATAERR() (在 os 模块中)
@anchor{library/os os EX_DATAERR}@anchor{1f29}
@deffn {数据} os.EX_DATAERR

退出代码，表示输入数据不正确。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_NOINPUT() (在 os 模块中)
@anchor{library/os os EX_NOINPUT}@anchor{1f2a}
@deffn {数据} os.EX_NOINPUT

退出代码，表示某个输入文件不存在或不可读。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_NOUSER() (在 os 模块中)
@anchor{library/os os EX_NOUSER}@anchor{1f2b}
@deffn {数据} os.EX_NOUSER

退出代码，表示指定的用户不存在。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_NOHOST() (在 os 模块中)
@anchor{library/os os EX_NOHOST}@anchor{1f2c}
@deffn {数据} os.EX_NOHOST

退出代码，表示指定的主机不存在。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_UNAVAILABLE() (在 os 模块中)
@anchor{library/os os EX_UNAVAILABLE}@anchor{1f2d}
@deffn {数据} os.EX_UNAVAILABLE

退出代码，表示所需的服务不可用。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_SOFTWARE() (在 os 模块中)
@anchor{library/os os EX_SOFTWARE}@anchor{1f2e}
@deffn {数据} os.EX_SOFTWARE

退出代码，表示检测到内部软件错误。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_OSERR() (在 os 模块中)
@anchor{library/os os EX_OSERR}@anchor{1f2f}
@deffn {数据} os.EX_OSERR

退出代码，表示检测到操作系统错误，例如无法 fork 或创建管道。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_OSFILE() (在 os 模块中)
@anchor{library/os os EX_OSFILE}@anchor{1f30}
@deffn {数据} os.EX_OSFILE

退出代码，表示某些系统文件不存在、无法打开或发生其他错误。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_CANTCREAT() (在 os 模块中)
@anchor{library/os os EX_CANTCREAT}@anchor{1f31}
@deffn {数据} os.EX_CANTCREAT

退出代码，表示无法创建用户指定的输出文件。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_IOERR() (在 os 模块中)
@anchor{library/os os EX_IOERR}@anchor{1f32}
@deffn {数据} os.EX_IOERR

退出代码，表示对某些文件进行读写时发生错误。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_TEMPFAIL() (在 os 模块中)
@anchor{library/os os EX_TEMPFAIL}@anchor{1f33}
@deffn {数据} os.EX_TEMPFAIL

退出代码，表示发生了暂时性故障。它可能并非意味着真正的错误，例如在可重试的情况下无法建立网络连接。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_PROTOCOL() (在 os 模块中)
@anchor{library/os os EX_PROTOCOL}@anchor{1f34}
@deffn {数据} os.EX_PROTOCOL

退出代码，表示协议交换是非法的、无效的或无法解读的。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_NOPERM() (在 os 模块中)
@anchor{library/os os EX_NOPERM}@anchor{1f35}
@deffn {数据} os.EX_NOPERM

退出代码，表示没有足够的权限执行该操作（但不适用于文件系统问题）。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_CONFIG() (在 os 模块中)
@anchor{library/os os EX_CONFIG}@anchor{1f36}
@deffn {数据} os.EX_CONFIG

退出代码，表示发生某种配置错误。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex EX_NOTFOUND() (在 os 模块中)
@anchor{library/os os EX_NOTFOUND}@anchor{1f37}
@deffn {数据} os.EX_NOTFOUND

退出代码，表示的内容类似于“找不到条目”。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex fork() (在 os 模块中)
@anchor{library/os os fork}@anchor{95b}
@deffn {函数} os.fork ()

Fork 出一个子进程。在子进程中返回 @code{0}，在父进程中返回子进程的进程号。如果发生错误，则抛出 @ref{1d3,,OSError} 异常。

注意，当从线程中使用 @code{fork()} 时，某些平台（包括 FreeBSD <= 6.3 和 Cygwin）存在已知问题。

引发一个 @ref{12d0,,审计事件} @code{os.fork}，没有附带参数。


在 3.8 版更改: 不再支持在子解释器中调用 @code{fork()} （将抛出 @ref{2ba,,RuntimeError} 异常）。


@cartouche
@quotation 警告 
有关 SSL 模块与 fork() 结合的应用，请参阅 @ref{f3,,ssl}。
@end quotation
@end cartouche

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex forkpty() (在 os 模块中)
@anchor{library/os os forkpty}@anchor{1f38}
@deffn {函数} os.forkpty ()

Fork 出一个子进程，使用新的伪终端作为子进程的控制终端。返回一对 @code{(pid, fd)}，其中 @emph{pid} 在子进程中为 @code{0}，这是父进程中新子进程的进程号，而 @emph{fd} 是伪终端主设备的文件描述符。对于更便于移植的方法，请使用 @ref{d5,,pty} 模块。如果发生错误，则抛出 @ref{1d3,,OSError} 异常。

引发一个 @ref{12d0,,审计事件} @code{os.forkpty}，没有附带参数。


在 3.8 版更改: 不再支持在子解释器中调用 @code{forkpty()} （将抛出 @ref{2ba,,RuntimeError} 异常）。


@ref{12f5,,可用性}: 某些 Unix。
@end deffn

@geindex kill() (在 os 模块中)
@anchor{library/os os kill}@anchor{cec}
@deffn {函数} os.kill (pid, sig)

@geindex process; killing
@geindex process; signalling

将信号 @emph{sig} 发送至进程 @emph{pid}。特定平台上可用的信号常量定义在 @ref{ea,,signal} 模块中。

Windows： @ref{1f39,,signal.CTRL_C_EVENT} 和 @ref{1f3a,,signal.CTRL_BREAK_EVENT} 信号是特殊信号，只能发送给共享同一个控制台窗口的控制台进程，如某些子进程。@emph{sig} 取任何其他值将导致该进程被 TerminateProcess API 无条件终止，且退出代码为 @emph{sig}。Windows 版本的 @ref{cec,,kill()} 还需要传入待结束进程的句柄。

另请参阅 @ref{a75,,signal.pthread_kill()}。

引发一个 @ref{12d0,,审计事件} @code{os.kill}，附带参数 @code{pid}、@code{sig}。


3.2 新版功能: Windows 支持。

@end deffn

@geindex killpg() (在 os 模块中)
@anchor{library/os os killpg}@anchor{ebe}
@deffn {函数} os.killpg (pgid, sig)

@geindex process; killing
@geindex process; signalling

将信号 @emph{sig} 发送给进程组 @emph{pgid}。

引发一个 @ref{12d0,,审计事件} @code{os.killpg}，附带参数 @code{pgid}、@code{sig}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex nice() (在 os 模块中)
@anchor{library/os os nice}@anchor{a43}
@deffn {函数} os.nice (increment)

将进程的优先级（nice 值）增加 @emph{increment}，返回新的 nice 值。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex plock() (在 os 模块中)
@anchor{library/os os plock}@anchor{1f3b}
@deffn {函数} os.plock (op)

将程序段锁定到内存中。@emph{op} 的值（定义在 @code{<sys/lock.h>} 中）决定了哪些段被锁定。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex popen() (在 os 模块中)
@anchor{library/os os popen}@anchor{2a9}
@deffn {函数} os.popen (cmd, mode='r', buffering=-1)

打开一个管道，它通往 / 接受自命令 @emph{cmd}。返回值是连接到管道的文件对象，根据 @emph{mode} 是 @code{'r'} （默认）还是 @code{'w'} 决定该对象可以读取还是写入。@emph{buffering} 参数与内置函数 @ref{4ea,,open()} 相应的参数含义相同。返回的文件对象只能读写文本字符串，不能是字节类型。

如果子进程成功退出，则 @code{close} 方法返回 @ref{157,,None}。如果发生错误，则返回子进程的返回码。在 POSIX 系统上，如果返回码为正，则它就是进程返回值左移一个字节后的值。如果返回码为负，则进程是被信号终止的，返回码取反后就是该信号。（例如，如果子进程被终止，则返回值可能是 @code{- signal.SIGKILL}。）在 Windows 系统上，返回值包含子进程的返回码（有符号整数）。

本方法是使用 @ref{2b9,,subprocess.Popen} 实现的，如需更强大的方法来管理和沟通子进程，请参阅该类的文档。
@end deffn

@geindex posix_spawn() (在 os 模块中)
@anchor{library/os os posix_spawn}@anchor{257}
@deffn {函数} os.posix_spawn (path, argv, env, *, file_actions=None, setpgroup=None, resetids=False, setsid=False, setsigmask=(), setsigdef=(), scheduler=None)

包装 @code{posix_spawn()} C 库 API，使其可以从 Python 调用。

大多数用户应使用 @ref{3e5,,subprocess.run()} 代替 @ref{257,,posix_spawn()}。

仅位置参数 (Positional-only arguments) @emph{path}、@emph{args} 和 @emph{env} 与 @ref{a3b,,execve()} 中的类似。

@emph{path} 参数是可执行文件的路径，@emph{path} 中应该包含目录。使用 @ref{fa8,,posix_spawnp()} 可直接传入可执行文件名称，不带有目录。

@emph{file_actions} 参数可以是由元组组成的序列，序列描述了对子进程中指定文件描述符采取的操作，这些操作会在 C 库实现的 @code{fork()} 和 @code{exec()} 步骤间完成。每个元组的第一个元素必须是下面列出的三个类型指示符之一，用于描述元组剩余的元素：

@geindex POSIX_SPAWN_OPEN() (在 os 模块中)
@anchor{library/os os POSIX_SPAWN_OPEN}@anchor{1f3c}
@deffn {数据} os.POSIX_SPAWN_OPEN

(@code{os.POSIX_SPAWN_OPEN}, @emph{fd}, @emph{path}, @emph{flags}, @emph{mode})

执行 @code{os.dup2(os.open(path, flags, mode), fd)}。
@end deffn

@geindex POSIX_SPAWN_CLOSE() (在 os 模块中)
@anchor{library/os os POSIX_SPAWN_CLOSE}@anchor{1f3d}
@deffn {数据} os.POSIX_SPAWN_CLOSE

(@code{os.POSIX_SPAWN_CLOSE}, @emph{fd})

执行 @code{os.close(fd)}。
@end deffn

@geindex POSIX_SPAWN_DUP2() (在 os 模块中)
@anchor{library/os os POSIX_SPAWN_DUP2}@anchor{1f3e}
@deffn {数据} os.POSIX_SPAWN_DUP2

(@code{os.POSIX_SPAWN_DUP2}, @emph{fd}, @emph{new_fd})

执行 @code{os.dup2(fd, new_fd)}。
@end deffn

这些元组对应于 C 库 @code{posix_spawn_file_actions_addopen()}， @code{posix_spawn_file_actions_addclose()} 和 @code{posix_spawn_file_actions_adddup2()} API 调用，它们为调用 @code{posix_spawn()} 自身做准备。

@emph{setpgroup} 参数将子进程的进程组设置为指定值。如果指定值为 0，则子进程的进程组 ID 将与其进程 ID 相同。如果未设置 @emph{setpgroup} 值，则子进程将继承父进程的进程组 ID。本参数对应于 C 库 @code{POSIX_SPAWN_SETPGROUP} 标志。

如果 @emph{resetids} 参数为 @code{True}，则会将子进程的有效用户 ID 和有效组 ID 重置为父进程的实际用户 ID 和实际组 ID。如果该参数为 @code{False}，则子进程保留父进程的有效用户 ID 和有效组 ID。无论哪种情况，若在可执行文件上启用了 “设置用户 ID” 和 “设置组 ID” 权限位，它们将覆盖有效用户 ID 和有效组 ID 的设置。本参数对应于 C 库 @code{POSIX_SPAWN_RESETIDS} 标志。

如果 @emph{setsid} 参数为 @code{True}，它将为 @cite{posix_spawn} 新建一个会话 ID。@emph{setsid} 需要 @code{POSIX_SPAWN_SETSID} 或 @code{POSIX_SPAWN_SETSID_NP} 标志，否则会抛出 @ref{609,,NotImplementedError} 异常。

@emph{setsigmask} 参数将信号掩码设置为指定的信号集合。如果未使用该参数，则子进程将继承父进程的信号掩码。本参数对应于 C 库 @code{POSIX_SPAWN_SETSIGMASK} 标志。

@emph{sigdef} 参数将集合中所有信号的操作全部重置为默认。本参数对应于 C 库 @code{POSIX_SPAWN_SETSIGDEF} 标志。

@emph{scheduler} 参数必须是一个元组，其中包含调度器策略（可选）以及携带了调度器参数的 @ref{1f3f,,sched_param} 实例。在调度器策略所在位置为 @code{None} 表示未提供该值。本参数是 C 库 @code{POSIX_SPAWN_SETSCHEDPARAM} 和 @code{POSIX_SPAWN_SETSCHEDULER} 标志的组合。

引发一个 @ref{12d0,,审计事件} @code{os.posix_spawn}，附带参数 @code{path}、@code{argv}、@code{env}。


3.8 新版功能.


@ref{12f5,,可用性}: Unix。
@end deffn

@geindex posix_spawnp() (在 os 模块中)
@anchor{library/os os posix_spawnp}@anchor{fa8}
@deffn {函数} os.posix_spawnp (path, argv, env, *, file_actions=None, setpgroup=None, resetids=False, setsid=False, setsigmask=(), setsigdef=(), scheduler=None)

包装 @code{posix_spawnp()} C 库 API，使其可以从 Python 调用。

与 @ref{257,,posix_spawn()} 相似，但是系统会在 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 环境变量指定的目录列表中搜索可执行文件 @emph{executable} （与 @code{execvp(3)} 相同）。

引发一个 @ref{12d0,,审计事件} @code{os.posix_spawn}，附带参数 @code{path}、@code{argv}、@code{env}。


3.8 新版功能.


@ref{12f5,,可用性}: 请参阅 @ref{257,,posix_spawn()} 文档。
@end deffn

@geindex register_at_fork() (在 os 模块中)
@anchor{library/os os register_at_fork}@anchor{3ae}
@deffn {函数} os.register_at_fork (*, before=None, after_in_parent=None, after_in_child=None)

注册可调用对象，在使用 @ref{95b,,os.fork()} 或类似的进程克隆 API 派生新的子进程时，这些对象会运行。参数是可选的，且为仅关键字 (Keyword-only) 参数。每个参数指定一个不同的调用点。


@itemize *

@item 
@emph{before} 是一个函数，在 fork 子进程前调用。

@item 
@emph{after_in_parent} 是一个函数，在 fork 子进程后从父进程调用。

@item 
@emph{after_in_child} 是一个函数，从子进程中调用。
@end itemize

只有希望控制权回到 Python 解释器时，才进行这些调用。典型的 @ref{f9,,子进程} 启动时不会触发它们，因为子进程不会重新进入解释器。

在注册的函数中，用于 fork 前运行的函数将按与注册相反的顺序调用。用于 fork 后（从父进程或子进程）运行的函数按注册顺序调用。

注意，第三方 C 代码的 @code{fork()} 调用可能不会调用这些函数，除非它显式调用了 @ref{42c,,PyOS_BeforeFork()}、@ref{42d,,PyOS_AfterFork_Parent()} 和 @ref{2cd,,PyOS_AfterFork_Child()}。

函数注册后无法注销。

@ref{12f5,,可用性}: Unix。


3.7 新版功能.

@end deffn

@geindex spawnl() (在 os 模块中)
@geindex spawnle() (在 os 模块中)
@geindex spawnlp() (在 os 模块中)
@geindex spawnlpe() (在 os 模块中)
@geindex spawnv() (在 os 模块中)
@geindex spawnve() (在 os 模块中)
@geindex spawnvp() (在 os 模块中)
@geindex spawnvpe() (在 os 模块中)
@anchor{library/os os spawnl}@anchor{1edc}
@deffn {函数} os.spawnl (mode, path, ...)
@anchor{library/os os spawnle}@anchor{1f40}
@deffnx {函数} os.spawnle (mode, path, ..., env)
@anchor{library/os os spawnlp}@anchor{1f41}
@deffnx {函数} os.spawnlp (mode, file, ...)
@anchor{library/os os spawnlpe}@anchor{1f42}
@deffnx {函数} os.spawnlpe (mode, file, ..., env)
@anchor{library/os os spawnv}@anchor{1f43}
@deffnx {函数} os.spawnv (mode, path, args)
@anchor{library/os os spawnve}@anchor{1f44}
@deffnx {函数} os.spawnve (mode, path, args, env)
@anchor{library/os os spawnvp}@anchor{1f45}
@deffnx {函数} os.spawnvp (mode, file, args)
@anchor{library/os os spawnvpe}@anchor{1f46}
@deffnx {函数} os.spawnvpe (mode, file, args, env)

在新进程中执行程序 @emph{path}。

（注意，@ref{f9,,subprocess} 模块提供了更强大的工具来生成新进程并跟踪执行结果，使用该模块比使用这些函数更好。尤其应当检查 @ref{ae5,,Replacing Older Functions with the subprocess Module} 部分。）

@emph{mode} 为 @ref{1f47,,P_NOWAIT} 时，本函数返回新进程的进程号。@emph{mode} 为 @ref{1f48,,P_WAIT} 时，如果进程正常退出，返回退出代码，如果被终止，返回 @code{-signal}，其中 @emph{signal} 是终止进程的信号。在 Windows 上，进程号实际上是进程句柄，因此可以与 @ref{667,,waitpid()} 函数一起使用。

注意在 VxWorks 上，新进程被终止时，本函数不会返回 @code{-signal}，而是会抛出 OSError 异常。

@ref{1edc,,spawn*} 函数的 "l" 和 "v" 变体不同在于命令行参数的传递方式。如果在编码时固定了参数数量，则 "l" 变体可能是最方便的，各参数作为 @code{spawnl*()} 函数的附加参数传入即可。当参数数量可变时，"v" 变体更方便，参数以列表或元组的形式作为 @emph{args} 参数传递。在这两种情况下，子进程的第一个参数都必须是即将运行的命令名称。

结尾包含第二个 "p" 的变体（@ref{1f41,,spawnlp()}、@ref{1f42,,spawnlpe()}、@ref{1f45,,spawnvp()} 和 @ref{1f46,,spawnvpe()}）将使用 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 环境变量来查找程序 @emph{file}。当环境被替换时（使用下一段讨论的 @ref{1edc,,spawn*e} 变体之一），
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 变量将来自于新环境。其他变体 @ref{1edc,,spawnl()}、@ref{1f40,,spawnle()}、@ref{1f43,,spawnv()} 和 @ref{1f44,,spawnve()} 不使用 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 变量来查找程序，因此 @emph{path} 必须包含正确的绝对或相对路径。

对于 @ref{1f40,,spawnle()}、@ref{1f42,,spawnlpe()}、@ref{1f44,,spawnve()} 和 @ref{1f46,,spawnvpe()} （都以 "e" 结尾），@emph{env} 参数是一个映射，用于定义新进程的环境变量（代替当前进程的环境变量）。而函数 @ref{1edc,,spawnl()}、@ref{1f41,,spawnlp()}、@ref{1f43,,spawnv()} 和 @ref{1f45,,spawnvp()} 会将当前进程的环境变量过继给新进程。注意，@emph{env} 字典中的键和值必须是字符串。无效的键或值将导致函数出错，返回值为 @code{127}。

例如，以下对 @ref{1f41,,spawnlp()} 和 @ref{1f46,,spawnvpe()} 的调用是等效的:

@example
import os
os.spawnlp(os.P_WAIT, 'cp', 'cp', 'index.html', '/dev/null')

L = ['cp', 'index.html', '/dev/null']
os.spawnvpe(os.P_WAIT, 'cp', L, os.environ)
@end example

引发一个 @ref{12d0,,审计事件} @code{os.spawn}，附带参数 @code{mode}、@code{path}、@code{args}、@code{env}。

@ref{12f5,,可用性}: Unix, Windows。@ref{1f41,,spawnlp()}、@ref{1f42,,spawnlpe()}、@ref{1f45,,spawnvp()} 和 @ref{1f46,,spawnvpe()} 在 Windows 上不可用。@ref{1f40,,spawnle()} 和 @ref{1f44,,spawnve()} 在 Windows 上不是线程安全的，建议使用 @ref{f9,,subprocess} 模块替代。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex P_NOWAIT() (在 os 模块中)
@geindex P_NOWAITO() (在 os 模块中)
@anchor{library/os os P_NOWAIT}@anchor{1f47}
@deffn {数据} os.P_NOWAIT
@anchor{library/os os P_NOWAITO}@anchor{1f49}
@deffnx {数据} os.P_NOWAITO

@ref{1edc,,spawn*} 系列函数的 @emph{mode} 参数的可取值。如果给出这些值中的任何一个，则 @code{spawn*()} 函数将在创建新进程后立即返回，且返回值为进程号。

@ref{12f5,,可用性}: Unix, Windows。
@end deffn

@geindex P_WAIT() (在 os 模块中)
@anchor{library/os os P_WAIT}@anchor{1f48}
@deffn {数据} os.P_WAIT

@ref{1edc,,spawn*} 系列函数的 @emph{mode} 参数的可取值。如果将 @emph{mode} 指定为该值，则 @code{spawn*()} 函数将在新进程运行完毕后返回，运行成功则返回进程的退出代码，被信号终止则返回 @code{-signal}。

@ref{12f5,,可用性}: Unix, Windows。
@end deffn

@geindex P_DETACH() (在 os 模块中)
@geindex P_OVERLAY() (在 os 模块中)
@anchor{library/os os P_DETACH}@anchor{1f4a}
@deffn {数据} os.P_DETACH
@anchor{library/os os P_OVERLAY}@anchor{1f4b}
@deffnx {数据} os.P_OVERLAY

@ref{1edc,,spawn*} 系列函数的 @emph{mode} 参数的可取值。它们比上面列出的值可移植性差。@ref{1f4a,,P_DETACH} 与 @ref{1f47,,P_NOWAIT} 相似，但是新进程会与父进程的控制台脱离。使用 @ref{1f4b,,P_OVERLAY} 则会替换当前进程，@ref{1edc,,spawn*} 函数将不会返回。

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex startfile() (在 os 模块中)
@anchor{library/os os startfile}@anchor{1f4c}
@deffn {函数} os.startfile (path[, operation])

使用已关联的应用程序打开文件。

当 @emph{operation} 未指定或指定为 @code{'open'} 时，这类似于在 Windows 资源管理器中双击文件，或在交互式命令行中将文件名作为 @code{start} 命令的参数：通过扩展名相关联的应用程序（如果有）打开文件。

当指定另一个 @emph{operation} 时，它必须是一个“命令动词” ("command verb")，该词指定对文件执行的操作。Microsoft 文档中的常用动词有 @code{'print'} 和 @code{'edit'} （用于文件），以及 @code{'explore'} 和 @code{'find'} （用于目录）。

关联的应用程序启动后 @ref{1f4c,,startfile()} 就会立即返回。本函数没有等待应用程序关闭的选项，也没有办法检索应用程序的退出状态。@emph{path} 参数是基于当前目录的相对路径。如果要使用绝对路径，请确保第一个字符不是斜杠 (@code{'/'})，是斜杠的话底层的 Win32 @code{ShellExecute()} 函数将失效。使用 @ref{ca8,,os.path.normpath()} 函数确保路径已针对 Win32 正确编码。

为了减少解释器的启动开销，直到第一次调用本函数后，才解析 Win32 @code{ShellExecute()} 函数。如果无法解析该函数​​，则抛出 @ref{609,,NotImplementedError} 异常。

引发一个 @ref{12d0,,审计事件} @code{os.startfile}，附带参数 @code{path}、@code{operation}。

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex system() (在 os 模块中)
@anchor{library/os os system}@anchor{dba}
@deffn {函数} os.system (command)

在子 shell 中执行命令（字符串）。这是调用标准 C 函数 @code{system()} 来实现的，因此限制条件与该函数相同。对 @ref{306,,sys.stdin} 等的更改不会反映在执行命令的环境中。@emph{command} 产生的任何输出将被发送到解释器标准输出流。

在 Unix 上，返回值是进程的退出状态，编码格式与为 @ref{665,,wait()} 指定的格式相同。注意，POSIX 没有指定 C 函数 @code{system()} 返回值的含义，因此 Python 函数的返回值与系统有关。

在 Windows 上，返回值是运行 @emph{command} 后系统 Shell 返回的值。该 Shell 由 Windows 环境变量 
@geindex COMSPEC
@geindex 环境变量; COMSPEC
@code{COMSPEC}: 给出：通常是 @code{cmd.exe}，它会返回命令的退出状态。在使用非原生 Shell 的系统上，请查阅 Shell 的文档。

@ref{f9,,subprocess} 模块提供了更强大的工具来生成新进程并跟踪执行结果，使用该模块比使用本函数更好。参阅 @ref{f9,,subprocess} 文档中的 @ref{ae5,,Replacing Older Functions with the subprocess Module} 部分以获取有用的帮助。

引发一个 @ref{12d0,,审计事件} @code{os.system}，附带参数 @code{command}。

@ref{12f5,,可用性}: Unix, Windows。
@end deffn

@geindex times() (在 os 模块中)
@anchor{library/os os times}@anchor{a57}
@deffn {函数} os.times ()

返回当前的全局进程时间。返回值是一个有 5 个属性的对象：


@itemize *

@item 
@code{user} - 用户时间

@item 
@ref{dba,,system} - 系统时间

@item 
@code{children_user} - 所有子进程的用户时间

@item 
@code{children_system} - 所有子进程的系统时间

@item 
@code{elapsed} - 从过去的固定时间点起，经过的真实时间
@end itemize

为了向后兼容，该对象的行为也类似于五元组，按照 @code{user}，@ref{dba,,system}，@code{children_user}，@code{children_system} 和 @code{elapsed} 顺序组成。

在 Unix 上请参阅 @code{times(2)} 和 @code{times(3)} 手册页，在 Windows 上请参阅 the GetProcessTimes MSDN@footnote{https://docs.microsoft.com/windows/win32/api/processthreadsapi/nf-processthreadsapi-getprocesstimes} 。在 Windows 上，只有 @code{user} 和 @ref{dba,,system} 是已知的，其他属性均为零。

@ref{12f5,,可用性}: Unix, Windows。


在 3.3 版更改: 返回结果的类型由元组变成一个类似元组的对象，同时具有命名的属性。

@end deffn

@geindex wait() (在 os 模块中)
@anchor{library/os os wait}@anchor{665}
@deffn {函数} os.wait ()

等待子进程执行完毕，返回一个元组，包含其 pid 和退出状态指示：一个 16 位数字，其低字节是终止该进程的信号编号，高字节是退出状态码（信号编号为零的情况下），如果生成了核心文件，则低字节的高位会置位。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex waitid() (在 os 模块中)
@anchor{library/os os waitid}@anchor{666}
@deffn {函数} os.waitid (idtype, id, options)

等待一个或多个子进程执行完毕。@emph{idtype} 可以是 @ref{1f4d,,P_PID}、@ref{1f4e,,P_PGID} 或 @ref{1f4f,,P_ALL}。@emph{id} 指定要等待的 pid。@emph{options} 是由 @ref{1f50,,WEXITED}、@ref{1f51,,WSTOPPED} 或 @ref{1f52,,WCONTINUED} 中的一个或多个进行或运算构造的，且额外可以与 @ref{1f53,,WNOHANG} 或 @ref{1f54,,WNOWAIT} 进行或运算。返回值是一个对象，对应着 @code{siginfo_t} 结构体中的数据，即： @code{si_pid}, @code{si_uid}, @code{si_signo}, @code{si_status}, @code{si_code} 或 @code{None} （如果指定了 @ref{1f53,,WNOHANG} 且没有子进程处于等待状态）。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex P_PID() (在 os 模块中)
@geindex P_PGID() (在 os 模块中)
@geindex P_ALL() (在 os 模块中)
@anchor{library/os os P_PID}@anchor{1f4d}
@deffn {数据} os.P_PID
@anchor{library/os os P_PGID}@anchor{1f4e}
@deffnx {数据} os.P_PGID
@anchor{library/os os P_ALL}@anchor{1f4f}
@deffnx {数据} os.P_ALL

@ref{666,,waitid()} 的 @emph{idtype} 参数的可取值。它们影响 @emph{id} 的解释方式。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex WEXITED() (在 os 模块中)
@geindex WSTOPPED() (在 os 模块中)
@geindex WNOWAIT() (在 os 模块中)
@anchor{library/os os WEXITED}@anchor{1f50}
@deffn {数据} os.WEXITED
@anchor{library/os os WSTOPPED}@anchor{1f51}
@deffnx {数据} os.WSTOPPED
@anchor{library/os os WNOWAIT}@anchor{1f54}
@deffnx {数据} os.WNOWAIT

用于 @ref{666,,waitid()} 的 @emph{options} 参数的标志位，指定要等待的子进程信号。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex CLD_EXITED() (在 os 模块中)
@geindex CLD_DUMPED() (在 os 模块中)
@geindex CLD_TRAPPED() (在 os 模块中)
@geindex CLD_CONTINUED() (在 os 模块中)
@anchor{library/os os CLD_EXITED}@anchor{1f55}
@deffn {数据} os.CLD_EXITED
@anchor{library/os os CLD_DUMPED}@anchor{1f56}
@deffnx {数据} os.CLD_DUMPED
@anchor{library/os os CLD_TRAPPED}@anchor{1f57}
@deffnx {数据} os.CLD_TRAPPED
@anchor{library/os os CLD_CONTINUED}@anchor{1f58}
@deffnx {数据} os.CLD_CONTINUED

@ref{666,,waitid()} 返回的结果中，@code{si_code} 的可取值。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex waitpid() (在 os 模块中)
@anchor{library/os os waitpid}@anchor{667}
@deffn {函数} os.waitpid (pid, options)

本函数的细节在 Unix 和 Windows 上有不同之处。

在 Unix 上：等待进程号为 @emph{pid} 的子进程执行完毕，返回一个元组，内含其进程 ID 和退出状态指示（编码与 @ref{665,,wait()} 相同）。调用的语义受整数 @emph{options} 的影响，常规操作下该值应为 @code{0}。

如果 @emph{pid} 大于 @code{0}，则 @ref{667,,waitpid()} 会获取该指定进程的状态信息。如果 @emph{pid} 为 @code{0}，则获取当前进程所在进程组中的所有子进程的状态。如果 @emph{pid} 为 @code{-1}，则获取当前进程的子进程状态。如果 @emph{pid} 小于 @code{-1}，则获取进程组 @code{-pid} （ @emph{pid} 的绝对值）中所有进程的状态。

当系统调用返回 -1 时，将抛出带有错误码的 @ref{1d3,,OSError} 异常。

在 Windows 上：等待句柄为 @emph{pid} 的进程执行完毕，返回一个元组，内含 @emph{pid} 以及左移 8 位后的退出状态码（移位简化了跨平台使用本函数）。小于或等于 @code{0} 的 @emph{pid} 在 Windows 上没有特殊含义，且会抛出异常。整数值 @emph{options} 无效。@emph{pid} 可以指向任何 ID 已知的进程，不一定是子进程。调用 @ref{1edc,,spawn*} 函数时传入 @ref{1f47,,P_NOWAIT} 将返回合适的进程句柄。


在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此函数现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex wait3() (在 os 模块中)
@anchor{library/os os wait3}@anchor{663}
@deffn {函数} os.wait3 (options)

与 @ref{667,,waitpid()} 相似，差别在于没有进程 ID 参数，且返回一个 3 元组，其中包括子进程 ID，退出状态指示和资源使用信息。关于资源使用信息的详情，请参考 @ref{e0,,resource}.@ref{d92,,getrusage()}。option 参数与传入 @ref{667,,waitpid()} 和 @ref{664,,wait4()} 的相同。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex wait4() (在 os 模块中)
@anchor{library/os os wait4}@anchor{664}
@deffn {函数} os.wait4 (pid, options)

与 @ref{667,,waitpid()} 相似，差别在本方法返回一个 3 元组，其中包括子进程 ID，退出状态指示和资源使用信息。关于资源使用信息的详情，请参考 @ref{e0,,resource}.@ref{d92,,getrusage()}。@ref{664,,wait4()} 的参数与 @ref{667,,waitpid()} 的参数相同。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WNOHANG() (在 os 模块中)
@anchor{library/os os WNOHANG}@anchor{1f53}
@deffn {数据} os.WNOHANG

用于 @ref{667,,waitpid()} 的选项，如果没有立即可用的子进程状态，则立即返回。在这种情况下，函数返回 @code{(0, 0)}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WCONTINUED() (在 os 模块中)
@anchor{library/os os WCONTINUED}@anchor{1f52}
@deffn {数据} os.WCONTINUED

被任务控制 (job control) 停止的子进程，如果上次报告状态后已恢复运行，则此选项将报告这些子进程。

@ref{12f5,,可用性}: 部分 Unix 系统。
@end deffn

@geindex WUNTRACED() (在 os 模块中)
@anchor{library/os os WUNTRACED}@anchor{1f59}
@deffn {数据} os.WUNTRACED

已停止的子进程，如果自停止以来尚未报告其当前状态，则此选项将报告这些子进程。

@ref{12f5,,可用性}: Unix。
@end deffn

下列函数采用进程状态码作为参数，状态码由 @ref{dba,,system()}、@ref{665,,wait()} 或 @ref{667,,waitpid()} 返回。它们可用于确定进程上发生的操作。

@geindex WCOREDUMP() (在 os 模块中)
@anchor{library/os os WCOREDUMP}@anchor{1f5a}
@deffn {函数} os.WCOREDUMP (status)

如果为该进程生成了核心转储，返回 @code{True}，否则返回 @code{False}。

此函数应当仅在 @ref{1f5b,,WIFSIGNALED()} 为真值时使用。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WIFCONTINUED() (在 os 模块中)
@anchor{library/os os WIFCONTINUED}@anchor{1f5c}
@deffn {函数} os.WIFCONTINUED (status)

如果一个已停止的子进程通过传送 @ref{1f5d,,SIGCONT} 获得恢复（如果该进程是从任务控制停止后再继续的）则返回 @code{True}，否则返回 @code{False}。

参见 @ref{1f52,,WCONTINUED} 选项。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WIFSTOPPED() (在 os 模块中)
@anchor{library/os os WIFSTOPPED}@anchor{1f5e}
@deffn {函数} os.WIFSTOPPED (status)

如果进程是通过传送一个信号来停止的则返回 @code{True}，否则返回 @code{False}。

@ref{1f5e,,WIFSTOPPED()} 只有在当 @ref{667,,waitpid()} 调用是通过使用 @ref{1f59,,WUNTRACED} 选项来完成或者当该进程正被追踪时 (参见 @code{ptrace(2)}) 才返回 @code{True}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WIFSIGNALED() (在 os 模块中)
@anchor{library/os os WIFSIGNALED}@anchor{1f5b}
@deffn {函数} os.WIFSIGNALED (status)

如果进程是通过一个信号来终止的则返回 @code{True} ，否则返回 @code{False}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WIFEXITED() (在 os 模块中)
@anchor{library/os os WIFEXITED}@anchor{1f5f}
@deffn {函数} os.WIFEXITED (status)

如果进程正常终止退出则返回 @code{True}，也就是说通过调用 @code{exit()} 或 @code{_exit()}，或者通过从 @code{main()} 返回；在其他情况下则返回 @code{False}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WEXITSTATUS() (在 os 模块中)
@anchor{library/os os WEXITSTATUS}@anchor{1f60}
@deffn {函数} os.WEXITSTATUS (status)

返回进程退出状态。

此函数应当仅在 @ref{1f5f,,WIFEXITED()} 为真值时使用。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WSTOPSIG() (在 os 模块中)
@anchor{library/os os WSTOPSIG}@anchor{1f61}
@deffn {函数} os.WSTOPSIG (status)

返回导致进程停止的信号。

此函数应当仅在 @ref{1f5e,,WIFSTOPPED()} 为真值时使用。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex WTERMSIG() (在 os 模块中)
@anchor{library/os os WTERMSIG}@anchor{1f62}
@deffn {函数} os.WTERMSIG (status)

返回导致进程终止的信号的编号。

此函数应当仅在 @ref{1f5b,,WIFSIGNALED()} 为真值时使用。

@ref{12f5,,可用性}: Unix。
@end deffn

@node 调度器接口,其他系统信息,进程管理,os --- 多种操作系统接口
@anchor{library/os interface-to-the-scheduler}@anchor{1f63}
@subsubsection 调度器接口


这些函数控制操作系统如何为进程分配 CPU 时间。 它们仅在某些 Unix 平台上可用。 更多细节信息请查阅你所用 Unix 的指南页面。


3.3 新版功能.


以下调度策略如果被操作系统支持就会对外公开。

@geindex SCHED_OTHER() (在 os 模块中)
@anchor{library/os os SCHED_OTHER}@anchor{1f64}
@deffn {数据} os.SCHED_OTHER

默认调度策略。
@end deffn

@geindex SCHED_BATCH() (在 os 模块中)
@anchor{library/os os SCHED_BATCH}@anchor{1f65}
@deffn {数据} os.SCHED_BATCH

用于 CPU 密集型进程的调度策略，它会尽量为计算机中的其余任务保留交互性。
@end deffn

@geindex SCHED_IDLE() (在 os 模块中)
@anchor{library/os os SCHED_IDLE}@anchor{1f66}
@deffn {数据} os.SCHED_IDLE

用于极低优先级的后台任务的调度策略。
@end deffn

@geindex SCHED_SPORADIC() (在 os 模块中)
@anchor{library/os os SCHED_SPORADIC}@anchor{1f67}
@deffn {数据} os.SCHED_SPORADIC

用于偶发型服务程序的调度策略。
@end deffn

@geindex SCHED_FIFO() (在 os 模块中)
@anchor{library/os os SCHED_FIFO}@anchor{1f68}
@deffn {数据} os.SCHED_FIFO

先进先出的调度策略。
@end deffn

@geindex SCHED_RR() (在 os 模块中)
@anchor{library/os os SCHED_RR}@anchor{1f69}
@deffn {数据} os.SCHED_RR

循环式的调度策略。
@end deffn

@geindex SCHED_RESET_ON_FORK() (在 os 模块中)
@anchor{library/os os SCHED_RESET_ON_FORK}@anchor{1f6a}
@deffn {数据} os.SCHED_RESET_ON_FORK

此旗标可与任何其他调度策略进行 OR 运算。 当带有此旗标的进程设置分叉时，其子进程的调度策略和优先级会被重置为默认值。
@end deffn

@geindex sched_param (os 中的类)
@anchor{library/os os sched_param}@anchor{1f3f}
@deffn {类} os.sched_param (sched_priority)

这个类表示在 @ref{a51,,sched_setparam()}, @ref{a52,,sched_setscheduler()} 和 @ref{a4d,,sched_getparam()} 中使用的可修改调度形参。 它属于不可变对象。

目前它只有一个可能的形参：

@geindex sched_priority (os.sched_param 属性)
@anchor{library/os os sched_param sched_priority}@anchor{1f6b}
@deffn {属性} sched_priority

一个调度策略的调度优先级。
@end deffn
@end deffn

@geindex sched_get_priority_min() (在 os 模块中)
@anchor{library/os os sched_get_priority_min}@anchor{a4b}
@deffn {函数} os.sched_get_priority_min (policy)

获取 @emph{policy} 的最低优先级数值。 @emph{policy} 是以上调度策略常量之一。
@end deffn

@geindex sched_get_priority_max() (在 os 模块中)
@anchor{library/os os sched_get_priority_max}@anchor{a4a}
@deffn {函数} os.sched_get_priority_max (policy)

获取 @emph{policy} 的最高优先级数值。 @emph{policy} 是以上调度策略常量之一。
@end deffn

@geindex sched_setscheduler() (在 os 模块中)
@anchor{library/os os sched_setscheduler}@anchor{a52}
@deffn {函数} os.sched_setscheduler (pid, policy, param)

设置 PID 为 @emph{pid} 的进程的调度策略。@emph{pid} 为 0 指的是调用本方法的进程。@emph{policy} 是以上调度策略常量之一。@emph{param} 是一个 @ref{1f3f,,sched_param} 实例。
@end deffn

@geindex sched_getscheduler() (在 os 模块中)
@anchor{library/os os sched_getscheduler}@anchor{a4e}
@deffn {函数} os.sched_getscheduler (pid)

返回 PID 为 @emph{pid} 的进程的调度策略。@emph{pid} 为 0 指的是调用本方法的进程。返回的结果是以上调度策略常量之一。
@end deffn

@geindex sched_setparam() (在 os 模块中)
@anchor{library/os os sched_setparam}@anchor{a51}
@deffn {函数} os.sched_setparam (pid, param)

设置 PID 为 @emph{pid} 的进程的某个调度参数。@emph{pid} 为 0 指的是调用本方法的进程。@emph{param} 是一个 @ref{1f3f,,sched_param} 实例。
@end deffn

@geindex sched_getparam() (在 os 模块中)
@anchor{library/os os sched_getparam}@anchor{a4d}
@deffn {函数} os.sched_getparam (pid)

返回 PID 为 @emph{pid} 的进程的调度参数为一个 @ref{1f3f,,sched_param} 实例。@emph{pid} 为 0 指的是调用本方法的进程。
@end deffn

@geindex sched_rr_get_interval() (在 os 模块中)
@anchor{library/os os sched_rr_get_interval}@anchor{a4f}
@deffn {函数} os.sched_rr_get_interval (pid)

返回 PID 为 @emph{pid} 的进程在时间片轮转调度下的时间片长度（单位为秒）。@emph{pid} 为 0 指的是调用本方法的进程。
@end deffn

@geindex sched_yield() (在 os 模块中)
@anchor{library/os os sched_yield}@anchor{a53}
@deffn {函数} os.sched_yield ()

自愿放弃 CPU。
@end deffn

@geindex sched_setaffinity() (在 os 模块中)
@anchor{library/os os sched_setaffinity}@anchor{a50}
@deffn {函数} os.sched_setaffinity (pid, mask)

将 PID 为 @emph{pid} 的进程（为零则为当前进程）限制到一组 CPU 上。@emph{mask} 是整数的可迭代对象，表示应将进程限制在其中的一组 CPU。
@end deffn

@geindex sched_getaffinity() (在 os 模块中)
@anchor{library/os os sched_getaffinity}@anchor{a4c}
@deffn {函数} os.sched_getaffinity (pid)

返回 PID 为 @emph{pid} 的进程（为零则为当前进程）被限制到的那一组 CPU。
@end deffn

@node 其他系统信息,随机数<2>,调度器接口,os --- 多种操作系统接口
@anchor{library/os miscellaneous-system-information}@anchor{1f6c}@anchor{library/os os-path}@anchor{1f6d}
@subsubsection 其他系统信息


@geindex confstr() (在 os 模块中)
@anchor{library/os os confstr}@anchor{1f6e}
@deffn {函数} os.confstr (name)

返回字符串格式的系统配置信息。@emph{name} 指定要查找的配置名称，它可以是字符串，是一个系统已定义的名称，这些名称定义在不同标准（POSIX，Unix 95，Unix 98 等）中。一些平台还定义了额外的其他名称。当前操作系统已定义的名称在 @code{confstr_names} 字典的键中给出。对于未包含在该映射中的配置名称，也可以传递一个整数作为 @emph{name}。

如果 @emph{name} 指定的配置值未定义，返回 @code{None}。

如果 @emph{name} 是一个字符串且不是已定义的名称，将抛出 @ref{1fb,,ValueError} 异常。如果当前系统不支持 @emph{name} 指定的配置名称，即使该名称存在于 @code{confstr_names}，也会抛出 @ref{1d3,,OSError} 异常，错误码为 @ref{f59,,errno.EINVAL}。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex confstr_names() (在 os 模块中)
@anchor{library/os os confstr_names}@anchor{1f6f}
@deffn {数据} os.confstr_names

字典，表示映射关系，为 @ref{1f6e,,confstr()} 可接受名称与操作系统为这些名称定义的整数值之间的映射。这可用于判断系统已定义了哪些名称。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex cpu_count() (在 os 模块中)
@anchor{library/os os cpu_count}@anchor{879}
@deffn {函数} os.cpu_count ()

返回系统的 CPU 数量。不确定则返回 @code{None}。

该数量不同于当前进程可以使用的CPU数量。可用的CPU数量可以由 @code{len(os.sched_getaffinity(0))} 方法获得。


3.4 新版功能.

@end deffn

@geindex getloadavg() (在 os 模块中)
@anchor{library/os os getloadavg}@anchor{1f70}
@deffn {函数} os.getloadavg ()

返回系统运行队列中最近 1、5 和 15 分钟内的平均进程数。无法获得平均负载则抛出 @ref{1d3,,OSError} 异常。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex sysconf() (在 os 模块中)
@anchor{library/os os sysconf}@anchor{1ecd}
@deffn {函数} os.sysconf (name)

返回整数格式的系统配置信息。如果 @emph{name} 指定的配置值未定义，返回 @code{-1}。对 @ref{1f6e,,confstr()} 的 @emph{name} 参数的注释在此处也适用。当前已知的配置名称在 @code{sysconf_names} 字典中提供。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex sysconf_names() (在 os 模块中)
@anchor{library/os os sysconf_names}@anchor{1f71}
@deffn {数据} os.sysconf_names

字典，表示映射关系，为 @ref{1ecd,,sysconf()} 可接受名称与操作系统为这些名称定义的整数值之间的映射。这可用于判断系统已定义了哪些名称。

@ref{12f5,,可用性}: Unix。
@end deffn

以下数据值用于支持对路径本身的操作。所有平台都有定义。

对路径的高级操作在 @ref{c5,,os.path} 模块中定义。

@geindex . (dot); in pathnames

@geindex curdir() (在 os 模块中)
@anchor{library/os os curdir}@anchor{1b84}
@deffn {数据} os.curdir

操作系统用来表示当前目录的常量字符串。在 Windows 和 POSIX 上是 @code{'.'}。在 @ref{c5,,os.path} 中也可用。
@end deffn

@geindex ..; in pathnames

@geindex pardir() (在 os 模块中)
@anchor{library/os os pardir}@anchor{1ee6}
@deffn {数据} os.pardir

操作系统用来表示父目录的常量字符串。在 Windows 和 POSIX 上是 @code{'..'}。在 @ref{c5,,os.path} 中也可用。
@end deffn

@geindex / (slash); in pathnames

@geindex \ (backslash); in pathnames (Windows)

@geindex sep() (在 os 模块中)
@anchor{library/os os sep}@anchor{1c0a}
@deffn {数据} os.sep

操作系统用来分隔路径不同部分的字符。在 POSIX 上是 @code{'/'}，在 Windows 上是是 @code{'\\'}。注意，仅了解它不足以能解析或连接路径，请使用 @ref{1b7e,,os.path.split()} 和 @ref{eeb,,os.path.join()}，但它有时是有用的。在 @ref{c5,,os.path} 中也可用。
@end deffn

@geindex / (slash); in pathnames

@geindex altsep() (在 os 模块中)
@anchor{library/os os altsep}@anchor{1c0b}
@deffn {数据} os.altsep

操作系统用来分隔路径不同部分的替代字符。如果仅存在一个分隔符，则为 @code{None}。在 @code{sep} 是反斜杠的 Windows 系统上，该值被设为 @code{'/'}。在 @ref{c5,,os.path} 中也可用。
@end deffn

@geindex . (dot); in pathnames

@geindex extsep() (在 os 模块中)
@anchor{library/os os extsep}@anchor{1f72}
@deffn {数据} os.extsep

分隔基本文件名与扩展名的字符，如 @code{os.py} 中的 @code{'.'}。在 @ref{c5,,os.path} 中也可用。
@end deffn

@geindex ; (colon); path separator (POSIX)
@geindex ; (semicolon)

@geindex pathsep() (在 os 模块中)
@anchor{library/os os pathsep}@anchor{12eb}
@deffn {数据} os.pathsep

操作系统通常用于分隔搜索路径（如 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH}）中不同部分的字符，如 POSIX 上是 @code{':'}，Windows 上是 @code{';'}。在 @ref{c5,,os.path} 中也可用。
@end deffn

@geindex defpath() (在 os 模块中)
@anchor{library/os os defpath}@anchor{f70}
@deffn {数据} os.defpath

在环境变量没有 @code{'PATH'} 键的情况下，@ref{1f20,,exec*p*} and @ref{1edc,,spawn*p*} 使用的默认搜索路径。在 @ref{c5,,os.path} 中也可用。
@end deffn

@geindex linesep() (在 os 模块中)
@anchor{library/os os linesep}@anchor{1594}
@deffn {数据} os.linesep

当前平台用于分隔（或终止）行的字符串。它可以是单个字符，如 POSIX 上是 @code{'\n'}，也可以是多个字符，如 Windows 上是 @code{'\r\n'}。在写入以文本模式（默认模式）打开的文件时，请不要使用 @emph{os.linesep} 作为行终止符，请在所有平台上都使用一个 @code{'\n'} 代替。
@end deffn

@geindex devnull() (在 os 模块中)
@anchor{library/os os devnull}@anchor{fad}
@deffn {数据} os.devnull

空设备的文件路径。如 POSIX 上为 @code{'/dev/null'}，Windows 上为 @code{'nul'}。在 @ref{c5,,os.path} 中也可用。
@end deffn

@geindex RTLD_LAZY() (在 os 模块中)
@geindex RTLD_NOW() (在 os 模块中)
@geindex RTLD_GLOBAL() (在 os 模块中)
@geindex RTLD_LOCAL() (在 os 模块中)
@geindex RTLD_NODELETE() (在 os 模块中)
@geindex RTLD_NOLOAD() (在 os 模块中)
@geindex RTLD_DEEPBIND() (在 os 模块中)
@anchor{library/os os RTLD_LAZY}@anchor{a5a}
@deffn {数据} os.RTLD_LAZY
@anchor{library/os os RTLD_NOW}@anchor{a5b}
@deffnx {数据} os.RTLD_NOW
@anchor{library/os os RTLD_GLOBAL}@anchor{a5c}
@deffnx {数据} os.RTLD_GLOBAL
@anchor{library/os os RTLD_LOCAL}@anchor{a5d}
@deffnx {数据} os.RTLD_LOCAL
@anchor{library/os os RTLD_NODELETE}@anchor{a5e}
@deffnx {数据} os.RTLD_NODELETE
@anchor{library/os os RTLD_NOLOAD}@anchor{a5f}
@deffnx {数据} os.RTLD_NOLOAD
@anchor{library/os os RTLD_DEEPBIND}@anchor{a60}
@deffnx {数据} os.RTLD_DEEPBIND

@ref{a61,,setdlopenflags()} 和 @ref{e47,,getdlopenflags()} 函数所使用的标志。请参阅 Unix 手册页 @code{dlopen(3)} 获取不同标志的含义。


3.3 新版功能.

@end deffn

@node 随机数<2>,,其他系统信息,os --- 多种操作系统接口
@anchor{library/os random-numbers}@anchor{1f73}
@subsubsection 随机数


@geindex getrandom() (在 os 模块中)
@anchor{library/os os getrandom}@anchor{564}
@deffn {函数} os.getrandom (size, flags=0)

获得最多为 @emph{size} 的随机字节。本函数返回的字节数可能少于请求的字节数。

这些字节可用于为用户空间的随机数生成器提供种子，或用于加密目的。

@code{getrandom()} 依赖于从设备驱动程序和其他环境噪声源收集的熵。不必要地读取大量数据将对使用 @code{/dev/random} 和 @code{/dev/urandom} 设备的其他用户产生负面影响。

flags 参数是一个位掩码，可以是零个或多个下列值以或运算组合： @ref{1f74,,os.GRND_RANDOM} 和 @ref{1f75,,GRND_NONBLOCK}。

另请参阅 Linux getrandom() 手册页@footnote{http://man7.org/linux/man-pages/man2/getrandom.2.html} 。

@ref{12f5,,可用性}：Linux 3.17 或更高版本。


3.6 新版功能.

@end deffn

@geindex urandom() (在 os 模块中)
@anchor{library/os os urandom}@anchor{4cb}
@deffn {函数} os.urandom (size)

返回大小为 @emph{size} 的字符串，它是适合加密使用的随机字节。

本函数从系统指定的随机源获取随机字节。对于加密应用程序，返回的数据应有足够的不可预测性，尽管其确切的品质取决于操作系统的实现。

在 Linux 上，如果 @code{getrandom()} 系统调用可用，它将以阻塞模式使用：阻塞直到系统的 urandom 熵池初始化完毕（内核收集了 128 位熵）。原理请参阅 
@geindex Python 提高建议; PEP 524
PEP 524@footnote{https://www.python.org/dev/peps/pep-0524}。在 Linux 上，@ref{564,,getrandom()} 可以以非阻塞模式（使用 @ref{1f75,,GRND_NONBLOCK} 标志）获取随机字节，或者轮询直到系统的 urandom 熵池初始化完毕。

在类 Unix 系统上，随机字节是从 @code{/dev/urandom} 设备读取的。如果 @code{/dev/urandom} 设备不可用或不可读，则抛出 @ref{609,,NotImplementedError} 异常。

在 Windows 上将使用 @code{CryptGenRandom()}。


@subsubheading 参见


@ref{e4,,secrets} 模块提供了更高级的功能。所在平台会提供随机数生成器，有关其易于使用的接口，请参阅 @ref{1a9a,,random.SystemRandom}。



在 3.6.0 版更改: 在 Linux 上，@code{getrandom()} 现在以阻塞模式使用，以提高安全性。



在 3.5.2 版更改: 在 Linux 上，如果 @code{getrandom()} 系统调用阻塞（urandom 熵池尚未初始化完毕），则退回一步读取 @code{/dev/urandom}。



在 3.5 版更改: 在 Linux 3.17 和更高版本上，现在使用 @code{getrandom()} 系统调用（如果可用）。在 OpenBSD 5.6 和更高版本上，现在使用 @code{getentropy()} C 函数。这些函数避免了使用内部文件描述符。

@end deffn

@geindex GRND_NONBLOCK() (在 os 模块中)
@anchor{library/os os GRND_NONBLOCK}@anchor{1f75}
@deffn {数据} os.GRND_NONBLOCK

默认情况下，从 @code{/dev/random} 读取时，如果没有可用的随机字节，则 @ref{564,,getrandom()} 会阻塞；从 @code{/dev/urandom} 读取时，如果熵池尚未初始化，则会阻塞。

如果设置了 @ref{1f75,,GRND_NONBLOCK} 标志，则这些情况下 @ref{564,,getrandom()} 不会阻塞，而是立即抛出 @ref{991,,BlockingIOError} 异常。


3.6 新版功能.

@end deffn

@geindex GRND_RANDOM() (在 os 模块中)
@anchor{library/os os GRND_RANDOM}@anchor{1f74}
@deffn {数据} os.GRND_RANDOM

如果设置了此标志位，那么将从 @code{/dev/random} 池而不是 @code{/dev/urandom} 池中提取随机字节。


3.6 新版功能.

@end deffn

@node io --- 处理流的核心工具,time --- 时间的访问和转换,os --- 多种操作系统接口,通用操作系统服务
@anchor{library/io doc}@anchor{1f76}@anchor{library/io io-core-tools-for-working-with-streams}@anchor{1f77}@anchor{library/io module-io}@anchor{a1}
@subsection @code{io} --- 处理流的核心工具


@geindex io (模块)

@strong{源代码:} Lib/io.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/io.py}


__________________________________________________________________


@menu
* 概述: 概述<8>. 
* 高阶模块接口:: 
* 类的层次结构:: 
* 性能: 性能<3>. 

@end menu

@node 概述<8>,高阶模块接口,,io --- 处理流的核心工具
@anchor{library/io io-overview}@anchor{158f}@anchor{library/io overview}@anchor{1f78}
@subsubsection 概述


@geindex file object; io module

@ref{a1,,io} 模块提供了 Python 用于处理各种 I/O 类型的主要工具。三种主要的 I/O类型分别为: @emph{文本 I/O}, @emph{二进制 I/O} 和 @emph{原始 I/O}。这些是泛型类型，有很多种后端存储可以用在他们上面。一个隶属于任何这些类型的具体对象被称作 @ref{b3b,,file object}。 其他同类的术语还有 @emph{流} 和 @emph{类文件对象}。

独立于其类别，每个具体流对象也将具有各种功能：它可以是只读，只写或读写。它还可以允许任意随机访问（向前或向后寻找任何位置），或仅允许顺序访问（例如在套接字或管道的情况下）。

所有流对提供给它们的数据类型都很敏感。例如将 @ref{329,,str} 对象给二进制流的 @code{write()} 方法会引发 @ref{192,,TypeError}。将 @ref{32a,,bytes} 对象提供给文本流的 @code{write()} 方法也是如此。


在 3.3 版更改: 由于 @ref{98c,,IOError} 现在是 @ref{1d3,,OSError} 的别名，因此用于引发 @ref{98c,,IOError} 的操作现在会引发 @ref{1d3,,OSError} 。


@menu
* 文本 I/O:: 
* 二进制 I/O:: 
* 原始 I/O:: 

@end menu

@node 文本 I/O,二进制 I/O,,概述<8>
@anchor{library/io text-i-o}@anchor{1f79}
@subsubsection 文本 I/O


文本I/O预期并生成 @ref{329,,str} 对象。这意味着，无论何时后台存储是由字节组成的（例如在文件的情况下），数据的编码和解码都是透明的，并且可以选择转换特定于平台的换行符。

创建文本流的最简单方法是使用 @ref{4ea,,open()}，可以选择指定编码：

@example
f = open("myfile.txt", "r", encoding="utf-8")
@end example

内存中文本流也可以作为 @ref{827,,StringIO} 对象使用：

@example
f = io.StringIO("some initial text data")
@end example

@ref{c32,,TextIOBase} 的文档中详细描述了文本流的API

@node 二进制 I/O,原始 I/O,文本 I/O,概述<8>
@anchor{library/io binary-i-o}@anchor{1f7a}
@subsubsection 二进制 I/O


二进制I/O（也称为缓冲I/O）预期 @ref{5e3,,bytes-like objects} 并生成  @ref{32a,,bytes} 对象。不执行编码、解码或换行转换。这种类型的流可以用于所有类型的非文本数据，并且还可以在需要手动控制文本数据的处理时使用。

创建二进制流的最简单方法是使用 @ref{4ea,,open()}，并在模式字符串中指定 @code{'b'} ：

@example
f = open("myfile.jpg", "rb")
@end example

内存中二进制流也可以作为 @ref{795,,BytesIO} 对象使用：

@example
f = io.BytesIO(b"some initial binary data: \x00\x01")
@end example

@ref{583,,BufferedIOBase} 的文档中详细描述了二进制流 API。

其他库模块可以提供额外的方式来创建文本或二进制流。参见 @ref{b12,,socket.socket.makefile()} 的示例。

@node 原始 I/O,,二进制 I/O,概述<8>
@anchor{library/io raw-i-o}@anchor{1f7b}
@subsubsection 原始 I/O


原始 I/O（也称为 @emph{非缓冲 I/O}）通常用作二进制和文本流的低级构建块。用户代码直接操作原始流的用法非常罕见。不过，可以通过在禁用缓冲的情况下以二进制模式打开文件来创建原始流：

@example
f = open("myfile.jpg", "rb", buffering=0)
@end example

@ref{a0e,,RawIOBase} 的文档中详细描述了原始流的API

@node 高阶模块接口,类的层次结构,概述<8>,io --- 处理流的核心工具
@anchor{library/io high-level-module-interface}@anchor{1f7c}
@subsubsection 高阶模块接口


@geindex DEFAULT_BUFFER_SIZE() (在 io 模块中)
@anchor{library/io io DEFAULT_BUFFER_SIZE}@anchor{1591}
@deffn {数据} io.DEFAULT_BUFFER_SIZE

包含模块缓冲 I/O 类使用的默认缓冲区大小的 int。 在可能的情况下 @ref{4ea,,open()} 将使用文件的 blksize（由 @ref{1f1,,os.stat()} 获得）。
@end deffn

@geindex open() (在 io 模块中)
@anchor{library/io io open}@anchor{654}
@deffn {函数} io.open (file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

这是内置的 @ref{4ea,,open()} 函数的别名。

@code{open} 附带参数 @code{path}、@code{mode}、@code{flags} 会引发 @ref{12d0,,审计事件}。
@end deffn

@geindex open_code() (在 io 模块中)
@anchor{library/io io open_code}@anchor{eb1}
@deffn {函数} io.open_code (path)

以 @code{'rb'} 模式打开提供的文件。如果目的是将文件内容做为可执行代码，则应使用此函数。

@code{path} 应当为 @ref{329,,str} 类型并且是一个绝对路径。

此函数的行为可以由对 @ref{1f7d,,PyFile_SetOpenCodeHook()} 的先期调用所重载。 但是，如果 @code{path} 为 @ref{329,,str} 类型并且是一个绝对路径，@code{open_code(path)} 的行为应当总是与 @code{open(path, 'rb')} 一致。 重载此行为的目的是为了给文件附加额外的验证或预处理。


3.8 新版功能.

@end deffn

@geindex BlockingIOError
@anchor{library/io io BlockingIOError}@anchor{1f7e}
@deffn {例外} io.BlockingIOError

这是内置的 @ref{991,,BlockingIOError} 异常的兼容性别名。
@end deffn

@geindex UnsupportedOperation
@anchor{library/io io UnsupportedOperation}@anchor{1f7f}
@deffn {例外} io.UnsupportedOperation

在流上调用不支持的操作时引发的继承 @ref{1d3,,OSError} 和 @ref{1fb,,ValueError} 的异常。
@end deffn

@menu
* 内存中的流:: 

@end menu

@node 内存中的流,,,高阶模块接口
@anchor{library/io in-memory-streams}@anchor{1f80}
@subsubsection 内存中的流


也可以使用 @ref{329,,str} 或 @ref{5e3,,bytes-like object} 作为文件进行读取和写入。对于字符串， @ref{827,,StringIO} 可以像在文本模式下打开的文件一样使用。 @ref{795,,BytesIO} 可以像以二进制模式打开的文件一样使用。两者都提供完整的随机读写功能。


@subsubheading 参见



@table @asis

@item @ref{fd,,sys}

包含标准IO流: @ref{306,,sys.stdin}, @ref{307,,sys.stdout} 和 @ref{308,,sys.stderr} 。
@end table


@node 类的层次结构,性能<3>,高阶模块接口,io --- 处理流的核心工具
@anchor{library/io class-hierarchy}@anchor{1f81}
@subsubsection 类的层次结构


I/O 流被安排为按类的层次结构实现。 首先是 @ref{b2c,,抽象基类} (ABC)，用于指定流的各种类别，然后是提供标准流实现的具体类。

@quotation

@cartouche
@quotation 注解 
抽象基类还提供某些方法的默认实现，以帮助实现具体的流类。例如 @ref{583,,BufferedIOBase} 提供了 @code{readinto()} 和 @ref{169c,,readline()} 的未优化实现。
@end quotation
@end cartouche
@end quotation

I/O层次结构的顶部是抽象基类 @ref{1db,,IOBase} 。它定义了流的基本接口。但是请注意，对流的读取和写入之间没有分离。如果实现不支持指定的操作，则会引发 @ref{1f7f,,UnsupportedOperation} 。

抽象基类 @ref{a0e,,RawIOBase} 是 @ref{1db,,IOBase} 的子类。它负责将字节读取和写入流中。 @ref{a0e,,RawIOBase} 的子类 @ref{c9d,,FileIO} 提供计算机文件系统中文件的接口。

抽象基类 @ref{583,,BufferedIOBase} 处理原始字节流（ @ref{a0e,,RawIOBase} ）上的缓冲。其子类 @ref{1595,,BufferedWriter} 、 @ref{b83,,BufferedReader} 和 @ref{1f82,,BufferedRWPair} 缓冲流是可读、可写以及可读写的。 @ref{1596,,BufferedRandom} 为随机访问流提供缓冲接口。 @ref{583,,BufferedIOBase} 的另一个子类 @ref{795,,BytesIO} 是内存中字节流。

抽象基类 @ref{c32,,TextIOBase} 是 @ref{1db,,IOBase} 的另一个子类，它处理字节表示文本的流，并处理字符串之间的编码和解码。其一个子类 @ref{5ee,,TextIOWrapper} 是原始缓冲流（ @ref{583,,BufferedIOBase} ）的缓冲文本接口。另一个子类 @ref{827,,StringIO} 用于文本的内存流。

参数名不是规范的一部分，只有 @ref{4ea,,open()} 的参数才用作关键字参数。

下表总结了抽象基类提供的 @ref{a1,,io} 模块：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

抽象基类

@tab

继承

@tab

抽象方法

@tab

Mixin方法和属性

@item

@ref{1db,,IOBase}

@tab

@tab

@code{fileno}, @code{seek}, 和 @code{truncate}

@tab

@code{close}, @code{closed}, @code{__enter__}, @code{__exit__}, @code{flush}, @code{isatty}, @code{__iter__}, @code{__next__}, @code{readable}, @code{readline}, @code{readlines}, @code{seekable}, @code{tell}, @code{writable} 和 @code{writelines}

@item

@ref{a0e,,RawIOBase}

@tab

@ref{1db,,IOBase}

@tab

@code{readinto} 和 @code{write}

@tab

继承 @ref{1db,,IOBase} 方法, @code{read}, 和 @code{readall}

@item

@ref{583,,BufferedIOBase}

@tab

@ref{1db,,IOBase}

@tab

@code{detach}, @code{read}, @code{read1}, 和 @code{write}

@tab

继承 @ref{1db,,IOBase} 方法, @code{readinto}, 和 @code{readinto1}

@item

@ref{c32,,TextIOBase}

@tab

@ref{1db,,IOBase}

@tab

@code{detach}, @code{read}, @code{readline}, 和 @code{write}

@tab

继承 @ref{1db,,IOBase} 方法, @code{encoding}, @code{errors}, 和 @code{newlines}

@end multitable


@menu
* I/O 基类:: 
* 原始文件 I/O:: 
* 缓冲流:: 
* 文本 I/O: 文本 I/O<2>. 

@end menu

@node I/O 基类,原始文件 I/O,,类的层次结构
@anchor{library/io i-o-base-classes}@anchor{1f83}
@subsubsection I/O 基类


@geindex IOBase (io 中的类)
@anchor{library/io io IOBase}@anchor{1db}
@deffn {类} io.IOBase

所有 I/O 类的抽象基类，作用于字节流。没有公共构造函数。

此类为许多方法提供了空的抽象实现，派生类可以有选择地重写。默认实现代表一个无法读取、写入或查找的文件。

尽管 @ref{1db,,IOBase} 没有声明 @code{read()} 或 @code{write()} ，因为它们的签名会有所不同，但是实现和客户端应该将这些方法视为接口的一部分。此外，当调用不支持的操作时可能会引发 @ref{1fb,,ValueError} （或 @ref{1f7f,,UnsupportedOperation} ）。

从文件读取或写入文件的二进制数据的基本类型为 @ref{32a,,bytes} 。其他 @ref{5e3,,bytes-like objects} 也可以作为方法参数。文本I/O类使用 @ref{329,,str} 数据。

请注意，在关闭的流上调用任何方法（甚至查询）都是未定义的（undefined）。在这种情况下，实现可能会引发 @ref{1fb,,ValueError} 。

@ref{1db,,IOBase} （及其子类）支持迭代器协议，这意味着可以迭代 @ref{1db,,IOBase} 对象以产生流中的行。根据流是二进制流（产生字节）还是文本流（产生字符串），行的定义略有不同。请参见下面的 @ref{169c,,readline()} 。

@ref{1db,,IOBase} 也是一个上下文管理器，因此支持 @ref{6e3,,with} 语句。 在这个示例中，@emph{file} 将在 @code{with} 语句块执行完成之后被关闭 --- 即使是发生了异常:

@example
with open('spam.txt', 'w') as file:
    file.write('Spam and eggs!')
@end example

@ref{1db,,IOBase} 提供以下数据属性和方法：

@geindex close() (io.IOBase 方法)
@anchor{library/io io IOBase close}@anchor{fa0}
@deffn {方法} close ()

刷新并关闭此流。如果文件已经关闭，则此方法无效。文件关闭后，对文件的任何操作（例如读取或写入）都会引发 @ref{1fb,,ValueError} 。

为方便起见，允许多次调用此方法。但是，只有第一个调用才会生效。
@end deffn

@geindex closed (io.IOBase 属性)
@anchor{library/io io IOBase closed}@anchor{fa1}
@deffn {属性} closed

如果流已关闭，则返回 True。
@end deffn

@geindex fileno() (io.IOBase 方法)
@anchor{library/io io IOBase fileno}@anchor{1ea0}
@deffn {方法} fileno ()

返回流的底层文件描述符（整数）---如果存在。如果 IO 对象不使用文件描述符，则会引发 @ref{1d3,,OSError} 。
@end deffn

@geindex flush() (io.IOBase 方法)
@anchor{library/io io IOBase flush}@anchor{1f84}
@deffn {方法} flush ()

刷新流的写入缓冲区（如果适用）。这对只读和非阻塞流不起作用。
@end deffn

@geindex isatty() (io.IOBase 方法)
@anchor{library/io io IOBase isatty}@anchor{1592}
@deffn {方法} isatty ()

如果流是交互式的（即连接到终端/tty设备），则返回 @code{True} 。
@end deffn

@geindex readable() (io.IOBase 方法)
@anchor{library/io io IOBase readable}@anchor{1f85}
@deffn {方法} readable ()

如果可以读取流，则返回 @code{True} 。否则为 @code{False} ，且 @code{read()} 将引发 @ref{1d3,,OSError} 错误。
@end deffn

@geindex readline() (io.IOBase 方法)
@anchor{library/io io IOBase readline}@anchor{169c}
@deffn {方法} readline (size=-1)

从流中读取并返回一行。如果指定了 @emph{size}，将至多读取 @emph{size} 个字节。

对于二进制文件行结束符总是 @code{b'\n'}；对于文本文件，可以用将 @emph{newline} 参数传给 @ref{4ea,,open()} 的方式来选择要识别的行结束符。
@end deffn

@geindex readlines() (io.IOBase 方法)
@anchor{library/io io IOBase readlines}@anchor{1725}
@deffn {方法} readlines (hint=-1)

从流中读取并返回包含多行的列表。可以指定 @emph{hint} 来控制要读取的行数：如果（以字节/字符数表示的）所有行的总大小超出了 @emph{hint} 则将不会读取更多的行。

请注意使用 @code{for line in file: ...} 就足够对文件对象进行迭代了，可以不必调用 @code{file.readlines()}。
@end deffn

@geindex seek() (io.IOBase 方法)
@anchor{library/io io IOBase seek}@anchor{1d2d}
@deffn {方法} seek (offset, whence=SEEK_SET)

将流位置修改到给定的字节 @emph{offset}。 @emph{offset} 将相对于由 @emph{whence} 指定的位置进行解析。 @emph{whence} 的默认值为 @code{SEEK_SET}。 @emph{whence} 的可用值有：


@itemize *

@item 
@code{SEEK_SET} 或 @code{0} -- 流的开头（默认值）；@emph{offset} 应为零或正值

@item 
@code{SEEK_CUR} or @code{1} -- 当前流位置；@emph{offset} 可以为负值

@item 
@code{SEEK_END} or @code{2} -- 流的末尾；@emph{offset} 通常为负值
@end itemize

返回新的绝对位置。


3.1 新版功能: @code{SEEK_*} 常量.



3.3 新版功能: 某些操作系统还可支持其他的值，例如 @code{os.SEEK_HOLE} 或 @code{os.SEEK_DATA}。特定文件的可用值还会取决于它是以文本还是二进制模式打开。

@end deffn

@geindex seekable() (io.IOBase 方法)
@anchor{library/io io IOBase seekable}@anchor{1f86}
@deffn {方法} seekable ()

如果流支持随机访问则返回 @code{True}。 如为 @code{False}，则 @ref{1d2d,,seek()}, @ref{1d2e,,tell()} 和 @ref{c9e,,truncate()} 将引发 @ref{1d3,,OSError}。
@end deffn

@geindex tell() (io.IOBase 方法)
@anchor{library/io io IOBase tell}@anchor{1d2e}
@deffn {方法} tell ()

返回当前流的位置。
@end deffn

@geindex truncate() (io.IOBase 方法)
@anchor{library/io io IOBase truncate}@anchor{c9e}
@deffn {方法} truncate (size=None)

将流的大小调整为给定的 @emph{size} 个字节（如果未指定 @emph{size} 则调整至当前位置）。 当前的流位置不变。 这个调整操作可扩展或减小当前文件大小。 在扩展的情况下，新文件区域的内容取决于具体平台（在大多数系统上，额外的字节会填充为零）。 返回新的文件大小。


在 3.5 版更改: 现在Windows在扩展时将文件填充为零。

@end deffn

@geindex writable() (io.IOBase 方法)
@anchor{library/io io IOBase writable}@anchor{1f87}
@deffn {方法} writable ()

如果流支持写入则返回 @code{True}。 如为 @code{False}，则 @code{write()} 和 @ref{c9e,,truncate()} 将引发 @ref{1d3,,OSError}。
@end deffn

@geindex writelines() (io.IOBase 方法)
@anchor{library/io io IOBase writelines}@anchor{1726}
@deffn {方法} writelines (lines)

将行列表写入到流。 不会添加行分隔符，因此通常所提供的每一行都带有末尾行分隔符。
@end deffn

@geindex __del__() (io.IOBase 方法)
@anchor{library/io io IOBase __del__}@anchor{1f88}
@deffn {方法} __del__ ()

为对象销毁进行准备。 @ref{1db,,IOBase} 提供了此方法的默认实现，该实现会调用实例的 @ref{fa0,,close()} 方法。
@end deffn
@end deffn

@geindex RawIOBase (io 中的类)
@anchor{library/io io RawIOBase}@anchor{a0e}
@deffn {类} io.RawIOBase

原始二进制 I/O 的基类。 它继承自 @ref{1db,,IOBase}。 没有公共构造器。

原始二进制 I/O 通常提供对下层 OS 设备或 API 的低层级访问，而不尝试将其封装到高层级的基元中（这是留给缓冲 I/O 和 Text I/O 的，将在下文中描述）。

在 @ref{1db,,IOBase} 的属性和方法之外，@ref{a0e,,RawIOBase} 还提供了下列方法:

@geindex read() (io.RawIOBase 方法)
@anchor{library/io io RawIOBase read}@anchor{6fc}
@deffn {方法} read (size=-1)

从对象中读取 @emph{size} 个字节并将其返回。 作为一个便捷选项，如果 @emph{size} 未指定或为 -1，则返回所有字节直到 EOF。 在其他情况下，仅会执行一次系统调用。 如果操作系统调用返回字节数少于 @emph{size} 则此方法也可能返回少于 @emph{size} 个字节。

如果返回 0 个字节而 @emph{size} 不为零 0，这表明到达文件末尾。 如果处于非阻塞模式并且没有更多字节可用，则返回 @code{None}。

默认实现会转至 @ref{1f89,,readall()} 和 @ref{6fd,,readinto()}。
@end deffn

@geindex readall() (io.RawIOBase 方法)
@anchor{library/io io RawIOBase readall}@anchor{1f89}
@deffn {方法} readall ()

从流中读取并返回所有字节直到 EOF，如有必要将对流执行多次调用。
@end deffn

@geindex readinto() (io.RawIOBase 方法)
@anchor{library/io io RawIOBase readinto}@anchor{6fd}
@deffn {方法} readinto (b)

将字节数据读入预先分配的可写 @ref{5e3,,bytes-like object} @emph{b}，并返回所读取的字节数。 例如，@emph{b} 可以是一个 @ref{32b,,bytearray}。 如果对象处理非阻塞模式并且没有更多字节可用，则返回 @code{None}。
@end deffn

@geindex write() (io.RawIOBase 方法)
@anchor{library/io io RawIOBase write}@anchor{1f8a}
@deffn {方法} write (b)

将给定的 @ref{5e3,,bytes-like object} @emph{b} 写入到下层的原始流，并返回所写入的字节数。 这可以少于 @emph{b} 的总字节数，具体取决于下层原始流的设定，特别是如果它处于非阻塞模式的话。 如果原始流设为非阻塞并且不能真正向其写入单个字节时则返回 @code{None}。 调用者可以在此方法返回后释放或改变 @emph{b}，因此该实现应该仅在方法调用期间访问 @emph{b}。
@end deffn
@end deffn

@geindex BufferedIOBase (io 中的类)
@anchor{library/io io BufferedIOBase}@anchor{583}
@deffn {类} io.BufferedIOBase

支持某种缓冲的二进制流的基类。 它继承自 @ref{1db,,IOBase}。 没有公共构造器。

与 @ref{a0e,,RawIOBase} 的主要差别在于 @ref{1ced,,read()}, @ref{1f8b,,readinto()} 和 @ref{584,,write()} 等方法将（分别）尝试按照要求读取尽可能多的输入或是耗尽所有给定的输出，其代价是可能会执行一次以上的系统调用。

除此之外，那些方法还可能引发 @ref{991,,BlockingIOError}，如果下层的原始数据流处于非阻塞模式并且无法接受或给出足够数据的话；不同于对应的 @ref{a0e,,RawIOBase} 方法，它们将永远不会返回 @code{None}。

并且，@ref{1ced,,read()} 方法也没有转向 @ref{1f8b,,readinto()} 的默认实现。

典型的 @ref{583,,BufferedIOBase} 实现不应当继承自 @ref{a0e,,RawIOBase} 实现，而要包装一个该实现，正如 @ref{1595,,BufferedWriter} 和 @ref{b83,,BufferedReader} 所做的那样。

@ref{583,,BufferedIOBase} 在 @ref{1db,,IOBase} 的现有成员以外还提供或重载了下列方法和属性:

@geindex raw (io.BufferedIOBase 属性)
@anchor{library/io io BufferedIOBase raw}@anchor{1f8c}
@deffn {属性} raw

由 @ref{583,,BufferedIOBase} 处理的下层原始流 (@ref{a0e,,RawIOBase} 的实例)。 它不是 @ref{583,,BufferedIOBase} API 的组成部分并且不存在于某些实现中。
@end deffn

@geindex detach() (io.BufferedIOBase 方法)
@anchor{library/io io BufferedIOBase detach}@anchor{1f8d}
@deffn {方法} detach ()

从缓冲区分离出下层原始流并将其返回。

在原始流被分离之后，缓冲区将处于不可用的状态。

某些缓冲区例如 @ref{795,,BytesIO} 并无可从此方法返回的单独原始流的概念。 它们将会引发 @ref{1f7f,,UnsupportedOperation}。


3.1 新版功能.

@end deffn

@geindex read() (io.BufferedIOBase 方法)
@anchor{library/io io BufferedIOBase read}@anchor{1ced}
@deffn {方法} read (size=-1)

读取并返回最多 @emph{size} 个字节。 如果省略此参数则返回 @code{None}，如果参数为负值则读取并返回所有数据直到 EOF。 如果流已经到达 EOF 则返回一个空的 @ref{32a,,bytes} 对象。

如果此参数为正值，并且下层原始流不可交互，则可能发起多个原始读取以满足字节计数（直至先遇到 EOF）。 但对于可交互原始流，则将至多发起一个原始读取，并且简短的结果并不意味着已到达 EOF。

@ref{991,,BlockingIOError} 会在下层原始流不处于阻塞模式，并且当前没有可用数据时被引发。
@end deffn

@geindex read1() (io.BufferedIOBase 方法)
@anchor{library/io io BufferedIOBase read1}@anchor{1cec}
@deffn {方法} read1 ([size])

通过至多一次对下层流的 @ref{6fc,,read()} (或 @ref{6fd,,readinto()}) 方法的调用读取并返回至多 @emph{size} 个字节。 这适用于在 @ref{583,,BufferedIOBase} 对象之上实现你自己的缓冲区的情况。

如果 @emph{size} 为 @code{-1} (默认值)，则返回任意数量的字节（多于零字节，除非已到达 EOF）。
@end deffn

@geindex readinto() (io.BufferedIOBase 方法)
@anchor{library/io io BufferedIOBase readinto}@anchor{1f8b}
@deffn {方法} readinto (b)

将字节数据读入预先分配的可写 @ref{5e3,,bytes-like object} @emph{b} 并返回所读取的字节数。 例如，@emph{b} 可以是一个 @ref{32b,,bytearray}。

类似于 @ref{1ced,,read()}，可能对下层原始流发起多次读取，除非后者为交互式。

@ref{991,,BlockingIOError} 会在下层原始流不处于阻塞模式，并且当前没有可用数据时被引发。
@end deffn

@geindex readinto1() (io.BufferedIOBase 方法)
@anchor{library/io io BufferedIOBase readinto1}@anchor{6fb}
@deffn {方法} readinto1 (b)

将字节数据读入预先分配的可写 @ref{5e3,,bytes-like object} @emph{b}，其中至多使用一次对下层原始流 @ref{6fc,,read()} (或 @ref{6fd,,readinto()}) 方法的调用。 返回所读取的字节数。

@ref{991,,BlockingIOError} 会在下层原始流不处于阻塞模式，并且当前没有可用数据时被引发。


3.5 新版功能.

@end deffn

@geindex write() (io.BufferedIOBase 方法)
@anchor{library/io io BufferedIOBase write}@anchor{584}
@deffn {方法} write (b)

写入给定的 @ref{5e3,,bytes-like object} @emph{b}，并返回写入的字节数 (总是等于 @emph{b} 的字节长度，因为如果写入失败则会引发 @ref{1d3,,OSError})。 根据具体实现的不同，这些字节可能被实际写入下层流，或是出于运行效率和冗余等考虑而暂存于缓冲区。

当处于非阻塞模式时，如果需要将数据写入原始流但它无法在不阻塞的情况下接受所有数据则将引发 @ref{991,,BlockingIOError}。

调用者可能会在此方法返回后释放或改变 @emph{b}，因此该实现应当仅在方法调用期间访问 @emph{b}。
@end deffn
@end deffn

@node 原始文件 I/O,缓冲流,I/O 基类,类的层次结构
@anchor{library/io raw-file-i-o}@anchor{1f8e}
@subsubsection 原始文件 I/O


@geindex FileIO (io 中的类)
@anchor{library/io io FileIO}@anchor{c9d}
@deffn {类} io.FileIO (name, mode='r', closefd=True, opener=None)

@ref{c9d,,FileIO} 代表在 OS 层级上包含文件的字节数据。 它实现了 @ref{a0e,,RawIOBase} 接口（因而也实现了 @ref{1db,,IOBase} 接口）。

@emph{name} 可以是以下两项之一：


@itemize *

@item 
代表将被打开的文件路径的字符串或 @ref{32a,,bytes} 对象。 在此情况下 closefd 必须为 @code{True} (默认值) 否则将会引发异常。

@item 
代表一个现有 OS 层级文件描述符的号码的整数，作为结果的 @ref{c9d,,FileIO} 对象将可访问该文件。 当 FileIO 对象被关闭时此 fd 也将被关闭，除非 @emph{closefd} 设为 @code{False}。
@end itemize

@emph{mode} 可以为 @code{'r'}, @code{'w'}, @code{'x'} 或 @code{'a'} 分别表示读取（默认模式）、写入、独占新建或添加。 如果以写入或添加模式打开的文件不存在将自动新建；当以写入模式打开时文件将先清空。 以新建模式打开时如果文件已存在则将引发 @ref{952,,FileExistsError}。 以新建模式打开文件也意味着要写入，因此该模式的行为与 @code{'w'} 类似。 在模式中附带 @code{'+'} 将允许同时读取和写入。

该类的 @code{read()} (当附带正值参数调用时), @code{readinto()} 和 @code{write()} 方法将只执行一次系统调用。

可以通过传入一个可调用对象作为 @emph{opener} 来使用自定义文件打开器。 然后通过调用 @emph{opener} 并传入 (@emph{name}, @emph{flags}) 来获取文件对象所对应的下层文件描述符。 @emph{opener} 必须返回一个打开文件描述符（传入 @ref{65f,,os.open} 作为 @emph{opener} 的结果在功能上将与传入 @code{None} 类似）。

新创建的文件是 @ref{7f4,,不可继承的}。

有关 opener 参数的示例，请参见内置函数 @ref{4ea,,open()} 。


在 3.3 版更改: 增加了 @emph{opener} 参数。增加了 @code{'x'} 模式。



在 3.4 版更改: 文件现在禁止继承。


除了来自 @ref{1db,,IOBase} 和 @ref{a0e,,RawIOBase} 的属性和方法之外，@ref{c9d,,FileIO} 还提供了下列数据属性:

@geindex mode (io.FileIO 属性)
@anchor{library/io io FileIO mode}@anchor{1f8f}
@deffn {属性} mode

构造函数中给定的模式。
@end deffn

@geindex name (io.FileIO 属性)
@anchor{library/io io FileIO name}@anchor{1d82}
@deffn {属性} name

文件名。当构造函数中没有给定名称时，这是文件的文件描述符。
@end deffn
@end deffn

@node 缓冲流,文本 I/O<2>,原始文件 I/O,类的层次结构
@anchor{library/io buffered-streams}@anchor{1f90}
@subsubsection 缓冲流


相比原始 I/O，缓冲 I/O 流提供了针对 I/O 设备的更高层级接口。

@geindex BytesIO (io 中的类)
@anchor{library/io io BytesIO}@anchor{795}
@deffn {类} io.BytesIO ([initial_bytes])

一个使用内存字节缓冲区的流实现。 它继承自 @ref{583,,BufferedIOBase}。 在 @ref{fa0,,close()} 方法被调用时将会丢弃缓冲区。

可选参数 @emph{initial_bytes} 是一个包含初始数据的 @ref{5e3,,bytes-like object}。

@ref{795,,BytesIO} 在继承自 @ref{583,,BufferedIOBase} 和 @ref{1db,,IOBase} 的成员以外还提供或重载了下列方法:

@geindex getbuffer() (io.BytesIO 方法)
@anchor{library/io io BytesIO getbuffer}@anchor{b66}
@deffn {方法} getbuffer ()

返回一个对应于缓冲区内容的可读写视图而不必拷贝其数据。 此外，改变视图将透明地更新缓冲区内容:

@example
>>> b = io.BytesIO(b"abcdef")
>>> view = b.getbuffer()
>>> view[2:4] = b"56"
>>> b.getvalue()
b'ab56ef'
@end example

@cartouche
@quotation 注解 
只要视图保持存在，@ref{795,,BytesIO} 对象就无法被改变大小或关闭。
@end quotation
@end cartouche


3.2 新版功能.

@end deffn

@geindex getvalue() (io.BytesIO 方法)
@anchor{library/io io BytesIO getvalue}@anchor{1cea}
@deffn {方法} getvalue ()

返回包含整个缓冲区内容的 @ref{32a,,bytes}。
@end deffn

@geindex read1() (io.BytesIO 方法)
@anchor{library/io io BytesIO read1}@anchor{1f91}
@deffn {方法} read1 ([size])

在 @ref{795,,BytesIO} 中，这与 @ref{1ced,,read()} 相同。


在 3.7 版更改: @emph{size} 参数现在是可选的。

@end deffn

@geindex readinto1() (io.BytesIO 方法)
@anchor{library/io io BytesIO readinto1}@anchor{1f92}
@deffn {方法} readinto1 (b)

在 @ref{795,,BytesIO} 中，这与 @ref{1f8b,,readinto()} 相同。


3.5 新版功能.

@end deffn
@end deffn

@geindex BufferedReader (io 中的类)
@anchor{library/io io BufferedReader}@anchor{b83}
@deffn {类} io.BufferedReader (raw, buffer_size=DEFAULT_BUFFER_SIZE)

一个提供对可读的序列型 @ref{a0e,,RawIOBase} 对象更高层级访问的缓冲区。 它继承自 @ref{583,,BufferedIOBase}。 当从此对象读取数据时，可能会从下层原始流请求更大量的数据，并存放到内部缓冲区中。 接下来可以在后续读取时直接返回缓冲数据。

根据给定的可读 @emph{raw} 流和 @emph{buffer_size} 创建 @ref{b83,,BufferedReader} 的构造器。 如果省略 @emph{buffer_size}，则会使用 @ref{1591,,DEFAULT_BUFFER_SIZE}。

@ref{b83,,BufferedReader} 在继承自 @ref{583,,BufferedIOBase} 和 @ref{1db,,IOBase} 的成员以外还提供或重载了下列方法:

@geindex peek() (io.BufferedReader 方法)
@anchor{library/io io BufferedReader peek}@anchor{1f93}
@deffn {方法} peek ([size])

从流返回字节数据而不前移位置。 完成此调用将至多读取一次原始流。 返回的字节数量可能少于或多于请求的数量。
@end deffn

@geindex read() (io.BufferedReader 方法)
@anchor{library/io io BufferedReader read}@anchor{1f94}
@deffn {方法} read ([size])

读取并返回 @emph{size} 个字节，如果 @emph{size} 未给定或为负值，则读取至 EOF 或是在非阻塞模式下读取调用将会阻塞。
@end deffn

@geindex read1() (io.BufferedReader 方法)
@anchor{library/io io BufferedReader read1}@anchor{1f95}
@deffn {方法} read1 ([size])

在原始流上通过单次调用读取并返回至多 @emph{size} 个字节。 如果至少缓冲了一个字节，则只返回缓冲的字节。 在其他情况下，将执行一次原始流读取。


在 3.7 版更改: @emph{size} 参数现在是可选的。

@end deffn
@end deffn

@geindex BufferedWriter (io 中的类)
@anchor{library/io io BufferedWriter}@anchor{1595}
@deffn {类} io.BufferedWriter (raw, buffer_size=DEFAULT_BUFFER_SIZE)

一个提供对可读的序列型 @ref{a0e,,RawIOBase} 对象更高层级访问的缓冲区。 它继承自 @ref{583,,BufferedIOBase}。 当写入到此对象时，数据通常会被放入到内部缓冲区中。 缓冲区将在满足某些条件的情况下被写到下层的 @ref{a0e,,RawIOBase} 对象，包括:


@itemize *

@item 
当缓冲区对于所有挂起数据而言太小时；

@item 
当 @ref{1f96,,flush()} 被调用时

@item 
当（为 @ref{1596,,BufferedRandom} 对象）请求 @code{seek()} 时；

@item 
当 @ref{1595,,BufferedWriter} 对象被关闭或销毁时。
@end itemize

该构造器会为给定的可写 @emph{raw} 流创建一个 @ref{1595,,BufferedWriter}。 如果未给定 @emph{buffer_size}，则使用默认的 @ref{1591,,DEFAULT_BUFFER_SIZE}。

@ref{1595,,BufferedWriter} 在继承自 @ref{583,,BufferedIOBase} 和 @ref{1db,,IOBase} 的成员以外还提供或重载了下列方法:

@geindex flush() (io.BufferedWriter 方法)
@anchor{library/io io BufferedWriter flush}@anchor{1f96}
@deffn {方法} flush ()

将缓冲区中保存的字节数据强制放入原始流。 如果原始流发生阻塞则应当引发 @ref{991,,BlockingIOError}。
@end deffn

@geindex write() (io.BufferedWriter 方法)
@anchor{library/io io BufferedWriter write}@anchor{1f97}
@deffn {方法} write (b)

写入 @ref{5e3,,bytes-like object} @emph{b} 并返回写入的字节数。 当处于非阻塞模式时，如果缓冲区需要被写入但原始流发生阻塞则将引发 @ref{991,,BlockingIOError}。
@end deffn
@end deffn

@geindex BufferedRandom (io 中的类)
@anchor{library/io io BufferedRandom}@anchor{1596}
@deffn {类} io.BufferedRandom (raw, buffer_size=DEFAULT_BUFFER_SIZE)

随机访问流的带缓冲的接口。 它继承自 @ref{b83,,BufferedReader} 和 @ref{1595,,BufferedWriter}。

该构造器会为在第一个参数中给定的可查找原始流创建一个读取器和定稿器。 如果省略 @emph{buffer_size} 则使用默认的 @ref{1591,,DEFAULT_BUFFER_SIZE}。

@ref{1596,,BufferedRandom} 能做到 @ref{b83,,BufferedReader} 或 @ref{1595,,BufferedWriter} 所能做的任何事。 此外，还会确保实现 @code{seek()} 和 @code{tell()}。
@end deffn

@geindex BufferedRWPair (io 中的类)
@anchor{library/io io BufferedRWPair}@anchor{1f82}
@deffn {类} io.BufferedRWPair (reader, writer, buffer_size=DEFAULT_BUFFER_SIZE)

一个带缓冲的 I/O 对象，它将两个单向 @ref{a0e,,RawIOBase} 对象 -- 一个可读，另一个可写 -- 组合为单个双向端点。 它继承自 @ref{583,,BufferedIOBase}。

@emph{reader} 和 @emph{writer} 分别是可读和可写的 @ref{a0e,,RawIOBase} 对象。 如果省略 @emph{buffer_size} 则使用默认的 @ref{1591,,DEFAULT_BUFFER_SIZE}。

@ref{1f82,,BufferedRWPair} 实现了 @ref{583,,BufferedIOBase} 的所有方法，但 @ref{1f8d,,detach()} 除外，调用该方法将引发 @ref{1f7f,,UnsupportedOperation}。

@cartouche
@quotation 警告 
@ref{1f82,,BufferedRWPair} 不会尝试同步访问其下层的原始流。 你不应当将传给它与读取器和写入器相同的对象；而要改用 @ref{1596,,BufferedRandom}。
@end quotation
@end cartouche
@end deffn

@node 文本 I/O<2>,,缓冲流,类的层次结构
@anchor{library/io id1}@anchor{1f98}
@subsubsection 文本 I/O


@geindex TextIOBase (io 中的类)
@anchor{library/io io TextIOBase}@anchor{c32}
@deffn {类} io.TextIOBase

文本流的基类。 该类提供了基于字符和行的流 I/O 接口。 它继承自 @ref{1db,,IOBase}。 该类无公有构造器。

@ref{c32,,TextIOBase} 在来自 @ref{1db,,IOBase} 的成员以外还提供或重载了以下数据属性和方法:

@geindex encoding (io.TextIOBase 属性)
@anchor{library/io io TextIOBase encoding}@anchor{1f99}
@deffn {属性} encoding

用于将流的字节串解码为字符串以及将字符串编码为字节串的编码格式名称。
@end deffn

@geindex errors (io.TextIOBase 属性)
@anchor{library/io io TextIOBase errors}@anchor{1f9a}
@deffn {属性} errors

解码器或编码器的错误设置。
@end deffn

@geindex newlines (io.TextIOBase 属性)
@anchor{library/io io TextIOBase newlines}@anchor{1f9b}
@deffn {属性} newlines

一个字符串、字符串元组或者 @code{None}，表示目前已经转写的新行。 根据具体实现和初始构造器旗标的不同，此属性或许会不可用。
@end deffn

@geindex buffer (io.TextIOBase 属性)
@anchor{library/io io TextIOBase buffer}@anchor{c33}
@deffn {属性} buffer

由 @ref{c32,,TextIOBase} 处理的下层二进制缓冲区（为一个 @ref{583,,BufferedIOBase} 的实例）。 它不是 @ref{c32,,TextIOBase} API 的组成部分并且不存在于某些实现中。
@end deffn

@geindex detach() (io.TextIOBase 方法)
@anchor{library/io io TextIOBase detach}@anchor{1f9c}
@deffn {方法} detach ()

从 @ref{c32,,TextIOBase} 分离出下层二进制缓冲区并将其返回。

在下层缓冲区被分离后，@ref{c32,,TextIOBase} 将处于不可用的状态。

某些 @ref{c32,,TextIOBase} 的实现，例如 @ref{827,,StringIO} 可能并无下层缓冲区的概念，因此调用此方法将引发 @ref{1f7f,,UnsupportedOperation}。


3.1 新版功能.

@end deffn

@geindex read() (io.TextIOBase 方法)
@anchor{library/io io TextIOBase read}@anchor{1f9d}
@deffn {方法} read (size=-1)

从流中读取至多 @emph{size} 个字符并以单个 @ref{329,,str} 的形式返回。 如果 @emph{size} 为负值或 @code{None}，则读取至 EOF。
@end deffn

@geindex readline() (io.TextIOBase 方法)
@anchor{library/io io TextIOBase readline}@anchor{1b90}
@deffn {方法} readline (size=-1)

读取至换行符或 EOF 并返回单个 @code{str}。 如果流已经到达 EOF，则将返回一个空字符串。

如果指定了 @emph{size} ，最多将读取 @emph{size} 个字符。
@end deffn

@geindex seek() (io.TextIOBase 方法)
@anchor{library/io io TextIOBase seek}@anchor{1f9e}
@deffn {方法} seek (offset, whence=SEEK_SET)

将流位置改为给定的偏移位置 @emph{offset}。 具体行为取决于 @emph{whence} 形参。 @emph{whence} 的默认值为 @code{SEEK_SET}。


@itemize *

@item 
@code{SEEK_SET} 或 @code{0}: 从流的开始位置起查找（默认值）；@emph{offset} 必须为 @ref{1f9f,,TextIOBase.tell()} 所返回的数值或为零。 任何其他 @emph{offset} 值都将导致未定义的行为。

@item 
@code{SEEK_CUR} 或 @code{1}: "查找" 到当前位置；@emph{offset} 必须为零，表示无操作（所有其他值均不受支持）。

@item 
@code{SEEK_END} 或 @code{2}: 查找到流的末尾；@emph{offset} 必须为零（所有其他值均不受支持）。
@end itemize

以不透明数字形式返回新的绝对位置。


3.1 新版功能: @code{SEEK_*} 常量.

@end deffn

@geindex tell() (io.TextIOBase 方法)
@anchor{library/io io TextIOBase tell}@anchor{1f9f}
@deffn {方法} tell ()

以不透明数字形式返回当前流的位置。 该数字通常并不代表下层二进制存储中对应的字节数。
@end deffn

@geindex write() (io.TextIOBase 方法)
@anchor{library/io io TextIOBase write}@anchor{1fa0}
@deffn {方法} write (s)

将字符串 @emph{s} 写入到流并返回写入的字符数。
@end deffn
@end deffn

@geindex TextIOWrapper (io 中的类)
@anchor{library/io io TextIOWrapper}@anchor{5ee}
@deffn {类} io.TextIOWrapper (buffer, encoding=None, errors=None, newline=None, line_buffering=False, write_through=False)

一个基于 @ref{583,,BufferedIOBase} 二进制流的缓冲文本流。 它继承自 @ref{c32,,TextIOBase}。

@emph{encoding} 给出流被解码或编码时将使用的编码格式。 它默认为 @ref{39d,,locale.getpreferredencoding(False)}。

@emph{errors} 是一个可选的字符串，它指明编码格式和编码格式错误的处理方式。 传入 @code{'strict'} 将在出现编码格式错误时引发 @ref{1fb,,ValueError} (默认值 @code{None} 具有相同的效果)，传入 @code{'ignore'} 将忽略错误。 (请注意忽略编码格式错误会导致数据丢失。)  @code{'replace'} 会在出现错误数据时插入一个替换标记 (例如 @code{'?'})。 @code{'backslashreplace'} 将把错误数据替换为一个反斜杠转义序列。 在写入时，还可以使用 @code{'xmlcharrefreplace'} (替换为适当的 XML 字符引用)  或 @code{'namereplace'} (替换为 @code{\N@{...@}} 转义序列)。 任何其他通过 @ref{dee,,codecs.register_error()} 注册的错误处理方式名称也可以被接受。

@geindex universal newlines; io.TextIOWrapper class

@emph{newline} 控制行结束符处理方式。 它可以为 @code{None}, @code{'@w{'}}, @code{'\n'}, @code{'\r'} 和 @code{'\r\n'}。 其工作原理如下:


@itemize *

@item 
当从流中读取输入时，如果 @emph{newline} 为 @code{None}，则会启用 @ref{5ef,,universal newlines} 模式。 输入中的行结束符可以为 @code{'\n'}, @code{'\r'} 或 @code{'\r\n'}，在返回给调用者之前它们会被统一转写为 @code{'\n'}。 如果参数为 @code{'@w{'}}，也会启用通用换行模式，但行结束符会不加转写即返回给调用者。 如果它具有任何其他合法的值，则输入行将仅由给定的字符串结束，并且行结束符会不加转写即返回给调用者。

@item 
将输出写入流时，如果 @emph{newline} 为 @code{None}，则写入的任何 @code{'\n'} 字符都将转换为系统默认行分隔符 @ref{1594,,os.linesep}。如果 @emph{newline} 是 @code{'@w{'}} 或 @code{'\n'}，则不进行翻译。如果 @emph{newline} 是任何其他合法值，则写入的任何 @code{'\n'} 字符将被转换为给定的字符串。
@end itemize

如果 @emph{line_buffering} 为 @code{True}，则当一个写入调用包含换行符或回车时将会应用 @code{flush()}。

如果 @emph{write_through} 为 @code{True}，对 @code{write()} 的调用会确保不被缓冲：在 @ref{5ee,,TextIOWrapper} 对象上写入的任何数据会立即交给其下层的 @emph{buffer} 来处理。


在 3.3 版更改: 已添加 @emph{write_through} 参数



在 3.3 版更改: 默认的 @emph{encoding} 现在将为 @code{locale.getpreferredencoding(False)} 而非 @code{locale.getpreferredencoding()}。 不要使用 @ref{1fa1,,locale.setlocale()} 来临时改变区域编码格式，要使用当前区域编码格式而不是用户的首选编码格式。


@ref{5ee,,TextIOWrapper} 在继承自 @ref{c32,,TextIOBase} 及其父类的现有成员以外还提供了下列成员:

@geindex line_buffering (io.TextIOWrapper 属性)
@anchor{library/io io TextIOWrapper line_buffering}@anchor{1fa2}
@deffn {属性} line_buffering

是否启用行缓冲。
@end deffn

@geindex write_through (io.TextIOWrapper 属性)
@anchor{library/io io TextIOWrapper write_through}@anchor{1fa3}
@deffn {属性} write_through

写入是否要立即传给下层的二进制缓冲。


3.7 新版功能.

@end deffn

@geindex reconfigure() (io.TextIOWrapper 方法)
@anchor{library/io io TextIOWrapper reconfigure}@anchor{395}
@deffn {方法} reconfigure (*[, encoding][, errors][, newline][,                      line_buffering][, write_through])

使用 @emph{encoding}, @emph{errors}, @emph{newline}, @emph{line_buffering} 和 @emph{write_through} 的新设置来重新配置此文本流。

未指定的形参将保留当前设定，例外情况是当指定了 @emph{encoding} 但未指定 @emph{errors} 时将会使用 @code{errors='strict'}。

如果已经有数据从流中被读取则将无法再改变编码格式或行结束符。 另一方面，在写入数据之后再改变编码格式则是可以的。

此方法会在设置新的形参之前执行隐式的流刷新。


3.7 新版功能.

@end deffn
@end deffn

@geindex StringIO (io 中的类)
@anchor{library/io io StringIO}@anchor{827}
@deffn {类} io.StringIO (initial_value='@w{'}, newline='\n')

用于文本 I/O 的内存数据流。 当调用 @ref{fa0,,close()} 方法时将会丢弃文本缓冲区。

缓冲区的初始值可通过提供 @emph{initial_value} 来设置。 如果启用了行结束符转写，换行将以 @ref{1fa0,,write()} 所用的方式被编码。 数据流位置将被设为缓冲区的开头。

@emph{newline} 参数的规则与 @ref{5ee,,TextIOWrapper} 所用的一致。 默认规则是仅将 @code{\n} 字符视为行结束符并且不执行换行符转写。 如果 @emph{newline} 设为 @code{None}，在所有平台上换行符都将被写入为 @code{\n}，但当读取时仍然会执行通用换行编码格式。

@ref{827,,StringIO} 在继承自 @ref{c32,,TextIOBase} 及其父类的现有成员以外还提供了以下方法:

@geindex getvalue() (io.StringIO 方法)
@anchor{library/io io StringIO getvalue}@anchor{1fa4}
@deffn {方法} getvalue ()

返回一个包含缓冲区全部内容的 @code{str}。 换行符会以与 @ref{1f9d,,read()} 相同的方式被编码，但是流的位置不会被改变。
@end deffn

用法示例：

@example
import io

output = io.StringIO()
output.write('First line.\n')
print('Second line.', file=output)

# Retrieve file contents -- this will be
# 'First line.\nSecond line.\n'
contents = output.getvalue()

# Close object and discard memory buffer --
# .getvalue() will now raise an exception.
output.close()
@end example
@end deffn

@geindex universal newlines; io.IncrementalNewlineDecoder class

@geindex IncrementalNewlineDecoder (io 中的类)
@anchor{library/io io IncrementalNewlineDecoder}@anchor{1fa5}
@deffn {类} io.IncrementalNewlineDecoder

用于在 @ref{5ef,,universal newlines} 模式下解码换行符的辅助编解码器。 它继承自 @ref{17c2,,codecs.IncrementalDecoder}。
@end deffn

@node 性能<3>,,类的层次结构,io --- 处理流的核心工具
@anchor{library/io performance}@anchor{1fa6}
@subsubsection 性能


本节讨论所提供的具体 I/O 实现的性能。

@menu
* 二进制 I/O: 二进制 I/O<2>. 
* 文本 I/O: 文本 I/O<3>. 
* 多线程: 多线程<4>. 
* 可重入性:: 

@end menu

@node 二进制 I/O<2>,文本 I/O<3>,,性能<3>
@anchor{library/io id2}@anchor{1fa7}
@subsubsection 二进制 I/O


即使在用户请求单个字节时，也只读取和写入大块数据。通过该方法，缓冲 I/O 隐藏了操作系统调用和执行无缓冲 I/O 例程时的任何低效性。增益取决于操作系统和执行的 I/O 类型。例如，在某些现代操作系统上（例如 Linux），无缓冲磁盘 I/O 可以与缓冲 I/O 一样快。但最重要的是，无论平台和支持设备如何，缓冲 I/O 都能提供可预测的性能。因此，对于二进制数据，应首选使用缓冲的 I/O 而不是未缓冲的 I/O 。

@node 文本 I/O<3>,多线程<4>,二进制 I/O<2>,性能<3>
@anchor{library/io id3}@anchor{1fa8}
@subsubsection 文本 I/O


二进制存储（如文件）上的文本 I/O 比同一存储上的二进制 I/O 慢得多，因为它需要使用字符编解码器在Unicode和二进制数据之间进行转换。这在处理大量文本数据（如大型日志文件）时会变得非常明显。此外，由于使用的重构算法 @code{TextIOWrapper.tell()} 和 @code{TextIOWrapper.seek()} 都相当慢。

@ref{827,,StringIO} 是原生的内存 Unicode 容器，速度与 @ref{795,,BytesIO} 相似。

@node 多线程<4>,可重入性,文本 I/O<3>,性能<3>
@anchor{library/io multi-threading}@anchor{1fa9}
@subsubsection 多线程


@ref{c9d,,FileIO} 对象是线程安全的，只要它们封装的操作系统调用（比如Unix下的 @code{read(2)} ）也是线程安全的。

二进制缓冲对象（例如 @ref{b83,,BufferedReader}, @ref{1595,,BufferedWriter}, @ref{1596,,BufferedRandom} 和 @ref{1f82,,BufferedRWPair}）使用锁来保护其内部结构；因此，可以安全地一次从多个线程中调用它们。

@ref{5ee,,TextIOWrapper} 对象不再是线程安全的。

@node 可重入性,,多线程<4>,性能<3>
@anchor{library/io reentrancy}@anchor{1faa}
@subsubsection 可重入性


二进制缓冲对象（ @ref{b83,,BufferedReader} ， @ref{1595,,BufferedWriter} ， @ref{1596,,BufferedRandom} 和 @ref{1f82,,BufferedRWPair} 的实例）不是可重入的。虽然在正常情况下不会发生可重入调用，但仍可能会在 @ref{ea,,signal} 处理程序执行 I/O 时产生。如果线程尝试重入已经访问的缓冲对象，则会引发 @ref{2ba,,RuntimeError} 。注意，这并不禁止其他线程进入缓冲对象。

上面的内容隐含地扩展到文本文件，因为 @ref{4ea,,open()} 函数会把缓冲对象封装在 @ref{5ee,,TextIOWrapper} 中。这包括标准流，因此也会影响内置函数 @ref{880,,print()} 。

@node time --- 时间的访问和转换,argparse --- 命令行选项、参数和子命令解析器,io --- 处理流的核心工具,通用操作系统服务
@anchor{library/time doc}@anchor{1fab}@anchor{library/time module-time}@anchor{10a}@anchor{library/time time-time-access-and-conversions}@anchor{1fac}
@subsection @code{time} --- 时间的访问和转换


@geindex time (模块)


__________________________________________________________________


该模块提供了各种时间相关的函数。相关功能还可以参阅 @ref{31,,datetime} 和 @ref{15,,calendar} 模块。

尽管此模块始终可用，但并非所有平台上都提供所有功能。 此模块中定义的大多数函数是调用了所在平台 C 语言库的同名函数。 因为这些函数的语义因平台而异,所以使用时最好查阅平台相关文档。

下面是一些术语和惯例的解释.
@anchor{library/time epoch}@anchor{1fad}
@geindex epoch


@itemize *

@item 
@emph{epoch} 是时间开始的点，并且取决于平台。对于Unix， epoch 是1970年1月1日00:00:00（UTC）。要找出给定平台上的 epoch ，请查看 @code{time.gmtime(0)} 。
@end itemize

@geindex seconds since the epoch


@itemize *

@item 
术语 @emph{Unix 纪元秒数} 是指自国际标准时间 1970 年 1 月 1 日零时以来经过的总秒数，通常不包括 闰秒@footnote{https://en.wikipedia.org/wiki/Leap_second}。 在所有符合 POSIX 标准的平台上，闰秒都会从总秒数中被扣除。
@end itemize

@geindex Year 2038


@itemize *

@item 
此模块中的功能可能无法处理纪元之前或将来的远期日期和时间。未来的截止点由C库决定；对于32位系统，它通常在2038年。
@end itemize

@geindex 2-digit years


@itemize *

@item 
函数 @ref{d8a,,strptime()} 在接收到 @code{%y} 格式代码时可以解析 2 位数的年份。  当解析 2 位数年份时，会按照 POSIX 和 ISO C 标准进行转换：数值 69--99 映射为 1969--1999，而数值 0--68 被映射为 2000--2068。
@end itemize

@geindex UTC
@geindex Coordinated Universal Time
@geindex Greenwich Mean Time


@itemize *

@item 
UTC是协调世界时（以前称为格林威治标准时间，或GMT）。缩写UTC不是错误，而是英语和法语之间的妥协。
@end itemize

@geindex Daylight Saving Time


@itemize *

@item 
DST是夏令时，在一年中的一部分时间（通常）调整时区一小时。 DST规则很神奇（由当地法律确定），并且每年都会发生变化。 C 库有一个包含本地规则的表（通常是从系统文件中读取以获得灵活性），并且在这方面是True Wisdom的唯一来源。

@item 
各种实时函数的精度可能低于表示其值或参数的单位所建议的精度。例如，在大多数Unix系统上，时钟 "ticks" 仅为每秒50或100次。

@item 
另一方面， @ref{316,,time()} 和 @ref{67a,,sleep()} 的精度优于它们的Unix等价物：时间表示为浮点数，@ref{316,,time()} 返回最准确的时间 （使用Unix @code{gettimeofday()} 如果可用），并且 @ref{67a,,sleep()} 将接受非零分数的时间（Unix @code{select()} 用于实现此功能，如果可用）。

@item 
时间值由 @ref{b38,,gmtime()}，@ref{edc,,localtime()} 和 @ref{d8a,,strptime()} 返回，并被 @ref{b5c,,asctime()}， @ref{b5d,,mktime()} 和 @ref{b5e,,strftime()} 接受，是一个 9 个整数的序列。 @ref{b38,,gmtime()}， @ref{edc,,localtime()} 和 @ref{d8a,,strptime()} 的返回值还提供各个字段的属性名称。

请参阅 @ref{594,,struct_time} 以获取这些对象的描述。


在 3.3 版更改: 在平台支持相应的 @code{struct tm} 成员时，@ref{594,,struct_time} 类型被扩展提供 @code{tm_gmtoff} 和 @code{tm_zone} 属性。



在 3.6 版更改: @ref{594,,struct_time} 的属性 @code{tm_gmtoff} 和 @code{tm_zone} 现在可在所有平台上使用。


@item 
使用以下函数在时间表示之间进行转换：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

从

@tab

到

@tab

使用

@item

自纪元以来的秒数

@tab

UTC 的 @ref{594,,struct_time}

@tab

@ref{b38,,gmtime()}

@item

自纪元以来的秒数

@tab

本地时间的 @ref{594,,struct_time}

@tab

@ref{edc,,localtime()}

@item

UTC 的 @ref{594,,struct_time}

@tab

自纪元以来的秒数

@tab

@ref{18b3,,calendar.timegm()}

@item

本地时间的 @ref{594,,struct_time}

@tab

自纪元以来的秒数

@tab

@ref{b5d,,mktime()}

@end multitable

@end itemize

@menu
* 函数: 函数<2>. 
* Clock ID 常量:: 
* 时区常量:: 

@end menu

@node 函数<2>,Clock ID 常量,,time --- 时间的访问和转换
@anchor{library/time functions}@anchor{1fae}@anchor{library/time time-functions}@anchor{1faf}
@subsubsection 函数


@geindex asctime() (在 time 模块中)
@anchor{library/time time asctime}@anchor{b5c}
@deffn {函数} time.asctime ([t])

转换由 @ref{b38,,gmtime()} 或 @ref{edc,,localtime()} 所返回的表示时间的元组或 @ref{594,,struct_time} 为以下形式的字符串: @code{'Sun Jun 20 23:21:05 1993'}。 日期字段的长度为两个字符，如果日期只有一个数字则会以零填充，例如: @code{'Wed Jun  9 04:26:40 1993'}。

如果未提供 @emph{t}，则会使用 @ref{edc,,localtime()} 所返回的当前时间。  @ref{b5c,,asctime()} 不会使用区域设置信息。

@cartouche
@quotation 注解 
与同名的C函数不同， @ref{b5c,,asctime()} 不添加尾随换行符。
@end quotation
@end cartouche
@end deffn

@geindex pthread_getcpuclockid() (在 time 模块中)
@anchor{library/time time pthread_getcpuclockid}@anchor{3f3}
@deffn {函数} time.pthread_getcpuclockid (thread_id)

返回指定的 @emph{thread_id} 的特定于线程的CPU时间时钟的 @emph{clk_id} 。

使用 @ref{234,,threading.Thread} 对象的 @ref{aaa,,threading.get_ident()} 或 @ref{1fb0,,ident} 属性为 @emph{thread_id} 获取合适的值。

@cartouche
@quotation 警告 
传递无效的或过期的 @emph{thread_id} 可能会导致未定义的行为，例如段错误。
@end quotation
@end cartouche

@ref{12f5,,可用性} ： Unix（有关详细信息，请参见 @code{pthread_getcpuclockid(3)} 的手册页）。


3.7 新版功能.

@end deffn

@geindex clock_getres() (在 time 模块中)
@anchor{library/time time clock_getres}@anchor{aad}
@deffn {函数} time.clock_getres (clk_id)

返回指定时钟 @emph{clk_id} 的分辨率（精度）。有关 @emph{clk_id} 的可接受值列表，请参阅 @ref{1fb1,,Clock ID 常量} 。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex clock_gettime() (在 time 模块中)
@anchor{library/time time clock_gettime}@anchor{aae}
@deffn {函数} time.clock_gettime (clk_id) -> float

返回指定 @emph{clk_id} 时钟的时间。有关 @emph{clk_id} 的可接受值列表，请参阅 @ref{1fb1,,Clock ID 常量} 。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex clock_gettime_ns() (在 time 模块中)
@anchor{library/time time clock_gettime_ns}@anchor{317}
@deffn {函数} time.clock_gettime_ns (clk_id) -> int

与 @ref{aae,,clock_gettime()} 相似，但返回时间为纳秒。

@ref{12f5,,可用性}: Unix。


3.7 新版功能.

@end deffn

@geindex clock_settime() (在 time 模块中)
@anchor{library/time time clock_settime}@anchor{aaf}
@deffn {函数} time.clock_settime (clk_id, time: float)

设置指定 @emph{clk_id} 时钟的时间。 目前， @ref{1fb2,,CLOCK_REALTIME} 是 @emph{clk_id} 唯一可接受的值。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex clock_settime_ns() (在 time 模块中)
@anchor{library/time time clock_settime_ns}@anchor{318}
@deffn {函数} time.clock_settime_ns (clk_id, time: int)

与 @ref{aaf,,clock_settime()} 相似，但设置时间为纳秒。

@ref{12f5,,可用性}: Unix。


3.7 新版功能.

@end deffn

@geindex ctime() (在 time 模块中)
@anchor{library/time time ctime}@anchor{184c}
@deffn {函数} time.ctime ([secs])

转换以距离初始纪元的秒数表示的时间为以下形式的字符串: @code{'Sun Jun 20 23:21:05 1993'} 代表本地时间。 日期字段的长度为两个字符，如果日期只有一个数字则会以零填充，例如: @code{'Wed Jun  9 04:26:40 1993'}。

如果 @emph{secs} 未提供或为 @ref{157,,None}，则使用 @ref{316,,time()} 所返回的当前时间。 @code{ctime(secs)} 等价于 @code{asctime(localtime(secs))}。 @ref{184c,,ctime()} 不会使用区域设置信息。
@end deffn

@geindex get_clock_info() (在 time 模块中)
@anchor{library/time time get_clock_info}@anchor{aac}
@deffn {函数} time.get_clock_info (name)

获取有关指定时钟的信息作为命名空间对象。 支持的时钟名称和读取其值的相应函数是：


@itemize *

@item 
@code{'monotonic'}: @ref{769,,time.monotonic()}

@item 
@code{'perf_counter'}: @ref{2aa,,time.perf_counter()}

@item 
@code{'process_time'}: @ref{2ab,,time.process_time()}

@item 
@code{'thread_time'}: @ref{3f1,,time.thread_time()}

@item 
@code{'time'}: @ref{316,,time.time()}
@end itemize

结果具有以下属性：


@itemize -

@item 
@emph{adjustable} ： 如果时钟可以自动更改（例如通过NTP守护程序）或由系统管理员手动更改，则为 @code{True} ，否则为 @code{False} 。

@item 
@emph{implementation} ： 用于获取时钟值的基础C函数的名称。有关可能的值，请参阅 @ref{1fb1,,Clock ID 常量} 。

@item 
@emph{monotonic} ：如果时钟不能倒退，则为 @code{True} ，否则为 @code{False} 。

@item 
@emph{resolution} ： 以秒为单位的时钟分辨率（ @ref{187,,float} ）
@end itemize


3.3 新版功能.

@end deffn

@geindex gmtime() (在 time 模块中)
@anchor{library/time time gmtime}@anchor{b38}
@deffn {函数} time.gmtime ([secs])

将以自 epoch 开始的秒数表示的时间转换为 UTC 的 @ref{594,,struct_time} ，其中 dst 标志始终为零。 如果未提供 @emph{secs} 或为 @ref{157,,None} ，则使用 @ref{316,,time()} 所返回的当前时间。 一秒以内的小数将被忽略。 有关 @ref{594,,struct_time} 对象的说明请参见上文。 有关此函数的逆操作请参阅 @ref{18b3,,calendar.timegm()}。
@end deffn

@geindex localtime() (在 time 模块中)
@anchor{library/time time localtime}@anchor{edc}
@deffn {函数} time.localtime ([secs])

与 @ref{b38,,gmtime()} 相似但转换为当地时间。如果未提供 @emph{secs} 或为 @ref{157,,None} ，则使用由 @ref{316,,time()} 返回的当前时间。当 DST 适用于给定时间时，dst标志设置为 @code{1} 。
@end deffn

@geindex mktime() (在 time 模块中)
@anchor{library/time time mktime}@anchor{b5d}
@deffn {函数} time.mktime (t)

这是 @ref{edc,,localtime()} 的反函数。它的参数是 @ref{594,,struct_time} 或者完整的 9 元组（因为需要 dst 标志；如果它是未知的则使用 @code{-1} 作为dst标志），它表示 @emph{local} 的时间，而不是 UTC 。它返回一个浮点数，以便与 @ref{316,,time()} 兼容。如果输入值不能表示为有效时间，则 @ref{95a,,OverflowError} 或 @ref{1fb,,ValueError} 将被引发（这取决于Python或底层C库是否捕获到无效值）。它可以生成时间的最早日期取决于平台。
@end deffn

@geindex monotonic() (在 time 模块中)
@anchor{library/time time monotonic}@anchor{769}
@deffn {函数} time.monotonic () -> float

返回单调时钟的值（以小数秒为单位），即不能倒退的时钟。时钟不受系统时钟更新的影响。返回值的参考点未定义，因此只有连续调用结果之间的差异才有效。


3.3 新版功能.



在 3.5 版更改: 该功能现在始终可用且始终在系统范围内。

@end deffn

@geindex monotonic_ns() (在 time 模块中)
@anchor{library/time time monotonic_ns}@anchor{319}
@deffn {函数} time.monotonic_ns () -> int

与 @ref{769,,monotonic()} 相似，但是返回时间为纳秒数。


3.7 新版功能.

@end deffn

@geindex perf_counter() (在 time 模块中)
@anchor{library/time time perf_counter}@anchor{2aa}
@deffn {函数} time.perf_counter () -> float

@geindex benchmarking

返回性能计数器的值（以小数秒为单位），即具有最高可用分辨率的时钟，以测量短持续时间。它确实包括睡眠期间经过的时间，并且是系统范围的。返回值的参考点未定义，因此只有连续调用结果之间的差异才有效。


3.3 新版功能.

@end deffn

@geindex perf_counter_ns() (在 time 模块中)
@anchor{library/time time perf_counter_ns}@anchor{31a}
@deffn {函数} time.perf_counter_ns () -> int

与 @ref{2aa,,perf_counter()} 相似，但是返回时间为纳秒。


3.7 新版功能.

@end deffn

@geindex process_time() (在 time 模块中)
@anchor{library/time time process_time}@anchor{2ab}
@deffn {函数} time.process_time () -> float

@geindex CPU time
@geindex processor time
@geindex benchmarking

返回当前进程的系统和用户CPU时间总和的值（以小数秒为单位）。它不包括睡眠期间经过的时间。根据定义，它在整个进程范围中。返回值的参考点未定义，因此只有连续调用结果之间的差异才有效。


3.3 新版功能.

@end deffn

@geindex process_time_ns() (在 time 模块中)
@anchor{library/time time process_time_ns}@anchor{31b}
@deffn {函数} time.process_time_ns () -> int

与 @ref{2ab,,process_time()} 相似，但是返回时间为纳秒。


3.7 新版功能.

@end deffn

@geindex sleep() (在 time 模块中)
@anchor{library/time time sleep}@anchor{67a}
@deffn {函数} time.sleep (secs)

暂停执行调用线程达到给定的秒数。参数可以是浮点数，以指示更精确的睡眠时间。实际的暂停时间可能小于请求的时间，因为任何捕获的信号将在执行该信号的捕获例程后终止 @ref{67a,,sleep()} 。此外，由于系统中其他活动的安排，暂停时间可能比请求的时间长任意量。


在 3.5 版更改: 即使睡眠被信号中断，该函数现在至少睡眠 @emph{secs} ，除非信号处理程序引发异常（参见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475} 作为基本原理）。

@end deffn

@geindex % (percent); datetime format

@geindex strftime() (在 time 模块中)
@anchor{library/time time strftime}@anchor{b5e}
@deffn {函数} time.strftime (format[, t])

转换一个元组或 @ref{594,,struct_time} 表示的由 @ref{b38,,gmtime()} 或 @ref{edc,,localtime()} 返回的时间到由 @emph{format} 参数指定的字符串。如果未提供 @emph{t} ，则使用由 @ref{edc,,localtime()} 返回的当前时间。 @emph{format} 必须是一个字符串。如果 @emph{t} 中的任何字段超出允许范围，则引发 @ref{1fb,,ValueError} 。

0是时间元组中任何位置的合法参数；如果它通常是非法的，则该值被强制改为正确的值。

以下指令可以嵌入 @emph{format} 字符串中。它们显示时没有可选的字段宽度和精度规范，并被 @ref{b5e,,strftime()} 结果中的指示字符替换：


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

指令

@tab

含义

@tab

注释

@item

@code{%a}

@tab

本地化的缩写星期中每日的名称。

@tab

@item

@code{%A}

@tab

本地化的星期中每日的完整名称。

@tab

@item

@code{%b}

@tab

本地化的月缩写名称。

@tab

@item

@code{%B}

@tab

本地化的月完整名称。

@tab

@item

@code{%c}

@tab

本地化的适当日期和时间表示。

@tab

@item

@code{%d}

@tab

十进制数 [01,31] 表示的月中日。

@tab

@item

@code{%H}

@tab

十进制数 [00,23] 表示的小时（24小时制）。

@tab

@item

@code{%I}

@tab

十进制数 [01,12] 表示的小时（12小时制）。

@tab

@item

@code{%j}

@tab

十进制数 [001,366] 表示的年中日。

@tab

@item

@code{%m}

@tab

十进制数 [01,12] 表示的月。

@tab

@item

@code{%M}

@tab

十进制数 [00,59] 表示的分钟。

@tab

@item

@code{%p}

@tab

本地化的 AM 或 PM 。

@tab

(1)

@item

@code{%S}

@tab

十进制数 [00,61] 表示的秒。

@tab

(2)

@item

@code{%U}

@tab

十进制数 [00,53] 表示的一年中的周数（星期日作为一周的第一天）作为。在第一个星期日之前的新年中的所有日子都被认为是在第0周。

@tab

(3)

@item

@code{%w}

@tab

十进制数 [0(星期日),6] 表示的周中日。

@tab

@item

@code{%W}

@tab

十进制数 [00,53] 表示的一年中的周数（星期一作为一周的第一天）作为。在第一个星期一之前的新年中的所有日子被认为是在第0周。

@tab

(3)

@item

@code{%x}

@tab

本地化的适当日期表示。

@tab

@item

@code{%X}

@tab

本地化的适当时间表示。

@tab

@item

@code{%y}

@tab

十进制数 [00,99] 表示的没有世纪的年份。

@tab

@item

@code{%Y}

@tab

十进制数表示的带世纪的年份。

@tab

@item

@code{%z}

@tab

时区偏移以格式 +HHMM 或 -HHMM 形式的 UTC/GMT 的正或负时差指示，其中H表示十进制小时数字，M表示小数分钟数字 [-23:59, +23:59] 。

@tab

@item

@code{%Z}

@tab

时区名称（如果不存在时区，则不包含字符）。

@tab

@item

@code{%%}

@tab

字面的 @code{'%'} 字符。

@tab

@end multitable


注释:


@enumerate 

@item 
当与 @ref{d8a,,strptime()} 函数一起使用时，如果使用 @code{%I} 指令来解析小时， @code{%p} 指令只影响输出小时字段。

@item 
范围真的是 @code{0} 到 @code{61} ；值 @code{60} 在表示 leap seconds@footnote{https://en.wikipedia.org/wiki/Leap_second} 的时间戳中有效，并且由于历史原因支持值 @code{61} 。

@item 
当与 @ref{d8a,,strptime()} 函数一起使用时， @code{%U} 和 @code{%W} 仅用于指定星期几和年份的计算。
@end enumerate

下面是一个示例，一个与 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html} Internet电子邮件标准以兼容的日期格式。  @footnote{@w{(1)} 
现在不推荐使用 @code{%Z} ，但是所有 ANSI C 库都不支持扩展为首选小时/分钟偏移量的`@w{`}%z`@w{`}转义符。 此外，严格的 1982 年原始 
@geindex RFC; RFC 822
@uref{https://tools.ietf.org/html/rfc822.html,RFC 822} 标准要求两位数的年份（%y而不是%Y），但是实际在2000年之前很久就转移到了4位数年。之后， 
@geindex RFC; RFC 822
@uref{https://tools.ietf.org/html/rfc822.html,RFC 822} 已经废弃了，4位数的年份首先被推荐 
@geindex RFC; RFC 1123
@uref{https://tools.ietf.org/html/rfc1123.html,RFC 1123} ，然后被 
@geindex RFC; RFC 2822
@uref{https://tools.ietf.org/html/rfc2822.html,RFC 2822} 强制执行。
}

@example
>>> from time import gmtime, strftime
>>> strftime("%a, %d %b %Y %H:%M:%S +0000", gmtime())
'Thu, 28 Jun 2001 14:17:15 +0000'
@end example

某些平台可能支持其他指令，但只有此处列出的指令具有 ANSI C 标准化的含义。要查看平台支持的完整格式代码集，请参阅 @code{strftime(3)} 文档。

在某些平台上，可选的字段宽度和精度规范可以按照以下顺序紧跟在指令的初始 @code{'%'} 之后；这也不可移植。字段宽度通常为2，除了 @code{%j} ，它是3。
@end deffn

@geindex % (percent); datetime format

@geindex strptime() (在 time 模块中)
@anchor{library/time time strptime}@anchor{d8a}
@deffn {函数} time.strptime (string[, format])

根据格式解析表示时间的字符串。 返回值为一个被 @ref{b38,,gmtime()} 或 @ref{edc,,localtime()} 返回的 @ref{594,,struct_time} 。

@emph{format} 参数使用与 @ref{b5e,,strftime()} ；使用的指令相同的指令。它默认为匹配 @ref{184c,,ctime()} 返回格式的 @code{"%a %b %d %H:%M:%S %Y"`} 。如果 @emph{string*不能根据 *format} 解析，或者解析后它有多余的数据，则引发 @ref{1fb,,ValueError} 。当无法推断出更准确的值时，用于填充任何缺失数据的默认值是 @code{(1900, 1, 1, 0, 0, 0, 0, 1, -1)} 。 @emph{string} 和 @emph{format} 都必须是字符串。

例如:

@example
>>> import time
>>> time.strptime("30 Nov 00", "%d %b %y")   
time.struct_time(tm_year=2000, tm_mon=11, tm_mday=30, tm_hour=0, tm_min=0,
                 tm_sec=0, tm_wday=3, tm_yday=335, tm_isdst=-1)
@end example

支持 @code{%Z} 指令是基于 @code{tzname} 中包含的值以及 @code{daylight} 是否为真。因此，它是特定于平台的，除了识别始终已知的 UTC 和 GMT （并且被认为是非夏令时时区）。

仅支持文档中指定的指令。因为每个平台都实现了 @code{strftime()} ，它有时会提供比列出的指令更多的指令。但是 @code{strptime()} 独立于任何平台，因此不一定支持所有未记录为支持的可用指令。
@end deffn

@geindex struct_time (time 中的类)
@anchor{library/time time struct_time}@anchor{594}
@deffn {类} time.struct_time

返回的时间值序列的类型为 @ref{b38,,gmtime()} 、 @ref{edc,,localtime()} 和 @ref{d8a,,strptime()} 。它是一个带有 @ref{a9e,,named tuple} 接口的对象：可以通过索引和属性名访问值。 存在以下值：


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

属性

@tab

值

@item

0

@tab

@code{tm_year}

@tab

（例如，1993）

@item

1

@tab

@code{tm_mon}

@tab

range [1, 12]

@item

2

@tab

@code{tm_mday}

@tab

range [1, 31]

@item

3

@tab

@code{tm_hour}

@tab

range [0, 23]

@item

4

@tab

@code{tm_min}

@tab

range [0, 59]

@item

5

@tab

@code{tm_sec}

@tab

range [0, 61]； 见 @ref{b5e,,strftime()} 介绍中的 @strong{(2)}

@item

6

@tab

@code{tm_wday}

@tab

range [0, 6] ，周一为 0

@item

7

@tab

@code{tm_yday}

@tab

range [1, 366]

@item

8

@tab

@code{tm_isdst}

@tab

0, 1 或 -1；如下所示

@item

N/A

@tab

@code{tm_zone}

@tab

时区名称的缩写

@item

N/A

@tab

@code{tm_gmtoff}

@tab

以秒为单位的UTC以东偏离

@end multitable


请注意，与C结构不同，月份值是 [1,12] 的范围，而不是 [0,11] 。

在调用 @ref{b5d,,mktime()} 时， @code{tm_isdst} 可以在夏令时生效时设置为1，而在夏令时不生效时设置为0。 值-1表示这是未知的，并且通常会导致填写正确的状态。

当一个长度不正确的元组被传递给期望 @ref{594,,struct_time} 的函数，或者具有错误类型的元素时，会引发 @ref{192,,TypeError} 。
@end deffn

@geindex time() (在 time 模块中)
@anchor{library/time time time}@anchor{316}
@deffn {函数} time.time () -> float

返回以浮点数表示的从 @ref{1fad,,epoch} 开始的秒数的时间值。 epoch 的具体日期和 leap seconds@footnote{https://en.wikipedia.org/wiki/Leap_second} 的处理取决于平台。 在 Windows 和大多数 Unix 系统中， epoch 是 1970 年 1 月 1 日 00:00:00 (UTC)，并且闰秒将不计入从 epoch 开始的秒数。 这通常被称为 Unix 时间@footnote{https://en.wikipedia.org/wiki/Unix_time}。 要了解给定平台上 epoch 的具体定义，请查看 @code{gmtime(0)}。

请注意，即使时间总是作为浮点数返回，但并非所有系统都提供高于1秒的精度。虽然此函数通常返回非递减值，但如果在两次调用之间设置了系统时钟，则它可以返回比先前调用更低的值。

返回的数字 @ref{316,,time()} 可以通过将其传递给 @ref{b38,,gmtime()} 函数或转换为UTC中更常见的时间格式（即年、月、日、小时等）或通过将它传递给 @ref{edc,,localtime()} 函数获得本地时间。在这两种情况下都返回一个 @ref{594,,struct_time} 对象，日历日期组件可以从中作为属性访问。
@end deffn

@geindex thread_time() (在 time 模块中)
@anchor{library/time time thread_time}@anchor{3f1}
@deffn {函数} time.thread_time () -> float

@geindex CPU time
@geindex processor time
@geindex benchmarking

返回当前线程的系统和用户CPU时间之和的值（以小数秒为单位）。它不包括睡眠期间经过的时间。根据定义，它是特定于线程的。返回值的参考点未定义，因此只有同一线程中连续调用结果之间的差异才有效。

@ref{12f5,,可用性} ： Windows、 Linux、 Unix 系统支持 @code{CLOCK_THREAD_CPUTIME_ID} 。


3.7 新版功能.

@end deffn

@geindex thread_time_ns() (在 time 模块中)
@anchor{library/time time thread_time_ns}@anchor{3f2}
@deffn {函数} time.thread_time_ns () -> int

与 @ref{3f1,,thread_time()} 相似，但返回纳秒时间。


3.7 新版功能.

@end deffn

@geindex time_ns() (在 time 模块中)
@anchor{library/time time time_ns}@anchor{31c}
@deffn {函数} time.time_ns () -> int

与 @ref{316,,time()} 相似，但返回时间为用整数表示的自 @ref{1fad,,epoch} 以来所经过的纳秒数。


3.7 新版功能.

@end deffn

@geindex tzset() (在 time 模块中)
@anchor{library/time time tzset}@anchor{1fb3}
@deffn {函数} time.tzset ()

重置库例程使用的时间转换规则。环境变量 
@geindex TZ
@geindex 环境变量; TZ
@code{TZ} 指定如何完成。它还将设置变量 @code{tzname} （来自 
@geindex TZ
@geindex 环境变量; TZ
@code{TZ} 环境变量）， @code{timezone} （UTC的西部非DST秒）， @code{altzone} （UTC以西的DST秒）和 @code{daylight} （如果此时区没有任何夏令时规则则为0，如果有夏令时适用的时间，无论过去、现在或未来，则为非零）。

@ref{12f5,,可用性}: Unix。

@cartouche
@quotation 注解 
虽然在很多情况下，更改 
@geindex TZ
@geindex 环境变量; TZ
@code{TZ} 环境变量而不调用 @ref{1fb3,,tzset()} 可能会影响函数的输出，例如 @ref{edc,,localtime()} ，不应该依赖此行为。

@geindex TZ
@geindex 环境变量; TZ
@code{TZ} 不应该包含空格。
@end quotation
@end cartouche

@geindex TZ
@geindex 环境变量; TZ
@code{TZ} 环境变量的标准格式是（为了清晰起见，添加了空格）:

@example
std offset [dst [offset [,start[/time], end[/time]]]]
@end example

组件的位置是：


@table @asis

@item @code{std} 和 @code{dst}

三个或更多字母数字，给出时区缩写。这些将传到 time.tzname

@item @code{offset}

偏移量的形式为： @code{± hh[:mm[:ss]]} 。这表示添加到达UTC的本地时间的值。如果前面有 '-' ，则时区位于本初子午线的东边；否则，在它是西边。如果dst之后没有偏移，则假设夏令时比标准时间提前一小时。

@item @code{start[/time], end[/time]}

指示何时更改为DST和从DST返回。开始日期和结束日期的格式为以下之一：


@table @asis

@item @code{J@emph{n}}

Julian日 @emph{n} （1 <= @emph{n} <= 365）。闰日不计算在内，因此在所有年份中，2月28日是第59天，3月1日是第60天。

@item @code{@emph{n}}

从零开始的Julian日（0 <= @emph{n} <= 365）。 闰日计入，可以引用2月29日。

@item @code{M@emph{m}.@emph{n}.@emph{d}}

一年中 @emph{m} 月的第 @emph{n} 周（1 <= @emph{n} <= 5 ，1 <= @emph{m} <= 12 ，第 5 周表示 “可能在 @emph{m} 月第 4 周或第 5 周出现的最后第 @emph{d} 日”）的第 @emph{d} 天（0 <= @emph{d} <= 6）。 第 1 周是第 @emph{d} 天发生的第一周。 第 0 天是星期天。
@end table

@code{time} 的格式与 @code{offset} 的格式相同，但不允许使用前导符号（ '-' 或 '+' ）。如果没有给出时间，则默认值为02:00:00。
@end table

@example
>>> os.environ['TZ'] = 'EST+05EDT,M4.1.0,M10.5.0'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'02:07:36 05/08/03 EDT'
>>> os.environ['TZ'] = 'AEST-10AEDT-11,M10.5.0,M3.5.0'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'16:08:12 05/08/03 AEST'
@end example

在许多Unix系统（包括 *BSD ， Linux ， Solaris 和 Darwin 上），使用系统的区域信息（ @code{tzfile(5)} ）数据库来指定时区规则会更方便。为此，将 
@geindex TZ
@geindex 环境变量; TZ
@code{TZ} 环境变量设置为所需时区数据文件的路径，相对于系统 'zoneinfo' 时区数据库的根目录，通常位于 @code{/usr/share/zoneinfo} 。 例如，@code{'US/Eastern'} 、 @code{'Australia/Melbourne'} 、 @code{'Egypt'} 或 @code{'Europe/Amsterdam'}。

@example
>>> os.environ['TZ'] = 'US/Eastern'
>>> time.tzset()
>>> time.tzname
('EST', 'EDT')
>>> os.environ['TZ'] = 'Egypt'
>>> time.tzset()
>>> time.tzname
('EET', 'EEST')
@end example
@end deffn

@node Clock ID 常量,时区常量,函数<2>,time --- 时间的访问和转换
@anchor{library/time clock-id-constants}@anchor{1fb4}@anchor{library/time time-clock-id-constants}@anchor{1fb1}
@subsubsection Clock ID 常量


这些常量用作 @ref{aad,,clock_getres()} 和 @ref{aae,,clock_gettime()} 的参数。

@geindex CLOCK_BOOTTIME() (在 time 模块中)
@anchor{library/time time CLOCK_BOOTTIME}@anchor{3ed}
@deffn {数据} time.CLOCK_BOOTTIME

与 @ref{3ee,,CLOCK_MONOTONIC} 相同，除了它还包括系统暂停的任何时间。

这允许应用程序获得一个暂停感知的单调时钟，而不必处理 @ref{1fb2,,CLOCK_REALTIME} 的复杂性，如果使用 @code{settimeofday()} 或类似的时间更改时间可能会有不连续性。

@ref{12f5,,可用性}: Linux 2.6.39 或更新


3.7 新版功能.

@end deffn

@geindex CLOCK_HIGHRES() (在 time 模块中)
@anchor{library/time time CLOCK_HIGHRES}@anchor{1fb5}
@deffn {数据} time.CLOCK_HIGHRES

Solaris OS 有一个 @code{CLOCK_HIGHRES} 计时器，试图使用最佳硬件源，并可能提供接近纳秒的分辨率。 @code{CLOCK_HIGHRES} 是不可调节的高分辨率时钟。

@ref{12f5,,可用性}: Solaris.


3.3 新版功能.

@end deffn

@geindex CLOCK_MONOTONIC() (在 time 模块中)
@anchor{library/time time CLOCK_MONOTONIC}@anchor{3ee}
@deffn {数据} time.CLOCK_MONOTONIC

无法设置的时钟，表示自某些未指定的起点以来的单调时间。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex CLOCK_MONOTONIC_RAW() (在 time 模块中)
@anchor{library/time time CLOCK_MONOTONIC_RAW}@anchor{1fb6}
@deffn {数据} time.CLOCK_MONOTONIC_RAW

类似于 @ref{3ee,,CLOCK_MONOTONIC} ，但可以访问不受NTP调整影响的原始硬件时间。

@ref{12f5,,可用性}: Linux 2.6.28 和更新版本， macOS 10.12 和更新版本。


3.3 新版功能.

@end deffn

@geindex CLOCK_PROCESS_CPUTIME_ID() (在 time 模块中)
@anchor{library/time time CLOCK_PROCESS_CPUTIME_ID}@anchor{1fb7}
@deffn {数据} time.CLOCK_PROCESS_CPUTIME_ID

来自CPU的高分辨率每进程计时器。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex CLOCK_PROF() (在 time 模块中)
@anchor{library/time time CLOCK_PROF}@anchor{3ef}
@deffn {数据} time.CLOCK_PROF

来自CPU的高分辨率每进程计时器。

@ref{12f5,,可用性}: FreeBSD， NetBSD 7 或更新， OpenBSD.


3.7 新版功能.

@end deffn

@geindex CLOCK_THREAD_CPUTIME_ID() (在 time 模块中)
@anchor{library/time time CLOCK_THREAD_CPUTIME_ID}@anchor{1fb8}
@deffn {数据} time.CLOCK_THREAD_CPUTIME_ID

特定于线程的CPU时钟。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex CLOCK_UPTIME() (在 time 模块中)
@anchor{library/time time CLOCK_UPTIME}@anchor{3f0}
@deffn {数据} time.CLOCK_UPTIME

该时间的绝对值是系统运行且未暂停的时间，提供准确的正常运行时间测量，包括绝对值和间隔值。

@ref{12f5,,可用性}: FreeBSD， OpenBSD 5.5 或更新。


3.7 新版功能.

@end deffn

@geindex CLOCK_UPTIME_RAW() (在 time 模块中)
@anchor{library/time time CLOCK_UPTIME_RAW}@anchor{239}
@deffn {数据} time.CLOCK_UPTIME_RAW

单调递增的时钟，记录从一个任意起点开始的时间，不受频率或时间调整的影响，并且当系统休眠时将不会递增。

@ref{12f5,,可用性}: macOS 10.12 和更新版本。


3.8 新版功能.

@end deffn

以下常量是唯一可以发送到 @ref{aaf,,clock_settime()} 的参数。

@geindex CLOCK_REALTIME() (在 time 模块中)
@anchor{library/time time CLOCK_REALTIME}@anchor{1fb2}
@deffn {数据} time.CLOCK_REALTIME

系统范围的实时时钟。 设置此时钟需要适当的权限。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@node 时区常量,,Clock ID 常量,time --- 时间的访问和转换
@anchor{library/time time-timezone-constants}@anchor{1fb9}@anchor{library/time timezone-constants}@anchor{1fba}
@subsubsection 时区常量


@geindex altzone() (在 time 模块中)
@anchor{library/time time altzone}@anchor{1fbb}
@deffn {数据} time.altzone

本地DST时区的偏移量，以UTC为单位的秒数，如果已定义。如果当地DST时区在UTC以东（如在西欧，包括英国），则是负数。 只有当 @code{daylight} 非零时才使用它。 见下面的注释。
@end deffn

@geindex daylight() (在 time 模块中)
@anchor{library/time time daylight}@anchor{1fbc}
@deffn {数据} time.daylight

如果定义了DST时区，则为非零。 见下面的注释。
@end deffn

@geindex timezone() (在 time 模块中)
@anchor{library/time time timezone}@anchor{1fbd}
@deffn {数据} time.timezone

本地（非DST）时区的偏移量，UTC以西的秒数（西欧大部分地区为负，美国为正，英国为零）。 见下面的注释。
@end deffn

@geindex tzname() (在 time 模块中)
@anchor{library/time time tzname}@anchor{1fbe}
@deffn {数据} time.tzname

两个字符串的元组：第一个是本地非DST时区的名称，第二个是本地DST时区的名称。 如果未定义DST时区，则不应使用第二个字符串。 见下面的注释。
@end deffn

@cartouche
@quotation 注解 
对于上述时区常量（ @ref{1fbb,,altzone} 、 @ref{1fbc,,daylight} 、 @ref{1fbd,,timezone} 和 @ref{1fbe,,tzname} ），该值由模块加载时有效的时区规则确定，或者最后一次 @ref{1fb3,,tzset()} 被调用时，并且在过去的时间可能不正确。建议使用来自 @ref{edc,,localtime()} 结果的 @code{tm_gmtoff} 和 @code{tm_zone} 来获取时区信息。
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@item 模块 @ref{31,,datetime}

更多面向对象的日期和时间接口。

@item 模块 @ref{a9,,locale}

国际化服务。 区域设置会影响 @ref{b5e,,strftime()} 和 @ref{d8a,,strptime()}  中许多格式说明符的解析。

@item 模块 @ref{15,,calendar}

一般日历相关功能。这个模块的 @code{timegm()} 是函数 @ref{b38,,gmtime()} 的反函数。
@end table


@subsubheading 备注


@node argparse --- 命令行选项、参数和子命令解析器,getopt --- C 风格的命令行选项解析器,time --- 时间的访问和转换,通用操作系统服务
@anchor{library/argparse doc}@anchor{1fbf}@anchor{library/argparse argparse-parser-for-command-line-options-arguments-and-sub-commands}@anchor{1fc0}@anchor{library/argparse module-argparse}@anchor{6}
@subsection @code{argparse} --- 命令行选项、参数和子命令解析器


@geindex argparse (模块)


3.2 新版功能.


@strong{源代码：} Lib/argparse.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/argparse.py}


__________________________________________________________________


@subsubheading 教程



此页面包含该 API 的参考信息。有关 Python 命令行解析更细致的介绍，请参阅 @ref{1fc1,,argparse 教程}。

@ref{6,,argparse} 模块可以让人轻松编写用户友好的命令行接口。程序定义它需要的参数，然后 @ref{6,,argparse} 将弄清如何从 @ref{bf4,,sys.argv} 解析出那些参数。 @ref{6,,argparse} 模块还会自动生成帮助和使用手册，并在用户给程序传入无效参数时报出错误信息。

@menu
* 示例: 示例<7>. 
* ArgumentParser 对象:: 
* add_argument() 方法: add_argument 方法. 
* parse_args() 方法: parse_args 方法. 
* 其它实用工具:: 
* 升级 optparse 代码:: 

@end menu

@node 示例<7>,ArgumentParser 对象,,argparse --- 命令行选项、参数和子命令解析器
@anchor{library/argparse example}@anchor{1fc2}
@subsubsection 示例


以下代码是一个 Python 程序，它获取一个整数列表并计算总和或者最大值：

@example
import argparse

parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument('integers', metavar='N', type=int, nargs='+',
                    help='an integer for the accumulator')
parser.add_argument('--sum', dest='accumulate', action='store_const',
                    const=sum, default=max,
                    help='sum the integers (default: find the max)')

args = parser.parse_args()
print(args.accumulate(args.integers))
@end example

假设上面的 Python 代码保存在名为 @code{prog.py} 的文件中，它可以在命令行运行并提供有用的帮助信息：

@example
$ python prog.py -h
usage: prog.py [-h] [--sum] N [N ...]

Process some integers.

positional arguments:
 N           an integer for the accumulator

optional arguments:
 -h, --help  show this help message and exit
 --sum       sum the integers (default: find the max)
@end example

当使用适当的参数运行时，它会输出命令行传入整数的总和或者最大值：

@example
$ python prog.py 1 2 3 4
4

$ python prog.py 1 2 3 4 --sum
10
@end example

如果传入无效参数，则会报出错误：

@example
$ python prog.py a b c
usage: prog.py [-h] [--sum] N [N ...]
prog.py: error: argument N: invalid int value: 'a'
@end example

以下部分将引导你完成这个示例。

@menu
* 创建一个解析器:: 
* 添加参数:: 
* 解析参数:: 

@end menu

@node 创建一个解析器,添加参数,,示例<7>
@anchor{library/argparse creating-a-parser}@anchor{1fc3}
@subsubsection 创建一个解析器


使用 @ref{6,,argparse} 的第一步是创建一个 @ref{68f,,ArgumentParser} 对象：

@example
>>> parser = argparse.ArgumentParser(description='Process some integers.')
@end example

@ref{68f,,ArgumentParser} 对象包含将命令行解析成 Python 数据类型所需的全部信息。

@node 添加参数,解析参数,创建一个解析器,示例<7>
@anchor{library/argparse adding-arguments}@anchor{1fc4}
@subsubsection 添加参数


给一个 @ref{68f,,ArgumentParser} 添加程序参数信息是通过调用 @ref{1fc5,,add_argument()} 方法完成的。通常，这些调用指定 @ref{68f,,ArgumentParser} 如何获取命令行字符串并将其转换为对象。这些信息在 @ref{1fc6,,parse_args()} 调用时被存储和使用。例如：

@example
>>> parser.add_argument('integers', metavar='N', type=int, nargs='+',
...                     help='an integer for the accumulator')
>>> parser.add_argument('--sum', dest='accumulate', action='store_const',
...                     const=sum, default=max,
...                     help='sum the integers (default: find the max)')
@end example

然后，调用 @ref{1fc6,,parse_args()} 将返回一个具有 @code{integers} 和 @code{accumulate} 两个属性的对象。@code{integers} 属性将是一个包含一个或多个整数的列表，而 @code{accumulate} 属性当命令行中指定了 @code{--sum} 参数时将是 @ref{1e5,,sum()} 函数，否则则是 @ref{804,,max()} 函数。

@node 解析参数,,添加参数,示例<7>
@anchor{library/argparse parsing-arguments}@anchor{1fc7}
@subsubsection 解析参数


@ref{68f,,ArgumentParser} 通过 @ref{1fc6,,parse_args()} 方法解析参数。它将检查命令行，把每个参数转换为适当的类型然后调用相应的操作。在大多数情况下，这意味着一个简单的 @ref{1fc8,,Namespace} 对象将从命令行解析出的属性构建：

@example
>>> parser.parse_args(['--sum', '7', '-1', '42'])
Namespace(accumulate=<built-in function sum>, integers=[7, -1, 42])
@end example

在脚本中，通常 @ref{1fc6,,parse_args()} 会被不带参数调用，而 @ref{68f,,ArgumentParser} 将自动从 @ref{bf4,,sys.argv} 中确定命令行参数。

@node ArgumentParser 对象,add_argument 方法,示例<7>,argparse --- 命令行选项、参数和子命令解析器
@anchor{library/argparse argumentparser-objects}@anchor{1fc9}
@subsubsection ArgumentParser 对象


@geindex ArgumentParser (argparse 中的类)
@anchor{library/argparse argparse ArgumentParser}@anchor{68f}
@deffn {类} argparse.ArgumentParser (prog=None, usage=None, description=None, epilog=None, parents=[], formatter_class=argparse.HelpFormatter, prefix_chars='-', fromfile_prefix_chars=None, argument_default=None, conflict_handler='error', add_help=True, allow_abbrev=True)

创建一个新的 @ref{68f,,ArgumentParser} 对象。所有的参数都应当作为关键字参数传入。每个参数在下面都有它更详细的描述，但简而言之，它们是：


@itemize *

@item 
@ref{1fca,,prog} - 程序的名称（默认值：@code{sys.argv[0]}）

@item 
@ref{1fcb,,usage} - 描述程序用途的字符串（默认值：从添加到解析器的参数生成）

@item 
@ref{1fcc,,description} - 在参数帮助文档之前显示的文本（默认值：无）

@item 
@ref{1fcd,,epilog} - 在参数帮助文档之后显示的文本（默认值：无）

@item 
@ref{1fce,,parents} - 一个 @ref{68f,,ArgumentParser} 对象的列表，它们的参数也应包含在内

@item 
@ref{1fcf,,formatter_class} - 用于自定义帮助文档输出格式的类

@item 
@ref{1fd0,,prefix_chars} - 可选参数的前缀字符集合（默认值： '-'）

@item 
@ref{1fd1,,fromfile_prefix_chars} - 当需要从文件中读取其他参数时，用于标识文件名的前缀字符集合（默认值： @code{None}）

@item 
@ref{1fd2,,argument_default} - 参数的全局默认值（默认值： @code{None}）

@item 
@ref{1fd3,,conflict_handler} - 解决冲突选项的策略（通常是不必要的）

@item 
@ref{1fd4,,add_help} - 为解析器添加一个 @code{-h/--help} 选项（默认值： @code{True}）

@item 
@ref{691,,allow_abbrev} - 如果缩写是无歧义的，则允许缩写长选项 （默认值：@code{True}）
@end itemize


在 3.5 版更改: 增加了 @emph{allow_abbrev} 参数。



在 3.8 版更改: 在之前的版本中，@emph{allow_abbrev} 还会禁用短旗标分组，例如 @code{-vv} 表示为 @code{-v -v}。

@end deffn

以下部分描述这些参数如何使用。

@menu
* prog:: 
* usage:: 
* description:: 
* epilog:: 
* parents:: 
* formatter_class:: 
* prefix_chars:: 
* fromfile_prefix_chars:: 
* argument_default:: 
* allow_abbrev:: 
* conflict_handler:: 
* add_help:: 

@end menu

@node prog,usage,,ArgumentParser 对象
@anchor{library/argparse prog}@anchor{1fca}
@subsubsection prog


默认情况下，@ref{68f,,ArgumentParser} 对象使用 @code{sys.argv[0]} 来确定如何在帮助消息中显示程序名称。这一默认值几乎总是可取的，因为它将使帮助消息与从命令行调用此程序的方式相匹配。例如，对于有如下代码的名为 @code{myprogram.py} 的文件：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--foo', help='foo help')
args = parser.parse_args()
@end example

该程序的帮助信息将显示 @code{myprogram.py} 作为程序名称（无论程序从何处被调用）：

@example
$ python myprogram.py --help
usage: myprogram.py [-h] [--foo FOO]

optional arguments:
 -h, --help  show this help message and exit
 --foo FOO   foo help
$ cd ..
$ python subdir/myprogram.py --help
usage: myprogram.py [-h] [--foo FOO]

optional arguments:
 -h, --help  show this help message and exit
 --foo FOO   foo help
@end example

要更改这样的默认行为，可以使用 @code{prog=} 参数为 @ref{68f,,ArgumentParser} 指定另一个值：

@example
>>> parser = argparse.ArgumentParser(prog='myprogram')
>>> parser.print_help()
usage: myprogram [-h]

optional arguments:
 -h, --help  show this help message and exit
@end example

需要注意的是，无论是从 @code{sys.argv[0]} 或是从 @code{prog=} 参数确定的程序名称，都可以在帮助消息里通过 @code{%(prog)s} 格式说明符来引用。

@example
>>> parser = argparse.ArgumentParser(prog='myprogram')
>>> parser.add_argument('--foo', help='foo of the %(prog)s program')
>>> parser.print_help()
usage: myprogram [-h] [--foo FOO]

optional arguments:
 -h, --help  show this help message and exit
 --foo FOO   foo of the myprogram program
@end example

@node usage,description,prog,ArgumentParser 对象
@anchor{library/argparse usage}@anchor{1fcb}
@subsubsection usage


默认情况下，@ref{68f,,ArgumentParser} 根据它包含的参数来构建用法消息：

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo', nargs='?', help='foo help')
>>> parser.add_argument('bar', nargs='+', help='bar help')
>>> parser.print_help()
usage: PROG [-h] [--foo [FOO]] bar [bar ...]

positional arguments:
 bar          bar help

optional arguments:
 -h, --help   show this help message and exit
 --foo [FOO]  foo help
@end example

可以通过 @code{usage=} 关键字参数覆盖这一默认消息：

@example
>>> parser = argparse.ArgumentParser(prog='PROG', usage='%(prog)s [options]')
>>> parser.add_argument('--foo', nargs='?', help='foo help')
>>> parser.add_argument('bar', nargs='+', help='bar help')
>>> parser.print_help()
usage: PROG [options]

positional arguments:
 bar          bar help

optional arguments:
 -h, --help   show this help message and exit
 --foo [FOO]  foo help
@end example

在用法消息中可以使用 @code{%(prog)s} 格式说明符来填入程序名称。

@node description,epilog,usage,ArgumentParser 对象
@anchor{library/argparse description}@anchor{1fcc}
@subsubsection description


大多数对 @ref{68f,,ArgumentParser} 构造方法的调用都会使用 @code{description=} 关键字参数。这个参数简要描述这个程度做什么以及怎么做。在帮助消息中，这个描述会显示在命令行用法字符串和各种参数的帮助消息之间：

@example
>>> parser = argparse.ArgumentParser(description='A foo that bars')
>>> parser.print_help()
usage: argparse.py [-h]

A foo that bars

optional arguments:
 -h, --help  show this help message and exit
@end example

在默认情况下，description 将被换行以便适应给定的空间。如果想改变这种行为，见 @ref{1fcf,,formatter_class} 参数。

@node epilog,parents,description,ArgumentParser 对象
@anchor{library/argparse epilog}@anchor{1fcd}
@subsubsection epilog


一些程序喜欢在 description 参数后显示额外的对程序的描述。这种文字能够通过给 @ref{68f,,ArgumentParser}:: 提供 @code{epilog=} 参数而被指定。

@example
>>> parser = argparse.ArgumentParser(
...     description='A foo that bars',
...     epilog="And that's how you'd foo a bar")
>>> parser.print_help()
usage: argparse.py [-h]

A foo that bars

optional arguments:
 -h, --help  show this help message and exit

And that's how you'd foo a bar
@end example

和 @ref{1fcc,,description} 参数一样，@code{epilog=} text 在默认情况下会换行，但是这种行为能够被调整通过提供 @ref{1fcf,,formatter_class} 参数给 @code{ArgumentParse}.

@node parents,formatter_class,epilog,ArgumentParser 对象
@anchor{library/argparse parents}@anchor{1fce}
@subsubsection parents


有些时候，少数解析器会使用同一系列参数。 单个解析器能够通过提供 @code{parents=} 参数给 @ref{68f,,ArgumentParser} 而使用相同的参数而不是重复这些参数的定义。@code{parents=} 参数使用 @ref{68f,,ArgumentParser} 对象的列表，从它们那里收集所有的位置和可选的行为，然后将这写行为加到正在构建的 @ref{68f,,ArgumentParser} 对象。

@example
>>> parent_parser = argparse.ArgumentParser(add_help=False)
>>> parent_parser.add_argument('--parent', type=int)

>>> foo_parser = argparse.ArgumentParser(parents=[parent_parser])
>>> foo_parser.add_argument('foo')
>>> foo_parser.parse_args(['--parent', '2', 'XXX'])
Namespace(foo='XXX', parent=2)

>>> bar_parser = argparse.ArgumentParser(parents=[parent_parser])
>>> bar_parser.add_argument('--bar')
>>> bar_parser.parse_args(['--bar', 'YYY'])
Namespace(bar='YYY', parent=None)
@end example

请注意大多数父解析器会指定 @code{add_help=False} . 否则， @code{ArgumentParse} 将会看到两个 @code{-h/--help} 选项（一个在父参数中一个在子参数中）并且产生一个错误。

@cartouche
@quotation 注解 
你在传`@w{`}parents=`@w{`}给那些解析器时必须完全初始化它们。如果你在子解析器之后改变父解析器是，这些改变不会反映在子解析器上。
@end quotation
@end cartouche

@node formatter_class,prefix_chars,parents,ArgumentParser 对象
@anchor{library/argparse formatter-class}@anchor{1fcf}
@subsubsection formatter_class


@ref{68f,,ArgumentParser} 对象允许通过指定备用格式化类来自定义帮助格式。目前，有四种这样的类。

@geindex RawDescriptionHelpFormatter (argparse 中的类)
@geindex RawTextHelpFormatter (argparse 中的类)
@geindex ArgumentDefaultsHelpFormatter (argparse 中的类)
@geindex MetavarTypeHelpFormatter (argparse 中的类)
@anchor{library/argparse argparse RawDescriptionHelpFormatter}@anchor{1fd5}
@deffn {类} argparse.RawDescriptionHelpFormatter
@anchor{library/argparse argparse RawTextHelpFormatter}@anchor{1fd6}
@deffnx {类} argparse.RawTextHelpFormatter
@anchor{library/argparse argparse ArgumentDefaultsHelpFormatter}@anchor{1fd7}
@deffnx {类} argparse.ArgumentDefaultsHelpFormatter
@anchor{library/argparse argparse MetavarTypeHelpFormatter}@anchor{1fd8}
@deffnx {类} argparse.MetavarTypeHelpFormatter
@end deffn

@ref{1fd5,,RawDescriptionHelpFormatter} 和 @ref{1fd6,,RawTextHelpFormatter} 在正文的描述和展示上给与了更多的控制。@ref{68f,,ArgumentParser} 对象会将 @ref{1fcc,,description} 和 @ref{1fcd,,epilog} 的文字在命令行中自动换行。

@example
>>> parser = argparse.ArgumentParser(
...     prog='PROG',
...     description='@w{'}'this description
...         was indented weird
...             but that is okay'@w{'}',
...     epilog='@w{'}'
...             likewise for this epilog whose whitespace will
...         be cleaned up and whose words will be wrapped
...         across a couple lines'@w{'}')
>>> parser.print_help()
usage: PROG [-h]

this description was indented weird but that is okay

optional arguments:
 -h, --help  show this help message and exit

likewise for this epilog whose whitespace will be cleaned up and whose words
will be wrapped across a couple lines
@end example

传 @ref{1fd5,,RawDescriptionHelpFormatter} 给 @code{formatter_class=} 表示 @ref{1fcc,,description} 和 @ref{1fcd,,epilog} 已经被正确的格式化了，不能在命令行中被自动换行:

@example
>>> parser = argparse.ArgumentParser(
...     prog='PROG',
...     formatter_class=argparse.RawDescriptionHelpFormatter,
...     description=textwrap.dedent('@w{'}'\
...         Please do not mess up this text!
...         --------------------------------
...             I have indented it
...             exactly the way
...             I want it
...         '@w{'}'))
>>> parser.print_help()
usage: PROG [-h]

Please do not mess up this text!
--------------------------------
   I have indented it
   exactly the way
   I want it

optional arguments:
 -h, --help  show this help message and exit
@end example

@ref{1fd6,,RawTextHelpFormatter} 保留所有种类文字的空格，包括参数的描述。然而，多重的新行会被替换成一行。如果你想保留多重的空白行，可以在新行之间加空格。

@ref{1fd7,,ArgumentDefaultsHelpFormatter} 自动添加默认的值的信息到每一个帮助信息的参数中:

@example
>>> parser = argparse.ArgumentParser(
...     prog='PROG',
...     formatter_class=argparse.ArgumentDefaultsHelpFormatter)
>>> parser.add_argument('--foo', type=int, default=42, help='FOO!')
>>> parser.add_argument('bar', nargs='*', default=[1, 2, 3], help='BAR!')
>>> parser.print_help()
usage: PROG [-h] [--foo FOO] [bar [bar ...]]

positional arguments:
 bar         BAR! (default: [1, 2, 3])

optional arguments:
 -h, --help  show this help message and exit
 --foo FOO   FOO! (default: 42)
@end example

@ref{1fd8,,MetavarTypeHelpFormatter} 为它的值在每一个参数中使用 @ref{1fd9,,type} 的参数名当作它的显示名（而不是使用通常的格式 @ref{1fda,,dest} ):

@example
>>> parser = argparse.ArgumentParser(
...     prog='PROG',
...     formatter_class=argparse.MetavarTypeHelpFormatter)
>>> parser.add_argument('--foo', type=int)
>>> parser.add_argument('bar', type=float)
>>> parser.print_help()
usage: PROG [-h] [--foo int] float

positional arguments:
  float

optional arguments:
  -h, --help  show this help message and exit
  --foo int
@end example

@node prefix_chars,fromfile_prefix_chars,formatter_class,ArgumentParser 对象
@anchor{library/argparse prefix-chars}@anchor{1fd0}
@subsubsection prefix_chars


许多命令行会使用 @code{-} 当作前缀，比如 @code{-f/--foo}。如果解析器需要支持不同的或者额外的字符，比如像 @code{+f} 或者 @code{/foo} 的选项，可以在参数解析构建器中使用 @code{prefix_chars=} 参数。

@example
>>> parser = argparse.ArgumentParser(prog='PROG', prefix_chars='-+')
>>> parser.add_argument('+f')
>>> parser.add_argument('++bar')
>>> parser.parse_args('+f X ++bar Y'.split())
Namespace(bar='Y', f='X')
@end example

The @code{prefix_chars=} 参数默认使用 @code{'-'}. 支持一系列字符，但是不包括 @code{-} ，这样会产生不被允许的 @code{-f/--foo} 选项。

@node fromfile_prefix_chars,argument_default,prefix_chars,ArgumentParser 对象
@anchor{library/argparse fromfile-prefix-chars}@anchor{1fd1}
@subsubsection fromfile_prefix_chars


有些时候，先举个例子，当处理一个特别长的参数列表的时候，把它存入一个文件中而不是在命令行打出来会很有意义。如果 @code{fromfile_prefix_chars=} 参数提供给 @ref{68f,,ArgumentParser} 构造函数，之后所有类型的字符的参数都会被当成文件处理，并且会被文件包含的参数替代。举个栗子:

@example
>>> with open('args.txt', 'w') as fp:
...     fp.write('-f\nbar')
>>> parser = argparse.ArgumentParser(fromfile_prefix_chars='@@')
>>> parser.add_argument('-f')
>>> parser.parse_args(['-f', 'foo', '@@args.txt'])
Namespace(f='bar')
@end example

从文件读取的参数在默认情况下必须一个一行（但是可参见  @ref{1fdb,,convert_arg_line_to_args()}）并且它们被视为与命令行上的原始文件引用参数位于同一位置。所以在以上例子中，@code{['-f', 'foo', '@@args.txt']} 的表示和 @code{['-f', 'foo', '-f', 'bar']} 的表示相同。

@code{fromfile_prefix_chars=} 参数默认为 @code{None}，意味着参数不会被当作文件对待。

@node argument_default,allow_abbrev,fromfile_prefix_chars,ArgumentParser 对象
@anchor{library/argparse argument-default}@anchor{1fd2}
@subsubsection argument_default


一般情况下，参数默认会通过设置一个默认到 @ref{1fc5,,add_argument()} 或者调用带一组指定键值对的 @ref{1fdc,,ArgumentParser.set_defaults()} 方法。但是有些时候，为参数指定一个普遍适用的解析器会更有用。这能够通过传输 @code{argument_default=} 关键词参数给 @ref{68f,,ArgumentParser} 来完成。举个栗子，要全局禁止在 @ref{1fc6,,parse_args()} 中创建属性，我们提供 @code{argument_default=SUPPRESS}:

@example
>>> parser = argparse.ArgumentParser(argument_default=argparse.SUPPRESS)
>>> parser.add_argument('--foo')
>>> parser.add_argument('bar', nargs='?')
>>> parser.parse_args(['--foo', '1', 'BAR'])
Namespace(bar='BAR', foo='1')
>>> parser.parse_args([])
Namespace()
@end example

@node allow_abbrev,conflict_handler,argument_default,ArgumentParser 对象
@anchor{library/argparse allow-abbrev}@anchor{691}@anchor{library/argparse id1}@anchor{1fdd}
@subsubsection allow_abbrev


正常情况下，当你向 @ref{68f,,ArgumentParser} 的 @ref{1fc6,,parse_args()} 方法传入一个参数列表时，它会 @ref{690,,recognizes abbreviations}。

这个特性可以设置 @code{allow_abbrev} 为 @code{False} 来关闭:

@example
>>> parser = argparse.ArgumentParser(prog='PROG', allow_abbrev=False)
>>> parser.add_argument('--foobar', action='store_true')
>>> parser.add_argument('--foonley', action='store_false')
>>> parser.parse_args(['--foon'])
usage: PROG [-h] [--foobar] [--foonley]
PROG: error: unrecognized arguments: --foon
@end example


3.5 新版功能.


@node conflict_handler,add_help,allow_abbrev,ArgumentParser 对象
@anchor{library/argparse conflict-handler}@anchor{1fd3}
@subsubsection conflict_handler


@ref{68f,,ArgumentParser} 对象不允许在相同选项字符串下有两种行为。默认情况下， @ref{68f,,ArgumentParser} 对象会产生一个异常如果去创建一个正在使用的选项字符串参数。

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-f', '--foo', help='old foo help')
>>> parser.add_argument('--foo', help='new foo help')
Traceback (most recent call last):
 ..
ArgumentError: argument --foo: conflicting option string(s): --foo
@end example

有些时候（例如：使用 @ref{1fce,,parents}），重写旧的有相同选项字符串的参数会更有用。为了产生这种行为， @code{'resolve'} 值可以提供给 @ref{68f,,ArgumentParser} 的 @code{conflict_handler=} 参数:

@example
>>> parser = argparse.ArgumentParser(prog='PROG', conflict_handler='resolve')
>>> parser.add_argument('-f', '--foo', help='old foo help')
>>> parser.add_argument('--foo', help='new foo help')
>>> parser.print_help()
usage: PROG [-h] [-f FOO] [--foo FOO]

optional arguments:
 -h, --help  show this help message and exit
 -f FOO      old foo help
 --foo FOO   new foo help
@end example

注意 @ref{68f,,ArgumentParser} 对象只能移除一个行为如果它所有的选项字符串都被重写。所以，在上面的例子中，旧的 @code{-f/--foo} 行为 回合 @code{-f} 行为保持一样, 因为只有 @code{--foo} 选项字符串被重写。

@node add_help,,conflict_handler,ArgumentParser 对象
@anchor{library/argparse add-help}@anchor{1fd4}
@subsubsection add_help


默认情况下，ArgumentParser 对象添加一个简单的显示解析器帮助信息的选项。举个栗子，考虑一个名为 @code{myprogram.py} 的文件包含如下代码:

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--foo', help='foo help')
args = parser.parse_args()
@end example

如果 @code{-h} or @code{--help} 在命令行中被提供, 参数解析器帮助信息会打印:

@example
$ python myprogram.py --help
usage: myprogram.py [-h] [--foo FOO]

optional arguments:
 -h, --help  show this help message and exit
 --foo FOO   foo help
@end example

有时候可能会需要关闭额外的帮助信息。这可以通过在 @ref{68f,,ArgumentParser} 中设置 @code{add_help=} 参数为 @code{False} 来实现。

@example
>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> parser.add_argument('--foo', help='foo help')
>>> parser.print_help()
usage: PROG [--foo FOO]

optional arguments:
 --foo FOO  foo help
@end example

帮助选项一般为 @code{-h/--help}。如果 @code{prefix_chars=} 被指定并且没有包含 @code{-} 字符，在这种情况下， @code{-h} @code{--help} 不是有效的选项。此时， @code{prefix_chars} 的第一个字符将用作帮助选项的前缀。

@example
>>> parser = argparse.ArgumentParser(prog='PROG', prefix_chars='+/')
>>> parser.print_help()
usage: PROG [+h]

optional arguments:
  +h, ++help  show this help message and exit
@end example

@node add_argument 方法,parse_args 方法,ArgumentParser 对象,argparse --- 命令行选项、参数和子命令解析器
@anchor{library/argparse the-add-argument-method}@anchor{1fde}
@subsubsection add_argument() 方法


@geindex add_argument() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser add_argument}@anchor{1fc5}
@deffn {方法} ArgumentParser.add_argument (name or flags...[, action][, nargs][, const][, default][, type][, choices][, required][, help][, metavar][, dest])

定义单个的命令行参数应当如何解析。每个形参都在下面有它自己更多的描述，长话短说有：


@itemize *

@item 
@ref{1fdf,,name or flags} - 一个命名或者一个选项字符串的列表，例如 @code{foo} 或 @code{-f, --foo}。

@item 
@ref{1fe0,,action} - 当参数在命令行中出现时使用的动作基本类型。

@item 
@ref{1fe1,,nargs} - 命令行参数应当消耗的数目。

@item 
@ref{1fe2,,const} - 被一些 @ref{1fe0,,action} 和 @ref{1fe1,,nargs} 选择所需求的常数。

@item 
@ref{1fe3,,default} - 当参数未在命令行中出现时使用的值。

@item 
@ref{1fd9,,type} - 命令行参数应当被转换成的类型。

@item 
@ref{1fe4,,choices} - 可用的参数的容器。

@item 
@ref{1fe5,,required} - 此命令行选项是否可省略 （仅选项可用）。

@item 
@ref{1fe6,,help} - 一个此选项作用的简单描述。

@item 
@ref{1fe7,,metavar} - 在使用方法消息中使用的参数值示例。

@item 
@ref{1fda,,dest} - 被添加到 @ref{1fc6,,parse_args()} 所返回对象上的属性名。
@end itemize
@end deffn

以下部分描述这些参数如何使用。

@menu
* name or flags:: 
* action:: 
* nargs:: 
* const:: 
* 默认值:: 
* type:: 
* choices:: 
* required:: 
* help:: 
* metavar:: 
* dest:: 
* Action 类:: 

@end menu

@node name or flags,action,,add_argument 方法
@anchor{library/argparse name-or-flags}@anchor{1fdf}
@subsubsection name or flags


@ref{1fc5,,add_argument()} 方法必须知道它是否是一个选项，例如 @code{-f} 或 @code{--foo}，或是一个位置参数，例如一组文件名。第一个传递给 @ref{1fc5,,add_argument()} 的参数必须是一系列 flags 或者是一个简单的参数名。例如，可以选项可以被这样创建:

@example
>>> parser.add_argument('-f', '--foo')
@end example

而位置参数可以这么创建:

@example
>>> parser.add_argument('bar')
@end example

当 @ref{1fc6,,parse_args()} 被调用，选项会以 @code{-} 前缀识别，剩下的参数则会被假定为位置参数:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-f', '--foo')
>>> parser.add_argument('bar')
>>> parser.parse_args(['BAR'])
Namespace(bar='BAR', foo=None)
>>> parser.parse_args(['BAR', '--foo', 'FOO'])
Namespace(bar='BAR', foo='FOO')
>>> parser.parse_args(['--foo', 'FOO'])
usage: PROG [-h] [-f FOO] bar
PROG: error: the following arguments are required: bar
@end example

@node action,nargs,name or flags,add_argument 方法
@anchor{library/argparse action}@anchor{1fe0}
@subsubsection action


@ref{68f,,ArgumentParser} 对象将命令行参数与动作相关联。这些动作可以做与它们相关联的命令行参数的任何事，尽管大多数动作只是简单的向 @ref{1fc6,,parse_args()} 返回的对象上添加属性。@code{action} 命名参数指定了这个命令行参数应当如何处理。供应的动作有：


@itemize *

@item 
@code{'store'} - 存储参数的值。这是默认的动作。例如:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.parse_args('--foo 1'.split())
Namespace(foo='1')
@end example

@item 
@code{'store_const'} - 存储被 @ref{1fe2,,const} 命名参数指定的值。 @code{'store_const'} 动作通常用在选项中来指定一些标志。例如:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_const', const=42)
>>> parser.parse_args(['--foo'])
Namespace(foo=42)
@end example

@item 
@code{'store_true'} and @code{'store_false'} - 这些是 @code{'store_const'} 分别用作存储 @code{True} 和 @code{False} 值的特殊用例。另外，它们的默认值分别为 @code{False} 和 @code{True}。例如:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_true')
>>> parser.add_argument('--bar', action='store_false')
>>> parser.add_argument('--baz', action='store_false')
>>> parser.parse_args('--foo --bar'.split())
Namespace(foo=True, bar=False, baz=True)
@end example

@item 
@code{'append'} - 存储一个列表，并且将每个参数值追加到列表中。在允许多次使用选项时很有用。例如:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='append')
>>> parser.parse_args('--foo 1 --foo 2'.split())
Namespace(foo=['1', '2'])
@end example

@item 
@code{'append_const'} - 这存储一个列表，并将 @ref{1fe2,,const} 命名参数指定的值追加到列表中。（注意 @ref{1fe2,,const} 命名参数默认为 @code{None}。）`@w{`}'append_const'`@w{`} 动作一般在多个参数需要在同一列表中存储常数时会有用。例如:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--str', dest='types', action='append_const', const=str)
>>> parser.add_argument('--int', dest='types', action='append_const', const=int)
>>> parser.parse_args('--str --int'.split())
Namespace(types=[<class 'str'>, <class 'int'>])
@end example

@item 
@code{'count'} - 计算一个关键字参数出现的数目或次数。例如，对于一个增长的详情等级来说有用:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--verbose', '-v', action='count', default=0)
>>> parser.parse_args(['-vvv'])
Namespace(verbose=3)
@end example

请注意，@emph{default} 将为 @code{None}，除非显式地设为 @emph{0}。

@item 
@code{'help'} - 打印所有当前解析器中的选项和参数的完整帮助信息，然后退出。默认情况下，一个 help 动作会被自动加入解析器。关于输出是如何创建的，参与 @ref{68f,,ArgumentParser}。

@item 
@code{'version'} - 期望有一个 @code{version=} 命名参数在 @ref{1fc5,,add_argument()} 调用中，并打印版本信息并在调用后退出:

@example
>>> import argparse
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--version', action='version', version='%(prog)s 2.0')
>>> parser.parse_args(['--version'])
PROG 2.0
@end example

@item 
@code{'extend'} - 这会存储一个列表，并将每个参数值加入到列表中。 示例用法:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument("--foo", action="extend", nargs="+", type=str)
>>> parser.parse_args(["--foo", "f1", "--foo", "f2", "f3", "f4"])
Namespace(foo=['f1', 'f2', 'f3', 'f4'])
@end example


3.8 新版功能.

@end itemize

您还可以通过传递 Action 子类或实现相同接口的其他对象来指定任意操作。建议的方法是扩展 @ref{1fe8,,Action}，覆盖 @code{__call__} 方法和可选的 @code{__init__} 方法。

一个自定义动作的例子:

@example
>>> class FooAction(argparse.Action):
...     def __init__(self, option_strings, dest, nargs=None, **kwargs):
...         if nargs is not None:
...             raise ValueError("nargs not allowed")
...         super(FooAction, self).__init__(option_strings, dest, **kwargs)
...     def __call__(self, parser, namespace, values, option_string=None):
...         print('%r %r %r' % (namespace, values, option_string))
...         setattr(namespace, self.dest, values)
...
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action=FooAction)
>>> parser.add_argument('bar', action=FooAction)
>>> args = parser.parse_args('1 --foo 2'.split())
Namespace(bar=None, foo=None) '1' None
Namespace(bar='1', foo=None) '2' '--foo'
>>> args
Namespace(bar='1', foo='2')
@end example

更多描述，见 @ref{1fe8,,Action}。

@node nargs,const,action,add_argument 方法
@anchor{library/argparse nargs}@anchor{1fe1}
@subsubsection nargs


ArgumentParser 对象通常关联一个单独的命令行参数到一个单独的被执行的动作。 @code{nargs} 命名参数关联不同数目的命令行参数到单一动作。支持的值有：


@itemize *

@item 
@code{N} （一个整数）。命令行中的 @code{N} 个参数会被聚集到一个列表中。 例如:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs=2)
>>> parser.add_argument('bar', nargs=1)
>>> parser.parse_args('c --foo a b'.split())
Namespace(bar=['c'], foo=['a', 'b'])
@end example

注意 @code{nargs=1} 会产生一个单元素列表。这和默认的元素本身是不同的。
@end itemize

@geindex ? (question mark); in argparse module


@itemize *

@item 
@code{'?'}。如果可能的话，会从命令行中消耗一个参数，并产生一个单一项。如果当前没有命令行参数，则会产生 @ref{1fe3,,default} 值。注意，对于选项，有另外的用例 - 选项字符串出现但没有跟随命令行参数，则会产生 @ref{1fe2,,const} 值。一些说用用例:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs='?', const='c', default='d')
>>> parser.add_argument('bar', nargs='?', default='d')
>>> parser.parse_args(['XX', '--foo', 'YY'])
Namespace(bar='XX', foo='YY')
>>> parser.parse_args(['XX', '--foo'])
Namespace(bar='XX', foo='c')
>>> parser.parse_args([])
Namespace(bar='d', foo='d')
@end example

@code{nargs='?'} 的一个更普遍用法是允许可选的输入或输出文件:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('infile', nargs='?', type=argparse.FileType('r'),
...                     default=sys.stdin)
>>> parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'),
...                     default=sys.stdout)
>>> parser.parse_args(['input.txt', 'output.txt'])
Namespace(infile=<_io.TextIOWrapper name='input.txt' encoding='UTF-8'>,
          outfile=<_io.TextIOWrapper name='output.txt' encoding='UTF-8'>)
>>> parser.parse_args([])
Namespace(infile=<_io.TextIOWrapper name='<stdin>' encoding='UTF-8'>,
          outfile=<_io.TextIOWrapper name='<stdout>' encoding='UTF-8'>)
@end example
@end itemize

@geindex * (asterisk); in argparse module


@itemize *

@item 
@code{'*'}。所有当前命令行参数被聚集到一个列表中。注意通过 @code{nargs='*'} 来实现多个位置参数通常没有意义，但是多个选项是可能的。例如:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs='*')
>>> parser.add_argument('--bar', nargs='*')
>>> parser.add_argument('baz', nargs='*')
>>> parser.parse_args('a b --foo x y --bar 1 2'.split())
Namespace(bar=['1', '2'], baz=['a', 'b'], foo=['x', 'y'])
@end example
@end itemize

@geindex + (plus); in argparse module


@itemize *

@item 
@code{'+'}。和 @code{'*'} 类似，所有当前命令行参数被聚集到一个列表中。另外，当前没有至少一个命令行参数时会产生一个错误信息。例如:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', nargs='+')
>>> parser.parse_args(['a', 'b'])
Namespace(foo=['a', 'b'])
>>> parser.parse_args([])
usage: PROG [-h] foo [foo ...]
PROG: error: the following arguments are required: foo
@end example
@end itemize
@anchor{library/argparse argparse-remainder}@anchor{1fe9}

@itemize *

@item 
@code{argarse.REMAINDER}。所有剩余的命令行参数被聚集到一个列表中。这通常在从一个命令行功能传递参数到另一个命令行功能中时有用:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo')
>>> parser.add_argument('command')
>>> parser.add_argument('args', nargs=argparse.REMAINDER)
>>> print(parser.parse_args('--foo B cmd --arg1 XX ZZ'.split()))
Namespace(args=['--arg1', 'XX', 'ZZ'], command='cmd', foo='B')
@end example
@end itemize

如果不提供 @code{nargs} 命名参数，则消耗参数的数目将被 @ref{1fe0,,action} 决定。通常这意味着单一项目（非列表）消耗单一命令行参数。

@node const,默认值,nargs,add_argument 方法
@anchor{library/argparse const}@anchor{1fe2}
@subsubsection const


@ref{1fc5,,add_argument()}  的`@w{`}const`@w{`} 参数用于保存不从命令行中读取但被各种 @ref{68f,,ArgumentParser} 动作需求的常数值。最常用的两例为：


@itemize *

@item 
当 @ref{1fc5,,add_argument()} 通过 @code{action='store_const'} 或 @code{action='append_const} 调用时。这些动作将 @code{const} 值添加到 @ref{1fc6,,parse_args()} 返回的对象的属性中。在 @ref{1fe0,,action} 的描述中查看案例。

@item 
当 @ref{1fc5,,add_argument()} 通过选项（例如 @code{-f} 或 @code{--foo}）调用并且 @code{nargs='?'} 时。这会创建一个可以跟随零个或一个命令行参数的选项。当解析命令行时，如果选项后没有参数，则将用 @code{const} 代替。在 @ref{1fe1,,nargs} 描述中查看案例。
@end itemize

对 @code{'store_const'} 和 @code{'append_const'} 动作， @code{const} 命名参数必须给出。对其他动作，默认为 @code{None}。

@node 默认值,type,const,add_argument 方法
@anchor{library/argparse default}@anchor{1fe3}
@subsubsection 默认值


所有选项和一些位置参数可能在命令行中被忽略。@ref{1fc5,,add_argument()} 的命名参数 @code{default}，默认值为 @code{None}，指定了在命令行参数未出现时应当使用的值。对于选项， @code{default} 值在选项未在命令行中出现时使用:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default=42)
>>> parser.parse_args(['--foo', '2'])
Namespace(foo='2')
>>> parser.parse_args([])
Namespace(foo=42)
@end example

如果 @code{default} 值是一个字符串，解析器解析此值就像一个命令行参数。特别是，在将属性设置在 @ref{1fc8,,Namespace} 的返回值之前，解析器应用任何提供的 @ref{1fd9,,type} 转换参数。否则解析器使用原值:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--length', default='10', type=int)
>>> parser.add_argument('--width', default=10.5, type=int)
>>> parser.parse_args()
Namespace(length=10, width=10.5)
@end example

对于 @ref{1fe1,,nargs} 等于 @code{?} 或 @code{*} 的位置参数， @code{default} 值在没有命令行参数出现时使用。

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', nargs='?', default=42)
>>> parser.parse_args(['a'])
Namespace(foo='a')
>>> parser.parse_args([])
Namespace(foo=42)
@end example

提供 @code{default=argparse.SUPPRESS} 导致命令行参数未出现时没有属性被添加:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default=argparse.SUPPRESS)
>>> parser.parse_args([])
Namespace()
>>> parser.parse_args(['--foo', '1'])
Namespace(foo='1')
@end example

@node type,choices,默认值,add_argument 方法
@anchor{library/argparse type}@anchor{1fd9}
@subsubsection type


默认情况下，@ref{68f,,ArgumentParser} 对象将命令行参数当作简单字符串读入。然而，命令行字符串经常需要被当作其它的类型，比如 @ref{187,,float} 或者 @ref{184,,int}。@ref{1fc5,,add_argument()} 的 @code{type} 关键词参数允许任何的类型检查和类型转换。一般的内建类型和函数可以直接被 @code{type} 参数使用。

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', type=int)
>>> parser.add_argument('bar', type=open)
>>> parser.parse_args('2 temp.txt'.split())
Namespace(bar=<_io.TextIOWrapper name='temp.txt' encoding='UTF-8'>, foo=2)
@end example

当 @code{type} 参数被应用到默认参数时，请参考 @ref{1fe3,,default} 参数的部分。

为方便使用不同类型的文件，argparse 模块提供了 FileType 工厂类，该类接受 @code{mode=}, @code{bufsize=}, @code{encoding=} 和 @code{errors=} 等 @ref{4ea,,open()} 函数参数。 例如，@code{FileType('w')} 可被用来创建一个可写文件:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('bar', type=argparse.FileType('w'))
>>> parser.parse_args(['out.txt'])
Namespace(bar=<_io.TextIOWrapper name='out.txt' encoding='UTF-8'>)
@end example

@code{type=} 可接受任意可调用对象，该对象应传入单个字符串参数并返回转换后的值:

@example
>>> def perfect_square(string):
...     value = int(string)
...     sqrt = math.sqrt(value)
...     if sqrt != int(sqrt):
...         msg = "%r is not a perfect square" % string
...         raise argparse.ArgumentTypeError(msg)
...     return value
...
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', type=perfect_square)
>>> parser.parse_args(['9'])
Namespace(foo=9)
>>> parser.parse_args(['7'])
usage: PROG [-h] foo
PROG: error: argument foo: '7' is not a perfect square
@end example

@ref{1fe4,,choices} 关键词参数可能会使类型检查者更方便的检查一个范围的值。

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', type=int, choices=range(5, 10))
>>> parser.parse_args(['7'])
Namespace(foo=7)
>>> parser.parse_args(['11'])
usage: PROG [-h] @{5,6,7,8,9@}
PROG: error: argument foo: invalid choice: 11 (choose from 5, 6, 7, 8, 9)
@end example

详情请查阅 @ref{1fe4,,choices} 段落。

@node choices,required,type,add_argument 方法
@anchor{library/argparse choices}@anchor{1fe4}
@subsubsection choices


某些命令行参数应当从一组受限值中选择。 这可通过将一个容器对象作为 @emph{choices} 关键字参数传给 @ref{1fc5,,add_argument()} 来处理。 当执行命令行解析时，参数值将被检查，如果参数不是可接受的值之一就将显示错误消息:

@example
>>> parser = argparse.ArgumentParser(prog='game.py')
>>> parser.add_argument('move', choices=['rock', 'paper', 'scissors'])
>>> parser.parse_args(['rock'])
Namespace(move='rock')
>>> parser.parse_args(['fire'])
usage: game.py [-h] @{rock,paper,scissors@}
game.py: error: argument move: invalid choice: 'fire' (choose from 'rock',
'paper', 'scissors')
@end example

请注意 @emph{choices} 容器包含的内容会在执行任意 @ref{1fd9,,type} 转换之后被检查，因此 @emph{choices} 容器中对象的类型应当与指定的 @ref{1fd9,,type} 相匹配:

@example
>>> parser = argparse.ArgumentParser(prog='doors.py')
>>> parser.add_argument('door', type=int, choices=range(1, 4))
>>> print(parser.parse_args(['3']))
Namespace(door=3)
>>> parser.parse_args(['4'])
usage: doors.py [-h] @{1,2,3@}
doors.py: error: argument door: invalid choice: 4 (choose from 1, 2, 3)
@end example

任何容器都可作为 @emph{choices} 值传入，因此 @ref{262,,list} 对象，@ref{b68,,set} 对象以及自定义容器都是受支持的。

@node required,help,choices,add_argument 方法
@anchor{library/argparse required}@anchor{1fe5}
@subsubsection required


通常，@ref{6,,argparse} 模块会认为 @code{-f} 和 @code{--bar} 等旗标是指明 @emph{可选的} 参数，它们总是可以在命令行中被忽略。 要让一个选项成为 @emph{必需的}，则可以将 @code{True} 作为 @code{required=} 关键字参数传给 @ref{1fc5,,add_argument()}:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', required=True)
>>> parser.parse_args(['--foo', 'BAR'])
Namespace(foo='BAR')
>>> parser.parse_args([])
usage: argparse.py [-h] [--foo FOO]
argparse.py: error: option --foo is required
@end example

如这个例子所示，如果一个选项被标记为 @code{required}，则当该选项未在命令行中出现时，@ref{1fc6,,parse_args()} 将会报告一个错误。

@cartouche
@quotation 注解 
必需的选项通常被认为是不适宜的，因为用户会预期 @emph{options} 都是 @emph{可选的}，因此在可能的情况下应当避免使用它们。
@end quotation
@end cartouche

@node help,metavar,required,add_argument 方法
@anchor{library/argparse help}@anchor{1fe6}
@subsubsection help


@code{help} 值是一个包含参数简短描述的字符串。 当用户请求帮助时（一般是通过在命令行中使用 @code{-h} 或 @code{--help} 的方式），这些 @code{help} 描述将随每个参数一同显示:

@example
>>> parser = argparse.ArgumentParser(prog='frobble')
>>> parser.add_argument('--foo', action='store_true',
...                     help='foo the bars before frobbling')
>>> parser.add_argument('bar', nargs='+',
...                     help='one of the bars to be frobbled')
>>> parser.parse_args(['-h'])
usage: frobble [-h] [--foo] bar [bar ...]

positional arguments:
 bar     one of the bars to be frobbled

optional arguments:
 -h, --help  show this help message and exit
 --foo   foo the bars before frobbling
@end example

@code{help} 字符串可包括各种格式描述符以避免重复使用程序名称或参数 @ref{1fe3,,default} 等文本。 有效的描述符包括程序名称 @code{%(prog)s} 和传给 @ref{1fc5,,add_argument()} 的大部分关键字参数，例如 @code{%(default)s}, @code{%(type)s} 等等:

@example
>>> parser = argparse.ArgumentParser(prog='frobble')
>>> parser.add_argument('bar', nargs='?', type=int, default=42,
...                     help='the bar to %(prog)s (default: %(default)s)')
>>> parser.print_help()
usage: frobble [-h] [bar]

positional arguments:
 bar     the bar to frobble (default: 42)

optional arguments:
 -h, --help  show this help message and exit
@end example

由于帮助字符串支持 %-formatting，如果你希望在帮助字符串中显示 @code{%} 字面值，你必须将其转义为 @code{%%}。

@ref{6,,argparse} 支持静默特定选项的帮助，具体做法是将 @code{help} 的值设为 @code{argparse.SUPPRESS}:

@example
>>> parser = argparse.ArgumentParser(prog='frobble')
>>> parser.add_argument('--foo', help=argparse.SUPPRESS)
>>> parser.print_help()
usage: frobble [-h]

optional arguments:
  -h, --help  show this help message and exit
@end example

@node metavar,dest,help,add_argument 方法
@anchor{library/argparse metavar}@anchor{1fe7}
@subsubsection metavar


当 @ref{68f,,ArgumentParser} 生成帮助消息时，它需要用某种方式来引用每个预期的参数。 默认情况下，ArgumentParser 对象使用 @ref{1fda,,dest} 值作为每个对象的 "name"。 默认情况下，对于位置参数动作，@ref{1fda,,dest} 值将被直接使用，而对于可选参数动作，@ref{1fda,,dest} 值将被转为大写形式。 因此，一个位置参数 @code{dest='bar'} 的引用形式将为 @code{bar}。 一个带有单独命令行参数的可选参数 @code{--foo} 的引用形式将为 @code{FOO}。 示例如下:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.add_argument('bar')
>>> parser.parse_args('X --foo Y'.split())
Namespace(bar='X', foo='Y')
>>> parser.print_help()
usage:  [-h] [--foo FOO] bar

positional arguments:
 bar

optional arguments:
 -h, --help  show this help message and exit
 --foo FOO
@end example

可以使用 @code{metavar} 来指定一个替代名称:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', metavar='YYY')
>>> parser.add_argument('bar', metavar='XXX')
>>> parser.parse_args('X --foo Y'.split())
Namespace(bar='X', foo='Y')
>>> parser.print_help()
usage:  [-h] [--foo YYY] XXX

positional arguments:
 XXX

optional arguments:
 -h, --help  show this help message and exit
 --foo YYY
@end example

请注意 @code{metavar} 仅改变 @emph{显示的} 名称 -  @ref{1fc6,,parse_args()} 对象的属性名称仍然会由 @ref{1fda,,dest} 值确定。

不同的 @code{nargs} 值可能导致 metavar 被多次使用。 提供一个元组给 @code{metavar} 即为每个参数指定不同的显示信息:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x', nargs=2)
>>> parser.add_argument('--foo', nargs=2, metavar=('bar', 'baz'))
>>> parser.print_help()
usage: PROG [-h] [-x X X] [--foo bar baz]

optional arguments:
 -h, --help     show this help message and exit
 -x X X
 --foo bar baz
@end example

@node dest,Action 类,metavar,add_argument 方法
@anchor{library/argparse dest}@anchor{1fda}
@subsubsection dest


大多数 @ref{68f,,ArgumentParser} 动作会添加一些值作为 @ref{1fc6,,parse_args()} 所返回对象的一个属性。 该属性的名称由 @ref{1fc5,,add_argument()} 的 @code{dest} 关键字参数确定。 对于位置参数动作，@code{dest} 通常会作为 @ref{1fc5,,add_argument()} 的第一个参数提供:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('bar')
>>> parser.parse_args(['XXX'])
Namespace(bar='XXX')
@end example

对于可选参数动作，@code{dest} 的值通常取自选项字符串。 @ref{68f,,ArgumentParser} 会通过接受第一个长选项字符串并去掉开头的 @code{--} 字符串来生成 @code{dest} 的值。 如果没有提供长选项字符串，则 @code{dest} 将通过接受第一个短选项字符串并去掉开头的 @code{-} 字符来获得。 任何内部的 @code{-} 字符都将被转换为 @code{_} 字符以确保字符串是有效的属性名称。 下面的例子显示了这种行为:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('-f', '--foo-bar', '--foo')
>>> parser.add_argument('-x', '-y')
>>> parser.parse_args('-f 1 -x 2'.split())
Namespace(foo_bar='1', x='2')
>>> parser.parse_args('--foo 1 -y 2'.split())
Namespace(foo_bar='1', x='2')
@end example

@code{dest} 允许提供自定义属性名称:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', dest='bar')
>>> parser.parse_args('--foo XXX'.split())
Namespace(bar='XXX')
@end example

@node Action 类,,dest,add_argument 方法
@anchor{library/argparse action-classes}@anchor{1fea}
@subsubsection Action 类


Action 类实现了 Action API，它是一个返回可调用对象的可调用对象，返回的可调用对象可处理来自命令行的参数。 任何遵循此 API 的对象均可作为 @code{action} 形参传给 @code{add_argument()}。

@geindex Action (argparse 中的类)
@anchor{library/argparse argparse Action}@anchor{1fe8}
@deffn {类} argparse.Action (option_strings, dest, nargs=None, const=None, default=None, type=None, choices=None, required=False, help=None, metavar=None)
@end deffn

Action 对象会被 ArgumentParser 用来表示解析从命令行中的一个或多个字符串中解析出单个参数所必须的信息。 Action 类必须接受两个位置参数以及传给 @ref{1fc5,,ArgumentParser.add_argument()} 的任何关键字参数，除了 @code{action} 本身。

Action 的实例（或作为or return value of any callable to the @code{action} 形参的任何可调用对象的返回值）应当定义 "dest", "option_strings", "default", "type", "required", "help" 等属性。 确保这些属性被定义的最容易方式是调用 @code{Action.__init__}。

Action 的实例应当为可调用对象，因此所有子类都必须重载 @code{__call__} 方法，该方法应当接受四个形参:


@itemize *

@item 
@code{parser} - 包含此动作的 ArgumentParser 对象。

@item 
@code{namespace} - 将由 @ref{1fc6,,parse_args()} 返回的 @ref{1fc8,,Namespace} 对象。 大多数动作会使用 @ref{1575,,setattr()} 为此对象添加属性。

@item 
@code{values} - 已关联的命令行参数，并提供相应的类型转换。 类型转换由 @ref{1fc5,,add_argument()} 的 @ref{1fd9,,type} 关键字参数来指定。

@item 
@code{option_string} - 被用来发起调用此动作的选项字符串。 @code{option_string} 参数是可选的，且此参数在动作关联到位置参数时将被略去。
@end itemize

@code{__call__} 方法可以执行任意动作，但通常将基于 @code{dest} 和 @code{values} 来设置 @code{namespace} 的属性。

@node parse_args 方法,其它实用工具,add_argument 方法,argparse --- 命令行选项、参数和子命令解析器
@anchor{library/argparse the-parse-args-method}@anchor{1feb}
@subsubsection parse_args() 方法


@geindex parse_args() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser parse_args}@anchor{1fc6}
@deffn {方法} ArgumentParser.parse_args (args=None, namespace=None)

将参数字符串转换为对象并将其设为命名空间的属性。 返回带有成员的命名空间。

之前对 @ref{1fc5,,add_argument()} 的调用决定了哪些对象被创建以及它们如何被赋值。 请参阅 @ref{1fc5,,add_argument()} 的文档了解详情。


@itemize *

@item 
@ref{1fec,,args} - 要解析的字符串列表。 默认值是从 @ref{bf4,,sys.argv} 获取。

@item 
@ref{1fed,,namespace} - 用于获取属性的对象。 默认值是一个新的空 @ref{1fc8,,Namespace} 对象。
@end itemize
@end deffn

@menu
* 选项值语法:: 
* 无效的参数:: 
* 包含 - 的参数:: 
* 参数缩写（前缀匹配）:: 
* 在 sys.argv 以外: 在 sys argv 以外. 
* 命名空间对象:: 

@end menu

@node 选项值语法,无效的参数,,parse_args 方法
@anchor{library/argparse option-value-syntax}@anchor{1fee}
@subsubsection 选项值语法


@ref{1fc6,,parse_args()} 方法支持多种指定选项值的方式（如果它接受选项的话）。 在最简单的情况下，选项和它的值是作为两个单独参数传入的:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x')
>>> parser.add_argument('--foo')
>>> parser.parse_args(['-x', 'X'])
Namespace(foo=None, x='X')
>>> parser.parse_args(['--foo', 'FOO'])
Namespace(foo='FOO', x=None)
@end example

对于长选项（名称长度超过一个字符的选项），选项和值也可以作为单个命令行参数传入，使用 @code{=} 分隔它们即可:

@example
>>> parser.parse_args(['--foo=FOO'])
Namespace(foo='FOO', x=None)
@end example

对于短选项（长度只有一个字符的选项），选项和它的值可以拼接在一起:

@example
>>> parser.parse_args(['-xX'])
Namespace(foo=None, x='X')
@end example

有些短选项可以使用单个 @code{-} 前缀来进行合并，如果仅有最后一个选项（或没有任何选项）需要值的话:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x', action='store_true')
>>> parser.add_argument('-y', action='store_true')
>>> parser.add_argument('-z')
>>> parser.parse_args(['-xyzZ'])
Namespace(x=True, y=True, z='Z')
@end example

@node 无效的参数,包含 - 的参数,选项值语法,parse_args 方法
@anchor{library/argparse invalid-arguments}@anchor{1fef}
@subsubsection 无效的参数


在解析命令行时，@ref{1fc6,,parse_args()} 会检测多种错误，包括有歧义的选项、无效的类型、无效的选项、错误的位置参数个数等等。 当遇到这种错误时，它将退出并打印出错误文本同时附带用法消息:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo', type=int)
>>> parser.add_argument('bar', nargs='?')

>>> # invalid type
>>> parser.parse_args(['--foo', 'spam'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: argument --foo: invalid int value: 'spam'

>>> # invalid option
>>> parser.parse_args(['--bar'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: no such option: --bar

>>> # wrong number of arguments
>>> parser.parse_args(['spam', 'badger'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: extra arguments found: badger
@end example

@node 包含 - 的参数,参数缩写（前缀匹配）,无效的参数,parse_args 方法
@anchor{library/argparse arguments-containing}@anchor{1ff0}
@subsubsection 包含 @code{-} 的参数


@ref{1fc6,,parse_args()} 方法会在用户明显出错时尝试给出错误信息，但某些情况本身就存在歧义。 例如，命令行参数 @code{-1} 可能是尝试指定一个选项也可能是尝试提供一个位置参数。 @ref{1fc6,,parse_args()} 方法在此会谨慎行事：位置参数只有在它们看起来像负数并且解析器中没有任何选项看起来像负数时才能以 @code{-} 打头。:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x')
>>> parser.add_argument('foo', nargs='?')

>>> # no negative number options, so -1 is a positional argument
>>> parser.parse_args(['-x', '-1'])
Namespace(foo=None, x='-1')

>>> # no negative number options, so -1 and -5 are positional arguments
>>> parser.parse_args(['-x', '-1', '-5'])
Namespace(foo='-5', x='-1')

>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-1', dest='one')
>>> parser.add_argument('foo', nargs='?')

>>> # negative number options present, so -1 is an option
>>> parser.parse_args(['-1', 'X'])
Namespace(foo=None, one='X')

>>> # negative number options present, so -2 is an option
>>> parser.parse_args(['-2'])
usage: PROG [-h] [-1 ONE] [foo]
PROG: error: no such option: -2

>>> # negative number options present, so both -1s are options
>>> parser.parse_args(['-1', '-1'])
usage: PROG [-h] [-1 ONE] [foo]
PROG: error: argument -1: expected one argument
@end example

如果你有必须以 @code{-} 打头的位置参数并且看起来不像负数，你可以插入伪参数 @code{'--'} 以告诉 @ref{1fc6,,parse_args()} 在那之后的内容是一个位置参数:

@example
>>> parser.parse_args(['--', '-f'])
Namespace(foo='-f', one=None)
@end example

@node 参数缩写（前缀匹配）,在 sys argv 以外,包含 - 的参数,parse_args 方法
@anchor{library/argparse argument-abbreviations-prefix-matching}@anchor{1ff1}@anchor{library/argparse prefix-matching}@anchor{690}
@subsubsection 参数缩写（前缀匹配）


@ref{1fc6,,parse_args()} 方法 @ref{691,,在默认情况下} 允许将长选项缩写为前缀，如果缩写无歧义（即前缀与一个特定选项相匹配）的话:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-bacon')
>>> parser.add_argument('-badger')
>>> parser.parse_args('-bac MMM'.split())
Namespace(bacon='MMM', badger=None)
>>> parser.parse_args('-bad WOOD'.split())
Namespace(bacon=None, badger='WOOD')
>>> parser.parse_args('-ba BA'.split())
usage: PROG [-h] [-bacon BACON] [-badger BADGER]
PROG: error: ambiguous option: -ba could match -badger, -bacon
@end example

可产生一个以上选项的参数会引发错误。 此特定可通过将 @ref{691,,allow_abbrev} 设为 @code{False} 来禁用。

@node 在 sys argv 以外,命名空间对象,参数缩写（前缀匹配）,parse_args 方法
@anchor{library/argparse args}@anchor{1fec}@anchor{library/argparse beyond-sys-argv}@anchor{1ff2}
@subsubsection 在 @code{sys.argv} 以外


有时在 @ref{bf4,,sys.argv} 以外用 ArgumentParser 解析参数也是有用的。 这可以通过将一个字符串列表传给 @ref{1fc6,,parse_args()} 来实现。 它适用于在交互提示符下进行检测:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument(
...     'integers', metavar='int', type=int, choices=range(10),
...     nargs='+', help='an integer in the range 0..9')
>>> parser.add_argument(
...     '--sum', dest='accumulate', action='store_const', const=sum,
...     default=max, help='sum the integers (default: find the max)')
>>> parser.parse_args(['1', '2', '3', '4'])
Namespace(accumulate=<built-in function max>, integers=[1, 2, 3, 4])
>>> parser.parse_args(['1', '2', '3', '4', '--sum'])
Namespace(accumulate=<built-in function sum>, integers=[1, 2, 3, 4])
@end example

@node 命名空间对象,,在 sys argv 以外,parse_args 方法
@anchor{library/argparse namespace}@anchor{1fed}@anchor{library/argparse the-namespace-object}@anchor{1ff3}
@subsubsection 命名空间对象


@geindex Namespace (argparse 中的类)
@anchor{library/argparse argparse Namespace}@anchor{1fc8}
@deffn {类} argparse.Namespace

由 @ref{1fc6,,parse_args()} 默认使用的简单类，可创建一个存放属性的对象并将其返回。
@end deffn

这个类被有意做得很简单，只是一个具有可读字符串表示形式的 @ref{2b0,,object}。 如果你更喜欢类似字典的属性视图，你可以使用标准 Python 中惯常的 @ref{fca,,vars()}:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> args = parser.parse_args(['--foo', 'BAR'])
>>> vars(args)
@{'foo': 'BAR'@}
@end example

另一个用处是让 @ref{68f,,ArgumentParser} 为一个已存在对象而不是为一个新的 @ref{1fc8,,Namespace} 对象的属性赋值。 这可以通过指定 @code{namespace=} 关键字参数来实现:

@example
>>> class C:
...     pass
...
>>> c = C()
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.parse_args(args=['--foo', 'BAR'], namespace=c)
>>> c.foo
'BAR'
@end example

@node 其它实用工具,升级 optparse 代码,parse_args 方法,argparse --- 命令行选项、参数和子命令解析器
@anchor{library/argparse other-utilities}@anchor{1ff4}
@subsubsection 其它实用工具


@menu
* 子命令:: 
* FileType 对象:: 
* 参数组:: 
* 互斥:: 
* 解析器默认值:: 
* 打印帮助:: 
* 部分解析:: 
* 自定义文件解析:: 
* 退出方法:: 
* 混合解析:: 

@end menu

@node 子命令,FileType 对象,,其它实用工具
@anchor{library/argparse sub-commands}@anchor{1ff5}
@subsubsection 子命令


@geindex add_subparsers() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser add_subparsers}@anchor{49f}
@deffn {方法} ArgumentParser.add_subparsers ([title][, description][, prog][, parser_class][, action][, option_string][, dest][, required][, help][, metavar])

许多程序都会将其功能拆分为一系列子命令，例如，@code{svn} 程序包含的子命令有 @code{svn checkout}, @code{svn update} 和 @code{svn commit}。 当一个程序能执行需要多组不同种类命令行参数时这种拆分功能的方式是一个非常好的主意。 @ref{68f,,ArgumentParser} 通过 @ref{49f,,add_subparsers()} 方法支持创建这样的子命令。 @ref{49f,,add_subparsers()} 方法通常不带参数地调用并返回一个特殊的动作对象。 这种对象只有一个方法 @code{add_parser()}，它接受一个命令名称和任意多个 @ref{68f,,ArgumentParser} 构造器参数，并返回一个可以通常方式进行修改的 @ref{68f,,ArgumentParser} 对象。

形参的描述


@itemize *

@item 
title - 输出帮助的子解析器分组的标题；如果提供了描述则默认为 "subcommands"，否则使用位置参数的标题

@item 
description - 输出帮助中对子解析器的描述，默认为 @code{None}

@item 
prog - 将与子命令帮助一同显示的用法信息，默认为程序名称和子解析器参数之前的任何位置参数。

@item 
parser_class - 将被用于创建子解析器实例的类，默认为当前解析器类（例如 ArgumentParser）

@item 
@ref{1fe0,,action} - 当此参数在命令行中出现时要执行动作的基本类型

@item 
@ref{1fda,,dest} - 将被用于保存子命令名称的属性名；默认为 @code{None} 即不保存任何值

@item 
@ref{1fe5,,required} - 是否必须要提供子命令，默认为 @code{False} (在 3.7 中新增)

@item 
@ref{1fe6,,help} - 在输出帮助中的子解析器分组帮助信息，默认为 @code{None}

@item 
@ref{1fe7,,metavar} - 帮助信息中表示可用子命令的字符串；默认为 @code{None} 并以 @{cmd1, cmd2, ..@} 的形式表示子命令
@end itemize

一些使用示例:

@example
>>> # create the top-level parser
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo', action='store_true', help='foo help')
>>> subparsers = parser.add_subparsers(help='sub-command help')
>>>
>>> # create the parser for the "a" command
>>> parser_a = subparsers.add_parser('a', help='a help')
>>> parser_a.add_argument('bar', type=int, help='bar help')
>>>
>>> # create the parser for the "b" command
>>> parser_b = subparsers.add_parser('b', help='b help')
>>> parser_b.add_argument('--baz', choices='XYZ', help='baz help')
>>>
>>> # parse some argument lists
>>> parser.parse_args(['a', '12'])
Namespace(bar=12, foo=False)
>>> parser.parse_args(['--foo', 'b', '--baz', 'Z'])
Namespace(baz='Z', foo=True)
@end example

请注意 @ref{1fc6,,parse_args()} 返回的对象将只包含主解析器和由命令行所选择的子解析器的属性（而没有任何其他子解析器）。 因此在上面的例子中，当指定了 @code{a} 命令时，将只存在 @code{foo} 和 @code{bar} 属性，而当指定了 @code{b} 命令时，则只存在 @code{foo} 和 @code{baz} 属性。

类似地，当从一个子解析器请求帮助消息时，只有该特定解析器的帮助消息会被打印出来。 帮助消息将不包括父解析器或同级解析器的消息。 （每个子解析器命令一条帮助消息，但是，也可以像上面那样通过提供 @code{help=} 参数给 @code{add_parser()} 来给出。）

@example
>>> parser.parse_args(['--help'])
usage: PROG [-h] [--foo] @{a,b@} ...

positional arguments:
  @{a,b@}   sub-command help
    a     a help
    b     b help

optional arguments:
  -h, --help  show this help message and exit
  --foo   foo help

>>> parser.parse_args(['a', '--help'])
usage: PROG a [-h] bar

positional arguments:
  bar     bar help

optional arguments:
  -h, --help  show this help message and exit

>>> parser.parse_args(['b', '--help'])
usage: PROG b [-h] [--baz @{X,Y,Z@}]

optional arguments:
  -h, --help     show this help message and exit
  --baz @{X,Y,Z@}  baz help
@end example

@ref{49f,,add_subparsers()} 方法也支持 @code{title} 和 @code{description} 关键字参数。 当两者都存在时，子解析器的命令将出现在输出帮助消息中它们自己的分组内。 例如:

@example
>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers(title='subcommands',
...                                    description='valid subcommands',
...                                    help='additional help')
>>> subparsers.add_parser('foo')
>>> subparsers.add_parser('bar')
>>> parser.parse_args(['-h'])
usage:  [-h] @{foo,bar@} ...

optional arguments:
  -h, --help  show this help message and exit

subcommands:
  valid subcommands

  @{foo,bar@}   additional help
@end example

此外，@code{add_parser} 还支持附加的 @code{aliases} 参数，它允许多个字符串指向同一子解析器。 这个例子类似于 @code{svn}，将别名 @code{co} 设为 @code{checkout} 的缩写形式:

@example
>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers()
>>> checkout = subparsers.add_parser('checkout', aliases=['co'])
>>> checkout.add_argument('foo')
>>> parser.parse_args(['co', 'bar'])
Namespace(foo='bar')
@end example

一个特别有效的处理子命令的方式是将 @ref{49f,,add_subparsers()} 方法与对 @ref{1fdc,,set_defaults()} 的调用结合起来使用，这样每个子解析器就能知道应当执行哪个 Python 函数。 例如:

@example
>>> # sub-command functions
>>> def foo(args):
...     print(args.x * args.y)
...
>>> def bar(args):
...     print('((%s))' % args.z)
...
>>> # create the top-level parser
>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers()
>>>
>>> # create the parser for the "foo" command
>>> parser_foo = subparsers.add_parser('foo')
>>> parser_foo.add_argument('-x', type=int, default=1)
>>> parser_foo.add_argument('y', type=float)
>>> parser_foo.set_defaults(func=foo)
>>>
>>> # create the parser for the "bar" command
>>> parser_bar = subparsers.add_parser('bar')
>>> parser_bar.add_argument('z')
>>> parser_bar.set_defaults(func=bar)
>>>
>>> # parse the args and call whatever function was selected
>>> args = parser.parse_args('foo 1 -x 2'.split())
>>> args.func(args)
2.0
>>>
>>> # parse the args and call whatever function was selected
>>> args = parser.parse_args('bar XYZYX'.split())
>>> args.func(args)
((XYZYX))
@end example

通过这种方式，你可以在参数解析结束后让 @ref{1fc6,,parse_args()} 执行调用适当函数的任务。 像这样将函数关联到动作通常是你处理每个子解析器的不同动作的最简便方式。 但是，如果有必要检查被发起调用的子解析器的名称，则 @ref{49f,,add_subparsers()} 调用的 @code{dest} 关键字参数将可实现:

@example
>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers(dest='subparser_name')
>>> subparser1 = subparsers.add_parser('1')
>>> subparser1.add_argument('-x')
>>> subparser2 = subparsers.add_parser('2')
>>> subparser2.add_argument('y')
>>> parser.parse_args(['2', 'frobble'])
Namespace(subparser_name='2', y='frobble')
@end example


在 3.7 版更改: 新增 @emph{required} 关键字参数。

@end deffn

@node FileType 对象,参数组,子命令,其它实用工具
@anchor{library/argparse filetype-objects}@anchor{1ff6}
@subsubsection FileType 对象


@geindex FileType (argparse 中的类)
@anchor{library/argparse argparse FileType}@anchor{81a}
@deffn {类} argparse.FileType (mode='r', bufsize=-1, encoding=None, errors=None)

@ref{81a,,FileType} 工厂类用于创建可作为 @ref{1fc5,,ArgumentParser.add_argument()} 的 type 参数传入的对象。 以 @ref{81a,,FileType} 对象作为其类型的参数将使用命令行参数以所请求模式、缓冲区大小、编码格式和错误处理方式打开文件（请参阅 @ref{4ea,,open()} 函数了解详情）:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--raw', type=argparse.FileType('wb', 0))
>>> parser.add_argument('out', type=argparse.FileType('w', encoding='UTF-8'))
>>> parser.parse_args(['--raw', 'raw.dat', 'file.txt'])
Namespace(out=<_io.TextIOWrapper name='file.txt' mode='w' encoding='UTF-8'>, raw=<_io.FileIO name='raw.dat' mode='wb'>)
@end example

FileType 对象能理解伪参数 @code{'-'} 并会自动将其转换为 @code{sys.stdin} 用于可读的 @ref{81a,,FileType} 对象，或是 @code{sys.stdout} 用于可写的 @ref{81a,,FileType} 对象:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('infile', type=argparse.FileType('r'))
>>> parser.parse_args(['-'])
Namespace(infile=<_io.TextIOWrapper name='<stdin>' encoding='UTF-8'>)
@end example


3.4 新版功能: @emph{encodings} 和 @emph{errors} 关键字参数。

@end deffn

@node 参数组,互斥,FileType 对象,其它实用工具
@anchor{library/argparse argument-groups}@anchor{1ff7}
@subsubsection 参数组


@geindex add_argument_group() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser add_argument_group}@anchor{1ff8}
@deffn {方法} ArgumentParser.add_argument_group (title=None, description=None)

在默认情况下，@ref{68f,,ArgumentParser} 会在显示帮助消息时将命令行参数分为“位置参数”和“可选参数”两组。 当存在比默认更好的参数分组概念时，可以使用 @ref{1ff8,,add_argument_group()} 方法来创建适当的分组:

@example
>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> group = parser.add_argument_group('group')
>>> group.add_argument('--foo', help='foo help')
>>> group.add_argument('bar', help='bar help')
>>> parser.print_help()
usage: PROG [--foo FOO] bar

group:
  bar    bar help
  --foo FOO  foo help
@end example

@ref{1ff8,,add_argument_group()} 方法返回一个具有 @ref{1fc5,,add_argument()} 方法的参数分组对象，这与常规的 @ref{68f,,ArgumentParser} 一样。 当一个参数被加入分组时，解析器会将它视为一个正常的参数，但是会在不同的帮助消息分组中显示该参数。 @ref{1ff8,,add_argument_group()} 方法接受 @emph{title} 和 @emph{description} 参数，它们可被用来定制显示内容:

@example
>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> group1 = parser.add_argument_group('group1', 'group1 description')
>>> group1.add_argument('foo', help='foo help')
>>> group2 = parser.add_argument_group('group2', 'group2 description')
>>> group2.add_argument('--bar', help='bar help')
>>> parser.print_help()
usage: PROG [--bar BAR] foo

group1:
  group1 description

  foo    foo help

group2:
  group2 description

  --bar BAR  bar help
@end example

请注意任意不在你的自定义分组中的参数最终都将回到通常的“位置参数”和“可选参数”分组中。
@end deffn

@node 互斥,解析器默认值,参数组,其它实用工具
@anchor{library/argparse mutual-exclusion}@anchor{1ff9}
@subsubsection 互斥


@geindex add_mutually_exclusive_group() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser add_mutually_exclusive_group}@anchor{1ffa}
@deffn {方法} ArgumentParser.add_mutually_exclusive_group (required=False)

创建一个互斥组。 @ref{6,,argparse} 将会确保互斥组中只有一个参数在命令行中可用:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> group = parser.add_mutually_exclusive_group()
>>> group.add_argument('--foo', action='store_true')
>>> group.add_argument('--bar', action='store_false')
>>> parser.parse_args(['--foo'])
Namespace(bar=True, foo=True)
>>> parser.parse_args(['--bar'])
Namespace(bar=False, foo=False)
>>> parser.parse_args(['--foo', '--bar'])
usage: PROG [-h] [--foo | --bar]
PROG: error: argument --bar: not allowed with argument --foo
@end example

@ref{1ffa,,add_mutually_exclusive_group()} 方法也接受一个 @emph{required} 参数，表示在互斥组中至少有一个参数是需要的:

@example
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> group = parser.add_mutually_exclusive_group(required=True)
>>> group.add_argument('--foo', action='store_true')
>>> group.add_argument('--bar', action='store_false')
>>> parser.parse_args([])
usage: PROG [-h] (--foo | --bar)
PROG: error: one of the arguments --foo --bar is required
@end example

注意，目前互斥参数组不支持 @ref{1ff8,,add_argument_group()} 的 @emph{title} 和 @emph{description} 参数。
@end deffn

@node 解析器默认值,打印帮助,互斥,其它实用工具
@anchor{library/argparse parser-defaults}@anchor{1ffb}
@subsubsection 解析器默认值


@geindex set_defaults() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser set_defaults}@anchor{1fdc}
@deffn {方法} ArgumentParser.set_defaults (**kwargs)

在大多数时候，@ref{1fc6,,parse_args()} 所返回对象的属性将完全通过检查命令行参数和参数动作来确定。 @ref{1fdc,,set_defaults()} 则允许加入一些无须任何命令行检查的额外属性:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', type=int)
>>> parser.set_defaults(bar=42, baz='badger')
>>> parser.parse_args(['736'])
Namespace(bar=42, baz='badger', foo=736)
@end example

请注意解析器层级的默认值总是会覆盖参数层级的默认值:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default='bar')
>>> parser.set_defaults(foo='spam')
>>> parser.parse_args([])
Namespace(foo='spam')
@end example

解析器层级默认值在需要多解析器时会特别有用。 请参阅 @ref{49f,,add_subparsers()} 方法了解此类型的一个示例。
@end deffn

@geindex get_default() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser get_default}@anchor{1ffc}
@deffn {方法} ArgumentParser.get_default (dest)

获取一个命名空间属性的默认值，该值是由 @ref{1fc5,,add_argument()} 或 @ref{1fdc,,set_defaults()} 设置的:

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default='badger')
>>> parser.get_default('foo')
'badger'
@end example
@end deffn

@node 打印帮助,部分解析,解析器默认值,其它实用工具
@anchor{library/argparse printing-help}@anchor{1ffd}
@subsubsection 打印帮助


在大多数典型应用中，@ref{1fc6,,parse_args()} 将负责任何用法和错误消息的格式化和打印。 但是，也可使用某些其他格式化方法:

@geindex print_usage() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser print_usage}@anchor{1ffe}
@deffn {方法} ArgumentParser.print_usage (file=None)

打印一段简短描述，说明应当如何在命令行中发起调用 @ref{68f,,ArgumentParser}。 如果 @emph{file} 为 @code{None}，则默认使用 @ref{307,,sys.stdout}。
@end deffn

@geindex print_help() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser print_help}@anchor{1fff}
@deffn {方法} ArgumentParser.print_help (file=None)

打印一条帮助消息，包括程序用法和通过 @ref{68f,,ArgumentParser} 注册的相关参数信息。 如果 @emph{file} 为 @code{None}，则默认使用 @ref{307,,sys.stdout}。
@end deffn

还存在这些方法的几个变化形式，它们只返回字符串而不打印消息:

@geindex format_usage() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser format_usage}@anchor{2000}
@deffn {方法} ArgumentParser.format_usage ()

返回一个包含简短描述的字符串，说明应当如何在命令行中发起调用 @ref{68f,,ArgumentParser}。
@end deffn

@geindex format_help() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser format_help}@anchor{2001}
@deffn {方法} ArgumentParser.format_help ()

反回一个包含帮助消息的字符串，包括程序用法和通过 @ref{68f,,ArgumentParser} 注册的相关参数信息。
@end deffn

@node 部分解析,自定义文件解析,打印帮助,其它实用工具
@anchor{library/argparse partial-parsing}@anchor{2002}
@subsubsection 部分解析


@geindex parse_known_args() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser parse_known_args}@anchor{2003}
@deffn {方法} ArgumentParser.parse_known_args (args=None, namespace=None)
@end deffn

有时一个脚本可能只解析部分命令行参数，而将其余的参数继续传递给另一个脚本或程序。 在这种情况下，@ref{2003,,parse_known_args()} 方法会很有用处。 它的作用方式很类似 @ref{1fc6,,parse_args()} 但区别在于当存在额外参数时它不会产生错误。 而是会返回一个由两个条目构成的元组，其中包含带成员的命名空间和剩余参数字符串的列表。

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_true')
>>> parser.add_argument('bar')
>>> parser.parse_known_args(['--foo', '--badger', 'BAR', 'spam'])
(Namespace(bar='BAR', foo=True), ['--badger', 'spam'])
@end example

@cartouche
@quotation 警告 
@ref{690,,前缀匹配} 规则应用于 @code{parse_known_args()}。 一个选项即使只是已知选项的前缀部分解析器也能识别该选项，不会将其放入剩余参数列表。
@end quotation
@end cartouche

@node 自定义文件解析,退出方法,部分解析,其它实用工具
@anchor{library/argparse customizing-file-parsing}@anchor{2004}
@subsubsection 自定义文件解析


@geindex convert_arg_line_to_args() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser convert_arg_line_to_args}@anchor{1fdb}
@deffn {方法} ArgumentParser.convert_arg_line_to_args (arg_line)

从文件读取的参数（见 @ref{68f,,ArgumentParser} 的 @emph{fromfile_prefix_chars} 关键字参数）将是一行读取一个参数。 @ref{1fdb,,convert_arg_line_to_args()} 可被重载以使用更复杂的读取方式。

此方法接受从参数文件读取的字符串形式的单个参数 @emph{arg_line}。 它返回从该字符串解析出的参数列表。 此方法将在每次按顺序从参数文件读取一行时被调用一次。

此方法的一个有用的重载是将每个以空格分隔的单词视为一个参数。 下面的例子演示了如何实现此重载:

@example
class MyArgumentParser(argparse.ArgumentParser):
    def convert_arg_line_to_args(self, arg_line):
        return arg_line.split()
@end example
@end deffn

@node 退出方法,混合解析,自定义文件解析,其它实用工具
@anchor{library/argparse exiting-methods}@anchor{2005}
@subsubsection 退出方法


@geindex exit() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser exit}@anchor{2006}
@deffn {方法} ArgumentParser.exit (status=0, message=None)

此方法将终结程序，退出时附带指定的 @emph{status}，并且如果给出了 @emph{message} 则会在退出前将其打印输出。 用户可重载此方法以不同方式来处理这些步骤:

@example
class ErrorCatchingArgumentParser(argparse.ArgumentParser):
    def exit(self, status=0, message=None):
        if status:
            raise Exception(f'Exiting because of an error: @{message@}')
        exit(status)
@end example
@end deffn

@geindex error() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser error}@anchor{2007}
@deffn {方法} ArgumentParser.error (message)

此方法将向标准错误打印包括 @emph{message} 的用法消息并附带状态码 2 终结程序。
@end deffn

@node 混合解析,,退出方法,其它实用工具
@anchor{library/argparse intermixed-parsing}@anchor{2008}
@subsubsection 混合解析


@geindex parse_intermixed_args() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser parse_intermixed_args}@anchor{33e}
@deffn {方法} ArgumentParser.parse_intermixed_args (args=None, namespace=None)
@end deffn

@geindex parse_known_intermixed_args() (argparse.ArgumentParser 方法)
@anchor{library/argparse argparse ArgumentParser parse_known_intermixed_args}@anchor{2009}
@deffn {方法} ArgumentParser.parse_known_intermixed_args (args=None, namespace=None)
@end deffn

许多 Unix 命令允许用户混用可选参数与位置参数。 @ref{33e,,parse_intermixed_args()} 和 @ref{2009,,parse_known_intermixed_args()} 方法均支持这种解析风格。

这些解析器并不支持所有的 argparse 特性，并且当未支持的特性被使用时将会引发异常。 特别地，子解析器，@code{argparse.REMAINDER} 以及同时包括可选与位置参数的互斥分组是不受支持的。

下面的例子显示了 @ref{2003,,parse_known_args()} 与 @ref{33e,,parse_intermixed_args()} 之间的差异：前者会将 @code{['2', '3']} 返回为未解析的参数，而后者会将所有位置参数收集至 @code{rest} 中。

@example
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.add_argument('cmd')
>>> parser.add_argument('rest', nargs='*', type=int)
>>> parser.parse_known_args('doit 1 --foo bar 2 3'.split())
(Namespace(cmd='doit', foo='bar', rest=[1]), ['2', '3'])
>>> parser.parse_intermixed_args('doit 1 --foo bar 2 3'.split())
Namespace(cmd='doit', foo='bar', rest=[1, 2, 3])
@end example

@ref{2009,,parse_known_intermixed_args()} 返回由两个条目组成的元组，其中包含带成员的命名空间以及剩余参数字符串列表。 当存在任何剩余的未解析参数字符串时 @ref{33e,,parse_intermixed_args()} 将引发一个错误。


3.7 新版功能.


@node 升级 optparse 代码,,其它实用工具,argparse --- 命令行选项、参数和子命令解析器
@anchor{library/argparse id2}@anchor{200a}@anchor{library/argparse upgrading-optparse-code}@anchor{b22}
@subsubsection 升级 optparse 代码


起初，@ref{6,,argparse} 曾经尝试通过 @ref{c3,,optparse} 来维持兼容性。 但是，@ref{c3,,optparse} 很难透明地扩展，特别是那些为支持新的 @code{nargs=} 描述方式和更好的用法消息所需的修改。当When most everything in @ref{c3,,optparse} 中几乎所有内容都已被复制粘贴或打上补丁时，维持向下兼容看来已是不切实际的。

@ref{6,,argparse} 模块在许多方面对标准库的 @ref{c3,,optparse} 模块进行了增强，包括:


@itemize *

@item 
处理位置参数。

@item 
支持子命令。

@item 
允许替代选项前缀例如 @code{+} 和 @code{/}。

@item 
处理零个或多个以及一个或多个风格的参数。

@item 
生成更具信息量的用法消息。

@item 
提供用于定制 @code{type} 和 @code{action} 的更为简单的接口。
@end itemize

从 @ref{c3,,optparse} 到 @ref{6,,argparse} 的部分升级路径:


@itemize *

@item 
将所有 @ref{200b,,optparse.OptionParser.add_option()} 调用替换为 @ref{1fc5,,ArgumentParser.add_argument()} 调用。

@item 
将 @code{(options, args) = parser.parse_args()} 替换为 @code{args = parser.parse_args()} 并为位置参数添加额外的 @ref{1fc5,,ArgumentParser.add_argument()} 调用。 请注意之前所谓的 @code{options} 在 @ref{6,,argparse} 上下文中被称为 @code{args}。

@item 
通过使用 @ref{33e,,parse_intermixed_args()} 而非 @ref{1fc6,,parse_args()} 来替换 @ref{200c,,optparse.OptionParser.disable_interspersed_args()}。

@item 
将回调动作和 @code{callback_*} 关键字参数替换为 @code{type} 或 @code{action} 参数。

@item 
将 @code{type} 关键字参数字符串名称替换为相应的类型对象（例如 int, float, complex 等）。

@item 
将 @code{optparse.Values} 替换为 @ref{1fc8,,Namespace} 并将 @code{optparse.OptionError} 和 @code{optparse.OptionValueError} 替换为 @code{ArgumentError}。

@item 
将隐式参数字符串例如使用标准 Python 字典语法的 @code{%default} 或 @code{%prog} 替换为格式字符串，即 @code{%(default)s} 和 @code{%(prog)s}。

@item 
将 OptionParser 构造器 @code{version} 参数替换为对 @code{parser.add_argument('--version', action='version', version='<the version>')} 的调用。
@end itemize

@node getopt --- C 风格的命令行选项解析器,logging --- Python 的日志记录工具,argparse --- 命令行选项、参数和子命令解析器,通用操作系统服务
@anchor{library/getopt doc}@anchor{200d}@anchor{library/getopt getopt-c-style-parser-for-command-line-options}@anchor{200e}@anchor{library/getopt module-getopt}@anchor{87}
@subsection @code{getopt} --- C 风格的命令行选项解析器


@geindex getopt (模块)

@strong{源代码:} Lib/getopt.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/getopt.py}

@cartouche
@quotation 注解 
@ref{87,,getopt} 模块是一个命令行选项解析器，其 API 设计会让 C @code{getopt()} 函数的用户感到熟悉。 不熟悉 C @code{getopt()} 函数或者希望写更少代码并获得更完善帮助和错误消息的用户应当考虑改用 @ref{6,,argparse} 模块。
@end quotation
@end cartouche


__________________________________________________________________


此模块可协助脚本解析 @code{sys.argv} 中的命令行参数。 它支持与 Unix @code{getopt()} 函数相同的惯例（包括形式如 '@code{-}' 与 '@code{--}' 的参数的特殊含义）。 也能通过可选的第三个参数来使用与 GNU 软件所支持形式相类似的长选项。

此模块提供了两个函数和一个异常:

@geindex getopt() (在 getopt 模块中)
@anchor{library/getopt getopt getopt}@anchor{200f}
@deffn {函数} getopt.getopt (args, shortopts, longopts=[])

解析命令行选项与形参列表。 @emph{args} 为要解析的参数列表，不包含最开头的对正在运行的程序的引用。 通常这意味着 @code{sys.argv[1:]}。 @emph{shortopts} 为脚本所要识别的字母选项，包含要求后缀一个冒号 (@code{':'}；即与 Unix @code{getopt()} 所用的格式相同) 的选项。

@cartouche
@quotation 注解 
与 GNU @code{getopt()} 不同，在非选项参数之后，所有后续参数都会被视为非选项。 这类似于非 GNU Unix 系统的运作方式。
@end quotation
@end cartouche

如果指定了 @emph{longopts}，则必须为一个由应当被支持的长选项名称组成的列表。 开头的 @code{'--'} 字符不应被包括在选项名称中。 要求参数的长选项后应当带一个等号 (@code{'='})。 可选参数不被支持。 如果想仅接受长选项，则 @emph{shortopts} 应为一个空字符串。 命令行中的长选项只要提供了恰好能匹配可接受选项之一的选项名称前缀即可被识别。 举例来说，如果 @emph{longopts} 为 @code{['foo', 'frob']}，则选项 @code{--fo} 将匹配为 @code{--foo}，但 @code{--f} 将不能得到唯一匹配，因此将引发 @ref{2010,,GetoptError}。

返回值由两个元素组成：第一个是 @code{(option, value)} 对的列表；第二个是在去除该选项列表后余下的程序参数列表（这也就是 @emph{args} 的尾部切片）。每个被返回的选项与值对的第一个元素是选项，短选项前缀一个连字符 (例如 @code{'-x'})，长选项则前缀两个连字符 (例如 @code{'--long-option'})，第二个元素是选项参数，如果选项不带参数则为空字符串。 列表中选项的排列顺序与它们被解析的顺序相同，因此允许多次出现。 长选项与短选项可以混用。
@end deffn

@geindex gnu_getopt() (在 getopt 模块中)
@anchor{library/getopt getopt gnu_getopt}@anchor{2011}
@deffn {函数} getopt.gnu_getopt (args, shortopts, longopts=[])

此函数与 @ref{87,,getopt()} 类似，区别在于它默认使用 GNU 风格的扫描模式。 这意味着选项和非选项参数可能会混在一起。 @ref{87,,getopt()} 函数将在遇到非选项参数时立即停止处理选项。

如果选项字符串的第一个字符为 @code{'+'}，或者如果设置了环境变量 
@geindex POSIXLY_CORRECT
@geindex 环境变量; POSIXLY_CORRECT
@code{POSIXLY_CORRECT}，则选项处理会在遇到非选项参数时立即停止。
@end deffn

@geindex GetoptError
@anchor{library/getopt getopt GetoptError}@anchor{2010}
@deffn {例外} getopt.GetoptError

This is raised当参数列表中出现不可识别的选项或者当一个需要参数的选项未带参数时将引发此异常。 此异常的参数是一个指明错误原因的字符串。 对于长选项，将一个参数传给不需要参数的选项也将导致引发此异常。 @code{msg} 和 @code{opt} 属性会给出错误消息和关联的选项；如果没有关联到异常的特定选项，则 @code{opt} 将为空字符串。
@end deffn

@c XXX deprecated?

@geindex error
@anchor{library/getopt getopt error}@anchor{2012}
@deffn {例外} getopt.error

@ref{2010,,GetoptError} 的别名；用于向后兼容。
@end deffn

一个仅使用 Unix 风格选项的例子:

@example
>>> import getopt
>>> args = '-a -b -cfoo -d bar a1 a2'.split()
>>> args
['-a', '-b', '-cfoo', '-d', 'bar', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'abc:d:')
>>> optlist
[('-a', '@w{'}), ('-b', '@w{'}), ('-c', 'foo'), ('-d', 'bar')]
>>> args
['a1', 'a2']
@end example

使用长选项名也同样容易:

@example
>>> s = '--condition=foo --testing --output-file abc.def -x a1 a2'
>>> args = s.split()
>>> args
['--condition=foo', '--testing', '--output-file', 'abc.def', '-x', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'x', [
...     'condition=', 'output-file=', 'testing'])
>>> optlist
[('--condition', 'foo'), ('--testing', '@w{'}), ('--output-file', 'abc.def'), ('-x', '@w{'})]
>>> args
['a1', 'a2']
@end example

在脚本中，典型的用法类似这样:

@example
import getopt, sys

def main():
    try:
        opts, args = getopt.getopt(sys.argv[1:], "ho:v", ["help", "output="])
    except getopt.GetoptError as err:
        # print help information and exit:
        print(err)  # will print something like "option -a not recognized"
        usage()
        sys.exit(2)
    output = None
    verbose = False
    for o, a in opts:
        if o == "-v":
            verbose = True
        elif o in ("-h", "--help"):
            usage()
            sys.exit()
        elif o in ("-o", "--output"):
            output = a
        else:
            assert False, "unhandled option"
    # ...

if __name__ == "__main__":
    main()
@end example

请注意通过 @ref{6,,argparse} 模块可以使用更少的代码并附带更详细的帮助与错误消息生成等价的命令行接口:

@example
import argparse

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('-o', '--output')
    parser.add_argument('-v', dest='verbose', action='store_true')
    args = parser.parse_args()
    # ... do something with args.output ...
    # ... do something with args.verbose ..
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{6,,argparse}

替代的命令行选项和参数解析库。
@end table


@node logging --- Python 的日志记录工具,logging config --- 日志记录配置,getopt --- C 风格的命令行选项解析器,通用操作系统服务
@anchor{library/logging doc}@anchor{2013}@anchor{library/logging logging-logging-facility-for-python}@anchor{2014}@anchor{library/logging module-logging}@anchor{aa}
@subsection @code{logging} --- Python 的日志记录工具


@geindex logging (模块)

@strong{源代码：} Lib/logging/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/logging/__init__.py}

@geindex Errors; logging

@subsubheading Important



此页面仅包含 API 参考信息。教程信息和更多高级用法的讨论，请参阅


@itemize *

@item 
@ref{b6b,,基础教程}

@item 
@ref{b6c,,进阶教程}

@item 
@ref{b6d,,日志操作手册}
@end itemize


__________________________________________________________________


这个模块为应用与库实现了灵活的事件日志系统的函数与类。

使用标准库提提供的 logging API 最主要的好处是，所有的 Python 模块都可能参与日志输出，包括你自己的日志消息和第三方模块的日志消息。

这个模块提供许多强大而灵活的功能。如果你对 logging 不太熟悉的话， 掌握它最好的方式就是查看它对应的教程（详见右侧的链接）。

该模块定义的基础类和函数都列在下面。


@itemize *

@item 
记录器暴露了应用程序代码直接使用的接口。

@item 
处理器将日志记录（由记录器创建）发送到适当的目标。

@item 
过滤器提供了更精细的附加功能，用于确定要输出的日志记录。

@item 
格式器指定最终输出中日志记录的样式。
@end itemize

@menu
* 记录器对象:: 
* 日志级别:: 
* 处理器对象:: 
* 格式器对象:: 
* Filter 对象:: 
* LogRecord 属性:: 
* LogRecord 属性: LogRecord 属性<2>. 
* LoggerAdapter 对象:: 
* 线程安全:: 
* 模块级别函数:: 
* 模块级属性:: 
* 与警告模块集成:: 

@end menu

@node 记录器对象,日志级别,,logging --- Python 的日志记录工具
@anchor{library/logging logger}@anchor{2015}@anchor{library/logging logger-objects}@anchor{2016}
@subsubsection 记录器对象


记录器有以下的属性和方法。注意 @emph{永远} 不要直接实例化记录器，应当通过模块级别的函数 @code{logging.getLogger(name)} 。多次使用相同的名字调用 @ref{2017,,getLogger()} 会一直返回相同的 Logger 对象的引用。

@code{name} 一般是句点分割的层级值, 像`@w{`}foo.bar.baz`@w{`} (尽管也可以只是普通的 @code{foo})。层次结构列表中位于下方的记录器是列表中较高位置的记录器的子级。例如，有个名叫 @code{foo} 的记录器，而名字是 @code{foo.bar}，@code{foo.bar.baz}，和 @code{foo.bam} 的记录器都是 @code{foo} 的子级。记录器的名字分级类似 Python 包的层级，如果您使用建议的结构 @code{logging.getLogger(__name__)} 在每个模块的基础上组织记录器，则与之完全相同。这是因为在模块里，@code{__name__} 是该模块在 Python 包命名空间中的名字。

@geindex Logger (logging 中的类)
@anchor{library/logging logging Logger}@anchor{39f}
@deffn {类} logging.Logger

@geindex propagate (logging.Logger 属性)
@anchor{library/logging logging Logger propagate}@anchor{2018}
@deffn {属性} propagate

如果这个属性为真，记录到这个记录器的事件除了会发送到此记录器的所有处理程序外，还会传递给更高级别（祖先）记录器的处理器，此外任何关联到这个记录器的处理器。消息会直接传递给祖先记录器的处理器 —— 不考虑祖先记录器的级别和过滤器。

如果为假，记录消息将不会传递给当前记录器的祖先记录器的处理器。

构造器将这个属性初始化为 @code{True}。

@cartouche
@quotation 注解 
如果你将一个处理器附加到一个记录器 @emph{和} 其一个或多个祖先记录器，它可能发出多次相同的记录。通常，您不需要将一个处理器附加到一个以上的记录器上 —— 如果您将它附加到记录器层次结构中最高的适当记录器上，则它将看到所有后代记录器记录的所有事件，前提是它们的传播设置保留为 @code{True}。一种常见的方案是仅将处理程序附加到根记录器，通过传播来处理其余部分。
@end quotation
@end cartouche
@end deffn

@geindex setLevel() (logging.Logger 方法)
@anchor{library/logging logging Logger setLevel}@anchor{2019}
@deffn {方法} setLevel (level)

给记录器设置阈值为 @emph{level} 。日志等级小于 @emph{level} 会被忽略。严重性为 @emph{level} 或更高的日志消息将由该记录器的任何一个或多个处理器发出，除非将处理器的级别设置为比 @emph{level} 更高的级别。

创建记录器时，级别默认设置为 @code{NOTSET} （当记录器是根记录器时，将处理所有消息；如果记录器不是根记录器，则将委托给父级）。请注意，根记录器的默认级别为 @code{WARNING}。

委派给父级的意思是如果一个记录器的级别设置为 NOTSET，将遍历其祖先记录器，直到找到级别不是 NOTSET 的记录器，或者到根记录器为止。

如果发现某个父级的级别不是 NOTSET ，那么该父级的级别将被视为发起搜索的记录器的有效级别，并用于确定如何处理日志事件。

如果搜索到达根记录器，并且其级别为 NOTSET，则将处理所有消息。否则，将使用根记录器的级别作为有效级别。

参见 @ref{201a,,日志级别} 级别列表。


在 3.2 版更改: 现在 @emph{level} 参数可以接受形如 'INFO' 的级别字符串表示形式，以代替形如 @code{INFO} 的整数常量。 但是请注意，级别在内部存储为整数，并且 @ref{201b,,getEffectiveLevel()} 和 @ref{201c,,isEnabledFor()} 等方法的传入/返回值也为整数。

@end deffn

@geindex isEnabledFor() (logging.Logger 方法)
@anchor{library/logging logging Logger isEnabledFor}@anchor{201c}
@deffn {方法} isEnabledFor (level)

指示此记录器是否将处理级别为 @emph{level} 的消息。此方法首先检查由 @code{logging.disable(level)} 设置的模块级的级别，然后检查由 @ref{201b,,getEffectiveLevel()} 确定的记录器的有效级别。
@end deffn

@geindex getEffectiveLevel() (logging.Logger 方法)
@anchor{library/logging logging Logger getEffectiveLevel}@anchor{201b}
@deffn {方法} getEffectiveLevel ()

指示此记录器的有效级别。如果通过 @ref{2019,,setLevel()} 设置了除 @code{NOTSET} 以外的值，则返回该值。否则，将层次结构遍历到根，直到找到除 @code{NOTSET} 以外的其他值，然后返回该值。返回的值是一个整数，通常为 @code{logging.DEBUG}、 @code{logging.INFO} 等等。
@end deffn

@geindex getChild() (logging.Logger 方法)
@anchor{library/logging logging Logger getChild}@anchor{c84}
@deffn {方法} getChild (suffix)

返回由后缀确定的，是该记录器的后代的记录器。 因此，@code{logging.getLogger('abc').getChild('def.ghi')} 与 @code{logging.getLogger('abc.def.ghi')} 将返回相同的记录器。 这是一个便捷方法，当使用如 @code{__name__} 而不是字符串字面值命名父记录器时很有用。


3.2 新版功能.

@end deffn

@geindex debug() (logging.Logger 方法)
@anchor{library/logging logging Logger debug}@anchor{70a}
@deffn {方法} debug (msg, *args, **kwargs)

在此纪录器上记录 @code{DEBUG} 级别的消息。 @emph{msg} 是消息格式字符串，而 @emph{args} 是用于字符串格式化操作合并到 @emph{msg} 的参数。（请注意，这意味着您可以在格式字符串中使用关键字以及单个字典参数。）当未提供 @emph{args} 时，不会对 @emph{msg} 执行 ％ 格式化操作。

在 @emph{kwargs} 中会检查四个关键字参数： @emph{exc_info}，@emph{stack_info}，@emph{stacklevel*和*extra}。

如果 @emph{exc_info} 的求值结果不为 false，则它将异常信息添加到日志消息中。如果提供了一个异常元组（按照 @ref{c58,,sys.exc_info()} 返回的格式）或一个异常实例，则将其使用；否则，调用 @ref{c58,,sys.exc_info()} 以获取异常信息。

第二个可选关键字参数是 @emph{stack_info}，默认为 @code{False}。如果为  True，则将堆栈信息添加到日志消息中，包括实际的日志调用。请注意，这与通过指定 @emph{exc_info} 显示的堆栈信息不同：前者是从堆栈底部到当前线程中的日志记录调用的堆栈帧，而后者是在搜索异常处理程序时，跟踪异常而打开的堆栈帧的信息。

您可以独立于 @emph{exc_info} 来指定 @emph{stack_info}，例如，即使在未引发任何异常的情况下，也可以显示如何到达代码中的特定点。堆栈帧在标题行之后打印：

@example
Stack (most recent call last):
@end example

这模仿了显示异常帧时所使用的 @code{Traceback (most recent call last):} 。

第三个可选关键字参数是 @emph{stacklevel}，默认为 @code{1}。如果大于 1，则在为日志记录事件创建的 @ref{900,,LogRecord} 中计算行号和函数名时，将跳过相应数量的堆栈帧。可以在记录帮助器时使用它，以便记录的函数名称，文件名和行号不是帮助器的函数/方法的信息，而是其调用方的信息。此参数是 @ref{126,,warnings} 模块中的同名等效参数。

第四个关键字参数是 @emph{extra} ，传递一个字典，该字典用于填充为日志记录事件创建的、带有用户自定义属性的 @ref{900,,LogRecord} 中的__dict__ 。然后可以按照需求使用这些自定义属性。例如，可以将它们合并到已记录的消息中：

@example
FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s'
logging.basicConfig(format=FORMAT)
d = @{'clientip': '192.168.0.1', 'user': 'fbloggs'@}
logger = logging.getLogger('tcpserver')
logger.warning('Protocol problem: %s', 'connection reset', extra=d)
@end example

输出类似于

@example
2006-02-08 22:20:02,165 192.168.0.1 fbloggs  Protocol problem: connection reset
@end example

The keys in the dictionary passed in @emph{extra} should not clash with the keys used
by the logging system. (See the @ref{201d,,Formatter} documentation for more
information on which keys are used by the logging system.)

如果在已记录的消息中使用这些属性，则需要格外小心。例如，在上面的示例中，@ref{201d,,Formatter} 已设置了格式字符串，其在 @ref{900,,LogRecord} 的属性字典中键值为 “clientip” 和 “user”。如果缺少这些内容，则将不会记录该消息，因为会引发字符串格式化异常。因此，在这种情况下，您始终需要使用这些键传递 @emph{extra} 字典。

尽管这可能很烦人，但此功能旨在用于特殊情况，例如在多个上下文中执行相同代码的多线程服务器，并且出现的有趣条件取决于此上下文（例如在上面的示例中就是远程客户端IP地址和已验证用户名）。在这种情况下，很可能将专门的 @ref{201d,,Formatter} 与特定的 @ref{201e,,Handler} 一起使用。


在 3.2 版更改: 增加了 @emph{stack_info} 参数。



在 3.5 版更改: The @emph{exc_info} parameter can now accept exception instances.



在 3.8 版更改: 增加了 @emph{stacklevel} 参数。

@end deffn

@geindex info() (logging.Logger 方法)
@anchor{library/logging logging Logger info}@anchor{201f}
@deffn {方法} info (msg, *args, **kwargs)

在此记录器上记录 @code{INFO} 级别的消息。参数解释同 @ref{2020,,debug()}。
@end deffn

@geindex warning() (logging.Logger 方法)
@anchor{library/logging logging Logger warning}@anchor{2021}
@deffn {方法} warning (msg, *args, **kwargs)

在此记录器上记录 @code{WARNING} 级别的消息。参数解释同 @ref{2020,,debug()}。

@cartouche
@quotation 注解 
有一个功能上与 @code{warning} 一致的方法 @code{warn}。由于 @code{warn} 已被弃用，请不要使用它 —— 改为使用 @code{warning}。
@end quotation
@end cartouche
@end deffn

@geindex error() (logging.Logger 方法)
@anchor{library/logging logging Logger error}@anchor{2022}
@deffn {方法} error (msg, *args, **kwargs)

在此记录器上记录 @code{ERROR} 级别的消息。参数解释同 @ref{2020,,debug()}。
@end deffn

@geindex critical() (logging.Logger 方法)
@anchor{library/logging logging Logger critical}@anchor{709}
@deffn {方法} critical (msg, *args, **kwargs)

在此记录器上记录 @code{CRITICAL} 级别的消息。参数解释同 @ref{2020,,debug()}。
@end deffn

@geindex log() (logging.Logger 方法)
@anchor{library/logging logging Logger log}@anchor{707}
@deffn {方法} log (level, msg, *args, **kwargs)

在此记录器上记录 @emph{level} 整数代表的级别的消息。参数解释同 @ref{2020,,debug()}。
@end deffn

@geindex exception() (logging.Logger 方法)
@anchor{library/logging logging Logger exception}@anchor{708}
@deffn {方法} exception (msg, *args, **kwargs)

在此记录器上记录 @code{ERROR} 级别的消息。参数解释同 @ref{2020,,debug()}。异常信息将添加到日志消息中。仅应从异常处理程序中调用此方法。
@end deffn

@geindex addFilter() (logging.Logger 方法)
@anchor{library/logging logging Logger addFilter}@anchor{2023}
@deffn {方法} addFilter (filter)

将指定的过滤器 @emph{filter} 添加到此记录器。
@end deffn

@geindex removeFilter() (logging.Logger 方法)
@anchor{library/logging logging Logger removeFilter}@anchor{2024}
@deffn {方法} removeFilter (filter)

从此记录器中删除指定的过滤器 @emph{filter}。
@end deffn

@geindex filter() (logging.Logger 方法)
@anchor{library/logging logging Logger filter}@anchor{2025}
@deffn {方法} filter (record)

将此记录器的过滤器应用于记录，如果记录能被处理则返回 @code{True}。过滤器会被依次使用，直到其中一个返回假值为止。如果它们都不返回假值，则记录将被处理（传递给处理器）。如果返回任一为假值，则不会对该记录做进一步处理。
@end deffn

@geindex addHandler() (logging.Logger 方法)
@anchor{library/logging logging Logger addHandler}@anchor{2026}
@deffn {方法} addHandler (hdlr)

将指定的处理器 @emph{hdlr} 添加到此记录器。
@end deffn

@geindex removeHandler() (logging.Logger 方法)
@anchor{library/logging logging Logger removeHandler}@anchor{2027}
@deffn {方法} removeHandler (hdlr)

从此记录器中删除指定的处理器 @emph{hdlr}。
@end deffn

@geindex findCaller() (logging.Logger 方法)
@anchor{library/logging logging Logger findCaller}@anchor{2028}
@deffn {方法} findCaller (stack_info=False, stacklevel=1)

查找调用源的文件名和行号，以 文件名，行号，函数名称和堆栈信息 4元素元组的形式返回。堆栈信息将返回 @code{None}，除非 @emph{stack_info} 为 @code{True}。

@emph{stacklevel} 参数用于调用 @ref{2020,,debug()} 和其他 API。如果大于 1，则多余部分将用于跳过堆栈帧，然后再确定要返回的值。当从帮助器/包装器代码调用日志记录 API 时，这通常很有用，以便事件日志中的信息不是来自帮助器/包装器代码，而是来自调用它的代码。
@end deffn

@geindex handle() (logging.Logger 方法)
@anchor{library/logging logging Logger handle}@anchor{2029}
@deffn {方法} handle (record)

通过将记录传递给与此记录器及其祖先关联的所有处理器来处理（直到某个 @emph{propagate} 值为 false）。此方法用于从套接字接收的未序列化的以及在本地创建的记录。使用 @ref{2025,,filter()} 进行记录器级别过滤。
@end deffn

@geindex makeRecord() (logging.Logger 方法)
@anchor{library/logging logging Logger makeRecord}@anchor{202a}
@deffn {方法} makeRecord (name, level, fn, lno, msg, args, exc_info, func=None, extra=None, sinfo=None)

这是一种工厂方法，可以在子类中对其进行重写以创建专门的 @ref{900,,LogRecord} 实例。
@end deffn

@geindex hasHandlers() (logging.Logger 方法)
@anchor{library/logging logging Logger hasHandlers}@anchor{202b}
@deffn {方法} hasHandlers ()

检查此记录器是否配置了任何处理器。通过在此记录器及其记录器层次结构中的父级中查找处理器完成此操作。如果找到处理器则返回 @code{True}，否则返回 @code{False}。只要找到 “propagate” 属性设置为假值的记录器，该方法就会停止搜索层次结构 —— 其将是最后一个检查处理器是否存在的记录器。


3.2 新版功能.

@end deffn


在 3.7 版更改: 现在可以对处理器进行序列化和反序列化。

@end deffn

@node 日志级别,处理器对象,记录器对象,logging --- Python 的日志记录工具
@anchor{library/logging levels}@anchor{201a}@anchor{library/logging logging-levels}@anchor{202c}
@subsubsection 日志级别


日志记录级别的数值在下表中给出。如果你想要定义自己的级别，并且需要它们具有相对于预定义级别的特定值，那么这些内容可能是你感兴趣的。如果你定义具有相同数值的级别，它将覆盖预定义的值; 预定义的名称丢失。


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} 
@headitem

级别

@tab

数值

@item

@code{CRITICAL}

@tab

50

@item

@code{ERROR}

@tab

40

@item

@code{WARNING}

@tab

30

@item

@code{INFO}

@tab

20

@item

@code{DEBUG}

@tab

10

@item

@code{NOTSET}

@tab

0

@end multitable


@node 处理器对象,格式器对象,日志级别,logging --- Python 的日志记录工具
@anchor{library/logging handler}@anchor{202d}@anchor{library/logging handler-objects}@anchor{202e}
@subsubsection 处理器对象


Handler 有以下属性和方法。注意不要直接实例化 @ref{201e,,Handler} ；这个类用来派生其他更有用的子类。但是，子类的 @ref{d57,,__init__()} 方法需要调用 @ref{202f,,Handler.__init__()} 。

@geindex Handler (logging 中的类)
@anchor{library/logging logging Handler}@anchor{201e}
@deffn {类} logging.Handler

@geindex __init__() (logging.Handler 方法)
@anchor{library/logging logging Handler __init__}@anchor{202f}
@deffn {方法} __init__ (level=NOTSET)

初始化 @ref{201e,,Handler} 实例时，需要设置它的级别，将过滤列表置为空，并且创建锁（通过 @ref{2030,,createLock()} ）来序列化对 I/O 的访问。
@end deffn

@geindex createLock() (logging.Handler 方法)
@anchor{library/logging logging Handler createLock}@anchor{2030}
@deffn {方法} createLock ()

初始化一个线程锁，用来序列化对底层的 I/O 功能的访问，底层的 I/O 功能可能不是线程安全的。
@end deffn

@geindex acquire() (logging.Handler 方法)
@anchor{library/logging logging Handler acquire}@anchor{2031}
@deffn {方法} acquire ()

使用 @ref{2030,,createLock()} 获取线程锁。
@end deffn

@geindex release() (logging.Handler 方法)
@anchor{library/logging logging Handler release}@anchor{2032}
@deffn {方法} release ()

使用 @ref{2031,,acquire()} 来释放线程锁。
@end deffn

@geindex setLevel() (logging.Handler 方法)
@anchor{library/logging logging Handler setLevel}@anchor{2033}
@deffn {方法} setLevel (level)

给处理器设置阈值为 @emph{level} 。日志级别小于 @emph{level} 将被忽略。创建处理器时，日志级别被设置为 @code{NOTSET} （所有的消息都会被处理）。

参见 @ref{201a,,日志级别} 级别列表。


在 3.2 版更改: @emph{level} 形参现在接受像 'INFO' 这样的字符串形式的级别表达方式，也可以使用像 @code{INFO} 这样的整数常量。

@end deffn

@geindex setFormatter() (logging.Handler 方法)
@anchor{library/logging logging Handler setFormatter}@anchor{2034}
@deffn {方法} setFormatter (fmt)

将此处理器的 @ref{201d,,Formatter} 设置为 @emph{fmt}。
@end deffn

@geindex addFilter() (logging.Handler 方法)
@anchor{library/logging logging Handler addFilter}@anchor{2035}
@deffn {方法} addFilter (filter)

将指定的过滤器 @emph{filter} 添加到此处理器。
@end deffn

@geindex removeFilter() (logging.Handler 方法)
@anchor{library/logging logging Handler removeFilter}@anchor{2036}
@deffn {方法} removeFilter (filter)

从此处理器中删除指定的过滤器 @emph{filter} 。
@end deffn

@geindex filter() (logging.Handler 方法)
@anchor{library/logging logging Handler filter}@anchor{2037}
@deffn {方法} filter (record)

将此处理器的过滤器应用于记录，在要处理记录时返回 @code{True} 。依次查询过滤器，直到其中一个返回假值为止。如果它们都不返回假值，则将发出记录。如果返回一个假值，则处理器将不会发出记录。
@end deffn

@geindex flush() (logging.Handler 方法)
@anchor{library/logging logging Handler flush}@anchor{2038}
@deffn {方法} flush ()

确保所有日志记录从缓存输出。此版本不执行任何操作，并且应由子类实现。
@end deffn

@geindex close() (logging.Handler 方法)
@anchor{library/logging logging Handler close}@anchor{2039}
@deffn {方法} close ()

整理处理器使用的所有资源。此版本不输出，但从内部处理器列表中删除处理器，内部处理器在 @ref{203a,,shutdown()} 被调用时关闭 。子类应确保从重写的 @ref{2039,,close()} 方法中调用此方法。
@end deffn

@geindex handle() (logging.Handler 方法)
@anchor{library/logging logging Handler handle}@anchor{203b}
@deffn {方法} handle (record)

经已添加到处理器的过滤器过滤后，有条件地发出指定的日志记录。用获取/释放 I/O 线程锁包装记录的实际发出行为。
@end deffn

@geindex handleError() (logging.Handler 方法)
@anchor{library/logging logging Handler handleError}@anchor{203c}
@deffn {方法} handleError (record)

调用 @ref{203d,,emit()} 期间遇到异常时，应从处理器中调用此方法。如果模块级属性 @code{raiseExceptions} 是 @code{False}，则异常将被静默忽略。这是大多数情况下日志系统需要的 —— 大多数用户不会关心日志系统中的错误，他们对应用程序错误更感兴趣。但是，你可以根据需要将其替换为自定义处理器。指定的记录是发生异常时正在处理的记录。（@code{raiseExceptions} 的默认值是 @code{True}，因为这在开发过程中是比较有用的）。
@end deffn

@geindex format() (logging.Handler 方法)
@anchor{library/logging logging Handler format}@anchor{203e}
@deffn {方法} format (record)

如果设置了格式器则用其对记录进行格式化。否则，使用模块的默认格式器。
@end deffn

@geindex emit() (logging.Handler 方法)
@anchor{library/logging logging Handler emit}@anchor{203d}
@deffn {方法} emit (record)

执行实际记录给定日志记录所需的操作。这个版本应由子类实现，因此这里直接引发 @ref{609,,NotImplementedError} 异常。
@end deffn
@end deffn

有关作为标准随附的处理程序列表，请参见 @ref{ac,,logging.handlers}。

@node 格式器对象,Filter 对象,处理器对象,logging --- Python 的日志记录工具
@anchor{library/logging formatter-objects}@anchor{203f}@anchor{library/logging id1}@anchor{2040}
@subsubsection 格式器对象


@ref{201d,,Formatter} 对象拥有以下的属性和方法。一般情况下，它们负责将 @ref{900,,LogRecord} 转换为可由人或外部系统解释的字符串。基础的 @ref{201d,,Formatter} 允许指定格式字符串。如果未提供任何值，则使用默认值 @code{'%(message)s'} ，它仅将消息包括在日志记录调用中。要在格式化输出中包含其他信息（如时间戳），请阅读下文。

格式器可以使用格式化字符串来初始化，该字符串利用 @ref{900,,LogRecord} 的属性 —— 例如上述默认值，用户的消息和参数预先格式化为 @ref{900,,LogRecord} 的 @emph{message} 属性后被使用。此格式字符串包含标准的 Python %-s 样式映射键。有关字符串格式的更多信息，请参见 @ref{11b9,,printf 风格的字符串格式化}。

The useful mapping keys in a @ref{900,,LogRecord} are given in the section on
@ref{2041,,LogRecord 属性}.

@geindex Formatter (logging 中的类)
@anchor{library/logging logging Formatter}@anchor{201d}
@deffn {类} logging.Formatter (fmt=None, datefmt=None, style='%')

返回 @ref{201d,,Formatter} 类的新实例。实例将使用整个消息的格式字符串以及消息的日期/时间部分的格式字符串进行初始化。如果未指定 @emph{fmt} ，则使用 @code{'%(message)s'}。如果未指定 @emph{datefmt}，则使用  @ref{2042,,formatTime()} 文档中描述的格式。

The @emph{style} parameter can be one of '%', '@{' or '$' and determines how
the format string will be merged with its data: using one of %-formatting,
@ref{4d4,,str.format()} or @ref{3e3,,string.Template}. See @ref{2043,,Using particular formatting styles throughout your application}
for more information on using @{- and $-formatting for log messages.


在 3.2 版更改: @emph{style}  参数已加入.



在 3.8 版更改: The @emph{validate} parameter was added. Incorrect or mismatched style and fmt
will raise a @code{ValueError}.
For example: @code{logging.Formatter('%(asctime)s - %(message)s', style='@{')}.


@geindex format() (logging.Formatter 方法)
@anchor{library/logging logging Formatter format}@anchor{2044}
@deffn {方法} format (record)

记录的属性字典用作字符串格式化操作的参数。返回结果字符串。在格式化字典之前，需要执行几个准备步骤。 使用 @emph{msg} % @emph{args} 计算记录的 @emph{message} 属性。如果格式化字符串包含 @code{'(asctime)'}，则调用 @ref{2042,,formatTime()} 来格式化事件时间。如果有异常信息，则使用 @ref{2045,,formatException()} 将其格式化并附加到消息中。请注意，格式化的异常信息缓存在属性 @emph{exc_text} 中。这很有用，因为可以对异常信息进行序列化并通过网络发送，但是如果您有不止一个定制了异常信息格式的 @ref{201d,,Formatter} 子类，则应格外小心。在这种情况下，您必须在格式器完成格式化后清除缓存的值，以便下一个处理事件的格式化程序不使用缓存的值，而是重新计算它。

如果栈信息可用，它将被添加在异常信息之后，如有必要请使用 @ref{2046,,formatStack()} 来转换它。
@end deffn

@geindex formatTime() (logging.Formatter 方法)
@anchor{library/logging logging Formatter formatTime}@anchor{2042}
@deffn {方法} formatTime (record, datefmt=None)

此方法应由想要使用格式化时间的格式器中的 @ref{4d5,,format()} 调用。可以在格式器中重写此方法以提供任何特定要求，但是基本行为如下：如果指定了 @emph{datefmt} （字符串），则将其用于 @ref{b5e,,time.strftime()} 来格式化记录的创建时间。否则，使用格式 '%Y-%m-%d %H:%M:%S,uuu'，其中 uuu 部分是毫秒值，其他字母根据 @ref{b5e,,time.strftime()} 文档。这种时间格式的示例为 @code{2003-01-23 00:29:50,411}。返回结果字符串。

此函数使用一个用户可配置函数将创建时间转换为元组。 默认情况下，使用 @ref{edc,,time.localtime()}；要为特定格式化程序实例更改此项，请将实例的 @code{converter} 属性设为具有与 @ref{edc,,time.localtime()} 或 @ref{b38,,time.gmtime()} 相同签名的函数。 要为所有格式化程序更改此项，例如当你希望所有日志时间都显示为 GMT，请在 @code{Formatter} 类中设置 @code{converter} 属性。


在 3.3 版更改: 在之前版本中，默认格式为写死的代码，例如这个例子: @code{2010-09-06 22:38:15,292} 其中逗号之前的部分由 strptime 格式字符串 (@code{'%Y-%m-%d %H:%M:%S'}) 处理，而逗号之后的部分为毫秒值。 因为 strptime 没有表示毫秒的占位符，毫秒值使用了另外的格式字符串来添加 @code{'%s,%03d'} --- 这两个格式字符串代码都是写死在该方法中的。 经过修改，这些字符串被定义为类层级的属性，当需要时可以在实例层级上被重载。 属性的名称为 @code{default_time_format} (用于 strptime 格式字符串) 和 @code{default_msec_format} (用于添加毫秒值)。

@end deffn

@geindex formatException() (logging.Formatter 方法)
@anchor{library/logging logging Formatter formatException}@anchor{2045}
@deffn {方法} formatException (exc_info)

将指定的异常信息（由 @ref{c58,,sys.exc_info()} 返回的标准异常元组）格式化为字符串。 这个默认实现只使用了 @ref{2047,,traceback.print_exception()}。 结果字符串将被返回。
@end deffn

@geindex formatStack() (logging.Formatter 方法)
@anchor{library/logging logging Formatter formatStack}@anchor{2046}
@deffn {方法} formatStack (stack_info)

将指定的堆栈信息（由 @ref{774,,traceback.print_stack()} 返回的字符串，但移除末尾的换行符）格式化为字符串。 这个默认实现只是返回输入值。
@end deffn
@end deffn

@node Filter 对象,LogRecord 属性,格式器对象,logging --- Python 的日志记录工具
@anchor{library/logging filter}@anchor{2048}@anchor{library/logging filter-objects}@anchor{2049}
@subsubsection Filter 对象


@code{Filters} 可被 @code{Handlers} 和 @code{Loggers} 用来实现比按层级提供更复杂的过滤操作。 基本过滤器类只允许低于日志记录器层级结构中低于特定层级的事件。 例如，一个用 'A.B' 初始化的过滤器将允许 'A.B', 'A.B.C', 'A.B.C.D', 'A.B.D' 等日志记录器所记录的事件。 但 'A.BB', 'B.A.B' 等则不允许。 如果用空字符串初始化，则所有事件都会被略过。

@geindex Filter (logging 中的类)
@anchor{library/logging logging Filter}@anchor{b70}
@deffn {类} logging.Filter (name='@w{'})

返回一个 @ref{b70,,Filter} 类的实例。 如果指定了 @emph{name}，则它将被用来为日志记录器命名，该类及其子类将通过该过滤器允许指定事件通过。 如果 @emph{name} 为空字符串，则允许所有事件通过。

@geindex filter() (logging.Filter 方法)
@anchor{library/logging logging Filter filter}@anchor{204a}
@deffn {方法} filter (record)

是否要记录指定的记录？返回零表示否，非零表示是。如果认为合适，则可以通过此方法就地修改记录。
@end deffn
@end deffn

请注意关联到处理程序的过滤器会在事件由处理程序发出之前被查询，而关联到日志记录器的过滤器则会在有事件被记录的的任何时候（使用 @ref{2020,,debug()}, @ref{204b,,info()} 等等）在将事件发送给处理程序之前被查询。 这意味着由后代日志记录器生成的事件将不会被日志记录器的过滤器设置所过滤，除非该过滤器也已被应用于后代日志记录器。

你实际上不需要子类化 @code{Filter}: 你可以将传入任何包含 @code{filter} 方法的具有相同语义的的实例。


在 3.2 版更改: 你不需要创建专门的 @code{Filter} 类，或使用具有 @code{filter} 方法的其他类：你可以使用一个函数（或其他可调用对象）作为过滤器。 过滤逻辑将检查过滤器对象是否文化的 @code{filter} 属性：如果有，就会将它当作是 @code{Filter} 并调用它的 @ref{204a,,filter()} 方法。 在其他情况下，则会将它当作是可调用对象并附带记录作为单一形参进行调用。 返回值应当与 @ref{204a,,filter()} 的返回值相一致。


虽然过滤器主要被用来根据比层级更复杂的规则来过滤记录，但它们可以查看 由它们关联的处理程序或日志记录器所处理的每条记录：当你想要执行统计特定日志记录器或处理程序处理了多少条记录，或是在所处理的 @ref{900,,LogRecord} 中添加、修改或移除属性这样的任务时该特性将很有用处。 显然改变 LogRecord 时需要相当小心，但将上下文信息注入日志确实是被允许的 (参见 @ref{204c,,使用过滤器传递上下文信息})。

@node LogRecord 属性,LogRecord 属性<2>,Filter 对象,logging --- Python 的日志记录工具
@anchor{library/logging log-record}@anchor{204d}@anchor{library/logging logrecord-objects}@anchor{204e}
@subsubsection LogRecord 属性


@ref{900,,LogRecord} 实例是每当有日志被记录时由 @ref{39f,,Logger} 自动创建的，并且可通过 @ref{204f,,makeLogRecord()} 手动创建（例如根据从网络接收的已封存事件创建）。

@geindex LogRecord (logging 中的类)
@anchor{library/logging logging LogRecord}@anchor{900}
@deffn {类} logging.LogRecord (name, level, pathname, lineno, msg, args, exc_info, func=None, sinfo=None)

包含与被记录的事件相关的所有信息。

主要信息是在 @code{msg} 和 @code{args} 中传递的，它们使用 @code{msg % args} 组合到一起以创建记录的 @code{message} 字段。

@*参数: 

@itemize *

@item 
@code{name} -- 用于记录由此 LogRecord 所表示 的事件的日志记录器名称。 请注意此名称将始终为该值，即使它可以是由附加到不同（祖先）日志记录器的处理程序所发出的。

@item 
@code{level} -- 以数字表示的日志记录事件层级（如 DEBUG, INFO 等）。 请注意这会转换为 LogRecord 的 @emph{两个} 属性: @code{levelno} 为数字值而 @code{levelname} 为对应的层级名称。

@item 
@code{pathname} -- 进行日志记录调用的文件的完整路径名。

@item 
@code{lineno} -- 记录调用所在源文件中的行号。

@item 
@code{msg} -- 事件描述消息，可能为带有可变数据占位符的格式字符串。

@item 
@code{args} -- 要合并到 @emph{msg} 参数以获得事件描述的可变数据。

@item 
@code{exc_info} -- 包含当前异常信息的异常元组，或者如果没有可用异常信息则为 @code{None}。

@item 
@code{func} -- 发起调用日志记录调用的函数或方法名称。

@item 
@code{sinfo} -- 一个文本字符串，表示当前线程中从堆栈底部直到日志记录调用的堆栈信息。
@end itemize


@geindex getMessage() (logging.LogRecord 方法)
@anchor{library/logging logging LogRecord getMessage}@anchor{2050}
@deffn {方法} getMessage ()

在将 @ref{900,,LogRecord} 实例与任何用户提供的参数合并之后，返回此实例的消息。 如果用户提供给日志记录调用的消息参数不是字符串，则会在其上调用 @ref{329,,str()} 以将它转换为字符串。 此方法允许将用户定义的类用作消息，类的 @code{__str__} 方法可以返回要使用的实际格式字符串。
@end deffn


在 3.2 版更改: 通过提供用于创建记录的工厂方法已使得 @ref{900,,LogRecord} 的创建更易于配置。 该工厂方法可使用 @ref{2051,,getLogRecordFactory()} 和 @ref{2052,,setLogRecordFactory()} 来设置（在此可查看工厂方法的签名）。


在创建时可使用此功能将你自己的值注入 @ref{900,,LogRecord}。 你可以使用以下模式:

@example
old_factory = logging.getLogRecordFactory()

def record_factory(*args, **kwargs):
    record = old_factory(*args, **kwargs)
    record.custom_attribute = 0xdecafbad
    return record

logging.setLogRecordFactory(record_factory)
@end example

通过此模式，多个工厂方法可以被链接起来，并且只要它们不重载彼此的属性或是在无意中覆盖了上面列出的标准属性，就不会发生意外。
@end deffn

@node LogRecord 属性<2>,LoggerAdapter 对象,LogRecord 属性,logging --- Python 的日志记录工具
@anchor{library/logging id2}@anchor{2053}@anchor{library/logging logrecord-attributes}@anchor{2041}
@subsubsection LogRecord 属性


LogRecord 具有许多属性，它们大多数来自于传递给构造器的形参。 （请注意 LogRecord 构造器形参与 LogRecord 属性的名称并不总是完全彼此对应的。） 这些属性可被用于将来自记录的数据合并到格式字符串中。 下面的表格（按字母顺序）列出了属性名称、它们的含义以及相应的 %-style 格式字符串内占位符。

如果是使用 @{@}-格式化 (@ref{4d4,,str.format()})，你可以将 @code{@{attrname@}} 用作格式字符串内的占位符。 如果是使用 $-格式化 (@ref{3e3,,string.Template})，则会使用 @code{$@{attrname@}} 的形式。 当然在这两种情况下，都应当将 @code{attrname} 替换为你想要使用的实际属性名称。

在 @{@}-格式化的情况下，你可以在属性名称之后放置指定的格式化旗标，并用冒号来分隔两者。 例如，占位符 @code{@{msecs:03d@}} 会将毫秒值 @code{4} 格式化为 @code{004}。 请参看 @ref{4d4,,str.format()} 文档了解你所能使用的选项的完整细节。


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性名称

@tab

格式

@tab

描述

@item

args

@tab

不需要格式化。

@tab

合并到 @code{msg} 以产生 @code{message} 的包含参数的元组，或是其中的值将被用于合并的字典（当只有一个参数且其类型为字典时）。

@item

asctime

@tab

@code{%(asctime)s}

@tab

表示 @ref{900,,LogRecord} 何时被创建的供人查看时间值。 默认形式为 '2003-07-08 16:49:45,896' (逗号之后的数字为时间的毫秒部分)。

@item

created

@tab

@code{%(created)f}

@tab

@ref{900,,LogRecord} 被创建的时间（即 @ref{316,,time.time()} 的返回值）。

@item

exc_info

@tab

不需要格式化。

@tab

异常元组 (例如 @code{sys.exc_info}) 或者如未发生异常则为 @code{None}。

@item

文件名

@tab

@code{%(filename)s}

@tab

@code{pathname} 的文件名部分。

@item

funcName

@tab

@code{%(funcName)s}

@tab

函数名包括调用日志记录.

@item

levelname

@tab

@code{%(levelname)s}

@tab

消息文本记录级别 (@code{'DEBUG'}, @code{'INFO'}, @code{'WARNING'}, @code{'ERROR'}, @code{'CRITICAL'}).

@item

levelno

@tab

@code{%(levelno)s}

@tab

消息数字记录级别 (@code{DEBUG}, @code{INFO}, @code{WARNING}, @code{ERROR}, @code{CRITICAL}).

@item

lineno

@tab

@code{%(lineno)d}

@tab

发出日志记录调用所在的源行号（如果可用）。

@item

message

@tab

@code{%(message)s}

@tab

记入日志的消息，即 @code{msg % args} 的结果。 这是在发起调用 @ref{2044,,Formatter.format()} 时设置的。

@item

module

@tab

@code{%(module)s}

@tab

模块 (@code{filename} 的名称部分)。

@item

msecs

@tab

@code{%(msecs)d}

@tab

@ref{900,,LogRecord} 被创建的时间的毫秒部分。

@item

msg

@tab

不需要格式化。

@tab

在原始日志记录调用中传入的格式字符串。 与 @code{args} 合并以产生 @code{message}，或是一个任意对象 (参见 @ref{2054,,使用任意对象作为消息})。

@item

名称

@tab

@code{%(name)s}

@tab

用于记录调用的日志记录器名称。

@item

pathname

@tab

@code{%(pathname)s}

@tab

发出日志记录调用的源文件的完整路径名（如果可用）。

@item

process

@tab

@code{%(process)d}

@tab

进程ID（如果可用）

@item

processName

@tab

@code{%(processName)s}

@tab

进程名（如果可用）

@item

relativeCreated

@tab

@code{%(relativeCreated)d}

@tab

以毫秒数表示的 LogRecord 被创建的时间，即相对于 logging 模块被加载时间的差值。

@item

stack_info

@tab

不需要格式化。

@tab

当前线程中从堆栈底部起向上直到包括日志记录调用并导致创建此记录的堆栈帧的堆栈帧信息（如果可用）。

@item

thread

@tab

@code{%(thread)d}

@tab

线程ID（如果可用）

@item

threadName

@tab

@code{%(threadName)s}

@tab

线程名（如果可用）

@end multitable



在 3.1 版更改: 添加了 @emph{processName}


@node LoggerAdapter 对象,线程安全,LogRecord 属性<2>,logging --- Python 的日志记录工具
@anchor{library/logging logger-adapter}@anchor{2055}@anchor{library/logging loggeradapter-objects}@anchor{2056}
@subsubsection LoggerAdapter 对象


@ref{c85,,LoggerAdapter} 实例会被用来方便地将上下文信息传入日志记录调用。 要获取用法示例，请参阅 @ref{2057,,添加上下文信息到你的日志记录输出} 部分。

@geindex LoggerAdapter (logging 中的类)
@anchor{library/logging logging LoggerAdapter}@anchor{c85}
@deffn {类} logging.LoggerAdapter (logger, extra)

返回一个 @ref{c85,,LoggerAdapter} 的实例，该实例的初始化带有一个下层的 @ref{39f,,Logger} 实例和一个字典类对象。

@geindex process() (logging.LoggerAdapter 方法)
@anchor{library/logging logging LoggerAdapter process}@anchor{2058}
@deffn {方法} process (msg, kwargs)

修改传递给日志记录调用的消息和/或关键字参数以便插入上下文信息。 此实现接受以 @emph{extra} 形式传给构造器的对象并使用 'extra' 键名将其加入 @emph{kwargs}。 返回值为一个 (@emph{msg}, @emph{kwargs}) 元组，其中传入了（可能经过修改的）参数版本。
@end deffn
@end deffn

在上述方法之外，@ref{c85,,LoggerAdapter} 还支持 @ref{39f,,Logger} 的下列方法: @ref{70a,,debug()}, @ref{201f,,info()}, @ref{2021,,warning()}, @ref{2022,,error()}, @ref{708,,exception()}, @ref{709,,critical()}, @ref{707,,log()}, @ref{201c,,isEnabledFor()}, @ref{201b,,getEffectiveLevel()}, @ref{2019,,setLevel()} 以及 @ref{202b,,hasHandlers()}。 这些方法具有与它们在 @ref{39f,,Logger} 中的对应方法相同的签名，因此你可以互换使用这两种类型的实例。


在 3.2 版更改: @ref{201c,,isEnabledFor()}, @ref{201b,,getEffectiveLevel()}, @ref{2019,,setLevel()} 和 @ref{202b,,hasHandlers()} 方法已被添加到 @ref{c85,,LoggerAdapter}。 这些方法会委托给下层的日志记录器。


@node 线程安全,模块级别函数,LoggerAdapter 对象,logging --- Python 的日志记录工具
@anchor{library/logging thread-safety}@anchor{2059}
@subsubsection 线程安全


logging 模块的目标是使客户端不必执行任何特殊操作即可确保线程安全。 它通过使用线程锁来达成这个目标；用一个锁来序列化对模块共享数据的访问，并且每个处理程序也会创建一个锁来序列化对其下层 I/O 的访问。

如果你要使用 @ref{ea,,signal} 模块来实现异步信号处理程序，则可能无法在这些处理程序中使用 logging。 这是因为 @ref{109,,threading} 模块中的锁实现并非总是可重入的，所以无法从此类信号处理程序发起调用。

@node 模块级别函数,模块级属性,线程安全,logging --- Python 的日志记录工具
@anchor{library/logging module-level-functions}@anchor{205a}
@subsubsection 模块级别函数


在上述的类之外，还有一些模块层级的函数。

@geindex getLogger() (在 logging 模块中)
@anchor{library/logging logging getLogger}@anchor{2017}
@deffn {函数} logging.getLogger (name=None)

返回具有指定 name 的日志记录器，或者当 name 为 @code{None} 时返回层级结构中作为根日志记录器的日志记录器。 如果指定了 name，它通常是以点号分隔的带层级结构的名称如 @emph{'a'}, @emph{'a.b'} 或 @emph{'a.b.c.d'}。 这些名称的选择完全取决于使用 logging 的开发者。

附带给定 name 的所有对此函数的调用都将返回相同的日志记录器实例。 这意味着日志记录器实例不需要在应用的不同部分间传递。
@end deffn

@geindex getLoggerClass() (在 logging 模块中)
@anchor{library/logging logging getLoggerClass}@anchor{205b}
@deffn {函数} logging.getLoggerClass ()

返回标准的 @ref{39f,,Logger} 类，或是最近传给 @ref{205c,,setLoggerClass()} 的类。 此函数可以从一个新的类定义中调用，以确保安装自定义的 @ref{39f,,Logger} 类不会撤销其他代码已经应用的自定义操作。 例如:

@example
class MyLogger(logging.getLoggerClass()):
    # ... override behaviour here
@end example
@end deffn

@geindex getLogRecordFactory() (在 logging 模块中)
@anchor{library/logging logging getLogRecordFactory}@anchor{2051}
@deffn {函数} logging.getLogRecordFactory ()

返回一个被用来创建 @ref{900,,LogRecord} 的可调用对象。


3.2 新版功能: 此函数与 @ref{2052,,setLogRecordFactory()} 一起提供，以便允许开发者对如何构造表示日志记录事件的 @ref{900,,LogRecord} 有更好的控制。


请参阅 @ref{2052,,setLogRecordFactory()} 了解有关如何调用该工厂方法的更多信息。
@end deffn

@geindex debug() (在 logging 模块中)
@anchor{library/logging logging debug}@anchor{2020}
@deffn {函数} logging.debug (msg, *args, **kwargs)

在根日志记录器上记录一条 @code{DEBUG} 级别的消息。 @emph{msg} 是消息格式字符串，而 @emph{args} 是要使用字符串格式化运算符合并到 @emph{msg} 的参数。 （请注意这意味着你可以在格式字符串中使用关键字以及单个字典参数。）

在 @emph{kwargs} 中有三个关键字参数会被检查: @emph{exc_info} 参数如果不为假值则会将异常信息添加到日志记录消息。 如果提供了异常元组（为 @ref{c58,,sys.exc_info()} 的返回值格式）或异常实例则它会被使用；在其他情况下，会调用 @ref{c58,,sys.exc_info()} 以获取异常信息。

第二个可选关键字参数是 @emph{stack_info}，默认为 @code{False}。如果为  True，则将堆栈信息添加到日志消息中，包括实际的日志调用。请注意，这与通过指定 @emph{exc_info} 显示的堆栈信息不同：前者是从堆栈底部到当前线程中的日志记录调用的堆栈帧，而后者是在搜索异常处理程序时，跟踪异常而打开的堆栈帧的信息。

您可以独立于 @emph{exc_info} 来指定 @emph{stack_info}，例如，即使在未引发任何异常的情况下，也可以显示如何到达代码中的特定点。堆栈帧在标题行之后打印：

@example
Stack (most recent call last):
@end example

这模仿了显示异常帧时所使用的 @code{Traceback (most recent call last):} 。

第三个可选关键字参数是 @emph{extra}，它可被用来传递一个字典，该字典会被用来填充为日志记录事件创建并附带用户自定义属性的 LogRecord 的 __dict__。 之后将可按你的需要使用这些自定义属性。 例如，可以将它们合并到已记录的消息中。 举例来说:

@example
FORMAT = '%(asctime)-15s %(clientip)s %(user)-8s %(message)s'
logging.basicConfig(format=FORMAT)
d = @{'clientip': '192.168.0.1', 'user': 'fbloggs'@}
logging.warning('Protocol problem: %s', 'connection reset', extra=d)
@end example

应当会打印出这样的内容:

@example
2006-02-08 22:20:02,165 192.168.0.1 fbloggs  Protocol problem: connection reset
@end example

The keys in the dictionary passed in @emph{extra} should not clash with the keys used
by the logging system. (See the @ref{201d,,Formatter} documentation for more
information on which keys are used by the logging system.)

如果你选择在已记录的消息中使用这些属性，则需要格外小心。 例如在上面的示例中，@ref{201d,,Formatter} 已设置了格式字符串，其在 LogRecord 的属性字典中应有 'clientip' 和 'user'。 如果缺少这些属性，消息将不被记录，因为会引发字符串格式化异常，你始终需要传入带有这些键的 @emph{extra} 字典。

尽管这可能很烦人，但此功能旨在用于特殊情况，例如在多个上下文中执行相同代码的多线程服务器，并且出现的有趣条件取决于此上下文（例如在上面的示例中就是远程客户端IP地址和已验证用户名）。在这种情况下，很可能将专门的 @ref{201d,,Formatter} 与特定的 @ref{201e,,Handler} 一起使用。


在 3.2 版更改: 增加了 @emph{stack_info} 参数。

@end deffn

@geindex info() (在 logging 模块中)
@anchor{library/logging logging info}@anchor{204b}
@deffn {函数} logging.info (msg, *args, **kwargs)

在根日志记录器上记录一条 @code{INFO} 级别的消息。 参数解释同 @ref{2020,,debug()}。
@end deffn

@geindex warning() (在 logging 模块中)
@anchor{library/logging logging warning}@anchor{205d}
@deffn {函数} logging.warning (msg, *args, **kwargs)

在根日志记录器上记录一条 @code{WARNING} 级别的消息。 参数解释同 @ref{2020,,debug()}。

@cartouche
@quotation 注解 
有一个已过时方法 @code{warn} 其功能与 @code{warning} 一致。 由于 @code{warn} 已被弃用，请不要使用它 —— 而要改用 @code{warning}。
@end quotation
@end cartouche
@end deffn

@geindex error() (在 logging 模块中)
@anchor{library/logging logging error}@anchor{205e}
@deffn {函数} logging.error (msg, *args, **kwargs)

在根日志记录器上记录一条 @code{ERROR} 级别的消息。 参数解释同 @ref{2020,,debug()}.
@end deffn

@geindex critical() (在 logging 模块中)
@anchor{library/logging logging critical}@anchor{205f}
@deffn {函数} logging.critical (msg, *args, **kwargs)

在根日志记录器上记录一条 @code{CRITICAL} 级别的消息。 参数解释同 @ref{2020,,debug()}。
@end deffn

@geindex exception() (在 logging 模块中)
@anchor{library/logging logging exception}@anchor{2060}
@deffn {函数} logging.exception (msg, *args, **kwargs)

在根日志记录器上记录一条 @code{ERROR} 级别的消息。 参数解释同 @ref{2020,,debug()}。 异常信息将被添加到日志消息中。 此函数应当仅从异常处理程序中调用。
@end deffn

@geindex log() (在 logging 模块中)
@anchor{library/logging logging log}@anchor{2061}
@deffn {函数} logging.log (level, msg, *args, **kwargs)

在根日志记录器上记录一条 @emph{level} 级别的消息。 其他参数解释同 @ref{2020,,debug()}。

@cartouche
@quotation 注解 
上述模块层级的便捷函数均委托给根日志记录器，它们会调用 @ref{1e0,,basicConfig()} 以确保至少有一个处理程序可用。 因此，它们 @emph{不应} 在线程中使用，在 Python 2.7.1 和 3.2 之前的版本中，除非线程启动 @emph{之前} 已向根日志记录器添加了至少一个处理程序方可使用。 在较早的 Python 版本中，由于 @ref{1e0,,basicConfig()} 中存在线程安全性的不足，这（在少数情况下）可能导致处理程序被多次加入根日志记录器，这会进一步导致同一事件出现多条消息。
@end quotation
@end cartouche
@end deffn

@geindex disable() (在 logging 模块中)
@anchor{library/logging logging disable}@anchor{2062}
@deffn {函数} logging.disable (level=CRITICAL)

为所有日志记录器提供重载的级别 @emph{level}，其优先级高于日志记录器自己的级别。 当需要临时限制整个应用程序中的日志记录输出时，此功能会很有用。 它的效果是禁用所有重要程度为 @emph{level} 及以下的日志记录调用，因此如果你附带 INFO 值调用它，则所有 INFO 和 DEBUG 事件就会被丢弃，而重要程度为 WARNING 以及上的事件将根据日志记录器的当前有效级别来处理。 如果 @code{logging.disable(logging.NOTSET)} 被调用，它将在实际上移除这个重载的级别，因此日志记录输出会再次取决于单个日志记录器的有效级别。

请注意如果你定义了任何高于 @code{CRITICAL} 的自定义日志级别（并不建议这样做），你就将无法沿用 @emph{level} 形参的默认值，而必须显式地提供适当的值。


在 3.7 版更改: @emph{level} 形参默认为 @code{CRITICAL} 级别。 请参阅问题 #28524 了解此项改变的更多细节。

@end deffn

@geindex addLevelName() (在 logging 模块中)
@anchor{library/logging logging addLevelName}@anchor{2063}
@deffn {函数} logging.addLevelName (level, levelName)

在一个内部字典中关联级别 @emph{level} 与文本 @emph{levelName}，该字典会被用来将数字级别映射为文本表示形式，例如在 @ref{201d,,Formatter} 格式化消息的时候。 此函数也可被用来定义你自己的级别。 唯一的限制是所用的所有级别必须使用此函数来注册，级别值必须为正整数并且它们应当按严重程度递增顺序逐一递增。

@cartouche
@quotation 注解 
如果你考虑要定义你自己的级别，请参阅 @ref{2064,,自定义级别} 部分。
@end quotation
@end cartouche
@end deffn

@geindex getLevelName() (在 logging 模块中)
@anchor{library/logging logging getLevelName}@anchor{2065}
@deffn {函数} logging.getLevelName (level)

返回日志记录级别 @emph{level} 的文本表示形式。 如果级别为预定义的级别 @code{CRITICAL}, @code{ERROR}, @code{WARNING}, @code{INFO} 或 @code{DEBUG} 之一则你会得到相应的字符串。 如果你使用 @ref{2063,,addLevelName()} 将级别关联到名称则会返回你为 @emph{level} 所关联的名称。 如果传入了与已定义级别相对应的数字值，则会返回相应的字符串表示形式。 在其他情况下，则返回级别字符串 'Level %s' % level。

@cartouche
@quotation 注解 
级别在内部为整数（它们需要在日志记录逻辑中相互比较）。 此函数被用于在整数级别与通过 @code{%(levelname)s} 格式描述符方式格式化的日志输出中显示的级别名称之间进行转换 (参见 @ref{2041,,LogRecord 属性})。
@end quotation
@end cartouche


在 3.4 版更改: 在早于 3.4 的 Python 版本中，此函数也可传入一个文本级别名称，并将返回对应的级别数字值。 此未记入文档的行为被视为是一个错误，并在 Python 3.4 中被移除，但又在 3.4.2 中被恢复以保持向下兼容性。

@end deffn

@geindex makeLogRecord() (在 logging 模块中)
@anchor{library/logging logging makeLogRecord}@anchor{204f}
@deffn {函数} logging.makeLogRecord (attrdict)

创建并返回一个新的 @ref{900,,LogRecord} 实例，实例属性由 @emph{attrdict} 定义。 此函数适用于接受一个封存的 @ref{900,,LogRecord} 属性字典，通过套接字传输，并在接收端将其重建为一个 @ref{900,,LogRecord} 实例。
@end deffn

@geindex basicConfig() (在 logging 模块中)
@anchor{library/logging logging basicConfig}@anchor{1e0}
@deffn {函数} logging.basicConfig (**kwargs)

通过使用默认的 @ref{201d,,Formatter} 创建一个 @ref{b6e,,StreamHandler} 并将其加入根日志记录器来为日志记录系统执行基本配置。 如果没有为根日志记录器定义处理程序则 @ref{2020,,debug()}, @ref{204b,,info()}, @ref{205d,,warning()}, @ref{205e,,error()} 和 @ref{205f,,critical()} 等函数将自动调用 @ref{1e0,,basicConfig()}。

如果根日志记录器已配置了处理程序则此函数将不执行任何操作，除非关键字参数 @emph{force} 被设为 @code{True}。

@cartouche
@quotation 注解 
此函数应当在其他线程启动之前从主线程被调用。 在 2.7.1 和 3.2 之前的 Python 版本中，如果此函数从多个线程被调用，一个处理程序（在极少的情况下）有可能被多次加入根日志记录器，导致非预期的结果例如日志中的消息出现重复。
@end quotation
@end cartouche

支持以下关键字参数。


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

格式

@tab

描述

@item

@emph{filename}

@tab

使用指定的文件名而不是 StreamHandler 创建 FileHandler。

@item

@emph{filemode}

@tab

如果指定了 @emph{filename}，则用此 @ref{158e,,模式} 打开该文件。 默认模式为 @code{'a'}。

@item

@emph{format}

@tab

处理器使用的指定格式字符串。

@item

@emph{datefmt}

@tab

使用指定的日期/时间格式，与 @ref{b5e,,time.strftime()} 所接受的格式相同。

@item

@emph{style}

@tab

如果指定了 @emph{format}，将为格式字符串使用此风格。 @code{'%'}, @code{'@{'} 或 @code{'$'} 分别对应于 @ref{11b9,,printf 风格}, @ref{4d4,,str.format()} 或 @ref{3e3,,string.Template}。 默认为 @code{'%'}。

@item

@emph{level}

@tab

设置根记录器级别去指定 @ref{201a,,level}.

@item

@emph{stream}

@tab

使用指定的流初始化 StreamHandler。 请注意此参数与 @emph{filename} 是不兼容的 - 如果两者同时存在，则会引发 @code{ValueError}。

@item

@emph{handlers}

@tab

如果指定，这应为一个包含要加入根日志记录器的已创建处理程序的可迭代对象。 任何尚未设置格式描述符的处理程序将被设置为在此函数中创建的默认格式描述符。 请注意此参数与 @emph{filename} 或 @emph{stream} 不兼容 —— 如果两者同时存在，则会引发 @code{ValueError}。

@item

@emph{force}

@tab

如果将此关键字参数指定为 true，则在执行其他参数指定的配置之前，将移除并关闭附加到根记录器的所有现有处理器。

@end multitable



在 3.2 版更改: 增加了 @emph{style} 参数。



在 3.3 版更改: 增加了 @emph{handlers} 参数。 增加了额外的检查来捕获指定不兼容参数的情况 (例如同时指定 @emph{handlers} 与 @emph{stream}  或 @emph{filename}，或者同时指定 @emph{stream} 与 @emph{filename})。



在 3.8 版更改: 增加了 @emph{force} 参数。

@end deffn

@geindex shutdown() (在 logging 模块中)
@anchor{library/logging logging shutdown}@anchor{203a}
@deffn {函数} logging.shutdown ()

通过刷新和关闭所有处理程序来通知日志记录系统执行有序停止。 此函数应当在应用退出时被调用并且在此调用之后不应再使用日志记录系统。

当 logging 模块被导入时，它会将此函数注册为退出处理程序 (参见 @ref{c,,atexit})，因此通常不需要手动执行该操作。
@end deffn

@geindex setLoggerClass() (在 logging 模块中)
@anchor{library/logging logging setLoggerClass}@anchor{205c}
@deffn {函数} logging.setLoggerClass (klass)

通知日志记录系统在实例化日志记录器时使用 @emph{klass} 类。 该类应当定义 @ref{d57,,__init__()} 使其只要求一个 name 参数，并且 @ref{d57,,__init__()} 应当调用 @code{Logger.__init__()}。 此函数通常会在需要使用自定义日志记录器行为的应用程序实例化任何日志记录器之前被调用。 在此调用之后，在任何其他时刻都不要使用该子类来直接实例化日志记录器：请继续使用 @ref{2017,,logging.getLogger()} API 来获取你的日志记录器。
@end deffn

@geindex setLogRecordFactory() (在 logging 模块中)
@anchor{library/logging logging setLogRecordFactory}@anchor{2052}
@deffn {函数} logging.setLogRecordFactory (factory)

设置一个用来创建 @ref{900,,LogRecord} 的可调用对象。

@*参数: 
@code{factory} -- 用来实例化日志记录的工厂可调用对象。



3.2 新版功能: 此函数与 @ref{2051,,getLogRecordFactory()} 一起提供，以便允许开发者对如何构造表示日志记录事件的 @ref{900,,LogRecord} 有更好的控制。


可调用对象 factory 具有如下签名:

@code{factory(name, level, fn, lno, msg, args, exc_info, func=None, sinfo=None, **kwargs)}

@quotation

@*名称: 
日志记录器名称


@*level: 
日志记录级别（数字）。


@*fn: 
进行日志记录调用的文件的完整路径名。


@*lno: 
记录调用所在文件中的行号。


@*msg: 
日志消息。


@*args: 
日志记录消息的参数。


@*exc_info: 
异常元组，或 @code{None} 。


@*func: 
调用日志记录调用的函数或方法的名称。


@*sinfo: 
与 @ref{774,,traceback.print_stack()} 所提供的类似的栈回溯信息，显示调用的层级结构。


@*kwargs: 
其他关键字参数。

@end quotation
@end deffn

@node 模块级属性,与警告模块集成,模块级别函数,logging --- Python 的日志记录工具
@anchor{library/logging module-level-attributes}@anchor{2066}
@subsubsection 模块级属性


@geindex lastResort() (在 logging 模块中)
@anchor{library/logging logging lastResort}@anchor{b6f}
@deffn {属性} logging.lastResort

通过此属性提供的“最后处理者”。 这是一个以 @code{WARNING} 级别写入到 @code{sys.stderr} 的 @ref{b6e,,StreamHandler}，用于在没有任何日志记录配置的情况下处理日志记录事件。 最终结果就是将消息打印到 @code{sys.stderr}，这会替代先前形式为 "no handlers could be found for logger XYZ" 的错误消息。 如果出于某种原因你需要先前的行为，可将 @code{lastResort} 设为 @code{None}。


3.2 新版功能.

@end deffn

@node 与警告模块集成,,模块级属性,logging --- Python 的日志记录工具
@anchor{library/logging integration-with-the-warnings-module}@anchor{2067}
@subsubsection 与警告模块集成


@ref{2068,,captureWarnings()} 函数可用来将 @ref{aa,,logging} 和 @ref{126,,warnings} 模块集成。

@geindex captureWarnings() (在 logging 模块中)
@anchor{library/logging logging captureWarnings}@anchor{2068}
@deffn {函数} logging.captureWarnings (capture)

此函数用于打开和关闭日志系统对警告的捕获。

如果 @emph{capture} 是 @code{True}，则 @ref{126,,warnings} 模块发出的警告将重定向到日志记录系统。具体来说，将使用 @ref{f83,,warnings.formatwarning()} 格式化警告信息，并将结果字符串使用 @code{WARNING} 等级记录到名为 @code{'py.warnings'} 的记录器中。

如果 @emph{capture} 是 @code{False}，则将停止将警告重定向到日志记录系统，并且将警告重定向到其原始目标（即在  @code{captureWarnings(True)}  调用之前的有效目标）。
@end deffn


@subsubheading 参见



@table @asis

@item @ref{ab,,logging.config} 模块

日志记录模块的配置 API 。

@item @ref{ac,,logging.handlers} 模块

日志记录模块附带的有用处理器。

@geindex Python 提高建议; PEP 282

@item PEP 282@footnote{https://www.python.org/dev/peps/pep-0282} - Logging 系统

该提案描述了Python标准库中包含的这个特性。

@item Original Python logging package@footnote{https://www.red-dove.com/python_logging.html}

这是该 @ref{aa,,logging} 包的原始来源。该站点提供的软件包版本适用于 Python 1.5.2、2.1.x 和 2.2.x，它们不被 @ref{aa,,logging} 包含在标准库中。
@end table


@node logging config --- 日志记录配置,logging handlers --- 日志处理,logging --- Python 的日志记录工具,通用操作系统服务
@anchor{library/logging config doc}@anchor{2069}@anchor{library/logging config logging-config-logging-configuration}@anchor{206a}@anchor{library/logging config module-logging config}@anchor{ab}
@subsection @code{logging.config} --- 日志记录配置


@geindex logging.config (模块)

@strong{源代码：} Lib/logging/config.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/logging/config.py}

@subsubheading Important



此页面仅包含参考信息。有关教程，请参阅


@itemize *

@item 
@ref{b6b,,基础教程}

@item 
@ref{b6c,,进阶教程}

@item 
@ref{b6d,,日志操作手册}
@end itemize


__________________________________________________________________


这一节描述了用于配置 logging 模块的 API。

@menu
* 配置函数:: 
* 配置字典架构:: 
* Configuration file format:: 

@end menu

@node 配置函数,配置字典架构,,logging config --- 日志记录配置
@anchor{library/logging config configuration-functions}@anchor{206b}@anchor{library/logging config logging-config-api}@anchor{c81}
@subsubsection 配置函数


下列函数可配置 logging 模块。 它们位于 @ref{ab,,logging.config} 模块中。 它们的使用是可选的 --- 要配置 logging 模块你可以使用这些函数，也可以通过调用主 API (在 @ref{aa,,logging} 本身定义) 并定义在 @ref{aa,,logging} 或 @ref{ac,,logging.handlers} 中声明的处理程序。

@geindex dictConfig() (在 logging.config 模块中)
@anchor{library/logging config logging config dictConfig}@anchor{b24}
@deffn {函数} logging.config.dictConfig (config)

@quotation

从一个字典获取日志记录配置。 字典的内容描述见下文的 @ref{206c,,配置字典架构}。

如果在配置期间遇到错误，此函数将引发 @ref{1fb,,ValueError}, @ref{192,,TypeError}, @ref{393,,AttributeError} 或 @ref{32d,,ImportError} 并附带适当的描述性消息。 下面是将会引发错误的（可能不完整的）条件列表:


@itemize *

@item 
@code{level} 不是字符串或者不是对应于实际日志记录级别的字符串。

@item 
@code{propagate} 值不是布尔类型。

@item 
id 没有对应的目标。

@item 
在增量调用期间发现不存在的处理程序 id。

@item 
无效的日志记录器名称。

@item 
无法解析为内部或外部对象。
@end itemize

解析由 @code{DictConfigurator} 类执行，该类的构造器可传入用于配置的字典，并且具有 @code{configure()} 方法。 @ref{ab,,logging.config} 模块具有可调用属性 @code{dictConfigClass}，其初始值设为 @code{DictConfigurator}。 你可以使用你自己的适当实现来替换 @code{dictConfigClass} 的值。

@ref{b24,,dictConfig()} 会调用 @code{dictConfigClass} 并传入指定的字典，然后在所返回的对象上调用 @code{configure()} 方法以使配置生效:

@example
def dictConfig(config):
    dictConfigClass(config).configure()
@end example

例如，@code{DictConfigurator} 的子类可以在它自己的 @ref{d57,,__init__()} 中调用 @code{DictConfigurator.__init__()}，然后设置可以在后续 @code{configure()} 调用中使用的自定义前缀。 @code{dictConfigClass} 将被绑定到这个新的子类，然后就可以与在默认的未定制状态下完全相同的方式调用 @ref{b24,,dictConfig()}。
@end quotation


3.2 新版功能.

@end deffn

@geindex fileConfig() (在 logging.config 模块中)
@anchor{library/logging config logging config fileConfig}@anchor{3a1}
@deffn {函数} logging.config.fileConfig (fname, defaults=None, disable_existing_loggers=True)

从一个 @ref{23,,configparser} 格式文件中读取日志记录配置。 文件格式应当与 @ref{206d,,Configuration file format} 中的描述一致。 此函数可在应用程序中被多次调用，以允许最终用户在多个预设配置中进行选择（如果开发者提供了展示选项并加载选定配置的机制）。

@*参数: 

@itemize *

@item 
@code{fname} -- 一个文件名，或一个文件类对象，或是一个派生自 @ref{86b,,RawConfigParser} 的实例。 如果传入了一个派生自 @code{RawConfigParser} 的实例，它会被原样使用。 否则，将会实例化一个 @code{Configparser}，并且它会从作为 @code{fname} 传入的对象中读取配置。 如果存在 @ref{de,,readline()} 方法，则它会被当作一个文件类对象并使用 @ref{1df1,,read_file()} 来读取；在其它情况下，它会被当作一个文件名并传递给 @ref{1037,,read()}。

@item 
@code{defaults} -- 要传递给 ConfigParser 的默认值可在此参数中指定。

@item 
@code{disable_existing_loggers} -- 如果指定为 @code{False}，则当执行此调用时已存在的日志记录器会保持启用。 默认值为 @code{True} 因为这将以向下兼容方式启用旧行为。 此行为是禁用任何现有的非根日志记录器除非它们或它们的上级在日志记录配置中被显式地命名。
@end itemize



在 3.4 版更改: 现在接受 @ref{86b,,RawConfigParser} 子类的实例作为 @code{fname} 的值。 这有助于:


@itemize *

@item 
使用一个配置文件，其中日志记录配置只是全部应用程序配置的一部分。

@item 
使用从一个文件读取的配置，它随后会在被传给 @code{fileConfig} 之前由使用配置的应用程序来修改（例如基于命令行参数或运行时环境的其他部分）。
@end itemize

@end deffn

@geindex listen() (在 logging.config 模块中)
@anchor{library/logging config logging config listen}@anchor{86c}
@deffn {函数} logging.config.listen (port=DEFAULT_LOGGING_CONFIG_PORT, verify=None)

在指定的端口上启动套接字服务器，并监听新的配置。 如果未指定端口，则会使用模块默认的 @code{DEFAULT_LOGGING_CONFIG_PORT}。 日志记录配置将作为适合由 @ref{b24,,dictConfig()} 或 @ref{3a1,,fileConfig()} 进行处理的文件来发送。 返回一个 @ref{234,,Thread} 实例，你可以在该实例上调用 @ref{206e,,start()} 来启动服务器，对该服务器你可以在适当的时候执行 @ref{b59,,join()}。 要停止该服务器，请调用 @ref{206f,,stopListening()}。

如果指定 @code{verify} 参数，则它应当是一个可调用对象，该对象应当验证通过套接字接收的字节数据是否有效且应被处理。 这可以通过对通过套接字发送的内容进行加密和/或签名来完成，这样 @code{verify} 可调用对象就能执行签名验证和/或解密。 @code{verify} 可调用对象的调用会附带一个参数 —— 通过套接字接收的字节数据 —— 并应当返回要处理的字节数据，或者返回 @code{None} 来指明这些字节数据应当被丢弃。 返回的字节数据可以与传入的字节数据相同（例如在只执行验证的时候），或者也可以完全不同（例如在可能执行了解密的时候）。

要将配置发送到套接字，请读取配置文件并将其作为字节序列发送到套接字，字节序列要以使用 @code{struct.pack('>L', n)} 打包为二进制格式的四字节长度的字符串打头。

@cartouche
@quotation 注解 
因为配置的各部分是通过 @ref{b89,,eval()} 传递的，使用此函数可能让用户面临安全风险。 虽然此函数仅绑定到 @code{localhost} 上的套接字，因此并不接受来自远端机器的连接，但在某些场景中不受信任的代码可以在调用 @ref{86c,,listen()} 的进程的账户下运行。 具体来说，如果如果调用 @ref{86c,,listen()} 的进程在用户无法彼此信任的多用户机器上运行，则恶意用户就能简单地通过连接到受害者的 @ref{86c,,listen()} 套接字并发送运行攻击者想在受害者的进程上执行的任何代码的配置的方式，安排运行几乎任意的代码。 如果是使用默认端口这会特别容易做到，即便使用了不同端口也不难做到。 要避免发生这种情况的风险，请在 @ref{86c,,listen()} 中使用 @code{verify} 参数来防止未经认可的配置被应用。
@end quotation
@end cartouche


在 3.4 版更改: 添加了 @code{verify} 参数。


@cartouche
@quotation 注解 
如果你希望将配置发送给未禁用现有日志记录器的监听器，你将需要使用 JSON 格式的配置，该格式将使用 @ref{b24,,dictConfig()} 进行配置。 此方法允许你在你发送的配置中将 @code{disable_existing_loggers} 指定为 @code{False}。
@end quotation
@end cartouche
@end deffn

@geindex stopListening() (在 logging.config 模块中)
@anchor{library/logging config logging config stopListening}@anchor{206f}
@deffn {函数} logging.config.stopListening ()

停止通过对 @ref{86c,,listen()} 的调用所创建的监听服务器。 此函数的调用通常会先于在 @ref{86c,,listen()} 的返回值上调用 @code{join()}。
@end deffn

@node 配置字典架构,Configuration file format,配置函数,logging config --- 日志记录配置
@anchor{library/logging config configuration-dictionary-schema}@anchor{2070}@anchor{library/logging config logging-config-dictschema}@anchor{206c}
@subsubsection 配置字典架构


描述日志记录配置需要列出要创建的不同对象及它们之间的连接；例如，你可以创建一个名为 'console' 的处理程序，然后名为 'startup' 的日志记录器将可以把它的消息发送给 'console' 处理程序。 这些对象并不仅限于 @ref{aa,,logging} 模块所提供的对象，因为你还可以编写你自己的格式化或处理程序类。 这些类的形参可能还需要包括 @code{sys.stderr} 这样的外部对象。 描述这些对象和连接的语法会在下面的 @ref{2071,,对象连接} 中定义。

@menu
* 字典架构细节:: 
* 增量配置:: 
* 对象连接:: 
* 用户定义对象:: 
* Access to external objects:: 
* Access to internal objects:: 
* Import resolution and custom importers:: 

@end menu

@node 字典架构细节,增量配置,,配置字典架构
@anchor{library/logging config dictionary-schema-details}@anchor{2072}
@subsubsection 字典架构细节


传给 @ref{b24,,dictConfig()} 的字典必须包含以下的键:


@itemize *

@item 
@emph{version} - 应设为代表架构版本的整数值。 目前唯一有效的值是 1，使用此键可允许架构在继续演化的同时保持向下兼容性。
@end itemize

所有其他键都是可选项，但如存在它们将根据下面的描述来解读。 在下面提到 'configuring dict' 的所有情况下，都将检查它的特殊键 @code{'()'} 以确定是否需要自定义实例化。 如果需要，则会使用下面 @ref{2073,,用户定义对象} 所描述的机制来创建一个实例；否则，会使用上下文来确定要实例化的对象。


@itemize *

@item 
@emph{formatters} - 对应的值将是一个字典，其中每个键是一个格式器 ID 而每个值则是一个描述如何配置相应 @ref{201d,,Formatter} 实例的字典。

将在配置字典中搜索键 @code{format} 和 @code{datefmt} (默认值均为 @code{None}) 并且这些键会被用于构造 @ref{201d,,Formatter} 实例。


在 3.8 版更改: 一个 @code{validate} 键 (默认值为 @code{True}) 可被添加到配置字典的 @code{formatters} 部分，这会被用来验证格式的有效性。


@item 
@emph{filters} - 对应的值将是一个字典，其中每个键是一个过滤器 ID 而每个值则是一个描述如何配置相应 Filter 实例的字典。

将在配置字典中搜索键 @code{name} (默认值为空字符串) 并且该键会被用于构造 @ref{b70,,logging.Filter} 实例。

@item 
@emph{handlers} - 对应的值将是一个字典，其中每个键是一个处理程序 ID 而每个值则是一个描述如何配置相应 Handler 实例的字典。

将在配置字典中搜索下列键:


@itemize *

@item 
@code{class} (强制)。 这是处理程序类的完整限定名称。

@item 
@code{level} (可选)。 处理程序的级别。

@item 
@code{formatter} (可选)。 处理程序所对应格式化器的 ID。

@item 
@code{filters} (可选)。 由处理程序所对应过滤器的 ID 组成的列表。
@end itemize

所有 @emph{其他} 键会被作为关键字参数传递给处理程序类的构造器。 例如，给定如下代码段:

@example
handlers:
  console:
    class : logging.StreamHandler
    formatter: brief
    level   : INFO
    filters: [allow_foo]
    stream  : ext://sys.stdout
  file:
    class : logging.handlers.RotatingFileHandler
    formatter: precise
    filename: logconfig.log
    maxBytes: 1024
    backupCount: 3
@end example

ID 为 @code{console} 的处理程序会被实例化为 @ref{b6e,,logging.StreamHandler}，并使用 @code{sys.stdout} 作为下层流。 ID 为 @code{file} 的处理程序会被实例化为 @ref{2074,,logging.handlers.RotatingFileHandler}，并附带关键字参数 @code{filename='logconfig.log', maxBytes=1024, backupCount=3}。

@item 
@emph{loggers} - 对应的值将是一个字典，其中每个键是一个日志记录器名称而每个值则是一个描述如何配置相应 Logger 实例的字典。

将在配置字典中搜索下列键:


@itemize *

@item 
@code{level} (可选)。 日志记录器的级别。

@item 
@code{propagate} (可选)。 日志记录器的传播设置。

@item 
@code{filters} (可选)。 由日志记录器对应过滤器的 ID 组成的列表。

@item 
@code{handlers} (可选)。 由日志记录器对应处理程序的 ID 组成的列表。
@end itemize

指定的日志记录器将根据指定的级别、传播、过滤器和处理程序来配置。

@item 
@emph{root} - 这将成为根日志记录器对应的配置。 配置的处理方式将与所有日志记录器一致，除了 @code{propagate} 设置将不可用之外。

@item 
@emph{incremental} - 配置是否要被解读为在现有配置上新增。 该值默认为 @code{False}，这意味着指定的配置将以与当前 @ref{3a1,,fileConfig()} API 所使用的相同语义来替代现有的配置。

如果指定的值为 @code{True}，配置会按照 @ref{2075,,增量配置} 部分所描述的方式来处理。

@item 
@emph{disable_existing_loggers} - 是否要禁用任何现有的非根日志记录器。 该设置对应于 @ref{3a1,,fileConfig()} 中的同名形参。 如果省略，则此形参默认为 @code{True}。 如果 @emph{incremental} 为 @code{True} 则该省会被忽略。
@end itemize

@node 增量配置,对象连接,字典架构细节,配置字典架构
@anchor{library/logging config incremental-configuration}@anchor{2076}@anchor{library/logging config logging-config-dict-incremental}@anchor{2075}
@subsubsection 增量配置


为增量配置提供完全的灵活性是很困难的。 例如，由于过滤器和格式化器这样的对象是匿名的，一旦完成配置，在增加配置时就不可能引用这些匿名对象。

此外，一旦完成了配置，在运行时任意改变日志记录器、处理程序、过滤器、格式化器的对象图就不是很有必要；日志记录器和处理程序的详细程度只需通过设置级别即可实现控制（对于日志记录器则可设置传播旗标）。 在多线程环境中以安全的方式任意改变对象图也许会导致问题；虽然并非不可能，但这样做的好处不足以抵销其所增加的实现复杂度。

这样，当配置字典的 @code{incremental} 键存在且为 @code{True} 时，系统将完全忽略任何 @code{formatters} 和 @code{filters} 条目，并仅会处理 @code{handlers} 条目中的 @code{level} 设置，以及 @code{loggers} 和 @code{root} 条目中的 @code{level} 和 @code{propagate} 设置。

使用配置字典中的值可让配置以封存字典对象的形式通过线路传送给套接字监听器。 这样，长时间运行的应用程序的日志记录的详细程度可随时间改变而无须停止并重新启动应用程序。

@node 对象连接,用户定义对象,增量配置,配置字典架构
@anchor{library/logging config logging-config-dict-connections}@anchor{2071}@anchor{library/logging config object-connections}@anchor{2077}
@subsubsection 对象连接


该架构描述了一组日志记录对象 —— 日志记录器、处理程序、格式化器、过滤器 —— 它们在对象图中彼此连接。 因此，该架构需要能表示对象之间的连接。 例如，在配置完成后，一个特定的日志记录器关联到了一个特定的处理程序。 出于讨论的目的，我们可以说该日志记录器代表两者间连接的源头，而处理程序则代表对应的目标。 当然在已配置对象中这是由包含对处理程序的引用的日志记录器来代表的。 在配置字典中，这是通过给每个目标对象一个 ID 来无歧义地标识它，然后在源头对象中使用该 ID 来实现的。

因此，举例来说，考虑以下 YAML 代码段:

@example
formatters:
  brief:
    # configuration for formatter with id 'brief' goes here
  precise:
    # configuration for formatter with id 'precise' goes here
handlers:
  h1: #This is an id
   # configuration of handler with id 'h1' goes here
   formatter: brief
  h2: #This is another id
   # configuration of handler with id 'h2' goes here
   formatter: precise
loggers:
  foo.bar.baz:
    # other configuration for logger 'foo.bar.baz'
    handlers: [h1, h2]
@end example

（注：这里使用 YAML 是因为它的可读性比表示字典的等价 Python 源码形式更好。）

日志记录器 ID 就是日志记录器的名称，它会在程序中被用来获取对日志记录器的引用，例如 @code{foo.bar.baz}。 格式化器和过滤器的 ID 可以是任意字符串值 (例如上面的 @code{brief}, @code{precise}) 并且它们是瞬态的，因为它们仅对处理配置字典有意义并会被用来确定对象之间的连接，而当配置调用完成时不会在任何地方保留。

上面的代码片段指明名为 @code{foo.bar.baz} 的日志记录器应当关联到两个处理程序，它们的 ID 是 @code{h1} 和 @code{h2}。 @code{h1} 的格式化器的 ID 是 @code{brief}，而 @code{h2} 的格式化器的 ID 是 @code{precise}。

@node 用户定义对象,Access to external objects,对象连接,配置字典架构
@anchor{library/logging config logging-config-dict-userdef}@anchor{2073}@anchor{library/logging config user-defined-objects}@anchor{2078}
@subsubsection 用户定义对象


此架构支持用户定义对象作为处理程序、过滤器和格式化器。 （日志记录器的不同实例不需要具有不同类型，因此这个配置架构并不支持用户定义日志记录器类。）

Objects to be configured are described by dictionaries
which detail their configuration.  In some places, the logging system
will be able to infer from the context how an object is to be
instantiated, but when a user-defined object is to be instantiated,
the system will not know how to do this.  In order to provide complete
flexibility for user-defined object instantiation, the user needs
to provide a 'factory' - a callable which is called with a
configuration dictionary and which returns the instantiated object.
This is signalled by an absolute import path to the factory being
made available under the special key @code{'()'}.  Here's a concrete
example:

@example
formatters:
  brief:
    format: '%(message)s'
  default:
    format: '%(asctime)s %(levelname)-8s %(name)-15s %(message)s'
    datefmt: '%Y-%m-%d %H:%M:%S'
  custom:
      (): my.package.customFormatterFactory
      bar: baz
      spam: 99.9
      answer: 42
@end example

The above YAML snippet defines three formatters.  The first, with id
@code{brief}, is a standard @ref{201d,,logging.Formatter} instance with the
specified format string.  The second, with id @code{default}, has a
longer format and also defines the time format explicitly, and will
result in a @ref{201d,,logging.Formatter} initialized with those two format
strings.  Shown in Python source form, the @code{brief} and @code{default}
formatters have configuration sub-dictionaries:

@example
@{
  'format' : '%(message)s'
@}
@end example

和:

@example
@{
  'format' : '%(asctime)s %(levelname)-8s %(name)-15s %(message)s',
  'datefmt' : '%Y-%m-%d %H:%M:%S'
@}
@end example

respectively, and as these dictionaries do not contain the special key
@code{'()'}, the instantiation is inferred from the context: as a result,
standard @ref{201d,,logging.Formatter} instances are created.  The
configuration sub-dictionary for the third formatter, with id
@code{custom}, is:

@example
@{
  '()' : 'my.package.customFormatterFactory',
  'bar' : 'baz',
  'spam' : 99.9,
  'answer' : 42
@}
@end example

and this contains the special key @code{'()'}, which means that
user-defined instantiation is wanted.  In this case, the specified
factory callable will be used. If it is an actual callable it will be
used directly - otherwise, if you specify a string (as in the example)
the actual callable will be located using normal import mechanisms.
The callable will be called with the @strong{remaining} items in the
configuration sub-dictionary as keyword arguments.  In the above
example, the formatter with id @code{custom} will be assumed to be
returned by the call:

@example
my.package.customFormatterFactory(bar='baz', spam=99.9, answer=42)
@end example

The key @code{'()'} has been used as the special key because it is not a
valid keyword parameter name, and so will not clash with the names of
the keyword arguments used in the call.  The @code{'()'} also serves as a
mnemonic that the corresponding value is a callable.

@node Access to external objects,Access to internal objects,用户定义对象,配置字典架构
@anchor{library/logging config access-to-external-objects}@anchor{2079}@anchor{library/logging config logging-config-dict-externalobj}@anchor{207a}
@subsubsection Access to external objects


There are times where a configuration needs to refer to objects
external to the configuration, for example @code{sys.stderr}.  If the
configuration dict is constructed using Python code, this is
straightforward, but a problem arises when the configuration is
provided via a text file (e.g. JSON, YAML).  In a text file, there is
no standard way to distinguish @code{sys.stderr} from the literal string
@code{'sys.stderr'}.  To facilitate this distinction, the configuration
system looks for certain special prefixes in string values and
treat them specially.  For example, if the literal string
@code{'ext://sys.stderr'} is provided as a value in the configuration,
then the @code{ext://} will be stripped off and the remainder of the
value processed using normal import mechanisms.

The handling of such prefixes is done in a way analogous to protocol
handling: there is a generic mechanism to look for prefixes which
match the regular expression @code{^(?P<prefix>[a-z]+)://(?P<suffix>.*)$}
whereby, if the @code{prefix} is recognised, the @code{suffix} is processed
in a prefix-dependent manner and the result of the processing replaces
the string value.  If the prefix is not recognised, then the string
value will be left as-is.

@node Access to internal objects,Import resolution and custom importers,Access to external objects,配置字典架构
@anchor{library/logging config access-to-internal-objects}@anchor{207b}@anchor{library/logging config logging-config-dict-internalobj}@anchor{207c}
@subsubsection Access to internal objects


As well as external objects, there is sometimes also a need to refer
to objects in the configuration.  This will be done implicitly by the
configuration system for things that it knows about.  For example, the
string value @code{'DEBUG'} for a @code{level} in a logger or handler will
automatically be converted to the value @code{logging.DEBUG}, and the
@code{handlers}, @code{filters} and @code{formatter} entries will take an
object id and resolve to the appropriate destination object.

However, a more generic mechanism is needed for user-defined
objects which are not known to the @ref{aa,,logging} module.  For
example, consider @ref{207d,,logging.handlers.MemoryHandler}, which takes
a @code{target} argument which is another handler to delegate to. Since
the system already knows about this class, then in the configuration,
the given @code{target} just needs to be the object id of the relevant
target handler, and the system will resolve to the handler from the
id.  If, however, a user defines a @code{my.package.MyHandler} which has
an @code{alternate} handler, the configuration system would not know that
the @code{alternate} referred to a handler.  To cater for this, a generic
resolution system allows the user to specify:

@example
handlers:
  file:
    # configuration of file handler goes here

  custom:
    (): my.package.MyHandler
    alternate: cfg://handlers.file
@end example

The literal string @code{'cfg://handlers.file'} will be resolved in an
analogous way to strings with the @code{ext://} prefix, but looking
in the configuration itself rather than the import namespace.  The
mechanism allows access by dot or by index, in a similar way to
that provided by @code{str.format}.  Thus, given the following snippet:

@example
handlers:
  email:
    class: logging.handlers.SMTPHandler
    mailhost: localhost
    fromaddr: my_app@@domain.tld
    toaddrs:
      - support_team@@domain.tld
      - dev_team@@domain.tld
    subject: Houston, we have a problem.
@end example

in the configuration, the string @code{'cfg://handlers'} would resolve to
the dict with key @code{handlers}, the string @code{'cfg://handlers.email}
would resolve to the dict with key @code{email} in the @code{handlers} dict,
and so on.  The string @code{'cfg://handlers.email.toaddrs[1]} would
resolve to @code{'dev_team.domain.tld'} and the string
@code{'cfg://handlers.email.toaddrs[0]'} would resolve to the value
@code{'support_team@@domain.tld'}. The @code{subject} value could be accessed
using either @code{'cfg://handlers.email.subject'} or, equivalently,
@code{'cfg://handlers.email[subject]'}.  The latter form only needs to be
used if the key contains spaces or non-alphanumeric characters.  If an
index value consists only of decimal digits, access will be attempted
using the corresponding integer value, falling back to the string
value if needed.

Given a string @code{cfg://handlers.myhandler.mykey.123}, this will
resolve to @code{config_dict['handlers']['myhandler']['mykey']['123']}.
If the string is specified as @code{cfg://handlers.myhandler.mykey[123]},
the system will attempt to retrieve the value from
@code{config_dict['handlers']['myhandler']['mykey'][123]}, and fall back
to @code{config_dict['handlers']['myhandler']['mykey']['123']} if that
fails.

@node Import resolution and custom importers,,Access to internal objects,配置字典架构
@anchor{library/logging config import-resolution-and-custom-importers}@anchor{207e}@anchor{library/logging config logging-import-resolution}@anchor{207f}
@subsubsection Import resolution and custom importers


Import resolution, by default, uses the builtin @ref{60b,,__import__()} function
to do its importing. You may want to replace this with your own importing
mechanism: if so, you can replace the @code{importer} attribute of the
@code{DictConfigurator} or its superclass, the
@code{BaseConfigurator} class. However, you need to be
careful because of the way functions are accessed from classes via
descriptors. If you are using a Python callable to do your imports, and you
want to define it at class level rather than instance level, you need to wrap
it with @ref{1d9,,staticmethod()}. For example:

@example
from importlib import import_module
from logging.config import BaseConfigurator

BaseConfigurator.importer = staticmethod(import_module)
@end example

You don't need to wrap with @ref{1d9,,staticmethod()} if you're setting the import
callable on a configurator @emph{instance}.

@node Configuration file format,,配置字典架构,logging config --- 日志记录配置
@anchor{library/logging config configuration-file-format}@anchor{2080}@anchor{library/logging config logging-config-fileformat}@anchor{206d}
@subsubsection Configuration file format


The configuration file format understood by @ref{3a1,,fileConfig()} is based on
@ref{23,,configparser} functionality. The file must contain sections called
@code{[loggers]}, @code{[handlers]} and @code{[formatters]} which identify by name the
entities of each type which are defined in the file. For each such entity, there
is a separate section which identifies how that entity is configured.  Thus, for
a logger named @code{log01} in the @code{[loggers]} section, the relevant
configuration details are held in a section @code{[logger_log01]}. Similarly, a
handler called @code{hand01} in the @code{[handlers]} section will have its
configuration held in a section called @code{[handler_hand01]}, while a formatter
called @code{form01} in the @code{[formatters]} section will have its configuration
specified in a section called @code{[formatter_form01]}. The root logger
configuration must be specified in a section called @code{[logger_root]}.

@cartouche
@quotation 注解 
The @ref{3a1,,fileConfig()} API is older than the @ref{b24,,dictConfig()} API and does
not provide functionality to cover certain aspects of logging. For example,
you cannot configure @ref{b70,,Filter} objects, which provide for
filtering of messages beyond simple integer levels, using @ref{3a1,,fileConfig()}.
If you need to have instances of @ref{b70,,Filter} in your logging
configuration, you will need to use @ref{b24,,dictConfig()}. Note that future
enhancements to configuration functionality will be added to
@ref{b24,,dictConfig()}, so it's worth considering transitioning to this newer
API when it's convenient to do so.
@end quotation
@end cartouche

Examples of these sections in the file are given below.

@example
[loggers]
keys=root,log02,log03,log04,log05,log06,log07

[handlers]
keys=hand01,hand02,hand03,hand04,hand05,hand06,hand07,hand08,hand09

[formatters]
keys=form01,form02,form03,form04,form05,form06,form07,form08,form09
@end example

The root logger must specify a level and a list of handlers. An example of a
root logger section is given below.

@example
[logger_root]
level=NOTSET
handlers=hand01
@end example

The @code{level} entry can be one of @code{DEBUG, INFO, WARNING, ERROR, CRITICAL} or
@code{NOTSET}. For the root logger only, @code{NOTSET} means that all messages will be
logged. Level values are @ref{b89,,eval()}uated in the context of the @code{logging}
package's namespace.

The @code{handlers} entry is a comma-separated list of handler names, which must
appear in the @code{[handlers]} section. These names must appear in the
@code{[handlers]} section and have corresponding sections in the configuration
file.

For loggers other than the root logger, some additional information is required.
This is illustrated by the following example.

@example
[logger_parser]
level=DEBUG
handlers=hand01
propagate=1
qualname=compiler.parser
@end example

The @code{level} and @code{handlers} entries are interpreted as for the root logger,
except that if a non-root logger's level is specified as @code{NOTSET}, the system
consults loggers higher up the hierarchy to determine the effective level of the
logger. The @code{propagate} entry is set to 1 to indicate that messages must
propagate to handlers higher up the logger hierarchy from this logger, or 0 to
indicate that messages are @strong{not} propagated to handlers up the hierarchy. The
@code{qualname} entry is the hierarchical channel name of the logger, that is to
say the name used by the application to get the logger.

Sections which specify handler configuration are exemplified by the following.

@example
[handler_hand01]
class=StreamHandler
level=NOTSET
formatter=form01
args=(sys.stdout,)
@end example

The @code{class} entry indicates the handler's class (as determined by @ref{b89,,eval()}
in the @code{logging} package's namespace). The @code{level} is interpreted as for
loggers, and @code{NOTSET} is taken to mean 'log everything'.

The @code{formatter} entry indicates the key name of the formatter for this
handler. If blank, a default formatter (@code{logging._defaultFormatter}) is used.
If a name is specified, it must appear in the @code{[formatters]} section and have
a corresponding section in the configuration file.

The @code{args} entry, when @ref{b89,,eval()}uated in the context of the @code{logging}
package's namespace, is the list of arguments to the constructor for the handler
class. Refer to the constructors for the relevant handlers, or to the examples
below, to see how typical entries are constructed. If not provided, it defaults
to @code{()}.

The optional @code{kwargs} entry, when @ref{b89,,eval()}uated in the context of the
@code{logging} package's namespace, is the keyword argument dict to the constructor
for the handler class. If not provided, it defaults to @code{@{@}}.

@example
[handler_hand02]
class=FileHandler
level=DEBUG
formatter=form02
args=('python.log', 'w')

[handler_hand03]
class=handlers.SocketHandler
level=INFO
formatter=form03
args=('localhost', handlers.DEFAULT_TCP_LOGGING_PORT)

[handler_hand04]
class=handlers.DatagramHandler
level=WARN
formatter=form04
args=('localhost', handlers.DEFAULT_UDP_LOGGING_PORT)

[handler_hand05]
class=handlers.SysLogHandler
level=ERROR
formatter=form05
args=(('localhost', handlers.SYSLOG_UDP_PORT), handlers.SysLogHandler.LOG_USER)

[handler_hand06]
class=handlers.NTEventLogHandler
level=CRITICAL
formatter=form06
args=('Python Application', '@w{'}, 'Application')

[handler_hand07]
class=handlers.SMTPHandler
level=WARN
formatter=form07
args=('localhost', 'from@@abc', ['user1@@abc', 'user2@@xyz'], 'Logger Subject')
kwargs=@{'timeout': 10.0@}

[handler_hand08]
class=handlers.MemoryHandler
level=NOTSET
formatter=form08
target=
args=(10, ERROR)

[handler_hand09]
class=handlers.HTTPHandler
level=NOTSET
formatter=form09
args=('localhost:9022', '/log', 'GET')
kwargs=@{'secure': True@}
@end example

Sections which specify formatter configuration are typified by the following.

@example
[formatter_form01]
format=F1 %(asctime)s %(levelname)s %(message)s
datefmt=
class=logging.Formatter
@end example

The @code{format} entry is the overall format string, and the @code{datefmt} entry is
the @code{strftime()}-compatible date/time format string.  If empty, the
package substitutes something which is almost equivalent to specifying the date
format string @code{'%Y-%m-%d %H:%M:%S'}.  This format also specifies milliseconds,
which are appended to the result of using the above format string, with a comma
separator.  An example time in this format is @code{2003-01-23 00:29:50,411}.

The @code{class} entry is optional.  It indicates the name of the formatter's class
(as a dotted module and class name.)  This option is useful for instantiating a
@ref{201d,,Formatter} subclass.  Subclasses of
@ref{201d,,Formatter} can present exception tracebacks in an expanded or
condensed format.

@cartouche
@quotation 注解 
Due to the use of @ref{b89,,eval()} as described above, there are
potential security risks which result from using the @ref{86c,,listen()} to send
and receive configurations via sockets. The risks are limited to where
multiple users with no mutual trust run code on the same machine; see the
@ref{86c,,listen()} documentation for more information.
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@item 模块 @ref{aa,,logging}

日志记录模块的 API 参考。

@item @ref{ac,,logging.handlers} 模块

日志记录模块附带的有用处理器。
@end table


@node logging handlers --- 日志处理,getpass --- 便携式密码输入工具,logging config --- 日志记录配置,通用操作系统服务
@anchor{library/logging handlers doc}@anchor{2081}@anchor{library/logging handlers logging-handlers-logging-handlers}@anchor{2082}@anchor{library/logging handlers module-logging handlers}@anchor{ac}
@subsection @code{logging.handlers} --- 日志处理


@geindex logging.handlers (模块)

@strong{源代码:} Lib/logging/handlers.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/logging/handlers.py}

@subsubheading Important



此页面仅包含参考信息。有关教程，请参阅


@itemize *

@item 
@ref{b6b,,基础教程}

@item 
@ref{b6c,,进阶教程}

@item 
@ref{b6d,,日志操作手册}
@end itemize


__________________________________________________________________


The following useful handlers are provided in the package. Note that three of
the handlers (@ref{b6e,,StreamHandler}, @ref{2083,,FileHandler} and
@ref{c15,,NullHandler}) are actually defined in the @ref{aa,,logging} module itself,
but have been documented here along with the other handlers.

@menu
* StreamHandler:: 
* FileHandler:: 
* NullHandler:: 
* WatchedFileHandler:: 
* BaseRotatingHandler:: 
* RotatingFileHandler:: 
* TimedRotatingFileHandler:: 
* SocketHandler:: 
* DatagramHandler:: 
* SysLogHandler:: 
* NTEventLogHandler:: 
* SMTPHandler:: 
* MemoryHandler:: 
* HTTPHandler:: 
* QueueHandler:: 
* QueueListener:: 

@end menu

@node StreamHandler,FileHandler,,logging handlers --- 日志处理
@anchor{library/logging handlers stream-handler}@anchor{2084}@anchor{library/logging handlers streamhandler}@anchor{2085}
@subsubsection StreamHandler


The @ref{b6e,,StreamHandler} class, located in the core @ref{aa,,logging} package,
sends logging output to streams such as @emph{sys.stdout}, @emph{sys.stderr} or any
file-like object (or, more precisely, any object which supports @code{write()}
and @code{flush()} methods).

@geindex StreamHandler (logging 中的类)
@anchor{library/logging handlers logging StreamHandler}@anchor{b6e}
@deffn {类} logging.StreamHandler (stream=None)

Returns a new instance of the @ref{b6e,,StreamHandler} class. If @emph{stream} is
specified, the instance will use it for logging output; otherwise, @emph{sys.stderr}
will be used.

@geindex emit() (logging.StreamHandler 方法)
@anchor{library/logging handlers logging StreamHandler emit}@anchor{2086}
@deffn {方法} emit (record)

If a formatter is specified, it is used to format the record. The record
is then written to the stream with a terminator. If exception information
is present, it is formatted using @ref{2047,,traceback.print_exception()} and
appended to the stream.
@end deffn

@geindex flush() (logging.StreamHandler 方法)
@anchor{library/logging handlers logging StreamHandler flush}@anchor{2087}
@deffn {方法} flush ()

Flushes the stream by calling its @ref{2087,,flush()} method. Note that the
@code{close()} method is inherited from @ref{201e,,Handler} and so
does no output, so an explicit @ref{2087,,flush()} call may be needed at times.
@end deffn

@geindex setStream() (logging.StreamHandler 方法)
@anchor{library/logging handlers logging StreamHandler setStream}@anchor{3a0}
@deffn {方法} setStream (stream)

Sets the instance's stream to the specified value, if it is different.
The old stream is flushed before the new stream is set.

@*参数: 
@code{stream} -- The stream that the handler should use.


@*返回: 
the old stream, if the stream was changed, or @emph{None} if it wasn't.

@end deffn


3.7 新版功能.

@end deffn


在 3.2 版更改: The @code{StreamHandler} class now has a @code{terminator} attribute, default
value @code{'\n'}, which is used as the terminator when writing a formatted
record to a stream. If you don't want this newline termination, you can
set the handler instance's @code{terminator} attribute to the empty string.
In earlier versions, the terminator was hardcoded as @code{'\n'}.


@node FileHandler,NullHandler,StreamHandler,logging handlers --- 日志处理
@anchor{library/logging handlers file-handler}@anchor{2088}@anchor{library/logging handlers filehandler}@anchor{2089}
@subsubsection FileHandler


The @ref{2083,,FileHandler} class, located in the core @ref{aa,,logging} package,
sends logging output to a disk file.  It inherits the output functionality from
@ref{b6e,,StreamHandler}.

@geindex FileHandler (logging 中的类)
@anchor{library/logging handlers logging FileHandler}@anchor{2083}
@deffn {类} logging.FileHandler (filename, mode='a', encoding=None, delay=False)

Returns a new instance of the @ref{2083,,FileHandler} class. The specified file is
opened and used as the stream for logging. If @emph{mode} is not specified,
@code{'a'} is used.  If @emph{encoding} is not @code{None}, it is used to open the file
with that encoding.  If @emph{delay} is true, then file opening is deferred until the
first call to @ref{208a,,emit()}. By default, the file grows indefinitely.


在 3.6 版更改: As well as string values, @ref{201,,Path} objects are also accepted
for the @emph{filename} argument.


@geindex close() (logging.FileHandler 方法)
@anchor{library/logging handlers logging FileHandler close}@anchor{208b}
@deffn {方法} close ()

关闭文件。
@end deffn

@geindex emit() (logging.FileHandler 方法)
@anchor{library/logging handlers logging FileHandler emit}@anchor{208a}
@deffn {方法} emit (record)

将记录输出到文件。
@end deffn
@end deffn

@node NullHandler,WatchedFileHandler,FileHandler,logging handlers --- 日志处理
@anchor{library/logging handlers null-handler}@anchor{208c}@anchor{library/logging handlers nullhandler}@anchor{208d}
@subsubsection NullHandler



3.1 新版功能.


The @ref{c15,,NullHandler} class, located in the core @ref{aa,,logging} package,
does not do any formatting or output. It is essentially a 'no-op' handler
for use by library developers.

@geindex NullHandler (logging 中的类)
@anchor{library/logging handlers logging NullHandler}@anchor{c15}
@deffn {类} logging.NullHandler

Returns a new instance of the @ref{c15,,NullHandler} class.

@geindex emit() (logging.NullHandler 方法)
@anchor{library/logging handlers logging NullHandler emit}@anchor{208e}
@deffn {方法} emit (record)

This method does nothing.
@end deffn

@geindex handle() (logging.NullHandler 方法)
@anchor{library/logging handlers logging NullHandler handle}@anchor{208f}
@deffn {方法} handle (record)

This method does nothing.
@end deffn

@geindex createLock() (logging.NullHandler 方法)
@anchor{library/logging handlers logging NullHandler createLock}@anchor{2090}
@deffn {方法} createLock ()

This method returns @code{None} for the lock, since there is no
underlying I/O to which access needs to be serialized.
@end deffn
@end deffn

See @ref{2091,,配置库的日志记录} for more information on how to use
@ref{c15,,NullHandler}.

@node WatchedFileHandler,BaseRotatingHandler,NullHandler,logging handlers --- 日志处理
@anchor{library/logging handlers watched-file-handler}@anchor{2092}@anchor{library/logging handlers watchedfilehandler}@anchor{2093}
@subsubsection WatchedFileHandler


The @ref{2094,,WatchedFileHandler} class, located in the @ref{ac,,logging.handlers}
module, is a @code{FileHandler} which watches the file it is logging to. If
the file changes, it is closed and reopened using the file name.

A file change can happen because of usage of programs such as @emph{newsyslog} and
@emph{logrotate} which perform log file rotation. This handler, intended for use
under Unix/Linux, watches the file to see if it has changed since the last emit.
(A file is deemed to have changed if its device or inode have changed.) If the
file has changed, the old file stream is closed, and the file opened to get a
new stream.

This handler is not appropriate for use under Windows, because under Windows
open log files cannot be moved or renamed - logging opens the files with
exclusive locks - and so there is no need for such a handler. Furthermore,
@emph{ST_INO} is not supported under Windows; @ref{1f1,,stat()} always returns zero
for this value.

@geindex WatchedFileHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers WatchedFileHandler}@anchor{2094}
@deffn {类} logging.handlers.WatchedFileHandler (filename, mode='a', encoding=None, delay=False)

Returns a new instance of the @ref{2094,,WatchedFileHandler} class. The specified
file is opened and used as the stream for logging. If @emph{mode} is not specified,
@code{'a'} is used.  If @emph{encoding} is not @code{None}, it is used to open the file
with that encoding.  If @emph{delay} is true, then file opening is deferred until the
first call to @ref{2095,,emit()}.  By default, the file grows indefinitely.


在 3.6 版更改: As well as string values, @ref{201,,Path} objects are also accepted
for the @emph{filename} argument.


@geindex reopenIfNeeded() (logging.handlers.WatchedFileHandler 方法)
@anchor{library/logging handlers logging handlers WatchedFileHandler reopenIfNeeded}@anchor{55d}
@deffn {方法} reopenIfNeeded ()

Checks to see if the file has changed.  If it has, the existing stream is
flushed and closed and the file opened again, typically as a precursor to
outputting the record to the file.


3.6 新版功能.

@end deffn

@geindex emit() (logging.handlers.WatchedFileHandler 方法)
@anchor{library/logging handlers logging handlers WatchedFileHandler emit}@anchor{2095}
@deffn {方法} emit (record)

Outputs the record to the file, but first calls @ref{55d,,reopenIfNeeded()} to
reopen the file if it has changed.
@end deffn
@end deffn

@node BaseRotatingHandler,RotatingFileHandler,WatchedFileHandler,logging handlers --- 日志处理
@anchor{library/logging handlers base-rotating-handler}@anchor{2096}@anchor{library/logging handlers baserotatinghandler}@anchor{2097}
@subsubsection BaseRotatingHandler


The @ref{2098,,BaseRotatingHandler} class, located in the @ref{ac,,logging.handlers}
module, is the base class for the rotating file handlers,
@ref{2074,,RotatingFileHandler} and @ref{868,,TimedRotatingFileHandler}. You should
not need to instantiate this class, but it has attributes and methods you may
need to override.

@geindex BaseRotatingHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers BaseRotatingHandler}@anchor{2098}
@deffn {类} logging.handlers.BaseRotatingHandler (filename, mode, encoding=None, delay=False)

The parameters are as for @code{FileHandler}. The attributes are:

@geindex namer (logging.handlers.BaseRotatingHandler 属性)
@anchor{library/logging handlers logging handlers BaseRotatingHandler namer}@anchor{2099}
@deffn {属性} namer

If this attribute is set to a callable, the @ref{209a,,rotation_filename()}
method delegates to this callable. The parameters passed to the callable
are those passed to @ref{209a,,rotation_filename()}.

@cartouche
@quotation 注解 
The namer function is called quite a few times during rollover,
so it should be as simple and as fast as possible. It should also
return the same output every time for a given input, otherwise the
rollover behaviour may not work as expected.
@end quotation
@end cartouche


3.3 新版功能.

@end deffn

@geindex rotator (logging.handlers.BaseRotatingHandler 属性)
@anchor{library/logging handlers logging handlers BaseRotatingHandler rotator}@anchor{209b}
@deffn {属性} rotator

If this attribute is set to a callable, the @ref{209c,,rotate()} method
delegates to this callable.  The parameters passed to the callable are
those passed to @ref{209c,,rotate()}.


3.3 新版功能.

@end deffn

@geindex rotation_filename() (logging.handlers.BaseRotatingHandler 方法)
@anchor{library/logging handlers logging handlers BaseRotatingHandler rotation_filename}@anchor{209a}
@deffn {方法} rotation_filename (default_name)

Modify the filename of a log file when rotating.

This is provided so that a custom filename can be provided.

The default implementation calls the 'namer' attribute of the handler,
if it's callable, passing the default name to it. If the attribute isn't
callable (the default is @code{None}), the name is returned unchanged.

@*参数: 
@code{default_name} -- The default name for the log file.



3.3 新版功能.

@end deffn

@geindex rotate() (logging.handlers.BaseRotatingHandler 方法)
@anchor{library/logging handlers logging handlers BaseRotatingHandler rotate}@anchor{209c}
@deffn {方法} rotate (source, dest)

When rotating, rotate the current log.

The default implementation calls the 'rotator' attribute of the handler,
if it's callable, passing the source and dest arguments to it. If the
attribute isn't callable (the default is @code{None}), the source is simply
renamed to the destination.

@*参数: 

@itemize *

@item 
@code{source} -- The source filename. This is normally the base
filename, e.g. 'test.log'.

@item 
@code{dest} -- The destination filename. This is normally
what the source is rotated to, e.g. 'test.log.1'.
@end itemize



3.3 新版功能.

@end deffn
@end deffn

The reason the attributes exist is to save you having to subclass - you can use
the same callables for instances of @ref{2074,,RotatingFileHandler} and
@ref{868,,TimedRotatingFileHandler}. If either the namer or rotator callable
raises an exception, this will be handled in the same way as any other
exception during an @code{emit()} call, i.e. via the @code{handleError()} method
of the handler.

If you need to make more significant changes to rotation processing, you can
override the methods.

For an example, see @ref{209d,,Using a rotator and namer to customize log rotation processing}.

@node RotatingFileHandler,TimedRotatingFileHandler,BaseRotatingHandler,logging handlers --- 日志处理
@anchor{library/logging handlers rotating-file-handler}@anchor{209e}@anchor{library/logging handlers rotatingfilehandler}@anchor{209f}
@subsubsection RotatingFileHandler


The @ref{2074,,RotatingFileHandler} class, located in the @ref{ac,,logging.handlers}
module, supports rotation of disk log files.

@geindex RotatingFileHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers RotatingFileHandler}@anchor{2074}
@deffn {类} logging.handlers.RotatingFileHandler (filename, mode='a', maxBytes=0, backupCount=0, encoding=None, delay=False)

Returns a new instance of the @ref{2074,,RotatingFileHandler} class. The specified
file is opened and used as the stream for logging. If @emph{mode} is not specified,
@code{'a'} is used.  If @emph{encoding} is not @code{None}, it is used to open the file
with that encoding.  If @emph{delay} is true, then file opening is deferred until the
first call to @ref{20a0,,emit()}.  By default, the file grows indefinitely.

You can use the @emph{maxBytes} and @emph{backupCount} values to allow the file to
@emph{rollover} at a predetermined size. When the size is about to be exceeded,
the file is closed and a new file is silently opened for output. Rollover occurs
whenever the current log file is nearly @emph{maxBytes} in length; but if either of
@emph{maxBytes} or @emph{backupCount} is zero, rollover never occurs, so you generally want
to set @emph{backupCount} to at least 1, and have a non-zero @emph{maxBytes}.
When @emph{backupCount} is non-zero, the system will save old log files by appending
the extensions '.1', '.2' etc., to the filename. For example, with a @emph{backupCount}
of 5 and a base file name of @code{app.log}, you would get @code{app.log},
@code{app.log.1}, @code{app.log.2}, up to @code{app.log.5}. The file being
written to is always @code{app.log}.  When this file is filled, it is closed
and renamed to @code{app.log.1}, and if files @code{app.log.1},
@code{app.log.2}, etc. exist, then they are renamed to @code{app.log.2},
@code{app.log.3} etc. respectively.


在 3.6 版更改: As well as string values, @ref{201,,Path} objects are also accepted
for the @emph{filename} argument.


@geindex doRollover() (logging.handlers.RotatingFileHandler 方法)
@anchor{library/logging handlers logging handlers RotatingFileHandler doRollover}@anchor{20a1}
@deffn {方法} doRollover ()

Does a rollover, as described above.
@end deffn

@geindex emit() (logging.handlers.RotatingFileHandler 方法)
@anchor{library/logging handlers logging handlers RotatingFileHandler emit}@anchor{20a0}
@deffn {方法} emit (record)

Outputs the record to the file, catering for rollover as described
previously.
@end deffn
@end deffn

@node TimedRotatingFileHandler,SocketHandler,RotatingFileHandler,logging handlers --- 日志处理
@anchor{library/logging handlers timed-rotating-file-handler}@anchor{20a2}@anchor{library/logging handlers timedrotatingfilehandler}@anchor{20a3}
@subsubsection TimedRotatingFileHandler


The @ref{868,,TimedRotatingFileHandler} class, located in the
@ref{ac,,logging.handlers} module, supports rotation of disk log files at certain
timed intervals.

@geindex TimedRotatingFileHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers TimedRotatingFileHandler}@anchor{868}
@deffn {类} logging.handlers.TimedRotatingFileHandler (filename, when='h', interval=1, backupCount=0, encoding=None, delay=False, utc=False, atTime=None)

Returns a new instance of the @ref{868,,TimedRotatingFileHandler} class. The
specified file is opened and used as the stream for logging. On rotating it also
sets the filename suffix. Rotating happens based on the product of @emph{when} and
@emph{interval}.

You can use the @emph{when} to specify the type of @emph{interval}. The list of possible
values is below.  Note that they are not case sensitive.


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

间隔类型

@tab

如果/如何使用 @emph{atTime}

@item

@code{'S'}

@tab

秒

@tab

忽略

@item

@code{'M'}

@tab

分钟

@tab

忽略

@item

@code{'H'}

@tab

小时

@tab

忽略

@item

@code{'D'}

@tab

天

@tab

忽略

@item

@code{'W0'-'W6'}

@tab

工作日(0=星期一)

@tab

Used to compute initial
rollover time

@item

@code{'midnight'}

@tab

Roll over at midnight, if
@emph{atTime} not specified,
else at time @emph{atTime}

@tab

Used to compute initial
rollover time

@end multitable


When using weekday-based rotation, specify 'W0' for Monday, 'W1' for
Tuesday, and so on up to 'W6' for Sunday. In this case, the value passed for
@emph{interval} isn't used.

The system will save old log files by appending extensions to the filename.
The extensions are date-and-time based, using the strftime format
@code{%Y-%m-%d_%H-%M-%S} or a leading portion thereof, depending on the
rollover interval.

When computing the next rollover time for the first time (when the handler
is created), the last modification time of an existing log file, or else
the current time, is used to compute when the next rotation will occur.

If the @emph{utc} argument is true, times in UTC will be used; otherwise
local time is used.

If @emph{backupCount} is nonzero, at most @emph{backupCount} files
will be kept, and if more would be created when rollover occurs, the oldest
one is deleted. The deletion logic uses the interval to determine which
files to delete, so changing the interval may leave old files lying around.

If @emph{delay} is true, then file opening is deferred until the first call to
@ref{20a4,,emit()}.

If @emph{atTime} is not @code{None}, it must be a @code{datetime.time} instance which
specifies the time of day when rollover occurs, for the cases where rollover
is set to happen "at midnight" or "on a particular weekday". Note that in
these cases, the @emph{atTime} value is effectively used to compute the @emph{initial}
rollover, and subsequent rollovers would be calculated via the normal
interval calculation.

@cartouche
@quotation 注解 
Calculation of the initial rollover time is done when the handler
is initialised. Calculation of subsequent rollover times is done only
when rollover occurs, and rollover occurs only when emitting output. If
this is not kept in mind, it might lead to some confusion. For example,
if an interval of "every minute" is set, that does not mean you will
always see log files with times (in the filename) separated by a minute;
if, during application execution, logging output is generated more
frequently than once a minute, @emph{then} you can expect to see log files
with times separated by a minute. If, on the other hand, logging messages
are only output once every five minutes (say), then there will be gaps in
the file times corresponding to the minutes where no output (and hence no
rollover) occurred.
@end quotation
@end cartouche


在 3.4 版更改: @emph{atTime} parameter was added.



在 3.6 版更改: As well as string values, @ref{201,,Path} objects are also accepted
for the @emph{filename} argument.


@geindex doRollover() (logging.handlers.TimedRotatingFileHandler 方法)
@anchor{library/logging handlers logging handlers TimedRotatingFileHandler doRollover}@anchor{20a5}
@deffn {方法} doRollover ()

Does a rollover, as described above.
@end deffn

@geindex emit() (logging.handlers.TimedRotatingFileHandler 方法)
@anchor{library/logging handlers logging handlers TimedRotatingFileHandler emit}@anchor{20a4}
@deffn {方法} emit (record)

Outputs the record to the file, catering for rollover as described above.
@end deffn
@end deffn

@node SocketHandler,DatagramHandler,TimedRotatingFileHandler,logging handlers --- 日志处理
@anchor{library/logging handlers socket-handler}@anchor{20a6}@anchor{library/logging handlers sockethandler}@anchor{20a7}
@subsubsection SocketHandler


The @ref{869,,SocketHandler} class, located in the @ref{ac,,logging.handlers} module,
sends logging output to a network socket. The base class uses a TCP socket.

@geindex SocketHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers SocketHandler}@anchor{869}
@deffn {类} logging.handlers.SocketHandler (host, port)

Returns a new instance of the @ref{869,,SocketHandler} class intended to
communicate with a remote machine whose address is given by @emph{host} and @emph{port}.


在 3.4 版更改: If @code{port} is specified as @code{None}, a Unix domain socket is created
using the value in @code{host} - otherwise, a TCP socket is created.


@geindex close() (logging.handlers.SocketHandler 方法)
@anchor{library/logging handlers logging handlers SocketHandler close}@anchor{20a8}
@deffn {方法} close ()

Closes the socket.
@end deffn

@geindex emit() (logging.handlers.SocketHandler 方法)
@anchor{library/logging handlers logging handlers SocketHandler emit}@anchor{20a9}
@deffn {方法} emit ()

Pickles the record's attribute dictionary and writes it to the socket in
binary format. If there is an error with the socket, silently drops the
packet. If the connection was previously lost, re-establishes the
connection. To unpickle the record at the receiving end into a
@ref{900,,LogRecord}, use the @ref{204f,,makeLogRecord()}
function.
@end deffn

@geindex handleError() (logging.handlers.SocketHandler 方法)
@anchor{library/logging handlers logging handlers SocketHandler handleError}@anchor{20aa}
@deffn {方法} handleError ()

Handles an error which has occurred during @ref{20a9,,emit()}. The most likely
cause is a lost connection. Closes the socket so that we can retry on the
next event.
@end deffn

@geindex makeSocket() (logging.handlers.SocketHandler 方法)
@anchor{library/logging handlers logging handlers SocketHandler makeSocket}@anchor{20ab}
@deffn {方法} makeSocket ()

This is a factory method which allows subclasses to define the precise
type of socket they want. The default implementation creates a TCP socket
(@ref{c83,,socket.SOCK_STREAM}).
@end deffn

@geindex makePickle() (logging.handlers.SocketHandler 方法)
@anchor{library/logging handlers logging handlers SocketHandler makePickle}@anchor{20ac}
@deffn {方法} makePickle (record)

Pickles the record's attribute dictionary in binary format with a length
prefix, and returns it ready for transmission across the socket. The
details of this operation are equivalent to:

@example
data = pickle.dumps(record_attr_dict, 1)
datalen = struct.pack('>L', len(data))
return datalen + data
@end example

Note that pickles aren't completely secure. If you are concerned about
security, you may want to override this method to implement a more secure
mechanism. For example, you can sign pickles using HMAC and then verify
them on the receiving end, or alternatively you can disable unpickling of
global objects on the receiving end.
@end deffn

@geindex send() (logging.handlers.SocketHandler 方法)
@anchor{library/logging handlers logging handlers SocketHandler send}@anchor{20ad}
@deffn {方法} send (packet)

Send a pickled byte-string @emph{packet} to the socket. The format of the sent
byte-string is as described in the documentation for
@ref{20ac,,makePickle()}.

This function allows for partial sends, which can happen when the network
is busy.
@end deffn

@geindex createSocket() (logging.handlers.SocketHandler 方法)
@anchor{library/logging handlers logging handlers SocketHandler createSocket}@anchor{20ae}
@deffn {方法} createSocket ()

Tries to create a socket; on failure, uses an exponential back-off
algorithm.  On initial failure, the handler will drop the message it was
trying to send.  When subsequent messages are handled by the same
instance, it will not try connecting until some time has passed.  The
default parameters are such that the initial delay is one second, and if
after that delay the connection still can't be made, the handler will
double the delay each time up to a maximum of 30 seconds.

This behaviour is controlled by the following handler attributes:


@itemize *

@item 
@code{retryStart} (initial delay, defaulting to 1.0 seconds).

@item 
@code{retryFactor} (multiplier, defaulting to 2.0).

@item 
@code{retryMax} (maximum delay, defaulting to 30.0 seconds).
@end itemize

This means that if the remote listener starts up @emph{after} the handler has
been used, you could lose messages (since the handler won't even attempt
a connection until the delay has elapsed, but just silently drop messages
during the delay period).
@end deffn
@end deffn

@node DatagramHandler,SysLogHandler,SocketHandler,logging handlers --- 日志处理
@anchor{library/logging handlers datagram-handler}@anchor{20af}@anchor{library/logging handlers datagramhandler}@anchor{20b0}
@subsubsection DatagramHandler


The @ref{86a,,DatagramHandler} class, located in the @ref{ac,,logging.handlers}
module, inherits from @ref{869,,SocketHandler} to support sending logging messages
over UDP sockets.

@geindex DatagramHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers DatagramHandler}@anchor{86a}
@deffn {类} logging.handlers.DatagramHandler (host, port)

Returns a new instance of the @ref{86a,,DatagramHandler} class intended to
communicate with a remote machine whose address is given by @emph{host} and @emph{port}.


在 3.4 版更改: If @code{port} is specified as @code{None}, a Unix domain socket is created
using the value in @code{host} - otherwise, a UDP socket is created.


@geindex emit() (logging.handlers.DatagramHandler 方法)
@anchor{library/logging handlers logging handlers DatagramHandler emit}@anchor{20b1}
@deffn {方法} emit ()

Pickles the record's attribute dictionary and writes it to the socket in
binary format. If there is an error with the socket, silently drops the
packet. To unpickle the record at the receiving end into a
@ref{900,,LogRecord}, use the @ref{204f,,makeLogRecord()}
function.
@end deffn

@geindex makeSocket() (logging.handlers.DatagramHandler 方法)
@anchor{library/logging handlers logging handlers DatagramHandler makeSocket}@anchor{20b2}
@deffn {方法} makeSocket ()

The factory method of @ref{869,,SocketHandler} is here overridden to create
a UDP socket (@ref{c82,,socket.SOCK_DGRAM}).
@end deffn

@geindex send() (logging.handlers.DatagramHandler 方法)
@anchor{library/logging handlers logging handlers DatagramHandler send}@anchor{20b3}
@deffn {方法} send (s)

Send a pickled byte-string to a socket. The format of the sent byte-string
is as described in the documentation for @ref{20ac,,SocketHandler.makePickle()}.
@end deffn
@end deffn

@node SysLogHandler,NTEventLogHandler,DatagramHandler,logging handlers --- 日志处理
@anchor{library/logging handlers syslog-handler}@anchor{20b4}@anchor{library/logging handlers sysloghandler}@anchor{20b5}
@subsubsection SysLogHandler


The @ref{a19,,SysLogHandler} class, located in the @ref{ac,,logging.handlers} module,
supports sending logging messages to a remote or local Unix syslog.

@geindex SysLogHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers SysLogHandler}@anchor{a19}
@deffn {类} logging.handlers.SysLogHandler (address=('localhost', SYSLOG_UDP_PORT), facility=LOG_USER, socktype=socket.SOCK_DGRAM)

Returns a new instance of the @ref{a19,,SysLogHandler} class intended to
communicate with a remote Unix machine whose address is given by @emph{address} in
the form of a @code{(host, port)} tuple.  If @emph{address} is not specified,
@code{('localhost', 514)} is used.  The address is used to open a socket.  An
alternative to providing a @code{(host, port)} tuple is providing an address as a
string, for example '/dev/log'. In this case, a Unix domain socket is used to
send the message to the syslog. If @emph{facility} is not specified,
@code{LOG_USER} is used. The type of socket opened depends on the
@emph{socktype} argument, which defaults to @ref{c82,,socket.SOCK_DGRAM} and thus
opens a UDP socket. To open a TCP socket (for use with the newer syslog
daemons such as rsyslog), specify a value of @ref{c83,,socket.SOCK_STREAM}.

Note that if your server is not listening on UDP port 514,
@ref{a19,,SysLogHandler} may appear not to work. In that case, check what
address you should be using for a domain socket - it's system dependent.
For example, on Linux it's usually '/dev/log' but on OS/X it's
'/var/run/syslog'. You'll need to check your platform and use the
appropriate address (you may need to do this check at runtime if your
application needs to run on several platforms). On Windows, you pretty
much have to use the UDP option.


在 3.2 版更改: @emph{socktype} was added.


@geindex close() (logging.handlers.SysLogHandler 方法)
@anchor{library/logging handlers logging handlers SysLogHandler close}@anchor{20b6}
@deffn {方法} close ()

Closes the socket to the remote host.
@end deffn

@geindex emit() (logging.handlers.SysLogHandler 方法)
@anchor{library/logging handlers logging handlers SysLogHandler emit}@anchor{20b7}
@deffn {方法} emit (record)

The record is formatted, and then sent to the syslog server. If exception
information is present, it is @emph{not} sent to the server.


在 3.2.1 版更改: (See: bpo-12168@footnote{https://bugs.python.org/issue12168}.) In earlier versions, the message sent to the
syslog daemons was always terminated with a NUL byte, because early
versions of these daemons expected a NUL terminated message - even
though it's not in the relevant specification (
@geindex RFC; RFC 5424
RFC 5424@footnote{https://tools.ietf.org/html/rfc5424.html}). More recent
versions of these daemons don't expect the NUL byte but strip it off
if it's there, and even more recent daemons (which adhere more closely
to RFC 5424) pass the NUL byte on as part of the message.

To enable easier handling of syslog messages in the face of all these
differing daemon behaviours, the appending of the NUL byte has been
made configurable, through the use of a class-level attribute,
@code{append_nul}. This defaults to @code{True} (preserving the existing
behaviour) but can be set to @code{False} on a @code{SysLogHandler} instance
in order for that instance to @emph{not} append the NUL terminator.



在 3.3 版更改: (See: bpo-12419@footnote{https://bugs.python.org/issue12419}.) In earlier versions, there was no facility for
an "ident" or "tag" prefix to identify the source of the message. This
can now be specified using a class-level attribute, defaulting to
@code{""} to preserve existing behaviour, but which can be overridden on
a @code{SysLogHandler} instance in order for that instance to prepend
the ident to every message handled. Note that the provided ident must
be text, not bytes, and is prepended to the message exactly as is.

@end deffn

@geindex encodePriority() (logging.handlers.SysLogHandler 方法)
@anchor{library/logging handlers logging handlers SysLogHandler encodePriority}@anchor{20b8}
@deffn {方法} encodePriority (facility, priority)

Encodes the facility and priority into an integer. You can pass in strings
or integers - if strings are passed, internal mapping dictionaries are
used to convert them to integers.

The symbolic @code{LOG_} values are defined in @ref{a19,,SysLogHandler} and
mirror the values defined in the @code{sys/syslog.h} header file.

@strong{优先级}


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} 
@headitem

名称（字符串）

@tab

符号值

@item

@code{alert}

@tab

LOG_ALERT

@item

@code{crit} 或 @code{critical}

@tab

LOG_CRIT

@item

@code{debug}

@tab

LOG_DEBUG

@item

@code{emerg} 或 @code{panic}

@tab

LOG_EMERG

@item

@code{err} 或 @code{error}

@tab

LOG_ERR

@item

@code{info}

@tab

LOG_INFO

@item

@code{notice}

@tab

LOG_NOTICE

@item

@code{warn} 或 @code{warning}

@tab

LOG_WARNING

@end multitable


@strong{设备}


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} 
@headitem

名称（字符串）

@tab

符号值

@item

@code{auth}

@tab

LOG_AUTH

@item

@code{authpriv}

@tab

LOG_AUTHPRIV

@item

@code{cron}

@tab

LOG_CRON

@item

@code{daemon}

@tab

LOG_DAEMON

@item

@code{ftp}

@tab

LOG_FTP

@item

@code{kern}

@tab

LOG_KERN

@item

@code{lpr}

@tab

LOG_LPR

@item

@code{mail}

@tab

LOG_MAIL

@item

@code{news}

@tab

LOG_NEWS

@item

@code{syslog}

@tab

LOG_SYSLOG

@item

@code{user}

@tab

LOG_USER

@item

@code{uucp}

@tab

LOG_UUCP

@item

@code{local0}

@tab

LOG_LOCAL0

@item

@code{local1}

@tab

LOG_LOCAL1

@item

@code{local2}

@tab

LOG_LOCAL2

@item

@code{local3}

@tab

LOG_LOCAL3

@item

@code{local4}

@tab

LOG_LOCAL4

@item

@code{local5}

@tab

LOG_LOCAL5

@item

@code{local6}

@tab

LOG_LOCAL6

@item

@code{local7}

@tab

LOG_LOCAL7

@end multitable

@end deffn

@geindex mapPriority() (logging.handlers.SysLogHandler 方法)
@anchor{library/logging handlers logging handlers SysLogHandler mapPriority}@anchor{20b9}
@deffn {方法} mapPriority (levelname)

Maps a logging level name to a syslog priority name.
You may need to override this if you are using custom levels, or
if the default algorithm is not suitable for your needs. The
default algorithm maps @code{DEBUG}, @code{INFO}, @code{WARNING}, @code{ERROR} and
@code{CRITICAL} to the equivalent syslog names, and all other level
names to 'warning'.
@end deffn
@end deffn

@node NTEventLogHandler,SMTPHandler,SysLogHandler,logging handlers --- 日志处理
@anchor{library/logging handlers nt-eventlog-handler}@anchor{20ba}@anchor{library/logging handlers nteventloghandler}@anchor{20bb}
@subsubsection NTEventLogHandler


The @ref{20bc,,NTEventLogHandler} class, located in the @ref{ac,,logging.handlers}
module, supports sending logging messages to a local Windows NT, Windows 2000 or
Windows XP event log. Before you can use it, you need Mark Hammond's Win32
extensions for Python installed.

@geindex NTEventLogHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers NTEventLogHandler}@anchor{20bc}
@deffn {类} logging.handlers.NTEventLogHandler (appname, dllname=None, logtype='Application')

Returns a new instance of the @ref{20bc,,NTEventLogHandler} class. The @emph{appname} is
used to define the application name as it appears in the event log. An
appropriate registry entry is created using this name. The @emph{dllname} should give
the fully qualified pathname of a .dll or .exe which contains message
definitions to hold in the log (if not specified, @code{'win32service.pyd'} is used
- this is installed with the Win32 extensions and contains some basic
placeholder message definitions. Note that use of these placeholders will make
your event logs big, as the entire message source is held in the log. If you
want slimmer logs, you have to pass in the name of your own .dll or .exe which
contains the message definitions you want to use in the event log). The
@emph{logtype} is one of @code{'Application'}, @code{'System'} or @code{'Security'}, and
defaults to @code{'Application'}.

@geindex close() (logging.handlers.NTEventLogHandler 方法)
@anchor{library/logging handlers logging handlers NTEventLogHandler close}@anchor{20bd}
@deffn {方法} close ()

At this point, you can remove the application name from the registry as a
source of event log entries. However, if you do this, you will not be able
to see the events as you intended in the Event Log Viewer - it needs to be
able to access the registry to get the .dll name. The current version does
not do this.
@end deffn

@geindex emit() (logging.handlers.NTEventLogHandler 方法)
@anchor{library/logging handlers logging handlers NTEventLogHandler emit}@anchor{20be}
@deffn {方法} emit (record)

Determines the message ID, event category and event type, and then logs
the message in the NT event log.
@end deffn

@geindex getEventCategory() (logging.handlers.NTEventLogHandler 方法)
@anchor{library/logging handlers logging handlers NTEventLogHandler getEventCategory}@anchor{20bf}
@deffn {方法} getEventCategory (record)

Returns the event category for the record. Override this if you want to
specify your own categories. This version returns 0.
@end deffn

@geindex getEventType() (logging.handlers.NTEventLogHandler 方法)
@anchor{library/logging handlers logging handlers NTEventLogHandler getEventType}@anchor{20c0}
@deffn {方法} getEventType (record)

Returns the event type for the record. Override this if you want to
specify your own types. This version does a mapping using the handler's
typemap attribute, which is set up in @ref{d57,,__init__()} to a dictionary
which contains mappings for @code{DEBUG}, @code{INFO},
@code{WARNING}, @code{ERROR} and @code{CRITICAL}. If you are using
your own levels, you will either need to override this method or place a
suitable dictionary in the handler's @emph{typemap} attribute.
@end deffn

@geindex getMessageID() (logging.handlers.NTEventLogHandler 方法)
@anchor{library/logging handlers logging handlers NTEventLogHandler getMessageID}@anchor{20c1}
@deffn {方法} getMessageID (record)

Returns the message ID for the record. If you are using your own messages,
you could do this by having the @emph{msg} passed to the logger being an ID
rather than a format string. Then, in here, you could use a dictionary
lookup to get the message ID. This version returns 1, which is the base
message ID in @code{win32service.pyd}.
@end deffn
@end deffn

@node SMTPHandler,MemoryHandler,NTEventLogHandler,logging handlers --- 日志处理
@anchor{library/logging handlers smtp-handler}@anchor{20c2}@anchor{library/logging handlers smtphandler}@anchor{20c3}
@subsubsection SMTPHandler


The @ref{20c4,,SMTPHandler} class, located in the @ref{ac,,logging.handlers} module,
supports sending logging messages to an email address via SMTP.

@geindex SMTPHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers SMTPHandler}@anchor{20c4}
@deffn {类} logging.handlers.SMTPHandler (mailhost, fromaddr, toaddrs, subject, credentials=None, secure=None, timeout=1.0)

Returns a new instance of the @ref{20c4,,SMTPHandler} class. The instance is
initialized with the from and to addresses and subject line of the email. The
@emph{toaddrs} should be a list of strings. To specify a non-standard SMTP port, use
the (host, port) tuple format for the @emph{mailhost} argument. If you use a string,
the standard SMTP port is used. If your SMTP server requires authentication, you
can specify a (username, password) tuple for the @emph{credentials} argument.

To specify the use of a secure protocol (TLS), pass in a tuple to the
@emph{secure} argument. This will only be used when authentication credentials are
supplied. The tuple should be either an empty tuple, or a single-value tuple
with the name of a keyfile, or a 2-value tuple with the names of the keyfile
and certificate file. (This tuple is passed to the
@ref{a7f,,smtplib.SMTP.starttls()} method.)

A timeout can be specified for communication with the SMTP server using the
@emph{timeout} argument.


3.3 新版功能: The @emph{timeout} argument was added.


@geindex emit() (logging.handlers.SMTPHandler 方法)
@anchor{library/logging handlers logging handlers SMTPHandler emit}@anchor{20c5}
@deffn {方法} emit (record)

Formats the record and sends it to the specified addressees.
@end deffn

@geindex getSubject() (logging.handlers.SMTPHandler 方法)
@anchor{library/logging handlers logging handlers SMTPHandler getSubject}@anchor{20c6}
@deffn {方法} getSubject (record)

If you want to specify a subject line which is record-dependent, override
this method.
@end deffn
@end deffn

@node MemoryHandler,HTTPHandler,SMTPHandler,logging handlers --- 日志处理
@anchor{library/logging handlers memory-handler}@anchor{20c7}@anchor{library/logging handlers memoryhandler}@anchor{20c8}
@subsubsection MemoryHandler


The @ref{207d,,MemoryHandler} class, located in the @ref{ac,,logging.handlers} module,
supports buffering of logging records in memory, periodically flushing them to a
@emph{target} handler. Flushing occurs whenever the buffer is full, or when an
event of a certain severity or greater is seen.

@ref{207d,,MemoryHandler} is a subclass of the more general
@ref{20c9,,BufferingHandler}, which is an abstract class. This buffers logging
records in memory. Whenever each record is added to the buffer, a check is made
by calling @code{shouldFlush()} to see if the buffer should be flushed.  If it
should, then @code{flush()} is expected to do the flushing.

@geindex BufferingHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers BufferingHandler}@anchor{20c9}
@deffn {类} logging.handlers.BufferingHandler (capacity)

Initializes the handler with a buffer of the specified capacity. Here,
@emph{capacity} means the number of logging records buffered.

@geindex emit() (logging.handlers.BufferingHandler 方法)
@anchor{library/logging handlers logging handlers BufferingHandler emit}@anchor{20ca}
@deffn {方法} emit (record)

Append the record to the buffer. If @ref{20cb,,shouldFlush()} returns true,
call @ref{20cc,,flush()} to process the buffer.
@end deffn

@geindex flush() (logging.handlers.BufferingHandler 方法)
@anchor{library/logging handlers logging handlers BufferingHandler flush}@anchor{20cc}
@deffn {方法} flush ()

You can override this to implement custom flushing behavior. This version
just zaps the buffer to empty.
@end deffn

@geindex shouldFlush() (logging.handlers.BufferingHandler 方法)
@anchor{library/logging handlers logging handlers BufferingHandler shouldFlush}@anchor{20cb}
@deffn {方法} shouldFlush (record)

Return @code{True} if the buffer is up to capacity. This method can be
overridden to implement custom flushing strategies.
@end deffn
@end deffn

@geindex MemoryHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers MemoryHandler}@anchor{207d}
@deffn {类} logging.handlers.MemoryHandler (capacity, flushLevel=ERROR, target=None, flushOnClose=True)

Returns a new instance of the @ref{207d,,MemoryHandler} class. The instance is
initialized with a buffer size of @emph{capacity} (number of records buffered).
If @emph{flushLevel} is not specified, @code{ERROR} is used. If no @emph{target} is
specified, the target will need to be set using @ref{20cd,,setTarget()} before this
handler does anything useful. If @emph{flushOnClose} is specified as @code{False},
then the buffer is @emph{not} flushed when the handler is closed. If not specified
or specified as @code{True}, the previous behaviour of flushing the buffer will
occur when the handler is closed.


在 3.6 版更改: The @emph{flushOnClose} parameter was added.


@geindex close() (logging.handlers.MemoryHandler 方法)
@anchor{library/logging handlers logging handlers MemoryHandler close}@anchor{20ce}
@deffn {方法} close ()

Calls @ref{20cf,,flush()}, sets the target to @code{None} and clears the
buffer.
@end deffn

@geindex flush() (logging.handlers.MemoryHandler 方法)
@anchor{library/logging handlers logging handlers MemoryHandler flush}@anchor{20cf}
@deffn {方法} flush ()

For a @ref{207d,,MemoryHandler}, flushing means just sending the buffered
records to the target, if there is one. The buffer is also cleared when
this happens. Override if you want different behavior.
@end deffn

@geindex setTarget() (logging.handlers.MemoryHandler 方法)
@anchor{library/logging handlers logging handlers MemoryHandler setTarget}@anchor{20cd}
@deffn {方法} setTarget (target)

Sets the target handler for this handler.
@end deffn

@geindex shouldFlush() (logging.handlers.MemoryHandler 方法)
@anchor{library/logging handlers logging handlers MemoryHandler shouldFlush}@anchor{20d0}
@deffn {方法} shouldFlush (record)

Checks for buffer full or a record at the @emph{flushLevel} or higher.
@end deffn
@end deffn

@node HTTPHandler,QueueHandler,MemoryHandler,logging handlers --- 日志处理
@anchor{library/logging handlers http-handler}@anchor{20d1}@anchor{library/logging handlers httphandler}@anchor{20d2}
@subsubsection HTTPHandler


The @ref{70b,,HTTPHandler} class, located in the @ref{ac,,logging.handlers} module,
supports sending logging messages to a Web server, using either @code{GET} or
@code{POST} semantics.

@geindex HTTPHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers HTTPHandler}@anchor{70b}
@deffn {类} logging.handlers.HTTPHandler (host, url, method='GET', secure=False, credentials=None, context=None)

Returns a new instance of the @ref{70b,,HTTPHandler} class. The @emph{host} can be
of the form @code{host:port}, should you need to use a specific port number.  If
no @emph{method} is specified, @code{GET} is used. If @emph{secure} is true, a HTTPS
connection will be used. The @emph{context} parameter may be set to a
@ref{3dc,,ssl.SSLContext} instance to configure the SSL settings used for the
HTTPS connection. If @emph{credentials} is specified, it should be a 2-tuple
consisting of userid and password, which will be placed in a HTTP
'Authorization' header using Basic authentication. If you specify
credentials, you should also specify secure=True so that your userid and
password are not passed in cleartext across the wire.


在 3.5 版更改: The @emph{context} parameter was added.


@geindex mapLogRecord() (logging.handlers.HTTPHandler 方法)
@anchor{library/logging handlers logging handlers HTTPHandler mapLogRecord}@anchor{20d3}
@deffn {方法} mapLogRecord (record)

Provides a dictionary, based on @code{record}, which is to be URL-encoded
and sent to the web server. The default implementation just returns
@code{record.__dict__}. This method can be overridden if e.g. only a
subset of @ref{900,,LogRecord} is to be sent to the web server, or
if more specific customization of what's sent to the server is required.
@end deffn

@geindex emit() (logging.handlers.HTTPHandler 方法)
@anchor{library/logging handlers logging handlers HTTPHandler emit}@anchor{20d4}
@deffn {方法} emit (record)

Sends the record to the Web server as a URL-encoded dictionary. The
@ref{20d3,,mapLogRecord()} method is used to convert the record to the
dictionary to be sent.
@end deffn

@cartouche
@quotation 注解 
Since preparing a record for sending it to a Web server is not
the same as a generic formatting operation, using
@ref{2034,,setFormatter()} to specify a
@ref{201d,,Formatter} for a @ref{70b,,HTTPHandler} has no effect.
Instead of calling @ref{203e,,format()}, this handler calls
@ref{20d3,,mapLogRecord()} and then @ref{785,,urllib.parse.urlencode()} to encode the
dictionary in a form suitable for sending to a Web server.
@end quotation
@end cartouche
@end deffn

@node QueueHandler,QueueListener,HTTPHandler,logging handlers --- 日志处理
@anchor{library/logging handlers queue-handler}@anchor{20d5}@anchor{library/logging handlers queuehandler}@anchor{20d6}
@subsubsection QueueHandler



3.2 新版功能.


The @ref{20d7,,QueueHandler} class, located in the @ref{ac,,logging.handlers} module,
supports sending logging messages to a queue, such as those implemented in the
@ref{da,,queue} or @ref{b7,,multiprocessing} modules.

Along with the @ref{70c,,QueueListener} class, @ref{20d7,,QueueHandler} can be used
to let handlers do their work on a separate thread from the one which does the
logging. This is important in Web applications and also other service
applications where threads servicing clients need to respond as quickly as
possible, while any potentially slow operations (such as sending an email via
@ref{20c4,,SMTPHandler}) are done on a separate thread.

@geindex QueueHandler (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers QueueHandler}@anchor{20d7}
@deffn {类} logging.handlers.QueueHandler (queue)

Returns a new instance of the @ref{20d7,,QueueHandler} class. The instance is
initialized with the queue to send messages to. The @emph{queue} can be any
queue-like object; it's used as-is by the @ref{20d8,,enqueue()} method, which
needs to know how to send messages to it. The queue is not @emph{required} to
have the task tracking API, which means that you can use
@ref{3be,,SimpleQueue} instances for @emph{queue}.

@geindex emit() (logging.handlers.QueueHandler 方法)
@anchor{library/logging handlers logging handlers QueueHandler emit}@anchor{20d9}
@deffn {方法} emit (record)

Enqueues the result of preparing the LogRecord. Should an exception
occur (e.g. because a bounded queue has filled up), the
@ref{203c,,handleError()} method is called to handle the
error. This can result in the record silently being dropped (if
@code{logging.raiseExceptions} is @code{False}) or a message printed to
@code{sys.stderr} (if @code{logging.raiseExceptions} is @code{True}).
@end deffn

@geindex prepare() (logging.handlers.QueueHandler 方法)
@anchor{library/logging handlers logging handlers QueueHandler prepare}@anchor{20da}
@deffn {方法} prepare (record)

Prepares a record for queuing. The object returned by this
method is enqueued.

The base implementation formats the record to merge the message,
arguments, and exception information, if present.  It also
removes unpickleable items from the record in-place.

You might want to override this method if you want to convert
the record to a dict or JSON string, or send a modified copy
of the record while leaving the original intact.
@end deffn

@geindex enqueue() (logging.handlers.QueueHandler 方法)
@anchor{library/logging handlers logging handlers QueueHandler enqueue}@anchor{20d8}
@deffn {方法} enqueue (record)

Enqueues the record on the queue using @code{put_nowait()}; you may
want to override this if you want to use blocking behaviour, or a
timeout, or a customized queue implementation.
@end deffn
@end deffn

@node QueueListener,,QueueHandler,logging handlers --- 日志处理
@anchor{library/logging handlers queue-listener}@anchor{20db}@anchor{library/logging handlers queuelistener}@anchor{20dc}
@subsubsection QueueListener



3.2 新版功能.


The @ref{70c,,QueueListener} class, located in the @ref{ac,,logging.handlers}
module, supports receiving logging messages from a queue, such as those
implemented in the @ref{da,,queue} or @ref{b7,,multiprocessing} modules. The
messages are received from a queue in an internal thread and passed, on
the same thread, to one or more handlers for processing. While
@ref{70c,,QueueListener} is not itself a handler, it is documented here
because it works hand-in-hand with @ref{20d7,,QueueHandler}.

Along with the @ref{20d7,,QueueHandler} class, @ref{70c,,QueueListener} can be used
to let handlers do their work on a separate thread from the one which does the
logging. This is important in Web applications and also other service
applications where threads servicing clients need to respond as quickly as
possible, while any potentially slow operations (such as sending an email via
@ref{20c4,,SMTPHandler}) are done on a separate thread.

@geindex QueueListener (logging.handlers 中的类)
@anchor{library/logging handlers logging handlers QueueListener}@anchor{70c}
@deffn {类} logging.handlers.QueueListener (queue, *handlers, respect_handler_level=False)

Returns a new instance of the @ref{70c,,QueueListener} class. The instance is
initialized with the queue to send messages to and a list of handlers which
will handle entries placed on the queue. The queue can be any queue-like
object; it's passed as-is to the @ref{20dd,,dequeue()} method, which needs
to know how to get messages from it. The queue is not @emph{required} to have the
task tracking API (though it's used if available), which means that you can
use @ref{3be,,SimpleQueue} instances for @emph{queue}.

If @code{respect_handler_level} is @code{True}, a handler's level is respected
(compared with the level for the message) when deciding whether to pass
messages to that handler; otherwise, the behaviour is as in previous Python
versions - to always pass each message to each handler.


在 3.5 版更改: The @code{respect_handler_level} argument was added.


@geindex dequeue() (logging.handlers.QueueListener 方法)
@anchor{library/logging handlers logging handlers QueueListener dequeue}@anchor{20dd}
@deffn {方法} dequeue (block)

Dequeues a record and return it, optionally blocking.

The base implementation uses @code{get()}. You may want to override this
method if you want to use timeouts or work with custom queue
implementations.
@end deffn

@geindex prepare() (logging.handlers.QueueListener 方法)
@anchor{library/logging handlers logging handlers QueueListener prepare}@anchor{20de}
@deffn {方法} prepare (record)

Prepare a record for handling.

This implementation just returns the passed-in record. You may want to
override this method if you need to do any custom marshalling or
manipulation of the record before passing it to the handlers.
@end deffn

@geindex handle() (logging.handlers.QueueListener 方法)
@anchor{library/logging handlers logging handlers QueueListener handle}@anchor{20df}
@deffn {方法} handle (record)

Handle a record.

This just loops through the handlers offering them the record
to handle. The actual object passed to the handlers is that which
is returned from @ref{20de,,prepare()}.
@end deffn

@geindex start() (logging.handlers.QueueListener 方法)
@anchor{library/logging handlers logging handlers QueueListener start}@anchor{20e0}
@deffn {方法} start ()

Starts the listener.

This starts up a background thread to monitor the queue for
LogRecords to process.
@end deffn

@geindex stop() (logging.handlers.QueueListener 方法)
@anchor{library/logging handlers logging handlers QueueListener stop}@anchor{20e1}
@deffn {方法} stop ()

Stops the listener.

This asks the thread to terminate, and then waits for it to do so.
Note that if you don't call this before your application exits, there
may be some records still left on the queue, which won't be processed.
@end deffn

@geindex enqueue_sentinel() (logging.handlers.QueueListener 方法)
@anchor{library/logging handlers logging handlers QueueListener enqueue_sentinel}@anchor{20e2}
@deffn {方法} enqueue_sentinel ()

Writes a sentinel to the queue to tell the listener to quit. This
implementation uses @code{put_nowait()}.  You may want to override this
method if you want to use timeouts or work with custom queue
implementations.


3.3 新版功能.

@end deffn
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{aa,,logging}

日志记录模块的 API 参考。

@item @ref{ab,,logging.config} 模块

日志记录模块的配置 API 。
@end table


@node getpass --- 便携式密码输入工具,curses --- 终端字符单元显示的处理,logging handlers --- 日志处理,通用操作系统服务
@anchor{library/getpass doc}@anchor{20e3}@anchor{library/getpass getpass-portable-password-input}@anchor{20e4}@anchor{library/getpass module-getpass}@anchor{88}
@subsection @code{getpass} --- 便携式密码输入工具


@geindex getpass (模块)

@c Windows (& Mac?) support by Guido van Rossum.

@strong{源代码:} Lib/getpass.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/getpass.py}


__________________________________________________________________


@ref{88,,getpass} 模块提供了两个函数：

@geindex getpass() (在 getpass 模块中)
@anchor{library/getpass getpass getpass}@anchor{20e5}
@deffn {函数} getpass.getpass (prompt='Password: ', stream=None)

提示用户输入一个密码且不会回显。 用户会看到字符串 @emph{prompt} 作为提示，其默认值为 @code{'Password: '}。 在 Unix 上，如有必要提示会使用替换错误句柄写入到文件类对象 @emph{stream}。 @emph{stream} 默认指向控制终端 (@code{/dev/tty})，如果不可用则指向 @code{sys.stderr} (此参数在 Windows 上会被忽略)。

如果回显自由输入不可用则 getpass() 将回退为打印一条警告消息到 @emph{stream} 并且从 @code{sys.stdin} 读取同时发出 @ref{20e6,,GetPassWarning}。

@cartouche
@quotation 注解 
如果你从 IDLE 内部调用 getpass，输入可能是在你启动 IDLE 的终端中而非在 IDEL 窗口本身中完成。
@end quotation
@end cartouche
@end deffn

@geindex GetPassWarning
@anchor{library/getpass getpass GetPassWarning}@anchor{20e6}
@deffn {例外} getpass.GetPassWarning

一个当密码输入可能被回显时发出的 @ref{16b0,,UserWarning} 子类。
@end deffn

@geindex getuser() (在 getpass 模块中)
@anchor{library/getpass getpass getuser}@anchor{1e86}
@deffn {函数} getpass.getuser ()

返回用户的“登录名称”。

此函数会按顺序检查环境变量 
@geindex LOGNAME
@geindex 环境变量; LOGNAME
@code{LOGNAME}, 
@geindex USER
@geindex 环境变量; USER
@code{USER}, 
@geindex LNAME
@geindex 环境变量; LNAME
@code{LNAME} 和 
@geindex USERNAME
@geindex 环境变量; USERNAME
@code{USERNAME}，并返回其中第一个被设置为非空字符串的值。 如果均未设置，则在支持 @ref{d6,,pwd} 模块的系统上将返回来自密码数据库的登录名，否则将引发一个异常。

通常情况下，此函数应优先于 @ref{1e85,,os.getlogin()} 使用。
@end deffn

@node curses --- 终端字符单元显示的处理,curses textpad --- Text input widget for curses programs,getpass --- 便携式密码输入工具,通用操作系统服务
@anchor{library/curses doc}@anchor{20e7}@anchor{library/curses curses-terminal-handling-for-character-cell-displays}@anchor{20e8}@anchor{library/curses module-curses}@anchor{2c}
@subsection @code{curses} --- 终端字符单元显示的处理


@geindex curses (模块)


__________________________________________________________________


@ref{2c,,curses} 模块提供了 curses 库的接口，这是可移植高级终端处理的事实标准。

虽然 curses 在 Unix 环境中使用最为广泛，但也有适用于 Windows，DOS 以及其他可能的系统的版本。此扩展模块旨在匹配 ncurses 的 API，这是一个部署在 Linux 和 Unix 的 BSD 变体上的开源 curses 库。

@cartouche
@quotation 注解 
每当文档提到 @strong{字符} 时，它可以被指定为一个整数，一个单字符 Unicode 字符串或者一个单字节的字节字符串。

每当此文档提到 @strong{字符串} 时，它可以被指定为一个 Unicode 字符串或者一个字节字符串。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
从 5.4 版本开始，ncurses 库使用 @code{nl_langinfo} 函数来决定如何解释非 ASCII 数据。这意味着你需要在程序中调用 @ref{1fa1,,locale.setlocale()} 函数，并使用一种系统中可用的编码方法来编码 Unicode 字符串。这个例子使用了系统默认的编码:

@example
import locale
locale.setlocale(locale.LC_ALL, '@w{'})
code = locale.getpreferredencoding()
@end example

然后使用 @emph{code} 作为 @ref{c30,,str.encode()} 调用的编码。
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@item 模块 @ref{2d,,curses.ascii}

在 ASCII 字符上工作的工具，无论你的区域设置是什么。

@item 模块 @ref{2e,,curses.panel}

A panel stack extension that adds depth to  curses windows.

@item Module @ref{2f,,curses.textpad}

Editable text widget for curses supporting  @code{Emacs}-like bindings.

@item @ref{20e9,,用 Python 进行 Curses 编程}

Tutorial material on using curses with Python, by Andrew Kuchling and Eric
Raymond.
@end table

The Tools/demo/@footnote{https://github.com/python/cpython/tree/3.8/Tools/demo/} directory in the Python source distribution contains
some example programs using the curses bindings provided by this module.


@menu
* 函数: 函数<3>. 
* Window Objects:: 
* 常量: 常量<6>. 

@end menu

@node 函数<3>,Window Objects,,curses --- 终端字符单元显示的处理
@anchor{library/curses curses-functions}@anchor{20ea}@anchor{library/curses functions}@anchor{20eb}
@subsubsection 函数


@ref{2c,,curses} 模块定义了以下异常：

@geindex error
@anchor{library/curses curses error}@anchor{20ec}
@deffn {例外} curses.error

当 curses 库中函数返回一个错误时引发的异常。
@end deffn

@cartouche
@quotation 注解 
Whenever @emph{x} or @emph{y} arguments to a function or a method are optional, they
default to the current cursor location. Whenever @emph{attr} is optional, it defaults
to @code{A_NORMAL}.
@end quotation
@end cartouche

@ref{2c,,curses} 模块定义了以下函数：

@geindex baudrate() (在 curses 模块中)
@anchor{library/curses curses baudrate}@anchor{20ed}
@deffn {函数} curses.baudrate ()

Return the output speed of the terminal in bits per second.  On software
terminal emulators it will have a fixed high value. Included for historical
reasons; in former times, it was used to  write output loops for time delays and
occasionally to change interfaces depending on the line speed.
@end deffn

@geindex beep() (在 curses 模块中)
@anchor{library/curses curses beep}@anchor{20ee}
@deffn {函数} curses.beep ()

Emit a short attention sound.
@end deffn

@geindex can_change_color() (在 curses 模块中)
@anchor{library/curses curses can_change_color}@anchor{20ef}
@deffn {函数} curses.can_change_color ()

Return @code{True} or @code{False}, depending on whether the programmer can change the colors
displayed by the terminal.
@end deffn

@geindex cbreak() (在 curses 模块中)
@anchor{library/curses curses cbreak}@anchor{20f0}
@deffn {函数} curses.cbreak ()

Enter cbreak mode.  In cbreak mode (sometimes called "rare" mode) normal tty
line buffering is turned off and characters are available to be read one by one.
However, unlike raw mode, special characters (interrupt, quit, suspend, and flow
control) retain their effects on the tty driver and calling program.  Calling
first @ref{20f1,,raw()} then @ref{20f0,,cbreak()} leaves the terminal in cbreak mode.
@end deffn

@geindex color_content() (在 curses 模块中)
@anchor{library/curses curses color_content}@anchor{20f2}
@deffn {函数} curses.color_content (color_number)

Return the intensity of the red, green, and blue (RGB) components in the color
@emph{color_number}, which must be between @code{0} and @code{COLORS}.  Return a 3-tuple,
containing the R,G,B values for the given color, which will be between
@code{0} (no component) and @code{1000} (maximum amount of component).
@end deffn

@geindex color_pair() (在 curses 模块中)
@anchor{library/curses curses color_pair}@anchor{20f3}
@deffn {函数} curses.color_pair (color_number)

Return the attribute value for displaying text in the specified color.  This
attribute value can be combined with @code{A_STANDOUT}, @code{A_REVERSE},
and the other @code{A_*} attributes.  @ref{20f4,,pair_number()} is the counterpart
to this function.
@end deffn

@geindex curs_set() (在 curses 模块中)
@anchor{library/curses curses curs_set}@anchor{20f5}
@deffn {函数} curses.curs_set (visibility)

Set the cursor state.  @emph{visibility} can be set to @code{0}, @code{1}, or @code{2}, for invisible,
normal, or very visible.  If the terminal supports the visibility requested, return the
previous cursor state; otherwise raise an exception.  On many
terminals, the "visible" mode is an underline cursor and the "very visible" mode
is a block cursor.
@end deffn

@geindex def_prog_mode() (在 curses 模块中)
@anchor{library/curses curses def_prog_mode}@anchor{20f6}
@deffn {函数} curses.def_prog_mode ()

Save the current terminal mode as the "program" mode, the mode when the running
program is using curses.  (Its counterpart is the "shell" mode, for when the
program is not in curses.)  Subsequent calls to @ref{20f7,,reset_prog_mode()} will
restore this mode.
@end deffn

@geindex def_shell_mode() (在 curses 模块中)
@anchor{library/curses curses def_shell_mode}@anchor{20f8}
@deffn {函数} curses.def_shell_mode ()

Save the current terminal mode as the "shell" mode, the mode when the running
program is not using curses.  (Its counterpart is the "program" mode, when the
program is using curses capabilities.) Subsequent calls to
@ref{20f9,,reset_shell_mode()} will restore this mode.
@end deffn

@geindex delay_output() (在 curses 模块中)
@anchor{library/curses curses delay_output}@anchor{20fa}
@deffn {函数} curses.delay_output (ms)

Insert an @emph{ms} millisecond pause in output.
@end deffn

@geindex doupdate() (在 curses 模块中)
@anchor{library/curses curses doupdate}@anchor{20fb}
@deffn {函数} curses.doupdate ()

Update the physical screen.  The curses library keeps two data structures, one
representing the current physical screen contents and a virtual screen
representing the desired next state.  The @ref{20fb,,doupdate()} ground updates the
physical screen to match the virtual screen.

The virtual screen may be updated by a @ref{20fc,,noutrefresh()} call after write
operations such as @ref{20fd,,addstr()} have been performed on a window.  The normal
@ref{20fe,,refresh()} call is simply @code{noutrefresh()} followed by @code{doupdate()};
if you have to update multiple windows, you can speed performance and perhaps
reduce screen flicker by issuing @code{noutrefresh()} calls on all windows,
followed by a single @code{doupdate()}.
@end deffn

@geindex echo() (在 curses 模块中)
@anchor{library/curses curses echo}@anchor{20ff}
@deffn {函数} curses.echo ()

Enter echo mode.  In echo mode, each character input is echoed to the screen as
it is entered.
@end deffn

@geindex endwin() (在 curses 模块中)
@anchor{library/curses curses endwin}@anchor{2100}
@deffn {函数} curses.endwin ()

De-initialize the library, and return terminal to normal status.
@end deffn

@geindex erasechar() (在 curses 模块中)
@anchor{library/curses curses erasechar}@anchor{2101}
@deffn {函数} curses.erasechar ()

Return the user's current erase character as a one-byte bytes object.  Under Unix operating systems this
is a property of the controlling tty of the curses program, and is not set by
the curses library itself.
@end deffn

@geindex filter() (在 curses 模块中)
@anchor{library/curses curses filter}@anchor{2102}
@deffn {函数} curses.filter ()

The @ref{2102,,filter()} routine, if used, must be called before @ref{2103,,initscr()} is
called.  The effect is that, during those calls, 
@geindex LINES
@geindex 环境变量; LINES
@code{LINES} is set to @code{1}; the
capabilities @code{clear}, @code{cup}, @code{cud}, @code{cud1}, @code{cuu1}, @code{cuu}, @code{vpa} are disabled; and the @code{home}
string is set to the value of @code{cr}. The effect is that the cursor is confined to
the current line, and so are screen updates.  This may be used for enabling
character-at-a-time  line editing without touching the rest of the screen.
@end deffn

@geindex flash() (在 curses 模块中)
@anchor{library/curses curses flash}@anchor{2104}
@deffn {函数} curses.flash ()

Flash the screen.  That is, change it to reverse-video and then change it back
in a short interval.  Some people prefer such as 'visible bell' to the audible
attention signal produced by @ref{20ee,,beep()}.
@end deffn

@geindex flushinp() (在 curses 模块中)
@anchor{library/curses curses flushinp}@anchor{2105}
@deffn {函数} curses.flushinp ()

Flush all input buffers.  This throws away any  typeahead  that  has been typed
by the user and has not yet been processed by the program.
@end deffn

@geindex getmouse() (在 curses 模块中)
@anchor{library/curses curses getmouse}@anchor{2106}
@deffn {函数} curses.getmouse ()

After @ref{2107,,getch()} returns @code{KEY_MOUSE} to signal a mouse event, this
method should be call to retrieve the queued mouse event, represented as a
5-tuple @code{(id, x, y, z, bstate)}. @emph{id} is an ID value used to distinguish
multiple devices, and @emph{x}, @emph{y}, @emph{z} are the event's coordinates.  (@emph{z} is
currently unused.)  @emph{bstate} is an integer value whose bits will be set to
indicate the type of event, and will be the bitwise OR of one or more of the
following constants, where @emph{n} is the button number from 1 to 4:
@code{BUTTONn_PRESSED}, @code{BUTTONn_RELEASED}, @code{BUTTONn_CLICKED},
@code{BUTTONn_DOUBLE_CLICKED}, @code{BUTTONn_TRIPLE_CLICKED},
@code{BUTTON_SHIFT}, @code{BUTTON_CTRL}, @code{BUTTON_ALT}.
@end deffn

@geindex getsyx() (在 curses 模块中)
@anchor{library/curses curses getsyx}@anchor{2108}
@deffn {函数} curses.getsyx ()

Return the current coordinates of the virtual screen cursor as a tuple
@code{(y, x)}.  If @ref{2109,,leaveok} is currently @code{True}, then return @code{(-1, -1)}.
@end deffn

@geindex getwin() (在 curses 模块中)
@anchor{library/curses curses getwin}@anchor{210a}
@deffn {函数} curses.getwin (file)

Read window related data stored in the file by an earlier @code{putwin()} call.
The routine then creates and initializes a new window using that data, returning
the new window object.
@end deffn

@geindex has_colors() (在 curses 模块中)
@anchor{library/curses curses has_colors}@anchor{210b}
@deffn {函数} curses.has_colors ()

Return @code{True} if the terminal can display colors; otherwise, return @code{False}.
@end deffn

@geindex has_ic() (在 curses 模块中)
@anchor{library/curses curses has_ic}@anchor{210c}
@deffn {函数} curses.has_ic ()

Return @code{True} if the terminal has insert- and delete-character capabilities.
This function is included for historical reasons only, as all modern software
terminal emulators have such capabilities.
@end deffn

@geindex has_il() (在 curses 模块中)
@anchor{library/curses curses has_il}@anchor{210d}
@deffn {函数} curses.has_il ()

Return @code{True} if the terminal has insert- and delete-line capabilities, or can
simulate  them  using scrolling regions. This function is included for
historical reasons only, as all modern software terminal emulators have such
capabilities.
@end deffn

@geindex has_key() (在 curses 模块中)
@anchor{library/curses curses has_key}@anchor{210e}
@deffn {函数} curses.has_key (ch)

Take a key value @emph{ch}, and return @code{True} if the current terminal type recognizes
a key with that value.
@end deffn

@geindex halfdelay() (在 curses 模块中)
@anchor{library/curses curses halfdelay}@anchor{210f}
@deffn {函数} curses.halfdelay (tenths)

Used for half-delay mode, which is similar to cbreak mode in that characters
typed by the user are immediately available to the program. However, after
blocking for @emph{tenths} tenths of seconds, raise an exception if nothing has
been typed.  The value of @emph{tenths} must be a number between @code{1} and @code{255}.  Use
@ref{2110,,nocbreak()} to leave half-delay mode.
@end deffn

@geindex init_color() (在 curses 模块中)
@anchor{library/curses curses init_color}@anchor{2111}
@deffn {函数} curses.init_color (color_number, r, g, b)

Change the definition of a color, taking the number of the color to be changed
followed by three RGB values (for the amounts of red, green, and blue
components).  The value of @emph{color_number} must be between @code{0} and
@code{COLORS}.  Each of @emph{r}, @emph{g}, @emph{b}, must be a value between @code{0} and
@code{1000}.  When @ref{2111,,init_color()} is used, all occurrences of that color on the
screen immediately change to the new definition.  This function is a no-op on
most terminals; it is active only if @ref{20ef,,can_change_color()} returns @code{True}.
@end deffn

@geindex init_pair() (在 curses 模块中)
@anchor{library/curses curses init_pair}@anchor{2112}
@deffn {函数} curses.init_pair (pair_number, fg, bg)

Change the definition of a color-pair.  It takes three arguments: the number of
the color-pair to be changed, the foreground color number, and the background
color number.  The value of @emph{pair_number} must be between @code{1} and
@code{COLOR_PAIRS - 1} (the @code{0} color pair is wired to white on black and cannot
be changed).  The value of @emph{fg} and @emph{bg} arguments must be between @code{0} and
@code{COLORS}.  If the color-pair was previously initialized, the screen is
refreshed and all occurrences of that color-pair are changed to the new
definition.
@end deffn

@geindex initscr() (在 curses 模块中)
@anchor{library/curses curses initscr}@anchor{2103}
@deffn {函数} curses.initscr ()

Initialize the library. Return a @ref{2113,,window} object
which represents the whole screen.

@cartouche
@quotation 注解 
If there is an error opening the terminal, the underlying curses library may
cause the interpreter to exit.
@end quotation
@end cartouche
@end deffn

@geindex is_term_resized() (在 curses 模块中)
@anchor{library/curses curses is_term_resized}@anchor{2114}
@deffn {函数} curses.is_term_resized (nlines, ncols)

Return @code{True} if @ref{2115,,resize_term()} would modify the window structure,
@code{False} otherwise.
@end deffn

@geindex isendwin() (在 curses 模块中)
@anchor{library/curses curses isendwin}@anchor{2116}
@deffn {函数} curses.isendwin ()

Return @code{True} if @ref{2100,,endwin()} has been called (that is, the  curses library has
been deinitialized).
@end deffn

@geindex keyname() (在 curses 模块中)
@anchor{library/curses curses keyname}@anchor{2117}
@deffn {函数} curses.keyname (k)

Return the name of the key numbered @emph{k} as a bytes object.  The name of a key generating printable
ASCII character is the key's character.  The name of a control-key combination
is a two-byte bytes object consisting of a caret (@code{b'^'}) followed by the corresponding
printable ASCII character.  The name of an alt-key combination (128--255) is a
bytes object consisting of the prefix @code{b'M-'} followed by the name of the corresponding
ASCII character.
@end deffn

@geindex killchar() (在 curses 模块中)
@anchor{library/curses curses killchar}@anchor{2118}
@deffn {函数} curses.killchar ()

Return the user's current line kill character as a one-byte bytes object. Under Unix operating systems
this is a property of the controlling tty of the curses program, and is not set
by the curses library itself.
@end deffn

@geindex longname() (在 curses 模块中)
@anchor{library/curses curses longname}@anchor{2119}
@deffn {函数} curses.longname ()

Return a bytes object containing the terminfo long name field describing the current
terminal.  The maximum length of a verbose description is 128 characters.  It is
defined only after the call to @ref{2103,,initscr()}.
@end deffn

@geindex meta() (在 curses 模块中)
@anchor{library/curses curses meta}@anchor{211a}
@deffn {函数} curses.meta (flag)

If @emph{flag} is @code{True}, allow 8-bit characters to be input.  If
@emph{flag} is @code{False},  allow only 7-bit chars.
@end deffn

@geindex mouseinterval() (在 curses 模块中)
@anchor{library/curses curses mouseinterval}@anchor{211b}
@deffn {函数} curses.mouseinterval (interval)

Set the maximum time in milliseconds that can elapse between press and release
events in order for them to be recognized as a click, and return the previous
interval value.  The default value is 200 msec, or one fifth of a second.
@end deffn

@geindex mousemask() (在 curses 模块中)
@anchor{library/curses curses mousemask}@anchor{211c}
@deffn {函数} curses.mousemask (mousemask)

Set the mouse events to be reported, and return a tuple @code{(availmask,
oldmask)}.   @emph{availmask} indicates which of the specified mouse events can be
reported; on complete failure it returns @code{0}.  @emph{oldmask} is the previous value of
the given window's mouse event mask.  If this function is never called, no mouse
events are ever reported.
@end deffn

@geindex napms() (在 curses 模块中)
@anchor{library/curses curses napms}@anchor{211d}
@deffn {函数} curses.napms (ms)

Sleep for @emph{ms} milliseconds.
@end deffn

@geindex newpad() (在 curses 模块中)
@anchor{library/curses curses newpad}@anchor{211e}
@deffn {函数} curses.newpad (nlines, ncols)

Create and return a pointer to a new pad data structure with the given number
of lines and columns.  Return a pad as a window object.

A pad is like a window, except that it is not restricted by the screen size, and
is not necessarily associated with a particular part of the screen.  Pads can be
used when a large window is needed, and only a part of the window will be on the
screen at one time.  Automatic refreshes of pads (such as from scrolling or
echoing of input) do not occur.  The @ref{20fe,,refresh()} and @ref{20fc,,noutrefresh()}
methods of a pad require 6 arguments to specify the part of the pad to be
displayed and the location on the screen to be used for the display. The
arguments are @emph{pminrow}, @emph{pmincol}, @emph{sminrow}, @emph{smincol}, @emph{smaxrow}, @emph{smaxcol}; the @emph{p}
arguments refer to the upper left corner of the pad region to be displayed and
the @emph{s} arguments define a clipping box on the screen within which the pad region
is to be displayed.
@end deffn

@geindex newwin() (在 curses 模块中)
@anchor{library/curses curses newwin}@anchor{211f}
@deffn {函数} curses.newwin (nlines, ncols)

@deffnx {函数} curses.newwin (nlines, ncols, begin_y, begin_x)

Return a new @ref{2113,,window}, whose left-upper corner
is at  @code{(begin_y, begin_x)}, and whose height/width is  @emph{nlines}/@emph{ncols}.

By default, the window will extend from the  specified position to the lower
right corner of the screen.
@end deffn

@geindex nl() (在 curses 模块中)
@anchor{library/curses curses nl}@anchor{2120}
@deffn {函数} curses.nl ()

Enter newline mode.  This mode translates the return key into newline on input,
and translates newline into return and line-feed on output. Newline mode is
initially on.
@end deffn

@geindex nocbreak() (在 curses 模块中)
@anchor{library/curses curses nocbreak}@anchor{2110}
@deffn {函数} curses.nocbreak ()

Leave cbreak mode.  Return to normal "cooked" mode with line buffering.
@end deffn

@geindex noecho() (在 curses 模块中)
@anchor{library/curses curses noecho}@anchor{2121}
@deffn {函数} curses.noecho ()

Leave echo mode.  Echoing of input characters is turned off.
@end deffn

@geindex nonl() (在 curses 模块中)
@anchor{library/curses curses nonl}@anchor{2122}
@deffn {函数} curses.nonl ()

Leave newline mode.  Disable translation of return into newline on input, and
disable low-level translation of newline into newline/return on output (but this
does not change the behavior of @code{addch('\n')}, which always does the
equivalent of return and line feed on the virtual screen).  With translation
off, curses can sometimes speed up vertical motion a little; also, it will be
able to detect the return key on input.
@end deffn

@geindex noqiflush() (在 curses 模块中)
@anchor{library/curses curses noqiflush}@anchor{2123}
@deffn {函数} curses.noqiflush ()

When the @code{noqiflush()} routine is used, normal flush of input and output queues
associated with the @code{INTR}, @code{QUIT} and @code{SUSP} characters will not be done.  You may
want to call @code{noqiflush()} in a signal handler if you want output to
continue as though the interrupt had not occurred, after the handler exits.
@end deffn

@geindex noraw() (在 curses 模块中)
@anchor{library/curses curses noraw}@anchor{2124}
@deffn {函数} curses.noraw ()

Leave raw mode. Return to normal "cooked" mode with line buffering.
@end deffn

@geindex pair_content() (在 curses 模块中)
@anchor{library/curses curses pair_content}@anchor{2125}
@deffn {函数} curses.pair_content (pair_number)

Return a tuple @code{(fg, bg)} containing the colors for the requested color pair.
The value of @emph{pair_number} must be between @code{1} and @code{COLOR_PAIRS - 1}.
@end deffn

@geindex pair_number() (在 curses 模块中)
@anchor{library/curses curses pair_number}@anchor{20f4}
@deffn {函数} curses.pair_number (attr)

Return the number of the color-pair set by the attribute value @emph{attr}.
@ref{20f3,,color_pair()} is the counterpart to this function.
@end deffn

@geindex putp() (在 curses 模块中)
@anchor{library/curses curses putp}@anchor{2126}
@deffn {函数} curses.putp (str)

Equivalent to @code{tputs(str, 1, putchar)}; emit the value of a specified
terminfo capability for the current terminal.  Note that the output of @ref{2126,,putp()}
always goes to standard output.
@end deffn

@geindex qiflush() (在 curses 模块中)
@anchor{library/curses curses qiflush}@anchor{2127}
@deffn {函数} curses.qiflush ([flag])

If @emph{flag} is @code{False}, the effect is the same as calling @ref{2123,,noqiflush()}. If
@emph{flag} is @code{True}, or no argument is provided, the queues will be flushed when
these control characters are read.
@end deffn

@geindex raw() (在 curses 模块中)
@anchor{library/curses curses raw}@anchor{20f1}
@deffn {函数} curses.raw ()

Enter raw mode.  In raw mode, normal line buffering and  processing of
interrupt, quit, suspend, and flow control keys are turned off; characters are
presented to curses input functions one by one.
@end deffn

@geindex reset_prog_mode() (在 curses 模块中)
@anchor{library/curses curses reset_prog_mode}@anchor{20f7}
@deffn {函数} curses.reset_prog_mode ()

Restore the  terminal  to "program" mode, as previously saved  by
@ref{20f6,,def_prog_mode()}.
@end deffn

@geindex reset_shell_mode() (在 curses 模块中)
@anchor{library/curses curses reset_shell_mode}@anchor{20f9}
@deffn {函数} curses.reset_shell_mode ()

Restore the  terminal  to "shell" mode, as previously saved  by
@ref{20f8,,def_shell_mode()}.
@end deffn

@geindex resetty() (在 curses 模块中)
@anchor{library/curses curses resetty}@anchor{2128}
@deffn {函数} curses.resetty ()

Restore the state of the terminal modes to what it was at the last call to
@ref{2129,,savetty()}.
@end deffn

@geindex resize_term() (在 curses 模块中)
@anchor{library/curses curses resize_term}@anchor{2115}
@deffn {函数} curses.resize_term (nlines, ncols)

Backend function used by @ref{212a,,resizeterm()}, performing most of the work;
when resizing the windows, @ref{2115,,resize_term()} blank-fills the areas that are
extended.  The calling application should fill in these areas with
appropriate data.  The @code{resize_term()} function attempts to resize all
windows.  However, due to the calling convention of pads, it is not possible
to resize these without additional interaction with the application.
@end deffn

@geindex resizeterm() (在 curses 模块中)
@anchor{library/curses curses resizeterm}@anchor{212a}
@deffn {函数} curses.resizeterm (nlines, ncols)

Resize the standard and current windows to the specified dimensions, and
adjusts other bookkeeping data used by the curses library that record the
window dimensions (in particular the SIGWINCH handler).
@end deffn

@geindex savetty() (在 curses 模块中)
@anchor{library/curses curses savetty}@anchor{2129}
@deffn {函数} curses.savetty ()

Save the current state of the terminal modes in a buffer, usable by
@ref{2128,,resetty()}.
@end deffn

@geindex setsyx() (在 curses 模块中)
@anchor{library/curses curses setsyx}@anchor{212b}
@deffn {函数} curses.setsyx (y, x)

Set the virtual screen cursor to @emph{y}, @emph{x}. If @emph{y} and @emph{x} are both @code{-1}, then
@ref{2109,,leaveok} is set @code{True}.
@end deffn

@geindex setupterm() (在 curses 模块中)
@anchor{library/curses curses setupterm}@anchor{212c}
@deffn {函数} curses.setupterm (term=None, fd=-1)

Initialize the terminal.  @emph{term} is a string giving
the terminal name, or @code{None}; if omitted or @code{None}, the value of the
@geindex TERM
@geindex 环境变量; TERM
@code{TERM} environment variable will be used.  @emph{fd} is the
file descriptor to which any initialization sequences will be sent; if not
supplied or @code{-1}, the file descriptor for @code{sys.stdout} will be used.
@end deffn

@geindex start_color() (在 curses 模块中)
@anchor{library/curses curses start_color}@anchor{212d}
@deffn {函数} curses.start_color ()

Must be called if the programmer wants to use colors, and before any other color
manipulation routine is called.  It is good practice to call this routine right
after @ref{2103,,initscr()}.

@ref{212d,,start_color()} initializes eight basic colors (black, red,  green, yellow,
blue, magenta, cyan, and white), and two global variables in the @ref{2c,,curses}
module, @code{COLORS} and @code{COLOR_PAIRS}, containing the maximum number
of colors and color-pairs the terminal can support.  It also restores the colors
on the terminal to the values they had when the terminal was just turned on.
@end deffn

@geindex termattrs() (在 curses 模块中)
@anchor{library/curses curses termattrs}@anchor{212e}
@deffn {函数} curses.termattrs ()

Return a logical OR of all video attributes supported by the terminal.  This
information is useful when a curses program needs complete control over the
appearance of the screen.
@end deffn

@geindex termname() (在 curses 模块中)
@anchor{library/curses curses termname}@anchor{212f}
@deffn {函数} curses.termname ()

Return the value of the environment variable 
@geindex TERM
@geindex 环境变量; TERM
@code{TERM}, as a bytes object,
truncated to 14 characters.
@end deffn

@geindex tigetflag() (在 curses 模块中)
@anchor{library/curses curses tigetflag}@anchor{2130}
@deffn {函数} curses.tigetflag (capname)

Return the value of the Boolean capability corresponding to the terminfo
capability name @emph{capname} as an integer.  Return the value @code{-1} if @emph{capname} is not a
Boolean capability, or @code{0} if it is canceled or absent from the terminal
description.
@end deffn

@geindex tigetnum() (在 curses 模块中)
@anchor{library/curses curses tigetnum}@anchor{2131}
@deffn {函数} curses.tigetnum (capname)

Return the value of the numeric capability corresponding to the terminfo
capability name @emph{capname} as an integer.  Return the value @code{-2} if @emph{capname} is not a
numeric capability, or @code{-1} if it is canceled or absent from the terminal
description.
@end deffn

@geindex tigetstr() (在 curses 模块中)
@anchor{library/curses curses tigetstr}@anchor{2132}
@deffn {函数} curses.tigetstr (capname)

Return the value of the string capability corresponding to the terminfo
capability name @emph{capname} as a bytes object.  Return @code{None} if @emph{capname}
is not a terminfo "string capability", or is canceled or absent from the
terminal description.
@end deffn

@geindex tparm() (在 curses 模块中)
@anchor{library/curses curses tparm}@anchor{2133}
@deffn {函数} curses.tparm (str[, ...])

Instantiate the bytes object @emph{str} with the supplied parameters, where @emph{str} should
be a parameterized string obtained from the terminfo database.  E.g.
@code{tparm(tigetstr("cup"), 5, 3)} could result in @code{b'\033[6;4H'}, the exact
result depending on terminal type.
@end deffn

@geindex typeahead() (在 curses 模块中)
@anchor{library/curses curses typeahead}@anchor{2134}
@deffn {函数} curses.typeahead (fd)

Specify that the file descriptor @emph{fd} be used for typeahead checking.  If @emph{fd}
is @code{-1}, then no typeahead checking is done.

The curses library does "line-breakout optimization" by looking for typeahead
periodically while updating the screen.  If input is found, and it is coming
from a tty, the current update is postponed until refresh or doupdate is called
again, allowing faster response to commands typed in advance. This function
allows specifying a different file descriptor for typeahead checking.
@end deffn

@geindex unctrl() (在 curses 模块中)
@anchor{library/curses curses unctrl}@anchor{2135}
@deffn {函数} curses.unctrl (ch)

Return a bytes object which is a printable representation of the character @emph{ch}.
Control characters are represented as a caret followed by the character, for
example as @code{b'^C'}. Printing characters are left as they are.
@end deffn

@geindex ungetch() (在 curses 模块中)
@anchor{library/curses curses ungetch}@anchor{2136}
@deffn {函数} curses.ungetch (ch)

Push @emph{ch} so the next @ref{2107,,getch()} will return it.

@cartouche
@quotation 注解 
Only one @emph{ch} can be pushed before @code{getch()} is called.
@end quotation
@end cartouche
@end deffn

@geindex update_lines_cols() (在 curses 模块中)
@anchor{library/curses curses update_lines_cols}@anchor{6c0}
@deffn {函数} curses.update_lines_cols ()

Update 
@geindex LINES
@geindex 环境变量; LINES
@code{LINES} and 
@geindex COLS
@geindex 环境变量; COLS
@code{COLS}. Useful for detecting manual screen resize.


3.5 新版功能.

@end deffn

@geindex unget_wch() (在 curses 模块中)
@anchor{library/curses curses unget_wch}@anchor{9da}
@deffn {函数} curses.unget_wch (ch)

Push @emph{ch} so the next @ref{9d9,,get_wch()} will return it.

@cartouche
@quotation 注解 
Only one @emph{ch} can be pushed before @code{get_wch()} is called.
@end quotation
@end cartouche


3.3 新版功能.

@end deffn

@geindex ungetmouse() (在 curses 模块中)
@anchor{library/curses curses ungetmouse}@anchor{2137}
@deffn {函数} curses.ungetmouse (id, x, y, z, bstate)

Push a @code{KEY_MOUSE} event onto the input queue, associating the given
state data with it.
@end deffn

@geindex use_env() (在 curses 模块中)
@anchor{library/curses curses use_env}@anchor{2138}
@deffn {函数} curses.use_env (flag)

If used, this function should be called before @ref{2103,,initscr()} or newterm are
called.  When @emph{flag} is @code{False}, the values of lines and columns specified in the
terminfo database will be used, even if environment variables 
@geindex LINES
@geindex 环境变量; LINES
@code{LINES}
and 
@geindex COLUMNS
@geindex 环境变量; COLUMNS
@code{COLUMNS} (used by default) are set, or if curses is running in a
window (in which case default behavior would be to use the window size if
@geindex LINES
@geindex 环境变量; LINES
@code{LINES} and 
@geindex COLUMNS
@geindex 环境变量; COLUMNS
@code{COLUMNS} are not set).
@end deffn

@geindex use_default_colors() (在 curses 模块中)
@anchor{library/curses curses use_default_colors}@anchor{2139}
@deffn {函数} curses.use_default_colors ()

Allow use of default values for colors on terminals supporting this feature. Use
this to support transparency in your application.  The default color is assigned
to the color number @code{-1}. After calling this function,  @code{init_pair(x,
curses.COLOR_RED, -1)} initializes, for instance, color pair @emph{x} to a red
foreground color on the default background.
@end deffn

@geindex wrapper() (在 curses 模块中)
@anchor{library/curses curses wrapper}@anchor{2a1}
@deffn {函数} curses.wrapper (func, ...)

Initialize curses and call another callable object, @emph{func}, which should be the
rest of your curses-using application.  If the application raises an exception,
this function will restore the terminal to a sane state before re-raising the
exception and generating a traceback.  The callable object @emph{func} is then passed
the main window 'stdscr' as its first argument, followed by any other arguments
passed to @code{wrapper()}.  Before calling @emph{func}, @code{wrapper()} turns on
cbreak mode, turns off echo, enables the terminal keypad, and initializes colors
if the terminal has color support.  On exit (whether normally or by exception)
it restores cooked mode, turns on echo, and disables the terminal keypad.
@end deffn

@node Window Objects,常量<6>,函数<3>,curses --- 终端字符单元显示的处理
@anchor{library/curses curses-window-objects}@anchor{2113}@anchor{library/curses window-objects}@anchor{213a}
@subsubsection Window Objects


Window objects, as returned by @ref{2103,,initscr()} and @ref{211f,,newwin()} above, have
the following methods and attributes:

@geindex addch() (curses.window 方法)
@anchor{library/curses curses window addch}@anchor{213b}
@deffn {方法} window.addch (ch[, attr])

@deffnx {方法} window.addch (y, x, ch[, attr])

Paint character @emph{ch} at @code{(y, x)} with attributes @emph{attr}, overwriting any
character previously painter at that location.  By default, the character
position and attributes are the current settings for the window object.

@cartouche
@quotation 注解 
Writing outside the window, subwindow, or pad raises a @ref{20ec,,curses.error}.
Attempting to write to the lower right corner of a window, subwindow,
or pad will cause an exception to be raised after the character is printed.
@end quotation
@end cartouche
@end deffn

@geindex addnstr() (curses.window 方法)
@anchor{library/curses curses window addnstr}@anchor{213c}
@deffn {方法} window.addnstr (str, n[, attr])

@deffnx {方法} window.addnstr (y, x, str, n[, attr])

Paint at most @emph{n} characters of the character string @emph{str} at
@code{(y, x)} with attributes
@emph{attr}, overwriting anything previously on the display.
@end deffn

@geindex addstr() (curses.window 方法)
@anchor{library/curses curses window addstr}@anchor{20fd}
@deffn {方法} window.addstr (str[, attr])

@deffnx {方法} window.addstr (y, x, str[, attr])

Paint the character string @emph{str} at @code{(y, x)} with attributes
@emph{attr}, overwriting anything previously on the display.

@cartouche
@quotation 注解 

@itemize *

@item 
Writing outside the window, subwindow, or pad raises @ref{20ec,,curses.error}.
Attempting to write to the lower right corner of a window, subwindow,
or pad will cause an exception to be raised after the string is printed.

@item 
A bug in ncurses@footnote{https://bugs.python.org/issue35924}, the backend
for this Python module, can cause SegFaults when resizing windows. This
is fixed in ncurses-6.1-20190511.  If you are stuck with an earlier
ncurses, you can avoid triggering this if you do not call @ref{20fd,,addstr()}
with a @emph{str} that has embedded newlines.  Instead, call @ref{20fd,,addstr()}
separately for each line.
@end itemize
@end quotation
@end cartouche
@end deffn

@geindex attroff() (curses.window 方法)
@anchor{library/curses curses window attroff}@anchor{213d}
@deffn {方法} window.attroff (attr)

Remove attribute @emph{attr} from the "background" set applied to all writes to the
current window.
@end deffn

@geindex attron() (curses.window 方法)
@anchor{library/curses curses window attron}@anchor{213e}
@deffn {方法} window.attron (attr)

Add attribute @emph{attr} from the "background" set applied to all writes to the
current window.
@end deffn

@geindex attrset() (curses.window 方法)
@anchor{library/curses curses window attrset}@anchor{213f}
@deffn {方法} window.attrset (attr)

Set the "background" set of attributes to @emph{attr}.  This set is initially
@code{0} (no attributes).
@end deffn

@geindex bkgd() (curses.window 方法)
@anchor{library/curses curses window bkgd}@anchor{2140}
@deffn {方法} window.bkgd (ch[, attr])

Set the background property of the window to the character @emph{ch}, with
attributes @emph{attr}.  The change is then applied to every character position in
that window:


@itemize *

@item 
The attribute of every character in the window  is changed to the new
background attribute.

@item 
Wherever  the  former background character appears, it is changed to the new
background character.
@end itemize
@end deffn

@geindex bkgdset() (curses.window 方法)
@anchor{library/curses curses window bkgdset}@anchor{2141}
@deffn {方法} window.bkgdset (ch[, attr])

Set the window's background.  A window's background consists of a character and
any combination of attributes.  The attribute part of the background is combined
(OR'ed) with all non-blank characters that are written into the window.  Both
the character and attribute parts of the background are combined with the blank
characters.  The background becomes a property of the character and moves with
the character through any scrolling and insert/delete line/character operations.
@end deffn

@geindex border() (curses.window 方法)
@anchor{library/curses curses window border}@anchor{2142}
@deffn {方法} window.border ([ls[, rs[, ts[, bs[, tl[, tr[, bl[, br]]]]]]]])

在窗口边缘绘制边框。每个参数指定用于边界特定部分的字符;请参阅下表了解更多详情。

@cartouche
@quotation 注解 
A @code{0} value for any parameter will cause the default character to be used for
that parameter.  Keyword parameters can @emph{not} be used.  The defaults are listed
in this table:
@end quotation
@end cartouche


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

参数

@tab

描述

@tab

默认值

@item

@emph{ls}

@tab

左侧

@tab

@code{ACS_VLINE}

@item

@emph{rs}

@tab

右侧

@tab

@code{ACS_VLINE}

@item

@emph{ts}

@tab

顶部

@tab

@code{ACS_HLINE}

@item

@emph{bs}

@tab

底部

@tab

@code{ACS_HLINE}

@item

@emph{tl}

@tab

左上角

@tab

@code{ACS_ULCORNER}

@item

@emph{tr}

@tab

右上角

@tab

@code{ACS_URCORNER}

@item

@emph{bl}

@tab

左下角

@tab

@code{ACS_LLCORNER}

@item

@emph{br}

@tab

右下角

@tab

@code{ACS_LRCORNER}

@end multitable

@end deffn

@geindex box() (curses.window 方法)
@anchor{library/curses curses window box}@anchor{2143}
@deffn {方法} window.box ([vertch, horch])

Similar to @ref{2142,,border()}, but both @emph{ls} and @emph{rs} are @emph{vertch} and both @emph{ts} and
@emph{bs} are @emph{horch}.  The default corner characters are always used by this function.
@end deffn

@geindex chgat() (curses.window 方法)
@anchor{library/curses curses window chgat}@anchor{2144}
@deffn {方法} window.chgat (attr)

@deffnx {方法} window.chgat (num, attr)

@deffnx {方法} window.chgat (y, x, attr)

@deffnx {方法} window.chgat (y, x, num, attr)

Set the attributes of @emph{num} characters at the current cursor position, or at
position @code{(y, x)} if supplied. If @emph{num} is not given or is @code{-1},
the attribute will be set on all the characters to the end of the line.  This
function moves cursor to position @code{(y, x)} if supplied. The changed line
will be touched using the @ref{2145,,touchline()} method so that the contents will
be redisplayed by the next window refresh.
@end deffn

@geindex clear() (curses.window 方法)
@anchor{library/curses curses window clear}@anchor{2146}
@deffn {方法} window.clear ()

Like @ref{2147,,erase()}, but also cause the whole window to be repainted upon next
call to @ref{20fe,,refresh()}.
@end deffn

@geindex clearok() (curses.window 方法)
@anchor{library/curses curses window clearok}@anchor{2148}
@deffn {方法} window.clearok (flag)

If @emph{flag} is @code{True}, the next call to @ref{20fe,,refresh()} will clear the window
completely.
@end deffn

@geindex clrtobot() (curses.window 方法)
@anchor{library/curses curses window clrtobot}@anchor{2149}
@deffn {方法} window.clrtobot ()

Erase from cursor to the end of the window: all lines below the cursor are
deleted, and then the equivalent of @ref{214a,,clrtoeol()} is performed.
@end deffn

@geindex clrtoeol() (curses.window 方法)
@anchor{library/curses curses window clrtoeol}@anchor{214a}
@deffn {方法} window.clrtoeol ()

Erase from cursor to the end of the line.
@end deffn

@geindex cursyncup() (curses.window 方法)
@anchor{library/curses curses window cursyncup}@anchor{214b}
@deffn {方法} window.cursyncup ()

Update the current cursor position of all the ancestors of the window to
reflect the current cursor position of the window.
@end deffn

@geindex delch() (curses.window 方法)
@anchor{library/curses curses window delch}@anchor{214c}
@deffn {方法} window.delch ([y, x])

Delete any character at @code{(y, x)}.
@end deffn

@geindex deleteln() (curses.window 方法)
@anchor{library/curses curses window deleteln}@anchor{214d}
@deffn {方法} window.deleteln ()

Delete the line under the cursor. All following lines are moved up by one line.
@end deffn

@geindex derwin() (curses.window 方法)
@anchor{library/curses curses window derwin}@anchor{214e}
@deffn {方法} window.derwin (begin_y, begin_x)

@deffnx {方法} window.derwin (nlines, ncols, begin_y, begin_x)

An abbreviation for "derive window", @ref{214e,,derwin()} is the same as calling
@ref{214f,,subwin()}, except that @emph{begin_y} and @emph{begin_x} are relative to the origin
of the window, rather than relative to the entire screen.  Return a window
object for the derived window.
@end deffn

@geindex echochar() (curses.window 方法)
@anchor{library/curses curses window echochar}@anchor{2150}
@deffn {方法} window.echochar (ch[, attr])

Add character @emph{ch} with attribute @emph{attr}, and immediately  call @ref{20fe,,refresh()}
on the window.
@end deffn

@geindex enclose() (curses.window 方法)
@anchor{library/curses curses window enclose}@anchor{2151}
@deffn {方法} window.enclose (y, x)

Test whether the given pair of screen-relative character-cell coordinates are
enclosed by the given window, returning @code{True} or @code{False}.  It is useful for
determining what subset of the screen windows enclose the location of a mouse
event.
@end deffn

@geindex encoding (curses.window 属性)
@anchor{library/curses curses window encoding}@anchor{9d8}
@deffn {属性} window.encoding

Encoding used to encode method arguments (Unicode strings and characters).
The encoding attribute is inherited from the parent window when a subwindow
is created, for example with @ref{214f,,window.subwin()}. By default, the locale
encoding is used (see @ref{39d,,locale.getpreferredencoding()}).


3.3 新版功能.

@end deffn

@geindex erase() (curses.window 方法)
@anchor{library/curses curses window erase}@anchor{2147}
@deffn {方法} window.erase ()

Clear the window.
@end deffn

@geindex getbegyx() (curses.window 方法)
@anchor{library/curses curses window getbegyx}@anchor{2152}
@deffn {方法} window.getbegyx ()

Return a tuple @code{(y, x)} of co-ordinates of upper-left corner.
@end deffn

@geindex getbkgd() (curses.window 方法)
@anchor{library/curses curses window getbkgd}@anchor{2153}
@deffn {方法} window.getbkgd ()

Return the given window's current background character/attribute pair.
@end deffn

@geindex getch() (curses.window 方法)
@anchor{library/curses curses window getch}@anchor{2107}
@deffn {方法} window.getch ([y, x])

Get a character. Note that the integer returned does @emph{not} have to be in ASCII
range: function keys, keypad keys and so on are represented by numbers higher
than 255.  In no-delay mode, return @code{-1} if there is no input, otherwise
wait until a key is pressed.
@end deffn

@geindex get_wch() (curses.window 方法)
@anchor{library/curses curses window get_wch}@anchor{9d9}
@deffn {方法} window.get_wch ([y, x])

Get a wide character. Return a character for most keys, or an integer for
function keys, keypad keys, and other special keys.
In no-delay mode, raise an exception if there is no input.


3.3 新版功能.

@end deffn

@geindex getkey() (curses.window 方法)
@anchor{library/curses curses window getkey}@anchor{2154}
@deffn {方法} window.getkey ([y, x])

Get a character, returning a string instead of an integer, as @ref{2107,,getch()}
does. Function keys, keypad keys and other special keys return a multibyte
string containing the key name.  In no-delay mode, raise an exception if
there is no input.
@end deffn

@geindex getmaxyx() (curses.window 方法)
@anchor{library/curses curses window getmaxyx}@anchor{2155}
@deffn {方法} window.getmaxyx ()

Return a tuple @code{(y, x)} of the height and width of the window.
@end deffn

@geindex getparyx() (curses.window 方法)
@anchor{library/curses curses window getparyx}@anchor{2156}
@deffn {方法} window.getparyx ()

Return the beginning coordinates of this window relative to its parent window
as a tuple @code{(y, x)}.  Return @code{(-1, -1)} if this window has no
parent.
@end deffn

@geindex getstr() (curses.window 方法)
@anchor{library/curses curses window getstr}@anchor{2157}
@deffn {方法} window.getstr ()

@deffnx {方法} window.getstr (n)

@deffnx {方法} window.getstr (y, x)

@deffnx {方法} window.getstr (y, x, n)

Read a bytes object from the user, with primitive line editing capacity.
@end deffn

@geindex getyx() (curses.window 方法)
@anchor{library/curses curses window getyx}@anchor{2158}
@deffn {方法} window.getyx ()

Return a tuple @code{(y, x)} of current cursor position  relative to the window's
upper-left corner.
@end deffn

@geindex hline() (curses.window 方法)
@anchor{library/curses curses window hline}@anchor{2159}
@deffn {方法} window.hline (ch, n)

@deffnx {方法} window.hline (y, x, ch, n)

Display a horizontal line starting at @code{(y, x)} with length @emph{n} consisting of
the character @emph{ch}.
@end deffn

@geindex idcok() (curses.window 方法)
@anchor{library/curses curses window idcok}@anchor{215a}
@deffn {方法} window.idcok (flag)

If @emph{flag} is @code{False}, curses no longer considers using the hardware insert/delete
character feature of the terminal; if @emph{flag} is @code{True}, use of character insertion
and deletion is enabled.  When curses is first initialized, use of character
insert/delete is enabled by default.
@end deffn

@geindex idlok() (curses.window 方法)
@anchor{library/curses curses window idlok}@anchor{215b}
@deffn {方法} window.idlok (flag)

If @emph{flag} is @code{True}, @ref{2c,,curses} will try and use hardware line
editing facilities. Otherwise, line insertion/deletion are disabled.
@end deffn

@geindex immedok() (curses.window 方法)
@anchor{library/curses curses window immedok}@anchor{215c}
@deffn {方法} window.immedok (flag)

If @emph{flag} is @code{True}, any change in the window image automatically causes the
window to be refreshed; you no longer have to call @ref{20fe,,refresh()} yourself.
However, it may degrade performance considerably, due to repeated calls to
wrefresh.  This option is disabled by default.
@end deffn

@geindex inch() (curses.window 方法)
@anchor{library/curses curses window inch}@anchor{215d}
@deffn {方法} window.inch ([y, x])

Return the character at the given position in the window. The bottom 8 bits are
the character proper, and upper bits are the attributes.
@end deffn

@geindex insch() (curses.window 方法)
@anchor{library/curses curses window insch}@anchor{215e}
@deffn {方法} window.insch (ch[, attr])

@deffnx {方法} window.insch (y, x, ch[, attr])

Paint character @emph{ch} at @code{(y, x)} with attributes @emph{attr}, moving the line from
position @emph{x} right by one character.
@end deffn

@geindex insdelln() (curses.window 方法)
@anchor{library/curses curses window insdelln}@anchor{215f}
@deffn {方法} window.insdelln (nlines)

Insert @emph{nlines} lines into the specified window above the current line.  The
@emph{nlines} bottom lines are lost.  For negative @emph{nlines}, delete @emph{nlines} lines
starting with the one under the cursor, and move the remaining lines up.  The
bottom @emph{nlines} lines are cleared.  The current cursor position remains the
same.
@end deffn

@geindex insertln() (curses.window 方法)
@anchor{library/curses curses window insertln}@anchor{2160}
@deffn {方法} window.insertln ()

Insert a blank line under the cursor. All following lines are moved down by one
line.
@end deffn

@geindex insnstr() (curses.window 方法)
@anchor{library/curses curses window insnstr}@anchor{2161}
@deffn {方法} window.insnstr (str, n[, attr])

@deffnx {方法} window.insnstr (y, x, str, n[, attr])

Insert a character string (as many characters as will fit on the line) before
the character under the cursor, up to @emph{n} characters.   If @emph{n} is zero or
negative, the entire string is inserted. All characters to the right of the
cursor are shifted right, with the rightmost characters on the line being lost.
The cursor position does not change (after moving to @emph{y}, @emph{x}, if specified).
@end deffn

@geindex insstr() (curses.window 方法)
@anchor{library/curses curses window insstr}@anchor{2162}
@deffn {方法} window.insstr (str[, attr])

@deffnx {方法} window.insstr (y, x, str[, attr])

Insert a character string (as many characters as will fit on the line) before
the character under the cursor.  All characters to the right of the cursor are
shifted right, with the rightmost characters on the line being lost.  The cursor
position does not change (after moving to @emph{y}, @emph{x}, if specified).
@end deffn

@geindex instr() (curses.window 方法)
@anchor{library/curses curses window instr}@anchor{2163}
@deffn {方法} window.instr ([n])

@deffnx {方法} window.instr (y, x[, n])

Return a bytes object of characters, extracted from the window starting at the
current cursor position, or at @emph{y}, @emph{x} if specified. Attributes are stripped
from the characters.  If @emph{n} is specified, @ref{2163,,instr()} returns a string
at most @emph{n} characters long (exclusive of the trailing NUL).
@end deffn

@geindex is_linetouched() (curses.window 方法)
@anchor{library/curses curses window is_linetouched}@anchor{2164}
@deffn {方法} window.is_linetouched (line)

Return @code{True} if the specified line was modified since the last call to
@ref{20fe,,refresh()}; otherwise return @code{False}.  Raise a @ref{20ec,,curses.error}
exception if @emph{line} is not valid for the given window.
@end deffn

@geindex is_wintouched() (curses.window 方法)
@anchor{library/curses curses window is_wintouched}@anchor{2165}
@deffn {方法} window.is_wintouched ()

Return @code{True} if the specified window was modified since the last call to
@ref{20fe,,refresh()}; otherwise return @code{False}.
@end deffn

@geindex keypad() (curses.window 方法)
@anchor{library/curses curses window keypad}@anchor{2166}
@deffn {方法} window.keypad (flag)

If @emph{flag} is @code{True}, escape sequences generated by some keys (keypad,  function keys)
will be interpreted by @ref{2c,,curses}. If @emph{flag} is @code{False}, escape sequences will be
left as is in the input stream.
@end deffn

@geindex leaveok() (curses.window 方法)
@anchor{library/curses curses window leaveok}@anchor{2109}
@deffn {方法} window.leaveok (flag)

If @emph{flag} is @code{True}, cursor is left where it is on update, instead of being at "cursor
position."  This reduces cursor movement where possible. If possible the cursor
will be made invisible.

If @emph{flag} is @code{False}, cursor will always be at "cursor position" after an update.
@end deffn

@geindex move() (curses.window 方法)
@anchor{library/curses curses window move}@anchor{2167}
@deffn {方法} window.move (new_y, new_x)

Move cursor to @code{(new_y, new_x)}.
@end deffn

@geindex mvderwin() (curses.window 方法)
@anchor{library/curses curses window mvderwin}@anchor{2168}
@deffn {方法} window.mvderwin (y, x)

Move the window inside its parent window.  The screen-relative parameters of
the window are not changed.  This routine is used to display different parts of
the parent window at the same physical position on the screen.
@end deffn

@geindex mvwin() (curses.window 方法)
@anchor{library/curses curses window mvwin}@anchor{2169}
@deffn {方法} window.mvwin (new_y, new_x)

Move the window so its upper-left corner is at @code{(new_y, new_x)}.
@end deffn

@geindex nodelay() (curses.window 方法)
@anchor{library/curses curses window nodelay}@anchor{216a}
@deffn {方法} window.nodelay (flag)

If @emph{flag} is @code{True}, @ref{2107,,getch()} will be non-blocking.
@end deffn

@geindex notimeout() (curses.window 方法)
@anchor{library/curses curses window notimeout}@anchor{216b}
@deffn {方法} window.notimeout (flag)

If @emph{flag} is @code{True}, escape sequences will not be timed out.

If @emph{flag} is @code{False}, after a few milliseconds, an escape sequence will not be
interpreted, and will be left in the input stream as is.
@end deffn

@geindex noutrefresh() (curses.window 方法)
@anchor{library/curses curses window noutrefresh}@anchor{20fc}
@deffn {方法} window.noutrefresh ()

Mark for refresh but wait.  This function updates the data structure
representing the desired state of the window, but does not force an update of
the physical screen.  To accomplish that, call  @ref{20fb,,doupdate()}.
@end deffn

@geindex overlay() (curses.window 方法)
@anchor{library/curses curses window overlay}@anchor{216c}
@deffn {方法} window.overlay (destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])

Overlay the window on top of @emph{destwin}. The windows need not be the same size,
only the overlapping region is copied. This copy is non-destructive, which means
that the current background character does not overwrite the old contents of
@emph{destwin}.

To get fine-grained control over the copied region, the second form of
@ref{216c,,overlay()} can be used. @emph{sminrow} and @emph{smincol} are the upper-left
coordinates of the source window, and the other variables mark a rectangle in
the destination window.
@end deffn

@geindex overwrite() (curses.window 方法)
@anchor{library/curses curses window overwrite}@anchor{216d}
@deffn {方法} window.overwrite (destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])

Overwrite the window on top of @emph{destwin}. The windows need not be the same size,
in which case only the overlapping region is copied. This copy is destructive,
which means that the current background character overwrites the old contents of
@emph{destwin}.

To get fine-grained control over the copied region, the second form of
@ref{216d,,overwrite()} can be used. @emph{sminrow} and @emph{smincol} are the upper-left
coordinates of the source window, the other variables mark a rectangle in the
destination window.
@end deffn

@geindex putwin() (curses.window 方法)
@anchor{library/curses curses window putwin}@anchor{216e}
@deffn {方法} window.putwin (file)

Write all data associated with the window into the provided file object.  This
information can be later retrieved using the @ref{210a,,getwin()} function.
@end deffn

@geindex redrawln() (curses.window 方法)
@anchor{library/curses curses window redrawln}@anchor{216f}
@deffn {方法} window.redrawln (beg, num)

Indicate that the @emph{num} screen lines, starting at line @emph{beg}, are corrupted and
should be completely redrawn on the next @ref{20fe,,refresh()} call.
@end deffn

@geindex redrawwin() (curses.window 方法)
@anchor{library/curses curses window redrawwin}@anchor{2170}
@deffn {方法} window.redrawwin ()

Touch the entire window, causing it to be completely redrawn on the next
@ref{20fe,,refresh()} call.
@end deffn

@geindex refresh() (curses.window 方法)
@anchor{library/curses curses window refresh}@anchor{20fe}
@deffn {方法} window.refresh ([pminrow, pmincol, sminrow, smincol, smaxrow, smaxcol])

Update the display immediately (sync actual screen with previous
drawing/deleting methods).

The 6 optional arguments can only be specified when the window is a pad created
with @ref{211e,,newpad()}.  The additional parameters are needed to indicate what part
of the pad and screen are involved. @emph{pminrow} and @emph{pmincol} specify the upper
left-hand corner of the rectangle to be displayed in the pad.  @emph{sminrow},
@emph{smincol}, @emph{smaxrow}, and @emph{smaxcol} specify the edges of the rectangle to be
displayed on the screen.  The lower right-hand corner of the rectangle to be
displayed in the pad is calculated from the screen coordinates, since the
rectangles must be the same size.  Both rectangles must be entirely contained
within their respective structures.  Negative values of @emph{pminrow}, @emph{pmincol},
@emph{sminrow}, or @emph{smincol} are treated as if they were zero.
@end deffn

@geindex resize() (curses.window 方法)
@anchor{library/curses curses window resize}@anchor{2171}
@deffn {方法} window.resize (nlines, ncols)

Reallocate storage for a curses window to adjust its dimensions to the
specified values.  If either dimension is larger than the current values, the
window's data is filled with blanks that have the current background
rendition (as set by @ref{2141,,bkgdset()}) merged into them.
@end deffn

@geindex scroll() (curses.window 方法)
@anchor{library/curses curses window scroll}@anchor{2172}
@deffn {方法} window.scroll ([lines=1])

Scroll the screen or scrolling region upward by @emph{lines} lines.
@end deffn

@geindex scrollok() (curses.window 方法)
@anchor{library/curses curses window scrollok}@anchor{2173}
@deffn {方法} window.scrollok (flag)

Control what happens when the cursor of a window is moved off the edge of the
window or scrolling region, either as a result of a newline action on the bottom
line, or typing the last character of the last line.  If @emph{flag} is @code{False}, the
cursor is left on the bottom line.  If @emph{flag} is @code{True}, the window is scrolled up
one line.  Note that in order to get the physical scrolling effect on the
terminal, it is also necessary to call @ref{215b,,idlok()}.
@end deffn

@geindex setscrreg() (curses.window 方法)
@anchor{library/curses curses window setscrreg}@anchor{2174}
@deffn {方法} window.setscrreg (top, bottom)

Set the scrolling region from line @emph{top} to line @emph{bottom}. All scrolling actions
will take place in this region.
@end deffn

@geindex standend() (curses.window 方法)
@anchor{library/curses curses window standend}@anchor{2175}
@deffn {方法} window.standend ()

Turn off the standout attribute.  On some terminals this has the side effect of
turning off all attributes.
@end deffn

@geindex standout() (curses.window 方法)
@anchor{library/curses curses window standout}@anchor{2176}
@deffn {方法} window.standout ()

Turn on attribute @emph{A_STANDOUT}.
@end deffn

@geindex subpad() (curses.window 方法)
@anchor{library/curses curses window subpad}@anchor{2177}
@deffn {方法} window.subpad (begin_y, begin_x)

@deffnx {方法} window.subpad (nlines, ncols, begin_y, begin_x)

Return a sub-window, whose upper-left corner is at @code{(begin_y, begin_x)}, and
whose width/height is @emph{ncols}/@emph{nlines}.
@end deffn

@geindex subwin() (curses.window 方法)
@anchor{library/curses curses window subwin}@anchor{214f}
@deffn {方法} window.subwin (begin_y, begin_x)

@deffnx {方法} window.subwin (nlines, ncols, begin_y, begin_x)

Return a sub-window, whose upper-left corner is at @code{(begin_y, begin_x)}, and
whose width/height is @emph{ncols}/@emph{nlines}.

By default, the sub-window will extend from the specified position to the lower
right corner of the window.
@end deffn

@geindex syncdown() (curses.window 方法)
@anchor{library/curses curses window syncdown}@anchor{2178}
@deffn {方法} window.syncdown ()

Touch each location in the window that has been touched in any of its ancestor
windows.  This routine is called by @ref{20fe,,refresh()}, so it should almost never
be necessary to call it manually.
@end deffn

@geindex syncok() (curses.window 方法)
@anchor{library/curses curses window syncok}@anchor{2179}
@deffn {方法} window.syncok (flag)

If @emph{flag} is @code{True}, then @ref{217a,,syncup()} is called automatically
whenever there is a change in the window.
@end deffn

@geindex syncup() (curses.window 方法)
@anchor{library/curses curses window syncup}@anchor{217a}
@deffn {方法} window.syncup ()

Touch all locations in ancestors of the window that have been changed in  the
window.
@end deffn

@geindex timeout() (curses.window 方法)
@anchor{library/curses curses window timeout}@anchor{217b}
@deffn {方法} window.timeout (delay)

Set blocking or non-blocking read behavior for the window.  If @emph{delay} is
negative, blocking read is used (which will wait indefinitely for input).  If
@emph{delay} is zero, then non-blocking read is used, and @ref{2107,,getch()} will
return @code{-1} if no input is waiting.  If @emph{delay} is positive, then
@ref{2107,,getch()} will block for @emph{delay} milliseconds, and return @code{-1} if there is
still no input at the end of that time.
@end deffn

@geindex touchline() (curses.window 方法)
@anchor{library/curses curses window touchline}@anchor{2145}
@deffn {方法} window.touchline (start, count[, changed])

Pretend @emph{count} lines have been changed, starting with line @emph{start}.  If
@emph{changed} is supplied, it specifies whether the affected lines are marked as
having been changed (@emph{changed}@code{=True}) or unchanged (@emph{changed}@code{=False}).
@end deffn

@geindex touchwin() (curses.window 方法)
@anchor{library/curses curses window touchwin}@anchor{217c}
@deffn {方法} window.touchwin ()

Pretend the whole window has been changed, for purposes of drawing
optimizations.
@end deffn

@geindex untouchwin() (curses.window 方法)
@anchor{library/curses curses window untouchwin}@anchor{217d}
@deffn {方法} window.untouchwin ()

Mark all lines in  the  window  as unchanged since the last call to
@ref{20fe,,refresh()}.
@end deffn

@geindex vline() (curses.window 方法)
@anchor{library/curses curses window vline}@anchor{217e}
@deffn {方法} window.vline (ch, n)

@deffnx {方法} window.vline (y, x, ch, n)

Display a vertical line starting at @code{(y, x)} with length @emph{n} consisting of the
character @emph{ch}.
@end deffn

@node 常量<6>,,Window Objects,curses --- 终端字符单元显示的处理
@anchor{library/curses constants}@anchor{217f}
@subsubsection 常量


The @ref{2c,,curses} module defines the following data members:

@geindex ERR() (在 curses 模块中)
@anchor{library/curses curses ERR}@anchor{2180}
@deffn {数据} curses.ERR

Some curses routines  that  return  an integer, such as @ref{2107,,getch()}, return
@ref{2180,,ERR} upon failure.
@end deffn

@geindex OK() (在 curses 模块中)
@anchor{library/curses curses OK}@anchor{2181}
@deffn {数据} curses.OK

Some curses routines  that  return  an integer, such as  @ref{211d,,napms()}, return
@ref{2181,,OK} upon success.
@end deffn

@geindex version() (在 curses 模块中)
@anchor{library/curses curses version}@anchor{2182}
@deffn {数据} curses.version

A bytes object representing the current version of the module.  Also available as
@code{__version__}.
@end deffn

@geindex ncurses_version() (在 curses 模块中)
@anchor{library/curses curses ncurses_version}@anchor{1bf}
@deffn {数据} curses.ncurses_version

A named tuple containing the three components of the ncurses library
version: @emph{major}, @emph{minor}, and @emph{patch}.  All values are integers.  The
components can also be accessed by name,  so @code{curses.ncurses_version[0]}
is equivalent to @code{curses.ncurses_version.major} and so on.

Availability: if the ncurses library is used.


3.8 新版功能.

@end deffn

Some constants are available to specify character cell attributes.
The exact constants available are system dependent.


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性

@tab

含义

@item

@code{A_ALTCHARSET}

@tab

备用字符集模式

@item

@code{A_BLINK}

@tab

闪烁模式

@item

@code{A_BOLD}

@tab

粗体模式

@item

@code{A_DIM}

@tab

暗淡模式

@item

@code{A_INVIS}

@tab

不可见或空白模式

@item

@code{A_ITALIC}

@tab

斜体模式

@item

@code{A_NORMAL}

@tab

正常属性

@item

@code{A_PROTECT}

@tab

保护模式

@item

@code{A_REVERSE}

@tab

反转背景色和前景色

@item

@code{A_STANDOUT}

@tab

突出模式

@item

@code{A_UNDERLINE}

@tab

下划线模式

@item

@code{A_HORIZONTAL}

@tab

水平突出显示

@item

@code{A_LEFT}

@tab

左高亮

@item

@code{A_LOW}

@tab

底部高亮

@item

@code{A_RIGHT}

@tab

右高亮

@item

@code{A_TOP}

@tab

顶部高亮

@item

@code{A_VERTICAL}

@tab

垂直突出显示

@item

@code{A_CHARTEXT}

@tab

用于提取字符的位掩码

@end multitable



3.7 新版功能: @code{A_ITALIC} was added.


有几个常量可用于提取某些方法返回的相应属性。


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

位掩码

@tab

含义

@item

@code{A_ATTRIBUTES}

@tab

用于提取属性的位掩码

@item

@code{A_CHARTEXT}

@tab

用于提取字符的位掩码

@item

@code{A_COLOR}

@tab

用于提取颜色对字段信息的位掩码

@end multitable


键由名称以 @code{KEY_} 开头的整数常量引用。确切的可用键取决于系统。

@c XXX this table is far too large! should it be alphabetized?


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

关键常数

@tab

键

@item

@code{KEY_MIN}

@tab

最小键值

@item

@code{KEY_BREAK}

@tab

中断键（不可靠）

@item

@code{KEY_DOWN}

@tab

向下箭头

@item

@code{KEY_UP}

@tab

向上箭头

@item

@code{KEY_LEFT}

@tab

向左箭头

@item

@code{KEY_RIGHT}

@tab

向右箭头

@item

@code{KEY_HOME}

@tab

Home key (upward+left arrow)

@item

@code{KEY_BACKSPACE}

@tab

退格（不可靠）

@item

@code{KEY_F0}

@tab

Function keys.  Up to 64 function keys are
supported.

@item

@code{KEY_Fn}

@tab

Value of function key @emph{n}

@item

@code{KEY_DL}

@tab

删除行

@item

@code{KEY_IL}

@tab

插入行

@item

@code{KEY_DC}

@tab

Delete character

@item

@code{KEY_IC}

@tab

Insert char or enter insert mode

@item

@code{KEY_EIC}

@tab

Exit insert char mode

@item

@code{KEY_CLEAR}

@tab

Clear screen

@item

@code{KEY_EOS}

@tab

Clear to end of screen

@item

@code{KEY_EOL}

@tab

Clear to end of line

@item

@code{KEY_SF}

@tab

Scroll 1 line forward

@item

@code{KEY_SR}

@tab

Scroll 1 line backward (reverse)

@item

@code{KEY_NPAGE}

@tab

下一页

@item

@code{KEY_PPAGE}

@tab

上一页

@item

@code{KEY_STAB}

@tab

Set tab

@item

@code{KEY_CTAB}

@tab

Clear tab

@item

@code{KEY_CATAB}

@tab

Clear all tabs

@item

@code{KEY_ENTER}

@tab

Enter or send (unreliable)

@item

@code{KEY_SRESET}

@tab

Soft (partial) reset (unreliable)

@item

@code{KEY_RESET}

@tab

Reset or hard reset (unreliable)

@item

@code{KEY_PRINT}

@tab

打印

@item

@code{KEY_LL}

@tab

Home down or bottom (lower left)

@item

@code{KEY_A1}

@tab

键盘的左上角

@item

@code{KEY_A3}

@tab

键盘的右上角

@item

@code{KEY_B2}

@tab

键盘的中心

@item

@code{KEY_C1}

@tab

键盘左下方

@item

@code{KEY_C3}

@tab

键盘右下方

@item

@code{KEY_BTAB}

@tab

Back tab

@item

@code{KEY_BEG}

@tab

Beg (beginning)

@item

@code{KEY_CANCEL}

@tab

取消

@item

@code{KEY_CLOSE}

@tab

关闭

@item

@code{KEY_COMMAND}

@tab

Cmd (命令行)

@item

@code{KEY_COPY}

@tab

复制

@item

@code{KEY_CREATE}

@tab

创建

@item

@code{KEY_END}

@tab

End

@item

@code{KEY_EXIT}

@tab

退出

@item

@code{KEY_FIND}

@tab

查找

@item

@code{KEY_HELP}

@tab

帮助

@item

@code{KEY_MARK}

@tab

标记

@item

@code{KEY_MESSAGE}

@tab

消息

@item

@code{KEY_MOVE}

@tab

移动

@item

@code{KEY_NEXT}

@tab

下一个

@item

@code{KEY_OPEN}

@tab

打开

@item

@code{KEY_OPTIONS}

@tab

选项

@item

@code{KEY_PREVIOUS}

@tab

Prev (previous)

@item

@code{KEY_REDO}

@tab

重做

@item

@code{KEY_REFERENCE}

@tab

Ref (reference)

@item

@code{KEY_REFRESH}

@tab

刷新

@item

@code{KEY_REPLACE}

@tab

替换

@item

@code{KEY_RESTART}

@tab

重启

@item

@code{KEY_RESUME}

@tab

恢复

@item

@code{KEY_SAVE}

@tab

保存

@item

@code{KEY_SBEG}

@tab

Shifted Beg (beginning)

@item

@code{KEY_SCANCEL}

@tab

Shifted Cancel

@item

@code{KEY_SCOMMAND}

@tab

Shifted Command

@item

@code{KEY_SCOPY}

@tab

Shifted Copy

@item

@code{KEY_SCREATE}

@tab

Shifted Create

@item

@code{KEY_SDC}

@tab

Shifted Delete char

@item

@code{KEY_SDL}

@tab

Shifted Delete line

@item

@code{KEY_SELECT}

@tab

Select

@item

@code{KEY_SEND}

@tab

Shifted End

@item

@code{KEY_SEOL}

@tab

Shifted Clear line

@item

@code{KEY_SEXIT}

@tab

Shifted Exit

@item

@code{KEY_SFIND}

@tab

Shifted Find

@item

@code{KEY_SHELP}

@tab

Shifted Help

@item

@code{KEY_SHOME}

@tab

Shifted Home

@item

@code{KEY_SIC}

@tab

Shifted Input

@item

@code{KEY_SLEFT}

@tab

Shifted Left arrow

@item

@code{KEY_SMESSAGE}

@tab

Shifted Message

@item

@code{KEY_SMOVE}

@tab

Shifted Move

@item

@code{KEY_SNEXT}

@tab

Shifted Next

@item

@code{KEY_SOPTIONS}

@tab

Shifted Options

@item

@code{KEY_SPREVIOUS}

@tab

Shifted Prev

@item

@code{KEY_SPRINT}

@tab

Shifted Print

@item

@code{KEY_SREDO}

@tab

Shifted Redo

@item

@code{KEY_SREPLACE}

@tab

Shifted Replace

@item

@code{KEY_SRIGHT}

@tab

Shifted Right arrow

@item

@code{KEY_SRSUME}

@tab

Shifted Resume

@item

@code{KEY_SSAVE}

@tab

Shifted Save

@item

@code{KEY_SSUSPEND}

@tab

Shifted Suspend

@item

@code{KEY_SUNDO}

@tab

Shifted Undo

@item

@code{KEY_SUSPEND}

@tab

Suspend

@item

@code{KEY_UNDO}

@tab

撤销操作

@item

@code{KEY_MOUSE}

@tab

Mouse event has occurred

@item

@code{KEY_RESIZE}

@tab

Terminal resize event

@item

@code{KEY_MAX}

@tab

Maximum key value

@end multitable


在VT100及其软件仿真（例如X终端仿真器）上，通常至少有四个功能键（ @code{KEY_F1}, @code{KEY_F2}, @code{KEY_F3}, @code{KEY_F4} ）可用，并且箭头键以明显的方式映射到 @code{KEY_UP}, @code{KEY_DOWN}, @code{KEY_LEFT} 和 @code{KEY_RIGHT} 。如果您的机器有一个PC键盘，可以安全地使用箭头键和十二个功能键（旧的PC键盘可能只有十个功能键）;此外，以下键盘映射是标准的：


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx} 
@headitem

键帽

@tab

常数

@item

@code{Insert}

@tab

KEY_IC

@item

@code{Delete}

@tab

KEY_DC

@item

@code{Home}

@tab

KEY_HOME

@item

@code{End}

@tab

KEY_END

@item

@code{Page Up}

@tab

KEY_PPAGE

@item

@code{Page Down}

@tab

KEY_NPAGE

@end multitable


The following table lists characters from the alternate character set. These are
inherited from the VT100 terminal, and will generally be  available on software
emulations such as X terminals.  When there is no graphic available, curses
falls back on a crude printable ASCII approximation.

@cartouche
@quotation 注解 
只有在调用 @ref{2103,,initscr()} 之后才能使用它们
@end quotation
@end cartouche


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

ACS代码

@tab

含义

@item

@code{ACS_BBSS}

@tab

右上角的别名

@item

@code{ACS_BLOCK}

@tab

实心方块

@item

@code{ACS_BOARD}

@tab

正方形

@item

@code{ACS_BSBS}

@tab

水平线的别名

@item

@code{ACS_BSSB}

@tab

左上角的别名

@item

@code{ACS_BSSS}

@tab

顶部 T 型的别名

@item

@code{ACS_BTEE}

@tab

底部 T 型

@item

@code{ACS_BULLET}

@tab

正方形

@item

@code{ACS_CKBOARD}

@tab

棋盘（点刻）

@item

@code{ACS_DARROW}

@tab

向下箭头

@item

@code{ACS_DEGREE}

@tab

等级符

@item

@code{ACS_DIAMOND}

@tab

菱形

@item

@code{ACS_GEQUAL}

@tab

大于或等于

@item

@code{ACS_HLINE}

@tab

水平线

@item

@code{ACS_LANTERN}

@tab

灯形符号

@item

@code{ACS_LARROW}

@tab

向左箭头

@item

@code{ACS_LEQUAL}

@tab

小于或等于

@item

@code{ACS_LLCORNER}

@tab

左下角

@item

@code{ACS_LRCORNER}

@tab

右下角

@item

@code{ACS_LTEE}

@tab

左侧 T 型

@item

@code{ACS_NEQUAL}

@tab

不等号

@item

@code{ACS_PI}

@tab

字母π

@item

@code{ACS_PLMINUS}

@tab

正负号

@item

@code{ACS_PLUS}

@tab

加号

@item

@code{ACS_RARROW}

@tab

向右箭头

@item

@code{ACS_RTEE}

@tab

右侧 T 型

@item

@code{ACS_S1}

@tab

扫描线 1

@item

@code{ACS_S3}

@tab

扫描线3

@item

@code{ACS_S7}

@tab

扫描线7

@item

@code{ACS_S9}

@tab

扫描线 9

@item

@code{ACS_SBBS}

@tab

右下角的别名

@item

@code{ACS_SBSB}

@tab

垂直线的别名

@item

@code{ACS_SBSS}

@tab

右侧 T 型的别名

@item

@code{ACS_SSBB}

@tab

左下角的别名

@item

@code{ACS_SSBS}

@tab

底部 T 型的别名

@item

@code{ACS_SSSB}

@tab

左侧 T 型的别名

@item

@code{ACS_SSSS}

@tab

alternate name for crossover or big plus

@item

@code{ACS_STERLING}

@tab

英镑

@item

@code{ACS_TTEE}

@tab

顶部 T 型

@item

@code{ACS_UARROW}

@tab

向上箭头

@item

@code{ACS_ULCORNER}

@tab

左上角

@item

@code{ACS_URCORNER}

@tab

右上角

@item

@code{ACS_VLINE}

@tab

垂线

@end multitable


下表列出了预定义的颜色：


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

颜色

@item

@code{COLOR_BLACK}

@tab

黑色

@item

@code{COLOR_BLUE}

@tab

蓝色

@item

@code{COLOR_CYAN}

@tab

青色（浅绿蓝色）

@item

@code{COLOR_GREEN}

@tab

绿色

@item

@code{COLOR_MAGENTA}

@tab

洋红色（紫红色）

@item

@code{COLOR_RED}

@tab

红色

@item

@code{COLOR_WHITE}

@tab

白色

@item

@code{COLOR_YELLOW}

@tab

黄色

@end multitable


@node curses textpad --- Text input widget for curses programs,curses ascii --- Utilities for ASCII characters,curses --- 终端字符单元显示的处理,通用操作系统服务
@anchor{library/curses curses-textpad-text-input-widget-for-curses-programs}@anchor{2183}@anchor{library/curses module-curses textpad}@anchor{2f}
@subsection @code{curses.textpad} --- Text input widget for curses programs


@geindex curses.textpad (模块)

The @ref{2f,,curses.textpad} module provides a @ref{2184,,Textbox} class that handles
elementary text editing in a curses window, supporting a set of keybindings
resembling those of Emacs (thus, also of Netscape Navigator, BBedit 6.x,
FrameMaker, and many other programs).  The module also provides a
rectangle-drawing function useful for framing text boxes or for other purposes.

The module @ref{2f,,curses.textpad} defines the following function:

@geindex rectangle() (在 curses.textpad 模块中)
@anchor{library/curses curses textpad rectangle}@anchor{2185}
@deffn {函数} curses.textpad.rectangle (win, uly, ulx, lry, lrx)

Draw a rectangle.  The first argument must be a window object; the remaining
arguments are coordinates relative to that window.  The second and third
arguments are the y and x coordinates of the upper left hand corner of the
rectangle to be drawn; the fourth and fifth arguments are the y and x
coordinates of the lower right hand corner. The rectangle will be drawn using
VT100/IBM PC forms characters on terminals that make this possible (including
xterm and most other software terminal emulators).  Otherwise it will be drawn
with ASCII  dashes, vertical bars, and plus signs.
@end deffn

@menu
* 文本框对象:: 

@end menu

@node 文本框对象,,,curses textpad --- Text input widget for curses programs
@anchor{library/curses curses-textpad-objects}@anchor{2186}@anchor{library/curses textbox-objects}@anchor{2187}
@subsubsection 文本框对象


You can instantiate a @ref{2184,,Textbox} object as follows:

@geindex Textbox (curses.textpad 中的类)
@anchor{library/curses curses textpad Textbox}@anchor{2184}
@deffn {类} curses.textpad.Textbox (win)

Return a textbox widget object.  The @emph{win} argument should be a curses
@ref{2113,,window} object in which the textbox is to
be contained. The edit cursor of the textbox is initially located at the
upper left hand corner of the containing window, with coordinates @code{(0, 0)}.
The instance's @ref{2188,,stripspaces} flag is initially on.

@ref{2184,,Textbox} objects have the following methods:

@geindex edit() (curses.textpad.Textbox 方法)
@anchor{library/curses curses textpad Textbox edit}@anchor{2189}
@deffn {方法} edit ([validator])

This is the entry point you will normally use.  It accepts editing
keystrokes until one of the termination keystrokes is entered.  If
@emph{validator} is supplied, it must be a function.  It will be called for
each keystroke entered with the keystroke as a parameter; command dispatch
is done on the result. This method returns the window contents as a
string; whether blanks in the window are included is affected by the
@ref{2188,,stripspaces} attribute.
@end deffn

@geindex do_command() (curses.textpad.Textbox 方法)
@anchor{library/curses curses textpad Textbox do_command}@anchor{218a}
@deffn {方法} do_command (ch)

处理单个按键命令。以下是支持的特殊按键：


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

按键

@tab

动作

@item

@code{Control-A}

@tab

转到窗口的左边缘。

@item

@code{Control-B}

@tab

光标向左，如果可能，包含前一行。

@item

@code{Control-D}

@tab

删除光标下的字符。

@item

@code{Control-E}

@tab

Go to right edge (stripspaces off) or end
of line (stripspaces on).

@item

@code{Control-F}

@tab

向右移动光标，适当时换行到下一行。

@item

@code{Control-G}

@tab

终止，返回窗口内容。

@item

@code{Control-H}

@tab

向后删除字符。

@item

@code{Control-J}

@tab

如果窗口是1行则终止，否则插入换行符。

@item

@code{Control-K}

@tab

如果行为空，则删除它，否则清除到行尾。

@item

@code{Control-L}

@tab

刷新屏幕。

@item

@code{Control-N}

@tab

光标向下;向下移动一行。

@item

@code{Control-O}

@tab

在光标位置插入一个空行。

@item

@code{Control-P}

@tab

光标向上;向上移动一行。

@end multitable


如果光标位于无法移动的边缘，则移动操作不执行任何操作。在可能的情况下，支持以下同义词：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

按键

@item

@code{KEY_LEFT}

@tab

@code{Control-B}

@item

@code{KEY_RIGHT}

@tab

@code{Control-F}

@item

@code{KEY_UP}

@tab

@code{Control-P}

@item

@code{KEY_DOWN}

@tab

@code{Control-N}

@item

@code{KEY_BACKSPACE}

@tab

@code{Control-h}

@end multitable


All other keystrokes are treated as a command to insert the given
character and move right (with line wrapping).
@end deffn

@geindex gather() (curses.textpad.Textbox 方法)
@anchor{library/curses curses textpad Textbox gather}@anchor{218b}
@deffn {方法} gather ()

Return the window contents as a string; whether blanks in the
window are included is affected by the @ref{2188,,stripspaces} member.
@end deffn

@geindex stripspaces (curses.textpad.Textbox 属性)
@anchor{library/curses curses textpad Textbox stripspaces}@anchor{2188}
@deffn {属性} stripspaces

This attribute is a flag which controls the interpretation of blanks in
the window.  When it is on, trailing blanks on each line are ignored; any
cursor motion that would land the cursor on a trailing blank goes to the
end of that line instead, and trailing blanks are stripped when the window
contents are gathered.
@end deffn
@end deffn

@node curses ascii --- Utilities for ASCII characters,curses panel --- A panel stack extension for curses,curses textpad --- Text input widget for curses programs,通用操作系统服务
@anchor{library/curses ascii doc}@anchor{218c}@anchor{library/curses ascii curses-ascii-utilities-for-ascii-characters}@anchor{218d}@anchor{library/curses ascii module-curses ascii}@anchor{2d}
@subsection @code{curses.ascii} --- Utilities for ASCII characters


@geindex curses.ascii (模块)


__________________________________________________________________


The @ref{2d,,curses.ascii} module supplies name constants for ASCII characters and
functions to test membership in various ASCII character classes.  The constants
supplied are names for control characters as follows:


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

名称

@tab

含义

@item

@code{NUL}

@tab

@item

@code{SOH}

@tab

标题开始，控制台中断

@item

@code{STX}

@tab

文本开始

@item

@code{ETX}

@tab

文本结束

@item

@code{EOT}

@tab

传输结束

@item

@code{ENQ}

@tab

查询，附带 @code{ACK} 流量控制

@item

@code{ACK}

@tab

确认

@item

@code{BEL}

@tab

蜂鸣器

@item

@code{BS}

@tab

退格

@item

@code{TAB}

@tab

Tab

@item

@code{HT}

@tab

@code{TAB} 的别名： "水平制表符”

@item

@code{LF}

@tab

换行

@item

@code{NL}

@tab

@code{LF} 的别名： "新行"

@item

@code{VT}

@tab

垂直制表符

@item

@code{FF}

@tab

换页

@item

@code{CR}

@tab

回车

@item

@code{SO}

@tab

Shift-out, begin alternate character set

@item

@code{SI}

@tab

Shift-in, resume default character set

@item

@code{DLE}

@tab

Data-link escape

@item

@code{DC1}

@tab

XON, for flow control

@item

@code{DC2}

@tab

Device control 2, block-mode flow control

@item

@code{DC3}

@tab

XOFF, for flow control

@item

@code{DC4}

@tab

设备控制4

@item

@code{NAK}

@tab

否定确认

@item

@code{SYN}

@tab

同步空闲

@item

@code{ETB}

@tab

末端传输块

@item

@code{CAN}

@tab

取消

@item

@code{EM}

@tab

媒体结束

@item

@code{SUB}

@tab

替换

@item

@code{ESC}

@tab

退出

@item

@code{FS}

@tab

文件分隔符

@item

@code{GS}

@tab

Group separator

@item

@code{RS}

@tab

记录分隔符，块模式终结器

@item

@code{US}

@tab

单位分隔符

@item

@code{SP}

@tab

空格

@item

@code{DEL}

@tab

删除

@end multitable


Note that many of these have little practical significance in modern usage.  The
mnemonics derive from teleprinter conventions that predate digital computers.

The module supplies the following functions, patterned on those in the standard
C library:

@geindex isalnum() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isalnum}@anchor{218e}
@deffn {函数} curses.ascii.isalnum (c)

Checks for an ASCII alphanumeric character; it is equivalent to @code{isalpha(c) or
isdigit(c)}.
@end deffn

@geindex isalpha() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isalpha}@anchor{218f}
@deffn {函数} curses.ascii.isalpha (c)

Checks for an ASCII alphabetic character; it is equivalent to @code{isupper(c) or
islower(c)}.
@end deffn

@geindex isascii() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isascii}@anchor{2190}
@deffn {函数} curses.ascii.isascii (c)

Checks for a character value that fits in the 7-bit ASCII set.
@end deffn

@geindex isblank() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isblank}@anchor{2191}
@deffn {函数} curses.ascii.isblank (c)

Checks for an ASCII whitespace character; space or horizontal tab.
@end deffn

@geindex iscntrl() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii iscntrl}@anchor{2192}
@deffn {函数} curses.ascii.iscntrl (c)

Checks for an ASCII control character (in the range 0x00 to 0x1f or 0x7f).
@end deffn

@geindex isdigit() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isdigit}@anchor{2193}
@deffn {函数} curses.ascii.isdigit (c)

Checks for an ASCII decimal digit, @code{'0'} through @code{'9'}.  This is equivalent
to @code{c in string.digits}.
@end deffn

@geindex isgraph() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isgraph}@anchor{2194}
@deffn {函数} curses.ascii.isgraph (c)

Checks for ASCII any printable character except space.
@end deffn

@geindex islower() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii islower}@anchor{2195}
@deffn {函数} curses.ascii.islower (c)

Checks for an ASCII lower-case character.
@end deffn

@geindex isprint() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isprint}@anchor{2196}
@deffn {函数} curses.ascii.isprint (c)

Checks for any ASCII printable character including space.
@end deffn

@geindex ispunct() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii ispunct}@anchor{2197}
@deffn {函数} curses.ascii.ispunct (c)

Checks for any printable ASCII character which is not a space or an alphanumeric
character.
@end deffn

@geindex isspace() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isspace}@anchor{2198}
@deffn {函数} curses.ascii.isspace (c)

Checks for ASCII white-space characters; space, line feed, carriage return, form
feed, horizontal tab, vertical tab.
@end deffn

@geindex isupper() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isupper}@anchor{2199}
@deffn {函数} curses.ascii.isupper (c)

Checks for an ASCII uppercase letter.
@end deffn

@geindex isxdigit() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isxdigit}@anchor{219a}
@deffn {函数} curses.ascii.isxdigit (c)

Checks for an ASCII hexadecimal digit.  This is equivalent to @code{c in
string.hexdigits}.
@end deffn

@geindex isctrl() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii isctrl}@anchor{219b}
@deffn {函数} curses.ascii.isctrl (c)

Checks for an ASCII control character (ordinal values 0 to 31).
@end deffn

@geindex ismeta() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii ismeta}@anchor{219c}
@deffn {函数} curses.ascii.ismeta (c)

Checks for a non-ASCII character (ordinal values 0x80 and above).
@end deffn

These functions accept either integers or single-character strings; when the argument is a
string, it is first converted using the built-in function @ref{13be,,ord()}.

Note that all these functions check ordinal bit values derived from the
character of the string you pass in; they do not actually know anything about
the host machine's character encoding.

The following two functions take either a single-character string or integer
byte value; they return a value of the same type.

@geindex ascii() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii ascii}@anchor{219d}
@deffn {函数} curses.ascii.ascii (c)

Return the ASCII value corresponding to the low 7 bits of @emph{c}.
@end deffn

@geindex ctrl() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii ctrl}@anchor{219e}
@deffn {函数} curses.ascii.ctrl (c)

Return the control character corresponding to the given character (the character
bit value is bitwise-anded with 0x1f).
@end deffn

@geindex alt() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii alt}@anchor{219f}
@deffn {函数} curses.ascii.alt (c)

Return the 8-bit character corresponding to the given ASCII character (the
character bit value is bitwise-ored with 0x80).
@end deffn

The following function takes either a single-character string or integer value;
it returns a string.

@geindex ^ (caret); in curses module
@geindex ! (exclamation); in curses module

@geindex unctrl() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii unctrl}@anchor{21a0}
@deffn {函数} curses.ascii.unctrl (c)

Return a string representation of the ASCII character @emph{c}.  If @emph{c} is printable,
this string is the character itself.  If the character is a control character
(0x00--0x1f) the string consists of a caret (@code{'^'}) followed by the
corresponding uppercase letter. If the character is an ASCII delete (0x7f) the
string is @code{'^?'}.  If the character has its meta bit (0x80) set, the meta bit
is stripped, the preceding rules applied, and @code{'!'} prepended to the result.
@end deffn

@geindex controlnames() (在 curses.ascii 模块中)
@anchor{library/curses ascii curses ascii controlnames}@anchor{21a1}
@deffn {数据} curses.ascii.controlnames

A 33-element string array that contains the ASCII mnemonics for the thirty-two
ASCII control characters from 0 (NUL) to 0x1f (US), in order, plus the mnemonic
@code{SP} for the space character.
@end deffn

@node curses panel --- A panel stack extension for curses,platform --- 获取底层平台的标识数据,curses ascii --- Utilities for ASCII characters,通用操作系统服务
@anchor{library/curses panel doc}@anchor{21a2}@anchor{library/curses panel curses-panel-a-panel-stack-extension-for-curses}@anchor{21a3}@anchor{library/curses panel module-curses panel}@anchor{2e}
@subsection @code{curses.panel} --- A panel stack extension for curses


@geindex curses.panel (模块)


__________________________________________________________________


Panels are windows with the added feature of depth, so they can be stacked on
top of each other, and only the visible portions of each window will be
displayed.  Panels can be added, moved up or down in the stack, and removed.

@menu
* 函数: 函数<4>. 
* Panel Objects:: 

@end menu

@node 函数<4>,Panel Objects,,curses panel --- A panel stack extension for curses
@anchor{library/curses panel cursespanel-functions}@anchor{21a4}@anchor{library/curses panel functions}@anchor{21a5}
@subsubsection 函数


The module @ref{2e,,curses.panel} defines the following functions:

@geindex bottom_panel() (在 curses.panel 模块中)
@anchor{library/curses panel curses panel bottom_panel}@anchor{21a6}
@deffn {函数} curses.panel.bottom_panel ()

Returns the bottom panel in the panel stack.
@end deffn

@geindex new_panel() (在 curses.panel 模块中)
@anchor{library/curses panel curses panel new_panel}@anchor{21a7}
@deffn {函数} curses.panel.new_panel (win)

Returns a panel object, associating it with the given window @emph{win}. Be aware
that you need to keep the returned panel object referenced explicitly.  If you
don't, the panel object is garbage collected and removed from the panel stack.
@end deffn

@geindex top_panel() (在 curses.panel 模块中)
@anchor{library/curses panel curses panel top_panel}@anchor{21a8}
@deffn {函数} curses.panel.top_panel ()

Returns the top panel in the panel stack.
@end deffn

@geindex update_panels() (在 curses.panel 模块中)
@anchor{library/curses panel curses panel update_panels}@anchor{21a9}
@deffn {函数} curses.panel.update_panels ()

Updates the virtual screen after changes in the panel stack. This does not call
@ref{20fb,,curses.doupdate()}, so you'll have to do this yourself.
@end deffn

@node Panel Objects,,函数<4>,curses panel --- A panel stack extension for curses
@anchor{library/curses panel curses-panel-objects}@anchor{21aa}@anchor{library/curses panel panel-objects}@anchor{21ab}
@subsubsection Panel Objects


Panel objects, as returned by @ref{21a7,,new_panel()} above, are windows with a
stacking order. There's always a window associated with a panel which determines
the content, while the panel methods are responsible for the window's depth in
the panel stack.

Panel objects have the following methods:

@geindex above() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel above}@anchor{21ac}
@deffn {方法} Panel.above ()

Returns the panel above the current panel.
@end deffn

@geindex below() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel below}@anchor{21ad}
@deffn {方法} Panel.below ()

Returns the panel below the current panel.
@end deffn

@geindex bottom() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel bottom}@anchor{21ae}
@deffn {方法} Panel.bottom ()

Push the panel to the bottom of the stack.
@end deffn

@geindex hidden() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel hidden}@anchor{21af}
@deffn {方法} Panel.hidden ()

Returns @code{True} if the panel is hidden (not visible), @code{False} otherwise.
@end deffn

@geindex hide() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel hide}@anchor{21b0}
@deffn {方法} Panel.hide ()

Hide the panel. This does not delete the object, it just makes the window on
screen invisible.
@end deffn

@geindex move() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel move}@anchor{21b1}
@deffn {方法} Panel.move (y, x)

Move the panel to the screen coordinates @code{(y, x)}.
@end deffn

@geindex replace() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel replace}@anchor{21b2}
@deffn {方法} Panel.replace (win)

Change the window associated with the panel to the window @emph{win}.
@end deffn

@geindex set_userptr() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel set_userptr}@anchor{21b3}
@deffn {方法} Panel.set_userptr (obj)

Set the panel's user pointer to @emph{obj}. This is used to associate an arbitrary
piece of data with the panel, and can be any Python object.
@end deffn

@geindex show() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel show}@anchor{21b4}
@deffn {方法} Panel.show ()

Display the panel (which might have been hidden).
@end deffn

@geindex top() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel top}@anchor{21b5}
@deffn {方法} Panel.top ()

Push panel to the top of the stack.
@end deffn

@geindex userptr() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel userptr}@anchor{21b6}
@deffn {方法} Panel.userptr ()

Returns the user pointer for the panel.  This might be any Python object.
@end deffn

@geindex window() (curses.panel.Panel 方法)
@anchor{library/curses panel curses panel Panel window}@anchor{21b7}
@deffn {方法} Panel.window ()

Returns the window object associated with the panel.
@end deffn

@node platform --- 获取底层平台的标识数据,errno --- 标准 errno 系统符号,curses panel --- A panel stack extension for curses,通用操作系统服务
@anchor{library/platform doc}@anchor{21b8}@anchor{library/platform module-platform}@anchor{ce}@anchor{library/platform platform-access-to-underlying-platform-s-identifying-data}@anchor{21b9}
@subsection @code{platform} ---  获取底层平台的标识数据


@geindex platform (模块)

@strong{示例代码：} Lib/platform.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/platform.py}


__________________________________________________________________


@cartouche
@quotation 注解 
Specific platforms listed alphabetically, with Linux included in the Unix
section.
@end quotation
@end cartouche

@menu
* 跨平台:: 
* Java平台:: 
* Windows平台:: 
* Mac OS平台:: 
* Unix Platforms:: 

@end menu

@node 跨平台,Java平台,,platform --- 获取底层平台的标识数据
@anchor{library/platform cross-platform}@anchor{21ba}
@subsubsection 跨平台


@geindex architecture() (在 platform 模块中)
@anchor{library/platform platform architecture}@anchor{fa9}
@deffn {函数} platform.architecture (executable=sys.executable, bits='@w{'}, linkage='@w{'})

Queries the given executable (defaults to the Python interpreter binary) for
various architecture information.

Returns a tuple @code{(bits, linkage)} which contain information about the bit
architecture and the linkage format used for the executable. Both values are
returned as strings.

Values that cannot be determined are returned as given by the parameter presets.
If bits is given as @code{'@w{'}}, the @code{sizeof(pointer)} (or
@code{sizeof(long)} on Python version < 1.5.2) is used as indicator for the
supported pointer size.

The function relies on the system's @code{file} command to do the actual work.
This is available on most if not all Unix  platforms and some non-Unix platforms
and then only if the executable points to the Python interpreter.  Reasonable
defaults are used when the above needs are not met.

@cartouche
@quotation 注解 
On Mac OS X (and perhaps other platforms), executable files may be
universal files containing multiple architectures.

To get at the "64-bitness" of the current interpreter, it is more
reliable to query the @ref{b3c,,sys.maxsize} attribute:

@example
is_64bits = sys.maxsize > 2**32
@end example
@end quotation
@end cartouche
@end deffn

@geindex machine() (在 platform 模块中)
@anchor{library/platform platform machine}@anchor{21bb}
@deffn {函数} platform.machine ()

Returns the machine type, e.g. @code{'i386'}. An empty string is returned if the
value cannot be determined.
@end deffn

@geindex node() (在 platform 模块中)
@anchor{library/platform platform node}@anchor{21bc}
@deffn {函数} platform.node ()

Returns the computer's network name (may not be fully qualified!). An empty
string is returned if the value cannot be determined.
@end deffn

@geindex platform() (在 platform 模块中)
@anchor{library/platform platform platform}@anchor{fae}
@deffn {函数} platform.platform (aliased=0, terse=0)

Returns a single string identifying the underlying platform with as much useful
information as possible.

The output is intended to be @emph{human readable} rather than machine parseable. It
may look different on different platforms and this is intended.

If @emph{aliased} is true, the function will use aliases for various platforms that
report system names which differ from their common names, for example SunOS will
be reported as Solaris.  The @ref{21bd,,system_alias()} function is used to implement
this.

Setting @emph{terse} to true causes the function to return only the absolute minimum
information needed to identify the platform.


在 3.8 版更改: On macOS, the function now uses @ref{faf,,mac_ver()}, if it returns a
non-empty release string, to get the macOS version rather than the darwin
version.

@end deffn

@geindex processor() (在 platform 模块中)
@anchor{library/platform platform processor}@anchor{21be}
@deffn {函数} platform.processor ()

Returns the (real) processor name, e.g. @code{'amdk6'}.

An empty string is returned if the value cannot be determined. Note that many
platforms do not provide this information or simply return the same value as for
@ref{21bb,,machine()}.  NetBSD does this.
@end deffn

@geindex python_build() (在 platform 模块中)
@anchor{library/platform platform python_build}@anchor{21bf}
@deffn {函数} platform.python_build ()

Returns a tuple @code{(buildno, builddate)} stating the Python build number and
date as strings.
@end deffn

@geindex python_compiler() (在 platform 模块中)
@anchor{library/platform platform python_compiler}@anchor{21c0}
@deffn {函数} platform.python_compiler ()

Returns a string identifying the compiler used for compiling Python.
@end deffn

@geindex python_branch() (在 platform 模块中)
@anchor{library/platform platform python_branch}@anchor{21c1}
@deffn {函数} platform.python_branch ()

Returns a string identifying the Python implementation SCM branch.
@end deffn

@geindex python_implementation() (在 platform 模块中)
@anchor{library/platform platform python_implementation}@anchor{21c2}
@deffn {函数} platform.python_implementation ()

Returns a string identifying the Python implementation. Possible return values
are: 'CPython', 'IronPython', 'Jython', 'PyPy'.
@end deffn

@geindex python_revision() (在 platform 模块中)
@anchor{library/platform platform python_revision}@anchor{21c3}
@deffn {函数} platform.python_revision ()

Returns a string identifying the Python implementation SCM revision.
@end deffn

@geindex python_version() (在 platform 模块中)
@anchor{library/platform platform python_version}@anchor{21c4}
@deffn {函数} platform.python_version ()

Returns the Python version as string @code{'major.minor.patchlevel'}.

Note that unlike the Python @code{sys.version}, the returned value will always
include the patchlevel (it defaults to 0).
@end deffn

@geindex python_version_tuple() (在 platform 模块中)
@anchor{library/platform platform python_version_tuple}@anchor{21c5}
@deffn {函数} platform.python_version_tuple ()

Returns the Python version as tuple @code{(major, minor, patchlevel)} of strings.

Note that unlike the Python @code{sys.version}, the returned value will always
include the patchlevel (it defaults to @code{'0'}).
@end deffn

@geindex release() (在 platform 模块中)
@anchor{library/platform platform release}@anchor{21c6}
@deffn {函数} platform.release ()

Returns the system's release, e.g. @code{'2.2.0'} or @code{'NT'} An empty string is
returned if the value cannot be determined.
@end deffn

@geindex system() (在 platform 模块中)
@anchor{library/platform platform system}@anchor{21c7}
@deffn {函数} platform.system ()

Returns the system/OS name, such as @code{'Linux'}, @code{'Darwin'}, @code{'Java'},
@code{'Windows'}. An empty string is returned if the value cannot be determined.
@end deffn

@geindex system_alias() (在 platform 模块中)
@anchor{library/platform platform system_alias}@anchor{21bd}
@deffn {函数} platform.system_alias (system, release, version)

Returns @code{(system, release, version)} aliased to common marketing names used
for some systems.  It also does some reordering of the information in some cases
where it would otherwise cause confusion.
@end deffn

@geindex version() (在 platform 模块中)
@anchor{library/platform platform version}@anchor{21c8}
@deffn {函数} platform.version ()

Returns the system's release version, e.g. @code{'#3 on degas'}. An empty string is
returned if the value cannot be determined.
@end deffn

@geindex uname() (在 platform 模块中)
@anchor{library/platform platform uname}@anchor{fac}
@deffn {函数} platform.uname ()

Fairly portable uname interface. Returns a @ref{1b6,,namedtuple()}
containing six attributes: @ref{21c7,,system}, @ref{21bc,,node}, @ref{21c6,,release},
@ref{21c8,,version}, @ref{21bb,,machine}, and @ref{21be,,processor}.

Note that this adds a sixth attribute (@ref{21be,,processor}) not present
in the @ref{a58,,os.uname()} result.  Also, the attribute names are different
for the first two attributes; @ref{a58,,os.uname()} names them
@code{sysname} and @code{nodename}.

Entries which cannot be determined are set to @code{'@w{'}}.


在 3.3 版更改: 将结果从元组改为命名元组。

@end deffn

@node Java平台,Windows平台,跨平台,platform --- 获取底层平台的标识数据
@anchor{library/platform java-platform}@anchor{21c9}
@subsubsection Java平台


@geindex java_ver() (在 platform 模块中)
@anchor{library/platform platform java_ver}@anchor{21ca}
@deffn {函数} platform.java_ver (release='@w{'}, vendor='@w{'}, vminfo=('@w{'}, '@w{'}, '@w{'}), osinfo=('@w{'}, '@w{'}, '@w{'}))

Jython的版本接口

Returns a tuple @code{(release, vendor, vminfo, osinfo)} with @emph{vminfo} being a
tuple @code{(vm_name, vm_release, vm_vendor)} and @emph{osinfo} being a tuple
@code{(os_name, os_version, os_arch)}. Values which cannot be determined are set to
the defaults given as parameters (which all default to @code{'@w{'}}).
@end deffn

@node Windows平台,Mac OS平台,Java平台,platform --- 获取底层平台的标识数据
@anchor{library/platform windows-platform}@anchor{21cb}
@subsubsection Windows平台


@geindex win32_ver() (在 platform 模块中)
@anchor{library/platform platform win32_ver}@anchor{ea6}
@deffn {函数} platform.win32_ver (release='@w{'}, version='@w{'}, csd='@w{'}, ptype='@w{'})

Get additional version information from the Windows Registry and return a tuple
@code{(release, version, csd, ptype)} referring to OS release, version number,
CSD level (service pack) and OS type (multi/single processor).

As a hint: @emph{ptype} is @code{'Uniprocessor Free'} on single processor NT machines
and @code{'Multiprocessor Free'} on multi processor machines. The @emph{'Free'} refers
to the OS version being free of debugging code. It could also state @emph{'Checked'}
which means the OS version uses debugging code, i.e. code that checks arguments,
ranges, etc.

@cartouche
@quotation 注解 
This function works best with Mark Hammond's
@code{win32all} package installed, but also on Python 2.3 and
later (support for this was added in Python 2.6). It obviously
only runs on Win32 compatible platforms.
@end quotation
@end cartouche
@end deffn

@geindex win32_edition() (在 platform 模块中)
@anchor{library/platform platform win32_edition}@anchor{21cc}
@deffn {函数} platform.win32_edition ()

Returns a string representing the current Windows edition.  Possible
values include but are not limited to @code{'Enterprise'}, @code{'IoTUAP'},
@code{'ServerStandard'}, and @code{'nanoserver'}.


3.8 新版功能.

@end deffn

@geindex win32_is_iot() (在 platform 模块中)
@anchor{library/platform platform win32_is_iot}@anchor{21cd}
@deffn {函数} platform.win32_is_iot ()

Return @code{True} if the Windows edition returned by @ref{21cc,,win32_edition()}
is recognized as an IoT edition.


3.8 新版功能.

@end deffn

@node Mac OS平台,Unix Platforms,Windows平台,platform --- 获取底层平台的标识数据
@anchor{library/platform mac-os-platform}@anchor{21ce}
@subsubsection Mac OS平台


@geindex mac_ver() (在 platform 模块中)
@anchor{library/platform platform mac_ver}@anchor{faf}
@deffn {函数} platform.mac_ver (release='@w{'}, versioninfo=('@w{'}, '@w{'}, '@w{'}), machine='@w{'})

Get Mac OS version information and return it as tuple @code{(release, versioninfo,
machine)} with @emph{versioninfo} being a tuple @code{(version, dev_stage,
non_release_version)}.

Entries which cannot be determined are set to @code{'@w{'}}.  All tuple entries are
strings.
@end deffn

@node Unix Platforms,,Mac OS平台,platform --- 获取底层平台的标识数据
@anchor{library/platform unix-platforms}@anchor{21cf}
@subsubsection Unix Platforms


@geindex libc_ver() (在 platform 模块中)
@anchor{library/platform platform libc_ver}@anchor{fab}
@deffn {函数} platform.libc_ver (executable=sys.executable, lib='@w{'}, version='@w{'}, chunksize=16384)

Tries to determine the libc version against which the file executable (defaults
to the Python interpreter) is linked.  Returns a tuple of strings @code{(lib,
version)} which default to the given parameters in case the lookup fails.

Note that this function has intimate knowledge of how different libc versions
add symbols to the executable is probably only usable for executables compiled
using @code{gcc}.

The file is read and scanned in chunks of @emph{chunksize} bytes.
@end deffn

@node errno --- 标准 errno 系统符号,ctypes --- Python 的外部函数库,platform --- 获取底层平台的标识数据,通用操作系统服务
@anchor{library/errno doc}@anchor{21d0}@anchor{library/errno errno-standard-errno-system-symbols}@anchor{21d1}@anchor{library/errno module-errno}@anchor{7c}
@subsection @code{errno} --- 标准 errno 系统符号


@geindex errno (模块)


__________________________________________________________________


本模块提供标准的 @code{errno} 系统符号。每个符号的值是其对应的整数值。符号的名称和描述来自 @code{linux/include/errno.h}，应该是非常全面的。

@geindex errorcode() (在 errno 模块中)
@anchor{library/errno errno errorcode}@anchor{21d2}
@deffn {数据} errno.errorcode

提供从 errno 值到底层系统中字符串名称的映射的字典。例如， @code{errno.errorcode[errno.EPERM]} 映射为 @code{'EPERM'} 。
@end deffn

如果要将数字的错误代码转换为错误信息，请使用 @ref{1e99,,os.strerror()}。

在下面的列表中，当前平台上没有使用的符号没有被本模块定义。 已定义的符号的具体列表可参见 @code{errno.errorcode.keys()}。 可用的符号包括：

@geindex EPERM() (在 errno 模块中)
@anchor{library/errno errno EPERM}@anchor{21d3}
@deffn {数据} errno.EPERM

Operation not permitted
@end deffn

@geindex ENOENT() (在 errno 模块中)
@anchor{library/errno errno ENOENT}@anchor{21d4}
@deffn {数据} errno.ENOENT

No such file or directory
@end deffn

@geindex ESRCH() (在 errno 模块中)
@anchor{library/errno errno ESRCH}@anchor{21d5}
@deffn {数据} errno.ESRCH

No such process
@end deffn

@geindex EINTR() (在 errno 模块中)
@anchor{library/errno errno EINTR}@anchor{652}
@deffn {数据} errno.EINTR

Interrupted system call.


@subsubheading 参见


This error is mapped to the exception @ref{653,,InterruptedError}.

@end deffn

@geindex EIO() (在 errno 模块中)
@anchor{library/errno errno EIO}@anchor{21d6}
@deffn {数据} errno.EIO

I/O error
@end deffn

@geindex ENXIO() (在 errno 模块中)
@anchor{library/errno errno ENXIO}@anchor{21d7}
@deffn {数据} errno.ENXIO

No such device or address
@end deffn

@geindex E2BIG() (在 errno 模块中)
@anchor{library/errno errno E2BIG}@anchor{21d8}
@deffn {数据} errno.E2BIG

Arg list too long
@end deffn

@geindex ENOEXEC() (在 errno 模块中)
@anchor{library/errno errno ENOEXEC}@anchor{21d9}
@deffn {数据} errno.ENOEXEC

Exec format error
@end deffn

@geindex EBADF() (在 errno 模块中)
@anchor{library/errno errno EBADF}@anchor{21da}
@deffn {数据} errno.EBADF

Bad file number
@end deffn

@geindex ECHILD() (在 errno 模块中)
@anchor{library/errno errno ECHILD}@anchor{21db}
@deffn {数据} errno.ECHILD

No child processes
@end deffn

@geindex EAGAIN() (在 errno 模块中)
@anchor{library/errno errno EAGAIN}@anchor{1ece}
@deffn {数据} errno.EAGAIN

Try again
@end deffn

@geindex ENOMEM() (在 errno 模块中)
@anchor{library/errno errno ENOMEM}@anchor{21dc}
@deffn {数据} errno.ENOMEM

Out of memory
@end deffn

@geindex EACCES() (在 errno 模块中)
@anchor{library/errno errno EACCES}@anchor{21dd}
@deffn {数据} errno.EACCES

Permission denied
@end deffn

@geindex EFAULT() (在 errno 模块中)
@anchor{library/errno errno EFAULT}@anchor{21de}
@deffn {数据} errno.EFAULT

Bad address
@end deffn

@geindex ENOTBLK() (在 errno 模块中)
@anchor{library/errno errno ENOTBLK}@anchor{21df}
@deffn {数据} errno.ENOTBLK

Block device required
@end deffn

@geindex EBUSY() (在 errno 模块中)
@anchor{library/errno errno EBUSY}@anchor{21e0}
@deffn {数据} errno.EBUSY

Device or resource busy
@end deffn

@geindex EEXIST() (在 errno 模块中)
@anchor{library/errno errno EEXIST}@anchor{21e1}
@deffn {数据} errno.EEXIST

File exists
@end deffn

@geindex EXDEV() (在 errno 模块中)
@anchor{library/errno errno EXDEV}@anchor{1ea4}
@deffn {数据} errno.EXDEV

Cross-device link
@end deffn

@geindex ENODEV() (在 errno 模块中)
@anchor{library/errno errno ENODEV}@anchor{21e2}
@deffn {数据} errno.ENODEV

No such device
@end deffn

@geindex ENOTDIR() (在 errno 模块中)
@anchor{library/errno errno ENOTDIR}@anchor{21e3}
@deffn {数据} errno.ENOTDIR

Not a directory
@end deffn

@geindex EISDIR() (在 errno 模块中)
@anchor{library/errno errno EISDIR}@anchor{21e4}
@deffn {数据} errno.EISDIR

Is a directory
@end deffn

@geindex EINVAL() (在 errno 模块中)
@anchor{library/errno errno EINVAL}@anchor{f59}
@deffn {数据} errno.EINVAL

Invalid argument
@end deffn

@geindex ENFILE() (在 errno 模块中)
@anchor{library/errno errno ENFILE}@anchor{21e5}
@deffn {数据} errno.ENFILE

File table overflow
@end deffn

@geindex EMFILE() (在 errno 模块中)
@anchor{library/errno errno EMFILE}@anchor{21e6}
@deffn {数据} errno.EMFILE

Too many open files
@end deffn

@geindex ENOTTY() (在 errno 模块中)
@anchor{library/errno errno ENOTTY}@anchor{21e7}
@deffn {数据} errno.ENOTTY

Not a typewriter
@end deffn

@geindex ETXTBSY() (在 errno 模块中)
@anchor{library/errno errno ETXTBSY}@anchor{21e8}
@deffn {数据} errno.ETXTBSY

Text file busy
@end deffn

@geindex EFBIG() (在 errno 模块中)
@anchor{library/errno errno EFBIG}@anchor{21e9}
@deffn {数据} errno.EFBIG

File too large
@end deffn

@geindex ENOSPC() (在 errno 模块中)
@anchor{library/errno errno ENOSPC}@anchor{21ea}
@deffn {数据} errno.ENOSPC

No space left on device
@end deffn

@geindex ESPIPE() (在 errno 模块中)
@anchor{library/errno errno ESPIPE}@anchor{21eb}
@deffn {数据} errno.ESPIPE

Illegal seek
@end deffn

@geindex EROFS() (在 errno 模块中)
@anchor{library/errno errno EROFS}@anchor{21ec}
@deffn {数据} errno.EROFS

Read-only file system
@end deffn

@geindex EMLINK() (在 errno 模块中)
@anchor{library/errno errno EMLINK}@anchor{21ed}
@deffn {数据} errno.EMLINK

Too many links
@end deffn

@geindex EPIPE() (在 errno 模块中)
@anchor{library/errno errno EPIPE}@anchor{21ee}
@deffn {数据} errno.EPIPE

Broken pipe
@end deffn

@geindex EDOM() (在 errno 模块中)
@anchor{library/errno errno EDOM}@anchor{21ef}
@deffn {数据} errno.EDOM

Math argument out of domain of func
@end deffn

@geindex ERANGE() (在 errno 模块中)
@anchor{library/errno errno ERANGE}@anchor{21f0}
@deffn {数据} errno.ERANGE

Math result not representable
@end deffn

@geindex EDEADLK() (在 errno 模块中)
@anchor{library/errno errno EDEADLK}@anchor{21f1}
@deffn {数据} errno.EDEADLK

Resource deadlock would occur
@end deffn

@geindex ENAMETOOLONG() (在 errno 模块中)
@anchor{library/errno errno ENAMETOOLONG}@anchor{21f2}
@deffn {数据} errno.ENAMETOOLONG

File name too long
@end deffn

@geindex ENOLCK() (在 errno 模块中)
@anchor{library/errno errno ENOLCK}@anchor{21f3}
@deffn {数据} errno.ENOLCK

No record locks available
@end deffn

@geindex ENOSYS() (在 errno 模块中)
@anchor{library/errno errno ENOSYS}@anchor{21f4}
@deffn {数据} errno.ENOSYS

Function not implemented
@end deffn

@geindex ENOTEMPTY() (在 errno 模块中)
@anchor{library/errno errno ENOTEMPTY}@anchor{21f5}
@deffn {数据} errno.ENOTEMPTY

Directory not empty
@end deffn

@geindex ELOOP() (在 errno 模块中)
@anchor{library/errno errno ELOOP}@anchor{21f6}
@deffn {数据} errno.ELOOP

Too many symbolic links encountered
@end deffn

@geindex EWOULDBLOCK() (在 errno 模块中)
@anchor{library/errno errno EWOULDBLOCK}@anchor{21f7}
@deffn {数据} errno.EWOULDBLOCK

Operation would block
@end deffn

@geindex ENOMSG() (在 errno 模块中)
@anchor{library/errno errno ENOMSG}@anchor{21f8}
@deffn {数据} errno.ENOMSG

No message of desired type
@end deffn

@geindex EIDRM() (在 errno 模块中)
@anchor{library/errno errno EIDRM}@anchor{21f9}
@deffn {数据} errno.EIDRM

Identifier removed
@end deffn

@geindex ECHRNG() (在 errno 模块中)
@anchor{library/errno errno ECHRNG}@anchor{21fa}
@deffn {数据} errno.ECHRNG

Channel number out of range
@end deffn

@geindex EL2NSYNC() (在 errno 模块中)
@anchor{library/errno errno EL2NSYNC}@anchor{21fb}
@deffn {数据} errno.EL2NSYNC

Level 2 not synchronized
@end deffn

@geindex EL3HLT() (在 errno 模块中)
@anchor{library/errno errno EL3HLT}@anchor{21fc}
@deffn {数据} errno.EL3HLT

Level 3 halted
@end deffn

@geindex EL3RST() (在 errno 模块中)
@anchor{library/errno errno EL3RST}@anchor{21fd}
@deffn {数据} errno.EL3RST

Level 3 reset
@end deffn

@geindex ELNRNG() (在 errno 模块中)
@anchor{library/errno errno ELNRNG}@anchor{21fe}
@deffn {数据} errno.ELNRNG

Link number out of range
@end deffn

@geindex EUNATCH() (在 errno 模块中)
@anchor{library/errno errno EUNATCH}@anchor{21ff}
@deffn {数据} errno.EUNATCH

Protocol driver not attached
@end deffn

@geindex ENOCSI() (在 errno 模块中)
@anchor{library/errno errno ENOCSI}@anchor{2200}
@deffn {数据} errno.ENOCSI

No CSI structure available
@end deffn

@geindex EL2HLT() (在 errno 模块中)
@anchor{library/errno errno EL2HLT}@anchor{2201}
@deffn {数据} errno.EL2HLT

Level 2 halted
@end deffn

@geindex EBADE() (在 errno 模块中)
@anchor{library/errno errno EBADE}@anchor{2202}
@deffn {数据} errno.EBADE

Invalid exchange
@end deffn

@geindex EBADR() (在 errno 模块中)
@anchor{library/errno errno EBADR}@anchor{2203}
@deffn {数据} errno.EBADR

Invalid request descriptor
@end deffn

@geindex EXFULL() (在 errno 模块中)
@anchor{library/errno errno EXFULL}@anchor{2204}
@deffn {数据} errno.EXFULL

Exchange full
@end deffn

@geindex ENOANO() (在 errno 模块中)
@anchor{library/errno errno ENOANO}@anchor{2205}
@deffn {数据} errno.ENOANO

No anode
@end deffn

@geindex EBADRQC() (在 errno 模块中)
@anchor{library/errno errno EBADRQC}@anchor{2206}
@deffn {数据} errno.EBADRQC

Invalid request code
@end deffn

@geindex EBADSLT() (在 errno 模块中)
@anchor{library/errno errno EBADSLT}@anchor{2207}
@deffn {数据} errno.EBADSLT

Invalid slot
@end deffn

@geindex EDEADLOCK() (在 errno 模块中)
@anchor{library/errno errno EDEADLOCK}@anchor{2208}
@deffn {数据} errno.EDEADLOCK

File locking deadlock error
@end deffn

@geindex EBFONT() (在 errno 模块中)
@anchor{library/errno errno EBFONT}@anchor{2209}
@deffn {数据} errno.EBFONT

Bad font file format
@end deffn

@geindex ENOSTR() (在 errno 模块中)
@anchor{library/errno errno ENOSTR}@anchor{220a}
@deffn {数据} errno.ENOSTR

Device not a stream
@end deffn

@geindex ENODATA() (在 errno 模块中)
@anchor{library/errno errno ENODATA}@anchor{220b}
@deffn {数据} errno.ENODATA

No data available
@end deffn

@geindex ETIME() (在 errno 模块中)
@anchor{library/errno errno ETIME}@anchor{220c}
@deffn {数据} errno.ETIME

Timer expired
@end deffn

@geindex ENOSR() (在 errno 模块中)
@anchor{library/errno errno ENOSR}@anchor{220d}
@deffn {数据} errno.ENOSR

Out of streams resources
@end deffn

@geindex ENONET() (在 errno 模块中)
@anchor{library/errno errno ENONET}@anchor{220e}
@deffn {数据} errno.ENONET

Machine is not on the network
@end deffn

@geindex ENOPKG() (在 errno 模块中)
@anchor{library/errno errno ENOPKG}@anchor{220f}
@deffn {数据} errno.ENOPKG

Package not installed
@end deffn

@geindex EREMOTE() (在 errno 模块中)
@anchor{library/errno errno EREMOTE}@anchor{2210}
@deffn {数据} errno.EREMOTE

Object is remote
@end deffn

@geindex ENOLINK() (在 errno 模块中)
@anchor{library/errno errno ENOLINK}@anchor{2211}
@deffn {数据} errno.ENOLINK

Link has been severed
@end deffn

@geindex EADV() (在 errno 模块中)
@anchor{library/errno errno EADV}@anchor{2212}
@deffn {数据} errno.EADV

Advertise error
@end deffn

@geindex ESRMNT() (在 errno 模块中)
@anchor{library/errno errno ESRMNT}@anchor{2213}
@deffn {数据} errno.ESRMNT

Srmount error
@end deffn

@geindex ECOMM() (在 errno 模块中)
@anchor{library/errno errno ECOMM}@anchor{2214}
@deffn {数据} errno.ECOMM

Communication error on send
@end deffn

@geindex EPROTO() (在 errno 模块中)
@anchor{library/errno errno EPROTO}@anchor{2215}
@deffn {数据} errno.EPROTO

Protocol error
@end deffn

@geindex EMULTIHOP() (在 errno 模块中)
@anchor{library/errno errno EMULTIHOP}@anchor{2216}
@deffn {数据} errno.EMULTIHOP

Multihop attempted
@end deffn

@geindex EDOTDOT() (在 errno 模块中)
@anchor{library/errno errno EDOTDOT}@anchor{2217}
@deffn {数据} errno.EDOTDOT

RFS specific error
@end deffn

@geindex EBADMSG() (在 errno 模块中)
@anchor{library/errno errno EBADMSG}@anchor{2218}
@deffn {数据} errno.EBADMSG

Not a data message
@end deffn

@geindex EOVERFLOW() (在 errno 模块中)
@anchor{library/errno errno EOVERFLOW}@anchor{2219}
@deffn {数据} errno.EOVERFLOW

Value too large for defined data type
@end deffn

@geindex ENOTUNIQ() (在 errno 模块中)
@anchor{library/errno errno ENOTUNIQ}@anchor{221a}
@deffn {数据} errno.ENOTUNIQ

Name not unique on network
@end deffn

@geindex EBADFD() (在 errno 模块中)
@anchor{library/errno errno EBADFD}@anchor{221b}
@deffn {数据} errno.EBADFD

File descriptor in bad state
@end deffn

@geindex EREMCHG() (在 errno 模块中)
@anchor{library/errno errno EREMCHG}@anchor{221c}
@deffn {数据} errno.EREMCHG

Remote address changed
@end deffn

@geindex ELIBACC() (在 errno 模块中)
@anchor{library/errno errno ELIBACC}@anchor{221d}
@deffn {数据} errno.ELIBACC

Can not access a needed shared library
@end deffn

@geindex ELIBBAD() (在 errno 模块中)
@anchor{library/errno errno ELIBBAD}@anchor{221e}
@deffn {数据} errno.ELIBBAD

Accessing a corrupted shared library
@end deffn

@geindex ELIBSCN() (在 errno 模块中)
@anchor{library/errno errno ELIBSCN}@anchor{221f}
@deffn {数据} errno.ELIBSCN

.lib section in a.out corrupted
@end deffn

@geindex ELIBMAX() (在 errno 模块中)
@anchor{library/errno errno ELIBMAX}@anchor{2220}
@deffn {数据} errno.ELIBMAX

Attempting to link in too many shared libraries
@end deffn

@geindex ELIBEXEC() (在 errno 模块中)
@anchor{library/errno errno ELIBEXEC}@anchor{2221}
@deffn {数据} errno.ELIBEXEC

Cannot exec a shared library directly
@end deffn

@geindex EILSEQ() (在 errno 模块中)
@anchor{library/errno errno EILSEQ}@anchor{2222}
@deffn {数据} errno.EILSEQ

Illegal byte sequence
@end deffn

@geindex ERESTART() (在 errno 模块中)
@anchor{library/errno errno ERESTART}@anchor{2223}
@deffn {数据} errno.ERESTART

Interrupted system call should be restarted
@end deffn

@geindex ESTRPIPE() (在 errno 模块中)
@anchor{library/errno errno ESTRPIPE}@anchor{2224}
@deffn {数据} errno.ESTRPIPE

Streams pipe error
@end deffn

@geindex EUSERS() (在 errno 模块中)
@anchor{library/errno errno EUSERS}@anchor{2225}
@deffn {数据} errno.EUSERS

Too many users
@end deffn

@geindex ENOTSOCK() (在 errno 模块中)
@anchor{library/errno errno ENOTSOCK}@anchor{2226}
@deffn {数据} errno.ENOTSOCK

Socket operation on non-socket
@end deffn

@geindex EDESTADDRREQ() (在 errno 模块中)
@anchor{library/errno errno EDESTADDRREQ}@anchor{2227}
@deffn {数据} errno.EDESTADDRREQ

Destination address required
@end deffn

@geindex EMSGSIZE() (在 errno 模块中)
@anchor{library/errno errno EMSGSIZE}@anchor{2228}
@deffn {数据} errno.EMSGSIZE

Message too long
@end deffn

@geindex EPROTOTYPE() (在 errno 模块中)
@anchor{library/errno errno EPROTOTYPE}@anchor{2229}
@deffn {数据} errno.EPROTOTYPE

Protocol wrong type for socket
@end deffn

@geindex ENOPROTOOPT() (在 errno 模块中)
@anchor{library/errno errno ENOPROTOOPT}@anchor{222a}
@deffn {数据} errno.ENOPROTOOPT

Protocol not available
@end deffn

@geindex EPROTONOSUPPORT() (在 errno 模块中)
@anchor{library/errno errno EPROTONOSUPPORT}@anchor{222b}
@deffn {数据} errno.EPROTONOSUPPORT

Protocol not supported
@end deffn

@geindex ESOCKTNOSUPPORT() (在 errno 模块中)
@anchor{library/errno errno ESOCKTNOSUPPORT}@anchor{222c}
@deffn {数据} errno.ESOCKTNOSUPPORT

Socket type not supported
@end deffn

@geindex EOPNOTSUPP() (在 errno 模块中)
@anchor{library/errno errno EOPNOTSUPP}@anchor{222d}
@deffn {数据} errno.EOPNOTSUPP

Operation not supported on transport endpoint
@end deffn

@geindex EPFNOSUPPORT() (在 errno 模块中)
@anchor{library/errno errno EPFNOSUPPORT}@anchor{222e}
@deffn {数据} errno.EPFNOSUPPORT

Protocol family not supported
@end deffn

@geindex EAFNOSUPPORT() (在 errno 模块中)
@anchor{library/errno errno EAFNOSUPPORT}@anchor{222f}
@deffn {数据} errno.EAFNOSUPPORT

Address family not supported by protocol
@end deffn

@geindex EADDRINUSE() (在 errno 模块中)
@anchor{library/errno errno EADDRINUSE}@anchor{2230}
@deffn {数据} errno.EADDRINUSE

Address already in use
@end deffn

@geindex EADDRNOTAVAIL() (在 errno 模块中)
@anchor{library/errno errno EADDRNOTAVAIL}@anchor{2231}
@deffn {数据} errno.EADDRNOTAVAIL

Cannot assign requested address
@end deffn

@geindex ENETDOWN() (在 errno 模块中)
@anchor{library/errno errno ENETDOWN}@anchor{2232}
@deffn {数据} errno.ENETDOWN

Network is down
@end deffn

@geindex ENETUNREACH() (在 errno 模块中)
@anchor{library/errno errno ENETUNREACH}@anchor{f75}
@deffn {数据} errno.ENETUNREACH

Network is unreachable
@end deffn

@geindex ENETRESET() (在 errno 模块中)
@anchor{library/errno errno ENETRESET}@anchor{2233}
@deffn {数据} errno.ENETRESET

Network dropped connection because of reset
@end deffn

@geindex ECONNABORTED() (在 errno 模块中)
@anchor{library/errno errno ECONNABORTED}@anchor{2234}
@deffn {数据} errno.ECONNABORTED

Software caused connection abort
@end deffn

@geindex ECONNRESET() (在 errno 模块中)
@anchor{library/errno errno ECONNRESET}@anchor{2235}
@deffn {数据} errno.ECONNRESET

Connection reset by peer
@end deffn

@geindex ENOBUFS() (在 errno 模块中)
@anchor{library/errno errno ENOBUFS}@anchor{2236}
@deffn {数据} errno.ENOBUFS

No buffer space available
@end deffn

@geindex EISCONN() (在 errno 模块中)
@anchor{library/errno errno EISCONN}@anchor{2237}
@deffn {数据} errno.EISCONN

Transport endpoint is already connected
@end deffn

@geindex ENOTCONN() (在 errno 模块中)
@anchor{library/errno errno ENOTCONN}@anchor{2238}
@deffn {数据} errno.ENOTCONN

Transport endpoint is not connected
@end deffn

@geindex ESHUTDOWN() (在 errno 模块中)
@anchor{library/errno errno ESHUTDOWN}@anchor{2239}
@deffn {数据} errno.ESHUTDOWN

Cannot send after transport endpoint shutdown
@end deffn

@geindex ETOOMANYREFS() (在 errno 模块中)
@anchor{library/errno errno ETOOMANYREFS}@anchor{223a}
@deffn {数据} errno.ETOOMANYREFS

Too many references: cannot splice
@end deffn

@geindex ETIMEDOUT() (在 errno 模块中)
@anchor{library/errno errno ETIMEDOUT}@anchor{223b}
@deffn {数据} errno.ETIMEDOUT

Connection timed out
@end deffn

@geindex ECONNREFUSED() (在 errno 模块中)
@anchor{library/errno errno ECONNREFUSED}@anchor{223c}
@deffn {数据} errno.ECONNREFUSED

Connection refused
@end deffn

@geindex EHOSTDOWN() (在 errno 模块中)
@anchor{library/errno errno EHOSTDOWN}@anchor{223d}
@deffn {数据} errno.EHOSTDOWN

Host is down
@end deffn

@geindex EHOSTUNREACH() (在 errno 模块中)
@anchor{library/errno errno EHOSTUNREACH}@anchor{223e}
@deffn {数据} errno.EHOSTUNREACH

No route to host
@end deffn

@geindex EALREADY() (在 errno 模块中)
@anchor{library/errno errno EALREADY}@anchor{223f}
@deffn {数据} errno.EALREADY

Operation already in progress
@end deffn

@geindex EINPROGRESS() (在 errno 模块中)
@anchor{library/errno errno EINPROGRESS}@anchor{2240}
@deffn {数据} errno.EINPROGRESS

Operation now in progress
@end deffn

@geindex ESTALE() (在 errno 模块中)
@anchor{library/errno errno ESTALE}@anchor{2241}
@deffn {数据} errno.ESTALE

Stale NFS file handle
@end deffn

@geindex EUCLEAN() (在 errno 模块中)
@anchor{library/errno errno EUCLEAN}@anchor{2242}
@deffn {数据} errno.EUCLEAN

Structure needs cleaning
@end deffn

@geindex ENOTNAM() (在 errno 模块中)
@anchor{library/errno errno ENOTNAM}@anchor{2243}
@deffn {数据} errno.ENOTNAM

Not a XENIX named type file
@end deffn

@geindex ENAVAIL() (在 errno 模块中)
@anchor{library/errno errno ENAVAIL}@anchor{2244}
@deffn {数据} errno.ENAVAIL

No XENIX semaphores available
@end deffn

@geindex EISNAM() (在 errno 模块中)
@anchor{library/errno errno EISNAM}@anchor{2245}
@deffn {数据} errno.EISNAM

Is a named type file
@end deffn

@geindex EREMOTEIO() (在 errno 模块中)
@anchor{library/errno errno EREMOTEIO}@anchor{2246}
@deffn {数据} errno.EREMOTEIO

Remote I/O error
@end deffn

@geindex EDQUOT() (在 errno 模块中)
@anchor{library/errno errno EDQUOT}@anchor{2247}
@deffn {数据} errno.EDQUOT

Quota exceeded
@end deffn

@node ctypes --- Python 的外部函数库,,errno --- 标准 errno 系统符号,通用操作系统服务
@anchor{library/ctypes doc}@anchor{2248}@anchor{library/ctypes ctypes-a-foreign-function-library-for-python}@anchor{2249}@anchor{library/ctypes module-ctypes}@anchor{2b}
@subsection @code{ctypes} --- Python 的外部函数库


@geindex ctypes (模块)


__________________________________________________________________


@ref{2b,,ctypes} 是 Python 的外部函数库。它提供了与 C 兼容的数据类型，并允许调用 DLL 或共享库中的函数。可使用该模块以纯 Python 形式对这些库进行封装。

@menu
* ctypes 教程:: 
* ctypes reference:: 

@end menu

@node ctypes 教程,ctypes reference,,ctypes --- Python 的外部函数库
@anchor{library/ctypes ctypes-ctypes-tutorial}@anchor{224a}@anchor{library/ctypes ctypes-tutorial}@anchor{224b}
@subsubsection ctypes 教程


注意：在本教程中的示例代码使用 @ref{67,,doctest} 进行过测试，保证其正确运行。由于有些代码在Linux，Windows或Mac OS X下的表现不同，这些代码会在 doctest 中包含相关的指令注解。

注意：部分示例代码引用了 ctypes @ref{224c,,c_int} 类型。在 @code{sizeof(long) == sizeof(int)} 的平台上此类型是 @ref{224d,,c_long} 的一个别名。所以，在程序输出 @ref{224d,,c_long} 而不是你期望的 @ref{224c,,c_int} 时不必感到迷惑 --- 它们实际上是同一种类型。

@menu
* 载入动态连接库:: 
* 操作导入的动态链接库中的函数:: 
* 调用函数:: 
* 基础数据类型:: 
* 调用函数，继续:: 
* 使用自定义的数据类型调用函数:: 
* Specifying the required argument types (function prototypes): Specifying the required argument types function prototypes. 
* Return types:: 
* Passing pointers (or; passing parameters by reference): Passing pointers or passing parameters by reference. 
* Structures and unions:: 
* Structure/union alignment and byte order:: 
* Bit fields in structures and unions:: 
* Arrays:: 
* Pointers:: 
* Type conversions:: 
* Incomplete Types:: 
* Callback functions:: 
* Accessing values exported from dlls:: 
* Surprises:: 
* Variable-sized data types:: 

@end menu

@node 载入动态连接库,操作导入的动态链接库中的函数,,ctypes 教程
@anchor{library/ctypes ctypes-loading-dynamic-link-libraries}@anchor{224e}@anchor{library/ctypes loading-dynamic-link-libraries}@anchor{224f}
@subsubsection 载入动态连接库


@ref{2b,,ctypes} 导出了 @emph{cdll} 对象，在 Windows 系统中还导出了 @emph{windll} 和 @emph{oledll} 对象用于载入动态连接库。

通过操作这些对象的属性，你可以载入外部的动态链接库。@emph{cdll} 载入按标准的 @code{cdecl} 调用协议导出的函数，而 @emph{windll} 导入的库按 @code{stdcall} 调用协议调用其中的函数。 @emph{oledll} 也按 @code{stdcall} 调用协议调用其中的函数，并假定该函数返回的是 Windows @code{HRESULT} 错误代码，并当函数调用失败时，自动根据该代码甩出一个 @ref{1d3,,OSError} 异常。


在 3.3 版更改: 原来在 Windows 下甩出的异常类型 @ref{98e,,WindowsError} 现在是 @ref{1d3,,OSError} 的一个别名。


这是一些 Windows 下的例子。注意：@code{msvcrt} 是微软 C 标准库，包含了大部分 C 标准函数，这些函数都是以 cdecl 调用协议进行调用的。

@example
>>> from ctypes import *
>>> print(windll.kernel32)  
<WinDLL 'kernel32', handle ... at ...>
>>> print(cdll.msvcrt)      
<CDLL 'msvcrt', handle ... at ...>
>>> libc = cdll.msvcrt      
>>>
@end example

Windows会自动添加通常的 @code{.dll} 文件扩展名。

@cartouche
@quotation 注解 
通过 @code{cdll.msvcrt} 调用的标准 C 函数，可能会导致调用一个过时的，与当前 Python 所不兼容的函数。因此，请尽量使用标准的 Python 函数，而不要使用 @code{msvcrt} 模块。
@end quotation
@end cartouche

在 Linux 下，必须使用 @emph{包含} 文件扩展名的文件名来导入共享库。因此不能简单使用对象属性的方式来导入库。因此，你可以使用方法 @code{LoadLibrary()}，或构造 CDLL 对象来导入库。

@example
>>> cdll.LoadLibrary("libc.so.6")  
<CDLL 'libc.so.6', handle ... at ...>
>>> libc = CDLL("libc.so.6")       
>>> libc                           
<CDLL 'libc.so.6', handle ... at ...>
>>>
@end example

@c XXX Add section for Mac OS X.

@node 操作导入的动态链接库中的函数,调用函数,载入动态连接库,ctypes 教程
@anchor{library/ctypes accessing-functions-from-loaded-dlls}@anchor{2250}@anchor{library/ctypes ctypes-accessing-functions-from-loaded-dlls}@anchor{2251}
@subsubsection 操作导入的动态链接库中的函数


通过操作dll对象的属性来操作这些函数。

@example
>>> from ctypes import *
>>> libc.printf
<_FuncPtr object at 0x...>
>>> print(windll.kernel32.GetModuleHandleA)  
<_FuncPtr object at 0x...>
>>> print(windll.kernel32.MyOwnFunction)     
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "ctypes.py", line 239, in __getattr__
    func = _StdcallFuncPtr(name, self)
AttributeError: function 'MyOwnFunction' not found
>>>
@end example

注意：Win32系统的动态库，比如 @code{kernel32} 和 @code{user32}，通常会同时导出同一个函数的 ANSI 版本和 UNICODE 版本。UNICODE 版本通常会在名字最后以 @code{W} 结尾，而 ANSI 版本的则以 @code{A} 结尾。 win32的 @code{GetModuleHandle} 函数会根据一个模块名返回一个 @emph{模块句柄}，该函数暨同时包含这样的两个版本的原型函数，并通过宏 UNICODE 是否定义，来决定宏 @code{GetModuleHandle} 导出的是哪个具体函数。

@example
/* ANSI version */
HMODULE GetModuleHandleA(LPCSTR lpModuleName);
/* UNICODE version */
HMODULE GetModuleHandleW(LPCWSTR lpModuleName);
@end example

@emph{windll} 不会通过这样的魔法手段来帮你决定选择哪一种函数，你必须显式的调用 @code{GetModuleHandleA} 或 @code{GetModuleHandleW}，并分别使用字节对象或字符串对象作参数。

有时候，dlls的导出的函数名不符合 Python 的标识符规范，比如 @code{"??2@@YAPAXI@@Z"}。此时，你必须使用 @ref{443,,getattr()} 方法来获得该函数。

@example
>>> getattr(cdll.msvcrt, "??2@@YAPAXI@@Z")  
<_FuncPtr object at 0x...>
>>>
@end example

Windows 下，有些 dll 导出的函数没有函数名，而是通过其顺序号调用。对此类函数，你也可以通过 dll 对象的数值索引来操作这些函数。

@example
>>> cdll.kernel32[1]  
<_FuncPtr object at 0x...>
>>> cdll.kernel32[0]  
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "ctypes.py", line 310, in __getitem__
    func = _StdcallFuncPtr(name, self)
AttributeError: function ordinal 0 not found
>>>
@end example

@node 调用函数,基础数据类型,操作导入的动态链接库中的函数,ctypes 教程
@anchor{library/ctypes calling-functions}@anchor{2252}@anchor{library/ctypes ctypes-calling-functions}@anchor{2253}
@subsubsection 调用函数


你可以貌似是调用其它 Python 函数那样直接调用这些函数。在这个例子中，我们调用了 @code{time()} 函数，该函数返回一个系统时间戳（从 Unix 时间起点到现在的秒数），而`@w{`}GetModuleHandleA()`@w{`} 函数返回一个 win32 模块句柄。

此函数中调用的两个函数都使用了空指针（用 @code{None} 作为空指针）:

@example
>>> print(libc.time(None))  
1150640792
>>> print(hex(windll.kernel32.GetModuleHandleA(None)))  
0x1d000000
>>>
@end example

如果你用 @code{cdecl} 调用方式调用 @code{stdcall} 约定的函数，则会甩出一个异常 @ref{1fb,,ValueError}。反之亦然。

@example
>>> cdll.kernel32.GetModuleHandleA(None)  
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Procedure probably called with not enough arguments (4 bytes missing)
>>>

>>> windll.msvcrt.printf(b"spam")  
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Procedure probably called with too many arguments (4 bytes in excess)
>>>
@end example

你必须阅读这些库的头文件或说明文档来确定它们的正确的调用协议。

在Windows中，@ref{2b,,ctypes} 使用 win32 结构化异常处理来防止由于在调用函数时使用非法参数导致的程序崩溃。

@example
>>> windll.kernel32.GetModuleHandleA(32)  
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: exception: access violation reading 0x00000020
>>>
@end example

然而，总有许多办法，通过调用 @ref{2b,,ctypes} 使得 Python 程序崩溃。因此，你必须小心使用。 @ref{7d,,faulthandler} 模块可以用于帮助诊断程序崩溃的原因。（比如由于错误的C库函数调用导致的段错误）。

@code{None}，整型，字节对象和（UNICODE）字符串是仅有的可以直接作为函数参数使用的四种Python本地数据类型。@cite{None`} 作为C的空指针 (@code{NULL})，字节和字符串类型作为一个指向其保存数据的内存块指针 （@code{char *} 或 @code{wchar_t *})。Python 的整型则作为平台默认的C的 @code{int} 类型，他们的数值被截断以适应C类型的整型长度。

在我们开始调用函数前，我们必须先了解作为函数参数的 @ref{2b,,ctypes} 数据类型。

@node 基础数据类型,调用函数，继续,调用函数,ctypes 教程
@anchor{library/ctypes ctypes-fundamental-data-types}@anchor{2254}@anchor{library/ctypes fundamental-data-types}@anchor{2255}
@subsubsection 基础数据类型


@ref{2b,,ctypes} 定义了一些和C兼容的基本数据类型：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

ctypes 类型

@tab

C 类型

@tab

Python 类型

@item

@ref{2256,,c_bool}

@tab

@code{_Bool}

@tab

bool (1)

@item

@ref{2257,,c_char}

@tab

@code{char}

@tab

单字符字节对象

@item

@ref{2258,,c_wchar}

@tab

@code{wchar_t}

@tab

单字符字符串

@item

@ref{2259,,c_byte}

@tab

@code{char}

@tab

int

@item

@ref{225a,,c_ubyte}

@tab

@code{unsigned char}

@tab

int

@item

@ref{225b,,c_short}

@tab

@code{short}

@tab

int

@item

@ref{225c,,c_ushort}

@tab

@code{unsigned short}

@tab

int

@item

@ref{224c,,c_int}

@tab

@code{int}

@tab

int

@item

@ref{225d,,c_uint}

@tab

@code{unsigned int}

@tab

int

@item

@ref{224d,,c_long}

@tab

@code{long}

@tab

int

@item

@ref{225e,,c_ulong}

@tab

@code{unsigned long}

@tab

int

@item

@ref{225f,,c_longlong}

@tab

@code{__int64} 或 @code{long long}

@tab

int

@item

@ref{2260,,c_ulonglong}

@tab

@code{unsigned __int64} 或 @code{unsigned long long}

@tab

int

@item

@ref{2261,,c_size_t}

@tab

@code{size_t}

@tab

int

@item

@ref{bca,,c_ssize_t}

@tab

@code{ssize_t} 或 @code{Py_ssize_t}

@tab

int

@item

@ref{2262,,c_float}

@tab

@code{float}

@tab

float

@item

@ref{2263,,c_double}

@tab

@code{double}

@tab

float

@item

@ref{2264,,c_longdouble}

@tab

@code{long double}

@tab

float

@item

@ref{2265,,c_char_p}

@tab

@code{char *} (以 NUL 结尾)

@tab

字节串对象或 @code{None}

@item

@ref{2266,,c_wchar_p}

@tab

@code{wchar_t *} (以 NUL 结尾)

@tab

字符串或 @code{None}

@item

@ref{2267,,c_void_p}

@tab

@code{void *}

@tab

int 或 @code{None}

@end multitable



@enumerate 

@item 
构造函数接受任何具有真值的对象。
@end enumerate

所有这些类型都可以通过使用正确类型和值的可选初始值调用它们来创建:

@example
>>> c_int()
c_long(0)
>>> c_wchar_p("Hello, World")
c_wchar_p(140018365411392)
>>> c_ushort(-3)
c_ushort(65533)
>>>
@end example

由于这些类型是可变的，它们的值也可以在以后更改:

@example
>>> i = c_int(42)
>>> print(i)
c_long(42)
>>> print(i.value)
42
>>> i.value = -99
>>> print(i.value)
-99
>>>
@end example

当给指针类型的对象 @ref{2265,,c_char_p}, @ref{2266,,c_wchar_p} 和 @ref{2267,,c_void_p} 等赋值时，将改变它们所指向的 @emph{内存地址}，而 @emph{不是} 它们所指向的内存区域的 @emph{内容} (这是理所当然的，因为 Python 的 bytes 对象是不可变的):

@example
>>> s = "Hello, World"
>>> c_s = c_wchar_p(s)
>>> print(c_s)
c_wchar_p(139966785747344)
>>> print(c_s.value)
Hello World
>>> c_s.value = "Hi, there"
>>> print(c_s)              # the memory location has changed
c_wchar_p(139966783348904)
>>> print(c_s.value)
Hi, there
>>> print(s)                # first object is unchanged
Hello, World
>>>
@end example

但你要注意不能将它们传递给会改变指针所指内存的函数。如果你需要可改变的内存块，ctypes 提供了 @ref{2268,,create_string_buffer()} 函数，它提供多种方式创建这种内存块。当前的内存块内容可以通过 @code{raw} 属性存取，如果你希望将它作为NUL结束的字符串，请使用 @code{value} 属性:

@example
>>> from ctypes import *
>>> p = create_string_buffer(3)            # create a 3 byte buffer, initialized to NUL bytes
>>> print(sizeof(p), repr(p.raw))
3 b'\x00\x00\x00'
>>> p = create_string_buffer(b"Hello")     # create a buffer containing a NUL terminated string
>>> print(sizeof(p), repr(p.raw))
6 b'Hello\x00'
>>> print(repr(p.value))
b'Hello'
>>> p = create_string_buffer(b"Hello", 10) # create a 10 byte buffer
>>> print(sizeof(p), repr(p.raw))
10 b'Hello\x00\x00\x00\x00\x00'
>>> p.value = b"Hi"
>>> print(sizeof(p), repr(p.raw))
10 b'Hi\x00lo\x00\x00\x00\x00\x00'
>>>
@end example

@ref{2268,,create_string_buffer()} 函数替代以前的ctypes版本中的 @code{c_buffer()} 函数 (仍然可当作别名使用)和 @code{c_string()} 函数。@ref{f3c,,create_unicode_buffer()} 函数创建包含 unicode 字符的可变内存块，与之对应的C语言类型是 @code{wchar_t}。

@node 调用函数，继续,使用自定义的数据类型调用函数,基础数据类型,ctypes 教程
@anchor{library/ctypes calling-functions-continued}@anchor{2269}@anchor{library/ctypes ctypes-calling-functions-continued}@anchor{226a}
@subsubsection 调用函数，继续


注意 printf 将打印到真正标准输出设备，而*不是* @ref{307,,sys.stdout}，因此这些实例只能在控制台提示符下工作，而不能在 @emph{IDLE} 或 @emph{PythonWin} 中运行。

@example
>>> printf = libc.printf
>>> printf(b"Hello, %s\n", b"World!")
Hello, World!
14
>>> printf(b"Hello, %S\n", "World!")
Hello, World!
14
>>> printf(b"%d bottles of beer\n", 42)
42 bottles of beer
19
>>> printf(b"%f bottles of beer\n", 42.5)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ArgumentError: argument 2: exceptions.TypeError: Don't know how to convert parameter 2
>>>
@end example

正如前面所提到过的，除了整数、字符串以及字节串之外，所有的 Python 类型都必须使用它们对应的 @ref{2b,,ctypes} 类型包装，才能够被正确地转换为所需的C语言类型。

@example
>>> printf(b"An int %d, a double %f\n", 1234, c_double(3.14))
An int 1234, a double 3.140000
31
>>>
@end example

@node 使用自定义的数据类型调用函数,Specifying the required argument types function prototypes,调用函数，继续,ctypes 教程
@anchor{library/ctypes calling-functions-with-your-own-custom-data-types}@anchor{226b}@anchor{library/ctypes ctypes-calling-functions-with-own-custom-data-types}@anchor{226c}
@subsubsection 使用自定义的数据类型调用函数


You can also customize @ref{2b,,ctypes} argument conversion to allow instances of
your own classes be used as function arguments.  @ref{2b,,ctypes} looks for an
@code{_as_parameter_} attribute and uses this as the function argument.  Of
course, it must be one of integer, string, or bytes:

@example
>>> class Bottles:
...     def __init__(self, number):
...         self._as_parameter_ = number
...
>>> bottles = Bottles(42)
>>> printf(b"%d bottles of beer\n", bottles)
42 bottles of beer
19
>>>
@end example

If you don't want to store the instance's data in the @code{_as_parameter_}
instance variable, you could define a @ref{1d7,,property} which makes the
attribute available on request.

@node Specifying the required argument types function prototypes,Return types,使用自定义的数据类型调用函数,ctypes 教程
@anchor{library/ctypes ctypes-specifying-required-argument-types}@anchor{226d}@anchor{library/ctypes specifying-the-required-argument-types-function-prototypes}@anchor{226e}
@subsubsection Specifying the required argument types (function prototypes)


It is possible to specify the required argument types of functions exported from
DLLs by setting the @code{argtypes} attribute.

@code{argtypes} must be a sequence of C data types (the @code{printf} function is
probably not a good example here, because it takes a variable number and
different types of parameters depending on the format string, on the other hand
this is quite handy to experiment with this feature):

@example
>>> printf.argtypes = [c_char_p, c_char_p, c_int, c_double]
>>> printf(b"String '%s', Int %d, Double %f\n", b"Hi", 10, 2.2)
String 'Hi', Int 10, Double 2.200000
37
>>>
@end example

Specifying a format protects against incompatible argument types (just as a
prototype for a C function), and tries to convert the arguments to valid types:

@example
>>> printf(b"%d %d %d", 1, 2, 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ArgumentError: argument 2: exceptions.TypeError: wrong type
>>> printf(b"%s %d %f\n", b"X", 2, 3)
X 2 3.000000
13
>>>
@end example

If you have defined your own classes which you pass to function calls, you have
to implement a @code{from_param()} class method for them to be able to use them
in the @code{argtypes} sequence. The @code{from_param()} class method receives
the Python object passed to the function call, it should do a typecheck or
whatever is needed to make sure this object is acceptable, and then return the
object itself, its @code{_as_parameter_} attribute, or whatever you want to
pass as the C function argument in this case. Again, the result should be an
integer, string, bytes, a @ref{2b,,ctypes} instance, or an object with an
@code{_as_parameter_} attribute.

@node Return types,Passing pointers or passing parameters by reference,Specifying the required argument types function prototypes,ctypes 教程
@anchor{library/ctypes ctypes-return-types}@anchor{226f}@anchor{library/ctypes return-types}@anchor{2270}
@subsubsection Return types


By default functions are assumed to return the C @code{int} type.  Other
return types can be specified by setting the @code{restype} attribute of the
function object.

Here is a more advanced example, it uses the @code{strchr} function, which expects
a string pointer and a char, and returns a pointer to a string:

@example
>>> strchr = libc.strchr
>>> strchr(b"abcdef", ord("d"))  
8059983
>>> strchr.restype = c_char_p    # c_char_p is a pointer to a string
>>> strchr(b"abcdef", ord("d"))
b'def'
>>> print(strchr(b"abcdef", ord("x")))
None
>>>
@end example

If you want to avoid the @code{ord("x")} calls above, you can set the
@code{argtypes} attribute, and the second argument will be converted from a
single character Python bytes object into a C char:

@example
>>> strchr.restype = c_char_p
>>> strchr.argtypes = [c_char_p, c_char]
>>> strchr(b"abcdef", b"d")
'def'
>>> strchr(b"abcdef", b"def")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ArgumentError: argument 2: exceptions.TypeError: one character string expected
>>> print(strchr(b"abcdef", b"x"))
None
>>> strchr(b"abcdef", b"d")
'def'
>>>
@end example

You can also use a callable Python object (a function or a class for example) as
the @code{restype} attribute, if the foreign function returns an integer.  The
callable will be called with the @emph{integer} the C function returns, and the
result of this call will be used as the result of your function call. This is
useful to check for error return values and automatically raise an exception:

@example
>>> GetModuleHandle = windll.kernel32.GetModuleHandleA  
>>> def ValidHandle(value):
...     if value == 0:
...         raise WinError()
...     return value
...
>>>
>>> GetModuleHandle.restype = ValidHandle  
>>> GetModuleHandle(None)  
486539264
>>> GetModuleHandle("something silly")  
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in ValidHandle
OSError: [Errno 126] The specified module could not be found.
>>>
@end example

@code{WinError} is a function which will call Windows @code{FormatMessage()} api to
get the string representation of an error code, and @emph{returns} an exception.
@code{WinError} takes an optional error code parameter, if no one is used, it calls
@ref{2271,,GetLastError()} to retrieve it.

Please note that a much more powerful error checking mechanism is available
through the @code{errcheck} attribute; see the reference manual for details.

@node Passing pointers or passing parameters by reference,Structures and unions,Return types,ctypes 教程
@anchor{library/ctypes ctypes-passing-pointers}@anchor{2272}@anchor{library/ctypes passing-pointers-or-passing-parameters-by-reference}@anchor{2273}
@subsubsection Passing pointers (or: passing parameters by reference)


Sometimes a C api function expects a @emph{pointer} to a data type as parameter,
probably to write into the corresponding location, or if the data is too large
to be passed by value. This is also known as @emph{passing parameters by reference}.

@ref{2b,,ctypes} exports the @ref{2274,,byref()} function which is used to pass parameters
by reference.  The same effect can be achieved with the @ref{2275,,pointer()} function,
although @ref{2275,,pointer()} does a lot more work since it constructs a real pointer
object, so it is faster to use @ref{2274,,byref()} if you don't need the pointer
object in Python itself:

@example
>>> i = c_int()
>>> f = c_float()
>>> s = create_string_buffer(b'\000' * 32)
>>> print(i.value, f.value, repr(s.value))
0 0.0 b'@w{'}
>>> libc.sscanf(b"1 3.14 Hello", b"%d %f %s",
...             byref(i), byref(f), s)
3
>>> print(i.value, f.value, repr(s.value))
1 3.1400001049 b'Hello'
>>>
@end example

@node Structures and unions,Structure/union alignment and byte order,Passing pointers or passing parameters by reference,ctypes 教程
@anchor{library/ctypes ctypes-structures-unions}@anchor{2276}@anchor{library/ctypes structures-and-unions}@anchor{2277}
@subsubsection Structures and unions


Structures and unions must derive from the @ref{2278,,Structure} and @ref{2279,,Union}
base classes which are defined in the @ref{2b,,ctypes} module. Each subclass must
define a @code{_fields_} attribute.  @code{_fields_} must be a list of
@emph{2-tuples}, containing a @emph{field name} and a @emph{field type}.

The field type must be a @ref{2b,,ctypes} type like @ref{224c,,c_int}, or any other
derived @ref{2b,,ctypes} type: structure, union, array, pointer.

Here is a simple example of a POINT structure, which contains two integers named
@emph{x} and @emph{y}, and also shows how to initialize a structure in the constructor:

@example
>>> from ctypes import *
>>> class POINT(Structure):
...     _fields_ = [("x", c_int),
...                 ("y", c_int)]
...
>>> point = POINT(10, 20)
>>> print(point.x, point.y)
10 20
>>> point = POINT(y=5)
>>> print(point.x, point.y)
0 5
>>> POINT(1, 2, 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: too many initializers
>>>
@end example

You can, however, build much more complicated structures.  A structure can
itself contain other structures by using a structure as a field type.

Here is a RECT structure which contains two POINTs named @emph{upperleft} and
@emph{lowerright}:

@example
>>> class RECT(Structure):
...     _fields_ = [("upperleft", POINT),
...                 ("lowerright", POINT)]
...
>>> rc = RECT(point)
>>> print(rc.upperleft.x, rc.upperleft.y)
0 5
>>> print(rc.lowerright.x, rc.lowerright.y)
0 0
>>>
@end example

Nested structures can also be initialized in the constructor in several ways:

@example
>>> r = RECT(POINT(1, 2), POINT(3, 4))
>>> r = RECT((1, 2), (3, 4))
@end example

Field @ref{159e,,descriptor}s can be retrieved from the @emph{class}, they are useful
for debugging because they can provide useful information:

@example
>>> print(POINT.x)
<Field type=c_long, ofs=0, size=4>
>>> print(POINT.y)
<Field type=c_long, ofs=4, size=4>
>>>
@end example
@anchor{library/ctypes ctypes-structureunion-alignment-byte-order}@anchor{227a}
@cartouche
@quotation 警告 
@ref{2b,,ctypes} does not support passing unions or structures with bit-fields
to functions by value.  While this may work on 32-bit x86, it's not
guaranteed by the library to work in the general case.  Unions and
structures with bit-fields should always be passed to functions by pointer.
@end quotation
@end cartouche

@node Structure/union alignment and byte order,Bit fields in structures and unions,Structures and unions,ctypes 教程
@anchor{library/ctypes structure-union-alignment-and-byte-order}@anchor{227b}
@subsubsection Structure/union alignment and byte order


By default, Structure and Union fields are aligned in the same way the C
compiler does it. It is possible to override this behavior by specifying a
@code{_pack_} class attribute in the subclass definition. This must be set to a
positive integer and specifies the maximum alignment for the fields. This is
what @code{#pragma pack(n)} also does in MSVC.

@ref{2b,,ctypes} uses the native byte order for Structures and Unions.  To build
structures with non-native byte order, you can use one of the
@ref{227c,,BigEndianStructure}, @ref{227d,,LittleEndianStructure},
@code{BigEndianUnion}, and @code{LittleEndianUnion} base classes.  These
classes cannot contain pointer fields.

@node Bit fields in structures and unions,Arrays,Structure/union alignment and byte order,ctypes 教程
@anchor{library/ctypes bit-fields-in-structures-and-unions}@anchor{227e}@anchor{library/ctypes ctypes-bit-fields-in-structures-unions}@anchor{227f}
@subsubsection Bit fields in structures and unions


It is possible to create structures and unions containing bit fields. Bit fields
are only possible for integer fields, the bit width is specified as the third
item in the @code{_fields_} tuples:

@example
>>> class Int(Structure):
...     _fields_ = [("first_16", c_int, 16),
...                 ("second_16", c_int, 16)]
...
>>> print(Int.first_16)
<Field type=c_long, ofs=0:0, bits=16>
>>> print(Int.second_16)
<Field type=c_long, ofs=0:16, bits=16>
>>>
@end example

@node Arrays,Pointers,Bit fields in structures and unions,ctypes 教程
@anchor{library/ctypes arrays}@anchor{2280}@anchor{library/ctypes ctypes-arrays}@anchor{2281}
@subsubsection Arrays


Arrays are sequences, containing a fixed number of instances of the same type.

The recommended way to create array types is by multiplying a data type with a
positive integer:

@example
TenPointsArrayType = POINT * 10
@end example

Here is an example of a somewhat artificial data type, a structure containing 4
POINTs among other stuff:

@example
>>> from ctypes import *
>>> class POINT(Structure):
...     _fields_ = ("x", c_int), ("y", c_int)
...
>>> class MyStruct(Structure):
...     _fields_ = [("a", c_int),
...                 ("b", c_float),
...                 ("point_array", POINT * 4)]
>>>
>>> print(len(MyStruct().point_array))
4
>>>
@end example

Instances are created in the usual way, by calling the class:

@example
arr = TenPointsArrayType()
for pt in arr:
    print(pt.x, pt.y)
@end example

The above code print a series of @code{0 0} lines, because the array contents is
initialized to zeros.

Initializers of the correct type can also be specified:

@example
>>> from ctypes import *
>>> TenIntegers = c_int * 10
>>> ii = TenIntegers(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
>>> print(ii)
<c_long_Array_10 object at 0x...>
>>> for i in ii: print(i, end=" ")
...
1 2 3 4 5 6 7 8 9 10
>>>
@end example

@node Pointers,Type conversions,Arrays,ctypes 教程
@anchor{library/ctypes ctypes-pointers}@anchor{2282}@anchor{library/ctypes pointers}@anchor{2283}
@subsubsection Pointers


Pointer instances are created by calling the @ref{2275,,pointer()} function on a
@ref{2b,,ctypes} type:

@example
>>> from ctypes import *
>>> i = c_int(42)
>>> pi = pointer(i)
>>>
@end example

Pointer instances have a @ref{2284,,contents} attribute which
returns the object to which the pointer points, the @code{i} object above:

@example
>>> pi.contents
c_long(42)
>>>
@end example

Note that @ref{2b,,ctypes} does not have OOR (original object return), it constructs a
new, equivalent object each time you retrieve an attribute:

@example
>>> pi.contents is i
False
>>> pi.contents is pi.contents
False
>>>
@end example

Assigning another @ref{224c,,c_int} instance to the pointer's contents attribute
would cause the pointer to point to the memory location where this is stored:

@example
>>> i = c_int(99)
>>> pi.contents = i
>>> pi.contents
c_long(99)
>>>
@end example

@c XXX Document dereferencing pointers, and that it is preferred over the
@c .contents attribute.

Pointer instances can also be indexed with integers:

@example
>>> pi[0]
99
>>>
@end example

Assigning to an integer index changes the pointed to value:

@example
>>> print(i)
c_long(99)
>>> pi[0] = 22
>>> print(i)
c_long(22)
>>>
@end example

It is also possible to use indexes different from 0, but you must know what
you're doing, just as in C: You can access or change arbitrary memory locations.
Generally you only use this feature if you receive a pointer from a C function,
and you @emph{know} that the pointer actually points to an array instead of a single
item.

Behind the scenes, the @ref{2275,,pointer()} function does more than simply create
pointer instances, it has to create pointer @emph{types} first. This is done with the
@ref{2285,,POINTER()} function, which accepts any @ref{2b,,ctypes} type, and returns a
new type:

@example
>>> PI = POINTER(c_int)
>>> PI
<class 'ctypes.LP_c_long'>
>>> PI(42)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: expected c_long instead of int
>>> PI(c_int(42))
<ctypes.LP_c_long object at 0x...>
>>>
@end example

Calling the pointer type without an argument creates a @code{NULL} pointer.
@code{NULL} pointers have a @code{False} boolean value:

@example
>>> null_ptr = POINTER(c_int)()
>>> print(bool(null_ptr))
False
>>>
@end example

@ref{2b,,ctypes} checks for @code{NULL} when dereferencing pointers (but dereferencing
invalid non-@code{NULL} pointers would crash Python):

@example
>>> null_ptr[0]
Traceback (most recent call last):
    ....
ValueError: NULL pointer access
>>>

>>> null_ptr[0] = 1234
Traceback (most recent call last):
    ....
ValueError: NULL pointer access
>>>
@end example

@node Type conversions,Incomplete Types,Pointers,ctypes 教程
@anchor{library/ctypes ctypes-type-conversions}@anchor{2286}@anchor{library/ctypes type-conversions}@anchor{2287}
@subsubsection Type conversions


Usually, ctypes does strict type checking.  This means, if you have
@code{POINTER(c_int)} in the @code{argtypes} list of a function or as the type of
a member field in a structure definition, only instances of exactly the same
type are accepted.  There are some exceptions to this rule, where ctypes accepts
other objects.  For example, you can pass compatible array instances instead of
pointer types.  So, for @code{POINTER(c_int)}, ctypes accepts an array of c_int:

@example
>>> class Bar(Structure):
...     _fields_ = [("count", c_int), ("values", POINTER(c_int))]
...
>>> bar = Bar()
>>> bar.values = (c_int * 3)(1, 2, 3)
>>> bar.count = 3
>>> for i in range(bar.count):
...     print(bar.values[i])
...
1
2
3
>>>
@end example

In addition, if a function argument is explicitly declared to be a pointer type
(such as @code{POINTER(c_int)}) in @code{argtypes}, an object of the pointed
type (@code{c_int} in this case) can be passed to the function.  ctypes will apply
the required @ref{2274,,byref()} conversion in this case automatically.

To set a POINTER type field to @code{NULL}, you can assign @code{None}:

@example
>>> bar.values = None
>>>
@end example

@c XXX list other conversions...

Sometimes you have instances of incompatible types.  In C, you can cast one type
into another type.  @ref{2b,,ctypes} provides a @ref{fa6,,cast()} function which can be
used in the same way.  The @code{Bar} structure defined above accepts
@code{POINTER(c_int)} pointers or @ref{224c,,c_int} arrays for its @code{values} field,
but not instances of other types:

@example
>>> bar.values = (c_byte * 4)()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: incompatible types, c_byte_Array_4 instance instead of LP_c_long instance
>>>
@end example

For these cases, the @ref{fa6,,cast()} function is handy.

The @ref{fa6,,cast()} function can be used to cast a ctypes instance into a pointer
to a different ctypes data type.  @ref{fa6,,cast()} takes two parameters, a ctypes
object that is or can be converted to a pointer of some kind, and a ctypes
pointer type.  It returns an instance of the second argument, which references
the same memory block as the first argument:

@example
>>> a = (c_byte * 4)()
>>> cast(a, POINTER(c_int))
<ctypes.LP_c_long object at ...>
>>>
@end example

So, @ref{fa6,,cast()} can be used to assign to the @code{values} field of @code{Bar} the
structure:

@example
>>> bar = Bar()
>>> bar.values = cast((c_byte * 4)(), POINTER(c_int))
>>> print(bar.values[0])
0
>>>
@end example

@node Incomplete Types,Callback functions,Type conversions,ctypes 教程
@anchor{library/ctypes ctypes-incomplete-types}@anchor{2288}@anchor{library/ctypes incomplete-types}@anchor{2289}
@subsubsection Incomplete Types


@emph{Incomplete Types} are structures, unions or arrays whose members are not yet
specified. In C, they are specified by forward declarations, which are defined
later:

@example
struct cell; /* forward declaration */

struct cell @{
    char *name;
    struct cell *next;
@};
@end example

The straightforward translation into ctypes code would be this, but it does not
work:

@example
>>> class cell(Structure):
...     _fields_ = [("name", c_char_p),
...                 ("next", POINTER(cell))]
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in cell
NameError: name 'cell' is not defined
>>>
@end example

because the new @code{class cell} is not available in the class statement itself.
In @ref{2b,,ctypes}, we can define the @code{cell} class and set the @code{_fields_}
attribute later, after the class statement:

@example
>>> from ctypes import *
>>> class cell(Structure):
...     pass
...
>>> cell._fields_ = [("name", c_char_p),
...                  ("next", POINTER(cell))]
>>>
@end example

Let's try it. We create two instances of @code{cell}, and let them point to each
other, and finally follow the pointer chain a few times:

@example
>>> c1 = cell()
>>> c1.name = "foo"
>>> c2 = cell()
>>> c2.name = "bar"
>>> c1.next = pointer(c2)
>>> c2.next = pointer(c1)
>>> p = c1
>>> for i in range(8):
...     print(p.name, end=" ")
...     p = p.next[0]
...
foo bar foo bar foo bar foo bar
>>>
@end example

@node Callback functions,Accessing values exported from dlls,Incomplete Types,ctypes 教程
@anchor{library/ctypes callback-functions}@anchor{228a}@anchor{library/ctypes ctypes-callback-functions}@anchor{228b}
@subsubsection Callback functions


@ref{2b,,ctypes} allows creating C callable function pointers from Python callables.
These are sometimes called @emph{callback functions}.

First, you must create a class for the callback function. The class knows the
calling convention, the return type, and the number and types of arguments this
function will receive.

The @ref{228c,,CFUNCTYPE()} factory function creates types for callback functions
using the @code{cdecl} calling convention. On Windows, the @ref{228d,,WINFUNCTYPE()}
factory function creates types for callback functions using the @code{stdcall}
calling convention.

Both of these factory functions are called with the result type as first
argument, and the callback functions expected argument types as the remaining
arguments.

I will present an example here which uses the standard C library's
@code{qsort()} function, that is used to sort items with the help of a callback
function.  @code{qsort()} will be used to sort an array of integers:

@example
>>> IntArray5 = c_int * 5
>>> ia = IntArray5(5, 1, 7, 33, 99)
>>> qsort = libc.qsort
>>> qsort.restype = None
>>>
@end example

@code{qsort()} must be called with a pointer to the data to sort, the number of
items in the data array, the size of one item, and a pointer to the comparison
function, the callback. The callback will then be called with two pointers to
items, and it must return a negative integer if the first item is smaller than
the second, a zero if they are equal, and a positive integer otherwise.

So our callback function receives pointers to integers, and must return an
integer. First we create the @code{type} for the callback function:

@example
>>> CMPFUNC = CFUNCTYPE(c_int, POINTER(c_int), POINTER(c_int))
>>>
@end example

To get started, here is a simple callback that shows the values it gets
passed:

@example
>>> def py_cmp_func(a, b):
...     print("py_cmp_func", a[0], b[0])
...     return 0
...
>>> cmp_func = CMPFUNC(py_cmp_func)
>>>
@end example

The result:

@example
>>> qsort(ia, len(ia), sizeof(c_int), cmp_func)  
py_cmp_func 5 1
py_cmp_func 33 99
py_cmp_func 7 33
py_cmp_func 5 7
py_cmp_func 1 7
>>>
@end example

Now we can actually compare the two items and return a useful result:

@example
>>> def py_cmp_func(a, b):
...     print("py_cmp_func", a[0], b[0])
...     return a[0] - b[0]
...
>>>
>>> qsort(ia, len(ia), sizeof(c_int), CMPFUNC(py_cmp_func)) 
py_cmp_func 5 1
py_cmp_func 33 99
py_cmp_func 7 33
py_cmp_func 1 7
py_cmp_func 5 7
>>>
@end example

As we can easily check, our array is sorted now:

@example
>>> for i in ia: print(i, end=" ")
...
1 5 7 33 99
>>>
@end example

The function factories can be used as decorator factories, so we may as well
write:

@example
>>> @@CFUNCTYPE(c_int, POINTER(c_int), POINTER(c_int))
... def py_cmp_func(a, b):
...     print("py_cmp_func", a[0], b[0])
...     return a[0] - b[0]
...
>>> qsort(ia, len(ia), sizeof(c_int), py_cmp_func)
py_cmp_func 5 1
py_cmp_func 33 99
py_cmp_func 7 33
py_cmp_func 1 7
py_cmp_func 5 7
>>>
@end example

@cartouche
@quotation 注解 
Make sure you keep references to @ref{228c,,CFUNCTYPE()} objects as long as they
are used from C code. @ref{2b,,ctypes} doesn't, and if you don't, they may be
garbage collected, crashing your program when a callback is made.

Also, note that if the callback function is called in a thread created
outside of Python's control (e.g. by the foreign code that calls the
callback), ctypes creates a new dummy Python thread on every invocation. This
behavior is correct for most purposes, but it means that values stored with
@ref{228e,,threading.local} will @emph{not} survive across different callbacks, even when
those calls are made from the same C thread.
@end quotation
@end cartouche

@node Accessing values exported from dlls,Surprises,Callback functions,ctypes 教程
@anchor{library/ctypes accessing-values-exported-from-dlls}@anchor{228f}@anchor{library/ctypes ctypes-accessing-values-exported-from-dlls}@anchor{2290}
@subsubsection Accessing values exported from dlls


Some shared libraries not only export functions, they also export variables. An
example in the Python library itself is the @ref{2291,,Py_OptimizeFlag}, an integer
set to 0, 1, or 2, depending on the @ref{685,,-O} or @ref{686,,-OO} flag given on
startup.

@ref{2b,,ctypes} can access values like this with the @code{in_dll()} class methods of
the type.  @emph{pythonapi} is a predefined symbol giving access to the Python C
api:

@example
>>> opt_flag = c_int.in_dll(pythonapi, "Py_OptimizeFlag")
>>> print(opt_flag)
c_long(0)
>>>
@end example

If the interpreter would have been started with @ref{685,,-O}, the sample would
have printed @code{c_long(1)}, or @code{c_long(2)} if @ref{686,,-OO} would have been
specified.

An extended example which also demonstrates the use of pointers accesses the
@ref{2292,,PyImport_FrozenModules} pointer exported by Python.

Quoting the docs for that value:

@quotation

This pointer is initialized to point to an array of @code{struct _frozen}
records, terminated by one whose members are all @code{NULL} or zero.  When a frozen
module is imported, it is searched in this table.  Third-party code could play
tricks with this to provide a dynamically created collection of frozen modules.
@end quotation

So manipulating this pointer could even prove useful. To restrict the example
size, we show only how this table can be read with @ref{2b,,ctypes}:

@example
>>> from ctypes import *
>>>
>>> class struct_frozen(Structure):
...     _fields_ = [("name", c_char_p),
...                 ("code", POINTER(c_ubyte)),
...                 ("size", c_int)]
...
>>>
@end example

We have defined the @code{struct _frozen} data type, so we can get the pointer
to the table:

@example
>>> FrozenTable = POINTER(struct_frozen)
>>> table = FrozenTable.in_dll(pythonapi, "PyImport_FrozenModules")
>>>
@end example

Since @code{table} is a @code{pointer} to the array of @code{struct_frozen} records, we
can iterate over it, but we just have to make sure that our loop terminates,
because pointers have no size. Sooner or later it would probably crash with an
access violation or whatever, so it's better to break out of the loop when we
hit the @code{NULL} entry:

@example
>>> for item in table:
...     if item.name is None:
...         break
...     print(item.name.decode("ascii"), item.size)
...
_frozen_importlib 31764
_frozen_importlib_external 41499
__hello__ 161
__phello__ -161
__phello__.spam 161
>>>
@end example

The fact that standard Python has a frozen module and a frozen package
(indicated by the negative @code{size} member) is not well known, it is only used
for testing. Try it out with @code{import __hello__} for example.

@node Surprises,Variable-sized data types,Accessing values exported from dlls,ctypes 教程
@anchor{library/ctypes ctypes-surprises}@anchor{2293}@anchor{library/ctypes surprises}@anchor{2294}
@subsubsection Surprises


There are some edges in @ref{2b,,ctypes} where you might expect something other
than what actually happens.

Consider the following example:

@example
>>> from ctypes import *
>>> class POINT(Structure):
...     _fields_ = ("x", c_int), ("y", c_int)
...
>>> class RECT(Structure):
...     _fields_ = ("a", POINT), ("b", POINT)
...
>>> p1 = POINT(1, 2)
>>> p2 = POINT(3, 4)
>>> rc = RECT(p1, p2)
>>> print(rc.a.x, rc.a.y, rc.b.x, rc.b.y)
1 2 3 4
>>> # now swap the two points
>>> rc.a, rc.b = rc.b, rc.a
>>> print(rc.a.x, rc.a.y, rc.b.x, rc.b.y)
3 4 3 4
>>>
@end example

Hm. We certainly expected the last statement to print @code{3 4 1 2}. What
happened? Here are the steps of the @code{rc.a, rc.b = rc.b, rc.a} line above:

@example
>>> temp0, temp1 = rc.b, rc.a
>>> rc.a = temp0
>>> rc.b = temp1
>>>
@end example

Note that @code{temp0} and @code{temp1} are objects still using the internal buffer of
the @code{rc} object above. So executing @code{rc.a = temp0} copies the buffer
contents of @code{temp0} into @code{rc} 's buffer.  This, in turn, changes the
contents of @code{temp1}. So, the last assignment @code{rc.b = temp1}, doesn't have
the expected effect.

Keep in mind that retrieving sub-objects from Structure, Unions, and Arrays
doesn't @emph{copy} the sub-object, instead it retrieves a wrapper object accessing
the root-object's underlying buffer.

Another example that may behave differently from what one would expect is this:

@example
>>> s = c_char_p()
>>> s.value = b"abc def ghi"
>>> s.value
b'abc def ghi'
>>> s.value is s.value
False
>>>
@end example

@cartouche
@quotation 注解 
Objects instantiated from @ref{2265,,c_char_p} can only have their value set to bytes
or integers.
@end quotation
@end cartouche

Why is it printing @code{False}?  ctypes instances are objects containing a memory
block plus some @ref{159e,,descriptor}s accessing the contents of the memory.
Storing a Python object in the memory block does not store the object itself,
instead the @code{contents} of the object is stored.  Accessing the contents again
constructs a new Python object each time!

@node Variable-sized data types,,Surprises,ctypes 教程
@anchor{library/ctypes ctypes-variable-sized-data-types}@anchor{2295}@anchor{library/ctypes variable-sized-data-types}@anchor{2296}
@subsubsection Variable-sized data types


@ref{2b,,ctypes} provides some support for variable-sized arrays and structures.

The @ref{2297,,resize()} function can be used to resize the memory buffer of an
existing ctypes object.  The function takes the object as first argument, and
the requested size in bytes as the second argument.  The memory block cannot be
made smaller than the natural memory block specified by the objects type, a
@ref{1fb,,ValueError} is raised if this is tried:

@example
>>> short_array = (c_short * 4)()
>>> print(sizeof(short_array))
8
>>> resize(short_array, 4)
Traceback (most recent call last):
    ...
ValueError: minimum size is 8
>>> resize(short_array, 32)
>>> sizeof(short_array)
32
>>> sizeof(type(short_array))
8
>>>
@end example

This is nice and fine, but how would one access the additional elements
contained in this array?  Since the type still only knows about 4 elements, we
get errors accessing other elements:

@example
>>> short_array[:]
[0, 0, 0, 0]
>>> short_array[7]
Traceback (most recent call last):
    ...
IndexError: invalid index
>>>
@end example

Another way to use variable-sized data types with @ref{2b,,ctypes} is to use the
dynamic nature of Python, and (re-)define the data type after the required size
is already known, on a case by case basis.

@node ctypes reference,,ctypes 教程,ctypes --- Python 的外部函数库
@anchor{library/ctypes ctypes-ctypes-reference}@anchor{2298}@anchor{library/ctypes ctypes-reference}@anchor{2299}
@subsubsection ctypes reference


@menu
* Finding shared libraries:: 
* Loading shared libraries:: 
* Foreign functions:: 
* Function prototypes:: 
* Utility functions:: 
* Data types:: 
* 基础数据类型: 基础数据类型<2>. 
* Structured data types:: 
* Arrays and pointers:: 

@end menu

@node Finding shared libraries,Loading shared libraries,,ctypes reference
@anchor{library/ctypes ctypes-finding-shared-libraries}@anchor{229a}@anchor{library/ctypes finding-shared-libraries}@anchor{229b}
@subsubsection Finding shared libraries


When programming in a compiled language, shared libraries are accessed when
compiling/linking a program, and when the program is run.

The purpose of the @code{find_library()} function is to locate a library in a way
similar to what the compiler or runtime loader does (on platforms with several
versions of a shared library the most recent should be loaded), while the ctypes
library loaders act like when a program is run, and call the runtime loader
directly.

The @code{ctypes.util} module provides a function which can help to determine
the library to load.


@deffn {数据} ctypes.util.find_library (name)

Try to find a library and return a pathname.  @emph{name} is the library name without
any prefix like @emph{lib}, suffix like @code{.so}, @code{.dylib} or version number (this
is the form used for the posix linker option @code{-l}).  If no library can
be found, returns @code{None}.
@end deffn

The exact functionality is system dependent.

On Linux, @code{find_library()} tries to run external programs
(@code{/sbin/ldconfig}, @code{gcc}, @code{objdump} and @code{ld}) to find the library file.
It returns the filename of the library file.


在 3.6 版更改: On Linux, the value of the environment variable @code{LD_LIBRARY_PATH} is used
when searching for libraries, if a library cannot be found by any other means.


Here are some examples:

@example
>>> from ctypes.util import find_library
>>> find_library("m")
'libm.so.6'
>>> find_library("c")
'libc.so.6'
>>> find_library("bz2")
'libbz2.so.1.0'
>>>
@end example

On OS X, @code{find_library()} tries several predefined naming schemes and paths
to locate the library, and returns a full pathname if successful:

@example
>>> from ctypes.util import find_library
>>> find_library("c")
'/usr/lib/libc.dylib'
>>> find_library("m")
'/usr/lib/libm.dylib'
>>> find_library("bz2")
'/usr/lib/libbz2.dylib'
>>> find_library("AGL")
'/System/Library/Frameworks/AGL.framework/AGL'
>>>
@end example

On Windows, @code{find_library()} searches along the system search path, and
returns the full pathname, but since there is no predefined naming scheme a call
like @code{find_library("c")} will fail and return @code{None}.

If wrapping a shared library with @ref{2b,,ctypes}, it @emph{may} be better to determine
the shared library name at development time, and hardcode that into the wrapper
module instead of using @code{find_library()} to locate the library at runtime.

@node Loading shared libraries,Foreign functions,Finding shared libraries,ctypes reference
@anchor{library/ctypes ctypes-loading-shared-libraries}@anchor{229c}@anchor{library/ctypes loading-shared-libraries}@anchor{229d}
@subsubsection Loading shared libraries


There are several ways to load shared libraries into the Python process.  One
way is to instantiate one of the following classes:

@geindex CDLL (ctypes 中的类)
@anchor{library/ctypes ctypes CDLL}@anchor{1c1}
@deffn {类} ctypes.CDLL (name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False, winmode=0)

Instances of this class represent loaded shared libraries. Functions in these
libraries use the standard C calling convention, and are assumed to return
@code{int}.
@end deffn

@geindex OleDLL (ctypes 中的类)
@anchor{library/ctypes ctypes OleDLL}@anchor{229e}
@deffn {类} ctypes.OleDLL (name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False, winmode=0)

Windows only: Instances of this class represent loaded shared libraries,
functions in these libraries use the @code{stdcall} calling convention, and are
assumed to return the windows specific @ref{229f,,HRESULT} code.  @ref{229f,,HRESULT}
values contain information specifying whether the function call failed or
succeeded, together with additional error code.  If the return value signals a
failure, an @ref{1d3,,OSError} is automatically raised.


在 3.3 版更改: @ref{98e,,WindowsError} used to be raised.

@end deffn

@geindex WinDLL (ctypes 中的类)
@anchor{library/ctypes ctypes WinDLL}@anchor{22a0}
@deffn {类} ctypes.WinDLL (name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False, winmode=0)

Windows only: Instances of this class represent loaded shared libraries,
functions in these libraries use the @code{stdcall} calling convention, and are
assumed to return @code{int} by default.

On Windows CE only the standard calling convention is used, for convenience the
@ref{22a0,,WinDLL} and @ref{229e,,OleDLL} use the standard calling convention on this
platform.
@end deffn

The Python @ref{500,,global interpreter lock} is released before calling any
function exported by these libraries, and reacquired afterwards.

@geindex PyDLL (ctypes 中的类)
@anchor{library/ctypes ctypes PyDLL}@anchor{22a1}
@deffn {类} ctypes.PyDLL (name, mode=DEFAULT_MODE, handle=None)

Instances of this class behave like @ref{1c1,,CDLL} instances, except that the
Python GIL is @emph{not} released during the function call, and after the function
execution the Python error flag is checked. If the error flag is set, a Python
exception is raised.

Thus, this is only useful to call Python C api functions directly.
@end deffn

All these classes can be instantiated by calling them with at least one
argument, the pathname of the shared library.  If you have an existing handle to
an already loaded shared library, it can be passed as the @code{handle} named
parameter, otherwise the underlying platforms @code{dlopen} or @code{LoadLibrary}
function is used to load the library into the process, and to get a handle to
it.

The @emph{mode} parameter can be used to specify how the library is loaded.  For
details, consult the @code{dlopen(3)} manpage.  On Windows, @emph{mode} is
ignored.  On posix systems, RTLD_NOW is always added, and is not
configurable.

The @emph{use_errno} parameter, when set to true, enables a ctypes mechanism that
allows accessing the system @ref{7c,,errno} error number in a safe way.
@ref{2b,,ctypes} maintains a thread-local copy of the systems @ref{7c,,errno}
variable; if you call foreign functions created with @code{use_errno=True} then the
@ref{7c,,errno} value before the function call is swapped with the ctypes private
copy, the same happens immediately after the function call.

The function @ref{22a2,,ctypes.get_errno()} returns the value of the ctypes private
copy, and the function @ref{22a3,,ctypes.set_errno()} changes the ctypes private copy
to a new value and returns the former value.

The @emph{use_last_error} parameter, when set to true, enables the same mechanism for
the Windows error code which is managed by the @ref{2271,,GetLastError()} and
@code{SetLastError()} Windows API functions; @ref{22a4,,ctypes.get_last_error()} and
@ref{22a5,,ctypes.set_last_error()} are used to request and change the ctypes private
copy of the windows error code.

The @emph{winmode} parameter is used on Windows to specify how the library is loaded
(since @emph{mode} is ignored). It takes any value that is valid for the Win32 API
@code{LoadLibraryEx} flags parameter. When omitted, the default is to use the flags
that result in the most secure DLL load to avoiding issues such as DLL
hijacking. Passing the full path to the DLL is the safest way to ensure the
correct library and dependencies are loaded.


在 3.8 版更改: Added @emph{winmode} parameter.



@deffn {数据} ctypes.RTLD_GLOBAL

Flag to use as @emph{mode} parameter.  On platforms where this flag is not available,
it is defined as the integer zero.
@end deffn


@deffn {数据} ctypes.RTLD_LOCAL

Flag to use as @emph{mode} parameter.  On platforms where this is not available, it
is the same as @emph{RTLD_GLOBAL}.
@end deffn


@deffn {数据} ctypes.DEFAULT_MODE

The default mode which is used to load shared libraries.  On OSX 10.3, this is
@emph{RTLD_GLOBAL}, otherwise it is the same as @emph{RTLD_LOCAL}.
@end deffn

Instances of these classes have no public methods.  Functions exported by the
shared library can be accessed as attributes or by index.  Please note that
accessing the function through an attribute caches the result and therefore
accessing it repeatedly returns the same object each time.  On the other hand,
accessing it through an index returns a new object each time:

@example
>>> from ctypes import CDLL
>>> libc = CDLL("libc.so.6")  # On Linux
>>> libc.time == libc.time
True
>>> libc['time'] == libc['time']
False
@end example

The following public attributes are available, their name starts with an
underscore to not clash with exported function names:

@geindex _handle (ctypes.PyDLL 属性)
@anchor{library/ctypes ctypes PyDLL _handle}@anchor{22a6}
@deffn {属性} PyDLL._handle

The system handle used to access the library.
@end deffn

@geindex _name (ctypes.PyDLL 属性)
@anchor{library/ctypes ctypes PyDLL _name}@anchor{22a7}
@deffn {属性} PyDLL._name

The name of the library passed in the constructor.
@end deffn

Shared libraries can also be loaded by using one of the prefabricated objects,
which are instances of the @ref{22a8,,LibraryLoader} class, either by calling the
@code{LoadLibrary()} method, or by retrieving the library as attribute of the
loader instance.

@geindex LibraryLoader (ctypes 中的类)
@anchor{library/ctypes ctypes LibraryLoader}@anchor{22a8}
@deffn {类} ctypes.LibraryLoader (dlltype)

Class which loads shared libraries.  @emph{dlltype} should be one of the
@ref{1c1,,CDLL}, @ref{22a1,,PyDLL}, @ref{22a0,,WinDLL}, or @ref{229e,,OleDLL} types.

@ref{313,,__getattr__()} has special behavior: It allows loading a shared library by
accessing it as attribute of a library loader instance.  The result is cached,
so repeated attribute accesses return the same library each time.

@geindex LoadLibrary() (ctypes.LibraryLoader 方法)
@anchor{library/ctypes ctypes LibraryLoader LoadLibrary}@anchor{22a9}
@deffn {方法} LoadLibrary (name)

Load a shared library into the process and return it.  This method always
returns a new instance of the library.
@end deffn
@end deffn

These prefabricated library loaders are available:


@deffn {数据} ctypes.cdll

Creates @ref{1c1,,CDLL} instances.
@end deffn


@deffn {数据} ctypes.windll

仅Windows中: 创建 @ref{22a0,,WinDLL} 实例.
@end deffn


@deffn {数据} ctypes.oledll

仅Windows中: 创建 @ref{229e,,OleDLL} 实例。
@end deffn


@deffn {数据} ctypes.pydll

创建 @ref{22a1,,PyDLL} 实例。
@end deffn

For accessing the C Python api directly, a ready-to-use Python shared library
object is available:


@deffn {数据} ctypes.pythonapi

An instance of @ref{22a1,,PyDLL} that exposes Python C API functions as
attributes.  Note that all these functions are assumed to return C
@code{int}, which is of course not always the truth, so you have to assign
the correct @code{restype} attribute to use these functions.
@end deffn


Loading a library through any of these objects raises an
@ref{12d0,,auditing event} @code{ctypes.dlopen} with string argument
@code{name}, the name used to load the library.



Accessing a function on a loaded library raises an auditing event
@code{ctypes.dlsym} with arguments @code{library} (the library object) and @code{name}
(the symbol's name as a string or integer).



In cases when only the library handle is available rather than the object,
accessing a function raises an auditing event @code{ctypes.dlsym/handle} with
arguments @code{handle} (the raw library handle) and @code{name}.


@node Foreign functions,Function prototypes,Loading shared libraries,ctypes reference
@anchor{library/ctypes ctypes-foreign-functions}@anchor{22aa}@anchor{library/ctypes foreign-functions}@anchor{22ab}
@subsubsection Foreign functions


As explained in the previous section, foreign functions can be accessed as
attributes of loaded shared libraries.  The function objects created in this way
by default accept any number of arguments, accept any ctypes data instances as
arguments, and return the default result type specified by the library loader.
They are instances of a private class:

@geindex _FuncPtr (ctypes 中的类)
@anchor{library/ctypes ctypes _FuncPtr}@anchor{22ac}
@deffn {类} ctypes._FuncPtr

Base class for C callable foreign functions.

Instances of foreign functions are also C compatible data types; they
represent C function pointers.

This behavior can be customized by assigning to special attributes of the
foreign function object.

@geindex restype (ctypes._FuncPtr 属性)
@anchor{library/ctypes ctypes _FuncPtr restype}@anchor{22ad}
@deffn {属性} restype

Assign a ctypes type to specify the result type of the foreign function.
Use @code{None} for @code{void}, a function not returning anything.

It is possible to assign a callable Python object that is not a ctypes
type, in this case the function is assumed to return a C @code{int}, and
the callable will be called with this integer, allowing further
processing or error checking.  Using this is deprecated, for more flexible
post processing or error checking use a ctypes data type as
@ref{22ad,,restype} and assign a callable to the @ref{22ae,,errcheck} attribute.
@end deffn

@geindex argtypes (ctypes._FuncPtr 属性)
@anchor{library/ctypes ctypes _FuncPtr argtypes}@anchor{22af}
@deffn {属性} argtypes

Assign a tuple of ctypes types to specify the argument types that the
function accepts.  Functions using the @code{stdcall} calling convention can
only be called with the same number of arguments as the length of this
tuple; functions using the C calling convention accept additional,
unspecified arguments as well.

When a foreign function is called, each actual argument is passed to the
@code{from_param()} class method of the items in the @ref{22af,,argtypes}
tuple, this method allows adapting the actual argument to an object that
the foreign function accepts.  For example, a @ref{2265,,c_char_p} item in
the @ref{22af,,argtypes} tuple will convert a string passed as argument into
a bytes object using ctypes conversion rules.

New: It is now possible to put items in argtypes which are not ctypes
types, but each item must have a @code{from_param()} method which returns a
value usable as argument (integer, string, ctypes instance).  This allows
defining adapters that can adapt custom objects as function parameters.
@end deffn

@geindex errcheck (ctypes._FuncPtr 属性)
@anchor{library/ctypes ctypes _FuncPtr errcheck}@anchor{22ae}
@deffn {属性} errcheck

Assign a Python function or another callable to this attribute. The
callable will be called with three or more arguments:


@deffn {函数} callable (result, func, arguments)

@emph{result} is what the foreign function returns, as specified by the
@code{restype} attribute.

@emph{func} is the foreign function object itself, this allows reusing the
same callable object to check or post process the results of several
functions.

@emph{arguments} is a tuple containing the parameters originally passed to
the function call, this allows specializing the behavior on the
arguments used.
@end deffn

The object that this function returns will be returned from the
foreign function call, but it can also check the result value
and raise an exception if the foreign function call failed.
@end deffn
@end deffn

@geindex ArgumentError
@anchor{library/ctypes ctypes ArgumentError}@anchor{22b0}
@deffn {例外} ctypes.ArgumentError

This exception is raised when a foreign function call cannot convert one of the
passed arguments.
@end deffn


On Windows, when a foreign function call raises a system exception (for
example, due to an access violation), it will be captured and replaced with
a suitable Python exception. Further, an auditing event
@code{ctypes.seh_exception} with argument @code{code} will be raised, allowing an
audit hook to replace the exception with its own.



Some ways to invoke foreign function calls may raise an auditing event
@code{ctypes.call_function} with arguments @code{function pointer} and @code{arguments}.


@node Function prototypes,Utility functions,Foreign functions,ctypes reference
@anchor{library/ctypes ctypes-function-prototypes}@anchor{22b1}@anchor{library/ctypes function-prototypes}@anchor{22b2}
@subsubsection Function prototypes


Foreign functions can also be created by instantiating function prototypes.
Function prototypes are similar to function prototypes in C; they describe a
function (return type, argument types, calling convention) without defining an
implementation.  The factory functions must be called with the desired result
type and the argument types of the function, and can be used as decorator
factories, and as such, be applied to functions through the @code{@@wrapper} syntax.
See @ref{228b,,Callback functions} for examples.

@geindex CFUNCTYPE() (在 ctypes 模块中)
@anchor{library/ctypes ctypes CFUNCTYPE}@anchor{228c}
@deffn {函数} ctypes.CFUNCTYPE (restype, *argtypes, use_errno=False, use_last_error=False)

The returned function prototype creates functions that use the standard C
calling convention.  The function will release the GIL during the call.  If
@emph{use_errno} is set to true, the ctypes private copy of the system
@ref{7c,,errno} variable is exchanged with the real @ref{7c,,errno} value before
and after the call; @emph{use_last_error} does the same for the Windows error
code.
@end deffn

@geindex WINFUNCTYPE() (在 ctypes 模块中)
@anchor{library/ctypes ctypes WINFUNCTYPE}@anchor{228d}
@deffn {函数} ctypes.WINFUNCTYPE (restype, *argtypes, use_errno=False, use_last_error=False)

Windows only: The returned function prototype creates functions that use the
@code{stdcall} calling convention, except on Windows CE where
@ref{228d,,WINFUNCTYPE()} is the same as @ref{228c,,CFUNCTYPE()}.  The function will
release the GIL during the call.  @emph{use_errno} and @emph{use_last_error} have the
same meaning as above.
@end deffn

@geindex PYFUNCTYPE() (在 ctypes 模块中)
@anchor{library/ctypes ctypes PYFUNCTYPE}@anchor{22b3}
@deffn {函数} ctypes.PYFUNCTYPE (restype, *argtypes)

The returned function prototype creates functions that use the Python calling
convention.  The function will @emph{not} release the GIL during the call.
@end deffn

Function prototypes created by these factory functions can be instantiated in
different ways, depending on the type and number of the parameters in the call:

@quotation


@deffn {函数} prototype (address)

Returns a foreign function at the specified address which must be an integer.
@end deffn


@deffn {函数} prototype (callable)

Create a C callable function (a callback function) from a Python @emph{callable}.
@end deffn


@deffn {函数} prototype (func_spec[, paramflags])

Returns a foreign function exported by a shared library. @emph{func_spec} must
be a 2-tuple @code{(name_or_ordinal, library)}. The first item is the name of
the exported function as string, or the ordinal of the exported function
as small integer.  The second item is the shared library instance.
@end deffn


@deffn {函数} prototype (vtbl_index, name[, paramflags[, iid]])

Returns a foreign function that will call a COM method. @emph{vtbl_index} is
the index into the virtual function table, a small non-negative
integer. @emph{name} is name of the COM method. @emph{iid} is an optional pointer to
the interface identifier which is used in extended error reporting.

COM methods use a special calling convention: They require a pointer to
the COM interface as first argument, in addition to those parameters that
are specified in the @code{argtypes} tuple.
@end deffn

The optional @emph{paramflags} parameter creates foreign function wrappers with much
more functionality than the features described above.

@emph{paramflags} must be a tuple of the same length as @code{argtypes}.

Each item in this tuple contains further information about a parameter, it must
be a tuple containing one, two, or three items.

The first item is an integer containing a combination of direction
flags for the parameter:

@quotation


@table @asis

@item 1

Specifies an input parameter to the function.

@item 2

Output parameter.  The foreign function fills in a value.

@item 4

Input parameter which defaults to the integer zero.
@end table
@end quotation

The optional second item is the parameter name as string.  If this is specified,
the foreign function can be called with named parameters.

The optional third item is the default value for this parameter.
@end quotation

This example demonstrates how to wrap the Windows @code{MessageBoxW} function so
that it supports default parameters and named arguments. The C declaration from
the windows header file is this:

@example
WINUSERAPI int WINAPI
MessageBoxW(
    HWND hWnd,
    LPCWSTR lpText,
    LPCWSTR lpCaption,
    UINT uType);
@end example

Here is the wrapping with @ref{2b,,ctypes}:

@example
>>> from ctypes import c_int, WINFUNCTYPE, windll
>>> from ctypes.wintypes import HWND, LPCWSTR, UINT
>>> prototype = WINFUNCTYPE(c_int, HWND, LPCWSTR, LPCWSTR, UINT)
>>> paramflags = (1, "hwnd", 0), (1, "text", "Hi"), (1, "caption", "Hello from ctypes"), (1, "flags", 0)
>>> MessageBox = prototype(("MessageBoxW", windll.user32), paramflags)
@end example

The @code{MessageBox} foreign function can now be called in these ways:

@example
>>> MessageBox()
>>> MessageBox(text="Spam, spam, spam")
>>> MessageBox(flags=2, text="foo bar")
@end example

A second example demonstrates output parameters.  The win32 @code{GetWindowRect}
function retrieves the dimensions of a specified window by copying them into
@code{RECT} structure that the caller has to supply.  Here is the C declaration:

@example
WINUSERAPI BOOL WINAPI
GetWindowRect(
     HWND hWnd,
     LPRECT lpRect);
@end example

Here is the wrapping with @ref{2b,,ctypes}:

@example
>>> from ctypes import POINTER, WINFUNCTYPE, windll, WinError
>>> from ctypes.wintypes import BOOL, HWND, RECT
>>> prototype = WINFUNCTYPE(BOOL, HWND, POINTER(RECT))
>>> paramflags = (1, "hwnd"), (2, "lprect")
>>> GetWindowRect = prototype(("GetWindowRect", windll.user32), paramflags)
>>>
@end example

Functions with output parameters will automatically return the output parameter
value if there is a single one, or a tuple containing the output parameter
values when there are more than one, so the GetWindowRect function now returns a
RECT instance, when called.

Output parameters can be combined with the @code{errcheck} protocol to do
further output processing and error checking.  The win32 @code{GetWindowRect} api
function returns a @code{BOOL} to signal success or failure, so this function could
do the error checking, and raises an exception when the api call failed:

@example
>>> def errcheck(result, func, args):
...     if not result:
...         raise WinError()
...     return args
...
>>> GetWindowRect.errcheck = errcheck
>>>
@end example

If the @code{errcheck} function returns the argument tuple it receives
unchanged, @ref{2b,,ctypes} continues the normal processing it does on the output
parameters.  If you want to return a tuple of window coordinates instead of a
@code{RECT} instance, you can retrieve the fields in the function and return them
instead, the normal processing will no longer take place:

@example
>>> def errcheck(result, func, args):
...     if not result:
...         raise WinError()
...     rc = args[1]
...     return rc.left, rc.top, rc.bottom, rc.right
...
>>> GetWindowRect.errcheck = errcheck
>>>
@end example

@node Utility functions,Data types,Function prototypes,ctypes reference
@anchor{library/ctypes ctypes-utility-functions}@anchor{22b4}@anchor{library/ctypes utility-functions}@anchor{22b5}
@subsubsection Utility functions


@geindex addressof() (在 ctypes 模块中)
@anchor{library/ctypes ctypes addressof}@anchor{22b6}
@deffn {函数} ctypes.addressof (obj)

Returns the address of the memory buffer as integer.  @emph{obj} must be an
instance of a ctypes type.

Raises an @ref{12d0,,auditing event} @code{ctypes.addressof} with argument @code{obj}.
@end deffn

@geindex alignment() (在 ctypes 模块中)
@anchor{library/ctypes ctypes alignment}@anchor{22b7}
@deffn {函数} ctypes.alignment (obj_or_type)

Returns the alignment requirements of a ctypes type. @emph{obj_or_type} must be a
ctypes type or instance.
@end deffn

@geindex byref() (在 ctypes 模块中)
@anchor{library/ctypes ctypes byref}@anchor{2274}
@deffn {函数} ctypes.byref (obj[, offset])

Returns a light-weight pointer to @emph{obj}, which must be an instance of a
ctypes type.  @emph{offset} defaults to zero, and must be an integer that will be
added to the internal pointer value.

@code{byref(obj, offset)} corresponds to this C code:

@example
(((char *)&obj) + offset)
@end example

The returned object can only be used as a foreign function call parameter.
It behaves similar to @code{pointer(obj)}, but the construction is a lot faster.
@end deffn

@geindex cast() (在 ctypes 模块中)
@anchor{library/ctypes ctypes cast}@anchor{fa6}
@deffn {函数} ctypes.cast (obj, type)

This function is similar to the cast operator in C. It returns a new instance
of @emph{type} which points to the same memory block as @emph{obj}.  @emph{type} must be a
pointer type, and @emph{obj} must be an object that can be interpreted as a
pointer.
@end deffn

@geindex create_string_buffer() (在 ctypes 模块中)
@anchor{library/ctypes ctypes create_string_buffer}@anchor{2268}
@deffn {函数} ctypes.create_string_buffer (init_or_size, size=None)

This function creates a mutable character buffer. The returned object is a
ctypes array of @ref{2257,,c_char}.

@emph{init_or_size} must be an integer which specifies the size of the array, or a
bytes object which will be used to initialize the array items.

If a bytes object is specified as first argument, the buffer is made one item
larger than its length so that the last element in the array is a NUL
termination character. An integer can be passed as second argument which allows
specifying the size of the array if the length of the bytes should not be used.

Raises an @ref{12d0,,auditing event} @code{ctypes.create_string_buffer} with arguments @code{init}, @code{size}.
@end deffn

@geindex create_unicode_buffer() (在 ctypes 模块中)
@anchor{library/ctypes ctypes create_unicode_buffer}@anchor{f3c}
@deffn {函数} ctypes.create_unicode_buffer (init_or_size, size=None)

This function creates a mutable unicode character buffer. The returned object is
a ctypes array of @ref{2258,,c_wchar}.

@emph{init_or_size} must be an integer which specifies the size of the array, or a
string which will be used to initialize the array items.

If a string is specified as first argument, the buffer is made one item
larger than the length of the string so that the last element in the array is a
NUL termination character. An integer can be passed as second argument which
allows specifying the size of the array if the length of the string should not
be used.

Raises an @ref{12d0,,auditing event} @code{ctypes.create_unicode_buffer} with arguments @code{init}, @code{size}.
@end deffn

@geindex DllCanUnloadNow() (在 ctypes 模块中)
@anchor{library/ctypes ctypes DllCanUnloadNow}@anchor{22b8}
@deffn {函数} ctypes.DllCanUnloadNow ()

Windows only: This function is a hook which allows implementing in-process
COM servers with ctypes.  It is called from the DllCanUnloadNow function that
the _ctypes extension dll exports.
@end deffn

@geindex DllGetClassObject() (在 ctypes 模块中)
@anchor{library/ctypes ctypes DllGetClassObject}@anchor{22b9}
@deffn {函数} ctypes.DllGetClassObject ()

Windows only: This function is a hook which allows implementing in-process
COM servers with ctypes.  It is called from the DllGetClassObject function
that the @code{_ctypes} extension dll exports.
@end deffn

@geindex find_library() (在 ctypes.util 模块中)
@anchor{library/ctypes ctypes util find_library}@anchor{605}
@deffn {函数} ctypes.util.find_library (name)

Try to find a library and return a pathname.  @emph{name} is the library name
without any prefix like @code{lib}, suffix like @code{.so}, @code{.dylib} or version
number (this is the form used for the posix linker option @code{-l}).  If
no library can be found, returns @code{None}.

The exact functionality is system dependent.
@end deffn

@geindex find_msvcrt() (在 ctypes.util 模块中)
@anchor{library/ctypes ctypes util find_msvcrt}@anchor{22ba}
@deffn {函数} ctypes.util.find_msvcrt ()

Windows only: return the filename of the VC runtime library used by Python,
and by the extension modules.  If the name of the library cannot be
determined, @code{None} is returned.

If you need to free memory, for example, allocated by an extension module
with a call to the @code{free(void *)}, it is important that you use the
function in the same library that allocated the memory.
@end deffn

@geindex FormatError() (在 ctypes 模块中)
@anchor{library/ctypes ctypes FormatError}@anchor{22bb}
@deffn {函数} ctypes.FormatError ([code])

Windows only: Returns a textual description of the error code @emph{code}.  If no
error code is specified, the last error code is used by calling the Windows
api function GetLastError.
@end deffn

@geindex GetLastError() (在 ctypes 模块中)
@anchor{library/ctypes ctypes GetLastError}@anchor{2271}
@deffn {函数} ctypes.GetLastError ()

Windows only: Returns the last error code set by Windows in the calling thread.
This function calls the Windows @cite{GetLastError()} function directly,
it does not return the ctypes-private copy of the error code.
@end deffn

@geindex get_errno() (在 ctypes 模块中)
@anchor{library/ctypes ctypes get_errno}@anchor{22a2}
@deffn {函数} ctypes.get_errno ()

Returns the current value of the ctypes-private copy of the system
@ref{7c,,errno} variable in the calling thread.

Raises an @ref{12d0,,auditing event} @code{ctypes.get_errno} with no arguments.
@end deffn

@geindex get_last_error() (在 ctypes 模块中)
@anchor{library/ctypes ctypes get_last_error}@anchor{22a4}
@deffn {函数} ctypes.get_last_error ()

Windows only: returns the current value of the ctypes-private copy of the system
@code{LastError} variable in the calling thread.

Raises an @ref{12d0,,auditing event} @code{ctypes.get_last_error} with no arguments.
@end deffn

@geindex memmove() (在 ctypes 模块中)
@anchor{library/ctypes ctypes memmove}@anchor{22bc}
@deffn {函数} ctypes.memmove (dst, src, count)

Same as the standard C memmove library function: copies @emph{count} bytes from
@emph{src} to @emph{dst}. @emph{dst} and @emph{src} must be integers or ctypes instances that can
be converted to pointers.
@end deffn

@geindex memset() (在 ctypes 模块中)
@anchor{library/ctypes ctypes memset}@anchor{22bd}
@deffn {函数} ctypes.memset (dst, c, count)

Same as the standard C memset library function: fills the memory block at
address @emph{dst} with @emph{count} bytes of value @emph{c}. @emph{dst} must be an integer
specifying an address, or a ctypes instance.
@end deffn

@geindex POINTER() (在 ctypes 模块中)
@anchor{library/ctypes ctypes POINTER}@anchor{2285}
@deffn {函数} ctypes.POINTER (type)

This factory function creates and returns a new ctypes pointer type. Pointer
types are cached and reused internally, so calling this function repeatedly is
cheap. @emph{type} must be a ctypes type.
@end deffn

@geindex pointer() (在 ctypes 模块中)
@anchor{library/ctypes ctypes pointer}@anchor{2275}
@deffn {函数} ctypes.pointer (obj)

This function creates a new pointer instance, pointing to @emph{obj}. The returned
object is of the type @code{POINTER(type(obj))}.

Note: If you just want to pass a pointer to an object to a foreign function
call, you should use @code{byref(obj)} which is much faster.
@end deffn

@geindex resize() (在 ctypes 模块中)
@anchor{library/ctypes ctypes resize}@anchor{2297}
@deffn {函数} ctypes.resize (obj, size)

This function resizes the internal memory buffer of @emph{obj}, which must be an
instance of a ctypes type.  It is not possible to make the buffer smaller
than the native size of the objects type, as given by @code{sizeof(type(obj))},
but it is possible to enlarge the buffer.
@end deffn

@geindex set_errno() (在 ctypes 模块中)
@anchor{library/ctypes ctypes set_errno}@anchor{22a3}
@deffn {函数} ctypes.set_errno (value)

Set the current value of the ctypes-private copy of the system @ref{7c,,errno}
variable in the calling thread to @emph{value} and return the previous value.

Raises an @ref{12d0,,auditing event} @code{ctypes.set_errno} with argument @code{errno}.
@end deffn

@geindex set_last_error() (在 ctypes 模块中)
@anchor{library/ctypes ctypes set_last_error}@anchor{22a5}
@deffn {函数} ctypes.set_last_error (value)

Windows only: set the current value of the ctypes-private copy of the system
@code{LastError} variable in the calling thread to @emph{value} and return the
previous value.

Raises an @ref{12d0,,auditing event} @code{ctypes.set_last_error} with argument @code{error}.
@end deffn

@geindex sizeof() (在 ctypes 模块中)
@anchor{library/ctypes ctypes sizeof}@anchor{22be}
@deffn {函数} ctypes.sizeof (obj_or_type)

Returns the size in bytes of a ctypes type or instance memory buffer.
Does the same as the C @code{sizeof} operator.
@end deffn

@geindex string_at() (在 ctypes 模块中)
@anchor{library/ctypes ctypes string_at}@anchor{22bf}
@deffn {函数} ctypes.string_at (address, size=-1)

This function returns the C string starting at memory address @emph{address} as a bytes
object. If size is specified, it is used as size, otherwise the string is assumed
to be zero-terminated.

Raises an @ref{12d0,,auditing event} @code{ctypes.string_at} with arguments @code{address}, @code{size}.
@end deffn

@geindex WinError() (在 ctypes 模块中)
@anchor{library/ctypes ctypes WinError}@anchor{22c0}
@deffn {函数} ctypes.WinError (code=None, descr=None)

Windows only: this function is probably the worst-named thing in ctypes. It
creates an instance of OSError.  If @emph{code} is not specified,
@code{GetLastError} is called to determine the error code. If @emph{descr} is not
specified, @ref{22bb,,FormatError()} is called to get a textual description of the
error.


在 3.3 版更改: An instance of @ref{98e,,WindowsError} used to be created.

@end deffn

@geindex wstring_at() (在 ctypes 模块中)
@anchor{library/ctypes ctypes wstring_at}@anchor{22c1}
@deffn {函数} ctypes.wstring_at (address, size=-1)

This function returns the wide character string starting at memory address
@emph{address} as a string.  If @emph{size} is specified, it is used as the number of
characters of the string, otherwise the string is assumed to be
zero-terminated.

Raises an @ref{12d0,,auditing event} @code{ctypes.wstring_at} with arguments @code{address}, @code{size}.
@end deffn

@node Data types,基础数据类型<2>,Utility functions,ctypes reference
@anchor{library/ctypes ctypes-data-types}@anchor{22c2}@anchor{library/ctypes data-types}@anchor{22c3}
@subsubsection Data types


@geindex _CData (ctypes 中的类)
@anchor{library/ctypes ctypes _CData}@anchor{1043}
@deffn {类} ctypes._CData

This non-public class is the common base class of all ctypes data types.
Among other things, all ctypes type instances contain a memory block that
hold C compatible data; the address of the memory block is returned by the
@ref{22b6,,addressof()} helper function. Another instance variable is exposed as
@ref{22c4,,_objects}; this contains other Python objects that need to be kept
alive in case the memory block contains pointers.

Common methods of ctypes data types, these are all class methods (to be
exact, they are methods of the @ref{22c5,,metaclass}):

@geindex from_buffer() (ctypes._CData 方法)
@anchor{library/ctypes ctypes _CData from_buffer}@anchor{22c6}
@deffn {方法} from_buffer (source[, offset])

This method returns a ctypes instance that shares the buffer of the
@emph{source} object.  The @emph{source} object must support the writeable buffer
interface.  The optional @emph{offset} parameter specifies an offset into the
source buffer in bytes; the default is zero.  If the source buffer is not
large enough a @ref{1fb,,ValueError} is raised.

Raises an @ref{12d0,,auditing event} @code{ctypes.cdata/buffer} with arguments @code{pointer}, @code{size}, @code{offset}.
@end deffn

@geindex from_buffer_copy() (ctypes._CData 方法)
@anchor{library/ctypes ctypes _CData from_buffer_copy}@anchor{22c7}
@deffn {方法} from_buffer_copy (source[, offset])

This method creates a ctypes instance, copying the buffer from the
@emph{source} object buffer which must be readable.  The optional @emph{offset}
parameter specifies an offset into the source buffer in bytes; the default
is zero.  If the source buffer is not large enough a @ref{1fb,,ValueError} is
raised.

Raises an @ref{12d0,,auditing event} @code{ctypes.cdata/buffer} with arguments @code{pointer}, @code{size}, @code{offset}.
@end deffn

@geindex from_address() (ctypes._CData 方法)
@anchor{library/ctypes ctypes _CData from_address}@anchor{22c8}
@deffn {方法} from_address (address)

This method returns a ctypes type instance using the memory specified by
@emph{address} which must be an integer.


This method, and others that indirectly call this method, raises an
@ref{12d0,,auditing event} @code{ctypes.cdata} with argument
@code{address}.

@end deffn

@geindex from_param() (ctypes._CData 方法)
@anchor{library/ctypes ctypes _CData from_param}@anchor{22c9}
@deffn {方法} from_param (obj)

This method adapts @emph{obj} to a ctypes type.  It is called with the actual
object used in a foreign function call when the type is present in the
foreign function's @code{argtypes} tuple; it must return an object that
can be used as a function call parameter.

All ctypes data types have a default implementation of this classmethod
that normally returns @emph{obj} if that is an instance of the type.  Some
types accept other objects as well.
@end deffn

@geindex in_dll() (ctypes._CData 方法)
@anchor{library/ctypes ctypes _CData in_dll}@anchor{22ca}
@deffn {方法} in_dll (library, name)

This method returns a ctypes type instance exported by a shared
library. @emph{name} is the name of the symbol that exports the data, @emph{library}
is the loaded shared library.
@end deffn

Common instance variables of ctypes data types:

@geindex _b_base_ (ctypes._CData 属性)
@anchor{library/ctypes ctypes _CData _b_base_}@anchor{22cb}
@deffn {属性} _b_base_

Sometimes ctypes data instances do not own the memory block they contain,
instead they share part of the memory block of a base object.  The
@ref{22cb,,_b_base_} read-only member is the root ctypes object that owns the
memory block.
@end deffn

@geindex _b_needsfree_ (ctypes._CData 属性)
@anchor{library/ctypes ctypes _CData _b_needsfree_}@anchor{22cc}
@deffn {属性} _b_needsfree_

This read-only variable is true when the ctypes data instance has
allocated the memory block itself, false otherwise.
@end deffn

@geindex _objects (ctypes._CData 属性)
@anchor{library/ctypes ctypes _CData _objects}@anchor{22c4}
@deffn {属性} _objects

This member is either @code{None} or a dictionary containing Python objects
that need to be kept alive so that the memory block contents is kept
valid.  This object is only exposed for debugging; never modify the
contents of this dictionary.
@end deffn
@end deffn

@node 基础数据类型<2>,Structured data types,Data types,ctypes reference
@anchor{library/ctypes ctypes-fundamental-data-types-2}@anchor{22cd}@anchor{library/ctypes id1}@anchor{22ce}
@subsubsection 基础数据类型


@geindex _SimpleCData (ctypes 中的类)
@anchor{library/ctypes ctypes _SimpleCData}@anchor{22cf}
@deffn {类} ctypes._SimpleCData

This non-public class is the base class of all fundamental ctypes data
types. It is mentioned here because it contains the common attributes of the
fundamental ctypes data types.  @ref{22cf,,_SimpleCData} is a subclass of
@ref{1043,,_CData}, so it inherits their methods and attributes. ctypes data
types that are not and do not contain pointers can now be pickled.

Instances have a single attribute:

@geindex value (ctypes._SimpleCData 属性)
@anchor{library/ctypes ctypes _SimpleCData value}@anchor{22d0}
@deffn {属性} value

This attribute contains the actual value of the instance. For integer and
pointer types, it is an integer, for character types, it is a single
character bytes object or string, for character pointer types it is a
Python bytes object or string.

When the @code{value} attribute is retrieved from a ctypes instance, usually
a new object is returned each time.  @ref{2b,,ctypes} does @emph{not} implement
original object return, always a new object is constructed.  The same is
true for all other ctypes object instances.
@end deffn
@end deffn

Fundamental data types, when returned as foreign function call results, or, for
example, by retrieving structure field members or array items, are transparently
converted to native Python types.  In other words, if a foreign function has a
@code{restype} of @ref{2265,,c_char_p}, you will always receive a Python bytes
object, @emph{not} a @ref{2265,,c_char_p} instance.

@c XXX above is false, it actually returns a Unicode string

Subclasses of fundamental data types do @emph{not} inherit this behavior. So, if a
foreign functions @code{restype} is a subclass of @ref{2267,,c_void_p}, you will
receive an instance of this subclass from the function call. Of course, you can
get the value of the pointer by accessing the @code{value} attribute.

These are the fundamental ctypes data types:

@geindex c_byte (ctypes 中的类)
@anchor{library/ctypes ctypes c_byte}@anchor{2259}
@deffn {类} ctypes.c_byte

Represents the C @code{signed char} datatype, and interprets the value as
small integer.  The constructor accepts an optional integer initializer; no
overflow checking is done.
@end deffn

@geindex c_char (ctypes 中的类)
@anchor{library/ctypes ctypes c_char}@anchor{2257}
@deffn {类} ctypes.c_char

Represents the C @code{char} datatype, and interprets the value as a single
character.  The constructor accepts an optional string initializer, the
length of the string must be exactly one character.
@end deffn

@geindex c_char_p (ctypes 中的类)
@anchor{library/ctypes ctypes c_char_p}@anchor{2265}
@deffn {类} ctypes.c_char_p

Represents the C @code{char *} datatype when it points to a zero-terminated
string.  For a general character pointer that may also point to binary data,
@code{POINTER(c_char)} must be used.  The constructor accepts an integer
address, or a bytes object.
@end deffn

@geindex c_double (ctypes 中的类)
@anchor{library/ctypes ctypes c_double}@anchor{2263}
@deffn {类} ctypes.c_double

Represents the C @code{double} datatype.  The constructor accepts an
optional float initializer.
@end deffn

@geindex c_longdouble (ctypes 中的类)
@anchor{library/ctypes ctypes c_longdouble}@anchor{2264}
@deffn {类} ctypes.c_longdouble

Represents the C @code{long double} datatype.  The constructor accepts an
optional float initializer.  On platforms where @code{sizeof(long double) ==
sizeof(double)} it is an alias to @ref{2263,,c_double}.
@end deffn

@geindex c_float (ctypes 中的类)
@anchor{library/ctypes ctypes c_float}@anchor{2262}
@deffn {类} ctypes.c_float

Represents the C @code{float} datatype.  The constructor accepts an
optional float initializer.
@end deffn

@geindex c_int (ctypes 中的类)
@anchor{library/ctypes ctypes c_int}@anchor{224c}
@deffn {类} ctypes.c_int

Represents the C @code{signed int} datatype.  The constructor accepts an
optional integer initializer; no overflow checking is done.  On platforms
where @code{sizeof(int) == sizeof(long)} it is an alias to @ref{224d,,c_long}.
@end deffn

@geindex c_int8 (ctypes 中的类)
@anchor{library/ctypes ctypes c_int8}@anchor{22d1}
@deffn {类} ctypes.c_int8

Represents the C 8-bit @code{signed int} datatype.  Usually an alias for
@ref{2259,,c_byte}.
@end deffn

@geindex c_int16 (ctypes 中的类)
@anchor{library/ctypes ctypes c_int16}@anchor{22d2}
@deffn {类} ctypes.c_int16

Represents the C 16-bit @code{signed int} datatype.  Usually an alias for
@ref{225b,,c_short}.
@end deffn

@geindex c_int32 (ctypes 中的类)
@anchor{library/ctypes ctypes c_int32}@anchor{22d3}
@deffn {类} ctypes.c_int32

Represents the C 32-bit @code{signed int} datatype.  Usually an alias for
@ref{224c,,c_int}.
@end deffn

@geindex c_int64 (ctypes 中的类)
@anchor{library/ctypes ctypes c_int64}@anchor{22d4}
@deffn {类} ctypes.c_int64

Represents the C 64-bit @code{signed int} datatype.  Usually an alias for
@ref{225f,,c_longlong}.
@end deffn

@geindex c_long (ctypes 中的类)
@anchor{library/ctypes ctypes c_long}@anchor{224d}
@deffn {类} ctypes.c_long

Represents the C @code{signed long} datatype.  The constructor accepts an
optional integer initializer; no overflow checking is done.
@end deffn

@geindex c_longlong (ctypes 中的类)
@anchor{library/ctypes ctypes c_longlong}@anchor{225f}
@deffn {类} ctypes.c_longlong

Represents the C @code{signed long long} datatype.  The constructor accepts
an optional integer initializer; no overflow checking is done.
@end deffn

@geindex c_short (ctypes 中的类)
@anchor{library/ctypes ctypes c_short}@anchor{225b}
@deffn {类} ctypes.c_short

Represents the C @code{signed short} datatype.  The constructor accepts an
optional integer initializer; no overflow checking is done.
@end deffn

@geindex c_size_t (ctypes 中的类)
@anchor{library/ctypes ctypes c_size_t}@anchor{2261}
@deffn {类} ctypes.c_size_t

Represents the C @code{size_t} datatype.
@end deffn

@geindex c_ssize_t (ctypes 中的类)
@anchor{library/ctypes ctypes c_ssize_t}@anchor{bca}
@deffn {类} ctypes.c_ssize_t

Represents the C @code{ssize_t} datatype.


3.2 新版功能.

@end deffn

@geindex c_ubyte (ctypes 中的类)
@anchor{library/ctypes ctypes c_ubyte}@anchor{225a}
@deffn {类} ctypes.c_ubyte

Represents the C @code{unsigned char} datatype, it interprets the value as
small integer.  The constructor accepts an optional integer initializer; no
overflow checking is done.
@end deffn

@geindex c_uint (ctypes 中的类)
@anchor{library/ctypes ctypes c_uint}@anchor{225d}
@deffn {类} ctypes.c_uint

Represents the C @code{unsigned int} datatype.  The constructor accepts an
optional integer initializer; no overflow checking is done.  On platforms
where @code{sizeof(int) == sizeof(long)} it is an alias for @ref{225e,,c_ulong}.
@end deffn

@geindex c_uint8 (ctypes 中的类)
@anchor{library/ctypes ctypes c_uint8}@anchor{22d5}
@deffn {类} ctypes.c_uint8

Represents the C 8-bit @code{unsigned int} datatype.  Usually an alias for
@ref{225a,,c_ubyte}.
@end deffn

@geindex c_uint16 (ctypes 中的类)
@anchor{library/ctypes ctypes c_uint16}@anchor{22d6}
@deffn {类} ctypes.c_uint16

Represents the C 16-bit @code{unsigned int} datatype.  Usually an alias for
@ref{225c,,c_ushort}.
@end deffn

@geindex c_uint32 (ctypes 中的类)
@anchor{library/ctypes ctypes c_uint32}@anchor{22d7}
@deffn {类} ctypes.c_uint32

Represents the C 32-bit @code{unsigned int} datatype.  Usually an alias for
@ref{225d,,c_uint}.
@end deffn

@geindex c_uint64 (ctypes 中的类)
@anchor{library/ctypes ctypes c_uint64}@anchor{22d8}
@deffn {类} ctypes.c_uint64

Represents the C 64-bit @code{unsigned int} datatype.  Usually an alias for
@ref{2260,,c_ulonglong}.
@end deffn

@geindex c_ulong (ctypes 中的类)
@anchor{library/ctypes ctypes c_ulong}@anchor{225e}
@deffn {类} ctypes.c_ulong

Represents the C @code{unsigned long} datatype.  The constructor accepts an
optional integer initializer; no overflow checking is done.
@end deffn

@geindex c_ulonglong (ctypes 中的类)
@anchor{library/ctypes ctypes c_ulonglong}@anchor{2260}
@deffn {类} ctypes.c_ulonglong

Represents the C @code{unsigned long long} datatype.  The constructor
accepts an optional integer initializer; no overflow checking is done.
@end deffn

@geindex c_ushort (ctypes 中的类)
@anchor{library/ctypes ctypes c_ushort}@anchor{225c}
@deffn {类} ctypes.c_ushort

Represents the C @code{unsigned short} datatype.  The constructor accepts
an optional integer initializer; no overflow checking is done.
@end deffn

@geindex c_void_p (ctypes 中的类)
@anchor{library/ctypes ctypes c_void_p}@anchor{2267}
@deffn {类} ctypes.c_void_p

Represents the C @code{void *} type.  The value is represented as integer.
The constructor accepts an optional integer initializer.
@end deffn

@geindex c_wchar (ctypes 中的类)
@anchor{library/ctypes ctypes c_wchar}@anchor{2258}
@deffn {类} ctypes.c_wchar

Represents the C @code{wchar_t} datatype, and interprets the value as a
single character unicode string.  The constructor accepts an optional string
initializer, the length of the string must be exactly one character.
@end deffn

@geindex c_wchar_p (ctypes 中的类)
@anchor{library/ctypes ctypes c_wchar_p}@anchor{2266}
@deffn {类} ctypes.c_wchar_p

Represents the C @code{wchar_t *} datatype, which must be a pointer to a
zero-terminated wide character string.  The constructor accepts an integer
address, or a string.
@end deffn

@geindex c_bool (ctypes 中的类)
@anchor{library/ctypes ctypes c_bool}@anchor{2256}
@deffn {类} ctypes.c_bool

Represent the C @code{bool} datatype (more accurately, @code{_Bool} from
C99).  Its value can be @code{True} or @code{False}, and the constructor accepts any object
that has a truth value.
@end deffn

@geindex HRESULT (ctypes 中的类)
@anchor{library/ctypes ctypes HRESULT}@anchor{229f}
@deffn {类} ctypes.HRESULT

Windows only: Represents a @code{HRESULT} value, which contains success or
error information for a function or method call.
@end deffn

@geindex py_object (ctypes 中的类)
@anchor{library/ctypes ctypes py_object}@anchor{22d9}
@deffn {类} ctypes.py_object

Represents the C @ref{4b5,,PyObject *} datatype.  Calling this without an
argument creates a @code{NULL} @ref{4b5,,PyObject *} pointer.
@end deffn

The @code{ctypes.wintypes} module provides quite some other Windows specific
data types, for example @code{HWND}, @code{WPARAM}, or @code{DWORD}.  Some
useful structures like @code{MSG} or @code{RECT} are also defined.

@node Structured data types,Arrays and pointers,基础数据类型<2>,ctypes reference
@anchor{library/ctypes ctypes-structured-data-types}@anchor{22da}@anchor{library/ctypes structured-data-types}@anchor{22db}
@subsubsection Structured data types


@geindex Union (ctypes 中的类)
@anchor{library/ctypes ctypes Union}@anchor{2279}
@deffn {类} ctypes.Union (*args, **kw)

Abstract base class for unions in native byte order.
@end deffn

@geindex BigEndianStructure (ctypes 中的类)
@anchor{library/ctypes ctypes BigEndianStructure}@anchor{227c}
@deffn {类} ctypes.BigEndianStructure (*args, **kw)

Abstract base class for structures in @emph{big endian} byte order.
@end deffn

@geindex LittleEndianStructure (ctypes 中的类)
@anchor{library/ctypes ctypes LittleEndianStructure}@anchor{227d}
@deffn {类} ctypes.LittleEndianStructure (*args, **kw)

Abstract base class for structures in @emph{little endian} byte order.
@end deffn

Structures with non-native byte order cannot contain pointer type fields, or any
other data types containing pointer type fields.

@geindex Structure (ctypes 中的类)
@anchor{library/ctypes ctypes Structure}@anchor{2278}
@deffn {类} ctypes.Structure (*args, **kw)

Abstract base class for structures in @emph{native} byte order.

Concrete structure and union types must be created by subclassing one of these
types, and at least define a @ref{22dc,,_fields_} class variable. @ref{2b,,ctypes} will
create @ref{159e,,descriptor}s which allow reading and writing the fields by direct
attribute accesses.  These are the

@geindex _fields_ (ctypes.Structure 属性)
@anchor{library/ctypes ctypes Structure _fields_}@anchor{22dc}
@deffn {属性} _fields_

A sequence defining the structure fields.  The items must be 2-tuples or
3-tuples.  The first item is the name of the field, the second item
specifies the type of the field; it can be any ctypes data type.

For integer type fields like @ref{224c,,c_int}, a third optional item can be
given.  It must be a small positive integer defining the bit width of the
field.

Field names must be unique within one structure or union.  This is not
checked, only one field can be accessed when names are repeated.

It is possible to define the @ref{22dc,,_fields_} class variable @emph{after} the
class statement that defines the Structure subclass, this allows creating
data types that directly or indirectly reference themselves:

@example
class List(Structure):
    pass
List._fields_ = [("pnext", POINTER(List)),
                 ...
                ]
@end example

The @ref{22dc,,_fields_} class variable must, however, be defined before the
type is first used (an instance is created, @ref{22be,,sizeof()} is called on it,
and so on).  Later assignments to the @ref{22dc,,_fields_} class variable will
raise an AttributeError.

It is possible to define sub-subclasses of structure types, they inherit
the fields of the base class plus the @ref{22dc,,_fields_} defined in the
sub-subclass, if any.
@end deffn

@geindex _pack_ (ctypes.Structure 属性)
@anchor{library/ctypes ctypes Structure _pack_}@anchor{22dd}
@deffn {属性} _pack_

An optional small integer that allows overriding the alignment of
structure fields in the instance.  @ref{22dd,,_pack_} must already be defined
when @ref{22dc,,_fields_} is assigned, otherwise it will have no effect.
@end deffn

@geindex _anonymous_ (ctypes.Structure 属性)
@anchor{library/ctypes ctypes Structure _anonymous_}@anchor{22de}
@deffn {属性} _anonymous_

An optional sequence that lists the names of unnamed (anonymous) fields.
@ref{22de,,_anonymous_} must be already defined when @ref{22dc,,_fields_} is
assigned, otherwise it will have no effect.

The fields listed in this variable must be structure or union type fields.
@ref{2b,,ctypes} will create descriptors in the structure type that allows
accessing the nested fields directly, without the need to create the
structure or union field.

Here is an example type (Windows):

@example
class _U(Union):
    _fields_ = [("lptdesc", POINTER(TYPEDESC)),
                ("lpadesc", POINTER(ARRAYDESC)),
                ("hreftype", HREFTYPE)]

class TYPEDESC(Structure):
    _anonymous_ = ("u",)
    _fields_ = [("u", _U),
                ("vt", VARTYPE)]
@end example

The @code{TYPEDESC} structure describes a COM data type, the @code{vt} field
specifies which one of the union fields is valid.  Since the @code{u} field
is defined as anonymous field, it is now possible to access the members
directly off the TYPEDESC instance. @code{td.lptdesc} and @code{td.u.lptdesc}
are equivalent, but the former is faster since it does not need to create
a temporary union instance:

@example
td = TYPEDESC()
td.vt = VT_PTR
td.lptdesc = POINTER(some_type)
td.u.lptdesc = POINTER(some_type)
@end example
@end deffn

It is possible to define sub-subclasses of structures, they inherit the
fields of the base class.  If the subclass definition has a separate
@ref{22dc,,_fields_} variable, the fields specified in this are appended to the
fields of the base class.

Structure and union constructors accept both positional and keyword
arguments.  Positional arguments are used to initialize member fields in the
same order as they are appear in @ref{22dc,,_fields_}.  Keyword arguments in the
constructor are interpreted as attribute assignments, so they will initialize
@ref{22dc,,_fields_} with the same name, or create new attributes for names not
present in @ref{22dc,,_fields_}.
@end deffn

@node Arrays and pointers,,Structured data types,ctypes reference
@anchor{library/ctypes arrays-and-pointers}@anchor{22df}@anchor{library/ctypes ctypes-arrays-pointers}@anchor{22e0}
@subsubsection Arrays and pointers


@geindex Array (ctypes 中的类)
@anchor{library/ctypes ctypes Array}@anchor{f9d}
@deffn {类} ctypes.Array (*args)

Abstract base class for arrays.

The recommended way to create concrete array types is by multiplying any
@ref{2b,,ctypes} data type with a positive integer.  Alternatively, you can subclass
this type and define @ref{22e1,,_length_} and @ref{22e2,,_type_} class variables.
Array elements can be read and written using standard
subscript and slice accesses; for slice reads, the resulting object is
@emph{not} itself an @ref{f9d,,Array}.

@geindex _length_ (ctypes.Array 属性)
@anchor{library/ctypes ctypes Array _length_}@anchor{22e1}
@deffn {属性} _length_

A positive integer specifying the number of elements in the array.
Out-of-range subscripts result in an @ref{e6e,,IndexError}. Will be
returned by @ref{150,,len()}.
@end deffn

@geindex _type_ (ctypes.Array 属性)
@anchor{library/ctypes ctypes Array _type_}@anchor{22e2}
@deffn {属性} _type_

Specifies the type of each element in the array.
@end deffn

Array subclass constructors accept positional arguments, used to
initialize the elements in order.
@end deffn

@geindex _Pointer (ctypes 中的类)
@anchor{library/ctypes ctypes _Pointer}@anchor{22e3}
@deffn {类} ctypes._Pointer

Private, abstract base class for pointers.

Concrete pointer types are created by calling @ref{2285,,POINTER()} with the
type that will be pointed to; this is done automatically by
@ref{2275,,pointer()}.

If a pointer points to an array, its elements can be read and
written using standard subscript and slice accesses.  Pointer objects
have no size, so @ref{150,,len()} will raise @ref{192,,TypeError}.  Negative
subscripts will read from the memory @emph{before} the pointer (as in C), and
out-of-range subscripts will probably crash with an access violation (if
you're lucky).

@geindex _type_ (ctypes._Pointer 属性)
@anchor{library/ctypes ctypes _Pointer _type_}@anchor{22e4}
@deffn {属性} _type_

Specifies the type pointed to.
@end deffn

@geindex contents (ctypes._Pointer 属性)
@anchor{library/ctypes ctypes _Pointer contents}@anchor{2284}
@deffn {属性} contents

Returns the object to which to pointer points.  Assigning to this
attribute changes the pointer to point to the assigned object.
@end deffn
@end deffn

@node 并发执行,contextvars --- Context Variables,通用操作系统服务,Python 标准库
@anchor{library/concurrency doc}@anchor{22e5}@anchor{library/concurrency concurrency}@anchor{22e6}@anchor{library/concurrency concurrent-execution}@anchor{22e7}
@section 并发执行


本章中描述的模块支持并发执行代码。 适当的工具选择取决于要执行的任务（CPU密集型或IO密集型）和偏好的开发风格（事件驱动的协作式多任务或抢占式多任务处理）。 这是一个概述：

@menu
* threading: threading --- 基于线程的并行. 基于线程的并行
* multiprocessing: multiprocessing --- 基于进程的并行. 基于进程的并行
* multiprocessing.shared_memory: multiprocessing shared_memory --- 可从进程直接访问的共享内存. 可从进程直接访问的共享内存
* concurrent 包:: 
* concurrent.futures: concurrent futures --- 启动并行任务. 启动并行任务
* subprocess: subprocess --- 子进程管理. 子进程管理
* sched: sched --- 事件调度器. 事件调度器
* queue: queue --- 一个同步的队列类. 一个同步的队列类
* _thread: _thread --- 底层多线程 API. 底层多线程 API
* _dummy_thread: _dummy_thread --- _thread 的替代模块. _thread 的替代模块
* dummy_threading: dummy_threading --- 可直接替代 threading 模块。. 可直接替代 threading 模块。

@end menu

@node threading --- 基于线程的并行,multiprocessing --- 基于进程的并行,,并发执行
@anchor{library/threading doc}@anchor{22e8}@anchor{library/threading module-threading}@anchor{109}@anchor{library/threading threading-thread-based-parallelism}@anchor{22e9}
@subsection @code{threading} --- 基于线程的并行


@geindex threading (模块)

@strong{源代码:} Lib/threading.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/threading.py}


__________________________________________________________________


这个模块在较低级的模块 @ref{3,,_thread} 基础上建立较高级的线程接口。参见： @ref{da,,queue}  模块。


在 3.7 版更改: 这个模块曾经为可选项，但现在总是可用。


@cartouche
@quotation 注解 
虽然他们没有在下面列出，这个模块仍然支持Python 2.x系列的这个模块下以 @code{camelCase} （驼峰法）命名的方法和函数。
@end quotation
@end cartouche

这个模块定义了以下函数：

@geindex active_count() (在 threading 模块中)
@anchor{library/threading threading active_count}@anchor{22ea}
@deffn {函数} threading.active_count ()

返回当前存活的线程类 @ref{234,,Thread} 对象。返回的计数等于 @ref{22eb,,enumerate()} 返回的列表长度。
@end deffn

@geindex current_thread() (在 threading 模块中)
@anchor{library/threading threading current_thread}@anchor{22ec}
@deffn {函数} threading.current_thread ()

返回当前对应调用者的控制线程的 @ref{234,,Thread} 对象。如果调用者的控制线程不是利用 @ref{109,,threading} 创建，会返回一个功能受限的虚拟线程对象。
@end deffn

@geindex excepthook() (在 threading 模块中)
@anchor{library/threading threading excepthook}@anchor{231}
@deffn {函数} threading.excepthook (args, /)

处理由 @ref{232,,Thread.run()} 引发的未捕获异常。

@emph{args} 参数具有以下属性:


@itemize *

@item 
@emph{exc_type}: 异常类型

@item 
@emph{exc_value}: 异常值，可以是 @code{None}.

@item 
@emph{exc_traceback}: 异常回溯，可以是 @code{None}.

@item 
@emph{thread}: 引发异常的线程，可以为 @code{None}。
@end itemize

如果 @emph{exc_type} 为 @ref{5f7,,SystemExit}，则异常会被静默地忽略。 在其他情况下，异常将被打印到 @ref{308,,sys.stderr}。

如果此函数引发了异常，则会调用 @ref{e5c,,sys.excepthook()} 来处理它。

@ref{231,,threading.excepthook()} 可以被重载以控制由 @ref{232,,Thread.run()} 引发的未捕获异常的处理方式。

使用定制钩子存放 @emph{exc_value} 可能会创建引用循环。 它应当在不再需要异常时被显式地清空以打破引用循环。

使用定制钩子存放 @emph{thread} 可能会在它设为被终结对象时将其重生。 请避免在定制钩子完成后存放 @emph{thread} 以避免对象的重生。


@subsubheading 参见


@ref{e5c,,sys.excepthook()} 处理未捕获的异常。



3.8 新版功能.

@end deffn

@geindex get_ident() (在 threading 模块中)
@anchor{library/threading threading get_ident}@anchor{aaa}
@deffn {函数} threading.get_ident ()

返回当前线程的 “线程标识符”。它是一个非零的整数。它的值没有直接含义，主要是用作 magic cookie，比如作为含有线程相关数据的字典的索引。线程标识符可能会在线程退出，新线程创建时被复用。


3.3 新版功能.

@end deffn

@geindex get_native_id() (在 threading 模块中)
@anchor{library/threading threading get_native_id}@anchor{233}
@deffn {函数} threading.get_native_id ()

返回内核分配给当前线程的原生集成线程 ID。 这是一个非负整数。 它的值可被用来在整个系统中唯一地标识这个特定线程（直到线程终结，在那之后该值可能会被 OS 回收再利用）。

@ref{12f5,,可用性}: Windows, FreeBSD, Linux, macOS, OpenBSD, NetBSD, AIX。


3.8 新版功能.

@end deffn

@geindex enumerate() (在 threading 模块中)
@anchor{library/threading threading enumerate}@anchor{22eb}
@deffn {函数} threading.enumerate ()

以列表形式返回当前所有存活的 @ref{234,,Thread} 对象。 该列表包含守护线程，@ref{22ec,,current_thread()} 创建的虚拟线程对象和主线程。它不包含已终结的线程和尚未开始的线程。
@end deffn

@geindex main_thread() (在 threading 模块中)
@anchor{library/threading threading main_thread}@anchor{8e9}
@deffn {函数} threading.main_thread ()

返回主 @ref{234,,Thread} 对象。一般情况下，主线程是Python解释器开始时创建的线程。


3.4 新版功能.

@end deffn

@geindex settrace() (在 threading 模块中)
@anchor{library/threading threading settrace}@anchor{22ed}
@deffn {函数} threading.settrace (func)

@geindex trace function

为所有 @ref{109,,threading} 模块开始的线程设置追踪函数。在每个线程的 @ref{232,,run()} 方法被调用前，@emph{func} 会被传递给 @ref{e37,,sys.settrace()} 。
@end deffn

@geindex setprofile() (在 threading 模块中)
@anchor{library/threading threading setprofile}@anchor{22ee}
@deffn {函数} threading.setprofile (func)

@geindex profile function

为所有 @ref{109,,threading} 模块开始的线程设置性能测试函数。在每个线程的 @ref{232,,run()} 方法被调用前，@emph{func} 会被传递给 @ref{e36,,sys.setprofile()} 。
@end deffn

@geindex stack_size() (在 threading 模块中)
@anchor{library/threading threading stack_size}@anchor{22ef}
@deffn {函数} threading.stack_size ([size])

返回创建线程时使用的堆栈大小。可选参数 @emph{size} 指定之后新建的线程的堆栈大小，而且一定要是0（根据平台或者默认配置）或者最小是32,768(32KiB)的一个正整数。如果 @emph{size} 没有指定，默认是0。如果不支持改变线程堆栈大小，会抛出 @ref{2ba,,RuntimeError} 错误。如果指定的堆栈大小不合法，会抛出 @ref{1fb,,ValueError} 错误并且不会修改堆栈大小。32KiB是当前最小的能保证解释器有足够堆栈空间的堆栈大小。需要注意的是部分平台对于堆栈大小会有特定的限制，例如要求大于32KiB的堆栈大小或者需要根据系统内存页面的整数倍进行分配 - 应当查阅平台文档有关详细信息（4KiB页面比较普遍，在没有更具体信息的情况下，建议的方法是使用4096的倍数作为堆栈大小）。

@ref{12f5,,适用于}: Windows，具有 POSIX 线程的系统。
@end deffn

这个模块同时定义了以下常量：

@geindex TIMEOUT_MAX() (在 threading 模块中)
@anchor{library/threading threading TIMEOUT_MAX}@anchor{22f0}
@deffn {数据} threading.TIMEOUT_MAX

阻塞函数（ @ref{766,,Lock.acquire()}, @ref{767,,RLock.acquire()}, @ref{22f1,,Condition.wait()}, ...）中形参 @emph{timeout} 允许的最大值。传入超过这个值的 timeout 会抛出 @ref{95a,,OverflowError} 异常。


3.2 新版功能.

@end deffn

这个模块定义了许多类，详见以下部分。

该模块的设计基于 Java的线程模型。 但是，在Java里面，锁和条件变量是每个对象的基础特性，而在Python里面，这些被独立成了单独的对象。 Python 的 @ref{234,,Thread} 类只是 Java 的 Thread 类的一个子集；目前还没有优先级，没有线程组，线程还不能被销毁、停止、暂停、恢复或中断。 Java 的 Thread 类的静态方法在实现时会映射为模块级函数。

下述方法的执行都是原子性的。

@menu
* 线程本地数据:: 
* 线程对象:: 
* 锁对象:: 
* 递归锁对象:: 
* 条件对象:: 
* 信号量对象:: 
* 事件对象:: 
* 定时器对象:: 
* 栅栏对象:: 
* 在 with 语句中使用锁、条件和信号量:: 

@end menu

@node 线程本地数据,线程对象,,threading --- 基于线程的并行
@anchor{library/threading thread-local-data}@anchor{22f2}
@subsubsection 线程本地数据


线程本地数据是特定线程的数据。管理线程本地数据，只需要创建一个 @ref{228e,,local} （或者一个子类型）的实例并在实例中储存属性：

@example
mydata = threading.local()
mydata.x = 1
@end example

在不同的线程中，实例的值会不同。

@geindex local (threading 中的类)
@anchor{library/threading threading local}@anchor{228e}
@deffn {类} threading.local

一个代表线程本地数据的类。

更多相关细节和大量示例，参见 @code{_threading_local} 模块的文档。
@end deffn

@node 线程对象,锁对象,线程本地数据,threading --- 基于线程的并行
@anchor{library/threading id1}@anchor{22f3}@anchor{library/threading thread-objects}@anchor{22f4}
@subsubsection 线程对象


The @ref{234,,Thread} class represents an activity that is run in a separate
thread of control.  There are two ways to specify the activity: by passing a
callable object to the constructor, or by overriding the @ref{232,,run()}
method in a subclass.  No other methods (except for the constructor) should be
overridden in a subclass.  In other words, @emph{only}  override the
@code{__init__()} and @ref{232,,run()} methods of this class.

当线程对象一但被创建，其活动一定会因调用线程的 @ref{206e,,start()} 方法开始。这会在独立的控制线程调用 @ref{232,,run()} 方法。

一旦线程活动开始，该线程会被认为是 '存活的' 。当它的 @ref{232,,run()} 方法终结了（不管是正常的还是抛出未被处理的异常），就不是'存活的'。 @ref{22f5,,is_alive()} 方法用于检查线程是否存活。

其他线程可以调用一个线程的 @ref{b59,,join()} 方法。这会阻塞调用该方法的线程，直到被调用 @ref{b59,,join()} 方法的线程终结。

线程有名字。名字可以传递给构造函数，也可以通过 @ref{22f6,,name} 属性读取或者修改。

如果 @ref{232,,run()} 方法引发了异常，则会调用 @ref{231,,threading.excepthook()} 来处理它。 在默认情况下，@ref{231,,threading.excepthook()} 会静默地忽略 @ref{5f7,,SystemExit}。

一个线程可以被标记成一个“守护线程”。 这个标志的意义是，当剩下的线程都是守护线程时，整个 Python 程序将会退出。 初始值继承于创建线程。 这个标志可以通过 @ref{22f7,,daemon} 特征属性或者 @emph{daemon} 构造器参数来设置。

@cartouche
@quotation 注解 
守护线程在程序关闭时会突然关闭。他们的资源（例如已经打开的文档，数据库事务等等）可能没有被正确释放。如果你想你的线程正常停止，设置他们成为非守护模式并且使用合适的信号机制，例如： @ref{aa8,,Event}。
@end quotation
@end cartouche

有个 "主线程" 对象；这对应Python程序里面初始的控制线程。它不是一个守护线程。

"虚拟线程对象" 是可以被创建的。这些是对应于“外部线程”的线程对象，它们是在线程模块外部启动的控制线程，例如直接来自C代码。虚拟线程对象功能受限；他们总是被认为是存活的和守护模式，不能被 @ref{b59,,join()} 。因为无法检测外来线程的终结，它们永远不会被删除。

@geindex Thread (threading 中的类)
@anchor{library/threading threading Thread}@anchor{234}
@deffn {类} threading.Thread (group=None, target=None, name=None, args=(), kwargs=@{@}, *, daemon=None)

调用这个构造函数时，必需带有关键字参数。参数如下：

@emph{group} 应该为 @code{None}；为了日后扩展 @code{ThreadGroup} 类实现而保留。

@emph{target} 是用于 @ref{232,,run()} 方法调用的可调用对象。默认是 @code{None}，表示不需要调用任何方法。

@emph{name} 是线程名称。默认情况下，由 "Thread-@emph{N}" 格式构成一个唯一的名称，其中 @emph{N} 是小的十进制数。

@emph{args} 是用于调用目标函数的参数元组。默认是 @code{()}。

@emph{kwargs} 是用于调用目标函数的关键字参数字典。默认是 @code{@{@}}。

如果不是 @code{None}，@emph{daemon} 参数将显式地设置该线程是否为守护模式。 如果是 @code{None} (默认值)，线程将继承当前线程的守护模式属性。

如果子类型重载了构造函数，它一定要确保在做任何事前，先发起调用基类构造器(@code{Thread.__init__()})。


在 3.3 版更改: 加入 @emph{daemon} 参数。


@geindex start() (threading.Thread 方法)
@anchor{library/threading threading Thread start}@anchor{206e}
@deffn {方法} start ()

开始线程活动。

它在一个线程里最多只能被调用一次。它安排对象的 @ref{232,,run()} 方法在一个独立的控制进程中调用。

如果同一个线程对象中调用这个方法的次数大于一次，会抛出 @ref{2ba,,RuntimeError} 。
@end deffn

@geindex run() (threading.Thread 方法)
@anchor{library/threading threading Thread run}@anchor{232}
@deffn {方法} run ()

代表线程活动的方法。

你可以在子类型里重载这个方法。 标准的 @ref{232,,run()} 方法会对作为 @emph{target} 参数传递给该对象构造器的可调用对象（如果存在）发起调用，并附带从 @emph{args} 和 @emph{kwargs} 参数分别获取的位置和关键字参数。
@end deffn

@geindex join() (threading.Thread 方法)
@anchor{library/threading threading Thread join}@anchor{b59}
@deffn {方法} join (timeout=None)

等待，直到线程终结。这会阻塞调用这个方法的线程，直到被调用 @ref{b59,,join()} 的线程终结 -- 不管是正常终结还是抛出未处理异常 -- 或者直到发生超时，超时选项是可选的。

当 @emph{timeout} 参数存在而且不是 @code{None} 时，它应该是一个用于指定操作超时的以秒为单位的浮点数或者分数。因为 @ref{b59,,join()} 总是返回 @code{None} ，所以你一定要在 @ref{b59,,join()} 后调用 @ref{22f5,,is_alive()} 才能判断是否发生超时 -- 如果线程仍然存活，则 @ref{b59,,join()} 超时。

当 @emph{timeout} 参数不存在或者是 @code{None} ，这个操作会阻塞直到线程终结。

一个线程可以被 @ref{b59,,join()} 很多次。

如果尝试加入当前线程会导致死锁， @ref{b59,,join()} 会引起 @ref{2ba,,RuntimeError}  异常。如果尝试 @ref{b59,,join()} 一个尚未开始的线程，也会抛出相同的异常。
@end deffn

@geindex name (threading.Thread 属性)
@anchor{library/threading threading Thread name}@anchor{22f6}
@deffn {属性} name

只用于识别的字符串。它没有语义。多个线程可以赋予相同的名称。 初始名称由构造函数设置。
@end deffn

@geindex getName() (threading.Thread 方法)
@geindex setName() (threading.Thread 方法)
@anchor{library/threading threading Thread getName}@anchor{22f8}
@deffn {方法} getName ()
@anchor{library/threading threading Thread setName}@anchor{22f9}
@deffnx {方法} setName ()

旧的 @ref{22f6,,name} 取值/设值 API；直接当做特征属性使用它。
@end deffn

@geindex ident (threading.Thread 属性)
@anchor{library/threading threading Thread ident}@anchor{1fb0}
@deffn {属性} ident

这个线程的 '线程标识符'，如果线程尚未开始则为 @code{None} 。这是个非零整数。参见  @ref{aaa,,get_ident()} 函数。当一个线程退出而另外一个线程被创建，线程标识符会被复用。即使线程退出后，仍可得到标识符。
@end deffn

@geindex native_id (threading.Thread 属性)
@anchor{library/threading threading Thread native_id}@anchor{235}
@deffn {属性} native_id

此线程的原生集成线程 ID。 这是一个非负整数，或者如果线程还未启动则为 @code{None}。 请参阅 @ref{233,,get_native_id()} 函数。 这表示线程 ID (@code{TID}) 已被 OS (内核) 赋值给线程。 它的值可能被用来在全系统范围内唯一地标识这个特定线程（直到线程终结，在那之后该值可能会被 OS 回收再利用）。

@cartouche
@quotation 注解 
类似于进程 ID，线程 ID 的有效期（全系统范围内保证唯一）将从线程被创建开始直到线程被终结。
@end quotation
@end cartouche

@ref{12f5,,可用性}: 需要 @ref{233,,get_native_id()} 函数。


3.8 新版功能.

@end deffn

@geindex is_alive() (threading.Thread 方法)
@anchor{library/threading threading Thread is_alive}@anchor{22f5}
@deffn {方法} is_alive ()

返回线程是否存活。

当 @ref{232,,run()} 方法刚开始直到 @ref{232,,run()} 方法刚结束，这个方法返回 @code{True} 。模块函数 @ref{22eb,,enumerate()} 返回包含所有存活线程的列表。
@end deffn

@geindex daemon (threading.Thread 属性)
@anchor{library/threading threading Thread daemon}@anchor{22f7}
@deffn {属性} daemon

一个表示这个线程是（True）否（False）守护线程的布尔值。一定要在调用 @ref{206e,,start()} 前设置好，不然会抛出 @ref{2ba,,RuntimeError} 。初始值继承于创建线程；主线程不是守护线程，因此主线程创建的所有线程默认都是 @ref{22f7,,daemon} = @code{False}。

当没有存活的非守护线程时，整个Python程序才会退出。
@end deffn

@geindex isDaemon() (threading.Thread 方法)
@geindex setDaemon() (threading.Thread 方法)
@anchor{library/threading threading Thread isDaemon}@anchor{22fa}
@deffn {方法} isDaemon ()
@anchor{library/threading threading Thread setDaemon}@anchor{22fb}
@deffnx {方法} setDaemon ()

旧的 @ref{22f6,,name} 取值/设值 API；建议直接当做特征属性使用它。
@end deffn
@end deffn

@strong{CPython implementation detail:} CPython下，因为 @ref{500,,Global Interpreter Lock}，一个时刻只有一个线程可以执行Python代码（尽管如此，某些性能导向的库可能会克服这个限制）。如果你想让你的应用更好的利用多核计算机的计算性能，推荐你使用 @ref{b7,,multiprocessing} 或者 @ref{2a3,,concurrent.futures.ProcessPoolExecutor} 。但是如果你想同时运行多个I/O绑定任务，线程仍然是一个合适的模型。

@node 锁对象,递归锁对象,线程对象,threading --- 基于线程的并行
@anchor{library/threading id2}@anchor{22fc}@anchor{library/threading lock-objects}@anchor{22fd}
@subsubsection 锁对象


原始锁是一个在锁定时不属于特定线程的同步基元组件。在Python中，它是能用的最低级的同步基元组件，由 @ref{3,,_thread}  扩展模块直接实现。

原始锁处于 "锁定" 或者 "非锁定" 两种状态之一。它被创建时为非锁定状态。它有两个基本方法， @ref{766,,acquire()} 和 @ref{22fe,,release()} 。当状态为非锁定时， @ref{766,,acquire()}  将状态改为 锁定 并立即返回。当状态是锁定时， @ref{766,,acquire()} 将阻塞至其他线程调用 @ref{22fe,,release()}  将其改为非锁定状态，然后 @ref{766,,acquire()} 调用重置其为锁定状态并返回。  @ref{22fe,,release()} 只在锁定状态下调用； 它将状态改为非锁定并立即返回。如果尝试释放一个非锁定的锁，则会引发 @ref{2ba,,RuntimeError}  异常。

锁同样支持 @ref{22ff,,上下文管理协议}。

当多个线程在 @ref{766,,acquire()} 等待状态转变为未锁定被阻塞，然后 @ref{22fe,,release()} 重置状态为未锁定时，只有一个线程能继续执行；至于哪个等待线程继续执行没有定义，并且会根据实现而不同。

所有方法的执行都是原子性的。

@geindex Lock (threading 中的类)
@anchor{library/threading threading Lock}@anchor{2300}
@deffn {类} threading.Lock

实现原始锁对象的类。一旦一个线程获得一个锁，会阻塞随后尝试获得锁的线程，直到它被释放；任何线程都可以释放它。

需要注意的是 @code{Lock} 其实是一个工厂函数，返回平台支持的具体锁类中最有效的版本的实例。

@geindex acquire() (threading.Lock 方法)
@anchor{library/threading threading Lock acquire}@anchor{766}
@deffn {方法} acquire (blocking=True, timeout=-1)

可以阻塞或非阻塞地获得锁。

当调用时参数 @emph{blocking} 设置为 @code{True} （缺省值），阻塞直到锁被释放，然后将锁锁定并返回 @code{True} 。

在参数 @emph{blocking} 被设置为 @code{False} 的情况下调用，将不会发生阻塞。如果调用时 @emph{blocking} 设为 @code{True} 会阻塞，并立即返回 @code{False} ；否则，将锁锁定并返回 @code{True}。

当浮点型 @emph{timeout} 参数被设置为正值调用时，只要无法获得锁，将最多阻塞 @emph{timeout} 设定的秒数。@emph{timeout} 参数被设置为  @code{-1} 时将无限等待。当 @emph{blocking} 为 false 时，@emph{timeout} 指定的值将被忽略。

如果成功获得锁，则返回 @code{True}，否则返回 @code{False} (例如发生 @emph{超时} 的时候)。


在 3.2 版更改: 新的 @emph{timeout} 形参。



在 3.2 版更改: 现在如果底层线程实现支持，则可以通过POSIX上的信号中断锁的获取。

@end deffn

@geindex release() (threading.Lock 方法)
@anchor{library/threading threading Lock release}@anchor{22fe}
@deffn {方法} release ()

释放一个锁。这个方法可以在任何线程中调用，不单指获得锁的线程。

当锁被锁定，将它重置为未锁定，并返回。如果其他线程正在等待这个锁解锁而被阻塞，只允许其中一个允许。

在未锁定的锁调用时，会引发 @ref{2ba,,RuntimeError} 异常。

没有返回值。
@end deffn

@geindex locked() (threading.Lock 方法)
@anchor{library/threading threading Lock locked}@anchor{2301}
@deffn {方法} locked ()

如果获得了锁则返回真值。
@end deffn
@end deffn

@node 递归锁对象,条件对象,锁对象,threading --- 基于线程的并行
@anchor{library/threading id3}@anchor{2302}@anchor{library/threading rlock-objects}@anchor{2303}
@subsubsection 递归锁对象


重入锁是一个可以被同一个线程多次获取的同步基元组件。在内部，它在基元锁的锁定/非锁定状态上附加了 "所属线程" 和 "递归等级" 的概念。在锁定状态下，某些线程拥有锁 ； 在非锁定状态下， 没有线程拥有它。

若要锁定锁，线程调用其 @ref{767,,acquire()} 方法；一旦线程拥有了锁，方法将返回。若要解锁，线程调用 @ref{22fe,,release()} 方法。 @ref{766,,acquire()}/@ref{22fe,,release()} 对可以嵌套；只有最终 @ref{22fe,,release()} (最外面一对的 @ref{22fe,,release()} ) 将锁解开，才能让其他线程继续处理 @ref{766,,acquire()} 阻塞。

递归锁也支持 @ref{22ff,,上下文管理协议}。

@geindex RLock (threading 中的类)
@anchor{library/threading threading RLock}@anchor{be8}
@deffn {类} threading.RLock

此类实现了重入锁对象。重入锁必须由获取它的线程释放。一旦线程获得了重入锁，同一个线程再次获取它将不阻塞；线程必须在每次获取它时释放一次。

需要注意的是 @code{RLock} 其实是一个工厂函数，返回平台支持的具体递归锁类中最有效的版本的实例。

@geindex acquire() (threading.RLock 方法)
@anchor{library/threading threading RLock acquire}@anchor{767}
@deffn {方法} acquire (blocking=True, timeout=-1)

可以阻塞或非阻塞地获得锁。

当无参数调用时： 如果这个线程已经拥有锁，递归级别增加一，并立即返回。否则，如果其他线程拥有该锁，则阻塞至该锁解锁。一旦锁被解锁(不属于任何线程)，则抢夺所有权，设置递归等级为一，并返回。如果多个线程被阻塞，等待锁被解锁，一次只有一个线程能抢到锁的所有权。在这种情况下，没有返回值。

当发起调用时将 @emph{blocking} 参数设为真值，则执行与无参数调用时一样的操作，然后返回 @code{True}。

当发起调用时将 @emph{blocking} 参数设为假值，则不进行阻塞。 如果一个无参数调用将要阻塞，则立即返回 @code{False}；在其他情况下，执行与无参数调用时一样的操作，然后返回 @code{True}。

当发起调用时将浮点数的 @emph{timeout} 参数设为正值时，只要无法获得锁，将最多阻塞 @emph{timeout} 所指定的秒数。 如果已经获得锁则返回 @code{True}，如果超时则返回假值。


在 3.2 版更改: 新的 @emph{timeout} 形参。

@end deffn

@geindex release() (threading.RLock 方法)
@anchor{library/threading threading RLock release}@anchor{2304}
@deffn {方法} release ()

释放锁，自减递归等级。如果减到零，则将锁重置为非锁定状态(不被任何线程拥有)，并且，如果其他线程正被阻塞着等待锁被解锁，则仅允许其中一个线程继续。如果自减后，递归等级仍然不是零，则锁保持锁定，仍由调用线程拥有。

只有当前线程拥有锁才能调用这个方法。如果锁被释放后调用这个方法，会引起 @ref{2ba,,RuntimeError} 异常。

没有返回值。
@end deffn
@end deffn

@node 条件对象,信号量对象,递归锁对象,threading --- 基于线程的并行
@anchor{library/threading condition-objects}@anchor{2305}@anchor{library/threading id4}@anchor{2306}
@subsubsection 条件对象


条件变量总是与某种类型的锁对象相关联，锁对象可以通过传入获得，或者在缺省的情况下自动创建。当多个条件变量需要共享同一个锁时，传入一个锁很有用。锁是条件对象的一部分，你不必单独地跟踪它。

条件变量服从 @ref{22ff,,上下文管理协议}：使用 @code{with} 语句会在它包围的代码块内获取关联的锁。 @ref{2307,,acquire()} 和 @ref{2308,,release()} 方法也能调用关联锁的相关方法。

其它方法必须在持有关联的锁的情况下调用。 @ref{22f1,,wait()} 方法释放锁，然后阻塞直到其它线程调用 @ref{2309,,notify()} 方法或 @ref{230a,,notify_all()} 方法唤醒它。一旦被唤醒， @ref{22f1,,wait()} 方法重新获取锁并返回。它也可以指定超时时间。

The @ref{2309,,notify()} method wakes up one of the threads waiting for
the condition variable, if any are waiting.  The @ref{230a,,notify_all()}
method wakes up all threads waiting for the condition variable.

注意： @ref{2309,,notify()} 方法和 @ref{230a,,notify_all()} 方法并不会释放锁，这意味着被唤醒的线程不会立即从它们的 @ref{22f1,,wait()} 方法调用中返回，而是会在调用了 @ref{2309,,notify()} 方法或 @ref{230a,,notify_all()} 方法的线程最终放弃了锁的所有权后返回。

使用条件变量的典型编程风格是将锁用于同步某些共享状态的权限，那些对状态的某些特定改变感兴趣的线程，它们重复调用 @ref{22f1,,wait()} 方法，直到看到所期望的改变发生；而对于修改状态的线程，它们将当前状态改变为可能是等待者所期待的新状态后，调用 @ref{2309,,notify()} 方法或者 @ref{230a,,notify_all()} 方法。例如，下面的代码是一个通用的无限缓冲区容量的生产者-消费者情形：

@example
# Consume one item
with cv:
    while not an_item_is_available():
        cv.wait()
    get_an_available_item()

# Produce one item
with cv:
    make_an_item_available()
    cv.notify()
@end example

使用 @code{while} 循环检查所要求的条件成立与否是有必要的，因为 @ref{22f1,,wait()} 方法可能要经过不确定长度的时间后才会返回，而此时导致 @ref{2309,,notify()} 方法调用的那个条件可能已经不再成立。这是多线程编程所固有的问题。 @ref{230b,,wait_for()} 方法可自动化条件检查，并简化超时计算。

@example
# Consume an item
with cv:
    cv.wait_for(an_item_is_available)
    get_an_available_item()
@end example

选择 @ref{2309,,notify()} 还是 @ref{230a,,notify_all()} ，取决于一次状态改变是只能被一个还是能被多个等待线程所用。例如在一个典型的生产者-消费者情形中，添加一个项目到缓冲区只需唤醒一个消费者线程。

@geindex Condition (threading 中的类)
@anchor{library/threading threading Condition}@anchor{aa5}
@deffn {类} threading.Condition (lock=None)

实现条件变量对象的类。一个条件变量对象允许一个或多个线程在被其它线程所通知之前进行等待。

如果给出了非 @code{None} 的 @emph{lock} 参数，则它必须为 @ref{2300,,Lock} 或者 @ref{be8,,RLock} 对象，并且它将被用作底层锁。否则，将会创建新的 @ref{be8,,RLock} 对象，并将其用作底层锁。


在 3.3 版更改: 从工厂函数变为类。


@geindex acquire() (threading.Condition 方法)
@anchor{library/threading threading Condition acquire}@anchor{2307}
@deffn {方法} acquire (*args)

请求底层锁。此方法调用底层锁的相应方法，返回值是底层锁相应方法的返回值。
@end deffn

@geindex release() (threading.Condition 方法)
@anchor{library/threading threading Condition release}@anchor{2308}
@deffn {方法} release ()

释放底层锁。此方法调用底层锁的相应方法。没有返回值。
@end deffn

@geindex wait() (threading.Condition 方法)
@anchor{library/threading threading Condition wait}@anchor{22f1}
@deffn {方法} wait (timeout=None)

等待直到被通知或发生超时。如果线程在调用此方法时没有获得锁，将会引发 @ref{2ba,,RuntimeError} 异常。

这个方法释放底层锁，然后阻塞，直到在另外一个线程中调用同一个条件变量的 @ref{2309,,notify()} 或 @ref{230a,,notify_all()} 唤醒它，或者直到可选的超时发生。一旦被唤醒或者超时，它重新获得锁并返回。

当提供了 @emph{timeout} 参数且不是 @code{None} 时，它应该是一个浮点数，代表操作的超时时间，以秒为单位（可以为小数）。

当底层锁是个 @ref{be8,,RLock} ，不会使用它的 @ref{2308,,release()} 方法释放锁，因为当它被递归多次获取时，实际上可能无法解锁。相反，使用了 @ref{be8,,RLock} 类的内部接口，即使多次递归获取它也能解锁它。 然后，在重新获取锁时，使用另一个内部接口来恢复递归级别。

返回 @code{True} ，除非提供的 @emph{timeout} 过期，这种情况下返回 @code{False}。


在 3.2 版更改: 很明显，方法总是返回 @code{None}。

@end deffn

@geindex wait_for() (threading.Condition 方法)
@anchor{library/threading threading Condition wait_for}@anchor{230b}
@deffn {方法} wait_for (predicate, timeout=None)

等待，直到条件计算为真。 @emph{predicate} 应该是一个可调用对象而且它的返回值可被解释为一个布尔值。可以提供 @emph{timeout} 参数给出最大等待时间。

这个实用方法会重复地调用 @ref{22f1,,wait()} 直到满足判断式或者发生超时。返回值是判断式最后一个返回值，而且如果方法发生超时会返回 @code{False} 。

忽略超时功能，调用此方法大致相当于编写:

@example
while not predicate():
    cv.wait()
@end example

因此，规则同样适用于 @ref{22f1,,wait()} ：锁必须在被调用时保持获取，并在返回时重新获取。 随着锁定执行判断式。


3.2 新版功能.

@end deffn

@geindex notify() (threading.Condition 方法)
@anchor{library/threading threading Condition notify}@anchor{2309}
@deffn {方法} notify (n=1)

默认唤醒一个等待这个条件的线程。如果调用线程在没有获得锁的情况下调用这个方法，会引发 @ref{2ba,,RuntimeError} 异常。

这个方法唤醒最多 @emph{n} 个正在等待这个条件变量的线程；如果没有线程在等待，这是一个空操作。

当前实现中，如果至少有 @emph{n} 个线程正在等待，准确唤醒 @emph{n} 个线程。但是依赖这个行为并不安全。未来，优化的实现有时会唤醒超过 @emph{n} 个线程。

注意：被唤醒的线程实际上不会返回它调用的 @ref{22f1,,wait()} ，直到它可以重新获得锁。因为 @ref{2309,,notify()} 不会释放锁，只有它的调用者应该这样做。
@end deffn

@geindex notify_all() (threading.Condition 方法)
@anchor{library/threading threading Condition notify_all}@anchor{230a}
@deffn {方法} notify_all ()

唤醒所有正在等待这个条件的线程。这个方法行为与 @ref{2309,,notify()} 相似，但并不只唤醒单一线程，而是唤醒所有等待线程。如果调用线程在调用这个方法时没有获得锁，会引发 @ref{2ba,,RuntimeError} 异常。
@end deffn
@end deffn

@node 信号量对象,事件对象,条件对象,threading --- 基于线程的并行
@anchor{library/threading id5}@anchor{230c}@anchor{library/threading semaphore-objects}@anchor{230d}
@subsubsection 信号量对象


这是计算机科学史上最古老的同步原语之一，早期的荷兰科学家 Edsger W. Dijkstra 发明了它。（他使用名称 @code{P()} 和 @code{V()} 而不是 @ref{be5,,acquire()} 和 @ref{230e,,release()} ）。

一个信号量管理一个内部计数器，该计数器因 @ref{be5,,acquire()} 方法的调用而递减，因 @ref{230e,,release()} 方法的调用而递增。 计数器的值永远不会小于零；当 @ref{be5,,acquire()} 方法发现计数器为零时，将会阻塞，直到其它线程调用 @ref{230e,,release()} 方法。

信号量对象也支持 @ref{22ff,,上下文管理协议} 。

@geindex Semaphore (threading 中的类)
@anchor{library/threading threading Semaphore}@anchor{aa6}
@deffn {类} threading.Semaphore (value=1)

该类实现信号量对象。信号量对象管理一个原子性的计数器，代表 @ref{230e,,release()} 方法的调用次数减去 @ref{be5,,acquire()} 的调用次数再加上一个初始值。如果需要， @ref{be5,,acquire()} 方法将会阻塞直到可以返回而不会使得计数器变成负数。在没有显式给出 @emph{value} 的值时，默认为1。

可选参数 @emph{value} 赋予内部计数器初始值，默认值为 @code{1} 。如果 @emph{value} 被赋予小于0的值，将会引发 @ref{1fb,,ValueError} 异常。


在 3.3 版更改: 从工厂函数变为类。


@geindex acquire() (threading.Semaphore 方法)
@anchor{library/threading threading Semaphore acquire}@anchor{be5}
@deffn {方法} acquire (blocking=True, timeout=None)

获取一个信号量。

在不带参数的情况下调用时：


@itemize *

@item 
如果在进入时内部计数器的值大于零，则将其减一并立即返回 @code{True}。

@item 
如果在进入时内部计数器的值为零，则将会阻塞直到被对 @ref{230e,,release()} 的调用唤醒。 一旦被唤醒（并且计数器的值大于 0），则将计数器减 1 并返回 @code{True}。 每次对 @ref{230e,,release()} 的调用将只唤醒一个线程。 线程被唤醒的次序是不可确定的。
@end itemize

当发起调用时将 @emph{blocking} 设为假值，则不进行阻塞。 如果一个无参数调用将要阻塞，则立即返回 @code{False}；在其他情况下，执行与无参数调用时一样的操作，然后返回 @code{True}。

当发起调用时如果 @emph{timeout} 不为 @code{None}，则它将阻塞最多 @emph{timeout} 秒。 请求在此时段时未能成功完成获取则将返回 @code{False}。 在其他情况下返回 @code{True}。


在 3.2 版更改: 新的 @emph{timeout} 形参。

@end deffn

@geindex release() (threading.Semaphore 方法)
@anchor{library/threading threading Semaphore release}@anchor{230e}
@deffn {方法} release ()

释放一个信号量，将内部计数器的值增加1。当计数器原先的值为0且有其它线程正在等待它再次大于0时，唤醒正在等待的线程。
@end deffn
@end deffn

@geindex BoundedSemaphore (threading 中的类)
@anchor{library/threading threading BoundedSemaphore}@anchor{aa7}
@deffn {类} threading.BoundedSemaphore (value=1)

该类实现有界信号量。有界信号量通过检查以确保它当前的值不会超过初始值。如果超过了初始值，将会引发 @ref{1fb,,ValueError} 异常。在大多情况下，信号量用于保护数量有限的资源。如果信号量被释放的次数过多，则表明出现了错误。没有指定时， @emph{value} 的值默认为1。


在 3.3 版更改: 从工厂函数变为类。

@end deffn

@menu
* Semaphore 例子:: 

@end menu

@node Semaphore 例子,,,信号量对象
@anchor{library/threading semaphore-example}@anchor{230f}@anchor{library/threading semaphore-examples}@anchor{2310}
@subsubsection @code{Semaphore} 例子


信号量通常用于保护数量有限的资源，例如数据库服务器。在资源数量固定的任何情况下，都应该使用有界信号量。在生成任何工作线程前，应该在主线程中初始化信号量。

@example
maxconnections = 5
# ...
pool_sema = BoundedSemaphore(value=maxconnections)
@end example

工作线程生成后，当需要连接服务器时，这些线程将调用信号量的 acquire 和 release 方法：

@example
with pool_sema:
    conn = connectdb()
    try:
        # ... use connection ...
    finally:
        conn.close()
@end example

使用有界信号量能减少这种编程错误：信号量的释放次数多于其请求次数。

@node 事件对象,定时器对象,信号量对象,threading --- 基于线程的并行
@anchor{library/threading event-objects}@anchor{2311}@anchor{library/threading id6}@anchor{2312}
@subsubsection 事件对象


这是线程之间通信的最简单机制之一：一个线程发出事件信号，而其他线程等待该信号。

一个事件对象管理一个内部标志，调用 @ref{2313,,set()} 方法可将其设置为true，调用  @ref{2314,,clear()} 方法可将其设置为false，调用 @ref{cb0,,wait()} 方法将进入阻塞直到标志为true。

@geindex Event (threading 中的类)
@anchor{library/threading threading Event}@anchor{aa8}
@deffn {类} threading.Event

实现事件对象的类。事件对象管理一个内部标志，调用 @ref{2313,,set()} 方法可将其设置为true。调用  @ref{2314,,clear()} 方法可将其设置为false。调用 @ref{cb0,,wait()} 方法将进入阻塞直到标志为true。这个标志初始时为false。


在 3.3 版更改: 从工厂函数变为类。


@geindex is_set() (threading.Event 方法)
@anchor{library/threading threading Event is_set}@anchor{2315}
@deffn {方法} is_set ()

当且仅当内部旗标为时返回 @code{True}。
@end deffn

@geindex set() (threading.Event 方法)
@anchor{library/threading threading Event set}@anchor{2313}
@deffn {方法} set ()

将内部标志设置为true。所有正在等待这个事件的线程将被唤醒。当标志为true时，调用 @ref{cb0,,wait()} 方法的线程不会被被阻塞。
@end deffn

@geindex clear() (threading.Event 方法)
@anchor{library/threading threading Event clear}@anchor{2314}
@deffn {方法} clear ()

将内部标志设置为false。之后调用 @ref{cb0,,wait()} 方法的线程将会被阻塞，直到调用 @ref{2313,,set()} 方法将内部标志再次设置为true。
@end deffn

@geindex wait() (threading.Event 方法)
@anchor{library/threading threading Event wait}@anchor{cb0}
@deffn {方法} wait (timeout=None)

阻塞线程直到内部变量为true。如果调用时内部标志为true，将立即返回。否则将阻塞线程，直到调用 @ref{2313,,set()} 方法将标志设置为true或者发生可选的超时。

当提供了timeout参数且不是 @code{None} 时，它应该是一个浮点数，代表操作的超时时间，以秒为单位（可以为小数）。

当且仅当内部旗标在等待调用之前或者等待开始之后被设为真值时此方法将返回 @code{True}，也就是说，它将总是返回 @code{True} 除非设定了超时且操作发生了超时。


在 3.1 版更改: 很明显，方法总是返回 @code{None}。

@end deffn
@end deffn

@node 定时器对象,栅栏对象,事件对象,threading --- 基于线程的并行
@anchor{library/threading id7}@anchor{2316}@anchor{library/threading timer-objects}@anchor{2317}
@subsubsection 定时器对象


此类表示一个操作应该在等待一定的时间之后运行 --- 相当于一个定时器。 @ref{aa9,,Timer} 类是 @ref{234,,Thread} 类的子类，因此可以像一个自定义线程一样工作。

与线程一样，通过调用 @code{start()} 方法启动定时器。而 @ref{2318,,cancel()} 方法可以停止计时器（在计时结束前）， 定时器在执行其操作之前等待的时间间隔可能与用户指定的时间间隔不完全相同。

例如

@example
def hello():
    print("hello, world")

t = Timer(30.0, hello)
t.start()  # after 30 seconds, "hello, world" will be printed
@end example

@geindex Timer (threading 中的类)
@anchor{library/threading threading Timer}@anchor{aa9}
@deffn {类} threading.Timer (interval, function, args=None, kwargs=None)

创建一个定时器，在经过 @emph{interval} 秒的间隔事件后，将会用参数 @emph{args} 和关键字参数 @emph{kwargs} 调用 @emph{function}。如果 @emph{args} 为 @code{None} （默认值），则会使用一个空列表。如果 @emph{kwargs} 为 @code{None} （默认值），则会使用一个空字典。


在 3.3 版更改: 从工厂函数变为类。


@geindex cancel() (threading.Timer 方法)
@anchor{library/threading threading Timer cancel}@anchor{2318}
@deffn {方法} cancel ()

停止定时器并取消执行计时器将要执行的操作。仅当计时器仍处于等待状态时有效。
@end deffn
@end deffn

@node 栅栏对象,在 with 语句中使用锁、条件和信号量,定时器对象,threading --- 基于线程的并行
@anchor{library/threading barrier-objects}@anchor{2319}
@subsubsection 栅栏对象



3.2 新版功能.


栅栏类提供一个简单的同步原语，用于应对固定数量的线程需要彼此相互等待的情况。线程调用 @ref{231a,,wait()} 方法后将阻塞，直到所有线程都调用了 @ref{231a,,wait()} 方法。此时所有线程将被同时释放。

栅栏对象可以被多次使用，但进程的数量不能改变。

这是一个使用简便的方法实现客户端进程与服务端进程同步的例子：

@example
b = Barrier(2, timeout=5)

def server():
    start_server()
    b.wait()
    while True:
        connection = accept_connection()
        process_server_connection(connection)

def client():
    b.wait()
    while True:
        connection = make_connection()
        process_client_connection(connection)
@end example

@geindex Barrier (threading 中的类)
@anchor{library/threading threading Barrier}@anchor{b58}
@deffn {类} threading.Barrier (parties, action=None, timeout=None)

创建一个需要 @emph{parties} 个线程的栅栏对象。如果提供了可调用的 @emph{action} 参数，它会在所有线程被释放时在其中一个线程中自动调用。 @emph{timeout} 是默认的超时时间，如果没有在 @ref{231a,,wait()} 方法中指定超时时间的话。

@geindex wait() (threading.Barrier 方法)
@anchor{library/threading threading Barrier wait}@anchor{231a}
@deffn {方法} wait (timeout=None)

冲出栅栏。当栅栏中所有线程都已经调用了这个函数，它们将同时被释放。如果提供了 @emph{timeout} 参数，这里的 @emph{timeout} 参数优先于创建栅栏对象时提供的 @emph{timeout} 参数。

函数返回值是一个整数，取值范围在0到 @emph{parties} -- 1，在每个线程中的返回值不相同。可用于从所有线程中选择唯一的一个线程执行一些特别的工作。例如：

@example
i = barrier.wait()
if i == 0:
    # Only one thread needs to print this
    print("passed the barrier")
@end example

如果创建栅栏对象时在构造函数中提供了 @emph{action} 参数，它将在其中一个线程释放前被调用。如果此调用引发了异常，栅栏对象将进入损坏态。

如果发生了超时，栅栏对象将进入破损态。

如果栅栏对象进入破损态，或重置栅栏时仍有线程等待释放，将会引发 @ref{b5a,,BrokenBarrierError} 异常。
@end deffn

@geindex reset() (threading.Barrier 方法)
@anchor{library/threading threading Barrier reset}@anchor{231b}
@deffn {方法} reset ()

重置栅栏为默认的初始态。如果栅栏中仍有线程等待释放，这些线程将会收到 @ref{b5a,,BrokenBarrierError} 异常。

请注意使用此函数时，如果存在状态未知的其他线程，则可能需要执行外部同步。 如果栅栏已损坏则最好将其废弃并新建一个。
@end deffn

@geindex abort() (threading.Barrier 方法)
@anchor{library/threading threading Barrier abort}@anchor{231c}
@deffn {方法} abort ()

使栅栏处于损坏状态。 这将导致任何现有和未来对 @ref{231a,,wait()} 的调用失败并引发 @ref{b5a,,BrokenBarrierError}。 例如可以在需要中止某个线程时使用此方法，以避免应用程序的死锁。

更好的方式是：创建栅栏时提供一个合理的超时时间，来自动避免某个线程出错。
@end deffn

@geindex parties (threading.Barrier 属性)
@anchor{library/threading threading Barrier parties}@anchor{231d}
@deffn {属性} parties

冲出栅栏所需要的线程数量。
@end deffn

@geindex n_waiting (threading.Barrier 属性)
@anchor{library/threading threading Barrier n_waiting}@anchor{231e}
@deffn {属性} n_waiting

当前时刻正在栅栏中阻塞的线程数量。
@end deffn

@geindex broken (threading.Barrier 属性)
@anchor{library/threading threading Barrier broken}@anchor{231f}
@deffn {属性} broken

一个布尔值，值为 @code{True} 表明栅栏为破损态。
@end deffn
@end deffn

@geindex BrokenBarrierError
@anchor{library/threading threading BrokenBarrierError}@anchor{b5a}
@deffn {例外} threading.BrokenBarrierError

异常类，是 @ref{2ba,,RuntimeError} 异常的子类，在 @ref{b58,,Barrier} 对象重置时仍有线程阻塞时和对象进入破损态时被引发。
@end deffn

@node 在 with 语句中使用锁、条件和信号量,,栅栏对象,threading --- 基于线程的并行
@anchor{library/threading using-locks-conditions-and-semaphores-in-the-with-statement}@anchor{2320}@anchor{library/threading with-locks}@anchor{22ff}
@subsubsection 在 @code{with} 语句中使用锁、条件和信号量


这个模块提供的带有 @code{acquire()} 和 @code{release()} 方法的对象，可以被用作 @ref{6e3,,with} 语句的上下文管理器。当进入语句块时 @code{acquire()} 方法会被调用，退出语句块时 @code{release()} 会被调用。因此，以下片段:

@example
with some_lock:
    # do something...
@end example

相当于:

@example
some_lock.acquire()
try:
    # do something...
finally:
    some_lock.release()
@end example

现在 @ref{2300,,Lock} 、 @ref{be8,,RLock} 、 @ref{aa5,,Condition} 、 @ref{aa6,,Semaphore} 和 @ref{aa7,,BoundedSemaphore} 对象可以用作 @ref{6e3,,with} 语句的上下文管理器。

@node multiprocessing --- 基于进程的并行,multiprocessing shared_memory --- 可从进程直接访问的共享内存,threading --- 基于线程的并行,并发执行
@anchor{library/multiprocessing doc}@anchor{2321}@anchor{library/multiprocessing module-multiprocessing}@anchor{b7}@anchor{library/multiprocessing multiprocessing-process-based-parallelism}@anchor{2322}
@subsection @code{multiprocessing} --- 基于进程的并行


@geindex multiprocessing (模块)

@strong{源代码} Lib/multiprocessing/@footnote{https://github.com/python/cpython/tree/3.8/Lib/multiprocessing/}


__________________________________________________________________


@menu
* 概述: 概述<9>. 
* 参考:: 
* 编程指导:: 
* 例子: 例子<10>. 

@end menu

@node 概述<9>,参考,,multiprocessing --- 基于进程的并行
@anchor{library/multiprocessing introduction}@anchor{2323}
@subsubsection 概述


@ref{b7,,multiprocessing} 是一个用于产生进程的包，具有与 @ref{109,,threading} 模块相似API。 @ref{b7,,multiprocessing} 包同时提供本地和远程并发，使用子进程代替线程，有效避免 @ref{500,,Global Interpreter Lock} 带来的影响。因此， @ref{b7,,multiprocessing} 模块允许程序员充分利用机器上的多核。可运行于 Unix 和 Windows 。

@ref{b7,,multiprocessing} 模块还引入了在 @ref{109,,threading} 模块中没有的API。一个主要的例子就是 @ref{875,,Pool} 对象，它提供了一种快捷的方法，赋予函数并行化处理一系列输入值的能力，可以将输入数据分配给不同进程处理（数据并行）。下面的例子演示了在模块中定义此类函数的常见做法，以便子进程可以成功导入该模块。这个数据并行的基本例子使用了 @ref{875,,Pool} ，

@example
from multiprocessing import Pool

def f(x):
    return x*x

if __name__ == '__main__':
    with Pool(5) as p:
        print(p.map(f, [1, 2, 3]))
@end example

将在标准输出中打印

@example
[1, 4, 9]
@end example

@menu
* Process 类:: 
* 上下文和启动方法:: 
* 在进程之间交换对象:: 
* 进程间同步:: 
* 进程间共享状态:: 
* 使用工作进程:: 

@end menu

@node Process 类,上下文和启动方法,,概述<9>
@anchor{library/multiprocessing the-process-class}@anchor{2324}
@subsubsection @code{Process} 类


在 @ref{b7,,multiprocessing} 中，通过创建一个 @ref{3aa,,Process} 对象然后调用它的 @code{start()} 方法来生成进程。 @ref{3aa,,Process} 和 @ref{234,,threading.Thread} API 相同。 一个简单的多进程程序示例是:

@example
from multiprocessing import Process

def f(name):
    print('hello', name)

if __name__ == '__main__':
    p = Process(target=f, args=('bob',))
    p.start()
    p.join()
@end example

要显示所涉及的各个进程ID，这是一个扩展示例:

@example
from multiprocessing import Process
import os

def info(title):
    print(title)
    print('module name:', __name__)
    print('parent process:', os.getppid())
    print('process id:', os.getpid())

def f(name):
    info('function f')
    print('hello', name)

if __name__ == '__main__':
    info('main line')
    p = Process(target=f, args=('bob',))
    p.start()
    p.join()
@end example

关于为什么 @code{if __name__ == '__main__'} 部分是必需的解释，请参见 @ref{2325,,编程指导}。

@node 上下文和启动方法,在进程之间交换对象,Process 类,概述<9>
@anchor{library/multiprocessing contexts-and-start-methods}@anchor{2326}
@subsubsection 上下文和启动方法

@anchor{library/multiprocessing multiprocessing-start-methods}@anchor{870}
根据不同的平台， @ref{b7,,multiprocessing} 支持三种启动进程的方法。这些 @emph{启动方法} 有

@quotation


@table @asis

@item @emph{spawn}

父进程启动一个新的Python解释器进程。子进程只会继承那些运行进程对象的 @ref{2327,,run()} 方法所需的资源。特别是父进程中非必须的文件描述符和句柄不会被继承。相对于使用 @emph{fork} 或者 @emph{forkserver}，使用这个方法启动进程相当慢。

可在Unix和Windows上使用。 Windows上的默认设置。

@item @emph{fork}

父进程使用 @ref{95b,,os.fork()} 来产生 Python 解释器分叉。子进程在开始时实际上与父进程相同。父进程的所有资源都由子进程继承。请注意，安全分叉多线程进程是棘手的。

只存在于Unix。Unix中的默认值。

@item @emph{forkserver}

程序启动并选择* forkserver * 启动方法时，将启动服务器进程。从那时起，每当需要一个新进程时，父进程就会连接到服务器并请求它分叉一个新进程。分叉服务器进程是单线程的，因此使用 @ref{95b,,os.fork()}  是安全的。没有不必要的资源被继承。

可在Unix平台上使用，支持通过Unix管道传递文件描述符。
@end table
@end quotation


在 3.8 版更改: 对于 macOS，@emph{spawn} 启动方式是默认方式。 因为 @emph{fork} 可能导致subprocess崩溃，被认为是不安全的，查看 bpo-33725@footnote{https://bugs.python.org/issue33725} 。



在 3.4 版更改: 在所有unix平台上添加支持了 @emph{spawn} ，并且为一些unix平台添加了 @emph{forkserver} 。在Windows上子进程不再继承所有可继承的父进程句柄。


在 Unix 上通过 @emph{spawn} 和 @emph{forkserver} 方式启动多进程会同时启动一个 @emph{资源追踪} 进程，负责追踪当前程序的进程产生的、并且不再被使用的命名系统资源(如命名信号量以及 @ref{2328,,SharedMemory}  对象)。当所有进程退出后，资源追踪会负责释放这些仍被追踪的的对象。通常情况下是不会有这种对象的，但是假如一个子进程被某个信号杀死，就可能存在这一类资源的“泄露”情况。（泄露的信号量以及共享内存不会被释放，直到下一次系统重启，对于这两类资源来说，这是一个比较大的问题，因为操作系统允许的命名信号量的数量是有限的，而共享内存也会占据主内存的一片空间）

要选择一个启动方法，你应该在主模块的 @code{if __name__ == '__main__'} 子句中调用 @ref{873,,set_start_method()} 。例如：

@example
import multiprocessing as mp

def foo(q):
    q.put('hello')

if __name__ == '__main__':
    mp.set_start_method('spawn')
    q = mp.Queue()
    p = mp.Process(target=foo, args=(q,))
    p.start()
    print(q.get())
    p.join()
@end example

在程序中 @ref{873,,set_start_method()} 不应该被多次调用。

或者，你可以使用 @ref{874,,get_context()} 来获取上下文对象。上下文对象与 multiprocessing 模块具有相同的API，并允许在同一程序中使用多种启动方法。:

@example
import multiprocessing as mp

def foo(q):
    q.put('hello')

if __name__ == '__main__':
    ctx = mp.get_context('spawn')
    q = ctx.Queue()
    p = ctx.Process(target=foo, args=(q,))
    p.start()
    print(q.get())
    p.join()
@end example

请注意，关联到不同上下文的对象和进程之前可能不兼容。特别是，使用 @emph{fork} 上下文创建的锁不能传递给使用 @emph{spawn} 或 @emph{forkserver} 启动方法启动的进程。

想要使用特定启动方法的库应该使用 @ref{874,,get_context()} 以避免干扰库用户的选择。

@cartouche
@quotation 警告 
@code{'spawn'} 和 @code{'forkserver'} 启动方法当前不能在Unix上和“冻结的”可执行内容一同使用（例如，有类似 @strong{PyInstaller} 和 @strong{cx_Freeze} 的包产生的二进制文件）。 @code{'fork'} 启动方法可以使用。
@end quotation
@end cartouche

@node 在进程之间交换对象,进程间同步,上下文和启动方法,概述<9>
@anchor{library/multiprocessing exchanging-objects-between-processes}@anchor{2329}
@subsubsection 在进程之间交换对象


@ref{b7,,multiprocessing} 支持进程之间的两种通信通道：

@strong{队列}

@quotation

@ref{232a,,Queue} 类是一个近似 @ref{d11,,queue.Queue} 的克隆。 例如:

@example
from multiprocessing import Process, Queue

def f(q):
    q.put([42, None, 'hello'])

if __name__ == '__main__':
    q = Queue()
    p = Process(target=f, args=(q,))
    p.start()
    print(q.get())    # prints "[42, None, 'hello']"
    p.join()
@end example

队列是线程和进程安全的。
@end quotation

@strong{管道}

@quotation

@ref{232b,,Pipe()} 函数返回一个由管道连接的连接对象，默认情况下是双工（双向）。例如:

@example
from multiprocessing import Process, Pipe

def f(conn):
    conn.send([42, None, 'hello'])
    conn.close()

if __name__ == '__main__':
    parent_conn, child_conn = Pipe()
    p = Process(target=f, args=(child_conn,))
    p.start()
    print(parent_conn.recv())   # prints "[42, None, 'hello']"
    p.join()
@end example

返回的两个连接对象 @ref{232b,,Pipe()} 表示管道的两端。每个连接对象都有 @code{send()} 和 @code{recv()} 方法（相互之间的）。请注意，如果两个进程（或线程）同时尝试读取或写入管道的 @emph{同一} 端，则管道中的数据可能会损坏。当然，在不同进程中同时使用管道的不同端的情况下不存在损坏的风险。
@end quotation

@node 进程间同步,进程间共享状态,在进程之间交换对象,概述<9>
@anchor{library/multiprocessing synchronization-between-processes}@anchor{232c}
@subsubsection 进程间同步


@ref{b7,,multiprocessing} 包含来自 @ref{109,,threading} 的所有同步原语的等价物。例如，可以使用锁来确保一次只有一个进程打印到标准输出:

@example
from multiprocessing import Process, Lock

def f(l, i):
    l.acquire()
    try:
        print('hello world', i)
    finally:
        l.release()

if __name__ == '__main__':
    lock = Lock()

    for num in range(10):
        Process(target=f, args=(lock, num)).start()
@end example

不使用锁的情况下，来自于多进程的输出很容易产生混淆。

@node 进程间共享状态,使用工作进程,进程间同步,概述<9>
@anchor{library/multiprocessing sharing-state-between-processes}@anchor{232d}
@subsubsection 进程间共享状态


如上所述，在进行并发编程时，通常最好尽量避免使用共享状态。使用多个进程时尤其如此。

但是，如果你真的需要使用一些共享数据，那么 @ref{b7,,multiprocessing} 提供了两种方法。

@strong{共享内存}

@quotation

可以使用 @ref{232e,,Value} 或 @ref{232f,,Array} 将数据存储在共享内存映射中。例如，以下代码:

@example
from multiprocessing import Process, Value, Array

def f(n, a):
    n.value = 3.1415927
    for i in range(len(a)):
        a[i] = -a[i]

if __name__ == '__main__':
    num = Value('d', 0.0)
    arr = Array('i', range(10))

    p = Process(target=f, args=(num, arr))
    p.start()
    p.join()

    print(num.value)
    print(arr[:])
@end example

将打印

@example
3.1415927
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
@end example

创建 @code{num} 和 @code{arr} 时使用的 @code{'d'} 和 @code{'i'} 参数是 @ref{7,,array} 模块使用的类型的 typecode ： @code{'d'} 表示双精度浮点数， @code{'i'} 表示有符号整数。这些共享对象将是进程和线程安全的。

为了更灵活地使用共享内存，可以使用 @ref{bd,,multiprocessing.sharedctypes} 模块，该模块支持创建从共享内存分配的任意ctypes对象。
@end quotation

@strong{服务进程}

@quotation

由 @code{Manager()} 返回的管理器对象控制一个服务进程，该进程保存Python对象并允许其他进程使用代理操作它们。

@code{Manager()} 返回的管理器支持类型： @ref{262,,list} 、 @ref{1b8,,dict} 、 @ref{2330,,Namespace} 、 @ref{2331,,Lock} 、 @ref{2332,,RLock} 、 @ref{2333,,Semaphore} 、 @ref{2334,,BoundedSemaphore} 、 @ref{2335,,Condition} 、 @ref{2336,,Event} 、 @ref{2337,,Barrier} 、 @ref{232a,,Queue} 、 @ref{232e,,Value} 和 @ref{232f,,Array} 。例如

@example
from multiprocessing import Process, Manager

def f(d, l):
    d[1] = '1'
    d['2'] = 2
    d[0.25] = None
    l.reverse()

if __name__ == '__main__':
    with Manager() as manager:
        d = manager.dict()
        l = manager.list(range(10))

        p = Process(target=f, args=(d, l))
        p.start()
        p.join()

        print(d)
        print(l)
@end example

将打印

@example
@{0.25: None, 1: '1', '2': 2@}
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
@end example

使用服务进程的管理器比使用共享内存对象更灵活，因为它们可以支持任意对象类型。此外，单个管理器可以通过网络由不同计算机上的进程共享。但是，它们比使用共享内存慢。
@end quotation

@node 使用工作进程,,进程间共享状态,概述<9>
@anchor{library/multiprocessing using-a-pool-of-workers}@anchor{2338}
@subsubsection 使用工作进程


@ref{875,,Pool} 类表示一个工作进程池。它具有允许以几种不同方式将任务分配到工作进程的方法。

例如

@example
from multiprocessing import Pool, TimeoutError
import time
import os

def f(x):
    return x*x

if __name__ == '__main__':
    # start 4 worker processes
    with Pool(processes=4) as pool:

        # print "[0, 1, 4,..., 81]"
        print(pool.map(f, range(10)))

        # print same numbers in arbitrary order
        for i in pool.imap_unordered(f, range(10)):
            print(i)

        # evaluate "f(20)" asynchronously
        res = pool.apply_async(f, (20,))      # runs in *only* one process
        print(res.get(timeout=1))             # prints "400"

        # evaluate "os.getpid()" asynchronously
        res = pool.apply_async(os.getpid, ()) # runs in *only* one process
        print(res.get(timeout=1))             # prints the PID of that process

        # launching multiple evaluations asynchronously *may* use more processes
        multiple_results = [pool.apply_async(os.getpid, ()) for i in range(4)]
        print([res.get(timeout=1) for res in multiple_results])

        # make a single worker sleep for 10 secs
        res = pool.apply_async(time.sleep, (10,))
        try:
            print(res.get(timeout=1))
        except TimeoutError:
            print("We lacked patience and got a multiprocessing.TimeoutError")

        print("For the moment, the pool remains available for more work")

    # exiting the 'with'-block has stopped the pool
    print("Now the pool is closed and no longer available")
@end example

请注意，进程池的方法只能由创建它的进程使用。

@cartouche
@quotation 注解 
这个包中的功能要求子进程可以导入 @code{__main__} 模块。虽然这在 @ref{2325,,编程指导} 中有描述，但还是需要提前说明一下。这意味着一些示例在交互式解释器中不起作用，比如 @ref{875,,multiprocessing.pool.Pool} 示例。例如:

@example
>>> from multiprocessing import Pool
>>> p = Pool(5)
>>> def f(x):
...     return x*x
...
>>> with p:
...   p.map(f, [1,2,3])
Process PoolWorker-1:
Process PoolWorker-2:
Process PoolWorker-3:
Traceback (most recent call last):
Traceback (most recent call last):
Traceback (most recent call last):
AttributeError: 'module' object has no attribute 'f'
AttributeError: 'module' object has no attribute 'f'
AttributeError: 'module' object has no attribute 'f'
@end example

（如果尝试执行上面的代码，它会以一种半随机的方式将三个完整的堆栈内容交替输出，然后你只能以某种方式停止父进程。)
@end quotation
@end cartouche

@node 参考,编程指导,概述<9>,multiprocessing --- 基于进程的并行
@anchor{library/multiprocessing reference}@anchor{2339}
@subsubsection 参考


@ref{b7,,multiprocessing} 包主要复制了 @ref{109,,threading} 模块的API。

@menu
* Process 和异常:: 
* 管道和队列:: 
* 杂项: 杂项<3>. 
* 连接对象（Connection）: 连接对象（Connection）<2>. 
* 同步原语:: 
* 共享 ctypes 对象:: 
* 管理器:: 
* 代理对象:: 
* 进程池:: 
* 监听者及客户端:: 
* 认证密码:: 
* 日志记录: 日志记录<2>. 
* multiprocessing.dummy 模块: multiprocessing dummy 模块. 

@end menu

@node Process 和异常,管道和队列,,参考
@anchor{library/multiprocessing process-and-exceptions}@anchor{233a}
@subsubsection @code{Process} 和异常


@geindex Process (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing Process}@anchor{3aa}
@deffn {类} multiprocessing.Process (group=None, target=None, name=None, args=(), kwargs=@{@}, *, daemon=None)

进程对象表示在单独进程中运行的活动。 @ref{3aa,,Process} 类拥有和 @ref{234,,threading.Thread} 等价的大部分方法。

应始终使用关键字参数调用构造函数。 @emph{group} 应该始终是 @code{None} ；它仅用于兼容 @ref{234,,threading.Thread} 。 @emph{target} 是由 @ref{2327,,run()} 方法调用的可调用对象。它默认为 @code{None} ，意味着什么都没有被调用。 @emph{name} 是进程名称（有关详细信息，请参阅 @ref{233b,,name} ）。 @emph{args} 是目标调用的参数元组。 @emph{kwargs} 是目标调用的关键字参数字典。如果提供，则键参数 @emph{daemon} 将进程 @ref{233c,,daemon} 标志设置为 @code{True} 或 @code{False} 。如果是 @code{None} （默认值），则该标志将从创建的进程继承。

默认情况下，不会将任何参数传递给 @emph{target} 。

如果子类重写构造函数，它必须确保它在对进程执行任何其他操作之前调用基类构造函数（ @code{Process.__init__()} ）。


在 3.3 版更改: 加入 @emph{daemon} 参数。


@geindex run() (multiprocessing.Process 方法)
@anchor{library/multiprocessing multiprocessing Process run}@anchor{2327}
@deffn {方法} run ()

表示进程活动的方法。

你可以在子类中重载此方法。标准 @ref{2327,,run()} 方法调用传递给对象构造函数的可调用对象作为目标参数（如果有），分别从 @emph{args} 和 @emph{kwargs} 参数中获取顺序和关键字参数。
@end deffn

@geindex start() (multiprocessing.Process 方法)
@anchor{library/multiprocessing multiprocessing Process start}@anchor{233d}
@deffn {方法} start ()

启动进程活动。

这个方法每个进程对象最多只能调用一次。它会将对象的 @ref{2327,,run()} 方法安排在一个单独的进程中调用。
@end deffn

@geindex join() (multiprocessing.Process 方法)
@anchor{library/multiprocessing multiprocessing Process join}@anchor{233e}
@deffn {方法} join ([timeout])

如果可选参数 @emph{timeout} 是 @code{None} （默认值），则该方法将阻塞，直到调用 @ref{233e,,join()} 方法的进程终止。如果 @emph{timeout} 是一个正数，它最多会阻塞 @emph{timeout} 秒。请注意，如果进程终止或方法超时，则该方法返回 @code{None} 。检查进程的 @ref{233f,,exitcode} 以确定它是否终止。

一个进程可以被 join 多次。

进程无法join自身，因为这会导致死锁。尝试在启动进程之前join进程是错误的。
@end deffn

@geindex name (multiprocessing.Process 属性)
@anchor{library/multiprocessing multiprocessing Process name}@anchor{233b}
@deffn {属性} name

进程的名称。该名称是一个字符串，仅用于识别目的。它没有语义。可以为多个进程指定相同的名称。

初始名称由构造器设定。 如果没有为构造器提供显式名称，则会构造一个形式为 'Process-N@w{[1]}:N@w{[2]}:...:N@w{[k]}' 的名称，其中每个 N@w{[k]} 是其父亲的第 N 个孩子。
@end deffn

@geindex is_alive() (multiprocessing.Process 方法)
@anchor{library/multiprocessing multiprocessing Process is_alive}@anchor{2340}
@deffn {方法} is_alive ()

返回进程是否还活着。

粗略地说，从 @ref{233d,,start()} 方法返回到子进程终止之前，进程对象仍处于活动状态。
@end deffn

@geindex daemon (multiprocessing.Process 属性)
@anchor{library/multiprocessing multiprocessing Process daemon}@anchor{233c}
@deffn {属性} daemon

进程的守护标志，一个布尔值。这必须在 @ref{233d,,start()} 被调用之前设置。

初始值继承自创建进程。

当进程退出时，它会尝试终止其所有守护进程子进程。

请注意，不允许守护进程创建子进程。否则，守护进程会在子进程退出时终止其子进程。 另外，这些 @strong{不是} Unix守护进程或服务，它们是正常进程，如果非守护进程已经退出，它们将被终止（并且不被合并）。
@end deffn

除了 @ref{234,,threading.Thread} API ，@ref{3aa,,Process} 对象还支持以下属性和方法：

@geindex pid (multiprocessing.Process 属性)
@anchor{library/multiprocessing multiprocessing Process pid}@anchor{2341}
@deffn {属性} pid

返回进程ID。在生成该进程之前，这将是 @code{None} 。
@end deffn

@geindex exitcode (multiprocessing.Process 属性)
@anchor{library/multiprocessing multiprocessing Process exitcode}@anchor{233f}
@deffn {属性} exitcode

子进程的退出代码。如果进程尚未终止，这将是 @code{None} 。负值 @emph{-N} 表示子进程被信号 @emph{N} 终止。
@end deffn

@geindex authkey (multiprocessing.Process 属性)
@anchor{library/multiprocessing multiprocessing Process authkey}@anchor{2342}
@deffn {属性} authkey

进程的身份验证密钥（字节字符串）。

当 @ref{b7,,multiprocessing} 初始化时，主进程使用 @ref{4cb,,os.urandom()} 分配一个随机字符串。

当创建 @ref{3aa,,Process} 对象时，它将继承其父进程的身份验证密钥，尽管可以通过将 @ref{2342,,authkey} 设置为另一个字节字符串来更改。

参见 @ref{2343,,认证密码} 。
@end deffn

@geindex sentinel (multiprocessing.Process 属性)
@anchor{library/multiprocessing multiprocessing Process sentinel}@anchor{a20}
@deffn {属性} sentinel

系统对象的数字句柄，当进程结束时将变为 "ready" 。

如果要使用 @ref{a1f,,multiprocessing.connection.wait()} 一次等待多个事件，可以使用此值。否则调用 @ref{233e,,join()} 更简单。

在Windows上，这是一个操作系统句柄，可以与 @code{WaitForSingleObject} 和 @code{WaitForMultipleObjects} 系列API调用一起使用。在Unix上，这是一个文件描述符，可以使用来自 @ref{e5,,select} 模块的原语。


3.3 新版功能.

@end deffn

@geindex terminate() (multiprocessing.Process 方法)
@anchor{library/multiprocessing multiprocessing Process terminate}@anchor{2344}
@deffn {方法} terminate ()

终止进程。 在Unix上，这是使用 @code{SIGTERM} 信号完成的；在Windows上使用 @code{TerminateProcess()} 。 请注意，不会执行退出处理程序和finally子句等。

请注意，进程的后代进程将不会被终止 —— 它们将简单地变成孤立的。

@cartouche
@quotation 警告 
如果在关联进程使用管道或队列时使用此方法，则管道或队列可能会损坏，并可能无法被其他进程使用。类似地，如果进程已获得锁或信号量等，则终止它可能导致其他进程死锁。
@end quotation
@end cartouche
@end deffn

@geindex kill() (multiprocessing.Process 方法)
@anchor{library/multiprocessing multiprocessing Process kill}@anchor{3a9}
@deffn {方法} kill ()

与 @ref{2344,,terminate()} 相同，但在Unix上使用 @code{SIGKILL} 信号。


3.7 新版功能.

@end deffn

@geindex close() (multiprocessing.Process 方法)
@anchor{library/multiprocessing multiprocessing Process close}@anchor{3a8}
@deffn {方法} close ()

关闭 @ref{3aa,,Process} 对象，释放与之关联的所有资源。如果底层进程仍在运行，则会引发 @ref{1fb,,ValueError} 。一旦 @ref{3a8,,close()} 成功返回， @ref{3aa,,Process} 对象的大多数其他方法和属性将引发 @ref{1fb,,ValueError} 。


3.7 新版功能.

@end deffn

注意 @ref{233d,,start()} 、 @ref{233e,,join()} 、 @ref{2340,,is_alive()} 、 @ref{2344,,terminate()} 和 @ref{233f,,exitcode} 方法只能由创建进程对象的进程调用。

@ref{3aa,,Process} 一些方法的示例用法：

@example
 >>> import multiprocessing, time, signal
 >>> p = multiprocessing.Process(target=time.sleep, args=(1000,))
 >>> print(p, p.is_alive())
 <Process ... initial> False
 >>> p.start()
 >>> print(p, p.is_alive())
 <Process ... started> True
 >>> p.terminate()
 >>> time.sleep(0.1)
 >>> print(p, p.is_alive())
 <Process ... stopped exitcode=-SIGTERM> False
 >>> p.exitcode == -signal.SIGTERM
 True
@end example
@end deffn

@geindex ProcessError
@anchor{library/multiprocessing multiprocessing ProcessError}@anchor{2345}
@deffn {例外} multiprocessing.ProcessError

所有 @ref{b7,,multiprocessing} 异常的基类。
@end deffn

@geindex BufferTooShort
@anchor{library/multiprocessing multiprocessing BufferTooShort}@anchor{2346}
@deffn {例外} multiprocessing.BufferTooShort

当提供的缓冲区对象太小而无法读取消息时， @code{Connection.recv_bytes_into()} 引发的异常。

如果 @code{e} 是一个 @ref{2346,,BufferTooShort} 实例，那么 @code{e.args[0]} 将把消息作为字节字符串给出。
@end deffn

@geindex AuthenticationError
@anchor{library/multiprocessing multiprocessing AuthenticationError}@anchor{2347}
@deffn {例外} multiprocessing.AuthenticationError

出现身份验证错误时引发。
@end deffn

@geindex TimeoutError
@anchor{library/multiprocessing multiprocessing TimeoutError}@anchor{2348}
@deffn {例外} multiprocessing.TimeoutError

有超时的方法超时时引发。
@end deffn

@node 管道和队列,杂项<3>,Process 和异常,参考
@anchor{library/multiprocessing pipes-and-queues}@anchor{2349}
@subsubsection 管道和队列


使用多进程时，一般使用消息机制实现进程间通信，尽可能避免使用同步原语，例如锁。

消息机制包含： @ref{232b,,Pipe()} (可以用于在两个进程间传递消息)，以及队列(能够在多个生产者和消费者之间通信)。

The @ref{232a,,Queue}, @ref{234a,,SimpleQueue} and @ref{234b,,JoinableQueue} types
are multi-producer, multi-consumer @abbr{FIFO}
queues modelled on the @ref{d11,,queue.Queue} class in the
standard library.  They differ in that @ref{232a,,Queue} lacks the
@ref{234c,,task_done()} and @ref{234d,,join()} methods introduced
into Python 2.5's @ref{d11,,queue.Queue} class.

如果你使用了 @ref{234b,,JoinableQueue} ，那么你**必须**对每个已经移出队列的任务调用 @ref{234e,,JoinableQueue.task_done()} 。不然的话用于统计未完成任务的信号量最终会溢出并抛出异常。

另外还可以通过使用一个管理器对象创建一个共享队列，详见  @ref{234f,,管理器} 。

@cartouche
@quotation 注解 
@ref{b7,,multiprocessing} 使用了普通的 @ref{2350,,queue.Empty} 和 @ref{2351,,queue.Full} 异常去表示超时。 你需要从 @ref{da,,queue} 中导入它们，因为它们并不在 @ref{b7,,multiprocessing} 的命名空间中。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
当一个对象被放入一个队列中时，这个对象首先会被一个后台线程用pickle序列化，并将序列化后的数据通过一个底层管道的管道传递到队列中。这种做法会有点让人惊讶，但一般不会出现什么问题。如果它们确实妨碍了你，你可以使用一个由管理器 @ref{234f,,manager} 创建的队列替换它。


@enumerate 

@item 
将一个对象放入一个空队列后，可能需要极小的延迟，队列的方法 @ref{2352,,empty()}  才会返回  @ref{380,,False} 。而  @ref{2353,,get_nowait()} 可以不抛出 @ref{2350,,queue.Empty} 直接返回。

@item 
如果有多个进程同时将对象放入队列，那么在队列的另一端接受到的对象可能是无序的。但是由同一个进程放入的多个对象的顺序在另一端输出时总是一样的。
@end enumerate
@end quotation
@end cartouche

@cartouche
@quotation 警告 
如果一个进程在尝试使用 @ref{232a,,Queue} 期间被 @ref{2344,,Process.terminate()} 或 @ref{cec,,os.kill()} 调用终止了，那么队列中的数据很可能被破坏。 这可能导致其他进程在尝试使用该队列时发生异常。
@end quotation
@end cartouche

@cartouche
@quotation 警告 
正如刚才提到的，如果一个子进程将一些对象放进队列中 (并且它没有用  @ref{2354,,JoinableQueue.cancel_join_thread} 方法)，那么这个进程在所有缓冲区的对象被刷新进管道之前，是不会终止的。

这意味着，除非你确定所有放入队列中的对象都已经被消费了，否则如果你试图等待这个进程，你可能会陷入死锁中。相似地，如果该子进程不是后台进程，那么父进程可能在试图等待所有非后台进程退出时挂起。

注意用管理器创建的队列不存在这个问题，详见  @ref{2325,,编程指导} 。
@end quotation
@end cartouche

该 @ref{2355,,例子} 展示了如何使用队列实现进程间通信。

@geindex Pipe() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing Pipe}@anchor{232b}
@deffn {函数} multiprocessing.Pipe ([duplex])

返回一对 @code{Connection`对象  `@w{`}(conn1, conn2)`} ， 分别表示管道的两端。

如果 @emph{duplex} 被置为 @code{True} (默认值)，那么该管道是双向的。如果 @emph{duplex} 被置为 @code{False} ，那么该管道是单向的，即 @code{conn1} 只能用于接收消息，而  @code{conn2} 仅能用于发送消息。
@end deffn

@geindex Queue (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing Queue}@anchor{232a}
@deffn {类} multiprocessing.Queue ([maxsize])

返回一个使用一个管道和少量锁和信号量实现的共享队列实例。当一个进程将一个对象放进队列中时，一个写入线程会启动并将对象从缓冲区写入管道中。

一旦超时，将抛出标准库 @ref{da,,queue}  模块中常见的异常 @ref{2350,,queue.Empty} 和 @ref{2351,,queue.Full}。

除了 @ref{234c,,task_done()} 和 @ref{234d,,join()} 之外，@ref{232a,,Queue}  实现了标准库类 @ref{d11,,queue.Queue} 中所有的方法。

@geindex qsize() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue qsize}@anchor{2356}
@deffn {方法} qsize ()

返回队列的大致长度。由于多线程或者多进程的上下文，这个数字是不可靠的。

注意，在 Unix 平台上，例如 Mac OS X ，这个方法可能会抛出 @ref{609,,NotImplementedError}  异常，因为该平台没有实现 @code{sem_getvalue()} 。
@end deffn

@geindex empty() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue empty}@anchor{2352}
@deffn {方法} empty ()

如果队列是空的，返回 @code{True} ，反之返回 @code{False} 。 由于多线程或多进程的环境，该状态是不可靠的。
@end deffn

@geindex full() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue full}@anchor{2357}
@deffn {方法} full ()

如果队列是满的，返回 @code{True} ，反之返回 @code{False} 。 由于多线程或多进程的环境，该状态是不可靠的。
@end deffn

@geindex put() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue put}@anchor{fbf}
@deffn {方法} put (obj[, block[, timeout]])

将 obj 放入队列。如果可选参数 @emph{block} 是 @code{True} (默认值) 而且 @emph{timeout} 是 @code{None} (默认值), 将会阻塞当前进程，直到有空的缓冲槽。如果 @emph{timeout} 是正数，将会在阻塞了最多 @emph{timeout} 秒之后还是没有可用的缓冲槽时抛出 @ref{2351,,queue.Full}  异常。反之 (@emph{block} 是 @code{False} 时)，仅当有可用缓冲槽时才放入对象，否则抛出 @ref{2351,,queue.Full} 异常 (在这种情形下 @emph{timeout} 参数会被忽略)。


在 3.8 版更改: 如果队列已经关闭，会抛出  @ref{1fb,,ValueError}  而不是  @ref{fc1,,AssertionError} 。

@end deffn

@geindex put_nowait() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue put_nowait}@anchor{2358}
@deffn {方法} put_nowait (obj)

相当于 @code{put(obj, False)}。
@end deffn

@geindex get() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue get}@anchor{fc0}
@deffn {方法} get ([block[, timeout]])

从队列中取出并返回对象。如果可选参数 @emph{block} 是 @code{True} (默认值) 而且 @emph{timeout} 是 @code{None} (默认值), 将会阻塞当前进程，直到队列中出现可用的对象。如果 @emph{timeout} 是正数，将会在阻塞了最多 @emph{timeout} 秒之后还是没有可用的对象时抛出 @ref{2350,,queue.Empty} 异常。反之 (@emph{block} 是 @code{False} 时)，仅当有可用对象能够取出时返回，否则抛出 @ref{2350,,queue.Empty} 异常 (在这种情形下 @emph{timeout} 参数会被忽略)。


在 3.8 版更改: 如果队列已经关闭，会抛出 @ref{1fb,,ValueError} 而不是 @ref{1d3,,OSError} 。

@end deffn

@geindex get_nowait() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue get_nowait}@anchor{2353}
@deffn {方法} get_nowait ()

相当于 @code{get(False)} 。
@end deffn

@ref{232a,,multiprocessing.Queue} 类有一些在 @ref{d11,,queue.Queue} 类中没有出现的方法。这些方法在大多数情形下并不是必须的。

@geindex close() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue close}@anchor{2359}
@deffn {方法} close ()

指示当前进程将不会再往队列中放入对象。一旦所有缓冲区中的数据被写入管道之后，后台的线程会退出。这个方法在队列被gc回收时会自动调用。
@end deffn

@geindex join_thread() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue join_thread}@anchor{235a}
@deffn {方法} join_thread ()

等待后台线程。这个方法仅在调用了 @ref{2359,,close()} 方法之后可用。这会阻塞当前进程，直到后台线程退出，确保所有缓冲区中的数据都被写入管道中。

默认情况下，如果一个不是队列创建者的进程试图退出，它会尝试等待这个队列的后台线程。这个进程可以使用  @ref{2354,,cancel_join_thread()} 让  @ref{235a,,join_thread()} 方法什么都不做直接跳过。
@end deffn

@geindex cancel_join_thread() (multiprocessing.Queue 方法)
@anchor{library/multiprocessing multiprocessing Queue cancel_join_thread}@anchor{2354}
@deffn {方法} cancel_join_thread ()

防止 @ref{235a,,join_thread()} 方法阻塞当前进程。具体而言，这防止进程退出时自动等待后台线程退出。详见 @ref{235a,,join_thread()}。

可能这个方法称为”@code{allow_exit_without_flush()}“ 会更好。这有可能会导致正在排队进入队列的数据丢失，大多数情况下你不需要用到这个方法，仅当你不关心底层管道中可能丢失的数据，只是希望进程能够马上退出时使用。
@end deffn

@cartouche
@quotation 注解 
该类的功能依赖于宿主操作系统具有可用的共享信号量实现。否则该类将被禁用，任何试图实例化一个 @ref{232a,,Queue} 对象的操作都会抛出 @ref{32d,,ImportError} 异常，更多信息详见 bpo-3770@footnote{https://bugs.python.org/issue3770} 。后续说明的任何专用队列对象亦如此。
@end quotation
@end cartouche
@end deffn

@geindex SimpleQueue (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing SimpleQueue}@anchor{234a}
@deffn {类} multiprocessing.SimpleQueue

这是一个简化的 @ref{232a,,Queue} 类的实现，很像带锁的 @ref{232b,,Pipe} 。

@geindex empty() (multiprocessing.SimpleQueue 方法)
@anchor{library/multiprocessing multiprocessing SimpleQueue empty}@anchor{235b}
@deffn {方法} empty ()

如果队列为空返回 @code{True} ，否则返回 @code{False} 。
@end deffn

@geindex get() (multiprocessing.SimpleQueue 方法)
@anchor{library/multiprocessing multiprocessing SimpleQueue get}@anchor{235c}
@deffn {方法} get ()

从队列中移出并返回一个对象。
@end deffn

@geindex put() (multiprocessing.SimpleQueue 方法)
@anchor{library/multiprocessing multiprocessing SimpleQueue put}@anchor{235d}
@deffn {方法} put (item)

将  @emph{item} 放入队列。
@end deffn
@end deffn

@geindex JoinableQueue (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing JoinableQueue}@anchor{234b}
@deffn {类} multiprocessing.JoinableQueue ([maxsize])

@ref{234b,,JoinableQueue} 类是 @ref{232a,,Queue} 的子类，额外添加了 @ref{234e,,task_done()} 和 @ref{235e,,join()} 方法。

@geindex task_done() (multiprocessing.JoinableQueue 方法)
@anchor{library/multiprocessing multiprocessing JoinableQueue task_done}@anchor{234e}
@deffn {方法} task_done ()

指出之前进入队列的任务已经完成。由队列的消费者进程使用。对于每次调用  @ref{fc0,,get()}  获取的任务，执行完成后调用  @ref{234e,,task_done()}  告诉队列该任务已经处理完成。

如果 @ref{234d,,join()} 方法正在阻塞之中，该方法会在所有对象都被处理完的时候返回 (即对之前使用  @ref{fbf,,put()}  放进队列中的所有对象都已经返回了对应的  @ref{234e,,task_done()}  ) 。

如果被调用的次数多于放入队列中的项目数量，将引发 @ref{1fb,,ValueError} 异常 。
@end deffn

@geindex join() (multiprocessing.JoinableQueue 方法)
@anchor{library/multiprocessing multiprocessing JoinableQueue join}@anchor{235e}
@deffn {方法} join ()

阻塞至队列中所有的元素都被接收和处理完毕。

当条目添加到队列的时候，未完成任务的计数就会增加。每当消费者进程调用 @ref{234e,,task_done()} 表示这个条目已经被回收，该条目所有工作已经完成，未完成计数就会减少。当未完成计数降到零的时候， @code{join()} 阻塞被解除。
@end deffn
@end deffn

@node 杂项<3>,连接对象（Connection）<2>,管道和队列,参考
@anchor{library/multiprocessing miscellaneous}@anchor{235f}
@subsubsection 杂项


@geindex active_children() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing active_children}@anchor{2360}
@deffn {函数} multiprocessing.active_children ()

返回当前进程存活的子进程的列表。

调用该方法有“等待”已经结束的进程的副作用。
@end deffn

@geindex cpu_count() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing cpu_count}@anchor{87a}
@deffn {函数} multiprocessing.cpu_count ()

返回系统的CPU数量。

该数量不同于当前进程可以使用的CPU数量。可用的CPU数量可以由 @code{len(os.sched_getaffinity(0))} 方法获得。

可能引发 @ref{609,,NotImplementedError} 。


@subsubheading 参见


@ref{879,,os.cpu_count()}

@end deffn

@geindex current_process() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing current_process}@anchor{2361}
@deffn {函数} multiprocessing.current_process ()

返回与当前进程相对应的 @ref{3aa,,Process} 对象。

和 @ref{22ec,,threading.current_thread()} 相同。
@end deffn

@geindex parent_process() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing parent_process}@anchor{2362}
@deffn {函数} multiprocessing.parent_process ()

返回父进程  @ref{3aa,,Process}  对象，和父进程调用 @ref{2361,,current_process()} 返回的对象一样。如果一个进程已经是主进程， @code{parent_process} 会返回 @code{None}.


3.8 新版功能.

@end deffn

@geindex freeze_support() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing freeze_support}@anchor{2363}
@deffn {函数} multiprocessing.freeze_support ()

为使用了 @ref{b7,,multiprocessing}  的程序，提供冻结以产生 Windows 可执行文件的支持。(在 @strong{py2exe}, @strong{PyInstaller} 和 @strong{cx_Freeze} 上测试通过)

需要在 main 模块的 @code{if __name__ == '__main__'} 该行之后马上调用该函数。例如：

@example
from multiprocessing import Process, freeze_support

def f():
    print('hello world!')

if __name__ == '__main__':
    freeze_support()
    Process(target=f).start()
@end example

如果没有调用  @code{freeze_support()} 在尝试运行被冻结的可执行文件时会抛出 @ref{2ba,,RuntimeError} 异常。

对  @code{freeze_support()} 的调用在非 Windows 平台上是无效的。如果该模块在 Windows 平台的 Python 解释器中正常运行 (该程序没有被冻结)， 调用`@w{`}freeze_support()`@w{`} 也是无效的。
@end deffn

@geindex get_all_start_methods() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing get_all_start_methods}@anchor{871}
@deffn {函数} multiprocessing.get_all_start_methods ()

返回支持的启动方法的列表，该列表的首项即为默认选项。可能的启动方法有  @code{'fork'}, @code{'spawn'} 和`@w{`}'forkserver'@code{。在 Windows 中，只有  `@w{`}'spawn'} 是可用的。Unix平台总是支持`@w{`}'fork'`@w{`} 和`@w{`}'spawn'@code{，且 `@w{`}'fork'} 是默认值。


3.4 新版功能.

@end deffn

@geindex get_context() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing get_context}@anchor{874}
@deffn {函数} multiprocessing.get_context (method=None)

返回一个 Context 对象。该对象具有和 @ref{b7,,multiprocessing} 模块相同的API。

如果 @emph{method} 设置成  @code{None}  那么将返回默认上下文对象。否则  @emph{method}  应该是 @code{'fork'}, @code{'spawn'}, @code{'forkserver'} 。 如果指定的启动方法不存在，将抛出  @ref{1fb,,ValueError}  异常。


3.4 新版功能.

@end deffn

@geindex get_start_method() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing get_start_method}@anchor{872}
@deffn {函数} multiprocessing.get_start_method (allow_none=False)

返回启动进程时使用的启动方法名。

如果启动方法已经固定，并且   @emph{allow_none} 被设置成 False ，那么启动方法将被固定为默认的启动方法，并且返回其方法名。如果启动方法没有设定，并且 @emph{allow_none} 被设置成 True ，那么将返回  @code{None}  。

返回值将为   @code{'fork'}  ,  @code{'spawn'} ,  @code{'forkserver'}   或者   @code{None}  。  @code{'fork'`@w{`}是 Unix 的默认值，   `@w{`}'spawn'}  是 Windows 的默认值。


3.4 新版功能.

@end deffn

@geindex set_executable() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing set_executable}@anchor{2364}
@deffn {函数} multiprocessing.set_executable ()

设置在启动子进程时使用的 Python 解释器路径。 ( 默认使用  @ref{274,,sys.executable}  ) 嵌入式编程人员可能需要这样做：

@example
set_executable(os.path.join(sys.exec_prefix, 'pythonw.exe'))
@end example

以使他们可以创建子进程。


在 3.4 版更改: 现在在 Unix 平台上使用  @code{'spawn'} 启动方法时支持调用该方法。

@end deffn

@geindex set_start_method() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing set_start_method}@anchor{873}
@deffn {函数} multiprocessing.set_start_method (method)

设置启动子进程的方法。 @emph{method}  可以是  @code{'fork'} ,  @code{'spawn'}  或者 @code{'forkserver'}  。

注意这最多只能调用一次，并且需要藏在 main 模块中，由  @code{if __name__ == '__main__'} 保护着。


3.4 新版功能.

@end deffn

@cartouche
@quotation 注解 
@ref{b7,,multiprocessing}   并没有包含类似  @ref{22ea,,threading.active_count()} , @ref{22eb,,threading.enumerate()} ,  @ref{22ed,,threading.settrace()} , @ref{22ee,,threading.setprofile()}, @ref{aa9,,threading.Timer} ,  或者 @ref{228e,,threading.local}  的方法和类。
@end quotation
@end cartouche

@node 连接对象（Connection）<2>,同步原语,杂项<3>,参考
@anchor{library/multiprocessing connection-objects}@anchor{2365}
@subsubsection 连接对象（Connection）


Connection 对象允许收发可以序列化的对象或字符串。它们可以看作面向消息的连接套接字。

通常使用  @ref{232b,,Pipe}   创建 Connection 对象。详见 ：  @ref{2366,,监听者及客户端}.

@geindex Connection (multiprocessing.connection 中的类)
@anchor{library/multiprocessing multiprocessing connection Connection}@anchor{2367}
@deffn {类} multiprocessing.connection.Connection

@geindex send() (multiprocessing.connection.Connection 方法)
@anchor{library/multiprocessing multiprocessing connection Connection send}@anchor{2368}
@deffn {方法} send (obj)

将一个对象发送到连接的另一端，可以用  @ref{2369,,recv()}  读取。

发送的对象必须是可以序列化的，过大的对象 (  接近 32MiB+ ，这个值取决于操作系统 ) 有可能引发   @ref{1fb,,ValueError}   异常。
@end deffn

@geindex recv() (multiprocessing.connection.Connection 方法)
@anchor{library/multiprocessing multiprocessing connection Connection recv}@anchor{2369}
@deffn {方法} recv ()

返回一个由另一端使用 @ref{2368,,send()} 发送的对象。该方法会一直阻塞直到接收到对象。 如果对端关闭了连接或者没有东西可接收，将抛出   @ref{c65,,EOFError} 异常。
@end deffn

@geindex fileno() (multiprocessing.connection.Connection 方法)
@anchor{library/multiprocessing multiprocessing connection Connection fileno}@anchor{236a}
@deffn {方法} fileno ()

返回由连接对象使用的描述符或者句柄。
@end deffn

@geindex close() (multiprocessing.connection.Connection 方法)
@anchor{library/multiprocessing multiprocessing connection Connection close}@anchor{236b}
@deffn {方法} close ()

关闭连接对象。

当连接对象被垃圾回收时会自动调用。
@end deffn

@geindex poll() (multiprocessing.connection.Connection 方法)
@anchor{library/multiprocessing multiprocessing connection Connection poll}@anchor{236c}
@deffn {方法} poll ([timeout])

返回连接对象中是否有可以读取的数据。

如果未指定  @emph{timeout} ，此方法会马上返回。如果  @emph{timeout} 是一个数字，则指定了最大阻塞的秒数。如果  @emph{timeout} 是   @code{None}，那么将一直等待，不会超时。

注意通过使用  @ref{a1f,,multiprocessing.connection.wait()}   可以一次轮询多个连接对象。
@end deffn

@geindex send_bytes() (multiprocessing.connection.Connection 方法)
@anchor{library/multiprocessing multiprocessing connection Connection send_bytes}@anchor{236d}
@deffn {方法} send_bytes (buffer[, offset[, size]])

从一个  @ref{5e3,,bytes-like object} 对象中取出字节数组并作为一条完整消息发送。

如果由  @emph{offset}  给定了在 @emph{buffer} 中读取数据的位置。 如果给定了 @emph{size} ，那么将会从缓冲区中读取多个字节。 过大的缓冲区 ( 接近 32MiB+ ，此值依赖于操作系统 ) 有可能引发   @ref{1fb,,ValueError}  异常。
@end deffn

@geindex recv_bytes() (multiprocessing.connection.Connection 方法)
@anchor{library/multiprocessing multiprocessing connection Connection recv_bytes}@anchor{236e}
@deffn {方法} recv_bytes ([maxlength])

以字符串形式返回一条从连接对象另一端发送过来的字节数据。此方法在接收到数据前将一直阻塞。 如果连接对象被对端关闭或者没有数据可读取，将抛出  @ref{c65,,EOFError} 异常。

如果给定了  @emph{maxlength} 并且消息长于  @emph{maxlength} 那么将抛出 @ref{1d3,,OSError} 并且该连接对象将不再可读。


在 3.3 版更改: 曾经该函数抛出 @ref{98c,,IOError}  ，现在这是 @ref{1d3,,OSError} 的别名。

@end deffn

@geindex recv_bytes_into() (multiprocessing.connection.Connection 方法)
@anchor{library/multiprocessing multiprocessing connection Connection recv_bytes_into}@anchor{236f}
@deffn {方法} recv_bytes_into (buffer[, offset])

将一条完整的字节数据消息读入  @emph{buffer}  中并返回消息的字节数。 此方法在接收到数据前将一直阻塞。 如果连接对象被对端关闭或者没有数据可读取，将抛出  @ref{c65,,EOFError}  异常。

@emph{buffer} must be a writable @ref{5e3,,bytes-like object}.  If
@emph{offset} is given then the message will be written into the buffer from
that position.  Offset must be a non-negative integer less than the
length of @emph{buffer} (in bytes).

如果缓冲区太小，则将引发  @code{BufferTooShort}  异常，并且完整的消息将会存放在异常实例      @code{e}  的 @code{e.args[0]}  中。
@end deffn


在 3.3 版更改: 现在连接对象自身可以通过 @ref{2368,,Connection.send()}   和  @ref{2369,,Connection.recv()}  在进程之间传递。



3.3 新版功能: 连接对象现已支持上下文管理协议 -- 参见 see @ref{1420,,上下文管理器类型}  。 @ref{1675,,__enter__()}   返回连接对象，   @ref{1677,,__exit__()}   会调用  @ref{236b,,close()}  。

@end deffn

例如:

@example
>>> from multiprocessing import Pipe
>>> a, b = Pipe()
>>> a.send([1, 'hello', None])
>>> b.recv()
[1, 'hello', None]
>>> b.send_bytes(b'thank you')
>>> a.recv_bytes()
b'thank you'
>>> import array
>>> arr1 = array.array('i', range(5))
>>> arr2 = array.array('i', [0] * 10)
>>> a.send_bytes(arr1)
>>> count = b.recv_bytes_into(arr2)
>>> assert count == len(arr1) * arr1.itemsize
>>> arr2
array('i', [0, 1, 2, 3, 4, 0, 0, 0, 0, 0])
@end example

@cartouche
@quotation 警告 
@ref{2369,,Connection.recv()} 方法会自动解封它收到的数据，除非你能够信任发送消息的进程，否则此处可能有安全风险。

因此，  除非连接对象是由 @code{Pipe()} 产生的，否则你应该仅在使用了某种认证手段之后才使用 @ref{2369,,recv()} 和 @ref{2368,,send()} 方法。 参考 @ref{2343,,认证密码}。
@end quotation
@end cartouche

@cartouche
@quotation 警告 
如果一个进程在试图读写管道时被终止了，那么管道中的数据很可能是不完整的，因为此时可能无法确定消息的边界。
@end quotation
@end cartouche

@node 同步原语,共享 ctypes 对象,连接对象（Connection）<2>,参考
@anchor{library/multiprocessing synchronization-primitives}@anchor{2370}
@subsubsection 同步原语


通常来说同步原语在多进程环境中并不像它们在多线程环境中那么必要。参考  @ref{109,,threading} 模块的文档。

注意可以使用管理器对象创建同步原语，参考 @ref{234f,,管理器} 。

@geindex Barrier (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing Barrier}@anchor{2337}
@deffn {类} multiprocessing.Barrier (parties[, action[, timeout]])

类似  @ref{b58,,threading.Barrier} 的栅栏对象。


3.3 新版功能.

@end deffn

@geindex BoundedSemaphore (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing BoundedSemaphore}@anchor{2334}
@deffn {类} multiprocessing.BoundedSemaphore ([value])

非常类似 @ref{aa7,,threading.BoundedSemaphore}  的有界信号量对象。

一个小小的不同在于，它的  @code{acquire}  方法的第一个参数名是和  @ref{2371,,Lock.acquire()} 一样的 @emph{block} 。

@cartouche
@quotation 注解 
在 Mac OS X 平台上， 该对象于  @ref{2333,,Semaphore}  不同在于  @code{sem_getvalue()} 方法并没有在该平台上实现。
@end quotation
@end cartouche
@end deffn

@geindex Condition (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing Condition}@anchor{2335}
@deffn {类} multiprocessing.Condition ([lock])

条件变量：   @ref{aa5,,threading.Condition} 的别名。

指定的 @emph{lock} 参数应该是 @ref{b7,,multiprocessing}  模块中的   @ref{2331,,Lock}   或者  @ref{2332,,RLock} 对象。


在 3.3 版更改: 新增了 @ref{230b,,wait_for()}  方法。

@end deffn

@geindex Event (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing Event}@anchor{2336}
@deffn {类} multiprocessing.Event

A clone of @ref{aa8,,threading.Event}.
@end deffn

@geindex Lock (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing Lock}@anchor{2331}
@deffn {类} multiprocessing.Lock

原始锁（非递归锁）对象，类似于   @ref{2300,,threading.Lock}  。一旦一个进程或者线程拿到了锁，后续的任何其他进程或线程的其他请求都会被阻塞直到锁被释放。任何进程或线程都可以释放锁。除非另有说明，否则 @ref{2331,,multiprocessing.Lock}  用于进程或者线程的概念和行为都和 @ref{2300,,threading.Lock}  一致。

注意   @ref{2331,,Lock}  实际上是一个工厂函数。它返回由默认上下文初始化的  @code{multiprocessing.synchronize.Lock}  对象。

@ref{2331,,Lock} supports the @ref{563,,context manager} protocol and thus may be
used in @ref{6e3,,with} statements.

@geindex acquire() (multiprocessing.Lock 方法)
@anchor{library/multiprocessing multiprocessing Lock acquire}@anchor{2371}
@deffn {方法} acquire (block=True, timeout=None)

可以阻塞或非阻塞地获得锁。

如果  @emph{block}   参数被设为  @code{True}   ( 默认值 ) ， 对该方法的调用在锁处于释放状态之前都会阻塞，然后将锁设置为锁住状态并返回   @code{True}  。需要注意的是第一个参数名与   @ref{766,,threading.Lock.acquire()}  的不同。

如果 @emph{block} 参数被设置成 @code{False} ，方法的调用将不会阻塞。 如果锁当前处于锁住状态，将返回   @code{False}  ； 否则将锁设置成锁住状态，并返回 @code{True} 。

当  @emph{timeout} 是一个正浮点数时，会在等待锁的过程中最多阻塞等待 @emph{timeout} 秒，当  @emph{timeout} 是负数时，效果和  @emph{timeout} 为0时一样，当  @emph{timeout} 是 @code{None} （默认值）时，等待时间是无限长。需要注意的是，对于 @emph{timeout} 参数是负数和 @code{None} 的情况, 其行为与  @ref{766,,threading.Lock.acquire()} 是不一样的。当 @emph{block} 参数 为 @code{False} 时，  @emph{timeout} 并没有实际用处，会直接忽略。否则，函数会在拿到锁后返回 @code{True} 或者 超时没拿到锁后返回 @code{False} 。
@end deffn

@geindex release() (multiprocessing.Lock 方法)
@anchor{library/multiprocessing multiprocessing Lock release}@anchor{2372}
@deffn {方法} release ()

释放锁，可以在任何进程、线程使用，并不限于锁的拥有者。

当尝试释放一个没有被持有的锁时，会抛出 @ref{1fb,,ValueError} 异常，除此之外其行为与 @ref{22fe,,threading.Lock.release()} 一样。
@end deffn
@end deffn

@geindex RLock (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing RLock}@anchor{2332}
@deffn {类} multiprocessing.RLock

递归锁对象: 类似于 @ref{be8,,threading.RLock} 。递归锁必须由持有线程、进程亲自释放。如果某个进程或者线程拿到了递归锁，这个进程或者线程可以再次拿到这个锁而不需要等待。但是这个进程或者线程的拿锁操作和释放锁操作的次数必须相同。

注意 @ref{2332,,RLock} 是一个工厂函数，调用后返回一个使用默认 context 初始化的 @code{multiprocessing.synchronize.RLock} 实例。

@ref{2332,,RLock} 支持 @ref{563,,context manager} 协议，因此可在 @ref{6e3,,with} 语句内使用。

@geindex acquire() (multiprocessing.RLock 方法)
@anchor{library/multiprocessing multiprocessing RLock acquire}@anchor{2373}
@deffn {方法} acquire (block=True, timeout=None)

可以阻塞或非阻塞地获得锁。

当 @emph{block} 参数设置为 @code{True} 时，会一直阻塞直到锁处于空闲状态（没有被任何进程、线程拥有），除非当前进程或线程已经拥有了这把锁。然后当前进程/线程会持有这把锁（在锁没有其他持有者的情况下），锁内的递归等级加一，并返回 @code{True} . 注意， 这个函数第一个参数的行为和 @ref{767,,threading.RLock.acquire()} 的实现有几个不同点，包括参数名本身。

当 @emph{block} 参数是 @code{False} , 将不会阻塞，如果此时锁被其他进程或者线程持有，当前进程、线程获取锁操作失败，锁的递归等级也不会改变，函数返回 @code{False} ,  如果当前锁已经处于释放状态，则当前进程、线程则会拿到锁，并且锁内的递归等级加一，函数返回 @code{True} 。

@emph{timeout} 参数的使用方法及行为与 @ref{2371,,Lock.acquire()} 一样。但是要注意 @emph{timeout} 的其中一些行为和 @ref{767,,threading.RLock.acquire()} 中实现的行为是不同的。
@end deffn

@geindex release() (multiprocessing.RLock 方法)
@anchor{library/multiprocessing multiprocessing RLock release}@anchor{2374}
@deffn {方法} release ()

释放锁，使锁内的递归等级减一。如果释放后锁内的递归等级降低为0，则会重置锁的状态为释放状态（即没有被任何进程、线程持有），重置后如果有有其他进程和线程在等待这把锁，他们中的一个会获得这个锁而继续运行。如果释放后锁内的递归等级还没到达0，则这个锁仍将保持未释放状态且当前进程和线程仍然是持有者。

只有当前进程或线程是锁的持有者时，才允许调用这个方法。如果当前进程或线程不是这个锁的拥有者，或者这个锁处于已释放的状态(即没有任何拥有者)，调用这个方法会抛出 @ref{fc1,,AssertionError} 异常。注意这里抛出的异常类型和 @ref{2304,,threading.RLock.release()} 中实现的行为不一样。
@end deffn
@end deffn

@geindex Semaphore (multiprocessing 中的类)
@anchor{library/multiprocessing multiprocessing Semaphore}@anchor{2333}
@deffn {类} multiprocessing.Semaphore ([value])

一种信号量对象:  类似于  @ref{aa6,,threading.Semaphore}.

一个小小的不同在于，它的  @code{acquire}  方法的第一个参数名是和  @ref{2371,,Lock.acquire()} 一样的 @emph{block} 。
@end deffn

@cartouche
@quotation 注解 
在 Mac OS X 上，不支持  @code{sem_timedwait} ，所以，调用 @code{acquire()} 时如果使用 timeout 参数，会通过循环sleep来模拟这个函数的行为。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
假如信号 SIGINT 是来自于 @code{Ctrl-C} ，并且主线程被 @code{BoundedSemaphore.acquire()}, @ref{2371,,Lock.acquire()}, @ref{2373,,RLock.acquire()}, @code{Semaphore.acquire()}, @code{Condition.acquire()} 或 @code{Condition.wait()} 阻塞，则调用会立即中断同时抛出 @ref{197,,KeyboardInterrupt} 异常。

这和 @ref{109,,threading} 的行为不同，此模块中当执行对应的阻塞式调用时，SIGINT 会被忽略。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
这个包的某些功能依赖于宿主机系统的共享信号量的实现，如果系统没有这个特性， @code{multiprocessing.synchronize} 会被禁用，尝试导入这个模块会引发 @ref{32d,,ImportError} 异常，详细信息请查看 bpo-3770@footnote{https://bugs.python.org/issue3770} 。
@end quotation
@end cartouche

@node 共享 ctypes 对象,管理器,同步原语,参考
@anchor{library/multiprocessing shared-ctypes-objects}@anchor{2375}
@subsubsection 共享 @code{ctypes} 对象


在共享内存上创建可被子进程继承的共享对象时是可行的。

@geindex Value() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing Value}@anchor{232e}
@deffn {函数} multiprocessing.Value (typecode_or_type, *args, lock=True)

返回一个从共享内存上创建的 @ref{2b,,ctypes} 对象。默认情况下返回的对象实际上是经过了同步器包装过的。可以通过 @ref{232e,,Value} 的 @emph{value} 属性访问这个对象本身。

@emph{typecode_or_type} 指明了返回的对象类型: 它可能是一个 ctypes 类型或者  @ref{7,,array}  模块中每个类型对应的单字符长度的字符串。 @emph{*args} 会透传给这个类的构造函数。

如果 @emph{lock} 参数是 @code{True} （默认值）, 将会新建一个递归锁用于同步对于此值的访问操作。 如果 @emph{lock} 是 @ref{2331,,Lock} 或者 @ref{2332,,RLock} 对象，那么这个传入的锁将会用于同步对这个值的访问操作，如果 @emph{lock} 是 @code{False} , 那么对这个对象的访问将没有锁保护，也就是说这个变量不是进程安全的。

诸如 @code{+=} 这类的操作会引发独立的读操作和写操作，也就是说这类操作符并不具有原子性。所以，如果你想让递增共享变量的操作具有原子性，仅仅以这样的方式并不能达到要求:

@example
counter.value += 1
@end example

共享对象内部关联的锁是递归锁(默认情况下就是)的情况下， 你可以采用这种方式

@example
with counter.get_lock():
    counter.value += 1
@end example

注意 @emph{lock} 只能是命名参数。
@end deffn

@geindex Array() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing Array}@anchor{232f}
@deffn {函数} multiprocessing.Array (typecode_or_type, size_or_initializer, *, lock=True)

从共享内存中申请并返回一个具有ctypes类型的数组对象。默认情况下返回值实际上是被同步器包装过的数组对象。

@emph{typecode_or_type} 指明了返回的数组中的元素类型: 它可能是一个 ctypes 类型或者  @ref{7,,array} 模块中每个类型对应的单字符长度的字符串。 如果 @emph{size_or_initializer} 是一个整数，那就会当做数组的长度，并且整个数组的内存会初始化为0。否则，如果  @emph{size_or_initializer} 会被当成一个序列用于初始化数组中的每一个元素，并且会根据元素个数自动判断数组的长度。

如果 @emph{lock} 为 @code{True} (默认值) 则将创建一个新的锁对象用于同步对值的访问。 如果 @emph{lock} 为一个 @ref{2331,,Lock} 或 @ref{2332,,RLock} 对象则该对象将被用于同步对值的访问。 如果 @emph{lock} 为 @code{False} 则对返回对象的访问将不会自动得到锁的保护，也就是说它不是“进程安全的”。

请注意 @emph{lock} 是一个仅限关键字参数。

请注意 @ref{2257,,ctypes.c_char} 的数组具有 @emph{value} 和 @emph{raw} 属性，允许被用来保存和提取字符串。
@end deffn

@menu
* multiprocessing.sharedctypes 模块: multiprocessing sharedctypes 模块. 

@end menu

@node multiprocessing sharedctypes 模块,,,共享 ctypes 对象
@anchor{library/multiprocessing module-multiprocessing sharedctypes}@anchor{bd}@anchor{library/multiprocessing the-multiprocessing-sharedctypes-module}@anchor{2376}
@subsubsection @code{multiprocessing.sharedctypes} 模块


@geindex multiprocessing.sharedctypes (模块)

@ref{bd,,multiprocessing.sharedctypes} 模块提供了一些函数，用于分配来自共享内存的、可被子进程继承的 @ref{2b,,ctypes} 对象。

@cartouche
@quotation 注解 
虽然可以将指针存储在共享内存中，但请记住它所引用的是特定进程地址空间中的位置。 而且，指针很可能在第二个进程的上下文中无效，尝试从第二个进程对指针进行解引用可能会导致崩溃。
@end quotation
@end cartouche

@geindex RawArray() (在 multiprocessing.sharedctypes 模块中)
@anchor{library/multiprocessing multiprocessing sharedctypes RawArray}@anchor{2377}
@deffn {函数} multiprocessing.sharedctypes.RawArray (typecode_or_type, size_or_initializer)

从共享内存中申请并返回一个 ctypes 数组。

@emph{typecode_or_type} 指明了返回的数组中的元素类型: 它可能是一个 ctypes 类型或者  @ref{7,,array} 模块中使用的类型字符。 如果 @emph{size_or_initializer} 是一个整数，那就会当做数组的长度，并且整个数组的内存会初始化为0。否则，如果  @emph{size_or_initializer} 会被当成一个序列用于初始化数组中的每一个元素，并且会根据元素个数自动判断数组的长度。

注意对元素的访问、赋值操作可能是非原子操作 - 使用 @ref{2378,,Array()} , 从而借助其中的锁保证操作的原子性。
@end deffn

@geindex RawValue() (在 multiprocessing.sharedctypes 模块中)
@anchor{library/multiprocessing multiprocessing sharedctypes RawValue}@anchor{2379}
@deffn {函数} multiprocessing.sharedctypes.RawValue (typecode_or_type, *args)

从共享内存中申请并返回一个 ctypes 对象。

@emph{typecode_or_type} 指明了返回的对象类型: 它可能是一个 ctypes 类型或者  @ref{7,,array}  模块中每个类型对应的单字符长度的字符串。 @emph{*args} 会透传给这个类的构造函数。

注意对 value 的访问、赋值操作可能是非原子操作 - 使用 @ref{237a,,Value()} ，从而借助其中的锁保证操作的原子性。

请注意 @ref{2257,,ctypes.c_char} 的数组具有 @emph{value} 和 @emph{raw} 属性，允许被用来保存和提取字符串 - 请查看 @ref{2b,,ctypes} 文档。
@end deffn

@geindex Array() (在 multiprocessing.sharedctypes 模块中)
@anchor{library/multiprocessing multiprocessing sharedctypes Array}@anchor{2378}
@deffn {函数} multiprocessing.sharedctypes.Array (typecode_or_type, size_or_initializer, *, lock=True)

返回一个纯 ctypes 数组, 或者在此之上经过同步器包装过的进程安全的对象，这取决于 @emph{lock} 参数的值，除此之外，和 @ref{2377,,RawArray()} 一样。

如果 @emph{lock} 为 @code{True} (默认值) 则将创建一个新的锁对象用于同步对值的访问。 如果 @emph{lock} 为一个 @ref{2331,,Lock} 或 @ref{2332,,RLock} 对象则该对象将被用于同步对值的访问。 如果 @emph{lock} 为 @code{False} 则对所返回对象的访问将不会自动得到锁的保护，也就是说它将不是“进程安全的”。

注意 @emph{lock} 只能是命名参数。
@end deffn

@geindex Value() (在 multiprocessing.sharedctypes 模块中)
@anchor{library/multiprocessing multiprocessing sharedctypes Value}@anchor{237a}
@deffn {函数} multiprocessing.sharedctypes.Value (typecode_or_type, *args, lock=True)

返回一个纯 ctypes 数组, 或者在此之上经过同步器包装过的进程安全的对象，这取决于 @emph{lock} 参数的值，除此之外，和 @code{RawArray()} 一样。

如果 @emph{lock} 为 @code{True} (默认值) 则将创建一个新的锁对象用于同步对值的访问。 如果 @emph{lock} 为一个 @ref{2331,,Lock} 或 @ref{2332,,RLock} 对象则该对象将被用于同步对值的访问。 如果 @emph{lock} 为 @code{False} 则对所返回对象的访问将不会自动得到锁的保护，也就是说它将不是“进程安全的”。

注意 @emph{lock} 只能是命名参数。
@end deffn

@geindex copy() (在 multiprocessing.sharedctypes 模块中)
@anchor{library/multiprocessing multiprocessing sharedctypes copy}@anchor{237b}
@deffn {函数} multiprocessing.sharedctypes.copy (obj)

从共享内存中申请一片空间将 ctypes 对象 @emph{obj} 过来，然后返回一个新的 ctypes 对象。
@end deffn

@geindex synchronized() (在 multiprocessing.sharedctypes 模块中)
@anchor{library/multiprocessing multiprocessing sharedctypes synchronized}@anchor{713}
@deffn {函数} multiprocessing.sharedctypes.synchronized (obj[, lock])

将一个 ctypes 对象包装为进程安全的对象并返回，使用 @emph{lock} 同步对于它的操作。如果 @emph{lock} 是 @code{None} (默认值) ，则会自动创建一个 @ref{2332,,multiprocessing.RLock} 对象。

同步器包装后的对象会在原有对象基础上额外增加两个方法: @code{get_obj()} 返回被包装的对象，  @code{get_lock()} 返回内部用于同步的锁。

需要注意的是，访问包装后的ctypes对象会比直接访问原来的纯 ctypes 对象慢得多。


在 3.5 版更改: 同步器包装后的对象支持 @ref{563,,context manager} 协议。

@end deffn

下面的表格对比了创建普通ctypes对象和基于共享内存上创建共享ctypes对象的语法。（表格中的 @code{MyStruct} 是 @ref{2278,,ctypes.Structure} 的子类）


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

ctypes

@tab

使用类型的共享ctypes

@tab

使用 typecode 的共享 ctypes

@item

c_double(2.4)

@tab

RawValue(c_double, 2.4)

@tab

RawValue('d', 2.4)

@item

MyStruct(4, 6)

@tab

RawValue(MyStruct, 4, 6)

@tab

@item

(c_short * 7)()

@tab

RawArray(c_short, 7)

@tab

RawArray('h', 7)

@item

(c_int * 3)(9, 2, 8)

@tab

RawArray(c_int, (9, 2, 8))

@tab

RawArray('i', (9, 2, 8))

@end multitable


下面是一个在子进程中修改多个ctypes对象的例子。

@example
from multiprocessing import Process, Lock
from multiprocessing.sharedctypes import Value, Array
from ctypes import Structure, c_double

class Point(Structure):
    _fields_ = [('x', c_double), ('y', c_double)]

def modify(n, x, s, A):
    n.value **= 2
    x.value **= 2
    s.value = s.value.upper()
    for a in A:
        a.x **= 2
        a.y **= 2

if __name__ == '__main__':
    lock = Lock()

    n = Value('i', 7)
    x = Value(c_double, 1.0/3.0, lock=False)
    s = Array('c', b'hello world', lock=lock)
    A = Array(Point, [(1.875,-6.25), (-5.75,2.0), (2.375,9.5)], lock=lock)

    p = Process(target=modify, args=(n, x, s, A))
    p.start()
    p.join()

    print(n.value)
    print(x.value)
    print(s.value)
    print([(a.x, a.y) for a in A])
@end example

输出如下

@example
49
0.1111111111111111
HELLO WORLD
[(3.515625, 39.0625), (33.0625, 4.0), (5.640625, 90.25)]
@end example

@node 管理器,代理对象,共享 ctypes 对象,参考
@anchor{library/multiprocessing managers}@anchor{237c}@anchor{library/multiprocessing multiprocessing-managers}@anchor{234f}
@subsubsection 管理器


管理器提供了一种创建共享数据的方法，从而可以在不同进程中共享，甚至可以通过网络跨机器共享数据。管理器维护一个用于管理 @emph{共享对象} 的服务。其他进程可以通过代理访问这些共享对象。

@geindex multiprocessing.Manager() (在 multiprocessing.sharedctypes 模块中)
@anchor{library/multiprocessing multiprocessing sharedctypes multiprocessing Manager}@anchor{237d}
@deffn {函数} multiprocessing.Manager ()

返回一个已启动的 @ref{237e,,SyncManager} 管理器对象，这个对象可以用于在不同进程中共享数据。返回的管理器对象对应了一个已经启动的子进程，并且拥有一系列方法可以用于创建共享对象、返回对应的代理。
@end deffn
@anchor{library/multiprocessing module-multiprocessing managers}@anchor{ba}
@geindex multiprocessing.managers (模块)

当管理器被垃圾回收或者父进程退出时，管理器进程会立即退出。管理器类定义在 @ref{ba,,multiprocessing.managers} 模块:

@geindex BaseManager (multiprocessing.managers 中的类)
@anchor{library/multiprocessing multiprocessing managers BaseManager}@anchor{237f}
@deffn {类} multiprocessing.managers.BaseManager ([address[, authkey]])

创建一个 BaseManager 对象。

一旦创建，应该及时调用 @ref{2380,,start()} 或者  @code{get_server().serve_forever()} 以确保管理器对象对应的管理进程已经启动。

@emph{address} 是管理器服务进程监听的地址。如果 @emph{address} 是 @code{None} ,则允许和任意主机的请求建立连接。

@emph{authkey} 是认证标识，用于检查连接服务进程的请求合法性。如果 @emph{authkey} 是 @code{None}, 则会使用 @code{current_process().authkey} , 否则，就使用 @emph{authkey} , 需要保证它必须是 byte 类型的字符串。

@geindex start() (multiprocessing.managers.BaseManager 方法)
@anchor{library/multiprocessing multiprocessing managers BaseManager start}@anchor{2380}
@deffn {方法} start ([initializer[, initargs]])

为管理器开启一个子进程，如果 @emph{initializer} 不是 @code{None} , 子进程在启动时将会调用  @code{initializer(*initargs)} 。
@end deffn

@geindex get_server() (multiprocessing.managers.BaseManager 方法)
@anchor{library/multiprocessing multiprocessing managers BaseManager get_server}@anchor{2381}
@deffn {方法} get_server ()

返回一个  @code{Server}  对象，它是管理器在后台控制的真实的服务。 @code{Server}  对象拥有 @code{serve_forever()} 方法。

@example
>>> from multiprocessing.managers import BaseManager
>>> manager = BaseManager(address=('@w{'}, 50000), authkey=b'abc')
>>> server = manager.get_server()
>>> server.serve_forever()
@end example

@code{Server} 额外拥有一个 @ref{2382,,address} 属性。
@end deffn

@geindex connect() (multiprocessing.managers.BaseManager 方法)
@anchor{library/multiprocessing multiprocessing managers BaseManager connect}@anchor{2383}
@deffn {方法} connect ()

将本地管理器对象连接到一个远程管理器进程:

@example
>>> from multiprocessing.managers import BaseManager
>>> m = BaseManager(address=('127.0.0.1', 50000), authkey=b'abc')
>>> m.connect()
@end example
@end deffn

@geindex shutdown() (multiprocessing.managers.BaseManager 方法)
@anchor{library/multiprocessing multiprocessing managers BaseManager shutdown}@anchor{2384}
@deffn {方法} shutdown ()

停止管理器的进程。这个方法只能用于已经使用 @ref{2380,,start()} 启动的服务进程。

它可以被多次调用。
@end deffn

@geindex register() (multiprocessing.managers.BaseManager 方法)
@anchor{library/multiprocessing multiprocessing managers BaseManager register}@anchor{2385}
@deffn {方法} register (typeid[, callable[, proxytype[, exposed[, method_to_typeid[, create_method]]]]])

一个 classmethod，可以将一个类型或者可调用对象注册到管理器类。

@emph{typeid} 是一种 "类型标识符"，用于唯一表示某种共享对象类型，必须是一个字符串。

@emph{callable} 是一个用来为此类型标识符创建对象的可调用对象。如果一个管理器实例将使用 @ref{2383,,connect()} 方法连接到服务器，或者 @emph{create_method} 参数为 @code{False}，那么这里可留下 @code{None}。

@emph{proxytype} 是  @ref{2386,,BaseProxy}  的子类，可以根据 @emph{typeid} 为共享对象创建一个代理，如果是 @code{None} , 则会自动创建一个代理类。

@emph{exposed} 是一个函数名组成的序列，用来指明只有这些方法可以使用 @ref{2387,,BaseProxy._callmethod()} 代理。(如果 @emph{exposed} 是 @code{None}, 则会在 @code{proxytype._exposed_} 存在的情况下转而使用它) 当暴露的方法列表没有指定的时候，共享对象的所有 “公共方法” 都会被代理。（这里的“公共方法”是指所有拥有 @ref{13c5,,__call__()} 方法并且不是以 @code{'_'} 开头的属性）

@emph{method_to_typeid} 是一个映射，用来指定那些应该返回代理对象的暴露方法所返回的类型。（如果 @emph{method_to_typeid} 是 @code{None}, 则 @code{proxytype._method_to_typeid_} 会在存在的情况下被使用）如果方法名称不在这个映射中或者映射是 @code{None} ,则方法返回的对象会是一个值拷贝。

@emph{create_method} 指明，是否要创建一个以 @emph{typeid} 命名并返回一个代理对象的方法，这个函数会被服务进程用于创建共享对象，默认为 @code{True} 。
@end deffn

@ref{237f,,BaseManager} 实例也有一个只读属性。

@geindex address (multiprocessing.managers.BaseManager 属性)
@anchor{library/multiprocessing multiprocessing managers BaseManager address}@anchor{2382}
@deffn {属性} address

管理器所用的地址。
@end deffn


在 3.3 版更改: 管理器对象支持上下文管理协议 - 查看 @ref{1420,,上下文管理器类型} 。@ref{1675,,__enter__()} 启动服务进程（如果它还没有启动）并且返回管理器对象， @ref{1677,,__exit__()} 会调用 @ref{2384,,shutdown()} 。

在之前的版本中，如果管理器服务进程没有启动， @ref{1675,,__enter__()} 不会负责启动它。

@end deffn

@geindex SyncManager (multiprocessing.managers 中的类)
@anchor{library/multiprocessing multiprocessing managers SyncManager}@anchor{237e}
@deffn {类} multiprocessing.managers.SyncManager

@ref{237f,,BaseManager} 的子类，可用于进程的同步。这个类型的对象使用 @code{multiprocessing.Manager()} 创建。

它拥有一系列方法，可以为大部分常用数据类型创建并返回 @ref{560,,代理对象} 代理，用于进程间同步。甚至包括共享列表和字典。

@geindex Barrier() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Barrier}@anchor{2388}
@deffn {方法} Barrier (parties[, action[, timeout]])

创建一个共享的 @ref{b58,,threading.Barrier} 对象并返回它的代理。


3.3 新版功能.

@end deffn

@geindex BoundedSemaphore() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager BoundedSemaphore}@anchor{2389}
@deffn {方法} BoundedSemaphore ([value])

创建一个共享的 @ref{aa7,,threading.BoundedSemaphore} 对象并返回它的代理。
@end deffn

@geindex Condition() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Condition}@anchor{238a}
@deffn {方法} Condition ([lock])

创建一个共享的 @ref{aa5,,threading.Condition} 对象并返回它的代理。

如果提供了 @emph{lock} 参数，那它必须是 @ref{2300,,threading.Lock} 或 @ref{be8,,threading.RLock} 的代理对象。


在 3.3 版更改: 新增了 @ref{230b,,wait_for()}  方法。

@end deffn

@geindex Event() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Event}@anchor{238b}
@deffn {方法} Event ()

创建一个共享的 @ref{aa8,,threading.Event} 对象并返回它的代理。
@end deffn

@geindex Lock() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Lock}@anchor{238c}
@deffn {方法} Lock ()

创建一个共享的 @ref{2300,,threading.Lock} 对象并返回它的代理。
@end deffn

@geindex Namespace() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Namespace}@anchor{238d}
@deffn {方法} Namespace ()

创建一个共享的 @ref{2330,,Namespace} 对象并返回它的代理。
@end deffn

@geindex Queue() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Queue}@anchor{238e}
@deffn {方法} Queue ([maxsize])

创建一个共享的 @ref{d11,,queue.Queue} 对象并返回它的代理。
@end deffn

@geindex RLock() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager RLock}@anchor{238f}
@deffn {方法} RLock ()

创建一个共享的 @ref{be8,,threading.RLock} 对象并返回它的代理。
@end deffn

@geindex Semaphore() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Semaphore}@anchor{2390}
@deffn {方法} Semaphore ([value])

创建一个共享的 @ref{aa6,,threading.Semaphore} 对象并返回它的代理。
@end deffn

@geindex Array() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Array}@anchor{2391}
@deffn {方法} Array (typecode, sequence)

创建一个数组并返回它的代理。
@end deffn

@geindex Value() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager Value}@anchor{2392}
@deffn {方法} Value (typecode, value)

创建一个具有可写 @code{value} 属性的对象并返回它的代理。
@end deffn

@geindex dict() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager dict}@anchor{2393}
@deffn {方法} dict ()

@deffnx {方法} dict (mapping)

@deffnx {方法} dict (sequence)

创建一个共享的 @ref{1b8,,dict} 对象并返回它的代理。
@end deffn

@geindex list() (multiprocessing.managers.SyncManager 方法)
@anchor{library/multiprocessing multiprocessing managers SyncManager list}@anchor{2394}
@deffn {方法} list ()

@deffnx {方法} list (sequence)

创建一个共享的 @ref{262,,list} 对象并返回它的代理。
@end deffn


在 3.6 版更改: 共享对象能够嵌套。例如, 共享的容器对象如共享列表，可以包含另一个共享对象，他们全都会在 @ref{237e,,SyncManager} 中进行管理和同步。

@end deffn

@geindex Namespace (multiprocessing.managers 中的类)
@anchor{library/multiprocessing multiprocessing managers Namespace}@anchor{2330}
@deffn {类} multiprocessing.managers.Namespace

一个可以注册到 @ref{237e,,SyncManager} 的类型。

命名空间对象没有公共方法，但是拥有可写的属性。直接print会显示所有属性的值。

值得一提的是，当对命名空间对象使用代理的时候，访问所有名称以 @code{'_'} 开头的属性都只是代理器上的属性，而不是命名空间对象的属性。

@example
>>> manager = multiprocessing.Manager()
>>> Global = manager.Namespace()
>>> Global.x = 10
>>> Global.y = 'hello'
>>> Global._z = 12.3    # this is an attribute of the proxy
>>> print(Global)
Namespace(x=10, y='hello')
@end example
@end deffn

@menu
* 自定义管理器:: 
* 使用远程管理器:: 

@end menu

@node 自定义管理器,使用远程管理器,,管理器
@anchor{library/multiprocessing customized-managers}@anchor{2395}
@subsubsection 自定义管理器


要创建一个自定义的管理器，需要新建一个 @ref{237f,,BaseManager} 的子类，然后使用这个管理器类上的 @ref{2385,,register()} 类方法将新类型或者可调用方法注册上去。例如:

@example
from multiprocessing.managers import BaseManager

class MathsClass:
    def add(self, x, y):
        return x + y
    def mul(self, x, y):
        return x * y

class MyManager(BaseManager):
    pass

MyManager.register('Maths', MathsClass)

if __name__ == '__main__':
    with MyManager() as manager:
        maths = manager.Maths()
        print(maths.add(4, 3))         # prints 7
        print(maths.mul(7, 8))         # prints 56
@end example

@node 使用远程管理器,,自定义管理器,管理器
@anchor{library/multiprocessing using-a-remote-manager}@anchor{2396}
@subsubsection 使用远程管理器


可以将管理器服务运行在一台机器上，然后使用客户端从其他机器上访问。(假设它们的防火墙允许)

运行下面的代码可以启动一个服务，此付包含了一个共享队列，允许远程客户端访问:

@example
>>> from multiprocessing.managers import BaseManager
>>> from queue import Queue
>>> queue = Queue()
>>> class QueueManager(BaseManager): pass
>>> QueueManager.register('get_queue', callable=lambda:queue)
>>> m = QueueManager(address=('@w{'}, 50000), authkey=b'abracadabra')
>>> s = m.get_server()
>>> s.serve_forever()
@end example

远程客户端可以通过下面的方式访问服务:

@example
>>> from multiprocessing.managers import BaseManager
>>> class QueueManager(BaseManager): pass
>>> QueueManager.register('get_queue')
>>> m = QueueManager(address=('foo.bar.org', 50000), authkey=b'abracadabra')
>>> m.connect()
>>> queue = m.get_queue()
>>> queue.put('hello')
@end example

也可以通过下面的方式:

@example
>>> from multiprocessing.managers import BaseManager
>>> class QueueManager(BaseManager): pass
>>> QueueManager.register('get_queue')
>>> m = QueueManager(address=('foo.bar.org', 50000), authkey=b'abracadabra')
>>> m.connect()
>>> queue = m.get_queue()
>>> queue.get()
'hello'
@end example

本地进程也可以访问这个队列，利用上面的客户端代码通过远程方式访问:

@example
>>> from multiprocessing import Process, Queue
>>> from multiprocessing.managers import BaseManager
>>> class Worker(Process):
...     def __init__(self, q):
...         self.q = q
...         super(Worker, self).__init__()
...     def run(self):
...         self.q.put('local hello')
...
>>> queue = Queue()
>>> w = Worker(queue)
>>> w.start()
>>> class QueueManager(BaseManager): pass
...
>>> QueueManager.register('get_queue', callable=lambda: queue)
>>> m = QueueManager(address=('@w{'}, 50000), authkey=b'abracadabra')
>>> s = m.get_server()
>>> s.serve_forever()
@end example

@node 代理对象,进程池,管理器,参考
@anchor{library/multiprocessing multiprocessing-proxy-objects}@anchor{560}@anchor{library/multiprocessing proxy-objects}@anchor{2397}
@subsubsection 代理对象


代理是一个 @emph{指向} 其他共享对象的对象，这个对象(很可能)在另外一个进程中。共享对象也可以说是代理 @emph{指涉} 的对象。多个代理对象可能指向同一个指涉对象。

代理对象代理了指涉对象的一系列方法调用(虽然并不是指涉对象的每个方法都有必要被代理)。通过这种方式，代理的使用方法可以和它的指涉对象一样:

@example
>>> from multiprocessing import Manager
>>> manager = Manager()
>>> l = manager.list([i*i for i in range(10)])
>>> print(l)
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
>>> print(repr(l))
<ListProxy object, typeid 'list' at 0x...>
>>> l[4]
16
>>> l[2:5]
[4, 9, 16]
@end example

注意，对代理使用 @ref{329,,str()} 函数会返回指涉对象的字符串表示，但是 @ref{7c6,,repr()} 却会返回代理本身的内部字符串表示。

被代理的对象很重要的一点是必须可以被序列化，这样才能允许他们在进程间传递。因此，指涉对象可以包含 @ref{560,,代理对象} 。这允许管理器中列表、字典或者其他 @ref{560,,代理对象} 对象之间的嵌套。

@example
>>> a = manager.list()
>>> b = manager.list()
>>> a.append(b)         # referent of a now contains referent of b
>>> print(a, b)
[<ListProxy object, typeid 'list' at ...>] []
>>> b.append('hello')
>>> print(a[0], b)
['hello'] ['hello']
@end example

类似地，字典和列表代理也可以相互嵌套:

@example
>>> l_outer = manager.list([ manager.dict() for i in range(2) ])
>>> d_first_inner = l_outer[0]
>>> d_first_inner['a'] = 1
>>> d_first_inner['b'] = 2
>>> l_outer[1]['c'] = 3
>>> l_outer[1]['z'] = 26
>>> print(l_outer[0])
@{'a': 1, 'b': 2@}
>>> print(l_outer[1])
@{'c': 3, 'z': 26@}
@end example

如果指涉对象包含了普通 @ref{262,,list} 或 @ref{1b8,,dict} 对象，对这些内部可变对象的修改不会通过管理器传播，因为代理无法得知被包含的值什么时候被修改了。但是把存放在容器代理中的值本身是会通过管理器传播的（会触发代理对象中的 @code{__setitem__} ）从而有效修改这些对象，所以可以把修改过的值重新赋值给容器代理:

@example
# create a list proxy and append a mutable object (a dictionary)
lproxy = manager.list()
lproxy.append(@{@})
# now mutate the dictionary
d = lproxy[0]
d['a'] = 1
d['b'] = 2
# at this point, the changes to d are not yet synced, but by
# updating the dictionary, the proxy is notified of the change
lproxy[0] = d
@end example

在大多是使用情形下，这种实现方式并不比嵌套 @ref{560,,代理对象} 方便，但是依然演示了对于同步的一种控制级别。

@cartouche
@quotation 注解 
@ref{b7,,multiprocessing} 中的代理类并没有提供任何对于代理值比较的支持。所以，我们会得到如下结果:

@example
>>> manager.list([1,2,3]) == [1,2,3]
False
@end example

当需要比较值的时候，应该替换为使用指涉对象的拷贝。
@end quotation
@end cartouche

@geindex BaseProxy (multiprocessing.managers 中的类)
@anchor{library/multiprocessing multiprocessing managers BaseProxy}@anchor{2386}
@deffn {类} multiprocessing.managers.BaseProxy

代理对象是 @ref{2386,,BaseProxy} 派生类的实例。

@geindex _callmethod() (multiprocessing.managers.BaseProxy 方法)
@anchor{library/multiprocessing multiprocessing managers BaseProxy _callmethod}@anchor{2387}
@deffn {方法} _callmethod (methodname[, args[, kwds]])

调用指涉对象的方法并返回结果。

如果 @code{proxy} 是一个代理且其指涉的是 @code{obj} , 那么下面的表达式:

@example
proxy._callmethod(methodname, args, kwds)
@end example

相当于求取以下表达式的值:

@example
getattr(obj, methodname)(*args, **kwds)
@end example

于管理器进程。

返回结果会是一个值拷贝或者一个新的共享对象的代理 - 见函数 @ref{2385,,BaseManager.register()} 中关于参数 @emph{method_to_typeid} 的文档。

如果这个调用熬出了异常，则这个异常会被 @ref{2387,,_callmethod()} 透传出来。如果是管理器进程本身抛出的一些其他异常，则会被 @ref{2387,,_callmethod()} 转换为 @code{RemoteError} 异常重新抛出。

特别注意，如果 @emph{methodname} 没有 @emph{暴露} 出来，将会引发一个异常。

@ref{2387,,_callmethod()} 的一个使用示例:

@example
>>> l = manager.list(range(10))
>>> l._callmethod('__len__')
10
>>> l._callmethod('__getitem__', (slice(2, 7),)) # equivalent to l[2:7]
[2, 3, 4, 5, 6]
>>> l._callmethod('__getitem__', (20,))          # equivalent to l[20]
Traceback (most recent call last):
...
IndexError: list index out of range
@end example
@end deffn

@geindex _getvalue() (multiprocessing.managers.BaseProxy 方法)
@anchor{library/multiprocessing multiprocessing managers BaseProxy _getvalue}@anchor{2398}
@deffn {方法} _getvalue ()

返回指涉对象的一份拷贝。

如果指涉对象无法序列化，则会抛出一个异常。
@end deffn

@geindex __repr__() (multiprocessing.managers.BaseProxy 方法)
@anchor{library/multiprocessing multiprocessing managers BaseProxy __repr__}@anchor{2399}
@deffn {方法} __repr__ ()

返回代理对象的内部字符串表示。
@end deffn

@geindex __str__() (multiprocessing.managers.BaseProxy 方法)
@anchor{library/multiprocessing multiprocessing managers BaseProxy __str__}@anchor{239a}
@deffn {方法} __str__ ()

返回指涉对象的内部字符串表示。
@end deffn
@end deffn

@menu
* 清理:: 

@end menu

@node 清理,,,代理对象
@anchor{library/multiprocessing cleanup}@anchor{239b}
@subsubsection 清理


代理对象使用了一个弱引用回调函数，当它被垃圾回收时，会将自己从拥有此指涉对象的管理器上反注册，

当共享对象没有被任何代理器引用时，会被管理器进程删除。

@node 进程池,监听者及客户端,代理对象,参考
@anchor{library/multiprocessing module-multiprocessing pool}@anchor{bb}@anchor{library/multiprocessing process-pools}@anchor{239c}
@subsubsection 进程池


@geindex multiprocessing.pool (模块)

可以创建一个进程池，它将使用 @ref{875,,Pool} 类执行提交给它的任务。

@geindex Pool (multiprocessing.pool 中的类)
@anchor{library/multiprocessing multiprocessing pool Pool}@anchor{875}
@deffn {类} multiprocessing.pool.Pool ([processes[, initializer[, initargs[, maxtasksperchild[, context]]]]])

一个进程池对象，它控制可以提交作业的工作进程池。它支持带有超时和回调的异步结果，以及一个并行的 map 实现。

@emph{processes} 是要使用的工作进程数目。如果 @emph{processes} 为 @code{None}，则使用 @ref{879,,os.cpu_count()} 返回的值。

如果 @emph{initializer} 不为 @code{None}，则每个工作进程将会在启动时调用 @code{initializer(*initargs)}。

@emph{maxtasksperchild} 是一个工作进程在它退出或被一个新的工作进程代替之前能完成的任务数量，为了释放未使用的资源。默认的 @emph{maxtasksperchild} 是 @code{None}，意味着工作进程寿与池齐。

@emph{context} 可被用于指定启动的工作进程的上下文。通常一个进程池是使用函数 @code{multiprocessing.Pool()} 或者一个上下文对象的 @ref{875,,Pool()} 方法创建的。在这两种情况下， @emph{context} 都是适当设置的。

注意，进程池对象的方法只有创建它的进程能够调用。

@cartouche
@quotation 警告 
@ref{bb,,multiprocessing.pool} 对象具有需要正确管理的内部资源 （像任何其他资源一样），具体方式是将进程池用作上下文管理器，或者手动调用 @ref{239d,,close()} 和 @ref{239e,,terminate()}。 未做此类操作将导致进程在终结阶段挂起。

请注意依赖垃圾回收器来销毁进程池是 @strong{不正确} 的做法，因为 CPython 并不保证会调用进程池终结程序（请参阅 @ref{919,,object.__del__()} 来了解详情）。
@end quotation
@end cartouche


3.2 新版功能: @emph{maxtasksperchild}



3.4 新版功能: @emph{context}


@cartouche
@quotation 注解 
通常来说，@ref{875,,Pool} 中的 Worker 进程的生命周期和进程池的工作队列一样长。一些其他系统中（如 Apache, mod_wsgi 等）也可以发现另一种模式，他们会让工作进程在完成一些任务后退出，清理、释放资源，然后启动一个新的进程代替旧的工作进程。 @ref{875,,Pool} 的 @emph{maxtasksperchild} 参数给用户提供了这种能力。
@end quotation
@end cartouche

@geindex apply() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool apply}@anchor{239f}
@deffn {方法} apply (func[, args[, kwds]])

使用 @emph{args} 参数以及 @emph{kwds} 命名参数调用 @emph{func} , 它会返回结果前阻塞。这种情况下，@ref{23a0,,apply_async()} 更适合并行化工作。另外 @emph{func} 只会在一个进程池中的一个工作进程中执行。
@end deffn

@geindex apply_async() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool apply_async}@anchor{23a0}
@deffn {方法} apply_async (func[, args[, kwds[, callback[, error_callback]]]])

@ref{239f,,apply()} 方法的一个变种，返回一个结果对象。

如果指定了 @emph{callback} , 它必须是一个接受单个参数的可调用对象。当执行成功时， @emph{callback} 会被用于处理执行后的返回结果，否则，调用 @emph{error_callback} 。

如果指定了 @emph{error_callback} , 它必须是一个接受单个参数的可调用对象。当目标函数执行失败时， 会将抛出的异常对象作为参数传递给 @emph{error_callback} 执行。

回调函数应该立即执行完成，否则会阻塞负责处理结果的线程。
@end deffn

@geindex map() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool map}@anchor{a24}
@deffn {方法} map (func, iterable[, chunksize])

内置 @ref{c26,,map()} 函数的并行版本 (但它只支持一个 @emph{iterable} 参数，对于多个可迭代对象请参阅 @ref{a21,,starmap()})。 它会保持阻塞直到获得结果。

这个方法会将可迭代对象分割为许多块，然后提交给进程池。可以将 @emph{chunksize} 设置为一个正整数从而（近似）指定每个块的大小可以。

注意对于很长的迭代对象，可能消耗很多内存。可以考虑使用 @ref{23a1,,imap()} 或 @ref{23a2,,imap_unordered()} 并且显示指定 @emph{chunksize} 以提升效率。
@end deffn

@geindex map_async() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool map_async}@anchor{a25}
@deffn {方法} map_async (func, iterable[, chunksize[, callback[, error_callback]]])

和 @ref{a24,,map()} 方法类似，但是返回一个可用于获取结果的对象。

如果指定了 @emph{callback} , 它必须是一个接受单个参数的可调用对象。当执行成功时， @emph{callback} 会被用于处理执行后的返回结果，否则，调用 @emph{error_callback} 。

如果指定了 @emph{error_callback} , 它必须是一个接受单个参数的可调用对象。当目标函数执行失败时， 会将抛出的异常对象作为参数传递给 @emph{error_callback} 执行。

回调函数应该立即执行完成，否则会阻塞负责处理结果的线程。
@end deffn

@geindex imap() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool imap}@anchor{23a1}
@deffn {方法} imap (func, iterable[, chunksize])

@ref{a24,,map()} 的延迟执行版本。

@emph{chunksize} 参数的作用和 @ref{a24,,map()} 方法的一样。对于很长的迭代器，给 @emph{chunksize} 设置一个很大的值会比默认值 @code{1} @strong{极大} 地加快执行速度。

同样，如果 @emph{chunksize} 是 @code{1} , 那么 @ref{23a1,,imap()} 方法所返回的迭代器的 @code{next()} 方法拥有一个可选的 @emph{timeout} 参数： 如果无法在 @emph{timeout} 秒内执行得到结果，则`@w{`}next(timeout)`@w{`} 会抛出 @ref{2348,,multiprocessing.TimeoutError} 异常。
@end deffn

@geindex imap_unordered() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool imap_unordered}@anchor{23a2}
@deffn {方法} imap_unordered (func, iterable[, chunksize])

和 @ref{23a1,,imap()} 相同，只不过通过迭代器返回的结果是任意的。（当进程池中只有一个工作进程的时候，返回结果的顺序才能认为是"有序"的）
@end deffn

@geindex starmap() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool starmap}@anchor{a21}
@deffn {方法} starmap (func, iterable[, chunksize])

和 @ref{c26,,map()} 类似，不过 @emph{iterable} 中的每一项会被解包再作为函数参数。

比如可迭代对象 @code{[(1,2), (3, 4)]} 会转化为等价于 @code{[func(1,2), func(3,4)]} 的调用。


3.3 新版功能.

@end deffn

@geindex starmap_async() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool starmap_async}@anchor{a22}
@deffn {方法} starmap_async (func, iterable[, chunksize[, callback[, error_callback]]])

相当于 @ref{a21,,starmap()} 与 @ref{a25,,map_async()} 的结合，迭代 @emph{iterable} 的每一项，解包作为 @emph{func} 的参数并执行，返回用于获取结果的对象。


3.3 新版功能.

@end deffn

@geindex close() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool close}@anchor{239d}
@deffn {方法} close ()

阻止后续任务提交到进程池，当所有任务执行完成后，工作进程会退出。
@end deffn

@geindex terminate() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool terminate}@anchor{239e}
@deffn {方法} terminate ()

不必等待未完成的任务，立即停止工作进程。当进程池对象呗垃圾回收时， 会立即调用 @ref{239e,,terminate()} 。
@end deffn

@geindex join() (multiprocessing.pool.Pool 方法)
@anchor{library/multiprocessing multiprocessing pool Pool join}@anchor{23a3}
@deffn {方法} join ()

等待工作进程结束。调用 @ref{23a3,,join()} 前必须先调用 @ref{239d,,close()} 或者 @ref{239e,,terminate()} 。
@end deffn


3.3 新版功能: 进程池对象现在支持上下文管理器协议 - 参见 @ref{1420,,上下文管理器类型} 。@ref{1675,,__enter__()} 返回进程池对象, @ref{1677,,__exit__()} 会调用 @ref{239e,,terminate()} 。

@end deffn

@geindex AsyncResult (multiprocessing.pool 中的类)
@anchor{library/multiprocessing multiprocessing pool AsyncResult}@anchor{23a4}
@deffn {类} multiprocessing.pool.AsyncResult

@ref{23a0,,Pool.apply_async()} 和 @ref{a25,,Pool.map_async()} 返回对象所属的类。

@geindex get() (multiprocessing.pool.AsyncResult 方法)
@anchor{library/multiprocessing multiprocessing pool AsyncResult get}@anchor{23a5}
@deffn {方法} get ([timeout])

用于获取执行结果。如果 @emph{timeout} 不是 @code{None} 并且在 @emph{timeout} 秒内仍然没有执行完得到结果，则抛出 @ref{2348,,multiprocessing.TimeoutError} 异常。如果远程调用发生异常，这个异常会通过 @ref{23a5,,get()} 重新抛出。
@end deffn

@geindex wait() (multiprocessing.pool.AsyncResult 方法)
@anchor{library/multiprocessing multiprocessing pool AsyncResult wait}@anchor{23a6}
@deffn {方法} wait ([timeout])

阻塞，直到返回结果，或者 @emph{timeout} 秒后超时。
@end deffn

@geindex ready() (multiprocessing.pool.AsyncResult 方法)
@anchor{library/multiprocessing multiprocessing pool AsyncResult ready}@anchor{23a7}
@deffn {方法} ready ()

返回执行状态，是否已经完成。
@end deffn

@geindex successful() (multiprocessing.pool.AsyncResult 方法)
@anchor{library/multiprocessing multiprocessing pool AsyncResult successful}@anchor{23a8}
@deffn {方法} successful ()

判断调用是否已经完成并且未引发异常。 如果还未获得结果则将引发 @ref{1fb,,ValueError}。


在 3.7 版更改: 如果没有执行完，会抛出 @ref{1fb,,ValueError}  异常而不是 @ref{fc1,,AssertionError} 。

@end deffn
@end deffn

下面的例子演示了进程池的用法:

@example
from multiprocessing import Pool
import time

def f(x):
    return x*x

if __name__ == '__main__':
    with Pool(processes=4) as pool:         # start 4 worker processes
        result = pool.apply_async(f, (10,)) # evaluate "f(10)" asynchronously in a single process
        print(result.get(timeout=1))        # prints "100" unless your computer is *very* slow

        print(pool.map(f, range(10)))       # prints "[0, 1, 4,..., 81]"

        it = pool.imap(f, range(10))
        print(next(it))                     # prints "0"
        print(next(it))                     # prints "1"
        print(it.next(timeout=1))           # prints "4" unless your computer is *very* slow

        result = pool.apply_async(time.sleep, (10,))
        print(result.get(timeout=1))        # raises multiprocessing.TimeoutError
@end example

@node 监听者及客户端,认证密码,进程池,参考
@anchor{library/multiprocessing listeners-and-clients}@anchor{23a9}@anchor{library/multiprocessing module-multiprocessing connection}@anchor{b8}@anchor{library/multiprocessing multiprocessing-listeners-clients}@anchor{2366}
@subsubsection 监听者及客户端


@geindex multiprocessing.connection (模块)

通常情况下，进程间通过队列或者 @ref{232b,,Pipe()} 返回的 @ref{2367,,Connection} 传递消息。

不过，@ref{b8,,multiprocessing.connection} 模块其实提供了一些更灵活的特性。最基础的用法是通过它抽象出来的高级API来操作socket或者Windows命名管道。也提供一些高级用法，如通过 @ref{8f,,hmac} 模块来支持 @emph{摘要认证}，以及同时监听多个管道连接。

@geindex deliver_challenge() (在 multiprocessing.connection 模块中)
@anchor{library/multiprocessing multiprocessing connection deliver_challenge}@anchor{23aa}
@deffn {函数} multiprocessing.connection.deliver_challenge (connection, authkey)

发送一个随机生成的消息到另一端，并等待回复。

如果收到的回复与使用 @emph{authkey} 作为键生成的信息摘要匹配成功，就会发送一个欢迎信息给管道另一端。否则抛出 @ref{2347,,AuthenticationError} 异常。
@end deffn

@geindex answer_challenge() (在 multiprocessing.connection 模块中)
@anchor{library/multiprocessing multiprocessing connection answer_challenge}@anchor{23ab}
@deffn {函数} multiprocessing.connection.answer_challenge (connection, authkey)

接收一条信息，使用 @emph{authkey} 作为键计算信息摘要，然后将摘要发送回去。

如果没有收到欢迎消息，就抛出 @ref{2347,,AuthenticationError} 异常。
@end deffn

@geindex Client() (在 multiprocessing.connection 模块中)
@anchor{library/multiprocessing multiprocessing connection Client}@anchor{23ac}
@deffn {函数} multiprocessing.connection.Client (address[, family[, authkey]])

尝试使用 @emph{address} 地址上的监听者建立一个连接，返回 @ref{2367,,Connection} 。

连接的类型取决于 @emph{family} 参数，但是通常可以省略，因为可以通过 @emph{address} 的格式推导出来。(查看 @ref{23ad,,地址格式} )

如果提供了 @emph{authkey} 参数并且不是 None，那它必须是一个字符串并且会被当做基于 HMAC 认证的密钥。如果 @emph{authkey} 是None 则不会有认证行为。认证失败抛出 @ref{2347,,AuthenticationError} 异常，请查看 See @ref{2343,,认证密码} 。
@end deffn

@geindex Listener (multiprocessing.connection 中的类)
@anchor{library/multiprocessing multiprocessing connection Listener}@anchor{23ae}
@deffn {类} multiprocessing.connection.Listener ([address[, family[, backlog[, authkey]]]])

可以监听连接请求，是对于绑定套接字或者 Windows 命名管道的封装。

@emph{address} 是监听器对象中的绑定套接字或命名管道使用的地址。

@cartouche
@quotation 注解 
如果使用 '0.0.0.0' 作为监听地址，那么在Windows上这个地址无法建立连接。想要建立一个可连接的端点，应该使用 '127.0.0.1' 。
@end quotation
@end cartouche

@emph{family} 是套接字(或者命名管道)使用的类型。它可以是以下一种:  @code{'AF_INET'} ( TCP 套接字类型), @code{'AF_UNIX'} ( Unix 域套接字) 或者 @code{'AF_PIPE'} ( Windows 命名管道)。其中只有第一个保证各平台可用。如果 @emph{family} 是 @code{None} ,那么 family 会根据 @emph{address} 的格式自动推导出来。如果 @emph{address} 也是 @code{None} , 则取默认值。默认值为可用类型中速度最快的。见 @ref{23ad,,地址格式} 。注意，如果 @emph{family} 是 @code{'AF_UNIX'} 而address是`@w{`}None`@w{`} ,套接字会在一个 @ref{1bfa,,tempfile.mkstemp()} 创建的私有临时目录中创建。

如果监听器对象使用了套接字，@emph{backlog} (默认值为1) 会在套接字绑定后传递给它的 @ref{745,,listen()} 方法。

如果提供了 @emph{authkey} 参数并且不是 None，那它必须是一个字符串并且会被当做基于 HMAC 认证的密钥。如果 @emph{authkey} 是None 则不会有认证行为。认证失败抛出 @ref{2347,,AuthenticationError} 异常，请查看 See @ref{2343,,认证密码} 。

@geindex accept() (multiprocessing.connection.Listener 方法)
@anchor{library/multiprocessing multiprocessing connection Listener accept}@anchor{23af}
@deffn {方法} accept ()

接受一个连接并返回一个 @ref{2367,,Connection} 对象，其连接到的监听器对象已绑定套接字或者命名管道。如果已经尝试过认证并且失败了，则会抛出 @ref{2347,,AuthenticationError} 异常。
@end deffn

@geindex close() (multiprocessing.connection.Listener 方法)
@anchor{library/multiprocessing multiprocessing connection Listener close}@anchor{23b0}
@deffn {方法} close ()

关闭监听器对象上的绑定套接字或者命名管道。此函数会在监听器被垃圾回收后自动调用。不过仍然建议显式调用函数关闭。
@end deffn

监听器对象拥有下列只读属性:

@geindex address (multiprocessing.connection.Listener 属性)
@anchor{library/multiprocessing multiprocessing connection Listener address}@anchor{23b1}
@deffn {属性} address

监听器对象使用的地址。
@end deffn

@geindex last_accepted (multiprocessing.connection.Listener 属性)
@anchor{library/multiprocessing multiprocessing connection Listener last_accepted}@anchor{23b2}
@deffn {属性} last_accepted

最后一个连接所使用的地址。如果没有的话就是 @code{None} 。
@end deffn


3.3 新版功能: 监听器对象现在支持了上下文管理协议 - 见 @ref{1420,,上下文管理器类型} 。 @ref{1675,,__enter__()} 返回一个监听器对象, @ref{1677,,__exit__()} 会调用 @ref{23b0,,close()} 。

@end deffn

@geindex wait() (在 multiprocessing.connection 模块中)
@anchor{library/multiprocessing multiprocessing connection wait}@anchor{a1f}
@deffn {函数} multiprocessing.connection.wait (object_list, timeout=None)

一直等待直到 @emph{object_list} 中某个对象处于就绪状态。返回 @emph{object_list} 中处于就绪状态的对象。如果 @emph{timeout} 是一个浮点型，该方法会最多阻塞这么多秒。如果 @emph{timeout} 是 @code{None} ，则会允许阻塞的事件没有限制。timeout为负数的情况下和为0的情况相同。

对于 Unix 和 Windows ，满足下列条件的对象可以出现在 @emph{object_list} 中


@itemize *

@item 
可读的 @ref{2367,,Connection} 对象；

@item 
一个已连接并且可读的 @ref{66e,,socket.socket} 对象；或者

@item 
@ref{3aa,,Process} 对象中的 @ref{a20,,sentinel} 属性。
@end itemize

当一个连接或者套接字对象拥有有效的数据可被读取的时候，或者另一端关闭后，这个对象就处于就绪状态。

@strong{Unix}: @code{wait(object_list, timeout)} 和 @code{select.select(object_list, [], [], timeout)} 几乎相同。差别在于，如果 @ref{66d,,select.select()} 被信号中断，它会抛出一个附带错误号为 @code{EINTR} 的 @ref{1d3,,OSError} 异常，而 @ref{a1f,,wait()} 不会。

@strong{Windows}: @emph{object_list} 中的元素必须是一个表示为整数的可等待的句柄(按照 Win32 函数 @code{WaitForMultipleObjects()} 的文档中所定义) 或者一个拥有 @code{fileno()} 方法的对象，这个对象返回一个套接字句柄或者管道句柄。（注意管道和套接字两种句柄 @strong{不是} 可等待的句柄）


3.3 新版功能.

@end deffn

@strong{示例}

下面的服务代码创建了一个使用 @code{'secret password'} 作为认证密码的监听器。它会等待连接然后发送一些数据给客户端:

@example
from multiprocessing.connection import Listener
from array import array

address = ('localhost', 6000)     # family is deduced to be 'AF_INET'

with Listener(address, authkey=b'secret password') as listener:
    with listener.accept() as conn:
        print('connection accepted from', listener.last_accepted)

        conn.send([2.25, None, 'junk', float])

        conn.send_bytes(b'hello')

        conn.send_bytes(array('i', [42, 1729]))
@end example

下面的代码连接到服务然后从服务器上j接收一些数据:

@example
from multiprocessing.connection import Client
from array import array

address = ('localhost', 6000)

with Client(address, authkey=b'secret password') as conn:
    print(conn.recv())                  # => [2.25, None, 'junk', float]

    print(conn.recv_bytes())            # => 'hello'

    arr = array('i', [0, 0, 0, 0, 0])
    print(conn.recv_bytes_into(arr))    # => 8
    print(arr)                          # => array('i', [42, 1729, 0, 0, 0])
@end example

下面的代码使用了 @ref{a1f,,wait()} ，以便在同时等待多个进程发来消息。

@example
import time, random
from multiprocessing import Process, Pipe, current_process
from multiprocessing.connection import wait

def foo(w):
    for i in range(10):
        w.send((i, current_process().name))
    w.close()

if __name__ == '__main__':
    readers = []

    for i in range(4):
        r, w = Pipe(duplex=False)
        readers.append(r)
        p = Process(target=foo, args=(w,))
        p.start()
        # We close the writable end of the pipe now to be sure that
        # p is the only process which owns a handle for it.  This
        # ensures that when p closes its handle for the writable end,
        # wait() will promptly report the readable end as being ready.
        w.close()

    while readers:
        for r in wait(readers):
            try:
                msg = r.recv()
            except EOFError:
                readers.remove(r)
            else:
                print(msg)
@end example

@menu
* 地址格式:: 

@end menu

@node 地址格式,,,监听者及客户端
@anchor{library/multiprocessing address-formats}@anchor{23b3}@anchor{library/multiprocessing multiprocessing-address-formats}@anchor{23ad}
@subsubsection 地址格式



@itemize *

@item 
@code{'AF_INET'} 地址是 @code{(hostname, port)}  形式的元组类型，其中 @emph{hostname} 是一个字符串，@emph{port} 是整数。

@item 
@code{'AF_UNIX'} 地址是文件系统上文件名的字符串。

@item 

@table @asis

@item @code{'AF_PIPE'} 是这种格式的字符串

@code{r'\.\pipe@{PipeName@}'} 。如果要用 @ref{23ac,,Client()} 连接到一个名为 @emph{ServerName} 的远程命名管道，应该替换为使用 @code{r'\@emph{ServerName}\pipe@{PipeName@}'} 这种格式。
@end table
@end itemize

注意，使用两个反斜线开头的字符串默认被当做 @code{'AF_PIPE'} 地址而不是 @code{'AF_UNIX'}  。

@node 认证密码,日志记录<2>,监听者及客户端,参考
@anchor{library/multiprocessing authentication-keys}@anchor{23b4}@anchor{library/multiprocessing multiprocessing-auth-keys}@anchor{2343}
@subsubsection 认证密码


当使用 @ref{2369,,Connection.recv} 接收数据时，数据会自动被反序列化。不幸的是，对于一个不可信的数据源发来的数据，反序列化是存在安全风险的。所以 @ref{23ae,,Listener} 和 @ref{23ac,,Client()} 之间使用 @ref{8f,,hmac} 模块进行摘要认证。

认证密钥是一个 byte 类型的字符串，可以认为是和密码一样的东西，连接建立好后，双方都会要求另一方证明知道认证密钥。（这个证明过程不会通过连接发送密钥）

如果要求认证但是没有指定认证密钥，则会使用 @code{current_process().authkey} 的返回值 (参见 @ref{3aa,,Process})。 这个值将被当前进程所创建的任何 @ref{3aa,,Process} 对象自动继承。 这意味着 (在默认情况下) 一个包含多进程的程序中的所有进程会在相互间建立连接的时候共享单个认证密钥。

@ref{4cb,,os.urandom()} 也可以用来生成合适的认证密钥。

@node 日志记录<2>,multiprocessing dummy 模块,认证密码,参考
@anchor{library/multiprocessing logging}@anchor{23b5}
@subsubsection 日志记录


当前模块也提供了一些对 logging 的支持。注意， @ref{aa,,logging} 模块本身并没有使用进程间共享的锁，所以来自于多个进程的日志可能（具体取决于使用的日志 handler 类型）相互覆盖或者混杂。

@geindex get_logger() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing get_logger}@anchor{23b6}
@deffn {函数} multiprocessing.get_logger ()

返回 @ref{b7,,multiprocessing} 使用的 logger，必要的话会创建一个新的。

如果创建的首个 logger 日志级别为 @code{logging.NOTSET} 并且没有默认 handler。通过这个 logger 打印的消息不会传递到根 logger。

注意在 Windows 上，子进程只会继承父进程 logger 的日志级别 - 对于logger的其他自定义项不会继承。
@end deffn

@geindex log_to_stderr() (在 multiprocessing 模块中)
@anchor{library/multiprocessing multiprocessing log_to_stderr}@anchor{23b7}
@deffn {函数} multiprocessing.log_to_stderr ()

此函数会调用 @ref{23b6,,get_logger()} 但是会在返回的 logger 上增加一个 handler，将所有输出都使用 @code{'[%(levelname)s/%(processName)s] %(message)s'} 的格式发送到 @ref{308,,sys.stderr} 。
@end deffn

下面是一个在交互式解释器中打开日志功能的例子:

@example
>>> import multiprocessing, logging
>>> logger = multiprocessing.log_to_stderr()
>>> logger.setLevel(logging.INFO)
>>> logger.warning('doomed')
[WARNING/MainProcess] doomed
>>> m = multiprocessing.Manager()
[INFO/SyncManager-...] child process calling self.run()
[INFO/SyncManager-...] created temp directory /.../pymp-...
[INFO/SyncManager-...] manager serving at '/.../listener-...'
>>> del m
[INFO/MainProcess] sending shutdown message to manager
[INFO/SyncManager-...] manager exiting with exitcode 0
@end example

要查看日志等级的完整列表，见 @ref{aa,,logging} 模块。

@node multiprocessing dummy 模块,,日志记录<2>,参考
@anchor{library/multiprocessing module-multiprocessing dummy}@anchor{b9}@anchor{library/multiprocessing the-multiprocessing-dummy-module}@anchor{23b8}
@subsubsection @code{multiprocessing.dummy} 模块


@geindex multiprocessing.dummy (模块)

@ref{b9,,multiprocessing.dummy} 复制了 @ref{b7,,multiprocessing} 的 API，不过是在 @ref{109,,threading} 模块之上包装了一层。

@node 编程指导,例子<10>,参考,multiprocessing --- 基于进程的并行
@anchor{library/multiprocessing multiprocessing-programming}@anchor{2325}@anchor{library/multiprocessing programming-guidelines}@anchor{23b9}
@subsubsection 编程指导


使用 @ref{b7,,multiprocessing} 时，应遵循一些指导原则和习惯用法。

@menu
* 所有start方法:: 
* spawn 和 forkserver 启动方式:: 

@end menu

@node 所有start方法,spawn 和 forkserver 启动方式,,编程指导
@anchor{library/multiprocessing all-start-methods}@anchor{23ba}
@subsubsection 所有start方法


下面这些适用于所有start方法。

避免共享状态

@quotation

应该尽可能避免在进程间传递大量数据，越少越好。

最好坚持使用队列或者管道进行进程间通信，而不是底层的同步原语。
@end quotation

可序列化

@quotation

保证所代理的方法的参数是可以序列化的。
@end quotation

代理的线程安全性

@quotation

不要在多线程中同时使用一个代理对象，除非你用锁保护它。

（而在不同进程中使用 @emph{相同} 的代理对象却没有问题。）
@end quotation

使用 Join 避免僵尸进程

@quotation

在 Unix 上，如果一个进程执行完成但是没有被 join，就会变成僵尸进程。一般来说，僵尸进程不会很多，因为每次新启动进程（或者 @ref{2360,,active_children()} 被调用）时，所有已执行完成且没有被 join 的进程都会自动被 join，而且对一个执行完的进程调用 @ref{2340,,Process.is_alive} 也会 join 这个进程。尽管如此，对自己启动的进程显式调用 join 依然是最佳实践。
@end quotation

继承优于序列化、反序列化

@quotation

当使用 @emph{spawn} 或者 @emph{forkserver} 的启动方式时，@ref{b7,,multiprocessing}  中的许多类型都必须是可序列化的，这样子进程才能使用它们。但是通常我们都应该避免使用管道和队列发送共享对象到另外一个进程，而是重新组织代码，对于其他进程创建出来的共享对象，让那些需要访问这些对象的子进程可以直接将这些对象从父进程继承过来。
@end quotation

避免杀死进程

@quotation

听过 @ref{2344,,Process.terminate}  停止一个进程很容易导致这个进程正在使用的共享资源（如锁、信号量、管道和队列）损坏或者变得不可用，无法在其他进程中继续使用。

所以，最好只对那些从来不使用共享资源的进程调用 @ref{2344,,Process.terminate} 。
@end quotation

Join 使用队列的进程

@quotation

记住，往队列放入数据的进程会一直等待直到队列中所有项被"feeder" 线程传给底层管道。（子进程可以调用队列的 @ref{2354,,Queue.cancel_join_thread} 方法禁止这种行为）

这意味着，任何使用队列的时候，你都要确保在进程join之前，所有存放到队列中的项将会被其他进程、线程完全消费。否则不能保证这个写过队列的进程可以正常终止。记住非精灵进程会自动 join 。

下面是一个会导致死锁的例子:

@example
from multiprocessing import Process, Queue

def f(q):
    q.put('X' * 1000000)

if __name__ == '__main__':
    queue = Queue()
    p = Process(target=f, args=(queue,))
    p.start()
    p.join()                    # this deadlocks
    obj = queue.get()
@end example

交换最后两行可以修复这个问题（或者直接删掉 @code{p.join()}）。
@end quotation

显示传递资源给子进程

@quotation

在Unix上，使用 @emph{fork} 方式启动的子进程可以使用父进程中全局创建的共享资源。不过，最好是显式将资源对象通过参数的形式传递给子进程。

除了（部分原因）让代码兼容 Windows 以及其他的进程启动方式外，这种形式还保证了在子进程生命期这个对象是不会被父进程垃圾回收的。如果父进程中的某些对象被垃圾回收会导致资源释放，这就变得很重要。

所以对于实例：

@example
from multiprocessing import Process, Lock

def f():
    ... do something using "lock" ...

if __name__ == '__main__':
    lock = Lock()
    for i in range(10):
        Process(target=f).start()
@end example

应当重写成这样：

@example
from multiprocessing import Process, Lock

def f(l):
    ... do something using "l" ...

if __name__ == '__main__':
    lock = Lock()
    for i in range(10):
        Process(target=f, args=(lock,)).start()
@end example
@end quotation

谨防将 @ref{306,,sys.stdin} 数据替换为 “类似文件的对象”

@quotation

@ref{b7,,multiprocessing} 原本会无条件地这样调用:

@example
os.close(sys.stdin.fileno())
@end example

在  @code{multiprocessing.Process._bootstrap()}  方法中 —— 这会导致与"进程中的进程"相关的一些问题。这已经被修改成了:

@example
sys.stdin.close()
sys.stdin = open(os.open(os.devnull, os.O_RDONLY), closefd=False)
@end example

它解决了进程相互冲突导致文件描述符错误的根本问题，但是对使用带缓冲的“文件类对象”替换 @ref{306,,sys.stdin()} 作为输出的应用程序造成了潜在的危险。如果多个进程调用了此文件类对象的 @ref{fa0,,close()} 方法，会导致相同的数据多次刷写到此对象，损坏数据。

如果你写入文件类对象并实现了自己的缓存，可以在每次追加缓存数据时记录当前进程id，从而将其变成 fork 安全的，当发现进程id变化后舍弃之前的缓存，例如:

@example
@@property
def cache(self):
    pid = os.getpid()
    if pid != self._pid:
        self._pid = pid
        self._cache = []
    return self._cache
@end example

需要更多信息，请查看 bpo-5155@footnote{https://bugs.python.org/issue5155}, bpo-5313@footnote{https://bugs.python.org/issue5313} 以及 bpo-5331@footnote{https://bugs.python.org/issue5331}
@end quotation

@node spawn 和 forkserver 启动方式,,所有start方法,编程指导
@anchor{library/multiprocessing the-spawn-and-forkserver-start-methods}@anchor{23bb}
@subsubsection @emph{spawn} 和 @emph{forkserver} 启动方式


相对于 @emph{fork} 启动方式，有一些额外的限制。

更依赖序列化

@quotation

@code{Process.__init__()} 的所有参数都必须可序列化。同样的，当你继承 @ref{3aa,,Process} 时，需要保证当调用 @ref{233d,,Process.start} 方法时，实例可以被序列化。
@end quotation

全局变量

@quotation

记住，如果子进程中的代码尝试访问一个全局变量，它所看到的值（如果有）可能和父进程中执行 @ref{233d,,Process.start} 那一刻的值不一样。

当全局变量知识模块级别的常量时，是不会有问题的。
@end quotation

安全导入主模块

@quotation

确保主模块可以被新启动的Python解释器安全导入而不会引发什么副作用（比如又启动了一个子进程）

例如，使用 @emph{spawn} 或 @emph{forkserver} 启动方式执行下面的模块，会引发 @ref{2ba,,RuntimeError} 异常而失败。

@example
from multiprocessing import Process

def foo():
    print('hello')

p = Process(target=foo)
p.start()
@end example

应该通过下面的方法使用 @code{if __name__ == '__main__':} ，从而保护程序"入口点":

@example
from multiprocessing import Process, freeze_support, set_start_method

def foo():
    print('hello')

if __name__ == '__main__':
    freeze_support()
    set_start_method('spawn')
    p = Process(target=foo)
    p.start()
@end example

（如果程序将正常运行而不是冻结，则可以省略 @code{freeze_support()} 行）

这允许新启动的 Python 解释器安全导入模块然后运行模块中的 @code{foo()} 函数。

如果主模块中创建了进程池或者管理器，这个规则也适用。
@end quotation

@node 例子<10>,,编程指导,multiprocessing --- 基于进程的并行
@anchor{library/multiprocessing examples}@anchor{23bc}@anchor{library/multiprocessing multiprocessing-examples}@anchor{2355}
@subsubsection 例子


创建和使用自定义管理器、代理的示例:

@example
from multiprocessing import freeze_support
from multiprocessing.managers import BaseManager, BaseProxy
import operator

##

class Foo:
    def f(self):
        print('you called Foo.f()')
    def g(self):
        print('you called Foo.g()')
    def _h(self):
        print('you called Foo._h()')

# A simple generator function
def baz():
    for i in range(10):
        yield i*i

# Proxy type for generator objects
class GeneratorProxy(BaseProxy):
    _exposed_ = ['__next__']
    def __iter__(self):
        return self
    def __next__(self):
        return self._callmethod('__next__')

# Function to return the operator module
def get_operator_module():
    return operator

##

class MyManager(BaseManager):
    pass

# register the Foo class; make `f()` and `g()` accessible via proxy
MyManager.register('Foo1', Foo)

# register the Foo class; make `g()` and `_h()` accessible via proxy
MyManager.register('Foo2', Foo, exposed=('g', '_h'))

# register the generator function baz; use `GeneratorProxy` to make proxies
MyManager.register('baz', baz, proxytype=GeneratorProxy)

# register get_operator_module(); make public functions accessible via proxy
MyManager.register('operator', get_operator_module)

##

def test():
    manager = MyManager()
    manager.start()

    print('-' * 20)

    f1 = manager.Foo1()
    f1.f()
    f1.g()
    assert not hasattr(f1, '_h')
    assert sorted(f1._exposed_) == sorted(['f', 'g'])

    print('-' * 20)

    f2 = manager.Foo2()
    f2.g()
    f2._h()
    assert not hasattr(f2, 'f')
    assert sorted(f2._exposed_) == sorted(['g', '_h'])

    print('-' * 20)

    it = manager.baz()
    for i in it:
        print('<%d>' % i, end=' ')
    print()

    print('-' * 20)

    op = manager.operator()
    print('op.add(23, 45) =', op.add(23, 45))
    print('op.pow(2, 94) =', op.pow(2, 94))
    print('op._exposed_ =', op._exposed_)

##

if __name__ == '__main__':
    freeze_support()
    test()
@end example

使用 @ref{875,,Pool}:

@example
import multiprocessing
import time
import random
import sys

#
# Functions used by test code
#

def calculate(func, args):
    result = func(*args)
    return '%s says that %s%s = %s' % (
        multiprocessing.current_process().name,
        func.__name__, args, result
        )

def calculatestar(args):
    return calculate(*args)

def mul(a, b):
    time.sleep(0.5 * random.random())
    return a * b

def plus(a, b):
    time.sleep(0.5 * random.random())
    return a + b

def f(x):
    return 1.0 / (x - 5.0)

def pow3(x):
    return x ** 3

def noop(x):
    pass

#
# Test code
#

def test():
    PROCESSES = 4
    print('Creating pool with %d processes\n' % PROCESSES)

    with multiprocessing.Pool(PROCESSES) as pool:
        #
        # Tests
        #

        TASKS = [(mul, (i, 7)) for i in range(10)] + \
                [(plus, (i, 8)) for i in range(10)]

        results = [pool.apply_async(calculate, t) for t in TASKS]
        imap_it = pool.imap(calculatestar, TASKS)
        imap_unordered_it = pool.imap_unordered(calculatestar, TASKS)

        print('Ordered results using pool.apply_async():')
        for r in results:
            print('\t', r.get())
        print()

        print('Ordered results using pool.imap():')
        for x in imap_it:
            print('\t', x)
        print()

        print('Unordered results using pool.imap_unordered():')
        for x in imap_unordered_it:
            print('\t', x)
        print()

        print('Ordered results using pool.map() --- will block till complete:')
        for x in pool.map(calculatestar, TASKS):
            print('\t', x)
        print()

        #
        # Test error handling
        #

        print('Testing error handling:')

        try:
            print(pool.apply(f, (5,)))
        except ZeroDivisionError:
            print('\tGot ZeroDivisionError as expected from pool.apply()')
        else:
            raise AssertionError('expected ZeroDivisionError')

        try:
            print(pool.map(f, list(range(10))))
        except ZeroDivisionError:
            print('\tGot ZeroDivisionError as expected from pool.map()')
        else:
            raise AssertionError('expected ZeroDivisionError')

        try:
            print(list(pool.imap(f, list(range(10)))))
        except ZeroDivisionError:
            print('\tGot ZeroDivisionError as expected from list(pool.imap())')
        else:
            raise AssertionError('expected ZeroDivisionError')

        it = pool.imap(f, list(range(10)))
        for i in range(10):
            try:
                x = next(it)
            except ZeroDivisionError:
                if i == 5:
                    pass
            except StopIteration:
                break
            else:
                if i == 5:
                    raise AssertionError('expected ZeroDivisionError')

        assert i == 9
        print('\tGot ZeroDivisionError as expected from IMapIterator.next()')
        print()

        #
        # Testing timeouts
        #

        print('Testing ApplyResult.get() with timeout:', end=' ')
        res = pool.apply_async(calculate, TASKS[0])
        while 1:
            sys.stdout.flush()
            try:
                sys.stdout.write('\n\t%s' % res.get(0.02))
                break
            except multiprocessing.TimeoutError:
                sys.stdout.write('.')
        print()
        print()

        print('Testing IMapIterator.next() with timeout:', end=' ')
        it = pool.imap(calculatestar, TASKS)
        while 1:
            sys.stdout.flush()
            try:
                sys.stdout.write('\n\t%s' % it.next(0.02))
            except StopIteration:
                break
            except multiprocessing.TimeoutError:
                sys.stdout.write('.')
        print()
        print()


if __name__ == '__main__':
    multiprocessing.freeze_support()
    test()
@end example

一个演示如何使用队列来向一组工作进程提供任务并收集结果的例子：

@example
import time
import random

from multiprocessing import Process, Queue, current_process, freeze_support

#
# Function run by worker processes
#

def worker(input, output):
    for func, args in iter(input.get, 'STOP'):
        result = calculate(func, args)
        output.put(result)

#
# Function used to calculate result
#

def calculate(func, args):
    result = func(*args)
    return '%s says that %s%s = %s' % \
        (current_process().name, func.__name__, args, result)

#
# Functions referenced by tasks
#

def mul(a, b):
    time.sleep(0.5*random.random())
    return a * b

def plus(a, b):
    time.sleep(0.5*random.random())
    return a + b

#
#
#

def test():
    NUMBER_OF_PROCESSES = 4
    TASKS1 = [(mul, (i, 7)) for i in range(20)]
    TASKS2 = [(plus, (i, 8)) for i in range(10)]

    # Create queues
    task_queue = Queue()
    done_queue = Queue()

    # Submit tasks
    for task in TASKS1:
        task_queue.put(task)

    # Start worker processes
    for i in range(NUMBER_OF_PROCESSES):
        Process(target=worker, args=(task_queue, done_queue)).start()

    # Get and print results
    print('Unordered results:')
    for i in range(len(TASKS1)):
        print('\t', done_queue.get())

    # Add more tasks using `put()`
    for task in TASKS2:
        task_queue.put(task)

    # Get and print some more results
    for i in range(len(TASKS2)):
        print('\t', done_queue.get())

    # Tell child processes to stop
    for i in range(NUMBER_OF_PROCESSES):
        task_queue.put('STOP')


if __name__ == '__main__':
    freeze_support()
    test()
@end example

@node multiprocessing shared_memory --- 可从进程直接访问的共享内存,concurrent 包,multiprocessing --- 基于进程的并行,并发执行
@anchor{library/multiprocessing shared_memory doc}@anchor{23bd}@anchor{library/multiprocessing shared_memory module-multiprocessing shared_memory}@anchor{bc}@anchor{library/multiprocessing shared_memory multiprocessing-shared-memory-provides-shared-memory-for-direct-access-across-processes}@anchor{23be}
@subsection @code{multiprocessing.shared_memory} --- 可从进程直接访问的共享内存


@geindex multiprocessing.shared_memory (模块)

@strong{源代码:} Lib/multiprocessing/shared_memory.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/multiprocessing/shared_memory.py}


3.8 新版功能.


@geindex Shared Memory
@geindex POSIX Shared Memory
@geindex Named Shared Memory


__________________________________________________________________


该模块提供了一个 @ref{2328,,SharedMemory} 类，用于分配和管理多核或对称多处理器（SMP）机器上进程间的共享内存。为了协助管理不同进程间的共享内存生命周期，@code{multiprocessing.managers} 模块也提供了一个 @ref{237f,,BaseManager} 的子类： @code{SharedMemoryManager}。

In this module, shared memory refers to "System V style" shared memory blocks
(though is not necessarily implemented explicitly as such) and does not refer
to "distributed shared memory".  This style of shared memory permits distinct
processes to potentially read and write to a common (or shared) region of
volatile memory.  Processes are conventionally limited to only have access to
their own process memory space but shared memory permits the sharing
of data between processes, avoiding the need to instead send messages between
processes containing that data.  Sharing data directly via memory can provide
significant performance benefits compared to sharing data via disk or socket
or other communications requiring the serialization/deserialization and
copying of data.

@geindex SharedMemory (multiprocessing.shared_memory 中的类)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory SharedMemory}@anchor{2328}
@deffn {类} multiprocessing.shared_memory.SharedMemory (name=None, create=False, size=0)

Creates a new shared memory block or attaches to an existing shared
memory block.  Each shared memory block is assigned a unique name.
In this way, one process can create a shared memory block with a
particular name and a different process can attach to that same shared
memory block using that same name.

As a resource for sharing data across processes, shared memory blocks
may outlive the original process that created them.  When one process
no longer needs access to a shared memory block that might still be
needed by other processes, the @ref{23bf,,close()} method should be called.
When a shared memory block is no longer needed by any process, the
@ref{23c0,,unlink()} method should be called to ensure proper cleanup.

@emph{name} is the unique name for the requested shared memory, specified as
a string.  When creating a new shared memory block, if @code{None} (the
default) is supplied for the name, a novel name will be generated.

@emph{create} controls whether a new shared memory block is created (@code{True})
or an existing shared memory block is attached (@code{False}).

@emph{size} specifies the requested number of bytes when creating a new shared
memory block.  Because some platforms choose to allocate chunks of memory
based upon that platform's memory page size, the exact size of the shared
memory block may be larger or equal to the size requested.  When attaching
to an existing shared memory block, the @code{size} parameter is ignored.

@geindex close() (multiprocessing.shared_memory.SharedMemory 方法)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory SharedMemory close}@anchor{23bf}
@deffn {方法} close ()

Closes access to the shared memory from this instance.  In order to
ensure proper cleanup of resources, all instances should call
@code{close()} once the instance is no longer needed.  Note that calling
@code{close()} does not cause the shared memory block itself to be
destroyed.
@end deffn

@geindex unlink() (multiprocessing.shared_memory.SharedMemory 方法)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory SharedMemory unlink}@anchor{23c0}
@deffn {方法} unlink ()

Requests that the underlying shared memory block be destroyed.  In
order to ensure proper cleanup of resources, @code{unlink()} should be
called once (and only once) across all processes which have need
for the shared memory block.  After requesting its destruction, a
shared memory block may or may not be immediately destroyed and
this behavior may differ across platforms.  Attempts to access data
inside the shared memory block after @code{unlink()} has been called may
result in memory access errors.  Note: the last process relinquishing
its hold on a shared memory block may call @code{unlink()} and
@ref{23bf,,close()} in either order.
@end deffn

@geindex buf (multiprocessing.shared_memory.SharedMemory 属性)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory SharedMemory buf}@anchor{23c1}
@deffn {属性} buf

A memoryview of contents of the shared memory block.
@end deffn

@geindex name (multiprocessing.shared_memory.SharedMemory 属性)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory SharedMemory name}@anchor{23c2}
@deffn {属性} name

Read-only access to the unique name of the shared memory block.
@end deffn

@geindex size (multiprocessing.shared_memory.SharedMemory 属性)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory SharedMemory size}@anchor{23c3}
@deffn {属性} size

Read-only access to size in bytes of the shared memory block.
@end deffn
@end deffn

The following example demonstrates low-level use of @ref{2328,,SharedMemory}
instances:

@example
>>> from multiprocessing import shared_memory
>>> shm_a = shared_memory.SharedMemory(create=True, size=10)
>>> type(shm_a.buf)
<class 'memoryview'>
>>> buffer = shm_a.buf
>>> len(buffer)
10
>>> buffer[:4] = bytearray([22, 33, 44, 55])  # Modify multiple at once
>>> buffer[4] = 100                           # Modify single byte at a time
>>> # Attach to an existing shared memory block
>>> shm_b = shared_memory.SharedMemory(shm_a.name)
>>> import array
>>> array.array('b', shm_b.buf[:5])  # Copy the data into a new array.array
array('b', [22, 33, 44, 55, 100])
>>> shm_b.buf[:5] = b'howdy'  # Modify via shm_b using bytes
>>> bytes(shm_a.buf[:5])      # Access via shm_a
b'howdy'
>>> shm_b.close()   # Close each SharedMemory instance
>>> shm_a.close()
>>> shm_a.unlink()  # Call unlink only once to release the shared memory
@end example

The following example demonstrates a practical use of the @ref{2328,,SharedMemory}
class with NumPy arrays@footnote{https://www.numpy.org/}, accessing the
same @code{numpy.ndarray} from two distinct Python shells:

@example
>>> # In the first Python interactive shell
>>> import numpy as np
>>> a = np.array([1, 1, 2, 3, 5, 8])  # Start with an existing NumPy array
>>> from multiprocessing import shared_memory
>>> shm = shared_memory.SharedMemory(create=True, size=a.nbytes)
>>> # Now create a NumPy array backed by shared memory
>>> b = np.ndarray(a.shape, dtype=a.dtype, buffer=shm.buf)
>>> b[:] = a[:]  # Copy the original data into shared memory
>>> b
array([1, 1, 2, 3, 5, 8])
>>> type(b)
<class 'numpy.ndarray'>
>>> type(a)
<class 'numpy.ndarray'>
>>> shm.name  # We did not specify a name so one was chosen for us
'psm_21467_46075'

>>> # In either the same shell or a new Python shell on the same machine
>>> import numpy as np
>>> from multiprocessing import shared_memory
>>> # Attach to the existing shared memory block
>>> existing_shm = shared_memory.SharedMemory(name='psm_21467_46075')
>>> # Note that a.shape is (6,) and a.dtype is np.int64 in this example
>>> c = np.ndarray((6,), dtype=np.int64, buffer=existing_shm.buf)
>>> c
array([1, 1, 2, 3, 5, 8])
>>> c[-1] = 888
>>> c
array([  1,   1,   2,   3,   5, 888])

>>> # Back in the first Python interactive shell, b reflects this change
>>> b
array([  1,   1,   2,   3,   5, 888])

>>> # Clean up from within the second Python shell
>>> del c  # Unnecessary; merely emphasizing the array is no longer used
>>> existing_shm.close()

>>> # Clean up from within the first Python shell
>>> del b  # Unnecessary; merely emphasizing the array is no longer used
>>> shm.close()
>>> shm.unlink()  # Free and release the shared memory block at the very end
@end example

@geindex SharedMemoryManager (multiprocessing.managers 中的类)
@anchor{library/multiprocessing shared_memory multiprocessing managers SharedMemoryManager}@anchor{23c4}
@deffn {类} multiprocessing.managers.SharedMemoryManager ([address[, authkey]])

A subclass of @ref{237f,,BaseManager} which can be
used for the management of shared memory blocks across processes.

A call to @ref{2380,,start()} on a
@ref{23c4,,SharedMemoryManager} instance causes a new process to be started.
This new process's sole purpose is to manage the life cycle
of all shared memory blocks created through it.  To trigger the release
of all shared memory blocks managed by that process, call
@ref{2384,,shutdown()} on the instance.
This triggers a @code{SharedMemory.unlink()} call on all of the
@ref{23c5,,SharedMemory} objects managed by that process and then
stops the process itself.  By creating @code{SharedMemory} instances
through a @code{SharedMemoryManager}, we avoid the need to manually track
and trigger the freeing of shared memory resources.

This class provides methods for creating and returning @ref{23c5,,SharedMemory}
instances and for creating a list-like object (@ref{23c6,,ShareableList})
backed by shared memory.

Refer to @ref{237f,,multiprocessing.managers.BaseManager} for a description
of the inherited @emph{address} and @emph{authkey} optional input arguments and how
they may be used to connect to an existing @code{SharedMemoryManager} service
from other processes.

@geindex SharedMemory() (multiprocessing.managers.SharedMemoryManager 方法)
@anchor{library/multiprocessing shared_memory multiprocessing managers SharedMemoryManager SharedMemory}@anchor{23c5}
@deffn {方法} SharedMemory (size)

Create and return a new @ref{23c5,,SharedMemory} object with the
specified @code{size} in bytes.
@end deffn

@geindex ShareableList() (multiprocessing.managers.SharedMemoryManager 方法)
@anchor{library/multiprocessing shared_memory multiprocessing managers SharedMemoryManager ShareableList}@anchor{23c6}
@deffn {方法} ShareableList (sequence)

Create and return a new @ref{23c6,,ShareableList} object, initialized
by the values from the input @code{sequence}.
@end deffn
@end deffn

The following example demonstrates the basic mechanisms of a
@code{SharedMemoryManager}:

@example
>>> from multiprocessing.managers import SharedMemoryManager
>>> smm = SharedMemoryManager()
>>> smm.start()  # Start the process that manages the shared memory blocks
>>> sl = smm.ShareableList(range(4))
>>> sl
ShareableList([0, 1, 2, 3], name='psm_6572_7512')
>>> raw_shm = smm.SharedMemory(size=128)
>>> another_sl = smm.ShareableList('alpha')
>>> another_sl
ShareableList(['a', 'l', 'p', 'h', 'a'], name='psm_6572_12221')
>>> smm.shutdown()  # Calls unlink() on sl, raw_shm, and another_sl
@end example

The following example depicts a potentially more convenient pattern for using
@code{SharedMemoryManager} objects via the @ref{6e3,,with} statement to
ensure that all shared memory blocks are released after they are no longer
needed:

@example
>>> with SharedMemoryManager() as smm:
...     sl = smm.ShareableList(range(2000))
...     # Divide the work among two processes, storing partial results in sl
...     p1 = Process(target=do_work, args=(sl, 0, 1000))
...     p2 = Process(target=do_work, args=(sl, 1000, 2000))
...     p1.start()
...     p2.start()  # A multiprocessing.Pool might be more efficient
...     p1.join()
...     p2.join()   # Wait for all work to complete in both processes
...     total_result = sum(sl)  # Consolidate the partial results now in sl
@end example

When using a @code{SharedMemoryManager} in a @ref{6e3,,with} statement, the
shared memory blocks created using that manager are all released when the
@ref{6e3,,with} statement's code block finishes execution.

@geindex ShareableList (multiprocessing.shared_memory 中的类)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory ShareableList}@anchor{23c7}
@deffn {类} multiprocessing.shared_memory.ShareableList (sequence=None, *, name=None)

Provides a mutable list-like object where all values stored within are
stored in a shared memory block.  This constrains storable values to
only the @code{int}, @code{float}, @code{bool}, @code{str} (less than 10M bytes each),
@code{bytes} (less than 10M bytes each), and @code{None} built-in data types.
It also notably differs from the built-in @code{list} type in that these
lists can not change their overall length (i.e. no append, insert, etc.)
and do not support the dynamic creation of new @ref{23c7,,ShareableList}
instances via slicing.

@emph{sequence} is used in populating a new @code{ShareableList} full of values.
Set to @code{None} to instead attach to an already existing
@code{ShareableList} by its unique shared memory name.

@emph{name} is the unique name for the requested shared memory, as described
in the definition for @ref{2328,,SharedMemory}.  When attaching to an
existing @code{ShareableList}, specify its shared memory block's unique
name while leaving @code{sequence} set to @code{None}.

@geindex count() (multiprocessing.shared_memory.ShareableList 方法)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory ShareableList count}@anchor{23c8}
@deffn {方法} count (value)

Returns the number of occurrences of @code{value}.
@end deffn

@geindex index() (multiprocessing.shared_memory.ShareableList 方法)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory ShareableList index}@anchor{23c9}
@deffn {方法} index (value)

Returns first index position of @code{value}.  Raises @ref{1fb,,ValueError} if
@code{value} is not present.
@end deffn

@geindex format (multiprocessing.shared_memory.ShareableList 属性)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory ShareableList format}@anchor{23ca}
@deffn {属性} format

Read-only attribute containing the @ref{f8,,struct} packing format used by
all currently stored values.
@end deffn

@geindex shm (multiprocessing.shared_memory.ShareableList 属性)
@anchor{library/multiprocessing shared_memory multiprocessing shared_memory ShareableList shm}@anchor{23cb}
@deffn {属性} shm

The @ref{2328,,SharedMemory} instance where the values are stored.
@end deffn
@end deffn

The following example demonstrates basic use of a @ref{23c7,,ShareableList}
instance:

@example
>>> from multiprocessing import shared_memory
>>> a = shared_memory.ShareableList(['howdy', b'HoWdY', -273.154, 100, None, True, 42])
>>> [ type(entry) for entry in a ]
[<class 'str'>, <class 'bytes'>, <class 'float'>, <class 'int'>, <class 'NoneType'>, <class 'bool'>, <class 'int'>]
>>> a[2]
-273.154
>>> a[2] = -78.5
>>> a[2]
-78.5
>>> a[2] = 'dry ice'  # Changing data types is supported as well
>>> a[2]
'dry ice'
>>> a[2] = 'larger than previously allocated storage space'
Traceback (most recent call last):
  ...
ValueError: exceeds available storage for existing str
>>> a[2]
'dry ice'
>>> len(a)
7
>>> a.index(42)
6
>>> a.count(b'howdy')
0
>>> a.count(b'HoWdY')
1
>>> a.shm.close()
>>> a.shm.unlink()
>>> del a  # Use of a ShareableList after call to unlink() is unsupported
@end example

The following example depicts how one, two, or many processes may access the
same @ref{23c7,,ShareableList} by supplying the name of the shared memory block
behind it:

@example
>>> b = shared_memory.ShareableList(range(5))         # In a first process
>>> c = shared_memory.ShareableList(name=b.shm.name)  # In a second process
>>> c
ShareableList([0, 1, 2, 3, 4], name='...')
>>> c[-1] = -999
>>> b[-1]
-999
>>> b.shm.close()
>>> c.shm.close()
>>> c.shm.unlink()
@end example

@node concurrent 包,concurrent futures --- 启动并行任务,multiprocessing shared_memory --- 可从进程直接访问的共享内存,并发执行
@anchor{library/concurrent doc}@anchor{23cc}@anchor{library/concurrent the-concurrent-package}@anchor{23cd}
@subsection @code{concurrent} 包


目前，此包中只有一个模块：


@itemize *

@item 
@ref{22,,concurrent.futures} —— 启动并行任务
@end itemize

@node concurrent futures --- 启动并行任务,subprocess --- 子进程管理,concurrent 包,并发执行
@anchor{library/concurrent futures doc}@anchor{23ce}@anchor{library/concurrent futures concurrent-futures-launching-parallel-tasks}@anchor{23cf}@anchor{library/concurrent futures module-concurrent futures}@anchor{22}
@subsection @code{concurrent.futures} --- 启动并行任务


@geindex concurrent.futures (模块)


3.2 新版功能.


@strong{源码:} Lib/concurrent/futures/thread.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/concurrent/futures/thread.py} 和 Lib/concurrent/futures/process.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/concurrent/futures/process.py}


__________________________________________________________________


@ref{22,,concurrent.futures} 模块提供异步执行可调用对象高层接口。

异步执行可以由 @ref{27a,,ThreadPoolExecutor} 使用线程或由 @ref{2a3,,ProcessPoolExecutor} 使用单独的进程来实现。 两者都是实现抽像类 @ref{23d0,,Executor} 定义的接口。

@menu
* 执行器对象:: 
* 线程池执行器:: 
* 进程池执行器:: 
* 期程对象:: 
* 模块函数:: 
* Exception类:: 

@end menu

@node 执行器对象,线程池执行器,,concurrent futures --- 启动并行任务
@anchor{library/concurrent futures executor-objects}@anchor{23d1}
@subsubsection 执行器对象


@geindex Executor (concurrent.futures 中的类)
@anchor{library/concurrent futures concurrent futures Executor}@anchor{23d0}
@deffn {类} concurrent.futures.Executor

抽象类提供异步执行调用方法。要通过它的子类调用，而不是直接调用。

@quotation

@geindex submit() (concurrent.futures.Executor 方法)
@anchor{library/concurrent futures concurrent futures Executor submit}@anchor{2a4}
@deffn {方法} submit (fn, *args, **kwargs)

调度可调用对象 @emph{fn}，以 @code{fn(*args **kwargs)} 方式执行并返回 @ref{b26,,Future} 对像代表可调用对象的执行。:

@example
with ThreadPoolExecutor(max_workers=1) as executor:
    future = executor.submit(pow, 323, 1235)
    print(future.result())
@end example
@end deffn

@geindex map() (concurrent.futures.Executor 方法)
@anchor{library/concurrent futures concurrent futures Executor map}@anchor{6b8}
@deffn {方法} map (func, *iterables, timeout=None, chunksize=1)

类似于 @ref{c26,,map(func@comma{} *iterables)} 除去：


@itemize *

@item 
应立即收集 @emph{iterables} 不要延迟再收集;

@item 
@emph{func} 是异步执行的以及对 @emph{func} 的调用可以同时执行。
@end itemize

如果从原始调用到 @ref{6b8,,Executor.map()} 经过 @emph{timeout} 秒后， @ref{c5d,,__next__()} 已被调用且返回的结果还不可用，那么已返回的迭代器将触发 @ref{23d2,,concurrent.futures.TimeoutError}  。 @emph{timeout} 可以是整数或浮点数。如果 @emph{timeout} 没有指定或为 @code{None} ，则没有超时限制。

如果 @emph{func} 调用引发一个异常，当从迭代器中取回它的值时这个异常将被引发。

使用 @ref{2a3,,ProcessPoolExecutor} 时，这个方法会将 @emph{iterables} 分割任务块并作为独立的任务并提交到执行池中。这些块的大概数量可以由 @emph{chunksize} 指定正整数设置。 对很长的迭代器来说，使用大的 @emph{chunksize} 值比默认值 1 能显著地提高性能。 @emph{chunksize} 对 @ref{27a,,ThreadPoolExecutor} 没有效果。


在 3.5 版更改: 加入 @emph{chunksize} 参数。

@end deffn

@geindex shutdown() (concurrent.futures.Executor 方法)
@anchor{library/concurrent futures concurrent futures Executor shutdown}@anchor{b27}
@deffn {方法} shutdown (wait=True)

当待执行的期程完成执行后向执行者发送信号，它就会释放正在使用的任何资源。在关闭后调用 @ref{2a4,,Executor.submit()} 和 @ref{2a4,,Executor.submit()} 会触发 @ref{2ba,,RuntimeError}。

如果 @emph{wait} 为 @code{True} 则此方法只有在所有待执行的期程完成执行且释放已分配的资源后才会返回。 如果 @emph{wait} 为 @code{False}，方法立即返回，所有待执行的期程完成执行后会释放已分配的资源。 不管 @emph{wait} 的值是什么，整个 Python 程序将等到所有待执行的期程完成执行后才退出。

如果使用 @ref{6e3,,with} 语句，你就可以避免显式调用这个方法，它将会停止 @ref{23d0,,Executor} (就好像 @ref{b27,,Executor.shutdown()} 调用时 @emph{wait} 设为 @code{True} 一样等待):

@example
import shutil
with ThreadPoolExecutor(max_workers=4) as e:
    e.submit(shutil.copy, 'src1.txt', 'dest1.txt')
    e.submit(shutil.copy, 'src2.txt', 'dest2.txt')
    e.submit(shutil.copy, 'src3.txt', 'dest3.txt')
    e.submit(shutil.copy, 'src4.txt', 'dest4.txt')
@end example
@end deffn
@end quotation
@end deffn

@node 线程池执行器,进程池执行器,执行器对象,concurrent futures --- 启动并行任务
@anchor{library/concurrent futures threadpoolexecutor}@anchor{23d3}
@subsubsection 线程池执行器


@ref{27a,,ThreadPoolExecutor} 是 @ref{23d0,,Executor} 的子类，它使用线程池来异步执行调用。

当回调已关联了一个 @ref{b26,,Future} 然后再等待另一个 @ref{b26,,Future} 的结果时就会发产死锁情况。例如:

@example
import time
def wait_on_b():
    time.sleep(5)
    print(b.result())  # b will never complete because it is waiting on a.
    return 5

def wait_on_a():
    time.sleep(5)
    print(a.result())  # a will never complete because it is waiting on b.
    return 6


executor = ThreadPoolExecutor(max_workers=2)
a = executor.submit(wait_on_b)
b = executor.submit(wait_on_a)
@end example

与:

@example
def wait_on_future():
    f = executor.submit(pow, 5, 2)
    # This will never complete because there is only one worker thread and
    # it is executing this function.
    print(f.result())

executor = ThreadPoolExecutor(max_workers=1)
executor.submit(wait_on_future)
@end example

@geindex ThreadPoolExecutor (concurrent.futures 中的类)
@anchor{library/concurrent futures concurrent futures ThreadPoolExecutor}@anchor{27a}
@deffn {类} concurrent.futures.ThreadPoolExecutor (max_workers=None, thread_name_prefix='@w{'}, initializer=None, initargs=())

@ref{23d0,,Executor} 子类使用最多 @emph{max_workers} 个线程的线程池来异步执行调用。

@emph{initializer} 是在每个工作者线程开始处调用的一个可选可调用对象。 @emph{initargs} 是传递给初始化器的元组参数。任何向池提交更多工作的尝试， @emph{initializer} 都将引发一个异常，当前所有等待的工作都会引发一个 @ref{23d4,,BrokenThreadPool}。


在 3.5 版更改: 如果 @emph{max_workers} 为 @code{None} 或没有指定，将默认为机器处理器的个数，假如 @ref{27a,,ThreadPoolExecutor} 则重于I/O操作而不是CPU运算，那么可以乘以 @code{5} ，同时工作线程的数量可以比 @ref{2a3,,ProcessPoolExecutor} 的数量高。



3.6 新版功能: 添加 @emph{thread_name_prefix} 参数允许用户控制由线程池创建的 @ref{234,,threading.Thread} 工作线程名称以方便调试。



在 3.7 版更改: 加入 @emph{initializer} 和*initargs* 参数。



在 3.8 版更改: @emph{max_workers} 的默认值已改为 @code{min(32, os.cpu_count() + 4)}。 这个默认值会保留至少 5 个工作线程用于 I/O 密集型任务。 它会使用至多 32 个 CPU 核心用于 CPU 密集型任务并将释放 GIL。 它还会避免在多核机器上隐式地使用非常大量的资源。

现在 ThreadPoolExecutor 在启动 @emph{max_workers} 个工作线程之前也会重用空闲的工作线程。

@end deffn

@menu
* ThreadPoolExecutor 例子:: 

@end menu

@node ThreadPoolExecutor 例子,,,线程池执行器
@anchor{library/concurrent futures id1}@anchor{23d5}@anchor{library/concurrent futures threadpoolexecutor-example}@anchor{b28}
@subsubsection ThreadPoolExecutor 例子


@example
import concurrent.futures
import urllib.request

URLS = ['http://www.foxnews.com/',
        'http://www.cnn.com/',
        'http://europe.wsj.com/',
        'http://www.bbc.co.uk/',
        'http://some-made-up-domain.com/']

# Retrieve a single page and report the URL and contents
def load_url(url, timeout):
    with urllib.request.urlopen(url, timeout=timeout) as conn:
        return conn.read()

# We can use a with statement to ensure threads are cleaned up promptly
with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
    # Start the load operations and mark each future with its URL
    future_to_url = @{executor.submit(load_url, url, 60): url for url in URLS@}
    for future in concurrent.futures.as_completed(future_to_url):
        url = future_to_url[future]
        try:
            data = future.result()
        except Exception as exc:
            print('%r generated an exception: %s' % (url, exc))
        else:
            print('%r page is %d bytes' % (url, len(data)))
@end example

@node 进程池执行器,期程对象,线程池执行器,concurrent futures --- 启动并行任务
@anchor{library/concurrent futures processpoolexecutor}@anchor{23d6}
@subsubsection 进程池执行器


@ref{2a3,,ProcessPoolExecutor} 是 @ref{23d0,,Executor} 的子类，它使用进程池来实现异步执行调用。 @ref{2a3,,ProcessPoolExecutor} 使用 @ref{b7,,multiprocessing} 回避 @ref{500,,Global Interpreter Lock} 但也意味着只可以处理和返回可序列化的对象。

@code{__main__} 模块必须可以被工作者子进程导入。这意味着 @ref{2a3,,ProcessPoolExecutor} 不可以工作在交互式解释器中。

从可调用对象中调用 @ref{23d0,,Executor} 或 @ref{b26,,Future} 的方法提交给 @ref{2a3,,ProcessPoolExecutor} 会导致死锁。

@geindex ProcessPoolExecutor (concurrent.futures 中的类)
@anchor{library/concurrent futures concurrent futures ProcessPoolExecutor}@anchor{2a3}
@deffn {类} concurrent.futures.ProcessPoolExecutor (max_workers=None, mp_context=None, initializer=None, initargs=())

异步执行调用的 @ref{23d0,,Executor} 子类使用一个最多有 @emph{max_workers} 个进程的进程池。 如果 @emph{max_workers} 为 @code{None} 或未给出，它将默认为机器的处理器个数。 如果 @emph{max_workers} 小于等于 @code{0}，则将引发 @ref{1fb,,ValueError}。 在 Windows 上，@emph{max_workers} 必须小于等于 @code{61}，否则将引发 @ref{1fb,,ValueError}。 如果 @emph{max_workers} 为 @code{None}，则所选择的默认最多为 @code{61}，即使存在更多处理器。 @emph{mp_context} 可以是一个多进程上下文或是 None。 它将被用来启动工作者。 如果 @emph{mp_context} 为 @code{None} 或未给出，将使用默认的多进程上下文。

@emph{initializer} 是在每个工作者进程开始处调用的一个可选可调用对象。 @emph{initargs} 是传递给初始化器的元组参数。任何向池提交更多工作的尝试， @emph{initializer} 都将引发一个异常，当前所有等待的工作都会引发一个 @code{BrokenProcessPool}。


在 3.3 版更改: 如果其中一个工作进程被突然终止，@code{BrokenProcessPool} 就会马上触发。可预计的行为没有定义，但执行器上的操作或它的期程会被冻结或死锁。



在 3.7 版更改: 添加 @emph{mp_context} 参数允许用户控制由进程池创建给工作者进程的开始方法 。

加入 @emph{initializer} 和*initargs* 参数。

@end deffn

@menu
* ProcessPoolExecutor 例子:: 

@end menu

@node ProcessPoolExecutor 例子,,,进程池执行器
@anchor{library/concurrent futures id2}@anchor{23d7}@anchor{library/concurrent futures processpoolexecutor-example}@anchor{b29}
@subsubsection ProcessPoolExecutor 例子


@example
import concurrent.futures
import math

PRIMES = [
    112272535095293,
    112582705942171,
    112272535095293,
    115280095190773,
    115797848077099,
    1099726899285419]

def is_prime(n):
    if n < 2:
        return False
    if n == 2:
        return True
    if n % 2 == 0:
        return False

    sqrt_n = int(math.floor(math.sqrt(n)))
    for i in range(3, sqrt_n + 1, 2):
        if n % i == 0:
            return False
    return True

def main():
    with concurrent.futures.ProcessPoolExecutor() as executor:
        for number, prime in zip(PRIMES, executor.map(is_prime, PRIMES)):
            print('%d is prime: %s' % (number, prime))

if __name__ == '__main__':
    main()
@end example

@node 期程对象,模块函数,进程池执行器,concurrent futures --- 启动并行任务
@anchor{library/concurrent futures future-objects}@anchor{23d8}
@subsubsection 期程对象


@ref{b26,,Future} 类将可调用对象封装为异步执行。@ref{b26,,Future} 实例由 @ref{2a4,,Executor.submit()} 创建。

@geindex Future (concurrent.futures 中的类)
@anchor{library/concurrent futures concurrent futures Future}@anchor{b26}
@deffn {类} concurrent.futures.Future

将可调用对象封装为异步执行。@ref{b26,,Future} 实例由 @ref{2a4,,Executor.submit()} 创建，除非测试，不应直接创建。

@quotation

@geindex cancel() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future cancel}@anchor{23d9}
@deffn {方法} cancel ()

尝试取消调用。 如果调用正在执行或已结束运行不能被取消则该方法将返回 @code{False}，否则调用会被取消并且该方法将返回 @code{True}。
@end deffn

@geindex cancelled() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future cancelled}@anchor{23da}
@deffn {方法} cancelled ()

如果调用成功取消返回 @code{True}。
@end deffn

@geindex running() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future running}@anchor{23db}
@deffn {方法} running ()

如果调用正在执行而且不能被取消那么返回 @code{True} 。
@end deffn

@geindex done() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future done}@anchor{23dc}
@deffn {方法} done ()

如果调用已被取消或正常结束那么返回 @code{True}。
@end deffn

@geindex result() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future result}@anchor{23dd}
@deffn {方法} result (timeout=None)

返回调用返回的值。如果调用还没完成那么这个方法将等待 @emph{timeout} 秒。如果在 @emph{timeout} 秒内没有执行完成，@ref{23d2,,concurrent.futures.TimeoutError} 将会被触发。@emph{timeout} 可以是整数或浮点数。如果 @emph{timeout} 没有指定或为 @code{None}，那么等待时间就没有限制。

如果期程在完成前被取消， @ref{1aa,,CancelledError} 将被触发。

如果调用引发了一个异常，这个方法也会引发同样的异常。
@end deffn

@geindex exception() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future exception}@anchor{23de}
@deffn {方法} exception (timeout=None)

返回由调用引发的异常。如果调用还没完成那么这个方法将等待 @emph{timeout} 秒。如果在 @emph{timeout} 秒内没有执行完成，@ref{23d2,,concurrent.futures.TimeoutError} 将会被触发。@emph{timeout} 可以是整数或浮点数。如果 @emph{timeout} 没有指定或为 @code{None}，那么等待时间就没有限制。

如果期程在完成前被取消， @ref{1aa,,CancelledError} 将被触发。

如果调用正常完成那么返回 @code{None}。
@end deffn

@geindex add_done_callback() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future add_done_callback}@anchor{23df}
@deffn {方法} add_done_callback (fn)

附加可调用 @emph{fn} 到期程。当期程被取消或完成运行时，将会调用 @emph{fn}，而这个期程将作为它唯一的参数。

加入的可调用对象总被属于添加它们的进程中的线程按加入的顺序调用。如果可调用对象引发一个 @ref{1a9,,Exception} 子类，它会被记录下来并被忽略掉。如果可调用对象引发一个 @ref{1a8,,BaseException} 子类，这个行为没有定义。

如果期程已经完成或已取消，@emph{fn} 会被立即调用。
@end deffn
@end quotation

下面这些 @ref{b26,,Future} 方法用于单元测试和 @ref{23d0,,Executor} 实现。

@quotation

@geindex set_running_or_notify_cancel() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future set_running_or_notify_cancel}@anchor{23e0}
@deffn {方法} set_running_or_notify_cancel ()

这个方法只可以在执行关联 @ref{b26,,Future}  工作之前由 @ref{23d0,,Executor} 实现调用或由单测试调用。

如果这个方法返回  @code{False} 那么 @ref{b26,,Future} 已被取消，即 @ref{23d9,,Future.cancel()} 已被调用并返回 @code{True} 。等待 @ref{b26,,Future} 完成 (即通过 @ref{1081,,as_completed()} 或 @ref{23e1,,wait()}) 的线程将被唤醒。

如果这个方法返回 @code{True} 那么 @ref{b26,,Future} 不会被取消并已将它变为正在运行状态，也就是说调用 @ref{23db,,Future.running()} 时将返回 @cite{True}。

这个方法只可以被调用一次并且不能在调用 @ref{23e2,,Future.set_result()} 或 @ref{23e3,,Future.set_exception()} 之后再调用。
@end deffn

@geindex set_result() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future set_result}@anchor{23e2}
@deffn {方法} set_result (result)

设置将 @ref{b26,,Future} 关联工作的结果给 @emph{result} 。

这个方法只可以由 @ref{23d0,,Executor} 实现和单元测试使用。


在 3.8 版更改: 如果 @ref{b26,,Future} 已经完成则此方法会引发 @ref{23e4,,concurrent.futures.InvalidStateError}。

@end deffn

@geindex set_exception() (concurrent.futures.Future 方法)
@anchor{library/concurrent futures concurrent futures Future set_exception}@anchor{23e3}
@deffn {方法} set_exception (exception)

设置 @ref{b26,,Future} 关联工作的结果给 @ref{1a9,,Exception} @emph{exception} 。

这个方法只可以由 @ref{23d0,,Executor} 实现和单元测试使用。


在 3.8 版更改: 如果 @ref{b26,,Future} 已经完成则此方法会引发 @ref{23e4,,concurrent.futures.InvalidStateError}。

@end deffn
@end quotation
@end deffn

@node 模块函数,Exception类,期程对象,concurrent futures --- 启动并行任务
@anchor{library/concurrent futures module-functions}@anchor{23e5}
@subsubsection 模块函数


@geindex wait() (在 concurrent.futures 模块中)
@anchor{library/concurrent futures concurrent futures wait}@anchor{23e1}
@deffn {函数} concurrent.futures.wait (fs, timeout=None, return_when=ALL_COMPLETED)

等待 @emph{fs} 指定的 @ref{b26,,Future} 实例（可能由不同的 @ref{23d0,,Executor} 实例创建）完成。 返回一个由集合构成的具名  2 元组。 第一个集合名称为 @code{done}，包含在等待完成之前已完成的期程（包括正常结束或被取消的期程）。 第二个集合名称为 @code{not_done}，包含未完成的期程（包括挂起的或正在运行的期程）。

@emph{timeout} 可以用来控制返回前最大的等待秒数。 @emph{timeout} 可以为 int 或 float 类型。 如果 @emph{timeout} 未指定或为 @code{None} ，则不限制等待时间。

@emph{return_when} 指定此函数应在何时返回。它必须为以下常数之一:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

描述

@item

@code{FIRST_COMPLETED}

@tab

函数将在任意可等待对象结束或取消时返回。

@item

@code{FIRST_EXCEPTION}

@tab

函数将在任意可等待对象因引发异常而结束时返回。当没有引发任何异常时它就相当于 @code{ALL_COMPLETED}。

@item

@code{ALL_COMPLETED}

@tab

函数将在所有可等待对象结束或取消时返回。

@end multitable

@end deffn

@geindex as_completed() (在 concurrent.futures 模块中)
@anchor{library/concurrent futures concurrent futures as_completed}@anchor{1081}
@deffn {函数} concurrent.futures.as_completed (fs, timeout=None)

返回一个包含 @emph{fs} 所指定的 @ref{b26,,Future} 实例（可能由不同的 @ref{23d0,,Executor} 实例创建）的迭代器，这些实例会在完成时生成期程（包括正常结束或被取消的期程）。 任何由 @emph{fs} 所指定的重复期程将只被返回一次。 任何在 @ref{1081,,as_completed()} 被调用之前完成的期程将优先被生成。 如果 @ref{c5d,,__next__()} 被调用并且在对 @ref{1081,,as_completed()} 的原始调用 @emph{timeout} 秒之后结果仍不可用，则返回的迭代器将引发 @ref{23d2,,concurrent.futures.TimeoutError}。 @emph{timeout} 可以为整数或浮点数。 如果 @emph{timeout} 未指定或为 @code{None}，则不限制等待时间。
@end deffn


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 3148

@item PEP 3148@footnote{https://www.python.org/dev/peps/pep-3148} -- 期程 - 异步执行指令。

该提案描述了Python标准库中包含的这个特性。
@end table


@node Exception类,,模块函数,concurrent futures --- 启动并行任务
@anchor{library/concurrent futures exception-classes}@anchor{23e6}
@subsubsection Exception类


@geindex CancelledError
@anchor{library/concurrent futures concurrent futures CancelledError}@anchor{1aa}
@deffn {例外} concurrent.futures.CancelledError

期程被取消时会触发。
@end deffn

@geindex TimeoutError
@anchor{library/concurrent futures concurrent futures TimeoutError}@anchor{23d2}
@deffn {例外} concurrent.futures.TimeoutError

期程运算超出给定的超时数值时引发。
@end deffn

@geindex BrokenExecutor
@anchor{library/concurrent futures concurrent futures BrokenExecutor}@anchor{23e7}
@deffn {例外} concurrent.futures.BrokenExecutor

当执行器被某些原因中断而且不能用来提交或执行新任务时就会被引发派生于 @ref{2ba,,RuntimeError} 的异常类。


3.7 新版功能.

@end deffn

@geindex InvalidStateError
@anchor{library/concurrent futures concurrent futures InvalidStateError}@anchor{23e4}
@deffn {例外} concurrent.futures.InvalidStateError

当某个操作在一个当前状态所不允许的 future 上执行时将被引发。


3.8 新版功能.

@end deffn

@geindex BrokenThreadPool
@anchor{library/concurrent futures concurrent futures thread BrokenThreadPool}@anchor{23d4}
@deffn {例外} concurrent.futures.thread.BrokenThreadPool

当 @code{ThreadPoolExecutor} 中的其中一个工作者初始化失败时会引发派生于 @ref{23e7,,BrokenExecutor} 的异常类。


3.7 新版功能.

@end deffn

@geindex BrokenProcessPool
@anchor{library/concurrent futures concurrent futures process BrokenProcessPool}@anchor{23e8}
@deffn {例外} concurrent.futures.process.BrokenProcessPool

当 @code{ThreadPoolExecutor} 中的其中一个工作者不完整终止时(比如，被外部杀死)会引发派生于 @ref{23e7,,BrokenExecutor} ( 原名 @ref{2ba,,RuntimeError} ) 的异常类。


3.3 新版功能.

@end deffn

@node subprocess --- 子进程管理,sched --- 事件调度器,concurrent futures --- 启动并行任务,并发执行
@anchor{library/subprocess doc}@anchor{23e9}@anchor{library/subprocess module-subprocess}@anchor{f9}@anchor{library/subprocess subprocess-subprocess-management}@anchor{23ea}
@subsection @code{subprocess} --- 子进程管理


@geindex subprocess (模块)

@strong{源代码:} Lib/subprocess.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/subprocess.py}


__________________________________________________________________


@ref{f9,,subprocess} 模块允许你生成新的进程，连接它们的输入、输出、错误管道，并且获取它们的返回码。此模块打算代替一些老旧的模块与功能：

@example
os.system
os.spawn*
@end example

在下面的段落中，你可以找到关于 @ref{f9,,subprocess} 模块如何代替这些模块和功能的相关信息。


@subsubheading 参见


@geindex Python 提高建议; PEP 324
PEP 324@footnote{https://www.python.org/dev/peps/pep-0324} -- 提出 subprocess 模块的 PEP


@menu
* 使用 subprocess 模块:: 
* 安全考量:: 
* Popen 对象:: 
* Windows Popen 助手:: 
* Older high-level API:: 
* Replacing Older Functions with the subprocess Module:: 
* Legacy Shell Invocation Functions:: 
* 注释: 注释<2>. 

@end menu

@node 使用 subprocess 模块,安全考量,,subprocess --- 子进程管理
@anchor{library/subprocess using-the-subprocess-module}@anchor{23eb}
@subsubsection 使用 @code{subprocess} 模块


推荐的调用子进程的方式是在任何它支持的用例中使用 @ref{3e5,,run()} 函数。对于更进阶的用例，也可以使用底层的 @ref{2b9,,Popen} 接口。

@ref{3e5,,run()} 函数是在 Python 3.5 被添加的；如果你需要与旧版本保持兼容，查看 @ref{23ec,,Older high-level API} 段落。

@geindex run() (在 subprocess 模块中)
@anchor{library/subprocess subprocess run}@anchor{3e5}
@deffn {函数} subprocess.run (args, *, stdin=None, input=None, stdout=None, stderr=None, capture_output=False, shell=False, cwd=None, timeout=None, check=False, encoding=None, errors=None, text=None, env=None, universal_newlines=None, **other_popen_kwargs)

运行被 @emph{arg} 描述的指令. 等待指令完成, 然后返回一个 @ref{75a,,CompletedProcess} 实例.

以上显示的参数仅仅是最简单的一些，下面 @ref{23ed,,常用参数} 描述（因此在缩写签名中使用仅关键字标示）。完整的函数头和 @ref{2b9,,Popen} 的构造函数一样，此函数接受的大多数参数都被传递给该接口。（@emph{timeout}, @emph{input}, @emph{check} 和 @emph{capture_output} 除外）。

如果 @emph{capture_output} 设为 true，stdout 和 stderr 将会被捕获。在使用时，内置的 @ref{2b9,,Popen} 对象将自动用 @code{stdout=PIPE} 和 @code{stderr=PIPE} 创建。@emph{stdout} 和 @emph{stderr} 参数不应当与 @emph{capture_output} 同时提供。如果你希望捕获并将两个流合并在一起，使用 @code{stdout=PIPE} 和 @code{stderr=STDOUT} 来代替 @emph{capture_output}。

@emph{timeout} 参数将被传递给 @ref{23ee,,Popen.communicate()}。如果发生超时，子进程将被杀死并等待。 @ref{23ef,,TimeoutExpired} 异常将在子进程中断后被抛出。

@emph{input} 参数将被传递给 @ref{23ee,,Popen.communicate()} 以及子进程的 stdin。 如果使用此参数，它必须是一个字节序列。 如果指定了 @emph{encoding} 或 @emph{errors} 或者将 @emph{text} 设置为 @code{True}，那么也可以是一个字符串。 当使用此参数时，在创建内部 @ref{2b9,,Popen} 对象时将自动带上 @code{stdin=PIPE}，并且不能再手动指定 @emph{stdin} 参数。

如果 @emph{check} 设为 True, 并且进程以非零状态码退出, 一个 @ref{cae,,CalledProcessError} 异常将被抛出. 这个异常的属性将设置为参数, 退出码, 以及标准输出和标准错误, 如果被捕获到.

如果 @emph{encoding} 或者 @emph{error} 被指定, 或者 @emph{text} 被设为 True, 标准输入, 标准输出和标准错误的文件对象将通过指定的 @emph{encoding} 和 @emph{errors} 以文本模式打开, 否则以默认的 @ref{5ee,,io.TextIOWrapper} 打开. @emph{universal_newline} 参数等同于 @emph{text} 并且提供了向后兼容性. 默认情况下, 文件对象是以二进制模式打开的.

如果 @emph{env} 不是 @code{None}, 它必须是一个字典, 为新的进程设置环境变量; 它用于替换继承的当前进程的环境的默认行为. 它将直接被传递给 @ref{2b9,,Popen}.

示例:

@example
>>> subprocess.run(["ls", "-l"])  # doesn't capture output
CompletedProcess(args=['ls', '-l'], returncode=0)

>>> subprocess.run("exit 1", shell=True, check=True)
Traceback (most recent call last):
  ...
subprocess.CalledProcessError: Command 'exit 1' returned non-zero exit status 1

>>> subprocess.run(["ls", "-l", "/dev/null"], capture_output=True)
CompletedProcess(args=['ls', '-l', '/dev/null'], returncode=0,
stdout=b'crw-rw-rw- 1 root root 1, 3 Jan 23 16:23 /dev/null\n', stderr=b'@w{'})
@end example


3.5 新版功能.



在 3.6 版更改: 添加了 @emph{encoding} 和 @emph{errors} 形参.



在 3.7 版更改: 添加了 @emph{text} 形参, 作为 @emph{universal_newlines} 的一个更好理解的别名. 添加了 @emph{capture_output} 形参.

@end deffn

@geindex CompletedProcess (subprocess 中的类)
@anchor{library/subprocess subprocess CompletedProcess}@anchor{75a}
@deffn {类} subprocess.CompletedProcess

@ref{3e5,,run()} 的返回值, 代表一个进程已经结束.

@geindex args (subprocess.CompletedProcess 属性)
@anchor{library/subprocess subprocess CompletedProcess args}@anchor{23f0}
@deffn {属性} args

被用作启动进程的参数. 可能是一个列表或字符串.
@end deffn

@geindex returncode (subprocess.CompletedProcess 属性)
@anchor{library/subprocess subprocess CompletedProcess returncode}@anchor{23f1}
@deffn {属性} returncode

子进程的退出状态码. 通常来说, 一个为 0 的退出码表示进程运行正常.

一个负值 @code{-N} 表示子进程被信号 @code{N} 中断 (仅 POSIX).
@end deffn

@geindex stdout (subprocess.CompletedProcess 属性)
@anchor{library/subprocess subprocess CompletedProcess stdout}@anchor{23f2}
@deffn {属性} stdout

从子进程捕获到的标准输出. 一个字节序列, 或一个字符串, 如果 @ref{3e5,,run()} 是设置了 @emph{encoding}, @emph{errors} 或者 @code{text=True} 来运行的. 如果未有捕获, 则为 @code{None}.

如果你通过 @code{stderr=subprocess.STDOUT} 运行, 标准输入和标准错误将被组合在一起, 并且 @code{stderr`} 将为 @code{None}.
@end deffn

@geindex stderr (subprocess.CompletedProcess 属性)
@anchor{library/subprocess subprocess CompletedProcess stderr}@anchor{23f3}
@deffn {属性} stderr

捕获到的子进程的标准错误. 一个字节序列, 或者一个字符串, 如果 @ref{3e5,,run()} 是设置了参数 @emph{encoding}, @emph{errors} 或者 @code{text=True} 运行的. 如果未有捕获, 则为 @code{None}.
@end deffn

@geindex check_returncode() (subprocess.CompletedProcess 方法)
@anchor{library/subprocess subprocess CompletedProcess check_returncode}@anchor{23f4}
@deffn {方法} check_returncode ()

如果 @ref{23f1,,returncode} 非零, 抛出 @ref{cae,,CalledProcessError}.
@end deffn


3.5 新版功能.

@end deffn

@geindex DEVNULL() (在 subprocess 模块中)
@anchor{library/subprocess subprocess DEVNULL}@anchor{a9b}
@deffn {数据} subprocess.DEVNULL

可被 @ref{2b9,,Popen} 的 @emph{stdin}, @emph{stdout} 或者 @emph{stderr} 参数使用的特殊值, 表示使用特殊文件 @ref{fad,,os.devnull}.


3.3 新版功能.

@end deffn

@geindex PIPE() (在 subprocess 模块中)
@anchor{library/subprocess subprocess PIPE}@anchor{3e6}
@deffn {数据} subprocess.PIPE

可被 @ref{2b9,,Popen} 的 @emph{stdin}, @emph{stdout} 或者 @emph{stderr} 参数使用的特殊值, 表示打开标准流的管道. 常用于 @ref{23ee,,Popen.communicate()}.
@end deffn

@geindex STDOUT() (在 subprocess 模块中)
@anchor{library/subprocess subprocess STDOUT}@anchor{23f5}
@deffn {数据} subprocess.STDOUT

可被 @ref{2b9,,Popen} 的 @emph{stdin} ， @emph{stdout} 或者 @emph{stderr} 参数使用的特殊值， 表示标准错误与标准输出使用同一句柄。
@end deffn

@geindex SubprocessError
@anchor{library/subprocess subprocess SubprocessError}@anchor{23f6}
@deffn {例外} subprocess.SubprocessError

此模块的其他异常的基类。


3.3 新版功能.

@end deffn

@geindex TimeoutExpired
@anchor{library/subprocess subprocess TimeoutExpired}@anchor{23ef}
@deffn {例外} subprocess.TimeoutExpired

@ref{23f6,,SubprocessError} 的子类，等待子进程的过程中发生超时时被抛出。

@geindex cmd (subprocess.TimeoutExpired 属性)
@anchor{library/subprocess subprocess TimeoutExpired cmd}@anchor{23f7}
@deffn {属性} cmd

用于创建子进程的指令。
@end deffn

@geindex timeout (subprocess.TimeoutExpired 属性)
@anchor{library/subprocess subprocess TimeoutExpired timeout}@anchor{23f8}
@deffn {属性} timeout

超时秒数。
@end deffn

@geindex output (subprocess.TimeoutExpired 属性)
@anchor{library/subprocess subprocess TimeoutExpired output}@anchor{23f9}
@deffn {属性} output

子进程的输出， 如果被 @ref{3e5,,run()} 或 @ref{8d5,,check_output()} 捕获。否则为 @code{None}。
@end deffn

@geindex stdout (subprocess.TimeoutExpired 属性)
@anchor{library/subprocess subprocess TimeoutExpired stdout}@anchor{23fa}
@deffn {属性} stdout

对 output 的别名，对应的有 @ref{23fb,,stderr}。
@end deffn

@geindex stderr (subprocess.TimeoutExpired 属性)
@anchor{library/subprocess subprocess TimeoutExpired stderr}@anchor{23fb}
@deffn {属性} stderr

子进程的标准错误输出，如果被 @ref{3e5,,run()} 捕获。 否则为 @code{None}。
@end deffn


3.3 新版功能.



在 3.5 版更改: 添加了 @emph{stdout} 和 @emph{stderr} 属性。

@end deffn

@geindex CalledProcessError
@anchor{library/subprocess subprocess CalledProcessError}@anchor{cae}
@deffn {例外} subprocess.CalledProcessError

@ref{23f6,,SubprocessError} 的子类，当一个被 @ref{23fc,,check_call()} 或 @ref{8d5,,check_output()} 函数运行的子进程返回了非零退出码时被抛出。

@geindex returncode (subprocess.CalledProcessError 属性)
@anchor{library/subprocess subprocess CalledProcessError returncode}@anchor{23fd}
@deffn {属性} returncode

子进程的退出状态。如果程序由一个信号终止，这将会被设为一个负的信号码。
@end deffn

@geindex cmd (subprocess.CalledProcessError 属性)
@anchor{library/subprocess subprocess CalledProcessError cmd}@anchor{23fe}
@deffn {属性} cmd

用于创建子进程的指令。
@end deffn

@geindex output (subprocess.CalledProcessError 属性)
@anchor{library/subprocess subprocess CalledProcessError output}@anchor{23ff}
@deffn {属性} output

子进程的输出， 如果被 @ref{3e5,,run()} 或 @ref{8d5,,check_output()} 捕获。否则为 @code{None}。
@end deffn

@geindex stdout (subprocess.CalledProcessError 属性)
@anchor{library/subprocess subprocess CalledProcessError stdout}@anchor{2400}
@deffn {属性} stdout

对 output 的别名，对应的有 @ref{2401,,stderr}。
@end deffn

@geindex stderr (subprocess.CalledProcessError 属性)
@anchor{library/subprocess subprocess CalledProcessError stderr}@anchor{2401}
@deffn {属性} stderr

子进程的标准错误输出，如果被 @ref{3e5,,run()} 捕获。 否则为 @code{None}。
@end deffn


在 3.5 版更改: 添加了 @emph{stdout} 和 @emph{stderr} 属性。

@end deffn

@menu
* 常用参数:: 
* Popen 构造函数:: 
* 异常: 异常<7>. 

@end menu

@node 常用参数,Popen 构造函数,,使用 subprocess 模块
@anchor{library/subprocess frequently-used-arguments}@anchor{23ed}@anchor{library/subprocess id1}@anchor{2402}
@subsubsection 常用参数


为了支持丰富的使用案例， @ref{2b9,,Popen} 的构造函数（以及方便的函数）接受大量可选的参数。对于大多数典型的用例，许多参数可以被安全地留以它们的默认值。通常需要的参数有：

@quotation

@emph{args} 被所有调用需要，应当为一个字符串，或者一个程序参数序列。提供一个参数序列通常更好，它可以更小心地使用参数中的转义字符以及引用（例如允许文件名中的空格）。如果传递一个简单的字符串，则 @emph{shell} 参数必须为 @ref{494,,True} （见下文）或者该字符串中将被运行的程序名必须用简单的命名而不指定任何参数。

@emph{stdin}， @emph{stdout} 和 @emph{stderr} 分别指定了执行的程序的标准输入、输出和标准错误文件句柄。合法的值有 @ref{3e6,,PIPE} 、 @ref{a9b,,DEVNULL} 、 一个现存的文件描述符（一个正整数）、一个现存的文件对象以及 @code{None}。 @ref{3e6,,PIPE} 表示应该新建一个对子进程的管道。 @ref{a9b,,DEVNULL} 表示使用特殊的文件 @ref{fad,,os.devnull}。当使用默认设置 @code{None} 时，将不会进行重定向，子进程的文件流将继承自父进程。另外， @emph{stderr} 可能为 @ref{23f5,,STDOUT}，表示来自于子进程的标准错误数据应该被 @emph{stdout} 相同的句柄捕获。

@geindex universal newlines; subprocess module

如果 @emph{encoding} 或 @emph{errors} 被指定，或者 @emph{text} （也名为 @emph{universal_newlines}）为真，则文件对象 @emph{stdin} 、 @emph{stdout} 与 @emph{stderr} 将会使用在此次调用中指定的 @emph{encoding} 和 @emph{errors} 以文本模式打开或者为默认的 @ref{5ee,,io.TextIOWrapper}。

当构造函数的 @emph{newline} 参数为 @code{None} 时。对于 @emph{stdin}， 输入的换行符 @code{'\n'} 将被转换为默认的换行符 @ref{1594,,os.linesep}。对于 @emph{stdout} 和 @emph{stderr}， 所有输出的换行符都被转换为 @code{'\n'}。更多信息，查看 @ref{5ee,,io.TextIOWrapper} 类的文档。

如果文本模式未被使用， @emph{stdin}， @emph{stdout} 和 @emph{stderr} 将会以二进制流模式打开。没有编码与换行符转换发生。


3.6 新版功能: 添加了 @emph{encoding} 和 @emph{errors} 形参。



3.7 新版功能: 添加了 @emph{text} 形参作为 @emph{universal_newlines} 的别名。


@cartouche
@quotation 注解 
文件对象 @ref{2403,,Popen.stdin} 、 @ref{2404,,Popen.stdout} 和 @ref{2405,,Popen.stderr} 的换行符属性不会被 @ref{23ee,,Popen.communicate()} 方法更新。
@end quotation
@end cartouche

如果 @emph{shell} 设为 @code{True},，则使用 shell 执行指定的指令。如果您主要使用 Python 增强的控制流（它比大多数系统 shell 提供的强大），并且仍然希望方便地使用其他 shell 功能，如 shell 管道、文件通配符、环境变量展开以及 @code{~} 展开到用户家目录，这将非常有用。但是，注意 Python 自己也实现了许多类似 shell 的特性（例如 @ref{8a,,glob}, @ref{81,,fnmatch}, @ref{64e,,os.walk()}, @ref{d3d,,os.path.expandvars()}, @ref{1fe,,os.path.expanduser()} 和 @ref{e9,,shutil}）。


在 3.3 版更改: 当 @emph{universal_newline} 被设为 @code{True}，则类使用 @ref{39d,,locale.getpreferredencoding(False)} 编码来代替 @code{locale.getpreferredencoding()}。关于它们的区别的更多信息，见 @ref{5ee,,io.TextIOWrapper}。


@cartouche
@quotation 注解 
在使用 @code{shell=True} 之前， 请阅读 @ref{2406,,Security Considerations} 段落。
@end quotation
@end cartouche
@end quotation

这些选项以及所有其他选项在 @ref{2b9,,Popen} 构造函数文档中有更详细的描述。

@node Popen 构造函数,异常<7>,常用参数,使用 subprocess 模块
@anchor{library/subprocess popen-constructor}@anchor{2407}
@subsubsection Popen 构造函数


此模块的底层的进程创建与管理由 @ref{2b9,,Popen} 类处理。它提供了很大的灵活性，因此开发者能够处理未被便利函数覆盖的不常见用例。

@geindex Popen (subprocess 中的类)
@anchor{library/subprocess subprocess Popen}@anchor{2b9}
@deffn {类} subprocess.Popen (args, bufsize=-1, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=True, shell=False, cwd=None, env=None, universal_newlines=None, startupinfo=None, creationflags=0, restore_signals=True, start_new_session=False, pass_fds=(), *, encoding=None, errors=None, text=None)

在一个新的进程中执行子程序。在 POSIX，此类使用类似于 @ref{1f25,,os.execvp()} 的行为来执行子程序。在 Windows，此类使用了 Windows @code{CreateProcess()} 函数。 @ref{2b9,,Popen} 的参数如下：

@emph{args} should be a sequence of program arguments or else a single string
or @ref{363,,path-like object}.
By default, the program to execute is the first item in @emph{args} if @emph{args} is
a sequence.  If @emph{args} is a string, the interpretation is
platform-dependent and described below.  See the @emph{shell} and @emph{executable}
arguments for additional differences from the default behavior.  Unless
otherwise stated, it is recommended to pass @emph{args} as a sequence.

An example of passing some arguments to an external program
as a sequence is:

@example
Popen(["/usr/bin/git", "commit", "-m", "Fixes a bug."])
@end example

在 POSIX，如果 @emph{args} 是一个字符串，此字符串被作为将被执行的程序的命名或路径解释。但是，只有在不传递任何参数给程序的情况下才能这么做。

@cartouche
@quotation 注解 
It may not be obvious how to break a shell command into a sequence of arguments,
especially in complex cases. @ref{218,,shlex.split()} can illustrate how to
determine the correct tokenization for @emph{args}:

@example
>>> import shlex, subprocess
>>> command_line = input()
/bin/vikings -input eggs.txt -output "spam spam.txt" -cmd "echo '$MONEY'"
>>> args = shlex.split(command_line)
>>> print(args)
['/bin/vikings', '-input', 'eggs.txt', '-output', 'spam spam.txt', '-cmd', "echo '$MONEY'"]
>>> p = subprocess.Popen(args) # Success!
@end example

特别注意，由 shell 中的空格分隔的选项（例如 @emph{-input}）和参数（例如 @emph{eggs.txt} ）位于分开的列表元素中，而在需要时使用引号或反斜杠转义的参数在 shell （例如包含空格的文件名或上面显示的 @emph{echo} 命令）是单独的列表元素。
@end quotation
@end cartouche

在 Windows，如果 @emph{args} 是一个序列，他将通过一个在 @ref{2408,,Converting an argument sequence to a string on Windows} 描述的方式被转换为一个字符串。这是因为底层的 @code{CreateProcess()} 只处理字符串。


在 3.6 版更改: @emph{args} parameter accepts a @ref{363,,path-like object} if @emph{shell} is
@code{False} and a sequence containing path-like objects on POSIX.



在 3.8 版更改: @emph{args} parameter accepts a @ref{363,,path-like object} if @emph{shell} is
@code{False} and a sequence containing bytes and path-like objects
on Windows.


参数 @emph{shell} （默认为 @code{False}）指定是否使用 shell 执行程序。如果 @emph{shell} 为 @code{True}，更推荐将 @emph{args} 作为字符串传递而非序列。

在 POSIX，当 @code{shell=True}， shell 默认为 @code{/bin/sh}。如果 @emph{args} 是一个字符串，此字符串指定将通过 shell 执行的命令。这意味着字符串的格式必须和在命令提示符中所输入的完全相同。这包括，例如，引号和反斜杠转义包含空格的文件名。如果 @emph{args} 是一个序列，第一项指定了命令，另外的项目将作为传递给 shell （而非命令） 的参数对待。也就是说， @ref{2b9,,Popen} 等同于:

@example
Popen(['/bin/sh', '-c', args[0], args[1], ...])
@end example

在 Windows，使用 @code{shell=True}，环境变量 
@geindex COMSPEC
@geindex 环境变量; COMSPEC
@code{COMSPEC} 指定了默认 shell。在 Windows 你唯一需要指定 @code{shell=True} 的情况是你想要执行内置在 shell 中的命令（例如 @code{dir} 或者 @code{copy}）。在运行一个批处理文件或者基于控制台的可执行文件时，不需要 @code{shell=True}。

@cartouche
@quotation 注解 
在使用 @code{shell=True} 之前， 请阅读 @ref{2406,,Security Considerations} 段落。
@end quotation
@end cartouche

@emph{bufsize} 将在 @ref{4ea,,open()} 函数创建了 stdin/stdout/stderr 管道文件对象时作为对应的参数供应:


@itemize -

@item 
@code{0} 表示不使用缓冲区 （读取与写入是一个系统调用并且可以返回短内容）

@item 
@code{1} 表示行缓冲（只有 @code{universal_newlines=True} 时才有用，例如，在文本模式中）

@item 
任何其他正值表示使用一个约为对应大小的缓冲区

@item 
负的 @emph{bufsize} （默认）表示使用系统默认的 io.DEFAULT_BUFFER_SIZE。
@end itemize


在 3.3.1 版更改: @emph{bufsize} 现在默认为 -1 来启用缓冲，以符合大多数代码所期望的行为。在 Python 3.2.4 和 3.3.1 之前的版本中，它错误地将默认值设为了为 @code{0}，这是无缓冲的并且允许短读取。这是无意的，并且与大多数代码所期望的 Python 2 的行为不一致。


@emph{executable} 参数指定一个要执行的替换程序。这很少需要。当 @code{shell=True}， @emph{executable} 替换 @emph{args} 指定运行的程序。但是，原始的 @emph{args} 仍然被传递给程序。大多数程序将被 @emph{args} 指定的程序作为命令名对待，这可以与实际运行的程序不同。在 POSIX， @emph{args} 名作为实际调用程序中可执行文件的显示名称，例如 @code{ps}。如果 @code{shell=True}，在 POSIX， @emph{executable} 参数指定用于替换默认 shell @code{/bin/sh} 的 shell。


在 3.6 版更改: @emph{executable} parameter accepts a @ref{363,,path-like object} on POSIX.



在 3.8 版更改: @emph{executable} parameter accepts a bytes and @ref{363,,path-like object}
on Windows.


@emph{stdin}, @emph{stdout} 和 @emph{stderr} 分别指定被运行的程序的标准输入、输出和标准错误的文件句柄。合法的值有 @ref{3e6,,PIPE} ， @ref{a9b,,DEVNULL} ， 一个存在的文件描述符（一个正整数），一个存在的 @ref{b3b,,文件对象} 以及 @code{None}。 @ref{3e6,,PIPE} 表示应创建一个新的对子进程的管道。 @ref{a9b,,DEVNULL} 表示使用特殊的 @ref{fad,,os.devnull} 文件。使用默认的 @code{None}，则不进行成定向；子进程的文件流将继承自父进程。另外， @emph{stderr} 可设为 @ref{23f5,,STDOUT}，表示应用程序的标准错误数据应和标准输出一同捕获。

如果 @emph{preexec_fn} 被设为一个可调用对象，此对象将在子进程刚创建时被调用。（仅 POSIX）

@cartouche
@quotation 警告 
@emph{preexec_fn} 形参在应用程序中存在多线程时是不安全的。子进程在调用前可能死锁。如果你必须使用它，保持警惕！最小化你调用的库的数量。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
如果你需要修改子进程环境，使用 @emph{env} 形参而非在 @emph{preexec_fn} 中进行。 @emph{start_new_session} 形参可以代替之前常用的 @emph{preexec_fn} 来在子进程中调用 os.setsid()。
@end quotation
@end cartouche


在 3.8 版更改: The @emph{preexec_fn} parameter is no longer supported in subinterpreters.
The use of the parameter in a subinterpreter raises
@ref{2ba,,RuntimeError}. The new restriction may affect applications that
are deployed in mod_wsgi, uWSGI, and other embedded environments.


如果 @emph{close_fds} 为真，所有文件描述符除了 @code{0}, @code{1}, @code{2} 之外都会在子进程执行前关闭。而当 @emph{close_fds} 为假时，文件描述符遵守它们继承的标志，如 @ref{7f4,,文件描述符的继承} 所述。

在 Windows，如果 @emph{close_fds} 为真， 则子进程不会继承任何句柄，除非在 @code{STARTUPINFO.IpAttributeList} 的 @code{handle_list} 的键中显式传递，或者通过标准句柄重定向传递。


在 3.2 版更改: @emph{close_fds} 的默认值已经从 @ref{380,,False} 修改为上述值。



在 3.7 版更改: 在 Windows，当重定向标准句柄时 @emph{close_fds} 的默认值从 @ref{380,,False} 变为 @ref{494,,True}。现在重定向标准句柄时有可能设置 @emph{close_fds} 为 @ref{494,,True}。（标准句柄指三个 stdio 的句柄）


@emph{pass_fds} 是一个可选的在父子进程间保持打开的文件描述符序列。提供任何 @emph{pass_fds} 将强制 @emph{close_fds} 为 @ref{494,,True}。（仅 POSIX）


在 3.2 版更改: 加入了 @emph{pass_fds} 形参。


If @emph{cwd} is not @code{None}, the function changes the working directory to
@emph{cwd} before executing the child.  @emph{cwd} can be a string, bytes or
@ref{363,,path-like} object.  In particular, the function
looks for @emph{executable} (or for the first item in @emph{args}) relative to @emph{cwd}
if the executable path is a relative path.


在 3.6 版更改: @emph{cwd} parameter accepts a @ref{363,,path-like object} on POSIX.



在 3.7 版更改: @emph{cwd} parameter accepts a @ref{363,,path-like object} on Windows.



在 3.8 版更改: @emph{cwd} parameter accepts a bytes object on Windows.


 如果 @emph{restore_signals} 为 true（默认值），则 Python 设置为 SIG_IGN 的所有信号将在 exec 之前的子进程中恢复为 SIG_DFL。目前，这包括 SIGPIPE ，SIGXFZ 和 SIGXFSZ 信号。 （仅 POSIX）


在 3.2 版更改: @emph{restore_signals} 被加入。


如果 @emph{start_new_session} 为 true，则 setsid() 系统调用将在子进程执行之前被执行。（仅 POSIX）


在 3.2 版更改: @emph{start_new_session} 被添加。


如果 @emph{env} 不为 @code{None}，则必须为一个为新进程定义了环境变量的字典；这些用于替换继承的当前进程环境的默认行为。

@cartouche
@quotation 注解 
如果指定， @emph{env} 必须提供所有被子进程需求的变量。在 Windows，为了运行一个 side-by-side assembly@footnote{https://en.wikipedia.org/wiki/Side-by-Side_Assembly} ，指定的 @emph{env} @strong{必须} 包含一个有效的 
@geindex SystemRoot
@geindex 环境变量; SystemRoot
@code{SystemRoot}。
@end quotation
@end cartouche

如果 @emph{encoding} 或 @emph{errors} 被指定，或者 @emph{text} 为 true，则文件对象 @emph{stdin}, @emph{stdout} 和 @emph{stderr} 将会以指定的编码和 @emph{errors} 以文本模式打开，如同 @ref{23ed,,常用参数} 所述。 @emph{universal_newlines} 参数等同于 @emph{text} 并且提供向后兼容性。默认情况下，文件对象都以二进制模式打开。


3.6 新版功能: @emph{encoding} 和 @emph{errors} 被添加。



3.7 新版功能: @emph{text} 作为 @emph{universal_newlines} 的一个更具可读性的别名被添加。


如果给出， @emph{startupinfo} 将是一个将被传递给底层的 @code{CreateProcess} 函数的 @ref{2409,,STARTUPINFO} 对象。 @emph{creationflags}，如果给出，可以是一个或多个以下标志之一：

@quotation


@itemize *

@item 
@ref{240a,,CREATE_NEW_CONSOLE}

@item 
@ref{240b,,CREATE_NEW_PROCESS_GROUP}

@item 
@ref{240c,,ABOVE_NORMAL_PRIORITY_CLASS}

@item 
@ref{240d,,BELOW_NORMAL_PRIORITY_CLASS}

@item 
@ref{240e,,HIGH_PRIORITY_CLASS}

@item 
@ref{240f,,IDLE_PRIORITY_CLASS}

@item 
@ref{2410,,NORMAL_PRIORITY_CLASS}

@item 
@ref{2411,,REALTIME_PRIORITY_CLASS}

@item 
@ref{2412,,CREATE_NO_WINDOW}

@item 
@ref{2413,,DETACHED_PROCESS}

@item 
@ref{2414,,CREATE_DEFAULT_ERROR_MODE}

@item 
@ref{2415,,CREATE_BREAKAWAY_FROM_JOB}
@end itemize
@end quotation

Popen 对象支持通过 @ref{6e3,,with} 语句作为上下文管理器，在退出时关闭文件描述符并等待进程:

@example
with Popen(["ifconfig"], stdout=PIPE) as proc:
    log.write(proc.stdout.read())
@end example


Popen and the other functions in this module that use it raise an
@ref{12d0,,auditing event} @code{subprocess.Popen} with arguments
@code{executable}, @code{args}, @code{cwd}, and @code{env}. The value for @code{args}
may be a single string or a list of strings, depending on platform.



在 3.2 版更改: 添加了上下文管理器支持。



在 3.6 版更改: 现在，如果 Popen 析构时子进程仍然在运行，则析构器会发送一个 @ref{4ca,,ResourceWarning} 警告。



在 3.8 版更改: Popen can use @ref{257,,os.posix_spawn()} in some cases for better
performance. On Windows Subsystem for Linux and QEMU User Emulation,
Popen constructor using @ref{257,,os.posix_spawn()} no longer raise an
exception on errors like missing program, but the child process fails
with a non-zero @ref{2416,,returncode}.

@end deffn

@node 异常<7>,,Popen 构造函数,使用 subprocess 模块
@anchor{library/subprocess exceptions}@anchor{2417}
@subsubsection 异常


在子进程中抛出的异常，在新的进程开始执行前，将会被再次在父进程中抛出。

最常见的被抛出异常是 @ref{1d3,,OSError}。例如，当尝试执行一个不存在的文件时就会发生。应用程序需要为 @ref{1d3,,OSError} 异常做好准备。

如果 @ref{2b9,,Popen} 调用时有无效的参数，则一个 @ref{1fb,,ValueError} 将被抛出。

@code{check_all()} 与 @ref{8d5,,check_output()} 在调用的进程返回非零退出码时将抛出 @ref{cae,,CalledProcessError}。

所有接受 @emph{timeout} 形参的函数与方法，例如 @ref{3e7,,call()} 和 @ref{23ee,,Popen.communicate()} 将会在进程退出前超时到期时抛出 @ref{23ef,,TimeoutExpired}。

此模块中定义的异常都继承自 @ref{23f6,,SubprocessError}。

@quotation


3.3 新版功能: 基类 @ref{23f6,,SubprocessError} 被添加。

@end quotation

@node 安全考量,Popen 对象,使用 subprocess 模块,subprocess --- 子进程管理
@anchor{library/subprocess security-considerations}@anchor{2406}
@subsubsection 安全考量


不像一些其他的 popen 功能，此实现绝不会隐式调用一个系统 shell。这意味着任何字符，包括 shell 元字符，可以安全地被传递给子进程。如果 shell 被明确地调用，通过 @code{shell=True} 设置，则确保所有空白字符和元字符被恰当地包裹在引号内以避免 shell 注入@footnote{https://en.wikipedia.org/wiki/Shell_injection#Shell_injection} 漏洞就由应用程序负责了。

当使用 @code{shell=True}， @ref{a6e,,shlex.quote()} 函数可以作为在将被用于构造 shell 指令的字符串中转义空白字符以及 shell 元字符的方案。

@node Popen 对象,Windows Popen 助手,安全考量,subprocess --- 子进程管理
@anchor{library/subprocess popen-objects}@anchor{2418}
@subsubsection Popen 对象


@ref{2b9,,Popen} 类的实例拥有以下方法：

@geindex poll() (subprocess.Popen 方法)
@anchor{library/subprocess subprocess Popen poll}@anchor{2419}
@deffn {方法} Popen.poll ()

检查子进程是否已被终止。设置并返回 @ref{2416,,returncode} 属性。否则返回 @code{None}。
@end deffn

@geindex wait() (subprocess.Popen 方法)
@anchor{library/subprocess subprocess Popen wait}@anchor{58d}
@deffn {方法} Popen.wait (timeout=None)

等待子进程被终止。设置并返回 @ref{2416,,returncode} 属性。

如果进程在 @emph{timeout} 秒后未中断，抛出一个 @ref{23ef,,TimeoutExpired} 异常，可以安全地捕获此异常并重新等待。

@cartouche
@quotation 注解 
当 @code{stdout=PIPE} 或者 @code{stderr=PIPE} 并且子进程产生了足以阻塞 OS 管道缓冲区接收更多数据的输出到管道时，将会发生死锁。当使用管道时用 @ref{23ee,,Popen.communicate()} 来规避它。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
此函数使用了一个 busy loop （非阻塞调用以及短睡眠） 实现。使用 @ref{a,,asyncio} 模块进行异步等待： 参阅 @ref{291,,asyncio.create_subprocess_exec}。
@end quotation
@end cartouche


在 3.3 版更改: @emph{timeout} 被添加

@end deffn

@geindex communicate() (subprocess.Popen 方法)
@anchor{library/subprocess subprocess Popen communicate}@anchor{23ee}
@deffn {方法} Popen.communicate (input=None, timeout=None)

Interact with process: Send data to stdin.  Read data from stdout and stderr,
until end-of-file is reached.  Wait for process to terminate and set the
@ref{2416,,returncode} attribute.  The optional @emph{input} argument should be
data to be sent to the child process, or @code{None}, if no data should be sent
to the child.  If streams were opened in text mode, @emph{input} must be a string.
Otherwise, it must be bytes.

@ref{23ee,,communicate()} 返回一个 @code{(stdout_data, stderr_data)} 元组。如果文件以文本模式打开则为字符串；否则字节。

注意如果你想要向进程的 stdin 传输数据，你需要通过 @code{stdin=PIPE} 创建此 Popen 对象。类似的，要从结果元组获取任何非 @code{None} 值，你同样需要设置 @code{stdout=PIPE} 或者 @code{stderr=PIPE}。

如果进程在 @emph{timeout} 秒后未终止，一个 @ref{23ef,,TimeoutExpired} 异常将被抛出。捕获此异常并重新等待将不会丢失任何输出。

如果超时到期，子进程不会被杀死，所以为了正确清理一个行为良好的应用程序应该杀死子进程并完成通讯。

@example
proc = subprocess.Popen(...)
try:
    outs, errs = proc.communicate(timeout=15)
except TimeoutExpired:
    proc.kill()
    outs, errs = proc.communicate()
@end example

@cartouche
@quotation 注解 
内存里数据读取是缓冲的，所以如果数据尺寸过大或无限，不要使用此方法。
@end quotation
@end cartouche


在 3.3 版更改: @emph{timeout} 被添加

@end deffn

@geindex send_signal() (subprocess.Popen 方法)
@anchor{library/subprocess subprocess Popen send_signal}@anchor{241a}
@deffn {方法} Popen.send_signal (signal)

将信号 @emph{signal} 发送给子进程。

@cartouche
@quotation 注解 
在 Windows， SIGTERM 是一个 @ref{241b,,terminate()} 的别名。 CTRL_C_EVENT 和 CTRL_BREAK_EVENT 可以被发送给以包含 @code{CREATE_NEW_PROCESS} 的 @emph{creationflags} 形参启动的进程。
@end quotation
@end cartouche
@end deffn

@geindex terminate() (subprocess.Popen 方法)
@anchor{library/subprocess subprocess Popen terminate}@anchor{241b}
@deffn {方法} Popen.terminate ()

Stop the child. On POSIX OSs the method sends SIGTERM to the
child. On Windows the Win32 API function @code{TerminateProcess()} is called
to stop the child.
@end deffn

@geindex kill() (subprocess.Popen 方法)
@anchor{library/subprocess subprocess Popen kill}@anchor{241c}
@deffn {方法} Popen.kill ()

Kills the child. On POSIX OSs the function sends SIGKILL to the child.
On Windows @ref{241c,,kill()} is an alias for @ref{241b,,terminate()}.
@end deffn

以下属性也是可用的：

@geindex args (subprocess.Popen 属性)
@anchor{library/subprocess subprocess Popen args}@anchor{241d}
@deffn {属性} Popen.args

@emph{args} 参数传递给 @ref{2b9,,Popen} -- 一个程序参数的序列或者一个简单字符串。


3.3 新版功能.

@end deffn

@geindex stdin (subprocess.Popen 属性)
@anchor{library/subprocess subprocess Popen stdin}@anchor{2403}
@deffn {属性} Popen.stdin

如果 @emph{stdin} 参数为 @ref{3e6,,PIPE}，此属性是一个类似 @ref{4ea,,open()} 返回的可写的流对象。如果 @emph{encoding} 或 @emph{errors} 参数被指定或者 @emph{universal_newlines} 参数为 @code{True}，则此流是一个文本流，否则是字节流。如果 @emph{stdin} 参数非 @ref{3e6,,PIPE}， 此属性为 @code{None}。
@end deffn

@geindex stdout (subprocess.Popen 属性)
@anchor{library/subprocess subprocess Popen stdout}@anchor{2404}
@deffn {属性} Popen.stdout

如果 @emph{stdout} 参数是 @ref{3e6,,PIPE}，此属性是一个类似 @ref{4ea,,open()} 返回的可读流。从流中读取子进程提供的输出。如果 @emph{encoding} 或 @emph{errors} 参数被指定或者 @emph{universal_newlines} 参数为 @code{True}，此流为文本流，否则为字节流。如果 @emph{stdout} 参数非 @ref{3e6,,PIPE}，此属性为 @code{None}。
@end deffn

@geindex stderr (subprocess.Popen 属性)
@anchor{library/subprocess subprocess Popen stderr}@anchor{2405}
@deffn {属性} Popen.stderr

如果 @emph{stderr} 参数是 @ref{3e6,,PIPE}，此属性是一个类似 @ref{4ea,,open()} 返回的可读流。从流中读取子进程提供的输出。如果 @emph{encoding} 或 @emph{errors} 参数被指定或者 @emph{universal_newlines} 参数为 @code{True}，此流为文本流，否则为字节流。如果 @emph{stderr} 参数非 @ref{3e6,,PIPE}，此属性为 @code{None}。
@end deffn

@cartouche
@quotation 警告 
使用 @ref{23ee,,communicate()} 而非 @ref{2403,,.stdin.write}， @ref{2404,,.stdout.read} 或者 @ref{2405,,.stderr.read} 来避免由于任意其他 OS 管道缓冲区被子进程填满阻塞而导致的死锁。
@end quotation
@end cartouche

@geindex pid (subprocess.Popen 属性)
@anchor{library/subprocess subprocess Popen pid}@anchor{241e}
@deffn {属性} Popen.pid

子进程的进程号。

注意如果你设置了 @emph{shell} 参数为 @code{True}，则这是生成的子 shell 的进程号。
@end deffn

@geindex returncode (subprocess.Popen 属性)
@anchor{library/subprocess subprocess Popen returncode}@anchor{2416}
@deffn {属性} Popen.returncode

此进程的退出码，由 @ref{2419,,poll()} 和 @ref{58d,,wait()} 设置（以及直接由 @ref{23ee,,communicate()} 设置）。一个 @code{None} 值 表示此进程仍未结束。

一个负值 @code{-N} 表示子进程被信号 @code{N} 中断 (仅 POSIX).
@end deffn

@node Windows Popen 助手,Older high-level API,Popen 对象,subprocess --- 子进程管理
@anchor{library/subprocess windows-popen-helpers}@anchor{241f}
@subsubsection Windows Popen 助手


@ref{2409,,STARTUPINFO} 类和以下常数仅在 Windows 有效。

@geindex STARTUPINFO (subprocess 中的类)
@anchor{library/subprocess subprocess STARTUPINFO}@anchor{2409}
@deffn {类} subprocess.STARTUPINFO (*, dwFlags=0, hStdInput=None, hStdOutput=None, hStdError=None, wShowWindow=0, lpAttributeList=None)

在 @ref{2b9,,Popen} 创建时部分支持 Windows 的 STARTUPINFO@footnote{https://msdn.microsoft.com/en-us/library/ms686331(v=vs.85).aspx} 结构。接下来的属性仅能通过关键词参数设置。


在 3.7 版更改: 仅关键词参数支持被加入。


@geindex dwFlags (subprocess.STARTUPINFO 属性)
@anchor{library/subprocess subprocess STARTUPINFO dwFlags}@anchor{2420}
@deffn {属性} dwFlags

一个位字段，用于确定进程在创建窗口时是否使用某些 @ref{2409,,STARTUPINFO} 属性。

@example
si = subprocess.STARTUPINFO()
si.dwFlags = subprocess.STARTF_USESTDHANDLES | subprocess.STARTF_USESHOWWINDOW
@end example
@end deffn

@geindex hStdInput (subprocess.STARTUPINFO 属性)
@anchor{library/subprocess subprocess STARTUPINFO hStdInput}@anchor{2421}
@deffn {属性} hStdInput

如果 @ref{2420,,dwFlags} 被指定为 @ref{2422,,STARTF_USESTDHANDLES}，则此属性是进程的标准输入句柄，如果 @ref{2422,,STARTF_USESTDHANDLES} 未指定，则默认的标准输入是键盘缓冲区。
@end deffn

@geindex hStdOutput (subprocess.STARTUPINFO 属性)
@anchor{library/subprocess subprocess STARTUPINFO hStdOutput}@anchor{2423}
@deffn {属性} hStdOutput

如果 @ref{2420,,dwFlags} 被指定为 @ref{2422,,STARTF_USESTDHANDLES}，则此属性是进程的标准输出句柄。除此之外，此此属性将被忽略并且默认标准输出是控制台窗口缓冲区。
@end deffn

@geindex hStdError (subprocess.STARTUPINFO 属性)
@anchor{library/subprocess subprocess STARTUPINFO hStdError}@anchor{2424}
@deffn {属性} hStdError

如果 @ref{2420,,dwFlags} 被指定为 @ref{2422,,STARTF_USESTDHANDLES}，则此属性是进程的标准错误句柄。除此之外，此属性将被忽略并且默认标准错误为控制台窗口的缓冲区。
@end deffn

@geindex wShowWindow (subprocess.STARTUPINFO 属性)
@anchor{library/subprocess subprocess STARTUPINFO wShowWindow}@anchor{2425}
@deffn {属性} wShowWindow

如果 @ref{2420,,dwFlags} 指定了 @ref{2426,,STARTF_USESHOWWINDOW}，此属性可为能被指定为 函数 ShowWindow@footnote{https://msdn.microsoft.com/en-us/library/ms633548(v=vs.85).aspx} 的nCmdShow 的形参的任意值，除了 @code{SW_SHOWDEFAULT}。如此之外，此属性被忽略。

@ref{2427,,SW_HIDE} 被提供给此属性。它在 @ref{2b9,,Popen} 由 @code{shell=True} 调用时使用。
@end deffn

@geindex lpAttributeList (subprocess.STARTUPINFO 属性)
@anchor{library/subprocess subprocess STARTUPINFO lpAttributeList}@anchor{495}
@deffn {属性} lpAttributeList

@code{STARTUPINFOEX} 给出的用于进程创建的额外属性字典，参阅 UpdateProcThreadAttribute@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/ms686880(v=vs.85).aspx}。

支持的属性：


@table @asis

@item @strong{handle_list}

将被继承的句柄的序列。如果非空， @emph{close_fds} 必须为 true。

当传递给 @ref{2b9,,Popen} 构造函数时，这些句柄必须暂时地能被 @ref{7f8,,os.set_handle_inheritable()} 继承，否则 @ref{1d3,,OSError} 将以 Windows error @code{ERROR_INVALID_PARAMETER} (87) 抛出。

@cartouche
@quotation 警告 
在多线程进程中，请谨慎使用，以便在将此功能与对继承所有句柄的其他进程创建函数——例如 @ref{dba,,os.system()} 的并发调用——相结合时，避免泄漏标记为可继承的句柄。这也应用于临时性创建可继承句柄的标准句柄重定向。
@end quotation
@end cartouche
@end table


3.7 新版功能.

@end deffn
@end deffn

@menu
* Windows 常数:: 

@end menu

@node Windows 常数,,,Windows Popen 助手
@anchor{library/subprocess windows-constants}@anchor{2428}
@subsubsection Windows 常数


@ref{f9,,subprocess} 模块曝出以下常数。

@geindex STD_INPUT_HANDLE() (在 subprocess 模块中)
@anchor{library/subprocess subprocess STD_INPUT_HANDLE}@anchor{2429}
@deffn {数据} subprocess.STD_INPUT_HANDLE

标准输入设备，这是控制台输入缓冲区 @code{CONIN$}。
@end deffn

@geindex STD_OUTPUT_HANDLE() (在 subprocess 模块中)
@anchor{library/subprocess subprocess STD_OUTPUT_HANDLE}@anchor{242a}
@deffn {数据} subprocess.STD_OUTPUT_HANDLE

标准输出设备。最初，这是活动控制台屏幕缓冲区 @code{CONOUT$}。
@end deffn

@geindex STD_ERROR_HANDLE() (在 subprocess 模块中)
@anchor{library/subprocess subprocess STD_ERROR_HANDLE}@anchor{242b}
@deffn {数据} subprocess.STD_ERROR_HANDLE

标准错误设备。最初，这是活动控制台屏幕缓冲区 @code{CONOUT$}。
@end deffn

@geindex SW_HIDE() (在 subprocess 模块中)
@anchor{library/subprocess subprocess SW_HIDE}@anchor{2427}
@deffn {数据} subprocess.SW_HIDE

隐藏窗口。另一个窗口将被激活。
@end deffn

@geindex STARTF_USESTDHANDLES() (在 subprocess 模块中)
@anchor{library/subprocess subprocess STARTF_USESTDHANDLES}@anchor{2422}
@deffn {数据} subprocess.STARTF_USESTDHANDLES

Specifies that the @ref{2421,,STARTUPINFO.hStdInput},
@ref{2423,,STARTUPINFO.hStdOutput}, and @ref{2424,,STARTUPINFO.hStdError} attributes
contain additional information.
@end deffn

@geindex STARTF_USESHOWWINDOW() (在 subprocess 模块中)
@anchor{library/subprocess subprocess STARTF_USESHOWWINDOW}@anchor{2426}
@deffn {数据} subprocess.STARTF_USESHOWWINDOW

Specifies that the @ref{2425,,STARTUPINFO.wShowWindow} attribute contains
additional information.
@end deffn

@geindex CREATE_NEW_CONSOLE() (在 subprocess 模块中)
@anchor{library/subprocess subprocess CREATE_NEW_CONSOLE}@anchor{240a}
@deffn {数据} subprocess.CREATE_NEW_CONSOLE

The new process has a new console, instead of inheriting its parent's
console (the default).
@end deffn

@geindex CREATE_NEW_PROCESS_GROUP() (在 subprocess 模块中)
@anchor{library/subprocess subprocess CREATE_NEW_PROCESS_GROUP}@anchor{240b}
@deffn {数据} subprocess.CREATE_NEW_PROCESS_GROUP

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
group will be created. This flag is necessary for using @ref{cec,,os.kill()}
on the subprocess.

This flag is ignored if @ref{240a,,CREATE_NEW_CONSOLE} is specified.
@end deffn

@geindex ABOVE_NORMAL_PRIORITY_CLASS() (在 subprocess 模块中)
@anchor{library/subprocess subprocess ABOVE_NORMAL_PRIORITY_CLASS}@anchor{240c}
@deffn {数据} subprocess.ABOVE_NORMAL_PRIORITY_CLASS

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
will have an above average priority.


3.7 新版功能.

@end deffn

@geindex BELOW_NORMAL_PRIORITY_CLASS() (在 subprocess 模块中)
@anchor{library/subprocess subprocess BELOW_NORMAL_PRIORITY_CLASS}@anchor{240d}
@deffn {数据} subprocess.BELOW_NORMAL_PRIORITY_CLASS

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
will have a below average priority.


3.7 新版功能.

@end deffn

@geindex HIGH_PRIORITY_CLASS() (在 subprocess 模块中)
@anchor{library/subprocess subprocess HIGH_PRIORITY_CLASS}@anchor{240e}
@deffn {数据} subprocess.HIGH_PRIORITY_CLASS

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
will have a high priority.


3.7 新版功能.

@end deffn

@geindex IDLE_PRIORITY_CLASS() (在 subprocess 模块中)
@anchor{library/subprocess subprocess IDLE_PRIORITY_CLASS}@anchor{240f}
@deffn {数据} subprocess.IDLE_PRIORITY_CLASS

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
will have an idle (lowest) priority.


3.7 新版功能.

@end deffn

@geindex NORMAL_PRIORITY_CLASS() (在 subprocess 模块中)
@anchor{library/subprocess subprocess NORMAL_PRIORITY_CLASS}@anchor{2410}
@deffn {数据} subprocess.NORMAL_PRIORITY_CLASS

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
will have an normal priority. (default)


3.7 新版功能.

@end deffn

@geindex REALTIME_PRIORITY_CLASS() (在 subprocess 模块中)
@anchor{library/subprocess subprocess REALTIME_PRIORITY_CLASS}@anchor{2411}
@deffn {数据} subprocess.REALTIME_PRIORITY_CLASS

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
will have realtime priority.
You should almost never use REALTIME_PRIORITY_CLASS, because this interrupts
system threads that manage mouse input, keyboard input, and background disk
flushing. This class can be appropriate for applications that "talk" directly
to hardware or that perform brief tasks that should have limited interruptions.


3.7 新版功能.

@end deffn

@geindex CREATE_NO_WINDOW() (在 subprocess 模块中)
@anchor{library/subprocess subprocess CREATE_NO_WINDOW}@anchor{2412}
@deffn {数据} subprocess.CREATE_NO_WINDOW

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
will not create a window.


3.7 新版功能.

@end deffn

@geindex DETACHED_PROCESS() (在 subprocess 模块中)
@anchor{library/subprocess subprocess DETACHED_PROCESS}@anchor{2413}
@deffn {数据} subprocess.DETACHED_PROCESS

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
will not inherit its parent's console.
This value cannot be used with CREATE_NEW_CONSOLE.


3.7 新版功能.

@end deffn

@geindex CREATE_DEFAULT_ERROR_MODE() (在 subprocess 模块中)
@anchor{library/subprocess subprocess CREATE_DEFAULT_ERROR_MODE}@anchor{2414}
@deffn {数据} subprocess.CREATE_DEFAULT_ERROR_MODE

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
does not inherit the error mode of the calling process. Instead, the new
process gets the default error mode.
This feature is particularly useful for multithreaded shell applications
that run with hard errors disabled.


3.7 新版功能.

@end deffn

@geindex CREATE_BREAKAWAY_FROM_JOB() (在 subprocess 模块中)
@anchor{library/subprocess subprocess CREATE_BREAKAWAY_FROM_JOB}@anchor{2415}
@deffn {数据} subprocess.CREATE_BREAKAWAY_FROM_JOB

A @ref{2b9,,Popen} @code{creationflags} parameter to specify that a new process
is not associated with the job.


3.7 新版功能.

@end deffn

@node Older high-level API,Replacing Older Functions with the subprocess Module,Windows Popen 助手,subprocess --- 子进程管理
@anchor{library/subprocess call-function-trio}@anchor{23ec}@anchor{library/subprocess older-high-level-api}@anchor{242c}
@subsubsection Older high-level API


Prior to Python 3.5, these three functions comprised the high level API to
subprocess. You can now use @ref{3e5,,run()} in many cases, but lots of existing code
calls these functions.

@geindex call() (在 subprocess 模块中)
@anchor{library/subprocess subprocess call}@anchor{3e7}
@deffn {函数} subprocess.call (args, *, stdin=None, stdout=None, stderr=None, shell=False, cwd=None, timeout=None, **other_popen_kwargs)

Run the command described by @emph{args}.  Wait for command to complete, then
return the @ref{2416,,returncode} attribute.

Code needing to capture stdout or stderr should use @ref{3e5,,run()} instead:

@example
run(...).returncode
@end example

To suppress stdout or stderr, supply a value of @ref{a9b,,DEVNULL}.

The arguments shown above are merely some common ones.
The full function signature is the
same as that of the @ref{2b9,,Popen} constructor - this function passes all
supplied arguments other than @emph{timeout} directly through to that interface.

@cartouche
@quotation 注解 
Do not use @code{stdout=PIPE} or @code{stderr=PIPE} with this
function.  The child process will block if it generates enough
output to a pipe to fill up the OS pipe buffer as the pipes are
not being read from.
@end quotation
@end cartouche


在 3.3 版更改: @emph{timeout} 被添加

@end deffn

@geindex check_call() (在 subprocess 模块中)
@anchor{library/subprocess subprocess check_call}@anchor{23fc}
@deffn {函数} subprocess.check_call (args, *, stdin=None, stdout=None, stderr=None, shell=False, cwd=None, timeout=None, **other_popen_kwargs)

Run command with arguments.  Wait for command to complete. If the return
code was zero then return, otherwise raise @ref{cae,,CalledProcessError}. The
@ref{cae,,CalledProcessError} object will have the return code in the
@ref{23fd,,returncode} attribute.

Code needing to capture stdout or stderr should use @ref{3e5,,run()} instead:

@example
run(..., check=True)
@end example

To suppress stdout or stderr, supply a value of @ref{a9b,,DEVNULL}.

The arguments shown above are merely some common ones.
The full function signature is the
same as that of the @ref{2b9,,Popen} constructor - this function passes all
supplied arguments other than @emph{timeout} directly through to that interface.

@cartouche
@quotation 注解 
Do not use @code{stdout=PIPE} or @code{stderr=PIPE} with this
function.  The child process will block if it generates enough
output to a pipe to fill up the OS pipe buffer as the pipes are
not being read from.
@end quotation
@end cartouche


在 3.3 版更改: @emph{timeout} 被添加

@end deffn

@geindex check_output() (在 subprocess 模块中)
@anchor{library/subprocess subprocess check_output}@anchor{8d5}
@deffn {函数} subprocess.check_output (args, *, stdin=None, stderr=None, shell=False, cwd=None, encoding=None, errors=None, universal_newlines=None, timeout=None, text=None, **other_popen_kwargs)

Run command with arguments and return its output.

If the return code was non-zero it raises a @ref{cae,,CalledProcessError}. The
@ref{cae,,CalledProcessError} object will have the return code in the
@ref{23fd,,returncode} attribute and any output in the
@ref{23ff,,output} attribute.

这相当于:

@example
run(..., check=True, stdout=PIPE).stdout
@end example

The arguments shown above are merely some common ones.
The full function signature is largely the same as that of @ref{3e5,,run()} -
most arguments are passed directly through to that interface.
However, explicitly passing @code{input=None} to inherit the parent's
standard input file handle is not supported.

By default, this function will return the data as encoded bytes. The actual
encoding of the output data may depend on the command being invoked, so the
decoding to text will often need to be handled at the application level.

This behaviour may be overridden by setting @emph{text}, @emph{encoding}, @emph{errors},
or @emph{universal_newlines} to @code{True} as described in
@ref{23ed,,常用参数} and @ref{3e5,,run()}.

To also capture standard error in the result, use
@code{stderr=subprocess.STDOUT}:

@example
>>> subprocess.check_output(
...     "ls non_existent_file; exit 0",
...     stderr=subprocess.STDOUT,
...     shell=True)
'ls: non_existent_file: No such file or directory\n'
@end example


3.1 新版功能.



在 3.3 版更改: @emph{timeout} 被添加



在 3.4 版更改: Support for the @emph{input} keyword argument was added.



在 3.6 版更改: @emph{encoding} and @emph{errors} were added.  See @ref{3e5,,run()} for details.



3.7 新版功能: @emph{text} 作为 @emph{universal_newlines} 的一个更具可读性的别名被添加。

@end deffn

@node Replacing Older Functions with the subprocess Module,Legacy Shell Invocation Functions,Older high-level API,subprocess --- 子进程管理
@anchor{library/subprocess replacing-older-functions-with-the-subprocess-module}@anchor{242d}@anchor{library/subprocess subprocess-replacements}@anchor{ae5}
@subsubsection Replacing Older Functions with the @code{subprocess} Module


In this section, "a becomes b" means that b can be used as a replacement for a.

@cartouche
@quotation 注解 
All "a" functions in this section fail (more or less) silently if the
executed program cannot be found; the "b" replacements raise @ref{1d3,,OSError}
instead.

In addition, the replacements using @ref{8d5,,check_output()} will fail with a
@ref{cae,,CalledProcessError} if the requested operation produces a non-zero
return code. The output is still available as the
@ref{23ff,,output} attribute of the raised exception.
@end quotation
@end cartouche

In the following examples, we assume that the relevant functions have already
been imported from the @ref{f9,,subprocess} module.

@menu
* Replacing /bin/sh shell command substitution:: 
* Replacing shell pipeline:: 
* Replacing os.system(): Replacing os system. 
* Replacing the os.spawn family: Replacing the os spawn family. 
* Replacing os.popen()@comma{} os.popen2()@comma{} os.popen3(): Replacing os popen os popen2 os popen3. 
* Replacing functions from the popen2 module:: 

@end menu

@node Replacing /bin/sh shell command substitution,Replacing shell pipeline,,Replacing Older Functions with the subprocess Module
@anchor{library/subprocess replacing-bin-sh-shell-command-substitution}@anchor{242e}
@subsubsection Replacing @code{/bin/sh} shell command substitution


@example
output=$(mycmd myarg)
@end example

becomes:

@example
output = check_output(["mycmd", "myarg"])
@end example

@node Replacing shell pipeline,Replacing os system,Replacing /bin/sh shell command substitution,Replacing Older Functions with the subprocess Module
@anchor{library/subprocess replacing-shell-pipeline}@anchor{242f}
@subsubsection Replacing shell pipeline


@example
output=$(dmesg | grep hda)
@end example

becomes:

@example
p1 = Popen(["dmesg"], stdout=PIPE)
p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
p1.stdout.close()  # Allow p1 to receive a SIGPIPE if p2 exits.
output = p2.communicate()[0]
@end example

The @code{p1.stdout.close()} call after starting the p2 is important in order for
p1 to receive a SIGPIPE if p2 exits before p1.

Alternatively, for trusted input, the shell's own pipeline support may still
be used directly:

@example
output=$(dmesg | grep hda)
@end example

becomes:

@example
output=check_output("dmesg | grep hda", shell=True)
@end example

@node Replacing os system,Replacing the os spawn family,Replacing shell pipeline,Replacing Older Functions with the subprocess Module
@anchor{library/subprocess replacing-os-system}@anchor{2430}
@subsubsection Replacing @code{os.system()}


@example
sts = os.system("mycmd" + " myarg")
# becomes
sts = call("mycmd" + " myarg", shell=True)
@end example

注释:


@itemize *

@item 
Calling the program through the shell is usually not required.
@end itemize

A more realistic example would look like this:

@example
try:
    retcode = call("mycmd" + " myarg", shell=True)
    if retcode < 0:
        print("Child was terminated by signal", -retcode, file=sys.stderr)
    else:
        print("Child returned", retcode, file=sys.stderr)
except OSError as e:
    print("Execution failed:", e, file=sys.stderr)
@end example

@node Replacing the os spawn family,Replacing os popen os popen2 os popen3,Replacing os system,Replacing Older Functions with the subprocess Module
@anchor{library/subprocess replacing-the-os-spawn-family}@anchor{2431}
@subsubsection Replacing the @code{os.spawn} family


P_NOWAIT example:

@example
pid = os.spawnlp(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg")
==>
pid = Popen(["/bin/mycmd", "myarg"]).pid
@end example

P_WAIT example:

@example
retcode = os.spawnlp(os.P_WAIT, "/bin/mycmd", "mycmd", "myarg")
==>
retcode = call(["/bin/mycmd", "myarg"])
@end example

Vector example:

@example
os.spawnvp(os.P_NOWAIT, path, args)
==>
Popen([path] + args[1:])
@end example

Environment example:

@example
os.spawnlpe(os.P_NOWAIT, "/bin/mycmd", "mycmd", "myarg", env)
==>
Popen(["/bin/mycmd", "myarg"], env=@{"PATH": "/usr/bin"@})
@end example

@node Replacing os popen os popen2 os popen3,Replacing functions from the popen2 module,Replacing the os spawn family,Replacing Older Functions with the subprocess Module
@anchor{library/subprocess replacing-os-popen-os-popen2-os-popen3}@anchor{2432}
@subsubsection Replacing @code{os.popen()}, @code{os.popen2()}, @code{os.popen3()}


@example
(child_stdin, child_stdout) = os.popen2(cmd, mode, bufsize)
==>
p = Popen(cmd, shell=True, bufsize=bufsize,
          stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdin, child_stdout) = (p.stdin, p.stdout)
@end example

@example
(child_stdin,
 child_stdout,
 child_stderr) = os.popen3(cmd, mode, bufsize)
==>
p = Popen(cmd, shell=True, bufsize=bufsize,
          stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=True)
(child_stdin,
 child_stdout,
 child_stderr) = (p.stdin, p.stdout, p.stderr)
@end example

@example
(child_stdin, child_stdout_and_stderr) = os.popen4(cmd, mode, bufsize)
==>
p = Popen(cmd, shell=True, bufsize=bufsize,
          stdin=PIPE, stdout=PIPE, stderr=STDOUT, close_fds=True)
(child_stdin, child_stdout_and_stderr) = (p.stdin, p.stdout)
@end example

Return code handling translates as follows:

@example
pipe = os.popen(cmd, 'w')
...
rc = pipe.close()
if rc is not None and rc >> 8:
    print("There were some errors")
==>
process = Popen(cmd, stdin=PIPE)
...
process.stdin.close()
if process.wait() != 0:
    print("There were some errors")
@end example

@node Replacing functions from the popen2 module,,Replacing os popen os popen2 os popen3,Replacing Older Functions with the subprocess Module
@anchor{library/subprocess replacing-functions-from-the-popen2-module}@anchor{2433}
@subsubsection Replacing functions from the @code{popen2} module


@cartouche
@quotation 注解 
If the cmd argument to popen2 functions is a string, the command is executed
through /bin/sh.  If it is a list, the command is directly executed.
@end quotation
@end cartouche

@example
(child_stdout, child_stdin) = popen2.popen2("somestring", bufsize, mode)
==>
p = Popen("somestring", shell=True, bufsize=bufsize,
          stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdout, child_stdin) = (p.stdout, p.stdin)
@end example

@example
(child_stdout, child_stdin) = popen2.popen2(["mycmd", "myarg"], bufsize, mode)
==>
p = Popen(["mycmd", "myarg"], bufsize=bufsize,
          stdin=PIPE, stdout=PIPE, close_fds=True)
(child_stdout, child_stdin) = (p.stdout, p.stdin)
@end example

@code{popen2.Popen3} and @code{popen2.Popen4} basically work as
@ref{2b9,,subprocess.Popen}, except that:


@itemize *

@item 
@ref{2b9,,Popen} raises an exception if the execution fails.

@item 
The @emph{capturestderr} argument is replaced with the @emph{stderr} argument.

@item 
@code{stdin=PIPE} and @code{stdout=PIPE} must be specified.

@item 
popen2 closes all file descriptors by default, but you have to specify
@code{close_fds=True} with @ref{2b9,,Popen} to guarantee this behavior on
all platforms or past Python versions.
@end itemize

@node Legacy Shell Invocation Functions,注释<2>,Replacing Older Functions with the subprocess Module,subprocess --- 子进程管理
@anchor{library/subprocess legacy-shell-invocation-functions}@anchor{2434}
@subsubsection Legacy Shell Invocation Functions


This module also provides the following legacy functions from the 2.x
@code{commands} module. These operations implicitly invoke the system shell and
none of the guarantees described above regarding security and exception
handling consistency are valid for these functions.

@geindex getstatusoutput() (在 subprocess 模块中)
@anchor{library/subprocess subprocess getstatusoutput}@anchor{8d6}
@deffn {函数} subprocess.getstatusoutput (cmd)

Return @code{(exitcode, output)} of executing @emph{cmd} in a shell.

Execute the string @emph{cmd} in a shell with @code{Popen.check_output()} and
return a 2-tuple @code{(exitcode, output)}. The locale encoding is used;
see the notes on @ref{23ed,,常用参数} for more details.

A trailing newline is stripped from the output.
The exit code for the command can be interpreted as the return code
of subprocess.  Example:

@example
>>> subprocess.getstatusoutput('ls /bin/ls')
(0, '/bin/ls')
>>> subprocess.getstatusoutput('cat /bin/junk')
(1, 'cat: /bin/junk: No such file or directory')
>>> subprocess.getstatusoutput('/bin/junk')
(127, 'sh: /bin/junk: not found')
>>> subprocess.getstatusoutput('/bin/kill $$')
(-15, '@w{'})
@end example

@ref{12f5,,Availability}: POSIX & Windows.


在 3.3.4 版更改: 添加了 Windows 支持。

The function now returns (exitcode, output) instead of (status, output)
as it did in Python 3.3.3 and earlier.  exitcode has the same value as
@ref{2416,,returncode}.

@end deffn

@geindex getoutput() (在 subprocess 模块中)
@anchor{library/subprocess subprocess getoutput}@anchor{2435}
@deffn {函数} subprocess.getoutput (cmd)

Return output (stdout and stderr) of executing @emph{cmd} in a shell.

Like @ref{8d6,,getstatusoutput()}, except the exit code is ignored and the return
value is a string containing the command's output.  Example:

@example
>>> subprocess.getoutput('ls /bin/ls')
'/bin/ls'
@end example

@ref{12f5,,Availability}: POSIX & Windows.


在 3.3.4 版更改: 添加了 Windows 支持

@end deffn

@node 注释<2>,,Legacy Shell Invocation Functions,subprocess --- 子进程管理
@anchor{library/subprocess notes}@anchor{2436}
@subsubsection 注释


@menu
* Converting an argument sequence to a string on Windows:: 

@end menu

@node Converting an argument sequence to a string on Windows,,,注释<2>
@anchor{library/subprocess converting-an-argument-sequence-to-a-string-on-windows}@anchor{2437}@anchor{library/subprocess converting-argument-sequence}@anchor{2408}
@subsubsection Converting an argument sequence to a string on Windows


On Windows, an @emph{args} sequence is converted to a string that can be parsed
using the following rules (which correspond to the rules used by the MS C
runtime):


@enumerate 

@item 
Arguments are delimited by white space, which is either a
space or a tab.

@item 
A string surrounded by double quotation marks is
interpreted as a single argument, regardless of white space
contained within.  A quoted string can be embedded in an
argument.

@item 
A double quotation mark preceded by a backslash is
interpreted as a literal double quotation mark.

@item 
Backslashes are interpreted literally, unless they
immediately precede a double quotation mark.

@item 
If backslashes immediately precede a double quotation mark,
every pair of backslashes is interpreted as a literal
backslash.  If the number of backslashes is odd, the last
backslash escapes the next double quotation mark as
described in rule 3.
@end enumerate


@subsubheading 参见



@table @asis

@item @ref{e8,,shlex}

Module which provides function to parse and escape command lines.
@end table


@node sched --- 事件调度器,queue --- 一个同步的队列类,subprocess --- 子进程管理,并发执行
@anchor{library/sched doc}@anchor{2438}@anchor{library/sched module-sched}@anchor{e3}@anchor{library/sched sched-event-scheduler}@anchor{2439}
@subsection @code{sched} --- 事件调度器


@geindex sched (模块)

@strong{源码：} Lib/sched.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/sched.py}

@geindex event scheduling


__________________________________________________________________


@ref{e3,,sched} 模块定义了一个实现通用事件调度程序的类：

@geindex scheduler (sched 中的类)
@anchor{library/sched sched scheduler}@anchor{a69}
@deffn {类} sched.scheduler (timefunc=time.monotonic, delayfunc=time.sleep)

@ref{a69,,scheduler} 类定义了一个调度事件的通用接口。 它需要两个函数来实际处理“外部世界” —— @emph{timefunc} 应当不带参数地调用，并返回一个数字（“时间”，可以为任意单位）。 @emph{delayfunc} 函数应当带一个参数调用，与 @emph{timefunc} 的输出相兼容，并且应当延迟其所指定的时间单位。 每个事件运行后还将调用 @emph{delayfunc} 并传入参数 @code{0} 以允许其他线程有机会在多线程应用中运行。


在 3.3 版更改: @emph{timefunc} 和 @emph{delayfunc} 参数是可选的。



在 3.3 版更改: @ref{a69,,scheduler} 类可以安全的在多线程环境中使用。

@end deffn

示例:

@example
>>> import sched, time
>>> s = sched.scheduler(time.time, time.sleep)
>>> def print_time(a='default'):
...     print("From print_time", time.time(), a)
...
>>> def print_some_times():
...     print(time.time())
...     s.enter(10, 1, print_time)
...     s.enter(5, 2, print_time, argument=('positional',))
...     s.enter(5, 1, print_time, kwargs=@{'a': 'keyword'@})
...     s.run()
...     print(time.time())
...
>>> print_some_times()
930343690.257
From print_time 930343695.274 positional
From print_time 930343695.275 keyword
From print_time 930343700.273 default
930343700.276
@end example

@menu
* 调度器对象:: 

@end menu

@node 调度器对象,,,sched --- 事件调度器
@anchor{library/sched id1}@anchor{243a}@anchor{library/sched scheduler-objects}@anchor{243b}
@subsubsection 调度器对象


@ref{a69,,scheduler} 实例拥有以下方法和属性：

@geindex enterabs() (sched.scheduler 方法)
@anchor{library/sched sched scheduler enterabs}@anchor{a6b}
@deffn {方法} scheduler.enterabs (time, priority, action, argument=(), kwargs=@{@})

安排一个新事件。 @emph{time} 参数应该有一个数字类型兼容的返回值，与传递给构造函数的 @emph{timefunc} 函数的返回值兼容。 计划在相同 @emph{time} 的事件将按其 @emph{priority} 的顺序执行。 数字越小表示优先级越高。

执行事件意为执行 @code{action(*argument, **kwargs)}。 @emph{argument} 是包含有 @emph{action} 的位置参数的序列。 @emph{kwargs} 是包含 @emph{action} 的关键字参数的字典。

返回值是一个事件，可用于以后取消事件（ 参见 @ref{243c,,cancel()} ）。


在 3.3 版更改: @emph{argument} 参数是可选的。



在 3.3 版更改: 添加了 @emph{kwargs} 形参。

@end deffn

@geindex enter() (sched.scheduler 方法)
@anchor{library/sched sched scheduler enter}@anchor{a6a}
@deffn {方法} scheduler.enter (delay, priority, action, argument=(), kwargs=@{@})

安排延后 @emph{delay} 时间单位的事件。 除了相对时间，其他参数、效果和返回值与 @ref{a6b,,enterabs()} 的相同。


在 3.3 版更改: @emph{argument} 参数是可选的。



在 3.3 版更改: 添加了 @emph{kwargs} 形参。

@end deffn

@geindex cancel() (sched.scheduler 方法)
@anchor{library/sched sched scheduler cancel}@anchor{243c}
@deffn {方法} scheduler.cancel (event)

从队列中删除事件。 如果 @emph{event} 不是当前队列中的事件，则此方法将引发 @ref{1fb,,ValueError}。
@end deffn

@geindex empty() (sched.scheduler 方法)
@anchor{library/sched sched scheduler empty}@anchor{243d}
@deffn {方法} scheduler.empty ()

如果事件队列为空则返回 @code{True}。
@end deffn

@geindex run() (sched.scheduler 方法)
@anchor{library/sched sched scheduler run}@anchor{a68}
@deffn {方法} scheduler.run (blocking=True)

运行所有预定事件。 此方法将等待（使用传递给构造函数的 @code{delayfunc()} 函数）进行下一个事件，然后执行它，依此类推，直到没有更多的计划事件。

如果 @emph{blocking} 为false，则执行由于最快到期（如果有）的预定事件，然后在调度程序中返回下一个预定调用的截止时间（如果有）。

@emph{action} 或 @emph{delayfunc} 都可以引发异常。 在任何一种情况下，调度程序都将保持一致状态并传播异常。 如果 @emph{action} 引发异常，则在将来调用 @ref{a68,,run()} 时不会尝试该事件。

如果一系列事件的运行时间比下一个事件之前的可用时间长，那么调度程序将完全落后。 不会发生任何事件；调用代码负责取消不再相关的事件。


在 3.3 版更改: 添加了 @emph{blocking} 形参。

@end deffn

@geindex queue (sched.scheduler 属性)
@anchor{library/sched sched scheduler queue}@anchor{243e}
@deffn {属性} scheduler.queue

只读属性按照将要运行的顺序返回即将发生的事件列表。 每个事件都显示为 @ref{a9e,,named tuple} ，包含以下字段：time、priority、action、argument、kwargs。
@end deffn

@node queue --- 一个同步的队列类,_thread --- 底层多线程 API,sched --- 事件调度器,并发执行
@anchor{library/queue doc}@anchor{243f}@anchor{library/queue module-queue}@anchor{da}@anchor{library/queue queue-a-synchronized-queue-class}@anchor{2440}
@subsection @code{queue} --- 一个同步的队列类


@geindex queue (模块)

@strong{源代码:} Lib/queue.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/queue.py}


__________________________________________________________________


@ref{da,,queue} 模块实现了多生产者、多消费者队列。这特别适用于消息必须安全地在多线程间交换的线程编程。模块中的 @ref{d11,,Queue} 类实现了所有所需的锁定语义。

模块实现了三种类型的队列，它们的区别仅仅是条目取回的顺序。在 @abbr{FIFO} 队列中，先添加的任务先取回。在 @abbr{LIFO} 队列中，最近被添加的条目先取回(操作类似一个堆栈)。优先级队列中，条目将保持排序( 使用 @ref{8e,,heapq} 模块 ) 并且最小值的条目第一个返回。

在内部，这三个类型的队列使用锁来临时阻塞竞争线程；然而，它们并未被设计用于线程的重入性处理。

此外，模块实现了一个 "简单的"  @abbr{FIFO} 队列类型， @ref{3be,,SimpleQueue} ，这个特殊实现为小功能在交换中提供额外的保障。

@ref{da,,queue} 模块定义了下列类和异常：

@geindex Queue (queue 中的类)
@anchor{library/queue queue Queue}@anchor{d11}
@deffn {类} queue.Queue (maxsize=0)

Constructor for a @abbr{FIFO} queue.  @emph{maxsize} is
an integer that sets the upperbound
limit on the number of items that can be placed in the queue.  Insertion will
block once this size has been reached, until queue items are consumed.  If
@emph{maxsize} is less than or equal to zero, the queue size is infinite.
@end deffn

@geindex LifoQueue (queue 中的类)
@anchor{library/queue queue LifoQueue}@anchor{2441}
@deffn {类} queue.LifoQueue (maxsize=0)

@abbr{LIFO} 队列构造函数。 @emph{maxsize} 是个整数，用于设置可以放入队列中的项目数的上限。当达到这个大小的时候，插入操作将阻塞至队列中的项目被消费掉。如果 @emph{maxsize} 小于等于零，队列尺寸为无限大。
@end deffn

@geindex PriorityQueue (queue 中的类)
@anchor{library/queue queue PriorityQueue}@anchor{2442}
@deffn {类} queue.PriorityQueue (maxsize=0)

优先级队列构造函数。 @emph{maxsize} 是个整数，用于设置可以放入队列中的项目数的上限。当达到这个大小的时候，插入操作将阻塞至队列中的项目被消费掉。如果 @emph{maxsize} 小于等于零，队列尺寸为无限大。

最小值先被取出( 最小值条目是由 @code{sorted(list(entries))[0]} 返回的条目)。条目的典型模式是一个以下形式的元组： @code{(priority_number, data)} 。

如果 @emph{data} 元素没有可比性，数据将被包装在一个类中，忽略数据值，仅仅比较优先级数字 ：

@example
from dataclasses import dataclass, field
from typing import Any

@@dataclass(order=True)
class PrioritizedItem:
    priority: int
    item: Any=field(compare=False)
@end example
@end deffn

@geindex SimpleQueue (queue 中的类)
@anchor{library/queue queue SimpleQueue}@anchor{3be}
@deffn {类} queue.SimpleQueue

无界的 @abbr{FIFO} 队列构造函数。简单的队列，缺少任务跟踪等高级功能。


3.7 新版功能.

@end deffn

@geindex Empty
@anchor{library/queue queue Empty}@anchor{2350}
@deffn {例外} queue.Empty

对空的 @ref{d11,,Queue} 对象，调用非阻塞的 @ref{2443,,get()} (or  @ref{2444,,get_nowait()}) 时，引发的异常。
@end deffn

@geindex Full
@anchor{library/queue queue Full}@anchor{2351}
@deffn {例外} queue.Full

对满的 @ref{d11,,Queue} 对象，调用非阻塞的 @ref{2445,,put()} (or @ref{2446,,put_nowait()}) 时，引发的异常。
@end deffn

@menu
* Queue对象:: 
* SimpleQueue 对象:: 

@end menu

@node Queue对象,SimpleQueue 对象,,queue --- 一个同步的队列类
@anchor{library/queue queue-objects}@anchor{2447}@anchor{library/queue queueobjects}@anchor{2448}
@subsubsection Queue对象


队列对象 (@ref{d11,,Queue}, @ref{2441,,LifoQueue}, 或者 @ref{2442,,PriorityQueue}) 提供下列描述的公共方法。

@geindex qsize() (queue.Queue 方法)
@anchor{library/queue queue Queue qsize}@anchor{2449}
@deffn {方法} Queue.qsize ()

返回队列的大致大小。注意，qsize() > 0 不保证后续的 get() 不被阻塞，qsize() < maxsize 也不保证 put() 不被阻塞。
@end deffn

@geindex empty() (queue.Queue 方法)
@anchor{library/queue queue Queue empty}@anchor{244a}
@deffn {方法} Queue.empty ()

如果队列为空，返回 @code{True} ，否则返回 @code{False} 。如果 empty() 返回 @code{True} ，不保证后续调用的 put() 不被阻塞。类似的，如果 empty() 返回 @code{False} ，也不保证后续调用的 get() 不被阻塞。
@end deffn

@geindex full() (queue.Queue 方法)
@anchor{library/queue queue Queue full}@anchor{244b}
@deffn {方法} Queue.full ()

如果队列是满的返回 @code{True} ，否则返回 @code{False} 。如果 full() 返回 @code{True} 不保证后续调用的 get() 不被阻塞。类似的，如果 full() 返回 @code{False} 也不保证后续调用的 put() 不被阻塞。
@end deffn

@geindex put() (queue.Queue 方法)
@anchor{library/queue queue Queue put}@anchor{2445}
@deffn {方法} Queue.put (item, block=True, timeout=None)

将 @emph{item} 放入队列。如果可选参数 @emph{block} 是 true 并且 @emph{timeout} 是 @code{None} (默认)，则在必要时阻塞至有空闲插槽可用。如果 @emph{timeout} 是个正数，将最多阻塞 @emph{timeout} 秒，如果在这段时间没有可用的空闲插槽，将引发 @ref{2351,,Full} 异常。反之 (@emph{block} 是 false)，如果空闲插槽立即可用，则把 @emph{item} 放入队列，否则引发 @ref{2351,,Full} 异常 ( 在这种情况下，@emph{timeout} 将被忽略)。
@end deffn

@geindex put_nowait() (queue.Queue 方法)
@anchor{library/queue queue Queue put_nowait}@anchor{2446}
@deffn {方法} Queue.put_nowait (item)

相当于 @code{put(item, False)} 。
@end deffn

@geindex get() (queue.Queue 方法)
@anchor{library/queue queue Queue get}@anchor{2443}
@deffn {方法} Queue.get (block=True, timeout=None)

从队列中移除并返回一个项目。如果可选参数 @emph{block} 是 true 并且 @emph{timeout} 是 @code{None} (默认值)，则在必要时阻塞至项目可得到。如果 @emph{timeout} 是个正数，将最多阻塞 @emph{timeout} 秒，如果在这段时间内项目不能得到，将引发 @ref{2350,,Empty} 异常。反之 (@emph{block} 是 false) , 如果一个项目立即可得到，则返回一个项目，否则引发 @ref{2350,,Empty} 异常 (这种情况下，@emph{timeout} 将被忽略)。

POSIX系统3.0之前，以及所有版本的Windows系统中，如果 @emph{block} 是 true 并且 @emph{timeout} 是 @code{None} ， 这个操作将进入基础锁的不间断等待。这意味着，没有异常能发生，尤其是 SIGINT 将不会触发 @ref{197,,KeyboardInterrupt} 异常。
@end deffn

@geindex get_nowait() (queue.Queue 方法)
@anchor{library/queue queue Queue get_nowait}@anchor{2444}
@deffn {方法} Queue.get_nowait ()

相当于 @code{get(False)} 。
@end deffn

提供了两个方法，用于支持跟踪 排队的任务 是否 被守护的消费者线程 完整的处理。

@geindex task_done() (queue.Queue 方法)
@anchor{library/queue queue Queue task_done}@anchor{234c}
@deffn {方法} Queue.task_done ()

表示前面排队的任务已经被完成。被队列的消费者线程使用。每个 @ref{2443,,get()} 被用于获取一个任务， 后续调用 @ref{234c,,task_done()} 告诉队列，该任务的处理已经完成。

如果 @ref{234d,,join()} 当前正在阻塞，在所有条目都被处理后，将解除阻塞(意味着每个 @ref{2445,,put()} 进队列的条目的 @ref{234c,,task_done()} 都被收到)。

如果被调用的次数多于放入队列中的项目数量，将引发 @ref{1fb,,ValueError} 异常 。
@end deffn

@geindex join() (queue.Queue 方法)
@anchor{library/queue queue Queue join}@anchor{234d}
@deffn {方法} Queue.join ()

阻塞至队列中所有的元素都被接收和处理完毕。

当条目添加到队列的时候，未完成任务的计数就会增加。每当消费者线程调用 @ref{234c,,task_done()} 表示这个条目已经被回收，该条目所有工作已经完成，未完成计数就会减少。当未完成计数降到零的时候， @ref{234d,,join()} 阻塞被解除。
@end deffn

如何等待排队的任务被完成的示例：

@example
import threading, queue

q = queue.Queue()

def worker():
    while True:
        item = q.get()
        print(f'Working on @{item@}')
        print(f'Finished @{item@}')
        q.task_done()

# turn-on the worker thread
threading.Thread(target=worker, daemon=True).start()

# send thirty task requests to the worker
for item in range(30):
    q.put(item)
print('All task requests sent\n', end='@w{'})

# block until all tasks are done
q.join()
print('All work completed')
@end example

@node SimpleQueue 对象,,Queue对象,queue --- 一个同步的队列类
@anchor{library/queue simplequeue-objects}@anchor{244c}
@subsubsection SimpleQueue 对象


@ref{3be,,SimpleQueue} 对象提供下列描述的公共方法。

@geindex qsize() (queue.SimpleQueue 方法)
@anchor{library/queue queue SimpleQueue qsize}@anchor{244d}
@deffn {方法} SimpleQueue.qsize ()

返回队列的大致大小。注意，qsize() > 0 不保证后续的 get() 不被阻塞。
@end deffn

@geindex empty() (queue.SimpleQueue 方法)
@anchor{library/queue queue SimpleQueue empty}@anchor{244e}
@deffn {方法} SimpleQueue.empty ()

如果队列为空，返回 @code{True} ，否则返回 @code{False} 。如果 empty() 返回 @code{False} ，不保证后续调用的 get() 不被阻塞。
@end deffn

@geindex put() (queue.SimpleQueue 方法)
@anchor{library/queue queue SimpleQueue put}@anchor{244f}
@deffn {方法} SimpleQueue.put (item, block=True, timeout=None)

将 @emph{item} 放入队列。此方法永不阻塞，始终成功（除了潜在的低级错误，例如内存分配失败）。可选参数 @emph{block} 和 @emph{timeout} 仅仅是为了保持 @ref{2445,,Queue.put()} 的兼容性而提供，其值被忽略。

@strong{CPython implementation detail:} This method has a C implementation which is reentrant.  That is, a
@code{put()} or @code{get()} call can be interrupted by another @code{put()}
call in the same thread without deadlocking or corrupting internal
state inside the queue.  This makes it appropriate for use in
destructors such as @code{__del__} methods or @ref{128,,weakref} callbacks.
@end deffn

@geindex put_nowait() (queue.SimpleQueue 方法)
@anchor{library/queue queue SimpleQueue put_nowait}@anchor{2450}
@deffn {方法} SimpleQueue.put_nowait (item)

相当于 @code{put(item)} ，仅为保持 @ref{2446,,Queue.put_nowait()} 兼容性而提供。
@end deffn

@geindex get() (queue.SimpleQueue 方法)
@anchor{library/queue queue SimpleQueue get}@anchor{2451}
@deffn {方法} SimpleQueue.get (block=True, timeout=None)

从队列中移除并返回一个项目。如果可选参数 @emph{block} 是 true 并且 @emph{timeout} 是 @code{None} (默认值)，则在必要时阻塞至项目可得到。如果 @emph{timeout} 是个正数，将最多阻塞 @emph{timeout} 秒，如果在这段时间内项目不能得到，将引发 @ref{2350,,Empty} 异常。反之 (@emph{block} 是 false) , 如果一个项目立即可得到，则返回一个项目，否则引发 @ref{2350,,Empty} 异常 (这种情况下，@emph{timeout} 将被忽略)。
@end deffn

@geindex get_nowait() (queue.SimpleQueue 方法)
@anchor{library/queue queue SimpleQueue get_nowait}@anchor{2452}
@deffn {方法} SimpleQueue.get_nowait ()

相当于 @code{get(False)} 。
@end deffn


@subsubheading 参见



@table @asis

@item 类 @ref{232a,,multiprocessing.Queue}

一个用于多进程上下文的队列类（而不是多线程）。
@end table

@ref{52b,,collections.deque} 是无界队列的一个替代实现，具有快速的不需要锁并且支持索引的原子化 @ref{18c5,,append()} 和 @ref{18cb,,popleft()} 操作。


以下是上述某些服务的支持模块：

@node _thread --- 底层多线程 API,_dummy_thread --- _thread 的替代模块,queue --- 一个同步的队列类,并发执行
@anchor{library/_thread doc}@anchor{2453}@anchor{library/_thread module-_thread}@anchor{3}@anchor{library/_thread thread-low-level-threading-api}@anchor{2454}
@subsection @code{_thread} --- 底层多线程 API


@geindex _thread (模块)

@geindex light-weight processes
@geindex processes@comma{} light-weight
@geindex binary semaphores
@geindex semaphores@comma{} binary


__________________________________________________________________


该模块提供了操作多个线程（也被称为 @emph{轻量级进程} 或 @emph{任务}）的底层原语 —— 多个控制线程共享全局数据空间。为了处理同步问题，也提供了简单的锁机制（也称为 @emph{互斥锁} 或 @emph{二进制信号}）。@ref{109,,threading} 模块基于该模块提供了更易用的高级多线程 API。

@geindex pthreads
@geindex threads; POSIX


在 3.7 版更改: 这个模块曾经为可选项，但现在总是可用。


这个模块定义了以下常量和函数：

@geindex error
@anchor{library/_thread _thread error}@anchor{2455}
@deffn {例外} _thread.error

发生线程相关错误时抛出。


在 3.3 版更改: 现在是内建异常 @ref{2ba,,RuntimeError} 的别名。

@end deffn

@geindex LockType() (在 _thread 模块中)
@anchor{library/_thread _thread LockType}@anchor{2456}
@deffn {数据} _thread.LockType

锁对象的类型。
@end deffn

@geindex start_new_thread() (在 _thread 模块中)
@anchor{library/_thread _thread start_new_thread}@anchor{f55}
@deffn {函数} _thread.start_new_thread (function, args[, kwargs])

开启一个新线程并返回其标识。 线程执行函数 @emph{function} 并附带参数列表 @emph{args} (必须是元组)。 可选的 @emph{kwargs} 参数指定一个关键字参数字典。

当函数返回时，线程会静默地退出。

当函数因某个未处理异常而终结时，@ref{22d,,sys.unraisablehook()} 会被调用以处理异常。 钩子参数的 @emph{object} 属性为 @emph{function}。 在默认情况下，会打印堆栈回溯然后该线程将退出（但其他线程会继续运行）。

当函数引发 @ref{5f7,,SystemExit} 异常时，它会被静默地忽略。


在 3.8 版更改: 现在会使用 @ref{22d,,sys.unraisablehook()} 来处理未处理的异常。

@end deffn

@geindex interrupt_main() (在 _thread 模块中)
@anchor{library/_thread _thread interrupt_main}@anchor{2457}
@deffn {函数} _thread.interrupt_main ()

模拟一个 @ref{2458,,signal.SIGINT} 信号到达主线程的效果。 线程可以使用这个函数来中断主线程。

如果 Python 没有处理 @ref{2458,,signal.SIGINT} (将它设为 @ref{2459,,signal.SIG_DFL} 或 @ref{245a,,signal.SIG_IGN})，此函数将不做任何事。
@end deffn

@geindex exit() (在 _thread 模块中)
@anchor{library/_thread _thread exit}@anchor{245b}
@deffn {函数} _thread.exit ()

抛出 @ref{5f7,,SystemExit} 异常。如果没有捕获的话，这个异常会使线程退出。
@end deffn

@c function:: exit_prog(status)
@c 
@c    Exit all threads and report the value of the integer argument
@c    *status* as the exit status of the entire program.
@c    **Caveat:** code in pending :keyword:`finally` clauses, in this thread
@c    or in other threads, is not executed.

@geindex allocate_lock() (在 _thread 模块中)
@anchor{library/_thread _thread allocate_lock}@anchor{245c}
@deffn {函数} _thread.allocate_lock ()

返回一个新的锁对象。锁中的方法在后面描述。初始情况下锁处于解锁状态。
@end deffn

@geindex get_ident() (在 _thread 模块中)
@anchor{library/_thread _thread get_ident}@anchor{245d}
@deffn {函数} _thread.get_ident ()

返回当前线程的 “线程标识符”。它是一个非零的整数。它的值没有直接含义，主要是用作 magic cookie，比如作为含有线程相关数据的字典的索引。线程标识符可能会在线程退出，新线程创建时被复用。
@end deffn

@geindex get_native_id() (在 _thread 模块中)
@anchor{library/_thread _thread get_native_id}@anchor{245e}
@deffn {函数} _thread.get_native_id ()

返回内核分配给当前线程的原生集成线程 ID。 这是一个非负整数。 它的值可被用来在整个系统中唯一地标识这个特定线程（直到线程终结，在那之后该值可能会被 OS 回收再利用）。

@ref{12f5,,可用性}: Windows, FreeBSD, Linux, macOS, OpenBSD, NetBSD, AIX。


3.8 新版功能.

@end deffn

@geindex stack_size() (在 _thread 模块中)
@anchor{library/_thread _thread stack_size}@anchor{245f}
@deffn {函数} _thread.stack_size ([size])

返回创建线程时使用的堆栈大小。可选参数 @emph{size} 指定之后新建的线程的堆栈大小，而且一定要是0（根据平台或者默认配置）或者最小是32,768(32KiB)的一个正整数。如果 @emph{size} 没有指定，默认是0。如果不支持改变线程堆栈大小，会抛出 @ref{2ba,,RuntimeError} 错误。如果指定的堆栈大小不合法，会抛出 @ref{1fb,,ValueError} 错误并且不会修改堆栈大小。32KiB是当前最小的能保证解释器有足够堆栈空间的堆栈大小。需要注意的是部分平台对于堆栈大小会有特定的限制，例如要求大于32KiB的堆栈大小或者需要根据系统内存页面的整数倍进行分配 - 应当查阅平台文档有关详细信息（4KiB页面比较普遍，在没有更具体信息的情况下，建议的方法是使用4096的倍数作为堆栈大小）。

@ref{12f5,,适用于}: Windows，具有 POSIX 线程的系统。
@end deffn

@geindex TIMEOUT_MAX() (在 _thread 模块中)
@anchor{library/_thread _thread TIMEOUT_MAX}@anchor{2460}
@deffn {数据} _thread.TIMEOUT_MAX

@code{Lock.acquire()} 方法中 @emph{timeout} 参数允许的最大值。传入超过这个值的 timeout 会抛出 @ref{95a,,OverflowError} 异常。


3.2 新版功能.

@end deffn

锁对象有以下方法：

@geindex acquire() (_thread.lock 方法)
@anchor{library/_thread _thread lock acquire}@anchor{2461}
@deffn {方法} lock.acquire (waitflag=1, timeout=-1)

没有任何可选参数时，该方法无条件申请获得锁，有必要的话会等待其他线程释放锁（同时只有一个线程能获得锁 —— 这正是锁存在的原因）。

如果传入了整型参数 @emph{waitflag}，具体的行为取决于传入的值：如果是 0 的话，只会在能够立刻获取到锁时才获取，不会等待，如果是非零的话，会像之前提到的一样，无条件获取锁。

如果传入正浮点数参数 @emph{timeout}，相当于指定了返回之前等待得最大秒数。如果传入负的 @emph{timeout}，相当于无限期等待。如果 @emph{waitflag} 是 0 的话，不能指定 @emph{timeout}。

如果成功获取到所会返回 @code{True}，否则返回 @code{False}。


在 3.2 版更改: 新的 @emph{timeout} 形参。



在 3.2 版更改: 现在获取锁的操作可以被 POSIX 信号中断。

@end deffn

@geindex release() (_thread.lock 方法)
@anchor{library/_thread _thread lock release}@anchor{2462}
@deffn {方法} lock.release ()

释放锁。锁必须已经被获取过，但不一定是同一个线程获取的。
@end deffn

@geindex locked() (_thread.lock 方法)
@anchor{library/_thread _thread lock locked}@anchor{2463}
@deffn {方法} lock.locked ()

返回锁的状态：如果已被某个线程获取，返回 @code{True}，否则返回 @code{False}。
@end deffn

除了这些方法之外，锁对象也可以通过 @ref{6e3,,with} 语句使用，例如：

@example
import _thread

a_lock = _thread.allocate_lock()

with a_lock:
    print("a_lock is locked while this executes")
@end example

@strong{注意事项：}

@quotation

@geindex 模块; signal
@end quotation


@itemize *

@item 
线程与中断奇怪地交互：@ref{197,,KeyboardInterrupt} 异常可能会被任意一个线程捕获。（如果 @ref{ea,,signal} 模块可用的话，中断总是会进入主线程。）

@item 
调用 @ref{cdb,,sys.exit()} 或是抛出 @ref{5f7,,SystemExit} 异常等效于调用 @ref{245b,,_thread.exit()}。

@item 
不可能中断锁的 @code{acquire()} 方法 —— @ref{197,,KeyboardInterrupt} 一场会在锁获取到之后发生。

@item 
当主线程退出时，由系统决定其他线程是否存活。在大多数系统中，这些线程会直接被杀掉，不会执行 @ref{d6b,,try} ... @ref{182,,finally} 语句，也不会执行对象析构函数。

@item 
当主线程退出时，不会进行正常的清理工作（除非使用了 @ref{d6b,,try} ... @ref{182,,finally} 语句），标准 I/O 文件也不会刷新。
@end itemize

@node _dummy_thread --- _thread 的替代模块,dummy_threading --- 可直接替代 threading 模块。,_thread --- 底层多线程 API,并发执行
@anchor{library/_dummy_thread doc}@anchor{2464}@anchor{library/_dummy_thread dummy-thread-drop-in-replacement-for-the-thread-module}@anchor{2465}@anchor{library/_dummy_thread module-_dummy_thread}@anchor{2}
@subsection @code{_dummy_thread} --- @code{_thread} 的替代模块


@geindex _dummy_thread (模块)

@strong{源代码：} Lib/_dummy_thread.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/_dummy_thread.py}


3.7 版后已移除: Python 现在总是会启用多线程。请改用 @ref{3,,_thread} (或者用 @ref{109,,threading} 更好)。



__________________________________________________________________


这个模块提供与 @ref{3,,_thread} 相同的接口。它主要用于在没有提供 @ref{3,,_thread} 模块的平台上被导入。

如果线程需要阻塞等待另一个线程被创建的话，可能会造成死锁，这通常是由于阻塞 I/O 引起的。这种场景下请不要使用这个模块。

@node dummy_threading --- 可直接替代 threading 模块。,,_dummy_thread --- _thread 的替代模块,并发执行
@anchor{library/dummy_threading doc}@anchor{2466}@anchor{library/dummy_threading dummy-threading-drop-in-replacement-for-the-threading-module}@anchor{2467}@anchor{library/dummy_threading module-dummy_threading}@anchor{68}
@subsection @code{dummy_threading} ---  可直接替代 @code{threading} 模块。


@geindex dummy_threading (模块)

@strong{源代码：} Lib/dummy_threading.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/dummy_threading.py}


3.7 版后已移除: 现在Python总是启用多线程。请使用 @ref{109,,threading} 代替。



__________________________________________________________________


这个模块提供了一个和 @ref{109,,threading} 模块重复的接口。当平台不提供 @ref{3,,_thread} 模块时，应导入这个模块。

如果线程需要阻塞等待另一个线程被创建的话，可能会造成死锁，这通常是由于阻塞 I/O 引起的。这种场景下请不要使用这个模块。

@node contextvars --- Context Variables,网络和进程间通信,并发执行,Python 标准库
@anchor{library/contextvars doc}@anchor{2468}@anchor{library/contextvars contextvars-context-variables}@anchor{2469}@anchor{library/contextvars module-contextvars}@anchor{25}
@section @code{contextvars} --- Context Variables


@geindex contextvars (模块)


__________________________________________________________________


This module provides APIs to manage, store, and access context-local
state.  The @ref{246a,,ContextVar} class is used to declare
and work with @emph{Context Variables}.  The @ref{246b,,copy_context()}
function and the @ref{246c,,Context} class should be used to
manage the current context in asynchronous frameworks.

Context managers that have state should use Context Variables
instead of @ref{228e,,threading.local()} to prevent their state from
bleeding to other code unexpectedly, when used in concurrent code.

See also 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} for additional details.


3.7 新版功能.


@menu
* Context Variables:: 
* Manual Context Management:: 
* asyncio support:: 

@end menu

@node Context Variables,Manual Context Management,,contextvars --- Context Variables
@anchor{library/contextvars context-variables}@anchor{246d}
@subsection Context Variables


@geindex ContextVar (contextvars 中的类)
@anchor{library/contextvars contextvars ContextVar}@anchor{246a}
@deffn {类} contextvars.ContextVar (name[, *, default])

This class is used to declare a new Context Variable, e.g.:

@example
var: ContextVar[int] = ContextVar('var', default=42)
@end example

The required @emph{name} parameter is used for introspection and debug
purposes.

The optional keyword-only @emph{default} parameter is returned by
@ref{246e,,ContextVar.get()} when no value for the variable is found
in the current context.

@strong{Important:} Context Variables should be created at the top module
level and never in closures.  @ref{246c,,Context} objects hold strong
references to context variables which prevents context variables
from being properly garbage collected.

@geindex name (contextvars.ContextVar 属性)
@anchor{library/contextvars contextvars ContextVar name}@anchor{246f}
@deffn {属性} name

The name of the variable.  This is a read-only property.


3.7.1 新版功能.

@end deffn

@geindex get() (contextvars.ContextVar 方法)
@anchor{library/contextvars contextvars ContextVar get}@anchor{246e}
@deffn {方法} get ([default])

Return a value for the context variable for the current context.

If there is no value for the variable in the current context,
the method will:


@itemize *

@item 
return the value of the @emph{default} argument of the method,
if provided; or

@item 
return the default value for the context variable,
if it was created with one; or

@item 
raise a @ref{15f6,,LookupError}.
@end itemize
@end deffn

@geindex set() (contextvars.ContextVar 方法)
@anchor{library/contextvars contextvars ContextVar set}@anchor{2470}
@deffn {方法} set (value)

Call to set a new value for the context variable in the current
context.

The required @emph{value} argument is the new value for the context
variable.

Returns a @ref{2471,,Token} object that can be used
to restore the variable to its previous value via the
@ref{2472,,ContextVar.reset()} method.
@end deffn

@geindex reset() (contextvars.ContextVar 方法)
@anchor{library/contextvars contextvars ContextVar reset}@anchor{2472}
@deffn {方法} reset (token)

Reset the context variable to the value it had before the
@ref{2470,,ContextVar.set()} that created the @emph{token} was used.

例如

@example
var = ContextVar('var')

token = var.set('new value')
# code that uses 'var'; var.get() returns 'new value'.
var.reset(token)

# After the reset call the var has no value again, so
# var.get() would raise a LookupError.
@end example
@end deffn
@end deffn

@geindex contextvars.Token (contextvars 中的类)
@anchor{library/contextvars contextvars contextvars Token}@anchor{2471}
@deffn {类} contextvars.Token

@emph{Token} objects are returned by the @ref{2470,,ContextVar.set()} method.
They can be passed to the @ref{2472,,ContextVar.reset()} method to revert
the value of the variable to what it was before the corresponding
@emph{set}.

@geindex var (contextvars.contextvars.Token.Token 属性)
@anchor{library/contextvars contextvars contextvars Token Token var}@anchor{2473}
@deffn {属性} Token.var

A read-only property.  Points to the @ref{246a,,ContextVar} object
that created the token.
@end deffn

@geindex old_value (contextvars.contextvars.Token.Token 属性)
@anchor{library/contextvars contextvars contextvars Token Token old_value}@anchor{2474}
@deffn {属性} Token.old_value

A read-only property.  Set to the value the variable had before
the @ref{2470,,ContextVar.set()} method call that created the token.
It points to @code{Token.MISSING} is the variable was not set
before the call.
@end deffn

@geindex MISSING (contextvars.contextvars.Token.Token 属性)
@anchor{library/contextvars contextvars contextvars Token Token MISSING}@anchor{2475}
@deffn {属性} Token.MISSING

A marker object used by @code{Token.old_value}.
@end deffn
@end deffn

@node Manual Context Management,asyncio support,Context Variables,contextvars --- Context Variables
@anchor{library/contextvars manual-context-management}@anchor{2476}
@subsection Manual Context Management


@geindex copy_context() (在 contextvars 模块中)
@anchor{library/contextvars contextvars copy_context}@anchor{246b}
@deffn {函数} contextvars.copy_context ()

Returns a copy of the current @ref{246c,,Context} object.

The following snippet gets a copy of the current context and prints
all variables and their values that are set in it:

@example
ctx: Context = copy_context()
print(list(ctx.items()))
@end example

The function has an O(1) complexity, i.e. works equally fast for
contexts with a few context variables and for contexts that have
a lot of them.
@end deffn

@geindex Context (contextvars 中的类)
@anchor{library/contextvars contextvars Context}@anchor{246c}
@deffn {类} contextvars.Context

A mapping of @ref{246a,,ContextVars} to their values.

@code{Context()} creates an empty context with no values in it.
To get a copy of the current context use the
@ref{246b,,copy_context()} function.

Context implements the @ref{18d9,,collections.abc.Mapping} interface.

@geindex run() (contextvars.Context 方法)
@anchor{library/contextvars contextvars Context run}@anchor{2477}
@deffn {方法} run (callable, *args, **kwargs)

Execute @code{callable(*args, **kwargs)} code in the context object
the @emph{run} method is called on.  Return the result of the execution
or propagate an exception if one occurred.

Any changes to any context variables that @emph{callable} makes will
be contained in the context object:

@example
var = ContextVar('var')
var.set('spam')

def main():
    # 'var' was set to 'spam' before
    # calling 'copy_context()' and 'ctx.run(main)', so:
    # var.get() == ctx[var] == 'spam'

    var.set('ham')

    # Now, after setting 'var' to 'ham':
    # var.get() == ctx[var] == 'ham'

ctx = copy_context()

# Any changes that the 'main' function makes to 'var'
# will be contained in 'ctx'.
ctx.run(main)

# The 'main()' function was run in the 'ctx' context,
# so changes to 'var' are contained in it:
# ctx[var] == 'ham'

# However, outside of 'ctx', 'var' is still set to 'spam':
# var.get() == 'spam'
@end example

The method raises a @ref{2ba,,RuntimeError} when called on the same
context object from more than one OS thread, or when called
recursively.
@end deffn

@geindex copy() (contextvars.Context 方法)
@anchor{library/contextvars contextvars Context copy}@anchor{2478}
@deffn {方法} copy ()

Return a shallow copy of the context object.
@end deffn


@deffn {Describe} var in context

Return @code{True} if the @emph{context} has a value for @emph{var} set;
return @code{False} otherwise.
@end deffn


@deffn {Describe} context[var]

Return the value of the @emph{var} @ref{246a,,ContextVar} variable.
If the variable is not set in the context object, a
@ref{2c7,,KeyError} is raised.
@end deffn

@geindex get() (contextvars.Context 方法)
@anchor{library/contextvars contextvars Context get}@anchor{2479}
@deffn {方法} get (var[, default])

Return the value for @emph{var} if @emph{var} has the value in the context
object.  Return @emph{default} otherwise.  If @emph{default} is not given,
return @code{None}.
@end deffn


@deffn {Describe} iter(context)

Return an iterator over the variables stored in the context
object.
@end deffn


@deffn {Describe} len(proxy)

Return the number of variables set in the context object.
@end deffn

@geindex keys() (contextvars.Context 方法)
@anchor{library/contextvars contextvars Context keys}@anchor{247a}
@deffn {方法} keys ()

Return a list of all variables in the context object.
@end deffn

@geindex values() (contextvars.Context 方法)
@anchor{library/contextvars contextvars Context values}@anchor{247b}
@deffn {方法} values ()

Return a list of all variables' values in the context object.
@end deffn

@geindex items() (contextvars.Context 方法)
@anchor{library/contextvars contextvars Context items}@anchor{247c}
@deffn {方法} items ()

Return a list of 2-tuples containing all variables and their
values in the context object.
@end deffn
@end deffn

@node asyncio support,,Manual Context Management,contextvars --- Context Variables
@anchor{library/contextvars asyncio-support}@anchor{247d}
@subsection asyncio support


Context variables are natively supported in @ref{a,,asyncio} and are
ready to be used without any extra configuration.  For example, here
is a simple echo server, that uses a context variable to make the
address of a remote client available in the Task that handles that
client:

@example
import asyncio
import contextvars

client_addr_var = contextvars.ContextVar('client_addr')

def render_goodbye():
    # The address of the currently handled client can be accessed
    # without passing it explicitly to this function.

    client_addr = client_addr_var.get()
    return f'Good bye, client @@ @{client_addr@}\n'.encode()

async def handle_request(reader, writer):
    addr = writer.transport.get_extra_info('socket').getpeername()
    client_addr_var.set(addr)

    # In any code that we call is now possible to get
    # client's address by calling 'client_addr_var.get()'.

    while True:
        line = await reader.readline()
        print(line)
        if not line.strip():
            break
        writer.write(line)

    writer.write(render_goodbye())
    writer.close()

async def main():
    srv = await asyncio.start_server(
        handle_request, '127.0.0.1', 8081)

    async with srv:
        await srv.serve_forever()

asyncio.run(main())

# To test it you can use telnet:
#     telnet 127.0.0.1 8081
@end example

@node 网络和进程间通信,互联网数据处理,contextvars --- Context Variables,Python 标准库
@anchor{library/ipc doc}@anchor{247e}@anchor{library/ipc ipc}@anchor{247f}@anchor{library/ipc networking-and-interprocess-communication}@anchor{2480}
@section 网络和进程间通信


本章介绍的模块提供了网络和进程间通信的机制。

某些模块仅适用于同一台机器上的两个进程，例如 @ref{ea,,signal} 和 @ref{b3,,mmap} 。 其他模块支持两个或多个进程可用于跨机器通信的网络协议。

本章中描述的模块列表是：

@menu
* asyncio: asyncio --- 异步 I/O. 异步 I/O
* socket: socket --- 底层网络接口. 底层网络接口
* ssl: ssl --- 套接字对象的TLS/SSL封装. 套接字对象的TLS/SSL封装
* select: select --- 等待 I/O 完成. 等待 I/O 完成
* selectors: selectors --- 高级 I/O 复用库. 高级 I/O 复用库
* asyncore: asyncore --- 异步socket处理器. 异步socket处理器
* asynchat: asynchat --- 异步 socket 指令/响应 处理器. 异步 socket 指令/响应 处理器
* signal: signal --- 设置异步事件处理程序. 设置异步事件处理程序
* mmap: mmap --- 内存映射文件支持. 内存映射文件支持

@end menu

@node asyncio --- 异步 I/O,socket --- 底层网络接口,,网络和进程间通信
@anchor{library/asyncio doc}@anchor{2481}@anchor{library/asyncio asyncio-asynchronous-i-o}@anchor{2482}@anchor{library/asyncio module-asyncio}@anchor{a}
@subsection @code{asyncio} --- 异步 I/O


@geindex asyncio (模块)


__________________________________________________________________


@subsubheading Hello World!



@example
import asyncio

async def main():
    print('Hello ...')
    await asyncio.sleep(1)
    print('... World!')

# Python 3.7+
asyncio.run(main())
@end example

asyncio 是用来编写 @strong{并发} 代码的库，使用 @strong{async/await} 语法。

asyncio 被用作多个提供高性能 Python 异步框架的基础，包括网络和网站服务，数据库连接库，分布式任务队列等等。

asyncio 往往是构建 IO 密集型和高层级 @strong{结构化} 网络代码的最佳选择。

asyncio 提供一组 @strong{高层级} API 用于:


@itemize *

@item 
并发地 @ref{2483,,运行 Python 协程} 并对其执行过程实现完全控制;

@item 
执行 @ref{2484,,网络 IO 和 IPC};

@item 
控制 @ref{2485,,子进程};

@item 
通过 @ref{2486,,队列} 实现分布式任务;

@item 
@ref{2487,,同步} 并发代码;
@end itemize

此外，还有一些 @strong{低层级} API 以支持 @emph{库和框架的开发者} 实现:


@itemize *

@item 
创建和管理 @ref{63e,,事件循环}，以提供异步 API 用于 @ref{356,,网络化}, 运行 @ref{2488,,子进程}，处理 @ref{2489,,OS 信号} 等等;

@item 
使用 @ref{248a,,transports} 实现高效率协议;

@item 
通过 async/await 语法 @ref{248b,,桥接} 基于回调的库和代码。
@end itemize

@c We use the "rubric" directive here to avoid creating
@c the "Reference" subsection in the TOC.

@subsubheading 参考


@menu
* 协程与任务:: 
* 流:: 
* Synchronization Primitives:: 
* 子进程集:: 
* 队列集:: 
* 异常: 异常<9>. 
* 事件循环:: 
* Futures:: 
* 传输和协议:: 
* 策略:: 
* 平台支持:: 
* 高级API索引:: 
* 底层API目录:: 
* 用 asyncio 开发:: 

@end menu

@node 协程与任务,流,,asyncio --- 异步 I/O
@anchor{library/asyncio-task doc}@anchor{248c}@anchor{library/asyncio-task coroutines-and-tasks}@anchor{248d}
@subsubsection 协程与任务


本节将简述用于协程与任务的高层级 API。

@menu
* 协程: 协程<3>. 
* 可等待对象: 可等待对象<2>. 
* 运行 asyncio 程序:: 
* 创建任务:: 
* 休眠:: 
* 并发运行任务:: 
* 屏蔽取消操作:: 
* 超时:: 
* 简单等待:: 
* 来自其他线程的日程安排:: 
* 内省:: 
* Task 对象:: 
* 基于生成器的协程:: 

@end menu

@node 协程<3>,可等待对象<2>,,协程与任务
@anchor{library/asyncio-task coroutine}@anchor{2483}@anchor{library/asyncio-task coroutines}@anchor{248e}
@subsubsection 协程


@ref{1a6,,协程} 通过 async/await 语法进行声明，是编写 asyncio 应用的推荐方式。 例如，以下代码段（需要 Python 3.7+）会打印 "hello"，等待 1 秒，再打印 "world":

@example
>>> import asyncio

>>> async def main():
...     print('hello')
...     await asyncio.sleep(1)
...     print('world')

>>> asyncio.run(main())
hello
world
@end example

注意：简单地调用一个协程并不会将其加入执行日程:

@example
>>> main()
<coroutine object main at 0x1053bb7c8>
@end example

要真正运行一个协程，asyncio 提供了三种主要机制:


@itemize *

@item 
@ref{1a5,,asyncio.run()} 函数用来运行最高层级的入口点 "main()" 函数 (参见上面的示例。)

@item 
等待一个协程。以下代码段会在等待 1 秒后打印 "hello"，然后 @emph{再次} 等待 2 秒后打印 "world":

@example
import asyncio
import time

async def say_after(delay, what):
    await asyncio.sleep(delay)
    print(what)

async def main():
    print(f"started at @{time.strftime('%X')@}")

    await say_after(1, 'hello')
    await say_after(2, 'world')

    print(f"finished at @{time.strftime('%X')@}")

asyncio.run(main())
@end example

预期的输出:

@example
started at 17:13:52
hello
world
finished at 17:13:55
@end example

@item 
@ref{1ae,,asyncio.create_task()} 函数用来并发运行作为 asyncio @ref{1ad,,任务} 的多个协程。

让我们修改以上示例，@emph{并发} 运行两个 @code{say_after} 协程:

@example
async def main():
    task1 = asyncio.create_task(
        say_after(1, 'hello'))

    task2 = asyncio.create_task(
        say_after(2, 'world'))

    print(f"started at @{time.strftime('%X')@}")

    # Wait until both tasks are completed (should take
    # around 2 seconds.)
    await task1
    await task2

    print(f"finished at @{time.strftime('%X')@}")
@end example

注意，预期的输出显示代码段的运行时间比之前快了 1 秒:

@example
started at 17:14:32
hello
world
finished at 17:14:34
@end example
@end itemize

@node 可等待对象<2>,运行 asyncio 程序,协程<3>,协程与任务
@anchor{library/asyncio-task asyncio-awaitables}@anchor{248f}@anchor{library/asyncio-task awaitables}@anchor{2490}
@subsubsection 可等待对象


如果一个对象可以在 @ref{1a3,,await}  语句中使用，那么它就是 @strong{可等待} 对象。许多 asyncio API 都被设计为接受可等待对象。

@emph{可等待} 对象有三种主要类型: @strong{协程}, @strong{任务} 和 @strong{Future}.

@subsubheading 协程


Python 协程属于 @emph{可等待} 对象，因此可以在其他协程中被等待:

@example
import asyncio

async def nested():
    return 42

async def main():
    # Nothing happens if we just call "nested()".
    # A coroutine object is created but not awaited,
    # so it *won't run at all*.
    nested()

    # Let's do it differently now and await it:
    print(await nested())  # will print "42".

asyncio.run(main())
@end example

@cartouche
@quotation 重要 
在本文档中 "协程" 可用来表示两个紧密关联的概念:


@itemize *

@item 
@emph{协程函数}: 定义形式为 @ref{284,,async def} 的函数;

@item 
@emph{协程对象}: 调用 @emph{协程函数} 所返回的对象。
@end itemize
@end quotation
@end cartouche

asyncio 也支持旧式的 @ref{2491,,基于生成器的} 协程。

@subsubheading 任务


@emph{任务} 被用来设置日程以便 @emph{并发} 执行协程。

当一个协程通过 @ref{1ae,,asyncio.create_task()} 等函数被打包为一个 @emph{任务}，该协程将自动排入日程准备立即运行:

@example
import asyncio

async def nested():
    return 42

async def main():
    # Schedule nested() to run soon concurrently
    # with "main()".
    task = asyncio.create_task(nested())

    # "task" can now be used to cancel "nested()", or
    # can simply be awaited to wait until it is complete:
    await task

asyncio.run(main())
@end example

@subsubheading Futures


@ref{43d,,Future} 是一种特殊的 @strong{低层级} 可等待对象，表示一个异步操作的 @strong{最终结果}。

当一个 Future 对象 @emph{被等待}，这意味着协程将保持等待直到该 Future 对象在其他地方操作完毕。

在 asyncio 中需要 Future 对象以便允许通过 async/await 使用基于回调的代码。

通常情况下 @strong{没有必要} 在应用层级的代码中创建 Future 对象。

Future 对象有时会由库和某些 asyncio API 暴露给用户，用作可等待对象:

@example
async def main():
    await function_that_returns_a_future_object()

    # this is also valid:
    await asyncio.gather(
        function_that_returns_a_future_object(),
        some_python_coroutine()
    )
@end example

一个很好的返回对象的低层级函数的示例是 @ref{2492,,loop.run_in_executor()}。

@node 运行 asyncio 程序,创建任务,可等待对象<2>,协程与任务
@anchor{library/asyncio-task running-an-asyncio-program}@anchor{2493}
@subsubsection 运行 asyncio 程序


@geindex run() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio run}@anchor{1a5}
@deffn {函数} asyncio.run (coro, *, debug=False)

执行 @ref{1a6,,coroutine} @emph{coro} 并返回结果。

此函数运行传入的协程，负责管理 asyncio 事件循环并 @emph{完结异步生成器}。

当有其他 asyncio 事件循环在同一线程中运行时，此函数不能被调用。

如果 @emph{debug} 为 @code{True}，事件循环将以调试模式运行。

此函数总是会创建一个新的事件循环并在结束时关闭之。它应当被用作  asyncio 程序的主入口点，理想情况下应当只被调用一次。

示例:

@example
async def main():
    await asyncio.sleep(1)
    print('hello')

asyncio.run(main())
@end example


3.7 新版功能.


@cartouche
@quotation 注解 
@code{asyncio.run()} 的源代码可以在 Lib/asyncio/runners.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/runners.py} 中找到。
@end quotation
@end cartouche
@end deffn

@node 创建任务,休眠,运行 asyncio 程序,协程与任务
@anchor{library/asyncio-task creating-tasks}@anchor{2494}
@subsubsection 创建任务


@geindex create_task() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio create_task}@anchor{1ae}
@deffn {函数} asyncio.create_task (coro, *, name=None)

将 @emph{coro} @ref{2483,,协程} 打包为一个 @ref{1ad,,Task} 排入日程准备执行。返回 Task 对象。

@emph{name} 不为 @code{None}，它将使用 @ref{1b0,,Task.set_name()} 来设为任务的名称。

该任务会在 @ref{34d,,get_running_loop()} 返回的循环中执行，如果当前线程没有在运行的循环则会引发 @ref{2ba,,RuntimeError}。

此函数 @strong{在 Python 3.7 中被加入}。在 Python 3.7 之前，可以改用低层级的 @ref{511,,asyncio.ensure_future()} 函数。

@example
async def coro():
    ...

# In Python 3.7+
task = asyncio.create_task(coro())
...

# This works in all Python versions but is less readable
task = asyncio.ensure_future(coro())
...
@end example


3.7 新版功能.



在 3.8 版更改: 添加了 @code{name} 形参。

@end deffn

@node 休眠,并发运行任务,创建任务,协程与任务
@anchor{library/asyncio-task sleeping}@anchor{2495}
@subsubsection 休眠


@geindex sleep() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio sleep}@anchor{285}
@deffn {函数} coroutine asyncio.sleep (delay, result=None, *, loop=None)

阻塞 @emph{delay} 指定的秒数。

如果指定了 @emph{result}，则当协程完成时将其返回给调用者。

@code{sleep()} 总是会挂起当前任务，以允许其他任务运行。


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@anchor{library/asyncio-task asyncio-example-sleep}@anchor{2496}
以下协程示例运行 5 秒，每秒显示一次当前日期:

@example
import asyncio
import datetime

async def display_date():
    loop = asyncio.get_running_loop()
    end_time = loop.time() + 5.0
    while True:
        print(datetime.datetime.now())
        if (loop.time() + 1.0) >= end_time:
            break
        await asyncio.sleep(1)

asyncio.run(display_date())
@end example
@end deffn

@node 并发运行任务,屏蔽取消操作,休眠,协程与任务
@anchor{library/asyncio-task running-tasks-concurrently}@anchor{2497}
@subsubsection 并发运行任务


@anchor{library/asyncio-task asyncio gather}@anchor{286}
@deffn {函数} awaitable asyncio.gather (*aws, loop=None, return_exceptions=False)

@emph{并发} 运行 @emph{aws} 序列中的 @ref{248f,,可等待对象}。

如果 @emph{aws} 中的某个可等待对象为协程，它将自动作为一个任务加入日程。

如果所有可等待对象都成功完成，结果将是一个由所有返回值聚合而成的列表。结果值的顺序与 @emph{aws} 中可等待对象的顺序一致。

如果 @emph{return_exceptions} 为 @code{False} (默认)，所引发的首个异常会立即传播给等待 @code{gather()} 的任务。@emph{aws} 序列中的其他可等待对象 @strong{不会被取消} 并将继续运行。

如果 @emph{return_exceptions} 为 @code{True}，异常会和成功的结果一样处理，并聚合至结果列表。

如果 @code{gather()} @emph{被取消}，所有被提交 (尚未完成) 的可等待对象也会 @emph{被取消}。

如果 @emph{aws} 序列中的任一 Task 或 Future 对象 @emph{被取消}，它将被当作引发了 @ref{1a7,,CancelledError} 一样处理 -- 在此情况下 @code{gather()} 调用 @strong{不会} 被取消。这是为了防止一个已提交的 Task/Future 被取消导致其他 Tasks/Future 也被取消。


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@anchor{library/asyncio-task asyncio-example-gather}@anchor{2498}
示例:

@example
import asyncio

async def factorial(name, number):
    f = 1
    for i in range(2, number + 1):
        print(f"Task @{name@}: Compute factorial(@{i@})...")
        await asyncio.sleep(1)
        f *= i
    print(f"Task @{name@}: factorial(@{number@}) = @{f@}")

async def main():
    # Schedule three calls *concurrently*:
    await asyncio.gather(
        factorial("A", 2),
        factorial("B", 3),
        factorial("C", 4),
    )

asyncio.run(main())

# Expected output:
#
#     Task A: Compute factorial(2)...
#     Task B: Compute factorial(2)...
#     Task C: Compute factorial(2)...
#     Task A: factorial(2) = 2
#     Task B: Compute factorial(3)...
#     Task C: Compute factorial(3)...
#     Task B: factorial(3) = 6
#     Task C: Compute factorial(4)...
#     Task C: factorial(4) = 24
@end example


在 3.7 版更改: 如果 @emph{gather} 本身被取消，则无论 @emph{return_exceptions} 取值为何，消息都会被传播。

@end deffn

@node 屏蔽取消操作,超时,并发运行任务,协程与任务
@anchor{library/asyncio-task shielding-from-cancellation}@anchor{2499}
@subsubsection 屏蔽取消操作


@anchor{library/asyncio-task asyncio shield}@anchor{287}
@deffn {函数} awaitable asyncio.shield (aw, *, loop=None)

保护一个 @ref{248f,,可等待对象} 防止其被 @ref{249a,,取消}。

如果 @emph{aw} 是一个协程，它将自动作为任务加入日程。

以下语句:

@example
res = await shield(something())
@end example

相当于:

@example
res = await something()
@end example

@emph{不同之处} 在于如果包含它的协程被取消，在 @code{something()} 中运行的任务不会被取消。从 @code{something()} 的角度看来，取消操作并没有发生。然而其调用者已被取消，因此 "await" 表达式仍然会引发 @ref{1a7,,CancelledError}。

如果通过其他方式取消 @code{something()} (例如在其内部操作) 则 @code{shield()} 也会取消。

如果希望完全忽略取消操作 (不推荐) 则 @code{shield()} 函数需要配合一个 try/except 代码段，如下所示:

@example
try:
    res = await shield(something())
except CancelledError:
    res = None
@end example


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@end deffn

@node 超时,简单等待,屏蔽取消操作,协程与任务
@anchor{library/asyncio-task timeouts}@anchor{249b}
@subsubsection 超时


@geindex wait_for() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio wait_for}@anchor{288}
@deffn {函数} coroutine asyncio.wait_for (aw, timeout, *, loop=None)

等待 @emph{aw} @ref{248f,,可等待对象} 完成，指定 timeout 秒数后超时。

如果 @emph{aw} 是一个协程，它将自动作为任务加入日程。

@emph{timeout} 可以为 @code{None}，也可以为 float 或 int 型数值表示的等待秒数。如果 @emph{timeout} 为 @code{None}，则等待直到完成。

如果发生超时，任务将取消并引发 @ref{249c,,asyncio.TimeoutError}.

要避免任务 @ref{249a,,取消}，可以加上 @ref{287,,shield()}。

函数将等待直到目标对象确实被取消，所以总等待时间可能超过 @emph{timeout} 指定的秒数。

如果等待被取消，则 @emph{aw} 指定的对象也会被取消。


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@anchor{library/asyncio-task asyncio-example-waitfor}@anchor{249d}
示例:

@example
async def eternity():
    # Sleep for one hour
    await asyncio.sleep(3600)
    print('yay!')

async def main():
    # Wait for at most 1 second
    try:
        await asyncio.wait_for(eternity(), timeout=1.0)
    except asyncio.TimeoutError:
        print('timeout!')

asyncio.run(main())

# Expected output:
#
#     timeout!
@end example


在 3.7 版更改: 当 @emph{aw} 因超时被取消，@code{wait_for} 会等待 @emph{aw} 被取消。之前版本则将立即引发 @ref{249c,,asyncio.TimeoutError}。

@end deffn

@node 简单等待,来自其他线程的日程安排,超时,协程与任务
@anchor{library/asyncio-task waiting-primitives}@anchor{249e}
@subsubsection 简单等待


@geindex wait() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio wait}@anchor{289}
@deffn {函数} coroutine asyncio.wait (aws, *, loop=None, timeout=None, return_when=ALL_COMPLETED)

并发运行 @emph{aws} 指定的 @ref{248f,,可等待对象} 并阻塞线程直到满足 @emph{return_when} 指定的条件。

返回两个 Task/Future 集合: @code{(done, pending)}。

用法:

@example
done, pending = await asyncio.wait(aws)
@end example

如指定 @emph{timeout} (float 或 int 类型) 则它将被用于控制返回之前等待的最长秒数。

请注意此函数不会引发 @ref{249c,,asyncio.TimeoutError}。当超时发生时，未完成的 Future 或 Task 将在指定秒数后被返回。

@emph{return_when} 指定此函数应在何时返回。它必须为以下常数之一:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

描述

@item

@code{FIRST_COMPLETED}

@tab

函数将在任意可等待对象结束或取消时返回。

@item

@code{FIRST_EXCEPTION}

@tab

函数将在任意可等待对象因引发异常而结束时返回。当没有引发任何异常时它就相当于 @code{ALL_COMPLETED}。

@item

@code{ALL_COMPLETED}

@tab

函数将在所有可等待对象结束或取消时返回。

@end multitable


与 @ref{288,,wait_for()} 不同，@code{wait()} 在超时发生时不会取消可等待对象。


3.8 版后已移除: 如果 @emph{aws} 中的某个可等待对象为协程，它将自动作为任务加入日程。直接向 @code{wait()} 传入协程对象已弃用，因为这会导致 @ref{249f,,令人迷惑的行为}。



Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@anchor{library/asyncio-task asyncio-example-wait-coroutine}@anchor{249f}
@cartouche
@quotation 注解 
@code{wait()} 会自动将协程作为任务加入日程，以后将以 @code{(done, pending)} 集合形式返回显式创建的任务对象。因此以下代码并不会有预期的行为:

@example
async def foo():
    return 42

coro = foo()
done, pending = await asyncio.wait(@{coro@})

if coro in done:
    # This branch will never be run!
@end example

以上代码段的修正方法如下:

@example
async def foo():
    return 42

task = asyncio.create_task(foo())
done, pending = await asyncio.wait(@{task@})

if task in done:
    # Everything will work as expected now.
@end example
@end quotation
@end cartouche


3.8 版后已移除: 直接向 @code{wait()} 传入协程对象的方式已弃用。

@end deffn

@geindex as_completed() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio as_completed}@anchor{28a}
@deffn {函数} asyncio.as_completed (aws, *, loop=None, timeout=None)

并发地运行 @emph{aws} 集合中的 @ref{248f,,可等待对象}。 返回一个协程的迭代器。 所返回的每个协程可被等待以从剩余的可等待对象集合中获得最早的下一个结果。

如果在所有 Future 对象完成前发生超时则将引发 @ref{249c,,asyncio.TimeoutError}。


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。


示例:

@example
for coro in as_completed(aws):
    earliest_result = await coro
    # ...
@end example
@end deffn

@node 来自其他线程的日程安排,内省,简单等待,协程与任务
@anchor{library/asyncio-task scheduling-from-other-threads}@anchor{24a0}
@subsubsection 来自其他线程的日程安排


@geindex run_coroutine_threadsafe() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio run_coroutine_threadsafe}@anchor{514}
@deffn {函数} asyncio.run_coroutine_threadsafe (coro, loop)

向指定事件循环提交一个协程。线程安全。

返回一个 @ref{b26,,concurrent.futures.Future} 以等待来自其他 OS 线程的结果。

此函数应该从另一个 OS 线程中调用，而非事件循环运行所在线程。示例:

@example
# Create a coroutine
coro = asyncio.sleep(1, result=3)

# Submit the coroutine to a given loop
future = asyncio.run_coroutine_threadsafe(coro, loop)

# Wait for the result with an optional timeout argument
assert future.result(timeout) == 3
@end example

如果在协程内产生了异常，将会通知返回的 Future 对象。它也可被用来取消事件循环中的任务:

@example
try:
    result = future.result(timeout)
except asyncio.TimeoutError:
    print('The coroutine took too long, cancelling the task...')
    future.cancel()
except Exception as exc:
    print(f'The coroutine raised an exception: @{exc!r@}')
else:
    print(f'The coroutine returned: @{result!r@}')
@end example

参见 @ref{24a1,,concurrency and multithreading} 部分的文档。

不同与其他 asyncio 函数，此函数要求显式地传入 @emph{loop} 参数。


3.5.1 新版功能.

@end deffn

@node 内省,Task 对象,来自其他线程的日程安排,协程与任务
@anchor{library/asyncio-task introspection}@anchor{24a2}
@subsubsection 内省


@geindex current_task() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio current_task}@anchor{349}
@deffn {函数} asyncio.current_task (loop=None)

返回当前运行的 @ref{1ad,,Task} 实例，如果没有正在运行的任务则返回 @code{None}。

如果 @emph{loop} 为 @code{None} 则会使用 @ref{34d,,get_running_loop()} 获取当前事件循环。


3.7 新版功能.

@end deffn

@geindex all_tasks() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio all_tasks}@anchor{34a}
@deffn {函数} asyncio.all_tasks (loop=None)

返回事件循环所运行的未完成的 @ref{1ad,,Task} 对象的集合。

如果 @emph{loop} 为 @code{None}，则会使用 @ref{34d,,get_running_loop()} 获取当前事件循环。


3.7 新版功能.

@end deffn

@node Task 对象,基于生成器的协程,内省,协程与任务
@anchor{library/asyncio-task task-object}@anchor{24a3}
@subsubsection Task 对象


@geindex Task (asyncio 中的类)
@anchor{library/asyncio-task asyncio Task}@anchor{1ad}
@deffn {类} asyncio.Task (coro, *, loop=None, name=None)

一个与 @ref{43d,,Future 类似} 的对象，可运行 Python @ref{2483,,协程}。非线程安全。

Task 对象被用来在事件循环中运行协程。如果一个协程在等待一个 Future 对象，Task 对象会挂起该协程的执行并等待该 Future 对象完成。当该 Future 对象 @emph{完成}，被打包的协程将恢复执行。

事件循环使用协同日程调度: 一个事件循环每次运行一个 Task 对象。而一个 Task 对象会等待一个 Future 对象完成，该事件循环会运行其他 Task、回调或执行 IO 操作。

使用高层级的 @ref{1ae,,asyncio.create_task()} 函数来创建 Task 对象，也可用低层级的 @ref{1af,,loop.create_task()} 或 @ref{511,,ensure_future()} 函数。不建议手动实例化 Task 对象。

要取消一个正在运行的 Task 对象可使用 @ref{249a,,cancel()} 方法。调用此方法将使该 Task 对象抛出一个 @ref{1a7,,CancelledError} 异常给打包的协程。如果取消期间一个协程正在等待一个 Future 对象，该 Future 对象也将被取消。

@ref{24a4,,cancelled()} 可被用来检测 Task 对象是否被取消。如果打包的协程没有抑制 @ref{1a7,,CancelledError} 异常并且确实被取消，该方法将返回 @code{True}。

@ref{1ad,,asyncio.Task} 从 @ref{43d,,Future} 继承了其除 @ref{24a5,,Future.set_result()} 和 @ref{24a6,,Future.set_exception()} 以外的所有 API。

Task 对象支持 @ref{25,,contextvars} 模块。当一个 Task 对象被创建，它将复制当前上下文，然后在复制的上下文中运行其协程。


在 3.7 版更改: 加入对 @ref{25,,contextvars} 模块的支持。



在 3.8 版更改: 添加了 @code{name} 形参。



Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。


@geindex cancel() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task cancel}@anchor{249a}
@deffn {方法} cancel ()

请求取消 Task 对象。

这将安排在下一轮事件循环中抛出一个 @ref{1a7,,CancelledError} 异常给被封包的协程。

协程在之后有机会进行清理甚至使用 @ref{d6b,,try} ... ... @code{except CancelledError} ... @ref{182,,finally} 代码块抑制异常来拒绝请求。不同于 @ref{24a7,,Future.cancel()}，@ref{249a,,Task.cancel()} 不保证 Task 会被取消，虽然抑制完全取消并不常见，也很不鼓励这样做。
@anchor{library/asyncio-task asyncio-example-task-cancel}@anchor{24a8}
以下示例演示了协程是如何侦听取消请求的:

@example
async def cancel_me():
    print('cancel_me(): before sleep')

    try:
        # Wait for 1 hour
        await asyncio.sleep(3600)
    except asyncio.CancelledError:
        print('cancel_me(): cancel sleep')
        raise
    finally:
        print('cancel_me(): after sleep')

async def main():
    # Create a "cancel_me" Task
    task = asyncio.create_task(cancel_me())

    # Wait for 1 second
    await asyncio.sleep(1)

    task.cancel()
    try:
        await task
    except asyncio.CancelledError:
        print("main(): cancel_me is cancelled now")

asyncio.run(main())

# Expected output:
#
#     cancel_me(): before sleep
#     cancel_me(): cancel sleep
#     cancel_me(): after sleep
#     main(): cancel_me is cancelled now
@end example
@end deffn

@geindex cancelled() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task cancelled}@anchor{24a4}
@deffn {方法} cancelled ()

如果 Task 对象 @emph{被取消} 则返回 @code{True}。

当使用 @ref{249a,,cancel()} 发出取消请求时 Task 会被 @emph{取消}，其封包的协程将传播被抛入的 @ref{1a7,,CancelledError} 异常。
@end deffn

@geindex done() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task done}@anchor{24a9}
@deffn {方法} done ()

如果 Task 对象 @emph{已完成} 则返回 @code{True}。

当 Task 所封包的协程返回一个值、引发一个异常或 Task 本身被取消时，则会被认为 @emph{已完成}。
@end deffn

@geindex result() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task result}@anchor{24aa}
@deffn {方法} result ()

返回 Task 的结果。

如果 Task 对象 @emph{已完成}，其封包的协程的结果会被返回 (或者当协程引发异常时，该异常会被重新引发。)

如果 Task 对象 @emph{被取消}，此方法会引发一个 @ref{1a7,,CancelledError} 异常。

如果 Task 对象的结果还不可用，此方法会引发一个 @ref{24ab,,InvalidStateError} 异常。
@end deffn

@geindex exception() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task exception}@anchor{24ac}
@deffn {方法} exception ()

返回 Task 对象的异常。

如果所封包的协程引发了一个异常，该异常将被返回。如果所封包的协程正常返回则该方法将返回 @code{None}。

如果 Task 对象 @emph{被取消}，此方法会引发一个 @ref{1a7,,CancelledError} 异常。

如果 Task 对象尚未 @emph{完成}，此方法将引发一个 @ref{24ab,,InvalidStateError} 异常。
@end deffn

@geindex add_done_callback() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task add_done_callback}@anchor{24ad}
@deffn {方法} add_done_callback (callback, *, context=None)

添加一个回调，将在 Task 对象 @emph{完成} 时被运行。

此方法应该仅在低层级的基于回调的代码中使用。

要了解更多细节请查看 @ref{346,,Future.add_done_callback()} 的文档。
@end deffn

@geindex remove_done_callback() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task remove_done_callback}@anchor{24ae}
@deffn {方法} remove_done_callback (callback)

从回调列表中移除 @emph{callback} 。

此方法应该仅在低层级的基于回调的代码中使用。

要了解更多细节请查看 @ref{24af,,Future.remove_done_callback()} 的文档。
@end deffn

@geindex get_stack() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task get_stack}@anchor{24b0}
@deffn {方法} get_stack (*, limit=None)

返回此 Task 对象的栈框架列表。

如果所封包的协程未完成，这将返回其挂起所在的栈。如果协程已成功完成或被取消，这将返回一个空列表。如果协程被一个异常终止，这将返回回溯框架列表。

框架总是从按从旧到新排序。

每个被挂起的协程只返回一个栈框架。

可选的 @emph{limit} 参数指定返回框架的数量上限；默认返回所有框架。返回列表的顺序要看是返回一个栈还是一个回溯：栈返回最新的框架，回溯返回最旧的框架。(这与 traceback 模块的行为保持一致。)
@end deffn

@geindex print_stack() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task print_stack}@anchor{24b1}
@deffn {方法} print_stack (*, limit=None, file=None)

打印此 Task 对象的栈或回溯。

此方法产生的输出类似于 traceback 模块通过 @ref{24b0,,get_stack()} 所获取的框架。

@emph{limit} 参数会直接传递给 @ref{24b0,,get_stack()}。

@emph{file} 参数是输出所写入的 I/O 流；默认情况下输出会写入 @ref{308,,sys.stderr}。
@end deffn

@geindex get_coro() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task get_coro}@anchor{1ac}
@deffn {方法} get_coro ()

返回由 @ref{1ad,,Task} 包装的协程对象。


3.8 新版功能.

@end deffn

@geindex get_name() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task get_name}@anchor{1b1}
@deffn {方法} get_name ()

返回 Task 的名称。

如果没有一个 Task 名称被显式地赋值，默认的 asyncio Task 实现会在实例化期间生成一个默认名称。


3.8 新版功能.

@end deffn

@geindex set_name() (asyncio.Task 方法)
@anchor{library/asyncio-task asyncio Task set_name}@anchor{1b0}
@deffn {方法} set_name (value)

设置 Task 的名称。

@emph{value} 参数可以为任意对象，它随后会被转换为字符串。

在默认的 Task 实现中，名称将在任务对象的 @ref{7c6,,repr()} 输出中可见。


3.8 新版功能.

@end deffn

@geindex all_tasks() (asyncio.Task 类方法)
@anchor{library/asyncio-task asyncio Task all_tasks}@anchor{34c}
@deffn {方法} classmethod all_tasks (loop=None)

返回一个事件循环中所有任务的集合。

默认情况下将返回当前事件循环中所有任务。如果 @emph{loop} 为 @code{None}，则会使用 @ref{34e,,get_event_loop()} 函数来获取当前事件循环。


Deprecated since version 3.7, will be removed in version 3.9: 请不要将此方法作为任务方法来调用。 应当改用 @ref{34a,,asyncio.all_tasks()} 函数。

@end deffn

@geindex current_task() (asyncio.Task 类方法)
@anchor{library/asyncio-task asyncio Task current_task}@anchor{34b}
@deffn {方法} classmethod current_task (loop=None)

返回当前运行任务或 @code{None}。

如果 @emph{loop} 为 @code{None}，则会使用 @ref{34e,,get_event_loop()} 函数来获取当前事件循环。


Deprecated since version 3.7, will be removed in version 3.9: 请不要将此方法作为任务方法来调用。 应当改用 @ref{349,,asyncio.current_task()} 函数。

@end deffn
@end deffn

@node 基于生成器的协程,,Task 对象,协程与任务
@anchor{library/asyncio-task asyncio-generator-based-coro}@anchor{2491}@anchor{library/asyncio-task generator-based-coroutines}@anchor{24b2}
@subsubsection 基于生成器的协程


@cartouche
@quotation 注解 
对基于生成器的协程的支持 @strong{已弃用} 并计划在 Python 3.10 中移除。
@end quotation
@end cartouche

基于生成器的协程是 async/await 语法的前身。它们是使用 @code{yield from} 语句创建的 Python 生成器，可以等待 Future 和其他协程。

基于生成器的协程应该使用 @ref{282,,@@asyncio.coroutine} 装饰，虽然这并非强制。

@geindex coroutine() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio coroutine}@anchor{282}
@deffn {函数} @@asyncio.coroutine

用来标记基于生成器的协程的装饰器。

此装饰器使得旧式的基于生成器的协程能与 async/await 代码相兼容:

@example
@@asyncio.coroutine
def old_style_coroutine():
    yield from asyncio.sleep(1)

async def main():
    await old_style_coroutine()
@end example

此装饰器不应该被用于 @ref{284,,async def} 协程。


Deprecated since version 3.8, will be removed in version 3.10: 请改用 @ref{284,,async def}。

@end deffn

@geindex iscoroutine() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio iscoroutine}@anchor{24b3}
@deffn {函数} asyncio.iscoroutine (obj)

如果 @emph{obj} 是一个 @ref{2483,,协程对象} 则返回 @code{True}。

此方法不同于 @ref{6f1,,inspect.iscoroutine()} 因为它对基于生成器的协程返回 @code{True}。
@end deffn

@geindex iscoroutinefunction() (在 asyncio 模块中)
@anchor{library/asyncio-task asyncio iscoroutinefunction}@anchor{24b4}
@deffn {函数} asyncio.iscoroutinefunction (func)

如果 @emph{func} 是一个 @ref{2483,,协程函数} 则返回 @code{True}。

此方法不同于 @ref{6f2,,inspect.iscoroutinefunction()} 因为它对以 @ref{282,,@@coroutine} 装饰的基于生成器的协程函数返回 @code{True}。
@end deffn

@node 流,Synchronization Primitives,协程与任务,asyncio --- 异步 I/O
@anchor{library/asyncio-stream doc}@anchor{24b5}@anchor{library/asyncio-stream asyncio-streams}@anchor{2484}@anchor{library/asyncio-stream streams}@anchor{24b6}
@subsubsection 流


@strong{源码:} Lib/asyncio/streams.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/streams.py}


__________________________________________________________________


流是用于处理网络连接的高级 async/await-ready 原语。流允许发送和接收数据，而不需要使用回调或低级协议和传输。
@anchor{library/asyncio-stream asyncio-example-stream}@anchor{24b7}
下面是一个使用 asyncio streams 编写的 TCP echo 客户端示例:

@example
import asyncio

async def tcp_echo_client(message):
    reader, writer = await asyncio.open_connection(
        '127.0.0.1', 8888)

    print(f'Send: @{message!r@}')
    writer.write(message.encode())
    await writer.drain()

    data = await reader.read(100)
    print(f'Received: @{data.decode()!r@}')

    print('Close the connection')
    writer.close()
    await writer.wait_closed()

asyncio.run(tcp_echo_client('Hello World!'))
@end example

参见下面的 @ref{24b8,,Examples} 部分。

@subsubheading Stream 函数


下面的高级 asyncio 函数可以用来创建和处理流:

@geindex open_connection() (在 asyncio 模块中)
@anchor{library/asyncio-stream asyncio open_connection}@anchor{35c}
@deffn {函数} coroutine asyncio.open_connection (host=None, port=None, *, loop=None, limit=None, ssl=None, family=0, proto=0, flags=0, sock=None, local_addr=None, server_hostname=None, ssl_handshake_timeout=None)

建立网络连接并返回一对 @code{(reader, writer)} 对象。

返回的 @emph{reader} 和 @emph{writer} 对象是 @ref{f5a,,StreamReader} 和 @ref{f5b,,StreamWriter} 类的实例。

@emph{loop} 参数是可选的，当从协程中等待该函数时，总是可以自动确定。

@emph{limit} 确定返回的 @ref{f5a,,StreamReader} 实例使用的缓冲区大小限制。默认情况下，@emph{limit} 设置为 64 KiB 。

其余的参数直接传递到 @ref{1b2,,loop.create_connection()} 。


3.7 新版功能: @emph{ssl_handshake_timeout} 形参。

@end deffn

@geindex start_server() (在 asyncio 模块中)
@anchor{library/asyncio-stream asyncio start_server}@anchor{35d}
@deffn {函数} coroutine asyncio.start_server (client_connected_cb, host=None, port=None, *, loop=None, limit=None, family=socket.AF_UNSPEC, flags=socket.AI_PASSIVE, sock=None, backlog=100, ssl=None, reuse_address=None, reuse_port=None, ssl_handshake_timeout=None, start_serving=True)

启动套接字服务。

当一个新的客户端连接被建立时，回调函数 @emph{client_connected_cb} 会被调用。该函数会接收到一对参数 @code{(reader, writer)} ，reader是类 @ref{f5a,,StreamReader} 的实例，而writer是类 @ref{f5b,,StreamWriter} 的实例。

@emph{client_connected_cb} 即可以是普通的可调用对象也可以是一个 @ref{2483,,协程函数}; 如果它是一个协程函数，它将自动作为 @ref{1ad,,Task} 被调度。

@emph{loop} 参数是可选的。当在一个协程中await该方法时，该参数始终可以自动确定。

@emph{limit} 确定返回的 @ref{f5a,,StreamReader} 实例使用的缓冲区大小限制。默认情况下，@emph{limit} 设置为 64 KiB 。

余下的参数将会直接传递给 @ref{356,,loop.create_server()}.


3.7 新版功能: The @emph{ssl_handshake_timeout} and @emph{start_serving} parameters.

@end deffn

@subsubheading Unix 套接字


@geindex open_unix_connection() (在 asyncio 模块中)
@anchor{library/asyncio-stream asyncio open_unix_connection}@anchor{24b9}
@deffn {函数} coroutine asyncio.open_unix_connection (path=None, *, loop=None, limit=None, ssl=None, sock=None, server_hostname=None, ssl_handshake_timeout=None)

建立一个 Unix 套接字连接并返回 @code{(reader, writer)} 这对返回值。

与 @ref{35c,,open_connection()} 相似，但是操作在 Unix 套接字上

请看文档 @ref{24ba,,loop.create_unix_connection()}.

@ref{12f5,,可用性}: Unix。


3.7 新版功能: @emph{ssl_handshake_timeout} 形参。



在 3.7 版更改: @emph{path} 现在是一个 @ref{363,,path-like object}

@end deffn

@geindex start_unix_server() (在 asyncio 模块中)
@anchor{library/asyncio-stream asyncio start_unix_server}@anchor{24bb}
@deffn {函数} coroutine asyncio.start_unix_server (client_connected_cb, path=None, *, loop=None, limit=None, sock=None, backlog=100, ssl=None, ssl_handshake_timeout=None, start_serving=True)

启动一个Unix socket服务。

与 @ref{35d,,start_server()} 相似，但是是在 Unix 套接字上的操作。

请看文档 @ref{357,,loop.create_unix_server()}.

@ref{12f5,,可用性}: Unix。


3.7 新版功能: The @emph{ssl_handshake_timeout} and @emph{start_serving} parameters.



在 3.7 版更改: @emph{path} 形参现在可以是 @ref{363,,path-like object} 对象。

@end deffn

@menu
* StreamReader:: 
* StreamWriter:: 
* 例子: 例子<11>. 

@end menu

@node StreamReader,StreamWriter,,流
@anchor{library/asyncio-stream streamreader}@anchor{24bc}
@subsubsection StreamReader


@geindex StreamReader (asyncio 中的类)
@anchor{library/asyncio-stream asyncio StreamReader}@anchor{f5a}
@deffn {类} asyncio.StreamReader

这个类表示一个提供api来从IO流中读取数据的读取器对象。

不推荐直接实例化 @emph{StreamReader} 对象，建议使用 @ref{35c,,open_connection()} 和 @ref{35d,,start_server()} 来获取 @emph{StreamReader} 实例。

@geindex read() (asyncio.StreamReader 方法)
@anchor{library/asyncio-stream asyncio StreamReader read}@anchor{24bd}
@deffn {方法} coroutine read (n=-1)

读取 @emph{n} 个byte.  如果没有设置 @emph{n} , 则自动置为 @code{-1} ，读至 EOF 并返回所有读取的byte。

如果读到EOF，且内部缓冲区为空，则返回一个空的 @code{bytes} 对象。
@end deffn

@geindex readline() (asyncio.StreamReader 方法)
@anchor{library/asyncio-stream asyncio StreamReader readline}@anchor{24be}
@deffn {方法} coroutine readline ()

读取一行，其中“行”指的是以 @code{\n} 结尾的字节序列。

如果读到EOF而没有找到 @code{\n} ，该方法返回部分读取的数据。

如果读到EOF，且内部缓冲区为空，则返回一个空的 @code{bytes} 对象。
@end deffn

@geindex readexactly() (asyncio.StreamReader 方法)
@anchor{library/asyncio-stream asyncio StreamReader readexactly}@anchor{519}
@deffn {方法} coroutine readexactly (n)

精准读取 @emph{n} 个 bytes，不能超过也不能少于。

如果在读取完 @emph{n} 个byte之前读取到EOF，则会抛出 @ref{24bf,,IncompleteReadError} 异常。使用 @ref{24c0,,IncompleteReadError.partial} 属性来获取到达流结束之前读取的 bytes 字符串。
@end deffn

@geindex readuntil() (asyncio.StreamReader 方法)
@anchor{library/asyncio-stream asyncio StreamReader readuntil}@anchor{518}
@deffn {方法} coroutine readuntil (separator=b'\n')

从流中读取数据直至遇到 @emph{分隔符}

成功后，数据和指定的separator将从内部缓冲区中删除(或者说被消费掉)。返回的数据将包括在末尾的指定separator。

如果读取的数据量超过了配置的流限制，将引发 @ref{24c1,,LimitOverrunError} 异常，数据将留在内部缓冲区中并可以再次读取。

如果在找到完整的separator之前到达EOF，则会引发 @ref{24bf,,IncompleteReadError} 异常，并重置内部缓冲区。 @ref{24c0,,IncompleteReadError.partial} 属性可能包含指定separator的一部分。


3.5.2 新版功能.

@end deffn

@geindex at_eof() (asyncio.StreamReader 方法)
@anchor{library/asyncio-stream asyncio StreamReader at_eof}@anchor{24c2}
@deffn {方法} at_eof ()

如果缓冲区为空并且 @code{feed_eof()} 被调用，则返回 @code{True} 。
@end deffn
@end deffn

@node StreamWriter,例子<11>,StreamReader,流
@anchor{library/asyncio-stream streamwriter}@anchor{24c3}
@subsubsection StreamWriter


@geindex StreamWriter (asyncio 中的类)
@anchor{library/asyncio-stream asyncio StreamWriter}@anchor{f5b}
@deffn {类} asyncio.StreamWriter

这个类表示一个写入器对象，该对象提供api以便于写数据至IO流中。

It is not recommended to instantiate @emph{StreamWriter} objects
directly; use @ref{35c,,open_connection()} and @ref{35d,,start_server()}
instead.

@geindex write() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter write}@anchor{24c4}
@deffn {方法} write (data)

The method attempts to write the @emph{data} to the underlying socket immediately.
If that fails, the data is queued in an internal write buffer until it can be
sent.

The method should be used along with the @code{drain()} method:

@example
stream.write(data)
await stream.drain()
@end example
@end deffn

@geindex writelines() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter writelines}@anchor{24c5}
@deffn {方法} writelines (data)

The method writes a list (or any iterable) of bytes to the underlying socket
immediately.
If that fails, the data is queued in an internal write buffer until it can be
sent.

The method should be used along with the @code{drain()} method:

@example
stream.writelines(lines)
await stream.drain()
@end example
@end deffn

@geindex close() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter close}@anchor{24c6}
@deffn {方法} close ()

The method closes the stream and the underlying socket.

The method should be used along with the @code{wait_closed()} method:

@example
stream.close()
await stream.wait_closed()
@end example
@end deffn

@geindex can_write_eof() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter can_write_eof}@anchor{24c7}
@deffn {方法} can_write_eof ()

Return @code{True} if the underlying transport supports
the @ref{24c8,,write_eof()} method, @code{False} otherwise.
@end deffn

@geindex write_eof() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter write_eof}@anchor{24c8}
@deffn {方法} write_eof ()

Close the write end of the stream after the buffered write
data is flushed.
@end deffn

@geindex transport (asyncio.StreamWriter 属性)
@anchor{library/asyncio-stream asyncio StreamWriter transport}@anchor{24c9}
@deffn {属性} transport

Return the underlying asyncio transport.
@end deffn

@geindex get_extra_info() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter get_extra_info}@anchor{24ca}
@deffn {方法} get_extra_info (name, default=None)

Access optional transport information; see
@ref{2c8,,BaseTransport.get_extra_info()} for details.
@end deffn

@geindex drain() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter drain}@anchor{24cb}
@deffn {方法} coroutine drain ()

Wait until it is appropriate to resume writing to the stream.
Example:

@example
writer.write(data)
await writer.drain()
@end example

This is a flow control method that interacts with the underlying
IO write buffer.  When the size of the buffer reaches
the high watermark, @emph{drain()} blocks until the size of the
buffer is drained down to the low watermark and writing can
be resumed.  When there is nothing to wait for, the @ref{24cb,,drain()}
returns immediately.
@end deffn

@geindex is_closing() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter is_closing}@anchor{350}
@deffn {方法} is_closing ()

Return @code{True} if the stream is closed or in the process of
being closed.


3.7 新版功能.

@end deffn

@geindex wait_closed() (asyncio.StreamWriter 方法)
@anchor{library/asyncio-stream asyncio StreamWriter wait_closed}@anchor{34f}
@deffn {方法} coroutine wait_closed ()

Wait until the stream is closed.

Should be called after @ref{24c6,,close()} to wait until the underlying
connection is closed.


3.7 新版功能.

@end deffn
@end deffn

@node 例子<11>,,StreamWriter,流
@anchor{library/asyncio-stream examples}@anchor{24b8}
@subsubsection 例子


@menu
* TCP echo client using streams:: 
* TCP echo server using streams:: 
* Get HTTP headers:: 
* Register an open socket to wait for data using streams:: 

@end menu

@node TCP echo client using streams,TCP echo server using streams,,例子<11>
@anchor{library/asyncio-stream asyncio-tcp-echo-client-streams}@anchor{24cc}@anchor{library/asyncio-stream tcp-echo-client-using-streams}@anchor{24cd}
@subsubsection TCP echo client using streams


TCP echo client using the @ref{35c,,asyncio.open_connection()} function:

@example
import asyncio

async def tcp_echo_client(message):
    reader, writer = await asyncio.open_connection(
        '127.0.0.1', 8888)

    print(f'Send: @{message!r@}')
    writer.write(message.encode())

    data = await reader.read(100)
    print(f'Received: @{data.decode()!r@}')

    print('Close the connection')
    writer.close()

asyncio.run(tcp_echo_client('Hello World!'))
@end example


@subsubheading 参见


The @ref{24ce,,TCP echo client protocol}
example uses the low-level @ref{1b2,,loop.create_connection()} method.


@node TCP echo server using streams,Get HTTP headers,TCP echo client using streams,例子<11>
@anchor{library/asyncio-stream asyncio-tcp-echo-server-streams}@anchor{24cf}@anchor{library/asyncio-stream tcp-echo-server-using-streams}@anchor{24d0}
@subsubsection TCP echo server using streams


TCP echo server using the @ref{35d,,asyncio.start_server()} function:

@example
import asyncio

async def handle_echo(reader, writer):
    data = await reader.read(100)
    message = data.decode()
    addr = writer.get_extra_info('peername')

    print(f"Received @{message!r@} from @{addr!r@}")

    print(f"Send: @{message!r@}")
    writer.write(data)
    await writer.drain()

    print("Close the connection")
    writer.close()

async def main():
    server = await asyncio.start_server(
        handle_echo, '127.0.0.1', 8888)

    addr = server.sockets[0].getsockname()
    print(f'Serving on @{addr@}')

    async with server:
        await server.serve_forever()

asyncio.run(main())
@end example


@subsubheading 参见


The @ref{24d1,,TCP echo server protocol}
example uses the @ref{356,,loop.create_server()} method.


@node Get HTTP headers,Register an open socket to wait for data using streams,TCP echo server using streams,例子<11>
@anchor{library/asyncio-stream get-http-headers}@anchor{24d2}
@subsubsection Get HTTP headers


Simple example querying HTTP headers of the URL passed on the command line:

@example
import asyncio
import urllib.parse
import sys

async def print_http_headers(url):
    url = urllib.parse.urlsplit(url)
    if url.scheme == 'https':
        reader, writer = await asyncio.open_connection(
            url.hostname, 443, ssl=True)
    else:
        reader, writer = await asyncio.open_connection(
            url.hostname, 80)

    query = (
        f"HEAD @{url.path or '/'@} HTTP/1.0\r\n"
        f"Host: @{url.hostname@}\r\n"
        f"\r\n"
    )

    writer.write(query.encode('latin-1'))
    while True:
        line = await reader.readline()
        if not line:
            break

        line = line.decode('latin1').rstrip()
        if line:
            print(f'HTTP header> @{line@}')

    # Ignore the body, close the socket
    writer.close()

url = sys.argv[1]
asyncio.run(print_http_headers(url))
@end example

用法:

@example
python example.py http://example.com/path/page.html
@end example

or with HTTPS:

@example
python example.py https://example.com/path/page.html
@end example

@node Register an open socket to wait for data using streams,,Get HTTP headers,例子<11>
@anchor{library/asyncio-stream asyncio-example-create-connection-streams}@anchor{24d3}@anchor{library/asyncio-stream register-an-open-socket-to-wait-for-data-using-streams}@anchor{24d4}
@subsubsection Register an open socket to wait for data using streams


Coroutine waiting until a socket receives data using the
@ref{35c,,open_connection()} function:

@example
import asyncio
import socket

async def wait_for_data():
    # Get a reference to the current event loop because
    # we want to access low-level APIs.
    loop = asyncio.get_running_loop()

    # Create a pair of connected sockets.
    rsock, wsock = socket.socketpair()

    # Register the open socket to wait for data.
    reader, writer = await asyncio.open_connection(sock=rsock)

    # Simulate the reception of data from the network
    loop.call_soon(wsock.send, 'abc'.encode())

    # Wait for data
    data = await reader.read(100)

    # Got data, we are done: close the socket
    print("Received:", data.decode())
    writer.close()

    # Close the second socket
    wsock.close()

asyncio.run(wait_for_data())
@end example


@subsubheading 参见


The @ref{24d5,,register an open socket to wait for data using a protocol} example uses a low-level protocol and
the @ref{1b2,,loop.create_connection()} method.

The @ref{24d6,,watch a file descriptor for read events} example uses the low-level
@ref{24d7,,loop.add_reader()} method to watch a file descriptor.


@node Synchronization Primitives,子进程集,流,asyncio --- 异步 I/O
@anchor{library/asyncio-sync doc}@anchor{24d8}@anchor{library/asyncio-sync asyncio-sync}@anchor{2487}@anchor{library/asyncio-sync synchronization-primitives}@anchor{24d9}
@subsubsection Synchronization Primitives


@strong{Source code:} Lib/asyncio/locks.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/locks.py}


__________________________________________________________________


asyncio synchronization primitives are designed to be similar to
those of the @ref{109,,threading} module with two important caveats:


@itemize *

@item 
asyncio primitives are not thread-safe, therefore they should not
be used for OS thread synchronization (use @ref{109,,threading} for
that);

@item 
methods of these synchronization primitives do not accept the @emph{timeout}
argument; use the @ref{288,,asyncio.wait_for()} function to perform
operations with timeouts.
@end itemize

asyncio has the following basic synchronization primitives:


@itemize *

@item 
@ref{28b,,Lock}

@item 
@ref{28c,,Event}

@item 
@ref{28d,,Condition}

@item 
@ref{28e,,Semaphore}

@item 
@ref{28f,,BoundedSemaphore}
@end itemize


__________________________________________________________________


@menu
* Lock:: 
* Event:: 
* Condition:: 
* Semaphore:: 
* BoundedSemaphore:: 

@end menu

@node Lock,Event,,Synchronization Primitives
@anchor{library/asyncio-sync lock}@anchor{24da}
@subsubsection Lock


@geindex Lock (asyncio 中的类)
@anchor{library/asyncio-sync asyncio Lock}@anchor{28b}
@deffn {类} asyncio.Lock (*, loop=None)

Implements a mutex lock for asyncio tasks.  Not thread-safe.

An asyncio lock can be used to guarantee exclusive access to a
shared resource.

The preferred way to use a Lock is an @ref{63d,,async with}
statement:

@example
lock = asyncio.Lock()

# ... later
async with lock:
    # access shared state
@end example

which is equivalent to:

@example
lock = asyncio.Lock()

# ... later
await lock.acquire()
try:
    # access shared state
finally:
    lock.release()
@end example


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。


@geindex acquire() (asyncio.Lock 方法)
@anchor{library/asyncio-sync asyncio Lock acquire}@anchor{24db}
@deffn {方法} coroutine acquire ()

Acquire the lock.

This method waits until the lock is @emph{unlocked}, sets it to
@emph{locked} and returns @code{True}.

When more than one coroutine is blocked in @ref{24db,,acquire()}
waiting for the lock to be unlocked, only one coroutine
eventually proceeds.

Acquiring a lock is @emph{fair}: the coroutine that proceeds will be
the first coroutine that started waiting on the lock.
@end deffn

@geindex release() (asyncio.Lock 方法)
@anchor{library/asyncio-sync asyncio Lock release}@anchor{24dc}
@deffn {方法} release ()

Release the lock.

When the lock is @emph{locked}, reset it to @emph{unlocked} and return.

If the lock is @emph{unlocked}, a @ref{2ba,,RuntimeError} is raised.
@end deffn

@geindex locked() (asyncio.Lock 方法)
@anchor{library/asyncio-sync asyncio Lock locked}@anchor{24dd}
@deffn {方法} locked ()

Return @code{True} if the lock is @emph{locked}.
@end deffn
@end deffn

@node Event,Condition,Lock,Synchronization Primitives
@anchor{library/asyncio-sync event}@anchor{24de}
@subsubsection Event


@geindex Event (asyncio 中的类)
@anchor{library/asyncio-sync asyncio Event}@anchor{28c}
@deffn {类} asyncio.Event (*, loop=None)

An event object.  Not thread-safe.

An asyncio event can be used to notify multiple asyncio tasks
that some event has happened.

An Event object manages an internal flag that can be set to @emph{true}
with the @ref{b68,,set()} method and reset to @emph{false} with the
@ref{24df,,clear()} method.  The @ref{289,,wait()} method blocks until the
flag is set to @emph{true}.  The flag is set to @emph{false} initially.


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@anchor{library/asyncio-sync asyncio-example-sync-event}@anchor{24e0}
示例:

@example
async def waiter(event):
    print('waiting for it ...')
    await event.wait()
    print('... got it!')

async def main():
    # Create an Event object.
    event = asyncio.Event()

    # Spawn a Task to wait until 'event' is set.
    waiter_task = asyncio.create_task(waiter(event))

    # Sleep for 1 second and set the event.
    await asyncio.sleep(1)
    event.set()

    # Wait until the waiter task is finished.
    await waiter_task

asyncio.run(main())
@end example

@geindex wait() (asyncio.Event 方法)
@anchor{library/asyncio-sync asyncio Event wait}@anchor{24e1}
@deffn {方法} coroutine wait ()

Wait until the event is set.

If the event is set, return @code{True} immediately.
Otherwise block until another task calls @ref{b68,,set()}.
@end deffn

@geindex set() (asyncio.Event 方法)
@anchor{library/asyncio-sync asyncio Event set}@anchor{24e2}
@deffn {方法} set ()

Set the event.

All tasks waiting for event to be set will be immediately
awakened.
@end deffn

@geindex clear() (asyncio.Event 方法)
@anchor{library/asyncio-sync asyncio Event clear}@anchor{24df}
@deffn {方法} clear ()

Clear (unset) the event.

Tasks awaiting on @ref{289,,wait()} will now block until the
@ref{b68,,set()} method is called again.
@end deffn

@geindex is_set() (asyncio.Event 方法)
@anchor{library/asyncio-sync asyncio Event is_set}@anchor{24e3}
@deffn {方法} is_set ()

Return @code{True} if the event is set.
@end deffn
@end deffn

@node Condition,Semaphore,Event,Synchronization Primitives
@anchor{library/asyncio-sync condition}@anchor{24e4}
@subsubsection Condition


@geindex Condition (asyncio 中的类)
@anchor{library/asyncio-sync asyncio Condition}@anchor{28d}
@deffn {类} asyncio.Condition (lock=None, *, loop=None)

A Condition object.  Not thread-safe.

An asyncio condition primitive can be used by a task to wait for
some event to happen and then get exclusive access to a shared
resource.

In essence, a Condition object combines the functionality
of an @ref{28c,,Event} and a @ref{28b,,Lock}.  It is possible to have
multiple Condition objects share one Lock, which allows coordinating
exclusive access to a shared resource between different tasks
interested in particular states of that shared resource.

The optional @emph{lock} argument must be a @ref{28b,,Lock} object or
@code{None}.  In the latter case a new Lock object is created
automatically.


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。


The preferred way to use a Condition is an @ref{63d,,async with}
statement:

@example
cond = asyncio.Condition()

# ... later
async with cond:
    await cond.wait()
@end example

which is equivalent to:

@example
cond = asyncio.Condition()

# ... later
await cond.acquire()
try:
    await cond.wait()
finally:
    cond.release()
@end example

@geindex acquire() (asyncio.Condition 方法)
@anchor{library/asyncio-sync asyncio Condition acquire}@anchor{24e5}
@deffn {方法} coroutine acquire ()

Acquire the underlying lock.

This method waits until the underlying lock is @emph{unlocked},
sets it to @emph{locked} and returns @code{True}.
@end deffn

@geindex notify() (asyncio.Condition 方法)
@anchor{library/asyncio-sync asyncio Condition notify}@anchor{24e6}
@deffn {方法} notify (n=1)

Wake up at most @emph{n} tasks (1 by default) waiting on this
condition.  The method is no-op if no tasks are waiting.

The lock must be acquired before this method is called and
released shortly after.  If called with an @emph{unlocked} lock
a @ref{2ba,,RuntimeError} error is raised.
@end deffn

@geindex locked() (asyncio.Condition 方法)
@anchor{library/asyncio-sync asyncio Condition locked}@anchor{24e7}
@deffn {方法} locked ()

Return @code{True} if the underlying lock is acquired.
@end deffn

@geindex notify_all() (asyncio.Condition 方法)
@anchor{library/asyncio-sync asyncio Condition notify_all}@anchor{24e8}
@deffn {方法} notify_all ()

Wake up all tasks waiting on this condition.

This method acts like @ref{24e6,,notify()}, but wakes up all waiting
tasks.

The lock must be acquired before this method is called and
released shortly after.  If called with an @emph{unlocked} lock
a @ref{2ba,,RuntimeError} error is raised.
@end deffn

@geindex release() (asyncio.Condition 方法)
@anchor{library/asyncio-sync asyncio Condition release}@anchor{24e9}
@deffn {方法} release ()

Release the underlying lock.

在未锁定的锁调用时，会引发 @ref{2ba,,RuntimeError} 异常。
@end deffn

@geindex wait() (asyncio.Condition 方法)
@anchor{library/asyncio-sync asyncio Condition wait}@anchor{24ea}
@deffn {方法} coroutine wait ()

Wait until notified.

If the calling task has not acquired the lock when this method is
called, a @ref{2ba,,RuntimeError} is raised.

This method releases the underlying lock, and then blocks until
it is awakened by a @ref{24e6,,notify()} or @ref{24e8,,notify_all()} call.
Once awakened, the Condition re-acquires its lock and this method
returns @code{True}.
@end deffn

@geindex wait_for() (asyncio.Condition 方法)
@anchor{library/asyncio-sync asyncio Condition wait_for}@anchor{24eb}
@deffn {方法} coroutine wait_for (predicate)

Wait until a predicate becomes @emph{true}.

The predicate must be a callable which result will be
interpreted as a boolean value.  The final value is the
return value.
@end deffn
@end deffn

@node Semaphore,BoundedSemaphore,Condition,Synchronization Primitives
@anchor{library/asyncio-sync semaphore}@anchor{24ec}
@subsubsection Semaphore


@geindex Semaphore (asyncio 中的类)
@anchor{library/asyncio-sync asyncio Semaphore}@anchor{28e}
@deffn {类} asyncio.Semaphore (value=1, *, loop=None)

A Semaphore object.  Not thread-safe.

A semaphore manages an internal counter which is decremented by each
@ref{24ed,,acquire()} call and incremented by each @ref{24ee,,release()} call.
The counter can never go below zero; when @ref{24ed,,acquire()} finds
that it is zero, it blocks, waiting until some task calls
@ref{24ee,,release()}.

The optional @emph{value} argument gives the initial value for the
internal counter (@code{1} by default). If the given value is
less than @code{0} a @ref{1fb,,ValueError} is raised.


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。


The preferred way to use a Semaphore is an @ref{63d,,async with}
statement:

@example
sem = asyncio.Semaphore(10)

# ... later
async with sem:
    # work with shared resource
@end example

which is equivalent to:

@example
sem = asyncio.Semaphore(10)

# ... later
await sem.acquire()
try:
    # work with shared resource
finally:
    sem.release()
@end example

@geindex acquire() (asyncio.Semaphore 方法)
@anchor{library/asyncio-sync asyncio Semaphore acquire}@anchor{24ed}
@deffn {方法} coroutine acquire ()

获取一个信号量。

If the internal counter is greater than zero, decrement
it by one and return @code{True} immediately.  If it is zero, wait
until a @ref{24ee,,release()} is called and return @code{True}.
@end deffn

@geindex locked() (asyncio.Semaphore 方法)
@anchor{library/asyncio-sync asyncio Semaphore locked}@anchor{24ef}
@deffn {方法} locked ()

Returns @code{True} if semaphore can not be acquired immediately.
@end deffn

@geindex release() (asyncio.Semaphore 方法)
@anchor{library/asyncio-sync asyncio Semaphore release}@anchor{24ee}
@deffn {方法} release ()

Release a semaphore, incrementing the internal counter by one.
Can wake up a task waiting to acquire the semaphore.

Unlike @ref{28f,,BoundedSemaphore}, @ref{28e,,Semaphore} allows
making more @code{release()} calls than @code{acquire()} calls.
@end deffn
@end deffn

@node BoundedSemaphore,,Semaphore,Synchronization Primitives
@anchor{library/asyncio-sync boundedsemaphore}@anchor{24f0}
@subsubsection BoundedSemaphore


@geindex BoundedSemaphore (asyncio 中的类)
@anchor{library/asyncio-sync asyncio BoundedSemaphore}@anchor{28f}
@deffn {类} asyncio.BoundedSemaphore (value=1, *, loop=None)

A bounded semaphore object.  Not thread-safe.

Bounded Semaphore is a version of @ref{28e,,Semaphore} that raises
a @ref{1fb,,ValueError} in @ref{24ee,,release()} if it
increases the internal counter above the initial @emph{value}.


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@end deffn


__________________________________________________________________



3.7 版后已移除: Acquiring a lock using @code{await lock} or @code{yield from lock} and/or
@ref{6e3,,with} statement (@code{with await lock}, @code{with (yield from
lock)}) is deprecated.  Use @code{async with lock} instead.


@node 子进程集,队列集,Synchronization Primitives,asyncio --- 异步 I/O
@anchor{library/asyncio-subprocess doc}@anchor{24f1}@anchor{library/asyncio-subprocess asyncio-subprocess}@anchor{2485}@anchor{library/asyncio-subprocess subprocesses}@anchor{24f2}
@subsubsection 子进程集


@strong{Source code:} Lib/asyncio/subprocess.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/subprocess.py},
Lib/asyncio/base_subprocess.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/base_subprocess.py}


__________________________________________________________________


This section describes high-level async/await asyncio APIs to
create and manage subprocesses.
@anchor{library/asyncio-subprocess asyncio-example-subprocess-shell}@anchor{24f3}
Here's an example of how asyncio can run a shell command and
obtain its result:

@example
import asyncio

async def run(cmd):
    proc = await asyncio.create_subprocess_shell(
        cmd,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE)

    stdout, stderr = await proc.communicate()

    print(f'[@{cmd!r@} exited with @{proc.returncode@}]')
    if stdout:
        print(f'[stdout]\n@{stdout.decode()@}')
    if stderr:
        print(f'[stderr]\n@{stderr.decode()@}')

asyncio.run(run('ls /zzz'))
@end example

will print:

@example
['ls /zzz' exited with 1]
[stderr]
ls: /zzz: No such file or directory
@end example

Because all asyncio subprocess functions are asynchronous and asyncio
provides many tools to work with such functions, it is easy to execute
and monitor multiple subprocesses in parallel.  It is indeed trivial
to modify the above example to run several commands simultaneously:

@example
async def main():
    await asyncio.gather(
        run('ls /zzz'),
        run('sleep 1; echo "hello"'))

asyncio.run(main())
@end example

See also the @ref{24f4,,Examples} subsection.

@menu
* Creating Subprocesses:: 
* 常量: 常量<7>. 
* Interacting with Subprocesses:: 

@end menu

@node Creating Subprocesses,常量<7>,,子进程集
@anchor{library/asyncio-subprocess creating-subprocesses}@anchor{24f5}
@subsubsection Creating Subprocesses


@geindex create_subprocess_exec() (在 asyncio 模块中)
@anchor{library/asyncio-subprocess asyncio create_subprocess_exec}@anchor{291}
@deffn {函数} coroutine asyncio.create_subprocess_exec (program, *args, stdin=None, stdout=None, stderr=None, loop=None, limit=None, **kwds)

创建一个子进程。

The @emph{limit} argument sets the buffer limit for @ref{f5a,,StreamReader}
wrappers for @code{Process.stdout} and @code{Process.stderr}
(if @ref{3e6,,subprocess.PIPE} is passed to @emph{stdout} and @emph{stderr} arguments).

Return a @ref{24f6,,Process} instance.

See the documentation of @ref{2488,,loop.subprocess_exec()} for other
parameters.


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@end deffn

@geindex create_subprocess_shell() (在 asyncio 模块中)
@anchor{library/asyncio-subprocess asyncio create_subprocess_shell}@anchor{292}
@deffn {函数} coroutine asyncio.create_subprocess_shell (cmd, stdin=None, stdout=None, stderr=None, loop=None, limit=None, **kwds)

Run the @emph{cmd} shell command.

The @emph{limit} argument sets the buffer limit for @ref{f5a,,StreamReader}
wrappers for @code{Process.stdout} and @code{Process.stderr}
(if @ref{3e6,,subprocess.PIPE} is passed to @emph{stdout} and @emph{stderr} arguments).

Return a @ref{24f6,,Process} instance.

See the documentation of @ref{24f7,,loop.subprocess_shell()} for other
parameters.

@cartouche
@quotation 重要 
It is the application's responsibility to ensure that all whitespace and
special characters are quoted appropriately to avoid shell injection@footnote{https://en.wikipedia.org/wiki/Shell_injection#Shell_injection}
vulnerabilities. The @ref{a6e,,shlex.quote()} function can be used to properly
escape whitespace and special shell characters in strings that are going
to be used to construct shell commands.
@end quotation
@end cartouche


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。

@end deffn

@cartouche
@quotation 注解 
The default asyncio event loop implementation on @strong{Windows} does not
support subprocesses. Subprocesses are available for Windows if a
@ref{1ab,,ProactorEventLoop} is used.
See @ref{24f8,,Subprocess Support on Windows}
for details.
@end quotation
@end cartouche


@subsubheading 参见


asyncio also has the following @emph{low-level} APIs to work with subprocesses:
@ref{2488,,loop.subprocess_exec()}, @ref{24f7,,loop.subprocess_shell()},
@ref{24f9,,loop.connect_read_pipe()}, @ref{24fa,,loop.connect_write_pipe()},
as well as the @ref{24fb,,Subprocess Transports}
and @ref{24fc,,Subprocess Protocols}.


@node 常量<7>,Interacting with Subprocesses,Creating Subprocesses,子进程集
@anchor{library/asyncio-subprocess constants}@anchor{24fd}
@subsubsection 常量


@geindex asyncio.subprocess.PIPE() (在 asyncio 模块中)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess PIPE}@anchor{24fe}
@deffn {数据} asyncio.subprocess.PIPE

Can be passed to the @emph{stdin}, @emph{stdout} or @emph{stderr} parameters.

If @emph{PIPE} is passed to @emph{stdin} argument, the
@ref{24ff,,Process.stdin} attribute
will point to a @ref{f5b,,StreamWriter} instance.

If @emph{PIPE} is passed to @emph{stdout} or @emph{stderr} arguments, the
@ref{2500,,Process.stdout} and
@ref{2501,,Process.stderr}
attributes will point to @ref{f5a,,StreamReader} instances.
@end deffn

@geindex asyncio.subprocess.STDOUT() (在 asyncio 模块中)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess STDOUT}@anchor{2502}
@deffn {数据} asyncio.subprocess.STDOUT

Special value that can be used as the @emph{stderr} argument and indicates
that standard error should be redirected into standard output.
@end deffn

@geindex asyncio.subprocess.DEVNULL() (在 asyncio 模块中)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess DEVNULL}@anchor{2503}
@deffn {数据} asyncio.subprocess.DEVNULL

Special value that can be used as the @emph{stdin}, @emph{stdout} or @emph{stderr} argument
to process creation functions.  It indicates that the special file
@ref{fad,,os.devnull} will be used for the corresponding subprocess stream.
@end deffn

@node Interacting with Subprocesses,,常量<7>,子进程集
@anchor{library/asyncio-subprocess interacting-with-subprocesses}@anchor{2504}
@subsubsection Interacting with Subprocesses


Both @ref{291,,create_subprocess_exec()} and @ref{292,,create_subprocess_shell()}
functions return instances of the @emph{Process} class.  @emph{Process} is a high-level
wrapper that allows communicating with subprocesses and watching for
their completion.

@geindex asyncio.subprocess.Process (asyncio 中的类)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process}@anchor{24f6}
@deffn {类} asyncio.subprocess.Process

An object that wraps OS processes created by the
@ref{291,,create_subprocess_exec()} and @ref{292,,create_subprocess_shell()}
functions.

This class is designed to have a similar API to the
@ref{2b9,,subprocess.Popen} class, but there are some
notable differences:


@itemize *

@item 
unlike Popen, Process instances do not have an equivalent to
the @ref{2419,,poll()} method;

@item 
the @ref{2505,,communicate()} and
@ref{2506,,wait()} methods don't have a
@emph{timeout} parameter: use the @ref{288,,wait_for()} function;

@item 
the @ref{2506,,Process.wait()} method
is asynchronous, whereas @ref{58d,,subprocess.Popen.wait()} method
is implemented as a blocking busy loop;

@item 
the @emph{universal_newlines} parameter is not supported.
@end itemize

这个类不是线程安全的（@ref{24a1,,not thread safe}）。

请参阅  @ref{2507,,子进程和线程} 部分。

@geindex wait() (asyncio.asyncio.subprocess.Process 方法)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process wait}@anchor{2506}
@deffn {方法} coroutine wait ()

Wait for the child process to terminate.

Set and return the @ref{2508,,returncode} attribute.

@cartouche
@quotation 注解 
This method can deadlock when using @code{stdout=PIPE} or
@code{stderr=PIPE} and the child process generates so much output
that it blocks waiting for the OS pipe buffer to accept
more data. Use the @ref{2505,,communicate()} method when using pipes
to avoid this condition.
@end quotation
@end cartouche
@end deffn

@geindex communicate() (asyncio.asyncio.subprocess.Process 方法)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process communicate}@anchor{2505}
@deffn {方法} coroutine communicate (input=None)

Interact with process:


@enumerate 

@item 
send data to @emph{stdin} (if @emph{input} is not @code{None});

@item 
read data from @emph{stdout} and @emph{stderr}, until EOF is reached;

@item 
wait for process to terminate.
@end enumerate

The optional @emph{input} argument is the data (@ref{32a,,bytes} object)
that will be sent to the child process.

Return a tuple @code{(stdout_data, stderr_data)}.

If either @ref{997,,BrokenPipeError} or @ref{99a,,ConnectionResetError}
exception is raised when writing @emph{input} into @emph{stdin}, the
exception is ignored.  This condition occurs when the process
exits before all data are written into @emph{stdin}.

If it is desired to send data to the process' @emph{stdin},
the process needs to be created with @code{stdin=PIPE}.  Similarly,
to get anything other than @code{None} in the result tuple, the
process has to be created with @code{stdout=PIPE} and/or
@code{stderr=PIPE} arguments.

Note, that the data read is buffered in memory, so do not use
this method if the data size is large or unlimited.
@end deffn

@geindex send_signal() (asyncio.asyncio.subprocess.Process 方法)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process send_signal}@anchor{2509}
@deffn {方法} send_signal (signal)

Sends the signal @emph{signal} to the child process.

@cartouche
@quotation 注解 
On Windows, @code{SIGTERM} is an alias for @ref{250a,,terminate()}.
@code{CTRL_C_EVENT} and @code{CTRL_BREAK_EVENT} can be sent to processes
started with a @emph{creationflags} parameter which includes
@code{CREATE_NEW_PROCESS_GROUP}.
@end quotation
@end cartouche
@end deffn

@geindex terminate() (asyncio.asyncio.subprocess.Process 方法)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process terminate}@anchor{250a}
@deffn {方法} terminate ()

Stop the child process.

On POSIX systems this method sends @ref{250b,,signal.SIGTERM} to the
child process.

On Windows the Win32 API function @code{TerminateProcess()} is
called to stop the child process.
@end deffn

@geindex kill() (asyncio.asyncio.subprocess.Process 方法)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process kill}@anchor{250c}
@deffn {方法} kill ()

Kill the child.

On POSIX systems this method sends @code{SIGKILL} to the child
process.

On Windows this method is an alias for @ref{250a,,terminate()}.
@end deffn

@geindex stdin (asyncio.asyncio.subprocess.Process 属性)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process stdin}@anchor{24ff}
@deffn {属性} stdin

Standard input stream (@ref{f5b,,StreamWriter}) or @code{None}
if the process was created with @code{stdin=None}.
@end deffn

@geindex stdout (asyncio.asyncio.subprocess.Process 属性)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process stdout}@anchor{2500}
@deffn {属性} stdout

Standard output stream (@ref{f5a,,StreamReader}) or @code{None}
if the process was created with @code{stdout=None}.
@end deffn

@geindex stderr (asyncio.asyncio.subprocess.Process 属性)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process stderr}@anchor{2501}
@deffn {属性} stderr

Standard error stream (@ref{f5a,,StreamReader}) or @code{None}
if the process was created with @code{stderr=None}.
@end deffn

@cartouche
@quotation 警告 
Use the @ref{2505,,communicate()} method rather than
@ref{24ff,,process.stdin.write()},
@ref{2500,,await process.stdout.read()} or
@ref{2501,,await process.stderr.read}.
This avoids deadlocks due to streams pausing reading or writing
and blocking the child process.
@end quotation
@end cartouche

@geindex pid (asyncio.asyncio.subprocess.Process 属性)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process pid}@anchor{250d}
@deffn {属性} pid

Process identification number (PID).

Note that for processes created by the @ref{292,,create_subprocess_shell()}
function, this attribute is the PID of the spawned shell.
@end deffn

@geindex returncode (asyncio.asyncio.subprocess.Process 属性)
@anchor{library/asyncio-subprocess asyncio asyncio subprocess Process returncode}@anchor{2508}
@deffn {属性} returncode

Return code of the process when it exits.

A @code{None} value indicates that the process has not terminated yet.

一个负值 @code{-N} 表示子进程被信号 @code{N} 中断 (仅 POSIX).
@end deffn
@end deffn

@menu
* Subprocess and Threads:: 
* 例子: 例子<12>. 

@end menu

@node Subprocess and Threads,例子<12>,,Interacting with Subprocesses
@anchor{library/asyncio-subprocess asyncio-subprocess-threads}@anchor{2507}@anchor{library/asyncio-subprocess subprocess-and-threads}@anchor{250e}
@subsubsection Subprocess and Threads


Standard asyncio event loop supports running subprocesses from different threads by
default.

On Windows subprocesses are provided by @ref{1ab,,ProactorEventLoop} only (default),
@ref{250f,,SelectorEventLoop} has no subprocess support.

On UNIX @emph{child watchers} are used for subprocess finish waiting, see
@ref{2510,,进程监视器} for more info.


在 3.8 版更改: UNIX switched to use @ref{2511,,ThreadedChildWatcher} for spawning subprocesses from
different threads without any limitation.

使用 @emph{不活动的} 当前子监视器生成子进程将引发 @ref{2ba,,RuntimeError}。


Note that alternative event loop implementations might have own limitations;
please refer to their documentation.


@subsubheading 参见


The @ref{24a1,,Concurrency and multithreading in asyncio} section.


@node 例子<12>,,Subprocess and Threads,Interacting with Subprocesses
@anchor{library/asyncio-subprocess examples}@anchor{24f4}
@subsubsection 例子


An example using the @ref{24f6,,Process} class to
control a subprocess and the @ref{f5a,,StreamReader} class to read from
its standard output.
@anchor{library/asyncio-subprocess asyncio-example-create-subprocess-exec}@anchor{2512}
The subprocess is created by the @ref{291,,create_subprocess_exec()}
function:

@example
import asyncio
import sys

async def get_date():
    code = 'import datetime; print(datetime.datetime.now())'

    # Create the subprocess; redirect the standard output
    # into a pipe.
    proc = await asyncio.create_subprocess_exec(
        sys.executable, '-c', code,
        stdout=asyncio.subprocess.PIPE)

    # Read one line of output.
    data = await proc.stdout.readline()
    line = data.decode('ascii').rstrip()

    # Wait for the subprocess exit.
    await proc.wait()
    return line

date = asyncio.run(get_date())
print(f"Current date: @{date@}")
@end example

See also the @ref{2513,,same example}
written using low-level APIs.

@node 队列集,异常<9>,子进程集,asyncio --- 异步 I/O
@anchor{library/asyncio-queue doc}@anchor{2514}@anchor{library/asyncio-queue asyncio-queues}@anchor{2486}@anchor{library/asyncio-queue queues}@anchor{2515}
@subsubsection 队列集


@strong{源代码:} Lib/asyncio/queues.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/queues.py}


__________________________________________________________________


asyncio 队列被设计成与 @ref{da,,queue} 模块类似。尽管 asyncio队列不是线程安全的，但是他们是被设计专用于 async/await 代码。

注意asyncio 的队列没有 @emph{timeout} 形参；请使用 @ref{288,,asyncio.wait_for()} 函数为队列添加超时操作。

参见下面的 @ref{2516,,Examples} 部分。

@menu
* Queue:: 
* 优先级队列:: 
* 后进先出队列:: 
* 异常: 异常<8>. 
* 例子: 例子<13>. 

@end menu

@node Queue,优先级队列,,队列集
@anchor{library/asyncio-queue queue}@anchor{2517}
@subsubsection Queue


@geindex Queue (asyncio 中的类)
@anchor{library/asyncio-queue asyncio Queue}@anchor{290}
@deffn {类} asyncio.Queue (maxsize=0, *, loop=None)

先进，先出（FIFO）队列

如果 @emph{maxsize} 小于等于零，则队列尺寸是无限的。如果是大于 @code{0} 的整数，则当队列达到 @emph{maxsize} 时， @code{await put()} 将阻塞至某个元素被 @ref{2518,,get()} 取出。

不像标准库中的并发型 @ref{da,,queue} ，队列的尺寸一直是已知的，可以通过调用 @ref{2519,,qsize()} 方法返回。


Deprecated since version 3.8, will be removed in version 3.10: @emph{loop} 形参。


这个类不是线程安全的（@ref{24a1,,not thread safe}）。

@geindex maxsize (asyncio.Queue 属性)
@anchor{library/asyncio-queue asyncio Queue maxsize}@anchor{251a}
@deffn {属性} maxsize

队列中可存放的元素数量。
@end deffn

@geindex empty() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue empty}@anchor{251b}
@deffn {方法} empty ()

如果队列为空返回 @code{True} ，否则返回 @code{False} 。
@end deffn

@geindex full() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue full}@anchor{251c}
@deffn {方法} full ()

如果有 @ref{251a,,maxsize} 个条目在队列中，则返回 @code{True} 。

如果队列用 @code{maxsize=0} （默认）初始化，则 @ref{251c,,full()} 永远不会返回 @code{True} 。
@end deffn

@geindex get() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue get}@anchor{2518}
@deffn {方法} coroutine get ()

从队列中删除并返回一个元素。如果队列为空，则等待，直到队列中有元素。
@end deffn

@geindex get_nowait() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue get_nowait}@anchor{251d}
@deffn {方法} get_nowait ()

立即返回一个队列中的元素，如果队列内有值，否则引发异常  @ref{251e,,QueueEmpty} 。
@end deffn

@geindex join() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue join}@anchor{699}
@deffn {方法} coroutine join ()

阻塞至队列中所有的元素都被接收和处理完毕。

当条目添加到队列的时候，未完成任务的计数就会增加。每当消费协程调用 @ref{69a,,task_done()} 表示这个条目已经被回收，该条目所有工作已经完成，未完成计数就会减少。当未完成计数降到零的时候， @ref{699,,join()} 阻塞被解除。
@end deffn

@geindex put() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue put}@anchor{251f}
@deffn {方法} coroutine put (item)

添加一个元素进队列。如果队列满了，在添加元素之前，会一直等待空闲插槽可用。
@end deffn

@geindex put_nowait() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue put_nowait}@anchor{2520}
@deffn {方法} put_nowait (item)

不阻塞的放一个元素入队列。

如果没有立即可用的空闲槽，引发 @ref{2521,,QueueFull} 异常。
@end deffn

@geindex qsize() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue qsize}@anchor{2519}
@deffn {方法} qsize ()

返回队列用的元素数量。
@end deffn

@geindex task_done() (asyncio.Queue 方法)
@anchor{library/asyncio-queue asyncio Queue task_done}@anchor{69a}
@deffn {方法} task_done ()

表明前面排队的任务已经完成，即get出来的元素相关操作已经完成。

由队列使用者控制。每个 @ref{2518,,get()} 用于获取一个任务，任务最后调用 @ref{69a,,task_done()} 告诉队列，这个任务已经完成。

如果 @ref{699,,join()} 当前正在阻塞，在所有条目都被处理后，将解除阻塞(意味着每个 @ref{251f,,put()} 进队列的条目的 @ref{69a,,task_done()} 都被收到)。

如果被调用的次数多于放入队列中的项目数量，将引发 @ref{1fb,,ValueError} 。
@end deffn
@end deffn

@node 优先级队列,后进先出队列,Queue,队列集
@anchor{library/asyncio-queue priority-queue}@anchor{2522}
@subsubsection 优先级队列


@geindex PriorityQueue (asyncio 中的类)
@anchor{library/asyncio-queue asyncio PriorityQueue}@anchor{2523}
@deffn {类} asyncio.PriorityQueue

@ref{290,,Queue} 的变体；按优先级顺序取出条目 (最小的先取出)。

条目通常是 @code{(priority_number, data)} 形式的元组。
@end deffn

@node 后进先出队列,异常<8>,优先级队列,队列集
@anchor{library/asyncio-queue lifo-queue}@anchor{2524}
@subsubsection 后进先出队列


@geindex LifoQueue (asyncio 中的类)
@anchor{library/asyncio-queue asyncio LifoQueue}@anchor{2525}
@deffn {类} asyncio.LifoQueue

@ref{290,,Queue} 的变体，先取出最近添加的条目（后进，先出）。
@end deffn

@node 异常<8>,例子<13>,后进先出队列,队列集
@anchor{library/asyncio-queue exceptions}@anchor{2526}
@subsubsection 异常


@geindex QueueEmpty
@anchor{library/asyncio-queue asyncio QueueEmpty}@anchor{251e}
@deffn {例外} asyncio.QueueEmpty

当队列为空的时候，调用 @ref{251d,,get_nowait()} 方法而引发这个异常。
@end deffn

@geindex QueueFull
@anchor{library/asyncio-queue asyncio QueueFull}@anchor{2521}
@deffn {例外} asyncio.QueueFull

当队列中条目数量已经达到它的 @emph{maxsize} 的时候，调用 @ref{2520,,put_nowait()} 方法而引发的异常。
@end deffn

@node 例子<13>,,异常<8>,队列集
@anchor{library/asyncio-queue examples}@anchor{2516}
@subsubsection 例子

@anchor{library/asyncio-queue asyncio-example-queue-dist}@anchor{2527}
队列能被用于多个的并发任务的工作量分配：

@example
import asyncio
import random
import time


async def worker(name, queue):
    while True:
        # Get a "work item" out of the queue.
        sleep_for = await queue.get()

        # Sleep for the "sleep_for" seconds.
        await asyncio.sleep(sleep_for)

        # Notify the queue that the "work item" has been processed.
        queue.task_done()

        print(f'@{name@} has slept for @{sleep_for:.2f@} seconds')


async def main():
    # Create a queue that we will use to store our "workload".
    queue = asyncio.Queue()

    # Generate random timings and put them into the queue.
    total_sleep_time = 0
    for _ in range(20):
        sleep_for = random.uniform(0.05, 1.0)
        total_sleep_time += sleep_for
        queue.put_nowait(sleep_for)

    # Create three worker tasks to process the queue concurrently.
    tasks = []
    for i in range(3):
        task = asyncio.create_task(worker(f'worker-@{i@}', queue))
        tasks.append(task)

    # Wait until the queue is fully processed.
    started_at = time.monotonic()
    await queue.join()
    total_slept_for = time.monotonic() - started_at

    # Cancel our worker tasks.
    for task in tasks:
        task.cancel()
    # Wait until all worker tasks are cancelled.
    await asyncio.gather(*tasks, return_exceptions=True)

    print('====')
    print(f'3 workers slept in parallel for @{total_slept_for:.2f@} seconds')
    print(f'total expected sleep time: @{total_sleep_time:.2f@} seconds')


asyncio.run(main())
@end example

@node 异常<9>,事件循环,队列集,asyncio --- 异步 I/O
@anchor{library/asyncio-exceptions doc}@anchor{2528}@anchor{library/asyncio-exceptions asyncio-exceptions}@anchor{2529}@anchor{library/asyncio-exceptions exceptions}@anchor{252a}
@subsubsection 异常


@strong{源代码:} Lib/asyncio/exceptions.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/exceptions.py}


__________________________________________________________________


@geindex TimeoutError
@anchor{library/asyncio-exceptions asyncio TimeoutError}@anchor{249c}
@deffn {例外} asyncio.TimeoutError

该操作已超过规定的截止日期。

@cartouche
@quotation 重要 
这个异常与内置 @ref{996,,TimeoutError} 异常不同。
@end quotation
@end cartouche
@end deffn

@geindex CancelledError
@anchor{library/asyncio-exceptions asyncio CancelledError}@anchor{1a7}
@deffn {例外} asyncio.CancelledError

该操作已被取消。

取消asyncio任务时，可以捕获此异常以执行自定义操作。在几乎所有情况下，都必须重新引发异常。


在 3.8 版更改: @ref{1a7,,CancelledError} 现在是 @ref{1a8,,BaseException} 的子类。

@end deffn

@geindex InvalidStateError
@anchor{library/asyncio-exceptions asyncio InvalidStateError}@anchor{24ab}
@deffn {例外} asyncio.InvalidStateError

@ref{1ad,,Task} 或 @ref{43d,,Future} 的内部状态无效。

在为已设置结果值的未来对象设置结果值等情况下，可以引发此问题。
@end deffn

@geindex SendfileNotAvailableError
@anchor{library/asyncio-exceptions asyncio SendfileNotAvailableError}@anchor{252b}
@deffn {例外} asyncio.SendfileNotAvailableError

"sendfile" 系统调用不适用于给定的套接字或文件类型。

子类 @ref{2ba,,RuntimeError} 。
@end deffn

@geindex IncompleteReadError
@anchor{library/asyncio-exceptions asyncio IncompleteReadError}@anchor{24bf}
@deffn {例外} asyncio.IncompleteReadError

请求的读取操作未完全完成。

由 @ref{2484,,asyncio stream APIs} 提出

此异常是 @ref{c65,,EOFError} 的子类。

@geindex expected (asyncio.IncompleteReadError 属性)
@anchor{library/asyncio-exceptions asyncio IncompleteReadError expected}@anchor{252c}
@deffn {属性} expected

预期字节的总数（ @ref{184,,int} ）。
@end deffn

@geindex partial (asyncio.IncompleteReadError 属性)
@anchor{library/asyncio-exceptions asyncio IncompleteReadError partial}@anchor{24c0}
@deffn {属性} partial

到达流结束之前读取的 @ref{32a,,bytes} 字符串。
@end deffn
@end deffn

@geindex LimitOverrunError
@anchor{library/asyncio-exceptions asyncio LimitOverrunError}@anchor{24c1}
@deffn {例外} asyncio.LimitOverrunError

在查找分隔符时达到缓冲区大小限制。

由 @ref{2484,,asyncio stream APIs} 提出

@geindex consumed (asyncio.LimitOverrunError 属性)
@anchor{library/asyncio-exceptions asyncio LimitOverrunError consumed}@anchor{252d}
@deffn {属性} consumed

要消耗的字节总数。
@end deffn
@end deffn

@node 事件循环,Futures,异常<9>,asyncio --- 异步 I/O
@anchor{library/asyncio-eventloop doc}@anchor{252e}@anchor{library/asyncio-eventloop event-loop}@anchor{252f}
@subsubsection 事件循环


@strong{Source code:} Lib/asyncio/events.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/events.py},
Lib/asyncio/base_events.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/base_events.py}


__________________________________________________________________


@subsubheading 前言


事件循环是每个 asyncio 应用的核心。 事件循环会运行异步任务和回调，执行网络 IO 操作，以及运行子进程。

应用开发者通常应当使用高层级的 asyncio 函数，例如 @ref{1a5,,asyncio.run()}，应当很少有必要引用循环对象或调用其方法。 本节所针对的主要是低层级代码、库和框架的编写者，他们需要更细致地控制事件循环行为。

@subsubheading 获取事件循环


以下低层级函数可被用于获取、设置或创建事件循环:

@geindex get_running_loop() (在 asyncio 模块中)
@anchor{library/asyncio-eventloop asyncio get_running_loop}@anchor{34d}
@deffn {函数} asyncio.get_running_loop ()

返回当前 OS 线程中正在运行的事件循环。

如果没有正在运行的事件循环则会引发 @ref{2ba,,RuntimeError}。 此函数只能由协程或回调来调用。


3.7 新版功能.

@end deffn

@geindex get_event_loop() (在 asyncio 模块中)
@anchor{library/asyncio-eventloop asyncio get_event_loop}@anchor{34e}
@deffn {函数} asyncio.get_event_loop ()

Get the current event loop.

If there is no current event loop set in the current OS thread,
the OS thread is main, and @ref{2530,,set_event_loop()} has not yet
been called, asyncio will create a new event loop and set it as the
current one.

由于此函数具有相当复杂的行为（特别是在使用了自定义事件循环策略的时候），更推荐在协程和回调中使用 @ref{34d,,get_running_loop()} 函数而非 @ref{34e,,get_event_loop()}。

应该考虑使用 @ref{1a5,,asyncio.run()} 函数而非使用低层级函数来手动创建和关闭事件循环。
@end deffn

@geindex set_event_loop() (在 asyncio 模块中)
@anchor{library/asyncio-eventloop asyncio set_event_loop}@anchor{2530}
@deffn {函数} asyncio.set_event_loop (loop)

将 @emph{loop} 设置为当前 OS 线程的当前事件循环。
@end deffn

@geindex new_event_loop() (在 asyncio 模块中)
@anchor{library/asyncio-eventloop asyncio new_event_loop}@anchor{2531}
@deffn {函数} asyncio.new_event_loop ()

创建一个新的事件循环。
@end deffn

请注意 @ref{34e,,get_event_loop()}, @ref{2530,,set_event_loop()} 以及 @ref{2531,,new_event_loop()} 函数的行为可以通过 @ref{2532,,设置自定义事件循环策略} 来改变。

@subsubheading 目录


本文档包含下列小节:


@itemize *

@item 
@ref{2533,,事件循环方法集} 章节是事件循环APIs的参考文档；

@item 
@ref{2534,,回调处理} 章节是从调度方法 例如 @ref{342,,loop.call_soon()}  和 @ref{344,,loop.call_later()} 中返回 @ref{1035,,Handle} 和 @ref{2535,,TimerHandle} 实例的文档。

@item 
@ref{2536,,Server Objects} 章节记录了从事件循环方法返回的类型，比如 @ref{356,,loop.create_server()} ；

@item 
@ref{2537,,Event Loop Implementations} 章节记录了 @ref{250f,,SelectorEventLoop} 和 @ref{1ab,,ProactorEventLoop} 类；

@item 
@ref{2538,,Examples} 章节展示了如何使用某些事件循环API。
@end itemize

@menu
* 事件循环方法集:: 
* 回调处理:: 
* Server Objects:: 
* 事件循环实现:: 
* 例子: 例子<14>. 

@end menu

@node 事件循环方法集,回调处理,,事件循环
@anchor{library/asyncio-eventloop asyncio-event-loop}@anchor{63e}@anchor{library/asyncio-eventloop event-loop-methods}@anchor{2533}
@subsubsection 事件循环方法集


事件循环有下列 @strong{低级} APIs：

@menu
* 运行和停止循环:: 
* 调度回调:: 
* 调度延迟回调:: 
* 创建 Futures 和 Tasks:: 
* 打开网络连接:: 
* 创建网络服务:: 
* 传输文件:: 
* TLS 升级:: 
* 监控文件描述符:: 
* 直接使用 socket 对象:: 
* DNS:: 
* 使用管道:: 
* Unix 信号:: 
* 在线程或者进程池中执行代码。:: 
* 错误处理API:: 
* 开启调试模式:: 
* 运行子进程:: 

@end menu

@node 运行和停止循环,调度回调,,事件循环方法集
@anchor{library/asyncio-eventloop running-and-stopping-the-loop}@anchor{2539}
@subsubsection 运行和停止循环


@geindex run_until_complete() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop run_until_complete}@anchor{512}
@deffn {方法} loop.run_until_complete (future)

运行直到 @emph{future} (  @ref{43d,,Future} 的实例 ) 被完成。

如果参数是 @ref{2483,,coroutine object} ，将被隐式调度为 @ref{1ad,,asyncio.Task} 来运行。

返回 Future 的结果 或者引发相关异常。
@end deffn

@geindex run_forever() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop run_forever}@anchor{253a}
@deffn {方法} loop.run_forever ()

运行事件循环直到 @ref{51a,,stop()} 被调用。

If @ref{51a,,stop()} is called before @ref{253a,,run_forever()} is called,
the loop will poll the I/O selector once with a timeout of zero,
run all callbacks scheduled in response to I/O events (and
those that were already scheduled), and then exit.

If @ref{51a,,stop()} is called while @ref{253a,,run_forever()} is running,
the loop will run the current batch of callbacks and then exit.
Note that new callbacks scheduled by callbacks will not run in this
case; instead, they will run the next time @ref{253a,,run_forever()} or
@ref{512,,run_until_complete()} is called.
@end deffn

@geindex stop() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop stop}@anchor{51a}
@deffn {方法} loop.stop ()

停止事件循环。
@end deffn

@geindex is_running() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop is_running}@anchor{253b}
@deffn {方法} loop.is_running ()

返回 @code{True} 如果事件循环当前正在运行。
@end deffn

@geindex is_closed() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop is_closed}@anchor{695}
@deffn {方法} loop.is_closed ()

如果事件循环已经被关闭，返回 @code{True} 。
@end deffn

@geindex close() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop close}@anchor{253c}
@deffn {方法} loop.close ()

关闭事件循环。

当这个函数被调用的时候，循环必须处于非运行状态。pending状态的回调将被丢弃。

此方法清除所有的队列并立即关闭执行器，不会等待执行器完成。

这个方法是幂等的和不可逆的。事件循环关闭后，不应调用其他方法。
@end deffn

@geindex shutdown_asyncgens() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop shutdown_asyncgens}@anchor{51b}
@deffn {方法} coroutine loop.shutdown_asyncgens ()

Schedule all currently open @ref{149c,,asynchronous generator} objects to
close with an @ref{14a4,,aclose()} call.  After calling this method,
the event loop will issue a warning if a new asynchronous generator
is iterated. This should be used to reliably finalize all scheduled
asynchronous generators.

运行请注意，当使用 @ref{1a5,,asyncio.run()} 时，无需调用此函数。

示例:

@example
try:
    loop.run_forever()
finally:
    loop.run_until_complete(loop.shutdown_asyncgens())
    loop.close()
@end example


3.6 新版功能.

@end deffn

@node 调度回调,调度延迟回调,运行和停止循环,事件循环方法集
@anchor{library/asyncio-eventloop scheduling-callbacks}@anchor{253d}
@subsubsection 调度回调


@geindex call_soon() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop call_soon}@anchor{342}
@deffn {方法} loop.call_soon (callback, *args, context=None)

Schedule the @emph{callback} @ref{253e,,callback} to be called with
@emph{args} arguments at the next iteration of the event loop.

回调按其注册顺序被调用。每个回调仅被调用一次。

可选键值类的参数 @emph{context} 允许 @emph{callback} 运行在一个指定的自定义 @ref{246c,,contextvars.Context} 对象中。如果没有提供 @emph{context} ，则使用当前上下文。

返回一个能用来取消回调的 @ref{1035,,asyncio.Handle} 实例。

这个方法不是线程安全的。
@end deffn

@geindex call_soon_threadsafe() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop call_soon_threadsafe}@anchor{343}
@deffn {方法} loop.call_soon_threadsafe (callback, *args, context=None)

@ref{342,,call_soon()} 的线程安全变体。必须被用于安排 @emph{来自其他线程} 的回调。

参见 @ref{24a1,,concurrency and multithreading} 部分的文档。
@end deffn


在 3.7 版更改: 加入键值类形参  @emph{context}。请参阅 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} 查看更多细节。

@anchor{library/asyncio-eventloop asyncio-pass-keywords}@anchor{253f}
@cartouche
@quotation 注解 
大多数 @ref{a,,asyncio} 的调度函数不让传递关键字参数。为此，请使用 @ref{7c2,,functools.partial()} ：

@example
# will schedule "print("Hello", flush=True)"
loop.call_soon(
    functools.partial(print, "Hello", flush=True))
@end example

使用 partial 对象通常比使用lambda更方便，asyncio 在调试和错误消息中能更好的呈现 partial 对象。
@end quotation
@end cartouche

@node 调度延迟回调,创建 Futures 和 Tasks,调度回调,事件循环方法集
@anchor{library/asyncio-eventloop asyncio-delayed-calls}@anchor{2540}@anchor{library/asyncio-eventloop scheduling-delayed-callbacks}@anchor{2541}
@subsubsection 调度延迟回调


事件循环提供安排调度函数在将来某个时刻调用的机制。事件循环使用单调时钟来跟踪时间。

@geindex call_later() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop call_later}@anchor{344}
@deffn {方法} loop.call_later (delay, callback, *args, context=None)

安排 @emph{callback} 在给定的 @emph{delay} 秒（可以是 int 或者 float）后被调用。

返回一个 @ref{2535,,asyncio.TimerHandle} 实例，该实例能用于取消回调。

@emph{callback} 只被调用一次。如果两个回调被安排在同样的时间点，执行顺序未限定。

可选的位置参数 @emph{args} 在被调用的时候传递给  @emph{callback}  。 如果你想把关键字参数传递给 @emph{callback} ，请使用 @ref{7c2,,functools.partial()} 。

可选键值类的参数 @emph{context} 允许 @emph{callback} 运行在一个指定的自定义 @ref{246c,,contextvars.Context} 对象中。如果没有提供 @emph{context} ，则使用当前上下文。


在 3.7 版更改: 加入键值类形参  @emph{context}。请参阅 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} 查看更多细节。



在 3.8 版更改: In Python 3.7 and earlier with the default event loop implementation,
the @emph{delay} could not exceed one day.
This has been fixed in Python 3.8.

@end deffn

@geindex call_at() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop call_at}@anchor{345}
@deffn {方法} loop.call_at (when, callback, *args, context=None)

安排 @emph{callback} 在给定的绝对时间戳的 @emph{时间} （一个 int 或者 float）被调用，使用与 @ref{2542,,loop.time()} 同样的时间参考。

本方法的行为和 @ref{344,,call_later()} 方法相同。

返回一个 @ref{2535,,asyncio.TimerHandle} 实例，该实例能用于取消回调。


在 3.7 版更改: 加入键值类形参  @emph{context}。请参阅 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} 查看更多细节。



在 3.8 版更改: In Python 3.7 and earlier with the default event loop implementation,
the difference between @emph{when} and the current time could not exceed
one day.  This has been fixed in Python 3.8.

@end deffn

@geindex time() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop time}@anchor{2542}
@deffn {方法} loop.time ()

根据时间循环内部的单调时钟，返回当前时间， @ref{187,,float} 值。
@end deffn

@cartouche
@quotation 注解 

在 3.8 版更改: In Python 3.7 and earlier timeouts (relative @emph{delay} or absolute @emph{when})
should not exceed one day.  This has been fixed in Python 3.8.

@end quotation
@end cartouche


@subsubheading 参见


@ref{285,,asyncio.sleep()} 函数。


@node 创建 Futures 和 Tasks,打开网络连接,调度延迟回调,事件循环方法集
@anchor{library/asyncio-eventloop creating-futures-and-tasks}@anchor{2543}
@subsubsection 创建 Futures 和 Tasks


@geindex create_future() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop create_future}@anchor{516}
@deffn {方法} loop.create_future ()

创建一个附加到事件循环中的 @ref{43d,,asyncio.Future} 对象。

这是在asyncio中创建Futures的首选方式。这让第三方事件循环可以提供Future 对象的替代实现(更好的性能或者功能)。


3.5.2 新版功能.

@end deffn

@geindex create_task() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop create_task}@anchor{1af}
@deffn {方法} loop.create_task (coro, *, name=None)

安排一个 @ref{2483,,协程} 的执行。返回一个  @ref{1ad,,Task}  对象。

第三方的事件循环可以使用它们自己的 @ref{1ad,,Task} 子类来满足互操作性。这种情况下结果类型是一个 @ref{1ad,,Task} 的子类。

If the @emph{name} argument is provided and not @code{None}, it is set as
the name of the task using @ref{1b0,,Task.set_name()}.


在 3.8 版更改: 添加了 @code{name} 形参。

@end deffn

@geindex set_task_factory() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop set_task_factory}@anchor{697}
@deffn {方法} loop.set_task_factory (factory)

设置一个 task 工厂 ， 被用于  @ref{1af,,loop.create_task()} 。

If @emph{factory} is @code{None} the default task factory will be set.
Otherwise, @emph{factory} must be a @emph{callable} with the signature matching
@code{(loop, coro)}, where @emph{loop} is a reference to the active
event loop, and @emph{coro} is a coroutine object.  The callable
must return a @ref{43d,,asyncio.Future}-compatible object.
@end deffn

@geindex get_task_factory() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop get_task_factory}@anchor{698}
@deffn {方法} loop.get_task_factory ()

Return a task factory or @code{None} if the default one is in use.
@end deffn

@node 打开网络连接,创建网络服务,创建 Futures 和 Tasks,事件循环方法集
@anchor{library/asyncio-eventloop opening-network-connections}@anchor{2544}
@subsubsection 打开网络连接


@geindex create_connection() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop create_connection}@anchor{1b2}
@deffn {方法} coroutine loop.create_connection (protocol_factory, host=None, port=None, *, ssl=None, family=0, proto=0, flags=0, sock=None, local_addr=None, server_hostname=None, ssl_handshake_timeout=None, happy_eyeballs_delay=None, interleave=None)

Open a streaming transport connection to a given
address specified by @emph{host} and @emph{port}.

The socket family can be either @ref{2545,,AF_INET} or
@ref{2546,,AF_INET6} depending on @emph{host} (or the @emph{family}
argument, if provided).

The socket type will be @ref{c83,,SOCK_STREAM}.

@emph{protocol_factory} must be a callable returning an
@ref{2547,,asyncio protocol} implementation.

这个方法会尝试在后台创建连接。当创建成功，返回 @code{(transport, protocol)} 组合。

底层操作的大致的执行顺序是这样的：


@enumerate 

@item 
The connection is established and a @ref{2548,,transport}
is created for it.

@item 
@emph{protocol_factory} is called without arguments and is expected to
return a @ref{2547,,protocol} instance.

@item 
The protocol instance is coupled with the transport by calling its
@ref{2549,,connection_made()} method.

@item 
成功时返回一个 @code{(transport, protocol)} 元组。
@end enumerate

被创建的传输对象是一个实现相关的双向流。

其他参数：


@itemize *

@item 
@emph{ssl}: if given and not false, a SSL/TLS transport is created
(by default a plain TCP transport is created).  If @emph{ssl} is
a @ref{3dc,,ssl.SSLContext} object, this context is used to create
the transport; if @emph{ssl} is @ref{494,,True}, a default context returned
from @ref{8bb,,ssl.create_default_context()} is used.


@subsubheading 参见


@ref{254a,,SSL/TLS security considerations}


@item 
@emph{server_hostname} sets or overrides the hostname that the target
server's certificate will be matched against.  Should only be passed
if @emph{ssl} is not @code{None}.  By default the value of the @emph{host} argument
is used.  If @emph{host} is empty, there is no default and you must pass a
value for @emph{server_hostname}.  If @emph{server_hostname} is an empty
string, hostname matching is disabled (which is a serious security
risk, allowing for potential man-in-the-middle attacks).

@item 
@emph{family}, @emph{proto}, @emph{flags}  是可选的地址族、协议和标志，它们会被传递给 getaddrinfo() 来对 @emph{host} 进行解析。如果要指定的话，这些都应该是来自于 @ref{ef,,socket} 模块的对应常量。

@item 
@emph{happy_eyeballs_delay}, if given, enables Happy Eyeballs for this
connection. It should
be a floating-point number representing the amount of time in seconds
to wait for a connection attempt to complete, before starting the next
attempt in parallel. This is the "Connection Attempt Delay" as defined
in 
@geindex RFC; RFC 8305
RFC 8305@footnote{https://tools.ietf.org/html/rfc8305.html}. A sensible default value recommended by the RFC is @code{0.25}
(250 milliseconds).

@item 
@emph{interleave} controls address reordering when a host name resolves to
multiple IP addresses.
If @code{0} or unspecified, no reordering is done, and addresses are
tried in the order returned by @ref{49c,,getaddrinfo()}. If a positive integer
is specified, the addresses are interleaved by address family, and the
given integer is interpreted as "First Address Family Count" as defined
in 
@geindex RFC; RFC 8305
RFC 8305@footnote{https://tools.ietf.org/html/rfc8305.html}. The default is @code{0} if @emph{happy_eyeballs_delay} is not
specified, and @code{1} if it is.

@item 
@emph{sock}, if given, should be an existing, already connected
@ref{66e,,socket.socket} object to be used by the transport.
If @emph{sock} is given, none of @emph{host}, @emph{port}, @emph{family}, @emph{proto}, @emph{flags},
@emph{happy_eyeballs_delay}, @emph{interleave}
and @emph{local_addr} should be specified.

@item 
@emph{local_addr}, if given, is a @code{(local_host, local_port)} tuple used
to bind the socket to locally.  The @emph{local_host} and @emph{local_port}
are looked up using @code{getaddrinfo()}, similarly to @emph{host} and @emph{port}.

@item 
@emph{ssl_handshake_timeout} is (for a TLS connection) the time in seconds
to wait for the TLS handshake to complete before aborting the connection.
@code{60.0} seconds if @code{None} (default).
@end itemize


3.8 新版功能: Added the @emph{happy_eyeballs_delay} and @emph{interleave} parameters.

Happy Eyeballs Algorithm: Success with Dual-Stack Hosts.
When a server's IPv4 path and protocol are working, but the server's
IPv6 path and protocol are not working, a dual-stack client
application experiences significant connection delay compared to an
IPv4-only client.  This is undesirable because it causes the dual-
stack client to have a worse user experience.  This document
specifies requirements for algorithms that reduce this user-visible
delay and provides an algorithm.

For more information: @indicateurl{https://tools.ietf.org/html/rfc6555}



3.7 新版功能: @emph{ssl_handshake_timeout} 形参。



在 3.6 版更改: The socket option @code{TCP_NODELAY} is set by default
for all TCP connections.



在 3.5 版更改: @ref{1ab,,ProactorEventLoop} 类中添加 SSL/TLS 支持。



@subsubheading 参见


The @ref{35c,,open_connection()} function is a high-level alternative
API.  It returns a pair of (@ref{f5a,,StreamReader}, @ref{f5b,,StreamWriter})
that can be used directly in async/await code.

@end deffn

@geindex create_datagram_endpoint() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop create_datagram_endpoint}@anchor{2e7}
@deffn {方法} coroutine loop.create_datagram_endpoint (protocol_factory, local_addr=None, remote_addr=None, *, family=0, proto=0, flags=0, reuse_address=None, reuse_port=None, allow_broadcast=None, sock=None)

@cartouche
@quotation 注解 
形参 @emph{reuse_address} 已不再受支持，因为使用 @code{SO_REUSEADDR} 会对 UDP 造成显著的安全问题。 显式地传入 @code{reuse_address=True} 将会引发异常。

When multiple processes with differing UIDs assign sockets to an
identical UDP socket address with @code{SO_REUSEADDR}, incoming packets can
become randomly distributed among the sockets.

对于受支持的平台，@emph{reuse_port} 可以被用作类似功能的替代。 通过 @emph{reuse_port} 将改用 @code{SO_REUSEPORT}，它能够防止具有不同 UID 的进程将套接字赋给相同的套接字地址。
@end quotation
@end cartouche

创建一个数据报连接。

The socket family can be either @ref{2545,,AF_INET},
@ref{2546,,AF_INET6}, or @ref{254b,,AF_UNIX},
depending on @emph{host} (or the @emph{family} argument, if provided).

socket类型将是 @ref{c82,,SOCK_DGRAM} 。

@emph{protocol_factory} must be a callable returning a
@ref{2547,,protocol} implementation.

A tuple of @code{(transport, protocol)} is returned on success.

其他参数：


@itemize *

@item 
@emph{local_addr}，如果指定的话，就是一个 @code{(local_host, local_port)} 元组，用于在本地绑定套接字。 @emph{local_host} 和 @emph{local_port} 是使用 @ref{49c,,getaddrinfo()} 来查找的。

@item 
@emph{remote_addr}，如果指定的话，就是一个 @code{(remote_host, remote_port)} 元组，用于同一个远程地址连接。@emph{remote_host} 和 @emph{remote_port} 是使用 @ref{49c,,getaddrinfo()} 来查找的。

@item 
@emph{family}, @emph{proto}, @emph{flags} 是可选的地址族，协议和标志，其会被传递给 @ref{49c,,getaddrinfo()} 来完成 @emph{host} 的解析。如果要指定的话，这些都应该是来自于 @ref{ef,,socket} 模块的对应常量。

@item 
@emph{reuse_port} tells the kernel to allow this endpoint to be bound to the
same port as other existing endpoints are bound to, so long as they all
set this flag when being created. This option is not supported on Windows
and some Unixes. If the @code{SO_REUSEPORT} constant is not
defined then this capability is unsupported.

@item 
@emph{allow_broadcast} 告知内核允许此端点向广播地址发送消息。

@item 
@emph{sock} 可选择通过指定此值用于使用一个预先存在的，已经处于连接状态的 @ref{66e,,socket.socket} 对象，并将其提供给此传输对象使用。如果指定了这个值， @emph{local_addr} 和 @emph{remote_addr} 就应该被忽略 (必须为 @ref{157,,None})。
@end itemize

参见 @ref{254c,,UDP echo 客户端协议}  和 @ref{254d,,UDP echo 服务端协议} 的例子。


在 3.4.4 版更改: 添加了 @emph{family}, @emph{proto}, @emph{flags}, @emph{reuse_address}, @emph{reuse_port}, @emph{allow_broadcast} 和 @emph{sock} 等参数。



在 3.8.1 版更改: The @emph{reuse_address} parameter is no longer supported due to security
concerns.



在 3.8 版更改: 添加WIndows的支持。

@end deffn

@geindex create_unix_connection() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop create_unix_connection}@anchor{24ba}
@deffn {方法} coroutine loop.create_unix_connection (protocol_factory, path=None, *, ssl=None, sock=None, server_hostname=None, ssl_handshake_timeout=None)

创建Unix 连接

The socket family will be @ref{254b,,AF_UNIX}; socket
type will be @ref{c83,,SOCK_STREAM}.

A tuple of @code{(transport, protocol)} is returned on success.

@emph{path} is the name of a Unix domain socket and is required,
unless a @emph{sock} parameter is specified.  Abstract Unix sockets,
@ref{329,,str}, @ref{32a,,bytes}, and @ref{201,,Path} paths are
supported.

See the documentation of the @ref{1b2,,loop.create_connection()} method
for information about arguments to this method.

@ref{12f5,,可用性}: Unix。


3.7 新版功能: @emph{ssl_handshake_timeout} 形参。



在 3.7 版更改: @emph{path} 形参现在可以是 @ref{363,,path-like object} 对象。

@end deffn

@node 创建网络服务,传输文件,打开网络连接,事件循环方法集
@anchor{library/asyncio-eventloop creating-network-servers}@anchor{254e}
@subsubsection 创建网络服务


@geindex create_server() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop create_server}@anchor{356}
@deffn {方法} coroutine loop.create_server (protocol_factory, host=None, port=None, *, family=socket.AF_UNSPEC, flags=socket.AI_PASSIVE, sock=None, backlog=100, ssl=None, reuse_address=None, reuse_port=None, ssl_handshake_timeout=None, start_serving=True)

创建TCP服务 (socket 类型 @ref{c83,,SOCK_STREAM} ) 监听 @emph{host} 地址的 @emph{port} 端口。

返回一个 @ref{355,,Server} 对象。

参数：


@itemize *

@item 
@emph{protocol_factory} must be a callable returning a
@ref{2547,,protocol} implementation.

@item 
The @emph{host} parameter can be set to several types which determine where
the server would be listening:


@itemize -

@item 
If @emph{host} is a string, the TCP server is bound to a single network
interface specified by @emph{host}.

@item 
If @emph{host} is a sequence of strings, the TCP server is bound to all
network interfaces specified by the sequence.

@item 
If @emph{host} is an empty string or @code{None}, all interfaces are
assumed and a list of multiple sockets will be returned (most likely
one for IPv4 and another one for IPv6).
@end itemize

@item 
@emph{family} can be set to either @ref{2545,,socket.AF_INET} or
@ref{2546,,AF_INET6} to force the socket to use IPv4 or IPv6.
If not set, the @emph{family} will be determined from host name
(defaults to @code{AF_UNSPEC}).

@item 
@emph{flags} 是用于 @ref{49c,,getaddrinfo()} 的位掩码。

@item 
@emph{sock} can optionally be specified in order to use a preexisting
socket object. If specified, @emph{host} and @emph{port} must not be specified.

@item 
@emph{backlog} 是传递给 @ref{745,,listen()} 的最大排队连接的数量（默认为100）。

@item 
@emph{ssl} can be set to an @ref{3dc,,SSLContext} instance to enable
TLS over the accepted connections.

@item 
@emph{reuse_address} tells the kernel to reuse a local socket in
@code{TIME_WAIT} state, without waiting for its natural timeout to
expire. If not specified will automatically be set to @code{True} on
Unix.

@item 
@emph{reuse_port} 告知内核，只要在创建的时候都设置了这个标志，就允许此端点绑定到其它端点列表所绑定的同样的端口上。这个选项在 Windows 上是不支持的。

@item 
@emph{ssl_handshake_timeout} is (for a TLS server) the time in seconds to wait
for the TLS handshake to complete before aborting the connection.
@code{60.0} seconds if @code{None} (default).

@item 
@emph{start_serving} 设置成 @code{True} (默认值) 会导致创建server并立即开始接受连接。设置成 @code{False} ，用户需要等待 @ref{358,,Server.start_serving()} 或者 @ref{359,,Server.serve_forever()} 以使server开始接受连接。
@end itemize


3.7 新版功能: Added @emph{ssl_handshake_timeout} and @emph{start_serving} parameters.



在 3.6 版更改: The socket option @code{TCP_NODELAY} is set by default
for all TCP connections.



在 3.5 版更改: @ref{1ab,,ProactorEventLoop} 类中添加 SSL/TLS 支持。



在 3.5.1 版更改: The @emph{host} parameter can be a sequence of strings.



@subsubheading 参见


The @ref{35d,,start_server()} function is a higher-level alternative API
that returns a pair of @ref{f5a,,StreamReader} and @ref{f5b,,StreamWriter}
that can be used in an async/await code.

@end deffn

@geindex create_unix_server() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop create_unix_server}@anchor{357}
@deffn {方法} coroutine loop.create_unix_server (protocol_factory, path=None, *, sock=None, backlog=100, ssl=None, ssl_handshake_timeout=None, start_serving=True)

Similar to @ref{356,,loop.create_server()} but works with the
@ref{254b,,AF_UNIX} socket family.

@emph{path} is the name of a Unix domain socket, and is required,
unless a @emph{sock} argument is provided.  Abstract Unix sockets,
@ref{329,,str}, @ref{32a,,bytes}, and @ref{201,,Path} paths
are supported.

See the documentation of the @ref{356,,loop.create_server()} method
for information about arguments to this method.

@ref{12f5,,可用性}: Unix。


3.7 新版功能: The @emph{ssl_handshake_timeout} and @emph{start_serving} parameters.



在 3.7 版更改: @emph{path} 形参现在可以是 @ref{201,,Path} 对象。

@end deffn

@geindex connect_accepted_socket() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop connect_accepted_socket}@anchor{35e}
@deffn {方法} coroutine loop.connect_accepted_socket (protocol_factory, sock, *, ssl=None, ssl_handshake_timeout=None)

Wrap an already accepted connection into a transport/protocol pair.

This method can be used by servers that accept connections outside
of asyncio but that use asyncio to handle them.

参数：


@itemize *

@item 
@emph{protocol_factory} must be a callable returning a
@ref{2547,,protocol} implementation.

@item 
@emph{sock} is a preexisting socket object returned from
@ref{66f,,socket.accept}.

@item 
@emph{ssl} 可被设置为一个 @ref{3dc,,SSLContext} 以在接受的连接上启用 SSL。

@item 
@emph{ssl_handshake_timeout} 是(为一个SSL连接)在中止连接前，等待SSL握手完成的时间【单位秒】。如果为 @code{None} (缺省) 则是 @code{60.0} 秒。
@end itemize

返回一个 @code{(transport, protocol)} 对。


3.7 新版功能: @emph{ssl_handshake_timeout} 形参。



3.5.3 新版功能.

@end deffn

@node 传输文件,TLS 升级,创建网络服务,事件循环方法集
@anchor{library/asyncio-eventloop transferring-files}@anchor{254f}
@subsubsection 传输文件


@geindex sendfile() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop sendfile}@anchor{2550}
@deffn {方法} coroutine loop.sendfile (transport, file, offset=0, count=None, *, fallback=True)

Send a @emph{file} over a @emph{transport}.  Return the total number of bytes
sent.

如果可用的化，该方法将使用高性能的 @ref{352,,os.sendfile()} 。

@emph{file} 必须是个二进制模式打开的常规文件对象。

@emph{offset} tells from where to start reading the file. If specified,
@emph{count} is the total number of bytes to transmit as opposed to
sending the file until EOF is reached. File position is always updated,
even when this method raises an error, and
@ref{1d2e,,file.tell()} can be used to obtain the actual
number of bytes sent.

@emph{fallback} set to @code{True} makes asyncio to manually read and send
the file when the platform does not support the sendfile system call
(e.g. Windows or SSL socket on Unix).

Raise @ref{252b,,SendfileNotAvailableError} if the system does not support
the @emph{sendfile} syscall and @emph{fallback} is @code{False}.


3.7 新版功能.

@end deffn

@node TLS 升级,监控文件描述符,传输文件,事件循环方法集
@anchor{library/asyncio-eventloop tls-upgrade}@anchor{2551}
@subsubsection TLS 升级


@geindex start_tls() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop start_tls}@anchor{347}
@deffn {方法} coroutine loop.start_tls (transport, protocol, sslcontext, *, server_side=False, server_hostname=None, ssl_handshake_timeout=None)

Upgrade an existing transport-based connection to TLS.

Return a new transport instance, that the @emph{protocol} must start using
immediately after the @emph{await}.  The @emph{transport} instance passed to
the @emph{start_tls} method should never be used again.

参数：


@itemize *

@item 
@emph{transport} and @emph{protocol} instances that methods like
@ref{356,,create_server()} and
@ref{1b2,,create_connection()} return.

@item 
@emph{sslcontext} ：一个已经配置好的 @ref{3dc,,SSLContext} 实例。

@item 
@emph{server_side} pass @code{True} when a server-side connection is being
upgraded (like the one created by @ref{356,,create_server()}).

@item 
@emph{server_hostname} ：设置或者覆盖目标服务器证书中相对应的主机名。

@item 
@emph{ssl_handshake_timeout} is (for a TLS connection) the time in seconds to
wait for the TLS handshake to complete before aborting the connection.
@code{60.0} seconds if @code{None} (default).
@end itemize


3.7 新版功能.

@end deffn

@node 监控文件描述符,直接使用 socket 对象,TLS 升级,事件循环方法集
@anchor{library/asyncio-eventloop watching-file-descriptors}@anchor{2552}
@subsubsection 监控文件描述符


@geindex add_reader() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop add_reader}@anchor{24d7}
@deffn {方法} loop.add_reader (fd, callback, *args)

开始监视 @emph{fd} 文件描述符以获取读取的可用性，一旦 @emph{fd} 可用于读取，使用指定的参数调用 @emph{callback} 。
@end deffn

@geindex remove_reader() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop remove_reader}@anchor{2553}
@deffn {方法} loop.remove_reader (fd)

停止对文件描述符 @emph{fd} 读取可用性的监视。
@end deffn

@geindex add_writer() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop add_writer}@anchor{2554}
@deffn {方法} loop.add_writer (fd, callback, *args)

开始监视 @emph{fd} 文件描述符的写入可用性，一旦 @emph{fd} 可用于写入，使用指定的参数调用 @emph{callback} 。

使用 @ref{7c2,,functools.partial()} @ref{253f,,传递关键字参数}  给 @emph{callback}.
@end deffn

@geindex remove_writer() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop remove_writer}@anchor{2555}
@deffn {方法} loop.remove_writer (fd)

停止对文件描述符 @emph{fd} 的写入可用性监视。
@end deffn

See also @ref{2556,,Platform Support} section
for some limitations of these methods.

@node 直接使用 socket 对象,DNS,监控文件描述符,事件循环方法集
@anchor{library/asyncio-eventloop working-with-socket-objects-directly}@anchor{2557}
@subsubsection 直接使用 socket 对象


In general, protocol implementations that use transport-based APIs
such as @ref{1b2,,loop.create_connection()} and @ref{356,,loop.create_server()}
are faster than implementations that work with sockets directly.
However, there are some use cases when performance is not critical, and
working with @ref{66e,,socket} objects directly is more
convenient.

@geindex sock_recv() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop sock_recv}@anchor{499}
@deffn {方法} coroutine loop.sock_recv (sock, nbytes)

Receive up to @emph{nbytes} from @emph{sock}.  Asynchronous version of
@ref{671,,socket.recv()}.

返回接收到的数据【bytes对象类型】。

@emph{sock} 必须是个非阻塞socket。


在 3.7 版更改: Even though this method was always documented as a coroutine
method, releases before Python 3.7 returned a @ref{43d,,Future}.
Since Python 3.7 this is an @code{async def} method.

@end deffn

@geindex sock_recv_into() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop sock_recv_into}@anchor{348}
@deffn {方法} coroutine loop.sock_recv_into (sock, buf)

Receive data from @emph{sock} into the @emph{buf} buffer.  Modeled after the blocking
@ref{cab,,socket.recv_into()} method.

返回写入缓冲区的字节数。

@emph{sock} 必须是个非阻塞socket。


3.7 新版功能.

@end deffn

@geindex sock_sendall() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop sock_sendall}@anchor{49a}
@deffn {方法} coroutine loop.sock_sendall (sock, data)

Send @emph{data} to the @emph{sock} socket. Asynchronous version of
@ref{675,,socket.sendall()}.

This method continues to send to the socket until either all data
in @emph{data} has been sent or an error occurs.  @code{None} is returned
on success.  On error, an exception is raised. Additionally, there is no way
to determine how much data, if any, was successfully processed by the
receiving end of the connection.

@emph{sock} 必须是个非阻塞socket。


在 3.7 版更改: 虽然这个方法一直被标记为协程方法。但是，Python 3.7 之前，该方法返回 @ref{43d,,Future} ，从Python 3.7 开始，这个方法是 @code{async def} 方法。

@end deffn

@geindex sock_connect() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop sock_connect}@anchor{69b}
@deffn {方法} coroutine loop.sock_connect (sock, address)

Connect @emph{sock} to a remote socket at @emph{address}.

Asynchronous version of @ref{670,,socket.connect()}.

@emph{sock} 必须是个非阻塞socket。


在 3.5.2 版更改: @code{address} no longer needs to be resolved.  @code{sock_connect}
will try to check if the @emph{address} is already resolved by calling
@ref{8b5,,socket.inet_pton()}.  If not,
@ref{49c,,loop.getaddrinfo()} will be used to resolve the
@emph{address}.



@subsubheading 参见


@ref{1b2,,loop.create_connection()} 和  @ref{35c,,asyncio.open_connection()} 。

@end deffn

@geindex sock_accept() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop sock_accept}@anchor{49b}
@deffn {方法} coroutine loop.sock_accept (sock)

Accept a connection.  Modeled after the blocking
@ref{66f,,socket.accept()} method.

此 @emph{scoket} 必须绑定到一个地址上并且监听连接。返回值是一个 @code{(conn, address)} 对，其中 @emph{conn} 是一个 @emph{新*的套接字对象，用于在此连接上收发数据，*address} 是连接的另一端的套接字所绑定的地址。

@emph{sock} 必须是个非阻塞socket。


在 3.7 版更改: 虽然这个方法一直被标记为协程方法。但是，Python 3.7 之前，该方法返回 @ref{43d,,Future} ，从Python 3.7 开始，这个方法是 @code{async def} 方法。



@subsubheading 参见


@ref{356,,loop.create_server()} and @ref{35d,,start_server()}.

@end deffn

@geindex sock_sendfile() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop sock_sendfile}@anchor{351}
@deffn {方法} coroutine loop.sock_sendfile (sock, file, offset=0, count=None, *, fallback=True)

Send a file using high-performance @ref{352,,os.sendfile} if possible.
Return the total number of bytes sent.

Asynchronous version of @ref{744,,socket.sendfile()}.

@emph{sock} must be a non-blocking @ref{c83,,socket.SOCK_STREAM}
@ref{66e,,socket}.

@emph{file} 必须是个用二进制方式打开的常规文件对象。

@emph{offset} tells from where to start reading the file. If specified,
@emph{count} is the total number of bytes to transmit as opposed to
sending the file until EOF is reached. File position is always updated,
even when this method raises an error, and
@ref{1d2e,,file.tell()} can be used to obtain the actual
number of bytes sent.

@emph{fallback}, when set to @code{True}, makes asyncio manually read and send
the file when the platform does not support the sendfile syscall
(e.g. Windows or SSL socket on Unix).

如果系统不支持 @emph{sendfile} 并且 @emph{fallback} 为 @code{False} ，引发 @ref{252b,,SendfileNotAvailableError} 异常。

@emph{sock} 必须是个非阻塞socket。


3.7 新版功能.

@end deffn

@node DNS,使用管道,直接使用 socket 对象,事件循环方法集
@anchor{library/asyncio-eventloop dns}@anchor{2558}
@subsubsection DNS


@geindex getaddrinfo() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop getaddrinfo}@anchor{49c}
@deffn {方法} coroutine loop.getaddrinfo (host, port, *, family=0, type=0, proto=0, flags=0)

异步版的 @ref{2559,,socket.getaddrinfo()} 。
@end deffn

@geindex getnameinfo() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop getnameinfo}@anchor{49d}
@deffn {方法} coroutine loop.getnameinfo (sockaddr, flags=0)

异步版的 @ref{255a,,socket.getnameinfo()} 。
@end deffn


在 3.7 版更改: @emph{getaddrinfo} 和 @emph{getnameinfo} 方法一直被标记返回一个协程，但是Python 3.7之前，实际返回的是 @ref{43d,,asyncio.Future} 对象。从Python 3.7 开始，这两个方法是协程。


@node 使用管道,Unix 信号,DNS,事件循环方法集
@anchor{library/asyncio-eventloop working-with-pipes}@anchor{255b}
@subsubsection 使用管道


@geindex connect_read_pipe() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop connect_read_pipe}@anchor{24f9}
@deffn {方法} coroutine loop.connect_read_pipe (protocol_factory, pipe)

Register the read end of @emph{pipe} in the event loop.

@emph{protocol_factory} must be a callable returning an
@ref{2547,,asyncio protocol} implementation.

@emph{pipe} 是个 @ref{b3b,,类似文件型对象}.

Return pair @code{(transport, protocol)}, where @emph{transport} supports
the @ref{255c,,ReadTransport} interface and @emph{protocol} is an object
instantiated by the @emph{protocol_factory}.

使用 @ref{250f,,SelectorEventLoop} 事件循环， @emph{pipe} 被设置为非阻塞模式。
@end deffn

@geindex connect_write_pipe() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop connect_write_pipe}@anchor{24fa}
@deffn {方法} coroutine loop.connect_write_pipe (protocol_factory, pipe)

Register the write end of @emph{pipe} in the event loop.

@emph{protocol_factory} must be a callable returning an
@ref{2547,,asyncio protocol} implementation.

@emph{pipe} 是个 @ref{b3b,,类似文件型对象}.

Return pair @code{(transport, protocol)}, where @emph{transport} supports
@ref{255d,,WriteTransport} interface and @emph{protocol} is an object
instantiated by the @emph{protocol_factory}.

使用 @ref{250f,,SelectorEventLoop} 事件循环， @emph{pipe} 被设置为非阻塞模式。
@end deffn

@cartouche
@quotation 注解 
@ref{250f,,SelectorEventLoop} does not support the above methods on
Windows.  Use @ref{1ab,,ProactorEventLoop} instead for Windows.
@end quotation
@end cartouche


@subsubheading 参见


The @ref{2488,,loop.subprocess_exec()} and
@ref{24f7,,loop.subprocess_shell()} methods.


@node Unix 信号,在线程或者进程池中执行代码。,使用管道,事件循环方法集
@anchor{library/asyncio-eventloop unix-signals}@anchor{255e}
@subsubsection Unix 信号


@geindex add_signal_handler() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop add_signal_handler}@anchor{2489}
@deffn {方法} loop.add_signal_handler (signum, callback, *args)

设置 @emph{callback} 作为 @emph{signum} 信号的处理程序。

The callback will be invoked by @emph{loop}, along with other queued callbacks
and runnable coroutines of that event loop. Unlike signal handlers
registered using @ref{a78,,signal.signal()}, a callback registered with this
function is allowed to interact with the event loop.

如果信号数字非法或者不可捕获，就抛出一个 @ref{1fb,,ValueError} 。如果建立处理器的过程中出现问题，会抛出一个 @ref{2ba,,RuntimeError} 。

使用 @ref{7c2,,functools.partial()} @ref{253f,,传递关键字参数}  给 @emph{callback}.

和 @ref{a78,,signal.signal()} 一样，这个函数只能在主线程中调用。
@end deffn

@geindex remove_signal_handler() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop remove_signal_handler}@anchor{255f}
@deffn {方法} loop.remove_signal_handler (sig)

移除 @emph{sig} 信号的处理程序。

Return @code{True} if the signal handler was removed, or @code{False} if
no handler was set for the given signal.

@ref{12f5,,可用性}: Unix。
@end deffn


@subsubheading 参见


@ref{ea,,signal} 模块。


@node 在线程或者进程池中执行代码。,错误处理API,Unix 信号,事件循环方法集
@anchor{library/asyncio-eventloop executing-code-in-thread-or-process-pools}@anchor{2560}
@subsubsection 在线程或者进程池中执行代码。


@geindex run_in_executor() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop run_in_executor}@anchor{2492}
@deffn {方法} awaitable loop.run_in_executor (executor, func, *args)

安排在指定的执行器中调用 @emph{func} 。

The @emph{executor} argument should be an @ref{23d0,,concurrent.futures.Executor}
instance. The default executor is used if @emph{executor} is @code{None}.

示例:

@example
import asyncio
import concurrent.futures

def blocking_io():
    # File operations (such as logging) can block the
    # event loop: run them in a thread pool.
    with open('/dev/urandom', 'rb') as f:
        return f.read(100)

def cpu_bound():
    # CPU-bound operations will block the event loop:
    # in general it is preferable to run them in a
    # process pool.
    return sum(i * i for i in range(10 ** 7))

async def main():
    loop = asyncio.get_running_loop()

    ## Options:

    # 1. Run in the default loop's executor:
    result = await loop.run_in_executor(
        None, blocking_io)
    print('default thread pool', result)

    # 2. Run in a custom thread pool:
    with concurrent.futures.ThreadPoolExecutor() as pool:
        result = await loop.run_in_executor(
            pool, blocking_io)
        print('custom thread pool', result)

    # 3. Run in a custom process pool:
    with concurrent.futures.ProcessPoolExecutor() as pool:
        result = await loop.run_in_executor(
            pool, cpu_bound)
        print('custom process pool', result)

asyncio.run(main())
@end example

这个方法返回一个 @ref{43d,,asyncio.Future} 对象。

使用 @ref{7c2,,functools.partial()} @ref{253f,,传递关键字参数}  给 @emph{func} 。


在 3.5.3 版更改: @ref{2492,,loop.run_in_executor()} no longer configures the
@code{max_workers} of the thread pool executor it creates, instead
leaving it up to the thread pool executor
(@ref{27a,,ThreadPoolExecutor}) to set the
default.

@end deffn

@geindex set_default_executor() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop set_default_executor}@anchor{27b}
@deffn {方法} loop.set_default_executor (executor)

Set @emph{executor} as the default executor used by @ref{2492,,run_in_executor()}.
@emph{executor} should be an instance of
@ref{27a,,ThreadPoolExecutor}.


3.8 版后已移除: Using an executor that is not an instance of
@ref{27a,,ThreadPoolExecutor} is deprecated and
will trigger an error in Python 3.9.


@emph{executor} 必须是个 @ref{27a,,concurrent.futures.ThreadPoolExecutor} 的实例。
@end deffn

@node 错误处理API,开启调试模式,在线程或者进程池中执行代码。,事件循环方法集
@anchor{library/asyncio-eventloop error-handling-api}@anchor{2561}
@subsubsection 错误处理API


允许自定义事件循环中如何去处理异常。

@geindex set_exception_handler() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop set_exception_handler}@anchor{2562}
@deffn {方法} loop.set_exception_handler (handler)

将 @emph{handler} 设置为新的事件循环异常处理器。

If @emph{handler} is @code{None}, the default exception handler will
be set.  Otherwise, @emph{handler} must be a callable with the signature
matching @code{(loop, context)}, where @code{loop}
is a reference to the active event loop, and @code{context}
is a @code{dict} object containing the details of the exception
(see @ref{2563,,call_exception_handler()} documentation for details
about context).
@end deffn

@geindex get_exception_handler() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop get_exception_handler}@anchor{517}
@deffn {方法} loop.get_exception_handler ()

返回当前的异常处理器，如果没有设置异常处理器，则返回 @code{None} 。


3.5.2 新版功能.

@end deffn

@geindex default_exception_handler() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop default_exception_handler}@anchor{2564}
@deffn {方法} loop.default_exception_handler (context)

默认的异常处理器。

This is called when an exception occurs and no exception
handler is set. This can be called by a custom exception
handler that wants to defer to the default handler behavior.

@emph{context} 参数和 @ref{2563,,call_exception_handler()} 中的同名参数完全相同。
@end deffn

@geindex call_exception_handler() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop call_exception_handler}@anchor{2563}
@deffn {方法} loop.call_exception_handler (context)

调用当前事件循环的异常处理器。

@emph{context} 是个包含下列键的 @code{dict} 对象(未来版本的Python可能会引入新键)：


@itemize *

@item 
'message': 错误消息；

@item 
'exception' （可选）: 异常对象；

@item 
'future' （可选）:  @ref{43d,,asyncio.Future} 实例；

@item 
'handle' （可选）: @ref{1035,,asyncio.Handle} 实例；

@item 
'protocol' （可选）: @ref{2547,,Protocol} 实例；

@item 
'transport' （可选）: @ref{2548,,Transport} 实例；

@item 
'socket' （可选）： @ref{66e,,socket.socket} 实例。
@end itemize

@cartouche
@quotation 注解 
This method should not be overloaded in subclassed
event loops.  For custom exception handling, use
the @ref{2562,,set_exception_handler()} method.
@end quotation
@end cartouche
@end deffn

@node 开启调试模式,运行子进程,错误处理API,事件循环方法集
@anchor{library/asyncio-eventloop enabling-debug-mode}@anchor{2565}
@subsubsection 开启调试模式


@geindex get_debug() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop get_debug}@anchor{694}
@deffn {方法} loop.get_debug ()

获取事件循环调试模式设置（@ref{183,,bool}）。

如果环境变量 
@geindex PYTHONASYNCIODEBUG
@geindex 环境变量; PYTHONASYNCIODEBUG
@ref{12f2,,PYTHONASYNCIODEBUG} 是一个非空字符串，就返回 @code{True} ，否则就返回 @code{False} 。
@end deffn

@geindex set_debug() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop set_debug}@anchor{693}
@deffn {方法} loop.set_debug (enabled: bool)

设置事件循环的调试模式。


在 3.7 版更改: The new @code{-X dev} command line option can now also be used
to enable the debug mode.

@end deffn


@subsubheading 参见


@ref{12e6,,debug mode of asyncio}.


@node 运行子进程,,开启调试模式,事件循环方法集
@anchor{library/asyncio-eventloop running-subprocesses}@anchor{2566}
@subsubsection 运行子进程


Methods described in this subsections are low-level.  In regular
async/await code consider using the high-level
@ref{292,,asyncio.create_subprocess_shell()} and
@ref{291,,asyncio.create_subprocess_exec()} convenience functions instead.

@cartouche
@quotation 注解 
The default asyncio event loop on @strong{Windows} does not support
subprocesses. See @ref{24f8,,Subprocess Support on Windows} for details.
@end quotation
@end cartouche

@geindex subprocess_exec() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop subprocess_exec}@anchor{2488}
@deffn {方法} coroutine loop.subprocess_exec (protocol_factory, *args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, **kwargs)

用 @emph{args} 指定的一个或者多个字符串型参数创建一个子进程。

@emph{args} 必须是个由下列形式的字符串组成的列表：


@itemize *

@item 
@ref{329,,str};

@item 
或者由 @ref{1e78,,文件熊编码} 编码的 @ref{32a,,bytes} 。
@end itemize

The first string specifies the program executable,
and the remaining strings specify the arguments.  Together, string
arguments form the @code{argv} of the program.

This is similar to the standard library @ref{2b9,,subprocess.Popen}
class called with @code{shell=False} and the list of strings passed as
the first argument; however, where @ref{2b9,,Popen} takes
a single argument which is list of strings, @emph{subprocess_exec}
takes multiple string arguments.

The @emph{protocol_factory} must be a callable returning a subclass of the
@ref{2567,,asyncio.SubprocessProtocol} class.

其他参数：


@itemize *

@item 
@emph{stdin} can be any of these:


@itemize *

@item 
a file-like object representing a pipe to be connected to the
subprocess's standard input stream using
@ref{24fa,,connect_write_pipe()}

@item 
the @ref{3e6,,subprocess.PIPE} constant (default) which will create a new
pipe and connect it,

@item 
the value @code{None} which will make the subprocess inherit the file
descriptor from this process

@item 
the @ref{a9b,,subprocess.DEVNULL} constant which indicates that the
special @ref{fad,,os.devnull} file will be used
@end itemize

@item 
@emph{stdout} can be any of these:


@itemize *

@item 
a file-like object representing a pipe to be connected to the
subprocess's standard output stream using
@ref{24fa,,connect_write_pipe()}

@item 
the @ref{3e6,,subprocess.PIPE} constant (default) which will create a new
pipe and connect it,

@item 
the value @code{None} which will make the subprocess inherit the file
descriptor from this process

@item 
the @ref{a9b,,subprocess.DEVNULL} constant which indicates that the
special @ref{fad,,os.devnull} file will be used
@end itemize

@item 
@emph{stderr} can be any of these:


@itemize *

@item 
a file-like object representing a pipe to be connected to the
subprocess's standard error stream using
@ref{24fa,,connect_write_pipe()}

@item 
the @ref{3e6,,subprocess.PIPE} constant (default) which will create a new
pipe and connect it,

@item 
the value @code{None} which will make the subprocess inherit the file
descriptor from this process

@item 
the @ref{a9b,,subprocess.DEVNULL} constant which indicates that the
special @ref{fad,,os.devnull} file will be used

@item 
the @ref{23f5,,subprocess.STDOUT} constant which will connect the standard
error stream to the process' standard output stream
@end itemize

@item 
All other keyword arguments are passed to @ref{2b9,,subprocess.Popen}
without interpretation, except for @emph{bufsize}, @emph{universal_newlines},
@emph{shell}, @emph{text}, @emph{encoding} and @emph{errors}, which should not be specified
at all.

The @code{asyncio} subprocess API does not support decoding the streams
as text. @ref{c31,,bytes.decode()} can be used to convert the bytes returned
from the stream to text.
@end itemize

其他参数的文档，请参阅 @ref{2b9,,subprocess.Popen} 类的构造函数。

Returns a pair of @code{(transport, protocol)}, where @emph{transport}
conforms to the @ref{2568,,asyncio.SubprocessTransport} base class and
@emph{protocol} is an object instantiated by the @emph{protocol_factory}.
@end deffn

@geindex subprocess_shell() (asyncio.loop 方法)
@anchor{library/asyncio-eventloop asyncio loop subprocess_shell}@anchor{24f7}
@deffn {方法} coroutine loop.subprocess_shell (protocol_factory, cmd, *, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, **kwargs)

Create a subprocess from @emph{cmd}, which can be a @ref{329,,str} or a
@ref{32a,,bytes} string encoded to the
@ref{1e78,,filesystem encoding},
using the platform's "shell" syntax.

这类似与用 @code{shell=True} 调用标准库的 @ref{2b9,,subprocess.Popen} 类。

The @emph{protocol_factory} must be a callable returning a subclass of the
@ref{2567,,SubprocessProtocol} class.

See @ref{2488,,subprocess_exec()} for more details about
the remaining arguments.

Returns a pair of @code{(transport, protocol)}, where @emph{transport}
conforms to the @ref{2568,,SubprocessTransport} base class and
@emph{protocol} is an object instantiated by the @emph{protocol_factory}.
@end deffn

@cartouche
@quotation 注解 
It is the application's responsibility to ensure that all whitespace
and special characters are quoted appropriately to avoid shell injection@footnote{https://en.wikipedia.org/wiki/Shell_injection#Shell_injection}
vulnerabilities. The @ref{a6e,,shlex.quote()} function can be used to
properly escape whitespace and special characters in strings that
are going to be used to construct shell commands.
@end quotation
@end cartouche

@node 回调处理,Server Objects,事件循环方法集,事件循环
@anchor{library/asyncio-eventloop callback-handles}@anchor{2534}
@subsubsection 回调处理


@geindex Handle (asyncio 中的类)
@anchor{library/asyncio-eventloop asyncio Handle}@anchor{1035}
@deffn {类} asyncio.Handle

A callback wrapper object returned by @ref{342,,loop.call_soon()},
@ref{343,,loop.call_soon_threadsafe()}.

@geindex cancel() (asyncio.Handle 方法)
@anchor{library/asyncio-eventloop asyncio Handle cancel}@anchor{2569}
@deffn {方法} cancel ()

Cancel the callback.  If the callback has already been canceled
or executed, this method has no effect.
@end deffn

@geindex cancelled() (asyncio.Handle 方法)
@anchor{library/asyncio-eventloop asyncio Handle cancelled}@anchor{35f}
@deffn {方法} cancelled ()

Return @code{True} if the callback was cancelled.


3.7 新版功能.

@end deffn
@end deffn

@geindex TimerHandle (asyncio 中的类)
@anchor{library/asyncio-eventloop asyncio TimerHandle}@anchor{2535}
@deffn {类} asyncio.TimerHandle

A callback wrapper object returned by @ref{344,,loop.call_later()},
and @ref{345,,loop.call_at()}.

This class is a subclass of @ref{1035,,Handle}.

@geindex when() (asyncio.TimerHandle 方法)
@anchor{library/asyncio-eventloop asyncio TimerHandle when}@anchor{35b}
@deffn {方法} when ()

Return a scheduled callback time as @ref{187,,float} seconds.

The time is an absolute timestamp, using the same time
reference as @ref{2542,,loop.time()}.


3.7 新版功能.

@end deffn
@end deffn

@node Server Objects,事件循环实现,回调处理,事件循环
@anchor{library/asyncio-eventloop server-objects}@anchor{2536}
@subsubsection Server Objects


Server objects are created by @ref{356,,loop.create_server()},
@ref{357,,loop.create_unix_server()}, @ref{35d,,start_server()},
and @ref{24bb,,start_unix_server()} functions.

Do not instantiate the class directly.

@geindex Server (asyncio 中的类)
@anchor{library/asyncio-eventloop asyncio Server}@anchor{355}
@deffn {类} asyncio.Server

@emph{Server} 对象是异步上下文管理器。当用于 @code{async with} 语句时，异步上下文管理器可以确保 Server 对象被关闭，并且在 @code{async with} 语句完成后，不接受新的连接。

@example
srv = await loop.create_server(...)

async with srv:
    # some code

# At this point, srv is closed and no longer accepts new connections.
@end example


在 3.7 版更改: Python3.7 开始，Server 对象是一个异步上下文管理器。


@geindex close() (asyncio.Server 方法)
@anchor{library/asyncio-eventloop asyncio Server close}@anchor{256a}
@deffn {方法} close ()

停止服务：关闭监听的套接字并且设置 @ref{49e,,sockets} 属性为 @code{None} 。

用于表示已经连进来的客户端连接会保持打开的状态。

服务器是被异步关闭的，使用 @ref{256b,,wait_closed()} 协程来等待服务器关闭。
@end deffn

@geindex get_loop() (asyncio.Server 方法)
@anchor{library/asyncio-eventloop asyncio Server get_loop}@anchor{354}
@deffn {方法} get_loop ()

Return the event loop associated with the server object.


3.7 新版功能.

@end deffn

@geindex start_serving() (asyncio.Server 方法)
@anchor{library/asyncio-eventloop asyncio Server start_serving}@anchor{358}
@deffn {方法} coroutine start_serving ()

开始接受连接。

这个方法是幂等的【相同参数重复执行，能获得相同的结果】，所以此方法能在服务已经运行的时候调用。

The @emph{start_serving} keyword-only parameter to
@ref{356,,loop.create_server()} and
@ref{35d,,asyncio.start_server()} allows creating a Server object
that is not accepting connections initially.  In this case
@code{Server.start_serving()}, or @ref{359,,Server.serve_forever()} can be used
to make the Server start accepting connections.


3.7 新版功能.

@end deffn

@geindex serve_forever() (asyncio.Server 方法)
@anchor{library/asyncio-eventloop asyncio Server serve_forever}@anchor{359}
@deffn {方法} coroutine serve_forever ()

开始接受连接，直到协程被取消。 @code{serve_forever} 任务的取消将导致服务器被关闭。

如果服务器已经在接受连接了，这个方法可以被调用。每个 @emph{Server} 对象，仅能有一个 @code{serve_forever} 任务。

示例:

@example
async def client_connected(reader, writer):
    # Communicate with the client with
    # reader/writer streams.  For example:
    await reader.readline()

async def main(host, port):
    srv = await asyncio.start_server(
        client_connected, host, port)
    await srv.serve_forever()

asyncio.run(main('127.0.0.1', 0))
@end example


3.7 新版功能.

@end deffn

@geindex is_serving() (asyncio.Server 方法)
@anchor{library/asyncio-eventloop asyncio Server is_serving}@anchor{35a}
@deffn {方法} is_serving ()

如果服务器正在接受新连接的状态，返回 @code{True} 。


3.7 新版功能.

@end deffn

@geindex wait_closed() (asyncio.Server 方法)
@anchor{library/asyncio-eventloop asyncio Server wait_closed}@anchor{256b}
@deffn {方法} coroutine wait_closed ()

等待 @ref{256a,,close()} 方法执行完毕。
@end deffn

@geindex sockets (asyncio.Server 属性)
@anchor{library/asyncio-eventloop asyncio Server sockets}@anchor{49e}
@deffn {属性} sockets

List of @ref{66e,,socket.socket} objects the server is listening on.


在 3.7 版更改: Prior to Python 3.7 @code{Server.sockets} used to return an
internal list of server sockets directly.  In 3.7 a copy
of that list is returned.

@end deffn
@end deffn

@node 事件循环实现,例子<14>,Server Objects,事件循环
@anchor{library/asyncio-eventloop asyncio-event-loops}@anchor{256c}@anchor{library/asyncio-eventloop event-loop-implementations}@anchor{2537}
@subsubsection 事件循环实现


asyncio ships with two different event loop implementations:
@ref{250f,,SelectorEventLoop} and @ref{1ab,,ProactorEventLoop}.

By default asyncio is configured to use @ref{250f,,SelectorEventLoop}
on Unix and @ref{1ab,,ProactorEventLoop} on Windows.

@geindex SelectorEventLoop (asyncio 中的类)
@anchor{library/asyncio-eventloop asyncio SelectorEventLoop}@anchor{250f}
@deffn {类} asyncio.SelectorEventLoop

An event loop based on the @ref{e6,,selectors} module.

Uses the most efficient @emph{selector} available for the given
platform.  It is also possible to manually configure the
exact selector implementation to be used:

@example
import asyncio
import selectors

selector = selectors.SelectSelector()
loop = asyncio.SelectorEventLoop(selector)
asyncio.set_event_loop(loop)
@end example

@ref{12f5,,可用性}: Unix, Windows。
@end deffn

@geindex ProactorEventLoop (asyncio 中的类)
@anchor{library/asyncio-eventloop asyncio ProactorEventLoop}@anchor{1ab}
@deffn {类} asyncio.ProactorEventLoop

用 "I/O Completion Ports" (IOCP) 构建的专为Windows 的事件循环。

@ref{12f5,,可用性}: Windows。


@subsubheading 参见


MSDN documentation on I/O Completion Ports@footnote{https://docs.microsoft.com/en-ca/windows/desktop/FileIO/i-o-completion-ports}.

@end deffn

@geindex AbstractEventLoop (asyncio 中的类)
@anchor{library/asyncio-eventloop asyncio AbstractEventLoop}@anchor{256d}
@deffn {类} asyncio.AbstractEventLoop

Abstract base class for asyncio-compliant event loops.

The @ref{63e,,Event Loop Methods} section lists all
methods that an alternative implementation of @code{AbstractEventLoop}
should have defined.
@end deffn

@node 例子<14>,,事件循环实现,事件循环
@anchor{library/asyncio-eventloop examples}@anchor{2538}
@subsubsection 例子


Note that all examples in this section @strong{purposefully} show how
to use the low-level event loop APIs, such as @ref{253a,,loop.run_forever()}
and @ref{342,,loop.call_soon()}.  Modern asyncio applications rarely
need to be written this way; consider using the high-level functions
like @ref{1a5,,asyncio.run()}.

@menu
* call_soon() 的 Hello World 示例。: call_soon 的 Hello World 示例。. 
* 使用 call_later() 来展示当前的日期: 使用 call_later 来展示当前的日期. 
* 监控一个文件描述符的读事件:: 
* 为SIGINT和SIGTERM设置信号处理器:: 

@end menu

@node call_soon 的 Hello World 示例。,使用 call_later 来展示当前的日期,,例子<14>
@anchor{library/asyncio-eventloop asyncio-example-lowlevel-helloworld}@anchor{256e}@anchor{library/asyncio-eventloop hello-world-with-call-soon}@anchor{256f}
@subsubsection call_soon() 的 Hello World 示例。


An example using the @ref{342,,loop.call_soon()} method to schedule a
callback. The callback displays @code{"Hello World"} and then stops the
event loop:

@example
import asyncio

def hello_world(loop):
    """A callback to print 'Hello World' and stop the event loop"""
    print('Hello World')
    loop.stop()

loop = asyncio.get_event_loop()

# Schedule a call to hello_world()
loop.call_soon(hello_world, loop)

# Blocking call interrupted by loop.stop()
try:
    loop.run_forever()
finally:
    loop.close()
@end example


@subsubheading 参见


A similar @ref{2483,,Hello World}
example created with a coroutine and the @ref{1a5,,run()} function.


@node 使用 call_later 来展示当前的日期,监控一个文件描述符的读事件,call_soon 的 Hello World 示例。,例子<14>
@anchor{library/asyncio-eventloop asyncio-example-call-later}@anchor{2570}@anchor{library/asyncio-eventloop display-the-current-date-with-call-later}@anchor{2571}
@subsubsection 使用 call_later() 来展示当前的日期


An example of a callback displaying the current date every second. The
callback uses the @ref{344,,loop.call_later()} method to reschedule itself
after 5 seconds, and then stops the event loop:

@example
import asyncio
import datetime

def display_date(end_time, loop):
    print(datetime.datetime.now())
    if (loop.time() + 1.0) < end_time:
        loop.call_later(1, display_date, end_time, loop)
    else:
        loop.stop()

loop = asyncio.get_event_loop()

# Schedule the first call to display_date()
end_time = loop.time() + 5.0
loop.call_soon(display_date, end_time, loop)

# Blocking call interrupted by loop.stop()
try:
    loop.run_forever()
finally:
    loop.close()
@end example


@subsubheading 参见


A similar @ref{2496,,current date} example
created with a coroutine and the @ref{1a5,,run()} function.


@node 监控一个文件描述符的读事件,为SIGINT和SIGTERM设置信号处理器,使用 call_later 来展示当前的日期,例子<14>
@anchor{library/asyncio-eventloop asyncio-example-watch-fd}@anchor{24d6}@anchor{library/asyncio-eventloop watch-a-file-descriptor-for-read-events}@anchor{2572}
@subsubsection 监控一个文件描述符的读事件


使用 @ref{24d7,,loop.add_reader()} 方法，等到文件描述符收到一些数据，然后关闭事件循环：

@example
import asyncio
from socket import socketpair

# Create a pair of connected file descriptors
rsock, wsock = socketpair()

loop = asyncio.get_event_loop()

def reader():
    data = rsock.recv(100)
    print("Received:", data.decode())

    # We are done: unregister the file descriptor
    loop.remove_reader(rsock)

    # Stop the event loop
    loop.stop()

# Register the file descriptor for read event
loop.add_reader(rsock, reader)

# Simulate the reception of data from the network
loop.call_soon(wsock.send, 'abc'.encode())

try:
    # Run the event loop
    loop.run_forever()
finally:
    # We are done. Close sockets and the event loop.
    rsock.close()
    wsock.close()
    loop.close()
@end example


@subsubheading 参见



@itemize *

@item 
A similar @ref{24d5,,example}
using transports, protocols, and the
@ref{1b2,,loop.create_connection()} method.

@item 
Another similar @ref{24d3,,example}
using the high-level @ref{35c,,asyncio.open_connection()} function
and streams.
@end itemize


@node 为SIGINT和SIGTERM设置信号处理器,,监控一个文件描述符的读事件,例子<14>
@anchor{library/asyncio-eventloop asyncio-example-unix-signals}@anchor{2573}@anchor{library/asyncio-eventloop set-signal-handlers-for-sigint-and-sigterm}@anchor{2574}
@subsubsection 为SIGINT和SIGTERM设置信号处理器


(This @code{signals} example only works on Unix.)

Register handlers for signals @code{SIGINT} and @code{SIGTERM}
using the @ref{2489,,loop.add_signal_handler()} method:

@example
import asyncio
import functools
import os
import signal

def ask_exit(signame, loop):
    print("got signal %s: exit" % signame)
    loop.stop()

async def main():
    loop = asyncio.get_running_loop()

    for signame in @{'SIGINT', 'SIGTERM'@}:
        loop.add_signal_handler(
            getattr(signal, signame),
            functools.partial(ask_exit, signame, loop))

    await asyncio.sleep(3600)

print("Event loop running for 1 hour, press Ctrl+C to interrupt.")
print(f"pid @{os.getpid()@}: send SIGINT or SIGTERM to exit.")

asyncio.run(main())
@end example

@node Futures,传输和协议,事件循环,asyncio --- 异步 I/O
@anchor{library/asyncio-future doc}@anchor{2575}@anchor{library/asyncio-future asyncio-futures}@anchor{248b}@anchor{library/asyncio-future futures}@anchor{2576}
@subsubsection Futures


@strong{源代码:} Lib/asyncio/futures.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/futures.py}, Lib/asyncio/base_futures.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/base_futures.py}


__________________________________________________________________


@emph{Future} 对象用来链接  @strong{底层回调式代码} 和高层异步/等待式代码。

@menu
* Future 函数:: 
* Future 对象:: 

@end menu

@node Future 函数,Future 对象,,Futures
@anchor{library/asyncio-future future-functions}@anchor{2577}
@subsubsection Future 函数


@geindex isfuture() (在 asyncio 模块中)
@anchor{library/asyncio-future asyncio isfuture}@anchor{2578}
@deffn {函数} asyncio.isfuture (obj)

如果 @emph{obj} 为下面任意对象，返回 @code{True}：


@itemize *

@item 
一个 @ref{43d,,asyncio.Future} 类的实例，

@item 
一个 @ref{1ad,,asyncio.Task} 类的实例，

@item 
带有  @code{_asyncio_future_blocking} 属性的类似 Future 的对象。
@end itemize


3.5 新版功能.

@end deffn

@geindex ensure_future() (在 asyncio 模块中)
@anchor{library/asyncio-future asyncio ensure_future}@anchor{511}
@deffn {函数} asyncio.ensure_future (obj, *, loop=None)

返回：


@itemize *

@item 
@emph{obj} 参数会是保持原样，如果 @emph{obj} 是 @ref{43d,,Future}、 @ref{1ad,,Task} 或 类似 Future 的对象(  @ref{2578,,isfuture()}  用于测试。)

@item 
封装了 @emph{obj} 的 @ref{1ad,,Task} 对象，如果 @emph{obj} 是一个协程 (使用 @ref{24b3,,iscoroutine()} 进行检测)；在此情况下该协程将通过 @code{ensure_future()} 加入执行计划。

@item 
等待 @emph{obj} 的 @ref{1ad,,Task} 对象，如果 @emph{obj} 是一个可等待对象( @ref{6f3,,inspect.isawaitable()} 用于测试)
@end itemize

如果 @emph{obj} 不是上述对象会引发一个 @ref{192,,TypeError} 异常。

@cartouche
@quotation 重要 
查看 @ref{1ae,,create_task()} 函数，它是创建新任务的首选途径。
@end quotation
@end cartouche


在 3.5.1 版更改: 这个函数接受任意 @ref{513,,awaitable} 对象。

@end deffn

@geindex wrap_future() (在 asyncio 模块中)
@anchor{library/asyncio-future asyncio wrap_future}@anchor{2579}
@deffn {函数} asyncio.wrap_future (future, *, loop=None)

将一个 @ref{b26,,concurrent.futures.Future} 对象封装到 @ref{43d,,asyncio.Future} 对象中。
@end deffn

@node Future 对象,,Future 函数,Futures
@anchor{library/asyncio-future future-object}@anchor{257a}
@subsubsection Future 对象


@geindex Future (asyncio 中的类)
@anchor{library/asyncio-future asyncio Future}@anchor{43d}
@deffn {类} asyncio.Future (*, loop=None)

一个 Future 代表一个异步运算的最终结果。线程不安全。

Future 是一个 @ref{513,,awaitable} 对象。协程可以等待 Future 对象直到它们有结果或异常集合或被取消。

通常 Future 用于支持底层回调式代码(例如在协议实现中使用asyncio @ref{248a,,transports}) 与高层异步/等待式代码交互。

经验告诉我们永远不要面向用户的接口暴露 Future 对象，同时建议使用 @ref{516,,loop.create_future()} 来创建 Future 对象。这种方法可以让 Future 对象使用其它的事件循环实现，它可以注入自己的优化实现。


在 3.7 版更改: 加入对 @ref{25,,contextvars} 模块的支持。


@geindex result() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future result}@anchor{257b}
@deffn {方法} result ()

返回 Future 的结果。

如果 Future 状态为 @emph{完成} ，并由 @ref{24a5,,set_result()} 方法设置一个结果，则返回这个结果。

如果 Future 状态为 @emph{完成} ，并由  @ref{24a6,,set_exception()} 方法设置一个异常，那么这个方法会引发异常。

如果 Future 已 @emph{取消}，方法会引发一个 @ref{1a7,,CancelledError} 异常。

如果 Future 的结果还不可用，此方法会引发一个 @ref{24ab,,InvalidStateError} 异常。
@end deffn

@geindex set_result() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future set_result}@anchor{24a5}
@deffn {方法} set_result (result)

将 Future 标记为 @emph{完成} 并设置结果。

如果 Future 已经 @emph{完成}  则抛出一个 @ref{24ab,,InvalidStateError} 错误。
@end deffn

@geindex set_exception() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future set_exception}@anchor{24a6}
@deffn {方法} set_exception (exception)

将 Future 标记为 @emph{完成} 并设置一个异常。

如果 Future 已经 @emph{完成}  则抛出一个 @ref{24ab,,InvalidStateError} 错误。
@end deffn

@geindex done() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future done}@anchor{257c}
@deffn {方法} done ()

如果 Future 为已 @emph{完成} 则返回 @code{True} 。

如果 Future 为 @emph{取消} 或调用 @ref{24a5,,set_result()} 设置了结果或调用 @ref{24a6,,set_exception()} 设置了异常，那么它就是 @emph{完成} 。
@end deffn

@geindex cancelled() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future cancelled}@anchor{257d}
@deffn {方法} cancelled ()

如果 Future 已 @emph{取消} 则返回 @code{True}

这个方法通常在设置结果或异常前用来检查 Future 是否已 @emph{取消} 。

@example
if not fut.cancelled():
    fut.set_result(42)
@end example
@end deffn

@geindex add_done_callback() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future add_done_callback}@anchor{346}
@deffn {方法} add_done_callback (callback, *, context=None)

添加一个在 Future @emph{完成} 时运行的回调函数。

调用 @emph{callback} 时，Future 对象是它的唯一参数。

调用这个方法时 Future 已经 @emph{完成} , 回调函数已被 @ref{342,,loop.call_soon()} 调度。

可选键值类的参数 @emph{context} 允许 @emph{callback} 运行在一个指定的自定义 @ref{246c,,contextvars.Context} 对象中。如果没有提供 @emph{context} ，则使用当前上下文。

可以用 @ref{7c2,,functools.partial()} 给回调函数传递参数，例如:

@example
# Call 'print("Future:", fut)' when "fut" is done.
fut.add_done_callback(
    functools.partial(print, "Future:"))
@end example


在 3.7 版更改: 加入键值类形参  @emph{context}。请参阅 
@geindex Python 提高建议; PEP 567
PEP 567@footnote{https://www.python.org/dev/peps/pep-0567} 查看更多细节。

@end deffn

@geindex remove_done_callback() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future remove_done_callback}@anchor{24af}
@deffn {方法} remove_done_callback (callback)

从回调列表中移除 @emph{callback} 。

返回被移除的回调函数的数量，通常为1，除非一个回调函数被添加多次。
@end deffn

@geindex cancel() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future cancel}@anchor{24a7}
@deffn {方法} cancel ()

取消 Future 并调度回调函数。

如果 Future 已经 @emph{完成} 或 @emph{取消} ，返回 @code{False} 。否则将 Future 状态改为 @emph{取消} 并在调度回调函数后返回 @code{True} 。
@end deffn

@geindex exception() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future exception}@anchor{257e}
@deffn {方法} exception ()

返回 Future 已设置的异常。

只有 Future 在 @emph{完成} 时才返回异常（或者 @code{None} ，如果没有设置异常）。

如果 Future 已 @emph{取消}，方法会引发一个 @ref{1a7,,CancelledError} 异常。

如果 Future 还没 @emph{完成} ，这个方法会引发一个 @ref{24ab,,InvalidStateError} 异常。
@end deffn

@geindex get_loop() (asyncio.Future 方法)
@anchor{library/asyncio-future asyncio Future get_loop}@anchor{353}
@deffn {方法} get_loop ()

返回 Future 对象已绑定的事件循环。


3.7 新版功能.

@end deffn
@end deffn
@anchor{library/asyncio-future asyncio-example-future}@anchor{257f}
这个例子创建一个 Future 对象，创建和调度一个异步任务去设置 Future 结果，然后等待其结果:

@example
async def set_after(fut, delay, value):
    # Sleep for *delay* seconds.
    await asyncio.sleep(delay)

    # Set *value* as a result of *fut* Future.
    fut.set_result(value)

async def main():
    # Get the current event loop.
    loop = asyncio.get_running_loop()

    # Create a new Future object.
    fut = loop.create_future()

    # Run "set_after()" coroutine in a parallel Task.
    # We are using the low-level "loop.create_task()" API here because
    # we already have a reference to the event loop at hand.
    # Otherwise we could have just used "asyncio.create_task()".
    loop.create_task(
        set_after(fut, 1, '... world'))

    print('hello ...')

    # Wait until *fut* has a result (1 second) and print it.
    print(await fut)

asyncio.run(main())
@end example

@cartouche
@quotation 重要 
该 Future 对象是为了模仿 @ref{b26,,concurrent.futures.Future} 类。主要差异包含：


@itemize -

@item 
与 asyncio 的 Future 不同，@ref{b26,,concurrent.futures.Future}  实例不是可等待对象。

@item 
@ref{257b,,asyncio.Future.result()} 和 @ref{257e,,asyncio.Future.exception()} 不接受 @emph{timeout} 参数。

@item 
Future 没有 @emph{完成} 时 @ref{257b,,asyncio.Future.result()} 和 @ref{257e,,asyncio.Future.exception()} 抛出一个 @ref{24ab,,InvalidStateError} 异常。

@item 
使用 @ref{346,,asyncio.Future.add_done_callback()} 注册的回调函数不会立即调用，而是被 @ref{342,,loop.call_soon()} 调度。

@item 
asyncio Future 不能兼容  @ref{23e1,,concurrent.futures.wait()} 和 @ref{1081,,concurrent.futures.as_completed()} 函数。
@end itemize
@end quotation
@end cartouche

@node 传输和协议,策略,Futures,asyncio --- 异步 I/O
@anchor{library/asyncio-protocol doc}@anchor{2580}@anchor{library/asyncio-protocol asyncio-transports-protocols}@anchor{248a}@anchor{library/asyncio-protocol transports-and-protocols}@anchor{2581}
@subsubsection 传输和协议


@subsubheading 前言


传输和协议会被像 @ref{1b2,,loop.create_connection()} 这类 @strong{底层} 事件循环接口使用。它们使用基于回调的编程风格支持网络或IPC协议（如HTTP）的高性能实现。

基本上，传输和协议应只在库和框架上使用，而不应该在高层的异步应用中使用它们。

本文档包含  @ref{2582,,Transports} 和 @ref{2583,,Protocols} 。

@subsubheading 概述


在最顶层，传输只关心 @strong{怎样} 传送字节内容，而协议决定传送 @strong{哪些} 字节内容(还要在一定程度上考虑何时)。

也可以这样说：从传输的角度来看，传输是套接字(或类似的I/O终端)的抽象，而协议是应用程序的抽象。

换另一种说法，传输和协议一起定义网络I/0和进程间I/O的抽象接口。

传输对象和协议对象总是一对一关系：协议调用传输方法来发送数据，而传输在接收到数据时调用协议方法传递数据。

大部分面向连接的事件循环方法(如 @ref{1b2,,loop.create_connection()} ) 通常接受  @emph{protocol_factory} 参数为接收到的链接创建 @emph{协议} 对象，并用 @emph{传输} 对象来表示。这些方法一般会返回 @code{(transport, protocol)} 元组。

@subsubheading 目录


本文档包含下列小节:


@itemize *

@item 
@ref{2582,,传输} 部分记载异步IO @ref{2584,,BaseTransport} 、 @ref{255c,,ReadTransport} 、 @ref{255d,,WriteTransport} 、 @ref{2585,,Transport} 、 @ref{2586,,DatagramTransport} 和 @ref{2568,,SubprocessTransport} 等类。

@item 
The @ref{2583,,Protocols} section documents asyncio @ref{2587,,BaseProtocol},
@ref{2588,,Protocol}, @ref{2c9,,BufferedProtocol},
@ref{2589,,DatagramProtocol}, and @ref{2567,,SubprocessProtocol} classes.

@item 
@ref{258a,,例子} 部分展示怎样使用传输、协议和底层事件循环接口。
@end itemize

@menu
* 传输:: 
* 协议:: 
* 例子: 例子<15>. 

@end menu

@node 传输,协议,,传输和协议
@anchor{library/asyncio-protocol asyncio-transport}@anchor{2548}@anchor{library/asyncio-protocol transports}@anchor{2582}
@subsubsection 传输


@strong{源码:} Lib/asyncio/transports.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/transports.py}


__________________________________________________________________


传输属于 @ref{a,,asyncio} 模块中的类，用来抽象各种通信通道。

传输对象总是由 @ref{63e,,异步IO事件循环} 实例化。

异步IO实现TCP、UDP、SSL和子进程管道的传输。传输上可用的方法由传输的类型决定。

传输类属于 @ref{24a1,,线程不安全} 。

@menu
* 传输层级:: 
* 基础传输:: 
* 只读传输:: 
* 只写传输:: 
* 数据报传输:: 
* 子进程传输:: 

@end menu

@node 传输层级,基础传输,,传输
@anchor{library/asyncio-protocol transports-hierarchy}@anchor{258b}
@subsubsection 传输层级


@geindex BaseTransport (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio BaseTransport}@anchor{2584}
@deffn {类} asyncio.BaseTransport

所有传输的基类。包含所有异步IO传输共用的方法。
@end deffn

@geindex WriteTransport (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio WriteTransport}@anchor{255d}
@deffn {类} asyncio.WriteTransport (BaseTransport)

只写链接的基础传输。

Instances of the @emph{WriteTransport} class are returned from
the @ref{24fa,,loop.connect_write_pipe()} event loop method and
are also used by subprocess-related methods like
@ref{2488,,loop.subprocess_exec()}.
@end deffn

@geindex ReadTransport (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio ReadTransport}@anchor{255c}
@deffn {类} asyncio.ReadTransport (BaseTransport)

只读链接的基础传输。

Instances of the @emph{ReadTransport} class are returned from
the @ref{24f9,,loop.connect_read_pipe()} event loop method and
are also used by subprocess-related methods like
@ref{2488,,loop.subprocess_exec()}.
@end deffn

@geindex Transport (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio Transport}@anchor{2585}
@deffn {类} asyncio.Transport (WriteTransport, ReadTransport)

接口代表一个双向传输，如TCP链接。

用户不用直接实例化传输；调用一个功能函数，给它传递协议工厂和其它需要的信息就可以创建传输和协议。

@emph{传输} 类实例由如  @ref{1b2,,loop.create_connection()} 、 @ref{24ba,,loop.create_unix_connection()} 、  @ref{356,,loop.create_server()} 、  @ref{2550,,loop.sendfile()} 等这类事件循环方法使用或返回。
@end deffn

@geindex DatagramTransport (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio DatagramTransport}@anchor{2586}
@deffn {类} asyncio.DatagramTransport (BaseTransport)

数据报(UDP)传输链接。

@emph{DatagramTransport} 类实例由事件循环方法 @ref{2e7,,loop.create_datagram_endpoint()} 返回。
@end deffn

@geindex SubprocessTransport (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio SubprocessTransport}@anchor{2568}
@deffn {类} asyncio.SubprocessTransport (BaseTransport)

表示父进程和子进程之间连接的抽象。

@emph{SubprocessTransport} 类的实例由事件循环方法 @ref{24f7,,loop.subprocess_shell()}  和  @ref{2488,,loop.subprocess_exec()} 返回。
@end deffn

@node 基础传输,只读传输,传输层级,传输
@anchor{library/asyncio-protocol base-transport}@anchor{258c}
@subsubsection 基础传输


@geindex close() (asyncio.BaseTransport 方法)
@anchor{library/asyncio-protocol asyncio BaseTransport close}@anchor{258d}
@deffn {方法} BaseTransport.close ()

关闭传输。

如果传输具有发送数据缓冲区，将会异步发送已缓存的数据。在所有已缓存的数据都已处理后，就会将 @ref{157,,None} 作为协议 @ref{258e,,protocol.connection_lost()} 方法的参数并进行调用。在这之后，传输不再接收任何数据。
@end deffn

@geindex is_closing() (asyncio.BaseTransport 方法)
@anchor{library/asyncio-protocol asyncio BaseTransport is_closing}@anchor{515}
@deffn {方法} BaseTransport.is_closing ()

返回 @code{True} ，如果传输正在关闭或已经关闭。
@end deffn

@geindex get_extra_info() (asyncio.BaseTransport 方法)
@anchor{library/asyncio-protocol asyncio BaseTransport get_extra_info}@anchor{2c8}
@deffn {方法} BaseTransport.get_extra_info (name, default=None)

返回 传输或它使用的相关资源信息。

@emph{name} 是表示要获取传输特定信息的字符串。

@emph{default} 是在信息不可用或传输不支持第三方事件循环实现或当前平台查询时返回的值。

例如下面代码尝试获取传输相关套接字对象:

@example
sock = transport.get_extra_info('socket')
if sock is not None:
    print(sock.getsockopt(...))
@end example

传输可查询信息类别:


@itemize *

@item 
套接字:


@itemize -

@item 
@code{'peername'}: 套接字链接时的远端地址，@ref{258f,,socket.socket.getpeername()} 方法的结果 (出错时为 @code{None} )

@item 
@code{'socket'}: @ref{66e,,socket.socket} 实例

@item 
@code{'sockname'}: 套接字本地地址， @ref{2590,,socket.socket.getsockname()} 方法的结果
@end itemize

@item 
SSL套接字


@itemize -

@item 
@code{'compression'}: 用字符串指定压缩算法，或者链接没有压缩时为 @code{None}  ；@ref{a90,,ssl.SSLSocket.compression()} 的结果。

@item 
@code{'cipher'}: 一个三值的元组，包含使用密码的名称，定义使用的SSL协议的版本，使用的加密位数。  @ref{2591,,ssl.SSLSocket.cipher()} 的结果。

@item 
@code{'peercert'}: 远端凭证；  @ref{8cb,,ssl.SSLSocket.getpeercert()} 结果。

@item 
@code{'sslcontext'}: @ref{3dc,,ssl.SSLContext} 实例

@item 
@code{'ssl_object'}: @ref{3db,,ssl.SSLObject} 或 @ref{3da,,ssl.SSLSocket} 实例
@end itemize

@item 
管道：


@itemize -

@item 
@code{'pipe'}: 管道对象
@end itemize

@item 
子进程：


@itemize -

@item 
@code{'subprocess'}: @ref{2b9,,subprocess.Popen} 实例
@end itemize
@end itemize
@end deffn

@geindex set_protocol() (asyncio.BaseTransport 方法)
@anchor{library/asyncio-protocol asyncio BaseTransport set_protocol}@anchor{2592}
@deffn {方法} BaseTransport.set_protocol (protocol)

设置一个新协议。

只有两种协议都写明支持切换才能完成切换协议。
@end deffn

@geindex get_protocol() (asyncio.BaseTransport 方法)
@anchor{library/asyncio-protocol asyncio BaseTransport get_protocol}@anchor{2593}
@deffn {方法} BaseTransport.get_protocol ()

返回当前协议。
@end deffn

@node 只读传输,只写传输,基础传输,传输
@anchor{library/asyncio-protocol read-only-transports}@anchor{2594}
@subsubsection 只读传输


@geindex is_reading() (asyncio.ReadTransport 方法)
@anchor{library/asyncio-protocol asyncio ReadTransport is_reading}@anchor{360}
@deffn {方法} ReadTransport.is_reading ()

如果传输接收到新数据时返回 @code{True} 。


3.7 新版功能.

@end deffn

@geindex pause_reading() (asyncio.ReadTransport 方法)
@anchor{library/asyncio-protocol asyncio ReadTransport pause_reading}@anchor{362}
@deffn {方法} ReadTransport.pause_reading ()

暂停传输的接收端。@ref{2595,,protocol.data_received()} 方法将不会收到数据，除非 @ref{361,,resume_reading()}  被调用。


在 3.7 版更改: 这个方法幂等的， 它可以在传输已经暂停或关闭时调用。

@end deffn

@geindex resume_reading() (asyncio.ReadTransport 方法)
@anchor{library/asyncio-protocol asyncio ReadTransport resume_reading}@anchor{361}
@deffn {方法} ReadTransport.resume_reading ()

恢复接收端。如果有数据可读取时，协议方法 @ref{2595,,protocol.data_received()} 将再次被调用。


在 3.7 版更改: 这个方法幂等的， 它可以在传输已经准备好读取数据时调用。

@end deffn

@node 只写传输,数据报传输,只读传输,传输
@anchor{library/asyncio-protocol write-only-transports}@anchor{2596}
@subsubsection 只写传输


@geindex abort() (asyncio.WriteTransport 方法)
@anchor{library/asyncio-protocol asyncio WriteTransport abort}@anchor{2597}
@deffn {方法} WriteTransport.abort ()

立即关闭传输，不会等待已提交的操作处理完毕。已缓存的数据将会丢失。不会接收更多数据。   最终 @ref{157,,None} 将作为协议的 @ref{258e,,protocol.connection_lost()}  方法的参数被调用。
@end deffn

@geindex can_write_eof() (asyncio.WriteTransport 方法)
@anchor{library/asyncio-protocol asyncio WriteTransport can_write_eof}@anchor{2598}
@deffn {方法} WriteTransport.can_write_eof ()

如果传输支持 @ref{2599,,write_eof()} 返回  @ref{494,,True} 否则返回  @ref{380,,False}  。
@end deffn

@geindex get_write_buffer_size() (asyncio.WriteTransport 方法)
@anchor{library/asyncio-protocol asyncio WriteTransport get_write_buffer_size}@anchor{259a}
@deffn {方法} WriteTransport.get_write_buffer_size ()

返回传输使用输出缓冲区的当前大小。
@end deffn

@geindex get_write_buffer_limits() (asyncio.WriteTransport 方法)
@anchor{library/asyncio-protocol asyncio WriteTransport get_write_buffer_limits}@anchor{696}
@deffn {方法} WriteTransport.get_write_buffer_limits ()

获取写入流控制 @emph{high} 和 @emph{low} 高低标记位。返回元组 @code{(low, high)} ， @emph{low} 和 @emph{high} 为正字节数。

使用 @ref{259b,,set_write_buffer_limits()} 设置限制。


3.4.2 新版功能.

@end deffn

@geindex set_write_buffer_limits() (asyncio.WriteTransport 方法)
@anchor{library/asyncio-protocol asyncio WriteTransport set_write_buffer_limits}@anchor{259b}
@deffn {方法} WriteTransport.set_write_buffer_limits (high=None, low=None)

设置写入流控制 @emph{high} 和 @emph{low} 高低标记位。

These two values (measured in number of
bytes) control when the protocol's
@ref{259c,,protocol.pause_writing()}
and @ref{259d,,protocol.resume_writing()}
methods are called. If specified, the low watermark must be less
than or equal to the high watermark.  Neither @emph{high} nor @emph{low}
can be negative.

@ref{259c,,pause_writing()} is called when the buffer size
becomes greater than or equal to the @emph{high} value. If writing has
been paused, @ref{259d,,resume_writing()} is called when
the buffer size becomes less than or equal to the @emph{low} value.

The defaults are implementation-specific.  If only the
high watermark is given, the low watermark defaults to an
implementation-specific value less than or equal to the
high watermark.  Setting @emph{high} to zero forces @emph{low} to zero as
well, and causes @ref{259c,,pause_writing()} to be called
whenever the buffer becomes non-empty.  Setting @emph{low} to zero causes
@ref{259d,,resume_writing()} to be called only once the
buffer is empty. Use of zero for either limit is generally
sub-optimal as it reduces opportunities for doing I/O and
computation concurrently.

Use @ref{696,,get_write_buffer_limits()}
to get the limits.
@end deffn

@geindex write() (asyncio.WriteTransport 方法)
@anchor{library/asyncio-protocol asyncio WriteTransport write}@anchor{259e}
@deffn {方法} WriteTransport.write (data)

Write some @emph{data} bytes to the transport.

This method does not block; it buffers the data and arranges for it
to be sent out asynchronously.
@end deffn

@geindex writelines() (asyncio.WriteTransport 方法)
@anchor{library/asyncio-protocol asyncio WriteTransport writelines}@anchor{259f}
@deffn {方法} WriteTransport.writelines (list_of_data)

Write a list (or any iterable) of data bytes to the transport.
This is functionally equivalent to calling @ref{259e,,write()} on each
element yielded by the iterable, but may be implemented more
efficiently.
@end deffn

@geindex write_eof() (asyncio.WriteTransport 方法)
@anchor{library/asyncio-protocol asyncio WriteTransport write_eof}@anchor{2599}
@deffn {方法} WriteTransport.write_eof ()

Close the write end of the transport after flushing all buffered data.
Data may still be received.

This method can raise @ref{609,,NotImplementedError} if the transport
(e.g. SSL) doesn't support half-closed connections.
@end deffn

@node 数据报传输,子进程传输,只写传输,传输
@anchor{library/asyncio-protocol datagram-transports}@anchor{25a0}
@subsubsection 数据报传输


@geindex sendto() (asyncio.DatagramTransport 方法)
@anchor{library/asyncio-protocol asyncio DatagramTransport sendto}@anchor{25a1}
@deffn {方法} DatagramTransport.sendto (data, addr=None)

Send the @emph{data} bytes to the remote peer given by @emph{addr} (a
transport-dependent target address).  If @emph{addr} is @ref{157,,None},
the data is sent to the target address given on transport
creation.

This method does not block; it buffers the data and arranges
for it to be sent out asynchronously.
@end deffn

@geindex abort() (asyncio.DatagramTransport 方法)
@anchor{library/asyncio-protocol asyncio DatagramTransport abort}@anchor{25a2}
@deffn {方法} DatagramTransport.abort ()

Close the transport immediately, without waiting for pending
operations to complete.  Buffered data will be lost.
No more data will be received.  The protocol's
@ref{258e,,protocol.connection_lost()}
method will eventually be called with @ref{157,,None} as its argument.
@end deffn

@node 子进程传输,,数据报传输,传输
@anchor{library/asyncio-protocol asyncio-subprocess-transports}@anchor{24fb}@anchor{library/asyncio-protocol subprocess-transports}@anchor{25a3}
@subsubsection 子进程传输


@geindex get_pid() (asyncio.SubprocessTransport 方法)
@anchor{library/asyncio-protocol asyncio SubprocessTransport get_pid}@anchor{25a4}
@deffn {方法} SubprocessTransport.get_pid ()

Return the subprocess process id as an integer.
@end deffn

@geindex get_pipe_transport() (asyncio.SubprocessTransport 方法)
@anchor{library/asyncio-protocol asyncio SubprocessTransport get_pipe_transport}@anchor{25a5}
@deffn {方法} SubprocessTransport.get_pipe_transport (fd)

Return the transport for the communication pipe corresponding to the
integer file descriptor @emph{fd}:


@itemize *

@item 
@code{0}: readable streaming transport of the standard input (@emph{stdin}),
or @ref{157,,None} if the subprocess was not created with @code{stdin=PIPE}

@item 
@code{1}: writable streaming transport of the standard output (@emph{stdout}),
or @ref{157,,None} if the subprocess was not created with @code{stdout=PIPE}

@item 
@code{2}: writable streaming transport of the standard error (@emph{stderr}),
or @ref{157,,None} if the subprocess was not created with @code{stderr=PIPE}

@item 
other @emph{fd}: @ref{157,,None}
@end itemize
@end deffn

@geindex get_returncode() (asyncio.SubprocessTransport 方法)
@anchor{library/asyncio-protocol asyncio SubprocessTransport get_returncode}@anchor{25a6}
@deffn {方法} SubprocessTransport.get_returncode ()

Return the subprocess return code as an integer or @ref{157,,None}
if it hasn't returned, which is similar to the
@ref{2416,,subprocess.Popen.returncode} attribute.
@end deffn

@geindex kill() (asyncio.SubprocessTransport 方法)
@anchor{library/asyncio-protocol asyncio SubprocessTransport kill}@anchor{25a7}
@deffn {方法} SubprocessTransport.kill ()

杀死子进程。

On POSIX systems, the function sends SIGKILL to the subprocess.
On Windows, this method is an alias for @ref{25a8,,terminate()}.

See also @ref{241c,,subprocess.Popen.kill()}.
@end deffn

@geindex send_signal() (asyncio.SubprocessTransport 方法)
@anchor{library/asyncio-protocol asyncio SubprocessTransport send_signal}@anchor{25a9}
@deffn {方法} SubprocessTransport.send_signal (signal)

Send the @emph{signal} number to the subprocess, as in
@ref{241a,,subprocess.Popen.send_signal()}.
@end deffn

@geindex terminate() (asyncio.SubprocessTransport 方法)
@anchor{library/asyncio-protocol asyncio SubprocessTransport terminate}@anchor{25a8}
@deffn {方法} SubprocessTransport.terminate ()

停止子进程。

On POSIX systems, this method sends SIGTERM to the subprocess.
On Windows, the Windows API function TerminateProcess() is called to
stop the subprocess.

See also @ref{241b,,subprocess.Popen.terminate()}.
@end deffn

@geindex close() (asyncio.SubprocessTransport 方法)
@anchor{library/asyncio-protocol asyncio SubprocessTransport close}@anchor{25aa}
@deffn {方法} SubprocessTransport.close ()

Kill the subprocess by calling the @ref{25a7,,kill()} method.

If the subprocess hasn't returned yet, and close transports of
@emph{stdin}, @emph{stdout}, and @emph{stderr} pipes.
@end deffn

@node 协议,例子<15>,传输,传输和协议
@anchor{library/asyncio-protocol asyncio-protocol}@anchor{2547}@anchor{library/asyncio-protocol protocols}@anchor{2583}
@subsubsection 协议


@strong{源码:} Lib/asyncio/protocols.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/protocols.py}


__________________________________________________________________


asyncio provides a set of abstract base classes that should be used
to implement network protocols.  Those classes are meant to be used
together with @ref{2548,,transports}.

Subclasses of abstract base protocol classes may implement some or
all methods.  All these methods are callbacks: they are called by
transports on certain events, for example when some data is received.
A base protocol method should be called by the corresponding transport.

@menu
* 基础协议:: 
* 基础协议: 基础协议<2>. 
* 流协议:: 
* 缓冲流协议:: 
* 数据报协议:: 
* 子进程协议:: 

@end menu

@node 基础协议,基础协议<2>,,协议
@anchor{library/asyncio-protocol base-protocols}@anchor{25ab}
@subsubsection 基础协议


@geindex BaseProtocol (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio BaseProtocol}@anchor{2587}
@deffn {类} asyncio.BaseProtocol

Base protocol with methods that all protocols share.
@end deffn

@geindex Protocol (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio Protocol}@anchor{2588}
@deffn {类} asyncio.Protocol (BaseProtocol)

The base class for implementing streaming protocols
(TCP, Unix sockets, etc).
@end deffn

@geindex BufferedProtocol (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio BufferedProtocol}@anchor{2c9}
@deffn {类} asyncio.BufferedProtocol (BaseProtocol)

A base class for implementing streaming protocols with manual
control of the receive buffer.
@end deffn

@geindex DatagramProtocol (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio DatagramProtocol}@anchor{2589}
@deffn {类} asyncio.DatagramProtocol (BaseProtocol)

The base class for implementing datagram (UDP) protocols.
@end deffn

@geindex SubprocessProtocol (asyncio 中的类)
@anchor{library/asyncio-protocol asyncio SubprocessProtocol}@anchor{2567}
@deffn {类} asyncio.SubprocessProtocol (BaseProtocol)

The base class for implementing protocols communicating with child
processes (unidirectional pipes).
@end deffn

@node 基础协议<2>,流协议,基础协议,协议
@anchor{library/asyncio-protocol base-protocol}@anchor{25ac}
@subsubsection 基础协议


All asyncio protocols can implement Base Protocol callbacks.

@subsubheading 链接回调函数


Connection callbacks are called on all protocols, exactly once per
a successful connection.  All other protocol callbacks can only be
called between those two methods.

@geindex connection_made() (asyncio.BaseProtocol 方法)
@anchor{library/asyncio-protocol asyncio BaseProtocol connection_made}@anchor{2549}
@deffn {方法} BaseProtocol.connection_made (transport)

链接建立时被调用。

The @emph{transport} argument is the transport representing the
connection.  The protocol is responsible for storing the reference
to its transport.
@end deffn

@geindex connection_lost() (asyncio.BaseProtocol 方法)
@anchor{library/asyncio-protocol asyncio BaseProtocol connection_lost}@anchor{258e}
@deffn {方法} BaseProtocol.connection_lost (exc)

链接丢失或关闭时被调用。

The argument is either an exception object or @ref{157,,None}.
The latter means a regular EOF is received, or the connection was
aborted or closed by this side of the connection.
@end deffn

@subsubheading 流控制回调函数


Flow control callbacks can be called by transports to pause or
resume writing performed by the protocol.

See the documentation of the @ref{259b,,set_write_buffer_limits()}
method for more details.

@geindex pause_writing() (asyncio.BaseProtocol 方法)
@anchor{library/asyncio-protocol asyncio BaseProtocol pause_writing}@anchor{259c}
@deffn {方法} BaseProtocol.pause_writing ()

Called when the transport's buffer goes over the high watermark.
@end deffn

@geindex resume_writing() (asyncio.BaseProtocol 方法)
@anchor{library/asyncio-protocol asyncio BaseProtocol resume_writing}@anchor{259d}
@deffn {方法} BaseProtocol.resume_writing ()

Called when the transport's buffer drains below the low watermark.
@end deffn

If the buffer size equals the high watermark,
@ref{259c,,pause_writing()} is not called: the buffer size must
go strictly over.

Conversely, @ref{259d,,resume_writing()} is called when the
buffer size is equal or lower than the low watermark.  These end
conditions are important to ensure that things go as expected when
either mark is zero.

@node 流协议,缓冲流协议,基础协议<2>,协议
@anchor{library/asyncio-protocol streaming-protocols}@anchor{25ad}
@subsubsection 流协议


Event methods, such as @ref{356,,loop.create_server()},
@ref{357,,loop.create_unix_server()}, @ref{1b2,,loop.create_connection()},
@ref{24ba,,loop.create_unix_connection()}, @ref{35e,,loop.connect_accepted_socket()},
@ref{24f9,,loop.connect_read_pipe()}, and @ref{24fa,,loop.connect_write_pipe()}
accept factories that return streaming protocols.

@geindex data_received() (asyncio.Protocol 方法)
@anchor{library/asyncio-protocol asyncio Protocol data_received}@anchor{2595}
@deffn {方法} Protocol.data_received (data)

Called when some data is received.  @emph{data} is a non-empty bytes
object containing the incoming data.

Whether the data is buffered, chunked or reassembled depends on
the transport.  In general, you shouldn't rely on specific semantics
and instead make your parsing generic and flexible. However,
data is always received in the correct order.

The method can be called an arbitrary number of times while
a connection is open.

However, @ref{25ae,,protocol.eof_received()}
is called at most once.  Once @cite{eof_received()} is called,
@code{data_received()} is not called anymore.
@end deffn

@geindex eof_received() (asyncio.Protocol 方法)
@anchor{library/asyncio-protocol asyncio Protocol eof_received}@anchor{25ae}
@deffn {方法} Protocol.eof_received ()

Called when the other end signals it won't send any more data
(for example by calling @ref{2599,,transport.write_eof()}, if the other end also uses
asyncio).

This method may return a false value (including @code{None}), in which case
the transport will close itself.  Conversely, if this method returns a
true value, the protocol used determines whether to close the transport.
Since the default implementation returns @code{None}, it implicitly closes the
connection.

Some transports, including SSL, don't support half-closed connections,
in which case returning true from this method will result in the connection
being closed.
@end deffn

状态机：

@example
start -> connection_made
    [-> data_received]*
    [-> eof_received]?
-> connection_lost -> end
@end example

@node 缓冲流协议,数据报协议,流协议,协议
@anchor{library/asyncio-protocol buffered-streaming-protocols}@anchor{25af}
@subsubsection 缓冲流协议



3.7 新版功能: @strong{Important:} this has been added to asyncio in Python 3.7
@emph{on a provisional basis}!  This is as an experimental API that
might be changed or removed completely in Python 3.8.


Buffered Protocols can be used with any event loop method
that supports @ref{25ad,,Streaming Protocols}.

@code{BufferedProtocol} implementations allow explicit manual allocation
and control of the receive buffer.  Event loops can then use the buffer
provided by the protocol to avoid unnecessary data copies.  This
can result in noticeable performance improvement for protocols that
receive big amounts of data.  Sophisticated protocol implementations
can significantly reduce the number of buffer allocations.

The following callbacks are called on @ref{2c9,,BufferedProtocol}
instances:

@geindex get_buffer() (asyncio.BufferedProtocol 方法)
@anchor{library/asyncio-protocol asyncio BufferedProtocol get_buffer}@anchor{25b0}
@deffn {方法} BufferedProtocol.get_buffer (sizehint)

调用后会分配新的接收缓冲区。

@emph{sizehint} is the recommended minimum size for the returned
buffer.  It is acceptable to return smaller or larger buffers
than what @emph{sizehint} suggests.  When set to -1, the buffer size
can be arbitrary. It is an error to return a buffer with a zero size.

@code{get_buffer()} must return an object implementing the
@ref{15d6,,buffer protocol}.
@end deffn

@geindex buffer_updated() (asyncio.BufferedProtocol 方法)
@anchor{library/asyncio-protocol asyncio BufferedProtocol buffer_updated}@anchor{25b1}
@deffn {方法} BufferedProtocol.buffer_updated (nbytes)

用接收的数据更新缓冲区时被调用。

@emph{nbytes} is the total number of bytes that were written to the buffer.
@end deffn

@geindex eof_received() (asyncio.BufferedProtocol 方法)
@anchor{library/asyncio-protocol asyncio BufferedProtocol eof_received}@anchor{25b2}
@deffn {方法} BufferedProtocol.eof_received ()

See the documentation of the @ref{25ae,,protocol.eof_received()} method.
@end deffn

@ref{25b0,,get_buffer()} can be called an arbitrary number
of times during a connection.  However, @ref{25ae,,protocol.eof_received()} is called at most once
and, if called, @ref{25b0,,get_buffer()} and
@ref{25b1,,buffer_updated()} won't be called after it.

状态机：

@example
start -> connection_made
    [-> get_buffer
        [-> buffer_updated]?
    ]*
    [-> eof_received]?
-> connection_lost -> end
@end example

@node 数据报协议,子进程协议,缓冲流协议,协议
@anchor{library/asyncio-protocol datagram-protocols}@anchor{25b3}
@subsubsection 数据报协议


Datagram Protocol instances should be constructed by protocol
factories passed to the @ref{2e7,,loop.create_datagram_endpoint()} method.

@geindex datagram_received() (asyncio.DatagramProtocol 方法)
@anchor{library/asyncio-protocol asyncio DatagramProtocol datagram_received}@anchor{25b4}
@deffn {方法} DatagramProtocol.datagram_received (data, addr)

Called when a datagram is received.  @emph{data} is a bytes object containing
the incoming data.  @emph{addr} is the address of the peer sending the data;
the exact format depends on the transport.
@end deffn

@geindex error_received() (asyncio.DatagramProtocol 方法)
@anchor{library/asyncio-protocol asyncio DatagramProtocol error_received}@anchor{25b5}
@deffn {方法} DatagramProtocol.error_received (exc)

Called when a previous send or receive operation raises an
@ref{1d3,,OSError}.  @emph{exc} is the @ref{1d3,,OSError} instance.

This method is called in rare conditions, when the transport (e.g. UDP)
detects that a datagram could not be delivered to its recipient.
In many conditions though, undeliverable datagrams will be silently
dropped.
@end deffn

@cartouche
@quotation 注解 
On BSD systems (macOS, FreeBSD, etc.) flow control is not supported
for datagram protocols, because there is no reliable way to detect send
failures caused by writing too many packets.

The socket always appears 'ready' and excess packets are dropped. An
@ref{1d3,,OSError} with @code{errno} set to @ref{2236,,errno.ENOBUFS} may
or may not be raised; if it is raised, it will be reported to
@ref{25b5,,DatagramProtocol.error_received()} but otherwise ignored.
@end quotation
@end cartouche

@node 子进程协议,,数据报协议,协议
@anchor{library/asyncio-protocol asyncio-subprocess-protocols}@anchor{24fc}@anchor{library/asyncio-protocol subprocess-protocols}@anchor{25b6}
@subsubsection 子进程协议


Datagram Protocol instances should be constructed by protocol
factories passed to the @ref{2488,,loop.subprocess_exec()} and
@ref{24f7,,loop.subprocess_shell()} methods.

@geindex pipe_data_received() (asyncio.SubprocessProtocol 方法)
@anchor{library/asyncio-protocol asyncio SubprocessProtocol pipe_data_received}@anchor{25b7}
@deffn {方法} SubprocessProtocol.pipe_data_received (fd, data)

Called when the child process writes data into its stdout or stderr
pipe.

@emph{fd} is the integer file descriptor of the pipe.

@emph{data} is a non-empty bytes object containing the received data.
@end deffn

@geindex pipe_connection_lost() (asyncio.SubprocessProtocol 方法)
@anchor{library/asyncio-protocol asyncio SubprocessProtocol pipe_connection_lost}@anchor{25b8}
@deffn {方法} SubprocessProtocol.pipe_connection_lost (fd, exc)

与子进程通信的其中一个管道关闭时被调用。

@emph{fd} is the integer file descriptor that was closed.
@end deffn

@geindex process_exited() (asyncio.SubprocessProtocol 方法)
@anchor{library/asyncio-protocol asyncio SubprocessProtocol process_exited}@anchor{25b9}
@deffn {方法} SubprocessProtocol.process_exited ()

子进程退出时被调用。
@end deffn

@node 例子<15>,,协议,传输和协议
@anchor{library/asyncio-protocol examples}@anchor{258a}
@subsubsection 例子


@menu
* TCP回应服务器:: 
* TCP回应客户端:: 
* UDP回应服务器:: 
* UDP回应客户端:: 
* 链接已存在的套接字:: 
* loop.subprocess_exec() and SubprocessProtocol: loop subprocess_exec and SubprocessProtocol. 

@end menu

@node TCP回应服务器,TCP回应客户端,,例子<15>
@anchor{library/asyncio-protocol asyncio-example-tcp-echo-server-protocol}@anchor{24d1}@anchor{library/asyncio-protocol tcp-echo-server}@anchor{25ba}
@subsubsection TCP回应服务器


Create a TCP echo server using the @ref{356,,loop.create_server()} method, send back
received data, and close the connection:

@example
import asyncio


class EchoServerProtocol(asyncio.Protocol):
    def connection_made(self, transport):
        peername = transport.get_extra_info('peername')
        print('Connection from @{@}'.format(peername))
        self.transport = transport

    def data_received(self, data):
        message = data.decode()
        print('Data received: @{!r@}'.format(message))

        print('Send: @{!r@}'.format(message))
        self.transport.write(data)

        print('Close the client socket')
        self.transport.close()


async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    server = await loop.create_server(
        lambda: EchoServerProtocol(),
        '127.0.0.1', 8888)

    async with server:
        await server.serve_forever()


asyncio.run(main())
@end example


@subsubheading 参见


The @ref{24cf,,TCP echo server using streams}
example uses the high-level @ref{35d,,asyncio.start_server()} function.


@node TCP回应客户端,UDP回应服务器,TCP回应服务器,例子<15>
@anchor{library/asyncio-protocol asyncio-example-tcp-echo-client-protocol}@anchor{24ce}@anchor{library/asyncio-protocol tcp-echo-client}@anchor{25bb}
@subsubsection TCP回应客户端


A TCP echo client using the @ref{1b2,,loop.create_connection()} method, sends
data, and waits until the connection is closed:

@example
import asyncio


class EchoClientProtocol(asyncio.Protocol):
    def __init__(self, message, on_con_lost):
        self.message = message
        self.on_con_lost = on_con_lost

    def connection_made(self, transport):
        transport.write(self.message.encode())
        print('Data sent: @{!r@}'.format(self.message))

    def data_received(self, data):
        print('Data received: @{!r@}'.format(data.decode()))

    def connection_lost(self, exc):
        print('The server closed the connection')
        self.on_con_lost.set_result(True)


async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    on_con_lost = loop.create_future()
    message = 'Hello World!'

    transport, protocol = await loop.create_connection(
        lambda: EchoClientProtocol(message, on_con_lost),
        '127.0.0.1', 8888)

    # Wait until the protocol signals that the connection
    # is lost and close the transport.
    try:
        await on_con_lost
    finally:
        transport.close()


asyncio.run(main())
@end example


@subsubheading 参见


The @ref{24cc,,TCP echo client using streams}
example uses the high-level @ref{35c,,asyncio.open_connection()} function.


@node UDP回应服务器,UDP回应客户端,TCP回应客户端,例子<15>
@anchor{library/asyncio-protocol asyncio-udp-echo-server-protocol}@anchor{254d}@anchor{library/asyncio-protocol udp-echo-server}@anchor{25bc}
@subsubsection UDP回应服务器


A UDP echo server, using the @ref{2e7,,loop.create_datagram_endpoint()}
method, sends back received data:

@example
import asyncio


class EchoServerProtocol:
    def connection_made(self, transport):
        self.transport = transport

    def datagram_received(self, data, addr):
        message = data.decode()
        print('Received %r from %s' % (message, addr))
        print('Send %r to %s' % (message, addr))
        self.transport.sendto(data, addr)


async def main():
    print("Starting UDP server")

    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    # One protocol instance will be created to serve all
    # client requests.
    transport, protocol = await loop.create_datagram_endpoint(
        lambda: EchoServerProtocol(),
        local_addr=('127.0.0.1', 9999))

    try:
        await asyncio.sleep(3600)  # Serve for 1 hour.
    finally:
        transport.close()


asyncio.run(main())
@end example

@node UDP回应客户端,链接已存在的套接字,UDP回应服务器,例子<15>
@anchor{library/asyncio-protocol asyncio-udp-echo-client-protocol}@anchor{254c}@anchor{library/asyncio-protocol udp-echo-client}@anchor{25bd}
@subsubsection UDP回应客户端


A UDP echo client, using the @ref{2e7,,loop.create_datagram_endpoint()}
method, sends data and closes the transport when it receives the answer:

@example
import asyncio


class EchoClientProtocol:
    def __init__(self, message, on_con_lost):
        self.message = message
        self.on_con_lost = on_con_lost
        self.transport = None

    def connection_made(self, transport):
        self.transport = transport
        print('Send:', self.message)
        self.transport.sendto(self.message.encode())

    def datagram_received(self, data, addr):
        print("Received:", data.decode())

        print("Close the socket")
        self.transport.close()

    def error_received(self, exc):
        print('Error received:', exc)

    def connection_lost(self, exc):
        print("Connection closed")
        self.on_con_lost.set_result(True)


async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    on_con_lost = loop.create_future()
    message = "Hello World!"

    transport, protocol = await loop.create_datagram_endpoint(
        lambda: EchoClientProtocol(message, on_con_lost),
        remote_addr=('127.0.0.1', 9999))

    try:
        await on_con_lost
    finally:
        transport.close()


asyncio.run(main())
@end example

@node 链接已存在的套接字,loop subprocess_exec and SubprocessProtocol,UDP回应客户端,例子<15>
@anchor{library/asyncio-protocol asyncio-example-create-connection}@anchor{24d5}@anchor{library/asyncio-protocol connecting-existing-sockets}@anchor{25be}
@subsubsection 链接已存在的套接字


Wait until a socket receives data using the
@ref{1b2,,loop.create_connection()} method with a protocol:

@example
import asyncio
import socket


class MyProtocol(asyncio.Protocol):

    def __init__(self, on_con_lost):
        self.transport = None
        self.on_con_lost = on_con_lost

    def connection_made(self, transport):
        self.transport = transport

    def data_received(self, data):
        print("Received:", data.decode())

        # We are done: close the transport;
        # connection_lost() will be called automatically.
        self.transport.close()

    def connection_lost(self, exc):
        # The socket has been closed
        self.on_con_lost.set_result(True)


async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()
    on_con_lost = loop.create_future()

    # Create a pair of connected sockets
    rsock, wsock = socket.socketpair()

    # Register the socket to wait for data.
    transport, protocol = await loop.create_connection(
        lambda: MyProtocol(on_con_lost), sock=rsock)

    # Simulate the reception of data from the network.
    loop.call_soon(wsock.send, 'abc'.encode())

    try:
        await protocol.on_con_lost
    finally:
        transport.close()
        wsock.close()

asyncio.run(main())
@end example


@subsubheading 参见


The @ref{24d6,,watch a file descriptor for read events} example uses the low-level
@ref{24d7,,loop.add_reader()} method to register an FD.

The @ref{24d3,,register an open socket to wait for data using streams} example uses high-level streams
created by the @ref{35c,,open_connection()} function in a coroutine.


@node loop subprocess_exec and SubprocessProtocol,,链接已存在的套接字,例子<15>
@anchor{library/asyncio-protocol asyncio-example-subprocess-proto}@anchor{2513}@anchor{library/asyncio-protocol loop-subprocess-exec-and-subprocessprotocol}@anchor{25bf}
@subsubsection loop.subprocess_exec() and SubprocessProtocol


An example of a subprocess protocol used to get the output of a
subprocess and to wait for the subprocess exit.

The subprocess is created by the @ref{2488,,loop.subprocess_exec()} method:

@example
import asyncio
import sys

class DateProtocol(asyncio.SubprocessProtocol):
    def __init__(self, exit_future):
        self.exit_future = exit_future
        self.output = bytearray()

    def pipe_data_received(self, fd, data):
        self.output.extend(data)

    def process_exited(self):
        self.exit_future.set_result(True)

async def get_date():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()

    code = 'import datetime; print(datetime.datetime.now())'
    exit_future = asyncio.Future(loop=loop)

    # Create the subprocess controlled by DateProtocol;
    # redirect the standard output into a pipe.
    transport, protocol = await loop.subprocess_exec(
        lambda: DateProtocol(exit_future),
        sys.executable, '-c', code,
        stdin=None, stderr=None)

    # Wait for the subprocess exit using the process_exited()
    # method of the protocol.
    await exit_future

    # Close the stdout pipe.
    transport.close()

    # Read the output which was collected by the
    # pipe_data_received() method of the protocol.
    data = bytes(protocol.output)
    return data.decode('ascii').rstrip()

date = asyncio.run(get_date())
print(f"Current date: @{date@}")
@end example

See also the @ref{2512,,same example}
written using high-level APIs.

@node 策略,平台支持,传输和协议,asyncio --- 异步 I/O
@anchor{library/asyncio-policy doc}@anchor{25c0}@anchor{library/asyncio-policy asyncio-policies}@anchor{2532}@anchor{library/asyncio-policy policies}@anchor{25c1}
@subsubsection 策略


事件循环策略是各个进程的全局对象 ，它控制事件循环的管理。每个事件循环都有一个默认策略，可以使用策略API更改和定制该策略。

策略定义了“上下文”的概念，每个上下文管理一个单独的事件循环。默认策略将*context*定义为当前线程。

通过使用自定义事件循环策略，可以自定义 @ref{34e,,get_event_loop()} 、 @ref{2530,,set_event_loop()}  和 @ref{2531,,new_event_loop()} 函数的行为。

策略对象应该实现 @ref{25c2,,AbstractEventLoopPolicy} 抽象基类中定义的API。

@menu
* 获取和设置策略:: 
* 策略对象:: 
* 进程监视器:: 
* 自定义策略:: 

@end menu

@node 获取和设置策略,策略对象,,策略
@anchor{library/asyncio-policy getting-and-setting-the-policy}@anchor{25c3}
@subsubsection 获取和设置策略


可以使用下面函数获取和设置当前进程的策略:

@geindex get_event_loop_policy() (在 asyncio 模块中)
@anchor{library/asyncio-policy asyncio get_event_loop_policy}@anchor{25c4}
@deffn {函数} asyncio.get_event_loop_policy ()

返回当前进程域的策略。
@end deffn

@geindex set_event_loop_policy() (在 asyncio 模块中)
@anchor{library/asyncio-policy asyncio set_event_loop_policy}@anchor{25c5}
@deffn {函数} asyncio.set_event_loop_policy (policy)

将 @emph{policy} 设置为当前进程域策略。

如果 @emph{policy} 设为 @code{None} 将恢复默认策略。
@end deffn

@node 策略对象,进程监视器,获取和设置策略,策略
@anchor{library/asyncio-policy policy-objects}@anchor{25c6}
@subsubsection 策略对象


抽象事件循环策略基类定义如下:

@geindex AbstractEventLoopPolicy (asyncio 中的类)
@anchor{library/asyncio-policy asyncio AbstractEventLoopPolicy}@anchor{25c2}
@deffn {类} asyncio.AbstractEventLoopPolicy

异步策略的抽象基类。

@geindex get_event_loop() (asyncio.AbstractEventLoopPolicy 方法)
@anchor{library/asyncio-policy asyncio AbstractEventLoopPolicy get_event_loop}@anchor{25c7}
@deffn {方法} get_event_loop ()

为当前上下文获取事件循环。

返回一个实现  @ref{256d,,AbstractEventLoop}  接口的事件循环对象。

该方法永远返回 @code{None}。


在 3.6 版更改.

@end deffn

@geindex set_event_loop() (asyncio.AbstractEventLoopPolicy 方法)
@anchor{library/asyncio-policy asyncio AbstractEventLoopPolicy set_event_loop}@anchor{25c8}
@deffn {方法} set_event_loop (loop)

将当前上下文的事件循环设置为  @emph{loop} 。
@end deffn

@geindex new_event_loop() (asyncio.AbstractEventLoopPolicy 方法)
@anchor{library/asyncio-policy asyncio AbstractEventLoopPolicy new_event_loop}@anchor{25c9}
@deffn {方法} new_event_loop ()

创建并返回一个新的事件循环对象。

该方法永远返回 @code{None}。
@end deffn

@geindex get_child_watcher() (asyncio.AbstractEventLoopPolicy 方法)
@anchor{library/asyncio-policy asyncio AbstractEventLoopPolicy get_child_watcher}@anchor{25ca}
@deffn {方法} get_child_watcher ()

获取子进程监视器对象。

返回一个实现 @ref{25cb,,AbstractChildWatcher} 接口的监视器对象。

该函数仅支持Unix。
@end deffn

@geindex set_child_watcher() (asyncio.AbstractEventLoopPolicy 方法)
@anchor{library/asyncio-policy asyncio AbstractEventLoopPolicy set_child_watcher}@anchor{25cc}
@deffn {方法} set_child_watcher (watcher)

将当前子进程监视器设置为 @emph{watcher} 。

该函数仅支持Unix。
@end deffn
@end deffn

asyncio附带下列内置策略:

@geindex DefaultEventLoopPolicy (asyncio 中的类)
@anchor{library/asyncio-policy asyncio DefaultEventLoopPolicy}@anchor{25cd}
@deffn {类} asyncio.DefaultEventLoopPolicy

默认的 asyncio 策略。 在 Unix 上使用 @ref{250f,,SelectorEventLoop} 而在 Windows 上使用 @ref{1ab,,ProactorEventLoop}。

不需要手动安装默认策略。asyncio已配置成自动使用默认策略。


在 3.8 版更改: 在 Windows 上，现在默认会使用 @ref{1ab,,ProactorEventLoop}。

@end deffn

@geindex WindowsSelectorEventLoopPolicy (asyncio 中的类)
@anchor{library/asyncio-policy asyncio WindowsSelectorEventLoopPolicy}@anchor{25ce}
@deffn {类} asyncio.WindowsSelectorEventLoopPolicy

一个使用 @ref{250f,,SelectorEventLoop} 事件循环实现的替代事件循环策略。

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex WindowsProactorEventLoopPolicy (asyncio 中的类)
@anchor{library/asyncio-policy asyncio WindowsProactorEventLoopPolicy}@anchor{25cf}
@deffn {类} asyncio.WindowsProactorEventLoopPolicy

使用  @ref{1ab,,ProactorEventLoop} 事件循环实现的另一种事件循环策略。

@ref{12f5,,可用性}: Windows。
@end deffn

@node 进程监视器,自定义策略,策略对象,策略
@anchor{library/asyncio-policy asyncio-watchers}@anchor{2510}@anchor{library/asyncio-policy process-watchers}@anchor{25d0}
@subsubsection 进程监视器


进程监视器允许定制事件循环如何监视Unix子进程。具体来说，事件循环需要知道子进程何时退出。

在asyncio中子进程由  @ref{291,,create_subprocess_exec()} 和 @ref{2488,,loop.subprocess_exec()} 函数创建。

asyncio 定义了 @ref{25cb,,AbstractChildWatcher} 抽象基类，子监视器必须要实现它，并具有四种不同实现: @ref{2511,,ThreadedChildWatcher} (已配置为默认使用), @ref{25d1,,MultiLoopChildWatcher}, @ref{25d2,,SafeChildWatcher} 和 @ref{25d3,,FastChildWatcher}。

请参阅  @ref{2507,,子进程和线程} 部分。

以下两个函数可用于自定义子进程监视器实现，它将被asyncio事件循环使用:

@geindex get_child_watcher() (在 asyncio 模块中)
@anchor{library/asyncio-policy asyncio get_child_watcher}@anchor{25d4}
@deffn {函数} asyncio.get_child_watcher ()

返回当前策略的当前子监视器。
@end deffn

@geindex set_child_watcher() (在 asyncio 模块中)
@anchor{library/asyncio-policy asyncio set_child_watcher}@anchor{25d5}
@deffn {函数} asyncio.set_child_watcher (watcher)

将当前策略的子监视器设置为 @emph{watcher} 。@emph{watcher} 必须实现 @ref{25cb,,AbstractChildWatcher} 基类定义的方法。
@end deffn

@cartouche
@quotation 注解 
第三方事件循环实现可能不支持自定义子监视器。对于这样的事件循环，禁止使用 @ref{25d5,,set_child_watcher()} 或不起作用。
@end quotation
@end cartouche

@geindex AbstractChildWatcher (asyncio 中的类)
@anchor{library/asyncio-policy asyncio AbstractChildWatcher}@anchor{25cb}
@deffn {类} asyncio.AbstractChildWatcher

@geindex add_child_handler() (asyncio.AbstractChildWatcher 方法)
@anchor{library/asyncio-policy asyncio AbstractChildWatcher add_child_handler}@anchor{25d6}
@deffn {方法} add_child_handler (pid, callback, *args)

注册一个新的子处理回调函数。

安排 @code{callback(pid, returncode, *args)} 在进程的PID与 @emph{pid} 相等时调用。指定另一个同进程的回调函数替换之前的回调处理函数。

回调函数 @emph{callback} 必须是线程安全。
@end deffn

@geindex remove_child_handler() (asyncio.AbstractChildWatcher 方法)
@anchor{library/asyncio-policy asyncio AbstractChildWatcher remove_child_handler}@anchor{25d7}
@deffn {方法} remove_child_handler (pid)

删除进程PID与 @emph{pid} 相等的进程的处理函数。

处理函数成功删除时返回 @code{True} ，没有删除时返回 @code{False} 。
@end deffn

@geindex attach_loop() (asyncio.AbstractChildWatcher 方法)
@anchor{library/asyncio-policy asyncio AbstractChildWatcher attach_loop}@anchor{25d8}
@deffn {方法} attach_loop (loop)

给一个事件循环绑定监视器。

如果监视器之前已绑定另一个事件循环，那么在绑定新循环前会先解绑原来的事件循环。

注意：循环有可能是 @code{None} 。
@end deffn

@geindex is_active() (asyncio.AbstractChildWatcher 方法)
@anchor{library/asyncio-policy asyncio AbstractChildWatcher is_active}@anchor{25d9}
@deffn {方法} is_active ()

如果监视器已准备好使用则返回 @code{True}。

使用 @emph{不活动的} 当前子监视器生成子进程将引发 @ref{2ba,,RuntimeError}。


3.8 新版功能.

@end deffn

@geindex close() (asyncio.AbstractChildWatcher 方法)
@anchor{library/asyncio-policy asyncio AbstractChildWatcher close}@anchor{25da}
@deffn {方法} close ()

关闭监视器。

必须调用这个方法以确保相关资源会被清理。
@end deffn
@end deffn

@geindex ThreadedChildWatcher (asyncio 中的类)
@anchor{library/asyncio-policy asyncio ThreadedChildWatcher}@anchor{2511}
@deffn {类} asyncio.ThreadedChildWatcher

此实现会为每个生成的子进程启动一具新的等待线程。

即使是当 asyncio 事件循环运行在非主 OS 线程上时它也能可靠地工作。

当处理大量子进程时也不存在显著的开销 (每个子进程结束时为 @emph{O(1)}) ，但当每个进程启动线程时则需要额外的内存。

此监视器会默认被使用。


3.8 新版功能.

@end deffn

@geindex MultiLoopChildWatcher (asyncio 中的类)
@anchor{library/asyncio-policy asyncio MultiLoopChildWatcher}@anchor{25d1}
@deffn {类} asyncio.MultiLoopChildWatcher

此实现会在实例化时注册一个 @code{SIGCHLD} 信号处理程序。 这可能会破坏为 @cite{SIGCHLD} 信号安装了自定义信号处理程序的第三方代码。

此监视器会在收到 @code{SIGCHLD} 信号时通过显式地轮询每个进程来避免干扰其他代码生成的进程。

该监视器一旦被安装就不会限制从不同线程运行子进程。

该解决方案是安全的，但在处理大量进程时会有显著的开销 (每收到一个 @code{SIGCHLD} 时为 @emph{O(n)})。


3.8 新版功能.

@end deffn

@geindex SafeChildWatcher (asyncio 中的类)
@anchor{library/asyncio-policy asyncio SafeChildWatcher}@anchor{25d2}
@deffn {类} asyncio.SafeChildWatcher

该实现会使用主线程中的活动事件循环来处理 @code{SIGCHLD} 信号。 如果主线程没有正在运行的事件循环，则其他线程无法生成子进程 (会引发 @ref{2ba,,RuntimeError})。

此监视器会在收到 @code{SIGCHLD} 信号时通过显式地轮询每个进程来避免干扰其他代码生成的进程。

该解决方案与 @ref{25d1,,MultiLoopChildWatcher} 同样安全并同样具有 @emph{O(N)} 复杂度，但需要主线程有正在运行的事件循环才能工作。
@end deffn

@geindex FastChildWatcher (asyncio 中的类)
@anchor{library/asyncio-policy asyncio FastChildWatcher}@anchor{25d3}
@deffn {类} asyncio.FastChildWatcher

这种实现直接调用  @code{os.waitpid(-1)} 来获取所有已结束的进程，可能会中断其它代码洐生进程并等待它们结束。

在处理大量子监视器时没有明显的开销( @emph{O(1)}  每次子监视器结束)。

该解决方案需要主线程有正在运行的事件循环才能工作，这与 @ref{25d2,,SafeChildWatcher} 一样。
@end deffn

@node 自定义策略,,进程监视器,策略
@anchor{library/asyncio-policy custom-policies}@anchor{25db}
@subsubsection 自定义策略


要实现一个新的事件循环策略，建议子类化 @ref{25cd,,DefaultEventLoopPolicy} 并重写需要定制行为的方法，例如:

@example
class MyEventLoopPolicy(asyncio.DefaultEventLoopPolicy):

    def get_event_loop(self):
        """Get the event loop.

        This may be None or an instance of EventLoop.
        """
        loop = super().get_event_loop()
        # Do something with loop ...
        return loop

asyncio.set_event_loop_policy(MyEventLoopPolicy())
@end example

@node 平台支持,高级API索引,策略,asyncio --- 异步 I/O
@anchor{library/asyncio-platforms doc}@anchor{25dc}@anchor{library/asyncio-platforms asyncio-platform-support}@anchor{2556}@anchor{library/asyncio-platforms platform-support}@anchor{25dd}
@subsubsection 平台支持


@ref{a,,asyncio} 模块被设计为可移植的,但由于平台的底层架构和功能，一些平台存在细微的差异和限制。

@menu
* 所有平台:: 
* Windows: Windows<47>. 
* macOS: macOS<20>. 

@end menu

@node 所有平台,Windows<47>,,平台支持
@anchor{library/asyncio-platforms all-platforms}@anchor{25de}
@subsubsection 所有平台



@itemize *

@item 
@ref{24d7,,loop.add_reader()} 和 @ref{2554,,loop.add_writer()} 不能用来监视文件I/O。
@end itemize

@node Windows<47>,macOS<20>,所有平台,平台支持
@anchor{library/asyncio-platforms windows}@anchor{25df}
@subsubsection Windows


@strong{源代码:} Lib/asyncio/proactor_events.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/proactor_events.py}, Lib/asyncio/windows_events.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/windows_events.py}, Lib/asyncio/windows_utils.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/windows_utils.py}


__________________________________________________________________



在 3.8 版更改: 在 Windows 上，@ref{1ab,,ProactorEventLoop} 现在是默认的事件循环。


Windows上的所有事件循环都不支持以下方法:


@itemize *

@item 
不支持 @ref{24ba,,loop.create_unix_connection()} 和 @ref{357,,loop.create_unix_server()} 。 @ref{254b,,socket.AF_UNIX} 套接字相关参数仅限于Unix。

@item 
不支持 @ref{2489,,loop.add_signal_handler()} 和 @ref{255f,,loop.remove_signal_handler()} 。
@end itemize

@ref{250f,,SelectorEventLoop} 有下列限制:


@itemize *

@item 
@ref{25e0,,SelectSelector} 只被用于等待套接字事件：它支持套接字且最多支持512个套接字。

@item 
@ref{24d7,,loop.add_reader()} 和 @ref{2554,,loop.add_writer()} 只接受套接字处理回调函数(如管道、文件描述符等都不支持)。

@item 
因为不支持管道，所以  @ref{24f9,,loop.connect_read_pipe()} 和 @ref{24fa,,loop.connect_write_pipe()} 方法没有实现。

@item 
不支持 @ref{2485,,Subprocesses} ，也就是  @ref{2488,,loop.subprocess_exec()} 和 @ref{24f7,,loop.subprocess_shell()} 方法没有实现。
@end itemize

@ref{1ab,,ProactorEventLoop} 有下列限制:


@itemize *

@item 
不支持  @ref{24d7,,loop.add_reader()} 和 @ref{2554,,loop.add_writer()} 方法。
@end itemize

Windows上单调时钟的分辨率大约为 15.6 毫秒。最佳的分辨率是 0.5 毫秒。分辨率依赖于具体的硬件（HPET@footnote{https://zh.wikipedia.org/wiki/高精度事件计时器}）和Windows的设置。

@menu
* Windows的子进程支持:: 

@end menu

@node Windows的子进程支持,,,Windows<47>
@anchor{library/asyncio-platforms asyncio-windows-subprocess}@anchor{24f8}@anchor{library/asyncio-platforms subprocess-support-on-windows}@anchor{25e1}
@subsubsection Windows的子进程支持


在 Windows 上，默认的事件循环 @ref{1ab,,ProactorEventLoop} 支持子进程，而 @ref{250f,,SelectorEventLoop} 则不支持。

也不支持 @ref{25cc,,policy.set_child_watcher()} 函数，@ref{1ab,,ProactorEventLoop} 有不同的机制来监视子进程。

@node macOS<20>,,Windows<47>,平台支持
@anchor{library/asyncio-platforms macos}@anchor{25e2}
@subsubsection macOS


完整支持流行的macOS版本。

@subsubheading macOS <= 10.8


在 macOS 10.6, 10.7 和 10.8 上，默认的事件循环使用 @ref{25e3,,selectors.KqueueSelector}，在这些版本上它并不支持字符设备。 可以手工配置 @ref{250f,,SelectorEventLoop} 来使用 @ref{25e0,,SelectSelector} 或 @ref{446,,PollSelector} 以在这些较老版本的 macOS 上支持字符设备。 例如:

@example
import asyncio
import selectors

selector = selectors.SelectSelector()
loop = asyncio.SelectorEventLoop(selector)
asyncio.set_event_loop(loop)
@end example

@node 高级API索引,底层API目录,平台支持,asyncio --- 异步 I/O
@anchor{library/asyncio-api-index doc}@anchor{25e4}@anchor{library/asyncio-api-index high-level-api-index}@anchor{25e5}
@subsubsection 高级API索引


这个页面列举了所有能用于 async/wait 的高级asyncio API 集。

@menu
* 任务:: 
* 队列集: 队列集<2>. 
* 子进程集: 子进程集<2>. 
* 流: 流<2>. 
* 同步:: 
* 异常: 异常<10>. 

@end menu

@node 任务,队列集<2>,,高级API索引
@anchor{library/asyncio-api-index tasks}@anchor{25e6}
@subsubsection 任务


运行异步程序，创建Task对象，等待多件事运行超时的公共集。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{1a5,,run()}

@tab

创建事件循环，运行一个协程，关闭事件循环。

@item

@ref{1ae,,create_task()}

@tab

启动一个asyncio的Task对象。

@item

@code{await} @ref{285,,sleep()}

@tab

休眠几秒。

@item

@code{await} @ref{286,,gather()}

@tab

并发执行所有事件的调度和等待。

@item

@code{await} @ref{288,,wait_for()}

@tab

有超时控制的运行。

@item

@code{await} @ref{287,,shield()}

@tab

屏蔽取消操作

@item

@code{await} @ref{289,,wait()}

@tab

完成情况的监控器

@item

@ref{349,,current_task()}

@tab

返回当前Task对象

@item

@ref{34a,,all_tasks()}

@tab

返回事件循环中所有的task对象。

@item

@ref{1ad,,Task}

@tab

Task对象

@item

@ref{514,,run_coroutine_threadsafe()}

@tab

从其他OS线程中调度一个协程。

@item

@code{for in} @ref{28a,,as_completed()}

@tab

用 @code{for} 循环监控完成情况。

@end multitable


@subsubheading 例子



@itemize *

@item 
@ref{2498,,使用 asyncio.gather() 并行运行}.

@item 
@ref{249d,,使用 asyncio.wait_for() 强制超时}.

@item 
@ref{24a8,,撤销协程}.

@item 
@ref{2496,,asyncio.sleep() 的用法}.

@item 
请主要参阅 @ref{2483,,协程与任务文档}.
@end itemize

@node 队列集<2>,子进程集<2>,任务,高级API索引
@anchor{library/asyncio-api-index queues}@anchor{25e7}
@subsubsection 队列集


队列集被用于多个异步Task对象的运行调度，实现连接池以及发布/订阅模式。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{290,,Queue}

@tab

先进先出队列

@item

@ref{2523,,PriorityQueue}

@tab

优先级队列。

@item

@ref{2525,,LifoQueue}

@tab

后进先出队列。

@end multitable


@subsubheading 例子



@itemize *

@item 
@ref{2527,,使用 asyncio.Queue 在多个并发任务间分配工作量}.

@item 
请参阅 @ref{2486,,队列集文档}.
@end itemize

@node 子进程集<2>,流<2>,队列集<2>,高级API索引
@anchor{library/asyncio-api-index subprocesses}@anchor{25e8}
@subsubsection 子进程集


用于生成子进程和运行shell命令的工具包。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{await} @ref{291,,create_subprocess_exec()}

@tab

创建一个子进程。

@item

@code{await} @ref{292,,create_subprocess_shell()}

@tab

运行一个shell命令。

@end multitable


@subsubheading 例子



@itemize *

@item 
@ref{24f3,,执行一个shell命令}.

@item 
请参阅 @ref{2485,,子进程 APIs} 相关文档.
@end itemize

@node 流<2>,同步,子进程集<2>,高级API索引
@anchor{library/asyncio-api-index streams}@anchor{25e9}
@subsubsection 流


用于网络IO处理的高级API集。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{await} @ref{35c,,open_connection()}

@tab

建立一个TCP连接。

@item

@code{await} @ref{24b9,,open_unix_connection()}

@tab

建立一个Unix socket连接。

@item

@code{await} @ref{35d,,start_server()}

@tab

启动TCP服务。

@item

@code{await} @ref{24bb,,start_unix_server()}

@tab

启动一个Unix socket服务。

@item

@ref{f5a,,StreamReader}

@tab

接收网络数据的高级async/await对象。

@item

@ref{f5b,,StreamWriter}

@tab

发送网络数据的高级async/await对象。

@end multitable


@subsubheading 例子



@itemize *

@item 
@ref{24b7,,TCP 客户端样例}.

@item 
请参阅 @ref{2484,,streams APIs} 文档。
@end itemize

@node 同步,异常<10>,流<2>,高级API索引
@anchor{library/asyncio-api-index synchronization}@anchor{25ea}
@subsubsection 同步


能被用于Task对象集的，类似线程的同步基元组件。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{28b,,Lock}

@tab

互斥锁。

@item

@ref{28c,,Event}

@tab

事件对象。

@item

@ref{28d,,Condition}

@tab

条件对象

@item

@ref{28e,,Semaphore}

@tab

信号量

@item

@ref{28f,,BoundedSemaphore}

@tab

有界的信号量。

@end multitable


@subsubheading 例子



@itemize *

@item 
@ref{24e0,,asyncio.Event 的用法}.

@item 
请参阅asyncio文档 @ref{2487,,synchronization primitives}.
@end itemize

@node 异常<10>,,同步,高级API索引
@anchor{library/asyncio-api-index exceptions}@anchor{25eb}
@subsubsection 异常



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{249c,,asyncio.TimeoutError}

@tab

类似 @ref{288,,wait_for()} 等函数在超时时候被引发。请注意 @code{asyncio.TimeoutError} 与内建异常 @ref{996,,TimeoutError} 无关。

@item

@ref{1a7,,asyncio.CancelledError}

@tab

当一个Task对象被取消的时候被引发。请参阅 @ref{249a,,Task.cancel()}。

@end multitable


@subsubheading 例子



@itemize *

@item 
@ref{24a8,,在取消请求发生的运行代码中如何处理CancelledError异常}.

@item 
请参阅完整的 @ref{2529,,asyncio 专用异常} 列表.
@end itemize

@node 底层API目录,用 asyncio 开发,高级API索引,asyncio --- 异步 I/O
@anchor{library/asyncio-llapi-index doc}@anchor{25ec}@anchor{library/asyncio-llapi-index low-level-api-index}@anchor{25ed}
@subsubsection 底层API目录


本页列出所有底层asyncio API。

@menu
* 获取事件循环:: 
* 事件循环方法集: 事件循环方法集<2>. 
* 传输: 传输<2>. 
* 协议: 协议<2>. 
* 事件循环策略:: 

@end menu

@node 获取事件循环,事件循环方法集<2>,,底层API目录
@anchor{library/asyncio-llapi-index obtaining-the-event-loop}@anchor{25ee}
@subsubsection 获取事件循环



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{34d,,asyncio.get_running_loop()}

@tab

获取当前运行的事件循环 @strong{首选} 函数。

@item

@ref{34e,,asyncio.get_event_loop()}

@tab

获得一个事件循环实例(当前或通过策略)。

@item

@ref{2530,,asyncio.set_event_loop()}

@tab

通过当前策略将事件循环设置当前事件循环。

@item

@ref{2531,,asyncio.new_event_loop()}

@tab

创建一个新的事件循环。

@end multitable


@subsubheading 例子



@itemize *

@item 
@ref{257f,,使用asyncio.get_running_loop()}。
@end itemize

@node 事件循环方法集<2>,传输<2>,获取事件循环,底层API目录
@anchor{library/asyncio-llapi-index event-loop-methods}@anchor{25ef}
@subsubsection 事件循环方法集


查阅 @ref{63e,,事件循环方法} 相关的主要文档段落 。

@subsubheading 生命周期



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{512,,loop.run_until_complete()}

@tab

运行一个期程/任务/可等待对象直到完成。

@item

@ref{253a,,loop.run_forever()}

@tab

一直运行事件循环。

@item

@ref{51a,,loop.stop()}

@tab

停止事件循环。

@item

@ref{253c,,loop.close()}

@tab

关闭事件循环。

@item

@ref{253b,,loop.is_running()}

@tab

返回 @code{True} ， 如果事件循环正在运行。

@item

@ref{695,,loop.is_closed()}

@tab

返回 @code{True} ，如果事件循环已经被关闭 。

@item

@code{await} @ref{51b,,loop.shutdown_asyncgens()}

@tab

关闭异步生成器。

@end multitable


@subsubheading 调试



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{693,,loop.set_debug()}

@tab

开启或禁用调试模式。

@item

@ref{694,,loop.get_debug()}

@tab

获取当前测试模式。

@end multitable


@subsubheading 调度回调函数



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{342,,loop.call_soon()}

@tab

尽快调用回调。

@item

@ref{343,,loop.call_soon_threadsafe()}

@tab

@ref{342,,loop.call_soon()} 方法线程安全的变体。

@item

@ref{344,,loop.call_later()}

@tab

在给定时间 @emph{之后} 调用回调函数。

@item

@ref{345,,loop.call_at()}

@tab

在 @emph{指定} 时间调用回调函数。

@end multitable


@subsubheading 线程/进程池



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{await} @ref{2492,,loop.run_in_executor()}

@tab

在  @ref{22,,concurrent.futures} 执行器中运行一个独占CPU或其它阻塞函数。

@item

@ref{27b,,loop.set_default_executor()}

@tab

设置  @ref{2492,,loop.run_in_executor()} 默认执行器。

@end multitable


@subsubheading 任务与期程



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{516,,loop.create_future()}

@tab

创建一个 @ref{43d,,Future} 对象。

@item

@ref{1af,,loop.create_task()}

@tab

将协程当作 @ref{1ad,,Task} 一样调度。

@item

@ref{697,,loop.set_task_factory()}

@tab

设置 @ref{1af,,loop.create_task()} 使用的工厂，它将用来创建  @ref{1ad,,Tasks}  。

@item

@ref{698,,loop.get_task_factory()}

@tab

获取 @ref{1af,,loop.create_task()} 使用的工厂，它用来创建  @ref{1ad,,Tasks}  。

@end multitable


@subsubheading DNS



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{await} @ref{49c,,loop.getaddrinfo()}

@tab

异步版的 @ref{2559,,socket.getaddrinfo()} 。

@item

@code{await} @ref{49d,,loop.getnameinfo()}

@tab

异步版的 @ref{255a,,socket.getnameinfo()} 。

@end multitable


@subsubheading 网络和IPC



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{await} @ref{1b2,,loop.create_connection()}

@tab

打开一个TCP链接。

@item

@code{await} @ref{356,,loop.create_server()}

@tab

创建一个TCP服务。

@item

@code{await} @ref{24ba,,loop.create_unix_connection()}

@tab

打开一个Unix socket连接。

@item

@code{await} @ref{357,,loop.create_unix_server()}

@tab

创建一个Unix socket服务。

@item

@code{await} @ref{35e,,loop.connect_accepted_socket()}

@tab

将 @ref{66e,,socket} 包装成  @code{(transport, protocol)} 对。

@item

@code{await} @ref{2e7,,loop.create_datagram_endpoint()}

@tab

打开一个数据报(UDP)连接。

@item

@code{await} @ref{2550,,loop.sendfile()}

@tab

通过传输通道发送一个文件。

@item

@code{await} @ref{347,,loop.start_tls()}

@tab

将一个已建立的链接升级到TLS。

@item

@code{await} @ref{24f9,,loop.connect_read_pipe()}

@tab

将管道读取端包装成  @code{(transport, protocol)} 对。

@item

@code{await} @ref{24fa,,loop.connect_write_pipe()}

@tab

将管道写入端包装成  @code{(transport, protocol)} 对。

@end multitable


@subsubheading 套接字



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{await} @ref{499,,loop.sock_recv()}

@tab

从 @ref{66e,,socket} 接收数据。

@item

@code{await} @ref{348,,loop.sock_recv_into()}

@tab

从 @ref{66e,,socket} 接收数据到一个缓冲区中。

@item

@code{await} @ref{49a,,loop.sock_sendall()}

@tab

发送数据到 @ref{66e,,socket} 。

@item

@code{await} @ref{69b,,loop.sock_connect()}

@tab

链接 @code{await} @ref{69b,,loop.sock_connect()} 。

@item

@code{await} @ref{49b,,loop.sock_accept()}

@tab

接受一个 @ref{66e,,socket} 链接。

@item

@code{await} @ref{351,,loop.sock_sendfile()}

@tab

利用 @ref{66e,,socket} 发送一个文件。

@item

@ref{24d7,,loop.add_reader()}

@tab

开始对一个文件描述符的可读性的监视。

@item

@ref{2553,,loop.remove_reader()}

@tab

停止对一个文件描述符的可读性的监视。

@item

@ref{2554,,loop.add_writer()}

@tab

开始对一个文件描述符的可写性的监视。

@item

@ref{2555,,loop.remove_writer()}

@tab

停止对一个文件描述符的可写性的监视。

@end multitable


@subsubheading Unix信号



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{2489,,loop.add_signal_handler()}

@tab

给 @ref{ea,,signal} 添加一个处理回调函数。

@item

@ref{255f,,loop.remove_signal_handler()}

@tab

删除 @ref{ea,,signal} 的处理回调函数。

@end multitable


@subsubheading 子进程集



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{2488,,loop.subprocess_exec()}

@tab

衍生一个子进程

@item

@ref{24f7,,loop.subprocess_shell()}

@tab

从终端命令衍生一个子进程。

@end multitable


@subsubheading 错误处理



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{2563,,loop.call_exception_handler()}

@tab

调用异常处理器。

@item

@ref{2562,,loop.set_exception_handler()}

@tab

设置一个新的异常处理器。

@item

@ref{517,,loop.get_exception_handler()}

@tab

获取当前异常处理器。

@item

@ref{2564,,loop.default_exception_handler()}

@tab

默认异常处理器实现。

@end multitable


@subsubheading 例子



@itemize *

@item 
@ref{256e,,使用 asyncio.get_event_loop() 和 loop.run_forever()}.

@item 
@ref{2570,,使用 loop.call_later()}.

@item 
使用 @code{loop.create_connection()} 实现 @ref{24ce,,echo客户端}.

@item 
使用 @code{loop.create_connection()} 去 @ref{24d5,,链接socket}.

@item 
@ref{24d6,,使用add_reader()监听FD(文件描述符)的读取事件}.

@item 
@ref{2573,,使用loop.add_signal_handler()}.

@item 
@ref{2513,,使用loop.add_signal_handler()}。
@end itemize

@node 传输<2>,协议<2>,事件循环方法集<2>,底层API目录
@anchor{library/asyncio-llapi-index transports}@anchor{25f0}
@subsubsection 传输


所有传输都实现以下方法:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{258d,,transport.close()}

@tab

关闭传输。

@item

@ref{515,,transport.is_closing()}

@tab

返回 @code{True} ，如果传输正在关闭或已经关闭。

@item

@ref{2c8,,transport.get_extra_info()}

@tab

请求传输的相关信息。

@item

@ref{2592,,transport.set_protocol()}

@tab

设置一个新协议。

@item

@ref{2593,,transport.get_protocol()}

@tab

返回当前协议。

@end multitable


传输可以接收数据(TCP和Unix链接，管道等)。它通过 @ref{1b2,,loop.create_connection()}, @ref{24ba,,loop.create_unix_connection()}, @ref{24f9,,loop.connect_read_pipe()} 等方法返回。

@subsubheading 读取传输



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{360,,transport.is_reading()}

@tab

返回 @code{True} ，如果传输正在接收。

@item

@ref{362,,transport.pause_reading()}

@tab

暂停接收。

@item

@ref{361,,transport.resume_reading()}

@tab

继续接收。

@end multitable


传输可以发送数据(TCP和Unix链接，管道等)。它通过 @ref{1b2,,loop.create_connection()}, @ref{24ba,,loop.create_unix_connection()}, @ref{24fa,,loop.connect_write_pipe()} 等方法返回。

@subsubheading 写入传输



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{259e,,transport.write()}

@tab

向传输写入数据。

@item

@ref{259e,,transport.write()}

@tab

向传输写入缓冲。

@item

@ref{2598,,transport.can_write_eof()}

@tab

返回  @ref{494,,True} ，如果传输支持发送 EOF。

@item

@ref{2599,,transport.write_eof()}

@tab

在冲洗已缓冲的数据后关闭传输和发送EOF。

@item

@ref{2597,,transport.abort()}

@tab

立即关闭传输。

@item

@ref{259a,,transport.get_write_buffer_size()}

@tab

返回写入流控制的高位标记位和低位标记位。

@item

@ref{259b,,transport.set_write_buffer_limits()}

@tab

设置新的写入流控制的高位标记位和低位标记位。

@end multitable


由 @ref{2e7,,loop.create_datagram_endpoint()} 返回的传输:

@subsubheading 数据报传输



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{25a1,,transport.sendto()}

@tab

发送数据到远程链接端。

@item

@ref{25a2,,transport.abort()}

@tab

立即关闭传输。

@end multitable


基于子进程的底层抽象传输，它由 @ref{2488,,loop.subprocess_exec()} 和 @ref{24f7,,loop.subprocess_shell()} 返回:

@subsubheading 子进程传输



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{25a4,,transport.get_pid()}

@tab

返回子进程的进程ID。

@item

@ref{25a5,,transport.get_pipe_transport()}

@tab

返回请求通信管道 (@emph{stdin}, @emph{stdout}, 或 @emph{stderr})的传输。

@item

@ref{25a6,,transport.get_returncode()}

@tab

返回子进程的返回代号。

@item

@ref{25a7,,transport.kill()}

@tab

杀死子进程。

@item

@ref{25a9,,transport.send_signal()}

@tab

发送一个信号到子进程。

@item

@ref{25a8,,transport.terminate()}

@tab

停止子进程。

@item

@ref{25aa,,transport.close()}

@tab

杀死子进程并关闭所有管道。

@end multitable


@node 协议<2>,事件循环策略,传输<2>,底层API目录
@anchor{library/asyncio-llapi-index protocols}@anchor{25f1}
@subsubsection 协议


协议类可以由下面 @strong{回调方法} 实现：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{callback} @ref{2549,,connection_made()}

@tab

链接建立时被调用。

@item

@code{callback} @ref{258e,,connection_lost()}

@tab

链接丢失或关闭时被调用。

@item

@code{callback} @ref{259c,,pause_writing()}

@tab

传输的缓冲区超过高位标记位时被调用。

@item

@code{callback} @ref{259d,,resume_writing()}

@tab

传输的缓冲区传送到低位标记位时被调用。

@end multitable


@subsubheading 流协议 (TCP, Unix 套接字, 管道)



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{callback} @ref{2595,,data_received()}

@tab

接收到数据时被调用。

@item

@code{callback} @ref{25ae,,eof_received()}

@tab

接收到EOF时被调用。

@end multitable


@subsubheading 缓冲流协议



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{callback} @ref{25b0,,get_buffer()}

@tab

调用后会分配新的接收缓冲区。

@item

@code{callback} @ref{25b1,,buffer_updated()}

@tab

用接收的数据更新缓冲区时被调用。

@item

@code{callback} @ref{25b2,,eof_received()}

@tab

接收到EOF时被调用。

@end multitable


@subsubheading 数据报协议



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{callback} @ref{25b4,,datagram_received()}

@tab

接收到数据报时被调用。

@item

@code{callback} @ref{25b5,,error_received()}

@tab

前一个发送或接收操作引发  @ref{1d3,,OSError} 时被调用。

@end multitable


@subsubheading 子进程协议



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{callback} @ref{25b7,,pipe_data_received()}

@tab

子进程向 @emph{stdout} 或 @emph{stderr} 管道写入数据时被调用。

@item

@code{callback} @ref{25b8,,pipe_connection_lost()}

@tab

与子进程通信的其中一个管道关闭时被调用。

@item

@code{callback} @ref{25b9,,process_exited()}

@tab

子进程退出时被调用。

@end multitable


@node 事件循环策略,,协议<2>,底层API目录
@anchor{library/asyncio-llapi-index event-loop-policies}@anchor{25f2}
@subsubsection 事件循环策略


策略是改变 @ref{34e,,asyncio.get_event_loop()} 这类函数行为的一个底层机制。更多细节可以查阅 @ref{2532,,策略部分}。

@subsubheading 访问策略



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@ref{25c4,,asyncio.get_event_loop_policy()}

@tab

返回当前进程域的策略。

@item

@ref{25c5,,asyncio.set_event_loop_policy()}

@tab

设置一个新的进程域策略。

@item

@ref{25c2,,AbstractEventLoopPolicy}

@tab

策略对象的基类。

@end multitable


@node 用 asyncio 开发,,底层API目录,asyncio --- 异步 I/O
@anchor{library/asyncio-dev doc}@anchor{25f3}@anchor{library/asyncio-dev asyncio-dev}@anchor{25f4}@anchor{library/asyncio-dev developing-with-asyncio}@anchor{25f5}
@subsubsection 用 asyncio 开发


异步编程与传统的“顺序”编程不同。

本页列出常见的错误和陷阱，并解释如何避免它们。

@menu
* Debug 模式:: 
* 并发性和多线程:: 
* 运行阻塞的代码:: 
* 日志记录: 日志记录<3>. 
* 检测 never-awaited 协同程序:: 
* 检测就再也没异常:: 

@end menu

@node Debug 模式,并发性和多线程,,用 asyncio 开发
@anchor{library/asyncio-dev asyncio-debug-mode}@anchor{12e6}@anchor{library/asyncio-dev debug-mode}@anchor{25f6}
@subsubsection Debug 模式


默认情况下，asyncio以生产模式运行。为了简化开发，asyncio还有一种*debug 模式* 。

有几种方法可以启用异步调试模式:


@itemize *

@item 
将 
@geindex PYTHONASYNCIODEBUG
@geindex 环境变量; PYTHONASYNCIODEBUG
@ref{12f2,,PYTHONASYNCIODEBUG} 环境变量设置为 @code{1} 。

@item 
使用 @ref{155,,-X} @code{dev} Python 命令行选项。

@item 
将 @code{debug=True} 传递给 @ref{1a5,,asyncio.run()} 。

@item 
调用 @ref{693,,loop.set_debug()} 。
@end itemize

除了启用调试模式外，还要考虑:


@itemize *

@item 
将 @ref{25f7,,asyncio logger} 的日志级别设置为 @code{logging.DEBUG}，例如，下面的代码片段可以在应用程序启动时运行:

@example
logging.basicConfig(level=logging.DEBUG)
@end example

@item 
配置 @ref{126,,warnings} 模块以显示 @ref{4ca,,ResourceWarning} 警告。一种方法是使用 @ref{40f,,-W} @code{default} 命令行选项。
@end itemize

启用调试模式时:


@itemize *

@item 
asyncio 检查 @ref{25f8,,未被等待的协程} 并记录他们；这将消除“被遗忘的等待”问题。

@item 
许多非线程安全的异步 APIs (例如 @ref{342,,loop.call_soon()} 和 @ref{345,,loop.call_at()} 方法)，如果从错误的线程调用，则会引发异常。

@item 
如果执行I/O操作花费的时间太长，则记录I/O选择器的执行时间。

@item 
执行时间超过100毫秒的回调将会载入日志。 属性 @code{loop.slow_callback_duration} 可用于设置以秒为单位的最小执行持续时间，这被视为“缓慢”。
@end itemize

@node 并发性和多线程,运行阻塞的代码,Debug 模式,用 asyncio 开发
@anchor{library/asyncio-dev asyncio-multithreading}@anchor{24a1}@anchor{library/asyncio-dev concurrency-and-multithreading}@anchor{25f9}
@subsubsection 并发性和多线程


事件循环在线程中运行(通常是主线程)，并在其线程中执行所有回调和任务。当一个任务在事件循环中运行时，没有其他任务可以在同一个线程中运行。当一个任务执行一个 @code{await} 表达式时，正在运行的任务被挂起，事件循环执行下一个任务。

要调度来自另一 OS 线程的 @ref{253e,,callback}，应该使用 @ref{343,,loop.call_soon_threadsafe()} 方法。 例如:

@example
loop.call_soon_threadsafe(callback, *args)
@end example

几乎所有异步对象都不是线程安全的，这通常不是问题，除非在任务或回调函数之外有代码可以使用它们。如果需要这样的代码来调用低级异步API，应该使用 @ref{343,,loop.call_soon_threadsafe()} 方法，例如:

@example
loop.call_soon_threadsafe(fut.cancel)
@end example

要从不同的OS线程调度一个协程对象，应该使用 @ref{514,,run_coroutine_threadsafe()} 函数。它返回一个 @ref{b26,,concurrent.futures.Future} 。查询结果:

@example
async def coro_func():
     return await asyncio.sleep(1, 42)

# Later in another OS thread:

future = asyncio.run_coroutine_threadsafe(coro_func(), loop)
# Wait for the result:
result = future.result()
@end example

为了能够处理信号和执行子进程，事件循环必须运行于主线程中。

方法 @ref{2492,,loop.run_in_executor()} 可以和 @ref{27a,,concurrent.futures.ThreadPoolExecutor} 一起使用，用于在一个不同的操作系统线程中执行阻塞代码，并避免阻塞运行事件循环的那个操作系统线程。

@node 运行阻塞的代码,日志记录<3>,并发性和多线程,用 asyncio 开发
@anchor{library/asyncio-dev asyncio-handle-blocking}@anchor{25fa}@anchor{library/asyncio-dev running-blocking-code}@anchor{25fb}
@subsubsection 运行阻塞的代码


不应该直接调用阻塞( CPU 绑定)代码。例如，如果一个函数执行1秒的 CPU 密集型计算，那么所有并发异步任务和 IO 操作都将延迟1秒。

可以用执行器在不同的线程甚至不同的进程中运行任务，以避免使用事件循环阻塞 OS 线程。 请参阅 @ref{2492,,loop.run_in_executor()} 方法了解详情。

@node 日志记录<3>,检测 never-awaited 协同程序,运行阻塞的代码,用 asyncio 开发
@anchor{library/asyncio-dev asyncio-logger}@anchor{25f7}@anchor{library/asyncio-dev logging}@anchor{25fc}
@subsubsection 日志记录


asyncio使用 @ref{aa,,logging} 模块，所有日志记录都是通过 @code{"asyncio"} logger执行的。

默认日志级别是 @code{logging.INFO} 。可以很容易地调整:

@example
logging.getLogger("asyncio").setLevel(logging.WARNING)
@end example

@node 检测 never-awaited 协同程序,检测就再也没异常,日志记录<3>,用 asyncio 开发
@anchor{library/asyncio-dev asyncio-coroutine-not-scheduled}@anchor{25f8}@anchor{library/asyncio-dev detect-never-awaited-coroutines}@anchor{25fd}
@subsubsection 检测 never-awaited 协同程序


当协程函数被调用而不是被等待时 (即执行 @code{coro()} 而不是 @code{await coro()}) 或者协程没有通过 @ref{1ae,,asyncio.create_task()} 被排入计划日程，asyncio 将会发出一条 @ref{2c0,,RuntimeWarning}:

@example
import asyncio

async def test():
    print("never scheduled")

async def main():
    test()

asyncio.run(main())
@end example

输出:

@example
test.py:7: RuntimeWarning: coroutine 'test' was never awaited
  test()
@end example

调试模式的输出:

@example
test.py:7: RuntimeWarning: coroutine 'test' was never awaited
Coroutine created at (most recent call last)
  File "../t.py", line 9, in <module>
    asyncio.run(main(), debug=True)

  < .. >

  File "../t.py", line 7, in main
    test()
  test()
@end example

通常的修复方法是等待协程或者调用 @ref{1ae,,asyncio.create_task()} 函数:

@example
async def main():
    await test()
@end example

@node 检测就再也没异常,,检测 never-awaited 协同程序,用 asyncio 开发
@anchor{library/asyncio-dev detect-never-retrieved-exceptions}@anchor{25fe}
@subsubsection 检测就再也没异常


如果调用 @ref{24a6,,Future.set_exception()} ，但不等待 Future 对象，将异常传播到用户代码。在这种情况下，当 Future 对象被垃圾收集时，asyncio将发出一条日志消息。

未处理异常的例子:

@example
import asyncio

async def bug():
    raise Exception("not consumed")

async def main():
    asyncio.create_task(bug())

asyncio.run(main())
@end example

输出:

@example
Task exception was never retrieved
future: <Task finished coro=<bug() done, defined at test.py:3>
  exception=Exception('not consumed')>

Traceback (most recent call last):
  File "test.py", line 4, in bug
    raise Exception("not consumed")
Exception: not consumed
@end example

@ref{12e6,,激活调试模式} 以获取任务创建处的跟踪信息:

@example
asyncio.run(main(), debug=True)
@end example

调试模式的输出:

@example
Task exception was never retrieved
future: <Task finished coro=<bug() done, defined at test.py:3>
    exception=Exception('not consumed') created at asyncio/tasks.py:321>

source_traceback: Object created at (most recent call last):
  File "../t.py", line 9, in <module>
    asyncio.run(main(), debug=True)

< .. >

Traceback (most recent call last):
  File "../t.py", line 4, in bug
    raise Exception("not consumed")
Exception: not consumed
@end example

@cartouche
@quotation 注解 
asyncio 的源代码可以在 Lib/asyncio/@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/} 中找到。
@end quotation
@end cartouche

@node socket --- 底层网络接口,ssl --- 套接字对象的TLS/SSL封装,asyncio --- 异步 I/O,网络和进程间通信
@anchor{library/socket doc}@anchor{25ff}@anchor{library/socket module-socket}@anchor{ef}@anchor{library/socket socket-low-level-networking-interface}@anchor{2600}
@subsection @code{socket} --- 底层网络接口


@geindex socket (模块)

@strong{源代码:} Lib/socket.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/socket.py}


__________________________________________________________________


这个模块提供了访问 BSD @emph{套接字} 的接口。在所有现代 Unix 系统、Windows、macOS 和其他一些平台上可用。

@cartouche
@quotation 注解 
一些行为可能因平台不同而异，因为调用的是操作系统的套接字API。
@end quotation
@end cartouche

@geindex 对象; socket

这个Python接口是用Python的面向对象风格对Unix系统调用和套接字库接口的直译：函数 @ref{66e,,socket()} 返回一个 @emph{套接字对象} ，其方法是对各种套接字系统调用的实现。形参类型一般与C接口相比更高级：例如在Python文件 @code{read()} 和 @code{write()} 操作中，接收操作的缓冲区分配是自动的，发送操作的缓冲区长度是隐式的。


@subsubheading 参见



@table @asis

@item 模块 @ref{f0,,socketserver}

用于简化网络服务端编写的类。

@item 模块 @ref{f3,,ssl}

套接字对象的TLS/SSL封装。
@end table


@menu
* 套接字协议族:: 
* 模块内容: 模块内容<4>. 
* 套接字对象:: 
* 关于套接字超时的说明:: 
* 示例: 示例<8>. 

@end menu

@node 套接字协议族,模块内容<4>,,socket --- 底层网络接口
@anchor{library/socket socket-families}@anchor{2601}
@subsubsection 套接字协议族


根据系统以及构建选项，此模块提供了各种套接字协议簇。

特定的套接字对象需要的地址格式将根据此套接字对象被创建时指定的地址族被自动选择。套接字地址表示如下：


@itemize -

@item 
一个绑定在文件系统节点上的 @ref{254b,,AF_UNIX} 套接字的地址表示为一个字符串，使用文件系统字符编码和 @code{'surrogateescape'} 错误回调方法（see 
@geindex Python 提高建议; PEP 383
PEP 383@footnote{https://www.python.org/dev/peps/pep-0383}）。一个地址在 Linux 的抽象命名空间被返回为带有初始的 null 字节的 @ref{5e3,,字节类对象} ；注意在这个命名空间种的套接字可能与普通文件系统套接字通信，所以打算运行在 Linux 上的程序可能需要解决两种地址类型。当传递为参数时，一个字符串或字节类对象可以用于任一类型的地址。

@quotation


在 3.3 版更改: 之前，@ref{254b,,AF_UNIX} 套接字路径被假设使用 UTF-8 编码。



在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。

@end quotation
@end itemize
@anchor{library/socket host-port}@anchor{2602}

@itemize -

@item 
一对 @code{(host, port)} 被用于 @ref{2545,,AF_INET} 地址族，@emph{host} 是一个表示为互联网域名表示法之内的主机名或者一个 IPv4 地址的字符串，例如 @code{'daring.cwi.nl'} 或 @code{'100.50.200.5'}，@emph{port} 是一个整数。


@itemize -

@item 
对于 IPv4 地址，有两种可接受的特殊形式被用来代替一个主机地址： @code{'@w{'}} 代表 @code{INADDR_ANY}，用来绑定到所有接口；字符串 @code{'<broadcast>'} 代表 @code{INADDR_BROADCAST}。此行为不兼容 IPv6，因此，如果你的 Python 程序打算支持 IPv6，则可能需要避开这些。
@end itemize

@item 
对于 @ref{2546,,AF_INET6} 地址族，使用一个四元组 @code{(host, port, flowinfo, scopeid)}，其中 @emph{flowinfo} 和 @emph{scopeid} 代表了 C 库 @code{struct sockaddr_in6} 中的 @code{sin6_flowinfo} 和 @code{sin6_scope_id} 成员。对于 @ref{ef,,socket} 模块中的方法， @emph{flowinfo} 和 @emph{scopeid} 可以被省略，只为了向后兼容。注意，省略 @emph{scopeid} 可能会导致操作带有领域 (Scope) 的 IPv6 地址时出错。


在 3.7 版更改: 对于多播地址（其 @emph{scopeid} 起作用），@emph{地址} 中可以不包含 @code{%scope} （或 @code{zone id} ）部分，这部分是多余的，可以放心省略（推荐）。


@item 
@code{AF_NETLINK} 套接字由一对 @code{(pid, groups)} 表示。

@item 
指定 @code{AF_TIPC} 地址族可以使用仅 Linux 支持的 TIPC 协议。TIPC 是一种开放的、非基于 IP 的网络协议，旨在用于集群计算环境。其地址用元组表示，其中的字段取决于地址类型。一般元组形式为 @code{(addr_type, v1, v2, v3 [, scope])}，其中：


@itemize -

@item 
@emph{addr_type} 取 @code{TIPC_ADDR_NAMESEQ}、@code{TIPC_ADDR_NAME} 或 @code{TIPC_ADDR_ID} 中的一个。

@item 
@emph{scope} 取 @code{TIPC_ZONE_SCOPE}、@code{TIPC_CLUSTER_SCOPE} 和 @code{TIPC_NODE_SCOPE} 中的一个。

@item 
如果 @emph{addr_type} 为 @code{TIPC_ADDR_NAME}，那么 @emph{v1} 是服务器类型，@emph{v2} 是端口标识符，@emph{v3} 应为 0。

如果 @emph{addr_type} 为 @code{TIPC_ADDR_NAMESEQ}，那么 @emph{v1} 是服务器类型，@emph{v2} 是端口号下限，而 @emph{v3} 是端口号上限。

如果 @emph{addr_type} 为 @code{TIPC_ADDR_ID}，那么 @emph{v1} 是节点 (node)，@emph{v2} 是 ref，@emph{v3} 应为 0。
@end itemize

@item 
@ref{2603,,AF_CAN} 地址族使用元组 @code{(interface, )}，其中 @emph{interface} 是表示网络接口名称的字符串，如 @code{'can0'}。网络接口名 @code{'@w{'}} 可以用于接收本族所有网络接口的数据包。


@itemize -

@item 
@ref{2604,,CAN_ISOTP} 协议接受一个元组 @code{(interface, rx_addr, tx_addr)}，其中两个额外参数都是无符号长整数，都表示 CAN 标识符（标准或扩展标识符）。
@end itemize

@item 
@code{PF_SYSTEM} 协议簇的 @code{SYSPROTO_CONTROL} 协议接受一个字符串或元组 @code{(id, unit)}。其中字符串是内核控件的名称，该控件使用动态分配的 ID。而如果 ID 和内核控件的单元 (unit) 编号都已知，或使用了已注册的 ID，可以采用元组。


3.3 新版功能.


@item 
@code{AF_BLUETOOTH} 支持以下协议和地址格式：


@itemize -

@item 
@code{BTPROTO_L2CAP} 接受 @code{(bdaddr, psm)}，其中 @code{bdaddr} 为字符串格式的蓝牙地址，@code{psm} 是一个整数。

@item 
@code{BTPROTO_RFCOMM} 接受 @code{(bdaddr, channel)}，其中 @code{bdaddr} 为字符串格式的蓝牙地址，@code{channel} 是一个整数。

@item 
@code{BTPROTO_HCI} 接受 @code{(device_id,)}，其中 @code{device_id} 为整数或字符串，它表示接口对应的蓝牙地址（具体取决于你的系统，NetBSD 和 DragonFlyBSD 需要蓝牙地址字符串，其他系统需要整数）。


在 3.2 版更改: 添加了对 NetBSD 和 DragonFlyBSD 的支持。


@item 
@code{BTPROTO_SCO} 接受 @code{bdaddr}，其中 @code{bdaddr} 是 @ref{32a,,bytes} 对象，其中含有字符串格式的蓝牙地址（如 @code{b'12:23:34:45:56:67'} ），FreeBSD 不支持此协议。
@end itemize

@item 
@ref{57f,,AF_ALG} 是一个仅 Linux 可用的、基于套接字的接口，用于连接内核加密算法。算法套接字可用包括 2 至 4 个元素的元组来配置 @code{(type, name [, feat [, mask]])}，其中：


@itemize -

@item 
@emph{type} 是表示算法类型的字符串，如 @code{aead}、@code{hash}、@code{skcipher} 或 @code{rng}。

@item 
@emph{name} 是表示算法类型和操作模式的字符串，如 @code{sha256}、@code{hmac(sha256)}、@code{cbc(aes)} 或 @code{drbg_nopr_ctr_aes256}。

@item 
@emph{feat} 和 @emph{mask} 是无符号 32 位整数。
@end itemize

@ref{12f5,,Availability}: Linux 2.6.38, some algorithm types require more recent Kernels.


3.6 新版功能.


@item 
@ref{3cb,,AF_VSOCK} 用于支持虚拟机与宿主机之间的通讯。该套接字用 @code{(CID, port)} 元组表示，其中 Context ID (CID) 和 port 都是整数。

@ref{12f5,,Availability}: Linux >= 4.8 QEMU >= 2.8 ESX >= 4.0 ESX Workstation >= 6.5.


3.7 新版功能.


@item 
@ref{2605,,AF_PACKET} 是一个底层接口，直接连接至网卡。数据包使用元组 @code{(ifname, proto[, pkttype[, hatype[, addr]]])} 表示，其中：


@itemize -

@item 
@emph{ifname} - 指定设备名称的字符串。

@item 
@emph{proto} - 一个用网络字节序表示的整数，指定以太网协议版本号。

@item 
@emph{pkttype} - 指定数据包类型的整数（可选）：


@itemize -

@item 
@code{PACKET_HOST} （默认） - 寻址到本地主机的数据包。

@item 
@code{PACKET_BROADCAST} - 物理层广播的数据包。

@item 
@code{PACKET_MULTIHOST} - 发送到物理层多播地址的数据包。

@item 
@code{PACKET_OTHERHOST} - 被（处于混杂模式的）网卡驱动捕获的、发送到其他主机的数据包。

@item 
@code{PACKET_OUTGOING} - 来自本地主机的、回环到一个套接字的数据包。
@end itemize

@item 
@emph{hatype} - 可选整数，指定 ARP 硬件地址类型。

@item 
@emph{addr} - 可选的类字节串对象，用于指定硬件物理地址，其解释取决于各设备。
@end itemize

@item 
@ref{2606,,AF_QIPCRTR} 是一个仅 Linux 可用的、基于套接字的接口，用于与高通平台中协处理器上运行的服务进行通信。该地址簇用一个 @code{(node, port)} 元组表示，其中 @emph{node} 和 @emph{port} 为非负整数。


3.8 新版功能.

@end itemize

如果你在 IPv4/v6 套接字地址的 @emph{host} 部分中使用了一个主机名，此程序可能会表现不确定行为，因为 Python 使用 DNS 解析返回的第一个地址。套接字地址在实际的 IPv4/v6 中以不同方式解析，根据 DNS 解析和/或 host 配置。为了确定行为，在 @emph{host} 部分中使用数字的地址。

所有的错误都抛出异常。对于无效的参数类型和内存溢出异常情况可能抛出普通异常；从 Python 3.3 开始，与套接字或地址语义有关的错误抛出 @ref{1d3,,OSError} 或它的子类之一（常用 @ref{98f,,socket.error}）。

可以用 @ref{1ea7,,setblocking()} 设置非阻塞模式。一个基于超时的 generalization 通过 @ref{2607,,settimeout()} 支持。

@node 模块内容<4>,套接字对象,套接字协议族,socket --- 底层网络接口
@anchor{library/socket module-contents}@anchor{2608}
@subsubsection 模块内容


@ref{ef,,socket} 模块导出以下元素。

@menu
* 异常: 异常<11>. 
* 常量: 常量<8>. 
* 函数: 函数<5>. 

@end menu

@node 异常<11>,常量<8>,,模块内容<4>
@anchor{library/socket exceptions}@anchor{2609}
@subsubsection 异常


@geindex error
@anchor{library/socket socket error}@anchor{98f}
@deffn {例外} socket.error

一个被弃用的 @ref{1d3,,OSError} 的别名。


在 3.3 版更改: 根据 
@geindex Python 提高建议; PEP 3151
PEP 3151@footnote{https://www.python.org/dev/peps/pep-3151}，这个类是 @ref{1d3,,OSError} 的别名。

@end deffn

@geindex herror
@anchor{library/socket socket herror}@anchor{260a}
@deffn {例外} socket.herror

@ref{1d3,,OSError} 的子类，本异常通常表示与地址相关的错误，比如那些在 POSIX C API 中使用了 @emph{h_errno} 的函数，包括 @ref{260b,,gethostbyname_ex()} 和 @ref{260c,,gethostbyaddr()}。附带的值是一对 @code{(h_errno, string)}，代表库调用返回的错误。@emph{h_errno} 是一个数字，而 @emph{string} 表示 @emph{h_errno} 的描述，它们由 C 函数 @code{hstrerror()} 返回。


在 3.3 版更改: 此类是 @ref{1d3,,OSError} 的子类。

@end deffn

@geindex gaierror
@anchor{library/socket socket gaierror}@anchor{260d}
@deffn {例外} socket.gaierror

@ref{1d3,,OSError} 的子类，本异常来自 @ref{2559,,getaddrinfo()} 和 @ref{255a,,getnameinfo()}，表示与地址相关的错误。附带的值是一对 @code{(error, string)}，代表库调用返回的错误。@emph{string} 表示 @emph{error} 的描述，它由 C 函数 @code{gai_strerror()} 返回。数字值 @emph{error} 与本模块中定义的 @code{EAI_*} 常量之一匹配。


在 3.3 版更改: 此类是 @ref{1d3,,OSError} 的子类。

@end deffn

@geindex timeout
@anchor{library/socket socket timeout}@anchor{c07}
@deffn {例外} socket.timeout

@ref{1d3,,OSError} 的子类，当套接字发生超时，且事先已调用过 @ref{2607,,settimeout()} （或隐式地通过 @ref{260e,,setdefaulttimeout()} ）启用了超时，则会抛出此异常。附带的值是一个字符串，其值总是 "timed out"。


在 3.3 版更改: 此类是 @ref{1d3,,OSError} 的子类。

@end deffn

@node 常量<8>,函数<5>,异常<11>,模块内容<4>
@anchor{library/socket constants}@anchor{260f}
@subsubsection 常量


@quotation

AF_* 和 SOCK_* 常量现在都在 @code{AddressFamily} 和 @code{SocketKind} 这两个 @ref{588,,IntEnum} 集合内。


3.4 新版功能.

@end quotation

@geindex AF_UNIX() (在 socket 模块中)
@geindex AF_INET() (在 socket 模块中)
@geindex AF_INET6() (在 socket 模块中)
@anchor{library/socket socket AF_UNIX}@anchor{254b}
@deffn {数据} socket.AF_UNIX
@anchor{library/socket socket AF_INET}@anchor{2545}
@deffnx {数据} socket.AF_INET
@anchor{library/socket socket AF_INET6}@anchor{2546}
@deffnx {数据} socket.AF_INET6

这些常量表示地址（和协议）簇，用于 @ref{66e,,socket()} 的第一个参数。如果 @ref{254b,,AF_UNIX} 常量未定义，即表示不支持该协议。不同系统可能会有更多其他常量可用。
@end deffn

@geindex SOCK_STREAM() (在 socket 模块中)
@geindex SOCK_DGRAM() (在 socket 模块中)
@geindex SOCK_RAW() (在 socket 模块中)
@geindex SOCK_RDM() (在 socket 模块中)
@geindex SOCK_SEQPACKET() (在 socket 模块中)
@anchor{library/socket socket SOCK_STREAM}@anchor{c83}
@deffn {数据} socket.SOCK_STREAM
@anchor{library/socket socket SOCK_DGRAM}@anchor{c82}
@deffnx {数据} socket.SOCK_DGRAM
@anchor{library/socket socket SOCK_RAW}@anchor{2610}
@deffnx {数据} socket.SOCK_RAW
@anchor{library/socket socket SOCK_RDM}@anchor{2611}
@deffnx {数据} socket.SOCK_RDM
@anchor{library/socket socket SOCK_SEQPACKET}@anchor{2612}
@deffnx {数据} socket.SOCK_SEQPACKET

这些常量表示套接字类型，用于 @ref{66e,,socket()} 的第二个参数。不同系统可能会有更多其他常量可用。（一般只有 @ref{c83,,SOCK_STREAM} 和 @ref{c82,,SOCK_DGRAM} 可用）
@end deffn

@geindex SOCK_CLOEXEC() (在 socket 模块中)
@geindex SOCK_NONBLOCK() (在 socket 模块中)
@anchor{library/socket socket SOCK_CLOEXEC}@anchor{492}
@deffn {数据} socket.SOCK_CLOEXEC
@anchor{library/socket socket SOCK_NONBLOCK}@anchor{491}
@deffnx {数据} socket.SOCK_NONBLOCK

这两个常量（如果已定义）可以与上述套接字类型结合使用，允许你设置这些原子性相关的 flags （从而避免可能的竞争条件和单独调用的需要）。


@subsubheading 参见


Secure File Descriptor Handling （安全地处理文件描述符）@footnote{http://udrepper.livejournal.com/20407.html} 提供了更详尽的解释。


@ref{12f5,,可用性}： Linux >= 2.6.27。


3.2 新版功能.

@end deffn

@geindex SOMAXCONN() (在 socket 模块中)

@deffn {数据} SO_*
@anchor{library/socket socket SOMAXCONN}@anchor{746}
@deffnx {数据} socket.SOMAXCONN

@deffnx {数据} MSG_*

@deffnx {数据} SOL_*

@deffnx {数据} SCM_*

@deffnx {数据} IPPROTO_*

@deffnx {数据} IPPORT_*

@deffnx {数据} INADDR_*

@deffnx {数据} IP_*

@deffnx {数据} IPV6_*

@deffnx {数据} EAI_*

@deffnx {数据} AI_*

@deffnx {数据} NI_*

@deffnx {数据} TCP_*

此列表内的许多常量，记载在 Unix 文档中的套接字和/或 IP 协议部分，同时也定义在本 socket 模块中。它们通常用于套接字对象的 @code{setsockopt()} 和 @code{getsockopt()} 方法的参数中。在大多数情况下，仅那些在 Unix 头文件中有定义的符号会在本模块中定义，部分符号提供了默认值。


在 3.6 版更改: 添加了 @code{SO_DOMAIN}, @code{SO_PROTOCOL}, @code{SO_PEERSEC}, @code{SO_PASSSEC}, @code{TCP_USER_TIMEOUT}, @code{TCP_CONGESTION}。



在 3.6.5 版更改: 在 Windows 上，如果 Windows 运行时支持，则 @code{TCP_FASTOPEN}、@code{TCP_KEEPCNT} 可用。



在 3.7 版更改: 添加了 @code{TCP_NOTSENT_LOWAT}。

在 Windows 上，如果 Windows 运行时支持，则 @code{TCP_KEEPIDLE}、@code{TCP_KEEPINTVL} 可用。

@end deffn

@geindex AF_CAN() (在 socket 模块中)
@geindex PF_CAN() (在 socket 模块中)
@anchor{library/socket socket AF_CAN}@anchor{2603}
@deffn {数据} socket.AF_CAN
@anchor{library/socket socket PF_CAN}@anchor{2613}
@deffnx {数据} socket.PF_CAN

@deffnx {数据} SOL_CAN_*

@deffnx {数据} CAN_*

此列表内的许多常量，记载在 Linux 文档中，同时也定义在本 socket 模块中。

@ref{12f5,,可用性}： Linux >= 2.6.25。


3.3 新版功能.

@end deffn

@geindex CAN_BCM() (在 socket 模块中)
@anchor{library/socket socket CAN_BCM}@anchor{8b3}
@deffn {数据} socket.CAN_BCM

@deffnx {数据} CAN_BCM_*

CAN 协议簇内的 CAN_BCM 是广播管理器（Bbroadcast Manager -- BCM）协议，广播管理器常量在 Linux 文档中有所记载，在本 socket 模块中也有定义。

@ref{12f5,,可用性}： Linux >= 2.6.25。

@cartouche
@quotation 注解 
@code{CAN_BCM_CAN_FD_FRAME} 旗标仅在 Linux >= 4.8 时可用。
@end quotation
@end cartouche


3.4 新版功能.

@end deffn

@geindex CAN_RAW_FD_FRAMES() (在 socket 模块中)
@anchor{library/socket socket CAN_RAW_FD_FRAMES}@anchor{7bf}
@deffn {数据} socket.CAN_RAW_FD_FRAMES

在 CAN_RAW 套接字中启用 CAN FD 支持，默认是禁用的。它使应用程序可以发送 CAN 和 CAN FD 帧。但是，从套接字读取时，也必须同时接受 CAN 和 CAN FD 帧。

此常量在 Linux 文档中有所记载。

@ref{12f5,,可用性}： Linux >= 3.6。


3.5 新版功能.

@end deffn

@geindex CAN_ISOTP() (在 socket 模块中)
@anchor{library/socket socket CAN_ISOTP}@anchor{2604}
@deffn {数据} socket.CAN_ISOTP

CAN 协议簇中的 CAN_ISOTP 就是 ISO-TP (ISO 15765-2) 协议。ISO-TP 常量在 Linux 文档中有所记载。

@ref{12f5,,可用性}： Linux >= 2.6.25。


3.7 新版功能.

@end deffn

@geindex AF_PACKET() (在 socket 模块中)
@geindex PF_PACKET() (在 socket 模块中)
@anchor{library/socket socket AF_PACKET}@anchor{2605}
@deffn {数据} socket.AF_PACKET
@anchor{library/socket socket PF_PACKET}@anchor{2614}
@deffnx {数据} socket.PF_PACKET

@deffnx {数据} PACKET_*

此列表内的许多常量，记载在 Linux 文档中，同时也定义在本 socket 模块中。

@ref{12f5,,可用性}： Linux >= 2.2。
@end deffn

@geindex AF_RDS() (在 socket 模块中)
@geindex PF_RDS() (在 socket 模块中)
@geindex SOL_RDS() (在 socket 模块中)
@anchor{library/socket socket AF_RDS}@anchor{2615}
@deffn {数据} socket.AF_RDS
@anchor{library/socket socket PF_RDS}@anchor{2616}
@deffnx {数据} socket.PF_RDS
@anchor{library/socket socket SOL_RDS}@anchor{2617}
@deffnx {数据} socket.SOL_RDS

@deffnx {数据} RDS_*

此列表内的许多常量，记载在 Linux 文档中，同时也定义在本 socket 模块中。

@ref{12f5,,可用性}： Linux >= 2.6.30。


3.3 新版功能.

@end deffn

@geindex SIO_RCVALL() (在 socket 模块中)
@geindex SIO_KEEPALIVE_VALS() (在 socket 模块中)
@geindex SIO_LOOPBACK_FAST_PATH() (在 socket 模块中)
@anchor{library/socket socket SIO_RCVALL}@anchor{2618}
@deffn {数据} socket.SIO_RCVALL
@anchor{library/socket socket SIO_KEEPALIVE_VALS}@anchor{2619}
@deffnx {数据} socket.SIO_KEEPALIVE_VALS
@anchor{library/socket socket SIO_LOOPBACK_FAST_PATH}@anchor{57c}
@deffnx {数据} socket.SIO_LOOPBACK_FAST_PATH

@deffnx {数据} RCVALL_*

Windows 的 WSAIoctl() 的常量。这些常量用于套接字对象的 @ref{57b,,ioctl()} 方法的参数。


在 3.6 版更改: 添加了 @code{SIO_LOOPBACK_FAST_PATH}。

@end deffn


@deffn {数据} TIPC_*

TIPC 相关常量，与 C socket API 导出的常量一致。更多信息请参阅 TIPC 文档。
@end deffn

@geindex AF_ALG() (在 socket 模块中)
@geindex SOL_ALG() (在 socket 模块中)
@anchor{library/socket socket AF_ALG}@anchor{57f}
@deffn {数据} socket.AF_ALG
@anchor{library/socket socket SOL_ALG}@anchor{261a}
@deffnx {数据} socket.SOL_ALG

@deffnx {数据} ALG_*

用于 Linux 内核加密算法的常量。

@ref{12f5,,可用性}： Linux >= 2.6.38。


3.6 新版功能.

@end deffn

@geindex AF_VSOCK() (在 socket 模块中)
@geindex IOCTL_VM_SOCKETS_GET_LOCAL_CID() (在 socket 模块中)
@anchor{library/socket socket AF_VSOCK}@anchor{3cb}
@deffn {数据} socket.AF_VSOCK
@anchor{library/socket socket IOCTL_VM_SOCKETS_GET_LOCAL_CID}@anchor{261b}
@deffnx {数据} socket.IOCTL_VM_SOCKETS_GET_LOCAL_CID

@deffnx {数据} VMADDR*

@deffnx {数据} SO_VM*

用于 Linux 宿主机/虚拟机通讯的常量。

@ref{12f5,,可用性}： Linux >= 4.8。


3.7 新版功能.

@end deffn

@geindex AF_LINK() (在 socket 模块中)
@anchor{library/socket socket AF_LINK}@anchor{8b4}
@deffn {数据} socket.AF_LINK

@ref{12f5,,可用性}： BSD、OSX。


3.4 新版功能.

@end deffn

@geindex has_ipv6() (在 socket 模块中)
@anchor{library/socket socket has_ipv6}@anchor{261c}
@deffn {数据} socket.has_ipv6

本常量为一个布尔值，该值指示当前平台是否支持 IPv6。
@end deffn

@geindex BDADDR_ANY() (在 socket 模块中)
@geindex BDADDR_LOCAL() (在 socket 模块中)
@anchor{library/socket socket BDADDR_ANY}@anchor{261d}
@deffn {数据} socket.BDADDR_ANY
@anchor{library/socket socket BDADDR_LOCAL}@anchor{261e}
@deffnx {数据} socket.BDADDR_LOCAL

这些是字符串常量，包含蓝牙地址，这些地址具有特殊含义。例如，当用 @code{BTPROTO_RFCOMM} 指定绑定套接字时， @ref{261d,,BDADDR_ANY} 表示“任何地址”。
@end deffn

@geindex HCI_FILTER() (在 socket 模块中)
@geindex HCI_TIME_STAMP() (在 socket 模块中)
@geindex HCI_DATA_DIR() (在 socket 模块中)
@anchor{library/socket socket HCI_FILTER}@anchor{261f}
@deffn {数据} socket.HCI_FILTER
@anchor{library/socket socket HCI_TIME_STAMP}@anchor{2620}
@deffnx {数据} socket.HCI_TIME_STAMP
@anchor{library/socket socket HCI_DATA_DIR}@anchor{2621}
@deffnx {数据} socket.HCI_DATA_DIR

与 @code{BTPROTO_HCI} 一起使用。 @ref{261f,,HCI_FILTER} 在 NetBSD 或 DragonFlyBSD 上不可用。 @ref{2620,,HCI_TIME_STAMP} 和 @ref{2621,,HCI_DATA_DIR} 在 FreeBSD、NetBSD 或 DragonFlyBSD 上不可用。
@end deffn

@geindex AF_QIPCRTR() (在 socket 模块中)
@anchor{library/socket socket AF_QIPCRTR}@anchor{2606}
@deffn {数据} socket.AF_QIPCRTR

高通 IPC 路由协议的常数，用于与提供远程处理器的服务进行通信。

@ref{12f5,,可用性}： Linux >= 4.7。
@end deffn

@node 函数<5>,,常量<8>,模块内容<4>
@anchor{library/socket functions}@anchor{2622}
@subsubsection 函数


@menu
* 创建套接字:: 
* 其他功能: 其他功能<2>. 

@end menu

@node 创建套接字,其他功能<2>,,函数<5>
@anchor{library/socket creating-sockets}@anchor{2623}
@subsubsection 创建套接字


下列函数都能创建 @ref{2624,,套接字对象}.

@geindex socket() (在 socket 模块中)
@anchor{library/socket socket socket}@anchor{66e}
@deffn {函数} socket.socket (family=AF_INET, type=SOCK_STREAM, proto=0, fileno=None)

使用给定的地址簇、套接字类型和协议号创建一个新的套接字。地址簇应为 @ref{2545,,AF_INET} （默认）、@ref{2546,,AF_INET6}、@ref{254b,,AF_UNIX}、@ref{2603,,AF_CAN}、@ref{2605,,AF_PACKET} 或 @ref{2615,,AF_RDS} 其中之一。套接字类型应为 @ref{c83,,SOCK_STREAM} （默认）、@ref{c82,,SOCK_DGRAM}、@ref{2610,,SOCK_RAW} 或其他 @code{SOCK_} 常量之一。协议号通常为零，可以省略，或者在地址簇为 @ref{2603,,AF_CAN} 的情况下，协议号应为 @code{CAN_RAW}、@ref{8b3,,CAN_BCM} 或 @ref{2604,,CAN_ISOTP} 之一。

如果指定了 @emph{fileno}，那么将从这一指定的文件描述符中自动检测 @emph{family}、@emph{type} 和 @emph{proto} 的值。如果调用本函数时显式指定了 @emph{family}、@emph{type} 或 @emph{proto} 参数，可以覆盖自动检测的值。这只会影响 Python 表示诸如 @ref{258f,,socket.getpeername()} 一类函数的返回值的方式，而不影响实际的操作系统资源。与 @ref{2625,,socket.fromfd()} 不同，@emph{fileno} 将返回原先的套接字，而不是复制出新的套接字。这有助于在分离的套接字上调用 @ref{3c9,,socket.close()} 来关闭它。

新创建的套接字是 @ref{7f4,,不可继承的}。

引发一个 @ref{12d0,,审计事件} @code{socket.__new__} 附带参数 @code{self}、@code{family}、@code{type}、@code{protocol}。


在 3.3 版更改: 添加了 AF_CAN 簇。添加了 AF_RDS 簇。



在 3.4 版更改: 添加了 CAN_BCM 协议。



在 3.4 版更改: 返回的套接字现在是不可继承的。



在 3.7 版更改: 添加了 CAN_ISOTP 协议。



在 3.7 版更改: 当将 @ref{491,,SOCK_NONBLOCK} 或 @ref{492,,SOCK_CLOEXEC} 标志位应用于 @emph{type} 上时，它们会被清除，且 @ref{493,,socket.type} 反映不出它们。但它们仍将传递给底层系统的 @cite{socket()} 调用。因此，

@example
sock = socket.socket(
    socket.AF_INET,
    socket.SOCK_STREAM | socket.SOCK_NONBLOCK)
@end example

仍将在支持 @code{SOCK_NONBLOCK} 的系统上创建一个非阻塞的套接字，但是 @code{sock.type} 会被置为 @code{socket.SOCK_STREAM}。

@end deffn

@geindex socketpair() (在 socket 模块中)
@anchor{library/socket socket socketpair}@anchor{47b}
@deffn {函数} socket.socketpair ([family[, type[, proto]]])

构建一对已连接的套接字对象，使用给定的地址簇、套接字类型和协议号。地址簇、套接字类型和协议号与上述 @ref{66e,,socket()} 函数相同。默认地址簇为 @ref{254b,,AF_UNIX} （需要当前平台支持，不支持则默认为 @ref{2545,,AF_INET} ）。

新创建的套接字都是 @ref{7f4,,不可继承的}。


在 3.2 版更改: 现在，返回的套接字对象支持全部套接字 API，而不是全部 API 的一个子集。



在 3.4 版更改: 返回的套接字现在都是不可继承的。



在 3.5 版更改: 添加了 Windows 支持。

@end deffn

@geindex create_connection() (在 socket 模块中)
@anchor{library/socket socket create_connection}@anchor{b97}
@deffn {函数} socket.create_connection (address[, timeout[, source_address]])

连接到一个 TCP 服务，该服务正在侦听 Internet @emph{address} （用二元组 @code{(host, port)} 表示）。连接后返回套接字对象。这是比 @ref{670,,socket.connect()} 更高级的函数：如果 @emph{host} 是非数字主机名，它将尝试从 @ref{2545,,AF_INET} 和 @ref{2546,,AF_INET6} 解析它，然后依次尝试连接到所有可能的地址，直到连接成功。这使得编写兼容 IPv4 和 IPv6 的客户端变得容易。

传入可选参数 @emph{timeout} 可以在套接字实例上设置超时（在尝试连接前）。如果未提供 @emph{timeout}，则使用由 @ref{2626,,getdefaulttimeout()} 返回的全局默认超时设置。

如果提供了 @emph{source_address}，它必须为二元组 @code{(host, port)}，以便套接字在连接之前绑定为其源地址。如果 host 或 port 分别为 '@w{'} 或 0，则使用操作系统默认行为。


在 3.2 版更改: 添加了*source_address* 参数

@end deffn

@geindex create_server() (在 socket 模块中)
@anchor{library/socket socket create_server}@anchor{21e}
@deffn {函数} socket.create_server (address, *, family=AF_INET, backlog=None, reuse_port=False, dualstack_ipv6=False)

便捷函数，创建绑定到 @emph{address} （二元组 @code{(host, port)} ）的 TCP 套接字，返回套接字对象。

@emph{family} 应设置为 @ref{2545,,AF_INET} 或 @ref{2546,,AF_INET6}。@emph{backlog} 是传递给 @ref{745,,socket.listen()} 的队列大小，当它为 @code{0} 则表示默认的合理值。@emph{reuse_port} 表示是否设置 @code{SO_REUSEPORT} 套接字选项。

如果 @emph{dualstack_ipv6} 为 true 且平台支持，则套接字能接受 IPv4 和 IPv6 连接，否则将抛出 @ref{1fb,,ValueError} 异常。大多数 POSIX 平台和 Windows 应该支持此功能。启用此功能后，@ref{258f,,socket.getpeername()} 在进行 IPv4 连接时返回的地址将是一个（映射到 IPv4 的）IPv6 地址。在默认启用该功能的平台上（如 Linux），如果 @emph{dualstack_ipv6} 为 false，即显式禁用此功能。该参数可以与 @ref{21f,,has_dualstack_ipv6()} 结合使用：

@example
import socket

addr = ("", 8080)  # all interfaces, port 8080
if socket.has_dualstack_ipv6():
    s = socket.create_server(addr, family=socket.AF_INET6, dualstack_ipv6=True)
else:
    s = socket.create_server(addr)
@end example

@cartouche
@quotation 注解 
在 POSIX 平台上，设置 @code{SO_REUSEADDR} 套接字选项是为了立即重用以前绑定在同一 @emph{address} 上并保持 TIME_WAIT 状态的套接字。
@end quotation
@end cartouche


3.8 新版功能.

@end deffn

@geindex has_dualstack_ipv6() (在 socket 模块中)
@anchor{library/socket socket has_dualstack_ipv6}@anchor{21f}
@deffn {函数} socket.has_dualstack_ipv6 ()

如果平台支持创建 IPv4 和 IPv6 连接都可以处理的 TCP 套接字，则返回 @code{True}。


3.8 新版功能.

@end deffn

@geindex fromfd() (在 socket 模块中)
@anchor{library/socket socket fromfd}@anchor{2625}
@deffn {函数} socket.fromfd (fd, family, type, proto=0)

复制文件描述符 @emph{fd} （一个由文件对象的 @code{fileno()} 方法返回的整数），然后从结果中构建一个套接字对象。地址簇、套接字类型和协议号与上述 @ref{66e,,socket()} 函数相同。文件描述符应指向一个套接字，但不会专门去检查——如果文件描述符是无效的，则对该对象的后续操作可能会失败。本函数很少用到，但是在将套接字作为标准输入或输出传递给程序（如 Unix inet 守护程序启动的服务器）时，可以使用本函数获取或设置套接字选项。套接字将处于阻塞模式。

新创建的套接字是 @ref{7f4,,不可继承的}。


在 3.4 版更改: 返回的套接字现在是不可继承的。

@end deffn

@geindex fromshare() (在 socket 模块中)
@anchor{library/socket socket fromshare}@anchor{48f}
@deffn {函数} socket.fromshare (data)

根据 @ref{48e,,socket.share()} 方法获得的数据实例化套接字。套接字将处于阻塞模式。

@ref{12f5,,可用性}: Windows。


3.3 新版功能.

@end deffn

@geindex SocketType() (在 socket 模块中)
@anchor{library/socket socket SocketType}@anchor{2627}
@deffn {数据} socket.SocketType

这是一个 Python 类型对象，表示套接字对象的类型。它等同于 @code{type(socket(...))}。
@end deffn

@node 其他功能<2>,,创建套接字,函数<5>
@anchor{library/socket other-functions}@anchor{2628}
@subsubsection 其他功能


@ref{ef,,socket} 模块还提供多种网络相关服务：

@geindex close() (在 socket 模块中)
@anchor{library/socket socket close}@anchor{3c9}
@deffn {函数} socket.close (fd)

关闭一个套接字文件描述符。它类似于 @ref{3ca,,os.close()}，但专用于套接字。在某些平台上（特别是在 Windows 上），@ref{3ca,,os.close()} 对套接字文件描述符无效。


3.7 新版功能.

@end deffn

@geindex getaddrinfo() (在 socket 模块中)
@anchor{library/socket socket getaddrinfo}@anchor{2559}
@deffn {函数} socket.getaddrinfo (host, port, family=0, type=0, proto=0, flags=0)

将 @emph{host}/@emph{port} 参数转换为 5 元组的序列，其中包含创建（连接到某服务的）套接字所需的所有参数。@emph{host} 是域名，是字符串格式的 IPv4/v6 地址或 @code{None}。@emph{port} 是字符串格式的服务名称，如 @code{'http'} 、端口号（数字）或 @code{None}。传入 @code{None} 作为 @emph{host} 和 @emph{port} 的值，相当于将 @code{NULL} 传递给底层 C API。

可以指定 @emph{family}、@emph{type} 和 @emph{proto} 参数，以缩小返回的地址列表。向这些参数分别传入 0 表示保留全部结果范围。@emph{flags} 参数可以是 @code{AI_*} 常量中的一个或多个，它会影响结果的计算和返回。例如，@code{AI_NUMERICHOST} 会禁用域名解析，此时如果 @emph{host} 是域名，则会抛出错误。

本函数返回一个列表，其中的 5 元组具有以下结构：

@code{(family, type, proto, canonname, sockaddr)}

在这些元组中，@emph{family}、@emph{type}、@emph{proto} 都是整数，可以用于传递给 @ref{66e,,socket()} 函数。如果 @emph{flags} 参数有一部分是 @code{AI_CANONNAME}，那么 @emph{canonname} 将是表示 @emph{host} 的规范名称的字符串。否则 @emph{canonname} 将为空。@emph{sockaddr} 是一个表示套接字地址的元组，具体格式取决于返回的 @emph{family} （对于 @ref{2545,,AF_INET}，是一个 @code{(address, port)} 二元组，对于 @ref{2546,,AF_INET6}，是一个 @code{(address, port, flow info, scope id)} 四元组），可以用于传递给 @ref{670,,socket.connect()} 方法。

引发一个 @ref{12d0,,审计事件} @code{socket.getaddrinfo} 附带参数 @code{host}、@code{port}、@code{family}、@code{type}、@code{protocol}。

下面的示例获取了 TCP 连接地址信息，假设该连接通过 80 端口连接至 @code{example.org} （如果系统未启用 IPv6，则结果可能会不同）:

@example
>>> socket.getaddrinfo("example.org", 80, proto=socket.IPPROTO_TCP)
[(<AddressFamily.AF_INET6: 10>, <SocketType.SOCK_STREAM: 1>,
 6, '@w{'}, ('2606:2800:220:1:248:1893:25c8:1946', 80, 0, 0)),
 (<AddressFamily.AF_INET: 2>, <SocketType.SOCK_STREAM: 1>,
 6, '@w{'}, ('93.184.216.34', 80))]
@end example


在 3.2 版更改: 现在可以使用关键字参数的形式来传递参数。



在 3.7 版更改: 对于 IPv6 多播地址，表示地址的字符串将不包含 @code{%scope} 部分。

@end deffn

@geindex getfqdn() (在 socket 模块中)
@anchor{library/socket socket getfqdn}@anchor{2629}
@deffn {函数} socket.getfqdn ([name])

返回 @emph{name} 的全限定域名 (Fully Qualified Domain Name -- FQDN)。如果 @emph{name} 省略或为空，则将其解释为本地主机。为了查找全限定名称，首先将检查由 @ref{260c,,gethostbyaddr()} 返回的主机名，然后是主机的别名（如果存在）。选中第一个包含句点的名字。如果无法获取全限定域名，则返回由 @ref{1e9b,,gethostname()} 返回的主机名。
@end deffn

@geindex gethostbyname() (在 socket 模块中)
@anchor{library/socket socket gethostbyname}@anchor{262a}
@deffn {函数} socket.gethostbyname (hostname)

将主机名转换为 IPv4 地址格式。IPv4 地址以字符串格式返回，如 @code{'100.50.200.5'}。如果主机名本身是 IPv4 地址，则原样返回。更完整的接口请参考 @ref{260b,,gethostbyname_ex()}。 @ref{262a,,gethostbyname()} 不支持 IPv6 名称解析，应使用 @ref{2559,,getaddrinfo()} 来支持 IPv4/v6 双协议栈。

引发一个 @ref{12d0,,审计事件} @code{socket.gethostbyname}，附带参数 @code{hostname}。
@end deffn

@geindex gethostbyname_ex() (在 socket 模块中)
@anchor{library/socket socket gethostbyname_ex}@anchor{260b}
@deffn {函数} socket.gethostbyname_ex (hostname)

将主机名转换为 IPv4 地址格式的扩展接口。返回三元组 @code{(hostname, aliaslist, ipaddrlist)}，其中 @emph{hostname} 是响应给定 @emph{ip_address} 的主要主机名，@emph{aliaslist} 是相同地址的其他可用主机名的列表（可能为空），而 @emph{ipaddrlist} 是 IPv4 地址列表，包含相同主机名、相同接口的不同地址（通常是一个地址，但不总是如此）。@ref{260b,,gethostbyname_ex()} 不支持 IPv6 名称解析，应使用 @ref{2559,,getaddrinfo()} 来支持 IPv4/v6 双协议栈。

引发一个 @ref{12d0,,审计事件} @code{socket.gethostbyname}，附带参数 @code{hostname}。
@end deffn

@geindex gethostname() (在 socket 模块中)
@anchor{library/socket socket gethostname}@anchor{1e9b}
@deffn {函数} socket.gethostname ()

返回一个字符串，包含当前正在运行 Python 解释器的机器的主机名。

引发一个 @ref{12d0,,审计事件} @code{socket.gethostname}，没有附带参数。

注意： @ref{1e9b,,gethostname()} 并不总是返回全限定域名，必要的话请使用 @ref{2629,,getfqdn()}。
@end deffn

@geindex gethostbyaddr() (在 socket 模块中)
@anchor{library/socket socket gethostbyaddr}@anchor{260c}
@deffn {函数} socket.gethostbyaddr (ip_address)

返回三元组 @code{(hostname, aliaslist, ipaddrlist)}，其中 @emph{hostname} 是响应给定 @emph{ip_address} 的主要主机名，@emph{aliaslist} 是相同地址的其他可用主机名的列表（可能为空），而 @emph{ipaddrlist} 是 IPv4/v6 地址列表，包含相同主机名、相同接口的不同地址（很可能仅包含一个地址）。要查询全限定域名，请使用函数 @ref{2629,,getfqdn()}。@ref{260c,,gethostbyaddr()} 支持 IPv4 和 IPv6。

引发一个 @ref{12d0,,审计事件} @code{socket.gethostbyaddr}，附带参数 @code{ip_address}。
@end deffn

@geindex getnameinfo() (在 socket 模块中)
@anchor{library/socket socket getnameinfo}@anchor{255a}
@deffn {函数} socket.getnameinfo (sockaddr, flags)

将套接字地址 @emph{sockaddr} 转换为二元组 @code{(host, port)}。@emph{host} 的形式可能是全限定域名，或是由数字表示的地址，具体取决于 @emph{flags} 的设置。同样，@emph{port} 可以包含字符串格式的端口名称或数字格式的端口号。

对于 IPv6 地址，如果 @emph{sockaddr} 包含有意义的 @emph{scopeid}，则将 @code{%scope} 附加到 host 部分。这种情况通常发生在多播地址上。

关于 @emph{flags} 的更多信息可参阅 @code{getnameinfo(3)}。

引发一个 @ref{12d0,,审计事件} @code{socket.getnameinfo}，附带参数 @code{sockaddr}。
@end deffn

@geindex getprotobyname() (在 socket 模块中)
@anchor{library/socket socket getprotobyname}@anchor{262b}
@deffn {函数} socket.getprotobyname (protocolname)

将 Internet 协议名称（如 @code{'icmp'} ）转换为常量，该常量适用于 @ref{66e,,socket()} 函数的第三个（可选）参数。通常只有在 "raw" 模式 (@ref{2610,,SOCK_RAW}) 中打开的套接字才需要使用该常量。在正常的套接字模式下，协议省略或为零时，会自动选择正确的协议。
@end deffn

@geindex getservbyname() (在 socket 模块中)
@anchor{library/socket socket getservbyname}@anchor{262c}
@deffn {函数} socket.getservbyname (servicename[, protocolname])

将 Internet 服务名称和协议名称转换为该服务的端口号。协议名称是可选的，如果提供的话应为 @code{'tcp'} 或 @code{'udp'}，否则将匹配出所有协议。

引发一个 @ref{12d0,,审计事件} @code{socket.getservbyname}，附带参数 @code{servicename}、@code{protocolname}。
@end deffn

@geindex getservbyport() (在 socket 模块中)
@anchor{library/socket socket getservbyport}@anchor{262d}
@deffn {函数} socket.getservbyport (port[, protocolname])

将 Internet 端口号和协议名称转换为该服务的服务名称。协议名称是可选的，如果提供的话应为 @code{'tcp'} 或 @code{'udp'}，否则将匹配出所有协议。

引发一个 @ref{12d0,,审计事件} @code{socket.getservbyport}，附带参数 @code{port}、@code{protocolname}。
@end deffn

@geindex ntohl() (在 socket 模块中)
@anchor{library/socket socket ntohl}@anchor{262e}
@deffn {函数} socket.ntohl (x)

将 32 位正整数从网络字节序转换为主机字节序。在主机字节序与网络字节序相同的计算机上，这是一个空操作。字节序不同将执行 4 字节交换操作。
@end deffn

@geindex ntohs() (在 socket 模块中)
@anchor{library/socket socket ntohs}@anchor{467}
@deffn {函数} socket.ntohs (x)

将 16 位正整数从网络字节序转换为主机字节序。在主机字节序与网络字节序相同的计算机上，这是一个空操作。字节序不同将执行 2 字节交换操作。


3.7 版后已移除: 如果 @emph{x} 不符合 16 位无符号整数，但符合 C 语言的正整数，则它会被静默截断为 16 位无符号整数。此静默截断功能已弃用，未来版本的 Python 将对此抛出异常。

@end deffn

@geindex htonl() (在 socket 模块中)
@anchor{library/socket socket htonl}@anchor{262f}
@deffn {函数} socket.htonl (x)

将 32 位正整数从主机字节序转换为网络字节序。在主机字节序与网络字节序相同的计算机上，这是一个空操作。字节序不同将执行 4 字节交换操作。
@end deffn

@geindex htons() (在 socket 模块中)
@anchor{library/socket socket htons}@anchor{466}
@deffn {函数} socket.htons (x)

将 16 位正整数从主机字节序转换为网络字节序。在主机字节序与网络字节序相同的计算机上，这是一个空操作。字节序不同将执行 2 字节交换操作。


3.7 版后已移除: 如果 @emph{x} 不符合 16 位无符号整数，但符合 C 语言的正整数，则它会被静默截断为 16 位无符号整数。此静默截断功能已弃用，未来版本的 Python 将对此抛出异常。

@end deffn

@geindex inet_aton() (在 socket 模块中)
@anchor{library/socket socket inet_aton}@anchor{2630}
@deffn {函数} socket.inet_aton (ip_string)

将 IPv4 地址从点分十进制字符串格式（如 '123.45.67.89' ）转换为 32 位压缩二进制格式，转换后为字节对象，长度为四个字符。与那些使用标准 C 库，且需要 @code{struct in_addr} 类型的对象的程序交换信息时，此功能很有用。 该类型即此函数返回的 32 位压缩二进制的 C 类型。

@ref{2630,,inet_aton()} 也接受句点数少于三的字符串，详情请参阅 Unix 手册 @code{inet(3)}。

如果传入本函数的 IPv4 地址字符串无效，则抛出 @ref{1d3,,OSError}。注意，具体什么样的地址有效取决于 @code{inet_aton()} 的底层 C 实现。

@ref{2630,,inet_aton()} 不支持 IPv6，在 IPv4/v6 双协议栈下应使用 @ref{8b5,,inet_pton()} 来代替。
@end deffn

@geindex inet_ntoa() (在 socket 模块中)
@anchor{library/socket socket inet_ntoa}@anchor{2631}
@deffn {函数} socket.inet_ntoa (packed_ip)

将 32 位压缩 IPv4 地址（一个 @ref{5e3,,类字节对象}，长 4 个字节）转换为标准的点分十进制字符串形式（如 '123.45.67.89' ）。与那些使用标准 C 库，且需要 @code{struct in_addr} 类型的对象的程序交换信息时，本函数很有用。 该类型即是本函数参数中的 32 位压缩二进制数据的 C 类型。

如果传入本函数的字节序列长度不是 4 个字节，则抛出 @ref{1d3,,OSError}。@ref{2631,,inet_ntoa()} 不支持 IPv6，在 IPv4/v6 双协议栈下应使用 @ref{8b6,,inet_ntop()} 来代替。


在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。

@end deffn

@geindex inet_pton() (在 socket 模块中)
@anchor{library/socket socket inet_pton}@anchor{8b5}
@deffn {函数} socket.inet_pton (address_family, ip_string)

将特定地址簇的 IP 地址（字符串）转换为压缩二进制格式。当库或网络协议需要接受 @code{struct in_addr} 类型的对象（类似 @ref{2630,,inet_aton()} ）或 @code{struct in6_addr} 类型的对象时，@ref{8b5,,inet_pton()} 很有用。

目前 @emph{address_family} 支持 @ref{2545,,AF_INET} 和 @ref{2546,,AF_INET6}。如果 IP 地址字符串 @emph{ip_string} 无效，则抛出 @ref{1d3,,OSError}。注意，具体什么地址有效取决于 @emph{address_family} 的值和 @code{inet_pton()} 的底层实现。

@ref{12f5,,可用性}： Unix（可能非所有平台都可用）、Windows。


在 3.4 版更改: 添加了 Windows 支持

@end deffn

@geindex inet_ntop() (在 socket 模块中)
@anchor{library/socket socket inet_ntop}@anchor{8b6}
@deffn {函数} socket.inet_ntop (address_family, packed_ip)

将压缩 IP 地址（一个 @ref{5e3,,类字节对象}，数个字节长）转换为标准的、特定地址簇的字符串形式（如 @code{'7.10.0.5'} 或 @code{'5aef:2b::8'} ）。当库或网络协议返回 @code{struct in_addr} 类型的对象（类似 @ref{2631,,inet_ntoa()} ）或 @code{struct in6_addr} 类型的对象时，@ref{8b6,,inet_ntop()} 很有用。

目前 @emph{address_family} 支持 @ref{2545,,AF_INET} 和 @ref{2546,,AF_INET6}。如果字节对象 @emph{packed_ip} 与指定的地址簇长度不符，则抛出 @ref{1fb,,ValueError}。针对 @ref{8b6,,inet_ntop()} 调用的错误则抛出 @ref{1d3,,OSError}。

@ref{12f5,,可用性}： Unix（可能非所有平台都可用）、Windows。


在 3.4 版更改: 添加了 Windows 支持



在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。

@end deffn

@c XXX: Are sendmsg(), recvmsg() and CMSG_*() available on any
@c non-Unix platforms?  The old (obsolete?) 4.2BSD form of the
@c interface, in which struct msghdr has no msg_control or
@c msg_controllen members, is not currently supported.

@geindex CMSG_LEN() (在 socket 模块中)
@anchor{library/socket socket CMSG_LEN}@anchor{fb4}
@deffn {函数} socket.CMSG_LEN (length)

返回给定 @emph{length} 所关联数据的辅助数据项的总长度（不带尾部填充）。此值通常用作 @ref{673,,recvmsg()} 接收一个辅助数据项的缓冲区大小，但是 
@geindex RFC; RFC 3542
RFC 3542@footnote{https://tools.ietf.org/html/rfc3542.html} 要求可移植应用程序使用 @ref{fb3,,CMSG_SPACE()}，以此将尾部填充的空间计入，即使该项在缓冲区的最后。如果 @emph{length} 超出允许范围，则抛出 @ref{95a,,OverflowError}。

@ref{12f5,,可用性}： 大多数 Unix 平台，其他平台也可能可用。


3.3 新版功能.

@end deffn

@geindex CMSG_SPACE() (在 socket 模块中)
@anchor{library/socket socket CMSG_SPACE}@anchor{fb3}
@deffn {函数} socket.CMSG_SPACE (length)

返回 @ref{673,,recvmsg()} 所需的缓冲区大小，以接收给定 @emph{length} 所关联数据的辅助数据项，带有尾部填充。接收多个项目所需的缓冲区空间是关联数据长度的 @ref{fb3,,CMSG_SPACE()} 值的总和。如果 @emph{length} 超出允许范围，则抛出 @ref{95a,,OverflowError}。

请注意，某些系统可能支持辅助数据，但不提供本函数。还需注意，如果使用本函数的结果来设置缓冲区大小，可能无法精确限制可接收的辅助数据量，因为可能会有其他数据写入尾部填充区域。

@ref{12f5,,可用性}： 大多数 Unix 平台，其他平台也可能可用。


3.3 新版功能.

@end deffn

@geindex getdefaulttimeout() (在 socket 模块中)
@anchor{library/socket socket getdefaulttimeout}@anchor{2626}
@deffn {函数} socket.getdefaulttimeout ()

返回用于新套接字对象的默认超时（以秒为单位的浮点数）。值 @code{None} 表示新套接字对象没有超时。首次导入 socket 模块时，默认值为 @code{None}。
@end deffn

@geindex setdefaulttimeout() (在 socket 模块中)
@anchor{library/socket socket setdefaulttimeout}@anchor{260e}
@deffn {函数} socket.setdefaulttimeout (timeout)

设置用于新套接字对象的默认超时（以秒为单位的浮点数）。首次导入 socket 模块时，默认值为 @code{None}。可能的取值及其各自的含义请参阅 @ref{2607,,settimeout()}。
@end deffn

@geindex sethostname() (在 socket 模块中)
@anchor{library/socket socket sethostname}@anchor{a82}
@deffn {函数} socket.sethostname (name)

将计算机的主机名设置为 @emph{name}。如果权限不足将抛出 @ref{1d3,,OSError}。

引发一个 @ref{12d0,,审计事件} @code{socket.sethostname}，附带参数 @code{name}。

@ref{12f5,,可用性}: Unix。


3.3 新版功能.

@end deffn

@geindex if_nameindex() (在 socket 模块中)
@anchor{library/socket socket if_nameindex}@anchor{220}
@deffn {函数} socket.if_nameindex ()

返回一个列表，包含网络接口（网卡）信息二元组（整数索引，名称字符串）。系统调用失败则抛出 @ref{1d3,,OSError}。

@ref{12f5,,可用性}: Unix, Windows。


3.3 新版功能.



在 3.8 版更改: 添加了 Windows 支持。

@end deffn

@geindex if_nametoindex() (在 socket 模块中)
@anchor{library/socket socket if_nametoindex}@anchor{221}
@deffn {函数} socket.if_nametoindex (if_name)

返回网络接口名称相对应的索引号。如果没有所给名称的接口，则抛出 @ref{1d3,,OSError}。

@ref{12f5,,可用性}: Unix, Windows。


3.3 新版功能.



在 3.8 版更改: 添加了 Windows 支持。

@end deffn

@geindex if_indextoname() (在 socket 模块中)
@anchor{library/socket socket if_indextoname}@anchor{222}
@deffn {函数} socket.if_indextoname (if_index)

返回网络接口索引号相对应的接口名称。如果没有所给索引号的接口，则抛出 @ref{1d3,,OSError}。

@ref{12f5,,可用性}: Unix, Windows。


3.3 新版功能.



在 3.8 版更改: 添加了 Windows 支持。

@end deffn

@node 套接字对象,关于套接字超时的说明,模块内容<4>,socket --- 底层网络接口
@anchor{library/socket id1}@anchor{2632}@anchor{library/socket socket-objects}@anchor{2624}
@subsubsection 套接字对象


套接字对象具有以下方法。除了 @ref{b12,,makefile()}，其他都与套接字专用的 Unix 系统调用相对应。


在 3.2 版更改: 添加了对 @ref{563,,上下文管理器} 协议的支持。退出上下文管理器与调用 @ref{3c9,,close()} 等效。


@geindex accept() (socket.socket 方法)
@anchor{library/socket socket socket accept}@anchor{66f}
@deffn {方法} socket.accept ()

接受一个连接。此 scoket 必须绑定到一个地址上并且监听连接。返回值是一个 @code{(conn, address)} 对，其中 @emph{conn} 是一个 @emph{新} 的套接字对象，用于在此连接上收发数据，@emph{address} 是连接另一端的套接字所绑定的地址。

新创建的套接字是 @ref{7f4,,不可继承的}。


在 3.4 版更改: 该套接字现在是不可继承的。



在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此方法现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex bind() (socket.socket 方法)
@anchor{library/socket socket socket bind}@anchor{2633}
@deffn {方法} socket.bind (address)

将套接字绑定到 @emph{address}。套接字必须尚未绑定。（ @emph{address} 的格式取决于地址簇 —— 参见上文）

引发一个 @ref{12d0,,审计事件} @code{socket.bind}，附带参数 @code{self}、@code{address}。
@end deffn

@geindex close() (socket.socket 方法)
@anchor{library/socket socket socket close}@anchor{5fb}
@deffn {方法} socket.close ()

将套接字标记为关闭。当 @ref{b12,,makefile()} 创建的所有文件对象都关闭时，底层系统资源（如文件描述符）也将关闭。一旦上述情况发生，将来对套接字对象的所有操作都会失败。对端将接收不到任何数据（清空队列数据后）。

垃圾回收时，套接字会自动关闭，但建议显式 @ref{3c9,,close()} 它们，或在它们周围使用 @ref{6e3,,with} 语句。


在 3.6 版更改: 现在，如果底层的 @code{close()} 调用出错，会抛出 @ref{1d3,,OSError}。


@cartouche
@quotation 注解 
@ref{3c9,,close()} 释放与连接相关联的资源，但不一定立即关闭连接。如果需要及时关闭连接，请在调用 @ref{3c9,,close()} 之前调用 @ref{2634,,shutdown()}。
@end quotation
@end cartouche
@end deffn

@geindex connect() (socket.socket 方法)
@anchor{library/socket socket socket connect}@anchor{670}
@deffn {方法} socket.connect (address)

连接到 @emph{address} 处的远程套接字。（ @emph{address} 的格式取决于地址簇 —— 参见上文）

如果连接被信号中断，则本方法将等待，直到连接完成。如果信号处理程序未抛出异常，且套接字阻塞中或已超时，则在超时后抛出 @ref{c07,,socket.timeout}。对于非阻塞套接字，如果连接被信号中断，则本方法将抛出 @ref{653,,InterruptedError} 异常（或信号处理程序抛出的异常）。

引发一个 @ref{12d0,,审计事件} @code{socket.connect}，附带参数 @code{self}、@code{address}。


在 3.5 版更改: 本方法现在将等待，直到连接完成，而不是在以下情况抛出 @ref{653,,InterruptedError} 异常。该情况为，连接被信号中断，信号处理程序未抛出异常，且套接字阻塞中或已超时（具体解释请参阅 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475} ）。

@end deffn

@geindex connect_ex() (socket.socket 方法)
@anchor{library/socket socket socket connect_ex}@anchor{2635}
@deffn {方法} socket.connect_ex (address)

类似于 @code{connect(address)}，但是对于 C 级别的 @code{connect()} 调用返回的错误，本函数将返回错误指示器，而不是抛出异常（对于其他问题，如“找不到主机”，仍然可以抛出异常）。如果操作成功，则错误指示器为 @code{0}，否则为 @code{errno} 变量的值。这对支持如异步连接很有用。

引发一个 @ref{12d0,,审计事件} @code{socket.connect}，附带参数 @code{self}、@code{address}。
@end deffn

@geindex detach() (socket.socket 方法)
@anchor{library/socket socket socket detach}@anchor{b96}
@deffn {方法} socket.detach ()

将套接字对象置于关闭状态，而底层的文件描述符实际并不关闭。返回该文件描述符，使其可以重新用于其他目的。


3.2 新版功能.

@end deffn

@geindex dup() (socket.socket 方法)
@anchor{library/socket socket socket dup}@anchor{2636}
@deffn {方法} socket.dup ()

创建套接字的副本。

新创建的套接字是 @ref{7f4,,不可继承的}。


在 3.4 版更改: 该套接字现在是不可继承的。

@end deffn

@geindex fileno() (socket.socket 方法)
@anchor{library/socket socket socket fileno}@anchor{2637}
@deffn {方法} socket.fileno ()

返回套接字的文件描述符（一个小整数），失败返回 -1。配合 @ref{66d,,select.select()} 使用很有用。

在 Windows 下，此方法返回的小整数在允许使用文件描述符的地方无法使用（如 @ref{13c9,,os.fdopen()} ）。Unix 无此限制。
@end deffn

@geindex get_inheritable() (socket.socket 方法)
@anchor{library/socket socket socket get_inheritable}@anchor{7f9}
@deffn {方法} socket.get_inheritable ()

获取套接字文件描述符或套接字句柄的 @ref{7f4,,可继承标志} ：如果子进程可以继承套接字则为 @code{True}，否则为 @code{False}。


3.4 新版功能.

@end deffn

@geindex getpeername() (socket.socket 方法)
@anchor{library/socket socket socket getpeername}@anchor{258f}
@deffn {方法} socket.getpeername ()

返回套接字连接到的远程地址。举例而言，这可以用于查找远程 IPv4/v6 套接字的端口号。（返回的地址格式取决于地址簇 —— 参见上文。）部分系统不支持此函数。
@end deffn

@geindex getsockname() (socket.socket 方法)
@anchor{library/socket socket socket getsockname}@anchor{2590}
@deffn {方法} socket.getsockname ()

返回套接字本身的地址。举例而言，这可以用于查找 IPv4/v6 套接字的端口号。（返回的地址格式取决于地址簇 —— 参见上文。）
@end deffn

@geindex getsockopt() (socket.socket 方法)
@anchor{library/socket socket socket getsockopt}@anchor{57d}
@deffn {方法} socket.getsockopt (level, optname[, buflen])

返回指定套接字选项的值（参阅 Unix 手册页 @code{getsockopt(2)} ）。所需的符号常量（ @code{SO_*} 等）已定义在本模块中。如果未指定 @emph{buflen}，则认为该选项值为整数，由本函数返回该整数值。如果指定 @emph{buflen}，则它定义了用于存放选项值的缓冲区的最大长度，且该缓冲区将作为字节对象返回。对缓冲区的解码工作由调用者自行完成（针对编码为字节串的 C 结构，其解码方法请参阅可选的内置模块 @ref{f8,,struct} ）。
@end deffn

@geindex getblocking() (socket.socket 方法)
@anchor{library/socket socket socket getblocking}@anchor{3c8}
@deffn {方法} socket.getblocking ()

如果套接字处于阻塞模式，返回 @code{True}，非阻塞模式返回 @code{False}。

这相当于检测 @code{socket.gettimeout() == 0}。


3.7 新版功能.

@end deffn

@geindex gettimeout() (socket.socket 方法)
@anchor{library/socket socket socket gettimeout}@anchor{2638}
@deffn {方法} socket.gettimeout ()

返回套接字操作相关的超时秒数（浮点数），未设置超时则返回 @code{None}。它反映最后一次调用 @ref{1ea7,,setblocking()} 或 @ref{2607,,settimeout()} 后的设置。
@end deffn

@geindex ioctl() (socket.socket 方法)
@anchor{library/socket socket socket ioctl}@anchor{57b}
@deffn {方法} socket.ioctl (control, option)

@*平台: 
Windows


@ref{57b,,ioctl()} 方法是 WSAIoctl 系统接口的有限接口。请参考 Win32 文档@footnote{https://msdn.microsoft.com/en-us/library/ms741621%28VS.85%29.aspx} 以获取更多信息。

在其他平台上，可以使用通用的 @ref{2639,,fcntl.fcntl()} 和 @ref{dd7,,fcntl.ioctl()} 函数，它们接受套接字对象作为第一个参数。

当前仅支持以下控制码： @code{SIO_RCVALL}、@code{SIO_KEEPALIVE_VALS} 和 @code{SIO_LOOPBACK_FAST_PATH}。


在 3.6 版更改: 添加了 @code{SIO_LOOPBACK_FAST_PATH}。

@end deffn

@geindex listen() (socket.socket 方法)
@anchor{library/socket socket socket listen}@anchor{745}
@deffn {方法} socket.listen ([backlog])

启动一个服务器用于接受连接。如果指定 @emph{backlog}，则它最低为 0（小于 0 会被置为 0），它指定系统允许暂未 accept 的连接数，超过后将拒绝新连接。未指定则自动设为合理的默认值。


在 3.5 版更改: @emph{backlog} 参数现在是可选的。

@end deffn

@geindex makefile() (socket.socket 方法)
@anchor{library/socket socket socket makefile}@anchor{b12}
@deffn {方法} socket.makefile (mode='r', buffering=None, *, encoding=None, errors=None, newline=None)

@geindex I/O control; buffering

返回与套接字关联的 @ref{b3b,,文件对象}。返回的对象的具体类型取决于 @ref{b12,,makefile()} 的参数。这些参数的解释方式与内置的 @ref{4ea,,open()} 函数相同，其中 @emph{mode} 的值仅支持 @code{'r'} （默认），@code{'w'} 和 @code{'b'}。

套接字必须处于阻塞模式，它可以有超时，但是如果发生超时，文件对象的内部缓冲区可能会以不一致的状态结尾。

关闭 @ref{b12,,makefile()} 返回的文件对象不会关闭原始套接字，除非所有其他文件对象都已关闭且在套接字对象上调用了 @ref{3c9,,socket.close()}。

@cartouche
@quotation 注解 
在 Windows 上，由 @ref{b12,,makefile()} 创建的文件类对象无法作为带文件描述符的文件对象使用，如无法作为 @ref{2b9,,subprocess.Popen()} 的流参数。
@end quotation
@end cartouche
@end deffn

@geindex recv() (socket.socket 方法)
@anchor{library/socket socket socket recv}@anchor{671}
@deffn {方法} socket.recv (bufsize[, flags])

从套接字接收数据。返回值是一个字节对象，表示接收到的数据。@emph{bufsize} 指定一次接收的最大数据量。可选参数 @emph{flags} 的含义请参阅 Unix 手册页 @code{recv(2)}，它默认为零。

@cartouche
@quotation 注解 
为了最佳匹配硬件和网络的实际情况，@emph{bufsize} 的值应为 2 的相对较小的幂，如 4096。
@end quotation
@end cartouche


在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此方法现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex recvfrom() (socket.socket 方法)
@anchor{library/socket socket socket recvfrom}@anchor{672}
@deffn {方法} socket.recvfrom (bufsize[, flags])

从套接字接收数据。返回值是一对 @code{(bytes, address)}，其中 @emph{bytes} 是字节对象，表示接收到的数据，@emph{address} 是发送端套接字的地址。可选参数 @emph{flags} 的含义请参阅 Unix 手册页 @code{recv(2)}，它默认为零。（ @emph{address} 的格式取决于地址簇 —— 参见上文）


在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此方法现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。



在 3.7 版更改: 对于多播 IPv6 地址，@emph{address} 的第一项不再包含 @code{%scope} 部分。要获得完整的 IPv6 地址，请使用 @ref{255a,,getnameinfo()}。

@end deffn

@geindex recvmsg() (socket.socket 方法)
@anchor{library/socket socket socket recvmsg}@anchor{673}
@deffn {方法} socket.recvmsg (bufsize[, ancbufsize[, flags]])

从套接字接收普通数据（至多 @emph{bufsize} 字节）和辅助数据。@emph{ancbufsize} 参数设置用于接收辅助数据的内部缓冲区的大小（以字节为单位），默认为 0，表示不接收辅助数据。可以使用 @ref{fb3,,CMSG_SPACE()} 或 @ref{fb4,,CMSG_LEN()} 计算辅助数据缓冲区的合适大小，无法放入缓冲区的项目可能会被截断或丢弃。@emph{flags} 参数默认为 0，其含义与 @ref{671,,recv()} 中的相同。

返回值是一个四元组： @code{(data, ancdata, msg_flags, address)}。@emph{data} 项是一个 @ref{32a,,bytes} 对象，用于保存接收到的非辅助数据。@emph{ancdata} 项是零个或多个元组 @code{(cmsg_level, cmsg_type, cmsg_data)} 组成的列表，表示接收到的辅助数据（控制消息）：@emph{cmsg_level} 和 @emph{cmsg_type} 是分别表示协议级别和协议类型的整数，而 @emph{cmsg_data} 是保存相关数据的 @ref{32a,,bytes} 对象。@emph{msg_flags} 项由各种标志按位或组成，表示接收消息的情况，详细信息请参阅系统文档。如果接收端套接字断开连接，则 @emph{address} 是发送端套接字的地址（如果有），否则该值无指定。

某些系统上可以利用 @ref{254b,,AF_UNIX} 套接字通过 @ref{676,,sendmsg()} 和 @ref{673,,recvmsg()} 在进程之间传递文件描述符。使用此功能时（通常仅限于 @ref{c83,,SOCK_STREAM} 套接字），@ref{673,,recvmsg()} 将在其辅助数据中返回以下格式的项 @code{(socket.SOL_SOCKET, socket.SCM_RIGHTS, fds)}，其中 @emph{fds} 是一个 @ref{32a,,bytes} 对象，是新文件描述符表示为原生 C @code{int} 类型的二进制数组。如果 @ref{673,,recvmsg()} 在系统调用返回后抛出异常，它将首先关闭此机制接收到的所有文件描述符。

对于仅接收到一部分的辅助数据项，一些系统没有指示其截断长度。如果某个项目可能超出了缓冲区的末尾，@ref{673,,recvmsg()} 将发出 @ref{2c0,,RuntimeWarning}，并返回其在缓冲区内的部分，前提是该对象被截断于关联数据开始后。

在支持 @code{SCM_RIGHTS} 机制的系统上，下方的函数将最多接收 @emph{maxfds} 个文件描述符，返回消息数据和包含描述符的列表（同时忽略意外情况，如接收到无关的控制消息）。另请参阅 @ref{676,,sendmsg()}。

@example
import socket, array

def recv_fds(sock, msglen, maxfds):
    fds = array.array("i")   # Array of ints
    msg, ancdata, flags, addr = sock.recvmsg(msglen, socket.CMSG_LEN(maxfds * fds.itemsize))
    for cmsg_level, cmsg_type, cmsg_data in ancdata:
        if cmsg_level == socket.SOL_SOCKET and cmsg_type == socket.SCM_RIGHTS:
            # Append data, ignoring any truncated integers at the end.
            fds.frombytes(cmsg_data[:len(cmsg_data) - (len(cmsg_data) % fds.itemsize)])
    return msg, list(fds)
@end example

@ref{12f5,,可用性}： 大多数 Unix 平台，其他平台也可能可用。


3.3 新版功能.



在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此方法现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex recvmsg_into() (socket.socket 方法)
@anchor{library/socket socket socket recvmsg_into}@anchor{a81}
@deffn {方法} socket.recvmsg_into (buffers[, ancbufsize[, flags]])

从套接字接收普通数据和辅助数据，其行为与 @ref{673,,recvmsg()} 相同，但将非辅助数据分散到一系列缓冲区中，而不是返回新的字节对象。@emph{buffers} 参数必须是可迭代对象，它迭代出可供写入的缓冲区（如 @ref{32b,,bytearray} 对象），这些缓冲区将被连续的非辅助数据块填充，直到数据全部写完或缓冲区用完为止。在允许使用的缓冲区数量上，操作系统可能会有限制（ @ref{1ecd,,sysconf()} 的 @code{SC_IOV_MAX} 值）。@emph{ancbufsize} 和 @emph{flags} 参数的含义与 @ref{673,,recvmsg()} 中的相同。

返回值为四元组： @code{(nbytes, ancdata, msg_flags, address)}，其中 @emph{nbytes} 是写入缓冲区的非辅助数据的字节总数，而 @emph{ancdata}、@emph{msg_flags} 和 @emph{address} 与 @ref{673,,recvmsg()} 中的相同。

示例:

@example
>>> import socket
>>> s1, s2 = socket.socketpair()
>>> b1 = bytearray(b'----')
>>> b2 = bytearray(b'0123456789')
>>> b3 = bytearray(b'--------------')
>>> s1.send(b'Mary had a little lamb')
22
>>> s2.recvmsg_into([b1, memoryview(b2)[2:9], b3])
(22, [], 0, None)
>>> [b1, b2, b3]
[bytearray(b'Mary'), bytearray(b'01 had a 9'), bytearray(b'little lamb---')]
@end example

@ref{12f5,,可用性}： 大多数 Unix 平台，其他平台也可能可用。


3.3 新版功能.

@end deffn

@geindex recvfrom_into() (socket.socket 方法)
@anchor{library/socket socket socket recvfrom_into}@anchor{cac}
@deffn {方法} socket.recvfrom_into (buffer[, nbytes[, flags]])

从套接字接收数据，将其写入 @emph{buffer} 而不是创建新的字节串。返回值是一对 @code{(nbytes, address)}，其中 @emph{nbytes} 是收到的字节数，@emph{address} 是发送端套接字的地址。可选参数 @emph{flags} 的含义请参阅 Unix 手册页 @code{recv(2)}，它默认为零。（ @emph{address} 的格式取决于地址簇 —— 参见上文）
@end deffn

@geindex recv_into() (socket.socket 方法)
@anchor{library/socket socket socket recv_into}@anchor{cab}
@deffn {方法} socket.recv_into (buffer[, nbytes[, flags]])

从套接字接收至多 @emph{nbytes} 个字节，将其写入缓冲区而不是创建新的字节串。如果 @emph{nbytes} 未指定（或指定为 0），则接收至所给缓冲区的最大可用大小。返回接收到的字节数。可选参数 @emph{flags} 的含义请参阅 Unix 手册页 @code{recv(2)}，它默认为零。
@end deffn

@geindex send() (socket.socket 方法)
@anchor{library/socket socket socket send}@anchor{674}
@deffn {方法} socket.send (bytes[, flags])

发送数据给套接字。本套接字必须已连接到远程套接字。可选参数 @emph{flags} 的含义与上述 @ref{671,,recv()} 中的相同。本方法返回已发送的字节数。应用程序要负责检查所有数据是否已发送，如果仅传输了部分数据，程序需要自行尝试传输其余数据。有关该主题的更多信息，请参考 @ref{263a,,套接字编程指南}。


在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此方法现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex sendall() (socket.socket 方法)
@anchor{library/socket socket socket sendall}@anchor{675}
@deffn {方法} socket.sendall (bytes[, flags])

发送数据给套接字。本套接字必须已连接到远程套接字。可选参数 @emph{flags} 的含义与上述 @ref{671,,recv()} 中的相同。与 @ref{674,,send()} 不同，本方法持续从 @emph{bytes} 发送数据，直到所有数据都已发送或发生错误为止。成功后会返回 @code{None}。出错后会抛出一个异常，此时并没有办法确定成功发送了多少数据。


在 3.5 版更改: 每次成功发送数据后，套接字超时不再重置。现在，套接字超时是发送所有数据的最大总持续时间。



在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此方法现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex sendto() (socket.socket 方法)
@anchor{library/socket socket socket sendto}@anchor{677}
@deffn {方法} socket.sendto (bytes, address)

@deffnx {方法} socket.sendto (bytes, flags, address)

发送数据给套接字。本套接字不应连接到远程套接字，而应由 @emph{address} 指定目标套接字。可选参数 @emph{flags} 的含义与上述 @ref{671,,recv()} 中的相同。本方法返回已发送的字节数。（ @emph{address} 的格式取决于地址簇 —— 参见上文。）

引发一个 @ref{12d0,,审计事件} @code{socket.sendto}，附带参数 @code{self}、@code{address}。


在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此方法现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex sendmsg() (socket.socket 方法)
@anchor{library/socket socket socket sendmsg}@anchor{676}
@deffn {方法} socket.sendmsg (buffers[, ancdata[, flags[, address]]])

将普通数据和辅助数据发送给套接字，将从一系列缓冲区中收集非辅助数据，并将其拼接为一条消息。@emph{buffers} 参数指定的非辅助数据应为可迭代的 @ref{5e3,,字节类对象} （如 @ref{32a,,bytes} 对象），在允许使用的缓冲区数量上，操作系统可能会有限制（ @ref{1ecd,,sysconf()} 的 @code{SC_IOV_MAX} 值）。@emph{ancdata} 参数指定的辅助数据（控制消息）应为可迭代对象，迭代出零个或多个 @code{(cmsg_level, cmsg_type, cmsg_data)} 元组，其中 @emph{cmsg_level} 和 @emph{cmsg_type} 是分别指定协议级别和协议类型的整数，而 @emph{cmsg_data} 是保存相关数据的字节类对象。请注意，某些系统（特别是没有 @ref{fb3,,CMSG_SPACE()} 的系统）可能每次调用仅支持发送一条控制消息。@emph{flags} 参数默认为 0，与 @ref{674,,send()} 中的含义相同。如果 @emph{address} 指定为除 @code{None} 以外的值，它将作为消息的目标地址。返回值是已发送的非辅助数据的字节数。

在支持 @code{SCM_RIGHTS} 机制的系统上，下方的函数通过一个 @ref{254b,,AF_UNIX} 套接字来发送文件描述符列表 @emph{fds}。另请参阅 @ref{673,,recvmsg()}。

@example
import socket, array

def send_fds(sock, msg, fds):
    return sock.sendmsg([msg], [(socket.SOL_SOCKET, socket.SCM_RIGHTS, array.array("i", fds))])
@end example

@ref{12f5,,可用性}： 大多数 Unix 平台，其他平台也可能可用。

引发一个 @ref{12d0,,审计事件} @code{socket.sendmsg}，附带参数 @code{self}、@code{address}。


3.3 新版功能.



在 3.5 版更改: 如果系统调用被中断，但信号处理程序没有触发异常，此方法现在会重试系统调用，而不是触发 @ref{653,,InterruptedError} 异常 (原因详见 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475})。

@end deffn

@geindex sendmsg_afalg() (socket.socket 方法)
@anchor{library/socket socket socket sendmsg_afalg}@anchor{580}
@deffn {方法} socket.sendmsg_afalg ([msg], *, op[, iv[, assoclen[, flags]]])

为 @ref{57f,,AF_ALG} 套接字定制的 @ref{676,,sendmsg()} 版本。可为 @ref{57f,,AF_ALG} 套接字设置模式、IV、AEAD 关联数据的长度和标志位。

@ref{12f5,,可用性}： Linux >= 2.6.38。


3.6 新版功能.

@end deffn

@geindex sendfile() (socket.socket 方法)
@anchor{library/socket socket socket sendfile}@anchor{744}
@deffn {方法} socket.sendfile (file, offset=0, count=None)

使用高性能的 @ref{352,,os.sendfile} 发送文件，直到达到文件的 EOF 为止，返回已发送的字节总数。@emph{file} 必须是一个以二进制模式打开的常规文件对象。如果 @ref{352,,os.sendfile} 不可用（如 Windows）或 @emph{file} 不是常规文件，将使用 @ref{674,,send()} 代替。@emph{offset} 指示从哪里开始读取文件。如果指定了 @emph{count}，它确定了要发送的字节总数，而不会持续发送直到达到文件的 EOF。返回时或发生错误时，文件位置将更新，在这种情况下，@ref{1d2e,,file.tell()} 可用于确定已发送的字节数。套接字必须为 @ref{c83,,SOCK_STREAM} 类型。不支持非阻塞的套接字。


3.5 新版功能.

@end deffn

@geindex set_inheritable() (socket.socket 方法)
@anchor{library/socket socket socket set_inheritable}@anchor{7fa}
@deffn {方法} socket.set_inheritable (inheritable)

设置套接字文件描述符或套接字句柄的 @ref{7f4,,可继承标志}。


3.4 新版功能.

@end deffn

@geindex setblocking() (socket.socket 方法)
@anchor{library/socket socket socket setblocking}@anchor{1ea7}
@deffn {方法} socket.setblocking (flag)

设置套接字为阻塞或非阻塞模式：如果 @emph{flag} 为 false，则将套接字设置为非阻塞，否则设置为阻塞。

本方法是某些 @ref{2607,,settimeout()} 调用的简写：


@itemize *

@item 
@code{sock.setblocking(True)} 相当于 @code{sock.settimeout(None)}

@item 
@code{sock.setblocking(False)} 相当于 @code{sock.settimeout(0.0)}
@end itemize


在 3.7 版更改: 本方法不再对 @ref{493,,socket.type} 属性设置 @ref{491,,SOCK_NONBLOCK} 标志。

@end deffn

@geindex settimeout() (socket.socket 方法)
@anchor{library/socket socket socket settimeout}@anchor{2607}
@deffn {方法} socket.settimeout (value)

为阻塞套接字的操作设置超时。@emph{value} 参数可以是非负浮点数，表示秒，也可以是 @code{None}。如果赋为一个非零值，那么如果在操作完成前超过了超时时间 @emph{value}，后续的套接字操作将抛出 @ref{c07,,timeout} 异常。如果赋为 0，则套接字将处于非阻塞模式。如果指定为 @code{None}，则套接字将处于阻塞模式。

更多信息请查阅 @ref{263b,,关于套接字超时的说明}。


在 3.7 版更改: 本方法不再修改 @ref{493,,socket.type} 属性的 @ref{491,,SOCK_NONBLOCK} 标志。

@end deffn

@geindex setsockopt() (socket.socket 方法)
@anchor{library/socket socket socket setsockopt}@anchor{57e}
@deffn {方法} socket.setsockopt (level, optname, value: int)
@end deffn

@geindex setsockopt() (socket.socket 方法)

@deffn {方法} socket.setsockopt (level, optname, value: buffer)
@end deffn

@geindex setsockopt() (socket.socket 方法)

@deffn {方法} socket.setsockopt (level, optname, None, optlen: int)

@geindex 模块; struct

设置给定套接字选项的值（参阅 Unix 手册页 @code{setsockopt(2)} ）。所需的符号常量（ @code{SO_*} 等）已定义在本 @ref{ef,,socket} 模块中。该值可以是整数、@code{None} 或表示缓冲区的 @ref{5e3,,字节类对象}。在后一种情况下，由调用者确保字节串中包含正确的数据位（关于将 C 结构体编码为字节串的方法，请参阅可选的内置模块 @ref{f8,,struct} ）。当 @emph{value} 设置为 @code{None} 时，必须设置 @emph{optlen} 参数。这相当于调用 @code{setsockopt()} C 函数时使用了 @code{optval=NULL} 和 @code{optlen=optlen} 参数。


在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。



在 3.6 版更改: 添加了 setsockopt(level, optname, None, optlen: int) 调用形式。

@end deffn

@geindex shutdown() (socket.socket 方法)
@anchor{library/socket socket socket shutdown}@anchor{2634}
@deffn {方法} socket.shutdown (how)

关闭一半或全部的连接。如果 @emph{how} 为 @code{SHUT_RD}，则后续不再允许接收。如果 @emph{how} 为 @code{SHUT_WR}，则后续不再允许发送。如果 @emph{how} 为 @code{SHUT_RDWR}，则后续的发送和接收都不允许。
@end deffn

@geindex share() (socket.socket 方法)
@anchor{library/socket socket socket share}@anchor{48e}
@deffn {方法} socket.share (process_id)

复制套接字，并准备将其与目标进程共享。目标进程必须以 @emph{process_id} 形式提供。然后可以利用某种形式的进程间通信，将返回的字节对象传递给目标进程，还可以使用 @ref{48f,,fromshare()} 在新进程中重新创建套接字。一旦本方法调用完毕，就可以安全地将套接字关闭，因为操作系统已经为目标进程复制了该套接字。

@ref{12f5,,可用性}: Windows。


3.3 新版功能.

@end deffn

注意此处没有 @code{read()} 或 @code{write()} 方法，请使用不带 @emph{flags} 参数的 @ref{671,,recv()} 和 @ref{674,,send()} 来替代。

套接字对象还具有以下（只读）属性，这些属性与传入 @ref{66e,,socket} 构造函数的值相对应。

@geindex family (socket.socket 属性)
@anchor{library/socket socket socket family}@anchor{263c}
@deffn {属性} socket.family

套接字的协议簇。
@end deffn

@geindex type (socket.socket 属性)
@anchor{library/socket socket socket type}@anchor{493}
@deffn {属性} socket.type

套接字的类型。
@end deffn

@geindex proto (socket.socket 属性)
@anchor{library/socket socket socket proto}@anchor{263d}
@deffn {属性} socket.proto

套接字的协议。
@end deffn

@node 关于套接字超时的说明,示例<8>,套接字对象,socket --- 底层网络接口
@anchor{library/socket notes-on-socket-timeouts}@anchor{263e}@anchor{library/socket socket-timeouts}@anchor{263b}
@subsubsection 关于套接字超时的说明


一个套接字对象可以处于以下三种模式之一：阻塞、非阻塞或超时。套接字默认以阻塞模式创建，但是可以调用 @ref{260e,,setdefaulttimeout()} 来更改。


@itemize *

@item 
在 @emph{blocking mode} （阻塞模式）中，操作将阻塞，直到操作完成或系统返回错误（如连接超时）。

@item 
在 @emph{non-blocking mode} （非阻塞模式）中，如果操作无法立即完成，则操作将失败（不幸的是，不同系统返回的错误不同）：位于 @ref{e5,,select} 中的函数可用于了解套接字何时以及是否可以读取或写入。

@item 
在 @emph{timeout mode} （超时模式）下，如果无法在指定的超时内完成操作（抛出 @ref{c07,,timeout} 异常），或如果系统返回错误，则操作将失败。
@end itemize

@cartouche
@quotation 注解 
在操作系统层面上，@emph{超时模式} 下的套接字在内部都设置为非阻塞模式。同时，阻塞和超时模式在文件描述符和套接字对象之间共享，这些描述符和对象均应指向同一个网络端点。如果，比如你决定使用套接字的 @ref{2637,,fileno()}，这一实现细节可能导致明显的结果。
@end quotation
@end cartouche

@menu
* 超时与 connect 方法:: 
* 超时与 accept 方法:: 

@end menu

@node 超时与 connect 方法,超时与 accept 方法,,关于套接字超时的说明
@anchor{library/socket timeouts-and-the-connect-method}@anchor{263f}
@subsubsection 超时与 @code{connect} 方法


@ref{670,,connect()} 操作也受超时设置的约束，通常建议在调用 @ref{670,,connect()} 之前调用 @ref{2607,,settimeout()}，或将超时参数直接传递给 @ref{b97,,create_connection()}。但是，无论 Python 套接字超时设置如何，系统网络栈都有可能返回自带的连接超时错误。

@node 超时与 accept 方法,,超时与 connect 方法,关于套接字超时的说明
@anchor{library/socket timeouts-and-the-accept-method}@anchor{2640}
@subsubsection 超时与 @code{accept} 方法


如果 @ref{2626,,getdefaulttimeout()} 的值不是 @ref{157,,None}，则 @ref{66f,,accept()} 方法返回的套接字将继承该超时值。若是 None，返回的套接字行为取决于侦听套接字的设置：


@itemize *

@item 
如果侦听套接字处于 @emph{阻塞模式} 或 @emph{超时模式}，则 @ref{66f,,accept()} 返回的套接字处于 @emph{阻塞模式}；

@item 
如果侦听套接字处于 @emph{非阻塞模式}，那么 @ref{66f,,accept()} 返回的套接字是阻塞还是非阻塞取决于操作系统。如果要确保跨平台时的正确行为，建议手动覆盖此设置。
@end itemize

@node 示例<8>,,关于套接字超时的说明,socket --- 底层网络接口
@anchor{library/socket example}@anchor{2641}@anchor{library/socket socket-example}@anchor{2642}
@subsubsection 示例


以下是 4 个使用 TCP/IP 协议的最小示例程序：一台服务器，它将收到的所有数据原样返回（仅服务于一个客户端），还有一个使用该服务器的客户端。注意，服务器必须按序执行 @ref{66e,,socket()}, @ref{2633,,bind()}, @ref{745,,listen()}, @ref{66f,,accept()} （可能需要重复执行 @ref{66f,,accept()} 以服务多个客户端），而客户端仅需要按序执行 @ref{66e,,socket()}, @ref{670,,connect()}。还须注意，服务器不在侦听套接字上发送 @ref{675,,sendall()}/@ref{671,,recv()}，而是在 @ref{66f,,accept()} 返回的新套接字上发送。

前两个示例仅支持 IPv4。

@example
# Echo server program
import socket

HOST = '@w{'}                 # Symbolic name meaning all available interfaces
PORT = 50007              # Arbitrary non-privileged port
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen(1)
    conn, addr = s.accept()
    with conn:
        print('Connected by', addr)
        while True:
            data = conn.recv(1024)
            if not data: break
            conn.sendall(data)
@end example

@example
# Echo client program
import socket

HOST = 'daring.cwi.nl'    # The remote host
PORT = 50007              # The same port as used by the server
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((HOST, PORT))
    s.sendall(b'Hello, world')
    data = s.recv(1024)
print('Received', repr(data))
@end example

下两个例子与上两个很像，但是同时支持 IPv4 和 IPv6。 服务端将监听第一个可用的地址族（它本应同时监听两个）。 在大多数支持 IPv6 的系统上，IPv6 将有优先权并且服务端可能不会接受 IPv4 流量。 客户端将尝试连接到作为名称解析结果被返回的所有地址，并将流量发送给连接成功的第一个地址。

@example
# Echo server program
import socket
import sys

HOST = None               # Symbolic name meaning all available interfaces
PORT = 50007              # Arbitrary non-privileged port
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC,
                              socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
    af, socktype, proto, canonname, sa = res
    try:
        s = socket.socket(af, socktype, proto)
    except OSError as msg:
        s = None
        continue
    try:
        s.bind(sa)
        s.listen(1)
    except OSError as msg:
        s.close()
        s = None
        continue
    break
if s is None:
    print('could not open socket')
    sys.exit(1)
conn, addr = s.accept()
with conn:
    print('Connected by', addr)
    while True:
        data = conn.recv(1024)
        if not data: break
        conn.send(data)
@end example

@example
# Echo client program
import socket
import sys

HOST = 'daring.cwi.nl'    # The remote host
PORT = 50007              # The same port as used by the server
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC, socket.SOCK_STREAM):
    af, socktype, proto, canonname, sa = res
    try:
        s = socket.socket(af, socktype, proto)
    except OSError as msg:
        s = None
        continue
    try:
        s.connect(sa)
    except OSError as msg:
        s.close()
        s = None
        continue
    break
if s is None:
    print('could not open socket')
    sys.exit(1)
with s:
    s.sendall(b'Hello, world')
    data = s.recv(1024)
print('Received', repr(data))
@end example

下面的例子演示了如何在 Windows 上使用原始套接字编写一个非常简单的网络嗅探器。 这个例子需要管理员权限来修改接口:

@example
import socket

# the public network interface
HOST = socket.gethostbyname(socket.gethostname())

# create a raw socket and bind it to the public interface
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_IP)
s.bind((HOST, 0))

# Include IP headers
s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

# receive all packages
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)

# receive a package
print(s.recvfrom(65565))

# disabled promiscuous mode
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)
@end example

下面的例子演示了如何使用 socket 接口与采用原始套接字协议的 CAN 网络进行通信。 要改为通过广播管理器协议来使用 CAN，则要用以下方式打开一个 socket:

@example
socket.socket(socket.AF_CAN, socket.SOCK_DGRAM, socket.CAN_BCM)
@end example

在绑定 (@code{CAN_RAW}) 或连接 (@ref{8b3,,CAN_BCM}) socket 之后，你将可以在 socket 对象上正常使用 @ref{674,,socket.send()} 以及 @ref{671,,socket.recv()} 操作（及同类操作）。

最后一个例子可能需要特别的权限:

@example
import socket
import struct


# CAN frame packing/unpacking (see 'struct can_frame' in <linux/can.h>)

can_frame_fmt = "=IB3x8s"
can_frame_size = struct.calcsize(can_frame_fmt)

def build_can_frame(can_id, data):
    can_dlc = len(data)
    data = data.ljust(8, b'\x00')
    return struct.pack(can_frame_fmt, can_id, can_dlc, data)

def dissect_can_frame(frame):
    can_id, can_dlc, data = struct.unpack(can_frame_fmt, frame)
    return (can_id, can_dlc, data[:can_dlc])


# create a raw socket and bind it to the 'vcan0' interface
s = socket.socket(socket.AF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
s.bind(('vcan0',))

while True:
    cf, addr = s.recvfrom(can_frame_size)

    print('Received: can_id=%x, can_dlc=%x, data=%s' % dissect_can_frame(cf))

    try:
        s.send(cf)
    except OSError:
        print('Error sending CAN frame')

    try:
        s.send(build_can_frame(0x01, b'\x01\x02\x03'))
    except OSError:
        print('Error sending CAN frame')
@end example

多次运行一个示例，且每次执行之间等待时间过短，可能导致这个错误:

@example
OSError: [Errno 98] Address already in use
@end example

这是因为前一次运行使套接字处于 @code{TIME_WAIT} 状态，无法立即重用。

要防止这种情况，需要设置一个 @ref{ef,,socket} 标志 @code{socket.SO_REUSEADDR}:

@example
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
@end example

@code{SO_REUSEADDR} 标志告诉内核将处于 @code{TIME_WAIT} 状态的本地套接字重新使用，而不必等到固有的超时到期。


@subsubheading 参见


关于套接字编程（C 语言）的介绍，请参阅以下文章：


@itemize -

@item 
@emph{An Introductory 4.3BSD Interprocess Communication Tutorial}，作者 Stuart Sechrest

@item 
@emph{An Advanced 4.3BSD Interprocess Communication Tutorial}，作者 Samuel J.  Leffler et al,
@end itemize

两篇文章都在 UNIX 开发者手册，补充文档 1（第 PS1:7 和 PS1:8 节）中。那些特定于平台的参考资料，它们包含与套接字有关的各种系统调用，也是套接字语义细节的宝贵信息来源。对于 Unix，请参考手册页。对于 Windows，请参阅 WinSock（或 Winsock 2）规范。如果需要支持 IPv6 的 API，读者可能希望参考 
@geindex RFC; RFC 3493
RFC 3493@footnote{https://tools.ietf.org/html/rfc3493.html}，标题为 Basic Socket Interface Extensions for IPv6。


@node ssl --- 套接字对象的TLS/SSL封装,select --- 等待 I/O 完成,socket --- 底层网络接口,网络和进程间通信
@anchor{library/ssl doc}@anchor{2643}@anchor{library/ssl module-ssl}@anchor{f3}@anchor{library/ssl ssl-tls-ssl-wrapper-for-socket-objects}@anchor{2644}
@subsection @code{ssl} --- 套接字对象的TLS/SSL封装


@geindex ssl (模块)

@strong{源代码:} Lib/ssl.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/ssl.py}

@geindex OpenSSL; (use in module ssl)

@geindex TLS
@geindex SSL
@geindex Transport Layer Security
@geindex Secure Sockets Layer


__________________________________________________________________


This module provides access to Transport Layer Security (often known as "Secure
Sockets Layer") encryption and peer authentication facilities for network
sockets, both client-side and server-side.  This module uses the OpenSSL
library. It is available on all modern Unix systems, Windows, Mac OS X, and
probably additional platforms, as long as OpenSSL is installed on that platform.

@cartouche
@quotation 注解 
Some behavior may be platform dependent, since calls are made to the
operating system socket APIs.  The installed version of OpenSSL may also
cause variations in behavior. For example, TLSv1.1 and TLSv1.2 come with
openssl version 1.0.1.
@end quotation
@end cartouche

@cartouche
@quotation 警告 
Don't use this module without reading the @ref{254a,,Security considerations}.  Doing so
may lead to a false sense of security, as the default settings of the
ssl module are not necessarily appropriate for your application.
@end quotation
@end cartouche

This section documents the objects and functions in the @code{ssl} module; for more
general information about TLS, SSL, and certificates, the reader is referred to
the documents in the "See Also" section at the bottom.

This module provides a class, @ref{3da,,ssl.SSLSocket}, which is derived from the
@ref{66e,,socket.socket} type, and provides a socket-like wrapper that also
encrypts and decrypts the data going over the socket with SSL.  It supports
additional methods such as @code{getpeercert()}, which retrieves the
certificate of the other side of the connection, and @code{cipher()}, which
retrieves the cipher being used for the secure connection.

For more sophisticated applications, the @ref{3dc,,ssl.SSLContext} class
helps manage settings and certificates, which can then be inherited
by SSL sockets created through the @ref{3dd,,SSLContext.wrap_socket()} method.


在 3.5.3 版更改: Updated to support linking with OpenSSL 1.1.0



在 3.6 版更改: OpenSSL 0.9.8, 1.0.0 and 1.0.1 are deprecated and no longer supported.
In the future the ssl module will require at least OpenSSL 1.0.2 or
1.1.0.


@menu
* Functions@comma{} Constants@comma{} and Exceptions: Functions Constants and Exceptions. 
* SSL Sockets:: 
* SSL Contexts:: 
* Certificates:: 
* 例子: 例子<16>. 
* Notes on non-blocking sockets:: 
* Memory BIO Support: Memory BIO Support<2>. 
* SSL session:: 
* Security considerations:: 
* TLS 1.3: TLS 1 3. 
* LibreSSL support:: 

@end menu

@node Functions Constants and Exceptions,SSL Sockets,,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl functions-constants-and-exceptions}@anchor{2645}
@subsubsection Functions, Constants, and Exceptions


@menu
* Socket creation:: 
* 上下文创建:: 
* 异常: 异常<12>. 
* Random generation:: 
* Certificate handling:: 
* 常量: 常量<9>. 

@end menu

@node Socket creation,上下文创建,,Functions Constants and Exceptions
@anchor{library/ssl socket-creation}@anchor{2646}
@subsubsection Socket creation


Since Python 3.2 and 2.7.9, it is recommended to use the
@ref{3dd,,SSLContext.wrap_socket()} of an @ref{3dc,,SSLContext} instance to wrap
sockets as @ref{3da,,SSLSocket} objects. The helper functions
@ref{8bb,,create_default_context()} returns a new context with secure default
settings. The old @ref{469,,wrap_socket()} function is deprecated since it is
both inefficient and has no support for server name indication (SNI) and
hostname matching.

Client socket example with default context and IPv4/IPv6 dual stack:

@example
import socket
import ssl

hostname = 'www.python.org'
context = ssl.create_default_context()

with socket.create_connection((hostname, 443)) as sock:
    with context.wrap_socket(sock, server_hostname=hostname) as ssock:
        print(ssock.version())
@end example

Client socket example with custom context and IPv4:

@example
hostname = 'www.python.org'
# PROTOCOL_TLS_CLIENT requires valid cert chain and hostname
context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
context.load_verify_locations('path/to/cabundle.pem')

with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock:
    with context.wrap_socket(sock, server_hostname=hostname) as ssock:
        print(ssock.version())
@end example

Server socket example listening on localhost IPv4:

@example
context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
context.load_cert_chain('/path/to/certchain.pem', '/path/to/private.key')

with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock:
    sock.bind(('127.0.0.1', 8443))
    sock.listen(5)
    with context.wrap_socket(sock, server_side=True) as ssock:
        conn, addr = ssock.accept()
        ...
@end example

@node 上下文创建,异常<12>,Socket creation,Functions Constants and Exceptions
@anchor{library/ssl context-creation}@anchor{2647}
@subsubsection 上下文创建


A convenience function helps create @ref{3dc,,SSLContext} objects for common
purposes.

@geindex create_default_context() (在 ssl 模块中)
@anchor{library/ssl ssl create_default_context}@anchor{8bb}
@deffn {函数} ssl.create_default_context (purpose=Purpose.SERVER_AUTH, cafile=None, capath=None, cadata=None)

Return a new @ref{3dc,,SSLContext} object with default settings for
the given @emph{purpose}.  The settings are chosen by the @ref{f3,,ssl} module,
and usually represent a higher security level than when calling the
@ref{3dc,,SSLContext} constructor directly.

@emph{cafile}, @emph{capath}, @emph{cadata} represent optional CA certificates to
trust for certificate verification, as in
@ref{7e5,,SSLContext.load_verify_locations()}.  If all three are
@ref{157,,None}, this function can choose to trust the system's default
CA certificates instead.

The settings are: @ref{2648,,PROTOCOL_TLS}, @ref{b99,,OP_NO_SSLv2}, and
@ref{2649,,OP_NO_SSLv3} with high encryption cipher suites without RC4 and
without unauthenticated cipher suites. Passing @ref{8c6,,SERVER_AUTH}
as @emph{purpose} sets @ref{264a,,verify_mode} to @ref{264b,,CERT_REQUIRED}
and either loads CA certificates (when at least one of @emph{cafile}, @emph{capath} or
@emph{cadata} is given) or uses @ref{8c5,,SSLContext.load_default_certs()} to load
default CA certificates.

When @ref{264c,,keylog_filename} is supported and the environment
variable 
@geindex SSLKEYLOGFILE
@geindex 环境变量; SSLKEYLOGFILE
@code{SSLKEYLOGFILE} is set, @ref{8bb,,create_default_context()}
enables key logging.

@cartouche
@quotation 注解 
The protocol, options, cipher and other settings may change to more
restrictive values anytime without prior deprecation.  The values
represent a fair balance between compatibility and security.

If your application needs specific settings, you should create a
@ref{3dc,,SSLContext} and apply the settings yourself.
@end quotation
@end cartouche

@cartouche
@quotation 注解 
If you find that when certain older clients or servers attempt to connect
with a @ref{3dc,,SSLContext} created by this function that they get an error
stating "Protocol or cipher suite mismatch", it may be that they only
support SSL3.0 which this function excludes using the
@ref{2649,,OP_NO_SSLv3}. SSL3.0 is widely considered to be completely broken@footnote{https://en.wikipedia.org/wiki/POODLE}. If you still wish to continue to
use this function but still allow SSL 3.0 connections you can re-enable
them using:

@example
ctx = ssl.create_default_context(Purpose.CLIENT_AUTH)
ctx.options &= ~ssl.OP_NO_SSLv3
@end example
@end quotation
@end cartouche


3.4 新版功能.



在 3.4.4 版更改: RC4 was dropped from the default cipher string.



在 3.6 版更改: ChaCha20/Poly1305 was added to the default cipher string.

3DES was dropped from the default cipher string.



在 3.8 版更改: Support for key logging to 
@geindex SSLKEYLOGFILE
@geindex 环境变量; SSLKEYLOGFILE
@code{SSLKEYLOGFILE} was added.

@end deffn

@node 异常<12>,Random generation,上下文创建,Functions Constants and Exceptions
@anchor{library/ssl exceptions}@anchor{264d}
@subsubsection 异常


@geindex SSLError
@anchor{library/ssl ssl SSLError}@anchor{c08}
@deffn {例外} ssl.SSLError

Raised to signal an error from the underlying SSL implementation
(currently provided by the OpenSSL library).  This signifies some
problem in the higher-level encryption and authentication layer that's
superimposed on the underlying network connection.  This error
is a subtype of @ref{1d3,,OSError}.  The error code and message of
@ref{c08,,SSLError} instances are provided by the OpenSSL library.


在 3.3 版更改: @ref{c08,,SSLError} used to be a subtype of @ref{98f,,socket.error}.


@geindex library (ssl.SSLError 属性)
@anchor{library/ssl ssl SSLError library}@anchor{a93}
@deffn {属性} library

A string mnemonic designating the OpenSSL submodule in which the error
occurred, such as @code{SSL}, @code{PEM} or @code{X509}.  The range of possible
values depends on the OpenSSL version.


3.3 新版功能.

@end deffn

@geindex reason (ssl.SSLError 属性)
@anchor{library/ssl ssl SSLError reason}@anchor{a94}
@deffn {属性} reason

A string mnemonic designating the reason this error occurred, for
example @code{CERTIFICATE_VERIFY_FAILED}.  The range of possible
values depends on the OpenSSL version.


3.3 新版功能.

@end deffn
@end deffn

@geindex SSLZeroReturnError
@anchor{library/ssl ssl SSLZeroReturnError}@anchor{264e}
@deffn {例外} ssl.SSLZeroReturnError

A subclass of @ref{c08,,SSLError} raised when trying to read or write and
the SSL connection has been closed cleanly.  Note that this doesn't
mean that the underlying transport (read TCP) has been closed.


3.3 新版功能.

@end deffn

@geindex SSLWantReadError
@anchor{library/ssl ssl SSLWantReadError}@anchor{750}
@deffn {例外} ssl.SSLWantReadError

A subclass of @ref{c08,,SSLError} raised by a @ref{264f,,non-blocking SSL socket} when trying to read or write data, but more data needs
to be received on the underlying TCP transport before the request can be
fulfilled.


3.3 新版功能.

@end deffn

@geindex SSLWantWriteError
@anchor{library/ssl ssl SSLWantWriteError}@anchor{751}
@deffn {例外} ssl.SSLWantWriteError

A subclass of @ref{c08,,SSLError} raised by a @ref{264f,,non-blocking SSL socket} when trying to read or write data, but more data needs
to be sent on the underlying TCP transport before the request can be
fulfilled.


3.3 新版功能.

@end deffn

@geindex SSLSyscallError
@anchor{library/ssl ssl SSLSyscallError}@anchor{2650}
@deffn {例外} ssl.SSLSyscallError

A subclass of @ref{c08,,SSLError} raised when a system error was encountered
while trying to fulfill an operation on a SSL socket.  Unfortunately,
there is no easy way to inspect the original errno number.


3.3 新版功能.

@end deffn

@geindex SSLEOFError
@anchor{library/ssl ssl SSLEOFError}@anchor{2651}
@deffn {例外} ssl.SSLEOFError

A subclass of @ref{c08,,SSLError} raised when the SSL connection has been
terminated abruptly.  Generally, you shouldn't try to reuse the underlying
transport when this error is encountered.


3.3 新版功能.

@end deffn

@geindex SSLCertVerificationError
@anchor{library/ssl ssl SSLCertVerificationError}@anchor{3d5}
@deffn {例外} ssl.SSLCertVerificationError

A subclass of @ref{c08,,SSLError} raised when certificate validation has
failed.


3.7 新版功能.


@geindex verify_code (ssl.SSLCertVerificationError 属性)
@anchor{library/ssl ssl SSLCertVerificationError verify_code}@anchor{2652}
@deffn {属性} verify_code

A numeric error number that denotes the verification error.
@end deffn

@geindex verify_message (ssl.SSLCertVerificationError 属性)
@anchor{library/ssl ssl SSLCertVerificationError verify_message}@anchor{2653}
@deffn {属性} verify_message

A human readable string of the verification error.
@end deffn
@end deffn

@geindex CertificateError
@anchor{library/ssl ssl CertificateError}@anchor{2654}
@deffn {例外} ssl.CertificateError

An alias for @ref{3d5,,SSLCertVerificationError}.


在 3.7 版更改: The exception is now an alias for @ref{3d5,,SSLCertVerificationError}.

@end deffn

@node Random generation,Certificate handling,异常<12>,Functions Constants and Exceptions
@anchor{library/ssl random-generation}@anchor{2655}
@subsubsection Random generation


@geindex RAND_bytes() (在 ssl 模块中)
@anchor{library/ssl ssl RAND_bytes}@anchor{a8a}
@deffn {函数} ssl.RAND_bytes (num)

Return @emph{num} cryptographically strong pseudo-random bytes. Raises an
@ref{c08,,SSLError} if the PRNG has not been seeded with enough data or if the
operation is not supported by the current RAND method. @ref{2656,,RAND_status()}
can be used to check the status of the PRNG and @ref{2657,,RAND_add()} can be used
to seed the PRNG.

For almost all applications @ref{4cb,,os.urandom()} is preferable.

Read the Wikipedia article, Cryptographically secure pseudorandom number generator (CSPRNG)@footnote{https://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator},
to get the requirements of a cryptographically generator.


3.3 新版功能.

@end deffn

@geindex RAND_pseudo_bytes() (在 ssl 模块中)
@anchor{library/ssl ssl RAND_pseudo_bytes}@anchor{a8b}
@deffn {函数} ssl.RAND_pseudo_bytes (num)

Return (bytes, is_cryptographic): bytes are @emph{num} pseudo-random bytes,
is_cryptographic is @code{True} if the bytes generated are cryptographically
strong. Raises an @ref{c08,,SSLError} if the operation is not supported by the
current RAND method.

Generated pseudo-random byte sequences will be unique if they are of
sufficient length, but are not necessarily unpredictable. They can be used
for non-cryptographic purposes and for certain purposes in cryptographic
protocols, but usually not for key generation etc.

For almost all applications @ref{4cb,,os.urandom()} is preferable.


3.3 新版功能.



3.6 版后已移除: OpenSSL has deprecated @ref{a8b,,ssl.RAND_pseudo_bytes()}, use
@ref{a8a,,ssl.RAND_bytes()} instead.

@end deffn

@geindex RAND_status() (在 ssl 模块中)
@anchor{library/ssl ssl RAND_status}@anchor{2656}
@deffn {函数} ssl.RAND_status ()

Return @code{True} if the SSL pseudo-random number generator has been seeded
with 'enough' randomness, and @code{False} otherwise.  You can use
@ref{2658,,ssl.RAND_egd()} and @ref{2657,,ssl.RAND_add()} to increase the randomness of
the pseudo-random number generator.
@end deffn

@geindex RAND_egd() (在 ssl 模块中)
@anchor{library/ssl ssl RAND_egd}@anchor{2658}
@deffn {函数} ssl.RAND_egd (path)

If you are running an entropy-gathering daemon (EGD) somewhere, and @emph{path}
is the pathname of a socket connection open to it, this will read 256 bytes
of randomness from the socket, and add it to the SSL pseudo-random number
generator to increase the security of generated secret keys.  This is
typically only necessary on systems without better sources of randomness.

See @indicateurl{http://egd.sourceforge.net/} or @indicateurl{http://prngd.sourceforge.net/} for sources
of entropy-gathering daemons.

@ref{12f5,,Availability}: not available with LibreSSL and OpenSSL > 1.1.0.
@end deffn

@geindex RAND_add() (在 ssl 模块中)
@anchor{library/ssl ssl RAND_add}@anchor{2657}
@deffn {函数} ssl.RAND_add (bytes, entropy)

Mix the given @emph{bytes} into the SSL pseudo-random number generator.  The
parameter @emph{entropy} (a float) is a lower bound on the entropy contained in
string (so you can always use @code{0.0}).  See 
@geindex RFC; RFC 1750
RFC 1750@footnote{https://tools.ietf.org/html/rfc1750.html} for more
information on sources of entropy.


在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。

@end deffn

@node Certificate handling,常量<9>,Random generation,Functions Constants and Exceptions
@anchor{library/ssl certificate-handling}@anchor{2659}
@subsubsection Certificate handling


@c import ssl

@geindex match_hostname() (在 ssl 模块中)
@anchor{library/ssl ssl match_hostname}@anchor{3d4}
@deffn {函数} ssl.match_hostname (cert, hostname)

Verify that @emph{cert} (in decoded format as returned by
@ref{8cb,,SSLSocket.getpeercert()}) matches the given @emph{hostname}.  The rules
applied are those for checking the identity of HTTPS servers as outlined
in 
@geindex RFC; RFC 2818
RFC 2818@footnote{https://tools.ietf.org/html/rfc2818.html}, 
@geindex RFC; RFC 5280
RFC 5280@footnote{https://tools.ietf.org/html/rfc5280.html} and 
@geindex RFC; RFC 6125
RFC 6125@footnote{https://tools.ietf.org/html/rfc6125.html}.  In addition to HTTPS, this
function should be suitable for checking the identity of servers in
various SSL-based protocols such as FTPS, IMAPS, POPS and others.

@ref{2654,,CertificateError} is raised on failure. On success, the function
returns nothing:

@example
>>> cert = @{'subject': ((('commonName', 'example.com'),),)@}
>>> ssl.match_hostname(cert, "example.com")
>>> ssl.match_hostname(cert, "example.org")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/py3k/Lib/ssl.py", line 130, in match_hostname
ssl.CertificateError: hostname 'example.org' doesn't match 'example.com'
@end example


3.2 新版功能.



在 3.3.3 版更改: The function now follows 
@geindex RFC; RFC 6125
RFC 6125@footnote{https://tools.ietf.org/html/rfc6125.html}, section 6.4.3 and does neither
match multiple wildcards (e.g. @code{*.*.com} or @code{*a*.example.org}) nor
a wildcard inside an internationalized domain names (IDN) fragment.
IDN A-labels such as @code{www*.xn--pthon-kva.org} are still supported,
but @code{x*.python.org} no longer matches @code{xn--tda.python.org}.



在 3.5 版更改: Matching of IP addresses, when present in the subjectAltName field
of the certificate, is now supported.



在 3.7 版更改: The function is no longer used to TLS connections. Hostname matching
is now performed by OpenSSL.

Allow wildcard when it is the leftmost and the only character
in that segment. Partial wildcards like @code{www*.example.com} are no
longer supported.



3.7 版后已移除.

@end deffn

@geindex cert_time_to_seconds() (在 ssl 模块中)
@anchor{library/ssl ssl cert_time_to_seconds}@anchor{752}
@deffn {函数} ssl.cert_time_to_seconds (cert_time)

Return the time in seconds since the Epoch, given the @code{cert_time}
string representing the "notBefore" or "notAfter" date from a
certificate in @code{"%b %d %H:%M:%S %Y %Z"} strptime format (C
locale).

Here's an example:

@example
>>> import ssl
>>> timestamp = ssl.cert_time_to_seconds("Jan  5 09:34:43 2018 GMT")
>>> timestamp  
1515144883
>>> from datetime import datetime
>>> print(datetime.utcfromtimestamp(timestamp))  
2018-01-05 09:34:43
@end example

"notBefore" or "notAfter" dates must use GMT (
@geindex RFC; RFC 5280
RFC 5280@footnote{https://tools.ietf.org/html/rfc5280.html}).


在 3.5 版更改: Interpret the input time as a time in UTC as specified by 'GMT'
timezone in the input string. Local timezone was used
previously. Return an integer (no fractions of a second in the
input format)

@end deffn

@geindex get_server_certificate() (在 ssl 模块中)
@anchor{library/ssl ssl get_server_certificate}@anchor{a95}
@deffn {函数} ssl.get_server_certificate (addr, ssl_version=PROTOCOL_TLS, ca_certs=None)

Given the address @code{addr} of an SSL-protected server, as a (@emph{hostname},
@emph{port-number}) pair, fetches the server's certificate, and returns it as a
PEM-encoded string.  If @code{ssl_version} is specified, uses that version of
the SSL protocol to attempt to connect to the server.  If @code{ca_certs} is
specified, it should be a file containing a list of root certificates, the
same format as used for the same parameter in
@ref{3dd,,SSLContext.wrap_socket()}.  The call will attempt to validate the
server certificate against that set of root certificates, and will fail
if the validation attempt fails.


在 3.3 版更改: This function is now IPv6-compatible.



在 3.5 版更改: The default @emph{ssl_version} is changed from @ref{265a,,PROTOCOL_SSLv3} to
@ref{2648,,PROTOCOL_TLS} for maximum compatibility with modern servers.

@end deffn

@geindex DER_cert_to_PEM_cert() (在 ssl 模块中)
@anchor{library/ssl ssl DER_cert_to_PEM_cert}@anchor{265b}
@deffn {函数} ssl.DER_cert_to_PEM_cert (DER_cert_bytes)

Given a certificate as a DER-encoded blob of bytes, returns a PEM-encoded
string version of the same certificate.
@end deffn

@geindex PEM_cert_to_DER_cert() (在 ssl 模块中)
@anchor{library/ssl ssl PEM_cert_to_DER_cert}@anchor{265c}
@deffn {函数} ssl.PEM_cert_to_DER_cert (PEM_cert_string)

Given a certificate as an ASCII PEM string, returns a DER-encoded sequence of
bytes for that same certificate.
@end deffn

@geindex get_default_verify_paths() (在 ssl 模块中)
@anchor{library/ssl ssl get_default_verify_paths}@anchor{8bc}
@deffn {函数} ssl.get_default_verify_paths ()

Returns a named tuple with paths to OpenSSL's default cafile and capath.
The paths are the same as used by
@ref{8bd,,SSLContext.set_default_verify_paths()}. The return value is a
@ref{a9e,,named tuple} @code{DefaultVerifyPaths}:


@itemize *

@item 
@code{cafile} - resolved path to cafile or @code{None} if the file doesn't exist,

@item 
@code{capath} - resolved path to capath or @code{None} if the directory doesn't exist,

@item 
@code{openssl_cafile_env} - OpenSSL's environment key that points to a cafile,

@item 
@code{openssl_cafile} - hard coded path to a cafile,

@item 
@code{openssl_capath_env} - OpenSSL's environment key that points to a capath,

@item 
@code{openssl_capath} - hard coded path to a capath directory
@end itemize

@ref{12f5,,Availability}: LibreSSL ignores the environment vars
@code{openssl_cafile_env} and @code{openssl_capath_env}.


3.4 新版功能.

@end deffn

@geindex enum_certificates() (在 ssl 模块中)
@anchor{library/ssl ssl enum_certificates}@anchor{8c8}
@deffn {函数} ssl.enum_certificates (store_name)

Retrieve certificates from Windows' system cert store. @emph{store_name} may be
one of @code{CA}, @code{ROOT} or @code{MY}. Windows may provide additional cert
stores, too.

The function returns a list of (cert_bytes, encoding_type, trust) tuples.
The encoding_type specifies the encoding of cert_bytes. It is either
@code{x509_asn} for X.509 ASN.1 data or @code{pkcs_7_asn} for
PKCS#7 ASN.1 data. Trust specifies the purpose of the certificate as a set
of OIDS or exactly @code{True} if the certificate is trustworthy for all
purposes.

示例:

@example
>>> ssl.enum_certificates("CA")
[(b'data...', 'x509_asn', @{'1.3.6.1.5.5.7.3.1', '1.3.6.1.5.5.7.3.2'@}),
 (b'data...', 'x509_asn', True)]
@end example

@ref{12f5,,可用性}: Windows。


3.4 新版功能.

@end deffn

@geindex enum_crls() (在 ssl 模块中)
@anchor{library/ssl ssl enum_crls}@anchor{8c9}
@deffn {函数} ssl.enum_crls (store_name)

Retrieve CRLs from Windows' system cert store. @emph{store_name} may be
one of @code{CA}, @code{ROOT} or @code{MY}. Windows may provide additional cert
stores, too.

The function returns a list of (cert_bytes, encoding_type, trust) tuples.
The encoding_type specifies the encoding of cert_bytes. It is either
@code{x509_asn} for X.509 ASN.1 data or @code{pkcs_7_asn} for
PKCS#7 ASN.1 data.

@ref{12f5,,可用性}: Windows。


3.4 新版功能.

@end deffn

@geindex wrap_socket() (在 ssl 模块中)
@anchor{library/ssl ssl wrap_socket}@anchor{469}
@deffn {函数} ssl.wrap_socket (sock, keyfile=None, certfile=None, server_side=False, cert_reqs=CERT_NONE, ssl_version=PROTOCOL_TLS, ca_certs=None, do_handshake_on_connect=True, suppress_ragged_eofs=True, ciphers=None)

Takes an instance @code{sock} of @ref{66e,,socket.socket}, and returns an instance
of @ref{3da,,ssl.SSLSocket}, a subtype of @ref{66e,,socket.socket}, which wraps
the underlying socket in an SSL context.  @code{sock} must be a
@ref{c83,,SOCK_STREAM} socket; other socket types are unsupported.

Internally, function creates a @ref{3dc,,SSLContext} with protocol
@emph{ssl_version} and @ref{265d,,SSLContext.options} set to @emph{cert_reqs}. If
parameters @emph{keyfile}, @emph{certfile}, @emph{ca_certs} or @emph{ciphers} are set, then
the values are passed to @ref{a8c,,SSLContext.load_cert_chain()},
@ref{7e5,,SSLContext.load_verify_locations()}, and
@ref{265e,,SSLContext.set_ciphers()}.

The arguments @emph{server_side}, @emph{do_handshake_on_connect}, and
@emph{suppress_ragged_eofs} have the same meaning as
@ref{3dd,,SSLContext.wrap_socket()}.


3.7 版后已移除: Since Python 3.2 and 2.7.9, it is recommended to use the
@ref{3dd,,SSLContext.wrap_socket()} instead of @ref{469,,wrap_socket()}. The
top-level function is limited and creates an insecure client socket
without server name indication or hostname matching.

@end deffn

@node 常量<9>,,Certificate handling,Functions Constants and Exceptions
@anchor{library/ssl constants}@anchor{265f}
@subsubsection 常量


@quotation

All constants are now @ref{588,,enum.IntEnum} or @ref{16f0,,enum.IntFlag} collections.


3.6 新版功能.

@end quotation

@geindex CERT_NONE() (在 ssl 模块中)
@anchor{library/ssl ssl CERT_NONE}@anchor{2660}
@deffn {数据} ssl.CERT_NONE

Possible value for @ref{264a,,SSLContext.verify_mode}, or the @code{cert_reqs}
parameter to @ref{469,,wrap_socket()}.  Except for @ref{2661,,PROTOCOL_TLS_CLIENT},
it is the default mode.  With client-side sockets, just about any
cert is accepted.  Validation errors, such as untrusted or expired cert,
are ignored and do not abort the TLS/SSL handshake.

In server mode, no certificate is requested from the client, so the client
does not send any for client cert authentication.

See the discussion of @ref{254a,,Security considerations} below.
@end deffn

@geindex CERT_OPTIONAL() (在 ssl 模块中)
@anchor{library/ssl ssl CERT_OPTIONAL}@anchor{2662}
@deffn {数据} ssl.CERT_OPTIONAL

Possible value for @ref{264a,,SSLContext.verify_mode}, or the @code{cert_reqs}
parameter to @ref{469,,wrap_socket()}.  In client mode, @ref{2662,,CERT_OPTIONAL}
has the same meaning as @ref{264b,,CERT_REQUIRED}. It is recommended to
use @ref{264b,,CERT_REQUIRED} for client-side sockets instead.

In server mode, a client certificate request is sent to the client.  The
client may either ignore the request or send a certificate in order
perform TLS client cert authentication.  If the client chooses to send
a certificate, it is verified.  Any verification error immediately aborts
the TLS handshake.

Use of this setting requires a valid set of CA certificates to
be passed, either to @ref{7e5,,SSLContext.load_verify_locations()} or as a
value of the @code{ca_certs} parameter to @ref{469,,wrap_socket()}.
@end deffn

@geindex CERT_REQUIRED() (在 ssl 模块中)
@anchor{library/ssl ssl CERT_REQUIRED}@anchor{264b}
@deffn {数据} ssl.CERT_REQUIRED

Possible value for @ref{264a,,SSLContext.verify_mode}, or the @code{cert_reqs}
parameter to @ref{469,,wrap_socket()}.  In this mode, certificates are
required from the other side of the socket connection; an @ref{c08,,SSLError}
will be raised if no certificate is provided, or if its validation fails.
This mode is @strong{not} sufficient to verify a certificate in client mode as
it does not match hostnames.  @ref{2663,,check_hostname} must be
enabled as well to verify the authenticity of a cert.
@ref{2661,,PROTOCOL_TLS_CLIENT} uses @ref{264b,,CERT_REQUIRED} and
enables @ref{2663,,check_hostname} by default.

With server socket, this mode provides mandatory TLS client cert
authentication.  A client certificate request is sent to the client and
the client must provide a valid and trusted certificate.

Use of this setting requires a valid set of CA certificates to
be passed, either to @ref{7e5,,SSLContext.load_verify_locations()} or as a
value of the @code{ca_certs} parameter to @ref{469,,wrap_socket()}.
@end deffn

@geindex VerifyMode (ssl 中的类)
@anchor{library/ssl ssl VerifyMode}@anchor{2664}
@deffn {类} ssl.VerifyMode

@ref{588,,enum.IntEnum} collection of CERT_* constants.


3.6 新版功能.

@end deffn

@geindex VERIFY_DEFAULT() (在 ssl 模块中)
@anchor{library/ssl ssl VERIFY_DEFAULT}@anchor{8c1}
@deffn {数据} ssl.VERIFY_DEFAULT

Possible value for @ref{8c0,,SSLContext.verify_flags}. In this mode, certificate
revocation lists (CRLs) are not checked. By default OpenSSL does neither
require nor verify CRLs.


3.4 新版功能.

@end deffn

@geindex VERIFY_CRL_CHECK_LEAF() (在 ssl 模块中)
@anchor{library/ssl ssl VERIFY_CRL_CHECK_LEAF}@anchor{8c2}
@deffn {数据} ssl.VERIFY_CRL_CHECK_LEAF

Possible value for @ref{8c0,,SSLContext.verify_flags}. In this mode, only the
peer cert is checked but none of the intermediate CA certificates. The mode
requires a valid CRL that is signed by the peer cert's issuer (its direct
ancestor CA). If no proper CRL has has been loaded with
@ref{7e5,,SSLContext.load_verify_locations}, validation will fail.


3.4 新版功能.

@end deffn

@geindex VERIFY_CRL_CHECK_CHAIN() (在 ssl 模块中)
@anchor{library/ssl ssl VERIFY_CRL_CHECK_CHAIN}@anchor{8c3}
@deffn {数据} ssl.VERIFY_CRL_CHECK_CHAIN

Possible value for @ref{8c0,,SSLContext.verify_flags}. In this mode, CRLs of
all certificates in the peer cert chain are checked.


3.4 新版功能.

@end deffn

@geindex VERIFY_X509_STRICT() (在 ssl 模块中)
@anchor{library/ssl ssl VERIFY_X509_STRICT}@anchor{8c4}
@deffn {数据} ssl.VERIFY_X509_STRICT

Possible value for @ref{8c0,,SSLContext.verify_flags} to disable workarounds
for broken X.509 certificates.


3.4 新版功能.

@end deffn

@geindex VERIFY_X509_TRUSTED_FIRST() (在 ssl 模块中)
@anchor{library/ssl ssl VERIFY_X509_TRUSTED_FIRST}@anchor{2665}
@deffn {数据} ssl.VERIFY_X509_TRUSTED_FIRST

Possible value for @ref{8c0,,SSLContext.verify_flags}. It instructs OpenSSL to
prefer trusted certificates when building the trust chain to validate a
certificate. This flag is enabled by default.


3.4.4 新版功能.

@end deffn

@geindex VerifyFlags (ssl 中的类)
@anchor{library/ssl ssl VerifyFlags}@anchor{2666}
@deffn {类} ssl.VerifyFlags

@ref{16f0,,enum.IntFlag} collection of VERIFY_* constants.


3.6 新版功能.

@end deffn

@geindex PROTOCOL_TLS() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_TLS}@anchor{2648}
@deffn {数据} ssl.PROTOCOL_TLS

Selects the highest protocol version that both the client and server support.
Despite the name, this option can select both "SSL" and "TLS" protocols.


3.6 新版功能.

@end deffn

@geindex PROTOCOL_TLS_CLIENT() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_TLS_CLIENT}@anchor{2661}
@deffn {数据} ssl.PROTOCOL_TLS_CLIENT

Auto-negotiate the highest protocol version like @ref{2648,,PROTOCOL_TLS},
but only support client-side @ref{3da,,SSLSocket} connections. The protocol
enables @ref{264b,,CERT_REQUIRED} and @ref{2663,,check_hostname} by
default.


3.6 新版功能.

@end deffn

@geindex PROTOCOL_TLS_SERVER() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_TLS_SERVER}@anchor{2667}
@deffn {数据} ssl.PROTOCOL_TLS_SERVER

Auto-negotiate the highest protocol version like @ref{2648,,PROTOCOL_TLS},
but only support server-side @ref{3da,,SSLSocket} connections.


3.6 新版功能.

@end deffn

@geindex PROTOCOL_SSLv23() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_SSLv23}@anchor{2668}
@deffn {数据} ssl.PROTOCOL_SSLv23

Alias for @ref{2648,,PROTOCOL_TLS}.


3.6 版后已移除: Use @ref{2648,,PROTOCOL_TLS} instead.

@end deffn

@geindex PROTOCOL_SSLv2() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_SSLv2}@anchor{2669}
@deffn {数据} ssl.PROTOCOL_SSLv2

Selects SSL version 2 as the channel encryption protocol.

This protocol is not available if OpenSSL is compiled with the
@code{OPENSSL_NO_SSL2} flag.

@cartouche
@quotation 警告 
SSL version 2 is insecure.  Its use is highly discouraged.
@end quotation
@end cartouche


3.6 版后已移除: OpenSSL has removed support for SSLv2.

@end deffn

@geindex PROTOCOL_SSLv3() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_SSLv3}@anchor{265a}
@deffn {数据} ssl.PROTOCOL_SSLv3

Selects SSL version 3 as the channel encryption protocol.

This protocol is not be available if OpenSSL is compiled with the
@code{OPENSSL_NO_SSLv3} flag.

@cartouche
@quotation 警告 
SSL version 3 is insecure.  Its use is highly discouraged.
@end quotation
@end cartouche


3.6 版后已移除: OpenSSL has deprecated all version specific protocols. Use the default
protocol @ref{2648,,PROTOCOL_TLS} with flags like @ref{2649,,OP_NO_SSLv3} instead.

@end deffn

@geindex PROTOCOL_TLSv1() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_TLSv1}@anchor{266a}
@deffn {数据} ssl.PROTOCOL_TLSv1

Selects TLS version 1.0 as the channel encryption protocol.


3.6 版后已移除: OpenSSL has deprecated all version specific protocols. Use the default
protocol @ref{2648,,PROTOCOL_TLS} with flags like @ref{2649,,OP_NO_SSLv3} instead.

@end deffn

@geindex PROTOCOL_TLSv1_1() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_TLSv1_1}@anchor{8b9}
@deffn {数据} ssl.PROTOCOL_TLSv1_1

Selects TLS version 1.1 as the channel encryption protocol.
Available only with openssl version 1.0.1+.


3.4 新版功能.



3.6 版后已移除: OpenSSL has deprecated all version specific protocols. Use the default
protocol @ref{2648,,PROTOCOL_TLS} with flags like @ref{2649,,OP_NO_SSLv3} instead.

@end deffn

@geindex PROTOCOL_TLSv1_2() (在 ssl 模块中)
@anchor{library/ssl ssl PROTOCOL_TLSv1_2}@anchor{8ba}
@deffn {数据} ssl.PROTOCOL_TLSv1_2

Selects TLS version 1.2 as the channel encryption protocol. This is the
most modern version, and probably the best choice for maximum protection,
if both sides can speak it.  Available only with openssl version 1.0.1+.


3.4 新版功能.



3.6 版后已移除: OpenSSL has deprecated all version specific protocols. Use the default
protocol @ref{2648,,PROTOCOL_TLS} with flags like @ref{2649,,OP_NO_SSLv3} instead.

@end deffn

@geindex OP_ALL() (在 ssl 模块中)
@anchor{library/ssl ssl OP_ALL}@anchor{266b}
@deffn {数据} ssl.OP_ALL

Enables workarounds for various bugs present in other SSL implementations.
This option is set by default.  It does not necessarily set the same
flags as OpenSSL's @code{SSL_OP_ALL} constant.


3.2 新版功能.

@end deffn

@geindex OP_NO_SSLv2() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_SSLv2}@anchor{b99}
@deffn {数据} ssl.OP_NO_SSLv2

Prevents an SSLv2 connection.  This option is only applicable in
conjunction with @ref{2648,,PROTOCOL_TLS}.  It prevents the peers from
choosing SSLv2 as the protocol version.


3.2 新版功能.



3.6 版后已移除: SSLv2 is deprecated

@end deffn

@geindex OP_NO_SSLv3() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_SSLv3}@anchor{2649}
@deffn {数据} ssl.OP_NO_SSLv3

Prevents an SSLv3 connection.  This option is only applicable in
conjunction with @ref{2648,,PROTOCOL_TLS}.  It prevents the peers from
choosing SSLv3 as the protocol version.


3.2 新版功能.



3.6 版后已移除: SSLv3 is deprecated

@end deffn

@geindex OP_NO_TLSv1() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_TLSv1}@anchor{266c}
@deffn {数据} ssl.OP_NO_TLSv1

Prevents a TLSv1 connection.  This option is only applicable in
conjunction with @ref{2648,,PROTOCOL_TLS}.  It prevents the peers from
choosing TLSv1 as the protocol version.


3.2 新版功能.



3.7 版后已移除: The option is deprecated since OpenSSL 1.1.0, use the new
@ref{3df,,SSLContext.minimum_version} and
@ref{3e0,,SSLContext.maximum_version} instead.

@end deffn

@geindex OP_NO_TLSv1_1() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_TLSv1_1}@anchor{266d}
@deffn {数据} ssl.OP_NO_TLSv1_1

Prevents a TLSv1.1 connection. This option is only applicable in conjunction
with @ref{2648,,PROTOCOL_TLS}. It prevents the peers from choosing TLSv1.1 as
the protocol version. Available only with openssl version 1.0.1+.


3.4 新版功能.



3.7 版后已移除: The option is deprecated since OpenSSL 1.1.0.

@end deffn

@geindex OP_NO_TLSv1_2() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_TLSv1_2}@anchor{266e}
@deffn {数据} ssl.OP_NO_TLSv1_2

Prevents a TLSv1.2 connection. This option is only applicable in conjunction
with @ref{2648,,PROTOCOL_TLS}. It prevents the peers from choosing TLSv1.2 as
the protocol version. Available only with openssl version 1.0.1+.


3.4 新版功能.



3.7 版后已移除: The option is deprecated since OpenSSL 1.1.0.

@end deffn

@geindex OP_NO_TLSv1_3() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_TLSv1_3}@anchor{266f}
@deffn {数据} ssl.OP_NO_TLSv1_3

Prevents a TLSv1.3 connection. This option is only applicable in conjunction
with @ref{2648,,PROTOCOL_TLS}. It prevents the peers from choosing TLSv1.3 as
the protocol version. TLS 1.3 is available with OpenSSL 1.1.1 or later.
When Python has been compiled against an older version of OpenSSL, the
flag defaults to @emph{0}.


3.7 新版功能.



3.7 版后已移除: The option is deprecated since OpenSSL 1.1.0. It was added to 2.7.15,
3.6.3 and 3.7.0 for backwards compatibility with OpenSSL 1.0.2.

@end deffn

@geindex OP_NO_RENEGOTIATION() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_RENEGOTIATION}@anchor{2670}
@deffn {数据} ssl.OP_NO_RENEGOTIATION

Disable all renegotiation in TLSv1.2 and earlier. Do not send
HelloRequest messages, and ignore renegotiation requests via ClientHello.

This option is only available with OpenSSL 1.1.0h and later.


3.7 新版功能.

@end deffn

@geindex OP_CIPHER_SERVER_PREFERENCE() (在 ssl 模块中)
@anchor{library/ssl ssl OP_CIPHER_SERVER_PREFERENCE}@anchor{a96}
@deffn {数据} ssl.OP_CIPHER_SERVER_PREFERENCE

Use the server's cipher ordering preference, rather than the client's.
This option has no effect on client sockets and SSLv2 server sockets.


3.3 新版功能.

@end deffn

@geindex OP_SINGLE_DH_USE() (在 ssl 模块中)
@anchor{library/ssl ssl OP_SINGLE_DH_USE}@anchor{2671}
@deffn {数据} ssl.OP_SINGLE_DH_USE

Prevents re-use of the same DH key for distinct SSL sessions.  This
improves forward secrecy but requires more computational resources.
This option only applies to server sockets.


3.3 新版功能.

@end deffn

@geindex OP_SINGLE_ECDH_USE() (在 ssl 模块中)
@anchor{library/ssl ssl OP_SINGLE_ECDH_USE}@anchor{2672}
@deffn {数据} ssl.OP_SINGLE_ECDH_USE

Prevents re-use of the same ECDH key for distinct SSL sessions.  This
improves forward secrecy but requires more computational resources.
This option only applies to server sockets.


3.3 新版功能.

@end deffn

@geindex OP_ENABLE_MIDDLEBOX_COMPAT() (在 ssl 模块中)
@anchor{library/ssl ssl OP_ENABLE_MIDDLEBOX_COMPAT}@anchor{2673}
@deffn {数据} ssl.OP_ENABLE_MIDDLEBOX_COMPAT

Send dummy Change Cipher Spec (CCS) messages in TLS 1.3 handshake to make
a TLS 1.3 connection look more like a TLS 1.2 connection.

This option is only available with OpenSSL 1.1.1 and later.


3.8 新版功能.

@end deffn

@geindex OP_NO_COMPRESSION() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_COMPRESSION}@anchor{a91}
@deffn {数据} ssl.OP_NO_COMPRESSION

Disable compression on the SSL channel.  This is useful if the application
protocol supports its own compression scheme.

This option is only available with OpenSSL 1.0.0 and later.


3.3 新版功能.

@end deffn

@geindex Options (ssl 中的类)
@anchor{library/ssl ssl Options}@anchor{2674}
@deffn {类} ssl.Options

@ref{16f0,,enum.IntFlag} collection of OP_* constants.
@end deffn

@geindex OP_NO_TICKET() (在 ssl 模块中)
@anchor{library/ssl ssl OP_NO_TICKET}@anchor{2675}
@deffn {数据} ssl.OP_NO_TICKET

Prevent client side from requesting a session ticket.


3.6 新版功能.

@end deffn

@geindex HAS_ALPN() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_ALPN}@anchor{74d}
@deffn {数据} ssl.HAS_ALPN

Whether the OpenSSL library has built-in support for the @emph{Application-Layer
Protocol Negotiation} TLS extension as described in 
@geindex RFC; RFC 7301
RFC 7301@footnote{https://tools.ietf.org/html/rfc7301.html}.


3.5 新版功能.

@end deffn

@geindex HAS_NEVER_CHECK_COMMON_NAME() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_NEVER_CHECK_COMMON_NAME}@anchor{2676}
@deffn {数据} ssl.HAS_NEVER_CHECK_COMMON_NAME

Whether the OpenSSL library has built-in support not checking subject
common name and @ref{3d6,,SSLContext.hostname_checks_common_name} is
writeable.


3.7 新版功能.

@end deffn

@geindex HAS_ECDH() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_ECDH}@anchor{2677}
@deffn {数据} ssl.HAS_ECDH

Whether the OpenSSL library has built-in support for the Elliptic Curve-based
Diffie-Hellman key exchange.  This should be true unless the feature was
explicitly disabled by the distributor.


3.3 新版功能.

@end deffn

@geindex HAS_SNI() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_SNI}@anchor{2678}
@deffn {数据} ssl.HAS_SNI

Whether the OpenSSL library has built-in support for the @emph{Server Name
Indication} extension (as defined in 
@geindex RFC; RFC 6066
RFC 6066@footnote{https://tools.ietf.org/html/rfc6066.html}).


3.2 新版功能.

@end deffn

@geindex HAS_NPN() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_NPN}@anchor{2679}
@deffn {数据} ssl.HAS_NPN

Whether the OpenSSL library has built-in support for the @emph{Next Protocol
Negotiation} as described in the Application Layer Protocol Negotiation@footnote{https://en.wikipedia.org/wiki/Application-Layer_Protocol_Negotiation}.
When true, you can use the @ref{a92,,SSLContext.set_npn_protocols()} method to advertise
which protocols you want to support.


3.3 新版功能.

@end deffn

@geindex HAS_SSLv2() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_SSLv2}@anchor{267a}
@deffn {数据} ssl.HAS_SSLv2

Whether the OpenSSL library has built-in support for the SSL 2.0 protocol.


3.7 新版功能.

@end deffn

@geindex HAS_SSLv3() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_SSLv3}@anchor{267b}
@deffn {数据} ssl.HAS_SSLv3

Whether the OpenSSL library has built-in support for the SSL 3.0 protocol.


3.7 新版功能.

@end deffn

@geindex HAS_TLSv1() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_TLSv1}@anchor{267c}
@deffn {数据} ssl.HAS_TLSv1

Whether the OpenSSL library has built-in support for the TLS 1.0 protocol.


3.7 新版功能.

@end deffn

@geindex HAS_TLSv1_1() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_TLSv1_1}@anchor{3e1}
@deffn {数据} ssl.HAS_TLSv1_1

Whether the OpenSSL library has built-in support for the TLS 1.1 protocol.


3.7 新版功能.

@end deffn

@geindex HAS_TLSv1_2() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_TLSv1_2}@anchor{267d}
@deffn {数据} ssl.HAS_TLSv1_2

Whether the OpenSSL library has built-in support for the TLS 1.2 protocol.


3.7 新版功能.

@end deffn

@geindex HAS_TLSv1_3() (在 ssl 模块中)
@anchor{library/ssl ssl HAS_TLSv1_3}@anchor{267e}
@deffn {数据} ssl.HAS_TLSv1_3

Whether the OpenSSL library has built-in support for the TLS 1.3 protocol.


3.7 新版功能.

@end deffn

@geindex CHANNEL_BINDING_TYPES() (在 ssl 模块中)
@anchor{library/ssl ssl CHANNEL_BINDING_TYPES}@anchor{267f}
@deffn {数据} ssl.CHANNEL_BINDING_TYPES

List of supported TLS channel binding types.  Strings in this list
can be used as arguments to @ref{a8f,,SSLSocket.get_channel_binding()}.


3.3 新版功能.

@end deffn

@geindex OPENSSL_VERSION() (在 ssl 模块中)
@anchor{library/ssl ssl OPENSSL_VERSION}@anchor{b9a}
@deffn {数据} ssl.OPENSSL_VERSION

The version string of the OpenSSL library loaded by the interpreter:

@example
>>> ssl.OPENSSL_VERSION
'OpenSSL 1.0.2k  26 Jan 2017'
@end example


3.2 新版功能.

@end deffn

@geindex OPENSSL_VERSION_INFO() (在 ssl 模块中)
@anchor{library/ssl ssl OPENSSL_VERSION_INFO}@anchor{b9b}
@deffn {数据} ssl.OPENSSL_VERSION_INFO

A tuple of five integers representing version information about the
OpenSSL library:

@example
>>> ssl.OPENSSL_VERSION_INFO
(1, 0, 2, 11, 15)
@end example


3.2 新版功能.

@end deffn

@geindex OPENSSL_VERSION_NUMBER() (在 ssl 模块中)
@anchor{library/ssl ssl OPENSSL_VERSION_NUMBER}@anchor{b9c}
@deffn {数据} ssl.OPENSSL_VERSION_NUMBER

The raw version number of the OpenSSL library, as a single integer:

@example
>>> ssl.OPENSSL_VERSION_NUMBER
268443839
>>> hex(ssl.OPENSSL_VERSION_NUMBER)
'0x100020bf'
@end example


3.2 新版功能.

@end deffn

@geindex ALERT_DESCRIPTION_HANDSHAKE_FAILURE() (在 ssl 模块中)
@geindex ALERT_DESCRIPTION_INTERNAL_ERROR() (在 ssl 模块中)
@anchor{library/ssl ssl ALERT_DESCRIPTION_HANDSHAKE_FAILURE}@anchor{2680}
@deffn {数据} ssl.ALERT_DESCRIPTION_HANDSHAKE_FAILURE
@anchor{library/ssl ssl ALERT_DESCRIPTION_INTERNAL_ERROR}@anchor{2681}
@deffnx {数据} ssl.ALERT_DESCRIPTION_INTERNAL_ERROR

@deffnx {数据} ALERT_DESCRIPTION_*

Alert Descriptions from 
@geindex RFC; RFC 5246
RFC 5246@footnote{https://tools.ietf.org/html/rfc5246.html} and others. The IANA TLS Alert Registry@footnote{https://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-6}
contains this list and references to the RFCs where their meaning is defined.

Used as the return value of the callback function in
@ref{8ca,,SSLContext.set_servername_callback()}.


3.4 新版功能.

@end deffn

@geindex AlertDescription (ssl 中的类)
@anchor{library/ssl ssl AlertDescription}@anchor{2682}
@deffn {类} ssl.AlertDescription

@ref{588,,enum.IntEnum} collection of ALERT_DESCRIPTION_* constants.


3.6 新版功能.

@end deffn

@geindex Purpose.SERVER_AUTH() (在 ssl 模块中)
@anchor{library/ssl ssl Purpose SERVER_AUTH}@anchor{8c6}
@deffn {数据} Purpose.SERVER_AUTH

Option for @ref{8bb,,create_default_context()} and
@ref{8c5,,SSLContext.load_default_certs()}.  This value indicates that the
context may be used to authenticate Web servers (therefore, it will
be used to create client-side sockets).


3.4 新版功能.

@end deffn

@geindex Purpose.CLIENT_AUTH() (在 ssl 模块中)
@anchor{library/ssl ssl Purpose CLIENT_AUTH}@anchor{8c7}
@deffn {数据} Purpose.CLIENT_AUTH

Option for @ref{8bb,,create_default_context()} and
@ref{8c5,,SSLContext.load_default_certs()}.  This value indicates that the
context may be used to authenticate Web clients (therefore, it will
be used to create server-side sockets).


3.4 新版功能.

@end deffn

@geindex SSLErrorNumber (ssl 中的类)
@anchor{library/ssl ssl SSLErrorNumber}@anchor{2683}
@deffn {类} ssl.SSLErrorNumber

@ref{588,,enum.IntEnum} collection of SSL_ERROR_* constants.


3.6 新版功能.

@end deffn

@geindex TLSVersion (ssl 中的类)
@anchor{library/ssl ssl TLSVersion}@anchor{2684}
@deffn {类} ssl.TLSVersion

@ref{588,,enum.IntEnum} collection of SSL and TLS versions for
@ref{3e0,,SSLContext.maximum_version} and @ref{3df,,SSLContext.minimum_version}.


3.7 新版功能.

@end deffn

@geindex MINIMUM_SUPPORTED (ssl.TLSVersion 属性)
@anchor{library/ssl ssl TLSVersion MINIMUM_SUPPORTED}@anchor{2685}
@deffn {属性} TLSVersion.MINIMUM_SUPPORTED
@end deffn

@geindex MAXIMUM_SUPPORTED (ssl.TLSVersion 属性)
@anchor{library/ssl ssl TLSVersion MAXIMUM_SUPPORTED}@anchor{2686}
@deffn {属性} TLSVersion.MAXIMUM_SUPPORTED

The minimum or maximum supported SSL or TLS version. These are magic
constants. Their values don't reflect the lowest and highest available
TLS/SSL versions.
@end deffn

@geindex SSLv3 (ssl.TLSVersion 属性)
@anchor{library/ssl ssl TLSVersion SSLv3}@anchor{2687}
@deffn {属性} TLSVersion.SSLv3
@end deffn

@geindex TLSv1 (ssl.TLSVersion 属性)
@anchor{library/ssl ssl TLSVersion TLSv1}@anchor{2688}
@deffn {属性} TLSVersion.TLSv1
@end deffn

@geindex TLSv1_1 (ssl.TLSVersion 属性)
@anchor{library/ssl ssl TLSVersion TLSv1_1}@anchor{2689}
@deffn {属性} TLSVersion.TLSv1_1
@end deffn

@geindex TLSv1_2 (ssl.TLSVersion 属性)
@anchor{library/ssl ssl TLSVersion TLSv1_2}@anchor{268a}
@deffn {属性} TLSVersion.TLSv1_2
@end deffn

@geindex TLSv1_3 (ssl.TLSVersion 属性)
@anchor{library/ssl ssl TLSVersion TLSv1_3}@anchor{268b}
@deffn {属性} TLSVersion.TLSv1_3

SSL 3.0 to TLS 1.3.
@end deffn

@node SSL Sockets,SSL Contexts,Functions Constants and Exceptions,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl ssl-sockets}@anchor{268c}
@subsubsection SSL Sockets


@geindex SSLSocket (ssl 中的类)
@anchor{library/ssl ssl SSLSocket}@anchor{3da}
@deffn {类} ssl.SSLSocket (socket.socket)

SSL sockets provide the following methods of @ref{2624,,套接字对象}:


@itemize -

@item 
@ref{66f,,accept()}

@item 
@ref{2633,,bind()}

@item 
@ref{5fb,,close()}

@item 
@ref{670,,connect()}

@item 
@ref{b96,,detach()}

@item 
@ref{2637,,fileno()}

@item 
@ref{258f,,getpeername()}, @ref{2590,,getsockname()}

@item 
@ref{57d,,getsockopt()}, @ref{57e,,setsockopt()}

@item 
@ref{2638,,gettimeout()}, @ref{2607,,settimeout()},
@ref{1ea7,,setblocking()}

@item 
@ref{745,,listen()}

@item 
@ref{b12,,makefile()}

@item 
@ref{671,,recv()}, @ref{cab,,recv_into()}
(but passing a non-zero @code{flags} argument is not allowed)

@item 
@ref{674,,send()}, @ref{675,,sendall()} (with
the same limitation)

@item 
@ref{744,,sendfile()} (but @ref{352,,os.sendfile} will be used
for plain-text sockets only, else @ref{674,,send()} will be used)

@item 
@ref{2634,,shutdown()}
@end itemize

However, since the SSL (and TLS) protocol has its own framing atop
of TCP, the SSL sockets abstraction can, in certain respects, diverge from
the specification of normal, OS-level sockets.  See especially the
@ref{264f,,notes on non-blocking sockets}.

Instances of @ref{3da,,SSLSocket} must be created using the
@ref{3dd,,SSLContext.wrap_socket()} method.


在 3.5 版更改: The @code{sendfile()} method was added.



在 3.5 版更改: The @code{shutdown()} does not reset the socket timeout each time bytes
are received or sent. The socket timeout is now to maximum total duration
of the shutdown.



3.6 版后已移除: It is deprecated to create a @ref{3da,,SSLSocket} instance directly, use
@ref{3dd,,SSLContext.wrap_socket()} to wrap a socket.



在 3.7 版更改: @ref{3da,,SSLSocket} instances must to created with
@ref{3dd,,wrap_socket()}. In earlier versions, it was possible
to create instances directly. This was never documented or officially
supported.

@end deffn

SSL sockets also have the following additional methods and attributes:

@geindex read() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket read}@anchor{755}
@deffn {方法} SSLSocket.read (len=1024, buffer=None)

Read up to @emph{len} bytes of data from the SSL socket and return the result as
a @code{bytes} instance. If @emph{buffer} is specified, then read into the buffer
instead, and return the number of bytes read.

Raise @ref{750,,SSLWantReadError} or @ref{751,,SSLWantWriteError} if the socket is
@ref{264f,,non-blocking} and the read would block.

As at any time a re-negotiation is possible, a call to @ref{755,,read()} can also
cause write operations.


在 3.5 版更改: The socket timeout is no more reset each time bytes are received or sent.
The socket timeout is now to maximum total duration to read up to @emph{len}
bytes.



3.6 版后已移除: Use @code{recv()} instead of @ref{755,,read()}.

@end deffn

@geindex write() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket write}@anchor{756}
@deffn {方法} SSLSocket.write (buf)

Write @emph{buf} to the SSL socket and return the number of bytes written. The
@emph{buf} argument must be an object supporting the buffer interface.

Raise @ref{750,,SSLWantReadError} or @ref{751,,SSLWantWriteError} if the socket is
@ref{264f,,non-blocking} and the write would block.

As at any time a re-negotiation is possible, a call to @ref{756,,write()} can
also cause read operations.


在 3.5 版更改: The socket timeout is no more reset each time bytes are received or sent.
The socket timeout is now to maximum total duration to write @emph{buf}.



3.6 版后已移除: Use @code{send()} instead of @ref{756,,write()}.

@end deffn

@cartouche
@quotation 注解 
The @ref{755,,read()} and @ref{756,,write()} methods are the
low-level methods that read and write unencrypted, application-level data
and decrypt/encrypt it to encrypted, wire-level data. These methods
require an active SSL connection, i.e. the handshake was completed and
@ref{268d,,SSLSocket.unwrap()} was not called.

Normally you should use the socket API methods like
@ref{671,,recv()} and @ref{674,,send()} instead of these
methods.
@end quotation
@end cartouche

@geindex do_handshake() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket do_handshake}@anchor{754}
@deffn {方法} SSLSocket.do_handshake ()

Perform the SSL setup handshake.


在 3.4 版更改: The handshake method also performs @ref{3d4,,match_hostname()} when the
@ref{2663,,check_hostname} attribute of the socket's
@ref{268e,,context} is true.



在 3.5 版更改: The socket timeout is no more reset each time bytes are received or sent.
The socket timeout is now to maximum total duration of the handshake.



在 3.7 版更改: Hostname or IP address is matched by OpenSSL during handshake. The
function @ref{3d4,,match_hostname()} is no longer used. In case OpenSSL
refuses a hostname or IP address, the handshake is aborted early and
a TLS alert message is send to the peer.

@end deffn

@geindex getpeercert() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket getpeercert}@anchor{8cb}
@deffn {方法} SSLSocket.getpeercert (binary_form=False)

If there is no certificate for the peer on the other end of the connection,
return @code{None}.  If the SSL handshake hasn't been done yet, raise
@ref{1fb,,ValueError}.

If the @code{binary_form} parameter is @ref{380,,False}, and a certificate was
received from the peer, this method returns a @ref{1b8,,dict} instance.  If the
certificate was not validated, the dict is empty.  If the certificate was
validated, it returns a dict with several keys, amongst them @code{subject}
(the principal for which the certificate was issued) and @code{issuer}
(the principal issuing the certificate).  If a certificate contains an
instance of the @emph{Subject Alternative Name} extension (see 
@geindex RFC; RFC 3280
RFC 3280@footnote{https://tools.ietf.org/html/rfc3280.html}),
there will also be a @code{subjectAltName} key in the dictionary.

The @code{subject} and @code{issuer} fields are tuples containing the sequence
of relative distinguished names (RDNs) given in the certificate's data
structure for the respective fields, and each RDN is a sequence of
name-value pairs.  Here is a real-world example:

@example
@{'issuer': ((('countryName', 'IL'),),
            (('organizationName', 'StartCom Ltd.'),),
            (('organizationalUnitName',
              'Secure Digital Certificate Signing'),),
            (('commonName',
              'StartCom Class 2 Primary Intermediate Server CA'),)),
 'notAfter': 'Nov 22 08:15:19 2013 GMT',
 'notBefore': 'Nov 21 03:09:52 2011 GMT',
 'serialNumber': '95F0',
 'subject': ((('description', '571208-SLe257oHY9fVQ07Z'),),
             (('countryName', 'US'),),
             (('stateOrProvinceName', 'California'),),
             (('localityName', 'San Francisco'),),
             (('organizationName', 'Electronic Frontier Foundation, Inc.'),),
             (('commonName', '*.eff.org'),),
             (('emailAddress', 'hostmaster@@eff.org'),)),
 'subjectAltName': (('DNS', '*.eff.org'), ('DNS', 'eff.org')),
 'version': 3@}
@end example

@cartouche
@quotation 注解 
To validate a certificate for a particular service, you can use the
@ref{3d4,,match_hostname()} function.
@end quotation
@end cartouche

If the @code{binary_form} parameter is @ref{494,,True}, and a certificate was
provided, this method returns the DER-encoded form of the entire certificate
as a sequence of bytes, or @ref{157,,None} if the peer did not provide a
certificate.  Whether the peer provides a certificate depends on the SSL
socket's role:


@itemize *

@item 
for a client SSL socket, the server will always provide a certificate,
regardless of whether validation was required;

@item 
for a server SSL socket, the client will only provide a certificate
when requested by the server; therefore @ref{8cb,,getpeercert()} will return
@ref{157,,None} if you used @ref{2660,,CERT_NONE} (rather than
@ref{2662,,CERT_OPTIONAL} or @ref{264b,,CERT_REQUIRED}).
@end itemize


在 3.2 版更改: The returned dictionary includes additional items such as @code{issuer}
and @code{notBefore}.



在 3.4 版更改: @ref{1fb,,ValueError} is raised when the handshake isn't done.
The returned dictionary includes additional X509v3 extension items
  such as @code{crlDistributionPoints}, @code{caIssuers} and @code{OCSP} URIs.



在 3.8.1 版更改: IPv6 address strings no longer have a trailing new line.

@end deffn

@geindex cipher() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket cipher}@anchor{2591}
@deffn {方法} SSLSocket.cipher ()

Returns a three-value tuple containing the name of the cipher being used, the
version of the SSL protocol that defines its use, and the number of secret
bits being used.  If no connection has been established, returns @code{None}.
@end deffn

@geindex shared_ciphers() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket shared_ciphers}@anchor{753}
@deffn {方法} SSLSocket.shared_ciphers ()

Return the list of ciphers shared by the client during the handshake.  Each
entry of the returned list is a three-value tuple containing the name of the
cipher, the version of the SSL protocol that defines its use, and the number
of secret bits the cipher uses.  @ref{753,,shared_ciphers()} returns
@code{None} if no connection has been established or the socket is a client
socket.


3.5 新版功能.

@end deffn

@geindex compression() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket compression}@anchor{a90}
@deffn {方法} SSLSocket.compression ()

Return the compression algorithm being used as a string, or @code{None}
if the connection isn't compressed.

If the higher-level protocol supports its own compression mechanism,
you can use @ref{a91,,OP_NO_COMPRESSION} to disable SSL-level compression.


3.3 新版功能.

@end deffn

@geindex get_channel_binding() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket get_channel_binding}@anchor{a8f}
@deffn {方法} SSLSocket.get_channel_binding (cb_type="tls-unique")

Get channel binding data for current connection, as a bytes object.  Returns
@code{None} if not connected or the handshake has not been completed.

The @emph{cb_type} parameter allow selection of the desired channel binding
type. Valid channel binding types are listed in the
@ref{267f,,CHANNEL_BINDING_TYPES} list.  Currently only the 'tls-unique' channel
binding, defined by 
@geindex RFC; RFC 5929
RFC 5929@footnote{https://tools.ietf.org/html/rfc5929.html}, is supported.  @ref{1fb,,ValueError} will be
raised if an unsupported channel binding type is requested.


3.3 新版功能.

@end deffn

@geindex selected_alpn_protocol() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket selected_alpn_protocol}@anchor{74c}
@deffn {方法} SSLSocket.selected_alpn_protocol ()

Return the protocol that was selected during the TLS handshake.  If
@ref{74b,,SSLContext.set_alpn_protocols()} was not called, if the other party does
not support ALPN, if this socket does not support any of the client's
proposed protocols, or if the handshake has not happened yet, @code{None} is
returned.


3.5 新版功能.

@end deffn

@geindex selected_npn_protocol() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket selected_npn_protocol}@anchor{268f}
@deffn {方法} SSLSocket.selected_npn_protocol ()

Return the higher-level protocol that was selected during the TLS/SSL
handshake. If @ref{a92,,SSLContext.set_npn_protocols()} was not called, or
if the other party does not support NPN, or if the handshake has not yet
happened, this will return @code{None}.


3.3 新版功能.

@end deffn

@geindex unwrap() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket unwrap}@anchor{268d}
@deffn {方法} SSLSocket.unwrap ()

Performs the SSL shutdown handshake, which removes the TLS layer from the
underlying socket, and returns the underlying socket object.  This can be
used to go from encrypted operation over a connection to unencrypted.  The
returned socket should always be used for further communication with the
other side of the connection, rather than the original socket.
@end deffn

@geindex verify_client_post_handshake() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket verify_client_post_handshake}@anchor{225}
@deffn {方法} SSLSocket.verify_client_post_handshake ()

Requests post-handshake authentication (PHA) from a TLS 1.3 client. PHA
can only be initiated for a TLS 1.3 connection from a server-side socket,
after the initial TLS handshake and with PHA enabled on both sides, see
@ref{224,,SSLContext.post_handshake_auth}.

The method does not perform a cert exchange immediately. The server-side
sends a CertificateRequest during the next write event and expects the
client to respond with a certificate on the next read event.

If any precondition isn't met (e.g. not TLS 1.3, PHA not enabled), an
@ref{c08,,SSLError} is raised.

@cartouche
@quotation 注解 
Only available with OpenSSL 1.1.1 and TLS 1.3 enabled. Without TLS 1.3
support, the method raises @ref{609,,NotImplementedError}.
@end quotation
@end cartouche


3.8 新版功能.

@end deffn

@geindex version() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket version}@anchor{74f}
@deffn {方法} SSLSocket.version ()

Return the actual SSL protocol version negotiated by the connection
as a string, or @code{None} is no secure connection is established.
As of this writing, possible return values include @code{"SSLv2"},
@code{"SSLv3"}, @code{"TLSv1"}, @code{"TLSv1.1"} and @code{"TLSv1.2"}.
Recent OpenSSL versions may define more return values.


3.5 新版功能.

@end deffn

@geindex pending() (ssl.SSLSocket 方法)
@anchor{library/ssl ssl SSLSocket pending}@anchor{2690}
@deffn {方法} SSLSocket.pending ()

Returns the number of already decrypted bytes available for read, pending on
the connection.
@end deffn

@geindex context (ssl.SSLSocket 属性)
@anchor{library/ssl ssl SSLSocket context}@anchor{268e}
@deffn {属性} SSLSocket.context

The @ref{3dc,,SSLContext} object this SSL socket is tied to.  If the SSL
socket was created using the deprecated @ref{469,,wrap_socket()} function
(rather than @ref{3dd,,SSLContext.wrap_socket()}), this is a custom context
object created for this SSL socket.


3.2 新版功能.

@end deffn

@geindex server_side (ssl.SSLSocket 属性)
@anchor{library/ssl ssl SSLSocket server_side}@anchor{2691}
@deffn {属性} SSLSocket.server_side

A boolean which is @code{True} for server-side sockets and @code{False} for
client-side sockets.


3.2 新版功能.

@end deffn

@geindex server_hostname (ssl.SSLSocket 属性)
@anchor{library/ssl ssl SSLSocket server_hostname}@anchor{3d8}
@deffn {属性} SSLSocket.server_hostname

Hostname of the server: @ref{329,,str} type, or @code{None} for server-side
socket or if the hostname was not specified in the constructor.


3.2 新版功能.



在 3.7 版更改: The attribute is now always ASCII text. When @code{server_hostname} is
an internationalized domain name (IDN), this attribute now stores the
A-label form (@code{"xn--pythn-mua.org"}), rather than the U-label form
(@code{"pythön.org"}).

@end deffn

@geindex session (ssl.SSLSocket 属性)
@anchor{library/ssl ssl SSLSocket session}@anchor{2692}
@deffn {属性} SSLSocket.session

The @ref{586,,SSLSession} for this SSL connection. The session is available
for client and server side sockets after the TLS handshake has been
performed. For client sockets the session can be set before
@ref{754,,do_handshake()} has been called to reuse a session.


3.6 新版功能.

@end deffn

@geindex session_reused (ssl.SSLSocket 属性)
@anchor{library/ssl ssl SSLSocket session_reused}@anchor{2693}
@deffn {属性} SSLSocket.session_reused


3.6 新版功能.

@end deffn

@node SSL Contexts,Certificates,SSL Sockets,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl ssl-contexts}@anchor{2694}
@subsubsection SSL Contexts



3.2 新版功能.


An SSL context holds various data longer-lived than single SSL connections,
such as SSL configuration options, certificate(s) and private key(s).
It also manages a cache of SSL sessions for server-side sockets, in order
to speed up repeated connections from the same clients.

@geindex SSLContext (ssl 中的类)
@anchor{library/ssl ssl SSLContext}@anchor{3dc}
@deffn {类} ssl.SSLContext (protocol=PROTOCOL_TLS)

Create a new SSL context.  You may pass @emph{protocol} which must be one
of the @code{PROTOCOL_*} constants defined in this module.  The parameter
specifies which version of the SSL protocol to use.  Typically, the
server chooses a particular protocol version, and the client must adapt
to the server's choice.  Most of the versions are not interoperable
with the other versions.  If not specified, the default is
@ref{2648,,PROTOCOL_TLS}; it provides the most compatibility with other
versions.

Here's a table showing which versions in a client (down the side) can connect
to which versions in a server (along the top):

@quotation


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxx} {xxxxxxxxxxxxx} 
@item

@emph{客户端} / @strong{服务器}

@tab

@strong{SSLv2}

@tab

@strong{SSLv3}

@tab

@strong{TLS} @footnote{@w{(3)} 
TLS 1.3 protocol will be available with @ref{2648,,PROTOCOL_TLS} in
OpenSSL >= 1.1.1. There is no dedicated PROTOCOL constant for just
TLS 1.3.
}

@tab

@strong{TLSv1}

@tab

@strong{TLSv1.1}

@tab

@strong{TLSv1.2}

@item

@emph{SSLv2}

@tab

是

@tab

否

@tab

否 @footnote{@w{(1)} 
@ref{3dc,,SSLContext} disables SSLv2 with @ref{b99,,OP_NO_SSLv2} by default.
}

@tab

否

@tab

否

@tab

否

@item

@emph{SSLv3}

@tab

否

@tab

是

@tab

否 @footnote{@w{(2)} 
@ref{3dc,,SSLContext} disables SSLv3 with @ref{2649,,OP_NO_SSLv3} by default.
}

@tab

否

@tab

否

@tab

否

@item

@emph{TLS} (@emph{SSLv23}) @footnote{@w{(3)} 
TLS 1.3 protocol will be available with @ref{2648,,PROTOCOL_TLS} in
OpenSSL >= 1.1.1. There is no dedicated PROTOCOL constant for just
TLS 1.3.
}

@tab

否 @footnote{@w{(1)} 
@ref{3dc,,SSLContext} disables SSLv2 with @ref{b99,,OP_NO_SSLv2} by default.
}

@tab

否 @footnote{@w{(2)} 
@ref{3dc,,SSLContext} disables SSLv3 with @ref{2649,,OP_NO_SSLv3} by default.
}

@tab

是

@tab

是

@tab

是

@tab

是

@item

@emph{TLSv1}

@tab

否

@tab

否

@tab

是

@tab

是

@tab

否

@tab

否

@item

@emph{TLSv1.1}

@tab

否

@tab

否

@tab

是

@tab

否

@tab

是

@tab

否

@item

@emph{TLSv1.2}

@tab

否

@tab

否

@tab

是

@tab

否

@tab

否

@tab

是

@end multitable

@end quotation

@subsubheading 备注



@subsubheading 参见


@ref{8bb,,create_default_context()} lets the @ref{f3,,ssl} module choose
security settings for a given purpose.



在 3.6 版更改: The context is created with secure default values. The options
@ref{a91,,OP_NO_COMPRESSION}, @ref{a96,,OP_CIPHER_SERVER_PREFERENCE},
@ref{2671,,OP_SINGLE_DH_USE}, @ref{2672,,OP_SINGLE_ECDH_USE},
@ref{b99,,OP_NO_SSLv2} (except for @ref{2669,,PROTOCOL_SSLv2}),
and @ref{2649,,OP_NO_SSLv3} (except for @ref{265a,,PROTOCOL_SSLv3}) are
set by default. The initial cipher suite list contains only @code{HIGH}
ciphers, no @code{NULL} ciphers and no @code{MD5} ciphers (except for
@ref{2669,,PROTOCOL_SSLv2}).

@end deffn

@ref{3dc,,SSLContext} objects have the following methods and attributes:

@geindex cert_store_stats() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext cert_store_stats}@anchor{8be}
@deffn {方法} SSLContext.cert_store_stats ()

Get statistics about quantities of loaded X.509 certificates, count of
X.509 certificates flagged as CA certificates and certificate revocation
lists as dictionary.

Example for a context with one CA cert and one other cert:

@example
>>> context.cert_store_stats()
@{'crl': 0, 'x509_ca': 1, 'x509': 2@}
@end example


3.4 新版功能.

@end deffn

@geindex load_cert_chain() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext load_cert_chain}@anchor{a8c}
@deffn {方法} SSLContext.load_cert_chain (certfile, keyfile=None, password=None)

Load a private key and the corresponding certificate.  The @emph{certfile}
string must be the path to a single file in PEM format containing the
certificate as well as any number of CA certificates needed to establish
the certificate's authenticity.  The @emph{keyfile} string, if present, must
point to a file containing the private key in.  Otherwise the private
key will be taken from @emph{certfile} as well.  See the discussion of
@ref{2695,,Certificates} for more information on how the certificate
is stored in the @emph{certfile}.

The @emph{password} argument may be a function to call to get the password for
decrypting the private key.  It will only be called if the private key is
encrypted and a password is necessary.  It will be called with no arguments,
and it should return a string, bytes, or bytearray.  If the return value is
a string it will be encoded as UTF-8 before using it to decrypt the key.
Alternatively a string, bytes, or bytearray value may be supplied directly
as the @emph{password} argument.  It will be ignored if the private key is not
encrypted and no password is needed.

If the @emph{password} argument is not specified and a password is required,
OpenSSL's built-in password prompting mechanism will be used to
interactively prompt the user for a password.

An @ref{c08,,SSLError} is raised if the private key doesn't
match with the certificate.


在 3.3 版更改: New optional argument @emph{password}.

@end deffn

@geindex load_default_certs() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext load_default_certs}@anchor{8c5}
@deffn {方法} SSLContext.load_default_certs (purpose=Purpose.SERVER_AUTH)

Load a set of default "certification authority" (CA) certificates from
default locations. On Windows it loads CA certs from the @code{CA} and
@code{ROOT} system stores. On other systems it calls
@ref{8bd,,SSLContext.set_default_verify_paths()}. In the future the method may
load CA certificates from other locations, too.

The @emph{purpose} flag specifies what kind of CA certificates are loaded. The
default settings @ref{8c6,,Purpose.SERVER_AUTH} loads certificates, that are
flagged and trusted for TLS web server authentication (client side
sockets). @ref{8c7,,Purpose.CLIENT_AUTH} loads CA certificates for client
certificate verification on the server side.


3.4 新版功能.

@end deffn

@geindex load_verify_locations() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext load_verify_locations}@anchor{7e5}
@deffn {方法} SSLContext.load_verify_locations (cafile=None, capath=None, cadata=None)

Load a set of "certification authority" (CA) certificates used to validate
other peers' certificates when @ref{264a,,verify_mode} is other than
@ref{2660,,CERT_NONE}.  At least one of @emph{cafile} or @emph{capath} must be specified.

This method can also load certification revocation lists (CRLs) in PEM or
DER format. In order to make use of CRLs, @ref{8c0,,SSLContext.verify_flags}
must be configured properly.

The @emph{cafile} string, if present, is the path to a file of concatenated
CA certificates in PEM format. See the discussion of
@ref{2695,,Certificates} for more information about how to arrange the
certificates in this file.

The @emph{capath} string, if present, is
the path to a directory containing several CA certificates in PEM format,
following an OpenSSL specific layout@footnote{https://www.openssl.org/docs/manmaster/man3/SSL_CTX_load_verify_locations.html}.

The @emph{cadata} object, if present, is either an ASCII string of one or more
PEM-encoded certificates or a @ref{5e3,,bytes-like object} of DER-encoded
certificates. Like with @emph{capath} extra lines around PEM-encoded
certificates are ignored but at least one certificate must be present.


在 3.4 版更改: New optional argument @emph{cadata}

@end deffn

@geindex get_ca_certs() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext get_ca_certs}@anchor{8bf}
@deffn {方法} SSLContext.get_ca_certs (binary_form=False)

Get a list of loaded "certification authority" (CA) certificates. If the
@code{binary_form} parameter is @ref{380,,False} each list
entry is a dict like the output of @ref{8cb,,SSLSocket.getpeercert()}. Otherwise
the method returns a list of DER-encoded certificates. The returned list
does not contain certificates from @emph{capath} unless a certificate was
requested and loaded by a SSL connection.

@cartouche
@quotation 注解 
Certificates in a capath directory aren't loaded unless they have
been used at least once.
@end quotation
@end cartouche


3.4 新版功能.

@end deffn

@geindex get_ciphers() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext get_ciphers}@anchor{587}
@deffn {方法} SSLContext.get_ciphers ()

Get a list of enabled ciphers. The list is in order of cipher priority.
See @ref{265e,,SSLContext.set_ciphers()}.

示例:

@example
>>> ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
>>> ctx.set_ciphers('ECDHE+AESGCM:!ECDSA')
>>> ctx.get_ciphers()  # OpenSSL 1.0.x
[@{'alg_bits': 256,
  'description': 'ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(256) Mac=AEAD',
  'id': 50380848,
  'name': 'ECDHE-RSA-AES256-GCM-SHA384',
  'protocol': 'TLSv1/SSLv3',
  'strength_bits': 256@},
 @{'alg_bits': 128,
  'description': 'ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(128) Mac=AEAD',
  'id': 50380847,
  'name': 'ECDHE-RSA-AES128-GCM-SHA256',
  'protocol': 'TLSv1/SSLv3',
  'strength_bits': 128@}]
@end example

On OpenSSL 1.1 and newer the cipher dict contains additional fields:

@example
>>> ctx.get_ciphers()  # OpenSSL 1.1+
[@{'aead': True,
  'alg_bits': 256,
  'auth': 'auth-rsa',
  'description': 'ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(256) Mac=AEAD',
  'digest': None,
  'id': 50380848,
  'kea': 'kx-ecdhe',
  'name': 'ECDHE-RSA-AES256-GCM-SHA384',
  'protocol': 'TLSv1.2',
  'strength_bits': 256,
  'symmetric': 'aes-256-gcm'@},
 @{'aead': True,
  'alg_bits': 128,
  'auth': 'auth-rsa',
  'description': 'ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  '
                 'Enc=AESGCM(128) Mac=AEAD',
  'digest': None,
  'id': 50380847,
  'kea': 'kx-ecdhe',
  'name': 'ECDHE-RSA-AES128-GCM-SHA256',
  'protocol': 'TLSv1.2',
  'strength_bits': 128,
  'symmetric': 'aes-128-gcm'@}]
@end example

@ref{12f5,,Availability}: OpenSSL 1.0.2+.


3.6 新版功能.

@end deffn

@geindex set_default_verify_paths() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext set_default_verify_paths}@anchor{8bd}
@deffn {方法} SSLContext.set_default_verify_paths ()

Load a set of default "certification authority" (CA) certificates from
a filesystem path defined when building the OpenSSL library.  Unfortunately,
there's no easy way to know whether this method succeeds: no error is
returned if no certificates are to be found.  When the OpenSSL library is
provided as part of the operating system, though, it is likely to be
configured properly.
@end deffn

@geindex set_ciphers() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext set_ciphers}@anchor{265e}
@deffn {方法} SSLContext.set_ciphers (ciphers)

Set the available ciphers for sockets created with this context.
It should be a string in the OpenSSL cipher list format@footnote{https://www.openssl.org/docs/manmaster/man1/ciphers.html}.
If no cipher can be selected (because compile-time options or other
configuration forbids use of all the specified ciphers), an
@ref{c08,,SSLError} will be raised.

@cartouche
@quotation 注解 
when connected, the @ref{2591,,SSLSocket.cipher()} method of SSL sockets will
give the currently selected cipher.

OpenSSL 1.1.1 has TLS 1.3 cipher suites enabled by default. The suites
cannot be disabled with @ref{265e,,set_ciphers()}.
@end quotation
@end cartouche
@end deffn

@geindex set_alpn_protocols() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext set_alpn_protocols}@anchor{74b}
@deffn {方法} SSLContext.set_alpn_protocols (protocols)

Specify which protocols the socket should advertise during the SSL/TLS
handshake. It should be a list of ASCII strings, like @code{['http/1.1',
'spdy/2']}, ordered by preference. The selection of a protocol will happen
during the handshake, and will play out according to 
@geindex RFC; RFC 7301
RFC 7301@footnote{https://tools.ietf.org/html/rfc7301.html}. After a
successful handshake, the @ref{74c,,SSLSocket.selected_alpn_protocol()} method will
return the agreed-upon protocol.

This method will raise @ref{609,,NotImplementedError} if @ref{74d,,HAS_ALPN} is
@code{False}.

OpenSSL 1.1.0 to 1.1.0e will abort the handshake and raise @ref{c08,,SSLError}
when both sides support ALPN but cannot agree on a protocol. 1.1.0f+
behaves like 1.0.2, @ref{74c,,SSLSocket.selected_alpn_protocol()} returns None.


3.5 新版功能.

@end deffn

@geindex set_npn_protocols() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext set_npn_protocols}@anchor{a92}
@deffn {方法} SSLContext.set_npn_protocols (protocols)

Specify which protocols the socket should advertise during the SSL/TLS
handshake. It should be a list of strings, like @code{['http/1.1', 'spdy/2']},
ordered by preference. The selection of a protocol will happen during the
handshake, and will play out according to the Application Layer Protocol Negotiation@footnote{https://en.wikipedia.org/wiki/Application-Layer_Protocol_Negotiation}. After a
successful handshake, the @ref{268f,,SSLSocket.selected_npn_protocol()} method will
return the agreed-upon protocol.

This method will raise @ref{609,,NotImplementedError} if @ref{2679,,HAS_NPN} is
@code{False}.


3.3 新版功能.

@end deffn

@geindex sni_callback (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext sni_callback}@anchor{2696}
@deffn {属性} SSLContext.sni_callback

Register a callback function that will be called after the TLS Client Hello
handshake message has been received by the SSL/TLS server when the TLS client
specifies a server name indication. The server name indication mechanism
is specified in 
@geindex RFC; RFC 6066
RFC 6066@footnote{https://tools.ietf.org/html/rfc6066.html} section 3 - Server Name Indication.

Only one callback can be set per @code{SSLContext}.  If @emph{sni_callback}
is set to @code{None} then the callback is disabled. Calling this function a
subsequent time will disable the previously registered callback.

The callback function will be called with three
arguments; the first being the @ref{3da,,ssl.SSLSocket}, the second is a string
that represents the server name that the client is intending to communicate
(or @ref{157,,None} if the TLS Client Hello does not contain a server name)
and the third argument is the original @ref{3dc,,SSLContext}. The server name
argument is text. For internationalized domain name, the server
name is an IDN A-label (@code{"xn--pythn-mua.org"}).

A typical use of this callback is to change the @ref{3da,,ssl.SSLSocket}'s
@ref{268e,,SSLSocket.context} attribute to a new object of type
@ref{3dc,,SSLContext} representing a certificate chain that matches the server
name.

Due to the early negotiation phase of the TLS connection, only limited
methods and attributes are usable like
@ref{74c,,SSLSocket.selected_alpn_protocol()} and @ref{268e,,SSLSocket.context}.
@ref{8cb,,SSLSocket.getpeercert()}, @ref{8cb,,SSLSocket.getpeercert()},
@ref{2591,,SSLSocket.cipher()} and @code{SSLSocket.compress()} methods require that
the TLS connection has progressed beyond the TLS Client Hello and therefore
will not contain return meaningful values nor can they be called safely.

The @emph{sni_callback} function must return @code{None} to allow the
TLS negotiation to continue.  If a TLS failure is required, a constant
@ref{2681,,ALERT_DESCRIPTION_*} can be
returned.  Other return values will result in a TLS fatal error with
@ref{2681,,ALERT_DESCRIPTION_INTERNAL_ERROR}.

If an exception is raised from the @emph{sni_callback} function the TLS
connection will terminate with a fatal TLS alert message
@ref{2680,,ALERT_DESCRIPTION_HANDSHAKE_FAILURE}.

This method will raise @ref{609,,NotImplementedError} if the OpenSSL library
had OPENSSL_NO_TLSEXT defined when it was built.


3.7 新版功能.

@end deffn

@geindex set_servername_callback (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext set_servername_callback}@anchor{8ca}
@deffn {属性} SSLContext.set_servername_callback (server_name_callback)

This is a legacy API retained for backwards compatibility. When possible,
you should use @ref{2696,,sni_callback} instead. The given @emph{server_name_callback}
is similar to @emph{sni_callback}, except that when the server hostname is an
IDN-encoded internationalized domain name, the @emph{server_name_callback}
receives a decoded U-label (@code{"pythön.org"}).

If there is an decoding error on the server name, the TLS connection will
terminate with an @ref{2681,,ALERT_DESCRIPTION_INTERNAL_ERROR} fatal TLS
alert message to the client.


3.4 新版功能.

@end deffn

@geindex load_dh_params() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext load_dh_params}@anchor{a8d}
@deffn {方法} SSLContext.load_dh_params (dhfile)

Load the key generation parameters for Diffie-Hellman (DH) key exchange.
Using DH key exchange improves forward secrecy at the expense of
computational resources (both on the server and on the client).
The @emph{dhfile} parameter should be the path to a file containing DH
parameters in PEM format.

This setting doesn't apply to client sockets.  You can also use the
@ref{2671,,OP_SINGLE_DH_USE} option to further improve security.


3.3 新版功能.

@end deffn

@geindex set_ecdh_curve() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext set_ecdh_curve}@anchor{a8e}
@deffn {方法} SSLContext.set_ecdh_curve (curve_name)

Set the curve name for Elliptic Curve-based Diffie-Hellman (ECDH) key
exchange.  ECDH is significantly faster than regular DH while arguably
as secure.  The @emph{curve_name} parameter should be a string describing
a well-known elliptic curve, for example @code{prime256v1} for a widely
supported curve.

This setting doesn't apply to client sockets.  You can also use the
@ref{2672,,OP_SINGLE_ECDH_USE} option to further improve security.

This method is not available if @ref{2677,,HAS_ECDH} is @code{False}.


3.3 新版功能.



@subsubheading 参见



@table @asis

@item SSL/TLS & Perfect Forward Secrecy@footnote{https://vincent.bernat.im/en/blog/2011-ssl-perfect-forward-secrecy}

Vincent Bernat.
@end table

@end deffn

@geindex wrap_socket() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext wrap_socket}@anchor{3dd}
@deffn {方法} SSLContext.wrap_socket (sock, server_side=False, do_handshake_on_connect=True, suppress_ragged_eofs=True, server_hostname=None, session=None)

Wrap an existing Python socket @emph{sock} and return an instance of
@ref{2697,,SSLContext.sslsocket_class} (default @ref{3da,,SSLSocket}). The
returned SSL socket is tied to the context, its settings and certificates.
@emph{sock} must be a @ref{c83,,SOCK_STREAM} socket; other
socket types are unsupported.

The parameter @code{server_side} is a boolean which identifies whether
server-side or client-side behavior is desired from this socket.

For client-side sockets, the context construction is lazy; if the
underlying socket isn't connected yet, the context construction will be
performed after @code{connect()} is called on the socket.  For
server-side sockets, if the socket has no remote peer, it is assumed
to be a listening socket, and the server-side SSL wrapping is
automatically performed on client connections accepted via the
@code{accept()} method. The method may raise @ref{c08,,SSLError}.

On client connections, the optional parameter @emph{server_hostname} specifies
the hostname of the service which we are connecting to.  This allows a
single server to host multiple SSL-based services with distinct certificates,
quite similarly to HTTP virtual hosts. Specifying @emph{server_hostname} will
raise a @ref{1fb,,ValueError} if @emph{server_side} is true.

The parameter @code{do_handshake_on_connect} specifies whether to do the SSL
handshake automatically after doing a @code{socket.connect()}, or whether the
application program will call it explicitly, by invoking the
@ref{754,,SSLSocket.do_handshake()} method.  Calling
@ref{754,,SSLSocket.do_handshake()} explicitly gives the program control over the
blocking behavior of the socket I/O involved in the handshake.

The parameter @code{suppress_ragged_eofs} specifies how the
@code{SSLSocket.recv()} method should signal unexpected EOF from the other end
of the connection.  If specified as @ref{494,,True} (the default), it returns a
normal EOF (an empty bytes object) in response to unexpected EOF errors
raised from the underlying socket; if @ref{380,,False}, it will raise the
exceptions back to the caller.

@emph{session}, see @ref{2692,,session}.


在 3.5 版更改: Always allow a server_hostname to be passed, even if OpenSSL does not
have SNI.



在 3.6 版更改: @emph{session} argument was added.


在 3.7 版更改: The method returns on instance of @ref{2697,,SSLContext.sslsocket_class}
instead of hard-coded @ref{3da,,SSLSocket}.


@end deffn

@geindex sslsocket_class (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext sslsocket_class}@anchor{2697}
@deffn {属性} SSLContext.sslsocket_class

The return type of @ref{3dd,,SSLContext.wrap_socket()}, defaults to
@ref{3da,,SSLSocket}. The attribute can be overridden on instance of class
in order to return a custom subclass of @ref{3da,,SSLSocket}.


3.7 新版功能.

@end deffn

@geindex wrap_bio() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext wrap_bio}@anchor{3de}
@deffn {方法} SSLContext.wrap_bio (incoming, outgoing, server_side=False, server_hostname=None, session=None)

Wrap the BIO objects @emph{incoming} and @emph{outgoing} and return an instance of
@ref{2698,,SSLContext.sslobject_class} (default @ref{3db,,SSLObject}). The SSL
routines will read input data from the incoming BIO and write data to the
outgoing BIO.

The @emph{server_side}, @emph{server_hostname} and @emph{session} parameters have the
same meaning as in @ref{3dd,,SSLContext.wrap_socket()}.


在 3.6 版更改: @emph{session} argument was added.



在 3.7 版更改: The method returns on instance of @ref{2698,,SSLContext.sslobject_class}
instead of hard-coded @ref{3db,,SSLObject}.

@end deffn

@geindex sslobject_class (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext sslobject_class}@anchor{2698}
@deffn {属性} SSLContext.sslobject_class

The return type of @ref{3de,,SSLContext.wrap_bio()}, defaults to
@ref{3db,,SSLObject}. The attribute can be overridden on instance of class
in order to return a custom subclass of @ref{3db,,SSLObject}.


3.7 新版功能.

@end deffn

@geindex session_stats() (ssl.SSLContext 方法)
@anchor{library/ssl ssl SSLContext session_stats}@anchor{2699}
@deffn {方法} SSLContext.session_stats ()

Get statistics about the SSL sessions created or managed by this context.
A dictionary is returned which maps the names of each piece of information@footnote{https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_sess_number.html} to their
numeric values.  For example, here is the total number of hits and misses
in the session cache since the context was created:

@example
>>> stats = context.session_stats()
>>> stats['hits'], stats['misses']
(0, 0)
@end example
@end deffn

@geindex check_hostname (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext check_hostname}@anchor{2663}
@deffn {属性} SSLContext.check_hostname

Whether to match the peer cert's hostname with @ref{3d4,,match_hostname()} in
@ref{754,,SSLSocket.do_handshake()}. The context's
@ref{264a,,verify_mode} must be set to @ref{2662,,CERT_OPTIONAL} or
@ref{264b,,CERT_REQUIRED}, and you must pass @emph{server_hostname} to
@ref{3dd,,wrap_socket()} in order to match the hostname.  Enabling
hostname checking automatically sets @ref{264a,,verify_mode} from
@ref{2660,,CERT_NONE} to @ref{264b,,CERT_REQUIRED}.  It cannot be set back to
@ref{2660,,CERT_NONE} as long as hostname checking is enabled. The
@ref{2661,,PROTOCOL_TLS_CLIENT} protocol enables hostname checking by default.
With other protocols, hostname checking must be enabled explicitly.

示例:

@example
import socket, ssl

context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
context.verify_mode = ssl.CERT_REQUIRED
context.check_hostname = True
context.load_default_certs()

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ssl_sock = context.wrap_socket(s, server_hostname='www.verisign.com')
ssl_sock.connect(('www.verisign.com', 443))
@end example


3.4 新版功能.



在 3.7 版更改: @ref{264a,,verify_mode} is now automatically changed
to @ref{264b,,CERT_REQUIRED}  when hostname checking is enabled and
@ref{264a,,verify_mode} is @ref{2660,,CERT_NONE}. Previously
the same operation would have failed with a @ref{1fb,,ValueError}.


@cartouche
@quotation 注解 
This features requires OpenSSL 0.9.8f or newer.
@end quotation
@end cartouche
@end deffn

@geindex keylog_filename (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext keylog_filename}@anchor{264c}
@deffn {属性} SSLContext.keylog_filename

Write TLS keys to a keylog file, whenever key material is generated or
received. The keylog file is designed for debugging purposes only. The
file format is specified by NSS and used by many traffic analyzers such
as Wireshark. The log file is opened in append-only mode. Writes are
synchronized between threads, but not between processes.


3.8 新版功能.


@cartouche
@quotation 注解 
This features requires OpenSSL 1.1.1 or newer.
@end quotation
@end cartouche
@end deffn

@geindex maximum_version (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext maximum_version}@anchor{3e0}
@deffn {属性} SSLContext.maximum_version

A @ref{2684,,TLSVersion} enum member representing the highest supported
TLS version. The value defaults to @ref{2686,,TLSVersion.MAXIMUM_SUPPORTED}.
The attribute is read-only for protocols other than @ref{2648,,PROTOCOL_TLS},
@ref{2661,,PROTOCOL_TLS_CLIENT}, and @ref{2667,,PROTOCOL_TLS_SERVER}.

The attributes @ref{3e0,,maximum_version},
@ref{3df,,minimum_version} and
@ref{265d,,SSLContext.options} all affect the supported SSL
and TLS versions of the context. The implementation does not prevent
invalid combination. For example a context with
@ref{266e,,OP_NO_TLSv1_2} in @ref{265d,,options} and
@ref{3e0,,maximum_version} set to @ref{268a,,TLSVersion.TLSv1_2}
will not be able to establish a TLS 1.2 connection.

@cartouche
@quotation 注解 
This attribute is not available unless the ssl module is compiled
with OpenSSL 1.1.0g or newer.
@end quotation
@end cartouche


3.7 新版功能.

@end deffn

@geindex minimum_version (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext minimum_version}@anchor{3df}
@deffn {属性} SSLContext.minimum_version

Like @ref{3e0,,SSLContext.maximum_version} except it is the lowest
supported version or @ref{2685,,TLSVersion.MINIMUM_SUPPORTED}.

@cartouche
@quotation 注解 
This attribute is not available unless the ssl module is compiled
with OpenSSL 1.1.0g or newer.
@end quotation
@end cartouche


3.7 新版功能.

@end deffn

@geindex num_tickets (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext num_tickets}@anchor{269a}
@deffn {属性} SSLContext.num_tickets

Control the number of TLS 1.3 session tickets of a
@code{TLS_PROTOCOL_SERVER} context. The setting has no impact on TLS
1.0 to 1.2 connections.

@cartouche
@quotation 注解 
This attribute is not available unless the ssl module is compiled
with OpenSSL 1.1.1 or newer.
@end quotation
@end cartouche


3.8 新版功能.

@end deffn

@geindex options (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext options}@anchor{265d}
@deffn {属性} SSLContext.options

An integer representing the set of SSL options enabled on this context.
The default value is @ref{266b,,OP_ALL}, but you can specify other options
such as @ref{b99,,OP_NO_SSLv2} by ORing them together.

@cartouche
@quotation 注解 
With versions of OpenSSL older than 0.9.8m, it is only possible
to set options, not to clear them.  Attempting to clear an option
(by resetting the corresponding bits) will raise a @ref{1fb,,ValueError}.
@end quotation
@end cartouche


在 3.6 版更改: @ref{265d,,SSLContext.options} returns @ref{2674,,Options} flags:

@example
>>> ssl.create_default_context().options  
<Options.OP_ALL|OP_NO_SSLv3|OP_NO_SSLv2|OP_NO_COMPRESSION: 2197947391>
@end example

@end deffn

@geindex post_handshake_auth (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext post_handshake_auth}@anchor{224}
@deffn {属性} SSLContext.post_handshake_auth

Enable TLS 1.3 post-handshake client authentication. Post-handshake auth
is disabled by default and a server can only request a TLS client
certificate during the initial handshake. When enabled, a server may
request a TLS client certificate at any time after the handshake.

When enabled on client-side sockets, the client signals the server that
it supports post-handshake authentication.

When enabled on server-side sockets, @ref{264a,,SSLContext.verify_mode} must
be set to @ref{2662,,CERT_OPTIONAL} or @ref{264b,,CERT_REQUIRED}, too. The
actual client cert exchange is delayed until
@ref{225,,SSLSocket.verify_client_post_handshake()} is called and some I/O is
performed.

@cartouche
@quotation 注解 
Only available with OpenSSL 1.1.1 and TLS 1.3 enabled. Without TLS 1.3
support, the property value is None and can't be modified
@end quotation
@end cartouche


3.8 新版功能.

@end deffn

@geindex protocol (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext protocol}@anchor{269b}
@deffn {属性} SSLContext.protocol

The protocol version chosen when constructing the context.  This attribute
is read-only.
@end deffn

@geindex hostname_checks_common_name (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext hostname_checks_common_name}@anchor{3d6}
@deffn {属性} SSLContext.hostname_checks_common_name

Whether @ref{2663,,check_hostname} falls back to verify the cert's
subject common name in the absence of a subject alternative name
extension (default: true).

@cartouche
@quotation 注解 
Only writeable with OpenSSL 1.1.0 or higher.
@end quotation
@end cartouche


3.7 新版功能.

@end deffn

@geindex verify_flags (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext verify_flags}@anchor{8c0}
@deffn {属性} SSLContext.verify_flags

The flags for certificate verification operations. You can set flags like
@ref{8c2,,VERIFY_CRL_CHECK_LEAF} by ORing them together. By default OpenSSL
does neither require nor verify certificate revocation lists (CRLs).
Available only with openssl version 0.9.8+.


3.4 新版功能.



在 3.6 版更改: @ref{8c0,,SSLContext.verify_flags} returns @ref{2666,,VerifyFlags} flags:

@example
>>> ssl.create_default_context().verify_flags  
<VerifyFlags.VERIFY_X509_TRUSTED_FIRST: 32768>
@end example

@end deffn

@geindex verify_mode (ssl.SSLContext 属性)
@anchor{library/ssl ssl SSLContext verify_mode}@anchor{264a}
@deffn {属性} SSLContext.verify_mode

Whether to try to verify other peers' certificates and how to behave
if verification fails.  This attribute must be one of
@ref{2660,,CERT_NONE}, @ref{2662,,CERT_OPTIONAL} or @ref{264b,,CERT_REQUIRED}.


在 3.6 版更改: @ref{264a,,SSLContext.verify_mode} returns @ref{2664,,VerifyMode} enum:

@example
>>> ssl.create_default_context().verify_mode
<VerifyMode.CERT_REQUIRED: 2>
@end example

@end deffn

@geindex certificates

@geindex X509 certificate

@node Certificates,例子<16>,SSL Contexts,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl certificates}@anchor{269c}@anchor{library/ssl ssl-certificates}@anchor{2695}
@subsubsection Certificates


Certificates in general are part of a public-key / private-key system.  In this
system, each @emph{principal}, (which may be a machine, or a person, or an
organization) is assigned a unique two-part encryption key.  One part of the key
is public, and is called the @emph{public key}; the other part is kept secret, and is
called the @emph{private key}.  The two parts are related, in that if you encrypt a
message with one of the parts, you can decrypt it with the other part, and
@strong{only} with the other part.

A certificate contains information about two principals.  It contains the name
of a @emph{subject}, and the subject's public key.  It also contains a statement by a
second principal, the @emph{issuer}, that the subject is who they claim to be, and
that this is indeed the subject's public key.  The issuer's statement is signed
with the issuer's private key, which only the issuer knows.  However, anyone can
verify the issuer's statement by finding the issuer's public key, decrypting the
statement with it, and comparing it to the other information in the certificate.
The certificate also contains information about the time period over which it is
valid.  This is expressed as two fields, called "notBefore" and "notAfter".

In the Python use of certificates, a client or server can use a certificate to
prove who they are.  The other side of a network connection can also be required
to produce a certificate, and that certificate can be validated to the
satisfaction of the client or server that requires such validation.  The
connection attempt can be set to raise an exception if the validation fails.
Validation is done automatically, by the underlying OpenSSL framework; the
application need not concern itself with its mechanics.  But the application
does usually need to provide sets of certificates to allow this process to take
place.

Python uses files to contain certificates.  They should be formatted as "PEM"
(see 
@geindex RFC; RFC 1422
RFC 1422@footnote{https://tools.ietf.org/html/rfc1422.html}), which is a base-64 encoded form wrapped with a header line
and a footer line:

@example
-----BEGIN CERTIFICATE-----
... (certificate in base64 PEM encoding) ...
-----END CERTIFICATE-----
@end example

@menu
* Certificate chains:: 
* CA certificates:: 
* Combined key and certificate:: 
* Self-signed certificates:: 

@end menu

@node Certificate chains,CA certificates,,Certificates
@anchor{library/ssl certificate-chains}@anchor{269d}
@subsubsection Certificate chains


The Python files which contain certificates can contain a sequence of
certificates, sometimes called a @emph{certificate chain}.  This chain should start
with the specific certificate for the principal who "is" the client or server,
and then the certificate for the issuer of that certificate, and then the
certificate for the issuer of @emph{that} certificate, and so on up the chain till
you get to a certificate which is @emph{self-signed}, that is, a certificate which
has the same subject and issuer, sometimes called a @emph{root certificate}.  The
certificates should just be concatenated together in the certificate file.  For
example, suppose we had a three certificate chain, from our server certificate
to the certificate of the certification authority that signed our server
certificate, to the root certificate of the agency which issued the
certification authority's certificate:

@example
-----BEGIN CERTIFICATE-----
... (certificate for your server)...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
... (the certificate for the CA)...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
... (the root certificate for the CA's issuer)...
-----END CERTIFICATE-----
@end example

@node CA certificates,Combined key and certificate,Certificate chains,Certificates
@anchor{library/ssl ca-certificates}@anchor{269e}
@subsubsection CA certificates


If you are going to require validation of the other side of the connection's
certificate, you need to provide a "CA certs" file, filled with the certificate
chains for each issuer you are willing to trust.  Again, this file just contains
these chains concatenated together.  For validation, Python will use the first
chain it finds in the file which matches.  The platform's certificates file can
be used by calling @ref{8c5,,SSLContext.load_default_certs()}, this is done
automatically with @ref{8bb,,create_default_context()}.

@node Combined key and certificate,Self-signed certificates,CA certificates,Certificates
@anchor{library/ssl combined-key-and-certificate}@anchor{269f}
@subsubsection Combined key and certificate


Often the private key is stored in the same file as the certificate; in this
case, only the @code{certfile} parameter to @ref{a8c,,SSLContext.load_cert_chain()}
and @ref{469,,wrap_socket()} needs to be passed.  If the private key is stored
with the certificate, it should come before the first certificate in
the certificate chain:

@example
-----BEGIN RSA PRIVATE KEY-----
... (private key in base64 encoding) ...
-----END RSA PRIVATE KEY-----
-----BEGIN CERTIFICATE-----
... (certificate in base64 PEM encoding) ...
-----END CERTIFICATE-----
@end example

@node Self-signed certificates,,Combined key and certificate,Certificates
@anchor{library/ssl self-signed-certificates}@anchor{26a0}
@subsubsection Self-signed certificates


If you are going to create a server that provides SSL-encrypted connection
services, you will need to acquire a certificate for that service.  There are
many ways of acquiring appropriate certificates, such as buying one from a
certification authority.  Another common practice is to generate a self-signed
certificate.  The simplest way to do this is with the OpenSSL package, using
something like the following:

@example
% openssl req -new -x509 -days 365 -nodes -out cert.pem -keyout cert.pem
Generating a 1024 bit RSA private key
.......++++++
.............................++++++
writing new private key to 'cert.pem'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:MyState
Locality Name (eg, city) []:Some City
Organization Name (eg, company) [Internet Widgits Pty Ltd]:My Organization, Inc.
Organizational Unit Name (eg, section) []:My Group
Common Name (eg, YOUR name) []:myserver.mygroup.myorganization.com
Email Address []:ops@@myserver.mygroup.myorganization.com
%
@end example

The disadvantage of a self-signed certificate is that it is its own root
certificate, and no one else will have it in their cache of known (and trusted)
root certificates.

@node 例子<16>,Notes on non-blocking sockets,Certificates,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl examples}@anchor{26a1}
@subsubsection 例子


@menu
* Testing for SSL support:: 
* Client-side operation:: 
* Server-side operation:: 

@end menu

@node Testing for SSL support,Client-side operation,,例子<16>
@anchor{library/ssl testing-for-ssl-support}@anchor{26a2}
@subsubsection Testing for SSL support


To test for the presence of SSL support in a Python installation, user code
should use the following idiom:

@example
try:
    import ssl
except ImportError:
    pass
else:
    ...  # do something that requires SSL support
@end example

@node Client-side operation,Server-side operation,Testing for SSL support,例子<16>
@anchor{library/ssl client-side-operation}@anchor{26a3}
@subsubsection Client-side operation


This example creates a SSL context with the recommended security settings
for client sockets, including automatic certificate verification:

@example
>>> context = ssl.create_default_context()
@end example

If you prefer to tune security settings yourself, you might create
a context from scratch (but beware that you might not get the settings
right):

@example
>>> context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
>>> context.load_verify_locations("/etc/ssl/certs/ca-bundle.crt")
@end example

(this snippet assumes your operating system places a bundle of all CA
certificates in @code{/etc/ssl/certs/ca-bundle.crt}; if not, you'll get an
error and have to adjust the location)

The @ref{2661,,PROTOCOL_TLS_CLIENT} protocol configures the context for cert
validation and hostname verification. @ref{264a,,verify_mode} is
set to @ref{264b,,CERT_REQUIRED} and @ref{2663,,check_hostname} is set
to @code{True}. All other protocols create SSL contexts with insecure defaults.

When you use the context to connect to a server, @ref{264b,,CERT_REQUIRED}
and @ref{2663,,check_hostname} validate the server certificate: it
ensures that the server certificate was signed with one of the CA
certificates, checks the signature for correctness, and verifies other
properties like validity and identity of the hostname:

@example
>>> conn = context.wrap_socket(socket.socket(socket.AF_INET),
...                            server_hostname="www.python.org")
>>> conn.connect(("www.python.org", 443))
@end example

You may then fetch the certificate:

@example
>>> cert = conn.getpeercert()
@end example

Visual inspection shows that the certificate does identify the desired service
(that is, the HTTPS host @code{www.python.org}):

@example
>>> pprint.pprint(cert)
@{'OCSP': ('http://ocsp.digicert.com',),
 'caIssuers': ('http://cacerts.digicert.com/DigiCertSHA2ExtendedValidationServerCA.crt',),
 'crlDistributionPoints': ('http://crl3.digicert.com/sha2-ev-server-g1.crl',
                           'http://crl4.digicert.com/sha2-ev-server-g1.crl'),
 'issuer': ((('countryName', 'US'),),
            (('organizationName', 'DigiCert Inc'),),
            (('organizationalUnitName', 'www.digicert.com'),),
            (('commonName', 'DigiCert SHA2 Extended Validation Server CA'),)),
 'notAfter': 'Sep  9 12:00:00 2016 GMT',
 'notBefore': 'Sep  5 00:00:00 2014 GMT',
 'serialNumber': '01BB6F00122B177F36CAB49CEA8B6B26',
 'subject': ((('businessCategory', 'Private Organization'),),
             (('1.3.6.1.4.1.311.60.2.1.3', 'US'),),
             (('1.3.6.1.4.1.311.60.2.1.2', 'Delaware'),),
             (('serialNumber', '3359300'),),
             (('streetAddress', '16 Allen Rd'),),
             (('postalCode', '03894-4801'),),
             (('countryName', 'US'),),
             (('stateOrProvinceName', 'NH'),),
             (('localityName', 'Wolfeboro'),),
             (('organizationName', 'Python Software Foundation'),),
             (('commonName', 'www.python.org'),)),
 'subjectAltName': (('DNS', 'www.python.org'),
                    ('DNS', 'python.org'),
                    ('DNS', 'pypi.org'),
                    ('DNS', 'docs.python.org'),
                    ('DNS', 'testpypi.org'),
                    ('DNS', 'bugs.python.org'),
                    ('DNS', 'wiki.python.org'),
                    ('DNS', 'hg.python.org'),
                    ('DNS', 'mail.python.org'),
                    ('DNS', 'packaging.python.org'),
                    ('DNS', 'pythonhosted.org'),
                    ('DNS', 'www.pythonhosted.org'),
                    ('DNS', 'test.pythonhosted.org'),
                    ('DNS', 'us.pycon.org'),
                    ('DNS', 'id.python.org')),
 'version': 3@}
@end example

Now the SSL channel is established and the certificate verified, you can
proceed to talk with the server:

@example
>>> conn.sendall(b"HEAD / HTTP/1.0\r\nHost: linuxfr.org\r\n\r\n")
>>> pprint.pprint(conn.recv(1024).split(b"\r\n"))
[b'HTTP/1.1 200 OK',
 b'Date: Sat, 18 Oct 2014 18:27:20 GMT',
 b'Server: nginx',
 b'Content-Type: text/html; charset=utf-8',
 b'X-Frame-Options: SAMEORIGIN',
 b'Content-Length: 45679',
 b'Accept-Ranges: bytes',
 b'Via: 1.1 varnish',
 b'Age: 2188',
 b'X-Served-By: cache-lcy1134-LCY',
 b'X-Cache: HIT',
 b'X-Cache-Hits: 11',
 b'Vary: Cookie',
 b'Strict-Transport-Security: max-age=63072000; includeSubDomains',
 b'Connection: close',
 b'@w{'},
 b'@w{'}]
@end example

See the discussion of @ref{254a,,Security considerations} below.

@node Server-side operation,,Client-side operation,例子<16>
@anchor{library/ssl server-side-operation}@anchor{26a4}
@subsubsection Server-side operation


For server operation, typically you'll need to have a server certificate, and
private key, each in a file.  You'll first create a context holding the key
and the certificate, so that clients can check your authenticity.  Then
you'll open a socket, bind it to a port, call @code{listen()} on it, and start
waiting for clients to connect:

@example
import socket, ssl

context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
context.load_cert_chain(certfile="mycertfile", keyfile="mykeyfile")

bindsocket = socket.socket()
bindsocket.bind(('myaddr.mydomain.com', 10023))
bindsocket.listen(5)
@end example

When a client connects, you'll call @code{accept()} on the socket to get the
new socket from the other end, and use the context's @ref{3dd,,SSLContext.wrap_socket()}
method to create a server-side SSL socket for the connection:

@example
while True:
    newsocket, fromaddr = bindsocket.accept()
    connstream = context.wrap_socket(newsocket, server_side=True)
    try:
        deal_with_client(connstream)
    finally:
        connstream.shutdown(socket.SHUT_RDWR)
        connstream.close()
@end example

Then you'll read data from the @code{connstream} and do something with it till you
are finished with the client (or the client is finished with you):

@example
def deal_with_client(connstream):
    data = connstream.recv(1024)
    # empty data means the client is finished with us
    while data:
        if not do_something(connstream, data):
            # we'll assume do_something returns False
            # when we're finished with client
            break
        data = connstream.recv(1024)
    # finished with client
@end example

And go back to listening for new client connections (of course, a real server
would probably handle each client connection in a separate thread, or put
the sockets in @ref{264f,,non-blocking mode} and use an event loop).

@node Notes on non-blocking sockets,Memory BIO Support<2>,例子<16>,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl notes-on-non-blocking-sockets}@anchor{26a5}@anchor{library/ssl ssl-nonblocking}@anchor{264f}
@subsubsection Notes on non-blocking sockets


SSL sockets behave slightly different than regular sockets in
non-blocking mode. When working with non-blocking sockets, there are
thus several things you need to be aware of:


@itemize -

@item 
Most @ref{3da,,SSLSocket} methods will raise either
@ref{751,,SSLWantWriteError} or @ref{750,,SSLWantReadError} instead of
@ref{991,,BlockingIOError} if an I/O operation would
block. @ref{750,,SSLWantReadError} will be raised if a read operation on
the underlying socket is necessary, and @ref{751,,SSLWantWriteError} for
a write operation on the underlying socket. Note that attempts to
@emph{write} to an SSL socket may require @emph{reading} from the underlying
socket first, and attempts to @emph{read} from the SSL socket may require
a prior @emph{write} to the underlying socket.


在 3.5 版更改: In earlier Python versions, the @code{SSLSocket.send()} method
returned zero instead of raising @ref{751,,SSLWantWriteError} or
@ref{750,,SSLWantReadError}.


@item 
Calling @ref{66d,,select()} tells you that the OS-level socket can be
read from (or written to), but it does not imply that there is sufficient
data at the upper SSL layer.  For example, only part of an SSL frame might
have arrived.  Therefore, you must be ready to handle @code{SSLSocket.recv()}
and @code{SSLSocket.send()} failures, and retry after another call to
@ref{66d,,select()}.

@item 
Conversely, since the SSL layer has its own framing, a SSL socket may
still have data available for reading without @ref{66d,,select()}
being aware of it.  Therefore, you should first call
@code{SSLSocket.recv()} to drain any potentially available data, and then
only block on a @ref{66d,,select()} call if still necessary.

(of course, similar provisions apply when using other primitives such as
@ref{26a6,,poll()}, or those in the @ref{e6,,selectors} module)

@item 
The SSL handshake itself will be non-blocking: the
@ref{754,,SSLSocket.do_handshake()} method has to be retried until it returns
successfully.  Here is a synopsis using @ref{66d,,select()} to wait for
the socket's readiness:

@example
while True:
    try:
        sock.do_handshake()
        break
    except ssl.SSLWantReadError:
        select.select([sock], [], [])
    except ssl.SSLWantWriteError:
        select.select([], [sock], [])
@end example
@end itemize


@subsubheading 参见


The @ref{a,,asyncio} module supports @ref{264f,,non-blocking SSL sockets} and provides a
higher level API. It polls for events using the @ref{e6,,selectors} module and
handles @ref{751,,SSLWantWriteError}, @ref{750,,SSLWantReadError} and
@ref{991,,BlockingIOError} exceptions. It runs the SSL handshake asynchronously
as well.


@node Memory BIO Support<2>,SSL session,Notes on non-blocking sockets,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl memory-bio-support}@anchor{26a7}
@subsubsection Memory BIO Support



3.5 新版功能.


Ever since the SSL module was introduced in Python 2.6, the @ref{3da,,SSLSocket}
class has provided two related but distinct areas of functionality:


@itemize -

@item 
SSL protocol handling

@item 
Network IO
@end itemize

The network IO API is identical to that provided by @ref{66e,,socket.socket},
from which @ref{3da,,SSLSocket} also inherits. This allows an SSL socket to be
used as a drop-in replacement for a regular socket, making it very easy to add
SSL support to an existing application.

Combining SSL protocol handling and network IO usually works well, but there
are some cases where it doesn't. An example is async IO frameworks that want to
use a different IO multiplexing model than the "select/poll on a file
descriptor" (readiness based) model that is assumed by @ref{66e,,socket.socket}
and by the internal OpenSSL socket IO routines. This is mostly relevant for
platforms like Windows where this model is not efficient. For this purpose, a
reduced scope variant of @ref{3da,,SSLSocket} called @ref{3db,,SSLObject} is
provided.

@geindex SSLObject (ssl 中的类)
@anchor{library/ssl ssl SSLObject}@anchor{3db}
@deffn {类} ssl.SSLObject

A reduced-scope variant of @ref{3da,,SSLSocket} representing an SSL protocol
instance that does not contain any network IO methods. This class is
typically used by framework authors that want to implement asynchronous IO
for SSL through memory buffers.

This class implements an interface on top of a low-level SSL object as
implemented by OpenSSL. This object captures the state of an SSL connection
but does not provide any network IO itself. IO needs to be performed through
separate "BIO" objects which are OpenSSL's IO abstraction layer.

This class has no public constructor.  An @ref{3db,,SSLObject} instance
must be created using the @ref{3de,,wrap_bio()} method. This
method will create the @ref{3db,,SSLObject} instance and bind it to a
pair of BIOs. The @emph{incoming} BIO is used to pass data from Python to the
SSL protocol instance, while the @emph{outgoing} BIO is used to pass data the
other way around.

可以使用以下方法：


@itemize -

@item 
@ref{268e,,context}

@item 
@ref{2691,,server_side}

@item 
@ref{3d8,,server_hostname}

@item 
@ref{2692,,session}

@item 
@ref{2693,,session_reused}

@item 
@ref{755,,read()}

@item 
@ref{756,,write()}

@item 
@ref{8cb,,getpeercert()}

@item 
@ref{74c,,selected_alpn_protocol()}

@item 
@ref{268f,,selected_npn_protocol()}

@item 
@ref{2591,,cipher()}

@item 
@ref{753,,shared_ciphers()}

@item 
@ref{a90,,compression()}

@item 
@ref{2690,,pending()}

@item 
@ref{754,,do_handshake()}

@item 
@ref{225,,verify_client_post_handshake()}

@item 
@ref{268d,,unwrap()}

@item 
@ref{a8f,,get_channel_binding()}

@item 
@ref{74f,,version()}
@end itemize

When compared to @ref{3da,,SSLSocket}, this object lacks the following
features:


@itemize -

@item 
Any form of network IO; @code{recv()} and @code{send()} read and write only to
the underlying @ref{749,,MemoryBIO} buffers.

@item 
There is no @emph{do_handshake_on_connect} machinery. You must always manually
call @ref{754,,do_handshake()} to start the handshake.

@item 
There is no handling of @emph{suppress_ragged_eofs}. All end-of-file conditions
that are in violation of the protocol are reported via the
@ref{2651,,SSLEOFError} exception.

@item 
The method @ref{268d,,unwrap()} call does not return anything,
unlike for an SSL socket where it returns the underlying socket.

@item 
The @emph{server_name_callback} callback passed to
@ref{8ca,,SSLContext.set_servername_callback()} will get an @ref{3db,,SSLObject}
instance instead of a @ref{3da,,SSLSocket} instance as its first parameter.
@end itemize

Some notes related to the use of @ref{3db,,SSLObject}:


@itemize -

@item 
All IO on an @ref{3db,,SSLObject} is @ref{264f,,non-blocking}.
This means that for example @ref{755,,read()} will raise an
@ref{750,,SSLWantReadError} if it needs more data than the incoming BIO has
available.

@item 
There is no module-level @code{wrap_bio()} call like there is for
@ref{3dd,,wrap_socket()}. An @ref{3db,,SSLObject} is always created
via an @ref{3dc,,SSLContext}.
@end itemize


在 3.7 版更改: @ref{3db,,SSLObject} instances must to created with
@ref{3de,,wrap_bio()}. In earlier versions, it was possible to
create instances directly. This was never documented or officially
supported.

@end deffn

An SSLObject communicates with the outside world using memory buffers. The
class @ref{749,,MemoryBIO} provides a memory buffer that can be used for this
purpose.  It wraps an OpenSSL memory BIO (Basic IO) object:

@geindex MemoryBIO (ssl 中的类)
@anchor{library/ssl ssl MemoryBIO}@anchor{749}
@deffn {类} ssl.MemoryBIO

A memory buffer that can be used to pass data between Python and an SSL
protocol instance.

@geindex pending (ssl.MemoryBIO 属性)
@anchor{library/ssl ssl MemoryBIO pending}@anchor{26a8}
@deffn {属性} pending

Return the number of bytes currently in the memory buffer.
@end deffn

@geindex eof (ssl.MemoryBIO 属性)
@anchor{library/ssl ssl MemoryBIO eof}@anchor{26a9}
@deffn {属性} eof

A boolean indicating whether the memory BIO is current at the end-of-file
position.
@end deffn

@geindex read() (ssl.MemoryBIO 方法)
@anchor{library/ssl ssl MemoryBIO read}@anchor{26aa}
@deffn {方法} read (n=-1)

Read up to @emph{n} bytes from the memory buffer. If @emph{n} is not specified or
negative, all bytes are returned.
@end deffn

@geindex write() (ssl.MemoryBIO 方法)
@anchor{library/ssl ssl MemoryBIO write}@anchor{26ab}
@deffn {方法} write (buf)

Write the bytes from @emph{buf} to the memory BIO. The @emph{buf} argument must be an
object supporting the buffer protocol.

The return value is the number of bytes written, which is always equal to
the length of @emph{buf}.
@end deffn

@geindex write_eof() (ssl.MemoryBIO 方法)
@anchor{library/ssl ssl MemoryBIO write_eof}@anchor{26ac}
@deffn {方法} write_eof ()

Write an EOF marker to the memory BIO. After this method has been called, it
is illegal to call @ref{26ab,,write()}. The attribute @ref{26a9,,eof} will
become true after all data currently in the buffer has been read.
@end deffn
@end deffn

@node SSL session,Security considerations,Memory BIO Support<2>,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl ssl-session}@anchor{26ad}
@subsubsection SSL session



3.6 新版功能.


@geindex SSLSession (ssl 中的类)
@anchor{library/ssl ssl SSLSession}@anchor{586}
@deffn {类} ssl.SSLSession

Session object used by @ref{2692,,session}.

@geindex id (ssl.SSLSession 属性)
@anchor{library/ssl ssl SSLSession id}@anchor{26ae}
@deffn {属性} id
@end deffn

@geindex time (ssl.SSLSession 属性)
@anchor{library/ssl ssl SSLSession time}@anchor{26af}
@deffn {属性} time
@end deffn

@geindex timeout (ssl.SSLSession 属性)
@anchor{library/ssl ssl SSLSession timeout}@anchor{26b0}
@deffn {属性} timeout
@end deffn

@geindex ticket_lifetime_hint (ssl.SSLSession 属性)
@anchor{library/ssl ssl SSLSession ticket_lifetime_hint}@anchor{26b1}
@deffn {属性} ticket_lifetime_hint
@end deffn

@geindex has_ticket (ssl.SSLSession 属性)
@anchor{library/ssl ssl SSLSession has_ticket}@anchor{26b2}
@deffn {属性} has_ticket
@end deffn
@end deffn

@node Security considerations,TLS 1 3,SSL session,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl security-considerations}@anchor{26b3}@anchor{library/ssl ssl-security}@anchor{254a}
@subsubsection Security considerations


@menu
* Best defaults:: 
* Manual settings:: 
* Multi-processing:: 

@end menu

@node Best defaults,Manual settings,,Security considerations
@anchor{library/ssl best-defaults}@anchor{26b4}
@subsubsection Best defaults


For @strong{client use}, if you don't have any special requirements for your
security policy, it is highly recommended that you use the
@ref{8bb,,create_default_context()} function to create your SSL context.
It will load the system's trusted CA certificates, enable certificate
validation and hostname checking, and try to choose reasonably secure
protocol and cipher settings.

For example, here is how you would use the @ref{a7c,,smtplib.SMTP} class to
create a trusted, secure connection to a SMTP server:

@example
>>> import ssl, smtplib
>>> smtp = smtplib.SMTP("mail.python.org", port=587)
>>> context = ssl.create_default_context()
>>> smtp.starttls(context=context)
(220, b'2.0.0 Ready to start TLS')
@end example

If a client certificate is needed for the connection, it can be added with
@ref{a8c,,SSLContext.load_cert_chain()}.

By contrast, if you create the SSL context by calling the @ref{3dc,,SSLContext}
constructor yourself, it will not have certificate validation nor hostname
checking enabled by default.  If you do so, please read the paragraphs below
to achieve a good security level.

@node Manual settings,Multi-processing,Best defaults,Security considerations
@anchor{library/ssl manual-settings}@anchor{26b5}
@subsubsection Manual settings


@menu
* Verifying certificates:: 
* Protocol versions:: 
* Cipher selection:: 

@end menu

@node Verifying certificates,Protocol versions,,Manual settings
@anchor{library/ssl verifying-certificates}@anchor{26b6}
@subsubsection Verifying certificates


When calling the @ref{3dc,,SSLContext} constructor directly,
@ref{2660,,CERT_NONE} is the default.  Since it does not authenticate the other
peer, it can be insecure, especially in client mode where most of time you
would like to ensure the authenticity of the server you're talking to.
Therefore, when in client mode, it is highly recommended to use
@ref{264b,,CERT_REQUIRED}.  However, it is in itself not sufficient; you also
have to check that the server certificate, which can be obtained by calling
@ref{8cb,,SSLSocket.getpeercert()}, matches the desired service.  For many
protocols and applications, the service can be identified by the hostname;
in this case, the @ref{3d4,,match_hostname()} function can be used.  This common
check is automatically performed when @ref{2663,,SSLContext.check_hostname} is
enabled.


在 3.7 版更改: Hostname matchings is now performed by OpenSSL. Python no longer uses
@ref{3d4,,match_hostname()}.


In server mode, if you want to authenticate your clients using the SSL layer
(rather than using a higher-level authentication mechanism), you'll also have
to specify @ref{264b,,CERT_REQUIRED} and similarly check the client certificate.

@node Protocol versions,Cipher selection,Verifying certificates,Manual settings
@anchor{library/ssl protocol-versions}@anchor{26b7}
@subsubsection Protocol versions


SSL versions 2 and 3 are considered insecure and are therefore dangerous to
use.  If you want maximum compatibility between clients and servers, it is
recommended to use @ref{2661,,PROTOCOL_TLS_CLIENT} or
@ref{2667,,PROTOCOL_TLS_SERVER} as the protocol version. SSLv2 and SSLv3 are
disabled by default.

@example
>>> client_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
>>> client_context.options |= ssl.OP_NO_TLSv1
>>> client_context.options |= ssl.OP_NO_TLSv1_1
@end example

The SSL context created above will only allow TLSv1.2 and later (if
supported by your system) connections to a server. @ref{2661,,PROTOCOL_TLS_CLIENT}
implies certificate validation and hostname checks by default. You have to
load certificates into the context.

@node Cipher selection,,Protocol versions,Manual settings
@anchor{library/ssl cipher-selection}@anchor{26b8}
@subsubsection Cipher selection


If you have advanced security requirements, fine-tuning of the ciphers
enabled when negotiating a SSL session is possible through the
@ref{265e,,SSLContext.set_ciphers()} method.  Starting from Python 3.2.3, the
ssl module disables certain weak ciphers by default, but you may want
to further restrict the cipher choice. Be sure to read OpenSSL's documentation
about the cipher list format@footnote{https://www.openssl.org/docs/manmaster/man1/ciphers.html#CIPHER-LIST-FORMAT}.
If you want to check which ciphers are enabled by a given cipher list, use
@ref{587,,SSLContext.get_ciphers()} or the @code{openssl ciphers} command on your
system.

@node Multi-processing,,Manual settings,Security considerations
@anchor{library/ssl multi-processing}@anchor{26b9}
@subsubsection Multi-processing


If using this module as part of a multi-processed application (using,
for example the @ref{b7,,multiprocessing} or @ref{22,,concurrent.futures} modules),
be aware that OpenSSL's internal random number generator does not properly
handle forked processes.  Applications must change the PRNG state of the
parent process if they use any SSL feature with @ref{95b,,os.fork()}.  Any
successful call of @ref{2657,,RAND_add()}, @ref{a8a,,RAND_bytes()} or
@ref{a8b,,RAND_pseudo_bytes()} is sufficient.

@node TLS 1 3,LibreSSL support,Security considerations,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl ssl-tlsv1-3}@anchor{3d9}@anchor{library/ssl tls-1-3}@anchor{26ba}
@subsubsection TLS 1.3



3.7 新版功能.


Python has provisional and experimental support for TLS 1.3 with OpenSSL
1.1.1.  The new protocol behaves slightly differently than previous version
of TLS/SSL.  Some new TLS 1.3 features are not yet available.


@itemize -

@item 
TLS 1.3 uses a disjunct set of cipher suites. All AES-GCM and
ChaCha20 cipher suites are enabled by default.  The method
@ref{265e,,SSLContext.set_ciphers()} cannot enable or disable any TLS 1.3
ciphers yet, but @ref{587,,SSLContext.get_ciphers()} returns them.

@item 
Session tickets are no longer sent as part of the initial handshake and
are handled differently.  @ref{2692,,SSLSocket.session} and @ref{586,,SSLSession}
are not compatible with TLS 1.3.

@item 
Client-side certificates are also no longer verified during the initial
handshake.  A server can request a certificate at any time.  Clients
process certificate requests while they send or receive application data
from the server.

@item 
TLS 1.3 features like early data, deferred TLS client cert request,
signature algorithm configuration, and rekeying are not supported yet.
@end itemize

@node LibreSSL support,,TLS 1 3,ssl --- 套接字对象的TLS/SSL封装
@anchor{library/ssl libressl-support}@anchor{26bb}@anchor{library/ssl ssl-libressl}@anchor{26bc}
@subsubsection LibreSSL support


LibreSSL is a fork of OpenSSL 1.0.1. The ssl module has limited support for
LibreSSL. Some features are not available when the ssl module is compiled
with LibreSSL.


@itemize *

@item 
LibreSSL >= 2.6.1 no longer supports NPN. The methods
@ref{a92,,SSLContext.set_npn_protocols()} and
@ref{268f,,SSLSocket.selected_npn_protocol()} are not available.

@item 
@ref{8bd,,SSLContext.set_default_verify_paths()} ignores the env vars
@geindex SSL_CERT_FILE
@geindex 环境变量; SSL_CERT_FILE
@code{SSL_CERT_FILE} and 
@geindex SSL_CERT_PATH
@geindex 环境变量; SSL_CERT_PATH
@code{SSL_CERT_PATH} although
@ref{8bc,,get_default_verify_paths()} still reports them.
@end itemize


@subsubheading 参见



@table @asis

@item Class @ref{66e,,socket.socket}

Documentation of underlying @ref{ef,,socket} class

@item SSL/TLS Strong Encryption: An Introduction@footnote{https://httpd.apache.org/docs/trunk/en/ssl/ssl_intro.html}

Apache HTTP Server文档介绍

@geindex RFC; RFC 1422

@item RFC 1422: Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management@footnote{https://tools.ietf.org/html/rfc1422.html}

Steve Kent

@geindex RFC; RFC 4086

@item RFC 4086: Randomness Requirements for Security@footnote{https://tools.ietf.org/html/rfc4086.html}

Donald E., Jeffrey I. Schiller

@geindex RFC; RFC 5280

@item RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile@footnote{https://tools.ietf.org/html/rfc5280.html}

D. Cooper

@geindex RFC; RFC 5246

@item RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2@footnote{https://tools.ietf.org/html/rfc5246.html}

T. Dierks et. al.

@geindex RFC; RFC 6066

@item RFC 6066: Transport Layer Security (TLS) Extensions@footnote{https://tools.ietf.org/html/rfc6066.html}

D. Eastlake

@item IANA TLS: Transport Layer Security (TLS) Parameters@footnote{https://www.iana.org/assignments/tls-parameters/tls-parameters.xml}

IANA

@geindex RFC; RFC 7525

@item RFC 7525: Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)@footnote{https://tools.ietf.org/html/rfc7525.html}

IETF

@item Mozilla's Server Side TLS recommendations@footnote{https://wiki.mozilla.org/Security/Server_Side_TLS}

Mozilla
@end table


@node select --- 等待 I/O 完成,selectors --- 高级 I/O 复用库,ssl --- 套接字对象的TLS/SSL封装,网络和进程间通信
@anchor{library/select doc}@anchor{26bd}@anchor{library/select module-select}@anchor{e5}@anchor{library/select select-waiting-for-i-o-completion}@anchor{26be}
@subsection @code{select} --- 等待 I/O 完成


@geindex select (模块)


__________________________________________________________________


该模块提供了对 @code{select()} 和 @code{poll()} 函数的访问，这些函数在大多数操作系统中是可用的。在 Solaris 及其衍生版本上可用 @code{devpoll()}，在 Linux 2.5+ 上可用 @code{epoll()}，在大多数 BSD 上可用 @code{kqueue()}。注意，在 Windows 上，本模块仅适用于套接字；在其他操作系统上，本模块也适用于其他文件类型（特别地，在 Unix 上也适用于管道）。本模块不能用于常规文件，不能检测出（自上次读取文件后）文件是否有新数据写入。

@cartouche
@quotation 注解 
@ref{e6,,selectors} 模块是在 @ref{e5,,select} 模块原型的基础上进行高级且高效的 I/O 复用。推荐用户改用 @ref{e6,,selectors} 模块，除非用户希望对 OS 级的函数原型进行精确控制。
@end quotation
@end cartouche

该模块定义以下内容：

@geindex error
@anchor{library/select select error}@anchor{990}
@deffn {例外} select.error

一个被弃用的 @ref{1d3,,OSError} 的别名。


在 3.3 版更改: 根据 
@geindex Python 提高建议; PEP 3151
PEP 3151@footnote{https://www.python.org/dev/peps/pep-3151}，这个类是 @ref{1d3,,OSError} 的别名。

@end deffn

@geindex devpoll() (在 select 模块中)
@anchor{library/select select devpoll}@anchor{8a5}
@deffn {函数} select.devpoll ()

（仅支持 Solaris 及其衍生版本）返回一个 @code{/dev/poll} 轮询对象，请参阅下方 @ref{26bf,,/dev/poll 轮询对象} 获取 devpoll 对象所支持的方法。

@code{devpoll()} 对象与实例化时允许的文件描述符数量有关，如果在程序中降低了此数值，@code{devpoll()} 调用将失败。如果程序提高了此数值，@code{devpoll()} 可能会返回一个不完整的活动文件描述符列表。

新的文件描述符是 @ref{7f4,,不可继承的}。


3.3 新版功能.



在 3.4 版更改: 新的文件描述符现在是不可继承的。

@end deffn

@geindex epoll() (在 select 模块中)
@anchor{library/select select epoll}@anchor{8a3}
@deffn {函数} select.epoll (sizehint=-1, flags=0)

（仅支持 Linux 2.5.44 或更高版本）返回一个 edge poll 对象，该对象可作为 I/O 事件的边缘触发或水平触发接口。

@emph{sizehint} 指示 epoll 预计需要注册的事件数。它必须为正数，或为 @cite{-1} 以使用默认值。它仅在 @code{epoll_create1()} 不可用的旧系统上会被用到，其他情况下它没有任何作用（尽管仍会检查其值）。

@emph{flags} 已经弃用且完全被忽略。但是，如果提供该值，则它必须是 @code{0} 或 @code{select.EPOLL_CLOEXEC}，否则会抛出 @code{OSError} 异常。

请参阅下方 @ref{26c0,,边缘触发和水平触发的轮询 (epoll) 对象} 获取 epoll 对象所支持的方法。

@code{epoll} 对象支持上下文管理器：当在 @ref{6e3,,with} 语句中使用时，新建的文件描述符会在运行至语句块结束时自动关闭。

新的文件描述符是 @ref{7f4,,不可继承的}。


在 3.3 版更改: 增加了 @emph{flags} 参数。



在 3.4 版更改: 增加了对 @ref{6e3,,with} 语句的支持。新的文件描述符现在是不可继承的。



3.4 版后已移除: @emph{flags} 参数。现在默认采用 @code{select.EPOLL_CLOEXEC} 标志。使用 @ref{7f6,,os.set_inheritable()} 来让文件描述符可继承。

@end deffn

@geindex poll() (在 select 模块中)
@anchor{library/select select poll}@anchor{26a6}
@deffn {函数} select.poll ()

（部分操作系统不支持）返回一个 poll 对象，该对象支持注册和注销文件描述符，支持对描述符进行轮询以获取 I/O 事件。请参阅下方 @ref{26c1,,Poll 对象} 获取 poll 对象所支持的方法。
@end deffn

@geindex kqueue() (在 select 模块中)
@anchor{library/select select kqueue}@anchor{26c2}
@deffn {函数} select.kqueue ()

（仅支持 BSD）返回一个内核队列对象，请参阅下方 @ref{26c3,,Kqueue 对象} 获取 kqueue 对象所支持的方法。

新的文件描述符是 @ref{7f4,,不可继承的}。


在 3.4 版更改: 新的文件描述符现在是不可继承的。

@end deffn

@geindex kevent() (在 select 模块中)
@anchor{library/select select kevent}@anchor{26c4}
@deffn {函数} select.kevent (ident, filter=KQ_FILTER_READ, flags=KQ_EV_ADD, fflags=0, data=0, udata=0)

（仅支持 BSD）返回一个内核事件对象，请参阅下方 @ref{26c5,,Kevent 对象} 获取 kevent 对象所支持的方法。
@end deffn

@geindex select() (在 select 模块中)
@anchor{library/select select select}@anchor{66d}
@deffn {函数} select.select (rlist, wlist, xlist[, timeout])

这是一个明白直观的 Unix @code{select()} 系统调用接口。 前三个参数是由‘可等待对象’组成的序列：可以是代表文件描述符的整数，或是带有名为 @ref{1ea0,,fileno()} 的返回这样的整数的无形参方法的对象:


@itemize *

@item 
@emph{rlist}：等待，直到可以开始读取

@item 
@emph{wlist}：等待，直到可以开始写入

@item 
@emph{xlist}：等待“异常情况”（请参阅当前系统的手册，以获取哪些情况称为异常情况）
@end itemize

允许空的可迭代对象，但是否接受三个空的可迭代对象则取决于具体平台。 （已知在 Unix 上可行但在 Windows 上不可行。） 可选的 @emph{timeout} 参数以一个浮点数表示超时秒数。 当省略 @emph{timeout} 参数时该函数将阻塞直到至少有一个文件描述符准备就绪。 超时值为零表示执行轮询且永不阻塞。

返回值是三个列表，包含已就绪对象，返回的三个列表是前三个参数的子集。当超时时间已到且没有文件描述符就绪时，返回三个空列表。

@geindex socket() (in module socket)
@geindex popen() (in module os)

可迭代对象中可接受的对象类型有 Python @ref{b3b,,文件对象} (例如 @code{sys.stdin} 以及 @ref{4ea,,open()} 或 @ref{2a9,,os.popen()} 所返回的对象)，由 @ref{66e,,socket.socket()} 返回的套接字对象等。 你也可以自定义一个 @emph{wrapper} 类，只要它具有适当的 @ref{1ea0,,fileno()} 方法（该方法要确实返回一个文件描述符，而不能只是一个随机整数）。

@cartouche
@quotation 注解 
@geindex WinSock

Windows 上不接受文件对象，但接受套接字。在 Windows 上，底层的 @code{select()} 函数由 WinSock 库提供，且不处理不是源自 WinSock 的文件描述符。
@end quotation
@end cartouche


在 3.5 版更改: 现在，当本函数被信号中断时，重试超时将从头开始计时，不会抛出 @ref{653,,InterruptedError} 异常。除非信号处理程序抛出异常（相关原理请参阅 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}）。

@end deffn

@geindex PIPE_BUF() (在 select 模块中)
@anchor{library/select select PIPE_BUF}@anchor{b7f}
@deffn {属性} select.PIPE_BUF

当一个管道已经被 @ref{66d,,select()}、@ref{26a6,,poll()} 或本模块中的某个接口报告为可写入时，可以在不阻塞该管道的情况下写入的最小字节数。它不适用于套接字等其他类型的文件类对象。

POSIX 上须保证该值不小于 512。

@ref{12f5,,可用性}: Unix


3.2 新版功能.

@end deffn

@menu
* /dev/poll 轮询对象:: 
* 边缘触发和水平触发的轮询 (epoll) 对象: 边缘触发和水平触发的轮询 epoll 对象. 
* Poll 对象:: 
* Kqueue 对象:: 
* Kevent 对象:: 

@end menu

@node /dev/poll 轮询对象,边缘触发和水平触发的轮询 epoll 对象,,select --- 等待 I/O 完成
@anchor{library/select dev-poll-polling-objects}@anchor{26c6}@anchor{library/select devpoll-objects}@anchor{26bf}
@subsubsection @code{/dev/poll} 轮询对象


Solaris 及其衍生版本具备 @code{/dev/poll}。@code{select()} 复杂度为 O（最高文件描述符），@code{poll()} 为 O（文件描述符数量），而 @code{/dev/poll} 为 O（活动的文件描述符）。

@code{/dev/poll} 的行为与标准 @code{poll()} 对象十分类似。

@geindex close() (select.devpoll 方法)
@anchor{library/select select devpoll close}@anchor{8a7}
@deffn {方法} devpoll.close ()

关闭轮询对象的文件描述符。


3.4 新版功能.

@end deffn

@geindex closed (select.devpoll 属性)
@anchor{library/select select devpoll closed}@anchor{8a8}
@deffn {属性} devpoll.closed

如果轮询对象已关闭，则返回 @code{True}。


3.4 新版功能.

@end deffn

@geindex fileno() (select.devpoll 方法)
@anchor{library/select select devpoll fileno}@anchor{8a6}
@deffn {方法} devpoll.fileno ()

返回轮询对象的文件描述符对应的数字。


3.4 新版功能.

@end deffn

@geindex register() (select.devpoll 方法)
@anchor{library/select select devpoll register}@anchor{26c7}
@deffn {方法} devpoll.register (fd[, eventmask])

在轮询对象中注册文件描述符。这样，将来调用 @ref{26a6,,poll()} 方法时将检查文件描述符是否有未处理的 I/O 事件。@emph{fd} 可以是整数，也可以是带有 @ref{1ea0,,fileno()} 方法的对象（该方法返回一个整数）。文件对象已经实现了 @code{fileno()}，因此它们也可以用作参数。

@emph{eventmask} 是可选的位掩码，用于指定要检查的事件类型。这些常量与 @code{poll()} 对象所用的相同。本参数的默认值是常量 @code{POLLIN}、@code{POLLPRI} 和 @code{POLLOUT} 的组合。

@cartouche
@quotation 警告 
注册已注册过的文件描述符不会报错，但是结果是不确定的。正确的操作是先注销或直接修改它。与 @code{poll()} 相比，这是一个重要的区别。
@end quotation
@end cartouche
@end deffn

@geindex modify() (select.devpoll 方法)
@anchor{library/select select devpoll modify}@anchor{26c8}
@deffn {方法} devpoll.modify (fd[, eventmask])

此方法先执行 @ref{26c9,,unregister()} 后执行 @ref{26c7,,register()}。直接执行此操作效率（稍微）高一些。
@end deffn

@geindex unregister() (select.devpoll 方法)
@anchor{library/select select devpoll unregister}@anchor{26c9}
@deffn {方法} devpoll.unregister (fd)

删除轮询对象正在跟踪的某个文件描述符。与 @ref{26c7,,register()} 方法类似，@emph{fd} 可以是整数，也可以是带有 @ref{1ea0,,fileno()} 方法的对象（该方法返回一个整数）。

尝试删除从未注册过的文件描述符将被安全地忽略。
@end deffn

@geindex poll() (select.devpoll 方法)
@anchor{library/select select devpoll poll}@anchor{669}
@deffn {方法} devpoll.poll ([timeout])

轮询已注册的文件描述符的集合，并返回一个列表，列表可能为空，也可能有多个 @code{(fd, event)} 二元组，其中包含了要报告事件或错误的描述符。@emph{fd} 是文件描述符，@emph{event} 是一个位掩码，表示该描述符所报告的事件 --- @code{POLLIN} 表示可以读取，@code{POLLOUT} 表示该描述符可以写入，依此类推。空列表表示调用超时，没有任何文件描述符报告事件。如果指定了 @emph{timeout}，它将指定系统等待事件时，等待多长时间后返回（以毫秒为单位）。如果 @emph{timeout} 为空，-1 或 @ref{157,,None}，则本调用将阻塞，直到轮询对象发生事件为止。


在 3.5 版更改: 现在，当本函数被信号中断时，重试超时将从头开始计时，不会抛出 @ref{653,,InterruptedError} 异常。除非信号处理程序抛出异常（相关原理请参阅 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}）。

@end deffn

@node 边缘触发和水平触发的轮询 epoll 对象,Poll 对象,/dev/poll 轮询对象,select --- 等待 I/O 完成
@anchor{library/select edge-and-level-trigger-polling-epoll-objects}@anchor{26ca}@anchor{library/select epoll-objects}@anchor{26c0}
@subsubsection 边缘触发和水平触发的轮询 (epoll) 对象


@quotation

@indicateurl{https://linux.die.net/man/4/epoll}

@emph{eventmask}


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{EPOLLIN}

@tab

可读

@item

@code{EPOLLOUT}

@tab

可写

@item

@code{EPOLLPRI}

@tab

紧急数据读取

@item

@code{EPOLLERR}

@tab

在关联的文件描述符上有错误情况发生

@item

@code{EPOLLHUP}

@tab

关联的文件描述符已挂起

@item

@code{EPOLLET}

@tab

设置触发方式为边缘触发，默认为水平触发

@item

@code{EPOLLONESHOT}

@tab

设置 one-shot 模式。触发一次事件后，该描述符会在轮询对象内部被禁用。

@item

@code{EPOLLEXCLUSIVE}

@tab

当已关联的描述符发生事件时，仅唤醒一个 epoll 对象。默认（如果未设置此标志）是唤醒所有轮询该描述符的 epoll 对象。

@item

@code{EPOLLRDHUP}

@tab

流套接字的对侧关闭了连接或关闭了写入到一半的连接。

@item

@code{EPOLLRDNORM}

@tab

等同于 @code{EPOLLIN}

@item

@code{EPOLLRDBAND}

@tab

可以读取优先数据带。

@item

@code{EPOLLWRNORM}

@tab

等同于 @code{EPOLLOUT}

@item

@code{EPOLLWRBAND}

@tab

可以写入优先级数据。

@item

@code{EPOLLMSG}

@tab

忽略

@end multitable



3.6 新版功能: 增加了 @code{EPOLLEXCLUSIVE}。仅支持 Linux Kernel 4.5 或更高版本。

@end quotation

@geindex close() (select.epoll 方法)
@anchor{library/select select epoll close}@anchor{8a4}
@deffn {方法} epoll.close ()

关闭用于控制 epoll 对象的文件描述符。
@end deffn

@geindex closed (select.epoll 属性)
@anchor{library/select select epoll closed}@anchor{26cb}
@deffn {属性} epoll.closed

如果 epoll 对象已关闭，则返回 @code{True}。
@end deffn

@geindex fileno() (select.epoll 方法)
@anchor{library/select select epoll fileno}@anchor{26cc}
@deffn {方法} epoll.fileno ()

返回文件描述符对应的数字，该描述符用于控制 epoll 对象。
@end deffn

@geindex fromfd() (select.epoll 方法)
@anchor{library/select select epoll fromfd}@anchor{26cd}
@deffn {方法} epoll.fromfd (fd)

根据给定的文件描述符创建 epoll 对象。
@end deffn

@geindex register() (select.epoll 方法)
@anchor{library/select select epoll register}@anchor{26ce}
@deffn {方法} epoll.register (fd[, eventmask])

在 epoll 对象中注册一个文件描述符。
@end deffn

@geindex modify() (select.epoll 方法)
@anchor{library/select select epoll modify}@anchor{26cf}
@deffn {方法} epoll.modify (fd, eventmask)

修改一个已注册的文件描述符。
@end deffn

@geindex unregister() (select.epoll 方法)
@anchor{library/select select epoll unregister}@anchor{26d0}
@deffn {方法} epoll.unregister (fd)

从 epoll 对象中删除一个已注册的文件描述符。
@end deffn

@geindex poll() (select.epoll 方法)
@anchor{library/select select epoll poll}@anchor{66a}
@deffn {方法} epoll.poll (timeout=None, maxevents=-1)

等待事件发生，timeout 是浮点数，单位为秒。


在 3.5 版更改: 现在，当本函数被信号中断时，重试超时将从头开始计时，不会抛出 @ref{653,,InterruptedError} 异常。除非信号处理程序抛出异常（相关原理请参阅 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}）。

@end deffn

@node Poll 对象,Kqueue 对象,边缘触发和水平触发的轮询 epoll 对象,select --- 等待 I/O 完成
@anchor{library/select poll-objects}@anchor{26c1}@anchor{library/select polling-objects}@anchor{26d1}
@subsubsection Poll 对象


大多数 Unix 系统支持 @code{poll()} 系统调用，为服务器提供了更好的可伸缩性，使服务器可以同时服务于大量客户端。@code{poll()} 的伸缩性更好，因为该调用内部仅列出所关注的文件描述符，而 @code{select()} 会构造一个 bitmap，在其中将所关注的描述符所对应的 bit 打开，然后重新遍历整个 bitmap。因此 @code{select()} 复杂度是 O（最高文件描述符），而 @code{poll()} 是 O（文件描述符数量）。

@geindex register() (select.poll 方法)
@anchor{library/select select poll register}@anchor{26d2}
@deffn {方法} poll.register (fd[, eventmask])

在轮询对象中注册文件描述符。这样，将来调用 @ref{26a6,,poll()} 方法时将检查文件描述符是否有未处理的 I/O 事件。@emph{fd} 可以是整数，也可以是带有 @ref{1ea0,,fileno()} 方法的对象（该方法返回一个整数）。文件对象已经实现了 @code{fileno()}，因此它们也可以用作参数。

@emph{eventmask} 是可选的位掩码，用于指定要检查的事件类型，它可以是常量 @code{POLLIN}、@code{POLLPRI} 和 @code{POLLOUT} 的组合，如下表所述。如果未指定本参数，默认将会检查所有 3 种类型的事件。


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{POLLIN}

@tab

有要读取的数据

@item

@code{POLLPRI}

@tab

有紧急数据需要读取

@item

@code{POLLOUT}

@tab

准备输出：写不会阻塞

@item

@code{POLLERR}

@tab

某种错误条件

@item

@code{POLLHUP}

@tab

挂起

@item

@code{POLLRDHUP}

@tab

流套接字的对侧关闭了连接，或关闭了写入到一半的连接

@item

@code{POLLNVAL}

@tab

无效的请求：描述符未打开

@end multitable


注册已注册过的文件描述符不会报错，且等同于只注册一次该描述符。
@end deffn

@geindex modify() (select.poll 方法)
@anchor{library/select select poll modify}@anchor{26d3}
@deffn {方法} poll.modify (fd, eventmask)

修改一个已注册的文件描述符，等同于 @code{register(fd, eventmask)}。尝试修改未注册的文件描述符会抛出 @ref{1d3,,OSError} 异常，错误码为 @code{ENOENT}。
@end deffn

@geindex unregister() (select.poll 方法)
@anchor{library/select select poll unregister}@anchor{26d4}
@deffn {方法} poll.unregister (fd)

删除轮询对象正在跟踪的某个文件描述符。与 @ref{26d2,,register()} 方法类似，@emph{fd} 可以是整数，也可以是带有 @ref{1ea0,,fileno()} 方法的对象（该方法返回一个整数）。

尝试删除从未注册过的文件描述符会抛出 @ref{2c7,,KeyError} 异常。
@end deffn

@geindex poll() (select.poll 方法)
@anchor{library/select select poll poll}@anchor{66c}
@deffn {方法} poll.poll ([timeout])

轮询已注册的文件描述符的集合，并返回一个列表，列表可能为空，也可能有多个 @code{(fd, event)} 二元组，其中包含了要报告事件或错误的描述符。@emph{fd} 是文件描述符，@emph{event} 是一个位掩码，表示该描述符所报告的事件 --- @code{POLLIN} 表示可以读取，@code{POLLOUT} 表示该描述符可以写入，依此类推。空列表表示调用超时，没有任何文件描述符报告事件。如果指定了 @emph{timeout}，它将指定系统等待事件时，等待多长时间后返回（以毫秒为单位）。如果 @emph{timeout} 为空、负数 或 @ref{157,,None}，则本调用将阻塞，直到轮询对象发生事件为止。


在 3.5 版更改: 现在，当本函数被信号中断时，重试超时将从头开始计时，不会抛出 @ref{653,,InterruptedError} 异常。除非信号处理程序抛出异常（相关原理请参阅 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}）。

@end deffn

@node Kqueue 对象,Kevent 对象,Poll 对象,select --- 等待 I/O 完成
@anchor{library/select id1}@anchor{26d5}@anchor{library/select kqueue-objects}@anchor{26c3}
@subsubsection Kqueue 对象


@geindex close() (select.kqueue 方法)
@anchor{library/select select kqueue close}@anchor{26d6}
@deffn {方法} kqueue.close ()

关闭用于控制 kqueue 对象的文件描述符。
@end deffn

@geindex closed (select.kqueue 属性)
@anchor{library/select select kqueue closed}@anchor{26d7}
@deffn {属性} kqueue.closed

如果 kqueue 对象已关闭，则返回 @code{True}。
@end deffn

@geindex fileno() (select.kqueue 方法)
@anchor{library/select select kqueue fileno}@anchor{26d8}
@deffn {方法} kqueue.fileno ()

返回文件描述符对应的数字，该描述符用于控制 epoll 对象。
@end deffn

@geindex fromfd() (select.kqueue 方法)
@anchor{library/select select kqueue fromfd}@anchor{26d9}
@deffn {方法} kqueue.fromfd (fd)

根据给定的文件描述符创建 kqueue 对象。
@end deffn

@geindex control() (select.kqueue 方法)
@anchor{library/select select kqueue control}@anchor{66b}
@deffn {方法} kqueue.control (changelist, max_events[, timeout]) -> eventlist

Kevent 的低级接口


@itemize -

@item 
changelist 必须是一个可迭代对象，迭代出 kevent 对象，否则置为 @code{None}。

@item 
max_events 必须是 0 或一个正整数。

@item 
timeout 单位为秒（一般为浮点数），默认为 @code{None}，即永不超时。
@end itemize


在 3.5 版更改: 现在，当本函数被信号中断时，重试超时将从头开始计时，不会抛出 @ref{653,,InterruptedError} 异常。除非信号处理程序抛出异常（相关原理请参阅 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475}）。

@end deffn

@node Kevent 对象,,Kqueue 对象,select --- 等待 I/O 完成
@anchor{library/select id2}@anchor{26da}@anchor{library/select kevent-objects}@anchor{26c5}
@subsubsection Kevent 对象


@indicateurl{https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2}

@geindex ident (select.kevent 属性)
@anchor{library/select select kevent ident}@anchor{26db}
@deffn {属性} kevent.ident

用于区分事件的标识值。其解释取决于筛选器，但该值通常是文件描述符。在构造函数中，该标识值可以是整数或带有 @ref{1ea0,,fileno()} 方法的对象。kevent 在内部存储整数。
@end deffn

@geindex filter (select.kevent 属性)
@anchor{library/select select kevent filter}@anchor{26dc}
@deffn {属性} kevent.filter

内核筛选器的名称。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{KQ_FILTER_READ}

@tab

获取描述符，并在有数据可读时返回

@item

@code{KQ_FILTER_WRITE}

@tab

获取描述符，并在有数据可写时返回

@item

@code{KQ_FILTER_AIO}

@tab

AIO 请求

@item

@code{KQ_FILTER_VNODE}

@tab

当在 @emph{fflag} 中监视的一个或多个请求事件发生时返回

@item

@code{KQ_FILTER_PROC}

@tab

监视进程ID上的事件

@item

@code{KQ_FILTER_NETDEV}

@tab

观察网络设备上的事件[在Mac OS X上不可用]

@item

@code{KQ_FILTER_SIGNAL}

@tab

每当监视的信号传递到进程时返回

@item

@code{KQ_FILTER_TIMER}

@tab

建立一个任意的计时器

@end multitable

@end deffn

@geindex flags (select.kevent 属性)
@anchor{library/select select kevent flags}@anchor{26dd}
@deffn {属性} kevent.flags

筛选器操作。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{KQ_EV_ADD}

@tab

添加或修改事件

@item

@code{KQ_EV_DELETE}

@tab

从队列中删除事件

@item

@code{KQ_EV_ENABLE}

@tab

Permitscontrol() 返回事件

@item

@code{KQ_EV_DISABLE}

@tab

禁用事件

@item

@code{KQ_EV_ONESHOT}

@tab

在第一次发生后删除事件

@item

@code{KQ_EV_CLEAR}

@tab

检索事件后重置状态

@item

@code{KQ_EV_SYSFLAGS}

@tab

内部事件

@item

@code{KQ_EV_FLAG1}

@tab

内部事件

@item

@code{KQ_EV_EOF}

@tab

筛选特定EOF条件

@item

@code{KQ_EV_ERROR}

@tab

请参阅返回值

@end multitable

@end deffn

@geindex fflags (select.kevent 属性)
@anchor{library/select select kevent fflags}@anchor{26de}
@deffn {属性} kevent.fflags

筛选特定标志。

@code{KQ_FILTER_READ} 和  @code{KQ_FILTER_WRITE} 筛选标志：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{KQ_NOTE_LOWAT}

@tab

套接字缓冲区的低水线

@end multitable


@code{KQ_FILTER_VNODE} 筛选标志：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{KQ_NOTE_DELETE}

@tab

已调用 @emph{unlink()}

@item

@code{KQ_NOTE_WRITE}

@tab

发生写入

@item

@code{KQ_NOTE_EXTEND}

@tab

文件已扩展

@item

@code{KQ_NOTE_ATTRIB}

@tab

属性已更改

@item

@code{KQ_NOTE_LINK}

@tab

链接计数已更改

@item

@code{KQ_NOTE_RENAME}

@tab

文件已重命名

@item

@code{KQ_NOTE_REVOKE}

@tab

对文件的访问权限已被撤销

@end multitable


@code{KQ_FILTER_PROC} filter flags:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{KQ_NOTE_EXIT}

@tab

进程已退出

@item

@code{KQ_NOTE_FORK}

@tab

该进程调用了 @emph{fork()}

@item

@code{KQ_NOTE_EXEC}

@tab

进程已执行新进程

@item

@code{KQ_NOTE_PCTRLMASK}

@tab

内部筛选器标志

@item

@code{KQ_NOTE_PDATAMASK}

@tab

内部筛选器标志

@item

@code{KQ_NOTE_TRACK}

@tab

跨  @emph{fork()} 执行进程

@item

@code{KQ_NOTE_CHILD}

@tab

在  @emph{NOTE_TRACK} 的子进程上返回

@item

@code{KQ_NOTE_TRACKERR}

@tab

无法附加到子对象

@end multitable


@code{KQ_FILTER_NETDEV} 筛选器标志（在 Mac OS X 上不可用）：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{KQ_NOTE_LINKUP}

@tab

链接已建立

@item

@code{KQ_NOTE_LINKDOWN}

@tab

链接已断开

@item

@code{KQ_NOTE_LINKINV}

@tab

链接状态无效

@end multitable

@end deffn

@geindex data (select.kevent 属性)
@anchor{library/select select kevent data}@anchor{26df}
@deffn {属性} kevent.data

筛选特定数据。
@end deffn

@geindex udata (select.kevent 属性)
@anchor{library/select select kevent udata}@anchor{26e0}
@deffn {属性} kevent.udata

用户自定义值。
@end deffn

@node selectors --- 高级 I/O 复用库,asyncore --- 异步socket处理器,select --- 等待 I/O 完成,网络和进程间通信
@anchor{library/selectors doc}@anchor{26e1}@anchor{library/selectors module-selectors}@anchor{e6}@anchor{library/selectors selectors-high-level-i-o-multiplexing}@anchor{26e2}
@subsection @code{selectors} --- 高级 I/O 复用库


@geindex selectors (模块)


3.4 新版功能.


@strong{源码:} Lib/selectors.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/selectors.py}


__________________________________________________________________


@menu
* 概述: 概述<10>. 
* 类: 类<3>. 
* 例子: 例子<17>. 

@end menu

@node 概述<10>,类<3>,,selectors --- 高级 I/O 复用库
@anchor{library/selectors introduction}@anchor{26e3}
@subsubsection 概述


This module allows high-level and efficient I/O multiplexing, built upon the
@ref{e5,,select} module primitives. Users are encouraged to use this module
instead, unless they want precise control over the OS-level primitives used.

It defines a @ref{26e4,,BaseSelector} abstract base class, along with several
concrete implementations (@ref{25e3,,KqueueSelector}, @ref{445,,EpollSelector}...),
that can be used to wait for I/O readiness notification on multiple file
objects. In the following, "file object" refers to any object with a
@code{fileno()} method, or a raw file descriptor. See @ref{b3b,,file object}.

@ref{26e5,,DefaultSelector} is an alias to the most efficient implementation
available on the current platform: this should be the default choice for most
users.

@cartouche
@quotation 注解 
The type of file objects supported depends on the platform: on Windows,
sockets are supported, but not pipes, whereas on Unix, both are supported
(some other types may be supported as well, such as fifos or special file
devices).
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@item @ref{e5,,select}

Low-level I/O multiplexing module.
@end table


@node 类<3>,例子<17>,概述<10>,selectors --- 高级 I/O 复用库
@anchor{library/selectors classes}@anchor{26e6}
@subsubsection 类


Classes hierarchy:

@example
BaseSelector
+-- SelectSelector
+-- PollSelector
+-- EpollSelector
+-- DevpollSelector
+-- KqueueSelector
@end example

In the following, @emph{events} is a bitwise mask indicating which I/O events should
be waited for on a given file object. It can be a combination of the modules
constants below:

@quotation


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{EVENT_READ}

@tab

可读

@item

@code{EVENT_WRITE}

@tab

可写

@end multitable

@end quotation

@geindex SelectorKey (selectors 中的类)
@anchor{library/selectors selectors SelectorKey}@anchor{26e7}
@deffn {类} selectors.SelectorKey

A @ref{26e7,,SelectorKey} is a @ref{1b6,,namedtuple} used to
associate a file object to its underlying file descriptor, selected event
mask and attached data. It is returned by several @ref{26e4,,BaseSelector}
methods.

@geindex fileobj (selectors.SelectorKey 属性)
@anchor{library/selectors selectors SelectorKey fileobj}@anchor{26e8}
@deffn {属性} fileobj

File object registered.
@end deffn

@geindex fd (selectors.SelectorKey 属性)
@anchor{library/selectors selectors SelectorKey fd}@anchor{26e9}
@deffn {属性} fd

Underlying file descriptor.
@end deffn

@geindex events (selectors.SelectorKey 属性)
@anchor{library/selectors selectors SelectorKey events}@anchor{26ea}
@deffn {属性} events

Events that must be waited for on this file object.
@end deffn

@geindex data (selectors.SelectorKey 属性)
@anchor{library/selectors selectors SelectorKey data}@anchor{26eb}
@deffn {属性} data

Optional opaque data associated to this file object: for example, this
could be used to store a per-client session ID.
@end deffn
@end deffn

@geindex BaseSelector (selectors 中的类)
@anchor{library/selectors selectors BaseSelector}@anchor{26e4}
@deffn {类} selectors.BaseSelector

A @ref{26e4,,BaseSelector} is used to wait for I/O event readiness on multiple
file objects. It supports file stream registration, unregistration, and a
method to wait for I/O events on those streams, with an optional timeout.
It's an abstract base class, so cannot be instantiated. Use
@ref{26e5,,DefaultSelector} instead, or one of @ref{25e0,,SelectSelector},
@ref{25e3,,KqueueSelector} etc. if you want to specifically use an
implementation, and your platform supports it.
@ref{26e4,,BaseSelector} and its concrete implementations support the
@ref{563,,context manager} protocol.

@geindex register() (selectors.BaseSelector 方法)
@anchor{library/selectors selectors BaseSelector register}@anchor{26ec}
@deffn {方法} abstractmethod register (fileobj, events, data=None)

Register a file object for selection, monitoring it for I/O events.

@emph{fileobj} is the file object to monitor.  It may either be an integer
file descriptor or an object with a @code{fileno()} method.
@emph{events} is a bitwise mask of events to monitor.
@emph{data} is an opaque object.

This returns a new @ref{26e7,,SelectorKey} instance, or raises a
@ref{1fb,,ValueError} in case of invalid event mask or file descriptor, or
@ref{2c7,,KeyError} if the file object is already registered.
@end deffn

@geindex unregister() (selectors.BaseSelector 方法)
@anchor{library/selectors selectors BaseSelector unregister}@anchor{26ed}
@deffn {方法} abstractmethod unregister (fileobj)

Unregister a file object from selection, removing it from monitoring. A
file object shall be unregistered prior to being closed.

@emph{fileobj} must be a file object previously registered.

This returns the associated @ref{26e7,,SelectorKey} instance, or raises a
@ref{2c7,,KeyError} if @emph{fileobj} is not registered.  It will raise
@ref{1fb,,ValueError} if @emph{fileobj} is invalid (e.g. it has no @code{fileno()}
method or its @code{fileno()} method has an invalid return value).
@end deffn

@geindex modify() (selectors.BaseSelector 方法)
@anchor{library/selectors selectors BaseSelector modify}@anchor{448}
@deffn {方法} modify (fileobj, events, data=None)

Change a registered file object's monitored events or attached data.

This is equivalent to @code{BaseSelector.unregister(fileobj)()} followed
by @code{BaseSelector.register(fileobj, events, data)()}, except that it
can be implemented more efficiently.

This returns a new @ref{26e7,,SelectorKey} instance, or raises a
@ref{1fb,,ValueError} in case of invalid event mask or file descriptor, or
@ref{2c7,,KeyError} if the file object is not registered.
@end deffn

@geindex select() (selectors.BaseSelector 方法)
@anchor{library/selectors selectors BaseSelector select}@anchor{26ee}
@deffn {方法} abstractmethod select (timeout=None)

Wait until some registered file objects become ready, or the timeout
expires.

If @code{timeout > 0}, this specifies the maximum wait time, in seconds.
If @code{timeout <= 0}, the call won't block, and will report the currently
ready file objects.
If @emph{timeout} is @code{None}, the call will block until a monitored file object
becomes ready.

This returns a list of @code{(key, events)} tuples, one for each ready file
object.

@emph{key} is the @ref{26e7,,SelectorKey} instance corresponding to a ready file
object.
@emph{events} is a bitmask of events ready on this file object.

@cartouche
@quotation 注解 
This method can return before any file object becomes ready or the
timeout has elapsed if the current process receives a signal: in this
case, an empty list will be returned.
@end quotation
@end cartouche


在 3.5 版更改: The selector is now retried with a recomputed timeout when interrupted
by a signal if the signal handler did not raise an exception (see
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475} for the rationale), instead of returning an empty list
of events before the timeout.

@end deffn

@geindex close() (selectors.BaseSelector 方法)
@anchor{library/selectors selectors BaseSelector close}@anchor{26ef}
@deffn {方法} close ()

Close the selector.

This must be called to make sure that any underlying resource is freed.
The selector shall not be used once it has been closed.
@end deffn

@geindex get_key() (selectors.BaseSelector 方法)
@anchor{library/selectors selectors BaseSelector get_key}@anchor{26f0}
@deffn {方法} get_key (fileobj)

Return the key associated with a registered file object.

This returns the @ref{26e7,,SelectorKey} instance associated to this file
object, or raises @ref{2c7,,KeyError} if the file object is not registered.
@end deffn

@geindex get_map() (selectors.BaseSelector 方法)
@anchor{library/selectors selectors BaseSelector get_map}@anchor{26f1}
@deffn {方法} abstractmethod get_map ()

Return a mapping of file objects to selector keys.

This returns a @ref{18d9,,Mapping} instance mapping
registered file objects to their associated @ref{26e7,,SelectorKey}
instance.
@end deffn
@end deffn

@geindex DefaultSelector (selectors 中的类)
@anchor{library/selectors selectors DefaultSelector}@anchor{26e5}
@deffn {类} selectors.DefaultSelector

The default selector class, using the most efficient implementation
available on the current platform. This should be the default choice for
most users.
@end deffn

@geindex SelectSelector (selectors 中的类)
@anchor{library/selectors selectors SelectSelector}@anchor{25e0}
@deffn {类} selectors.SelectSelector

@ref{66d,,select.select()}-based selector.
@end deffn

@geindex PollSelector (selectors 中的类)
@anchor{library/selectors selectors PollSelector}@anchor{446}
@deffn {类} selectors.PollSelector

@ref{26a6,,select.poll()}-based selector.
@end deffn

@geindex EpollSelector (selectors 中的类)
@anchor{library/selectors selectors EpollSelector}@anchor{445}
@deffn {类} selectors.EpollSelector

@ref{8a3,,select.epoll()}-based selector.

@geindex fileno() (selectors.EpollSelector 方法)
@anchor{library/selectors selectors EpollSelector fileno}@anchor{26f2}
@deffn {方法} fileno ()

This returns the file descriptor used by the underlying
@ref{8a3,,select.epoll()} object.
@end deffn
@end deffn

@geindex DevpollSelector (selectors 中的类)
@anchor{library/selectors selectors DevpollSelector}@anchor{447}
@deffn {类} selectors.DevpollSelector

@ref{8a5,,select.devpoll()}-based selector.

@geindex fileno() (selectors.DevpollSelector 方法)
@anchor{library/selectors selectors DevpollSelector fileno}@anchor{26f3}
@deffn {方法} fileno ()

This returns the file descriptor used by the underlying
@ref{8a5,,select.devpoll()} object.
@end deffn


3.5 新版功能.

@end deffn

@geindex KqueueSelector (selectors 中的类)
@anchor{library/selectors selectors KqueueSelector}@anchor{25e3}
@deffn {类} selectors.KqueueSelector

@ref{26c2,,select.kqueue()}-based selector.

@geindex fileno() (selectors.KqueueSelector 方法)
@anchor{library/selectors selectors KqueueSelector fileno}@anchor{26f4}
@deffn {方法} fileno ()

This returns the file descriptor used by the underlying
@ref{26c2,,select.kqueue()} object.
@end deffn
@end deffn

@node 例子<17>,,类<3>,selectors --- 高级 I/O 复用库
@anchor{library/selectors examples}@anchor{26f5}
@subsubsection 例子


Here is a simple echo server implementation:

@example
import selectors
import socket

sel = selectors.DefaultSelector()

def accept(sock, mask):
    conn, addr = sock.accept()  # Should be ready
    print('accepted', conn, 'from', addr)
    conn.setblocking(False)
    sel.register(conn, selectors.EVENT_READ, read)

def read(conn, mask):
    data = conn.recv(1000)  # Should be ready
    if data:
        print('echoing', repr(data), 'to', conn)
        conn.send(data)  # Hope it won't block
    else:
        print('closing', conn)
        sel.unregister(conn)
        conn.close()

sock = socket.socket()
sock.bind(('localhost', 1234))
sock.listen(100)
sock.setblocking(False)
sel.register(sock, selectors.EVENT_READ, accept)

while True:
    events = sel.select()
    for key, mask in events:
        callback = key.data
        callback(key.fileobj, mask)
@end example

@node asyncore --- 异步socket处理器,asynchat --- 异步 socket 指令/响应 处理器,selectors --- 高级 I/O 复用库,网络和进程间通信
@anchor{library/asyncore doc}@anchor{26f6}@anchor{library/asyncore asyncore-asynchronous-socket-handler}@anchor{26f7}@anchor{library/asyncore module-asyncore}@anchor{b}
@subsection @code{asyncore} --- 异步socket处理器


@geindex asyncore (模块)

@c heavily adapted from original documentation by Sam Rushing

@strong{源码：} Lib/asyncore.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncore.py}


3.6 版后已移除: 请使用 @ref{a,,asyncio} 替代。



__________________________________________________________________


@cartouche
@quotation 注解 
该模块仅为提供向后兼容。我们推荐在新代码中使用 @ref{a,,asyncio} 。
@end quotation
@end cartouche

该模块提供用于编写异步套接字服务客户端与服务端的基础构件。

只有两种方法让单个处理器上的程序“同一时间完成不止一件事”。 多线程编程是最简单和最流行的方法，但是还有另一种非常不同的技术，它可以让你拥有多线程的几乎所有优点，而无需实际使用多线程。 它仅仅在你的程序主要受 I/O 限制时有用，那么。 如果你的程序受处理器限制，那么先发制人的预定线程可能就是你真正需要的。 但是，网络服务器很少受处理器限制。

如果你的操作系统在其 I/O 库中支持 @code{select()} 系统调用（几乎所有操作系统），那么你可以使用它来同时处理多个通信通道；在 I/O 正在“后台”时进行其他工作。 虽然这种策略看起来很奇怪和复杂，特别是起初，它在很多方面比多线程编程更容易理解和控制。 @ref{b,,asyncore} 模块为您解决了许多难题，使得构建复杂的高性能网络服务器和客户端的任务变得轻而易举。 对于“会话”应用程序和协议，伴侣 @ref{9,,asynchat} 模块是非常宝贵的。

这两个模块背后的基本思想是创建一个或多个网络 @emph{通道} ，类的实例 @ref{bbc,,asyncore.dispatcher} 和 @ref{8af,,asynchat.async_chat} 。 创建通道会将它们添加到全局映射中，如果你不为它提供自己的 @emph{映射} ，则由 @ref{26f8,,loop()} 函数使用。

一旦创建了初始通道，调用 @ref{26f8,,loop()} 函数将激活通道服务，该服务将一直持续到最后一个通道（包括在异步服务期间已添加到映射中的任何通道）关闭。

@geindex loop() (在 asyncore 模块中)
@anchor{library/asyncore asyncore loop}@anchor{26f8}
@deffn {函数} asyncore.loop ([timeout[, use_poll[, map[, count]]]])

进入一个轮询循环，其在循环计数超出或所有打开的通道关闭后终止。 所有参数都是可选的。 @emph{count} 形参默认为 @code{None} ，导致循环仅在所有通道关闭时终止。 @emph{timeout} 形参为适当的 @ref{66d,,select()} 或 @ref{26a6,,poll()} 调用设置超时参数，以秒为单位; 默认值为30秒。 @emph{use_poll} 形参，如果为 True ，则表示 @ref{26a6,,poll()} 应优先使用 @code{select`（默认为`@w{`}False`()}）。

The @emph{map} parameter is a dictionary whose items are the channels to watch.
As channels are closed they are deleted from their map.  If @emph{map} is
omitted, a global map is used. Channels (instances of
@ref{bbc,,asyncore.dispatcher}, @ref{8af,,asynchat.async_chat} and subclasses
thereof) can freely be mixed in the map.
@end deffn

@geindex dispatcher (asyncore 中的类)
@anchor{library/asyncore asyncore dispatcher}@anchor{bbc}
@deffn {类} asyncore.dispatcher

The @ref{bbc,,dispatcher} class is a thin wrapper around a low-level socket
object. To make it more useful, it has a few methods for event-handling
which are called from the asynchronous loop.   Otherwise, it can be treated
as a normal non-blocking socket object.

The firing of low-level events at certain times or in certain connection
states tells the asynchronous loop that certain higher-level events have
taken place.  For example, if we have asked for a socket to connect to
another host, we know that the connection has been made when the socket
becomes writable for the first time (at this point you know that you may
write to it with the expectation of success).  The implied higher-level
events are:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Event

@tab

描述

@item

@code{handle_connect()}

@tab

Implied by the first read or write
event

@item

@code{handle_close()}

@tab

Implied by a read event with no data
available

@item

@code{handle_accepted()}

@tab

Implied by a read event on a listening
socket

@end multitable


During asynchronous processing, each mapped channel's @ref{26f9,,readable()} and
@ref{26fa,,writable()} methods are used to determine whether the channel's socket
should be added to the list of channels @code{select()}ed or
@code{poll()}ed for read and write events.

Thus, the set of channel events is larger than the basic socket events.  The
full set of methods that can be overridden in your subclass follows:

@geindex handle_read() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher handle_read}@anchor{26fb}
@deffn {方法} handle_read ()

Called when the asynchronous loop detects that a @code{read()} call on the
channel's socket will succeed.
@end deffn

@geindex handle_write() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher handle_write}@anchor{26fc}
@deffn {方法} handle_write ()

Called when the asynchronous loop detects that a writable socket can be
written.  Often this method will implement the necessary buffering for
performance.  For example:

@example
def handle_write(self):
    sent = self.send(self.buffer)
    self.buffer = self.buffer[sent:]
@end example
@end deffn

@geindex handle_expt() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher handle_expt}@anchor{26fd}
@deffn {方法} handle_expt ()

Called when there is out of band (OOB) data for a socket connection.  This
will almost never happen, as OOB is tenuously supported and rarely used.
@end deffn

@geindex handle_connect() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher handle_connect}@anchor{26fe}
@deffn {方法} handle_connect ()

Called when the active opener's socket actually makes a connection.  Might
send a "welcome" banner, or initiate a protocol negotiation with the
remote endpoint, for example.
@end deffn

@geindex handle_close() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher handle_close}@anchor{26ff}
@deffn {方法} handle_close ()

Called when the socket is closed.
@end deffn

@geindex handle_error() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher handle_error}@anchor{2700}
@deffn {方法} handle_error ()

Called when an exception is raised and not otherwise handled.  The default
version prints a condensed traceback.
@end deffn

@geindex handle_accept() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher handle_accept}@anchor{bbe}
@deffn {方法} handle_accept ()

Called on listening channels (passive openers) when a connection can be
established with a new remote endpoint that has issued a @ref{2701,,connect()}
call for the local endpoint. Deprecated in version 3.2; use
@ref{bbd,,handle_accepted()} instead.


3.2 版后已移除.

@end deffn

@geindex handle_accepted() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher handle_accepted}@anchor{bbd}
@deffn {方法} handle_accepted (sock, addr)

Called on listening channels (passive openers) when a connection has been
established with a new remote endpoint that has issued a @ref{2701,,connect()}
call for the local endpoint.  @emph{sock} is a @emph{new} socket object usable to
send and receive data on the connection, and @emph{addr} is the address
bound to the socket on the other end of the connection.


3.2 新版功能.

@end deffn

@geindex readable() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher readable}@anchor{26f9}
@deffn {方法} readable ()

Called each time around the asynchronous loop to determine whether a
channel's socket should be added to the list on which read events can
occur.  The default method simply returns @code{True}, indicating that by
default, all channels will be interested in read events.
@end deffn

@geindex writable() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher writable}@anchor{26fa}
@deffn {方法} writable ()

Called each time around the asynchronous loop to determine whether a
channel's socket should be added to the list on which write events can
occur.  The default method simply returns @code{True}, indicating that by
default, all channels will be interested in write events.
@end deffn

In addition, each channel delegates or extends many of the socket methods.
Most of these are nearly identical to their socket partners.

@geindex create_socket() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher create_socket}@anchor{2702}
@deffn {方法} create_socket (family=socket.AF_INET, type=socket.SOCK_STREAM)

This is identical to the creation of a normal socket, and will use the
same options for creation.  Refer to the @ref{ef,,socket} documentation for
information on creating sockets.


在 3.3 版更改: @emph{family} and @emph{type} arguments can be omitted.

@end deffn

@geindex connect() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher connect}@anchor{2701}
@deffn {方法} connect (address)

As with the normal socket object, @emph{address} is a tuple with the first
element the host to connect to, and the second the port number.
@end deffn

@geindex send() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher send}@anchor{2703}
@deffn {方法} send (data)

Send @emph{data} to the remote end-point of the socket.
@end deffn

@geindex recv() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher recv}@anchor{2704}
@deffn {方法} recv (buffer_size)

Read at most @emph{buffer_size} bytes from the socket's remote end-point.  An
empty bytes object implies that the channel has been closed from the
other end.

Note that @ref{2704,,recv()} may raise @ref{991,,BlockingIOError} , even though
@ref{66d,,select.select()} or @ref{26a6,,select.poll()} has reported the socket
ready for reading.
@end deffn

@geindex listen() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher listen}@anchor{2705}
@deffn {方法} listen (backlog)

Listen for connections made to the socket.  The @emph{backlog} argument
specifies the maximum number of queued connections and should be at least
1; the maximum value is system-dependent (usually 5).
@end deffn

@geindex bind() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher bind}@anchor{2706}
@deffn {方法} bind (address)

Bind the socket to @emph{address}.  The socket must not already be bound.  (The
format of @emph{address} depends on the address family --- refer to the
@ref{ef,,socket} documentation for more information.)  To mark
the socket as re-usable (setting the @code{SO_REUSEADDR} option), call
the @ref{bbc,,dispatcher} object's @code{set_reuse_addr()} method.
@end deffn

@geindex accept() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher accept}@anchor{bbf}
@deffn {方法} accept ()

Accept a connection.  The socket must be bound to an address and listening
for connections.  The return value can be either @code{None} or a pair
@code{(conn, address)} where @emph{conn} is a @emph{new} socket object usable to send
and receive data on the connection, and @emph{address} is the address bound to
the socket on the other end of the connection.
When @code{None} is returned it means the connection didn't take place, in
which case the server should just ignore this event and keep listening
for further incoming connections.
@end deffn

@geindex close() (asyncore.dispatcher 方法)
@anchor{library/asyncore asyncore dispatcher close}@anchor{2707}
@deffn {方法} close ()

Close the socket.  All future operations on the socket object will fail.
The remote end-point will receive no more data (after queued data is
flushed).  Sockets are automatically closed when they are
garbage-collected.
@end deffn
@end deffn

@geindex dispatcher_with_send (asyncore 中的类)
@anchor{library/asyncore asyncore dispatcher_with_send}@anchor{2708}
@deffn {类} asyncore.dispatcher_with_send

A @ref{bbc,,dispatcher} subclass which adds simple buffered output capability,
useful for simple clients. For more sophisticated usage use
@ref{8af,,asynchat.async_chat}.
@end deffn

@geindex file_dispatcher (asyncore 中的类)
@anchor{library/asyncore asyncore file_dispatcher}@anchor{2709}
@deffn {类} asyncore.file_dispatcher

A file_dispatcher takes a file descriptor or @ref{b3b,,file object} along
with an optional map argument and wraps it for use with the @code{poll()}
or @code{loop()} functions.  If provided a file object or anything with a
@code{fileno()} method, that method will be called and passed to the
@ref{270a,,file_wrapper} constructor.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex file_wrapper (asyncore 中的类)
@anchor{library/asyncore asyncore file_wrapper}@anchor{270a}
@deffn {类} asyncore.file_wrapper

A file_wrapper takes an integer file descriptor and calls @ref{f23,,os.dup()} to
duplicate the handle so that the original handle may be closed independently
of the file_wrapper.  This class implements sufficient methods to emulate a
socket for use by the @ref{2709,,file_dispatcher} class.

@ref{12f5,,可用性}: Unix。
@end deffn

@menu
* asyncore Example basic HTTP client:: 
* asyncore Example basic echo server:: 

@end menu

@node asyncore Example basic HTTP client,asyncore Example basic echo server,,asyncore --- 异步socket处理器
@anchor{library/asyncore asyncore-example-1}@anchor{270b}@anchor{library/asyncore asyncore-example-basic-http-client}@anchor{270c}
@subsubsection asyncore Example basic HTTP client


Here is a very basic HTTP client that uses the @ref{bbc,,dispatcher} class to
implement its socket handling:

@example
import asyncore

class HTTPClient(asyncore.dispatcher):

    def __init__(self, host, path):
        asyncore.dispatcher.__init__(self)
        self.create_socket()
        self.connect( (host, 80) )
        self.buffer = bytes('GET %s HTTP/1.0\r\nHost: %s\r\n\r\n' %
                            (path, host), 'ascii')

    def handle_connect(self):
        pass

    def handle_close(self):
        self.close()

    def handle_read(self):
        print(self.recv(8192))

    def writable(self):
        return (len(self.buffer) > 0)

    def handle_write(self):
        sent = self.send(self.buffer)
        self.buffer = self.buffer[sent:]


client = HTTPClient('www.python.org', '/')
asyncore.loop()
@end example

@node asyncore Example basic echo server,,asyncore Example basic HTTP client,asyncore --- 异步socket处理器
@anchor{library/asyncore asyncore-example-2}@anchor{270d}@anchor{library/asyncore asyncore-example-basic-echo-server}@anchor{270e}
@subsubsection asyncore Example basic echo server


Here is a basic echo server that uses the @ref{bbc,,dispatcher} class to accept
connections and dispatches the incoming connections to a handler:

@example
import asyncore

class EchoHandler(asyncore.dispatcher_with_send):

    def handle_read(self):
        data = self.recv(8192)
        if data:
            self.send(data)

class EchoServer(asyncore.dispatcher):

    def __init__(self, host, port):
        asyncore.dispatcher.__init__(self)
        self.create_socket()
        self.set_reuse_addr()
        self.bind((host, port))
        self.listen(5)

    def handle_accepted(self, sock, addr):
        print('Incoming connection from %s' % repr(addr))
        handler = EchoHandler(sock)

server = EchoServer('localhost', 8080)
asyncore.loop()
@end example

@node asynchat --- 异步 socket 指令/响应 处理器,signal --- 设置异步事件处理程序,asyncore --- 异步socket处理器,网络和进程间通信
@anchor{library/asynchat doc}@anchor{270f}@anchor{library/asynchat asynchat-asynchronous-socket-command-response-handler}@anchor{2710}@anchor{library/asynchat module-asynchat}@anchor{9}
@subsection @code{asynchat} --- 异步 socket 指令/响应 处理器


@geindex asynchat (模块)

@strong{Source code:} Lib/asynchat.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asynchat.py}


3.6 版后已移除: 请使用 @ref{a,,asyncio} 替代。



__________________________________________________________________


@cartouche
@quotation 注解 
该模块仅为提供向后兼容。我们推荐在新代码中使用 @ref{a,,asyncio} 。
@end quotation
@end cartouche

This module builds on the @ref{b,,asyncore} infrastructure, simplifying
asynchronous clients and servers and making it easier to handle protocols
whose elements are terminated by arbitrary strings, or are of variable length.
@ref{9,,asynchat} defines the abstract class @ref{8af,,async_chat} that you
subclass, providing implementations of the @code{collect_incoming_data()} and
@code{found_terminator()} methods. It uses the same asynchronous loop as
@ref{b,,asyncore}, and the two types of channel, @ref{bbc,,asyncore.dispatcher}
and @ref{8af,,asynchat.async_chat}, can freely be mixed in the channel map.
Typically an @ref{bbc,,asyncore.dispatcher} server channel generates new
@ref{8af,,asynchat.async_chat} channel objects as it receives incoming
connection requests.

@geindex async_chat (asynchat 中的类)
@anchor{library/asynchat asynchat async_chat}@anchor{8af}
@deffn {类} asynchat.async_chat

This class is an abstract subclass of @ref{bbc,,asyncore.dispatcher}. To make
practical use of the code you must subclass @ref{8af,,async_chat}, providing
meaningful @ref{2711,,collect_incoming_data()} and @ref{2712,,found_terminator()}
methods.
The @ref{bbc,,asyncore.dispatcher} methods can be used, although not all make
sense in a message/response context.

Like @ref{bbc,,asyncore.dispatcher}, @ref{8af,,async_chat} defines a set of
events that are generated by an analysis of socket conditions after a
@code{select()} call. Once the polling loop has been started the
@ref{8af,,async_chat} object's methods are called by the event-processing
framework with no action on the part of the programmer.

Two class attributes can be modified, to improve performance, or possibly
even to conserve memory.

@geindex async_chat.ac_in_buffer_size() (在 asynchat 模块中)
@anchor{library/asynchat asynchat async_chat ac_in_buffer_size}@anchor{2713}
@deffn {数据} ac_in_buffer_size

The asynchronous input buffer size (default @code{4096}).
@end deffn

@geindex async_chat.ac_out_buffer_size() (在 asynchat 模块中)
@anchor{library/asynchat asynchat async_chat ac_out_buffer_size}@anchor{2714}
@deffn {数据} ac_out_buffer_size

The asynchronous output buffer size (default @code{4096}).
@end deffn

Unlike @ref{bbc,,asyncore.dispatcher}, @ref{8af,,async_chat} allows you to
define a @abbr{FIFO} queue of @emph{producers}. A producer need
have only one method, @code{more()}, which should return data to be
transmitted on the channel.
The producer indicates exhaustion (@emph{i.e.} that it contains no more data) by
having its @code{more()} method return the empty bytes object. At this point
the @ref{8af,,async_chat} object removes the producer from the queue and starts
using the next producer, if any. When the producer queue is empty the
@code{handle_write()} method does nothing. You use the channel object's
@ref{2715,,set_terminator()} method to describe how to recognize the end of, or
an important breakpoint in, an incoming transmission from the remote
endpoint.

To build a functioning @ref{8af,,async_chat} subclass your  input methods
@ref{2711,,collect_incoming_data()} and @ref{2712,,found_terminator()} must handle the
data that the channel receives asynchronously. The methods are described
below.
@end deffn

@geindex close_when_done() (asynchat.async_chat 方法)
@anchor{library/asynchat asynchat async_chat close_when_done}@anchor{2716}
@deffn {方法} async_chat.close_when_done ()

Pushes a @code{None} on to the producer queue. When this producer is popped off
the queue it causes the channel to be closed.
@end deffn

@geindex collect_incoming_data() (asynchat.async_chat 方法)
@anchor{library/asynchat asynchat async_chat collect_incoming_data}@anchor{2711}
@deffn {方法} async_chat.collect_incoming_data (data)

Called with @emph{data} holding an arbitrary amount of received data.  The
default method, which must be overridden, raises a
@ref{609,,NotImplementedError} exception.
@end deffn

@geindex discard_buffers() (asynchat.async_chat 方法)
@anchor{library/asynchat asynchat async_chat discard_buffers}@anchor{2717}
@deffn {方法} async_chat.discard_buffers ()

In emergencies this method will discard any data held in the input and/or
output buffers and the producer queue.
@end deffn

@geindex found_terminator() (asynchat.async_chat 方法)
@anchor{library/asynchat asynchat async_chat found_terminator}@anchor{2712}
@deffn {方法} async_chat.found_terminator ()

Called when the incoming data stream  matches the termination condition set
by @ref{2715,,set_terminator()}. The default method, which must be overridden,
raises a @ref{609,,NotImplementedError} exception. The buffered input data
should be available via an instance attribute.
@end deffn

@geindex get_terminator() (asynchat.async_chat 方法)
@anchor{library/asynchat asynchat async_chat get_terminator}@anchor{2718}
@deffn {方法} async_chat.get_terminator ()

Returns the current terminator for the channel.
@end deffn

@geindex push() (asynchat.async_chat 方法)
@anchor{library/asynchat asynchat async_chat push}@anchor{2719}
@deffn {方法} async_chat.push (data)

Pushes data on to the channel's queue to ensure its transmission.
This is all you need to do to have the channel write the data out to the
network, although it is possible to use your own producers in more complex
schemes to implement encryption and chunking, for example.
@end deffn

@geindex push_with_producer() (asynchat.async_chat 方法)
@anchor{library/asynchat asynchat async_chat push_with_producer}@anchor{271a}
@deffn {方法} async_chat.push_with_producer (producer)

Takes a producer object and adds it to the producer queue associated with
the channel.  When all currently-pushed producers have been exhausted the
channel will consume this producer's data by calling its @code{more()}
method and send the data to the remote endpoint.
@end deffn

@geindex set_terminator() (asynchat.async_chat 方法)
@anchor{library/asynchat asynchat async_chat set_terminator}@anchor{2715}
@deffn {方法} async_chat.set_terminator (term)

Sets the terminating condition to be recognized on the channel.  @code{term}
may be any of three types of value, corresponding to three different ways
to handle incoming protocol data.


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

term

@tab

描述

@item

@emph{string}

@tab

Will call @ref{2712,,found_terminator()} when the
string is found in the input stream

@item

@emph{integer}

@tab

Will call @ref{2712,,found_terminator()} when the
indicated number of characters have been
received

@item

@code{None}

@tab

The channel continues to collect data
forever

@end multitable


Note that any data following the terminator will be available for reading
by the channel after @ref{2712,,found_terminator()} is called.
@end deffn

@menu
* asynchat Example:: 

@end menu

@node asynchat Example,,,asynchat --- 异步 socket 指令/响应 处理器
@anchor{library/asynchat asynchat-example}@anchor{271b}@anchor{library/asynchat id1}@anchor{271c}
@subsubsection asynchat Example


The following partial example shows how HTTP requests can be read with
@ref{8af,,async_chat}.  A web server might create an
@code{http_request_handler} object for each incoming client connection.
Notice that initially the channel terminator is set to match the blank line at
the end of the HTTP headers, and a flag indicates that the headers are being
read.

Once the headers have been read, if the request is of type POST (indicating
that further data are present in the input stream) then the
@code{Content-Length:} header is used to set a numeric terminator to read the
right amount of data from the channel.

The @code{handle_request()} method is called once all relevant input has been
marshalled, after setting the channel terminator to @code{None} to ensure that
any extraneous data sent by the web client are ignored.

@example
import asynchat

class http_request_handler(asynchat.async_chat):

    def __init__(self, sock, addr, sessions, log):
        asynchat.async_chat.__init__(self, sock=sock)
        self.addr = addr
        self.sessions = sessions
        self.ibuffer = []
        self.obuffer = b""
        self.set_terminator(b"\r\n\r\n")
        self.reading_headers = True
        self.handling = False
        self.cgi_data = None
        self.log = log

    def collect_incoming_data(self, data):
        """Buffer the data"""
        self.ibuffer.append(data)

    def found_terminator(self):
        if self.reading_headers:
            self.reading_headers = False
            self.parse_headers(b"".join(self.ibuffer))
            self.ibuffer = []
            if self.op.upper() == b"POST":
                clen = self.headers.getheader("content-length")
                self.set_terminator(int(clen))
            else:
                self.handling = True
                self.set_terminator(None)
                self.handle_request()
        elif not self.handling:
            self.set_terminator(None)  # browsers sometimes over-send
            self.cgi_data = parse(self.headers, b"".join(self.ibuffer))
            self.handling = True
            self.ibuffer = []
            self.handle_request()
@end example

@node signal --- 设置异步事件处理程序,mmap --- 内存映射文件支持,asynchat --- 异步 socket 指令/响应 处理器,网络和进程间通信
@anchor{library/signal doc}@anchor{271d}@anchor{library/signal module-signal}@anchor{ea}@anchor{library/signal signal-set-handlers-for-asynchronous-events}@anchor{271e}
@subsection @code{signal} --- 设置异步事件处理程序


@geindex signal (模块)


__________________________________________________________________


该模块提供了在 Python 中使用信号处理程序的机制。

@menu
* 一般规则:: 
* 模块内容: 模块内容<5>. 
* 示例: 示例<9>. 
* Note on SIGPIPE:: 

@end menu

@node 一般规则,模块内容<5>,,signal --- 设置异步事件处理程序
@anchor{library/signal general-rules}@anchor{271f}
@subsubsection 一般规则


@ref{a78,,signal.signal()} 函数允许定义在接收到信号时执行的自定义处理程序。少量的默认处理程序已经设置： @ref{2720,,SIGPIPE} 被忽略（因此管道和套接字上的写入错误可以报告为普通的 Python 异常）以及如果父进程没有更改 @ref{2458,,SIGINT} ，则其会被翻译成 @ref{197,,KeyboardInterrupt} 异常。

一旦设置，特定信号的处理程序将保持安装，直到它被显式重置（ Python 模拟 BSD 样式接口而不管底层实现），但 @ref{2721,,SIGCHLD} 的处理程序除外，它遵循底层实现。

@menu
* 执行 Python 信号处理程序:: 
* 信号与线程:: 

@end menu

@node 执行 Python 信号处理程序,信号与线程,,一般规则
@anchor{library/signal execution-of-python-signal-handlers}@anchor{2722}
@subsubsection 执行 Python 信号处理程序


Python 信号处理程序不会在低级（ C ）信号处理程序中执行。相反，低级信号处理程序设置一个标志，告诉 @ref{2723,,virtual machine} 稍后执行相应的 Python 信号处理程序（例如在下一个 @ref{60f,,bytecode} 指令）。这会导致：


@itemize *

@item 
捕获同步错误是没有意义的，例如 @ref{2724,,SIGFPE} 或 @ref{2725,,SIGSEGV} ，它们是由 C 代码中的无效操作引起的。Python 将从信号处理程序返回到 C 代码，这可能会再次引发相同的信号，导致 Python 显然的挂起。 从Python 3.3开始，你可以使用 @ref{7d,,faulthandler} 模块来报告同步错误。

@item 
纯 C 中实现的长时间运行的计算（例如在大量文本上的正则表达式匹配）可以在任意时间内不间断地运行，而不管接收到任何信号。计算完成后将调用 Python 信号处理程序。
@end itemize

@node 信号与线程,,执行 Python 信号处理程序,一般规则
@anchor{library/signal id1}@anchor{2726}@anchor{library/signal signals-and-threads}@anchor{2727}
@subsubsection 信号与线程


Python 信号处理程序总是在主 Python 线程中执行，即使信号是在另一个线程中接收的。这意味着信号不能用作线程间通信的手段。 你可以使用 @ref{109,,threading} 模块中的同步原函数。

此外，只允许主线程设置新的信号处理程序。

@node 模块内容<5>,示例<9>,一般规则,signal --- 设置异步事件处理程序
@anchor{library/signal module-contents}@anchor{2728}
@subsubsection 模块内容



在 3.5 版更改: 信号（ SIG* ），处理程序（ @ref{2459,,SIG_DFL} ， @ref{245a,,SIG_IGN}）和 sigmask（ @ref{2729,,SIG_BLOCK} ， @ref{272a,,SIG_UNBLOCK} ， @ref{272b,,SIG_SETMASK} ）下面列出的相关常量变成了 @ref{588,,enums} 。 @ref{272c,,getsignal()} ， @ref{a74,,pthread_sigmask()} ， @ref{a76,,sigpending()} 和 @ref{a77,,sigwait()} 函数返回人类可读的 @ref{588,,enums} 。


在 @ref{ea,,signal} 模块中定义的变量是：

@geindex SIG_DFL() (在 signal 模块中)
@anchor{library/signal signal SIG_DFL}@anchor{2459}
@deffn {数据} signal.SIG_DFL

这是两种标准信号处理选项之一；它只会执行信号的默认函数。 例如，在大多数系统上，对于 @code{SIGQUIT} 的默认操作是转储核心并退出，而对于 @ref{2721,,SIGCHLD} 的默认操作是简单地忽略它。
@end deffn

@geindex SIG_IGN() (在 signal 模块中)
@anchor{library/signal signal SIG_IGN}@anchor{245a}
@deffn {数据} signal.SIG_IGN

这是另一个标准信号处理程序，它将简单地忽略给定的信号。
@end deffn

@geindex SIGABRT() (在 signal 模块中)
@anchor{library/signal signal SIGABRT}@anchor{272d}
@deffn {数据} signal.SIGABRT

Abort signal from @code{abort(3)}.
@end deffn

@geindex SIGALRM() (在 signal 模块中)
@anchor{library/signal signal SIGALRM}@anchor{272e}
@deffn {数据} signal.SIGALRM

Timer signal from @code{alarm(2)}.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex SIGBREAK() (在 signal 模块中)
@anchor{library/signal signal SIGBREAK}@anchor{272f}
@deffn {数据} signal.SIGBREAK

Interrupt from keyboard (CTRL + BREAK).

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex SIGBUS() (在 signal 模块中)
@anchor{library/signal signal SIGBUS}@anchor{2730}
@deffn {数据} signal.SIGBUS

Bus error (bad memory access).

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex SIGCHLD() (在 signal 模块中)
@anchor{library/signal signal SIGCHLD}@anchor{2721}
@deffn {数据} signal.SIGCHLD

Child process stopped or terminated.

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex SIGCLD() (在 signal 模块中)
@anchor{library/signal signal SIGCLD}@anchor{2731}
@deffn {数据} signal.SIGCLD

Alias to @ref{2721,,SIGCHLD}.
@end deffn

@geindex SIGCONT() (在 signal 模块中)
@anchor{library/signal signal SIGCONT}@anchor{1f5d}
@deffn {数据} signal.SIGCONT

Continue the process if it is currently stopped

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex SIGFPE() (在 signal 模块中)
@anchor{library/signal signal SIGFPE}@anchor{2724}
@deffn {数据} signal.SIGFPE

Floating-point exception. For example, division by zero.


@subsubheading 参见


@ref{1241,,ZeroDivisionError} is raised when the second argument of a division
or modulo operation is zero.

@end deffn

@geindex SIGHUP() (在 signal 模块中)
@anchor{library/signal signal SIGHUP}@anchor{2732}
@deffn {数据} signal.SIGHUP

Hangup detected on controlling terminal or death of controlling process.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex SIGILL() (在 signal 模块中)
@anchor{library/signal signal SIGILL}@anchor{2733}
@deffn {数据} signal.SIGILL

Illegal instruction.
@end deffn

@geindex SIGINT() (在 signal 模块中)
@anchor{library/signal signal SIGINT}@anchor{2458}
@deffn {数据} signal.SIGINT

Interrupt from keyboard (CTRL + C).

Default action is to raise @ref{197,,KeyboardInterrupt}.
@end deffn

@geindex SIGKILL() (在 signal 模块中)
@anchor{library/signal signal SIGKILL}@anchor{2734}
@deffn {数据} signal.SIGKILL

Kill signal.

It cannot be caught, blocked, or ignored.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex SIGPIPE() (在 signal 模块中)
@anchor{library/signal signal SIGPIPE}@anchor{2720}
@deffn {数据} signal.SIGPIPE

Broken pipe: write to pipe with no readers.

Default action is to ignore the signal.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex SIGSEGV() (在 signal 模块中)
@anchor{library/signal signal SIGSEGV}@anchor{2725}
@deffn {数据} signal.SIGSEGV

Segmentation fault: invalid memory reference.
@end deffn

@geindex SIGTERM() (在 signal 模块中)
@anchor{library/signal signal SIGTERM}@anchor{250b}
@deffn {数据} signal.SIGTERM

Termination signal.
@end deffn

@geindex SIGUSR1() (在 signal 模块中)
@anchor{library/signal signal SIGUSR1}@anchor{2735}
@deffn {数据} signal.SIGUSR1

User-defined signal 1.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex SIGUSR2() (在 signal 模块中)
@anchor{library/signal signal SIGUSR2}@anchor{2736}
@deffn {数据} signal.SIGUSR2

User-defined signal 2.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex SIGWINCH() (在 signal 模块中)
@anchor{library/signal signal SIGWINCH}@anchor{2737}
@deffn {数据} signal.SIGWINCH

Window resize signal.

@ref{12f5,,可用性}: Unix。
@end deffn


@deffn {数据} SIG*

All the signal numbers are defined symbolically.  For example, the hangup signal
is defined as @ref{2732,,signal.SIGHUP}; the variable names are identical to the
names used in C programs, as found in @code{<signal.h>}.  The Unix man page for
'@code{signal()}' lists the existing signals (on some systems this is
@code{signal(2)}, on others the list is in @code{signal(7)}). Note that
not all systems define the same set of signal names; only those names defined by
the system are defined by this module.
@end deffn

@geindex CTRL_C_EVENT() (在 signal 模块中)
@anchor{library/signal signal CTRL_C_EVENT}@anchor{1f39}
@deffn {数据} signal.CTRL_C_EVENT

对应于 @code{Ctrl+C} 击键事件的信号。此信号只能用于 @ref{cec,,os.kill()} 。

@ref{12f5,,可用性}: Windows。


3.2 新版功能.

@end deffn

@geindex CTRL_BREAK_EVENT() (在 signal 模块中)
@anchor{library/signal signal CTRL_BREAK_EVENT}@anchor{1f3a}
@deffn {数据} signal.CTRL_BREAK_EVENT

对应于 @code{Ctrl+Break} 击键事件的信号。此信号只能用于 @ref{cec,,os.kill()} 。

@ref{12f5,,可用性}: Windows。


3.2 新版功能.

@end deffn

@geindex NSIG() (在 signal 模块中)
@anchor{library/signal signal NSIG}@anchor{2738}
@deffn {数据} signal.NSIG

比最高信号数多一。
@end deffn

@geindex ITIMER_REAL() (在 signal 模块中)
@anchor{library/signal signal ITIMER_REAL}@anchor{2739}
@deffn {数据} signal.ITIMER_REAL

实时递减间隔计时器，并在到期时发送 @ref{272e,,SIGALRM} 。
@end deffn

@geindex ITIMER_VIRTUAL() (在 signal 模块中)
@anchor{library/signal signal ITIMER_VIRTUAL}@anchor{273a}
@deffn {数据} signal.ITIMER_VIRTUAL

仅在进程执行时递减间隔计时器，并在到期时发送 SIGVTALRM 。
@end deffn

@geindex ITIMER_PROF() (在 signal 模块中)
@anchor{library/signal signal ITIMER_PROF}@anchor{273b}
@deffn {数据} signal.ITIMER_PROF

Decrements interval timer both when the process executes and when the
system is executing on behalf of the process. Coupled with ITIMER_VIRTUAL,
this timer is usually used to profile the time spent by the application
in user and kernel space. SIGPROF is delivered upon expiration.
@end deffn

@geindex SIG_BLOCK() (在 signal 模块中)
@anchor{library/signal signal SIG_BLOCK}@anchor{2729}
@deffn {数据} signal.SIG_BLOCK

A possible value for the @emph{how} parameter to @ref{a74,,pthread_sigmask()}
indicating that signals are to be blocked.


3.3 新版功能.

@end deffn

@geindex SIG_UNBLOCK() (在 signal 模块中)
@anchor{library/signal signal SIG_UNBLOCK}@anchor{272a}
@deffn {数据} signal.SIG_UNBLOCK

A possible value for the @emph{how} parameter to @ref{a74,,pthread_sigmask()}
indicating that signals are to be unblocked.


3.3 新版功能.

@end deffn

@geindex SIG_SETMASK() (在 signal 模块中)
@anchor{library/signal signal SIG_SETMASK}@anchor{272b}
@deffn {数据} signal.SIG_SETMASK

A possible value for the @emph{how} parameter to @ref{a74,,pthread_sigmask()}
indicating that the signal mask is to be replaced.


3.3 新版功能.

@end deffn

The @ref{ea,,signal} module defines one exception:

@geindex ItimerError
@anchor{library/signal signal ItimerError}@anchor{273c}
@deffn {例外} signal.ItimerError

Raised to signal an error from the underlying @ref{273d,,setitimer()} or
@ref{273e,,getitimer()} implementation. Expect this error if an invalid
interval timer or a negative time is passed to @ref{273d,,setitimer()}.
This error is a subtype of @ref{1d3,,OSError}.


3.3 新版功能: This error used to be a subtype of @ref{98c,,IOError}, which is now an
alias of @ref{1d3,,OSError}.

@end deffn

The @ref{ea,,signal} module defines the following functions:

@geindex alarm() (在 signal 模块中)
@anchor{library/signal signal alarm}@anchor{273f}
@deffn {函数} signal.alarm (time)

If @emph{time} is non-zero, this function requests that a @ref{272e,,SIGALRM} signal be
sent to the process in @emph{time} seconds. Any previously scheduled alarm is
canceled (only one alarm can be scheduled at any time).  The returned value is
then the number of seconds before any previously set alarm was to have been
delivered. If @emph{time} is zero, no alarm is scheduled, and any scheduled alarm is
canceled.  If the return value is zero, no alarm is currently scheduled.

@ref{12f5,,Availability}: Unix.  See the man page @code{alarm(2)} for further
information.
@end deffn

@geindex getsignal() (在 signal 模块中)
@anchor{library/signal signal getsignal}@anchor{272c}
@deffn {函数} signal.getsignal (signalnum)

Return the current signal handler for the signal @emph{signalnum}. The returned value
may be a callable Python object, or one of the special values
@ref{245a,,signal.SIG_IGN}, @ref{2459,,signal.SIG_DFL} or @ref{157,,None}.  Here,
@ref{245a,,signal.SIG_IGN} means that the signal was previously ignored,
@ref{2459,,signal.SIG_DFL} means that the default way of handling the signal was
previously in use, and @code{None} means that the previous signal handler was not
installed from Python.
@end deffn

@geindex strsignal() (在 signal 模块中)
@anchor{library/signal signal strsignal}@anchor{fc2}
@deffn {函数} signal.strsignal (signalnum)

Return the system description of the signal @emph{signalnum}, such as
"Interrupt", "Segmentation fault", etc. Returns @ref{157,,None} if the signal
is not recognized.


3.8 新版功能.

@end deffn

@geindex valid_signals() (在 signal 模块中)
@anchor{library/signal signal valid_signals}@anchor{2740}
@deffn {函数} signal.valid_signals ()

Return the set of valid signal numbers on this platform.  This can be
less than @code{range(1, NSIG)} if some signals are reserved by the system
for internal use.


3.8 新版功能.

@end deffn

@geindex pause() (在 signal 模块中)
@anchor{library/signal signal pause}@anchor{2741}
@deffn {函数} signal.pause ()

Cause the process to sleep until a signal is received; the appropriate handler
will then be called.  Returns nothing.

@ref{12f5,,Availability}: Unix.  See the man page @code{signal(2)} for further
information.

See also @ref{a77,,sigwait()}, @ref{679,,sigwaitinfo()}, @ref{678,,sigtimedwait()} and
@ref{a76,,sigpending()}.
@end deffn

@geindex raise_signal() (在 signal 模块中)
@anchor{library/signal signal raise_signal}@anchor{2742}
@deffn {函数} signal.raise_signal (signum)

Sends a signal to the calling process. Returns nothing.


3.8 新版功能.

@end deffn

@geindex pthread_kill() (在 signal 模块中)
@anchor{library/signal signal pthread_kill}@anchor{a75}
@deffn {函数} signal.pthread_kill (thread_id, signalnum)

Send the signal @emph{signalnum} to the thread @emph{thread_id}, another thread in the
same process as the caller.  The target thread can be executing any code
(Python or not).  However, if the target thread is executing the Python
interpreter, the Python signal handlers will be @ref{2727,,executed by the main thread}.  Therefore, the only point of sending a
signal to a particular Python thread would be to force a running system call
to fail with @ref{653,,InterruptedError}.

Use @ref{aaa,,threading.get_ident()} or the @ref{1fb0,,ident}
attribute of @ref{234,,threading.Thread} objects to get a suitable value
for @emph{thread_id}.

If @emph{signalnum} is 0, then no signal is sent, but error checking is still
performed; this can be used to check if the target thread is still running.

Raises an @ref{12d0,,auditing event} @code{signal.pthread_kill} with arguments @code{thread_id}, @code{signalnum}.

@ref{12f5,,Availability}: Unix.  See the man page @code{pthread_kill(3)} for further
information.

See also @ref{cec,,os.kill()}.


3.3 新版功能.

@end deffn

@geindex pthread_sigmask() (在 signal 模块中)
@anchor{library/signal signal pthread_sigmask}@anchor{a74}
@deffn {函数} signal.pthread_sigmask (how, mask)

Fetch and/or change the signal mask of the calling thread.  The signal mask
is the set of signals whose delivery is currently blocked for the caller.
Return the old signal mask as a set of signals.

The behavior of the call is dependent on the value of @emph{how}, as follows.


@itemize *

@item 
@ref{2729,,SIG_BLOCK}: The set of blocked signals is the union of the current
set and the @emph{mask} argument.

@item 
@ref{272a,,SIG_UNBLOCK}: The signals in @emph{mask} are removed from the current
set of blocked signals.  It is permissible to attempt to unblock a
signal which is not blocked.

@item 
@ref{272b,,SIG_SETMASK}: The set of blocked signals is set to the @emph{mask}
argument.
@end itemize

@emph{mask} is a set of signal numbers (e.g. @{@ref{2458,,signal.SIGINT},
@ref{250b,,signal.SIGTERM}@}). Use @ref{2740,,valid_signals()} for a full
mask including all signals.

For example, @code{signal.pthread_sigmask(signal.SIG_BLOCK, [])} reads the
signal mask of the calling thread.

@ref{2734,,SIGKILL} and @code{SIGSTOP} cannot be blocked.

@ref{12f5,,Availability}: Unix.  See the man page @code{sigprocmask(3)} and
@code{pthread_sigmask(3)} for further information.

See also @ref{2741,,pause()}, @ref{a76,,sigpending()} and @ref{a77,,sigwait()}.


3.3 新版功能.

@end deffn

@geindex setitimer() (在 signal 模块中)
@anchor{library/signal signal setitimer}@anchor{273d}
@deffn {函数} signal.setitimer (which, seconds, interval=0.0)

Sets given interval timer (one of @ref{2739,,signal.ITIMER_REAL},
@ref{273a,,signal.ITIMER_VIRTUAL} or @ref{273b,,signal.ITIMER_PROF}) specified
by @emph{which} to fire after @emph{seconds} (float is accepted, different from
@ref{273f,,alarm()}) and after that every @emph{interval} seconds (if @emph{interval}
is non-zero). The interval timer specified by @emph{which} can be cleared by
setting @emph{seconds} to zero.

When an interval timer fires, a signal is sent to the process.
The signal sent is dependent on the timer being used;
@ref{2739,,signal.ITIMER_REAL} will deliver @ref{272e,,SIGALRM},
@ref{273a,,signal.ITIMER_VIRTUAL} sends @code{SIGVTALRM},
and @ref{273b,,signal.ITIMER_PROF} will deliver @code{SIGPROF}.

The old values are returned as a tuple: (delay, interval).

Attempting to pass an invalid interval timer will cause an
@ref{273c,,ItimerError}.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex getitimer() (在 signal 模块中)
@anchor{library/signal signal getitimer}@anchor{273e}
@deffn {函数} signal.getitimer (which)

Returns current value of a given interval timer specified by @emph{which}.

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex set_wakeup_fd() (在 signal 模块中)
@anchor{library/signal signal set_wakeup_fd}@anchor{3c6}
@deffn {函数} signal.set_wakeup_fd (fd, *, warn_on_full_buffer=True)

Set the wakeup file descriptor to @emph{fd}.  When a signal is received, the
signal number is written as a single byte into the fd.  This can be used by
a library to wakeup a poll or select call, allowing the signal to be fully
processed.

The old wakeup fd is returned (or -1 if file descriptor wakeup was not
enabled).  If @emph{fd} is -1, file descriptor wakeup is disabled.
If not -1, @emph{fd} must be non-blocking.  It is up to the library to remove
any bytes from @emph{fd} before calling poll or select again.

When threads are enabled, this function can only be called from the main thread;
attempting to call it from other threads will cause a @ref{1fb,,ValueError}
exception to be raised.

There are two common ways to use this function. In both approaches,
you use the fd to wake up when a signal arrives, but then they
differ in how they determine @emph{which} signal or signals have
arrived.

In the first approach, we read the data out of the fd's buffer, and
the byte values give you the signal numbers. This is simple, but in
rare cases it can run into a problem: generally the fd will have a
limited amount of buffer space, and if too many signals arrive too
quickly, then the buffer may become full, and some signals may be
lost. If you use this approach, then you should set
@code{warn_on_full_buffer=True}, which will at least cause a warning
to be printed to stderr when signals are lost.

In the second approach, we use the wakeup fd @emph{only} for wakeups,
and ignore the actual byte values. In this case, all we care about
is whether the fd's buffer is empty or non-empty; a full buffer
doesn't indicate a problem at all. If you use this approach, then
you should set @code{warn_on_full_buffer=False}, so that your users
are not confused by spurious warning messages.


在 3.5 版更改: On Windows, the function now also supports socket handles.



在 3.7 版更改: Added @code{warn_on_full_buffer} parameter.

@end deffn

@geindex siginterrupt() (在 signal 模块中)
@anchor{library/signal signal siginterrupt}@anchor{a79}
@deffn {函数} signal.siginterrupt (signalnum, flag)

Change system call restart behaviour: if @emph{flag} is @ref{380,,False}, system
calls will be restarted when interrupted by signal @emph{signalnum}, otherwise
system calls will be interrupted.  Returns nothing.

@ref{12f5,,Availability}: Unix.  See the man page @code{siginterrupt(3)}
for further information.

Note that installing a signal handler with @ref{ea,,signal()} will reset the
restart behaviour to interruptible by implicitly calling
@code{siginterrupt()} with a true @emph{flag} value for the given signal.
@end deffn

@geindex signal() (在 signal 模块中)
@anchor{library/signal signal signal}@anchor{a78}
@deffn {函数} signal.signal (signalnum, handler)

Set the handler for signal @emph{signalnum} to the function @emph{handler}.  @emph{handler} can
be a callable Python object taking two arguments (see below), or one of the
special values @ref{245a,,signal.SIG_IGN} or @ref{2459,,signal.SIG_DFL}.  The previous
signal handler will be returned (see the description of @ref{272c,,getsignal()}
above).  (See the Unix man page @code{signal(2)} for further information.)

When threads are enabled, this function can only be called from the main thread;
attempting to call it from other threads will cause a @ref{1fb,,ValueError}
exception to be raised.

The @emph{handler} is called with two arguments: the signal number and the current
stack frame (@code{None} or a frame object; for a description of frame objects,
see the @ref{13ca,,description in the type hierarchy} or see the
attribute descriptions in the @ref{a0,,inspect} module).

On Windows, @ref{ea,,signal()} can only be called with @ref{272d,,SIGABRT},
@ref{2724,,SIGFPE}, @ref{2733,,SIGILL}, @ref{2458,,SIGINT}, @ref{2725,,SIGSEGV},
@ref{250b,,SIGTERM}, or @ref{272f,,SIGBREAK}.
A @ref{1fb,,ValueError} will be raised in any other case.
Note that not all systems define the same set of signal names; an
@ref{393,,AttributeError} will be raised if a signal name is not defined as
@code{SIG*} module level constant.
@end deffn

@geindex sigpending() (在 signal 模块中)
@anchor{library/signal signal sigpending}@anchor{a76}
@deffn {函数} signal.sigpending ()

Examine the set of signals that are pending for delivery to the calling
thread (i.e., the signals which have been raised while blocked).  Return the
set of the pending signals.

@ref{12f5,,Availability}: Unix.  See the man page @code{sigpending(2)} for further
information.

See also @ref{2741,,pause()}, @ref{a74,,pthread_sigmask()} and @ref{a77,,sigwait()}.


3.3 新版功能.

@end deffn

@geindex sigwait() (在 signal 模块中)
@anchor{library/signal signal sigwait}@anchor{a77}
@deffn {函数} signal.sigwait (sigset)

Suspend execution of the calling thread until the delivery of one of the
signals specified in the signal set @emph{sigset}.  The function accepts the signal
(removes it from the pending list of signals), and returns the signal number.

@ref{12f5,,Availability}: Unix.  See the man page @code{sigwait(3)} for further
information.

See also @ref{2741,,pause()}, @ref{a74,,pthread_sigmask()}, @ref{a76,,sigpending()},
@ref{679,,sigwaitinfo()} and @ref{678,,sigtimedwait()}.


3.3 新版功能.

@end deffn

@geindex sigwaitinfo() (在 signal 模块中)
@anchor{library/signal signal sigwaitinfo}@anchor{679}
@deffn {函数} signal.sigwaitinfo (sigset)

Suspend execution of the calling thread until the delivery of one of the
signals specified in the signal set @emph{sigset}.  The function accepts the
signal and removes it from the pending list of signals. If one of the
signals in @emph{sigset} is already pending for the calling thread, the function
will return immediately with information about that signal. The signal
handler is not called for the delivered signal. The function raises an
@ref{653,,InterruptedError} if it is interrupted by a signal that is not in
@emph{sigset}.

The return value is an object representing the data contained in the
@code{siginfo_t} structure, namely: @code{si_signo}, @code{si_code},
@code{si_errno}, @code{si_pid}, @code{si_uid}, @code{si_status},
@code{si_band}.

@ref{12f5,,Availability}: Unix.  See the man page @code{sigwaitinfo(2)} for further
information.

See also @ref{2741,,pause()}, @ref{a77,,sigwait()} and @ref{678,,sigtimedwait()}.


3.3 新版功能.



在 3.5 版更改: The function is now retried if interrupted by a signal not in @emph{sigset}
and the signal handler does not raise an exception (see 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475} for
the rationale).

@end deffn

@geindex sigtimedwait() (在 signal 模块中)
@anchor{library/signal signal sigtimedwait}@anchor{678}
@deffn {函数} signal.sigtimedwait (sigset, timeout)

Like @ref{679,,sigwaitinfo()}, but takes an additional @emph{timeout} argument
specifying a timeout. If @emph{timeout} is specified as @code{0}, a poll is
performed. Returns @ref{157,,None} if a timeout occurs.

@ref{12f5,,Availability}: Unix.  See the man page @code{sigtimedwait(2)} for further
information.

See also @ref{2741,,pause()}, @ref{a77,,sigwait()} and @ref{679,,sigwaitinfo()}.


3.3 新版功能.



在 3.5 版更改: The function is now retried with the recomputed @emph{timeout} if interrupted
by a signal not in @emph{sigset} and the signal handler does not raise an
exception (see 
@geindex Python 提高建议; PEP 475
PEP 475@footnote{https://www.python.org/dev/peps/pep-0475} for the rationale).

@end deffn

@node 示例<9>,Note on SIGPIPE,模块内容<5>,signal --- 设置异步事件处理程序
@anchor{library/signal example}@anchor{2743}@anchor{library/signal signal-example}@anchor{2744}
@subsubsection 示例


Here is a minimal example program. It uses the @ref{273f,,alarm()} function to limit
the time spent waiting to open a file; this is useful if the file is for a
serial device that may not be turned on, which would normally cause the
@ref{65f,,os.open()} to hang indefinitely.  The solution is to set a 5-second alarm
before opening the file; if the operation takes too long, the alarm signal will
be sent, and the handler raises an exception.

@example
import signal, os

def handler(signum, frame):
    print('Signal handler called with signal', signum)
    raise OSError("Couldn't open device!")

# Set the signal handler and a 5-second alarm
signal.signal(signal.SIGALRM, handler)
signal.alarm(5)

# This open() may hang indefinitely
fd = os.open('/dev/ttyS0', os.O_RDWR)

signal.alarm(0)          # Disable the alarm
@end example

@node Note on SIGPIPE,,示例<9>,signal --- 设置异步事件处理程序
@anchor{library/signal note-on-sigpipe}@anchor{2745}
@subsubsection Note on SIGPIPE


Piping output of your program to tools like @code{head(1)} will
cause a @ref{2720,,SIGPIPE} signal to be sent to your process when the receiver
of its standard output closes early.  This results in an exception
like @code{BrokenPipeError: [Errno 32] Broken pipe}.  To handle this
case, wrap your entry point to catch this exception as follows:

@example
import os
import sys

def main():
    try:
        # simulate large output (your code replaces this loop)
        for x in range(10000):
            print("y")
        # flush output here to force SIGPIPE to be triggered
        # while inside this try block.
        sys.stdout.flush()
    except BrokenPipeError:
        # Python flushes standard streams on exit; redirect remaining output
        # to devnull to avoid another BrokenPipeError at shutdown
        devnull = os.open(os.devnull, os.O_WRONLY)
        os.dup2(devnull, sys.stdout.fileno())
        sys.exit(1)  # Python exits with error code 1 on EPIPE

if __name__ == '__main__':
    main()
@end example

Do not set @ref{2720,,SIGPIPE}'s disposition to @ref{2459,,SIG_DFL}
in order to avoid @ref{997,,BrokenPipeError}.  Doing that would cause
your program to exit unexpectedly also whenever any socket connection
is interrupted while your program is still writing to it.

@node mmap --- 内存映射文件支持,,signal --- 设置异步事件处理程序,网络和进程间通信
@anchor{library/mmap doc}@anchor{2746}@anchor{library/mmap mmap-memory-mapped-file-support}@anchor{2747}@anchor{library/mmap module-mmap}@anchor{b3}
@subsection @code{mmap} --- 内存映射文件支持


@geindex mmap (模块)


__________________________________________________________________


内存映射文件对象的行为既像 @ref{32b,,bytearray} 又像 @ref{b3b,,文件对象}。 你可以在大部分接受 @ref{32b,,bytearray} 的地方使用 mmap 对象；例如，你可以使用 @ref{dd,,re} 模块来搜索一个内存映射文件。 你也可以通过执行 @code{obj[index] = 97} 来修改单个字节，或者通过对切片赋值来修改一个子序列: @code{obj[i1:i2] = b'...'}。 你还可以在文件的当前位置开始读取和写入数据，并使用 @code{seek()} 前往另一个位置。

内存映射文件是由 @ref{1ec,,mmap} 构造函数创建的，其在 Unix 和 Windows 上是不同的。 无论哪种情况，你都必须为一个打开的文件提供文件描述符以进行更新。 如果你希望映射一个已有的 Python 文件对象，请使用该对象的 @code{fileno()} 方法来获取 @emph{fileno} 参数的正确值。 否则，你可以使用 @ref{65f,,os.open()} 函数来打开这个文件，这会直接返回一个文件描述符（结束时仍然需要关闭该文件）。

@cartouche
@quotation 注解 
如果要为可写的缓冲文件创建内存映射，则应当首先 @ref{1f84,,flush()} 该文件。 这确保了对缓冲区的本地修改在内存映射中可用。
@end quotation
@end cartouche

对于 Unix 和 Windows 版本的构造函数，可以将 @emph{access} 指定为可选的关键字参数。 @emph{access} 接受以下四个值之一： @code{ACCESS_READ} ， @code{ACCESS_WRITE} 或 @code{ACCESS_COPY} 分别指定只读，直写或写时复制内存，或 @code{ACCESS_DEFAULT} 推迟到 @emph{prot} 。 @emph{access} 可以在 Unix 和 Windows 上使用。如果未指定 @emph{access} ，则 Windows mmap 返回直写映射。这三种访问类型的初始内存值均取自指定的文件。向 @code{ACCESS_READ} 内存映射赋值会引发 @ref{192,,TypeError} 异常。 向 @code{ACCESS_WRITE} 内存映射赋值会影响内存和底层的文件。 向 @code{ACCESS_COPY} 内存映射赋值会影响内存，但不会更新底层的文件。


在 3.7 版更改: 添加了 @code{ACCESS_DEFAULT} 常量。


要映射匿名内存，应将 -1 作为 fileno 和 length 一起传递。

@geindex mmap (mmap 中的类)
@anchor{library/mmap mmap mmap}@anchor{1ec}
@deffn {类} mmap.mmap (fileno, length, tagname=None, access=ACCESS_DEFAULT[, offset])

@strong{（ Windows 版本）} 映射被文件句柄 @emph{fileno} 指定的文件的 @emph{length} 个字节，并创建一个 mmap 对象。如果 @emph{length} 大于当前文件大小，则文件将扩展为包含 @emph{length} 个字节。如果 @emph{length} 为 @code{0}，则映射的最大长度为当前文件大小。如果文件为空， Windows 会引发异常（你无法在Windows上创建空映射）。

如果 @emph{tagname} 被指定且不是 @code{None} ，则是为映射提供标签名称的字符串。 Windows 允许你对同一文件拥有许多不同的映射。如果指定现有标签的名称，则会打开该标签，否则将创建该名称的新标签。如果省略此参数或设置为 @code{None} ，则创建的映射不带名称。避免使用 tag 参数将有助于使代码在Unix和Windows之间可移植。

@emph{offset} 可以被指定为非负整数偏移量。 mmap 引用将相对于从文件开头的偏移。 @emph{offset} 默认为0。 @emph{offeset} 必须是 @code{ALLOCATIONGRANULARITY} 的倍数。

引发一个 @ref{12d0,,审计事件} @code{mmap.__new__} 附带参数 @code{fileno}, @code{length}, @code{access}, @code{offset}。
@end deffn


@deffn {类} mmap.mmap (fileno, length, flags=MAP_SHARED, prot=PROT_WRITE|PROT_READ, access=ACCESS_DEFAULT[, offset])

@strong{(Unix 版本)} 映射文件描述符 @emph{fileno} 指定的文件的 @emph{length} 个字节，并返回一个 mmap 对象。如果 @emph{length} 为 @code{0} ，则当调用 @ref{1ec,,mmap} 时，映射的最大长度将为文件的当前大小。

@emph{flags} specifies the nature of the mapping. @code{MAP_PRIVATE} creates a
private copy-on-write mapping, so changes to the contents of the mmap
object will be private to this process, and @code{MAP_SHARED} creates a
mapping that's shared with all other processes mapping the same areas of
the file.  The default value is @code{MAP_SHARED}.

@emph{prot}, if specified, gives the desired memory protection; the two most
useful values are @code{PROT_READ} and @code{PROT_WRITE}, to specify
that the pages may be read or written.  @emph{prot} defaults to
@code{PROT_READ | PROT_WRITE}.

@emph{access} may be specified in lieu of @emph{flags} and @emph{prot} as an optional
keyword parameter.  It is an error to specify both @emph{flags}, @emph{prot} and
@emph{access}.  See the description of @emph{access} above for information on how to
use this parameter.

@emph{offset} may be specified as a non-negative integer offset. mmap references
will be relative to the offset from the beginning of the file. @emph{offset}
defaults to 0. @emph{offset} must be a multiple of @code{ALLOCATIONGRANULARITY}
which is equal to @code{PAGESIZE} on Unix systems.

To ensure validity of the created memory mapping the file specified
by the descriptor @emph{fileno} is internally automatically synchronized
with physical backing store on Mac OS X and OpenVMS.

This example shows a simple way of using @ref{1ec,,mmap}:

@example
import mmap

# write a simple example file
with open("hello.txt", "wb") as f:
    f.write(b"Hello Python!\n")

with open("hello.txt", "r+b") as f:
    # memory-map the file, size 0 means whole file
    mm = mmap.mmap(f.fileno(), 0)
    # read content via standard file methods
    print(mm.readline())  # prints b"Hello Python!\n"
    # read content via slice notation
    print(mm[:5])  # prints b"Hello"
    # update content using slice notation;
    # note that new content must have same size
    mm[6:] = b" world!\n"
    # ... and read again using standard file methods
    mm.seek(0)
    print(mm.readline())  # prints b"Hello  world!\n"
    # close the map
    mm.close()
@end example

@ref{1ec,,mmap} can also be used as a context manager in a @ref{6e3,,with}
statement:

@example
import mmap

with mmap.mmap(-1, 13) as mm:
    mm.write(b"Hello world!")
@end example


3.2 新版功能: Context manager support.


The next example demonstrates how to create an anonymous map and exchange
data between the parent and child processes:

@example
import mmap
import os

mm = mmap.mmap(-1, 13)
mm.write(b"Hello world!")

pid = os.fork()

if pid == 0:  # In a child process
    mm.seek(0)
    print(mm.readline())

    mm.close()
@end example

引发一个 @ref{12d0,,审计事件} @code{mmap.__new__} 附带参数 @code{fileno}, @code{length}, @code{access}, @code{offset}。

Memory-mapped file objects support the following methods:

@geindex close() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap close}@anchor{2748}
@deffn {方法} close ()

Closes the mmap. Subsequent calls to other methods of the object will
result in a ValueError exception being raised. This will not close
the open file.
@end deffn

@geindex closed (mmap.mmap 属性)
@anchor{library/mmap mmap mmap closed}@anchor{2749}
@deffn {属性} closed

@code{True} if the file is closed.


3.2 新版功能.

@end deffn

@geindex find() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap find}@anchor{274a}
@deffn {方法} find (sub[, start[, end]])

Returns the lowest index in the object where the subsequence @emph{sub} is
found, such that @emph{sub} is contained in the range [@emph{start}, @emph{end}].
Optional arguments @emph{start} and @emph{end} are interpreted as in slice notation.
Returns @code{-1} on failure.


在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。

@end deffn

@geindex flush() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap flush}@anchor{2c3}
@deffn {方法} flush ([offset[, size]])

Flushes changes made to the in-memory copy of a file back to disk. Without
use of this call there is no guarantee that changes are written back before
the object is destroyed.  If @emph{offset} and @emph{size} are specified, only
changes to the given range of bytes will be flushed to disk; otherwise, the
whole extent of the mapping is flushed.  @emph{offset} must be a multiple of the
@code{PAGESIZE} or @code{ALLOCATIONGRANULARITY}.

@code{None} is returned to indicate success.  An exception is raised when the
call failed.


在 3.8 版更改: Previously, a nonzero value was returned on success; zero was returned
on error under Windows.  A zero value was returned on success; an
exception was raised on error under Unix.

@end deffn

@geindex madvise() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap madvise}@anchor{1ed}
@deffn {方法} madvise (option[, start[, length]])

Send advice @emph{option} to the kernel about the memory region beginning at
@emph{start} and extending @emph{length} bytes.  @emph{option} must be one of the
@ref{274b,,MADV_* constants} available on the system.  If
@emph{start} and @emph{length} are omitted, the entire mapping is spanned.  On
some systems (including Linux), @emph{start} must be a multiple of the
@code{PAGESIZE}.

Availability: Systems with the @code{madvise()} system call.


3.8 新版功能.

@end deffn

@geindex move() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap move}@anchor{274c}
@deffn {方法} move (dest, src, count)

Copy the @emph{count} bytes starting at offset @emph{src} to the destination index
@emph{dest}.  If the mmap was created with @code{ACCESS_READ}, then calls to
move will raise a @ref{192,,TypeError} exception.
@end deffn

@geindex read() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap read}@anchor{a1d}
@deffn {方法} read ([n])

Return a @ref{32a,,bytes} containing up to @emph{n} bytes starting from the
current file position. If the argument is omitted, @code{None} or negative,
return all bytes from the current file position to the end of the
mapping. The file position is updated to point after the bytes that were
returned.


在 3.3 版更改: Argument can be omitted or @code{None}.

@end deffn

@geindex read_byte() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap read_byte}@anchor{274d}
@deffn {方法} read_byte ()

Returns a byte at the current file position as an integer, and advances
the file position by 1.
@end deffn

@geindex readline() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap readline}@anchor{274e}
@deffn {方法} readline ()

Returns a single line, starting at the current file position and up to the
next newline.
@end deffn

@geindex resize() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap resize}@anchor{274f}
@deffn {方法} resize (newsize)

Resizes the map and the underlying file, if any. If the mmap was created
with @code{ACCESS_READ} or @code{ACCESS_COPY}, resizing the map will
raise a @ref{192,,TypeError} exception.
@end deffn

@geindex rfind() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap rfind}@anchor{2750}
@deffn {方法} rfind (sub[, start[, end]])

Returns the highest index in the object where the subsequence @emph{sub} is
found, such that @emph{sub} is contained in the range [@emph{start}, @emph{end}].
Optional arguments @emph{start} and @emph{end} are interpreted as in slice notation.
Returns @code{-1} on failure.


在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。

@end deffn

@geindex seek() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap seek}@anchor{2751}
@deffn {方法} seek (pos[, whence])

Set the file's current position.  @emph{whence} argument is optional and
defaults to @code{os.SEEK_SET} or @code{0} (absolute file positioning); other
values are @code{os.SEEK_CUR} or @code{1} (seek relative to the current
position) and @code{os.SEEK_END} or @code{2} (seek relative to the file's end).
@end deffn

@geindex size() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap size}@anchor{2752}
@deffn {方法} size ()

Return the length of the file, which can be larger than the size of the
memory-mapped area.
@end deffn

@geindex tell() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap tell}@anchor{2753}
@deffn {方法} tell ()

Returns the current position of the file pointer.
@end deffn

@geindex write() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap write}@anchor{2754}
@deffn {方法} write (bytes)

Write the bytes in @emph{bytes} into memory at the current position of the
file pointer and return the number of bytes written (never less than
@code{len(bytes)}, since if the write fails, a @ref{1fb,,ValueError} will be
raised).  The file position is updated to point after the bytes that
were written.  If the mmap was created with @code{ACCESS_READ}, then
writing to it will raise a @ref{192,,TypeError} exception.


在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。



在 3.6 版更改: The number of bytes written is now returned.

@end deffn

@geindex write_byte() (mmap.mmap 方法)
@anchor{library/mmap mmap mmap write_byte}@anchor{2755}
@deffn {方法} write_byte (byte)

Write the integer @emph{byte} into memory at the current
position of the file pointer; the file position is advanced by @code{1}. If
the mmap was created with @code{ACCESS_READ}, then writing to it will
raise a @ref{192,,TypeError} exception.
@end deffn
@end deffn

@menu
* MADV_* Constants:: 

@end menu

@node MADV_* Constants,,,mmap --- 内存映射文件支持
@anchor{library/mmap madv-constants}@anchor{2756}@anchor{library/mmap madvise-constants}@anchor{274b}
@subsubsection MADV_* Constants


@geindex MADV_NORMAL() (在 mmap 模块中)
@geindex MADV_RANDOM() (在 mmap 模块中)
@geindex MADV_SEQUENTIAL() (在 mmap 模块中)
@geindex MADV_WILLNEED() (在 mmap 模块中)
@geindex MADV_DONTNEED() (在 mmap 模块中)
@geindex MADV_REMOVE() (在 mmap 模块中)
@geindex MADV_DONTFORK() (在 mmap 模块中)
@geindex MADV_DOFORK() (在 mmap 模块中)
@geindex MADV_HWPOISON() (在 mmap 模块中)
@geindex MADV_MERGEABLE() (在 mmap 模块中)
@geindex MADV_UNMERGEABLE() (在 mmap 模块中)
@geindex MADV_SOFT_OFFLINE() (在 mmap 模块中)
@geindex MADV_HUGEPAGE() (在 mmap 模块中)
@geindex MADV_NOHUGEPAGE() (在 mmap 模块中)
@geindex MADV_DONTDUMP() (在 mmap 模块中)
@geindex MADV_DODUMP() (在 mmap 模块中)
@geindex MADV_FREE() (在 mmap 模块中)
@geindex MADV_NOSYNC() (在 mmap 模块中)
@geindex MADV_AUTOSYNC() (在 mmap 模块中)
@geindex MADV_NOCORE() (在 mmap 模块中)
@geindex MADV_CORE() (在 mmap 模块中)
@geindex MADV_PROTECT() (在 mmap 模块中)
@anchor{library/mmap mmap MADV_NORMAL}@anchor{2757}
@deffn {数据} mmap.MADV_NORMAL
@anchor{library/mmap mmap MADV_RANDOM}@anchor{2758}
@deffnx {数据} mmap.MADV_RANDOM
@anchor{library/mmap mmap MADV_SEQUENTIAL}@anchor{2759}
@deffnx {数据} mmap.MADV_SEQUENTIAL
@anchor{library/mmap mmap MADV_WILLNEED}@anchor{275a}
@deffnx {数据} mmap.MADV_WILLNEED
@anchor{library/mmap mmap MADV_DONTNEED}@anchor{275b}
@deffnx {数据} mmap.MADV_DONTNEED
@anchor{library/mmap mmap MADV_REMOVE}@anchor{275c}
@deffnx {数据} mmap.MADV_REMOVE
@anchor{library/mmap mmap MADV_DONTFORK}@anchor{275d}
@deffnx {数据} mmap.MADV_DONTFORK
@anchor{library/mmap mmap MADV_DOFORK}@anchor{275e}
@deffnx {数据} mmap.MADV_DOFORK
@anchor{library/mmap mmap MADV_HWPOISON}@anchor{275f}
@deffnx {数据} mmap.MADV_HWPOISON
@anchor{library/mmap mmap MADV_MERGEABLE}@anchor{2760}
@deffnx {数据} mmap.MADV_MERGEABLE
@anchor{library/mmap mmap MADV_UNMERGEABLE}@anchor{2761}
@deffnx {数据} mmap.MADV_UNMERGEABLE
@anchor{library/mmap mmap MADV_SOFT_OFFLINE}@anchor{2762}
@deffnx {数据} mmap.MADV_SOFT_OFFLINE
@anchor{library/mmap mmap MADV_HUGEPAGE}@anchor{2763}
@deffnx {数据} mmap.MADV_HUGEPAGE
@anchor{library/mmap mmap MADV_NOHUGEPAGE}@anchor{2764}
@deffnx {数据} mmap.MADV_NOHUGEPAGE
@anchor{library/mmap mmap MADV_DONTDUMP}@anchor{2765}
@deffnx {数据} mmap.MADV_DONTDUMP
@anchor{library/mmap mmap MADV_DODUMP}@anchor{2766}
@deffnx {数据} mmap.MADV_DODUMP
@anchor{library/mmap mmap MADV_FREE}@anchor{2767}
@deffnx {数据} mmap.MADV_FREE
@anchor{library/mmap mmap MADV_NOSYNC}@anchor{2768}
@deffnx {数据} mmap.MADV_NOSYNC
@anchor{library/mmap mmap MADV_AUTOSYNC}@anchor{2769}
@deffnx {数据} mmap.MADV_AUTOSYNC
@anchor{library/mmap mmap MADV_NOCORE}@anchor{276a}
@deffnx {数据} mmap.MADV_NOCORE
@anchor{library/mmap mmap MADV_CORE}@anchor{276b}
@deffnx {数据} mmap.MADV_CORE
@anchor{library/mmap mmap MADV_PROTECT}@anchor{276c}
@deffnx {数据} mmap.MADV_PROTECT

These options can be passed to @ref{1ed,,mmap.madvise()}.  Not every option will
be present on every system.

Availability: Systems with the madvise() system call.


3.8 新版功能.

@end deffn

@node 互联网数据处理,结构化标记处理工具,网络和进程间通信,Python 标准库
@anchor{library/netdata doc}@anchor{276d}@anchor{library/netdata internet-data-handling}@anchor{276e}@anchor{library/netdata netdata}@anchor{276f}
@section 互联网数据处理


本章介绍了支持处理互联网上常用数据格式的模块。

@menu
* email: email --- 电子邮件与 MIME 处理包. 电子邮件与 MIME 处理包
* json: json --- JSON 编码和解码器. JSON 编码和解码器
* mailcap: mailcap --- Mailcap 文件处理. Mailcap 文件处理
* mailbox: mailbox --- Manipulate mailboxes in various formats. Manipulate mailboxes in various formats
* mimetypes: mimetypes --- Map filenames to MIME types. Map filenames to MIME types
* base64: base64 --- Base16 Base32 Base64 Base85 数据编码. Base16, Base32, Base64, Base85 数据编码
* binhex: binhex --- 对binhex4文件进行编码和解码. 对binhex4文件进行编码和解码
* binascii: binascii --- 二进制和 ASCII 码互转. 二进制和 ASCII 码互转
* quopri: quopri --- 编码与解码经过 MIME 转码的可打印数据. 编码与解码经过 MIME 转码的可打印数据
* uu: uu --- 对 uuencode 文件进行编码与解码. 对 uuencode 文件进行编码与解码

@end menu

@node email --- 电子邮件与 MIME 处理包,json --- JSON 编码和解码器,,互联网数据处理
@anchor{library/email doc}@anchor{2770}@anchor{library/email email-an-email-and-mime-handling-package}@anchor{2771}@anchor{library/email module-email}@anchor{69}
@subsection @code{email} --- 电子邮件与 MIME 处理包


@geindex email (模块)

@strong{源码:} Lib/email/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/__init__.py}


__________________________________________________________________


The @ref{69,,email} package is a library for managing email messages.  It is
specifically @emph{not} designed to do any sending of email messages to SMTP
(
@geindex RFC; RFC 2821
RFC 2821@footnote{https://tools.ietf.org/html/rfc2821.html}), NNTP, or other servers; those are functions of modules such as
@ref{ed,,smtplib} and @ref{c0,,nntplib}.  The @ref{69,,email} package attempts to be as
RFC-compliant as possible, supporting 
@geindex RFC; RFC 5233
RFC 5233@footnote{https://tools.ietf.org/html/rfc5233.html} and 
@geindex RFC; RFC 6532
RFC 6532@footnote{https://tools.ietf.org/html/rfc6532.html}, as well as
such MIME-related RFCs as 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html}, 
@geindex RFC; RFC 2046
RFC 2046@footnote{https://tools.ietf.org/html/rfc2046.html}, 
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html}, 
@geindex RFC; RFC 2183
RFC 2183@footnote{https://tools.ietf.org/html/rfc2183.html},
and 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html}.

The overall structure of the email package can be divided into three major
components, plus a fourth component that controls the behavior of the other
components.

The central component of the package is an "object model" that represents email
messages.  An application interacts with the package primarily through the
object model interface defined in the @ref{72,,message} sub-module.  The
application can use this API to ask questions about an existing email, to
construct a new email, or to add or remove email subcomponents that themselves
use the same object model interface.  That is, following the nature of email
messages and their MIME subcomponents, the email object model is a tree
structure of objects that all provide the @ref{53d,,EmailMessage}
API.

The other two major components of the package are the @ref{74,,parser} and
the @ref{6e,,generator}.  The parser takes the serialized version of an
email message (a stream of bytes) and converts it into a tree of
@ref{53d,,EmailMessage} objects.  The generator takes an
@ref{53d,,EmailMessage} and turns it back into a serialized byte
stream.  (The parser and generator also handle streams of text characters, but
this usage is discouraged as it is too easy to end up with messages that are
not valid in one way or another.)

The control component is the @ref{75,,policy} module.  Every
@ref{53d,,EmailMessage}, every @ref{6e,,generator}, and every
@ref{74,,parser} has an associated @ref{75,,policy} object that
controls its behavior.  Usually an application only needs to specify the policy
when an @ref{53d,,EmailMessage} is created, either by directly
instantiating an @ref{53d,,EmailMessage}  to create a new email,
or by parsing an input stream using a @ref{74,,parser}.  But the policy can
be changed when the message is serialized using a @ref{6e,,generator}.
This allows, for example, a generic email message to be parsed from disk, but
to serialize it using standard SMTP settings when sending it to an email
server.

The email package does its best to hide the details of the various governing
RFCs from the application.  Conceptually the application should be able to
treat the email message as a structured tree of unicode text and binary
attachments, without having to worry about how these are represented when
serialized.  In practice, however, it is often necessary to be aware of at
least some of the rules governing MIME messages and their structure,
specifically the names and nature of the MIME "content types" and how they
identify multipart documents.  For the most part this knowledge should only be
required for more complex applications, and even then it should only be the
high level structure in question, and not the details of how those structures
are represented.  Since MIME content types are used widely in modern internet
software (not just email), this will be a familiar concept to many programmers.

The following sections describe the functionality of the @ref{69,,email} package.
We start with the @ref{72,,message} object model, which is the primary
interface an application will use, and follow that with the
@ref{74,,parser} and @ref{6e,,generator} components.  Then we cover the
@ref{75,,policy} controls, which completes the treatment of the main
components of the library.

The next three sections cover the exceptions the package may raise and the
defects (non-compliance with the RFCs) that the @ref{74,,parser} may
detect.  Then we cover the @ref{70,,headerregistry} and the
@ref{6b,,contentmanager} sub-components, which provide tools for doing more
detailed manipulation of headers and payloads, respectively.  Both of these
components contain features relevant to consuming and producing non-trivial
messages, but also document their extensibility APIs, which will be of interest
to advanced applications.

Following those is a set of examples of using the fundamental parts of the APIs
covered in the preceding sections.

The foregoing represent the modern (unicode friendly) API of the email package.
The remaining sections, starting with the @ref{53c,,Message}
class, cover the legacy @ref{53b,,compat32} API that deals much more
directly with the details of how email messages are represented.  The
@ref{53b,,compat32} API does @emph{not} hide the details of the RFCs from
the application, but for applications that need to operate at that level, they
can be useful tools.  This documentation is also relevant for applications that
are still using the @ref{53b,,compat32} API for backward
compatibility reasons.


在 3.6 版更改: Docs reorganized and rewritten to promote the new
@ref{53d,,EmailMessage}/@ref{9f2,,EmailPolicy}
API.


Contents of the @ref{69,,email} package documentation:

@menu
* email.message; Representing an email message: email message Representing an email message. 
* email.parser; Parsing email messages: email parser Parsing email messages. 
* email.generator; Generating MIME documents: email generator Generating MIME documents. 
* email.policy; Policy Objects: email policy Policy Objects. 
* email.errors; 异常和缺陷类: email errors 异常和缺陷类. 
* email.headerregistry; Custom Header Objects: email headerregistry Custom Header Objects. 
* email.contentmanager; Managing MIME Content: email contentmanager Managing MIME Content. 
* email; 示例: email 示例. 
* email.message.Message; Representing an email message using the compat32 API: email message Message Representing an email message using the compat32 API. 
* email.mime; Creating email and MIME objects from scratch: email mime Creating email and MIME objects from scratch. 
* email.header; Internationalized headers: email header Internationalized headers. 
* email.charset; Representing character sets: email charset Representing character sets. 
* email.encoders; 编码器: email encoders 编码器. 
* email.utils; 其他工具: email utils 其他工具. 
* email.iterators; 迭代器: email iterators 迭代器. 

@end menu

@node email message Representing an email message,email parser Parsing email messages,,email --- 电子邮件与 MIME 处理包
@anchor{library/email message doc}@anchor{2772}@anchor{library/email message email-message-representing-an-email-message}@anchor{2773}@anchor{library/email message module-email message}@anchor{72}
@subsubsection @code{email.message}: Representing an email message


@geindex email.message (模块)

@strong{Source code:} Lib/email/message.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/message.py}


__________________________________________________________________



3.6 新版功能: @footnote{@w{(1)} 
Originally added in 3.4 as a @ref{97a,,provisional module}.  Docs for legacy message class moved to
@ref{2774,,email.message.Message; Representing an email message using the compat32 API}.
}


The central class in the @ref{69,,email} package is the @ref{53d,,EmailMessage}
class, imported from the @ref{72,,email.message} module.  It is the base class for
the @ref{69,,email} object model.  @ref{53d,,EmailMessage} provides the core
functionality for setting and querying header fields, for accessing message
bodies, and for creating or modifying structured messages.

An email message consists of @emph{headers} and a @emph{payload} (which is also referred
to as the @emph{content}).  Headers are 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} or 
@geindex RFC; RFC 6532
RFC 6532@footnote{https://tools.ietf.org/html/rfc6532.html} style field names
and values, where the field name and value are separated by a colon.  The colon
is not part of either the field name or the field value.  The payload may be a
simple text message, or a binary object, or a structured sequence of
sub-messages each with their own set of headers and their own payload.  The
latter type of payload is indicated by the message having a MIME type such as
@code{multipart/*} or @code{message/rfc822}.

The conceptual model provided by an @ref{53d,,EmailMessage} object is that of an
ordered dictionary of headers coupled with a @emph{payload} that represents the
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} body of the message, which might be a list of sub-@code{EmailMessage}
objects.  In addition to the normal dictionary methods for accessing the header
names and values, there are methods for accessing specialized information from
the headers (for example the MIME content type), for operating on the payload,
for generating a serialized version of the message, and for recursively walking
over the object tree.

The @ref{53d,,EmailMessage} dictionary-like interface is indexed by the header
names, which must be ASCII values.  The values of the dictionary are strings
with some extra methods.  Headers are stored and returned in case-preserving
form, but field names are matched case-insensitively.  Unlike a real dict,
there is an ordering to the keys, and there can be duplicate keys.  Additional
methods are provided for working with headers that have duplicate keys.

The @emph{payload} is either a string or bytes object, in the case of simple message
objects, or a list of @ref{53d,,EmailMessage} objects, for MIME container
documents such as @code{multipart/*} and @code{message/rfc822}
message objects.

@geindex EmailMessage (email.message 中的类)
@anchor{library/email message email message EmailMessage}@anchor{53d}
@deffn {类} email.message.EmailMessage (policy=default)

If @emph{policy} is specified use the rules it specifies to update and serialize
the representation of the message.  If @emph{policy} is not set, use the
@ref{2775,,default} policy, which follows the rules of the email
RFCs except for line endings (instead of the RFC mandated @code{\r\n}, it uses
the Python standard @code{\n} line endings).  For more information see the
@ref{75,,policy} documentation.

@geindex as_string() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage as_string}@anchor{2776}
@deffn {方法} as_string (unixfrom=False, maxheaderlen=None, policy=None)

Return the entire message flattened as a string.  When optional
@emph{unixfrom} is true, the envelope header is included in the returned
string.  @emph{unixfrom} defaults to @code{False}.  For backward compatibility
with the base @ref{53c,,Message} class @emph{maxheaderlen} is
accepted, but defaults to @code{None}, which means that by default the line
length is controlled by the
@code{max_line_length} of the policy.  The
@emph{policy} argument may be used to override the default policy obtained
from the message instance.  This can be used to control some of the
formatting produced by the method, since the specified @emph{policy} will be
passed to the @ref{b45,,Generator}.

Flattening the message may trigger changes to the @ref{53d,,EmailMessage}
if defaults need to be filled in to complete the transformation to a
string (for example, MIME boundaries may be generated or modified).

Note that this method is provided as a convenience and may not be the
most useful way to serialize messages in your application, especially if
you are dealing with multiple messages.  See
@ref{b45,,email.generator.Generator} for a more flexible API for
serializing messages.  Note also that this method is restricted to
producing messages serialized as "7 bit clean" when
@ref{6cc,,utf8} is @code{False}, which is the default.


在 3.6 版更改: the default behavior when @emph{maxheaderlen}
is not specified was changed from defaulting to 0 to defaulting
to the value of @emph{max_line_length} from the policy.

@end deffn

@geindex __str__() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage __str__}@anchor{2777}
@deffn {方法} __str__ ()

Equivalent to @code{as_string(policy=self.policy.clone(utf8=True))}.  Allows
@code{str(msg)} to produce a string containing the serialized message in a
readable format.


在 3.4 版更改: the method was changed to use @code{utf8=True},
thus producing an 
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html}-like message representation, instead of
being a direct alias for @ref{2776,,as_string()}.

@end deffn

@geindex as_bytes() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage as_bytes}@anchor{2778}
@deffn {方法} as_bytes (unixfrom=False, policy=None)

Return the entire message flattened as a bytes object.  When optional
@emph{unixfrom} is true, the envelope header is included in the returned
string.  @emph{unixfrom} defaults to @code{False}.  The @emph{policy} argument may be
used to override the default policy obtained from the message instance.
This can be used to control some of the formatting produced by the
method, since the specified @emph{policy} will be passed to the
@ref{b46,,BytesGenerator}.

Flattening the message may trigger changes to the @ref{53d,,EmailMessage}
if defaults need to be filled in to complete the transformation to a
string (for example, MIME boundaries may be generated or modified).

Note that this method is provided as a convenience and may not be the
most useful way to serialize messages in your application, especially if
you are dealing with multiple messages.  See
@ref{b46,,email.generator.BytesGenerator} for a more flexible API for
serializing messages.
@end deffn

@geindex __bytes__() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage __bytes__}@anchor{2779}
@deffn {方法} __bytes__ ()

Equivalent to @ref{2778,,as_bytes()}.  Allows @code{bytes(msg)} to produce a
bytes object containing the serialized message.
@end deffn

@geindex is_multipart() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage is_multipart}@anchor{277a}
@deffn {方法} is_multipart ()

Return @code{True} if the message's payload is a list of
sub-@ref{53d,,EmailMessage} objects, otherwise return @code{False}.  When
@ref{277a,,is_multipart()} returns @code{False}, the payload should be a string
object (which might be a CTE encoded binary payload).  Note that
@ref{277a,,is_multipart()} returning @code{True} does not necessarily mean that
"msg.get_content_maintype() == 'multipart'" will return the @code{True}.
For example, @code{is_multipart} will return @code{True} when the
@ref{53d,,EmailMessage} is of type @code{message/rfc822}.
@end deffn

@geindex set_unixfrom() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage set_unixfrom}@anchor{277b}
@deffn {方法} set_unixfrom (unixfrom)

Set the message's envelope header to @emph{unixfrom}, which should be a
string.  (See @ref{277c,,mboxMessage} for a brief description of
this header.)
@end deffn

@geindex get_unixfrom() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_unixfrom}@anchor{277d}
@deffn {方法} get_unixfrom ()

Return the message's envelope header.  Defaults to @code{None} if the
envelope header was never set.
@end deffn

The following methods implement the mapping-like interface for accessing the
message's headers.  Note that there are some semantic differences
between these methods and a normal mapping (i.e. dictionary) interface.  For
example, in a dictionary there are no duplicate keys, but here there may be
duplicate message headers.  Also, in dictionaries there is no guaranteed
order to the keys returned by @ref{277e,,keys()}, but in an @ref{53d,,EmailMessage}
object, headers are always returned in the order they appeared in the
original message, or in which they were added to the message later.  Any
header deleted and then re-added is always appended to the end of the
header list.

These semantic differences are intentional and are biased toward
convenience in the most common use cases.

Note that in all cases, any envelope header present in the message is not
included in the mapping interface.

@geindex __len__() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage __len__}@anchor{277f}
@deffn {方法} __len__ ()

Return the total number of headers, including duplicates.
@end deffn

@geindex __contains__() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage __contains__}@anchor{2780}
@deffn {方法} __contains__ (name)

Return @code{True} if the message object has a field named @emph{name}. Matching is
done without regard to case and @emph{name} does not include the trailing
colon.  Used for the @code{in} operator.  For example:

@example
if 'message-id' in myMessage:
   print('Message-ID:', myMessage['message-id'])
@end example
@end deffn

@geindex __getitem__() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage __getitem__}@anchor{2781}
@deffn {方法} __getitem__ (name)

Return the value of the named header field.  @emph{name} does not include the
colon field separator.  If the header is missing, @code{None} is returned; a
@ref{2c7,,KeyError} is never raised.

Note that if the named field appears more than once in the message's
headers, exactly which of those field values will be returned is
undefined.  Use the @ref{2782,,get_all()} method to get the values of all the
extant headers named @emph{name}.

Using the standard (non-@code{compat32}) policies, the returned value is an
instance of a subclass of @ref{2783,,email.headerregistry.BaseHeader}.
@end deffn

@geindex __setitem__() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage __setitem__}@anchor{2784}
@deffn {方法} __setitem__ (name, val)

Add a header to the message with field name @emph{name} and value @emph{val}.  The
field is appended to the end of the message's existing headers.

Note that this does @emph{not} overwrite or delete any existing header with the same
name.  If you want to ensure that the new header is the only one present in the
message with field name @emph{name}, delete the field first, e.g.:

@example
del msg['subject']
msg['subject'] = 'Python roolz!'
@end example

If the @code{policy} defines certain headers to be unique (as the standard
policies do), this method may raise a @ref{1fb,,ValueError} when an attempt
is made to assign a value to such a header when one already exists.  This
behavior is intentional for consistency's sake, but do not depend on it
as we may choose to make such assignments do an automatic deletion of the
existing header in the future.
@end deffn

@geindex __delitem__() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage __delitem__}@anchor{2785}
@deffn {方法} __delitem__ (name)

Delete all occurrences of the field with name @emph{name} from the message's
headers.  No exception is raised if the named field isn't present in the
headers.
@end deffn

@geindex keys() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage keys}@anchor{277e}
@deffn {方法} keys ()

Return a list of all the message's header field names.
@end deffn

@geindex values() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage values}@anchor{2786}
@deffn {方法} values ()

Return a list of all the message's field values.
@end deffn

@geindex items() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage items}@anchor{2787}
@deffn {方法} items ()

Return a list of 2-tuples containing all the message's field headers and
values.
@end deffn

@geindex get() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get}@anchor{2788}
@deffn {方法} get (name, failobj=None)

Return the value of the named header field.  This is identical to
@ref{2781,,__getitem__()} except that optional @emph{failobj} is returned if the
named header is missing (@emph{failobj} defaults to @code{None}).
@end deffn

Here are some additional useful header related methods:

@geindex get_all() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_all}@anchor{2782}
@deffn {方法} get_all (name, failobj=None)

Return a list of all the values for the field named @emph{name}. If there are
no such named headers in the message, @emph{failobj} is returned (defaults to
@code{None}).
@end deffn

@geindex add_header() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage add_header}@anchor{2789}
@deffn {方法} add_header (_name, _value, **_params)

Extended header setting.  This method is similar to @ref{2784,,__setitem__()}
except that additional header parameters can be provided as keyword
arguments.  @emph{_name} is the header field to add and @emph{_value} is the
@emph{primary} value for the header.

For each item in the keyword argument dictionary @emph{_params}, the key is
taken as the parameter name, with underscores converted to dashes (since
dashes are illegal in Python identifiers).  Normally, the parameter will
be added as @code{key="value"} unless the value is @code{None}, in which case
only the key will be added.

If the value contains non-ASCII characters, the charset and language may
be explicitly controlled by specifying the value as a three tuple in the
format @code{(CHARSET, LANGUAGE, VALUE)}, where @code{CHARSET} is a string
naming the charset to be used to encode the value, @code{LANGUAGE} can
usually be set to @code{None} or the empty string (see 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html} for other
possibilities), and @code{VALUE} is the string value containing non-ASCII
code points.  If a three tuple is not passed and the value contains
non-ASCII characters, it is automatically encoded in 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html} format
using a @code{CHARSET} of @code{utf-8} and a @code{LANGUAGE} of @code{None}.

Here is an example:

@example
msg.add_header('Content-Disposition', 'attachment', filename='bud.gif')
@end example

This will add a header that looks like

@example
Content-Disposition: attachment; filename="bud.gif"
@end example

An example of the extended interface with non-ASCII characters:

@example
msg.add_header('Content-Disposition', 'attachment',
               filename=('iso-8859-1', '@w{'}, 'Fußballer.ppt'))
@end example
@end deffn

@geindex replace_header() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage replace_header}@anchor{278a}
@deffn {方法} replace_header (_name, _value)

Replace a header.  Replace the first header found in the message that
matches @emph{_name}, retaining header order and field name case of the
original header.  If no matching header is found, raise a
@ref{2c7,,KeyError}.
@end deffn

@geindex get_content_type() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_content_type}@anchor{278b}
@deffn {方法} get_content_type ()

Return the message's content type, coerced to lower case of the form
@code{maintype/subtype}.  If there is no @code{Content-Type}
header in the message return the value returned by
@ref{278c,,get_default_type()}.  If the @code{Content-Type} header is
invalid, return @code{text/plain}.

(According to 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html}, messages always have a default type,
@ref{278b,,get_content_type()} will always return a value.  
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html} defines
a message's default type to be @code{text/plain} unless it appears
inside a @code{multipart/digest} container, in which case it would
be @code{message/rfc822}.  If the @code{Content-Type} header
has an invalid type specification, 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html} mandates that the default
type be @code{text/plain}.)
@end deffn

@geindex get_content_maintype() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_content_maintype}@anchor{278d}
@deffn {方法} get_content_maintype ()

Return the message's main content type.  This is the @code{maintype}
part of the string returned by @ref{278b,,get_content_type()}.
@end deffn

@geindex get_content_subtype() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_content_subtype}@anchor{278e}
@deffn {方法} get_content_subtype ()

Return the message's sub-content type.  This is the @code{subtype}
part of the string returned by @ref{278b,,get_content_type()}.
@end deffn

@geindex get_default_type() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_default_type}@anchor{278c}
@deffn {方法} get_default_type ()

Return the default content type.  Most messages have a default content
type of @code{text/plain}, except for messages that are subparts of
@code{multipart/digest} containers.  Such subparts have a default
content type of @code{message/rfc822}.
@end deffn

@geindex set_default_type() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage set_default_type}@anchor{278f}
@deffn {方法} set_default_type (ctype)

Set the default content type.  @emph{ctype} should either be
@code{text/plain} or @code{message/rfc822}, although this is
not enforced.  The default content type is not stored in the
@code{Content-Type} header, so it only affects the return value of
the @code{get_content_type} methods when no @code{Content-Type}
header is present in the message.
@end deffn

@geindex set_param() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage set_param}@anchor{2790}
@deffn {方法} set_param (param, value, header='Content-Type', requote=True, charset=None, language='@w{'}, replace=False)

Set a parameter in the @code{Content-Type} header.  If the
parameter already exists in the header, replace its value with @emph{value}.
When @emph{header} is @code{Content-Type} (the default) and the header does not
yet exist in the message, add it, set its value to
@code{text/plain}, and append the new parameter value.  Optional
@emph{header} specifies an alternative header to @code{Content-Type}.

If the value contains non-ASCII characters, the charset and language may
be explicitly specified using the optional @emph{charset} and @emph{language}
parameters.  Optional @emph{language} specifies the 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html} language,
defaulting to the empty string.  Both @emph{charset} and @emph{language} should be
strings.  The default is to use the @code{utf8} @emph{charset} and @code{None} for
the @emph{language}.

If @emph{replace} is @code{False} (the default) the header is moved to the
end of the list of headers.  If @emph{replace} is @code{True}, the header
will be updated in place.

Use of the @emph{requote} parameter with @ref{53d,,EmailMessage} objects is
deprecated.

Note that existing parameter values of headers may be accessed through
the @code{params} attribute of the
header value (for example, @code{msg['Content-Type'].params['charset']}).


在 3.4 版更改: @code{replace} keyword was added.

@end deffn

@geindex del_param() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage del_param}@anchor{2791}
@deffn {方法} del_param (param, header='content-type', requote=True)

Remove the given parameter completely from the @code{Content-Type}
header.  The header will be re-written in place without the parameter or
its value.  Optional @emph{header} specifies an alternative to
@code{Content-Type}.

Use of the @emph{requote} parameter with @ref{53d,,EmailMessage} objects is
deprecated.
@end deffn

@geindex get_filename() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_filename}@anchor{2792}
@deffn {方法} get_filename (failobj=None)

Return the value of the @code{filename} parameter of the
@code{Content-Disposition} header of the message.  If the header
does not have a @code{filename} parameter, this method falls back to looking
for the @code{name} parameter on the @code{Content-Type} header.  If
neither is found, or the header is missing, then @emph{failobj} is returned.
The returned string will always be unquoted as per
@ref{2793,,email.utils.unquote()}.
@end deffn

@geindex get_boundary() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_boundary}@anchor{2794}
@deffn {方法} get_boundary (failobj=None)

Return the value of the @code{boundary} parameter of the
@code{Content-Type} header of the message, or @emph{failobj} if either
the header is missing, or has no @code{boundary} parameter.  The returned
string will always be unquoted as per @ref{2793,,email.utils.unquote()}.
@end deffn

@geindex set_boundary() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage set_boundary}@anchor{2795}
@deffn {方法} set_boundary (boundary)

Set the @code{boundary} parameter of the @code{Content-Type} header to
@emph{boundary}.  @ref{2795,,set_boundary()} will always quote @emph{boundary} if
necessary.  A @ref{2796,,HeaderParseError} is raised if the
message object has no @code{Content-Type} header.

Note that using this method is subtly different from deleting the old
@code{Content-Type} header and adding a new one with the new
boundary via @ref{2789,,add_header()}, because @ref{2795,,set_boundary()} preserves
the order of the @code{Content-Type} header in the list of
headers.
@end deffn

@geindex get_content_charset() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_content_charset}@anchor{2797}
@deffn {方法} get_content_charset (failobj=None)

Return the @code{charset} parameter of the @code{Content-Type} header,
coerced to lower case.  If there is no @code{Content-Type} header, or if
that header has no @code{charset} parameter, @emph{failobj} is returned.
@end deffn

@geindex get_charsets() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_charsets}@anchor{2798}
@deffn {方法} get_charsets (failobj=None)

Return a list containing the character set names in the message.  If the
message is a @code{multipart}, then the list will contain one element
for each subpart in the payload, otherwise, it will be a list of length 1.

Each item in the list will be a string which is the value of the
@code{charset} parameter in the @code{Content-Type} header for the
represented subpart.  If the subpart has no @code{Content-Type}
header, no @code{charset} parameter, or is not of the @code{text} main
MIME type, then that item in the returned list will be @emph{failobj}.
@end deffn

@geindex is_attachment() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage is_attachment}@anchor{2799}
@deffn {方法} is_attachment ()

Return @code{True} if there is a @code{Content-Disposition} header
and its (case insensitive) value is @code{attachment}, @code{False} otherwise.


在 3.4.2 版更改: is_attachment is now a method instead of a property, for consistency
with @ref{279a,,is_multipart()}.

@end deffn

@geindex get_content_disposition() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_content_disposition}@anchor{279b}
@deffn {方法} get_content_disposition ()

Return the lowercased value (without parameters) of the message's
@code{Content-Disposition} header if it has one, or @code{None}.  The
possible values for this method are @emph{inline}, @emph{attachment} or @code{None}
if the message follows 
@geindex RFC; RFC 2183
RFC 2183@footnote{https://tools.ietf.org/html/rfc2183.html}.


3.5 新版功能.

@end deffn

The following methods relate to interrogating and manipulating the content
(payload) of the message.

@geindex walk() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage walk}@anchor{279c}
@deffn {方法} walk ()

The @ref{279c,,walk()} method is an all-purpose generator which can be used to
iterate over all the parts and subparts of a message object tree, in
depth-first traversal order.  You will typically use @ref{279c,,walk()} as the
iterator in a @code{for} loop; each iteration returns the next subpart.

Here's an example that prints the MIME type of every part of a multipart
message structure:

@c from email import message_from_binary_file
@c with open('../Lib/test/test_email/data/msg_16.txt', 'rb') as f:
@c     msg = message_from_binary_file(f)

@example
>>> for part in msg.walk():
...     print(part.get_content_type())
multipart/report
text/plain
message/delivery-status
text/plain
text/plain
message/rfc822
text/plain
@end example

@code{walk} iterates over the subparts of any part where
@ref{277a,,is_multipart()} returns @code{True}, even though
@code{msg.get_content_maintype() == 'multipart'} may return @code{False}.  We
can see this in our example by making use of the @code{_structure} debug
helper function:

@example
>>> from email.iterators import _structure
>>> for part in msg.walk():
...     print(part.get_content_maintype() == 'multipart',
...           part.is_multipart())
True True
False False
False True
False False
False False
False True
False False
>>> _structure(msg)
multipart/report
    text/plain
    message/delivery-status
        text/plain
        text/plain
    message/rfc822
        text/plain
@end example

Here the @code{message} parts are not @code{multiparts}, but they do contain
subparts. @code{is_multipart()} returns @code{True} and @code{walk} descends
into the subparts.
@end deffn

@geindex get_body() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_body}@anchor{279d}
@deffn {方法} get_body (preferencelist=('related', 'html', 'plain'))

Return the MIME part that is the best candidate to be the "body" of the
message.

@emph{preferencelist} must be a sequence of strings from the set @code{related},
@code{html}, and @code{plain}, and indicates the order of preference for the
content type of the part returned.

Start looking for candidate matches with the object on which the
@code{get_body} method is called.

If @code{related} is not included in @emph{preferencelist}, consider the root
part (or subpart of the root part) of any related encountered as a
candidate if the (sub-)part matches a preference.

When encountering a @code{multipart/related}, check the @code{start} parameter
and if a part with a matching @code{Content-ID} is found, consider
only it when looking for candidate matches.  Otherwise consider only the
first (default root) part of the @code{multipart/related}.

If a part has a @code{Content-Disposition} header, only consider
the part a candidate match if the value of the header is @code{inline}.

If none of the candidates matches any of the preferences in
@emph{preferencelist}, return @code{None}.

Notes: (1) For most applications the only @emph{preferencelist} combinations
that really make sense are @code{('plain',)}, @code{('html', 'plain')}, and the
default @code{('related', 'html', 'plain')}.  (2) Because matching starts
with the object on which @code{get_body} is called, calling @code{get_body} on
a @code{multipart/related} will return the object itself unless
@emph{preferencelist} has a non-default value. (3) Messages (or message parts)
that do not specify a @code{Content-Type} or whose
@code{Content-Type} header is invalid will be treated as if they
are of type @code{text/plain}, which may occasionally cause @code{get_body} to
return unexpected results.
@end deffn

@geindex iter_attachments() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage iter_attachments}@anchor{279e}
@deffn {方法} iter_attachments ()

Return an iterator over all of the immediate sub-parts of the message
that are not candidate "body" parts.  That is, skip the first occurrence
of each of @code{text/plain}, @code{text/html}, @code{multipart/related}, or
@code{multipart/alternative} (unless they are explicitly marked as
attachments via @code{Content-Disposition: attachment}), and
return all remaining parts.  When applied directly to a
@code{multipart/related}, return an iterator over the all the related parts
except the root part (ie: the part pointed to by the @code{start} parameter,
or the first part if there is no @code{start} parameter or the @code{start}
parameter doesn't match the @code{Content-ID} of any of the
parts).  When applied directly to a @code{multipart/alternative} or a
non-@code{multipart}, return an empty iterator.
@end deffn

@geindex iter_parts() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage iter_parts}@anchor{279f}
@deffn {方法} iter_parts ()

Return an iterator over all of the immediate sub-parts of the message,
which will be empty for a non-@code{multipart}.  (See also
@ref{279c,,walk()}.)
@end deffn

@geindex get_content() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage get_content}@anchor{27a0}
@deffn {方法} get_content (*args, content_manager=None, **kw)

Call the @ref{27a1,,get_content()} method
of the @emph{content_manager}, passing self as the message object, and passing
along any other arguments or keywords as additional arguments.  If
@emph{content_manager} is not specified, use the @code{content_manager} specified
by the current @ref{75,,policy}.
@end deffn

@geindex set_content() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage set_content}@anchor{27a2}
@deffn {方法} set_content (*args, content_manager=None, **kw)

Call the @ref{27a3,,set_content()} method
of the @emph{content_manager}, passing self as the message object, and passing
along any other arguments or keywords as additional arguments.  If
@emph{content_manager} is not specified, use the @code{content_manager} specified
by the current @ref{75,,policy}.
@end deffn

@geindex make_related() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage make_related}@anchor{27a4}
@deffn {方法} make_related (boundary=None)

Convert a non-@code{multipart} message into a @code{multipart/related} message,
moving any existing @code{Content-} headers and payload into a
(new) first part of the @code{multipart}.  If @emph{boundary} is specified, use
it as the boundary string in the multipart, otherwise leave the boundary
to be automatically created when it is needed (for example, when the
message is serialized).
@end deffn

@geindex make_alternative() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage make_alternative}@anchor{27a5}
@deffn {方法} make_alternative (boundary=None)

Convert a non-@code{multipart} or a @code{multipart/related} into a
@code{multipart/alternative}, moving any existing @code{Content-}
headers and payload into a (new) first part of the @code{multipart}.  If
@emph{boundary} is specified, use it as the boundary string in the multipart,
otherwise leave the boundary to be automatically created when it is
needed (for example, when the message is serialized).
@end deffn

@geindex make_mixed() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage make_mixed}@anchor{27a6}
@deffn {方法} make_mixed (boundary=None)

Convert a non-@code{multipart}, a @code{multipart/related}, or a
@code{multipart-alternative} into a @code{multipart/mixed}, moving any existing
@code{Content-} headers and payload into a (new) first part of the
@code{multipart}.  If @emph{boundary} is specified, use it as the boundary string
in the multipart, otherwise leave the boundary to be automatically
created when it is needed (for example, when the message is serialized).
@end deffn

@geindex add_related() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage add_related}@anchor{27a7}
@deffn {方法} add_related (*args, content_manager=None, **kw)

If the message is a @code{multipart/related}, create a new message
object, pass all of the arguments to its @ref{27a2,,set_content()} method,
and @ref{27a8,,attach()} it to the @code{multipart}.  If
the message is a non-@code{multipart}, call @ref{27a4,,make_related()} and then
proceed as above.  If the message is any other type of @code{multipart},
raise a @ref{192,,TypeError}. If @emph{content_manager} is not specified, use
the @code{content_manager} specified by the current @ref{75,,policy}.
If the added part has no @code{Content-Disposition} header,
add one with the value @code{inline}.
@end deffn

@geindex add_alternative() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage add_alternative}@anchor{27a9}
@deffn {方法} add_alternative (*args, content_manager=None, **kw)

If the message is a @code{multipart/alternative}, create a new message
object, pass all of the arguments to its @ref{27a2,,set_content()} method, and
@ref{27a8,,attach()} it to the @code{multipart}.  If the
message is a non-@code{multipart} or @code{multipart/related}, call
@ref{27a5,,make_alternative()} and then proceed as above.  If the message is
any other type of @code{multipart}, raise a @ref{192,,TypeError}. If
@emph{content_manager} is not specified, use the @code{content_manager} specified
by the current @ref{75,,policy}.
@end deffn

@geindex add_attachment() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage add_attachment}@anchor{27aa}
@deffn {方法} add_attachment (*args, content_manager=None, **kw)

If the message is a @code{multipart/mixed}, create a new message object,
pass all of the arguments to its @ref{27a2,,set_content()} method, and
@ref{27a8,,attach()} it to the @code{multipart}.  If the
message is a non-@code{multipart}, @code{multipart/related}, or
@code{multipart/alternative}, call @ref{27a6,,make_mixed()} and then proceed as
above. If @emph{content_manager} is not specified, use the @code{content_manager}
specified by the current @ref{75,,policy}.  If the added part
has no @code{Content-Disposition} header, add one with the value
@code{attachment}.  This method can be used both for explicit attachments
(@code{Content-Disposition: attachment}) and @code{inline} attachments
(@code{Content-Disposition: inline}), by passing appropriate
options to the @code{content_manager}.
@end deffn

@geindex clear() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage clear}@anchor{27ab}
@deffn {方法} clear ()

Remove the payload and all of the headers.
@end deffn

@geindex clear_content() (email.message.EmailMessage 方法)
@anchor{library/email message email message EmailMessage clear_content}@anchor{27ac}
@deffn {方法} clear_content ()

Remove the payload and all of the @code{Content-} headers, leaving
all other headers intact and in their original order.
@end deffn

@ref{53d,,EmailMessage} objects have the following instance attributes:

@geindex preamble (email.message.EmailMessage 属性)
@anchor{library/email message email message EmailMessage preamble}@anchor{27ad}
@deffn {属性} preamble

The format of a MIME document allows for some text between the blank line
following the headers, and the first multipart boundary string. Normally,
this text is never visible in a MIME-aware mail reader because it falls
outside the standard MIME armor.  However, when viewing the raw text of
the message, or when viewing the message in a non-MIME aware reader, this
text can become visible.

The @emph{preamble} attribute contains this leading extra-armor text for MIME
documents.  When the @ref{b11,,Parser} discovers some text
after the headers but before the first boundary string, it assigns this
text to the message's @emph{preamble} attribute.  When the
@ref{b45,,Generator} is writing out the plain text
representation of a MIME message, and it finds the
message has a @emph{preamble} attribute, it will write this text in the area
between the headers and the first boundary.  See @ref{74,,email.parser} and
@ref{6e,,email.generator} for details.

Note that if the message object has no preamble, the @emph{preamble} attribute
will be @code{None}.
@end deffn

@geindex epilogue (email.message.EmailMessage 属性)
@anchor{library/email message email message EmailMessage epilogue}@anchor{27ae}
@deffn {属性} epilogue

The @emph{epilogue} attribute acts the same way as the @emph{preamble} attribute,
except that it contains text that appears between the last boundary and
the end of the message.  As with the @ref{27ad,,preamble},
if there is no epilog text this attribute will be @code{None}.
@end deffn

@geindex defects (email.message.EmailMessage 属性)
@anchor{library/email message email message EmailMessage defects}@anchor{27af}
@deffn {属性} defects

The @emph{defects} attribute contains a list of all the problems found when
parsing this message.  See @ref{6d,,email.errors} for a detailed description
of the possible parsing defects.
@end deffn
@end deffn

@geindex MIMEPart (email.message 中的类)
@anchor{library/email message email message MIMEPart}@anchor{83d}
@deffn {类} email.message.MIMEPart (policy=default)

This class represents a subpart of a MIME message.  It is identical to
@ref{53d,,EmailMessage}, except that no @code{MIME-Version} headers are
added when @ref{27a2,,set_content()} is called, since sub-parts do
not need their own @code{MIME-Version} headers.
@end deffn

@subsubheading 备注


@node email parser Parsing email messages,email generator Generating MIME documents,email message Representing an email message,email --- 电子邮件与 MIME 处理包
@anchor{library/email parser doc}@anchor{27b0}@anchor{library/email parser email-parser-parsing-email-messages}@anchor{27b1}@anchor{library/email parser module-email parser}@anchor{74}
@subsubsection @code{email.parser}: Parsing email messages


@geindex email.parser (模块)

@strong{Source code:} Lib/email/parser.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/parser.py}


__________________________________________________________________


Message object structures can be created in one of two ways: they can be
created from whole cloth by creating an @ref{53d,,EmailMessage}
object, adding headers using the dictionary interface, and adding payload(s)
using @ref{27a2,,set_content()} and related methods, or
they can be created by parsing a serialized representation of the email
message.

The @ref{69,,email} package provides a standard parser that understands most email
document structures, including MIME documents.  You can pass the parser a
bytes, string or file object, and the parser will return to you the root
@ref{53d,,EmailMessage} instance of the object structure.  For
simple, non-MIME messages the payload of this root object will likely be a
string containing the text of the message.  For MIME messages, the root object
will return @code{True} from its @ref{277a,,is_multipart()}
method, and the subparts can be accessed via the payload manipulation methods,
such as @ref{279d,,get_body()},
@ref{279f,,iter_parts()}, and
@ref{279c,,walk()}.

There are actually two parser interfaces available for use, the @ref{b11,,Parser}
API and the incremental @ref{27b2,,FeedParser} API.  The @ref{b11,,Parser} API is
most useful if you have the entire text of the message in memory, or if the
entire message lives in a file on the file system.  @ref{27b2,,FeedParser} is more
appropriate when you are reading the message from a stream which might block
waiting for more input (such as reading an email message from a socket).  The
@ref{27b2,,FeedParser} can consume and parse the message incrementally, and only
returns the root object when you close the parser.

Note that the parser can be extended in limited ways, and of course you can
implement your own parser completely from scratch.  All of the logic that
connects the @ref{69,,email} package's bundled parser and the
@ref{53d,,EmailMessage} class is embodied in the @code{policy}
class, so a custom parser can create message object trees any way it finds
necessary by implementing custom versions of the appropriate @code{policy}
methods.

@menu
* FeedParser API:: 
* Parser API:: 
* Additional notes:: 

@end menu

@node FeedParser API,Parser API,,email parser Parsing email messages
@anchor{library/email parser feedparser-api}@anchor{27b3}
@subsubsection FeedParser API


The @ref{b42,,BytesFeedParser}, imported from the @code{email.feedparser} module,
provides an API that is conducive to incremental parsing of email messages,
such as would be necessary when reading the text of an email message from a
source that can block (such as a socket).  The @ref{b42,,BytesFeedParser} can of
course be used to parse an email message fully contained in a @ref{5e3,,bytes-like object}, string, or file, but the @ref{b43,,BytesParser} API may be more
convenient for such use cases.  The semantics and results of the two parser
APIs are identical.

The @ref{b42,,BytesFeedParser}'s API is simple; you create an instance, feed it a
bunch of bytes until there's no more to feed it, then close the parser to
retrieve the root message object.  The @ref{b42,,BytesFeedParser} is extremely
accurate when parsing standards-compliant messages, and it does a very good job
of parsing non-compliant messages, providing information about how a message
was deemed broken.  It will populate a message object's
@ref{27af,,defects} attribute with a list of any
problems it found in a message.  See the @ref{6d,,email.errors} module for the
list of defects that it can find.

Here is the API for the @ref{b42,,BytesFeedParser}:

@geindex BytesFeedParser (email.parser 中的类)
@anchor{library/email parser email parser BytesFeedParser}@anchor{b42}
@deffn {类} email.parser.BytesFeedParser (_factory=None, *, policy=policy.compat32)

Create a @ref{b42,,BytesFeedParser} instance.  Optional @emph{_factory} is a
no-argument callable; if not specified use the
@ref{53a,,message_factory} from the @emph{policy}.  Call
@emph{_factory} whenever a new message object is needed.

If @emph{policy} is specified use the rules it specifies to update the
representation of the message.  If @emph{policy} is not set, use the
@ref{9ef,,compat32} policy, which maintains backward
compatibility with the Python 3.2 version of the email package and provides
@ref{53c,,Message} as the default factory.  All other policies
provide @ref{53d,,EmailMessage} as the default @emph{_factory}. For
more information on what else @emph{policy} controls, see the
@ref{75,,policy} documentation.

Note: @strong{The policy keyword should always be specified}; The default will
change to @ref{2775,,email.policy.default} in a future version of Python.


3.2 新版功能.



在 3.3 版更改: Added the @emph{policy} keyword.



在 3.6 版更改: @emph{_factory} defaults to the policy @code{message_factory}.


@geindex feed() (email.parser.BytesFeedParser 方法)
@anchor{library/email parser email parser BytesFeedParser feed}@anchor{27b4}
@deffn {方法} feed (data)

Feed the parser some more data.  @emph{data} should be a @ref{5e3,,bytes-like object} containing one or more lines.  The lines can be partial and the
parser will stitch such partial lines together properly.  The lines can
have any of the three common line endings: carriage return, newline, or
carriage return and newline (they can even be mixed).
@end deffn

@geindex close() (email.parser.BytesFeedParser 方法)
@anchor{library/email parser email parser BytesFeedParser close}@anchor{27b5}
@deffn {方法} close ()

Complete the parsing of all previously fed data and return the root
message object.  It is undefined what happens if @ref{27b4,,feed()} is called
after this method has been called.
@end deffn
@end deffn

@geindex FeedParser (email.parser 中的类)
@anchor{library/email parser email parser FeedParser}@anchor{27b2}
@deffn {类} email.parser.FeedParser (_factory=None, *, policy=policy.compat32)

Works like @ref{b42,,BytesFeedParser} except that the input to the
@ref{27b4,,feed()} method must be a string.  This is of limited
utility, since the only way for such a message to be valid is for it to
contain only ASCII text or, if @code{utf8} is
@code{True}, no binary attachments.


在 3.3 版更改: Added the @emph{policy} keyword.

@end deffn

@node Parser API,Additional notes,FeedParser API,email parser Parsing email messages
@anchor{library/email parser parser-api}@anchor{27b6}
@subsubsection Parser API


The @ref{b43,,BytesParser} class, imported from the @ref{74,,email.parser} module,
provides an API that can be used to parse a message when the complete contents
of the message are available in a @ref{5e3,,bytes-like object} or file.  The
@ref{74,,email.parser} module also provides @ref{b11,,Parser} for parsing strings,
and header-only parsers, @ref{9f6,,BytesHeaderParser} and
@ref{9f7,,HeaderParser}, which can be used if you're only interested in the
headers of the message.  @ref{9f6,,BytesHeaderParser} and @ref{9f7,,HeaderParser}
can be much faster in these situations, since they do not attempt to parse the
message body, instead setting the payload to the raw body.

@geindex BytesParser (email.parser 中的类)
@anchor{library/email parser email parser BytesParser}@anchor{b43}
@deffn {类} email.parser.BytesParser (_class=None, *, policy=policy.compat32)

Create a @ref{b43,,BytesParser} instance.  The @emph{_class} and @emph{policy}
arguments have the same meaning and semantics as the @emph{_factory}
and @emph{policy} arguments of @ref{b42,,BytesFeedParser}.

Note: @strong{The policy keyword should always be specified}; The default will
change to @ref{2775,,email.policy.default} in a future version of Python.


在 3.3 版更改: Removed the @emph{strict} argument that was deprecated in 2.4.  Added the
@emph{policy} keyword.



在 3.6 版更改: @emph{_class} defaults to the policy @code{message_factory}.


@geindex parse() (email.parser.BytesParser 方法)
@anchor{library/email parser email parser BytesParser parse}@anchor{27b7}
@deffn {方法} parse (fp, headersonly=False)

Read all the data from the binary file-like object @emph{fp}, parse the
resulting bytes, and return the message object.  @emph{fp} must support
both the @ref{169c,,readline()} and the @code{read()}
methods.

The bytes contained in @emph{fp} must be formatted as a block of 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}
(or, if @code{utf8} is @code{True}, 
@geindex RFC; RFC 6532
RFC 6532@footnote{https://tools.ietf.org/html/rfc6532.html})
style headers and header continuation lines, optionally preceded by an
envelope header.  The header block is terminated either by the end of the
data or by a blank line.  Following the header block is the body of the
message (which may contain MIME-encoded subparts, including subparts
with a @code{Content-Transfer-Encoding} of @code{8bit}).

Optional @emph{headersonly} is a flag specifying whether to stop parsing after
reading the headers or not.  The default is @code{False}, meaning it parses
the entire contents of the file.
@end deffn

@geindex parsebytes() (email.parser.BytesParser 方法)
@anchor{library/email parser email parser BytesParser parsebytes}@anchor{27b8}
@deffn {方法} parsebytes (bytes, headersonly=False)

Similar to the @ref{27b7,,parse()} method, except it takes a @ref{5e3,,bytes-like object} instead of a file-like object.  Calling this method on a
@ref{5e3,,bytes-like object} is equivalent to wrapping @emph{bytes} in a
@ref{795,,BytesIO} instance first and calling @ref{27b7,,parse()}.

Optional @emph{headersonly} is as with the @ref{27b7,,parse()} method.
@end deffn


3.2 新版功能.

@end deffn

@geindex BytesHeaderParser (email.parser 中的类)
@anchor{library/email parser email parser BytesHeaderParser}@anchor{9f6}
@deffn {类} email.parser.BytesHeaderParser (_class=None, *, policy=policy.compat32)

Exactly like @ref{b43,,BytesParser}, except that @emph{headersonly}
defaults to @code{True}.


3.3 新版功能.

@end deffn

@geindex Parser (email.parser 中的类)
@anchor{library/email parser email parser Parser}@anchor{b11}
@deffn {类} email.parser.Parser (_class=None, *, policy=policy.compat32)

This class is parallel to @ref{b43,,BytesParser}, but handles string input.


在 3.3 版更改: Removed the @emph{strict} argument.  Added the @emph{policy} keyword.



在 3.6 版更改: @emph{_class} defaults to the policy @code{message_factory}.


@geindex parse() (email.parser.Parser 方法)
@anchor{library/email parser email parser Parser parse}@anchor{27b9}
@deffn {方法} parse (fp, headersonly=False)

Read all the data from the text-mode file-like object @emph{fp}, parse the
resulting text, and return the root message object.  @emph{fp} must support
both the @ref{1b90,,readline()} and the
@ref{1f9d,,read()} methods on file-like objects.

Other than the text mode requirement, this method operates like
@ref{27b7,,BytesParser.parse()}.
@end deffn

@geindex parsestr() (email.parser.Parser 方法)
@anchor{library/email parser email parser Parser parsestr}@anchor{27ba}
@deffn {方法} parsestr (text, headersonly=False)

Similar to the @ref{27b9,,parse()} method, except it takes a string object
instead of a file-like object.  Calling this method on a string is
equivalent to wrapping @emph{text} in a @ref{827,,StringIO} instance first
and calling @ref{27b9,,parse()}.

Optional @emph{headersonly} is as with the @ref{27b9,,parse()} method.
@end deffn
@end deffn

@geindex HeaderParser (email.parser 中的类)
@anchor{library/email parser email parser HeaderParser}@anchor{9f7}
@deffn {类} email.parser.HeaderParser (_class=None, *, policy=policy.compat32)

Exactly like @ref{b11,,Parser}, except that @emph{headersonly}
defaults to @code{True}.
@end deffn

Since creating a message object structure from a string or a file object is such
a common task, four functions are provided as a convenience.  They are available
in the top-level @ref{69,,email} package namespace.

@geindex message_from_bytes() (在 email 模块中)
@anchor{library/email parser email message_from_bytes}@anchor{b40}
@deffn {函数} email.message_from_bytes (s, _class=None, *, policy=policy.compat32)

Return a message object structure from a @ref{5e3,,bytes-like object}.  This is
equivalent to @code{BytesParser().parsebytes(s)}.  Optional @emph{_class} and
@emph{policy} are interpreted as with the @ref{b43,,BytesParser} class
constructor.


3.2 新版功能.



在 3.3 版更改: Removed the @emph{strict} argument.  Added the @emph{policy} keyword.

@end deffn

@geindex message_from_binary_file() (在 email 模块中)
@anchor{library/email parser email message_from_binary_file}@anchor{b41}
@deffn {函数} email.message_from_binary_file (fp, _class=None, *, policy=policy.compat32)

Return a message object structure tree from an open binary @ref{b3b,,file object}.  This is equivalent to @code{BytesParser().parse(fp)}.  @emph{_class} and
@emph{policy} are interpreted as with the @ref{b43,,BytesParser} class
constructor.


3.2 新版功能.



在 3.3 版更改: Removed the @emph{strict} argument.  Added the @emph{policy} keyword.

@end deffn

@geindex message_from_string() (在 email 模块中)
@anchor{library/email parser email message_from_string}@anchor{27bb}
@deffn {函数} email.message_from_string (s, _class=None, *, policy=policy.compat32)

Return a message object structure from a string.  This is equivalent to
@code{Parser().parsestr(s)}.  @emph{_class} and @emph{policy} are interpreted as
with the @ref{b11,,Parser} class constructor.


在 3.3 版更改: Removed the @emph{strict} argument.  Added the @emph{policy} keyword.

@end deffn

@geindex message_from_file() (在 email 模块中)
@anchor{library/email parser email message_from_file}@anchor{27bc}
@deffn {函数} email.message_from_file (fp, _class=None, *, policy=policy.compat32)

Return a message object structure tree from an open @ref{b3b,,file object}.
This is equivalent to @code{Parser().parse(fp)}.  @emph{_class} and @emph{policy} are
interpreted as with the @ref{b11,,Parser} class constructor.


在 3.3 版更改: Removed the @emph{strict} argument.  Added the @emph{policy} keyword.



在 3.6 版更改: @emph{_class} defaults to the policy @code{message_factory}.

@end deffn

Here's an example of how you might use @ref{b40,,message_from_bytes()} at an
interactive Python prompt:

@example
>>> import email
>>> msg = email.message_from_bytes(myBytes)  
@end example

@node Additional notes,,Parser API,email parser Parsing email messages
@anchor{library/email parser additional-notes}@anchor{27bd}
@subsubsection Additional notes


Here are some notes on the parsing semantics:


@itemize *

@item 
Most non-@code{multipart} type messages are parsed as a single message
object with a string payload.  These objects will return @code{False} for
@ref{277a,,is_multipart()}, and
@ref{279f,,iter_parts()} will yield an empty list.

@item 
All @code{multipart} type messages will be parsed as a container message
object with a list of sub-message objects for their payload.  The outer
container message will return @code{True} for
@ref{277a,,is_multipart()}, and
@ref{279f,,iter_parts()} will yield a list of subparts.

@item 
Most messages with a content type of @code{message/*} (such as
@code{message/delivery-status} and @code{message/rfc822}) will also
be parsed as container object containing a list payload of length 1.  Their
@ref{277a,,is_multipart()} method will return @code{True}.
The single element yielded by @ref{279f,,iter_parts()}
will be a sub-message object.

@item 
Some non-standards-compliant messages may not be internally consistent about
their @code{multipart}-edness.  Such messages may have a
@code{Content-Type} header of type @code{multipart}, but their
@ref{277a,,is_multipart()} method may return @code{False}.
If such messages were parsed with the @ref{27b2,,FeedParser},
they will have an instance of the
@code{MultipartInvariantViolationDefect} class in their
@emph{defects} attribute list.  See @ref{6d,,email.errors} for details.
@end itemize

@node email generator Generating MIME documents,email policy Policy Objects,email parser Parsing email messages,email --- 电子邮件与 MIME 处理包
@anchor{library/email generator doc}@anchor{27be}@anchor{library/email generator email-generator-generating-mime-documents}@anchor{27bf}@anchor{library/email generator module-email generator}@anchor{6e}
@subsubsection @code{email.generator}: Generating MIME documents


@geindex email.generator (模块)

@strong{Source code:} Lib/email/generator.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/generator.py}


__________________________________________________________________


One of the most common tasks is to generate the flat (serialized) version of
the email message represented by a message object structure.  You will need to
do this if you want to send your message via @ref{73e,,smtplib.SMTP.sendmail()} or
the @ref{c0,,nntplib} module, or print the message on the console.  Taking a
message object structure and producing a serialized representation is the job
of the generator classes.

As with the @ref{74,,email.parser} module, you aren't limited to the functionality
of the bundled generator; you could write one from scratch yourself.  However
the bundled generator knows how to generate most email in a standards-compliant
way, should handle MIME and non-MIME email messages just fine, and is designed
so that the bytes-oriented parsing and generation operations are inverses,
assuming the same non-transforming @ref{75,,policy} is used for both.  That
is, parsing the serialized byte stream via the
@ref{b43,,BytesParser} class and then regenerating the serialized
byte stream using @ref{b46,,BytesGenerator} should produce output identical to
the input @footnote{@w{(1)} 
This statement assumes that you use the appropriate setting for
@code{unixfrom}, and that there are no @code{policy} settings calling for
automatic adjustments (for example,
@code{refold_source} must be @code{none}, which is
@emph{not} the default).  It is also not 100% true, since if the message
does not conform to the RFC standards occasionally information about the
exact original text is lost during parsing error recovery.  It is a goal
to fix these latter edge cases when possible.
}.  (On the other hand, using the generator on an
@ref{53d,,EmailMessage} constructed by program may result in
changes to the @ref{53d,,EmailMessage} object as defaults are
filled in.)

The @ref{b45,,Generator} class can be used to flatten a message into a text (as
opposed to binary) serialized representation, but since Unicode cannot
represent binary data directly, the message is of necessity transformed into
something that contains only ASCII characters, using the standard email RFC
Content Transfer Encoding techniques for encoding email messages for transport
over channels that are not "8 bit clean".

To accommodate reproducible processing of SMIME-signed messages
@ref{b45,,Generator} disables header folding for message parts of type
@code{multipart/signed} and all subparts.

@geindex BytesGenerator (email.generator 中的类)
@anchor{library/email generator email generator BytesGenerator}@anchor{b46}
@deffn {类} email.generator.BytesGenerator (outfp, mangle_from_=None, maxheaderlen=None, *, policy=None)

Return a @ref{b46,,BytesGenerator} object that will write any message provided
to the @ref{27c0,,flatten()} method, or any surrogateescape encoded text provided
to the @ref{27c1,,write()} method, to the @ref{1bfc,,file-like object} @emph{outfp}.
@emph{outfp} must support a @code{write} method that accepts binary data.

If optional @emph{mangle_from_} is @code{True}, put a @code{>} character in front of
any line in the body that starts with the exact string @code{"From "}, that is
@code{From} followed by a space at the beginning of a line.  @emph{mangle_from_}
defaults to the value of the @ref{6ca,,mangle_from_}
setting of the @emph{policy} (which is @code{True} for the
@ref{53b,,compat32} policy and @code{False} for all others).
@emph{mangle_from_} is intended for use when messages are stored in unix mbox
format (see @ref{ae,,mailbox} and WHY THE CONTENT-LENGTH FORMAT IS BAD@footnote{https://www.jwz.org/doc/content-length.html}).

If @emph{maxheaderlen} is not @code{None}, refold any header lines that are longer
than @emph{maxheaderlen}, or if @code{0}, do not rewrap any headers.  If
@emph{manheaderlen} is @code{None} (the default), wrap headers and other message
lines according to the @emph{policy} settings.

If @emph{policy} is specified, use that policy to control message generation.  If
@emph{policy} is @code{None} (the default), use the policy associated with the
@ref{53c,,Message} or @ref{53d,,EmailMessage}
object passed to @code{flatten} to control the message generation.  See
@ref{75,,email.policy} for details on what @emph{policy} controls.


3.2 新版功能.



在 3.3 版更改: Added the @emph{policy} keyword.



在 3.6 版更改: The default behavior of the @emph{mangle_from_}
and @emph{maxheaderlen} parameters is to follow the policy.


@geindex flatten() (email.generator.BytesGenerator 方法)
@anchor{library/email generator email generator BytesGenerator flatten}@anchor{27c0}
@deffn {方法} flatten (msg, unixfrom=False, linesep=None)

Print the textual representation of the message object structure rooted
at @emph{msg} to the output file specified when the @ref{b46,,BytesGenerator}
instance was created.

If the @ref{75,,policy} option @ref{27c2,,cte_type}
is @code{8bit} (the default), copy any headers in the original parsed
message that have not been modified to the output with any bytes with the
high bit set reproduced as in the original, and preserve the non-ASCII
@code{Content-Transfer-Encoding} of any body parts that have them.
If @code{cte_type} is @code{7bit}, convert the bytes with the high bit set as
needed using an ASCII-compatible @code{Content-Transfer-Encoding}.
That is, transform parts with non-ASCII
@code{Content-Transfer-Encoding}
(@code{Content-Transfer-Encoding: 8bit}) to an ASCII compatible
@code{Content-Transfer-Encoding}, and encode RFC-invalid non-ASCII
bytes in headers using the MIME @code{unknown-8bit} character set, thus
rendering them RFC-compliant.

@c XXX: There should be an option that just does the RFC
@c compliance transformation on headers but leaves CTE 8bit parts alone.

If @emph{unixfrom} is @code{True}, print the envelope header delimiter used by
the Unix mailbox format (see @ref{ae,,mailbox}) before the first of the
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} headers of the root message object.  If the root object has
no envelope header, craft a standard one.  The default is @code{False}.
Note that for subparts, no envelope header is ever printed.

If @emph{linesep} is not @code{None}, use it as the separator character between
all the lines of the flattened message.  If @emph{linesep} is @code{None} (the
default), use the value specified in the @emph{policy}.

@c XXX: flatten should take a *policy* keyword.
@end deffn

@geindex clone() (email.generator.BytesGenerator 方法)
@anchor{library/email generator email generator BytesGenerator clone}@anchor{27c3}
@deffn {方法} clone (fp)

Return an independent clone of this @ref{b46,,BytesGenerator} instance with
the exact same option settings, and @emph{fp} as the new @emph{outfp}.
@end deffn

@geindex write() (email.generator.BytesGenerator 方法)
@anchor{library/email generator email generator BytesGenerator write}@anchor{27c1}
@deffn {方法} write (s)

Encode @emph{s} using the @code{ASCII} codec and the @code{surrogateescape} error
handler, and pass it to the @emph{write} method of the @emph{outfp} passed to the
@ref{b46,,BytesGenerator}'s constructor.
@end deffn
@end deffn

As a convenience, @ref{53d,,EmailMessage} provides the methods
@ref{2778,,as_bytes()} and @code{bytes(aMessage)} (a.k.a.
@ref{2779,,__bytes__()}), which simplify the generation of
a serialized binary representation of a message object.  For more detail, see
@ref{72,,email.message}.

Because strings cannot represent binary data, the @ref{b45,,Generator} class must
convert any binary data in any message it flattens to an ASCII compatible
format, by converting them to an ASCII compatible
@code{Content-Transfer_Encoding}.  Using the terminology of the email
RFCs, you can think of this as @ref{b45,,Generator} serializing to an I/O stream
that is not "8 bit clean".  In other words, most applications will want
to be using @ref{b46,,BytesGenerator}, and not @ref{b45,,Generator}.

@geindex Generator (email.generator 中的类)
@anchor{library/email generator email generator Generator}@anchor{b45}
@deffn {类} email.generator.Generator (outfp, mangle_from_=None, maxheaderlen=None, *, policy=None)

Return a @ref{b45,,Generator} object that will write any message provided
to the @ref{27c4,,flatten()} method, or any text provided to the @ref{27c5,,write()}
method, to the @ref{1bfc,,file-like object} @emph{outfp}.  @emph{outfp} must support a
@code{write} method that accepts string data.

If optional @emph{mangle_from_} is @code{True}, put a @code{>} character in front of
any line in the body that starts with the exact string @code{"From "}, that is
@code{From} followed by a space at the beginning of a line.  @emph{mangle_from_}
defaults to the value of the @ref{6ca,,mangle_from_}
setting of the @emph{policy} (which is @code{True} for the
@ref{53b,,compat32} policy and @code{False} for all others).
@emph{mangle_from_} is intended for use when messages are stored in unix mbox
format (see @ref{ae,,mailbox} and WHY THE CONTENT-LENGTH FORMAT IS BAD@footnote{https://www.jwz.org/doc/content-length.html}).

If @emph{maxheaderlen} is not @code{None}, refold any header lines that are longer
than @emph{maxheaderlen}, or if @code{0}, do not rewrap any headers.  If
@emph{manheaderlen} is @code{None} (the default), wrap headers and other message
lines according to the @emph{policy} settings.

If @emph{policy} is specified, use that policy to control message generation.  If
@emph{policy} is @code{None} (the default), use the policy associated with the
@ref{53c,,Message} or @ref{53d,,EmailMessage}
object passed to @code{flatten} to control the message generation.  See
@ref{75,,email.policy} for details on what @emph{policy} controls.


在 3.3 版更改: Added the @emph{policy} keyword.



在 3.6 版更改: The default behavior of the @emph{mangle_from_}
and @emph{maxheaderlen} parameters is to follow the policy.


@geindex flatten() (email.generator.Generator 方法)
@anchor{library/email generator email generator Generator flatten}@anchor{27c4}
@deffn {方法} flatten (msg, unixfrom=False, linesep=None)

Print the textual representation of the message object structure rooted
at @emph{msg} to the output file specified when the @ref{b45,,Generator}
instance was created.

If the @ref{75,,policy} option @ref{27c2,,cte_type}
is @code{8bit}, generate the message as if the option were set to @code{7bit}.
(This is required because strings cannot represent non-ASCII bytes.)
Convert any bytes with the high bit set as needed using an
ASCII-compatible @code{Content-Transfer-Encoding}.  That is,
transform parts with non-ASCII @code{Content-Transfer-Encoding}
(@code{Content-Transfer-Encoding: 8bit}) to an ASCII compatible
@code{Content-Transfer-Encoding}, and encode RFC-invalid non-ASCII
bytes in headers using the MIME @code{unknown-8bit} character set, thus
rendering them RFC-compliant.

If @emph{unixfrom} is @code{True}, print the envelope header delimiter used by
the Unix mailbox format (see @ref{ae,,mailbox}) before the first of the
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} headers of the root message object.  If the root object has
no envelope header, craft a standard one.  The default is @code{False}.
Note that for subparts, no envelope header is ever printed.

If @emph{linesep} is not @code{None}, use it as the separator character between
all the lines of the flattened message.  If @emph{linesep} is @code{None} (the
default), use the value specified in the @emph{policy}.

@c XXX: flatten should take a *policy* keyword.


在 3.2 版更改: Added support for re-encoding @code{8bit} message bodies, and the
@emph{linesep} argument.

@end deffn

@geindex clone() (email.generator.Generator 方法)
@anchor{library/email generator email generator Generator clone}@anchor{27c6}
@deffn {方法} clone (fp)

Return an independent clone of this @ref{b45,,Generator} instance with the
exact same options, and @emph{fp} as the new @emph{outfp}.
@end deffn

@geindex write() (email.generator.Generator 方法)
@anchor{library/email generator email generator Generator write}@anchor{27c5}
@deffn {方法} write (s)

Write @emph{s} to the @emph{write} method of the @emph{outfp} passed to the
@ref{b45,,Generator}'s constructor.  This provides just enough file-like
API for @ref{b45,,Generator} instances to be used in the @ref{880,,print()}
function.
@end deffn
@end deffn

As a convenience, @ref{53d,,EmailMessage} provides the methods
@ref{2776,,as_string()} and @code{str(aMessage)} (a.k.a.
@ref{2777,,__str__()}), which simplify the generation of
a formatted string representation of a message object.  For more detail, see
@ref{72,,email.message}.

The @ref{6e,,email.generator} module also provides a derived class,
@ref{539,,DecodedGenerator}, which is like the @ref{b45,,Generator} base class,
except that non-@code{text} parts are not serialized, but are instead
represented in the output stream by a string derived from a template filled
in with information about the part.

@geindex DecodedGenerator (email.generator 中的类)
@anchor{library/email generator email generator DecodedGenerator}@anchor{539}
@deffn {类} email.generator.DecodedGenerator (outfp, mangle_from_=None, maxheaderlen=None, fmt=None, *, policy=None)

Act like @ref{b45,,Generator}, except that for any subpart of the message
passed to @ref{27c4,,Generator.flatten()}, if the subpart is of main type
@code{text}, print the decoded payload of the subpart, and if the main
type is not @code{text}, instead of printing it fill in the string
@emph{fmt} using information from the part and print the resulting
filled-in string.

To fill in @emph{fmt}, execute @code{fmt % part_info}, where @code{part_info}
is a dictionary composed of the following keys and values:


@itemize *

@item 
@code{type} -- Full MIME type of the non-@code{text} part

@item 
@code{maintype} -- Main MIME type of the non-@code{text} part

@item 
@code{subtype} -- Sub-MIME type of the non-@code{text} part

@item 
@code{filename} -- Filename of the non-@code{text} part

@item 
@code{description} -- Description associated with the non-@code{text} part

@item 
@code{encoding} -- Content transfer encoding of the non-@code{text} part
@end itemize

If @emph{fmt} is @code{None}, use the following default @emph{fmt}:

@quotation

"[Non-text (%(type)s) part of message omitted, filename %(filename)s]"
@end quotation

Optional @emph{_mangle_from_} and @emph{maxheaderlen} are as with the
@ref{b45,,Generator} base class.
@end deffn

@subsubheading 备注


@node email policy Policy Objects,email errors 异常和缺陷类,email generator Generating MIME documents,email --- 电子邮件与 MIME 处理包
@anchor{library/email policy doc}@anchor{27c7}@anchor{library/email policy email-policy-policy-objects}@anchor{27c8}@anchor{library/email policy module-email policy}@anchor{75}
@subsubsection @code{email.policy}: Policy Objects


@geindex email.policy (模块)


3.3 新版功能.


@strong{Source code:} Lib/email/policy.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/policy.py}


__________________________________________________________________


The @ref{69,,email} package's prime focus is the handling of email messages as
described by the various email and MIME RFCs.  However, the general format of
email messages (a block of header fields each consisting of a name followed by
a colon followed by a value, the whole block followed by a blank line and an
arbitrary 'body'), is a format that has found utility outside of the realm of
email.  Some of these uses conform fairly closely to the main email RFCs, some
do not.  Even when working with email, there are times when it is desirable to
break strict compliance with the RFCs, such as generating emails that
interoperate with email servers that do not themselves follow the standards, or
that implement extensions you want to use in ways that violate the
standards.

Policy objects give the email package the flexibility to handle all these
disparate use cases.

A @ref{9ee,,Policy} object encapsulates a set of attributes and methods that
control the behavior of various components of the email package during use.
@ref{9ee,,Policy} instances can be passed to various classes and methods in the
email package to alter the default behavior.  The settable values and their
defaults are described below.

There is a default policy used by all classes in the email package.  For all of
the @ref{74,,parser} classes and the related convenience functions, and for
the @ref{53c,,Message} class, this is the @ref{9ef,,Compat32}
policy, via its corresponding pre-defined instance @ref{53b,,compat32}.  This
policy provides for complete backward compatibility (in some cases, including
bug compatibility) with the pre-Python3.3 version of the email package.

This default value for the @emph{policy} keyword to
@ref{53d,,EmailMessage} is the @ref{9f2,,EmailPolicy} policy, via
its pre-defined instance @ref{2775,,default}.

When a @ref{53c,,Message} or @ref{53d,,EmailMessage}
object is created, it acquires a policy.  If the message is created by a
@ref{74,,parser}, a policy passed to the parser will be the policy used by
the message it creates.  If the message is created by the program, then the
policy can be specified when it is created.  When a message is passed to a
@ref{6e,,generator}, the generator uses the policy from the message by
default, but you can also pass a specific policy to the generator that will
override the one stored on the message object.

The default value for the @emph{policy} keyword for the @ref{74,,email.parser} classes
and the parser convenience functions @strong{will be changing} in a future version of
Python.  Therefore you should @strong{always specify explicitly which policy you want
to use} when calling any of the classes and functions described in the
@ref{74,,parser} module.

The first part of this documentation covers the features of @ref{9ee,,Policy}, an
@ref{b2c,,abstract base class} that defines the features that are common to all
policy objects, including @ref{53b,,compat32}.  This includes certain hook
methods that are called internally by the email package, which a custom policy
could override to obtain different behavior.  The second part describes the
concrete classes @ref{9f2,,EmailPolicy} and @ref{9ef,,Compat32}, which implement
the hooks that provide the standard behavior and the backward compatible
behavior and features, respectively.

@ref{9ee,,Policy} instances are immutable, but they can be cloned, accepting the
same keyword arguments as the class constructor and returning a new
@ref{9ee,,Policy} instance that is a copy of the original but with the specified
attributes values changed.

As an example, the following code could be used to read an email message from a
file on disk and pass it to the system @code{sendmail} program on a Unix system:

@c from unittest import mock
@c mocker = mock.patch('subprocess.Popen')
@c m = mocker.start()
@c proc = mock.MagicMock()
@c m.return_value = proc
@c proc.stdin.close.return_value = None
@c mymsg = open('mymsg.txt', 'w')
@c mymsg.write('To: abc@xyz.com\n\n')
@c mymsg.flush()

@example
>>> from email import message_from_binary_file
>>> from email.generator import BytesGenerator
>>> from email import policy
>>> from subprocess import Popen, PIPE
>>> with open('mymsg.txt', 'rb') as f:
...     msg = message_from_binary_file(f, policy=policy.default)
>>> p = Popen(['sendmail', msg['To'].addresses[0]], stdin=PIPE)
>>> g = BytesGenerator(p.stdin, policy=msg.policy.clone(linesep='\r\n'))
>>> g.flatten(msg)
>>> p.stdin.close()
>>> rc = p.wait()
@end example

@c mymsg.close()
@c mocker.stop()
@c import os
@c os.remove('mymsg.txt')

Here we are telling @ref{b46,,BytesGenerator} to use the RFC
correct line separator characters when creating the binary string to feed into
@code{sendmail's} @code{stdin}, where the default policy would use @code{\n} line
separators.

Some email package methods accept a @emph{policy} keyword argument, allowing the
policy to be overridden for that method.  For example, the following code uses
the @ref{83a,,as_bytes()} method of the @emph{msg} object from
the previous example and writes the message to a file using the native line
separators for the platform on which it is running:

@example
>>> import os
>>> with open('converted.txt', 'wb') as f:
...     f.write(msg.as_bytes(policy=msg.policy.clone(linesep=os.linesep)))
17
@end example

Policy objects can also be combined using the addition operator, producing a
policy object whose settings are a combination of the non-default values of the
summed objects:

@example
>>> compat_SMTP = policy.compat32.clone(linesep='\r\n')
>>> compat_strict = policy.compat32.clone(raise_on_defect=True)
>>> compat_strict_SMTP = compat_SMTP + compat_strict
@end example

This operation is not commutative; that is, the order in which the objects are
added matters.  To illustrate:

@example
>>> policy100 = policy.compat32.clone(max_line_length=100)
>>> policy80 = policy.compat32.clone(max_line_length=80)
>>> apolicy = policy100 + policy80
>>> apolicy.max_line_length
80
>>> apolicy = policy80 + policy100
>>> apolicy.max_line_length
100
@end example

@geindex Policy (email.policy 中的类)
@anchor{library/email policy email policy Policy}@anchor{9ee}
@deffn {类} email.policy.Policy (**kw)

This is the @ref{b2c,,abstract base class} for all policy classes.  It provides
default implementations for a couple of trivial methods, as well as the
implementation of the immutability property, the @ref{9f0,,clone()} method, and
the constructor semantics.

The constructor of a policy class can be passed various keyword arguments.
The arguments that may be specified are any non-method properties on this
class, plus any additional non-method properties on the concrete class.  A
value specified in the constructor will override the default value for the
corresponding attribute.

This class defines the following properties, and thus values for the
following may be passed in the constructor of any policy class:

@geindex max_line_length (email.policy.Policy 属性)
@anchor{library/email policy email policy Policy max_line_length}@anchor{27c9}
@deffn {属性} max_line_length

The maximum length of any line in the serialized output, not counting the
end of line character(s).  Default is 78, per 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}.  A value of
@code{0} or @ref{157,,None} indicates that no line wrapping should be
done at all.
@end deffn

@geindex linesep (email.policy.Policy 属性)
@anchor{library/email policy email policy Policy linesep}@anchor{27ca}
@deffn {属性} linesep

The string to be used to terminate lines in serialized output.  The
default is @code{\n} because that's the internal end-of-line discipline used
by Python, though @code{\r\n} is required by the RFCs.
@end deffn

@geindex cte_type (email.policy.Policy 属性)
@anchor{library/email policy email policy Policy cte_type}@anchor{27c2}
@deffn {属性} cte_type

Controls the type of Content Transfer Encodings that may be or are
required to be used.  The possible values are:


@multitable {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{7bit}

@tab

all data must be "7 bit clean" (ASCII-only).  This means that
where necessary data will be encoded using either
quoted-printable or base64 encoding.

@item

@code{8bit}

@tab

data is not constrained to be 7 bit clean.  Data in headers is
still required to be ASCII-only and so will be encoded (see
@ref{27cb,,fold_binary()} and @ref{6cc,,utf8} below for
exceptions), but body parts may use the @code{8bit} CTE.

@end multitable


A @code{cte_type} value of @code{8bit} only works with @code{BytesGenerator}, not
@code{Generator}, because strings cannot contain binary data.  If a
@code{Generator} is operating under a policy that specifies
@code{cte_type=8bit}, it will act as if @code{cte_type} is @code{7bit}.
@end deffn

@geindex raise_on_defect (email.policy.Policy 属性)
@anchor{library/email policy email policy Policy raise_on_defect}@anchor{27cc}
@deffn {属性} raise_on_defect

If @ref{494,,True}, any defects encountered will be raised as errors.  If
@ref{380,,False} (the default), defects will be passed to the
@ref{27cd,,register_defect()} method.
@end deffn

@geindex mangle_from_ (email.policy.Policy 属性)
@anchor{library/email policy email policy Policy mangle_from_}@anchor{6ca}
@deffn {属性} mangle_from_

If @ref{494,,True}, lines starting with @emph{"From "} in the body are
escaped by putting a @code{>} in front of them. This parameter is used when
the message is being serialized by a generator.
Default: @ref{380,,False}.


3.5 新版功能: The @emph{mangle_from_} parameter.

@end deffn

@geindex message_factory (email.policy.Policy 属性)
@anchor{library/email policy email policy Policy message_factory}@anchor{53a}
@deffn {属性} message_factory

A factory function for constructing a new empty message object.  Used
by the parser when building messages.  Defaults to @code{None}, in
which case @ref{53c,,Message} is used.


3.6 新版功能.

@end deffn

The following @ref{9ee,,Policy} method is intended to be called by code using
the email library to create policy instances with custom settings:

@geindex clone() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy clone}@anchor{9f0}
@deffn {方法} clone (**kw)

Return a new @ref{9ee,,Policy} instance whose attributes have the same
values as the current instance, except where those attributes are
given new values by the keyword arguments.
@end deffn

The remaining @ref{9ee,,Policy} methods are called by the email package code,
and are not intended to be called by an application using the email package.
A custom policy must implement all of these methods.

@geindex handle_defect() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy handle_defect}@anchor{27ce}
@deffn {方法} handle_defect (obj, defect)

Handle a @emph{defect} found on @emph{obj}.  When the email package calls this
method, @emph{defect} will always be a subclass of
@code{Defect}.

The default implementation checks the @ref{27cc,,raise_on_defect} flag.  If
it is @code{True}, @emph{defect} is raised as an exception.  If it is @code{False}
(the default), @emph{obj} and @emph{defect} are passed to @ref{27cd,,register_defect()}.
@end deffn

@geindex register_defect() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy register_defect}@anchor{27cd}
@deffn {方法} register_defect (obj, defect)

Register a @emph{defect} on @emph{obj}.  In the email package, @emph{defect} will always
be a subclass of @code{Defect}.

The default implementation calls the @code{append} method of the @code{defects}
attribute of @emph{obj}.  When the email package calls @ref{27ce,,handle_defect},
@emph{obj} will normally have a @code{defects} attribute that has an @code{append}
method.  Custom object types used with the email package (for example,
custom @code{Message} objects) should also provide such an attribute,
otherwise defects in parsed messages will raise unexpected errors.
@end deffn

@geindex header_max_count() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy header_max_count}@anchor{27cf}
@deffn {方法} header_max_count (name)

Return the maximum allowed number of headers named @emph{name}.

Called when a header is added to an @ref{53d,,EmailMessage}
or @ref{53c,,Message} object.  If the returned value is not
@code{0} or @code{None}, and there are already a number of headers with the
name @emph{name} greater than or equal to the value returned, a
@ref{1fb,,ValueError} is raised.

Because the default behavior of @code{Message.__setitem__} is to append the
value to the list of headers, it is easy to create duplicate headers
without realizing it.  This method allows certain headers to be limited
in the number of instances of that header that may be added to a
@code{Message} programmatically.  (The limit is not observed by the parser,
which will faithfully produce as many headers as exist in the message
being parsed.)

The default implementation returns @code{None} for all header names.
@end deffn

@geindex header_source_parse() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy header_source_parse}@anchor{27d0}
@deffn {方法} header_source_parse (sourcelines)

The email package calls this method with a list of strings, each string
ending with the line separation characters found in the source being
parsed.  The first line includes the field header name and separator.
All whitespace in the source is preserved.  The method should return the
@code{(name, value)} tuple that is to be stored in the @code{Message} to
represent the parsed header.

If an implementation wishes to retain compatibility with the existing
email package policies, @emph{name} should be the case preserved name (all
characters up to the '@code{:}' separator), while @emph{value} should be the
unfolded value (all line separator characters removed, but whitespace
kept intact), stripped of leading whitespace.

@emph{sourcelines} may contain surrogateescaped binary data.

There is no default implementation
@end deffn

@geindex header_store_parse() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy header_store_parse}@anchor{27d1}
@deffn {方法} header_store_parse (name, value)

The email package calls this method with the name and value provided by
the application program when the application program is modifying a
@code{Message} programmatically (as opposed to a @code{Message} created by a
parser).  The method should return the @code{(name, value)} tuple that is to
be stored in the @code{Message} to represent the header.

If an implementation wishes to retain compatibility with the existing
email package policies, the @emph{name} and @emph{value} should be strings or
string subclasses that do not change the content of the passed in
arguments.

There is no default implementation
@end deffn

@geindex header_fetch_parse() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy header_fetch_parse}@anchor{27d2}
@deffn {方法} header_fetch_parse (name, value)

The email package calls this method with the @emph{name} and @emph{value} currently
stored in the @code{Message} when that header is requested by the
application program, and whatever the method returns is what is passed
back to the application as the value of the header being retrieved.
Note that there may be more than one header with the same name stored in
the @code{Message}; the method is passed the specific name and value of the
header destined to be returned to the application.

@emph{value} may contain surrogateescaped binary data.  There should be no
surrogateescaped binary data in the value returned by the method.

There is no default implementation
@end deffn

@geindex fold() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy fold}@anchor{27d3}
@deffn {方法} fold (name, value)

The email package calls this method with the @emph{name} and @emph{value} currently
stored in the @code{Message} for a given header.  The method should return a
string that represents that header "folded" correctly (according to the
policy settings) by composing the @emph{name} with the @emph{value} and inserting
@ref{27ca,,linesep} characters at the appropriate places.  See 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}
for a discussion of the rules for folding email headers.

@emph{value} may contain surrogateescaped binary data.  There should be no
surrogateescaped binary data in the string returned by the method.
@end deffn

@geindex fold_binary() (email.policy.Policy 方法)
@anchor{library/email policy email policy Policy fold_binary}@anchor{27cb}
@deffn {方法} fold_binary (name, value)

The same as @ref{27d3,,fold()}, except that the returned value should be a
bytes object rather than a string.

@emph{value} may contain surrogateescaped binary data.  These could be
converted back into binary data in the returned bytes object.
@end deffn
@end deffn

@geindex EmailPolicy (email.policy 中的类)
@anchor{library/email policy email policy EmailPolicy}@anchor{9f2}
@deffn {类} email.policy.EmailPolicy (**kw)

This concrete @ref{9ee,,Policy} provides behavior that is intended to be fully
compliant with the current email RFCs.  These include (but are not limited
to) 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}, 
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html}, and the current MIME RFCs.

This policy adds new header parsing and folding algorithms.  Instead of
simple strings, headers are @code{str} subclasses with attributes that depend
on the type of the field.  The parsing and folding algorithm fully implement
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html} and 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}.

The default value for the @ref{53a,,message_factory}
attribute is @ref{53d,,EmailMessage}.

In addition to the settable attributes listed above that apply to all
policies, this policy adds the following additional attributes:


3.6 新版功能: @footnote{@w{(1)} 
Originally added in 3.3 as a @ref{97a,,provisional feature}.
}


@geindex utf8 (email.policy.EmailPolicy 属性)
@anchor{library/email policy email policy EmailPolicy utf8}@anchor{6cc}
@deffn {属性} utf8

If @code{False}, follow 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}, supporting non-ASCII characters in
headers by encoding them as "encoded words".  If @code{True}, follow
@geindex RFC; RFC 6532
RFC 6532@footnote{https://tools.ietf.org/html/rfc6532.html} and use @code{utf-8} encoding for headers.  Messages
formatted in this way may be passed to SMTP servers that support
the @code{SMTPUTF8} extension (
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html}).
@end deffn

@geindex refold_source (email.policy.EmailPolicy 属性)
@anchor{library/email policy email policy EmailPolicy refold_source}@anchor{27d4}
@deffn {属性} refold_source

If the value for a header in the @code{Message} object originated from a
@ref{74,,parser} (as opposed to being set by a program), this
attribute indicates whether or not a generator should refold that value
when transforming the message back into serialized form.  The possible
values are:


@multitable {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{none}

@tab

all source values use original folding

@item

@code{long}

@tab

source values that have any line that is longer than
@code{max_line_length} will be refolded

@item

@code{all}

@tab

all values are refolded.

@end multitable


The default is @code{long}.
@end deffn

@geindex header_factory (email.policy.EmailPolicy 属性)
@anchor{library/email policy email policy EmailPolicy header_factory}@anchor{27d5}
@deffn {属性} header_factory

A callable that takes two arguments, @code{name} and @code{value}, where
@code{name} is a header field name and @code{value} is an unfolded header field
value, and returns a string subclass that represents that header.  A
default @code{header_factory} (see @ref{70,,headerregistry}) is provided
that supports custom parsing for the various address and date 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}
header field types, and the major MIME header field stypes.  Support for
additional custom parsing will be added in the future.
@end deffn

@geindex content_manager (email.policy.EmailPolicy 属性)
@anchor{library/email policy email policy EmailPolicy content_manager}@anchor{83e}
@deffn {属性} content_manager

An object with at least two methods: get_content and set_content.  When
the @ref{27a0,,get_content()} or
@ref{27a2,,set_content()} method of an
@ref{53d,,EmailMessage} object is called, it calls the
corresponding method of this object, passing it the message object as its
first argument, and any arguments or keywords that were passed to it as
additional arguments.  By default @code{content_manager} is set to
@ref{27d6,,raw_data_manager}.


3.4 新版功能.

@end deffn

The class provides the following concrete implementations of the abstract
methods of @ref{9ee,,Policy}:

@geindex header_max_count() (email.policy.EmailPolicy 方法)
@anchor{library/email policy email policy EmailPolicy header_max_count}@anchor{27d7}
@deffn {方法} header_max_count (name)

Returns the value of the
@ref{27d8,,max_count} attribute of the
specialized class used to represent the header with the given name.
@end deffn

@geindex header_source_parse() (email.policy.EmailPolicy 方法)
@anchor{library/email policy email policy EmailPolicy header_source_parse}@anchor{27d9}
@deffn {方法} header_source_parse (sourcelines)

The name is parsed as everything up to the '@code{:}' and returned
unmodified.  The value is determined by stripping leading whitespace off
the remainder of the first line, joining all subsequent lines together,
and stripping any trailing carriage return or linefeed characters.
@end deffn

@geindex header_store_parse() (email.policy.EmailPolicy 方法)
@anchor{library/email policy email policy EmailPolicy header_store_parse}@anchor{27da}
@deffn {方法} header_store_parse (name, value)

The name is returned unchanged.  If the input value has a @code{name}
attribute and it matches @emph{name} ignoring case, the value is returned
unchanged.  Otherwise the @emph{name} and @emph{value} are passed to
@code{header_factory}, and the resulting header object is returned as
the value.  In this case a @code{ValueError} is raised if the input value
contains CR or LF characters.
@end deffn

@geindex header_fetch_parse() (email.policy.EmailPolicy 方法)
@anchor{library/email policy email policy EmailPolicy header_fetch_parse}@anchor{27db}
@deffn {方法} header_fetch_parse (name, value)

If the value has a @code{name} attribute, it is returned to unmodified.
Otherwise the @emph{name}, and the @emph{value} with any CR or LF characters
removed, are passed to the @code{header_factory}, and the resulting
header object is returned.  Any surrogateescaped bytes get turned into
the unicode unknown-character glyph.
@end deffn

@geindex fold() (email.policy.EmailPolicy 方法)
@anchor{library/email policy email policy EmailPolicy fold}@anchor{27dc}
@deffn {方法} fold (name, value)

Header folding is controlled by the @ref{27d4,,refold_source} policy setting.
A value is considered to be a 'source value' if and only if it does not
have a @code{name} attribute (having a @code{name} attribute means it is a
header object of some sort).  If a source value needs to be refolded
according to the policy, it is converted into a header object by
passing the @emph{name} and the @emph{value} with any CR and LF characters removed
to the @code{header_factory}.  Folding of a header object is done by
calling its @code{fold} method with the current policy.

Source values are split into lines using @ref{15f2,,splitlines()}.  If
the value is not to be refolded, the lines are rejoined using the
@code{linesep} from the policy and returned.  The exception is lines
containing non-ascii binary data.  In that case the value is refolded
regardless of the @code{refold_source} setting, which causes the binary data
to be CTE encoded using the @code{unknown-8bit} charset.
@end deffn

@geindex fold_binary() (email.policy.EmailPolicy 方法)
@anchor{library/email policy email policy EmailPolicy fold_binary}@anchor{27dd}
@deffn {方法} fold_binary (name, value)

The same as @ref{27dc,,fold()} if @ref{27c2,,cte_type} is @code{7bit}, except
that the returned value is bytes.

If @ref{27c2,,cte_type} is @code{8bit}, non-ASCII binary data is
converted back
into bytes.  Headers with binary data are not refolded, regardless of the
@code{refold_header} setting, since there is no way to know whether the
binary data consists of single byte characters or multibyte characters.
@end deffn
@end deffn

The following instances of @ref{9f2,,EmailPolicy} provide defaults suitable for
specific application domains.  Note that in the future the behavior of these
instances (in particular the @code{HTTP} instance) may be adjusted to conform even
more closely to the RFCs relevant to their domains.

@geindex default() (在 email.policy 模块中)
@anchor{library/email policy email policy default}@anchor{2775}
@deffn {数据} email.policy.default

An instance of @code{EmailPolicy} with all defaults unchanged.  This policy
uses the standard Python @code{\n} line endings rather than the RFC-correct
@code{\r\n}.
@end deffn

@geindex SMTP() (在 email.policy 模块中)
@anchor{library/email policy email policy SMTP}@anchor{27de}
@deffn {数据} email.policy.SMTP

Suitable for serializing messages in conformance with the email RFCs.
Like @code{default}, but with @code{linesep} set to @code{\r\n}, which is RFC
compliant.
@end deffn

@geindex SMTPUTF8() (在 email.policy 模块中)
@anchor{library/email policy email policy SMTPUTF8}@anchor{27df}
@deffn {数据} email.policy.SMTPUTF8

The same as @code{SMTP} except that @ref{6cc,,utf8} is @code{True}.
Useful for serializing messages to a message store without using encoded
words in the headers.  Should only be used for SMTP transmission if the
sender or recipient addresses have non-ASCII characters (the
@ref{73f,,smtplib.SMTP.send_message()} method handles this automatically).
@end deffn

@geindex HTTP() (在 email.policy 模块中)
@anchor{library/email policy email policy HTTP}@anchor{27e0}
@deffn {数据} email.policy.HTTP

Suitable for serializing headers with for use in HTTP traffic.  Like
@code{SMTP} except that @code{max_line_length} is set to @code{None} (unlimited).
@end deffn

@geindex strict() (在 email.policy 模块中)
@anchor{library/email policy email policy strict}@anchor{27e1}
@deffn {数据} email.policy.strict

Convenience instance.  The same as @code{default} except that
@code{raise_on_defect} is set to @code{True}.  This allows any policy to be made
strict by writing:

@example
somepolicy + policy.strict
@end example
@end deffn

With all of these @ref{9f2,,EmailPolicies}, the effective API of
the email package is changed from the Python 3.2 API in the following ways:

@quotation


@itemize *

@item 
Setting a header on a @ref{53c,,Message} results in that
header being parsed and a header object created.

@item 
Fetching a header value from a @ref{53c,,Message} results
in that header being parsed and a header object created and
returned.

@item 
Any header object, or any header that is refolded due to the
policy settings, is folded using an algorithm that fully implements the
RFC folding algorithms, including knowing where encoded words are required
and allowed.
@end itemize
@end quotation

From the application view, this means that any header obtained through the
@ref{53d,,EmailMessage} is a header object with extra
attributes, whose string value is the fully decoded unicode value of the
header.  Likewise, a header may be assigned a new value, or a new header
created, using a unicode string, and the policy will take care of converting
the unicode string into the correct RFC encoded form.

The header objects and their attributes are described in
@ref{70,,headerregistry}.

@geindex Compat32 (email.policy 中的类)
@anchor{library/email policy email policy Compat32}@anchor{9ef}
@deffn {类} email.policy.Compat32 (**kw)

This concrete @ref{9ee,,Policy} is the backward compatibility policy.  It
replicates the behavior of the email package in Python 3.2.  The
@ref{75,,policy} module also defines an instance of this class,
@ref{53b,,compat32}, that is used as the default policy.  Thus the default
behavior of the email package is to maintain compatibility with Python 3.2.

The following attributes have values that are different from the
@ref{9ee,,Policy} default:

@geindex mangle_from_ (email.policy.Compat32 属性)
@anchor{library/email policy email policy Compat32 mangle_from_}@anchor{27e2}
@deffn {属性} mangle_from_

The default is @code{True}.
@end deffn

The class provides the following concrete implementations of the
abstract methods of @ref{9ee,,Policy}:

@geindex header_source_parse() (email.policy.Compat32 方法)
@anchor{library/email policy email policy Compat32 header_source_parse}@anchor{27e3}
@deffn {方法} header_source_parse (sourcelines)

The name is parsed as everything up to the '@code{:}' and returned
unmodified.  The value is determined by stripping leading whitespace off
the remainder of the first line, joining all subsequent lines together,
and stripping any trailing carriage return or linefeed characters.
@end deffn

@geindex header_store_parse() (email.policy.Compat32 方法)
@anchor{library/email policy email policy Compat32 header_store_parse}@anchor{27e4}
@deffn {方法} header_store_parse (name, value)

The name and value are returned unmodified.
@end deffn

@geindex header_fetch_parse() (email.policy.Compat32 方法)
@anchor{library/email policy email policy Compat32 header_fetch_parse}@anchor{27e5}
@deffn {方法} header_fetch_parse (name, value)

If the value contains binary data, it is converted into a
@ref{27e6,,Header} object using the @code{unknown-8bit} charset.
Otherwise it is returned unmodified.
@end deffn

@geindex fold() (email.policy.Compat32 方法)
@anchor{library/email policy email policy Compat32 fold}@anchor{27e7}
@deffn {方法} fold (name, value)

Headers are folded using the @ref{27e6,,Header} folding
algorithm, which preserves existing line breaks in the value, and wraps
each resulting line to the @code{max_line_length}.  Non-ASCII binary data are
CTE encoded using the @code{unknown-8bit} charset.
@end deffn

@geindex fold_binary() (email.policy.Compat32 方法)
@anchor{library/email policy email policy Compat32 fold_binary}@anchor{27e8}
@deffn {方法} fold_binary (name, value)

Headers are folded using the @ref{27e6,,Header} folding
algorithm, which preserves existing line breaks in the value, and wraps
each resulting line to the @code{max_line_length}.  If @code{cte_type} is
@code{7bit}, non-ascii binary data is CTE encoded using the @code{unknown-8bit}
charset.  Otherwise the original source header is used, with its existing
line breaks and any (RFC invalid) binary data it may contain.
@end deffn
@end deffn

@geindex compat32() (在 email.policy 模块中)
@anchor{library/email policy email policy compat32}@anchor{53b}
@deffn {数据} email.policy.compat32

An instance of @ref{9ef,,Compat32}, providing  backward compatibility with the
behavior of the email package in Python 3.2.
@end deffn

@subsubheading 备注


@node email errors 异常和缺陷类,email headerregistry Custom Header Objects,email policy Policy Objects,email --- 电子邮件与 MIME 处理包
@anchor{library/email errors doc}@anchor{27e9}@anchor{library/email errors email-errors-exception-and-defect-classes}@anchor{27ea}@anchor{library/email errors module-email errors}@anchor{6d}
@subsubsection @code{email.errors}: 异常和缺陷类


@geindex email.errors (模块)

@strong{源代码:} Lib/email/errors.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/errors.py}


__________________________________________________________________


以下异常类在 @ref{6d,,email.errors} 模块中定义：

@geindex MessageError
@anchor{library/email errors email errors MessageError}@anchor{27eb}
@deffn {例外} email.errors.MessageError

这是 @ref{69,,email} 包可以引发的所有异常的基类。 它源自标准异常 @ref{1a9,,Exception} 类，这个类没有定义其他方法。
@end deffn

@geindex MessageParseError
@anchor{library/email errors email errors MessageParseError}@anchor{27ec}
@deffn {例外} email.errors.MessageParseError

这是由 @ref{b11,,Parser} 类引发的异常的基类。它派生自 @ref{27eb,,MessageError}。 @ref{70,,headerregistry} 使用的解析器也在内部使用这个类。
@end deffn

@geindex HeaderParseError
@anchor{library/email errors email errors HeaderParseError}@anchor{2796}
@deffn {例外} email.errors.HeaderParseError

在解析消息的 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} 标头时，某些错误条件下会触发，此类派生自 @ref{27ec,,MessageParseError}。 如果在调用方法时内容类型未知，则 @ref{2795,,set_boundary()} 方法将引发此错误。 当尝试创建一个看起来包含嵌入式标头的标头时 @ref{27e6,,Header} 可能会针对某些 base64 解码错误引发此错误（也就是说，应该是一个 没有前导空格并且看起来像标题的延续行）。
@end deffn

@geindex BoundaryError
@anchor{library/email errors email errors BoundaryError}@anchor{27ed}
@deffn {例外} email.errors.BoundaryError

已弃用和不再使用的。
@end deffn

@geindex MultipartConversionError
@anchor{library/email errors email errors MultipartConversionError}@anchor{27ee}
@deffn {例外} email.errors.MultipartConversionError

当使用 @code{add_payload()} 将有效负载添加到 @ref{53c,,Message} 对象时，有效负载已经是一个标量，而消息的 @code{Content-Type} 主类型不是 @code{multipart} 或者缺少时触发该异常。 @ref{27ee,,MultipartConversionError} 多重继承自 @ref{27eb,,MessageError} 和内置的 @ref{192,,TypeError}。

由于 @code{Message.add_payload()} 已被弃用，此异常实际上极少会被引发。 但是如果在派生自 @ref{27ef,,MIMENonMultipart} 的类 (例如 @ref{27f0,,MIMEImage}) 的实例上调用 @ref{27a8,,attach()} 方法也可以引发此异常。
@end deffn

以下是 @ref{27b2,,FeedParser} 在解析消息时可发现的缺陷列表。 请注意这些缺陷会在问题被发现时加入到消息中，因此举例来说，如果某条嵌套在 @code{multipart/alternative} 中的消息具有错误的标头，该嵌套消息对象就会有一条缺陷，但外层消息对象则没有。

所有缺陷类都是 @code{email.errors.MessageDefect} 的子类。


@itemize *

@item 
@code{NoBoundaryInMultipartDefect} -- 一条消息宣称有多个部分，但却没有 @code{boundary} 形参。

@item 
@code{StartBoundaryNotFoundDefect} -- 在 @code{Content-Type} 标头中宣称的开始边界无法被找到。

@item 
@code{CloseBoundaryNotFoundDefect} -- 找到了开始边界，但相应的结束边界无法被找到。


3.3 新版功能.


@item 
@code{FirstHeaderLineIsContinuationDefect} -- 消息以一个继续行作为其第一个标头行。

@item 
@code{MisplacedEnvelopeHeaderDefect} - 在标头块中间发现了一个 "Unix From" 标头。

@item 
@code{MissingHeaderBodySeparatorDefect} - 在解析没有前缀空格但又不包含 ':' 的标头期间找到一行内容。 解析将假定该行表示消息体的第一行以继续执行。


3.3 新版功能.


@item 
@code{MalformedHeaderDefect} -- 找到一个缺失了冒号或格式错误的标头。


3.3 版后已移除: 此缺陷在近几个 Python 版本中已不再使用。


@item 
@code{MultipartInvariantViolationDefect} -- 一条消息宣称为 @code{multipart}，但无法找到任何子部分。 请注意当一条消息有此缺陷时，其 @ref{279a,,is_multipart()} 方法可能返回 @code{False}，即使其内容类型宣称为 @code{multipart}。

@item 
@code{InvalidBase64PaddingDefect} -- 当解码一个 base64 编码的字节分块时，填充的数据不正确。 虽然添加了足够的填充数据以执行解码，但作为结果的已解码字节串可能无效。

@item 
@code{InvalidBase64CharactersDefect} -- 当解码一个 base64 编码的字节分块时，遇到了 base64 字符表以外的字符。 这些字符会被忽略，但作为结果的已解码字节串可能无效。

@item 
@code{InvalidBase64LengthDefect} -- 当解码一个 base64 编码的字节分块时，非填充 base64 字符的数量无效（比 4 的倍数多 1）。 已编码分块会保持原样。
@end itemize

@node email headerregistry Custom Header Objects,email contentmanager Managing MIME Content,email errors 异常和缺陷类,email --- 电子邮件与 MIME 处理包
@anchor{library/email headerregistry doc}@anchor{27f1}@anchor{library/email headerregistry email-headerregistry-custom-header-objects}@anchor{27f2}@anchor{library/email headerregistry module-email headerregistry}@anchor{70}
@subsubsection @code{email.headerregistry}: Custom Header Objects


@geindex email.headerregistry (模块)

@strong{Source code:} Lib/email/headerregistry.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/headerregistry.py}


__________________________________________________________________



3.6 新版功能: @footnote{@w{(1)} 
Originally added in 3.3 as a @ref{97a,,provisional module}
}


Headers are represented by customized subclasses of @ref{329,,str}.  The
particular class used to represent a given header is determined by the
@ref{27d5,,header_factory} of the @ref{75,,policy} in
effect when the headers are created.  This section documents the particular
@code{header_factory} implemented by the email package for handling 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}
compliant email messages, which not only provides customized header objects for
various header types, but also provides an extension mechanism for applications
to add their own custom header types.

When using any of the policy objects derived from
@ref{9f2,,EmailPolicy}, all headers are produced by
@ref{27f3,,HeaderRegistry} and have @ref{2783,,BaseHeader} as their last base
class.  Each header class has an additional base class that is determined by
the type of the header.  For example, many headers have the class
@ref{27f4,,UnstructuredHeader} as their other base class.  The specialized second
class for a header is determined by the name of the header, using a lookup
table stored in the @ref{27f3,,HeaderRegistry}.  All of this is managed
transparently for the typical application program, but interfaces are provided
for modifying the default behavior for use by more complex applications.

The sections below first document the header base classes and their attributes,
followed by the API for modifying the behavior of @ref{27f3,,HeaderRegistry}, and
finally the support classes used to represent the data parsed from structured
headers.

@geindex BaseHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry BaseHeader}@anchor{2783}
@deffn {类} email.headerregistry.BaseHeader (name, value)

@emph{name} and @emph{value} are passed to @code{BaseHeader} from the
@ref{27d5,,header_factory} call.  The string value of
any header object is the @emph{value} fully decoded to unicode.

This base class defines the following read-only properties:

@geindex name (email.headerregistry.BaseHeader 属性)
@anchor{library/email headerregistry email headerregistry BaseHeader name}@anchor{27f5}
@deffn {属性} name

The name of the header (the portion of the field before the ':').  This
is exactly the value passed in the
@ref{27d5,,header_factory} call for @emph{name}; that
is, case is preserved.
@end deffn

@geindex defects (email.headerregistry.BaseHeader 属性)
@anchor{library/email headerregistry email headerregistry BaseHeader defects}@anchor{27f6}
@deffn {属性} defects

A tuple of @code{HeaderDefect} instances reporting any
RFC compliance problems found during parsing.  The email package tries to
be complete about detecting compliance issues.  See the @ref{6d,,errors}
module for a discussion of the types of defects that may be reported.
@end deffn

@geindex max_count (email.headerregistry.BaseHeader 属性)
@anchor{library/email headerregistry email headerregistry BaseHeader max_count}@anchor{27d8}
@deffn {属性} max_count

The maximum number of headers of this type that can have the same
@code{name}.  A value of @code{None} means unlimited.  The @code{BaseHeader} value
for this attribute is @code{None}; it is expected that specialized header
classes will override this value as needed.
@end deffn

@code{BaseHeader} also provides the following method, which is called by the
email library code and should not in general be called by application
programs:

@geindex fold() (email.headerregistry.BaseHeader 方法)
@anchor{library/email headerregistry email headerregistry BaseHeader fold}@anchor{27f7}
@deffn {方法} fold (*, policy)

Return a string containing @ref{27ca,,linesep}
characters as required to correctly fold the header according to
@emph{policy}.  A @ref{27c2,,cte_type} of @code{8bit} will be
treated as if it were @code{7bit}, since headers may not contain arbitrary
binary data.  If @ref{6cc,,utf8} is @code{False},
non-ASCII data will be 
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html} encoded.
@end deffn

@code{BaseHeader} by itself cannot be used to create a header object.  It
defines a protocol that each specialized header cooperates with in order to
produce the header object.  Specifically, @code{BaseHeader} requires that
the specialized class provide a @ref{1d8,,classmethod()} named @code{parse}.  This
method is called as follows:

@example
parse(string, kwds)
@end example

@code{kwds} is a dictionary containing one pre-initialized key, @code{defects}.
@code{defects} is an empty list.  The parse method should append any detected
defects to this list.  On return, the @code{kwds} dictionary @emph{must} contain
values for at least the keys @code{decoded} and @code{defects}.  @code{decoded}
should be the string value for the header (that is, the header value fully
decoded to unicode).  The parse method should assume that @emph{string} may
contain content-transfer-encoded parts, but should correctly handle all valid
unicode characters as well so that it can parse un-encoded header values.

@code{BaseHeader}'s @code{__new__} then creates the header instance, and calls its
@code{init} method.  The specialized class only needs to provide an @code{init}
method if it wishes to set additional attributes beyond those provided by
@code{BaseHeader} itself.  Such an @code{init} method should look like this:

@example
def init(self, /, *args, **kw):
    self._myattr = kw.pop('myattr')
    super().init(*args, **kw)
@end example

That is, anything extra that the specialized class puts in to the @code{kwds}
dictionary should be removed and handled, and the remaining contents of
@code{kw} (and @code{args}) passed to the @code{BaseHeader} @code{init} method.
@end deffn

@geindex UnstructuredHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry UnstructuredHeader}@anchor{27f4}
@deffn {类} email.headerregistry.UnstructuredHeader

An "unstructured" header is the default type of header in 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}.
Any header that does not have a specified syntax is treated as
unstructured.  The classic example of an unstructured header is the
@code{Subject} header.

In 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}, an unstructured header is a run of arbitrary text in the
ASCII character set.  
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html}, however, has an 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} compatible
mechanism for encoding non-ASCII text as ASCII characters within a header
value.  When a @emph{value} containing encoded words is passed to the
constructor, the @code{UnstructuredHeader} parser converts such encoded words
into unicode, following the 
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html} rules for unstructured text.  The
parser uses heuristics to attempt to decode certain non-compliant encoded
words.  Defects are registered in such cases, as well as defects for issues
such as invalid characters within the encoded words or the non-encoded text.

This header type provides no additional attributes.
@end deffn

@geindex DateHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry DateHeader}@anchor{27f8}
@deffn {类} email.headerregistry.DateHeader

@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} specifies a very specific format for dates within email headers.
The @code{DateHeader} parser recognizes that date format, as well as
recognizing a number of variant forms that are sometimes found "in the
wild".

This header type provides the following additional attributes:

@geindex datetime (email.headerregistry.DateHeader 属性)
@anchor{library/email headerregistry email headerregistry DateHeader datetime}@anchor{27f9}
@deffn {属性} datetime

If the header value can be recognized as a valid date of one form or
another, this attribute will contain a @ref{194,,datetime}
instance representing that date.  If the timezone of the input date is
specified as @code{-0000} (indicating it is in UTC but contains no
information about the source timezone), then @ref{27f9,,datetime} will be a
naive @ref{194,,datetime}.  If a specific timezone offset is
found (including @cite{+0000}), then @ref{27f9,,datetime} will contain an aware
@code{datetime} that uses @ref{9fb,,datetime.timezone} to record the timezone
offset.
@end deffn

The @code{decoded} value of the header is determined by formatting the
@code{datetime} according to the 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} rules; that is, it is set to:

@example
email.utils.format_datetime(self.datetime)
@end example

When creating a @code{DateHeader}, @emph{value} may be
@ref{194,,datetime} instance.  This means, for example, that
the following code is valid and does what one would expect:

@example
msg['Date'] = datetime(2011, 7, 15, 21)
@end example

Because this is a naive @code{datetime} it will be interpreted as a UTC
timestamp, and the resulting value will have a timezone of @code{-0000}.  Much
more useful is to use the @ref{9fa,,localtime()} function from the
@ref{76,,utils} module:

@example
msg['Date'] = utils.localtime()
@end example

This example sets the date header to the current time and date using
the current timezone offset.
@end deffn

@geindex AddressHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry AddressHeader}@anchor{27fa}
@deffn {类} email.headerregistry.AddressHeader

Address headers are one of the most complex structured header types.
The @code{AddressHeader} class provides a generic interface to any address
header.

This header type provides the following additional attributes:

@geindex groups (email.headerregistry.AddressHeader 属性)
@anchor{library/email headerregistry email headerregistry AddressHeader groups}@anchor{27fb}
@deffn {属性} groups

A tuple of @ref{27fc,,Group} objects encoding the
addresses and groups found in the header value.  Addresses that are
not part of a group are represented in this list as single-address
@code{Groups} whose @ref{27fd,,display_name} is @code{None}.
@end deffn

@geindex addresses (email.headerregistry.AddressHeader 属性)
@anchor{library/email headerregistry email headerregistry AddressHeader addresses}@anchor{27fe}
@deffn {属性} addresses

A tuple of @ref{27ff,,Address} objects encoding all
of the individual addresses from the header value.  If the header value
contains any groups, the individual addresses from the group are included
in the list at the point where the group occurs in the value (that is,
the list of addresses is "flattened" into a one dimensional list).
@end deffn

The @code{decoded} value of the header will have all encoded words decoded to
unicode.  @ref{77,,idna} encoded domain names are also decoded to
unicode.  The @code{decoded} value is set by @ref{15ca,,join}ing the
@ref{329,,str} value of the elements of the @code{groups} attribute with @code{',
'}.

A list of @ref{27ff,,Address} and @ref{27fc,,Group} objects in any combination
may be used to set the value of an address header.  @code{Group} objects whose
@code{display_name} is @code{None} will be interpreted as single addresses, which
allows an address list to be copied with groups intact by using the list
obtained from the @code{groups} attribute of the source header.
@end deffn

@geindex SingleAddressHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry SingleAddressHeader}@anchor{2800}
@deffn {类} email.headerregistry.SingleAddressHeader

A subclass of @ref{27fa,,AddressHeader} that adds one
additional attribute:

@geindex address (email.headerregistry.SingleAddressHeader 属性)
@anchor{library/email headerregistry email headerregistry SingleAddressHeader address}@anchor{2801}
@deffn {属性} address

The single address encoded by the header value.  If the header value
actually contains more than one address (which would be a violation of
the RFC under the default @ref{75,,policy}), accessing this attribute
will result in a @ref{1fb,,ValueError}.
@end deffn
@end deffn

Many of the above classes also have a @code{Unique} variant (for example,
@code{UniqueUnstructuredHeader}).  The only difference is that in the @code{Unique}
variant, @ref{27d8,,max_count} is set to 1.

@geindex MIMEVersionHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry MIMEVersionHeader}@anchor{2802}
@deffn {类} email.headerregistry.MIMEVersionHeader

There is really only one valid value for the @code{MIME-Version}
header, and that is @code{1.0}.  For future proofing, this header class
supports other valid version numbers.  If a version number has a valid value
per 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html}, then the header object will have non-@code{None} values for
the following attributes:

@geindex version (email.headerregistry.MIMEVersionHeader 属性)
@anchor{library/email headerregistry email headerregistry MIMEVersionHeader version}@anchor{2803}
@deffn {属性} version

The version number as a string, with any whitespace and/or comments
removed.
@end deffn

@geindex major (email.headerregistry.MIMEVersionHeader 属性)
@anchor{library/email headerregistry email headerregistry MIMEVersionHeader major}@anchor{2804}
@deffn {属性} major

The major version number as an integer
@end deffn

@geindex minor (email.headerregistry.MIMEVersionHeader 属性)
@anchor{library/email headerregistry email headerregistry MIMEVersionHeader minor}@anchor{2805}
@deffn {属性} minor

The minor version number as an integer
@end deffn
@end deffn

@geindex ParameterizedMIMEHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry ParameterizedMIMEHeader}@anchor{2806}
@deffn {类} email.headerregistry.ParameterizedMIMEHeader

MIME headers all start with the prefix 'Content-'.  Each specific header has
a certain value, described under the class for that header.  Some can
also take a list of supplemental parameters, which have a common format.
This class serves as a base for all the MIME headers that take parameters.

@geindex params (email.headerregistry.ParameterizedMIMEHeader 属性)
@anchor{library/email headerregistry email headerregistry ParameterizedMIMEHeader params}@anchor{2807}
@deffn {属性} params

A dictionary mapping parameter names to parameter values.
@end deffn
@end deffn

@geindex ContentTypeHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry ContentTypeHeader}@anchor{2808}
@deffn {类} email.headerregistry.ContentTypeHeader

A @ref{2806,,ParameterizedMIMEHeader} class that handles the
@code{Content-Type} header.

@geindex content_type (email.headerregistry.ContentTypeHeader 属性)
@anchor{library/email headerregistry email headerregistry ContentTypeHeader content_type}@anchor{2809}
@deffn {属性} content_type

The content type string, in the form @code{maintype/subtype}.
@end deffn

@geindex maintype (email.headerregistry.ContentTypeHeader 属性)
@anchor{library/email headerregistry email headerregistry ContentTypeHeader maintype}@anchor{280a}
@deffn {属性} maintype
@end deffn

@geindex subtype (email.headerregistry.ContentTypeHeader 属性)
@anchor{library/email headerregistry email headerregistry ContentTypeHeader subtype}@anchor{280b}
@deffn {属性} subtype
@end deffn
@end deffn

@geindex ContentDispositionHeader (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry ContentDispositionHeader}@anchor{280c}
@deffn {类} email.headerregistry.ContentDispositionHeader

A @ref{2806,,ParameterizedMIMEHeader} class that handles the
@code{Content-Disposition} header.


@deffn {属性} content@w{-}disposition

@code{inline} and @code{attachment} are the only valid values in common use.
@end deffn
@end deffn

@geindex ContentTransferEncoding (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry ContentTransferEncoding}@anchor{280d}
@deffn {类} email.headerregistry.ContentTransferEncoding

Handles the @code{Content-Transfer-Encoding} header.

@geindex cte (email.headerregistry.ContentTransferEncoding 属性)
@anchor{library/email headerregistry email headerregistry ContentTransferEncoding cte}@anchor{280e}
@deffn {属性} cte

Valid values are @code{7bit}, @code{8bit}, @code{base64}, and
@code{quoted-printable}.  See 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html} for more information.
@end deffn
@end deffn

@geindex HeaderRegistry (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry HeaderRegistry}@anchor{27f3}
@deffn {类} email.headerregistry.HeaderRegistry (base_class=BaseHeader, default_class=UnstructuredHeader, use_default_map=True)

This is the factory used by @ref{9f2,,EmailPolicy} by default.
@code{HeaderRegistry} builds the class used to create a header instance
dynamically, using @emph{base_class} and a specialized class retrieved from a
registry that it holds.  When a given header name does not appear in the
registry, the class specified by @emph{default_class} is used as the specialized
class.  When @emph{use_default_map} is @code{True} (the default), the standard
mapping of header names to classes is copied in to the registry during
initialization.  @emph{base_class} is always the last class in the generated
class's @code{__bases__} list.

The default mappings are:

@quotation

@*subject: 
UniqueUnstructuredHeader


@*date: 
UniqueDateHeader


@*resent-date: 
DateHeader


@*orig-date: 
UniqueDateHeader


@*sender: 
UniqueSingleAddressHeader


@*resent-sender: 
SingleAddressHeader


@*到: 
UniqueAddressHeader


@*resent-to: 
AddressHeader


@*cc: 
UniqueAddressHeader


@*resent-cc: 
AddressHeader


@*bcc: 
UniqueAddressHeader


@*resent-bcc: 
AddressHeader


@*从: 
UniqueAddressHeader


@*resent-from: 
AddressHeader


@*reply-to: 
UniqueAddressHeader


@*mime-version: 
MIMEVersionHeader


@*content-type: 
ContentTypeHeader


@*content-disposition: 
ContentDispositionHeader


@*content-transfer-encoding: 
ContentTransferEncodingHeader


@*message-id: 
MessageIDHeader

@end quotation

@code{HeaderRegistry} has the following methods:

@geindex map_to_type() (email.headerregistry.HeaderRegistry 方法)
@anchor{library/email headerregistry email headerregistry HeaderRegistry map_to_type}@anchor{280f}
@deffn {方法} map_to_type (self, name, cls)

@emph{name} is the name of the header to be mapped.  It will be converted to
lower case in the registry.  @emph{cls} is the specialized class to be used,
along with @emph{base_class}, to create the class used to instantiate headers
that match @emph{name}.
@end deffn

@geindex __getitem__() (email.headerregistry.HeaderRegistry 方法)
@anchor{library/email headerregistry email headerregistry HeaderRegistry __getitem__}@anchor{2810}
@deffn {方法} __getitem__ (name)

Construct and return a class to handle creating a @emph{name} header.
@end deffn

@geindex __call__() (email.headerregistry.HeaderRegistry 方法)
@anchor{library/email headerregistry email headerregistry HeaderRegistry __call__}@anchor{2811}
@deffn {方法} __call__ (name, value)

Retrieves the specialized header associated with @emph{name} from the
registry (using @emph{default_class} if @emph{name} does not appear in the
registry) and composes it with @emph{base_class} to produce a class,
calls the constructed class's constructor, passing it the same
argument list, and finally returns the class instance created thereby.
@end deffn
@end deffn

The following classes are the classes used to represent data parsed from
structured headers and can, in general, be used by an application program to
construct structured values to assign to specific headers.

@geindex Address (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry Address}@anchor{27ff}
@deffn {类} email.headerregistry.Address (display_name='@w{'}, username='@w{'}, domain='@w{'}, addr_spec=None)

The class used to represent an email address.  The general form of an
address is:

@example
[display_name] <username@@domain>
@end example

或者：

@example
username@@domain
@end example

where each part must conform to specific syntax rules spelled out in
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}.

As a convenience @emph{addr_spec} can be specified instead of @emph{username} and
@emph{domain}, in which case @emph{username} and @emph{domain} will be parsed from the
@emph{addr_spec}.  An @emph{addr_spec} must be a properly RFC quoted string; if it is
not @code{Address} will raise an error.  Unicode characters are allowed and
will be property encoded when serialized.  However, per the RFCs, unicode is
@emph{not} allowed in the username portion of the address.

@geindex display_name (email.headerregistry.Address 属性)
@anchor{library/email headerregistry email headerregistry Address display_name}@anchor{2812}
@deffn {属性} display_name

The display name portion of the address, if any, with all quoting
removed.  If the address does not have a display name, this attribute
will be an empty string.
@end deffn

@geindex username (email.headerregistry.Address 属性)
@anchor{library/email headerregistry email headerregistry Address username}@anchor{2813}
@deffn {属性} username

The @code{username} portion of the address, with all quoting removed.
@end deffn

@geindex domain (email.headerregistry.Address 属性)
@anchor{library/email headerregistry email headerregistry Address domain}@anchor{2814}
@deffn {属性} domain

The @code{domain} portion of the address.
@end deffn

@geindex addr_spec (email.headerregistry.Address 属性)
@anchor{library/email headerregistry email headerregistry Address addr_spec}@anchor{2815}
@deffn {属性} addr_spec

The @code{username@@domain} portion of the address, correctly quoted
for use as a bare address (the second form shown above).  This
attribute is not mutable.
@end deffn

@geindex __str__() (email.headerregistry.Address 方法)
@anchor{library/email headerregistry email headerregistry Address __str__}@anchor{2816}
@deffn {方法} __str__ ()

The @code{str} value of the object is the address quoted according to
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html} rules, but with no Content Transfer Encoding of any non-ASCII
characters.
@end deffn

To support SMTP (
@geindex RFC; RFC 5321
RFC 5321@footnote{https://tools.ietf.org/html/rfc5321.html}), @code{Address} handles one special case: if
@code{username} and @code{domain} are both the empty string (or @code{None}), then
the string value of the @code{Address} is @code{<>}.
@end deffn

@geindex Group (email.headerregistry 中的类)
@anchor{library/email headerregistry email headerregistry Group}@anchor{27fc}
@deffn {类} email.headerregistry.Group (display_name=None, addresses=None)

The class used to represent an address group.  The general form of an
address group is:

@example
display_name: [address-list];
@end example

As a convenience for processing lists of addresses that consist of a mixture
of groups and single addresses, a @code{Group} may also be used to represent
single addresses that are not part of a group by setting @emph{display_name} to
@code{None} and providing a list of the single address as @emph{addresses}.

@geindex display_name (email.headerregistry.Group 属性)
@anchor{library/email headerregistry email headerregistry Group display_name}@anchor{27fd}
@deffn {属性} display_name

The @code{display_name} of the group.  If it is @code{None} and there is
exactly one @code{Address} in @code{addresses}, then the @code{Group} represents a
single address that is not in a group.
@end deffn

@geindex addresses (email.headerregistry.Group 属性)
@anchor{library/email headerregistry email headerregistry Group addresses}@anchor{2817}
@deffn {属性} addresses

A possibly empty tuple of @ref{27ff,,Address} objects representing the
addresses in the group.
@end deffn

@geindex __str__() (email.headerregistry.Group 方法)
@anchor{library/email headerregistry email headerregistry Group __str__}@anchor{2818}
@deffn {方法} __str__ ()

The @code{str} value of a @code{Group} is formatted according to 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html},
but with no Content Transfer Encoding of any non-ASCII characters.  If
@code{display_name} is none and there is a single @code{Address} in the
@code{addresses} list, the @code{str} value will be the same as the @code{str} of
that single @code{Address}.
@end deffn
@end deffn

@subsubheading 备注


@node email contentmanager Managing MIME Content,email 示例,email headerregistry Custom Header Objects,email --- 电子邮件与 MIME 处理包
@anchor{library/email contentmanager doc}@anchor{2819}@anchor{library/email contentmanager email-contentmanager-managing-mime-content}@anchor{281a}@anchor{library/email contentmanager module-email contentmanager}@anchor{6b}
@subsubsection @code{email.contentmanager}: Managing MIME Content


@geindex email.contentmanager (模块)

@strong{Source code:} Lib/email/contentmanager.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/contentmanager.py}


__________________________________________________________________



3.6 新版功能: @footnote{@w{(1)} 
Originally added in 3.4 as a @ref{97a,,provisional module}
}


@geindex ContentManager (email.contentmanager 中的类)
@anchor{library/email contentmanager email contentmanager ContentManager}@anchor{281b}
@deffn {类} email.contentmanager.ContentManager

Base class for content managers.  Provides the standard registry mechanisms
to register converters between MIME content and other representations, as
well as the @code{get_content} and @code{set_content} dispatch methods.

@geindex get_content() (email.contentmanager.ContentManager 方法)
@anchor{library/email contentmanager email contentmanager ContentManager get_content}@anchor{27a1}
@deffn {方法} get_content (msg, *args, **kw)

Look up a handler function based on the @code{mimetype} of @emph{msg} (see next
paragraph), call it, passing through all arguments, and return the result
of the call.  The expectation is that the handler will extract the
payload from @emph{msg} and return an object that encodes information about
the extracted data.

To find the handler, look for the following keys in the registry,
stopping with the first one found:

@quotation


@itemize *

@item 
the string representing the full MIME type (@code{maintype/subtype})

@item 
the string representing the @code{maintype}

@item 
the empty string
@end itemize
@end quotation

If none of these keys produce a handler, raise a @ref{2c7,,KeyError} for the
full MIME type.
@end deffn

@geindex set_content() (email.contentmanager.ContentManager 方法)
@anchor{library/email contentmanager email contentmanager ContentManager set_content}@anchor{27a3}
@deffn {方法} set_content (msg, obj, *args, **kw)

If the @code{maintype} is @code{multipart}, raise a @ref{192,,TypeError}; otherwise
look up a handler function based on the type of @emph{obj} (see next
paragraph), call @ref{27ac,,clear_content()} on the
@emph{msg}, and call the handler function, passing through all arguments.  The
expectation is that the handler will transform and store @emph{obj} into
@emph{msg}, possibly making other changes to @emph{msg} as well, such as adding
various MIME headers to encode information needed to interpret the stored
data.

To find the handler, obtain the type of @emph{obj} (@code{typ = type(obj)}), and
look for the following keys in the registry, stopping with the first one
found:

@quotation


@itemize *

@item 
the type itself (@code{typ})

@item 
the type's fully qualified name (@code{typ.__module__ + '.' +
typ.__qualname__}).

@item 
the type's qualname (@code{typ.__qualname__})

@item 
the type's name (@code{typ.__name__}).
@end itemize
@end quotation

If none of the above match, repeat all of the checks above for each of
the types in the @ref{281c,,MRO} (@code{typ.__mro__}).  Finally, if no other key
yields a handler, check for a handler for the key @code{None}.  If there is
no handler for @code{None}, raise a @ref{2c7,,KeyError} for the fully
qualified name of the type.

Also add a @code{MIME-Version} header if one is not present (see
also @ref{83d,,MIMEPart}).
@end deffn

@geindex add_get_handler() (email.contentmanager.ContentManager 方法)
@anchor{library/email contentmanager email contentmanager ContentManager add_get_handler}@anchor{281d}
@deffn {方法} add_get_handler (key, handler)

Record the function @emph{handler} as the handler for @emph{key}.  For the possible
values of @emph{key}, see @ref{281e,,get_content()}.
@end deffn

@geindex add_set_handler() (email.contentmanager.ContentManager 方法)
@anchor{library/email contentmanager email contentmanager ContentManager add_set_handler}@anchor{281f}
@deffn {方法} add_set_handler (typekey, handler)

Record @emph{handler} as the function to call when an object of a type
matching @emph{typekey} is passed to @ref{2820,,set_content()}.  For the possible
values of @emph{typekey}, see @ref{2820,,set_content()}.
@end deffn
@end deffn

@menu
* Content Manager Instances:: 

@end menu

@node Content Manager Instances,,,email contentmanager Managing MIME Content
@anchor{library/email contentmanager content-manager-instances}@anchor{2821}
@subsubsection Content Manager Instances


Currently the email package provides only one concrete content manager,
@ref{27d6,,raw_data_manager}, although more may be added in the future.
@ref{27d6,,raw_data_manager} is the
@ref{83e,,content_manager} provided by
@ref{9f2,,EmailPolicy} and its derivatives.

@geindex raw_data_manager() (在 email.contentmanager 模块中)
@anchor{library/email contentmanager email contentmanager raw_data_manager}@anchor{27d6}
@deffn {数据} email.contentmanager.raw_data_manager

This content manager provides only a minimum interface beyond that provided
by @ref{53c,,Message} itself:  it deals only with text, raw
byte strings, and @ref{53c,,Message} objects.  Nevertheless, it
provides significant advantages compared to the base API: @code{get_content} on
a text part will return a unicode string without the application needing to
manually decode it, @code{set_content} provides a rich set of options for
controlling the headers added to a part and controlling the content transfer
encoding, and it enables the use of the various @code{add_} methods, thereby
simplifying the creation of multipart messages.

@geindex get_content() (在 email.contentmanager 模块中)
@anchor{library/email contentmanager email contentmanager get_content}@anchor{281e}
@deffn {方法} email.contentmanager.get_content (msg, errors='replace')

Return the payload of the part as either a string (for @code{text} parts), an
@ref{53d,,EmailMessage} object (for @code{message/rfc822}
parts), or a @code{bytes} object (for all other non-multipart types).  Raise
a @ref{2c7,,KeyError} if called on a @code{multipart}.  If the part is a
@code{text} part and @emph{errors} is specified, use it as the error handler when
decoding the payload to unicode.  The default error handler is
@code{replace}.
@end deffn

@geindex set_content() (在 email.contentmanager 模块中)
@anchor{library/email contentmanager email contentmanager set_content}@anchor{2820}
@deffn {方法} email.contentmanager.set_content (msg, <'str'>, subtype="plain", charset='utf-8'                     cte=None, disposition=None, filename=None, cid=None, params=None, headers=None)

@deffnx {方法} email.contentmanager.set_content (msg, <'bytes'>, maintype, subtype, cte="base64", disposition=None, filename=None, cid=None, params=None, headers=None)

@deffnx {方法} email.contentmanager.set_content (msg, <'EmailMessage'>, cte=None, disposition=None, filename=None, cid=None, params=None, headers=None)

Add headers and payload to @emph{msg}:

Add a @code{Content-Type} header with a @code{maintype/subtype}
value.

@quotation


@itemize *

@item 
For @code{str}, set the MIME @code{maintype} to @code{text}, and set the
subtype to @emph{subtype} if it is specified, or @code{plain} if it is not.

@item 
For @code{bytes}, use the specified @emph{maintype} and @emph{subtype}, or
raise a @ref{192,,TypeError} if they are not specified.

@item 
For @ref{53d,,EmailMessage} objects, set the maintype
to @code{message}, and set the subtype to @emph{subtype} if it is
specified or @code{rfc822} if it is not.  If @emph{subtype} is
@code{partial}, raise an error (@code{bytes} objects must be used to
construct @code{message/partial} parts).
@end itemize
@end quotation

If @emph{charset} is provided (which is valid only for @code{str}), encode the
string to bytes using the specified character set.  The default is
@code{utf-8}.  If the specified @emph{charset} is a known alias for a standard
MIME charset name, use the standard charset instead.

If @emph{cte} is set, encode the payload using the specified content transfer
encoding, and set the @code{Content-Transfer-Encoding} header to
that value.  Possible values for @emph{cte} are @code{quoted-printable},
@code{base64}, @code{7bit}, @code{8bit}, and @code{binary}.  If the input cannot be
encoded in the specified encoding (for example, specifying a @emph{cte} of
@code{7bit} for an input that contains non-ASCII values), raise a
@ref{1fb,,ValueError}.

@quotation


@itemize *

@item 
For @code{str} objects, if @emph{cte} is not set use heuristics to
determine the most compact encoding.

@item 
For @ref{53d,,EmailMessage}, per 
@geindex RFC; RFC 2046
RFC 2046@footnote{https://tools.ietf.org/html/rfc2046.html}, raise
an error if a @emph{cte} of @code{quoted-printable} or @code{base64} is
requested for @emph{subtype} @code{rfc822}, and for any @emph{cte} other than
@code{7bit} for @emph{subtype} @code{external-body}.  For
@code{message/rfc822}, use @code{8bit} if @emph{cte} is not specified.  For
all other values of @emph{subtype}, use @code{7bit}.
@end itemize
@end quotation

@cartouche
@quotation 注解 
A @emph{cte} of @code{binary} does not actually work correctly yet.
The @code{EmailMessage} object as modified by @code{set_content} is
correct, but @ref{b46,,BytesGenerator} does not
serialize it correctly.
@end quotation
@end cartouche

If @emph{disposition} is set, use it as the value of the
@code{Content-Disposition} header.  If not specified, and
@emph{filename} is specified, add the header with the value @code{attachment}.
If @emph{disposition} is not specified and @emph{filename} is also not specified,
do not add the header.  The only valid values for @emph{disposition} are
@code{attachment} and @code{inline}.

If @emph{filename} is specified, use it as the value of the @code{filename}
parameter of the @code{Content-Disposition} header.

If @emph{cid} is specified, add a @code{Content-ID} header with
@emph{cid} as its value.

If @emph{params} is specified, iterate its @code{items} method and use the
resulting @code{(key, value)} pairs to set additional parameters on the
@code{Content-Type} header.

If @emph{headers} is specified and is a list of strings of the form
@code{headername: headervalue} or a list of @code{header} objects
(distinguished from strings by having a @code{name} attribute), add the
headers to @emph{msg}.
@end deffn
@end deffn

@subsubheading 备注


@node email 示例,email message Message Representing an email message using the compat32 API,email contentmanager Managing MIME Content,email --- 电子邮件与 MIME 处理包
@anchor{library/email examples doc}@anchor{2822}@anchor{library/email examples email-examples}@anchor{83f}@anchor{library/email examples id1}@anchor{2823}
@subsubsection @code{email}: 示例


以下是一些如何使用 @ref{69,,email} 包来读取、写入和发送简单电子邮件以及更复杂的MIME邮件的示例。

首先，让我们看看如何创建和发送简单的文本消息（文本内容和地址都可能包含unicode字符）：

@example
# Import smtplib for the actual sending function
import smtplib

# Import the email modules we'll need
from email.message import EmailMessage

# Open the plain text file whose name is in textfile for reading.
with open(textfile) as fp:
    # Create a text/plain message
    msg = EmailMessage()
    msg.set_content(fp.read())

# me == the sender's email address
# you == the recipient's email address
msg['Subject'] = f'The contents of @{textfile@}'
msg['From'] = me
msg['To'] = you

# Send the message via our own SMTP server.
s = smtplib.SMTP('localhost')
s.send_message(msg)
s.quit()
@end example

解析 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html} 标题可以通过使用 @ref{74,,parser} 模块中的类来轻松完成：

@example
# Import the email modules we'll need
from email.parser import BytesParser, Parser
from email.policy import default

# If the e-mail headers are in a file, uncomment these two lines:
# with open(messagefile, 'rb') as fp:
#     headers = BytesParser(policy=default).parse(fp)

#  Or for parsing headers in a string (this is an uncommon operation), use:
headers = Parser(policy=default).parsestr(
        'From: Foo Bar <user@@example.com>\n'
        'To: <someone_else@@example.com>\n'
        'Subject: Test message\n'
        '\n'
        'Body would go here\n')

#  Now the header items can be accessed as a dictionary:
print('To: @{@}'.format(headers['to']))
print('From: @{@}'.format(headers['from']))
print('Subject: @{@}'.format(headers['subject']))

# You can also access the parts of the addresses:
print('Recipient username: @{@}'.format(headers['to'].addresses[0].username))
print('Sender name: @{@}'.format(headers['from'].addresses[0].display_name))
@end example

以下是如何发送包含可能在目录中的一系列家庭照片的MIME消息示例：

@example
# Import smtplib for the actual sending function
import smtplib

# And imghdr to find the types of our images
import imghdr

# Here are the email package modules we'll need
from email.message import EmailMessage

# Create the container email message.
msg = EmailMessage()
msg['Subject'] = 'Our family reunion'
# me == the sender's email address
# family = the list of all recipients' email addresses
msg['From'] = me
msg['To'] = ', '.join(family)
msg.preamble = 'You will not see this in a MIME-aware mail reader.\n'

# Open the files in binary mode.  Use imghdr to figure out the
# MIME subtype for each specific image.
for file in pngfiles:
    with open(file, 'rb') as fp:
        img_data = fp.read()
    msg.add_attachment(img_data, maintype='image',
                                 subtype=imghdr.what(None, img_data))

# Send the email via our own SMTP server.
with smtplib.SMTP('localhost') as s:
    s.send_message(msg)
@end example

以下是如何将目录的全部内容作为电子邮件消息发送的示例： @footnote{@w{(1)} 
感谢 Matthew Dixon Cowles 提供最初的灵感和示例。
}

@example
#!/usr/bin/env python3

"""Send the contents of a directory as a MIME message."""

import os
import smtplib
# For guessing MIME type based on file name extension
import mimetypes

from argparse import ArgumentParser

from email.message import EmailMessage
from email.policy import SMTP


def main():
    parser = ArgumentParser(description="""\
Send the contents of a directory as a MIME message.
Unless the -o option is given, the email is sent by forwarding to your local
SMTP server, which then does the normal delivery process.  Your local machine
must be running an SMTP server.
""")
    parser.add_argument('-d', '--directory',
                        help="""Mail the contents of the specified directory,
                        otherwise use the current directory.  Only the regular
                        files in the directory are sent, and we don't recurse to
                        subdirectories.""")
    parser.add_argument('-o', '--output',
                        metavar='FILE',
                        help="""Print the composed message to FILE instead of
                        sending the message to the SMTP server.""")
    parser.add_argument('-s', '--sender', required=True,
                        help='The value of the From: header (required)')
    parser.add_argument('-r', '--recipient', required=True,
                        action='append', metavar='RECIPIENT',
                        default=[], dest='recipients',
                        help='A To: header value (at least one required)')
    args = parser.parse_args()
    directory = args.directory
    if not directory:
        directory = '.'
    # Create the message
    msg = EmailMessage()
    msg['Subject'] = f'Contents of directory @{os.path.abspath(directory)@}'
    msg['To'] = ', '.join(args.recipients)
    msg['From'] = args.sender
    msg.preamble = 'You will not see this in a MIME-aware mail reader.\n'

    for filename in os.listdir(directory):
        path = os.path.join(directory, filename)
        if not os.path.isfile(path):
            continue
        # Guess the content type based on the file's extension.  Encoding
        # will be ignored, although we should check for simple things like
        # gzip'd or compressed files.
        ctype, encoding = mimetypes.guess_type(path)
        if ctype is None or encoding is not None:
            # No guess could be made, or the file is encoded (compressed), so
            # use a generic bag-of-bits type.
            ctype = 'application/octet-stream'
        maintype, subtype = ctype.split('/', 1)
        with open(path, 'rb') as fp:
            msg.add_attachment(fp.read(),
                               maintype=maintype,
                               subtype=subtype,
                               filename=filename)
    # Now send or store the message
    if args.output:
        with open(args.output, 'wb') as fp:
            fp.write(msg.as_bytes(policy=SMTP))
    else:
        with smtplib.SMTP('localhost') as s:
            s.send_message(msg)


if __name__ == '__main__':
    main()
@end example

以下是如何将上述MIME消息解压缩到文件目录中的示例：

@example
#!/usr/bin/env python3

"""Unpack a MIME message into a directory of files."""

import os
import email
import mimetypes

from email.policy import default

from argparse import ArgumentParser


def main():
    parser = ArgumentParser(description="""\
Unpack a MIME message into a directory of files.
""")
    parser.add_argument('-d', '--directory', required=True,
                        help="""Unpack the MIME message into the named
                        directory, which will be created if it doesn't already
                        exist.""")
    parser.add_argument('msgfile')
    args = parser.parse_args()

    with open(args.msgfile, 'rb') as fp:
        msg = email.message_from_binary_file(fp, policy=default)

    try:
        os.mkdir(args.directory)
    except FileExistsError:
        pass

    counter = 1
    for part in msg.walk():
        # multipart/* are just containers
        if part.get_content_maintype() == 'multipart':
            continue
        # Applications should really sanitize the given filename so that an
        # email message can't be used to overwrite important files
        filename = part.get_filename()
        if not filename:
            ext = mimetypes.guess_extension(part.get_content_type())
            if not ext:
                # Use a generic bag-of-bits extension
                ext = '.bin'
            filename = f'part-@{counter:03d@}@{ext@}'
        counter += 1
        with open(os.path.join(args.directory, filename), 'wb') as fp:
            fp.write(part.get_payload(decode=True))


if __name__ == '__main__':
    main()
@end example

以下是如何使用备用纯文本版本创建 HTML 消息的示例。 为了让事情变得更有趣，我们在 html 部分中包含了一个相关的图像，我们保存了一份我们要发送的内容到硬盘中，然后发送它。

@example
#!/usr/bin/env python3

import smtplib

from email.message import EmailMessage
from email.headerregistry import Address
from email.utils import make_msgid

# Create the base text message.
msg = EmailMessage()
msg['Subject'] = "Ayons asperges pour le déjeuner"
msg['From'] = Address("Pepé Le Pew", "pepe", "example.com")
msg['To'] = (Address("Penelope Pussycat", "penelope", "example.com"),
             Address("Fabrette Pussycat", "fabrette", "example.com"))
msg.set_content("""\
Salut!

Cela ressemble à un excellent recipie[1] déjeuner.

[1] http://www.yummly.com/recipe/Roasted-Asparagus-Epicurious-203718

--Pepé
""")

# Add the html version.  This converts the message into a multipart/alternative
# container, with the original text message as the first part and the new html
# message as the second part.
asparagus_cid = make_msgid()
msg.add_alternative("""\
<html>
  <head></head>
  <body>
    <p>Salut!</p>
    <p>Cela ressemble à un excellent
        <a href="http://www.yummly.com/recipe/Roasted-Asparagus-Epicurious-203718">
            recipie
        </a> déjeuner.
    </p>
    <img src="cid:@{asparagus_cid@}" />
  </body>
</html>
""".format(asparagus_cid=asparagus_cid[1:-1]), subtype='html')
# note that we needed to peel the <> off the msgid for use in the html.

# Now add the related image to the html part.
with open("roasted-asparagus.jpg", 'rb') as img:
    msg.get_payload()[1].add_related(img.read(), 'image', 'jpeg',
                                     cid=asparagus_cid)

# Make a local copy of what we are going to send.
with open('outgoing.msg', 'wb') as f:
    f.write(bytes(msg))

# Send the message via local SMTP server.
with smtplib.SMTP('localhost') as s:
    s.send_message(msg)
@end example

如果我们发送最后一个示例中的消息，这是我们可以处理它的一种方法：

@example
import os
import sys
import tempfile
import mimetypes
import webbrowser

# Import the email modules we'll need
from email import policy
from email.parser import BytesParser

# An imaginary module that would make this work and be safe.
from imaginary import magic_html_parser

# In a real program you'd get the filename from the arguments.
with open('outgoing.msg', 'rb') as fp:
    msg = BytesParser(policy=policy.default).parse(fp)

# Now the header items can be accessed as a dictionary, and any non-ASCII will
# be converted to unicode:
print('To:', msg['to'])
print('From:', msg['from'])
print('Subject:', msg['subject'])

# If we want to print a preview of the message content, we can extract whatever
# the least formatted payload is and print the first three lines.  Of course,
# if the message has no plain text part printing the first three lines of html
# is probably useless, but this is just a conceptual example.
simplest = msg.get_body(preferencelist=('plain', 'html'))
print()
print('@w{'}.join(simplest.get_content().splitlines(keepends=True)[:3]))

ans = input("View full message?")
if ans.lower()[0] == 'n':
    sys.exit()

# We can extract the richest alternative in order to display it:
richest = msg.get_body()
partfiles = @{@}
if richest['content-type'].maintype == 'text':
    if richest['content-type'].subtype == 'plain':
        for line in richest.get_content().splitlines():
            print(line)
        sys.exit()
    elif richest['content-type'].subtype == 'html':
        body = richest
    else:
        print("Don't know how to display @{@}".format(richest.get_content_type()))
        sys.exit()
elif richest['content-type'].content_type == 'multipart/related':
    body = richest.get_body(preferencelist=('html'))
    for part in richest.iter_attachments():
        fn = part.get_filename()
        if fn:
            extension = os.path.splitext(part.get_filename())[1]
        else:
            extension = mimetypes.guess_extension(part.get_content_type())
        with tempfile.NamedTemporaryFile(suffix=extension, delete=False) as f:
            f.write(part.get_content())
            # again strip the <> to go from email form of cid to html form.
            partfiles[part['content-id'][1:-1]] = f.name
else:
    print("Don't know how to display @{@}".format(richest.get_content_type()))
    sys.exit()
with tempfile.NamedTemporaryFile(mode='w', delete=False) as f:
    # The magic_html_parser has to rewrite the href="cid:...." attributes to
    # point to the filenames in partfiles.  It also has to do a safety-sanitize
    # of the html.  It could be written using html.parser.
    f.write(magic_html_parser(body.get_content(), partfiles))
webbrowser.open(f.name)
os.remove(f.name)
for fn in partfiles.values():
    os.remove(fn)

# Of course, there are lots of email messages that could break this simple
# minded program, but it will handle the most common ones.
@end example

直到输出提示，上面的输出是：

@example
To: Penelope Pussycat <penelope@@example.com>, Fabrette Pussycat <fabrette@@example.com>
From: Pepé Le Pew <pepe@@example.com>
Subject: Ayons asperges pour le déjeuner

Salut!

Cela ressemble à un excellent recipie[1] déjeuner.
@end example

@subsubheading 备注


Legacy API:

@node email message Message Representing an email message using the compat32 API,email mime Creating email and MIME objects from scratch,email 示例,email --- 电子邮件与 MIME 处理包
@anchor{library/email compat32-message doc}@anchor{2824}@anchor{library/email compat32-message compat32-message}@anchor{2774}@anchor{library/email compat32-message email-message-message-representing-an-email-message-using-the-compat32-api}@anchor{2825}
@subsubsection @code{email.message.Message}: Representing an email message using the @code{compat32} API


The @ref{53c,,Message} class is very similar to the
@ref{53d,,EmailMessage} class, without the methods added by that
class, and with the default behavior of certain other methods being slightly
different.  We also document here some methods that, while supported by the
@ref{53d,,EmailMessage} class, are not recommended unless you are
dealing with legacy code.

The philosophy and structure of the two classes is otherwise the same.

This document describes the behavior under the default (for @ref{53c,,Message})
policy @ref{9ef,,Compat32}.  If you are going to use another policy,
you should be using the @ref{53d,,EmailMessage} class instead.

An email message consists of @emph{headers} and a @emph{payload}.  Headers must be
@geindex RFC; RFC 5233
RFC 5233@footnote{https://tools.ietf.org/html/rfc5233.html} style names and values, where the field name and value are
separated by a colon.  The colon is not part of either the field name or the
field value.  The payload may be a simple text message, or a binary object, or
a structured sequence of sub-messages each with their own set of headers and
their own payload.  The latter type of payload is indicated by the message
having a MIME type such as @code{multipart/*} or
@code{message/rfc822}.

The conceptual model provided by a @ref{53c,,Message} object is that of an
ordered dictionary of headers with additional methods for accessing both
specialized information from the headers, for accessing the payload, for
generating a serialized version of the message, and for recursively walking
over the object tree.  Note that duplicate headers are supported but special
methods must be used to access them.

The @ref{53c,,Message} pseudo-dictionary is indexed by the header names, which
must be ASCII values.  The values of the dictionary are strings that are
supposed to contain only ASCII characters; there is some special handling for
non-ASCII input, but it doesn't always produce the correct results.  Headers
are stored and returned in case-preserving form, but field names are matched
case-insensitively.  There may also be a single envelope header, also known as
the @emph{Unix-From} header or the @code{From_} header.  The @emph{payload} is either a
string or bytes, in the case of simple message objects, or a list of
@ref{53c,,Message} objects, for MIME container documents (e.g.
@code{multipart/*} and @code{message/rfc822}).

Here are the methods of the @ref{53c,,Message} class:

@geindex Message (email.message 中的类)
@anchor{library/email compat32-message email message Message}@anchor{53c}
@deffn {类} email.message.Message (policy=compat32)

If @emph{policy} is specified (it must be an instance of a @ref{75,,policy}
class) use the rules it specifies to update and serialize the representation
of the message.  If @emph{policy} is not set, use the @ref{9ef,,compat32} policy, which maintains backward compatibility with
the Python 3.2 version of the email package.  For more information see the
@ref{75,,policy} documentation.


在 3.3 版更改: The @emph{policy} keyword argument was added.


@geindex as_string() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message as_string}@anchor{839}
@deffn {方法} as_string (unixfrom=False, maxheaderlen=0, policy=None)

Return the entire message flattened as a string.  When optional @emph{unixfrom}
is true, the envelope header is included in the returned string.
@emph{unixfrom} defaults to @code{False}.  For backward compatibility reasons,
@emph{maxheaderlen} defaults to @code{0}, so if you want a different value you
must override it explicitly (the value specified for @emph{max_line_length} in
the policy will be ignored by this method).  The @emph{policy} argument may be
used to override the default policy obtained from the message instance.
This can be used to control some of the formatting produced by the
method, since the specified @emph{policy} will be passed to the @code{Generator}.

Flattening the message may trigger changes to the @ref{53c,,Message} if
defaults need to be filled in to complete the transformation to a string
(for example, MIME boundaries may be generated or modified).

Note that this method is provided as a convenience and may not always
format the message the way you want.  For example, by default it does
not do the mangling of lines that begin with @code{From} that is
required by the unix mbox format.  For more flexibility, instantiate a
@ref{b45,,Generator} instance and use its
@ref{27c4,,flatten()} method directly.  For example:

@example
from io import StringIO
from email.generator import Generator
fp = StringIO()
g = Generator(fp, mangle_from_=True, maxheaderlen=60)
g.flatten(msg)
text = fp.getvalue()
@end example

If the message object contains binary data that is not encoded according
to RFC standards, the non-compliant data will be replaced by unicode
"unknown character" code points.  (See also @ref{83a,,as_bytes()} and
@ref{b46,,BytesGenerator}.)


在 3.4 版更改: the @emph{policy} keyword argument was added.

@end deffn

@geindex __str__() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message __str__}@anchor{2826}
@deffn {方法} __str__ ()

Equivalent to @ref{839,,as_string()}.  Allows @code{str(msg)} to produce a
string containing the formatted message.
@end deffn

@geindex as_bytes() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message as_bytes}@anchor{83a}
@deffn {方法} as_bytes (unixfrom=False, policy=None)

Return the entire message flattened as a bytes object.  When optional
@emph{unixfrom} is true, the envelope header is included in the returned
string.  @emph{unixfrom} defaults to @code{False}.  The @emph{policy} argument may be
used to override the default policy obtained from the message instance.
This can be used to control some of the formatting produced by the
method, since the specified @emph{policy} will be passed to the
@code{BytesGenerator}.

Flattening the message may trigger changes to the @ref{53c,,Message} if
defaults need to be filled in to complete the transformation to a string
(for example, MIME boundaries may be generated or modified).

Note that this method is provided as a convenience and may not always
format the message the way you want.  For example, by default it does
not do the mangling of lines that begin with @code{From} that is
required by the unix mbox format.  For more flexibility, instantiate a
@ref{b46,,BytesGenerator} instance and use its
@ref{27c0,,flatten()} method directly.
For example:

@example
from io import BytesIO
from email.generator import BytesGenerator
fp = BytesIO()
g = BytesGenerator(fp, mangle_from_=True, maxheaderlen=60)
g.flatten(msg)
text = fp.getvalue()
@end example


3.4 新版功能.

@end deffn

@geindex __bytes__() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message __bytes__}@anchor{83b}
@deffn {方法} __bytes__ ()

Equivalent to @ref{83a,,as_bytes()}.  Allows @code{bytes(msg)} to produce a
bytes object containing the formatted message.


3.4 新版功能.

@end deffn

@geindex is_multipart() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message is_multipart}@anchor{279a}
@deffn {方法} is_multipart ()

Return @code{True} if the message's payload is a list of
sub-@ref{53c,,Message} objects, otherwise return @code{False}.  When
@ref{279a,,is_multipart()} returns @code{False}, the payload should be a string
object (which might be a CTE encoded binary payload).  (Note that
@ref{279a,,is_multipart()} returning @code{True} does not necessarily mean that
"msg.get_content_maintype() == 'multipart'" will return the @code{True}.
For example, @code{is_multipart} will return @code{True} when the
@ref{53c,,Message} is of type @code{message/rfc822}.)
@end deffn

@geindex set_unixfrom() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message set_unixfrom}@anchor{2827}
@deffn {方法} set_unixfrom (unixfrom)

Set the message's envelope header to @emph{unixfrom}, which should be a string.
@end deffn

@geindex get_unixfrom() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_unixfrom}@anchor{2828}
@deffn {方法} get_unixfrom ()

Return the message's envelope header.  Defaults to @code{None} if the
envelope header was never set.
@end deffn

@geindex attach() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message attach}@anchor{27a8}
@deffn {方法} attach (payload)

Add the given @emph{payload} to the current payload, which must be @code{None} or
a list of @ref{53c,,Message} objects before the call. After the call, the
payload will always be a list of @ref{53c,,Message} objects.  If you want to
set the payload to a scalar object (e.g. a string), use
@ref{2829,,set_payload()} instead.

This is a legacy method.  On the
@code{EmailMessage} class its functionality is
replaced by @ref{27a2,,set_content()} and the
related @code{make} and @code{add} methods.
@end deffn

@geindex get_payload() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_payload}@anchor{b44}
@deffn {方法} get_payload (i=None, decode=False)

Return the current payload, which will be a list of
@ref{53c,,Message} objects when @ref{279a,,is_multipart()} is @code{True}, or a
string when @ref{279a,,is_multipart()} is @code{False}.  If the payload is a list
and you mutate the list object, you modify the message's payload in place.

With optional argument @emph{i}, @ref{b44,,get_payload()} will return the @emph{i}-th
element of the payload, counting from zero, if @ref{279a,,is_multipart()} is
@code{True}.  An @ref{e6e,,IndexError} will be raised if @emph{i} is less than 0 or
greater than or equal to the number of items in the payload.  If the
payload is a string (i.e.  @ref{279a,,is_multipart()} is @code{False}) and @emph{i} is
given, a @ref{192,,TypeError} is raised.

Optional @emph{decode} is a flag indicating whether the payload should be
decoded or not, according to the @code{Content-Transfer-Encoding}
header. When @code{True} and the message is not a multipart, the payload will
be decoded if this header's value is @code{quoted-printable} or @code{base64}.
If some other encoding is used, or @code{Content-Transfer-Encoding}
header is missing, the payload is
returned as-is (undecoded).  In all cases the returned value is binary
data.  If the message is a multipart and the @emph{decode} flag is @code{True},
then @code{None} is returned.  If the payload is base64 and it was not
perfectly formed (missing padding, characters outside the base64
alphabet), then an appropriate defect will be added to the message's
defect property (@code{InvalidBase64PaddingDefect} or
@code{InvalidBase64CharactersDefect}, respectively).

When @emph{decode} is @code{False} (the default) the body is returned as a string
without decoding the @code{Content-Transfer-Encoding}.  However,
for a @code{Content-Transfer-Encoding} of 8bit, an attempt is made
to decode the original bytes using the @code{charset} specified by the
@code{Content-Type} header, using the @code{replace} error handler.
If no @code{charset} is specified, or if the @code{charset} given is not
recognized by the email package, the body is decoded using the default
ASCII charset.

This is a legacy method.  On the
@code{EmailMessage} class its functionality is
replaced by @ref{27a0,,get_content()} and
@ref{279f,,iter_parts()}.
@end deffn

@geindex set_payload() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message set_payload}@anchor{2829}
@deffn {方法} set_payload (payload, charset=None)

Set the entire message object's payload to @emph{payload}.  It is the client's
responsibility to ensure the payload invariants.  Optional @emph{charset} sets
the message's default character set; see @ref{282a,,set_charset()} for details.

This is a legacy method.  On the
@code{EmailMessage} class its functionality is
replaced by @ref{27a2,,set_content()}.
@end deffn

@geindex set_charset() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message set_charset}@anchor{282a}
@deffn {方法} set_charset (charset)

Set the character set of the payload to @emph{charset}, which can either be a
@ref{6ce,,Charset} instance (see @ref{6a,,email.charset}), a
string naming a character set, or @code{None}.  If it is a string, it will
be converted to a @ref{6ce,,Charset} instance.  If @emph{charset}
is @code{None}, the @code{charset} parameter will be removed from the
@code{Content-Type} header (the message will not be otherwise
modified).  Anything else will generate a @ref{192,,TypeError}.

If there is no existing @code{MIME-Version} header one will be
added.  If there is no existing @code{Content-Type} header, one
will be added with a value of @code{text/plain}.  Whether the
@code{Content-Type} header already exists or not, its @code{charset}
parameter will be set to @emph{charset.output_charset}.   If
@emph{charset.input_charset} and @emph{charset.output_charset} differ, the payload
will be re-encoded to the @emph{output_charset}.  If there is no existing
@code{Content-Transfer-Encoding} header, then the payload will be
transfer-encoded, if needed, using the specified
@ref{6ce,,Charset}, and a header with the appropriate value
will be added.  If a @code{Content-Transfer-Encoding} header
already exists, the payload is assumed to already be correctly encoded
using that @code{Content-Transfer-Encoding} and is not modified.

This is a legacy method.  On the
@code{EmailMessage} class its functionality is
replaced by the @emph{charset} parameter of the
@code{email.emailmessage.EmailMessage.set_content()} method.
@end deffn

@geindex get_charset() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_charset}@anchor{282b}
@deffn {方法} get_charset ()

Return the @ref{6ce,,Charset} instance associated with the
message's payload.

This is a legacy method.  On the
@code{EmailMessage} class it always returns
@code{None}.
@end deffn

The following methods implement a mapping-like interface for accessing the
message's 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html} headers.  Note that there are some semantic differences
between these methods and a normal mapping (i.e. dictionary) interface.  For
example, in a dictionary there are no duplicate keys, but here there may be
duplicate message headers.  Also, in dictionaries there is no guaranteed
order to the keys returned by @ref{282c,,keys()}, but in a @ref{53c,,Message} object,
headers are always returned in the order they appeared in the original
message, or were added to the message later.  Any header deleted and then
re-added are always appended to the end of the header list.

These semantic differences are intentional and are biased toward maximal
convenience.

Note that in all cases, any envelope header present in the message is not
included in the mapping interface.

In a model generated from bytes, any header values that (in contravention of
the RFCs) contain non-ASCII bytes will, when retrieved through this
interface, be represented as @ref{27e6,,Header} objects with
a charset of @cite{unknown-8bit}.

@geindex __len__() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message __len__}@anchor{282d}
@deffn {方法} __len__ ()

Return the total number of headers, including duplicates.
@end deffn

@geindex __contains__() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message __contains__}@anchor{282e}
@deffn {方法} __contains__ (name)

Return @code{True} if the message object has a field named @emph{name}. Matching is
done case-insensitively and @emph{name} should not include the trailing colon.
Used for the @code{in} operator, e.g.:

@example
if 'message-id' in myMessage:
   print('Message-ID:', myMessage['message-id'])
@end example
@end deffn

@geindex __getitem__() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message __getitem__}@anchor{282f}
@deffn {方法} __getitem__ (name)

Return the value of the named header field.  @emph{name} should not include the
colon field separator.  If the header is missing, @code{None} is returned; a
@ref{2c7,,KeyError} is never raised.

Note that if the named field appears more than once in the message's
headers, exactly which of those field values will be returned is
undefined.  Use the @ref{2830,,get_all()} method to get the values of all the
extant named headers.
@end deffn

@geindex __setitem__() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message __setitem__}@anchor{2831}
@deffn {方法} __setitem__ (name, val)

Add a header to the message with field name @emph{name} and value @emph{val}.  The
field is appended to the end of the message's existing fields.

Note that this does @emph{not} overwrite or delete any existing header with the same
name.  If you want to ensure that the new header is the only one present in the
message with field name @emph{name}, delete the field first, e.g.:

@example
del msg['subject']
msg['subject'] = 'Python roolz!'
@end example
@end deffn

@geindex __delitem__() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message __delitem__}@anchor{2832}
@deffn {方法} __delitem__ (name)

Delete all occurrences of the field with name @emph{name} from the message's
headers.  No exception is raised if the named field isn't present in the
headers.
@end deffn

@geindex keys() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message keys}@anchor{282c}
@deffn {方法} keys ()

Return a list of all the message's header field names.
@end deffn

@geindex values() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message values}@anchor{2833}
@deffn {方法} values ()

Return a list of all the message's field values.
@end deffn

@geindex items() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message items}@anchor{2834}
@deffn {方法} items ()

Return a list of 2-tuples containing all the message's field headers and
values.
@end deffn

@geindex get() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get}@anchor{2835}
@deffn {方法} get (name, failobj=None)

Return the value of the named header field.  This is identical to
@ref{282f,,__getitem__()} except that optional @emph{failobj} is returned if the
named header is missing (defaults to @code{None}).
@end deffn

Here are some additional useful methods:

@geindex get_all() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_all}@anchor{2830}
@deffn {方法} get_all (name, failobj=None)

Return a list of all the values for the field named @emph{name}. If there are
no such named headers in the message, @emph{failobj} is returned (defaults to
@code{None}).
@end deffn

@geindex add_header() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message add_header}@anchor{2836}
@deffn {方法} add_header (_name, _value, **_params)

Extended header setting.  This method is similar to @ref{2831,,__setitem__()}
except that additional header parameters can be provided as keyword
arguments.  @emph{_name} is the header field to add and @emph{_value} is the
@emph{primary} value for the header.

For each item in the keyword argument dictionary @emph{_params}, the key is
taken as the parameter name, with underscores converted to dashes (since
dashes are illegal in Python identifiers).  Normally, the parameter will
be added as @code{key="value"} unless the value is @code{None}, in which case
only the key will be added.  If the value contains non-ASCII characters,
it can be specified as a three tuple in the format
@code{(CHARSET, LANGUAGE, VALUE)}, where @code{CHARSET} is a string naming the
charset to be used to encode the value, @code{LANGUAGE} can usually be set
to @code{None} or the empty string (see 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html} for other possibilities),
and @code{VALUE} is the string value containing non-ASCII code points.  If
a three tuple is not passed and the value contains non-ASCII characters,
it is automatically encoded in 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html} format using a @code{CHARSET}
of @code{utf-8} and a @code{LANGUAGE} of @code{None}.

Here's an example:

@example
msg.add_header('Content-Disposition', 'attachment', filename='bud.gif')
@end example

This will add a header that looks like

@example
Content-Disposition: attachment; filename="bud.gif"
@end example

An example with non-ASCII characters:

@example
msg.add_header('Content-Disposition', 'attachment',
               filename=('iso-8859-1', '@w{'}, 'Fußballer.ppt'))
@end example

Which produces

@example
Content-Disposition: attachment; filename*="iso-8859-1'@w{'}Fu%DFballer.ppt"
@end example
@end deffn

@geindex replace_header() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message replace_header}@anchor{2837}
@deffn {方法} replace_header (_name, _value)

Replace a header.  Replace the first header found in the message that
matches @emph{_name}, retaining header order and field name case.  If no
matching header was found, a @ref{2c7,,KeyError} is raised.
@end deffn

@geindex get_content_type() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_content_type}@anchor{2838}
@deffn {方法} get_content_type ()

Return the message's content type.  The returned string is coerced to
lower case of the form @code{maintype/subtype}.  If there was no
@code{Content-Type} header in the message the default type as given
by @ref{2839,,get_default_type()} will be returned.  Since according to
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html}, messages always have a default type, @ref{2838,,get_content_type()}
will always return a value.

@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html} defines a message's default type to be @code{text/plain}
unless it appears inside a @code{multipart/digest} container, in
which case it would be @code{message/rfc822}.  If the
@code{Content-Type} header has an invalid type specification,
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html} mandates that the default type be @code{text/plain}.
@end deffn

@geindex get_content_maintype() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_content_maintype}@anchor{283a}
@deffn {方法} get_content_maintype ()

Return the message's main content type.  This is the @code{maintype}
part of the string returned by @ref{2838,,get_content_type()}.
@end deffn

@geindex get_content_subtype() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_content_subtype}@anchor{283b}
@deffn {方法} get_content_subtype ()

Return the message's sub-content type.  This is the @code{subtype}
part of the string returned by @ref{2838,,get_content_type()}.
@end deffn

@geindex get_default_type() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_default_type}@anchor{2839}
@deffn {方法} get_default_type ()

Return the default content type.  Most messages have a default content
type of @code{text/plain}, except for messages that are subparts of
@code{multipart/digest} containers.  Such subparts have a default
content type of @code{message/rfc822}.
@end deffn

@geindex set_default_type() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message set_default_type}@anchor{283c}
@deffn {方法} set_default_type (ctype)

Set the default content type.  @emph{ctype} should either be
@code{text/plain} or @code{message/rfc822}, although this is not
enforced.  The default content type is not stored in the
@code{Content-Type} header.
@end deffn

@geindex get_params() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_params}@anchor{283d}
@deffn {方法} get_params (failobj=None, header='content-type', unquote=True)

Return the message's @code{Content-Type} parameters, as a list.
The elements of the returned list are 2-tuples of key/value pairs, as
split on the @code{'='} sign.  The left hand side of the @code{'='} is the key,
while the right hand side is the value.  If there is no @code{'='} sign in
the parameter the value is the empty string, otherwise the value is as
described in @ref{283e,,get_param()} and is unquoted if optional @emph{unquote} is
@code{True} (the default).

Optional @emph{failobj} is the object to return if there is no
@code{Content-Type} header.  Optional @emph{header} is the header to
search instead of @code{Content-Type}.

This is a legacy method.  On the
@code{EmailMessage} class its functionality is
replaced by the @emph{params} property of the individual header objects
returned by the header access methods.
@end deffn

@geindex get_param() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_param}@anchor{283e}
@deffn {方法} get_param (param, failobj=None, header='content-type', unquote=True)

Return the value of the @code{Content-Type} header's parameter
@emph{param} as a string.  If the message has no @code{Content-Type}
header or if there is no such parameter, then @emph{failobj} is returned
(defaults to @code{None}).

Optional @emph{header} if given, specifies the message header to use instead of
@code{Content-Type}.

Parameter keys are always compared case insensitively.  The return value
can either be a string, or a 3-tuple if the parameter was 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html}
encoded.  When it's a 3-tuple, the elements of the value are of the form
@code{(CHARSET, LANGUAGE, VALUE)}.  Note that both @code{CHARSET} and
@code{LANGUAGE} can be @code{None}, in which case you should consider @code{VALUE}
to be encoded in the @code{us-ascii} charset.  You can usually ignore
@code{LANGUAGE}.

If your application doesn't care whether the parameter was encoded as in
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html}, you can collapse the parameter value by calling
@ref{283f,,email.utils.collapse_rfc2231_value()}, passing in the return value
from @ref{283e,,get_param()}.  This will return a suitably decoded Unicode
string when the value is a tuple, or the original string unquoted if it
isn't.  For example:

@example
rawparam = msg.get_param('foo')
param = email.utils.collapse_rfc2231_value(rawparam)
@end example

In any case, the parameter value (either the returned string, or the
@code{VALUE} item in the 3-tuple) is always unquoted, unless @emph{unquote} is set
to @code{False}.

This is a legacy method.  On the
@code{EmailMessage} class its functionality is
replaced by the @emph{params} property of the individual header objects
returned by the header access methods.
@end deffn

@geindex set_param() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message set_param}@anchor{83c}
@deffn {方法} set_param (param, value, header='Content-Type', requote=True, charset=None, language='@w{'}, replace=False)

Set a parameter in the @code{Content-Type} header.  If the
parameter already exists in the header, its value will be replaced with
@emph{value}.  If the @code{Content-Type} header as not yet been defined
for this message, it will be set to @code{text/plain} and the new
parameter value will be appended as per 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html}.

Optional @emph{header} specifies an alternative header to
@code{Content-Type}, and all parameters will be quoted as necessary
unless optional @emph{requote} is @code{False} (the default is @code{True}).

If optional @emph{charset} is specified, the parameter will be encoded
according to 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html}. Optional @emph{language} specifies the RFC 2231
language, defaulting to the empty string.  Both @emph{charset} and @emph{language}
should be strings.

If @emph{replace} is @code{False} (the default) the header is moved to the
end of the list of headers.  If @emph{replace} is @code{True}, the header
will be updated in place.


在 3.4 版更改: @code{replace} keyword was added.

@end deffn

@geindex del_param() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message del_param}@anchor{2840}
@deffn {方法} del_param (param, header='content-type', requote=True)

Remove the given parameter completely from the @code{Content-Type}
header.  The header will be re-written in place without the parameter or
its value.  All values will be quoted as necessary unless @emph{requote} is
@code{False} (the default is @code{True}).  Optional @emph{header} specifies an
alternative to @code{Content-Type}.
@end deffn

@geindex set_type() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message set_type}@anchor{2841}
@deffn {方法} set_type (type, header='Content-Type', requote=True)

Set the main type and subtype for the @code{Content-Type}
header. @emph{type} must be a string in the form @code{maintype/subtype},
otherwise a @ref{1fb,,ValueError} is raised.

This method replaces the @code{Content-Type} header, keeping all
the parameters in place.  If @emph{requote} is @code{False}, this leaves the
existing header's quoting as is, otherwise the parameters will be quoted
(the default).

An alternative header can be specified in the @emph{header} argument. When the
@code{Content-Type} header is set a @code{MIME-Version}
header is also added.

This is a legacy method.  On the
@code{EmailMessage} class its functionality is
replaced by the @code{make_} and @code{add_} methods.
@end deffn

@geindex get_filename() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_filename}@anchor{2842}
@deffn {方法} get_filename (failobj=None)

Return the value of the @code{filename} parameter of the
@code{Content-Disposition} header of the message.  If the header
does not have a @code{filename} parameter, this method falls back to looking
for the @code{name} parameter on the @code{Content-Type} header.  If
neither is found, or the header is missing, then @emph{failobj} is returned.
The returned string will always be unquoted as per
@ref{2793,,email.utils.unquote()}.
@end deffn

@geindex get_boundary() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_boundary}@anchor{2843}
@deffn {方法} get_boundary (failobj=None)

Return the value of the @code{boundary} parameter of the
@code{Content-Type} header of the message, or @emph{failobj} if either
the header is missing, or has no @code{boundary} parameter.  The returned
string will always be unquoted as per @ref{2793,,email.utils.unquote()}.
@end deffn

@geindex set_boundary() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message set_boundary}@anchor{2844}
@deffn {方法} set_boundary (boundary)

Set the @code{boundary} parameter of the @code{Content-Type} header to
@emph{boundary}.  @ref{2844,,set_boundary()} will always quote @emph{boundary} if
necessary.  A @ref{2796,,HeaderParseError} is raised if the
message object has no @code{Content-Type} header.

Note that using this method is subtly different than deleting the old
@code{Content-Type} header and adding a new one with the new
boundary via @ref{2836,,add_header()}, because @ref{2844,,set_boundary()} preserves
the order of the @code{Content-Type} header in the list of
headers. However, it does @emph{not} preserve any continuation lines which may
have been present in the original @code{Content-Type} header.
@end deffn

@geindex get_content_charset() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_content_charset}@anchor{2845}
@deffn {方法} get_content_charset (failobj=None)

Return the @code{charset} parameter of the @code{Content-Type} header,
coerced to lower case.  If there is no @code{Content-Type} header, or if
that header has no @code{charset} parameter, @emph{failobj} is returned.

Note that this method differs from @ref{282b,,get_charset()} which returns the
@ref{6ce,,Charset} instance for the default encoding of the message body.
@end deffn

@geindex get_charsets() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_charsets}@anchor{2846}
@deffn {方法} get_charsets (failobj=None)

Return a list containing the character set names in the message.  If the
message is a @code{multipart}, then the list will contain one element
for each subpart in the payload, otherwise, it will be a list of length 1.

Each item in the list will be a string which is the value of the
@code{charset} parameter in the @code{Content-Type} header for the
represented subpart.  However, if the subpart has no
@code{Content-Type} header, no @code{charset} parameter, or is not of
the @code{text} main MIME type, then that item in the returned list
will be @emph{failobj}.
@end deffn

@geindex get_content_disposition() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message get_content_disposition}@anchor{6cb}
@deffn {方法} get_content_disposition ()

Return the lowercased value (without parameters) of the message's
@code{Content-Disposition} header if it has one, or @code{None}.  The
possible values for this method are @emph{inline}, @emph{attachment} or @code{None}
if the message follows 
@geindex RFC; RFC 2183
RFC 2183@footnote{https://tools.ietf.org/html/rfc2183.html}.


3.5 新版功能.

@end deffn

@geindex walk() (email.message.Message 方法)
@anchor{library/email compat32-message email message Message walk}@anchor{2847}
@deffn {方法} walk ()

The @ref{2847,,walk()} method is an all-purpose generator which can be used to
iterate over all the parts and subparts of a message object tree, in
depth-first traversal order.  You will typically use @ref{2847,,walk()} as the
iterator in a @code{for} loop; each iteration returns the next subpart.

Here's an example that prints the MIME type of every part of a multipart
message structure:

@c import email
@c from email import message_from_binary_file
@c from os.path import join, dirname
@c lib_dir = dirname(dirname(email.__file__))
@c file_path = join(lib_dir, 'test/test_email/data/msg_16.txt')
@c with open(file_path, 'rb') as f:
@c     msg = message_from_binary_file(f)
@c from email.iterators import _structure

@example
>>> for part in msg.walk():
...     print(part.get_content_type())
multipart/report
text/plain
message/delivery-status
text/plain
text/plain
message/rfc822
text/plain
@end example

@code{walk} iterates over the subparts of any part where
@ref{279a,,is_multipart()} returns @code{True}, even though
@code{msg.get_content_maintype() == 'multipart'} may return @code{False}.  We
can see this in our example by making use of the @code{_structure} debug
helper function:

@example
>>> for part in msg.walk():
...     print(part.get_content_maintype() == 'multipart',
...           part.is_multipart())
True True
False False
False True
False False
False False
False True
False False
>>> _structure(msg)
multipart/report
    text/plain
    message/delivery-status
        text/plain
        text/plain
    message/rfc822
        text/plain
@end example

Here the @code{message} parts are not @code{multiparts}, but they do contain
subparts. @code{is_multipart()} returns @code{True} and @code{walk} descends
into the subparts.
@end deffn

@ref{53c,,Message} objects can also optionally contain two instance attributes,
which can be used when generating the plain text of a MIME message.

@geindex preamble (email.message.Message 属性)
@anchor{library/email compat32-message email message Message preamble}@anchor{2848}
@deffn {属性} preamble

The format of a MIME document allows for some text between the blank line
following the headers, and the first multipart boundary string. Normally,
this text is never visible in a MIME-aware mail reader because it falls
outside the standard MIME armor.  However, when viewing the raw text of
the message, or when viewing the message in a non-MIME aware reader, this
text can become visible.

The @emph{preamble} attribute contains this leading extra-armor text for MIME
documents.  When the @ref{b11,,Parser} discovers some text
after the headers but before the first boundary string, it assigns this
text to the message's @emph{preamble} attribute.  When the
@ref{b45,,Generator} is writing out the plain text
representation of a MIME message, and it finds the
message has a @emph{preamble} attribute, it will write this text in the area
between the headers and the first boundary.  See @ref{74,,email.parser} and
@ref{6e,,email.generator} for details.

Note that if the message object has no preamble, the @emph{preamble} attribute
will be @code{None}.
@end deffn

@geindex epilogue (email.message.Message 属性)
@anchor{library/email compat32-message email message Message epilogue}@anchor{2849}
@deffn {属性} epilogue

The @emph{epilogue} attribute acts the same way as the @emph{preamble} attribute,
except that it contains text that appears between the last boundary and
the end of the message.

You do not need to set the epilogue to the empty string in order for the
@ref{b45,,Generator} to print a newline at the end of the
file.
@end deffn

@geindex defects (email.message.Message 属性)
@anchor{library/email compat32-message email message Message defects}@anchor{284a}
@deffn {属性} defects

The @emph{defects} attribute contains a list of all the problems found when
parsing this message.  See @ref{6d,,email.errors} for a detailed description
of the possible parsing defects.
@end deffn
@end deffn

@node email mime Creating email and MIME objects from scratch,email header Internationalized headers,email message Message Representing an email message using the compat32 API,email --- 电子邮件与 MIME 处理包
@anchor{library/email mime doc}@anchor{284b}@anchor{library/email mime email-mime-creating-email-and-mime-objects-from-scratch}@anchor{284c}@anchor{library/email mime module-email mime}@anchor{73}
@subsubsection @code{email.mime}: Creating email and MIME objects from scratch


@geindex email.mime (模块)

@strong{Source code:} Lib/email/mime/@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/mime/}


__________________________________________________________________


This module is part of the legacy (@code{Compat32}) email API.  Its functionality
is partially replaced by the @ref{6b,,contentmanager} in the new API, but
in certain applications these classes may still be useful, even in non-legacy
code.

Ordinarily, you get a message object structure by passing a file or some text to
a parser, which parses the text and returns the root message object.  However
you can also build a complete message structure from scratch, or even individual
@ref{53c,,Message} objects by hand.  In fact, you can also take an
existing structure and add new @ref{53c,,Message} objects, move them
around, etc.  This makes a very convenient interface for slicing-and-dicing MIME
messages.

You can create a new object structure by creating @ref{53c,,Message}
instances, adding attachments and all the appropriate headers manually.  For MIME
messages though, the @ref{69,,email} package provides some convenient subclasses to
make things easier.

Here are the classes:

@geindex MIMEBase (email.mime.base 中的类)
@anchor{library/email mime email mime base MIMEBase}@anchor{284d}
@deffn {类} email.mime.base.MIMEBase (_maintype, _subtype, *, policy=compat32, **_params)

Module: @code{email.mime.base}

This is the base class for all the MIME-specific subclasses of
@ref{53c,,Message}.  Ordinarily you won't create instances
specifically of @ref{284d,,MIMEBase}, although you could.  @ref{284d,,MIMEBase}
is provided primarily as a convenient base class for more specific
MIME-aware subclasses.

@emph{_maintype} is the @code{Content-Type} major type (e.g. @code{text}
or @code{image}), and @emph{_subtype} is the @code{Content-Type} minor
type  (e.g. @code{plain} or @code{gif}).  @emph{_params} is a parameter
key/value dictionary and is passed directly to @ref{2836,,Message.add_header}.

If @emph{policy} is specified, (defaults to the
@ref{9ef,,compat32} policy) it will be passed to
@ref{53c,,Message}.

The @ref{284d,,MIMEBase} class always adds a @code{Content-Type} header
(based on @emph{_maintype}, @emph{_subtype}, and @emph{_params}), and a
@code{MIME-Version} header (always set to @code{1.0}).


在 3.6 版更改: Added @emph{policy} keyword-only parameter.

@end deffn

@geindex MIMENonMultipart (email.mime.nonmultipart 中的类)
@anchor{library/email mime email mime nonmultipart MIMENonMultipart}@anchor{27ef}
@deffn {类} email.mime.nonmultipart.MIMENonMultipart

Module: @code{email.mime.nonmultipart}

A subclass of @ref{284d,,MIMEBase}, this is an intermediate base
class for MIME messages that are not @code{multipart}.  The primary
purpose of this class is to prevent the use of the
@ref{27a8,,attach()} method, which only makes sense for
@code{multipart} messages.  If @ref{27a8,,attach()}
is called, a @ref{27ee,,MultipartConversionError} exception is raised.
@end deffn

@geindex MIMEMultipart (email.mime.multipart 中的类)
@anchor{library/email mime email mime multipart MIMEMultipart}@anchor{284e}
@deffn {类} email.mime.multipart.MIMEMultipart (_subtype='mixed', boundary=None, _subparts=None, *, policy=compat32, **_params)

Module: @code{email.mime.multipart}

A subclass of @ref{284d,,MIMEBase}, this is an intermediate base
class for MIME messages that are @code{multipart}.  Optional @emph{_subtype}
defaults to @code{mixed}, but can be used to specify the subtype of the
message.  A @code{Content-Type} header of @code{multipart/_subtype}
will be added to the message object.  A @code{MIME-Version} header will
also be added.

Optional @emph{boundary} is the multipart boundary string.  When @code{None} (the
default), the boundary is calculated when needed (for example, when the
message is serialized).

@emph{_subparts} is a sequence of initial subparts for the payload.  It must be
possible to convert this sequence to a list.  You can always attach new subparts
to the message by using the @ref{27a8,,Message.attach} method.

Optional @emph{policy} argument defaults to @ref{9ef,,compat32}.

Additional parameters for the @code{Content-Type} header are taken from
the keyword arguments, or passed into the @emph{_params} argument, which is a keyword
dictionary.


在 3.6 版更改: Added @emph{policy} keyword-only parameter.

@end deffn

@geindex MIMEApplication (email.mime.application 中的类)
@anchor{library/email mime email mime application MIMEApplication}@anchor{284f}
@deffn {类} email.mime.application.MIMEApplication (_data, _subtype='octet-stream', _encoder=email.encoders.encode_base64, *, policy=compat32, **_params)

Module: @code{email.mime.application}

A subclass of @ref{27ef,,MIMENonMultipart}, the
@ref{284f,,MIMEApplication} class is used to represent MIME message objects of
major type @code{application}.  @emph{_data} is a string containing the raw
byte data.  Optional @emph{_subtype} specifies the MIME subtype and defaults to
@code{octet-stream}.

Optional @emph{_encoder} is a callable (i.e. function) which will perform the actual
encoding of the data for transport.  This callable takes one argument, which is
the @ref{284f,,MIMEApplication} instance. It should use
@ref{b44,,get_payload()} and
@ref{2829,,set_payload()} to change the payload to encoded
form.  It should also add
any @code{Content-Transfer-Encoding} or other headers to the message
object as necessary.  The default encoding is base64.  See the
@ref{6c,,email.encoders} module for a list of the built-in encoders.

Optional @emph{policy} argument defaults to @ref{9ef,,compat32}.

@emph{_params} are passed straight through to the base class constructor.


在 3.6 版更改: Added @emph{policy} keyword-only parameter.

@end deffn

@geindex MIMEAudio (email.mime.audio 中的类)
@anchor{library/email mime email mime audio MIMEAudio}@anchor{2850}
@deffn {类} email.mime.audio.MIMEAudio (_audiodata, _subtype=None, _encoder=email.encoders.encode_base64, *, policy=compat32, **_params)

Module: @code{email.mime.audio}

A subclass of @ref{27ef,,MIMENonMultipart}, the
@ref{2850,,MIMEAudio} class is used to create MIME message objects of major type
@code{audio}. @emph{_audiodata} is a string containing the raw audio data.  If
this data can be decoded by the standard Python module @ref{ee,,sndhdr}, then the
subtype will be automatically included in the @code{Content-Type} header.
Otherwise you can explicitly specify the audio subtype via the @emph{_subtype}
argument.  If the minor type could not be guessed and @emph{_subtype} was not given,
then @ref{192,,TypeError} is raised.

Optional @emph{_encoder} is a callable (i.e. function) which will perform the actual
encoding of the audio data for transport.  This callable takes one argument,
which is the @ref{2850,,MIMEAudio} instance. It should use
@ref{b44,,get_payload()} and
@ref{2829,,set_payload()} to change the payload to encoded
form.  It should also add
any @code{Content-Transfer-Encoding} or other headers to the message
object as necessary.  The default encoding is base64.  See the
@ref{6c,,email.encoders} module for a list of the built-in encoders.

Optional @emph{policy} argument defaults to @ref{9ef,,compat32}.

@emph{_params} are passed straight through to the base class constructor.


在 3.6 版更改: Added @emph{policy} keyword-only parameter.

@end deffn

@geindex MIMEImage (email.mime.image 中的类)
@anchor{library/email mime email mime image MIMEImage}@anchor{27f0}
@deffn {类} email.mime.image.MIMEImage (_imagedata, _subtype=None, _encoder=email.encoders.encode_base64, *, policy=compat32, **_params)

Module: @code{email.mime.image}

A subclass of @ref{27ef,,MIMENonMultipart}, the
@ref{27f0,,MIMEImage} class is used to create MIME message objects of major type
@code{image}. @emph{_imagedata} is a string containing the raw image data.  If
this data can be decoded by the standard Python module @ref{99,,imghdr}, then the
subtype will be automatically included in the @code{Content-Type} header.
Otherwise you can explicitly specify the image subtype via the @emph{_subtype}
argument.  If the minor type could not be guessed and @emph{_subtype} was not given,
then @ref{192,,TypeError} is raised.

Optional @emph{_encoder} is a callable (i.e. function) which will perform the actual
encoding of the image data for transport.  This callable takes one argument,
which is the @ref{27f0,,MIMEImage} instance. It should use
@ref{b44,,get_payload()} and
@ref{2829,,set_payload()} to change the payload to encoded
form.  It should also add
any @code{Content-Transfer-Encoding} or other headers to the message
object as necessary.  The default encoding is base64.  See the
@ref{6c,,email.encoders} module for a list of the built-in encoders.

Optional @emph{policy} argument defaults to @ref{9ef,,compat32}.

@emph{_params} are passed straight through to the @ref{284d,,MIMEBase}
constructor.


在 3.6 版更改: Added @emph{policy} keyword-only parameter.

@end deffn

@geindex MIMEMessage (email.mime.message 中的类)
@anchor{library/email mime email mime message MIMEMessage}@anchor{2851}
@deffn {类} email.mime.message.MIMEMessage (_msg, _subtype='rfc822', *, policy=compat32)

Module: @code{email.mime.message}

A subclass of @ref{27ef,,MIMENonMultipart}, the
@ref{2851,,MIMEMessage} class is used to create MIME objects of main type
@code{message}. @emph{_msg} is used as the payload, and must be an instance
of class @ref{53c,,Message} (or a subclass thereof), otherwise
a @ref{192,,TypeError} is raised.

Optional @emph{_subtype} sets the subtype of the message; it defaults to
@code{rfc822}.

Optional @emph{policy} argument defaults to @ref{9ef,,compat32}.


在 3.6 版更改: Added @emph{policy} keyword-only parameter.

@end deffn

@geindex MIMEText (email.mime.text 中的类)
@anchor{library/email mime email mime text MIMEText}@anchor{6cd}
@deffn {类} email.mime.text.MIMEText (_text, _subtype='plain', _charset=None, *, policy=compat32)

Module: @code{email.mime.text}

A subclass of @ref{27ef,,MIMENonMultipart}, the
@ref{6cd,,MIMEText} class is used to create MIME objects of major type
@code{text}. @emph{_text} is the string for the payload.  @emph{_subtype} is the
minor type and defaults to @code{plain}.  @emph{_charset} is the character
set of the text and is passed as an argument to the
@ref{27ef,,MIMENonMultipart} constructor; it defaults
to @code{us-ascii} if the string contains only @code{ascii} code points, and
@code{utf-8} otherwise.  The @emph{_charset} parameter accepts either a string or a
@ref{6ce,,Charset} instance.

Unless the @emph{_charset} argument is explicitly set to @code{None}, the
MIMEText object created will have both a @code{Content-Type} header
with a @code{charset} parameter, and a @code{Content-Transfer-Encoding}
header.  This means that a subsequent @code{set_payload} call will not result
in an encoded payload, even if a charset is passed in the @code{set_payload}
command.  You can "reset" this behavior by deleting the
@code{Content-Transfer-Encoding} header, after which a @code{set_payload} call
will automatically encode the new payload (and add a new
@code{Content-Transfer-Encoding} header).

Optional @emph{policy} argument defaults to @ref{9ef,,compat32}.


在 3.5 版更改: @emph{_charset} also accepts @ref{6ce,,Charset} instances.



在 3.6 版更改: Added @emph{policy} keyword-only parameter.

@end deffn

@node email header Internationalized headers,email charset Representing character sets,email mime Creating email and MIME objects from scratch,email --- 电子邮件与 MIME 处理包
@anchor{library/email header doc}@anchor{2852}@anchor{library/email header email-header-internationalized-headers}@anchor{2853}@anchor{library/email header module-email header}@anchor{6f}
@subsubsection @code{email.header}: Internationalized headers


@geindex email.header (模块)

@strong{Source code:} Lib/email/header.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/header.py}


__________________________________________________________________


This module is part of the legacy (@code{Compat32}) email API.  In the current API
encoding and decoding of headers is handled transparently by the
dictionary-like API of the @ref{53d,,EmailMessage} class.  In
addition to uses in legacy code, this module can be useful in applications that
need to completely control the character sets used when encoding headers.

本段落中的剩余文本是该模块的原始文档。

@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html} is the base standard that describes the format of email messages.
It derives from the older 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html} standard which came into widespread use at
a time when most email was composed of ASCII characters only.  
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html} is a
specification written assuming email contains only 7-bit ASCII characters.

Of course, as email has been deployed worldwide, it has become
internationalized, such that language specific character sets can now be used in
email messages.  The base standard still requires email messages to be
transferred using only 7-bit ASCII characters, so a slew of RFCs have been
written describing how to encode email containing non-ASCII characters into
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}-compliant format. These RFCs include 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html}, 
@geindex RFC; RFC 2046
RFC 2046@footnote{https://tools.ietf.org/html/rfc2046.html},
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html}, and 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html}. The @ref{69,,email} package supports these standards
in its @ref{6f,,email.header} and @ref{6a,,email.charset} modules.

If you want to include non-ASCII characters in your email headers, say in the
@code{Subject} or @code{To} fields, you should use the
@ref{27e6,,Header} class and assign the field in the @ref{53c,,Message}
object to an instance of @ref{27e6,,Header} instead of using a string for the header
value.  Import the @ref{27e6,,Header} class from the @ref{6f,,email.header} module.
For example:

@example
>>> from email.message import Message
>>> from email.header import Header
>>> msg = Message()
>>> h = Header('p\xf6stal', 'iso-8859-1')
>>> msg['Subject'] = h
>>> msg.as_string()
'Subject: =?iso-8859-1?q?p=F6stal?=\n\n'
@end example

Notice here how we wanted the @code{Subject} field to contain a non-ASCII
character?  We did this by creating a @ref{27e6,,Header} instance and passing in
the character set that the byte string was encoded in.  When the subsequent
@ref{53c,,Message} instance was flattened, the @code{Subject}
field was properly 
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html} encoded.  MIME-aware mail readers would show this
header using the embedded ISO-8859-1 character.

Here is the @ref{27e6,,Header} class description:

@geindex Header (email.header 中的类)
@anchor{library/email header email header Header}@anchor{27e6}
@deffn {类} email.header.Header (s=None, charset=None, maxlinelen=None, header_name=None, continuation_ws=' ', errors='strict')

Create a MIME-compliant header that can contain strings in different character
sets.

Optional @emph{s} is the initial header value.  If @code{None} (the default), the
initial header value is not set.  You can later append to the header with
@ref{2854,,append()} method calls.  @emph{s} may be an instance of @ref{32a,,bytes} or
@ref{329,,str}, but see the @ref{2854,,append()} documentation for semantics.

Optional @emph{charset} serves two purposes: it has the same meaning as the @emph{charset}
argument to the @ref{2854,,append()} method.  It also sets the default character set
for all subsequent @ref{2854,,append()} calls that omit the @emph{charset} argument.  If
@emph{charset} is not provided in the constructor (the default), the @code{us-ascii}
character set is used both as @emph{s}'s initial charset and as the default for
subsequent @ref{2854,,append()} calls.

The maximum line length can be specified explicitly via @emph{maxlinelen}.  For
splitting the first line to a shorter value (to account for the field header
which isn't included in @emph{s}, e.g. @code{Subject}) pass in the name of the
field in @emph{header_name}.  The default @emph{maxlinelen} is 76, and the default value
for @emph{header_name} is @code{None}, meaning it is not taken into account for the
first line of a long, split header.

Optional @emph{continuation_ws} must be 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}-compliant folding
whitespace, and is usually either a space or a hard tab character.  This
character will be prepended to continuation lines.  @emph{continuation_ws}
defaults to a single space character.

Optional @emph{errors} is passed straight through to the @ref{2854,,append()} method.

@geindex append() (email.header.Header 方法)
@anchor{library/email header email header Header append}@anchor{2854}
@deffn {方法} append (s, charset=None, errors='strict')

Append the string @emph{s} to the MIME header.

Optional @emph{charset}, if given, should be a @ref{6ce,,Charset}
instance (see @ref{6a,,email.charset}) or the name of a character set, which
will be converted to a @ref{6ce,,Charset} instance.  A value
of @code{None} (the default) means that the @emph{charset} given in the constructor
is used.

@emph{s} may be an instance of @ref{32a,,bytes} or @ref{329,,str}.  If it is an
instance of @ref{32a,,bytes}, then @emph{charset} is the encoding of that byte
string, and a @ref{c34,,UnicodeError} will be raised if the string cannot be
decoded with that character set.

If @emph{s} is an instance of @ref{329,,str}, then @emph{charset} is a hint specifying
the character set of the characters in the string.

In either case, when producing an 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}-compliant header using
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html} rules, the string will be encoded using the output codec of
the charset.  If the string cannot be encoded using the output codec, a
UnicodeError will be raised.

Optional @emph{errors} is passed as the errors argument to the decode call
if @emph{s} is a byte string.
@end deffn

@geindex encode() (email.header.Header 方法)
@anchor{library/email header email header Header encode}@anchor{2855}
@deffn {方法} encode (splitchars=';, \t', maxlinelen=None, linesep='\n')

Encode a message header into an RFC-compliant format, possibly wrapping
long lines and encapsulating non-ASCII parts in base64 or quoted-printable
encodings.

Optional @emph{splitchars} is a string containing characters which should be
given extra weight by the splitting algorithm during normal header
wrapping.  This is in very rough support of 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}'s 'higher level
syntactic breaks':  split points preceded by a splitchar are preferred
during line splitting, with the characters preferred in the order in
which they appear in the string.  Space and tab may be included in the
string to indicate whether preference should be given to one over the
other as a split point when other split chars do not appear in the line
being split.  Splitchars does not affect 
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html} encoded lines.

@emph{maxlinelen}, if given, overrides the instance's value for the maximum
line length.

@emph{linesep} specifies the characters used to separate the lines of the
folded header.  It defaults to the most useful value for Python
application code (@code{\n}), but @code{\r\n} can be specified in order
to produce headers with RFC-compliant line separators.


在 3.2 版更改: Added the @emph{linesep} argument.

@end deffn

The @ref{27e6,,Header} class also provides a number of methods to support
standard operators and built-in functions.

@geindex __str__() (email.header.Header 方法)
@anchor{library/email header email header Header __str__}@anchor{2856}
@deffn {方法} __str__ ()

Returns an approximation of the @ref{27e6,,Header} as a string, using an
unlimited line length.  All pieces are converted to unicode using the
specified encoding and joined together appropriately.  Any pieces with a
charset of @code{'unknown-8bit'} are decoded as ASCII using the @code{'replace'}
error handler.


在 3.2 版更改: Added handling for the @code{'unknown-8bit'} charset.

@end deffn

@geindex __eq__() (email.header.Header 方法)
@anchor{library/email header email header Header __eq__}@anchor{2857}
@deffn {方法} __eq__ (other)

This method allows you to compare two @ref{27e6,,Header} instances for
equality.
@end deffn

@geindex __ne__() (email.header.Header 方法)
@anchor{library/email header email header Header __ne__}@anchor{2858}
@deffn {方法} __ne__ (other)

This method allows you to compare two @ref{27e6,,Header} instances for
inequality.
@end deffn
@end deffn

The @ref{6f,,email.header} module also provides the following convenient functions.

@geindex decode_header() (在 email.header 模块中)
@anchor{library/email header email header decode_header}@anchor{9f3}
@deffn {函数} email.header.decode_header (header)

Decode a message header value without converting the character set. The header
value is in @emph{header}.

This function returns a list of @code{(decoded_string, charset)} pairs containing
each of the decoded parts of the header.  @emph{charset} is @code{None} for non-encoded
parts of the header, otherwise a lower case string containing the name of the
character set specified in the encoded string.

Here's an example:

@example
>>> from email.header import decode_header
>>> decode_header('=?iso-8859-1?q?p=F6stal?=')
[(b'p\xf6stal', 'iso-8859-1')]
@end example
@end deffn

@geindex make_header() (在 email.header 模块中)
@anchor{library/email header email header make_header}@anchor{9f4}
@deffn {函数} email.header.make_header (decoded_seq, maxlinelen=None, header_name=None, continuation_ws=' ')

Create a @ref{27e6,,Header} instance from a sequence of pairs as returned by
@ref{9f3,,decode_header()}.

@ref{9f3,,decode_header()} takes a header value string and returns a sequence of
pairs of the format @code{(decoded_string, charset)} where @emph{charset} is the name of
the character set.

This function takes one of those sequence of pairs and returns a
@ref{27e6,,Header} instance.  Optional @emph{maxlinelen}, @emph{header_name}, and
@emph{continuation_ws} are as in the @ref{27e6,,Header} constructor.
@end deffn

@node email charset Representing character sets,email encoders 编码器,email header Internationalized headers,email --- 电子邮件与 MIME 处理包
@anchor{library/email charset doc}@anchor{2859}@anchor{library/email charset email-charset-representing-character-sets}@anchor{285a}@anchor{library/email charset module-email charset}@anchor{6a}
@subsubsection @code{email.charset}: Representing character sets


@geindex email.charset (模块)

@strong{Source code:} Lib/email/charset.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/charset.py}


__________________________________________________________________


This module is part of the legacy (@code{Compat32}) email API.  In the new
API only the aliases table is used.

本段落中的剩余文本是该模块的原始文档。

This module provides a class @ref{6ce,,Charset} for representing character sets
and character set conversions in email messages, as well as a character set
registry and several convenience methods for manipulating this registry.
Instances of @ref{6ce,,Charset} are used in several other modules within the
@ref{69,,email} package.

Import this class from the @ref{6a,,email.charset} module.

@geindex Charset (email.charset 中的类)
@anchor{library/email charset email charset Charset}@anchor{6ce}
@deffn {类} email.charset.Charset (input_charset=DEFAULT_CHARSET)

Map character sets to their email properties.

This class provides information about the requirements imposed on email for a
specific character set.  It also provides convenience routines for converting
between character sets, given the availability of the applicable codecs.  Given
a character set, it will do its best to provide information on how to use that
character set in an email message in an RFC-compliant way.

Certain character sets must be encoded with quoted-printable or base64 when used
in email headers or bodies.  Certain character sets must be converted outright,
and are not allowed in email.

Optional @emph{input_charset} is as described below; it is always coerced to lower
case.  After being alias normalized it is also used as a lookup into the
registry of character sets to find out the header encoding, body encoding, and
output conversion codec to be used for the character set.  For example, if
@emph{input_charset} is @code{iso-8859-1}, then headers and bodies will be encoded using
quoted-printable and no output conversion codec is necessary.  If
@emph{input_charset} is @code{euc-jp}, then headers will be encoded with base64, bodies
will not be encoded, but output text will be converted from the @code{euc-jp}
character set to the @code{iso-2022-jp} character set.

@ref{6ce,,Charset} instances have the following data attributes:

@geindex input_charset (email.charset.Charset 属性)
@anchor{library/email charset email charset Charset input_charset}@anchor{285b}
@deffn {属性} input_charset

The initial character set specified.  Common aliases are converted to
their @emph{official} email names (e.g. @code{latin_1} is converted to
@code{iso-8859-1}).  Defaults to 7-bit @code{us-ascii}.
@end deffn

@geindex header_encoding (email.charset.Charset 属性)
@anchor{library/email charset email charset Charset header_encoding}@anchor{285c}
@deffn {属性} header_encoding

If the character set must be encoded before it can be used in an email
header, this attribute will be set to @code{Charset.QP} (for
quoted-printable), @code{Charset.BASE64} (for base64 encoding), or
@code{Charset.SHORTEST} for the shortest of QP or BASE64 encoding. Otherwise,
it will be @code{None}.
@end deffn

@geindex body_encoding (email.charset.Charset 属性)
@anchor{library/email charset email charset Charset body_encoding}@anchor{285d}
@deffn {属性} body_encoding

Same as @emph{header_encoding}, but describes the encoding for the mail
message's body, which indeed may be different than the header encoding.
@code{Charset.SHORTEST} is not allowed for @emph{body_encoding}.
@end deffn

@geindex output_charset (email.charset.Charset 属性)
@anchor{library/email charset email charset Charset output_charset}@anchor{285e}
@deffn {属性} output_charset

Some character sets must be converted before they can be used in email
headers or bodies.  If the @emph{input_charset} is one of them, this attribute
will contain the name of the character set output will be converted to.
Otherwise, it will be @code{None}.
@end deffn

@geindex input_codec (email.charset.Charset 属性)
@anchor{library/email charset email charset Charset input_codec}@anchor{285f}
@deffn {属性} input_codec

The name of the Python codec used to convert the @emph{input_charset} to
Unicode.  If no conversion codec is necessary, this attribute will be
@code{None}.
@end deffn

@geindex output_codec (email.charset.Charset 属性)
@anchor{library/email charset email charset Charset output_codec}@anchor{2860}
@deffn {属性} output_codec

The name of the Python codec used to convert Unicode to the
@emph{output_charset}.  If no conversion codec is necessary, this attribute
will have the same value as the @emph{input_codec}.
@end deffn

@ref{6ce,,Charset} instances also have the following methods:

@geindex get_body_encoding() (email.charset.Charset 方法)
@anchor{library/email charset email charset Charset get_body_encoding}@anchor{2861}
@deffn {方法} get_body_encoding ()

Return the content transfer encoding used for body encoding.

This is either the string @code{quoted-printable} or @code{base64} depending on
the encoding used, or it is a function, in which case you should call the
function with a single argument, the Message object being encoded.  The
function should then set the @code{Content-Transfer-Encoding}
header itself to whatever is appropriate.

Returns the string @code{quoted-printable} if @emph{body_encoding} is @code{QP},
returns the string @code{base64} if @emph{body_encoding} is @code{BASE64}, and
returns the string @code{7bit} otherwise.
@end deffn

@geindex get_output_charset() (email.charset.Charset 方法)
@anchor{library/email charset email charset Charset get_output_charset}@anchor{2862}
@deffn {方法} get_output_charset ()

Return the output character set.

This is the @emph{output_charset} attribute if that is not @code{None}, otherwise
it is @emph{input_charset}.
@end deffn

@geindex header_encode() (email.charset.Charset 方法)
@anchor{library/email charset email charset Charset header_encode}@anchor{2863}
@deffn {方法} header_encode (string)

Header-encode the string @emph{string}.

The type of encoding (base64 or quoted-printable) will be based on the
@emph{header_encoding} attribute.
@end deffn

@geindex header_encode_lines() (email.charset.Charset 方法)
@anchor{library/email charset email charset Charset header_encode_lines}@anchor{2864}
@deffn {方法} header_encode_lines (string, maxlengths)

Header-encode a @emph{string} by converting it first to bytes.

This is similar to @ref{2863,,header_encode()} except that the string is fit
into maximum line lengths as given by the argument @emph{maxlengths}, which
must be an iterator: each element returned from this iterator will provide
the next maximum line length.
@end deffn

@geindex body_encode() (email.charset.Charset 方法)
@anchor{library/email charset email charset Charset body_encode}@anchor{2865}
@deffn {方法} body_encode (string)

Body-encode the string @emph{string}.

The type of encoding (base64 or quoted-printable) will be based on the
@emph{body_encoding} attribute.
@end deffn

The @ref{6ce,,Charset} class also provides a number of methods to support
standard operations and built-in functions.

@geindex __str__() (email.charset.Charset 方法)
@anchor{library/email charset email charset Charset __str__}@anchor{2866}
@deffn {方法} __str__ ()

Returns @emph{input_charset} as a string coerced to lower
case. @ref{337,,__repr__()} is an alias for @ref{2866,,__str__()}.
@end deffn

@geindex __eq__() (email.charset.Charset 方法)
@anchor{library/email charset email charset Charset __eq__}@anchor{2867}
@deffn {方法} __eq__ (other)

This method allows you to compare two @ref{6ce,,Charset} instances for
equality.
@end deffn

@geindex __ne__() (email.charset.Charset 方法)
@anchor{library/email charset email charset Charset __ne__}@anchor{2868}
@deffn {方法} __ne__ (other)

This method allows you to compare two @ref{6ce,,Charset} instances for
inequality.
@end deffn
@end deffn

The @ref{6a,,email.charset} module also provides the following functions for adding
new entries to the global character set, alias, and codec registries:

@geindex add_charset() (在 email.charset 模块中)
@anchor{library/email charset email charset add_charset}@anchor{2869}
@deffn {函数} email.charset.add_charset (charset, header_enc=None, body_enc=None, output_charset=None)

Add character properties to the global registry.

@emph{charset} is the input character set, and must be the canonical name of a
character set.

Optional @emph{header_enc} and @emph{body_enc} is either @code{Charset.QP} for
quoted-printable, @code{Charset.BASE64} for base64 encoding,
@code{Charset.SHORTEST} for the shortest of quoted-printable or base64 encoding,
or @code{None} for no encoding.  @code{SHORTEST} is only valid for
@emph{header_enc}. The default is @code{None} for no encoding.

Optional @emph{output_charset} is the character set that the output should be in.
Conversions will proceed from input charset, to Unicode, to the output charset
when the method @code{Charset.convert()} is called.  The default is to output in
the same character set as the input.

Both @emph{input_charset} and @emph{output_charset} must have Unicode codec entries in the
module's character set-to-codec mapping; use @ref{286a,,add_codec()} to add codecs the
module does not know about.  See the @ref{1c,,codecs} module's documentation for
more information.

The global character set registry is kept in the module global dictionary
@code{CHARSETS}.
@end deffn

@geindex add_alias() (在 email.charset 模块中)
@anchor{library/email charset email charset add_alias}@anchor{286b}
@deffn {函数} email.charset.add_alias (alias, canonical)

Add a character set alias.  @emph{alias} is the alias name, e.g. @code{latin-1}.
@emph{canonical} is the character set's canonical name, e.g. @code{iso-8859-1}.

The global charset alias registry is kept in the module global dictionary
@code{ALIASES}.
@end deffn

@geindex add_codec() (在 email.charset 模块中)
@anchor{library/email charset email charset add_codec}@anchor{286a}
@deffn {函数} email.charset.add_codec (charset, codecname)

Add a codec that map characters in the given character set to and from Unicode.

@emph{charset} is the canonical name of a character set. @emph{codecname} is the name of a
Python codec, as appropriate for the second argument to the @ref{329,,str}'s
@ref{c30,,encode()} method.
@end deffn

@node email encoders 编码器,email utils 其他工具,email charset Representing character sets,email --- 电子邮件与 MIME 处理包
@anchor{library/email encoders doc}@anchor{286c}@anchor{library/email encoders email-encoders-encoders}@anchor{286d}@anchor{library/email encoders module-email encoders}@anchor{6c}
@subsubsection @code{email.encoders}: 编码器


@geindex email.encoders (模块)

@strong{源代码:} Lib/email/encoders.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/encoders.py}


__________________________________________________________________


此模块是旧版 (@code{Compat32}) email API 的组成部分。 在新版 API 中将由 @ref{27a2,,set_content()} 方法的 @emph{cte} 形参提供该功能。

此模块在 Python 3 中已弃用。 这里提供的函数不应被显式地调用，因为 @ref{6cd,,MIMEText} 类会在类实例化期间使用 @emph{_subtype} 和 @emph{_charset} 值来设置内容类型和 CTE 头。

本段落中的剩余文本是该模块的原始文档。

当创建全新的 @ref{53c,,Message} 对象时，你经常需要对载荷编码以便通过兼容的邮件服务器进行传输。 对于包含二进制数据的 @code{image/*} 和 @code{text/*} 类型的消息来说尤其如此。

@ref{69,,email} 包在其 @code{encoders} 模块中提供了一些方便的编码器。 这些编码器实际上由 @ref{2850,,MIMEAudio} 和 @ref{27f0,,MIMEImage} 类构造器所使用以提供默认编码格式。 所有编码器函数都只接受一个参数，即要编码的消息对象。 它们通常会提取有效载荷，对其进行编码，并将载荷重置为这种新编码的值。  它们还应当相应地设置 @code{Content-Transfer-Encoding} 标头。

请注意，这些函数对于多段消息没有意义。 它们必须应用到各个单独的段上面，而不是整体。如果直接传递一个多段类型的消息，会产生一个 @ref{192,,TypeError} 错误。

下面是提供的编码函数：

@geindex encode_quopri() (在 email.encoders 模块中)
@anchor{library/email encoders email encoders encode_quopri}@anchor{286e}
@deffn {函数} email.encoders.encode_quopri (msg)

将有效数据编码为经转换的可打印形式，并将 @code{Content-Transfer-Encoding} 标头设置为 @code{quoted-printable} @footnote{@w{(1)} 
请注意使用 @ref{286e,,encode_quopri()} 编码格式还会对数据中的所有制表符和空格符进行编码。
}。 当大多数实际的数据是普通的可打印数据但包含少量不可打印的字符时，这是一个很好的编码。
@end deffn

@geindex encode_base64() (在 email.encoders 模块中)
@anchor{library/email encoders email encoders encode_base64}@anchor{286f}
@deffn {函数} email.encoders.encode_base64 (msg)

将有效载荷编码为 base64 形式，并将 @code{Content-Transfer-Encoding} 标头设为 @code{base64}。 当你的载荷主要包含不可打印数据时这是一种很好用的编码格式，因为它比 quoted-printable 更紧凑。 base64 编码格式的缺点是它会使文本变成人类不可读的形式。
@end deffn

@geindex encode_7or8bit() (在 email.encoders 模块中)
@anchor{library/email encoders email encoders encode_7or8bit}@anchor{2870}
@deffn {函数} email.encoders.encode_7or8bit (msg)

此函数并不实际改变消息的有效载荷，但它会基于载荷数据将 @code{Content-Transfer-Encoding} 标头相应地设为 @code{7bit} 或 @code{8bit}。
@end deffn

@geindex encode_noop() (在 email.encoders 模块中)
@anchor{library/email encoders email encoders encode_noop}@anchor{2871}
@deffn {函数} email.encoders.encode_noop (msg)

此函数什么都不会做；它甚至不会设置 @code{Content-Transfer-Encoding} 标头。
@end deffn

@subsubheading 备注


@node email utils 其他工具,email iterators 迭代器,email encoders 编码器,email --- 电子邮件与 MIME 处理包
@anchor{library/email utils doc}@anchor{2872}@anchor{library/email utils email-utils-miscellaneous-utilities}@anchor{2873}@anchor{library/email utils module-email utils}@anchor{76}
@subsubsection @code{email.utils}: 其他工具


@geindex email.utils (模块)

@strong{源代码:} Lib/email/utils.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/utils.py}


__________________________________________________________________


@ref{76,,email.utils} 模块提供如下几个工具

@geindex localtime() (在 email.utils 模块中)
@anchor{library/email utils email utils localtime}@anchor{9fa}
@deffn {函数} email.utils.localtime (dt=None)

以感知型 datetime 对象返回当地时间。 如果调用时参数为空，则返回当前时间。 否则 @emph{dt} 参数应该是一个 @ref{194,,datetime} 实例，并根据系统时区数据库转换为当地时区。 如果 @emph{dt} 是简单型的 (即 @code{dt.tzinfo} 是 @code{None} )，则假定为当地时间。 在这种情况下，为正值或零的 @emph{isdst} 会使 @code{localtime} 假定夏季时间（例如，夏令时）对指定时间生效或不生效。 负值 @emph{isdst} 会使 @code{localtime} 预测夏季时间对指定时间是否生效。


3.3 新版功能.

@end deffn

@geindex make_msgid() (在 email.utils 模块中)
@anchor{library/email utils email utils make_msgid}@anchor{2874}
@deffn {函数} email.utils.make_msgid (idstring=None, domain=None)

Returns a string suitable for an 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}-compliant
@code{Message-ID} header.  Optional @emph{idstring} if given, is a string
used to strengthen the uniqueness of the message id.  Optional @emph{domain} if
given provides the portion of the msgid after the '@@'.  The default is the
local hostname.  It is not normally necessary to override this default, but
may be useful certain cases, such as a constructing distributed system that
uses a consistent domain name across multiple hosts.


在 3.2 版更改: 增加了关键字 @emph{domain}

@end deffn

The remaining functions are part of the legacy (@code{Compat32}) email API.  There
is no need to directly use these with the new API, since the parsing and
formatting they provide is done automatically by the header parsing machinery
of the new API.

@geindex quote() (在 email.utils 模块中)
@anchor{library/email utils email utils quote}@anchor{2875}
@deffn {函数} email.utils.quote (str)

Return a new string with backslashes in @emph{str} replaced by two backslashes, and
double quotes replaced by backslash-double quote.
@end deffn

@geindex unquote() (在 email.utils 模块中)
@anchor{library/email utils email utils unquote}@anchor{2793}
@deffn {函数} email.utils.unquote (str)

Return a new string which is an @emph{unquoted} version of @emph{str}. If @emph{str} ends and
begins with double quotes, they are stripped off.  Likewise if @emph{str} ends and
begins with angle brackets, they are stripped off.
@end deffn

@geindex parseaddr() (在 email.utils 模块中)
@anchor{library/email utils email utils parseaddr}@anchor{2876}
@deffn {函数} email.utils.parseaddr (address)

Parse address -- which should be the value of some address-containing field such
as @code{To} or @code{Cc} -- into its constituent @emph{realname} and
@emph{email address} parts.  Returns a tuple of that information, unless the parse
fails, in which case a 2-tuple of @code{('@w{'}, '@w{'})} is returned.
@end deffn

@geindex formataddr() (在 email.utils 模块中)
@anchor{library/email utils email utils formataddr}@anchor{b0e}
@deffn {函数} email.utils.formataddr (pair, charset='utf-8')

The inverse of @ref{2876,,parseaddr()}, this takes a 2-tuple of the form @code{(realname,
email_address)} and returns the string value suitable for a @code{To} or
@code{Cc} header.  If the first element of @emph{pair} is false, then the
second element is returned unmodified.

Optional @emph{charset} is the character set that will be used in the 
@geindex RFC; RFC 2047
RFC 2047@footnote{https://tools.ietf.org/html/rfc2047.html}
encoding of the @code{realname} if the @code{realname} contains non-ASCII
characters.  Can be an instance of @ref{329,,str} or a
@ref{6ce,,Charset}.  Defaults to @code{utf-8}.


在 3.3 版更改: Added the @emph{charset} option.

@end deffn

@geindex getaddresses() (在 email.utils 模块中)
@anchor{library/email utils email utils getaddresses}@anchor{2877}
@deffn {函数} email.utils.getaddresses (fieldvalues)

This method returns a list of 2-tuples of the form returned by @code{parseaddr()}.
@emph{fieldvalues} is a sequence of header field values as might be returned by
@ref{2830,,Message.get_all}.  Here's a simple
example that gets all the recipients of a message:

@example
from email.utils import getaddresses

tos = msg.get_all('to', [])
ccs = msg.get_all('cc', [])
resent_tos = msg.get_all('resent-to', [])
resent_ccs = msg.get_all('resent-cc', [])
all_recipients = getaddresses(tos + ccs + resent_tos + resent_ccs)
@end example
@end deffn

@geindex parsedate() (在 email.utils 模块中)
@anchor{library/email utils email utils parsedate}@anchor{2878}
@deffn {函数} email.utils.parsedate (date)

Attempts to parse a date according to the rules in 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}. however, some
mailers don't follow that format as specified, so @ref{2878,,parsedate()} tries to
guess correctly in such cases.  @emph{date} is a string containing an 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}
date, such as  @code{"Mon, 20 Nov 1995 19:12:08 -0500"}.  If it succeeds in parsing
the date, @ref{2878,,parsedate()} returns a 9-tuple that can be passed directly to
@ref{b5d,,time.mktime()}; otherwise @code{None} will be returned.  Note that indexes 6,
7, and 8 of the result tuple are not usable.
@end deffn

@geindex parsedate_tz() (在 email.utils 模块中)
@anchor{library/email utils email utils parsedate_tz}@anchor{2879}
@deffn {函数} email.utils.parsedate_tz (date)

Performs the same function as @ref{2878,,parsedate()}, but returns either @code{None} or
a 10-tuple; the first 9 elements make up a tuple that can be passed directly to
@ref{b5d,,time.mktime()}, and the tenth is the offset of the date's timezone from UTC
(which is the official term for Greenwich Mean Time) @footnote{@w{(1)} 
Note that the sign of the timezone offset is the opposite of the sign of the
@code{time.timezone} variable for the same timezone; the latter variable follows
the POSIX standard while this module follows 
@geindex RFC; RFC 2822
@uref{https://tools.ietf.org/html/rfc2822.html,RFC 2822}.
}.  If the input string
has no timezone, the last element of the tuple returned is @code{0}, which represents
UTC. Note that indexes 6, 7, and 8 of the result tuple are not usable.
@end deffn

@geindex parsedate_to_datetime() (在 email.utils 模块中)
@anchor{library/email utils email utils parsedate_to_datetime}@anchor{9f9}
@deffn {函数} email.utils.parsedate_to_datetime (date)

The inverse of @ref{9f8,,format_datetime()}.  Performs the same function as
@ref{2878,,parsedate()}, but on success returns a @ref{194,,datetime}.  If
the input date has a timezone of @code{-0000}, the @code{datetime} will be a naive
@code{datetime}, and if the date is conforming to the RFCs it will represent a
time in UTC but with no indication of the actual source timezone of the
message the date comes from.  If the input date has any other valid timezone
offset, the @code{datetime} will be an aware @code{datetime} with the
corresponding a @ref{9fb,,timezone} @ref{378,,tzinfo}.


3.3 新版功能.

@end deffn

@geindex mktime_tz() (在 email.utils 模块中)
@anchor{library/email utils email utils mktime_tz}@anchor{287a}
@deffn {函数} email.utils.mktime_tz (tuple)

Turn a 10-tuple as returned by @ref{2879,,parsedate_tz()} into a UTC
timestamp (seconds since the Epoch).  If the timezone item in the
tuple is @code{None}, assume local time.
@end deffn

@geindex formatdate() (在 email.utils 模块中)
@anchor{library/email utils email utils formatdate}@anchor{287b}
@deffn {函数} email.utils.formatdate (timeval=None, localtime=False, usegmt=False)

Returns a date string as per 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}, e.g.:

@example
Fri, 09 Nov 2001 01:08:47 -0000
@end example

Optional @emph{timeval} if given is a floating point time value as accepted by
@ref{b38,,time.gmtime()} and @ref{edc,,time.localtime()}, otherwise the current time is
used.

Optional @emph{localtime} is a flag that when @code{True}, interprets @emph{timeval}, and
returns a date relative to the local timezone instead of UTC, properly taking
daylight savings time into account. The default is @code{False} meaning UTC is
used.

Optional @emph{usegmt} is a flag that when @code{True}, outputs a  date string with the
timezone as an ascii string @code{GMT}, rather than a numeric @code{-0000}. This is
needed for some protocols (such as HTTP). This only applies when @emph{localtime} is
@code{False}.  The default is @code{False}.
@end deffn

@geindex format_datetime() (在 email.utils 模块中)
@anchor{library/email utils email utils format_datetime}@anchor{9f8}
@deffn {函数} email.utils.format_datetime (dt, usegmt=False)

Like @code{formatdate}, but the input is a @ref{31,,datetime} instance.  If it is
a naive datetime, it is assumed to be "UTC with no information about the
source timezone", and the conventional @code{-0000} is used for the timezone.
If it is an aware @code{datetime}, then the numeric timezone offset is used.
If it is an aware timezone with offset zero, then @emph{usegmt} may be set to
@code{True}, in which case the string @code{GMT} is used instead of the numeric
timezone offset.  This provides a way to generate standards conformant HTTP
date headers.


3.3 新版功能.

@end deffn

@geindex decode_rfc2231() (在 email.utils 模块中)
@anchor{library/email utils email utils decode_rfc2231}@anchor{287c}
@deffn {函数} email.utils.decode_rfc2231 (s)

Decode the string @emph{s} according to 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html}.
@end deffn

@geindex encode_rfc2231() (在 email.utils 模块中)
@anchor{library/email utils email utils encode_rfc2231}@anchor{287d}
@deffn {函数} email.utils.encode_rfc2231 (s, charset=None, language=None)

Encode the string @emph{s} according to 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html}.  Optional @emph{charset} and
@emph{language}, if given is the character set name and language name to use.  If
neither is given, @emph{s} is returned as-is.  If @emph{charset} is given but @emph{language}
is not, the string is encoded using the empty string for @emph{language}.
@end deffn

@geindex collapse_rfc2231_value() (在 email.utils 模块中)
@anchor{library/email utils email utils collapse_rfc2231_value}@anchor{283f}
@deffn {函数} email.utils.collapse_rfc2231_value (value, errors='replace', fallback_charset='us-ascii')

When a header parameter is encoded in 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html} format,
@ref{283e,,Message.get_param} may return a
3-tuple containing the character set,
language, and value.  @ref{283f,,collapse_rfc2231_value()} turns this into a unicode
string.  Optional @emph{errors} is passed to the @emph{errors} argument of @ref{329,,str}'s
@ref{c30,,encode()} method; it defaults to @code{'replace'}.  Optional
@emph{fallback_charset} specifies the character set to use if the one in the
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html} header is not known by Python; it defaults to @code{'us-ascii'}.

For convenience, if the @emph{value} passed to @ref{283f,,collapse_rfc2231_value()} is not
a tuple, it should be a string and it is returned unquoted.
@end deffn

@geindex decode_params() (在 email.utils 模块中)
@anchor{library/email utils email utils decode_params}@anchor{287e}
@deffn {函数} email.utils.decode_params (params)

Decode parameters list according to 
@geindex RFC; RFC 2231
RFC 2231@footnote{https://tools.ietf.org/html/rfc2231.html}.  @emph{params} is a sequence of
2-tuples containing elements of the form @code{(content-type, string-value)}.
@end deffn

@subsubheading 备注


@node email iterators 迭代器,,email utils 其他工具,email --- 电子邮件与 MIME 处理包
@anchor{library/email iterators doc}@anchor{287f}@anchor{library/email iterators email-iterators-iterators}@anchor{2880}@anchor{library/email iterators module-email iterators}@anchor{71}
@subsubsection @code{email.iterators}: 迭代器


@geindex email.iterators (模块)

@strong{源代码:} Lib/email/iterators.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/email/iterators.py}


__________________________________________________________________


通过 @ref{2847,,Message.walk} 方法来迭代消息对象树是相当容易的。 @ref{71,,email.iterators} 模块提供了一些适用于消息对象树的高层级迭代器。

@geindex body_line_iterator() (在 email.iterators 模块中)
@anchor{library/email iterators email iterators body_line_iterator}@anchor{2881}
@deffn {函数} email.iterators.body_line_iterator (msg, decode=False)

此函数会迭代 @emph{msg} 的所有子部分中的所有载荷，逐行返回字符串载荷。 它会跳过所有子部分的标头，并且它也会跳过任何包含不为 Python 字符串的载荷的子部分。 这基本上等价于使用 @ref{1b90,,readline()} 从一个文件读取消息的纯文本表示形式，并跳过所有中间的标头。

可选的 @emph{decode} 会被传递给 @ref{b44,,Message.get_payload}。
@end deffn

@geindex typed_subpart_iterator() (在 email.iterators 模块中)
@anchor{library/email iterators email iterators typed_subpart_iterator}@anchor{2882}
@deffn {函数} email.iterators.typed_subpart_iterator (msg, maintype='text', subtype=None)

此函数会迭代 @emph{msg} 的所有子部分，只返回其中与 @emph{maintype} 和 @emph{subtype} 所指定的 MIME 类型相匹配的子部分。

请注意 @emph{subtype} 是可选项；如果省略，则仅使用主类型来进行子部分 MIME 类型的匹配。 @emph{maintype} 也是可选项；它的默认值为 @code{text}。

因此，在默认情况下 @ref{2882,,typed_subpart_iterator()} 会返回每一个 MIME 类型为 @code{text/*} 的子部分。
@end deffn

增加了以下函数作为有用的调试工具。 它 @emph{不应当} 被视为该包所支持的公共接口的组成部分。

@geindex _structure() (在 email.iterators 模块中)
@anchor{library/email iterators email iterators _structure}@anchor{2883}
@deffn {函数} email.iterators._structure (msg, fp=None, level=0, include_default=False)

打印消息对象结构的内容类型的缩进表示形式。 例如:

@c import email
@c from email.iterators import _structure
@c somefile = open('../Lib/test/test_email/data/msg_02.txt')

@example
>>> msg = email.message_from_file(somefile)
>>> _structure(msg)
multipart/mixed
    text/plain
    text/plain
    multipart/digest
        message/rfc822
            text/plain
        message/rfc822
            text/plain
        message/rfc822
            text/plain
        message/rfc822
            text/plain
        message/rfc822
            text/plain
    text/plain
@end example

@c somefile.close()

可选项 @emph{fp} 是一个作为打印输出目标的文件类对象。 它必须适用于 Python 的 @ref{880,,print()} 函数。 @emph{level} 是供内部使用的。 @emph{include_default} 如果为真值，则会同时打印默认类型。
@end deffn


@subsubheading 参见



@table @asis

@item Module @ref{ed,,smtplib}

SMTP (Simple Mail Transport Protocol) client

@item Module @ref{d0,,poplib}

POP (Post Office Protocol) client

@item Module @ref{98,,imaplib}

IMAP (Internet Message Access Protocol) client

@item Module @ref{c0,,nntplib}

NNTP (Net News Transport Protocol) client

@item Module @ref{ae,,mailbox}

Tools for creating, reading, and managing collections of messages on disk
using a variety standard formats.

@item Module @ref{ec,,smtpd}

SMTP server framework (primarily useful for testing)
@end table


@node json --- JSON 编码和解码器,mailcap --- Mailcap 文件处理,email --- 电子邮件与 MIME 处理包,互联网数据处理
@anchor{library/json doc}@anchor{2884}@anchor{library/json json-json-encoder-and-decoder}@anchor{2885}@anchor{library/json module-json}@anchor{a4}
@subsection @code{json} --- JSON 编码和解码器


@geindex json (模块)

@strong{源代码:} Lib/json/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/json/__init__.py}


__________________________________________________________________


JSON (JavaScript Object Notation)@footnote{http://json.org}，由 
@geindex RFC; RFC 7159
RFC 7159@footnote{https://tools.ietf.org/html/rfc7159.html}  (which obsoletes 
@geindex RFC; RFC 4627
RFC 4627@footnote{https://tools.ietf.org/html/rfc4627.html}) 和 ECMA-404@footnote{http://www.ecma-international.org/publications/standards/Ecma-404.htm} 指定，是一个受 JavaScript@footnote{https://en.wikipedia.org/wiki/JavaScript} 的对象字面量语法启发的轻量级数据交换格式，尽管它不仅仅是一个严格意义上的 JavaScript 的字集 @footnote{@w{(1)} 
正如 @uref{https://www.rfc-editor.org/errata_search.php?rfc=7159,RFC 7159 的勘误表} 所说明的，JSON 允许以字符串表示字面值字符 U+2028 (LINE SEPARATOR) 和 U+2029 (PARAGRAPH SEPARATOR)，而 JavaScript (在 ECMAScript 5.1 版中) 不允许。
}。

@ref{a4,,json} 提供了与标准库 @ref{b0,,marshal} 和 @ref{ca,,pickle} 相似的API接口。

对基本的 Python 对象层次结构进行编码：

@example
>>> import json
>>> json.dumps(['foo', @{'bar': ('baz', None, 1.0, 2)@}])
'["foo", @{"bar": ["baz", null, 1.0, 2]@}]'
>>> print(json.dumps("\"foo\bar"))
"\"foo\bar"
>>> print(json.dumps('\u1234'))
"\u1234"
>>> print(json.dumps('\\'))
"\\"
>>> print(json.dumps(@{"c": 0, "b": 0, "a": 0@}, sort_keys=True))
@{"a": 0, "b": 0, "c": 0@}
>>> from io import StringIO
>>> io = StringIO()
>>> json.dump(['streaming API'], io)
>>> io.getvalue()
'["streaming API"]'
@end example

紧凑编码：

@example
>>> import json
>>> json.dumps([1, 2, 3, @{'4': 5, '6': 7@}], separators=(',', ':'))
'[1,2,3,@{"4":5,"6":7@}]'
@end example

美化输出：

@example
>>> import json
>>> print(json.dumps(@{'4': 5, '6': 7@}, sort_keys=True, indent=4))
@{
    "4": 5,
    "6": 7
@}
@end example

JSON解码：

@example
>>> import json
>>> json.loads('["foo", @{"bar":["baz", null, 1.0, 2]@}]')
['foo', @{'bar': ['baz', None, 1.0, 2]@}]
>>> json.loads('"\\"foo\\bar"')
'"foo\x08ar'
>>> from io import StringIO
>>> io = StringIO('["streaming API"]')
>>> json.load(io)
['streaming API']
@end example

特殊 JSON 对象解码：

@example
>>> import json
>>> def as_complex(dct):
...     if '__complex__' in dct:
...         return complex(dct['real'], dct['imag'])
...     return dct
...
>>> json.loads('@{"__complex__": true, "real": 1, "imag": 2@}',
...     object_hook=as_complex)
(1+2j)
>>> import decimal
>>> json.loads('1.1', parse_float=decimal.Decimal)
Decimal('1.1')
@end example

扩展 @ref{601,,JSONEncoder}：

@example
>>> import json
>>> class ComplexEncoder(json.JSONEncoder):
...     def default(self, obj):
...         if isinstance(obj, complex):
...             return [obj.real, obj.imag]
...         # Let the base class default method raise the TypeError
...         return json.JSONEncoder.default(self, obj)
...
>>> json.dumps(2 + 1j, cls=ComplexEncoder)
'[2.0, 1.0]'
>>> ComplexEncoder().encode(2 + 1j)
'[2.0, 1.0]'
>>> list(ComplexEncoder().iterencode(2 + 1j))
['[2.0', ', 1.0', ']']
@end example

从命令行使用 @ref{a5,,json.tool} 来验证并美化输出：

@example
$ echo '@{"json":"obj"@}' | python -m json.tool
@{
    "json": "obj"
@}
$ echo '@{1.2:3.4@}' | python -m json.tool
Expecting property name enclosed in double quotes: line 1 column 2 (char 1)
@end example

详细文档请参见 @ref{2886,,命令行界面}。

@cartouche
@quotation 注解 
JSON 是 YAML@footnote{http://yaml.org/} 1.2 的一个子集。由该模块的默认设置生成的 JSON （尤其是默认的 “分隔符” 设置值）也是 YAML 1.0 and 1.1 的一个子集。因此该模块也能够用于序列化为 YAML。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
这个模块的编码器和解码器默认保护输入和输出的顺序。仅当底层的容器未排序时才会失去顺序。

在 Python 3.7 之前，@ref{1b8,,dict} 并不保证有序，因此输入和输出通常都是乱序的，除非是明确地请求 @ref{1b9,,collections.OrderedDict}。 从 Python 3.7 开始，普通的 @ref{1b8,,dict} 会保留顺序，因此不必再为 JSON 的生成和解析指定使用 @ref{1b9,,collections.OrderedDict}。
@end quotation
@end cartouche

@menu
* 基本使用:: 
* 编码器和解码器:: 
* 异常: 异常<13>. 
* 标准符合性和互操作性:: 
* 命令行界面: 命令行界面<4>. 

@end menu

@node 基本使用,编码器和解码器,,json --- JSON 编码和解码器
@anchor{library/json basic-usage}@anchor{2887}
@subsubsection 基本使用


@geindex dump() (在 json 模块中)
@anchor{library/json json dump}@anchor{5ff}
@deffn {函数} json.dump (obj, fp, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw)

使用这个 @ref{2888,,转换表} 将 @emph{obj} 序列化为 JSON 格式化流形式的 @emph{fp} (支持 @code{.write()} 的 @ref{1bfc,,file-like object})。

如果 @emph{skipkeys} 是 true （默认为 @code{False}），那么那些不是基本对象（包括 @ref{329,,str}, @ref{184,,int}、@ref{187,,float}、@ref{183,,bool}、@code{None}）的字典的键会被跳过；否则引发一个 @ref{192,,TypeError}。

@ref{a4,,json} 模块始终产生 @ref{329,,str} 对象而非 @ref{32a,,bytes} 对象。因此，@code{fp.write()} 必须支持 @ref{329,,str} 输入。

如果 @emph{ensure_ascii} 是 true （即默认值），输出保证将所有输入的非 ASCII 字符转义。如果 @emph{ensure_ascii} 是 false，这些字符会原样输出。

如果 @emph{check_circular} 是为假值 (默认为 @code{True})，那么容器类型的循环引用检验会被跳过并且循环引用会引发一个 @ref{95a,,OverflowError} (或者更糟的情况)。

如果 @emph{allow_nan} 是 false（默认为 @code{True}），那么在对严格 JSON 规格范围外的 @ref{187,,float} 类型值（@code{nan}、@code{inf} 和 @code{-inf}）进行序列化时会引发一个 @ref{1fb,,ValueError}。如果 @emph{allow_nan} 是 true，则使用它们的 JavaScript 等价形式（@code{NaN}、@code{Infinity} 和 @code{-Infinity}）。

如果 @emph{indent} 是一个非负整数或者字符串，那么 JSON 数组元素和对象成员会被美化输出为该值指定的缩进等级。如果缩进等级为 0、负数或者 @code{""}，则只会添加换行符。@code{None`@w{`}（默认值）选择最紧凑的表达。使用一个正整数会让每一层缩进同样数量的空格。如果 *indent* 是一个字符串（比如 `@w{`}"\t"}），那个字符串会被用于缩进每一层。


在 3.2 版更改: 现允许使用字符串作为 @emph{indent} 而不再仅仅是整数。


当被指定时，@emph{separators} 应当是一个 @code{(item_separator, key_separator)} 元组。当 @emph{indent} 为 @code{None} 时，默认值取 @code{(', ', ': ')}，否则取 @code{(',', ': ')}。为了得到最紧凑的 JSON 表达式，你应该指定其为 @code{(',', ':')} 以消除空白字符。


在 3.4 版更改: 现当 @emph{indent} 不是 @code{None} 时，采用 @code{(',', ': ')} 作为默认值。


当 @emph{default} 被指定时，其应该是一个函数，每当某个对象无法被序列化时它会被调用。它应该返回该对象的一个可以被 JSON 编码的版本或者引发一个 @ref{192,,TypeError}。如果没有被指定，则会直接引发 @ref{192,,TypeError}。

如果 @emph{sort_keys} 是 true（默认为 @code{False}），那么字典的输出会以键的顺序排序。

为了使用一个自定义的 @ref{601,,JSONEncoder} 子类（比如：覆盖了 @code{default()} 方法来序列化额外的类型）， 通过 @emph{cls} 关键字参数来指定；否则将使用 @ref{601,,JSONEncoder}。


在 3.6 版更改: 所有可选形参现在都是 @ref{2ac,,仅限关键字参数}。


@cartouche
@quotation 注解 
与 @ref{ca,,pickle} 和 @ref{b0,,marshal} 不同，JSON 不是一个具有框架的协议，所以尝试多次使用同一个 @emph{fp} 调用 @ref{5ff,,dump()} 来序列化多个对象会产生一个不合规的 JSON 文件。
@end quotation
@end cartouche
@end deffn

@geindex dumps() (在 json 模块中)
@anchor{library/json json dumps}@anchor{600}
@deffn {函数} json.dumps (obj, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw)

使用这个 @ref{2888,,转换表} 将 @emph{obj} 序列化为 JSON 格式的 @ref{329,,str}。 其参数的含义与 @ref{5ff,,dump()} 中的相同。

@cartouche
@quotation 注解 
JSON 中的键-值对中的键永远是 @ref{329,,str} 类型的。当一个对象被转化为 JSON 时，字典中所有的键都会被强制转换为字符串。这所造成的结果是字典被转换为 JSON 然后转换回字典时可能和原来的不相等。换句话说，如果 x 具有非字符串的键，则有 @code{loads(dumps(x)) != x}。
@end quotation
@end cartouche
@end deffn

@geindex load() (在 json 模块中)
@anchor{library/json json load}@anchor{55a}
@deffn {函数} json.load (fp, *, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)

使用这个 @ref{2889,,转换表} 将 @emph{fp} (一个支持 @code{.read()} 并包含一个 JSON 文档的 @ref{1239,,text file} 或者 @ref{1c37,,binary file}) 反序列化为一个 Python 对象。

@emph{object_hook} 是一个可选的函数，它会被调用于每一个解码出的对象字面量（即一个 @ref{1b8,,dict}）。@emph{object_hook} 的返回值会取代原本的 @ref{1b8,,dict}。这一特性能够被用于实现自定义解码器（如 JSON-RPC@footnote{http://www.jsonrpc.org} 的类型提示)。

@emph{object_pairs_hook} 是一个可选的函数，它会被调用于每一个有序列表对解码出的对象字面量。 @emph{object_pairs_hook} 的返回值将会取代原本的 @ref{1b8,,dict} 。这一特性能够被用于实现自定义解码器。如果 @emph{object_hook} 也被定义， @emph{object_pairs_hook} 优先。


在 3.1 版更改: 添加了对 @emph{object_pairs_hook} 的支持。


@emph{parse_float} ，如果指定，将与每个要解码 JSON 浮点数的字符串一同调用。默认状态下，相当于 @code{float(num_str)} 。可以用于对 JSON 浮点数使用其它数据类型和语法分析程序 （比如 @ref{188,,decimal.Decimal} ）。

@emph{parse_int} ，如果指定，将与每个要解码 JSON 整数的字符串一同调用。默认状态下，相当于 @code{int(num_str)} 。可以用于对 JSON 整数使用其它数据类型和语法分析程序 （比如 @ref{187,,float} ）。

@emph{parse_constant} ，如果指定，将要与以下字符串中的一个一同调用： @code{'-Infinity'} ， @code{'Infinity'} ， @code{'NaN'} 。如果遇到无效的 JSON 数字则可以使用它引发异常。


在 3.1 版更改: @emph{parse_constant} 不再调用 'null' ， 'true' ， 'false' 。


要使用自定义的 @ref{602,,JSONDecoder} 子类，用 @code{cls} 指定他；否则使用 @ref{602,,JSONDecoder} 。额外的关键词参数会通过类的构造函数传递。

如果反序列化的数据不是有效 JSON 文档，引发 @ref{700,,JSONDecodeError} 错误。


在 3.6 版更改: 所有可选形参现在都是 @ref{2ac,,仅限关键字参数}。



在 3.6 版更改: @emph{fp} 现在可以是 @ref{1c37,,binary file} 。输入编码应当是 UTF-8 ， UTF-16 或者 UTF-32 。

@end deffn

@geindex loads() (在 json 模块中)
@anchor{library/json json loads}@anchor{55b}
@deffn {函数} json.loads (s, *, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)

使用这个 @ref{2889,,转换表} 将 @emph{s} (一个包含 JSON 文档的 @ref{329,,str}, @ref{32a,,bytes} 或 @ref{32b,,bytearray} 实例) 反序列化为 Python 对象。

除了*encoding*被忽略和弃用自 Python 3.1 以来，其他参数的含义与 @ref{55a,,load()} 中相同。

如果反序列化的数据不是有效 JSON 文档，引发 @ref{700,,JSONDecodeError} 错误。


Deprecated since version 3.1, will be removed in version 3.9: @emph{encoding} 关键字参数。



在 3.6 版更改: @emph{s} 现在可以为 @ref{32a,,bytes} 或 @ref{32b,,bytearray} 类型。 输入编码应为 UTF-8, UTF-16 或 UTF-32。

@end deffn

@node 编码器和解码器,异常<13>,基本使用,json --- JSON 编码和解码器
@anchor{library/json encoders-and-decoders}@anchor{288a}
@subsubsection 编码器和解码器


@geindex JSONDecoder (json 中的类)
@anchor{library/json json JSONDecoder}@anchor{602}
@deffn {类} json.JSONDecoder (*, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, strict=True, object_pairs_hook=None)

简单的JSON解码器。

默认情况下，解码执行以下翻译:
@anchor{library/json json-to-py-table}@anchor{2889}

@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx} 
@headitem

JSON

@tab

Python

@item

object

@tab

dict

@item

array

@tab

list

@item

string

@tab

str

@item

number (int)

@tab

int

@item

number (real)

@tab

float

@item

true

@tab

True

@item

false

@tab

False

@item

null

@tab

None

@end multitable


它还将“NaN”、“Infinity”和“-Infinity”理解为它们对应的“float”值，这超出了JSON规范。

@emph{object_hook} ，如果指定，会被每个解码的 JSON 对象的结果调用，并且返回值会替代给定 @ref{1b8,,dict} 。它可被用于提供自定义反序列化（比如去支持 JSON-RPC 类的暗示）。

如果指定了 @emph{object_pairs_hook} 则它将被调用并传入以对照值有序列表进行解码的每个 JSON 对象的结果。 @emph{object_pairs_hook} 的结果值将被用来替代 @ref{1b8,,dict}。 这一特性可被用于实现自定义解码器。 如果还定义了 @emph{object_hook}，则 @emph{object_pairs_hook} 的优先级更高。


在 3.1 版更改: 添加了对 @emph{object_pairs_hook} 的支持。


@emph{parse_float} ，如果指定，将与每个要解码 JSON 浮点数的字符串一同调用。默认状态下，相当于 @code{float(num_str)} 。可以用于对 JSON 浮点数使用其它数据类型和语法分析程序 （比如 @ref{188,,decimal.Decimal} ）。

@emph{parse_int} ，如果指定，将与每个要解码 JSON 整数的字符串一同调用。默认状态下，相当于 @code{int(num_str)} 。可以用于对 JSON 整数使用其它数据类型和语法分析程序 （比如 @ref{187,,float} ）。

@emph{parse_constant} ，如果指定，将要与以下字符串中的一个一同调用： @code{'-Infinity'} ， @code{'Infinity'} ， @code{'NaN'} 。如果遇到无效的 JSON 数字则可以使用它引发异常。

如果 @emph{strict} 为 false （默认为 @code{True} ），那么控制字符将被允许在字符串内。在此上下文中的控制字符编码在范围 0--31 内的字符，包括 @code{'\t'} (制表符）， @code{'\n'} ， @code{'\r'} 和 @code{'\0'} 。

如果反序列化的数据不是有效 JSON 文档，引发 @ref{700,,JSONDecodeError} 错误。


在 3.6 版更改: 所有形参现在都是 @ref{2ac,,仅限关键字参数}。


@geindex decode() (json.JSONDecoder 方法)
@anchor{library/json json JSONDecoder decode}@anchor{288b}
@deffn {方法} decode (s)

返回 @emph{s} 的 Python 表示形式（包含一个 JSON 文档的 @ref{329,,str} 实例）。

如果给定的 JSON 文档无效则将引发 @ref{700,,JSONDecodeError}。
@end deffn

@geindex raw_decode() (json.JSONDecoder 方法)
@anchor{library/json json JSONDecoder raw_decode}@anchor{288c}
@deffn {方法} raw_decode (s)

从 @emph{s} 中解码出 JSON 文档（以 JSON 文档开头的一个 @ref{329,,str} 对象）并返回一个 Python 表示形式为 2 元组以及指明该文档在 @emph{s} 中结束位置的序号。

这可以用于从一个字符串解码JSON文档，该字符串的末尾可能有无关的数据。
@end deffn
@end deffn

@geindex JSONEncoder (json 中的类)
@anchor{library/json json JSONEncoder}@anchor{601}
@deffn {类} json.JSONEncoder (*, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, sort_keys=False, indent=None, separators=None, default=None)

用于Python数据结构的可扩展JSON编码器。

默认支持以下对象和类型：
@anchor{library/json py-to-json-table}@anchor{2888}

@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} 
@headitem

Python

@tab

JSON

@item

dict

@tab

object

@item

list, tuple

@tab

array

@item

str

@tab

string

@item

int, float, int 和 float 派生的枚举

@tab

number

@item

True

@tab

true

@item

False

@tab

false

@item

None

@tab

null

@end multitable



在 3.4 版更改: 添加了对 int 和 float 派生的枚举类的支持


为了将其拓展至识别其他对象，需要子类化并实现 @ref{288d,,default()} 方法于另一种返回 @code{o} 的可序列化对象的方法如果可行，否则它应该调用超类实现（来引发 @ref{192,,TypeError} ）。

如果 @emph{skipkeys} 为假值（默认），则尝试对不是 @ref{329,,str}, @ref{184,,int}, @ref{187,,float} 或 @code{None} 的键进行编码将会引发 @ref{192,,TypeError}。 如果 @emph{skipkeys} 为真值，这些条目将被直接跳过。

如果 @emph{ensure_ascii} 是 true （即默认值），输出保证将所有输入的非 ASCII 字符转义。如果 @emph{ensure_ascii} 是 false，这些字符会原样输出。

如果 @emph{check_circular} 为 true （默认），那么列表，字典，和自定义编码的对象在编码期间会被检查重复循环引用防止无限递归（无限递归将导致 @ref{95a,,OverflowError} ）。否则，这样进行检查。

如果 @emph{allow_nan} 为 true （默认），那么 @code{NaN} ， @code{Infinity} ，和 @code{-Infinity} 进行编码。此行为不符合 JSON 规范，但与大多数的基于 Javascript 的编码器和解码器一致。否则，它将是一个 @ref{1fb,,ValueError} 来编码这些浮点数。

如果 @emph{sort_keys} 为 true （默认为： @code{False} ），那么字典的输出是按照键排序；这对回归测试很有用，以确保可以每天比较 JSON 序列化。

如果 @emph{indent} 是一个非负整数或者字符串，那么 JSON 数组元素和对象成员会被美化输出为该值指定的缩进等级。如果缩进等级为 0、负数或者 @code{""}，则只会添加换行符。@code{None`@w{`}（默认值）选择最紧凑的表达。使用一个正整数会让每一层缩进同样数量的空格。如果 *indent* 是一个字符串（比如 `@w{`}"\t"}），那个字符串会被用于缩进每一层。


在 3.2 版更改: 现允许使用字符串作为 @emph{indent} 而不再仅仅是整数。


当被指定时，@emph{separators} 应当是一个 @code{(item_separator, key_separator)} 元组。当 @emph{indent} 为 @code{None} 时，默认值取 @code{(', ', ': ')}，否则取 @code{(',', ': ')}。为了得到最紧凑的 JSON 表达式，你应该指定其为 @code{(',', ':')} 以消除空白字符。


在 3.4 版更改: 现当 @emph{indent} 不是 @code{None} 时，采用 @code{(',', ': ')} 作为默认值。


当 @emph{default} 被指定时，其应该是一个函数，每当某个对象无法被序列化时它会被调用。它应该返回该对象的一个可以被 JSON 编码的版本或者引发一个 @ref{192,,TypeError}。如果没有被指定，则会直接引发 @ref{192,,TypeError}。


在 3.6 版更改: 所有形参现在都是 @ref{2ac,,仅限关键字参数}。


@geindex default() (json.JSONEncoder 方法)
@anchor{library/json json JSONEncoder default}@anchor{288d}
@deffn {方法} default (o)

在子类中实现这种方法使其返回 @emph{o} 的可序列化对象，或者调用基础实现（引发 @ref{192,,TypeError} ）。

比如说，为了支持任意迭代器，你可以像这样实现默认设置:

@example
def default(self, o):
   try:
       iterable = iter(o)
   except TypeError:
       pass
   else:
       return list(iterable)
   # Let the base class default method raise the TypeError
   return json.JSONEncoder.default(self, o)
@end example
@end deffn

@geindex encode() (json.JSONEncoder 方法)
@anchor{library/json json JSONEncoder encode}@anchor{288e}
@deffn {方法} encode (o)

返回 Python @emph{o} 数据结构的 JSON 字符串表达方式。例如:

@example
>>> json.JSONEncoder().encode(@{"foo": ["bar", "baz"]@})
'@{"foo": ["bar", "baz"]@}'
@end example
@end deffn

@geindex iterencode() (json.JSONEncoder 方法)
@anchor{library/json json JSONEncoder iterencode}@anchor{288f}
@deffn {方法} iterencode (o)

编码给定对象 @emph{o} ，并且让每个可用的字符串表达方式。例如:

@example
for chunk in json.JSONEncoder().iterencode(bigobject):
    mysocket.write(chunk)
@end example
@end deffn
@end deffn

@node 异常<13>,标准符合性和互操作性,编码器和解码器,json --- JSON 编码和解码器
@anchor{library/json exceptions}@anchor{2890}
@subsubsection 异常


@geindex JSONDecodeError
@anchor{library/json json JSONDecodeError}@anchor{700}
@deffn {例外} json.JSONDecodeError (msg, doc, pos)

拥有以下附加属性的 @ref{1fb,,ValueError} 的子类：

@geindex msg (json.JSONDecodeError 属性)
@anchor{library/json json JSONDecodeError msg}@anchor{2891}
@deffn {属性} msg

未格式化的错误消息。
@end deffn

@geindex doc (json.JSONDecodeError 属性)
@anchor{library/json json JSONDecodeError doc}@anchor{2892}
@deffn {属性} doc

正在解析的 JSON 文档。
@end deffn

@geindex pos (json.JSONDecodeError 属性)
@anchor{library/json json JSONDecodeError pos}@anchor{2893}
@deffn {属性} pos

The start index of @emph{doc} where parsing failed.
@end deffn

@geindex lineno (json.JSONDecodeError 属性)
@anchor{library/json json JSONDecodeError lineno}@anchor{2894}
@deffn {属性} lineno

The line corresponding to @emph{pos}.
@end deffn

@geindex colno (json.JSONDecodeError 属性)
@anchor{library/json json JSONDecodeError colno}@anchor{2895}
@deffn {属性} colno

The column corresponding to @emph{pos}.
@end deffn


3.5 新版功能.

@end deffn

@node 标准符合性和互操作性,命令行界面<4>,异常<13>,json --- JSON 编码和解码器
@anchor{library/json standard-compliance-and-interoperability}@anchor{2896}
@subsubsection 标准符合性和互操作性


JSON 格式由 
@geindex RFC; RFC 7159
RFC 7159@footnote{https://tools.ietf.org/html/rfc7159.html} 和 ECMA-404@footnote{http://www.ecma-international.org/publications/standards/Ecma-404.htm} 指定。此段落详细讲了这个模块符合 RFC 的级别。简单来说， @ref{601,,JSONEncoder} 和 @ref{602,,JSONDecoder} 子类，和明确提到的参数以外的参数，不作考虑。

此模块不严格遵循于 RFC ，它实现了一些扩展是有效的 Javascript 但不是有效的 JSON。尤其是：


@itemize -

@item 
无限和 NaN 数值是被接受并输出；

@item 
对象内的重复名称是接受的，并且仅使用最后一对属性-值对的值。
@end itemize

自从 RFC 允许符合 RFC 的语法分析程序接收 不符合 RFC 的输入文本以来，这个模块的解串器在默认状态下默认符合 RFC 。

@menu
* 字符编码:: 
* Infinite 和 NaN 数值:: 
* 对象中的重复名称:: 
* 顶级非对象，非数组值:: 
* 实现限制:: 

@end menu

@node 字符编码,Infinite 和 NaN 数值,,标准符合性和互操作性
@anchor{library/json character-encodings}@anchor{2897}
@subsubsection 字符编码


RFC 要求使用 UTF-8 ， UTF-16 ，或 UTF-32 之一来表示 JSON ，为了最大互通性推荐使用 UTF-8 。

RFC允许，尽管不是必须的，这个模块的序列化默认设置为 @emph{ensure_ascii=True} ，这样消除输出以便结果字符串至容纳 ASCII 字符。

@emph{ensure_ascii} 参数以外，此模块是严格的按照在 Python 对象和 @ref{329,,Unicode strings} 间的转换定义的，并且因此不能直接解决字符编码的问题。

RFC 禁止添加字符顺序标记（ BOM ）在 JSON 文本的开头，这个模块的序列化器不添加 BOM 标记在它的输出上。 RFC，准许 JSON 反序列化器忽略它们输入中的初始 BOM 标记，但不要求。此模块的反序列化器引发 @ref{1fb,,ValueError} 当存在初始 BOM 标记。

RFC 不会明确禁止包含字节序列的 JSON 字符串这不对应有效的 Unicode 字符（比如 不成对的 UTF-16 的替代物），但是它确实指出它们可能会导致互操作性问题。默认下，模块对这样的序列接受和输出（当在原始 @ref{329,,str} 存在时）代码点。

@node Infinite 和 NaN 数值,对象中的重复名称,字符编码,标准符合性和互操作性
@anchor{library/json infinite-and-nan-number-values}@anchor{2898}
@subsubsection Infinite 和 NaN 数值


RFC 不允许 infinite 或者 NaN 数值的表达方式。尽管这样，默认情况下，此模块接受并且输出 @code{Infinity} ， @code{-Infinity}，和 @code{NaN} 好像它们是有效的JSON数字字面值

@example
>>> # Neither of these calls raises an exception, but the results are not valid JSON
>>> json.dumps(float('-inf'))
'-Infinity'
>>> json.dumps(float('nan'))
'NaN'
>>> # Same when deserializing
>>> json.loads('-Infinity')
-inf
>>> json.loads('NaN')
nan
@end example

序列化器中， @emph{allow_nan} 参数可用于替代这个行为。反序列化器中， @emph{parse_constant} 参数，可用于替代这个行为。

@node 对象中的重复名称,顶级非对象，非数组值,Infinite 和 NaN 数值,标准符合性和互操作性
@anchor{library/json repeated-names-within-an-object}@anchor{2899}
@subsubsection 对象中的重复名称


RFC 具体说明了 在 JSON对象里的名字应该是唯一的，但没有规定如何处理JSON对象中的重复名称。默认下，此模块不引发异常；作为替代，对于给定名它将忽略除姓-值对之外的所有对:

@example
>>> weird_json = '@{"x": 1, "x": 2, "x": 3@}'
>>> json.loads(weird_json)
@{'x': 3@}
@end example

The @emph{object_pairs_hook} parameter can be used to alter this behavior.

@node 顶级非对象，非数组值,实现限制,对象中的重复名称,标准符合性和互操作性
@anchor{library/json top-level-non-object-non-array-values}@anchor{289a}
@subsubsection 顶级非对象，非数组值


过时的 
@geindex RFC; RFC 4627
RFC 4627@footnote{https://tools.ietf.org/html/rfc4627.html} 指定的旧版本 JSON 要求 JSON 文本顶级值必须是 JSON 对象或数组（ Python @ref{1b8,,dict} 或 @ref{262,,list} ），并且不能是 JSON null 值，布尔值，数值或者字符串值。 
@geindex RFC; RFC 7159
RFC 7159@footnote{https://tools.ietf.org/html/rfc7159.html} 移除这个限制，此模块没有并且从未在序列化器和反序列化器中实现这个限制。

无论如何，为了最大化地获取互操作性，你可能希望自己遵守该原则。

@node 实现限制,,顶级非对象，非数组值,标准符合性和互操作性
@anchor{library/json implementation-limitations}@anchor{289b}
@subsubsection 实现限制


一些 JSON 反序列化器的实现应该在以下方面做出限制：


@itemize *

@item 
可接受的 JSON 文本大小

@item 
嵌套 JSON 对象和数组的最高水平

@item 
JSON 数字的范围和精度

@item 
JSON 字符串的内容和最大长度
@end itemize

此模块不强制执行任何上述限制，除了相关的 Python 数据类型本身或者 Python 解释器本身的限制以外。

当序列化为 JSON ，在应用中当心此类限制这可能破坏你的 JSON 。特别是，通常将 JSON 数字反序列化为 IEEE 754 双精度数字，从而受到该表示方式的范围和精度限制。这是特别相关的，当序列化非常大的 Python @ref{184,,int} 值时，或者当序列化 "exotic" 数值类型的实例时比如 @ref{188,,decimal.Decimal} 。

@node 命令行界面<4>,,标准符合性和互操作性,json --- JSON 编码和解码器
@anchor{library/json command-line-interface}@anchor{289c}@anchor{library/json json-commandline}@anchor{2886}@anchor{library/json module-json tool}@anchor{a5}
@subsubsection 命令行界面


@geindex json.tool (模块)

@strong{源代码：} Lib/json/tool.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/json/tool.py}


__________________________________________________________________


The @ref{a5,,json.tool} module provides a simple command line interface to validate
and pretty-print JSON objects.

如果未指定可选的 @code{infile} 和 @code{outfile} 参数，则将分别使用 @ref{306,,sys.stdin} 和 @ref{307,,sys.stdout}:

@example
$ echo '@{"json": "obj"@}' | python -m json.tool
@{
    "json": "obj"
@}
$ echo '@{1.2:3.4@}' | python -m json.tool
Expecting property name enclosed in double quotes: line 1 column 2 (char 1)
@end example


在 3.5 版更改: 输出现在将与输入顺序保持一致。 请使用 @ref{289d,,--sort-keys} 选项来将输出按照键的字母顺序排序。


@menu
* 命令行选项: 命令行选项<4>. 

@end menu

@node 命令行选项<4>,,,命令行界面<4>
@anchor{library/json command-line-options}@anchor{289e}
@subsubsection 命令行选项


@geindex json.tool command line option; infile
@anchor{library/json cmdoption-json-tool-arg-infile}@anchor{289f}
@deffn {程序选项} infile

要被验证或美化打印的 JSON 文件：

@example
$ python -m json.tool mp_films.json
[
    @{
        "title": "And Now for Something Completely Different",
        "year": 1971
    @},
    @{
        "title": "Monty Python and the Holy Grail",
        "year": 1975
    @}
]
@end example

如果 @emph{infile} 未指定，则从 @ref{306,,sys.stdin} 读取。
@end deffn

@geindex json.tool command line option; outfile
@anchor{library/json cmdoption-json-tool-arg-outfile}@anchor{28a0}
@deffn {程序选项} outfile

将 @emph{infile} 输出写入到给定的 @emph{outfile}。 在其他情况下写入到 @ref{307,,sys.stdout}。
@end deffn

@geindex json.tool command line option; --sort-keys
@anchor{library/json cmdoption-json-tool-sort-keys}@anchor{289d}
@deffn {程序选项} @w{-}@w{-}sort@w{-}keys

将字典输出按照键的字母顺序排序。


3.5 新版功能.

@end deffn

@geindex json.tool command line option; --json-lines
@anchor{library/json cmdoption-json-tool-json-lines}@anchor{28a1}
@deffn {程序选项} @w{-}@w{-}json@w{-}lines

将每个输入行解析为单独的 JSON 对象。


3.8 新版功能.

@end deffn

@geindex json.tool command line option; -h
@geindex json.tool command line option; --help
@anchor{library/json cmdoption-json-tool-h}@anchor{28a2}
@deffn {程序选项} @w{-}h, @w{-}@w{-}help

显示帮助消息。
@end deffn

@subsubheading 备注


@node mailcap --- Mailcap 文件处理,mailbox --- Manipulate mailboxes in various formats,json --- JSON 编码和解码器,互联网数据处理
@anchor{library/mailcap doc}@anchor{28a3}@anchor{library/mailcap mailcap-mailcap-file-handling}@anchor{28a4}@anchor{library/mailcap module-mailcap}@anchor{af}
@subsection @code{mailcap} --- Mailcap 文件处理


@geindex mailcap (模块)

@strong{源代码:} Lib/mailcap.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/mailcap.py}


__________________________________________________________________


Mailcap 文件可用来配置支持 MIME 的应用例如邮件阅读器和 Web 浏览器如何响应具有不同 MIME 类型的文件。 （"mailcap" 这个名称源自短语"mail capability"。） 例如，一个 mailcap 文件可能包含 @code{video/mpeg; xmpeg %s} 这样的行。 然后，如果用户遇到 MIME 类型为 @code{video/mpeg} 的邮件消息或 Web 文档时，@code{%s} 将被替换为一个文件名（通常是一个临时文件）并且将自动启动 @code{xmpeg} 程序来查看该文件。

mailcap 格式的文档见 
@geindex RFC; RFC 1524
RFC 1524@footnote{https://tools.ietf.org/html/rfc1524.html}, "A User Agent Configuration Mechanism For Multimedia Mail Format Information"，但它并不是一个因特网标准。 不过，mailcap 文件在大多数 Unix 系统上都受到支持。

@geindex findmatch() (在 mailcap 模块中)
@anchor{library/mailcap mailcap findmatch}@anchor{28a5}
@deffn {函数} mailcap.findmatch (caps, MIMEtype, key='view', filename='/dev/null', plist=[])

返回一个 2 元组；其中第一个元素是包含所要执行命令的字符串 (它可被传递给 @ref{dba,,os.system()})，第二个元素是对应于给定 MIME 类型的 mailcap 条目。 如果找不到匹配的 MIME 类型，则将返回 @code{(None, None)}。

@emph{key} 是所需字段的名称，它代表要执行的活动类型；默认值是 'view'，因为在最通常的情况下你只是想要查看 MIME 类型数据的正文。 其他可能的值还有 'compose' 和 'edit'，分别用于想要创建给定 MIME 类型正文或修改现有正文数据的情况。 请参阅 
@geindex RFC; RFC 1524
RFC 1524@footnote{https://tools.ietf.org/html/rfc1524.html} 获取这些字段的完整列表。

@emph{filename} 是在命令行中用来替换 @code{%s} 的文件名；默认值 @code{'/dev/null'} 几乎肯定不是你想要的，因此通常你要通过指定一个文件名来重载它。

@emph{plist} 可以是一个包含命名形参的列表；默认值只是一个空列表。 列表中的每个条目必须为包含形参名称的字符串、等于号 (@code{'='}) 以及形参的值。 Mailcap 条目可以包含形如 @code{%@{foo@}} 的命名形参，它将由名为 'foo' 的形参的值所替换。 例如，如果命令行 @code{showpartial %@{id@} %@{number@} %@{total@}} 是在一个 mailcap 文件中，并且 @emph{plist} 被设为 @code{['id=1', 'number=2', 'total=3']}，则结果命令行将为 @code{'showpartial 1 2 3'}。

在 mailcap 文件中，可以指定可选的 "test" 字段来检测某些外部条件（例如所使用的机器架构或窗口系统）来确定是否要应用 mailcap 行。 @ref{28a5,,findmatch()} 将自动检查此类条件并在检查未通过时跳过条目。
@end deffn

@geindex getcaps() (在 mailcap 模块中)
@anchor{library/mailcap mailcap getcaps}@anchor{28a6}
@deffn {函数} mailcap.getcaps ()

返回一个将 MIME 类型映射到 mailcap 文件条目列表的字典。 此字典必须被传给 @ref{28a5,,findmatch()} 函数。 条目会被存储为字典列表，但并不需要了解此表示形式的细节。

此信息来自在系统中找到的所有 mailcap 文件。 用户的 mailcap 文件 @code{$HOME/.mailcap} 中的设置将覆盖系统 mailcap 文件 @code{/etc/mailcap}, @code{/usr/etc/mailcap} 和 @code{/usr/local/etc/mailcap} 中的设置。
@end deffn

一个用法示例:

@example
>>> import mailcap
>>> d = mailcap.getcaps()
>>> mailcap.findmatch(d, 'video/mpeg', filename='tmp1223')
('xmpeg tmp1223', @{'view': 'xmpeg %s'@})
@end example

@node mailbox --- Manipulate mailboxes in various formats,mimetypes --- Map filenames to MIME types,mailcap --- Mailcap 文件处理,互联网数据处理
@anchor{library/mailbox doc}@anchor{28a7}@anchor{library/mailbox mailbox-manipulate-mailboxes-in-various-formats}@anchor{28a8}@anchor{library/mailbox module-mailbox}@anchor{ae}
@subsection @code{mailbox} --- Manipulate mailboxes in various formats


@geindex mailbox (模块)

@strong{源代码：} Lib/mailbox.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/mailbox.py}


__________________________________________________________________


This module defines two classes, @ref{bdc,,Mailbox} and @ref{be0,,Message}, for
accessing and manipulating on-disk mailboxes and the messages they contain.
@ref{bdc,,Mailbox} offers a dictionary-like mapping from keys to messages.
@ref{be0,,Message} extends the @ref{72,,email.message} module's
@ref{53c,,Message} class with format-specific state and behavior.
Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.


@subsubheading 参见



@table @asis

@item 模块 @ref{69,,email}

Represent and manipulate messages.
@end table


@menu
* Mailbox 对象:: 
* Message objects:: 
* 异常: 异常<14>. 
* 例子: 例子<18>. 

@end menu

@node Mailbox 对象,Message objects,,mailbox --- Manipulate mailboxes in various formats
@anchor{library/mailbox id1}@anchor{28a9}@anchor{library/mailbox mailbox-objects}@anchor{28aa}
@subsubsection @code{Mailbox} 对象


@geindex Mailbox (mailbox 中的类)
@anchor{library/mailbox mailbox Mailbox}@anchor{bdc}
@deffn {类} mailbox.Mailbox

A mailbox, which may be inspected and modified.

The @ref{bdc,,Mailbox} class defines an interface and is not intended to be
instantiated.  Instead, format-specific subclasses should inherit from
@ref{bdc,,Mailbox} and your code should instantiate a particular subclass.

The @ref{bdc,,Mailbox} interface is dictionary-like, with small keys
corresponding to messages. Keys are issued by the @ref{bdc,,Mailbox} instance
with which they will be used and are only meaningful to that @ref{bdc,,Mailbox}
instance. A key continues to identify a message even if the corresponding
message is modified, such as by replacing it with another message.

Messages may be added to a @ref{bdc,,Mailbox} instance using the set-like
method @ref{bdb,,add()} and removed using a @code{del} statement or the set-like
methods @ref{28ab,,remove()} and @ref{28ac,,discard()}.

@ref{bdc,,Mailbox} interface semantics differ from dictionary semantics in some
noteworthy ways. Each time a message is requested, a new representation
(typically a @ref{be0,,Message} instance) is generated based upon the current
state of the mailbox. Similarly, when a message is added to a
@ref{bdc,,Mailbox} instance, the provided message representation's contents are
copied. In neither case is a reference to the message representation kept by
the @ref{bdc,,Mailbox} instance.

The default @ref{bdc,,Mailbox} iterator iterates over message representations,
not keys as the default dictionary iterator does. Moreover, modification of a
mailbox during iteration is safe and well-defined. Messages added to the
mailbox after an iterator is created will not be seen by the
iterator. Messages removed from the mailbox before the iterator yields them
will be silently skipped, though using a key from an iterator may result in a
@ref{2c7,,KeyError} exception if the corresponding message is subsequently
removed.

@cartouche
@quotation 警告 
Be very cautious when modifying mailboxes that might be simultaneously
changed by some other process.  The safest mailbox format to use for such
tasks is Maildir; try to avoid using single-file formats such as mbox for
concurrent writing.  If you're modifying a mailbox, you @emph{must} lock it by
calling the @ref{28ad,,lock()} and @ref{28ae,,unlock()} methods @emph{before} reading any
messages in the file or making any changes by adding or deleting a
message.  Failing to lock the mailbox runs the risk of losing messages or
corrupting the entire mailbox.
@end quotation
@end cartouche

@ref{bdc,,Mailbox} instances have the following methods:

@geindex add() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox add}@anchor{bdb}
@deffn {方法} add (message)

Add @emph{message} to the mailbox and return the key that has been assigned to
it.

Parameter @emph{message} may be a @ref{be0,,Message} instance, an
@ref{53c,,email.message.Message} instance, a string, a byte string, or a
file-like object (which should be open in binary mode). If @emph{message} is
an instance of the
appropriate format-specific @ref{be0,,Message} subclass (e.g., if it's an
@ref{277c,,mboxMessage} instance and this is an @ref{28af,,mbox} instance), its
format-specific information is used. Otherwise, reasonable defaults for
format-specific information are used.


在 3.2 版更改: Support for binary input was added.

@end deffn

@geindex remove() (mailbox.Mailbox 方法)
@geindex __delitem__() (mailbox.Mailbox 方法)
@geindex discard() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox remove}@anchor{28ab}
@deffn {方法} remove (key)
@anchor{library/mailbox mailbox Mailbox __delitem__}@anchor{28b0}
@deffnx {方法} __delitem__ (key)
@anchor{library/mailbox mailbox Mailbox discard}@anchor{28ac}
@deffnx {方法} discard (key)

Delete the message corresponding to @emph{key} from the mailbox.

If no such message exists, a @ref{2c7,,KeyError} exception is raised if the
method was called as @ref{28ab,,remove()} or @ref{28b0,,__delitem__()} but no
exception is raised if the method was called as @ref{28ac,,discard()}. The
behavior of @ref{28ac,,discard()} may be preferred if the underlying mailbox
format supports concurrent modification by other processes.
@end deffn

@geindex __setitem__() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox __setitem__}@anchor{28b1}
@deffn {方法} __setitem__ (key, message)

Replace the message corresponding to @emph{key} with @emph{message}. Raise a
@ref{2c7,,KeyError} exception if no message already corresponds to @emph{key}.

As with @ref{bdb,,add()}, parameter @emph{message} may be a @ref{be0,,Message}
instance, an @ref{53c,,email.message.Message} instance, a string, a byte
string, or a file-like object (which should be open in binary mode). If
@emph{message} is an
instance of the appropriate format-specific @ref{be0,,Message} subclass
(e.g., if it's an @ref{277c,,mboxMessage} instance and this is an
@ref{28af,,mbox} instance), its format-specific information is
used. Otherwise, the format-specific information of the message that
currently corresponds to @emph{key} is left unchanged.
@end deffn

@geindex iterkeys() (mailbox.Mailbox 方法)
@geindex keys() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox iterkeys}@anchor{28b2}
@deffn {方法} iterkeys ()
@anchor{library/mailbox mailbox Mailbox keys}@anchor{28b3}
@deffnx {方法} keys ()

Return an iterator over all keys if called as @ref{28b2,,iterkeys()} or return a
list of keys if called as @ref{28b3,,keys()}.
@end deffn

@geindex itervalues() (mailbox.Mailbox 方法)
@geindex __iter__() (mailbox.Mailbox 方法)
@geindex values() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox itervalues}@anchor{28b4}
@deffn {方法} itervalues ()
@anchor{library/mailbox mailbox Mailbox __iter__}@anchor{28b5}
@deffnx {方法} __iter__ ()
@anchor{library/mailbox mailbox Mailbox values}@anchor{28b6}
@deffnx {方法} values ()

Return an iterator over representations of all messages if called as
@ref{28b4,,itervalues()} or @ref{28b5,,__iter__()} or return a list of such
representations if called as @ref{28b6,,values()}. The messages are represented
as instances of the appropriate format-specific @ref{be0,,Message} subclass
unless a custom message factory was specified when the @ref{bdc,,Mailbox}
instance was initialized.

@cartouche
@quotation 注解 
The behavior of @ref{28b5,,__iter__()} is unlike that of dictionaries, which
iterate over keys.
@end quotation
@end cartouche
@end deffn

@geindex iteritems() (mailbox.Mailbox 方法)
@geindex items() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox iteritems}@anchor{28b7}
@deffn {方法} iteritems ()
@anchor{library/mailbox mailbox Mailbox items}@anchor{28b8}
@deffnx {方法} items ()

Return an iterator over (@emph{key}, @emph{message}) pairs, where @emph{key} is a key and
@emph{message} is a message representation, if called as @ref{28b7,,iteritems()} or
return a list of such pairs if called as @ref{28b8,,items()}. The messages are
represented as instances of the appropriate format-specific
@ref{be0,,Message} subclass unless a custom message factory was specified
when the @ref{bdc,,Mailbox} instance was initialized.
@end deffn

@geindex get() (mailbox.Mailbox 方法)
@geindex __getitem__() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox get}@anchor{28b9}
@deffn {方法} get (key, default=None)
@anchor{library/mailbox mailbox Mailbox __getitem__}@anchor{28ba}
@deffnx {方法} __getitem__ (key)

Return a representation of the message corresponding to @emph{key}. If no such
message exists, @emph{default} is returned if the method was called as
@ref{28b9,,get()} and a @ref{2c7,,KeyError} exception is raised if the method was
called as @ref{28ba,,__getitem__()}. The message is represented as an instance
of the appropriate format-specific @ref{be0,,Message} subclass unless a
custom message factory was specified when the @ref{bdc,,Mailbox} instance
was initialized.
@end deffn

@geindex get_message() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox get_message}@anchor{28bb}
@deffn {方法} get_message (key)

Return a representation of the message corresponding to @emph{key} as an
instance of the appropriate format-specific @ref{be0,,Message} subclass, or
raise a @ref{2c7,,KeyError} exception if no such message exists.
@end deffn

@geindex get_bytes() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox get_bytes}@anchor{bde}
@deffn {方法} get_bytes (key)

Return a byte representation of the message corresponding to @emph{key}, or
raise a @ref{2c7,,KeyError} exception if no such message exists.


3.2 新版功能.

@end deffn

@geindex get_string() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox get_string}@anchor{bdf}
@deffn {方法} get_string (key)

Return a string representation of the message corresponding to @emph{key}, or
raise a @ref{2c7,,KeyError} exception if no such message exists.  The
message is processed through @ref{53c,,email.message.Message} to
convert it to a 7bit clean representation.
@end deffn

@geindex get_file() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox get_file}@anchor{bdd}
@deffn {方法} get_file (key)

Return a file-like representation of the message corresponding to @emph{key},
or raise a @ref{2c7,,KeyError} exception if no such message exists.  The
file-like object behaves as if open in binary mode.  This file should be
closed once it is no longer needed.


在 3.2 版更改: The file object really is a binary file; previously it was incorrectly
returned in text mode.  Also, the file-like object now supports the
context management protocol: you can use a @ref{6e3,,with} statement to
automatically close it.


@cartouche
@quotation 注解 
Unlike other representations of messages, file-like representations are
not necessarily independent of the @ref{bdc,,Mailbox} instance that
created them or of the underlying mailbox.  More specific documentation
is provided by each subclass.
@end quotation
@end cartouche
@end deffn

@geindex __contains__() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox __contains__}@anchor{28bc}
@deffn {方法} __contains__ (key)

Return @code{True} if @emph{key} corresponds to a message, @code{False} otherwise.
@end deffn

@geindex __len__() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox __len__}@anchor{28bd}
@deffn {方法} __len__ ()

Return a count of messages in the mailbox.
@end deffn

@geindex clear() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox clear}@anchor{28be}
@deffn {方法} clear ()

Delete all messages from the mailbox.
@end deffn

@geindex pop() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox pop}@anchor{28bf}
@deffn {方法} pop (key, default=None)

Return a representation of the message corresponding to @emph{key} and delete
the message. If no such message exists, return @emph{default}. The message is
represented as an instance of the appropriate format-specific
@ref{be0,,Message} subclass unless a custom message factory was specified
when the @ref{bdc,,Mailbox} instance was initialized.
@end deffn

@geindex popitem() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox popitem}@anchor{28c0}
@deffn {方法} popitem ()

Return an arbitrary (@emph{key}, @emph{message}) pair, where @emph{key} is a key and
@emph{message} is a message representation, and delete the corresponding
message. If the mailbox is empty, raise a @ref{2c7,,KeyError} exception. The
message is represented as an instance of the appropriate format-specific
@ref{be0,,Message} subclass unless a custom message factory was specified
when the @ref{bdc,,Mailbox} instance was initialized.
@end deffn

@geindex update() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox update}@anchor{28c1}
@deffn {方法} update (arg)

Parameter @emph{arg} should be a @emph{key}-to-@emph{message} mapping or an iterable of
(@emph{key}, @emph{message}) pairs. Updates the mailbox so that, for each given
@emph{key} and @emph{message}, the message corresponding to @emph{key} is set to
@emph{message} as if by using @ref{28b1,,__setitem__()}. As with @ref{28b1,,__setitem__()},
each @emph{key} must already correspond to a message in the mailbox or else a
@ref{2c7,,KeyError} exception will be raised, so in general it is incorrect
for @emph{arg} to be a @ref{bdc,,Mailbox} instance.

@cartouche
@quotation 注解 
Unlike with dictionaries, keyword arguments are not supported.
@end quotation
@end cartouche
@end deffn

@geindex flush() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox flush}@anchor{28c2}
@deffn {方法} flush ()

Write any pending changes to the filesystem. For some @ref{bdc,,Mailbox}
subclasses, changes are always written immediately and @ref{28c2,,flush()} does
nothing, but you should still make a habit of calling this method.
@end deffn

@geindex lock() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox lock}@anchor{28ad}
@deffn {方法} lock ()

Acquire an exclusive advisory lock on the mailbox so that other processes
know not to modify it. An @ref{28c3,,ExternalClashError} is raised if the lock
is not available. The particular locking mechanisms used depend upon the
mailbox format.  You should @emph{always} lock the mailbox before making any
modifications to its contents.
@end deffn

@geindex unlock() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox unlock}@anchor{28ae}
@deffn {方法} unlock ()

Release the lock on the mailbox, if any.
@end deffn

@geindex close() (mailbox.Mailbox 方法)
@anchor{library/mailbox mailbox Mailbox close}@anchor{28c4}
@deffn {方法} close ()

Flush the mailbox, unlock it if necessary, and close any open files. For
some @ref{bdc,,Mailbox} subclasses, this method does nothing.
@end deffn
@end deffn

@menu
* Maildir:: 
* mbox:: 
* MH:: 
* Babyl:: 
* MMDF:: 

@end menu

@node Maildir,mbox,,Mailbox 对象
@anchor{library/mailbox mailbox-maildir}@anchor{28c5}@anchor{library/mailbox maildir}@anchor{28c6}
@subsubsection @code{Maildir}


@geindex Maildir (mailbox 中的类)
@anchor{library/mailbox mailbox Maildir}@anchor{ca1}
@deffn {类} mailbox.Maildir (dirname, factory=None, create=True)

A subclass of @ref{bdc,,Mailbox} for mailboxes in Maildir format. Parameter
@emph{factory} is a callable object that accepts a file-like message representation
(which behaves as if opened in binary mode) and returns a custom representation.
If @emph{factory} is @code{None}, @ref{28c7,,MaildirMessage} is used as the default message
representation. If @emph{create} is @code{True}, the mailbox is created if it does not
exist.

If @emph{create} is @code{True} and the @emph{dirname} path exists, it will be treated as
an existing maildir without attempting to verify its directory layout.

It is for historical reasons that @emph{dirname} is named as such rather than @emph{path}.

Maildir is a directory-based mailbox format invented for the qmail mail
transfer agent and now widely supported by other programs. Messages in a
Maildir mailbox are stored in separate files within a common directory
structure. This design allows Maildir mailboxes to be accessed and modified
by multiple unrelated programs without data corruption, so file locking is
unnecessary.

Maildir mailboxes contain three subdirectories, namely: @code{tmp},
@code{new}, and @code{cur}. Messages are created momentarily in the
@code{tmp} subdirectory and then moved to the @code{new} subdirectory to
finalize delivery. A mail user agent may subsequently move the message to the
@code{cur} subdirectory and store information about the state of the message
in a special "info" section appended to its file name.

Folders of the style introduced by the Courier mail transfer agent are also
supported. Any subdirectory of the main mailbox is considered a folder if
@code{'.'} is the first character in its name. Folder names are represented by
@ref{ca1,,Maildir} without the leading @code{'.'}. Each folder is itself a Maildir
mailbox but should not contain other folders. Instead, a logical nesting is
indicated using @code{'.'} to delimit levels, e.g., "Archived.2005.07".

@cartouche
@quotation 注解 
The Maildir specification requires the use of a colon (@code{':'}) in certain
message file names. However, some operating systems do not permit this
character in file names, If you wish to use a Maildir-like format on such
an operating system, you should specify another character to use
instead. The exclamation point (@code{'!'}) is a popular choice. For
example:

@example
import mailbox
mailbox.Maildir.colon = '!'
@end example

The @code{colon} attribute may also be set on a per-instance basis.
@end quotation
@end cartouche

@ref{ca1,,Maildir} instances have all of the methods of @ref{bdc,,Mailbox} in
addition to the following:

@geindex list_folders() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir list_folders}@anchor{28c8}
@deffn {方法} list_folders ()

Return a list of the names of all folders.
@end deffn

@geindex get_folder() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir get_folder}@anchor{28c9}
@deffn {方法} get_folder (folder)

Return a @ref{ca1,,Maildir} instance representing the folder whose name is
@emph{folder}. A @ref{28ca,,NoSuchMailboxError} exception is raised if the folder
does not exist.
@end deffn

@geindex add_folder() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir add_folder}@anchor{28cb}
@deffn {方法} add_folder (folder)

Create a folder whose name is @emph{folder} and return a @ref{ca1,,Maildir}
instance representing it.
@end deffn

@geindex remove_folder() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir remove_folder}@anchor{28cc}
@deffn {方法} remove_folder (folder)

Delete the folder whose name is @emph{folder}. If the folder contains any
messages, a @ref{28cd,,NotEmptyError} exception will be raised and the folder
will not be deleted.
@end deffn

@geindex clean() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir clean}@anchor{28ce}
@deffn {方法} clean ()

Delete temporary files from the mailbox that have not been accessed in the
last 36 hours. The Maildir specification says that mail-reading programs
should do this occasionally.
@end deffn

Some @ref{bdc,,Mailbox} methods implemented by @ref{ca1,,Maildir} deserve special
remarks:

@geindex add() (mailbox.Maildir 方法)
@geindex __setitem__() (mailbox.Maildir 方法)
@geindex update() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir add}@anchor{28cf}
@deffn {方法} add (message)
@anchor{library/mailbox mailbox Maildir __setitem__}@anchor{28d0}
@deffnx {方法} __setitem__ (key, message)
@anchor{library/mailbox mailbox Maildir update}@anchor{28d1}
@deffnx {方法} update (arg)

@cartouche
@quotation 警告 
These methods generate unique file names based upon the current process
ID. When using multiple threads, undetected name clashes may occur and
cause corruption of the mailbox unless threads are coordinated to avoid
using these methods to manipulate the same mailbox simultaneously.
@end quotation
@end cartouche
@end deffn

@geindex flush() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir flush}@anchor{28d2}
@deffn {方法} flush ()

All changes to Maildir mailboxes are immediately applied, so this method
does nothing.
@end deffn

@geindex lock() (mailbox.Maildir 方法)
@geindex unlock() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir lock}@anchor{28d3}
@deffn {方法} lock ()
@anchor{library/mailbox mailbox Maildir unlock}@anchor{28d4}
@deffnx {方法} unlock ()

Maildir mailboxes do not support (or require) locking, so these methods do
nothing.
@end deffn

@geindex close() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir close}@anchor{28d5}
@deffn {方法} close ()

@ref{ca1,,Maildir} instances do not keep any open files and the underlying
mailboxes do not support locking, so this method does nothing.
@end deffn

@geindex get_file() (mailbox.Maildir 方法)
@anchor{library/mailbox mailbox Maildir get_file}@anchor{28d6}
@deffn {方法} get_file (key)

Depending upon the host platform, it may not be possible to modify or
remove the underlying message while the returned file remains open.
@end deffn
@end deffn


@subsubheading 参见



@table @asis

@item maildir man page from qmail@footnote{http://www.qmail.org/man/man5/maildir.html}

The original specification of the format.

@item Using maildir format@footnote{https://cr.yp.to/proto/maildir.html}

Notes on Maildir by its inventor. Includes an updated name-creation scheme and
details on "info" semantics.

@item maildir man page from Courier@footnote{http://www.courier-mta.org/maildir.html}

Another specification of the format. Describes a common extension for supporting
folders.
@end table


@node mbox,MH,Maildir,Mailbox 对象
@anchor{library/mailbox mailbox-mbox}@anchor{28d7}@anchor{library/mailbox mbox}@anchor{28d8}
@subsubsection @code{mbox}


@geindex mbox (mailbox 中的类)
@anchor{library/mailbox mailbox mbox}@anchor{28af}
@deffn {类} mailbox.mbox (path, factory=None, create=True)

A subclass of @ref{bdc,,Mailbox} for mailboxes in mbox format. Parameter @emph{factory}
is a callable object that accepts a file-like message representation (which
behaves as if opened in binary mode) and returns a custom representation. If
@emph{factory} is @code{None}, @ref{277c,,mboxMessage} is used as the default message
representation. If @emph{create} is @code{True}, the mailbox is created if it does not
exist.

The mbox format is the classic format for storing mail on Unix systems. All
messages in an mbox mailbox are stored in a single file with the beginning of
each message indicated by a line whose first five characters are "From ".

Several variations of the mbox format exist to address perceived shortcomings in
the original. In the interest of compatibility, @ref{28af,,mbox} implements the
original format, which is sometimes referred to as @emph{mboxo}. This means that
the @code{Content-Length} header, if present, is ignored and that any
occurrences of "From " at the beginning of a line in a message body are
transformed to ">From " when storing the message, although occurrences of ">From
" are not transformed to "From " when reading the message.

Some @ref{bdc,,Mailbox} methods implemented by @ref{28af,,mbox} deserve special
remarks:

@geindex get_file() (mailbox.mbox 方法)
@anchor{library/mailbox mailbox mbox get_file}@anchor{28d9}
@deffn {方法} get_file (key)

Using the file after calling @code{flush()} or @code{close()} on the
@ref{28af,,mbox} instance may yield unpredictable results or raise an
exception.
@end deffn

@geindex lock() (mailbox.mbox 方法)
@geindex unlock() (mailbox.mbox 方法)
@anchor{library/mailbox mailbox mbox lock}@anchor{28da}
@deffn {方法} lock ()
@anchor{library/mailbox mailbox mbox unlock}@anchor{28db}
@deffnx {方法} unlock ()

Three locking mechanisms are used---dot locking and, if available, the
@code{flock()} and @code{lockf()} system calls.
@end deffn
@end deffn


@subsubheading 参见



@table @asis

@item mbox man page from qmail@footnote{http://www.qmail.org/man/man5/mbox.html}

A specification of the format and its variations.

@item mbox man page from tin@footnote{http://www.tin.org/bin/man.cgi?section=5&topic=mbox}

Another specification of the format, with details on locking.

@item Configuring Netscape Mail on Unix: Why The Content-Length Format is Bad@footnote{https://www.jwz.org/doc/content-length.html}

An argument for using the original mbox format rather than a variation.

@item "mbox" is a family of several mutually incompatible mailbox formats@footnote{https://www.loc.gov/preservation/digital/formats/fdd/fdd000383.shtml}

A history of mbox variations.
@end table


@node MH,Babyl,mbox,Mailbox 对象
@anchor{library/mailbox mailbox-mh}@anchor{28dc}@anchor{library/mailbox mh}@anchor{28dd}
@subsubsection @code{MH}


@geindex MH (mailbox 中的类)
@anchor{library/mailbox mailbox MH}@anchor{28de}
@deffn {类} mailbox.MH (path, factory=None, create=True)

A subclass of @ref{bdc,,Mailbox} for mailboxes in MH format. Parameter @emph{factory}
is a callable object that accepts a file-like message representation (which
behaves as if opened in binary mode) and returns a custom representation. If
@emph{factory} is @code{None}, @ref{28df,,MHMessage} is used as the default message
representation. If @emph{create} is @code{True}, the mailbox is created if it does not
exist.

MH is a directory-based mailbox format invented for the MH Message Handling
System, a mail user agent. Each message in an MH mailbox resides in its own
file. An MH mailbox may contain other MH mailboxes (called @emph{folders}) in
addition to messages. Folders may be nested indefinitely. MH mailboxes also
support @emph{sequences}, which are named lists used to logically group
messages without moving them to sub-folders. Sequences are defined in a file
called @code{.mh_sequences} in each folder.

The @ref{28de,,MH} class manipulates MH mailboxes, but it does not attempt to
emulate all of @code{mh}'s behaviors. In particular, it does not modify
and is not affected by the @code{context} or @code{.mh_profile} files that
are used by @code{mh} to store its state and configuration.

@ref{28de,,MH} instances have all of the methods of @ref{bdc,,Mailbox} in addition
to the following:

@geindex list_folders() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH list_folders}@anchor{28e0}
@deffn {方法} list_folders ()

Return a list of the names of all folders.
@end deffn

@geindex get_folder() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH get_folder}@anchor{28e1}
@deffn {方法} get_folder (folder)

Return an @ref{28de,,MH} instance representing the folder whose name is
@emph{folder}. A @ref{28ca,,NoSuchMailboxError} exception is raised if the folder
does not exist.
@end deffn

@geindex add_folder() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH add_folder}@anchor{28e2}
@deffn {方法} add_folder (folder)

Create a folder whose name is @emph{folder} and return an @ref{28de,,MH} instance
representing it.
@end deffn

@geindex remove_folder() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH remove_folder}@anchor{28e3}
@deffn {方法} remove_folder (folder)

Delete the folder whose name is @emph{folder}. If the folder contains any
messages, a @ref{28cd,,NotEmptyError} exception will be raised and the folder
will not be deleted.
@end deffn

@geindex get_sequences() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH get_sequences}@anchor{28e4}
@deffn {方法} get_sequences ()

Return a dictionary of sequence names mapped to key lists. If there are no
sequences, the empty dictionary is returned.
@end deffn

@geindex set_sequences() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH set_sequences}@anchor{28e5}
@deffn {方法} set_sequences (sequences)

Re-define the sequences that exist in the mailbox based upon @emph{sequences},
a dictionary of names mapped to key lists, like returned by
@ref{28e4,,get_sequences()}.
@end deffn

@geindex pack() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH pack}@anchor{28e6}
@deffn {方法} pack ()

Rename messages in the mailbox as necessary to eliminate gaps in
numbering.  Entries in the sequences list are updated correspondingly.

@cartouche
@quotation 注解 
Already-issued keys are invalidated by this operation and should not be
subsequently used.
@end quotation
@end cartouche
@end deffn

Some @ref{bdc,,Mailbox} methods implemented by @ref{28de,,MH} deserve special
remarks:

@geindex remove() (mailbox.MH 方法)
@geindex __delitem__() (mailbox.MH 方法)
@geindex discard() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH remove}@anchor{28e7}
@deffn {方法} remove (key)
@anchor{library/mailbox mailbox MH __delitem__}@anchor{28e8}
@deffnx {方法} __delitem__ (key)
@anchor{library/mailbox mailbox MH discard}@anchor{28e9}
@deffnx {方法} discard (key)

These methods immediately delete the message. The MH convention of marking
a message for deletion by prepending a comma to its name is not used.
@end deffn

@geindex lock() (mailbox.MH 方法)
@geindex unlock() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH lock}@anchor{28ea}
@deffn {方法} lock ()
@anchor{library/mailbox mailbox MH unlock}@anchor{28eb}
@deffnx {方法} unlock ()

Three locking mechanisms are used---dot locking and, if available, the
@code{flock()} and @code{lockf()} system calls. For MH mailboxes, locking
the mailbox means locking the @code{.mh_sequences} file and, only for the
duration of any operations that affect them, locking individual message
files.
@end deffn

@geindex get_file() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH get_file}@anchor{28ec}
@deffn {方法} get_file (key)

Depending upon the host platform, it may not be possible to remove the
underlying message while the returned file remains open.
@end deffn

@geindex flush() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH flush}@anchor{28ed}
@deffn {方法} flush ()

All changes to MH mailboxes are immediately applied, so this method does
nothing.
@end deffn

@geindex close() (mailbox.MH 方法)
@anchor{library/mailbox mailbox MH close}@anchor{28ee}
@deffn {方法} close ()

@ref{28de,,MH} instances do not keep any open files, so this method is
equivalent to @ref{28eb,,unlock()}.
@end deffn
@end deffn


@subsubheading 参见



@table @asis

@item nmh - Message Handling System@footnote{http://www.nongnu.org/nmh/}

Home page of @code{nmh}, an updated version of the original @code{mh}.

@item MH & nmh: Email for Users & Programmers@footnote{https://rand-mh.sourceforge.io/book/}

A GPL-licensed book on @code{mh} and @code{nmh}, with some information
on the mailbox format.
@end table


@node Babyl,MMDF,MH,Mailbox 对象
@anchor{library/mailbox babyl}@anchor{28ef}@anchor{library/mailbox mailbox-babyl}@anchor{28f0}
@subsubsection @code{Babyl}


@geindex Babyl (mailbox 中的类)
@anchor{library/mailbox mailbox Babyl}@anchor{28f1}
@deffn {类} mailbox.Babyl (path, factory=None, create=True)

A subclass of @ref{bdc,,Mailbox} for mailboxes in Babyl format. Parameter
@emph{factory} is a callable object that accepts a file-like message representation
(which behaves as if opened in binary mode) and returns a custom representation.
If @emph{factory} is @code{None}, @ref{28f2,,BabylMessage} is used as the default message
representation. If @emph{create} is @code{True}, the mailbox is created if it does not
exist.

Babyl is a single-file mailbox format used by the Rmail mail user agent
included with Emacs. The beginning of a message is indicated by a line
containing the two characters Control-Underscore (@code{'\037'}) and Control-L
(@code{'\014'}). The end of a message is indicated by the start of the next
message or, in the case of the last message, a line containing a
Control-Underscore (@code{'\037'}) character.

Messages in a Babyl mailbox have two sets of headers, original headers and
so-called visible headers. Visible headers are typically a subset of the
original headers that have been reformatted or abridged to be more
attractive. Each message in a Babyl mailbox also has an accompanying list of
@emph{labels}, or short strings that record extra information about the
message, and a list of all user-defined labels found in the mailbox is kept
in the Babyl options section.

@ref{28f1,,Babyl} instances have all of the methods of @ref{bdc,,Mailbox} in
addition to the following:

@geindex get_labels() (mailbox.Babyl 方法)
@anchor{library/mailbox mailbox Babyl get_labels}@anchor{28f3}
@deffn {方法} get_labels ()

Return a list of the names of all user-defined labels used in the mailbox.

@cartouche
@quotation 注解 
The actual messages are inspected to determine which labels exist in
the mailbox rather than consulting the list of labels in the Babyl
options section, but the Babyl section is updated whenever the mailbox
is modified.
@end quotation
@end cartouche
@end deffn

Some @ref{bdc,,Mailbox} methods implemented by @ref{28f1,,Babyl} deserve special
remarks:

@geindex get_file() (mailbox.Babyl 方法)
@anchor{library/mailbox mailbox Babyl get_file}@anchor{28f4}
@deffn {方法} get_file (key)

In Babyl mailboxes, the headers of a message are not stored contiguously
with the body of the message. To generate a file-like representation, the
headers and body are copied together into an @ref{795,,io.BytesIO} instance,
which has an API identical to that of a
file. As a result, the file-like object is truly independent of the
underlying mailbox but does not save memory compared to a string
representation.
@end deffn

@geindex lock() (mailbox.Babyl 方法)
@geindex unlock() (mailbox.Babyl 方法)
@anchor{library/mailbox mailbox Babyl lock}@anchor{28f5}
@deffn {方法} lock ()
@anchor{library/mailbox mailbox Babyl unlock}@anchor{28f6}
@deffnx {方法} unlock ()

Three locking mechanisms are used---dot locking and, if available, the
@code{flock()} and @code{lockf()} system calls.
@end deffn
@end deffn


@subsubheading 参见



@table @asis

@item Format of Version 5 Babyl Files@footnote{https://quimby.gnus.org/notes/BABYL}

A specification of the Babyl format.

@item Reading Mail with Rmail@footnote{https://www.gnu.org/software/emacs/manual/html_node/emacs/Rmail.html}

The Rmail manual, with some information on Babyl semantics.
@end table


@node MMDF,,Babyl,Mailbox 对象
@anchor{library/mailbox mailbox-mmdf}@anchor{28f7}@anchor{library/mailbox mmdf}@anchor{28f8}
@subsubsection @code{MMDF}


@geindex MMDF (mailbox 中的类)
@anchor{library/mailbox mailbox MMDF}@anchor{28f9}
@deffn {类} mailbox.MMDF (path, factory=None, create=True)

A subclass of @ref{bdc,,Mailbox} for mailboxes in MMDF format. Parameter @emph{factory}
is a callable object that accepts a file-like message representation (which
behaves as if opened in binary mode) and returns a custom representation. If
@emph{factory} is @code{None}, @ref{28fa,,MMDFMessage} is used as the default message
representation. If @emph{create} is @code{True}, the mailbox is created if it does not
exist.

MMDF is a single-file mailbox format invented for the Multichannel Memorandum
Distribution Facility, a mail transfer agent. Each message is in the same
form as an mbox message but is bracketed before and after by lines containing
four Control-A (@code{'\001'}) characters. As with the mbox format, the
beginning of each message is indicated by a line whose first five characters
are "From ", but additional occurrences of "From " are not transformed to
">From " when storing messages because the extra message separator lines
prevent mistaking such occurrences for the starts of subsequent messages.

Some @ref{bdc,,Mailbox} methods implemented by @ref{28f9,,MMDF} deserve special
remarks:

@geindex get_file() (mailbox.MMDF 方法)
@anchor{library/mailbox mailbox MMDF get_file}@anchor{28fb}
@deffn {方法} get_file (key)

Using the file after calling @code{flush()} or @code{close()} on the
@ref{28f9,,MMDF} instance may yield unpredictable results or raise an
exception.
@end deffn

@geindex lock() (mailbox.MMDF 方法)
@geindex unlock() (mailbox.MMDF 方法)
@anchor{library/mailbox mailbox MMDF lock}@anchor{28fc}
@deffn {方法} lock ()
@anchor{library/mailbox mailbox MMDF unlock}@anchor{28fd}
@deffnx {方法} unlock ()

Three locking mechanisms are used---dot locking and, if available, the
@code{flock()} and @code{lockf()} system calls.
@end deffn
@end deffn


@subsubheading 参见



@table @asis

@item mmdf man page from tin@footnote{http://www.tin.org/bin/man.cgi?section=5&topic=mmdf}

A specification of MMDF format from the documentation of tin, a newsreader.

@item MMDF@footnote{https://en.wikipedia.org/wiki/MMDF}

A Wikipedia article describing the Multichannel Memorandum Distribution
Facility.
@end table


@node Message objects,异常<14>,Mailbox 对象,mailbox --- Manipulate mailboxes in various formats
@anchor{library/mailbox mailbox-message-objects}@anchor{28fe}@anchor{library/mailbox message-objects}@anchor{28ff}
@subsubsection @code{Message} objects


@geindex Message (mailbox 中的类)
@anchor{library/mailbox mailbox Message}@anchor{be0}
@deffn {类} mailbox.Message (message=None)

A subclass of the @ref{72,,email.message} module's
@ref{53c,,Message}. Subclasses of @ref{be0,,mailbox.Message} add
mailbox-format-specific state and behavior.

If @emph{message} is omitted, the new instance is created in a default, empty state.
If @emph{message} is an @ref{53c,,email.message.Message} instance, its contents are
copied; furthermore, any format-specific information is converted insofar as
possible if @emph{message} is a @ref{be0,,Message} instance. If @emph{message} is a string,
a byte string,
or a file, it should contain an 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html}-compliant message, which is read
and parsed.  Files should be open in binary mode, but text mode files
are accepted for backward compatibility.

The format-specific state and behaviors offered by subclasses vary, but in
general it is only the properties that are not specific to a particular
mailbox that are supported (although presumably the properties are specific
to a particular mailbox format). For example, file offsets for single-file
mailbox formats and file names for directory-based mailbox formats are not
retained, because they are only applicable to the original mailbox. But state
such as whether a message has been read by the user or marked as important is
retained, because it applies to the message itself.

There is no requirement that @ref{be0,,Message} instances be used to represent
messages retrieved using @ref{bdc,,Mailbox} instances. In some situations, the
time and memory required to generate @ref{be0,,Message} representations might
not be acceptable. For such situations, @ref{bdc,,Mailbox} instances also
offer string and file-like representations, and a custom message factory may
be specified when a @ref{bdc,,Mailbox} instance is initialized.
@end deffn

@menu
* MaildirMessage:: 
* mboxMessage:: 
* MHMessage:: 
* BabylMessage:: 
* MMDFMessage:: 

@end menu

@node MaildirMessage,mboxMessage,,Message objects
@anchor{library/mailbox mailbox-maildirmessage}@anchor{2900}@anchor{library/mailbox maildirmessage}@anchor{2901}
@subsubsection @code{MaildirMessage}


@geindex MaildirMessage (mailbox 中的类)
@anchor{library/mailbox mailbox MaildirMessage}@anchor{28c7}
@deffn {类} mailbox.MaildirMessage (message=None)

A message with Maildir-specific behaviors. Parameter @emph{message} has the same
meaning as with the @ref{be0,,Message} constructor.

Typically, a mail user agent application moves all of the messages in the
@code{new} subdirectory to the @code{cur} subdirectory after the first time
the user opens and closes the mailbox, recording that the messages are old
whether or not they've actually been read. Each message in @code{cur} has an
"info" section added to its file name to store information about its state.
(Some mail readers may also add an "info" section to messages in
@code{new}.)  The "info" section may take one of two forms: it may contain
"2," followed by a list of standardized flags (e.g., "2,FR") or it may
contain "1," followed by so-called experimental information. Standard flags
for Maildir messages are as follows:


@multitable {xxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Flag

@tab

含义

@tab

说明

@item

D

@tab

草稿

@tab

Under composition

@item

F

@tab

已标记

@tab

标记为重要

@item

P

@tab

已读

@tab

转发，重新发送或退回

@item

R

@tab

已回复

@tab

回复给

@item

S

@tab

查看

@tab

读取

@item

T

@tab

已删除

@tab

标记为以后删除

@end multitable


@ref{28c7,,MaildirMessage} 实例提供以下方法：

@geindex get_subdir() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage get_subdir}@anchor{2902}
@deffn {方法} get_subdir ()

Return either "new" (if the message should be stored in the @code{new}
subdirectory) or "cur" (if the message should be stored in the @code{cur}
subdirectory).

@cartouche
@quotation 注解 
A message is typically moved from @code{new} to @code{cur} after its
mailbox has been accessed, whether or not the message is has been
read. A message @code{msg} has been read if @code{"S" in msg.get_flags()} is
@code{True}.
@end quotation
@end cartouche
@end deffn

@geindex set_subdir() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage set_subdir}@anchor{2903}
@deffn {方法} set_subdir (subdir)

Set the subdirectory the message should be stored in. Parameter @emph{subdir}
must be either "new" or "cur".
@end deffn

@geindex get_flags() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage get_flags}@anchor{2904}
@deffn {方法} get_flags ()

Return a string specifying the flags that are currently set. If the
message complies with the standard Maildir format, the result is the
concatenation in alphabetical order of zero or one occurrence of each of
@code{'D'}, @code{'F'}, @code{'P'}, @code{'R'}, @code{'S'}, and @code{'T'}. The empty string
is returned if no flags are set or if "info" contains experimental
semantics.
@end deffn

@geindex set_flags() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage set_flags}@anchor{2905}
@deffn {方法} set_flags (flags)

Set the flags specified by @emph{flags} and unset all others.
@end deffn

@geindex add_flag() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage add_flag}@anchor{2906}
@deffn {方法} add_flag (flag)

Set the flag(s) specified by @emph{flag} without changing other flags. To add
more than one flag at a time, @emph{flag} may be a string of more than one
character. The current "info" is overwritten whether or not it contains
experimental information rather than flags.
@end deffn

@geindex remove_flag() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage remove_flag}@anchor{2907}
@deffn {方法} remove_flag (flag)

Unset the flag(s) specified by @emph{flag} without changing other flags. To
remove more than one flag at a time, @emph{flag} maybe a string of more than
one character.  If "info" contains experimental information rather than
flags, the current "info" is not modified.
@end deffn

@geindex get_date() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage get_date}@anchor{2908}
@deffn {方法} get_date ()

Return the delivery date of the message as a floating-point number
representing seconds since the epoch.
@end deffn

@geindex set_date() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage set_date}@anchor{2909}
@deffn {方法} set_date (date)

Set the delivery date of the message to @emph{date}, a floating-point number
representing seconds since the epoch.
@end deffn

@geindex get_info() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage get_info}@anchor{290a}
@deffn {方法} get_info ()

Return a string containing the "info" for a message. This is useful for
accessing and modifying "info" that is experimental (i.e., not a list of
flags).
@end deffn

@geindex set_info() (mailbox.MaildirMessage 方法)
@anchor{library/mailbox mailbox MaildirMessage set_info}@anchor{290b}
@deffn {方法} set_info (info)

Set "info" to @emph{info}, which should be a string.
@end deffn
@end deffn

When a @ref{28c7,,MaildirMessage} instance is created based upon an
@ref{277c,,mboxMessage} or @ref{28fa,,MMDFMessage} instance, the @code{Status}
and @code{X-Status} headers are omitted and the following conversions
take place:


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{277c,,mboxMessage} 或 @ref{28fa,,MMDFMessage} 状态

@item

"cur" 子目录

@tab

O 标记

@item

F 标记

@tab

F 标记

@item

R 标记

@tab

A 标记

@item

S 标记

@tab

R 标记

@item

T 标记

@tab

D 标记

@end multitable


When a @ref{28c7,,MaildirMessage} instance is created based upon an
@ref{28df,,MHMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28df,,MHMessage} 状态

@item

"cur" 子目录

@tab

"unseen" 序列

@item

"cur" subdirectory and S flag

@tab

非 "unseen" 序列

@item

F 标记

@tab

"flagged" 序列

@item

R 标记

@tab

"replied" 序列

@end multitable


When a @ref{28c7,,MaildirMessage} instance is created based upon a
@ref{28f2,,BabylMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28f2,,BabylMessage} 状态

@item

"cur" 子目录

@tab

"unseen" 标签

@item

"cur" subdirectory and S flag

@tab

非 "unseen" 标签

@item

P 标记

@tab

"forwarded" 或 "resent" 标签

@item

R 标记

@tab

"answered" 标签

@item

T 标记

@tab

"deleted" 标签

@end multitable


@node mboxMessage,MHMessage,MaildirMessage,Message objects
@anchor{library/mailbox mailbox-mboxmessage}@anchor{290c}@anchor{library/mailbox mboxmessage}@anchor{290d}
@subsubsection @code{mboxMessage}


@geindex mboxMessage (mailbox 中的类)
@anchor{library/mailbox mailbox mboxMessage}@anchor{277c}
@deffn {类} mailbox.mboxMessage (message=None)

A message with mbox-specific behaviors. Parameter @emph{message} has the same meaning
as with the @ref{be0,,Message} constructor.

Messages in an mbox mailbox are stored together in a single file. The
sender's envelope address and the time of delivery are typically stored in a
line beginning with "From " that is used to indicate the start of a message,
though there is considerable variation in the exact format of this data among
mbox implementations. Flags that indicate the state of the message, such as
whether it has been read or marked as important, are typically stored in
@code{Status} and @code{X-Status} headers.

Conventional flags for mbox messages are as follows:


@multitable {xxxxxxxx} {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Flag

@tab

含义

@tab

说明

@item

R

@tab

读取

@tab

读取

@item

O

@tab

Old

@tab

以前由MUA检测

@item

D

@tab

已删除

@tab

标记为以后删除

@item

F

@tab

已标记

@tab

标记为重要

@item

A

@tab

已回复

@tab

回复给

@end multitable


The "R" and "O" flags are stored in the @code{Status} header, and the
"D", "F", and "A" flags are stored in the @code{X-Status} header. The
flags and headers typically appear in the order mentioned.

@ref{277c,,mboxMessage} instances offer the following methods:

@geindex get_from() (mailbox.mboxMessage 方法)
@anchor{library/mailbox mailbox mboxMessage get_from}@anchor{290e}
@deffn {方法} get_from ()

Return a string representing the "From " line that marks the start of the
message in an mbox mailbox. The leading "From " and the trailing newline
are excluded.
@end deffn

@geindex set_from() (mailbox.mboxMessage 方法)
@anchor{library/mailbox mailbox mboxMessage set_from}@anchor{290f}
@deffn {方法} set_from (from_, time_=None)

Set the "From " line to @emph{from_}, which should be specified without a
leading "From " or trailing newline. For convenience, @emph{time_} may be
specified and will be formatted appropriately and appended to @emph{from_}. If
@emph{time_} is specified, it should be a @ref{594,,time.struct_time} instance, a
tuple suitable for passing to @ref{b5e,,time.strftime()}, or @code{True} (to use
@ref{b38,,time.gmtime()}).
@end deffn

@geindex get_flags() (mailbox.mboxMessage 方法)
@anchor{library/mailbox mailbox mboxMessage get_flags}@anchor{2910}
@deffn {方法} get_flags ()

Return a string specifying the flags that are currently set. If the
message complies with the conventional format, the result is the
concatenation in the following order of zero or one occurrence of each of
@code{'R'}, @code{'O'}, @code{'D'}, @code{'F'}, and @code{'A'}.
@end deffn

@geindex set_flags() (mailbox.mboxMessage 方法)
@anchor{library/mailbox mailbox mboxMessage set_flags}@anchor{2911}
@deffn {方法} set_flags (flags)

Set the flags specified by @emph{flags} and unset all others. Parameter @emph{flags}
should be the concatenation in any order of zero or more occurrences of
each of @code{'R'}, @code{'O'}, @code{'D'}, @code{'F'}, and @code{'A'}.
@end deffn

@geindex add_flag() (mailbox.mboxMessage 方法)
@anchor{library/mailbox mailbox mboxMessage add_flag}@anchor{2912}
@deffn {方法} add_flag (flag)

Set the flag(s) specified by @emph{flag} without changing other flags. To add
more than one flag at a time, @emph{flag} may be a string of more than one
character.
@end deffn

@geindex remove_flag() (mailbox.mboxMessage 方法)
@anchor{library/mailbox mailbox mboxMessage remove_flag}@anchor{2913}
@deffn {方法} remove_flag (flag)

Unset the flag(s) specified by @emph{flag} without changing other flags. To
remove more than one flag at a time, @emph{flag} maybe a string of more than
one character.
@end deffn
@end deffn

When an @ref{277c,,mboxMessage} instance is created based upon a
@ref{28c7,,MaildirMessage} instance, a "From " line is generated based upon the
@ref{28c7,,MaildirMessage} instance's delivery date, and the following conversions
take place:


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28c7,,MaildirMessage} 状态

@item

R 标记

@tab

S 标记

@item

O 标记

@tab

"cur" 子目录

@item

D 标记

@tab

T 标记

@item

F 标记

@tab

F 标记

@item

A 标记

@tab

R 标记

@end multitable


When an @ref{277c,,mboxMessage} instance is created based upon an
@ref{28df,,MHMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28df,,MHMessage} 状态

@item

R 标记 和 O 标记

@tab

非 "unseen" 序列

@item

O 标记

@tab

"unseen" 序列

@item

F 标记

@tab

"flagged" 序列

@item

A 标记

@tab

"replied" 序列

@end multitable


When an @ref{277c,,mboxMessage} instance is created based upon a
@ref{28f2,,BabylMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28f2,,BabylMessage} 状态

@item

R 标记 和 O 标记

@tab

非 "unseen" 标签

@item

O 标记

@tab

"unseen" 标签

@item

D 标记

@tab

"deleted" 标签

@item

A 标记

@tab

"answered" 标签

@end multitable


When a @ref{be0,,Message} instance is created based upon an @ref{28fa,,MMDFMessage}
instance, the "From " line is copied and all flags directly correspond:


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28fa,,MMDFMessage} 状态

@item

R 标记

@tab

R 标记

@item

O 标记

@tab

O 标记

@item

D 标记

@tab

D 标记

@item

F 标记

@tab

F 标记

@item

A 标记

@tab

A 标记

@end multitable


@node MHMessage,BabylMessage,mboxMessage,Message objects
@anchor{library/mailbox mailbox-mhmessage}@anchor{2914}@anchor{library/mailbox mhmessage}@anchor{2915}
@subsubsection @code{MHMessage}


@geindex MHMessage (mailbox 中的类)
@anchor{library/mailbox mailbox MHMessage}@anchor{28df}
@deffn {类} mailbox.MHMessage (message=None)

A message with MH-specific behaviors. Parameter @emph{message} has the same meaning
as with the @ref{be0,,Message} constructor.

MH messages do not support marks or flags in the traditional sense, but they
do support sequences, which are logical groupings of arbitrary messages. Some
mail reading programs (although not the standard @code{mh} and
@code{nmh}) use sequences in much the same way flags are used with other
formats, as follows:


@multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

序列

@tab

说明

@item

未读

@tab

未读取，但先前被MUA检测到

@item

已回复

@tab

回复给

@item

已标记

@tab

标记为重要

@end multitable


@ref{28df,,MHMessage} instances offer the following methods:

@geindex get_sequences() (mailbox.MHMessage 方法)
@anchor{library/mailbox mailbox MHMessage get_sequences}@anchor{2916}
@deffn {方法} get_sequences ()

Return a list of the names of sequences that include this message.
@end deffn

@geindex set_sequences() (mailbox.MHMessage 方法)
@anchor{library/mailbox mailbox MHMessage set_sequences}@anchor{2917}
@deffn {方法} set_sequences (sequences)

Set the list of sequences that include this message.
@end deffn

@geindex add_sequence() (mailbox.MHMessage 方法)
@anchor{library/mailbox mailbox MHMessage add_sequence}@anchor{2918}
@deffn {方法} add_sequence (sequence)

Add @emph{sequence} to the list of sequences that include this message.
@end deffn

@geindex remove_sequence() (mailbox.MHMessage 方法)
@anchor{library/mailbox mailbox MHMessage remove_sequence}@anchor{2919}
@deffn {方法} remove_sequence (sequence)

Remove @emph{sequence} from the list of sequences that include this message.
@end deffn
@end deffn

When an @ref{28df,,MHMessage} instance is created based upon a
@ref{28c7,,MaildirMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28c7,,MaildirMessage} 状态

@item

"unseen" 序列

@tab

非 S 标记

@item

"replied" 序列

@tab

R 标记

@item

"flagged" 序列

@tab

F 标记

@end multitable


When an @ref{28df,,MHMessage} instance is created based upon an
@ref{277c,,mboxMessage} or @ref{28fa,,MMDFMessage} instance, the @code{Status}
and @code{X-Status} headers are omitted and the following conversions
take place:


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{277c,,mboxMessage} 或 @ref{28fa,,MMDFMessage} 状态

@item

"unseen" 序列

@tab

非 R 标记

@item

"replied" 序列

@tab

A 标记

@item

"flagged" 序列

@tab

F 标记

@end multitable


When an @ref{28df,,MHMessage} instance is created based upon a
@ref{28f2,,BabylMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28f2,,BabylMessage} 状态

@item

"unseen" 序列

@tab

"unseen" 标签

@item

"replied" 序列

@tab

"answered" 标签

@end multitable


@node BabylMessage,MMDFMessage,MHMessage,Message objects
@anchor{library/mailbox babylmessage}@anchor{291a}@anchor{library/mailbox mailbox-babylmessage}@anchor{291b}
@subsubsection @code{BabylMessage}


@geindex BabylMessage (mailbox 中的类)
@anchor{library/mailbox mailbox BabylMessage}@anchor{28f2}
@deffn {类} mailbox.BabylMessage (message=None)

A message with Babyl-specific behaviors. Parameter @emph{message} has the same
meaning as with the @ref{be0,,Message} constructor.

Certain message labels, called @emph{attributes}, are defined by convention
to have special meanings. The attributes are as follows:


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

标签

@tab

说明

@item

未读

@tab

未读取，但先前被MUA检测到

@item

deleted

@tab

标记为以后删除

@item

filed

@tab

复制到另一个文件或邮箱

@item

answered

@tab

回复给

@item

forwarded

@tab

已转发

@item

edited

@tab

由用户修改

@item

resent

@tab

已重发

@end multitable


By default, Rmail displays only visible headers. The @ref{28f2,,BabylMessage}
class, though, uses the original headers because they are more
complete. Visible headers may be accessed explicitly if desired.

@ref{28f2,,BabylMessage} instances offer the following methods:

@geindex get_labels() (mailbox.BabylMessage 方法)
@anchor{library/mailbox mailbox BabylMessage get_labels}@anchor{291c}
@deffn {方法} get_labels ()

返回邮件上的标签列表。
@end deffn

@geindex set_labels() (mailbox.BabylMessage 方法)
@anchor{library/mailbox mailbox BabylMessage set_labels}@anchor{291d}
@deffn {方法} set_labels (labels)

将消息上的标签列表设置为 @emph{labels} 。
@end deffn

@geindex add_label() (mailbox.BabylMessage 方法)
@anchor{library/mailbox mailbox BabylMessage add_label}@anchor{291e}
@deffn {方法} add_label (label)

将 @emph{label} 添加到消息上的标签列表中。
@end deffn

@geindex remove_label() (mailbox.BabylMessage 方法)
@anchor{library/mailbox mailbox BabylMessage remove_label}@anchor{291f}
@deffn {方法} remove_label (label)

从消息上的标签列表中删除 @emph{label} 。
@end deffn

@geindex get_visible() (mailbox.BabylMessage 方法)
@anchor{library/mailbox mailbox BabylMessage get_visible}@anchor{2920}
@deffn {方法} get_visible ()

Return an @ref{be0,,Message} instance whose headers are the message's
visible headers and whose body is empty.
@end deffn

@geindex set_visible() (mailbox.BabylMessage 方法)
@anchor{library/mailbox mailbox BabylMessage set_visible}@anchor{2921}
@deffn {方法} set_visible (visible)

Set the message's visible headers to be the same as the headers in
@emph{message}.  Parameter @emph{visible} should be a @ref{be0,,Message} instance, an
@ref{53c,,email.message.Message} instance, a string, or a file-like object
(which should be open in text mode).
@end deffn

@geindex update_visible() (mailbox.BabylMessage 方法)
@anchor{library/mailbox mailbox BabylMessage update_visible}@anchor{2922}
@deffn {方法} update_visible ()

When a @ref{28f2,,BabylMessage} instance's original headers are modified, the
visible headers are not automatically modified to correspond. This method
updates the visible headers as follows: each visible header with a
corresponding original header is set to the value of the original header,
each visible header without a corresponding original header is removed,
and any of @code{Date}, @code{From}, @code{Reply-To},
@code{To}, @code{CC}, and @code{Subject} that are
present in the original headers but not the visible headers are added to
the visible headers.
@end deffn
@end deffn

When a @ref{28f2,,BabylMessage} instance is created based upon a
@ref{28c7,,MaildirMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28c7,,MaildirMessage} 状态

@item

"unseen" 标签

@tab

非 S 标记

@item

"deleted" 标签

@tab

T 标记

@item

"answered" 标签

@tab

R 标记

@item

"forwarded" 标签

@tab

P 标记

@end multitable


When a @ref{28f2,,BabylMessage} instance is created based upon an
@ref{277c,,mboxMessage} or @ref{28fa,,MMDFMessage} instance, the @code{Status}
and @code{X-Status} headers are omitted and the following conversions
take place:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{277c,,mboxMessage} 或 @ref{28fa,,MMDFMessage} 状态

@item

"unseen" 标签

@tab

非 R 标记

@item

"deleted" 标签

@tab

D 标记

@item

"answered" 标签

@tab

A 标记

@end multitable


When a @ref{28f2,,BabylMessage} instance is created based upon an
@ref{28df,,MHMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28df,,MHMessage} 状态

@item

"unseen" 标签

@tab

"unseen" 序列

@item

"answered" 标签

@tab

"replied" 序列

@end multitable


@node MMDFMessage,,BabylMessage,Message objects
@anchor{library/mailbox mailbox-mmdfmessage}@anchor{2923}@anchor{library/mailbox mmdfmessage}@anchor{2924}
@subsubsection @code{MMDFMessage}


@geindex MMDFMessage (mailbox 中的类)
@anchor{library/mailbox mailbox MMDFMessage}@anchor{28fa}
@deffn {类} mailbox.MMDFMessage (message=None)

A message with MMDF-specific behaviors. Parameter @emph{message} has the same meaning
as with the @ref{be0,,Message} constructor.

As with message in an mbox mailbox, MMDF messages are stored with the
sender's address and the delivery date in an initial line beginning with
"From ".  Likewise, flags that indicate the state of the message are
typically stored in @code{Status} and @code{X-Status} headers.

Conventional flags for MMDF messages are identical to those of mbox message
and are as follows:


@multitable {xxxxxxxx} {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Flag

@tab

含义

@tab

说明

@item

R

@tab

读取

@tab

读取

@item

O

@tab

Old

@tab

以前由MUA检测

@item

D

@tab

已删除

@tab

标记为以后删除

@item

F

@tab

已标记

@tab

标记为重要

@item

A

@tab

已回复

@tab

回复给

@end multitable


The "R" and "O" flags are stored in the @code{Status} header, and the
"D", "F", and "A" flags are stored in the @code{X-Status} header. The
flags and headers typically appear in the order mentioned.

@ref{28fa,,MMDFMessage} instances offer the following methods, which are
identical to those offered by @ref{277c,,mboxMessage}:

@geindex get_from() (mailbox.MMDFMessage 方法)
@anchor{library/mailbox mailbox MMDFMessage get_from}@anchor{2925}
@deffn {方法} get_from ()

Return a string representing the "From " line that marks the start of the
message in an mbox mailbox. The leading "From " and the trailing newline
are excluded.
@end deffn

@geindex set_from() (mailbox.MMDFMessage 方法)
@anchor{library/mailbox mailbox MMDFMessage set_from}@anchor{2926}
@deffn {方法} set_from (from_, time_=None)

Set the "From " line to @emph{from_}, which should be specified without a
leading "From " or trailing newline. For convenience, @emph{time_} may be
specified and will be formatted appropriately and appended to @emph{from_}. If
@emph{time_} is specified, it should be a @ref{594,,time.struct_time} instance, a
tuple suitable for passing to @ref{b5e,,time.strftime()}, or @code{True} (to use
@ref{b38,,time.gmtime()}).
@end deffn

@geindex get_flags() (mailbox.MMDFMessage 方法)
@anchor{library/mailbox mailbox MMDFMessage get_flags}@anchor{2927}
@deffn {方法} get_flags ()

Return a string specifying the flags that are currently set. If the
message complies with the conventional format, the result is the
concatenation in the following order of zero or one occurrence of each of
@code{'R'}, @code{'O'}, @code{'D'}, @code{'F'}, and @code{'A'}.
@end deffn

@geindex set_flags() (mailbox.MMDFMessage 方法)
@anchor{library/mailbox mailbox MMDFMessage set_flags}@anchor{2928}
@deffn {方法} set_flags (flags)

Set the flags specified by @emph{flags} and unset all others. Parameter @emph{flags}
should be the concatenation in any order of zero or more occurrences of
each of @code{'R'}, @code{'O'}, @code{'D'}, @code{'F'}, and @code{'A'}.
@end deffn

@geindex add_flag() (mailbox.MMDFMessage 方法)
@anchor{library/mailbox mailbox MMDFMessage add_flag}@anchor{2929}
@deffn {方法} add_flag (flag)

Set the flag(s) specified by @emph{flag} without changing other flags. To add
more than one flag at a time, @emph{flag} may be a string of more than one
character.
@end deffn

@geindex remove_flag() (mailbox.MMDFMessage 方法)
@anchor{library/mailbox mailbox MMDFMessage remove_flag}@anchor{292a}
@deffn {方法} remove_flag (flag)

Unset the flag(s) specified by @emph{flag} without changing other flags. To
remove more than one flag at a time, @emph{flag} maybe a string of more than
one character.
@end deffn
@end deffn

When an @ref{28fa,,MMDFMessage} instance is created based upon a
@ref{28c7,,MaildirMessage} instance, a "From " line is generated based upon the
@ref{28c7,,MaildirMessage} instance's delivery date, and the following conversions
take place:


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28c7,,MaildirMessage} 状态

@item

R 标记

@tab

S 标记

@item

O 标记

@tab

"cur" 子目录

@item

D 标记

@tab

T 标记

@item

F 标记

@tab

F 标记

@item

A 标记

@tab

R 标记

@end multitable


When an @ref{28fa,,MMDFMessage} instance is created based upon an
@ref{28df,,MHMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28df,,MHMessage} 状态

@item

R 标记 和 O 标记

@tab

非 "unseen" 序列

@item

O 标记

@tab

"unseen" 序列

@item

F 标记

@tab

"flagged" 序列

@item

A 标记

@tab

"replied" 序列

@end multitable


When an @ref{28fa,,MMDFMessage} instance is created based upon a
@ref{28f2,,BabylMessage} instance, the following conversions take place:


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{28f2,,BabylMessage} 状态

@item

R 标记 和 O 标记

@tab

非 "unseen" 标签

@item

O 标记

@tab

"unseen" 标签

@item

D 标记

@tab

"deleted" 标签

@item

A 标记

@tab

"answered" 标签

@end multitable


When an @ref{28fa,,MMDFMessage} instance is created based upon an
@ref{277c,,mboxMessage} instance, the "From " line is copied and all flags directly
correspond:


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

结果状态

@tab

@ref{277c,,mboxMessage} 状态

@item

R 标记

@tab

R 标记

@item

O 标记

@tab

O 标记

@item

D 标记

@tab

D 标记

@item

F 标记

@tab

F 标记

@item

A 标记

@tab

A 标记

@end multitable


@node 异常<14>,例子<18>,Message objects,mailbox --- Manipulate mailboxes in various formats
@anchor{library/mailbox exceptions}@anchor{292b}
@subsubsection 异常


The following exception classes are defined in the @ref{ae,,mailbox} module:

@geindex Error
@anchor{library/mailbox mailbox Error}@anchor{292c}
@deffn {例外} mailbox.Error

The based class for all other module-specific exceptions.
@end deffn

@geindex NoSuchMailboxError
@anchor{library/mailbox mailbox NoSuchMailboxError}@anchor{28ca}
@deffn {例外} mailbox.NoSuchMailboxError

Raised when a mailbox is expected but is not found, such as when instantiating a
@ref{bdc,,Mailbox} subclass with a path that does not exist (and with the @emph{create}
parameter set to @code{False}), or when opening a folder that does not exist.
@end deffn

@geindex NotEmptyError
@anchor{library/mailbox mailbox NotEmptyError}@anchor{28cd}
@deffn {例外} mailbox.NotEmptyError

Raised when a mailbox is not empty but is expected to be, such as when deleting
a folder that contains messages.
@end deffn

@geindex ExternalClashError
@anchor{library/mailbox mailbox ExternalClashError}@anchor{28c3}
@deffn {例外} mailbox.ExternalClashError

Raised when some mailbox-related condition beyond the control of the program
causes it to be unable to proceed, such as when failing to acquire a lock that
another program already holds a lock, or when a uniquely-generated file name
already exists.
@end deffn

@geindex FormatError
@anchor{library/mailbox mailbox FormatError}@anchor{292d}
@deffn {例外} mailbox.FormatError

Raised when the data in a file cannot be parsed, such as when an @ref{28de,,MH}
instance attempts to read a corrupted @code{.mh_sequences} file.
@end deffn

@node 例子<18>,,异常<14>,mailbox --- Manipulate mailboxes in various formats
@anchor{library/mailbox examples}@anchor{292e}@anchor{library/mailbox mailbox-examples}@anchor{292f}
@subsubsection 例子


A simple example of printing the subjects of all messages in a mailbox that seem
interesting:

@example
import mailbox
for message in mailbox.mbox('~/mbox'):
    subject = message['subject']       # Could possibly be None.
    if subject and 'python' in subject.lower():
        print(subject)
@end example

To copy all mail from a Babyl mailbox to an MH mailbox, converting all of the
format-specific information that can be converted:

@example
import mailbox
destination = mailbox.MH('~/Mail')
destination.lock()
for message in mailbox.Babyl('~/RMAIL'):
    destination.add(mailbox.MHMessage(message))
destination.flush()
destination.unlock()
@end example

This example sorts mail from several mailing lists into different mailboxes,
being careful to avoid mail corruption due to concurrent modification by other
programs, mail loss due to interruption of the program, or premature termination
due to malformed messages in the mailbox:

@example
import mailbox
import email.errors

list_names = ('python-list', 'python-dev', 'python-bugs')

boxes = @{name: mailbox.mbox('~/email/%s' % name) for name in list_names@}
inbox = mailbox.Maildir('~/Maildir', factory=None)

for key in inbox.iterkeys():
    try:
        message = inbox[key]
    except email.errors.MessageParseError:
        continue                # The message is malformed. Just leave it.

    for name in list_names:
        list_id = message['list-id']
        if list_id and name in list_id:
            # Get mailbox to use
            box = boxes[name]

            # Write copy to disk before removing original.
            # If there's a crash, you might duplicate a message, but
            # that's better than losing a message completely.
            box.lock()
            box.add(message)
            box.flush()
            box.unlock()

            # Remove original message
            inbox.lock()
            inbox.discard(key)
            inbox.flush()
            inbox.unlock()
            break               # Found destination, so stop looking.

for box in boxes.itervalues():
    box.close()
@end example

@node mimetypes --- Map filenames to MIME types,base64 --- Base16 Base32 Base64 Base85 数据编码,mailbox --- Manipulate mailboxes in various formats,互联网数据处理
@anchor{library/mimetypes doc}@anchor{2930}@anchor{library/mimetypes mimetypes-map-filenames-to-mime-types}@anchor{2931}@anchor{library/mimetypes module-mimetypes}@anchor{b2}
@subsection @code{mimetypes} --- Map filenames to MIME types


@geindex mimetypes (模块)

@strong{Source code:} Lib/mimetypes.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/mimetypes.py}

@geindex MIME; content type


__________________________________________________________________


The @ref{b2,,mimetypes} module converts between a filename or URL and the MIME type
associated with the filename extension.  Conversions are provided from filename
to MIME type and from MIME type to filename extension; encodings are not
supported for the latter conversion.

The module provides one class and a number of convenience functions. The
functions are the normal interface to this module, but some applications may be
interested in the class as well.

The functions described below provide the primary interface for this module.  If
the module has not been initialized, they will call @ref{2932,,init()} if they rely on
the information @ref{2932,,init()} sets up.

@geindex guess_type() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes guess_type}@anchor{ef8}
@deffn {函数} mimetypes.guess_type (url, strict=True)

@geindex MIME; headers

Guess the type of a file based on its filename, path or URL, given by @emph{url}.
URL can be a string or a @ref{363,,path-like object}.

The return value is a tuple @code{(type, encoding)} where @emph{type} is @code{None} if the
type can't be guessed (missing or unknown suffix) or a string of the form
@code{'type/subtype'}, usable for a MIME @code{content-type} header.

@emph{encoding} is @code{None} for no encoding or the name of the program used to encode
(e.g. @code{compress} or @code{gzip}). The encoding is suitable for use
as a @code{Content-Encoding} header, @strong{not} as a
@code{Content-Transfer-Encoding} header. The mappings are table driven.
Encoding suffixes are case sensitive; type suffixes are first tried case
sensitively, then case insensitively.

The optional @emph{strict} argument is a flag specifying whether the list of known MIME types
is limited to only the official types registered with IANA@footnote{https://www.iana.org/assignments/media-types/media-types.xhtml}.
When @emph{strict} is @code{True} (the default), only the IANA types are supported; when
@emph{strict} is @code{False}, some additional non-standard but commonly used MIME types
are also recognized.


在 3.8 版更改: Added support for url being a @ref{363,,path-like object}.

@end deffn

@geindex guess_all_extensions() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes guess_all_extensions}@anchor{2933}
@deffn {函数} mimetypes.guess_all_extensions (type, strict=True)

Guess the extensions for a file based on its MIME type, given by @emph{type}. The
return value is a list of strings giving all possible filename extensions,
including the leading dot (@code{'.'}).  The extensions are not guaranteed to have
been associated with any particular data stream, but would be mapped to the MIME
type @emph{type} by @ref{ef8,,guess_type()}.

The optional @emph{strict} argument has the same meaning as with the @ref{ef8,,guess_type()} function.
@end deffn

@geindex guess_extension() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes guess_extension}@anchor{2934}
@deffn {函数} mimetypes.guess_extension (type, strict=True)

Guess the extension for a file based on its MIME type, given by @emph{type}. The
return value is a string giving a filename extension, including the leading dot
(@code{'.'}).  The extension is not guaranteed to have been associated with any
particular data stream, but would be mapped to the MIME type @emph{type} by
@ref{ef8,,guess_type()}.  If no extension can be guessed for @emph{type}, @code{None} is
returned.

The optional @emph{strict} argument has the same meaning as with the @ref{ef8,,guess_type()} function.
@end deffn

Some additional functions and data items are available for controlling the
behavior of the module.

@geindex init() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes init}@anchor{2932}
@deffn {函数} mimetypes.init (files=None)

Initialize the internal data structures.  If given, @emph{files} must be a sequence
of file names which should be used to augment the default type map.  If omitted,
the file names to use are taken from @ref{2935,,knownfiles}; on Windows, the
current registry settings are loaded.  Each file named in @emph{files} or
@ref{2935,,knownfiles} takes precedence over those named before it.  Calling
@ref{2932,,init()} repeatedly is allowed.

Specifying an empty list for @emph{files} will prevent the system defaults from
being applied: only the well-known values will be present from a built-in list.

If @emph{files} is @code{None} the internal data structure is completely rebuilt to its
initial default value. This is a stable operation and will produce the same results
when called multiple times.


在 3.2 版更改: Previously, Windows registry settings were ignored.

@end deffn

@geindex read_mime_types() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes read_mime_types}@anchor{e96}
@deffn {函数} mimetypes.read_mime_types (filename)

Load the type map given in the file @emph{filename}, if it exists.  The type map is
returned as a dictionary mapping filename extensions, including the leading dot
(@code{'.'}), to strings of the form @code{'type/subtype'}.  If the file @emph{filename}
does not exist or cannot be read, @code{None} is returned.
@end deffn

@geindex add_type() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes add_type}@anchor{2936}
@deffn {函数} mimetypes.add_type (type, ext, strict=True)

Add a mapping from the MIME type @emph{type} to the extension @emph{ext}. When the
extension is already known, the new type will replace the old one. When the type
is already known the extension will be added to the list of known extensions.

When @emph{strict} is @code{True} (the default), the mapping will be added to the
official MIME types, otherwise to the non-standard ones.
@end deffn

@geindex inited() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes inited}@anchor{2937}
@deffn {数据} mimetypes.inited

Flag indicating whether or not the global data structures have been initialized.
This is set to @code{True} by @ref{2932,,init()}.
@end deffn

@geindex knownfiles() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes knownfiles}@anchor{2935}
@deffn {数据} mimetypes.knownfiles

@geindex file; mime.types

List of type map file names commonly installed.  These files are typically named
@code{mime.types} and are installed in different locations by different
packages.
@end deffn

@geindex suffix_map() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes suffix_map}@anchor{2938}
@deffn {数据} mimetypes.suffix_map

Dictionary mapping suffixes to suffixes.  This is used to allow recognition of
encoded files for which the encoding and the type are indicated by the same
extension.  For example, the @code{.tgz} extension is mapped to @code{.tar.gz}
to allow the encoding and type to be recognized separately.
@end deffn

@geindex encodings_map() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes encodings_map}@anchor{2939}
@deffn {数据} mimetypes.encodings_map

Dictionary mapping filename extensions to encoding types.
@end deffn

@geindex types_map() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes types_map}@anchor{293a}
@deffn {数据} mimetypes.types_map

Dictionary mapping filename extensions to MIME types.
@end deffn

@geindex common_types() (在 mimetypes 模块中)
@anchor{library/mimetypes mimetypes common_types}@anchor{293b}
@deffn {数据} mimetypes.common_types

Dictionary mapping filename extensions to non-standard, but commonly found MIME
types.
@end deffn

An example usage of the module:

@example
>>> import mimetypes
>>> mimetypes.init()
>>> mimetypes.knownfiles
['/etc/mime.types', '/etc/httpd/mime.types', ... ]
>>> mimetypes.suffix_map['.tgz']
'.tar.gz'
>>> mimetypes.encodings_map['.gz']
'gzip'
>>> mimetypes.types_map['.tgz']
'application/x-tar-gz'
@end example

@menu
* MimeTypes Objects:: 

@end menu

@node MimeTypes Objects,,,mimetypes --- Map filenames to MIME types
@anchor{library/mimetypes id1}@anchor{293c}@anchor{library/mimetypes mimetypes-objects}@anchor{293d}
@subsubsection MimeTypes Objects


The @ref{293e,,MimeTypes} class may be useful for applications which may want more
than one MIME-type database; it provides an interface similar to the one of the
@ref{b2,,mimetypes} module.

@geindex MimeTypes (mimetypes 中的类)
@anchor{library/mimetypes mimetypes MimeTypes}@anchor{293e}
@deffn {类} mimetypes.MimeTypes (filenames=(), strict=True)

This class represents a MIME-types database.  By default, it provides access to
the same database as the rest of this module. The initial database is a copy of
that provided by the module, and may be extended by loading additional
@code{mime.types}-style files into the database using the @ref{293f,,read()} or
@ref{2940,,readfp()} methods.  The mapping dictionaries may also be cleared before
loading additional data if the default data is not desired.

The optional @emph{filenames} parameter can be used to cause additional files to be
loaded "on top" of the default database.

@geindex suffix_map (mimetypes.MimeTypes 属性)
@anchor{library/mimetypes mimetypes MimeTypes suffix_map}@anchor{2941}
@deffn {属性} suffix_map

Dictionary mapping suffixes to suffixes.  This is used to allow recognition of
encoded files for which the encoding and the type are indicated by the same
extension.  For example, the @code{.tgz} extension is mapped to @code{.tar.gz}
to allow the encoding and type to be recognized separately.  This is initially a
copy of the global @ref{2938,,suffix_map} defined in the module.
@end deffn

@geindex encodings_map (mimetypes.MimeTypes 属性)
@anchor{library/mimetypes mimetypes MimeTypes encodings_map}@anchor{2942}
@deffn {属性} encodings_map

Dictionary mapping filename extensions to encoding types.  This is initially a
copy of the global @ref{2939,,encodings_map} defined in the module.
@end deffn

@geindex types_map (mimetypes.MimeTypes 属性)
@anchor{library/mimetypes mimetypes MimeTypes types_map}@anchor{2943}
@deffn {属性} types_map

Tuple containing two dictionaries, mapping filename extensions to MIME types:
the first dictionary is for the non-standards types and the second one is for
the standard types. They are initialized by @ref{293b,,common_types} and
@ref{293a,,types_map}.
@end deffn

@geindex types_map_inv (mimetypes.MimeTypes 属性)
@anchor{library/mimetypes mimetypes MimeTypes types_map_inv}@anchor{2944}
@deffn {属性} types_map_inv

Tuple containing two dictionaries, mapping MIME types to a list of filename
extensions: the first dictionary is for the non-standards types and the
second one is for the standard types. They are initialized by
@ref{293b,,common_types} and @ref{293a,,types_map}.
@end deffn

@geindex guess_extension() (mimetypes.MimeTypes 方法)
@anchor{library/mimetypes mimetypes MimeTypes guess_extension}@anchor{2945}
@deffn {方法} guess_extension (type, strict=True)

Similar to the @ref{2934,,guess_extension()} function, using the tables stored as part
of the object.
@end deffn

@geindex guess_type() (mimetypes.MimeTypes 方法)
@anchor{library/mimetypes mimetypes MimeTypes guess_type}@anchor{fb7}
@deffn {方法} guess_type (url, strict=True)

Similar to the @ref{ef8,,guess_type()} function, using the tables stored as part of
the object.
@end deffn

@geindex guess_all_extensions() (mimetypes.MimeTypes 方法)
@anchor{library/mimetypes mimetypes MimeTypes guess_all_extensions}@anchor{2946}
@deffn {方法} guess_all_extensions (type, strict=True)

Similar to the @ref{2933,,guess_all_extensions()} function, using the tables stored
as part of the object.
@end deffn

@geindex read() (mimetypes.MimeTypes 方法)
@anchor{library/mimetypes mimetypes MimeTypes read}@anchor{293f}
@deffn {方法} read (filename, strict=True)

Load MIME information from a file named @emph{filename}.  This uses @ref{2940,,readfp()} to
parse the file.

If @emph{strict} is @code{True}, information will be added to list of standard types,
else to the list of non-standard types.
@end deffn

@geindex readfp() (mimetypes.MimeTypes 方法)
@anchor{library/mimetypes mimetypes MimeTypes readfp}@anchor{2940}
@deffn {方法} readfp (fp, strict=True)

Load MIME type information from an open file @emph{fp}.  The file must have the format of
the standard @code{mime.types} files.

If @emph{strict} is @code{True}, information will be added to the list of standard
types, else to the list of non-standard types.
@end deffn

@geindex read_windows_registry() (mimetypes.MimeTypes 方法)
@anchor{library/mimetypes mimetypes MimeTypes read_windows_registry}@anchor{2947}
@deffn {方法} read_windows_registry (strict=True)

Load MIME type information from the Windows registry.

@ref{12f5,,可用性}: Windows。

If @emph{strict} is @code{True}, information will be added to the list of standard
types, else to the list of non-standard types.


3.2 新版功能.

@end deffn
@end deffn

@node base64 --- Base16 Base32 Base64 Base85 数据编码,binhex --- 对binhex4文件进行编码和解码,mimetypes --- Map filenames to MIME types,互联网数据处理
@anchor{library/base64 doc}@anchor{2948}@anchor{library/base64 base64-base16-base32-base64-base85-data-encodings}@anchor{2949}@anchor{library/base64 module-base64}@anchor{e}
@subsection @code{base64} --- Base16, Base32, Base64, Base85 数据编码


@geindex base64 (模块)

@strong{源代码：} Lib/base64.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/base64.py}

@geindex base64; encoding
@geindex MIME; base64 encoding


__________________________________________________________________


此模块提供了将二进制数据编码为可打印的 ASCII 字符以及将这些编码解码回二进制数据的函数。它为 
@geindex RFC; RFC 3548
RFC 3548@footnote{https://tools.ietf.org/html/rfc3548.html} 指定的 Base16, Base32 和 Base64 编码以及已被广泛接受的 Ascii85 和 Base85 编码提供了编码和解码函数。

@geindex RFC; RFC 3548
RFC 3548@footnote{https://tools.ietf.org/html/rfc3548.html} 编码的目的是使得二进制数据可以作为电子邮件的内容正确地发送，用作 URL 的一部分，或者作为 HTTP POST 请求的一部分。其中的编码算法和 @code{uuencode} 程序是不同的。

此模块提供了两个接口。新的接口提供了从 @ref{5e3,,类字节对象} 到 ASCII 字节 @ref{32a,,bytes} 的编码，以及将 ASCII 的 @ref{5e3,,类字节对象} 或字符串解码到 @ref{32a,,bytes} 的操作。此模块支持定义在 
@geindex RFC; RFC 3548
RFC 3548@footnote{https://tools.ietf.org/html/rfc3548.html} 中的所有 base-64 字母表 （普通的、URL 安全的和文件系统安全的）。

旧的接口不提供从字符串的解码操作，但提供了操作 @ref{b3b,,文件对象} 的编码和解码函数。旧接口只支持标准的 Base64 字母表，并且按照 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html} 的规范每 76 个字符增加一个换行符。注意：如果你需要支持 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html}，那么使用 @ref{69,,email} 模块可能更加合适。


在 3.3 版更改: 新的接口提供的解码函数现在已经支持只包含 ASCII 的 Unicode 字符串。



在 3.4 版更改: 所有 @ref{5e3,,类字节对象} 现在已经被所有编码和解码函数接受。添加了对 Ascii85/Base85 的支持。


新的接口提供：

@geindex b64encode() (在 base64 模块中)
@anchor{library/base64 base64 b64encode}@anchor{294a}
@deffn {函数} base64.b64encode (s, altchars=None)

对 @ref{5e3,,bytes-like object} @emph{s} 进行 Base64 编码，并返回编码后的 @ref{32a,,bytes}。

可选项 @emph{altchars} 必须是一个长 2 字节的 @ref{5e3,,bytes-like object}，它指定了用于替换 @code{+} 和 @code{/} 的字符。这允许应用程序生成 URL 或文件系统安全的 Base64 字符串。默认值是 @code{None}，使用标准 Base64 字母表。
@end deffn

@geindex b64decode() (在 base64 模块中)
@anchor{library/base64 base64 b64decode}@anchor{ed9}
@deffn {函数} base64.b64decode (s, altchars=None, validate=False)

解码 Base64 编码过的 @ref{5e3,,bytes-like object} 或 ASCII 字符串 @emph{s} 并返回解码过的 @ref{32a,,bytes}。

可选项 @emph{altchars} 必须是一个长 2 字节的 @ref{5e3,,bytes-like object}，它指定了用于替换 @code{+} 和 @code{/} 的字符。

如果 @emph{s} 被不正确地填写，一个 @ref{958,,binascii.Error} 错误将被抛出。

如果 @emph{validate} 值为 @code{False} （默认情况），则在填充检查前，将丢弃既不在标准 base-64 字母表之中也不在备用字母表中的字符。如果 @emph{validate} 为 @code{True}，这些非 base64 字符将导致 @ref{958,,binascii.Error}。
@end deffn

@geindex standard_b64encode() (在 base64 模块中)
@anchor{library/base64 base64 standard_b64encode}@anchor{294b}
@deffn {函数} base64.standard_b64encode (s)

编码 @ref{5e3,,bytes-like object} @emph{s}，使用标准 Base64 字母表并返回编码过的 @ref{32a,,bytes}。
@end deffn

@geindex standard_b64decode() (在 base64 模块中)
@anchor{library/base64 base64 standard_b64decode}@anchor{294c}
@deffn {函数} base64.standard_b64decode (s)

解码 @ref{5e3,,bytes-like object} 或 ASCII 字符串 @emph{s}，使用标准 Base64 字母表并返回编码过的 @ref{32a,,bytes}。
@end deffn

@geindex urlsafe_b64encode() (在 base64 模块中)
@anchor{library/base64 base64 urlsafe_b64encode}@anchor{294d}
@deffn {函数} base64.urlsafe_b64encode (s)

编码 @ref{5e3,,bytes-like object} @emph{s}，使用 URL 与文件系统安全的字母表，使用 @code{-} 以及 @code{_} 代替标准 Base64 字母表中的 @code{+} 和 @code{/}。返回编码过的 @ref{32a,,bytes}。结果中可能包含 @code{=}。
@end deffn

@geindex urlsafe_b64decode() (在 base64 模块中)
@anchor{library/base64 base64 urlsafe_b64decode}@anchor{294e}
@deffn {函数} base64.urlsafe_b64decode (s)

解码 @ref{5e3,,bytes-like object} 或 ASCII 字符串 @emph{s}，使用 URL 与文件系统安全的字母表，使用 @code{-} 以及 @code{_} 代替标准 Base64 字母表中的 @code{+} 和 @code{/}。返回解码过的 @ref{32a,,bytes}
@end deffn

@geindex b32encode() (在 base64 模块中)
@anchor{library/base64 base64 b32encode}@anchor{294f}
@deffn {函数} base64.b32encode (s)

用 Base32 编码 @ref{5e3,,bytes-like object} @emph{s} 并返回编码过的 @ref{32a,,bytes}
@end deffn

@geindex b32decode() (在 base64 模块中)
@anchor{library/base64 base64 b32decode}@anchor{957}
@deffn {函数} base64.b32decode (s, casefold=False, map01=None)

解码 Base32 编码过的 @ref{5e3,,bytes-like object} 或 ASCII 字符串 @emph{s} 并返回解码过的 @ref{32a,,bytes}。

可选的 @emph{casefold} 是一个指定小写字幕是否可接受为输入的标志。为了安全考虑，默认值为 @code{False}。

@geindex RFC; RFC 3548
RFC 3548@footnote{https://tools.ietf.org/html/rfc3548.html} 允许将字母 0(zero) 映射为字母 O(oh)，并可以选择是否将字母 1(one) 映射为 I(eye) 或 L(el)。可选参数 @emph{map01} 不是 @code{None} 时，它的值指定 1 的映射目标 (I 或 l)，当 @emph{map01} 非 @code{None} 时， 0 总是被映射为 O。为了安全考虑，默认值被设为 @code{None}，如果是这样， 0 和 1 不允许被作为输入。

如果 @emph{s} 被错误地填写或输入中存在字母表之外的字符，将抛出 @ref{958,,binascii.Error}。
@end deffn

@geindex b16encode() (在 base64 模块中)
@anchor{library/base64 base64 b16encode}@anchor{2950}
@deffn {函数} base64.b16encode (s)

用 Base16 编码 @ref{5e3,,bytes-like object} @emph{s} 并返回编码过的 @ref{32a,,bytes}
@end deffn

@geindex b16decode() (在 base64 模块中)
@anchor{library/base64 base64 b16decode}@anchor{2951}
@deffn {函数} base64.b16decode (s, casefold=False)

解码 Base16 编码过的 @ref{5e3,,bytes-like object} 或 ASCII 字符串 @emph{s} 并返回解码过的 @ref{32a,,bytes}。

可选的 @emph{casefold} 是一个指定小写字幕是否可接受为输入的标志。为了安全考虑，默认值为 @code{False}。

如果 @emph{s} 被错误地填写或输入中存在字母表之外的字符，将抛出 @ref{958,,binascii.Error}。
@end deffn

@geindex a85encode() (在 base64 模块中)
@anchor{library/base64 base64 a85encode}@anchor{81e}
@deffn {函数} base64.a85encode (b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False)

用 Ascii85 编码 @ref{5e3,,bytes-like object} @emph{s} 并返回编码过的 @ref{32a,,bytes}

@emph{foldspaces} 是一个可选的标志，使用特殊的短序列 'y' 代替 'btoa' 提供的 4 个连续空格 (ASCII 0x20)。这个特性不被 "标准" Ascii85 编码支持。

@emph{wrapcol} 控制了输出是否包含换行符 (@code{b'\n'}). 如果该值非零, 则每一行只有该值所限制的字符长度.

@emph{pad} 控制在编码之前输入是否填充为4的倍数。请注意，@code{btoa} 实现总是填充。

@emph{adobe} 控制编码后的字节序列是否要加上 @code{<~} 和 @code{~>}，这是 Adobe 实现所使用的。


3.4 新版功能.

@end deffn

@geindex a85decode() (在 base64 模块中)
@anchor{library/base64 base64 a85decode}@anchor{81f}
@deffn {函数} base64.a85decode (b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v')

解码 Ascii85 编码过的 @ref{5e3,,bytes-like object} 或 ASCII 字符串 @emph{s} 并返回解码过的 @ref{32a,,bytes}。

@emph{foldspaces} 旗标指明是否应接受 'y' 短序列作为 4 个连续空格 (ASCII 0x20) 的快捷方式。 此特性不被 "标准" Ascii85 编码格式所支持。

@emph{adobe} 控制输入序列是否为 Adobe Ascii85 格式 (即附加 <~ 和 ~>)。

@emph{ignorechars} 应当是一个 @ref{5e3,,bytes-like object} 或 ASCII 字符串，其中包含要从输入中忽略的字符。 这应当只包含空白字符，并且默认包含 ASCII 中所有的空白字符。


3.4 新版功能.

@end deffn

@geindex b85encode() (在 base64 模块中)
@anchor{library/base64 base64 b85encode}@anchor{820}
@deffn {函数} base64.b85encode (b, pad=False)

用 base85（如 git 风格的二进制 diff 数据所用格式）编码 @ref{5e3,,bytes-like object} @emph{b} 并返回编码后的 @ref{32a,,bytes}。

如果 @emph{pad} 为真值，输入将以 @code{b'\0'} 填充以使其编码前长度为 4 字节的倍数。


3.4 新版功能.

@end deffn

@geindex b85decode() (在 base64 模块中)
@anchor{library/base64 base64 b85decode}@anchor{821}
@deffn {函数} base64.b85decode (b)

解码 base85 编码过的 @ref{5e3,,bytes-like object} 或 ASCII 字符串 @emph{b} 并返回解码过的 @ref{32a,,bytes}。 如有必要，填充会被隐式地移除。


3.4 新版功能.

@end deffn

旧式接口:

@geindex decode() (在 base64 模块中)
@anchor{library/base64 base64 decode}@anchor{2952}
@deffn {函数} base64.decode (input, output)

解码二进制 @emph{input} 文件的内容并将结果二进制数据写入 @emph{output} 文件。 @emph{input} 和 @emph{output} 必须为 @ref{b3b,,文件对象}. @emph{input} 将被读取直至 @code{input.readline()} 返回空字节串对象。
@end deffn

@geindex decodebytes() (在 base64 模块中)
@anchor{library/base64 base64 decodebytes}@anchor{180a}
@deffn {函数} base64.decodebytes (s)

解码 @ref{5e3,,bytes-like object} @emph{s}，该对象必须包含一行或多行 base64 编码的数据，并返回已解码的 @ref{32a,,bytes}。


3.1 新版功能.

@end deffn

@geindex decodestring() (在 base64 模块中)
@anchor{library/base64 base64 decodestring}@anchor{2953}
@deffn {函数} base64.decodestring (s)

已弃用的 @ref{180a,,decodebytes()} 的别名。


3.1 版后已移除.

@end deffn

@geindex encode() (在 base64 模块中)
@anchor{library/base64 base64 encode}@anchor{2954}
@deffn {函数} base64.encode (input, output)

编码二进制 @emph{input} 文件的内容并将经 base64 编码的数据写入 @emph{output} 文件。 @emph{input} 和 @emph{output} 必须为 @ref{b3b,,文件对象}。 @emph{input} 将被读取直到 @code{input.read()} 返回空字节串对象。 @ref{2954,,encode()} 会在每输出 76 个字节之后插入一个换行符 (@code{b'\n'})，并会确保输出总是以换行符来结束，如 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html} (MIME) 所规定的那样。
@end deffn

@geindex encodebytes() (在 base64 模块中)
@anchor{library/base64 base64 encodebytes}@anchor{1809}
@deffn {函数} base64.encodebytes (s)

编码 @ref{5e3,,bytes-like object} @emph{s}，其中可以包含任意二进制数据，并返回包含经 base64 编码数据的 @ref{32a,,bytes}，每输出 76 个字节之后将带一个换行符 (@code{b'\n'})，并会确保在末尾也有一个换行符，如 
@geindex RFC; RFC 2045
RFC 2045@footnote{https://tools.ietf.org/html/rfc2045.html} (MIME) 所规定的那样。


3.1 新版功能.

@end deffn

@geindex encodestring() (在 base64 模块中)
@anchor{library/base64 base64 encodestring}@anchor{2955}
@deffn {函数} base64.encodestring (s)

一个被弃用的 @ref{1809,,encodebytes()} 的别名。


3.1 版后已移除.

@end deffn

此模块的一个使用示例:

@example
>>> import base64
>>> encoded = base64.b64encode(b'data to be encoded')
>>> encoded
b'ZGF0YSB0byBiZSBlbmNvZGVk'
>>> data = base64.b64decode(encoded)
>>> data
b'data to be encoded'
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{10,,binascii}

支持模块，包含ASCII到二进制和二进制到ASCII转换。

@geindex RFC; RFC 1521

@item RFC 1521@footnote{https://tools.ietf.org/html/rfc1521.html} - MIME (Multipurpose Internet Mail Extensions) 第一部分：规定并描述因特网消息体的格式的机制。

第 5.2 节，“Base64 内容转换编码格式” 提供了 base64 编码格式的定义。
@end table


@node binhex --- 对binhex4文件进行编码和解码,binascii --- 二进制和 ASCII 码互转,base64 --- Base16 Base32 Base64 Base85 数据编码,互联网数据处理
@anchor{library/binhex doc}@anchor{2956}@anchor{library/binhex binhex-encode-and-decode-binhex4-files}@anchor{2957}@anchor{library/binhex module-binhex}@anchor{11}
@subsection @code{binhex} --- 对binhex4文件进行编码和解码


@geindex binhex (模块)

@strong{源代码:} Lib/binhex.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/binhex.py}


__________________________________________________________________


此模块以binhe4格式对文件进行编码和解码，该格式允许Macintosh文件以ASCII格式表示。仅处理数据分支。

@ref{11,,binhex} 模块定义了以下功能：

@geindex binhex() (在 binhex 模块中)
@anchor{library/binhex binhex binhex}@anchor{2958}
@deffn {函数} binhex.binhex (input, output)

将带有文件名 @emph{输入} 的二进制文件转换为binhex文件 @emph{输出} 。输出参数可以是文件名或类文件对象（ @code{write()} 和 @code{close()} 方法的任何对象）。
@end deffn

@geindex hexbin() (在 binhex 模块中)
@anchor{library/binhex binhex hexbin}@anchor{2959}
@deffn {函数} binhex.hexbin (input, output)

解码binhex文件输入。  @emph{输入} 可以是支持 @code{read()} 和 @code{close()} 方法的文件名或类文件对象。生成的文件将写入名为 @emph{output} 的文件，除非参数为 @code{None} ，在这种情况下，从binhex文件中读取输出文件名。
@end deffn

还定义了以下异常：

@geindex Error
@anchor{library/binhex binhex Error}@anchor{295a}
@deffn {例外} binhex.Error

当无法使用binhex格式编码某些内容时（例如，文件名太长而无法放入文件名字段中），或者输入未正确编码的binhex数据时，会引发异常。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{10,,binascii}

支持模块，包含ASCII到二进制和二进制到ASCII转换。
@end table


@menu
* 注释: 注释<3>. 

@end menu

@node 注释<3>,,,binhex --- 对binhex4文件进行编码和解码
@anchor{library/binhex binhex-notes}@anchor{295b}@anchor{library/binhex notes}@anchor{295c}
@subsubsection 注释


还有一个替代的、功能更强大的编码器和解码器接口，详细信息请参见源代码。

如果您在非Macintosh平台上编码或解码文本文件，它们仍将使用旧的Macintosh换行符约定（回车符作为行尾）。

@node binascii --- 二进制和 ASCII 码互转,quopri --- 编码与解码经过 MIME 转码的可打印数据,binhex --- 对binhex4文件进行编码和解码,互联网数据处理
@anchor{library/binascii doc}@anchor{295d}@anchor{library/binascii binascii-convert-between-binary-and-ascii}@anchor{295e}@anchor{library/binascii module-binascii}@anchor{10}
@subsection @code{binascii} --- 二进制和 ASCII 码互转


@geindex binascii (模块)

@geindex 模块; uu
@geindex 模块; base64
@geindex 模块; binhex


__________________________________________________________________


@ref{10,,binascii} 模块包含很多在二进制和二进制表示的各种ASCII码之间转换的方法。 通常情况不会直接使用这些函数，而是使用像  @ref{123,,uu} ， @ref{e,,base64} ，或 @ref{11,,binhex} 这样的封装模块。 为了执行效率高，@ref{10,,binascii} 模块含有许多用 C 写的低级函数，这些底层函数被一些高级模块所使用。

@cartouche
@quotation 注解 
@code{a2b_*} 函数接受只含有 ASCII 码的Unicode 字符串。其他函数只接受 @ref{5e3,,字节类对象} （例如 @ref{32a,,bytes}，@ref{32b,,bytearray} 和其他支持缓冲区协议的对象）。


在 3.3 版更改: ASCII-only unicode strings are now accepted by the @code{a2b_*} functions.

@end quotation
@end cartouche

@ref{10,,binascii} 模块定义了以下函数：

@geindex a2b_uu() (在 binascii 模块中)
@anchor{library/binascii binascii a2b_uu}@anchor{295f}
@deffn {函数} binascii.a2b_uu (string)

将单行 uu 编码数据转换成二进制数据并返回。uu 编码每行的数据通常包含45 个（二进制）字节，最后一行除外。每行数据后面可能跟有空格。
@end deffn

@geindex b2a_uu() (在 binascii 模块中)
@anchor{library/binascii binascii b2a_uu}@anchor{366}
@deffn {函数} binascii.b2a_uu (data, *, backtick=False)

将二进制数据转换为 ASCII 编码字符，返回值是转换后的行数据，包括换行符。 @emph{data} 的长度最多为45。如果 @emph{backtick} 为ture，则零由 @code{'`'} 而不是空格表示。


在 3.7 版更改: 增加 @emph{backtick} 形参。

@end deffn

@geindex a2b_base64() (在 binascii 模块中)
@anchor{library/binascii binascii a2b_base64}@anchor{2960}
@deffn {函数} binascii.a2b_base64 (string)

将 base64 数据块转换成二进制并以二进制数据形式返回。一次可以传递多行数据。
@end deffn

@geindex b2a_base64() (在 binascii 模块中)
@anchor{library/binascii binascii b2a_base64}@anchor{51d}
@deffn {函数} binascii.b2a_base64 (data, *, newline=True)

将二进制数据转换为一行用 base64 编码的ASCII字符串。返回值是转换后的行数据，如果 @emph{newline} 为true，则返回值包括换行符。该函数的输出符合：rfc：@cite{3548}。


在 3.6 版更改: 增加 @emph{newline} 形参。

@end deffn

@geindex a2b_qp() (在 binascii 模块中)
@anchor{library/binascii binascii a2b_qp}@anchor{2961}
@deffn {函数} binascii.a2b_qp (data, header=False)

将一个引号可打印的数据块转换成二进制数据并返回。一次可以转换多行。如果可选参数 @emph{header} 存在且为true，则数据中的下划线将被解码成空格。
@end deffn

@geindex b2a_qp() (在 binascii 模块中)
@anchor{library/binascii binascii b2a_qp}@anchor{2962}
@deffn {函数} binascii.b2a_qp (data, quotetabs=False, istext=True, header=False)

将二进制数据转换为一行或多行带引号可打印编码的ASCII字符串。返回值是转换后的行数据。如果可选参数 @emph{quotetabs} 存在且为真值，则对所有制表符和空格进行编码。如果可选参数 @emph{istext} 存在且为真值，则不对新行进行编码，但将对尾随空格进行编码。如果可选参数 @emph{header} 存在且为true，则空格将被编码为下划线 
@geindex RFC; RFC 1522
RFC 1522@footnote{https://tools.ietf.org/html/rfc1522.html}。如果可选参数 @emph{header} 存在且为假值，则也会对换行符进行编码;不进行换行转换编码可能会破坏二进制数据流。
@end deffn

@geindex a2b_hqx() (在 binascii 模块中)
@anchor{library/binascii binascii a2b_hqx}@anchor{2963}
@deffn {函数} binascii.a2b_hqx (string)

将 binhex4 格式的 ASCII 数据不进行 RLE 解压缩直接转换为二进制数据。该字符串应包含完整数量的二进制字节，或者（在binhex4 数据最后部分）剩余位为零。
@end deffn

@geindex rledecode_hqx() (在 binascii 模块中)
@anchor{library/binascii binascii rledecode_hqx}@anchor{2964}
@deffn {函数} binascii.rledecode_hqx (data)

根据 binhex4 标准对数据执行 RLE 解压缩。该算法在一个字节的数据后使用 @code{0x90} 作为重复指示符，然后计数。计数 @code{0} 指定字节值 @code{0x90} 。该例程返回解压缩的数据，输入数据以孤立的重复指示符结束的情况下，将引发 @ref{2965,,Incomplete} 异常。


在 3.2 版更改: 仅接受 bytestring 或 bytearray 对象作为输入。

@end deffn

@geindex rlecode_hqx() (在 binascii 模块中)
@anchor{library/binascii binascii rlecode_hqx}@anchor{2966}
@deffn {函数} binascii.rlecode_hqx (data)

在 @emph{data} 上执行 binhex4 游程编码压缩并返回结果。
@end deffn

@geindex b2a_hqx() (在 binascii 模块中)
@anchor{library/binascii binascii b2a_hqx}@anchor{2967}
@deffn {函数} binascii.b2a_hqx (data)

执行 hexbin4 类型二进制到 ASCII 码的转换并返回结果字符串。输入数据应经过 RLE 编码，且数据长度可被3整除（除了最后一个片段）。
@end deffn

@geindex crc_hqx() (在 binascii 模块中)
@anchor{library/binascii binascii crc_hqx}@anchor{2968}
@deffn {函数} binascii.crc_hqx (data, value)

以 @emph{value} 作为初始 CRC 计算 @emph{data} 的16位 CRC 值，返回其结果。这里使用 CRC-CCITT 生成多项式 @emph{x}@w{^16} + @emph{x}@w{^12} + @emph{x}@w{^5} + 1 ，通常表示为0x1021。该 CRC 被用于 binhex4 格式。
@end deffn

@geindex crc32() (在 binascii 模块中)
@anchor{library/binascii binascii crc32}@anchor{2969}
@deffn {函数} binascii.crc32 (data[, value])

计算 CRC-32 ，从 @emph{value} 的初始 CRC 开始计算 @emph{data} 的32位校验和。默认初始 CRC 为零。该算法与 ZIP 文件校验和一致。由于该算法被设计用作校验和算法，因此不适合用作通用散列算法。使用方法如下：

@example
print(binascii.crc32(b"hello world"))
# Or, in two pieces:
crc = binascii.crc32(b"hello")
crc = binascii.crc32(b" world", crc)
print('crc32 = @{:#010x@}'.format(crc))
@end example


在 3.0 版更改: 校验结果始终是无符号类型的。要在所有Python版本和平台上生成相同的数值，请使用 @code{crc32(data) & 0xffffffff} 。

@end deffn

@geindex b2a_hex() (在 binascii 模块中)
@geindex hexlify() (在 binascii 模块中)
@anchor{library/binascii binascii b2a_hex}@anchor{180c}
@deffn {函数} binascii.b2a_hex (data[, sep[, bytes_per_sep=1]])
@anchor{library/binascii binascii hexlify}@anchor{f4d}
@deffnx {函数} binascii.hexlify (data[, sep[, bytes_per_sep=1]])

返回二进制数据 @emph{data} 的十六进制表示形式。 @emph{data} 的每个字节都被转换为相应的2位十六进制表示形式。因此返回的字节对象的长度是 @emph{data} 的两倍。

使用：@ref{62b,,bytes.hex()} 方法也可以方便地实现相似的功能（但仅返回文本字符串）。

如果指定了 @emph{sep}，它必须为单字符 str 或 bytes 对象。 它将被插入每个 @emph{bytes_per_sep} 输入字节之后。 分隔符位置默认从输出的右端开始计数，如果你希望从左端开始计数，请提供一个负的 @emph{bytes_per_sep} 值。

@example
>>> import binascii
>>> binascii.b2a_hex(b'\xb9\x01\xef')
b'b901ef'
>>> binascii.hexlify(b'\xb9\x01\xef', '-')
b'b9-01-ef'
>>> binascii.b2a_hex(b'\xb9\x01\xef', b'_', 2)
b'b9_01ef'
>>> binascii.b2a_hex(b'\xb9\x01\xef', b' ', -2)
b'b901 ef'
@end example


在 3.8 版更改: 添加了 @emph{sep} 和 @emph{bytes_per_sep} 形参。

@end deffn

@geindex a2b_hex() (在 binascii 模块中)
@geindex unhexlify() (在 binascii 模块中)
@anchor{library/binascii binascii a2b_hex}@anchor{180d}
@deffn {函数} binascii.a2b_hex (hexstr)
@anchor{library/binascii binascii unhexlify}@anchor{fd1}
@deffnx {函数} binascii.unhexlify (hexstr)

返回由十六进制字符串  @emph{hexstr} 表示的二进制数据。此函数功能与 @ref{180c,,b2a_hex()} 相反。 @emph{hexstr} 必须包含偶数个十六进制数字（可以是大写或小写），否则会引发  @ref{958,,Error} 异常。

使用：@ref{327,,bytes.fromhex()}  类方法也实现相似的功能（仅接受文本字符串参数，不限制其中的空白字符）。
@end deffn

@geindex Error
@anchor{library/binascii binascii Error}@anchor{958}
@deffn {例外} binascii.Error

通常是因为编程错误引发的异常。
@end deffn

@geindex Incomplete
@anchor{library/binascii binascii Incomplete}@anchor{2965}
@deffn {例外} binascii.Incomplete

数据不完整引发的异常。通常不是编程错误导致的，可以通过读取更多的数据并再次尝试来处理该异常。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{e,,base64}

支持在16，32，64，85进制中进行符合 RFC 协议的 base64 样式编码。

@item 模块 @ref{11,,binhex}

支持在 Macintosh 上使用的 binhex 格式。

@item 模块 @ref{123,,uu}

支持在 Unix 上使用的 UU 编码。

@item 模块 @ref{db,,quopri}

支持在 MIME 版本电子邮件中使用引号可打印编码。
@end table


@node quopri --- 编码与解码经过 MIME 转码的可打印数据,uu --- 对 uuencode 文件进行编码与解码,binascii --- 二进制和 ASCII 码互转,互联网数据处理
@anchor{library/quopri doc}@anchor{296a}@anchor{library/quopri module-quopri}@anchor{db}@anchor{library/quopri quopri-encode-and-decode-mime-quoted-printable-data}@anchor{296b}
@subsection @code{quopri} --- 编码与解码经过 MIME 转码的可打印数据


@geindex quopri (模块)

@strong{源代码:} Lib/quopri.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/quopri.py}

@geindex quoted-printable; encoding
@geindex MIME; quoted-printable encoding


__________________________________________________________________


此模块会执行转换后可打印的传输编码与解码，具体定义见 
@geindex RFC; RFC 1521
RFC 1521@footnote{https://tools.ietf.org/html/rfc1521.html}: "MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies"。 转换后可打印的编码格式被设计用于只包含相对较少的不可打印字符的数据；如果存在大量这样的字符，通过 @ref{e,,base64} 模块所提供的 base64 编码方案会更为紧凑，例如当发送图片文件时。

@geindex decode() (在 quopri 模块中)
@anchor{library/quopri quopri decode}@anchor{180f}
@deffn {函数} quopri.decode (input, output, header=False)

解码 @emph{input} 文件的内容并将已解码二进制数据结果写入 @emph{output} 文件。 @emph{input} 和 @emph{output} 必须为 @ref{b3b,,二进制文件对象}。 如果提供了可选参数 @emph{header} 且为真值，下划线将被解码为空格。 此函数可用于解码“Q”编码的头数据，具体描述见 
@geindex RFC; RFC 1522
RFC 1522@footnote{https://tools.ietf.org/html/rfc1522.html}: "MIME (Multipurpose Internet Mail Extensions) Part Two: Message Header Extensions for Non-ASCII Text"。
@end deffn

@geindex encode() (在 quopri 模块中)
@anchor{library/quopri quopri encode}@anchor{180e}
@deffn {函数} quopri.encode (input, output, quotetabs, header=False)

编码 @emph{input} 文件的内容并将转换后可打印的数据结果写入 @emph{output} 文件。 @emph{input} 和 @emph{output} 必须为 @ref{b3b,,二进制文件对象}. @emph{quotetabs} 是一个非可选的旗标，它控制是否要编码内嵌的空格与制表符；当为真值时将编码此类内嵌空白符，当为假值时则保持原样不进行编码。 请注意出现在行尾的空格与制表符总是会被编码，具体描述见 
@geindex RFC; RFC 1521
RFC 1521@footnote{https://tools.ietf.org/html/rfc1521.html}。 @emph{header} 旗标控制空格符是否要编码为下划线，具体描述见 
@geindex RFC; RFC 1522
RFC 1522@footnote{https://tools.ietf.org/html/rfc1522.html}。
@end deffn

@geindex decodestring() (在 quopri 模块中)
@anchor{library/quopri quopri decodestring}@anchor{296c}
@deffn {函数} quopri.decodestring (s, header=False)

类似 @ref{180f,,decode()}，区别在于它接受一个源 @ref{32a,,bytes} 并返回对应的已解码 @ref{32a,,bytes}。
@end deffn

@geindex encodestring() (在 quopri 模块中)
@anchor{library/quopri quopri encodestring}@anchor{296d}
@deffn {函数} quopri.encodestring (s, quotetabs=False, header=False)

类型 @ref{180e,,encode()}，区别在于它接受一个源 @ref{32a,,bytes} 并返回对应的已编码 @ref{32a,,bytes}。 在默认情况下，它会发送 @code{False} 值给 @ref{180e,,encode()} 函数的 @emph{quotetabs} 形参。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{e,,base64}

编码与解码 MIME base64 数据
@end table


@node uu --- 对 uuencode 文件进行编码与解码,,quopri --- 编码与解码经过 MIME 转码的可打印数据,互联网数据处理
@anchor{library/uu doc}@anchor{296e}@anchor{library/uu module-uu}@anchor{123}@anchor{library/uu uu-encode-and-decode-uuencode-files}@anchor{296f}
@subsection @code{uu} --- 对 uuencode 文件进行编码与解码


@geindex uu (模块)

@strong{源代码:} Lib/uu.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/uu.py}


__________________________________________________________________


此模块使用 uuencode 格式来编码和解码文件，以便任意二进制数据可通过仅限 ASCII 码的连接进行传输。 在任何要求文件参数的地方，这些方法都接受文件类对象。 为了保持向下兼容，也接受包含路径名称的字符串，并且将打开相应的文件进行读写；路径名称 @code{'-'} 被解读为标准输入或输出。 但是，此接口已被弃用；在 Windows 中调用者最好是自行打开文件，并在需要时确保模式为 @code{'rb'} or @code{'wb'}。

@geindex Jansen@comma{} Jack
@geindex Ellinghouse@comma{} Lance

此代码由 Lance Ellinghouse 贡献，并由 Jack Jansen 修改。

@ref{123,,uu} 模块定义了以下函数：

@geindex encode() (在 uu 模块中)
@anchor{library/uu uu encode}@anchor{407}
@deffn {函数} uu.encode (in_file, out_file, name=None, mode=None, *, backtick=False)

使用 uuencode 将 @emph{in_file} 文件编码为 @emph{out_file} 文件。 经过 uuencoded 编码的文件将具有指定 @emph{name} 和 @emph{mode} 作为解码该文件默认结果的标头。 默认值会相应地从 @emph{in_file} 或 @code{'-'} 以及 @code{0o666} 中提取。 如果 @emph{backtick} 为真值，零会用 @code{'`'} 而不是空格来表示。


在 3.7 版更改: 增加 @emph{backtick} 形参。

@end deffn

@geindex decode() (在 uu 模块中)
@anchor{library/uu uu decode}@anchor{1810}
@deffn {函数} uu.decode (in_file, out_file=None, mode=None, quiet=False)

调用此函数会解码 uuencod 编码的 @emph{in_file} 文件并将结果放入 @emph{out_file} 文件。 如果 @emph{out_file} 是一个路径名称，@emph{mode} 会在必须创建文件时用于设置权限位。 @emph{out_file} 和 @emph{mode} 的默认值会从 uuencode 标头中提取。 但是，如果标头中指定的文件已存在，则会引发 @ref{2970,,uu.Error}。

如果输入由不正确的 uuencode 编码器生成，@ref{1810,,decode()} 可能会打印一条警告到标准错误 ，这样 Python 可以从该错误中恢复。 将 @emph{quiet} 设为真值可以屏蔽此警告。
@end deffn

@geindex Error
@anchor{library/uu uu Error}@anchor{2970}
@deffn {例外} uu.Error

@ref{1a9,,Exception} 的子类，此异常可由 @ref{1810,,uu.decode()} 在多种情况下引发，如上文所述，此外还包括格式错误的标头或被截断的输入文件等。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{10,,binascii}

支持模块，包含ASCII到二进制和二进制到ASCII转换。
@end table


@node 结构化标记处理工具,互联网协议和支持,互联网数据处理,Python 标准库
@anchor{library/markup doc}@anchor{2971}@anchor{library/markup markup}@anchor{2972}@anchor{library/markup structured-markup-processing-tools}@anchor{2973}
@section 结构化标记处理工具


Python 支持各种模块，以处理各种形式的结构化数据标记。 这包括使用标准通用标记语言（SGML）和超文本标记语言（HTML）的模块，以及使用可扩展标记语言（XML）的几个接口。

@menu
* html: html --- 超文本标记语言支持. 超文本标记语言支持
* html.parser: html parser --- 简单的 HTML 和 XHTML 解析器. 简单的 HTML 和 XHTML 解析器
* html.entities: html entities --- HTML 一般实体的定义. HTML 一般实体的定义
* XML处理模块:: 
* xml.etree.ElementTree: xml etree ElementTree --- ElementTree XML API. ElementTree XML API
* xml.dom: xml dom --- The Document Object Model API. The Document Object Model API
* xml.dom.minidom: xml dom minidom --- Minimal DOM implementation. Minimal DOM implementation
* xml.dom.pulldom: xml dom pulldom --- Support for building partial DOM trees. Support for building partial DOM trees
* xml.sax: xml sax --- Support for SAX2 parsers. Support for SAX2 parsers
* xml.sax.handler: xml sax handler --- Base classes for SAX handlers. Base classes for SAX handlers
* xml.sax.saxutils: xml sax saxutils --- SAX 工具集. SAX 工具集
* xml.sax.xmlreader: xml sax xmlreader --- Interface for XML parsers. Interface for XML parsers
* xml.parsers.expat: xml parsers expat --- Fast XML parsing using Expat. Fast XML parsing using Expat

@end menu

@node html --- 超文本标记语言支持,html parser --- 简单的 HTML 和 XHTML 解析器,,结构化标记处理工具
@anchor{library/html doc}@anchor{2974}@anchor{library/html html-hypertext-markup-language-support}@anchor{2975}@anchor{library/html module-html}@anchor{90}
@subsection @code{html} --- 超文本标记语言支持


@geindex html (模块)

@strong{源码：} Lib/html/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/html/__init__.py}


__________________________________________________________________


该模块定义了操作HTML的工具。

@geindex escape() (在 html 模块中)
@anchor{library/html html escape}@anchor{92e}
@deffn {函数} html.escape (s, quote=True)

将字符串 @emph{s} 中的字符`@w{`}&`@w{`} 、 @code{<} 和 @code{>} 转换为安全的HTML序列。 如果需要在 HTML 中显示可能包含此类字符的文本，请使用此选项。 如果可选的标志 @emph{quote} 为真值，则字符 (@code{"}) 和 (@code{'}) 也被转换；这有助于包含在由引号分隔的 HTML 属性中，如 @code{<a href="...">}。


3.2 新版功能.

@end deffn

@geindex unescape() (在 html 模块中)
@anchor{library/html html unescape}@anchor{854}
@deffn {函数} html.unescape (s)

将字符串 @emph{s} 中的所有命名和数字字符引用 (例如 @code{&gt;}, @code{&#62;}, @code{&#x3e;}) 转换为相应的Unicode字符。 此函数使用HTML 5标准为有效和无效字符引用定义的规则，以及 @ref{a10,,HTML 5 命名字符引用列表}。


3.4 新版功能.

@end deffn


__________________________________________________________________


@code{html} 包中的子模块是：


@itemize *

@item 
@ref{92,,html.parser} —— 具有宽松解析模式的HTML / XHTML解析器

@item 
@ref{91,,html.entities} -- HTML 实体定义
@end itemize

@node html parser --- 简单的 HTML 和 XHTML 解析器,html entities --- HTML 一般实体的定义,html --- 超文本标记语言支持,结构化标记处理工具
@anchor{library/html parser doc}@anchor{2976}@anchor{library/html parser html-parser-simple-html-and-xhtml-parser}@anchor{2977}@anchor{library/html parser module-html parser}@anchor{92}
@subsection @code{html.parser} --- 简单的 HTML 和 XHTML 解析器


@geindex html.parser (模块)

@strong{源代码：} Lib/html/parser.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/html/parser.py}

@geindex HTML
@geindex XHTML


__________________________________________________________________


这个模块定义了一个 @ref{7b9,,HTMLParser} 类，为 HTML（超文本标记语言）和 XHTML 文本文件解析提供基础。

@geindex HTMLParser (html.parser 中的类)
@anchor{library/html parser html parser HTMLParser}@anchor{7b9}
@deffn {类} html.parser.HTMLParser (*, convert_charrefs=True)

创建一个能解析无效标记的解析器实例。

如果 @emph{convert_charrefs} 为 @code{True} (默认值)，则所有字符引用( @code{script}/@code{style}   元素中的除外)都会自动转换为相应的 Unicode 字符。

一个 @ref{7b9,,HTMLParser} 类的实例用来接受 HTML 数据，并在标记开始、标记结束、文本、注释和其他元素标记出现的时候调用对应的方法。要实现具体的行为，请使用 @ref{7b9,,HTMLParser} 的子类并重载其方法。

这个解析器不检查结束标记是否与开始标记匹配，也不会因外层元素完毕而隐式关闭了的元素引发结束标记处理。


在 3.4 版更改: @emph{convert_charrefs} 关键字参数被添加。



在 3.5 版更改: @emph{convert_charrefs} 参数的默认值现在为 @code{True}。

@end deffn

@menu
* HTML 解析器的示例程序:: 
* HTMLParser 方法:: 
* 例子: 例子<19>. 

@end menu

@node HTML 解析器的示例程序,HTMLParser 方法,,html parser --- 简单的 HTML 和 XHTML 解析器
@anchor{library/html parser example-html-parser-application}@anchor{2978}
@subsubsection HTML 解析器的示例程序


下面是简单的 HTML 解析器的一个基本示例，使用 @ref{7b9,,HTMLParser} 类，当遇到开始标记、结束标记以及数据的时候将内容打印出来。

@example
from html.parser import HTMLParser

class MyHTMLParser(HTMLParser):
    def handle_starttag(self, tag, attrs):
        print("Encountered a start tag:", tag)

    def handle_endtag(self, tag):
        print("Encountered an end tag :", tag)

    def handle_data(self, data):
        print("Encountered some data  :", data)

parser = MyHTMLParser()
parser.feed('<html><head><title>Test</title></head>'
            '<body><h1>Parse me!</h1></body></html>')
@end example

输出是:

@example
Encountered a start tag: html
Encountered a start tag: head
Encountered a start tag: title
Encountered some data  : Test
Encountered an end tag : title
Encountered an end tag : head
Encountered a start tag: body
Encountered a start tag: h1
Encountered some data  : Parse me!
Encountered an end tag : h1
Encountered an end tag : body
Encountered an end tag : html
@end example

@node HTMLParser 方法,例子<19>,HTML 解析器的示例程序,html parser --- 简单的 HTML 和 XHTML 解析器
@anchor{library/html parser htmlparser-methods}@anchor{2979}
@subsubsection @code{HTMLParser} 方法


@ref{7b9,,HTMLParser} 实例有下列方法：

@geindex feed() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser feed}@anchor{297a}
@deffn {方法} HTMLParser.feed (data)

填充一些文本到解析器中。如果包含完整的元素，则被处理；如果数据不完整，将被缓冲直到更多的数据被填充，或者 @ref{297b,,close()} 被调用。@emph{data} 必须为 @ref{329,,str} 类型。
@end deffn

@geindex close() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser close}@anchor{297b}
@deffn {方法} HTMLParser.close ()

如同后面跟着一个文件结束标记一样，强制处理所有缓冲数据。这个方法能被派生类重新定义，用于在输入的末尾定义附加处理，但是重定义的版本应当始终调用基类 @ref{7b9,,HTMLParser} 的 @ref{297b,,close()} 方法。
@end deffn

@geindex reset() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser reset}@anchor{297c}
@deffn {方法} HTMLParser.reset ()

重置实例。丢失所有未处理的数据。在实例化阶段被隐式调用。
@end deffn

@geindex getpos() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser getpos}@anchor{297d}
@deffn {方法} HTMLParser.getpos ()

返回当前行号和偏移值。
@end deffn

@geindex get_starttag_text() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser get_starttag_text}@anchor{297e}
@deffn {方法} HTMLParser.get_starttag_text ()

返回最近打开的开始标记中的文本。 结构化处理时通常应该不需要这个，但在处理“已部署”的 HTML 或是在以最小改变来重新生成输入时可能会有用处（例如可以保留属性间的空格等）。
@end deffn

下列方法将在遇到数据或者标记元素的时候被调用。他们需要在子类中重载。基类的实现中没有任何实际操作（除了 @ref{297f,,handle_startendtag()} ）：

@geindex handle_starttag() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_starttag}@anchor{2980}
@deffn {方法} HTMLParser.handle_starttag (tag, attrs)

这个方法在标签开始的时候被调用（例如： @code{<div id="main">} ）。

@emph{tag} 参数是小写的标记名。@emph{attrs} 参数是一个 @code{(name, value)} 形式的列表，包含了所有在标记的 @code{<>}  括号中找到的属性。@emph{name} 转换为小写，@emph{value} 的引号被去除，字符和实体引用都会被替换。

实例中，对于标签 @code{<A HREF="https://www.cwi.nl/">}，这个方法将以下列形式被调用 @code{handle_starttag('a', [('href', 'https://www.cwi.nl/')])} 。

@ref{91,,html.entities} 中的所有实体引用，会被替换为属性值。
@end deffn

@geindex handle_endtag() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_endtag}@anchor{2981}
@deffn {方法} HTMLParser.handle_endtag (tag)

此方法被用来处理元素的结束标记（例如： @code{</div>} ）。

@emph{tag} 参数是小写的标签名。
@end deffn

@geindex handle_startendtag() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_startendtag}@anchor{297f}
@deffn {方法} HTMLParser.handle_startendtag (tag, attrs)

类似于 @ref{2980,,handle_starttag()}, 只是在解析器遇到 XHTML 样式的空标记时被调用（ @code{<img ... />}）。这个方法能被需要这种特殊词法信息的子类重载；默认实现仅简单调用 @ref{2980,,handle_starttag()} 和 @ref{2981,,handle_endtag()} 。
@end deffn

@geindex handle_data() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_data}@anchor{2982}
@deffn {方法} HTMLParser.handle_data (data)

这个方法被用来处理任意数据（例如：文本节点和 @code{<script>...</script>} 以及 @code{<style>...</style>} 中的内容）。
@end deffn

@geindex handle_entityref() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_entityref}@anchor{2983}
@deffn {方法} HTMLParser.handle_entityref (name)

这个方法被用于处理 @code{&name;} 形式的命名字符引用（例如 @code{&gt;}），其中 @emph{name} 是通用的实体引用（例如： @code{'gt'}）。如果 @emph{convert_charrefs} 为 @code{True}，该方法永远不会被调用。
@end deffn

@geindex handle_charref() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_charref}@anchor{2984}
@deffn {方法} HTMLParser.handle_charref (name)

这个方法被用来处理 @code{&#NNN;} 和 @code{&#xNNN;} 形式的十进制和十六进制字符引用。例如，@code{&gt;} 等效的十进制形式为 @code{&#62;} ，而十六进制形式为 @code{&#x3E;} ；在这种情况下，方法将收到  @code{'62'} 或 @code{'x3E'} 。如果 @emph{convert_charrefs} 为 @code{True} ，则该方法永远不会被调用。
@end deffn

@geindex handle_comment() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_comment}@anchor{2985}
@deffn {方法} HTMLParser.handle_comment (data)

这个方法在遇到注释的时候被调用（例如： @code{<!--comment-->} ）。

例如， @code{<!-- comment -->} 这个注释会用 @code{' comment '} 作为参数调用此方法。

Internet Explorer 条件注释（condcoms）的内容也被发送到这个方法，因此，对于 @code{<!--[if IE 9]>IE9-specific content<![endif]-->} ，这个方法将接收到 @code{'[if IE 9]>IE9-specific content<![endif]'} 。
@end deffn

@geindex handle_decl() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_decl}@anchor{2986}
@deffn {方法} HTMLParser.handle_decl (decl)

这个方法用来处理 HTML doctype 申明（例如 @code{<!DOCTYPE html>} ）。

@emph{decl} 形参为 @code{<!...>} 标记中的所有内容（例如： @code{'DOCTYPE html'} ）。
@end deffn

@geindex handle_pi() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser handle_pi}@anchor{2987}
@deffn {方法} HTMLParser.handle_pi (data)

此方法在遇到处理指令的时候被调用。@emph{data} 形参将包含整个处理指令。例如，对于处理指令 @code{<?proc color='red'>} ，这个方法将以 @code{handle_pi("proc color='red'")} 形式被调用。它旨在被派生类重载；基类实现中无任何实际操作。

@cartouche
@quotation 注解 
@ref{7b9,,HTMLParser} 类使用 SGML 语法规则处理指令。使用 @code{'?'} 结尾的 XHTML 处理指令将导致 @code{'?'} 包含在 @emph{data} 中。
@end quotation
@end cartouche
@end deffn

@geindex unknown_decl() (html.parser.HTMLParser 方法)
@anchor{library/html parser html parser HTMLParser unknown_decl}@anchor{2988}
@deffn {方法} HTMLParser.unknown_decl (data)

当解析器读到无法识别的声明时，此方法被调用。

@emph{data} 形参为 @code{<![...]>} 标记中的所有内容。某些时候对派生类的重载很有用。基类实现中无任何实际操作。
@end deffn

@node 例子<19>,,HTMLParser 方法,html parser --- 简单的 HTML 和 XHTML 解析器
@anchor{library/html parser examples}@anchor{2989}@anchor{library/html parser htmlparser-examples}@anchor{298a}
@subsubsection 例子


下面的类实现了一个解析器，用于更多示例的演示:

@example
from html.parser import HTMLParser
from html.entities import name2codepoint

class MyHTMLParser(HTMLParser):
    def handle_starttag(self, tag, attrs):
        print("Start tag:", tag)
        for attr in attrs:
            print("     attr:", attr)

    def handle_endtag(self, tag):
        print("End tag  :", tag)

    def handle_data(self, data):
        print("Data     :", data)

    def handle_comment(self, data):
        print("Comment  :", data)

    def handle_entityref(self, name):
        c = chr(name2codepoint[name])
        print("Named ent:", c)

    def handle_charref(self, name):
        if name.startswith('x'):
            c = chr(int(name[1:], 16))
        else:
            c = chr(int(name))
        print("Num ent  :", c)

    def handle_decl(self, data):
        print("Decl     :", data)

parser = MyHTMLParser()
@end example

解析一个文档类型声明:

@example
>>> parser.feed('<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" '
...             '"http://www.w3.org/TR/html4/strict.dtd">')
Decl     : DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"
@end example

解析一个具有一些属性和标题的元素:

@example
>>> parser.feed('<img src="python-logo.png" alt="The Python logo">')
Start tag: img
     attr: ('src', 'python-logo.png')
     attr: ('alt', 'The Python logo')
>>>
>>> parser.feed('<h1>Python</h1>')
Start tag: h1
Data     : Python
End tag  : h1
@end example

@code{script} 和 @code{style} 元素中的内容原样返回，无需进一步解析:

@example
>>> parser.feed('<style type="text/css">#python @{ color: green @}</style>')
Start tag: style
     attr: ('type', 'text/css')
Data     : #python @{ color: green @}
End tag  : style

>>> parser.feed('<script type="text/javascript">'
...             'alert("<strong>hello!</strong>");</script>')
Start tag: script
     attr: ('type', 'text/javascript')
Data     : alert("<strong>hello!</strong>");
End tag  : script
@end example

解析注释:

@example
>>> parser.feed('<!-- a comment -->'
...             '<!--[if IE 9]>IE-specific content<![endif]-->')
Comment  :  a comment
Comment  : [if IE 9]>IE-specific content<![endif]
@end example

解析命名或数字形式的字符引用，并把他们转换到正确的字符（注意：这 3 种转义都是 @code{'>'} ）:

@example
>>> parser.feed('&gt;&#62;&#x3E;')
Named ent: >
Num ent  : >
Num ent  : >
@end example

填充不完整的块给 @ref{297a,,feed()} 执行，@ref{2982,,handle_data()} 可能会多次调用（除非 @emph{convert_charrefs} 被设置为 @code{True} ）:

@example
>>> for chunk in ['<sp', 'an>buff', 'ered ', 'text</s', 'pan>']:
...     parser.feed(chunk)
...
Start tag: span
Data     : buff
Data     : ered
Data     : text
End tag  : span
@end example

解析无效的 HTML (例如：未引用的属性）也能正常运行:

@example
>>> parser.feed('<p><a class=link href=#main>tag soup</p ></a>')
Start tag: p
Start tag: a
     attr: ('class', 'link')
     attr: ('href', '#main')
Data     : tag soup
End tag  : p
End tag  : a
@end example

@node html entities --- HTML 一般实体的定义,XML处理模块,html parser --- 简单的 HTML 和 XHTML 解析器,结构化标记处理工具
@anchor{library/html entities doc}@anchor{298b}@anchor{library/html entities html-entities-definitions-of-html-general-entities}@anchor{298c}@anchor{library/html entities module-html entities}@anchor{91}
@subsection @code{html.entities} --- HTML 一般实体的定义


@geindex html.entities (模块)

@strong{源码：} Lib/html/entities.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/html/entities.py}


__________________________________________________________________


该模块定义了四个词典， @ref{a10,,html5}、 @ref{298d,,name2codepoint}、 @ref{298e,,codepoint2name}、以及 @ref{298f,,entitydefs}。

@geindex html5() (在 html.entities 模块中)
@anchor{library/html entities html entities html5}@anchor{a10}
@deffn {数据} html.entities.html5

将 HTML5 命名字符引用 @footnote{@w{(1)} 
参见 @indicateurl{https://www.w3.org/TR/html5/syntax.html#named-character-references}
} 映射到等效的 Unicode 字符的字典，例如 @code{html5['gt;'] == '>'}。 请注意，尾随的分号包含在名称中（例如 @code{'gt;'} ），但是即使没有分号，一些名称也会被标准接受，在这种情况下，名称出现时带有和不带有 @code{';'}。另见 @ref{854,,html.unescape()}。


3.3 新版功能.

@end deffn

@geindex entitydefs() (在 html.entities 模块中)
@anchor{library/html entities html entities entitydefs}@anchor{298f}
@deffn {数据} html.entities.entitydefs

将 XHTML 1.0 实体定义映射到 ISO Latin-1 中的替换文本的字典。
@end deffn

@geindex name2codepoint() (在 html.entities 模块中)
@anchor{library/html entities html entities name2codepoint}@anchor{298d}
@deffn {数据} html.entities.name2codepoint

将 HTML 实体名称映射到 Unicode 代码点的字典。
@end deffn

@geindex codepoint2name() (在 html.entities 模块中)
@anchor{library/html entities html entities codepoint2name}@anchor{298e}
@deffn {数据} html.entities.codepoint2name

将 Unicode 代码点映射到 HTML 实体名称的字典。
@end deffn

@subsubheading 备注


@node XML处理模块,xml etree ElementTree --- ElementTree XML API,html entities --- HTML 一般实体的定义,结构化标记处理工具
@anchor{library/xml doc}@anchor{2990}@anchor{library/xml module-xml}@anchor{133}@anchor{library/xml xml}@anchor{2991}@anchor{library/xml xml-processing-modules}@anchor{2992}
@subsection XML处理模块


@geindex xml (模块)

@strong{源码：} Lib/xml/@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/}


__________________________________________________________________


用于处理XML的Python接口分组在 @code{xml} 包中。

@cartouche
@quotation 警告 
XML 模块对于错误或恶意构造的数据是不安全的。 如果需要解析不受信任或未经身份验证的数据，请参阅 @ref{2993,,XML 漏洞} 和 @ref{2994,,defusedxml 和 defusedexpat 软件包} 部分。
@end quotation
@end cartouche

值得注意的是 @ref{133,,xml} 包中的模块要求至少有一个 SAX 兼容的 XML 解析器可用。在 Python 中包含 Expat 解析器，因此 @ref{138,,xml.parsers.expat} 模块将始终可用。

@ref{134,,xml.dom} 和 @ref{13b,,xml.sax} 包的文档是 DOM 和 SAX 接口的 Python 绑定的定义。

XML 处理子模块包括:


@itemize *

@item 
@ref{137,,xml.etree.ElementTree}： ElementTree API，一个简单而轻量级的XML处理器
@end itemize



@itemize *

@item 
@ref{134,,xml.dom}：DOM API 定义

@item 
@ref{135,,xml.dom.minidom}：最小的 DOM 实现

@item 
@ref{136,,xml.dom.pulldom}：支持构建部分 DOM 树
@end itemize



@itemize *

@item 
@ref{13b,,xml.sax}：SAX2 基类和便利函数

@item 
@ref{138,,xml.parsers.expat}：Expat解析器绑定
@end itemize

@menu
* XML 漏洞:: 
* defusedxml 和 defusedexpat 软件包:: 

@end menu

@node XML 漏洞,defusedxml 和 defusedexpat 软件包,,XML处理模块
@anchor{library/xml id1}@anchor{2995}@anchor{library/xml xml-vulnerabilities}@anchor{2993}
@subsubsection XML 漏洞


XML 处理模块对于恶意构造的数据是不安全的。 攻击者可能滥用 XML 功能来执行拒绝服务攻击、访问本地文件、生成与其它计算机的网络连接或绕过防火墙。

下表概述了已知的攻击以及各种模块是否容易受到攻击。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} 
@headitem

种类

@tab

sax

@tab

etree

@tab

minidom

@tab

pulldom

@tab

xmlrpc

@item

billion laughs

@tab

@strong{易受攻击}

@tab

@strong{易受攻击}

@tab

@strong{易受攻击}

@tab

@strong{易受攻击}

@tab

@strong{易受攻击}

@item

quadratic blowup

@tab

@strong{易受攻击}

@tab

@strong{易受攻击}

@tab

@strong{易受攻击}

@tab

@strong{易受攻击}

@tab

@strong{易受攻击}

@item

external entity expansion

@tab

安全 (4)

@tab

安全 (1)

@tab

安全 (2)

@tab

安全 (4)

@tab

安全 (3)

@item

DTD@footnote{https://en.wikipedia.org/wiki/Document_type_definition} retrieval

@tab

安全 (4)

@tab

安全

@tab

安全

@tab

安全 (4)

@tab

安全

@item

decompression bomb

@tab

安全

@tab

安全

@tab

安全

@tab

安全

@tab

@strong{易受攻击}

@end multitable



@enumerate 

@item 
@ref{137,,xml.etree.ElementTree} 不会扩展外部实体并在实体发生时引发 @code{ParserError}。

@item 
@ref{135,,xml.dom.minidom} 不会扩展外部实体，只是简单地返回未扩展的实体。

@item 
@code{xmlrpclib} 不扩展外部实体并省略它们。

@item 
从 Python 3.7.1 开始，默认情况下不再处理外部通用实体。
@end enumerate


@table @asis

@item billion laughs / exponential entity expansion （狂笑/递归实体扩展）

Billion Laughs@footnote{https://en.wikipedia.org/wiki/Billion_laughs} 攻击 -- 也称为递归实体扩展 -- 使用多级嵌套实体。 每个实体多次引用另一个实体，最终实体定义包含一个小字符串。 指数级扩展导致几千 GB 的文本，并消耗大量内存和 CPU 时间。

@item quadratic blowup entity expansion（二次爆炸实体扩展）

二次爆炸攻击类似于 Billion Laughs@footnote{https://en.wikipedia.org/wiki/Billion_laughs} 攻击，它也滥用实体扩展。 它不是嵌套实体，而是一遍又一遍地重复一个具有几千个字符的大型实体。攻击不如递归情况有效，但它避免触发禁止深度嵌套实体的解析器对策。

@item external entity expansion

实体声明可以包含的不仅仅是替换文本。 它们还可以指向外部资源或本地文件。 XML 解析器访问资源并将内容嵌入到 XML 文档中。

@item DTD@footnote{https://en.wikipedia.org/wiki/Document_type_definition} retrieval

Python 的一些 XML 库 @ref{136,,xml.dom.pulldom} 从远程或本地位置检索文档类型定义。 该功能与外部实体扩展问题具有相似的含义。

@item decompression bomb

Decompression bombs（解压炸弹，又名 ZIP bomb@footnote{https://en.wikipedia.org/wiki/Zip_bomb}）适用于所有可以解析压缩 XML 流（例如 gzip 压缩的 HTTP 流或 LZMA 压缩的文件）的 XML 库。 对于攻击者来说，它可以将传输的数据量减少三个量级或更多。
@end table

PyPI上 defusedxml@footnote{https://pypi.org/project/defusedxml/} 的文档包含有关所有已知攻击向量的更多信息以及示例和参考。

@node defusedxml 和 defusedexpat 软件包,,XML 漏洞,XML处理模块
@anchor{library/xml defused-packages}@anchor{2994}@anchor{library/xml the-defusedxml-and-defusedexpat-packages}@anchor{2996}
@subsubsection @code{defusedxml} 和 @code{defusedexpat} 软件包


defusedxml@footnote{https://pypi.org/project/defusedxml/} 是一个纯 Python 软件包，它修改了所有标准库 XML 解析器的子类，可以防止任何潜在的恶意操作。 对于解析不受信任的XML数据的任何服务器代码，建议使用此程序包。 该软件包还提供了有关更多 XML 漏洞（如 XPath 注入）的示例漏洞和扩展文档。

defusedexpat@footnote{https://pypi.org/project/defusedexpat/} 提供了一个修改过的 libexpat 和一个打过补丁的 @code{pyexpat} 模块，它有针对实体扩展DoS攻击的对策。 @code{defusedexpat} 模块仍然允许合理且可配置的实体扩展量。 这些修改可能包含在 Python 的某些未来版本中，但不会包含在 Python 的任何修复版本中，因为它们会破坏向后兼容性。

@node xml etree ElementTree --- ElementTree XML API,xml dom --- The Document Object Model API,XML处理模块,结构化标记处理工具
@anchor{library/xml etree elementtree doc}@anchor{2997}@anchor{library/xml etree elementtree dtd}@anchor{2998}@anchor{library/xml etree elementtree module-xml etree ElementTree}@anchor{137}@anchor{library/xml etree elementtree xml-etree-elementtree-the-elementtree-xml-api}@anchor{2999}
@subsection @code{xml.etree.ElementTree} ---  ElementTree XML API


@geindex xml.etree.ElementTree (模块)

@strong{源代码：} Lib/xml/etree/ElementTree.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/etree/ElementTree.py}


__________________________________________________________________


@ref{137,,xml.etree.ElementTree} 模块实现了一个简单高效的API，用于解析和创建XML数据。


在 3.3 版更改: 只要有可能，这个模块将使用快速实现。@code{xml.etree.cElementTree} 模块已弃用。


@cartouche
@quotation 警告 
@ref{137,,xml.etree.ElementTree} 模块对于恶意构建的数据是不安全的。如果需要解析不可信或未经身份验证的数据，请参见 @ref{2993,,XML 漏洞} 。
@end quotation
@end cartouche

@menu
* 教程:: 
* XPath支持:: 
* 参考: 参考<2>. 
* XInclude 支持:: 
* 参考: 参考<3>. 

@end menu

@node 教程,XPath支持,,xml etree ElementTree --- ElementTree XML API
@anchor{library/xml etree elementtree tutorial}@anchor{299a}
@subsubsection 教程


这是一个使用 @ref{137,,xml.etree.ElementTree} （简称 @code{ET} ）的简短教程。目标是演示模块的一些构建块和基本概念。

@menu
* XML树和元素:: 
* 解析XML:: 
* Pull API进行非阻塞解析:: 
* 查找感兴趣的元素:: 
* 修改XML文件:: 
* 构建XML文档:: 
* 使用命名空间解析XML:: 
* 其他资源: 其他资源<2>. 

@end menu

@node XML树和元素,解析XML,,教程
@anchor{library/xml etree elementtree xml-tree-and-elements}@anchor{299b}
@subsubsection XML树和元素


XML是一种固有的分层数据格式，最自然的表示方法是使用树。为此， @code{ET} 有两个类： @ref{911,,ElementTree} 将整个XML文档表示为一个树， @ref{abf,,Element} 表示该树中的单个节点。与整个文档的交互（读写文件）通常在 @ref{911,,ElementTree} 级别完成。与单个XML元素及其子元素的交互是在 @ref{abf,,Element} 级别完成的。

@node 解析XML,Pull API进行非阻塞解析,XML树和元素,教程
@anchor{library/xml etree elementtree elementtree-parsing-xml}@anchor{299c}@anchor{library/xml etree elementtree parsing-xml}@anchor{299d}
@subsubsection 解析XML


我们将使用以下XML文档作为本节的示例数据：

@example
<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank>1</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank>4</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
    <country name="Panama">
        <rank>68</rank>
        <year>2011</year>
        <gdppc>13600</gdppc>
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>
@end example

可以通过从文件中读取来导入此数据：

@example
import xml.etree.ElementTree as ET
tree = ET.parse('country_data.xml')
root = tree.getroot()
@end example

或直接从字符串中解析：

@example
root = ET.fromstring(country_data_as_string)
@end example

@ref{299e,,fromstring()} 将XML从字符串直接解析为 @ref{abf,,Element} ，该元素是已解析树的根元素。其他解析函数可能会创建一个 @ref{911,,ElementTree} 。确切信息请查阅文档。

作为 @ref{abf,,Element} ， @code{root} 具有标签和属性字典:

@example
>>> root.tag
'data'
>>> root.attrib
@{@}
@end example

还有可以迭代的子节点：

@example
>>> for child in root:
...     print(child.tag, child.attrib)
...
country @{'name': 'Liechtenstein'@}
country @{'name': 'Singapore'@}
country @{'name': 'Panama'@}
@end example

子级是可以嵌套的，我们可以通过索引访问特定的子级节点：

@example
>>> root[0][1].text
'2008'
@end example

@cartouche
@quotation 注解 
并非XML输入的所有元素都将作为解析树的元素结束。目前，此模块跳过输入中的任何XML注释、处理指令和文档类型声明。然而，使用这个模块的API而不是从XML文本解析构建的树可以包含注释和处理指令，生成XML输出时同样包含这些注释和处理指令。可以通过将自定义 @ref{253,,TreeBuilder} 实例传递给 @ref{252,,XMLParser} 构造函数来访问文档类型声明。
@end quotation
@end cartouche

@node Pull API进行非阻塞解析,查找感兴趣的元素,解析XML,教程
@anchor{library/xml etree elementtree elementtree-pull-parsing}@anchor{90e}@anchor{library/xml etree elementtree pull-api-for-non-blocking-parsing}@anchor{299f}
@subsubsection Pull API进行非阻塞解析


Most parsing functions provided by this module require the whole document
to be read at once before returning any result.  It is possible to use an
@ref{252,,XMLParser} and feed data into it incrementally, but it is a push API that
calls methods on a callback target, which is too low-level and inconvenient for
most needs.  Sometimes what the user really wants is to be able to parse XML
incrementally, without blocking operations, while enjoying the convenience of
fully constructed @ref{abf,,Element} objects.

The most powerful tool for doing this is @ref{90d,,XMLPullParser}.  It does not
require a blocking read to obtain the XML data, and is instead fed with data
incrementally with @ref{29a0,,XMLPullParser.feed()} calls.  To get the parsed XML
elements, call @ref{29a1,,XMLPullParser.read_events()}.  Here is an example:

@example
>>> parser = ET.XMLPullParser(['start', 'end'])
>>> parser.feed('<mytag>sometext')
>>> list(parser.read_events())
[('start', <Element 'mytag' at 0x7fa66db2be58>)]
>>> parser.feed(' more text</mytag>')
>>> for event, elem in parser.read_events():
...     print(event)
...     print(elem.tag, 'text=', elem.text)
...
end
@end example

The obvious use case is applications that operate in a non-blocking fashion
where the XML data is being received from a socket or read incrementally from
some storage device.  In such cases, blocking reads are unacceptable.

Because it's so flexible, @ref{90d,,XMLPullParser} can be inconvenient to use for
simpler use-cases.  If you don't mind your application blocking on reading XML
data but would still like to have incremental parsing capabilities, take a look
at @ref{942,,iterparse()}.  It can be useful when you're reading a large XML document
and don't want to hold it wholly in memory.

@node 查找感兴趣的元素,修改XML文件,Pull API进行非阻塞解析,教程
@anchor{library/xml etree elementtree finding-interesting-elements}@anchor{29a2}
@subsubsection 查找感兴趣的元素


@ref{abf,,Element} 有一些很有效的方法，可帮助递归遍历其下的所有子树（包括子级，子级的子级，等等）。例如 @ref{ce0,,Element.iter()}:

@example
>>> for neighbor in root.iter('neighbor'):
...     print(neighbor.attrib)
...
@{'name': 'Austria', 'direction': 'E'@}
@{'name': 'Switzerland', 'direction': 'W'@}
@{'name': 'Malaysia', 'direction': 'N'@}
@{'name': 'Costa Rica', 'direction': 'W'@}
@{'name': 'Colombia', 'direction': 'E'@}
@end example

@ref{29a3,,Element.findall()} 仅查找当前元素的直接子元素中带有指定标签的元素。 @ref{29a4,,Element.find()} 找带有特定标签的 @emph{第一个} 子级，然后可以用 @ref{29a5,,Element.text} 访问元素的文本内容。 @ref{29a6,,Element.get} 访问元素的属性:

@example
>>> for country in root.findall('country'):
...     rank = country.find('rank').text
...     name = country.get('name')
...     print(name, rank)
...
Liechtenstein 1
Singapore 4
Panama 68
@end example

通过使用 @ref{412,,XPath} ，可以更精确地指定要查找的元素。

@node 修改XML文件,构建XML文档,查找感兴趣的元素,教程
@anchor{library/xml etree elementtree modifying-an-xml-file}@anchor{29a7}
@subsubsection 修改XML文件


@ref{911,,ElementTree} 提供了一种构建XML文档并将其写入文件的简单方法。调用 @ref{912,,ElementTree.write()} 方法就可以实现。

创建后可以直接操作 @ref{abf,,Element} 对象。例如：使用 @ref{29a5,,Element.text} 修改文本字段，使用 @ref{29a8,,Element.set()} 方法添加和修改属性，以及使用  @ref{29a9,,Element.append()} 添加新的子元素。

假设我们要为每个国家/地区的中添加一个排名，并在排名元素中添加一个 @code{updated} 属性：

@example
>>> for rank in root.iter('rank'):
...     new_rank = int(rank.text) + 1
...     rank.text = str(new_rank)
...     rank.set('updated', 'yes')
...
>>> tree.write('output.xml')
@end example

生成的XML现在看起来像这样：

@example
<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank updated="yes">2</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank updated="yes">5</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
    <country name="Panama">
        <rank updated="yes">69</rank>
        <year>2011</year>
        <gdppc>13600</gdppc>
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>
@end example

可以使用 @ref{29aa,,Element.remove()} 删除元素。假设我们要删除排名高于50的所有国家/地区:

@example
>>> for country in root.findall('country'):
...     rank = int(country.find('rank').text)
...     if rank > 50:
...         root.remove(country)
...
>>> tree.write('output.xml')
@end example

生成的XML现在看起来像这样：

@example
<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank updated="yes">2</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank updated="yes">5</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
</data>
@end example

@node 构建XML文档,使用命名空间解析XML,修改XML文件,教程
@anchor{library/xml etree elementtree building-xml-documents}@anchor{29ab}
@subsubsection 构建XML文档


@ref{29ac,,SubElement()} 函数还提供了一种便捷方法来为给定元素创建新的子元素:

@example
>>> a = ET.Element('a')
>>> b = ET.SubElement(a, 'b')
>>> c = ET.SubElement(a, 'c')
>>> d = ET.SubElement(c, 'd')
>>> ET.dump(a)
<a><b /><c><d /></c></a>
@end example

@node 使用命名空间解析XML,其他资源<2>,构建XML文档,教程
@anchor{library/xml etree elementtree parsing-xml-with-namespaces}@anchor{29ad}
@subsubsection 使用命名空间解析XML


If the XML input has namespaces@footnote{https://en.wikipedia.org/wiki/XML_namespace}, tags and attributes
with prefixes in the form @code{prefix:sometag} get expanded to
@code{@{uri@}sometag} where the @emph{prefix} is replaced by the full @emph{URI}.
Also, if there is a default namespace@footnote{https://www.w3.org/TR/xml-names/#defaulting},
that full URI gets prepended to all of the non-prefixed tags.

Here is an XML example that incorporates two namespaces, one with the
prefix "fictional" and the other serving as the default namespace:

@example
<?xml version="1.0"?>
<actors xmlns:fictional="http://characters.example.com"
        xmlns="http://people.example.com">
    <actor>
        <name>John Cleese</name>
        <fictional:character>Lancelot</fictional:character>
        <fictional:character>Archie Leach</fictional:character>
    </actor>
    <actor>
        <name>Eric Idle</name>
        <fictional:character>Sir Robin</fictional:character>
        <fictional:character>Gunther</fictional:character>
        <fictional:character>Commander Clement</fictional:character>
    </actor>
</actors>
@end example

One way to search and explore this XML example is to manually add the
URI to every tag or attribute in the xpath of a
@ref{29a4,,find()} or @ref{29a3,,findall()}:

@example
root = fromstring(xml_text)
for actor in root.findall('@{http://people.example.com@}actor'):
    name = actor.find('@{http://people.example.com@}name')
    print(name.text)
    for char in actor.findall('@{http://characters.example.com@}character'):
        print(' |-->', char.text)
@end example

A better way to search the namespaced XML example is to create a
dictionary with your own prefixes and use those in the search functions:

@example
ns = @{'real_person': 'http://people.example.com',
      'role': 'http://characters.example.com'@}

for actor in root.findall('real_person:actor', ns):
    name = actor.find('real_person:name', ns)
    print(name.text)
    for char in actor.findall('role:character', ns):
        print(' |-->', char.text)
@end example

These two approaches both output:

@example
John Cleese
 |--> Lancelot
 |--> Archie Leach
Eric Idle
 |--> Sir Robin
 |--> Gunther
 |--> Commander Clement
@end example

@node 其他资源<2>,,使用命名空间解析XML,教程
@anchor{library/xml etree elementtree additional-resources}@anchor{29ae}
@subsubsection 其他资源


See @indicateurl{http://effbot.org/zone/element-index.htm} for tutorials and links to other
docs.

@node XPath支持,参考<2>,教程,xml etree ElementTree --- ElementTree XML API
@anchor{library/xml etree elementtree elementtree-xpath}@anchor{412}@anchor{library/xml etree elementtree xpath-support}@anchor{29af}
@subsubsection XPath支持


This module provides limited support for
XPath expressions@footnote{https://www.w3.org/TR/xpath} for locating elements in a
tree.  The goal is to support a small subset of the abbreviated syntax; a full
XPath engine is outside the scope of the module.

@menu
* 示例: 示例<10>. 
* 支持的XPath语法:: 

@end menu

@node 示例<10>,支持的XPath语法,,XPath支持
@anchor{library/xml etree elementtree example}@anchor{29b0}
@subsubsection 示例


Here's an example that demonstrates some of the XPath capabilities of the
module.  We'll be using the @code{countrydata} XML document from the
@ref{299c,,Parsing XML} section:

@example
import xml.etree.ElementTree as ET

root = ET.fromstring(countrydata)

# Top-level elements
root.findall(".")

# All 'neighbor' grand-children of 'country' children of the top-level
# elements
root.findall("./country/neighbor")

# Nodes with name='Singapore' that have a 'year' child
root.findall(".//year/..[@@name='Singapore']")

# 'year' nodes that are children of nodes with name='Singapore'
root.findall(".//*[@@name='Singapore']/year")

# All 'neighbor' nodes that are the second child of their parent
root.findall(".//neighbor[2]")
@end example

For XML with namespaces, use the usual qualified @code{@{namespace@}tag} notation:

@example
# All dublin-core "title" tags in the document
root.findall(".//@{http://purl.org/dc/elements/1.1/@}title")
@end example

@node 支持的XPath语法,,示例<10>,XPath支持
@anchor{library/xml etree elementtree supported-xpath-syntax}@anchor{29b1}
@subsubsection 支持的XPath语法



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

语法

@tab

含义

@item

@code{tag}

@tab

Selects all child elements with the given tag.
For example, @code{spam} selects all child elements
named @code{spam}, and @code{spam/egg} selects all
grandchildren named @code{egg} in all children named
@code{spam}.  @code{@{namespace@}*} selects all tags in the
given namespace, @code{@{*@}spam} selects tags named
@code{spam} in any (or no) namespace, and @code{@{@}*}
only selects tags that are not in a namespace.


在 3.8 版更改: Support for star-wildcards was added.


@item

@code{*}

@tab

选择所有子元素，包括注释和处理说明。例如 @code{*/egg} 选择所有名为 @code{egg} 的孙元素。

@item

@code{.}

@tab

选择当前节点。这在路径的开头非常有用，用于指示它是相对路径。

@item

@code{//}

@tab

Selects all subelements, on all levels beneath the
current  element.  For example, @code{.//egg} selects
all @code{egg} elements in the entire tree.

@item

@code{..}

@tab

Selects the parent element.  Returns @code{None} if the
path attempts to reach the ancestors of the start
element (the element @code{find} was called on).

@item

@code{[@@attrib]}

@tab

选择具有给定属性的所有元素。

@item

@code{[@@attrib='value']}

@tab

选择给定属性具有给定值的所有元素。该值不能包含引号。

@item

@code{[tag]}

@tab

选择所有包含 @code{tag} 子元素的元素。只支持直系子元素。

@item

@code{[.='text']}

@tab

选择完整文本内容等于 @code{text} 的所有元素（包括后代）。


3.7 新版功能.


@item

@code{[tag='text']}

@tab

选择所有包含名为 @code{tag} 的子元素的元素，这些子元素（包括后代）的完整文本内容等于给定的 @code{text} 。

@item

@code{[position]}

@tab

Selects all elements that are located at the given
position.  The position can be either an integer
(1 is the first position), the expression @code{last()}
(for the last position), or a position relative to
the last position (e.g. @code{last()-1}).

@end multitable


谓词（方括号内的表达式）之前必须带有标签名称，星号或其他谓词。@code{position} 谓词前必须有标签名称。

@node 参考<2>,XInclude 支持,XPath支持,xml etree ElementTree --- ElementTree XML API
@anchor{library/xml etree elementtree reference}@anchor{29b2}
@subsubsection 参考


@menu
* 函数: 函数<6>. 

@end menu

@node 函数<6>,,,参考<2>
@anchor{library/xml etree elementtree elementtree-functions}@anchor{29b3}@anchor{library/xml etree elementtree functions}@anchor{29b4}
@subsubsection 函数


@geindex canonicalize() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree canonicalize}@anchor{29b5}
@deffn {函数} xml.etree.ElementTree.canonicalize (xml_data=None, *, out=None, from_file=None, **options)

C14N 2.0@footnote{https://www.w3.org/TR/xml-c14n2/}  转换功能。.

Canonicalization is a way to normalise XML output in a way that allows
byte-by-byte comparisons and digital signatures.  It reduced the freedom
that XML serializers have and instead generates a more constrained XML
representation.  The main restrictions regard the placement of namespace
declarations, the ordering of attributes, and ignorable whitespace.

This function takes an XML data string (@emph{xml_data}) or a file path or
file-like object (@emph{from_file}) as input, converts it to the canonical
form, and writes it out using the @emph{out} file(-like) object, if provided,
or returns it as a text string if not.  The output file receives text,
not bytes.  It should therefore be opened in text mode with @code{utf-8}
encoding.

典型使用:

@example
xml_data = "<root>...</root>"
print(canonicalize(xml_data))

with open("c14n_output.xml", mode='w', encoding='utf-8') as out_file:
    canonicalize(xml_data, out=out_file)

with open("c14n_output.xml", mode='w', encoding='utf-8') as out_file:
    canonicalize(from_file="inputfile.xml", out=out_file)
@end example

The configuration @emph{options} are as follows:


@itemize -

@item 
@emph{with_comments}: set to true to include comments (default: false)

@item 

@table @asis

@item @emph{strip_text}: set to true to strip whitespace before and after text content

（默认值：否）
@end table

@item 

@table @asis

@item @emph{rewrite_prefixes}: set to true to replace namespace prefixes by "n@{number@}"

（默认值：否）
@end table

@item 

@table @asis

@item @emph{qname_aware_tags}: a set of qname aware tag names in which prefixes

should be replaced in text content (default: empty)
@end table

@item 

@table @asis

@item @emph{qname_aware_attrs}: a set of qname aware attribute names in which prefixes

should be replaced in text content (default: empty)
@end table

@item 
@emph{exclude_attrs}: a set of attribute names that should not be serialised

@item 
@emph{exclude_tags}: a set of tag names that should not be serialised
@end itemize

In the option list above, "a set" refers to any collection or iterable of
strings, no ordering is expected.


3.8 新版功能.

@end deffn

@geindex Comment() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree Comment}@anchor{29b6}
@deffn {函数} xml.etree.ElementTree.Comment (text=None)

Comment element factory.  This factory function creates a special element
that will be serialized as an XML comment by the standard serializer.  The
comment string can be either a bytestring or a Unicode string.  @emph{text} is a
string containing the comment string.  Returns an element instance
representing a comment.

Note that @ref{252,,XMLParser} skips over comments in the input
instead of creating comment objects for them. An @ref{911,,ElementTree} will
only contain comment nodes if they have been inserted into to
the tree using one of the @ref{abf,,Element} methods.
@end deffn

@geindex dump() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree dump}@anchor{29b7}
@deffn {函数} xml.etree.ElementTree.dump (elem)

Writes an element tree or element structure to sys.stdout.  This function
should be used for debugging only.

The exact output format is implementation dependent.  In this version, it's
written as an ordinary XML file.

@emph{elem} is an element tree or an individual element.


在 3.8 版更改: The @ref{29b7,,dump()} function now preserves the attribute order specified
by the user.

@end deffn

@geindex fromstring() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree fromstring}@anchor{299e}
@deffn {函数} xml.etree.ElementTree.fromstring (text, parser=None)

Parses an XML section from a string constant.  Same as @ref{29b8,,XML()}.  @emph{text}
is a string containing XML data.  @emph{parser} is an optional parser instance.
If not given, the standard @ref{252,,XMLParser} parser is used.
Returns an @ref{abf,,Element} instance.
@end deffn

@geindex fromstringlist() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree fromstringlist}@anchor{b48}
@deffn {函数} xml.etree.ElementTree.fromstringlist (sequence, parser=None)

Parses an XML document from a sequence of string fragments.  @emph{sequence} is a
list or other sequence containing XML data fragments.  @emph{parser} is an
optional parser instance.  If not given, the standard @ref{252,,XMLParser}
parser is used.  Returns an @ref{abf,,Element} instance.


3.2 新版功能.

@end deffn

@geindex iselement() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree iselement}@anchor{29b9}
@deffn {函数} xml.etree.ElementTree.iselement (element)

Check if an object appears to be a valid element object.  @emph{element} is an
element instance.  Return @code{True} if this is an element object.
@end deffn

@geindex iterparse() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree iterparse}@anchor{942}
@deffn {函数} xml.etree.ElementTree.iterparse (source, events=None, parser=None)

Parses an XML section into an element tree incrementally, and reports what's
going on to the user.  @emph{source} is a filename or @ref{b3b,,file object}
containing XML data.  @emph{events} is a sequence of events to report back.  The
supported events are the strings @code{"start"}, @code{"end"}, @code{"comment"},
@code{"pi"}, @code{"start-ns"} and @code{"end-ns"}
(the "ns" events are used to get detailed namespace
information).  If @emph{events} is omitted, only @code{"end"} events are reported.
@emph{parser} is an optional parser instance.  If not given, the standard
@ref{252,,XMLParser} parser is used.  @emph{parser} must be a subclass of
@ref{252,,XMLParser} and can only use the default @ref{253,,TreeBuilder} as a
target.  Returns an @ref{fce,,iterator} providing @code{(event, elem)} pairs.

Note that while @ref{942,,iterparse()} builds the tree incrementally, it issues
blocking reads on @emph{source} (or the file it names).  As such, it's unsuitable
for applications where blocking reads can't be made.  For fully non-blocking
parsing, see @ref{90d,,XMLPullParser}.

@cartouche
@quotation 注解 
@ref{942,,iterparse()} only guarantees that it has seen the ">" character of a
starting tag when it emits a "start" event, so the attributes are defined,
but the contents of the text and tail attributes are undefined at that
point.  The same applies to the element children; they may or may not be
present.

If you need a fully populated element, look for "end" events instead.
@end quotation
@end cartouche


3.4 版后已移除: @emph{parser} 参数。



在 3.8 版更改: The @code{comment} and @code{pi} events were added.

@end deffn

@geindex parse() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree parse}@anchor{29ba}
@deffn {函数} xml.etree.ElementTree.parse (source, parser=None)

Parses an XML section into an element tree.  @emph{source} is a filename or file
object containing XML data.  @emph{parser} is an optional parser instance.  If
not given, the standard @ref{252,,XMLParser} parser is used.  Returns an
@ref{911,,ElementTree} instance.
@end deffn

@geindex ProcessingInstruction() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree ProcessingInstruction}@anchor{29bb}
@deffn {函数} xml.etree.ElementTree.ProcessingInstruction (target, text=None)

PI element factory.  This factory function creates a special element that
will be serialized as an XML processing instruction.  @emph{target} is a string
containing the PI target.  @emph{text} is a string containing the PI contents, if
given.  Returns an element instance, representing a processing instruction.

Note that @ref{252,,XMLParser} skips over processing instructions
in the input instead of creating comment objects for them. An
@ref{911,,ElementTree} will only contain processing instruction nodes if
they have been inserted into to the tree using one of the
@ref{abf,,Element} methods.
@end deffn

@geindex register_namespace() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree register_namespace}@anchor{b49}
@deffn {函数} xml.etree.ElementTree.register_namespace (prefix, uri)

Registers a namespace prefix.  The registry is global, and any existing
mapping for either the given prefix or the namespace URI will be removed.
@emph{prefix} is a namespace prefix.  @emph{uri} is a namespace uri.  Tags and
attributes in this namespace will be serialized with the given prefix, if at
all possible.


3.2 新版功能.

@end deffn

@geindex SubElement() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree SubElement}@anchor{29ac}
@deffn {函数} xml.etree.ElementTree.SubElement (parent, tag, attrib=@{@}, **extra)

Subelement factory.  This function creates an element instance, and appends
it to an existing element.

The element name, attribute names, and attribute values can be either
bytestrings or Unicode strings.  @emph{parent} is the parent element.  @emph{tag} is
the subelement name.  @emph{attrib} is an optional dictionary, containing element
attributes.  @emph{extra} contains additional attributes, given as keyword
arguments.  Returns an element instance.
@end deffn

@geindex tostring() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree tostring}@anchor{90f}
@deffn {函数} xml.etree.ElementTree.tostring (element, encoding="us-ascii", method="xml", *, xml_declaration=None, default_namespace=None, short_empty_elements=True)

Generates a string representation of an XML element, including all
subelements.  @emph{element} is an @ref{abf,,Element} instance.  @emph{encoding} @footnote{@w{(1)} 
The encoding string included in XML output should conform to the
appropriate standards.  For example, "UTF-8" is valid, but "UTF8" is
not.  See @indicateurl{https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl}
and @indicateurl{https://www.iana.org/assignments/character-sets/character-sets.xhtml}.
} is
the output encoding (default is US-ASCII).  Use @code{encoding="unicode"} to
generate a Unicode string (otherwise, a bytestring is generated).  @emph{method}
is either @code{"xml"}, @code{"html"} or @code{"text"} (default is @code{"xml"}).
@emph{xml_declaration}, @emph{default_namespace} and @emph{short_empty_elements} has the same
meaning as in @ref{912,,ElementTree.write()}. Returns an (optionally) encoded string
containing the XML data.


3.4 新版功能: @emph{short_empty_elements} 形参。



3.8 新版功能: The @emph{xml_declaration} and @emph{default_namespace} parameters.



在 3.8 版更改: The @ref{90f,,tostring()} function now preserves the attribute order
specified by the user.

@end deffn

@geindex tostringlist() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree tostringlist}@anchor{910}
@deffn {函数} xml.etree.ElementTree.tostringlist (element, encoding="us-ascii", method="xml", *, xml_declaration=None, default_namespace=None, short_empty_elements=True)

Generates a string representation of an XML element, including all
subelements.  @emph{element} is an @ref{abf,,Element} instance.  @emph{encoding} @footnote{@w{(1)} 
The encoding string included in XML output should conform to the
appropriate standards.  For example, "UTF-8" is valid, but "UTF8" is
not.  See @indicateurl{https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl}
and @indicateurl{https://www.iana.org/assignments/character-sets/character-sets.xhtml}.
} is
the output encoding (default is US-ASCII).  Use @code{encoding="unicode"} to
generate a Unicode string (otherwise, a bytestring is generated).  @emph{method}
is either @code{"xml"}, @code{"html"} or @code{"text"} (default is @code{"xml"}).
@emph{xml_declaration}, @emph{default_namespace} and @emph{short_empty_elements} has the same
meaning as in @ref{912,,ElementTree.write()}. Returns a list of (optionally) encoded
strings containing the XML data. It does not guarantee any specific sequence,
except that @code{b"".join(tostringlist(element)) == tostring(element)}.


3.2 新版功能.



3.4 新版功能: @emph{short_empty_elements} 形参。



3.8 新版功能: The @emph{xml_declaration} and @emph{default_namespace} parameters.



在 3.8 版更改: The @ref{910,,tostringlist()} function now preserves the attribute order
specified by the user.

@end deffn

@geindex XML() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree XML}@anchor{29b8}
@deffn {函数} xml.etree.ElementTree.XML (text, parser=None)

Parses an XML section from a string constant.  This function can be used to
embed "XML literals" in Python code.  @emph{text} is a string containing XML
data.  @emph{parser} is an optional parser instance.  If not given, the standard
@ref{252,,XMLParser} parser is used.  Returns an @ref{abf,,Element} instance.
@end deffn

@geindex XMLID() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree XMLID}@anchor{29bc}
@deffn {函数} xml.etree.ElementTree.XMLID (text, parser=None)

Parses an XML section from a string constant, and also returns a dictionary
which maps from element id:s to elements.  @emph{text} is a string containing XML
data.  @emph{parser} is an optional parser instance.  If not given, the standard
@ref{252,,XMLParser} parser is used.  Returns a tuple containing an
@ref{abf,,Element} instance and a dictionary.
@end deffn

@node XInclude 支持,参考<3>,参考<2>,xml etree ElementTree --- ElementTree XML API
@anchor{library/xml etree elementtree elementtree-xinclude}@anchor{29bd}@anchor{library/xml etree elementtree xinclude-support}@anchor{29be}
@subsubsection XInclude 支持


This module provides limited support for
XInclude directives@footnote{https://www.w3.org/TR/xinclude/}, via the @code{xml.etree.ElementInclude} helper module.  This module can be used to insert subtrees and text strings into element trees, based on information in the tree.

@menu
* 示例: 示例<11>. 

@end menu

@node 示例<11>,,,XInclude 支持
@anchor{library/xml etree elementtree id3}@anchor{29bf}
@subsubsection 示例


Here's an example that demonstrates use of the XInclude module. To include an XML document in the current document, use the @code{@{http://www.w3.org/2001/XInclude@}include} element and set the @strong{parse} attribute to @code{"xml"}, and use the @strong{href} attribute to specify the document to include.

@example
<?xml version="1.0"?>
<document xmlns:xi="http://www.w3.org/2001/XInclude">
  <xi:include href="source.xml" parse="xml" />
</document>
@end example

By default, the @strong{href} attribute is treated as a file name. You can use custom loaders to override this behaviour. Also note that the standard helper does not support XPointer syntax.

To process this file, load it as usual, and pass the root element to the @ref{137,,xml.etree.ElementTree} module:

@example
from xml.etree import ElementTree, ElementInclude

tree = ElementTree.parse("document.xml")
root = tree.getroot()

ElementInclude.include(root)
@end example

The ElementInclude module replaces the @code{@{http://www.w3.org/2001/XInclude@}include} element with the root element from the @strong{source.xml} document. The result might look something like this:

@example
<document xmlns:xi="http://www.w3.org/2001/XInclude">
  <para>This is a paragraph.</para>
</document>
@end example

If the @strong{parse} attribute is omitted, it defaults to "xml". The href attribute is required.

To include a text document, use the @code{@{http://www.w3.org/2001/XInclude@}include} element, and set the @strong{parse} attribute to "text":

@example
<?xml version="1.0"?>
<document xmlns:xi="http://www.w3.org/2001/XInclude">
  Copyright (c) <xi:include href="year.txt" parse="text" />.
</document>
@end example

结果可能如下所示：

@example
<document xmlns:xi="http://www.w3.org/2001/XInclude">
  Copyright (c) 2003.
</document>
@end example

@node 参考<3>,,XInclude 支持,xml etree ElementTree --- ElementTree XML API
@anchor{library/xml etree elementtree id4}@anchor{29c0}
@subsubsection 参考


@menu
* 函数: 函数<7>. 
* 元素对象:: 
* ElementTree 对象:: 
* QName Objects:: 
* TreeBuilder Objects:: 
* XMLParser对象:: 
* XMLPullParser对象:: 
* 异常: 异常<15>. 

@end menu

@node 函数<7>,元素对象,,参考<3>
@anchor{library/xml etree elementtree elementinclude-functions}@anchor{29c1}@anchor{library/xml etree elementtree id5}@anchor{29c2}
@subsubsection 函数


@geindex xml.etree.ElementInclude.default_loader() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree xml etree ElementInclude default_loader}@anchor{29c3}
@deffn {函数} xml.etree.ElementInclude.default_loader (href, parse, encoding=None)

Default loader. This default loader reads an included resource from disk.  @emph{href} is a URL.
@emph{parse} is for parse mode either "xml" or "text".  @emph{encoding}
is an optional text encoding.  If not given, encoding is @code{utf-8}.  Returns the
expanded resource.  If the parse mode is @code{"xml"}, this is an ElementTree
instance.  If the parse mode is "text", this is a Unicode string.  If the
loader fails, it can return None or raise an exception.
@end deffn

@geindex xml.etree.ElementInclude.include() (在 xml.etree.ElementTree 模块中)
@anchor{library/xml etree elementtree xml etree ElementTree xml etree ElementInclude include}@anchor{29c4}
@deffn {函数} xml.etree.ElementInclude.include (elem, loader=None)

This function expands XInclude directives.  @emph{elem} is the root element.  @emph{loader} is
an optional resource loader.  If omitted, it defaults to @ref{29c3,,default_loader()}.
If given, it should be a callable that implements the same interface as
@ref{29c3,,default_loader()}.  Returns the expanded resource.  If the parse mode is
@code{"xml"}, this is an ElementTree instance.  If the parse mode is "text",
this is a Unicode string.  If the loader fails, it can return None or
raise an exception.
@end deffn

@node 元素对象,ElementTree 对象,函数<7>,参考<3>
@anchor{library/xml etree elementtree element-objects}@anchor{29c5}@anchor{library/xml etree elementtree elementtree-element-objects}@anchor{29c6}
@subsubsection 元素对象


@geindex Element (xml.etree.ElementTree 中的类)
@anchor{library/xml etree elementtree xml etree ElementTree Element}@anchor{abf}
@deffn {类} xml.etree.ElementTree.Element (tag, attrib=@{@}, **extra)

Element class.  This class defines the Element interface, and provides a
reference implementation of this interface.

The element name, attribute names, and attribute values can be either
bytestrings or Unicode strings.  @emph{tag} is the element name.  @emph{attrib} is
an optional dictionary, containing element attributes.  @emph{extra} contains
additional attributes, given as keyword arguments.

@geindex tag (xml.etree.ElementTree.Element 属性)
@anchor{library/xml etree elementtree xml etree ElementTree Element tag}@anchor{29c7}
@deffn {属性} tag

一个标识此元素意味着何种数据的字符串(换句话说，元素类型)。
@end deffn

@geindex text (xml.etree.ElementTree.Element 属性)
@geindex tail (xml.etree.ElementTree.Element 属性)
@anchor{library/xml etree elementtree xml etree ElementTree Element text}@anchor{29a5}
@deffn {属性} text
@anchor{library/xml etree elementtree xml etree ElementTree Element tail}@anchor{29c8}
@deffnx {属性} tail

These attributes can be used to hold additional data associated with
the element.  Their values are usually strings but may be any
application-specific object.  If the element is created from
an XML file, the @emph{text} attribute holds either the text between
the element's start tag and its first child or end tag, or @code{None}, and
the @emph{tail} attribute holds either the text between the element's
end tag and the next tag, or @code{None}.  For the XML data

@example
<a><b>1<c>2<d/>3</c></b>4</a>
@end example

the @emph{a} element has @code{None} for both @emph{text} and @emph{tail} attributes,
the @emph{b} element has @emph{text} @code{"1"} and @emph{tail} @code{"4"},
the @emph{c} element has @emph{text} @code{"2"} and @emph{tail} @code{None},
and the @emph{d} element has @emph{text} @code{None} and @emph{tail} @code{"3"}.

To collect the inner text of an element, see @ref{b4c,,itertext()}, for
example @code{"".join(element.itertext())}.

Applications may store arbitrary objects in these attributes.
@end deffn

@geindex attrib (xml.etree.ElementTree.Element 属性)
@anchor{library/xml etree elementtree xml etree ElementTree Element attrib}@anchor{29c9}
@deffn {属性} attrib

A dictionary containing the element's attributes.  Note that while the
@emph{attrib} value is always a real mutable Python dictionary, an ElementTree
implementation may choose to use another internal representation, and
create the dictionary only if someone asks for it.  To take advantage of
such implementations, use the dictionary methods below whenever possible.
@end deffn

The following dictionary-like methods work on the element attributes.

@geindex clear() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element clear}@anchor{29ca}
@deffn {方法} clear ()

Resets an element.  This function removes all subelements, clears all
attributes, and sets the text and tail attributes to @code{None}.
@end deffn

@geindex get() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element get}@anchor{29a6}
@deffn {方法} get (key, default=None)

Gets the element attribute named @emph{key}.

Returns the attribute value, or @emph{default} if the attribute was not found.
@end deffn

@geindex items() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element items}@anchor{29cb}
@deffn {方法} items ()

Returns the element attributes as a sequence of (name, value) pairs.  The
attributes are returned in an arbitrary order.
@end deffn

@geindex keys() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element keys}@anchor{29cc}
@deffn {方法} keys ()

Returns the elements attribute names as a list.  The names are returned
in an arbitrary order.
@end deffn

@geindex set() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element set}@anchor{29a8}
@deffn {方法} set (key, value)

Set the attribute @emph{key} on the element to @emph{value}.
@end deffn

The following methods work on the element's children (subelements).

@geindex append() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element append}@anchor{29a9}
@deffn {方法} append (subelement)

Adds the element @emph{subelement} to the end of this element's internal list
of subelements.  Raises @ref{192,,TypeError} if @emph{subelement} is not an
@ref{abf,,Element}.
@end deffn

@geindex extend() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element extend}@anchor{b4a}
@deffn {方法} extend (subelements)

Appends @emph{subelements} from a sequence object with zero or more elements.
Raises @ref{192,,TypeError} if a subelement is not an @ref{abf,,Element}.


3.2 新版功能.

@end deffn

@geindex find() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element find}@anchor{29a4}
@deffn {方法} find (match, namespaces=None)

Finds the first subelement matching @emph{match}.  @emph{match} may be a tag name
or a @ref{412,,path}.  Returns an element instance
or @code{None}.  @emph{namespaces} is an optional mapping from namespace prefix
to full name.  Pass @code{'@w{'}} as prefix to move all unprefixed tag names
in the expression into the given namespace.
@end deffn

@geindex findall() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element findall}@anchor{29a3}
@deffn {方法} findall (match, namespaces=None)

Finds all matching subelements, by tag name or
@ref{412,,path}.  Returns a list containing all matching
elements in document order.  @emph{namespaces} is an optional mapping from
namespace prefix to full name.  Pass @code{'@w{'}} as prefix to move all
unprefixed tag names in the expression into the given namespace.
@end deffn

@geindex findtext() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element findtext}@anchor{29cd}
@deffn {方法} findtext (match, default=None, namespaces=None)

Finds text for the first subelement matching @emph{match}.  @emph{match} may be
a tag name or a @ref{412,,path}.  Returns the text content
of the first matching element, or @emph{default} if no element was found.
Note that if the matching element has no text content an empty string
is returned. @emph{namespaces} is an optional mapping from namespace prefix
to full name.  Pass @code{'@w{'}} as prefix to move all unprefixed tag names
in the expression into the given namespace.
@end deffn

@geindex getchildren() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element getchildren}@anchor{29ce}
@deffn {方法} getchildren ()


Deprecated since version 3.2, will be removed in version 3.9: Use @code{list(elem)} or iteration.

@end deffn

@geindex getiterator() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element getiterator}@anchor{29cf}
@deffn {方法} getiterator (tag=None)


Deprecated since version 3.2, will be removed in version 3.9: Use method @ref{ce0,,Element.iter()} instead.

@end deffn

@geindex insert() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element insert}@anchor{29d0}
@deffn {方法} insert (index, subelement)

Inserts @emph{subelement} at the given position in this element.  Raises
@ref{192,,TypeError} if @emph{subelement} is not an @ref{abf,,Element}.
@end deffn

@geindex iter() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element iter}@anchor{ce0}
@deffn {方法} iter (tag=None)

Creates a tree @ref{fce,,iterator} with the current element as the root.
The iterator iterates over this element and all elements below it, in
document (depth first) order.  If @emph{tag} is not @code{None} or @code{'*'}, only
elements whose tag equals @emph{tag} are returned from the iterator.  If the
tree structure is modified during iteration, the result is undefined.


3.2 新版功能.

@end deffn

@geindex iterfind() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element iterfind}@anchor{b4b}
@deffn {方法} iterfind (match, namespaces=None)

Finds all matching subelements, by tag name or
@ref{412,,path}.  Returns an iterable yielding all
matching elements in document order. @emph{namespaces} is an optional mapping
from namespace prefix to full name.


3.2 新版功能.

@end deffn

@geindex itertext() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element itertext}@anchor{b4c}
@deffn {方法} itertext ()

Creates a text iterator.  The iterator loops over this element and all
subelements, in document order, and returns all inner text.


3.2 新版功能.

@end deffn

@geindex makeelement() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element makeelement}@anchor{29d1}
@deffn {方法} makeelement (tag, attrib)

Creates a new element object of the same type as this element.  Do not
call this method, use the @ref{29ac,,SubElement()} factory function instead.
@end deffn

@geindex remove() (xml.etree.ElementTree.Element 方法)
@anchor{library/xml etree elementtree xml etree ElementTree Element remove}@anchor{29aa}
@deffn {方法} remove (subelement)

Removes @emph{subelement} from the element.  Unlike the find* methods this
method compares elements based on the instance identity, not on tag value
or contents.
@end deffn

@ref{abf,,Element} objects also support the following sequence type methods
for working with subelements: @ref{c5c,,__delitem__()},
@ref{27f,,__getitem__()}, @ref{c5b,,__setitem__()},
@ref{dc4,,__len__()}.

Caution: Elements with no subelements will test as @code{False}.  This behavior
will change in future versions.  Use specific @code{len(elem)} or @code{elem is
None} test instead.

@example
element = root.find('foo')

if not element:  # careful!
    print("element not found, or element has no subelements")

if element is None:
    print("element not found")
@end example

Prior to Python 3.8, the serialisation order of the XML attributes of
elements was artificially made predictable by sorting the attributes by
their name. Based on the now guaranteed ordering of dicts, this arbitrary
reordering was removed in Python 3.8 to preserve the order in which
attributes were originally parsed or created by user code.

In general, user code should try not to depend on a specific ordering of
attributes, given that the XML Information Set@footnote{https://www.w3.org/TR/xml-infoset/} explicitly excludes the attribute
order from conveying information. Code should be prepared to deal with
any ordering on input. In cases where deterministic XML output is required,
e.g. for cryptographic signing or test data sets, canonical serialisation
is available with the @ref{29b5,,canonicalize()} function.

In cases where canonical output is not applicable but a specific attribute
order is still desirable on output, code should aim for creating the
attributes directly in the desired order, to avoid perceptual mismatches
for readers of the code. In cases where this is difficult to achieve, a
recipe like the following can be applied prior to serialisation to enforce
an order independently from the Element creation:

@example
def reorder_attributes(root):
    for el in root.iter():
        attrib = el.attrib
        if len(attrib) > 1:
            # adjust attribute order, e.g. by sorting
            attribs = sorted(attrib.items())
            attrib.clear()
            attrib.update(attribs)
@end example
@end deffn

@node ElementTree 对象,QName Objects,元素对象,参考<3>
@anchor{library/xml etree elementtree elementtree-elementtree-objects}@anchor{29d2}@anchor{library/xml etree elementtree elementtree-objects}@anchor{29d3}
@subsubsection ElementTree 对象


@geindex ElementTree (xml.etree.ElementTree 中的类)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree}@anchor{911}
@deffn {类} xml.etree.ElementTree.ElementTree (element=None, file=None)

ElementTree wrapper class.  This class represents an entire element
hierarchy, and adds some extra support for serialization to and from
standard XML.

@emph{element} is the root element.  The tree is initialized with the contents
of the XML @emph{file} if given.

@geindex _setroot() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree _setroot}@anchor{29d4}
@deffn {方法} _setroot (element)

Replaces the root element for this tree.  This discards the current
contents of the tree, and replaces it with the given element.  Use with
care.  @emph{element} is an element instance.
@end deffn

@geindex find() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree find}@anchor{29d5}
@deffn {方法} find (match, namespaces=None)

Same as @ref{29a4,,Element.find()}, starting at the root of the tree.
@end deffn

@geindex findall() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree findall}@anchor{29d6}
@deffn {方法} findall (match, namespaces=None)

Same as @ref{29a3,,Element.findall()}, starting at the root of the tree.
@end deffn

@geindex findtext() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree findtext}@anchor{29d7}
@deffn {方法} findtext (match, default=None, namespaces=None)

Same as @ref{29cd,,Element.findtext()}, starting at the root of the tree.
@end deffn

@geindex getiterator() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree getiterator}@anchor{29d8}
@deffn {方法} getiterator (tag=None)


Deprecated since version 3.2, will be removed in version 3.9: Use method @ref{29d9,,ElementTree.iter()} instead.

@end deffn

@geindex getroot() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree getroot}@anchor{29da}
@deffn {方法} getroot ()

Returns the root element for this tree.
@end deffn

@geindex iter() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree iter}@anchor{29d9}
@deffn {方法} iter (tag=None)

Creates and returns a tree iterator for the root element.  The iterator
loops over all elements in this tree, in section order.  @emph{tag} is the tag
to look for (default is to return all elements).
@end deffn

@geindex iterfind() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree iterfind}@anchor{29db}
@deffn {方法} iterfind (match, namespaces=None)

Same as @ref{b4b,,Element.iterfind()}, starting at the root of the tree.


3.2 新版功能.

@end deffn

@geindex parse() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree parse}@anchor{29dc}
@deffn {方法} parse (source, parser=None)

Loads an external XML section into this element tree.  @emph{source} is a file
name or @ref{b3b,,file object}.  @emph{parser} is an optional parser instance.
If not given, the standard @ref{252,,XMLParser} parser is used.  Returns the
section root element.
@end deffn

@geindex write() (xml.etree.ElementTree.ElementTree 方法)
@anchor{library/xml etree elementtree xml etree ElementTree ElementTree write}@anchor{912}
@deffn {方法} write (file, encoding="us-ascii", xml_declaration=None, default_namespace=None, method="xml", *, short_empty_elements=True)

Writes the element tree to a file, as XML.  @emph{file} is a file name, or a
@ref{b3b,,file object} opened for writing.  @emph{encoding} @footnote{@w{(1)} 
The encoding string included in XML output should conform to the
appropriate standards.  For example, "UTF-8" is valid, but "UTF8" is
not.  See @indicateurl{https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl}
and @indicateurl{https://www.iana.org/assignments/character-sets/character-sets.xhtml}.
} is the output
encoding (default is US-ASCII).
@emph{xml_declaration} controls if an XML declaration should be added to the
file.  Use @code{False} for never, @code{True} for always, @code{None}
for only if not US-ASCII or UTF-8 or Unicode (default is @code{None}).
@emph{default_namespace} sets the default XML namespace (for "xmlns").
@emph{method} is either @code{"xml"}, @code{"html"} or @code{"text"} (default is
@code{"xml"}).
The keyword-only @emph{short_empty_elements} parameter controls the formatting
of elements that contain no content.  If @code{True} (the default), they are
emitted as a single self-closed tag, otherwise they are emitted as a pair
of start/end tags.

The output is either a string (@ref{329,,str}) or binary (@ref{32a,,bytes}).
This is controlled by the @emph{encoding} argument.  If @emph{encoding} is
@code{"unicode"}, the output is a string; otherwise, it's binary.  Note that
this may conflict with the type of @emph{file} if it's an open
@ref{b3b,,file object}; make sure you do not try to write a string to a
binary stream and vice versa.


3.4 新版功能: @emph{short_empty_elements} 形参。



在 3.8 版更改: The @ref{912,,write()} method now preserves the attribute order specified
by the user.

@end deffn
@end deffn

This is the XML file that is going to be manipulated:

@example
<html>
    <head>
        <title>Example page</title>
    </head>
    <body>
        <p>Moved to <a href="http://example.org/">example.org</a>
        or <a href="http://example.com/">example.com</a>.</p>
    </body>
</html>
@end example

Example of changing the attribute "target" of every link in first paragraph:

@example
>>> from xml.etree.ElementTree import ElementTree
>>> tree = ElementTree()
>>> tree.parse("index.xhtml")
<Element 'html' at 0xb77e6fac>
>>> p = tree.find("body/p")     # Finds first occurrence of tag p in body
>>> p
<Element 'p' at 0xb77ec26c>
>>> links = list(p.iter("a"))   # Returns list of all links
>>> links
[<Element 'a' at 0xb77ec2ac>, <Element 'a' at 0xb77ec1cc>]
>>> for i in links:             # Iterates through all found links
...     i.attrib["target"] = "blank"
>>> tree.write("output.xhtml")
@end example

@node QName Objects,TreeBuilder Objects,ElementTree 对象,参考<3>
@anchor{library/xml etree elementtree elementtree-qname-objects}@anchor{29dd}@anchor{library/xml etree elementtree qname-objects}@anchor{29de}
@subsubsection QName Objects


@geindex QName (xml.etree.ElementTree 中的类)
@anchor{library/xml etree elementtree xml etree ElementTree QName}@anchor{29df}
@deffn {类} xml.etree.ElementTree.QName (text_or_uri, tag=None)

QName wrapper.  This can be used to wrap a QName attribute value, in order
to get proper namespace handling on output.  @emph{text_or_uri} is a string
containing the QName value, in the form @{uri@}local, or, if the tag argument
is given, the URI part of a QName.  If @emph{tag} is given, the first argument is
interpreted as a URI, and this argument is interpreted as a local name.
@ref{29df,,QName} instances are opaque.
@end deffn

@node TreeBuilder Objects,XMLParser对象,QName Objects,参考<3>
@anchor{library/xml etree elementtree elementtree-treebuilder-objects}@anchor{29e0}@anchor{library/xml etree elementtree treebuilder-objects}@anchor{29e1}
@subsubsection TreeBuilder Objects


@geindex TreeBuilder (xml.etree.ElementTree 中的类)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder}@anchor{253}
@deffn {类} xml.etree.ElementTree.TreeBuilder (element_factory=None, *, comment_factory=None, pi_factory=None, insert_comments=False, insert_pis=False)

Generic element structure builder.  This builder converts a sequence of
start, data, end, comment and pi method calls to a well-formed element
structure.  You can use this class to build an element structure using
a custom XML parser, or a parser for some other XML-like format.

@emph{element_factory}, when given, must be a callable accepting two positional
arguments: a tag and a dict of attributes.  It is expected to return a new
element instance.

The @emph{comment_factory} and @emph{pi_factory} functions, when given, should behave
like the @ref{29b6,,Comment()} and @ref{29bb,,ProcessingInstruction()} functions to
create comments and processing instructions.  When not given, the default
factories will be used.  When @emph{insert_comments} and/or @emph{insert_pis} is true,
comments/pis will be inserted into the tree if they appear within the root
element (but not outside of it).

@geindex close() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder close}@anchor{29e2}
@deffn {方法} close ()

Flushes the builder buffers, and returns the toplevel document
element.  Returns an @ref{abf,,Element} instance.
@end deffn

@geindex data() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder data}@anchor{29e3}
@deffn {方法} data (data)

Adds text to the current element.  @emph{data} is a string.  This should be
either a bytestring, or a Unicode string.
@end deffn

@geindex end() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder end}@anchor{b4d}
@deffn {方法} end (tag)

Closes the current element.  @emph{tag} is the element name.  Returns the
closed element.
@end deffn

@geindex start() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder start}@anchor{29e4}
@deffn {方法} start (tag, attrs)

Opens a new element.  @emph{tag} is the element name.  @emph{attrs} is a dictionary
containing element attributes.  Returns the opened element.
@end deffn

@geindex comment() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder comment}@anchor{29e5}
@deffn {方法} comment (text)

Creates a comment with the given @emph{text}.  If @code{insert_comments} is true,
this will also add it to the tree.


3.8 新版功能.

@end deffn

@geindex pi() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder pi}@anchor{29e6}
@deffn {方法} pi (target, text)

Creates a comment with the given @emph{target} name and @emph{text}.  If
@code{insert_pis} is true, this will also add it to the tree.


3.8 新版功能.

@end deffn

In addition, a custom @ref{253,,TreeBuilder} object can provide the
following methods:

@geindex doctype() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder doctype}@anchor{2c1}
@deffn {方法} doctype (name, pubid, system)

Handles a doctype declaration.  @emph{name} is the doctype name.  @emph{pubid} is
the public identifier.  @emph{system} is the system identifier.  This method
does not exist on the default @ref{253,,TreeBuilder} class.


3.2 新版功能.

@end deffn

@geindex start_ns() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder start_ns}@anchor{29e7}
@deffn {方法} start_ns (prefix, uri)

Is called whenever the parser encounters a new namespace declaration,
before the @code{start()} callback for the opening element that defines it.
@emph{prefix} is @code{'@w{'}} for the default namespace and the declared
namespace prefix name otherwise.  @emph{uri} is the namespace URI.


3.8 新版功能.

@end deffn

@geindex end_ns() (xml.etree.ElementTree.TreeBuilder 方法)
@anchor{library/xml etree elementtree xml etree ElementTree TreeBuilder end_ns}@anchor{29e8}
@deffn {方法} end_ns (prefix)

Is called after the @code{end()} callback of an element that declared
a namespace prefix mapping, with the name of the @emph{prefix} that went
out of scope.


3.8 新版功能.

@end deffn
@end deffn

@geindex C14NWriterTarget (xml.etree.ElementTree 中的类)
@anchor{library/xml etree elementtree xml etree ElementTree C14NWriterTarget}@anchor{29e9}
@deffn {类} xml.etree.ElementTree.C14NWriterTarget (write, *, with_comments=False, strip_text=False, rewrite_prefixes=False, qname_aware_tags=None, qname_aware_attrs=None, exclude_attrs=None, exclude_tags=None)

A C14N 2.0@footnote{https://www.w3.org/TR/xml-c14n2/} writer.  Arguments are the
same as for the @ref{29b5,,canonicalize()} function.  This class does not build a
tree but translates the callback events directly into a serialised form
using the @emph{write} function.


3.8 新版功能.

@end deffn

@node XMLParser对象,XMLPullParser对象,TreeBuilder Objects,参考<3>
@anchor{library/xml etree elementtree elementtree-xmlparser-objects}@anchor{29ea}@anchor{library/xml etree elementtree xmlparser-objects}@anchor{29eb}
@subsubsection XMLParser对象


@geindex XMLParser (xml.etree.ElementTree 中的类)
@anchor{library/xml etree elementtree xml etree ElementTree XMLParser}@anchor{252}
@deffn {类} xml.etree.ElementTree.XMLParser (*, target=None, encoding=None)

This class is the low-level building block of the module.  It uses
@ref{138,,xml.parsers.expat} for efficient, event-based parsing of XML.  It can
be fed XML data incrementally with the @ref{29ec,,feed()} method, and parsing
events are translated to a push API - by invoking callbacks on the @emph{target}
object.  If @emph{target} is omitted, the standard @ref{253,,TreeBuilder} is used.
If @emph{encoding} @footnote{@w{(1)} 
The encoding string included in XML output should conform to the
appropriate standards.  For example, "UTF-8" is valid, but "UTF8" is
not.  See @indicateurl{https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl}
and @indicateurl{https://www.iana.org/assignments/character-sets/character-sets.xhtml}.
} is given, the value overrides the
encoding specified in the XML file.


在 3.8 版更改: Parameters are now @ref{2ac,,keyword-only}.
The @emph{html} argument no longer supported.


@geindex close() (xml.etree.ElementTree.XMLParser 方法)
@anchor{library/xml etree elementtree xml etree ElementTree XMLParser close}@anchor{29ed}
@deffn {方法} close ()

Finishes feeding data to the parser.  Returns the result of calling the
@code{close()} method of the @emph{target} passed during construction; by default,
this is the toplevel document element.
@end deffn

@geindex feed() (xml.etree.ElementTree.XMLParser 方法)
@anchor{library/xml etree elementtree xml etree ElementTree XMLParser feed}@anchor{29ec}
@deffn {方法} feed (data)

Feeds data to the parser.  @emph{data} is encoded data.
@end deffn

@ref{29ec,,XMLParser.feed()} calls @emph{target}'s @code{start(tag, attrs_dict)} method
for each opening tag, its @code{end(tag)} method for each closing tag, and data
is processed by method @code{data(data)}.  For further supported callback
methods, see the @ref{253,,TreeBuilder} class.  @ref{29ed,,XMLParser.close()} calls
@emph{target}'s method @code{close()}. @ref{252,,XMLParser} can be used not only for
building a tree structure. This is an example of counting the maximum depth
of an XML file:

@example
>>> from xml.etree.ElementTree import XMLParser
>>> class MaxDepth:                     # The target object of the parser
...     maxDepth = 0
...     depth = 0
...     def start(self, tag, attrib):   # Called for each opening tag.
...         self.depth += 1
...         if self.depth > self.maxDepth:
...             self.maxDepth = self.depth
...     def end(self, tag):             # Called for each closing tag.
...         self.depth -= 1
...     def data(self, data):
...         pass            # We do not need to do anything with data.
...     def close(self):    # Called when all data has been parsed.
...         return self.maxDepth
...
>>> target = MaxDepth()
>>> parser = XMLParser(target=target)
>>> exampleXml = """
... <a>
...   <b>
...   </b>
...   <b>
...     <c>
...       <d>
...       </d>
...     </c>
...   </b>
... </a>"""
>>> parser.feed(exampleXml)
>>> parser.close()
4
@end example
@end deffn

@node XMLPullParser对象,异常<15>,XMLParser对象,参考<3>
@anchor{library/xml etree elementtree elementtree-xmlpullparser-objects}@anchor{29ee}@anchor{library/xml etree elementtree xmlpullparser-objects}@anchor{29ef}
@subsubsection XMLPullParser对象


@geindex XMLPullParser (xml.etree.ElementTree 中的类)
@anchor{library/xml etree elementtree xml etree ElementTree XMLPullParser}@anchor{90d}
@deffn {类} xml.etree.ElementTree.XMLPullParser (events=None)

A pull parser suitable for non-blocking applications.  Its input-side API is
similar to that of @ref{252,,XMLParser}, but instead of pushing calls to a
callback target, @ref{90d,,XMLPullParser} collects an internal list of parsing
events and lets the user read from it. @emph{events} is a sequence of events to
report back.  The supported events are the strings @code{"start"}, @code{"end"},
@code{"comment"}, @code{"pi"}, @code{"start-ns"} and @code{"end-ns"} (the "ns" events
are used to get detailed namespace information).  If @emph{events} is omitted,
only @code{"end"} events are reported.

@geindex feed() (xml.etree.ElementTree.XMLPullParser 方法)
@anchor{library/xml etree elementtree xml etree ElementTree XMLPullParser feed}@anchor{29a0}
@deffn {方法} feed (data)

Feed the given bytes data to the parser.
@end deffn

@geindex close() (xml.etree.ElementTree.XMLPullParser 方法)
@anchor{library/xml etree elementtree xml etree ElementTree XMLPullParser close}@anchor{29f0}
@deffn {方法} close ()

Signal the parser that the data stream is terminated. Unlike
@ref{29ed,,XMLParser.close()}, this method always returns @ref{157,,None}.
Any events not yet retrieved when the parser is closed can still be
read with @ref{29a1,,read_events()}.
@end deffn

@geindex read_events() (xml.etree.ElementTree.XMLPullParser 方法)
@anchor{library/xml etree elementtree xml etree ElementTree XMLPullParser read_events}@anchor{29a1}
@deffn {方法} read_events ()

Return an iterator over the events which have been encountered in the
data fed to the
parser.  The iterator yields @code{(event, elem)} pairs, where @emph{event} is a
string representing the type of event (e.g. @code{"end"}) and @emph{elem} is the
encountered @ref{abf,,Element} object, or other context value as follows.


@itemize *

@item 
@code{start}, @code{end}: the current Element.

@item 
@code{comment}, @code{pi}: the current comment / processing instruction

@item 
@code{start-ns}: a tuple @code{(prefix, uri)} naming the declared namespace
mapping.

@item 
@code{end-ns}: @ref{157,,None} (this may change in a future version)
@end itemize

Events provided in a previous call to @ref{29a1,,read_events()} will not be
yielded again.  Events are consumed from the internal queue only when
they are retrieved from the iterator, so multiple readers iterating in
parallel over iterators obtained from @ref{29a1,,read_events()} will have
unpredictable results.
@end deffn

@cartouche
@quotation 注解 
@ref{90d,,XMLPullParser} only guarantees that it has seen the ">"
character of a starting tag when it emits a "start" event, so the
attributes are defined, but the contents of the text and tail attributes
are undefined at that point.  The same applies to the element children;
they may or may not be present.

If you need a fully populated element, look for "end" events instead.
@end quotation
@end cartouche


3.4 新版功能.



在 3.8 版更改: The @code{comment} and @code{pi} events were added.

@end deffn

@node 异常<15>,,XMLPullParser对象,参考<3>
@anchor{library/xml etree elementtree exceptions}@anchor{29f1}
@subsubsection 异常


@geindex ParseError (xml.etree.ElementTree 中的类)
@anchor{library/xml etree elementtree xml etree ElementTree ParseError}@anchor{c05}
@deffn {类} xml.etree.ElementTree.ParseError

XML parse error, raised by the various parsing methods in this module when
parsing fails.  The string representation of an instance of this exception
will contain a user-friendly error message.  In addition, it will have
the following attributes available:

@geindex code (xml.etree.ElementTree.ParseError 属性)
@anchor{library/xml etree elementtree xml etree ElementTree ParseError code}@anchor{29f2}
@deffn {属性} code

A numeric error code from the expat parser. See the documentation of
@ref{138,,xml.parsers.expat} for the list of error codes and their meanings.
@end deffn

@geindex position (xml.etree.ElementTree.ParseError 属性)
@anchor{library/xml etree elementtree xml etree ElementTree ParseError position}@anchor{29f3}
@deffn {属性} position

A tuple of @emph{line}, @emph{column} numbers, specifying where the error occurred.
@end deffn
@end deffn

@subsubheading 备注


@node xml dom --- The Document Object Model API,xml dom minidom --- Minimal DOM implementation,xml etree ElementTree --- ElementTree XML API,结构化标记处理工具
@anchor{library/xml dom doc}@anchor{29f4}@anchor{library/xml dom module-xml dom}@anchor{134}@anchor{library/xml dom xml-dom-the-document-object-model-api}@anchor{29f5}
@subsection @code{xml.dom} --- The Document Object Model API


@geindex xml.dom (模块)

@strong{Source code:} Lib/xml/dom/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/dom/__init__.py}


__________________________________________________________________


The Document Object Model, or "DOM," is a cross-language API from the World Wide
Web Consortium (W3C) for accessing and modifying XML documents.  A DOM
implementation presents an XML document as a tree structure, or allows client
code to build such a structure from scratch.  It then gives access to the
structure through a set of objects which provided well-known interfaces.

The DOM is extremely useful for random-access applications.  SAX only allows you
a view of one bit of the document at a time.  If you are looking at one SAX
element, you have no access to another.  If you are looking at a text node, you
have no access to a containing element. When you write a SAX application, you
need to keep track of your program's position in the document somewhere in your
own code.  SAX does not do it for you.  Also, if you need to look ahead in the
XML document, you are just out of luck.

Some applications are simply impossible in an event driven model with no access
to a tree.  Of course you could build some sort of tree yourself in SAX events,
but the DOM allows you to avoid writing that code.  The DOM is a standard tree
representation for XML data.

The Document Object Model is being defined by the W3C in stages, or "levels" in
their terminology.  The Python mapping of the API is substantially based on the
DOM Level 2 recommendation.

@c What if your needs are somewhere between SAX and the DOM?  Perhaps
@c you cannot afford to load the entire tree in memory but you find the
@c SAX model somewhat cumbersome and low-level.  There is also a module
@c called xml.dom.pulldom that allows you to build trees of only the
@c parts of a document that you need structured access to.  It also has
@c features that allow you to find your way around the DOM.
@c See http://www.prescod.net/python/pulldom

DOM applications typically start by parsing some XML into a DOM.  How this is
accomplished is not covered at all by DOM Level 1, and Level 2 provides only
limited improvements: There is a @code{DOMImplementation} object class which
provides access to @code{Document} creation methods, but no way to access an
XML reader/parser/Document builder in an implementation-independent way. There
is also no well-defined way to access these methods without an existing
@code{Document} object.  In Python, each DOM implementation will provide a
function @ref{29f6,,getDOMImplementation()}. DOM Level 3 adds a Load/Store
specification, which defines an interface to the reader, but this is not yet
available in the Python standard library.

Once you have a DOM document object, you can access the parts of your XML
document through its properties and methods.  These properties are defined in
the DOM specification; this portion of the reference manual describes the
interpretation of the specification in Python.

The specification provided by the W3C defines the DOM API for Java, ECMAScript,
and OMG IDL.  The Python mapping defined here is based in large part on the IDL
version of the specification, but strict compliance is not required (though
implementations are free to support the strict mapping from IDL).  See section
@ref{29f7,,一致性} for a detailed discussion of mapping requirements.


@subsubheading 参见



@table @asis

@item Document Object Model (DOM) Level 2 Specification@footnote{https://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113/}

The W3C recommendation upon which the Python DOM API is based.

@item Document Object Model (DOM) Level 1 Specification@footnote{https://www.w3.org/TR/REC-DOM-Level-1/}

The W3C recommendation for the DOM supported by @ref{135,,xml.dom.minidom}.

@item Python Language Mapping Specification@footnote{http://www.omg.org/cgi-bin/doc?formal/02-11-05.pdf}

This specifies the mapping from OMG IDL to Python.
@end table


@menu
* 模块内容: 模块内容<6>. 
* Objects in the DOM:: 
* 一致性:: 

@end menu

@node 模块内容<6>,Objects in the DOM,,xml dom --- The Document Object Model API
@anchor{library/xml dom module-contents}@anchor{29f8}
@subsubsection 模块内容


The @ref{134,,xml.dom} contains the following functions:

@geindex registerDOMImplementation() (在 xml.dom 模块中)
@anchor{library/xml dom xml dom registerDOMImplementation}@anchor{29f9}
@deffn {函数} xml.dom.registerDOMImplementation (name, factory)

Register the @emph{factory} function with the name @emph{name}.  The factory function
should return an object which implements the @code{DOMImplementation}
interface.  The factory function can return the same object every time, or a new
one for each call, as appropriate for the specific implementation (e.g. if that
implementation supports some customization).
@end deffn

@geindex getDOMImplementation() (在 xml.dom 模块中)
@anchor{library/xml dom xml dom getDOMImplementation}@anchor{29f6}
@deffn {函数} xml.dom.getDOMImplementation (name=None, features=())

Return a suitable DOM implementation. The @emph{name} is either well-known, the
module name of a DOM implementation, or @code{None}. If it is not @code{None}, imports
the corresponding module and returns a @code{DOMImplementation} object if the
import succeeds.  If no name is given, and if the environment variable
@geindex PYTHON_DOM
@geindex 环境变量; PYTHON_DOM
@code{PYTHON_DOM} is set, this variable is used to find the implementation.

If name is not given, this examines the available implementations to find one
with the required feature set.  If no implementation can be found, raise an
@ref{32d,,ImportError}.  The features list must be a sequence of @code{(feature,
version)} pairs which are passed to the @code{hasFeature()} method on available
@code{DOMImplementation} objects.
@end deffn

Some convenience constants are also provided:

@geindex EMPTY_NAMESPACE() (在 xml.dom 模块中)
@anchor{library/xml dom xml dom EMPTY_NAMESPACE}@anchor{29fa}
@deffn {数据} xml.dom.EMPTY_NAMESPACE

The value used to indicate that no namespace is associated with a node in the
DOM.  This is typically found as the @code{namespaceURI} of a node, or used as
the @emph{namespaceURI} parameter to a namespaces-specific method.
@end deffn

@geindex XML_NAMESPACE() (在 xml.dom 模块中)
@anchor{library/xml dom xml dom XML_NAMESPACE}@anchor{29fb}
@deffn {数据} xml.dom.XML_NAMESPACE

The namespace URI associated with the reserved prefix @code{xml}, as defined by
Namespaces in XML@footnote{https://www.w3.org/TR/REC-xml-names/} (section 4).
@end deffn

@geindex XMLNS_NAMESPACE() (在 xml.dom 模块中)
@anchor{library/xml dom xml dom XMLNS_NAMESPACE}@anchor{29fc}
@deffn {数据} xml.dom.XMLNS_NAMESPACE

The namespace URI for namespace declarations, as defined by Document Object Model (DOM) Level 2 Core Specification@footnote{https://www.w3.org/TR/DOM-Level-2-Core/core.html} (section 1.1.8).
@end deffn

@geindex XHTML_NAMESPACE() (在 xml.dom 模块中)
@anchor{library/xml dom xml dom XHTML_NAMESPACE}@anchor{29fd}
@deffn {数据} xml.dom.XHTML_NAMESPACE

The URI of the XHTML namespace as defined by XHTML 1.0: The Extensible HyperText Markup Language@footnote{https://www.w3.org/TR/xhtml1/} (section 3.1.1).
@end deffn

In addition, @ref{134,,xml.dom} contains a base @code{Node} class and the DOM
exception classes.  The @code{Node} class provided by this module does not
implement any of the methods or attributes defined by the DOM specification;
concrete DOM implementations must provide those.  The @code{Node} class
provided as part of this module does provide the constants used for the
@code{nodeType} attribute on concrete @code{Node} objects; they are located
within the class rather than at the module level to conform with the DOM
specifications.

@c Should the Node documentation go here?

@node Objects in the DOM,一致性,模块内容<6>,xml dom --- The Document Object Model API
@anchor{library/xml dom dom-objects}@anchor{29fe}@anchor{library/xml dom objects-in-the-dom}@anchor{29ff}
@subsubsection Objects in the DOM


DOM的权威文档是来自W3C的DOM规范。

请注意，DOM属性也可以作为节点而不是简单的字符串进行操作。然而，必须这样做的情况相当少见，所以这种用法还没有记录下来。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

接口

@tab

部件

@tab

目的

@item

@code{DOMImplementation}

@tab

@ref{2a00,,DOMImplementation Objects}

@tab

底层实现的接口。

@item

@code{Node}

@tab

@ref{2a01,,节点对象}

@tab

文档中大多数对象的基本接口。

@item

@code{NodeList}

@tab

@ref{2a02,,节点列表对象}

@tab

节点序列的接口。

@item

@code{DocumentType}

@tab

@ref{2a03,,文档类型对象}

@tab

有关处理文档所需声明的信息。

@item

@code{Document}

@tab

@ref{2a04,,文档对象}

@tab

表示整个文档的对象。

@item

@code{Element}

@tab

@ref{2a05,,元素对象}

@tab

文档层次结构中的元素节点。

@item

@code{Attr}

@tab

@ref{2a06,,Attr 对象}

@tab

元素节点上的属性值节点。

@item

@code{Comment}

@tab

@ref{2a07,,注释对象}

@tab

源文档中注释的表示形式。

@item

@code{Text}

@tab

@ref{2a08,,Text 和 CDATASection 对象}

@tab

包含文档中文本内容的节点。

@item

@code{ProcessingInstruction}

@tab

@ref{2a09,,ProcessingInstruction 对象}

@tab

Processing instruction
representation.

@end multitable


另一节描述了在Python中使用DOM定义的异常。

@menu
* DOMImplementation Objects:: 
* 节点对象:: 
* 节点列表对象:: 
* 文档类型对象:: 
* 文档对象:: 
* 元素对象: 元素对象<2>. 
* Attr 对象:: 
* NamedNodeMap 对象:: 
* 注释对象:: 
* Text 和 CDATASection 对象:: 
* ProcessingInstruction 对象:: 
* 异常: 异常<16>. 

@end menu

@node DOMImplementation Objects,节点对象,,Objects in the DOM
@anchor{library/xml dom dom-implementation-objects}@anchor{2a00}@anchor{library/xml dom domimplementation-objects}@anchor{2a0a}
@subsubsection DOMImplementation Objects


The @code{DOMImplementation} interface provides a way for applications to
determine the availability of particular features in the DOM they are using.
DOM Level 2 added the ability to create new @code{Document} and
@code{DocumentType} objects using the @code{DOMImplementation} as well.

@geindex hasFeature() (xml.dom.DOMImplementation 方法)
@anchor{library/xml dom xml dom DOMImplementation hasFeature}@anchor{2a0b}
@deffn {方法} DOMImplementation.hasFeature (feature, version)

Return @code{True} if the feature identified by the pair of strings @emph{feature} and
@emph{version} is implemented.
@end deffn

@geindex createDocument() (xml.dom.DOMImplementation 方法)
@anchor{library/xml dom xml dom DOMImplementation createDocument}@anchor{2a0c}
@deffn {方法} DOMImplementation.createDocument (namespaceUri, qualifiedName, doctype)

Return a new @code{Document} object (the root of the DOM), with a child
@code{Element} object having the given @emph{namespaceUri} and @emph{qualifiedName}. The
@emph{doctype} must be a @code{DocumentType} object created by
@ref{2a0d,,createDocumentType()}, or @code{None}. In the Python DOM API, the first two
arguments can also be @code{None} in order to indicate that no @code{Element}
child is to be created.
@end deffn

@geindex createDocumentType() (xml.dom.DOMImplementation 方法)
@anchor{library/xml dom xml dom DOMImplementation createDocumentType}@anchor{2a0d}
@deffn {方法} DOMImplementation.createDocumentType (qualifiedName, publicId, systemId)

Return a new @code{DocumentType} object that encapsulates the given
@emph{qualifiedName}, @emph{publicId}, and @emph{systemId} strings, representing the
information contained in an XML document type declaration.
@end deffn

@node 节点对象,节点列表对象,DOMImplementation Objects,Objects in the DOM
@anchor{library/xml dom dom-node-objects}@anchor{2a01}@anchor{library/xml dom node-objects}@anchor{2a0e}
@subsubsection 节点对象


All of the components of an XML document are subclasses of @code{Node}.

@geindex nodeType (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node nodeType}@anchor{2a0f}
@deffn {属性} Node.nodeType

An integer representing the node type.  Symbolic constants for the types are on
the @code{Node} object: @code{ELEMENT_NODE}, @code{ATTRIBUTE_NODE},
@code{TEXT_NODE}, @code{CDATA_SECTION_NODE}, @code{ENTITY_NODE},
@code{PROCESSING_INSTRUCTION_NODE}, @code{COMMENT_NODE},
@code{DOCUMENT_NODE}, @code{DOCUMENT_TYPE_NODE}, @code{NOTATION_NODE}.
This is a read-only attribute.
@end deffn

@geindex parentNode (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node parentNode}@anchor{2a10}
@deffn {属性} Node.parentNode

The parent of the current node, or @code{None} for the document node. The value is
always a @code{Node} object or @code{None}.  For @code{Element} nodes, this
will be the parent element, except for the root element, in which case it will
be the @code{Document} object. For @code{Attr} nodes, this is always
@code{None}. This is a read-only attribute.
@end deffn

@geindex attributes (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node attributes}@anchor{2a11}
@deffn {属性} Node.attributes

A @code{NamedNodeMap} of attribute objects.  Only elements have actual values
for this; others provide @code{None} for this attribute. This is a read-only
attribute.
@end deffn

@geindex previousSibling (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node previousSibling}@anchor{2a12}
@deffn {属性} Node.previousSibling

The node that immediately precedes this one with the same parent.  For
instance the element with an end-tag that comes just before the @emph{self}
element's start-tag.  Of course, XML documents are made up of more than just
elements so the previous sibling could be text, a comment, or something else.
If this node is the first child of the parent, this attribute will be
@code{None}. This is a read-only attribute.
@end deffn

@geindex nextSibling (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node nextSibling}@anchor{2a13}
@deffn {属性} Node.nextSibling

The node that immediately follows this one with the same parent.  See also
@ref{2a12,,previousSibling}.  If this is the last child of the parent, this
attribute will be @code{None}. This is a read-only attribute.
@end deffn

@geindex childNodes (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node childNodes}@anchor{2a14}
@deffn {属性} Node.childNodes

A list of nodes contained within this node. This is a read-only attribute.
@end deffn

@geindex firstChild (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node firstChild}@anchor{2a15}
@deffn {属性} Node.firstChild

The first child of the node, if there are any, or @code{None}. This is a read-only
attribute.
@end deffn

@geindex lastChild (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node lastChild}@anchor{2a16}
@deffn {属性} Node.lastChild

The last child of the node, if there are any, or @code{None}. This is a read-only
attribute.
@end deffn

@geindex localName (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node localName}@anchor{2a17}
@deffn {属性} Node.localName

The part of the @code{tagName} following the colon if there is one, else the
entire @code{tagName}.  The value is a string.
@end deffn

@geindex prefix (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node prefix}@anchor{2a18}
@deffn {属性} Node.prefix

The part of the @code{tagName} preceding the colon if there is one, else the
empty string.  The value is a string, or @code{None}.
@end deffn

@geindex namespaceURI (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node namespaceURI}@anchor{2a19}
@deffn {属性} Node.namespaceURI

The namespace associated with the element name.  This will be a string or
@code{None}.  This is a read-only attribute.
@end deffn

@geindex nodeName (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node nodeName}@anchor{2a1a}
@deffn {属性} Node.nodeName

This has a different meaning for each node type; see the DOM specification for
details.  You can always get the information you would get here from another
property such as the @code{tagName} property for elements or the @code{name}
property for attributes. For all node types, the value of this attribute will be
either a string or @code{None}.  This is a read-only attribute.
@end deffn

@geindex nodeValue (xml.dom.Node 属性)
@anchor{library/xml dom xml dom Node nodeValue}@anchor{2a1b}
@deffn {属性} Node.nodeValue

This has a different meaning for each node type; see the DOM specification for
details.  The situation is similar to that with @ref{2a1a,,nodeName}.  The value is
a string or @code{None}.
@end deffn

@geindex hasAttributes() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node hasAttributes}@anchor{2a1c}
@deffn {方法} Node.hasAttributes ()

Return @code{True} if the node has any attributes.
@end deffn

@geindex hasChildNodes() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node hasChildNodes}@anchor{2a1d}
@deffn {方法} Node.hasChildNodes ()

Return @code{True} if the node has any child nodes.
@end deffn

@geindex isSameNode() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node isSameNode}@anchor{2a1e}
@deffn {方法} Node.isSameNode (other)

Return @code{True} if @emph{other} refers to the same node as this node. This is especially
useful for DOM implementations which use any sort of proxy architecture (because
more than one object can refer to the same node).

@cartouche
@quotation 注解 
This is based on a proposed DOM Level 3 API which is still in the "working
draft" stage, but this particular interface appears uncontroversial.  Changes
from the W3C will not necessarily affect this method in the Python DOM interface
(though any new W3C API for this would also be supported).
@end quotation
@end cartouche
@end deffn

@geindex appendChild() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node appendChild}@anchor{2a1f}
@deffn {方法} Node.appendChild (newChild)

Add a new child node to this node at the end of the list of
children, returning @emph{newChild}. If the node was already in
the tree, it is removed first.
@end deffn

@geindex insertBefore() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node insertBefore}@anchor{2a20}
@deffn {方法} Node.insertBefore (newChild, refChild)

Insert a new child node before an existing child.  It must be the case that
@emph{refChild} is a child of this node; if not, @ref{1fb,,ValueError} is raised.
@emph{newChild} is returned. If @emph{refChild} is @code{None}, it inserts @emph{newChild} at the
end of the children's list.
@end deffn

@geindex removeChild() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node removeChild}@anchor{2a21}
@deffn {方法} Node.removeChild (oldChild)

Remove a child node.  @emph{oldChild} must be a child of this node; if not,
@ref{1fb,,ValueError} is raised.  @emph{oldChild} is returned on success.  If @emph{oldChild}
will not be used further, its @code{unlink()} method should be called.
@end deffn

@geindex replaceChild() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node replaceChild}@anchor{2a22}
@deffn {方法} Node.replaceChild (newChild, oldChild)

Replace an existing node with a new node. It must be the case that  @emph{oldChild}
is a child of this node; if not, @ref{1fb,,ValueError} is raised.
@end deffn

@geindex normalize() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node normalize}@anchor{2a23}
@deffn {方法} Node.normalize ()

Join adjacent text nodes so that all stretches of text are stored as single
@code{Text} instances.  This simplifies processing text from a DOM tree for
many applications.
@end deffn

@geindex cloneNode() (xml.dom.Node 方法)
@anchor{library/xml dom xml dom Node cloneNode}@anchor{2a24}
@deffn {方法} Node.cloneNode (deep)

Clone this node.  Setting @emph{deep} means to clone all child nodes as well.  This
returns the clone.
@end deffn

@node 节点列表对象,文档类型对象,节点对象,Objects in the DOM
@anchor{library/xml dom dom-nodelist-objects}@anchor{2a02}@anchor{library/xml dom nodelist-objects}@anchor{2a25}
@subsubsection 节点列表对象


A @code{NodeList} represents a sequence of nodes.  These objects are used in
two ways in the DOM Core recommendation:  an @code{Element} object provides
one as its list of child nodes, and the @code{getElementsByTagName()} and
@code{getElementsByTagNameNS()} methods of @code{Node} return objects with this
interface to represent query results.

The DOM Level 2 recommendation defines one method and one attribute for these
objects:

@geindex item() (xml.dom.NodeList 方法)
@anchor{library/xml dom xml dom NodeList item}@anchor{2a26}
@deffn {方法} NodeList.item (i)

Return the @emph{i}'th item from the sequence, if there is one, or @code{None}.  The
index @emph{i} is not allowed to be less than zero or greater than or equal to the
length of the sequence.
@end deffn

@geindex length (xml.dom.NodeList 属性)
@anchor{library/xml dom xml dom NodeList length}@anchor{2a27}
@deffn {属性} NodeList.length

The number of nodes in the sequence.
@end deffn

In addition, the Python DOM interface requires that some additional support is
provided to allow @code{NodeList} objects to be used as Python sequences.  All
@code{NodeList} implementations must include support for
@ref{dc4,,__len__()} and
@ref{27f,,__getitem__()}; this allows iteration over the @code{NodeList} in
@ref{c29,,for} statements and proper support for the @ref{150,,len()} built-in
function.

If a DOM implementation supports modification of the document, the
@code{NodeList} implementation must also support the
@ref{c5b,,__setitem__()} and @ref{c5c,,__delitem__()} methods.

@node 文档类型对象,文档对象,节点列表对象,Objects in the DOM
@anchor{library/xml dom documenttype-objects}@anchor{2a28}@anchor{library/xml dom dom-documenttype-objects}@anchor{2a03}
@subsubsection 文档类型对象


Information about the notations and entities declared by a document (including
the external subset if the parser uses it and can provide the information) is
available from a @code{DocumentType} object.  The @code{DocumentType} for a
document is available from the @code{Document} object's @code{doctype}
attribute; if there is no @code{DOCTYPE} declaration for the document, the
document's @code{doctype} attribute will be set to @code{None} instead of an
instance of this interface.

@code{DocumentType} is a specialization of @code{Node}, and adds the
following attributes:

@geindex publicId (xml.dom.DocumentType 属性)
@anchor{library/xml dom xml dom DocumentType publicId}@anchor{2a29}
@deffn {属性} DocumentType.publicId

The public identifier for the external subset of the document type definition.
This will be a string or @code{None}.
@end deffn

@geindex systemId (xml.dom.DocumentType 属性)
@anchor{library/xml dom xml dom DocumentType systemId}@anchor{2a2a}
@deffn {属性} DocumentType.systemId

The system identifier for the external subset of the document type definition.
This will be a URI as a string, or @code{None}.
@end deffn

@geindex internalSubset (xml.dom.DocumentType 属性)
@anchor{library/xml dom xml dom DocumentType internalSubset}@anchor{2a2b}
@deffn {属性} DocumentType.internalSubset

A string giving the complete internal subset from the document. This does not
include the brackets which enclose the subset.  If the document has no internal
subset, this should be @code{None}.
@end deffn

@geindex name (xml.dom.DocumentType 属性)
@anchor{library/xml dom xml dom DocumentType name}@anchor{2a2c}
@deffn {属性} DocumentType.name

The name of the root element as given in the @code{DOCTYPE} declaration, if
present.
@end deffn

@geindex entities (xml.dom.DocumentType 属性)
@anchor{library/xml dom xml dom DocumentType entities}@anchor{2a2d}
@deffn {属性} DocumentType.entities

This is a @code{NamedNodeMap} giving the definitions of external entities.
For entity names defined more than once, only the first definition is provided
(others are ignored as required by the XML recommendation).  This may be
@code{None} if the information is not provided by the parser, or if no entities are
defined.
@end deffn

@geindex notations (xml.dom.DocumentType 属性)
@anchor{library/xml dom xml dom DocumentType notations}@anchor{2a2e}
@deffn {属性} DocumentType.notations

This is a @code{NamedNodeMap} giving the definitions of notations. For
notation names defined more than once, only the first definition is provided
(others are ignored as required by the XML recommendation).  This may be
@code{None} if the information is not provided by the parser, or if no notations
are defined.
@end deffn

@node 文档对象,元素对象<2>,文档类型对象,Objects in the DOM
@anchor{library/xml dom document-objects}@anchor{2a2f}@anchor{library/xml dom dom-document-objects}@anchor{2a04}
@subsubsection 文档对象


A @code{Document} represents an entire XML document, including its constituent
elements, attributes, processing instructions, comments etc.  Remember that it
inherits properties from @code{Node}.

@geindex documentElement (xml.dom.Document 属性)
@anchor{library/xml dom xml dom Document documentElement}@anchor{2a30}
@deffn {属性} Document.documentElement

The one and only root element of the document.
@end deffn

@geindex createElement() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document createElement}@anchor{2a31}
@deffn {方法} Document.createElement (tagName)

Create and return a new element node.  The element is not inserted into the
document when it is created.  You need to explicitly insert it with one of the
other methods such as @code{insertBefore()} or @code{appendChild()}.
@end deffn

@geindex createElementNS() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document createElementNS}@anchor{2a32}
@deffn {方法} Document.createElementNS (namespaceURI, tagName)

Create and return a new element with a namespace.  The @emph{tagName} may have a
prefix.  The element is not inserted into the document when it is created.  You
need to explicitly insert it with one of the other methods such as
@code{insertBefore()} or @code{appendChild()}.
@end deffn

@geindex createTextNode() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document createTextNode}@anchor{2a33}
@deffn {方法} Document.createTextNode (data)

Create and return a text node containing the data passed as a parameter.  As
with the other creation methods, this one does not insert the node into the
tree.
@end deffn

@geindex createComment() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document createComment}@anchor{2a34}
@deffn {方法} Document.createComment (data)

Create and return a comment node containing the data passed as a parameter.  As
with the other creation methods, this one does not insert the node into the
tree.
@end deffn

@geindex createProcessingInstruction() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document createProcessingInstruction}@anchor{2a35}
@deffn {方法} Document.createProcessingInstruction (target, data)

Create and return a processing instruction node containing the @emph{target} and
@emph{data} passed as parameters.  As with the other creation methods, this one does
not insert the node into the tree.
@end deffn

@geindex createAttribute() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document createAttribute}@anchor{2a36}
@deffn {方法} Document.createAttribute (name)

Create and return an attribute node.  This method does not associate the
attribute node with any particular element.  You must use
@code{setAttributeNode()} on the appropriate @code{Element} object to use the
newly created attribute instance.
@end deffn

@geindex createAttributeNS() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document createAttributeNS}@anchor{2a37}
@deffn {方法} Document.createAttributeNS (namespaceURI, qualifiedName)

Create and return an attribute node with a namespace.  The @emph{tagName} may have a
prefix.  This method does not associate the attribute node with any particular
element.  You must use @code{setAttributeNode()} on the appropriate
@code{Element} object to use the newly created attribute instance.
@end deffn

@geindex getElementsByTagName() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document getElementsByTagName}@anchor{2a38}
@deffn {方法} Document.getElementsByTagName (tagName)

Search for all descendants (direct children, children's children, etc.) with a
particular element type name.
@end deffn

@geindex getElementsByTagNameNS() (xml.dom.Document 方法)
@anchor{library/xml dom xml dom Document getElementsByTagNameNS}@anchor{2a39}
@deffn {方法} Document.getElementsByTagNameNS (namespaceURI, localName)

Search for all descendants (direct children, children's children, etc.) with a
particular namespace URI and localname.  The localname is the part of the
namespace after the prefix.
@end deffn

@node 元素对象<2>,Attr 对象,文档对象,Objects in the DOM
@anchor{library/xml dom dom-element-objects}@anchor{2a05}@anchor{library/xml dom element-objects}@anchor{2a3a}
@subsubsection 元素对象


@code{Element} is a subclass of @code{Node}, so inherits all the attributes
of that class.

@geindex tagName (xml.dom.Element 属性)
@anchor{library/xml dom xml dom Element tagName}@anchor{2a3b}
@deffn {属性} Element.tagName

The element type name.  In a namespace-using document it may have colons in it.
The value is a string.
@end deffn

@geindex getElementsByTagName() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element getElementsByTagName}@anchor{2a3c}
@deffn {方法} Element.getElementsByTagName (tagName)

Same as equivalent method in the @code{Document} class.
@end deffn

@geindex getElementsByTagNameNS() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element getElementsByTagNameNS}@anchor{2a3d}
@deffn {方法} Element.getElementsByTagNameNS (namespaceURI, localName)

Same as equivalent method in the @code{Document} class.
@end deffn

@geindex hasAttribute() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element hasAttribute}@anchor{2a3e}
@deffn {方法} Element.hasAttribute (name)

Return @code{True} if the element has an attribute named by @emph{name}.
@end deffn

@geindex hasAttributeNS() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element hasAttributeNS}@anchor{2a3f}
@deffn {方法} Element.hasAttributeNS (namespaceURI, localName)

Return @code{True} if the element has an attribute named by @emph{namespaceURI} and
@emph{localName}.
@end deffn

@geindex getAttribute() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element getAttribute}@anchor{2a40}
@deffn {方法} Element.getAttribute (name)

Return the value of the attribute named by @emph{name} as a string. If no such
attribute exists, an empty string is returned, as if the attribute had no value.
@end deffn

@geindex getAttributeNode() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element getAttributeNode}@anchor{2a41}
@deffn {方法} Element.getAttributeNode (attrname)

Return the @code{Attr} node for the attribute named by @emph{attrname}.
@end deffn

@geindex getAttributeNS() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element getAttributeNS}@anchor{2a42}
@deffn {方法} Element.getAttributeNS (namespaceURI, localName)

Return the value of the attribute named by @emph{namespaceURI} and @emph{localName} as a
string. If no such attribute exists, an empty string is returned, as if the
attribute had no value.
@end deffn

@geindex getAttributeNodeNS() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element getAttributeNodeNS}@anchor{2a43}
@deffn {方法} Element.getAttributeNodeNS (namespaceURI, localName)

Return an attribute value as a node, given a @emph{namespaceURI} and @emph{localName}.
@end deffn

@geindex removeAttribute() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element removeAttribute}@anchor{2a44}
@deffn {方法} Element.removeAttribute (name)

Remove an attribute by name.  If there is no matching attribute, a
@ref{2a45,,NotFoundErr} is raised.
@end deffn

@geindex removeAttributeNode() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element removeAttributeNode}@anchor{2a46}
@deffn {方法} Element.removeAttributeNode (oldAttr)

Remove and return @emph{oldAttr} from the attribute list, if present. If @emph{oldAttr} is
not present, @ref{2a45,,NotFoundErr} is raised.
@end deffn

@geindex removeAttributeNS() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element removeAttributeNS}@anchor{2a47}
@deffn {方法} Element.removeAttributeNS (namespaceURI, localName)

Remove an attribute by name.  Note that it uses a localName, not a qname.  No
exception is raised if there is no matching attribute.
@end deffn

@geindex setAttribute() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element setAttribute}@anchor{2a48}
@deffn {方法} Element.setAttribute (name, value)

Set an attribute value from a string.
@end deffn

@geindex setAttributeNode() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element setAttributeNode}@anchor{2a49}
@deffn {方法} Element.setAttributeNode (newAttr)

Add a new attribute node to the element, replacing an existing attribute if
necessary if the @code{name} attribute matches.  If a replacement occurs, the
old attribute node will be returned.  If @emph{newAttr} is already in use,
@ref{2a4a,,InuseAttributeErr} will be raised.
@end deffn

@geindex setAttributeNodeNS() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element setAttributeNodeNS}@anchor{2a4b}
@deffn {方法} Element.setAttributeNodeNS (newAttr)

Add a new attribute node to the element, replacing an existing attribute if
necessary if the @code{namespaceURI} and @code{localName} attributes match.
If a replacement occurs, the old attribute node will be returned.  If @emph{newAttr}
is already in use, @ref{2a4a,,InuseAttributeErr} will be raised.
@end deffn

@geindex setAttributeNS() (xml.dom.Element 方法)
@anchor{library/xml dom xml dom Element setAttributeNS}@anchor{2a4c}
@deffn {方法} Element.setAttributeNS (namespaceURI, qname, value)

Set an attribute value from a string, given a @emph{namespaceURI} and a @emph{qname}.
Note that a qname is the whole attribute name.  This is different than above.
@end deffn

@node Attr 对象,NamedNodeMap 对象,元素对象<2>,Objects in the DOM
@anchor{library/xml dom attr-objects}@anchor{2a4d}@anchor{library/xml dom dom-attr-objects}@anchor{2a06}
@subsubsection Attr 对象


@code{Attr} inherits from @code{Node}, so inherits all its attributes.

@geindex name (xml.dom.Attr 属性)
@anchor{library/xml dom xml dom Attr name}@anchor{2a4e}
@deffn {属性} Attr.name

The attribute name.
In a namespace-using document it may include a colon.
@end deffn

@geindex localName (xml.dom.Attr 属性)
@anchor{library/xml dom xml dom Attr localName}@anchor{2a4f}
@deffn {属性} Attr.localName

The part of the name following the colon if there is one, else the
entire name.
This is a read-only attribute.
@end deffn

@geindex prefix (xml.dom.Attr 属性)
@anchor{library/xml dom xml dom Attr prefix}@anchor{2a50}
@deffn {属性} Attr.prefix

The part of the name preceding the colon if there is one, else the
empty string.
@end deffn

@geindex value (xml.dom.Attr 属性)
@anchor{library/xml dom xml dom Attr value}@anchor{2a51}
@deffn {属性} Attr.value

The text value of the attribute.  This is a synonym for the
@code{nodeValue} attribute.
@end deffn

@node NamedNodeMap 对象,注释对象,Attr 对象,Objects in the DOM
@anchor{library/xml dom dom-attributelist-objects}@anchor{2a52}@anchor{library/xml dom namednodemap-objects}@anchor{2a53}
@subsubsection NamedNodeMap 对象


@code{NamedNodeMap} does @emph{not} inherit from @code{Node}.

@geindex length (xml.dom.NamedNodeMap 属性)
@anchor{library/xml dom xml dom NamedNodeMap length}@anchor{2a54}
@deffn {属性} NamedNodeMap.length

The length of the attribute list.
@end deffn

@geindex item() (xml.dom.NamedNodeMap 方法)
@anchor{library/xml dom xml dom NamedNodeMap item}@anchor{2a55}
@deffn {方法} NamedNodeMap.item (index)

Return an attribute with a particular index.  The order you get the attributes
in is arbitrary but will be consistent for the life of a DOM.  Each item is an
attribute node.  Get its value with the @code{value} attribute.
@end deffn

There are also experimental methods that give this class more mapping behavior.
You can use them or you can use the standardized @code{getAttribute*()} family
of methods on the @code{Element} objects.

@node 注释对象,Text 和 CDATASection 对象,NamedNodeMap 对象,Objects in the DOM
@anchor{library/xml dom comment-objects}@anchor{2a56}@anchor{library/xml dom dom-comment-objects}@anchor{2a07}
@subsubsection 注释对象


@code{Comment} represents a comment in the XML document.  It is a subclass of
@code{Node}, but cannot have child nodes.

@geindex data (xml.dom.Comment 属性)
@anchor{library/xml dom xml dom Comment data}@anchor{2a57}
@deffn {属性} Comment.data

The content of the comment as a string.  The attribute contains all characters
between the leading @code{<!-}@code{-} and trailing @code{-}@code{->}, but does not
include them.
@end deffn

@node Text 和 CDATASection 对象,ProcessingInstruction 对象,注释对象,Objects in the DOM
@anchor{library/xml dom dom-text-objects}@anchor{2a08}@anchor{library/xml dom text-and-cdatasection-objects}@anchor{2a58}
@subsubsection Text 和 CDATASection 对象


The @code{Text} interface represents text in the XML document.  If the parser
and DOM implementation support the DOM's XML extension, portions of the text
enclosed in CDATA marked sections are stored in @code{CDATASection} objects.
These two interfaces are identical, but provide different values for the
@code{nodeType} attribute.

These interfaces extend the @code{Node} interface.  They cannot have child
nodes.

@geindex data (xml.dom.Text 属性)
@anchor{library/xml dom xml dom Text data}@anchor{2a59}
@deffn {属性} Text.data

The content of the text node as a string.
@end deffn

@cartouche
@quotation 注解 
The use of a @code{CDATASection} node does not indicate that the node
represents a complete CDATA marked section, only that the content of the node
was part of a CDATA section.  A single CDATA section may be represented by more
than one node in the document tree.  There is no way to determine whether two
adjacent @code{CDATASection} nodes represent different CDATA marked sections.
@end quotation
@end cartouche

@node ProcessingInstruction 对象,异常<16>,Text 和 CDATASection 对象,Objects in the DOM
@anchor{library/xml dom dom-pi-objects}@anchor{2a09}@anchor{library/xml dom processinginstruction-objects}@anchor{2a5a}
@subsubsection ProcessingInstruction 对象


Represents a processing instruction in the XML document; this inherits from the
@code{Node} interface and cannot have child nodes.

@geindex target (xml.dom.ProcessingInstruction 属性)
@anchor{library/xml dom xml dom ProcessingInstruction target}@anchor{2a5b}
@deffn {属性} ProcessingInstruction.target

The content of the processing instruction up to the first whitespace character.
This is a read-only attribute.
@end deffn

@geindex data (xml.dom.ProcessingInstruction 属性)
@anchor{library/xml dom xml dom ProcessingInstruction data}@anchor{2a5c}
@deffn {属性} ProcessingInstruction.data

The content of the processing instruction following the first whitespace
character.
@end deffn

@node 异常<16>,,ProcessingInstruction 对象,Objects in the DOM
@anchor{library/xml dom dom-exceptions}@anchor{2a5d}@anchor{library/xml dom exceptions}@anchor{2a5e}
@subsubsection 异常


The DOM Level 2 recommendation defines a single exception, @ref{2a5f,,DOMException},
and a number of constants that allow applications to determine what sort of
error occurred. @ref{2a5f,,DOMException} instances carry a @ref{1b,,code} attribute
that provides the appropriate value for the specific exception.

The Python DOM interface provides the constants, but also expands the set of
exceptions so that a specific exception exists for each of the exception codes
defined by the DOM.  The implementations must raise the appropriate specific
exception, each of which carries the appropriate value for the @ref{1b,,code}
attribute.

@geindex DOMException
@anchor{library/xml dom xml dom DOMException}@anchor{2a5f}
@deffn {例外} xml.dom.DOMException

Base exception class used for all specific DOM exceptions.  This exception class
cannot be directly instantiated.
@end deffn

@geindex DomstringSizeErr
@anchor{library/xml dom xml dom DomstringSizeErr}@anchor{2a60}
@deffn {例外} xml.dom.DomstringSizeErr

Raised when a specified range of text does not fit into a string. This is not
known to be used in the Python DOM implementations, but may be received from DOM
implementations not written in Python.
@end deffn

@geindex HierarchyRequestErr
@anchor{library/xml dom xml dom HierarchyRequestErr}@anchor{2a61}
@deffn {例外} xml.dom.HierarchyRequestErr

Raised when an attempt is made to insert a node where the node type is not
allowed.
@end deffn

@geindex IndexSizeErr
@anchor{library/xml dom xml dom IndexSizeErr}@anchor{2a62}
@deffn {例外} xml.dom.IndexSizeErr

Raised when an index or size parameter to a method is negative or exceeds the
allowed values.
@end deffn

@geindex InuseAttributeErr
@anchor{library/xml dom xml dom InuseAttributeErr}@anchor{2a4a}
@deffn {例外} xml.dom.InuseAttributeErr

Raised when an attempt is made to insert an @code{Attr} node that is already
present elsewhere in the document.
@end deffn

@geindex InvalidAccessErr
@anchor{library/xml dom xml dom InvalidAccessErr}@anchor{2a63}
@deffn {例外} xml.dom.InvalidAccessErr

Raised if a parameter or an operation is not supported on the underlying object.
@end deffn

@geindex InvalidCharacterErr
@anchor{library/xml dom xml dom InvalidCharacterErr}@anchor{2a64}
@deffn {例外} xml.dom.InvalidCharacterErr

This exception is raised when a string parameter contains a character that is
not permitted in the context it's being used in by the XML 1.0 recommendation.
For example, attempting to create an @code{Element} node with a space in the
element type name will cause this error to be raised.
@end deffn

@geindex InvalidModificationErr
@anchor{library/xml dom xml dom InvalidModificationErr}@anchor{2a65}
@deffn {例外} xml.dom.InvalidModificationErr

Raised when an attempt is made to modify the type of a node.
@end deffn

@geindex InvalidStateErr
@anchor{library/xml dom xml dom InvalidStateErr}@anchor{2a66}
@deffn {例外} xml.dom.InvalidStateErr

Raised when an attempt is made to use an object that is not defined or is no
longer usable.
@end deffn

@geindex NamespaceErr
@anchor{library/xml dom xml dom NamespaceErr}@anchor{2a67}
@deffn {例外} xml.dom.NamespaceErr

If an attempt is made to change any object in a way that is not permitted with
regard to the Namespaces in XML@footnote{https://www.w3.org/TR/REC-xml-names/}
recommendation, this exception is raised.
@end deffn

@geindex NotFoundErr
@anchor{library/xml dom xml dom NotFoundErr}@anchor{2a45}
@deffn {例外} xml.dom.NotFoundErr

Exception when a node does not exist in the referenced context.  For example,
@code{NamedNodeMap.removeNamedItem()} will raise this if the node passed in does
not exist in the map.
@end deffn

@geindex NotSupportedErr
@anchor{library/xml dom xml dom NotSupportedErr}@anchor{2a68}
@deffn {例外} xml.dom.NotSupportedErr

Raised when the implementation does not support the requested type of object or
operation.
@end deffn

@geindex NoDataAllowedErr
@anchor{library/xml dom xml dom NoDataAllowedErr}@anchor{2a69}
@deffn {例外} xml.dom.NoDataAllowedErr

This is raised if data is specified for a node which does not support data.

@c XXX  a better explanation is needed!
@end deffn

@geindex NoModificationAllowedErr
@anchor{library/xml dom xml dom NoModificationAllowedErr}@anchor{2a6a}
@deffn {例外} xml.dom.NoModificationAllowedErr

Raised on attempts to modify an object where modifications are not allowed (such
as for read-only nodes).
@end deffn

@geindex SyntaxErr
@anchor{library/xml dom xml dom SyntaxErr}@anchor{2a6b}
@deffn {例外} xml.dom.SyntaxErr

Raised when an invalid or illegal string is specified.

@c XXX  how is this different from InvalidCharacterErr?
@end deffn

@geindex WrongDocumentErr
@anchor{library/xml dom xml dom WrongDocumentErr}@anchor{2a6c}
@deffn {例外} xml.dom.WrongDocumentErr

Raised when a node is inserted in a different document than it currently belongs
to, and the implementation does not support migrating the node from one document
to the other.
@end deffn

The exception codes defined in the DOM recommendation map to the exceptions
described above according to this table:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

异常

@item

@code{DOMSTRING_SIZE_ERR}

@tab

@ref{2a60,,DomstringSizeErr}

@item

@code{HIERARCHY_REQUEST_ERR}

@tab

@ref{2a61,,HierarchyRequestErr}

@item

@code{INDEX_SIZE_ERR}

@tab

@ref{2a62,,IndexSizeErr}

@item

@code{INUSE_ATTRIBUTE_ERR}

@tab

@ref{2a4a,,InuseAttributeErr}

@item

@code{INVALID_ACCESS_ERR}

@tab

@ref{2a63,,InvalidAccessErr}

@item

@code{INVALID_CHARACTER_ERR}

@tab

@ref{2a64,,InvalidCharacterErr}

@item

@code{INVALID_MODIFICATION_ERR}

@tab

@ref{2a65,,InvalidModificationErr}

@item

@code{INVALID_STATE_ERR}

@tab

@ref{2a66,,InvalidStateErr}

@item

@code{NAMESPACE_ERR}

@tab

@ref{2a67,,NamespaceErr}

@item

@code{NOT_FOUND_ERR}

@tab

@ref{2a45,,NotFoundErr}

@item

@code{NOT_SUPPORTED_ERR}

@tab

@ref{2a68,,NotSupportedErr}

@item

@code{NO_DATA_ALLOWED_ERR}

@tab

@ref{2a69,,NoDataAllowedErr}

@item

@code{NO_MODIFICATION_ALLOWED_ERR}

@tab

@ref{2a6a,,NoModificationAllowedErr}

@item

@code{SYNTAX_ERR}

@tab

@ref{2a6b,,SyntaxErr}

@item

@code{WRONG_DOCUMENT_ERR}

@tab

@ref{2a6c,,WrongDocumentErr}

@end multitable


@node 一致性,,Objects in the DOM,xml dom --- The Document Object Model API
@anchor{library/xml dom conformance}@anchor{2a6d}@anchor{library/xml dom dom-conformance}@anchor{29f7}
@subsubsection 一致性


This section describes the conformance requirements and relationships between
the Python DOM API, the W3C DOM recommendations, and the OMG IDL mapping for
Python.

@menu
* 类型映射:: 
* Accessor Methods:: 

@end menu

@node 类型映射,Accessor Methods,,一致性
@anchor{library/xml dom dom-type-mapping}@anchor{2a6e}@anchor{library/xml dom type-mapping}@anchor{2a6f}
@subsubsection 类型映射


将根据下表，将DOM规范中使用的IDL类型映射为Python类型。


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

IDL  类型

@tab

Python 类型

@item

@code{boolean}

@tab

@code{bool} 或 @code{int}

@item

@code{int}

@tab

@code{int}

@item

@code{long int}

@tab

@code{int}

@item

@code{unsigned int}

@tab

@code{int}

@item

@code{DOMString}

@tab

@code{str} 或 @code{bytes}

@item

@code{null}

@tab

@code{None}

@end multitable


@node Accessor Methods,,类型映射,一致性
@anchor{library/xml dom accessor-methods}@anchor{2a70}@anchor{library/xml dom dom-accessor-methods}@anchor{2a71}
@subsubsection Accessor Methods


The mapping from OMG IDL to Python defines accessor functions for IDL
@code{attribute} declarations in much the way the Java mapping does.
Mapping the IDL declarations

@example
readonly attribute string someValue;
         attribute string anotherValue;
@end example

yields three accessor functions:  a "get" method for @code{someValue}
(@code{_get_someValue()}), and "get" and "set" methods for @code{anotherValue}
(@code{_get_anotherValue()} and @code{_set_anotherValue()}).  The mapping, in
particular, does not require that the IDL attributes are accessible as normal
Python attributes:  @code{object.someValue} is @emph{not} required to work, and may
raise an @ref{393,,AttributeError}.

The Python DOM API, however, @emph{does} require that normal attribute access work.
This means that the typical surrogates generated by Python IDL compilers are not
likely to work, and wrapper objects may be needed on the client if the DOM
objects are accessed via CORBA. While this does require some additional
consideration for CORBA DOM clients, the implementers with experience using DOM
over CORBA from Python do not consider this a problem.  Attributes that are
declared @code{readonly} may not restrict write access in all DOM
implementations.

In the Python DOM API, accessor functions are not required.  If provided, they
should take the form defined by the Python IDL mapping, but these methods are
considered unnecessary since the attributes are accessible directly from Python.
"Set" accessors should never be provided for @code{readonly} attributes.

The IDL definitions do not fully embody the requirements of the W3C DOM API,
such as the notion of certain objects, such as the return value of
@code{getElementsByTagName()}, being "live".  The Python DOM API does not require
implementations to enforce such requirements.

@node xml dom minidom --- Minimal DOM implementation,xml dom pulldom --- Support for building partial DOM trees,xml dom --- The Document Object Model API,结构化标记处理工具
@anchor{library/xml dom minidom doc}@anchor{2a72}@anchor{library/xml dom minidom module-xml dom minidom}@anchor{135}@anchor{library/xml dom minidom xml-dom-minidom-minimal-dom-implementation}@anchor{2a73}
@subsection @code{xml.dom.minidom} --- Minimal DOM implementation


@geindex xml.dom.minidom (模块)

@strong{Source code:} Lib/xml/dom/minidom.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/dom/minidom.py}


__________________________________________________________________


@ref{135,,xml.dom.minidom} is a minimal implementation of the Document Object
Model interface, with an API similar to that in other languages.  It is intended
to be simpler than the full DOM and also significantly smaller.  Users who are
not already proficient with the DOM should consider using the
@ref{137,,xml.etree.ElementTree} module for their XML processing instead.

@cartouche
@quotation 警告 
The @ref{135,,xml.dom.minidom} module is not secure against
maliciously constructed data.  If you need to parse untrusted or
unauthenticated data see @ref{2993,,XML 漏洞}.
@end quotation
@end cartouche

DOM applications typically start by parsing some XML into a DOM.  With
@ref{135,,xml.dom.minidom}, this is done through the parse functions:

@example
from xml.dom.minidom import parse, parseString

dom1 = parse('c:\\temp\\mydata.xml')  # parse an XML file by name

datasource = open('c:\\temp\\mydata.xml')
dom2 = parse(datasource)  # parse an open file

dom3 = parseString('<myxml>Some data<empty/> some more data</myxml>')
@end example

The @ref{2a74,,parse()} function can take either a filename or an open file object.

@geindex parse() (在 xml.dom.minidom 模块中)
@anchor{library/xml dom minidom xml dom minidom parse}@anchor{2a74}
@deffn {函数} xml.dom.minidom.parse (filename_or_file, parser=None, bufsize=None)

Return a @code{Document} from the given input. @emph{filename_or_file} may be
either a file name, or a file-like object. @emph{parser}, if given, must be a SAX2
parser object. This function will change the document handler of the parser and
activate namespace support; other parser configuration (like setting an entity
resolver) must have been done in advance.
@end deffn

If you have XML in a string, you can use the @ref{2a75,,parseString()} function
instead:

@geindex parseString() (在 xml.dom.minidom 模块中)
@anchor{library/xml dom minidom xml dom minidom parseString}@anchor{2a75}
@deffn {函数} xml.dom.minidom.parseString (string, parser=None)

Return a @code{Document} that represents the @emph{string}. This method creates an
@ref{827,,io.StringIO} object for the string and passes that on to @ref{2a74,,parse()}.
@end deffn

Both functions return a @code{Document} object representing the content of the
document.

What the @ref{2a74,,parse()} and @ref{2a75,,parseString()} functions do is connect an XML
parser with a "DOM builder" that can accept parse events from any SAX parser and
convert them into a DOM tree.  The name of the functions are perhaps misleading,
but are easy to grasp when learning the interfaces.  The parsing of the document
will be completed before these functions return; it's simply that these
functions do not provide a parser implementation themselves.

You can also create a @code{Document} by calling a method on a "DOM
Implementation" object.  You can get this object either by calling the
@code{getDOMImplementation()} function in the @ref{134,,xml.dom} package or the
@ref{135,,xml.dom.minidom} module.  Once you have a @code{Document}, you
can add child nodes to it to populate the DOM:

@example
from xml.dom.minidom import getDOMImplementation

impl = getDOMImplementation()

newdoc = impl.createDocument(None, "some_tag", None)
top_element = newdoc.documentElement
text = newdoc.createTextNode('Some textual content.')
top_element.appendChild(text)
@end example

Once you have a DOM document object, you can access the parts of your XML
document through its properties and methods.  These properties are defined in
the DOM specification.  The main property of the document object is the
@code{documentElement} property.  It gives you the main element in the XML
document: the one that holds all others.  Here is an example program:

@example
dom3 = parseString("<myxml>Some data</myxml>")
assert dom3.documentElement.tagName == "myxml"
@end example

When you are finished with a DOM tree, you may optionally call the
@code{unlink()} method to encourage early cleanup of the now-unneeded
objects.  @code{unlink()} is an @ref{135,,xml.dom.minidom}-specific
extension to the DOM API that renders the node and its descendants are
essentially useless.  Otherwise, Python's garbage collector will
eventually take care of the objects in the tree.


@subsubheading 参见



@table @asis

@item Document Object Model (DOM) Level 1 Specification@footnote{https://www.w3.org/TR/REC-DOM-Level-1/}

The W3C recommendation for the DOM supported by @ref{135,,xml.dom.minidom}.
@end table


@menu
* DOM Objects:: 
* DOM Example:: 
* minidom and the DOM standard:: 

@end menu

@node DOM Objects,DOM Example,,xml dom minidom --- Minimal DOM implementation
@anchor{library/xml dom minidom dom-objects}@anchor{2a76}@anchor{library/xml dom minidom minidom-objects}@anchor{2a77}
@subsubsection DOM Objects


The definition of the DOM API for Python is given as part of the @ref{134,,xml.dom}
module documentation.  This section lists the differences between the API and
@ref{135,,xml.dom.minidom}.

@geindex unlink() (xml.dom.minidom.Node 方法)
@anchor{library/xml dom minidom xml dom minidom Node unlink}@anchor{2a78}
@deffn {方法} Node.unlink ()

Break internal references within the DOM so that it will be garbage collected on
versions of Python without cyclic GC.  Even when cyclic GC is available, using
this can make large amounts of memory available sooner, so calling this on DOM
objects as soon as they are no longer needed is good practice.  This only needs
to be called on the @code{Document} object, but may be called on child nodes
to discard children of that node.

You can avoid calling this method explicitly by using the @ref{6e3,,with}
statement. The following code will automatically unlink @emph{dom} when the
@code{with} block is exited:

@example
with xml.dom.minidom.parse(datasource) as dom:
    ... # Work with dom.
@end example
@end deffn

@geindex writexml() (xml.dom.minidom.Node 方法)
@anchor{library/xml dom minidom xml dom minidom Node writexml}@anchor{2a79}
@deffn {方法} Node.writexml (writer, indent="", addindent="", newl="")

Write XML to the writer object.  The writer receives texts but not bytes as input,
it should have a @code{write()} method which matches that of the file object
interface.  The @emph{indent} parameter is the indentation of the current node.
The @emph{addindent} parameter is the incremental indentation to use for subnodes
of the current one.  The @emph{newl} parameter specifies the string to use to
terminate newlines.

For the @code{Document} node, an additional keyword argument @emph{encoding} can
be used to specify the encoding field of the XML header.


在 3.8 版更改: The @ref{2a79,,writexml()} method now preserves the attribute order specified
by the user.

@end deffn

@geindex toxml() (xml.dom.minidom.Node 方法)
@anchor{library/xml dom minidom xml dom minidom Node toxml}@anchor{2a7a}
@deffn {方法} Node.toxml (encoding=None)

Return a string or byte string containing the XML represented by
the DOM node.

With an explicit @emph{encoding} @footnote{@w{(1)} 
The encoding name included in the XML output should conform to
the appropriate standards. For example, "UTF-8" is valid, but
"UTF8" is not valid in an XML document's declaration, even though
Python accepts it as an encoding name.
See @indicateurl{https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl}
and @indicateurl{https://www.iana.org/assignments/character-sets/character-sets.xhtml}.
} argument, the result is a byte
string in the specified encoding.
With no @emph{encoding} argument, the result is a Unicode string, and the
XML declaration in the resulting string does not specify an
encoding. Encoding this string in an encoding other than UTF-8 is
likely incorrect, since UTF-8 is the default encoding of XML.


在 3.8 版更改: The @ref{2a7a,,toxml()} method now preserves the attribute order specified
by the user.

@end deffn

@geindex toprettyxml() (xml.dom.minidom.Node 方法)
@anchor{library/xml dom minidom xml dom minidom Node toprettyxml}@anchor{2a7b}
@deffn {方法} Node.toprettyxml (indent="\t", newl="\n", encoding=None)

Return a pretty-printed version of the document. @emph{indent} specifies the
indentation string and defaults to a tabulator; @emph{newl} specifies the string
emitted at the end of each line and defaults to @code{\n}.

The @emph{encoding} argument behaves like the corresponding argument of
@ref{2a7a,,toxml()}.


在 3.8 版更改: The @ref{2a7b,,toprettyxml()} method now preserves the attribute order specified
by the user.

@end deffn

@node DOM Example,minidom and the DOM standard,DOM Objects,xml dom minidom --- Minimal DOM implementation
@anchor{library/xml dom minidom dom-example}@anchor{2a7c}@anchor{library/xml dom minidom id2}@anchor{2a7d}
@subsubsection DOM Example


This example program is a fairly realistic example of a simple program. In this
particular case, we do not take much advantage of the flexibility of the DOM.

@example
import xml.dom.minidom

document = """\
<slideshow>
<title>Demo slideshow</title>
<slide><title>Slide title</title>
<point>This is a demo</point>
<point>Of a program for processing slides</point>
</slide>

<slide><title>Another demo slide</title>
<point>It is important</point>
<point>To have more than</point>
<point>one slide</point>
</slide>
</slideshow>
"""

dom = xml.dom.minidom.parseString(document)

def getText(nodelist):
    rc = []
    for node in nodelist:
        if node.nodeType == node.TEXT_NODE:
            rc.append(node.data)
    return '@w{'}.join(rc)

def handleSlideshow(slideshow):
    print("<html>")
    handleSlideshowTitle(slideshow.getElementsByTagName("title")[0])
    slides = slideshow.getElementsByTagName("slide")
    handleToc(slides)
    handleSlides(slides)
    print("</html>")

def handleSlides(slides):
    for slide in slides:
        handleSlide(slide)

def handleSlide(slide):
    handleSlideTitle(slide.getElementsByTagName("title")[0])
    handlePoints(slide.getElementsByTagName("point"))

def handleSlideshowTitle(title):
    print("<title>%s</title>" % getText(title.childNodes))

def handleSlideTitle(title):
    print("<h2>%s</h2>" % getText(title.childNodes))

def handlePoints(points):
    print("<ul>")
    for point in points:
        handlePoint(point)
    print("</ul>")

def handlePoint(point):
    print("<li>%s</li>" % getText(point.childNodes))

def handleToc(slides):
    for slide in slides:
        title = slide.getElementsByTagName("title")[0]
        print("<p>%s</p>" % getText(title.childNodes))

handleSlideshow(dom)
@end example

@node minidom and the DOM standard,,DOM Example,xml dom minidom --- Minimal DOM implementation
@anchor{library/xml dom minidom minidom-and-dom}@anchor{2a7e}@anchor{library/xml dom minidom minidom-and-the-dom-standard}@anchor{2a7f}
@subsubsection minidom and the DOM standard


The @ref{135,,xml.dom.minidom} module is essentially a DOM 1.0-compatible DOM with
some DOM 2 features (primarily namespace features).

Usage of the DOM interface in Python is straight-forward.  The following mapping
rules apply:


@itemize *

@item 
Interfaces are accessed through instance objects. Applications should not
instantiate the classes themselves; they should use the creator functions
available on the @code{Document} object. Derived interfaces support all
operations (and attributes) from the base interfaces, plus any new operations.

@item 
Operations are used as methods. Since the DOM uses only @ref{79d,,in}
parameters, the arguments are passed in normal order (from left to right).
There are no optional arguments. @code{void} operations return @code{None}.

@item 
IDL attributes map to instance attributes. For compatibility with the OMG IDL
language mapping for Python, an attribute @code{foo} can also be accessed through
accessor methods @code{_get_foo()} and @code{_set_foo()}.  @code{readonly}
attributes must not be changed; this is not enforced at runtime.

@item 
The types @code{short int}, @code{unsigned int}, @code{unsigned long long}, and
@code{boolean} all map to Python integer objects.

@item 
The type @code{DOMString} maps to Python strings. @ref{135,,xml.dom.minidom} supports
either bytes or strings, but will normally produce strings.
Values of type @code{DOMString} may also be @code{None} where allowed to have the IDL
@code{null} value by the DOM specification from the W3C.

@item 
@code{const} declarations map to variables in their respective scope (e.g.
@code{xml.dom.minidom.Node.PROCESSING_INSTRUCTION_NODE}); they must not be changed.

@item 
@code{DOMException} is currently not supported in @ref{135,,xml.dom.minidom}.
Instead, @ref{135,,xml.dom.minidom} uses standard Python exceptions such as
@ref{192,,TypeError} and @ref{393,,AttributeError}.

@item 
@code{NodeList} objects are implemented using Python's built-in list type.
These objects provide the interface defined in the DOM specification, but with
earlier versions of Python they do not support the official API.  They are,
however, much more "Pythonic" than the interface defined in the W3C
recommendations.
@end itemize

The following interfaces have no implementation in @ref{135,,xml.dom.minidom}:


@itemize *

@item 
@code{DOMTimeStamp}

@item 
@code{EntityReference}
@end itemize

Most of these reflect information in the XML document that is not of general
utility to most DOM users.

@subsubheading 备注


@node xml dom pulldom --- Support for building partial DOM trees,xml sax --- Support for SAX2 parsers,xml dom minidom --- Minimal DOM implementation,结构化标记处理工具
@anchor{library/xml dom pulldom doc}@anchor{2a80}@anchor{library/xml dom pulldom module-xml dom pulldom}@anchor{136}@anchor{library/xml dom pulldom xml-dom-pulldom-support-for-building-partial-dom-trees}@anchor{2a81}
@subsection @code{xml.dom.pulldom} --- Support for building partial DOM trees


@geindex xml.dom.pulldom (模块)

@strong{Source code:} Lib/xml/dom/pulldom.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/dom/pulldom.py}


__________________________________________________________________


The @ref{136,,xml.dom.pulldom} module provides a "pull parser" which can also be
asked to produce DOM-accessible fragments of the document where necessary. The
basic concept involves pulling "events" from a stream of incoming XML and
processing them. In contrast to SAX which also employs an event-driven
processing model together with callbacks, the user of a pull parser is
responsible for explicitly pulling events from the stream, looping over those
events until either processing is finished or an error condition occurs.

@cartouche
@quotation 警告 
The @ref{136,,xml.dom.pulldom} module is not secure against
maliciously constructed data.  If you need to parse untrusted or
unauthenticated data see @ref{2993,,XML 漏洞}.
@end quotation
@end cartouche


在 3.7.1 版更改: The SAX parser no longer processes general external entities by default to
increase security by default. To enable processing of external entities,
pass a custom parser instance in:

@example
from xml.dom.pulldom import parse
from xml.sax import make_parser
from xml.sax.handler import feature_external_ges

parser = make_parser()
parser.setFeature(feature_external_ges, True)
parse(filename, parser=parser)
@end example


示例:

@example
from xml.dom import pulldom

doc = pulldom.parse('sales_items.xml')
for event, node in doc:
    if event == pulldom.START_ELEMENT and node.tagName == 'item':
        if int(node.getAttribute('price')) > 50:
            doc.expandNode(node)
            print(node.toxml())
@end example

@code{event} is a constant and can be one of:


@itemize *

@item 
@code{START_ELEMENT}

@item 
@code{END_ELEMENT}

@item 
@code{COMMENT}

@item 
@code{START_DOCUMENT}

@item 
@code{END_DOCUMENT}

@item 
@code{CHARACTERS}

@item 
@code{PROCESSING_INSTRUCTION}

@item 
@code{IGNORABLE_WHITESPACE}
@end itemize

@code{node} is an object of type @code{xml.dom.minidom.Document},
@code{xml.dom.minidom.Element} or @code{xml.dom.minidom.Text}.

Since the document is treated as a "flat" stream of events, the document "tree"
is implicitly traversed and the desired elements are found regardless of their
depth in the tree. In other words, one does not need to consider hierarchical
issues such as recursive searching of the document nodes, although if the
context of elements were important, one would either need to maintain some
context-related state (i.e. remembering where one is in the document at any
given point) or to make use of the @ref{2a82,,DOMEventStream.expandNode()} method
and switch to DOM-related processing.

@geindex PullDom (xml.dom.pulldom 中的类)
@anchor{library/xml dom pulldom xml dom pulldom PullDom}@anchor{2a83}
@deffn {类} xml.dom.pulldom.PullDom (documentFactory=None)

Subclass of @ref{2a84,,xml.sax.handler.ContentHandler}.
@end deffn

@geindex SAX2DOM (xml.dom.pulldom 中的类)
@anchor{library/xml dom pulldom xml dom pulldom SAX2DOM}@anchor{2a85}
@deffn {类} xml.dom.pulldom.SAX2DOM (documentFactory=None)

Subclass of @ref{2a84,,xml.sax.handler.ContentHandler}.
@end deffn

@geindex parse() (在 xml.dom.pulldom 模块中)
@anchor{library/xml dom pulldom xml dom pulldom parse}@anchor{2a86}
@deffn {函数} xml.dom.pulldom.parse (stream_or_string, parser=None, bufsize=None)

Return a @ref{27c,,DOMEventStream} from the given input. @emph{stream_or_string} may be
either a file name, or a file-like object. @emph{parser}, if given, must be an
@ref{2a87,,XMLReader} object. This function will change the
document handler of the
parser and activate namespace support; other parser configuration (like
setting an entity resolver) must have been done in advance.
@end deffn

If you have XML in a string, you can use the @ref{2a88,,parseString()} function instead:

@geindex parseString() (在 xml.dom.pulldom 模块中)
@anchor{library/xml dom pulldom xml dom pulldom parseString}@anchor{2a88}
@deffn {函数} xml.dom.pulldom.parseString (string, parser=None)

Return a @ref{27c,,DOMEventStream} that represents the (Unicode) @emph{string}.
@end deffn

@geindex default_bufsize() (在 xml.dom.pulldom 模块中)
@anchor{library/xml dom pulldom xml dom pulldom default_bufsize}@anchor{2a89}
@deffn {数据} xml.dom.pulldom.default_bufsize

Default value for the @emph{bufsize} parameter to @ref{2a86,,parse()}.

The value of this variable can be changed before calling @ref{2a86,,parse()} and
the new value will take effect.
@end deffn

@menu
* DOMEventStream Objects:: 

@end menu

@node DOMEventStream Objects,,,xml dom pulldom --- Support for building partial DOM trees
@anchor{library/xml dom pulldom domeventstream-objects}@anchor{2a8a}@anchor{library/xml dom pulldom id1}@anchor{2a8b}
@subsubsection DOMEventStream Objects


@geindex DOMEventStream (xml.dom.pulldom 中的类)
@anchor{library/xml dom pulldom xml dom pulldom DOMEventStream}@anchor{27c}
@deffn {类} xml.dom.pulldom.DOMEventStream (stream, parser, bufsize)


3.8 版后已移除: Support for @ref{27f,,sequence protocol} is deprecated.


@geindex getEvent() (xml.dom.pulldom.DOMEventStream 方法)
@anchor{library/xml dom pulldom xml dom pulldom DOMEventStream getEvent}@anchor{2a8c}
@deffn {方法} getEvent ()

Return a tuple containing @emph{event} and the current @emph{node} as
@code{xml.dom.minidom.Document} if event equals @code{START_DOCUMENT},
@code{xml.dom.minidom.Element} if event equals @code{START_ELEMENT} or
@code{END_ELEMENT} or @code{xml.dom.minidom.Text} if event equals
@code{CHARACTERS}.
The current node does not contain information about its children, unless
@ref{2a82,,expandNode()} is called.
@end deffn

@geindex expandNode() (xml.dom.pulldom.DOMEventStream 方法)
@anchor{library/xml dom pulldom xml dom pulldom DOMEventStream expandNode}@anchor{2a82}
@deffn {方法} expandNode (node)

Expands all children of @emph{node} into @emph{node}. Example:

@example
from xml.dom import pulldom

xml = '<html><title>Foo</title> <p>Some text <div>and more</div></p> </html>'
doc = pulldom.parseString(xml)
for event, node in doc:
    if event == pulldom.START_ELEMENT and node.tagName == 'p':
        # Following statement only prints '<p/>'
        print(node.toxml())
        doc.expandNode(node)
        # Following statement prints node with all its children '<p>Some text <div>and more</div></p>'
        print(node.toxml())
@end example
@end deffn

@geindex reset() (xml.dom.pulldom.DOMEventStream 方法)
@anchor{library/xml dom pulldom xml dom pulldom DOMEventStream reset}@anchor{2a8d}
@deffn {方法} reset ()
@end deffn
@end deffn

@node xml sax --- Support for SAX2 parsers,xml sax handler --- Base classes for SAX handlers,xml dom pulldom --- Support for building partial DOM trees,结构化标记处理工具
@anchor{library/xml sax doc}@anchor{2a8e}@anchor{library/xml sax module-xml sax}@anchor{13b}@anchor{library/xml sax xml-sax-support-for-sax2-parsers}@anchor{2a8f}
@subsection @code{xml.sax} --- Support for SAX2 parsers


@geindex xml.sax (模块)

@strong{Source code:} Lib/xml/sax/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/sax/__init__.py}


__________________________________________________________________


The @ref{13b,,xml.sax} package provides a number of modules which implement the
Simple API for XML (SAX) interface for Python.  The package itself provides the
SAX exceptions and the convenience functions which will be most used by users of
the SAX API.

@cartouche
@quotation 警告 
The @ref{13b,,xml.sax} module is not secure against maliciously
constructed data.  If you need to parse untrusted or unauthenticated data see
@ref{2993,,XML 漏洞}.
@end quotation
@end cartouche


在 3.7.1 版更改: The SAX parser no longer processes general external entities by default
to increase security. Before, the parser created network connections
to fetch remote files or loaded local files from the file
system for DTD and entities. The feature can be enabled again with method
@ref{2a90,,setFeature()} on the parser object
and argument @ref{2a91,,feature_external_ges}.


The convenience functions are:

@geindex make_parser() (在 xml.sax 模块中)
@anchor{library/xml sax xml sax make_parser}@anchor{fbb}
@deffn {函数} xml.sax.make_parser (parser_list=[])

Create and return a SAX @ref{2a87,,XMLReader} object.  The
first parser found will
be used.  If @emph{parser_list} is provided, it must be an iterable of strings which
name modules that have a function named @code{create_parser()}.  Modules listed
in @emph{parser_list} will be used before modules in the default list of parsers.


在 3.8 版更改: The @emph{parser_list} argument can be any iterable, not just a list.

@end deffn

@geindex parse() (在 xml.sax 模块中)
@anchor{library/xml sax xml sax parse}@anchor{f72}
@deffn {函数} xml.sax.parse (filename_or_stream, handler, error_handler=handler.ErrorHandler())

Create a SAX parser and use it to parse a document.  The document, passed in as
@emph{filename_or_stream}, can be a filename or a file object.  The @emph{handler}
parameter needs to be a SAX @ref{2a84,,ContentHandler} instance.  If
@emph{error_handler} is given, it must be a SAX @ref{2a92,,ErrorHandler}
instance; if
omitted,  @ref{2a93,,SAXParseException} will be raised on all errors.  There is no
return value; all work must be done by the @emph{handler} passed in.
@end deffn

@geindex parseString() (在 xml.sax 模块中)
@anchor{library/xml sax xml sax parseString}@anchor{78d}
@deffn {函数} xml.sax.parseString (string, handler, error_handler=handler.ErrorHandler())

Similar to @ref{f72,,parse()}, but parses from a buffer @emph{string} received as a
parameter.  @emph{string} must be a @ref{329,,str} instance or a
@ref{5e3,,bytes-like object}.


在 3.5 版更改: Added support of @ref{329,,str} instances.

@end deffn

A typical SAX application uses three kinds of objects: readers, handlers and
input sources.  "Reader" in this context is another term for parser, i.e. some
piece of code that reads the bytes or characters from the input source, and
produces a sequence of events. The events then get distributed to the handler
objects, i.e. the reader invokes a method on the handler.  A SAX application
must therefore obtain a reader object, create or open the input sources, create
the handlers, and connect these objects all together.  As the final step of
preparation, the reader is called to parse the input. During parsing, methods on
the handler objects are called based on structural and syntactic events from the
input data.

For these objects, only the interfaces are relevant; they are normally not
instantiated by the application itself.  Since Python does not have an explicit
notion of interface, they are formally introduced as classes, but applications
may use implementations which do not inherit from the provided classes.  The
@ref{78c,,InputSource}, @ref{2a94,,Locator},
@code{Attributes}, @code{AttributesNS},
and @ref{2a87,,XMLReader} interfaces are defined in the
module @ref{13e,,xml.sax.xmlreader}.  The handler interfaces are defined in
@ref{13c,,xml.sax.handler}.  For convenience,
@ref{78c,,InputSource} (which is often
instantiated directly) and the handler classes are also available from
@ref{13b,,xml.sax}.  These interfaces are described below.

In addition to these classes, @ref{13b,,xml.sax} provides the following exception
classes.

@geindex SAXException
@anchor{library/xml sax xml sax SAXException}@anchor{2a95}
@deffn {例外} xml.sax.SAXException (msg, exception=None)

Encapsulate an XML error or warning.  This class can contain basic error or
warning information from either the XML parser or the application: it can be
subclassed to provide additional functionality or to add localization.  Note
that although the handlers defined in the
@ref{2a92,,ErrorHandler} interface
receive instances of this exception, it is not required to actually raise the
exception --- it is also useful as a container for information.

When instantiated, @emph{msg} should be a human-readable description of the error.
The optional @emph{exception} parameter, if given, should be @code{None} or an exception
that was caught by the parsing code and is being passed along as information.

This is the base class for the other SAX exception classes.
@end deffn

@geindex SAXParseException
@anchor{library/xml sax xml sax SAXParseException}@anchor{2a93}
@deffn {例外} xml.sax.SAXParseException (msg, exception, locator)

Subclass of @ref{2a95,,SAXException} raised on parse errors. Instances of this
class are passed to the methods of the SAX
@ref{2a92,,ErrorHandler} interface to provide information
about the parse error.  This class supports the SAX
@ref{2a94,,Locator} interface as well as the
@ref{2a95,,SAXException} interface.
@end deffn

@geindex SAXNotRecognizedException
@anchor{library/xml sax xml sax SAXNotRecognizedException}@anchor{2a96}
@deffn {例外} xml.sax.SAXNotRecognizedException (msg, exception=None)

Subclass of @ref{2a95,,SAXException} raised when a SAX
@ref{2a87,,XMLReader} is
confronted with an unrecognized feature or property.  SAX applications and
extensions may use this class for similar purposes.
@end deffn

@geindex SAXNotSupportedException
@anchor{library/xml sax xml sax SAXNotSupportedException}@anchor{2a97}
@deffn {例外} xml.sax.SAXNotSupportedException (msg, exception=None)

Subclass of @ref{2a95,,SAXException} raised when a SAX
@ref{2a87,,XMLReader} is asked to
enable a feature that is not supported, or to set a property to a value that the
implementation does not support.  SAX applications and extensions may use this
class for similar purposes.
@end deffn


@subsubheading 参见



@table @asis

@item SAX: The Simple API for XML@footnote{http://www.saxproject.org/}

This site is the focal point for the definition of the SAX API.  It provides a
Java implementation and online documentation.  Links to implementations and
historical information are also available.

@item Module @ref{13c,,xml.sax.handler}

Definitions of the interfaces for application-provided objects.

@item Module @ref{13d,,xml.sax.saxutils}

Convenience functions for use in SAX applications.

@item Module @ref{13e,,xml.sax.xmlreader}

Definitions of the interfaces for parser-provided objects.
@end table


@menu
* SAXException Objects:: 

@end menu

@node SAXException Objects,,,xml sax --- Support for SAX2 parsers
@anchor{library/xml sax sax-exception-objects}@anchor{2a98}@anchor{library/xml sax saxexception-objects}@anchor{2a99}
@subsubsection SAXException Objects


The @ref{2a95,,SAXException} exception class supports the following methods:

@geindex getMessage() (xml.sax.SAXException 方法)
@anchor{library/xml sax xml sax SAXException getMessage}@anchor{2a9a}
@deffn {方法} SAXException.getMessage ()

Return a human-readable message describing the error condition.
@end deffn

@geindex getException() (xml.sax.SAXException 方法)
@anchor{library/xml sax xml sax SAXException getException}@anchor{2a9b}
@deffn {方法} SAXException.getException ()

Return an encapsulated exception object, or @code{None}.
@end deffn

@node xml sax handler --- Base classes for SAX handlers,xml sax saxutils --- SAX 工具集,xml sax --- Support for SAX2 parsers,结构化标记处理工具
@anchor{library/xml sax handler doc}@anchor{2a9c}@anchor{library/xml sax handler module-xml sax handler}@anchor{13c}@anchor{library/xml sax handler xml-sax-handler-base-classes-for-sax-handlers}@anchor{2a9d}
@subsection @code{xml.sax.handler} --- Base classes for SAX handlers


@geindex xml.sax.handler (模块)

@strong{Source code:} Lib/xml/sax/handler.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/sax/handler.py}


__________________________________________________________________


The SAX API defines four kinds of handlers: content handlers, DTD handlers,
error handlers, and entity resolvers. Applications normally only need to
implement those interfaces whose events they are interested in; they can
implement the interfaces in a single object or in multiple objects. Handler
implementations should inherit from the base classes provided in the module
@ref{13c,,xml.sax.handler}, so that all methods get default implementations.

@geindex ContentHandler (xml.sax.handler 中的类)
@anchor{library/xml sax handler xml sax handler ContentHandler}@anchor{2a84}
@deffn {类} xml.sax.handler.ContentHandler

This is the main callback interface in SAX, and the one most important to
applications. The order of events in this interface mirrors the order of the
information in the document.
@end deffn

@geindex DTDHandler (xml.sax.handler 中的类)
@anchor{library/xml sax handler xml sax handler DTDHandler}@anchor{2a9e}
@deffn {类} xml.sax.handler.DTDHandler

Handle DTD events.

This interface specifies only those DTD events required for basic parsing
(unparsed entities and attributes).
@end deffn

@geindex EntityResolver (xml.sax.handler 中的类)
@anchor{library/xml sax handler xml sax handler EntityResolver}@anchor{2a9f}
@deffn {类} xml.sax.handler.EntityResolver

Basic interface for resolving entities. If you create an object implementing
this interface, then register the object with your Parser, the parser will call
the method in your object to resolve all external entities.
@end deffn

@geindex ErrorHandler (xml.sax.handler 中的类)
@anchor{library/xml sax handler xml sax handler ErrorHandler}@anchor{2a92}
@deffn {类} xml.sax.handler.ErrorHandler

Interface used by the parser to present error and warning messages to the
application.  The methods of this object control whether errors are immediately
converted to exceptions or are handled in some other way.
@end deffn

In addition to these classes, @ref{13c,,xml.sax.handler} provides symbolic constants
for the feature and property names.

@geindex feature_namespaces() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler feature_namespaces}@anchor{2aa0}
@deffn {数据} xml.sax.handler.feature_namespaces


@display
value: @code{"http://xml.org/sax/features/namespaces"}@w{ }
true: Perform Namespace processing.@w{ }
false: Optionally do not perform Namespace processing (implies namespace-prefixes; default).@w{ }
access: (parsing) read-only; (not parsing) read/write@w{ }
@end display


@end deffn

@geindex feature_namespace_prefixes() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler feature_namespace_prefixes}@anchor{2aa1}
@deffn {数据} xml.sax.handler.feature_namespace_prefixes


@display
value: @code{"http://xml.org/sax/features/namespace-prefixes"}@w{ }
true: Report the original prefixed names and attributes used for Namespace declarations.@w{ }
false: Do not report attributes used for Namespace declarations, and optionally do not report original prefixed names (default).@w{ }
access: (parsing) read-only; (not parsing) read/write@w{ }
@end display


@end deffn

@geindex feature_string_interning() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler feature_string_interning}@anchor{2aa2}
@deffn {数据} xml.sax.handler.feature_string_interning


@display
value: @code{"http://xml.org/sax/features/string-interning"}@w{ }
true: All element names, prefixes, attribute names, Namespace URIs, and local names are interned using the built-in intern function.@w{ }
false: Names are not necessarily interned, although they may be (default).@w{ }
access: (parsing) read-only; (not parsing) read/write@w{ }
@end display


@end deffn

@geindex feature_validation() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler feature_validation}@anchor{2aa3}
@deffn {数据} xml.sax.handler.feature_validation


@display
value: @code{"http://xml.org/sax/features/validation"}@w{ }
true: Report all validation errors (implies external-general-entities and external-parameter-entities).@w{ }
false: Do not report validation errors.@w{ }
access: (parsing) read-only; (not parsing) read/write@w{ }
@end display


@end deffn

@geindex feature_external_ges() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler feature_external_ges}@anchor{2a91}
@deffn {数据} xml.sax.handler.feature_external_ges


@display
value: @code{"http://xml.org/sax/features/external-general-entities"}@w{ }
true: Include all external general (text) entities.@w{ }
false: Do not include external general entities.@w{ }
access: (parsing) read-only; (not parsing) read/write@w{ }
@end display


@end deffn

@geindex feature_external_pes() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler feature_external_pes}@anchor{2aa4}
@deffn {数据} xml.sax.handler.feature_external_pes


@display
value: @code{"http://xml.org/sax/features/external-parameter-entities"}@w{ }
true: Include all external parameter entities, including the external DTD subset.@w{ }
false: Do not include any external parameter entities, even the external DTD subset.@w{ }
access: (parsing) read-only; (not parsing) read/write@w{ }
@end display


@end deffn

@geindex all_features() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler all_features}@anchor{2aa5}
@deffn {数据} xml.sax.handler.all_features

List of all features.
@end deffn

@geindex property_lexical_handler() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler property_lexical_handler}@anchor{2aa6}
@deffn {数据} xml.sax.handler.property_lexical_handler


@display
value: @code{"http://xml.org/sax/properties/lexical-handler"}@w{ }
data type: xml.sax.sax2lib.LexicalHandler (not supported in Python 2)@w{ }
description: An optional extension handler for lexical events like comments.@w{ }
access: read/write@w{ }
@end display


@end deffn

@geindex property_declaration_handler() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler property_declaration_handler}@anchor{2aa7}
@deffn {数据} xml.sax.handler.property_declaration_handler


@display
value: @code{"http://xml.org/sax/properties/declaration-handler"}@w{ }
data type: xml.sax.sax2lib.DeclHandler (not supported in Python 2)@w{ }
description: An optional extension handler for DTD-related events other than notations and unparsed entities.@w{ }
access: read/write@w{ }
@end display


@end deffn

@geindex property_dom_node() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler property_dom_node}@anchor{2aa8}
@deffn {数据} xml.sax.handler.property_dom_node


@display
value: @code{"http://xml.org/sax/properties/dom-node"}@w{ }
data type: org.w3c.dom.Node (not supported in Python 2)@w{ }
description: When parsing, the current DOM node being visited if this is a DOM iterator; when not parsing, the root DOM node for iteration.@w{ }
access: (parsing) read-only; (not parsing) read/write@w{ }
@end display


@end deffn

@geindex property_xml_string() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler property_xml_string}@anchor{2aa9}
@deffn {数据} xml.sax.handler.property_xml_string


@display
value: @code{"http://xml.org/sax/properties/xml-string"}@w{ }
data type: String@w{ }
description: The literal string of characters that was the source for the current event.@w{ }
access: read-only@w{ }
@end display


@end deffn

@geindex all_properties() (在 xml.sax.handler 模块中)
@anchor{library/xml sax handler xml sax handler all_properties}@anchor{2aaa}
@deffn {数据} xml.sax.handler.all_properties

List of all known property names.
@end deffn

@menu
* ContentHandler 对象:: 
* DTDHandler 对象:: 
* EntityResolver 对象:: 
* ErrorHandler 对象:: 

@end menu

@node ContentHandler 对象,DTDHandler 对象,,xml sax handler --- Base classes for SAX handlers
@anchor{library/xml sax handler content-handler-objects}@anchor{2aab}@anchor{library/xml sax handler contenthandler-objects}@anchor{2aac}
@subsubsection ContentHandler 对象


Users are expected to subclass @ref{2a84,,ContentHandler} to support their
application.  The following methods are called by the parser on the appropriate
events in the input document:

@geindex setDocumentLocator() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler setDocumentLocator}@anchor{2aad}
@deffn {方法} ContentHandler.setDocumentLocator (locator)

Called by the parser to give the application a locator for locating the origin
of document events.

SAX parsers are strongly encouraged (though not absolutely required) to supply a
locator: if it does so, it must supply the locator to the application by
invoking this method before invoking any of the other methods in the
DocumentHandler interface.

The locator allows the application to determine the end position of any
document-related event, even if the parser is not reporting an error. Typically,
the application will use this information for reporting its own errors (such as
character content that does not match an application's business rules). The
information returned by the locator is probably not sufficient for use with a
search engine.

Note that the locator will return correct information only during the invocation
of the events in this interface. The application should not attempt to use it at
any other time.
@end deffn

@geindex startDocument() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler startDocument}@anchor{2aae}
@deffn {方法} ContentHandler.startDocument ()

Receive notification of the beginning of a document.

The SAX parser will invoke this method only once, before any other methods in
this interface or in DTDHandler (except for @ref{2aad,,setDocumentLocator()}).
@end deffn

@geindex endDocument() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler endDocument}@anchor{2aaf}
@deffn {方法} ContentHandler.endDocument ()

Receive notification of the end of a document.

The SAX parser will invoke this method only once, and it will be the last method
invoked during the parse. The parser shall not invoke this method until it has
either abandoned parsing (because of an unrecoverable error) or reached the end
of input.
@end deffn

@geindex startPrefixMapping() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler startPrefixMapping}@anchor{2ab0}
@deffn {方法} ContentHandler.startPrefixMapping (prefix, uri)

Begin the scope of a prefix-URI Namespace mapping.

The information from this event is not necessary for normal Namespace
processing: the SAX XML reader will automatically replace prefixes for element
and attribute names when the @code{feature_namespaces} feature is enabled (the
default).

There are cases, however, when applications need to use prefixes in character
data or in attribute values, where they cannot safely be expanded automatically;
the @ref{2ab0,,startPrefixMapping()} and @ref{2ab1,,endPrefixMapping()} events supply the
information to the application to expand prefixes in those contexts itself, if
necessary.

@c XXX This is not really the default, is it? MvL

Note that @ref{2ab0,,startPrefixMapping()} and @ref{2ab1,,endPrefixMapping()} events are not
guaranteed to be properly nested relative to each-other: all
@ref{2ab0,,startPrefixMapping()} events will occur before the corresponding
@ref{2ab2,,startElement()} event, and all @ref{2ab1,,endPrefixMapping()} events will occur
after the corresponding @ref{2ab3,,endElement()} event, but their order is not
guaranteed.
@end deffn

@geindex endPrefixMapping() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler endPrefixMapping}@anchor{2ab1}
@deffn {方法} ContentHandler.endPrefixMapping (prefix)

End the scope of a prefix-URI mapping.

See @ref{2ab0,,startPrefixMapping()} for details. This event will always occur after
the corresponding @ref{2ab3,,endElement()} event, but the order of
@ref{2ab1,,endPrefixMapping()} events is not otherwise guaranteed.
@end deffn

@geindex startElement() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler startElement}@anchor{2ab2}
@deffn {方法} ContentHandler.startElement (name, attrs)

Signals the start of an element in non-namespace mode.

The @emph{name} parameter contains the raw XML 1.0 name of the element type as a
string and the @emph{attrs} parameter holds an object of the
@code{Attributes}
interface (see @ref{2ab4,,The Attributes Interface}) containing the attributes of
the element.  The object passed as @emph{attrs} may be re-used by the parser; holding
on to a reference to it is not a reliable way to keep a copy of the attributes.
To keep a copy of the attributes, use the @ref{26,,copy()} method of the @emph{attrs}
object.
@end deffn

@geindex endElement() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler endElement}@anchor{2ab3}
@deffn {方法} ContentHandler.endElement (name)

Signals the end of an element in non-namespace mode.

The @emph{name} parameter contains the name of the element type, just as with the
@ref{2ab2,,startElement()} event.
@end deffn

@geindex startElementNS() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler startElementNS}@anchor{2ab5}
@deffn {方法} ContentHandler.startElementNS (name, qname, attrs)

Signals the start of an element in namespace mode.

The @emph{name} parameter contains the name of the element type as a @code{(uri,
localname)} tuple, the @emph{qname} parameter contains the raw XML 1.0 name used in
the source document, and the @emph{attrs} parameter holds an instance of the
@code{AttributesNS} interface (see
@ref{2ab6,,The AttributesNS Interface})
containing the attributes of the element.  If no namespace is associated with
the element, the @emph{uri} component of @emph{name} will be @code{None}.  The object passed
as @emph{attrs} may be re-used by the parser; holding on to a reference to it is not
a reliable way to keep a copy of the attributes.  To keep a copy of the
attributes, use the @ref{26,,copy()} method of the @emph{attrs} object.

Parsers may set the @emph{qname} parameter to @code{None}, unless the
@code{feature_namespace_prefixes} feature is activated.
@end deffn

@geindex endElementNS() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler endElementNS}@anchor{2ab7}
@deffn {方法} ContentHandler.endElementNS (name, qname)

Signals the end of an element in namespace mode.

The @emph{name} parameter contains the name of the element type, just as with the
@ref{2ab5,,startElementNS()} method, likewise the @emph{qname} parameter.
@end deffn

@geindex characters() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler characters}@anchor{2ab8}
@deffn {方法} ContentHandler.characters (content)

Receive notification of character data.

The Parser will call this method to report each chunk of character data. SAX
parsers may return all contiguous character data in a single chunk, or they may
split it into several chunks; however, all of the characters in any single event
must come from the same external entity so that the Locator provides useful
information.

@emph{content} may be a string or bytes instance; the @code{expat} reader module
always produces strings.

@cartouche
@quotation 注解 
The earlier SAX 1 interface provided by the Python XML Special Interest Group
used a more Java-like interface for this method.  Since most parsers used from
Python did not take advantage of the older interface, the simpler signature was
chosen to replace it.  To convert old code to the new interface, use @emph{content}
instead of slicing content with the old @emph{offset} and @emph{length} parameters.
@end quotation
@end cartouche
@end deffn

@geindex ignorableWhitespace() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler ignorableWhitespace}@anchor{2ab9}
@deffn {方法} ContentHandler.ignorableWhitespace (whitespace)

Receive notification of ignorable whitespace in element content.

Validating Parsers must use this method to report each chunk of ignorable
whitespace (see the W3C XML 1.0 recommendation, section 2.10): non-validating
parsers may also use this method if they are capable of parsing and using
content models.

SAX parsers may return all contiguous whitespace in a single chunk, or they may
split it into several chunks; however, all of the characters in any single event
must come from the same external entity, so that the Locator provides useful
information.
@end deffn

@geindex processingInstruction() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler processingInstruction}@anchor{2aba}
@deffn {方法} ContentHandler.processingInstruction (target, data)

Receive notification of a processing instruction.

The Parser will invoke this method once for each processing instruction found:
note that processing instructions may occur before or after the main document
element.

A SAX parser should never report an XML declaration (XML 1.0, section 2.8) or a
text declaration (XML 1.0, section 4.3.1) using this method.
@end deffn

@geindex skippedEntity() (xml.sax.handler.ContentHandler 方法)
@anchor{library/xml sax handler xml sax handler ContentHandler skippedEntity}@anchor{2abb}
@deffn {方法} ContentHandler.skippedEntity (name)

Receive notification of a skipped entity.

The Parser will invoke this method once for each entity skipped. Non-validating
processors may skip entities if they have not seen the declarations (because,
for example, the entity was declared in an external DTD subset). All processors
may skip external entities, depending on the values of the
@code{feature_external_ges} and the @code{feature_external_pes} properties.
@end deffn

@node DTDHandler 对象,EntityResolver 对象,ContentHandler 对象,xml sax handler --- Base classes for SAX handlers
@anchor{library/xml sax handler dtd-handler-objects}@anchor{2abc}@anchor{library/xml sax handler dtdhandler-objects}@anchor{2abd}
@subsubsection DTDHandler 对象


@ref{2a9e,,DTDHandler} instances provide the following methods:

@geindex notationDecl() (xml.sax.handler.DTDHandler 方法)
@anchor{library/xml sax handler xml sax handler DTDHandler notationDecl}@anchor{2abe}
@deffn {方法} DTDHandler.notationDecl (name, publicId, systemId)

Handle a notation declaration event.
@end deffn

@geindex unparsedEntityDecl() (xml.sax.handler.DTDHandler 方法)
@anchor{library/xml sax handler xml sax handler DTDHandler unparsedEntityDecl}@anchor{2abf}
@deffn {方法} DTDHandler.unparsedEntityDecl (name, publicId, systemId, ndata)

Handle an unparsed entity declaration event.
@end deffn

@node EntityResolver 对象,ErrorHandler 对象,DTDHandler 对象,xml sax handler --- Base classes for SAX handlers
@anchor{library/xml sax handler entity-resolver-objects}@anchor{2ac0}@anchor{library/xml sax handler entityresolver-objects}@anchor{2ac1}
@subsubsection EntityResolver 对象


@geindex resolveEntity() (xml.sax.handler.EntityResolver 方法)
@anchor{library/xml sax handler xml sax handler EntityResolver resolveEntity}@anchor{2ac2}
@deffn {方法} EntityResolver.resolveEntity (publicId, systemId)

Resolve the system identifier of an entity and return either the system
identifier to read from as a string, or an InputSource to read from. The default
implementation returns @emph{systemId}.
@end deffn

@node ErrorHandler 对象,,EntityResolver 对象,xml sax handler --- Base classes for SAX handlers
@anchor{library/xml sax handler errorhandler-objects}@anchor{2ac3}@anchor{library/xml sax handler sax-error-handler}@anchor{2ac4}
@subsubsection ErrorHandler 对象


Objects with this interface are used to receive error and warning information
from the @ref{2a87,,XMLReader}.  If you create an object that
implements this interface, then register the object with your
@ref{2a87,,XMLReader}, the parser
will call the methods in your object to report all warnings and errors. There
are three levels of errors available: warnings, (possibly) recoverable errors,
and unrecoverable errors.  All methods take a @code{SAXParseException} as the
only parameter.  Errors and warnings may be converted to an exception by raising
the passed-in exception object.

@geindex error() (xml.sax.handler.ErrorHandler 方法)
@anchor{library/xml sax handler xml sax handler ErrorHandler error}@anchor{2ac5}
@deffn {方法} ErrorHandler.error (exception)

Called when the parser encounters a recoverable error.  If this method does not
raise an exception, parsing may continue, but further document information
should not be expected by the application.  Allowing the parser to continue may
allow additional errors to be discovered in the input document.
@end deffn

@geindex fatalError() (xml.sax.handler.ErrorHandler 方法)
@anchor{library/xml sax handler xml sax handler ErrorHandler fatalError}@anchor{2ac6}
@deffn {方法} ErrorHandler.fatalError (exception)

Called when the parser encounters an error it cannot recover from; parsing is
expected to terminate when this method returns.
@end deffn

@geindex warning() (xml.sax.handler.ErrorHandler 方法)
@anchor{library/xml sax handler xml sax handler ErrorHandler warning}@anchor{2ac7}
@deffn {方法} ErrorHandler.warning (exception)

Called when the parser presents minor warning information to the application.
Parsing is expected to continue when this method returns, and document
information will continue to be passed to the application. Raising an exception
in this method will cause parsing to end.
@end deffn

@node xml sax saxutils --- SAX 工具集,xml sax xmlreader --- Interface for XML parsers,xml sax handler --- Base classes for SAX handlers,结构化标记处理工具
@anchor{library/xml sax utils doc}@anchor{2ac8}@anchor{library/xml sax utils module-xml sax saxutils}@anchor{13d}@anchor{library/xml sax utils xml-sax-saxutils-sax-utilities}@anchor{2ac9}
@subsection @code{xml.sax.saxutils} --- SAX 工具集


@geindex xml.sax.saxutils (模块)

@strong{源代码:} Lib/xml/sax/saxutils.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/sax/saxutils.py}


__________________________________________________________________


@ref{13d,,xml.sax.saxutils} 模块包含一些在创建 SAX 应用程序时十分有用的类和函数，它们可以被直接使用，或者是作为基类使用。

@geindex escape() (在 xml.sax.saxutils 模块中)
@anchor{library/xml sax utils xml sax saxutils escape}@anchor{2aca}
@deffn {函数} xml.sax.saxutils.escape (data, entities=@{@})

对数据字符串中的 @code{'&'}, @code{'<'} 和 @code{'>'} 进行转义。

你可以通过传入一个字典作为可选的 @emph{entities} 形参来对其他字符串数据进行转义。 字典的键和值必须为字符串；每个键将被替换为其所对应的值。 字符 @code{'&'}, @code{'<'} 和 @code{'>'} 总是会被转义，即使提供了 @emph{entities}。
@end deffn

@geindex unescape() (在 xml.sax.saxutils 模块中)
@anchor{library/xml sax utils xml sax saxutils unescape}@anchor{2acb}
@deffn {函数} xml.sax.saxutils.unescape (data, entities=@{@})

对字符串数据中的 @code{'&amp;'}, @code{'&lt;'} 和 @code{'&gt;'} 进行反转义。

你可以通过传入一个字典作为可选的 @emph{entities} 形参来对其他数据字符串进行转义。 字典的键和值必须都为字符串；每个键将被替换为所对应的值。 @code{'&amp'}, @code{'&lt;'} 和 @code{'&gt;'} 将总是保持不被转义，即使提供了 @emph{entities}。
@end deffn

@geindex quoteattr() (在 xml.sax.saxutils 模块中)
@anchor{library/xml sax utils xml sax saxutils quoteattr}@anchor{2acc}
@deffn {函数} xml.sax.saxutils.quoteattr (data, entities=@{@})

类似于 @ref{2aca,,escape()}，但还会对 @emph{data} 进行处理以将其用作属性值。 返回值是 @emph{data} 加上任何额外要求的替换的带引号版本。@ref{2acc,,quoteattr()} 将基于 @emph{data} 的内容选择一个引号字符，以尽量避免在字符串中编码任何引号字符。 如果单双引号字符在 @emph{data} 中都存在，则双引号字符将被编码并且 @emph{data} 将使用双引号来标记。 结果字符串可被直接用作属性值:

@example
>>> print("<element attr=%s>" % quoteattr("ab ' cd \" ef"))
<element attr="ab ' cd &quot; ef">
@end example

此函数适用于为 HTML 或任何使用引用实体语法的 SGML 生成属性值。
@end deffn

@geindex XMLGenerator (xml.sax.saxutils 中的类)
@anchor{library/xml sax utils xml sax saxutils XMLGenerator}@anchor{2acd}
@deffn {类} xml.sax.saxutils.XMLGenerator (out=None, encoding='iso-8859-1', short_empty_elements=False)

这个类通过将 SAX 事件写回到 XML 文档来实现 @ref{2a84,,ContentHandler} 接口。 换句话说，使用 @ref{2acd,,XMLGenerator} 作为内容处理程序将重新产生所解析的原始文档。 @emph{out} 应当为一个文件类对象，它默认将为 @emph{sys.stdout}。 @emph{encoding} 为输出流的编码格式，它默认将为 @code{'iso-8859-1'}。 @emph{short_empty_elements} 控制不包含内容的元素的格式化：如为 @code{False} (默认值) 则它们会以开始/结束标记对的形式被发送，如果设为 @code{True} 则它们会以单个自结束标记的形式被发送。


3.2 新版功能: @emph{short_empty_elements} 形参。

@end deffn

@geindex XMLFilterBase (xml.sax.saxutils 中的类)
@anchor{library/xml sax utils xml sax saxutils XMLFilterBase}@anchor{2ace}
@deffn {类} xml.sax.saxutils.XMLFilterBase (base)

这个类被设计用来分隔 @ref{2a87,,XMLReader} 和客户端应用的事件处理程序。 在默认情况下，它除了将请求传送给读取器并将事件传送给处理程序之外什么都不做，但其子类可以重载特定的方法以在传送它们的时候修改事件流或配置请求。
@end deffn

@geindex prepare_input_source() (在 xml.sax.saxutils 模块中)
@anchor{library/xml sax utils xml sax saxutils prepare_input_source}@anchor{2acf}
@deffn {函数} xml.sax.saxutils.prepare_input_source (source, base='@w{'})

此函数接受一个输入源和一个可选的基准 URL 并返回一个经过完整解析可供读取的 @ref{78c,,InputSource}。 输入源的给出形式可以为字符串、文件类对象或 @ref{78c,,InputSource} 对象；解析器将使用此函数来针对它们的 @code{parse()} 方法实现多态 @emph{source} 参数。
@end deffn

@node xml sax xmlreader --- Interface for XML parsers,xml parsers expat --- Fast XML parsing using Expat,xml sax saxutils --- SAX 工具集,结构化标记处理工具
@anchor{library/xml sax reader doc}@anchor{2ad0}@anchor{library/xml sax reader module-xml sax xmlreader}@anchor{13e}@anchor{library/xml sax reader xml-sax-xmlreader-interface-for-xml-parsers}@anchor{2ad1}
@subsection @code{xml.sax.xmlreader} --- Interface for XML parsers


@geindex xml.sax.xmlreader (模块)

@strong{Source code:} Lib/xml/sax/xmlreader.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xml/sax/xmlreader.py}


__________________________________________________________________


SAX parsers implement the @ref{2a87,,XMLReader} interface. They are implemented in
a Python module, which must provide a function @code{create_parser()}. This
function is invoked by  @ref{fbb,,xml.sax.make_parser()} with no arguments to create
a new  parser object.

@geindex XMLReader (xml.sax.xmlreader 中的类)
@anchor{library/xml sax reader xml sax xmlreader XMLReader}@anchor{2a87}
@deffn {类} xml.sax.xmlreader.XMLReader

Base class which can be inherited by SAX parsers.
@end deffn

@geindex IncrementalParser (xml.sax.xmlreader 中的类)
@anchor{library/xml sax reader xml sax xmlreader IncrementalParser}@anchor{2ad2}
@deffn {类} xml.sax.xmlreader.IncrementalParser

In some cases, it is desirable not to parse an input source at once, but to feed
chunks of the document as they get available. Note that the reader will normally
not read the entire file, but read it in chunks as well; still @code{parse()}
won't return until the entire document is processed. So these interfaces should
be used if the blocking behaviour of @code{parse()} is not desirable.

When the parser is instantiated it is ready to begin accepting data from the
feed method immediately. After parsing has been finished with a call to close
the reset method must be called to make the parser ready to accept new data,
either from feed or using the parse method.

Note that these methods must @emph{not} be called during parsing, that is, after
parse has been called and before it returns.

By default, the class also implements the parse method of the XMLReader
interface using the feed, close and reset methods of the IncrementalParser
interface as a convenience to SAX 2.0 driver writers.
@end deffn

@geindex Locator (xml.sax.xmlreader 中的类)
@anchor{library/xml sax reader xml sax xmlreader Locator}@anchor{2a94}
@deffn {类} xml.sax.xmlreader.Locator

Interface for associating a SAX event with a document location. A locator object
will return valid results only during calls to DocumentHandler methods; at any
other time, the results are unpredictable. If information is not available,
methods may return @code{None}.
@end deffn

@geindex InputSource (xml.sax.xmlreader 中的类)
@anchor{library/xml sax reader xml sax xmlreader InputSource}@anchor{78c}
@deffn {类} xml.sax.xmlreader.InputSource (system_id=None)

Encapsulation of the information needed by the @ref{2a87,,XMLReader} to read
entities.

This class may include information about the public identifier, system
identifier, byte stream (possibly with character encoding information) and/or
the character stream of an entity.

Applications will create objects of this class for use in the
@ref{2ad3,,XMLReader.parse()} method and for returning from
EntityResolver.resolveEntity.

An @ref{78c,,InputSource} belongs to the application, the @ref{2a87,,XMLReader} is
not allowed to modify @ref{78c,,InputSource} objects passed to it from the
application, although it may make copies and modify those.
@end deffn

@geindex AttributesImpl (xml.sax.xmlreader 中的类)
@anchor{library/xml sax reader xml sax xmlreader AttributesImpl}@anchor{2ad4}
@deffn {类} xml.sax.xmlreader.AttributesImpl (attrs)

This is an implementation of the @code{Attributes} interface (see section
@ref{2ab4,,The Attributes Interface}).  This is a dictionary-like object which
represents the element attributes in a @code{startElement()} call. In addition
to the most useful dictionary operations, it supports a number of other
methods as described by the interface. Objects of this class should be
instantiated by readers; @emph{attrs} must be a dictionary-like object containing
a mapping from attribute names to attribute values.
@end deffn

@geindex AttributesNSImpl (xml.sax.xmlreader 中的类)
@anchor{library/xml sax reader xml sax xmlreader AttributesNSImpl}@anchor{2ad5}
@deffn {类} xml.sax.xmlreader.AttributesNSImpl (attrs, qnames)

Namespace-aware variant of @ref{2ad4,,AttributesImpl}, which will be passed to
@code{startElementNS()}. It is derived from @ref{2ad4,,AttributesImpl}, but
understands attribute names as two-tuples of @emph{namespaceURI} and
@emph{localname}. In addition, it provides a number of methods expecting qualified
names as they appear in the original document.  This class implements the
@code{AttributesNS} interface (see section @ref{2ab6,,The AttributesNS Interface}).
@end deffn

@menu
* XMLReader 对象:: 
* IncrementalParser 对象:: 
* Locator 对象:: 
* InputSource 对象:: 
* The Attributes Interface:: 
* The AttributesNS Interface:: 

@end menu

@node XMLReader 对象,IncrementalParser 对象,,xml sax xmlreader --- Interface for XML parsers
@anchor{library/xml sax reader id1}@anchor{2ad6}@anchor{library/xml sax reader xmlreader-objects}@anchor{2ad7}
@subsubsection XMLReader 对象


The @ref{2a87,,XMLReader} interface supports the following methods:

@geindex parse() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader parse}@anchor{2ad3}
@deffn {方法} XMLReader.parse (source)

Process an input source, producing SAX events. The @emph{source} object can be a
system identifier (a string identifying the input source -- typically a file
name or a URL), a @ref{201,,pathlib.Path} or @ref{363,,path-like}
object, or an @ref{78c,,InputSource} object. When
@ref{2ad3,,parse()} returns, the input is completely processed, and the parser object
can be discarded or reset.


在 3.5 版更改: Added support of character streams.



在 3.8 版更改: Added support of path-like objects.

@end deffn

@geindex getContentHandler() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader getContentHandler}@anchor{2ad8}
@deffn {方法} XMLReader.getContentHandler ()

Return the current @ref{2a84,,ContentHandler}.
@end deffn

@geindex setContentHandler() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader setContentHandler}@anchor{2ad9}
@deffn {方法} XMLReader.setContentHandler (handler)

Set the current @ref{2a84,,ContentHandler}.  If no
@ref{2a84,,ContentHandler} is set, content events will be
discarded.
@end deffn

@geindex getDTDHandler() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader getDTDHandler}@anchor{2ada}
@deffn {方法} XMLReader.getDTDHandler ()

Return the current @ref{2a9e,,DTDHandler}.
@end deffn

@geindex setDTDHandler() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader setDTDHandler}@anchor{2adb}
@deffn {方法} XMLReader.setDTDHandler (handler)

Set the current @ref{2a9e,,DTDHandler}.  If no
@ref{2a9e,,DTDHandler} is set, DTD
events will be discarded.
@end deffn

@geindex getEntityResolver() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader getEntityResolver}@anchor{2adc}
@deffn {方法} XMLReader.getEntityResolver ()

Return the current @ref{2a9f,,EntityResolver}.
@end deffn

@geindex setEntityResolver() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader setEntityResolver}@anchor{2add}
@deffn {方法} XMLReader.setEntityResolver (handler)

Set the current @ref{2a9f,,EntityResolver}.  If no
@ref{2a9f,,EntityResolver} is set,
attempts to resolve an external entity will result in opening the system
identifier for the entity, and fail if it is not available.
@end deffn

@geindex getErrorHandler() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader getErrorHandler}@anchor{2ade}
@deffn {方法} XMLReader.getErrorHandler ()

Return the current @ref{2a92,,ErrorHandler}.
@end deffn

@geindex setErrorHandler() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader setErrorHandler}@anchor{2adf}
@deffn {方法} XMLReader.setErrorHandler (handler)

Set the current error handler.  If no @ref{2a92,,ErrorHandler}
is set, errors will be raised as exceptions, and warnings will be printed.
@end deffn

@geindex setLocale() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader setLocale}@anchor{2ae0}
@deffn {方法} XMLReader.setLocale (locale)

Allow an application to set the locale for errors and warnings.

SAX parsers are not required to provide localization for errors and warnings; if
they cannot support the requested locale, however, they must raise a SAX
exception.  Applications may request a locale change in the middle of a parse.
@end deffn

@geindex getFeature() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader getFeature}@anchor{2ae1}
@deffn {方法} XMLReader.getFeature (featurename)

Return the current setting for feature @emph{featurename}.  If the feature is not
recognized, @code{SAXNotRecognizedException} is raised. The well-known
featurenames are listed in the module @ref{13c,,xml.sax.handler}.
@end deffn

@geindex setFeature() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader setFeature}@anchor{2a90}
@deffn {方法} XMLReader.setFeature (featurename, value)

Set the @emph{featurename} to @emph{value}. If the feature is not recognized,
@code{SAXNotRecognizedException} is raised. If the feature or its setting is not
supported by the parser, @emph{SAXNotSupportedException} is raised.
@end deffn

@geindex getProperty() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader getProperty}@anchor{2ae2}
@deffn {方法} XMLReader.getProperty (propertyname)

Return the current setting for property @emph{propertyname}. If the property is not
recognized, a @code{SAXNotRecognizedException} is raised. The well-known
propertynames are listed in the module @ref{13c,,xml.sax.handler}.
@end deffn

@geindex setProperty() (xml.sax.xmlreader.XMLReader 方法)
@anchor{library/xml sax reader xml sax xmlreader XMLReader setProperty}@anchor{2ae3}
@deffn {方法} XMLReader.setProperty (propertyname, value)

Set the @emph{propertyname} to @emph{value}. If the property is not recognized,
@code{SAXNotRecognizedException} is raised. If the property or its setting is
not supported by the parser, @emph{SAXNotSupportedException} is raised.
@end deffn

@node IncrementalParser 对象,Locator 对象,XMLReader 对象,xml sax xmlreader --- Interface for XML parsers
@anchor{library/xml sax reader incremental-parser-objects}@anchor{2ae4}@anchor{library/xml sax reader incrementalparser-objects}@anchor{2ae5}
@subsubsection IncrementalParser 对象


Instances of @ref{2ad2,,IncrementalParser} offer the following additional methods:

@geindex feed() (xml.sax.xmlreader.IncrementalParser 方法)
@anchor{library/xml sax reader xml sax xmlreader IncrementalParser feed}@anchor{2ae6}
@deffn {方法} IncrementalParser.feed (data)

Process a chunk of @emph{data}.
@end deffn

@geindex close() (xml.sax.xmlreader.IncrementalParser 方法)
@anchor{library/xml sax reader xml sax xmlreader IncrementalParser close}@anchor{2ae7}
@deffn {方法} IncrementalParser.close ()

Assume the end of the document. That will check well-formedness conditions that
can be checked only at the end, invoke handlers, and may clean up resources
allocated during parsing.
@end deffn

@geindex reset() (xml.sax.xmlreader.IncrementalParser 方法)
@anchor{library/xml sax reader xml sax xmlreader IncrementalParser reset}@anchor{2ae8}
@deffn {方法} IncrementalParser.reset ()

This method is called after close has been called to reset the parser so that it
is ready to parse new documents. The results of calling parse or feed after
close without calling reset are undefined.
@end deffn

@node Locator 对象,InputSource 对象,IncrementalParser 对象,xml sax xmlreader --- Interface for XML parsers
@anchor{library/xml sax reader id2}@anchor{2ae9}@anchor{library/xml sax reader locator-objects}@anchor{2aea}
@subsubsection Locator 对象


Instances of @ref{2a94,,Locator} provide these methods:

@geindex getColumnNumber() (xml.sax.xmlreader.Locator 方法)
@anchor{library/xml sax reader xml sax xmlreader Locator getColumnNumber}@anchor{2aeb}
@deffn {方法} Locator.getColumnNumber ()

Return the column number where the current event begins.
@end deffn

@geindex getLineNumber() (xml.sax.xmlreader.Locator 方法)
@anchor{library/xml sax reader xml sax xmlreader Locator getLineNumber}@anchor{2aec}
@deffn {方法} Locator.getLineNumber ()

Return the line number where the current event begins.
@end deffn

@geindex getPublicId() (xml.sax.xmlreader.Locator 方法)
@anchor{library/xml sax reader xml sax xmlreader Locator getPublicId}@anchor{2aed}
@deffn {方法} Locator.getPublicId ()

Return the public identifier for the current event.
@end deffn

@geindex getSystemId() (xml.sax.xmlreader.Locator 方法)
@anchor{library/xml sax reader xml sax xmlreader Locator getSystemId}@anchor{2aee}
@deffn {方法} Locator.getSystemId ()

Return the system identifier for the current event.
@end deffn

@node InputSource 对象,The Attributes Interface,Locator 对象,xml sax xmlreader --- Interface for XML parsers
@anchor{library/xml sax reader input-source-objects}@anchor{2aef}@anchor{library/xml sax reader inputsource-objects}@anchor{2af0}
@subsubsection InputSource 对象


@geindex setPublicId() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource setPublicId}@anchor{2af1}
@deffn {方法} InputSource.setPublicId (id)

Sets the public identifier of this @ref{78c,,InputSource}.
@end deffn

@geindex getPublicId() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource getPublicId}@anchor{2af2}
@deffn {方法} InputSource.getPublicId ()

Returns the public identifier of this @ref{78c,,InputSource}.
@end deffn

@geindex setSystemId() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource setSystemId}@anchor{2af3}
@deffn {方法} InputSource.setSystemId (id)

Sets the system identifier of this @ref{78c,,InputSource}.
@end deffn

@geindex getSystemId() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource getSystemId}@anchor{2af4}
@deffn {方法} InputSource.getSystemId ()

Returns the system identifier of this @ref{78c,,InputSource}.
@end deffn

@geindex setEncoding() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource setEncoding}@anchor{2af5}
@deffn {方法} InputSource.setEncoding (encoding)

Sets the character encoding of this @ref{78c,,InputSource}.

The encoding must be a string acceptable for an XML encoding declaration (see
section 4.3.3 of the XML recommendation).

The encoding attribute of the @ref{78c,,InputSource} is ignored if the
@ref{78c,,InputSource} also contains a character stream.
@end deffn

@geindex getEncoding() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource getEncoding}@anchor{2af6}
@deffn {方法} InputSource.getEncoding ()

Get the character encoding of this InputSource.
@end deffn

@geindex setByteStream() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource setByteStream}@anchor{2af7}
@deffn {方法} InputSource.setByteStream (bytefile)

Set the byte stream (a @ref{1c37,,binary file}) for this input source.

The SAX parser will ignore this if there is also a character stream specified,
but it will use a byte stream in preference to opening a URI connection itself.

If the application knows the character encoding of the byte stream, it should
set it with the setEncoding method.
@end deffn

@geindex getByteStream() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource getByteStream}@anchor{2af8}
@deffn {方法} InputSource.getByteStream ()

Get the byte stream for this input source.

The getEncoding method will return the character encoding for this byte stream,
or @code{None} if unknown.
@end deffn

@geindex setCharacterStream() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource setCharacterStream}@anchor{2af9}
@deffn {方法} InputSource.setCharacterStream (charfile)

Set the character stream (a @ref{1239,,text file}) for this input source.

If there is a character stream specified, the SAX parser will ignore any byte
stream and will not attempt to open a URI connection to the system identifier.
@end deffn

@geindex getCharacterStream() (xml.sax.xmlreader.InputSource 方法)
@anchor{library/xml sax reader xml sax xmlreader InputSource getCharacterStream}@anchor{2afa}
@deffn {方法} InputSource.getCharacterStream ()

Get the character stream for this input source.
@end deffn

@node The Attributes Interface,The AttributesNS Interface,InputSource 对象,xml sax xmlreader --- Interface for XML parsers
@anchor{library/xml sax reader attributes-objects}@anchor{2ab4}@anchor{library/xml sax reader the-attributes-interface}@anchor{2afb}
@subsubsection The @code{Attributes} Interface


@code{Attributes} objects implement a portion of the @ref{b32,,mapping protocol}, including the methods @code{copy()},
@code{get()}, @ref{d21,,__contains__()},
@code{items()}, @code{keys()},
and @code{values()}.  The following methods
are also provided:

@geindex getLength() (xml.sax.xmlreader.Attributes 方法)
@anchor{library/xml sax reader xml sax xmlreader Attributes getLength}@anchor{2afc}
@deffn {方法} Attributes.getLength ()

Return the number of attributes.
@end deffn

@geindex getNames() (xml.sax.xmlreader.Attributes 方法)
@anchor{library/xml sax reader xml sax xmlreader Attributes getNames}@anchor{2afd}
@deffn {方法} Attributes.getNames ()

Return the names of the attributes.
@end deffn

@geindex getType() (xml.sax.xmlreader.Attributes 方法)
@anchor{library/xml sax reader xml sax xmlreader Attributes getType}@anchor{2afe}
@deffn {方法} Attributes.getType (name)

Returns the type of the attribute @emph{name}, which is normally @code{'CDATA'}.
@end deffn

@geindex getValue() (xml.sax.xmlreader.Attributes 方法)
@anchor{library/xml sax reader xml sax xmlreader Attributes getValue}@anchor{2aff}
@deffn {方法} Attributes.getValue (name)

Return the value of attribute @emph{name}.
@end deffn

@c getValueByQName, getNameByQName, getQNameByName, getQNames available

@c here already, but documented only for derived class.

@node The AttributesNS Interface,,The Attributes Interface,xml sax xmlreader --- Interface for XML parsers
@anchor{library/xml sax reader attributes-ns-objects}@anchor{2ab6}@anchor{library/xml sax reader the-attributesns-interface}@anchor{2b00}
@subsubsection The @code{AttributesNS} Interface


This interface is a subtype of the @code{Attributes} interface (see section
@ref{2ab4,,The Attributes Interface}).  All methods supported by that interface are also
available on @code{AttributesNS} objects.

The following methods are also available:

@geindex getValueByQName() (xml.sax.xmlreader.AttributesNS 方法)
@anchor{library/xml sax reader xml sax xmlreader AttributesNS getValueByQName}@anchor{2b01}
@deffn {方法} AttributesNS.getValueByQName (name)

Return the value for a qualified name.
@end deffn

@geindex getNameByQName() (xml.sax.xmlreader.AttributesNS 方法)
@anchor{library/xml sax reader xml sax xmlreader AttributesNS getNameByQName}@anchor{2b02}
@deffn {方法} AttributesNS.getNameByQName (name)

Return the @code{(namespace, localname)} pair for a qualified @emph{name}.
@end deffn

@geindex getQNameByName() (xml.sax.xmlreader.AttributesNS 方法)
@anchor{library/xml sax reader xml sax xmlreader AttributesNS getQNameByName}@anchor{2b03}
@deffn {方法} AttributesNS.getQNameByName (name)

Return the qualified name for a @code{(namespace, localname)} pair.
@end deffn

@geindex getQNames() (xml.sax.xmlreader.AttributesNS 方法)
@anchor{library/xml sax reader xml sax xmlreader AttributesNS getQNames}@anchor{2b04}
@deffn {方法} AttributesNS.getQNames ()

Return the qualified names of all attributes.
@end deffn

@node xml parsers expat --- Fast XML parsing using Expat,,xml sax xmlreader --- Interface for XML parsers,结构化标记处理工具
@anchor{library/pyexpat doc}@anchor{2b05}@anchor{library/pyexpat module-xml parsers expat}@anchor{138}@anchor{library/pyexpat xml-parsers-expat-fast-xml-parsing-using-expat}@anchor{2b06}
@subsection @code{xml.parsers.expat} --- Fast XML parsing using Expat


@geindex xml.parsers.expat (模块)


__________________________________________________________________


@c Markup notes:
@c 
@c Many of the attributes of the XMLParser objects are callbacks.  Since
@c signature information must be presented, these are described using the method
@c directive.  Since they are attributes which are set by client code, in-text
@c references to these attributes should be marked using the :member: role.

@cartouche
@quotation 警告 
The @code{pyexpat} module is not secure against maliciously
constructed data.  If you need to parse untrusted or unauthenticated data see
@ref{2993,,XML 漏洞}.
@end quotation
@end cartouche

@geindex Expat

The @ref{138,,xml.parsers.expat} module is a Python interface to the Expat
non-validating XML parser. The module provides a single extension type,
@code{xmlparser}, that represents the current state of an XML parser.  After
an @code{xmlparser} object has been created, various attributes of the object
can be set to handler functions.  When an XML document is then fed to the
parser, the handler functions are called for the character data and markup in
the XML document.

@geindex 模块; pyexpat

This module uses the @code{pyexpat} module to provide access to the Expat
parser.  Direct use of the @code{pyexpat} module is deprecated.

This module provides one exception and one type object:

@geindex ExpatError
@anchor{library/pyexpat xml parsers expat ExpatError}@anchor{c06}
@deffn {例外} xml.parsers.expat.ExpatError

The exception raised when Expat reports an error.  See section
@ref{2b07,,ExpatError Exceptions} for more information on interpreting Expat errors.
@end deffn

@geindex error
@anchor{library/pyexpat xml parsers expat error}@anchor{2b08}
@deffn {例外} xml.parsers.expat.error

Alias for @ref{c06,,ExpatError}.
@end deffn

@geindex XMLParserType() (在 xml.parsers.expat 模块中)
@anchor{library/pyexpat xml parsers expat XMLParserType}@anchor{2b09}
@deffn {数据} xml.parsers.expat.XMLParserType

The type of the return values from the @ref{2b0a,,ParserCreate()} function.
@end deffn

The @ref{138,,xml.parsers.expat} module contains two functions:

@geindex ErrorString() (在 xml.parsers.expat 模块中)
@anchor{library/pyexpat xml parsers expat ErrorString}@anchor{2b0b}
@deffn {函数} xml.parsers.expat.ErrorString (errno)

Returns an explanatory string for a given error number @emph{errno}.
@end deffn

@geindex ParserCreate() (在 xml.parsers.expat 模块中)
@anchor{library/pyexpat xml parsers expat ParserCreate}@anchor{2b0a}
@deffn {函数} xml.parsers.expat.ParserCreate (encoding=None, namespace_separator=None)

Creates and returns a new @code{xmlparser} object.   @emph{encoding}, if specified,
must be a string naming the encoding  used by the XML data.  Expat doesn't
support as many encodings as Python does, and its repertoire of encodings can't
be extended; it supports UTF-8, UTF-16, ISO-8859-1 (Latin1), and ASCII.  If
@emph{encoding} @footnote{@w{(1)} 
The encoding string included in XML output should conform to the
appropriate standards. For example, "UTF-8" is valid, but "UTF8" is
not. See @indicateurl{https://www.w3.org/TR/2006/REC-xml11-20060816/#NT-EncodingDecl}
and @indicateurl{https://www.iana.org/assignments/character-sets/character-sets.xhtml}.
} is given it will override the implicit or explicit encoding of the
document.

Expat can optionally do XML namespace processing for you, enabled by providing a
value for @emph{namespace_separator}.  The value must be a one-character string; a
@ref{1fb,,ValueError} will be raised if the string has an illegal length (@code{None}
is considered the same as omission).  When namespace processing is enabled,
element type names and attribute names that belong to a namespace will be
expanded.  The element name passed to the element handlers
@code{StartElementHandler} and @code{EndElementHandler} will be the
concatenation of the namespace URI, the namespace separator character, and the
local part of the name.  If the namespace separator is a zero byte (@code{chr(0)})
then the namespace URI and the local part will be concatenated without any
separator.

For example, if @emph{namespace_separator} is set to a space character (@code{' '}) and
the following document is parsed:

@example
<?xml version="1.0"?>
<root xmlns    = "http://default-namespace.org/"
      xmlns:py = "http://www.python.org/ns/">
  <py:elem1 />
  <elem2 xmlns="" />
</root>
@end example

@code{StartElementHandler} will receive the following strings for each
element:

@example
http://default-namespace.org/ root
http://www.python.org/ns/ elem1
elem2
@end example

Due to limitations in the @code{Expat} library used by @code{pyexpat},
the @code{xmlparser} instance returned can only be used to parse a single
XML document.  Call @code{ParserCreate} for each document to provide unique
parser instances.
@end deffn


@subsubheading 参见



@table @asis

@item The Expat XML Parser@footnote{http://www.libexpat.org/}

Home page of the Expat project.
@end table


@menu
* XMLParser对象: XMLParser对象<2>. 
* ExpatError Exceptions:: 
* 示例: 示例<12>. 
* Content Model Descriptions:: 
* Expat error constants:: 

@end menu

@node XMLParser对象<2>,ExpatError Exceptions,,xml parsers expat --- Fast XML parsing using Expat
@anchor{library/pyexpat id2}@anchor{2b0c}@anchor{library/pyexpat xmlparser-objects}@anchor{2b0d}
@subsubsection XMLParser对象


@code{xmlparser} objects have the following methods:

@geindex Parse() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser Parse}@anchor{2b0e}
@deffn {方法} xmlparser.Parse (data[, isfinal])

Parses the contents of the string @emph{data}, calling the appropriate handler
functions to process the parsed data.  @emph{isfinal} must be true on the final call
to this method; it allows the parsing of a single file in fragments,
not the submission of multiple files.
@emph{data} can be the empty string at any time.
@end deffn

@geindex ParseFile() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser ParseFile}@anchor{2b0f}
@deffn {方法} xmlparser.ParseFile (file)

Parse XML data reading from the object @emph{file}.  @emph{file} only needs to provide
the @code{read(nbytes)} method, returning the empty string when there's no more
data.
@end deffn

@geindex SetBase() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser SetBase}@anchor{2b10}
@deffn {方法} xmlparser.SetBase (base)

Sets the base to be used for resolving relative URIs in system identifiers in
declarations.  Resolving relative identifiers is left to the application: this
value will be passed through as the @emph{base} argument to the
@ref{2b11,,ExternalEntityRefHandler()}, @ref{2b12,,NotationDeclHandler()}, and
@ref{2b13,,UnparsedEntityDeclHandler()} functions.
@end deffn

@geindex GetBase() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser GetBase}@anchor{2b14}
@deffn {方法} xmlparser.GetBase ()

Returns a string containing the base set by a previous call to @ref{2b10,,SetBase()},
or @code{None} if  @ref{2b10,,SetBase()} hasn't been called.
@end deffn

@geindex GetInputContext() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser GetInputContext}@anchor{2b15}
@deffn {方法} xmlparser.GetInputContext ()

Returns the input data that generated the current event as a string. The data is
in the encoding of the entity which contains the text. When called while an
event handler is not active, the return value is @code{None}.
@end deffn

@geindex ExternalEntityParserCreate() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser ExternalEntityParserCreate}@anchor{2b16}
@deffn {方法} xmlparser.ExternalEntityParserCreate (context[, encoding])

Create a "child" parser which can be used to parse an external parsed entity
referred to by content parsed by the parent parser.  The @emph{context} parameter
should be the string passed to the @ref{2b11,,ExternalEntityRefHandler()} handler
function, described below. The child parser is created with the
@ref{2b17,,ordered_attributes} and @ref{2b18,,specified_attributes} set to the values of
this parser.
@end deffn

@geindex SetParamEntityParsing() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser SetParamEntityParsing}@anchor{2b19}
@deffn {方法} xmlparser.SetParamEntityParsing (flag)

Control parsing of parameter entities (including the external DTD subset).
Possible @emph{flag} values are @code{XML_PARAM_ENTITY_PARSING_NEVER},
@code{XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE} and
@code{XML_PARAM_ENTITY_PARSING_ALWAYS}.  Return true if setting the flag
was successful.
@end deffn

@geindex UseForeignDTD() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser UseForeignDTD}@anchor{2b1a}
@deffn {方法} xmlparser.UseForeignDTD ([flag])

Calling this with a true value for @emph{flag} (the default) will cause Expat to call
the @ref{2b11,,ExternalEntityRefHandler} with @ref{157,,None} for all arguments to
allow an alternate DTD to be loaded.  If the document does not contain a
document type declaration, the @ref{2b11,,ExternalEntityRefHandler} will still be
called, but the @ref{2b1b,,StartDoctypeDeclHandler} and
@ref{2b1c,,EndDoctypeDeclHandler} will not be called.

Passing a false value for @emph{flag} will cancel a previous call that passed a true
value, but otherwise has no effect.

This method can only be called before the @ref{2b0e,,Parse()} or @ref{2b0f,,ParseFile()}
methods are called; calling it after either of those have been called causes
@ref{c06,,ExpatError} to be raised with the @ref{1b,,code} attribute set to
@code{errors.codes[errors.XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING]}.
@end deffn

@code{xmlparser} objects have the following attributes:

@geindex buffer_size (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser buffer_size}@anchor{2b1d}
@deffn {属性} xmlparser.buffer_size

The size of the buffer used when @ref{2b1e,,buffer_text} is true.
A new buffer size can be set by assigning a new integer value
to this attribute.
When the size is changed, the buffer will be flushed.
@end deffn

@geindex buffer_text (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser buffer_text}@anchor{2b1e}
@deffn {属性} xmlparser.buffer_text

Setting this to true causes the @code{xmlparser} object to buffer textual
content returned by Expat to avoid multiple calls to the
@ref{2b1f,,CharacterDataHandler()} callback whenever possible.  This can improve
performance substantially since Expat normally breaks character data into chunks
at every line ending.  This attribute is false by default, and may be changed at
any time.
@end deffn

@geindex buffer_used (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser buffer_used}@anchor{2b20}
@deffn {属性} xmlparser.buffer_used

If @ref{2b1e,,buffer_text} is enabled, the number of bytes stored in the buffer.
These bytes represent UTF-8 encoded text.  This attribute has no meaningful
interpretation when @ref{2b1e,,buffer_text} is false.
@end deffn

@geindex ordered_attributes (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser ordered_attributes}@anchor{2b17}
@deffn {属性} xmlparser.ordered_attributes

Setting this attribute to a non-zero integer causes the attributes to be
reported as a list rather than a dictionary.  The attributes are presented in
the order found in the document text.  For each attribute, two list entries are
presented: the attribute name and the attribute value.  (Older versions of this
module also used this format.)  By default, this attribute is false; it may be
changed at any time.
@end deffn

@geindex specified_attributes (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser specified_attributes}@anchor{2b18}
@deffn {属性} xmlparser.specified_attributes

If set to a non-zero integer, the parser will report only those attributes which
were specified in the document instance and not those which were derived from
attribute declarations.  Applications which set this need to be especially
careful to use what additional information is available from the declarations as
needed to comply with the standards for the behavior of XML processors.  By
default, this attribute is false; it may be changed at any time.
@end deffn

The following attributes contain values relating to the most recent error
encountered by an @code{xmlparser} object, and will only have correct values
once a call to @code{Parse()} or @code{ParseFile()} has raised an
@ref{c06,,xml.parsers.expat.ExpatError} exception.

@geindex ErrorByteIndex (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser ErrorByteIndex}@anchor{2b21}
@deffn {属性} xmlparser.ErrorByteIndex

Byte index at which an error occurred.
@end deffn

@geindex ErrorCode (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser ErrorCode}@anchor{2b22}
@deffn {属性} xmlparser.ErrorCode

Numeric code specifying the problem.  This value can be passed to the
@ref{2b0b,,ErrorString()} function, or compared to one of the constants defined in the
@code{errors} object.
@end deffn

@geindex ErrorColumnNumber (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser ErrorColumnNumber}@anchor{2b23}
@deffn {属性} xmlparser.ErrorColumnNumber

Column number at which an error occurred.
@end deffn

@geindex ErrorLineNumber (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser ErrorLineNumber}@anchor{2b24}
@deffn {属性} xmlparser.ErrorLineNumber

Line number at which an error occurred.
@end deffn

The following attributes contain values relating to the current parse location
in an @code{xmlparser} object.  During a callback reporting a parse event they
indicate the location of the first of the sequence of characters that generated
the event.  When called outside of a callback, the position indicated will be
just past the last parse event (regardless of whether there was an associated
callback).

@geindex CurrentByteIndex (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser CurrentByteIndex}@anchor{2b25}
@deffn {属性} xmlparser.CurrentByteIndex

Current byte index in the parser input.
@end deffn

@geindex CurrentColumnNumber (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser CurrentColumnNumber}@anchor{2b26}
@deffn {属性} xmlparser.CurrentColumnNumber

Current column number in the parser input.
@end deffn

@geindex CurrentLineNumber (xml.parsers.expat.xmlparser 属性)
@anchor{library/pyexpat xml parsers expat xmlparser CurrentLineNumber}@anchor{2b27}
@deffn {属性} xmlparser.CurrentLineNumber

Current line number in the parser input.
@end deffn

Here is the list of handlers that can be set.  To set a handler on an
@code{xmlparser} object @emph{o}, use @code{o.handlername = func}.  @emph{handlername} must
be taken from the following list, and @emph{func} must be a callable object accepting
the correct number of arguments.  The arguments are all strings, unless
otherwise stated.

@geindex XmlDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser XmlDeclHandler}@anchor{2b28}
@deffn {方法} xmlparser.XmlDeclHandler (version, encoding, standalone)

Called when the XML declaration is parsed.  The XML declaration is the
(optional) declaration of the applicable version of the XML recommendation, the
encoding of the document text, and an optional "standalone" declaration.
@emph{version} and @emph{encoding} will be strings, and @emph{standalone} will be @code{1} if the
document is declared standalone, @code{0} if it is declared not to be standalone,
or @code{-1} if the standalone clause was omitted. This is only available with
Expat version 1.95.0 or newer.
@end deffn

@geindex StartDoctypeDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser StartDoctypeDeclHandler}@anchor{2b1b}
@deffn {方法} xmlparser.StartDoctypeDeclHandler (doctypeName, systemId, publicId, has_internal_subset)

Called when Expat begins parsing the document type declaration (@code{<!DOCTYPE
...}).  The @emph{doctypeName} is provided exactly as presented.  The @emph{systemId} and
@emph{publicId} parameters give the system and public identifiers if specified, or
@code{None} if omitted.  @emph{has_internal_subset} will be true if the document
contains and internal document declaration subset. This requires Expat version
1.2 or newer.
@end deffn

@geindex EndDoctypeDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser EndDoctypeDeclHandler}@anchor{2b1c}
@deffn {方法} xmlparser.EndDoctypeDeclHandler ()

Called when Expat is done parsing the document type declaration. This requires
Expat version 1.2 or newer.
@end deffn

@geindex ElementDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser ElementDeclHandler}@anchor{2b29}
@deffn {方法} xmlparser.ElementDeclHandler (name, model)

Called once for each element type declaration.  @emph{name} is the name of the
element type, and @emph{model} is a representation of the content model.
@end deffn

@geindex AttlistDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser AttlistDeclHandler}@anchor{2b2a}
@deffn {方法} xmlparser.AttlistDeclHandler (elname, attname, type, default, required)

Called for each declared attribute for an element type.  If an attribute list
declaration declares three attributes, this handler is called three times, once
for each attribute.  @emph{elname} is the name of the element to which the
declaration applies and @emph{attname} is the name of the attribute declared.  The
attribute type is a string passed as @emph{type}; the possible values are
@code{'CDATA'}, @code{'ID'}, @code{'IDREF'}, ... @emph{default} gives the default value for
the attribute used when the attribute is not specified by the document instance,
or @code{None} if there is no default value (@code{#IMPLIED} values).  If the
attribute is required to be given in the document instance, @emph{required} will be
true. This requires Expat version 1.95.0 or newer.
@end deffn

@geindex StartElementHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser StartElementHandler}@anchor{2b2b}
@deffn {方法} xmlparser.StartElementHandler (name, attributes)

Called for the start of every element.  @emph{name} is a string containing the
element name, and @emph{attributes} is the element attributes. If
@ref{2b17,,ordered_attributes} is true, this is a list (see
@ref{2b17,,ordered_attributes} for a full description). Otherwise it's a
dictionary mapping names to values.
@end deffn

@geindex EndElementHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser EndElementHandler}@anchor{2b2c}
@deffn {方法} xmlparser.EndElementHandler (name)

Called for the end of every element.
@end deffn

@geindex ProcessingInstructionHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser ProcessingInstructionHandler}@anchor{2b2d}
@deffn {方法} xmlparser.ProcessingInstructionHandler (target, data)

Called for every processing instruction.
@end deffn

@geindex CharacterDataHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser CharacterDataHandler}@anchor{2b1f}
@deffn {方法} xmlparser.CharacterDataHandler (data)

Called for character data.  This will be called for normal character data, CDATA
marked content, and ignorable whitespace.  Applications which must distinguish
these cases can use the @ref{2b2e,,StartCdataSectionHandler},
@ref{2b2f,,EndCdataSectionHandler}, and @ref{2b29,,ElementDeclHandler} callbacks to
collect the required information.
@end deffn

@geindex UnparsedEntityDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser UnparsedEntityDeclHandler}@anchor{2b13}
@deffn {方法} xmlparser.UnparsedEntityDeclHandler (entityName, base, systemId, publicId, notationName)

Called for unparsed (NDATA) entity declarations.  This is only present for
version 1.2 of the Expat library; for more recent versions, use
@ref{2b30,,EntityDeclHandler} instead.  (The underlying function in the Expat
library has been declared obsolete.)
@end deffn

@geindex EntityDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser EntityDeclHandler}@anchor{2b30}
@deffn {方法} xmlparser.EntityDeclHandler (entityName, is_parameter_entity, value, base, systemId, publicId, notationName)

Called for all entity declarations.  For parameter and internal entities,
@emph{value} will be a string giving the declared contents of the entity; this will
be @code{None} for external entities.  The @emph{notationName} parameter will be
@code{None} for parsed entities, and the name of the notation for unparsed
entities. @emph{is_parameter_entity} will be true if the entity is a parameter entity
or false for general entities (most applications only need to be concerned with
general entities). This is only available starting with version 1.95.0 of the
Expat library.
@end deffn

@geindex NotationDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser NotationDeclHandler}@anchor{2b12}
@deffn {方法} xmlparser.NotationDeclHandler (notationName, base, systemId, publicId)

Called for notation declarations.  @emph{notationName}, @emph{base}, and @emph{systemId}, and
@emph{publicId} are strings if given.  If the public identifier is omitted,
@emph{publicId} will be @code{None}.
@end deffn

@geindex StartNamespaceDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser StartNamespaceDeclHandler}@anchor{2b31}
@deffn {方法} xmlparser.StartNamespaceDeclHandler (prefix, uri)

Called when an element contains a namespace declaration.  Namespace declarations
are processed before the @ref{2b2b,,StartElementHandler} is called for the element
on which declarations are placed.
@end deffn

@geindex EndNamespaceDeclHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser EndNamespaceDeclHandler}@anchor{2b32}
@deffn {方法} xmlparser.EndNamespaceDeclHandler (prefix)

Called when the closing tag is reached for an element  that contained a
namespace declaration.  This is called once for each namespace declaration on
the element in the reverse of the order for which the
@ref{2b31,,StartNamespaceDeclHandler} was called to indicate the start of each
namespace declaration's scope.  Calls to this handler are made after the
corresponding @ref{2b2c,,EndElementHandler} for the end of the element.
@end deffn

@geindex CommentHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser CommentHandler}@anchor{2b33}
@deffn {方法} xmlparser.CommentHandler (data)

Called for comments.  @emph{data} is the text of the comment, excluding the leading
@code{'<!-}@code{-'} and trailing @code{'-}@code{->'}.
@end deffn

@geindex StartCdataSectionHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser StartCdataSectionHandler}@anchor{2b2e}
@deffn {方法} xmlparser.StartCdataSectionHandler ()

Called at the start of a CDATA section.  This and @ref{2b2f,,EndCdataSectionHandler}
are needed to be able to identify the syntactical start and end for CDATA
sections.
@end deffn

@geindex EndCdataSectionHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser EndCdataSectionHandler}@anchor{2b2f}
@deffn {方法} xmlparser.EndCdataSectionHandler ()

Called at the end of a CDATA section.
@end deffn

@geindex DefaultHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser DefaultHandler}@anchor{2b34}
@deffn {方法} xmlparser.DefaultHandler (data)

Called for any characters in the XML document for which no applicable handler
has been specified.  This means characters that are part of a construct which
could be reported, but for which no handler has been supplied.
@end deffn

@geindex DefaultHandlerExpand() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser DefaultHandlerExpand}@anchor{2b35}
@deffn {方法} xmlparser.DefaultHandlerExpand (data)

This is the same as the @ref{2b34,,DefaultHandler()},  but doesn't inhibit expansion
of internal entities. The entity reference will not be passed to the default
handler.
@end deffn

@geindex NotStandaloneHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser NotStandaloneHandler}@anchor{2b36}
@deffn {方法} xmlparser.NotStandaloneHandler ()

Called if the XML document hasn't been declared as being a standalone document.
This happens when there is an external subset or a reference to a parameter
entity, but the XML declaration does not set standalone to @code{yes} in an XML
declaration.  If this handler returns @code{0}, then the parser will raise an
@code{XML_ERROR_NOT_STANDALONE} error.  If this handler is not set, no
exception is raised by the parser for this condition.
@end deffn

@geindex ExternalEntityRefHandler() (xml.parsers.expat.xmlparser 方法)
@anchor{library/pyexpat xml parsers expat xmlparser ExternalEntityRefHandler}@anchor{2b11}
@deffn {方法} xmlparser.ExternalEntityRefHandler (context, base, systemId, publicId)

Called for references to external entities.  @emph{base} is the current base, as set
by a previous call to @ref{2b10,,SetBase()}.  The public and system identifiers,
@emph{systemId} and @emph{publicId}, are strings if given; if the public identifier is not
given, @emph{publicId} will be @code{None}.  The @emph{context} value is opaque and should
only be used as described below.

For external entities to be parsed, this handler must be implemented. It is
responsible for creating the sub-parser using
@code{ExternalEntityParserCreate(context)}, initializing it with the appropriate
callbacks, and parsing the entity.  This handler should return an integer; if it
returns @code{0}, the parser will raise an
@code{XML_ERROR_EXTERNAL_ENTITY_HANDLING} error, otherwise parsing will
continue.

If this handler is not provided, external entities are reported by the
@ref{2b34,,DefaultHandler} callback, if provided.
@end deffn

@node ExpatError Exceptions,示例<12>,XMLParser对象<2>,xml parsers expat --- Fast XML parsing using Expat
@anchor{library/pyexpat expaterror-exceptions}@anchor{2b37}@anchor{library/pyexpat expaterror-objects}@anchor{2b07}
@subsubsection ExpatError Exceptions


@ref{c06,,ExpatError} exceptions have a number of interesting attributes:

@geindex code (xml.parsers.expat.ExpatError 属性)
@anchor{library/pyexpat xml parsers expat ExpatError code}@anchor{2b38}
@deffn {属性} ExpatError.code

Expat's internal error number for the specific error.  The
@ref{2b39,,errors.messages} dictionary maps
these error numbers to Expat's error messages.  For example:

@example
from xml.parsers.expat import ParserCreate, ExpatError, errors

p = ParserCreate()
try:
    p.Parse(some_xml_document)
except ExpatError as err:
    print("Error:", errors.messages[err.code])
@end example

The @ref{139,,errors} module also provides error message
constants and a dictionary @ref{2b3a,,codes} mapping
these messages back to the error codes, see below.
@end deffn

@geindex lineno (xml.parsers.expat.ExpatError 属性)
@anchor{library/pyexpat xml parsers expat ExpatError lineno}@anchor{2b3b}
@deffn {属性} ExpatError.lineno

Line number on which the error was detected.  The first line is numbered @code{1}.
@end deffn

@geindex offset (xml.parsers.expat.ExpatError 属性)
@anchor{library/pyexpat xml parsers expat ExpatError offset}@anchor{2b3c}
@deffn {属性} ExpatError.offset

Character offset into the line where the error occurred.  The first column is
numbered @code{0}.
@end deffn

@node 示例<12>,Content Model Descriptions,ExpatError Exceptions,xml parsers expat --- Fast XML parsing using Expat
@anchor{library/pyexpat example}@anchor{2b3d}@anchor{library/pyexpat expat-example}@anchor{2b3e}
@subsubsection 示例


The following program defines three handlers that just print out their
arguments.

@example
import xml.parsers.expat

# 3 handler functions
def start_element(name, attrs):
    print('Start element:', name, attrs)
def end_element(name):
    print('End element:', name)
def char_data(data):
    print('Character data:', repr(data))

p = xml.parsers.expat.ParserCreate()

p.StartElementHandler = start_element
p.EndElementHandler = end_element
p.CharacterDataHandler = char_data

p.Parse("""<?xml version="1.0"?>
<parent id="top"><child1 name="paul">Text goes here</child1>
<child2 name="fred">More text</child2>
</parent>""", 1)
@end example

The output from this program is:

@example
Start element: parent @{'id': 'top'@}
Start element: child1 @{'name': 'paul'@}
Character data: 'Text goes here'
End element: child1
Character data: '\n'
Start element: child2 @{'name': 'fred'@}
Character data: 'More text'
End element: child2
Character data: '\n'
End element: parent
@end example

@node Content Model Descriptions,Expat error constants,示例<12>,xml parsers expat --- Fast XML parsing using Expat
@anchor{library/pyexpat content-model-descriptions}@anchor{2b3f}@anchor{library/pyexpat expat-content-models}@anchor{2b40}@anchor{library/pyexpat module-xml parsers expat model}@anchor{13a}
@subsubsection Content Model Descriptions


@geindex xml.parsers.expat.model (模块)

Content models are described using nested tuples.  Each tuple contains four
values: the type, the quantifier, the name, and a tuple of children.  Children
are simply additional content model descriptions.

The values of the first two fields are constants defined in the
@ref{13a,,xml.parsers.expat.model} module.  These constants can be collected in two
groups: the model type group and the quantifier group.

The constants in the model type group are:


@deffn {数据} xml.parsers.expat.model.XML_CTYPE_ANY

The element named by the model name was declared to have a content model of
@code{ANY}.
@end deffn


@deffn {数据} xml.parsers.expat.model.XML_CTYPE_CHOICE

The named element allows a choice from a number of options; this is used for
content models such as @code{(A | B | C)}.
@end deffn


@deffn {数据} xml.parsers.expat.model.XML_CTYPE_EMPTY

Elements which are declared to be @code{EMPTY} have this model type.
@end deffn


@deffn {数据} xml.parsers.expat.model.XML_CTYPE_MIXED
@end deffn


@deffn {数据} xml.parsers.expat.model.XML_CTYPE_NAME
@end deffn


@deffn {数据} xml.parsers.expat.model.XML_CTYPE_SEQ

Models which represent a series of models which follow one after the other are
indicated with this model type.  This is used for models such as @code{(A, B, C)}.
@end deffn

The constants in the quantifier group are:


@deffn {数据} xml.parsers.expat.model.XML_CQUANT_NONE

No modifier is given, so it can appear exactly once, as for @code{A}.
@end deffn


@deffn {数据} xml.parsers.expat.model.XML_CQUANT_OPT

The model is optional: it can appear once or not at all, as for @code{A?}.
@end deffn


@deffn {数据} xml.parsers.expat.model.XML_CQUANT_PLUS

The model must occur one or more times (like @code{A+}).
@end deffn


@deffn {数据} xml.parsers.expat.model.XML_CQUANT_REP

The model must occur zero or more times, as for @code{A*}.
@end deffn

@node Expat error constants,,Content Model Descriptions,xml parsers expat --- Fast XML parsing using Expat
@anchor{library/pyexpat expat-error-constants}@anchor{2b41}@anchor{library/pyexpat expat-errors}@anchor{2b42}@anchor{library/pyexpat module-xml parsers expat errors}@anchor{139}
@subsubsection Expat error constants


@geindex xml.parsers.expat.errors (模块)

The following constants are provided in the @ref{139,,xml.parsers.expat.errors}
module.  These constants are useful in interpreting some of the attributes of
the @code{ExpatError} exception objects raised when an error has occurred.
Since for backwards compatibility reasons, the constants' value is the error
@emph{message} and not the numeric error @emph{code}, you do this by comparing its
@ref{1b,,code} attribute with
@code{errors.codes[errors.XML_ERROR_@emph{CONSTANT_NAME}]}.

The @code{errors} module has the following attributes:

@geindex codes() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors codes}@anchor{2b3a}
@deffn {数据} xml.parsers.expat.errors.codes

A dictionary mapping numeric error codes to their string descriptions.


3.2 新版功能.

@end deffn

@geindex messages() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors messages}@anchor{2b39}
@deffn {数据} xml.parsers.expat.errors.messages

A dictionary mapping string descriptions to their error codes.


3.2 新版功能.

@end deffn

@geindex XML_ERROR_ASYNC_ENTITY() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_ASYNC_ENTITY}@anchor{2b43}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_ASYNC_ENTITY
@end deffn

@geindex XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF}@anchor{2b44}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_ATTRIBUTE_EXTERNAL_ENTITY_REF

An entity reference in an attribute value referred to an external entity instead
of an internal entity.
@end deffn

@geindex XML_ERROR_BAD_CHAR_REF() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_BAD_CHAR_REF}@anchor{2b45}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_BAD_CHAR_REF

A character reference referred to a character which is illegal in XML (for
example, character @code{0}, or '@code{&#0;}').
@end deffn

@geindex XML_ERROR_BINARY_ENTITY_REF() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_BINARY_ENTITY_REF}@anchor{2b46}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_BINARY_ENTITY_REF

An entity reference referred to an entity which was declared with a notation, so
cannot be parsed.
@end deffn

@geindex XML_ERROR_DUPLICATE_ATTRIBUTE() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_DUPLICATE_ATTRIBUTE}@anchor{2b47}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_DUPLICATE_ATTRIBUTE

An attribute was used more than once in a start tag.
@end deffn

@geindex XML_ERROR_INCORRECT_ENCODING() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_INCORRECT_ENCODING}@anchor{2b48}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_INCORRECT_ENCODING
@end deffn

@geindex XML_ERROR_INVALID_TOKEN() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_INVALID_TOKEN}@anchor{2b49}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_INVALID_TOKEN

Raised when an input byte could not properly be assigned to a character; for
example, a NUL byte (value @code{0}) in a UTF-8 input stream.
@end deffn

@geindex XML_ERROR_JUNK_AFTER_DOC_ELEMENT() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_JUNK_AFTER_DOC_ELEMENT}@anchor{2b4a}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_JUNK_AFTER_DOC_ELEMENT

Something other than whitespace occurred after the document element.
@end deffn

@geindex XML_ERROR_MISPLACED_XML_PI() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_MISPLACED_XML_PI}@anchor{2b4b}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_MISPLACED_XML_PI

An XML declaration was found somewhere other than the start of the input data.
@end deffn

@geindex XML_ERROR_NO_ELEMENTS() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_NO_ELEMENTS}@anchor{2b4c}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_NO_ELEMENTS

The document contains no elements (XML requires all documents to contain exactly
one top-level element)..
@end deffn

@geindex XML_ERROR_NO_MEMORY() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_NO_MEMORY}@anchor{2b4d}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_NO_MEMORY

Expat was not able to allocate memory internally.
@end deffn

@geindex XML_ERROR_PARAM_ENTITY_REF() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_PARAM_ENTITY_REF}@anchor{2b4e}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_PARAM_ENTITY_REF

A parameter entity reference was found where it was not allowed.
@end deffn

@geindex XML_ERROR_PARTIAL_CHAR() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_PARTIAL_CHAR}@anchor{2b4f}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_PARTIAL_CHAR

An incomplete character was found in the input.
@end deffn

@geindex XML_ERROR_RECURSIVE_ENTITY_REF() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_RECURSIVE_ENTITY_REF}@anchor{2b50}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_RECURSIVE_ENTITY_REF

An entity reference contained another reference to the same entity; possibly via
a different name, and possibly indirectly.
@end deffn

@geindex XML_ERROR_SYNTAX() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_SYNTAX}@anchor{2b51}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_SYNTAX

Some unspecified syntax error was encountered.
@end deffn

@geindex XML_ERROR_TAG_MISMATCH() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_TAG_MISMATCH}@anchor{2b52}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_TAG_MISMATCH

An end tag did not match the innermost open start tag.
@end deffn

@geindex XML_ERROR_UNCLOSED_TOKEN() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_UNCLOSED_TOKEN}@anchor{2b53}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_UNCLOSED_TOKEN

Some token (such as a start tag) was not closed before the end of the stream or
the next token was encountered.
@end deffn

@geindex XML_ERROR_UNDEFINED_ENTITY() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_UNDEFINED_ENTITY}@anchor{2b54}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_UNDEFINED_ENTITY

A reference was made to an entity which was not defined.
@end deffn

@geindex XML_ERROR_UNKNOWN_ENCODING() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_UNKNOWN_ENCODING}@anchor{2b55}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_UNKNOWN_ENCODING

The document encoding is not supported by Expat.
@end deffn

@geindex XML_ERROR_UNCLOSED_CDATA_SECTION() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_UNCLOSED_CDATA_SECTION}@anchor{2b56}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_UNCLOSED_CDATA_SECTION

A CDATA marked section was not closed.
@end deffn

@geindex XML_ERROR_EXTERNAL_ENTITY_HANDLING() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_EXTERNAL_ENTITY_HANDLING}@anchor{2b57}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_EXTERNAL_ENTITY_HANDLING
@end deffn

@geindex XML_ERROR_NOT_STANDALONE() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_NOT_STANDALONE}@anchor{2b58}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_NOT_STANDALONE

The parser determined that the document was not "standalone" though it declared
itself to be in the XML declaration, and the @code{NotStandaloneHandler} was
set and returned @code{0}.
@end deffn

@geindex XML_ERROR_UNEXPECTED_STATE() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_UNEXPECTED_STATE}@anchor{2b59}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_UNEXPECTED_STATE
@end deffn

@geindex XML_ERROR_ENTITY_DECLARED_IN_PE() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_ENTITY_DECLARED_IN_PE}@anchor{2b5a}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_ENTITY_DECLARED_IN_PE
@end deffn

@geindex XML_ERROR_FEATURE_REQUIRES_XML_DTD() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_FEATURE_REQUIRES_XML_DTD}@anchor{2b5b}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_FEATURE_REQUIRES_XML_DTD

An operation was requested that requires DTD support to be compiled in, but
Expat was configured without DTD support.  This should never be reported by a
standard build of the @ref{138,,xml.parsers.expat} module.
@end deffn

@geindex XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING}@anchor{2b5c}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_CANT_CHANGE_FEATURE_ONCE_PARSING

A behavioral change was requested after parsing started that can only be changed
before parsing has started.  This is (currently) only raised by
@code{UseForeignDTD()}.
@end deffn

@geindex XML_ERROR_UNBOUND_PREFIX() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_UNBOUND_PREFIX}@anchor{2b5d}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_UNBOUND_PREFIX

An undeclared prefix was found when namespace processing was enabled.
@end deffn

@geindex XML_ERROR_UNDECLARING_PREFIX() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_UNDECLARING_PREFIX}@anchor{2b5e}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_UNDECLARING_PREFIX

The document attempted to remove the namespace declaration associated with a
prefix.
@end deffn

@geindex XML_ERROR_INCOMPLETE_PE() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_INCOMPLETE_PE}@anchor{2b5f}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_INCOMPLETE_PE

A parameter entity contained incomplete markup.
@end deffn

@geindex XML_ERROR_XML_DECL() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_XML_DECL}@anchor{2b60}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_XML_DECL

The document contained no document element at all.
@end deffn

@geindex XML_ERROR_TEXT_DECL() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_TEXT_DECL}@anchor{2b61}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_TEXT_DECL

There was an error parsing a text declaration in an external entity.
@end deffn

@geindex XML_ERROR_PUBLICID() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_PUBLICID}@anchor{2b62}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_PUBLICID

Characters were found in the public id that are not allowed.
@end deffn

@geindex XML_ERROR_SUSPENDED() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_SUSPENDED}@anchor{2b63}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_SUSPENDED

The requested operation was made on a suspended parser, but isn't allowed.  This
includes attempts to provide additional input or to stop the parser.
@end deffn

@geindex XML_ERROR_NOT_SUSPENDED() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_NOT_SUSPENDED}@anchor{2b64}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_NOT_SUSPENDED

An attempt to resume the parser was made when the parser had not been suspended.
@end deffn

@geindex XML_ERROR_ABORTED() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_ABORTED}@anchor{2b65}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_ABORTED

This should not be reported to Python applications.
@end deffn

@geindex XML_ERROR_FINISHED() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_FINISHED}@anchor{2b66}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_FINISHED

The requested operation was made on a parser which was finished parsing input,
but isn't allowed.  This includes attempts to provide additional input or to
stop the parser.
@end deffn

@geindex XML_ERROR_SUSPEND_PE() (在 xml.parsers.expat.errors 模块中)
@anchor{library/pyexpat xml parsers expat errors XML_ERROR_SUSPEND_PE}@anchor{2b67}
@deffn {数据} xml.parsers.expat.errors.XML_ERROR_SUSPEND_PE
@end deffn

@subsubheading 备注


@node 互联网协议和支持,多媒体服务,结构化标记处理工具,Python 标准库
@anchor{library/internet doc}@anchor{2b68}@anchor{library/internet internet}@anchor{2b69}@anchor{library/internet internet-protocols-and-support}@anchor{2b6a}
@section 互联网协议和支持


@geindex WWW
@geindex Internet
@geindex World Wide Web

@geindex 模块; socket

本章介绍的模块实现了互联网协议并支持相关技术。 它们都是用 Python 实现的。 这些模块中的大多数都需要存在依赖于系统的模块 @ref{ef,,socket} ，目前大多数流行平台都支持它。 这是一个概述：

@menu
* webbrowser: webbrowser --- 方便的Web浏览器控制器. 方便的Web浏览器控制器
* cgi: cgi --- Common Gateway Interface support. Common Gateway Interface support
* cgitb: cgitb --- 用于 CGI 脚本的回溯管理器. 用于 CGI 脚本的回溯管理器
* wsgiref: wsgiref --- WSGI Utilities and Reference Implementation. WSGI Utilities and Reference Implementation
* urllib: urllib --- URL 处理模块. URL 处理模块
* urllib.request: urllib request --- 用于打开 URL 的可扩展库. 用于打开 URL 的可扩展库
* urllib.response: urllib response --- urllib 使用的 Response 类. urllib 使用的 Response 类
* urllib.parse: urllib parse --- Parse URLs into components. Parse URLs into components
* urllib.error: urllib error --- urllib request 引发的异常类. urllib.request 引发的异常类
* urllib.robotparser: urllib robotparser --- robots txt 语法分析程序. robots.txt 语法分析程序
* http: http --- HTTP 模块. HTTP 模块
* http.client: http client --- HTTP 协议客户端. HTTP 协议客户端
* ftplib: ftplib --- FTP 协议客户端. FTP 协议客户端
* poplib: poplib --- POP3 protocol client. POP3 protocol client
* imaplib: imaplib --- IMAP4 protocol client. IMAP4 protocol client
* nntplib: nntplib --- NNTP protocol client. NNTP protocol client
* smtplib ---SMTP协议客户端:: 
* smtpd: smtpd --- SMTP 服务器. SMTP 服务器
* telnetlib: telnetlib --- Telnet client. Telnet client
* uuid: uuid --- UUID objects according to RFC 4122. UUID objects according to RFC 4122
* socketserver: socketserver --- A framework for network servers. A framework for network servers
* http.server: http server --- HTTP 服务器. HTTP 服务器
* http.cookies: http cookies --- HTTP状态管理. HTTP状态管理
* http.cookiejar —— HTTP 客户端的 Cookie 处理: http cookiejar —— HTTP 客户端的 Cookie 处理. 
* xmlrpc: xmlrpc --- XMLRPC 服务端与客户端模块. XMLRPC 服务端与客户端模块
* xmlrpc.client: xmlrpc client --- XML-RPC client access. XML-RPC client access
* xmlrpc.server: xmlrpc server --- Basic XML-RPC servers. Basic XML-RPC servers
* ipaddress: ipaddress --- IPv4/IPv6 操作库. IPv4/IPv6 操作库

@end menu

@node webbrowser --- 方便的Web浏览器控制器,cgi --- Common Gateway Interface support,,互联网协议和支持
@anchor{library/webbrowser doc}@anchor{2b6b}@anchor{library/webbrowser module-webbrowser}@anchor{129}@anchor{library/webbrowser webbrowser-convenient-web-browser-controller}@anchor{2b6c}
@subsection @code{webbrowser} --- 方便的Web浏览器控制器


@geindex webbrowser (模块)

@strong{源码：} Lib/webbrowser.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/webbrowser.py}


__________________________________________________________________


@ref{129,,webbrowser} 模块提供了一个高级接口，允许向用户显示基于Web的文档。 在大多数情况下，只需从该模块调用 @ref{2b6d,,open()} 函数就可以了。

在 Unix 下，图形浏览器在 X11 下是首选，但如果图形浏览器不可用或 X11 显示不可用，则将使用文本模式浏览器。 如果使用文本模式浏览器，则调用进程将阻塞，直到用户退出浏览器。

如果存在环境变量 
@geindex BROWSER
@geindex 环境变量; BROWSER
@code{BROWSER} ，则将其解释为 @ref{12eb,,os.pathsep} 分隔的浏览器列表，以便在平台默认值之前尝试。 当列表部分的值包含字符串 @code{％s} 时，它被解释为一个文字浏览器命令行，用于替换 @code{％s} 的参数 URL ；如果该部分不包含 @code{％s}，则它只被解释为要启动的浏览器的名称。 @footnote{@w{(1)} 
这里命名的不带完整路径的可执行文件将在 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 环境变量给出的目录中搜索。
}

对于非 Unix 平台，或者当 Unix 上有远程浏览器时，控制过程不会等待用户完成浏览器，而是允许远程浏览器在显示界面上维护自己的窗口。 如果 Unix 上没有远程浏览器，控制进程将启动一个新的浏览器并等待。

脚本 @code{webbrowser} 可以用作模块的命令行界面。它接受一个 URL 作为参数。还接受以下可选参数：@code{-n} 如果可能，在新的浏览器窗口中打开 URL ； @code{-t} 在新的浏览器页面（“标签”）中打开 URL。这些选择当然是相互排斥的。用法示例:

@example
python -m webbrowser -t "http://www.python.org"
@end example

定义了以下异常：

@geindex Error
@anchor{library/webbrowser webbrowser Error}@anchor{2b6e}
@deffn {例外} webbrowser.Error

发生浏览器控件错误时引发异常。
@end deffn

定义了以下函数：

@geindex open() (在 webbrowser 模块中)
@anchor{library/webbrowser webbrowser open}@anchor{2b6d}
@deffn {函数} webbrowser.open (url, new=0, autoraise=True)

使用默认浏览器显示 @emph{url}。 如果 @emph{new} 为 0，则尽可能在同一浏览器窗口中打开 @emph{url}。 如果 @emph{new} 为 1，则尽可能打开新的浏览器窗口。 如果 @emph{new} 为 2，则尽可能打开新的浏览器页面（“标签”）。 如果 @emph{autoraise} 为 “True”，则会尽可能置前窗口（请注意，在许多窗口管理器下，无论此变量的设置如何，都会置前窗口）。

请注意，在某些平台上，尝试使用此函数打开文件名，可能会起作用并启动操作系统的关联程序。 但是，这种方式不被支持也不可移植。

使用 @code{url} 参数会引发  @ref{12d0,,auditing event} @code{webbrowser.open} 。
@end deffn

@geindex open_new() (在 webbrowser 模块中)
@anchor{library/webbrowser webbrowser open_new}@anchor{2b6f}
@deffn {函数} webbrowser.open_new (url)

如果可能，在默认浏览器的新窗口中打开 @emph{url}，否则，在唯一的浏览器窗口中打开 @emph{url}。
@end deffn

@geindex open_new_tab() (在 webbrowser 模块中)
@anchor{library/webbrowser webbrowser open_new_tab}@anchor{2b70}
@deffn {函数} webbrowser.open_new_tab (url)

如果可能，在默认浏览器的新页面（“标签”）中打开 @emph{url}，否则等效于 @ref{2b6f,,open_new()}。
@end deffn

@geindex get() (在 webbrowser 模块中)
@anchor{library/webbrowser webbrowser get}@anchor{2b71}
@deffn {函数} webbrowser.get (using=None)

返回浏览器类型为 @emph{using} 指定的控制器对象。 如果 @emph{using} 为 @code{None}，则返回适用于调用者环境的默认浏览器的控制器。
@end deffn

@geindex register() (在 webbrowser 模块中)
@anchor{library/webbrowser webbrowser register}@anchor{2b72}
@deffn {函数} webbrowser.register (name, constructor, instance=None, *, preferred=False)

注册 @emph{name} 浏览器类型。 注册浏览器类型后， @ref{2b71,,get()} 函数可以返回该浏览器类型的控制器。 如果没有提供 @emph{instance}，或者为 @code{None}，@emph{constructor} 将在没有参数的情况下被调用，以在需要时创建实例。 如果提供了 @emph{instance}，则永远不会调用 @emph{constructor}，并且可能是 @code{None}。

将 @emph{preferred} 设置为 @code{True} 使得这个浏览器成为 @ref{2b71,,get()} 不带参数调用的首选结果。 否则，只有在您计划设置 
@geindex BROWSER
@geindex 环境变量; BROWSER
@code{BROWSER} 变量，或使用与您声明的处理程序的名称相匹配的非空参数调用 @ref{2b71,,get()} 时，此入口点才有用。


在 3.7 版更改: 添加了仅关键字参数 @emph{preferred}。

@end deffn

预定义了许多浏览器类型。 此表给出了可以传递给 @ref{2b71,,get()} 函数的类型名称以及控制器类的相应实例化，这些都在此模块中定义。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

类型名

@tab

类名

@tab

注释

@item

@code{'mozilla'}

@tab

@code{Mozilla('mozilla')}

@tab

@item

@code{'firefox'}

@tab

@code{Mozilla('mozilla')}

@tab

@item

@code{'netscape'}

@tab

@code{Mozilla('netscape')}

@tab

@item

@code{'galeon'}

@tab

@code{Galeon('galeon')}

@tab

@item

@code{'epiphany'}

@tab

@code{Galeon('epiphany')}

@tab

@item

@code{'skipstone'}

@tab

@code{BackgroundBrowser('skipstone')}

@tab

@item

@code{'kfmclient'}

@tab

@code{Konqueror()}

@tab

(1)

@item

@code{'konqueror'}

@tab

@code{Konqueror()}

@tab

(1)

@item

@code{'kfm'}

@tab

@code{Konqueror()}

@tab

(1)

@item

@code{'mosaic'}

@tab

@code{BackgroundBrowser('mosaic')}

@tab

@item

@code{'opera'}

@tab

@code{Opera()}

@tab

@item

@code{'grail'}

@tab

@code{Grail()}

@tab

@item

@code{'links'}

@tab

@code{GenericBrowser('links')}

@tab

@item

@code{'elinks'}

@tab

@code{Elinks('elinks')}

@tab

@item

@code{'lynx'}

@tab

@code{GenericBrowser('lynx')}

@tab

@item

@code{'w3m'}

@tab

@code{GenericBrowser('w3m')}

@tab

@item

@code{'windows-default'}

@tab

@code{WindowsDefault}

@tab

(2)

@item

@code{'macosx'}

@tab

@code{MacOSX('default')}

@tab

(3)

@item

@code{'safari'}

@tab

@code{MacOSX('safari')}

@tab

(3)

@item

@code{'google-chrome'}

@tab

@code{Chrome('google-chrome')}

@tab

@item

@code{'chrome'}

@tab

@code{Chrome('chrome')}

@tab

@item

@code{'chromium'}

@tab

@code{Chromium('chromium')}

@tab

@item

@code{'chromium-browser'}

@tab

@code{Chromium('chromium-browser')}

@tab

@end multitable


注释:


@enumerate 

@item 
“Konqueror” 是 Unix 的 KDE 桌面环境的文件管理器，只有在 KDE 运行时才有意义。 一些可靠地检测 KDE 的方法会很好；仅检查 
@geindex KDEDIR
@geindex 环境变量; KDEDIR
@code{KDEDIR} 变量是不够的。 另请注意，KDE 2的 @code{konqueror} 命令，会使用名称 “kfm”---此实现选择运行的 Konqueror 的最佳策略。

@item 
仅限 Windows 平台。

@item 
仅限 Mac OS X 平台。
@end enumerate


3.3 新版功能: 添加了对 Chrome/Chromium 的支持。


以下是一些简单的例子:

@example
url = 'http://docs.python.org/'

# Open URL in a new tab, if a browser window is already open.
webbrowser.open_new_tab(url)

# Open URL in new window, raising the window if possible.
webbrowser.open_new(url)
@end example

@menu
* 浏览器控制器对象:: 

@end menu

@node 浏览器控制器对象,,,webbrowser --- 方便的Web浏览器控制器
@anchor{library/webbrowser browser-controller-objects}@anchor{2b73}@anchor{library/webbrowser browser-controllers}@anchor{2b74}
@subsubsection 浏览器控制器对象


浏览器控制器提供三个与模块级便捷函数相同的方法：

@geindex open() (webbrowser.controller 方法)
@anchor{library/webbrowser webbrowser controller open}@anchor{2b75}
@deffn {方法} controller.open (url, new=0, autoraise=True)

使用此控制器处理的浏览器显示 @emph{url}。 如果 @emph{new} 为 1，则尽可能打开新的浏览器窗口。 如果 @emph{new} 为 2，则尽可能打开新的浏览器页面（“标签”）。
@end deffn

@geindex open_new() (webbrowser.controller 方法)
@anchor{library/webbrowser webbrowser controller open_new}@anchor{2b76}
@deffn {方法} controller.open_new (url)

如果可能，在此控制器处理的浏览器的新窗口中打开 @emph{url} ，否则，在唯一的浏览器窗口中打开 @emph{url} 。 别名 @ref{2b6f,,open_new()}。
@end deffn

@geindex open_new_tab() (webbrowser.controller 方法)
@anchor{library/webbrowser webbrowser controller open_new_tab}@anchor{2b77}
@deffn {方法} controller.open_new_tab (url)

如果可能，在此控制器处理的浏览器的新页面（“标签”）中打开 @emph{url}，否则等效于 @ref{2b6f,,open_new()}。
@end deffn

@subsubheading 备注


@node cgi --- Common Gateway Interface support,cgitb --- 用于 CGI 脚本的回溯管理器,webbrowser --- 方便的Web浏览器控制器,互联网协议和支持
@anchor{library/cgi doc}@anchor{2b78}@anchor{library/cgi cgi-common-gateway-interface-support}@anchor{2b79}@anchor{library/cgi module-cgi}@anchor{16}
@subsection @code{cgi} --- Common Gateway Interface support


@geindex cgi (模块)

@strong{源代码：} Lib/cgi.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/cgi.py}

@geindex WWW; server
@geindex CGI; protocol
@geindex HTTP; protocol
@geindex MIME; headers
@geindex URL
@geindex Common Gateway Interface


__________________________________________________________________


Support module for Common Gateway Interface (CGI) scripts.

This module defines a number of utilities for use by CGI scripts written in
Python.

@menu
* 概述: 概述<11>. 
* 使用cgi模块。:: 
* Higher Level Interface:: 
* 函数: 函数<8>. 
* Caring about security:: 
* Installing your CGI script on a Unix system:: 
* Testing your CGI script:: 
* Debugging CGI scripts:: 
* Common problems and solutions:: 

@end menu

@node 概述<11>,使用cgi模块。,,cgi --- Common Gateway Interface support
@anchor{library/cgi introduction}@anchor{2b7a}
@subsubsection 概述

@anchor{library/cgi cgi-intro}@anchor{2b7b}
A CGI script is invoked by an HTTP server, usually to process user input
submitted through an HTML @code{<FORM>} or @code{<ISINDEX>} element.

Most often, CGI scripts live in the server's special @code{cgi-bin} directory.
The HTTP server places all sorts of information about the request (such as the
client's hostname, the requested URL, the query string, and lots of other
goodies) in the script's shell environment, executes the script, and sends the
script's output back to the client.

The script's input is connected to the client too, and sometimes the form data
is read this way; at other times the form data is passed via the "query string"
part of the URL.  This module is intended to take care of the different cases
and provide a simpler interface to the Python script.  It also provides a number
of utilities that help in debugging scripts, and the latest addition is support
for file uploads from a form (if your browser supports it).

The output of a CGI script should consist of two sections, separated by a blank
line.  The first section contains a number of headers, telling the client what
kind of data is following.  Python code to generate a minimal header section
looks like this:

@example
print("Content-Type: text/html")    # HTML is following
print()                             # blank line, end of headers
@end example

The second section is usually HTML, which allows the client software to display
nicely formatted text with header, in-line images, etc. Here's Python code that
prints a simple piece of HTML:

@example
print("<TITLE>CGI script output</TITLE>")
print("<H1>This is my first CGI script</H1>")
print("Hello, world!")
@end example

@node 使用cgi模块。,Higher Level Interface,概述<11>,cgi --- Common Gateway Interface support
@anchor{library/cgi id1}@anchor{2b7c}@anchor{library/cgi using-the-cgi-module}@anchor{2b7d}
@subsubsection 使用cgi模块。


通过敲下 @code{import cgi} 来开始。

当你在写一个新脚本时，考虑加上这些语句:

@example
import cgitb
cgitb.enable()
@end example

This activates a special exception handler that will display detailed reports in
the Web browser if any errors occur.  If you'd rather not show the guts of your
program to users of your script, you can have the reports saved to files
instead, with code like this:

@example
import cgitb
cgitb.enable(display=0, logdir="/path/to/logdir")
@end example

It's very helpful to use this feature during script development. The reports
produced by @ref{17,,cgitb} provide information that can save you a lot of time in
tracking down bugs.  You can always remove the @code{cgitb} line later when you
have tested your script and are confident that it works correctly.

To get at submitted form data, use the @code{FieldStorage} class. If the form
contains non-ASCII characters, use the @emph{encoding} keyword parameter set to the
value of the encoding defined for the document. It is usually contained in the
META tag in the HEAD section of the HTML document or by the
@code{Content-Type} header).  This reads the form contents from the
standard input or the environment (depending on the value of various
environment variables set according to the CGI standard).  Since it may consume
standard input, it should be instantiated only once.

The @code{FieldStorage} instance can be indexed like a Python dictionary.
It allows membership testing with the @ref{79d,,in} operator, and also supports
the standard dictionary method @ref{c23,,keys()} and the built-in function
@ref{150,,len()}.  Form fields containing empty strings are ignored and do not appear
in the dictionary; to keep such values, provide a true value for the optional
@emph{keep_blank_values} keyword parameter when creating the @code{FieldStorage}
instance.

For instance, the following code (which assumes that the
@code{Content-Type} header and blank line have already been printed)
checks that the fields @code{name} and @code{addr} are both set to a non-empty
string:

@example
form = cgi.FieldStorage()
if "name" not in form or "addr" not in form:
    print("<H1>Error</H1>")
    print("Please fill in the name and addr fields.")
    return
print("<p>name:", form["name"].value)
print("<p>addr:", form["addr"].value)
...further form processing here...
@end example

Here the fields, accessed through @code{form[key]}, are themselves instances of
@code{FieldStorage} (or @code{MiniFieldStorage}, depending on the form
encoding). The @code{value} attribute of the instance yields
the string value of the field.  The @code{getvalue()} method
returns this string value directly; it also accepts an optional second argument
as a default to return if the requested key is not present.

If the submitted form data contains more than one field with the same name, the
object retrieved by @code{form[key]} is not a @code{FieldStorage} or
@code{MiniFieldStorage} instance but a list of such instances.  Similarly, in
this situation, @code{form.getvalue(key)} would return a list of strings. If you
expect this possibility (when your HTML form contains multiple fields with the
same name), use the @ref{2b7e,,getlist()} method, which always returns
a list of values (so that you do not need to special-case the single item
case).  For example, this code concatenates any number of username fields,
separated by commas:

@example
value = form.getlist("username")
usernames = ",".join(value)
@end example

If a field represents an uploaded file, accessing the value via the
@code{value} attribute or the @code{getvalue()}
method reads the entire file in memory as bytes.  This may not be what you
want.  You can test for an uploaded file by testing either the
@code{filename} attribute or the @code{file}
attribute.  You can then read the data from the @code{file}
attribute before it is automatically closed as part of the garbage collection of
the @code{FieldStorage} instance
(the @ref{6fc,,read()} and @ref{169c,,readline()} methods will
return bytes):

@example
fileitem = form["userfile"]
if fileitem.file:
    # It's an uploaded file; count lines
    linecount = 0
    while True:
        line = fileitem.file.readline()
        if not line: break
        linecount = linecount + 1
@end example

@code{FieldStorage} objects also support being used in a @ref{6e3,,with}
statement, which will automatically close them when done.

If an error is encountered when obtaining the contents of an uploaded file
(for example, when the user interrupts the form submission by clicking on
a Back or Cancel button) the @code{done} attribute of the
object for the field will be set to the value -1.

The file upload draft standard entertains the possibility of uploading multiple
files from one field (using a recursive @code{multipart/*} encoding).
When this occurs, the item will be a dictionary-like @code{FieldStorage} item.
This can be determined by testing its @code{type} attribute, which should be
@code{multipart/form-data} (or perhaps another MIME type matching
@code{multipart/*}).  In this case, it can be iterated over recursively
just like the top-level form object.

When a form is submitted in the "old" format (as the query string or as a single
data part of type @code{application/x-www-form-urlencoded}), the items will
actually be instances of the class @code{MiniFieldStorage}.  In this case, the
@code{list}, @code{file}, and @code{filename} attributes are always @code{None}.

A form submitted via POST that also has a query string will contain both
@code{FieldStorage} and @code{MiniFieldStorage} items.


在 3.4 版更改: The @code{file} attribute is automatically closed upon the
garbage collection of the creating @code{FieldStorage} instance.



在 3.5 版更改: Added support for the context management protocol to the
@code{FieldStorage} class.


@node Higher Level Interface,函数<8>,使用cgi模块。,cgi --- Common Gateway Interface support
@anchor{library/cgi higher-level-interface}@anchor{2b7f}
@subsubsection Higher Level Interface


The previous section explains how to read CGI form data using the
@code{FieldStorage} class.  This section describes a higher level interface
which was added to this class to allow one to do it in a more readable and
intuitive way.  The interface doesn't make the techniques described in previous
sections obsolete --- they are still useful to process file uploads efficiently,
for example.

@c XXX: Is this true ?

The interface consists of two simple methods. Using the methods you can process
form data in a generic way, without the need to worry whether only one or more
values were posted under one name.

In the previous section, you learned to write following code anytime you
expected a user to post more than one value under one name:

@example
item = form.getvalue("item")
if isinstance(item, list):
    # The user is requesting more than one item.
else:
    # The user is requesting only one item.
@end example

This situation is common for example when a form contains a group of multiple
checkboxes with the same name:

@example
<input type="checkbox" name="item" value="1" />
<input type="checkbox" name="item" value="2" />
@end example

In most situations, however, there's only one form control with a particular
name in a form and then you expect and need only one value associated with this
name.  So you write a script containing for example this code:

@example
user = form.getvalue("user").upper()
@end example

The problem with the code is that you should never expect that a client will
provide valid input to your scripts.  For example, if a curious user appends
another @code{user=foo} pair to the query string, then the script would crash,
because in this situation the @code{getvalue("user")} method call returns a list
instead of a string.  Calling the @ref{15f7,,upper()} method on a list is not valid
(since lists do not have a method of this name) and results in an
@ref{393,,AttributeError} exception.

Therefore, the appropriate way to read form data values was to always use the
code which checks whether the obtained value is a single value or a list of
values.  That's annoying and leads to less readable scripts.

A more convenient approach is to use the methods @ref{2b80,,getfirst()}
and @ref{2b7e,,getlist()} provided by this higher level interface.

@geindex getfirst() (cgi.FieldStorage 方法)
@anchor{library/cgi cgi FieldStorage getfirst}@anchor{2b80}
@deffn {方法} FieldStorage.getfirst (name, default=None)

This method always returns only one value associated with form field @emph{name}.
The method returns only the first value in case that more values were posted
under such name.  Please note that the order in which the values are received
may vary from browser to browser and should not be counted on. @footnote{@w{(1)} 
Note that some recent versions of the HTML specification do state what
order the field values should be supplied in, but knowing whether a request
was received from a conforming browser, or even from a browser at all, is
tedious and error-prone.
}  If no such
form field or value exists then the method returns the value specified by the
optional parameter @emph{default}.  This parameter defaults to @code{None} if not
specified.
@end deffn

@geindex getlist() (cgi.FieldStorage 方法)
@anchor{library/cgi cgi FieldStorage getlist}@anchor{2b7e}
@deffn {方法} FieldStorage.getlist (name)

This method always returns a list of values associated with form field @emph{name}.
The method returns an empty list if no such form field or value exists for
@emph{name}.  It returns a list consisting of one item if only one such value exists.
@end deffn

Using these methods you can write nice compact code:

@example
import cgi
form = cgi.FieldStorage()
user = form.getfirst("user", "").upper()    # This way it's safe.
for item in form.getlist("item"):
    do_something(item)
@end example

@node 函数<8>,Caring about security,Higher Level Interface,cgi --- Common Gateway Interface support
@anchor{library/cgi functions}@anchor{2b81}@anchor{library/cgi functions-in-cgi-module}@anchor{2b82}
@subsubsection 函数


These are useful if you want more control, or if you want to employ some of the
algorithms implemented in this module in other circumstances.

@geindex parse() (在 cgi 模块中)
@anchor{library/cgi cgi parse}@anchor{2b83}
@deffn {函数} cgi.parse (fp=None, environ=os.environ, keep_blank_values=False, strict_parsing=False)

Parse a query in the environment or from a file (the file defaults to
@code{sys.stdin}).  The @emph{keep_blank_values} and @emph{strict_parsing} parameters are
passed to @ref{2b84,,urllib.parse.parse_qs()} unchanged.
@end deffn

@geindex parse_multipart() (在 cgi 模块中)
@anchor{library/cgi cgi parse_multipart}@anchor{48d}
@deffn {函数} cgi.parse_multipart (fp, pdict, encoding="utf-8", errors="replace")

Parse input of type @code{multipart/form-data} (for  file uploads).
Arguments are @emph{fp} for the input file, @emph{pdict} for a dictionary containing
other parameters in the @code{Content-Type} header, and @emph{encoding},
the request encoding.

Returns a dictionary just like @ref{2b84,,urllib.parse.parse_qs()}: keys are the
field names, each value is a list of values for that field. For non-file
fields, the value is a list of strings.

This is easy to use but not much good if you are expecting megabytes to be
uploaded --- in that case, use the @code{FieldStorage} class instead
which is much more flexible.


在 3.7 版更改: Added the @emph{encoding} and @emph{errors} parameters.  For non-file fields, the
value is now a list of strings, not bytes.

@end deffn

@geindex parse_header() (在 cgi 模块中)
@anchor{library/cgi cgi parse_header}@anchor{2b85}
@deffn {函数} cgi.parse_header (string)

Parse a MIME header (such as @code{Content-Type}) into a main value and a
dictionary of parameters.
@end deffn

@geindex test() (在 cgi 模块中)
@anchor{library/cgi cgi test}@anchor{2b86}
@deffn {函数} cgi.test ()

Robust test CGI script, usable as main program. Writes minimal HTTP headers and
formats all information provided to the script in HTML form.
@end deffn

@geindex print_environ() (在 cgi 模块中)
@anchor{library/cgi cgi print_environ}@anchor{2b87}
@deffn {函数} cgi.print_environ ()

Format the shell environment in HTML.
@end deffn

@geindex print_form() (在 cgi 模块中)
@anchor{library/cgi cgi print_form}@anchor{2b88}
@deffn {函数} cgi.print_form (form)

Format a form in HTML.
@end deffn

@geindex print_directory() (在 cgi 模块中)
@anchor{library/cgi cgi print_directory}@anchor{2b89}
@deffn {函数} cgi.print_directory ()

Format the current directory in HTML.
@end deffn

@geindex print_environ_usage() (在 cgi 模块中)
@anchor{library/cgi cgi print_environ_usage}@anchor{2b8a}
@deffn {函数} cgi.print_environ_usage ()

Print a list of useful (used by CGI) environment variables in HTML.
@end deffn

@node Caring about security,Installing your CGI script on a Unix system,函数<8>,cgi --- Common Gateway Interface support
@anchor{library/cgi caring-about-security}@anchor{2b8b}@anchor{library/cgi cgi-security}@anchor{2b8c}
@subsubsection Caring about security


@geindex CGI; security

There's one important rule: if you invoke an external program (via the
@ref{dba,,os.system()} or @ref{2a9,,os.popen()} functions. or others with similar
functionality), make very sure you don't pass arbitrary strings received from
the client to the shell.  This is a well-known security hole whereby clever
hackers anywhere on the Web can exploit a gullible CGI script to invoke
arbitrary shell commands.  Even parts of the URL or field names cannot be
trusted, since the request doesn't have to come from your form!

To be on the safe side, if you must pass a string gotten from a form to a shell
command, you should make sure the string contains only alphanumeric characters,
dashes, underscores, and periods.

@node Installing your CGI script on a Unix system,Testing your CGI script,Caring about security,cgi --- Common Gateway Interface support
@anchor{library/cgi installing-your-cgi-script-on-a-unix-system}@anchor{2b8d}
@subsubsection Installing your CGI script on a Unix system


Read the documentation for your HTTP server and check with your local system
administrator to find the directory where CGI scripts should be installed;
usually this is in a directory @code{cgi-bin} in the server tree.

Make sure that your script is readable and executable by "others"; the Unix file
mode should be @code{0o755} octal (use @code{chmod 0755 filename}).  Make sure that the
first line of the script contains @code{#!} starting in column 1 followed by the
pathname of the Python interpreter, for instance:

@example
#!/usr/local/bin/python
@end example

Make sure the Python interpreter exists and is executable by "others".

Make sure that any files your script needs to read or write are readable or
writable, respectively, by "others" --- their mode should be @code{0o644} for
readable and @code{0o666} for writable.  This is because, for security reasons, the
HTTP server executes your script as user "nobody", without any special
privileges.  It can only read (write, execute) files that everybody can read
(write, execute).  The current directory at execution time is also different (it
is usually the server's cgi-bin directory) and the set of environment variables
is also different from what you get when you log in.  In particular, don't count
on the shell's search path for executables (
@geindex PATH
@geindex 环境变量; PATH
@code{PATH}) or the Python module
search path (
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH}) to be set to anything interesting.

If you need to load modules from a directory which is not on Python's default
module search path, you can change the path in your script, before importing
other modules.  For example:

@example
import sys
sys.path.insert(0, "/usr/home/joe/lib/python")
sys.path.insert(0, "/usr/local/lib/python")
@end example

(This way, the directory inserted last will be searched first!)

Instructions for non-Unix systems will vary; check your HTTP server's
documentation (it will usually have a section on CGI scripts).

@node Testing your CGI script,Debugging CGI scripts,Installing your CGI script on a Unix system,cgi --- Common Gateway Interface support
@anchor{library/cgi testing-your-cgi-script}@anchor{2b8e}
@subsubsection Testing your CGI script


Unfortunately, a CGI script will generally not run when you try it from the
command line, and a script that works perfectly from the command line may fail
mysteriously when run from the server.  There's one reason why you should still
test your script from the command line: if it contains a syntax error, the
Python interpreter won't execute it at all, and the HTTP server will most likely
send a cryptic error to the client.

Assuming your script has no syntax errors, yet it does not work, you have no
choice but to read the next section.

@node Debugging CGI scripts,Common problems and solutions,Testing your CGI script,cgi --- Common Gateway Interface support
@anchor{library/cgi debugging-cgi-scripts}@anchor{2b8f}
@subsubsection Debugging CGI scripts


@geindex CGI; debugging

First of all, check for trivial installation errors --- reading the section
above on installing your CGI script carefully can save you a lot of time.  If
you wonder whether you have understood the installation procedure correctly, try
installing a copy of this module file (@code{cgi.py}) as a CGI script.  When
invoked as a script, the file will dump its environment and the contents of the
form in HTML form. Give it the right mode etc, and send it a request.  If it's
installed in the standard @code{cgi-bin} directory, it should be possible to
send it a request by entering a URL into your browser of the form:

@example
http://yourhostname/cgi-bin/cgi.py?name=Joe+Blow&addr=At+Home
@end example

If this gives an error of type 404, the server cannot find the script -- perhaps
you need to install it in a different directory.  If it gives another error,
there's an installation problem that you should fix before trying to go any
further.  If you get a nicely formatted listing of the environment and form
content (in this example, the fields should be listed as "addr" with value "At
Home" and "name" with value "Joe Blow"), the @code{cgi.py} script has been
installed correctly.  If you follow the same procedure for your own script, you
should now be able to debug it.

The next step could be to call the @ref{16,,cgi} module's @ref{105,,test()} function
from your script: replace its main code with the single statement

@example
cgi.test()
@end example

This should produce the same results as those gotten from installing the
@code{cgi.py} file itself.

When an ordinary Python script raises an unhandled exception (for whatever
reason: of a typo in a module name, a file that can't be opened, etc.), the
Python interpreter prints a nice traceback and exits.  While the Python
interpreter will still do this when your CGI script raises an exception, most
likely the traceback will end up in one of the HTTP server's log files, or be
discarded altogether.

Fortunately, once you have managed to get your script to execute @emph{some} code,
you can easily send tracebacks to the Web browser using the @ref{17,,cgitb} module.
If you haven't done so already, just add the lines:

@example
import cgitb
cgitb.enable()
@end example

to the top of your script.  Then try running it again; when a problem occurs,
you should see a detailed report that will likely make apparent the cause of the
crash.

If you suspect that there may be a problem in importing the @ref{17,,cgitb} module,
you can use an even more robust approach (which only uses built-in modules):

@example
import sys
sys.stderr = sys.stdout
print("Content-Type: text/plain")
print()
...your code here...
@end example

This relies on the Python interpreter to print the traceback.  The content type
of the output is set to plain text, which disables all HTML processing.  If your
script works, the raw HTML will be displayed by your client.  If it raises an
exception, most likely after the first two lines have been printed, a traceback
will be displayed. Because no HTML interpretation is going on, the traceback
will be readable.

@node Common problems and solutions,,Debugging CGI scripts,cgi --- Common Gateway Interface support
@anchor{library/cgi common-problems-and-solutions}@anchor{2b90}
@subsubsection Common problems and solutions



@itemize *

@item 
Most HTTP servers buffer the output from CGI scripts until the script is
completed.  This means that it is not possible to display a progress report on
the client's display while the script is running.

@item 
Check the installation instructions above.

@item 
Check the HTTP server's log files.  (@code{tail -f logfile} in a separate window
may be useful!)

@item 
Always check a script for syntax errors first, by doing something like
@code{python script.py}.

@item 
If your script does not have any syntax errors, try adding @code{import cgitb;
cgitb.enable()} to the top of the script.

@item 
When invoking external programs, make sure they can be found. Usually, this
means using absolute path names --- 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} is usually not set to a very
useful value in a CGI script.

@item 
When reading or writing external files, make sure they can be read or written
by the userid under which your CGI script will be running: this is typically the
userid under which the web server is running, or some explicitly specified
userid for a web server's @code{suexec} feature.

@item 
Don't try to give a CGI script a set-uid mode.  This doesn't work on most
systems, and is a security liability as well.
@end itemize

@subsubheading 备注


@node cgitb --- 用于 CGI 脚本的回溯管理器,wsgiref --- WSGI Utilities and Reference Implementation,cgi --- Common Gateway Interface support,互联网协议和支持
@anchor{library/cgitb doc}@anchor{2b91}@anchor{library/cgitb cgitb-traceback-manager-for-cgi-scripts}@anchor{2b92}@anchor{library/cgitb module-cgitb}@anchor{17}
@subsection @code{cgitb} --- 用于 CGI 脚本的回溯管理器


@geindex cgitb (模块)

@strong{源代码:} Lib/cgitb.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/cgitb.py}

@geindex CGI; exceptions
@geindex CGI; tracebacks
@geindex exceptions; in CGI scripts
@geindex tracebacks; in CGI scripts


__________________________________________________________________


@ref{17,,cgitb} 模块提供了用于 Python 脚本的特殊异常处理程序。 （这个名称有一点误导性。 它最初是设计用来显示 HTML 格式的 CGI 脚本详细回溯信息。 但后来被一般化为也可显示纯文本格式的回溯信息。） 激活这个模块之后，如果发生了未被捕获的异常，将会显示详细的已格式化的报告。 报告显示内容包括每个层级的源代码摘录，还有当前正在运行的函数的参数和局部变量值，以帮助你调试问题。 你也可以选择将此信息保存至文件而不是将其发送至浏览器。

要启用此特性，只需简单地将此代码添加到你的 CGI 脚本的最顶端:

@example
import cgitb
cgitb.enable()
@end example

@ref{2b93,,enable()} 函数的选项可以控制是将报告显示在浏览器中，还是将报告记录到文件供以后进行分析。

@geindex enable() (在 cgitb 模块中)
@anchor{library/cgitb cgitb enable}@anchor{2b93}
@deffn {函数} cgitb.enable (display=1, logdir=None, context=5, format="html")

@geindex excepthook() (in module sys)

此函数可通过设置 @ref{e5c,,sys.excepthook} 的值以使 @ref{17,,cgitb} 模块接管解释器默认的异常处理机制。

可选参数 @emph{display} 默认为 @code{1} 并可被设为 @code{0} 来停止将回溯发送至浏览器。 如果给出了参数 @emph{logdir}，则回溯会被写入文件。 @emph{logdir} 的值应当是一个用于存放所写入文件的目录。 可选参数 @emph{context} 是要在回溯中的当前源代码行前后显示的上下文行数；默认为 @code{5}。 如果可选参数 @emph{format} 为 @code{"html"}，输出将为 HTML 格式。 任何其它值都会强制启用纯文本输出。 默认取值为 @code{"html"}。
@end deffn

@geindex text() (在 cgitb 模块中)
@anchor{library/cgitb cgitb text}@anchor{2b94}
@deffn {函数} cgitb.text (info, context=5)

此函数用于处理 @emph{info} (一个包含 @ref{c58,,sys.exc_info()} 返回结果的 3 元组) 所描述的异常，将其回溯格式化为文本并将结果作为字符串返回。 可选参数 @emph{context} 是要在回溯中的当前源码行前后显示的上下文行数；默认为 @code{5}。
@end deffn

@geindex html() (在 cgitb 模块中)
@anchor{library/cgitb cgitb html}@anchor{2b95}
@deffn {函数} cgitb.html (info, context=5)

此函数用于处理 @emph{info} (一个包含 @ref{c58,,sys.exc_info()} 返回结果的 3 元组) 所描述的异常，将其回溯格式化为 HTML 并将结果作为字符串返回。 可选参数 @emph{context} 是要在回溯中的当前源码行前后显示的上下文行数；默认为 @code{5}。
@end deffn

@geindex handler() (在 cgitb 模块中)
@anchor{library/cgitb cgitb handler}@anchor{2b96}
@deffn {函数} cgitb.handler (info=None)

此函数使用默认设置处理异常（即在浏览器中显示报告，但不记录到文件）。 当你捕获了一个异常并希望使用 @ref{17,,cgitb} 来报告它时可以使用此函数。 可选的 @emph{info} 参数应为一个包含异常类型，异常值和回溯对象的 3 元组，与 @ref{c58,,sys.exc_info()} 所返回的元组完全一致。 如果未提供 @emph{info} 参数，则会从 @ref{c58,,sys.exc_info()} 获取当前异常。
@end deffn

@node wsgiref --- WSGI Utilities and Reference Implementation,urllib --- URL 处理模块,cgitb --- 用于 CGI 脚本的回溯管理器,互联网协议和支持
@anchor{library/wsgiref doc}@anchor{2b97}@anchor{library/wsgiref module-wsgiref}@anchor{12c}@anchor{library/wsgiref wsgiref-wsgi-utilities-and-reference-implementation}@anchor{2b98}
@subsection @code{wsgiref} --- WSGI Utilities and Reference Implementation


@geindex wsgiref (模块)


__________________________________________________________________


The Web Server Gateway Interface (WSGI) is a standard interface between web
server software and web applications written in Python. Having a standard
interface makes it easy to use an application that supports WSGI with a number
of different web servers.

Only authors of web servers and programming frameworks need to know every detail
and corner case of the WSGI design.  You don't need to understand every detail
of WSGI just to install a WSGI application or to write a web application using
an existing framework.

@ref{12c,,wsgiref} is a reference implementation of the WSGI specification that can
be used to add WSGI support to a web server or framework.  It provides utilities
for manipulating WSGI environment variables and response headers, base classes
for implementing WSGI servers, a demo HTTP server that serves WSGI applications,
and a validation tool that checks WSGI servers and applications for conformance
to the WSGI specification (
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}).

See wsgi.readthedocs.io@footnote{https://wsgi.readthedocs.io/} for more information about WSGI, and links
to tutorials and other resources.

@c XXX If you're just trying to write a web application...

@menu
* wsgiref.util: wsgiref util -- WSGI environment utilities. WSGI environment utilities
* wsgiref.headers: wsgiref headers -- WSGI response header tools. WSGI response header tools
* wsgiref.simple_server: wsgiref simple_server -- a simple WSGI HTTP server. a simple WSGI HTTP server
* wsgiref.validate: wsgiref validate --- WSGI conformance checker. WSGI conformance checker
* wsgiref.handlers: wsgiref handlers -- server/gateway base classes. server/gateway base classes
* 例子: 例子<20>. 

@end menu

@node wsgiref util -- WSGI environment utilities,wsgiref headers -- WSGI response header tools,,wsgiref --- WSGI Utilities and Reference Implementation
@anchor{library/wsgiref module-wsgiref util}@anchor{130}@anchor{library/wsgiref wsgiref-util-wsgi-environment-utilities}@anchor{2b99}
@subsubsection @code{wsgiref.util} -- WSGI environment utilities


@geindex wsgiref.util (模块)

This module provides a variety of utility functions for working with WSGI
environments.  A WSGI environment is a dictionary containing HTTP request
variables as described in 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}.  All of the functions taking an @emph{environ}
parameter expect a WSGI-compliant dictionary to be supplied; please see
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333} for a detailed specification.

@geindex guess_scheme() (在 wsgiref.util 模块中)
@anchor{library/wsgiref wsgiref util guess_scheme}@anchor{2b9a}
@deffn {函数} wsgiref.util.guess_scheme (environ)

Return a guess for whether @code{wsgi.url_scheme} should be "http" or "https", by
checking for a @code{HTTPS} environment variable in the @emph{environ} dictionary.  The
return value is a string.

This function is useful when creating a gateway that wraps CGI or a CGI-like
protocol such as FastCGI.  Typically, servers providing such protocols will
include a @code{HTTPS} variable with a value of "1", "yes", or "on" when a request
is received via SSL.  So, this function returns "https" if such a value is
found, and "http" otherwise.
@end deffn

@geindex request_uri() (在 wsgiref.util 模块中)
@anchor{library/wsgiref wsgiref util request_uri}@anchor{2b9b}
@deffn {函数} wsgiref.util.request_uri (environ, include_query=True)

Return the full request URI, optionally including the query string, using the
algorithm found in the "URL Reconstruction" section of 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}.  If
@emph{include_query} is false, the query string is not included in the resulting URI.
@end deffn

@geindex application_uri() (在 wsgiref.util 模块中)
@anchor{library/wsgiref wsgiref util application_uri}@anchor{2b9c}
@deffn {函数} wsgiref.util.application_uri (environ)

Similar to @ref{2b9b,,request_uri()}, except that the @code{PATH_INFO} and
@code{QUERY_STRING} variables are ignored.  The result is the base URI of the
application object addressed by the request.
@end deffn

@geindex shift_path_info() (在 wsgiref.util 模块中)
@anchor{library/wsgiref wsgiref util shift_path_info}@anchor{2b9d}
@deffn {函数} wsgiref.util.shift_path_info (environ)

Shift a single name from @code{PATH_INFO} to @code{SCRIPT_NAME} and return the name.
The @emph{environ} dictionary is @emph{modified} in-place; use a copy if you need to keep
the original @code{PATH_INFO} or @code{SCRIPT_NAME} intact.

If there are no remaining path segments in @code{PATH_INFO}, @code{None} is returned.

Typically, this routine is used to process each portion of a request URI path,
for example to treat the path as a series of dictionary keys. This routine
modifies the passed-in environment to make it suitable for invoking another WSGI
application that is located at the target URI. For example, if there is a WSGI
application at @code{/foo}, and the request URI path is @code{/foo/bar/baz}, and the
WSGI application at @code{/foo} calls @ref{2b9d,,shift_path_info()}, it will receive the
string "bar", and the environment will be updated to be suitable for passing to
a WSGI application at @code{/foo/bar}.  That is, @code{SCRIPT_NAME} will change from
@code{/foo} to @code{/foo/bar}, and @code{PATH_INFO} will change from @code{/bar/baz} to
@code{/baz}.

When @code{PATH_INFO} is just a "/", this routine returns an empty string and
appends a trailing slash to @code{SCRIPT_NAME}, even though empty path segments are
normally ignored, and @code{SCRIPT_NAME} doesn't normally end in a slash.  This is
intentional behavior, to ensure that an application can tell the difference
between URIs ending in @code{/x} from ones ending in @code{/x/} when using this
routine to do object traversal.
@end deffn

@geindex setup_testing_defaults() (在 wsgiref.util 模块中)
@anchor{library/wsgiref wsgiref util setup_testing_defaults}@anchor{2b9e}
@deffn {函数} wsgiref.util.setup_testing_defaults (environ)

Update @emph{environ} with trivial defaults for testing purposes.

This routine adds various parameters required for WSGI, including @code{HTTP_HOST},
@code{SERVER_NAME}, @code{SERVER_PORT}, @code{REQUEST_METHOD}, @code{SCRIPT_NAME},
@code{PATH_INFO}, and all of the 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}-defined @code{wsgi.*} variables.  It
only supplies default values, and does not replace any existing settings for
these variables.

This routine is intended to make it easier for unit tests of WSGI servers and
applications to set up dummy environments.  It should NOT be used by actual WSGI
servers or applications, since the data is fake!

用法示例：

@example
from wsgiref.util import setup_testing_defaults
from wsgiref.simple_server import make_server

# A relatively simple WSGI application. It's going to print out the
# environment dictionary after being updated by setup_testing_defaults
def simple_app(environ, start_response):
    setup_testing_defaults(environ)

    status = '200 OK'
    headers = [('Content-type', 'text/plain; charset=utf-8')]

    start_response(status, headers)

    ret = [("%s: %s\n" % (key, value)).encode("utf-8")
           for key, value in environ.items()]
    return ret

with make_server('@w{'}, 8000, simple_app) as httpd:
    print("Serving on port 8000...")
    httpd.serve_forever()
@end example
@end deffn

In addition to the environment functions above, the @ref{130,,wsgiref.util} module
also provides these miscellaneous utilities:

@geindex is_hop_by_hop() (在 wsgiref.util 模块中)
@anchor{library/wsgiref wsgiref util is_hop_by_hop}@anchor{2b9f}
@deffn {函数} wsgiref.util.is_hop_by_hop (header_name)

Return @code{True} if 'header_name' is an HTTP/1.1 "Hop-by-Hop" header, as defined by
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html}.
@end deffn

@geindex FileWrapper (wsgiref.util 中的类)
@anchor{library/wsgiref wsgiref util FileWrapper}@anchor{27d}
@deffn {类} wsgiref.util.FileWrapper (filelike, blksize=8192)

A wrapper to convert a file-like object to an @ref{fce,,iterator}.  The resulting objects
support both @ref{27f,,__getitem__()} and @ref{509,,__iter__()} iteration styles, for
compatibility with Python 2.1 and Jython. As the object is iterated over, the
optional @emph{blksize} parameter will be repeatedly passed to the @emph{filelike}
object's @code{read()} method to obtain bytestrings to yield.  When @code{read()}
returns an empty bytestring, iteration is ended and is not resumable.

If @emph{filelike} has a @code{close()} method, the returned object will also have a
@code{close()} method, and it will invoke the @emph{filelike} object's @code{close()}
method when called.

用法示例：

@example
from io import StringIO
from wsgiref.util import FileWrapper

# We're using a StringIO-buffer for as the file-like object
filelike = StringIO("This is an example file-like object"*10)
wrapper = FileWrapper(filelike, blksize=5)

for chunk in wrapper:
    print(chunk)
@end example


3.8 版后已移除: Support for @ref{27f,,sequence protocol} is deprecated.

@end deffn

@node wsgiref headers -- WSGI response header tools,wsgiref simple_server -- a simple WSGI HTTP server,wsgiref util -- WSGI environment utilities,wsgiref --- WSGI Utilities and Reference Implementation
@anchor{library/wsgiref module-wsgiref headers}@anchor{12e}@anchor{library/wsgiref wsgiref-headers-wsgi-response-header-tools}@anchor{2ba0}
@subsubsection @code{wsgiref.headers} -- WSGI response header tools


@geindex wsgiref.headers (模块)

This module provides a single class, @ref{789,,Headers}, for convenient
manipulation of WSGI response headers using a mapping-like interface.

@geindex Headers (wsgiref.headers 中的类)
@anchor{library/wsgiref wsgiref headers Headers}@anchor{789}
@deffn {类} wsgiref.headers.Headers ([headers])

Create a mapping-like object wrapping @emph{headers}, which must be a list of header
name/value tuples as described in 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}. The default value of @emph{headers} is
an empty list.

@ref{789,,Headers} objects support typical mapping operations including
@ref{27f,,__getitem__()}, @code{get()}, @ref{c5b,,__setitem__()}, @code{setdefault()},
@ref{c5c,,__delitem__()} and @ref{d21,,__contains__()}.  For each of
these methods, the key is the header name (treated case-insensitively), and the
value is the first value associated with that header name.  Setting a header
deletes any existing values for that header, then adds a new value at the end of
the wrapped header list.  Headers' existing order is generally maintained, with
new headers added to the end of the wrapped list.

Unlike a dictionary, @ref{789,,Headers} objects do not raise an error when you try
to get or delete a key that isn't in the wrapped header list. Getting a
nonexistent header just returns @code{None}, and deleting a nonexistent header does
nothing.

@ref{789,,Headers} objects also support @code{keys()}, @code{values()}, and
@code{items()} methods.  The lists returned by @code{keys()} and @code{items()} can
include the same key more than once if there is a multi-valued header.  The
@code{len()} of a @ref{789,,Headers} object is the same as the length of its
@code{items()}, which is the same as the length of the wrapped header list.  In
fact, the @code{items()} method just returns a copy of the wrapped header list.

Calling @code{bytes()} on a @ref{789,,Headers} object returns a formatted bytestring
suitable for transmission as HTTP response headers.  Each header is placed on a
line with its value, separated by a colon and a space. Each line is terminated
by a carriage return and line feed, and the bytestring is terminated with a
blank line.

In addition to their mapping interface and formatting features, @ref{789,,Headers}
objects also have the following methods for querying and adding multi-valued
headers, and for adding headers with MIME parameters:

@geindex get_all() (wsgiref.headers.Headers 方法)
@anchor{library/wsgiref wsgiref headers Headers get_all}@anchor{2ba1}
@deffn {方法} get_all (name)

Return a list of all the values for the named header.

The returned list will be sorted in the order they appeared in the original
header list or were added to this instance, and may contain duplicates.  Any
fields deleted and re-inserted are always appended to the header list.  If no
fields exist with the given name, returns an empty list.
@end deffn

@geindex add_header() (wsgiref.headers.Headers 方法)
@anchor{library/wsgiref wsgiref headers Headers add_header}@anchor{2ba2}
@deffn {方法} add_header (name, value, **_params)

Add a (possibly multi-valued) header, with optional MIME parameters specified
via keyword arguments.

@emph{name} is the header field to add.  Keyword arguments can be used to set MIME
parameters for the header field.  Each parameter must be a string or @code{None}.
Underscores in parameter names are converted to dashes, since dashes are illegal
in Python identifiers, but many MIME parameter names include dashes.  If the
parameter value is a string, it is added to the header value parameters in the
form @code{name="value"}. If it is @code{None}, only the parameter name is added.
(This is used for MIME parameters without a value.)  Example usage:

@example
h.add_header('content-disposition', 'attachment', filename='bud.gif')
@end example

The above will add a header that looks like this:

@example
Content-Disposition: attachment; filename="bud.gif"
@end example
@end deffn


在 3.5 版更改: @emph{headers} parameter is optional.

@end deffn

@node wsgiref simple_server -- a simple WSGI HTTP server,wsgiref validate --- WSGI conformance checker,wsgiref headers -- WSGI response header tools,wsgiref --- WSGI Utilities and Reference Implementation
@anchor{library/wsgiref module-wsgiref simple_server}@anchor{12f}@anchor{library/wsgiref wsgiref-simple-server-a-simple-wsgi-http-server}@anchor{2ba3}
@subsubsection @code{wsgiref.simple_server} -- a simple WSGI HTTP server


@geindex wsgiref.simple_server (模块)

This module implements a simple HTTP server (based on @ref{97,,http.server})
that serves WSGI applications.  Each server instance serves a single WSGI
application on a given host and port.  If you want to serve multiple
applications on a single host and port, you should create a WSGI application
that parses @code{PATH_INFO} to select which application to invoke for each
request.  (E.g., using the @code{shift_path_info()} function from
@ref{130,,wsgiref.util}.)

@geindex make_server() (在 wsgiref.simple_server 模块中)
@anchor{library/wsgiref wsgiref simple_server make_server}@anchor{2ba4}
@deffn {函数} wsgiref.simple_server.make_server (host, port, app, server_class=WSGIServer, handler_class=WSGIRequestHandler)

Create a new WSGI server listening on @emph{host} and @emph{port}, accepting connections
for @emph{app}.  The return value is an instance of the supplied @emph{server_class}, and
will process requests using the specified @emph{handler_class}.  @emph{app} must be a WSGI
application object, as defined by 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}.

用法示例：

@example
from wsgiref.simple_server import make_server, demo_app

with make_server('@w{'}, 8000, demo_app) as httpd:
    print("Serving HTTP on port 8000...")

    # Respond to requests until process is killed
    httpd.serve_forever()

    # Alternative: serve one request, then exit
    httpd.handle_request()
@end example
@end deffn

@geindex demo_app() (在 wsgiref.simple_server 模块中)
@anchor{library/wsgiref wsgiref simple_server demo_app}@anchor{2ba5}
@deffn {函数} wsgiref.simple_server.demo_app (environ, start_response)

This function is a small but complete WSGI application that returns a text page
containing the message "Hello world!" and a list of the key/value pairs provided
in the @emph{environ} parameter.  It's useful for verifying that a WSGI server (such
as @ref{12f,,wsgiref.simple_server}) is able to run a simple WSGI application
correctly.
@end deffn

@geindex WSGIServer (wsgiref.simple_server 中的类)
@anchor{library/wsgiref wsgiref simple_server WSGIServer}@anchor{2ba6}
@deffn {类} wsgiref.simple_server.WSGIServer (server_address, RequestHandlerClass)

Create a @ref{2ba6,,WSGIServer} instance.  @emph{server_address} should be a
@code{(host,port)} tuple, and @emph{RequestHandlerClass} should be the subclass of
@ref{a09,,http.server.BaseHTTPRequestHandler} that will be used to process
requests.

You do not normally need to call this constructor, as the @ref{2ba4,,make_server()}
function can handle all the details for you.

@ref{2ba6,,WSGIServer} is a subclass of @ref{2ba7,,http.server.HTTPServer}, so all
of its methods (such as @code{serve_forever()} and @code{handle_request()}) are
available. @ref{2ba6,,WSGIServer} also provides these WSGI-specific methods:

@geindex set_app() (wsgiref.simple_server.WSGIServer 方法)
@anchor{library/wsgiref wsgiref simple_server WSGIServer set_app}@anchor{2ba8}
@deffn {方法} set_app (application)

Sets the callable @emph{application} as the WSGI application that will receive
requests.
@end deffn

@geindex get_app() (wsgiref.simple_server.WSGIServer 方法)
@anchor{library/wsgiref wsgiref simple_server WSGIServer get_app}@anchor{2ba9}
@deffn {方法} get_app ()

Returns the currently-set application callable.
@end deffn

Normally, however, you do not need to use these additional methods, as
@ref{2ba8,,set_app()} is normally called by @ref{2ba4,,make_server()}, and the
@ref{2ba9,,get_app()} exists mainly for the benefit of request handler instances.
@end deffn

@geindex WSGIRequestHandler (wsgiref.simple_server 中的类)
@anchor{library/wsgiref wsgiref simple_server WSGIRequestHandler}@anchor{2baa}
@deffn {类} wsgiref.simple_server.WSGIRequestHandler (request, client_address, server)

Create an HTTP handler for the given @emph{request} (i.e. a socket), @emph{client_address}
(a @code{(host,port)} tuple), and @emph{server} (@ref{2ba6,,WSGIServer} instance).

You do not need to create instances of this class directly; they are
automatically created as needed by @ref{2ba6,,WSGIServer} objects.  You can,
however, subclass this class and supply it as a @emph{handler_class} to the
@ref{2ba4,,make_server()} function.  Some possibly relevant methods for overriding in
subclasses:

@geindex get_environ() (wsgiref.simple_server.WSGIRequestHandler 方法)
@anchor{library/wsgiref wsgiref simple_server WSGIRequestHandler get_environ}@anchor{2bab}
@deffn {方法} get_environ ()

Returns a dictionary containing the WSGI environment for a request.  The default
implementation copies the contents of the @ref{2ba6,,WSGIServer} object's
@code{base_environ} dictionary attribute and then adds various headers derived
from the HTTP request.  Each call to this method should return a new dictionary
containing all of the relevant CGI environment variables as specified in
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}.
@end deffn

@geindex get_stderr() (wsgiref.simple_server.WSGIRequestHandler 方法)
@anchor{library/wsgiref wsgiref simple_server WSGIRequestHandler get_stderr}@anchor{2bac}
@deffn {方法} get_stderr ()

Return the object that should be used as the @code{wsgi.errors} stream. The default
implementation just returns @code{sys.stderr}.
@end deffn

@geindex handle() (wsgiref.simple_server.WSGIRequestHandler 方法)
@anchor{library/wsgiref wsgiref simple_server WSGIRequestHandler handle}@anchor{2bad}
@deffn {方法} handle ()

Process the HTTP request.  The default implementation creates a handler instance
using a @ref{12d,,wsgiref.handlers} class to implement the actual WSGI application
interface.
@end deffn
@end deffn

@node wsgiref validate --- WSGI conformance checker,wsgiref handlers -- server/gateway base classes,wsgiref simple_server -- a simple WSGI HTTP server,wsgiref --- WSGI Utilities and Reference Implementation
@anchor{library/wsgiref module-wsgiref validate}@anchor{131}@anchor{library/wsgiref wsgiref-validate-wsgi-conformance-checker}@anchor{2bae}
@subsubsection @code{wsgiref.validate} --- WSGI conformance checker


@geindex wsgiref.validate (模块)

When creating new WSGI application objects, frameworks, servers, or middleware,
it can be useful to validate the new code's conformance using
@ref{131,,wsgiref.validate}.  This module provides a function that creates WSGI
application objects that validate communications between a WSGI server or
gateway and a WSGI application object, to check both sides for protocol
conformance.

Note that this utility does not guarantee complete 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333} compliance; an
absence of errors from this module does not necessarily mean that errors do not
exist.  However, if this module does produce an error, then it is virtually
certain that either the server or application is not 100% compliant.

This module is based on the @code{paste.lint} module from Ian Bicking's "Python
Paste" library.

@geindex validator() (在 wsgiref.validate 模块中)
@anchor{library/wsgiref wsgiref validate validator}@anchor{2baf}
@deffn {函数} wsgiref.validate.validator (application)

Wrap @emph{application} and return a new WSGI application object.  The returned
application will forward all requests to the original @emph{application}, and will
check that both the @emph{application} and the server invoking it are conforming to
the WSGI specification and to 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html}.

Any detected nonconformance results in an @ref{fc1,,AssertionError} being raised;
note, however, that how these errors are handled is server-dependent.  For
example, @ref{12f,,wsgiref.simple_server} and other servers based on
@ref{12d,,wsgiref.handlers} (that don't override the error handling methods to do
something else) will simply output a message that an error has occurred, and
dump the traceback to @code{sys.stderr} or some other error stream.

This wrapper may also generate output using the @ref{126,,warnings} module to
indicate behaviors that are questionable but which may not actually be
prohibited by 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}.  Unless they are suppressed using Python command-line
options or the @ref{126,,warnings} API, any such warnings will be written to
@code{sys.stderr} (@emph{not} @code{wsgi.errors}, unless they happen to be the same
object).

用法示例：

@example
from wsgiref.validate import validator
from wsgiref.simple_server import make_server

# Our callable object which is intentionally not compliant to the
# standard, so the validator is going to break
def simple_app(environ, start_response):
    status = '200 OK'  # HTTP Status
    headers = [('Content-type', 'text/plain')]  # HTTP Headers
    start_response(status, headers)

    # This is going to break because we need to return a list, and
    # the validator is going to inform us
    return b"Hello World"

# This is the application wrapped in a validator
validator_app = validator(simple_app)

with make_server('@w{'}, 8000, validator_app) as httpd:
    print("Listening on port 8000....")
    httpd.serve_forever()
@end example
@end deffn

@node wsgiref handlers -- server/gateway base classes,例子<20>,wsgiref validate --- WSGI conformance checker,wsgiref --- WSGI Utilities and Reference Implementation
@anchor{library/wsgiref module-wsgiref handlers}@anchor{12d}@anchor{library/wsgiref wsgiref-handlers-server-gateway-base-classes}@anchor{2bb0}
@subsubsection @code{wsgiref.handlers} -- server/gateway base classes


@geindex wsgiref.handlers (模块)

This module provides base handler classes for implementing WSGI servers and
gateways.  These base classes handle most of the work of communicating with a
WSGI application, as long as they are given a CGI-like environment, along with
input, output, and error streams.

@geindex CGIHandler (wsgiref.handlers 中的类)
@anchor{library/wsgiref wsgiref handlers CGIHandler}@anchor{2bb1}
@deffn {类} wsgiref.handlers.CGIHandler

CGI-based invocation via @code{sys.stdin}, @code{sys.stdout}, @code{sys.stderr} and
@code{os.environ}.  This is useful when you have a WSGI application and want to run
it as a CGI script.  Simply invoke @code{CGIHandler().run(app)}, where @code{app} is
the WSGI application object you wish to invoke.

This class is a subclass of @ref{2bb2,,BaseCGIHandler} that sets @code{wsgi.run_once}
to true, @code{wsgi.multithread} to false, and @code{wsgi.multiprocess} to true, and
always uses @ref{fd,,sys} and @ref{c4,,os} to obtain the necessary CGI streams and
environment.
@end deffn

@geindex IISCGIHandler (wsgiref.handlers 中的类)
@anchor{library/wsgiref wsgiref handlers IISCGIHandler}@anchor{2bb3}
@deffn {类} wsgiref.handlers.IISCGIHandler

A specialized alternative to @ref{2bb1,,CGIHandler}, for use when deploying on
Microsoft's IIS web server, without having set the config allowPathInfo
option (IIS>=7) or metabase allowPathInfoForScriptMappings (IIS<7).

By default, IIS gives a @code{PATH_INFO} that duplicates the @code{SCRIPT_NAME} at
the front, causing problems for WSGI applications that wish to implement
routing. This handler strips any such duplicated path.

IIS can be configured to pass the correct @code{PATH_INFO}, but this causes
another bug where @code{PATH_TRANSLATED} is wrong. Luckily this variable is
rarely used and is not guaranteed by WSGI. On IIS<7, though, the
setting can only be made on a vhost level, affecting all other script
mappings, many of which break when exposed to the @code{PATH_TRANSLATED} bug.
For this reason IIS<7 is almost never deployed with the fix. (Even IIS7
rarely uses it because there is still no UI for it.)

There is no way for CGI code to tell whether the option was set, so a
separate handler class is provided.  It is used in the same way as
@ref{2bb1,,CGIHandler}, i.e., by calling @code{IISCGIHandler().run(app)}, where
@code{app} is the WSGI application object you wish to invoke.


3.2 新版功能.

@end deffn

@geindex BaseCGIHandler (wsgiref.handlers 中的类)
@anchor{library/wsgiref wsgiref handlers BaseCGIHandler}@anchor{2bb2}
@deffn {类} wsgiref.handlers.BaseCGIHandler (stdin, stdout, stderr, environ, multithread=True, multiprocess=False)

Similar to @ref{2bb1,,CGIHandler}, but instead of using the @ref{fd,,sys} and
@ref{c4,,os} modules, the CGI environment and I/O streams are specified explicitly.
The @emph{multithread} and @emph{multiprocess} values are used to set the
@code{wsgi.multithread} and @code{wsgi.multiprocess} flags for any applications run by
the handler instance.

This class is a subclass of @ref{2bb4,,SimpleHandler} intended for use with
software other than HTTP "origin servers".  If you are writing a gateway
protocol implementation (such as CGI, FastCGI, SCGI, etc.) that uses a
@code{Status:} header to send an HTTP status, you probably want to subclass this
instead of @ref{2bb4,,SimpleHandler}.
@end deffn

@geindex SimpleHandler (wsgiref.handlers 中的类)
@anchor{library/wsgiref wsgiref handlers SimpleHandler}@anchor{2bb4}
@deffn {类} wsgiref.handlers.SimpleHandler (stdin, stdout, stderr, environ, multithread=True, multiprocess=False)

Similar to @ref{2bb2,,BaseCGIHandler}, but designed for use with HTTP origin
servers.  If you are writing an HTTP server implementation, you will probably
want to subclass this instead of @ref{2bb2,,BaseCGIHandler}.

This class is a subclass of @ref{f5c,,BaseHandler}.  It overrides the
@ref{d57,,__init__()}, @code{get_stdin()}, @code{get_stderr()}, @code{add_cgi_vars()},
@code{_write()}, and @code{_flush()} methods to support explicitly setting the
environment and streams via the constructor.  The supplied environment and
streams are stored in the @code{stdin}, @code{stdout}, @code{stderr}, and
@code{environ} attributes.

The @ref{584,,write()} method of @emph{stdout} should write
each chunk in full, like @ref{583,,io.BufferedIOBase}.
@end deffn

@geindex BaseHandler (wsgiref.handlers 中的类)
@anchor{library/wsgiref wsgiref handlers BaseHandler}@anchor{f5c}
@deffn {类} wsgiref.handlers.BaseHandler

This is an abstract base class for running WSGI applications.  Each instance
will handle a single HTTP request, although in principle you could create a
subclass that was reusable for multiple requests.

@ref{f5c,,BaseHandler} instances have only one method intended for external use:

@geindex run() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler run}@anchor{2bb5}
@deffn {方法} run (app)

Run the specified WSGI application, @emph{app}.
@end deffn

All of the other @ref{f5c,,BaseHandler} methods are invoked by this method in the
process of running the application, and thus exist primarily to allow
customizing the process.

The following methods MUST be overridden in a subclass:

@geindex _write() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler _write}@anchor{2bb6}
@deffn {方法} _write (data)

Buffer the bytes @emph{data} for transmission to the client.  It's okay if this
method actually transmits the data; @ref{f5c,,BaseHandler} just separates write
and flush operations for greater efficiency when the underlying system actually
has such a distinction.
@end deffn

@geindex _flush() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler _flush}@anchor{2bb7}
@deffn {方法} _flush ()

Force buffered data to be transmitted to the client.  It's okay if this method
is a no-op (i.e., if @ref{2bb6,,_write()} actually sends the data).
@end deffn

@geindex get_stdin() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler get_stdin}@anchor{2bb8}
@deffn {方法} get_stdin ()

Return an input stream object suitable for use as the @code{wsgi.input} of the
request currently being processed.
@end deffn

@geindex get_stderr() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler get_stderr}@anchor{2bb9}
@deffn {方法} get_stderr ()

Return an output stream object suitable for use as the @code{wsgi.errors} of the
request currently being processed.
@end deffn

@geindex add_cgi_vars() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler add_cgi_vars}@anchor{2bba}
@deffn {方法} add_cgi_vars ()

Insert CGI variables for the current request into the @code{environ} attribute.
@end deffn

Here are some other methods and attributes you may wish to override. This list
is only a summary, however, and does not include every method that can be
overridden.  You should consult the docstrings and source code for additional
information before attempting to create a customized @ref{f5c,,BaseHandler}
subclass.

Attributes and methods for customizing the WSGI environment:

@geindex wsgi_multithread (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler wsgi_multithread}@anchor{2bbb}
@deffn {属性} wsgi_multithread

The value to be used for the @code{wsgi.multithread} environment variable.  It
defaults to true in @ref{f5c,,BaseHandler}, but may have a different default (or
be set by the constructor) in the other subclasses.
@end deffn

@geindex wsgi_multiprocess (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler wsgi_multiprocess}@anchor{2bbc}
@deffn {属性} wsgi_multiprocess

The value to be used for the @code{wsgi.multiprocess} environment variable.  It
defaults to true in @ref{f5c,,BaseHandler}, but may have a different default (or
be set by the constructor) in the other subclasses.
@end deffn

@geindex wsgi_run_once (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler wsgi_run_once}@anchor{2bbd}
@deffn {属性} wsgi_run_once

The value to be used for the @code{wsgi.run_once} environment variable.  It
defaults to false in @ref{f5c,,BaseHandler}, but @ref{2bb1,,CGIHandler} sets it to
true by default.
@end deffn

@geindex os_environ (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler os_environ}@anchor{2bbe}
@deffn {属性} os_environ

The default environment variables to be included in every request's WSGI
environment.  By default, this is a copy of @code{os.environ} at the time that
@ref{12d,,wsgiref.handlers} was imported, but subclasses can either create their own
at the class or instance level.  Note that the dictionary should be considered
read-only, since the default value is shared between multiple classes and
instances.
@end deffn

@geindex server_software (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler server_software}@anchor{2bbf}
@deffn {属性} server_software

If the @ref{2bc0,,origin_server} attribute is set, this attribute's value is used to
set the default @code{SERVER_SOFTWARE} WSGI environment variable, and also to set a
default @code{Server:} header in HTTP responses.  It is ignored for handlers (such
as @ref{2bb2,,BaseCGIHandler} and @ref{2bb1,,CGIHandler}) that are not HTTP origin
servers.


在 3.3 版更改: The term "Python" is replaced with implementation specific term like
"CPython", "Jython" etc.

@end deffn

@geindex get_scheme() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler get_scheme}@anchor{2bc1}
@deffn {方法} get_scheme ()

Return the URL scheme being used for the current request.  The default
implementation uses the @code{guess_scheme()} function from @ref{130,,wsgiref.util}
to guess whether the scheme should be "http" or "https", based on the current
request's @code{environ} variables.
@end deffn

@geindex setup_environ() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler setup_environ}@anchor{2bc2}
@deffn {方法} setup_environ ()

Set the @code{environ} attribute to a fully-populated WSGI environment.  The
default implementation uses all of the above methods and attributes, plus the
@ref{2bb8,,get_stdin()}, @ref{2bb9,,get_stderr()}, and @ref{2bba,,add_cgi_vars()} methods and the
@ref{2bc3,,wsgi_file_wrapper} attribute.  It also inserts a @code{SERVER_SOFTWARE} key
if not present, as long as the @ref{2bc0,,origin_server} attribute is a true value
and the @ref{2bbf,,server_software} attribute is set.
@end deffn

Methods and attributes for customizing exception handling:

@geindex log_exception() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler log_exception}@anchor{2bc4}
@deffn {方法} log_exception (exc_info)

Log the @emph{exc_info} tuple in the server log.  @emph{exc_info} is a @code{(type, value,
traceback)} tuple.  The default implementation simply writes the traceback to
the request's @code{wsgi.errors} stream and flushes it.  Subclasses can override
this method to change the format or retarget the output, mail the traceback to
an administrator, or whatever other action may be deemed suitable.
@end deffn

@geindex traceback_limit (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler traceback_limit}@anchor{2bc5}
@deffn {属性} traceback_limit

The maximum number of frames to include in tracebacks output by the default
@ref{2bc4,,log_exception()} method.  If @code{None}, all frames are included.
@end deffn

@geindex error_output() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler error_output}@anchor{2bc6}
@deffn {方法} error_output (environ, start_response)

This method is a WSGI application to generate an error page for the user.  It is
only invoked if an error occurs before headers are sent to the client.

This method can access the current error information using @code{sys.exc_info()},
and should pass that information to @emph{start_response} when calling it (as
described in the "Error Handling" section of 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}).

The default implementation just uses the @ref{2bc7,,error_status},
@ref{2bc8,,error_headers}, and @ref{2bc9,,error_body} attributes to generate an output
page.  Subclasses can override this to produce more dynamic error output.

Note, however, that it's not recommended from a security perspective to spit out
diagnostics to any old user; ideally, you should have to do something special to
enable diagnostic output, which is why the default implementation doesn't
include any.
@end deffn

@geindex error_status (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler error_status}@anchor{2bc7}
@deffn {属性} error_status

The HTTP status used for error responses.  This should be a status string as
defined in 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}; it defaults to a 500 code and message.
@end deffn

@geindex error_headers (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler error_headers}@anchor{2bc8}
@deffn {属性} error_headers

The HTTP headers used for error responses.  This should be a list of WSGI
response headers (@code{(name, value)} tuples), as described in 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}.  The
default list just sets the content type to @code{text/plain}.
@end deffn

@geindex error_body (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler error_body}@anchor{2bc9}
@deffn {属性} error_body

The error response body.  This should be an HTTP response body bytestring. It
defaults to the plain text, "A server error occurred.  Please contact the
administrator."
@end deffn

Methods and attributes for 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333}'s "Optional Platform-Specific File
Handling" feature:

@geindex wsgi_file_wrapper (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler wsgi_file_wrapper}@anchor{2bc3}
@deffn {属性} wsgi_file_wrapper

A @code{wsgi.file_wrapper} factory, or @code{None}.  The default value of this
attribute is the @ref{27d,,wsgiref.util.FileWrapper} class.
@end deffn

@geindex sendfile() (wsgiref.handlers.BaseHandler 方法)
@anchor{library/wsgiref wsgiref handlers BaseHandler sendfile}@anchor{2bca}
@deffn {方法} sendfile ()

Override to implement platform-specific file transmission.  This method is
called only if the application's return value is an instance of the class
specified by the @ref{2bc3,,wsgi_file_wrapper} attribute.  It should return a true
value if it was able to successfully transmit the file, so that the default
transmission code will not be executed. The default implementation of this
method just returns a false value.
@end deffn

Miscellaneous methods and attributes:

@geindex origin_server (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler origin_server}@anchor{2bc0}
@deffn {属性} origin_server

This attribute should be set to a true value if the handler's @ref{2bb6,,_write()} and
@ref{2bb7,,_flush()} are being used to communicate directly to the client, rather than
via a CGI-like gateway protocol that wants the HTTP status in a special
@code{Status:} header.

This attribute's default value is true in @ref{f5c,,BaseHandler}, but false in
@ref{2bb2,,BaseCGIHandler} and @ref{2bb1,,CGIHandler}.
@end deffn

@geindex http_version (wsgiref.handlers.BaseHandler 属性)
@anchor{library/wsgiref wsgiref handlers BaseHandler http_version}@anchor{2bcb}
@deffn {属性} http_version

If @ref{2bc0,,origin_server} is true, this string attribute is used to set the HTTP
version of the response set to the client.  It defaults to @code{"1.0"}.
@end deffn
@end deffn

@geindex read_environ() (在 wsgiref.handlers 模块中)
@anchor{library/wsgiref wsgiref handlers read_environ}@anchor{b2f}
@deffn {函数} wsgiref.handlers.read_environ ()

Transcode CGI variables from @code{os.environ} to 
@geindex Python 提高建议; PEP 3333
PEP 3333@footnote{https://www.python.org/dev/peps/pep-3333} "bytes in unicode"
strings, returning a new dictionary.  This function is used by
@ref{2bb1,,CGIHandler} and @ref{2bb3,,IISCGIHandler} in place of directly using
@code{os.environ}, which is not necessarily WSGI-compliant on all platforms
and web servers using Python 3 -- specifically, ones where the OS's
actual environment is Unicode (i.e. Windows), or ones where the environment
is bytes, but the system encoding used by Python to decode it is anything
other than ISO-8859-1 (e.g. Unix systems using UTF-8).

If you are implementing a CGI-based handler of your own, you probably want
to use this routine instead of just copying values out of @code{os.environ}
directly.


3.2 新版功能.

@end deffn

@node 例子<20>,,wsgiref handlers -- server/gateway base classes,wsgiref --- WSGI Utilities and Reference Implementation
@anchor{library/wsgiref examples}@anchor{2bcc}
@subsubsection 例子


This is a working "Hello World" WSGI application:

@example
from wsgiref.simple_server import make_server

# Every WSGI application must have an application object - a callable
# object that accepts two arguments. For that purpose, we're going to
# use a function (note that you're not limited to a function, you can
# use a class for example). The first argument passed to the function
# is a dictionary containing CGI-style environment variables and the
# second variable is the callable object.
def hello_world_app(environ, start_response):
    status = '200 OK'  # HTTP Status
    headers = [('Content-type', 'text/plain; charset=utf-8')]  # HTTP Headers
    start_response(status, headers)

    # The returned object is going to be printed
    return [b"Hello World"]

with make_server('@w{'}, 8000, hello_world_app) as httpd:
    print("Serving on port 8000...")

    # Serve until process is killed
    httpd.serve_forever()
@end example

Example of a WSGI application serving the current directory, accept optional
directory and port number (default: 8000) on the command line:

@example
#!/usr/bin/env python3
'@w{'}'
Small wsgiref based web server. Takes a path to serve from and an
optional port number (defaults to 8000), then tries to serve files.
Mime types are guessed from the file names, 404 errors are raised
if the file is not found. Used for the make serve target in Doc.
'@w{'}'
import sys
import os
import mimetypes
from wsgiref import simple_server, util

def app(environ, respond):

    fn = os.path.join(path, environ['PATH_INFO'][1:])
    if '.' not in fn.split(os.path.sep)[-1]:
        fn = os.path.join(fn, 'index.html')
    type = mimetypes.guess_type(fn)[0]

    if os.path.exists(fn):
        respond('200 OK', [('Content-Type', type)])
        return util.FileWrapper(open(fn, "rb"))
    else:
        respond('404 Not Found', [('Content-Type', 'text/plain')])
        return [b'not found']

if __name__ == '__main__':
    path = sys.argv[1] if len(sys.argv) > 1 else os.getcwd()
    port = int(sys.argv[2]) if len(sys.argv) > 2 else 8000
    httpd = simple_server.make_server('@w{'}, port, app)
    print("Serving @{@} on port @{@}, control-C to stop".format(path, port))
    try:
        httpd.serve_forever()
    except KeyboardInterrupt:
        print("Shutting down.")
        httpd.server_close()
@end example

@node urllib --- URL 处理模块,urllib request --- 用于打开 URL 的可扩展库,wsgiref --- WSGI Utilities and Reference Implementation,互联网协议和支持
@anchor{library/urllib doc}@anchor{2bcd}@anchor{library/urllib module-urllib}@anchor{11d}@anchor{library/urllib urllib-url-handling-modules}@anchor{2bce}
@subsection @code{urllib} --- URL 处理模块


@geindex urllib (模块)

@strong{源代码:} Lib/urllib/@footnote{https://github.com/python/cpython/tree/3.8/Lib/urllib/}


__________________________________________________________________


@code{urllib} 是一个收集了多个涉及 URL 的模块的包：


@itemize *

@item 
@ref{120,,urllib.request} 打开和读取 URL

@item 
@ref{11e,,urllib.error} 包含 @ref{120,,urllib.request} 抛出的异常

@item 
@ref{11f,,urllib.parse}  用于解析 URL

@item 
@ref{122,,urllib.robotparser} 用于解析 @code{robots.txt} 文件
@end itemize

@node urllib request --- 用于打开 URL 的可扩展库,urllib response --- urllib 使用的 Response 类,urllib --- URL 处理模块,互联网协议和支持
@anchor{library/urllib request doc}@anchor{2bcf}@anchor{library/urllib request module-urllib request}@anchor{120}@anchor{library/urllib request urllib-request-extensible-library-for-opening-urls}@anchor{2bd0}
@subsection @code{urllib.request} --- 用于打开 URL 的可扩展库


@geindex urllib.request (模块)

@strong{源码：} Lib/urllib/request.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/urllib/request.py}


__________________________________________________________________


@ref{120,,urllib.request} 模块定义了适用于在各种复杂情况下打开 URL（主要为 HTTP）的函数和类 --- 例如基本认证、摘要认证、重定向、cookies 及其它。


@subsubheading 参见


The Requests package@footnote{https://requests.readthedocs.io/en/master/}
is recommended for a higher-level HTTP client interface.


@ref{120,,urllib.request} 模块定义了以下函数：

@geindex urlopen() (在 urllib.request 模块中)
@anchor{library/urllib request urllib request urlopen}@anchor{786}
@deffn {函数} urllib.request.urlopen (url, data=None[, timeout], *, cafile=None, capath=None, cadefault=False, context=None)

打开统一资源定位地址 @emph{url}，可以是一个字符串或一个 @ref{8f0,,Request} 对象。

@emph{data} must be an object specifying additional data to be sent to the
server, or @code{None} if no such data is needed.  See @ref{8f0,,Request}
for details.

urllib.request 模块使用 HTTP/1.1 并且在其 HTTP 请求中包含 @code{Connection:close} 头。

The optional @emph{timeout} parameter specifies a timeout in seconds for
blocking operations like the connection attempt (if not specified,
the global default timeout setting will be used).  This actually
only works for HTTP, HTTPS and FTP connections.

If @emph{context} is specified, it must be a @ref{3dc,,ssl.SSLContext} instance
describing the various SSL options. See @ref{38b,,HTTPSConnection}
for more details.

The optional @emph{cafile} and @emph{capath} parameters specify a set of trusted
CA certificates for HTTPS requests.  @emph{cafile} should point to a single
file containing a bundle of CA certificates, whereas @emph{capath} should
point to a directory of hashed certificate files.  More information can
be found in @ref{7e5,,ssl.SSLContext.load_verify_locations()}.

The @emph{cadefault} parameter is ignored.

This function always returns an object which can work as a
@ref{563,,context manager} and has methods such as


@itemize *

@item 
@code{geturl()} --- return the URL of the resource retrieved,
commonly used to determine if a redirect was followed

@item 
@code{info()} --- return the meta-information of the page, such as headers,
in the form of an @ref{27bb,,email.message_from_string()} instance (see
Quick Reference to HTTP Headers@footnote{http://jkorpela.fi/http.html})

@item 
@code{getcode()} -- return the HTTP status code of the response.
@end itemize

For HTTP and HTTPS URLs, this function returns a
@ref{a0c,,http.client.HTTPResponse} object slightly modified. In addition
to the three new methods above, the msg attribute contains the
same information as the @ref{2bd1,,reason}
attribute --- the reason phrase returned by server --- instead of
the response headers as it is specified in the documentation for
@ref{a0c,,HTTPResponse}.

For FTP, file, and data URLs and requests explicitly handled by legacy
@ref{2bd2,,URLopener} and @ref{2bd3,,FancyURLopener} classes, this function
returns a @code{urllib.response.addinfourl} object.

协议错误时引发 @ref{2bd4,,URLError}。

Note that @code{None} may be returned if no handler handles the request (though
the default installed global @ref{2bd5,,OpenerDirector} uses
@ref{2bd6,,UnknownHandler} to ensure this never happens).

In addition, if proxy settings are detected (for example, when a @code{*_proxy}
environment variable like 
@geindex http_proxy
@geindex 环境变量; http_proxy
@code{http_proxy} is set),
@ref{f0a,,ProxyHandler} is default installed and makes sure the requests are
handled through the proxy.

The legacy @code{urllib.urlopen} function from Python 2.6 and earlier has been
discontinued; @ref{786,,urllib.request.urlopen()} corresponds to the old
@code{urllib2.urlopen}.  Proxy handling, which was done by passing a dictionary
parameter to @code{urllib.urlopen}, can be obtained by using
@ref{f0a,,ProxyHandler} objects.


The default opener raises an @ref{12d0,,auditing event}
@code{urllib.Request} with arguments @code{fullurl}, @code{data}, @code{headers},
@code{method} taken from the request object.



在 3.2 版更改: 增加了 @emph{cafile} 与 @emph{capath}。



在 3.2 版更改: 现在如果可行（指 @ref{2678,,ssl.HAS_SNI} 为真），支持 HTTPS 虚拟主机



3.2 新版功能: @emph{data} 可以是一个可迭代对象。



在 3.3 版更改: 增加了 @emph{cadefault}。



在 3.4.3 版更改: 增加了 @emph{context}。



3.6 版后已移除: @emph{cafile}, @emph{capath} and @emph{cadefault} are deprecated in favor of @emph{context}.
Please use @ref{a8c,,ssl.SSLContext.load_cert_chain()} instead, or let
@ref{8bb,,ssl.create_default_context()} select the system's trusted CA
certificates for you.

@end deffn

@geindex install_opener() (在 urllib.request 模块中)
@anchor{library/urllib request urllib request install_opener}@anchor{2bd7}
@deffn {函数} urllib.request.install_opener (opener)

Install an @ref{2bd5,,OpenerDirector} instance as the default global opener.
Installing an opener is only necessary if you want urlopen to use that
opener; otherwise, simply call @ref{8f4,,OpenerDirector.open()} instead of
@ref{786,,urlopen()}.  The code does not check for a real
@ref{2bd5,,OpenerDirector}, and any class with the appropriate interface will
work.
@end deffn

@geindex build_opener() (在 urllib.request 模块中)
@anchor{library/urllib request urllib request build_opener}@anchor{2bd8}
@deffn {函数} urllib.request.build_opener ([handler, ...])

Return an @ref{2bd5,,OpenerDirector} instance, which chains the handlers in the
order given. @emph{handler}s can be either instances of @ref{2bd9,,BaseHandler}, or
subclasses of @ref{2bd9,,BaseHandler} (in which case it must be possible to call
the constructor without any parameters).  Instances of the following classes
will be in front of the @emph{handler}s, unless the @emph{handler}s contain them,
instances of them or subclasses of them: @ref{f0a,,ProxyHandler} (if proxy
settings are detected), @ref{2bd6,,UnknownHandler}, @ref{2bda,,HTTPHandler},
@ref{2bdb,,HTTPDefaultErrorHandler}, @ref{2bdc,,HTTPRedirectHandler},
@ref{2bdd,,FTPHandler}, @ref{2bde,,FileHandler}, @ref{2bdf,,HTTPErrorProcessor}.

若 Python 安装有 SLL 支持（指可以导入 @ref{f3,,ssl} 模块），亦会加入 @ref{ba1,,HTTPSHandler}。

A @ref{2bd9,,BaseHandler} subclass may also change its @code{handler_order}
attribute to modify its position in the handlers list.
@end deffn

@geindex pathname2url() (在 urllib.request 模块中)
@anchor{library/urllib request urllib request pathname2url}@anchor{2be0}
@deffn {函数} urllib.request.pathname2url (path)

Convert the pathname @emph{path} from the local syntax for a path to the form used in
the path component of a URL.  This does not produce a complete URL.  The return
value will already be quoted using the @ref{405,,quote()} function.
@end deffn

@geindex url2pathname() (在 urllib.request 模块中)
@anchor{library/urllib request urllib request url2pathname}@anchor{2be1}
@deffn {函数} urllib.request.url2pathname (path)

Convert the path component @emph{path} from a percent-encoded URL to the local syntax for a
path.  This does not accept a complete URL.  This function uses
@ref{2be2,,unquote()} to decode @emph{path}.
@end deffn

@geindex getproxies() (在 urllib.request 模块中)
@anchor{library/urllib request urllib request getproxies}@anchor{2be3}
@deffn {函数} urllib.request.getproxies ()

This helper function returns a dictionary of scheme to proxy server URL
mappings. It scans the environment for variables named @code{<scheme>_proxy},
in a case insensitive approach, for all operating systems first, and when it
cannot find it, looks for proxy information from Mac OSX System
Configuration for Mac OS X and Windows Systems Registry for Windows.
If both lowercase and uppercase environment variables exist (and disagree),
lowercase is preferred.

@cartouche
@quotation 注解 
If the environment variable @code{REQUEST_METHOD} is set, which usually
indicates your script is running in a CGI environment, the environment
variable @code{HTTP_PROXY} (uppercase @code{_PROXY}) will be ignored. This is
because that variable can be injected by a client using the "Proxy:" HTTP
header. If you need to use an HTTP proxy in a CGI environment, either use
@code{ProxyHandler} explicitly, or make sure the variable name is in
lowercase (or at least the @code{_proxy} suffix).
@end quotation
@end cartouche
@end deffn

提供了以下类：

@geindex Request (urllib.request 中的类)
@anchor{library/urllib request urllib request Request}@anchor{8f0}
@deffn {类} urllib.request.Request (url, data=None, headers=@{@}, origin_req_host=None, unverifiable=False, method=None)

This class is an abstraction of a URL request.

@emph{url} 应是一个含有一个有效 URL 的字符串。

@emph{data} must be an object specifying additional data to send to the
server, or @code{None} if no such data is needed.  Currently HTTP
requests are the only ones that use @emph{data}.  The supported object
types include bytes, file-like objects, and iterables of bytes-like objects.
If no @code{Content-Length} nor @code{Transfer-Encoding} header field
has been provided, @ref{2bda,,HTTPHandler} will set these headers according
to the type of @emph{data}.  @code{Content-Length} will be used to send
bytes objects, while @code{Transfer-Encoding: chunked} as specified in
@geindex RFC; RFC 7230
RFC 7230@footnote{https://tools.ietf.org/html/rfc7230.html}, Section 3.3.1 will be used to send files and other iterables.

For an HTTP POST request method, @emph{data} should be a buffer in the
standard @code{application/x-www-form-urlencoded} format.  The
@ref{785,,urllib.parse.urlencode()} function takes a mapping or sequence
of 2-tuples and returns an ASCII string in this format. It should
be encoded to bytes before being used as the @emph{data} parameter.

@emph{headers} should be a dictionary, and will be treated as if
@ref{2be4,,add_header()} was called with each key and value as arguments.
This is often used to "spoof" the @code{User-Agent} header value, which is
used by a browser to identify itself -- some HTTP servers only
allow requests coming from common browsers as opposed to scripts.
For example, Mozilla Firefox may identify itself as @code{"Mozilla/5.0
(X11; U; Linux i686) Gecko/20071127 Firefox/2.0.0.11"}, while
@ref{11d,,urllib}'s default user agent string is
@code{"Python-urllib/2.6"} (on Python 2.6).

An appropriate @code{Content-Type} header should be included if the @emph{data}
argument is present.  If this header has not been provided and @emph{data}
is not None, @code{Content-Type: application/x-www-form-urlencoded} will
be added as a default.

The next two arguments are only of interest for correct handling
of third-party HTTP cookies:

@emph{origin_req_host} should be the request-host of the origin
transaction, as defined by 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html}.  It defaults to
@code{http.cookiejar.request_host(self)}.  This is the host name or IP
address of the original request that was initiated by the user.
For example, if the request is for an image in an HTML document,
this should be the request-host of the request for the page
containing the image.

@emph{unverifiable} should indicate whether the request is unverifiable,
as defined by 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html}.  It defaults to @code{False}.  An unverifiable
request is one whose URL the user did not have the option to
approve.  For example, if the request is for an image in an HTML
document, and the user had no option to approve the automatic
fetching of the image, this should be true.

@emph{method} should be a string that indicates the HTTP request method that
will be used (e.g. @code{'HEAD'}).  If provided, its value is stored in the
@ref{8f1,,method} attribute and is used by @ref{abc,,get_method()}.
The default is @code{'GET'} if @emph{data} is @code{None} or @code{'POST'} otherwise.
Subclasses may indicate a different default method by setting the
@ref{8f1,,method} attribute in the class itself.

@cartouche
@quotation 注解 
The request will not work as expected if the data object is unable
to deliver its content more than once (e.g. a file or an iterable
that can produce the content only once) and the request is retried
for HTTP redirects or authentication.  The @emph{data} is sent to the
HTTP server right away after the headers.  There is no support for
a 100-continue expectation in the library.
@end quotation
@end cartouche


在 3.3 版更改: Request 类增加了 @ref{8f1,,Request.method} 参数。



在 3.4 版更改: Default @ref{8f1,,Request.method} may be indicated at the class level.



在 3.6 版更改: Do not raise an error if the @code{Content-Length} has not been
provided and @emph{data} is neither @code{None} nor a bytes object.
Fall back to use chunked transfer encoding instead.

@end deffn

@geindex OpenerDirector (urllib.request 中的类)
@anchor{library/urllib request urllib request OpenerDirector}@anchor{2bd5}
@deffn {类} urllib.request.OpenerDirector

The @ref{2bd5,,OpenerDirector} class opens URLs via @ref{2bd9,,BaseHandler}s chained
together. It manages the chaining of handlers, and recovery from errors.
@end deffn

@geindex BaseHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request BaseHandler}@anchor{2bd9}
@deffn {类} urllib.request.BaseHandler

This is the base class for all registered handlers --- and handles only the
simple mechanics of registration.
@end deffn

@geindex HTTPDefaultErrorHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPDefaultErrorHandler}@anchor{2bdb}
@deffn {类} urllib.request.HTTPDefaultErrorHandler

A class which defines a default handler for HTTP error responses; all responses
are turned into @ref{8f6,,HTTPError} exceptions.
@end deffn

@geindex HTTPRedirectHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPRedirectHandler}@anchor{2bdc}
@deffn {类} urllib.request.HTTPRedirectHandler

一个用于处理重定向的类。
@end deffn

@geindex HTTPCookieProcessor (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPCookieProcessor}@anchor{2be5}
@deffn {类} urllib.request.HTTPCookieProcessor (cookiejar=None)

一个用于处理 HTTP Cookies 的类。
@end deffn

@geindex ProxyHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request ProxyHandler}@anchor{f0a}
@deffn {类} urllib.request.ProxyHandler (proxies=None)

Cause requests to go through a proxy. If @emph{proxies} is given, it must be a
dictionary mapping protocol names to URLs of proxies. The default is to read
the list of proxies from the environment variables
@code{<protocol>_proxy}.  If no proxy environment variables are set, then
in a Windows environment proxy settings are obtained from the registry's
Internet Settings section, and in a Mac OS X environment proxy information
is retrieved from the OS X System Configuration Framework.

To disable autodetected proxy pass an empty dictionary.

The 
@geindex no_proxy
@geindex 环境变量; no_proxy
@code{no_proxy} environment variable can be used to specify hosts
which shouldn't be reached via proxy; if set, it should be a comma-separated
list of hostname suffixes, optionally with @code{:port} appended, for example
@code{cern.ch,ncsa.uiuc.edu,some.host:8080}.

@quotation

@cartouche
@quotation 注解 
@code{HTTP_PROXY} will be ignored if a variable @code{REQUEST_METHOD} is set;
see the documentation on @ref{2be3,,getproxies()}.
@end quotation
@end cartouche
@end quotation
@end deffn

@geindex HTTPPasswordMgr (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPPasswordMgr}@anchor{2be6}
@deffn {类} urllib.request.HTTPPasswordMgr

Keep a database of  @code{(realm, uri) -> (user, password)} mappings.
@end deffn

@geindex HTTPPasswordMgrWithDefaultRealm (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPPasswordMgrWithDefaultRealm}@anchor{2be7}
@deffn {类} urllib.request.HTTPPasswordMgrWithDefaultRealm

Keep a database of  @code{(realm, uri) -> (user, password)} mappings. A realm of
@code{None} is considered a catch-all realm, which is searched if no other realm
fits.
@end deffn

@geindex HTTPPasswordMgrWithPriorAuth (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPPasswordMgrWithPriorAuth}@anchor{784}
@deffn {类} urllib.request.HTTPPasswordMgrWithPriorAuth

A variant of @ref{2be7,,HTTPPasswordMgrWithDefaultRealm} that also has a
database of @code{uri -> is_authenticated} mappings.  Can be used by a
BasicAuth handler to determine when to send authentication credentials
immediately instead of waiting for a @code{401} response first.


3.5 新版功能.

@end deffn

@geindex AbstractBasicAuthHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request AbstractBasicAuthHandler}@anchor{eac}
@deffn {类} urllib.request.AbstractBasicAuthHandler (password_mgr=None)

This is a mixin class that helps with HTTP authentication, both to the remote
host and to a proxy. @emph{password_mgr}, if given, should be something that is
compatible with @ref{2be6,,HTTPPasswordMgr}; refer to section
@ref{2be8,,HTTPPasswordMgr 对象} for information on the interface that must be
supported.  If @emph{passwd_mgr} also provides @code{is_authenticated} and
@code{update_authenticated} methods (see
@ref{2be9,,HTTPPasswordMgrWithPriorAuth 对象}), then the handler will use the
@code{is_authenticated} result for a given URI to determine whether or not to
send authentication credentials with the request.  If @code{is_authenticated}
returns @code{True} for the URI, credentials are sent.  If @code{is_authenticated}
is @code{False}, credentials are not sent, and then if a @code{401} response is
received the request is re-sent with the authentication credentials.  If
authentication succeeds, @code{update_authenticated} is called to set
@code{is_authenticated} @code{True} for the URI, so that subsequent requests to
the URI or any of its super-URIs will automatically include the
authentication credentials.


3.5 新版功能: 增加了对 @code{is_authenticated} 的支持。

@end deffn

@geindex HTTPBasicAuthHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPBasicAuthHandler}@anchor{2bea}
@deffn {类} urllib.request.HTTPBasicAuthHandler (password_mgr=None)

Handle authentication with the remote host. @emph{password_mgr}, if given, should
be something that is compatible with @ref{2be6,,HTTPPasswordMgr}; refer to
section @ref{2be8,,HTTPPasswordMgr 对象} for information on the interface that must
be supported. HTTPBasicAuthHandler will raise a @ref{1fb,,ValueError} when
presented with a wrong Authentication scheme.
@end deffn

@geindex ProxyBasicAuthHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request ProxyBasicAuthHandler}@anchor{2beb}
@deffn {类} urllib.request.ProxyBasicAuthHandler (password_mgr=None)

Handle authentication with the proxy. @emph{password_mgr}, if given, should be
something that is compatible with @ref{2be6,,HTTPPasswordMgr}; refer to section
@ref{2be8,,HTTPPasswordMgr 对象} for information on the interface that must be
supported.
@end deffn

@geindex AbstractDigestAuthHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request AbstractDigestAuthHandler}@anchor{eb6}
@deffn {类} urllib.request.AbstractDigestAuthHandler (password_mgr=None)

This is a mixin class that helps with HTTP authentication, both to the remote
host and to a proxy. @emph{password_mgr}, if given, should be something that is
compatible with @ref{2be6,,HTTPPasswordMgr}; refer to section
@ref{2be8,,HTTPPasswordMgr 对象} for information on the interface that must be
supported.
@end deffn

@geindex HTTPDigestAuthHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPDigestAuthHandler}@anchor{2bec}
@deffn {类} urllib.request.HTTPDigestAuthHandler (password_mgr=None)

Handle authentication with the remote host. @emph{password_mgr}, if given, should
be something that is compatible with @ref{2be6,,HTTPPasswordMgr}; refer to
section @ref{2be8,,HTTPPasswordMgr 对象} for information on the interface that must
be supported. When both Digest Authentication Handler and Basic
Authentication Handler are both added, Digest Authentication is always tried
first. If the Digest Authentication returns a 40x response again, it is sent
to Basic Authentication handler to Handle.  This Handler method will raise a
@ref{1fb,,ValueError} when presented with an authentication scheme other than
Digest or Basic.


在 3.3 版更改: Raise @ref{1fb,,ValueError} on unsupported Authentication Scheme.

@end deffn

@geindex ProxyDigestAuthHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request ProxyDigestAuthHandler}@anchor{2bed}
@deffn {类} urllib.request.ProxyDigestAuthHandler (password_mgr=None)

Handle authentication with the proxy. @emph{password_mgr}, if given, should be
something that is compatible with @ref{2be6,,HTTPPasswordMgr}; refer to section
@ref{2be8,,HTTPPasswordMgr 对象} for information on the interface that must be
supported.
@end deffn

@geindex HTTPHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPHandler}@anchor{2bda}
@deffn {类} urllib.request.HTTPHandler

A class to handle opening of HTTP URLs.
@end deffn

@geindex HTTPSHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPSHandler}@anchor{ba1}
@deffn {类} urllib.request.HTTPSHandler (debuglevel=0, context=None, check_hostname=None)

A class to handle opening of HTTPS URLs.  @emph{context} and @emph{check_hostname}
have the same meaning as in @ref{38b,,http.client.HTTPSConnection}.


在 3.2 版更改: @emph{context} and @emph{check_hostname} were added.

@end deffn

@geindex FileHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request FileHandler}@anchor{2bde}
@deffn {类} urllib.request.FileHandler

打开本地文件。
@end deffn

@geindex DataHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request DataHandler}@anchor{8ef}
@deffn {类} urllib.request.DataHandler

Open data URLs.


3.4 新版功能.

@end deffn

@geindex FTPHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request FTPHandler}@anchor{2bdd}
@deffn {类} urllib.request.FTPHandler

打开 FTP URLs。
@end deffn

@geindex CacheFTPHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request CacheFTPHandler}@anchor{2bee}
@deffn {类} urllib.request.CacheFTPHandler

Open FTP URLs, keeping a cache of open FTP connections to minimize delays.
@end deffn

@geindex UnknownHandler (urllib.request 中的类)
@anchor{library/urllib request urllib request UnknownHandler}@anchor{2bd6}
@deffn {类} urllib.request.UnknownHandler

A catch-all class to handle unknown URLs.
@end deffn

@geindex HTTPErrorProcessor (urllib.request 中的类)
@anchor{library/urllib request urllib request HTTPErrorProcessor}@anchor{2bdf}
@deffn {类} urllib.request.HTTPErrorProcessor

Process HTTP error responses.
@end deffn

@menu
* Request 对象:: 
* OpenerDirector 对象:: 
* BaseHandler 对象:: 
* HTTPRedirectHandler 对象:: 
* HTTPCookieProcessor 对象:: 
* ProxyHandler 对象:: 
* HTTPPasswordMgr 对象:: 
* HTTPPasswordMgrWithPriorAuth 对象:: 
* AbstractBasicAuthHandler 对象:: 
* HTTPBasicAuthHandler 对象:: 
* ProxyBasicAuthHandler 对象:: 
* AbstractDigestAuthHandler 对象:: 
* HTTPDigestAuthHandler 对象:: 
* ProxyDigestAuthHandler 对象:: 
* HTTPHandler 对象:: 
* HTTPSHandler 对象:: 
* FileHandler 对象:: 
* DataHandler 对象:: 
* FTPHandler 对象:: 
* CacheFTPHandler 对象:: 
* UnknownHandler 对象:: 
* HTTPErrorProcessor 对象:: 
* 例子: 例子<21>. 
* Legacy interface:: 
* urllib.request Restrictions: urllib request Restrictions. 

@end menu

@node Request 对象,OpenerDirector 对象,,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request id1}@anchor{2bef}@anchor{library/urllib request request-objects}@anchor{2bf0}
@subsubsection Request 对象


The following methods describe @ref{8f0,,Request}'s public interface,
and so all may be overridden in subclasses.  It also defines several
public attributes that can be used by clients to inspect the parsed
request.

@geindex full_url (urllib.request.Request 属性)
@anchor{library/urllib request urllib request Request full_url}@anchor{8f2}
@deffn {属性} Request.full_url

传给构造函数的原始 URL。


在 3.4 版更改.


Request.full_url is a property with setter, getter and a deleter. Getting
@ref{8f2,,full_url} returns the original request URL with the
fragment, if it was present.
@end deffn

@geindex type (urllib.request.Request 属性)
@anchor{library/urllib request urllib request Request type}@anchor{2bf1}
@deffn {属性} Request.type

The URI scheme.
@end deffn

@geindex host (urllib.request.Request 属性)
@anchor{library/urllib request urllib request Request host}@anchor{2bf2}
@deffn {属性} Request.host

The URI authority, typically a host, but may also contain a port
separated by a colon.
@end deffn

@geindex origin_req_host (urllib.request.Request 属性)
@anchor{library/urllib request urllib request Request origin_req_host}@anchor{2bf3}
@deffn {属性} Request.origin_req_host

请求的原始主机，不含端口。
@end deffn

@geindex selector (urllib.request.Request 属性)
@anchor{library/urllib request urllib request Request selector}@anchor{2bf4}
@deffn {属性} Request.selector

URI 路径。若 @ref{8f0,,Request} 使用代理，选择器将会是传给代理的完整 URL。
@end deffn

@geindex data (urllib.request.Request 属性)
@anchor{library/urllib request urllib request Request data}@anchor{8f3}
@deffn {属性} Request.data

The entity body for the request, or @code{None} if not specified.


在 3.4 版更改: Changing value of @ref{8f3,,Request.data} now deletes "Content-Length"
header if it was previously set or calculated.

@end deffn

@geindex unverifiable (urllib.request.Request 属性)
@anchor{library/urllib request urllib request Request unverifiable}@anchor{2bf5}
@deffn {属性} Request.unverifiable

布尔，表明请求是否为 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} 中定义的无法证实的。
@end deffn

@geindex method (urllib.request.Request 属性)
@anchor{library/urllib request urllib request Request method}@anchor{8f1}
@deffn {属性} Request.method

The HTTP request method to use.  By default its value is @ref{157,,None},
which means that @ref{abc,,get_method()} will do its normal computation
of the method to be used.  Its value can be set (thus overriding the default
computation in @ref{abc,,get_method()}) either by providing a default
value by setting it at the class level in a @ref{8f0,,Request} subclass, or by
passing a value in to the @ref{8f0,,Request} constructor via the @emph{method}
argument.


3.3 新版功能.



在 3.4 版更改: A default value can now be set in subclasses; previously it could only
be set via the constructor argument.

@end deffn

@geindex get_method() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request get_method}
@deffn {方法} Request.get_method ()

Return a string indicating the HTTP request method.  If
@ref{8f1,,Request.method} is not @code{None}, return its value, otherwise return
@code{'GET'} if @ref{8f3,,Request.data} is @code{None}, or @code{'POST'} if it's not.
This is only meaningful for HTTP requests.


在 3.3 版更改: get_method now looks at the value of @ref{8f1,,Request.method}.

@end deffn

@geindex add_header() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request add_header}@anchor{2be4}
@deffn {方法} Request.add_header (key, val)

Add another header to the request.  Headers are currently ignored by all
handlers except HTTP handlers, where they are added to the list of headers sent
to the server.  Note that there cannot be more than one header with the same
name, and later calls will overwrite previous calls in case the @emph{key} collides.
Currently, this is no loss of HTTP functionality, since all headers which have
meaning when used more than once have a (header-specific) way of gaining the
same functionality using only one header.
@end deffn

@geindex add_unredirected_header() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request add_unredirected_header}@anchor{2bf6}
@deffn {方法} Request.add_unredirected_header (key, header)

添加一个不会被加入重定向请求的头部。
@end deffn

@geindex has_header() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request has_header}@anchor{2bf7}
@deffn {方法} Request.has_header (header)

Return whether the instance has the named header (checks both regular and
unredirected).
@end deffn

@geindex remove_header() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request remove_header}@anchor{8f5}
@deffn {方法} Request.remove_header (header)

Remove named header from the request instance (both from regular and
unredirected headers).


3.4 新版功能.

@end deffn

@geindex get_full_url() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request get_full_url}@anchor{2bf8}
@deffn {方法} Request.get_full_url ()

返回构造器中给定的 URL。


在 3.4 版更改.


返回 @ref{8f2,,Request.full_url}
@end deffn

@geindex set_proxy() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request set_proxy}@anchor{2bf9}
@deffn {方法} Request.set_proxy (host, type)

Prepare the request by connecting to a proxy server. The @emph{host} and @emph{type} will
replace those of the instance, and the instance's selector will be the original
URL given in the constructor.
@end deffn

@geindex get_header() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request get_header}@anchor{2bfa}
@deffn {方法} Request.get_header (header_name, default=None)

Return the value of the given header. If the header is not present, return
the default value.
@end deffn

@geindex header_items() (urllib.request.Request 方法)
@anchor{library/urllib request urllib request Request header_items}@anchor{2bfb}
@deffn {方法} Request.header_items ()

Return a list of tuples (header_name, header_value) of the Request headers.
@end deffn


在 3.4 版更改: The request methods add_data, has_data, get_data, get_type, get_host,
get_selector, get_origin_req_host and is_unverifiable that were deprecated
since 3.3 have been removed.


@node OpenerDirector 对象,BaseHandler 对象,Request 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request opener-director-objects}@anchor{2bfc}@anchor{library/urllib request openerdirector-objects}@anchor{2bfd}
@subsubsection OpenerDirector 对象


@ref{2bd5,,OpenerDirector} 实例有以下方法：

@geindex add_handler() (urllib.request.OpenerDirector 方法)
@anchor{library/urllib request urllib request OpenerDirector add_handler}@anchor{2bfe}
@deffn {方法} OpenerDirector.add_handler (handler)

@emph{handler} should be an instance of @ref{2bd9,,BaseHandler}.  The following methods
are searched, and added to the possible chains (note that HTTP errors are a
special case).  Note that, in the following, @emph{protocol} should be replaced
with the actual protocol to handle, for example @code{http_response()} would
be the HTTP protocol response handler.  Also @emph{type} should be replaced with
the actual HTTP code, for example @code{http_error_404()} would handle HTTP
404 errors.


@itemize *

@item 
@code{<protocol>_open()} — 句柄知道如何打开 @emph{protocol} URLs 的信号。

查看 @ref{2bff,,BaseHandler.<protocol>_open()} 以获取更多信息。

@item 
@code{http_error_<type>()} --- signal that the handler knows how to handle HTTP
errors with HTTP error code @emph{type}.

查看 @ref{2c00,,BaseHandler.http_error_<nnn>()} 以获取更多信息。

@item 
@code{<protocol>_error()} — 句柄知道如何处理来自（非-@code{http}）*protocol* 的错误的信号。

@item 
@code{<protocol>_request()} — 句柄知道如何预处理 @emph{protocol} 请求的信号。

查看 @ref{2c01,,BaseHandler.<protocol>_request()} 以获取更多信息。

@item 
@code{<protocol>_response()} — 句柄知道如何后处理 @emph{protocol} 响应的信号。

查看 @ref{2c02,,BaseHandler.<protocol>_response()} 以获取更多信息。
@end itemize
@end deffn

@geindex open() (urllib.request.OpenerDirector 方法)
@anchor{library/urllib request urllib request OpenerDirector open}@anchor{8f4}
@deffn {方法} OpenerDirector.open (url, data=None[, timeout])

Open the given @emph{url} (which can be a request object or a string), optionally
passing the given @emph{data}. Arguments, return values and exceptions raised are
the same as those of @ref{786,,urlopen()} (which simply calls the @ref{4ea,,open()}
method on the currently installed global @ref{2bd5,,OpenerDirector}).  The
optional @emph{timeout} parameter specifies a timeout in seconds for blocking
operations like the connection attempt (if not specified, the global default
timeout setting will be used). The timeout feature actually works only for
HTTP, HTTPS and FTP connections).
@end deffn

@geindex error() (urllib.request.OpenerDirector 方法)
@anchor{library/urllib request urllib request OpenerDirector error}@anchor{2c03}
@deffn {方法} OpenerDirector.error (proto, *args)

Handle an error of the given protocol.  This will call the registered error
handlers for the given protocol with the given arguments (which are protocol
specific).  The HTTP protocol is a special case which uses the HTTP response
code to determine the specific error handler; refer to the @code{http_error_<type>()}
methods of the handler classes.

Return values and exceptions raised are the same as those of @ref{786,,urlopen()}.
@end deffn

OpenerDirector objects open URLs in three stages:

The order in which these methods are called within each stage is determined by
sorting the handler instances.


@enumerate 

@item 
Every handler with a method named like @code{<protocol>_request()} has that
method called to pre-process the request.

@item 
Handlers with a method named like @code{<protocol>_open()} are called to handle
the request. This stage ends when a handler either returns a non-@ref{157,,None}
value (ie. a response), or raises an exception (usually
@ref{2bd4,,URLError}).  Exceptions are allowed to propagate.

In fact, the above algorithm is first tried for methods named
@code{default_open()}.  If all such methods return @ref{157,,None}, the algorithm
is repeated for methods named like @code{<protocol>_open()}.  If all such methods
return @ref{157,,None}, the algorithm is repeated for methods named
@code{unknown_open()}.

Note that the implementation of these methods may involve calls of the parent
@ref{2bd5,,OpenerDirector} instance's @ref{8f4,,open()} and
@ref{2c03,,error()} methods.

@item 
Every handler with a method named like @code{<protocol>_response()} has that
method called to post-process the response.
@end enumerate

@node BaseHandler 对象,HTTPRedirectHandler 对象,OpenerDirector 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request base-handler-objects}@anchor{2c04}@anchor{library/urllib request basehandler-objects}@anchor{2c05}
@subsubsection BaseHandler 对象


@ref{2bd9,,BaseHandler} objects provide a couple of methods that are directly
useful, and others that are meant to be used by derived classes.  These are
intended for direct use:

@geindex add_parent() (urllib.request.BaseHandler 方法)
@anchor{library/urllib request urllib request BaseHandler add_parent}@anchor{2c06}
@deffn {方法} BaseHandler.add_parent (director)

Add a director as parent.
@end deffn

@geindex close() (urllib.request.BaseHandler 方法)
@anchor{library/urllib request urllib request BaseHandler close}@anchor{2c07}
@deffn {方法} BaseHandler.close ()

Remove any parents.
@end deffn

The following attribute and methods should only be used by classes derived from
@ref{2bd9,,BaseHandler}.

@cartouche
@quotation 注解 
The convention has been adopted that subclasses defining
@code{<protocol>_request()} or @code{<protocol>_response()} methods are named
@code{*Processor}; all others are named @code{*Handler}.
@end quotation
@end cartouche

@geindex parent (urllib.request.BaseHandler 属性)
@anchor{library/urllib request urllib request BaseHandler parent}@anchor{2c08}
@deffn {属性} BaseHandler.parent

A valid @ref{2bd5,,OpenerDirector}, which can be used to open using a different
protocol, or handle errors.
@end deffn

@geindex default_open() (urllib.request.BaseHandler 方法)
@anchor{library/urllib request urllib request BaseHandler default_open}@anchor{2c09}
@deffn {方法} BaseHandler.default_open (req)

This method is @emph{not} defined in @ref{2bd9,,BaseHandler}, but subclasses should
define it if they want to catch all URLs.

This method, if implemented, will be called by the parent
@ref{2bd5,,OpenerDirector}.  It should return a file-like object as described in
the return value of the @ref{4ea,,open()} of @ref{2bd5,,OpenerDirector}, or @code{None}.
It should raise @ref{2bd4,,URLError}, unless a truly exceptional
thing happens (for example, @ref{f9f,,MemoryError} should not be mapped to
@code{URLError}).

This method will be called before any protocol-specific open method.
@end deffn
@anchor{library/urllib request protocol-open}@anchor{2bff}

@deffn {方法} BaseHandler.<protocol>_open(req)

This method is @emph{not} defined in @ref{2bd9,,BaseHandler}, but subclasses should
define it if they want to handle URLs with the given protocol.

This method, if defined, will be called by the parent @ref{2bd5,,OpenerDirector}.
Return values should be the same as for  @code{default_open()}.
@end deffn

@geindex unknown_open() (urllib.request.BaseHandler 方法)
@anchor{library/urllib request urllib request BaseHandler unknown_open}@anchor{2c0a}
@deffn {方法} BaseHandler.unknown_open (req)

This method is @emph{not} defined in @ref{2bd9,,BaseHandler}, but subclasses should
define it if they want to catch all URLs with no specific registered handler to
open it.

This method, if implemented, will be called by the @ref{2c08,,parent}
@ref{2bd5,,OpenerDirector}.  Return values should be the same as for
@ref{2c09,,default_open()}.
@end deffn

@geindex http_error_default() (urllib.request.BaseHandler 方法)
@anchor{library/urllib request urllib request BaseHandler http_error_default}@anchor{2c0b}
@deffn {方法} BaseHandler.http_error_default (req, fp, code, msg, hdrs)

This method is @emph{not} defined in @ref{2bd9,,BaseHandler}, but subclasses should
override it if they intend to provide a catch-all for otherwise unhandled HTTP
errors.  It will be called automatically by the  @ref{2bd5,,OpenerDirector} getting
the error, and should not normally be called in other circumstances.

@emph{req} will be a @ref{8f0,,Request} object, @emph{fp} will be a file-like object with
the HTTP error body, @emph{code} will be the three-digit code of the error, @emph{msg}
will be the user-visible explanation of the code and @emph{hdrs} will be a mapping
object with the headers of the error.

Return values and exceptions raised should be the same as those of
@ref{786,,urlopen()}.
@end deffn
@anchor{library/urllib request http-error-nnn}@anchor{2c00}

@deffn {方法} BaseHandler.http_error_<nnn>(req, fp, code, msg, hdrs)

@emph{nnn} should be a three-digit HTTP error code.  This method is also not defined
in @ref{2bd9,,BaseHandler}, but will be called, if it exists, on an instance of a
subclass, when an HTTP error with code @emph{nnn} occurs.

Subclasses should override this method to handle specific HTTP errors.

Arguments, return values and exceptions raised should be the same as for
@code{http_error_default()}.
@end deffn
@anchor{library/urllib request protocol-request}@anchor{2c01}

@deffn {方法} BaseHandler.<protocol>_request(req)

This method is @emph{not} defined in @ref{2bd9,,BaseHandler}, but subclasses should
define it if they want to pre-process requests of the given protocol.

This method, if defined, will be called by the parent @ref{2bd5,,OpenerDirector}.
@emph{req} will be a @ref{8f0,,Request} object. The return value should be a
@ref{8f0,,Request} object.
@end deffn
@anchor{library/urllib request protocol-response}@anchor{2c02}

@deffn {方法} BaseHandler.<protocol>_response(req, response)

This method is @emph{not} defined in @ref{2bd9,,BaseHandler}, but subclasses should
define it if they want to post-process responses of the given protocol.

This method, if defined, will be called by the parent @ref{2bd5,,OpenerDirector}.
@emph{req} will be a @ref{8f0,,Request} object. @emph{response} will be an object
implementing the same interface as the return value of @ref{786,,urlopen()}.  The
return value should implement the same interface as the return value of
@ref{786,,urlopen()}.
@end deffn

@node HTTPRedirectHandler 对象,HTTPCookieProcessor 对象,BaseHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request http-redirect-handler}@anchor{2c0c}@anchor{library/urllib request httpredirecthandler-objects}@anchor{2c0d}
@subsubsection HTTPRedirectHandler 对象


@cartouche
@quotation 注解 
Some HTTP redirections require action from this module's client code.  If this
is the case, @ref{8f6,,HTTPError} is raised.  See 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html} for
details of the precise meanings of the various redirection codes.

An @code{HTTPError} exception raised as a security consideration if the
HTTPRedirectHandler is presented with a redirected URL which is not an HTTP,
HTTPS or FTP URL.
@end quotation
@end cartouche

@geindex redirect_request() (urllib.request.HTTPRedirectHandler 方法)
@anchor{library/urllib request urllib request HTTPRedirectHandler redirect_request}@anchor{2c0e}
@deffn {方法} HTTPRedirectHandler.redirect_request (req, fp, code, msg, hdrs, newurl)

Return a @ref{8f0,,Request} or @code{None} in response to a redirect. This is called
by the default implementations of the @code{http_error_30*()} methods when a
redirection is received from the server.  If a redirection should take place,
return a new @ref{8f0,,Request} to allow @code{http_error_30*()} to perform the
redirect to @emph{newurl}.  Otherwise, raise @ref{8f6,,HTTPError} if
no other handler should try to handle this URL, or return @code{None} if you
can't but another handler might.

@cartouche
@quotation 注解 
The default implementation of this method does not strictly follow 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html},
which says that 301 and 302 responses to @code{POST} requests must not be
automatically redirected without confirmation by the user.  In reality, browsers
do allow automatic redirection of these responses, changing the POST to a
@code{GET}, and the default implementation reproduces this behavior.
@end quotation
@end cartouche
@end deffn

@geindex http_error_301() (urllib.request.HTTPRedirectHandler 方法)
@anchor{library/urllib request urllib request HTTPRedirectHandler http_error_301}@anchor{2c0f}
@deffn {方法} HTTPRedirectHandler.http_error_301 (req, fp, code, msg, hdrs)

Redirect to the @code{Location:} or @code{URI:} URL.  This method is called by the
parent @ref{2bd5,,OpenerDirector} when getting an HTTP 'moved permanently' response.
@end deffn

@geindex http_error_302() (urllib.request.HTTPRedirectHandler 方法)
@anchor{library/urllib request urllib request HTTPRedirectHandler http_error_302}@anchor{2c10}
@deffn {方法} HTTPRedirectHandler.http_error_302 (req, fp, code, msg, hdrs)

The same as @ref{2c0f,,http_error_301()}, but called for the 'found' response.
@end deffn

@geindex http_error_303() (urllib.request.HTTPRedirectHandler 方法)
@anchor{library/urllib request urllib request HTTPRedirectHandler http_error_303}@anchor{2c11}
@deffn {方法} HTTPRedirectHandler.http_error_303 (req, fp, code, msg, hdrs)

The same as @ref{2c0f,,http_error_301()}, but called for the 'see other' response.
@end deffn

@geindex http_error_307() (urllib.request.HTTPRedirectHandler 方法)
@anchor{library/urllib request urllib request HTTPRedirectHandler http_error_307}@anchor{2c12}
@deffn {方法} HTTPRedirectHandler.http_error_307 (req, fp, code, msg, hdrs)

The same as @ref{2c0f,,http_error_301()}, but called for the 'temporary redirect'
response.
@end deffn

@node HTTPCookieProcessor 对象,ProxyHandler 对象,HTTPRedirectHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request http-cookie-processor}@anchor{2c13}@anchor{library/urllib request httpcookieprocessor-objects}@anchor{2c14}
@subsubsection HTTPCookieProcessor 对象


@ref{2be5,,HTTPCookieProcessor} instances have one attribute:

@geindex cookiejar (urllib.request.HTTPCookieProcessor 属性)
@anchor{library/urllib request urllib request HTTPCookieProcessor cookiejar}@anchor{2c15}
@deffn {属性} HTTPCookieProcessor.cookiejar

The @ref{2c16,,http.cookiejar.CookieJar} in which cookies are stored.
@end deffn

@node ProxyHandler 对象,HTTPPasswordMgr 对象,HTTPCookieProcessor 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request proxy-handler}@anchor{2c17}@anchor{library/urllib request proxyhandler-objects}@anchor{2c18}
@subsubsection ProxyHandler 对象



@deffn {方法} ProxyHandler.<protocol>_open(request)

The @ref{f0a,,ProxyHandler} will have a method @code{<protocol>_open()} for every
@emph{protocol} which has a proxy in the @emph{proxies} dictionary given in the
constructor.  The method will modify requests to go through the proxy, by
calling @code{request.set_proxy()}, and call the next handler in the chain to
actually execute the protocol.
@end deffn

@node HTTPPasswordMgr 对象,HTTPPasswordMgrWithPriorAuth 对象,ProxyHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request http-password-mgr}@anchor{2be8}@anchor{library/urllib request httppasswordmgr-objects}@anchor{2c19}
@subsubsection HTTPPasswordMgr 对象


These methods are available on @ref{2be6,,HTTPPasswordMgr} and
@ref{2be7,,HTTPPasswordMgrWithDefaultRealm} objects.

@geindex add_password() (urllib.request.HTTPPasswordMgr 方法)
@anchor{library/urllib request urllib request HTTPPasswordMgr add_password}@anchor{2c1a}
@deffn {方法} HTTPPasswordMgr.add_password (realm, uri, user, passwd)

@emph{uri} can be either a single URI, or a sequence of URIs. @emph{realm}, @emph{user} and
@emph{passwd} must be strings. This causes @code{(user, passwd)} to be used as
authentication tokens when authentication for @emph{realm} and a super-URI of any of
the given URIs is given.
@end deffn

@geindex find_user_password() (urllib.request.HTTPPasswordMgr 方法)
@anchor{library/urllib request urllib request HTTPPasswordMgr find_user_password}@anchor{2c1b}
@deffn {方法} HTTPPasswordMgr.find_user_password (realm, authuri)

Get user/password for given realm and URI, if any.  This method will return
@code{(None, None)} if there is no matching user/password.

For @ref{2be7,,HTTPPasswordMgrWithDefaultRealm} objects, the realm @code{None} will be
searched if the given @emph{realm} has no matching user/password.
@end deffn

@node HTTPPasswordMgrWithPriorAuth 对象,AbstractBasicAuthHandler 对象,HTTPPasswordMgr 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request http-password-mgr-with-prior-auth}@anchor{2be9}@anchor{library/urllib request httppasswordmgrwithpriorauth-objects}@anchor{2c1c}
@subsubsection HTTPPasswordMgrWithPriorAuth 对象


This password manager extends @ref{2be7,,HTTPPasswordMgrWithDefaultRealm} to support
tracking URIs for which authentication credentials should always be sent.

@geindex add_password() (urllib.request.HTTPPasswordMgrWithPriorAuth 方法)
@anchor{library/urllib request urllib request HTTPPasswordMgrWithPriorAuth add_password}@anchor{2c1d}
@deffn {方法} HTTPPasswordMgrWithPriorAuth.add_password (realm, uri, user, passwd, is_authenticated=False)

@emph{realm}, @emph{uri}, @emph{user}, @emph{passwd} are as for
@ref{2c1a,,HTTPPasswordMgr.add_password()}.  @emph{is_authenticated} sets the initial
value of the @code{is_authenticated} flag for the given URI or list of URIs.
If @emph{is_authenticated} is specified as @code{True}, @emph{realm} is ignored.
@end deffn

@geindex find_user_password() (urllib.request.HTTPPasswordMgr 方法)

@deffn {方法} HTTPPasswordMgr.find_user_password (realm, authuri)

Same as for @ref{2be7,,HTTPPasswordMgrWithDefaultRealm} objects
@end deffn

@geindex update_authenticated() (urllib.request.HTTPPasswordMgrWithPriorAuth 方法)
@anchor{library/urllib request urllib request HTTPPasswordMgrWithPriorAuth update_authenticated}@anchor{2c1e}
@deffn {方法} HTTPPasswordMgrWithPriorAuth.update_authenticated (self, uri, is_authenticated=False)

Update the @code{is_authenticated} flag for the given @emph{uri} or list
of URIs.
@end deffn

@geindex is_authenticated() (urllib.request.HTTPPasswordMgrWithPriorAuth 方法)
@anchor{library/urllib request urllib request HTTPPasswordMgrWithPriorAuth is_authenticated}@anchor{2c1f}
@deffn {方法} HTTPPasswordMgrWithPriorAuth.is_authenticated (self, authuri)

Returns the current state of the @code{is_authenticated} flag for
the given URI.
@end deffn

@node AbstractBasicAuthHandler 对象,HTTPBasicAuthHandler 对象,HTTPPasswordMgrWithPriorAuth 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request abstract-basic-auth-handler}@anchor{2c20}@anchor{library/urllib request abstractbasicauthhandler-objects}@anchor{2c21}
@subsubsection AbstractBasicAuthHandler 对象


@geindex http_error_auth_reqed() (urllib.request.AbstractBasicAuthHandler 方法)
@anchor{library/urllib request urllib request AbstractBasicAuthHandler http_error_auth_reqed}@anchor{2c22}
@deffn {方法} AbstractBasicAuthHandler.http_error_auth_reqed (authreq, host, req, headers)

Handle an authentication request by getting a user/password pair, and re-trying
the request.  @emph{authreq} should be the name of the header where the information
about the realm is included in the request, @emph{host} specifies the URL and path to
authenticate for, @emph{req} should be the (failed) @ref{8f0,,Request} object, and
@emph{headers} should be the error headers.

@emph{host} is either an authority (e.g. @code{"python.org"}) or a URL containing an
authority component (e.g. @code{"http://python.org/"}). In either case, the
authority must not contain a userinfo component (so, @code{"python.org"} and
@code{"python.org:80"} are fine, @code{"joe:password@@python.org"} is not).
@end deffn

@node HTTPBasicAuthHandler 对象,ProxyBasicAuthHandler 对象,AbstractBasicAuthHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request http-basic-auth-handler}@anchor{2c23}@anchor{library/urllib request httpbasicauthhandler-objects}@anchor{2c24}
@subsubsection HTTPBasicAuthHandler 对象


@geindex http_error_401() (urllib.request.HTTPBasicAuthHandler 方法)
@anchor{library/urllib request urllib request HTTPBasicAuthHandler http_error_401}@anchor{2c25}
@deffn {方法} HTTPBasicAuthHandler.http_error_401 (req, fp, code, msg, hdrs)

Retry the request with authentication information, if available.
@end deffn

@node ProxyBasicAuthHandler 对象,AbstractDigestAuthHandler 对象,HTTPBasicAuthHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request proxy-basic-auth-handler}@anchor{2c26}@anchor{library/urllib request proxybasicauthhandler-objects}@anchor{2c27}
@subsubsection ProxyBasicAuthHandler 对象


@geindex http_error_407() (urllib.request.ProxyBasicAuthHandler 方法)
@anchor{library/urllib request urllib request ProxyBasicAuthHandler http_error_407}@anchor{2c28}
@deffn {方法} ProxyBasicAuthHandler.http_error_407 (req, fp, code, msg, hdrs)

Retry the request with authentication information, if available.
@end deffn

@node AbstractDigestAuthHandler 对象,HTTPDigestAuthHandler 对象,ProxyBasicAuthHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request abstract-digest-auth-handler}@anchor{2c29}@anchor{library/urllib request abstractdigestauthhandler-objects}@anchor{2c2a}
@subsubsection AbstractDigestAuthHandler 对象


@geindex http_error_auth_reqed() (urllib.request.AbstractDigestAuthHandler 方法)
@anchor{library/urllib request urllib request AbstractDigestAuthHandler http_error_auth_reqed}@anchor{2c2b}
@deffn {方法} AbstractDigestAuthHandler.http_error_auth_reqed (authreq, host, req, headers)

@emph{authreq} should be the name of the header where the information about the realm
is included in the request, @emph{host} should be the host to authenticate to, @emph{req}
should be the (failed) @ref{8f0,,Request} object, and @emph{headers} should be the
error headers.
@end deffn

@node HTTPDigestAuthHandler 对象,ProxyDigestAuthHandler 对象,AbstractDigestAuthHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request http-digest-auth-handler}@anchor{2c2c}@anchor{library/urllib request httpdigestauthhandler-objects}@anchor{2c2d}
@subsubsection HTTPDigestAuthHandler 对象


@geindex http_error_401() (urllib.request.HTTPDigestAuthHandler 方法)
@anchor{library/urllib request urllib request HTTPDigestAuthHandler http_error_401}@anchor{2c2e}
@deffn {方法} HTTPDigestAuthHandler.http_error_401 (req, fp, code, msg, hdrs)

Retry the request with authentication information, if available.
@end deffn

@node ProxyDigestAuthHandler 对象,HTTPHandler 对象,HTTPDigestAuthHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request proxy-digest-auth-handler}@anchor{2c2f}@anchor{library/urllib request proxydigestauthhandler-objects}@anchor{2c30}
@subsubsection ProxyDigestAuthHandler 对象


@geindex http_error_407() (urllib.request.ProxyDigestAuthHandler 方法)
@anchor{library/urllib request urllib request ProxyDigestAuthHandler http_error_407}@anchor{2c31}
@deffn {方法} ProxyDigestAuthHandler.http_error_407 (req, fp, code, msg, hdrs)

Retry the request with authentication information, if available.
@end deffn

@node HTTPHandler 对象,HTTPSHandler 对象,ProxyDigestAuthHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request http-handler-objects}@anchor{2c32}@anchor{library/urllib request httphandler-objects}@anchor{2c33}
@subsubsection HTTPHandler 对象


@geindex http_open() (urllib.request.HTTPHandler 方法)
@anchor{library/urllib request urllib request HTTPHandler http_open}@anchor{2c34}
@deffn {方法} HTTPHandler.http_open (req)

Send an HTTP request, which can be either GET or POST, depending on
@code{req.has_data()}.
@end deffn

@node HTTPSHandler 对象,FileHandler 对象,HTTPHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request https-handler-objects}@anchor{2c35}@anchor{library/urllib request httpshandler-objects}@anchor{2c36}
@subsubsection HTTPSHandler 对象


@geindex https_open() (urllib.request.HTTPSHandler 方法)
@anchor{library/urllib request urllib request HTTPSHandler https_open}@anchor{2c37}
@deffn {方法} HTTPSHandler.https_open (req)

Send an HTTPS request, which can be either GET or POST, depending on
@code{req.has_data()}.
@end deffn

@node FileHandler 对象,DataHandler 对象,HTTPSHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request file-handler-objects}@anchor{2c38}@anchor{library/urllib request filehandler-objects}@anchor{2c39}
@subsubsection FileHandler 对象


@geindex file_open() (urllib.request.FileHandler 方法)
@anchor{library/urllib request urllib request FileHandler file_open}@anchor{2c3a}
@deffn {方法} FileHandler.file_open (req)

Open the file locally, if there is no host name, or the host name is
@code{'localhost'}.


在 3.2 版更改: This method is applicable only for local hostnames.  When a remote
hostname is given, an @ref{2bd4,,URLError} is raised.

@end deffn

@node DataHandler 对象,FTPHandler 对象,FileHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request data-handler-objects}@anchor{2c3b}@anchor{library/urllib request datahandler-objects}@anchor{2c3c}
@subsubsection DataHandler 对象


@geindex data_open() (urllib.request.DataHandler 方法)
@anchor{library/urllib request urllib request DataHandler data_open}@anchor{2c3d}
@deffn {方法} DataHandler.data_open (req)

Read a data URL. This kind of URL contains the content encoded in the URL
itself. The data URL syntax is specified in 
@geindex RFC; RFC 2397
RFC 2397@footnote{https://tools.ietf.org/html/rfc2397.html}. This implementation
ignores white spaces in base64 encoded data URLs so the URL may be wrapped
in whatever source file it comes from. But even though some browsers don't
mind about a missing padding at the end of a base64 encoded data URL, this
implementation will raise an @ref{1fb,,ValueError} in that case.
@end deffn

@node FTPHandler 对象,CacheFTPHandler 对象,DataHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request ftp-handler-objects}@anchor{2c3e}@anchor{library/urllib request ftphandler-objects}@anchor{2c3f}
@subsubsection FTPHandler 对象


@geindex ftp_open() (urllib.request.FTPHandler 方法)
@anchor{library/urllib request urllib request FTPHandler ftp_open}@anchor{2c40}
@deffn {方法} FTPHandler.ftp_open (req)

Open the FTP file indicated by @emph{req}. The login is always done with empty
username and password.
@end deffn

@node CacheFTPHandler 对象,UnknownHandler 对象,FTPHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request cacheftp-handler-objects}@anchor{2c41}@anchor{library/urllib request cacheftphandler-objects}@anchor{2c42}
@subsubsection CacheFTPHandler 对象


@ref{2bee,,CacheFTPHandler} objects are @ref{2bdd,,FTPHandler} objects with the
following additional methods:

@geindex setTimeout() (urllib.request.CacheFTPHandler 方法)
@anchor{library/urllib request urllib request CacheFTPHandler setTimeout}@anchor{2c43}
@deffn {方法} CacheFTPHandler.setTimeout (t)

Set timeout of connections to @emph{t} seconds.
@end deffn

@geindex setMaxConns() (urllib.request.CacheFTPHandler 方法)
@anchor{library/urllib request urllib request CacheFTPHandler setMaxConns}@anchor{2c44}
@deffn {方法} CacheFTPHandler.setMaxConns (m)

Set maximum number of cached connections to @emph{m}.
@end deffn

@node UnknownHandler 对象,HTTPErrorProcessor 对象,CacheFTPHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request unknown-handler-objects}@anchor{2c45}@anchor{library/urllib request unknownhandler-objects}@anchor{2c46}
@subsubsection UnknownHandler 对象


@geindex unknown_open() (urllib.request.UnknownHandler 方法)
@anchor{library/urllib request urllib request UnknownHandler unknown_open}@anchor{2c47}
@deffn {方法} UnknownHandler.unknown_open ()

Raise a @ref{2bd4,,URLError} exception.
@end deffn

@node HTTPErrorProcessor 对象,例子<21>,UnknownHandler 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request http-error-processor-objects}@anchor{2c48}@anchor{library/urllib request httperrorprocessor-objects}@anchor{2c49}
@subsubsection HTTPErrorProcessor 对象


@geindex http_response() (urllib.request.HTTPErrorProcessor 方法)
@anchor{library/urllib request urllib request HTTPErrorProcessor http_response}@anchor{2c4a}
@deffn {方法} HTTPErrorProcessor.http_response (request, response)

Process HTTP error responses.

For 200 error codes, the response object is returned immediately.

For non-200 error codes, this simply passes the job on to the
@code{http_error_<type>()} handler methods, via @ref{2c03,,OpenerDirector.error()}.
Eventually, @ref{2bdb,,HTTPDefaultErrorHandler} will raise an
@ref{8f6,,HTTPError} if no other handler handles the error.
@end deffn

@geindex https_response() (urllib.request.HTTPErrorProcessor 方法)
@anchor{library/urllib request urllib request HTTPErrorProcessor https_response}@anchor{2c4b}
@deffn {方法} HTTPErrorProcessor.https_response (request, response)

Process HTTPS error responses.

The behavior is same as @ref{2c4a,,http_response()}.
@end deffn

@node 例子<21>,Legacy interface,HTTPErrorProcessor 对象,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request examples}@anchor{2c4c}@anchor{library/urllib request urllib-request-examples}@anchor{2c4d}
@subsubsection 例子


In addition to the examples below, more examples are given in
@ref{2c4e,,HOWTO 使用 urllib 包获取网络资源}.

This example gets the python.org main page and displays the first 300 bytes of
it.

@example
>>> import urllib.request
>>> with urllib.request.urlopen('http://www.python.org/') as f:
...     print(f.read(300))
...
b'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">\n\n\n<html
xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">\n\n<head>\n
<meta http-equiv="content-type" content="text/html; charset=utf-8" />\n
<title>Python Programming '
@end example

Note that urlopen returns a bytes object.  This is because there is no way
for urlopen to automatically determine the encoding of the byte stream
it receives from the HTTP server. In general, a program will decode
the returned bytes object to string once it determines or guesses
the appropriate encoding.

The following W3C document, @indicateurl{https://www.w3.org/International/O-charset}, lists
the various ways in which an (X)HTML or an XML document could have specified its
encoding information.

As the python.org website uses @emph{utf-8} encoding as specified in its meta tag, we
will use the same for decoding the bytes object.

@example
>>> with urllib.request.urlopen('http://www.python.org/') as f:
...     print(f.read(100).decode('utf-8'))
...
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtm
@end example

It is also possible to achieve the same result without using the
@ref{563,,context manager} approach.

@example
>>> import urllib.request
>>> f = urllib.request.urlopen('http://www.python.org/')
>>> print(f.read(100).decode('utf-8'))
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtm
@end example

In the following example, we are sending a data-stream to the stdin of a CGI
and reading the data it returns to us. Note that this example will only work
when the Python installation supports SSL.

@example
>>> import urllib.request
>>> req = urllib.request.Request(url='https://localhost/cgi-bin/test.cgi',
...                       data=b'This data is passed to stdin of the CGI')
>>> with urllib.request.urlopen(req) as f:
...     print(f.read().decode('utf-8'))
...
Got Data: "This data is passed to stdin of the CGI"
@end example

The code for the sample CGI used in the above example is:

@example
#!/usr/bin/env python
import sys
data = sys.stdin.read()
print('Content-type: text/plain\n\nGot Data: "%s"' % data)
@end example

Here is an example of doing a @code{PUT} request using @ref{8f0,,Request}:

@example
import urllib.request
DATA = b'some data'
req = urllib.request.Request(url='http://localhost:8080', data=DATA,method='PUT')
with urllib.request.urlopen(req) as f:
    pass
print(f.status)
print(f.reason)
@end example

Use of Basic HTTP Authentication:

@example
import urllib.request
# Create an OpenerDirector with support for Basic HTTP Authentication...
auth_handler = urllib.request.HTTPBasicAuthHandler()
auth_handler.add_password(realm='PDQ Application',
                          uri='https://mahler:8092/site-updates.py',
                          user='klem',
                          passwd='kadidd!ehopper')
opener = urllib.request.build_opener(auth_handler)
# ...and install it globally so it can be used with urlopen.
urllib.request.install_opener(opener)
urllib.request.urlopen('http://www.example.com/login.html')
@end example

@ref{2bd8,,build_opener()} provides many handlers by default, including a
@ref{f0a,,ProxyHandler}.  By default, @ref{f0a,,ProxyHandler} uses the environment
variables named @code{<scheme>_proxy}, where @code{<scheme>} is the URL scheme
involved.  For example, the 
@geindex http_proxy
@geindex 环境变量; http_proxy
@code{http_proxy} environment variable is read to
obtain the HTTP proxy's URL.

This example replaces the default @ref{f0a,,ProxyHandler} with one that uses
programmatically-supplied proxy URLs, and adds proxy authorization support with
@ref{2beb,,ProxyBasicAuthHandler}.

@example
proxy_handler = urllib.request.ProxyHandler(@{'http': 'http://www.example.com:3128/'@})
proxy_auth_handler = urllib.request.ProxyBasicAuthHandler()
proxy_auth_handler.add_password('realm', 'host', 'username', 'password')

opener = urllib.request.build_opener(proxy_handler, proxy_auth_handler)
# This time, rather than install the OpenerDirector, we use it directly:
opener.open('http://www.example.com/login.html')
@end example

Adding HTTP headers:

Use the @emph{headers} argument to the @ref{8f0,,Request} constructor, or:

@example
import urllib.request
req = urllib.request.Request('http://www.example.com/')
req.add_header('Referer', 'http://www.python.org/')
# Customize the default User-Agent header value:
req.add_header('User-Agent', 'urllib-example/0.1 (Contact: . . .)')
r = urllib.request.urlopen(req)
@end example

@ref{2bd5,,OpenerDirector} automatically adds a @code{User-Agent} header to
every @ref{8f0,,Request}.  To change this:

@example
import urllib.request
opener = urllib.request.build_opener()
opener.addheaders = [('User-agent', 'Mozilla/5.0')]
opener.open('http://www.example.com/')
@end example

Also, remember that a few standard headers (@code{Content-Length},
@code{Content-Type} and @code{Host})
are added when the @ref{8f0,,Request} is passed to @ref{786,,urlopen()} (or
@ref{8f4,,OpenerDirector.open()}).
@anchor{library/urllib request urllib-examples}@anchor{2c4f}
Here is an example session that uses the @code{GET} method to retrieve a URL
containing parameters:

@example
>>> import urllib.request
>>> import urllib.parse
>>> params = urllib.parse.urlencode(@{'spam': 1, 'eggs': 2, 'bacon': 0@})
>>> url = "http://www.musi-cal.com/cgi-bin/query?%s" % params
>>> with urllib.request.urlopen(url) as f:
...     print(f.read().decode('utf-8'))
...
@end example

The following example uses the @code{POST} method instead. Note that params output
from urlencode is encoded to bytes before it is sent to urlopen as data:

@example
>>> import urllib.request
>>> import urllib.parse
>>> data = urllib.parse.urlencode(@{'spam': 1, 'eggs': 2, 'bacon': 0@})
>>> data = data.encode('ascii')
>>> with urllib.request.urlopen("http://requestb.in/xrbl82xr", data) as f:
...     print(f.read().decode('utf-8'))
...
@end example

The following example uses an explicitly specified HTTP proxy, overriding
environment settings:

@example
>>> import urllib.request
>>> proxies = @{'http': 'http://proxy.example.com:8080/'@}
>>> opener = urllib.request.FancyURLopener(proxies)
>>> with opener.open("http://www.python.org") as f:
...     f.read().decode('utf-8')
...
@end example

The following example uses no proxies at all, overriding environment settings:

@example
>>> import urllib.request
>>> opener = urllib.request.FancyURLopener(@{@})
>>> with opener.open("http://www.python.org/") as f:
...     f.read().decode('utf-8')
...
@end example

@node Legacy interface,urllib request Restrictions,例子<21>,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request legacy-interface}@anchor{2c50}
@subsubsection Legacy interface


The following functions and classes are ported from the Python 2 module
@code{urllib} (as opposed to @code{urllib2}).  They might become deprecated at
some point in the future.

@geindex urlretrieve() (在 urllib.request 模块中)
@anchor{library/urllib request urllib request urlretrieve}@anchor{2c51}
@deffn {函数} urllib.request.urlretrieve (url, filename=None, reporthook=None, data=None)

Copy a network object denoted by a URL to a local file. If the URL
points to a local file, the object will not be copied unless filename is supplied.
Return a tuple @code{(filename, headers)} where @emph{filename} is the
local file name under which the object can be found, and @emph{headers} is whatever
the @code{info()} method of the object returned by @ref{786,,urlopen()} returned (for
a remote object). Exceptions are the same as for @ref{786,,urlopen()}.

The second argument, if present, specifies the file location to copy to (if
absent, the location will be a tempfile with a generated name). The third
argument, if present, is a callable that will be called once on
establishment of the network connection and once after each block read
thereafter.  The callable will be passed three arguments; a count of blocks
transferred so far, a block size in bytes, and the total size of the file.  The
third argument may be @code{-1} on older FTP servers which do not return a file
size in response to a retrieval request.

The following example illustrates the most common usage scenario:

@example
>>> import urllib.request
>>> local_filename, headers = urllib.request.urlretrieve('http://python.org/')
>>> html = open(local_filename)
>>> html.close()
@end example

If the @emph{url} uses the @code{http:} scheme identifier, the optional @emph{data}
argument may be given to specify a @code{POST} request (normally the request
type is @code{GET}).  The @emph{data} argument must be a bytes object in standard
@code{application/x-www-form-urlencoded} format; see the
@ref{785,,urllib.parse.urlencode()} function.

@ref{2c51,,urlretrieve()} will raise @code{ContentTooShortError} when it detects that
the amount of data available  was less than the expected amount (which is the
size reported by a  @emph{Content-Length} header). This can occur, for example, when
the  download is interrupted.

The @emph{Content-Length} is treated as a lower bound: if there's more data  to read,
urlretrieve reads more data, but if less data is available,  it raises the
exception.

You can still retrieve the downloaded data in this case, it is stored  in the
@code{content} attribute of the exception instance.

If no @emph{Content-Length} header was supplied, urlretrieve can not check the size
of the data it has downloaded, and just returns it.  In this case you just have
to assume that the download was successful.
@end deffn

@geindex urlcleanup() (在 urllib.request 模块中)
@anchor{library/urllib request urllib request urlcleanup}@anchor{2c52}
@deffn {函数} urllib.request.urlcleanup ()

Cleans up temporary files that may have been left behind by previous
calls to @ref{2c51,,urlretrieve()}.
@end deffn

@geindex URLopener (urllib.request 中的类)
@anchor{library/urllib request urllib request URLopener}@anchor{2bd2}
@deffn {类} urllib.request.URLopener (proxies=None, **x509)


3.3 版后已移除.


Base class for opening and reading URLs.  Unless you need to support opening
objects using schemes other than @code{http:}, @code{ftp:}, or @code{file:},
you probably want to use @ref{2bd3,,FancyURLopener}.

By default, the @ref{2bd2,,URLopener} class sends a @code{User-Agent} header
of @code{urllib/VVV}, where @emph{VVV} is the @ref{11d,,urllib} version number.
Applications can define their own @code{User-Agent} header by subclassing
@ref{2bd2,,URLopener} or @ref{2bd3,,FancyURLopener} and setting the class attribute
@ref{2c53,,version} to an appropriate string value in the subclass definition.

The optional @emph{proxies} parameter should be a dictionary mapping scheme names to
proxy URLs, where an empty dictionary turns proxies off completely.  Its default
value is @code{None}, in which case environmental proxy settings will be used if
present, as discussed in the definition of @ref{786,,urlopen()}, above.

Additional keyword parameters, collected in @emph{x509}, may be used for
authentication of the client when using the @code{https:} scheme.  The keywords
@emph{key_file} and @emph{cert_file} are supported to provide an  SSL key and certificate;
both are needed to support client authentication.

@ref{2bd2,,URLopener} objects will raise an @ref{1d3,,OSError} exception if the server
returns an error code.

@geindex open() (urllib.request.URLopener 方法)
@anchor{library/urllib request urllib request URLopener open}@anchor{2c54}
@deffn {方法} open (fullurl, data=None)

Open @emph{fullurl} using the appropriate protocol.  This method sets up cache and
proxy information, then calls the appropriate open method with its input
arguments.  If the scheme is not recognized, @ref{2c55,,open_unknown()} is called.
The @emph{data} argument has the same meaning as the @emph{data} argument of
@ref{786,,urlopen()}.

This method always quotes @emph{fullurl} using @ref{405,,quote()}.
@end deffn

@geindex open_unknown() (urllib.request.URLopener 方法)
@anchor{library/urllib request urllib request URLopener open_unknown}@anchor{2c55}
@deffn {方法} open_unknown (fullurl, data=None)

Overridable interface to open unknown URL types.
@end deffn

@geindex retrieve() (urllib.request.URLopener 方法)
@anchor{library/urllib request urllib request URLopener retrieve}@anchor{f58}
@deffn {方法} retrieve (url, filename=None, reporthook=None, data=None)

Retrieves the contents of @emph{url} and places it in @emph{filename}.  The return value
is a tuple consisting of a local filename and either an
@ref{53c,,email.message.Message} object containing the response headers (for remote
URLs) or @code{None} (for local URLs).  The caller must then open and read the
contents of @emph{filename}.  If @emph{filename} is not given and the URL refers to a
local file, the input filename is returned.  If the URL is non-local and
@emph{filename} is not given, the filename is the output of @ref{1c06,,tempfile.mktemp()}
with a suffix that matches the suffix of the last path component of the input
URL.  If @emph{reporthook} is given, it must be a function accepting three numeric
parameters: A chunk number, the maximum size chunks are read in and the total size of the download
(-1 if unknown).  It will be called once at the start and after each chunk of data is read from the
network.  @emph{reporthook} is ignored for local URLs.

If the @emph{url} uses the @code{http:} scheme identifier, the optional @emph{data}
argument may be given to specify a @code{POST} request (normally the request type
is @code{GET}).  The @emph{data} argument must in standard
@code{application/x-www-form-urlencoded} format; see the
@ref{785,,urllib.parse.urlencode()} function.
@end deffn

@geindex version (urllib.request.URLopener 属性)
@anchor{library/urllib request urllib request URLopener version}@anchor{2c53}
@deffn {属性} version

Variable that specifies the user agent of the opener object.  To get
@ref{11d,,urllib} to tell servers that it is a particular user agent, set this in a
subclass as a class variable or in the constructor before calling the base
constructor.
@end deffn
@end deffn

@geindex FancyURLopener (urllib.request 中的类)
@anchor{library/urllib request urllib request FancyURLopener}@anchor{2bd3}
@deffn {类} urllib.request.FancyURLopener (...)


3.3 版后已移除.


@ref{2bd3,,FancyURLopener} subclasses @ref{2bd2,,URLopener} providing default handling
for the following HTTP response codes: 301, 302, 303, 307 and 401.  For the 30x
response codes listed above, the @code{Location} header is used to fetch
the actual URL.  For 401 response codes (authentication required), basic HTTP
authentication is performed.  For the 30x response codes, recursion is bounded
by the value of the @emph{maxtries} attribute, which defaults to 10.

For all other response codes, the method @code{http_error_default()} is called
which you can override in subclasses to handle the error appropriately.

@cartouche
@quotation 注解 
According to the letter of 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html}, 301 and 302 responses to POST requests
must not be automatically redirected without confirmation by the user.  In
reality, browsers do allow automatic redirection of these responses, changing
the POST to a GET, and @ref{11d,,urllib} reproduces this behaviour.
@end quotation
@end cartouche

The parameters to the constructor are the same as those for @ref{2bd2,,URLopener}.

@cartouche
@quotation 注解 
When performing basic authentication, a @ref{2bd3,,FancyURLopener} instance calls
its @ref{2c56,,prompt_user_passwd()} method.  The default implementation asks the
users for the required information on the controlling terminal.  A subclass may
override this method to support more appropriate behavior if needed.
@end quotation
@end cartouche

The @ref{2bd3,,FancyURLopener} class offers one additional method that should be
overloaded to provide the appropriate behavior:

@geindex prompt_user_passwd() (urllib.request.FancyURLopener 方法)
@anchor{library/urllib request urllib request FancyURLopener prompt_user_passwd}@anchor{2c56}
@deffn {方法} prompt_user_passwd (host, realm)

Return information needed to authenticate the user at the given host in the
specified security realm.  The return value should be a tuple, @code{(user,
password)}, which can be used for basic authentication.

The implementation prompts for this information on the terminal; an application
should override this method to use an appropriate interaction model in the local
environment.
@end deffn
@end deffn

@node urllib request Restrictions,,Legacy interface,urllib request --- 用于打开 URL 的可扩展库
@anchor{library/urllib request urllib-request-restrictions}@anchor{2c57}
@subsubsection @code{urllib.request} Restrictions


@quotation

@geindex HTTP; protocol
@geindex FTP; protocol
@end quotation


@itemize *

@item 
Currently, only the following protocols are supported: HTTP (versions 0.9 and
1.0), FTP, local files, and data URLs.


在 3.4 版更改: Added support for data URLs.


@item 
The caching feature of @ref{2c51,,urlretrieve()} has been disabled until someone
finds the time to hack proper processing of Expiration time headers.

@item 
There should be a function to query whether a particular URL is in the cache.

@item 
For backward compatibility, if a URL appears to point to a local file but the
file can't be opened, the URL is re-interpreted using the FTP protocol.  This
can sometimes cause confusing error messages.

@item 
The @ref{786,,urlopen()} and @ref{2c51,,urlretrieve()} functions can cause arbitrarily
long delays while waiting for a network connection to be set up.  This means
that it is difficult to build an interactive Web client using these functions
without using threads.

@geindex HTML
@geindex HTTP; protocol

@item 
The data returned by @ref{786,,urlopen()} or @ref{2c51,,urlretrieve()} is the raw data
returned by the server.  This may be binary data (such as an image), plain text
or (for example) HTML.  The HTTP protocol provides type information in the reply
header, which can be inspected by looking at the @code{Content-Type}
header.  If the returned data is HTML, you can use the module
@ref{92,,html.parser} to parse it.

@geindex FTP

@item 
The code handling the FTP protocol cannot differentiate between a file and a
directory.  This can lead to unexpected behavior when attempting to read a URL
that points to a file that is not accessible.  If the URL ends in a @code{/}, it is
assumed to refer to a directory and will be handled accordingly.  But if an
attempt to read a file leads to a 550 error (meaning the URL cannot be found or
is not accessible, often for permission reasons), then the path is treated as a
directory in order to handle the case when a directory is specified by a URL but
the trailing @code{/} has been left off.  This can cause misleading results when
you try to fetch a file whose read permissions make it inaccessible; the FTP
code will try to read it, fail with a 550 error, and then perform a directory
listing for the unreadable file. If fine-grained control is needed, consider
using the @ref{84,,ftplib} module, subclassing @ref{2bd3,,FancyURLopener}, or changing
@emph{_urlopener} to meet your needs.
@end itemize

@node urllib response --- urllib 使用的 Response 类,urllib parse --- Parse URLs into components,urllib request --- 用于打开 URL 的可扩展库,互联网协议和支持
@anchor{library/urllib request module-urllib response}@anchor{121}@anchor{library/urllib request urllib-response-response-classes-used-by-urllib}@anchor{2c58}
@subsection @code{urllib.response} --- urllib 使用的 Response 类


@geindex urllib.response (模块)

The @ref{121,,urllib.response} module defines functions and classes which define a
minimal file like interface, including @code{read()} and @code{readline()}. The
typical response object is an addinfourl instance, which defines an @code{info()}
method and that returns headers and a @code{geturl()} method that returns the url.
Functions defined by this module are used internally by the
@ref{120,,urllib.request} module.

@node urllib parse --- Parse URLs into components,urllib error --- urllib request 引发的异常类,urllib response --- urllib 使用的 Response 类,互联网协议和支持
@anchor{library/urllib parse doc}@anchor{2c59}@anchor{library/urllib parse module-urllib parse}@anchor{11f}@anchor{library/urllib parse urllib-parse-parse-urls-into-components}@anchor{2c5a}
@subsection @code{urllib.parse} --- Parse URLs into components


@geindex urllib.parse (模块)

@strong{源代码:} Lib/urllib/parse.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/urllib/parse.py}

@geindex WWW
@geindex World Wide Web
@geindex URL
@geindex URL; parsing
@geindex relative; URL


__________________________________________________________________


This module defines a standard interface to break Uniform Resource Locator (URL)
strings up in components (addressing scheme, network location, path etc.), to
combine the components back into a URL string, and to convert a "relative URL"
to an absolute URL given a "base URL."

The module has been designed to match the Internet RFC on Relative Uniform
Resource Locators. It supports the following URL schemes: @code{file}, @code{ftp},
@code{gopher}, @code{hdl}, @code{http}, @code{https}, @code{imap}, @code{mailto}, @code{mms},
@code{news}, @code{nntp}, @code{prospero}, @code{rsync}, @code{rtsp}, @code{rtspu}, @code{sftp},
@code{shttp}, @code{sip}, @code{sips}, @code{snews}, @code{svn}, @code{svn+ssh}, @code{telnet},
@code{wais}, @code{ws}, @code{wss}.

The @ref{11f,,urllib.parse} module defines functions that fall into two broad
categories: URL parsing and URL quoting. These are covered in detail in
the following sections.

@menu
* URL 解析:: 
* 解析ASCII编码字节:: 
* 结构化解析结果:: 
* URL Quoting:: 

@end menu

@node URL 解析,解析ASCII编码字节,,urllib parse --- Parse URLs into components
@anchor{library/urllib parse url-parsing}@anchor{2c5b}
@subsubsection URL 解析


The URL parsing functions focus on splitting a URL string into its components,
or on combining URL components into a URL string.

@geindex urlparse() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse urlparse}@anchor{5f5}
@deffn {函数} urllib.parse.urlparse (urlstring, scheme='@w{'}, allow_fragments=True)

Parse a URL into six components, returning a 6-item @ref{a9e,,named tuple}.  This
corresponds to the general structure of a URL:
@code{scheme://netloc/path;parameters?query#fragment}.
Each tuple item is a string, possibly empty. The components are not broken up in
smaller parts (for example, the network location is a single string), and %
escapes are not expanded. The delimiters as shown above are not part of the
result, except for a leading slash in the @emph{path} component, which is retained if
present.  For example:

@example
>>> from urllib.parse import urlparse
>>> o = urlparse('http://www.cwi.nl:80/%7Eguido/Python.html')
>>> o   
ParseResult(scheme='http', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
            params='@w{'}, query='@w{'}, fragment='@w{'})
>>> o.scheme
'http'
>>> o.port
80
>>> o.geturl()
'http://www.cwi.nl:80/%7Eguido/Python.html'
@end example

Following the syntax specifications in 
@geindex RFC; RFC 1808
RFC 1808@footnote{https://tools.ietf.org/html/rfc1808.html}, urlparse recognizes
a netloc only if it is properly introduced by '//'.  Otherwise the
input is presumed to be a relative URL and thus to start with
a path component.

@example
>>> from urllib.parse import urlparse
>>> urlparse('//www.cwi.nl:80/%7Eguido/Python.html')
ParseResult(scheme='@w{'}, netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
            params='@w{'}, query='@w{'}, fragment='@w{'})
>>> urlparse('www.cwi.nl/%7Eguido/Python.html')
ParseResult(scheme='@w{'}, netloc='@w{'}, path='www.cwi.nl/%7Eguido/Python.html',
            params='@w{'}, query='@w{'}, fragment='@w{'})
>>> urlparse('help/Python.html')
ParseResult(scheme='@w{'}, netloc='@w{'}, path='help/Python.html', params='@w{'},
            query='@w{'}, fragment='@w{'})
@end example

The @emph{scheme} argument gives the default addressing scheme, to be
used only if the URL does not specify one.  It should be the same type
(text or bytes) as @emph{urlstring}, except that the default value @code{'@w{'}} is
always allowed, and is automatically converted to @code{b'@w{'}} if appropriate.

If the @emph{allow_fragments} argument is false, fragment identifiers are not
recognized.  Instead, they are parsed as part of the path, parameters
or query component, and @code{fragment} is set to the empty string in
the return value.

The return value is a @ref{a9e,,named tuple}, which means that its items can
be accessed by index or as named attributes, which are:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性

@tab

索引

@tab

值

@tab

值（如果不存在）

@item

@code{scheme}

@tab

0

@tab

URL方案说明符

@tab

@emph{scheme} parameter

@item

@code{netloc}

@tab

1

@tab

网络位置部分

@tab

空字符串

@item

@code{path}

@tab

2

@tab

分层路径

@tab

空字符串

@item

@code{params}

@tab

3

@tab

最后路径元素的参数

@tab

空字符串

@item

@code{query}

@tab

4

@tab

查询组件

@tab

空字符串

@item

@code{fragment}

@tab

5

@tab

片段识别

@tab

空字符串

@item

@code{username}

@tab

@tab

用户名

@tab

@ref{157,,None}

@item

@code{password}

@tab

@tab

密码

@tab

@ref{157,,None}

@item

@code{hostname}

@tab

@tab

主机名（小写）

@tab

@ref{157,,None}

@item

@code{port}

@tab

@tab

端口号为整数（如果存在）

@tab

@ref{157,,None}

@end multitable


Reading the @code{port} attribute will raise a @ref{1fb,,ValueError} if
an invalid port is specified in the URL.  See section
@ref{2c5c,,结构化解析结果} for more information on the result object.

Unmatched square brackets in the @code{netloc} attribute will raise a
@ref{1fb,,ValueError}.

Characters in the @code{netloc} attribute that decompose under NFKC
normalization (as used by the IDNA encoding) into any of @code{/}, @code{?},
@code{#}, @code{@@}, or @code{:} will raise a @ref{1fb,,ValueError}. If the URL is
decomposed before parsing, no error will be raised.

As is the case with all named tuples, the subclass has a few additional methods
and attributes that are particularly useful. One such method is @code{_replace()}.
The @code{_replace()} method will return a new ParseResult object replacing specified
fields with new values.

@example
>>> from urllib.parse import urlparse
>>> u = urlparse('//www.cwi.nl:80/%7Eguido/Python.html')
>>> u
ParseResult(scheme='@w{'}, netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
            params='@w{'}, query='@w{'}, fragment='@w{'})
>>> u._replace(scheme='http')
ParseResult(scheme='http', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html',
            params='@w{'}, query='@w{'}, fragment='@w{'})
@end example


在 3.2 版更改: 添加了IPv6 URL解析功能。



在 3.3 版更改: The fragment is now parsed for all URL schemes (unless @emph{allow_fragment} is
false), in accordance with 
@geindex RFC; RFC 3986
RFC 3986@footnote{https://tools.ietf.org/html/rfc3986.html}.  Previously, a whitelist of
schemes that support fragments existed.



在 3.6 版更改: Out-of-range port numbers now raise @ref{1fb,,ValueError}, instead of
returning @ref{157,,None}.



在 3.8 版更改: Characters that affect netloc parsing under NFKC normalization will
now raise @ref{1fb,,ValueError}.

@end deffn

@geindex parse_qs() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse parse_qs}@anchor{2b84}
@deffn {函数} urllib.parse.parse_qs (qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None)

Parse a query string given as a string argument (data of type
@code{application/x-www-form-urlencoded}).  Data are returned as a
dictionary.  The dictionary keys are the unique query variable names and the
values are lists of values for each name.

The optional argument @emph{keep_blank_values} is a flag indicating whether blank
values in percent-encoded queries should be treated as blank strings. A true value
indicates that blanks should be retained as  blank strings.  The default false
value indicates that blank values are to be ignored and treated as if they were
not included.

The optional argument @emph{strict_parsing} is a flag indicating what to do with
parsing errors.  If false (the default), errors are silently ignored.  If true,
errors raise a @ref{1fb,,ValueError} exception.

The optional @emph{encoding} and @emph{errors} parameters specify how to decode
percent-encoded sequences into Unicode characters, as accepted by the
@ref{c31,,bytes.decode()} method.

The optional argument @emph{max_num_fields} is the maximum number of fields to
read. If set, then throws a @ref{1fb,,ValueError} if there are more than
@emph{max_num_fields} fields read.

Use the @ref{785,,urllib.parse.urlencode()} function (with the @code{doseq}
parameter set to @code{True}) to convert such dictionaries into query
strings.


在 3.2 版更改: Add @emph{encoding} and @emph{errors} parameters.



在 3.8 版更改: Added @emph{max_num_fields} parameter.

@end deffn

@geindex parse_qsl() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse parse_qsl}@anchor{2c5d}
@deffn {函数} urllib.parse.parse_qsl (qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None)

Parse a query string given as a string argument (data of type
@code{application/x-www-form-urlencoded}).  Data are returned as a list of
name, value pairs.

The optional argument @emph{keep_blank_values} is a flag indicating whether blank
values in percent-encoded queries should be treated as blank strings. A true value
indicates that blanks should be retained as  blank strings.  The default false
value indicates that blank values are to be ignored and treated as if they were
not included.

The optional argument @emph{strict_parsing} is a flag indicating what to do with
parsing errors.  If false (the default), errors are silently ignored.  If true,
errors raise a @ref{1fb,,ValueError} exception.

The optional @emph{encoding} and @emph{errors} parameters specify how to decode
percent-encoded sequences into Unicode characters, as accepted by the
@ref{c31,,bytes.decode()} method.

The optional argument @emph{max_num_fields} is the maximum number of fields to
read. If set, then throws a @ref{1fb,,ValueError} if there are more than
@emph{max_num_fields} fields read.

Use the @ref{785,,urllib.parse.urlencode()} function to convert such lists of pairs into
query strings.


在 3.2 版更改: Add @emph{encoding} and @emph{errors} parameters.



在 3.8 版更改: Added @emph{max_num_fields} parameter.

@end deffn

@geindex urlunparse() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse urlunparse}@anchor{2c5e}
@deffn {函数} urllib.parse.urlunparse (parts)

Construct a URL from a tuple as returned by @code{urlparse()}. The @emph{parts}
argument can be any six-item iterable. This may result in a slightly
different, but equivalent URL, if the URL that was parsed originally had
unnecessary delimiters (for example, a @code{?} with an empty query; the RFC
states that these are equivalent).
@end deffn

@geindex urlsplit() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse urlsplit}@anchor{5f4}
@deffn {函数} urllib.parse.urlsplit (urlstring, scheme='@w{'}, allow_fragments=True)

This is similar to @ref{5f5,,urlparse()}, but does not split the params from the URL.
This should generally be used instead of @ref{5f5,,urlparse()} if the more recent URL
syntax allowing parameters to be applied to each segment of the @emph{path} portion
of the URL (see 
@geindex RFC; RFC 2396
RFC 2396@footnote{https://tools.ietf.org/html/rfc2396.html}) is wanted.  A separate function is needed to
separate the path segments and parameters.  This function returns a 5-item
@ref{a9e,,named tuple}:

@example
(addressing scheme, network location, path, query, fragment identifier).
@end example

The return value is a @ref{a9e,,named tuple}, its items can be accessed by index
or as named attributes:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性

@tab

索引

@tab

值

@tab

值（如果不存在）

@item

@code{scheme}

@tab

0

@tab

URL方案说明符

@tab

@emph{scheme} parameter

@item

@code{netloc}

@tab

1

@tab

网络位置部分

@tab

空字符串

@item

@code{path}

@tab

2

@tab

分层路径

@tab

空字符串

@item

@code{query}

@tab

3

@tab

查询组件

@tab

空字符串

@item

@code{fragment}

@tab

4

@tab

片段识别

@tab

空字符串

@item

@code{username}

@tab

@tab

用户名

@tab

@ref{157,,None}

@item

@code{password}

@tab

@tab

密码

@tab

@ref{157,,None}

@item

@code{hostname}

@tab

@tab

主机名（小写）

@tab

@ref{157,,None}

@item

@code{port}

@tab

@tab

端口号为整数（如果存在）

@tab

@ref{157,,None}

@end multitable


Reading the @code{port} attribute will raise a @ref{1fb,,ValueError} if
an invalid port is specified in the URL.  See section
@ref{2c5c,,结构化解析结果} for more information on the result object.

Unmatched square brackets in the @code{netloc} attribute will raise a
@ref{1fb,,ValueError}.

Characters in the @code{netloc} attribute that decompose under NFKC
normalization (as used by the IDNA encoding) into any of @code{/}, @code{?},
@code{#}, @code{@@}, or @code{:} will raise a @ref{1fb,,ValueError}. If the URL is
decomposed before parsing, no error will be raised.


在 3.6 版更改: Out-of-range port numbers now raise @ref{1fb,,ValueError}, instead of
returning @ref{157,,None}.



在 3.8 版更改: Characters that affect netloc parsing under NFKC normalization will
now raise @ref{1fb,,ValueError}.

@end deffn

@geindex urlunsplit() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse urlunsplit}@anchor{2c5f}
@deffn {函数} urllib.parse.urlunsplit (parts)

Combine the elements of a tuple as returned by @ref{5f4,,urlsplit()} into a
complete URL as a string. The @emph{parts} argument can be any five-item
iterable. This may result in a slightly different, but equivalent URL, if the
URL that was parsed originally had unnecessary delimiters (for example, a ?
with an empty query; the RFC states that these are equivalent).
@end deffn

@geindex urljoin() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse urljoin}@anchor{787}
@deffn {函数} urllib.parse.urljoin (base, url, allow_fragments=True)

Construct a full ("absolute") URL by combining a "base URL" (@emph{base}) with
another URL (@emph{url}).  Informally, this uses components of the base URL, in
particular the addressing scheme, the network location and (part of) the
path, to provide missing components in the relative URL.  For example:

@example
>>> from urllib.parse import urljoin
>>> urljoin('http://www.cwi.nl/%7Eguido/Python.html', 'FAQ.html')
'http://www.cwi.nl/%7Eguido/FAQ.html'
@end example

The @emph{allow_fragments} argument has the same meaning and default as for
@ref{5f5,,urlparse()}.

@cartouche
@quotation 注解 
If @emph{url} is an absolute URL (that is, starting with @code{//} or @code{scheme://}),
the @emph{url}'s host name and/or scheme will be present in the result.  For example:
@end quotation
@end cartouche

@example
>>> urljoin('http://www.cwi.nl/%7Eguido/Python.html',
...         '//www.python.org/%7Eguido')
'http://www.python.org/%7Eguido'
@end example

If you do not want that behavior, preprocess the @emph{url} with @ref{5f4,,urlsplit()} and
@ref{2c5f,,urlunsplit()}, removing possible @emph{scheme} and @emph{netloc} parts.


在 3.5 版更改: Behaviour updated to match the semantics defined in 
@geindex RFC; RFC 3986
RFC 3986@footnote{https://tools.ietf.org/html/rfc3986.html}.

@end deffn

@geindex urldefrag() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse urldefrag}@anchor{bd7}
@deffn {函数} urllib.parse.urldefrag (url)

If @emph{url} contains a fragment identifier, return a modified version of @emph{url}
with no fragment identifier, and the fragment identifier as a separate
string.  If there is no fragment identifier in @emph{url}, return @emph{url} unmodified
and an empty string.

The return value is a @ref{a9e,,named tuple}, its items can be accessed by index
or as named attributes:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性

@tab

索引

@tab

值

@tab

值（如果不存在）

@item

@code{url}

@tab

0

@tab

URL with no fragment

@tab

空字符串

@item

@code{fragment}

@tab

1

@tab

片段识别

@tab

空字符串

@end multitable


See section @ref{2c5c,,结构化解析结果} for more information on the result
object.


在 3.2 版更改: Result is a structured object rather than a simple 2-tuple.

@end deffn

@geindex unwrap() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse unwrap}@anchor{2c60}
@deffn {函数} urllib.parse.unwrap (url)

Extract the url from a wrapped URL (that is, a string formatted as
@code{<URL:scheme://host/path>}, @code{<scheme://host/path>}, @code{URL:scheme://host/path}
or @code{scheme://host/path}). If @emph{url} is not a wrapped URL, it is returned
without changes.
@end deffn

@node 解析ASCII编码字节,结构化解析结果,URL 解析,urllib parse --- Parse URLs into components
@anchor{library/urllib parse id1}@anchor{2c61}@anchor{library/urllib parse parsing-ascii-encoded-bytes}@anchor{bd9}
@subsubsection 解析ASCII编码字节


The URL parsing functions were originally designed to operate on character
strings only. In practice, it is useful to be able to manipulate properly
quoted and encoded URLs as sequences of ASCII bytes. Accordingly, the
URL parsing functions in this module all operate on @ref{32a,,bytes} and
@ref{32b,,bytearray} objects in addition to @ref{329,,str} objects.

If @ref{329,,str} data is passed in, the result will also contain only
@ref{329,,str} data. If @ref{32a,,bytes} or @ref{32b,,bytearray} data is
passed in, the result will contain only @ref{32a,,bytes} data.

Attempting to mix @ref{329,,str} data with @ref{32a,,bytes} or
@ref{32b,,bytearray} in a single function call will result in a
@ref{192,,TypeError} being raised, while attempting to pass in non-ASCII
byte values will trigger @ref{1fd,,UnicodeDecodeError}.

To support easier conversion of result objects between @ref{329,,str} and
@ref{32a,,bytes}, all return values from URL parsing functions provide
either an @code{encode()} method (when the result contains @ref{329,,str}
data) or a @code{decode()} method (when the result contains @ref{32a,,bytes}
data). The signatures of these methods match those of the corresponding
@ref{329,,str} and @ref{32a,,bytes} methods (except that the default encoding
is @code{'ascii'} rather than @code{'utf-8'}). Each produces a value of a
corresponding type that contains either @ref{32a,,bytes} data (for
@code{encode()} methods) or @ref{329,,str} data (for
@code{decode()} methods).

Applications that need to operate on potentially improperly quoted URLs
that may contain non-ASCII data will need to do their own decoding from
bytes to characters before invoking the URL parsing methods.

The behaviour described in this section applies only to the URL parsing
functions. The URL quoting functions use their own rules when producing
or consuming byte sequences as detailed in the documentation of the
individual URL quoting functions.


在 3.2 版更改: URL parsing functions now accept ASCII encoded byte sequences


@node 结构化解析结果,URL Quoting,解析ASCII编码字节,urllib parse --- Parse URLs into components
@anchor{library/urllib parse structured-parse-results}@anchor{2c62}@anchor{library/urllib parse urlparse-result-object}@anchor{2c5c}
@subsubsection 结构化解析结果


The result objects from the @ref{5f5,,urlparse()}, @ref{5f4,,urlsplit()}  and
@ref{bd7,,urldefrag()} functions are subclasses of the @ref{478,,tuple} type.
These subclasses add the attributes listed in the documentation for
those functions, the encoding and decoding support described in the
previous section, as well as an additional method:

@geindex geturl() (urllib.parse.urllib.parse.SplitResult 方法)
@anchor{library/urllib parse urllib parse urllib parse SplitResult geturl}@anchor{2c63}
@deffn {方法} urllib.parse.SplitResult.geturl ()

Return the re-combined version of the original URL as a string. This may
differ from the original URL in that the scheme may be normalized to lower
case and empty components may be dropped. Specifically, empty parameters,
queries, and fragment identifiers will be removed.

For @ref{bd7,,urldefrag()} results, only empty fragment identifiers will be removed.
For @ref{5f4,,urlsplit()} and @ref{5f5,,urlparse()} results, all noted changes will be
made to the URL returned by this method.

The result of this method remains unchanged if passed back through the original
parsing function:

@example
>>> from urllib.parse import urlsplit
>>> url = 'HTTP://www.Python.org/doc/#'
>>> r1 = urlsplit(url)
>>> r1.geturl()
'http://www.Python.org/doc/'
>>> r2 = urlsplit(r1.geturl())
>>> r2.geturl()
'http://www.Python.org/doc/'
@end example
@end deffn

The following classes provide the implementations of the structured parse
results when operating on @ref{329,,str} objects:

@geindex DefragResult (urllib.parse 中的类)
@anchor{library/urllib parse urllib parse DefragResult}@anchor{2c64}
@deffn {类} urllib.parse.DefragResult (url, fragment)

Concrete class for @ref{bd7,,urldefrag()} results containing @ref{329,,str}
data. The @code{encode()} method returns a @ref{2c65,,DefragResultBytes}
instance.


3.2 新版功能.

@end deffn

@geindex ParseResult (urllib.parse 中的类)
@anchor{library/urllib parse urllib parse ParseResult}@anchor{2c66}
@deffn {类} urllib.parse.ParseResult (scheme, netloc, path, params, query, fragment)

Concrete class for @ref{5f5,,urlparse()} results containing @ref{329,,str}
data. The @code{encode()} method returns a @ref{2c67,,ParseResultBytes}
instance.
@end deffn

@geindex SplitResult (urllib.parse 中的类)
@anchor{library/urllib parse urllib parse SplitResult}@anchor{2c68}
@deffn {类} urllib.parse.SplitResult (scheme, netloc, path, query, fragment)

Concrete class for @ref{5f4,,urlsplit()} results containing @ref{329,,str}
data. The @code{encode()} method returns a @ref{2c69,,SplitResultBytes}
instance.
@end deffn

The following classes provide the implementations of the parse results when
operating on @ref{32a,,bytes} or @ref{32b,,bytearray} objects:

@geindex DefragResultBytes (urllib.parse 中的类)
@anchor{library/urllib parse urllib parse DefragResultBytes}@anchor{2c65}
@deffn {类} urllib.parse.DefragResultBytes (url, fragment)

Concrete class for @ref{bd7,,urldefrag()} results containing @ref{32a,,bytes}
data. The @code{decode()} method returns a @ref{2c64,,DefragResult}
instance.


3.2 新版功能.

@end deffn

@geindex ParseResultBytes (urllib.parse 中的类)
@anchor{library/urllib parse urllib parse ParseResultBytes}@anchor{2c67}
@deffn {类} urllib.parse.ParseResultBytes (scheme, netloc, path, params, query, fragment)

Concrete class for @ref{5f5,,urlparse()} results containing @ref{32a,,bytes}
data. The @code{decode()} method returns a @ref{2c66,,ParseResult}
instance.


3.2 新版功能.

@end deffn

@geindex SplitResultBytes (urllib.parse 中的类)
@anchor{library/urllib parse urllib parse SplitResultBytes}@anchor{2c69}
@deffn {类} urllib.parse.SplitResultBytes (scheme, netloc, path, query, fragment)

Concrete class for @ref{5f4,,urlsplit()} results containing @ref{32a,,bytes}
data. The @code{decode()} method returns a @ref{2c68,,SplitResult}
instance.


3.2 新版功能.

@end deffn

@node URL Quoting,,结构化解析结果,urllib parse --- Parse URLs into components
@anchor{library/urllib parse url-quoting}@anchor{2c6a}
@subsubsection URL Quoting


The URL quoting functions focus on taking program data and making it safe
for use as URL components by quoting special characters and appropriately
encoding non-ASCII text. They also support reversing these operations to
recreate the original data from the contents of a URL component if that
task isn't already covered by the URL parsing functions above.

@geindex quote() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse quote}@anchor{405}
@deffn {函数} urllib.parse.quote (string, safe='/', encoding=None, errors=None)

Replace special characters in @emph{string} using the @code{%xx} escape. Letters,
digits, and the characters @code{'_.-~'} are never quoted. By default, this
function is intended for quoting the path section of URL. The optional @emph{safe}
parameter specifies additional ASCII characters that should not be quoted
--- its default value is @code{'/'}.

@emph{string} may be either a @ref{329,,str} or a @ref{32a,,bytes}.


在 3.7 版更改: Moved from 
@geindex RFC; RFC 2396
RFC 2396@footnote{https://tools.ietf.org/html/rfc2396.html} to 
@geindex RFC; RFC 3986
RFC 3986@footnote{https://tools.ietf.org/html/rfc3986.html} for quoting URL strings. "~" is now
included in the set of unreserved characters.


The optional @emph{encoding} and @emph{errors} parameters specify how to deal with
non-ASCII characters, as accepted by the @ref{c30,,str.encode()} method.
@emph{encoding} defaults to @code{'utf-8'}.
@emph{errors} defaults to @code{'strict'}, meaning unsupported characters raise a
@ref{1fc,,UnicodeEncodeError}.
@emph{encoding} and @emph{errors} must not be supplied if @emph{string} is a
@ref{32a,,bytes}, or a @ref{192,,TypeError} is raised.

Note that @code{quote(string, safe, encoding, errors)} is equivalent to
@code{quote_from_bytes(string.encode(encoding, errors), safe)}.

Example: @code{quote('/El Niño/')} yields @code{'/El%20Ni%C3%B1o/'}.
@end deffn

@geindex quote_plus() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse quote_plus}@anchor{bd8}
@deffn {函数} urllib.parse.quote_plus (string, safe='@w{'}, encoding=None, errors=None)

Like @ref{405,,quote()}, but also replace spaces by plus signs, as required for
quoting HTML form values when building up a query string to go into a URL.
Plus signs in the original string are escaped unless they are included in
@emph{safe}.  It also does not have @emph{safe} default to @code{'/'}.

Example: @code{quote_plus('/El Niño/')} yields @code{'%2FEl+Ni%C3%B1o%2F'}.
@end deffn

@geindex quote_from_bytes() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse quote_from_bytes}@anchor{2c6b}
@deffn {函数} urllib.parse.quote_from_bytes (bytes, safe='/')

Like @ref{405,,quote()}, but accepts a @ref{32a,,bytes} object rather than a
@ref{329,,str}, and does not perform string-to-bytes encoding.

Example: @code{quote_from_bytes(b'a&\xef')} yields
@code{'a%26%EF'}.
@end deffn

@geindex unquote() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse unquote}@anchor{2be2}
@deffn {函数} urllib.parse.unquote (string, encoding='utf-8', errors='replace')

Replace @code{%xx} escapes by their single-character equivalent.
The optional @emph{encoding} and @emph{errors} parameters specify how to decode
percent-encoded sequences into Unicode characters, as accepted by the
@ref{c31,,bytes.decode()} method.

@emph{string} must be a @ref{329,,str}.

@emph{encoding} defaults to @code{'utf-8'}.
@emph{errors} defaults to @code{'replace'}, meaning invalid sequences are replaced
by a placeholder character.

Example: @code{unquote('/El%20Ni%C3%B1o/')} yields @code{'/El Niño/'}.
@end deffn

@geindex unquote_plus() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse unquote_plus}@anchor{2c6c}
@deffn {函数} urllib.parse.unquote_plus (string, encoding='utf-8', errors='replace')

Like @ref{2be2,,unquote()}, but also replace plus signs by spaces, as required for
unquoting HTML form values.

@emph{string} must be a @ref{329,,str}.

Example: @code{unquote_plus('/El+Ni%C3%B1o/')} yields @code{'/El Niño/'}.
@end deffn

@geindex unquote_to_bytes() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse unquote_to_bytes}@anchor{2c6d}
@deffn {函数} urllib.parse.unquote_to_bytes (string)

Replace @code{%xx} escapes by their single-octet equivalent, and return a
@ref{32a,,bytes} object.

@emph{string} may be either a @ref{329,,str} or a @ref{32a,,bytes}.

If it is a @ref{329,,str}, unescaped non-ASCII characters in @emph{string}
are encoded into UTF-8 bytes.

Example: @code{unquote_to_bytes('a%26%EF')} yields @code{b'a&\xef'}.
@end deffn

@geindex urlencode() (在 urllib.parse 模块中)
@anchor{library/urllib parse urllib parse urlencode}@anchor{785}
@deffn {函数} urllib.parse.urlencode (query, doseq=False, safe='@w{'}, encoding=None, errors=None, quote_via=quote_plus)

Convert a mapping object or a sequence of two-element tuples, which may
contain @ref{329,,str} or @ref{32a,,bytes} objects, to a percent-encoded ASCII
text string.  If the resultant string is to be used as a @emph{data} for POST
operation with the @ref{786,,urlopen()} function, then
it should be encoded to bytes, otherwise it would result in a
@ref{192,,TypeError}.

The resulting string is a series of @code{key=value} pairs separated by @code{'&'}
characters, where both @emph{key} and @emph{value} are quoted using the @emph{quote_via}
function.  By default, @ref{bd8,,quote_plus()} is used to quote the values, which
means spaces are quoted as a @code{'+'} character and '/' characters are
encoded as @code{%2F}, which follows the standard for GET requests
(@code{application/x-www-form-urlencoded}).  An alternate function that can be
passed as @emph{quote_via} is @ref{405,,quote()}, which will encode spaces as @code{%20}
and not encode '/' characters.  For maximum control of what is quoted, use
@code{quote} and specify a value for @emph{safe}.

When a sequence of two-element tuples is used as the @emph{query}
argument, the first element of each tuple is a key and the second is a
value. The value element in itself can be a sequence and in that case, if
the optional parameter @emph{doseq} is evaluates to @code{True}, individual
@code{key=value} pairs separated by @code{'&'} are generated for each element of
the value sequence for the key.  The order of parameters in the encoded
string will match the order of parameter tuples in the sequence.

The @emph{safe}, @emph{encoding}, and @emph{errors} parameters are passed down to
@emph{quote_via} (the @emph{encoding} and @emph{errors} parameters are only passed
when a query element is a @ref{329,,str}).

To reverse this encoding process, @ref{2b84,,parse_qs()} and @ref{2c5d,,parse_qsl()} are
provided in this module to parse query strings into Python data structures.

Refer to @ref{2c4f,,urllib examples} to find out how urlencode
method can be used for generating query string for a URL or data for POST.


在 3.2 版更改: 查询参数支持字节和字符串对象。



3.5 新版功能: @emph{quote_via} 参数.

@end deffn


@subsubheading 参见



@table @asis

@geindex RFC; RFC 3986

@item RFC 3986@footnote{https://tools.ietf.org/html/rfc3986.html} - 统一资源标识符

This is the current standard (STD66). Any changes to urllib.parse module
should conform to this. Certain deviations could be observed, which are
mostly for backward compatibility purposes and for certain de-facto
parsing requirements as commonly observed in major browsers.

@geindex RFC; RFC 2732

@item RFC 2732@footnote{https://tools.ietf.org/html/rfc2732.html} - Format for Literal IPv6 Addresses in URL's.

This specifies the parsing requirements of IPv6 URLs.

@geindex RFC; RFC 2396

@item RFC 2396@footnote{https://tools.ietf.org/html/rfc2396.html} - 统一资源标识符（URI）：通用语法

Document describing the generic syntactic requirements for both Uniform Resource
Names (URNs) and Uniform Resource Locators (URLs).

@geindex RFC; RFC 2368

@item RFC 2368@footnote{https://tools.ietf.org/html/rfc2368.html} - The mailto URL scheme.

Parsing requirements for mailto URL schemes.

@geindex RFC; RFC 1808

@item RFC 1808@footnote{https://tools.ietf.org/html/rfc1808.html} - Relative Uniform Resource Locators

This Request For Comments includes the rules for joining an absolute and a
relative URL, including a fair number of "Abnormal Examples" which govern the
treatment of border cases.

@geindex RFC; RFC 1738

@item RFC 1738@footnote{https://tools.ietf.org/html/rfc1738.html} - Uniform Resource Locators (URL)

This specifies the formal syntax and semantics of absolute URLs.
@end table


@node urllib error --- urllib request 引发的异常类,urllib robotparser --- robots txt 语法分析程序,urllib parse --- Parse URLs into components,互联网协议和支持
@anchor{library/urllib error doc}@anchor{2c6e}@anchor{library/urllib error module-urllib error}@anchor{11e}@anchor{library/urllib error urllib-error-exception-classes-raised-by-urllib-request}@anchor{2c6f}
@subsection @code{urllib.error} --- urllib.request 引发的异常类


@geindex urllib.error (模块)

@strong{源代码：} Lib/urllib/error.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/urllib/error.py}


__________________________________________________________________


@ref{11e,,urllib.error} 模块为 @ref{120,,urllib.request} 所引发的异常定义了异常类。 基础异常类是 @ref{2bd4,,URLError}。

下列异常会被 @ref{11e,,urllib.error} 按需引发：

@geindex URLError
@anchor{library/urllib error urllib error URLError}@anchor{2bd4}
@deffn {例外} urllib.error.URLError

处理程序在遇到问题时会引发此异常（或其派生的异常）。 它是 @ref{1d3,,OSError} 的一个子类。

@geindex reason (urllib.error.URLError 属性)
@anchor{library/urllib error urllib error URLError reason}@anchor{2c70}
@deffn {属性} reason

此错误的原因。 它可以是一个消息字符串或另一个异常实例。
@end deffn


在 3.3 版更改: @ref{2bd4,,URLError} 已被设为 @ref{1d3,,OSError} 而不是 @ref{98c,,IOError} 的子类。

@end deffn

@geindex HTTPError
@anchor{library/urllib error urllib error HTTPError}@anchor{8f6}
@deffn {例外} urllib.error.HTTPError

虽然是一个异常（@ref{2bd4,,URLError} 的一个子类），@ref{8f6,,HTTPError} 也可以作为一个非异常的文件类返回值（与 @ref{786,,urlopen()} 返所回的对象相同）。 这适用于处理特殊 HTTP 错误例如作为认证请求的时候。

@geindex code (urllib.error.HTTPError 属性)
@anchor{library/urllib error urllib error HTTPError code}@anchor{2c71}
@deffn {属性} code

一个 HTTP 状态码，具体定义见 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html}。 这个数字的值对应于存放在 @ref{2c72,,http.server.BaseHTTPRequestHandler.responses} 代码字典中的某个值。
@end deffn

@geindex reason (urllib.error.HTTPError 属性)
@anchor{library/urllib error urllib error HTTPError reason}@anchor{2c73}
@deffn {属性} reason

这通常是一个解释本次错误原因的字符串。
@end deffn

@geindex headers (urllib.error.HTTPError 属性)
@anchor{library/urllib error urllib error HTTPError headers}@anchor{8f7}
@deffn {属性} headers

导致 @ref{8f6,,HTTPError} 的特定 HTTP 请求的 HTTP 响应头。


3.4 新版功能.

@end deffn
@end deffn

@geindex ContentTooShortError
@anchor{library/urllib error urllib error ContentTooShortError}@anchor{2c74}
@deffn {例外} urllib.error.ContentTooShortError (msg, content)

此异常会在 @ref{2c51,,urlretrieve()} 函数检测到已下载的数据量小于期待的数据量（由 @emph{Content-Length} 头给定）时被引发。 @code{content} 属性中将存放已下载（可能被截断）的数据。
@end deffn

@node urllib robotparser --- robots txt 语法分析程序,http --- HTTP 模块,urllib error --- urllib request 引发的异常类,互联网协议和支持
@anchor{library/urllib robotparser doc}@anchor{2c75}@anchor{library/urllib robotparser module-urllib robotparser}@anchor{122}@anchor{library/urllib robotparser urllib-robotparser-parser-for-robots-txt}@anchor{2c76}
@subsection @code{urllib.robotparser} --- robots.txt 语法分析程序


@geindex urllib.robotparser (模块)

@strong{源代码：} Lib/urllib/robotparser.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/urllib/robotparser.py}

@geindex WWW
@geindex World Wide Web
@geindex URL
@geindex robots.txt


__________________________________________________________________


此模块提供了一个单独的类 @ref{5a8,,RobotFileParser}，它可以回答关于某个特定用户代理是否能在 Web 站点获取发布 @code{robots.txt} 文件的 URL 的问题。 有关 @code{robots.txt} 文件结构的更多细节请参阅 @indicateurl{http://www.robotstxt.org/orig.html}。

@geindex RobotFileParser (urllib.robotparser 中的类)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser}@anchor{5a8}
@deffn {类} urllib.robotparser.RobotFileParser (url='@w{'})

这个类提供了一些可以读取、解析和回答关于 @emph{url} 上的 @code{robots.txt} 文件的问题的方法。

@geindex set_url() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser set_url}@anchor{2c77}
@deffn {方法} set_url (url)

设置指向 @code{robots.txt} 文件的 URL。
@end deffn

@geindex read() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser read}@anchor{2c78}
@deffn {方法} read ()

读取 @code{robots.txt} URL 并将其输入解析器。
@end deffn

@geindex parse() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser parse}@anchor{1034}
@deffn {方法} parse (lines)

解析行参数。
@end deffn

@geindex can_fetch() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser can_fetch}@anchor{2c79}
@deffn {方法} can_fetch (useragent, url)

如果允许 @emph{useragent} 按照被解析 @code{robots.txt} 文件中的规则来获取 @emph{url} 则返回 @code{True}。
@end deffn

@geindex mtime() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser mtime}@anchor{2c7a}
@deffn {方法} mtime ()

返回最近一次获取 @code{robots.txt} 文件的时间。 这适用于需要定期检查 @code{robots.txt} 文件更新情况的长时间运行的网页爬虫。
@end deffn

@geindex modified() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser modified}@anchor{2c7b}
@deffn {方法} modified ()

将最近一次获取 @code{robots.txt} 文件的时间设置为当前时间。
@end deffn

@geindex crawl_delay() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser crawl_delay}@anchor{2c7c}
@deffn {方法} crawl_delay (useragent)

为指定的 @emph{useragent} 从 @code{robots.txt} 返回 @code{Crawl-delay} 形参。 如果此形参不存在或不适用于指定的 @emph{useragent} 或者此形参的 @code{robots.txt} 条目存在语法错误，则返回 @code{None}。


3.6 新版功能.

@end deffn

@geindex request_rate() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser request_rate}@anchor{2c7d}
@deffn {方法} request_rate (useragent)

以 @ref{a9e,,named tuple} @code{RequestRate(requests, seconds)} 的形式从 @code{robots.txt} 返回 @code{Request-rate} 形参的内容。 如果此形参不存在或不适用于指定的 @emph{useragent} 或者此形参的 @code{robots.txt} 条目存在语法错误，则返回 @code{None}。


3.6 新版功能.

@end deffn

@geindex site_maps() (urllib.robotparser.RobotFileParser 方法)
@anchor{library/urllib robotparser urllib robotparser RobotFileParser site_maps}@anchor{fc9}
@deffn {方法} site_maps ()

以 @ref{262,,list()} 的形式从 @code{robots.txt} 返回 @code{Sitemap} 形参的内容。 如果此形参不存在或者此形参的 @code{robots.txt} 条目存在语法错误，则返回 @code{None}。


3.8 新版功能.

@end deffn
@end deffn

下面的例子演示了 @ref{5a8,,RobotFileParser} 类的基本用法:

@example
>>> import urllib.robotparser
>>> rp = urllib.robotparser.RobotFileParser()
>>> rp.set_url("http://www.musi-cal.com/robots.txt")
>>> rp.read()
>>> rrate = rp.request_rate("*")
>>> rrate.requests
3
>>> rrate.seconds
20
>>> rp.crawl_delay("*")
6
>>> rp.can_fetch("*", "http://www.musi-cal.com/cgi-bin/search?city=San+Francisco")
False
>>> rp.can_fetch("*", "http://www.musi-cal.com/")
True
@end example

@node http --- HTTP 模块,http client --- HTTP 协议客户端,urllib robotparser --- robots txt 语法分析程序,互联网协议和支持
@anchor{library/http doc}@anchor{2c7e}@anchor{library/http http-http-modules}@anchor{2c7f}@anchor{library/http module-http}@anchor{93}
@subsection @code{http} --- HTTP 模块


@geindex http (模块)

@strong{源代码:} Lib/http/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/http/__init__.py}

@geindex HTTP; protocol
@geindex HTTP; http (standard module)


__________________________________________________________________


@ref{93,,http} 是一个包，它收集了多个用于处理超文本传输协议的模块:


@itemize *

@item 
@ref{94,,http.client} 是一个低层级的 HTTP 协议客户端；对于高层级的 URL 访问请使用 @ref{120,,urllib.request}

@item 
@ref{97,,http.server} 包含基于 @ref{f0,,socketserver} 的基本 HTTP 服务类

@item 
@ref{96,,http.cookies} 包含一些有用来实现通过 cookies 进行状态管理的工具

@item 
@ref{95,,http.cookiejar} 提供了 cookies 的持久化
@end itemize

@ref{93,,http} 也是一个通过 @ref{6dc,,http.HTTPStatus} 枚举定义了一些 HTTP 状态码以及相关联消息的模块

@geindex HTTPStatus (http 中的类)
@anchor{library/http http HTTPStatus}@anchor{6dc}
@deffn {类} http.HTTPStatus


3.5 新版功能.


@ref{588,,enum.IntEnum} 的子类，它定义了组 HTTP 状态码，原理短语以及用英语书写的长描述文本。

用法:

@example
>>> from http import HTTPStatus
>>> HTTPStatus.OK
<HTTPStatus.OK: 200>
>>> HTTPStatus.OK == 200
True
>>> HTTPStatus.OK.value
200
>>> HTTPStatus.OK.phrase
'OK'
>>> HTTPStatus.OK.description
'Request fulfilled, document follows'
>>> list(HTTPStatus)
[<HTTPStatus.CONTINUE: 100>, <HTTPStatus.SWITCHING_PROTOCOLS: 101>, ...]
@end example
@end deffn

@menu
* HTTP 状态码:: 

@end menu

@node HTTP 状态码,,,http --- HTTP 模块
@anchor{library/http http-status-codes}@anchor{2c80}@anchor{library/http id1}@anchor{2c81}
@subsubsection HTTP 状态码


已支持并且已在 @ref{6dc,,http.HTTPStatus} IANA 注册@footnote{https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml} 的状态码有：


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

双字母代码

@tab

映射名

@tab

详情

@item

@code{100}

@tab

@code{CONTINUE}：继续

@tab

HTTP/1.1 
@geindex RFC; RFC 7231
RFC 7231@footnote{https://tools.ietf.org/html/rfc7231.html},  6.2.1 节

@item

@code{101}

@tab

@code{SWITCHING_PROTOCOLS}

@tab

HTTP/1.1 RFC 7231,  6.2.2 节

@item

@code{102}

@tab

@code{PROCESSING}

@tab

WebDAV RFC 2518,  10.1 节

@item

@code{200}

@tab

@code{OK}

@tab

HTTP/1.1 RFC 7231,  6.3.1 节

@item

@code{201}

@tab

@code{CREATED}

@tab

HTTP/1.1 RFC 7231,  6.3.2 节

@item

@code{202}

@tab

@code{ACCEPTED}

@tab

HTTP/1.1 RFC 7231,  6.3.3 节

@item

@code{203}

@tab

@code{NON_AUTHORITATIVE_INFORMATION}

@tab

HTTP/1.1 RFC 7231,  6.3.4 节

@item

@code{204}

@tab

@code{NO_CONTENT}: 没有内容

@tab

HTTP/1.1 RFC 7231,  6.3.5 节

@item

@code{205}

@tab

@code{RESET_CONTENT}

@tab

HTTP/1.1 RFC 7231,  6.3.6 节

@item

@code{206}

@tab

@code{PARTIAL_CONTENT}

@tab

HTTP/1.1 RFC 7233,  4.1 节

@item

@code{207}

@tab

@code{MULTI_STATUS}

@tab

WebDAV RFC 4918,  11.1 节

@item

@code{208}

@tab

@code{ALREADY_REPORTED}

@tab

WebDAV Binding Extensions RFC 5842, 7.1 节（实验性）

@item

@code{226}

@tab

@code{IM_USED}

@tab

Delta Encoding in HTTP RFC 3229,  10.4.1 节

@item

@code{300}

@tab

@code{MULTIPLE_CHOICES}：有多种资源可选择

@tab

HTTP/1.1 RFC 7231,  6.4.1 节

@item

@code{301}

@tab

@code{MOVED_PERMANENTLY}：永久移动

@tab

HTTP/1.1 RFC 7231,  6.4.2 节

@item

@code{302}

@tab

@code{FOUND}：临时移动

@tab

HTTP/1.1 RFC 7231,  6.4.3 节

@item

@code{303}

@tab

@code{SEE_OTHER}：已经移动

@tab

HTTP/1.1 RFC 7231, 6.4.4 节

@item

@code{304}

@tab

@code{NOT_MODIFIED}：没有修改

@tab

HTTP/1.1 RFC 7232, 4.1 节

@item

@code{305}

@tab

@code{USE_PROXY}：使用代理

@tab

HTTP/1.1 RFC 7231, 6.4.5 节

@item

@code{307}

@tab

@code{TEMPORARY_REDIRECT}：临时重定向

@tab

HTTP/1.1 
@geindex RFC; RFC 7231
RFC 7231@footnote{https://tools.ietf.org/html/rfc7231.html}, 6.4.7 节

@item

@code{308}

@tab

@code{PERMANENT_REDIRECT}：永久重定向

@tab

Permanent Redirect 
@geindex RFC; RFC 7238
RFC 7238@footnote{https://tools.ietf.org/html/rfc7238.html}, Section 3 (Experimental)

@item

@code{400}

@tab

@code{BAD_REQUEST}：错误请求

@tab

HTTP/1.1 RFC 7231, 6.5.1 节

@item

@code{401}

@tab

@code{UNAUTHORIZED}：未授权

@tab

HTTP/1.1 Authentication RFC 7235, 3.1 节

@item

@code{402}

@tab

@code{PAYMENT_REQUIRED}：保留，将来使用

@tab

HTTP/1.1 RFC 7231, 6.5.2 节

@item

@code{403}

@tab

@code{FORBIDDEN}：禁止

@tab

HTTP/1.1 RFC 7231, 6.5.3 节

@item

@code{404}

@tab

@code{NOT_FOUND}：没有找到

@tab

HTTP/1.1 RFC 7231, 6.5.4 节

@item

@code{405}

@tab

@code{METHOD_NOT_ALLOWED}：该请求方法不允许

@tab

HTTP/1.1 RFC 7231, 6.5.5 节

@item

@code{406}

@tab

@code{NOT_ACCEPTABLE}：不可接受

@tab

HTTP/1.1 RFC 7231, 6.5.6 节

@item

@code{407}

@tab

@code{PROXY_AUTHENTICATION_REQUIRED}：要求使用代理验明正身

@tab

HTTP/1.1 Authentication RFC 7235, 3.1 节

@item

@code{408}

@tab

@code{REQUEST_TIMEOUT}：请求超时

@tab

HTTP/1.1 
@geindex RFC; RFC 7231
RFC 7231@footnote{https://tools.ietf.org/html/rfc7231.html}, 6.5.7 节

@item

@code{409}

@tab

@code{CONFLICT}：冲突

@tab

HTTP/1.1 RFC 7231, 6.5.8 节

@item

@code{410}

@tab

@code{GONE}：已经不在了

@tab

HTTP/1.1 RFC 7231, 6.5.9 节

@item

@code{411}

@tab

@code{LENGTH_REQUIRED}：长度要求

@tab

HTTP/1.1 RFC 7231, 6.5.10 节

@item

@code{412}

@tab

@code{PRECONDITION_FAILED}：前提条件错误

@tab

HTTP/1.1 RFC 7232, 4.2 节

@item

@code{413}

@tab

@code{REQUEST_ENTITY_TOO_LARGE}：请求体太大了

@tab

HTTP/1.1 RFC 7231, 6.5.11 节

@item

@code{414}

@tab

@code{REQUEST_URI_TOO_LONG}：请求URI太长了

@tab

HTTP/1.1 RFC 7231, 6.5.12 节

@item

@code{415}

@tab

@code{UNSUPPORTED_MEDIA_TYPE}：不支持的媒体格式

@tab

HTTP/1.1 RFC 7231,  6.5.13 节

@item

@code{416}

@tab

@code{REQUESTED_RANGE_NOT_SATISFIABLE}

@tab

HTTP/1.1 Range Requests RFC 7233, 4.4 节

@item

@code{417}

@tab

@code{EXPECTATION_FAILED}：期望失败

@tab

HTTP/1.1 RFC 7231,  6.5.14 节

@item

@code{421}

@tab

@code{MISDIRECTED_REQUEST}

@tab

HTTP/2 
@geindex RFC; RFC 7540
RFC 7540@footnote{https://tools.ietf.org/html/rfc7540.html}, 9.1.2 节

@item

@code{422}

@tab

@code{UNPROCESSABLE_ENTITY}：可加工实体

@tab

WebDAV RFC 4918, 11.2 节

@item

@code{423}

@tab

@code{LOCKED}：锁着

@tab

WebDAV RFC 4918, 11.3 节

@item

@code{424}

@tab

@code{FAILED_DEPENDENCY}：失败的依赖

@tab

WebDAV RFC 4918, 11.4 节

@item

@code{426}

@tab

@code{UPGRADE_REQUIRED}：升级需要

@tab

HTTP/1.1 RFC 7231, 6.5.15 节

@item

@code{428}

@tab

@code{PRECONDITION_REQUIRED}：先决条件要求

@tab

Additional HTTP Status Codes RFC 6585

@item

@code{429}

@tab

@code{TOO_MANY_REQUESTS}：太多的请求

@tab

Additional HTTP Status Codes RFC 6585

@item

@code{431}

@tab

@code{REQUEST_HEADER_FIELDS_TOO_LARGE}：请求头太大

@tab

Additional HTTP Status Codes RFC 6585

@item

@code{451}

@tab

@code{UNAVAILABLE_FOR_LEGAL_REASONS}

@tab

HTTP 状态码用于报告法律障碍 
@geindex RFC; RFC 7725
RFC 7725@footnote{https://tools.ietf.org/html/rfc7725.html}

@item

@code{500}

@tab

@code{INTERNAL_SERVER_ERROR}：内部服务错误

@tab

HTTP/1.1 RFC 7231, 6.6.1 节

@item

@code{501}

@tab

@code{NOT_IMPLEMENTED}：不可执行

@tab

HTTP/1.1 RFC 7231, 6.6.2 节

@item

@code{502}

@tab

@code{BAD_GATEWAY}：无效网关

@tab

HTTP/1.1 RFC 7231, 6.6.3 节

@item

@code{503}

@tab

@code{SERVICE_UNAVAILABLE}：服务不可用

@tab

HTTP/1.1 RFC 7231, 6.6.4 节

@item

@code{504}

@tab

@code{GATEWAY_TIMEOUT}：网关超时

@tab

HTTP/1.1 RFC 7231, 6.6.5 节

@item

@code{505}

@tab

@code{HTTP_VERSION_NOT_SUPPORTED}：HTTP版本不支持

@tab

HTTP/1.1 RFC 7231, 6.6.6 节

@item

@code{506}

@tab

@code{VARIANT_ALSO_NEGOTIATES}：服务器存在内部配置错误

@tab

透明内容协商在： HTTP 
@geindex RFC; RFC 2295
RFC 2295@footnote{https://tools.ietf.org/html/rfc2295.html},  8.1 节（实验性）

@item

@code{507}

@tab

@code{INSUFFICIENT_STORAGE}：存储不足

@tab

WebDAV RFC 4918, 11.5 节

@item

@code{508}

@tab

@code{LOOP_DETECTED}：循环检测

@tab

WebDAV Binding Extensions RFC 5842,  7.2 节（实验性）

@item

@code{510}

@tab

@code{NOT_EXTENDED}：不扩展

@tab

WebDAV Binding Extensions RFC 5842, 7.2 节（实验性）

@item

@code{511}

@tab

@code{NETWORK_AUTHENTICATION_REQUIRED}：要求网络身份验证

@tab

Additional HTTP Status Codes 
@geindex RFC; RFC 6585
RFC 6585@footnote{https://tools.ietf.org/html/rfc6585.html},  6 节

@end multitable


为了保持向后兼容性，枚举值也以常量形式出现在 @ref{94,,http.client} 模块中，。 枚举名等于常量名 (例如 @code{http.HTTPStatus.OK} 也可以是 @code{http.client.OK})。


在 3.7 版更改: 添加了 @code{421 MISDIRECTED_REQUEST} 状态码。



3.8 新版功能: 添加了 @code{451 UNAVAILABLE_FOR_LEGAL_REASONS} 状态码。


@node http client --- HTTP 协议客户端,ftplib --- FTP 协议客户端,http --- HTTP 模块,互联网协议和支持
@anchor{library/http client doc}@anchor{2c82}@anchor{library/http client http-client-http-protocol-client}@anchor{2c83}@anchor{library/http client module-http client}@anchor{94}
@subsection @code{http.client} --- HTTP 协议客户端


@geindex http.client (模块)

@strong{源代码：} Lib/http/client.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/http/client.py}

@geindex HTTP; protocol
@geindex HTTP; http.client (standard module)

@geindex 模块; urllib.request


__________________________________________________________________


这个模块定义了实现 HTTP 和 HTTPS 协议客户端的类。 它通常不直接使用 --- 模块 @ref{120,,urllib.request} 用它来处理使用 HTTP 和 HTTPS 的 URL。


@subsubheading 参见


The Requests package@footnote{https://requests.readthedocs.io/en/master/}
is recommended for a higher-level HTTP client interface.


@cartouche
@quotation 注解 
HTTPS 支持仅在编译 Python 时启用了 SSL 支持的情况下（通过 @ref{f3,,ssl} 模块）可用。
@end quotation
@end cartouche

该模块支持以下类：

@geindex HTTPConnection (http.client 中的类)
@anchor{library/http client http client HTTPConnection}@anchor{38a}
@deffn {类} http.client.HTTPConnection (host, port=None[, timeout], source_address=None, blocksize=8192)

@ref{38a,,HTTPConnection} 的实例代表与 HTTP 的一个连接事务。 它的实例化应当传入一个主机和可选的端口号。 如果没有传入端口号，如果主机字符串的形式为 @code{主机:端口} 则会从中提取端口，否则将使用默认的 HTTP 端口（80）。 如果给出了可选的 @emph{timeout} 参数，则阻塞操作（例如连接尝试）将在指定的秒数之后超时（如果未给出，则使用全局默认超时设置）。 可选的 @emph{source_address} 参数可以为一个 (主机, 端口) 元组，用作进行 HTTP 连接的源地址。 可选的 @emph{blocksize} 参数可以字节为单位设置缓冲区的大小，用来发送文件类消息体。

举个例子，以下调用都是创建连接到同一主机和端口的服务器的实例：

@example
>>> h1 = http.client.HTTPConnection('www.python.org')
>>> h2 = http.client.HTTPConnection('www.python.org:80')
>>> h3 = http.client.HTTPConnection('www.python.org', 80)
>>> h4 = http.client.HTTPConnection('www.python.org', 80, timeout=10)
@end example


在 3.2 版更改: 添加了*source_address* 参数



在 3.4 版更改: 删除了 @emph{strict} 参数，不再支持 HTTP 0.9 风格的“简单响应”。



在 3.7 版更改: 添加了 @emph{blocksize} 参数。

@end deffn

@geindex HTTPSConnection (http.client 中的类)
@anchor{library/http client http client HTTPSConnection}@anchor{38b}
@deffn {类} http.client.HTTPSConnection (host, port=None, key_file=None, cert_file=None[, timeout], source_address=None, *, context=None, check_hostname=None, blocksize=8192)

@ref{38a,,HTTPConnection} 的子类，使用 SSL 与安全服务器进行通信。 默认端口为 @code{443}。 如果指定了 @emph{context}，它必须为一个描述 SSL 各选项的 @ref{3dc,,ssl.SSLContext} 实例。

请参阅 @ref{254a,,Security considerations} 了解有关最佳实践的更多信息。


在 3.2 版更改: 添加了 @emph{source_address}, @emph{context} 和 @emph{check_hostname}。



在 3.2 版更改: 这个类目前会在可能的情况下（即如果 @ref{2678,,ssl.HAS_SNI} 为真值）支持 HTTPS 虚拟主机。



在 3.4 版更改: 删除了 @emph{strict} 参数，不再支持 HTTP 0.9 风格的“简单响应”。



在 3.4.3 版更改: 目前这个类在默认情况下会执行所有必要的证书和主机检查。 要回复到先前的非验证行为，可以将 @code{ssl._create_unverified_context()} 传递给 @emph{context} 参数。



在 3.8 版更改: 该类现在对于默认的 @emph{context} 或在传入 @emph{cert_file} 并附带自定义 @emph{context} 时会启用 TLS 1.3 @ref{224,,ssl.SSLContext.post_handshake_auth}。



3.6 版后已移除: @emph{key_file} 和 @emph{cert_file} 已弃用并转而推荐 @emph{context}。 请改用 @ref{a8c,,ssl.SSLContext.load_cert_chain()} 或让 @ref{8bb,,ssl.create_default_context()} 为你选择系统所信任的 CA 证书。

@emph{check_hostname} 参数也已弃用；应当改用 @emph{context} 的 @ref{2663,,ssl.SSLContext.check_hostname} 属性。

@end deffn

@geindex HTTPResponse (http.client 中的类)
@anchor{library/http client http client HTTPResponse}@anchor{a0c}
@deffn {类} http.client.HTTPResponse (sock, debuglevel=0, method=None, url=None)

在成功连接后返回类的实例，而不是由用户直接实例化。


在 3.4 版更改: 删除了 @emph{strict} 参数，不再支持HTTP 0.9 风格的“简单响应”。

@end deffn

This module provides the following function:

@geindex parse_headers() (在 http.client 模块中)
@anchor{library/http client http client parse_headers}@anchor{fd3}
@deffn {函数} http.client.parse_headers (fp)

Parse the headers from a file pointer @emph{fp} representing a HTTP
request/response. The file has to be a @code{BufferedIOBase} reader
(i.e. not text) and must provide a valid 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html} style header.

This function returns an instance of @code{http.client.HTTPMessage}
that holds the header fields, but no payload
(the same as @ref{2c84,,HTTPResponse.msg}
and @ref{2c85,,http.server.BaseHTTPRequestHandler.headers}).
After returning, the file pointer @emph{fp} is ready to read the HTTP body.

@cartouche
@quotation 注解 
@ref{fd3,,parse_headers()} does not parse the start-line of a HTTP message;
it only parses the @code{Name: value} lines. The file has to be ready to
read these field lines, so the first line should already be consumed
before calling the function.
@end quotation
@end cartouche
@end deffn

下列异常可以适当地被引发:

@geindex HTTPException
@anchor{library/http client http client HTTPException}@anchor{2c86}
@deffn {例外} http.client.HTTPException

此模块中其他异常的基类。 它是 @ref{1a9,,Exception} 的一个子类。
@end deffn

@geindex NotConnected
@anchor{library/http client http client NotConnected}@anchor{2c87}
@deffn {例外} http.client.NotConnected

@ref{2c86,,HTTPException} 的一个子类。
@end deffn

@geindex InvalidURL
@anchor{library/http client http client InvalidURL}@anchor{2c88}
@deffn {例外} http.client.InvalidURL

@ref{2c86,,HTTPException} 的一个子类，如果给出了一个非数字或为空值的端口就会被引发。
@end deffn

@geindex UnknownProtocol
@anchor{library/http client http client UnknownProtocol}@anchor{2c89}
@deffn {例外} http.client.UnknownProtocol

@ref{2c86,,HTTPException} 的一个子类。
@end deffn

@geindex UnknownTransferEncoding
@anchor{library/http client http client UnknownTransferEncoding}@anchor{2c8a}
@deffn {例外} http.client.UnknownTransferEncoding

@ref{2c86,,HTTPException} 的一个子类。
@end deffn

@geindex UnimplementedFileMode
@anchor{library/http client http client UnimplementedFileMode}@anchor{2c8b}
@deffn {例外} http.client.UnimplementedFileMode

@ref{2c86,,HTTPException} 的一个子类。
@end deffn

@geindex IncompleteRead
@anchor{library/http client http client IncompleteRead}@anchor{2c8c}
@deffn {例外} http.client.IncompleteRead

@ref{2c86,,HTTPException} 的一个子类。
@end deffn

@geindex ImproperConnectionState
@anchor{library/http client http client ImproperConnectionState}@anchor{2c8d}
@deffn {例外} http.client.ImproperConnectionState

@ref{2c86,,HTTPException} 的一个子类。
@end deffn

@geindex CannotSendRequest
@anchor{library/http client http client CannotSendRequest}@anchor{2c8e}
@deffn {例外} http.client.CannotSendRequest

@ref{2c8d,,ImproperConnectionState} 的一个子类。
@end deffn

@geindex CannotSendHeader
@anchor{library/http client http client CannotSendHeader}@anchor{2c8f}
@deffn {例外} http.client.CannotSendHeader

@ref{2c8d,,ImproperConnectionState} 的一个子类。
@end deffn

@geindex ResponseNotReady
@anchor{library/http client http client ResponseNotReady}@anchor{2c90}
@deffn {例外} http.client.ResponseNotReady

@ref{2c8d,,ImproperConnectionState} 的一个子类。
@end deffn

@geindex BadStatusLine
@anchor{library/http client http client BadStatusLine}@anchor{2c91}
@deffn {例外} http.client.BadStatusLine

@ref{2c86,,HTTPException} 的一个子类。 如果服务器反馈了一个我们不理解的 HTTP 状态码就会被引发。
@end deffn

@geindex LineTooLong
@anchor{library/http client http client LineTooLong}@anchor{2c92}
@deffn {例外} http.client.LineTooLong

@ref{2c86,,HTTPException} 的一个子类。 如果在 HTTP 协议中从服务器接收到过长的行就会被引发。
@end deffn

@geindex RemoteDisconnected
@anchor{library/http client http client RemoteDisconnected}@anchor{6df}
@deffn {例外} http.client.RemoteDisconnected

@ref{99a,,ConnectionResetError} 和 @ref{2c91,,BadStatusLine} 的一个子类。 当尝试读取响应时的结果是未从连接读取到数据时由 @ref{6de,,HTTPConnection.getresponse()} 引发，表明远端已关闭连接。


3.5 新版功能: 在此之前引发的异常为 @ref{2c91,,BadStatusLine}@code{('@w{'})}。

@end deffn

此模块中定义的常量为：

@geindex HTTP_PORT() (在 http.client 模块中)
@anchor{library/http client http client HTTP_PORT}@anchor{2c93}
@deffn {数据} http.client.HTTP_PORT

HTTP 协议默认的端口号 (总是 @code{80})。
@end deffn

@geindex HTTPS_PORT() (在 http.client 模块中)
@anchor{library/http client http client HTTPS_PORT}@anchor{2c94}
@deffn {数据} http.client.HTTPS_PORT

HTTPS 协议默认的端口号 (总是 @code{443})。
@end deffn

@geindex responses() (在 http.client 模块中)
@anchor{library/http client http client responses}@anchor{2c95}
@deffn {数据} http.client.responses

这个字典把 HTTP 1.1 状态码映射到 W3C 名称。

例如：@code{http.client.responses[http.client.NOT_FOUND]} 是 @code{'NOT FOUND} （未发现）。
@end deffn

本模块中可用的 HTTP 状态码常量可以参见 @ref{2c80,,HTTP 状态码} 。

@menu
* HTTPConnection 对象:: 
* HTTPResponse 对象:: 
* 例子: 例子<22>. 
* HTTPMessage Objects:: 

@end menu

@node HTTPConnection 对象,HTTPResponse 对象,,http client --- HTTP 协议客户端
@anchor{library/http client httpconnection-objects}@anchor{2c96}@anchor{library/http client id1}@anchor{2c97}
@subsubsection HTTPConnection 对象


@ref{38a,,HTTPConnection} 实例拥有以下方法：

@geindex request() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection request}@anchor{54a}
@deffn {方法} HTTPConnection.request (method, url, body=None, headers=@{@}, *, encode_chunked=False)

这会使用 HTTP 请求方法 @emph{method} 和选择器 @emph{url} 向服务器发送请求。

如果给定 @emph{body}，那么给定的数据会在信息头完成之后发送。它可能是一个 @ref{329,,str} 、一个 @ref{5e3,,bytes-like object} 、一个打开的 @ref{b3b,,file object}，或者 @ref{32a,,bytes} 迭代器。如果 @emph{body} 是字符串，它会按 HTTP 默认的 ISO-8859-1 编码；如果是一个字节类对象，它会按原样发送；如果是 @ref{b3b,,file object} ，文件的内容会被发送，这个文件对象应该支持 @code{read()} 方法。如果这个文件对象是一个 @ref{c32,,io.TextIOBase} 实例， @code{read()} 方法返回的数据会按 ISO-8859-1 编码，否则 @code{read()} 方法返回的数据会按原样发送；如果 @emph{body} 是一个迭代器，迭代器中的元素会被发送，直到迭代器耗尽。

@emph{headers} 参数应是额外的随请求发送的 HTTP 信息头的字典。

如果 @emph{headers} 既不包含 Content-Length 也没有 Transfer-Encoding，但存在请求正文，那么这些头字段中的一个会自动设定。如果 @emph{body} 是 @code{None}，那么对于要求正文的方法 (@code{PUT}，@code{POST}，和 @code{PATCH})，Content-Length 头会被设为 @code{0}。如果 @emph{body} 是字符串或者类似字节的对象，并且也不是 @ref{b3b,,文件}，Content-Length 头会设为正文的长度。任何其他类型的 @emph{body} （一般是文件或迭代器）会按块编码，这时会自动设定 Transfer-Encoding 头以代替 Content-Length。

在 @emph{headers} 中指定 Transfer-Encoding 时， @emph{encode_chunked} 是唯一相关的参数。如果 @emph{encode_chunked} 为 @code{False}，HTTPConnection 对象会假定所有的编码都由调用代码处理。如果为 @code{True}，正文会按块编码。

@cartouche
@quotation 注解 
HTTP 协议在 1.1 版中添加了块传输编码。除非明确知道 HTTP 服务器可以处理 HTTP 1.1，调用者要么必须指定 Content-Length，要么必须传入 @ref{329,,str} 或字节类对象，注意该对象不能是表达 body 的文件。
@end quotation
@end cartouche


3.2 新版功能: @emph{body} 现在可以是可迭代对象了。



在 3.6 版更改: 如果 Content-Length 和 Transfer-Encoding 都没有在 @emph{headers} 中设置，文件和可迭代的 @emph{body} 对象现在会按块编码。添加了 @emph{encode_chunked} 参数。不会尝试去确定文件对象的 Content-Length。

@end deffn

@geindex getresponse() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection getresponse}@anchor{6de}
@deffn {方法} HTTPConnection.getresponse ()

应当在发送一个请求从服务器获取响应时被调用。 返回一个 @ref{a0c,,HTTPResponse} 的实例。

@cartouche
@quotation 注解 
请注意你必须在读取了整个响应之后才能向服务器发送新的请求。
@end quotation
@end cartouche


在 3.5 版更改: 如果引发了 @ref{6e0,,ConnectionError} 或其子类， @ref{38a,,HTTPConnection} 对象将在发送新的请求时准备好重新连接。

@end deffn

@geindex set_debuglevel() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection set_debuglevel}@anchor{2c98}
@deffn {方法} HTTPConnection.set_debuglevel (level)

设置调试等级。 默认的调试等级为 @code{0}，意味着不会打印调试输出。 任何大于 @code{0} 的值将使得所有当前定义的调试输出被打印到 stdout。 @code{debuglevel} 会被传给任何新创建的 @ref{a0c,,HTTPResponse} 对象。


3.1 新版功能.

@end deffn

@geindex set_tunnel() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection set_tunnel}@anchor{ba6}
@deffn {方法} HTTPConnection.set_tunnel (host, port=None, headers=None)

为 HTTP 连接隧道设置主机和端口。 这将允许通过代理服务器运行连接。

host 和 port 参数指明隧道连接的位置（即 CONNECT 请求所包含的地址，而 @emph{不是} 代理服务器的地址）。

headers 参数应为一个随 CONNECT 请求发送的额外 HTTP 标头的映射。

例如，要通过一个运行于本机 8080 端口的 HTTPS 代理服务器隧道，我们应当向 @ref{38b,,HTTPSConnection} 构造器传入代理的地址，并将我们最终想要访问的主机地址传给 @ref{ba6,,set_tunnel()} 方法:

@example
>>> import http.client
>>> conn = http.client.HTTPSConnection("localhost", 8080)
>>> conn.set_tunnel("www.python.org")
>>> conn.request("HEAD","/index.html")
@end example


3.2 新版功能.

@end deffn

@geindex connect() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection connect}@anchor{2c99}
@deffn {方法} HTTPConnection.connect ()

当对象被创建后连接到指定的服务器。 默认情况下，如果客户端还未建立连接，此函数会在发送请求时自动被调用。
@end deffn

@geindex close() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection close}@anchor{2c9a}
@deffn {方法} HTTPConnection.close ()

关闭到服务器的连接。
@end deffn

@geindex blocksize (http.client.HTTPConnection 属性)
@anchor{library/http client http client HTTPConnection blocksize}@anchor{2c9b}
@deffn {属性} HTTPConnection.blocksize

用于发送文件类消息体的缓冲区大小。


3.7 新版功能.

@end deffn

作为对使用上述 @code{request()} 方法的替代同，你也可以通过使用下面的四个函数，分步骤发送请的请求。

@geindex putrequest() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection putrequest}@anchor{2c9c}
@deffn {方法} HTTPConnection.putrequest (method, url, skip_host=False, skip_accept_encoding=False)

This should be the first call after the connection to the server has been
made. It sends a line to the server consisting of the @emph{method} string,
the @emph{url} string, and the HTTP version (@code{HTTP/1.1}).  To disable automatic
sending of @code{Host:} or @code{Accept-Encoding:} headers (for example to accept
additional content encodings), specify @emph{skip_host} or @emph{skip_accept_encoding}
with non-False values.
@end deffn

@geindex putheader() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection putheader}@anchor{2c9d}
@deffn {方法} HTTPConnection.putheader (header, argument[, ...])

Send an 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html}-style header to the server.  It sends a line to the server
consisting of the header, a colon and a space, and the first argument.  If more
arguments are given, continuation lines are sent, each consisting of a tab and
an argument.
@end deffn

@geindex endheaders() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection endheaders}@anchor{54b}
@deffn {方法} HTTPConnection.endheaders (message_body=None, *, encode_chunked=False)

Send a blank line to the server, signalling the end of the headers. The
optional @emph{message_body} argument can be used to pass a message body
associated with the request.

If @emph{encode_chunked} is @code{True}, the result of each iteration of
@emph{message_body} will be chunk-encoded as specified in 
@geindex RFC; RFC 7230
RFC 7230@footnote{https://tools.ietf.org/html/rfc7230.html},
Section 3.3.1.  How the data is encoded is dependent on the type of
@emph{message_body}.  If @emph{message_body} implements the @ref{15d6,,buffer interface} the encoding will result in a single chunk.
If @emph{message_body} is a @ref{18e7,,collections.abc.Iterable}, each iteration
of @emph{message_body} will result in a chunk.  If @emph{message_body} is a
@ref{b3b,,file object}, each call to @code{.read()} will result in a chunk.
The method automatically signals the end of the chunk-encoded data
immediately after @emph{message_body}.

@cartouche
@quotation 注解 
Due to the chunked encoding specification, empty chunks
yielded by an iterator body will be ignored by the chunk-encoder.
This is to avoid premature termination of the read of the request by
the target server due to malformed encoding.
@end quotation
@end cartouche


3.6 新版功能: Chunked encoding support.  The @emph{encode_chunked} parameter was
added.

@end deffn

@geindex send() (http.client.HTTPConnection 方法)
@anchor{library/http client http client HTTPConnection send}@anchor{2c9e}
@deffn {方法} HTTPConnection.send (data)

Send data to the server.  This should be used directly only after the
@ref{54b,,endheaders()} method has been called and before @ref{6de,,getresponse()} is
called.
@end deffn

@node HTTPResponse 对象,例子<22>,HTTPConnection 对象,http client --- HTTP 协议客户端
@anchor{library/http client httpresponse-objects}@anchor{2c9f}@anchor{library/http client id2}@anchor{2ca0}
@subsubsection HTTPResponse 对象


An @ref{a0c,,HTTPResponse} instance wraps the HTTP response from the
server.  It provides access to the request headers and the entity
body.  The response is an iterable object and can be used in a with
statement.


在 3.5 版更改: The @ref{583,,io.BufferedIOBase} interface is now implemented and
all of its reader operations are supported.


@geindex read() (http.client.HTTPResponse 方法)
@anchor{library/http client http client HTTPResponse read}@anchor{2ca1}
@deffn {方法} HTTPResponse.read ([amt])

Reads and returns the response body, or up to the next @emph{amt} bytes.
@end deffn

@geindex readinto() (http.client.HTTPResponse 方法)
@anchor{library/http client http client HTTPResponse readinto}@anchor{a0d}
@deffn {方法} HTTPResponse.readinto (b)

Reads up to the next len(b) bytes of the response body into the buffer @emph{b}.
Returns the number of bytes read.


3.3 新版功能.

@end deffn

@geindex getheader() (http.client.HTTPResponse 方法)
@anchor{library/http client http client HTTPResponse getheader}@anchor{2ca2}
@deffn {方法} HTTPResponse.getheader (name, default=None)

Return the value of the header @emph{name}, or @emph{default} if there is no header
matching @emph{name}.  If there is more than one  header with the name @emph{name},
return all of the values joined by ', '.  If 'default' is any iterable other
than a single string, its elements are similarly returned joined by commas.
@end deffn

@geindex getheaders() (http.client.HTTPResponse 方法)
@anchor{library/http client http client HTTPResponse getheaders}@anchor{2ca3}
@deffn {方法} HTTPResponse.getheaders ()

Return a list of (header, value) tuples.
@end deffn

@geindex fileno() (http.client.HTTPResponse 方法)
@anchor{library/http client http client HTTPResponse fileno}@anchor{2ca4}
@deffn {方法} HTTPResponse.fileno ()

Return the @code{fileno} of the underlying socket.
@end deffn

@geindex msg (http.client.HTTPResponse 属性)
@anchor{library/http client http client HTTPResponse msg}@anchor{2c84}
@deffn {属性} HTTPResponse.msg

A @code{http.client.HTTPMessage} instance containing the response
headers.  @code{http.client.HTTPMessage} is a subclass of
@ref{53c,,email.message.Message}.
@end deffn

@geindex version (http.client.HTTPResponse 属性)
@anchor{library/http client http client HTTPResponse version}@anchor{2ca5}
@deffn {属性} HTTPResponse.version

HTTP protocol version used by server.  10 for HTTP/1.0, 11 for HTTP/1.1.
@end deffn

@geindex status (http.client.HTTPResponse 属性)
@anchor{library/http client http client HTTPResponse status}@anchor{2ca6}
@deffn {属性} HTTPResponse.status

由服务器返回的状态码。
@end deffn

@geindex reason (http.client.HTTPResponse 属性)
@anchor{library/http client http client HTTPResponse reason}@anchor{2bd1}
@deffn {属性} HTTPResponse.reason

Reason phrase returned by server.
@end deffn

@geindex debuglevel (http.client.HTTPResponse 属性)
@anchor{library/http client http client HTTPResponse debuglevel}@anchor{2ca7}
@deffn {属性} HTTPResponse.debuglevel

A debugging hook.  If @ref{2ca7,,debuglevel} is greater than zero, messages
will be printed to stdout as the response is read and parsed.
@end deffn

@geindex closed (http.client.HTTPResponse 属性)
@anchor{library/http client http client HTTPResponse closed}@anchor{2ca8}
@deffn {属性} HTTPResponse.closed

Is @code{True} if the stream is closed.
@end deffn

@node 例子<22>,HTTPMessage Objects,HTTPResponse 对象,http client --- HTTP 协议客户端
@anchor{library/http client examples}@anchor{2ca9}
@subsubsection 例子


Here is an example session that uses the @code{GET} method:

@example
>>> import http.client
>>> conn = http.client.HTTPSConnection("www.python.org")
>>> conn.request("GET", "/")
>>> r1 = conn.getresponse()
>>> print(r1.status, r1.reason)
200 OK
>>> data1 = r1.read()  # This will return entire content.
>>> # The following example demonstrates reading data in chunks.
>>> conn.request("GET", "/")
>>> r1 = conn.getresponse()
>>> while chunk := r1.read(200):
...     print(repr(chunk))
b'<!doctype html>\n<!--[if"...
...
>>> # Example of an invalid request
>>> conn = http.client.HTTPSConnection("docs.python.org")
>>> conn.request("GET", "/parrot.spam")
>>> r2 = conn.getresponse()
>>> print(r2.status, r2.reason)
404 Not Found
>>> data2 = r2.read()
>>> conn.close()
@end example

Here is an example session that uses the @code{HEAD} method.  Note that the
@code{HEAD} method never returns any data.

@example
>>> import http.client
>>> conn = http.client.HTTPSConnection("www.python.org")
>>> conn.request("HEAD", "/")
>>> res = conn.getresponse()
>>> print(res.status, res.reason)
200 OK
>>> data = res.read()
>>> print(len(data))
0
>>> data == b'@w{'}
True
@end example

Here is an example session that shows how to @code{POST} requests:

@example
>>> import http.client, urllib.parse
>>> params = urllib.parse.urlencode(@{'@@number': 12524, '@@type': 'issue', '@@action': 'show'@})
>>> headers = @{"Content-type": "application/x-www-form-urlencoded",
...            "Accept": "text/plain"@}
>>> conn = http.client.HTTPConnection("bugs.python.org")
>>> conn.request("POST", "", params, headers)
>>> response = conn.getresponse()
>>> print(response.status, response.reason)
302 Found
>>> data = response.read()
>>> data
b'Redirecting to <a href="http://bugs.python.org/issue12524">http://bugs.python.org/issue12524</a>'
>>> conn.close()
@end example

Client side @code{HTTP PUT} requests are very similar to @code{POST} requests. The
difference lies only the server side where HTTP server will allow resources to
be created via @code{PUT} request. It should be noted that custom HTTP methods
are also handled in @ref{8f0,,urllib.request.Request} by setting the appropriate
method attribute. Here is an example session that shows how to send a @code{PUT}
request using http.client:

@example
>>> # This creates an HTTP message
>>> # with the content of BODY as the enclosed representation
>>> # for the resource http://localhost:8080/file
...
>>> import http.client
>>> BODY = "***filecontents***"
>>> conn = http.client.HTTPConnection("localhost", 8080)
>>> conn.request("PUT", "/file", BODY)
>>> response = conn.getresponse()
>>> print(response.status, response.reason)
200, OK
@end example

@node HTTPMessage Objects,,例子<22>,http client --- HTTP 协议客户端
@anchor{library/http client httpmessage-objects}@anchor{2caa}@anchor{library/http client id3}@anchor{2cab}
@subsubsection HTTPMessage Objects


An @code{http.client.HTTPMessage} instance holds the headers from an HTTP
response.  It is implemented using the @ref{53c,,email.message.Message} class.

@c XXX Define the methods that clients can depend upon between versions.

@node ftplib --- FTP 协议客户端,poplib --- POP3 protocol client,http client --- HTTP 协议客户端,互联网协议和支持
@anchor{library/ftplib doc}@anchor{2cac}@anchor{library/ftplib ftplib-ftp-protocol-client}@anchor{2cad}@anchor{library/ftplib module-ftplib}@anchor{84}
@subsection @code{ftplib} --- FTP 协议客户端


@geindex ftplib (模块)

@strong{源代码：} Lib/ftplib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/ftplib.py}

@geindex FTP; protocol
@geindex FTP; ftplib (standard module)


__________________________________________________________________


This module defines the class @ref{9fd,,FTP} and a few related items. The
@ref{9fd,,FTP} class implements the client side of the FTP protocol.  You can use
this to write Python programs that perform a variety of automated FTP jobs, such
as mirroring other FTP servers.  It is also used by the module
@ref{120,,urllib.request} to handle URLs that use FTP.  For more information on FTP
(File Transfer Protocol), see Internet 
@geindex RFC; RFC 959
RFC 959@footnote{https://tools.ietf.org/html/rfc959.html}.

Here's a sample session using the @ref{84,,ftplib} module:

@example
>>> from ftplib import FTP
>>> ftp = FTP('ftp.debian.org')     # connect to host, default port
>>> ftp.login()                     # user anonymous, passwd anonymous@@
'230 Login successful.'
>>> ftp.cwd('debian')               # change into "debian" directory
>>> ftp.retrlines('LIST')           # list directory contents
-rw-rw-r--    1 1176     1176         1063 Jun 15 10:18 README
...
drwxr-sr-x    5 1176     1176         4096 Dec 19  2000 pool
drwxr-sr-x    4 1176     1176         4096 Nov 17  2008 project
drwxr-xr-x    3 1176     1176         4096 Oct 10  2012 tools
'226 Directory send OK.'
>>> with open('README', 'wb') as fp:
>>>     ftp.retrbinary('RETR README', fp.write)
'226 Transfer complete.'
>>> ftp.quit()
@end example

这个模块定义了以下内容：

@geindex FTP (ftplib 中的类)
@anchor{library/ftplib ftplib FTP}@anchor{9fd}
@deffn {类} ftplib.FTP (host='@w{'}, user='@w{'}, passwd='@w{'}, acct='@w{'}, timeout=None, source_address=None)

Return a new instance of the @ref{9fd,,FTP} class.  When @emph{host} is given, the
method call @code{connect(host)} is made.  When @emph{user} is given, additionally
the method call @code{login(user, passwd, acct)} is made (where @emph{passwd} and
@emph{acct} default to the empty string when not given).  The optional @emph{timeout}
parameter specifies a timeout in seconds for blocking operations like the
connection attempt (if is not specified, the global default timeout setting
will be used). @emph{source_address} is a 2-tuple @code{(host, port)} for the socket
to bind to as its source address before connecting.

The @ref{9fd,,FTP} class supports the @ref{6e3,,with} statement, e.g.:

@example
>>> from ftplib import FTP
>>> with FTP("ftp1.at.proftpd.org") as ftp:
...     ftp.login()
...     ftp.dir()
... 
'230 Anonymous login ok, restrictions apply.'
dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 .
dr-xr-xr-x   9 ftp      ftp           154 May  6 10:43 ..
dr-xr-xr-x   5 ftp      ftp          4096 May  6 10:43 CentOS
dr-xr-xr-x   3 ftp      ftp            18 Jul 10  2008 Fedora
>>>
@end example


在 3.2 版更改: 添加了对 @ref{6e3,,with} 语句的支持。



在 3.3 版更改: @emph{source_address} parameter was added.

@end deffn

@geindex FTP_TLS (ftplib 中的类)
@anchor{library/ftplib ftplib FTP_TLS}@anchor{9fe}
@deffn {类} ftplib.FTP_TLS (host='@w{'}, user='@w{'}, passwd='@w{'}, acct='@w{'}, keyfile=None, certfile=None, context=None, timeout=None, source_address=None)

A @ref{9fd,,FTP} subclass which adds TLS support to FTP as described in
@geindex RFC; RFC 4217
RFC 4217@footnote{https://tools.ietf.org/html/rfc4217.html}.
Connect as usual to port 21 implicitly securing the FTP control connection
before authenticating. Securing the data connection requires the user to
explicitly ask for it by calling the @ref{2cae,,prot_p()} method.  @emph{context}
is a @ref{3dc,,ssl.SSLContext} object which allows bundling SSL configuration
options, certificates and private keys into a single (potentially
long-lived) structure.  Please read @ref{254a,,Security considerations} for best practices.

@emph{keyfile} and @emph{certfile} are a legacy alternative to @emph{context} -- they
can point to PEM-formatted private key and certificate chain files
(respectively) for the SSL connection.


3.2 新版功能.



在 3.3 版更改: @emph{source_address} parameter was added.



在 3.4 版更改: The class now supports hostname check with
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).



3.6 版后已移除: @emph{keyfile} and @emph{certfile} are deprecated in favor of @emph{context}.
Please use @ref{a8c,,ssl.SSLContext.load_cert_chain()} instead, or let
@ref{8bb,,ssl.create_default_context()} select the system's trusted CA
certificates for you.


Here's a sample session using the @ref{9fe,,FTP_TLS} class:

@example
>>> ftps = FTP_TLS('ftp.pureftpd.org')
>>> ftps.login()
'230 Anonymous user logged in'
>>> ftps.prot_p()
'200 Data protection level set to "private"'
>>> ftps.nlst()
['6jack', 'OpenBSD', 'antilink', 'blogbench', 'bsdcam', 'clockspeed', 'djbdns-jedi', 'docs', 'eaccelerator-jedi', 'favicon.ico', 'francotone', 'fugu', 'ignore', 'libpuzzle', 'metalog', 'minidentd', 'misc', 'mysql-udf-global-user-variables', 'php-jenkins-hash', 'php-skein-hash', 'php-webdav', 'phpaudit', 'phpbench', 'pincaster', 'ping', 'posto', 'pub', 'public', 'public_keys', 'pure-ftpd', 'qscan', 'qtc', 'sharedance', 'skycache', 'sound', 'tmp', 'ucarp']
@end example
@end deffn

@geindex error_reply
@anchor{library/ftplib ftplib error_reply}@anchor{2caf}
@deffn {例外} ftplib.error_reply

Exception raised when an unexpected reply is received from the server.
@end deffn

@geindex error_temp
@anchor{library/ftplib ftplib error_temp}@anchor{2cb0}
@deffn {例外} ftplib.error_temp

Exception raised when an error code signifying a temporary error (response
codes in the range 400--499) is received.
@end deffn

@geindex error_perm
@anchor{library/ftplib ftplib error_perm}@anchor{2cb1}
@deffn {例外} ftplib.error_perm

Exception raised when an error code signifying a permanent error (response
codes in the range 500--599) is received.
@end deffn

@geindex error_proto
@anchor{library/ftplib ftplib error_proto}@anchor{2cb2}
@deffn {例外} ftplib.error_proto

Exception raised when a reply is received from the server that does not fit
the response specifications of the File Transfer Protocol, i.e. begin with a
digit in the range 1--5.
@end deffn

@geindex all_errors() (在 ftplib 模块中)
@anchor{library/ftplib ftplib all_errors}@anchor{2cb3}
@deffn {数据} ftplib.all_errors

The set of all exceptions (as a tuple) that methods of @ref{9fd,,FTP}
instances may raise as a result of problems with the FTP connection (as
opposed to programming errors made by the caller).  This set includes the
four exceptions listed above as well as @ref{1d3,,OSError} and @ref{c65,,EOFError}.
@end deffn


@subsubheading 参见



@table @asis

@item Module @ref{be,,netrc}

Parser for the @code{.netrc} file format.  The file @code{.netrc} is
typically used by FTP clients to load user authentication information
before prompting the user.
@end table


@menu
* FTP Objects:: 
* FTP_TLS Objects:: 

@end menu

@node FTP Objects,FTP_TLS Objects,,ftplib --- FTP 协议客户端
@anchor{library/ftplib ftp-objects}@anchor{2cb4}@anchor{library/ftplib id1}@anchor{2cb5}
@subsubsection FTP Objects


Several methods are available in two flavors: one for handling text files and
another for binary files.  These are named for the command which is used
followed by @code{lines} for the text version or @code{binary} for the binary version.

@ref{9fd,,FTP} instances have the following methods:

@geindex set_debuglevel() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP set_debuglevel}@anchor{2cb6}
@deffn {方法} FTP.set_debuglevel (level)

Set the instance's debugging level.  This controls the amount of debugging
output printed.  The default, @code{0}, produces no debugging output.  A value of
@code{1} produces a moderate amount of debugging output, generally a single line
per request.  A value of @code{2} or higher produces the maximum amount of
debugging output, logging each line sent and received on the control connection.
@end deffn

@geindex connect() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP connect}@anchor{2cb7}
@deffn {方法} FTP.connect (host='@w{'}, port=0, timeout=None, source_address=None)

Connect to the given host and port.  The default port number is @code{21}, as
specified by the FTP protocol specification.  It is rarely needed to specify a
different port number.  This function should be called only once for each
instance; it should not be called at all if a host was given when the instance
was created.  All other methods can only be used after a connection has been
made.
The optional @emph{timeout} parameter specifies a timeout in seconds for the
connection attempt. If no @emph{timeout} is passed, the global default timeout
setting will be used.
@emph{source_address} is a 2-tuple @code{(host, port)} for the socket to bind to as
its source address before connecting.

Raises an @ref{12d0,,auditing event} @code{ftplib.connect} with arguments @code{self}, @code{host}, @code{port}.


在 3.3 版更改: @emph{source_address} parameter was added.

@end deffn

@geindex getwelcome() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP getwelcome}@anchor{2cb8}
@deffn {方法} FTP.getwelcome ()

Return the welcome message sent by the server in reply to the initial
connection.  (This message sometimes contains disclaimers or help information
that may be relevant to the user.)
@end deffn

@geindex login() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP login}@anchor{2cb9}
@deffn {方法} FTP.login (user='anonymous', passwd='@w{'}, acct='@w{'})

Log in as the given @emph{user}.  The @emph{passwd} and @emph{acct} parameters are optional and
default to the empty string.  If no @emph{user} is specified, it defaults to
@code{'anonymous'}.  If @emph{user} is @code{'anonymous'}, the default @emph{passwd} is
@code{'anonymous@@'}.  This function should be called only once for each instance,
after a connection has been established; it should not be called at all if a
host and user were given when the instance was created.  Most FTP commands are
only allowed after the client has logged in.  The @emph{acct} parameter supplies
"accounting information"; few systems implement this.
@end deffn

@geindex abort() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP abort}@anchor{2cba}
@deffn {方法} FTP.abort ()

Abort a file transfer that is in progress.  Using this does not always work, but
it's worth a try.
@end deffn

@geindex sendcmd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP sendcmd}@anchor{2cbb}
@deffn {方法} FTP.sendcmd (cmd)

Send a simple command string to the server and return the response string.

Raises an @ref{12d0,,auditing event} @code{ftplib.sendcmd} with arguments @code{self}, @code{cmd}.
@end deffn

@geindex voidcmd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP voidcmd}@anchor{2cbc}
@deffn {方法} FTP.voidcmd (cmd)

Send a simple command string to the server and handle the response.  Return
nothing if a response code corresponding to success (codes in the range
200--299) is received.  Raise @ref{2caf,,error_reply} otherwise.

Raises an @ref{12d0,,auditing event} @code{ftplib.sendcmd} with arguments @code{self}, @code{cmd}.
@end deffn

@geindex retrbinary() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP retrbinary}@anchor{2cbd}
@deffn {方法} FTP.retrbinary (cmd, callback, blocksize=8192, rest=None)

Retrieve a file in binary transfer mode.  @emph{cmd} should be an appropriate
@code{RETR} command: @code{'RETR filename'}. The @emph{callback} function is called for
each block of data received, with a single bytes argument giving the data
block. The optional @emph{blocksize} argument specifies the maximum chunk size to
read on the low-level socket object created to do the actual transfer (which
will also be the largest size of the data blocks passed to @emph{callback}).  A
reasonable default is chosen. @emph{rest} means the same thing as in the
@ref{2cbe,,transfercmd()} method.
@end deffn

@geindex retrlines() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP retrlines}@anchor{2cbf}
@deffn {方法} FTP.retrlines (cmd, callback=None)

Retrieve a file or directory listing in ASCII transfer mode.  @emph{cmd} should be
an appropriate @code{RETR} command (see @ref{2cbd,,retrbinary()}) or a command such as
@code{LIST} or @code{NLST} (usually just the string @code{'LIST'}).
@code{LIST} retrieves a list of files and information about those files.
@code{NLST} retrieves a list of file names.
The @emph{callback} function is called for each line with a string argument
containing the line with the trailing CRLF stripped.  The default @emph{callback}
prints the line to @code{sys.stdout}.
@end deffn

@geindex set_pasv() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP set_pasv}@anchor{2cc0}
@deffn {方法} FTP.set_pasv (val)

Enable "passive" mode if @emph{val} is true, otherwise disable passive mode.
Passive mode is on by default.
@end deffn

@geindex storbinary() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP storbinary}@anchor{c98}
@deffn {方法} FTP.storbinary (cmd, fp, blocksize=8192, callback=None, rest=None)

Store a file in binary transfer mode.  @emph{cmd} should be an appropriate
@code{STOR} command: @code{"STOR filename"}. @emph{fp} is a @ref{b3b,,file object}
(opened in binary mode) which is read until EOF using its @code{read()}
method in blocks of size @emph{blocksize} to provide the data to be stored.
The @emph{blocksize} argument defaults to 8192.  @emph{callback} is an optional single
parameter callable that is called on each block of data after it is sent.
@emph{rest} means the same thing as in the @ref{2cbe,,transfercmd()} method.


在 3.2 版更改: @emph{rest} parameter added.

@end deffn

@geindex storlines() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP storlines}@anchor{2cc1}
@deffn {方法} FTP.storlines (cmd, fp, callback=None)

Store a file in ASCII transfer mode.  @emph{cmd} should be an appropriate
@code{STOR} command (see @ref{c98,,storbinary()}).  Lines are read until EOF from the
@ref{b3b,,file object} @emph{fp} (opened in binary mode) using its @ref{169c,,readline()}
method to provide the data to be stored.  @emph{callback} is an optional single
parameter callable that is called on each line after it is sent.
@end deffn

@geindex transfercmd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP transfercmd}@anchor{2cbe}
@deffn {方法} FTP.transfercmd (cmd, rest=None)

Initiate a transfer over the data connection.  If the transfer is active, send an
@code{EPRT} or  @code{PORT} command and the transfer command specified by @emph{cmd}, and
accept the connection.  If the server is passive, send an @code{EPSV} or @code{PASV}
command, connect to it, and start the transfer command.  Either way, return the
socket for the connection.

If optional @emph{rest} is given, a @code{REST} command is sent to the server, passing
@emph{rest} as an argument.  @emph{rest} is usually a byte offset into the requested file,
telling the server to restart sending the file's bytes at the requested offset,
skipping over the initial bytes.  Note however that 
@geindex RFC; RFC 959
RFC 959@footnote{https://tools.ietf.org/html/rfc959.html} requires only that
@emph{rest} be a string containing characters in the printable range from ASCII code
33 to ASCII code 126.  The @ref{2cbe,,transfercmd()} method, therefore, converts
@emph{rest} to a string, but no check is performed on the string's contents.  If the
server does not recognize the @code{REST} command, an @ref{2caf,,error_reply} exception
will be raised.  If this happens, simply call @ref{2cbe,,transfercmd()} without a
@emph{rest} argument.
@end deffn

@geindex ntransfercmd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP ntransfercmd}@anchor{2cc2}
@deffn {方法} FTP.ntransfercmd (cmd, rest=None)

Like @ref{2cbe,,transfercmd()}, but returns a tuple of the data connection and the
expected size of the data.  If the expected size could not be computed, @code{None}
will be returned as the expected size.  @emph{cmd} and @emph{rest} means the same thing as
in @ref{2cbe,,transfercmd()}.
@end deffn

@geindex mlsd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP mlsd}@anchor{a00}
@deffn {方法} FTP.mlsd (path="", facts=[])

List a directory in a standardized format by using @code{MLSD} command
(
@geindex RFC; RFC 3659
RFC 3659@footnote{https://tools.ietf.org/html/rfc3659.html}).  If @emph{path} is omitted the current directory is assumed.
@emph{facts} is a list of strings representing the type of information desired
(e.g. @code{["type", "size", "perm"]}).  Return a generator object yielding a
tuple of two elements for every file found in path.  First element is the
file name, the second one is a dictionary containing facts about the file
name.  Content of this dictionary might be limited by the @emph{facts} argument
but server is not guaranteed to return all requested facts.


3.3 新版功能.

@end deffn

@geindex nlst() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP nlst}@anchor{a01}
@deffn {方法} FTP.nlst (argument[, ...])

Return a list of file names as returned by the @code{NLST} command.  The
optional @emph{argument} is a directory to list (default is the current server
directory).  Multiple arguments can be used to pass non-standard options to
the @code{NLST} command.

@cartouche
@quotation 注解 
If your server supports the command, @ref{a00,,mlsd()} offers a better API.
@end quotation
@end cartouche
@end deffn

@geindex dir() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP dir}@anchor{a02}
@deffn {方法} FTP.dir (argument[, ...])

Produce a directory listing as returned by the @code{LIST} command, printing it to
standard output.  The optional @emph{argument} is a directory to list (default is the
current server directory).  Multiple arguments can be used to pass non-standard
options to the @code{LIST} command.  If the last argument is a function, it is used
as a @emph{callback} function as for @ref{2cbf,,retrlines()}; the default prints to
@code{sys.stdout}.  This method returns @code{None}.

@cartouche
@quotation 注解 
If your server supports the command, @ref{a00,,mlsd()} offers a better API.
@end quotation
@end cartouche
@end deffn

@geindex rename() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP rename}@anchor{2cc3}
@deffn {方法} FTP.rename (fromname, toname)

Rename file @emph{fromname} on the server to @emph{toname}.
@end deffn

@geindex delete() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP delete}@anchor{2cc4}
@deffn {方法} FTP.delete (filename)

Remove the file named @emph{filename} from the server.  If successful, returns the
text of the response, otherwise raises @ref{2cb1,,error_perm} on permission errors or
@ref{2caf,,error_reply} on other errors.
@end deffn

@geindex cwd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP cwd}@anchor{2cc5}
@deffn {方法} FTP.cwd (pathname)

Set the current directory on the server.
@end deffn

@geindex mkd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP mkd}@anchor{2cc6}
@deffn {方法} FTP.mkd (pathname)

Create a new directory on the server.
@end deffn

@geindex pwd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP pwd}@anchor{2cc7}
@deffn {方法} FTP.pwd ()

Return the pathname of the current directory on the server.
@end deffn

@geindex rmd() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP rmd}@anchor{2cc8}
@deffn {方法} FTP.rmd (dirname)

Remove the directory named @emph{dirname} on the server.
@end deffn

@geindex size() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP size}@anchor{2cc9}
@deffn {方法} FTP.size (filename)

Request the size of the file named @emph{filename} on the server.  On success, the
size of the file is returned as an integer, otherwise @code{None} is returned.
Note that the @code{SIZE} command is not  standardized, but is supported by many
common server implementations.
@end deffn

@geindex quit() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP quit}@anchor{2cca}
@deffn {方法} FTP.quit ()

Send a @code{QUIT} command to the server and close the connection. This is the
"polite" way to close a connection, but it may raise an exception if the server
responds with an error to the @code{QUIT} command.  This implies a call to the
@ref{2ccb,,close()} method which renders the @ref{9fd,,FTP} instance useless for
subsequent calls (see below).
@end deffn

@geindex close() (ftplib.FTP 方法)
@anchor{library/ftplib ftplib FTP close}@anchor{2ccb}
@deffn {方法} FTP.close ()

Close the connection unilaterally.  This should not be applied to an already
closed connection such as after a successful call to @ref{2cca,,quit()}.
After this call the @ref{9fd,,FTP} instance should not be used any more (after
a call to @ref{2ccb,,close()} or @ref{2cca,,quit()} you cannot reopen the
connection by issuing another @ref{2cb9,,login()} method).
@end deffn

@node FTP_TLS Objects,,FTP Objects,ftplib --- FTP 协议客户端
@anchor{library/ftplib ftp-tls-objects}@anchor{2ccc}
@subsubsection FTP_TLS Objects


@ref{9fe,,FTP_TLS} class inherits from @ref{9fd,,FTP}, defining these additional objects:

@geindex ssl_version (ftplib.FTP_TLS 属性)
@anchor{library/ftplib ftplib FTP_TLS ssl_version}@anchor{2ccd}
@deffn {属性} FTP_TLS.ssl_version

The SSL version to use (defaults to @ref{2668,,ssl.PROTOCOL_SSLv23}).
@end deffn

@geindex auth() (ftplib.FTP_TLS 方法)
@anchor{library/ftplib ftplib FTP_TLS auth}@anchor{2cce}
@deffn {方法} FTP_TLS.auth ()

Set up a secure control connection by using TLS or SSL, depending on what
is specified in the @ref{2ccd,,ssl_version} attribute.


在 3.4 版更改: The method now supports hostname check with
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).

@end deffn

@geindex ccc() (ftplib.FTP_TLS 方法)
@anchor{library/ftplib ftplib FTP_TLS ccc}@anchor{9ff}
@deffn {方法} FTP_TLS.ccc ()

Revert control channel back to plaintext.  This can be useful to take
advantage of firewalls that know how to handle NAT with non-secure FTP
without opening fixed ports.


3.3 新版功能.

@end deffn

@geindex prot_p() (ftplib.FTP_TLS 方法)
@anchor{library/ftplib ftplib FTP_TLS prot_p}@anchor{2cae}
@deffn {方法} FTP_TLS.prot_p ()

Set up secure data connection.
@end deffn

@geindex prot_c() (ftplib.FTP_TLS 方法)
@anchor{library/ftplib ftplib FTP_TLS prot_c}@anchor{2ccf}
@deffn {方法} FTP_TLS.prot_c ()

Set up clear text data connection.
@end deffn

@node poplib --- POP3 protocol client,imaplib --- IMAP4 protocol client,ftplib --- FTP 协议客户端,互联网协议和支持
@anchor{library/poplib doc}@anchor{2cd0}@anchor{library/poplib module-poplib}@anchor{d0}@anchor{library/poplib poplib-pop3-protocol-client}@anchor{2cd1}
@subsection @code{poplib} --- POP3 protocol client


@geindex poplib (模块)

@c revised by ESR, January 2000

@strong{Source code:} Lib/poplib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/poplib.py}

@geindex POP3; protocol


__________________________________________________________________


This module defines a class, @ref{2cd2,,POP3}, which encapsulates a connection to a
POP3 server and implements the protocol as defined in 
@geindex RFC; RFC 1939
RFC 1939@footnote{https://tools.ietf.org/html/rfc1939.html}. The
@ref{2cd2,,POP3} class supports both the minimal and optional command sets from
@geindex RFC; RFC 1939
RFC 1939@footnote{https://tools.ietf.org/html/rfc1939.html}. The @ref{2cd2,,POP3} class also supports the @code{STLS} command introduced
in 
@geindex RFC; RFC 2595
RFC 2595@footnote{https://tools.ietf.org/html/rfc2595.html} to enable encrypted communication on an already established connection.

Additionally, this module provides a class @ref{bba,,POP3_SSL}, which provides
support for connecting to POP3 servers that use SSL as an underlying protocol
layer.

Note that POP3, though widely supported, is obsolescent.  The implementation
quality of POP3 servers varies widely, and too many are quite poor. If your
mailserver supports IMAP, you would be better off using the
@ref{606,,imaplib.IMAP4} class, as IMAP servers tend to be better implemented.

The @ref{d0,,poplib} module provides two classes:

@geindex POP3 (poplib 中的类)
@anchor{library/poplib poplib POP3}@anchor{2cd2}
@deffn {类} poplib.POP3 (host, port=POP3_PORT[, timeout])

This class implements the actual POP3 protocol.  The connection is created when
the instance is initialized. If @emph{port} is omitted, the standard POP3 port (110)
is used. The optional @emph{timeout} parameter specifies a timeout in seconds for the
connection attempt (if not specified, the global default timeout setting will
be used).

Raises an @ref{12d0,,auditing event} @code{poplib.connect} with arguments @code{self}, @code{host}, @code{port}.


All commands will raise an @ref{12d0,,auditing event}
@code{poplib.putline} with arguments @code{self} and @code{line},
where @code{line} is the bytes about to be sent to the remote host.

@end deffn

@geindex POP3_SSL (poplib 中的类)
@anchor{library/poplib poplib POP3_SSL}@anchor{bba}
@deffn {类} poplib.POP3_SSL (host, port=POP3_SSL_PORT, keyfile=None, certfile=None, timeout=None, context=None)

This is a subclass of @ref{2cd2,,POP3} that connects to the server over an SSL
encrypted socket.  If @emph{port} is not specified, 995, the standard POP3-over-SSL
port is used.  @emph{timeout} works as in the @ref{2cd2,,POP3} constructor.
@emph{context} is an optional @ref{3dc,,ssl.SSLContext} object which allows
bundling SSL configuration options, certificates and private keys into a
single (potentially long-lived) structure.  Please read @ref{254a,,Security considerations}
for best practices.

@emph{keyfile} and @emph{certfile} are a legacy alternative to @emph{context} - they can
point to PEM-formatted private key and certificate chain files,
respectively, for the SSL connection.

Raises an @ref{12d0,,auditing event} @code{poplib.connect} with arguments @code{self}, @code{host}, @code{port}.


All commands will raise an @ref{12d0,,auditing event}
@code{poplib.putline} with arguments @code{self} and @code{line},
where @code{line} is the bytes about to be sent to the remote host.



在 3.2 版更改: @emph{context} parameter added.



在 3.4 版更改: The class now supports hostname check with
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).



3.6 版后已移除: @emph{keyfile} and @emph{certfile} are deprecated in favor of @emph{context}.
Please use @ref{a8c,,ssl.SSLContext.load_cert_chain()} instead, or let
@ref{8bb,,ssl.create_default_context()} select the system's trusted CA
certificates for you.

@end deffn

One exception is defined as an attribute of the @ref{d0,,poplib} module:

@geindex error_proto
@anchor{library/poplib poplib error_proto}@anchor{b10}
@deffn {例外} poplib.error_proto

Exception raised on any errors from this module (errors from @ref{ef,,socket}
module are not caught). The reason for the exception is passed to the
constructor as a string.
@end deffn


@subsubheading 参见



@table @asis

@item Module @ref{98,,imaplib}

The standard Python IMAP module.

@item Frequently Asked Questions About Fetchmail@footnote{http://www.catb.org/~esr/fetchmail/fetchmail-FAQ.html}

The FAQ for the @code{fetchmail} POP/IMAP client collects information on
POP3 server variations and RFC noncompliance that may be useful if you need to
write an application based on the POP protocol.
@end table


@menu
* POP3 Objects:: 
* POP3 Example:: 

@end menu

@node POP3 Objects,POP3 Example,,poplib --- POP3 protocol client
@anchor{library/poplib id1}@anchor{2cd3}@anchor{library/poplib pop3-objects}@anchor{2cd4}
@subsubsection POP3 Objects


All POP3 commands are represented by methods of the same name, in lower-case;
most return the response text sent by the server.

An @ref{2cd2,,POP3} instance has the following methods:

@geindex set_debuglevel() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 set_debuglevel}@anchor{2cd5}
@deffn {方法} POP3.set_debuglevel (level)

Set the instance's debugging level.  This controls the amount of debugging
output printed.  The default, @code{0}, produces no debugging output.  A value of
@code{1} produces a moderate amount of debugging output, generally a single line
per request.  A value of @code{2} or higher produces the maximum amount of
debugging output, logging each line sent and received on the control connection.
@end deffn

@geindex getwelcome() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 getwelcome}@anchor{2cd6}
@deffn {方法} POP3.getwelcome ()

Returns the greeting string sent by the POP3 server.
@end deffn

@geindex capa() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 capa}@anchor{88c}
@deffn {方法} POP3.capa ()

Query the server's capabilities as specified in 
@geindex RFC; RFC 2449
RFC 2449@footnote{https://tools.ietf.org/html/rfc2449.html}.
Returns a dictionary in the form @code{@{'name': ['param'...]@}}.


3.4 新版功能.

@end deffn

@geindex user() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 user}@anchor{2cd7}
@deffn {方法} POP3.user (username)

Send user command, response should indicate that a password is required.
@end deffn

@geindex pass_() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 pass_}@anchor{2cd8}
@deffn {方法} POP3.pass_ (password)

Send password, response includes message count and mailbox size. Note: the
mailbox on the server is locked until @code{quit()} is called.
@end deffn

@geindex apop() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 apop}@anchor{2cd9}
@deffn {方法} POP3.apop (user, secret)

Use the more secure APOP authentication to log into the POP3 server.
@end deffn

@geindex rpop() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 rpop}@anchor{2cda}
@deffn {方法} POP3.rpop (user)

Use RPOP authentication (similar to UNIX r-commands) to log into POP3 server.
@end deffn

@geindex stat() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 stat}@anchor{2cdb}
@deffn {方法} POP3.stat ()

Get mailbox status.  The result is a tuple of 2 integers: @code{(message count,
mailbox size)}.
@end deffn

@geindex list() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 list}@anchor{2cdc}
@deffn {方法} POP3.list ([which])

Request message list, result is in the form @code{(response, ['mesg_num octets',
...], octets)}. If @emph{which} is set, it is the message to list.
@end deffn

@geindex retr() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 retr}@anchor{2cdd}
@deffn {方法} POP3.retr (which)

Retrieve whole message number @emph{which}, and set its seen flag. Result is in form
@code{(response, ['line', ...], octets)}.
@end deffn

@geindex dele() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 dele}@anchor{2cde}
@deffn {方法} POP3.dele (which)

Flag message number @emph{which} for deletion.  On most servers deletions are not
actually performed until QUIT (the major exception is Eudora QPOP, which
deliberately violates the RFCs by doing pending deletes on any disconnect).
@end deffn

@geindex rset() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 rset}@anchor{2cdf}
@deffn {方法} POP3.rset ()

Remove any deletion marks for the mailbox.
@end deffn

@geindex noop() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 noop}@anchor{2ce0}
@deffn {方法} POP3.noop ()

Do nothing.  Might be used as a keep-alive.
@end deffn

@geindex quit() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 quit}@anchor{b0f}
@deffn {方法} POP3.quit ()

Signoff:  commit changes, unlock mailbox, drop connection.
@end deffn

@geindex top() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 top}@anchor{2ce1}
@deffn {方法} POP3.top (which, howmuch)

Retrieves the message header plus @emph{howmuch} lines of the message after the
header of message number @emph{which}. Result is in form @code{(response, ['line', ...],
octets)}.

The POP3 TOP command this method uses, unlike the RETR command, doesn't set the
message's seen flag; unfortunately, TOP is poorly specified in the RFCs and is
frequently broken in off-brand servers. Test this method by hand against the
POP3 servers you will use before trusting it.
@end deffn

@geindex uidl() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 uidl}@anchor{2ce2}
@deffn {方法} POP3.uidl (which=None)

Return message digest (unique id) list. If @emph{which} is specified, result contains
the unique id for that message in the form @code{'response mesgnum uid}, otherwise
result is list @code{(response, ['mesgnum uid', ...], octets)}.
@end deffn

@geindex utf8() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 utf8}@anchor{72c}
@deffn {方法} POP3.utf8 ()

Try to switch to UTF-8 mode. Returns the server response if successful,
raises @ref{b10,,error_proto} if not. Specified in 
@geindex RFC; RFC 6856
RFC 6856@footnote{https://tools.ietf.org/html/rfc6856.html}.


3.5 新版功能.

@end deffn

@geindex stls() (poplib.POP3 方法)
@anchor{library/poplib poplib POP3 stls}@anchor{88d}
@deffn {方法} POP3.stls (context=None)

Start a TLS session on the active connection as specified in 
@geindex RFC; RFC 2595
RFC 2595@footnote{https://tools.ietf.org/html/rfc2595.html}.
This is only allowed before user authentication

@emph{context} parameter is a @ref{3dc,,ssl.SSLContext} object which allows
bundling SSL configuration options, certificates and private keys into
a single (potentially long-lived) structure.  Please read @ref{254a,,Security considerations}
for best practices.

This method supports hostname checking via
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).


3.4 新版功能.

@end deffn

Instances of @ref{bba,,POP3_SSL} have no additional methods. The interface of this
subclass is identical to its parent.

@node POP3 Example,,POP3 Objects,poplib --- POP3 protocol client
@anchor{library/poplib id2}@anchor{2ce3}@anchor{library/poplib pop3-example}@anchor{2ce4}
@subsubsection POP3 Example


Here is a minimal example (without error checking) that opens a mailbox and
retrieves and prints all messages:

@example
import getpass, poplib

M = poplib.POP3('localhost')
M.user(getpass.getuser())
M.pass_(getpass.getpass())
numMessages = len(M.list()[1])
for i in range(numMessages):
    for j in M.retr(i+1)[1]:
        print(j)
@end example

At the end of the module, there is a test section that contains a more extensive
example of usage.

@node imaplib --- IMAP4 protocol client,nntplib --- NNTP protocol client,poplib --- POP3 protocol client,互联网协议和支持
@anchor{library/imaplib doc}@anchor{2ce5}@anchor{library/imaplib imaplib-imap4-protocol-client}@anchor{2ce6}@anchor{library/imaplib module-imaplib}@anchor{98}
@subsection @code{imaplib} --- IMAP4 protocol client


@geindex imaplib (模块)

@c revised by ESR, January 2000

@c changes for IMAP4_SSL by Tino Lange <Tino.Lange@isg.de>, March 2002

@c changes for IMAP4_stream by Piers Lauder <piers@communitysolutions.com.au>,
@c November 2002

@strong{Source code:} Lib/imaplib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/imaplib.py}

@geindex IMAP4; protocol
@geindex IMAP4_SSL; protocol
@geindex IMAP4_stream; protocol


__________________________________________________________________


This module defines three classes, @ref{606,,IMAP4}, @ref{a12,,IMAP4_SSL} and
@ref{2ce7,,IMAP4_stream}, which encapsulate a connection to an IMAP4 server and
implement a large subset of the IMAP4rev1 client protocol as defined in
@geindex RFC; RFC 2060
RFC 2060@footnote{https://tools.ietf.org/html/rfc2060.html}. It is backward compatible with IMAP4 (
@geindex RFC; RFC 1730
RFC 1730@footnote{https://tools.ietf.org/html/rfc1730.html}) servers, but
note that the @code{STATUS} command is not supported in IMAP4.

Three classes are provided by the @ref{98,,imaplib} module, @ref{606,,IMAP4} is the
base class:

@geindex IMAP4 (imaplib 中的类)
@anchor{library/imaplib imaplib IMAP4}@anchor{606}
@deffn {类} imaplib.IMAP4 (host='@w{'}, port=IMAP4_PORT)

This class implements the actual IMAP4 protocol.  The connection is created and
protocol version (IMAP4 or IMAP4rev1) is determined when the instance is
initialized. If @emph{host} is not specified, @code{'@w{'}} (the local host) is used. If
@emph{port} is omitted, the standard IMAP4 port (143) is used.

The @ref{606,,IMAP4} class supports the @ref{6e3,,with} statement.  When used
like this, the IMAP4 @code{LOGOUT} command is issued automatically when the
@code{with} statement exits.  E.g.:

@example
>>> from imaplib import IMAP4
>>> with IMAP4("domain.org") as M:
...     M.noop()
...
('OK', [b'Nothing Accomplished. d25if65hy903weo.87'])
@end example


在 3.5 版更改: 添加了对 @ref{6e3,,with} 语句的支持。

@end deffn

Three exceptions are defined as attributes of the @ref{606,,IMAP4} class:

@geindex IMAP4.error
@anchor{library/imaplib imaplib IMAP4 error}@anchor{2ce8}
@deffn {例外} IMAP4.error

Exception raised on any errors.  The reason for the exception is passed to the
constructor as a string.
@end deffn

@geindex IMAP4.abort
@anchor{library/imaplib imaplib IMAP4 abort}@anchor{2ce9}
@deffn {例外} IMAP4.abort

IMAP4 server errors cause this exception to be raised.  This is a sub-class of
@ref{2ce8,,IMAP4.error}.  Note that closing the instance and instantiating a new one
will usually allow recovery from this exception.
@end deffn

@geindex IMAP4.readonly
@anchor{library/imaplib imaplib IMAP4 readonly}@anchor{2cea}
@deffn {例外} IMAP4.readonly

This exception is raised when a writable mailbox has its status changed by the
server.  This is a sub-class of @ref{2ce8,,IMAP4.error}.  Some other client now has
write permission, and the mailbox will need to be re-opened to re-obtain write
permission.
@end deffn

There's also a subclass for secure connections:

@geindex IMAP4_SSL (imaplib 中的类)
@anchor{library/imaplib imaplib IMAP4_SSL}@anchor{a12}
@deffn {类} imaplib.IMAP4_SSL (host='@w{'}, port=IMAP4_SSL_PORT, keyfile=None, certfile=None, ssl_context=None)

This is a subclass derived from @ref{606,,IMAP4} that connects over an SSL
encrypted socket (to use this class you need a socket module that was compiled
with SSL support).  If @emph{host} is not specified, @code{'@w{'}} (the local host) is used.
If @emph{port} is omitted, the standard IMAP4-over-SSL port (993) is used.
@emph{ssl_context} is a @ref{3dc,,ssl.SSLContext} object which allows bundling
SSL configuration options, certificates and private keys into a single
(potentially long-lived) structure.  Please read @ref{254a,,Security considerations} for
best practices.

@emph{keyfile} and @emph{certfile} are a legacy alternative to @emph{ssl_context} - they
can point to PEM-formatted private key and certificate chain files for
the SSL connection.  Note that the @emph{keyfile}/@emph{certfile} parameters are
mutually exclusive with @emph{ssl_context}, a @ref{1fb,,ValueError} is raised
if @emph{keyfile}/@emph{certfile} is provided along with @emph{ssl_context}.


在 3.3 版更改: @emph{ssl_context} parameter added.



在 3.4 版更改: The class now supports hostname check with
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).



3.6 版后已移除: @emph{keyfile} and @emph{certfile} are deprecated in favor of @emph{ssl_context}.
Please use @ref{a8c,,ssl.SSLContext.load_cert_chain()} instead, or let
@ref{8bb,,ssl.create_default_context()} select the system's trusted CA
certificates for you.

@end deffn

The second subclass allows for connections created by a child process:

@geindex IMAP4_stream (imaplib 中的类)
@anchor{library/imaplib imaplib IMAP4_stream}@anchor{2ce7}
@deffn {类} imaplib.IMAP4_stream (command)

This is a subclass derived from @ref{606,,IMAP4} that connects to the
@code{stdin/stdout} file descriptors created by passing @emph{command} to
@code{subprocess.Popen()}.
@end deffn

The following utility functions are defined:

@geindex Internaldate2tuple() (在 imaplib 模块中)
@anchor{library/imaplib imaplib Internaldate2tuple}@anchor{2ceb}
@deffn {函数} imaplib.Internaldate2tuple (datestr)

Parse an IMAP4 @code{INTERNALDATE} string and return corresponding local
time.  The return value is a @ref{594,,time.struct_time} tuple or
@code{None} if the string has wrong format.
@end deffn

@geindex Int2AP() (在 imaplib 模块中)
@anchor{library/imaplib imaplib Int2AP}@anchor{2cec}
@deffn {函数} imaplib.Int2AP (num)

Converts an integer into a string representation using characters from the set
[@code{A} .. @code{P}].
@end deffn

@geindex ParseFlags() (在 imaplib 模块中)
@anchor{library/imaplib imaplib ParseFlags}@anchor{2ced}
@deffn {函数} imaplib.ParseFlags (flagstr)

Converts an IMAP4 @code{FLAGS} response to a tuple of individual flags.
@end deffn

@geindex Time2Internaldate() (在 imaplib 模块中)
@anchor{library/imaplib imaplib Time2Internaldate}@anchor{2cee}
@deffn {函数} imaplib.Time2Internaldate (date_time)

Convert @emph{date_time} to an IMAP4 @code{INTERNALDATE} representation.
The return value is a string in the form: @code{"DD-Mmm-YYYY HH:MM:SS
+HHMM"} (including double-quotes).  The @emph{date_time} argument can
be a number (int or float) representing seconds since epoch (as
returned by @ref{316,,time.time()}), a 9-tuple representing local time
an instance of @ref{594,,time.struct_time} (as returned by
@ref{edc,,time.localtime()}), an aware instance of
@ref{194,,datetime.datetime}, or a double-quoted string.  In the last
case, it is assumed to already be in the correct format.
@end deffn

Note that IMAP4 message numbers change as the mailbox changes; in particular,
after an @code{EXPUNGE} command performs deletions the remaining messages are
renumbered. So it is highly advisable to use UIDs instead, with the UID command.

At the end of the module, there is a test section that contains a more extensive
example of usage.


@subsubheading 参见


Documents describing the protocol, and sources and binaries  for servers
implementing it, can all be found at the University of Washington's @emph{IMAP
Information Center} (@indicateurl{https://www.washington.edu/imap/}).


@menu
* IMAP4 Objects:: 
* IMAP4 Example:: 

@end menu

@node IMAP4 Objects,IMAP4 Example,,imaplib --- IMAP4 protocol client
@anchor{library/imaplib id1}@anchor{2cef}@anchor{library/imaplib imap4-objects}@anchor{2cf0}
@subsubsection IMAP4 Objects


All IMAP4rev1 commands are represented by methods of the same name, either
upper-case or lower-case.

All arguments to commands are converted to strings, except for @code{AUTHENTICATE},
and the last argument to @code{APPEND} which is passed as an IMAP4 literal.  If
necessary (the string contains IMAP4 protocol-sensitive characters and isn't
enclosed with either parentheses or double quotes) each string is quoted.
However, the @emph{password} argument to the @code{LOGIN} command is always quoted. If
you want to avoid having an argument string quoted (eg: the @emph{flags} argument to
@code{STORE}) then enclose the string in parentheses (eg: @code{r'(\Deleted)'}).

Each command returns a tuple: @code{(type, [data, ...])} where @emph{type} is usually
@code{'OK'} or @code{'NO'}, and @emph{data} is either the text from the command response,
or mandated results from the command. Each @emph{data} is either a string, or a
tuple. If a tuple, then the first part is the header of the response, and the
second part contains the data (ie: 'literal' value).

The @emph{message_set} options to commands below is a string specifying one or more
messages to be acted upon.  It may be a simple message number (@code{'1'}), a range
of message numbers (@code{'2:4'}), or a group of non-contiguous ranges separated by
commas (@code{'1:3,6:9'}).  A range can contain an asterisk to indicate an infinite
upper bound (@code{'3:*'}).

An @ref{606,,IMAP4} instance has the following methods:

@geindex append() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 append}@anchor{2cf1}
@deffn {方法} IMAP4.append (mailbox, flags, date_time, message)

Append @emph{message} to named mailbox.
@end deffn

@geindex authenticate() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 authenticate}@anchor{2cf2}
@deffn {方法} IMAP4.authenticate (mechanism, authobject)

Authenticate command --- requires response processing.

@emph{mechanism} specifies which authentication mechanism is to be used - it should
appear in the instance variable @code{capabilities} in the form @code{AUTH=mechanism}.

@emph{authobject} must be a callable object:

@example
data = authobject(response)
@end example

It will be called to process server continuation responses; the @emph{response}
argument it is passed will be @code{bytes}.  It should return @code{bytes} @emph{data}
that will be base64 encoded and sent to the server.  It should return
@code{None} if the client abort response @code{*} should be sent instead.


在 3.5 版更改: string usernames and passwords are now encoded to @code{utf-8} instead of
being limited to ASCII.

@end deffn

@geindex check() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 check}@anchor{2cf3}
@deffn {方法} IMAP4.check ()

Checkpoint mailbox on server.
@end deffn

@geindex close() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 close}@anchor{2cf4}
@deffn {方法} IMAP4.close ()

Close currently selected mailbox. Deleted messages are removed from writable
mailbox. This is the recommended command before @code{LOGOUT}.
@end deffn

@geindex copy() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 copy}@anchor{2cf5}
@deffn {方法} IMAP4.copy (message_set, new_mailbox)

Copy @emph{message_set} messages onto end of @emph{new_mailbox}.
@end deffn

@geindex create() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 create}@anchor{2cf6}
@deffn {方法} IMAP4.create (mailbox)

Create new mailbox named @emph{mailbox}.
@end deffn

@geindex delete() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 delete}@anchor{2cf7}
@deffn {方法} IMAP4.delete (mailbox)

Delete old mailbox named @emph{mailbox}.
@end deffn

@geindex deleteacl() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 deleteacl}@anchor{2cf8}
@deffn {方法} IMAP4.deleteacl (mailbox, who)

Delete the ACLs (remove any rights) set for who on mailbox.
@end deffn

@geindex enable() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 enable}@anchor{6e4}
@deffn {方法} IMAP4.enable (capability)

Enable @emph{capability} (see 
@geindex RFC; RFC 5161
RFC 5161@footnote{https://tools.ietf.org/html/rfc5161.html}).  Most capabilities do not need to be
enabled.  Currently only the @code{UTF8=ACCEPT} capability is supported
(see 
@geindex RFC; RFC 6855
RFC 6855@footnote{https://tools.ietf.org/html/rfc6855.html}).


3.5 新版功能: The @ref{6e4,,enable()} method itself, and 
@geindex RFC; RFC 6855
RFC 6855@footnote{https://tools.ietf.org/html/rfc6855.html} support.

@end deffn

@geindex expunge() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 expunge}@anchor{2cf9}
@deffn {方法} IMAP4.expunge ()

Permanently remove deleted items from selected mailbox. Generates an @code{EXPUNGE}
response for each deleted message. Returned data contains a list of @code{EXPUNGE}
message numbers in order received.
@end deffn

@geindex fetch() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 fetch}@anchor{2cfa}
@deffn {方法} IMAP4.fetch (message_set, message_parts)

Fetch (parts of) messages.  @emph{message_parts} should be a string of message part
names enclosed within parentheses, eg: @code{"(UID BODY[TEXT])"}.  Returned data
are tuples of message part envelope and data.
@end deffn

@geindex getacl() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 getacl}@anchor{2cfb}
@deffn {方法} IMAP4.getacl (mailbox)

Get the @code{ACL}s for @emph{mailbox}. The method is non-standard, but is supported
by the @code{Cyrus} server.
@end deffn

@geindex getannotation() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 getannotation}@anchor{2cfc}
@deffn {方法} IMAP4.getannotation (mailbox, entry, attribute)

Retrieve the specified @code{ANNOTATION}s for @emph{mailbox}. The method is
non-standard, but is supported by the @code{Cyrus} server.
@end deffn

@geindex getquota() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 getquota}@anchor{2cfd}
@deffn {方法} IMAP4.getquota (root)

Get the @code{quota} @emph{root}'s resource usage and limits. This method is part of the
IMAP4 QUOTA extension defined in rfc2087.
@end deffn

@geindex getquotaroot() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 getquotaroot}@anchor{2cfe}
@deffn {方法} IMAP4.getquotaroot (mailbox)

Get the list of @code{quota} @code{roots} for the named @emph{mailbox}. This method is part
of the IMAP4 QUOTA extension defined in rfc2087.
@end deffn

@geindex list() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 list}@anchor{2cff}
@deffn {方法} IMAP4.list ([directory[, pattern]])

List mailbox names in @emph{directory} matching @emph{pattern}.  @emph{directory} defaults to
the top-level mail folder, and @emph{pattern} defaults to match anything.  Returned
data contains a list of @code{LIST} responses.
@end deffn

@geindex login() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 login}@anchor{2d00}
@deffn {方法} IMAP4.login (user, password)

Identify the client using a plaintext password. The @emph{password} will be quoted.
@end deffn

@geindex login_cram_md5() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 login_cram_md5}@anchor{2d01}
@deffn {方法} IMAP4.login_cram_md5 (user, password)

Force use of @code{CRAM-MD5} authentication when identifying the client to protect
the password.  Will only work if the server @code{CAPABILITY} response includes the
phrase @code{AUTH=CRAM-MD5}.
@end deffn

@geindex logout() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 logout}@anchor{2d02}
@deffn {方法} IMAP4.logout ()

Shutdown connection to server. Returns server @code{BYE} response.


在 3.8 版更改: The method no longer ignores silently arbitrary exceptions.

@end deffn

@geindex lsub() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 lsub}@anchor{2d03}
@deffn {方法} IMAP4.lsub (directory='""', pattern='*')

List subscribed mailbox names in directory matching pattern. @emph{directory}
defaults to the top level directory and @emph{pattern} defaults to match any mailbox.
Returned data are tuples of message part envelope and data.
@end deffn

@geindex myrights() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 myrights}@anchor{2d04}
@deffn {方法} IMAP4.myrights (mailbox)

Show my ACLs for a mailbox (i.e. the rights that I have on mailbox).
@end deffn

@geindex namespace() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 namespace}@anchor{2d05}
@deffn {方法} IMAP4.namespace ()

Returns IMAP namespaces as defined in 
@geindex RFC; RFC 2342
RFC 2342@footnote{https://tools.ietf.org/html/rfc2342.html}.
@end deffn

@geindex noop() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 noop}@anchor{2d06}
@deffn {方法} IMAP4.noop ()

Send @code{NOOP} to server.
@end deffn

@geindex open() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 open}@anchor{2d07}
@deffn {方法} IMAP4.open (host, port)

Opens socket to @emph{port} at @emph{host}.  This method is implicitly called by
the @ref{606,,IMAP4} constructor.  The connection objects established by this
method will be used in the @ref{2d08,,IMAP4.read()}, @ref{2d09,,IMAP4.readline()},
@ref{2d0a,,IMAP4.send()}, and @ref{2d0b,,IMAP4.shutdown()} methods.  You may override
this method.

Raises an @ref{12d0,,auditing event} @code{imaplib.open} with arguments @code{self}, @code{host}, @code{port}.
@end deffn

@geindex partial() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 partial}@anchor{2d0c}
@deffn {方法} IMAP4.partial (message_num, message_part, start, length)

Fetch truncated part of a message. Returned data is a tuple of message part
envelope and data.
@end deffn

@geindex proxyauth() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 proxyauth}@anchor{2d0d}
@deffn {方法} IMAP4.proxyauth (user)

Assume authentication as @emph{user}. Allows an authorised administrator to proxy
into any user's mailbox.
@end deffn

@geindex read() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 read}@anchor{2d08}
@deffn {方法} IMAP4.read (size)

Reads @emph{size} bytes from the remote server. You may override this method.
@end deffn

@geindex readline() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 readline}@anchor{2d09}
@deffn {方法} IMAP4.readline ()

Reads one line from the remote server. You may override this method.
@end deffn

@geindex recent() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 recent}@anchor{2d0e}
@deffn {方法} IMAP4.recent ()

Prompt server for an update. Returned data is @code{None} if no new messages, else
value of @code{RECENT} response.
@end deffn

@geindex rename() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 rename}@anchor{2d0f}
@deffn {方法} IMAP4.rename (oldmailbox, newmailbox)

Rename mailbox named @emph{oldmailbox} to @emph{newmailbox}.
@end deffn

@geindex response() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 response}@anchor{2d10}
@deffn {方法} IMAP4.response (code)

Return data for response @emph{code} if received, or @code{None}. Returns the given
code, instead of the usual type.
@end deffn

@geindex search() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 search}@anchor{2d11}
@deffn {方法} IMAP4.search (charset, criterion[, ...])

Search mailbox for matching messages.  @emph{charset} may be @code{None}, in which case
no @code{CHARSET} will be specified in the request to the server.  The IMAP
protocol requires that at least one criterion be specified; an exception will be
raised when the server returns an error.  @emph{charset} must be @code{None} if
the @code{UTF8=ACCEPT} capability was enabled using the @ref{6e4,,enable()}
command.

示例:

@example
# M is a connected IMAP4 instance...
typ, msgnums = M.search(None, 'FROM', '"LDJ"')

# or:
typ, msgnums = M.search(None, '(FROM "LDJ")')
@end example
@end deffn

@geindex select() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 select}@anchor{2d12}
@deffn {方法} IMAP4.select (mailbox='INBOX', readonly=False)

Select a mailbox. Returned data is the count of messages in @emph{mailbox}
(@code{EXISTS} response).  The default @emph{mailbox} is @code{'INBOX'}.  If the @emph{readonly}
flag is set, modifications to the mailbox are not allowed.
@end deffn

@geindex send() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 send}@anchor{2d0a}
@deffn {方法} IMAP4.send (data)

Sends @code{data} to the remote server. You may override this method.

Raises an @ref{12d0,,auditing event} @code{imaplib.send} with arguments @code{self}, @code{data}.
@end deffn

@geindex setacl() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 setacl}@anchor{2d13}
@deffn {方法} IMAP4.setacl (mailbox, who, what)

Set an @code{ACL} for @emph{mailbox}. The method is non-standard, but is supported by
the @code{Cyrus} server.
@end deffn

@geindex setannotation() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 setannotation}@anchor{2d14}
@deffn {方法} IMAP4.setannotation (mailbox, entry, attribute[, ...])

Set @code{ANNOTATION}s for @emph{mailbox}. The method is non-standard, but is
supported by the @code{Cyrus} server.
@end deffn

@geindex setquota() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 setquota}@anchor{2d15}
@deffn {方法} IMAP4.setquota (root, limits)

Set the @code{quota} @emph{root}'s resource @emph{limits}. This method is part of the IMAP4
QUOTA extension defined in rfc2087.
@end deffn

@geindex shutdown() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 shutdown}@anchor{2d0b}
@deffn {方法} IMAP4.shutdown ()

Close connection established in @code{open}.  This method is implicitly
called by @ref{2d02,,IMAP4.logout()}.  You may override this method.
@end deffn

@geindex socket() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 socket}@anchor{2d16}
@deffn {方法} IMAP4.socket ()

Returns socket instance used to connect to server.
@end deffn

@geindex sort() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 sort}@anchor{2d17}
@deffn {方法} IMAP4.sort (sort_criteria, charset, search_criterion[, ...])

The @code{sort} command is a variant of @code{search} with sorting semantics for the
results.  Returned data contains a space separated list of matching message
numbers.

Sort has two arguments before the @emph{search_criterion} argument(s); a
parenthesized list of @emph{sort_criteria}, and the searching @emph{charset}.  Note that
unlike @code{search}, the searching @emph{charset} argument is mandatory.  There is also
a @code{uid sort} command which corresponds to @code{sort} the way that @code{uid search}
corresponds to @code{search}.  The @code{sort} command first searches the mailbox for
messages that match the given searching criteria using the charset argument for
the interpretation of strings in the searching criteria.  It then returns the
numbers of matching messages.

This is an @code{IMAP4rev1} extension command.
@end deffn

@geindex starttls() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 starttls}@anchor{ba3}
@deffn {方法} IMAP4.starttls (ssl_context=None)

Send a @code{STARTTLS} command.  The @emph{ssl_context} argument is optional
and should be a @ref{3dc,,ssl.SSLContext} object.  This will enable
encryption on the IMAP connection.  Please read @ref{254a,,Security considerations} for
best practices.


3.2 新版功能.



在 3.4 版更改: The method now supports hostname check with
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).

@end deffn

@geindex status() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 status}@anchor{2d18}
@deffn {方法} IMAP4.status (mailbox, names)

Request named status conditions for @emph{mailbox}.
@end deffn

@geindex store() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 store}@anchor{2d19}
@deffn {方法} IMAP4.store (message_set, command, flag_list)

Alters flag dispositions for messages in mailbox.  @emph{command} is specified by
section 6.4.6 of 
@geindex RFC; RFC 2060
RFC 2060@footnote{https://tools.ietf.org/html/rfc2060.html} as being one of "FLAGS", "+FLAGS", or "-FLAGS",
optionally with a suffix of ".SILENT".

For example, to set the delete flag on all messages:

@example
typ, data = M.search(None, 'ALL')
for num in data[0].split():
   M.store(num, '+FLAGS', '\\Deleted')
M.expunge()
@end example

@cartouche
@quotation 注解 
Creating flags containing ']' (for example: "[test]") violates
@geindex RFC; RFC 3501
RFC 3501@footnote{https://tools.ietf.org/html/rfc3501.html} (the IMAP protocol).  However, imaplib has historically
allowed creation of such tags, and popular IMAP servers, such as Gmail,
accept and produce such flags.  There are non-Python programs which also
create such tags.  Although it is an RFC violation and IMAP clients and
servers are supposed to be strict, imaplib nonetheless continues to allow
such tags to be created for backward compatibility reasons, and as of
Python 3.6, handles them if they are sent from the server, since this
improves real-world compatibility.
@end quotation
@end cartouche
@end deffn

@geindex subscribe() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 subscribe}@anchor{2d1a}
@deffn {方法} IMAP4.subscribe (mailbox)

Subscribe to new mailbox.
@end deffn

@geindex thread() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 thread}@anchor{2d1b}
@deffn {方法} IMAP4.thread (threading_algorithm, charset, search_criterion[, ...])

The @code{thread} command is a variant of @code{search} with threading semantics for
the results.  Returned data contains a space separated list of thread members.

Thread members consist of zero or more messages numbers, delimited by spaces,
indicating successive parent and child.

Thread has two arguments before the @emph{search_criterion} argument(s); a
@emph{threading_algorithm}, and the searching @emph{charset}.  Note that unlike
@code{search}, the searching @emph{charset} argument is mandatory.  There is also a
@code{uid thread} command which corresponds to @code{thread} the way that @code{uid
search} corresponds to @code{search}.  The @code{thread} command first searches the
mailbox for messages that match the given searching criteria using the charset
argument for the interpretation of strings in the searching criteria. It then
returns the matching messages threaded according to the specified threading
algorithm.

This is an @code{IMAP4rev1} extension command.
@end deffn

@geindex uid() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 uid}@anchor{2d1c}
@deffn {方法} IMAP4.uid (command, arg[, ...])

Execute command args with messages identified by UID, rather than message
number.  Returns response appropriate to command.  At least one argument must be
supplied; if none are provided, the server will return an error and an exception
will be raised.
@end deffn

@geindex unsubscribe() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 unsubscribe}@anchor{2d1d}
@deffn {方法} IMAP4.unsubscribe (mailbox)

Unsubscribe from old mailbox.
@end deffn

@geindex xatom() (imaplib.IMAP4 方法)
@anchor{library/imaplib imaplib IMAP4 xatom}@anchor{2d1e}
@deffn {方法} IMAP4.xatom (name[, ...])

Allow simple extension commands notified by server in @code{CAPABILITY} response.
@end deffn

The following attributes are defined on instances of @ref{606,,IMAP4}:

@geindex PROTOCOL_VERSION (imaplib.IMAP4 属性)
@anchor{library/imaplib imaplib IMAP4 PROTOCOL_VERSION}@anchor{2d1f}
@deffn {属性} IMAP4.PROTOCOL_VERSION

The most recent supported protocol in the @code{CAPABILITY} response from the
server.
@end deffn

@geindex debug (imaplib.IMAP4 属性)
@anchor{library/imaplib imaplib IMAP4 debug}@anchor{2d20}
@deffn {属性} IMAP4.debug

Integer value to control debugging output.  The initialize value is taken from
the module variable @code{Debug}.  Values greater than three trace each command.
@end deffn

@geindex utf8_enabled (imaplib.IMAP4 属性)
@anchor{library/imaplib imaplib IMAP4 utf8_enabled}@anchor{6e5}
@deffn {属性} IMAP4.utf8_enabled

Boolean value that is normally @code{False}, but is set to @code{True} if an
@ref{6e4,,enable()} command is successfully issued for the @code{UTF8=ACCEPT}
capability.


3.5 新版功能.

@end deffn

@node IMAP4 Example,,IMAP4 Objects,imaplib --- IMAP4 protocol client
@anchor{library/imaplib id2}@anchor{2d21}@anchor{library/imaplib imap4-example}@anchor{2d22}
@subsubsection IMAP4 Example


Here is a minimal example (without error checking) that opens a mailbox and
retrieves and prints all messages:

@example
import getpass, imaplib

M = imaplib.IMAP4()
M.login(getpass.getuser(), getpass.getpass())
M.select()
typ, data = M.search(None, 'ALL')
for num in data[0].split():
    typ, data = M.fetch(num, '(RFC822)')
    print('Message %s\n%s\n' % (num, data[0][1]))
M.close()
M.logout()
@end example

@node nntplib --- NNTP protocol client,smtplib ---SMTP协议客户端,imaplib --- IMAP4 protocol client,互联网协议和支持
@anchor{library/nntplib doc}@anchor{2d23}@anchor{library/nntplib module-nntplib}@anchor{c0}@anchor{library/nntplib nntplib-nntp-protocol-client}@anchor{2d24}
@subsection @code{nntplib} --- NNTP protocol client


@geindex nntplib (模块)

@strong{Source code:} Lib/nntplib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/nntplib.py}

@geindex NNTP; protocol
@geindex Network News Transfer Protocol


__________________________________________________________________


This module defines the class @ref{a27,,NNTP} which implements the client side of
the Network News Transfer Protocol.  It can be used to implement a news reader
or poster, or automated news processors.  It is compatible with 
@geindex RFC; RFC 3977
RFC 3977@footnote{https://tools.ietf.org/html/rfc3977.html}
as well as the older 
@geindex RFC; RFC 977
RFC 977@footnote{https://tools.ietf.org/html/rfc977.html} and 
@geindex RFC; RFC 2980
RFC 2980@footnote{https://tools.ietf.org/html/rfc2980.html}.

Here are two small examples of how it can be used.  To list some statistics
about a newsgroup and print the subjects of the last 10 articles:

@example
>>> s = nntplib.NNTP('news.gmane.io')
>>> resp, count, first, last, name = s.group('gmane.comp.python.committers')
>>> print('Group', name, 'has', count, 'articles, range', first, 'to', last)
Group gmane.comp.python.committers has 1096 articles, range 1 to 1096
>>> resp, overviews = s.over((last - 9, last))
>>> for id, over in overviews:
...     print(id, nntplib.decode_header(over['subject']))
...
1087 Re: Commit privileges for Łukasz Langa
1088 Re: 3.2 alpha 2 freeze
1089 Re: 3.2 alpha 2 freeze
1090 Re: Commit privileges for Łukasz Langa
1091 Re: Commit privileges for Łukasz Langa
1092 Updated ssh key
1093 Re: Updated ssh key
1094 Re: Updated ssh key
1095 Hello fellow committers!
1096 Re: Hello fellow committers!
>>> s.quit()
'205 Bye!'
@end example

To post an article from a binary file (this assumes that the article has valid
headers, and that you have right to post on the particular newsgroup):

@example
>>> s = nntplib.NNTP('news.gmane.io')
>>> f = open('article.txt', 'rb')
>>> s.post(f)
'240 Article posted successfully.'
>>> s.quit()
'205 Bye!'
@end example

The module itself defines the following classes:

@geindex NNTP (nntplib 中的类)
@anchor{library/nntplib nntplib NNTP}@anchor{a27}
@deffn {类} nntplib.NNTP (host, port=119, user=None, password=None, readermode=None, usenetrc=False[, timeout])

Return a new @ref{a27,,NNTP} object, representing a connection
to the NNTP server running on host @emph{host}, listening at port @emph{port}.
An optional @emph{timeout} can be specified for the socket connection.
If the optional @emph{user} and @emph{password} are provided, or if suitable
credentials are present in @code{/.netrc} and the optional flag @emph{usenetrc}
is true, the @code{AUTHINFO USER} and @code{AUTHINFO PASS} commands are used
to identify and authenticate the user to the server.  If the optional
flag @emph{readermode} is true, then a @code{mode reader} command is sent before
authentication is performed.  Reader mode is sometimes necessary if you are
connecting to an NNTP server on the local machine and intend to call
reader-specific commands, such as @code{group}.  If you get unexpected
@ref{2d25,,NNTPPermanentError}s, you might need to set @emph{readermode}.
The @ref{a27,,NNTP} class supports the @ref{6e3,,with} statement to
unconditionally consume @ref{1d3,,OSError} exceptions and to close the NNTP
connection when done, e.g.:

@example
>>> from nntplib import NNTP
>>> with NNTP('news.gmane.io') as n:
...     n.group('gmane.comp.python.committers')
... 
('211 1755 1 1755 gmane.comp.python.committers', 1755, 1, 1755, 'gmane.comp.python.committers')
>>>
@end example

Raises an @ref{12d0,,auditing event} @code{nntplib.connect} with arguments @code{self}, @code{host}, @code{port}.


All commands will raise an @ref{12d0,,auditing event}
@code{nntplib.putline} with arguments @code{self} and @code{line},
where @code{line} is the bytes about to be sent to the remote host.



在 3.2 版更改: @emph{usenetrc} is now @code{False} by default.



在 3.3 版更改: 添加了对 @ref{6e3,,with} 语句的支持。

@end deffn

@geindex NNTP_SSL (nntplib 中的类)
@anchor{library/nntplib nntplib NNTP_SSL}@anchor{b9e}
@deffn {类} nntplib.NNTP_SSL (host, port=563, user=None, password=None, ssl_context=None, readermode=None, usenetrc=False[, timeout])

Return a new @ref{b9e,,NNTP_SSL} object, representing an encrypted
connection to the NNTP server running on host @emph{host}, listening at
port @emph{port}.  @ref{b9e,,NNTP_SSL} objects have the same methods as
@ref{a27,,NNTP} objects.  If @emph{port} is omitted, port 563 (NNTPS) is used.
@emph{ssl_context} is also optional, and is a @ref{3dc,,SSLContext} object.
Please read @ref{254a,,Security considerations} for best practices.
All other parameters behave the same as for @ref{a27,,NNTP}.

Note that SSL-on-563 is discouraged per 
@geindex RFC; RFC 4642
RFC 4642@footnote{https://tools.ietf.org/html/rfc4642.html}, in favor of
STARTTLS as described below.  However, some servers only support the
former.

Raises an @ref{12d0,,auditing event} @code{nntplib.connect} with arguments @code{self}, @code{host}, @code{port}.


All commands will raise an @ref{12d0,,auditing event}
@code{nntplib.putline} with arguments @code{self} and @code{line},
where @code{line} is the bytes about to be sent to the remote host.



3.2 新版功能.



在 3.4 版更改: The class now supports hostname check with
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).

@end deffn

@geindex NNTPError
@anchor{library/nntplib nntplib NNTPError}@anchor{2d26}
@deffn {例外} nntplib.NNTPError

Derived from the standard exception @ref{1a9,,Exception}, this is the base
class for all exceptions raised by the @ref{c0,,nntplib} module.  Instances
of this class have the following attribute:

@geindex response (nntplib.NNTPError 属性)
@anchor{library/nntplib nntplib NNTPError response}@anchor{2d27}
@deffn {属性} response

The response of the server if available, as a @ref{329,,str} object.
@end deffn
@end deffn

@geindex NNTPReplyError
@anchor{library/nntplib nntplib NNTPReplyError}@anchor{2d28}
@deffn {例外} nntplib.NNTPReplyError

Exception raised when an unexpected reply is received from the server.
@end deffn

@geindex NNTPTemporaryError
@anchor{library/nntplib nntplib NNTPTemporaryError}@anchor{2d29}
@deffn {例外} nntplib.NNTPTemporaryError

Exception raised when a response code in the range 400--499 is received.
@end deffn

@geindex NNTPPermanentError
@anchor{library/nntplib nntplib NNTPPermanentError}@anchor{2d25}
@deffn {例外} nntplib.NNTPPermanentError

Exception raised when a response code in the range 500--599 is received.
@end deffn

@geindex NNTPProtocolError
@anchor{library/nntplib nntplib NNTPProtocolError}@anchor{2d2a}
@deffn {例外} nntplib.NNTPProtocolError

Exception raised when a reply is received from the server that does not begin
with a digit in the range 1--5.
@end deffn

@geindex NNTPDataError
@anchor{library/nntplib nntplib NNTPDataError}@anchor{2d2b}
@deffn {例外} nntplib.NNTPDataError

Exception raised when there is some error in the response data.
@end deffn

@menu
* NNTP Objects:: 
* Utility functions: Utility functions<2>. 

@end menu

@node NNTP Objects,Utility functions<2>,,nntplib --- NNTP protocol client
@anchor{library/nntplib id1}@anchor{2d2c}@anchor{library/nntplib nntp-objects}@anchor{2d2d}
@subsubsection NNTP Objects


When connected, @ref{a27,,NNTP} and @ref{b9e,,NNTP_SSL} objects support the
following methods and attributes.

@menu
* Attributes:: 
* 方法: 方法<3>. 

@end menu

@node Attributes,方法<3>,,NNTP Objects
@anchor{library/nntplib attributes}@anchor{2d2e}
@subsubsection Attributes


@geindex nntp_version (nntplib.NNTP 属性)
@anchor{library/nntplib nntplib NNTP nntp_version}@anchor{2d2f}
@deffn {属性} NNTP.nntp_version

An integer representing the version of the NNTP protocol supported by the
server.  In practice, this should be @code{2} for servers advertising
@geindex RFC; RFC 3977
RFC 3977@footnote{https://tools.ietf.org/html/rfc3977.html} compliance and @code{1} for others.


3.2 新版功能.

@end deffn

@geindex nntp_implementation (nntplib.NNTP 属性)
@anchor{library/nntplib nntplib NNTP nntp_implementation}@anchor{2d30}
@deffn {属性} NNTP.nntp_implementation

A string describing the software name and version of the NNTP server,
or @ref{157,,None} if not advertised by the server.


3.2 新版功能.

@end deffn

@node 方法<3>,,Attributes,NNTP Objects
@anchor{library/nntplib methods}@anchor{2d31}
@subsubsection 方法


The @emph{response} that is returned as the first item in the return tuple of almost
all methods is the server's response: a string beginning with a three-digit
code.  If the server's response indicates an error, the method raises one of
the above exceptions.

Many of the following methods take an optional keyword-only argument @emph{file}.
When the @emph{file} argument is supplied, it must be either a @ref{b3b,,file object}
opened for binary writing, or the name of an on-disk file to be written to.
The method will then write any data returned by the server (except for the
response line and the terminating dot) to the file; any list of lines,
tuples or objects that the method normally returns will be empty.


在 3.2 版更改: Many of the following methods have been reworked and fixed, which makes
them incompatible with their 3.1 counterparts.


@geindex quit() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP quit}@anchor{2d32}
@deffn {方法} NNTP.quit ()

Send a @code{QUIT} command and close the connection.  Once this method has been
called, no other methods of the NNTP object should be called.
@end deffn

@geindex getwelcome() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP getwelcome}@anchor{2d33}
@deffn {方法} NNTP.getwelcome ()

Return the welcome message sent by the server in reply to the initial
connection.  (This message sometimes contains disclaimers or help information
that may be relevant to the user.)
@end deffn

@geindex getcapabilities() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP getcapabilities}@anchor{2d34}
@deffn {方法} NNTP.getcapabilities ()

Return the 
@geindex RFC; RFC 3977
RFC 3977@footnote{https://tools.ietf.org/html/rfc3977.html} capabilities advertised by the server, as a
@ref{1b8,,dict} instance mapping capability names to (possibly empty) lists
of values. On legacy servers which don't understand the @code{CAPABILITIES}
command, an empty dictionary is returned instead.

@example
>>> s = NNTP('news.gmane.io')
>>> 'POST' in s.getcapabilities()
True
@end example


3.2 新版功能.

@end deffn

@geindex login() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP login}@anchor{2d35}
@deffn {方法} NNTP.login (user=None, password=None, usenetrc=True)

Send @code{AUTHINFO} commands with the user name and password.  If @emph{user}
and @emph{password} are @code{None} and @emph{usenetrc} is true, credentials from
@code{~/.netrc} will be used if possible.

Unless intentionally delayed, login is normally performed during the
@ref{a27,,NNTP} object initialization and separately calling this function
is unnecessary.  To force authentication to be delayed, you must not set
@emph{user} or @emph{password} when creating the object, and must set @emph{usenetrc} to
False.


3.2 新版功能.

@end deffn

@geindex starttls() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP starttls}@anchor{b9f}
@deffn {方法} NNTP.starttls (context=None)

Send a @code{STARTTLS} command.  This will enable encryption on the NNTP
connection.  The @emph{context} argument is optional and should be a
@ref{3dc,,ssl.SSLContext} object.  Please read @ref{254a,,Security considerations} for best
practices.

Note that this may not be done after authentication information has
been transmitted, and authentication occurs by default if possible during a
@ref{a27,,NNTP} object initialization.  See @ref{2d35,,NNTP.login()} for information
on suppressing this behavior.


3.2 新版功能.



在 3.4 版更改: The method now supports hostname check with
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).

@end deffn

@geindex newgroups() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP newgroups}@anchor{2d36}
@deffn {方法} NNTP.newgroups (date, *, file=None)

Send a @code{NEWGROUPS} command.  The @emph{date} argument should be a
@ref{193,,datetime.date} or @ref{194,,datetime.datetime} object.
Return a pair @code{(response, groups)} where @emph{groups} is a list representing
the groups that are new since the given @emph{date}. If @emph{file} is supplied,
though, then @emph{groups} will be empty.

@example
>>> from datetime import date, timedelta
>>> resp, groups = s.newgroups(date.today() - timedelta(days=3))
>>> len(groups) 
85
>>> groups[0] 
GroupInfo(group='gmane.network.tor.devel', last='4', first='1', flag='m')
@end example
@end deffn

@geindex newnews() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP newnews}@anchor{2d37}
@deffn {方法} NNTP.newnews (group, date, *, file=None)

Send a @code{NEWNEWS} command.  Here, @emph{group} is a group name or @code{'*'}, and
@emph{date} has the same meaning as for @ref{2d36,,newgroups()}.  Return a pair
@code{(response, articles)} where @emph{articles} is a list of message ids.

This command is frequently disabled by NNTP server administrators.
@end deffn

@geindex list() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP list}@anchor{2d38}
@deffn {方法} NNTP.list (group_pattern=None, *, file=None)

Send a @code{LIST} or @code{LIST ACTIVE} command.  Return a pair
@code{(response, list)} where @emph{list} is a list of tuples representing all
the groups available from this NNTP server, optionally matching the
pattern string @emph{group_pattern}.  Each tuple has the form
@code{(group, last, first, flag)}, where @emph{group} is a group name, @emph{last}
and @emph{first} are the last and first article numbers, and @emph{flag} usually
takes one of these values:


@itemize *

@item 
@code{y}: Local postings and articles from peers are allowed.

@item 
@code{m}: The group is moderated and all postings must be approved.

@item 
@code{n}: No local postings are allowed, only articles from peers.

@item 
@code{j}: Articles from peers are filed in the junk group instead.

@item 
@code{x}: No local postings, and articles from peers are ignored.

@item 
@code{=foo.bar}: Articles are filed in the @code{foo.bar} group instead.
@end itemize

If @emph{flag} has another value, then the status of the newsgroup should be
considered unknown.

This command can return very large results, especially if @emph{group_pattern}
is not specified.  It is best to cache the results offline unless you
really need to refresh them.


在 3.2 版更改: @emph{group_pattern} was added.

@end deffn

@geindex descriptions() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP descriptions}@anchor{2d39}
@deffn {方法} NNTP.descriptions (grouppattern)

Send a @code{LIST NEWSGROUPS} command, where @emph{grouppattern} is a wildmat string as
specified in 
@geindex RFC; RFC 3977
RFC 3977@footnote{https://tools.ietf.org/html/rfc3977.html} (it's essentially the same as DOS or UNIX shell wildcard
strings).  Return a pair @code{(response, descriptions)}, where @emph{descriptions}
is a dictionary mapping group names to textual descriptions.

@example
>>> resp, descs = s.descriptions('gmane.comp.python.*')
>>> len(descs) 
295
>>> descs.popitem() 
('gmane.comp.python.bio.general', 'BioPython discussion list (Moderated)')
@end example
@end deffn

@geindex description() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP description}@anchor{2d3a}
@deffn {方法} NNTP.description (group)

Get a description for a single group @emph{group}.  If more than one group matches
(if 'group' is a real wildmat string), return the first match.   If no group
matches, return an empty string.

This elides the response code from the server.  If the response code is needed,
use @ref{2d39,,descriptions()}.
@end deffn

@geindex group() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP group}@anchor{2d3b}
@deffn {方法} NNTP.group (name)

Send a @code{GROUP} command, where @emph{name} is the group name.  The group is
selected as the current group, if it exists.  Return a tuple
@code{(response, count, first, last, name)} where @emph{count} is the (estimated)
number of articles in the group, @emph{first} is the first article number in
the group, @emph{last} is the last article number in the group, and @emph{name}
is the group name.
@end deffn

@geindex over() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP over}@anchor{2d3c}
@deffn {方法} NNTP.over (message_spec, *, file=None)

Send an @code{OVER} command, or an @code{XOVER} command on legacy servers.
@emph{message_spec} can be either a string representing a message id, or
a @code{(first, last)} tuple of numbers indicating a range of articles in
the current group, or a @code{(first, None)} tuple indicating a range of
articles starting from @emph{first} to the last article in the current group,
or @ref{157,,None} to select the current article in the current group.

Return a pair @code{(response, overviews)}.  @emph{overviews} is a list of
@code{(article_number, overview)} tuples, one for each article selected
by @emph{message_spec}.  Each @emph{overview} is a dictionary with the same number
of items, but this number depends on the server.  These items are either
message headers (the key is then the lower-cased header name) or metadata
items (the key is then the metadata name prepended with @code{":"}).  The
following items are guaranteed to be present by the NNTP specification:


@itemize *

@item 
the @code{subject}, @code{from}, @code{date}, @code{message-id} and @code{references}
headers

@item 
the @code{:bytes} metadata: the number of bytes in the entire raw article
(including headers and body)

@item 
the @code{:lines} metadata: the number of lines in the article body
@end itemize

The value of each item is either a string, or @ref{157,,None} if not present.

It is advisable to use the @ref{2d3d,,decode_header()} function on header
values when they may contain non-ASCII characters:

@example
>>> _, _, first, last, _ = s.group('gmane.comp.python.devel')
>>> resp, overviews = s.over((last, last))
>>> art_num, over = overviews[0]
>>> art_num
117216
>>> list(over.keys())
['xref', 'from', ':lines', ':bytes', 'references', 'date', 'message-id', 'subject']
>>> over['from']
'=?UTF-8?B?Ik1hcnRpbiB2LiBMw7Z3aXMi?= <martin@@v.loewis.de>'
>>> nntplib.decode_header(over['from'])
'"Martin v. Löwis" <martin@@v.loewis.de>'
@end example


3.2 新版功能.

@end deffn

@geindex help() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP help}@anchor{2d3e}
@deffn {方法} NNTP.help (*, file=None)

Send a @code{HELP} command.  Return a pair @code{(response, list)} where @emph{list} is a
list of help strings.
@end deffn

@geindex stat() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP stat}@anchor{2d3f}
@deffn {方法} NNTP.stat (message_spec=None)

Send a @code{STAT} command, where @emph{message_spec} is either a message id
(enclosed in @code{'<'} and @code{'>'}) or an article number in the current group.
If @emph{message_spec} is omitted or @ref{157,,None}, the current article in the
current group is considered.  Return a triple @code{(response, number, id)}
where @emph{number} is the article number and @emph{id} is the message id.

@example
>>> _, _, first, last, _ = s.group('gmane.comp.python.devel')
>>> resp, number, message_id = s.stat(first)
>>> number, message_id
(9099, '<20030112190404.GE29873@@epoch.metaslash.com>')
@end example
@end deffn

@geindex next() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP next}@anchor{2d40}
@deffn {方法} NNTP.next ()

Send a @code{NEXT} command.  Return as for @ref{2d3f,,stat()}.
@end deffn

@geindex last() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP last}@anchor{2d41}
@deffn {方法} NNTP.last ()

Send a @code{LAST} command.  Return as for @ref{2d3f,,stat()}.
@end deffn

@geindex article() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP article}@anchor{2d42}
@deffn {方法} NNTP.article (message_spec=None, *, file=None)

Send an @code{ARTICLE} command, where @emph{message_spec} has the same meaning as
for @ref{2d3f,,stat()}.  Return a tuple @code{(response, info)} where @emph{info}
is a @ref{1b6,,namedtuple} with three attributes @emph{number},
@emph{message_id} and @emph{lines} (in that order).  @emph{number} is the article number
in the group (or 0 if the information is not available), @emph{message_id} the
message id as a string, and @emph{lines} a list of lines (without terminating
newlines) comprising the raw message including headers and body.

@example
>>> resp, info = s.article('<20030112190404.GE29873@@epoch.metaslash.com>')
>>> info.number
0
>>> info.message_id
'<20030112190404.GE29873@@epoch.metaslash.com>'
>>> len(info.lines)
65
>>> info.lines[0]
b'Path: main.gmane.org!not-for-mail'
>>> info.lines[1]
b'From: Neal Norwitz <neal@@metaslash.com>'
>>> info.lines[-3:]
[b'There is a patch for 2.3 as well as 2.2.', b'@w{'}, b'Neal']
@end example
@end deffn

@geindex head() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP head}@anchor{2d43}
@deffn {方法} NNTP.head (message_spec=None, *, file=None)

Same as @ref{2d42,,article()}, but sends a @code{HEAD} command.  The @emph{lines}
returned (or written to @emph{file}) will only contain the message headers, not
the body.
@end deffn

@geindex body() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP body}@anchor{2d44}
@deffn {方法} NNTP.body (message_spec=None, *, file=None)

Same as @ref{2d42,,article()}, but sends a @code{BODY} command.  The @emph{lines}
returned (or written to @emph{file}) will only contain the message body, not the
headers.
@end deffn

@geindex post() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP post}@anchor{2d45}
@deffn {方法} NNTP.post (data)

Post an article using the @code{POST} command.  The @emph{data} argument is either
a @ref{b3b,,file object} opened for binary reading, or any iterable of bytes
objects (representing raw lines of the article to be posted).  It should
represent a well-formed news article, including the required headers.  The
@ref{2d45,,post()} method automatically escapes lines beginning with @code{.} and
appends the termination line.

If the method succeeds, the server's response is returned.  If the server
refuses posting, a @ref{2d28,,NNTPReplyError} is raised.
@end deffn

@geindex ihave() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP ihave}@anchor{2d46}
@deffn {方法} NNTP.ihave (message_id, data)

Send an @code{IHAVE} command. @emph{message_id} is the id of the message to send
to the server (enclosed in  @code{'<'} and @code{'>'}).  The @emph{data} parameter
and the return value are the same as for @ref{2d45,,post()}.
@end deffn

@geindex date() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP date}@anchor{2d47}
@deffn {方法} NNTP.date ()

Return a pair @code{(response, date)}.  @emph{date} is a @ref{194,,datetime}
object containing the current date and time of the server.
@end deffn

@geindex slave() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP slave}@anchor{2d48}
@deffn {方法} NNTP.slave ()

Send a @code{SLAVE} command.  Return the server's @emph{response}.
@end deffn

@geindex set_debuglevel() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP set_debuglevel}@anchor{2d49}
@deffn {方法} NNTP.set_debuglevel (level)

Set the instance's debugging level.  This controls the amount of debugging
output printed.  The default, @code{0}, produces no debugging output.  A value of
@code{1} produces a moderate amount of debugging output, generally a single line
per request or response.  A value of @code{2} or higher produces the maximum amount
of debugging output, logging each line sent and received on the connection
(including message text).
@end deffn

The following are optional NNTP extensions defined in 
@geindex RFC; RFC 2980
RFC 2980@footnote{https://tools.ietf.org/html/rfc2980.html}.  Some of
them have been superseded by newer commands in 
@geindex RFC; RFC 3977
RFC 3977@footnote{https://tools.ietf.org/html/rfc3977.html}.

@geindex xhdr() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP xhdr}@anchor{2d4a}
@deffn {方法} NNTP.xhdr (hdr, str, *, file=None)

Send an @code{XHDR} command.  The @emph{hdr} argument is a header keyword, e.g.
@code{'subject'}.  The @emph{str} argument should have the form @code{'first-last'}
where @emph{first} and @emph{last} are the first and last article numbers to search.
Return a pair @code{(response, list)}, where @emph{list} is a list of pairs @code{(id,
text)}, where @emph{id} is an article number (as a string) and @emph{text} is the text of
the requested header for that article. If the @emph{file} parameter is supplied, then
the output of the  @code{XHDR} command is stored in a file.  If @emph{file} is a string,
then the method will open a file with that name, write to it  then close it.
If @emph{file} is a @ref{b3b,,file object}, then it will start calling @code{write()} on
it to store the lines of the command output. If @emph{file} is supplied, then the
returned @emph{list} is an empty list.
@end deffn

@geindex xover() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP xover}@anchor{2d4b}
@deffn {方法} NNTP.xover (start, end, *, file=None)

Send an @code{XOVER} command.  @emph{start} and @emph{end} are article numbers
delimiting the range of articles to select.  The return value is the
same of for @ref{2d3c,,over()}.  It is recommended to use @ref{2d3c,,over()}
instead, since it will automatically use the newer @code{OVER} command
if available.
@end deffn

@geindex xpath() (nntplib.NNTP 方法)
@anchor{library/nntplib nntplib NNTP xpath}@anchor{2d4c}
@deffn {方法} NNTP.xpath (id)

Return a pair @code{(resp, path)}, where @emph{path} is the directory path to the
article with message ID @emph{id}.  Most of the time, this extension is not
enabled by NNTP server administrators.


3.3 版后已移除: The XPATH extension is not actively used.

@end deffn

@c XXX deprecated:
@c 
@c .. method:: NNTP.xgtitle(name, *, file=None)
@c 
@c    Process an ``XGTITLE`` command, returning a pair ``(response, list)``, where
@c    *list* is a list of tuples containing ``(name, title)``. If the *file* parameter
@c    is supplied, then the output of the  ``XGTITLE`` command is stored in a file.
@c    If *file* is a string,  then the method will open a file with that name, write
@c    to it  then close it.  If *file* is a :term:`file object`, then it will start
@c    calling :meth:`write` on it to store the lines of the command output. If *file*
@c    is supplied, then the returned *list* is an empty list. This is an optional NNTP
@c    extension, and may not be supported by all servers.
@c 
@c    :rfc:`2980` says "It is suggested that this extension be deprecated".  Use
@c    :meth:`descriptions` or :meth:`description` instead.

@node Utility functions<2>,,NNTP Objects,nntplib --- NNTP protocol client
@anchor{library/nntplib utility-functions}@anchor{2d4d}
@subsubsection Utility functions


The module also defines the following utility function:

@geindex decode_header() (在 nntplib 模块中)
@anchor{library/nntplib nntplib decode_header}@anchor{2d3d}
@deffn {函数} nntplib.decode_header (header_str)

Decode a header value, un-escaping any escaped non-ASCII characters.
@emph{header_str} must be a @ref{329,,str} object.  The unescaped value is
returned.  Using this function is recommended to display some headers
in a human readable form:

@example
>>> decode_header("Some subject")
'Some subject'
>>> decode_header("=?ISO-8859-15?Q?D=E9buter_en_Python?=")
'Débuter en Python'
>>> decode_header("Re: =?UTF-8?B?cHJvYmzDqG1lIGRlIG1hdHJpY2U=?=")
'Re: problème de matrice'
@end example
@end deffn

@node smtplib ---SMTP协议客户端,smtpd --- SMTP 服务器,nntplib --- NNTP protocol client,互联网协议和支持
@anchor{library/smtplib doc}@anchor{2d4e}@anchor{library/smtplib module-smtplib}@anchor{ed}@anchor{library/smtplib smtplib-smtp-protocol-client}@anchor{2d4f}
@subsection @code{smtplib} ---SMTP协议客户端


@geindex smtplib (模块)

@strong{Source code:} Lib/smtplib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/smtplib.py}

@geindex SMTP; protocol
@geindex Simple Mail Transfer Protocol


__________________________________________________________________


The @ref{ed,,smtplib} module defines an SMTP client session object that can be used
to send mail to any Internet machine with an SMTP or ESMTP listener daemon.  For
details of SMTP and ESMTP operation, consult 
@geindex RFC; RFC 821
RFC 821@footnote{https://tools.ietf.org/html/rfc821.html} (Simple Mail Transfer
Protocol) and 
@geindex RFC; RFC 1869
RFC 1869@footnote{https://tools.ietf.org/html/rfc1869.html} (SMTP Service Extensions).

@geindex SMTP (smtplib 中的类)
@anchor{library/smtplib smtplib SMTP}@anchor{a7c}
@deffn {类} smtplib.SMTP (host='@w{'}, port=0, local_hostname=None[, timeout], source_address=None)

An @ref{a7c,,SMTP} instance encapsulates an SMTP connection.  It has methods
that support a full repertoire of SMTP and ESMTP operations. If the optional
host and port parameters are given, the SMTP @ref{2d50,,connect()} method is
called with those parameters during initialization.  If specified,
@emph{local_hostname} is used as the FQDN of the local host in the HELO/EHLO
command.  Otherwise, the local hostname is found using
@ref{2629,,socket.getfqdn()}.  If the @ref{2d50,,connect()} call returns anything other
than a success code, an @ref{2d51,,SMTPConnectError} is raised. The optional
@emph{timeout} parameter specifies a timeout in seconds for blocking operations
like the connection attempt (if not specified, the global default timeout
setting will be used).  If the timeout expires, @ref{c07,,socket.timeout} is
raised.  The optional source_address parameter allows binding
to some specific source address in a machine with multiple network
interfaces, and/or to some specific source TCP port. It takes a 2-tuple
(host, port), for the socket to bind to as its source address before
connecting. If omitted (or if host or port are @code{'@w{'}} and/or 0 respectively)
the OS default behavior will be used.

For normal use, you should only require the initialization/connect,
@ref{73e,,sendmail()}, and @ref{2d52,,SMTP.quit()} methods.
An example is included below.

The @ref{a7c,,SMTP} class supports the @ref{6e3,,with} statement.  When used
like this, the SMTP @code{QUIT} command is issued automatically when the
@code{with} statement exits.  E.g.:

@example
>>> from smtplib import SMTP
>>> with SMTP("domain.org") as smtp:
...     smtp.noop()
...
(250, b'Ok')
>>>
@end example


All commands will raise an @ref{12d0,,auditing event}
@code{smtplib.SMTP.send} with arguments @code{self} and @code{data},
where @code{data} is the bytes about to be sent to the remote host.



在 3.3 版更改: 添加了对 @ref{6e3,,with} 语句的支持。



在 3.3 版更改: source_address argument was added.



3.5 新版功能: The SMTPUTF8 extension (
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html}) is now supported.

@end deffn

@geindex SMTP_SSL (smtplib 中的类)
@anchor{library/smtplib smtplib SMTP_SSL}@anchor{a7d}
@deffn {类} smtplib.SMTP_SSL (host='@w{'}, port=0, local_hostname=None, keyfile=None, certfile=None[, timeout], context=None, source_address=None)

An @ref{a7d,,SMTP_SSL} instance behaves exactly the same as instances of
@ref{a7c,,SMTP}. @ref{a7d,,SMTP_SSL} should be used for situations where SSL is
required from the beginning of the connection and using @code{starttls()} is
not appropriate. If @emph{host} is not specified, the local host is used. If
@emph{port} is zero, the standard SMTP-over-SSL port (465) is used.  The optional
arguments @emph{local_hostname}, @emph{timeout} and @emph{source_address} have the same
meaning as they do in the @ref{a7c,,SMTP} class.  @emph{context}, also optional,
can contain a @ref{3dc,,SSLContext} and allows configuring various
aspects of the secure connection.  Please read @ref{254a,,Security considerations} for
best practices.

@emph{keyfile} and @emph{certfile} are a legacy alternative to @emph{context}, and can
point to a PEM formatted private key and certificate chain file for the
SSL connection.


在 3.3 版更改: 增加了 @emph{context}。



在 3.3 版更改: source_address argument was added.



在 3.4 版更改: The class now supports hostname check with
@ref{2663,,ssl.SSLContext.check_hostname} and @emph{Server Name Indication} (see
@ref{2678,,ssl.HAS_SNI}).



3.6 版后已移除: @emph{keyfile} and @emph{certfile} are deprecated in favor of @emph{context}.
Please use @ref{a8c,,ssl.SSLContext.load_cert_chain()} instead, or let
@ref{8bb,,ssl.create_default_context()} select the system's trusted CA
certificates for you.

@end deffn

@geindex LMTP (smtplib 中的类)
@anchor{library/smtplib smtplib LMTP}@anchor{a7e}
@deffn {类} smtplib.LMTP (host='@w{'}, port=LMTP_PORT, local_hostname=None, source_address=None)

The LMTP protocol, which is very similar to ESMTP, is heavily based on the
standard SMTP client. It's common to use Unix sockets for LMTP, so our
@code{connect()} method must support that as well as a regular host:port
server. The optional arguments local_hostname and source_address have the
same meaning as they do in the @ref{a7c,,SMTP} class. To specify a Unix
socket, you must use an absolute path for @emph{host}, starting with a '/'.

Authentication is supported, using the regular SMTP mechanism. When using a
Unix socket, LMTP generally don't support or require any authentication, but
your mileage might vary.
@end deffn

A nice selection of exceptions is defined as well:

@geindex SMTPException
@anchor{library/smtplib smtplib SMTPException}@anchor{8b1}
@deffn {例外} smtplib.SMTPException

Subclass of @ref{1d3,,OSError} that is the base exception class for all
the other exceptions provided by this module.


在 3.4 版更改: SMTPException became subclass of @ref{1d3,,OSError}

@end deffn

@geindex SMTPServerDisconnected
@anchor{library/smtplib smtplib SMTPServerDisconnected}@anchor{2d53}
@deffn {例外} smtplib.SMTPServerDisconnected

This exception is raised when the server unexpectedly disconnects, or when an
attempt is made to use the @ref{a7c,,SMTP} instance before connecting it to a
server.
@end deffn

@geindex SMTPResponseException
@anchor{library/smtplib smtplib SMTPResponseException}@anchor{2d54}
@deffn {例外} smtplib.SMTPResponseException

Base class for all exceptions that include an SMTP error code. These exceptions
are generated in some instances when the SMTP server returns an error code.  The
error code is stored in the @code{smtp_code} attribute of the error, and the
@code{smtp_error} attribute is set to the error message.
@end deffn

@geindex SMTPSenderRefused
@anchor{library/smtplib smtplib SMTPSenderRefused}@anchor{2d55}
@deffn {例外} smtplib.SMTPSenderRefused

Sender address refused.  In addition to the attributes set by on all
@ref{2d54,,SMTPResponseException} exceptions, this sets 'sender' to the string that
the SMTP server refused.
@end deffn

@geindex SMTPRecipientsRefused
@anchor{library/smtplib smtplib SMTPRecipientsRefused}@anchor{2d56}
@deffn {例外} smtplib.SMTPRecipientsRefused

All recipient addresses refused.  The errors for each recipient are accessible
through the attribute @code{recipients}, which is a dictionary of exactly the
same sort as @ref{73e,,SMTP.sendmail()} returns.
@end deffn

@geindex SMTPDataError
@anchor{library/smtplib smtplib SMTPDataError}@anchor{2d57}
@deffn {例外} smtplib.SMTPDataError

The SMTP server refused to accept the message data.
@end deffn

@geindex SMTPConnectError
@anchor{library/smtplib smtplib SMTPConnectError}@anchor{2d51}
@deffn {例外} smtplib.SMTPConnectError

Error occurred during establishment of a connection  with the server.
@end deffn

@geindex SMTPHeloError
@anchor{library/smtplib smtplib SMTPHeloError}@anchor{2d58}
@deffn {例外} smtplib.SMTPHeloError

The server refused our @code{HELO} message.
@end deffn

@geindex SMTPNotSupportedError
@anchor{library/smtplib smtplib SMTPNotSupportedError}@anchor{efc}
@deffn {例外} smtplib.SMTPNotSupportedError

The command or option attempted is not supported by the server.


3.5 新版功能.

@end deffn

@geindex SMTPAuthenticationError
@anchor{library/smtplib smtplib SMTPAuthenticationError}@anchor{2d59}
@deffn {例外} smtplib.SMTPAuthenticationError

SMTP authentication went wrong.  Most probably the server didn't accept the
username/password combination provided.
@end deffn


@subsubheading 参见



@table @asis

@geindex RFC; RFC 821

@item RFC 821@footnote{https://tools.ietf.org/html/rfc821.html} - Simple Mail Transfer Protocol

Protocol definition for SMTP.  This document covers the model, operating
procedure, and protocol details for SMTP.

@geindex RFC; RFC 1869

@item RFC 1869@footnote{https://tools.ietf.org/html/rfc1869.html} - SMTP Service Extensions

Definition of the ESMTP extensions for SMTP.  This describes a framework for
extending SMTP with new commands, supporting dynamic discovery of the commands
provided by the server, and defines a few additional commands.
@end table


@menu
* SMTP Objects:: 
* SMTP Example:: 

@end menu

@node SMTP Objects,SMTP Example,,smtplib ---SMTP协议客户端
@anchor{library/smtplib id1}@anchor{2d5a}@anchor{library/smtplib smtp-objects}@anchor{2d5b}
@subsubsection SMTP Objects


An @ref{a7c,,SMTP} instance has the following methods:

@geindex set_debuglevel() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP set_debuglevel}@anchor{73d}
@deffn {方法} SMTP.set_debuglevel (level)

Set the debug output level.  A value of 1 or @code{True} for @emph{level} results in
debug messages for connection and for all messages sent to and received from
the server.  A value of 2 for @emph{level} results in these messages being
timestamped.


在 3.5 版更改: Added debuglevel 2.

@end deffn

@geindex docmd() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP docmd}@anchor{2d5c}
@deffn {方法} SMTP.docmd (cmd, args='@w{'})

Send a command @emph{cmd} to the server.  The optional argument @emph{args} is simply
concatenated to the command, separated by a space.

This returns a 2-tuple composed of a numeric response code and the actual
response line (multiline responses are joined into one long line.)

In normal operation it should not be necessary to call this method explicitly.
It is used to implement other methods and may be useful for testing private
extensions.

If the connection to the server is lost while waiting for the reply,
@ref{2d53,,SMTPServerDisconnected} will be raised.
@end deffn

@geindex connect() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP connect}@anchor{2d50}
@deffn {方法} SMTP.connect (host='localhost', port=0)

Connect to a host on a given port.  The defaults are to connect to the local
host at the standard SMTP port (25). If the hostname ends with a colon (@code{':'})
followed by a number, that suffix will be stripped off and the number
interpreted as the port number to use. This method is automatically invoked by
the constructor if a host is specified during instantiation.  Returns a
2-tuple of the response code and message sent by the server in its
connection response.

Raises an @ref{12d0,,auditing event} @code{smtplib.connect} with arguments @code{self}, @code{host}, @code{port}.
@end deffn

@geindex helo() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP helo}@anchor{2d5d}
@deffn {方法} SMTP.helo (name='@w{'})

Identify yourself to the SMTP server using @code{HELO}.  The hostname argument
defaults to the fully qualified domain name of the local host.
The message returned by the server is stored as the @code{helo_resp} attribute
of the object.

In normal operation it should not be necessary to call this method explicitly.
It will be implicitly called by the @ref{73e,,sendmail()} when necessary.
@end deffn

@geindex ehlo() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP ehlo}@anchor{2d5e}
@deffn {方法} SMTP.ehlo (name='@w{'})

Identify yourself to an ESMTP server using @code{EHLO}.  The hostname argument
defaults to the fully qualified domain name of the local host.  Examine the
response for ESMTP option and store them for use by @ref{2d5f,,has_extn()}.
Also sets several informational attributes: the message returned by
the server is stored as the @code{ehlo_resp} attribute, @code{does_esmtp}
is set to true or false depending on whether the server supports ESMTP, and
@code{esmtp_features} will be a dictionary containing the names of the
SMTP service extensions this server supports, and their parameters (if any).

Unless you wish to use @ref{2d5f,,has_extn()} before sending mail, it should not be
necessary to call this method explicitly.  It will be implicitly called by
@ref{73e,,sendmail()} when necessary.
@end deffn

@geindex ehlo_or_helo_if_needed() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP ehlo_or_helo_if_needed}@anchor{2d60}
@deffn {方法} SMTP.ehlo_or_helo_if_needed ()

This method calls @ref{2d5e,,ehlo()} and/or @ref{2d5d,,helo()} if there has been no
previous @code{EHLO} or @code{HELO} command this session.  It tries ESMTP @code{EHLO}
first.


@table @asis

@item @ref{2d58,,SMTPHeloError}

The server didn't reply properly to the @code{HELO} greeting.
@end table
@end deffn

@geindex has_extn() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP has_extn}@anchor{2d5f}
@deffn {方法} SMTP.has_extn (name)

Return @ref{494,,True} if @emph{name} is in the set of SMTP service extensions returned
by the server, @ref{380,,False} otherwise. Case is ignored.
@end deffn

@geindex verify() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP verify}@anchor{2d61}
@deffn {方法} SMTP.verify (address)

Check the validity of an address on this server using SMTP @code{VRFY}. Returns a
tuple consisting of code 250 and a full 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html} address (including human
name) if the user address is valid. Otherwise returns an SMTP error code of 400
or greater and an error string.

@cartouche
@quotation 注解 
Many sites disable SMTP @code{VRFY} in order to foil spammers.
@end quotation
@end cartouche
@end deffn

@geindex login() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP login}@anchor{2d62}
@deffn {方法} SMTP.login (user, password, *, initial_response_ok=True)

Log in on an SMTP server that requires authentication. The arguments are the
username and the password to authenticate with. If there has been no previous
@code{EHLO} or @code{HELO} command this session, this method tries ESMTP @code{EHLO}
first. This method will return normally if the authentication was successful, or
may raise the following exceptions:


@table @asis

@item @ref{2d58,,SMTPHeloError}

The server didn't reply properly to the @code{HELO} greeting.

@item @ref{2d59,,SMTPAuthenticationError}

The server didn't accept the username/password combination.

@item @ref{efc,,SMTPNotSupportedError}

The @code{AUTH} command is not supported by the server.

@item @ref{8b1,,SMTPException}

No suitable authentication method was found.
@end table

Each of the authentication methods supported by @ref{ed,,smtplib} are tried in
turn if they are advertised as supported by the server.  See @ref{73c,,auth()}
for a list of supported authentication methods.  @emph{initial_response_ok} is
passed through to @ref{73c,,auth()}.

Optional keyword argument @emph{initial_response_ok} specifies whether, for
authentication methods that support it, an "initial response" as specified
in 
@geindex RFC; RFC 4954
RFC 4954@footnote{https://tools.ietf.org/html/rfc4954.html} can be sent along with the @code{AUTH} command, rather than
requiring a challenge/response.


在 3.5 版更改: @ref{efc,,SMTPNotSupportedError} may be raised, and the
@emph{initial_response_ok} parameter was added.

@end deffn

@geindex auth() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP auth}@anchor{73c}
@deffn {方法} SMTP.auth (mechanism, authobject, *, initial_response_ok=True)

Issue an @code{SMTP} @code{AUTH} command for the specified authentication
@emph{mechanism}, and handle the challenge response via @emph{authobject}.

@emph{mechanism} specifies which authentication mechanism is to
be used as argument to the @code{AUTH} command; the valid values are
those listed in the @code{auth} element of @code{esmtp_features}.

@emph{authobject} must be a callable object taking an optional single argument:

@quotation

data = authobject(challenge=None)
@end quotation

If optional keyword argument @emph{initial_response_ok} is true,
@code{authobject()} will be called first with no argument.  It can return the
@geindex RFC; RFC 4954
RFC 4954@footnote{https://tools.ietf.org/html/rfc4954.html} "initial response" ASCII @code{str} which will be encoded and sent with
the @code{AUTH} command as below.  If the @code{authobject()} does not support an
initial response (e.g. because it requires a challenge), it should return
@code{None} when called with @code{challenge=None}.  If @emph{initial_response_ok} is
false, then @code{authobject()} will not be called first with @code{None}.

If the initial response check returns @code{None}, or if @emph{initial_response_ok} is
false, @code{authobject()} will be called to process the server's challenge
response; the @emph{challenge} argument it is passed will be a @code{bytes}.  It
should return ASCII @code{str} @emph{data} that will be base64 encoded and sent to the
server.

The @code{SMTP} class provides @code{authobjects} for the @code{CRAM-MD5}, @code{PLAIN},
and @code{LOGIN} mechanisms; they are named @code{SMTP.auth_cram_md5},
@code{SMTP.auth_plain}, and @code{SMTP.auth_login} respectively.  They all require
that the @code{user} and @code{password} properties of the @code{SMTP} instance are
set to appropriate values.

User code does not normally need to call @code{auth} directly, but can instead
call the @ref{2d62,,login()} method, which will try each of the above mechanisms
in turn, in the order listed.  @code{auth} is exposed to facilitate the
implementation of authentication methods not (or not yet) supported
directly by @ref{ed,,smtplib}.


3.5 新版功能.

@end deffn

@geindex starttls() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP starttls}@anchor{a7f}
@deffn {方法} SMTP.starttls (keyfile=None, certfile=None, context=None)

Put the SMTP connection in TLS (Transport Layer Security) mode.  All SMTP
commands that follow will be encrypted.  You should then call @ref{2d5e,,ehlo()}
again.

If @emph{keyfile} and @emph{certfile} are provided, they are used to create an
@ref{3dc,,ssl.SSLContext}.

Optional @emph{context} parameter is an @ref{3dc,,ssl.SSLContext} object; This is
an alternative to using a keyfile and a certfile and if specified both
@emph{keyfile} and @emph{certfile} should be @code{None}.

If there has been no previous @code{EHLO} or @code{HELO} command this session,
this method tries ESMTP @code{EHLO} first.


3.6 版后已移除: @emph{keyfile} and @emph{certfile} are deprecated in favor of @emph{context}.
Please use @ref{a8c,,ssl.SSLContext.load_cert_chain()} instead, or let
@ref{8bb,,ssl.create_default_context()} select the system's trusted CA
certificates for you.



@table @asis

@item @ref{2d58,,SMTPHeloError}

The server didn't reply properly to the @code{HELO} greeting.

@item @ref{efc,,SMTPNotSupportedError}

The server does not support the STARTTLS extension.

@item @ref{2ba,,RuntimeError}

SSL/TLS support is not available to your Python interpreter.
@end table


在 3.3 版更改: 增加了 @emph{context}。



在 3.4 版更改: The method now supports hostname check with
@code{SSLContext.check_hostname} and @emph{Server Name Indicator} (see
@ref{2678,,HAS_SNI}).



在 3.5 版更改: The error raised for lack of STARTTLS support is now the
@ref{efc,,SMTPNotSupportedError} subclass instead of the base
@ref{8b1,,SMTPException}.

@end deffn

@geindex sendmail() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP sendmail}@anchor{73e}
@deffn {方法} SMTP.sendmail (from_addr, to_addrs, msg, mail_options=(), rcpt_options=())

Send mail.  The required arguments are an 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html} from-address string, a list
of 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html} to-address strings (a bare string will be treated as a list with 1
address), and a message string.  The caller may pass a list of ESMTP options
(such as @code{8bitmime}) to be used in @code{MAIL FROM} commands as @emph{mail_options}.
ESMTP options (such as @code{DSN} commands) that should be used with all @code{RCPT}
commands can be passed as @emph{rcpt_options}.  (If you need to use different ESMTP
options to different recipients you have to use the low-level methods such as
@code{mail()}, @code{rcpt()} and @code{data()} to send the message.)

@cartouche
@quotation 注解 
The @emph{from_addr} and @emph{to_addrs} parameters are used to construct the message
envelope used by the transport agents.  @code{sendmail} does not modify the
message headers in any way.
@end quotation
@end cartouche

@emph{msg} may be a string containing characters in the ASCII range, or a byte
string.  A string is encoded to bytes using the ascii codec, and lone @code{\r}
and @code{\n} characters are converted to @code{\r\n} characters.  A byte string is
not modified.

If there has been no previous @code{EHLO} or @code{HELO} command this session, this
method tries ESMTP @code{EHLO} first. If the server does ESMTP, message size and
each of the specified options will be passed to it (if the option is in the
feature set the server advertises).  If @code{EHLO} fails, @code{HELO} will be tried
and ESMTP options suppressed.

This method will return normally if the mail is accepted for at least one
recipient. Otherwise it will raise an exception.  That is, if this method does
not raise an exception, then someone should get your mail. If this method does
not raise an exception, it returns a dictionary, with one entry for each
recipient that was refused.  Each entry contains a tuple of the SMTP error code
and the accompanying error message sent by the server.

If @code{SMTPUTF8} is included in @emph{mail_options}, and the server supports it,
@emph{from_addr} and @emph{to_addrs} may contain non-ASCII characters.

This method may raise the following exceptions:


@table @asis

@item @ref{2d56,,SMTPRecipientsRefused}

All recipients were refused.  Nobody got the mail.  The @code{recipients}
attribute of the exception object is a dictionary with information about the
refused recipients (like the one returned when at least one recipient was
accepted).

@item @ref{2d58,,SMTPHeloError}

The server didn't reply properly to the @code{HELO} greeting.

@item @ref{2d55,,SMTPSenderRefused}

The server didn't accept the @emph{from_addr}.

@item @ref{2d57,,SMTPDataError}

The server replied with an unexpected error code (other than a refusal of a
recipient).

@item @ref{efc,,SMTPNotSupportedError}

@code{SMTPUTF8} was given in the @emph{mail_options} but is not supported by the
server.
@end table

Unless otherwise noted, the connection will be open even after an exception is
raised.


在 3.2 版更改: @emph{msg} may be a byte string.



在 3.5 版更改: @code{SMTPUTF8} support added, and @ref{efc,,SMTPNotSupportedError} may be
raised if @code{SMTPUTF8} is specified but the server does not support it.

@end deffn

@geindex send_message() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP send_message}@anchor{73f}
@deffn {方法} SMTP.send_message (msg, from_addr=None, to_addrs=None, mail_options=(), rcpt_options=())

This is a convenience method for calling @ref{73e,,sendmail()} with the message
represented by an @ref{53c,,email.message.Message} object.  The arguments have
the same meaning as for @ref{73e,,sendmail()}, except that @emph{msg} is a @code{Message}
object.

If @emph{from_addr} is @code{None} or @emph{to_addrs} is @code{None}, @code{send_message} fills
those arguments with addresses extracted from the headers of @emph{msg} as
specified in 
@geindex RFC; RFC 5322
RFC 5322@footnote{https://tools.ietf.org/html/rfc5322.html}: @emph{from_addr} is set to the @code{Sender}
field if it is present, and otherwise to the @code{From} field.
@emph{to_addrs} combines the values (if any) of the @code{To},
@code{Cc}, and @code{Bcc} fields from @emph{msg}.  If exactly one
set of @code{Resent-*} headers appear in the message, the regular
headers are ignored and the @code{Resent-*} headers are used instead.
If the message contains more than one set of @code{Resent-*} headers,
a @ref{1fb,,ValueError} is raised, since there is no way to unambiguously detect
the most recent set of @code{Resent-} headers.

@code{send_message} serializes @emph{msg} using
@ref{b46,,BytesGenerator} with @code{\r\n} as the @emph{linesep}, and
calls @ref{73e,,sendmail()} to transmit the resulting message.  Regardless of the
values of @emph{from_addr} and @emph{to_addrs}, @code{send_message} does not transmit any
@code{Bcc} or @code{Resent-Bcc} headers that may appear
in @emph{msg}.  If any of the addresses in @emph{from_addr} and @emph{to_addrs} contain
non-ASCII characters and the server does not advertise @code{SMTPUTF8} support,
an @code{SMTPNotSupported} error is raised.  Otherwise the @code{Message} is
serialized with a clone of its @ref{75,,policy} with the
@ref{6cc,,utf8} attribute set to @code{True}, and
@code{SMTPUTF8} and @code{BODY=8BITMIME} are added to @emph{mail_options}.


3.2 新版功能.



3.5 新版功能: Support for internationalized addresses (@code{SMTPUTF8}).

@end deffn

@geindex quit() (smtplib.SMTP 方法)
@anchor{library/smtplib smtplib SMTP quit}@anchor{2d52}
@deffn {方法} SMTP.quit ()

Terminate the SMTP session and close the connection.  Return the result of
the SMTP @code{QUIT} command.
@end deffn

Low-level methods corresponding to the standard SMTP/ESMTP commands @code{HELP},
@code{RSET}, @code{NOOP}, @code{MAIL}, @code{RCPT}, and @code{DATA} are also supported.
Normally these do not need to be called directly, so they are not documented
here.  For details, consult the module code.

@node SMTP Example,,SMTP Objects,smtplib ---SMTP协议客户端
@anchor{library/smtplib id2}@anchor{2d63}@anchor{library/smtplib smtp-example}@anchor{2d64}
@subsubsection SMTP Example


This example prompts the user for addresses needed in the message envelope ('To'
and 'From' addresses), and the message to be delivered.  Note that the headers
to be included with the message must be included in the message as entered; this
example doesn't do any processing of the 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html} headers.  In particular, the
'To' and 'From' addresses must be included in the message headers explicitly.

@example
import smtplib

def prompt(prompt):
    return input(prompt).strip()

fromaddr = prompt("From: ")
toaddrs  = prompt("To: ").split()
print("Enter message, end with ^D (Unix) or ^Z (Windows):")

# Add the From: and To: headers at the start!
msg = ("From: %s\r\nTo: %s\r\n\r\n"
       % (fromaddr, ", ".join(toaddrs)))
while True:
    try:
        line = input()
    except EOFError:
        break
    if not line:
        break
    msg = msg + line

print("Message length is", len(msg))

server = smtplib.SMTP('localhost')
server.set_debuglevel(1)
server.sendmail(fromaddr, toaddrs, msg)
server.quit()
@end example

@cartouche
@quotation 注解 
In general, you will want to use the @ref{69,,email} package's features to
construct an email message, which you can then send
via @ref{73f,,send_message()}; see @ref{83f,,email; 示例}.
@end quotation
@end cartouche

@node smtpd --- SMTP 服务器,telnetlib --- Telnet client,smtplib ---SMTP协议客户端,互联网协议和支持
@anchor{library/smtpd doc}@anchor{2d65}@anchor{library/smtpd module-smtpd}@anchor{ec}@anchor{library/smtpd smtpd-smtp-server}@anchor{2d66}
@subsection @code{smtpd} --- SMTP 服务器


@geindex smtpd (模块)

@strong{源代码:} Lib/smtpd.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/smtpd.py}


__________________________________________________________________


This module offers several classes to implement SMTP (email) servers.


@subsubheading 参见


The aiosmtpd@footnote{http://aiosmtpd.readthedocs.io/} package is a recommended
replacement for this module.  It is based on @ref{a,,asyncio} and provides a
more straightforward API.  @ref{ec,,smtpd} should be considered deprecated.


Several server implementations are present; one is a generic
do-nothing implementation, which can be overridden, while the other two offer
specific mail-sending strategies.

Additionally the SMTPChannel may be extended to implement very specific
interaction behaviour with SMTP clients.

The code supports 
@geindex RFC; RFC 5321
RFC 5321@footnote{https://tools.ietf.org/html/rfc5321.html}, plus the 
@geindex RFC; RFC 1870
RFC 1870@footnote{https://tools.ietf.org/html/rfc1870.html} SIZE and 
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html}
SMTPUTF8 extensions.

@menu
* SMTPServer 对象:: 
* DebuggingServer 对象:: 
* PureProxy对象:: 
* MailmanProxy 对象:: 
* SMTPChannel 对象:: 

@end menu

@node SMTPServer 对象,DebuggingServer 对象,,smtpd --- SMTP 服务器
@anchor{library/smtpd smtpserver-objects}@anchor{2d67}
@subsubsection SMTPServer 对象


@geindex SMTPServer (smtpd 中的类)
@anchor{library/smtpd smtpd SMTPServer}@anchor{5fd}
@deffn {类} smtpd.SMTPServer (localaddr, remoteaddr, data_size_limit=33554432, map=None, enable_SMTPUTF8=False, decode_data=False)

Create a new @ref{5fd,,SMTPServer} object, which binds to local address
@emph{localaddr}.  It will treat @emph{remoteaddr} as an upstream SMTP relayer.  Both
@emph{localaddr} and @emph{remoteaddr} should be a @ref{2602,,(host@comma{} port)}
tuple.  The object inherits from @ref{bbc,,asyncore.dispatcher}, and so will
insert itself into @ref{b,,asyncore}'s event loop on instantiation.

@emph{data_size_limit} specifies the maximum number of bytes that will be
accepted in a @code{DATA} command.  A value of @code{None} or @code{0} means no
limit.

@emph{map} is the socket map to use for connections (an initially empty
dictionary is a suitable value).  If not specified the @ref{b,,asyncore}
global socket map is used.

@emph{enable_SMTPUTF8} determines whether the @code{SMTPUTF8} extension (as defined
in 
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html}) should be enabled.  The default is @code{False}.
When @code{True}, @code{SMTPUTF8} is accepted as a parameter to the @code{MAIL}
command and when present is passed to @ref{5fe,,process_message()} in the
@code{kwargs['mail_options']} list.  @emph{decode_data} and @emph{enable_SMTPUTF8}
cannot be set to @code{True} at the same time.

@emph{decode_data} specifies whether the data portion of the SMTP transaction
should be decoded using UTF-8.  When @emph{decode_data} is @code{False} (the
default), the server advertises the @code{8BITMIME}
extension (
@geindex RFC; RFC 6152
RFC 6152@footnote{https://tools.ietf.org/html/rfc6152.html}), accepts the @code{BODY=8BITMIME} parameter to
the @code{MAIL} command, and when present passes it to @ref{5fe,,process_message()}
in the @code{kwargs['mail_options']} list. @emph{decode_data} and @emph{enable_SMTPUTF8}
cannot be set to @code{True} at the same time.

@geindex process_message() (smtpd.SMTPServer 方法)
@anchor{library/smtpd smtpd SMTPServer process_message}@anchor{5fe}
@deffn {方法} process_message (peer, mailfrom, rcpttos, data, **kwargs)

Raise a @ref{609,,NotImplementedError} exception. Override this in subclasses to
do something useful with this message. Whatever was passed in the
constructor as @emph{remoteaddr} will be available as the @code{_remoteaddr}
attribute. @emph{peer} is the remote host's address, @emph{mailfrom} is the envelope
originator, @emph{rcpttos} are the envelope recipients and @emph{data} is a string
containing the contents of the e-mail (which should be in 
@geindex RFC; RFC 5321
RFC 5321@footnote{https://tools.ietf.org/html/rfc5321.html}
format).

If the @emph{decode_data} constructor keyword is set to @code{True}, the @emph{data}
argument will be a unicode string.  If it is set to @code{False}, it
will be a bytes object.

@emph{kwargs} is a dictionary containing additional information. It is empty
if @code{decode_data=True} was given as an init argument, otherwise
it contains the following keys:

@quotation


@table @asis

@item @emph{mail_options}:

a list of all received parameters to the @code{MAIL}
command (the elements are uppercase strings; example:
@code{['BODY=8BITMIME', 'SMTPUTF8']}).

@item @emph{rcpt_options}:

same as @emph{mail_options} but for the @code{RCPT} command.
Currently no @code{RCPT TO} options are supported, so for now
this will always be an empty list.
@end table
@end quotation

Implementations of @code{process_message} should use the @code{**kwargs}
signature to accept arbitrary keyword arguments, since future feature
enhancements may add keys to the kwargs dictionary.

Return @code{None} to request a normal @code{250 Ok} response; otherwise
return the desired response string in 
@geindex RFC; RFC 5321
RFC 5321@footnote{https://tools.ietf.org/html/rfc5321.html} format.
@end deffn

@geindex channel_class (smtpd.SMTPServer 属性)
@anchor{library/smtpd smtpd SMTPServer channel_class}@anchor{2d68}
@deffn {属性} channel_class

Override this in subclasses to use a custom @ref{5fc,,SMTPChannel} for
managing SMTP clients.
@end deffn


3.4 新版功能: The @emph{map} constructor argument.



在 3.5 版更改: @emph{localaddr} and @emph{remoteaddr} may now contain IPv6 addresses.



3.5 新版功能: The @emph{decode_data} and @emph{enable_SMTPUTF8} constructor parameters, and the
@emph{kwargs} parameter to @ref{5fe,,process_message()} when @emph{decode_data} is
@code{False}.



在 3.6 版更改: @emph{decode_data} is now @code{False} by default.

@end deffn

@node DebuggingServer 对象,PureProxy对象,SMTPServer 对象,smtpd --- SMTP 服务器
@anchor{library/smtpd debuggingserver-objects}@anchor{2d69}
@subsubsection DebuggingServer 对象


@geindex DebuggingServer (smtpd 中的类)
@anchor{library/smtpd smtpd DebuggingServer}@anchor{2d6a}
@deffn {类} smtpd.DebuggingServer (localaddr, remoteaddr)

Create a new debugging server.  Arguments are as per @ref{5fd,,SMTPServer}.
Messages will be discarded, and printed on stdout.
@end deffn

@node PureProxy对象,MailmanProxy 对象,DebuggingServer 对象,smtpd --- SMTP 服务器
@anchor{library/smtpd pureproxy-objects}@anchor{2d6b}
@subsubsection PureProxy对象


@geindex PureProxy (smtpd 中的类)
@anchor{library/smtpd smtpd PureProxy}@anchor{2d6c}
@deffn {类} smtpd.PureProxy (localaddr, remoteaddr)

Create a new pure proxy server. Arguments are as per @ref{5fd,,SMTPServer}.
Everything will be relayed to @emph{remoteaddr}.  Note that running this has a good
chance to make you into an open relay, so please be careful.
@end deffn

@node MailmanProxy 对象,SMTPChannel 对象,PureProxy对象,smtpd --- SMTP 服务器
@anchor{library/smtpd mailmanproxy-objects}@anchor{2d6d}
@subsubsection MailmanProxy 对象


@geindex MailmanProxy (smtpd 中的类)
@anchor{library/smtpd smtpd MailmanProxy}@anchor{2d6e}
@deffn {类} smtpd.MailmanProxy (localaddr, remoteaddr)

Create a new pure proxy server. Arguments are as per @ref{5fd,,SMTPServer}.
Everything will be relayed to @emph{remoteaddr}, unless local mailman configurations
knows about an address, in which case it will be handled via mailman.  Note that
running this has a good chance to make you into an open relay, so please be
careful.
@end deffn

@node SMTPChannel 对象,,MailmanProxy 对象,smtpd --- SMTP 服务器
@anchor{library/smtpd smtpchannel-objects}@anchor{2d6f}
@subsubsection SMTPChannel 对象


@geindex SMTPChannel (smtpd 中的类)
@anchor{library/smtpd smtpd SMTPChannel}@anchor{5fc}
@deffn {类} smtpd.SMTPChannel (server, conn, addr, data_size_limit=33554432, map=None, enable_SMTPUTF8=False, decode_data=False)

Create a new @ref{5fc,,SMTPChannel} object which manages the communication
between the server and a single SMTP client.

@emph{conn} and @emph{addr} are as per the instance variables described below.

@emph{data_size_limit} specifies the maximum number of bytes that will be
accepted in a @code{DATA} command.  A value of @code{None} or @code{0} means no
limit.

@emph{enable_SMTPUTF8} determines whether the @code{SMTPUTF8} extension (as defined
in 
@geindex RFC; RFC 6531
RFC 6531@footnote{https://tools.ietf.org/html/rfc6531.html}) should be enabled.  The default is @code{False}.
@emph{decode_data} and @emph{enable_SMTPUTF8} cannot be set to @code{True} at the same
time.

A dictionary can be specified in @emph{map} to avoid using a global socket map.

@emph{decode_data} specifies whether the data portion of the SMTP transaction
should be decoded using UTF-8.  The default is @code{False}.
@emph{decode_data} and @emph{enable_SMTPUTF8} cannot be set to @code{True} at the same
time.

To use a custom SMTPChannel implementation you need to override the
@ref{2d68,,SMTPServer.channel_class} of your @ref{5fd,,SMTPServer}.


在 3.5 版更改: The @emph{decode_data} and @emph{enable_SMTPUTF8} parameters were added.



在 3.6 版更改: @emph{decode_data} is now @code{False} by default.


The @ref{5fc,,SMTPChannel} has the following instance variables:

@geindex smtp_server (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel smtp_server}@anchor{2d70}
@deffn {属性} smtp_server

Holds the @ref{5fd,,SMTPServer} that spawned this channel.
@end deffn

@geindex conn (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel conn}@anchor{2d71}
@deffn {属性} conn

Holds the socket object connecting to the client.
@end deffn

@geindex addr (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel addr}@anchor{2d72}
@deffn {属性} addr

Holds the address of the client, the second value returned by
@ref{66f,,socket.accept}
@end deffn

@geindex received_lines (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel received_lines}@anchor{2d73}
@deffn {属性} received_lines

Holds a list of the line strings (decoded using UTF-8) received from
the client. The lines have their @code{"\r\n"} line ending translated to
@code{"\n"}.
@end deffn

@geindex smtp_state (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel smtp_state}@anchor{2d74}
@deffn {属性} smtp_state

Holds the current state of the channel. This will be either
@code{COMMAND} initially and then @code{DATA} after the client sends
a "DATA" line.
@end deffn

@geindex seen_greeting (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel seen_greeting}@anchor{2d75}
@deffn {属性} seen_greeting

Holds a string containing the greeting sent by the client in its "HELO".
@end deffn

@geindex mailfrom (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel mailfrom}@anchor{2d76}
@deffn {属性} mailfrom

Holds a string containing the address identified in the "MAIL FROM:" line
from the client.
@end deffn

@geindex rcpttos (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel rcpttos}@anchor{2d77}
@deffn {属性} rcpttos

Holds a list of strings containing the addresses identified in the
"RCPT TO:" lines from the client.
@end deffn

@geindex received_data (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel received_data}@anchor{2d78}
@deffn {属性} received_data

Holds a string containing all of the data sent by the client during the
DATA state, up to but not including the terminating @code{"\r\n.\r\n"}.
@end deffn

@geindex fqdn (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel fqdn}@anchor{2d79}
@deffn {属性} fqdn

Holds the fully-qualified domain name of the server as returned by
@ref{2629,,socket.getfqdn()}.
@end deffn

@geindex peer (smtpd.SMTPChannel 属性)
@anchor{library/smtpd smtpd SMTPChannel peer}@anchor{2d7a}
@deffn {属性} peer

Holds the name of the client peer as returned by @code{conn.getpeername()}
where @code{conn} is @ref{2d71,,conn}.
@end deffn

The @ref{5fc,,SMTPChannel} operates by invoking methods named @code{smtp_<command>}
upon reception of a command line from the client. Built into the base
@ref{5fc,,SMTPChannel} class are methods for handling the following commands
(and responding to them appropriately):


@multitable {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

命令

@tab

所采取的行动

@item

HELO

@tab

接受来自客户端的问候语，并将其存储在 @ref{2d75,,seen_greeting} 中。将服务器设置为基本命令模式。

@item

EHLO

@tab

接受来自客户的问候并将其存储在 @ref{2d75,,seen_greeting} 中。将服务器设置为扩展命令模式。

@item

NOOP

@tab

不采取任何措施。

@item

QUIT

@tab

干净地关闭连接。

@item

MAIL

@tab

Accepts the "MAIL FROM:" syntax and stores the supplied address as
@ref{2d76,,mailfrom}.  In extended command mode, accepts the
@geindex RFC; RFC 1870
RFC 1870@footnote{https://tools.ietf.org/html/rfc1870.html} SIZE attribute and responds appropriately based on the
value of @emph{data_size_limit}.

@item

RCPT

@tab

Accepts the "RCPT TO:" syntax and stores the supplied addresses in
the @ref{2d77,,rcpttos} list.

@item

RSET

@tab

重置 @ref{2d76,,mailfrom}, @ref{2d77,,rcpttos}, 和 @ref{2d78,,received_data} ，但不重置问候语。

@item

DATA

@tab

Sets the internal state to @code{DATA} and stores remaining lines
from the client in @ref{2d78,,received_data} until the terminator
@code{"\r\n.\r\n"} is received.

@item

HELP

@tab

返回有关命令语法的最少信息

@item

VRFY

@tab

返回代码252（服务器不知道该地址是否有效）

@item

EXPN

@tab

报告该命令未实现。

@end multitable

@end deffn

@node telnetlib --- Telnet client,uuid --- UUID objects according to RFC 4122,smtpd --- SMTP 服务器,互联网协议和支持
@anchor{library/telnetlib doc}@anchor{2d7b}@anchor{library/telnetlib module-telnetlib}@anchor{102}@anchor{library/telnetlib telnetlib-telnet-client}@anchor{2d7c}
@subsection @code{telnetlib} --- Telnet client


@geindex telnetlib (模块)

@strong{Source code:} Lib/telnetlib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/telnetlib.py}

@geindex protocol; Telnet


__________________________________________________________________


The @ref{102,,telnetlib} module provides a @ref{592,,Telnet} class that implements the
Telnet protocol.  See 
@geindex RFC; RFC 854
RFC 854@footnote{https://tools.ietf.org/html/rfc854.html} for details about the protocol. In addition, it
provides symbolic constants for the protocol characters (see below), and for the
telnet options. The symbolic names of the telnet options follow the definitions
in @code{arpa/telnet.h}, with the leading @code{TELOPT_} removed. For symbolic names
of options which are traditionally not included in @code{arpa/telnet.h}, see the
module source itself.

The symbolic constants for the telnet commands are: IAC, DONT, DO, WONT, WILL,
SE (Subnegotiation End), NOP (No Operation), DM (Data Mark), BRK (Break), IP
(Interrupt process), AO (Abort output), AYT (Are You There), EC (Erase
Character), EL (Erase Line), GA (Go Ahead), SB (Subnegotiation Begin).

@geindex Telnet (telnetlib 中的类)
@anchor{library/telnetlib telnetlib Telnet}@anchor{592}
@deffn {类} telnetlib.Telnet (host=None, port=0[, timeout])

@ref{592,,Telnet} represents a connection to a Telnet server. The instance is
initially not connected by default; the @ref{2d7d,,open()} method must be used to
establish a connection.  Alternatively, the host name and optional port
number can be passed to the constructor too, in which case the connection to
the server will be established before the constructor returns.  The optional
@emph{timeout} parameter specifies a timeout in seconds for blocking operations
like the connection attempt (if not specified, the global default timeout
setting will be used).

Do not reopen an already connected instance.

This class has many @code{read_*()} methods.  Note that some of them  raise
@ref{c65,,EOFError} when the end of the connection is read, because they can return
an empty string for other reasons.  See the individual descriptions below.

A @ref{592,,Telnet} object is a context manager and can be used in a
@ref{6e3,,with} statement.  When the @code{with} block ends, the
@ref{2d7e,,close()} method is called:

@example
>>> from telnetlib import Telnet
>>> with Telnet('localhost', 23) as tn:
...     tn.interact()
...
@end example


在 3.6 版更改: Context manager support added

@end deffn


@subsubheading 参见



@table @asis

@geindex RFC; RFC 854

@item RFC 854@footnote{https://tools.ietf.org/html/rfc854.html} - Telnet Protocol Specification

Definition of the Telnet protocol.
@end table


@menu
* Telnet Objects:: 
* Telnet Example:: 

@end menu

@node Telnet Objects,Telnet Example,,telnetlib --- Telnet client
@anchor{library/telnetlib id1}@anchor{2d7f}@anchor{library/telnetlib telnet-objects}@anchor{2d80}
@subsubsection Telnet Objects


@ref{592,,Telnet} instances have the following methods:

@geindex read_until() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet read_until}@anchor{2d81}
@deffn {方法} Telnet.read_until (expected, timeout=None)

Read until a given byte string, @emph{expected}, is encountered or until @emph{timeout}
seconds have passed.

When no match is found, return whatever is available instead, possibly empty
bytes.  Raise @ref{c65,,EOFError} if the connection is closed and no cooked data
is available.
@end deffn

@geindex read_all() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet read_all}@anchor{2d82}
@deffn {方法} Telnet.read_all ()

Read all data until EOF as bytes; block until connection closed.
@end deffn

@geindex read_some() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet read_some}@anchor{2d83}
@deffn {方法} Telnet.read_some ()

Read at least one byte of cooked data unless EOF is hit. Return @code{b'@w{'}} if
EOF is hit.  Block if no data is immediately available.
@end deffn

@geindex read_very_eager() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet read_very_eager}@anchor{2d84}
@deffn {方法} Telnet.read_very_eager ()

Read everything that can be without blocking in I/O (eager).

Raise @ref{c65,,EOFError} if connection closed and no cooked data available.
Return @code{b'@w{'}} if no cooked data available otherwise. Do not block unless in
the midst of an IAC sequence.
@end deffn

@geindex read_eager() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet read_eager}@anchor{2d85}
@deffn {方法} Telnet.read_eager ()

Read readily available data.

Raise @ref{c65,,EOFError} if connection closed and no cooked data available.
Return @code{b'@w{'}} if no cooked data available otherwise. Do not block unless in
the midst of an IAC sequence.
@end deffn

@geindex read_lazy() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet read_lazy}@anchor{2d86}
@deffn {方法} Telnet.read_lazy ()

Process and return data already in the queues (lazy).

Raise @ref{c65,,EOFError} if connection closed and no data available. Return
@code{b'@w{'}} if no cooked data available otherwise.  Do not block unless in the
midst of an IAC sequence.
@end deffn

@geindex read_very_lazy() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet read_very_lazy}@anchor{2d87}
@deffn {方法} Telnet.read_very_lazy ()

Return any data available in the cooked queue (very lazy).

Raise @ref{c65,,EOFError} if connection closed and no data available. Return
@code{b'@w{'}} if no cooked data available otherwise.  This method never blocks.
@end deffn

@geindex read_sb_data() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet read_sb_data}@anchor{2d88}
@deffn {方法} Telnet.read_sb_data ()

Return the data collected between a SB/SE pair (suboption begin/end). The
callback should access these data when it was invoked with a @code{SE} command.
This method never blocks.
@end deffn

@geindex open() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet open}@anchor{2d7d}
@deffn {方法} Telnet.open (host, port=0[, timeout])

Connect to a host. The optional second argument is the port number, which
defaults to the standard Telnet port (23). The optional @emph{timeout} parameter
specifies a timeout in seconds for blocking operations like the connection
attempt (if not specified, the global default timeout setting will be used).

Do not try to reopen an already connected instance.

Raises an @ref{12d0,,auditing event} @code{telnetlib.Telnet.open} with arguments @code{self}, @code{host}, @code{port}.
@end deffn

@geindex msg() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet msg}@anchor{2d89}
@deffn {方法} Telnet.msg (msg, *args)

Print a debug message when the debug level is @code{>} 0. If extra arguments are
present, they are substituted in the message using the standard string
formatting operator.
@end deffn

@geindex set_debuglevel() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet set_debuglevel}@anchor{2d8a}
@deffn {方法} Telnet.set_debuglevel (debuglevel)

Set the debug level.  The higher the value of @emph{debuglevel}, the more debug
output you get (on @code{sys.stdout}).
@end deffn

@geindex close() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet close}@anchor{2d7e}
@deffn {方法} Telnet.close ()

关闭连接对象。
@end deffn

@geindex get_socket() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet get_socket}@anchor{2d8b}
@deffn {方法} Telnet.get_socket ()

Return the socket object used internally.
@end deffn

@geindex fileno() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet fileno}@anchor{2d8c}
@deffn {方法} Telnet.fileno ()

Return the file descriptor of the socket object used internally.
@end deffn

@geindex write() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet write}@anchor{2d8d}
@deffn {方法} Telnet.write (buffer)

Write a byte string to the socket, doubling any IAC characters. This can
block if the connection is blocked.  May raise @ref{1d3,,OSError} if the
connection is closed.

Raises an @ref{12d0,,auditing event} @code{telnetlib.Telnet.write} with arguments @code{self}, @code{buffer}.


在 3.3 版更改: This method used to raise @ref{98f,,socket.error}, which is now an alias
of @ref{1d3,,OSError}.

@end deffn

@geindex interact() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet interact}@anchor{2d8e}
@deffn {方法} Telnet.interact ()

Interaction function, emulates a very dumb Telnet client.
@end deffn

@geindex mt_interact() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet mt_interact}@anchor{2d8f}
@deffn {方法} Telnet.mt_interact ()

Multithreaded version of @ref{2d8e,,interact()}.
@end deffn

@geindex expect() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet expect}@anchor{2d90}
@deffn {方法} Telnet.expect (list, timeout=None)

Read until one from a list of a regular expressions matches.

The first argument is a list of regular expressions, either compiled
(@ref{896,,regex objects}) or uncompiled (byte strings). The
optional second argument is a timeout, in seconds; the default is to block
indefinitely.

Return a tuple of three items: the index in the list of the first regular
expression that matches; the match object returned; and the bytes read up
till and including the match.

If end of file is found and no bytes were read, raise @ref{c65,,EOFError}.
Otherwise, when nothing matches, return @code{(-1, None, data)} where @emph{data} is
the bytes received so far (may be empty bytes if a timeout happened).

If a regular expression ends with a greedy match (such as @code{.*}) or if more
than one expression can match the same input, the results are
non-deterministic, and may depend on the I/O timing.
@end deffn

@geindex set_option_negotiation_callback() (telnetlib.Telnet 方法)
@anchor{library/telnetlib telnetlib Telnet set_option_negotiation_callback}@anchor{2d91}
@deffn {方法} Telnet.set_option_negotiation_callback (callback)

Each time a telnet option is read on the input flow, this @emph{callback} (if set) is
called with the following parameters: callback(telnet socket, command
(DO/DONT/WILL/WONT), option).  No other action is done afterwards by telnetlib.
@end deffn

@node Telnet Example,,Telnet Objects,telnetlib --- Telnet client
@anchor{library/telnetlib id2}@anchor{2d92}@anchor{library/telnetlib telnet-example}@anchor{2d93}
@subsubsection Telnet Example


A simple example illustrating typical use:

@example
import getpass
import telnetlib

HOST = "localhost"
user = input("Enter your remote account: ")
password = getpass.getpass()

tn = telnetlib.Telnet(HOST)

tn.read_until(b"login: ")
tn.write(user.encode('ascii') + b"\n")
if password:
    tn.read_until(b"Password: ")
    tn.write(password.encode('ascii') + b"\n")

tn.write(b"ls\n")
tn.write(b"exit\n")

print(tn.read_all().decode('ascii'))
@end example

@node uuid --- UUID objects according to RFC 4122,socketserver --- A framework for network servers,telnetlib --- Telnet client,互联网协议和支持
@anchor{library/uuid doc}@anchor{2d94}@anchor{library/uuid module-uuid}@anchor{124}@anchor{library/uuid uuid-uuid-objects-according-to-rfc-4122}@anchor{2d95}
@subsection @code{uuid} --- UUID objects according to @strong{RFC 4122}


@geindex RFC; RFC 4122

@geindex uuid (模块)

@strong{Source code:} Lib/uuid.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/uuid.py}


__________________________________________________________________


This module provides immutable @ref{260,,UUID} objects (the @ref{260,,UUID} class)
and the functions @ref{40b,,uuid1()}, @ref{2d96,,uuid3()}, @ref{2d97,,uuid4()}, @ref{2d98,,uuid5()} for
generating version 1, 3, 4, and 5 UUIDs as specified in 
@geindex RFC; RFC 4122
RFC 4122@footnote{https://tools.ietf.org/html/rfc4122.html}.

If all you want is a unique ID, you should probably call @ref{40b,,uuid1()} or
@ref{2d97,,uuid4()}.  Note that @ref{40b,,uuid1()} may compromise privacy since it creates
a UUID containing the computer's network address.  @ref{2d97,,uuid4()} creates a
random UUID.

Depending on support from the underlying platform, @ref{40b,,uuid1()} may or may
not return a "safe" UUID.  A safe UUID is one which is generated using
synchronization methods that ensure no two processes can obtain the same
UUID.  All instances of @ref{260,,UUID} have an @code{is_safe} attribute
which relays any information about the UUID's safety, using this enumeration:

@geindex SafeUUID (uuid 中的类)
@anchor{library/uuid uuid SafeUUID}@anchor{2d99}
@deffn {类} uuid.SafeUUID


3.7 新版功能.


@geindex safe (uuid.SafeUUID 属性)
@anchor{library/uuid uuid SafeUUID safe}@anchor{2d9a}
@deffn {属性} safe

The UUID was generated by the platform in a multiprocessing-safe way.
@end deffn

@geindex unsafe (uuid.SafeUUID 属性)
@anchor{library/uuid uuid SafeUUID unsafe}@anchor{2d9b}
@deffn {属性} unsafe

The UUID was not generated in a multiprocessing-safe way.
@end deffn

@geindex unknown (uuid.SafeUUID 属性)
@anchor{library/uuid uuid SafeUUID unknown}@anchor{2d9c}
@deffn {属性} unknown

The platform does not provide information on whether the UUID was
generated safely or not.
@end deffn
@end deffn

@geindex UUID (uuid 中的类)
@anchor{library/uuid uuid UUID}@anchor{260}
@deffn {类} uuid.UUID (hex=None, bytes=None, bytes_le=None, fields=None, int=None, version=None, *, is_safe=SafeUUID.unknown)

Create a UUID from either a string of 32 hexadecimal digits, a string of 16
bytes in big-endian order as the @emph{bytes} argument, a string of 16 bytes in
little-endian order as the @emph{bytes_le} argument, a tuple of six integers
(32-bit @emph{time_low}, 16-bit @emph{time_mid}, 16-bit @emph{time_hi_version},
8-bit @emph{clock_seq_hi_variant}, 8-bit @emph{clock_seq_low}, 48-bit @emph{node}) as the
@emph{fields} argument, or a single 128-bit integer as the @emph{int} argument.
When a string of hex digits is given, curly braces, hyphens,
and a URN prefix are all optional.  For example, these
expressions all yield the same UUID:

@example
UUID('@{12345678-1234-5678-1234-567812345678@}')
UUID('12345678123456781234567812345678')
UUID('urn:uuid:12345678-1234-5678-1234-567812345678')
UUID(bytes=b'\x12\x34\x56\x78'*4)
UUID(bytes_le=b'\x78\x56\x34\x12\x34\x12\x78\x56' +
              b'\x12\x34\x56\x78\x12\x34\x56\x78')
UUID(fields=(0x12345678, 0x1234, 0x5678, 0x12, 0x34, 0x567812345678))
UUID(int=0x12345678123456781234567812345678)
@end example

Exactly one of @emph{hex}, @emph{bytes}, @emph{bytes_le}, @emph{fields}, or @emph{int} must be given.
The @emph{version} argument is optional; if given, the resulting UUID will have its
variant and version number set according to 
@geindex RFC; RFC 4122
RFC 4122@footnote{https://tools.ietf.org/html/rfc4122.html}, overriding bits in the
given @emph{hex}, @emph{bytes}, @emph{bytes_le}, @emph{fields}, or @emph{int}.

Comparison of UUID objects are made by way of comparing their
@ref{2d9d,,UUID.int} attributes.  Comparison with a non-UUID object
raises a @ref{192,,TypeError}.

@code{str(uuid)} returns a string in the form
@code{12345678-1234-5678-1234-567812345678} where the 32 hexadecimal digits
represent the UUID.
@end deffn

@ref{260,,UUID} instances have these read-only attributes:

@geindex bytes (uuid.UUID 属性)
@anchor{library/uuid uuid UUID bytes}@anchor{2d9e}
@deffn {属性} UUID.bytes

The UUID as a 16-byte string (containing the six integer fields in big-endian
byte order).
@end deffn

@geindex bytes_le (uuid.UUID 属性)
@anchor{library/uuid uuid UUID bytes_le}@anchor{2d9f}
@deffn {属性} UUID.bytes_le

The UUID as a 16-byte string (with @emph{time_low}, @emph{time_mid}, and @emph{time_hi_version}
in little-endian byte order).
@end deffn

@geindex fields (uuid.UUID 属性)
@anchor{library/uuid uuid UUID fields}@anchor{2da0}
@deffn {属性} UUID.fields

以元组形式存放的UUID的6个整数域，有六个单独的属性和两个派生属性：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

含义

@item

@code{time_low}

@tab

UUID的前32位

@item

@code{time_mid}

@tab

接前一域的16位

@item

@code{time_hi_version}

@tab

接前一域的16位

@item

@code{clock_seq_hi_variant}

@tab

接前一域的8位

@item

@code{clock_seq_low}

@tab

接前一域的8位

@item

@code{node}

@tab

UUID的最后48位

@item

@ref{10a,,time}

@tab

UUID的总长60位的时间戳

@item

@code{clock_seq}

@tab

14位的序列号

@end multitable

@end deffn

@geindex hex (uuid.UUID 属性)
@anchor{library/uuid uuid UUID hex}@anchor{2da1}
@deffn {属性} UUID.hex

The UUID as a 32-character hexadecimal string.
@end deffn

@geindex int (uuid.UUID 属性)
@anchor{library/uuid uuid UUID int}@anchor{2d9d}
@deffn {属性} UUID.int

The UUID as a 128-bit integer.
@end deffn

@geindex urn (uuid.UUID 属性)
@anchor{library/uuid uuid UUID urn}@anchor{2da2}
@deffn {属性} UUID.urn

The UUID as a URN as specified in 
@geindex RFC; RFC 4122
RFC 4122@footnote{https://tools.ietf.org/html/rfc4122.html}.
@end deffn

@geindex variant (uuid.UUID 属性)
@anchor{library/uuid uuid UUID variant}@anchor{2da3}
@deffn {属性} UUID.variant

The UUID variant, which determines the internal layout of the UUID. This will be
one of the constants @ref{2da4,,RESERVED_NCS}, @ref{2da5,,RFC_4122},
@ref{2da6,,RESERVED_MICROSOFT}, or @ref{2da7,,RESERVED_FUTURE}.
@end deffn

@geindex version (uuid.UUID 属性)
@anchor{library/uuid uuid UUID version}@anchor{2da8}
@deffn {属性} UUID.version

The UUID version number (1 through 5, meaningful only when the variant is
@ref{2da5,,RFC_4122}).
@end deffn

@geindex is_safe (uuid.UUID 属性)
@anchor{library/uuid uuid UUID is_safe}@anchor{409}
@deffn {属性} UUID.is_safe

An enumeration of @ref{2d99,,SafeUUID} which indicates whether the platform
generated the UUID in a multiprocessing-safe way.


3.7 新版功能.

@end deffn

The @ref{124,,uuid} module defines the following functions:

@geindex getnode() (在 uuid 模块中)
@anchor{library/uuid uuid getnode}@anchor{40a}
@deffn {函数} uuid.getnode ()

Get the hardware address as a 48-bit positive integer.  The first time this
runs, it may launch a separate program, which could be quite slow.  If all
attempts to obtain the hardware address fail, we choose a random 48-bit
number with the multicast bit (least significant bit of the first octet)
set to 1 as recommended in 
@geindex RFC; RFC 4122
RFC 4122@footnote{https://tools.ietf.org/html/rfc4122.html}.  "Hardware address" means the MAC
address of a network interface.  On a machine with multiple network
interfaces, universally administered MAC addresses (i.e. where the second
least significant bit of the first octet is @emph{unset}) will be preferred over
locally administered MAC addresses, but with no other ordering guarantees.


在 3.7 版更改: Universally administered MAC addresses are preferred over locally
administered MAC addresses, since the former are guaranteed to be
globally unique, while the latter are not.

@end deffn

@geindex getnode

@geindex uuid1() (在 uuid 模块中)
@anchor{library/uuid uuid uuid1}@anchor{40b}
@deffn {函数} uuid.uuid1 (node=None, clock_seq=None)

Generate a UUID from a host ID, sequence number, and the current time. If @emph{node}
is not given, @ref{40a,,getnode()} is used to obtain the hardware address. If
@emph{clock_seq} is given, it is used as the sequence number; otherwise a random
14-bit sequence number is chosen.
@end deffn

@geindex uuid1

@geindex uuid3() (在 uuid 模块中)
@anchor{library/uuid uuid uuid3}@anchor{2d96}
@deffn {函数} uuid.uuid3 (namespace, name)

Generate a UUID based on the MD5 hash of a namespace identifier (which is a
UUID) and a name (which is a string).
@end deffn

@geindex uuid3

@geindex uuid4() (在 uuid 模块中)
@anchor{library/uuid uuid uuid4}@anchor{2d97}
@deffn {函数} uuid.uuid4 ()

Generate a random UUID.
@end deffn

@geindex uuid4

@geindex uuid5() (在 uuid 模块中)
@anchor{library/uuid uuid uuid5}@anchor{2d98}
@deffn {函数} uuid.uuid5 (namespace, name)

Generate a UUID based on the SHA-1 hash of a namespace identifier (which is a
UUID) and a name (which is a string).
@end deffn

@geindex uuid5

The @ref{124,,uuid} module defines the following namespace identifiers for use with
@ref{2d96,,uuid3()} or @ref{2d98,,uuid5()}.

@geindex NAMESPACE_DNS() (在 uuid 模块中)
@anchor{library/uuid uuid NAMESPACE_DNS}@anchor{2da9}
@deffn {数据} uuid.NAMESPACE_DNS

When this namespace is specified, the @emph{name} string is a fully-qualified domain
name.
@end deffn

@geindex NAMESPACE_URL() (在 uuid 模块中)
@anchor{library/uuid uuid NAMESPACE_URL}@anchor{2daa}
@deffn {数据} uuid.NAMESPACE_URL

When this namespace is specified, the @emph{name} string is a URL.
@end deffn

@geindex NAMESPACE_OID() (在 uuid 模块中)
@anchor{library/uuid uuid NAMESPACE_OID}@anchor{2dab}
@deffn {数据} uuid.NAMESPACE_OID

When this namespace is specified, the @emph{name} string is an ISO OID.
@end deffn

@geindex NAMESPACE_X500() (在 uuid 模块中)
@anchor{library/uuid uuid NAMESPACE_X500}@anchor{2dac}
@deffn {数据} uuid.NAMESPACE_X500

When this namespace is specified, the @emph{name} string is an X.500 DN in DER or a
text output format.
@end deffn

The @ref{124,,uuid} module defines the following constants for the possible values
of the @code{variant} attribute:

@geindex RESERVED_NCS() (在 uuid 模块中)
@anchor{library/uuid uuid RESERVED_NCS}@anchor{2da4}
@deffn {数据} uuid.RESERVED_NCS

Reserved for NCS compatibility.
@end deffn

@geindex RFC_4122() (在 uuid 模块中)
@anchor{library/uuid uuid RFC_4122}@anchor{2da5}
@deffn {数据} uuid.RFC_4122

Specifies the UUID layout given in 
@geindex RFC; RFC 4122
RFC 4122@footnote{https://tools.ietf.org/html/rfc4122.html}.
@end deffn

@geindex RESERVED_MICROSOFT() (在 uuid 模块中)
@anchor{library/uuid uuid RESERVED_MICROSOFT}@anchor{2da6}
@deffn {数据} uuid.RESERVED_MICROSOFT

Reserved for Microsoft compatibility.
@end deffn

@geindex RESERVED_FUTURE() (在 uuid 模块中)
@anchor{library/uuid uuid RESERVED_FUTURE}@anchor{2da7}
@deffn {数据} uuid.RESERVED_FUTURE

Reserved for future definition.
@end deffn


@subsubheading 参见



@table @asis

@geindex RFC; RFC 4122

@item RFC 4122@footnote{https://tools.ietf.org/html/rfc4122.html} - A Universally Unique IDentifier (UUID) URN Namespace

This specification defines a Uniform Resource Name namespace for UUIDs, the
internal format of UUIDs, and methods of generating UUIDs.
@end table


@menu
* 示例: 示例<13>. 

@end menu

@node 示例<13>,,,uuid --- UUID objects according to RFC 4122
@anchor{library/uuid example}@anchor{2dad}@anchor{library/uuid uuid-example}@anchor{2dae}
@subsubsection 示例


Here are some examples of typical usage of the @ref{124,,uuid} module:

@example
>>> import uuid

>>> # make a UUID based on the host ID and current time
>>> uuid.uuid1()
UUID('a8098c1a-f86e-11da-bd1a-00112444be1e')

>>> # make a UUID using an MD5 hash of a namespace UUID and a name
>>> uuid.uuid3(uuid.NAMESPACE_DNS, 'python.org')
UUID('6fa459ea-ee8a-3ca4-894e-db77e160355e')

>>> # make a random UUID
>>> uuid.uuid4()
UUID('16fd2706-8baf-433b-82eb-8c7fada847da')

>>> # make a UUID using a SHA-1 hash of a namespace UUID and a name
>>> uuid.uuid5(uuid.NAMESPACE_DNS, 'python.org')
UUID('886313e1-3b8a-5372-9b90-0c9aee199e5d')

>>> # make a UUID from a string of hex digits (braces and hyphens ignored)
>>> x = uuid.UUID('@{00010203-0405-0607-0809-0a0b0c0d0e0f@}')

>>> # convert a UUID to a string of hex digits in standard form
>>> str(x)
'00010203-0405-0607-0809-0a0b0c0d0e0f'

>>> # get the raw 16 bytes of the UUID
>>> x.bytes
b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f'

>>> # make a UUID from a 16-byte string
>>> uuid.UUID(bytes=x.bytes)
UUID('00010203-0405-0607-0809-0a0b0c0d0e0f')
@end example

@node socketserver --- A framework for network servers,http server --- HTTP 服务器,uuid --- UUID objects according to RFC 4122,互联网协议和支持
@anchor{library/socketserver doc}@anchor{2daf}@anchor{library/socketserver module-socketserver}@anchor{f0}@anchor{library/socketserver socketserver-a-framework-for-network-servers}@anchor{2db0}
@subsection @code{socketserver} --- A framework for network servers


@geindex socketserver (模块)

@strong{Source code:} Lib/socketserver.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/socketserver.py}


__________________________________________________________________


The @ref{f0,,socketserver} module simplifies the task of writing network servers.

There are four basic concrete server classes:

@geindex TCPServer (socketserver 中的类)
@anchor{library/socketserver socketserver TCPServer}@anchor{2db1}
@deffn {类} socketserver.TCPServer (server_address, RequestHandlerClass, bind_and_activate=True)

This uses the Internet TCP protocol, which provides for
continuous streams of data between the client and server.
If @emph{bind_and_activate} is true, the constructor automatically attempts to
invoke @ref{2db2,,server_bind()} and
@ref{2db3,,server_activate()}.  The other parameters are passed to
the @ref{a84,,BaseServer} base class.
@end deffn

@geindex UDPServer (socketserver 中的类)
@anchor{library/socketserver socketserver UDPServer}@anchor{2db4}
@deffn {类} socketserver.UDPServer (server_address, RequestHandlerClass, bind_and_activate=True)

This uses datagrams, which are discrete packets of information that may
arrive out of order or be lost while in transit.  The parameters are
the same as for @ref{2db1,,TCPServer}.
@end deffn

@geindex UnixStreamServer (socketserver 中的类)
@geindex UnixDatagramServer (socketserver 中的类)
@anchor{library/socketserver socketserver UnixStreamServer}@anchor{2db5}
@deffn {类} socketserver.UnixStreamServer (server_address, RequestHandlerClass, bind_and_activate=True)
@anchor{library/socketserver socketserver UnixDatagramServer}@anchor{2db6}
@deffnx {类} socketserver.UnixDatagramServer (server_address, RequestHandlerClass, bind_and_activate=True)

These more infrequently used classes are similar to the TCP and
UDP classes, but use Unix domain sockets; they're not available on
non-Unix platforms.  The parameters are the same as for
@ref{2db1,,TCPServer}.
@end deffn

These four classes process requests @emph{synchronously}; each request must be
completed before the next request can be started.  This isn't suitable if each
request takes a long time to complete, because it requires a lot of computation,
or because it returns a lot of data which the client is slow to process.  The
solution is to create a separate process or thread to handle each request; the
@ref{3cd,,ForkingMixIn} and @ref{3ce,,ThreadingMixIn} mix-in classes can be used to
support asynchronous behaviour.

Creating a server requires several steps.  First, you must create a request
handler class by subclassing the @ref{2db7,,BaseRequestHandler} class and
overriding its @ref{2db8,,handle()} method;
this method will process incoming
requests.  Second, you must instantiate one of the server classes, passing it
the server's address and the request handler class. It is recommended to use
the server in a @ref{6e3,,with} statement. Then call the
@ref{2db9,,handle_request()} or
@ref{a86,,serve_forever()} method of the server object to
process one or many requests.  Finally, call @ref{2dba,,server_close()}
to close the socket (unless you used a @code{with} statement).

When inheriting from @ref{3ce,,ThreadingMixIn} for threaded connection behavior,
you should explicitly declare how you want your threads to behave on an abrupt
shutdown.  The @ref{3ce,,ThreadingMixIn} class defines an attribute
@emph{daemon_threads}, which indicates whether or not the server should wait for
thread termination.  You should set the flag explicitly if you would like
threads to behave autonomously; the default is @ref{380,,False}, meaning that
Python will not exit until all threads created by @ref{3ce,,ThreadingMixIn} have
exited.

Server classes have the same external methods and attributes, no matter what
network protocol they use.

@menu
* Server Creation Notes:: 
* Server Objects: Server Objects<2>. 
* Request Handler Objects:: 
* 例子: 例子<23>. 

@end menu

@node Server Creation Notes,Server Objects<2>,,socketserver --- A framework for network servers
@anchor{library/socketserver server-creation-notes}@anchor{2dbb}
@subsubsection Server Creation Notes


There are five classes in an inheritance diagram, four of which represent
synchronous servers of four types:

@example
+------------+
| BaseServer |
+------------+
      |
      v
+-----------+        +------------------+
| TCPServer |------->| UnixStreamServer |
+-----------+        +------------------+
      |
      v
+-----------+        +--------------------+
| UDPServer |------->| UnixDatagramServer |
+-----------+        +--------------------+
@end example

Note that @ref{2db6,,UnixDatagramServer} derives from @ref{2db4,,UDPServer}, not from
@ref{2db5,,UnixStreamServer} --- the only difference between an IP and a Unix
stream server is the address family, which is simply repeated in both Unix
server classes.

@geindex ForkingMixIn (socketserver 中的类)
@geindex ThreadingMixIn (socketserver 中的类)
@anchor{library/socketserver socketserver ForkingMixIn}@anchor{3cd}
@deffn {类} socketserver.ForkingMixIn
@anchor{library/socketserver socketserver ThreadingMixIn}@anchor{3ce}
@deffnx {类} socketserver.ThreadingMixIn

Forking and threading versions of each type of server can be created
using these mix-in classes.  For instance, @ref{2dbc,,ThreadingUDPServer}
is created as follows:

@example
class ThreadingUDPServer(ThreadingMixIn, UDPServer):
    pass
@end example

The mix-in class comes first, since it overrides a method defined in
@ref{2db4,,UDPServer}.  Setting the various attributes also changes the
behavior of the underlying server mechanism.

@ref{3cd,,ForkingMixIn} and the Forking classes mentioned below are
only available on POSIX platforms that support @ref{95b,,fork()}.

@code{socketserver.ForkingMixIn.server_close()} waits until all child
processes complete, except if
@code{socketserver.ForkingMixIn.block_on_close} attribute is false.

@code{socketserver.ThreadingMixIn.server_close()} waits until all non-daemon
threads complete, except if
@code{socketserver.ThreadingMixIn.block_on_close} attribute is false. Use
daemonic threads by setting
@code{ThreadingMixIn.daemon_threads} to @code{True} to not wait until threads
complete.


在 3.7 版更改: @code{socketserver.ForkingMixIn.server_close()} and
@code{socketserver.ThreadingMixIn.server_close()} now waits until all
child processes and non-daemonic threads complete.
Add a new @code{socketserver.ForkingMixIn.block_on_close} class
attribute to opt-in for the pre-3.7 behaviour.

@end deffn

@geindex ForkingTCPServer (socketserver 中的类)
@geindex ForkingUDPServer (socketserver 中的类)
@geindex ThreadingTCPServer (socketserver 中的类)
@geindex ThreadingUDPServer (socketserver 中的类)
@anchor{library/socketserver socketserver ForkingTCPServer}@anchor{2dbd}
@deffn {类} socketserver.ForkingTCPServer
@anchor{library/socketserver socketserver ForkingUDPServer}@anchor{2dbe}
@deffnx {类} socketserver.ForkingUDPServer
@anchor{library/socketserver socketserver ThreadingTCPServer}@anchor{2dbf}
@deffnx {类} socketserver.ThreadingTCPServer
@anchor{library/socketserver socketserver ThreadingUDPServer}@anchor{2dbc}
@deffnx {类} socketserver.ThreadingUDPServer

These classes are pre-defined using the mix-in classes.
@end deffn

To implement a service, you must derive a class from @ref{2db7,,BaseRequestHandler}
and redefine its @ref{2db8,,handle()} method.
You can then run various versions of
the service by combining one of the server classes with your request handler
class.  The request handler class must be different for datagram or stream
services.  This can be hidden by using the handler subclasses
@ref{582,,StreamRequestHandler} or @ref{2dc0,,DatagramRequestHandler}.

Of course, you still have to use your head!  For instance, it makes no sense to
use a forking server if the service contains state in memory that can be
modified by different requests, since the modifications in the child process
would never reach the initial state kept in the parent process and passed to
each child.  In this case, you can use a threading server, but you will probably
have to use locks to protect the integrity of the shared data.

On the other hand, if you are building an HTTP server where all data is stored
externally (for instance, in the file system), a synchronous class will
essentially render the service "deaf" while one request is being handled --
which may be for a very long time if a client is slow to receive all the data it
has requested.  Here a threading or forking server is appropriate.

In some cases, it may be appropriate to process part of a request synchronously,
but to finish processing in a forked child depending on the request data.  This
can be implemented by using a synchronous server and doing an explicit fork in
the request handler class @ref{2db8,,handle()} method.

Another approach to handling multiple simultaneous requests in an environment
that supports neither threads nor @ref{95b,,fork()} (or where these are too
expensive or inappropriate for the service) is to maintain an explicit table of
partially finished requests and to use @ref{e6,,selectors} to decide which
request to work on next (or whether to handle a new incoming request).  This is
particularly important for stream services where each client can potentially be
connected for a long time (if threads or subprocesses cannot be used).  See
@ref{b,,asyncore} for another way to manage this.

@c XXX should data and methods be intermingled, or separate?
@c how should the distinction between class and instance variables be drawn?

@node Server Objects<2>,Request Handler Objects,Server Creation Notes,socketserver --- A framework for network servers
@anchor{library/socketserver server-objects}@anchor{2dc1}
@subsubsection Server Objects


@geindex BaseServer (socketserver 中的类)
@anchor{library/socketserver socketserver BaseServer}@anchor{a84}
@deffn {类} socketserver.BaseServer (server_address, RequestHandlerClass)

This is the superclass of all Server objects in the module.  It defines the
interface, given below, but does not implement most of the methods, which is
done in subclasses.  The two parameters are stored in the respective
@ref{2dc2,,server_address} and @ref{2dc3,,RequestHandlerClass} attributes.

@geindex fileno() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer fileno}@anchor{2dc4}
@deffn {方法} fileno ()

Return an integer file descriptor for the socket on which the server is
listening.  This function is most commonly passed to @ref{e6,,selectors}, to
allow monitoring multiple servers in the same process.
@end deffn

@geindex handle_request() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer handle_request}@anchor{2db9}
@deffn {方法} handle_request ()

Process a single request.  This function calls the following methods in
order: @ref{2dc5,,get_request()}, @ref{2dc6,,verify_request()}, and
@ref{2dc7,,process_request()}.  If the user-provided
@ref{2db8,,handle()} method of the
handler class raises an exception, the server's @ref{5f8,,handle_error()} method
will be called.  If no request is received within @ref{2dc8,,timeout}
seconds, @ref{2dc9,,handle_timeout()} will be called and @ref{2db9,,handle_request()}
will return.
@end deffn

@geindex serve_forever() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer serve_forever}@anchor{a86}
@deffn {方法} serve_forever (poll_interval=0.5)

Handle requests until an explicit @ref{fb0,,shutdown()} request.  Poll for
shutdown every @emph{poll_interval} seconds.
Ignores the @ref{2dc8,,timeout} attribute.  It
also calls @ref{a85,,service_actions()}, which may be used by a subclass or mixin
to provide actions specific to a given service.  For example, the
@ref{3cd,,ForkingMixIn} class uses @ref{a85,,service_actions()} to clean up zombie
child processes.


在 3.3 版更改: Added @code{service_actions} call to the @code{serve_forever} method.

@end deffn

@geindex service_actions() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer service_actions}@anchor{a85}
@deffn {方法} service_actions ()

This is called in the @ref{a86,,serve_forever()} loop. This method can be
overridden by subclasses or mixin classes to perform actions specific to
a given service, such as cleanup actions.


3.3 新版功能.

@end deffn

@geindex shutdown() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer shutdown}@anchor{fb0}
@deffn {方法} shutdown ()

Tell the @ref{a86,,serve_forever()} loop to stop and wait until it does.
@ref{fb0,,shutdown()} must be called while @ref{a86,,serve_forever()} is running in a
different thread otherwise it will deadlock.
@end deffn

@geindex server_close() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer server_close}@anchor{2dba}
@deffn {方法} server_close ()

Clean up the server. May be overridden.
@end deffn

@geindex address_family (socketserver.BaseServer 属性)
@anchor{library/socketserver socketserver BaseServer address_family}@anchor{2dca}
@deffn {属性} address_family

The family of protocols to which the server's socket belongs.
Common examples are @ref{2545,,socket.AF_INET} and @ref{254b,,socket.AF_UNIX}.
@end deffn

@geindex RequestHandlerClass (socketserver.BaseServer 属性)
@anchor{library/socketserver socketserver BaseServer RequestHandlerClass}@anchor{2dc3}
@deffn {属性} RequestHandlerClass

The user-provided request handler class; an instance of this class is created
for each request.
@end deffn

@geindex server_address (socketserver.BaseServer 属性)
@anchor{library/socketserver socketserver BaseServer server_address}@anchor{2dc2}
@deffn {属性} server_address

The address on which the server is listening.  The format of addresses varies
depending on the protocol family;
see the documentation for the @ref{ef,,socket} module
for details.  For Internet protocols, this is a tuple containing a string giving
the address, and an integer port number: @code{('127.0.0.1', 80)}, for example.
@end deffn

@geindex socket (socketserver.BaseServer 属性)
@anchor{library/socketserver socketserver BaseServer socket}@anchor{2dcb}
@deffn {属性} socket

The socket object on which the server will listen for incoming requests.
@end deffn

The server classes support the following class variables:

@c XXX should class variables be covered before instance variables, or vice versa?

@geindex allow_reuse_address (socketserver.BaseServer 属性)
@anchor{library/socketserver socketserver BaseServer allow_reuse_address}@anchor{2dcc}
@deffn {属性} allow_reuse_address

Whether the server will allow the reuse of an address.  This defaults to
@ref{380,,False}, and can be set in subclasses to change the policy.
@end deffn

@geindex request_queue_size (socketserver.BaseServer 属性)
@anchor{library/socketserver socketserver BaseServer request_queue_size}@anchor{2dcd}
@deffn {属性} request_queue_size

The size of the request queue.  If it takes a long time to process a single
request, any requests that arrive while the server is busy are placed into a
queue, up to @ref{2dcd,,request_queue_size} requests.  Once the queue is full,
further requests from clients will get a "Connection denied" error.  The default
value is usually 5, but this can be overridden by subclasses.
@end deffn

@geindex socket_type (socketserver.BaseServer 属性)
@anchor{library/socketserver socketserver BaseServer socket_type}@anchor{2dce}
@deffn {属性} socket_type

The type of socket used by the server; @ref{c83,,socket.SOCK_STREAM} and
@ref{c82,,socket.SOCK_DGRAM} are two common values.
@end deffn

@geindex timeout (socketserver.BaseServer 属性)
@anchor{library/socketserver socketserver BaseServer timeout}@anchor{2dc8}
@deffn {属性} timeout

Timeout duration, measured in seconds, or @ref{157,,None} if no timeout is
desired.  If @ref{2db9,,handle_request()} receives no incoming requests within the
timeout period, the @ref{2dc9,,handle_timeout()} method is called.
@end deffn

There are various server methods that can be overridden by subclasses of base
server classes like @ref{2db1,,TCPServer}; these methods aren't useful to external
users of the server object.

@c XXX should the default implementations of these be documented, or should
@c it be assumed that the user will look at socketserver.py?

@geindex finish_request() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer finish_request}@anchor{2dcf}
@deffn {方法} finish_request (request, client_address)

Actually processes the request by instantiating @ref{2dc3,,RequestHandlerClass} and
calling its @ref{2db8,,handle()} method.
@end deffn

@geindex get_request() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer get_request}@anchor{2dc5}
@deffn {方法} get_request ()

Must accept a request from the socket, and return a 2-tuple containing the @emph{new}
socket object to be used to communicate with the client, and the client's
address.
@end deffn

@geindex handle_error() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer handle_error}@anchor{5f8}
@deffn {方法} handle_error (request, client_address)

This function is called if the @ref{2db8,,handle()}
method of a @ref{2dc3,,RequestHandlerClass} instance raises
an exception.  The default action is to print the traceback to
standard error and continue handling further requests.


在 3.6 版更改: Now only called for exceptions derived from the @ref{1a9,,Exception}
class.

@end deffn

@geindex handle_timeout() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer handle_timeout}@anchor{2dc9}
@deffn {方法} handle_timeout ()

This function is called when the @ref{2dc8,,timeout} attribute has been set to a
value other than @ref{157,,None} and the timeout period has passed with no
requests being received.  The default action for forking servers is
to collect the status of any child processes that have exited, while
in threading servers this method does nothing.
@end deffn

@geindex process_request() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer process_request}@anchor{2dc7}
@deffn {方法} process_request (request, client_address)

Calls @ref{2dcf,,finish_request()} to create an instance of the
@ref{2dc3,,RequestHandlerClass}.  If desired, this function can create a new process
or thread to handle the request; the @ref{3cd,,ForkingMixIn} and
@ref{3ce,,ThreadingMixIn} classes do this.
@end deffn

@c Is there any point in documenting the following two functions?
@c What would the purpose of overriding them be: initializing server
@c instance variables, adding new network families?

@geindex server_activate() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer server_activate}@anchor{2db3}
@deffn {方法} server_activate ()

Called by the server's constructor to activate the server.  The default behavior
for a TCP server just invokes @ref{745,,listen()}
on the server's socket.  May be overridden.
@end deffn

@geindex server_bind() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer server_bind}@anchor{2db2}
@deffn {方法} server_bind ()

Called by the server's constructor to bind the socket to the desired address.
May be overridden.
@end deffn

@geindex verify_request() (socketserver.BaseServer 方法)
@anchor{library/socketserver socketserver BaseServer verify_request}@anchor{2dc6}
@deffn {方法} verify_request (request, client_address)

Must return a Boolean value; if the value is @ref{494,,True}, the request will
be processed, and if it's @ref{380,,False}, the request will be denied.  This
function can be overridden to implement access controls for a server. The
default implementation always returns @ref{494,,True}.
@end deffn


在 3.6 版更改: Support for the @ref{563,,context manager} protocol was added.  Exiting the
context manager is equivalent to calling @ref{2dba,,server_close()}.

@end deffn

@node Request Handler Objects,例子<23>,Server Objects<2>,socketserver --- A framework for network servers
@anchor{library/socketserver request-handler-objects}@anchor{2dd0}
@subsubsection Request Handler Objects


@geindex BaseRequestHandler (socketserver 中的类)
@anchor{library/socketserver socketserver BaseRequestHandler}@anchor{2db7}
@deffn {类} socketserver.BaseRequestHandler

This is the superclass of all request handler objects.  It defines
the interface, given below.  A concrete request handler subclass must
define a new @ref{2db8,,handle()} method, and can override any of
the other methods.  A new instance of the subclass is created for each
request.

@geindex setup() (socketserver.BaseRequestHandler 方法)
@anchor{library/socketserver socketserver BaseRequestHandler setup}@anchor{2dd1}
@deffn {方法} setup ()

Called before the @ref{2db8,,handle()} method to perform any initialization actions
required.  The default implementation does nothing.
@end deffn

@geindex handle() (socketserver.BaseRequestHandler 方法)
@anchor{library/socketserver socketserver BaseRequestHandler handle}@anchor{2db8}
@deffn {方法} handle ()

This function must do all the work required to service a request.  The
default implementation does nothing.  Several instance attributes are
available to it; the request is available as @code{self.request}; the client
address as @code{self.client_address}; and the server instance as
@code{self.server}, in case it needs access to per-server information.

The type of @code{self.request} is different for datagram or stream
services.  For stream services, @code{self.request} is a socket object; for
datagram services, @code{self.request} is a pair of string and socket.
@end deffn

@geindex finish() (socketserver.BaseRequestHandler 方法)
@anchor{library/socketserver socketserver BaseRequestHandler finish}@anchor{2dd2}
@deffn {方法} finish ()

Called after the @ref{2db8,,handle()} method to perform any clean-up actions
required.  The default implementation does nothing.  If @ref{2dd1,,setup()}
raises an exception, this function will not be called.
@end deffn
@end deffn

@geindex StreamRequestHandler (socketserver 中的类)
@geindex DatagramRequestHandler (socketserver 中的类)
@anchor{library/socketserver socketserver StreamRequestHandler}@anchor{582}
@deffn {类} socketserver.StreamRequestHandler
@anchor{library/socketserver socketserver DatagramRequestHandler}@anchor{2dc0}
@deffnx {类} socketserver.DatagramRequestHandler

These @ref{2db7,,BaseRequestHandler} subclasses override the
@ref{2dd1,,setup()} and @ref{2dd2,,finish()}
methods, and provide @code{self.rfile} and @code{self.wfile} attributes.
The @code{self.rfile} and @code{self.wfile} attributes can be
read or written, respectively, to get the request data or return data
to the client.

The @code{rfile} attributes of both classes support the
@ref{583,,io.BufferedIOBase} readable interface, and
@code{DatagramRequestHandler.wfile} supports the
@ref{583,,io.BufferedIOBase} writable interface.


在 3.6 版更改: @code{StreamRequestHandler.wfile} also supports the
@ref{583,,io.BufferedIOBase} writable interface.

@end deffn

@node 例子<23>,,Request Handler Objects,socketserver --- A framework for network servers
@anchor{library/socketserver examples}@anchor{2dd3}
@subsubsection 例子


@menu
* socketserver.TCPServer Example: socketserver TCPServer Example. 
* socketserver.UDPServer Example: socketserver UDPServer Example. 
* Asynchronous Mixins:: 

@end menu

@node socketserver TCPServer Example,socketserver UDPServer Example,,例子<23>
@anchor{library/socketserver socketserver-tcpserver-example}@anchor{2dd4}
@subsubsection @code{socketserver.TCPServer} Example


This is the server side:

@example
import socketserver

class MyTCPHandler(socketserver.BaseRequestHandler):
    """
    The request handler class for our server.

    It is instantiated once per connection to the server, and must
    override the handle() method to implement communication to the
    client.
    """

    def handle(self):
        # self.request is the TCP socket connected to the client
        self.data = self.request.recv(1024).strip()
        print("@{@} wrote:".format(self.client_address[0]))
        print(self.data)
        # just send back the same data, but upper-cased
        self.request.sendall(self.data.upper())

if __name__ == "__main__":
    HOST, PORT = "localhost", 9999

    # Create the server, binding to localhost on port 9999
    with socketserver.TCPServer((HOST, PORT), MyTCPHandler) as server:
        # Activate the server; this will keep running until you
        # interrupt the program with Ctrl-C
        server.serve_forever()
@end example

An alternative request handler class that makes use of streams (file-like
objects that simplify communication by providing the standard file interface):

@example
class MyTCPHandler(socketserver.StreamRequestHandler):

    def handle(self):
        # self.rfile is a file-like object created by the handler;
        # we can now use e.g. readline() instead of raw recv() calls
        self.data = self.rfile.readline().strip()
        print("@{@} wrote:".format(self.client_address[0]))
        print(self.data)
        # Likewise, self.wfile is a file-like object used to write back
        # to the client
        self.wfile.write(self.data.upper())
@end example

The difference is that the @code{readline()} call in the second handler will call
@code{recv()} multiple times until it encounters a newline character, while the
single @code{recv()} call in the first handler will just return what has been sent
from the client in one @code{sendall()} call.

This is the client side:

@example
import socket
import sys

HOST, PORT = "localhost", 9999
data = " ".join(sys.argv[1:])

# Create a socket (SOCK_STREAM means a TCP socket)
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
    # Connect to server and send data
    sock.connect((HOST, PORT))
    sock.sendall(bytes(data + "\n", "utf-8"))

    # Receive data from the server and shut down
    received = str(sock.recv(1024), "utf-8")

print("Sent:     @{@}".format(data))
print("Received: @{@}".format(received))
@end example

The output of the example should look something like this:

Server:

@example
$ python TCPServer.py
127.0.0.1 wrote:
b'hello world with TCP'
127.0.0.1 wrote:
b'python is nice'
@end example

Client:

@example
$ python TCPClient.py hello world with TCP
Sent:     hello world with TCP
Received: HELLO WORLD WITH TCP
$ python TCPClient.py python is nice
Sent:     python is nice
Received: PYTHON IS NICE
@end example

@node socketserver UDPServer Example,Asynchronous Mixins,socketserver TCPServer Example,例子<23>
@anchor{library/socketserver socketserver-udpserver-example}@anchor{2dd5}
@subsubsection @code{socketserver.UDPServer} Example


This is the server side:

@example
import socketserver

class MyUDPHandler(socketserver.BaseRequestHandler):
    """
    This class works similar to the TCP handler class, except that
    self.request consists of a pair of data and client socket, and since
    there is no connection the client address must be given explicitly
    when sending data back via sendto().
    """

    def handle(self):
        data = self.request[0].strip()
        socket = self.request[1]
        print("@{@} wrote:".format(self.client_address[0]))
        print(data)
        socket.sendto(data.upper(), self.client_address)

if __name__ == "__main__":
    HOST, PORT = "localhost", 9999
    with socketserver.UDPServer((HOST, PORT), MyUDPHandler) as server:
        server.serve_forever()
@end example

This is the client side:

@example
import socket
import sys

HOST, PORT = "localhost", 9999
data = " ".join(sys.argv[1:])

# SOCK_DGRAM is the socket type to use for UDP sockets
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# As you can see, there is no connect() call; UDP has no connections.
# Instead, data is directly sent to the recipient via sendto().
sock.sendto(bytes(data + "\n", "utf-8"), (HOST, PORT))
received = str(sock.recv(1024), "utf-8")

print("Sent:     @{@}".format(data))
print("Received: @{@}".format(received))
@end example

The output of the example should look exactly like for the TCP server example.

@node Asynchronous Mixins,,socketserver UDPServer Example,例子<23>
@anchor{library/socketserver asynchronous-mixins}@anchor{2dd6}
@subsubsection Asynchronous Mixins


To build asynchronous handlers, use the @ref{3ce,,ThreadingMixIn} and
@ref{3cd,,ForkingMixIn} classes.

An example for the @ref{3ce,,ThreadingMixIn} class:

@example
import socket
import threading
import socketserver

class ThreadedTCPRequestHandler(socketserver.BaseRequestHandler):

    def handle(self):
        data = str(self.request.recv(1024), 'ascii')
        cur_thread = threading.current_thread()
        response = bytes("@{@}: @{@}".format(cur_thread.name, data), 'ascii')
        self.request.sendall(response)

class ThreadedTCPServer(socketserver.ThreadingMixIn, socketserver.TCPServer):
    pass

def client(ip, port, message):
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
        sock.connect((ip, port))
        sock.sendall(bytes(message, 'ascii'))
        response = str(sock.recv(1024), 'ascii')
        print("Received: @{@}".format(response))

if __name__ == "__main__":
    # Port 0 means to select an arbitrary unused port
    HOST, PORT = "localhost", 0

    server = ThreadedTCPServer((HOST, PORT), ThreadedTCPRequestHandler)
    with server:
        ip, port = server.server_address

        # Start a thread with the server -- that thread will then start one
        # more thread for each request
        server_thread = threading.Thread(target=server.serve_forever)
        # Exit the server thread when the main thread terminates
        server_thread.daemon = True
        server_thread.start()
        print("Server loop running in thread:", server_thread.name)

        client(ip, port, "Hello World 1")
        client(ip, port, "Hello World 2")
        client(ip, port, "Hello World 3")

        server.shutdown()
@end example

The output of the example should look something like this:

@example
$ python ThreadedTCPServer.py
Server loop running in thread: Thread-1
Received: Thread-2: Hello World 1
Received: Thread-3: Hello World 2
Received: Thread-4: Hello World 3
@end example

The @ref{3cd,,ForkingMixIn} class is used in the same way, except that the server
will spawn a new process for each request.
Available only on POSIX platforms that support @ref{95b,,fork()}.

@node http server --- HTTP 服务器,http cookies --- HTTP状态管理,socketserver --- A framework for network servers,互联网协议和支持
@anchor{library/http server doc}@anchor{2dd7}@anchor{library/http server http-server-http-servers}@anchor{2dd8}@anchor{library/http server module-http server}@anchor{97}
@subsection @code{http.server} --- HTTP 服务器


@geindex http.server (模块)

@strong{源代码：} Lib/http/server.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/http/server.py}

@geindex WWW; server
@geindex HTTP; protocol
@geindex URL
@geindex httpd


__________________________________________________________________


这个模块定义了实现 HTTP 服务器（ Web 服务器）的类。

@cartouche
@quotation 警告 
不推荐在生产环境中使用 @ref{97,,http.server} 。它只实现了基本的安全检查功能。
@end quotation
@end cartouche

@ref{2ba7,,HTTPServer} 是 @ref{2db1,,socketserver.TCPServer} 的一个子类。它会创建和侦听 HTTP 套接字，并将请求调度给处理程序。用于创建和运行服务器的代码看起来像这样：

@example
def run(server_class=HTTPServer, handler_class=BaseHTTPRequestHandler):
    server_address = ('@w{'}, 8000)
    httpd = server_class(server_address, handler_class)
    httpd.serve_forever()
@end example

@geindex HTTPServer (http.server 中的类)
@anchor{library/http server http server HTTPServer}@anchor{2ba7}
@deffn {类} http.server.HTTPServer (server_address, RequestHandlerClass)

该类基于 @ref{2db1,,TCPServer} 类，并会将服务器地址存入名为 @code{server_name} 和 @code{server_port} 的实例变量中。服务器可被处理程序通过 @code{server} 实例变量访问。
@end deffn

@geindex ThreadingHTTPServer (http.server 中的类)
@anchor{library/http server http server ThreadingHTTPServer}@anchor{38e}
@deffn {类} http.server.ThreadingHTTPServer (server_address, RequestHandlerClass)

This class is identical to HTTPServer but uses threads to handle
requests by using the @ref{3ce,,ThreadingMixIn}. This
is useful to handle web browsers pre-opening sockets, on which
@ref{2ba7,,HTTPServer} would wait indefinitely.


3.7 新版功能.

@end deffn

The @ref{2ba7,,HTTPServer} and @ref{38e,,ThreadingHTTPServer} must be given
a @emph{RequestHandlerClass} on instantiation, of which this module
provides three different variants:

@geindex BaseHTTPRequestHandler (http.server 中的类)
@anchor{library/http server http server BaseHTTPRequestHandler}@anchor{a09}
@deffn {类} http.server.BaseHTTPRequestHandler (request, client_address, server)

This class is used to handle the HTTP requests that arrive at the server.  By
itself, it cannot respond to any actual HTTP requests; it must be subclassed
to handle each request method (e.g. GET or POST).
@ref{a09,,BaseHTTPRequestHandler} provides a number of class and instance
variables, and methods for use by subclasses.

The handler will parse the request and the headers, then call a method
specific to the request type. The method name is constructed from the
request. For example, for the request method @code{SPAM}, the @code{do_SPAM()}
method will be called with no arguments. All of the relevant information is
stored in instance variables of the handler.  Subclasses should not need to
override or extend the @ref{d57,,__init__()} method.

@ref{a09,,BaseHTTPRequestHandler} has the following instance variables:

@geindex client_address (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler client_address}@anchor{2dd9}
@deffn {属性} client_address

Contains a tuple of the form @code{(host, port)} referring to the client's
address.
@end deffn

@geindex server (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler server}@anchor{2dda}
@deffn {属性} server

Contains the server instance.
@end deffn

@geindex close_connection (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler close_connection}@anchor{2ddb}
@deffn {属性} close_connection

Boolean that should be set before @ref{2ddc,,handle_one_request()} returns,
indicating if another request may be expected, or if the connection should
be shut down.
@end deffn

@geindex requestline (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler requestline}@anchor{2ddd}
@deffn {属性} requestline

Contains the string representation of the HTTP request line. The
terminating CRLF is stripped. This attribute should be set by
@ref{2ddc,,handle_one_request()}. If no valid request line was processed, it
should be set to the empty string.
@end deffn

@geindex command (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler command}@anchor{2dde}
@deffn {属性} command

Contains the command (request type). For example, @code{'GET'}.
@end deffn

@geindex path (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler path}@anchor{2ddf}
@deffn {属性} path

Contains the request path.
@end deffn

@geindex request_version (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler request_version}@anchor{2de0}
@deffn {属性} request_version

Contains the version string from the request. For example, @code{'HTTP/1.0'}.
@end deffn

@geindex headers (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler headers}@anchor{2c85}
@deffn {属性} headers

Holds an instance of the class specified by the @ref{2de1,,MessageClass} class
variable. This instance parses and manages the headers in the HTTP
request. The @ref{fd3,,parse_headers()} function from
@ref{94,,http.client} is used to parse the headers and it requires that the
HTTP request provide a valid 
@geindex RFC; RFC 2822
RFC 2822@footnote{https://tools.ietf.org/html/rfc2822.html} style header.
@end deffn

@geindex rfile (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler rfile}@anchor{2de2}
@deffn {属性} rfile

An @ref{583,,io.BufferedIOBase} input stream, ready to read from
the start of the optional input data.
@end deffn

@geindex wfile (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler wfile}@anchor{2de3}
@deffn {属性} wfile

Contains the output stream for writing a response back to the
client. Proper adherence to the HTTP protocol must be used when writing to
this stream in order to achieve successful interoperation with HTTP
clients.


在 3.6 版更改: This is an @ref{583,,io.BufferedIOBase} stream.

@end deffn

@ref{a09,,BaseHTTPRequestHandler} has the following attributes:

@geindex server_version (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler server_version}@anchor{2de4}
@deffn {属性} server_version

Specifies the server software version.  You may want to override this. The
format is multiple whitespace-separated strings, where each string is of
the form name[/version]. For example, @code{'BaseHTTP/0.2'}.
@end deffn

@geindex sys_version (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler sys_version}@anchor{2de5}
@deffn {属性} sys_version

Contains the Python system version, in a form usable by the
@ref{2de6,,version_string} method and the @ref{2de4,,server_version} class
variable. For example, @code{'Python/1.4'}.
@end deffn

@geindex error_message_format (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler error_message_format}@anchor{2de7}
@deffn {属性} error_message_format

Specifies a format string that should be used by @ref{856,,send_error()} method
for building an error response to the client. The string is filled by
default with variables from @ref{2c72,,responses} based on the status code
that passed to @ref{856,,send_error()}.
@end deffn

@geindex error_content_type (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler error_content_type}@anchor{2de8}
@deffn {属性} error_content_type

Specifies the Content-Type HTTP header of error responses sent to the
client.  The default value is @code{'text/html'}.
@end deffn

@geindex protocol_version (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler protocol_version}@anchor{2de9}
@deffn {属性} protocol_version

This specifies the HTTP protocol version used in responses.  If set to
@code{'HTTP/1.1'}, the server will permit HTTP persistent connections;
however, your server @emph{must} then include an accurate @code{Content-Length}
header (using @ref{2dea,,send_header()}) in all of its responses to clients.
For backwards compatibility, the setting defaults to @code{'HTTP/1.0'}.
@end deffn

@geindex MessageClass (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler MessageClass}@anchor{2de1}
@deffn {属性} MessageClass

Specifies an @ref{53c,,email.message.Message}-like class to parse HTTP
headers.  Typically, this is not overridden, and it defaults to
@code{http.client.HTTPMessage}.
@end deffn

@geindex responses (http.server.BaseHTTPRequestHandler 属性)
@anchor{library/http server http server BaseHTTPRequestHandler responses}@anchor{2c72}
@deffn {属性} responses

This attribute contains a mapping of error code integers to two-element tuples
containing a short and long message. For example, @code{@{code: (shortmessage,
longmessage)@}}. The @emph{shortmessage} is usually used as the @emph{message} key in an
error response, and @emph{longmessage} as the @emph{explain} key.  It is used by
@ref{2deb,,send_response_only()} and @ref{856,,send_error()} methods.
@end deffn

A @ref{a09,,BaseHTTPRequestHandler} instance has the following methods:

@geindex handle() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler handle}@anchor{2dec}
@deffn {方法} handle ()

Calls @ref{2ddc,,handle_one_request()} once (or, if persistent connections are
enabled, multiple times) to handle incoming HTTP requests. You should
never need to override it; instead, implement appropriate @code{do_*()}
methods.
@end deffn

@geindex handle_one_request() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler handle_one_request}@anchor{2ddc}
@deffn {方法} handle_one_request ()

This method will parse and dispatch the request to the appropriate
@code{do_*()} method.  You should never need to override it.
@end deffn

@geindex handle_expect_100() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler handle_expect_100}@anchor{2ded}
@deffn {方法} handle_expect_100 ()

When a HTTP/1.1 compliant server receives an @code{Expect: 100-continue}
request header it responds back with a @code{100 Continue} followed by @code{200
OK} headers.
This method can be overridden to raise an error if the server does not
want the client to continue.  For e.g. server can chose to send @code{417
Expectation Failed} as a response header and @code{return False}.


3.2 新版功能.

@end deffn

@geindex send_error() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler send_error}@anchor{856}
@deffn {方法} send_error (code, message=None, explain=None)

Sends and logs a complete error reply to the client. The numeric @emph{code}
specifies the HTTP error code, with @emph{message} as an optional, short, human
readable description of the error.  The @emph{explain} argument can be used to
provide more detailed information about the error; it will be formatted
using the @ref{2de7,,error_message_format} attribute and emitted, after
a complete set of headers, as the response body.  The @ref{2c72,,responses}
attribute holds the default values for @emph{message} and @emph{explain} that
will be used if no value is provided; for unknown codes the default value
for both is the string @code{???}. The body will be empty if the method is
HEAD or the response code is one of the following: @code{1xx},
@code{204 No Content}, @code{205 Reset Content}, @code{304 Not Modified}.


在 3.4 版更改: The error response includes a Content-Length header.
Added the @emph{explain} argument.

@end deffn

@geindex send_response() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler send_response}@anchor{2dee}
@deffn {方法} send_response (code, message=None)

Adds a response header to the headers buffer and logs the accepted
request. The HTTP response line is written to the internal buffer,
followed by @emph{Server} and @emph{Date} headers. The values for these two headers
are picked up from the @ref{2de6,,version_string()} and
@ref{2def,,date_time_string()} methods, respectively. If the server does not
intend to send any other headers using the @ref{2dea,,send_header()} method,
then @ref{2dee,,send_response()} should be followed by an @ref{a0a,,end_headers()}
call.


在 3.3 版更改: Headers are stored to an internal buffer and @ref{a0a,,end_headers()}
needs to be called explicitly.

@end deffn

@geindex send_header() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler send_header}@anchor{2dea}
@deffn {方法} send_header (keyword, value)

Adds the HTTP header to an internal buffer which will be written to the
output stream when either @ref{a0a,,end_headers()} or @ref{a0b,,flush_headers()} is
invoked. @emph{keyword} should specify the header keyword, with @emph{value}
specifying its value. Note that, after the send_header calls are done,
@ref{a0a,,end_headers()} MUST BE called in order to complete the operation.


在 3.2 版更改: Headers are stored in an internal buffer.

@end deffn

@geindex send_response_only() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler send_response_only}@anchor{2deb}
@deffn {方法} send_response_only (code, message=None)

Sends the response header only, used for the purposes when @code{100
Continue} response is sent by the server to the client. The headers not
buffered and sent directly the output stream.If the @emph{message} is not
specified, the HTTP message corresponding the response @emph{code}  is sent.


3.2 新版功能.

@end deffn

@geindex end_headers() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler end_headers}@anchor{a0a}
@deffn {方法} end_headers ()

Adds a blank line
(indicating the end of the HTTP headers in the response)
to the headers buffer and calls @ref{a0b,,flush_headers()}.


在 3.2 版更改: The buffered headers are written to the output stream.

@end deffn

@geindex flush_headers() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler flush_headers}@anchor{a0b}
@deffn {方法} flush_headers ()

Finally send the headers to the output stream and flush the internal
headers buffer.


3.3 新版功能.

@end deffn

@geindex log_request() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler log_request}@anchor{2df0}
@deffn {方法} log_request (code='-', size='-')

Logs an accepted (successful) request. @emph{code} should specify the numeric
HTTP code associated with the response. If a size of the response is
available, then it should be passed as the @emph{size} parameter.
@end deffn

@geindex log_error() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler log_error}@anchor{2df1}
@deffn {方法} log_error (...)

Logs an error when a request cannot be fulfilled. By default, it passes
the message to @ref{2df2,,log_message()}, so it takes the same arguments
(@emph{format} and additional values).
@end deffn

@geindex log_message() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler log_message}@anchor{2df2}
@deffn {方法} log_message (format, ...)

Logs an arbitrary message to @code{sys.stderr}. This is typically overridden
to create custom error logging mechanisms. The @emph{format} argument is a
standard printf-style format string, where the additional arguments to
@ref{2df2,,log_message()} are applied as inputs to the formatting. The client
ip address and current date and time are prefixed to every message logged.
@end deffn

@geindex version_string() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler version_string}@anchor{2de6}
@deffn {方法} version_string ()

Returns the server software's version string. This is a combination of the
@ref{2de4,,server_version} and @ref{2de5,,sys_version} attributes.
@end deffn

@geindex date_time_string() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler date_time_string}@anchor{2def}
@deffn {方法} date_time_string (timestamp=None)

Returns the date and time given by @emph{timestamp} (which must be @code{None} or in
the format returned by @ref{316,,time.time()}), formatted for a message
header. If @emph{timestamp} is omitted, it uses the current date and time.

The result looks like @code{'Sun, 06 Nov 1994 08:49:37 GMT'}.
@end deffn

@geindex log_date_time_string() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler log_date_time_string}@anchor{2df3}
@deffn {方法} log_date_time_string ()

Returns the current date and time, formatted for logging.
@end deffn

@geindex address_string() (http.server.BaseHTTPRequestHandler 方法)
@anchor{library/http server http server BaseHTTPRequestHandler address_string}@anchor{2df4}
@deffn {方法} address_string ()

Returns the client address.


在 3.3 版更改: Previously, a name lookup was performed. To avoid name resolution
delays, it now always returns the IP address.

@end deffn
@end deffn

@geindex SimpleHTTPRequestHandler (http.server 中的类)
@anchor{library/http server http server SimpleHTTPRequestHandler}@anchor{38d}
@deffn {类} http.server.SimpleHTTPRequestHandler (request, client_address, server, directory=None)

This class serves files from the current directory and below, directly
mapping the directory structure to HTTP requests.

A lot of the work, such as parsing the request, is done by the base class
@ref{a09,,BaseHTTPRequestHandler}.  This class implements the @ref{2df5,,do_GET()}
and @ref{2df6,,do_HEAD()} functions.

The following are defined as class-level attributes of
@ref{38d,,SimpleHTTPRequestHandler}:

@geindex server_version (http.server.SimpleHTTPRequestHandler 属性)
@anchor{library/http server http server SimpleHTTPRequestHandler server_version}@anchor{2df7}
@deffn {属性} server_version

This will be @code{"SimpleHTTP/" + __version__}, where @code{__version__} is
defined at the module level.
@end deffn

@geindex extensions_map (http.server.SimpleHTTPRequestHandler 属性)
@anchor{library/http server http server SimpleHTTPRequestHandler extensions_map}@anchor{2df8}
@deffn {属性} extensions_map

A dictionary mapping suffixes into MIME types. The default is
signified by an empty string, and is considered to be
@code{application/octet-stream}. The mapping is used case-insensitively,
and so should contain only lower-cased keys.
@end deffn

@geindex directory (http.server.SimpleHTTPRequestHandler 属性)
@anchor{library/http server http server SimpleHTTPRequestHandler directory}@anchor{2df9}
@deffn {属性} directory

If not specified, the directory to serve is the current working directory.
@end deffn

The @ref{38d,,SimpleHTTPRequestHandler} class defines the following methods:

@geindex do_HEAD() (http.server.SimpleHTTPRequestHandler 方法)
@anchor{library/http server http server SimpleHTTPRequestHandler do_HEAD}@anchor{2df6}
@deffn {方法} do_HEAD ()

This method serves the @code{'HEAD'} request type: it sends the headers it
would send for the equivalent @code{GET} request. See the @ref{2df5,,do_GET()}
method for a more complete explanation of the possible headers.
@end deffn

@geindex do_GET() (http.server.SimpleHTTPRequestHandler 方法)
@anchor{library/http server http server SimpleHTTPRequestHandler do_GET}@anchor{2df5}
@deffn {方法} do_GET ()

The request is mapped to a local file by interpreting the request as a
path relative to the current working directory.

If the request was mapped to a directory, the directory is checked for a
file named @code{index.html} or @code{index.htm} (in that order). If found, the
file's contents are returned; otherwise a directory listing is generated
by calling the @code{list_directory()} method. This method uses
@ref{a3c,,os.listdir()} to scan the directory, and returns a @code{404} error
response if the @ref{a3c,,listdir()} fails.

If the request was mapped to a file, it is opened. Any @ref{1d3,,OSError}
exception in opening the requested file is mapped to a @code{404},
@code{'File not found'} error. If there was a @code{'If-Modified-Since'}
header in the request, and the file was not modified after this time,
a @code{304}, @code{'Not Modified'} response is sent. Otherwise, the content
type is guessed by calling the @code{guess_type()} method, which in turn
uses the @emph{extensions_map} variable, and the file contents are returned.

A @code{'Content-type:'} header with the guessed content type is output,
followed by a @code{'Content-Length:'} header with the file's size and a
@code{'Last-Modified:'} header with the file's modification time.

Then follows a blank line signifying the end of the headers, and then the
contents of the file are output. If the file's MIME type starts with
@code{text/} the file is opened in text mode; otherwise binary mode is used.

For example usage, see the implementation of the @ref{105,,test()} function
invocation in the @ref{97,,http.server} module.


在 3.7 版更改: Support of the @code{'If-Modified-Since'} header.

@end deffn
@end deffn

The @ref{38d,,SimpleHTTPRequestHandler} class can be used in the following
manner in order to create a very basic webserver serving files relative to
the current directory:

@example
import http.server
import socketserver

PORT = 8000

Handler = http.server.SimpleHTTPRequestHandler

with socketserver.TCPServer(("", PORT), Handler) as httpd:
    print("serving at port", PORT)
    httpd.serve_forever()
@end example
@anchor{library/http server http-server-cli}@anchor{857}
@ref{97,,http.server} can also be invoked directly using the @ref{330,,-m}
switch of the interpreter with a @code{port number} argument.  Similar to
the previous example, this serves files relative to the current directory:

@example
python -m http.server 8000
@end example

By default, server binds itself to all interfaces.  The option @code{-b/--bind}
specifies a specific address to which it should bind. Both IPv4 and IPv6
addresses are supported. For example, the following command causes the server
to bind to localhost only:

@example
python -m http.server 8000 --bind 127.0.0.1
@end example


3.4 新版功能: @code{--bind} argument was introduced.



3.8 新版功能: @code{--bind} argument enhanced to support IPv6


By default, server uses the current directory. The option @code{-d/--directory}
specifies a directory to which it should serve the files. For example,
the following command uses a specific directory:

@example
python -m http.server --directory /tmp/
@end example


3.7 新版功能: @code{--directory} specify alternate directory


@geindex CGIHTTPRequestHandler (http.server 中的类)
@anchor{library/http server http server CGIHTTPRequestHandler}@anchor{2dfa}
@deffn {类} http.server.CGIHTTPRequestHandler (request, client_address, server)

This class is used to serve either files or output of CGI scripts from the
current directory and below. Note that mapping HTTP hierarchic structure to
local directory structure is exactly as in @ref{38d,,SimpleHTTPRequestHandler}.

@cartouche
@quotation 注解 
CGI scripts run by the @ref{2dfa,,CGIHTTPRequestHandler} class cannot execute
redirects (HTTP code 302), because code 200 (script output follows) is
sent prior to execution of the CGI script.  This pre-empts the status
code.
@end quotation
@end cartouche

The class will however, run the CGI script, instead of serving it as a file,
if it guesses it to be a CGI script.  Only directory-based CGI are used ---
the other common server configuration is to treat special extensions as
denoting CGI scripts.

The @code{do_GET()} and @code{do_HEAD()} functions are modified to run CGI scripts
and serve the output, instead of serving files, if the request leads to
somewhere below the @code{cgi_directories} path.

The @ref{2dfa,,CGIHTTPRequestHandler} defines the following data member:

@geindex cgi_directories (http.server.CGIHTTPRequestHandler 属性)
@anchor{library/http server http server CGIHTTPRequestHandler cgi_directories}@anchor{2dfb}
@deffn {属性} cgi_directories

This defaults to @code{['/cgi-bin', '/htbin']} and describes directories to
treat as containing CGI scripts.
@end deffn

The @ref{2dfa,,CGIHTTPRequestHandler} defines the following method:

@geindex do_POST() (http.server.CGIHTTPRequestHandler 方法)
@anchor{library/http server http server CGIHTTPRequestHandler do_POST}@anchor{2dfc}
@deffn {方法} do_POST ()

This method serves the @code{'POST'} request type, only allowed for CGI
scripts.  Error 501, "Can only POST to CGI scripts", is output when trying
to POST to a non-CGI url.
@end deffn

Note that CGI scripts will be run with UID of user nobody, for security
reasons.  Problems with the CGI script will be translated to error 403.
@end deffn

@ref{2dfa,,CGIHTTPRequestHandler} can be enabled in the command line by passing
the @code{--cgi} option:

@example
python -m http.server --cgi 8000
@end example

@node http cookies --- HTTP状态管理,http cookiejar —— HTTP 客户端的 Cookie 处理,http server --- HTTP 服务器,互联网协议和支持
@anchor{library/http cookies doc}@anchor{2dfd}@anchor{library/http cookies http-cookies-http-state-management}@anchor{2dfe}@anchor{library/http cookies module-http cookies}@anchor{96}
@subsection @code{http.cookies} --- HTTP状态管理


@geindex http.cookies (模块)

@strong{源代码:} Lib/http/cookies.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/http/cookies.py}


__________________________________________________________________


The @ref{96,,http.cookies} module defines classes for abstracting the concept of
cookies, an HTTP state management mechanism. It supports both simple string-only
cookies, and provides an abstraction for having any serializable data-type as
cookie value.

The module formerly strictly applied the parsing rules described in the
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} and 
@geindex RFC; RFC 2068
RFC 2068@footnote{https://tools.ietf.org/html/rfc2068.html} specifications.  It has since been discovered that
MSIE 3.0x doesn't follow the character rules outlined in those specs and also
many current day browsers and servers have relaxed parsing rules when comes to
Cookie handling.  As a result, the parsing rules used are a bit less strict.

The character set, @ref{c55,,string.ascii_letters}, @ref{16ba,,string.digits} and
@code{!#$%&'*+-.^_`|~:} denote the set of valid characters allowed by this module
in Cookie name (as @ref{488,,key}).


在 3.3 版更改: Allowed ':' as a valid Cookie name character.


@cartouche
@quotation 注解 
On encountering an invalid cookie, @ref{2dff,,CookieError} is raised, so if your
cookie data comes from a browser you should always prepare for invalid data
and catch @ref{2dff,,CookieError} on parsing.
@end quotation
@end cartouche

@geindex CookieError
@anchor{library/http cookies http cookies CookieError}@anchor{2dff}
@deffn {例外} http.cookies.CookieError

Exception failing because of 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} invalidity: incorrect attributes,
incorrect @code{Set-Cookie} header, etc.
@end deffn

@geindex BaseCookie (http.cookies 中的类)
@anchor{library/http cookies http cookies BaseCookie}@anchor{2e00}
@deffn {类} http.cookies.BaseCookie ([input])

This class is a dictionary-like object whose keys are strings and whose values
are @ref{487,,Morsel} instances. Note that upon setting a key to a value, the
value is first converted to a @ref{487,,Morsel} containing the key and the value.

If @emph{input} is given, it is passed to the @ref{2e01,,load()} method.
@end deffn

@geindex SimpleCookie (http.cookies 中的类)
@anchor{library/http cookies http cookies SimpleCookie}@anchor{fcb}
@deffn {类} http.cookies.SimpleCookie ([input])

This class derives from @ref{2e00,,BaseCookie} and overrides @code{value_decode()}
and @code{value_encode()}. SimpleCookie supports strings as cookie values.
When setting the value, SimpleCookie calls the builtin @ref{329,,str()} to convert
the value to a string. Values received from HTTP are kept as strings.
@end deffn


@subsubheading 参见



@table @asis

@item Module @ref{95,,http.cookiejar}

HTTP cookie handling for web @emph{clients}.  The @ref{95,,http.cookiejar} and
@ref{96,,http.cookies} modules do not depend on each other.

@geindex RFC; RFC 2109

@item RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} - HTTP State Management Mechanism

This is the state management specification implemented by this module.
@end table


@menu
* Cookie 对象:: 
* Morsel 对象:: 
* 示例: 示例<14>. 

@end menu

@node Cookie 对象,Morsel 对象,,http cookies --- HTTP状态管理
@anchor{library/http cookies cookie-objects}@anchor{2e02}@anchor{library/http cookies id1}@anchor{2e03}
@subsubsection Cookie 对象


@geindex value_decode() (http.cookies.BaseCookie 方法)
@anchor{library/http cookies http cookies BaseCookie value_decode}@anchor{2e04}
@deffn {方法} BaseCookie.value_decode (val)

Return a tuple @code{(real_value, coded_value)} from a string representation.
@code{real_value} can be any type. This method does no decoding in
@ref{2e00,,BaseCookie} --- it exists so it can be overridden.
@end deffn

@geindex value_encode() (http.cookies.BaseCookie 方法)
@anchor{library/http cookies http cookies BaseCookie value_encode}@anchor{2e05}
@deffn {方法} BaseCookie.value_encode (val)

Return a tuple @code{(real_value, coded_value)}. @emph{val} can be any type, but
@code{coded_value} will always be converted to a string.
This method does no encoding in @ref{2e00,,BaseCookie} --- it exists so it can
be overridden.

In general, it should be the case that @ref{2e05,,value_encode()} and
@ref{2e04,,value_decode()} are inverses on the range of @emph{value_decode}.
@end deffn

@geindex output() (http.cookies.BaseCookie 方法)
@anchor{library/http cookies http cookies BaseCookie output}@anchor{2e06}
@deffn {方法} BaseCookie.output (attrs=None, header='Set-Cookie:', sep='\r\n')

Return a string representation suitable to be sent as HTTP headers. @emph{attrs} and
@emph{header} are sent to each @ref{487,,Morsel}'s @ref{2e06,,output()} method. @emph{sep} is used
to join the headers together, and is by default the combination @code{'\r\n'}
(CRLF).
@end deffn

@geindex js_output() (http.cookies.BaseCookie 方法)
@anchor{library/http cookies http cookies BaseCookie js_output}@anchor{2e07}
@deffn {方法} BaseCookie.js_output (attrs=None)

Return an embeddable JavaScript snippet, which, if run on a browser which
supports JavaScript, will act the same as if the HTTP headers was sent.

The meaning for @emph{attrs} is the same as in @ref{2e06,,output()}.
@end deffn

@geindex load() (http.cookies.BaseCookie 方法)
@anchor{library/http cookies http cookies BaseCookie load}@anchor{2e01}
@deffn {方法} BaseCookie.load (rawdata)

If @emph{rawdata} is a string, parse it as an @code{HTTP_COOKIE} and add the values
found there as @ref{487,,Morsel}s. If it is a dictionary, it is equivalent to:

@example
for k, v in rawdata.items():
    cookie[k] = v
@end example
@end deffn

@node Morsel 对象,示例<14>,Cookie 对象,http cookies --- HTTP状态管理
@anchor{library/http cookies id2}@anchor{2e08}@anchor{library/http cookies morsel-objects}@anchor{2e09}
@subsubsection Morsel 对象


@geindex Morsel (http.cookies 中的类)
@anchor{library/http cookies http cookies Morsel}@anchor{487}
@deffn {类} http.cookies.Morsel

Abstract a key/value pair, which has some 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} attributes.

Morsels are dictionary-like objects, whose set of keys is constant --- the valid
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} attributes, which are


@itemize *

@item 
@code{expires}

@item 
@code{path}

@item 
@code{comment}

@item 
@code{domain}

@item 
@code{max-age}

@item 
@code{secure}

@item 
@code{version}

@item 
@code{httponly}

@item 
@code{samesite}
@end itemize

The attribute @code{httponly} specifies that the cookie is only transferred
in HTTP requests, and is not accessible through JavaScript. This is intended
to mitigate some forms of cross-site scripting.

The attribute @code{samesite} specifies that the browser is not allowed to
send the cookie along with cross-site requests. This helps to mitigate CSRF
attacks. Valid values for this attribute are "Strict" and "Lax".

The keys are case-insensitive and their default value is @code{'@w{'}}.


在 3.5 版更改: @code{__eq__()} now takes @ref{488,,key} and @ref{489,,value}
into account.



在 3.7 版更改: Attributes @ref{488,,key}, @ref{489,,value} and
@ref{48a,,coded_value} are read-only.  Use @ref{48b,,set()} for
setting them.



在 3.8 版更改: Added support for the @code{samesite} attribute.

@end deffn

@geindex value (http.cookies.Morsel 属性)
@anchor{library/http cookies http cookies Morsel value}@anchor{489}
@deffn {属性} Morsel.value

Cookie的值。
@end deffn

@geindex coded_value (http.cookies.Morsel 属性)
@anchor{library/http cookies http cookies Morsel coded_value}@anchor{48a}
@deffn {属性} Morsel.coded_value

The encoded value of the cookie --- this is what should be sent.
@end deffn

@geindex key (http.cookies.Morsel 属性)
@anchor{library/http cookies http cookies Morsel key}@anchor{488}
@deffn {属性} Morsel.key

The name of the cookie.
@end deffn

@geindex set() (http.cookies.Morsel 方法)
@anchor{library/http cookies http cookies Morsel set}@anchor{48b}
@deffn {方法} Morsel.set (key, value, coded_value)

Set the @emph{key}, @emph{value} and @emph{coded_value} attributes.
@end deffn

@geindex isReservedKey() (http.cookies.Morsel 方法)
@anchor{library/http cookies http cookies Morsel isReservedKey}@anchor{2e0a}
@deffn {方法} Morsel.isReservedKey (K)

Whether @emph{K} is a member of the set of keys of a @ref{487,,Morsel}.
@end deffn

@geindex output() (http.cookies.Morsel 方法)
@anchor{library/http cookies http cookies Morsel output}@anchor{2e0b}
@deffn {方法} Morsel.output (attrs=None, header='Set-Cookie:')

Return a string representation of the Morsel, suitable to be sent as an HTTP
header. By default, all the attributes are included, unless @emph{attrs} is given, in
which case it should be a list of attributes to use. @emph{header} is by default
@code{"Set-Cookie:"}.
@end deffn

@geindex js_output() (http.cookies.Morsel 方法)
@anchor{library/http cookies http cookies Morsel js_output}@anchor{2e0c}
@deffn {方法} Morsel.js_output (attrs=None)

Return an embeddable JavaScript snippet, which, if run on a browser which
supports JavaScript, will act the same as if the HTTP header was sent.

The meaning for @emph{attrs} is the same as in @ref{2e0b,,output()}.
@end deffn

@geindex OutputString() (http.cookies.Morsel 方法)
@anchor{library/http cookies http cookies Morsel OutputString}@anchor{2e0d}
@deffn {方法} Morsel.OutputString (attrs=None)

Return a string representing the Morsel, without any surrounding HTTP or
JavaScript.

The meaning for @emph{attrs} is the same as in @ref{2e0b,,output()}.
@end deffn

@geindex update() (http.cookies.Morsel 方法)
@anchor{library/http cookies http cookies Morsel update}@anchor{7be}
@deffn {方法} Morsel.update (values)

Update the values in the Morsel dictionary with the values in the dictionary
@emph{values}.  Raise an error if any of the keys in the @emph{values} dict is not a
valid 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} attribute.


在 3.5 版更改: an error is raised for invalid keys.

@end deffn

@geindex copy() (http.cookies.Morsel 方法)
@anchor{library/http cookies http cookies Morsel copy}@anchor{7bd}
@deffn {方法} Morsel.copy (value)

Return a shallow copy of the Morsel object.


在 3.5 版更改: return a Morsel object instead of a dict.

@end deffn

@geindex setdefault() (http.cookies.Morsel 方法)
@anchor{library/http cookies http cookies Morsel setdefault}@anchor{2e0e}
@deffn {方法} Morsel.setdefault (key, value=None)

Raise an error if key is not a valid 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} attribute, otherwise
behave the same as @ref{9b9,,dict.setdefault()}.
@end deffn

@node 示例<14>,,Morsel 对象,http cookies --- HTTP状态管理
@anchor{library/http cookies cookie-example}@anchor{2e0f}@anchor{library/http cookies example}@anchor{2e10}
@subsubsection 示例


The following example demonstrates how to use the @ref{96,,http.cookies} module.

@example
>>> from http import cookies
>>> C = cookies.SimpleCookie()
>>> C["fig"] = "newton"
>>> C["sugar"] = "wafer"
>>> print(C) # generate HTTP headers
Set-Cookie: fig=newton
Set-Cookie: sugar=wafer
>>> print(C.output()) # same thing
Set-Cookie: fig=newton
Set-Cookie: sugar=wafer
>>> C = cookies.SimpleCookie()
>>> C["rocky"] = "road"
>>> C["rocky"]["path"] = "/cookie"
>>> print(C.output(header="Cookie:"))
Cookie: rocky=road; Path=/cookie
>>> print(C.output(attrs=[], header="Cookie:"))
Cookie: rocky=road
>>> C = cookies.SimpleCookie()
>>> C.load("chips=ahoy; vienna=finger") # load from a string (HTTP header)
>>> print(C)
Set-Cookie: chips=ahoy
Set-Cookie: vienna=finger
>>> C = cookies.SimpleCookie()
>>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=\\012;";')
>>> print(C)
Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=\012;"
>>> C = cookies.SimpleCookie()
>>> C["oreo"] = "doublestuff"
>>> C["oreo"]["path"] = "/"
>>> print(C)
Set-Cookie: oreo=doublestuff; Path=/
>>> C = cookies.SimpleCookie()
>>> C["twix"] = "none for you"
>>> C["twix"].value
'none for you'
>>> C = cookies.SimpleCookie()
>>> C["number"] = 7 # equivalent to C["number"] = str(7)
>>> C["string"] = "seven"
>>> C["number"].value
'7'
>>> C["string"].value
'seven'
>>> print(C)
Set-Cookie: number=7
Set-Cookie: string=seven
@end example

@node http cookiejar —— HTTP 客户端的 Cookie 处理,xmlrpc --- XMLRPC 服务端与客户端模块,http cookies --- HTTP状态管理,互联网协议和支持
@anchor{library/http cookiejar doc}@anchor{2e11}@anchor{library/http cookiejar http-cookiejar-cookie-handling-for-http-clients}@anchor{2e12}@anchor{library/http cookiejar module-http cookiejar}@anchor{95}
@subsection @code{http.cookiejar} —— HTTP 客户端的 Cookie 处理


@geindex http.cookiejar (模块)

@strong{源代码：} Lib/http/cookiejar.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/http/cookiejar.py}


__________________________________________________________________


@ref{95,,http.cookiejar} 模块定义了用于自动处理 HTTP cookie 的类。这对访问需要小段数据 —— @emph{cookies} 的网站很有用，这些数据由 Web 服务器的 HTTP 响应在客户端计算机上设置，然后在以后的 HTTP 请求中返回给服务器。

常规的 Netscape Cookie 协议和 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} 定义的协议都可以处理。RFC 2965 处理默认情况下处于关闭状态。 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} cookie 被解析为 Netscape cookie，随后根据有效的 'policy' 被视为 Netscape 或 RFC 2965 cookie。 请注意，Internet 上的大多数 cookie 是 Netscape cookie。 @ref{95,,http.cookiejar} 尝试遵循事实上的 Netscape cookie 协议（与原始 Netscape 规范中所设定的协议大不相同），包括注意 @code{max-age} 和 @code{port} RFC 2965 引入的 cookie 属性。

@cartouche
@quotation 注解 
在 @code{Set-Cookie} 和 @code{Set-Cookie2} 头中找到的各种命名参数通常指 @emph{attributes}。为了不与 Python 属性相混淆，模块文档使用 @emph{cookie-attribute} 代替。
@end quotation
@end cartouche

此模块定义了以下异常：

@geindex LoadError
@anchor{library/http cookiejar http cookiejar LoadError}@anchor{2e13}
@deffn {例外} http.cookiejar.LoadError

@ref{2e14,,FileCookieJar} 实例在从文件加载 cookies 出错时抛出这个异常。 @ref{2e13,,LoadError} 是 @ref{1d3,,OSError} 的一个子类。


在 3.3 版更改: LoadError 成为 @ref{1d3,,OSError} 的子类而不是 @ref{98c,,IOError}。

@end deffn

提供了以下类：

@geindex CookieJar (http.cookiejar 中的类)
@anchor{library/http cookiejar http cookiejar CookieJar}@anchor{2c16}
@deffn {类} http.cookiejar.CookieJar (policy=None)

@emph{policy} 是实现了 @ref{2e15,,CookiePolicy} 接口的一个对象。

@ref{2c16,,CookieJar} 类储存 HTTP cookies。它从 HTTP 请求提取 cookies，并在 HTTP 响应中返回它们。 @ref{2c16,,CookieJar} 实例在必要时自动处理包含 cookie 的到期情况。子类还负责储存和从文件或数据库中查找 cookies。
@end deffn

@geindex FileCookieJar (http.cookiejar 中的类)
@anchor{library/http cookiejar http cookiejar FileCookieJar}@anchor{2e14}
@deffn {类} http.cookiejar.FileCookieJar (filename, delayload=None, policy=None)

@emph{policy} 是实现了 @ref{2e15,,CookiePolicy} 接口的一个对象。对于其他参数，参考相应属性的文档。

一个可以从硬盘中文件加载或保存 cookie 的 @ref{2c16,,CookieJar}。 Cookies @strong{不} 会在 @ref{2e16,,load()} 或 @ref{2e17,,revert()} 方法调用前从命名的文件中加载。子类的文档位于段落 @ref{2e18,,FileCookieJar subclasses and co-operation with web browsers}。


在 3.8 版更改: 文件名形参支持 @ref{363,,path-like object}。

@end deffn

@geindex CookiePolicy (http.cookiejar 中的类)
@anchor{library/http cookiejar http cookiejar CookiePolicy}@anchor{2e15}
@deffn {类} http.cookiejar.CookiePolicy

此类负责确定是否应从服务器接受每个 cookie 或将其返回给服务器。
@end deffn

@geindex DefaultCookiePolicy (http.cookiejar 中的类)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy}@anchor{f7f}
@deffn {类} http.cookiejar.DefaultCookiePolicy (blocked_domains=None, allowed_domains=None, netscape=True, rfc2965=False, rfc2109_as_netscape=None, hide_cookie2=False, strict_domain=False, strict_rfc2965_unverifiable=True, strict_ns_unverifiable=False, strict_ns_domain=DefaultCookiePolicy.DomainLiberal, strict_ns_set_initial_dollar=False, strict_ns_set_path=False, secure_protocols=("https", "wss"))

构造参数只能以关键字参数传递，@emph{blocked_domains} 是一个我们既不会接受也不会返回 cookie 的域名序列。@emph{allowed_domains} 如果不是 @ref{157,,None}，则是仅有的我们会接受或返回的域名序列。@emph{secure_protocols} 是可以添加安全 cookies 的协议序列。默认将 @emph{https} 和 @emph{wss} （安全 WebSocket）考虑为安全协议。对于其他参数，参考 @ref{2e15,,CookiePolicy} 和 @ref{f7f,,DefaultCookiePolicy} 对象的文档。

@ref{f7f,,DefaultCookiePolicy} implements the standard accept / reject rules for
Netscape and 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} cookies.  By default, 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} cookies (ie. cookies
received in a @code{Set-Cookie} header with a version cookie-attribute of
1) are treated according to the RFC 2965 rules.  However, if RFC 2965 handling
is turned off or @ref{2e19,,rfc2109_as_netscape} is @code{True}, RFC 2109 cookies are
'downgraded' by the @ref{2c16,,CookieJar} instance to Netscape cookies, by
setting the @code{version} attribute of the @ref{2e1a,,Cookie} instance to 0.
@ref{f7f,,DefaultCookiePolicy} also provides some parameters to allow some
fine-tuning of policy.
@end deffn

@geindex Cookie (http.cookiejar 中的类)
@anchor{library/http cookiejar http cookiejar Cookie}@anchor{2e1a}
@deffn {类} http.cookiejar.Cookie

This class represents Netscape, 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} and 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} cookies.  It is not
expected that users of @ref{95,,http.cookiejar} construct their own @ref{2e1a,,Cookie}
instances.  Instead, if necessary, call @code{make_cookies()} on a
@ref{2c16,,CookieJar} instance.
@end deffn


@subsubheading 参见



@table @asis

@item Module @ref{120,,urllib.request}

URL opening with automatic cookie handling.

@item Module @ref{96,,http.cookies}

HTTP cookie classes, principally useful for server-side code.  The
@ref{95,,http.cookiejar} and @ref{96,,http.cookies} modules do not depend on each
other.

@item @indicateurl{https://curl.haxx.se/rfc/cookie_spec.html}

The specification of the original Netscape cookie protocol.  Though this is
still the dominant protocol, the 'Netscape cookie protocol' implemented by all
the major browsers (and @ref{95,,http.cookiejar}) only bears a passing resemblance to
the one sketched out in @code{cookie_spec.html}.

@geindex RFC; RFC 2109

@item RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} - HTTP State Management Mechanism

Obsoleted by 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html}. Uses @code{Set-Cookie} with version=1.

@geindex RFC; RFC 2965

@item RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} - HTTP State Management Mechanism

The Netscape protocol with the bugs fixed.  Uses @code{Set-Cookie2} in
place of @code{Set-Cookie}.  Not widely used.

@item @indicateurl{http://kristol.org/cookie/errata.html}

Unfinished errata to 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html}.
@end table

@geindex RFC; RFC 2964
RFC 2964@footnote{https://tools.ietf.org/html/rfc2964.html} - Use of HTTP State Management


@menu
* CookieJar 和 FileCookieJar 对象:: 
* FileCookieJar subclasses and co-operation with web browsers:: 
* CookiePolicy 对象:: 
* DefaultCookiePolicy 对象:: 
* Cookie 对象: Cookie 对象<2>. 
* 例子: 例子<24>. 

@end menu

@node CookieJar 和 FileCookieJar 对象,FileCookieJar subclasses and co-operation with web browsers,,http cookiejar —— HTTP 客户端的 Cookie 处理
@anchor{library/http cookiejar cookie-jar-objects}@anchor{2e1b}@anchor{library/http cookiejar cookiejar-and-filecookiejar-objects}@anchor{2e1c}
@subsubsection CookieJar 和 FileCookieJar 对象


@ref{2c16,,CookieJar} objects support the @ref{fce,,iterator} protocol for iterating over
contained @ref{2e1a,,Cookie} objects.

@ref{2c16,,CookieJar} has the following methods:

@geindex add_cookie_header() (http.cookiejar.CookieJar 方法)
@anchor{library/http cookiejar http cookiejar CookieJar add_cookie_header}@anchor{2e1d}
@deffn {方法} CookieJar.add_cookie_header (request)

Add correct @code{Cookie} header to @emph{request}.

If policy allows (ie. the @code{rfc2965} and @code{hide_cookie2} attributes of
the @ref{2c16,,CookieJar}'s @ref{2e15,,CookiePolicy} instance are true and false
respectively), the @code{Cookie2} header is also added when appropriate.

The @emph{request} object (usually a @ref{8f0,,urllib.request.Request} instance)
must support the methods @code{get_full_url()}, @code{get_host()},
@code{get_type()}, @code{unverifiable()}, @code{has_header()},
@code{get_header()}, @code{header_items()}, @code{add_unredirected_header()}
and @code{origin_req_host} attribute as documented by
@ref{120,,urllib.request}.


在 3.3 版更改: @emph{request} object needs @code{origin_req_host} attribute. Dependency on a
deprecated method @code{get_origin_req_host()} has been removed.

@end deffn

@geindex extract_cookies() (http.cookiejar.CookieJar 方法)
@anchor{library/http cookiejar http cookiejar CookieJar extract_cookies}@anchor{2e1e}
@deffn {方法} CookieJar.extract_cookies (response, request)

Extract cookies from HTTP @emph{response} and store them in the @ref{2c16,,CookieJar},
where allowed by policy.

The @ref{2c16,,CookieJar} will look for allowable @code{Set-Cookie} and
@code{Set-Cookie2} headers in the @emph{response} argument, and store cookies
as appropriate (subject to the @ref{2e1f,,CookiePolicy.set_ok()} method's approval).

The @emph{response} object (usually the result of a call to
@ref{786,,urllib.request.urlopen()}, or similar) should support an @code{info()}
method, which returns an @ref{53c,,email.message.Message} instance.

The @emph{request} object (usually a @ref{8f0,,urllib.request.Request} instance)
must support the methods @code{get_full_url()}, @code{get_host()},
@code{unverifiable()}, and @code{origin_req_host} attribute, as documented
by @ref{120,,urllib.request}.  The request is used to set default values for
cookie-attributes as well as for checking that the cookie is allowed to be
set.


在 3.3 版更改: @emph{request} object needs @code{origin_req_host} attribute. Dependency on a
deprecated method @code{get_origin_req_host()} has been removed.

@end deffn

@geindex set_policy() (http.cookiejar.CookieJar 方法)
@anchor{library/http cookiejar http cookiejar CookieJar set_policy}@anchor{2e20}
@deffn {方法} CookieJar.set_policy (policy)

Set the @ref{2e15,,CookiePolicy} instance to be used.
@end deffn

@geindex make_cookies() (http.cookiejar.CookieJar 方法)
@anchor{library/http cookiejar http cookiejar CookieJar make_cookies}@anchor{2e21}
@deffn {方法} CookieJar.make_cookies (response, request)

Return sequence of @ref{2e1a,,Cookie} objects extracted from @emph{response} object.

See the documentation for @ref{2e1e,,extract_cookies()} for the interfaces required of
the @emph{response} and @emph{request} arguments.
@end deffn

@geindex set_cookie_if_ok() (http.cookiejar.CookieJar 方法)
@anchor{library/http cookiejar http cookiejar CookieJar set_cookie_if_ok}@anchor{2e22}
@deffn {方法} CookieJar.set_cookie_if_ok (cookie, request)

Set a @ref{2e1a,,Cookie} if policy says it's OK to do so.
@end deffn

@geindex set_cookie() (http.cookiejar.CookieJar 方法)
@anchor{library/http cookiejar http cookiejar CookieJar set_cookie}@anchor{2e23}
@deffn {方法} CookieJar.set_cookie (cookie)

Set a @ref{2e1a,,Cookie}, without checking with policy to see whether or not it
should be set.
@end deffn

@geindex clear() (http.cookiejar.CookieJar 方法)
@anchor{library/http cookiejar http cookiejar CookieJar clear}@anchor{2e24}
@deffn {方法} CookieJar.clear ([domain[, path[, name]]])

Clear some cookies.

If invoked without arguments, clear all cookies.  If given a single argument,
only cookies belonging to that @emph{domain} will be removed. If given two arguments,
cookies belonging to the specified @emph{domain} and URL @emph{path} are removed.  If
given three arguments, then the cookie with the specified @emph{domain}, @emph{path} and
@emph{name} is removed.

Raises @ref{2c7,,KeyError} if no matching cookie exists.
@end deffn

@geindex clear_session_cookies() (http.cookiejar.CookieJar 方法)
@anchor{library/http cookiejar http cookiejar CookieJar clear_session_cookies}@anchor{2e25}
@deffn {方法} CookieJar.clear_session_cookies ()

Discard all session cookies.

Discards all contained cookies that have a true @code{discard} attribute
(usually because they had either no @code{max-age} or @code{expires} cookie-attribute,
or an explicit @code{discard} cookie-attribute).  For interactive browsers, the end
of a session usually corresponds to closing the browser window.

Note that the @code{save()} method won't save session cookies anyway, unless you
ask otherwise by passing a true @emph{ignore_discard} argument.
@end deffn

@ref{2e14,,FileCookieJar} implements the following additional methods:

@geindex save() (http.cookiejar.FileCookieJar 方法)
@anchor{library/http cookiejar http cookiejar FileCookieJar save}@anchor{2e26}
@deffn {方法} FileCookieJar.save (filename=None, ignore_discard=False, ignore_expires=False)

Save cookies to a file.

This base class raises @ref{609,,NotImplementedError}.  Subclasses may leave this
method unimplemented.

@emph{filename} is the name of file in which to save cookies.  If @emph{filename} is not
specified, @code{self.filename} is used (whose default is the value passed to
the constructor, if any); if @code{self.filename} is @ref{157,,None},
@ref{1fb,,ValueError} is raised.

@emph{ignore_discard}: save even cookies set to be discarded. @emph{ignore_expires}: save
even cookies that have expired

The file is overwritten if it already exists, thus wiping all the cookies it
contains.  Saved cookies can be restored later using the @ref{2e16,,load()} or
@ref{2e17,,revert()} methods.
@end deffn

@geindex load() (http.cookiejar.FileCookieJar 方法)
@anchor{library/http cookiejar http cookiejar FileCookieJar load}@anchor{2e16}
@deffn {方法} FileCookieJar.load (filename=None, ignore_discard=False, ignore_expires=False)

Load cookies from a file.

Old cookies are kept unless overwritten by newly loaded ones.

Arguments are as for @ref{2e26,,save()}.

The named file must be in the format understood by the class, or
@ref{2e13,,LoadError} will be raised.  Also, @ref{1d3,,OSError} may be raised, for
example if the file does not exist.


在 3.3 版更改: 过去触发的 @ref{98c,,IOError}，现在是 @ref{1d3,,OSError} 的别名。

@end deffn

@geindex revert() (http.cookiejar.FileCookieJar 方法)
@anchor{library/http cookiejar http cookiejar FileCookieJar revert}@anchor{2e17}
@deffn {方法} FileCookieJar.revert (filename=None, ignore_discard=False, ignore_expires=False)

Clear all cookies and reload cookies from a saved file.

@ref{2e17,,revert()} can raise the same exceptions as @ref{2e16,,load()}. If there is a
failure, the object's state will not be altered.
@end deffn

@ref{2e14,,FileCookieJar} instances have the following public attributes:

@geindex filename (http.cookiejar.FileCookieJar 属性)
@anchor{library/http cookiejar http cookiejar FileCookieJar filename}@anchor{2e27}
@deffn {属性} FileCookieJar.filename

Filename of default file in which to keep cookies.  This attribute may be
assigned to.
@end deffn

@geindex delayload (http.cookiejar.FileCookieJar 属性)
@anchor{library/http cookiejar http cookiejar FileCookieJar delayload}@anchor{2e28}
@deffn {属性} FileCookieJar.delayload

If true, load cookies lazily from disk.  This attribute should not be assigned
to.  This is only a hint, since this only affects performance, not behaviour
(unless the cookies on disk are changing). A @ref{2c16,,CookieJar} object may
ignore it.  None of the @ref{2e14,,FileCookieJar} classes included in the standard
library lazily loads cookies.
@end deffn

@node FileCookieJar subclasses and co-operation with web browsers,CookiePolicy 对象,CookieJar 和 FileCookieJar 对象,http cookiejar —— HTTP 客户端的 Cookie 处理
@anchor{library/http cookiejar file-cookie-jar-classes}@anchor{2e18}@anchor{library/http cookiejar filecookiejar-subclasses-and-co-operation-with-web-browsers}@anchor{2e29}
@subsubsection FileCookieJar subclasses and co-operation with web browsers


The following @ref{2c16,,CookieJar} subclasses are provided for reading and
writing.

@geindex MozillaCookieJar (http.cookiejar 中的类)
@anchor{library/http cookiejar http cookiejar MozillaCookieJar}@anchor{2e2a}
@deffn {类} http.cookiejar.MozillaCookieJar (filename, delayload=None, policy=None)

A @ref{2e14,,FileCookieJar} that can load from and save cookies to disk in the
Mozilla @code{cookies.txt} file format (which is also used by the Lynx and Netscape
browsers).

@cartouche
@quotation 注解 
This loses information about 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} cookies, and also about newer or
non-standard cookie-attributes such as @code{port}.
@end quotation
@end cartouche

@cartouche
@quotation 警告 
Back up your cookies before saving if you have cookies whose loss / corruption
would be inconvenient (there are some subtleties which may lead to slight
changes in the file over a load / save round-trip).
@end quotation
@end cartouche

Also note that cookies saved while Mozilla is running will get clobbered by
Mozilla.
@end deffn

@geindex LWPCookieJar (http.cookiejar 中的类)
@anchor{library/http cookiejar http cookiejar LWPCookieJar}@anchor{2e2b}
@deffn {类} http.cookiejar.LWPCookieJar (filename, delayload=None, policy=None)

A @ref{2e14,,FileCookieJar} that can load from and save cookies to disk in format
compatible with the libwww-perl library's @code{Set-Cookie3} file format.  This is
convenient if you want to store cookies in a human-readable file.


在 3.8 版更改: 文件名形参支持 @ref{363,,path-like object}。

@end deffn

@node CookiePolicy 对象,DefaultCookiePolicy 对象,FileCookieJar subclasses and co-operation with web browsers,http cookiejar —— HTTP 客户端的 Cookie 处理
@anchor{library/http cookiejar cookie-policy-objects}@anchor{2e2c}@anchor{library/http cookiejar cookiepolicy-objects}@anchor{2e2d}
@subsubsection CookiePolicy 对象


Objects implementing the @ref{2e15,,CookiePolicy} interface have the following
methods:

@geindex set_ok() (http.cookiejar.CookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar CookiePolicy set_ok}@anchor{2e1f}
@deffn {方法} CookiePolicy.set_ok (cookie, request)

Return boolean value indicating whether cookie should be accepted from server.

@emph{cookie} is a @ref{2e1a,,Cookie} instance.  @emph{request} is an object
implementing the interface defined by the documentation for
@ref{2e1e,,CookieJar.extract_cookies()}.
@end deffn

@geindex return_ok() (http.cookiejar.CookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar CookiePolicy return_ok}@anchor{2e2e}
@deffn {方法} CookiePolicy.return_ok (cookie, request)

Return boolean value indicating whether cookie should be returned to server.

@emph{cookie} is a @ref{2e1a,,Cookie} instance.  @emph{request} is an object
implementing the interface defined by the documentation for
@ref{2e1d,,CookieJar.add_cookie_header()}.
@end deffn

@geindex domain_return_ok() (http.cookiejar.CookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar CookiePolicy domain_return_ok}@anchor{2e2f}
@deffn {方法} CookiePolicy.domain_return_ok (domain, request)

Return @code{False} if cookies should not be returned, given cookie domain.

This method is an optimization.  It removes the need for checking every cookie
with a particular domain (which might involve reading many files).  Returning
true from @ref{2e2f,,domain_return_ok()} and @ref{2e30,,path_return_ok()} leaves all the
work to @ref{2e2e,,return_ok()}.

If @ref{2e2f,,domain_return_ok()} returns true for the cookie domain,
@ref{2e30,,path_return_ok()} is called for the cookie path.  Otherwise,
@ref{2e30,,path_return_ok()} and @ref{2e2e,,return_ok()} are never called for that cookie
domain.  If @ref{2e30,,path_return_ok()} returns true, @ref{2e2e,,return_ok()} is called
with the @ref{2e1a,,Cookie} object itself for a full check.  Otherwise,
@ref{2e2e,,return_ok()} is never called for that cookie path.

Note that @ref{2e2f,,domain_return_ok()} is called for every @emph{cookie} domain, not just
for the @emph{request} domain.  For example, the function might be called with both
@code{".example.com"} and @code{"www.example.com"} if the request domain is
@code{"www.example.com"}.  The same goes for @ref{2e30,,path_return_ok()}.

The @emph{request} argument is as documented for @ref{2e2e,,return_ok()}.
@end deffn

@geindex path_return_ok() (http.cookiejar.CookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar CookiePolicy path_return_ok}@anchor{2e30}
@deffn {方法} CookiePolicy.path_return_ok (path, request)

Return @code{False} if cookies should not be returned, given cookie path.

See the documentation for @ref{2e2f,,domain_return_ok()}.
@end deffn

In addition to implementing the methods above, implementations of the
@ref{2e15,,CookiePolicy} interface must also supply the following attributes,
indicating which protocols should be used, and how.  All of these attributes may
be assigned to.

@geindex netscape (http.cookiejar.CookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar CookiePolicy netscape}@anchor{2e31}
@deffn {属性} CookiePolicy.netscape

Implement Netscape protocol.
@end deffn

@geindex rfc2965 (http.cookiejar.CookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar CookiePolicy rfc2965}@anchor{2e32}
@deffn {属性} CookiePolicy.rfc2965

Implement 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} protocol.
@end deffn

@geindex hide_cookie2 (http.cookiejar.CookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar CookiePolicy hide_cookie2}@anchor{2e33}
@deffn {属性} CookiePolicy.hide_cookie2

Don't add @code{Cookie2} header to requests (the presence of this header
indicates to the server that we understand 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} cookies).
@end deffn

The most useful way to define a @ref{2e15,,CookiePolicy} class is by subclassing
from @ref{f7f,,DefaultCookiePolicy} and overriding some or all of the methods
above.  @ref{2e15,,CookiePolicy} itself may be used as a 'null policy' to allow
setting and receiving any and all cookies (this is unlikely to be useful).

@node DefaultCookiePolicy 对象,Cookie 对象<2>,CookiePolicy 对象,http cookiejar —— HTTP 客户端的 Cookie 处理
@anchor{library/http cookiejar default-cookie-policy-objects}@anchor{2e34}@anchor{library/http cookiejar defaultcookiepolicy-objects}@anchor{2e35}
@subsubsection DefaultCookiePolicy 对象


Implements the standard rules for accepting and returning cookies.

Both 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} and Netscape cookies are covered.  RFC 2965 handling is switched
off by default.

The easiest way to provide your own policy is to override this class and call
its methods in your overridden implementations before adding your own additional
checks:

@example
import http.cookiejar
class MyCookiePolicy(http.cookiejar.DefaultCookiePolicy):
    def set_ok(self, cookie, request):
        if not http.cookiejar.DefaultCookiePolicy.set_ok(self, cookie, request):
            return False
        if i_dont_want_to_store_this_cookie(cookie):
            return False
        return True
@end example

In addition to the features required to implement the @ref{2e15,,CookiePolicy}
interface, this class allows you to block and allow domains from setting and
receiving cookies.  There are also some strictness switches that allow you to
tighten up the rather loose Netscape protocol rules a little bit (at the cost of
blocking some benign cookies).

A domain blacklist and whitelist is provided (both off by default). Only domains
not in the blacklist and present in the whitelist (if the whitelist is active)
participate in cookie setting and returning.  Use the @emph{blocked_domains}
constructor argument, and @code{blocked_domains()} and
@code{set_blocked_domains()} methods (and the corresponding argument and methods
for @emph{allowed_domains}).  If you set a whitelist, you can turn it off again by
setting it to @ref{157,,None}.

Domains in block or allow lists that do not start with a dot must equal the
cookie domain to be matched.  For example, @code{"example.com"} matches a blacklist
entry of @code{"example.com"}, but @code{"www.example.com"} does not.  Domains that do
start with a dot are matched by more specific domains too. For example, both
@code{"www.example.com"} and @code{"www.coyote.example.com"} match @code{".example.com"}
(but @code{"example.com"} itself does not).  IP addresses are an exception, and
must match exactly.  For example, if blocked_domains contains @code{"192.168.1.2"}
and @code{".168.1.2"}, 192.168.1.2 is blocked, but 193.168.1.2 is not.

@ref{f7f,,DefaultCookiePolicy} implements the following additional methods:

@geindex blocked_domains() (http.cookiejar.DefaultCookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy blocked_domains}@anchor{2e36}
@deffn {方法} DefaultCookiePolicy.blocked_domains ()

Return the sequence of blocked domains (as a tuple).
@end deffn

@geindex set_blocked_domains() (http.cookiejar.DefaultCookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy set_blocked_domains}@anchor{2e37}
@deffn {方法} DefaultCookiePolicy.set_blocked_domains (blocked_domains)

Set the sequence of blocked domains.
@end deffn

@geindex is_blocked() (http.cookiejar.DefaultCookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy is_blocked}@anchor{2e38}
@deffn {方法} DefaultCookiePolicy.is_blocked (domain)

Return whether @emph{domain} is on the blacklist for setting or receiving cookies.
@end deffn

@geindex allowed_domains() (http.cookiejar.DefaultCookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy allowed_domains}@anchor{2e39}
@deffn {方法} DefaultCookiePolicy.allowed_domains ()

Return @ref{157,,None}, or the sequence of allowed domains (as a tuple).
@end deffn

@geindex set_allowed_domains() (http.cookiejar.DefaultCookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy set_allowed_domains}@anchor{2e3a}
@deffn {方法} DefaultCookiePolicy.set_allowed_domains (allowed_domains)

Set the sequence of allowed domains, or @ref{157,,None}.
@end deffn

@geindex is_not_allowed() (http.cookiejar.DefaultCookiePolicy 方法)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy is_not_allowed}@anchor{2e3b}
@deffn {方法} DefaultCookiePolicy.is_not_allowed (domain)

Return whether @emph{domain} is not on the whitelist for setting or receiving
cookies.
@end deffn

@ref{f7f,,DefaultCookiePolicy} instances have the following attributes, which are
all initialised from the constructor arguments of the same name, and which may
all be assigned to.

@geindex rfc2109_as_netscape (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy rfc2109_as_netscape}@anchor{2e19}
@deffn {属性} DefaultCookiePolicy.rfc2109_as_netscape

If true, request that the @ref{2c16,,CookieJar} instance downgrade 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} cookies
(ie. cookies received in a @code{Set-Cookie} header with a version
cookie-attribute of 1) to Netscape cookies by setting the version attribute of
the @ref{2e1a,,Cookie} instance to 0.  The default value is @ref{157,,None}, in which
case RFC 2109 cookies are downgraded if and only if 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} handling is turned
off.  Therefore, RFC 2109 cookies are downgraded by default.
@end deffn

General strictness switches:

@geindex strict_domain (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy strict_domain}@anchor{2e3c}
@deffn {属性} DefaultCookiePolicy.strict_domain

Don't allow sites to set two-component domains with country-code top-level
domains like @code{.co.uk}, @code{.gov.uk}, @code{.co.nz}.etc.  This is far from perfect
and isn't guaranteed to work!
@end deffn

@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} protocol strictness switches:

@geindex strict_rfc2965_unverifiable (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy strict_rfc2965_unverifiable}@anchor{2e3d}
@deffn {属性} DefaultCookiePolicy.strict_rfc2965_unverifiable

Follow 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} rules on unverifiable transactions (usually, an unverifiable
transaction is one resulting from a redirect or a request for an image hosted on
another site).  If this is false, cookies are @emph{never} blocked on the basis of
verifiability
@end deffn

Netscape protocol strictness switches:

@geindex strict_ns_unverifiable (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy strict_ns_unverifiable}@anchor{2e3e}
@deffn {属性} DefaultCookiePolicy.strict_ns_unverifiable

Apply 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} rules on unverifiable transactions even to Netscape cookies.
@end deffn

@geindex strict_ns_domain (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy strict_ns_domain}@anchor{2e3f}
@deffn {属性} DefaultCookiePolicy.strict_ns_domain

Flags indicating how strict to be with domain-matching rules for Netscape
cookies.  See below for acceptable values.
@end deffn

@geindex strict_ns_set_initial_dollar (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy strict_ns_set_initial_dollar}@anchor{2e40}
@deffn {属性} DefaultCookiePolicy.strict_ns_set_initial_dollar

Ignore cookies in Set-Cookie: headers that have names starting with @code{'$'}.
@end deffn

@geindex strict_ns_set_path (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy strict_ns_set_path}@anchor{2e41}
@deffn {属性} DefaultCookiePolicy.strict_ns_set_path

Don't allow setting cookies whose path doesn't path-match request URI.
@end deffn

@code{strict_ns_domain} is a collection of flags.  Its value is constructed by
or-ing together (for example, @code{DomainStrictNoDots|DomainStrictNonDomain} means
both flags are set).

@geindex DomainStrictNoDots (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy DomainStrictNoDots}@anchor{2e42}
@deffn {属性} DefaultCookiePolicy.DomainStrictNoDots

When setting cookies, the 'host prefix' must not contain a dot (eg.
@code{www.foo.bar.com} can't set a cookie for @code{.bar.com}, because @code{www.foo}
contains a dot).
@end deffn

@geindex DomainStrictNonDomain (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy DomainStrictNonDomain}@anchor{2e43}
@deffn {属性} DefaultCookiePolicy.DomainStrictNonDomain

Cookies that did not explicitly specify a @code{domain} cookie-attribute can only
be returned to a domain equal to the domain that set the cookie (eg.
@code{spam.example.com} won't be returned cookies from @code{example.com} that had no
@code{domain} cookie-attribute).
@end deffn

@geindex DomainRFC2965Match (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy DomainRFC2965Match}@anchor{2e44}
@deffn {属性} DefaultCookiePolicy.DomainRFC2965Match

When setting cookies, require a full 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} domain-match.
@end deffn

The following attributes are provided for convenience, and are the most useful
combinations of the above flags:

@geindex DomainLiberal (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy DomainLiberal}@anchor{2e45}
@deffn {属性} DefaultCookiePolicy.DomainLiberal

Equivalent to 0 (ie. all of the above Netscape domain strictness flags switched
off).
@end deffn

@geindex DomainStrict (http.cookiejar.DefaultCookiePolicy 属性)
@anchor{library/http cookiejar http cookiejar DefaultCookiePolicy DomainStrict}@anchor{2e46}
@deffn {属性} DefaultCookiePolicy.DomainStrict

Equivalent to @code{DomainStrictNoDots|DomainStrictNonDomain}.
@end deffn

@node Cookie 对象<2>,例子<24>,DefaultCookiePolicy 对象,http cookiejar —— HTTP 客户端的 Cookie 处理
@anchor{library/http cookiejar cookie-objects}@anchor{2e47}
@subsubsection Cookie 对象


@ref{2e1a,,Cookie} instances have Python attributes roughly corresponding to the
standard cookie-attributes specified in the various cookie standards.  The
correspondence is not one-to-one, because there are complicated rules for
assigning default values, because the @code{max-age} and @code{expires}
cookie-attributes contain equivalent information, and because 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} cookies
may be 'downgraded' by @ref{95,,http.cookiejar} from version 1 to version 0 (Netscape)
cookies.

Assignment to these attributes should not be necessary other than in rare
circumstances in a @ref{2e15,,CookiePolicy} method.  The class does not enforce
internal consistency, so you should know what you're doing if you do that.

@geindex version (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie version}@anchor{2e48}
@deffn {属性} Cookie.version

Integer or @ref{157,,None}.  Netscape cookies have @ref{2e48,,version} 0. 
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} and
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} cookies have a @code{version} cookie-attribute of 1.  However, note that
@ref{95,,http.cookiejar} may 'downgrade' RFC 2109 cookies to Netscape cookies, in which
case @ref{2e48,,version} is 0.
@end deffn

@geindex name (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie name}@anchor{2e49}
@deffn {属性} Cookie.name

Cookie name (a string).
@end deffn

@geindex value (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie value}@anchor{2e4a}
@deffn {属性} Cookie.value

Cookie value (a string), or @ref{157,,None}.
@end deffn

@geindex port (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie port}@anchor{2e4b}
@deffn {属性} Cookie.port

String representing a port or a set of ports (eg. '80', or '80,8080'), or
@ref{157,,None}.
@end deffn

@geindex path (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie path}@anchor{2e4c}
@deffn {属性} Cookie.path

Cookie path (a string, eg. @code{'/acme/rocket_launchers'}).
@end deffn

@geindex secure (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie secure}@anchor{2e4d}
@deffn {属性} Cookie.secure

@code{True} if cookie should only be returned over a secure connection.
@end deffn

@geindex expires (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie expires}@anchor{2e4e}
@deffn {属性} Cookie.expires

Integer expiry date in seconds since epoch, or @ref{157,,None}.  See also the
@ref{2e4f,,is_expired()} method.
@end deffn

@geindex discard (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie discard}@anchor{2e50}
@deffn {属性} Cookie.discard

@code{True} if this is a session cookie.
@end deffn

@geindex comment (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie comment}@anchor{2e51}
@deffn {属性} Cookie.comment

String comment from the server explaining the function of this cookie, or
@ref{157,,None}.
@end deffn

@geindex comment_url (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie comment_url}@anchor{2e52}
@deffn {属性} Cookie.comment_url

URL linking to a comment from the server explaining the function of this cookie,
or @ref{157,,None}.
@end deffn

@geindex rfc2109 (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie rfc2109}@anchor{2e53}
@deffn {属性} Cookie.rfc2109

@code{True} if this cookie was received as an 
@geindex RFC; RFC 2109
RFC 2109@footnote{https://tools.ietf.org/html/rfc2109.html} cookie (ie. the cookie
arrived in a @code{Set-Cookie} header, and the value of the Version
cookie-attribute in that header was 1).  This attribute is provided because
@ref{95,,http.cookiejar} may 'downgrade' RFC 2109 cookies to Netscape cookies, in
which case @ref{2e48,,version} is 0.
@end deffn

@geindex port_specified (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie port_specified}@anchor{2e54}
@deffn {属性} Cookie.port_specified

@code{True} if a port or set of ports was explicitly specified by the server (in the
@code{Set-Cookie} / @code{Set-Cookie2} header).
@end deffn

@geindex domain_specified (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie domain_specified}@anchor{2e55}
@deffn {属性} Cookie.domain_specified

@code{True} if a domain was explicitly specified by the server.
@end deffn

@geindex domain_initial_dot (http.cookiejar.Cookie 属性)
@anchor{library/http cookiejar http cookiejar Cookie domain_initial_dot}@anchor{2e56}
@deffn {属性} Cookie.domain_initial_dot

@code{True} if the domain explicitly specified by the server began with a dot
(@code{'.'}).
@end deffn

Cookies may have additional non-standard cookie-attributes.  These may be
accessed using the following methods:

@geindex has_nonstandard_attr() (http.cookiejar.Cookie 方法)
@anchor{library/http cookiejar http cookiejar Cookie has_nonstandard_attr}@anchor{2e57}
@deffn {方法} Cookie.has_nonstandard_attr (name)

Return @code{True} if cookie has the named cookie-attribute.
@end deffn

@geindex get_nonstandard_attr() (http.cookiejar.Cookie 方法)
@anchor{library/http cookiejar http cookiejar Cookie get_nonstandard_attr}@anchor{2e58}
@deffn {方法} Cookie.get_nonstandard_attr (name, default=None)

If cookie has the named cookie-attribute, return its value. Otherwise, return
@emph{default}.
@end deffn

@geindex set_nonstandard_attr() (http.cookiejar.Cookie 方法)
@anchor{library/http cookiejar http cookiejar Cookie set_nonstandard_attr}@anchor{2e59}
@deffn {方法} Cookie.set_nonstandard_attr (name, value)

Set the value of the named cookie-attribute.
@end deffn

The @ref{2e1a,,Cookie} class also defines the following method:

@geindex is_expired() (http.cookiejar.Cookie 方法)
@anchor{library/http cookiejar http cookiejar Cookie is_expired}@anchor{2e4f}
@deffn {方法} Cookie.is_expired (now=None)

@code{True} if cookie has passed the time at which the server requested it should
expire.  If @emph{now} is given (in seconds since the epoch), return whether the
cookie has expired at the specified time.
@end deffn

@node 例子<24>,,Cookie 对象<2>,http cookiejar —— HTTP 客户端的 Cookie 处理
@anchor{library/http cookiejar examples}@anchor{2e5a}
@subsubsection 例子


The first example shows the most common usage of @ref{95,,http.cookiejar}:

@example
import http.cookiejar, urllib.request
cj = http.cookiejar.CookieJar()
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")
@end example

This example illustrates how to open a URL using your Netscape, Mozilla, or Lynx
cookies (assumes Unix/Netscape convention for location of the cookies file):

@example
import os, http.cookiejar, urllib.request
cj = http.cookiejar.MozillaCookieJar()
cj.load(os.path.join(os.path.expanduser("~"), ".netscape", "cookies.txt"))
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")
@end example

The next example illustrates the use of @ref{f7f,,DefaultCookiePolicy}. Turn on
@geindex RFC; RFC 2965
RFC 2965@footnote{https://tools.ietf.org/html/rfc2965.html} cookies, be more strict about domains when setting and returning
Netscape cookies, and block some domains from setting cookies or having them
returned:

@example
import urllib.request
from http.cookiejar import CookieJar, DefaultCookiePolicy
policy = DefaultCookiePolicy(
    rfc2965=True, strict_ns_domain=Policy.DomainStrict,
    blocked_domains=["ads.net", ".ads.net"])
cj = CookieJar(policy)
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
r = opener.open("http://example.com/")
@end example

@node xmlrpc --- XMLRPC 服务端与客户端模块,xmlrpc client --- XML-RPC client access,http cookiejar —— HTTP 客户端的 Cookie 处理,互联网协议和支持
@anchor{library/xmlrpc doc}@anchor{2e5b}@anchor{library/xmlrpc xmlrpc-xmlrpc-server-and-client-modules}@anchor{2e5c}
@subsection @code{xmlrpc} --- XMLRPC 服务端与客户端模块


XML-RPC 是一种远程过程调用方法，它使用通过 HTTP 传递的 XML 作为载体。 有了它，客户端可以在远程服务器上调用带参数的方法（服务器以 URI 命名）并获取结构化的数据。

@code{xmlrpc} 是一个集合了 XML-RPC 服务端与客户端实现模块的包。 这些模块是:


@itemize *

@item 
@ref{13f,,xmlrpc.client}

@item 
@ref{140,,xmlrpc.server}
@end itemize

@node xmlrpc client --- XML-RPC client access,xmlrpc server --- Basic XML-RPC servers,xmlrpc --- XMLRPC 服务端与客户端模块,互联网协议和支持
@anchor{library/xmlrpc client doc}@anchor{2e5d}@anchor{library/xmlrpc client module-xmlrpc client}@anchor{13f}@anchor{library/xmlrpc client xmlrpc-client-xml-rpc-client-access}@anchor{2e5e}
@subsection @code{xmlrpc.client} --- XML-RPC client access


@geindex xmlrpc.client (模块)

@strong{源代码:} Lib/xmlrpc/client.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xmlrpc/client.py}

@c XXX Not everything is documented yet.  It might be good to describe
@c Marshaller, Unmarshaller, getparser and Transport.


__________________________________________________________________


XML-RPC is a Remote Procedure Call method that uses XML passed via HTTP(S) as a
transport.  With it, a client can call methods with parameters on a remote
server (the server is named by a URI) and get back structured data.  This module
supports writing XML-RPC client code; it handles all the details of translating
between conformable Python objects and XML on the wire.

@cartouche
@quotation 警告 
The @ref{13f,,xmlrpc.client} module is not secure against maliciously
constructed data.  If you need to parse untrusted or unauthenticated data see
@ref{2993,,XML 漏洞}.
@end quotation
@end cartouche


在 3.5 版更改: For HTTPS URIs, @ref{13f,,xmlrpc.client} now performs all the necessary
certificate and hostname checks by default.


@geindex ServerProxy (xmlrpc.client 中的类)
@anchor{library/xmlrpc client xmlrpc client ServerProxy}@anchor{255}
@deffn {类} xmlrpc.client.ServerProxy (uri, transport=None, encoding=None, verbose=False, allow_none=False, use_datetime=False, use_builtin_types=False, *, headers=(), context=None)

A @ref{255,,ServerProxy} instance is an object that manages communication with a
remote XML-RPC server.  The required first argument is a URI (Uniform Resource
Indicator), and will normally be the URL of the server.  The optional second
argument is a transport factory instance; by default it is an internal
@code{SafeTransport} instance for https: URLs and an internal HTTP
@code{Transport} instance otherwise.  The optional third argument is an
encoding, by default UTF-8. The optional fourth argument is a debugging flag.

The following parameters govern the use of the returned proxy instance.
If @emph{allow_none} is true,  the Python constant @code{None} will be translated into
XML; the default behaviour is for @code{None} to raise a @ref{192,,TypeError}. This is
a commonly-used extension to the XML-RPC specification, but isn't supported by
all clients and servers; see http://ontosys.com/xml-rpc/extensions.php@footnote{https://web.archive.org/web/20130120074804/http://ontosys.com/xml-rpc/extensions.php}
for a description.
The @emph{use_builtin_types} flag can be used to cause date/time values
to be presented as @ref{194,,datetime.datetime} objects and binary data to be
presented as @ref{32a,,bytes} objects; this flag is false by default.
@ref{194,,datetime.datetime}, @ref{32a,,bytes} and @ref{32b,,bytearray} objects
may be passed to calls.
The @emph{headers} parameter is an optional sequence of HTTP headers to send with
each request, expressed as a sequence of 2-tuples representing the header
name and value. (e.g. @cite{[('Header-Name'@comma{} 'value')]}).
The obsolete @emph{use_datetime} flag is similar to @emph{use_builtin_types} but it
applies only to date/time values.
@end deffn


在 3.3 版更改: The @emph{use_builtin_types} flag was added.



在 3.8 版更改: The @emph{headers} parameter was added.

Both the HTTP and HTTPS transports support the URL syntax extension for HTTP
Basic Authentication: @code{http://user:pass@@host:port/path}.  The  @code{user:pass}
portion will be base64-encoded as an HTTP 'Authorization' header, and sent to
the remote server as part of the connection process when invoking an XML-RPC
method.  You only need to use this if the remote server requires a Basic
Authentication user and password. If an HTTPS URL is provided, @emph{context} may
be @ref{3dc,,ssl.SSLContext} and configures the SSL settings of the underlying
HTTPS connection.

The returned instance is a proxy object with methods that can be used to invoke
corresponding RPC calls on the remote server.  If the remote server supports the
introspection API, the proxy can also be used to query the remote server for the
methods it supports (service discovery) and fetch other server-associated
metadata.

Types that are conformable (e.g. that can be marshalled through XML),
include the following (and except where noted, they are unmarshalled
as the same Python type):


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

XML-RPC类型

@tab

Python 类型

@item

@code{boolean}

@tab

@ref{183,,bool}

@item

@code{int}, @code{i1}, @code{i2},  @code{i4}, @code{i8} 或者 @code{biginteger}

@tab

@ref{184,,int} 的范围从 -2147483648 到 2147483647。值将获得 @code{<int>} 标志。

@item

@code{double} 或 @code{float}

@tab

@ref{187,,float}。值将获得 @code{<double>} 标志。

@item

@code{string}

@tab

@ref{329,,str}

@item

@code{array}

@tab

@ref{262,,list} 或 @ref{478,,tuple} 包含整合元素。数组以 @ref{262,,lists} 形式返回。

@item

@code{struct}

@tab

@ref{1b8,,dict}.  Keys must be strings, values may be
any conformable type.  Objects of user-defined
classes can be passed in; only their
@ref{4f6,,__dict__} attribute is transmitted.

@item

@code{dateTime.iso8601}

@tab

@ref{2e5f,,DateTime} 或 @ref{194,,datetime.datetime}。返回的类型取决于 @emph{use_builtin_types} 和 @emph{use_datetime} 标志的值。

@item

@code{base64}

@tab

@ref{2e60,,Binary}, @ref{32a,,bytes} 或 @ref{32b,,bytearray}。返回的类型取决于 @emph{use_builtin_types} 标志的值。

@item

@code{nil}

@tab

@code{None} 常量。仅当 @emph{allow_none} 为true时才允许传递。

@item

@code{bigdecimal}

@tab

@ref{188,,decimal.Decimal}.  仅返回类型。

@end multitable


This is the full set of data types supported by XML-RPC.  Method calls may also
raise a special @ref{2e61,,Fault} instance, used to signal XML-RPC server errors, or
@ref{2e62,,ProtocolError} used to signal an error in the HTTP/HTTPS transport layer.
Both @ref{2e61,,Fault} and @ref{2e62,,ProtocolError} derive from a base class called
@code{Error}.  Note that the xmlrpc client module currently does not marshal
instances of subclasses of built-in types.

When passing strings, characters special to XML such as @code{<}, @code{>}, and @code{&}
will be automatically escaped.  However, it's the caller's responsibility to
ensure that the string is free of characters that aren't allowed in XML, such as
the control characters with ASCII values between 0 and 31 (except, of course,
tab, newline and carriage return); failing to do this will result in an XML-RPC
request that isn't well-formed XML.  If you have to pass arbitrary bytes
via XML-RPC, use @ref{32a,,bytes} or @ref{32b,,bytearray} classes or the
@ref{2e60,,Binary} wrapper class described below.

@code{Server} is retained as an alias for @ref{255,,ServerProxy} for backwards
compatibility.  New code should use @ref{255,,ServerProxy}.


在 3.5 版更改: Added the @emph{context} argument.



在 3.6 版更改: Added support of type tags with prefixes (e.g. @code{ex:nil}).
Added support of unmarshalling additional types used by Apache XML-RPC
implementation for numerics: @code{i1}, @code{i2}, @code{i8}, @code{biginteger},
@code{float} and @code{bigdecimal}.
See @indicateurl{http://ws.apache.org/xmlrpc/types.html} for a description.




@subsubheading 参见



@table @asis

@item XML-RPC HOWTO@footnote{http://www.tldp.org/HOWTO/XML-RPC-HOWTO/index.html}

A good description of XML-RPC operation and client software in several languages.
Contains pretty much everything an XML-RPC client developer needs to know.

@item XML-RPC Introspection@footnote{http://xmlrpc-c.sourceforge.net/introspection.html}

Describes the XML-RPC protocol extension for introspection.

@item XML-RPC Specification@footnote{http://xmlrpc.scripting.com/spec.html}

The official specification.

@item Unofficial XML-RPC Errata@footnote{http://effbot.org/zone/xmlrpc-errata.htm}

Fredrik Lundh's "unofficial errata, intended to clarify certain
details in the XML-RPC specification, as well as hint at
'best practices' to use when designing your own XML-RPC
implementations."
@end table


@menu
* ServerProxy 对象:: 
* DateTime 对象:: 
* Binary 对象:: 
* Fault 对象:: 
* ProtocolError 对象:: 
* MultiCall 对象:: 
* Convenience Functions:: 
* Example of Client Usage:: 
* Example of Client and Server Usage:: 

@end menu

@node ServerProxy 对象,DateTime 对象,,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client id1}@anchor{2e63}@anchor{library/xmlrpc client serverproxy-objects}@anchor{2e64}
@subsubsection ServerProxy 对象


A @ref{255,,ServerProxy} instance has a method corresponding to each remote
procedure call accepted by the XML-RPC server.  Calling the method performs an
RPC, dispatched by both name and argument signature (e.g. the same method name
can be overloaded with multiple argument signatures).  The RPC finishes by
returning a value, which may be either returned data in a conformant type or a
@ref{2e61,,Fault} or @ref{2e62,,ProtocolError} object indicating an error.

Servers that support the XML introspection API support some common methods
grouped under the reserved @code{system} attribute:

@geindex listMethods() (xmlrpc.client.ServerProxy.system 方法)
@anchor{library/xmlrpc client xmlrpc client ServerProxy system listMethods}@anchor{2e65}
@deffn {方法} ServerProxy.system.listMethods ()

This method returns a list of strings, one for each (non-system) method
supported by the XML-RPC server.
@end deffn

@geindex methodSignature() (xmlrpc.client.ServerProxy.system 方法)
@anchor{library/xmlrpc client xmlrpc client ServerProxy system methodSignature}@anchor{2e66}
@deffn {方法} ServerProxy.system.methodSignature (name)

This method takes one parameter, the name of a method implemented by the XML-RPC
server. It returns an array of possible signatures for this method. A signature
is an array of types. The first of these types is the return type of the method,
the rest are parameters.

Because multiple signatures (ie. overloading) is permitted, this method returns
a list of signatures rather than a singleton.

Signatures themselves are restricted to the top level parameters expected by a
method. For instance if a method expects one array of structs as a parameter,
and it returns a string, its signature is simply "string, array". If it expects
three integers and returns a string, its signature is "string, int, int, int".

If no signature is defined for the method, a non-array value is returned. In
Python this means that the type of the returned  value will be something other
than list.
@end deffn

@geindex methodHelp() (xmlrpc.client.ServerProxy.system 方法)
@anchor{library/xmlrpc client xmlrpc client ServerProxy system methodHelp}@anchor{2e67}
@deffn {方法} ServerProxy.system.methodHelp (name)

This method takes one parameter, the name of a method implemented by the XML-RPC
server.  It returns a documentation string describing the use of that method. If
no such string is available, an empty string is returned. The documentation
string may contain HTML markup.
@end deffn


在 3.5 版更改: Instances of @ref{255,,ServerProxy} support the @ref{563,,context manager} protocol
for closing the underlying transport.


A working example follows. The server code:

@example
from xmlrpc.server import SimpleXMLRPCServer

def is_even(n):
    return n % 2 == 0

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(is_even, "is_even")
server.serve_forever()
@end example

The client code for the preceding server:

@example
import xmlrpc.client

with xmlrpc.client.ServerProxy("http://localhost:8000/") as proxy:
    print("3 is even: %s" % str(proxy.is_even(3)))
    print("100 is even: %s" % str(proxy.is_even(100)))
@end example

@node DateTime 对象,Binary 对象,ServerProxy 对象,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client datetime-objects}@anchor{2e68}@anchor{library/xmlrpc client id2}@anchor{2e69}
@subsubsection DateTime 对象


@geindex DateTime (xmlrpc.client 中的类)
@anchor{library/xmlrpc client xmlrpc client DateTime}@anchor{2e5f}
@deffn {类} xmlrpc.client.DateTime

This class may be initialized with seconds since the epoch, a time
tuple, an ISO 8601 time/date string, or a @ref{194,,datetime.datetime}
instance.  It has the following methods, supported mainly for internal
use by the marshalling/unmarshalling code:

@geindex decode() (xmlrpc.client.DateTime 方法)
@anchor{library/xmlrpc client xmlrpc client DateTime decode}@anchor{2e6a}
@deffn {方法} decode (string)

Accept a string as the instance's new time value.
@end deffn

@geindex encode() (xmlrpc.client.DateTime 方法)
@anchor{library/xmlrpc client xmlrpc client DateTime encode}@anchor{2e6b}
@deffn {方法} encode (out)

Write the XML-RPC encoding of this @ref{2e5f,,DateTime} item to the @emph{out} stream
object.
@end deffn

It also supports certain of Python's built-in operators through rich comparison
and @ref{337,,__repr__()} methods.
@end deffn

A working example follows. The server code:

@example
import datetime
from xmlrpc.server import SimpleXMLRPCServer
import xmlrpc.client

def today():
    today = datetime.datetime.today()
    return xmlrpc.client.DateTime(today)

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(today, "today")
server.serve_forever()
@end example

The client code for the preceding server:

@example
import xmlrpc.client
import datetime

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")

today = proxy.today()
# convert the ISO8601 string to a datetime object
converted = datetime.datetime.strptime(today.value, "%Y%m%dT%H:%M:%S")
print("Today: %s" % converted.strftime("%d.%m.%Y, %H:%M"))
@end example

@node Binary 对象,Fault 对象,DateTime 对象,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client binary-objects}@anchor{2e6c}@anchor{library/xmlrpc client id3}@anchor{2e6d}
@subsubsection Binary 对象


@geindex Binary (xmlrpc.client 中的类)
@anchor{library/xmlrpc client xmlrpc client Binary}@anchor{2e60}
@deffn {类} xmlrpc.client.Binary

This class may be initialized from bytes data (which may include NULs). The
primary access to the content of a @ref{2e60,,Binary} object is provided by an
attribute:

@geindex data (xmlrpc.client.Binary 属性)
@anchor{library/xmlrpc client xmlrpc client Binary data}@anchor{2e6e}
@deffn {属性} data

The binary data encapsulated by the @ref{2e60,,Binary} instance.  The data is
provided as a @ref{32a,,bytes} object.
@end deffn

@ref{2e60,,Binary} objects have the following methods, supported mainly for
internal use by the marshalling/unmarshalling code:

@geindex decode() (xmlrpc.client.Binary 方法)
@anchor{library/xmlrpc client xmlrpc client Binary decode}@anchor{2e6f}
@deffn {方法} decode (bytes)

Accept a base64 @ref{32a,,bytes} object and decode it as the instance's new data.
@end deffn

@geindex encode() (xmlrpc.client.Binary 方法)
@anchor{library/xmlrpc client xmlrpc client Binary encode}@anchor{2e70}
@deffn {方法} encode (out)

Write the XML-RPC base 64 encoding of this binary item to the @emph{out} stream object.

The encoded data will have newlines every 76 characters as per
@geindex RFC; RFC 2045#section-6.8
RFC 2045 section 6.8@footnote{https://tools.ietf.org/html/rfc2045.html#section-6.8},
which was the de facto standard base64 specification when the
XML-RPC spec was written.
@end deffn

It also supports certain of Python's built-in operators through @ref{338,,__eq__()}
and @ref{e4f,,__ne__()} methods.
@end deffn

Example usage of the binary objects.  We're going to transfer an image over
XMLRPC:

@example
from xmlrpc.server import SimpleXMLRPCServer
import xmlrpc.client

def python_logo():
    with open("python_logo.jpg", "rb") as handle:
        return xmlrpc.client.Binary(handle.read())

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(python_logo, 'python_logo')

server.serve_forever()
@end example

The client gets the image and saves it to a file:

@example
import xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
with open("fetched_python_logo.jpg", "wb") as handle:
    handle.write(proxy.python_logo().data)
@end example

@node Fault 对象,ProtocolError 对象,Binary 对象,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client fault-objects}@anchor{2e71}@anchor{library/xmlrpc client id4}@anchor{2e72}
@subsubsection Fault 对象


@geindex Fault (xmlrpc.client 中的类)
@anchor{library/xmlrpc client xmlrpc client Fault}@anchor{2e61}
@deffn {类} xmlrpc.client.Fault

A @ref{2e61,,Fault} object encapsulates the content of an XML-RPC fault tag. Fault
objects have the following attributes:

@geindex faultCode (xmlrpc.client.Fault 属性)
@anchor{library/xmlrpc client xmlrpc client Fault faultCode}@anchor{2e73}
@deffn {属性} faultCode

A string indicating the fault type.
@end deffn

@geindex faultString (xmlrpc.client.Fault 属性)
@anchor{library/xmlrpc client xmlrpc client Fault faultString}@anchor{2e74}
@deffn {属性} faultString

A string containing a diagnostic message associated with the fault.
@end deffn
@end deffn

In the following example we're going to intentionally cause a @ref{2e61,,Fault} by
returning a complex type object.  The server code:

@example
from xmlrpc.server import SimpleXMLRPCServer

# A marshalling error is going to occur because we're returning a
# complex number
def add(x, y):
    return x+y+0j

server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_function(add, 'add')

server.serve_forever()
@end example

The client code for the preceding server:

@example
import xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
try:
    proxy.add(2, 5)
except xmlrpc.client.Fault as err:
    print("A fault occurred")
    print("Fault code: %d" % err.faultCode)
    print("Fault string: %s" % err.faultString)
@end example

@node ProtocolError 对象,MultiCall 对象,Fault 对象,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client protocol-error-objects}@anchor{2e75}@anchor{library/xmlrpc client protocolerror-objects}@anchor{2e76}
@subsubsection ProtocolError 对象


@geindex ProtocolError (xmlrpc.client 中的类)
@anchor{library/xmlrpc client xmlrpc client ProtocolError}@anchor{2e62}
@deffn {类} xmlrpc.client.ProtocolError

A @ref{2e62,,ProtocolError} object describes a protocol error in the underlying
transport layer (such as a 404 'not found' error if the server named by the URI
does not exist).  It has the following attributes:

@geindex url (xmlrpc.client.ProtocolError 属性)
@anchor{library/xmlrpc client xmlrpc client ProtocolError url}@anchor{2e77}
@deffn {属性} url

The URI or URL that triggered the error.
@end deffn

@geindex errcode (xmlrpc.client.ProtocolError 属性)
@anchor{library/xmlrpc client xmlrpc client ProtocolError errcode}@anchor{2e78}
@deffn {属性} errcode

The error code.
@end deffn

@geindex errmsg (xmlrpc.client.ProtocolError 属性)
@anchor{library/xmlrpc client xmlrpc client ProtocolError errmsg}@anchor{2e79}
@deffn {属性} errmsg

The error message or diagnostic string.
@end deffn

@geindex headers (xmlrpc.client.ProtocolError 属性)
@anchor{library/xmlrpc client xmlrpc client ProtocolError headers}@anchor{2e7a}
@deffn {属性} headers

A dict containing the headers of the HTTP/HTTPS request that triggered the
error.
@end deffn
@end deffn

In the following example we're going to intentionally cause a @ref{2e62,,ProtocolError}
by providing an invalid URI:

@example
import xmlrpc.client

# create a ServerProxy with a URI that doesn't respond to XMLRPC requests
proxy = xmlrpc.client.ServerProxy("http://google.com/")

try:
    proxy.some_method()
except xmlrpc.client.ProtocolError as err:
    print("A protocol error occurred")
    print("URL: %s" % err.url)
    print("HTTP/HTTPS headers: %s" % err.headers)
    print("Error code: %d" % err.errcode)
    print("Error message: %s" % err.errmsg)
@end example

@node MultiCall 对象,Convenience Functions,ProtocolError 对象,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client multicall-objects}@anchor{2e7b}
@subsubsection MultiCall 对象


The @ref{2e7c,,MultiCall} object provides a way to encapsulate multiple calls to a
remote server into a single request @footnote{@w{(1)} 
This approach has been first presented in @uref{https://web.archive.org/web/20060624230303/http://www.xmlrpc.com/discuss/msgReader$1208?mode=topic,a discussion on xmlrpc.com}.
}.

@geindex MultiCall (xmlrpc.client 中的类)
@anchor{library/xmlrpc client xmlrpc client MultiCall}@anchor{2e7c}
@deffn {类} xmlrpc.client.MultiCall (server)

Create an object used to boxcar method calls. @emph{server} is the eventual target of
the call. Calls can be made to the result object, but they will immediately
return @code{None}, and only store the call name and parameters in the
@ref{2e7c,,MultiCall} object. Calling the object itself causes all stored calls to
be transmitted as a single @code{system.multicall} request. The result of this call
is a @ref{99c,,generator}; iterating over this generator yields the individual
results.
@end deffn

A usage example of this class follows.  The server code:

@example
from xmlrpc.server import SimpleXMLRPCServer

def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

def multiply(x, y):
    return x * y

def divide(x, y):
    return x // y

# A simple server with simple arithmetic functions
server = SimpleXMLRPCServer(("localhost", 8000))
print("Listening on port 8000...")
server.register_multicall_functions()
server.register_function(add, 'add')
server.register_function(subtract, 'subtract')
server.register_function(multiply, 'multiply')
server.register_function(divide, 'divide')
server.serve_forever()
@end example

The client code for the preceding server:

@example
import xmlrpc.client

proxy = xmlrpc.client.ServerProxy("http://localhost:8000/")
multicall = xmlrpc.client.MultiCall(proxy)
multicall.add(7, 3)
multicall.subtract(7, 3)
multicall.multiply(7, 3)
multicall.divide(7, 3)
result = multicall()

print("7+3=%d, 7-3=%d, 7*3=%d, 7//3=%d" % tuple(result))
@end example

@node Convenience Functions,Example of Client Usage,MultiCall 对象,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client convenience-functions}@anchor{2e7d}
@subsubsection Convenience Functions


@geindex dumps() (在 xmlrpc.client 模块中)
@anchor{library/xmlrpc client xmlrpc client dumps}@anchor{2e7e}
@deffn {函数} xmlrpc.client.dumps (params, methodname=None, methodresponse=None, encoding=None, allow_none=False)

Convert @emph{params} into an XML-RPC request. or into a response if @emph{methodresponse}
is true. @emph{params} can be either a tuple of arguments or an instance of the
@ref{2e61,,Fault} exception class.  If @emph{methodresponse} is true, only a single value
can be returned, meaning that @emph{params} must be of length 1. @emph{encoding}, if
supplied, is the encoding to use in the generated XML; the default is UTF-8.
Python's @ref{157,,None} value cannot be used in standard XML-RPC; to allow using
it via an extension,  provide a true value for @emph{allow_none}.
@end deffn

@geindex loads() (在 xmlrpc.client 模块中)
@anchor{library/xmlrpc client xmlrpc client loads}@anchor{2e7f}
@deffn {函数} xmlrpc.client.loads (data, use_datetime=False, use_builtin_types=False)

Convert an XML-RPC request or response into Python objects, a @code{(params,
methodname)}.  @emph{params} is a tuple of argument; @emph{methodname} is a string, or
@code{None} if no method name is present in the packet. If the XML-RPC packet
represents a fault condition, this function will raise a @ref{2e61,,Fault} exception.
The @emph{use_builtin_types} flag can be used to cause date/time values to be
presented as @ref{194,,datetime.datetime} objects and binary data to be
presented as @ref{32a,,bytes} objects; this flag is false by default.

The obsolete @emph{use_datetime} flag is similar to @emph{use_builtin_types} but it
applies only to date/time values.


在 3.3 版更改: The @emph{use_builtin_types} flag was added.

@end deffn

@node Example of Client Usage,Example of Client and Server Usage,Convenience Functions,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client example-of-client-usage}@anchor{2e80}@anchor{library/xmlrpc client xmlrpc-client-example}@anchor{2e81}
@subsubsection Example of Client Usage


@example
# simple test program (from the XML-RPC specification)
from xmlrpc.client import ServerProxy, Error

# server = ServerProxy("http://localhost:8000") # local server
with ServerProxy("http://betty.userland.com") as proxy:

    print(proxy)

    try:
        print(proxy.examples.getStateName(41))
    except Error as v:
        print("ERROR", v)
@end example

To access an XML-RPC server through a HTTP proxy, you need to define a custom
transport.  The following example shows how:

@example
import http.client
import xmlrpc.client

class ProxiedTransport(xmlrpc.client.Transport):

    def set_proxy(self, host, port=None, headers=None):
        self.proxy = host, port
        self.proxy_headers = headers

    def make_connection(self, host):
        connection = http.client.HTTPConnection(*self.proxy)
        connection.set_tunnel(host, headers=self.proxy_headers)
        self._connection = host, connection
        return connection

transport = ProxiedTransport()
transport.set_proxy('proxy-server', 8080)
server = xmlrpc.client.ServerProxy('http://betty.userland.com', transport=transport)
print(server.examples.getStateName(41))
@end example

@node Example of Client and Server Usage,,Example of Client Usage,xmlrpc client --- XML-RPC client access
@anchor{library/xmlrpc client example-of-client-and-server-usage}@anchor{2e82}
@subsubsection Example of Client and Server Usage


See @ref{2e83,,SimpleXMLRPCServer Example}.

@subsubheading 备注


@c the link now points to webarchive since the one at

@c http://www.xmlrpc.com/discuss/msgReader%241208 is broken (and webadmin

@c doesn't reply)

@node xmlrpc server --- Basic XML-RPC servers,ipaddress --- IPv4/IPv6 操作库,xmlrpc client --- XML-RPC client access,互联网协议和支持
@anchor{library/xmlrpc server doc}@anchor{2e84}@anchor{library/xmlrpc server module-xmlrpc server}@anchor{140}@anchor{library/xmlrpc server xmlrpc-server-basic-xml-rpc-servers}@anchor{2e85}
@subsection @code{xmlrpc.server} --- Basic XML-RPC servers


@geindex xmlrpc.server (模块)

@strong{Source code:} Lib/xmlrpc/server.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/xmlrpc/server.py}


__________________________________________________________________


The @ref{140,,xmlrpc.server} module provides a basic server framework for XML-RPC
servers written in Python.  Servers can either be free standing, using
@ref{2e86,,SimpleXMLRPCServer}, or embedded in a CGI environment, using
@ref{2e87,,CGIXMLRPCRequestHandler}.

@cartouche
@quotation 警告 
The @ref{140,,xmlrpc.server} module is not secure against maliciously
constructed data.  If you need to parse untrusted or unauthenticated data see
@ref{2993,,XML 漏洞}.
@end quotation
@end cartouche

@geindex SimpleXMLRPCServer (xmlrpc.server 中的类)
@anchor{library/xmlrpc server xmlrpc server SimpleXMLRPCServer}@anchor{2e86}
@deffn {类} xmlrpc.server.SimpleXMLRPCServer (addr, requestHandler=SimpleXMLRPCRequestHandler, logRequests=True, allow_none=False, encoding=None, bind_and_activate=True, use_builtin_types=False)

Create a new server instance.  This class provides methods for registration of
functions that can be called by the XML-RPC protocol.  The @emph{requestHandler}
parameter should be a factory for request handler instances; it defaults to
@ref{2e88,,SimpleXMLRPCRequestHandler}.  The @emph{addr} and @emph{requestHandler} parameters
are passed to the @ref{2db1,,socketserver.TCPServer} constructor.  If @emph{logRequests}
is true (the default), requests will be logged; setting this parameter to false
will turn off logging.   The @emph{allow_none} and @emph{encoding} parameters are passed
on to @ref{13f,,xmlrpc.client} and control the XML-RPC responses that will be returned
from the server. The @emph{bind_and_activate} parameter controls whether
@code{server_bind()} and @code{server_activate()} are called immediately by the
constructor; it defaults to true. Setting it to false allows code to manipulate
the @emph{allow_reuse_address} class variable before the address is bound.
The @emph{use_builtin_types} parameter is passed to the
@ref{2e7f,,loads()} function and controls which types are processed
when date/times values or binary data are received; it defaults to false.


在 3.3 版更改: The @emph{use_builtin_types} flag was added.

@end deffn

@geindex CGIXMLRPCRequestHandler (xmlrpc.server 中的类)
@anchor{library/xmlrpc server xmlrpc server CGIXMLRPCRequestHandler}@anchor{2e87}
@deffn {类} xmlrpc.server.CGIXMLRPCRequestHandler (allow_none=False, encoding=None, use_builtin_types=False)

Create a new instance to handle XML-RPC requests in a CGI environment.  The
@emph{allow_none} and @emph{encoding} parameters are passed on to @ref{13f,,xmlrpc.client}
and control the XML-RPC responses that will be returned from the server.
The @emph{use_builtin_types} parameter is passed to the
@ref{2e7f,,loads()} function and controls which types are processed
when date/times values or binary data are received; it defaults to false.


在 3.3 版更改: The @emph{use_builtin_types} flag was added.

@end deffn

@geindex SimpleXMLRPCRequestHandler (xmlrpc.server 中的类)
@anchor{library/xmlrpc server xmlrpc server SimpleXMLRPCRequestHandler}@anchor{2e88}
@deffn {类} xmlrpc.server.SimpleXMLRPCRequestHandler

Create a new request handler instance.  This request handler supports @code{POST}
requests and modifies logging so that the @emph{logRequests} parameter to the
@ref{2e86,,SimpleXMLRPCServer} constructor parameter is honored.
@end deffn

@menu
* SimpleXMLRPCServer Objects:: 
* CGIXMLRPCRequestHandler:: 
* Documenting XMLRPC server:: 
* DocXMLRPCServer Objects:: 
* DocCGIXMLRPCRequestHandler:: 

@end menu

@node SimpleXMLRPCServer Objects,CGIXMLRPCRequestHandler,,xmlrpc server --- Basic XML-RPC servers
@anchor{library/xmlrpc server simple-xmlrpc-servers}@anchor{2e89}@anchor{library/xmlrpc server simplexmlrpcserver-objects}@anchor{2e8a}
@subsubsection SimpleXMLRPCServer Objects


The @ref{2e86,,SimpleXMLRPCServer} class is based on
@ref{2db1,,socketserver.TCPServer} and provides a means of creating simple, stand
alone XML-RPC servers.

@geindex register_function() (xmlrpc.server.SimpleXMLRPCServer 方法)
@anchor{library/xmlrpc server xmlrpc server SimpleXMLRPCServer register_function}@anchor{2e8b}
@deffn {方法} SimpleXMLRPCServer.register_function (function=None, name=None)

Register a function that can respond to XML-RPC requests.  If @emph{name} is given,
it will be the method name associated with @emph{function}, otherwise
@code{function.__name__} will be used.  @emph{name} is a string, and may contain
characters not legal in Python identifiers, including the period character.

This method can also be used as a decorator.  When used as a decorator,
@emph{name} can only be given as a keyword argument to register @emph{function} under
@emph{name}.  If no @emph{name} is given, @code{function.__name__} will be used.


在 3.7 版更改: @ref{2e8b,,register_function()} can be used as a decorator.

@end deffn

@geindex register_instance() (xmlrpc.server.SimpleXMLRPCServer 方法)
@anchor{library/xmlrpc server xmlrpc server SimpleXMLRPCServer register_instance}@anchor{2e8c}
@deffn {方法} SimpleXMLRPCServer.register_instance (instance, allow_dotted_names=False)

Register an object which is used to expose method names which have not been
registered using @ref{2e8b,,register_function()}.  If @emph{instance} contains a
@code{_dispatch()} method, it is called with the requested method name and the
parameters from the request.  Its API is @code{def _dispatch(self, method, params)}
(note that @emph{params} does not represent a variable argument list).  If it calls
an underlying function to perform its task, that function is called as
@code{func(*params)}, expanding the parameter list. The return value from
@code{_dispatch()} is returned to the client as the result.  If @emph{instance} does
not have a @code{_dispatch()} method, it is searched for an attribute matching
the name of the requested method.

If the optional @emph{allow_dotted_names} argument is true and the instance does not
have a @code{_dispatch()} method, then if the requested method name contains
periods, each component of the method name is searched for individually, with
the effect that a simple hierarchical search is performed.  The value found from
this search is then called with the parameters from the request, and the return
value is passed back to the client.

@cartouche
@quotation 警告 
Enabling the @emph{allow_dotted_names} option allows intruders to access your
module's global variables and may allow intruders to execute arbitrary code on
your machine.  Only use this option on a secure, closed network.
@end quotation
@end cartouche
@end deffn

@geindex register_introspection_functions() (xmlrpc.server.SimpleXMLRPCServer 方法)
@anchor{library/xmlrpc server xmlrpc server SimpleXMLRPCServer register_introspection_functions}@anchor{2e8d}
@deffn {方法} SimpleXMLRPCServer.register_introspection_functions ()

Registers the XML-RPC introspection functions @code{system.listMethods},
@code{system.methodHelp} and @code{system.methodSignature}.
@end deffn

@geindex register_multicall_functions() (xmlrpc.server.SimpleXMLRPCServer 方法)
@anchor{library/xmlrpc server xmlrpc server SimpleXMLRPCServer register_multicall_functions}@anchor{2e8e}
@deffn {方法} SimpleXMLRPCServer.register_multicall_functions ()

Registers the XML-RPC multicall function system.multicall.
@end deffn

@geindex rpc_paths (xmlrpc.server.SimpleXMLRPCRequestHandler 属性)
@anchor{library/xmlrpc server xmlrpc server SimpleXMLRPCRequestHandler rpc_paths}@anchor{2e8f}
@deffn {属性} SimpleXMLRPCRequestHandler.rpc_paths

An attribute value that must be a tuple listing valid path portions of the URL
for receiving XML-RPC requests.  Requests posted to other paths will result in a
404 "no such page" HTTP error.  If this tuple is empty, all paths will be
considered valid. The default value is @code{('/', '/RPC2')}.
@end deffn

@menu
* SimpleXMLRPCServer Example:: 

@end menu

@node SimpleXMLRPCServer Example,,,SimpleXMLRPCServer Objects
@anchor{library/xmlrpc server id1}@anchor{2e90}@anchor{library/xmlrpc server simplexmlrpcserver-example}@anchor{2e83}
@subsubsection SimpleXMLRPCServer Example


Server code:

@example
from xmlrpc.server import SimpleXMLRPCServer
from xmlrpc.server import SimpleXMLRPCRequestHandler

# Restrict to a particular path.
class RequestHandler(SimpleXMLRPCRequestHandler):
    rpc_paths = ('/RPC2',)

# Create server
with SimpleXMLRPCServer(('localhost', 8000),
                        requestHandler=RequestHandler) as server:
    server.register_introspection_functions()

    # Register pow() function; this will use the value of
    # pow.__name__ as the name, which is just 'pow'.
    server.register_function(pow)

    # Register a function under a different name
    def adder_function(x, y):
        return x + y
    server.register_function(adder_function, 'add')

    # Register an instance; all the methods of the instance are
    # published as XML-RPC methods (in this case, just 'mul').
    class MyFuncs:
        def mul(self, x, y):
            return x * y

    server.register_instance(MyFuncs())

    # Run the server's main loop
    server.serve_forever()
@end example

The following client code will call the methods made available by the preceding
server:

@example
import xmlrpc.client

s = xmlrpc.client.ServerProxy('http://localhost:8000')
print(s.pow(2,3))  # Returns 2**3 = 8
print(s.add(2,3))  # Returns 5
print(s.mul(5,2))  # Returns 5*2 = 10

# Print list of available methods
print(s.system.listMethods())
@end example

@code{register_function()} can also be used as a decorator. The previous server
example can register functions in a decorator way:

@example
from xmlrpc.server import SimpleXMLRPCServer
from xmlrpc.server import SimpleXMLRPCRequestHandler

class RequestHandler(SimpleXMLRPCRequestHandler):
    rpc_paths = ('/RPC2',)

with SimpleXMLRPCServer(('localhost', 8000),
                        requestHandler=RequestHandler) as server:
    server.register_introspection_functions()

    # Register pow() function; this will use the value of
    # pow.__name__ as the name, which is just 'pow'.
    server.register_function(pow)

    # Register a function under a different name, using
    # register_function as a decorator. *name* can only be given
    # as a keyword argument.
    @@server.register_function(name='add')
    def adder_function(x, y):
        return x + y

    # Register a function under function.__name__.
    @@server.register_function
    def mul(x, y):
        return x * y

    server.serve_forever()
@end example

The following example included in the @code{Lib/xmlrpc/server.py} module shows
a server allowing dotted names and registering a multicall function.

@cartouche
@quotation 警告 
Enabling the @emph{allow_dotted_names} option allows intruders to access your
module's global variables and may allow intruders to execute arbitrary code on
your machine.  Only use this example only within a secure, closed network.
@end quotation
@end cartouche

@example
import datetime

class ExampleService:
    def getData(self):
        return '42'

    class currentTime:
        @@staticmethod
        def getCurrentTime():
            return datetime.datetime.now()

with SimpleXMLRPCServer(("localhost", 8000)) as server:
    server.register_function(pow)
    server.register_function(lambda x,y: x+y, 'add')
    server.register_instance(ExampleService(), allow_dotted_names=True)
    server.register_multicall_functions()
    print('Serving XML-RPC on localhost port 8000')
    try:
        server.serve_forever()
    except KeyboardInterrupt:
        print("\nKeyboard interrupt received, exiting.")
        sys.exit(0)
@end example

This ExampleService demo can be invoked from the command line:

@example
python -m xmlrpc.server
@end example

The client that interacts with the above server is included in
@cite{Lib/xmlrpc/client.py}:

@example
server = ServerProxy("http://localhost:8000")

try:
    print(server.currentTime.getCurrentTime())
except Error as v:
    print("ERROR", v)

multi = MultiCall(server)
multi.getData()
multi.pow(2,9)
multi.add(1,2)
try:
    for response in multi():
        print(response)
except Error as v:
    print("ERROR", v)
@end example

This client which interacts with the demo XMLRPC server can be invoked as:

@example
python -m xmlrpc.client
@end example

@node CGIXMLRPCRequestHandler,Documenting XMLRPC server,SimpleXMLRPCServer Objects,xmlrpc server --- Basic XML-RPC servers
@anchor{library/xmlrpc server cgixmlrpcrequesthandler}@anchor{2e91}
@subsubsection CGIXMLRPCRequestHandler


The @ref{2e87,,CGIXMLRPCRequestHandler} class can be used to handle XML-RPC
requests sent to Python CGI scripts.

@geindex register_function() (xmlrpc.server.CGIXMLRPCRequestHandler 方法)
@anchor{library/xmlrpc server xmlrpc server CGIXMLRPCRequestHandler register_function}@anchor{2e92}
@deffn {方法} CGIXMLRPCRequestHandler.register_function (function=None, name=None)

Register a function that can respond to XML-RPC requests.  If @emph{name} is given,
it will be the method name associated with @emph{function}, otherwise
@code{function.__name__} will be used.  @emph{name} is a string, and may contain
characters not legal in Python identifiers, including the period character.

This method can also be used as a decorator.  When used as a decorator,
@emph{name} can only be given as a keyword argument to register @emph{function} under
@emph{name}.  If no @emph{name} is given, @code{function.__name__} will be used.


在 3.7 版更改: @ref{2e92,,register_function()} can be used as a decorator.

@end deffn

@geindex register_instance() (xmlrpc.server.CGIXMLRPCRequestHandler 方法)
@anchor{library/xmlrpc server xmlrpc server CGIXMLRPCRequestHandler register_instance}@anchor{2e93}
@deffn {方法} CGIXMLRPCRequestHandler.register_instance (instance)

Register an object which is used to expose method names  which have not been
registered using @ref{2e92,,register_function()}. If  instance contains a
@code{_dispatch()} method, it is called with the  requested method name and the
parameters from the  request; the return value is returned to the client as the
result. If instance does not have a @code{_dispatch()} method, it is searched
for an attribute matching the name of the requested method; if  the requested
method name contains periods, each  component of the method name is searched for
individually,  with the effect that a simple hierarchical search is performed.
The value found from this search is then called with the  parameters from the
request, and the return value is passed  back to the client.
@end deffn

@geindex register_introspection_functions() (xmlrpc.server.CGIXMLRPCRequestHandler 方法)
@anchor{library/xmlrpc server xmlrpc server CGIXMLRPCRequestHandler register_introspection_functions}@anchor{2e94}
@deffn {方法} CGIXMLRPCRequestHandler.register_introspection_functions ()

Register the XML-RPC introspection functions  @code{system.listMethods},
@code{system.methodHelp} and  @code{system.methodSignature}.
@end deffn

@geindex register_multicall_functions() (xmlrpc.server.CGIXMLRPCRequestHandler 方法)
@anchor{library/xmlrpc server xmlrpc server CGIXMLRPCRequestHandler register_multicall_functions}@anchor{2e95}
@deffn {方法} CGIXMLRPCRequestHandler.register_multicall_functions ()

Register the XML-RPC multicall function @code{system.multicall}.
@end deffn

@geindex handle_request() (xmlrpc.server.CGIXMLRPCRequestHandler 方法)
@anchor{library/xmlrpc server xmlrpc server CGIXMLRPCRequestHandler handle_request}@anchor{2e96}
@deffn {方法} CGIXMLRPCRequestHandler.handle_request (request_text=None)

Handle an XML-RPC request. If @emph{request_text} is given, it should be the POST
data provided by the HTTP server,  otherwise the contents of stdin will be used.
@end deffn

示例:

@example
class MyFuncs:
    def mul(self, x, y):
        return x * y


handler = CGIXMLRPCRequestHandler()
handler.register_function(pow)
handler.register_function(lambda x,y: x+y, 'add')
handler.register_introspection_functions()
handler.register_instance(MyFuncs())
handler.handle_request()
@end example

@node Documenting XMLRPC server,DocXMLRPCServer Objects,CGIXMLRPCRequestHandler,xmlrpc server --- Basic XML-RPC servers
@anchor{library/xmlrpc server documenting-xmlrpc-server}@anchor{2e97}
@subsubsection Documenting XMLRPC server


These classes extend the above classes to serve HTML documentation in response
to HTTP GET requests.  Servers can either be free standing, using
@ref{f06,,DocXMLRPCServer}, or embedded in a CGI environment, using
@ref{2e98,,DocCGIXMLRPCRequestHandler}.

@geindex DocXMLRPCServer (xmlrpc.server 中的类)
@anchor{library/xmlrpc server xmlrpc server DocXMLRPCServer}@anchor{f06}
@deffn {类} xmlrpc.server.DocXMLRPCServer (addr, requestHandler=DocXMLRPCRequestHandler, logRequests=True, allow_none=False, encoding=None, bind_and_activate=True, use_builtin_types=True)

Create a new server instance. All parameters have the same meaning as for
@ref{2e86,,SimpleXMLRPCServer}; @emph{requestHandler} defaults to
@ref{2e99,,DocXMLRPCRequestHandler}.


在 3.3 版更改: The @emph{use_builtin_types} flag was added.

@end deffn

@geindex DocCGIXMLRPCRequestHandler (xmlrpc.server 中的类)
@anchor{library/xmlrpc server xmlrpc server DocCGIXMLRPCRequestHandler}@anchor{2e98}
@deffn {类} xmlrpc.server.DocCGIXMLRPCRequestHandler

Create a new instance to handle XML-RPC requests in a CGI environment.
@end deffn

@geindex DocXMLRPCRequestHandler (xmlrpc.server 中的类)
@anchor{library/xmlrpc server xmlrpc server DocXMLRPCRequestHandler}@anchor{2e99}
@deffn {类} xmlrpc.server.DocXMLRPCRequestHandler

Create a new request handler instance. This request handler supports XML-RPC
POST requests, documentation GET requests, and modifies logging so that the
@emph{logRequests} parameter to the @ref{f06,,DocXMLRPCServer} constructor parameter is
honored.
@end deffn

@node DocXMLRPCServer Objects,DocCGIXMLRPCRequestHandler,Documenting XMLRPC server,xmlrpc server --- Basic XML-RPC servers
@anchor{library/xmlrpc server doc-xmlrpc-servers}@anchor{2e9a}@anchor{library/xmlrpc server docxmlrpcserver-objects}@anchor{2e9b}
@subsubsection DocXMLRPCServer Objects


The @ref{f06,,DocXMLRPCServer} class is derived from @ref{2e86,,SimpleXMLRPCServer}
and provides a means of creating self-documenting, stand alone XML-RPC
servers. HTTP POST requests are handled as XML-RPC method calls. HTTP GET
requests are handled by generating pydoc-style HTML documentation. This allows a
server to provide its own web-based documentation.

@geindex set_server_title() (xmlrpc.server.DocXMLRPCServer 方法)
@anchor{library/xmlrpc server xmlrpc server DocXMLRPCServer set_server_title}@anchor{2e9c}
@deffn {方法} DocXMLRPCServer.set_server_title (server_title)

Set the title used in the generated HTML documentation. This title will be used
inside the HTML "title" element.
@end deffn

@geindex set_server_name() (xmlrpc.server.DocXMLRPCServer 方法)
@anchor{library/xmlrpc server xmlrpc server DocXMLRPCServer set_server_name}@anchor{2e9d}
@deffn {方法} DocXMLRPCServer.set_server_name (server_name)

Set the name used in the generated HTML documentation. This name will appear at
the top of the generated documentation inside a "h1" element.
@end deffn

@geindex set_server_documentation() (xmlrpc.server.DocXMLRPCServer 方法)
@anchor{library/xmlrpc server xmlrpc server DocXMLRPCServer set_server_documentation}@anchor{2e9e}
@deffn {方法} DocXMLRPCServer.set_server_documentation (server_documentation)

Set the description used in the generated HTML documentation. This description
will appear as a paragraph, below the server name, in the documentation.
@end deffn

@node DocCGIXMLRPCRequestHandler,,DocXMLRPCServer Objects,xmlrpc server --- Basic XML-RPC servers
@anchor{library/xmlrpc server doccgixmlrpcrequesthandler}@anchor{2e9f}
@subsubsection DocCGIXMLRPCRequestHandler


The @ref{2e98,,DocCGIXMLRPCRequestHandler} class is derived from
@ref{2e87,,CGIXMLRPCRequestHandler} and provides a means of creating
self-documenting, XML-RPC CGI scripts. HTTP POST requests are handled as XML-RPC
method calls. HTTP GET requests are handled by generating pydoc-style HTML
documentation. This allows a server to provide its own web-based documentation.

@geindex set_server_title() (xmlrpc.server.DocCGIXMLRPCRequestHandler 方法)
@anchor{library/xmlrpc server xmlrpc server DocCGIXMLRPCRequestHandler set_server_title}@anchor{2ea0}
@deffn {方法} DocCGIXMLRPCRequestHandler.set_server_title (server_title)

Set the title used in the generated HTML documentation. This title will be used
inside the HTML "title" element.
@end deffn

@geindex set_server_name() (xmlrpc.server.DocCGIXMLRPCRequestHandler 方法)
@anchor{library/xmlrpc server xmlrpc server DocCGIXMLRPCRequestHandler set_server_name}@anchor{2ea1}
@deffn {方法} DocCGIXMLRPCRequestHandler.set_server_name (server_name)

Set the name used in the generated HTML documentation. This name will appear at
the top of the generated documentation inside a "h1" element.
@end deffn

@geindex set_server_documentation() (xmlrpc.server.DocCGIXMLRPCRequestHandler 方法)
@anchor{library/xmlrpc server xmlrpc server DocCGIXMLRPCRequestHandler set_server_documentation}@anchor{2ea2}
@deffn {方法} DocCGIXMLRPCRequestHandler.set_server_documentation (server_documentation)

Set the description used in the generated HTML documentation. This description
will appear as a paragraph, below the server name, in the documentation.
@end deffn

@node ipaddress --- IPv4/IPv6 操作库,,xmlrpc server --- Basic XML-RPC servers,互联网协议和支持
@anchor{library/ipaddress doc}@anchor{2ea3}@anchor{library/ipaddress ipaddress-ipv4-ipv6-manipulation-library}@anchor{2ea4}@anchor{library/ipaddress module-ipaddress}@anchor{a2}
@subsection @code{ipaddress} --- IPv4/IPv6 操作库


@geindex ipaddress (模块)

@strong{源代码：} Lib/ipaddress.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/ipaddress.py}


__________________________________________________________________


@ref{a2,,ipaddress} 提供了创建、处理和操作 IPv4 和 IPv6 地址和网络的功能。

该模块中的函数和类可以直接处理与IP地址相关的各种任务，包括检查两个主机是否在同一个子网中，遍历某个子网中的所有主机，检查一个字符串是否是一个有效的IP地址或网络定义等等。

这是完整的模块 API 参考—若要查看概述，请见 @ref{2ea5,,ipaddress模块介绍}.


3.3 新版功能.


@c import ipaddress
@c from ipaddress import (
@c     ip_network, IPv4Address, IPv4Interface, IPv4Network,
@c )

@menu
* 方便的工厂函数:: 
* IP 地址:: 
* IP Network definitions:: 
* Interface objects:: 
* Other Module Level Functions:: 
* Custom Exceptions:: 

@end menu

@node 方便的工厂函数,IP 地址,,ipaddress --- IPv4/IPv6 操作库
@anchor{library/ipaddress convenience-factory-functions}@anchor{2ea6}
@subsubsection 方便的工厂函数


@ref{a2,,ipaddress} 模块提供来工厂函数来方便地创建 IP 地址，网络和接口：

@geindex ip_address() (在 ipaddress 模块中)
@anchor{library/ipaddress ipaddress ip_address}@anchor{2ea7}
@deffn {函数} ipaddress.ip_address (address)

返回一个 @ref{2ea8,,IPv4Address} 或 @ref{2ea9,,IPv6Address} 对象，取决于作为参数传递的 IP 地址。可以提供IPv4或IPv6地址，小于 2**32 的整数默认被认为是 IPv4。如果 @emph{address} 不是有效的 IPv4 或 IPv6 地址，则会抛出 @ref{1fb,,ValueError}。

@example
>>> ipaddress.ip_address('192.168.0.1')
IPv4Address('192.168.0.1')
>>> ipaddress.ip_address('2001:db8::')
IPv6Address('2001:db8::')
@end example
@end deffn

@geindex ip_network() (在 ipaddress 模块中)
@anchor{library/ipaddress ipaddress ip_network}@anchor{2eaa}
@deffn {函数} ipaddress.ip_network (address, strict=True)

返回一个 @ref{398,,IPv4Network} 或 @ref{397,,IPv6Network} 对象，具体取决于作为参数传入的 IP 地址。 @emph{address} 是表示 IP 网址的字符串或整数。 可以提供 IPv4 或 IPv6 网址；小于 2**32 的整数默认被视为 IPv4。 @emph{strict} 会被传给 @ref{398,,IPv4Network} 或 @ref{397,,IPv6Network} 构造器。 如果 @emph{address} 不表示有效的 IPv4 或 IPv6 网址，或者网络设置了 host 比特位，则会引发 @ref{1fb,,ValueError}。

@example
>>> ipaddress.ip_network('192.168.0.0/28')
IPv4Network('192.168.0.0/28')
@end example
@end deffn

@geindex ip_interface() (在 ipaddress 模块中)
@anchor{library/ipaddress ipaddress ip_interface}@anchor{2eab}
@deffn {函数} ipaddress.ip_interface (address)

返回一个 @ref{2eac,,IPv4Interface} 或 @ref{2ead,,IPv6Interface} 对象，取决于作为参数传递的 IP 地址。 @emph{address} 是代表 IP 地址的字符串或整数。 可以提供 IPv4 或 IPv6 地址，小于 2**32 的整数默认认为是 IPv4。 如果 @emph{address} 不是有效的IPv4 或 IPv6 地址，则会抛出一个 @ref{1fb,,ValueError}。
@end deffn

这些方便的函数的一个缺点是需要同时处理IPv4和IPv6格式，这意味着提供的错误信息并不精准，因为函数不知道是打算采用IPv4还是IPv6格式。更详细的错误报告可以通过直接调用相应版本的类构造函数来获得。

@node IP 地址,IP Network definitions,方便的工厂函数,ipaddress --- IPv4/IPv6 操作库
@anchor{library/ipaddress ip-addresses}@anchor{2eae}
@subsubsection IP 地址


@menu
* 地址对象:: 
* Conversion to Strings and Integers:: 
* 运算符: 运算符<3>. 

@end menu

@node 地址对象,Conversion to Strings and Integers,,IP 地址
@anchor{library/ipaddress address-objects}@anchor{2eaf}
@subsubsection 地址对象


@ref{2ea8,,IPv4Address} 和 @ref{2ea9,,IPv6Address} 对象有很多共同的属性。一些只对IPv6 地址有意义的属性也在 @ref{2ea8,,IPv4Address} 对象实现，以便更容易编写正确处理两种 IP 版本的代码。地址对象是可哈希的 @ref{13c0,,hashable}，所以它们可以作为字典中的键来使用。

@geindex IPv4Address (ipaddress 中的类)
@anchor{library/ipaddress ipaddress IPv4Address}@anchor{2ea8}
@deffn {类} ipaddress.IPv4Address (address)

构造一个 IPv4 地址。 如果 @emph{address} 不是一个有效的 IPv4 地址，会抛出 @ref{2eb0,,AddressValueError} 。

以下是有效的 IPv4 地址：


@enumerate 

@item 
以十进制小数点表示的字符串，由四个十进制整数组成，范围为0--255，用点隔开(例如 @code{192.168.0.1} )。每个整数代表地址中的八位（一个字节）。只有对于小于8的值，才允许使用前导零(因为对这种字符串的十进制和八进制解释之间没有任何歧义)。

@item 
一个32位可容纳的整数。

@item 
一个长度为 4 的封装在 @ref{32a,,bytes} 对象中的整数(高位优先)。
@end enumerate

@example
>>> ipaddress.IPv4Address('192.168.0.1')
IPv4Address('192.168.0.1')
>>> ipaddress.IPv4Address(3232235521)
IPv4Address('192.168.0.1')
>>> ipaddress.IPv4Address(b'\xC0\xA8\x00\x01')
IPv4Address('192.168.0.1')
@end example

@geindex version (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address version}@anchor{2eb1}
@deffn {属性} version

The appropriate version number: @code{4} for IPv4, @code{6} for IPv6.
@end deffn

@geindex max_prefixlen (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address max_prefixlen}@anchor{2eb2}
@deffn {属性} max_prefixlen

The total number of bits in the address representation for this
version: @code{32} for IPv4, @code{128} for IPv6.

The prefix defines the number of leading bits in an  address that
are compared to determine whether or not an address is part of a
network.
@end deffn

@geindex compressed (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address compressed}@anchor{2eb3}
@deffn {属性} compressed
@end deffn

@geindex exploded (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address exploded}@anchor{2eb4}
@deffn {属性} exploded

The string representation in dotted decimal notation. Leading zeroes
are never included in the representation.

As IPv4 does not define a shorthand notation for addresses with octets
set to zero, these two attributes are always the same as @code{str(addr)}
for IPv4 addresses. Exposing these attributes makes it easier to
write display code that can handle both IPv4 and IPv6 addresses.
@end deffn

@geindex packed (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address packed}@anchor{2eb5}
@deffn {属性} packed

The binary representation of this address - a @ref{32a,,bytes} object of
the appropriate length (most significant octet first). This is 4 bytes
for IPv4 and 16 bytes for IPv6.
@end deffn

@geindex reverse_pointer (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address reverse_pointer}@anchor{2eb6}
@deffn {属性} reverse_pointer

The name of the reverse DNS PTR record for the IP address, e.g.:

@example
>>> ipaddress.ip_address("127.0.0.1").reverse_pointer
'1.0.0.127.in-addr.arpa'
>>> ipaddress.ip_address("2001:db8::1").reverse_pointer
'1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa'
@end example

This is the name that could be used for performing a PTR lookup, not the
resolved hostname itself.


3.5 新版功能.

@end deffn

@geindex is_multicast (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address is_multicast}@anchor{2eb7}
@deffn {属性} is_multicast

@code{True} if the address is reserved for multicast use.  See
@geindex RFC; RFC 3171
RFC 3171@footnote{https://tools.ietf.org/html/rfc3171.html} (for IPv4) or 
@geindex RFC; RFC 2373
RFC 2373@footnote{https://tools.ietf.org/html/rfc2373.html} (for IPv6).
@end deffn

@geindex is_private (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address is_private}@anchor{2eb8}
@deffn {属性} is_private

@code{True} if the address is allocated for private networks.  See
iana-ipv4-special-registry@footnote{https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml} (for IPv4) or iana-ipv6-special-registry@footnote{https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml}
(for IPv6).
@end deffn

@geindex is_global (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address is_global}@anchor{866}
@deffn {属性} is_global

@code{True} if the address is allocated for public networks.  See
iana-ipv4-special-registry@footnote{https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml} (for IPv4) or iana-ipv6-special-registry@footnote{https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml}
(for IPv6).


3.4 新版功能.

@end deffn

@geindex is_unspecified (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address is_unspecified}@anchor{2eb9}
@deffn {属性} is_unspecified

@code{True} if the address is unspecified.  See 
@geindex RFC; RFC 5735
RFC 5735@footnote{https://tools.ietf.org/html/rfc5735.html} (for IPv4)
or 
@geindex RFC; RFC 2373
RFC 2373@footnote{https://tools.ietf.org/html/rfc2373.html} (for IPv6).
@end deffn

@geindex is_reserved (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address is_reserved}@anchor{2eba}
@deffn {属性} is_reserved

@code{True} if the address is otherwise IETF reserved.
@end deffn

@geindex is_loopback (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address is_loopback}@anchor{2ebb}
@deffn {属性} is_loopback

@code{True} if this is a loopback address.  See 
@geindex RFC; RFC 3330
RFC 3330@footnote{https://tools.ietf.org/html/rfc3330.html} (for IPv4)
or 
@geindex RFC; RFC 2373
RFC 2373@footnote{https://tools.ietf.org/html/rfc2373.html} (for IPv6).
@end deffn

@geindex is_link_local (ipaddress.IPv4Address 属性)
@anchor{library/ipaddress ipaddress IPv4Address is_link_local}@anchor{2ebc}
@deffn {属性} is_link_local

@code{True} if the address is reserved for link-local usage.  See
@geindex RFC; RFC 3927
RFC 3927@footnote{https://tools.ietf.org/html/rfc3927.html}.
@end deffn
@end deffn

@geindex IPv6Address (ipaddress 中的类)
@anchor{library/ipaddress ipaddress IPv6Address}@anchor{2ea9}
@deffn {类} ipaddress.IPv6Address (address)

Construct an IPv6 address.  An @ref{2eb0,,AddressValueError} is raised if
@emph{address} is not a valid IPv6 address.

The following constitutes a valid IPv6 address:


@enumerate 

@item 
A string consisting of eight groups of four hexadecimal digits, each
group representing 16 bits.  The groups are separated by colons.
This describes an @emph{exploded} (longhand) notation.  The string can
also be @emph{compressed} (shorthand notation) by various means.  See
@geindex RFC; RFC 4291
RFC 4291@footnote{https://tools.ietf.org/html/rfc4291.html} for details.  For example,
@code{"0000:0000:0000:0000:0000:0abc:0007:0def"} can be compressed to
@code{"::abc:7:def"}.

@item 
An integer that fits into 128 bits.

@item 
An integer packed into a @ref{32a,,bytes} object of length 16, big-endian.
@end enumerate

@example
>>> ipaddress.IPv6Address('2001:db8::1000')
IPv6Address('2001:db8::1000')
@end example

@geindex compressed (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address compressed}@anchor{2ebd}
@deffn {属性} compressed
@end deffn

The short form of the address representation, with leading zeroes in
groups omitted and the longest sequence of groups consisting entirely of
zeroes collapsed to a single empty group.

This is also the value returned by @code{str(addr)} for IPv6 addresses.

@geindex exploded (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address exploded}@anchor{2ebe}
@deffn {属性} exploded
@end deffn

The long form of the address representation, with all leading zeroes and
groups consisting entirely of zeroes included.

For the following attributes, see the corresponding documentation of the
@ref{2ea8,,IPv4Address} class:

@geindex packed (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address packed}@anchor{2ebf}
@deffn {属性} packed
@end deffn

@geindex reverse_pointer (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address reverse_pointer}@anchor{2ec0}
@deffn {属性} reverse_pointer
@end deffn

@geindex version (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address version}@anchor{2ec1}
@deffn {属性} version
@end deffn

@geindex max_prefixlen (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address max_prefixlen}@anchor{2ec2}
@deffn {属性} max_prefixlen
@end deffn

@geindex is_multicast (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address is_multicast}@anchor{2ec3}
@deffn {属性} is_multicast
@end deffn

@geindex is_private (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address is_private}@anchor{2ec4}
@deffn {属性} is_private
@end deffn

@geindex is_global (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address is_global}@anchor{2ec5}
@deffn {属性} is_global
@end deffn

@geindex is_unspecified (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address is_unspecified}@anchor{2ec6}
@deffn {属性} is_unspecified
@end deffn

@geindex is_reserved (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address is_reserved}@anchor{2ec7}
@deffn {属性} is_reserved
@end deffn

@geindex is_loopback (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address is_loopback}@anchor{2ec8}
@deffn {属性} is_loopback
@end deffn

@geindex is_link_local (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address is_link_local}@anchor{2ec9}
@deffn {属性} is_link_local


3.4 新版功能: is_global

@end deffn

@geindex is_site_local (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address is_site_local}@anchor{2eca}
@deffn {属性} is_site_local

@code{True} if the address is reserved for site-local usage.  Note that
the site-local address space has been deprecated by 
@geindex RFC; RFC 3879
RFC 3879@footnote{https://tools.ietf.org/html/rfc3879.html}. Use
@ref{2eb8,,is_private} to test if this address is in the
space of unique local addresses as defined by 
@geindex RFC; RFC 4193
RFC 4193@footnote{https://tools.ietf.org/html/rfc4193.html}.
@end deffn

@geindex ipv4_mapped (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address ipv4_mapped}@anchor{2ecb}
@deffn {属性} ipv4_mapped

For addresses that appear to be IPv4 mapped addresses (starting with
@code{::FFFF/96}), this property will report the embedded IPv4 address.
For any other address, this property will be @code{None}.
@end deffn

@geindex sixtofour (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address sixtofour}@anchor{2ecc}
@deffn {属性} sixtofour

For addresses that appear to be 6to4 addresses  (starting with
@code{2002::/16}) as defined by 
@geindex RFC; RFC 3056
RFC 3056@footnote{https://tools.ietf.org/html/rfc3056.html}, this property will report
the embedded IPv4 address.  For any other address, this property will
be @code{None}.
@end deffn

@geindex teredo (ipaddress.IPv6Address 属性)
@anchor{library/ipaddress ipaddress IPv6Address teredo}@anchor{2ecd}
@deffn {属性} teredo

For addresses that appear to be Teredo addresses (starting with
@code{2001::/32}) as defined by 
@geindex RFC; RFC 4380
RFC 4380@footnote{https://tools.ietf.org/html/rfc4380.html}, this property will report
the embedded @code{(server, client)} IP address pair.  For any other
address, this property will be @code{None}.
@end deffn
@end deffn

@node Conversion to Strings and Integers,运算符<3>,地址对象,IP 地址
@anchor{library/ipaddress conversion-to-strings-and-integers}@anchor{2ece}
@subsubsection Conversion to Strings and Integers


To interoperate with networking interfaces such as the socket module,
addresses must be converted to strings or integers. This is handled using
the @ref{329,,str()} and @ref{184,,int()} builtin functions:

@example
>>> str(ipaddress.IPv4Address('192.168.0.1'))
'192.168.0.1'
>>> int(ipaddress.IPv4Address('192.168.0.1'))
3232235521
>>> str(ipaddress.IPv6Address('::1'))
'::1'
>>> int(ipaddress.IPv6Address('::1'))
1
@end example

@node 运算符<3>,,Conversion to Strings and Integers,IP 地址
@anchor{library/ipaddress operators}@anchor{2ecf}
@subsubsection 运算符


Address objects support some operators.  Unless stated otherwise, operators can
only be applied between compatible objects (i.e. IPv4 with IPv4, IPv6 with
IPv6).

@menu
* Comparison operators:: 
* Arithmetic operators:: 

@end menu

@node Comparison operators,Arithmetic operators,,运算符<3>
@anchor{library/ipaddress comparison-operators}@anchor{2ed0}
@subsubsection Comparison operators


Address objects can be compared with the usual set of comparison operators.  Some
examples:

@example
>>> IPv4Address('127.0.0.2') > IPv4Address('127.0.0.1')
True
>>> IPv4Address('127.0.0.2') == IPv4Address('127.0.0.1')
False
>>> IPv4Address('127.0.0.2') != IPv4Address('127.0.0.1')
True
@end example

@node Arithmetic operators,,Comparison operators,运算符<3>
@anchor{library/ipaddress arithmetic-operators}@anchor{2ed1}
@subsubsection Arithmetic operators


Integers can be added to or subtracted from address objects.  Some examples:

@example
>>> IPv4Address('127.0.0.2') + 3
IPv4Address('127.0.0.5')
>>> IPv4Address('127.0.0.2') - 3
IPv4Address('126.255.255.255')
>>> IPv4Address('255.255.255.255') + 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ipaddress.AddressValueError: 4294967296 (>= 2**32) is not permitted as an IPv4 address
@end example

@node IP Network definitions,Interface objects,IP 地址,ipaddress --- IPv4/IPv6 操作库
@anchor{library/ipaddress ip-network-definitions}@anchor{2ed2}
@subsubsection IP Network definitions


The @ref{398,,IPv4Network} and @ref{397,,IPv6Network} objects provide a mechanism
for defining and inspecting IP network definitions.  A network definition
consists of a @emph{mask} and a @emph{network address}, and as such defines a range of
IP addresses that equal the network address when masked (binary AND) with the
mask.  For example, a network definition with the mask @code{255.255.255.0} and
the network address @code{192.168.1.0} consists of IP addresses in the inclusive
range @code{192.168.1.0} to @code{192.168.1.255}.

@menu
* Prefix@comma{} net mask and host mask: Prefix net mask and host mask. 
* Network objects:: 
* 运算符: 运算符<4>. 

@end menu

@node Prefix net mask and host mask,Network objects,,IP Network definitions
@anchor{library/ipaddress prefix-net-mask-and-host-mask}@anchor{2ed3}
@subsubsection Prefix, net mask and host mask


There are several equivalent ways to specify IP network masks.  A @emph{prefix}
@code{/<nbits>} is a notation that denotes how many high-order bits are set in
the network mask.  A @emph{net mask} is an IP address with some number of
high-order bits set.  Thus the prefix @code{/24} is equivalent to the net mask
@code{255.255.255.0} in IPv4, or @code{ffff:ff00::} in IPv6.  In addition, a
@emph{host mask} is the logical inverse of a @emph{net mask}, and is sometimes used
(for example in Cisco access control lists) to denote a network mask.  The
host mask equivalent to @code{/24} in IPv4 is @code{0.0.0.255}.

@node Network objects,运算符<4>,Prefix net mask and host mask,IP Network definitions
@anchor{library/ipaddress network-objects}@anchor{2ed4}
@subsubsection Network objects


All attributes implemented by address objects are implemented by network
objects as well.  In addition, network objects implement additional attributes.
All of these are common between @ref{398,,IPv4Network} and @ref{397,,IPv6Network},
so to avoid duplication they are only documented for @ref{398,,IPv4Network}.
Network objects are @ref{13c0,,hashable}, so they can be used as keys in
dictionaries.

@geindex IPv4Network (ipaddress 中的类)
@anchor{library/ipaddress ipaddress IPv4Network}@anchor{398}
@deffn {类} ipaddress.IPv4Network (address, strict=True)

Construct an IPv4 network definition.  @emph{address} can be one of the following:


@enumerate 

@item 
A string consisting of an IP address and an optional mask, separated by
a slash (@code{/}).  The IP address is the network address, and the mask
can be either a single number, which means it's a @emph{prefix}, or a string
representation of an IPv4 address.  If it's the latter, the mask is
interpreted as a @emph{net mask} if it starts with a non-zero field, or as a
@emph{host mask} if it starts with a zero field, with the single exception of
an all-zero mask which is treated as a @emph{net mask}.  If no mask is provided,
it's considered to be @code{/32}.

For example, the following @emph{address} specifications are equivalent:
@code{192.168.1.0/24}, @code{192.168.1.0/255.255.255.0} and
@code{192.168.1.0/0.0.0.255}.

@item 
An integer that fits into 32 bits.  This is equivalent to a
single-address network, with the network address being @emph{address} and
the mask being @code{/32}.

@item 
An integer packed into a @ref{32a,,bytes} object of length 4, big-endian.
The interpretation is similar to an integer @emph{address}.

@item 
A two-tuple of an address description and a netmask, where the address
description is either a string, a 32-bits integer, a 4-bytes packed
integer, or an existing IPv4Address object; and the netmask is either
an integer representing the prefix length (e.g. @code{24}) or a string
representing the prefix mask (e.g. @code{255.255.255.0}).
@end enumerate

An @ref{2eb0,,AddressValueError} is raised if @emph{address} is not a valid IPv4
address.  A @ref{2ed5,,NetmaskValueError} is raised if the mask is not valid for
an IPv4 address.

If @emph{strict} is @code{True} and host bits are set in the supplied address,
then @ref{1fb,,ValueError} is raised.  Otherwise, the host bits are masked out
to determine the appropriate network address.

Unless stated otherwise, all network methods accepting other network/address
objects will raise @ref{192,,TypeError} if the argument's IP version is
incompatible to @code{self}.


在 3.5 版更改: Added the two-tuple form for the @emph{address} constructor parameter.


@geindex version (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network version}@anchor{2ed6}
@deffn {属性} version
@end deffn

@geindex max_prefixlen (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network max_prefixlen}@anchor{2ed7}
@deffn {属性} max_prefixlen

Refer to the corresponding attribute documentation in
@ref{2ea8,,IPv4Address}.
@end deffn

@geindex is_multicast (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network is_multicast}@anchor{2ed8}
@deffn {属性} is_multicast
@end deffn

@geindex is_private (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network is_private}@anchor{2ed9}
@deffn {属性} is_private
@end deffn

@geindex is_unspecified (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network is_unspecified}@anchor{2eda}
@deffn {属性} is_unspecified
@end deffn

@geindex is_reserved (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network is_reserved}@anchor{2edb}
@deffn {属性} is_reserved
@end deffn

@geindex is_loopback (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network is_loopback}@anchor{2edc}
@deffn {属性} is_loopback
@end deffn

@geindex is_link_local (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network is_link_local}@anchor{2edd}
@deffn {属性} is_link_local

These attributes are true for the network as a whole if they are true
for both the network address and the broadcast address.
@end deffn

@geindex network_address (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network network_address}@anchor{2ede}
@deffn {属性} network_address

The network address for the network. The network address and the
prefix length together uniquely define a network.
@end deffn

@geindex broadcast_address (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network broadcast_address}@anchor{2edf}
@deffn {属性} broadcast_address

The broadcast address for the network. Packets sent to the broadcast
address should be received by every host on the network.
@end deffn

@geindex hostmask (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network hostmask}@anchor{2ee0}
@deffn {属性} hostmask

The host mask, as an @ref{2ea8,,IPv4Address} object.
@end deffn

@geindex netmask (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network netmask}@anchor{2ee1}
@deffn {属性} netmask

The net mask, as an @ref{2ea8,,IPv4Address} object.
@end deffn

@geindex with_prefixlen (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network with_prefixlen}@anchor{2ee2}
@deffn {属性} with_prefixlen
@end deffn

@geindex compressed (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network compressed}@anchor{2ee3}
@deffn {属性} compressed
@end deffn

@geindex exploded (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network exploded}@anchor{2ee4}
@deffn {属性} exploded

A string representation of the network, with the mask in prefix
notation.

@code{with_prefixlen} and @code{compressed} are always the same as
@code{str(network)}.
@code{exploded} uses the exploded form the network address.
@end deffn

@geindex with_netmask (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network with_netmask}@anchor{2ee5}
@deffn {属性} with_netmask

A string representation of the network, with the mask in net mask
notation.
@end deffn

@geindex with_hostmask (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network with_hostmask}@anchor{2ee6}
@deffn {属性} with_hostmask

A string representation of the network, with the mask in host mask
notation.
@end deffn

@geindex num_addresses (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network num_addresses}@anchor{2ee7}
@deffn {属性} num_addresses

The total number of addresses in the network.
@end deffn

@geindex prefixlen (ipaddress.IPv4Network 属性)
@anchor{library/ipaddress ipaddress IPv4Network prefixlen}@anchor{2ee8}
@deffn {属性} prefixlen

Length of the network prefix, in bits.
@end deffn

@geindex hosts() (ipaddress.IPv4Network 方法)
@anchor{library/ipaddress ipaddress IPv4Network hosts}@anchor{2ee9}
@deffn {方法} hosts ()

Returns an iterator over the usable hosts in the network.  The usable
hosts are all the IP addresses that belong to the network, except the
network address itself and the network broadcast address.  For networks
with a mask length of 31, the network address and network broadcast
address are also included in the result.

@example
>>> list(ip_network('192.0.2.0/29').hosts())  
[IPv4Address('192.0.2.1'), IPv4Address('192.0.2.2'),
 IPv4Address('192.0.2.3'), IPv4Address('192.0.2.4'),
 IPv4Address('192.0.2.5'), IPv4Address('192.0.2.6')]
>>> list(ip_network('192.0.2.0/31').hosts())
[IPv4Address('192.0.2.0'), IPv4Address('192.0.2.1')]
@end example
@end deffn

@geindex overlaps() (ipaddress.IPv4Network 方法)
@anchor{library/ipaddress ipaddress IPv4Network overlaps}@anchor{2eea}
@deffn {方法} overlaps (other)

@code{True} if this network is partly or wholly contained in @emph{other} or
@emph{other} is wholly contained in this network.
@end deffn

@geindex address_exclude() (ipaddress.IPv4Network 方法)
@anchor{library/ipaddress ipaddress IPv4Network address_exclude}@anchor{2eeb}
@deffn {方法} address_exclude (network)

Computes the network definitions resulting from removing the given
@emph{network} from this one.  Returns an iterator of network objects.
Raises @ref{1fb,,ValueError} if @emph{network} is not completely contained in
this network.

@example
>>> n1 = ip_network('192.0.2.0/28')
>>> n2 = ip_network('192.0.2.1/32')
>>> list(n1.address_exclude(n2))  
[IPv4Network('192.0.2.8/29'), IPv4Network('192.0.2.4/30'),
 IPv4Network('192.0.2.2/31'), IPv4Network('192.0.2.0/32')]
@end example
@end deffn

@geindex subnets() (ipaddress.IPv4Network 方法)
@anchor{library/ipaddress ipaddress IPv4Network subnets}@anchor{791}
@deffn {方法} subnets (prefixlen_diff=1, new_prefix=None)

The subnets that join to make the current network definition, depending
on the argument values.  @emph{prefixlen_diff} is the amount our prefix
length should be increased by.  @emph{new_prefix} is the desired new
prefix of the subnets; it must be larger than our prefix.  One and
only one of @emph{prefixlen_diff} and @emph{new_prefix} must be set.  Returns an
iterator of network objects.

@example
>>> list(ip_network('192.0.2.0/24').subnets())
[IPv4Network('192.0.2.0/25'), IPv4Network('192.0.2.128/25')]
>>> list(ip_network('192.0.2.0/24').subnets(prefixlen_diff=2))  
[IPv4Network('192.0.2.0/26'), IPv4Network('192.0.2.64/26'),
 IPv4Network('192.0.2.128/26'), IPv4Network('192.0.2.192/26')]
>>> list(ip_network('192.0.2.0/24').subnets(new_prefix=26))  
[IPv4Network('192.0.2.0/26'), IPv4Network('192.0.2.64/26'),
 IPv4Network('192.0.2.128/26'), IPv4Network('192.0.2.192/26')]
>>> list(ip_network('192.0.2.0/24').subnets(new_prefix=23))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    raise ValueError('new prefix must be longer')
ValueError: new prefix must be longer
>>> list(ip_network('192.0.2.0/24').subnets(new_prefix=25))
[IPv4Network('192.0.2.0/25'), IPv4Network('192.0.2.128/25')]
@end example
@end deffn

@geindex supernet() (ipaddress.IPv4Network 方法)
@anchor{library/ipaddress ipaddress IPv4Network supernet}@anchor{792}
@deffn {方法} supernet (prefixlen_diff=1, new_prefix=None)

The supernet containing this network definition, depending on the
argument values.  @emph{prefixlen_diff} is the amount our prefix length
should be decreased by.  @emph{new_prefix} is the desired new prefix of
the supernet; it must be smaller than our prefix.  One and only one
of @emph{prefixlen_diff} and @emph{new_prefix} must be set.  Returns a single
network object.

@example
>>> ip_network('192.0.2.0/24').supernet()
IPv4Network('192.0.2.0/23')
>>> ip_network('192.0.2.0/24').supernet(prefixlen_diff=2)
IPv4Network('192.0.0.0/22')
>>> ip_network('192.0.2.0/24').supernet(new_prefix=20)
IPv4Network('192.0.0.0/20')
@end example
@end deffn

@geindex subnet_of() (ipaddress.IPv4Network 方法)
@anchor{library/ipaddress ipaddress IPv4Network subnet_of}@anchor{2eec}
@deffn {方法} subnet_of (other)

Return @code{True} if this network is a subnet of @emph{other}.

@example
>>> a = ip_network('192.168.1.0/24')
>>> b = ip_network('192.168.1.128/30')
>>> b.subnet_of(a)
True
@end example


3.7 新版功能.

@end deffn

@geindex supernet_of() (ipaddress.IPv4Network 方法)
@anchor{library/ipaddress ipaddress IPv4Network supernet_of}@anchor{2eed}
@deffn {方法} supernet_of (other)

Return @code{True} if this network is a supernet of @emph{other}.

@example
>>> a = ip_network('192.168.1.0/24')
>>> b = ip_network('192.168.1.128/30')
>>> a.supernet_of(b)
True
@end example


3.7 新版功能.

@end deffn

@geindex compare_networks() (ipaddress.IPv4Network 方法)
@anchor{library/ipaddress ipaddress IPv4Network compare_networks}@anchor{2eee}
@deffn {方法} compare_networks (other)

Compare this network to @emph{other}.  In this comparison only the network
addresses are considered; host bits aren't.  Returns either @code{-1},
@code{0} or @code{1}.

@example
>>> ip_network('192.0.2.1/32').compare_networks(ip_network('192.0.2.2/32'))
-1
>>> ip_network('192.0.2.1/32').compare_networks(ip_network('192.0.2.0/32'))
1
>>> ip_network('192.0.2.1/32').compare_networks(ip_network('192.0.2.1/32'))
0
@end example


3.7 版后已移除: It uses the same ordering and comparison algorithm as "<", "==", and ">"

@end deffn
@end deffn

@geindex IPv6Network (ipaddress 中的类)
@anchor{library/ipaddress ipaddress IPv6Network}@anchor{397}
@deffn {类} ipaddress.IPv6Network (address, strict=True)

Construct an IPv6 network definition.  @emph{address} can be one of the following:


@enumerate 

@item 
A string consisting of an IP address and an optional prefix length,
separated by a slash (@code{/}).  The IP address is the network address,
and the prefix length must be a single number, the @emph{prefix}.  If no
prefix length is provided, it's considered to be @code{/128}.

Note that currently expanded netmasks are not supported.  That means
@code{2001:db00::0/24} is a valid argument while @code{2001:db00::0/ffff:ff00::}
not.

@item 
An integer that fits into 128 bits.  This is equivalent to a
single-address network, with the network address being @emph{address} and
the mask being @code{/128}.

@item 
An integer packed into a @ref{32a,,bytes} object of length 16, big-endian.
The interpretation is similar to an integer @emph{address}.

@item 
A two-tuple of an address description and a netmask, where the address
description is either a string, a 128-bits integer, a 16-bytes packed
integer, or an existing IPv6Address object; and the netmask is an
integer representing the prefix length.
@end enumerate

An @ref{2eb0,,AddressValueError} is raised if @emph{address} is not a valid IPv6
address.  A @ref{2ed5,,NetmaskValueError} is raised if the mask is not valid for
an IPv6 address.

If @emph{strict} is @code{True} and host bits are set in the supplied address,
then @ref{1fb,,ValueError} is raised.  Otherwise, the host bits are masked out
to determine the appropriate network address.


在 3.5 版更改: Added the two-tuple form for the @emph{address} constructor parameter.


@geindex version (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network version}@anchor{2eef}
@deffn {属性} version
@end deffn

@geindex max_prefixlen (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network max_prefixlen}@anchor{2ef0}
@deffn {属性} max_prefixlen
@end deffn

@geindex is_multicast (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network is_multicast}@anchor{2ef1}
@deffn {属性} is_multicast
@end deffn

@geindex is_private (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network is_private}@anchor{2ef2}
@deffn {属性} is_private
@end deffn

@geindex is_unspecified (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network is_unspecified}@anchor{2ef3}
@deffn {属性} is_unspecified
@end deffn

@geindex is_reserved (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network is_reserved}@anchor{2ef4}
@deffn {属性} is_reserved
@end deffn

@geindex is_loopback (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network is_loopback}@anchor{2ef5}
@deffn {属性} is_loopback
@end deffn

@geindex is_link_local (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network is_link_local}@anchor{2ef6}
@deffn {属性} is_link_local
@end deffn

@geindex network_address (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network network_address}@anchor{2ef7}
@deffn {属性} network_address
@end deffn

@geindex broadcast_address (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network broadcast_address}@anchor{2ef8}
@deffn {属性} broadcast_address
@end deffn

@geindex hostmask (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network hostmask}@anchor{2ef9}
@deffn {属性} hostmask
@end deffn

@geindex netmask (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network netmask}@anchor{2efa}
@deffn {属性} netmask
@end deffn

@geindex with_prefixlen (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network with_prefixlen}@anchor{2efb}
@deffn {属性} with_prefixlen
@end deffn

@geindex compressed (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network compressed}@anchor{2efc}
@deffn {属性} compressed
@end deffn

@geindex exploded (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network exploded}@anchor{2efd}
@deffn {属性} exploded
@end deffn

@geindex with_netmask (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network with_netmask}@anchor{2efe}
@deffn {属性} with_netmask
@end deffn

@geindex with_hostmask (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network with_hostmask}@anchor{2eff}
@deffn {属性} with_hostmask
@end deffn

@geindex num_addresses (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network num_addresses}@anchor{2f00}
@deffn {属性} num_addresses
@end deffn

@geindex prefixlen (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network prefixlen}@anchor{2f01}
@deffn {属性} prefixlen
@end deffn

@geindex hosts() (ipaddress.IPv6Network 方法)
@anchor{library/ipaddress ipaddress IPv6Network hosts}@anchor{2f02}
@deffn {方法} hosts ()

Returns an iterator over the usable hosts in the network.  The usable
hosts are all the IP addresses that belong to the network, except the
Subnet-Router anycast address.  For networks with a mask length of 127,
the Subnet-Router anycast address is also included in the result.
@end deffn

@geindex overlaps() (ipaddress.IPv6Network 方法)
@anchor{library/ipaddress ipaddress IPv6Network overlaps}@anchor{2f03}
@deffn {方法} overlaps (other)
@end deffn

@geindex address_exclude() (ipaddress.IPv6Network 方法)
@anchor{library/ipaddress ipaddress IPv6Network address_exclude}@anchor{2f04}
@deffn {方法} address_exclude (network)
@end deffn

@geindex subnets() (ipaddress.IPv6Network 方法)
@anchor{library/ipaddress ipaddress IPv6Network subnets}@anchor{2f05}
@deffn {方法} subnets (prefixlen_diff=1, new_prefix=None)
@end deffn

@geindex supernet() (ipaddress.IPv6Network 方法)
@anchor{library/ipaddress ipaddress IPv6Network supernet}@anchor{2f06}
@deffn {方法} supernet (prefixlen_diff=1, new_prefix=None)
@end deffn

@geindex subnet_of() (ipaddress.IPv6Network 方法)
@anchor{library/ipaddress ipaddress IPv6Network subnet_of}@anchor{2f07}
@deffn {方法} subnet_of (other)
@end deffn

@geindex supernet_of() (ipaddress.IPv6Network 方法)
@anchor{library/ipaddress ipaddress IPv6Network supernet_of}@anchor{2f08}
@deffn {方法} supernet_of (other)
@end deffn

@geindex compare_networks() (ipaddress.IPv6Network 方法)
@anchor{library/ipaddress ipaddress IPv6Network compare_networks}@anchor{2f09}
@deffn {方法} compare_networks (other)

Refer to the corresponding attribute documentation in
@ref{398,,IPv4Network}.
@end deffn

@geindex is_site_local (ipaddress.IPv6Network 属性)
@anchor{library/ipaddress ipaddress IPv6Network is_site_local}@anchor{2f0a}
@deffn {属性} is_site_local

These attribute is true for the network as a whole if it is true
for both the network address and the broadcast address.
@end deffn
@end deffn

@node 运算符<4>,,Network objects,IP Network definitions
@anchor{library/ipaddress id1}@anchor{2f0b}
@subsubsection 运算符


Network objects support some operators.  Unless stated otherwise, operators can
only be applied between compatible objects (i.e. IPv4 with IPv4, IPv6 with
IPv6).

@menu
* Logical operators:: 
* 迭代: 迭代<2>. 
* Networks as containers of addresses:: 

@end menu

@node Logical operators,迭代<2>,,运算符<4>
@anchor{library/ipaddress logical-operators}@anchor{2f0c}
@subsubsection Logical operators


Network objects can be compared with the usual set of logical operators.
Network objects are ordered first by network address, then by net mask.

@node 迭代<2>,Networks as containers of addresses,Logical operators,运算符<4>
@anchor{library/ipaddress iteration}@anchor{2f0d}
@subsubsection 迭代


Network objects can be iterated to list all the addresses belonging to the
network.  For iteration, @emph{all} hosts are returned, including unusable hosts
(for usable hosts, use the @ref{2ee9,,hosts()} method).  An
example:

@example
>>> for addr in IPv4Network('192.0.2.0/28'):
...     addr
...
IPv4Address('192.0.2.0')
IPv4Address('192.0.2.1')
IPv4Address('192.0.2.2')
IPv4Address('192.0.2.3')
IPv4Address('192.0.2.4')
IPv4Address('192.0.2.5')
IPv4Address('192.0.2.6')
IPv4Address('192.0.2.7')
IPv4Address('192.0.2.8')
IPv4Address('192.0.2.9')
IPv4Address('192.0.2.10')
IPv4Address('192.0.2.11')
IPv4Address('192.0.2.12')
IPv4Address('192.0.2.13')
IPv4Address('192.0.2.14')
IPv4Address('192.0.2.15')
@end example

@node Networks as containers of addresses,,迭代<2>,运算符<4>
@anchor{library/ipaddress networks-as-containers-of-addresses}@anchor{2f0e}
@subsubsection Networks as containers of addresses


Network objects can act as containers of addresses.  Some examples:

@example
>>> IPv4Network('192.0.2.0/28')[0]
IPv4Address('192.0.2.0')
>>> IPv4Network('192.0.2.0/28')[15]
IPv4Address('192.0.2.15')
>>> IPv4Address('192.0.2.6') in IPv4Network('192.0.2.0/28')
True
>>> IPv4Address('192.0.3.6') in IPv4Network('192.0.2.0/28')
False
@end example

@node Interface objects,Other Module Level Functions,IP Network definitions,ipaddress --- IPv4/IPv6 操作库
@anchor{library/ipaddress interface-objects}@anchor{2f0f}
@subsubsection Interface objects


Interface objects are @ref{13c0,,hashable}, so they can be used as keys in
dictionaries.

@geindex IPv4Interface (ipaddress 中的类)
@anchor{library/ipaddress ipaddress IPv4Interface}@anchor{2eac}
@deffn {类} ipaddress.IPv4Interface (address)

Construct an IPv4 interface.  The meaning of @emph{address} is as in the
constructor of @ref{398,,IPv4Network}, except that arbitrary host addresses
are always accepted.

@ref{2eac,,IPv4Interface} is a subclass of @ref{2ea8,,IPv4Address}, so it inherits
all the attributes from that class.  In addition, the following attributes
are available:

@geindex ip (ipaddress.IPv4Interface 属性)
@anchor{library/ipaddress ipaddress IPv4Interface ip}@anchor{2f10}
@deffn {属性} ip

The address (@ref{2ea8,,IPv4Address}) without network information.

@example
>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.ip
IPv4Address('192.0.2.5')
@end example
@end deffn

@geindex network (ipaddress.IPv4Interface 属性)
@anchor{library/ipaddress ipaddress IPv4Interface network}@anchor{2f11}
@deffn {属性} network

The network (@ref{398,,IPv4Network}) this interface belongs to.

@example
>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.network
IPv4Network('192.0.2.0/24')
@end example
@end deffn

@geindex with_prefixlen (ipaddress.IPv4Interface 属性)
@anchor{library/ipaddress ipaddress IPv4Interface with_prefixlen}@anchor{2f12}
@deffn {属性} with_prefixlen

A string representation of the interface with the mask in prefix notation.

@example
>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.with_prefixlen
'192.0.2.5/24'
@end example
@end deffn

@geindex with_netmask (ipaddress.IPv4Interface 属性)
@anchor{library/ipaddress ipaddress IPv4Interface with_netmask}@anchor{2f13}
@deffn {属性} with_netmask

A string representation of the interface with the network as a net mask.

@example
>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.with_netmask
'192.0.2.5/255.255.255.0'
@end example
@end deffn

@geindex with_hostmask (ipaddress.IPv4Interface 属性)
@anchor{library/ipaddress ipaddress IPv4Interface with_hostmask}@anchor{2f14}
@deffn {属性} with_hostmask

A string representation of the interface with the network as a host mask.

@example
>>> interface = IPv4Interface('192.0.2.5/24')
>>> interface.with_hostmask
'192.0.2.5/0.0.0.255'
@end example
@end deffn
@end deffn

@geindex IPv6Interface (ipaddress 中的类)
@anchor{library/ipaddress ipaddress IPv6Interface}@anchor{2ead}
@deffn {类} ipaddress.IPv6Interface (address)

Construct an IPv6 interface.  The meaning of @emph{address} is as in the
constructor of @ref{397,,IPv6Network}, except that arbitrary host addresses
are always accepted.

@ref{2ead,,IPv6Interface} is a subclass of @ref{2ea9,,IPv6Address}, so it inherits
all the attributes from that class.  In addition, the following attributes
are available:

@geindex ip (ipaddress.IPv6Interface 属性)
@anchor{library/ipaddress ipaddress IPv6Interface ip}@anchor{2f15}
@deffn {属性} ip
@end deffn

@geindex network (ipaddress.IPv6Interface 属性)
@anchor{library/ipaddress ipaddress IPv6Interface network}@anchor{2f16}
@deffn {属性} network
@end deffn

@geindex with_prefixlen (ipaddress.IPv6Interface 属性)
@anchor{library/ipaddress ipaddress IPv6Interface with_prefixlen}@anchor{2f17}
@deffn {属性} with_prefixlen
@end deffn

@geindex with_netmask (ipaddress.IPv6Interface 属性)
@anchor{library/ipaddress ipaddress IPv6Interface with_netmask}@anchor{2f18}
@deffn {属性} with_netmask
@end deffn

@geindex with_hostmask (ipaddress.IPv6Interface 属性)
@anchor{library/ipaddress ipaddress IPv6Interface with_hostmask}@anchor{2f19}
@deffn {属性} with_hostmask

Refer to the corresponding attribute documentation in
@ref{2eac,,IPv4Interface}.
@end deffn
@end deffn

@menu
* 运算符: 运算符<5>. 

@end menu

@node 运算符<5>,,,Interface objects
@anchor{library/ipaddress id2}@anchor{2f1a}
@subsubsection 运算符


Interface objects support some operators.  Unless stated otherwise, operators
can only be applied between compatible objects (i.e. IPv4 with IPv4, IPv6 with
IPv6).

@menu
* Logical operators: Logical operators<2>. 

@end menu

@node Logical operators<2>,,,运算符<5>
@anchor{library/ipaddress id3}@anchor{2f1b}
@subsubsection Logical operators


Interface objects can be compared with the usual set of logical operators.

For equality comparison (@code{==} and @code{!=}), both the IP address and network
must be the same for the objects to be equal.  An interface will not compare
equal to any address or network object.

For ordering (@code{<}, @code{>}, etc) the rules are different.  Interface and
address objects with the same IP version can be compared, and the address
objects will always sort before the interface objects.  Two interface objects
are first compared by their networks and, if those are the same, then by their
IP addresses.

@node Other Module Level Functions,Custom Exceptions,Interface objects,ipaddress --- IPv4/IPv6 操作库
@anchor{library/ipaddress other-module-level-functions}@anchor{2f1c}
@subsubsection Other Module Level Functions


The module also provides the following module level functions:

@geindex v4_int_to_packed() (在 ipaddress 模块中)
@anchor{library/ipaddress ipaddress v4_int_to_packed}@anchor{2f1d}
@deffn {函数} ipaddress.v4_int_to_packed (address)

Represent an address as 4 packed bytes in network (big-endian) order.
@emph{address} is an integer representation of an IPv4 IP address.  A
@ref{1fb,,ValueError} is raised if the integer is negative or too large to be an
IPv4 IP address.

@example
>>> ipaddress.ip_address(3221225985)
IPv4Address('192.0.2.1')
>>> ipaddress.v4_int_to_packed(3221225985)
b'\xc0\x00\x02\x01'
@end example
@end deffn

@geindex v6_int_to_packed() (在 ipaddress 模块中)
@anchor{library/ipaddress ipaddress v6_int_to_packed}@anchor{2f1e}
@deffn {函数} ipaddress.v6_int_to_packed (address)

Represent an address as 16 packed bytes in network (big-endian) order.
@emph{address} is an integer representation of an IPv6 IP address.  A
@ref{1fb,,ValueError} is raised if the integer is negative or too large to be an
IPv6 IP address.
@end deffn

@geindex summarize_address_range() (在 ipaddress 模块中)
@anchor{library/ipaddress ipaddress summarize_address_range}@anchor{793}
@deffn {函数} ipaddress.summarize_address_range (first, last)

Return an iterator of the summarized network range given the first and last
IP addresses.  @emph{first} is the first @ref{2ea8,,IPv4Address} or
@ref{2ea9,,IPv6Address} in the range and @emph{last} is the last @ref{2ea8,,IPv4Address}
or @ref{2ea9,,IPv6Address} in the range.  A @ref{192,,TypeError} is raised if
@emph{first} or @emph{last} are not IP addresses or are not of the same version.  A
@ref{1fb,,ValueError} is raised if @emph{last} is not greater than @emph{first} or if
@emph{first} address version is not 4 or 6.

@example
>>> [ipaddr for ipaddr in ipaddress.summarize_address_range(
...    ipaddress.IPv4Address('192.0.2.0'),
...    ipaddress.IPv4Address('192.0.2.130'))]
[IPv4Network('192.0.2.0/25'), IPv4Network('192.0.2.128/31'), IPv4Network('192.0.2.130/32')]
@end example
@end deffn

@geindex collapse_addresses() (在 ipaddress 模块中)
@anchor{library/ipaddress ipaddress collapse_addresses}@anchor{794}
@deffn {函数} ipaddress.collapse_addresses (addresses)

Return an iterator of the collapsed @ref{398,,IPv4Network} or
@ref{397,,IPv6Network} objects.  @emph{addresses} is an iterator of
@ref{398,,IPv4Network} or @ref{397,,IPv6Network} objects.  A @ref{192,,TypeError} is
raised if @emph{addresses} contains mixed version objects.

@example
>>> [ipaddr for ipaddr in
... ipaddress.collapse_addresses([ipaddress.IPv4Network('192.0.2.0/25'),
... ipaddress.IPv4Network('192.0.2.128/25')])]
[IPv4Network('192.0.2.0/24')]
@end example
@end deffn

@geindex get_mixed_type_key() (在 ipaddress 模块中)
@anchor{library/ipaddress ipaddress get_mixed_type_key}@anchor{2f1f}
@deffn {函数} ipaddress.get_mixed_type_key (obj)

Return a key suitable for sorting between networks and addresses.  Address
and Network objects are not sortable by default; they're fundamentally
different, so the expression:

@example
IPv4Address('192.0.2.0') <= IPv4Network('192.0.2.0/24')
@end example

doesn't make sense.  There are some times however, where you may wish to
have @ref{a2,,ipaddress} sort these anyway.  If you need to do this, you can use
this function as the @emph{key} argument to @ref{43e,,sorted()}.

@emph{obj} is either a network or address object.
@end deffn

@node Custom Exceptions,,Other Module Level Functions,ipaddress --- IPv4/IPv6 操作库
@anchor{library/ipaddress custom-exceptions}@anchor{2f20}
@subsubsection Custom Exceptions


To support more specific error reporting from class constructors, the
module defines the following exceptions:

@geindex AddressValueError
@anchor{library/ipaddress ipaddress AddressValueError}@anchor{2eb0}
@deffn {例外} ipaddress.AddressValueError (ValueError)

Any value error related to the address.
@end deffn

@geindex NetmaskValueError
@anchor{library/ipaddress ipaddress NetmaskValueError}@anchor{2ed5}
@deffn {例外} ipaddress.NetmaskValueError (ValueError)

Any value error related to the net mask.
@end deffn

@node 多媒体服务,国际化,互联网协议和支持,Python 标准库
@anchor{library/mm doc}@anchor{2f21}@anchor{library/mm mmedia}@anchor{2f22}@anchor{library/mm multimedia-services}@anchor{2f23}
@section 多媒体服务


本章描述的模块实现了主要用于多媒体应用的各种算法或接口。 它们可在安装时自行决定。 这是一个概述：

@menu
* audioop: audioop --- Manipulate raw audio data. Manipulate raw audio data
* aifc: aifc --- Read and write AIFF and AIFC files. Read and write AIFF and AIFC files
* sunau: sunau --- 读写 Sun AU 文件. 读写 Sun AU 文件
* wave: wave --- 读写WAV格式文件. 读写WAV格式文件
* chunk: chunk --- 读取 IFF 分块数据. 读取 IFF 分块数据
* colorsys: colorsys --- 颜色系统间的转换. 颜色系统间的转换
* imghdr: imghdr --- 推测图像类型. 推测图像类型
* sndhdr: sndhdr --- 推测声音文件的类型. 推测声音文件的类型
* ossaudiodev: ossaudiodev --- Access to OSS-compatible audio devices. Access to OSS-compatible audio devices

@end menu

@node audioop --- Manipulate raw audio data,aifc --- Read and write AIFF and AIFC files,,多媒体服务
@anchor{library/audioop doc}@anchor{2f24}@anchor{library/audioop audioop-manipulate-raw-audio-data}@anchor{2f25}@anchor{library/audioop module-audioop}@anchor{d}
@subsection @code{audioop} --- Manipulate raw audio data


@geindex audioop (模块)


__________________________________________________________________


The @ref{d,,audioop} module contains some useful operations on sound fragments.
It operates on sound fragments consisting of signed integer samples 8, 16, 24
or 32 bits wide, stored in @ref{5e3,,bytes-like objects}.  All scalar items are
integers, unless specified otherwise.


在 3.4 版更改: Support for 24-bit samples was added.
All functions now accept any @ref{5e3,,bytes-like object}.
String input now results in an immediate error.


@geindex Intel/DVI ADPCM
@geindex ADPCM@comma{} Intel/DVI
@geindex a-LAW
@geindex u-LAW

This module provides support for a-LAW, u-LAW and Intel/DVI ADPCM encodings.

@c This para is mostly here to provide an excuse for the index entries...

A few of the more complicated operations only take 16-bit samples, otherwise the
sample size (in bytes) is always a parameter of the operation.

The module defines the following variables and functions:

@geindex error
@anchor{library/audioop audioop error}@anchor{2f26}
@deffn {例外} audioop.error

This exception is raised on all errors, such as unknown number of bytes per
sample, etc.
@end deffn

@geindex add() (在 audioop 模块中)
@anchor{library/audioop audioop add}@anchor{2f27}
@deffn {函数} audioop.add (fragment1, fragment2, width)

Return a fragment which is the addition of the two samples passed as parameters.
@emph{width} is the sample width in bytes, either @code{1}, @code{2}, @code{3} or @code{4}.  Both
fragments should have the same length.  Samples are truncated in case of overflow.
@end deffn

@geindex adpcm2lin() (在 audioop 模块中)
@anchor{library/audioop audioop adpcm2lin}@anchor{2f28}
@deffn {函数} audioop.adpcm2lin (adpcmfragment, width, state)

Decode an Intel/DVI ADPCM coded fragment to a linear fragment.  See the
description of @ref{2f29,,lin2adpcm()} for details on ADPCM coding. Return a tuple
@code{(sample, newstate)} where the sample has the width specified in @emph{width}.
@end deffn

@geindex alaw2lin() (在 audioop 模块中)
@anchor{library/audioop audioop alaw2lin}@anchor{2f2a}
@deffn {函数} audioop.alaw2lin (fragment, width)

Convert sound fragments in a-LAW encoding to linearly encoded sound fragments.
a-LAW encoding always uses 8 bits samples, so @emph{width} refers only to the sample
width of the output fragment here.
@end deffn

@geindex avg() (在 audioop 模块中)
@anchor{library/audioop audioop avg}@anchor{2f2b}
@deffn {函数} audioop.avg (fragment, width)

Return the average over all samples in the fragment.
@end deffn

@geindex avgpp() (在 audioop 模块中)
@anchor{library/audioop audioop avgpp}@anchor{2f2c}
@deffn {函数} audioop.avgpp (fragment, width)

Return the average peak-peak value over all samples in the fragment. No
filtering is done, so the usefulness of this routine is questionable.
@end deffn

@geindex bias() (在 audioop 模块中)
@anchor{library/audioop audioop bias}@anchor{2f2d}
@deffn {函数} audioop.bias (fragment, width, bias)

Return a fragment that is the original fragment with a bias added to each
sample.  Samples wrap around in case of overflow.
@end deffn

@geindex byteswap() (在 audioop 模块中)
@anchor{library/audioop audioop byteswap}@anchor{81c}
@deffn {函数} audioop.byteswap (fragment, width)

"Byteswap" all samples in a fragment and returns the modified fragment.
Converts big-endian samples to little-endian and vice versa.


3.4 新版功能.

@end deffn

@geindex cross() (在 audioop 模块中)
@anchor{library/audioop audioop cross}@anchor{2f2e}
@deffn {函数} audioop.cross (fragment, width)

Return the number of zero crossings in the fragment passed as an argument.
@end deffn

@geindex findfactor() (在 audioop 模块中)
@anchor{library/audioop audioop findfactor}@anchor{2f2f}
@deffn {函数} audioop.findfactor (fragment, reference)

Return a factor @emph{F} such that @code{rms(add(fragment, mul(reference, -F)))} is
minimal, i.e., return the factor with which you should multiply @emph{reference} to
make it match as well as possible to @emph{fragment}.  The fragments should both
contain 2-byte samples.

The time taken by this routine is proportional to @code{len(fragment)}.
@end deffn

@geindex findfit() (在 audioop 模块中)
@anchor{library/audioop audioop findfit}@anchor{2f30}
@deffn {函数} audioop.findfit (fragment, reference)

Try to match @emph{reference} as well as possible to a portion of @emph{fragment} (which
should be the longer fragment).  This is (conceptually) done by taking slices
out of @emph{fragment}, using @ref{2f2f,,findfactor()} to compute the best match, and
minimizing the result.  The fragments should both contain 2-byte samples.
Return a tuple @code{(offset, factor)} where @emph{offset} is the (integer) offset into
@emph{fragment} where the optimal match started and @emph{factor} is the (floating-point)
factor as per @ref{2f2f,,findfactor()}.
@end deffn

@geindex findmax() (在 audioop 模块中)
@anchor{library/audioop audioop findmax}@anchor{2f31}
@deffn {函数} audioop.findmax (fragment, length)

Search @emph{fragment} for a slice of length @emph{length} samples (not bytes!) with
maximum energy, i.e., return @emph{i} for which @code{rms(fragment[i*2:(i+length)*2])}
is maximal.  The fragments should both contain 2-byte samples.

The routine takes time proportional to @code{len(fragment)}.
@end deffn

@geindex getsample() (在 audioop 模块中)
@anchor{library/audioop audioop getsample}@anchor{2f32}
@deffn {函数} audioop.getsample (fragment, width, index)

Return the value of sample @emph{index} from the fragment.
@end deffn

@geindex lin2adpcm() (在 audioop 模块中)
@anchor{library/audioop audioop lin2adpcm}@anchor{2f29}
@deffn {函数} audioop.lin2adpcm (fragment, width, state)

Convert samples to 4 bit Intel/DVI ADPCM encoding.  ADPCM coding is an adaptive
coding scheme, whereby each 4 bit number is the difference between one sample
and the next, divided by a (varying) step.  The Intel/DVI ADPCM algorithm has
been selected for use by the IMA, so it may well become a standard.

@emph{state} is a tuple containing the state of the coder.  The coder returns a tuple
@code{(adpcmfrag, newstate)}, and the @emph{newstate} should be passed to the next call
of @ref{2f29,,lin2adpcm()}.  In the initial call, @code{None} can be passed as the state.
@emph{adpcmfrag} is the ADPCM coded fragment packed 2 4-bit values per byte.
@end deffn

@geindex lin2alaw() (在 audioop 模块中)
@anchor{library/audioop audioop lin2alaw}@anchor{2f33}
@deffn {函数} audioop.lin2alaw (fragment, width)

Convert samples in the audio fragment to a-LAW encoding and return this as a
bytes object.  a-LAW is an audio encoding format whereby you get a dynamic
range of about 13 bits using only 8 bit samples.  It is used by the Sun audio
hardware, among others.
@end deffn

@geindex lin2lin() (在 audioop 模块中)
@anchor{library/audioop audioop lin2lin}@anchor{2f34}
@deffn {函数} audioop.lin2lin (fragment, width, newwidth)

Convert samples between 1-, 2-, 3- and 4-byte formats.

@cartouche
@quotation 注解 
In some audio formats, such as .WAV files, 16, 24 and 32 bit samples are
signed, but 8 bit samples are unsigned.  So when converting to 8 bit wide
samples for these formats, you need to also add 128 to the result:

@example
new_frames = audioop.lin2lin(frames, old_width, 1)
new_frames = audioop.bias(new_frames, 1, 128)
@end example

The same, in reverse, has to be applied when converting from 8 to 16, 24
or 32 bit width samples.
@end quotation
@end cartouche
@end deffn

@geindex lin2ulaw() (在 audioop 模块中)
@anchor{library/audioop audioop lin2ulaw}@anchor{2f35}
@deffn {函数} audioop.lin2ulaw (fragment, width)

Convert samples in the audio fragment to u-LAW encoding and return this as a
bytes object.  u-LAW is an audio encoding format whereby you get a dynamic
range of about 14 bits using only 8 bit samples.  It is used by the Sun audio
hardware, among others.
@end deffn

@geindex max() (在 audioop 模块中)
@anchor{library/audioop audioop max}@anchor{2f36}
@deffn {函数} audioop.max (fragment, width)

Return the maximum of the @emph{absolute value} of all samples in a fragment.
@end deffn

@geindex maxpp() (在 audioop 模块中)
@anchor{library/audioop audioop maxpp}@anchor{2f37}
@deffn {函数} audioop.maxpp (fragment, width)

Return the maximum peak-peak value in the sound fragment.
@end deffn

@geindex minmax() (在 audioop 模块中)
@anchor{library/audioop audioop minmax}@anchor{2f38}
@deffn {函数} audioop.minmax (fragment, width)

Return a tuple consisting of the minimum and maximum values of all samples in
the sound fragment.
@end deffn

@geindex mul() (在 audioop 模块中)
@anchor{library/audioop audioop mul}@anchor{2f39}
@deffn {函数} audioop.mul (fragment, width, factor)

Return a fragment that has all samples in the original fragment multiplied by
the floating-point value @emph{factor}.  Samples are truncated in case of overflow.
@end deffn

@geindex ratecv() (在 audioop 模块中)
@anchor{library/audioop audioop ratecv}@anchor{2f3a}
@deffn {函数} audioop.ratecv (fragment, width, nchannels, inrate, outrate, state[, weightA[, weightB]])

Convert the frame rate of the input fragment.

@emph{state} is a tuple containing the state of the converter.  The converter returns
a tuple @code{(newfragment, newstate)}, and @emph{newstate} should be passed to the next
call of @ref{2f3a,,ratecv()}.  The initial call should pass @code{None} as the state.

The @emph{weightA} and @emph{weightB} arguments are parameters for a simple digital filter
and default to @code{1} and @code{0} respectively.
@end deffn

@geindex reverse() (在 audioop 模块中)
@anchor{library/audioop audioop reverse}@anchor{2f3b}
@deffn {函数} audioop.reverse (fragment, width)

Reverse the samples in a fragment and returns the modified fragment.
@end deffn

@geindex rms() (在 audioop 模块中)
@anchor{library/audioop audioop rms}@anchor{2f3c}
@deffn {函数} audioop.rms (fragment, width)

Return the root-mean-square of the fragment, i.e. @code{sqrt(sum(S_i^2)/n)}.

This is a measure of the power in an audio signal.
@end deffn

@geindex tomono() (在 audioop 模块中)
@anchor{library/audioop audioop tomono}@anchor{2f3d}
@deffn {函数} audioop.tomono (fragment, width, lfactor, rfactor)

Convert a stereo fragment to a mono fragment.  The left channel is multiplied by
@emph{lfactor} and the right channel by @emph{rfactor} before adding the two channels to
give a mono signal.
@end deffn

@geindex tostereo() (在 audioop 模块中)
@anchor{library/audioop audioop tostereo}@anchor{2f3e}
@deffn {函数} audioop.tostereo (fragment, width, lfactor, rfactor)

Generate a stereo fragment from a mono fragment.  Each pair of samples in the
stereo fragment are computed from the mono sample, whereby left channel samples
are multiplied by @emph{lfactor} and right channel samples by @emph{rfactor}.
@end deffn

@geindex ulaw2lin() (在 audioop 模块中)
@anchor{library/audioop audioop ulaw2lin}@anchor{2f3f}
@deffn {函数} audioop.ulaw2lin (fragment, width)

Convert sound fragments in u-LAW encoding to linearly encoded sound fragments.
u-LAW encoding always uses 8 bits samples, so @emph{width} refers only to the sample
width of the output fragment here.
@end deffn

Note that operations such as @ref{2f39,,mul()} or @ref{2f36,,max()} make no distinction
between mono and stereo fragments, i.e. all samples are treated equal.  If this
is a problem the stereo fragment should be split into two mono fragments first
and recombined later.  Here is an example of how to do that:

@example
def mul_stereo(sample, width, lfactor, rfactor):
    lsample = audioop.tomono(sample, width, 1, 0)
    rsample = audioop.tomono(sample, width, 0, 1)
    lsample = audioop.mul(lsample, width, lfactor)
    rsample = audioop.mul(rsample, width, rfactor)
    lsample = audioop.tostereo(lsample, width, 1, 0)
    rsample = audioop.tostereo(rsample, width, 0, 1)
    return audioop.add(lsample, rsample, width)
@end example

If you use the ADPCM coder to build network packets and you want your protocol
to be stateless (i.e. to be able to tolerate packet loss) you should not only
transmit the data but also the state.  Note that you should send the @emph{initial}
state (the one you passed to @ref{2f29,,lin2adpcm()}) along to the decoder, not the
final state (as returned by the coder).  If you want to use
@ref{17a2,,struct.Struct} to store the state in binary you can code the first
element (the predicted value) in 16 bits and the second (the delta index) in 8.

The ADPCM coders have never been tried against other ADPCM coders, only against
themselves.  It could well be that I misinterpreted the standards in which case
they will not be interoperable with the respective standards.

The @code{find*()} routines might look a bit funny at first sight. They are
primarily meant to do echo cancellation.  A reasonably fast way to do this is to
pick the most energetic piece of the output sample, locate that in the input
sample and subtract the whole output sample from the input sample:

@example
def echocancel(outputdata, inputdata):
    pos = audioop.findmax(outputdata, 800)    # one tenth second
    out_test = outputdata[pos*2:]
    in_test = inputdata[pos*2:]
    ipos, factor = audioop.findfit(in_test, out_test)
    # Optional (for better cancellation):
    # factor = audioop.findfactor(in_test[ipos*2:ipos*2+len(out_test)],
    #              out_test)
    prefill = '\0'*(pos+ipos)*2
    postfill = '\0'*(len(inputdata)-len(prefill)-len(outputdata))
    outputdata = prefill + audioop.mul(outputdata, 2, -factor) + postfill
    return audioop.add(inputdata, outputdata, 2)
@end example

@node aifc --- Read and write AIFF and AIFC files,sunau --- 读写 Sun AU 文件,audioop --- Manipulate raw audio data,多媒体服务
@anchor{library/aifc doc}@anchor{2f40}@anchor{library/aifc aifc-read-and-write-aiff-and-aifc-files}@anchor{2f41}@anchor{library/aifc module-aifc}@anchor{5}
@subsection @code{aifc} --- Read and write AIFF and AIFC files


@geindex aifc (模块)

@strong{Source code:} Lib/aifc.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/aifc.py}

@geindex Audio Interchange File Format
@geindex AIFF
@geindex AIFF-C


__________________________________________________________________


This module provides support for reading and writing AIFF and AIFF-C files.
AIFF is Audio Interchange File Format, a format for storing digital audio
samples in a file.  AIFF-C is a newer version of the format that includes the
ability to compress the audio data.

Audio files have a number of parameters that describe the audio data. The
sampling rate or frame rate is the number of times per second the sound is
sampled.  The number of channels indicate if the audio is mono, stereo, or
quadro.  Each frame consists of one sample per channel.  The sample size is the
size in bytes of each sample.  Thus a frame consists of
@code{nchannels * samplesize} bytes, and a second's worth of audio consists of
@code{nchannels * samplesize * framerate} bytes.

For example, CD quality audio has a sample size of two bytes (16 bits), uses two
channels (stereo) and has a frame rate of 44,100 frames/second.  This gives a
frame size of 4 bytes (2*2), and a second's worth occupies 2*2*44100 bytes
(176,400 bytes).

Module @ref{5,,aifc} defines the following function:

@geindex open() (在 aifc 模块中)
@anchor{library/aifc aifc open}@anchor{455}
@deffn {函数} aifc.open (file, mode=None)

Open an AIFF or AIFF-C file and return an object instance with methods that are
described below.  The argument @emph{file} is either a string naming a file or a
@ref{b3b,,file object}.  @emph{mode} must be @code{'r'} or @code{'rb'} when the file must be
opened for reading, or @code{'w'}  or @code{'wb'} when the file must be opened for writing.
If omitted, @code{file.mode} is used if it exists, otherwise @code{'rb'} is used.  When
used for writing, the file object should be seekable, unless you know ahead of
time how many samples you are going to write in total and use
@code{writeframesraw()} and @code{setnframes()}.
The @ref{455,,open()} function may be used in a @ref{6e3,,with} statement.  When
the @code{with} block completes, the @ref{816,,close()} method is called.


在 3.4 版更改: 添加了对 @ref{6e3,,with} 语句的支持。

@end deffn

Objects returned by @ref{455,,open()} when a file is opened for reading have the
following methods:

@geindex getnchannels() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getnchannels}@anchor{2f42}
@deffn {方法} aifc.getnchannels ()

Return the number of audio channels (1 for mono, 2 for stereo).
@end deffn

@geindex getsampwidth() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getsampwidth}@anchor{2f43}
@deffn {方法} aifc.getsampwidth ()

Return the size in bytes of individual samples.
@end deffn

@geindex getframerate() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getframerate}@anchor{2f44}
@deffn {方法} aifc.getframerate ()

Return the sampling rate (number of audio frames per second).
@end deffn

@geindex getnframes() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getnframes}@anchor{2f45}
@deffn {方法} aifc.getnframes ()

Return the number of audio frames in the file.
@end deffn

@geindex getcomptype() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getcomptype}@anchor{2f46}
@deffn {方法} aifc.getcomptype ()

Return a bytes array of length 4 describing the type of compression
used in the audio file.  For AIFF files, the returned value is
@code{b'NONE'}.
@end deffn

@geindex getcompname() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getcompname}@anchor{2f47}
@deffn {方法} aifc.getcompname ()

Return a bytes array convertible to a human-readable description
of the type of compression used in the audio file.  For AIFF files,
the returned value is @code{b'not compressed'}.
@end deffn

@geindex getparams() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getparams}@anchor{815}
@deffn {方法} aifc.getparams ()

返回一个 @ref{1b6,,namedtuple()} @code{(nchannels, sampwidth, framerate, nframes, comptype, compname)}，与 @code{get*()} 方法的输出相同。
@end deffn

@geindex getmarkers() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getmarkers}@anchor{2f48}
@deffn {方法} aifc.getmarkers ()

Return a list of markers in the audio file.  A marker consists of a tuple of
three elements.  The first is the mark ID (an integer), the second is the mark
position in frames from the beginning of the data (an integer), the third is the
name of the mark (a string).
@end deffn

@geindex getmark() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc getmark}@anchor{2f49}
@deffn {方法} aifc.getmark (id)

Return the tuple as described in @ref{2f48,,getmarkers()} for the mark with the given
@emph{id}.
@end deffn

@geindex readframes() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc readframes}@anchor{2f4a}
@deffn {方法} aifc.readframes (nframes)

Read and return the next @emph{nframes} frames from the audio file.  The returned
data is a string containing for each frame the uncompressed samples of all
channels.
@end deffn

@geindex rewind() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc rewind}@anchor{2f4b}
@deffn {方法} aifc.rewind ()

Rewind the read pointer.  The next @ref{2f4a,,readframes()} will start from the
beginning.
@end deffn

@geindex setpos() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc setpos}@anchor{2f4c}
@deffn {方法} aifc.setpos (pos)

Seek to the specified frame number.
@end deffn

@geindex tell() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc tell}@anchor{2f4d}
@deffn {方法} aifc.tell ()

Return the current frame number.
@end deffn

@geindex close() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc close}@anchor{816}
@deffn {方法} aifc.close ()

Close the AIFF file.  After calling this method, the object can no longer be
used.
@end deffn

Objects returned by @ref{455,,open()} when a file is opened for writing have all the
above methods, except for @code{readframes()} and @code{setpos()}.  In addition
the following methods exist.  The @code{get*()} methods can only be called after
the corresponding @code{set*()} methods have been called.  Before the first
@code{writeframes()} or @code{writeframesraw()}, all parameters except for the
number of frames must be filled in.

@geindex aiff() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc aiff}@anchor{2f4e}
@deffn {方法} aifc.aiff ()

Create an AIFF file.  The default is that an AIFF-C file is created, unless the
name of the file ends in @code{'.aiff'} in which case the default is an AIFF file.
@end deffn

@geindex aifc() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc aifc}@anchor{2f4f}
@deffn {方法} aifc.aifc ()

Create an AIFF-C file.  The default is that an AIFF-C file is created, unless
the name of the file ends in @code{'.aiff'} in which case the default is an AIFF
file.
@end deffn

@geindex setnchannels() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc setnchannels}@anchor{2f50}
@deffn {方法} aifc.setnchannels (nchannels)

Specify the number of channels in the audio file.
@end deffn

@geindex setsampwidth() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc setsampwidth}@anchor{2f51}
@deffn {方法} aifc.setsampwidth (width)

Specify the size in bytes of audio samples.
@end deffn

@geindex setframerate() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc setframerate}@anchor{2f52}
@deffn {方法} aifc.setframerate (rate)

Specify the sampling frequency in frames per second.
@end deffn

@geindex setnframes() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc setnframes}@anchor{2f53}
@deffn {方法} aifc.setnframes (nframes)

Specify the number of frames that are to be written to the audio file. If this
parameter is not set, or not set correctly, the file needs to support seeking.
@end deffn

@geindex setcomptype() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc setcomptype}@anchor{2f54}
@deffn {方法} aifc.setcomptype (type, name)

@geindex u-LAW
@geindex A-LAW
@geindex G.722

Specify the compression type.  If not specified, the audio data will
not be compressed.  In AIFF files, compression is not possible.
The name parameter should be a human-readable description of the
compression type as a bytes array, the type parameter should be a
bytes array of length 4.  Currently the following compression types
are supported: @code{b'NONE'}, @code{b'ULAW'}, @code{b'ALAW'}, @code{b'G722'}.
@end deffn

@geindex setparams() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc setparams}@anchor{2f55}
@deffn {方法} aifc.setparams (nchannels, sampwidth, framerate, comptype, compname)

Set all the above parameters at once.  The argument is a tuple consisting of the
various parameters.  This means that it is possible to use the result of a
@ref{815,,getparams()} call as argument to @ref{2f55,,setparams()}.
@end deffn

@geindex setmark() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc setmark}@anchor{2f56}
@deffn {方法} aifc.setmark (id, pos, name)

Add a mark with the given id (larger than 0), and the given name at the given
position.  This method can be called at any time before @ref{816,,close()}.
@end deffn

@geindex tell() (aifc.aifc 方法)

@deffn {方法} aifc.tell ()

Return the current write position in the output file.  Useful in combination
with @ref{2f56,,setmark()}.
@end deffn

@geindex writeframes() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc writeframes}@anchor{818}
@deffn {方法} aifc.writeframes (data)

Write data to the output file.  This method can only be called after the audio
file parameters have been set.


在 3.4 版更改: 现在可接受任意 @ref{5e3,,bytes-like object}。

@end deffn

@geindex writeframesraw() (aifc.aifc 方法)
@anchor{library/aifc aifc aifc writeframesraw}@anchor{817}
@deffn {方法} aifc.writeframesraw (data)

Like @ref{818,,writeframes()}, except that the header of the audio file is not
updated.


在 3.4 版更改: 现在可接受任意 @ref{5e3,,bytes-like object}。

@end deffn

@geindex close() (aifc.aifc 方法)

@deffn {方法} aifc.close ()

Close the AIFF file.  The header of the file is updated to reflect the actual
size of the audio data. After calling this method, the object can no longer be
used.
@end deffn

@node sunau --- 读写 Sun AU 文件,wave --- 读写WAV格式文件,aifc --- Read and write AIFF and AIFC files,多媒体服务
@anchor{library/sunau doc}@anchor{2f57}@anchor{library/sunau module-sunau}@anchor{fa}@anchor{library/sunau sunau-read-and-write-sun-au-files}@anchor{2f58}
@subsection @code{sunau} --- 读写 Sun AU 文件


@geindex sunau (模块)

@strong{源代码:} Lib/sunau.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/sunau.py}


__________________________________________________________________


@ref{fa,,sunau} 模拟提供了一个处理 Sun AU 声音格式的便利接口。请注意此模块与 @ref{5,,aifc} 和 @ref{127,,wave} 是兼容接口的。

音频文件由标头和数据组成。标头的字段为：


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

目录

@item

magic word

@tab

四个字节 @code{.snd}

@item

header size

@tab

标头的大小，包括信息，以字节为单位。

@item

data size

@tab

数据的物理大小，以字节为单位。

@item

编码

@tab

指示音频样本的编码方式。

@item

sample rate

@tab

采样率

@item

# of channels

@tab

采样中的通道数。

@item

info

@tab

提供音频文件描述的ASCII字符串（用空字节填充）。

@end multitable


Apart from the info field, all header fields are 4 bytes in size. They are all
32-bit unsigned integers encoded in big-endian byte order.

The @ref{fa,,sunau} module defines the following functions:

@geindex open() (在 sunau 模块中)
@anchor{library/sunau sunau open}@anchor{46c}
@deffn {函数} sunau.open (file, mode)

If @emph{file} is a string, open the file by that name, otherwise treat it as a
seekable file-like object. @emph{mode} can be any of


@table @asis

@item @code{'r'}

只读模式。

@item @code{'w'}

只写模式。
@end table

Note that it does not allow read/write files.

A @emph{mode} of @code{'r'} returns an @code{AU_read} object, while a @emph{mode} of @code{'w'}
or @code{'wb'} returns an @code{AU_write} object.
@end deffn

@geindex openfp() (在 sunau 模块中)
@anchor{library/sunau sunau openfp}@anchor{46b}
@deffn {函数} sunau.openfp (file, mode)

同 @ref{46c,,open()}，用于向后兼容。


Deprecated since version 3.7, will be removed in version 3.9.

@end deffn

The @ref{fa,,sunau} module defines the following exception:

@geindex Error
@anchor{library/sunau sunau Error}@anchor{2f59}
@deffn {例外} sunau.Error

An error raised when something is impossible because of Sun AU specs or
implementation deficiency.
@end deffn

The @ref{fa,,sunau} module defines the following data items:

@geindex AUDIO_FILE_MAGIC() (在 sunau 模块中)
@anchor{library/sunau sunau AUDIO_FILE_MAGIC}@anchor{2f5a}
@deffn {数据} sunau.AUDIO_FILE_MAGIC

An integer every valid Sun AU file begins with, stored in big-endian form.  This
is the string @code{.snd} interpreted as an integer.
@end deffn

@geindex AUDIO_FILE_ENCODING_MULAW_8() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_LINEAR_8() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_LINEAR_16() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_LINEAR_24() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_LINEAR_32() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_ALAW_8() (在 sunau 模块中)
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_MULAW_8}@anchor{2f5b}
@deffn {数据} sunau.AUDIO_FILE_ENCODING_MULAW_8
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_LINEAR_8}@anchor{2f5c}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_LINEAR_8
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_LINEAR_16}@anchor{2f5d}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_LINEAR_16
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_LINEAR_24}@anchor{2f5e}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_LINEAR_24
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_LINEAR_32}@anchor{2f5f}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_LINEAR_32
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_ALAW_8}@anchor{2f60}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_ALAW_8

Values of the encoding field from the AU header which are supported by this
module.
@end deffn

@geindex AUDIO_FILE_ENCODING_FLOAT() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_DOUBLE() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_ADPCM_G721() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_ADPCM_G722() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_ADPCM_G723_3() (在 sunau 模块中)
@geindex AUDIO_FILE_ENCODING_ADPCM_G723_5() (在 sunau 模块中)
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_FLOAT}@anchor{2f61}
@deffn {数据} sunau.AUDIO_FILE_ENCODING_FLOAT
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_DOUBLE}@anchor{2f62}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_DOUBLE
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_ADPCM_G721}@anchor{2f63}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_ADPCM_G721
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_ADPCM_G722}@anchor{2f64}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_ADPCM_G722
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_ADPCM_G723_3}@anchor{2f65}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_ADPCM_G723_3
@anchor{library/sunau sunau AUDIO_FILE_ENCODING_ADPCM_G723_5}@anchor{2f66}
@deffnx {数据} sunau.AUDIO_FILE_ENCODING_ADPCM_G723_5

Additional known values of the encoding field from the AU header, but which are
not supported by this module.
@end deffn

@menu
* AU_read 对象:: 
* AU_write 对象:: 

@end menu

@node AU_read 对象,AU_write 对象,,sunau --- 读写 Sun AU 文件
@anchor{library/sunau au-read-objects}@anchor{2f67}@anchor{library/sunau id1}@anchor{2f68}
@subsubsection AU_read 对象


AU_read objects, as returned by @ref{46c,,open()} above, have the following methods:

@geindex close() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read close}@anchor{2f69}
@deffn {方法} AU_read.close ()

Close the stream, and make the instance unusable. (This is  called automatically
on deletion.)
@end deffn

@geindex getnchannels() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getnchannels}@anchor{2f6a}
@deffn {方法} AU_read.getnchannels ()

Returns number of audio channels (1 for mono, 2 for stereo).
@end deffn

@geindex getsampwidth() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getsampwidth}@anchor{2f6b}
@deffn {方法} AU_read.getsampwidth ()

返回采样字节长度。
@end deffn

@geindex getframerate() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getframerate}@anchor{2f6c}
@deffn {方法} AU_read.getframerate ()

返回采样频率。
@end deffn

@geindex getnframes() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getnframes}@anchor{2f6d}
@deffn {方法} AU_read.getnframes ()

返回音频总帧数。
@end deffn

@geindex getcomptype() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getcomptype}@anchor{2f6e}
@deffn {方法} AU_read.getcomptype ()

Returns compression type. Supported compression types are @code{'ULAW'}, @code{'ALAW'}
and @code{'NONE'}.
@end deffn

@geindex getcompname() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getcompname}@anchor{2f6f}
@deffn {方法} AU_read.getcompname ()

Human-readable version of @ref{2f6e,,getcomptype()}.  The supported types have the
respective names @code{'CCITT G.711 u-law'}, @code{'CCITT G.711 A-law'} and @code{'not
compressed'}.
@end deffn

@geindex getparams() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getparams}@anchor{2f70}
@deffn {方法} AU_read.getparams ()

返回一个 @ref{1b6,,namedtuple()} @code{(nchannels, sampwidth, framerate, nframes, comptype, compname)}，与 @code{get*()} 方法的输出相同。
@end deffn

@geindex readframes() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read readframes}@anchor{2f71}
@deffn {方法} AU_read.readframes (n)

Reads and returns at most @emph{n} frames of audio, as a @ref{32a,,bytes} object.  The data
will be returned in linear format.  If the original data is in u-LAW format, it
will be converted.
@end deffn

@geindex rewind() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read rewind}@anchor{2f72}
@deffn {方法} AU_read.rewind ()

重置文件指针至音频开头.
@end deffn

以下两个方法都使用指针，具体实现由其底层决定。

@geindex setpos() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read setpos}@anchor{2f73}
@deffn {方法} AU_read.setpos (pos)

Set the file pointer to the specified position.  Only values returned from
@ref{2f74,,tell()} should be used for @emph{pos}.
@end deffn

@geindex tell() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read tell}@anchor{2f74}
@deffn {方法} AU_read.tell ()

Return current file pointer position.  Note that the returned value has nothing
to do with the actual position in the file.
@end deffn

The following two functions are defined for compatibility with the  @ref{5,,aifc},
and don't do anything interesting.

@geindex getmarkers() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getmarkers}@anchor{2f75}
@deffn {方法} AU_read.getmarkers ()

返回 @code{None}。
@end deffn

@geindex getmark() (sunau.AU_read 方法)
@anchor{library/sunau sunau AU_read getmark}@anchor{2f76}
@deffn {方法} AU_read.getmark (id)

引发错误异常。
@end deffn

@node AU_write 对象,,AU_read 对象,sunau --- 读写 Sun AU 文件
@anchor{library/sunau au-write-objects}@anchor{2f77}@anchor{library/sunau id2}@anchor{2f78}
@subsubsection AU_write 对象


AU_write objects, as returned by @ref{46c,,open()} above, have the following methods:

@geindex setnchannels() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write setnchannels}@anchor{2f79}
@deffn {方法} AU_write.setnchannels (n)

设置声道数。
@end deffn

@geindex setsampwidth() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write setsampwidth}@anchor{8d8}
@deffn {方法} AU_write.setsampwidth (n)

Set the sample width (in bytes.)


在 3.4 版更改: Added support for 24-bit samples.

@end deffn

@geindex setframerate() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write setframerate}@anchor{2f7a}
@deffn {方法} AU_write.setframerate (n)

Set the frame rate.
@end deffn

@geindex setnframes() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write setnframes}@anchor{2f7b}
@deffn {方法} AU_write.setnframes (n)

Set the number of frames. This can be later changed, when and if more  frames
are written.
@end deffn

@geindex setcomptype() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write setcomptype}@anchor{2f7c}
@deffn {方法} AU_write.setcomptype (type, name)

Set the compression type and description. Only @code{'NONE'} and @code{'ULAW'} are
supported on output.
@end deffn

@geindex setparams() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write setparams}@anchor{2f7d}
@deffn {方法} AU_write.setparams (tuple)

The @emph{tuple} should be @code{(nchannels, sampwidth, framerate, nframes, comptype,
compname)}, with values valid for the @code{set*()} methods.  Set all
parameters.
@end deffn

@geindex tell() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write tell}@anchor{2f7e}
@deffn {方法} AU_write.tell ()

Return current position in the file, with the same disclaimer for the
@ref{2f74,,AU_read.tell()} and @ref{2f73,,AU_read.setpos()} methods.
@end deffn

@geindex writeframesraw() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write writeframesraw}@anchor{8d9}
@deffn {方法} AU_write.writeframesraw (data)

写入音频数据但不更新 @emph{nframes}。


在 3.4 版更改: 现在可接受任意 @ref{5e3,,bytes-like object}。

@end deffn

@geindex writeframes() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write writeframes}@anchor{8da}
@deffn {方法} AU_write.writeframes (data)

写入音频数据并更新 @emph{nframes}。


在 3.4 版更改: 现在可接受任意 @ref{5e3,,bytes-like object}。

@end deffn

@geindex close() (sunau.AU_write 方法)
@anchor{library/sunau sunau AU_write close}@anchor{2f7f}
@deffn {方法} AU_write.close ()

Make sure @emph{nframes} is correct, and close the file.

This method is called upon deletion.
@end deffn

Note that it is invalid to set any parameters after calling  @code{writeframes()}
or @code{writeframesraw()}.

@node wave --- 读写WAV格式文件,chunk --- 读取 IFF 分块数据,sunau --- 读写 Sun AU 文件,多媒体服务
@anchor{library/wave doc}@anchor{2f80}@anchor{library/wave module-wave}@anchor{127}@anchor{library/wave wave-read-and-write-wav-files}@anchor{2f81}
@subsection @code{wave} --- 读写WAV格式文件


@geindex wave (模块)

@c Documentations stolen from comments in file.

@strong{源代码:} Lib/wave.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/wave.py}


__________________________________________________________________


@ref{127,,wave} 模块提供了一个处理 WAV 声音格式的便利接口。它不支持压缩/解压，但是支持单声道/立体声。

@ref{127,,wave} 模块定义了以下函数和异常:

@geindex open() (在 wave 模块中)
@anchor{library/wave wave open}@anchor{470}
@deffn {函数} wave.open (file, mode=None)

如果 @emph{file} 是一个字符串，打开对应文件名的文件。否则就把它作为文件类对象来处理。@emph{mode} 可以为以下值：


@table @asis

@item @code{'rb'}

只读模式。

@item @code{'wb'}

只写模式。
@end table

注意不支持同时读写WAV文件。

@emph{mode} 设为 @code{'rb'} 时返回一个 @code{Wave_read} 对象，而 @emph{mode} 设为 @code{'wb'} 时返回一个 @code{Wave_write} 对象。如果省略 @emph{mode} 并指定 @emph{file} 来传入一个文件类对象，则 @code{file.mode} 会被用作 @emph{mode} 的默认值。

如果操作的是文件对象，当使用 wave 对象的 @code{close()} 方法时，并不会真正关闭文件对象，这需要调用者负责来关闭文件对象。

@ref{470,,open()} 函数可以在 @ref{6e3,,with} 语句中使用。 当 @code{with} 阻塞结束时，@ref{2f82,,Wave_read.close()} 或 @ref{2f83,,Wave_write.close()} 方法会被调用。


在 3.4 版更改: 添加了对不可搜索文件的支持。

@end deffn

@geindex openfp() (在 wave 模块中)
@anchor{library/wave wave openfp}@anchor{46f}
@deffn {函数} wave.openfp (file, mode)

同 @ref{470,,open()}，用于向后兼容。


Deprecated since version 3.7, will be removed in version 3.9.

@end deffn

@geindex Error
@anchor{library/wave wave Error}@anchor{2f84}
@deffn {例外} wave.Error

当不符合WAV格式或无法操作时引发的错误。
@end deffn

@menu
* Wave_read对象:: 
* Wave_write 对象:: 

@end menu

@node Wave_read对象,Wave_write 对象,,wave --- 读写WAV格式文件
@anchor{library/wave id1}@anchor{2f85}@anchor{library/wave wave-read-objects}@anchor{2f86}
@subsubsection Wave_read对象


由 @ref{470,,open()} 返回的 Wave_read 对象，有以下几种方法:

@geindex close() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read close}@anchor{2f82}
@deffn {方法} Wave_read.close ()

关闭 @ref{127,,wave} 打开的数据流并使对象不可用。当对象销毁时会自动调用。
@end deffn

@geindex getnchannels() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getnchannels}@anchor{2f87}
@deffn {方法} Wave_read.getnchannels ()

返回声道数量（@code{1} 为单声道，@code{2} 为立体声）
@end deffn

@geindex getsampwidth() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getsampwidth}@anchor{2f88}
@deffn {方法} Wave_read.getsampwidth ()

返回采样字节长度。
@end deffn

@geindex getframerate() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getframerate}@anchor{2f89}
@deffn {方法} Wave_read.getframerate ()

返回采样频率。
@end deffn

@geindex getnframes() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getnframes}@anchor{2f8a}
@deffn {方法} Wave_read.getnframes ()

返回音频总帧数。
@end deffn

@geindex getcomptype() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getcomptype}@anchor{2f8b}
@deffn {方法} Wave_read.getcomptype ()

返回压缩类型（只支持 @code{'NONE'} 类型）
@end deffn

@geindex getcompname() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getcompname}@anchor{2f8c}
@deffn {方法} Wave_read.getcompname ()

@ref{2f8b,,getcomptype()} 的通俗版本。使用 @code{'not compressed'} 代替 @code{'NONE'}。
@end deffn

@geindex getparams() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getparams}@anchor{2f8d}
@deffn {方法} Wave_read.getparams ()

返回一个 @ref{1b6,,namedtuple()} @code{(nchannels, sampwidth, framerate, nframes, comptype, compname)}，与 @code{get*()} 方法的输出相同。
@end deffn

@geindex readframes() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read readframes}@anchor{2f8e}
@deffn {方法} Wave_read.readframes (n)

读取并返回以 @ref{32a,,bytes} 对象表示的最多 @emph{n} 帧音频。
@end deffn

@geindex rewind() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read rewind}@anchor{2f8f}
@deffn {方法} Wave_read.rewind ()

重置文件指针至音频开头.
@end deffn

后面两个方法是为了和 @ref{5,,aifc} 保持兼容，实际不做任何事情。

@geindex getmarkers() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getmarkers}@anchor{2f90}
@deffn {方法} Wave_read.getmarkers ()

返回 @code{None}。
@end deffn

@geindex getmark() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read getmark}@anchor{2f91}
@deffn {方法} Wave_read.getmark (id)

引发错误异常。
@end deffn

以下两个方法都使用指针，具体实现由其底层决定。

@geindex setpos() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read setpos}@anchor{2f92}
@deffn {方法} Wave_read.setpos (pos)

设置文件指针到指定位置。
@end deffn

@geindex tell() (wave.Wave_read 方法)
@anchor{library/wave wave Wave_read tell}@anchor{2f93}
@deffn {方法} Wave_read.tell ()

返回当前文件指针位置。
@end deffn

@node Wave_write 对象,,Wave_read对象,wave --- 读写WAV格式文件
@anchor{library/wave id2}@anchor{2f94}@anchor{library/wave wave-write-objects}@anchor{905}
@subsubsection Wave_write 对象


对于可查找的输出流，@code{wave} 头将自动更新以反映实际写入的帧数。 对于不可查找的流，当写入第一帧时 @emph{nframes} 值必须准确。 获取准确的 @emph{nframes} 值可以通过调用 @ref{2f95,,setnframes()} 或 @ref{2f96,,setparams()} 并附带 @ref{2f83,,close()} 被调用之前将要写入的帧数，然后使用 @ref{906,,writeframesraw()} 来写入帧数据，或者通过调用 @ref{907,,writeframes()} 并附带所有要写入的帧。 在后一种情况下 @ref{907,,writeframes()} 将计算数据中的帧数并在写入帧数据之前相应地设置 @emph{nframes}。

由 @ref{470,,open()} 返回的 Wave_write 对象，有以下几种方法:


在 3.4 版更改: 添加了对不可搜索文件的支持。


@geindex close() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write close}@anchor{2f83}
@deffn {方法} Wave_write.close ()

确保 @emph{nframes} 是正确的，并在文件被 @ref{127,,wave} 打开时关闭它。 此方法会在对象收集时被调用。 如果输出流不可查找且 @emph{nframes} 与实际写入的帧数不匹配时引发异常。
@end deffn

@geindex setnchannels() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write setnchannels}@anchor{2f97}
@deffn {方法} Wave_write.setnchannels (n)

设置声道数。
@end deffn

@geindex setsampwidth() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write setsampwidth}@anchor{2f98}
@deffn {方法} Wave_write.setsampwidth (n)

设置采样字节长度为 @emph{n}。
@end deffn

@geindex setframerate() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write setframerate}@anchor{2f99}
@deffn {方法} Wave_write.setframerate (n)

设置采样频率为 @emph{n}。


在 3.2 版更改: 对此方法的非整数输入会被舍入到最接近的整数。

@end deffn

@geindex setnframes() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write setnframes}@anchor{2f95}
@deffn {方法} Wave_write.setnframes (n)

设置总帧数为 @emph{n}。 如果与之后实际写入的帧数不一致此值将会被更改（ 如果输出流不可查找则此更改尝试将引发错误）。
@end deffn

@geindex setcomptype() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write setcomptype}@anchor{2f9a}
@deffn {方法} Wave_write.setcomptype (type, name)

设置压缩格式。目前只支持 @code{NONE} 即无压缩格式。
@end deffn

@geindex setparams() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write setparams}@anchor{2f96}
@deffn {方法} Wave_write.setparams (tuple)

@emph{tuple} 应该是 @code{(nchannels, sampwidth, framerate, nframes, comptype, compname)}，每项的值应可用于 @code{set*()} 方法。设置所有形参。
@end deffn

@geindex tell() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write tell}@anchor{2f9b}
@deffn {方法} Wave_write.tell ()

返回当前文件指针，其指针含义和 @ref{2f93,,Wave_read.tell()} 以及 @ref{2f92,,Wave_read.setpos()} 是一致的。
@end deffn

@geindex writeframesraw() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write writeframesraw}@anchor{906}
@deffn {方法} Wave_write.writeframesraw (data)

写入音频数据但不更新 @emph{nframes}。


在 3.4 版更改: 现在可接受任意 @ref{5e3,,bytes-like object}。

@end deffn

@geindex writeframes() (wave.Wave_write 方法)
@anchor{library/wave wave Wave_write writeframes}@anchor{907}
@deffn {方法} Wave_write.writeframes (data)

写入音频帧并确保 @emph{nframes} 是正确的。 如果输出流不可查找且在 @emph{data} 被写入之后写入的总帧数与之前设定的has been written does not match the previously set value for @emph{nframes} 值不匹配将会引发错误。


在 3.4 版更改: 现在可接受任意 @ref{5e3,,bytes-like object}。

@end deffn

注意在调用 @code{writeframes()} 或 @code{writeframesraw()} 之后再设置任何格式参数是无效的，而且任何这样的尝试将引发 @ref{2f84,,wave.Error}。

@node chunk --- 读取 IFF 分块数据,colorsys --- 颜色系统间的转换,wave --- 读写WAV格式文件,多媒体服务
@anchor{library/chunk doc}@anchor{2f9c}@anchor{library/chunk chunk-read-iff-chunked-data}@anchor{2f9d}@anchor{library/chunk module-chunk}@anchor{18}
@subsection @code{chunk} --- 读取 IFF 分块数据


@geindex chunk (模块)

@strong{源代码:} Lib/chunk.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/chunk.py}

@geindex Audio Interchange File Format
@geindex AIFF
@geindex AIFF-C
@geindex Real Media File Format
@geindex RMFF


__________________________________________________________________


本模块提供了一个读取使用 EA IFF 85 分块的数据的接口chunks. @footnote{@w{(1)} 
"EA IFF 85" 交换格式文件标准, Jerry Morrison, Electronic Arts, 1985 年 1 月。
}  这种格式使用的场合有 Audio Interchange File Format (AIFF/AIFF-C) 和 Real Media File Format (RMFF) 等。 与它们密切相关的 WAVE 音频文件也可使用此模块来读取。

一个分块具有以下结构:


@multitable {xxxxxxxxxxx} {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

偏移

@tab

长度

@tab

目录

@item

0

@tab

4

@tab

区块ID

@item

4

@tab

4

@tab

大端字节顺序的块大小，不包括头

@item

8

@tab

@emph{n}

@tab

数据字节，其中 @emph{n} 是前一字段中给出的大小

@item

8 + @emph{n}

@tab

0 或 1

@tab

如果 @emph{n} 为奇数且使用块对齐，则需要填充字节

@end multitable


ID是一个4字节的字符串，用于标识块的类型。

大小字段（32 位的值，使用大端字节序编码）给出分块数据的大小，不包括 8 字节的标头。

使用由一个或更多分块组成的 IFF 类型文件。 此处定义的 @ref{2f9e,,Chunk} 类的建议使用方式是在每个分块开始时实例化一个实例并从实例读取直到其末尾，在那之后可以再实例化新的实例。 到达文件末尾时，创建新实例将会失败并引发 @ref{c65,,EOFError} 异常。

@geindex Chunk (chunk 中的类)
@anchor{library/chunk chunk Chunk}@anchor{2f9e}
@deffn {类} chunk.Chunk (file, align=True, bigendian=True, inclheader=False)

代表一个分块的类。 @emph{file} 参数预期为一个文件类对象。 特别地也允许该类的实例。 唯一必需的方法是 @code{read()}。 如果存在 @ref{1d2d,,seek()} 和 @ref{1d2e,,tell()} 方法并且没有引发异常，它们也会被使用。 如果存在这些方法并且引发了异常，则它们不应改变目标对象。 如果可选参数 @emph{align} 为真值，则分块应当以 2 字节边界对齐。 如果 @emph{align} 为假值，则不使用对齐。 此参数默认为真值。 如果可选参数 @emph{bigendian} 为假值，分块大小应当为小端序。 这对于 WAVE 音频文件是必须的。 此参数默认为真值。 如果可选参数 @emph{inclheader} 为真值，则分块标头中给出的大小将包括标头的大小。 此参数默认为假值。

@ref{2f9e,,Chunk} 对象支持下列方法：

@geindex getname() (chunk.Chunk 方法)
@anchor{library/chunk chunk Chunk getname}@anchor{2f9f}
@deffn {方法} getname ()

返回分块的名称（ID）。 这是分块的头 4 个字节。
@end deffn

@geindex getsize() (chunk.Chunk 方法)
@anchor{library/chunk chunk Chunk getsize}@anchor{2fa0}
@deffn {方法} getsize ()

返回分块的大小。
@end deffn

@geindex close() (chunk.Chunk 方法)
@anchor{library/chunk chunk Chunk close}@anchor{2fa1}
@deffn {方法} close ()

关闭并跳转到分块的末尾。 这不会关闭下层的文件。
@end deffn

在 @ref{2fa1,,close()} 方法已被调用后其余方法将会引发 @ref{1d3,,OSError}。 在 Python 3.3 之前，它们曾会引发 @ref{98c,,IOError}，现在这是 @ref{1d3,,OSError} 的一个别名。

@geindex isatty() (chunk.Chunk 方法)
@anchor{library/chunk chunk Chunk isatty}@anchor{2fa2}
@deffn {方法} isatty ()

返回 @code{False}。
@end deffn

@geindex seek() (chunk.Chunk 方法)
@anchor{library/chunk chunk Chunk seek}@anchor{2fa3}
@deffn {方法} seek (pos, whence=0)

设置分块的当前位置。 @emph{whence} 参数为可选项并且默认为 @code{0} (绝对文件定位)；其他值还有 @code{1} (相对当前位置查找) 和 @code{2} (相对文件末尾查找)。 没有返回值。 如果下层文件不支持查找，则只允许向前查找。
@end deffn

@geindex tell() (chunk.Chunk 方法)
@anchor{library/chunk chunk Chunk tell}@anchor{2fa4}
@deffn {方法} tell ()

将当前位置返回到分块。
@end deffn

@geindex read() (chunk.Chunk 方法)
@anchor{library/chunk chunk Chunk read}@anchor{2fa5}
@deffn {方法} read (size=-1)

从分块读取至多 @emph{size} 个字节（如果在获得 @emph{size} 个字节之前已到达分块末尾则读取的字节会少于此数量）。 如果 @emph{size} 参数为负值或被省略，则读取所有字节直到分块末尾。 当立即遇到分块末尾则返回空字节串对象。
@end deffn

@geindex skip() (chunk.Chunk 方法)
@anchor{library/chunk chunk Chunk skip}@anchor{2fa6}
@deffn {方法} skip ()

跳到分块末尾。此后对分块再次调用 @ref{2fa5,,read()} 将返回 @code{b'@w{'}}。 如果你对分块的内容不感兴趣，则应当调用此方法以使文件指向下一分块的开头。
@end deffn
@end deffn

@subsubheading 备注


@node colorsys --- 颜色系统间的转换,imghdr --- 推测图像类型,chunk --- 读取 IFF 分块数据,多媒体服务
@anchor{library/colorsys doc}@anchor{2fa7}@anchor{library/colorsys colorsys-conversions-between-color-systems}@anchor{2fa8}@anchor{library/colorsys module-colorsys}@anchor{20}
@subsection @code{colorsys} --- 颜色系统间的转换


@geindex colorsys (模块)

@strong{源代码：} Lib/colorsys.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/colorsys.py}


__________________________________________________________________


@ref{20,,colorsys} 模块定义了计算机显示器所用的 RGB (Red Green Blue) 色彩空间与三种其他色彩坐标系统 YIQ, HLS (Hue Lightness Saturation) 和 HSV (Hue Saturation Value) 表示的颜色值之间的双向转换。 所有这些色彩空间的坐标都使用浮点数值来表示。 在 YIQ 空间中，Y 坐标取值为 0 和 1 之间，而 I 和 Q 坐标均可以为正数或负数。 在所有其他空间中，坐标取值均为 0 和 1 之间。


@subsubheading 参见


有关色彩空间的更多信息可访问 @indicateurl{http://poynton.ca/ColorFAQ.html} 和 @indicateurl{https://www.cambridgeincolour.com/tutorials/color-spaces.htm}.


@ref{20,,colorsys} 模块定义了如下函数：

@geindex rgb_to_yiq() (在 colorsys 模块中)
@anchor{library/colorsys colorsys rgb_to_yiq}@anchor{2fa9}
@deffn {函数} colorsys.rgb_to_yiq (r, g, b)

把颜色从RGB值转为YIQ值。
@end deffn

@geindex yiq_to_rgb() (在 colorsys 模块中)
@anchor{library/colorsys colorsys yiq_to_rgb}@anchor{2faa}
@deffn {函数} colorsys.yiq_to_rgb (y, i, q)

把颜色从YIQ值转为RGB值。
@end deffn

@geindex rgb_to_hls() (在 colorsys 模块中)
@anchor{library/colorsys colorsys rgb_to_hls}@anchor{2fab}
@deffn {函数} colorsys.rgb_to_hls (r, g, b)

把颜色从RGB值转为HLS值。
@end deffn

@geindex hls_to_rgb() (在 colorsys 模块中)
@anchor{library/colorsys colorsys hls_to_rgb}@anchor{2fac}
@deffn {函数} colorsys.hls_to_rgb (h, l, s)

把颜色从HLS值转为RGB值。
@end deffn

@geindex rgb_to_hsv() (在 colorsys 模块中)
@anchor{library/colorsys colorsys rgb_to_hsv}@anchor{2fad}
@deffn {函数} colorsys.rgb_to_hsv (r, g, b)

把颜色从RGB值转为HSV值。
@end deffn

@geindex hsv_to_rgb() (在 colorsys 模块中)
@anchor{library/colorsys colorsys hsv_to_rgb}@anchor{2fae}
@deffn {函数} colorsys.hsv_to_rgb (h, s, v)

把颜色从HSV值转为RGB值。
@end deffn

示例:

@example
>>> import colorsys
>>> colorsys.rgb_to_hsv(0.2, 0.4, 0.4)
(0.5, 0.5, 0.4)
>>> colorsys.hsv_to_rgb(0.5, 0.5, 0.4)
(0.2, 0.4, 0.4)
@end example

@node imghdr --- 推测图像类型,sndhdr --- 推测声音文件的类型,colorsys --- 颜色系统间的转换,多媒体服务
@anchor{library/imghdr doc}@anchor{2faf}@anchor{library/imghdr imghdr-determine-the-type-of-an-image}@anchor{2fb0}@anchor{library/imghdr module-imghdr}@anchor{99}
@subsection @code{imghdr} --- 推测图像类型


@geindex imghdr (模块)

@strong{源代码} Lib/imghdr.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/imghdr.py}


__________________________________________________________________


@ref{99,,imghdr} 模块推测文件或字节流中的图像的类型。

@ref{99,,imghdr} 模块定义了以下类型：

@geindex what() (在 imghdr 模块中)
@anchor{library/imghdr imghdr what}@anchor{6e7}
@deffn {函数} imghdr.what (filename, h=None)

测试包含在命名为 @emph{filename} 的文件中的图像数据，并且返回描述此类图片的字符串。如果可选的 @emph{h} 被提供， @emph{filename} 将被忽略并且 @emph{h} 包含将被测试的二进制流。


在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

接下来的图像类型是可识别的，返回值来自 @ref{6e7,,what()}：


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

图像格式

@item

@code{'rgb'}

@tab

SGI 图像库文件

@item

@code{'gif'}

@tab

GIF 87a 和 89a 文件

@item

@code{'pbm'}

@tab

便携式位图文件

@item

@code{'pgm'}

@tab

便携式灰度图文件

@item

@code{'ppm'}

@tab

便携式像素表文件

@item

@code{'tiff'}

@tab

TIFF 文件

@item

@code{'rast'}

@tab

Sun 光栅文件

@item

@code{'xbm'}

@tab

X 位图文件

@item

@code{'jpeg'}

@tab

JFIF 或 Exif 格式的 JPEG 数据

@item

@code{'bmp'}

@tab

BMP 文件

@item

@code{'png'}

@tab

便携式网络图像

@item

@code{'webp'}

@tab

WebP 文件

@item

@code{'exr'}

@tab

OpenEXR 文件

@end multitable



3.5 新版功能: @emph{exr} 和 @emph{webp} 格式被添加。


你可以扩展此 @ref{99,,imghdr} 可以被追加的这个变量识别的文件格式的列表：

@geindex tests() (在 imghdr 模块中)
@anchor{library/imghdr imghdr tests}@anchor{2fb1}
@deffn {数据} imghdr.tests

执行单个测试的函数列表。每个函数都有两个参数：字节流和类似开放文件的对象。当 @ref{6e7,,what()} 用字节流调用时，类文件对象将是 @code{None}。

如果测试成功，这个测试函数应当返回一个描述图像类型的字符串，否则返回 @code{None}。
@end deffn

示例:

@example
>>> import imghdr
>>> imghdr.what('bass.gif')
'gif'
@end example

@node sndhdr --- 推测声音文件的类型,ossaudiodev --- Access to OSS-compatible audio devices,imghdr --- 推测图像类型,多媒体服务
@anchor{library/sndhdr doc}@anchor{2fb2}@anchor{library/sndhdr module-sndhdr}@anchor{ee}@anchor{library/sndhdr sndhdr-determine-type-of-sound-file}@anchor{2fb3}
@subsection @code{sndhdr} --- 推测声音文件的类型


@geindex sndhdr (模块)

@c Based on comments in the module source file.

@strong{源代码} Lib/sndhdr.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/sndhdr.py}

@geindex A-LAW
@geindex u-LAW


__________________________________________________________________


@ref{ee,,sndhdr} 提供了企图猜测文件中的声音数据类型的功能函数。当这些函数可以推测出存储在文件中的声音数据的类型是，它们返回一个 @ref{1b6,,collections.namedtuple()}，包含了五种属性：（@code{filetype}, @code{framerate}, @code{nchannels}, @code{nframes}, @code{sampwidth}）。这些 @emph{type} 的值表示数据的类型，会是以下字符串之一： @code{'aifc'}, @code{'aiff'}, @code{'au'}, @code{'hcom'}, @code{'sndr'}, @code{'sndt'}, @code{'voc'}, @code{'wav'}, @code{'8svx'}, @code{'sb'}, @code{'ub'}, or @code{'ul'} 。 @emph{sampling_rate} 可能是实际值或者当未知或者难以解码时的 @code{0}。类似的， @emph{channels} 也会返回实际值或者在无法推测或者难以解码时返回 @code{0}。 @emph{frames} 则是实际值或 @code{-1}。 元组的最后一项， @emph{bits_per_sample} 将会为比特表示的 sample 大小或者 A-LAW 时为 @code{'A'}， u-LAW 时为 @code{'U'}。

@geindex what() (在 sndhdr 模块中)
@anchor{library/sndhdr sndhdr what}@anchor{741}
@deffn {函数} sndhdr.what (filename)

使用 @ref{742,,whathdr()} 推测存储在 @emph{filename} 文件中的声音数据的类型。如果成功，返回上述的命名元组，否则返回 @code{None}。


在 3.5 版更改: 将结果从元组改为命名元组。

@end deffn

@geindex whathdr() (在 sndhdr 模块中)
@anchor{library/sndhdr sndhdr whathdr}@anchor{742}
@deffn {函数} sndhdr.whathdr (filename)

基于文件头推测存储在文件中的声音数据类型。文件名由 @emph{filename} 给出。这个函数在成功时返回上述命名元组，或者在失败时返回 @code{None}。


在 3.5 版更改: 将结果从元组改为命名元组。

@end deffn

@node ossaudiodev --- Access to OSS-compatible audio devices,,sndhdr --- 推测声音文件的类型,多媒体服务
@anchor{library/ossaudiodev doc}@anchor{2fb4}@anchor{library/ossaudiodev module-ossaudiodev}@anchor{c6}@anchor{library/ossaudiodev ossaudiodev-access-to-oss-compatible-audio-devices}@anchor{2fb5}
@subsection @code{ossaudiodev} --- Access to OSS-compatible audio devices


@geindex ossaudiodev (模块)


__________________________________________________________________


This module allows you to access the OSS (Open Sound System) audio interface.
OSS is available for a wide range of open-source and commercial Unices, and is
the standard audio interface for Linux and recent versions of FreeBSD.

@c Things will get more complicated for future Linux versions, since
@c ALSA is in the standard kernel as of 2.5.x.  Presumably if you
@c use ALSA, you'll have to make sure its OSS compatibility layer
@c is active to use ossaudiodev, but you're going to need it for the vast
@c majority of Linux audio apps anyway.
@c 
@c Sounds like things are also complicated for other BSDs.  In response
@c to my python-dev query, Thomas Wouters said:
@c 
@c > Likewise, googling shows OpenBSD also uses OSS/Free -- the commercial
@c > OSS installation manual tells you to remove references to OSS/Free from the
@c > kernel :)
@c 
@c but Aleksander Piotrowsk actually has an OpenBSD box, and he quotes
@c from its <soundcard.h>:
@c >  * WARNING!  WARNING!
@c >  * This is an OSS (Linux) audio emulator.
@c >  * Use the Native NetBSD API for developing new code, and this
@c >  * only for compiling Linux programs.
@c 
@c There's also an ossaudio manpage on OpenBSD that explains things
@c further.  Presumably NetBSD and OpenBSD have a different standard
@c audio interface.  That's the great thing about standards, there are so
@c many to choose from ... ;-)
@c 
@c This probably all warrants a footnote or two, but I don't understand
@c things well enough right now to write it!   --GPW


在 3.3 版更改: Operations in this module now raise @ref{1d3,,OSError} where @ref{98c,,IOError}
was raised.



@subsubheading 参见



@table @asis

@item Open Sound System Programmer's Guide@footnote{http://www.opensound.com/pguide/oss.pdf}

the official documentation for the OSS C API
@end table

The module defines a large number of constants supplied by the OSS device
driver; see @code{<sys/soundcard.h>} on either Linux or FreeBSD for a listing.


@ref{c6,,ossaudiodev} defines the following variables and functions:

@geindex OSSAudioError
@anchor{library/ossaudiodev ossaudiodev OSSAudioError}@anchor{2fb6}
@deffn {例外} ossaudiodev.OSSAudioError

This exception is raised on certain errors.  The argument is a string describing
what went wrong.

(If @ref{c6,,ossaudiodev} receives an error from a system call such as
@code{open()}, @code{write()}, or @code{ioctl()}, it raises @ref{1d3,,OSError}.
Errors detected directly by @ref{c6,,ossaudiodev} result in @ref{2fb6,,OSSAudioError}.)

(For backwards compatibility, the exception class is also available as
@code{ossaudiodev.error}.)
@end deffn

@geindex open() (在 ossaudiodev 模块中)
@anchor{library/ossaudiodev ossaudiodev open}@anchor{2fb7}
@deffn {函数} ossaudiodev.open (mode)

@deffnx {函数} ossaudiodev.open (device, mode)

Open an audio device and return an OSS audio device object.  This object
supports many file-like methods, such as @code{read()}, @code{write()}, and
@code{fileno()} (although there are subtle differences between conventional Unix
read/write semantics and those of OSS audio devices).  It also supports a number
of audio-specific methods; see below for the complete list of methods.

@emph{device} is the audio device filename to use.  If it is not specified, this
module first looks in the environment variable 
@geindex AUDIODEV
@geindex 环境变量; AUDIODEV
@code{AUDIODEV} for a device
to use.  If not found, it falls back to @code{/dev/dsp}.

@emph{mode} is one of @code{'r'} for read-only (record) access, @code{'w'} for
write-only (playback) access and @code{'rw'} for both. Since many sound cards
only allow one process to have the recorder or player open at a time, it is a
good idea to open the device only for the activity needed.  Further, some
sound cards are half-duplex: they can be opened for reading or writing, but
not both at once.

Note the unusual calling syntax: the @emph{first} argument is optional, and the
second is required.  This is a historical artifact for compatibility with the
older @code{linuxaudiodev} module which @ref{c6,,ossaudiodev} supersedes.

@c XXX it might also be motivated
@c by my unfounded-but-still-possibly-true belief that the default
@c audio device varies unpredictably across operating systems.  -GW
@end deffn

@geindex openmixer() (在 ossaudiodev 模块中)
@anchor{library/ossaudiodev ossaudiodev openmixer}@anchor{2fb8}
@deffn {函数} ossaudiodev.openmixer ([device])

Open a mixer device and return an OSS mixer device object.   @emph{device} is the
mixer device filename to use.  If it is not specified, this module first looks
in the environment variable 
@geindex MIXERDEV
@geindex 环境变量; MIXERDEV
@code{MIXERDEV} for a device to use.  If not
found, it falls back to @code{/dev/mixer}.
@end deffn

@menu
* Audio Device Objects:: 
* Mixer Device Objects:: 

@end menu

@node Audio Device Objects,Mixer Device Objects,,ossaudiodev --- Access to OSS-compatible audio devices
@anchor{library/ossaudiodev audio-device-objects}@anchor{2fb9}@anchor{library/ossaudiodev ossaudio-device-objects}@anchor{2fba}
@subsubsection Audio Device Objects


Before you can write to or read from an audio device, you must call three
methods in the correct order:


@enumerate 

@item 
@code{setfmt()} to set the output format

@item 
@code{channels()} to set the number of channels

@item 
@code{speed()} to set the sample rate
@end enumerate

Alternately, you can use the @code{setparameters()} method to set all three audio
parameters at once.  This is more convenient, but may not be as flexible in all
cases.

The audio device objects returned by @ref{2fb7,,open()} define the following methods
and (read-only) attributes:

@geindex close() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device close}@anchor{2fbb}
@deffn {方法} oss_audio_device.close ()

Explicitly close the audio device.  When you are done writing to or reading from
an audio device, you should explicitly close it.  A closed device cannot be used
again.
@end deffn

@geindex fileno() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device fileno}@anchor{2fbc}
@deffn {方法} oss_audio_device.fileno ()

Return the file descriptor associated with the device.
@end deffn

@geindex read() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device read}@anchor{2fbd}
@deffn {方法} oss_audio_device.read (size)

Read @emph{size} bytes from the audio input and return them as a Python string.
Unlike most Unix device drivers, OSS audio devices in blocking mode (the
default) will block @ref{2fbd,,read()} until the entire requested amount of data is
available.
@end deffn

@geindex write() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device write}@anchor{2fbe}
@deffn {方法} oss_audio_device.write (data)

Write a @ref{5e3,,bytes-like object} @emph{data} to the audio device and return the
number of bytes written.  If the audio device is in blocking mode (the
default), the entire data is always written (again, this is different from
usual Unix device semantics).  If the device is in non-blocking mode, some
data may not be written---see @ref{2fbf,,writeall()}.


在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。

@end deffn

@geindex writeall() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device writeall}@anchor{2fbf}
@deffn {方法} oss_audio_device.writeall (data)

Write a @ref{5e3,,bytes-like object} @emph{data} to the audio device: waits until
the audio device is able to accept data, writes as much data as it will
accept, and repeats until @emph{data} has been completely written. If the device
is in blocking mode (the default), this has the same effect as
@ref{2fbe,,write()}; @ref{2fbf,,writeall()} is only useful in non-blocking mode.  Has
no return value, since the amount of data written is always equal to the
amount of data supplied.


在 3.5 版更改: 现在支持可写的 @ref{5e3,,字节类对象}。

@end deffn


在 3.2 版更改: Audio device objects also support the context management protocol, i.e. they can
be used in a @ref{6e3,,with} statement.


The following methods each map to exactly one @code{ioctl()} system call.  The
correspondence is obvious: for example, @code{setfmt()} corresponds to the
@code{SNDCTL_DSP_SETFMT} ioctl, and @code{sync()} to @code{SNDCTL_DSP_SYNC} (this can
be useful when consulting the OSS documentation).  If the underlying
@code{ioctl()} fails, they all raise @ref{1d3,,OSError}.

@geindex nonblock() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device nonblock}@anchor{2fc0}
@deffn {方法} oss_audio_device.nonblock ()

Put the device into non-blocking mode.  Once in non-blocking mode, there is no
way to return it to blocking mode.
@end deffn

@geindex getfmts() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device getfmts}@anchor{2fc1}
@deffn {方法} oss_audio_device.getfmts ()

Return a bitmask of the audio output formats supported by the soundcard.  Some
of the formats supported by OSS are:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

格式

@tab

描述

@item

@code{AFMT_MU_LAW}

@tab

a logarithmic encoding (used by Sun @code{.au}
files and @code{/dev/audio})

@item

@code{AFMT_A_LAW}

@tab

a logarithmic encoding

@item

@code{AFMT_IMA_ADPCM}

@tab

a 4:1 compressed format defined by the
Interactive Multimedia Association

@item

@code{AFMT_U8}

@tab

Unsigned, 8-bit audio

@item

@code{AFMT_S16_LE}

@tab

Signed, 16-bit audio, little-endian byte
order (as used by Intel processors)

@item

@code{AFMT_S16_BE}

@tab

Signed, 16-bit audio, big-endian byte order
(as used by 68k, PowerPC, Sparc)

@item

@code{AFMT_S8}

@tab

Signed, 8 bit audio

@item

@code{AFMT_U16_LE}

@tab

Unsigned, 16-bit little-endian audio

@item

@code{AFMT_U16_BE}

@tab

Unsigned, 16-bit big-endian audio

@end multitable


Consult the OSS documentation for a full list of audio formats, and note that
most devices support only a subset of these formats.  Some older devices only
support @code{AFMT_U8}; the most common format used today is
@code{AFMT_S16_LE}.
@end deffn

@geindex setfmt() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device setfmt}@anchor{2fc2}
@deffn {方法} oss_audio_device.setfmt (format)

Try to set the current audio format to @emph{format}---see @ref{2fc1,,getfmts()} for a
list.  Returns the audio format that the device was set to, which may not be the
requested format.  May also be used to return the current audio format---do this
by passing an "audio format" of @code{AFMT_QUERY}.
@end deffn

@geindex channels() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device channels}@anchor{2fc3}
@deffn {方法} oss_audio_device.channels (nchannels)

Set the number of output channels to @emph{nchannels}.  A value of 1 indicates
monophonic sound, 2 stereophonic.  Some devices may have more than 2 channels,
and some high-end devices may not support mono. Returns the number of channels
the device was set to.
@end deffn

@geindex speed() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device speed}@anchor{2fc4}
@deffn {方法} oss_audio_device.speed (samplerate)

Try to set the audio sampling rate to @emph{samplerate} samples per second.  Returns
the rate actually set.  Most sound devices don't support arbitrary sampling
rates.  Common rates are:


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

采样率

@tab

描述

@item

8000

@tab

@code{/dev/audio} 的默认采样率

@item

11025

@tab

语音录音

@item

22050

@tab

@item

44100

@tab

CD品质的音频（16位采样和2通道）

@item

96000

@tab

DVD品质的音频（24位采样）

@end multitable

@end deffn

@geindex sync() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device sync}@anchor{2fc5}
@deffn {方法} oss_audio_device.sync ()

Wait until the sound device has played every byte in its buffer.  (This happens
implicitly when the device is closed.)  The OSS documentation recommends closing
and re-opening the device rather than using @ref{2fc5,,sync()}.
@end deffn

@geindex reset() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device reset}@anchor{2fc6}
@deffn {方法} oss_audio_device.reset ()

Immediately stop playing or recording and return the device to a state where it
can accept commands.  The OSS documentation recommends closing and re-opening
the device after calling @ref{2fc6,,reset()}.
@end deffn

@geindex post() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device post}@anchor{2fc7}
@deffn {方法} oss_audio_device.post ()

Tell the driver that there is likely to be a pause in the output, making it
possible for the device to handle the pause more intelligently.  You might use
this after playing a spot sound effect, before waiting for user input, or before
doing disk I/O.
@end deffn

The following convenience methods combine several ioctls, or one ioctl and some
simple calculations.

@geindex setparameters() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device setparameters}@anchor{2fc8}
@deffn {方法} oss_audio_device.setparameters (format, nchannels, samplerate[, strict=False])

Set the key audio sampling parameters---sample format, number of channels, and
sampling rate---in one method call.  @emph{format},  @emph{nchannels}, and @emph{samplerate}
should be as specified in the @ref{2fc2,,setfmt()}, @ref{2fc3,,channels()}, and
@ref{2fc4,,speed()}  methods.  If @emph{strict} is true, @ref{2fc8,,setparameters()} checks to
see if each parameter was actually set to the requested value, and raises
@ref{2fb6,,OSSAudioError} if not.  Returns a tuple (@emph{format}, @emph{nchannels},
@emph{samplerate}) indicating the parameter values that were actually set by the
device driver (i.e., the same as the return values of @ref{2fc2,,setfmt()},
@ref{2fc3,,channels()}, and @ref{2fc4,,speed()}).

For example,

@example
(fmt, channels, rate) = dsp.setparameters(fmt, channels, rate)
@end example

is equivalent to

@example
fmt = dsp.setfmt(fmt)
channels = dsp.channels(channels)
rate = dsp.rate(rate)
@end example
@end deffn

@geindex bufsize() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device bufsize}@anchor{2fc9}
@deffn {方法} oss_audio_device.bufsize ()

Returns the size of the hardware buffer, in samples.
@end deffn

@geindex obufcount() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device obufcount}@anchor{2fca}
@deffn {方法} oss_audio_device.obufcount ()

Returns the number of samples that are in the hardware buffer yet to be played.
@end deffn

@geindex obuffree() (ossaudiodev.oss_audio_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device obuffree}@anchor{2fcb}
@deffn {方法} oss_audio_device.obuffree ()

Returns the number of samples that could be queued into the hardware buffer to
be played without blocking.
@end deffn

Audio device objects also support several read-only attributes:

@geindex closed (ossaudiodev.oss_audio_device 属性)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device closed}@anchor{2fcc}
@deffn {属性} oss_audio_device.closed

Boolean indicating whether the device has been closed.
@end deffn

@geindex name (ossaudiodev.oss_audio_device 属性)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device name}@anchor{2fcd}
@deffn {属性} oss_audio_device.name

String containing the name of the device file.
@end deffn

@geindex mode (ossaudiodev.oss_audio_device 属性)
@anchor{library/ossaudiodev ossaudiodev oss_audio_device mode}@anchor{2fce}
@deffn {属性} oss_audio_device.mode

The I/O mode for the file, either @code{"r"}, @code{"rw"}, or @code{"w"}.
@end deffn

@node Mixer Device Objects,,Audio Device Objects,ossaudiodev --- Access to OSS-compatible audio devices
@anchor{library/ossaudiodev id1}@anchor{2fcf}@anchor{library/ossaudiodev mixer-device-objects}@anchor{2fd0}
@subsubsection Mixer Device Objects


The mixer object provides two file-like methods:

@geindex close() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device close}@anchor{2fd1}
@deffn {方法} oss_mixer_device.close ()

This method closes the open mixer device file.  Any further attempts to use the
mixer after this file is closed will raise an @ref{1d3,,OSError}.
@end deffn

@geindex fileno() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device fileno}@anchor{2fd2}
@deffn {方法} oss_mixer_device.fileno ()

Returns the file handle number of the open mixer device file.
@end deffn


在 3.2 版更改: Mixer objects also support the context management protocol.


The remaining methods are specific to audio mixing:

@geindex controls() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device controls}@anchor{2fd3}
@deffn {方法} oss_mixer_device.controls ()

This method returns a bitmask specifying the available mixer controls ("Control"
being a specific mixable "channel", such as @code{SOUND_MIXER_PCM} or
@code{SOUND_MIXER_SYNTH}).  This bitmask indicates a subset of all available
mixer controls---the @code{SOUND_MIXER_*} constants defined at module level.
To determine if, for example, the current mixer object supports a PCM mixer, use
the following Python code:

@example
mixer=ossaudiodev.openmixer()
if mixer.controls() & (1 << ossaudiodev.SOUND_MIXER_PCM):
    # PCM is supported
    ... code ...
@end example

For most purposes, the @code{SOUND_MIXER_VOLUME} (master volume) and
@code{SOUND_MIXER_PCM} controls should suffice---but code that uses the mixer
should be flexible when it comes to choosing mixer controls.  On the Gravis
Ultrasound, for example, @code{SOUND_MIXER_VOLUME} does not exist.
@end deffn

@geindex stereocontrols() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device stereocontrols}@anchor{2fd4}
@deffn {方法} oss_mixer_device.stereocontrols ()

Returns a bitmask indicating stereo mixer controls.  If a bit is set, the
corresponding control is stereo; if it is unset, the control is either
monophonic or not supported by the mixer (use in combination with
@ref{2fd3,,controls()} to determine which).

See the code example for the @ref{2fd3,,controls()} function for an example of getting
data from a bitmask.
@end deffn

@geindex reccontrols() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device reccontrols}@anchor{2fd5}
@deffn {方法} oss_mixer_device.reccontrols ()

Returns a bitmask specifying the mixer controls that may be used to record.  See
the code example for @ref{2fd3,,controls()} for an example of reading from a bitmask.
@end deffn

@geindex get() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device get}@anchor{2fd6}
@deffn {方法} oss_mixer_device.get (control)

Returns the volume of a given mixer control.  The returned volume is a 2-tuple
@code{(left_volume,right_volume)}.  Volumes are specified as numbers from 0
(silent) to 100 (full volume).  If the control is monophonic, a 2-tuple is still
returned, but both volumes are the same.

Raises @ref{2fb6,,OSSAudioError} if an invalid control is specified, or
@ref{1d3,,OSError} if an unsupported control is specified.
@end deffn

@geindex set() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device set}@anchor{2fd7}
@deffn {方法} oss_mixer_device.set (control, (left, right))

Sets the volume for a given mixer control to @code{(left,right)}. @code{left} and
@code{right} must be ints and between 0 (silent) and 100 (full volume).  On
success, the new volume is returned as a 2-tuple. Note that this may not be
exactly the same as the volume specified, because of the limited resolution of
some soundcard's mixers.

Raises @ref{2fb6,,OSSAudioError} if an invalid mixer control was specified, or if the
specified volumes were out-of-range.
@end deffn

@geindex get_recsrc() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device get_recsrc}@anchor{2fd8}
@deffn {方法} oss_mixer_device.get_recsrc ()

This method returns a bitmask indicating which control(s) are currently being
used as a recording source.
@end deffn

@geindex set_recsrc() (ossaudiodev.oss_mixer_device 方法)
@anchor{library/ossaudiodev ossaudiodev oss_mixer_device set_recsrc}@anchor{2fd9}
@deffn {方法} oss_mixer_device.set_recsrc (bitmask)

Call this function to specify a recording source.  Returns a bitmask indicating
the new recording source (or sources) if successful; raises @ref{1d3,,OSError} if an
invalid source was specified.  To set the current recording source to the
microphone input:

@example
mixer.setrecsrc (1 << ossaudiodev.SOUND_MIXER_MIC)
@end example
@end deffn

@node 国际化,程序框架,多媒体服务,Python 标准库
@anchor{library/i18n doc}@anchor{2fda}@anchor{library/i18n i18n}@anchor{2fdb}@anchor{library/i18n internationalization}@anchor{2fdc}
@section 国际化


本章中介绍的模块通过提供选择要在程序信息中使用的语言的机制或通过定制输出以匹配本地约定来帮助你编写不依赖于语言和区域设置的软件。

本章中描述的模块列表是：

@menu
* gettext: gettext --- 多语种国际化服务. 多语种国际化服务
* locale: locale --- 国际化服务. 国际化服务

@end menu

@node gettext --- 多语种国际化服务,locale --- 国际化服务,,国际化
@anchor{library/gettext doc}@anchor{2fdd}@anchor{library/gettext gettext-multilingual-internationalization-services}@anchor{2fde}@anchor{library/gettext module-gettext}@anchor{89}
@subsection @code{gettext} --- 多语种国际化服务


@geindex gettext (模块)

@strong{源代码：} Lib/gettext.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/gettext.py}


__________________________________________________________________


The @ref{89,,gettext} module provides internationalization (I18N) and localization
(L10N) services for your Python modules and applications. It supports both the
GNU @code{gettext} message catalog API and a higher level, class-based API that may
be more appropriate for Python files.  The interface described below allows you
to write your module and application messages in one natural language, and
provide a catalog of translated messages for running under different natural
languages.

同时还给出一些本地化 Python 模块及应用程序的小技巧。

@menu
* GNU gettext API:: 
* Class-based API:: 
* Internationalizing your programs and modules:: 
* 致谢: 致谢<9>. 

@end menu

@node GNU gettext API,Class-based API,,gettext --- 多语种国际化服务
@anchor{library/gettext gnu-gettext-api}@anchor{2fdf}
@subsubsection GNU @code{gettext} API


模块 @ref{89,,gettext} 定义了下列  API，这与 @code{gettext} API 类似。如果你使用该 API，将会对整个应用程序产生全局的影响。如果你的应用程序支持多语种，而语言选择取决于用户的区域设置，这通常正是你所想要的。而如果你正在本地化某个 Python 模块，或者你的应用程序需要在运行时切换语言，相反你或许想用基于类的API。

@geindex bindtextdomain() (在 gettext 模块中)
@anchor{library/gettext gettext bindtextdomain}@anchor{2fe0}
@deffn {函数} gettext.bindtextdomain (domain, localedir=None)

Bind the @emph{domain} to the locale directory @emph{localedir}.  More concretely,
@ref{89,,gettext} will look for binary @code{.mo} files for the given domain using
the path (on Unix): @code{@emph{localedir}/@emph{language}/LC_MESSAGES/@emph{domain}.mo}, where
@emph{language} is searched for in the environment variables 
@geindex LANGUAGE
@geindex 环境变量; LANGUAGE
@code{LANGUAGE},
@geindex LC_ALL
@geindex 环境变量; LC_ALL
@code{LC_ALL}, 
@geindex LC_MESSAGES
@geindex 环境变量; LC_MESSAGES
@code{LC_MESSAGES}, and 
@geindex LANG
@geindex 环境变量; LANG
@code{LANG} respectively.

如果遗漏了 @emph{localedir} 或者设置为 @code{None}，那么将返回当前 @emph{domain} 所绑定的值 @footnote{@w{(1)} 
The default locale directory is system dependent; for example, on RedHat Linux
it is @code{/usr/share/locale}, but on Solaris it is @code{/usr/lib/locale}.
The @ref{89,,gettext} module does not try to support these system dependent
defaults; instead its default is @code{@emph{sys.base_prefix}/share/locale} (see
@ref{2fe1,,sys.base_prefix}). For this reason, it is always best to call
@ref{2fe0,,bindtextdomain()} with an explicit absolute path at the start of your
application.
}
@end deffn

@geindex bind_textdomain_codeset() (在 gettext 模块中)
@anchor{library/gettext gettext bind_textdomain_codeset}@anchor{297}
@deffn {函数} gettext.bind_textdomain_codeset (domain, codeset=None)

Bind the @emph{domain} to @emph{codeset}, changing the encoding of byte strings
returned by the @ref{293,,lgettext()}, @ref{294,,ldgettext()}, @ref{295,,lngettext()}
and @ref{296,,ldngettext()} functions.
If @emph{codeset} is omitted, then the current binding is returned.


Deprecated since version 3.8, will be removed in version 3.10.

@end deffn

@geindex textdomain() (在 gettext 模块中)
@anchor{library/gettext gettext textdomain}@anchor{2fe2}
@deffn {函数} gettext.textdomain (domain=None)

Change or query the current global domain.  If @emph{domain} is @code{None}, then the
current global domain is returned, otherwise the global domain is set to
@emph{domain}, which is returned.
@end deffn

@geindex _ (underscore); gettext

@geindex gettext() (在 gettext 模块中)
@anchor{library/gettext gettext gettext}@anchor{dc6}
@deffn {函数} gettext.gettext (message)

Return the localized translation of @emph{message}, based on the current global
domain, language, and locale directory.  This function is usually aliased as
@code{_()} in the local namespace (see examples below).
@end deffn

@geindex dgettext() (在 gettext 模块中)
@anchor{library/gettext gettext dgettext}@anchor{2fe3}
@deffn {函数} gettext.dgettext (domain, message)

Like @ref{dc6,,gettext()}, but look the message up in the specified @emph{domain}.
@end deffn

@geindex ngettext() (在 gettext 模块中)
@anchor{library/gettext gettext ngettext}@anchor{2fe4}
@deffn {函数} gettext.ngettext (singular, plural, n)

Like @ref{dc6,,gettext()}, but consider plural forms. If a translation is found,
apply the plural formula to @emph{n}, and return the resulting message (some
languages have more than two plural forms). If no translation is found, return
@emph{singular} if @emph{n} is 1; return @emph{plural} otherwise.

The Plural formula is taken from the catalog header. It is a C or Python
expression that has a free variable @emph{n}; the expression evaluates to the index
of the plural in the catalog. See
the GNU gettext documentation@footnote{https://www.gnu.org/software/gettext/manual/gettext.html}
for the precise syntax to be used in @code{.po} files and the
formulas for a variety of languages.
@end deffn

@geindex dngettext() (在 gettext 模块中)
@anchor{library/gettext gettext dngettext}@anchor{2fe5}
@deffn {函数} gettext.dngettext (domain, singular, plural, n)

Like @ref{2fe4,,ngettext()}, but look the message up in the specified @emph{domain}.
@end deffn

@geindex pgettext() (在 gettext 模块中)
@anchor{library/gettext gettext pgettext}@anchor{1cf}
@deffn {函数} gettext.pgettext (context, message)
@end deffn

@geindex dpgettext() (在 gettext 模块中)
@anchor{library/gettext gettext dpgettext}@anchor{2fe6}
@deffn {函数} gettext.dpgettext (domain, context, message)
@end deffn

@geindex npgettext() (在 gettext 模块中)
@anchor{library/gettext gettext npgettext}@anchor{2fe7}
@deffn {函数} gettext.npgettext (context, singular, plural, n)
@end deffn

@geindex dnpgettext() (在 gettext 模块中)
@anchor{library/gettext gettext dnpgettext}@anchor{2fe8}
@deffn {函数} gettext.dnpgettext (domain, context, singular, plural, n)

Similar to the corresponding functions without the @code{p} in the prefix (that
is, @ref{89,,gettext()}, @ref{2fe3,,dgettext()}, @ref{2fe4,,ngettext()}, @ref{2fe5,,dngettext()}),
but the translation is restricted to the given message @emph{context}.


3.8 新版功能.

@end deffn

@geindex lgettext() (在 gettext 模块中)
@anchor{library/gettext gettext lgettext}@anchor{293}
@deffn {函数} gettext.lgettext (message)
@end deffn

@geindex ldgettext() (在 gettext 模块中)
@anchor{library/gettext gettext ldgettext}@anchor{294}
@deffn {函数} gettext.ldgettext (domain, message)
@end deffn

@geindex lngettext() (在 gettext 模块中)
@anchor{library/gettext gettext lngettext}@anchor{295}
@deffn {函数} gettext.lngettext (singular, plural, n)
@end deffn

@geindex ldngettext() (在 gettext 模块中)
@anchor{library/gettext gettext ldngettext}@anchor{296}
@deffn {函数} gettext.ldngettext (domain, singular, plural, n)

Equivalent to the corresponding functions without the @code{l} prefix
(@ref{dc6,,gettext()}, @ref{2fe3,,dgettext()}, @ref{2fe4,,ngettext()} and @ref{2fe5,,dngettext()}),
but the translation is returned as a byte string encoded in the preferred
system encoding if no other encoding was explicitly set with
@ref{297,,bind_textdomain_codeset()}.

@cartouche
@quotation 警告 
These functions should be avoided in Python 3, because they return
encoded bytes.  It's much better to use alternatives which return
Unicode strings instead, since most Python applications will want to
manipulate human readable text as strings instead of bytes.  Further,
it's possible that you may get unexpected Unicode-related exceptions
if there are encoding problems with the translated strings.
@end quotation
@end cartouche


Deprecated since version 3.8, will be removed in version 3.10.

@end deffn

Note that GNU @code{gettext} also defines a @code{dcgettext()} method, but
this was deemed not useful and so it is currently unimplemented.

Here's an example of typical usage for this API:

@example
import gettext
gettext.bindtextdomain('myapplication', '/path/to/my/language/directory')
gettext.textdomain('myapplication')
_ = gettext.gettext
# ...
print(_('This is a translatable string.'))
@end example

@node Class-based API,Internationalizing your programs and modules,GNU gettext API,gettext --- 多语种国际化服务
@anchor{library/gettext class-based-api}@anchor{2fe9}
@subsubsection Class-based API


The class-based API of the @ref{89,,gettext} module gives you more flexibility and
greater convenience than the GNU @code{gettext} API.  It is the recommended
way of localizing your Python applications and modules.  @code{gettext} defines
a @ref{2fea,,GNUTranslations} class which implements the parsing of GNU @code{.mo} format
files, and has methods for returning strings. Instances of this class can also
install themselves in the built-in namespace as the function @code{_()}.

@geindex find() (在 gettext 模块中)
@anchor{library/gettext gettext find}@anchor{2feb}
@deffn {函数} gettext.find (domain, localedir=None, languages=None, all=False)

This function implements the standard @code{.mo} file search algorithm.  It
takes a @emph{domain}, identical to what @ref{2fe2,,textdomain()} takes.  Optional
@emph{localedir} is as in @ref{2fe0,,bindtextdomain()}. Optional @emph{languages} is a list of
strings, where each string is a language code.

If @emph{localedir} is not given, then the default system locale directory is used.
@footnote{@w{(2)} 
See the footnote for @ref{2fe0,,bindtextdomain()} above.
}  If @emph{languages} is not given, then the following environment variables are
searched: 
@geindex LANGUAGE
@geindex 环境变量; LANGUAGE
@code{LANGUAGE}, 
@geindex LC_ALL
@geindex 环境变量; LC_ALL
@code{LC_ALL}, 
@geindex LC_MESSAGES
@geindex 环境变量; LC_MESSAGES
@code{LC_MESSAGES}, and
@geindex LANG
@geindex 环境变量; LANG
@code{LANG}.  The first one returning a non-empty value is used for the
@emph{languages} variable. The environment variables should contain a colon separated
list of languages, which will be split on the colon to produce the expected list
of language code strings.

@ref{2feb,,find()} then expands and normalizes the languages, and then iterates
through them, searching for an existing file built of these components:

@code{@emph{localedir}/@emph{language}/LC_MESSAGES/@emph{domain}.mo}

The first such file name that exists is returned by @ref{2feb,,find()}. If no such
file is found, then @code{None} is returned. If @emph{all} is given, it returns a list
of all file names, in the order in which they appear in the languages list or
the environment variables.
@end deffn

@geindex translation() (在 gettext 模块中)
@anchor{library/gettext gettext translation}@anchor{29a}
@deffn {函数} gettext.translation (domain, localedir=None, languages=None, class_=None, fallback=False, codeset=None)

Return a @code{*Translations} instance based on the @emph{domain}, @emph{localedir},
and @emph{languages}, which are first passed to @ref{2feb,,find()} to get a list of the
associated @code{.mo} file paths.  Instances with identical @code{.mo} file
names are cached.  The actual class instantiated is @emph{class_} if
provided, otherwise @ref{2fea,,GNUTranslations}.  The class's constructor must
take a single @ref{b3b,,file object} argument.  If provided, @emph{codeset} will change
the charset used to encode translated strings in the
@ref{2fec,,lgettext()} and @ref{2fed,,lngettext()}
methods.

If multiple files are found, later files are used as fallbacks for earlier ones.
To allow setting the fallback, @ref{3c3,,copy.copy()} is used to clone each
translation object from the cache; the actual instance data is still shared with
the cache.

If no @code{.mo} file is found, this function raises @ref{1d3,,OSError} if
@emph{fallback} is false (which is the default), and returns a
@ref{2fee,,NullTranslations} instance if @emph{fallback} is true.


在 3.3 版更改: 曾经是 @ref{98c,,IOError} 被引发而不是 @ref{1d3,,OSError} 。



Deprecated since version 3.8, will be removed in version 3.10: The @emph{codeset} parameter.

@end deffn

@geindex install() (在 gettext 模块中)
@anchor{library/gettext gettext install}@anchor{29b}
@deffn {函数} gettext.install (domain, localedir=None, codeset=None, names=None)

This installs the function @code{_()} in Python's builtins namespace, based on
@emph{domain}, @emph{localedir}, and @emph{codeset} which are passed to the function
@ref{29a,,translation()}.

For the @emph{names} parameter, please see the description of the translation
object's @ref{2fef,,install()} method.

As seen below, you usually mark the strings in your application that are
candidates for translation, by wrapping them in a call to the @code{_()}
function, like this:

@example
print(_('This string will be translated.'))
@end example

For convenience, you want the @code{_()} function to be installed in Python's
builtins namespace, so it is easily accessible in all modules of your
application.


Deprecated since version 3.8, will be removed in version 3.10: The @emph{codeset} parameter.

@end deffn

@menu
* The NullTranslations class:: 
* The GNUTranslations class:: 
* Solaris message catalog support:: 
* The Catalog constructor:: 

@end menu

@node The NullTranslations class,The GNUTranslations class,,Class-based API
@anchor{library/gettext the-nulltranslations-class}@anchor{2ff0}
@subsubsection The @code{NullTranslations} class


Translation classes are what actually implement the translation of original
source file message strings to translated message strings. The base class used
by all translation classes is @ref{2fee,,NullTranslations}; this provides the basic
interface you can use to write your own specialized translation classes.  Here
are the methods of @code{NullTranslations}:

@geindex NullTranslations (gettext 中的类)
@anchor{library/gettext gettext NullTranslations}@anchor{2fee}
@deffn {类} gettext.NullTranslations (fp=None)

Takes an optional @ref{b3b,,file object} @emph{fp}, which is ignored by the base class.
Initializes "protected" instance variables @emph{_info} and @emph{_charset} which are set
by derived classes, as well as @emph{_fallback}, which is set through
@ref{2ff1,,add_fallback()}.  It then calls @code{self._parse(fp)} if @emph{fp} is not
@code{None}.

@geindex _parse() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations _parse}@anchor{2ff2}
@deffn {方法} _parse (fp)

No-op in the base class, this method takes file object @emph{fp}, and reads
the data from the file, initializing its message catalog.  If you have an
unsupported message catalog file format, you should override this method
to parse your format.
@end deffn

@geindex add_fallback() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations add_fallback}@anchor{2ff1}
@deffn {方法} add_fallback (fallback)

Add @emph{fallback} as the fallback object for the current translation object.
A translation object should consult the fallback if it cannot provide a
translation for a given message.
@end deffn

@geindex gettext() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations gettext}@anchor{2ff3}
@deffn {方法} gettext (message)

If a fallback has been set, forward @code{gettext()} to the fallback.
Otherwise, return @emph{message}.  Overridden in derived classes.
@end deffn

@geindex ngettext() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations ngettext}@anchor{2ff4}
@deffn {方法} ngettext (singular, plural, n)

If a fallback has been set, forward @code{ngettext()} to the fallback.
Otherwise, return @emph{singular} if @emph{n} is 1; return @emph{plural} otherwise.
Overridden in derived classes.
@end deffn

@geindex pgettext() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations pgettext}@anchor{2ff5}
@deffn {方法} pgettext (context, message)

If a fallback has been set, forward @ref{1cf,,pgettext()} to the fallback.
Otherwise, return the translated message.  Overridden in derived classes.


3.8 新版功能.

@end deffn

@geindex npgettext() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations npgettext}@anchor{2ff6}
@deffn {方法} npgettext (context, singular, plural, n)

If a fallback has been set, forward @ref{2fe7,,npgettext()} to the fallback.
Otherwise, return the translated message.  Overridden in derived classes.


3.8 新版功能.

@end deffn

@geindex lgettext() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations lgettext}@anchor{2fec}
@deffn {方法} lgettext (message)
@end deffn

@geindex lngettext() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations lngettext}@anchor{2fed}
@deffn {方法} lngettext (singular, plural, n)

Equivalent to @ref{2ff3,,gettext()} and @ref{2ff4,,ngettext()}, but the translation
is returned as a byte string encoded in the preferred system encoding
if no encoding was explicitly set with @ref{299,,set_output_charset()}.
Overridden in derived classes.

@cartouche
@quotation 警告 
These methods should be avoided in Python 3.  See the warning for the
@ref{293,,lgettext()} function.
@end quotation
@end cartouche


Deprecated since version 3.8, will be removed in version 3.10.

@end deffn

@geindex info() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations info}@anchor{2ff7}
@deffn {方法} info ()

Return the "protected" @code{_info} variable, a dictionary containing
the metadata found in the message catalog file.
@end deffn

@geindex charset() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations charset}@anchor{2ff8}
@deffn {方法} charset ()

Return the encoding of the message catalog file.
@end deffn

@geindex output_charset() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations output_charset}@anchor{298}
@deffn {方法} output_charset ()

Return the encoding used to return translated messages in @ref{2fec,,lgettext()}
and @ref{2fed,,lngettext()}.


Deprecated since version 3.8, will be removed in version 3.10.

@end deffn

@geindex set_output_charset() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations set_output_charset}@anchor{299}
@deffn {方法} set_output_charset (charset)

Change the encoding used to return translated messages.


Deprecated since version 3.8, will be removed in version 3.10.

@end deffn

@geindex install() (gettext.NullTranslations 方法)
@anchor{library/gettext gettext NullTranslations install}@anchor{2fef}
@deffn {方法} install (names=None)

This method installs @ref{2ff3,,gettext()} into the built-in namespace,
binding it to @code{_}.

If the @emph{names} parameter is given, it must be a sequence containing the
names of functions you want to install in the builtins namespace in
addition to @code{_()}.  Supported names are @code{'gettext'}, @code{'ngettext'},
@code{'pgettext'}, @code{'npgettext'}, @code{'lgettext'}, and @code{'lngettext'}.

Note that this is only one way, albeit the most convenient way, to make
the @code{_()} function available to your application.  Because it affects
the entire application globally, and specifically the built-in namespace,
localized modules should never install @code{_()}. Instead, they should use
this code to make @code{_()} available to their module:

@example
import gettext
t = gettext.translation('mymodule', ...)
_ = t.gettext
@end example

This puts @code{_()} only in the module's global namespace and so only
affects calls within this module.


在 3.8 版更改: Added @code{'pgettext'} and @code{'npgettext'}.

@end deffn
@end deffn

@node The GNUTranslations class,Solaris message catalog support,The NullTranslations class,Class-based API
@anchor{library/gettext the-gnutranslations-class}@anchor{2ff9}
@subsubsection The @code{GNUTranslations} class


The @ref{89,,gettext} module provides one additional class derived from
@ref{2fee,,NullTranslations}: @ref{2fea,,GNUTranslations}.  This class overrides
@code{_parse()} to enable reading GNU @code{gettext} format @code{.mo} files
in both big-endian and little-endian format.

@ref{2fea,,GNUTranslations} parses optional metadata out of the translation
catalog. It is convention with GNU @code{gettext} to include metadata as
the translation for the empty string. This metadata is in 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html}-style
@code{key: value} pairs, and should contain the @code{Project-Id-Version} key.  If the
key @code{Content-Type} is found, then the @code{charset} property is used to
initialize the "protected" @code{_charset} instance variable, defaulting to
@code{None} if not found.  If the charset encoding is specified, then all message
ids and message strings read from the catalog are converted to Unicode using
this encoding, else ASCII is assumed.

Since message ids are read as Unicode strings too, all @code{*gettext()} methods
will assume message ids as Unicode strings, not byte strings.

The entire set of key/value pairs are placed into a dictionary and set as the
"protected" @code{_info} instance variable.

If the @code{.mo} file's magic number is invalid, the major version number is
unexpected, or if other problems occur while reading the file, instantiating a
@ref{2fea,,GNUTranslations} class can raise @ref{1d3,,OSError}.

@geindex GNUTranslations (gettext 中的类)
@anchor{library/gettext gettext GNUTranslations}@anchor{2fea}
@deffn {类} gettext.GNUTranslations

The following methods are overridden from the base class implementation:

@geindex gettext() (gettext.GNUTranslations 方法)
@anchor{library/gettext gettext GNUTranslations gettext}@anchor{2ffa}
@deffn {方法} gettext (message)

Look up the @emph{message} id in the catalog and return the corresponding message
string, as a Unicode string.  If there is no entry in the catalog for the
@emph{message} id, and a fallback has been set, the look up is forwarded to the
fallback's @ref{2ff3,,gettext()} method.  Otherwise, the
@emph{message} id is returned.
@end deffn

@geindex ngettext() (gettext.GNUTranslations 方法)
@anchor{library/gettext gettext GNUTranslations ngettext}@anchor{2ffb}
@deffn {方法} ngettext (singular, plural, n)

Do a plural-forms lookup of a message id.  @emph{singular} is used as the message id
for purposes of lookup in the catalog, while @emph{n} is used to determine which
plural form to use.  The returned message string is a Unicode string.

If the message id is not found in the catalog, and a fallback is specified,
the request is forwarded to the fallback's @ref{2ff4,,ngettext()}
method.  Otherwise, when @emph{n} is 1 @emph{singular} is returned, and @emph{plural} is
returned in all other cases.

Here is an example:

@example
n = len(os.listdir('.'))
cat = GNUTranslations(somefile)
message = cat.ngettext(
    'There is %(num)d file in this directory',
    'There are %(num)d files in this directory',
    n) % @{'num': n@}
@end example
@end deffn

@geindex pgettext() (gettext.GNUTranslations 方法)
@anchor{library/gettext gettext GNUTranslations pgettext}@anchor{2ffc}
@deffn {方法} pgettext (context, message)

Look up the @emph{context} and @emph{message} id in the catalog and return the
corresponding message string, as a Unicode string.  If there is no
entry in the catalog for the @emph{message} id and @emph{context}, and a fallback
has been set, the look up is forwarded to the fallback's
@ref{1cf,,pgettext()} method.  Otherwise, the @emph{message} id is returned.


3.8 新版功能.

@end deffn

@geindex npgettext() (gettext.GNUTranslations 方法)
@anchor{library/gettext gettext GNUTranslations npgettext}@anchor{2ffd}
@deffn {方法} npgettext (context, singular, plural, n)

Do a plural-forms lookup of a message id.  @emph{singular} is used as the
message id for purposes of lookup in the catalog, while @emph{n} is used to
determine which plural form to use.

If the message id for @emph{context} is not found in the catalog, and a
fallback is specified, the request is forwarded to the fallback's
@ref{2fe7,,npgettext()} method.  Otherwise, when @emph{n} is 1 @emph{singular} is
returned, and @emph{plural} is returned in all other cases.


3.8 新版功能.

@end deffn

@geindex lgettext() (gettext.GNUTranslations 方法)
@anchor{library/gettext gettext GNUTranslations lgettext}@anchor{2ffe}
@deffn {方法} lgettext (message)
@end deffn

@geindex lngettext() (gettext.GNUTranslations 方法)
@anchor{library/gettext gettext GNUTranslations lngettext}@anchor{2fff}
@deffn {方法} lngettext (singular, plural, n)

Equivalent to @ref{2ffa,,gettext()} and @ref{2ffb,,ngettext()}, but the translation
is returned as a byte string encoded in the preferred system encoding
if no encoding  was explicitly set with
@ref{299,,set_output_charset()}.

@cartouche
@quotation 警告 
These methods should be avoided in Python 3.  See the warning for the
@ref{293,,lgettext()} function.
@end quotation
@end cartouche


Deprecated since version 3.8, will be removed in version 3.10.

@end deffn
@end deffn

@node Solaris message catalog support,The Catalog constructor,The GNUTranslations class,Class-based API
@anchor{library/gettext solaris-message-catalog-support}@anchor{3000}
@subsubsection Solaris message catalog support


The Solaris operating system defines its own binary @code{.mo} file format, but
since no documentation can be found on this format, it is not supported at this
time.

@node The Catalog constructor,,Solaris message catalog support,Class-based API
@anchor{library/gettext the-catalog-constructor}@anchor{3001}
@subsubsection The Catalog constructor


@geindex GNOME

GNOME uses a version of the @ref{89,,gettext} module by James Henstridge, but this
version has a slightly different API.  Its documented usage was:

@example
import gettext
cat = gettext.Catalog(domain, localedir)
_ = cat.gettext
print(_('hello world'))
@end example

For compatibility with this older module, the function @code{Catalog()} is an
alias for the @ref{29a,,translation()} function described above.

One difference between this module and Henstridge's: his catalog objects
supported access through a mapping API, but this appears to be unused and so is
not currently supported.

@node Internationalizing your programs and modules,致谢<9>,Class-based API,gettext --- 多语种国际化服务
@anchor{library/gettext internationalizing-your-programs-and-modules}@anchor{3002}
@subsubsection Internationalizing your programs and modules


Internationalization (I18N) refers to the operation by which a program is made
aware of multiple languages.  Localization (L10N) refers to the adaptation of
your program, once internationalized, to the local language and cultural habits.
In order to provide multilingual messages for your Python programs, you need to
take the following steps:


@enumerate 

@item 
prepare your program or module by specially marking translatable strings

@item 
run a suite of tools over your marked files to generate raw messages catalogs

@item 
create language-specific translations of the message catalogs

@item 
use the @ref{89,,gettext} module so that message strings are properly translated
@end enumerate

In order to prepare your code for I18N, you need to look at all the strings in
your files.  Any string that needs to be translated should be marked by wrapping
it in @code{_('...')} --- that is, a call to the function @code{_()}.  For example:

@example
filename = 'mylog.txt'
message = _('writing a log message')
with open(filename, 'w') as fp:
    fp.write(message)
@end example

In this example, the string @code{'writing a log message'} is marked as a candidate
for translation, while the strings @code{'mylog.txt'} and @code{'w'} are not.

There are a few tools to extract the strings meant for translation.
The original GNU @code{gettext} only supported C or C++ source
code but its extended version @code{xgettext} scans code written
in a number of languages, including Python, to find strings marked as
translatable.  Babel@footnote{http://babel.pocoo.org/} is a Python
internationalization library that includes a @code{pybabel} script to
extract and compile message catalogs.  François Pinard's program
called @code{xpot} does a similar job and is available as part of
his po-utils package@footnote{https://github.com/pinard/po-utils}.

(Python also includes pure-Python versions of these programs, called
@code{pygettext.py} and @code{msgfmt.py}; some Python distributions
will install them for you.  @code{pygettext.py} is similar to
@code{xgettext}, but only understands Python source code and
cannot handle other programming languages such as C or C++.
@code{pygettext.py} supports a command-line interface similar to
@code{xgettext}; for details on its use, run @code{pygettext.py
--help}.  @code{msgfmt.py} is binary compatible with GNU
@code{msgfmt}.  With these two programs, you may not need the GNU
@code{gettext} package to internationalize your Python
applications.)

@code{xgettext}, @code{pygettext}, and similar tools generate
@code{.po} files that are message catalogs.  They are structured
human-readable files that contain every marked string in the source
code, along with a placeholder for the translated versions of these
strings.

Copies of these @code{.po} files are then handed over to the
individual human translators who write translations for every
supported natural language.  They send back the completed
language-specific versions as a @code{<language-name>.po} file that's
compiled into a machine-readable @code{.mo} binary catalog file using
the @code{msgfmt} program.  The @code{.mo} files are used by the
@ref{89,,gettext} module for the actual translation processing at
run-time.

How you use the @ref{89,,gettext} module in your code depends on whether you are
internationalizing a single module or your entire application. The next two
sections will discuss each case.

@menu
* Localizing your module:: 
* Localizing your application:: 
* Changing languages on the fly:: 
* Deferred translations:: 

@end menu

@node Localizing your module,Localizing your application,,Internationalizing your programs and modules
@anchor{library/gettext localizing-your-module}@anchor{3003}
@subsubsection Localizing your module


If you are localizing your module, you must take care not to make global
changes, e.g. to the built-in namespace. You should not use the GNU @code{gettext}
API but instead the class-based API.

Let's say your module is called "spam" and the module's various natural language
translation @code{.mo} files reside in @code{/usr/share/locale} in GNU
@code{gettext} format.  Here's what you would put at the top of your
module:

@example
import gettext
t = gettext.translation('spam', '/usr/share/locale')
_ = t.gettext
@end example

@node Localizing your application,Changing languages on the fly,Localizing your module,Internationalizing your programs and modules
@anchor{library/gettext localizing-your-application}@anchor{3004}
@subsubsection Localizing your application


If you are localizing your application, you can install the @code{_()} function
globally into the built-in namespace, usually in the main driver file of your
application.  This will let all your application-specific files just use
@code{_('...')} without having to explicitly install it in each file.

In the simple case then, you need only add the following bit of code to the main
driver file of your application:

@example
import gettext
gettext.install('myapplication')
@end example

If you need to set the locale directory, you can pass it into the
@ref{29b,,install()} function:

@example
import gettext
gettext.install('myapplication', '/usr/share/locale')
@end example

@node Changing languages on the fly,Deferred translations,Localizing your application,Internationalizing your programs and modules
@anchor{library/gettext changing-languages-on-the-fly}@anchor{3005}
@subsubsection Changing languages on the fly


If your program needs to support many languages at the same time, you may want
to create multiple translation instances and then switch between them
explicitly, like so:

@example
import gettext

lang1 = gettext.translation('myapplication', languages=['en'])
lang2 = gettext.translation('myapplication', languages=['fr'])
lang3 = gettext.translation('myapplication', languages=['de'])

# start by using language1
lang1.install()

# ... time goes by, user selects language 2
lang2.install()

# ... more time goes by, user selects language 3
lang3.install()
@end example

@node Deferred translations,,Changing languages on the fly,Internationalizing your programs and modules
@anchor{library/gettext deferred-translations}@anchor{3006}
@subsubsection Deferred translations


In most coding situations, strings are translated where they are coded.
Occasionally however, you need to mark strings for translation, but defer actual
translation until later.  A classic example is:

@example
animals = ['mollusk',
           'albatross',
           'rat',
           'penguin',
           'python', ]
# ...
for a in animals:
    print(a)
@end example

Here, you want to mark the strings in the @code{animals} list as being
translatable, but you don't actually want to translate them until they are
printed.

Here is one way you can handle this situation:

@example
def _(message): return message

animals = [_('mollusk'),
           _('albatross'),
           _('rat'),
           _('penguin'),
           _('python'), ]

del _

# ...
for a in animals:
    print(_(a))
@end example

This works because the dummy definition of @code{_()} simply returns the string
unchanged.  And this dummy definition will temporarily override any definition
of @code{_()} in the built-in namespace (until the @ref{1202,,del} command). Take
care, though if you have a previous definition of @code{_()} in the local
namespace.

Note that the second use of @code{_()} will not identify "a" as being
translatable to the @code{gettext} program, because the parameter
is not a string literal.

Another way to handle this is with the following example:

@example
def N_(message): return message

animals = [N_('mollusk'),
           N_('albatross'),
           N_('rat'),
           N_('penguin'),
           N_('python'), ]

# ...
for a in animals:
    print(_(a))
@end example

In this case, you are marking translatable strings with the function
@code{N_()}, which won't conflict with any definition of @code{_()}.
However, you will need to teach your message extraction program to
look for translatable strings marked with @code{N_()}. @code{xgettext},
@code{pygettext}, @code{pybabel extract}, and @code{xpot} all
support this through the use of the @code{-k} command-line switch.
The choice of @code{N_()} here is totally arbitrary; it could have just
as easily been @code{MarkThisStringForTranslation()}.

@node 致谢<9>,,Internationalizing your programs and modules,gettext --- 多语种国际化服务
@anchor{library/gettext acknowledgements}@anchor{3007}
@subsubsection 致谢


以下人员为创建此模块贡献了代码、反馈、设计建议、早期实现和宝贵的经验：


@itemize *

@item 
Peter Funk

@item 
James Henstridge

@item 
Juan David Ibáñez Palomar

@item 
Marc-André Lemburg

@item 
Martin von Löwis

@item 
François Pinard

@item 
Barry Warsaw

@item 
Gustavo Niemeyer
@end itemize

@subsubheading 备注


@node locale --- 国际化服务,,gettext --- 多语种国际化服务,国际化
@anchor{library/locale doc}@anchor{3008}@anchor{library/locale locale-internationalization-services}@anchor{3009}@anchor{library/locale module-locale}@anchor{a9}
@subsection @code{locale} --- 国际化服务


@geindex locale (模块)

@strong{源代码：} Lib/locale.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/locale.py}


__________________________________________________________________


The @ref{a9,,locale} module opens access to the POSIX locale database and
functionality. The POSIX locale mechanism allows programmers to deal with
certain cultural issues in an application, without requiring the programmer to
know all the specifics of each country where the software is executed.

@geindex 模块; _locale

The @ref{a9,,locale} module is implemented on top of the @code{_locale} module,
which in turn uses an ANSI C locale implementation if available.

The @ref{a9,,locale} module defines the following exception and functions:

@geindex Error
@anchor{library/locale locale Error}@anchor{300a}
@deffn {例外} locale.Error

Exception raised when the locale passed to @ref{1fa1,,setlocale()} is not
recognized.
@end deffn

@geindex setlocale() (在 locale 模块中)
@anchor{library/locale locale setlocale}@anchor{1fa1}
@deffn {函数} locale.setlocale (category, locale=None)

If @emph{locale} is given and not @code{None}, @ref{1fa1,,setlocale()} modifies the locale
setting for the @emph{category}. The available categories are listed in the data
description below. @emph{locale} may be a string, or an iterable of two strings
(language code and encoding). If it's an iterable, it's converted to a locale
name using the locale aliasing engine. An empty string specifies the user's
default settings. If the modification of the locale fails, the exception
@ref{300a,,Error} is raised. If successful, the new locale setting is returned.

If @emph{locale} is omitted or @code{None}, the current setting for @emph{category} is
returned.

@ref{1fa1,,setlocale()} is not thread-safe on most systems. Applications typically
start with a call of

@example
import locale
locale.setlocale(locale.LC_ALL, '@w{'})
@end example

This sets the locale for all categories to the user's default setting (typically
specified in the 
@geindex LANG
@geindex 环境变量; LANG
@code{LANG} environment variable).  If the locale is not
changed thereafter, using multithreading should not cause problems.
@end deffn

@geindex localeconv() (在 locale 模块中)
@anchor{library/locale locale localeconv}@anchor{484}
@deffn {函数} locale.localeconv ()

以字典的形式返回本地约定的数据库。此字典具有以下字符串作为键：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

类别

@tab

键

@tab

含义

@item

@ref{300b,,LC_NUMERIC}

@tab

@code{'decimal_point'}

@tab

小数点字符。

@item

@tab

@code{'grouping'}

@tab

Sequence of numbers specifying
which relative positions the
@code{'thousands_sep'} is
expected.  If the sequence is
terminated with
@ref{300c,,CHAR_MAX}, no further
grouping is performed. If the
sequence terminates with a
@code{0},  the last group size is
repeatedly used.

@item

@tab

@code{'thousands_sep'}

@tab

组之间使用的字符。

@item

@ref{300d,,LC_MONETARY}

@tab

@code{'int_curr_symbol'}

@tab

国际货币符号。

@item

@tab

@code{'currency_symbol'}

@tab

当地货币符号。

@item

@tab

@code{'p_cs_precedes/n_cs_precedes'}

@tab

货币符号是否在值之前（对于正值或负值）。

@item

@tab

@code{'p_sep_by_space/n_sep_by_space'}

@tab

货币符号是否通过空格与值分隔（对于正值或负值）。

@item

@tab

@code{'mon_decimal_point'}

@tab

用于货币金额的小数点。

@item

@tab

@code{'frac_digits'}

@tab

货币值的本地格式中使用的小数位数。

@item

@tab

@code{'int_frac_digits'}

@tab

货币价值的国际格式中使用的小数位数。

@item

@tab

@code{'mon_thousands_sep'}

@tab

用于货币值的组分隔符。

@item

@tab

@code{'mon_grouping'}

@tab

相当于 @code{'grouping'} ，用于货币价值。

@item

@tab

@code{'positive_sign'}

@tab

用于标注正货币价值的符号。

@item

@tab

@code{'negative_sign'}

@tab

用于注释负货币价值的符号。

@item

@tab

@code{'p_sign_posn/n_sign_posn'}

@tab

符号的位置（对于正值或负值），见下文。

@end multitable


可以将所有数值设置为 @ref{300c,,CHAR_MAX} ，以指示此语言环境中未指定任何值。

下面给出了 @code{'p_sign_posn'} 和 @code{'n_sign_posn'} 的可能值。


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

说明

@item

@code{0}

@tab

被括号括起来的货币和金额。

@item

@code{1}

@tab

该标志应位于值和货币符号之前。

@item

@code{2}

@tab

该标志应位于值和货币符号之后。

@item

@code{3}

@tab

标志应该紧跟在值之前。

@item

@code{4}

@tab

标志应该紧跟值项。

@item

@code{CHAR_MAX}

@tab

此语言环境中未指定任何内容。

@end multitable


The function sets temporarily the @code{LC_CTYPE} locale to the @code{LC_NUMERIC}
locale or the @code{LC_MONETARY} locale if locales are different and numeric or
monetary strings are non-ASCII. This temporary change affects other threads.


在 3.7 版更改: The function now sets temporarily the @code{LC_CTYPE} locale to the
@code{LC_NUMERIC} locale in some cases.

@end deffn

@geindex nl_langinfo() (在 locale 模块中)
@anchor{library/locale locale nl_langinfo}@anchor{300e}
@deffn {函数} locale.nl_langinfo (option)

Return some locale-specific information as a string.  This function is not
available on all systems, and the set of possible options might also vary
across platforms.  The possible argument values are numbers, for which
symbolic constants are available in the locale module.

The @ref{300e,,nl_langinfo()} function accepts one of the following keys.  Most
descriptions are taken from the corresponding description in the GNU C
library.

@geindex CODESET() (在 locale 模块中)
@anchor{library/locale locale CODESET}@anchor{300f}
@deffn {数据} locale.CODESET

Get a string with the name of the character encoding used in the
selected locale.
@end deffn

@geindex D_T_FMT() (在 locale 模块中)
@anchor{library/locale locale D_T_FMT}@anchor{3010}
@deffn {数据} locale.D_T_FMT

Get a string that can be used as a format string for @ref{b5e,,time.strftime()} to
represent date and time in a locale-specific way.
@end deffn

@geindex D_FMT() (在 locale 模块中)
@anchor{library/locale locale D_FMT}@anchor{3011}
@deffn {数据} locale.D_FMT

Get a string that can be used as a format string for @ref{b5e,,time.strftime()} to
represent a date in a locale-specific way.
@end deffn

@geindex T_FMT() (在 locale 模块中)
@anchor{library/locale locale T_FMT}@anchor{3012}
@deffn {数据} locale.T_FMT

Get a string that can be used as a format string for @ref{b5e,,time.strftime()} to
represent a time in a locale-specific way.
@end deffn

@geindex T_FMT_AMPM() (在 locale 模块中)
@anchor{library/locale locale T_FMT_AMPM}@anchor{3013}
@deffn {数据} locale.T_FMT_AMPM

Get a format string for @ref{b5e,,time.strftime()} to represent time in the am/pm
format.
@end deffn


@deffn {数据} DAY_1 ... DAY_7

Get the name of the n-th day of the week.

@cartouche
@quotation 注解 
This follows the US convention of @code{DAY_1} being Sunday, not the
international convention (ISO 8601) that Monday is the first day of the
week.
@end quotation
@end cartouche
@end deffn


@deffn {数据} ABDAY_1 ... ABDAY_7

Get the abbreviated name of the n-th day of the week.
@end deffn


@deffn {数据} MON_1 ... MON_12

Get the name of the n-th month.
@end deffn


@deffn {数据} ABMON_1 ... ABMON_12

Get the abbreviated name of the n-th month.
@end deffn

@geindex RADIXCHAR() (在 locale 模块中)
@anchor{library/locale locale RADIXCHAR}@anchor{3014}
@deffn {数据} locale.RADIXCHAR

Get the radix character (decimal dot, decimal comma, etc.).
@end deffn

@geindex THOUSEP() (在 locale 模块中)
@anchor{library/locale locale THOUSEP}@anchor{3015}
@deffn {数据} locale.THOUSEP

Get the separator character for thousands (groups of three digits).
@end deffn

@geindex YESEXPR() (在 locale 模块中)
@anchor{library/locale locale YESEXPR}@anchor{3016}
@deffn {数据} locale.YESEXPR

Get a regular expression that can be used with the regex function to
recognize a positive response to a yes/no question.

@cartouche
@quotation 注解 
The expression is in the syntax suitable for the @code{regex()} function
from the C library, which might differ from the syntax used in @ref{dd,,re}.
@end quotation
@end cartouche
@end deffn

@geindex NOEXPR() (在 locale 模块中)
@anchor{library/locale locale NOEXPR}@anchor{3017}
@deffn {数据} locale.NOEXPR

Get a regular expression that can be used with the regex(3) function to
recognize a negative response to a yes/no question.
@end deffn

@geindex CRNCYSTR() (在 locale 模块中)
@anchor{library/locale locale CRNCYSTR}@anchor{3018}
@deffn {数据} locale.CRNCYSTR

Get the currency symbol, preceded by "-" if the symbol should appear before
the value, "+" if the symbol should appear after the value, or "." if the
symbol should replace the radix character.
@end deffn

@geindex ERA() (在 locale 模块中)
@anchor{library/locale locale ERA}@anchor{3019}
@deffn {数据} locale.ERA

Get a string that represents the era used in the current locale.

Most locales do not define this value.  An example of a locale which does
define this value is the Japanese one.  In Japan, the traditional
representation of dates includes the name of the era corresponding to the
then-emperor's reign.

Normally it should not be necessary to use this value directly. Specifying
the @code{E} modifier in their format strings causes the @ref{b5e,,time.strftime()}
function to use this information.  The format of the returned string is not
specified, and therefore you should not assume knowledge of it on different
systems.
@end deffn

@geindex ERA_D_T_FMT() (在 locale 模块中)
@anchor{library/locale locale ERA_D_T_FMT}@anchor{301a}
@deffn {数据} locale.ERA_D_T_FMT

Get a format string for @ref{b5e,,time.strftime()} to represent date and time in a
locale-specific era-based way.
@end deffn

@geindex ERA_D_FMT() (在 locale 模块中)
@anchor{library/locale locale ERA_D_FMT}@anchor{301b}
@deffn {数据} locale.ERA_D_FMT

Get a format string for @ref{b5e,,time.strftime()} to represent a date in a
locale-specific era-based way.
@end deffn

@geindex ERA_T_FMT() (在 locale 模块中)
@anchor{library/locale locale ERA_T_FMT}@anchor{301c}
@deffn {数据} locale.ERA_T_FMT

Get a format string for @ref{b5e,,time.strftime()} to represent a time in a
locale-specific era-based way.
@end deffn

@geindex ALT_DIGITS() (在 locale 模块中)
@anchor{library/locale locale ALT_DIGITS}@anchor{301d}
@deffn {数据} locale.ALT_DIGITS

Get a representation of up to 100 values used to represent the values
0 to 99.
@end deffn
@end deffn

@geindex getdefaultlocale() (在 locale 模块中)
@anchor{library/locale locale getdefaultlocale}@anchor{12f6}
@deffn {函数} locale.getdefaultlocale ([envvars])

Tries to determine the default locale settings and returns them as a tuple of
the form @code{(language code, encoding)}.

According to POSIX, a program which has not called @code{setlocale(LC_ALL, '@w{'})}
runs using the portable @code{'C'} locale.  Calling @code{setlocale(LC_ALL, '@w{'})} lets
it use the default locale as defined by the 
@geindex LANG
@geindex 环境变量; LANG
@code{LANG} variable.  Since we
do not want to interfere with the current locale setting we thus emulate the
behavior in the way described above.

To maintain compatibility with other platforms, not only the 
@geindex LANG
@geindex 环境变量; LANG
@code{LANG}
variable is tested, but a list of variables given as envvars parameter.  The
first found to be defined will be used.  @emph{envvars} defaults to the search
path used in GNU gettext; it must always contain the variable name
@code{'LANG'}.  The GNU gettext search path contains @code{'LC_ALL'},
@code{'LC_CTYPE'}, @code{'LANG'} and @code{'LANGUAGE'}, in that order.

Except for the code @code{'C'}, the language code corresponds to 
@geindex RFC; RFC 1766
RFC 1766@footnote{https://tools.ietf.org/html/rfc1766.html}.
@emph{language code} and @emph{encoding} may be @code{None} if their values cannot be
determined.
@end deffn

@geindex getlocale() (在 locale 模块中)
@anchor{library/locale locale getlocale}@anchor{1889}
@deffn {函数} locale.getlocale (category=LC_CTYPE)

Returns the current setting for the given locale category as sequence containing
@emph{language code}, @emph{encoding}. @emph{category} may be one of the @code{LC_*} values
except @ref{301e,,LC_ALL}.  It defaults to @ref{301f,,LC_CTYPE}.

Except for the code @code{'C'}, the language code corresponds to 
@geindex RFC; RFC 1766
RFC 1766@footnote{https://tools.ietf.org/html/rfc1766.html}.
@emph{language code} and @emph{encoding} may be @code{None} if their values cannot be
determined.
@end deffn

@geindex getpreferredencoding() (在 locale 模块中)
@anchor{library/locale locale getpreferredencoding}@anchor{39d}
@deffn {函数} locale.getpreferredencoding (do_setlocale=True)

Return the encoding used for text data, according to user preferences.  User
preferences are expressed differently on different systems, and might not be
available programmatically on some systems, so this function only returns a
guess.

On some systems, it is necessary to invoke @ref{1fa1,,setlocale()} to obtain the user
preferences, so this function is not thread-safe. If invoking setlocale is not
necessary or desired, @emph{do_setlocale} should be set to @code{False}.

On Android or in the UTF-8 mode (@ref{155,,-X} @code{utf8} option), always
return @code{'UTF-8'}, the locale and the @emph{do_setlocale} argument are ignored.


在 3.7 版更改: The function now always returns @code{UTF-8} on Android or if the UTF-8 mode
is enabled.

@end deffn

@geindex normalize() (在 locale 模块中)
@anchor{library/locale locale normalize}@anchor{3020}
@deffn {函数} locale.normalize (localename)

Returns a normalized locale code for the given locale name.  The returned locale
code is formatted for use with @ref{1fa1,,setlocale()}.  If normalization fails, the
original name is returned unchanged.

If the given encoding is not known, the function defaults to the default
encoding for the locale code just like @ref{1fa1,,setlocale()}.
@end deffn

@geindex resetlocale() (在 locale 模块中)
@anchor{library/locale locale resetlocale}@anchor{3021}
@deffn {函数} locale.resetlocale (category=LC_ALL)

Sets the locale for @emph{category} to the default setting.

The default setting is determined by calling @ref{12f6,,getdefaultlocale()}.
@emph{category} defaults to @ref{301e,,LC_ALL}.
@end deffn

@geindex strcoll() (在 locale 模块中)
@anchor{library/locale locale strcoll}@anchor{3022}
@deffn {函数} locale.strcoll (string1, string2)

Compares two strings according to the current @ref{3023,,LC_COLLATE} setting. As
any other compare function, returns a negative, or a positive value, or @code{0},
depending on whether @emph{string1} collates before or after @emph{string2} or is equal to
it.
@end deffn

@geindex strxfrm() (在 locale 模块中)
@anchor{library/locale locale strxfrm}@anchor{3024}
@deffn {函数} locale.strxfrm (string)

Transforms a string to one that can be used in locale-aware
comparisons.  For example, @code{strxfrm(s1) < strxfrm(s2)} is
equivalent to @code{strcoll(s1, s2) < 0}.  This function can be used
when the same string is compared repeatedly, e.g. when collating a
sequence of strings.
@end deffn

@geindex format_string() (在 locale 模块中)
@anchor{library/locale locale format_string}@anchor{39c}
@deffn {函数} locale.format_string (format, val, grouping=False, monetary=False)

Formats a number @emph{val} according to the current @ref{300b,,LC_NUMERIC} setting.
The format follows the conventions of the @code{%} operator.  For floating point
values, the decimal point is modified if appropriate.  If @emph{grouping} is true,
also takes the grouping into account.

If @emph{monetary} is true, the conversion uses monetary thousands separator and
grouping strings.

Processes formatting specifiers as in @code{format % val}, but takes the current
locale settings into account.


在 3.7 版更改: The @emph{monetary} keyword parameter was added.

@end deffn

@geindex format() (在 locale 模块中)
@anchor{library/locale locale format}@anchor{462}
@deffn {函数} locale.format (format, val, grouping=False, monetary=False)

Please note that this function works like @ref{39c,,format_string()} but will
only work for exactly one @code{%char} specifier.  For example, @code{'%f'} and
@code{'%.0f'} are both valid specifiers, but @code{'%f KiB'} is not.

For whole format strings, use @ref{39c,,format_string()}.


3.7 版后已移除: Use @ref{39c,,format_string()} instead.

@end deffn

@geindex currency() (在 locale 模块中)
@anchor{library/locale locale currency}@anchor{3025}
@deffn {函数} locale.currency (val, symbol=True, grouping=False, international=False)

Formats a number @emph{val} according to the current @ref{300d,,LC_MONETARY} settings.

The returned string includes the currency symbol if @emph{symbol} is true, which is
the default. If @emph{grouping} is true (which is not the default), grouping is done
with the value. If @emph{international} is true (which is not the default), the
international currency symbol is used.

Note that this function will not work with the 'C' locale, so you have to set a
locale via @ref{1fa1,,setlocale()} first.
@end deffn

@geindex str() (在 locale 模块中)
@anchor{library/locale locale str}@anchor{3026}
@deffn {函数} locale.str (float)

Formats a floating point number using the same format as the built-in function
@code{str(float)}, but takes the decimal point into account.
@end deffn

@geindex delocalize() (在 locale 模块中)
@anchor{library/locale locale delocalize}@anchor{705}
@deffn {函数} locale.delocalize (string)

Converts a string into a normalized number string, following the
@ref{300b,,LC_NUMERIC} settings.


3.5 新版功能.

@end deffn

@geindex atof() (在 locale 模块中)
@anchor{library/locale locale atof}@anchor{3027}
@deffn {函数} locale.atof (string)

Converts a string to a floating point number, following the @ref{300b,,LC_NUMERIC}
settings.
@end deffn

@geindex atoi() (在 locale 模块中)
@anchor{library/locale locale atoi}@anchor{3028}
@deffn {函数} locale.atoi (string)

Converts a string to an integer, following the @ref{300b,,LC_NUMERIC} conventions.
@end deffn

@geindex LC_CTYPE() (在 locale 模块中)
@anchor{library/locale locale LC_CTYPE}@anchor{301f}
@deffn {数据} locale.LC_CTYPE

@geindex 模块; string

Locale category for the character type functions.  Depending on the settings of
this category, the functions of module @ref{f6,,string} dealing with case change
their behaviour.
@end deffn

@geindex LC_COLLATE() (在 locale 模块中)
@anchor{library/locale locale LC_COLLATE}@anchor{3023}
@deffn {数据} locale.LC_COLLATE

Locale category for sorting strings.  The functions @ref{3022,,strcoll()} and
@ref{3024,,strxfrm()} of the @ref{a9,,locale} module are affected.
@end deffn

@geindex LC_TIME() (在 locale 模块中)
@anchor{library/locale locale LC_TIME}@anchor{3029}
@deffn {数据} locale.LC_TIME

Locale category for the formatting of time.  The function @ref{b5e,,time.strftime()}
follows these conventions.
@end deffn

@geindex LC_MONETARY() (在 locale 模块中)
@anchor{library/locale locale LC_MONETARY}@anchor{300d}
@deffn {数据} locale.LC_MONETARY

Locale category for formatting of monetary values.  The available options are
available from the @ref{484,,localeconv()} function.
@end deffn

@geindex LC_MESSAGES() (在 locale 模块中)
@anchor{library/locale locale LC_MESSAGES}@anchor{302a}
@deffn {数据} locale.LC_MESSAGES

Locale category for message display. Python currently does not support
application specific locale-aware messages.  Messages displayed by the operating
system, like those returned by @ref{1e99,,os.strerror()} might be affected by this
category.
@end deffn

@geindex LC_NUMERIC() (在 locale 模块中)
@anchor{library/locale locale LC_NUMERIC}@anchor{300b}
@deffn {数据} locale.LC_NUMERIC

Locale category for formatting numbers.  The functions @ref{462,,format()},
@ref{3028,,atoi()}, @ref{3027,,atof()} and @ref{3026,,str()} of the @ref{a9,,locale} module are
affected by that category.  All other numeric formatting operations are not
affected.
@end deffn

@geindex LC_ALL() (在 locale 模块中)
@anchor{library/locale locale LC_ALL}@anchor{301e}
@deffn {数据} locale.LC_ALL

Combination of all locale settings.  If this flag is used when the locale is
changed, setting the locale for all categories is attempted. If that fails for
any category, no category is changed at all.  When the locale is retrieved using
this flag, a string indicating the setting for all categories is returned. This
string can be later used to restore the settings.
@end deffn

@geindex CHAR_MAX() (在 locale 模块中)
@anchor{library/locale locale CHAR_MAX}@anchor{300c}
@deffn {数据} locale.CHAR_MAX

This is a symbolic constant used for different values returned by
@ref{484,,localeconv()}.
@end deffn

示例:

@example
>>> import locale
>>> loc = locale.getlocale()  # get current locale
# use German locale; name might vary with platform
>>> locale.setlocale(locale.LC_ALL, 'de_DE')
>>> locale.strcoll('f\xe4n', 'foo')  # compare a string containing an umlaut
>>> locale.setlocale(locale.LC_ALL, '@w{'})   # use user's preferred locale
>>> locale.setlocale(locale.LC_ALL, 'C')  # use default (C) locale
>>> locale.setlocale(locale.LC_ALL, loc)  # restore saved locale
@end example

@menu
* Background@comma{} details@comma{} hints@comma{} tips and caveats: Background details hints tips and caveats. 
* For extension writers and programs that embed Python:: 
* Access to message catalogs:: 

@end menu

@node Background details hints tips and caveats,For extension writers and programs that embed Python,,locale --- 国际化服务
@anchor{library/locale background-details-hints-tips-and-caveats}@anchor{302b}
@subsubsection Background, details, hints, tips and caveats


The C standard defines the locale as a program-wide property that may be
relatively expensive to change.  On top of that, some implementation are broken
in such a way that frequent locale changes may cause core dumps.  This makes the
locale somewhat painful to use correctly.

Initially, when a program is started, the locale is the @code{C} locale, no matter
what the user's preferred locale is.  There is one exception: the
@ref{301f,,LC_CTYPE} category is changed at startup to set the current locale
encoding to the user's preferred locale encoding. The program must explicitly
say that it wants the user's preferred locale settings for other categories by
calling @code{setlocale(LC_ALL, '@w{'})}.

It is generally a bad idea to call @ref{1fa1,,setlocale()} in some library routine,
since as a side effect it affects the entire program.  Saving and restoring it
is almost as bad: it is expensive and affects other threads that happen to run
before the settings have been restored.

If, when coding a module for general use, you need a locale independent version
of an operation that is affected by the locale (such as
certain formats used with @ref{b5e,,time.strftime()}), you will have to find a way to
do it without using the standard library routine.  Even better is convincing
yourself that using locale settings is okay.  Only as a last resort should you
document that your module is not compatible with non-@code{C} locale settings.

The only way to perform numeric operations according to the locale is to use the
special functions defined by this module: @ref{3027,,atof()}, @ref{3028,,atoi()},
@ref{462,,format()}, @ref{3026,,str()}.

There is no way to perform case conversions and character classifications
according to the locale.  For (Unicode) text strings these are done according
to the character value only, while for byte strings, the conversions and
classifications are done according to the ASCII value of the byte, and bytes
whose high bit is set (i.e., non-ASCII bytes) are never converted or considered
part of a character class such as letter or whitespace.

@node For extension writers and programs that embed Python,Access to message catalogs,Background details hints tips and caveats,locale --- 国际化服务
@anchor{library/locale embedding-locale}@anchor{302c}@anchor{library/locale for-extension-writers-and-programs-that-embed-python}@anchor{302d}
@subsubsection For extension writers and programs that embed Python


Extension modules should never call @ref{1fa1,,setlocale()}, except to find out what
the current locale is.  But since the return value can only be used portably to
restore it, that is not very useful (except perhaps to find out whether or not
the locale is @code{C}).

When Python code uses the @ref{a9,,locale} module to change the locale, this also
affects the embedding application.  If the embedding application doesn't want
this to happen, it should remove the @code{_locale} extension module (which does
all the work) from the table of built-in modules in the @code{config.c} file,
and make sure that the @code{_locale} module is not accessible as a shared
library.

@node Access to message catalogs,,For extension writers and programs that embed Python,locale --- 国际化服务
@anchor{library/locale access-to-message-catalogs}@anchor{302e}@anchor{library/locale locale-gettext}@anchor{302f}
@subsubsection Access to message catalogs


@geindex gettext() (在 locale 模块中)
@anchor{library/locale locale gettext}@anchor{3030}
@deffn {函数} locale.gettext (msg)
@end deffn

@geindex dgettext() (在 locale 模块中)
@anchor{library/locale locale dgettext}@anchor{3031}
@deffn {函数} locale.dgettext (domain, msg)
@end deffn

@geindex dcgettext() (在 locale 模块中)
@anchor{library/locale locale dcgettext}@anchor{3032}
@deffn {函数} locale.dcgettext (domain, msg, category)
@end deffn

@geindex textdomain() (在 locale 模块中)
@anchor{library/locale locale textdomain}@anchor{3033}
@deffn {函数} locale.textdomain (domain)
@end deffn

@geindex bindtextdomain() (在 locale 模块中)
@anchor{library/locale locale bindtextdomain}@anchor{3034}
@deffn {函数} locale.bindtextdomain (domain, dir)
@end deffn

The locale module exposes the C library's gettext interface on systems that
provide this interface.  It consists of the functions @code{gettext()},
@code{dgettext()}, @code{dcgettext()}, @code{textdomain()}, @code{bindtextdomain()},
and @code{bind_textdomain_codeset()}.  These are similar to the same functions in
the @ref{89,,gettext} module, but use the C library's binary format for message
catalogs, and the C library's search algorithms for locating message catalogs.

Python applications should normally find no need to invoke these functions, and
should use @ref{89,,gettext} instead.  A known exception to this rule are
applications that link with additional C libraries which internally invoke
@code{gettext()} or @code{dcgettext()}.  For these applications, it may be
necessary to bind the text domain, so that the libraries can properly locate
their message catalogs.

@node 程序框架,Tk图形用户界面 GUI,国际化,Python 标准库
@anchor{library/frameworks doc}@anchor{3035}@anchor{library/frameworks frameworks}@anchor{3036}@anchor{library/frameworks program-frameworks}@anchor{3037}
@section 程序框架


本章中描述的模块是很大程度上决定程序结构的框架。 目前，这里描述的模块都面向编写命令行接口。

本章描述的完整模块列表如下：

@menu
* turtle: turtle --- 海龟绘图. 海龟绘图
* cmd: cmd --- 支持面向行的命令解释器. 支持面向行的命令解释器
* shlex: shlex --- Simple lexical analysis. Simple lexical analysis

@end menu

@node turtle --- 海龟绘图,cmd --- 支持面向行的命令解释器,,程序框架
@anchor{library/turtle doc}@anchor{3038}@anchor{library/turtle module-turtle}@anchor{116}@anchor{library/turtle turtle-turtle-graphics}@anchor{3039}
@subsection @code{turtle} --- 海龟绘图


@geindex turtle (模块)

@strong{源码：} Lib/turtle.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/turtle.py}

@c from turtle import *
@c turtle = Turtle()


__________________________________________________________________


@menu
* 概述: 概述<12>. 
* 可用的 Turtle 和 Screen 方法概览:: 
* RawTurtle/Turtle 方法和对应函数:: 
* TurtleScreen/Screen 方法及对应函数:: 
* 公共类:: 
* 帮助与配置:: 
* turtledemo: turtledemo --- 演示脚本集. 演示脚本集
* Python 2.6 之后的变化: Python 2 6 之后的变化. 
* Python 3.0 之后的变化: Python 3 0 之后的变化. 

@end menu

@node 概述<12>,可用的 Turtle 和 Screen 方法概览,,turtle --- 海龟绘图
@anchor{library/turtle introduction}@anchor{303a}
@subsubsection 概述


海龟绘图很适合用来引导孩子学习编程。 最初来自于 Wally Feurzeig, Seymour Papert 和 Cynthia Solomon 于 1967 年所创造的 Logo 编程语言。

请想象绘图区有一只机器海龟，起始位置在 x-y 平面的 (0, 0) 点。先执行 @code{import turtle}，再执行 @code{turtle.forward(15)}，它将(在屏幕上)朝所面对的 x 轴正方向前进 15 像素，随着它的移动画出一条线段。再执行 @code{turtle.right(25)}，它将原地右转 25 度。

@subsubheading Turtle star



使用海龟绘图可以编写重复执行简单动作的程序画出精细复杂的形状。

@image{python-figures/turtle-star,,,,png}

@example
from turtle import *
color('red', 'yellow')
begin_fill()
while True:
    forward(200)
    left(170)
    if abs(pos()) < 1:
        break
end_fill()
done()
@end example

通过组合使用此类命令，可以轻松地绘制出精美的形状和图案。

@ref{116,,turtle} 模块是基于 Python 标准发行版 2.5 以来的同名模块重新编写并进行了功能扩展。

新模块尽量保持了原模块的特点，并且(几乎)100%与其兼容。这就意味着初学编程者能够以交互方式使用模块的所有命令、类和方法——运行 IDLE 时注意加 @code{-n} 参数。

turtle 模块提供面向对象和面向过程两种形式的海龟绘图基本组件。由于它使用 @ref{10c,,tkinter} 实现基本图形界面，因此需要安装了 Tk 支持的 Python 版本。

面向对象的接口主要使用“2+2”个类：


@enumerate 

@item 
@ref{303b,,TurtleScreen} 类定义图形窗口作为绘图海龟的运动场。它的构造器需要一个 @code{tkinter.Canvas} 或 @ref{303c,,ScrolledCanvas} 作为参数。应在 @ref{116,,turtle} 作为某个程序的一部分的时候使用。

@ref{303d,,Screen()} 函数返回一个 @ref{303b,,TurtleScreen} 子类的单例对象。此函数应在 @ref{116,,turtle} 作为独立绘图工具时使用。作为一个单例对象，其所属的类是不可被继承的。

TurtleScreen/Screen 的所有方法还存在对应的函数，即作为面向过程的接口组成部分。

@item 
@ref{303e,,RawTurtle} (别名: @ref{303f,,RawPen}) 类定义海龟对象在 @ref{303b,,TurtleScreen} 上绘图。它的构造器需要一个 Canvas, ScrolledCanvas 或 TurtleScreen 作为参数，以指定 RawTurtle 对象在哪里绘图。

从 RawTurtle 派生出子类 @ref{3040,,Turtle} (别名: @code{Pen})，该类对象在 @ref{303d,,Screen} 实例上绘图，如果实例不存在则会自动创建。

RawTurtle/Turtle 的所有方法也存在对应的函数，即作为面向过程的接口组成部分。
@end enumerate

过程式接口提供与 @ref{303d,,Screen} 和 @ref{3040,,Turtle} 类的方法相对应的函数。函数名与对应的方法名相同。当 Screen 类的方法对应函数被调用时会自动创建一个 Screen 对象。当 Turtle 类的方法对应函数被调用时会自动创建一个 (匿名的) Turtle 对象。

如果屏幕上需要有多个海龟，就必须使用面向对象的接口。

@cartouche
@quotation 注解 
以下文档给出了函数的参数列表。对于方法来说当然还有额外的第一个参数 @emph{self}，这里省略了。
@end quotation
@end cartouche

@node 可用的 Turtle 和 Screen 方法概览,RawTurtle/Turtle 方法和对应函数,概述<12>,turtle --- 海龟绘图
@anchor{library/turtle overview-of-available-turtle-and-screen-methods}@anchor{3041}
@subsubsection 可用的 Turtle 和 Screen 方法概览


@menu
* Turtle 方法:: 
* TurtleScreen/Screen 方法:: 

@end menu

@node Turtle 方法,TurtleScreen/Screen 方法,,可用的 Turtle 和 Screen 方法概览
@anchor{library/turtle turtle-methods}@anchor{3042}
@subsubsection Turtle 方法



@table @asis

@item 海龟动作


@table @asis

@item 移动和绘制


@display
@ref{3043,,forward()} | @ref{3044,,fd()} 前进@w{ }
@ref{3045,,backward()} | @ref{3046,,bk()} | @ref{3047,,back()} 后退@w{ }
@ref{3048,,right()} | @ref{3049,,rt()} 右转@w{ }
@ref{304a,,left()} | @ref{304b,,lt()} 左转@w{ }
@ref{304c,,goto()} | @ref{304d,,setpos()} | @ref{304e,,setposition()} 前往/定位@w{ }
@ref{304f,,setx()} 设置x坐标@w{ }
@ref{3050,,sety()} 设置y坐标@w{ }
@ref{3051,,setheading()} | @ref{3052,,seth()} 设置朝向@w{ }
@ref{3053,,home()} 返回原点@w{ }
@ref{3054,,circle()} 画圆@w{ }
@ref{3055,,dot()} 画点@w{ }
@ref{3056,,stamp()} 印章@w{ }
@ref{3057,,clearstamp()} 清除印章@w{ }
@ref{3058,,clearstamps()} 清除多个印章@w{ }
@ref{3059,,undo()} 撤消@w{ }
@ref{305a,,speed()} 速度@w{ }
@end display



@item 获取海龟的状态


@display
@ref{305b,,position()} | @ref{305c,,pos()} 位置@w{ }
@ref{305d,,towards()} 目标方向@w{ }
@ref{305e,,xcor()} x坐标@w{ }
@ref{305f,,ycor()} y坐标@w{ }
@ref{3060,,heading()} 朝向@w{ }
@ref{3061,,distance()} 距离@w{ }
@end display



@item 设置与度量单位


@display
@ref{3062,,degrees()} 角度@w{ }
@ref{3063,,radians()} 弧度@w{ }
@end display


@end table

@item 画笔控制


@table @asis

@item 绘图状态


@display
@ref{3064,,pendown()} | @ref{3065,,pd()} | @ref{3066,,down()} 画笔落下@w{ }
@ref{3067,,penup()} | @ref{3068,,pu()} | @ref{3069,,up()} 画笔抬起@w{ }
@ref{306a,,pensize()} | @ref{306b,,width()} 画笔粗细@w{ }
@ref{306c,,pen()} 画笔@w{ }
@ref{306d,,isdown()} 画笔是否落下@w{ }
@end display



@item 颜色控制


@display
@ref{306e,,color()} 颜色@w{ }
@ref{306f,,pencolor()} 画笔颜色@w{ }
@ref{3070,,fillcolor()} 填充颜色@w{ }
@end display



@item 填充


@display
@ref{3071,,filling()} 是否填充@w{ }
@ref{3072,,begin_fill()} 开始填充@w{ }
@ref{3073,,end_fill()} 结束填充@w{ }
@end display



@item 更多绘图控制


@display
@ref{3074,,reset()} 重置@w{ }
@ref{3075,,clear()} 清空@w{ }
@ref{3076,,write()} 书写@w{ }
@end display


@end table

@item 海龟状态


@table @asis

@item 可见性


@display
@ref{3077,,showturtle()} | @ref{3078,,st()} 显示海龟@w{ }
@ref{3079,,hideturtle()} | @ref{307a,,ht()} 隐藏海龟@w{ }
@ref{307b,,isvisible()} 是否可见@w{ }
@end display



@item 外观


@display
@ref{307c,,shape()} 形状@w{ }
@ref{307d,,resizemode()} 大小调整模式@w{ }
@ref{307e,,shapesize()} | @ref{307f,,turtlesize()} 形状大小@w{ }
@ref{3080,,shearfactor()} 剪切因子@w{ }
@ref{3081,,settiltangle()} 设置倾角@w{ }
@ref{3082,,tiltangle()} 倾角@w{ }
@ref{3083,,tilt()} 倾斜@w{ }
@ref{3084,,shapetransform()} 变形@w{ }
@ref{3085,,get_shapepoly()} 获取形状多边形@w{ }
@end display


@end table

@item 使用事件


@display
@ref{3086,,onclick()} 当鼠标点击@w{ }
@ref{3087,,onrelease()} 当鼠标释放@w{ }
@ref{3088,,ondrag()} 当鼠标拖动@w{ }
@end display



@item 特殊海龟方法


@display
@ref{3089,,begin_poly()} 开始记录多边形@w{ }
@ref{308a,,end_poly()} 结束记录多边形@w{ }
@ref{308b,,get_poly()} 获取多边形@w{ }
@ref{308c,,clone()} 克隆@w{ }
@ref{308d,,getturtle()} | @ref{308e,,getpen()} 获取海龟画笔@w{ }
@ref{308f,,getscreen()} 获取屏幕@w{ }
@ref{3090,,setundobuffer()} 设置撤消缓冲区@w{ }
@ref{3091,,undobufferentries()} 撤消缓冲区条目数@w{ }
@end display


@end table

@node TurtleScreen/Screen 方法,,Turtle 方法,可用的 Turtle 和 Screen 方法概览
@anchor{library/turtle methods-of-turtlescreen-screen}@anchor{3092}
@subsubsection TurtleScreen/Screen 方法



@table @asis

@item 窗口控制


@display
@ref{3093,,bgcolor()} 背景颜色@w{ }
@ref{3094,,bgpic()} 背景图片@w{ }
@ref{3075,,clear()} | @ref{3095,,clearscreen()} 清屏@w{ }
@ref{3074,,reset()} | @ref{3096,,resetscreen()} 重置@w{ }
@ref{3097,,screensize()} 屏幕大小@w{ }
@ref{3098,,setworldcoordinates()} 设置世界坐标系@w{ }
@end display



@item 动画控制


@display
@ref{3099,,delay()} 延迟@w{ }
@ref{309a,,tracer()} 追踪@w{ }
@ref{309b,,update()} 更新@w{ }
@end display



@item 使用屏幕事件


@display
@ref{309c,,listen()} 监听@w{ }
@ref{309d,,onkey()} | @ref{309e,,onkeyrelease()} 当键盘按下并释放@w{ }
@ref{309f,,onkeypress()} 当键盘按下@w{ }
@ref{3086,,onclick()} | @ref{30a0,,onscreenclick()} 当点击屏幕@w{ }
@ref{30a1,,ontimer()} 当达到定时@w{ }
@ref{30a2,,mainloop()} | @ref{30a3,,done()} 主循环@w{ }
@end display



@item 设置与特殊方法


@display
@ref{30a4,,mode()}@w{ }
@ref{30a5,,colormode()} 颜色模式@w{ }
@ref{30a6,,getcanvas()} 获取画布@w{ }
@ref{30a7,,getshapes()} 获取形状@w{ }
@ref{30a8,,register_shape()} | @ref{30a9,,addshape()} 添加形状@w{ }
@ref{30aa,,turtles()} 所有海龟@w{ }
@ref{30ab,,window_height()} 窗口高度@w{ }
@ref{30ac,,window_width()} 窗口宽度@w{ }
@end display



@item 输入方法


@display
@ref{30ad,,textinput()} 文本输入@w{ }
@ref{30ae,,numinput()} 数字输入@w{ }
@end display



@item Screen 专有方法


@display
@ref{30af,,bye()} 退出@w{ }
@ref{30b0,,exitonclick()} 当点击时退出@w{ }
@ref{30b1,,setup()} 设置@w{ }
@ref{30b2,,title()} 标题@w{ }
@end display


@end table

@node RawTurtle/Turtle 方法和对应函数,TurtleScreen/Screen 方法及对应函数,可用的 Turtle 和 Screen 方法概览,turtle --- 海龟绘图
@anchor{library/turtle methods-of-rawturtle-turtle-and-corresponding-functions}@anchor{30b3}
@subsubsection RawTurtle/Turtle 方法和对应函数


本节中的大部分示例都使用 Turtle 类的一个实例，命名为 @code{turtle}。

@menu
* 海龟动作:: 
* 获取海龟的状态:: 
* 度量单位设置:: 
* 画笔控制:: 
* 海龟状态:: 
* 使用事件:: 
* 特殊海龟方法:: 
* 复合形状:: 

@end menu

@node 海龟动作,获取海龟的状态,,RawTurtle/Turtle 方法和对应函数
@anchor{library/turtle turtle-motion}@anchor{30b4}
@subsubsection 海龟动作


@geindex forward() (在 turtle 模块中)
@geindex fd() (在 turtle 模块中)
@anchor{library/turtle turtle forward}@anchor{3043}
@deffn {函数} turtle.forward (distance)
@anchor{library/turtle turtle fd}@anchor{3044}
@deffnx {函数} turtle.fd (distance)

@*参数: 
@code{distance} -- 一个数值 (整型或浮点型)


海龟前进 @emph{distance} 指定的距离，方向为海龟的朝向。

@example
>>> turtle.position()
(0.00,0.00)
>>> turtle.forward(25)
>>> turtle.position()
(25.00,0.00)
>>> turtle.forward(-75)
>>> turtle.position()
(-50.00,0.00)
@end example
@end deffn

@geindex back() (在 turtle 模块中)
@geindex bk() (在 turtle 模块中)
@geindex backward() (在 turtle 模块中)
@anchor{library/turtle turtle back}@anchor{3047}
@deffn {函数} turtle.back (distance)
@anchor{library/turtle turtle bk}@anchor{3046}
@deffnx {函数} turtle.bk (distance)
@anchor{library/turtle turtle backward}@anchor{3045}
@deffnx {函数} turtle.backward (distance)

@*参数: 
@code{distance} -- 一个数值


海龟后退 @emph{distance} 指定的距离，方向与海龟的朝向相反。不改变海龟的朝向。

@c >>> turtle.goto(0, 0)

@example
>>> turtle.position()
(0.00,0.00)
>>> turtle.backward(30)
>>> turtle.position()
(-30.00,0.00)
@end example
@end deffn

@geindex right() (在 turtle 模块中)
@geindex rt() (在 turtle 模块中)
@anchor{library/turtle turtle right}@anchor{3048}
@deffn {函数} turtle.right (angle)
@anchor{library/turtle turtle rt}@anchor{3049}
@deffnx {函数} turtle.rt (angle)

@*参数: 
@code{angle} -- 一个数值 (整型或浮点型)


海龟右转 @emph{angle} 个单位。(单位默认为角度，但可通过 @ref{3062,,degrees()} 和 @ref{3063,,radians()} 函数改变设置。) 角度的正负由海龟模式确定，参见 @ref{30a4,,mode()}。

@c >>> turtle.setheading(22)

@example
>>> turtle.heading()
22.0
>>> turtle.right(45)
>>> turtle.heading()
337.0
@end example
@end deffn

@geindex left() (在 turtle 模块中)
@geindex lt() (在 turtle 模块中)
@anchor{library/turtle turtle left}@anchor{304a}
@deffn {函数} turtle.left (angle)
@anchor{library/turtle turtle lt}@anchor{304b}
@deffnx {函数} turtle.lt (angle)

@*参数: 
@code{angle} -- 一个数值 (整型或浮点型)


海龟左转 @emph{angle} 个单位。(单位默认为角度，但可通过 @ref{3062,,degrees()} 和 @ref{3063,,radians()} 函数改变设置。) 角度的正负由海龟模式确定，参见 @ref{30a4,,mode()}。

@c >>> turtle.setheading(22)

@example
>>> turtle.heading()
22.0
>>> turtle.left(45)
>>> turtle.heading()
67.0
@end example
@end deffn

@geindex goto() (在 turtle 模块中)
@geindex setpos() (在 turtle 模块中)
@geindex setposition() (在 turtle 模块中)
@anchor{library/turtle turtle goto}@anchor{304c}
@deffn {函数} turtle.goto (x, y=None)
@anchor{library/turtle turtle setpos}@anchor{304d}
@deffnx {函数} turtle.setpos (x, y=None)
@anchor{library/turtle turtle setposition}@anchor{304e}
@deffnx {函数} turtle.setposition (x, y=None)

@*参数: 

@itemize *

@item 
@code{x} -- 一个数值或数值对/向量

@item 
@code{y} -- 一个数值或 @code{None}
@end itemize


如果 @emph{y} 为 @code{None}，@emph{x} 应为一个表示坐标的数值对或 @ref{30b5,,Vec2D} 类对象 (例如 @ref{305c,,pos()} 返回的对象).

海龟移动到一个绝对坐标。如果画笔已落下将会画线。不改变海龟的朝向。

@c >>> turtle.goto(0, 0)

@example
 >>> tp = turtle.pos()
 >>> tp
 (0.00,0.00)
 >>> turtle.setpos(60,30)
 >>> turtle.pos()
 (60.00,30.00)
 >>> turtle.setpos((20,80))
 >>> turtle.pos()
 (20.00,80.00)
 >>> turtle.setpos(tp)
 >>> turtle.pos()
 (0.00,0.00)
@end example
@end deffn

@geindex setx() (在 turtle 模块中)
@anchor{library/turtle turtle setx}@anchor{304f}
@deffn {函数} turtle.setx (x)

@*参数: 
@code{x} -- 一个数值 (整型或浮点型)


设置海龟的横坐标为 @emph{x}，纵坐标保持不变。

@c >>> turtle.goto(0, 240)

@example
>>> turtle.position()
(0.00,240.00)
>>> turtle.setx(10)
>>> turtle.position()
(10.00,240.00)
@end example
@end deffn

@geindex sety() (在 turtle 模块中)
@anchor{library/turtle turtle sety}@anchor{3050}
@deffn {函数} turtle.sety (y)

@*参数: 
@code{y} -- 一个数值 (整型或浮点型)


设置海龟的纵坐标为 @emph{y}，横坐标保持不变。

@c >>> turtle.goto(0, 40)

@example
>>> turtle.position()
(0.00,40.00)
>>> turtle.sety(-10)
>>> turtle.position()
(0.00,-10.00)
@end example
@end deffn

@geindex setheading() (在 turtle 模块中)
@geindex seth() (在 turtle 模块中)
@anchor{library/turtle turtle setheading}@anchor{3051}
@deffn {函数} turtle.setheading (to_angle)
@anchor{library/turtle turtle seth}@anchor{3052}
@deffnx {函数} turtle.seth (to_angle)

@*参数: 
@code{to_angle} -- 一个数值 (整型或浮点型)


设置海龟的朝向为 @emph{to_angle}。以下是以角度表示的几个常用方向：


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} 
@headitem

标准模式

@tab

logo 模式

@item

0 - 东

@tab

0 - 北

@item

90 - 北

@tab

90 - 东

@item

180 - 西

@tab

180 - 南

@item

270 - 南

@tab

270 - 西

@end multitable


@example
>>> turtle.setheading(90)
>>> turtle.heading()
90.0
@end example
@end deffn

@geindex home() (在 turtle 模块中)
@anchor{library/turtle turtle home}@anchor{3053}
@deffn {函数} turtle.home ()

海龟移至初始坐标 (0,0)，并设置朝向为初始方向 (由海龟模式确定，参见 @ref{30a4,,mode()})。

@c >>> turtle.setheading(90)
@c >>> turtle.goto(0, -10)

@example
>>> turtle.heading()
90.0
>>> turtle.position()
(0.00,-10.00)
>>> turtle.home()
>>> turtle.position()
(0.00,0.00)
>>> turtle.heading()
0.0
@end example
@end deffn

@geindex circle() (在 turtle 模块中)
@anchor{library/turtle turtle circle}@anchor{3054}
@deffn {函数} turtle.circle (radius, extent=None, steps=None)

@*参数: 

@itemize *

@item 
@code{radius} -- 一个数值

@item 
@code{extent} -- 一个数值 (或 @code{None})

@item 
@code{steps} -- 一个整型数 (或 @code{None})
@end itemize


绘制一个 @emph{radius} 指定半径的圆。圆心在海龟左边 @emph{radius} 个单位；@emph{extent} 为一个夹角，用来决定绘制圆的一部分。如未指定 @emph{extent*则绘制整个圆。如果 *extent} 不是完整圆周，则以当前画笔位置为一个端点绘制圆弧。如果 @emph{radius} 为正值则朝逆时针方向绘制圆弧，否则朝顺时针方向。最终海龟的朝向会依据 @emph{extent} 的值而改变。

圆实际是以其内切正多边形来近似表示的，其边的数量由 @emph{steps} 指定。如果未指定边数则会自动确定。此方法也可用来绘制正多边形。

@example
>>> turtle.home()
>>> turtle.position()
(0.00,0.00)
>>> turtle.heading()
0.0
>>> turtle.circle(50)
>>> turtle.position()
(-0.00,0.00)
>>> turtle.heading()
0.0
>>> turtle.circle(120, 180)  # draw a semicircle
>>> turtle.position()
(0.00,240.00)
>>> turtle.heading()
180.0
@end example
@end deffn

@geindex dot() (在 turtle 模块中)
@anchor{library/turtle turtle dot}@anchor{3055}
@deffn {函数} turtle.dot (size=None, *color)

@*参数: 

@itemize *

@item 
@code{size} -- 一个整型数 >= 1 (如果指定)

@item 
@code{color} -- 一个颜色字符串或颜色数值元组
@end itemize


绘制一个直径为 @emph{size}，颜色为 @emph{color} 的圆点。如果 @emph{size} 未指定，则直径取 pensize+4 和 2*pensize 中的较大值。

@example
>>> turtle.home()
>>> turtle.dot()
>>> turtle.fd(50); turtle.dot(20, "blue"); turtle.fd(50)
>>> turtle.position()
(100.00,-0.00)
>>> turtle.heading()
0.0
@end example
@end deffn

@geindex stamp() (在 turtle 模块中)
@anchor{library/turtle turtle stamp}@anchor{3056}
@deffn {函数} turtle.stamp ()

在海龟当前位置印制一个海龟形状。返回该印章的 stamp_id，印章可以通过调用 @code{clearstamp(stamp_id)} 来删除。

@example
>>> turtle.color("blue")
>>> turtle.stamp()
11
>>> turtle.fd(50)
@end example
@end deffn

@geindex clearstamp() (在 turtle 模块中)
@anchor{library/turtle turtle clearstamp}@anchor{3057}
@deffn {函数} turtle.clearstamp (stampid)

@*参数: 
@code{stampid} -- 一个整型数，必须是之前 @ref{3056,,stamp()} 调用的返回值


删除 @emph{stampid} 指定的印章。

@example
>>> turtle.position()
(150.00,-0.00)
>>> turtle.color("blue")
>>> astamp = turtle.stamp()
>>> turtle.fd(50)
>>> turtle.position()
(200.00,-0.00)
>>> turtle.clearstamp(astamp)
>>> turtle.position()
(200.00,-0.00)
@end example
@end deffn

@geindex clearstamps() (在 turtle 模块中)
@anchor{library/turtle turtle clearstamps}@anchor{3058}
@deffn {函数} turtle.clearstamps (n=None)

@*参数: 
@code{n} -- 一个整型数 (或 @code{None})


删除全部或前/后 @emph{n} 个海龟印章。如果 @emph{n} 为 @code{None} 则删除全部印章，如果 @emph{n} > 0 则删除前 @emph{n} 个印章，否则如果 @emph{n} < 0 则删除后 @emph{n} 个印章。

@example
>>> for i in range(8):
...     turtle.stamp(); turtle.fd(30)
13
14
15
16
17
18
19
20
>>> turtle.clearstamps(2)
>>> turtle.clearstamps(-2)
>>> turtle.clearstamps()
@end example
@end deffn

@geindex undo() (在 turtle 模块中)
@anchor{library/turtle turtle undo}@anchor{3059}
@deffn {函数} turtle.undo ()

撤消 (或连续撤消) 最近的一个 (或多个) 海龟动作。可撤消的次数由撤消缓冲区的大小决定。

@example
>>> for i in range(4):
...     turtle.fd(50); turtle.lt(80)
...
>>> for i in range(8):
...     turtle.undo()
@end example
@end deffn

@geindex speed() (在 turtle 模块中)
@anchor{library/turtle turtle speed}@anchor{305a}
@deffn {函数} turtle.speed (speed=None)

@*参数: 
@code{speed} -- 一个 0..10 范围内的整型数或速度字符串 (见下)


设置海龟移动的速度为 0..10 表示的整型数值。如未指定参数则返回当前速度。

如果输入数值大于 10 或小于 0.5 则速度设为 0。速度字符串与速度值的对应关系如下:


@itemize *

@item 
"fastest":  0 最快

@item 
"fast":  10 快

@item 
"normal":  6 正常

@item 
"slow":  3 慢

@item 
"slowest":  1 最慢
@end itemize

速度值从 1 到 10，画线和海龟转向的动画效果逐级加快。

注意: @emph{speed} = 0 表示 @emph{没有} 动画效果。forward/back 将使海龟向前/向后跳跃，同样的 left/right 将使海龟立即改变朝向。

@example
>>> turtle.speed()
3
>>> turtle.speed('normal')
>>> turtle.speed()
6
>>> turtle.speed(9)
>>> turtle.speed()
9
@end example
@end deffn

@node 获取海龟的状态,度量单位设置,海龟动作,RawTurtle/Turtle 方法和对应函数
@anchor{library/turtle tell-turtle-s-state}@anchor{30b6}
@subsubsection 获取海龟的状态


@geindex position() (在 turtle 模块中)
@geindex pos() (在 turtle 模块中)
@anchor{library/turtle turtle position}@anchor{305b}
@deffn {函数} turtle.position ()
@anchor{library/turtle turtle pos}@anchor{305c}
@deffnx {函数} turtle.pos ()

返回海龟当前的坐标 (x,y) (为 @ref{30b5,,Vec2D} 矢量类对象)。

@example
>>> turtle.pos()
(440.00,-0.00)
@end example
@end deffn

@geindex towards() (在 turtle 模块中)
@anchor{library/turtle turtle towards}@anchor{305d}
@deffn {函数} turtle.towards (x, y=None)

@*参数: 

@itemize *

@item 
@code{x} -- 一个数值或数值对/矢量，或一个海龟实例

@item 
@code{y} -- 一个数值——如果 @emph{x} 是一个数值，否则为 @code{None}
@end itemize


从海龟位置到由 (x,y)，矢量或另一海龟对应位置的连线的夹角。此数值依赖于海龟初始朝向  - 由 "standard"/"world" 或 "logo" 模式设置所决定)。

@example
>>> turtle.goto(10, 10)
>>> turtle.towards(0,0)
225.0
@end example
@end deffn

@geindex xcor() (在 turtle 模块中)
@anchor{library/turtle turtle xcor}@anchor{305e}
@deffn {函数} turtle.xcor ()

返回海龟的 x 坐标。

@example
>>> turtle.home()
>>> turtle.left(50)
>>> turtle.forward(100)
>>> turtle.pos()
(64.28,76.60)
>>> print(round(turtle.xcor(), 5))
64.27876
@end example
@end deffn

@geindex ycor() (在 turtle 模块中)
@anchor{library/turtle turtle ycor}@anchor{305f}
@deffn {函数} turtle.ycor ()

返回海龟的 y 坐标。

@example
>>> turtle.home()
>>> turtle.left(60)
>>> turtle.forward(100)
>>> print(turtle.pos())
(50.00,86.60)
>>> print(round(turtle.ycor(), 5))
86.60254
@end example
@end deffn

@geindex heading() (在 turtle 模块中)
@anchor{library/turtle turtle heading}@anchor{3060}
@deffn {函数} turtle.heading ()

返回海龟当前的朝向 (数值依赖于海龟模式参见 @ref{30a4,,mode()})。

@example
>>> turtle.home()
>>> turtle.left(67)
>>> turtle.heading()
67.0
@end example
@end deffn

@geindex distance() (在 turtle 模块中)
@anchor{library/turtle turtle distance}@anchor{3061}
@deffn {函数} turtle.distance (x, y=None)

@*参数: 

@itemize *

@item 
@code{x} -- 一个数值或数值对/矢量，或一个海龟实例

@item 
@code{y} -- 一个数值——如果 @emph{x} 是一个数值，否则为 @code{None}
@end itemize


返回从海龟位置到由 (x,y)，适量或另一海龟对应位置的单位距离。

@example
>>> turtle.home()
>>> turtle.distance(30,40)
50.0
>>> turtle.distance((30,40))
50.0
>>> joe = Turtle()
>>> joe.forward(77)
>>> turtle.distance(joe)
77.0
@end example
@end deffn

@node 度量单位设置,画笔控制,获取海龟的状态,RawTurtle/Turtle 方法和对应函数
@anchor{library/turtle settings-for-measurement}@anchor{30b7}
@subsubsection 度量单位设置


@geindex degrees() (在 turtle 模块中)
@anchor{library/turtle turtle degrees}@anchor{3062}
@deffn {函数} turtle.degrees (fullcircle=360.0)

@*参数: 
@code{fullcircle} -- 一个数值


设置角度的度量单位，即设置一个圆周为多少 "度"。默认值为 360 度。

@example
>>> turtle.home()
>>> turtle.left(90)
>>> turtle.heading()
90.0

Change angle measurement unit to grad (also known as gon,
grade, or gradian and equals 1/100-th of the right angle.)
>>> turtle.degrees(400.0)
>>> turtle.heading()
100.0
>>> turtle.degrees(360)
>>> turtle.heading()
90.0
@end example
@end deffn

@geindex radians() (在 turtle 模块中)
@anchor{library/turtle turtle radians}@anchor{3063}
@deffn {函数} turtle.radians ()

设置角度的度量单位为弧度。其值等于 @code{degrees(2*math.pi)}。

@example
>>> turtle.home()
>>> turtle.left(90)
>>> turtle.heading()
90.0
>>> turtle.radians()
>>> turtle.heading()
1.5707963267948966
@end example

@c >>> turtle.degrees(360)
@end deffn

@node 画笔控制,海龟状态,度量单位设置,RawTurtle/Turtle 方法和对应函数
@anchor{library/turtle pen-control}@anchor{30b8}
@subsubsection 画笔控制


@menu
* 绘图状态:: 
* 颜色控制:: 
* 填充:: 
* 更多绘图控制:: 

@end menu

@node 绘图状态,颜色控制,,画笔控制
@anchor{library/turtle drawing-state}@anchor{30b9}
@subsubsection 绘图状态


@geindex pendown() (在 turtle 模块中)
@geindex pd() (在 turtle 模块中)
@geindex down() (在 turtle 模块中)
@anchor{library/turtle turtle pendown}@anchor{3064}
@deffn {函数} turtle.pendown ()
@anchor{library/turtle turtle pd}@anchor{3065}
@deffnx {函数} turtle.pd ()
@anchor{library/turtle turtle down}@anchor{3066}
@deffnx {函数} turtle.down ()

画笔落下 -- 移动时将画线。
@end deffn

@geindex penup() (在 turtle 模块中)
@geindex pu() (在 turtle 模块中)
@geindex up() (在 turtle 模块中)
@anchor{library/turtle turtle penup}@anchor{3067}
@deffn {函数} turtle.penup ()
@anchor{library/turtle turtle pu}@anchor{3068}
@deffnx {函数} turtle.pu ()
@anchor{library/turtle turtle up}@anchor{3069}
@deffnx {函数} turtle.up ()

画笔抬起 -- 移动时不画线。
@end deffn

@geindex pensize() (在 turtle 模块中)
@geindex width() (在 turtle 模块中)
@anchor{library/turtle turtle pensize}@anchor{306a}
@deffn {函数} turtle.pensize (width=None)
@anchor{library/turtle turtle width}@anchor{306b}
@deffnx {函数} turtle.width (width=None)

@*参数: 
@code{width} -- 一个正数值


设置线条的粗细为 @emph{width} 或返回该值。如果 resizemode 设为 "auto" 并且 turtleshape 为多边形，该多边形也以同样组细的线条绘制。如未指定参数，则返回当前的 pensize。

@example
>>> turtle.pensize()
1
>>> turtle.pensize(10)   # from here on lines of width 10 are drawn
@end example
@end deffn

@geindex pen() (在 turtle 模块中)
@anchor{library/turtle turtle pen}@anchor{306c}
@deffn {函数} turtle.pen (pen=None, **pendict)

@*参数: 

@itemize *

@item 
@code{pen} -- 一个包含部分或全部下列键的字典

@item 
@code{pendict} -- 一个或多个以下列键为关键字的关键字参数
@end itemize


返回或设置画笔的属性，以一个包含以下键值对的 "画笔字典" 表示:


@itemize *

@item 
"shown": True/False

@item 
"pendown": True/False

@item 
"pencolor": 颜色字符串或颜色元组

@item 
"fillcolor": 颜色字符串或颜色元组

@item 
"pensize": 正数值

@item 
"speed": 0..10 范围内的数值

@item 
"resizemode": "auto" 或 "user" 或 "noresize"

@item 
"stretchfactor": (正数值, 正数值)

@item 
"outline": 正数值

@item 
"tilt": 数值
@end itemize

此字典可作为后续调用 @ref{306c,,pen()} 时的参数，以恢复之前的画笔状态。另外还可将这些属性作为关键词参数提交。使用此方式可以用一条语句设置画笔的多个属性。

@example
>>> turtle.pen(fillcolor="black", pencolor="red", pensize=10)
>>> sorted(turtle.pen().items())
[('fillcolor', 'black'), ('outline', 1), ('pencolor', 'red'),
 ('pendown', True), ('pensize', 10), ('resizemode', 'noresize'),
 ('shearfactor', 0.0), ('shown', True), ('speed', 9),
 ('stretchfactor', (1.0, 1.0)), ('tilt', 0.0)]
>>> penstate=turtle.pen()
>>> turtle.color("yellow", "")
>>> turtle.penup()
>>> sorted(turtle.pen().items())[:3]
[('fillcolor', '@w{'}), ('outline', 1), ('pencolor', 'yellow')]
>>> turtle.pen(penstate, fillcolor="green")
>>> sorted(turtle.pen().items())[:3]
[('fillcolor', 'green'), ('outline', 1), ('pencolor', 'red')]
@end example
@end deffn

@geindex isdown() (在 turtle 模块中)
@anchor{library/turtle turtle isdown}@anchor{306d}
@deffn {函数} turtle.isdown ()

如果画笔落下返回 @code{True}，如果画笔抬起返回 @code{False}。

@example
>>> turtle.penup()
>>> turtle.isdown()
False
>>> turtle.pendown()
>>> turtle.isdown()
True
@end example
@end deffn

@node 颜色控制,填充,绘图状态,画笔控制
@anchor{library/turtle color-control}@anchor{30ba}
@subsubsection 颜色控制


@geindex pencolor() (在 turtle 模块中)
@anchor{library/turtle turtle pencolor}@anchor{306f}
@deffn {函数} turtle.pencolor (*args)

返回或设置画笔颜色。

允许以下四种输入格式:


@table @asis

@item @code{pencolor()}

返回以颜色描述字符串或元组 (见示例) 表示的当前画笔颜色。可用作其他 color/pencolor/fillcolor 调用的输入。

@item @code{pencolor(colorstring)}

设置画笔颜色为 @emph{colorstring} 指定的 Tk 颜色描述字符串，例如 @code{"red"}、@code{"yellow"} 或 @code{"#33cc8c"}。

@item @code{pencolor((r, g, b))}

设置画笔颜色为以 @emph{r}, @emph{g}, @emph{b} 元组表示的 RGB 颜色。@emph{r}, @emph{g}, @emph{b} 的取值范围应为 0..colormode，colormode 的值为 1.0 或 255 (参见 @ref{30a5,,colormode()})。

@item @code{pencolor(r, g, b)}

@quotation

设置画笔颜色为以 @emph{r}, @emph{g}, @emph{b} 表示的 RGB 颜色。@emph{r}, @emph{g}, @emph{b} 的取值范围应为 0..colormode。
@end quotation

如果 turtleshape 为多边形，该多边形轮廓也以新设置的画笔颜色绘制。
@end table

@example
 >>> colormode()
 1.0
 >>> turtle.pencolor()
 'red'
 >>> turtle.pencolor("brown")
 >>> turtle.pencolor()
 'brown'
 >>> tup = (0.2, 0.8, 0.55)
 >>> turtle.pencolor(tup)
 >>> turtle.pencolor()
 (0.2, 0.8, 0.5490196078431373)
 >>> colormode(255)
 >>> turtle.pencolor()
 (51.0, 204.0, 140.0)
 >>> turtle.pencolor('#32c18f')
 >>> turtle.pencolor()
 (50.0, 193.0, 143.0)
@end example
@end deffn

@geindex fillcolor() (在 turtle 模块中)
@anchor{library/turtle turtle fillcolor}@anchor{3070}
@deffn {函数} turtle.fillcolor (*args)

返回或设置填充颜色。

允许以下四种输入格式:


@table @asis

@item @code{fillcolor()}

返回以颜色描述字符串或元组 (见示例) 表示的当前填充颜色。可用作其他 color/pencolor/fillcolor 调用的输入。

@item @code{fillcolor(colorstring)}

设置填充颜色为 @emph{colorstring} 指定的 Tk 颜色描述字符串，例如 @code{"red"}、@code{"yellow"} 或 @code{"#33cc8c"}。

@item @code{fillcolor((r, g, b))}

设置填充颜色为以 @emph{r}, @emph{g}, @emph{b} 元组表示的 RGB 颜色。@emph{r}, @emph{g}, @emph{b} 的取值范围应为 0..colormode，colormode 的值为 1.0 或 255 (参见 @ref{30a5,,colormode()})。

@item @code{fillcolor(r, g, b)}

@quotation

设置填充颜色为 @emph{r}, @emph{g}, @emph{b} 表示的 RGB 颜色。@emph{r}, @emph{g}, @emph{b} 的取值范围应为 0..colormode。
@end quotation

如果 turtleshape 为多边形，该多边形内部也以新设置的填充颜色填充。
@end table

@example
 >>> turtle.fillcolor("violet")
 >>> turtle.fillcolor()
 'violet'
 >>> turtle.pencolor()
 (50.0, 193.0, 143.0)
 >>> turtle.fillcolor((50, 193, 143))  # Integers, not floats
 >>> turtle.fillcolor()
 (50.0, 193.0, 143.0)
 >>> turtle.fillcolor('#ffffff')
 >>> turtle.fillcolor()
 (255.0, 255.0, 255.0)
@end example
@end deffn

@geindex color() (在 turtle 模块中)
@anchor{library/turtle turtle color}@anchor{306e}
@deffn {函数} turtle.color (*args)

返回或设置画笔颜色和填充颜色。

允许多种输入格式。使用如下 0 至 3 个参数:


@table @asis

@item @code{color()}

返回以一对颜色描述字符串或元组表示的当前画笔颜色和填充颜色，两者可分别由 @ref{306f,,pencolor()} 和 @ref{3070,,fillcolor()} 返回。

@item @code{color(colorstring)}, @code{color((r,g,b))}, @code{color(r,g,b)}

输入格式与 @ref{306f,,pencolor()} 相同，同时设置填充颜色和画笔颜色为指定的值。

@item @code{color(colorstring1, colorstring2)}, @code{color((r1,g1,b1), (r2,g2,b2))}

@quotation

相当于 @code{pencolor(colorstring1)} 加 @code{fillcolor(colorstring2)}，使用其他输入格式的方法也与之类似。
@end quotation

如果 turtleshape 为多边形，该多边形轮廓与填充也使用新设置的颜色。
@end table

@example
 >>> turtle.color("red", "green")
 >>> turtle.color()
 ('red', 'green')
 >>> color("#285078", "#a0c8f0")
 >>> color()
 ((40.0, 80.0, 120.0), (160.0, 200.0, 240.0))
@end example
@end deffn

另参见: Screen 方法 @ref{30a5,,colormode()}。

@node 填充,更多绘图控制,颜色控制,画笔控制
@anchor{library/turtle filling}@anchor{30bb}
@subsubsection 填充


@c >>> turtle.home()

@geindex filling() (在 turtle 模块中)
@anchor{library/turtle turtle filling}@anchor{3071}
@deffn {函数} turtle.filling ()

返回填充状态 (填充为 @code{True}，否则为 @code{False})。

@example
 >>> turtle.begin_fill()
 >>> if turtle.filling():
 ...    turtle.pensize(5)
 ... else:
 ...    turtle.pensize(3)
@end example
@end deffn

@geindex begin_fill() (在 turtle 模块中)
@anchor{library/turtle turtle begin_fill}@anchor{3072}
@deffn {函数} turtle.begin_fill ()

在绘制要填充的形状之前调用。
@end deffn

@geindex end_fill() (在 turtle 模块中)
@anchor{library/turtle turtle end_fill}@anchor{3073}
@deffn {函数} turtle.end_fill ()

填充上次调用 @ref{3072,,begin_fill()} 之后绘制的形状。

自相交多边形或多个形状间的重叠区域是否填充取决于操作系统的图形引擎、重叠的类型以及重叠的层数。 例如上面的 Turtle 多芒星可能会全部填充为黄色，也可能会有一些白色区域。

@example
>>> turtle.color("black", "red")
>>> turtle.begin_fill()
>>> turtle.circle(80)
>>> turtle.end_fill()
@end example
@end deffn

@node 更多绘图控制,,填充,画笔控制
@anchor{library/turtle more-drawing-control}@anchor{30bc}
@subsubsection 更多绘图控制


@geindex reset() (在 turtle 模块中)
@anchor{library/turtle turtle reset}@anchor{3074}
@deffn {函数} turtle.reset ()

从屏幕中删除海龟的绘图，海龟回到原点并设置所有变量为默认值。

@example
>>> turtle.goto(0,-22)
>>> turtle.left(100)
>>> turtle.position()
(0.00,-22.00)
>>> turtle.heading()
100.0
>>> turtle.reset()
>>> turtle.position()
(0.00,0.00)
>>> turtle.heading()
0.0
@end example
@end deffn

@geindex clear() (在 turtle 模块中)
@anchor{library/turtle turtle clear}@anchor{3075}
@deffn {函数} turtle.clear ()

从屏幕中删除指定海龟的绘图。不移动海龟。海龟的状态和位置以及其他海龟的绘图不受影响。
@end deffn

@geindex write() (在 turtle 模块中)
@anchor{library/turtle turtle write}@anchor{3076}
@deffn {函数} turtle.write (arg, move=False, align="left", font=("Arial", 8, "normal"))

@*参数: 

@itemize *

@item 
@code{arg} -- 要书写到 TurtleScreen 的对象

@item 
@code{move} -- True/False

@item 
@code{align} -- 字符串 "left", "center" 或 "right"

@item 
@code{font} -- 一个三元组 (fontname, fontsize, fonttype)
@end itemize


书写文本 - @emph{arg} 指定的字符串 - 到当前海龟位置，@emph{align} 指定对齐方式 ("left", "center" 或 right")，font 指定字体。如果 @emph{move} 为 True，画笔会移动到文本的右下角。默认 @emph{move} 为 @code{False}。

@example
>>> turtle.write("Home = ", True, align="center")
>>> turtle.write((0,0), True)
@end example
@end deffn

@node 海龟状态,使用事件,画笔控制,RawTurtle/Turtle 方法和对应函数
@anchor{library/turtle turtle-state}@anchor{30bd}
@subsubsection 海龟状态


@menu
* 可见性:: 
* 外观:: 

@end menu

@node 可见性,外观,,海龟状态
@anchor{library/turtle visibility}@anchor{30be}
@subsubsection 可见性


@geindex hideturtle() (在 turtle 模块中)
@geindex ht() (在 turtle 模块中)
@anchor{library/turtle turtle hideturtle}@anchor{3079}
@deffn {函数} turtle.hideturtle ()
@anchor{library/turtle turtle ht}@anchor{307a}
@deffnx {函数} turtle.ht ()

使海龟不可见。当你绘制复杂图形时这是个好主意，因为隐藏海龟可显著加快绘制速度。

@example
>>> turtle.hideturtle()
@end example
@end deffn

@geindex showturtle() (在 turtle 模块中)
@geindex st() (在 turtle 模块中)
@anchor{library/turtle turtle showturtle}@anchor{3077}
@deffn {函数} turtle.showturtle ()
@anchor{library/turtle turtle st}@anchor{3078}
@deffnx {函数} turtle.st ()

使海龟可见。

@example
>>> turtle.showturtle()
@end example
@end deffn

@geindex isvisible() (在 turtle 模块中)
@anchor{library/turtle turtle isvisible}@anchor{307b}
@deffn {函数} turtle.isvisible ()

如果海龟显示返回 @code{True}，如果海龟隐藏返回 @code{False}。

@example
>>> turtle.hideturtle()
>>> turtle.isvisible()
False
>>> turtle.showturtle()
>>> turtle.isvisible()
True
@end example
@end deffn

@node 外观,,可见性,海龟状态
@anchor{library/turtle appearance}@anchor{30bf}
@subsubsection 外观


@geindex shape() (在 turtle 模块中)
@anchor{library/turtle turtle shape}@anchor{307c}
@deffn {函数} turtle.shape (name=None)

@*参数: 
@code{name} -- 一个有效的形状名字符串


设置海龟形状为 @emph{name} 指定的形状名，如未指定形状名则返回当前的形状名。@emph{name} 指定的形状名应存在于 TurtleScreen 的 shape 字典中。多边形的形状初始时有以下几种: "arrow", "turtle", "circle", "square", "triangle", "classic"。要了解如何处理形状请参看 Screen 方法 @ref{30a8,,register_shape()}。

@example
>>> turtle.shape()
'classic'
>>> turtle.shape("turtle")
>>> turtle.shape()
'turtle'
@end example
@end deffn

@geindex resizemode() (在 turtle 模块中)
@anchor{library/turtle turtle resizemode}@anchor{307d}
@deffn {函数} turtle.resizemode (rmode=None)

@*参数: 
@code{rmode} -- 字符串 "auto", "user", "noresize" 其中之一


设置大小调整模式为以下值之一: "auto", "user", "noresize"。如未指定 @emph{rmode} 则返回当前的大小调整模式。不同的大小调整模式的效果如下:


@itemize -

@item 
"auto": 根据画笔粗细值调整海龟的外观。

@item 
"user": 根据拉伸因子和轮廓宽度 (outline) 值调整海龟的外观，两者是由 @ref{307e,,shapesize()} 设置的。

@item 
"noresize": 不调整海龟的外观大小。
@end itemize

大小调整模式 ("user") 会在 @ref{307e,,shapesize()} 带参数调用时生效。

@example
>>> turtle.resizemode()
'noresize'
>>> turtle.resizemode("auto")
>>> turtle.resizemode()
'auto'
@end example
@end deffn

@geindex shapesize() (在 turtle 模块中)
@geindex turtlesize() (在 turtle 模块中)
@anchor{library/turtle turtle shapesize}@anchor{307e}
@deffn {函数} turtle.shapesize (stretch_wid=None, stretch_len=None, outline=None)
@anchor{library/turtle turtle turtlesize}@anchor{307f}
@deffnx {函数} turtle.turtlesize (stretch_wid=None, stretch_len=None, outline=None)

@*参数: 

@itemize *

@item 
@code{stretch_wid} -- 正数值

@item 
@code{stretch_len} -- 正数值

@item 
@code{outline} -- 正数值
@end itemize


返回或设置画笔的属性 x/y-拉伸因子和/或轮廓。设置大小调整模式为 "user"。当且仅当大小调整模式设为 "user" 时海龟会基于其拉伸因子调整外观: @emph{stretch_wid} 为垂直于其朝向的宽度拉伸因子，@emph{stretch_len} 为平等于其朝向的长度拉伸因子，决定形状轮廓线的粗细。

@example
>>> turtle.shapesize()
(1.0, 1.0, 1)
>>> turtle.resizemode("user")
>>> turtle.shapesize(5, 5, 12)
>>> turtle.shapesize()
(5, 5, 12)
>>> turtle.shapesize(outline=8)
>>> turtle.shapesize()
(5, 5, 8)
@end example
@end deffn

@geindex shearfactor() (在 turtle 模块中)
@anchor{library/turtle turtle shearfactor}@anchor{3080}
@deffn {函数} turtle.shearfactor (shear=None)

@*参数: 
@code{shear} -- 数值 (可选)


设置或返回当前的剪切因子。根据 share 指定的剪切因子即剪切角度的切线来剪切海龟形状。@emph{不} 改变海龟的朝向 (移动方向)。如未指定 shear 参数: 返回当前的剪切因子即剪切角度的切线，与海龟朝向平行的线条将被剪切。

@example
 >>> turtle.shape("circle")
 >>> turtle.shapesize(5,2)
 >>> turtle.shearfactor(0.5)
 >>> turtle.shearfactor()
 0.5
@end example
@end deffn

@geindex tilt() (在 turtle 模块中)
@anchor{library/turtle turtle tilt}@anchor{3083}
@deffn {函数} turtle.tilt (angle)

@*参数: 
@code{angle} -- 一个数值


海龟形状自其当前的倾角转动 @emph{angle} 指定的角度，但 @emph{不} 改变海龟的朝向 (移动方向)。

@example
>>> turtle.reset()
>>> turtle.shape("circle")
>>> turtle.shapesize(5,2)
>>> turtle.tilt(30)
>>> turtle.fd(50)
>>> turtle.tilt(30)
>>> turtle.fd(50)
@end example
@end deffn

@geindex settiltangle() (在 turtle 模块中)
@anchor{library/turtle turtle settiltangle}@anchor{3081}
@deffn {函数} turtle.settiltangle (angle)

@*参数: 
@code{angle} -- 一个数值


旋转海龟形状使其指向 @emph{angle} 指定的方向，忽略其当前的倾角，@emph{不} 改变海龟的朝向 (移动方向)。

@example
>>> turtle.reset()
>>> turtle.shape("circle")
>>> turtle.shapesize(5,2)
>>> turtle.settiltangle(45)
>>> turtle.fd(50)
>>> turtle.settiltangle(-45)
>>> turtle.fd(50)
@end example


3.1 版后已移除.

@end deffn

@geindex tiltangle() (在 turtle 模块中)
@anchor{library/turtle turtle tiltangle}@anchor{3082}
@deffn {函数} turtle.tiltangle (angle=None)

@*参数: 
@code{angle} -- 一个数值 (可选)


设置或返回当前的倾角。如果指定 angle 则旋转海龟形状使其指向 angle 指定的方向，忽略其当前的倾角。@emph{不} 改变海龟的朝向 (移动方向)。如果未指定 angle: 返回当前的倾角，即海龟形状的方向和海龟朝向 (移动方向) 之间的夹角。

@example
>>> turtle.reset()
>>> turtle.shape("circle")
>>> turtle.shapesize(5,2)
>>> turtle.tilt(45)
>>> turtle.tiltangle()
45.0
@end example
@end deffn

@geindex shapetransform() (在 turtle 模块中)
@anchor{library/turtle turtle shapetransform}@anchor{3084}
@deffn {函数} turtle.shapetransform (t11=None, t12=None, t21=None, t22=None)

@*参数: 

@itemize *

@item 
@code{t11} -- 一个数值 (可选)

@item 
@code{t12} -- 一个数值 (可选)

@item 
@code{t21} -- 一个数值 (可选)

@item 
@code{t12} -- 一个数值 (可选)
@end itemize


设置或返回海龟形状的当前变形矩阵。

如不指定任何矩阵元素，则返回以4元素元组表示的变形矩阵。否则使用指定元素设置变形矩阵改变海龟形状，矩阵第一排的值为 t11, t12，第二排的值为 t21, t22。行列式 t11 * t22 - t12 * t21 的值不能为零，否则会出错。根据指定的矩阵修改拉伸因子，剪切因子和倾角。

@example
>>> turtle = Turtle()
>>> turtle.shape("square")
>>> turtle.shapesize(4,2)
>>> turtle.shearfactor(-0.5)
>>> turtle.shapetransform()
(4.0, -1.0, -0.0, 2.0)
@end example
@end deffn

@geindex get_shapepoly() (在 turtle 模块中)
@anchor{library/turtle turtle get_shapepoly}@anchor{3085}
@deffn {函数} turtle.get_shapepoly ()

返回以坐标值对元组表示的当前形状多边形。这可以用于定义一个新形状或一个复合形状的多个组成部分。

@example
>>> turtle.shape("square")
>>> turtle.shapetransform(4, -1, 0, 2)
>>> turtle.get_shapepoly()
((50, -20), (30, 20), (-50, 20), (-30, -20))
@end example
@end deffn

@node 使用事件,特殊海龟方法,海龟状态,RawTurtle/Turtle 方法和对应函数
@anchor{library/turtle using-events}@anchor{30c0}
@subsubsection 使用事件


@geindex onclick() (在 turtle 模块中)
@anchor{library/turtle turtle onclick}@anchor{3086}
@deffn {函数} turtle.onclick (fun, btn=1, add=None)

@*参数: 

@itemize *

@item 
@code{fun} -- 一个函数，调用时将传入两个参数表示在画布上点击的坐标。

@item 
@code{btn} -- 鼠标按钮编号，默认值为 1 (鼠标左键)

@item 
@code{add} -- @code{True} 或 @code{False} -- 如为 @code{True} 则将添加一个新绑定，否则将取代先前的绑定
@end itemize


将 @emph{fun} 指定的函数绑定到鼠标点击此海龟事件。如果 @emph{fun} 值为 @code{None}，则移除现有的绑定。以下为使用匿名海龟即过程式的示例:

@example
>>> def turn(x, y):
...     left(180)
...
>>> onclick(turn)  # Now clicking into the turtle will turn it.
>>> onclick(None)  # event-binding will be removed
@end example
@end deffn

@geindex onrelease() (在 turtle 模块中)
@anchor{library/turtle turtle onrelease}@anchor{3087}
@deffn {函数} turtle.onrelease (fun, btn=1, add=None)

@*参数: 

@itemize *

@item 
@code{fun} -- 一个函数，调用时将传入两个参数表示在画布上点击的坐标。

@item 
@code{btn} -- 鼠标按钮编号，默认值为 1 (鼠标左键)

@item 
@code{add} -- @code{True} 或 @code{False} -- 如为 @code{True} 则将添加一个新绑定，否则将取代先前的绑定
@end itemize


将 @emph{fun} 指定的函数绑定到在此海龟上释放鼠标按键事件。如果 @emph{fun} 值为 @code{None}，则移除现有的绑定。

@example
>>> class MyTurtle(Turtle):
...     def glow(self,x,y):
...         self.fillcolor("red")
...     def unglow(self,x,y):
...         self.fillcolor("")
...
>>> turtle = MyTurtle()
>>> turtle.onclick(turtle.glow)     # clicking on turtle turns fillcolor red,
>>> turtle.onrelease(turtle.unglow) # releasing turns it to transparent.
@end example
@end deffn

@geindex ondrag() (在 turtle 模块中)
@anchor{library/turtle turtle ondrag}@anchor{3088}
@deffn {函数} turtle.ondrag (fun, btn=1, add=None)

@*参数: 

@itemize *

@item 
@code{fun} -- 一个函数，调用时将传入两个参数表示在画布上点击的坐标。

@item 
@code{btn} -- 鼠标按钮编号，默认值为 1 (鼠标左键)

@item 
@code{add} -- @code{True} 或 @code{False} -- 如为 @code{True} 则将添加一个新绑定，否则将取代先前的绑定
@end itemize


将 @emph{fun} 指定的函数绑定到在此海龟上移动鼠标事件。如果 @emph{fun} 值为 @code{None}，则移除现有的绑定。

注: 在海龟上移动鼠标事件之前应先发生在此海龟上点击鼠标事件。

@example
>>> turtle.ondrag(turtle.goto)
@end example

在此之后点击并拖动海龟可在屏幕上手绘线条 (如果画笔为落下)。
@end deffn

@node 特殊海龟方法,复合形状,使用事件,RawTurtle/Turtle 方法和对应函数
@anchor{library/turtle special-turtle-methods}@anchor{30c1}
@subsubsection 特殊海龟方法


@geindex begin_poly() (在 turtle 模块中)
@anchor{library/turtle turtle begin_poly}@anchor{3089}
@deffn {函数} turtle.begin_poly ()

开始记录多边形的顶点。当前海龟位置为多边形的第一个顶点。
@end deffn

@geindex end_poly() (在 turtle 模块中)
@anchor{library/turtle turtle end_poly}@anchor{308a}
@deffn {函数} turtle.end_poly ()

停止记录多边形的顶点。当前海龟位置为多边形的最后一个顶点。它将连线到第一个顶点。
@end deffn

@geindex get_poly() (在 turtle 模块中)
@anchor{library/turtle turtle get_poly}@anchor{308b}
@deffn {函数} turtle.get_poly ()

返回最新记录的多边形。

@example
>>> turtle.home()
>>> turtle.begin_poly()
>>> turtle.fd(100)
>>> turtle.left(20)
>>> turtle.fd(30)
>>> turtle.left(60)
>>> turtle.fd(50)
>>> turtle.end_poly()
>>> p = turtle.get_poly()
>>> register_shape("myFavouriteShape", p)
@end example
@end deffn

@geindex clone() (在 turtle 模块中)
@anchor{library/turtle turtle clone}@anchor{308c}
@deffn {函数} turtle.clone ()

创建并返回海龟的克隆体，具有相同的位置、朝向和海龟属性。

@example
>>> mick = Turtle()
>>> joe = mick.clone()
@end example
@end deffn

@geindex getturtle() (在 turtle 模块中)
@geindex getpen() (在 turtle 模块中)
@anchor{library/turtle turtle getturtle}@anchor{308d}
@deffn {函数} turtle.getturtle ()
@anchor{library/turtle turtle getpen}@anchor{308e}
@deffnx {函数} turtle.getpen ()

返回海龟对象自身。唯一合理的用法: 作为一个函数来返回 "匿名海龟":

@example
>>> pet = getturtle()
>>> pet.fd(50)
>>> pet
<turtle.Turtle object at 0x...>
@end example
@end deffn

@geindex getscreen() (在 turtle 模块中)
@anchor{library/turtle turtle getscreen}@anchor{308f}
@deffn {函数} turtle.getscreen ()

返回作为海龟绘图场所的 @ref{303b,,TurtleScreen} 类对象。该对象将可调用 TurtleScreen 方法。

@example
>>> ts = turtle.getscreen()
>>> ts
<turtle._Screen object at 0x...>
>>> ts.bgcolor("pink")
@end example
@end deffn

@geindex setundobuffer() (在 turtle 模块中)
@anchor{library/turtle turtle setundobuffer}@anchor{3090}
@deffn {函数} turtle.setundobuffer (size)

@*参数: 
@code{size} -- 一个整型数值或 @code{None}


设置或禁用撤消缓冲区。如果 @emph{size} 为一个整型数则将开辟一个指定大小的空缓冲区。@emph{size} 表示可使用 @ref{3059,,undo()} 方法/函数撤消的海龟命令的次数上限。如果 @emph{size} 为 @code{None} 则禁用撤消缓冲区。

@example
>>> turtle.setundobuffer(42)
@end example
@end deffn

@geindex undobufferentries() (在 turtle 模块中)
@anchor{library/turtle turtle undobufferentries}@anchor{3091}
@deffn {函数} turtle.undobufferentries ()

返回撤销缓冲区里的条目数。

@example
>>> while undobufferentries():
...     undo()
@end example
@end deffn

@node 复合形状,,特殊海龟方法,RawTurtle/Turtle 方法和对应函数
@anchor{library/turtle compound-shapes}@anchor{30c2}@anchor{library/turtle compoundshapes}@anchor{30c3}
@subsubsection 复合形状


要使用由多个不同颜色多边形构成的复合海龟形状，你必须明确地使用辅助类 @ref{30c4,,Shape}，具体步骤如下:


@enumerate 

@item 
创建一个空 Shape 对象，类型为 "compound"。

@item 
按照需要使用 @code{addcomponent()} 方法向此对象添加多个部件。

例如:

@example
>>> s = Shape("compound")
>>> poly1 = ((0,0),(10,-5),(0,10),(-10,-5))
>>> s.addcomponent(poly1, "red", "blue")
>>> poly2 = ((0,0),(10,-5),(-10,-5))
>>> s.addcomponent(poly2, "blue", "red")
@end example

@item 
接下来将 Shape 对象添加到 Screen 对象的形状列表并使用它:

@example
>>> register_shape("myshape", s)
>>> shape("myshape")
@end example
@end enumerate

@cartouche
@quotation 注解 
@ref{30c4,,Shape} 类在 @ref{30a8,,register_shape()} 方法的内部以多种方式使用。应用程序编写者 @emph{只有} 在使用上述的复合形状时才需要处理 Shape 类。
@end quotation
@end cartouche

@node TurtleScreen/Screen 方法及对应函数,公共类,RawTurtle/Turtle 方法和对应函数,turtle --- 海龟绘图
@anchor{library/turtle methods-of-turtlescreen-screen-and-corresponding-functions}@anchor{30c5}
@subsubsection TurtleScreen/Screen 方法及对应函数


本节中的大部分示例都使用 TurtleScreen 类的一个实例，命名为 @code{screen}。

@c >>> screen = Screen()

@menu
* 窗口控制:: 
* 动画控制:: 
* 使用屏幕事件:: 
* 输入方法:: 
* 设置与特殊方法:: 
* Screen 专有方法@comma{} 而非继承自 TurtleScreen: Screen 专有方法 而非继承自 TurtleScreen. 

@end menu

@node 窗口控制,动画控制,,TurtleScreen/Screen 方法及对应函数
@anchor{library/turtle window-control}@anchor{30c6}
@subsubsection 窗口控制


@geindex bgcolor() (在 turtle 模块中)
@anchor{library/turtle turtle bgcolor}@anchor{3093}
@deffn {函数} turtle.bgcolor (*args)

@*参数: 
@code{args} -- 一个颜色字符串或三个取值范围 0..colormode 内的数值或一个取值范围相同的数值3元组


设置或返回 TurtleScreen 的背景颜色。

@example
>>> screen.bgcolor("orange")
>>> screen.bgcolor()
'orange'
>>> screen.bgcolor("#800080")
>>> screen.bgcolor()
(128.0, 0.0, 128.0)
@end example
@end deffn

@geindex bgpic() (在 turtle 模块中)
@anchor{library/turtle turtle bgpic}@anchor{3094}
@deffn {函数} turtle.bgpic (picname=None)

@*参数: 
@code{picname} -- 一个字符串, gif-文件名, @code{"nopic"}, 或 @code{None}


设置背景图片或返回当前背景图片名称。如果 @emph{picname} 为一个文件名，则将相应图片设为背景。如果 @emph{picname} 为 @code{"nopic"}，则删除当前背景图片。如果 @emph{picname} 为 @code{None}，则返回当前背景图片文件名。:

@example
>>> screen.bgpic()
'nopic'
>>> screen.bgpic("landscape.gif")
>>> screen.bgpic()
"landscape.gif"
@end example
@end deffn

@geindex clear() (在 turtle 模块中)
@geindex clearscreen() (在 turtle 模块中)

@deffn {函数} turtle.clear ()
@anchor{library/turtle turtle clearscreen}@anchor{3095}
@deffnx {函数} turtle.clearscreen ()

从中删除所有海龟的全部绘图。将已清空的 TurtleScreen 重置为初始状态: 白色背景，无背景片，无事件绑定并启用追踪。

@cartouche
@quotation 注解 
此 TurtleScreen 方法作为全局函数时只有一个名字 @code{clearscreen}。全局函数 @code{clear} 所对应的是 Turtle 方法 @code{clear}。
@end quotation
@end cartouche
@end deffn

@geindex reset() (在 turtle 模块中)
@geindex resetscreen() (在 turtle 模块中)

@deffn {函数} turtle.reset ()
@anchor{library/turtle turtle resetscreen}@anchor{3096}
@deffnx {函数} turtle.resetscreen ()

重置屏幕上的所有海龟为其初始状态。

@cartouche
@quotation 注解 
此 TurtleScreen 方法作为全局函数时只有一个名字 @code{resetscreen}。全局函数 @code{reset} 所对应的是 Turtle 方法 @code{reset}。
@end quotation
@end cartouche
@end deffn

@geindex screensize() (在 turtle 模块中)
@anchor{library/turtle turtle screensize}@anchor{3097}
@deffn {函数} turtle.screensize (canvwidth=None, canvheight=None, bg=None)

@*参数: 

@itemize *

@item 
@code{canvwidth} -- 正整型数，以像素表示画布的新宽度值

@item 
@code{canvheight} -- 正整型数，以像素表示画面的新高度值

@item 
@code{bg} -- 颜色字符串或颜色元组，新的背景颜色
@end itemize


如未指定任何参数，则返回当前的 (canvaswidth, canvasheight)。否则改变作为海龟绘图场所的画布大小。不改变绘图窗口。要观察画布的隐藏区域，可以使用滚动条。通过此方法可以令之前绘制于画布之外的图形变为可见。

@example
>>> screen.screensize()
(400, 300)
>>> screen.screensize(2000,1500)
>>> screen.screensize()
(2000, 1500)
@end example

也可以用来寻找意外逃走的海龟 ;-)
@end deffn

@geindex setworldcoordinates() (在 turtle 模块中)
@anchor{library/turtle turtle setworldcoordinates}@anchor{3098}
@deffn {函数} turtle.setworldcoordinates (llx, lly, urx, ury)

@*参数: 

@itemize *

@item 
@code{llx} -- 一个数值, 画布左下角的 x-坐标

@item 
@code{lly} -- 一个数值, 画布左下角的 y-坐标

@item 
@code{urx} -- 一个数值, 画面右上角的 x-坐标

@item 
@code{ury} -- 一个数值, 画布右上角的 y-坐标
@end itemize


设置用户自定义坐标系并在必要时切换模式为 "world"。这会执行一次 @code{screen.reset()}。如果 "world" 模式已激活，则所有图形将根据新的坐标系重绘。

@strong{注意}: 在用户自定义坐标系中，角度可能显得扭曲。

@example
>>> screen.reset()
>>> screen.setworldcoordinates(-50,-7.5,50,7.5)
>>> for _ in range(72):
...     left(10)
...
>>> for _ in range(8):
...     left(45); fd(2)   # a regular octagon
@end example

@c >>> screen.reset()
@c >>> for t in turtles():
@c ...      t.reset()
@end deffn

@node 动画控制,使用屏幕事件,窗口控制,TurtleScreen/Screen 方法及对应函数
@anchor{library/turtle animation-control}@anchor{30c7}
@subsubsection 动画控制


@geindex delay() (在 turtle 模块中)
@anchor{library/turtle turtle delay}@anchor{3099}
@deffn {函数} turtle.delay (delay=None)

@*参数: 
@code{delay} -- 正整型数


设置或返回以毫秒数表示的延迟值 @emph{delay}。(这约等于连续两次画布刷新的间隔时间。) 绘图延迟越长，动画速度越慢。

可选参数:

@example
>>> screen.delay()
10
>>> screen.delay(5)
>>> screen.delay()
5
@end example
@end deffn

@geindex tracer() (在 turtle 模块中)
@anchor{library/turtle turtle tracer}@anchor{309a}
@deffn {函数} turtle.tracer (n=None, delay=None)

@*参数: 

@itemize *

@item 
@code{n} -- 非负整型数

@item 
@code{delay} -- 非负整型数
@end itemize


启用/禁用海龟动画并设置刷新图形的延迟时间。如果指定 @emph{n} 值，则只有每第 n 次屏幕刷新会实际执行。(可被用来加速复杂图形的绘制。) 如果调用时不带参数，则返回当前保存的 n 值。第二个参数设置延迟值 (参见 @ref{3099,,delay()})。

@example
>>> screen.tracer(8, 25)
>>> dist = 2
>>> for i in range(200):
...     fd(dist)
...     rt(90)
...     dist += 2
@end example
@end deffn

@geindex update() (在 turtle 模块中)
@anchor{library/turtle turtle update}@anchor{309b}
@deffn {函数} turtle.update ()

执行一次 TurtleScreen 刷新。在禁用追踪时使用。
@end deffn

另参见 RawTurtle/Turtle 方法 @ref{305a,,speed()}。

@node 使用屏幕事件,输入方法,动画控制,TurtleScreen/Screen 方法及对应函数
@anchor{library/turtle using-screen-events}@anchor{30c8}
@subsubsection 使用屏幕事件


@geindex listen() (在 turtle 模块中)
@anchor{library/turtle turtle listen}@anchor{309c}
@deffn {函数} turtle.listen (xdummy=None, ydummy=None)

设置焦点到 TurtleScreen (以便接收按键事件)。使用两个 Dummy 参数以便能够传递 @ref{309c,,listen()} 给 onclick 方法。
@end deffn

@geindex onkey() (在 turtle 模块中)
@geindex onkeyrelease() (在 turtle 模块中)
@anchor{library/turtle turtle onkey}@anchor{309d}
@deffn {函数} turtle.onkey (fun, key)
@anchor{library/turtle turtle onkeyrelease}@anchor{309e}
@deffnx {函数} turtle.onkeyrelease (fun, key)

@*参数: 

@itemize *

@item 
@code{fun} -- 一个无参数的函数或 @code{None}

@item 
@code{key} -- 一个字符串: 键 (例如 "a") 或键标 (例如 "space")
@end itemize


绑定 @emph{fun} 指定的函数到按键释放事件。如果 @emph{fun} 值为 @code{None}，则移除事件绑定。注: 为了能够注册按键事件，TurtleScreen 必须得到焦点。(参见 method @ref{309c,,listen()} 方法。)

@example
>>> def f():
...     fd(50)
...     lt(60)
...
>>> screen.onkey(f, "Up")
>>> screen.listen()
@end example
@end deffn

@geindex onkeypress() (在 turtle 模块中)
@anchor{library/turtle turtle onkeypress}@anchor{309f}
@deffn {函数} turtle.onkeypress (fun, key=None)

@*参数: 

@itemize *

@item 
@code{fun} -- 一个无参数的函数或 @code{None}

@item 
@code{key} -- 一个字符串: 键 (例如 "a") 或键标 (例如 "space")
@end itemize


绑定 @emph{fun} 指定的函数到指定键的按下事件。如未指定键则绑定到任意键的按下事件。注: 为了能够注册按键事件，必须得到焦点。(参见 @ref{309c,,listen()} 方法。)

@example
>>> def f():
...     fd(50)
...
>>> screen.onkey(f, "Up")
>>> screen.listen()
@end example
@end deffn

@geindex onclick() (在 turtle 模块中)
@geindex onscreenclick() (在 turtle 模块中)

@deffn {函数} turtle.onclick (fun, btn=1, add=None)
@anchor{library/turtle turtle onscreenclick}@anchor{30a0}
@deffnx {函数} turtle.onscreenclick (fun, btn=1, add=None)

@*参数: 

@itemize *

@item 
@code{fun} -- 一个函数，调用时将传入两个参数表示在画布上点击的坐标。

@item 
@code{btn} -- 鼠标按钮编号，默认值为 1 (鼠标左键)

@item 
@code{add} -- @code{True} 或 @code{False} -- 如为 @code{True} 则将添加一个新绑定，否则将取代先前的绑定
@end itemize


绑定 @emph{fun} 指定的函数到鼠标点击屏幕事件。如果 @emph{fun} 值为 @code{None}，则移除现有的绑定。

以下示例使用一个 TurtleScreen 实例 @code{screen} 和一个 Turtle 实例 turtle:

@example
>>> screen.onclick(turtle.goto) # Subsequently clicking into the TurtleScreen will
>>>                             # make the turtle move to the clicked point.
>>> screen.onclick(None)        # remove event binding again
@end example

@cartouche
@quotation 注解 
此 TurtleScreen 方法作为全局函数时只有一个名字 @code{onscreenclick}。全局函数 @code{onclick} 所对应的是 Turtle 方法 @code{onclick}。
@end quotation
@end cartouche
@end deffn

@geindex ontimer() (在 turtle 模块中)
@anchor{library/turtle turtle ontimer}@anchor{30a1}
@deffn {函数} turtle.ontimer (fun, t=0)

@*参数: 

@itemize *

@item 
@code{fun} -- 一个无参数的函数

@item 
@code{t} -- 一个数值 >= 0
@end itemize


安装一个计时器，在 @emph{t} 毫秒后调用 @emph{fun} 函数。

@example
>>> running = True
>>> def f():
...     if running:
...         fd(50)
...         lt(60)
...         screen.ontimer(f, 250)
>>> f()   ### makes the turtle march around
>>> running = False
@end example
@end deffn

@geindex mainloop() (在 turtle 模块中)
@geindex done() (在 turtle 模块中)
@anchor{library/turtle turtle mainloop}@anchor{30a2}
@deffn {函数} turtle.mainloop ()
@anchor{library/turtle turtle done}@anchor{30a3}
@deffnx {函数} turtle.done ()

开始事件循环 - 调用 Tkinter 的 mainloop 函数。必须作为一个海龟绘图程序的结束语句。如果一个脚本是在以 -n 模式 (无子进程) 启动的 IDLE 中运行时 @emph{不可} 使用 - 用于实现海龟绘图的交互功能。:

@example
>>> screen.mainloop()
@end example
@end deffn

@node 输入方法,设置与特殊方法,使用屏幕事件,TurtleScreen/Screen 方法及对应函数
@anchor{library/turtle input-methods}@anchor{30c9}
@subsubsection 输入方法


@geindex textinput() (在 turtle 模块中)
@anchor{library/turtle turtle textinput}@anchor{30ad}
@deffn {函数} turtle.textinput (title, prompt)

@*参数: 

@itemize *

@item 
@code{title} -- string

@item 
@code{prompt} -- string
@end itemize


弹出一个对话框窗口用来输入一个字符串。形参 title 为对话框窗口的标题，prompt 为一条文本，通常用来提示要输入什么信息。返回输入的字符串。如果对话框被取消则返回 @code{None}。:

@example
>>> screen.textinput("NIM", "Name of first player:")
@end example
@end deffn

@geindex numinput() (在 turtle 模块中)
@anchor{library/turtle turtle numinput}@anchor{30ae}
@deffn {函数} turtle.numinput (title, prompt, default=None, minval=None, maxval=None)

@*参数: 

@itemize *

@item 
@code{title} -- string

@item 
@code{prompt} -- string

@item 
@code{default} -- 数值 (可选)

@item 
@code{minval} -- 数值 (可选)

@item 
@code{maxval} -- 数值 (可选)
@end itemize


弹出一个对话框窗口用来输入一个数值。title 为对话框窗口的标题，prompt 为一条文本，通常用来描述要输入的数值信息。default: 默认值, minval: 可输入的最小值, maxval: 可输入的最大值。输入数值的必须在指定的 minval .. maxval 范围之内，否则将给出一条提示，对话框保持打开等待修改。返回输入的数值。如果对话框被取消则返回 @code{None}。:

@example
>>> screen.numinput("Poker", "Your stakes:", 1000, minval=10, maxval=10000)
@end example
@end deffn

@node 设置与特殊方法,Screen 专有方法 而非继承自 TurtleScreen,输入方法,TurtleScreen/Screen 方法及对应函数
@anchor{library/turtle settings-and-special-methods}@anchor{30ca}
@subsubsection 设置与特殊方法


@geindex mode() (在 turtle 模块中)
@anchor{library/turtle turtle mode}@anchor{30a4}
@deffn {函数} turtle.mode (mode=None)

@*参数: 
@code{mode} -- 字符串 "standard", "logo" 或 "world" 其中之一


设置海龟模式 ("standard", "logo" 或 "world") 并执行重置。如未指定模式则返回当前的模式。

"standard" 模式与旧的 @ref{116,,turtle} 兼容。"logo" 模式与大部分 Logo 海龟绘图兼容。"world" 模式使用用户自定义的 "世界坐标系"。@strong{注意}: 在此模式下，如果 @code{x/y} 单位比率不等于 1 则角度会显得扭曲。


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx} 
@headitem

模式

@tab

初始海龟朝向

@tab

正数角度

@item

"standard"

@tab

朝右 (东)

@tab

逆时针

@item

"logo"

@tab

朝上 (北)

@tab

顺时针

@end multitable


@example
>>> mode("logo")   # resets turtle heading to north
>>> mode()
'logo'
@end example
@end deffn

@geindex colormode() (在 turtle 模块中)
@anchor{library/turtle turtle colormode}@anchor{30a5}
@deffn {函数} turtle.colormode (cmode=None)

@*参数: 
@code{cmode} -- 数值 1.0 或 255 其中之一


返回颜色模式或将其设为 1.0 或 255。构成颜色三元组的 @emph{r}, @emph{g}, @emph{b} 数值必须在 0..@emph{cmode} 范围之内。

@example
>>> screen.colormode(1)
>>> turtle.pencolor(240, 160, 80)
Traceback (most recent call last):
     ...
TurtleGraphicsError: bad color sequence: (240, 160, 80)
>>> screen.colormode()
1.0
>>> screen.colormode(255)
>>> screen.colormode()
255
>>> turtle.pencolor(240,160,80)
@end example
@end deffn

@geindex getcanvas() (在 turtle 模块中)
@anchor{library/turtle turtle getcanvas}@anchor{30a6}
@deffn {函数} turtle.getcanvas ()

返回此 TurtleScreen 的 Canvas 对象。供了解 Tkinter 的 Canvas 对象内部机理的人士使用。

@example
>>> cv = screen.getcanvas()
>>> cv
<turtle.ScrolledCanvas object ...>
@end example
@end deffn

@geindex getshapes() (在 turtle 模块中)
@anchor{library/turtle turtle getshapes}@anchor{30a7}
@deffn {函数} turtle.getshapes ()

返回所有当前可用海龟形状的列表。

@example
>>> screen.getshapes()
['arrow', 'blank', 'circle', ..., 'turtle']
@end example
@end deffn

@geindex register_shape() (在 turtle 模块中)
@geindex addshape() (在 turtle 模块中)
@anchor{library/turtle turtle register_shape}@anchor{30a8}
@deffn {函数} turtle.register_shape (name, shape=None)
@anchor{library/turtle turtle addshape}@anchor{30a9}
@deffnx {函数} turtle.addshape (name, shape=None)

调用此函数有三种不同方式:


@enumerate 

@item 
@emph{name} 为一个 gif 文件的文件名， @emph{shape} 为 @code{None}: 安装相应的图像形状。:

@example
>>> screen.register_shape("turtle.gif")
@end example

@cartouche
@quotation 注解 
当海龟转向时图像形状 @emph{不会} 转动，因此无法显示海龟的朝向!
@end quotation
@end cartouche

@item 
@emph{name} 为指定的字符串，@emph{shape} 为由坐标值对构成的元组: 安装相应的多边形形状。

@example
>>> screen.register_shape("triangle", ((5,-3), (0,5), (-5,-3)))
@end example

@item 
@emph{name} 为指定的字符串， 为一个 (复合) @ref{30c4,,Shape} 类对象: 安装相应的复合形状。
@end enumerate

将一个海龟形状加入 TurtleScreen 的形状列表。只有这样注册过的形状才能通过执行 @code{shape(shapename)} 命令来使用。
@end deffn

@geindex turtles() (在 turtle 模块中)
@anchor{library/turtle turtle turtles}@anchor{30aa}
@deffn {函数} turtle.turtles ()

返回屏幕上的海龟列表。

@example
>>> for turtle in screen.turtles():
...     turtle.color("red")
@end example
@end deffn

@geindex window_height() (在 turtle 模块中)
@anchor{library/turtle turtle window_height}@anchor{30ab}
@deffn {函数} turtle.window_height ()

返回海龟窗口的高度。:

@example
>>> screen.window_height()
480
@end example
@end deffn

@geindex window_width() (在 turtle 模块中)
@anchor{library/turtle turtle window_width}@anchor{30ac}
@deffn {函数} turtle.window_width ()

返回海龟窗口的宽度。:

@example
>>> screen.window_width()
640
@end example
@end deffn

@node Screen 专有方法 而非继承自 TurtleScreen,,设置与特殊方法,TurtleScreen/Screen 方法及对应函数
@anchor{library/turtle methods-specific-to-screen-not-inherited-from-turtlescreen}@anchor{30cb}@anchor{library/turtle screenspecific}@anchor{30cc}
@subsubsection Screen 专有方法, 而非继承自 TurtleScreen


@geindex bye() (在 turtle 模块中)
@anchor{library/turtle turtle bye}@anchor{30af}
@deffn {函数} turtle.bye ()

关闭海龟绘图窗口。
@end deffn

@geindex exitonclick() (在 turtle 模块中)
@anchor{library/turtle turtle exitonclick}@anchor{30b0}
@deffn {函数} turtle.exitonclick ()

将 bye() 方法绑定到 Screen 上的鼠标点击事件。

如果配置字典中 "using_IDLE" 的值为 @code{False} (默认值) 则同时进入主事件循环。注: 如果启动 IDLE 时使用了 @code{-n} 开关 (无子进程)，@code{turtle.cfg} 中此数值应设为 @code{True}。在此情况下 IDLE 本身的主事件循环同样会作用于客户脚本。
@end deffn

@geindex setup() (在 turtle 模块中)
@anchor{library/turtle turtle setup}@anchor{30b1}
@deffn {函数} turtle.setup (width=_CFG["width"], height=_CFG["height"], startx=_CFG["leftright"], starty=_CFG["topbottom"])

设置主窗口的大小和位置。默认参数值保存在配置字典中，可通过 @code{turtle.cfg} 文件进行修改。

@*参数: 

@itemize *

@item 
@code{width} -- 如为一个整型数值，表示大小为多少像素，如为一个浮点数值，则表示屏幕的占比；默认为屏幕的 50%

@item 
@code{height} -- 如为一个整型数值，表示高度为多少像素，如为一个浮点数值，则表示屏幕的占比；默认为屏幕的 75%

@item 
@code{startx} -- 如为正值，表示初始位置距离屏幕左边缘多少像素，负值表示距离右边缘，@code{None} 表示窗口水平居中

@item 
@code{starty} -- 如为正值，表示初始位置距离屏幕上边缘多少像素，负值表示距离下边缘，@code{None} 表示窗口垂直居中
@end itemize


@example
>>> screen.setup (width=200, height=200, startx=0, starty=0)
>>>              # sets window to 200x200 pixels, in upper left of screen
>>> screen.setup(width=.75, height=0.5, startx=None, starty=None)
>>>              # sets window to 75% of screen by 50% of screen and centers
@end example
@end deffn

@geindex title() (在 turtle 模块中)
@anchor{library/turtle turtle title}@anchor{30b2}
@deffn {函数} turtle.title (titlestring)

@*参数: 
@code{titlestring} -- 一个字符串，显示为海龟绘图窗口的标题栏文本


设置海龟窗口标题为 @emph{titlestring} 指定的文本。

@example
>>> screen.title("Welcome to the turtle zoo!")
@end example
@end deffn

@node 公共类,帮助与配置,TurtleScreen/Screen 方法及对应函数,turtle --- 海龟绘图
@anchor{library/turtle public-classes}@anchor{30cd}
@subsubsection 公共类


@geindex RawTurtle (turtle 中的类)
@geindex RawPen (turtle 中的类)
@anchor{library/turtle turtle RawTurtle}@anchor{303e}
@deffn {类} turtle.RawTurtle (canvas)
@anchor{library/turtle turtle RawPen}@anchor{303f}
@deffnx {类} turtle.RawPen (canvas)

@*参数: 
@code{canvas} -- 一个 @code{tkinter.Canvas} , @ref{303c,,ScrolledCanvas} 或 @ref{303b,,TurtleScreen} 类对象


创建一个海龟。海龟对象具有 "Turtle/RawTurtle 方法" 一节所述的全部方法。
@end deffn

@geindex Turtle (turtle 中的类)
@anchor{library/turtle turtle Turtle}@anchor{3040}
@deffn {类} turtle.Turtle

RawTurtle 的子类，具有相同的接口，但其绘图场所为默认的 @ref{303d,,Screen} 类对象，在首次使用时自动创建。
@end deffn

@geindex TurtleScreen (turtle 中的类)
@anchor{library/turtle turtle TurtleScreen}@anchor{303b}
@deffn {类} turtle.TurtleScreen (cv)

@*参数: 
@code{cv} -- 一个 @code{tkinter.Canvas} 类对象


提供面向屏幕的方法例如 @code{setbg()} 等。说明见上文。
@end deffn

@geindex Screen (turtle 中的类)
@anchor{library/turtle turtle Screen}@anchor{303d}
@deffn {类} turtle.Screen

TurtleScreen 的子类，@ref{30cc,,增加了四个方法}.
@end deffn

@geindex ScrolledCanvas (turtle 中的类)
@anchor{library/turtle turtle ScrolledCanvas}@anchor{303c}
@deffn {类} turtle.ScrolledCanvas (master)

@*参数: 
@code{master} -- 可容纳 ScrolledCanvas 的 Tkinter 部件，即添加了滚动条的 Tkinter-canvas


由 Screen 类使用，使其能够自动提供一个 ScrolledCanvas 作为海龟的绘图场所。
@end deffn

@geindex Shape (turtle 中的类)
@anchor{library/turtle turtle Shape}@anchor{30c4}
@deffn {类} turtle.Shape (type_, data)

@*参数: 
@code{type_} -- 字符串 "polygon", "image", "compound" 其中之一


实现形状的数据结构。@code{(type_, data)} 必须遵循以下定义:


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

@emph{type_}

@tab

@emph{data}

@item

"polygon"

@tab

一个多边形元组，即由坐标值对构成的元组

@item

"image"

@tab

一个图片  (此形式仅限内部使用!)

@item

"compound"

@tab

@code{None} (复合形状必须使用 @ref{30ce,,addcomponent()} 方法来构建)

@end multitable


@geindex addcomponent() (turtle.Shape 方法)
@anchor{library/turtle turtle Shape addcomponent}@anchor{30ce}
@deffn {方法} addcomponent (poly, fill, outline=None)

@*参数: 

@itemize *

@item 
@code{poly} -- 一个多边形，即由数值对构成的元组

@item 
@code{fill} -- 一种颜色，将用来填充 @emph{poly} 指定的多边形

@item 
@code{outline} -- 一种颜色，用于多边形的轮廓 (如有指定)
@end itemize


示例:

@example
>>> poly = ((0,0),(10,-5),(0,10),(-10,-5))
>>> s = Shape("compound")
>>> s.addcomponent(poly, "red", "blue")
>>> # ... add more components and then use register_shape()
@end example

参见 @ref{30c3,,复合形状}。
@end deffn
@end deffn

@geindex Vec2D (turtle 中的类)
@anchor{library/turtle turtle Vec2D}@anchor{30b5}
@deffn {类} turtle.Vec2D (x, y)

一个二维矢量类，用来作为实现海龟绘图的辅助类。也可能在海龟绘图程序中使用。派生自元组，因此矢量也属于元组!

提供的运算 (@emph{a}, @emph{b} 为矢量, @emph{k} 为数值):


@itemize *

@item 
@code{a + b} 矢量加法

@item 
@code{a - b} 矢量减法

@item 
@code{a * b} 内积

@item 
@code{k * a} 和 @code{a * k} 与标量相乘

@item 
@code{abs(a)} a 的绝对值

@item 
@code{a.rotate(angle)} 旋转
@end itemize
@end deffn

@node 帮助与配置,turtledemo --- 演示脚本集,公共类,turtle --- 海龟绘图
@anchor{library/turtle help-and-configuration}@anchor{30cf}
@subsubsection 帮助与配置


@menu
* 如何使用帮助:: 
* 文档字符串翻译为不同的语言:: 
* 如何配置 Screen 和 Turtle:: 

@end menu

@node 如何使用帮助,文档字符串翻译为不同的语言,,帮助与配置
@anchor{library/turtle how-to-use-help}@anchor{30d0}
@subsubsection 如何使用帮助


Screen 和 Turtle 类的公用方法以文档字符串提供了详细的文档。因此可以利用 Python 帮助工具获取这些在线帮助信息:


@itemize -

@item 
当使用 IDLE 时，输入函数/方法调用将弹出工具提示显示其签名和文档字符串的头几行。

@item 
对文法或函数调用 @ref{56d,,help()} 将显示其文档字符串:

@example
>>> help(Screen.bgcolor)
Help on method bgcolor in module turtle:

bgcolor(self, *args) unbound turtle.Screen method
    Set or return backgroundcolor of the TurtleScreen.

    Arguments (if given): a color string or three numbers
    in the range 0..colormode or a 3-tuple of such numbers.


      >>> screen.bgcolor("orange")
      >>> screen.bgcolor()
      "orange"
      >>> screen.bgcolor(0.5,0,0.5)
      >>> screen.bgcolor()
      "#800080"

>>> help(Turtle.penup)
Help on method penup in module turtle:

penup(self) unbound turtle.Turtle method
    Pull the pen up -- no drawing when moving.

    Aliases: penup | pu | up

    No argument

    >>> turtle.penup()
@end example

@item 
方法对应函数的文档字符串的形式会有一些修改:

@example
>>> help(bgcolor)
Help on function bgcolor in module turtle:

bgcolor(*args)
    Set or return backgroundcolor of the TurtleScreen.

    Arguments (if given): a color string or three numbers
    in the range 0..colormode or a 3-tuple of such numbers.

    Example::

      >>> bgcolor("orange")
      >>> bgcolor()
      "orange"
      >>> bgcolor(0.5,0,0.5)
      >>> bgcolor()
      "#800080"

>>> help(penup)
Help on function penup in module turtle:

penup()
    Pull the pen up -- no drawing when moving.

    Aliases: penup | pu | up

    No argument

    Example:
    >>> penup()
@end example
@end itemize

这些修改版文档字符串是在导入时与方法对应函数的定义一起自动生成的。

@node 文档字符串翻译为不同的语言,如何配置 Screen 和 Turtle,如何使用帮助,帮助与配置
@anchor{library/turtle translation-of-docstrings-into-different-languages}@anchor{30d1}
@subsubsection 文档字符串翻译为不同的语言


可使用工具创建一个字典，键为方法名，值为 Screen 和 Turtle 类公共方法的文档字符串。

@geindex write_docstringdict() (在 turtle 模块中)
@anchor{library/turtle turtle write_docstringdict}@anchor{30d2}
@deffn {函数} turtle.write_docstringdict (filename="turtle_docstringdict")

@*参数: 
@code{filename} -- 一个字符串，表示文件名


创建文档字符串字典并将其写入 filename 指定的 Python 脚本文件。此函数必须显示地调用 (海龟绘图类并不使用此函数)。文档字符串字典将被写入到 Python 脚本文件 @code{@emph{filename}.py}。该文件可作为模板用来将文档字符串翻译为不同语言。
@end deffn

如果你 (或你的学生) 想使用本国语言版本的 @ref{116,,turtle} 在线帮助，你必须翻译文档字符串并保存结果文件，例如 @code{turtle_docstringdict_german.py}.

如果你在 @code{turtle.cfg} 文件中加入了相应的条目，此字典将在导入模块时被读取并替代原有的英文版文档字符串。

在撰写本文档时已经有了德语和意大利语版的文档字符串字典。(更多需求请联系 @email{glingl@@aon.at})

@node 如何配置 Screen 和 Turtle,,文档字符串翻译为不同的语言,帮助与配置
@anchor{library/turtle how-to-configure-screen-and-turtles}@anchor{30d3}
@subsubsection 如何配置 Screen 和 Turtle


内置的默认配置是模仿旧 turtle 模块的外观和行为，以便尽可能地与其保持兼容。

如果你想使用不同的配置，以便更好地反映此模块的特性或是更适合你的需求，例如在课堂中使用，你可以准备一个配置文件 @code{turtle.cfg}，该文件将在导入模块时被读取并根据其中的设定修改模块配置。

内置的配置对应以下的 turtle.cfg:

@example
width = 0.5
height = 0.75
leftright = None
topbottom = None
canvwidth = 400
canvheight = 300
mode = standard
colormode = 1.0
delay = 10
undobuffersize = 1000
shape = classic
pencolor = black
fillcolor = black
resizemode = noresize
visible = True
language = english
exampleturtle = turtle
examplescreen = screen
title = Python Turtle Graphics
using_IDLE = False
@end example

选定条目的简短说明:


@itemize -

@item 
开头的四行对应 @code{Screen.setup()} 方法的参数。

@item 
第 5 和 6 行对应 @code{Screen.screensize()} 方法的参数。

@item 
@emph{shape} 可以是任何内置形状，即: arrow, turtle 等。更多信息可用 @code{help(shape)} 查看。

@item 
如果你想使用无填充色 (即令海龟变透明)，你必须写 @code{fillcolor = ""} (但 cfg 文件中所有非空字符串都不可加引号)。

@item 
如果你想令海龟反映其状态，你必须使用 @code{resizemode = auto}。

@item 
如果你设置语言例如 @code{language = italian} 则文档字符串字典 @code{turtle_docstringdict_italian.py} 将在导入模块时被加载 (如果导入路径即 @ref{116,,turtle} 的目录中存在此文件。

@item 
@emph{exampleturtle} 和 @emph{examplescreen} 条目定义了相应对象在文档字符串中显示的名称。方法文档字符串转换为函数文档字符串时将从文档字符串中删去这些名称。

@item 
@emph{using_IDLE}: 如果你经常使用 IDLE 并启用其 -n 开关 ("无子进程") 则应将此项设为 @code{True}，这将阻止 @ref{30b0,,exitonclick()} 进入主事件循环。
@end itemize

@code{turtle.cfg} 文件可以保存于 @ref{116,,turtle} 所在目录，当前工作目录也可以有一个同名文件。后者会重载覆盖前者的设置。

@code{Lib/turtledemo} 目录中也有一个 @code{turtle.cfg} 文件。你可以将其作为示例进行研究，并在运行演示时查看其作用效果 (但最好不要在演示查看器中运行)。

@node turtledemo --- 演示脚本集,Python 2 6 之后的变化,帮助与配置,turtle --- 海龟绘图
@anchor{library/turtle module-turtledemo}@anchor{117}@anchor{library/turtle turtledemo-demo-scripts}@anchor{30d4}
@subsubsection @code{turtledemo} --- 演示脚本集


@geindex turtledemo (模块)

@ref{117,,turtledemo} 包汇集了一组演示脚本。这些脚本可以通过以下命令打开所提供的演示查看器运行和查看:

@example
python -m turtledemo
@end example

此外，你也可以单独运行其中的演示脚本。例如，:

@example
python -m turtledemo.bytedesign
@end example

@ref{117,,turtledemo} 包目录中的内容:


@itemize -

@item 
一个演示查看器 @code{__main__.py}，可用来查看脚本的源码并即时运行。

@item 
多个脚本文件，演示 @ref{116,,turtle} 模块的不同特性。所有示例可通过 Examples 菜单打开。也可以单独运行每个脚本。

@item 
一个 @code{turtle.cfg} 文件，作为说明如何编写并使用模块配置文件的示例模板。
@end itemize

演示脚本清单如下:


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

名称

@tab

描述

@tab

相关特性

@item

bytedesign

@tab

复杂的传统海龟绘图模式

@tab

@code{tracer()}, delay,
@code{update()}

@item

chaos

@tab

绘制 Verhulst 动态模型，演示通过计算机的运算可能会生成令人惊叹的结果

@tab

世界坐标系

@item

clock

@tab

绘制模拟时钟显示本机的当前时间

@tab

海龟作为表针, ontimer

@item

colormixer

@tab

试验 r, g, b 颜色模式

@tab

@code{ondrag()} 当鼠标拖动

@item

forest

@tab

绘制 3 棵广度优先树

@tab

随机化

@item

fractalcurves

@tab

绘制 Hilbert & Koch 曲线

@tab

递归

@item

lindenmayer

@tab

文化数学 (印度装饰艺术)

@tab

L-系统

@item

minimal_hanoi

@tab

汉诺塔

@tab

矩形海龟作为汉诺盘 (shape, shapesize)

@item

nim

@tab

玩经典的“尼姆”游戏，开始时有三堆小棒，与电脑对战。

@tab

海龟作为小棒，事件驱动 (鼠标, 键盘)

@item

paint

@tab

超极简主义绘画程序

@tab

@code{onclick()} 当鼠标点击

@item

peace

@tab

初级技巧

@tab

海龟: 外观与动画

@item

penrose

@tab

非周期性地使用风筝和飞镖形状铺满平面

@tab

@code{stamp()} 印章

@item

planet_and_moon

@tab

模拟引力系统

@tab

复合开关, @code{Vec2D} 类

@item

round_dance

@tab

两两相对并不断旋转舞蹈的海龟

@tab

复合形状, clone shapesize, tilt, get_shapepoly, update

@item

sorting_animate

@tab

动态演示不同的排序方法

@tab

简单对齐, 随机化

@item

tree

@tab

一棵 (图形化的) 广度优先树 (使用生成器)

@tab

@code{clone()} 克隆

@item

two_canvases

@tab

简单设计

@tab

两块画布上的海龟

@item

wikipedia

@tab

一个来自介绍海龟绘图的维基百科文章的图案

@tab

@code{clone()},
@code{undo()}

@item

yinyang

@tab

另一个初级示例

@tab

@code{circle()} 画圆

@end multitable


祝你玩得开心！

@node Python 2 6 之后的变化,Python 3 0 之后的变化,turtledemo --- 演示脚本集,turtle --- 海龟绘图
@anchor{library/turtle changes-since-python-2-6}@anchor{30d5}
@subsubsection Python 2.6 之后的变化



@itemize -

@item 
@code{Turtle.tracer()}, @code{Turtle.window_width()} 和 @code{Turtle.window_height()} 方法已被去除。具有这些名称和功能的方法现在只限于 @code{Screen} 类的方法。但其对应的函数仍然可用。(实际上在 Python 2.6 中这些方法就已经只是从对应的 @code{TurtleScreen}/@code{Screen} 类的方法复制而来。)

@item 
@code{Turtle.fill()} 方法已被去除。@code{begin_fill()} 和 @code{end_fill()} 的行为则有细微改变: 现在每个填充过程必须以一个 @code{end_fill()} 调用来结束。

@item 
新增了一个 @code{Turtle.filling()} 方法。该方法返回一个布尔值: 如果填充过程正在进行为 @code{True}，否则为 @code{False}。此行为相当于 Python 2.6 中不带参数的 @code{fill()} 调用。
@end itemize

@node Python 3 0 之后的变化,,Python 2 6 之后的变化,turtle --- 海龟绘图
@anchor{library/turtle changes-since-python-3-0}@anchor{30d6}
@subsubsection Python 3.0 之后的变化



@itemize -

@item 
新增了 @code{Turtle.shearfactor()}, @code{Turtle.shapetransform()} 和 @code{Turtle.get_shapepoly()} 方法。这样就可以使用所有标准线性变换来调整海龟形状。@code{Turtle.tiltangle()} 的功能已被加强: 现在可被用来获取或设置倾角。@code{Turtle.settiltangle()} 已弃用。

@item 
新增了 @code{Screen.onkeypress()} 方法作为对 @code{Screen.onkey()} 的补充，实际就是将行为绑定到 keyrelease 事件。后者相应增加了一个别名: @code{Screen.onkeyrelease()}。

@item 
新增了  @code{Screen.mainloop()} 方法。这样当仅需使用 Screen 和 Turtle 对象时不需要再额外导入 @code{mainloop()}。

@item 
新增了两个方法 @code{Screen.textinput()} 和 @code{Screen.numinput()}。用来弹出对话框接受输入并分别返回字符串和数值。

@item 
两个新的示例脚本 @code{tdemo_nim.py} 和 @code{tdemo_round_dance.py} 被加入到 @code{Lib/turtledemo} 目录中。
@end itemize

@c >>> for turtle in turtles():
@c ...      turtle.reset()
@c >>> turtle.penup()
@c >>> turtle.goto(-200,25)
@c >>> turtle.pendown()
@c >>> turtle.write("No one expects the Spanish Inquisition!",
@c ...      font=("Arial", 20, "normal"))
@c >>> turtle.penup()
@c >>> turtle.goto(-100,-50)
@c >>> turtle.pendown()
@c >>> turtle.write("Our two chief Turtles are...",
@c ...      font=("Arial", 16, "normal"))
@c >>> turtle.penup()
@c >>> turtle.goto(-450,-75)
@c >>> turtle.write(str(turtles()))

@node cmd --- 支持面向行的命令解释器,shlex --- Simple lexical analysis,turtle --- 海龟绘图,程序框架
@anchor{library/cmd doc}@anchor{30d7}@anchor{library/cmd cmd-support-for-line-oriented-command-interpreters}@anchor{30d8}@anchor{library/cmd module-cmd}@anchor{1a}
@subsection @code{cmd} --- 支持面向行的命令解释器


@geindex cmd (模块)

@strong{源代码:} Lib/cmd.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/cmd.py}


__________________________________________________________________


@ref{30d9,,Cmd} 类提供简单框架用于编写面向行的命令解释器。  这些通常对测试工具，管理工具和原型有用，这些工具随后将被包含在更复杂的接口中。

@geindex Cmd (cmd 中的类)
@anchor{library/cmd cmd Cmd}@anchor{30d9}
@deffn {类} cmd.Cmd (completekey='tab', stdin=None, stdout=None)

一个 @ref{30d9,,Cmd} 实例或子类实例是面向行的解释器框架结构。 实例化 @ref{30d9,,Cmd} 本身是没有充分理由的， 它作为自定义解释器类的超类是非常有用的为了继承 @ref{30d9,,Cmd} 的方法并且封装动作方法。

可选参数 @emph{completekey} 是完成键的 @ref{de,,readline} 名称；默认是 @code{Tab} 。如果 @emph{completekey} 不是 @ref{157,,None} 并且 @ref{de,,readline} 是可用的， 命令完成会自动完成。

可选参数 @emph{stdin} 和 @emph{stdout} 指定了Cmd实例或子类实例将用于输入和输出的输入和输出文件对象。如果没有指定，他们将默认为 @ref{306,,sys.stdin} 和 @ref{307,,sys.stdout} 。

如果你想要使用一个给定的 @emph{stdin} ，确保将实例的 @ref{30da,,use_rawinput} 属性设置为 @code{False} ，否则 @emph{stdin} 将被忽略。
@end deffn

@menu
* Cmd 对象:: 
* Cmd 例子:: 

@end menu

@node Cmd 对象,Cmd 例子,,cmd --- 支持面向行的命令解释器
@anchor{library/cmd cmd-objects}@anchor{30db}@anchor{library/cmd id1}@anchor{30dc}
@subsubsection Cmd 对象


@ref{30d9,,Cmd} 实例有下列方法：

@geindex cmdloop() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd cmdloop}@anchor{30dd}
@deffn {方法} Cmd.cmdloop (intro=None)

反复发出提示，接受输入，从收到的输入中解析出一个初始前缀，并分派给操作方法，将其余的行作为参数传递给它们。

可选参数是在第一个提示之前发布的横幅或介绍字符串（这将覆盖 @ref{30de,,intro} 类属性）。

如果 @ref{de,,readline} 继承模块被加载，输入将自动继承类似 @code{bash}的历史列表编辑（例如， @code{Control-P} 滚动回到最后一个命令， @code{Control-N} 转到下一个命令，以 @code{Control-F} 非破坏性的方式向右 @code{Control-B} 移动光标，破坏性地等）。

输入的文件结束符被作为字符串传回 @code{'EOF'} 。

@geindex ? (question mark); in a command interpreter
@geindex ! (exclamation); in a command interpreter

解释器实例将会识别命令名称 @code{foo} 当且仅当它有方法 @code{do_foo()} 。有一个特殊情况，分派始于字符 @code{'?'} 的行到方法 @code{do_help()} 。另一种特殊情况，分派始于字符 @code{'!'} 的行到方法 @code{do_shell()} （如果定义了这个方法）

这个方法将返回当 @ref{30df,,postcmd()} 方法返回一个真值 。参数 @emph{stop} 到 @ref{30df,,postcmd()} 是命令对应的返回值 @code{do_*()} 的方法。

如果激活了完成，全部命令将会自动完成，并且通过调用 @code{complete_foo()} 参数 @emph{text} , @emph{line}, @emph{begidx} ,和 @emph{endidx} 完成全部命令参数。 @emph{text} 是我们试图匹配的字符串前缀，所有返回的匹配项必须以它为开头。 @emph{line} 是删除了前导空格的当前的输入行， @emph{begidx} 和 @emph{endidx} 是前缀文本的开始和结束索引。，可以用于根据参数位置提供不同的完成。

所有 @ref{30d9,,Cmd} 的子类继承一个预定义 @code{do_help()} 。 这个方法使用参数 @code{'bar'} 调用， 调用对应的方法 @code{help_bar()} ，如果不存在，打印 @code{do_bar()} 的文档字符串，如果可用。没有参数的情况下， @code{do_help()} 方法会列出所有可用的帮助主题 （即所有具有相应的 @code{help_*()} 方法或命令的 文档字符串），也会列举所有未被记录的命令。
@end deffn

@geindex onecmd() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd onecmd}@anchor{30e0}
@deffn {方法} Cmd.onecmd (str)

解释该参数，就好像它是为响应提示而键入的一样。 这可能会被覆盖，但通常不应该被覆盖; 请参阅： @ref{30e1,,precmd()} 和 @ref{30df,,postcmd()} 方法，用于执行有用的挂钩。 返回值是一个标志，指示解释器对命令的解释是否应该停止。 如果命令 @emph{str} 有一个 @code{do_*()} 方法，则返回该方法的返回值，否则返回 @ref{30e2,,default()} 方法的返回值。
@end deffn

@geindex emptyline() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd emptyline}@anchor{30e3}
@deffn {方法} Cmd.emptyline ()

在响应提示输入空行时调用的方法。如果此方法未被覆盖，则重复输入的最后一个非空命令。
@end deffn

@geindex default() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd default}@anchor{30e2}
@deffn {方法} Cmd.default (line)

当命令前缀不能被识别的时候在输入行调用的方法。如果此方法未被覆盖，它将输出一个错误信息并返回。
@end deffn

@geindex completedefault() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd completedefault}@anchor{30e4}
@deffn {方法} Cmd.completedefault (text, line, begidx, endidx)

当没有特定于命令的 @code{complete_*()} 方法可用时，调用此方法完成输入行。默认情况下，它返回一个空列表。
@end deffn

@geindex precmd() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd precmd}@anchor{30e1}
@deffn {方法} Cmd.precmd (line)

钩方法在命令行 @emph{line} 被解释之前执行，但是在输入提示被生成和发出后。这个方法是一个在 @ref{30d9,,Cmd} 中的存根；它的存在是为了被子类覆盖。返回值被用作  @ref{30e0,,onecmd()} 方法执行的命令； @ref{30e1,,precmd()} 的实现或许会重写命令或者简单的返回 @emph{line} 不变。
@end deffn

@geindex postcmd() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd postcmd}@anchor{30df}
@deffn {方法} Cmd.postcmd (stop, line)

钩方法只在命令调度完成后执行。这个方法是一个在 @ref{30d9,,Cmd} 中的存根；它的存在是为了子类被覆盖。 @emph{line} 是被执行的命令行， @emph{stop} 是一个表示在调用 @ref{30df,,postcmd()} 之后是否终止执行的标志；这将作为 @ref{30e0,,onecmd()} 方法的返回值。这个方法的返回值被用作与 @emph{stop} 相关联的内部标志的新值；返回 false 将导致解释继续。
@end deffn

@geindex preloop() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd preloop}@anchor{30e5}
@deffn {方法} Cmd.preloop ()

钩方法当 @ref{30dd,,cmdloop()} 被调用时执行一次。方法是一个在 @ref{30d9,,Cmd} 中的存根；它的存在是为了被子类覆盖。
@end deffn

@geindex postloop() (cmd.Cmd 方法)
@anchor{library/cmd cmd Cmd postloop}@anchor{30e6}
@deffn {方法} Cmd.postloop ()

钩方法在 @ref{30dd,,cmdloop()} 即将返回时执行一次。这个方法是一个在 @ref{30d9,,Cmd} 中的存根；塔顶存在是为了被子类覆盖。
@end deffn

Instances of @ref{30d9,,Cmd} subclasses have some public instance variables:

@geindex prompt (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd prompt}@anchor{30e7}
@deffn {属性} Cmd.prompt

发出提示以请求输入。
@end deffn

@geindex identchars (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd identchars}@anchor{30e8}
@deffn {属性} Cmd.identchars

接受命令前缀的字符串。
@end deffn

@geindex lastcmd (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd lastcmd}@anchor{30e9}
@deffn {属性} Cmd.lastcmd

看到最后一个非空命令前缀。
@end deffn

@geindex cmdqueue (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd cmdqueue}@anchor{30ea}
@deffn {属性} Cmd.cmdqueue

排队的输入行列表。当需要新的输入时，在 @ref{30dd,,cmdloop()} 中检查 cmdqueue 列表；如果它不是空的，它的元素将被按顺序处理，就像在提示符处输入一样。
@end deffn

@geindex intro (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd intro}@anchor{30de}
@deffn {属性} Cmd.intro

要作为简介或横幅发出的字符串。 可以通过给 @ref{30dd,,cmdloop()} 方法一个参数来覆盖它。
@end deffn

@geindex doc_header (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd doc_header}@anchor{30eb}
@deffn {属性} Cmd.doc_header

如果帮助输出具有记录命令的段落，则发出头文件。
@end deffn

@geindex misc_header (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd misc_header}@anchor{30ec}
@deffn {属性} Cmd.misc_header

如果帮助输出其他帮助主题的部分（即与 @code{do_*()} 方法没有关联的 @code{help_*()} 方法），则发出头文件。
@end deffn

@geindex undoc_header (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd undoc_header}@anchor{30ed}
@deffn {属性} Cmd.undoc_header

如果帮助输出未被记录命令的部分（即与 @code{help_*()} 方法没有关联的 @code{do_*()} 方法），则发出头文件。
@end deffn

@geindex ruler (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd ruler}@anchor{30ee}
@deffn {属性} Cmd.ruler

用于在帮助信息标题的下方绘制分隔符的字符，如果为空，则不绘制标尺线。这个字符默认是 @code{'='} 。
@end deffn

@geindex use_rawinput (cmd.Cmd 属性)
@anchor{library/cmd cmd Cmd use_rawinput}@anchor{30da}
@deffn {属性} Cmd.use_rawinput

这是一个标志，默认为 true 。如果为 true ，, @ref{30dd,,cmdloop()} 使用 @ref{c64,,input()} 先是提示并且阅读下一个命令；如果为 false ， @code{sys.stdout.write()} 和 @code{sys.stdin.readline()} 被使用。（这意味着解释器将会自动支持类似于 @code{Emacs}的行编辑和命令历史记录按键操作，通过导入 @ref{de,,readline} 在支持它的系统上。）
@end deffn

@node Cmd 例子,,Cmd 对象,cmd --- 支持面向行的命令解释器
@anchor{library/cmd cmd-example}@anchor{30ef}@anchor{library/cmd id2}@anchor{30f0}
@subsubsection Cmd 例子


The @ref{1a,,cmd} module is mainly useful for building custom shells that let a
user work with a program interactively.

这部分提供了一个简单的例子来介绍如何使用一部分在 @ref{116,,turtle} 模块中的命令构建一个 shell 。

基础的 turtle 命令比如 @ref{3043,,forward()} 被添加进一个 @ref{30d9,,Cmd} 子类，方法名为 @code{do_forward()} 。参数被转换成数字并且分发至 turtle 模块中。 docstring 是 shell 提供的帮助实用程序。

例子也包含使用 @ref{30e1,,precmd()} 方法实现基础的记录和回放的功能，这个方法负责将输入转换为小写并且将命令写入文件。 @code{do_playback()} 方法读取文件并添加记录命令至 @code{cmdqueue} 用于即时回放:

@example
import cmd, sys
from turtle import *

class TurtleShell(cmd.Cmd):
    intro = 'Welcome to the turtle shell.   Type help or ? to list commands.\n'
    prompt = '(turtle) '
    file = None

    # ----- basic turtle commands -----
    def do_forward(self, arg):
        'Move the turtle forward by the specified distance:  FORWARD 10'
        forward(*parse(arg))
    def do_right(self, arg):
        'Turn turtle right by given number of degrees:  RIGHT 20'
        right(*parse(arg))
    def do_left(self, arg):
        'Turn turtle left by given number of degrees:  LEFT 90'
        left(*parse(arg))
    def do_goto(self, arg):
        'Move turtle to an absolute position with changing orientation.  GOTO 100 200'
        goto(*parse(arg))
    def do_home(self, arg):
        'Return turtle to the home position:  HOME'
        home()
    def do_circle(self, arg):
        'Draw circle with given radius an options extent and steps:  CIRCLE 50'
        circle(*parse(arg))
    def do_position(self, arg):
        'Print the current turtle position:  POSITION'
        print('Current position is %d %d\n' % position())
    def do_heading(self, arg):
        'Print the current turtle heading in degrees:  HEADING'
        print('Current heading is %d\n' % (heading(),))
    def do_color(self, arg):
        'Set the color:  COLOR BLUE'
        color(arg.lower())
    def do_undo(self, arg):
        'Undo (repeatedly) the last turtle action(s):  UNDO'
    def do_reset(self, arg):
        'Clear the screen and return turtle to center:  RESET'
        reset()
    def do_bye(self, arg):
        'Stop recording, close the turtle window, and exit:  BYE'
        print('Thank you for using Turtle')
        self.close()
        bye()
        return True

    # ----- record and playback -----
    def do_record(self, arg):
        'Save future commands to filename:  RECORD rose.cmd'
        self.file = open(arg, 'w')
    def do_playback(self, arg):
        'Playback commands from a file:  PLAYBACK rose.cmd'
        self.close()
        with open(arg) as f:
            self.cmdqueue.extend(f.read().splitlines())
    def precmd(self, line):
        line = line.lower()
        if self.file and 'playback' not in line:
            print(line, file=self.file)
        return line
    def close(self):
        if self.file:
            self.file.close()
            self.file = None

def parse(arg):
    'Convert a series of zero or more numbers to an argument tuple'
    return tuple(map(int, arg.split()))

if __name__ == '__main__':
    TurtleShell().cmdloop()
@end example

这是一个示例会话，其中 turtle shell 显示帮助功能，使用空行重复命令，以及简单的记录和回放功能：

@example
Welcome to the turtle shell.   Type help or ? to list commands.

(turtle) ?

Documented commands (type help <topic>):
========================================
bye     color    goto     home  playback  record  right
circle  forward  heading  left  position  reset   undo

(turtle) help forward
Move the turtle forward by the specified distance:  FORWARD 10
(turtle) record spiral.cmd
(turtle) position
Current position is 0 0

(turtle) heading
Current heading is 0

(turtle) reset
(turtle) circle 20
(turtle) right 30
(turtle) circle 40
(turtle) right 30
(turtle) circle 60
(turtle) right 30
(turtle) circle 80
(turtle) right 30
(turtle) circle 100
(turtle) right 30
(turtle) circle 120
(turtle) right 30
(turtle) circle 120
(turtle) heading
Current heading is 180

(turtle) forward 100
(turtle)
(turtle) right 90
(turtle) forward 100
(turtle)
(turtle) right 90
(turtle) forward 400
(turtle) right 90
(turtle) forward 500
(turtle) right 90
(turtle) forward 400
(turtle) right 90
(turtle) forward 300
(turtle) playback spiral.cmd
Current position is 0 0

Current heading is 0

Current heading is 180

(turtle) bye
Thank you for using Turtle
@end example

@node shlex --- Simple lexical analysis,,cmd --- 支持面向行的命令解释器,程序框架
@anchor{library/shlex doc}@anchor{30f1}@anchor{library/shlex module-shlex}@anchor{e8}@anchor{library/shlex shlex-simple-lexical-analysis}@anchor{30f2}
@subsection @code{shlex} --- Simple lexical analysis


@geindex shlex (模块)

@strong{Source code:} Lib/shlex.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/shlex.py}


__________________________________________________________________


The @ref{575,,shlex} class makes it easy to write lexical analyzers for
simple syntaxes resembling that of the Unix shell.  This will often be useful
for writing minilanguages, (for example, in run control files for Python
applications) or for parsing quoted strings.

The @ref{e8,,shlex} module defines the following functions:

@geindex split() (在 shlex 模块中)
@anchor{library/shlex shlex split}@anchor{218}
@deffn {函数} shlex.split (s, comments=False, posix=True)

Split the string @emph{s} using shell-like syntax. If @emph{comments} is @ref{380,,False}
(the default), the parsing of comments in the given string will be disabled
(setting the @ref{30f3,,commenters} attribute of the
@ref{575,,shlex} instance to the empty string).  This function operates
in POSIX mode by default, but uses non-POSIX mode if the @emph{posix} argument is
false.

@cartouche
@quotation 注解 
Since the @ref{218,,split()} function instantiates a @ref{575,,shlex}
instance, passing @code{None} for @emph{s} will read the string to split from
standard input.
@end quotation
@end cartouche
@end deffn

@geindex join() (在 shlex 模块中)
@anchor{library/shlex shlex join}@anchor{217}
@deffn {函数} shlex.join (split_command)

Concatenate the tokens of the list @emph{split_command} and return a string.
This function is the inverse of @ref{218,,split()}.

@example
>>> from shlex import join
>>> print(join(['echo', '-n', 'Multiple words']))
echo -n 'Multiple words'
@end example

The returned value is shell-escaped to protect against injection
vulnerabilities (see @ref{a6e,,quote()}).


3.8 新版功能.

@end deffn

@geindex quote() (在 shlex 模块中)
@anchor{library/shlex shlex quote}@anchor{a6e}
@deffn {函数} shlex.quote (s)

Return a shell-escaped version of the string @emph{s}.  The returned value is a
string that can safely be used as one token in a shell command line, for
cases where you cannot use a list.

This idiom would be unsafe:

@example
>>> filename = 'somefile; rm -rf ~'
>>> command = 'ls -l @{@}'.format(filename)
>>> print(command)  # executed by a shell: boom!
ls -l somefile; rm -rf ~
@end example

@ref{a6e,,quote()} lets you plug the security hole:

@example
>>> from shlex import quote
>>> command = 'ls -l @{@}'.format(quote(filename))
>>> print(command)
ls -l 'somefile; rm -rf ~'
>>> remote_command = 'ssh home @{@}'.format(quote(command))
>>> print(remote_command)
ssh home 'ls -l '"'"'somefile; rm -rf ~'"'"'@w{'}
@end example

The quoting is compatible with UNIX shells and with @ref{218,,split()}:

@example
>>> from shlex import split
>>> remote_command = split(remote_command)
>>> remote_command
['ssh', 'home', "ls -l 'somefile; rm -rf ~'"]
>>> command = split(remote_command[-1])
>>> command
['ls', '-l', 'somefile; rm -rf ~']
@end example


3.3 新版功能.

@end deffn

The @ref{e8,,shlex} module defines the following class:

@geindex shlex (shlex 中的类)
@anchor{library/shlex shlex shlex}@anchor{575}
@deffn {类} shlex.shlex (instream=None, infile=None, posix=False, punctuation_chars=False)

A @ref{575,,shlex} instance or subclass instance is a lexical analyzer
object.  The initialization argument, if present, specifies where to read
characters from.  It must be a file-/stream-like object with
@ref{1f9d,,read()} and @ref{1b90,,readline()} methods, or
a string.  If no argument is given, input will be taken from @code{sys.stdin}.
The second optional argument is a filename string, which sets the initial
value of the @ref{30f4,,infile} attribute.  If the @emph{instream}
argument is omitted or equal to @code{sys.stdin}, this second argument
defaults to "stdin".  The @emph{posix} argument defines the operational mode:
when @emph{posix} is not true (default), the @ref{575,,shlex} instance will
operate in compatibility mode.  When operating in POSIX mode,
@ref{575,,shlex} will try to be as close as possible to the POSIX shell
parsing rules.  The @emph{punctuation_chars} argument provides a way to make the
behaviour even closer to how real shells parse.  This can take a number of
values: the default value, @code{False}, preserves the behaviour seen under
Python 3.5 and earlier.  If set to @code{True}, then parsing of the characters
@code{();<>|&} is changed: any run of these characters (considered punctuation
characters) is returned as a single token.  If set to a non-empty string of
characters, those characters will be used as the punctuation characters.  Any
characters in the @ref{30f5,,wordchars} attribute that appear in
@emph{punctuation_chars} will be removed from @ref{30f5,,wordchars}.  See
@ref{576,,Improved Compatibility with Shells} for more information. @emph{punctuation_chars}
can be set only upon @ref{575,,shlex} instance creation and can't be
modified later.


在 3.6 版更改: The @emph{punctuation_chars} parameter was added.

@end deffn


@subsubheading 参见



@table @asis

@item Module @ref{23,,configparser}

Parser for configuration files similar to the Windows @code{.ini} files.
@end table


@menu
* shlex Objects:: 
* Parsing Rules:: 
* Improved Compatibility with Shells:: 

@end menu

@node shlex Objects,Parsing Rules,,shlex --- Simple lexical analysis
@anchor{library/shlex id1}@anchor{30f6}@anchor{library/shlex shlex-objects}@anchor{30f7}
@subsubsection shlex Objects


A @ref{575,,shlex} instance has the following methods:

@geindex get_token() (shlex.shlex 方法)
@anchor{library/shlex shlex shlex get_token}@anchor{30f8}
@deffn {方法} shlex.get_token ()

Return a token.  If tokens have been stacked using @ref{30f9,,push_token()}, pop a
token off the stack.  Otherwise, read one from the input stream.  If reading
encounters an immediate end-of-file, @ref{30fa,,eof} is returned (the empty
string (@code{'@w{'}}) in non-POSIX mode, and @code{None} in POSIX mode).
@end deffn

@geindex push_token() (shlex.shlex 方法)
@anchor{library/shlex shlex shlex push_token}@anchor{30f9}
@deffn {方法} shlex.push_token (str)

Push the argument onto the token stack.
@end deffn

@geindex read_token() (shlex.shlex 方法)
@anchor{library/shlex shlex shlex read_token}@anchor{30fb}
@deffn {方法} shlex.read_token ()

Read a raw token.  Ignore the pushback stack, and do not interpret source
requests.  (This is not ordinarily a useful entry point, and is documented here
only for the sake of completeness.)
@end deffn

@geindex sourcehook() (shlex.shlex 方法)
@anchor{library/shlex shlex shlex sourcehook}@anchor{30fc}
@deffn {方法} shlex.sourcehook (filename)

When @ref{575,,shlex} detects a source request (see @ref{30fd,,source}
below) this method is given the following token as argument, and expected
to return a tuple consisting of a filename and an open file-like object.

Normally, this method first strips any quotes off the argument.  If the result
is an absolute pathname, or there was no previous source request in effect, or
the previous source was a stream (such as @code{sys.stdin}), the result is left
alone.  Otherwise, if the result is a relative pathname, the directory part of
the name of the file immediately before it on the source inclusion stack is
prepended (this behavior is like the way the C preprocessor handles @code{#include
"file.h"}).

The result of the manipulations is treated as a filename, and returned as the
first component of the tuple, with @ref{4ea,,open()} called on it to yield the second
component. (Note: this is the reverse of the order of arguments in instance
initialization!)

This hook is exposed so that you can use it to implement directory search paths,
addition of file extensions, and other namespace hacks. There is no
corresponding 'close' hook, but a shlex instance will call the
@ref{fa0,,close()} method of the sourced input stream when it returns
EOF.

For more explicit control of source stacking, use the @ref{30fe,,push_source()} and
@ref{30ff,,pop_source()} methods.
@end deffn

@geindex push_source() (shlex.shlex 方法)
@anchor{library/shlex shlex shlex push_source}@anchor{30fe}
@deffn {方法} shlex.push_source (newstream, newfile=None)

Push an input source stream onto the input stack.  If the filename argument is
specified it will later be available for use in error messages.  This is the
same method used internally by the @ref{30fc,,sourcehook()} method.
@end deffn

@geindex pop_source() (shlex.shlex 方法)
@anchor{library/shlex shlex shlex pop_source}@anchor{30ff}
@deffn {方法} shlex.pop_source ()

Pop the last-pushed input source from the input stack. This is the same method
used internally when the lexer reaches EOF on a stacked input stream.
@end deffn

@geindex error_leader() (shlex.shlex 方法)
@anchor{library/shlex shlex shlex error_leader}@anchor{3100}
@deffn {方法} shlex.error_leader (infile=None, lineno=None)

This method generates an error message leader in the format of a Unix C compiler
error label; the format is @code{'"%s", line %d: '}, where the @code{%s} is replaced
with the name of the current source file and the @code{%d} with the current input
line number (the optional arguments can be used to override these).

This convenience is provided to encourage @ref{e8,,shlex} users to generate error
messages in the standard, parseable format understood by Emacs and other Unix
tools.
@end deffn

Instances of @ref{575,,shlex} subclasses have some public instance
variables which either control lexical analysis or can be used for debugging:

@geindex commenters (shlex.shlex 属性)
@anchor{library/shlex shlex shlex commenters}@anchor{30f3}
@deffn {属性} shlex.commenters

The string of characters that are recognized as comment beginners. All
characters from the comment beginner to end of line are ignored. Includes just
@code{'#'} by default.
@end deffn

@geindex wordchars (shlex.shlex 属性)
@anchor{library/shlex shlex shlex wordchars}@anchor{30f5}
@deffn {属性} shlex.wordchars

The string of characters that will accumulate into multi-character tokens.  By
default, includes all ASCII alphanumerics and underscore.  In POSIX mode, the
accented characters in the Latin-1 set are also included.  If
@ref{f0b,,punctuation_chars} is not empty, the characters @code{~-./*?=}, which can
appear in filename specifications and command line parameters, will also be
included in this attribute, and any characters which appear in
@code{punctuation_chars} will be removed from @code{wordchars} if they are present
there. If @ref{3101,,whitespace_split} is set to @code{True}, this will have no
effect.
@end deffn

@geindex whitespace (shlex.shlex 属性)
@anchor{library/shlex shlex shlex whitespace}@anchor{3102}
@deffn {属性} shlex.whitespace

Characters that will be considered whitespace and skipped.  Whitespace bounds
tokens.  By default, includes space, tab, linefeed and carriage-return.
@end deffn

@geindex escape (shlex.shlex 属性)
@anchor{library/shlex shlex shlex escape}@anchor{3103}
@deffn {属性} shlex.escape

Characters that will be considered as escape. This will be only used in POSIX
mode, and includes just @code{'\'} by default.
@end deffn

@geindex quotes (shlex.shlex 属性)
@anchor{library/shlex shlex shlex quotes}@anchor{3104}
@deffn {属性} shlex.quotes

Characters that will be considered string quotes.  The token accumulates until
the same quote is encountered again (thus, different quote types protect each
other as in the shell.)  By default, includes ASCII single and double quotes.
@end deffn

@geindex escapedquotes (shlex.shlex 属性)
@anchor{library/shlex shlex shlex escapedquotes}@anchor{3105}
@deffn {属性} shlex.escapedquotes

Characters in @ref{3104,,quotes} that will interpret escape characters defined in
@ref{3103,,escape}.  This is only used in POSIX mode, and includes just @code{'"'} by
default.
@end deffn

@geindex whitespace_split (shlex.shlex 属性)
@anchor{library/shlex shlex shlex whitespace_split}@anchor{3101}
@deffn {属性} shlex.whitespace_split

If @code{True}, tokens will only be split in whitespaces.  This is useful, for
example, for parsing command lines with @ref{575,,shlex}, getting
tokens in a similar way to shell arguments.  When used in combination with
@ref{f0b,,punctuation_chars}, tokens will be split on whitespace in addition to
those characters.


在 3.8 版更改: The @ref{f0b,,punctuation_chars} attribute was made compatible with the
@ref{3101,,whitespace_split} attribute.

@end deffn

@geindex infile (shlex.shlex 属性)
@anchor{library/shlex shlex shlex infile}@anchor{30f4}
@deffn {属性} shlex.infile

The name of the current input file, as initially set at class instantiation time
or stacked by later source requests.  It may be useful to examine this when
constructing error messages.
@end deffn

@geindex instream (shlex.shlex 属性)
@anchor{library/shlex shlex shlex instream}@anchor{3106}
@deffn {属性} shlex.instream

The input stream from which this @ref{575,,shlex} instance is reading
characters.
@end deffn

@geindex source (shlex.shlex 属性)
@anchor{library/shlex shlex shlex source}@anchor{30fd}
@deffn {属性} shlex.source

This attribute is @code{None} by default.  If you assign a string to it, that
string will be recognized as a lexical-level inclusion request similar to the
@code{source} keyword in various shells.  That is, the immediately following token
will be opened as a filename and input will be taken from that stream until
EOF, at which point the @ref{fa0,,close()} method of that stream will be
called and the input source will again become the original input stream.  Source
requests may be stacked any number of levels deep.
@end deffn

@geindex debug (shlex.shlex 属性)
@anchor{library/shlex shlex shlex debug}@anchor{3107}
@deffn {属性} shlex.debug

If this attribute is numeric and @code{1} or more, a @ref{575,,shlex}
instance will print verbose progress output on its behavior.  If you need
to use this, you can read the module source code to learn the details.
@end deffn

@geindex lineno (shlex.shlex 属性)
@anchor{library/shlex shlex shlex lineno}@anchor{3108}
@deffn {属性} shlex.lineno

Source line number (count of newlines seen so far plus one).
@end deffn

@geindex token (shlex.shlex 属性)
@anchor{library/shlex shlex shlex token}@anchor{3109}
@deffn {属性} shlex.token

The token buffer.  It may be useful to examine this when catching exceptions.
@end deffn

@geindex eof (shlex.shlex 属性)
@anchor{library/shlex shlex shlex eof}@anchor{30fa}
@deffn {属性} shlex.eof

Token used to determine end of file. This will be set to the empty string
(@code{'@w{'}}), in non-POSIX mode, and to @code{None} in POSIX mode.
@end deffn

@geindex punctuation_chars (shlex.shlex 属性)
@anchor{library/shlex shlex shlex punctuation_chars}@anchor{f0b}
@deffn {属性} shlex.punctuation_chars

A read-only property. Characters that will be considered punctuation. Runs of
punctuation characters will be returned as a single token. However, note that no
semantic validity checking will be performed: for example, '>>>' could be
returned as a token, even though it may not be recognised as such by shells.


3.6 新版功能.

@end deffn

@node Parsing Rules,Improved Compatibility with Shells,shlex Objects,shlex --- Simple lexical analysis
@anchor{library/shlex parsing-rules}@anchor{310a}@anchor{library/shlex shlex-parsing-rules}@anchor{310b}
@subsubsection Parsing Rules


When operating in non-POSIX mode, @ref{575,,shlex} will try to obey to the
following rules.


@itemize *

@item 
Quote characters are not recognized within words (@code{Do"Not"Separate} is
parsed as the single word @code{Do"Not"Separate});

@item 
Escape characters are not recognized;

@item 
Enclosing characters in quotes preserve the literal value of all characters
within the quotes;

@item 
Closing quotes separate words (@code{"Do"Separate} is parsed as @code{"Do"} and
@code{Separate});

@item 
If @ref{3101,,whitespace_split} is @code{False}, any character not
declared to be a word character, whitespace, or a quote will be returned as
a single-character token. If it is @code{True}, @ref{575,,shlex} will only
split words in whitespaces;

@item 
EOF is signaled with an empty string (@code{'@w{'}});

@item 
It's not possible to parse empty strings, even if quoted.
@end itemize

When operating in POSIX mode, @ref{575,,shlex} will try to obey to the
following parsing rules.


@itemize *

@item 
Quotes are stripped out, and do not separate words (@code{"Do"Not"Separate"} is
parsed as the single word @code{DoNotSeparate});

@item 
Non-quoted escape characters (e.g. @code{'\'}) preserve the literal value of the
next character that follows;

@item 
Enclosing characters in quotes which are not part of
@ref{3105,,escapedquotes} (e.g. @code{"'"}) preserve the literal value
of all characters within the quotes;

@item 
Enclosing characters in quotes which are part of
@ref{3105,,escapedquotes} (e.g. @code{'"'}) preserves the literal value
of all characters within the quotes, with the exception of the characters
mentioned in @ref{3103,,escape}.  The escape characters retain its
special meaning only when followed by the quote in use, or the escape
character itself. Otherwise the escape character will be considered a
normal character.

@item 
EOF is signaled with a @ref{157,,None} value;

@item 
Quoted empty strings (@code{'@w{'}}) are allowed.
@end itemize

@node Improved Compatibility with Shells,,Parsing Rules,shlex --- Simple lexical analysis
@anchor{library/shlex improved-compatibility-with-shells}@anchor{310c}@anchor{library/shlex improved-shell-compatibility}@anchor{576}
@subsubsection Improved Compatibility with Shells



3.6 新版功能.


The @ref{e8,,shlex} class provides compatibility with the parsing performed by
common Unix shells like @code{bash}, @code{dash}, and @code{sh}.  To take advantage of
this compatibility, specify the @code{punctuation_chars} argument in the
constructor.  This defaults to @code{False}, which preserves pre-3.6 behaviour.
However, if it is set to @code{True}, then parsing of the characters @code{();<>|&}
is changed: any run of these characters is returned as a single token.  While
this is short of a full parser for shells (which would be out of scope for the
standard library, given the multiplicity of shells out there), it does allow
you to perform processing of command lines more easily than you could
otherwise.  To illustrate, you can see the difference in the following snippet:

@example
 >>> import shlex
 >>> text = "a && b; c && d || e; f >'abc'; (def \"ghi\")"
 >>> s = shlex.shlex(text, posix=True)
 >>> s.whitespace_split = True
 >>> list(s)
 ['a', '&&', 'b;', 'c', '&&', 'd', '||', 'e;', 'f', '>abc;', '(def', 'ghi)']
 >>> s = shlex.shlex(text, posix=True, punctuation_chars=True)
 >>> s.whitespace_split = True
 >>> list(s)
 ['a', '&&', 'b', ';', 'c', '&&', 'd', '||', 'e', ';', 'f', '>', 'abc', ';',
 '(', 'def', 'ghi', ')']
@end example

Of course, tokens will be returned which are not valid for shells, and you'll
need to implement your own error checks on the returned tokens.

Instead of passing @code{True} as the value for the punctuation_chars parameter,
you can pass a string with specific characters, which will be used to determine
which characters constitute punctuation. For example:

@example
>>> import shlex
>>> s = shlex.shlex("a && b || c", punctuation_chars="|")
>>> list(s)
['a', '&', '&', 'b', '||', 'c']
@end example

@cartouche
@quotation 注解 
When @code{punctuation_chars} is specified, the @ref{30f5,,wordchars}
attribute is augmented with the characters @code{~-./*?=}.  That is because these
characters can appear in file names (including wildcards) and command-line
arguments (e.g. @code{--color=auto}). Hence:

@example
>>> import shlex
>>> s = shlex.shlex('~/a && b-c --color=auto || d *.py?',
...                 punctuation_chars=True)
>>> list(s)
['~/a', '&&', 'b-c', '--color=auto', '||', 'd', '*.py?']
@end example

However, to match the shell as closely as possible, it is recommended to
always use @code{posix} and @ref{3101,,whitespace_split} when using
@ref{f0b,,punctuation_chars}, which will negate
@ref{30f5,,wordchars} entirely.
@end quotation
@end cartouche

For best effect, @code{punctuation_chars} should be set in conjunction with
@code{posix=True}. (Note that @code{posix=False} is the default for
@ref{575,,shlex}.)

@node Tk图形用户界面 GUI,开发工具,程序框架,Python 标准库
@anchor{library/tk doc}@anchor{310d}@anchor{library/tk graphical-user-interfaces-with-tk}@anchor{310e}@anchor{library/tk tkinter}@anchor{310f}
@section Tk图形用户界面(GUI)


@geindex GUI
@geindex Graphical User Interface
@geindex Tkinter
@geindex Tk

Tcl/Tk集成到Python中已经有一些年头了。Python程序员可以通过 @ref{10c,,tkinter} 包和它的扩展， @ref{10e,,tkinter.tix} 模块和 @ref{10f,,tkinter.ttk} 模块，来使用这套鲁棒的、平台无关的窗口工具集。

@ref{10c,,tkinter} 包使用面向对象的方式对Tcl/Tk进行了一层薄包装。使用 @ref{10c,,tkinter} ，你不需要写Tcl代码，但可能需要参考Tk文档，甚至Tcl文档。 @ref{10c,,tkinter} 使用Python类，对Tk的窗体小部件（Widgets）进行了一系列的封装。除此之外，内部模块 @code{_tkinter} 针对Python和Tcl之间的交互，提供了一套线程安全的机制。

@ref{10c,,tkinter} 最大的优点就一个字：快，再一个，是Python自带的。尽管官方文档不太完整，但有其他资源可以参考，比如Tk手册，教程等。 @ref{10c,,tkinter} 也以比较过时的外观为人所知，但在Tk 8.5中，这一点得到了极大的改观。除此之外，如果有兴趣，还有其他的一些GUI库可供使用。更多信息，请参考 @ref{3110,,其他图形用户界面（GUI）包}  小节。

@menu
* tkinter: tkinter --- Tcl/Tk的Python接口. Tcl/Tk的Python接口
* tkinter.ttk: tkinter ttk --- Tk主题小部件. Tk主题小部件
* tkinter.tix: tkinter tix --- Extension widgets for Tk. Extension widgets for Tk
* tkinter.scrolledtext: tkinter scrolledtext --- 滚动文字控件. 滚动文字控件
* IDLE: IDLE<48>. 
* 其他图形用户界面（GUI）包:: 

@end menu

@node tkinter --- Tcl/Tk的Python接口,tkinter ttk --- Tk主题小部件,,Tk图形用户界面 GUI
@anchor{library/tkinter doc}@anchor{3111}@anchor{library/tkinter module-tkinter}@anchor{10c}@anchor{library/tkinter tkinter-python-interface-to-tcl-tk}@anchor{3112}
@subsection @code{tkinter} --- Tcl/Tk的Python接口


@geindex tkinter (模块)

@strong{源代码:} Lib/tkinter/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tkinter/__init__.py}


__________________________________________________________________


The @ref{10c,,tkinter} package ("Tk interface") is the standard Python interface to
the Tk GUI toolkit.  Both Tk and @ref{10c,,tkinter} are available on most Unix
platforms, as well as on Windows systems.  (Tk itself is not part of Python; it
is maintained at ActiveState.)

在命令行中运行 @code{python -m tkinter}，应该会弹出一个Tk界面的窗口，表明 @ref{10c,,tkinter} 包已经正确安装，而且告诉你 Tcl/Tk 的版本号，通过这个版本号，你就可以参考对应的 Tcl/Tk 文档了。


@subsubheading 参见


Tkinter文档：


@table @asis

@item Python Tkinter 资源@footnote{https://wiki.python.org/moin/TkInter}

The Python Tkinter Topic Guide 提供了在 Python 中使用 Tk 的很多信息， 同时包含了Tk其他信息的链接。

@item TKDocs@footnote{http://www.tkdocs.com/}

大量的教程，部分可视化组件的介绍说明。

@item Tkinter 8.5 reference: a GUI for Python@footnote{https://web.archive.org/web/20190524140835/https://infohost.nmt.edu/tcc/help/pubs/tkinter/web/index.html}

在线参考资料。

@item Tkinter docs from effbot@footnote{http://effbot.org/tkinterbook/}

effbot.org 提供的 tkinter 在线参考资料。

@item 使用 Python 编程@footnote{http://learning-python.com/about-pp4e.html}

由 Mark Lutz 所著的书籍，对 Tkinter 进行了完美的介绍。

@item 为繁忙的 Python 开发者所准备的现代 Tkinter@footnote{https://www.amazon.com/Modern-Tkinter-Python-Developers-ebook/dp/B0071QDNLO/}

由 Mark Rozerman 所著的关于如何使用 Python 和 Tkinter 来搭建有吸引力的和现代化的图形用户界面的书籍

@item Python 和 Tkinter 编程@footnote{https://www.manning.com/books/python-and-tkinter-programming}

作者： John Grayson (ISBN 1-884777-81-3).
@end table

Tcl/Tk 文档:


@table @asis

@item Tk 命令@footnote{https://www.tcl.tk/man/tcl8.6/TkCmd/contents.htm}

多数命令以 @ref{10c,,tkinter} 或者 @ref{10f,,tkinter.ttk} 类的形式存在。改变 '8.6' 以匹配所安装的 Tcl/Tk 版本。

@item Tcl/Tk 最新手册页面@footnote{https://www.tcl.tk/doc/}

www.tcl.tk 上面最新的 Tcl/Tk 手册。

@item ActiveState Tcl 主页@footnote{https://tcl.tk}

Tk/Tcl 的多数开发工作发生在 ActiveState 。

@item Tcl 及 Tk 工具集@footnote{https://www.amazon.com/exec/obidos/ASIN/020163337X}

由 Tcl 发明者 John Ousterhout 所著的书籍。

@item ` Tcl 和 Tk 编程实战 <@indicateurl{http://www.beedub.com/book/}>`_

Brent Welch 所著的百科全局式书籍。
@end table


@menu
* Tkinter 模块:: 
* Tkinter Life Preserver:: 
* A (Very) Quick Look at Tcl/Tk: A Very Quick Look at Tcl/Tk. 
* Mapping Basic Tk into Tkinter:: 
* How Tk and Tkinter are Related:: 
* Handy Reference:: 
* File Handlers:: 

@end menu

@node Tkinter 模块,Tkinter Life Preserver,,tkinter --- Tcl/Tk的Python接口
@anchor{library/tkinter tkinter-modules}@anchor{3113}
@subsubsection Tkinter 模块


在大多数时候你只需要 @ref{10c,,tkinter} 就足够了，但也有一些额外的模块可供使用。Tk 接口位于一个名字 @code{_tkinter} 的二进制模块当中。此模块包含了低层级的 Tk 接口，它不应该被应用程序员所直接使用。它通常是一个共享库（或 DLL），但在某些情况下也可能被静态链接到 Python 解释器。

除了Tk接口， @ref{10c,,tkinter} 也包含了若干 Python 模块，@code{tkinter.constants} 是其中最重要的。导入 @ref{10c,,tkinter} 会自动导入 @code{tkinter.constants} ，所以，要使用 Tkinter 通常你只需要一条简单的 import 语句:

@example
import tkinter
@end example

或者更常用的:

@example
from tkinter import *
@end example

@geindex Tk (tkinter 中的类)
@anchor{library/tkinter tkinter Tk}@anchor{3114}
@deffn {类} tkinter.Tk (screenName=None, baseName=None, className='Tk', useTk=1)

The @ref{3114,,Tk} class is instantiated without arguments. This creates a toplevel
widget of Tk which usually is the main window of an application. Each instance
has its own associated Tcl interpreter.

@c FIXME: The following keyword arguments are currently recognized:
@end deffn

@geindex Tcl() (在 tkinter 模块中)
@anchor{library/tkinter tkinter Tcl}@anchor{3115}
@deffn {函数} tkinter.Tcl (screenName=None, baseName=None, className='Tk', useTk=0)

The @ref{3115,,Tcl()} function is a factory function which creates an object much like
that created by the @ref{3114,,Tk} class, except that it does not initialize the Tk
subsystem.  This is most often useful when driving the Tcl interpreter in an
environment where one doesn't want to create extraneous toplevel windows, or
where one cannot (such as Unix/Linux systems without an X server).  An object
created by the @ref{3115,,Tcl()} object can have a Toplevel window created (and the Tk
subsystem initialized) by calling its @code{loadtk()} method.
@end deffn

Other modules that provide Tk support include:


@table @asis

@item @ref{10d,,tkinter.scrolledtext}

Text widget with a vertical scroll bar built in.

@item @code{tkinter.colorchooser}

Dialog to let the user choose a color.

@item @code{tkinter.commondialog}

Base class for the dialogs defined in the other modules listed here.

@item @code{tkinter.filedialog}

Common dialogs to allow the user to specify a file to open or save.

@item @code{tkinter.font}

Utilities to help work with fonts.

@item @code{tkinter.messagebox}

Access to standard Tk dialog boxes.

@item @code{tkinter.simpledialog}

Basic dialogs and convenience functions.

@item @code{tkinter.dnd}

Drag-and-drop support for @ref{10c,,tkinter}. This is experimental and should
become deprecated when it is replaced  with the Tk DND.

@item @ref{116,,turtle}

Turtle graphics in a Tk window.
@end table

@node Tkinter Life Preserver,A Very Quick Look at Tcl/Tk,Tkinter 模块,tkinter --- Tcl/Tk的Python接口
@anchor{library/tkinter tkinter-life-preserver}@anchor{3116}
@subsubsection Tkinter Life Preserver


This section is not designed to be an exhaustive tutorial on either Tk or
Tkinter.  Rather, it is intended as a stop gap, providing some introductory
orientation on the system.

Credits:


@itemize *

@item 
Tk was written by John Ousterhout while at Berkeley.

@item 
Tkinter was written by Steen Lumholt and Guido van Rossum.

@item 
This Life Preserver was written by Matt Conway at the University of Virginia.

@item 
The HTML rendering, and some liberal editing, was produced from a FrameMaker
version by Ken Manheimer.

@item 
Fredrik Lundh elaborated and revised the class interface descriptions, to get
them current with Tk 4.2.

@item 
Mike Clarkson converted the documentation to LaTeX, and compiled the  User
Interface chapter of the reference manual.
@end itemize

@menu
* How To Use This Section:: 
* A Simple Hello World Program:: 

@end menu

@node How To Use This Section,A Simple Hello World Program,,Tkinter Life Preserver
@anchor{library/tkinter how-to-use-this-section}@anchor{3117}
@subsubsection How To Use This Section


This section is designed in two parts: the first half (roughly) covers
background material, while the second half can be taken to the keyboard as a
handy reference.

When trying to answer questions of the form "how do I do blah", it is often best
to find out how to do "blah" in straight Tk, and then convert this back into the
corresponding @ref{10c,,tkinter} call. Python programmers can often guess at the
correct Python command by looking at the Tk documentation. This means that in
order to use Tkinter, you will have to know a little bit about Tk. This document
can't fulfill that role, so the best we can do is point you to the best
documentation that exists. Here are some hints:


@itemize *

@item 
The authors strongly suggest getting a copy of the Tk man pages.
Specifically, the man pages in the @code{manN} directory are most useful.
The @code{man3} man pages describe the C interface to the Tk library and thus
are not especially helpful for script writers.

@item 
Addison-Wesley publishes a book called Tcl and the Tk Toolkit by John
Ousterhout (ISBN 0-201-63337-X) which is a good introduction to Tcl and Tk for
the novice.  The book is not exhaustive, and for many details it defers to the
man pages.

@item 
@code{tkinter/__init__.py} is a last resort for most, but can be a good
place to go when nothing else makes sense.
@end itemize

@node A Simple Hello World Program,,How To Use This Section,Tkinter Life Preserver
@anchor{library/tkinter a-simple-hello-world-program}@anchor{3118}
@subsubsection A Simple Hello World Program


@example
import tkinter as tk

class Application(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.master = master
        self.pack()
        self.create_widgets()

    def create_widgets(self):
        self.hi_there = tk.Button(self)
        self.hi_there["text"] = "Hello World\n(click me)"
        self.hi_there["command"] = self.say_hi
        self.hi_there.pack(side="top")

        self.quit = tk.Button(self, text="QUIT", fg="red",
                              command=self.master.destroy)
        self.quit.pack(side="bottom")

    def say_hi(self):
        print("hi there, everyone!")

root = tk.Tk()
app = Application(master=root)
app.mainloop()
@end example

@node A Very Quick Look at Tcl/Tk,Mapping Basic Tk into Tkinter,Tkinter Life Preserver,tkinter --- Tcl/Tk的Python接口
@anchor{library/tkinter a-very-quick-look-at-tcl-tk}@anchor{3119}
@subsubsection A (Very) Quick Look at Tcl/Tk


The class hierarchy looks complicated, but in actual practice, application
programmers almost always refer to the classes at the very bottom of the
hierarchy.

注释:


@itemize *

@item 
These classes are provided for the purposes of organizing certain functions
under one namespace. They aren't meant to be instantiated independently.

@item 
The @ref{3114,,Tk} class is meant to be instantiated only once in an application.
Application programmers need not instantiate one explicitly, the system creates
one whenever any of the other classes are instantiated.

@item 
The @code{Widget} class is not meant to be instantiated, it is meant only
for subclassing to make "real" widgets (in C++, this is called an 'abstract
class').
@end itemize

To make use of this reference material, there will be times when you will need
to know how to read short passages of Tk and how to identify the various parts
of a Tk command.   (See section @ref{311a,,Mapping Basic Tk into Tkinter} for the
@ref{10c,,tkinter} equivalents of what's below.)

Tk scripts are Tcl programs.  Like all Tcl programs, Tk scripts are just lists
of tokens separated by spaces.  A Tk widget is just its @emph{class}, the @emph{options}
that help configure it, and the @emph{actions} that make it do useful things.

To make a widget in Tk, the command is always of the form:

@example
classCommand newPathname options
@end example


@table @asis

@item @emph{classCommand}

denotes which kind of widget to make (a button, a label, a menu...)
@end table

@geindex . (dot); in Tkinter


@table @asis

@item @emph{newPathname}

is the new name for this widget.  All names in Tk must be unique.  To help
enforce this, widgets in Tk are named with @emph{pathnames}, just like files in a
file system.  The top level widget, the @emph{root}, is called @code{.} (period) and
children are delimited by more periods.  For example,
@code{.myApp.controlPanel.okButton} might be the name of a widget.

@item @emph{options}

configure the widget's appearance and in some cases, its behavior.  The options
come in the form of a list of flags and values. Flags are preceded by a '-',
like Unix shell command flags, and values are put in quotes if they are more
than one word.
@end table

例如

@example
button   .fred   -fg red -text "hi there"
   ^       ^     \______________________/
   |       |                |
 class    new            options
command  widget  (-opt val -opt val ...)
@end example

Once created, the pathname to the widget becomes a new command.  This new
@emph{widget command} is the programmer's handle for getting the new widget to
perform some @emph{action}.  In C, you'd express this as someAction(fred,
someOptions), in C++, you would express this as fred.someAction(someOptions),
and in Tk, you say:

@example
.fred someAction someOptions
@end example

Note that the object name, @code{.fred}, starts with a dot.

As you'd expect, the legal values for @emph{someAction} will depend on the widget's
class: @code{.fred disable} works if fred is a button (fred gets greyed out), but
does not work if fred is a label (disabling of labels is not supported in Tk).

The legal values of @emph{someOptions} is action dependent.  Some actions, like
@code{disable}, require no arguments, others, like a text-entry box's @code{delete}
command, would need arguments to specify what range of text to delete.

@node Mapping Basic Tk into Tkinter,How Tk and Tkinter are Related,A Very Quick Look at Tcl/Tk,tkinter --- Tcl/Tk的Python接口
@anchor{library/tkinter mapping-basic-tk-into-tkinter}@anchor{311b}@anchor{library/tkinter tkinter-basic-mapping}@anchor{311a}
@subsubsection Mapping Basic Tk into Tkinter


Class commands in Tk correspond to class constructors in Tkinter.

@example
button .fred                =====>  fred = Button()
@end example

The master of an object is implicit in the new name given to it at creation
time.  In Tkinter, masters are specified explicitly.

@example
button .panel.fred          =====>  fred = Button(panel)
@end example

The configuration options in Tk are given in lists of hyphened tags followed by
values.  In Tkinter, options are specified as keyword-arguments in the instance
constructor, and keyword-args for configure calls or as instance indices, in
dictionary style, for established instances.  See section
@ref{311c,,Setting Options} on setting options.

@example
button .fred -fg red        =====>  fred = Button(panel, fg="red")
.fred configure -fg red     =====>  fred["fg"] = red
                            OR ==>  fred.config(fg="red")
@end example

In Tk, to perform an action on a widget, use the widget name as a command, and
follow it with an action name, possibly with arguments (options).  In Tkinter,
you call methods on the class instance to invoke actions on the widget.  The
actions (methods) that a given widget can perform are listed in
@code{tkinter/__init__.py}.

@example
.fred invoke                =====>  fred.invoke()
@end example

To give a widget to the packer (geometry manager), you call pack with optional
arguments.  In Tkinter, the Pack class holds all this functionality, and the
various forms of the pack command are implemented as methods.  All widgets in
@ref{10c,,tkinter} are subclassed from the Packer, and so inherit all the packing
methods. See the @ref{10e,,tkinter.tix} module documentation for additional
information on the Form geometry manager.

@example
pack .fred -side left       =====>  fred.pack(side="left")
@end example

@node How Tk and Tkinter are Related,Handy Reference,Mapping Basic Tk into Tkinter,tkinter --- Tcl/Tk的Python接口
@anchor{library/tkinter how-tk-and-tkinter-are-related}@anchor{311d}
@subsubsection How Tk and Tkinter are Related


From the top down:


@table @asis

@item Your App Here (Python)

A Python application makes a @ref{10c,,tkinter} call.

@item tkinter (Python Package)

This call (say, for example, creating a button widget), is implemented in
the @ref{10c,,tkinter} package, which is written in Python.  This Python
function will parse the commands and the arguments and convert them into a
form that makes them look as if they had come from a Tk script instead of
a Python script.

@item _tkinter (C)

These commands and their arguments will be passed to a C function in the
@code{_tkinter} - note the underscore - extension module.

@item Tk Widgets (C and Tcl)

This C function is able to make calls into other C modules, including the C
functions that make up the Tk library.  Tk is implemented in C and some Tcl.
The Tcl part of the Tk widgets is used to bind certain default behaviors to
widgets, and is executed once at the point where the Python @ref{10c,,tkinter}
package is imported. (The user never sees this stage).

@item Tk (C)

The Tk part of the Tk Widgets implement the final mapping to ...

@item Xlib (C)

the Xlib library to draw graphics on the screen.
@end table

@node Handy Reference,File Handlers,How Tk and Tkinter are Related,tkinter --- Tcl/Tk的Python接口
@anchor{library/tkinter handy-reference}@anchor{311e}
@subsubsection Handy Reference


@menu
* Setting Options:: 
* The Packer:: 
* Packer Options:: 
* Coupling Widget Variables:: 
* The Window Manager:: 
* Tk Option Data Types:: 
* Bindings and Events:: 
* The index Parameter:: 
* Images:: 

@end menu

@node Setting Options,The Packer,,Handy Reference
@anchor{library/tkinter setting-options}@anchor{311f}@anchor{library/tkinter tkinter-setting-options}@anchor{311c}
@subsubsection Setting Options


Options control things like the color and border width of a widget. Options can
be set in three ways:


@table @asis

@item At object creation time, using keyword arguments

@example
fred = Button(self, fg="red", bg="blue")
@end example

@item After object creation, treating the option name like a dictionary index

@example
fred["fg"] = "red"
fred["bg"] = "blue"
@end example

@item Use the config() method to update multiple attrs subsequent to object creation

@example
fred.config(fg="red", bg="blue")
@end example
@end table

For a complete explanation of a given option and its behavior, see the Tk man
pages for the widget in question.

Note that the man pages list "STANDARD OPTIONS" and "WIDGET SPECIFIC OPTIONS"
for each widget.  The former is a list of options that are common to many
widgets, the latter are the options that are idiosyncratic to that particular
widget.  The Standard Options are documented on the @code{options(3)} man
page.

No distinction between standard and widget-specific options is made in this
document.  Some options don't apply to some kinds of widgets. Whether a given
widget responds to a particular option depends on the class of the widget;
buttons have a @code{command} option, labels do not.

The options supported by a given widget are listed in that widget's man page, or
can be queried at runtime by calling the @code{config()} method without
arguments, or by calling the @code{keys()} method on that widget.  The return
value of these calls is a dictionary whose key is the name of the option as a
string (for example, @code{'relief'}) and whose values are 5-tuples.

Some options, like @code{bg} are synonyms for common options with long names
(@code{bg} is shorthand for "background"). Passing the @code{config()} method the name
of a shorthand option will return a 2-tuple, not 5-tuple. The 2-tuple passed
back will contain the name of the synonym and the "real" option (such as
@code{('bg', 'background')}).


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

含义

@tab

示例

@item

0

@tab

选项名称

@tab

@code{'relief'}

@item

1

@tab

数据库查找的选项名称

@tab

@code{'relief'}

@item

2

@tab

数据库查找的选项类

@tab

@code{'Relief'}

@item

3

@tab

默认值

@tab

@code{'raised'}

@item

4

@tab

当前值

@tab

@code{'groove'}

@end multitable


示例:

@example
>>> print(fred.config())
@{'relief': ('relief', 'relief', 'Relief', 'raised', 'groove')@}
@end example

Of course, the dictionary printed will include all the options available and
their values.  This is meant only as an example.

@node The Packer,Packer Options,Setting Options,Handy Reference
@anchor{library/tkinter the-packer}@anchor{3120}
@subsubsection The Packer


@geindex packing (widgets)

The packer is one of Tk's geometry-management mechanisms.    Geometry managers
are used to specify the relative positioning of the positioning of widgets
within their container - their mutual @emph{master}.  In contrast to the more
cumbersome @emph{placer} (which is used less commonly, and we do not cover here), the
packer takes qualitative relationship specification - @emph{above}, @emph{to the left of},
@emph{filling}, etc - and works everything out to determine the exact placement
coordinates for you.

The size of any @emph{master} widget is determined by the size of the "slave widgets"
inside.  The packer is used to control where slave widgets appear inside the
master into which they are packed.  You can pack widgets into frames, and frames
into other frames, in order to achieve the kind of layout you desire.
Additionally, the arrangement is dynamically adjusted to accommodate incremental
changes to the configuration, once it is packed.

Note that widgets do not appear until they have had their geometry specified
with a geometry manager.  It's a common early mistake to leave out the geometry
specification, and then be surprised when the widget is created but nothing
appears.  A widget will appear only after it has had, for example, the packer's
@code{pack()} method applied to it.

The pack() method can be called with keyword-option/value pairs that control
where the widget is to appear within its container, and how it is to behave when
the main application window is resized.  Here are some examples:

@example
fred.pack()                     # defaults to side = "top"
fred.pack(side="left")
fred.pack(expand=1)
@end example

@node Packer Options,Coupling Widget Variables,The Packer,Handy Reference
@anchor{library/tkinter packer-options}@anchor{3121}
@subsubsection Packer Options


For more extensive information on the packer and the options that it can take,
see the man pages and page 183 of John Ousterhout's book.


@table @asis

@item anchor

Anchor type.  Denotes where the packer is to place each slave in its parcel.

@item expand

Boolean, @code{0} or @code{1}.

@item fill

Legal values: @code{'x'}, @code{'y'}, @code{'both'}, @code{'none'}.

@item ipadx and ipady

A distance - designating internal padding on each side of the slave widget.

@item padx and pady

A distance - designating external padding on each side of the slave widget.

@item side

Legal values are: @code{'left'}, @code{'right'}, @code{'top'}, @code{'bottom'}.
@end table

@node Coupling Widget Variables,The Window Manager,Packer Options,Handy Reference
@anchor{library/tkinter coupling-widget-variables}@anchor{3122}
@subsubsection Coupling Widget Variables


The current-value setting of some widgets (like text entry widgets) can be
connected directly to application variables by using special options.  These
options are @code{variable}, @code{textvariable}, @code{onvalue}, @code{offvalue}, and
@code{value}.  This connection works both ways: if the variable changes for any
reason, the widget it's connected to will be updated to reflect the new value.

Unfortunately, in the current implementation of @ref{10c,,tkinter} it is not
possible to hand over an arbitrary Python variable to a widget through a
@code{variable} or @code{textvariable} option.  The only kinds of variables for which
this works are variables that are subclassed from a class called Variable,
defined in @ref{10c,,tkinter}.

There are many useful subclasses of Variable already defined:
@code{StringVar}, @code{IntVar}, @code{DoubleVar}, and
@code{BooleanVar}.  To read the current value of such a variable, call the
@code{get()} method on it, and to change its value you call the @code{set()}
method.  If you follow this protocol, the widget will always track the value of
the variable, with no further intervention on your part.

例如

@example
class App(Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()

        self.entrythingy = Entry()
        self.entrythingy.pack()

        # here is the application variable
        self.contents = StringVar()
        # set it to some value
        self.contents.set("this is a variable")
        # tell the entry widget to watch this variable
        self.entrythingy["textvariable"] = self.contents

        # and here we get a callback when the user hits return.
        # we will have the program print out the value of the
        # application variable when the user hits return
        self.entrythingy.bind('<Key-Return>',
                              self.print_contents)

    def print_contents(self, event):
        print("hi. contents of entry is now ---->",
              self.contents.get())
@end example

@node The Window Manager,Tk Option Data Types,Coupling Widget Variables,Handy Reference
@anchor{library/tkinter the-window-manager}@anchor{3123}
@subsubsection The Window Manager


@geindex window manager (widgets)

In Tk, there is a utility command, @code{wm}, for interacting with the window
manager.  Options to the @code{wm} command allow you to control things like titles,
placement, icon bitmaps, and the like.  In @ref{10c,,tkinter}, these commands have
been implemented as methods on the @code{Wm} class.  Toplevel widgets are
subclassed from the @code{Wm} class, and so can call the @code{Wm} methods
directly.

To get at the toplevel window that contains a given widget, you can often just
refer to the widget's master.  Of course if the widget has been packed inside of
a frame, the master won't represent a toplevel window.  To get at the toplevel
window that contains an arbitrary widget, you can call the @code{_root()} method.
This method begins with an underscore to denote the fact that this function is
part of the implementation, and not an interface to Tk functionality.

Here are some examples of typical usage:

@example
import tkinter as tk

class App(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()

# create the application
myapp = App()

#
# here are method calls to the window manager class
#
myapp.master.title("My Do-Nothing Application")
myapp.master.maxsize(1000, 400)

# start the program
myapp.mainloop()
@end example

@node Tk Option Data Types,Bindings and Events,The Window Manager,Handy Reference
@anchor{library/tkinter tk-option-data-types}@anchor{3124}
@subsubsection Tk Option Data Types


@geindex Tk Option Data Types


@table @asis

@item anchor

Legal values are points of the compass: @code{"n"}, @code{"ne"}, @code{"e"}, @code{"se"},
@code{"s"}, @code{"sw"}, @code{"w"}, @code{"nw"}, and also @code{"center"}.

@item bitmap

There are eight built-in, named bitmaps: @code{'error'}, @code{'gray25'},
@code{'gray50'}, @code{'hourglass'}, @code{'info'}, @code{'questhead'}, @code{'question'},
@code{'warning'}.  To specify an X bitmap filename, give the full path to the file,
preceded with an @code{@@}, as in @code{"@@/usr/contrib/bitmap/gumby.bit"}.

@item boolean

You can pass integers 0 or 1 or the strings @code{"yes"} or @code{"no"}.

@item callback -- 回调

This is any Python function that takes no arguments.  For example:

@example
def print_it():
    print("hi there")
fred["command"] = print_it
@end example

@item color

Colors can be given as the names of X colors in the rgb.txt file, or as strings
representing RGB values in 4 bit: @code{"#RGB"}, 8 bit: @code{"#RRGGBB"}, 12 bit"
@code{"#RRRGGGBBB"}, or 16 bit @code{"#RRRRGGGGBBBB"} ranges, where R,G,B here
represent any legal hex digit.  See page 160 of Ousterhout's book for details.

@item cursor

The standard X cursor names from @code{cursorfont.h} can be used, without the
@code{XC_} prefix.  For example to get a hand cursor (@code{XC_hand2}), use the
string @code{"hand2"}.  You can also specify a bitmap and mask file of your own.
See page 179 of Ousterhout's book.

@item distance

Screen distances can be specified in either pixels or absolute distances.
Pixels are given as numbers and absolute distances as strings, with the trailing
character denoting units: @code{c} for centimetres, @code{i} for inches, @code{m} for
millimetres, @code{p} for printer's points.  For example, 3.5 inches is expressed
as @code{"3.5i"}.

@item font

Tk uses a list font name format, such as @code{@{courier 10 bold@}}. Font sizes with
positive numbers are measured in points; sizes with negative numbers are
measured in pixels.

@item geometry

This is a string of the form @code{widthxheight}, where width and height are
measured in pixels for most widgets (in characters for widgets displaying text).
For example: @code{fred["geometry"] = "200x100"}.

@item justify

Legal values are the strings: @code{"left"}, @code{"center"}, @code{"right"}, and
@code{"fill"}.

@item region

This is a string with four space-delimited elements, each of which is a legal
distance (see above).  For example: @code{"2 3 4 5"} and @code{"3i 2i 4.5i 2i"} and
@code{"3c 2c 4c 10.43c"}  are all legal regions.

@item relief

Determines what the border style of a widget will be.  Legal values are:
@code{"raised"}, @code{"sunken"}, @code{"flat"}, @code{"groove"}, and @code{"ridge"}.

@item scrollcommand

This is almost always the @code{set()} method of some scrollbar widget, but can
be any widget method that takes a single argument.

@item wrap:

Must be one of: @code{"none"}, @code{"char"}, or @code{"word"}.
@end table

@node Bindings and Events,The index Parameter,Tk Option Data Types,Handy Reference
@anchor{library/tkinter bindings-and-events}@anchor{3125}
@subsubsection Bindings and Events


@geindex bind (widgets)
@geindex events (widgets)

The bind method from the widget command allows you to watch for certain events
and to have a callback function trigger when that event type occurs.  The form
of the bind method is:

@example
def bind(self, sequence, func, add='@w{'}):
@end example

where:


@table @asis

@item sequence -- 序列

is a string that denotes the target kind of event.  (See the bind man page and
page 201 of John Ousterhout's book for details).

@item func

is a Python function, taking one argument, to be invoked when the event occurs.
An Event instance will be passed as the argument. (Functions deployed this way
are commonly known as @emph{callbacks}.)

@item add

is optional, either @code{'@w{'}} or @code{'+'}.  Passing an empty string denotes that
this binding is to replace any other bindings that this event is associated
with.  Passing a @code{'+'} means that this function is to be added to the list
of functions bound to this event type.
@end table

例如

@example
def turn_red(self, event):
    event.widget["activeforeground"] = "red"

self.button.bind("<Enter>", self.turn_red)
@end example

Notice how the widget field of the event is being accessed in the
@code{turn_red()} callback.  This field contains the widget that caught the X
event.  The following table lists the other event fields you can access, and how
they are denoted in Tk, which can be useful when referring to the Tk man pages.


@multitable {xxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Tk

@tab

Tkinter Event Field

@tab

Tk

@tab

Tkinter Event Field

@item

%f

@tab

焦点

@tab

%A

@tab

char

@item

%h

@tab

height

@tab

%E

@tab

send_event

@item

%k

@tab

keycode

@tab

%K

@tab

keysym

@item

%s

@tab

状况

@tab

%N

@tab

keysym_num

@item

%t

@tab

time

@tab

%T

@tab

type

@item

%w

@tab

宽度

@tab

%W

@tab

widget

@item

%x

@tab

x

@tab

%X

@tab

x_root

@item

%y

@tab

y

@tab

%Y

@tab

y_root

@end multitable


@node The index Parameter,Images,Bindings and Events,Handy Reference
@anchor{library/tkinter the-index-parameter}@anchor{3126}
@subsubsection The index Parameter


A number of widgets require "index" parameters to be passed.  These are used to
point at a specific place in a Text widget, or to particular characters in an
Entry widget, or to particular menu items in a Menu widget.


@table @asis

@item Entry widget indexes (index, view index, etc.)

Entry widgets have options that refer to character positions in the text being
displayed.  You can use these @ref{10c,,tkinter} functions to access these special
points in text widgets:

@item Text widget indexes

The index notation for Text widgets is very rich and is best described in the Tk
man pages.

@item Menu indexes (menu.invoke(), menu.entryconfig(), etc.)

Some options and methods for menus manipulate specific menu entries. Anytime a
menu index is needed for an option or a parameter, you may pass in:


@itemize *

@item 
an integer which refers to the numeric position of the entry in the widget,
counted from the top, starting with 0;

@item 
the string @code{"active"}, which refers to the menu position that is currently
under the cursor;

@item 
the string @code{"last"} which refers to the last menu item;

@item 
An integer preceded by @code{@@}, as in @code{@@6}, where the integer is interpreted
as a y pixel coordinate in the menu's coordinate system;

@item 
the string @code{"none"}, which indicates no menu entry at all, most often used
with menu.activate() to deactivate all entries, and finally,

@item 
a text string that is pattern matched against the label of the menu entry, as
scanned from the top of the menu to the bottom.  Note that this index type is
considered after all the others, which means that matches for menu items
labelled @code{last}, @code{active}, or @code{none} may be interpreted as the above
literals, instead.
@end itemize
@end table

@node Images,,The index Parameter,Handy Reference
@anchor{library/tkinter images}@anchor{3127}
@subsubsection Images


Images of different formats can be created through the corresponding subclass
of @code{tkinter.Image}:


@itemize *

@item 
@code{BitmapImage} for images in XBM format.

@item 
@code{PhotoImage} for images in PGM, PPM, GIF and PNG formats. The latter
is supported starting with Tk 8.6.
@end itemize

Either type of image is created through either the @code{file} or the @code{data}
option (other options are available as well).

The image object can then be used wherever an @code{image} option is supported by
some widget (e.g. labels, buttons, menus). In these cases, Tk will not keep a
reference to the image. When the last Python reference to the image object is
deleted, the image data is deleted as well, and Tk will display an empty box
wherever the image was used.


@subsubheading 参见


The Pillow@footnote{http://python-pillow.org/} package adds support for
formats such as BMP, JPEG, TIFF, and WebP, among others.


@node File Handlers,,Handy Reference,tkinter --- Tcl/Tk的Python接口
@anchor{library/tkinter file-handlers}@anchor{3128}@anchor{library/tkinter tkinter-file-handlers}@anchor{3129}
@subsubsection File Handlers


Tk allows you to register and unregister a callback function which will be
called from the Tk mainloop when I/O is possible on a file descriptor.
Only one handler may be registered per file descriptor. Example code:

@example
import tkinter
widget = tkinter.Tk()
mask = tkinter.READABLE | tkinter.WRITABLE
widget.tk.createfilehandler(file, mask, callback)
...
widget.tk.deletefilehandler(file)
@end example

This feature is not available on Windows.

Since you don't know how many bytes are available for reading, you may not
want to use the @ref{583,,BufferedIOBase} or @ref{c32,,TextIOBase}
@ref{1ced,,read()} or @ref{169c,,readline()} methods,
since these will insist on reading a predefined number of bytes.
For sockets, the @ref{671,,recv()} or
@ref{672,,recvfrom()} methods will work fine; for other files,
use raw reads or @code{os.read(file.fileno(), maxbytecount)}.

@geindex createfilehandler() (tkinter.Widget.tk 方法)
@anchor{library/tkinter tkinter Widget tk createfilehandler}@anchor{312a}
@deffn {方法} Widget.tk.createfilehandler (file, mask, func)

Registers the file handler callback function @emph{func}. The @emph{file} argument
may either be an object with a @ref{1ea0,,fileno()} method (such as
a file or socket object), or an integer file descriptor. The @emph{mask}
argument is an ORed combination of any of the three constants below.
The callback is called as follows:

@example
callback(file, mask)
@end example
@end deffn

@geindex deletefilehandler() (tkinter.Widget.tk 方法)
@anchor{library/tkinter tkinter Widget tk deletefilehandler}@anchor{312b}
@deffn {方法} Widget.tk.deletefilehandler (file)

Unregisters a file handler.
@end deffn

@geindex READABLE() (在 tkinter 模块中)
@geindex WRITABLE() (在 tkinter 模块中)
@geindex EXCEPTION() (在 tkinter 模块中)
@anchor{library/tkinter tkinter READABLE}@anchor{312c}
@deffn {数据} tkinter.READABLE
@anchor{library/tkinter tkinter WRITABLE}@anchor{312d}
@deffnx {数据} tkinter.WRITABLE
@anchor{library/tkinter tkinter EXCEPTION}@anchor{312e}
@deffnx {数据} tkinter.EXCEPTION

Constants used in the @emph{mask} arguments.
@end deffn

@node tkinter ttk --- Tk主题小部件,tkinter tix --- Extension widgets for Tk,tkinter --- Tcl/Tk的Python接口,Tk图形用户界面 GUI
@anchor{library/tkinter ttk doc}@anchor{312f}@anchor{library/tkinter ttk module-tkinter ttk}@anchor{10f}@anchor{library/tkinter ttk tkinter-ttk-tk-themed-widgets}@anchor{3130}
@subsection @code{tkinter.ttk} --- Tk主题小部件


@geindex tkinter.ttk (模块)

@strong{源代码:} Lib/tkinter/ttk.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tkinter/ttk.py}

@geindex ttk


__________________________________________________________________


The @ref{10f,,tkinter.ttk} module provides access to the Tk themed widget set,
introduced in Tk 8.5. If Python has not been compiled against Tk 8.5, this
module can still be accessed if @emph{Tile} has been installed.  The former
method using Tk 8.5 provides additional benefits including anti-aliased font
rendering under X11 and window transparency (requiring a composition
window manager on X11).

The basic idea for @ref{10f,,tkinter.ttk} is to separate, to the extent possible,
the code implementing a widget's behavior from the code implementing its
appearance.


@subsubheading 参见



@table @asis

@item Tk Widget Styling Support@footnote{https://core.tcl.tk/tips/doc/trunk/tip/48.md}

一份文档介绍Tk支持的主题
@end table


@menu
* 使用 Ttk:: 
* Ttk 部件:: 
* 控件:: 
* 组合框:: 
* Spinbox:: 
* 笔记本:: 
* Progressbar:: 
* Separator:: 
* Sizegrip:: 
* Treeview:: 
* Ttk Styling:: 

@end menu

@node 使用 Ttk,Ttk 部件,,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk using-ttk}@anchor{3131}
@subsubsection 使用 Ttk


开始使用 Ttk, 导入模块:

@example
from tkinter import ttk
@end example

重写基础Tk部件,导入应跟随Tk导入:

@example
from tkinter import *
from tkinter.ttk import *
@end example

That code causes several @ref{10f,,tkinter.ttk} widgets (@code{Button},
@code{Checkbutton}, @code{Entry}, @code{Frame}, @code{Label},
@code{LabelFrame}, @code{Menubutton}, @code{PanedWindow},
@code{Radiobutton}, @code{Scale} and @code{Scrollbar}) to
automatically replace the Tk widgets.

This has the direct benefit of using the new widgets which gives a better
look and feel across platforms; however, the replacement widgets are not
completely compatible. The main difference is that widget options such as
"fg", "bg" and others related to widget styling are no
longer present in Ttk widgets.  Instead, use  the @code{ttk.Style} class
for improved styling effects.


@subsubheading 参见



@table @asis

@item Converting existing applications to use Tile widgets@footnote{http://tktable.sourceforge.net/tile/doc/converting.txt}

A monograph (using Tcl terminology) about differences typically
encountered when moving applications to use the new widgets.
@end table


@node Ttk 部件,控件,使用 Ttk,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk ttk-widgets}@anchor{3132}
@subsubsection Ttk 部件


ttk 中有 18 种部件 ，其中十二种已存在于 tkinter 中: @code{Button}, @code{Checkbutton}, @code{Entry}, @code{Frame}, @code{Label}, @code{LabelFrame}, @code{Menubutton}, @code{PanedWindow}, @code{Radiobutton}, @code{Scale}, @code{Scrollbar} 以及 @ref{3f5,,Spinbox}。 另外六种是新增的: @ref{3133,,Combobox}, @ref{3134,,Notebook}, @ref{3135,,Progressbar}, @code{Separator}, @code{Sizegrip} 以及 @ref{2bc,,Treeview}。 它们全都是 @ref{3136,,Widget} 的子类。

Using the Ttk widgets gives the application an improved look and feel.
As discussed above, there are differences in how the styling is coded.

Tk 代码:

@example
l1 = tkinter.Label(text="Test", fg="black", bg="white")
l2 = tkinter.Label(text="Test", fg="black", bg="white")
@end example

Ttk 代码:

@example
style = ttk.Style()
style.configure("BW.TLabel", foreground="black", background="white")

l1 = ttk.Label(text="Test", style="BW.TLabel")
l2 = ttk.Label(text="Test", style="BW.TLabel")
@end example

有关 @ref{3137,,TtkStyling} 的更多信息，请参阅 @ref{3138,,Style} 类文档。

@node 控件,组合框,Ttk 部件,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk widget}@anchor{3139}
@subsubsection 控件


@code{ttk.Widget} 定义了 Tk 主题小部件支持的标准选项和方法，不应该直接实例化。

@menu
* 标准选项:: 
* 可滚动控件选项:: 
* 标签选项:: 
* 兼容性选项:: 
* 控件状态:: 
* ttk.Widget: ttk Widget. 

@end menu

@node 标准选项,可滚动控件选项,,控件
@anchor{library/tkinter ttk standard-options}@anchor{313a}
@subsubsection 标准选项


所有 @code{ttk} 小部件接受以下选项：

@quotation


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

class -- 类

@tab

指定窗口类。在查询选项数据库中窗口的其他选项时，使用该类，确定窗口的默认绑定标签，以及选择窗口小部件的默认布局和样式。此选项仅为只读，并且只能在创建窗口时指定。

@item

cursor

@tab

指定要用于窗口小部件的鼠标光标。如果设置为空字符串（默认值），则为父窗口小部件继承光标.

@item

takefocus

@tab

确定窗口是否在键盘遍历期间接受焦点。返回0或1，返回空字符串。如果返回0，则表示在键盘遍历期间应该跳过该窗口。如果为1，则表示只要可以查看窗口就应该接收输入焦点。并且空字符串意味着遍历脚本决定是否关注窗口。

@item

style

@tab

可用于指定自定义窗口小部件样式。

@end multitable

@end quotation

@node 可滚动控件选项,标签选项,标准选项,控件
@anchor{library/tkinter ttk scrollable-widget-options}@anchor{313b}
@subsubsection 可滚动控件选项


控件支持以下选项使用滚动条控制.

@quotation


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

xscroll命令

@tab

用于与垂直滚动条通讯.

当视图在部件窗口改变,部件将会基于scroll命令生成Tcl命令.

Usually this option consists of the method
@code{Scrollbar.set()} of some scrollbar. This will cause
the scrollbar to be updated whenever the view in the
window changes.

@item

yscroll命令

@tab

用于与垂直滚动条通讯.更多信息请参考上面的信息.

@end multitable

@end quotation

@node 标签选项,兼容性选项,可滚动控件选项,控件
@anchor{library/tkinter ttk label-options}@anchor{313c}
@subsubsection 标签选项


以下选项支持标签,按钮已经其他类按钮的控件.

@quotation


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

文本

@tab

Specifies a text string to be displayed inside the widget.

@item

文本变量

@tab

Specifies a name whose value will be used in place of the
text option resource.

@item

下划线

@tab

If set, specifies the index (0-based) of a character to
underline in the text string. The underline character is
used for mnemonic activation.

@item

图片

@tab

Specifies an image to display. This is a list of 1 or more
elements. The first element is the default image name. The
rest of the list if a sequence of statespec/value pairs as
defined by @ref{313d,,Style.map()}, specifying different images
to use when the widget is in a particular state or a
combination of states. All images in the list should have
the same size.

@item

compound

@tab

Specifies how to display the image relative to the text,
in the case both text and images options are present.
Valid values are:


@itemize *

@item 
text: 只显示文本

@item 
image: 只显示图片

@item 
top, bottom, left, right: 分别显示图片的上,下,左,右的文本.

@item 
none: 默认. 如果设置显示图片, 否则文本.
@end itemize

@item

宽度

@tab

If greater than zero, specifies how much space, in
character widths, to allocate for the text label, if less
than zero, specifies a minimum width. If zero or
unspecified, the natural width of the text label is used.

@end multitable

@end quotation

@node 兼容性选项,控件状态,标签选项,控件
@anchor{library/tkinter ttk compatibility-options}@anchor{313e}
@subsubsection 兼容性选项


@quotation


@multitable {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

状况

@tab

May be set to "normal" or "disabled" to control the "disabled"
state bit. This is a write-only option: setting it changes the
widget state, but the @ref{313f,,Widget.state()} method does not
affect this option.

@end multitable

@end quotation

@node 控件状态,ttk Widget,兼容性选项,控件
@anchor{library/tkinter ttk widget-states}@anchor{3140}
@subsubsection 控件状态


控件状态是无关状态标志的位图.

@quotation


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Flag

@tab

描述

@item

活动

@tab

The mouse cursor is over the widget and pressing a mouse
button will cause some action to occur

@item

禁用

@tab

在程序控制下控件是禁用的

@item

焦点

@tab

控件有键盘焦点

@item

按压

@tab

Widget is being pressed

@item

选择

@tab

"On", "true", or "current" for things like Checkbuttons and
radiobuttons

@item

背景

@tab

Windows and Mac have a notion of an "active" or foreground
window. The @emph{background} state is set for widgets in a
background window, and cleared for those in the foreground
window

@item

只读

@tab

Widget should not allow user modification

@item

alternate

@tab

A widget-specific alternate display format

@item

无效的

@tab

控件的值是无效的

@end multitable

@end quotation

A state specification is a sequence of state names, optionally prefixed with
an exclamation point indicating that the bit is off.

@node ttk Widget,,控件状态,控件
@anchor{library/tkinter ttk ttk-widget}@anchor{3141}
@subsubsection ttk.Widget


Besides the methods described below, the @code{ttk.Widget} supports the
methods @code{tkinter.Widget.cget()} and @code{tkinter.Widget.configure()}.

@geindex Widget (tkinter.ttk 中的类)
@anchor{library/tkinter ttk tkinter ttk Widget}@anchor{3136}
@deffn {类} tkinter.ttk.Widget

@geindex identify() (tkinter.ttk.Widget 方法)
@anchor{library/tkinter ttk tkinter ttk Widget identify}@anchor{3142}
@deffn {方法} identify (x, y)

Returns the name of the element at position @emph{x} @emph{y}, or the empty string
if the point does not lie within any element.

@emph{x} and @emph{y} are pixel coordinates relative to the widget.
@end deffn

@geindex instate() (tkinter.ttk.Widget 方法)
@anchor{library/tkinter ttk tkinter ttk Widget instate}@anchor{3143}
@deffn {方法} instate (statespec, callback=None, *args, **kw)

Test the widget's state. If a callback is not specified, returns @code{True}
if the widget state matches @emph{statespec} and @code{False} otherwise. If callback
is specified then it is called with args if widget state matches
@emph{statespec}.
@end deffn

@geindex state() (tkinter.ttk.Widget 方法)
@anchor{library/tkinter ttk tkinter ttk Widget state}@anchor{313f}
@deffn {方法} state (statespec=None)

Modify or inquire widget state. If @emph{statespec} is specified, sets the
widget state according to it and return a new @emph{statespec} indicating
which flags were changed. If @emph{statespec} is not specified, returns
the currently-enabled state flags.
@end deffn

@emph{statespec} will usually be a list or a tuple.
@end deffn

@node 组合框,Spinbox,控件,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk combobox}@anchor{3144}
@subsubsection 组合框


The @code{ttk.Combobox} widget combines a text field with a pop-down list of
values. This widget is a subclass of @code{Entry}.

Besides the methods inherited from @ref{3136,,Widget}: @code{Widget.cget()},
@code{Widget.configure()}, @ref{3142,,Widget.identify()}, @ref{3143,,Widget.instate()}
and @ref{313f,,Widget.state()}, and the following inherited from @code{Entry}:
@code{Entry.bbox()}, @code{Entry.delete()}, @code{Entry.icursor()},
@code{Entry.index()}, @code{Entry.insert()}, @code{Entry.selection()},
@code{Entry.xview()}, it has some other methods, described at
@code{ttk.Combobox}.

@menu
* 选项:: 
* 虚拟事件:: 
* ttk.Combobox: ttk Combobox. 

@end menu

@node 选项,虚拟事件,,组合框
@anchor{library/tkinter ttk options}@anchor{3145}
@subsubsection 选项


This widget accepts the following specific options:

@quotation


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

exportselection

@tab

Boolean value. If set, the widget selection is linked
to the Window Manager selection (which can be returned
by invoking Misc.selection_get, for example).

@item

justify

@tab

Specifies how the text is aligned within the widget.
One of "left", "center", or "right".

@item

height

@tab

Specifies the height of the pop-down listbox, in rows.

@item

postcommand

@tab

A script (possibly registered with Misc.register) that
is called immediately before displaying the values. It
may specify which values to display.

@item

状况

@tab

One of "normal", "readonly", or "disabled". In the
"readonly" state, the value may not be edited directly,
and the user can only selection of the values from the
dropdown list. In the "normal" state, the text field is
directly editable. In the "disabled" state, no
interaction is possible.

@item

文本变量

@tab

Specifies a name whose value is linked to the widget
value. Whenever the value associated with that name
changes, the widget value is updated, and vice versa.
See @code{tkinter.StringVar}.

@item

值

@tab

Specifies the list of values to display in the
drop-down listbox.

@item

宽度

@tab

Specifies an integer value indicating the desired width
of the entry window, in average-size characters of the
widget's font.

@end multitable

@end quotation

@node 虚拟事件,ttk Combobox,选项,组合框
@anchor{library/tkinter ttk virtual-events}@anchor{3146}
@subsubsection 虚拟事件


The combobox widgets generates a @strong{<<ComboboxSelected>>} virtual event
when the user selects an element from the list of values.

@node ttk Combobox,,虚拟事件,组合框
@anchor{library/tkinter ttk ttk-combobox}@anchor{3147}
@subsubsection ttk.Combobox


@geindex Combobox (tkinter.ttk 中的类)
@anchor{library/tkinter ttk tkinter ttk Combobox}@anchor{3133}
@deffn {类} tkinter.ttk.Combobox

@geindex current() (tkinter.ttk.Combobox 方法)
@anchor{library/tkinter ttk tkinter ttk Combobox current}@anchor{3148}
@deffn {方法} current (newindex=None)

If @emph{newindex} is specified, sets the combobox value to the element
position @emph{newindex}. Otherwise, returns the index of the current value or
-1 if the current value is not in the values list.
@end deffn

@geindex get() (tkinter.ttk.Combobox 方法)
@anchor{library/tkinter ttk tkinter ttk Combobox get}@anchor{3149}
@deffn {方法} get ()

Returns the current value of the combobox.
@end deffn

@geindex set() (tkinter.ttk.Combobox 方法)
@anchor{library/tkinter ttk tkinter ttk Combobox set}@anchor{314a}
@deffn {方法} set (value)

Sets the value of the combobox to @emph{value}.
@end deffn
@end deffn

@node Spinbox,笔记本,组合框,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk spinbox}@anchor{314b}
@subsubsection Spinbox


The @code{ttk.Spinbox} widget is a @code{ttk.Entry} enhanced with increment
and decrement arrows.  It can be used for numbers or lists of string values.
This widget is a subclass of @code{Entry}.

Besides the methods inherited from @ref{3136,,Widget}: @code{Widget.cget()},
@code{Widget.configure()}, @ref{3142,,Widget.identify()}, @ref{3143,,Widget.instate()}
and @ref{313f,,Widget.state()}, and the following inherited from @code{Entry}:
@code{Entry.bbox()}, @code{Entry.delete()}, @code{Entry.icursor()},
@code{Entry.index()}, @code{Entry.insert()}, @code{Entry.xview()},
it has some other methods, described at @code{ttk.Spinbox}.

@menu
* 选项: 选项<2>. 
* 虚拟事件: 虚拟事件<2>. 
* ttk.Spinbox: ttk Spinbox. 

@end menu

@node 选项<2>,虚拟事件<2>,,Spinbox
@anchor{library/tkinter ttk id1}@anchor{314c}
@subsubsection 选项


This widget accepts the following specific options:

@quotation
@end quotation


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

从

@tab

Float value.  If set, this is the minimum value to
which the decrement button will decrement.  Must be
spelled as @code{from_} when used as an argument, since
@code{from} is a Python keyword.

@item

到

@tab

Float value.  If set, this is the maximum value to
which the increment button will increment.

@item

增加

@tab

Float value.  Specifies the amount which the
increment/decrement buttons change the
value. Defaults to 1.0.

@item

值

@tab

Sequence of string or float values.  If specified,
the increment/decrement buttons will cycle through
the items in this sequence rather than incrementing
or decrementing numbers.

@item

wrap

@tab

Boolean value.  If @code{True}, increment and decrement
buttons will cycle from the @code{to} value to the
@code{from} value or the @code{from} value to the @code{to}
value, respectively.

@item

format

@tab

String value.  This specifies the format of numbers
set by the increment/decrement buttons.  It must be
in the form "%W.Pf", where W is the padded width of
the value, P is the precision, and '%' and 'f' are
literal.

@item

命令

@tab

Python callable.  Will be called with no arguments
whenever either of the increment or decrement buttons
are pressed.

@end multitable


@node 虚拟事件<2>,ttk Spinbox,选项<2>,Spinbox
@anchor{library/tkinter ttk id2}@anchor{314d}
@subsubsection 虚拟事件


The spinbox widget generates an @strong{<<Increment>>} virtual event when the
user presses <Up>, and a @strong{<<Decrement>>} virtual event when the user
presses <Down>.

@node ttk Spinbox,,虚拟事件<2>,Spinbox
@anchor{library/tkinter ttk ttk-spinbox}@anchor{314e}
@subsubsection ttk.Spinbox


@geindex Spinbox (tkinter.ttk 中的类)
@anchor{library/tkinter ttk tkinter ttk Spinbox}@anchor{3f5}
@deffn {类} tkinter.ttk.Spinbox

@geindex get() (tkinter.ttk.Spinbox 方法)
@anchor{library/tkinter ttk tkinter ttk Spinbox get}@anchor{314f}
@deffn {方法} get ()

返回spinbox当前值
@end deffn

@geindex set() (tkinter.ttk.Spinbox 方法)
@anchor{library/tkinter ttk tkinter ttk Spinbox set}@anchor{3150}
@deffn {方法} set (value)

设置spinbox的值为*value*.
@end deffn
@end deffn

@node 笔记本,Progressbar,Spinbox,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk notebook}@anchor{3151}
@subsubsection 笔记本


Ttk Notebook widget manages a collection of windows and displays a single
one at a time. Each child window is associated with a tab, which the user
may select to change the currently-displayed window.

@menu
* 选项: 选项<3>. 
* Tab 选项:: 
* Tab Identifiers:: 
* Virtual Events:: 
* ttk.Notebook: ttk Notebook. 

@end menu

@node 选项<3>,Tab 选项,,笔记本
@anchor{library/tkinter ttk id3}@anchor{3152}
@subsubsection 选项


This widget accepts the following specific options:

@quotation


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

height

@tab

If present and greater than zero, specifies the desired height
of the pane area (not including internal padding or tabs).
Otherwise, the maximum height of all panes is used.

@item

padding

@tab

Specifies the amount of extra space to add around the outside
of the notebook. The padding is a list up to four length
specifications left top right bottom. If fewer than four
elements are specified, bottom defaults to top, right defaults
to left, and top defaults to left.

@item

宽度

@tab

If present and greater than zero, specified the desired width
of the pane area (not including internal padding). Otherwise,
the maximum width of all panes is used.

@end multitable

@end quotation

@node Tab 选项,Tab Identifiers,选项<3>,笔记本
@anchor{library/tkinter ttk tab-options}@anchor{3153}
@subsubsection Tab 选项


There are also specific options for tabs:

@quotation


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

状况

@tab

Either "normal", "disabled" or "hidden". If "disabled", then
the tab is not selectable. If "hidden", then the tab is not
shown.

@item

sticky

@tab

Specifies how the child window is positioned within the pane
area. Value is a string containing zero or more of the
characters "n", "s", "e" or "w". Each letter refers to a
side (north, south, east or west) that the child window will
stick to, as per the @code{grid()} geometry manager.

@item

padding

@tab

Specifies the amount of extra space to add between the
notebook and this pane. Syntax is the same as for the option
padding used by this widget.

@item

文本

@tab

Specifies a text to be displayed in the tab.

@item

图片

@tab

Specifies an image to display in the tab. See the option
image described in @ref{3136,,Widget}.

@item

compound

@tab

Specifies how to display the image relative to the text, in
the case both options text and image are present. See
@ref{313c,,Label Options} for legal values.

@item

下划线

@tab

Specifies the index (0-based) of a character to underline in
the text string. The underlined character is used for
mnemonic activation if @ref{3154,,Notebook.enable_traversal()} is
called.

@end multitable

@end quotation

@node Tab Identifiers,Virtual Events,Tab 选项,笔记本
@anchor{library/tkinter ttk tab-identifiers}@anchor{3155}
@subsubsection Tab Identifiers


The tab_id present in several methods of @code{ttk.Notebook} may take any
of the following forms:


@itemize *

@item 
An integer between zero and the number of tabs

@item 
The name of a child window

@item 
A positional specification of the form "@@x,y", which identifies the tab

@item 
The literal string "current", which identifies the currently-selected tab

@item 
The literal string "end", which returns the number of tabs (only valid for
@ref{3156,,Notebook.index()})
@end itemize

@node Virtual Events,ttk Notebook,Tab Identifiers,笔记本
@anchor{library/tkinter ttk id4}@anchor{3157}
@subsubsection Virtual Events


This widget generates a @strong{<<NotebookTabChanged>>} virtual event after a new
tab is selected.

@node ttk Notebook,,Virtual Events,笔记本
@anchor{library/tkinter ttk ttk-notebook}@anchor{3158}
@subsubsection ttk.Notebook


@geindex Notebook (tkinter.ttk 中的类)
@anchor{library/tkinter ttk tkinter ttk Notebook}@anchor{3134}
@deffn {类} tkinter.ttk.Notebook

@geindex add() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook add}@anchor{3159}
@deffn {方法} add (child, **kw)

Adds a new tab to the notebook.

If window is currently managed by the notebook but hidden, it is
restored to its previous position.

See @ref{3153,,Tab Options} for the list of available options.
@end deffn

@geindex forget() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook forget}@anchor{315a}
@deffn {方法} forget (tab_id)

Removes the tab specified by @emph{tab_id}, unmaps and unmanages the
associated window.
@end deffn

@geindex hide() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook hide}@anchor{315b}
@deffn {方法} hide (tab_id)

Hides the tab specified by @emph{tab_id}.

The tab will not be displayed, but the associated window remains
managed by the notebook and its configuration remembered. Hidden tabs
may be restored with the @ref{3159,,add()} command.
@end deffn

@geindex identify() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook identify}@anchor{315c}
@deffn {方法} identify (x, y)

Returns the name of the tab element at position @emph{x}, @emph{y}, or the empty
string if none.
@end deffn

@geindex index() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook index}@anchor{3156}
@deffn {方法} index (tab_id)

Returns the numeric index of the tab specified by @emph{tab_id}, or the total
number of tabs if @emph{tab_id} is the string "end".
@end deffn

@geindex insert() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook insert}@anchor{315d}
@deffn {方法} insert (pos, child, **kw)

Inserts a pane at the specified position.

@emph{pos} is either the string "end", an integer index, or the name of a
managed child. If @emph{child} is already managed by the notebook, moves it to
the specified position.

See @ref{3153,,Tab Options} for the list of available options.
@end deffn

@geindex select() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook select}@anchor{315e}
@deffn {方法} select (tab_id=None)

Selects the specified @emph{tab_id}.

The associated child window will be displayed, and the
previously-selected window (if different) is unmapped. If @emph{tab_id} is
omitted, returns the widget name of the currently selected pane.
@end deffn

@geindex tab() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook tab}@anchor{315f}
@deffn {方法} tab (tab_id, option=None, **kw)

Query or modify the options of the specific @emph{tab_id}.

If @emph{kw} is not given, returns a dictionary of the tab option values. If
@emph{option} is specified, returns the value of that @emph{option}. Otherwise,
sets the options to the corresponding values.
@end deffn

@geindex tabs() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook tabs}@anchor{3160}
@deffn {方法} tabs ()

Returns a list of windows managed by the notebook.
@end deffn

@geindex enable_traversal() (tkinter.ttk.Notebook 方法)
@anchor{library/tkinter ttk tkinter ttk Notebook enable_traversal}@anchor{3154}
@deffn {方法} enable_traversal ()

Enable keyboard traversal for a toplevel window containing this notebook.

This will extend the bindings for the toplevel window containing the
notebook as follows:


@itemize *

@item 
@code{Control-Tab}: selects the tab following the currently selected one.

@item 
@code{Shift-Control-Tab}: selects the tab preceding the currently selected one.

@item 
@code{Alt-K}: where @emph{K} is the mnemonic (underlined) character of any tab, will
select that tab.
@end itemize

Multiple notebooks in a single toplevel may be enabled for traversal,
including nested notebooks. However, notebook traversal only works
properly if all panes have the notebook they are in as master.
@end deffn
@end deffn

@node Progressbar,Separator,笔记本,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk progressbar}@anchor{3161}
@subsubsection Progressbar


The @code{ttk.Progressbar} widget shows the status of a long-running
operation. It can operate in two modes:  1) the determinate mode which shows the
amount completed relative to the total amount of work to be done and 2) the
indeterminate mode which provides an animated display to let the user know that
work is progressing.

@menu
* 选项: 选项<4>. 
* ttk.Progressbar: ttk Progressbar. 

@end menu

@node 选项<4>,ttk Progressbar,,Progressbar
@anchor{library/tkinter ttk id5}@anchor{3162}
@subsubsection 选项


This widget accepts the following specific options:

@quotation


@multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

orient

@tab

One of "horizontal" or "vertical". Specifies the orientation
of the progress bar.

@item

length

@tab

Specifies the length of the long axis of the progress bar
(width if horizontal, height if vertical).

@item

模式

@tab

One of "determinate" or "indeterminate".

@item

maximum

@tab

A number specifying the maximum value. Defaults to 100.

@item

值

@tab

The current value of the progress bar. In "determinate" mode,
this represents the amount of work completed. In
"indeterminate" mode, it is interpreted as modulo @emph{maximum};
that is, the progress bar completes one "cycle" when its value
increases by @emph{maximum}.

@item

variable

@tab

A name which is linked to the option value. If specified, the
value of the progress bar is automatically set to the value of
this name whenever the latter is modified.

@item

phase

@tab

Read-only option. The widget periodically increments the value
of this option whenever its value is greater than 0 and, in
determinate mode, less than maximum. This option may be used
by the current theme to provide additional animation effects.

@end multitable

@end quotation

@node ttk Progressbar,,选项<4>,Progressbar
@anchor{library/tkinter ttk ttk-progressbar}@anchor{3163}
@subsubsection ttk.Progressbar


@geindex Progressbar (tkinter.ttk 中的类)
@anchor{library/tkinter ttk tkinter ttk Progressbar}@anchor{3135}
@deffn {类} tkinter.ttk.Progressbar

@geindex start() (tkinter.ttk.Progressbar 方法)
@anchor{library/tkinter ttk tkinter ttk Progressbar start}@anchor{3164}
@deffn {方法} start (interval=None)

Begin autoincrement mode: schedules a recurring timer event that calls
@ref{3165,,Progressbar.step()} every @emph{interval} milliseconds. If omitted,
@emph{interval} defaults to 50 milliseconds.
@end deffn

@geindex step() (tkinter.ttk.Progressbar 方法)
@anchor{library/tkinter ttk tkinter ttk Progressbar step}@anchor{3165}
@deffn {方法} step (amount=None)

Increments the progress bar's value by @emph{amount}.

@emph{amount} defaults to 1.0 if omitted.
@end deffn

@geindex stop() (tkinter.ttk.Progressbar 方法)
@anchor{library/tkinter ttk tkinter ttk Progressbar stop}@anchor{3166}
@deffn {方法} stop ()

Stop autoincrement mode: cancels any recurring timer event initiated by
@ref{3164,,Progressbar.start()} for this progress bar.
@end deffn
@end deffn

@node Separator,Sizegrip,Progressbar,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk separator}@anchor{3167}
@subsubsection Separator


The @code{ttk.Separator} widget displays a horizontal or vertical separator
bar.

It has no other methods besides the ones inherited from @code{ttk.Widget}.

@menu
* 选项: 选项<5>. 

@end menu

@node 选项<5>,,,Separator
@anchor{library/tkinter ttk id6}@anchor{3168}
@subsubsection 选项


This widget accepts the following specific option:

@quotation


@multitable {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

orient

@tab

One of "horizontal" or "vertical". Specifies the orientation of
the separator.

@end multitable

@end quotation

@node Sizegrip,Treeview,Separator,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk sizegrip}@anchor{3169}
@subsubsection Sizegrip


The @code{ttk.Sizegrip} widget (also known as a grow box) allows the user to
resize the containing toplevel window by pressing and dragging the grip.

This widget has neither specific options nor specific methods, besides the
ones inherited from @code{ttk.Widget}.

@menu
* Platform-specific notes:: 
* Bugs:: 

@end menu

@node Platform-specific notes,Bugs,,Sizegrip
@anchor{library/tkinter ttk platform-specific-notes}@anchor{316a}
@subsubsection Platform-specific notes



@itemize *

@item 
On MacOS X, toplevel windows automatically include a built-in size grip
by default. Adding a @code{Sizegrip} is harmless, since the built-in
grip will just mask the widget.
@end itemize

@node Bugs,,Platform-specific notes,Sizegrip
@anchor{library/tkinter ttk bugs}@anchor{316b}
@subsubsection Bugs



@itemize *

@item 
If the containing toplevel's position was specified relative to the right
or bottom of the screen (e.g. ....), the @code{Sizegrip} widget will
not resize the window.

@item 
This widget supports only "southeast" resizing.
@end itemize

@node Treeview,Ttk Styling,Sizegrip,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk treeview}@anchor{316c}
@subsubsection Treeview


The @code{ttk.Treeview} widget displays a hierarchical collection of items.
Each item has a textual label, an optional image, and an optional list of data
values. The data values are displayed in successive columns after the tree
label.

The order in which data values are displayed may be controlled by setting
the widget option @code{displaycolumns}. The tree widget can also display column
headings. Columns may be accessed by number or symbolic names listed in the
widget option columns. See @ref{316d,,Column Identifiers}.

Each item is identified by a unique name. The widget will generate item IDs
if they are not supplied by the caller. There is a distinguished root item,
named @code{@{@}}. The root item itself is not displayed; its children appear at the
top level of the hierarchy.

Each item also has a list of tags, which can be used to associate event bindings
with individual items and control the appearance of the item.

The Treeview widget supports horizontal and vertical scrolling, according to
the options described in @ref{313b,,Scrollable Widget Options} and the methods
@ref{316e,,Treeview.xview()} and @ref{316f,,Treeview.yview()}.

@menu
* 选项: 选项<6>. 
* Item Options:: 
* Tag Options:: 
* Column Identifiers:: 
* Virtual Events: Virtual Events<2>. 
* ttk.Treeview: ttk Treeview. 

@end menu

@node 选项<6>,Item Options,,Treeview
@anchor{library/tkinter ttk id7}@anchor{3170}
@subsubsection 选项


This widget accepts the following specific options:

@quotation


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

columns

@tab

A list of column identifiers, specifying the number of
columns and their names.

@item

displaycolumns

@tab

A list of column identifiers (either symbolic or
integer indices) specifying which data columns are
displayed and the order in which they appear, or the
string "#all".

@item

height

@tab

Specifies the number of rows which should be visible.
Note: the requested width is determined from the sum
of the column widths.

@item

padding

@tab

Specifies the internal padding for the widget. The
padding is a list of up to four length specifications.

@item

selectmode

@tab

Controls how the built-in class bindings manage the
selection. One of "extended", "browse" or "none".
If set to "extended" (the default), multiple items may
be selected. If "browse", only a single item will be
selected at a time. If "none", the selection will not
be changed.

Note that the application code and tag bindings can set
the selection however they wish, regardless of the
value  of this option.

@item

show

@tab

A list containing zero or more of the following values,
specifying which elements of the tree to display.


@itemize *

@item 
tree: display tree labels in column #0.

@item 
headings: display the heading row.
@end itemize

The default is "tree headings", i.e., show all
elements.

@strong{Note}: Column #0 always refers to the tree column,
even if show="tree" is not specified.

@end multitable

@end quotation

@node Item Options,Tag Options,选项<6>,Treeview
@anchor{library/tkinter ttk item-options}@anchor{3171}
@subsubsection Item Options


The following item options may be specified for items in the insert and item
widget commands.

@quotation


@multitable {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

文本

@tab

The textual label to display for the item.

@item

图片

@tab

A Tk Image, displayed to the left of the label.

@item

值

@tab

The list of values associated with the item.

Each item should have the same number of values as the widget
option columns. If there are fewer values than columns, the
remaining values are assumed empty. If there are more values
than columns, the extra values are ignored.

@item

open

@tab

@code{True}/@code{False} value indicating whether the item's
children should be displayed or hidden.

@item

tags

@tab

A list of tags associated with this item.

@end multitable

@end quotation

@node Tag Options,Column Identifiers,Item Options,Treeview
@anchor{library/tkinter ttk tag-options}@anchor{3172}
@subsubsection Tag Options


The following options may be specified on tags:

@quotation


@multitable {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

选项

@tab

描述

@item

foreground

@tab

Specifies the text foreground color.

@item

背景

@tab

Specifies the cell or item background color.

@item

font

@tab

Specifies the font to use when drawing text.

@item

图片

@tab

Specifies the item image, in case the item's image option
is empty.

@end multitable

@end quotation

@node Column Identifiers,Virtual Events<2>,Tag Options,Treeview
@anchor{library/tkinter ttk column-identifiers}@anchor{316d}
@subsubsection Column Identifiers


Column identifiers take any of the following forms:


@itemize *

@item 
A symbolic name from the list of columns option.

@item 
An integer n, specifying the nth data column.

@item 
A string of the form #n, where n is an integer, specifying the nth display
column.
@end itemize

注释:


@itemize *

@item 
Item's option values may be displayed in a different order than the order
in which they are stored.

@item 
Column #0 always refers to the tree column, even if show="tree" is not
specified.
@end itemize

A data column number is an index into an item's option values list; a display
column number is the column number in the tree where the values are displayed.
Tree labels are displayed in column #0. If option displaycolumns is not set,
then data column n is displayed in column #n+1. Again, @strong{column #0 always
refers to the tree column}.

@node Virtual Events<2>,ttk Treeview,Column Identifiers,Treeview
@anchor{library/tkinter ttk id8}@anchor{3173}
@subsubsection Virtual Events


The Treeview widget generates the following virtual events.

@quotation


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Event

@tab

描述

@item

<<TreeviewSelect>>

@tab

Generated whenever the selection changes.

@item

<<TreeviewOpen>>

@tab

Generated just before settings the focus item to
open=True.

@item

<<TreeviewClose>>

@tab

Generated just after setting the focus item to
open=False.

@end multitable

@end quotation

The @ref{3174,,Treeview.focus()} and @ref{2bd,,Treeview.selection()} methods can be used
to determine the affected item or items.

@node ttk Treeview,,Virtual Events<2>,Treeview
@anchor{library/tkinter ttk ttk-treeview}@anchor{3175}
@subsubsection ttk.Treeview


@geindex Treeview (tkinter.ttk 中的类)
@anchor{library/tkinter ttk tkinter ttk Treeview}@anchor{2bc}
@deffn {类} tkinter.ttk.Treeview

@geindex bbox() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview bbox}@anchor{3176}
@deffn {方法} bbox (item, column=None)

Returns the bounding box (relative to the treeview widget's window) of
the specified @emph{item} in the form (x, y, width, height).

If @emph{column} is specified, returns the bounding box of that cell. If the
@emph{item} is not visible (i.e., if it is a descendant of a closed item or is
scrolled offscreen), returns an empty string.
@end deffn

@geindex get_children() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview get_children}@anchor{3177}
@deffn {方法} get_children (item=None)

Returns the list of children belonging to @emph{item}.

If @emph{item} is not specified, returns root children.
@end deffn

@geindex set_children() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview set_children}@anchor{3178}
@deffn {方法} set_children (item, *newchildren)

Replaces @emph{item}'s child with @emph{newchildren}.

Children present in @emph{item} that are not present in @emph{newchildren} are
detached from the tree. No items in @emph{newchildren} may be an ancestor of
@emph{item}. Note that not specifying @emph{newchildren} results in detaching
@emph{item}'s children.
@end deffn

@geindex column() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview column}@anchor{3179}
@deffn {方法} column (column, option=None, **kw)

Query or modify the options for the specified @emph{column}.

If @emph{kw} is not given, returns a dict of the column option values. If
@emph{option} is specified then the value for that @emph{option} is returned.
Otherwise, sets the options to the corresponding values.

The valid options/values are:


@itemize *

@item 

@table @asis

@item id

Returns the column name. This is a read-only option.
@end table

@item 

@table @asis

@item anchor: One of the standard Tk anchor values.

Specifies how the text in this column should be aligned with respect
to the cell.
@end table

@item 

@table @asis

@item minwidth: width

The minimum width of the column in pixels. The treeview widget will
not make the column any smaller than specified by this option when
the widget is resized or the user drags a column.
@end table

@item 

@table @asis

@item stretch: @code{True}/@code{False}

指明列宽度是否应该在部件大小被改变时进行相应的调整。
@end table

@item 

@table @asis

@item width: width

以像素表示的列宽度。
@end table
@end itemize

要配置树的列，则调用此方法并附带参数 column = "#0"
@end deffn

@geindex delete() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview delete}@anchor{317a}
@deffn {方法} delete (*items)

Delete all specified @emph{items} and all their descendants.

The root item may not be deleted.
@end deffn

@geindex detach() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview detach}@anchor{317b}
@deffn {方法} detach (*items)

Unlinks all of the specified @emph{items} from the tree.

The items and all of their descendants are still present, and may be
reinserted at another point in the tree, but will not be displayed.

The root item may not be detached.
@end deffn

@geindex exists() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview exists}@anchor{317c}
@deffn {方法} exists (item)

Returns @code{True} if the specified @emph{item} is present in the tree.
@end deffn

@geindex focus() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview focus}@anchor{3174}
@deffn {方法} focus (item=None)

If @emph{item} is specified, sets the focus item to @emph{item}. Otherwise, returns
the current focus item, or '@w{'} if there is none.
@end deffn

@geindex heading() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview heading}@anchor{317d}
@deffn {方法} heading (column, option=None, **kw)

Query or modify the heading options for the specified @emph{column}.

If @emph{kw} is not given, returns a dict of the heading option values. If
@emph{option} is specified then the value for that @emph{option} is returned.
Otherwise, sets the options to the corresponding values.

The valid options/values are:


@itemize *

@item 

@table @asis

@item text: text

The text to display in the column heading.
@end table

@item 

@table @asis

@item image: imageName

Specifies an image to display to the right of the column heading.
@end table

@item 

@table @asis

@item anchor: anchor

Specifies how the heading text should be aligned. One of the standard
Tk anchor values.
@end table

@item 

@table @asis

@item command: callback

A callback to be invoked when the heading label is pressed.
@end table
@end itemize

To configure the tree column heading, call this with column = "#0".
@end deffn

@geindex identify() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview identify}@anchor{317e}
@deffn {方法} identify (component, x, y)

Returns a description of the specified @emph{component} under the point given
by @emph{x} and @emph{y}, or the empty string if no such @emph{component} is present at
that position.
@end deffn

@geindex identify_row() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview identify_row}@anchor{317f}
@deffn {方法} identify_row (y)

Returns the item ID of the item at position @emph{y}.
@end deffn

@geindex identify_column() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview identify_column}@anchor{3180}
@deffn {方法} identify_column (x)

Returns the data column identifier of the cell at position @emph{x}.

The tree column has ID #0.
@end deffn

@geindex identify_region() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview identify_region}@anchor{3181}
@deffn {方法} identify_region (x, y)

Returns one of:


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

region

@tab

meaning

@item

heading

@tab

Tree heading area.

@item

separator

@tab

Space between two columns headings.

@item

tree

@tab

The tree area.

@item

cell

@tab

A data cell.

@end multitable


Availability: Tk 8.6.
@end deffn

@geindex identify_element() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview identify_element}@anchor{3182}
@deffn {方法} identify_element (x, y)

Returns the element at position @emph{x}, @emph{y}.

Availability: Tk 8.6.
@end deffn

@geindex index() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview index}@anchor{3183}
@deffn {方法} index (item)

Returns the integer index of @emph{item} within its parent's list of children.
@end deffn

@geindex insert() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview insert}@anchor{3184}
@deffn {方法} insert (parent, index, iid=None, **kw)

Creates a new item and returns the item identifier of the newly created
item.

@emph{parent} is the item ID of the parent item, or the empty string to create
a new top-level item. @emph{index} is an integer, or the value "end",
specifying where in the list of parent's children to insert the new item.
If @emph{index} is less than or equal to zero, the new node is inserted at
the beginning; if @emph{index} is greater than or equal to the current number
of children, it is inserted at the end. If @emph{iid} is specified, it is used
as the item identifier; @emph{iid} must not already exist in the tree.
Otherwise, a new unique identifier is generated.

See @ref{3171,,Item Options} for the list of available points.
@end deffn

@geindex item() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview item}@anchor{3185}
@deffn {方法} item (item, option=None, **kw)

Query or modify the options for the specified @emph{item}.

If no options are given, a dict with options/values for the item is
returned.
If @emph{option} is specified then the value for that option is returned.
Otherwise, sets the options to the corresponding values as given by @emph{kw}.
@end deffn

@geindex move() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview move}@anchor{3186}
@deffn {方法} move (item, parent, index)

Moves @emph{item} to position @emph{index} in @emph{parent}'s list of children.

It is illegal to move an item under one of its descendants. If @emph{index} is
less than or equal to zero, @emph{item} is moved to the beginning; if greater
than or equal to the number of children, it is moved to the end. If @emph{item}
was detached it is reattached.
@end deffn

@geindex next() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview next}@anchor{3187}
@deffn {方法} next (item)

Returns the identifier of @emph{item}'s next sibling, or '@w{'} if @emph{item} is the
last child of its parent.
@end deffn

@geindex parent() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview parent}@anchor{3188}
@deffn {方法} parent (item)

Returns the ID of the parent of @emph{item}, or '@w{'} if @emph{item} is at the top
level of the hierarchy.
@end deffn

@geindex prev() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview prev}@anchor{3189}
@deffn {方法} prev (item)

Returns the identifier of @emph{item}'s previous sibling, or '@w{'} if @emph{item} is
the first child of its parent.
@end deffn

@geindex reattach() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview reattach}@anchor{318a}
@deffn {方法} reattach (item, parent, index)

An alias for @ref{3186,,Treeview.move()}.
@end deffn

@geindex see() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview see}@anchor{318b}
@deffn {方法} see (item)

Ensure that @emph{item} is visible.

Sets all of @emph{item}'s ancestors open option to @code{True}, and scrolls the
widget if necessary so that @emph{item} is within the visible portion of
the tree.
@end deffn

@geindex selection() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview selection}@anchor{2bd}
@deffn {方法} selection ()

Returns a tuple of selected items.


在 3.8 版更改: @code{selection()} no longer takes arguments.  For changing the selection
state use the following selection methods.

@end deffn

@geindex selection_set() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview selection_set}@anchor{2be}
@deffn {方法} selection_set (*items)

@emph{items} becomes the new selection.


在 3.6 版更改: @emph{items} can be passed as separate arguments, not just as a single tuple.

@end deffn

@geindex selection_add() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview selection_add}@anchor{318c}
@deffn {方法} selection_add (*items)

Add @emph{items} to the selection.


在 3.6 版更改: @emph{items} can be passed as separate arguments, not just as a single tuple.

@end deffn

@geindex selection_remove() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview selection_remove}@anchor{318d}
@deffn {方法} selection_remove (*items)

Remove @emph{items} from the selection.


在 3.6 版更改: @emph{items} can be passed as separate arguments, not just as a single tuple.

@end deffn

@geindex selection_toggle() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview selection_toggle}@anchor{318e}
@deffn {方法} selection_toggle (*items)

Toggle the selection state of each item in @emph{items}.


在 3.6 版更改: @emph{items} can be passed as separate arguments, not just as a single tuple.

@end deffn

@geindex set() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview set}@anchor{318f}
@deffn {方法} set (item, column=None, value=None)

With one argument, returns a dictionary of column/value pairs for the
specified @emph{item}. With two arguments, returns the current value of the
specified @emph{column}. With three arguments, sets the value of given
@emph{column} in given @emph{item} to the specified @emph{value}.
@end deffn

@geindex tag_bind() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview tag_bind}@anchor{3190}
@deffn {方法} tag_bind (tagname, sequence=None, callback=None)

Bind a callback for the given event @emph{sequence} to the tag @emph{tagname}.
When an event is delivered to an item, the callbacks for each of the
item's tags option are called.
@end deffn

@geindex tag_configure() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview tag_configure}@anchor{3191}
@deffn {方法} tag_configure (tagname, option=None, **kw)

Query or modify the options for the specified @emph{tagname}.

If @emph{kw} is not given, returns a dict of the option settings for
@emph{tagname}. If @emph{option} is specified, returns the value for that @emph{option}
for the specified @emph{tagname}. Otherwise, sets the options to the
corresponding values for the given @emph{tagname}.
@end deffn

@geindex tag_has() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview tag_has}@anchor{3192}
@deffn {方法} tag_has (tagname, item=None)

If @emph{item} is specified, returns 1 or 0 depending on whether the specified
@emph{item} has the given @emph{tagname}. Otherwise, returns a list of all items
that have the specified tag.

Availability: Tk 8.6
@end deffn

@geindex xview() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview xview}@anchor{316e}
@deffn {方法} xview (*args)

Query or modify horizontal position of the treeview.
@end deffn

@geindex yview() (tkinter.ttk.Treeview 方法)
@anchor{library/tkinter ttk tkinter ttk Treeview yview}@anchor{316f}
@deffn {方法} yview (*args)

Query or modify vertical position of the treeview.
@end deffn
@end deffn

@node Ttk Styling,,Treeview,tkinter ttk --- Tk主题小部件
@anchor{library/tkinter ttk ttk-styling}@anchor{3193}@anchor{library/tkinter ttk ttkstyling}@anchor{3137}
@subsubsection Ttk Styling


Each widget in @code{ttk} is assigned a style, which specifies the set of
elements making up the widget and how they are arranged, along with dynamic
and default settings for element options. By default the style name is the
same as the widget's class name, but it may be overridden by the widget's style
option. If you don't know the class name of a widget, use the method
@code{Misc.winfo_class()} (somewidget.winfo_class()).


@subsubheading 参见



@table @asis

@item Tcl'2004 conference presentation@footnote{http://tktable.sourceforge.net/tile/tile-tcl2004.pdf}

This document explains how the theme engine works
@end table


@geindex Style (tkinter.ttk 中的类)
@anchor{library/tkinter ttk tkinter ttk Style}@anchor{3138}
@deffn {类} tkinter.ttk.Style

This class is used to manipulate the style database.

@geindex configure() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style configure}@anchor{3194}
@deffn {方法} configure (style, query_opt=None, **kw)

Query or set the default value of the specified option(s) in @emph{style}.

Each key in @emph{kw} is an option and each value is a string identifying
the value for that option.

For example, to change every default button to be a flat button with
some padding and a different background color:

@example
from tkinter import ttk
import tkinter

root = tkinter.Tk()

ttk.Style().configure("TButton", padding=6, relief="flat",
   background="#ccc")

btn = ttk.Button(text="Sample")
btn.pack()

root.mainloop()
@end example
@end deffn

@geindex map() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style map}@anchor{313d}
@deffn {方法} map (style, query_opt=None, **kw)

Query or sets dynamic values of the specified option(s) in @emph{style}.

Each key in @emph{kw} is an option and each value should be a list or a
tuple (usually) containing statespecs grouped in tuples, lists, or
some other preference. A statespec is a compound of one
or more states and then a value.

An example may make it more understandable:

@example
import tkinter
from tkinter import ttk

root = tkinter.Tk()

style = ttk.Style()
style.map("C.TButton",
    foreground=[('pressed', 'red'), ('active', 'blue')],
    background=[('pressed', '!disabled', 'black'), ('active', 'white')]
    )

colored_btn = ttk.Button(text="Test", style="C.TButton").pack()

root.mainloop()
@end example

Note that the order of the (states, value) sequences for an option does
matter, if the order is changed to @code{[('active', 'blue'), ('pressed',
'red')]} in the foreground option, for example, the result would be a
blue foreground when the widget were in active or pressed states.
@end deffn

@geindex lookup() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style lookup}@anchor{3195}
@deffn {方法} lookup (style, option, state=None, default=None)

Returns the value specified for @emph{option} in @emph{style}.

If @emph{state} is specified, it is expected to be a sequence of one or more
states. If the @emph{default} argument is set, it is used as a fallback value
in case no specification for option is found.

To check what font a Button uses by default:

@example
from tkinter import ttk

print(ttk.Style().lookup("TButton", "font"))
@end example
@end deffn

@geindex layout() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style layout}@anchor{3196}
@deffn {方法} layout (style, layoutspec=None)

Define the widget layout for given @emph{style}. If @emph{layoutspec} is omitted,
return the layout specification for given style.

@emph{layoutspec}, if specified, is expected to be a list or some other
sequence type (excluding strings), where each item should be a tuple and
the first item is the layout name and the second item should have the
format described in @ref{3197,,Layouts}.

To understand the format, see the following example (it is not
intended to do anything useful):

@example
from tkinter import ttk
import tkinter

root = tkinter.Tk()

style = ttk.Style()
style.layout("TMenubutton", [
   ("Menubutton.background", None),
   ("Menubutton.button", @{"children":
       [("Menubutton.focus", @{"children":
           [("Menubutton.padding", @{"children":
               [("Menubutton.label", @{"side": "left", "expand": 1@})]
           @})]
       @})]
   @}),
])

mbtn = ttk.Menubutton(text='Text')
mbtn.pack()
root.mainloop()
@end example
@end deffn

@geindex element_create() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style element_create}@anchor{3198}
@deffn {方法} element_create (elementname, etype, *args, **kw)

Create a new element in the current theme, of the given @emph{etype} which is
expected to be either "image", "from" or "vsapi". The latter is only
available in Tk 8.6a for Windows XP and Vista and is not described here.

If "image" is used, @emph{args} should contain the default image name followed
by statespec/value pairs (this is the imagespec), and @emph{kw} may have the
following options:

@quotation


@itemize *

@item 

@table @asis

@item border=padding

padding is a list of up to four integers, specifying the left, top,
right, and bottom borders, respectively.
@end table

@item 

@table @asis

@item height=height

Specifies a minimum height for the element. If less than zero, the
base image's height is used as a default.
@end table

@item 

@table @asis

@item padding=padding

Specifies the element's interior padding. Defaults to border's value
if not specified.
@end table

@item 

@table @asis

@item sticky=spec

Specifies how the image is placed within the final parcel. spec
contains zero or more characters "n", "s", "w", or "e".
@end table

@item 

@table @asis

@item width=width

Specifies a minimum width for the element. If less than zero, the
base image's width is used as a default.
@end table
@end itemize
@end quotation

If "from" is used as the value of @emph{etype},
@ref{3198,,element_create()} will clone an existing
element. @emph{args} is expected to contain a themename, from which
the element will be cloned, and optionally an element to clone from.
If this element to clone from is not specified, an empty element will
be used. @emph{kw} is discarded.
@end deffn

@geindex element_names() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style element_names}@anchor{3199}
@deffn {方法} element_names ()

Returns the list of elements defined in the current theme.
@end deffn

@geindex element_options() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style element_options}@anchor{319a}
@deffn {方法} element_options (elementname)

Returns the list of @emph{elementname}'s options.
@end deffn

@geindex theme_create() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style theme_create}@anchor{319b}
@deffn {方法} theme_create (themename, parent=None, settings=None)

Create a new theme.

It is an error if @emph{themename} already exists. If @emph{parent} is specified,
the new theme will inherit styles, elements and layouts from the parent
theme. If @emph{settings} are present they are expected to have the same
syntax used for @ref{319c,,theme_settings()}.
@end deffn

@geindex theme_settings() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style theme_settings}@anchor{319c}
@deffn {方法} theme_settings (themename, settings)

Temporarily sets the current theme to @emph{themename}, apply specified
@emph{settings} and then restore the previous theme.

Each key in @emph{settings} is a style and each value may contain the keys
'configure', 'map', 'layout' and 'element create' and they are expected
to have the same format as specified by the methods
@ref{3194,,Style.configure()}, @ref{313d,,Style.map()}, @ref{3196,,Style.layout()} and
@ref{3198,,Style.element_create()} respectively.

As an example, let's change the Combobox for the default theme a bit:

@example
from tkinter import ttk
import tkinter

root = tkinter.Tk()

style = ttk.Style()
style.theme_settings("default", @{
   "TCombobox": @{
       "configure": @{"padding": 5@},
       "map": @{
           "background": [("active", "green2"),
                          ("!disabled", "green4")],
           "fieldbackground": [("!disabled", "green3")],
           "foreground": [("focus", "OliveDrab1"),
                          ("!disabled", "OliveDrab2")]
       @}
   @}
@})

combo = ttk.Combobox().pack()

root.mainloop()
@end example
@end deffn

@geindex theme_names() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style theme_names}@anchor{319d}
@deffn {方法} theme_names ()

Returns a list of all known themes.
@end deffn

@geindex theme_use() (tkinter.ttk.Style 方法)
@anchor{library/tkinter ttk tkinter ttk Style theme_use}@anchor{319e}
@deffn {方法} theme_use (themename=None)

If @emph{themename} is not given, returns the theme in use.  Otherwise, sets
the current theme to @emph{themename}, refreshes all widgets and emits a
<<ThemeChanged>> event.
@end deffn
@end deffn

@menu
* Layouts:: 

@end menu

@node Layouts,,,Ttk Styling
@anchor{library/tkinter ttk layouts}@anchor{3197}
@subsubsection Layouts


A layout can be just @code{None}, if it takes no options, or a dict of
options specifying how to arrange the element. The layout mechanism
uses a simplified version of the pack geometry manager: given an
initial cavity, each element is allocated a parcel. Valid
options/values are:

@quotation


@itemize *

@item 

@table @asis

@item side: whichside

Specifies which side of the cavity to place the element; one of
top, right, bottom or left. If omitted, the element occupies the
entire cavity.
@end table

@item 

@table @asis

@item sticky: nswe

Specifies where the element is placed inside its allocated parcel.
@end table

@item 

@table @asis

@item unit: 0 or 1

If set to 1, causes the element and all of its descendants to be treated as
a single element for the purposes of @ref{3142,,Widget.identify()} et al. It's
used for things like scrollbar thumbs with grips.
@end table

@item 

@table @asis

@item children: [sublayout... ]

Specifies a list of elements to place inside the element. Each
element is a tuple (or other sequence type) where the first item is
the layout name, and the other is a @ref{3197,,Layout}.
@end table
@end itemize
@end quotation

@node tkinter tix --- Extension widgets for Tk,tkinter scrolledtext --- 滚动文字控件,tkinter ttk --- Tk主题小部件,Tk图形用户界面 GUI
@anchor{library/tkinter tix doc}@anchor{319f}@anchor{library/tkinter tix layout}@anchor{31a0}@anchor{library/tkinter tix layouts}@anchor{31a1}@anchor{library/tkinter tix module-tkinter tix}@anchor{10e}@anchor{library/tkinter tix tkinter-tix-extension-widgets-for-tk}@anchor{31a2}
@subsection @code{tkinter.tix} --- Extension widgets for Tk


@geindex tkinter.tix (模块)

@strong{Source code:} Lib/tkinter/tix.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tkinter/tix.py}

@geindex Tix


3.6 版后已移除: This Tk extension is unmaintained and should not be used in new code.  Use
@ref{10f,,tkinter.ttk} instead.



__________________________________________________________________


The @ref{10e,,tkinter.tix} (Tk Interface Extension) module provides an additional
rich set of widgets. Although the standard Tk library has many useful widgets,
they are far from complete. The @ref{10e,,tkinter.tix} library provides most of the
commonly needed widgets that are missing from standard Tk: @ref{31a3,,HList},
@ref{31a4,,ComboBox}, @ref{31a5,,Control} (a.k.a. SpinBox) and an assortment of
scrollable widgets.
@ref{10e,,tkinter.tix} also includes many more widgets that are generally useful in
a wide range of applications: @ref{31a6,,NoteBook}, @ref{31a7,,FileEntry},
@ref{31a8,,PanedWindow}, etc; there are more than 40 of them.

With all these new widgets, you can introduce new interaction techniques into
applications, creating more useful and more intuitive user interfaces. You can
design your application by choosing the most appropriate widgets to match the
special needs of your application and users.


@subsubheading 参见



@table @asis

@item Tix Homepage@footnote{http://tix.sourceforge.net/}

The home page for @code{Tix}.  This includes links to additional documentation
and downloads.

@item Tix Man Pages@footnote{http://tix.sourceforge.net/dist/current/man/}

On-line version of the man pages and reference material.

@item Tix Programming Guide@footnote{http://tix.sourceforge.net/dist/current/docs/tix-book/tix.book.html}

On-line version of the programmer's reference material.

@item Tix Development Applications@footnote{http://tix.sourceforge.net/Tixapps/src/Tide.html}

Tix applications for development of Tix and Tkinter programs. Tide applications
work under Tk or Tkinter, and include @code{TixInspect}, an inspector to
remotely modify and debug Tix/Tk/Tkinter applications.
@end table


@menu
* Using Tix:: 
* Tix Widgets:: 
* Tix Commands:: 

@end menu

@node Using Tix,Tix Widgets,,tkinter tix --- Extension widgets for Tk
@anchor{library/tkinter tix using-tix}@anchor{31a9}
@subsubsection Using Tix


@geindex Tk (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix Tk}@anchor{31aa}
@deffn {类} tkinter.tix.Tk (screenName=None, baseName=None, className='Tix')

Toplevel widget of Tix which represents mostly the main window of an
application. It has an associated Tcl interpreter.

Classes in the @ref{10e,,tkinter.tix} module subclasses the classes in the
@ref{10c,,tkinter}. The former imports the latter, so to use @ref{10e,,tkinter.tix}
with Tkinter, all you need to do is to import one module. In general, you
can just import @ref{10e,,tkinter.tix}, and replace the toplevel call to
@ref{3114,,tkinter.Tk} with @code{tix.Tk}:

@example
from tkinter import tix
from tkinter.constants import *
root = tix.Tk()
@end example
@end deffn

To use @ref{10e,,tkinter.tix}, you must have the Tix widgets installed, usually
alongside your installation of the Tk widgets. To test your installation, try
the following:

@example
from tkinter import tix
root = tix.Tk()
root.tk.eval('package require Tix')
@end example

@node Tix Widgets,Tix Commands,Using Tix,tkinter tix --- Extension widgets for Tk
@anchor{library/tkinter tix tix-widgets}@anchor{31ab}
@subsubsection Tix Widgets


Tix@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/TixIntro.htm}
introduces over 40 widget classes to the @ref{10c,,tkinter} repertoire.

@menu
* Basic Widgets:: 
* File Selectors:: 
* Hierarchical ListBox:: 
* Tabular ListBox:: 
* Manager Widgets:: 
* Image Types:: 
* Miscellaneous Widgets:: 
* Form Geometry Manager:: 

@end menu

@node Basic Widgets,File Selectors,,Tix Widgets
@anchor{library/tkinter tix basic-widgets}@anchor{31ac}
@subsubsection Basic Widgets


@geindex Balloon (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix Balloon}@anchor{31ad}
@deffn {类} tkinter.tix.Balloon

A Balloon@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixBalloon.htm} that
pops up over a widget to provide help.  When the user moves the cursor inside a
widget to which a Balloon widget has been bound, a small pop-up window with a
descriptive message will be shown on the screen.
@end deffn

@c Python Demo of:

@c \ulink{Balloon}{http://tix.sourceforge.net/dist/current/demos/samples/Balloon.tcl}

@geindex ButtonBox (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix ButtonBox}@anchor{31ae}
@deffn {类} tkinter.tix.ButtonBox

The ButtonBox@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixButtonBox.htm}
widget creates a box of buttons, such as is commonly used for @code{Ok Cancel}.
@end deffn

@c Python Demo of:

@c \ulink{ButtonBox}{http://tix.sourceforge.net/dist/current/demos/samples/BtnBox.tcl}

@geindex ComboBox (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix ComboBox}@anchor{31a4}
@deffn {类} tkinter.tix.ComboBox

The ComboBox@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixComboBox.htm}
widget is similar to the combo box control in MS Windows. The user can select a
choice by either typing in the entry subwidget or selecting from the listbox
subwidget.
@end deffn

@c Python Demo of:

@c \ulink{ComboBox}{http://tix.sourceforge.net/dist/current/demos/samples/ComboBox.tcl}

@geindex Control (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix Control}@anchor{31a5}
@deffn {类} tkinter.tix.Control

The Control@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixControl.htm}
widget is also known as the @code{SpinBox} widget. The user can adjust the
value by pressing the two arrow buttons or by entering the value directly into
the entry. The new value will be checked against the user-defined upper and
lower limits.
@end deffn

@c Python Demo of:

@c \ulink{Control}{http://tix.sourceforge.net/dist/current/demos/samples/Control.tcl}

@geindex LabelEntry (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix LabelEntry}@anchor{31af}
@deffn {类} tkinter.tix.LabelEntry

The LabelEntry@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixLabelEntry.htm}
widget packages an entry widget and a label into one mega widget. It can
be used to simplify the creation of "entry-form" type of interface.
@end deffn

@c Python Demo of:

@c \ulink{LabelEntry}{http://tix.sourceforge.net/dist/current/demos/samples/LabEntry.tcl}

@geindex LabelFrame (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix LabelFrame}@anchor{31b0}
@deffn {类} tkinter.tix.LabelFrame

The LabelFrame@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixLabelFrame.htm}
widget packages a frame widget and a label into one mega widget.  To create
widgets inside a LabelFrame widget, one creates the new widgets relative to the
@code{frame} subwidget and manage them inside the @code{frame} subwidget.
@end deffn

@c Python Demo of:

@c \ulink{LabelFrame}{http://tix.sourceforge.net/dist/current/demos/samples/LabFrame.tcl}

@geindex Meter (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix Meter}@anchor{31b1}
@deffn {类} tkinter.tix.Meter

The Meter@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixMeter.htm} widget
can be used to show the progress of a background job which may take a long time
to execute.
@end deffn

@c Python Demo of:

@c \ulink{Meter}{http://tix.sourceforge.net/dist/current/demos/samples/Meter.tcl}

@geindex OptionMenu (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix OptionMenu}@anchor{31b2}
@deffn {类} tkinter.tix.OptionMenu

The OptionMenu@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixOptionMenu.htm}
creates a menu button of options.
@end deffn

@c Python Demo of:

@c \ulink{OptionMenu}{http://tix.sourceforge.net/dist/current/demos/samples/OptMenu.tcl}

@geindex PopupMenu (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix PopupMenu}@anchor{31b3}
@deffn {类} tkinter.tix.PopupMenu

The PopupMenu@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixPopupMenu.htm}
widget can be used as a replacement of the @code{tk_popup} command. The advantage
of the @code{Tix} @ref{31b3,,PopupMenu} widget is it requires less application code
to manipulate.
@end deffn

@c Python Demo of:

@c \ulink{PopupMenu}{http://tix.sourceforge.net/dist/current/demos/samples/PopMenu.tcl}

@geindex Select (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix Select}@anchor{31b4}
@deffn {类} tkinter.tix.Select

The Select@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixSelect.htm} widget
is a container of button subwidgets. It can be used to provide radio-box or
check-box style of selection options for the user.
@end deffn

@c Python Demo of:

@c \ulink{Select}{http://tix.sourceforge.net/dist/current/demos/samples/Select.tcl}

@geindex StdButtonBox (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix StdButtonBox}@anchor{31b5}
@deffn {类} tkinter.tix.StdButtonBox

The StdButtonBox@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixStdButtonBox.htm}
widget is a group of standard buttons for Motif-like dialog boxes.
@end deffn

@c Python Demo of:

@c \ulink{StdButtonBox}{http://tix.sourceforge.net/dist/current/demos/samples/StdBBox.tcl}

@node File Selectors,Hierarchical ListBox,Basic Widgets,Tix Widgets
@anchor{library/tkinter tix file-selectors}@anchor{31b6}
@subsubsection File Selectors


@geindex DirList (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix DirList}@anchor{31b7}
@deffn {类} tkinter.tix.DirList

The DirList@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixDirList.htm}
widget displays a list view of a directory, its previous directories and its
sub-directories. The user can choose one of the directories displayed in the
list or change to another directory.
@end deffn

@c Python Demo of:

@c \ulink{DirList}{http://tix.sourceforge.net/dist/current/demos/samples/DirList.tcl}

@geindex DirTree (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix DirTree}@anchor{31b8}
@deffn {类} tkinter.tix.DirTree

The DirTree@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixDirTree.htm}
widget displays a tree view of a directory, its previous directories and its
sub-directories. The user can choose one of the directories displayed in the
list or change to another directory.
@end deffn

@c Python Demo of:

@c \ulink{DirTree}{http://tix.sourceforge.net/dist/current/demos/samples/DirTree.tcl}

@geindex DirSelectDialog (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix DirSelectDialog}@anchor{31b9}
@deffn {类} tkinter.tix.DirSelectDialog

The DirSelectDialog@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixDirSelectDialog.htm}
widget presents the directories in the file system in a dialog window.  The user
can use this dialog window to navigate through the file system to select the
desired directory.
@end deffn

@c Python Demo of:

@c \ulink{DirSelectDialog}{http://tix.sourceforge.net/dist/current/demos/samples/DirDlg.tcl}

@geindex DirSelectBox (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix DirSelectBox}@anchor{31ba}
@deffn {类} tkinter.tix.DirSelectBox

The @ref{31ba,,DirSelectBox} is similar to the standard Motif(TM)
directory-selection box. It is generally used for the user to choose a
directory.  DirSelectBox stores the directories mostly recently selected into
a ComboBox widget so that they can be quickly selected again.
@end deffn

@geindex ExFileSelectBox (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix ExFileSelectBox}@anchor{31bb}
@deffn {类} tkinter.tix.ExFileSelectBox

The ExFileSelectBox@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixExFileSelectBox.htm}
widget is usually embedded in a tixExFileSelectDialog widget. It provides a
convenient method for the user to select files. The style of the
@ref{31bb,,ExFileSelectBox} widget is very similar to the standard file dialog on
MS Windows 3.1.
@end deffn

@c Python Demo of:

@c \ulink{ExFileSelectDialog}{http://tix.sourceforge.net/dist/current/demos/samples/EFileDlg.tcl}

@geindex FileSelectBox (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix FileSelectBox}@anchor{31bc}
@deffn {类} tkinter.tix.FileSelectBox

The FileSelectBox@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixFileSelectBox.htm}
is similar to the standard Motif(TM) file-selection box. It is generally used
for the user to choose a file. FileSelectBox stores the files mostly recently
selected into a @ref{31a4,,ComboBox} widget so that they can be quickly selected
again.
@end deffn

@c Python Demo of:

@c \ulink{FileSelectDialog}{http://tix.sourceforge.net/dist/current/demos/samples/FileDlg.tcl}

@geindex FileEntry (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix FileEntry}@anchor{31a7}
@deffn {类} tkinter.tix.FileEntry

The FileEntry@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixFileEntry.htm}
widget can be used to input a filename. The user can type in the filename
manually. Alternatively, the user can press the button widget that sits next to
the entry, which will bring up a file selection dialog.
@end deffn

@c Python Demo of:

@c \ulink{FileEntry}{http://tix.sourceforge.net/dist/current/demos/samples/FileEnt.tcl}

@node Hierarchical ListBox,Tabular ListBox,File Selectors,Tix Widgets
@anchor{library/tkinter tix hierarchical-listbox}@anchor{31bd}
@subsubsection Hierarchical ListBox


@geindex HList (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix HList}@anchor{31a3}
@deffn {类} tkinter.tix.HList

The HList@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixHList.htm} widget
can be used to display any data that have a hierarchical structure, for example,
file system directory trees. The list entries are indented and connected by
branch lines according to their places in the hierarchy.
@end deffn

@c Python Demo of:

@c \ulink{HList}{http://tix.sourceforge.net/dist/current/demos/samples/HList1.tcl}

@geindex CheckList (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix CheckList}@anchor{31be}
@deffn {类} tkinter.tix.CheckList

The CheckList@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixCheckList.htm}
widget displays a list of items to be selected by the user. CheckList acts
similarly to the Tk checkbutton or radiobutton widgets, except it is capable of
handling many more items than checkbuttons or radiobuttons.
@end deffn

@c Python Demo of:

@c \ulink{ CheckList}{http://tix.sourceforge.net/dist/current/demos/samples/ChkList.tcl}

@c Python Demo of:

@c \ulink{ScrolledHList (1)}{http://tix.sourceforge.net/dist/current/demos/samples/SHList.tcl}

@c Python Demo of:

@c \ulink{ScrolledHList (2)}{http://tix.sourceforge.net/dist/current/demos/samples/SHList2.tcl}

@geindex Tree (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix Tree}@anchor{31bf}
@deffn {类} tkinter.tix.Tree

The Tree@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixTree.htm} widget
can be used to display hierarchical data in a tree form. The user can adjust the
view of the tree by opening or closing parts of the tree.
@end deffn

@c Python Demo of:

@c \ulink{Tree}{http://tix.sourceforge.net/dist/current/demos/samples/Tree.tcl}

@c Python Demo of:

@c \ulink{Tree (Dynamic)}{http://tix.sourceforge.net/dist/current/demos/samples/DynTree.tcl}

@node Tabular ListBox,Manager Widgets,Hierarchical ListBox,Tix Widgets
@anchor{library/tkinter tix tabular-listbox}@anchor{31c0}
@subsubsection Tabular ListBox


@geindex TList (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix TList}@anchor{31c1}
@deffn {类} tkinter.tix.TList

The TList@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixTList.htm} widget
can be used to display data in a tabular format. The list entries of a
@ref{31c1,,TList} widget are similar to the entries in the Tk listbox widget.  The
main differences are (1) the @ref{31c1,,TList} widget can display the list entries
in a two dimensional format and (2) you can use graphical images as well as
multiple colors and fonts for the list entries.
@end deffn

@c Python Demo of:

@c \ulink{ScrolledTList (1)}{http://tix.sourceforge.net/dist/current/demos/samples/STList1.tcl}

@c Python Demo of:

@c \ulink{ScrolledTList (2)}{http://tix.sourceforge.net/dist/current/demos/samples/STList2.tcl}

@c Grid has yet to be added to Python

@c \subsubsection{Grid Widget}

@c Python Demo of:

@c \ulink{Simple Grid}{http://tix.sourceforge.net/dist/current/demos/samples/SGrid0.tcl}

@c Python Demo of:

@c \ulink{ScrolledGrid}{http://tix.sourceforge.net/dist/current/demos/samples/SGrid1.tcl}

@c Python Demo of:

@c \ulink{Editable Grid}{http://tix.sourceforge.net/dist/current/demos/samples/EditGrid.tcl}

@node Manager Widgets,Image Types,Tabular ListBox,Tix Widgets
@anchor{library/tkinter tix manager-widgets}@anchor{31c2}
@subsubsection Manager Widgets


@geindex PanedWindow (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix PanedWindow}@anchor{31a8}
@deffn {类} tkinter.tix.PanedWindow

The PanedWindow@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixPanedWindow.htm}
widget allows the user to interactively manipulate the sizes of several panes.
The panes can be arranged either vertically or horizontally.  The user changes
the sizes of the panes by dragging the resize handle between two panes.
@end deffn

@c Python Demo of:

@c \ulink{PanedWindow}{http://tix.sourceforge.net/dist/current/demos/samples/PanedWin.tcl}

@geindex ListNoteBook (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix ListNoteBook}@anchor{31c3}
@deffn {类} tkinter.tix.ListNoteBook

The ListNoteBook@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixListNoteBook.htm}
widget is very similar to the @code{TixNoteBook} widget: it can be used to
display many windows in a limited space using a notebook metaphor. The notebook
is divided into a stack of pages (windows). At one time only one of these pages
can be shown. The user can navigate through these pages by choosing the name of
the desired page in the @code{hlist} subwidget.
@end deffn

@c Python Demo of:

@c \ulink{ListNoteBook}{http://tix.sourceforge.net/dist/current/demos/samples/ListNBK.tcl}

@geindex NoteBook (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix NoteBook}@anchor{31a6}
@deffn {类} tkinter.tix.NoteBook

The NoteBook@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixNoteBook.htm}
widget can be used to display many windows in a limited space using a notebook
metaphor. The notebook is divided into a stack of pages. At one time only one of
these pages can be shown. The user can navigate through these pages by choosing
the visual "tabs" at the top of the NoteBook widget.
@end deffn

@c Python Demo of:

@c \ulink{NoteBook}{http://tix.sourceforge.net/dist/current/demos/samples/NoteBook.tcl}

@c \subsubsection{Scrolled Widgets}

@c Python Demo of:

@c \ulink{ScrolledListBox}{http://tix.sourceforge.net/dist/current/demos/samples/SListBox.tcl}

@c Python Demo of:

@c \ulink{ScrolledText}{http://tix.sourceforge.net/dist/current/demos/samples/SText.tcl}

@c Python Demo of:

@c \ulink{ScrolledWindow}{http://tix.sourceforge.net/dist/current/demos/samples/SWindow.tcl}

@c Python Demo of:

@c \ulink{Canvas Object View}{http://tix.sourceforge.net/dist/current/demos/samples/CObjView.tcl}

@node Image Types,Miscellaneous Widgets,Manager Widgets,Tix Widgets
@anchor{library/tkinter tix image-types}@anchor{31c4}
@subsubsection Image Types


The @ref{10e,,tkinter.tix} module adds:


@itemize *

@item 
pixmap@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/pixmap.htm}
capabilities to all @ref{10e,,tkinter.tix} and @ref{10c,,tkinter} widgets to create
color images from XPM files.

@c Python Demo of:

@c \ulink{XPM Image In Button}{http://tix.sourceforge.net/dist/current/demos/samples/Xpm.tcl}

@c Python Demo of:

@c \ulink{XPM Image In Menu}{http://tix.sourceforge.net/dist/current/demos/samples/Xpm1.tcl}

@item 
Compound@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/compound.htm} image
types can be used to create images that consists of multiple horizontal lines;
each line is composed of a series of items (texts, bitmaps, images or spaces)
arranged from left to right. For example, a compound image can be used to
display a bitmap and a text string simultaneously in a Tk @code{Button}
widget.

@c Python Demo of:

@c \ulink{Compound Image In Buttons}{http://tix.sourceforge.net/dist/current/demos/samples/CmpImg.tcl}

@c Python Demo of:

@c \ulink{Compound Image In NoteBook}{http://tix.sourceforge.net/dist/current/demos/samples/CmpImg2.tcl}

@c Python Demo of:

@c \ulink{Compound Image Notebook Color Tabs}{http://tix.sourceforge.net/dist/current/demos/samples/CmpImg4.tcl}

@c Python Demo of:

@c \ulink{Compound Image Icons}{http://tix.sourceforge.net/dist/current/demos/samples/CmpImg3.tcl}
@end itemize

@node Miscellaneous Widgets,Form Geometry Manager,Image Types,Tix Widgets
@anchor{library/tkinter tix miscellaneous-widgets}@anchor{31c5}
@subsubsection Miscellaneous Widgets


@geindex InputOnly (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix InputOnly}@anchor{31c6}
@deffn {类} tkinter.tix.InputOnly

The InputOnly@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixInputOnly.htm}
widgets are to accept inputs from the user, which can be done with the @code{bind}
command (Unix only).
@end deffn

@node Form Geometry Manager,,Miscellaneous Widgets,Tix Widgets
@anchor{library/tkinter tix form-geometry-manager}@anchor{31c7}
@subsubsection Form Geometry Manager


In addition, @ref{10e,,tkinter.tix} augments @ref{10c,,tkinter} by providing:

@geindex Form (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix Form}@anchor{31c8}
@deffn {类} tkinter.tix.Form

The Form@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tixForm.htm} geometry
manager based on attachment rules for all Tk widgets.
@end deffn

@node Tix Commands,,Tix Widgets,tkinter tix --- Extension widgets for Tk
@anchor{library/tkinter tix tix-commands}@anchor{31c9}
@subsubsection Tix Commands


@geindex tixCommand (tkinter.tix 中的类)
@anchor{library/tkinter tix tkinter tix tixCommand}@anchor{31ca}
@deffn {类} tkinter.tix.tixCommand

The tix commands@footnote{http://tix.sourceforge.net/dist/current/man/html/TixCmd/tix.htm} provide
access to miscellaneous elements of @code{Tix}'s internal state and the
@code{Tix} application context.  Most of the information manipulated by these
methods pertains to the application as a whole, or to a screen or display,
rather than to a particular window.

To view the current settings, the common usage is:

@example
from tkinter import tix
root = tix.Tk()
print(root.tix_configure())
@end example
@end deffn

@geindex tix_configure() (tkinter.tix.tixCommand 方法)
@anchor{library/tkinter tix tkinter tix tixCommand tix_configure}@anchor{31cb}
@deffn {方法} tixCommand.tix_configure (cnf=None, **kw)

Query or modify the configuration options of the Tix application context. If no
option is specified, returns a dictionary all of the available options.  If
option is specified with no value, then the method returns a list describing the
one named option (this list will be identical to the corresponding sublist of
the value returned if no option is specified).  If one or more option-value
pairs are specified, then the method modifies the given option(s) to have the
given value(s); in this case the method returns an empty string. Option may be
any of the configuration options.
@end deffn

@geindex tix_cget() (tkinter.tix.tixCommand 方法)
@anchor{library/tkinter tix tkinter tix tixCommand tix_cget}@anchor{31cc}
@deffn {方法} tixCommand.tix_cget (option)

Returns the current value of the configuration option given by @emph{option}. Option
may be any of the configuration options.
@end deffn

@geindex tix_getbitmap() (tkinter.tix.tixCommand 方法)
@anchor{library/tkinter tix tkinter tix tixCommand tix_getbitmap}@anchor{31cd}
@deffn {方法} tixCommand.tix_getbitmap (name)

Locates a bitmap file of the name @code{name.xpm} or @code{name} in one of the bitmap
directories (see the @ref{31ce,,tix_addbitmapdir()} method).  By using
@ref{31cd,,tix_getbitmap()}, you can avoid hard coding the pathnames of the bitmap
files in your application. When successful, it returns the complete pathname of
the bitmap file, prefixed with the character @code{@@}.  The returned value can be
used to configure the @code{bitmap} option of the Tk and Tix widgets.
@end deffn

@geindex tix_addbitmapdir() (tkinter.tix.tixCommand 方法)
@anchor{library/tkinter tix tkinter tix tixCommand tix_addbitmapdir}@anchor{31ce}
@deffn {方法} tixCommand.tix_addbitmapdir (directory)

Tix maintains a list of directories under which the @ref{31cf,,tix_getimage()} and
@ref{31cd,,tix_getbitmap()} methods will search for image files.  The standard bitmap
directory is @code{$TIX_LIBRARY/bitmaps}. The @ref{31ce,,tix_addbitmapdir()} method
adds @emph{directory} into this list. By using this method, the image files of an
applications can also be located using the @ref{31cf,,tix_getimage()} or
@ref{31cd,,tix_getbitmap()} method.
@end deffn

@geindex tix_filedialog() (tkinter.tix.tixCommand 方法)
@anchor{library/tkinter tix tkinter tix tixCommand tix_filedialog}@anchor{31d0}
@deffn {方法} tixCommand.tix_filedialog ([dlgclass])

Returns the file selection dialog that may be shared among different calls from
this application.  This method will create a file selection dialog widget when
it is called the first time. This dialog will be returned by all subsequent
calls to @ref{31d0,,tix_filedialog()}.  An optional dlgclass parameter can be passed
as a string to specified what type of file selection dialog widget is desired.
Possible options are @code{tix}, @code{FileSelectDialog} or @code{tixExFileSelectDialog}.
@end deffn

@geindex tix_getimage() (tkinter.tix.tixCommand 方法)
@anchor{library/tkinter tix tkinter tix tixCommand tix_getimage}@anchor{31cf}
@deffn {方法} tixCommand.tix_getimage (self, name)

Locates an image file of the name @code{name.xpm}, @code{name.xbm} or
@code{name.ppm} in one of the bitmap directories (see the
@ref{31ce,,tix_addbitmapdir()} method above). If more than one file with the same name
(but different extensions) exist, then the image type is chosen according to the
depth of the X display: xbm images are chosen on monochrome displays and color
images are chosen on color displays. By using @ref{31cf,,tix_getimage()}, you can
avoid hard coding the pathnames of the image files in your application. When
successful, this method returns the name of the newly created image, which can
be used to configure the @code{image} option of the Tk and Tix widgets.
@end deffn

@geindex tix_option_get() (tkinter.tix.tixCommand 方法)
@anchor{library/tkinter tix tkinter tix tixCommand tix_option_get}@anchor{31d1}
@deffn {方法} tixCommand.tix_option_get (name)

Gets the options maintained by the Tix scheme mechanism.
@end deffn

@geindex tix_resetoptions() (tkinter.tix.tixCommand 方法)
@anchor{library/tkinter tix tkinter tix tixCommand tix_resetoptions}@anchor{31d2}
@deffn {方法} tixCommand.tix_resetoptions (newScheme, newFontSet[, newScmPrio])

Resets the scheme and fontset of the Tix application to @emph{newScheme} and
@emph{newFontSet}, respectively.  This affects only those widgets created after this
call.  Therefore, it is best to call the resetoptions method before the creation
of any widgets in a Tix application.

The optional parameter @emph{newScmPrio} can be given to reset the priority level of
the Tk options set by the Tix schemes.

Because of the way Tk handles the X option database, after Tix has been has
imported and inited, it is not possible to reset the color schemes and font sets
using the @code{tix_config()} method. Instead, the @ref{31d2,,tix_resetoptions()}
method must be used.
@end deffn

@node tkinter scrolledtext --- 滚动文字控件,IDLE<48>,tkinter tix --- Extension widgets for Tk,Tk图形用户界面 GUI
@anchor{library/tkinter scrolledtext doc}@anchor{31d3}@anchor{library/tkinter scrolledtext module-tkinter scrolledtext}@anchor{10d}@anchor{library/tkinter scrolledtext tkinter-scrolledtext-scrolled-text-widget}@anchor{31d4}
@subsection @code{tkinter.scrolledtext} --- 滚动文字控件


@geindex tkinter.scrolledtext (模块)

@strong{源代码：} Lib/tkinter/scrolledtext.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tkinter/scrolledtext.py}


__________________________________________________________________


@ref{10d,,tkinter.scrolledtext} 模块提供一个同名的类，实现了一个带有垂直滚动条的文字控件。使用 @code{ScrolledText}  类会比直接配置一个文本控件和滚动条简单。它的构造函数与 @code{tkinter.Text} 类相同。

文本控件与滚动条打包在一个 @code{Frame} 中， @code{Grid} 方法和 @code{Pack} 方法的布局管理器从 @code{Frame} 对象中获得。这允许 @code{ScrolledText} 控件可以直接用于实现大多数正常的布局管理行为。

如果需要更具体的控制，可以使用以下属性：

@geindex frame (tkinter.scrolledtext.ScrolledText 属性)
@anchor{library/tkinter scrolledtext tkinter scrolledtext ScrolledText frame}@anchor{31d5}
@deffn {属性} ScrolledText.frame

围绕文本和滚动条控件的框架。
@end deffn

@geindex vbar (tkinter.scrolledtext.ScrolledText 属性)
@anchor{library/tkinter scrolledtext tkinter scrolledtext ScrolledText vbar}@anchor{31d6}
@deffn {属性} ScrolledText.vbar

滚动条控件。
@end deffn

@node IDLE<48>,其他图形用户界面（GUI）包,tkinter scrolledtext --- 滚动文字控件,Tk图形用户界面 GUI
@anchor{library/idle doc}@anchor{31d7}@anchor{library/idle id1}@anchor{31d8}@anchor{library/idle idle}@anchor{944}
@subsection IDLE


@strong{源代码：} Lib/idlelib/@footnote{https://github.com/python/cpython/tree/3.8/Lib/idlelib/}

@geindex IDLE
@geindex Python Editor
@geindex Integrated Development Environment


__________________________________________________________________


IDLE 是 Python 所内置的开发与学习环境。

IDLE 具有以下特性：


@itemize *

@item 
编码于 100% 纯正的 Python，使用名为 @ref{10c,,tkinter} 的图形用户界面工具

@item 
跨平台：在 Windows、Unix 和 macOS 上工作近似。

@item 
提供输入输出高亮和错误信息的 Python 命令行窗口 （交互解释器）

@item 
提供多次撤销操作、Python 语法高亮、智能缩进、函数调用提示、自动补全等功能的多窗口文本编辑器

@item 
在多个窗口中检索，在编辑器中替换文本，以及在多个文件中检索（通过 grep）

@item 
提供持久保存的断点调试、单步调试、查看本地和全局命名空间功能的调试器

@item 
配置、浏览以及其它对话框
@end itemize

@menu
* 目录:: 
* 编辑和导航:: 
* 启动和代码执行:: 
* 帮助和偏好:: 

@end menu

@node 目录,编辑和导航,,IDLE<48>
@anchor{library/idle menus}@anchor{31d9}
@subsubsection 目录


IDEL 具有两个主要窗口类型，分别是命令行窗口和编辑器窗口。用户可以同时打开多个编辑器窗口。对于 Windows 和 Linux 平台，都有各自的主菜单。如下记录的每个菜单标识着与之关联的窗口类型。

导出窗口，例如使用 编辑=>在文件中查找 是编辑器窗口的的一个子类型。它们目前有着相同的主菜单，但是默认标题和上下文菜单不同。

在macOS上，只有一个应用程序菜单。它根据当前选择的窗口动态变化。它具有一个IDLE菜单，并且下面描述的某些条目已移动到符合Apple准则的位置。

@menu
* 文件菜单 （命令行和编辑器）:: 
* 编辑菜单（命令行和编辑器）:: 
* 格式菜单（仅 window 编辑器）:: 
* 运行菜单（仅 window 编辑器）:: 
* Shell 菜单（仅 window 编辑器）:: 
* 调试菜单（仅 window 编辑器）:: 
* 选项菜单（命令行和编辑器）:: 
* Window 菜单（命令行和编辑器）:: 
* 帮助菜单（命令行和编辑器）:: 
* 上下文菜单:: 

@end menu

@node 文件菜单 （命令行和编辑器）,编辑菜单（命令行和编辑器）,,目录
@anchor{library/idle file-menu-shell-and-editor}@anchor{31da}
@subsubsection 文件菜单 （命令行和编辑器）



@table @asis

@item 新建文件

创建一个文件编辑器窗口。

@item 打开...

使用打开窗口以打开一个已存在的文件。

@item 近期文件

打开一个近期文件列表，选取一个以打开它。

@item 打开模块...

打开一个已存在的模块 （搜索 sys.path）
@end table

@geindex Class browser
@geindex Path browser


@table @asis

@item 类浏览器

于当前所编辑的文件中使用树形结构展示函数、类以及方法。在命令行中，首先打开一个模块。

@item 路径浏览

在树状结构中展示 sys.path 目录、模块、函数、类和方法。

@item 保存

如果文件已经存在，则将当前窗口保存至对应的文件。自打开或上次保存之后经过修改的文件的窗口标题栏首尾将出现星号 * 。如果没有对应的文件，则使用“另存为”代替。

@item 保存为...

使用“保存为”对话框保存当前窗口。被保存的文件将作为当前窗口新的对应文件。

@item 另存为副本...

保存当前窗口至另一个文件，而不修改当前对应文件。

@item 打印窗口

通过默认打印机打印当前窗口。

@item 关闭

关闭当前窗口（如果未保存则询问）。

@item 退出

关闭所有窗口并退出 IDLE（如果未保存则询问）
@end table

@node 编辑菜单（命令行和编辑器）,格式菜单（仅 window 编辑器）,文件菜单 （命令行和编辑器）,目录
@anchor{library/idle edit-menu-shell-and-editor}@anchor{31db}
@subsubsection 编辑菜单（命令行和编辑器）



@table @asis

@item 撤销操作

撤销当前窗口的最近一次操作。最高可以撤回 1000 条操作记录。

@item 重做

重做当前窗口最近一次所撤销的操作。

@item 剪切

复制选区至系统剪贴板，然后删除选区。

@item 复制

复制选区至系统剪贴板。

@item 粘贴

插入系统剪贴板的内容至当前窗口。
@end table

剪贴板功能也可用于上下文目录。


@table @asis

@item 全选

选择当前窗口的全部内容。

@item 查找...

打开一个提供多选项的查找窗口。

@item 再次查找

重复上次搜索，如果结果存在。

@item 查找选区

查找当前选中的字符串，如果存在

@item 在文件中查找...

打开文件查找对话框。将结果输出至新的输出窗口。

@item 替换...

打开 查找并替换 对话框。

@item 前往行

Move the cursor to the beginning of the line requested and make that
line visible.  A request past the end of the file goes to the end.
Clear any selection and update the line and column status.

@item 提示完成

Open a scrollable list allowing selection of existing names. See
@ref{31dc,,Completions} in the Editing and navigation section below.

@item 展开文本

展开键入的前缀以匹配同一窗口中的完整单词；重复以获得不同的扩展。

@item 显示调用贴士

在函数的右括号后，打开一个带有函数参数提示的小窗口。请参阅下面的“编辑和导航”部分中的 @ref{31dd,,Calltips} 。

@item 显示周围括号

突出显示周围的括号。
@end table

@node 格式菜单（仅 window 编辑器）,运行菜单（仅 window 编辑器）,编辑菜单（命令行和编辑器）,目录
@anchor{library/idle format-menu}@anchor{31de}@anchor{library/idle format-menu-editor-window-only}@anchor{31df}
@subsubsection 格式菜单（仅 window 编辑器）



@table @asis

@item 增加缩进

将选定的行右移缩进宽度（默认为4个空格）。

@item 减少缩进

将选定的行向左移动缩进宽度（默认为4个空格）。

@item 注释

在所选行的前面插入 ##。

@item 取消注释

从所选行中删除开头的 ＃ 或 ##。

@item 制表符化

将 @emph{前导} 空格变成制表符。 （注意：我们建议使用4个空格来缩进Python代码。）

@item 取消制表符化

将 @emph{所有} 制表符转换为正确的空格数。

@item 缩进方式切换

打开一个对话框，以在制表符和空格之间切换。

@item 缩进宽度调整

打开一个对话框以更改缩进宽度。 Python社区接受的默认值为4个空格。

@item 格式段落

在注释块或多行字符串或字符串中的选定行中，重新格式化当前以空行分隔的段落。段落中的所有行的格式都将少于N列，其中N默认为72。

@item 删除尾随空格

通过将 str.rstrip 应用于每行（包括多行字符串中的行），删除行尾非空白字符之后的尾随空格和其他空白字符。除Shell窗口外，在文件末尾删除多余的换行符。
@end table

@geindex Run script

@node 运行菜单（仅 window 编辑器）,Shell 菜单（仅 window 编辑器）,格式菜单（仅 window 编辑器）,目录
@anchor{library/idle run-menu-editor-window-only}@anchor{31e0}
@subsubsection 运行菜单（仅 window 编辑器）

@anchor{library/idle run-module}@anchor{31e1}

@table @asis

@item 运行模块

执行 @ref{31e2,,检查模块} 。如果没有错误，重新启动 shell 以清理环境，然后执行模块。输出显示在 shell 窗口中。请注意，输出需要使用 “打印” 或 “写入”。执行完成后，Shell 将保留焦点并显示提示。此时，可以交互地探索执行的结果。这类似于在命令行执行带有 @code{python -i file} 的文件。
@end table
@anchor{library/idle run-custom}@anchor{31e3}

@table @asis

@item 运行... 定制

与 @ref{31e1,,运行模块} 相同，但使用自定义设置运行该模块。@emph{命令行参数} 扩展 @ref{bf4,,sys.argv} ，就像在命令行上传递一样。该模块可以在命令行管理程序中运行，而无需重新启动。
@end table
@anchor{library/idle check-module}@anchor{31e2}

@table @asis

@item 检查模块

检查 “编辑器” 窗口中当前打开的模块的语法。如果尚未保存该模块，则 IDLE会提示用户保存或自动保存，如在 “空闲设置” 对话框的 “常规” 选项卡中所选择的那样。如果存在语法错误，则会在 “编辑器” 窗口中指示大概位置。
@end table
@anchor{library/idle python-shell}@anchor{31e4}

@table @asis

@item Python Shell

打开或唤醒Python Shell窗口。
@end table

@node Shell 菜单（仅 window 编辑器）,调试菜单（仅 window 编辑器）,运行菜单（仅 window 编辑器）,目录
@anchor{library/idle shell-menu-shell-window-only}@anchor{31e5}
@subsubsection Shell 菜单（仅 window 编辑器）



@table @asis

@item 查看最近重启

将Shell窗口滚动到上一次Shell重启。

@item 重启Shell

重新启动shell 以清理环境。

@item 上一条历史记录

循环浏览历史记录中与当前条目匹配的早期命令。

@item 下一条历史记录

循环浏览历史记录中与当前条目匹配的后续命令。

@item 中断执行

停止正在运行的程序。
@end table

@node 调试菜单（仅 window 编辑器）,选项菜单（命令行和编辑器）,Shell 菜单（仅 window 编辑器）,目录
@anchor{library/idle debug-menu-shell-window-only}@anchor{31e6}
@subsubsection 调试菜单（仅 window 编辑器）



@table @asis

@item 跳转到文件/行

Look on the current line. with the cursor, and the line above for a filename
and line number.  If found, open the file if not already open, and show the
line.  Use this to view source lines referenced in an exception traceback
and lines found by Find in Files. Also available in the context menu of
the Shell window and Output windows.
@end table

@geindex debugger
@geindex stack viewer


@table @asis

@item 调试器（切换）

激活后，在Shell中输入的代码或从编辑器中运行的代码将在调试器下运行。在编辑器中，可以使用上下文菜单设置断点。此功能不完整，具有实验性。

@item 堆栈查看器

在树状目录中显示最后一个异常的堆栈回溯，可以访问本地和全局。

@item 自动打开堆栈查看器

在未处理的异常上切换自动打开堆栈查看器。
@end table

@node 选项菜单（命令行和编辑器）,Window 菜单（命令行和编辑器）,调试菜单（仅 window 编辑器）,目录
@anchor{library/idle options-menu-shell-and-editor}@anchor{31e7}
@subsubsection 选项菜单（命令行和编辑器）



@table @asis

@item 配置 IDLE

打开配置对话框并更改以下各项的首选项：字体、缩进、键绑定、文本颜色主题、启动窗口和大小、其他帮助源和扩展名。在MacOS上，通过在应用程序菜单中选择首选项来打开配置对话框。有关详细信息，请参阅：帮助和首选项下的 @ref{31e8,,首选项设置}。
@end table

大多数配置选项适用于所有窗口或将来的所有窗口。以下选项仅适用于活动窗口。


@table @asis

@item 显示/隐藏代码上下文（仅 window 编辑器）

Open a pane at the top of the edit window which shows the block context
of the code which has scrolled above the top of the window.  See
@ref{31e9,,Code Context} in the Editing and Navigation section
below.

@item 显示/隐藏行号（仅 window 编辑器）

Open a column to the left of the edit window which shows the number
of each line of text.  The default is off, which may be changed in the
preferences (see @ref{31e8,,Setting preferences}).

@item 缩放/还原高度

Toggles the window between normal size and maximum height. The initial size
defaults to 40 lines by 80 chars unless changed on the General tab of the
Configure IDLE dialog.  The maximum height for a screen is determined by
momentarily maximizing a window the first time one is zoomed on the screen.
Changing screen settings may invalidate the saved height.  This toggle has
no effect when a window is maximized.
@end table

@node Window 菜单（命令行和编辑器）,帮助菜单（命令行和编辑器）,选项菜单（命令行和编辑器）,目录
@anchor{library/idle window-menu-shell-and-editor}@anchor{31ea}
@subsubsection Window 菜单（命令行和编辑器）


列出所有打开的窗口的名称；选择一个将其带到前台（必要时对其进行去符号化）。

@node 帮助菜单（命令行和编辑器）,上下文菜单,Window 菜单（命令行和编辑器）,目录
@anchor{library/idle help-menu-shell-and-editor}@anchor{31eb}
@subsubsection 帮助菜单（命令行和编辑器）



@table @asis

@item 关于 IDLE

显示版本，版权，许可证，荣誉等。

@item IDLE 帮助

显示此 IDLE 文档，详细介绍菜单选项，基本编辑和导航以及其他技巧。

@item Python 文档

访问本地Python文档（如果已安装），或启动Web浏览器并打开docs.python.org显示最新的Python文档。

@item 海龟演示

使用示例Python代码和turtle绘图运行turtledemo模块。
@end table

可以在“常规”选项卡下的“配置IDLE”对话框中添加其他帮助源。有关“帮助”菜单选项的更多信息，请参见下面的 @ref{31ec,,帮助源} 小节。

@geindex Cut
@geindex Copy
@geindex Paste
@geindex Set Breakpoint
@geindex Clear Breakpoint
@geindex breakpoints

@node 上下文菜单,,帮助菜单（命令行和编辑器）,目录
@anchor{library/idle context-menus}@anchor{31ed}
@subsubsection 上下文菜单


Open a context menu by right-clicking in a window (Control-click on macOS).
Context menus have the standard clipboard functions also on the Edit menu.


@table @asis

@item 剪切

复制选区至系统剪贴板，然后删除选区。

@item 复制

复制选区至系统剪贴板。

@item 粘贴

插入系统剪贴板的内容至当前窗口。
@end table

Editor windows also have breakpoint functions.  Lines with a breakpoint set are
specially marked.  Breakpoints only have an effect when running under the
debugger.  Breakpoints for a file are saved in the user's @code{.idlerc}
directory.


@table @asis

@item 设置断点

在当前行设置断点

@item 清除断点

清除当前行断点
@end table

shell 和输出窗口还具有以下内容。


@table @asis

@item 跳转到文件/行

与调试菜单相同。
@end table

The Shell window also has an output squeezing facility explained in the @emph{Python
Shell window} subsection below.


@table @asis

@item 压缩

If the cursor is over an output line, squeeze all the output between
the code above and the prompt below down to a 'Squeezed text' label.
@end table

@node 编辑和导航,启动和代码执行,目录,IDLE<48>
@anchor{library/idle editing-and-navigation}@anchor{31ee}@anchor{library/idle id2}@anchor{31ef}
@subsubsection 编辑和导航


@menu
* 编辑窗口:: 
* 按键绑定:: 
* 自动缩进:: 
* 完成:: 
* 提示:: 
* 代码上下文:: 
* Python Shell 窗口:: 
* 文本颜色:: 

@end menu

@node 编辑窗口,按键绑定,,编辑和导航
@anchor{library/idle editor-windows}@anchor{31f0}
@subsubsection 编辑窗口


IDLE may open editor windows when it starts, depending on settings
and how you start IDLE.  Thereafter, use the File menu.  There can be only
one open editor window for a given file.

The title bar contains the name of the file, the full path, and the version
of Python and IDLE running the window.  The status bar contains the line
number ('Ln') and column number ('Col').  Line numbers start with 1;
column numbers with 0.

IDLE assumes that files with a known .py* extension contain Python code
and that other files do not.  Run Python code with the Run menu.

@node 按键绑定,自动缩进,编辑窗口,编辑和导航
@anchor{library/idle key-bindings}@anchor{31f1}
@subsubsection 按键绑定


在本节中，'C' 是指 Windows 和 Unix 上的 @code{Control} 键，以及 macOS 上的 @code{Command} 键。


@itemize *

@item 
@code{Backspace} 向左删除; @code{Del} 向右删除

@item 
@code{C-Backspace} 向左删除单词; @code{C-Del} 向右删除单词

@item 
方向键和 @code{Page Up}/@code{Page Down} 移动

@item 
@code{C-LeftArrow} 和 @code{C-RightArrow} 按单词移动

@item 
@code{Home}/@code{End} 跳转到行首/尾

@item 
@code{C-Home}/@code{C-End} 跳转到文档首/尾

@item 
一些有用的Emacs绑定是从Tcl / Tk继承的：

@quotation


@itemize *

@item 
@code{C-a} 行首

@item 
@code{C-e} 行尾

@item 
@code{C-k} 删除行（但未将其放入剪贴板）

@item 
@code{C-l} center window around the insertion point

@item 
@code{C-b} go backward one character without deleting (usually you can
also use the cursor key for this)

@item 
@code{C-f} go forward one character without deleting (usually you can
also use the cursor key for this)

@item 
@code{C-p} go up one line (usually you can also use the cursor key for
this)

@item 
@code{C-d} 删除下一个字符
@end itemize
@end quotation
@end itemize

Standard keybindings (like @code{C-c} to copy and @code{C-v} to paste)
may work.  Keybindings are selected in the Configure IDLE dialog.

@node 自动缩进,完成,按键绑定,编辑和导航
@anchor{library/idle automatic-indentation}@anchor{31f2}
@subsubsection 自动缩进


After a block-opening statement, the next line is indented by 4 spaces (in the
Python Shell window by one tab).  After certain keywords (break, return etc.)
the next line is dedented.  In leading indentation, @code{Backspace} deletes up
to 4 spaces if they are there. @code{Tab} inserts spaces (in the Python
Shell window one tab), number depends on Indent width. Currently, tabs
are restricted to four spaces due to Tcl/Tk limitations.

See also the indent/dedent region commands on the
@ref{31de,,Format menu}.

@node 完成,提示,自动缩进,编辑和导航
@anchor{library/idle completions}@anchor{31dc}@anchor{library/idle id3}@anchor{31f3}
@subsubsection 完成


Completions are supplied, when requested and available, for module
names, attributes of classes or functions, or filenames.  Each request
method displays a completion box with existing names.  (See tab
completions below for an exception.) For any box, change the name
being completed and the item highlighted in the box by
typing and deleting characters; by hitting @code{Up}, @code{Down},
@code{PageUp}, @code{PageDown}, @code{Home}, and @code{End} keys;
and by a single click within the box.  Close the box with @code{Escape},
@code{Enter}, and double @code{Tab} keys or clicks outside the box.
A double click within the box selects and closes.

One way to open a box is to type a key character and wait for a
predefined interval.  This defaults to 2 seconds; customize it
in the settings dialog.  (To prevent auto popups, set the delay to a
large number of milliseconds, such as 100000000.) For imported module
names or class or function attributes, type '.'.
For filenames in the root directory, type @ref{1c0a,,os.sep} or
data:@cite{os.altsep} immediately after an opening quote.  (On Windows,
one can specify a drive first.)  Move into subdirectories by typing a
directory name and a separator.

Instead of waiting, or after a box is closed, open a completion box
immediately with Show Completions on the Edit menu.  The default hot
key is @code{C-space}.  If one types a prefix for the desired name
before opening the box, the first match or near miss is made visible.
The result is the same as if one enters a prefix
after the box is displayed.  Show Completions after a quote completes
filenames in the current directory instead of a root directory.

Hitting @code{Tab} after a prefix usually has the same effect as Show
Completions.  (With no prefix, it indents.)  However, if there is only
one match to the prefix, that match is immediately added to the editor
text without opening a box.

Invoking 'Show Completions', or hitting @code{Tab} after a prefix,
outside of a string and without a preceding '.' opens a box with
keywords, builtin names, and available module-level names.

When editing code in an editor (as oppose to Shell), increase the
available module-level names by running your code
and not restarting the Shell thereafter.  This is especially useful
after adding imports at the top of a file.  This also increases
possible attribute completions.

Completion boxes intially exclude names beginning with '_' or, for
modules, not included in '__all__'.  The hidden names can be accessed
by typing '_' after '.', either before or after the box is opened.

@node 提示,代码上下文,完成,编辑和导航
@anchor{library/idle calltips}@anchor{31dd}@anchor{library/idle id4}@anchor{31f4}
@subsubsection 提示


A calltip is shown when one types @code{(} after the name of an @emph{accessible}
function.  A name expression may include dots and subscripts.  A calltip
remains until it is clicked, the cursor is moved out of the argument area,
or @code{)} is typed.  When the cursor is in the argument part of a definition,
the menu or shortcut display a calltip.

A calltip consists of the function signature and the first line of the
docstring.  For builtins without an accessible signature, the calltip
consists of all lines up the fifth line or the first blank line.  These
details may change.

The set of @emph{accessible} functions depends on what modules have been imported
into the user process, including those imported by Idle itself,
and what definitions have been run, all since the last restart.

For example, restart the Shell and enter @code{itertools.count(}.  A calltip
appears because Idle imports itertools into the user process for its own use.
(This could change.)  Enter @code{turtle.write(} and nothing appears.  Idle does
not import turtle.  The menu or shortcut do nothing either.  Enter
@code{import turtle} and then @code{turtle.write(} will work.

In an editor, import statements have no effect until one runs the file.  One
might want to run a file after writing the import statements at the top,
or immediately run an existing file before editing.

@node 代码上下文,Python Shell 窗口,提示,编辑和导航
@anchor{library/idle code-context}@anchor{31e9}@anchor{library/idle id5}@anchor{31f5}
@subsubsection 代码上下文


Within an editor window containing Python code, code context can be toggled
in order to show or hide a pane at the top of the window.  When shown, this
pane freezes the opening lines for block code, such as those beginning with
@code{class}, @code{def}, or @code{if} keywords, that would have otherwise scrolled
out of view.  The size of the pane will be expanded and contracted as needed
to show the all current levels of context, up to the maximum number of
lines defined in the Configure IDLE dialog (which defaults to 15).  If there
are no current context lines and the feature is toggled on, a single blank
line will display.  Clicking on a line in the context pane will move that
line to the top of the editor.

The text and background colors for the context pane can be configured under
the Highlights tab in the Configure IDLE dialog.

@node Python Shell 窗口,文本颜色,代码上下文,编辑和导航
@anchor{library/idle python-shell-window}@anchor{31f6}
@subsubsection Python Shell 窗口


With IDLE's Shell, one enters, edits, and recalls complete statements.
Most consoles and terminals only work with a single physical line at a time.

When one pastes code into Shell, it is not compiled and possibly executed
until one hits @code{Return}.  One may edit pasted code first.
If one pastes more that one statement into Shell, the result will be a
@ref{452,,SyntaxError} when multiple statements are compiled as if they were one.

The editing features described in previous subsections work when entering
code interactively.  IDLE's Shell window also responds to the following keys.


@itemize *

@item 
@code{C-c} 中断执行命令

@item 
@code{C-d} sends end-of-file; closes window if typed at a @code{>>>} prompt

@item 
@code{Alt-/} (Expand word) is also useful to reduce typing

历史命令


@itemize *

@item 
@code{Alt-p} retrieves previous command matching what you have typed. On
macOS use @code{C-p}.

@item 
@code{Alt-n} retrieves next. On macOS use @code{C-n}.

@item 
@code{Return} while on any previous command retrieves that command
@end itemize
@end itemize

@node 文本颜色,,Python Shell 窗口,编辑和导航
@anchor{library/idle text-colors}@anchor{31f7}
@subsubsection 文本颜色


Idle defaults to black on white text, but colors text with special meanings.
For the shell, these are shell output, shell error, user output, and
user error.  For Python code, at the shell prompt or in an editor, these are
keywords, builtin class and function names, names following @code{class} and
@code{def}, strings, and comments. For any text window, these are the cursor (when
present), found text (when possible), and selected text.

Text coloring is done in the background, so uncolorized text is occasionally
visible.  To change the color scheme, use the Configure IDLE dialog
Highlighting tab.  The marking of debugger breakpoint lines in the editor and
text in popups and dialogs is not user-configurable.

@node 启动和代码执行,帮助和偏好,编辑和导航,IDLE<48>
@anchor{library/idle startup-and-code-execution}@anchor{31f8}
@subsubsection 启动和代码执行


Upon startup with the @code{-s} option, IDLE will execute the file referenced by
the environment variables 
@geindex IDLESTARTUP
@geindex 环境变量; IDLESTARTUP
@code{IDLESTARTUP} or 
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP}.
IDLE first checks for @code{IDLESTARTUP}; if @code{IDLESTARTUP} is present the file
referenced is run.  If @code{IDLESTARTUP} is not present, IDLE checks for
@code{PYTHONSTARTUP}.  Files referenced by these environment variables are
convenient places to store functions that are used frequently from the IDLE
shell, or for executing import statements to import common modules.

In addition, @code{Tk} also loads a startup file if it is present.  Note that the
Tk file is loaded unconditionally.  This additional file is @code{.Idle.py} and is
looked for in the user's home directory.  Statements in this file will be
executed in the Tk namespace, so this file is not useful for importing
functions to be used from IDLE's Python shell.

@menu
* 命令行语法:: 
* 启动失败:: 
* 运行用户代码:: 
* Shell中的用户输出:: 
* 开发 tkinter 应用程序:: 
* 在没有子进程的情况下运行:: 

@end menu

@node 命令行语法,启动失败,,启动和代码执行
@anchor{library/idle command-line-usage}@anchor{31f9}
@subsubsection 命令行语法


@example
idle.py [-c command] [-d] [-e] [-h] [-i] [-r file] [-s] [-t title] [-] [arg] ...

-c command  run command in the shell window
-d          enable debugger and open shell window
-e          open editor window
-h          print help message with legal combinations and exit
-i          open shell window
-r file     run file in shell window
-s          run $IDLESTARTUP or $PYTHONSTARTUP first, in shell window
-t title    set title of shell window
-           run stdin in shell (- must be last option before args)
@end example

如果有参数：


@itemize *

@item 
If @code{-}, @code{-c}, or @code{r} is used, all arguments are placed in
@code{sys.argv[1:...]} and @code{sys.argv[0]} is set to @code{'@w{'}}, @code{'-c'},
or @code{'-r'}.  No editor window is opened, even if that is the default
set in the Options dialog.

@item 
Otherwise, arguments are files opened for editing and
@code{sys.argv} reflects the arguments passed to IDLE itself.
@end itemize

@node 启动失败,运行用户代码,命令行语法,启动和代码执行
@anchor{library/idle startup-failure}@anchor{31fa}
@subsubsection 启动失败


IDLE uses a socket to communicate between the IDLE GUI process and the user
code execution process.  A connection must be established whenever the Shell
starts or restarts.  (The latter is indicated by a divider line that says
'RESTART'). If the user process fails to connect to the GUI process, it
displays a @code{Tk} error box with a 'cannot connect' message that directs the
user here.  It then exits.

A common cause of failure is a user-written file with the same name as a
standard library module, such as @emph{random.py} and @emph{tkinter.py}. When such a
file is located in the same directory as a file that is about to be run,
IDLE cannot import the stdlib file.  The current fix is to rename the
user file.

Though less common than in the past, an antivirus or firewall program may
stop the connection.  If the program cannot be taught to allow the
connection, then it must be turned off for IDLE to work.  It is safe to
allow this internal connection because no data is visible on external
ports.  A similar problem is a network mis-configuration that blocks
connections.

Python installation issues occasionally stop IDLE: multiple versions can
clash, or a single installation might need admin access.  If one undo the
clash, or cannot or does not want to run as admin, it might be easiest to
completely remove Python and start over.

A zombie pythonw.exe process could be a problem.  On Windows, use Task
Manager to check for one and stop it if there is.  Sometimes a restart
initiated by a program crash or Keyboard Interrupt (control-C) may fail
to connect.  Dismissing the error box or using Restart Shell on the Shell
menu may fix a temporary problem.

When IDLE first starts, it attempts to read user configuration files in
@code{~/.idlerc/} (~ is one's home directory).  If there is a problem, an error
message should be displayed.  Leaving aside random disk glitches, this can
be prevented by never editing the files by hand.  Instead, use the
configuration dialog, under Options.  Once there is an error in a user
configuration file, the best solution may be to delete it and start over
with the settings dialog.

If IDLE quits with no message, and it was not started from a console, try
starting it from a console or terminal (@code{python -m idlelib}) and see if
this results in an error message.

@node 运行用户代码,Shell中的用户输出,启动失败,启动和代码执行
@anchor{library/idle running-user-code}@anchor{31fb}
@subsubsection 运行用户代码


With rare exceptions, the result of executing Python code with IDLE is
intended to be the same as executing the same code by the default method,
directly with Python in a text-mode system console or terminal window.
However, the different interface and operation occasionally affect
visible results.  For instance, @code{sys.modules} starts with more entries,
and @code{threading.activeCount()} returns 2 instead of 1.

By default, IDLE runs user code in a separate OS process rather than in
the user interface process that runs the shell and editor.  In the execution
process, it replaces @code{sys.stdin}, @code{sys.stdout}, and @code{sys.stderr}
with objects that get input from and send output to the Shell window.
The original values stored in @code{sys.__stdin__}, @code{sys.__stdout__}, and
@code{sys.__stderr__} are not touched, but may be @code{None}.

When Shell has the focus, it controls the keyboard and screen.  This is
normally transparent, but functions that directly access the keyboard
and screen will not work.  These include system-specific functions that
determine whether a key has been pressed and if so, which.

IDLE's standard stream replacements are not inherited by subprocesses
created in the execution process, whether directly by user code or by modules
such as multiprocessing.  If such subprocess use @code{input} from sys.stdin
or @code{print} or @code{write} to sys.stdout or sys.stderr,
IDLE should be started in a command line window.  The secondary subprocess
will then be attached to that window for input and output.

The IDLE code running in the execution process adds frames to the call stack
that would not be there otherwise.  IDLE wraps @code{sys.getrecursionlimit} and
@code{sys.setrecursionlimit} to reduce the effect of the additional stack frames.

If @code{sys} is reset by user code, such as with @code{importlib.reload(sys)},
IDLE's changes are lost and input from the keyboard and output to the screen
will not work correctly.

When user code raises SystemExit either directly or by calling sys.exit, IDLE
returns to a Shell prompt instead of exiting.

@node Shell中的用户输出,开发 tkinter 应用程序,运行用户代码,启动和代码执行
@anchor{library/idle user-output-in-shell}@anchor{31fc}
@subsubsection Shell中的用户输出


When a program outputs text, the result is determined by the
corresponding output device.  When IDLE executes user code, @code{sys.stdout}
and @code{sys.stderr} are connected to the display area of IDLE's Shell.  Some of
its features are inherited from the underlying Tk Text widget.  Others
are programmed additions.  Where it matters, Shell is designed for development
rather than production runs.

For instance, Shell never throws away output.  A program that sends unlimited
output to Shell will eventually fill memory, resulting in a memory error.
In contrast, some system text windows only keep the last n lines of output.
A Windows console, for instance, keeps a user-settable 1 to 9999 lines,
with 300 the default.

A Tk Text widget, and hence IDLE's Shell, displays characters (codepoints) in
the BMP (Basic Multilingual Plane) subset of Unicode.  Which characters are
displayed with a proper glyph and which with a replacement box depends on the
operating system and installed fonts.  Tab characters cause the following text
to begin after the next tab stop. (They occur every 8 'characters').  Newline
characters cause following text to appear on a new line.  Other control
characters are ignored or displayed as a space, box, or something else,
depending on the operating system and font.  (Moving the text cursor through
such output with arrow keys may exhibit some surprising spacing behavior.)

@example
>>> s = 'a\tb\a<\x02><\r>\bc\nd'  # Enter 22 chars.
>>> len(s)
14
>>> s  # Display repr(s)
'a\tb\x07<\x02><\r>\x08c\nd'
>>> print(s, end='@w{'})  # Display s as is.
# Result varies by OS and font.  Try it.
@end example

The @code{repr} function is used for interactive echo of expression
values.  It returns an altered version of the input string in which
control codes, some BMP codepoints, and all non-BMP codepoints are
replaced with escape codes. As demonstrated above, it allows one to
identify the characters in a string, regardless of how they are displayed.

Normal and error output are generally kept separate (on separate lines)
from code input and each other.  They each get different highlight colors.

For SyntaxError tracebacks, the normal '^' marking where the error was
detected is replaced by coloring the text with an error highlight.
When code run from a file causes other exceptions, one may right click
on a traceback line to jump to the corresponding line in an IDLE editor.
The file will be opened if necessary.

Shell has a special facility for squeezing output lines down to a
'Squeezed text' label.  This is done automatically
for output over N lines (N = 50 by default).
N can be changed in the PyShell section of the General
page of the Settings dialog.  Output with fewer lines can be squeezed by
right clicking on the output.  This can be useful lines long enough to slow
down scrolling.

Squeezed output is expanded in place by double-clicking the label.
It can also be sent to the clipboard or a separate view window by
right-clicking the label.

@node 开发 tkinter 应用程序,在没有子进程的情况下运行,Shell中的用户输出,启动和代码执行
@anchor{library/idle developing-tkinter-applications}@anchor{31fd}
@subsubsection 开发 tkinter 应用程序


IDLE is intentionally different from standard Python in order to
facilitate development of tkinter programs.  Enter @code{import tkinter as tk;
root = tk.Tk()} in standard Python and nothing appears.  Enter the same
in IDLE and a tk window appears.  In standard Python, one must also enter
@code{root.update()} to see the window.  IDLE does the equivalent in the
background, about 20 times a second, which is about every 50 milliseconds.
Next enter @code{b = tk.Button(root, text='button'); b.pack()}.  Again,
nothing visibly changes in standard Python until one enters @code{root.update()}.

Most tkinter programs run @code{root.mainloop()}, which usually does not
return until the tk app is destroyed.  If the program is run with
@code{python -i} or from an IDLE editor, a @code{>>>} shell prompt does not
appear until @code{mainloop()} returns, at which time there is nothing left
to interact with.

When running a tkinter program from an IDLE editor, one can comment out
the mainloop call.  One then gets a shell prompt immediately and can
interact with the live application.  One just has to remember to
re-enable the mainloop call when running in standard Python.

@node 在没有子进程的情况下运行,,开发 tkinter 应用程序,启动和代码执行
@anchor{library/idle running-without-a-subprocess}@anchor{31fe}
@subsubsection 在没有子进程的情况下运行


By default, IDLE executes user code in a separate subprocess via a socket,
which uses the internal loopback interface.  This connection is not
externally visible and no data is sent to or received from the Internet.
If firewall software complains anyway, you can ignore it.

If the attempt to make the socket connection fails, Idle will notify you.
Such failures are sometimes transient, but if persistent, the problem
may be either a firewall blocking the connection or misconfiguration of
a particular system.  Until the problem is fixed, one can run Idle with
the -n command line switch.

If IDLE is started with the -n command line switch it will run in a
single process and will not create the subprocess which runs the RPC
Python execution server.  This can be useful if Python cannot create
the subprocess or the RPC socket interface on your platform.  However,
in this mode user code is not isolated from IDLE itself.  Also, the
environment is not restarted when Run/Run Module (F5) is selected.  If
your code has been modified, you must reload() the affected modules and
re-import any specific items (e.g. from foo import baz) if the changes
are to take effect.  For these reasons, it is preferable to run IDLE
with the default subprocess if at all possible.


3.4 版后已移除.


@node 帮助和偏好,,启动和代码执行,IDLE<48>
@anchor{library/idle help-and-preferences}@anchor{31ff}
@subsubsection 帮助和偏好


@menu
* 帮助源:: 
* 首选项设置:: 
* macOS 上的IDLE:: 
* 扩展:: 

@end menu

@node 帮助源,首选项设置,,帮助和偏好
@anchor{library/idle help-sources}@anchor{31ec}@anchor{library/idle id6}@anchor{3200}
@subsubsection 帮助源


Help menu entry "IDLE Help" displays a formatted html version of the
IDLE chapter of the Library Reference.  The result, in a read-only
tkinter text window, is close to what one sees in a web browser.
Navigate through the text with a mousewheel,
the scrollbar, or up and down arrow keys held down.
Or click the TOC (Table of Contents) button and select a section
header in the opened box.

Help menu entry "Python Docs" opens the extensive sources of help,
including tutorials, available at @code{docs.python.org/x.y}, where 'x.y'
is the currently running Python version.  If your system
has an off-line copy of the docs (this may be an installation option),
that will be opened instead.

Selected URLs can be added or removed from the help menu at any time using the
General tab of the Configure IDLE dialog.

@node 首选项设置,macOS 上的IDLE,帮助源,帮助和偏好
@anchor{library/idle preferences}@anchor{31e8}@anchor{library/idle setting-preferences}@anchor{3201}
@subsubsection 首选项设置


The font preferences, highlighting, keys, and general preferences can be
changed via Configure IDLE on the Option menu.
Non-default user settings are saved in a @code{.idlerc} directory in the user's
home directory.  Problems caused by bad user configuration files are solved
by editing or deleting one or more of the files in @code{.idlerc}.

On the Font tab, see the text sample for the effect of font face and size
on multiple characters in multiple languages.  Edit the sample to add
other characters of personal interest.  Use the sample to select
monospaced fonts.  If particular characters have problems in Shell or an
editor, add them to the top of the sample and try changing first size
and then font.

On the Highlights and Keys tab, select a built-in or custom color theme
and key set.  To use a newer built-in color theme or key set with older
IDLEs, save it as a new custom theme or key set and it well be accessible
to older IDLEs.

@node macOS 上的IDLE,扩展,首选项设置,帮助和偏好
@anchor{library/idle idle-on-macos}@anchor{3202}
@subsubsection macOS 上的IDLE


Under System Preferences: Dock, one can set "Prefer tabs when opening
documents" to "Always".  This setting is not compatible with the tk/tkinter
GUI framework used by IDLE, and it breaks a few IDLE features.

@node 扩展,,macOS 上的IDLE,帮助和偏好
@anchor{library/idle extensions}@anchor{3203}
@subsubsection 扩展


IDLE contains an extension facility.  Preferences for extensions can be
changed with the Extensions tab of the preferences dialog. See the
beginning of config-extensions.def in the idlelib directory for further
information.  The only current default extension is zzdummy, an example
also used for testing.

@node 其他图形用户界面（GUI）包,,IDLE<48>,Tk图形用户界面 GUI
@anchor{library/othergui doc}@anchor{3204}@anchor{library/othergui other-graphical-user-interface-packages}@anchor{3205}@anchor{library/othergui other-gui-packages}@anchor{3110}
@subsection 其他图形用户界面（GUI）包


Python 可用的主要跨平台（Windows，Mac OS X，类Unix）GUI 工具：


@subsubheading 参见



@table @asis

@item PyGObject@footnote{https://wiki.gnome.org/Projects/PyGObject}

PyGObject 使用 GObject@footnote{https://developer.gnome.org/gobject/stable/} 提供针对 C 库的内省绑定。 GTK+ 3@footnote{https://www.gtk.org/} 可视化部件集就是此类函数库中的一个。 GTK+ 附带的部件比 Tkinter 所提供的更多。 请在线参阅 Python GTK+ 3 教程@footnote{https://python-gtk-3-tutorial.readthedocs.io/}。

@item PyGTK@footnote{http://www.pygtk.org/}

PyGTK 提供了对较旧版本的库 GTK+ 2 的绑定。 它使用面向对象接口，比 C 库的抽象层级略高。 此外也有对 GNOME@footnote{https://www.gnome.org/} 的绑定。 请参阅在线 教程@footnote{http://www.pygtk.org/pygtk2tutorial/index.html}。

@item PyQt@footnote{https://riverbankcomputing.com/software/pyqt/intro}

PyQt 是一个针对 Qt 工具集通过 @code{sip} 包装的绑定。 Qt 是一个庞大的 C++ GUI 应用开发框架，同时适用于 Unix, Windows 和 Mac OS X。 @code{sip} 是一个用于为 C++ 库生成 Python 类绑定的库，它是针对 Python 特别设计的。

@item PySide2@footnote{https://doc.qt.io/qtforpython/}

或称为 Qt for Python 项目，PySide2 是一个较新的针对 Qt 工具集的绑定。 它由 The Qt Company 发布，旨在提供一个完整的用于 Qt 5 的 PySide 移植版。 与 PyQt 相比，它的许可方案对非开源应用更为友好。

@item wxPython@footnote{https://www.wxpython.org}

wxPython 是一个针对 Python 的跨平台 GUI 工具集，它基于热门的 wxWidgets@footnote{https://www.wxwidgets.org/} (原名 wxWindows) C++ 工具集进行构建。 它为 Windows, Mac OS X 和 Unix 系统上的应用提供了原生的外观效果，在可能的情况下尽量使用各平台的原生可视化部件。 （在类 Unix 系统上使用 GTK+）。 除了包含庞大的可视化部件集，wxPython 还提供了许多类用于在线文档和上下文感知帮助、打印、HTML 视图、低层级设备上下文绘图、拖放操作、系统剪贴板访问、基于 XML 的资源格式等等，并且包含一个不断增长的用户贡献模块库。
@end table


PyGTK, PyQt, PySide2 和 wxPython 都拥有比 Tkinter 更现代的外观效果和更多的可视化部件。 此外还存在许多其他适用于 Python 的 GUI 工具集，即有跨平台的，也有特定平台专属的。 请参阅 Python Wiki 中的 GUI 编程@footnote{https://wiki.python.org/moin/GuiProgramming} 页面查看更完整的列表，以及不同 GUI 工具集对比文档的链接。

@c Other sections I have in mind are
@c Tkinter internals
@c Freezing Tkinter applications

@node 开发工具,调试和分析,Tk图形用户界面 GUI,Python 标准库
@anchor{library/development doc}@anchor{3206}@anchor{library/development development}@anchor{3207}@anchor{library/development development-tools}@anchor{3208}
@section 开发工具


本章中描述的各模块可帮你编写 Python 程序。例如，@ref{d9,,pydoc} 模块接受一个模块并根据该模块的内容来生成文档。@ref{67,,doctest} 和 @ref{11b,,unittest} 这两个模块包含了用于编写单元测试的框架，并可用于自动测试所编写的代码，验证预期的输出是否产生。@code{2to3} 程序能够将 Python 2.x 源代码翻译成有效的 Python 3.x 源代码。

本章中描述的模块列表是：

@menu
* typing: typing --- 类型标注支持. 类型标注支持
* pydoc: pydoc --- 文档生成器和在线帮助系统. 文档生成器和在线帮助系统
* doctest: doctest --- 测试交互性的Python示例. 测试交互性的Python示例
* unittest: unittest --- 单元测试框架. 单元测试框架
* unittest.mock: unittest mock --- 模拟对象库. 模拟对象库
* unittest.mock 上手指南: unittest mock 上手指南. 
* 2to3 - 自动将 Python 2 代码转为 Python 3 代码:: 
* test: test --- Python回归测试包. Python回归测试包
* test.support: test support --- Utilities for the Python test suite. Utilities for the Python test suite
* test.support.script_helper: test support script_helper --- Utilities for the Python execution tests. Utilities for the Python execution tests

@end menu

@node typing --- 类型标注支持,pydoc --- 文档生成器和在线帮助系统,,开发工具
@anchor{library/typing doc}@anchor{3209}@anchor{library/typing module-typing}@anchor{119}@anchor{library/typing typing-support-for-type-hints}@anchor{320a}
@subsection @code{typing} --- 类型标注支持


@geindex typing (模块)


3.5 新版功能.


@strong{源码：} Lib/typing.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/typing.py}

@cartouche
@quotation 注解 
The Python runtime does not enforce function and variable type annotations.
They can be used by third party tools such as type checkers, IDEs, linters,
etc.
@end quotation
@end cartouche


__________________________________________________________________


This module provides runtime support for type hints as specified by
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484}, 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526}, 
@geindex Python 提高建议; PEP 544
PEP 544@footnote{https://www.python.org/dev/peps/pep-0544}, 
@geindex Python 提高建议; PEP 586
PEP 586@footnote{https://www.python.org/dev/peps/pep-0586}, 
@geindex Python 提高建议; PEP 589
PEP 589@footnote{https://www.python.org/dev/peps/pep-0589}, and 
@geindex Python 提高建议; PEP 591
PEP 591@footnote{https://www.python.org/dev/peps/pep-0591}.
The most fundamental support consists of the types @ref{64c,,Any}, @ref{fc7,,Union},
@ref{320b,,Tuple}, @ref{320c,,Callable}, @ref{eb0,,TypeVar}, and
@ref{320d,,Generic}.  For full specification please see 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484}.  For
a simplified introduction to type hints see 
@geindex Python 提高建议; PEP 483
PEP 483@footnote{https://www.python.org/dev/peps/pep-0483}.

函数接受并返回一个字符串，注释像下面这样:

@example
def greeting(name: str) -> str:
    return 'Hello ' + name
@end example

在函数 @code{greeting} 中，参数 @code{name} 预期是 @ref{329,,str} 类型，并且返回 @ref{329,,str} 类型。子类型允许作为参数。

@menu
* 类型别名:: 
* NewType:: 
* Callable:: 
* 泛型(Generic): 泛型 Generic. 
* 用户定义的泛型类型:: 
* Any 类型:: 
* Nominal vs structural subtyping:: 
* 类@comma{}函数和修饰器.: 类 函数和修饰器. 

@end menu

@node 类型别名,NewType,,typing --- 类型标注支持
@anchor{library/typing type-aliases}@anchor{320e}
@subsubsection 类型别名


类型别名通过将类型分配给别名来定义。在这个例子中， @code{Vector} 和 @code{List[float]} 将被视为可互换的同义词:

@example
from typing import List
Vector = List[float]

def scale(scalar: float, vector: Vector) -> Vector:
    return [scalar * num for num in vector]

# typechecks; a list of floats qualifies as a Vector.
new_vector = scale(2.0, [1.0, -4.2, 5.4])
@end example

类型别名可用于简化复杂类型签名。例如:

@example
from typing import Dict, Tuple, Sequence

ConnectionOptions = Dict[str, str]
Address = Tuple[str, int]
Server = Tuple[Address, ConnectionOptions]

def broadcast_message(message: str, servers: Sequence[Server]) -> None:
    ...

# The static type checker will treat the previous type signature as
# being exactly equivalent to this one.
def broadcast_message(
        message: str,
        servers: Sequence[Tuple[Tuple[str, int], Dict[str, str]]]) -> None:
    ...
@end example

请注意，@code{None} 作为类型提示是一种特殊情况，并且由 @code{type(None)} 取代。

@node NewType,Callable,类型别名,typing --- 类型标注支持
@anchor{library/typing distinct}@anchor{320f}@anchor{library/typing newtype}@anchor{3210}
@subsubsection NewType


使用 @ref{5a0,,NewType()} 辅助函数创建不同的类型:

@example
from typing import NewType

UserId = NewType('UserId', int)
some_id = UserId(524313)
@end example

静态类型检查器会将新类型视为它是原始类型的子类。这对于帮助捕捉逻辑错误非常有用:

@example
def get_user_name(user_id: UserId) -> str:
    ...

# typechecks
user_a = get_user_name(UserId(42351))

# does not typecheck; an int is not a UserId
user_b = get_user_name(-1)
@end example

您仍然可以对 @code{UserId} 类型的变量执行所有的 @code{int} 支持的操作，但结果将始终为 @code{int} 类型。这可以让你在需要 @code{int} 的地方传入 @code{UserId}，但会阻止你以无效的方式无意中创建 @code{UserId}:

@example
# 'output' is of type 'int', not 'UserId'
output = UserId(23413) + UserId(54341)
@end example

Note that these checks are enforced only by the static type checker. At runtime,
the statement @code{Derived = NewType('Derived', Base)} will make @code{Derived} a
function that immediately returns whatever parameter you pass it. That means
the expression @code{Derived(some_value)} does not create a new class or introduce
any overhead beyond that of a regular function call.

更确切地说，表达式 @code{some_value is Derived(some_value)} 在运行时总是为真。

这也意味着无法创建 @code{Derived} 的子类型，因为它是运行时的标识函数，而不是实际的类型:

@example
from typing import NewType

UserId = NewType('UserId', int)

# Fails at runtime and does not typecheck
class AdminUserId(UserId): pass
@end example

但是，可以基于'derived' @code{NewType} 创建 @ref{5a0,,NewType()}

@example
from typing import NewType

UserId = NewType('UserId', int)

ProUserId = NewType('ProUserId', UserId)
@end example

并且 @code{ProUserId} 的类型检查将按预期工作。

有关更多详细信息，请参阅 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484}。

@cartouche
@quotation 注解 
回想一下，使用类型别名声明两种类型彼此 @emph{等效} 。@code{Alias = Original} 将使静态类型检查对待所有情况下 @code{Alias} @emph{完全等同于} @code{Original}。当您想简化复杂类型签名时，这很有用。

相反，@code{NewType} 声明一种类型是另一种类型的子类型。@code{Derived = NewType('Derived', Original)} 将使静态类型检查器将 @code{Derived} 当作 @code{Original} 的 @emph{子类} ，这意味着 @code{Original} 类型的值不能用于 @code{Derived} 类型的值需要的地方。当您想以最小的运行时间成本防止逻辑错误时，这非常有用。
@end quotation
@end cartouche


3.5.2 新版功能.


@node Callable,泛型 Generic,NewType,typing --- 类型标注支持
@anchor{library/typing callable}@anchor{3211}
@subsubsection Callable


期望特定签名的回调函数的框架可以将类型标注为 @code{Callable[[Arg1Type, Arg2Type], ReturnType]}。

例如

@example
from typing import Callable

def feeder(get_next_item: Callable[[], str]) -> None:
    # Body

def async_query(on_success: Callable[[int], None],
                on_error: Callable[[int, Exception], None]) -> None:
    # Body
@end example

通过用文字省略号替换类型提示中的参数列表： @code{Callable[...，ReturnType]}，可以声明可调用的返回类型，而无需指定调用签名。

@node 泛型 Generic,用户定义的泛型类型,Callable,typing --- 类型标注支持
@anchor{library/typing generics}@anchor{3212}@anchor{library/typing id1}@anchor{3213}
@subsubsection 泛型(Generic)


由于无法以通用方式静态推断有关保存在容器中的对象的类型信息，因此抽象基类已扩展为支持订阅以表示容器元素的预期类型。

@example
from typing import Mapping, Sequence

def notify_by_email(employees: Sequence[Employee],
                    overrides: Mapping[str, str]) -> None: ...
@end example

泛型可以通过使用typing模块中名为 @ref{eb0,,TypeVar} 的新工厂进行参数化。

@example
from typing import Sequence, TypeVar

T = TypeVar('T')      # Declare type variable

def first(l: Sequence[T]) -> T:   # Generic function
    return l[0]
@end example

@node 用户定义的泛型类型,Any 类型,泛型 Generic,typing --- 类型标注支持
@anchor{library/typing user-defined-generic-types}@anchor{3214}
@subsubsection 用户定义的泛型类型


用户定义的类可以定义为泛型类。

@example
from typing import TypeVar, Generic
from logging import Logger

T = TypeVar('T')

class LoggedVar(Generic[T]):
    def __init__(self, value: T, name: str, logger: Logger) -> None:
        self.name = name
        self.logger = logger
        self.value = value

    def set(self, new: T) -> None:
        self.log('Set ' + repr(self.value))
        self.value = new

    def get(self) -> T:
        self.log('Get ' + repr(self.value))
        return self.value

    def log(self, message: str) -> None:
        self.logger.info('%s: %s', self.name, message)
@end example

@code{Generic[T]} 作为基类定义了类 @code{LoggedVar} 采用单个类型参数 @code{T}。这也使得 @code{T} 作为类体内的一个类型有效。

The @ref{320d,,Generic} base class defines @ref{320,,__class_getitem__()} so that
@code{LoggedVar[t]} is valid as a type:

@example
from typing import Iterable

def zero_all_vars(vars: Iterable[LoggedVar[int]]) -> None:
    for var in vars:
        var.set(0)
@end example

泛型类型可以有任意数量的类型变量，并且类型变量可能会受到限制:

@example
from typing import TypeVar, Generic
...

T = TypeVar('T')
S = TypeVar('S', int, str)

class StrangePair(Generic[T, S]):
    ...
@end example

@ref{320d,,Generic} 每个参数的类型变量必须是不同的。这是无效的:

@example
from typing import TypeVar, Generic
...

T = TypeVar('T')

class Pair(Generic[T, T]):   # INVALID
    ...
@end example

您可以对 @ref{320d,,Generic} 使用多重继承:

@example
from typing import TypeVar, Generic, Sized

T = TypeVar('T')

class LinkedList(Sized, Generic[T]):
    ...
@end example

从泛型类继承时，某些类型变量可能是固定的:

@example
from typing import TypeVar, Mapping

T = TypeVar('T')

class MyDict(Mapping[str, T]):
    ...
@end example

在这种情况下，@code{MyDict} 只有一个参数，@code{T}。

在不指定类型参数的情况下使用泛型类别会为每个位置假设 @ref{64c,,Any}。在下面的例子中，@code{MyIterable} 不是泛型，但是隐式继承自 @code{Iterable[Any]}:

@example
from typing import Iterable

class MyIterable(Iterable): # Same as Iterable[Any]
@end example

用户定义的通用类型别名也受支持。例子:

@example
from typing import TypeVar, Iterable, Tuple, Union
S = TypeVar('S')
Response = Union[Iterable[S], int]

# Return type here is same as Union[Iterable[str], int]
def response(query: str) -> Response[str]:
    ...

T = TypeVar('T', int, float, complex)
Vec = Iterable[Tuple[T, T]]

def inproduct(v: Vec[T]) -> T: # Same as Iterable[Tuple[T, T]]
    return sum(x*y for x, y in v)
@end example


在 3.7 版更改: @ref{320d,,Generic} no longer has a custom metaclass.


A user-defined generic class can have ABCs as base classes without a metaclass
conflict. Generic metaclasses are not supported. The outcome of parameterizing
generics is cached, and most types in the typing module are hashable and
comparable for equality.

@node Any 类型,Nominal vs structural subtyping,用户定义的泛型类型,typing --- 类型标注支持
@anchor{library/typing the-any-type}@anchor{3215}
@subsubsection @code{Any} 类型


@ref{64c,,Any} 是一种特殊的类型。静态类型检查器将所有类型视为与 @ref{64c,,Any} 兼容，反之亦然， @ref{64c,,Any} 也与所有类型相兼容。

这意味着可对类型为 @ref{64c,,Any} 的值执行任何操作或方法调用，并将其赋值给任何变量:

@example
from typing import Any

a = None    # type: Any
a = []      # OK
a = 2       # OK

s = '@w{'}      # type: str
s = a       # OK

def foo(item: Any) -> int:
    # Typechecks; 'item' could be any type,
    # and that type might have a 'bar' method
    item.bar()
    ...
@end example

需要注意的是，将 @ref{64c,,Any} 类型的值赋值给另一个更具体的类型时，Python不会执行类型检查。例如，当把 @code{a} 赋值给 @code{s} 时，即使 @code{s} 被声明为 @ref{329,,str} 类型，在运行时接收到的是 @ref{184,,int} 值，静态类型检查器也不会报错。

此外，所有返回值无类型或形参无类型的函数将隐式地默认使用 @ref{64c,,Any} 类型:

@example
def legacy_parser(text):
    ...
    return data

# A static type checker will treat the above
# as having the same signature as:
def legacy_parser(text: Any) -> Any:
    ...
    return data
@end example

当需要混用动态类型和静态类型的代码时，上述行为可以让 @ref{64c,,Any} 被用作 @emph{应急出口} 。

@ref{64c,,Any} 和 @ref{2b0,,object} 的行为对比。与 @ref{64c,,Any} 相似，所有的类型都是 @ref{2b0,,object} 的子类型。然而不同于 @ref{64c,,Any}，反之并不成立： @ref{2b0,,object} @emph{不是} 其他所有类型的子类型。

这意味着当一个值的类型是 @ref{2b0,,object} 的时候，类型检查器会拒绝对它的几乎所有的操作。把它赋值给一个指定了类型的变量（或者当作返回值）是一个类型错误。比如说：

@example
def hash_a(item: object) -> int:
    # Fails; an object does not have a 'magic' method.
    item.magic()
    ...

def hash_b(item: Any) -> int:
    # Typechecks
    item.magic()
    ...

# Typechecks, since ints and strs are subclasses of object
hash_a(42)
hash_a("foo")

# Typechecks, since Any is compatible with all types
hash_b(42)
hash_b("foo")
@end example

使用 @ref{2b0,,object} 示意一个值可以类型安全地兼容任何类型。使用 @ref{64c,,Any} 示意一个值地类型是动态定义的。

@node Nominal vs structural subtyping,类 函数和修饰器,Any 类型,typing --- 类型标注支持
@anchor{library/typing nominal-vs-structural-subtyping}@anchor{3216}
@subsubsection Nominal vs structural subtyping


Initially 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} defined Python static type system as using
@emph{nominal subtyping}. This means that a class @code{A} is allowed where
a class @code{B} is expected if and only if @code{A} is a subclass of @code{B}.

This requirement previously also applied to abstract base classes, such as
@ref{3217,,Iterable}. The problem with this approach is that a class had
to be explicitly marked to support them, which is unpythonic and unlike
what one would normally do in idiomatic dynamically typed Python code.
For example, this conforms to the 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484}:

@example
from typing import Sized, Iterable, Iterator

class Bucket(Sized, Iterable[int]):
    ...
    def __len__(self) -> int: ...
    def __iter__(self) -> Iterator[int]: ...
@end example

@geindex Python 提高建议; PEP 544
PEP 544@footnote{https://www.python.org/dev/peps/pep-0544} allows to solve this problem by allowing users to write
the above code without explicit base classes in the class definition,
allowing @code{Bucket} to be implicitly considered a subtype of both @code{Sized}
and @code{Iterable[int]} by static type checkers. This is known as
@emph{structural subtyping} (or static duck-typing):

@example
from typing import Iterator, Iterable

class Bucket:  # Note: no base classes
    ...
    def __len__(self) -> int: ...
    def __iter__(self) -> Iterator[int]: ...

def collect(items: Iterable[int]) -> int: ...
result = collect(Bucket())  # Passes type check
@end example

Moreover, by subclassing a special class @ref{23f,,Protocol}, a user
can define new custom protocols to fully enjoy structural subtyping
(see examples below).

@node 类 函数和修饰器,,Nominal vs structural subtyping,typing --- 类型标注支持
@anchor{library/typing classes-functions-and-decorators}@anchor{3218}
@subsubsection 类,函数和修饰器.


这个模块定义了如下的类,模块和修饰器.

@geindex TypeVar (typing 中的类)
@anchor{library/typing typing TypeVar}@anchor{eb0}
@deffn {类} typing.TypeVar

类型变量

用法:

@example
T = TypeVar('T')  # Can be anything
A = TypeVar('A', str, bytes)  # Must be str or bytes
@end example

Type variables exist primarily for the benefit of static type
checkers.  They serve as the parameters for generic types as well
as for generic function definitions.  See class Generic for more
information on generic types.  Generic functions work as follows:

@example
def repeat(x: T, n: int) -> Sequence[T]:
    """Return a list containing n references to x."""
    return [x]*n

def longest(x: A, y: A) -> A:
    """Return the longest of two strings."""
    return x if len(x) >= len(y) else y
@end example

The latter example's signature is essentially the overloading
of @code{(str, str) -> str} and @code{(bytes, bytes) -> bytes}.  Also note
that if the arguments are instances of some subclass of @ref{329,,str},
the return type is still plain @ref{329,,str}.

@code{isinstance(x, T)} 会在运行时抛出 @ref{192,,TypeError} 异常。一般地说， @ref{449,,isinstance()} 和 @ref{44a,,issubclass()} 不应该和类型一起使用。

Type variables may be marked covariant or contravariant by passing
@code{covariant=True} or @code{contravariant=True}.  See 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} for more
details.  By default type variables are invariant.  Alternatively,
a type variable may specify an upper bound using @code{bound=<type>}.
This means that an actual type substituted (explicitly or implicitly)
for the type variable must be a subclass of the boundary type,
see 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484}.
@end deffn

@geindex Generic (typing 中的类)
@anchor{library/typing typing Generic}@anchor{320d}
@deffn {类} typing.Generic

Abstract base class for generic types.

A generic type is typically declared by inheriting from an
instantiation of this class with one or more type variables.
For example, a generic mapping type might be defined as:

@example
class Mapping(Generic[KT, VT]):
    def __getitem__(self, key: KT) -> VT:
        ...
        # Etc.
@end example

这个类之后可以被这样用:

@example
X = TypeVar('X')
Y = TypeVar('Y')

def lookup_name(mapping: Mapping[X, Y], key: X, default: Y) -> Y:
    try:
        return mapping[key]
    except KeyError:
        return default
@end example
@end deffn

@geindex Protocol (typing 中的类)
@anchor{library/typing typing Protocol}@anchor{23f}
@deffn {类} typing.Protocol (Generic)

Base class for protocol classes. Protocol classes are defined like this:

@example
class Proto(Protocol):
    def meth(self) -> int:
        ...
@end example

Such classes are primarily used with static type checkers that recognize
structural subtyping (static duck-typing), for example:

@example
class C:
    def meth(self) -> int:
        return 0

def func(x: Proto) -> int:
    return x.meth()

func(C())  # Passes static type check
@end example

See 
@geindex Python 提高建议; PEP 544
PEP 544@footnote{https://www.python.org/dev/peps/pep-0544} for details. Protocol classes decorated with
@ref{240,,runtime_checkable()} (described later) act as simple-minded runtime
protocols that check only the presence of given attributes, ignoring their
type signatures.

Protocol classes can be generic, for example:

@example
class GenProto(Protocol[T]):
    def meth(self) -> T:
        ...
@end example


3.8 新版功能.

@end deffn

@geindex Type (typing 中的类)
@anchor{library/typing typing Type}@anchor{3219}
@deffn {类} typing.Type (Generic[CT_co])

A variable annotated with @code{C} may accept a value of type @code{C}. In
contrast, a variable annotated with @code{Type[C]} may accept values that are
classes themselves -- specifically, it will accept the @emph{class object} of
@code{C}. For example:

@example
a = 3         # Has type 'int'
b = int       # Has type 'Type[int]'
c = type(a)   # Also has type 'Type[int]'
@end example

Note that @code{Type[C]} is covariant:

@example
class User: ...
class BasicUser(User): ...
class ProUser(User): ...
class TeamUser(User): ...

# Accepts User, BasicUser, ProUser, TeamUser, ...
def make_new_user(user_class: Type[User]) -> User:
    # ...
    return user_class()
@end example

The fact that @code{Type[C]} is covariant implies that all subclasses of
@code{C} should implement the same constructor signature and class method
signatures as @code{C}. The type checker should flag violations of this,
but should also allow constructor calls in subclasses that match the
constructor calls in the indicated base class. How the type checker is
required to handle this particular case may change in future revisions of
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484}.

The only legal parameters for @ref{3219,,Type} are classes, @ref{64c,,Any},
@ref{3212,,type variables}, and unions of any of these types.
For example:

@example
def new_non_team_user(user_class: Type[Union[BaseUser, ProUser]]): ...
@end example

@code{Type[Any]} is equivalent to @code{Type} which in turn is equivalent
to @code{type}, which is the root of Python's metaclass hierarchy.


3.5.2 新版功能.

@end deffn

@geindex Iterable (typing 中的类)
@anchor{library/typing typing Iterable}@anchor{3217}
@deffn {类} typing.Iterable (Generic[T_co])

@ref{18e7,,collections.abc.Iterable} 的泛型版本。
@end deffn

@geindex Iterator (typing 中的类)
@anchor{library/typing typing Iterator}@anchor{321a}
@deffn {类} typing.Iterator (Iterable[T_co])

@ref{18e8,,collections.abc.Iterator} 的泛型版本。
@end deffn

@geindex Reversible (typing 中的类)
@anchor{library/typing typing Reversible}@anchor{321b}
@deffn {类} typing.Reversible (Iterable[T_co])

@ref{528,,collections.abc.Reversible} 的泛型版本。
@end deffn

@geindex SupportsInt (typing 中的类)
@anchor{library/typing typing SupportsInt}@anchor{241}
@deffn {类} typing.SupportsInt

An ABC with one abstract method @code{__int__}.
@end deffn

@geindex SupportsFloat (typing 中的类)
@anchor{library/typing typing SupportsFloat}@anchor{321c}
@deffn {类} typing.SupportsFloat

An ABC with one abstract method @code{__float__}.
@end deffn

@geindex SupportsComplex (typing 中的类)
@anchor{library/typing typing SupportsComplex}@anchor{321d}
@deffn {类} typing.SupportsComplex

An ABC with one abstract method @code{__complex__}.
@end deffn

@geindex SupportsBytes (typing 中的类)
@anchor{library/typing typing SupportsBytes}@anchor{321e}
@deffn {类} typing.SupportsBytes

An ABC with one abstract method @code{__bytes__}.
@end deffn

@geindex SupportsIndex (typing 中的类)
@anchor{library/typing typing SupportsIndex}@anchor{242}
@deffn {类} typing.SupportsIndex

An ABC with one abstract method @code{__index__}.


3.8 新版功能.

@end deffn

@geindex SupportsAbs (typing 中的类)
@anchor{library/typing typing SupportsAbs}@anchor{321f}
@deffn {类} typing.SupportsAbs

An ABC with one abstract method @code{__abs__} that is covariant
in its return type.
@end deffn

@geindex SupportsRound (typing 中的类)
@anchor{library/typing typing SupportsRound}@anchor{3220}
@deffn {类} typing.SupportsRound

An ABC with one abstract method @code{__round__}
that is covariant in its return type.
@end deffn

@geindex Container (typing 中的类)
@anchor{library/typing typing Container}@anchor{3221}
@deffn {类} typing.Container (Generic[T_co])

@ref{18e5,,collections.abc.Container} 的泛型版本。
@end deffn

@geindex Hashable (typing 中的类)
@anchor{library/typing typing Hashable}@anchor{3222}
@deffn {类} typing.Hashable

@ref{18e6,,collections.abc.Hashable} 的别名。
@end deffn

@geindex Sized (typing 中的类)
@anchor{library/typing typing Sized}@anchor{3223}
@deffn {类} typing.Sized

@ref{18e9,,collections.abc.Sized} 的别名。
@end deffn

@geindex Collection (typing 中的类)
@anchor{library/typing typing Collection}@anchor{59d}
@deffn {类} typing.Collection (Sized, Iterable[T_co], Container[T_co])

@ref{527,,collections.abc.Collection} 的泛型版本。


3.6.0 新版功能.

@end deffn

@geindex AbstractSet (typing 中的类)
@anchor{library/typing typing AbstractSet}@anchor{3224}
@deffn {类} typing.AbstractSet (Sized, Collection[T_co])

@ref{1673,,collections.abc.Set}  的泛型版本。
@end deffn

@geindex MutableSet (typing 中的类)
@anchor{library/typing typing MutableSet}@anchor{3225}
@deffn {类} typing.MutableSet (AbstractSet[T])

@ref{18ec,,collections.abc.MutableSet} 的泛型版本。
@end deffn

@geindex Mapping (typing 中的类)
@anchor{library/typing typing Mapping}@anchor{3226}
@deffn {类} typing.Mapping (Sized, Collection[KT], Generic[VT_co])

@ref{18d9,,collections.abc.Mapping} 的泛型版本。这个类型可以如下使用:

@example
def get_position_in_index(word_list: Mapping[str, int], word: str) -> int:
    return word_list[word]
@end example
@end deffn

@geindex MutableMapping (typing 中的类)
@anchor{library/typing typing MutableMapping}@anchor{3227}
@deffn {类} typing.MutableMapping (Mapping[KT, VT])

@ref{9e9,,collections.abc.MutableMapping} 的泛型版本。
@end deffn

@geindex Sequence (typing 中的类)
@anchor{library/typing typing Sequence}@anchor{3228}
@deffn {类} typing.Sequence (Reversible[T_co], Collection[T_co])

@ref{15c8,,collections.abc.Sequence} 的泛型版本。
@end deffn

@geindex MutableSequence (typing 中的类)
@anchor{library/typing typing MutableSequence}@anchor{3229}
@deffn {类} typing.MutableSequence (Sequence[T])

@ref{6a6,,collections.abc.MutableSequence} 的泛型版本。
@end deffn

@geindex ByteString (typing 中的类)
@anchor{library/typing typing ByteString}@anchor{322a}
@deffn {类} typing.ByteString (Sequence[int])

@ref{18eb,,collections.abc.ByteString} 的泛型版本。

This type represents the types @ref{32a,,bytes}, @ref{32b,,bytearray},
and @ref{25c,,memoryview} of byte sequences.

As a shorthand for this type, @ref{32a,,bytes} can be used to
annotate arguments of any of the types mentioned above.
@end deffn

@geindex Deque (typing 中的类)
@anchor{library/typing typing Deque}@anchor{322b}
@deffn {类} typing.Deque (deque, MutableSequence[T])

@ref{52b,,collections.deque} 的泛型版本。


3.5.4 新版功能.



3.6.1 新版功能.

@end deffn

@geindex List (typing 中的类)
@anchor{library/typing typing List}@anchor{322c}
@deffn {类} typing.List (list, MutableSequence[T])

Generic version of @ref{262,,list}.
Useful for annotating return types. To annotate arguments it is preferred
to use an abstract collection type such as @ref{3228,,Sequence} or
@ref{3217,,Iterable}.

这个类型可以这样用:

@example
T = TypeVar('T', int, float)

def vec2(x: T, y: T) -> List[T]:
    return [x, y]

def keep_positives(vector: Sequence[T]) -> List[T]:
    return [item for item in vector if item > 0]
@end example
@end deffn

@geindex Set (typing 中的类)
@anchor{library/typing typing Set}@anchor{322d}
@deffn {类} typing.Set (set, MutableSet[T])

A generic version of @ref{b68,,builtins.set}.
Useful for annotating return types. To annotate arguments it is preferred
to use an abstract collection type such as @ref{3224,,AbstractSet}.
@end deffn

@geindex FrozenSet (typing 中的类)
@anchor{library/typing typing FrozenSet}@anchor{322e}
@deffn {类} typing.FrozenSet (frozenset, AbstractSet[T_co])

A generic version of @ref{be7,,builtins.frozenset}.
@end deffn

@geindex MappingView (typing 中的类)
@anchor{library/typing typing MappingView}@anchor{322f}
@deffn {类} typing.MappingView (Sized, Iterable[T_co])

@ref{18ed,,collections.abc.MappingView} 的泛型版本。
@end deffn

@geindex KeysView (typing 中的类)
@anchor{library/typing typing KeysView}@anchor{3230}
@deffn {类} typing.KeysView (MappingView[KT_co], AbstractSet[KT_co])

@ref{18ef,,collections.abc.KeysView} 的泛型版本。
@end deffn

@geindex ItemsView (typing 中的类)
@anchor{library/typing typing ItemsView}@anchor{3231}
@deffn {类} typing.ItemsView (MappingView, Generic[KT_co, VT_co])

@ref{18ee,,collections.abc.ItemsView} 的泛型版本。
@end deffn

@geindex ValuesView (typing 中的类)
@anchor{library/typing typing ValuesView}@anchor{3232}
@deffn {类} typing.ValuesView (MappingView[VT_co])

@ref{18f0,,collections.abc.ValuesView} 的泛型版本。
@end deffn

@geindex Awaitable (typing 中的类)
@anchor{library/typing typing Awaitable}@anchor{3233}
@deffn {类} typing.Awaitable (Generic[T_co])

@ref{6b0,,collections.abc.Awaitable} 的泛型版本。


3.5.2 新版功能.

@end deffn

@geindex Coroutine (typing 中的类)
@anchor{library/typing typing Coroutine}@anchor{3234}
@deffn {类} typing.Coroutine (Awaitable[V_co], Generic[T_co T_contra, V_co])

A generic version of @ref{6b1,,collections.abc.Coroutine}.
The variance and order of type variables
correspond to those of @ref{3235,,Generator}, for example:

@example
from typing import List, Coroutine
c = None # type: Coroutine[List[str], str, int]
...
x = c.send('hi') # type: List[str]
async def bar() -> None:
    x = await c # type: int
@end example


3.5.3 新版功能.

@end deffn

@geindex AsyncIterable (typing 中的类)
@anchor{library/typing typing AsyncIterable}@anchor{3236}
@deffn {类} typing.AsyncIterable (Generic[T_co])

@ref{6b3,,collections.abc.AsyncIterable} 的泛型版本。


3.5.2 新版功能.

@end deffn

@geindex AsyncIterator (typing 中的类)
@anchor{library/typing typing AsyncIterator}@anchor{3237}
@deffn {类} typing.AsyncIterator (AsyncIterable[T_co])

@ref{6b2,,collections.abc.AsyncIterator} 的泛型版本。


3.5.2 新版功能.

@end deffn

@geindex ContextManager (typing 中的类)
@anchor{library/typing typing ContextManager}@anchor{52f}
@deffn {类} typing.ContextManager (Generic[T_co])

@ref{52e,,contextlib.AbstractContextManager} 的泛型版本。


3.5.4 新版功能.



3.6.0 新版功能.

@end deffn

@geindex AsyncContextManager (typing 中的类)
@anchor{library/typing typing AsyncContextManager}@anchor{3238}
@deffn {类} typing.AsyncContextManager (Generic[T_co])

@ref{371,,contextlib.AbstractAsyncContextManager} 的泛型版本。


3.5.4 新版功能.



3.6.2 新版功能.

@end deffn

@geindex Dict (typing 中的类)
@anchor{library/typing typing Dict}@anchor{3239}
@deffn {类} typing.Dict (dict, MutableMapping[KT, VT])

@ref{1b8,,dict} 的泛型版本。对标注返回类型比较有用。如果要标注参数的话，使用如 @ref{3226,,Mapping} 的抽象容器类型是更好的选择。

这个类型可以这样使用:

@example
def count_words(text: str) -> Dict[str, int]:
    ...
@end example
@end deffn

@geindex DefaultDict (typing 中的类)
@anchor{library/typing typing DefaultDict}@anchor{323a}
@deffn {类} typing.DefaultDict (collections.defaultdict, MutableMapping[KT, VT])

@ref{b33,,collections.defaultdict} 的泛型版本。


3.5.2 新版功能.

@end deffn

@geindex OrderedDict (typing 中的类)
@anchor{library/typing typing OrderedDict}@anchor{323b}
@deffn {类} typing.OrderedDict (collections.OrderedDict, MutableMapping[KT, VT])

@ref{1b9,,collections.OrderedDict} 的泛型版本。


3.7.2 新版功能.

@end deffn

@geindex Counter (typing 中的类)
@anchor{library/typing typing Counter}@anchor{323c}
@deffn {类} typing.Counter (collections.Counter, Dict[T, int])

@ref{9d4,,collections.Counter} 的泛型版本。


3.5.4 新版功能.



3.6.1 新版功能.

@end deffn

@geindex ChainMap (typing 中的类)
@anchor{library/typing typing ChainMap}@anchor{323d}
@deffn {类} typing.ChainMap (collections.ChainMap, MutableMapping[KT, VT])

@ref{4a4,,collections.ChainMap} 的泛型版本。


3.5.4 新版功能.



3.6.1 新版功能.

@end deffn

@geindex Generator (typing 中的类)
@anchor{library/typing typing Generator}@anchor{3235}
@deffn {类} typing.Generator (Iterator[T_co], Generic[T_co, T_contra, V_co])

A generator can be annotated by the generic type
@code{Generator[YieldType, SendType, ReturnType]}. For example:

@example
def echo_round() -> Generator[int, float, str]:
    sent = yield 0
    while sent >= 0:
        sent = yield round(sent)
    return 'Done'
@end example

Note that unlike many other generics in the typing module, the @code{SendType}
of @ref{3235,,Generator} behaves contravariantly, not covariantly or
invariantly.

If your generator will only yield values, set the @code{SendType} and
@code{ReturnType} to @code{None}:

@example
def infinite_stream(start: int) -> Generator[int, None, None]:
    while True:
        yield start
        start += 1
@end example

Alternatively, annotate your generator as having a return type of
either @code{Iterable[YieldType]} or @code{Iterator[YieldType]}:

@example
def infinite_stream(start: int) -> Iterator[int]:
    while True:
        yield start
        start += 1
@end example
@end deffn

@geindex AsyncGenerator (typing 中的类)
@anchor{library/typing typing AsyncGenerator}@anchor{323e}
@deffn {类} typing.AsyncGenerator (AsyncIterator[T_co], Generic[T_co, T_contra])

An async generator can be annotated by the generic type
@code{AsyncGenerator[YieldType, SendType]}. For example:

@example
async def echo_round() -> AsyncGenerator[int, float]:
    sent = yield 0
    while sent >= 0.0:
        rounded = await round(sent)
        sent = yield rounded
@end example

Unlike normal generators, async generators cannot return a value, so there
is no @code{ReturnType} type parameter. As with @ref{3235,,Generator}, the
@code{SendType} behaves contravariantly.

If your generator will only yield values, set the @code{SendType} to
@code{None}:

@example
async def infinite_stream(start: int) -> AsyncGenerator[int, None]:
    while True:
        yield start
        start = await increment(start)
@end example

Alternatively, annotate your generator as having a return type of
either @code{AsyncIterable[YieldType]} or @code{AsyncIterator[YieldType]}:

@example
async def infinite_stream(start: int) -> AsyncIterator[int]:
    while True:
        yield start
        start = await increment(start)
@end example


3.6.1 新版功能.

@end deffn

@geindex Text (typing 中的类)
@anchor{library/typing typing Text}@anchor{323f}
@deffn {类} typing.Text

@code{Text} is an alias for @code{str}. It is provided to supply a forward
compatible path for Python 2 code: in Python 2, @code{Text} is an alias for
@code{unicode}.

Use @code{Text} to indicate that a value must contain a unicode string in
a manner that is compatible with both Python 2 and Python 3:

@example
def add_unicode_checkmark(text: Text) -> Text:
    return text + u' \u2713'
@end example


3.5.2 新版功能.

@end deffn

@geindex IO (typing 中的类)
@geindex TextIO (typing 中的类)
@geindex BinaryIO (typing 中的类)
@anchor{library/typing typing IO}@anchor{3240}
@deffn {类} typing.IO
@anchor{library/typing typing TextIO}@anchor{3241}
@deffnx {类} typing.TextIO
@anchor{library/typing typing BinaryIO}@anchor{3242}
@deffnx {类} typing.BinaryIO

Generic type @code{IO[AnyStr]} and its subclasses @code{TextIO(IO[str])}
and @code{BinaryIO(IO[bytes])}
represent the types of I/O streams such as returned by
@ref{4ea,,open()}.
@end deffn

@geindex Pattern (typing 中的类)
@geindex Match (typing 中的类)
@anchor{library/typing typing Pattern}@anchor{3243}
@deffn {类} typing.Pattern
@anchor{library/typing typing Match}@anchor{3244}
@deffnx {类} typing.Match

These type aliases
correspond to the return types from @ref{444,,re.compile()} and
@ref{bac,,re.match()}.  These types (and the corresponding functions)
are generic in @code{AnyStr} and can be made specific by writing
@code{Pattern[str]}, @code{Pattern[bytes]}, @code{Match[str]}, or
@code{Match[bytes]}.
@end deffn

@geindex NamedTuple (typing 中的类)
@anchor{library/typing typing NamedTuple}@anchor{280}
@deffn {类} typing.NamedTuple

Typed version of @ref{1b6,,collections.namedtuple()}.

用法:

@example
class Employee(NamedTuple):
    name: str
    id: int
@end example

这相当于:

@example
Employee = collections.namedtuple('Employee', ['name', 'id'])
@end example

To give a field a default value, you can assign to it in the class body:

@example
class Employee(NamedTuple):
    name: str
    id: int = 3

employee = Employee('Guido')
assert employee.id == 3
@end example

Fields with a default value must come after any fields without a default.

The resulting class has an extra attribute @code{__annotations__} giving a
dict that maps the field names to the field types.  (The field names are in
the @code{_fields} attribute and the default values are in the
@code{_field_defaults} attribute both of which are part of the namedtuple
API.)

@code{NamedTuple} subclasses can also have docstrings and methods:

@example
class Employee(NamedTuple):
    """Represents an employee."""
    name: str
    id: int = 3

    def __repr__(self) -> str:
        return f'<Employee @{self.name@}, id=@{self.id@}>'
@end example

Backward-compatible usage:

@example
Employee = NamedTuple('Employee', [('name', str), ('id', int)])
@end example


在 3.6 版更改: Added support for 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} variable annotation syntax.



在 3.6.1 版更改: Added support for default values, methods, and docstrings.



Deprecated since version 3.8, will be removed in version 3.9: Deprecated the @code{_field_types} attribute in favor of the more
standard @code{__annotations__} attribute which has the same information.



在 3.8 版更改: The @code{_field_types} and @code{__annotations__} attributes are
now regular dictionaries instead of instances of @code{OrderedDict}.

@end deffn

@geindex TypedDict (typing 中的类)
@anchor{library/typing typing TypedDict}@anchor{23b}
@deffn {类} typing.TypedDict (dict)

A simple typed namespace. At runtime it is equivalent to
a plain @ref{1b8,,dict}.

@code{TypedDict} creates a dictionary type that expects all of its
instances to have a certain set of keys, where each key is
associated with a value of a consistent type. This expectation
is not checked at runtime but is only enforced by type checkers.
Usage:

@example
class Point2D(TypedDict):
    x: int
    y: int
    label: str

a: Point2D = @{'x': 1, 'y': 2, 'label': 'good'@}  # OK
b: Point2D = @{'z': 3, 'label': 'bad'@}           # Fails type check

assert Point2D(x=1, y=2, label='first') == dict(x=1, y=2, label='first')
@end example

The type info for introspection can be accessed via @code{Point2D.__annotations__}
and @code{Point2D.__total__}.  To allow using this feature with older versions
of Python that do not support 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526}, @code{TypedDict} supports two additional
equivalent syntactic forms:

@example
Point2D = TypedDict('Point2D', x=int, y=int, label=str)
Point2D = TypedDict('Point2D', @{'x': int, 'y': int, 'label': str@})
@end example

By default, all keys must be present in a TypedDict. It is possible
to override this by specifying totality.
Usage:

@example
class point2D(TypedDict, total=False):
    x: int
    y: int
@end example

This means that a point2D TypedDict can have any of the keys omitted. A type
checker is only expected to support a literal False or True as the value of
the total argument. True is the default, and makes all items defined in the
class body be required.

See 
@geindex Python 提高建议; PEP 589
PEP 589@footnote{https://www.python.org/dev/peps/pep-0589} for more examples and detailed rules of using @code{TypedDict}.


3.8 新版功能.

@end deffn

@geindex ForwardRef (typing 中的类)
@anchor{library/typing typing ForwardRef}@anchor{3245}
@deffn {类} typing.ForwardRef

A class used for internal typing representation of string forward references.
For example, @code{List["SomeClass"]} is implicitly transformed into
@code{List[ForwardRef("SomeClass")]}.  This class should not be instantiated by
a user, but may be used by introspection tools.
@end deffn

@geindex NewType() (在 typing 模块中)
@anchor{library/typing typing NewType}@anchor{5a0}
@deffn {函数} typing.NewType (name, tp)

A helper function to indicate a distinct type to a typechecker,
see @ref{320f,,NewType}. At runtime it returns a function that returns
its argument. Usage:

@example
UserId = NewType('UserId', int)
first_user = UserId(1)
@end example


3.5.2 新版功能.

@end deffn

@geindex cast() (在 typing 模块中)
@anchor{library/typing typing cast}@anchor{3246}
@deffn {函数} typing.cast (typ, val)

Cast a value to a type.

This returns the value unchanged.  To the type checker this
signals that the return value has the designated type, but at
runtime we intentionally don't check anything (we want this
to be as fast as possible).
@end deffn

@geindex get_type_hints() (在 typing 模块中)
@anchor{library/typing typing get_type_hints}@anchor{303}
@deffn {函数} typing.get_type_hints (obj[, globals[, locals]])

返回一个字典，字典内含有函数、方法、模块或类对象的类型提示。

This is often the same as @code{obj.__annotations__}. In addition,
forward references encoded as string literals are handled by evaluating
them in @code{globals} and @code{locals} namespaces. If necessary,
@code{Optional[t]} is added for function and method annotations if a default
value equal to @code{None} is set. For a class @code{C}, return
a dictionary constructed by merging all the @code{__annotations__} along
@code{C.__mro__} in reverse order.
@end deffn

@geindex get_origin() (在 typing 模块中)
@anchor{library/typing typing get_origin}@anchor{243}
@deffn {函数} typing.get_origin (tp)
@end deffn

@geindex get_args() (在 typing 模块中)
@anchor{library/typing typing get_args}@anchor{244}
@deffn {函数} typing.get_args (tp)

Provide basic introspection for generic types and special typing forms.

For a typing object of the form @code{X[Y, Z, ...]} these functions return
@code{X} and @code{(Y, Z, ...)}. If @code{X} is a generic alias for a builtin or
@ref{1e,,collections} class, it gets normalized to the original class.
For unsupported objects return @code{None} and @code{()} correspondingly.
Examples:

@example
assert get_origin(Dict[str, int]) is dict
assert get_args(Dict[int, str]) == (int, str)

assert get_origin(Union[int, str]) is Union
assert get_args(Union[int, str]) == (int, str)
@end example


3.8 新版功能.

@end deffn

@geindex overload() (在 typing 模块中)
@anchor{library/typing typing overload}@anchor{3247}
@deffn {函数} @@typing.overload

The @code{@@overload} decorator allows describing functions and methods
that support multiple different combinations of argument types. A series
of @code{@@overload}-decorated definitions must be followed by exactly one
non-@code{@@overload}-decorated definition (for the same function/method).
The @code{@@overload}-decorated definitions are for the benefit of the
type checker only, since they will be overwritten by the
non-@code{@@overload}-decorated definition, while the latter is used at
runtime but should be ignored by a type checker.  At runtime, calling
a @code{@@overload}-decorated function directly will raise
@ref{609,,NotImplementedError}. An example of overload that gives a more
precise type than can be expressed using a union or a type variable:

@example
@@overload
def process(response: None) -> None:
    ...
@@overload
def process(response: int) -> Tuple[int, str]:
    ...
@@overload
def process(response: bytes) -> str:
    ...
def process(response):
    <actual implementation>
@end example

See 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} for details and comparison with other typing semantics.
@end deffn

@geindex final() (在 typing 模块中)
@anchor{library/typing typing final}@anchor{23e}
@deffn {函数} @@typing.final

A decorator to indicate to type checkers that the decorated method
cannot be overridden, and the decorated class cannot be subclassed.
For example:

@example
class Base:
    @@final
    def done(self) -> None:
        ...
class Sub(Base):
    def done(self) -> None:  # Error reported by type checker
          ...

@@final
class Leaf:
    ...
class Other(Leaf):  # Error reported by type checker
    ...
@end example

There is no runtime checking of these properties. See 
@geindex Python 提高建议; PEP 591
PEP 591@footnote{https://www.python.org/dev/peps/pep-0591} for
more details.


3.8 新版功能.

@end deffn

@geindex no_type_check() (在 typing 模块中)
@anchor{library/typing typing no_type_check}@anchor{3248}
@deffn {函数} @@typing.no_type_check

用于指明标注不是类型提示的装饰器。

此 @ref{283,,decorator} 装饰器生效于类或函数上。如果作用于类上的话，它会递归地作用于这个类的所定义的所有方法上（但是对于超类或子类所定义的方法不会生效）。

此方法会就地地修改函数。
@end deffn

@geindex no_type_check_decorator() (在 typing 模块中)
@anchor{library/typing typing no_type_check_decorator}@anchor{3249}
@deffn {函数} @@typing.no_type_check_decorator

使其它装饰器起到 @ref{3248,,no_type_check()} 效果的装饰器。

This wraps the decorator with something that wraps the decorated
function in @ref{3248,,no_type_check()}.
@end deffn

@geindex type_check_only() (在 typing 模块中)
@anchor{library/typing typing type_check_only}@anchor{324a}
@deffn {函数} @@typing.type_check_only

标记一个类或函数在运行时内不可用的装饰器。

This decorator is itself not available at runtime. It is mainly
intended to mark classes that are defined in type stub files if
an implementation returns an instance of a private class:

@example
@@type_check_only
class Response:  # private or not available at runtime
    code: int
    def get_header(self, name: str) -> str: ...

def fetch_response() -> Response: ...
@end example

Note that returning instances of private classes is not recommended.
It is usually preferable to make such classes public.
@end deffn

@geindex runtime_checkable() (在 typing 模块中)
@anchor{library/typing typing runtime_checkable}@anchor{240}
@deffn {函数} @@typing.runtime_checkable

Mark a protocol class as a runtime protocol.

Such a protocol can be used with @ref{449,,isinstance()} and @ref{44a,,issubclass()}.
This raises @ref{192,,TypeError} when applied to a non-protocol class.  This
allows a simple-minded structural check, very similar to "one trick ponies"
in @ref{1f,,collections.abc} such as @ref{3217,,Iterable}.  For example:

@example
@@runtime_checkable
class Closable(Protocol):
    def close(self): ...

assert isinstance(open('/some/file'), Closable)
@end example

@strong{Warning:} this will check only the presence of the required methods,
not their type signatures!


3.8 新版功能.

@end deffn

@geindex Any() (在 typing 模块中)
@anchor{library/typing typing Any}@anchor{64c}
@deffn {数据} typing.Any

特殊类型，表明类型没有任何限制。


@itemize *

@item 
每一个类型都对 @ref{64c,,Any} 兼容。

@item 
@ref{64c,,Any} 对每一个类型都兼容。
@end itemize
@end deffn

@geindex NoReturn() (在 typing 模块中)
@anchor{library/typing typing NoReturn}@anchor{324b}
@deffn {数据} typing.NoReturn

标记一个函数没有返回值的特殊类型。比如说:

@example
from typing import NoReturn

def stop() -> NoReturn:
    raise RuntimeError('no way')
@end example


3.5.4 新版功能.



3.6.2 新版功能.

@end deffn

@geindex Union() (在 typing 模块中)
@anchor{library/typing typing Union}@anchor{fc7}
@deffn {数据} typing.Union

联合类型； @code{Union[X, Y]} 意味着：要不是 X，要不是 Y。

使用形如 @code{Union[int, str]} 的形式来定义一个联合类型。细节如下:


@itemize *

@item 
参数必须是类型，而且必须至少有一个参数。

@item 
联合类型的联合类型会被展开打平，比如:

@example
Union[Union[int, str], float] == Union[int, str, float]
@end example

@item 
仅有一个参数的联合类型会坍缩成参数自身，比如:

@example
Union[int] == int  # The constructor actually returns int
@end example

@item 
多余的参数会被跳过，比如:

@example
Union[int, str, int] == Union[int, str]
@end example

@item 
在比较联合类型的时候，参数顺序会被忽略，比如:

@example
Union[int, str] == Union[str, int]
@end example

@item 
你不能继承或者实例化一个联合类型。

@item 
你不能写成 @code{Union[X][Y]} 。

@item 
你可以使用 @code{Optional[X]} 作为 @code{Union[X, None]} 的缩写。
@end itemize


在 3.7 版更改: 不要在运行时内从联合类型中移除显式说明的子类。

@end deffn

@geindex Optional() (在 typing 模块中)
@anchor{library/typing typing Optional}@anchor{324c}
@deffn {数据} typing.Optional

Optional type.

@code{Optional[X]} is equivalent to @code{Union[X, None]}.

Note that this is not the same concept as an optional argument,
which is one that has a default.  An optional argument with a
default does not require the @code{Optional} qualifier on its type
annotation just because it is optional. For example:

@example
def foo(arg: int = 0) -> None:
    ...
@end example

On the other hand, if an explicit value of @code{None} is allowed, the
use of @code{Optional} is appropriate, whether the argument is optional
or not. For example:

@example
def foo(arg: Optional[int] = None) -> None:
    ...
@end example
@end deffn

@geindex Tuple() (在 typing 模块中)
@anchor{library/typing typing Tuple}@anchor{320b}
@deffn {数据} typing.Tuple

Tuple type; @code{Tuple[X, Y]} is the type of a tuple of two items
with the first item of type X and the second of type Y. The type of
the empty tuple can be written as @code{Tuple[()]}.

Example: @code{Tuple[T1, T2]} is a tuple of two elements corresponding
to type variables T1 and T2.  @code{Tuple[int, float, str]} is a tuple
of an int, a float and a string.

To specify a variable-length tuple of homogeneous type,
use literal ellipsis, e.g. @code{Tuple[int, ...]}. A plain @ref{320b,,Tuple}
is equivalent to @code{Tuple[Any, ...]}, and in turn to @ref{478,,tuple}.
@end deffn

@geindex Callable() (在 typing 模块中)
@anchor{library/typing typing Callable}@anchor{320c}
@deffn {数据} typing.Callable

Callable type; @code{Callable[[int], str]} is a function of (int) -> str.

The subscription syntax must always be used with exactly two
values: the argument list and the return type.  The argument list
must be a list of types or an ellipsis; the return type must be
a single type.

There is no syntax to indicate optional or keyword arguments;
such function types are rarely used as callback types.
@code{Callable[..., ReturnType]} (literal ellipsis) can be used to
type hint a callable taking any number of arguments and returning
@code{ReturnType}.  A plain @ref{320c,,Callable} is equivalent to
@code{Callable[..., Any]}, and in turn to
@ref{18ea,,collections.abc.Callable}.
@end deffn

@geindex Literal() (在 typing 模块中)
@anchor{library/typing typing Literal}@anchor{23c}
@deffn {数据} typing.Literal

A type that can be used to indicate to type checkers that the
corresponding variable or function parameter has a value equivalent to
the provided literal (or one of several literals). For example:

@example
def validate_simple(data: Any) -> Literal[True]:  # always returns True
    ...

MODE = Literal['r', 'rb', 'w', 'wb']
def open_helper(file: str, mode: MODE) -> str:
    ...

open_helper('/some/path', 'r')  # Passes type check
open_helper('/other/path', 'typo')  # Error in type checker
@end example

@code{Literal[...]} cannot be subclassed. At runtime, an arbitrary value
is allowed as type argument to @code{Literal[...]}, but type checkers may
impose restrictions. See 
@geindex Python 提高建议; PEP 586
PEP 586@footnote{https://www.python.org/dev/peps/pep-0586} for more details about literal types.


3.8 新版功能.

@end deffn

@geindex ClassVar() (在 typing 模块中)
@anchor{library/typing typing ClassVar}@anchor{59e}
@deffn {数据} typing.ClassVar

Special type construct to mark class variables.

As introduced in 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526}, a variable annotation wrapped in ClassVar
indicates that a given attribute is intended to be used as a class variable
and should not be set on instances of that class. Usage:

@example
class Starship:
    stats: ClassVar[Dict[str, int]] = @{@} # class variable
    damage: int = 10                     # instance variable
@end example

@ref{59e,,ClassVar} accepts only types and cannot be further subscribed.

@ref{59e,,ClassVar} is not a class itself, and should not
be used with @ref{449,,isinstance()} or @ref{44a,,issubclass()}.
@ref{59e,,ClassVar} does not change Python runtime behavior, but
it can be used by third-party type checkers. For example, a type checker
might flag the following code as an error:

@example
enterprise_d = Starship(3000)
enterprise_d.stats = @{@} # Error, setting class variable on instance
Starship.stats = @{@}     # This is OK
@end example


3.5.3 新版功能.

@end deffn

@geindex Final() (在 typing 模块中)
@anchor{library/typing typing Final}@anchor{23d}
@deffn {数据} typing.Final

A special typing construct to indicate to type checkers that a name
cannot be re-assigned or overridden in a subclass. For example:

@example
MAX_SIZE: Final = 9000
MAX_SIZE += 1  # Error reported by type checker

class Connection:
    TIMEOUT: Final[int] = 10

class FastConnector(Connection):
    TIMEOUT = 1  # Error reported by type checker
@end example

There is no runtime checking of these properties. See 
@geindex Python 提高建议; PEP 591
PEP 591@footnote{https://www.python.org/dev/peps/pep-0591} for
more details.


3.8 新版功能.

@end deffn

@geindex AnyStr() (在 typing 模块中)
@anchor{library/typing typing AnyStr}@anchor{324d}
@deffn {数据} typing.AnyStr

@code{AnyStr} is a type variable defined as
@code{AnyStr = TypeVar('AnyStr', str, bytes)}.

It is meant to be used for functions that may accept any kind of string
without allowing different kinds of strings to mix. For example:

@example
def concat(a: AnyStr, b: AnyStr) -> AnyStr:
    return a + b

concat(u"foo", u"bar")  # Ok, output has type 'unicode'
concat(b"foo", b"bar")  # Ok, output has type 'bytes'
concat(u"foo", b"bar")  # Error, cannot mix unicode and bytes
@end example
@end deffn

@geindex TYPE_CHECKING() (在 typing 模块中)
@anchor{library/typing typing TYPE_CHECKING}@anchor{59f}
@deffn {数据} typing.TYPE_CHECKING

A special constant that is assumed to be @code{True} by 3rd party static
type checkers. It is @code{False} at runtime. Usage:

@example
if TYPE_CHECKING:
    import expensive_mod

def fun(arg: 'expensive_mod.SomeType') -> None:
    local_var: expensive_mod.AnotherType = other_fun()
@end example

Note that the first type annotation must be enclosed in quotes, making it a
"forward reference", to hide the @code{expensive_mod} reference from the
interpreter runtime.  Type annotations for local variables are not
evaluated, so the second annotation does not need to be enclosed in quotes.


3.5.2 新版功能.

@end deffn

@node pydoc --- 文档生成器和在线帮助系统,doctest --- 测试交互性的Python示例,typing --- 类型标注支持,开发工具
@anchor{library/pydoc doc}@anchor{324e}@anchor{library/pydoc module-pydoc}@anchor{d9}@anchor{library/pydoc pydoc-documentation-generator-and-online-help-system}@anchor{324f}
@subsection @code{pydoc} --- 文档生成器和在线帮助系统


@geindex pydoc (模块)

@strong{源代码:} Lib/pydoc.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pydoc.py}

@geindex documentation; generation
@geindex documentation; online
@geindex help; online


__________________________________________________________________


The @ref{d9,,pydoc} module automatically generates documentation from Python
modules.  The documentation can be presented as pages of text on the console,
served to a Web browser, or saved to HTML files.

对于模块、类、函数和方法，显示的文档内容取自文档字符串（即 @code{__doc__} 属性），并会递归地从其带文档的成员中获取。 如果没有文档字符串，@ref{d9,,pydoc} 会尝试从类、函数或方法定义上方，或是模块顶部的注释行段落获取 (参见 @ref{3250,,inspect.getcomments()}).

内置函数 @ref{56d,,help()} 会发起调用交互式解释器的在线帮助系统，该系统使用 @ref{d9,,pydoc} 在终端上生成文本形式的文档内容。 同样的文本文档也可以在 Python 解释器以外通过在操作系统的命令提示符下以脚本方式运行 @code{pydoc} 来查看。 例如，运行

@example
pydoc sys
@end example

在终端提示符下将通过 @ref{fd,,sys} 模块显示文档内容，其样式类似于 Unix @code{man} 命令所显示的指南页面。 @code{pydoc} 的参数可以为函数、模块、包，或带点号的对模块中的类、方法或函数以及包中的模块的引用。 如果传给 @code{pydoc} 的参数像是一个路径（即包含所在操作系统的路径分隔符，例如 Unix 的正斜杠），并且其指向一个现有的 Python 源文件，则会为该文件生成文档内容。

@cartouche
@quotation 注解 
为了找到对象及其文档内容，@ref{d9,,pydoc} 会导入文档所在的模块。 因此，任何模块层级的代码都将被执行。 请使用 @code{if __name__ == '__main__':} 语句来确保一个文件的特定代码仅在作为脚本被发起调用时执行而不是在被导入时执行。
@end quotation
@end cartouche

当打印输出到控制台时，@code{pydoc} 会尝试对输出进行分页以方便阅读。 如果设置了 
@geindex PAGER
@geindex 环境变量; PAGER
@code{PAGER} 环境变量，@code{pydoc} 将使用该变量值作为分页程序。

在参数前指定 @code{-w} 旗标将把 HTML 文档写入到当前目录下的一个文件中，而不是在控制台中显示文本。

在参数前指定 @code{-k} 旗标将在全部可用模块的提要行中搜索参数所给定的关键字，具体方式同样类似于 Unix @code{man} 命令。 模块的提要行就是其文档字符串的第一行。

你还可以使用 @code{pydoc} 在本机上启动一个 HTTP 服务，这将向来访的 Web 浏览器提供文档服务。 @code{pydoc -p 1234} 将在 1234 端口上启动 HTTP 服务，允许你在你喜欢的 Web 服务器中通过 @code{http://localhost:1234/} 浏览文档内容。 指定 @code{0} 作为端口号将会任意选择一个未使用的端口。

@code{pydoc -n <hostname>} 将启动在给定主机名上执行监听的服务。 默认主机名为 'localhost' 但如果你希望能从其他机器搜索该服务器，你可能会想要改变服务器所响应的主机名。 在开发阶段此特性会特别有用，因为这样你将能在一个容器中运行 pydoc。

@code{pydoc -b} 将启动服务并额外打开一个 Web 浏览器访问模块索引页。 所发布的每个页面顶端都带有导航栏，你可以点击 @emph{Get} 获取特定条目的帮助，点击 @emph{Search} 在所有模块的提要行中搜索特定关键词，或是点击 @emph{Module index}, @emph{Topics} 和 @emph{Keywords} 前往相应的页面。

当 @code{pydoc} 生成文档内容时，它会使用当前环境和路径来定位模块。 因此，发起调用 @code{pydoc spam} 得到的文档版本会与你启动 Python 解释器并输入 @code{import spam} 时得到的模块版本完全相同。

核心模块的模块文档位置对应于 @code{https://docs.python.org/X.Y/library/} 其中 @code{X} 和 @code{Y} 是 Python 解释器的主要版本号和小版本号。 这可通过设置 
@geindex PYTHONDOCS
@geindex 环境变量; PYTHONDOCS
@code{PYTHONDOCS} 环境变量来重载为指向不同的 URL 或包含 Library Reference Manual 页面的本地目录。


在 3.2 版更改: 添加 @code{-b} 选项。



在 3.3 版更改: 命令行选项 @code{-g} 已经移除。



在 3.4 版更改: @ref{d9,,pydoc} 现在会使用 @ref{556,,inspect.signature()} 而非 @ref{558,,inspect.getfullargspec()} 来从可调用对象中提取签名信息。



在 3.7 版更改: 添加 @code{-n} 选项。


@node doctest --- 测试交互性的Python示例,unittest --- 单元测试框架,pydoc --- 文档生成器和在线帮助系统,开发工具
@anchor{library/doctest doc}@anchor{3251}@anchor{library/doctest doctest-test-interactive-python-examples}@anchor{3252}@anchor{library/doctest module-doctest}@anchor{67}
@subsection @code{doctest} --- 测试交互性的Python示例


@geindex doctest (模块)

** 源代码 ** Lib/doctest.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/doctest.py}


__________________________________________________________________


@ref{67,,doctest} 模块寻找像Python交互式代码的文本，然后执行这些代码来确保它们的确就像展示的那样正确运行，有许多方法来使用doctest：


@itemize *

@item 
通过验证所有交互式示例仍然按照记录的方式工作，以此来检查模块的文档字符串是否是最新的。

@item 
To perform regression testing by verifying that interactive examples from a
test file or a test object work as expected.

@item 
To write tutorial documentation for a package, liberally illustrated with
input-output examples.  Depending on whether the examples or the expository text
are emphasized, this has the flavor of "literate testing" or "executable
documentation".
@end itemize

下面是一个小却完整的示例模块:

@example
"""
This is the "example" module.

The example module supplies one function, factorial().  For example,

>>> factorial(5)
120
"""

def factorial(n):
    """Return the factorial of n, an exact integer >= 0.

    >>> [factorial(n) for n in range(6)]
    [1, 1, 2, 6, 24, 120]
    >>> factorial(30)
    265252859812191058636308480000000
    >>> factorial(-1)
    Traceback (most recent call last):
        ...
    ValueError: n must be >= 0

    Factorials of floats are OK, but the float must be an exact integer:
    >>> factorial(30.1)
    Traceback (most recent call last):
        ...
    ValueError: n must be exact integer
    >>> factorial(30.0)
    265252859812191058636308480000000

    It must also not be ridiculously large:
    >>> factorial(1e100)
    Traceback (most recent call last):
        ...
    OverflowError: n too large
    """

    import math
    if not n >= 0:
        raise ValueError("n must be >= 0")
    if math.floor(n) != n:
        raise ValueError("n must be exact integer")
    if n+1 == n:  # catch a value like 1e300
        raise OverflowError("n too large")
    result = 1
    factor = 2
    while factor <= n:
        result *= factor
        factor += 1
    return result


if __name__ == "__main__":
    import doctest
    doctest.testmod()
@end example

如果你直接在命令行里运行 @code{example.py} ， @ref{67,,doctest} 将发挥它的作用。

@example
$ python example.py
$
@end example

There's no output!  That's normal, and it means all the examples worked.  Pass
@code{-v} to the script, and @ref{67,,doctest} prints a detailed log of what
it's trying, and prints a summary at the end:

@example
$ python example.py -v
Trying:
    factorial(5)
Expecting:
    120
ok
Trying:
    [factorial(n) for n in range(6)]
Expecting:
    [1, 1, 2, 6, 24, 120]
ok
@end example

And so on, eventually ending with:

@example
Trying:
    factorial(1e100)
Expecting:
    Traceback (most recent call last):
        ...
    OverflowError: n too large
ok
2 items passed all tests:
   1 tests in __main__
   8 tests in __main__.factorial
9 tests in 2 items.
9 passed and 0 failed.
Test passed.
$
@end example

That's all you need to know to start making productive use of @ref{67,,doctest}!
Jump in.  The following sections provide full details.  Note that there are many
examples of doctests in the standard Python test suite and libraries.
Especially useful examples can be found in the standard test file
@code{Lib/test/test_doctest.py}.

@menu
* 简单用法：检查Docstrings中的示例:: 
* Simple Usage; Checking Examples in a Text File: Simple Usage Checking Examples in a Text File. 
* How It Works:: 
* Basic API:: 
* Unittest API:: 
* Advanced API:: 
* 调试:: 
* Soapbox:: 

@end menu

@node 简单用法：检查Docstrings中的示例,Simple Usage Checking Examples in a Text File,,doctest --- 测试交互性的Python示例
@anchor{library/doctest doctest-simple-testmod}@anchor{3253}@anchor{library/doctest simple-usage-checking-examples-in-docstrings}@anchor{3254}
@subsubsection 简单用法：检查Docstrings中的示例


开始使用doctest的最简单方法（但不一定是你将继续这样做的方式）是结束每个模块 @code{M} 使用:

@example
if __name__ == "__main__":
    import doctest
    doctest.testmod()
@end example

@ref{67,,doctest} then examines docstrings in module @code{M}.

Running the module as a script causes the examples in the docstrings to get
executed and verified:

@example
python M.py
@end example

This won't display anything unless an example fails, in which case the failing
example(s) and the cause(s) of the failure(s) are printed to stdout, and the
final line of output is @code{***Test Failed*** N failures.}, where @emph{N} is the
number of examples that failed.

Run it with the @code{-v} switch instead:

@example
python M.py -v
@end example

and a detailed report of all examples tried is printed to standard output, along
with assorted summaries at the end.

You can force verbose mode by passing @code{verbose=True} to @ref{dc9,,testmod()}, or
prohibit it by passing @code{verbose=False}.  In either of those cases,
@code{sys.argv} is not examined by @ref{dc9,,testmod()} (so passing @code{-v} or not
has no effect).

There is also a command line shortcut for running @ref{dc9,,testmod()}.  You can
instruct the Python interpreter to run the doctest module directly from the
standard library and pass the module name(s) on the command line:

@example
python -m doctest -v example.py
@end example

This will import @code{example.py} as a standalone module and run
@ref{dc9,,testmod()} on it.  Note that this may not work correctly if the file is
part of a package and imports other submodules from that package.

For more information on @ref{dc9,,testmod()}, see section @ref{3255,,Basic API}.

@node Simple Usage Checking Examples in a Text File,How It Works,简单用法：检查Docstrings中的示例,doctest --- 测试交互性的Python示例
@anchor{library/doctest doctest-simple-testfile}@anchor{3256}@anchor{library/doctest simple-usage-checking-examples-in-a-text-file}@anchor{3257}
@subsubsection Simple Usage: Checking Examples in a Text File


Another simple application of doctest is testing interactive examples in a text
file.  This can be done with the @ref{3258,,testfile()} function:

@example
import doctest
doctest.testfile("example.txt")
@end example

That short script executes and verifies any interactive Python examples
contained in the file @code{example.txt}.  The file content is treated as if it
were a single giant docstring; the file doesn't need to contain a Python
program!   For example, perhaps @code{example.txt} contains this:

@example
The `@w{`}example`@w{`} module
======================

Using `@w{`}factorial`@w{`}
-------------------

This is an example text file in reStructuredText format.  First import
`@w{`}factorial`@w{`} from the `@w{`}example`@w{`} module:

    >>> from example import factorial

Now use it:

    >>> factorial(6)
    120
@end example

Running @code{doctest.testfile("example.txt")} then finds the error in this
documentation:

@example
File "./example.txt", line 14, in example.txt
Failed example:
    factorial(6)
Expected:
    120
Got:
    720
@end example

As with @ref{dc9,,testmod()}, @ref{3258,,testfile()} won't display anything unless an
example fails.  If an example does fail, then the failing example(s) and the
cause(s) of the failure(s) are printed to stdout, using the same format as
@ref{dc9,,testmod()}.

By default, @ref{3258,,testfile()} looks for files in the calling module's directory.
See section @ref{3255,,Basic API} for a description of the optional arguments
that can be used to tell it to look for files in other locations.

Like @ref{dc9,,testmod()}, @ref{3258,,testfile()}'s verbosity can be set with the
@code{-v} command-line switch or with the optional keyword argument
@emph{verbose}.

There is also a command line shortcut for running @ref{3258,,testfile()}.  You can
instruct the Python interpreter to run the doctest module directly from the
standard library and pass the file name(s) on the command line:

@example
python -m doctest -v example.txt
@end example

Because the file name does not end with @code{.py}, @ref{67,,doctest} infers that
it must be run with @ref{3258,,testfile()}, not @ref{dc9,,testmod()}.

For more information on @ref{3258,,testfile()}, see section @ref{3255,,Basic API}.

@node How It Works,Basic API,Simple Usage Checking Examples in a Text File,doctest --- 测试交互性的Python示例
@anchor{library/doctest doctest-how-it-works}@anchor{3259}@anchor{library/doctest how-it-works}@anchor{325a}
@subsubsection How It Works


This section examines in detail how doctest works: which docstrings it looks at,
how it finds interactive examples, what execution context it uses, how it
handles exceptions, and how option flags can be used to control its behavior.
This is the information that you need to know to write doctest examples; for
information about actually running doctest on these examples, see the following
sections.

@menu
* Which Docstrings Are Examined?:: 
* How are Docstring Examples Recognized?:: 
* What's the Execution Context?:: 
* What About Exceptions?:: 
* Option Flags:: 
* Directives:: 
* 警告: 警告<2>. 

@end menu

@node Which Docstrings Are Examined?,How are Docstring Examples Recognized?,,How It Works
@anchor{library/doctest doctest-which-docstrings}@anchor{325b}@anchor{library/doctest which-docstrings-are-examined}@anchor{325c}
@subsubsection Which Docstrings Are Examined?


The module docstring, and all function, class and method docstrings are
searched.  Objects imported into the module are not searched.

In addition, if @code{M.__test__} exists and "is true", it must be a dict, and each
entry maps a (string) name to a function object, class object, or string.
Function and class object docstrings found from @code{M.__test__} are searched, and
strings are treated as if they were docstrings.  In output, a key @code{K} in
@code{M.__test__} appears with name

@example
<name of M>.__test__.K
@end example

Any classes found are recursively searched similarly, to test docstrings in
their contained methods and nested classes.

@strong{CPython implementation detail:} Prior to version 3.4, extension modules written in C were not fully
searched by doctest.

@node How are Docstring Examples Recognized?,What's the Execution Context?,Which Docstrings Are Examined?,How It Works
@anchor{library/doctest doctest-finding-examples}@anchor{325d}@anchor{library/doctest how-are-docstring-examples-recognized}@anchor{325e}
@subsubsection How are Docstring Examples Recognized?


In most cases a copy-and-paste of an interactive console session works fine,
but doctest isn't trying to do an exact emulation of any specific Python shell.

@example
>>> # comments are ignored
>>> x = 12
>>> x
12
>>> if x == 13:
...     print("yes")
... else:
...     print("no")
...     print("NO")
...     print("NO!!!")
...
no
NO
NO!!!
>>>
@end example

@geindex >>>; interpreter prompt
@geindex ...; interpreter prompt

Any expected output must immediately follow the final @code{'>>> '} or @code{'... '}
line containing the code, and the expected output (if any) extends to the next
@code{'>>> '} or all-whitespace line.

The fine print:


@itemize *

@item 
Expected output cannot contain an all-whitespace line, since such a line is
taken to signal the end of expected output.  If expected output does contain a
blank line, put @code{<BLANKLINE>} in your doctest example each place a blank line
is expected.

@item 
All hard tab characters are expanded to spaces, using 8-column tab stops.
Tabs in output generated by the tested code are not modified.  Because any
hard tabs in the sample output @emph{are} expanded, this means that if the code
output includes hard tabs, the only way the doctest can pass is if the
@ref{325f,,NORMALIZE_WHITESPACE} option or @ref{3260,,directive}
is in effect.
Alternatively, the test can be rewritten to capture the output and compare it
to an expected value as part of the test.  This handling of tabs in the
source was arrived at through trial and error, and has proven to be the least
error prone way of handling them.  It is possible to use a different
algorithm for handling tabs by writing a custom @ref{3261,,DocTestParser} class.

@item 
Output to stdout is captured, but not output to stderr (exception tracebacks
are captured via a different means).

@item 
If you continue a line via backslashing in an interactive session, or for any
other reason use a backslash, you should use a raw docstring, which will
preserve your backslashes exactly as you type them:

@example
>>> def f(x):
...     r'@w{'}'Backslashes in a raw docstring: m\n'@w{'}'
>>> print(f.__doc__)
Backslashes in a raw docstring: m\n
@end example

Otherwise, the backslash will be interpreted as part of the string. For example,
the @code{\n} above would be interpreted as a newline character.  Alternatively, you
can double each backslash in the doctest version (and not use a raw string):

@example
>>> def f(x):
...     '@w{'}'Backslashes in a raw docstring: m\\n'@w{'}'
>>> print(f.__doc__)
Backslashes in a raw docstring: m\n
@end example

@item 
The starting column doesn't matter:

@example
>>> assert "Easy!"
      >>> import math
          >>> math.floor(1.9)
          1
@end example

and as many leading whitespace characters are stripped from the expected output
as appeared in the initial @code{'>>> '} line that started the example.
@end itemize

@node What's the Execution Context?,What About Exceptions?,How are Docstring Examples Recognized?,How It Works
@anchor{library/doctest doctest-execution-context}@anchor{3262}@anchor{library/doctest what-s-the-execution-context}@anchor{3263}
@subsubsection What's the Execution Context?


By default, each time @ref{67,,doctest} finds a docstring to test, it uses a
@emph{shallow copy} of @code{M}'s globals, so that running tests doesn't change the
module's real globals, and so that one test in @code{M} can't leave behind
crumbs that accidentally allow another test to work.  This means examples can
freely use any names defined at top-level in @code{M}, and names defined earlier
in the docstring being run. Examples cannot see names defined in other
docstrings.

You can force use of your own dict as the execution context by passing
@code{globs=your_dict} to @ref{dc9,,testmod()} or @ref{3258,,testfile()} instead.

@node What About Exceptions?,Option Flags,What's the Execution Context?,How It Works
@anchor{library/doctest doctest-exceptions}@anchor{3264}@anchor{library/doctest what-about-exceptions}@anchor{3265}
@subsubsection What About Exceptions?


No problem, provided that the traceback is the only output produced by the
example:  just paste in the traceback. @footnote{@w{(1)} 
Examples containing both expected output and an exception are not supported.
Trying to guess where one ends and the other begins is too error-prone, and that
also makes for a confusing test.
} Since tracebacks contain details
that are likely to change rapidly (for example, exact file paths and line
numbers), this is one case where doctest works hard to be flexible in what it
accepts.

Simple example:

@example
>>> [1, 2, 3].remove(42)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: list.remove(x): x not in list
@end example

That doctest succeeds if @ref{1fb,,ValueError} is raised, with the @code{list.remove(x):
x not in list} detail as shown.

The expected output for an exception must start with a traceback header, which
may be either of the following two lines, indented the same as the first line of
the example:

@example
Traceback (most recent call last):
Traceback (innermost last):
@end example

The traceback header is followed by an optional traceback stack, whose contents
are ignored by doctest.  The traceback stack is typically omitted, or copied
verbatim from an interactive session.

The traceback stack is followed by the most interesting part: the line(s)
containing the exception type and detail.  This is usually the last line of a
traceback, but can extend across multiple lines if the exception has a
multi-line detail:

@example
>>> raise ValueError('multi\n    line\ndetail')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: multi
    line
detail
@end example

The last three lines (starting with @ref{1fb,,ValueError}) are compared against the
exception's type and detail, and the rest are ignored.

Best practice is to omit the traceback stack, unless it adds significant
documentation value to the example.  So the last example is probably better as:

@example
>>> raise ValueError('multi\n    line\ndetail')
Traceback (most recent call last):
    ...
ValueError: multi
    line
detail
@end example

Note that tracebacks are treated very specially.  In particular, in the
rewritten example, the use of @code{...} is independent of doctest's
@ref{dca,,ELLIPSIS} option.  The ellipsis in that example could be left out, or
could just as well be three (or three hundred) commas or digits, or an indented
transcript of a Monty Python skit.

Some details you should read once, but won't need to remember:


@itemize *

@item 
Doctest can't guess whether your expected output came from an exception
traceback or from ordinary printing.  So, e.g., an example that expects
@code{ValueError: 42 is prime} will pass whether @ref{1fb,,ValueError} is actually
raised or if the example merely prints that traceback text.  In practice,
ordinary output rarely begins with a traceback header line, so this doesn't
create real problems.

@item 
Each line of the traceback stack (if present) must be indented further than
the first line of the example, @emph{or} start with a non-alphanumeric character.
The first line following the traceback header indented the same and starting
with an alphanumeric is taken to be the start of the exception detail.  Of
course this does the right thing for genuine tracebacks.

@item 
When the @ref{3266,,IGNORE_EXCEPTION_DETAIL} doctest option is specified,
everything following the leftmost colon and any module information in the
exception name is ignored.

@item 
The interactive shell omits the traceback header line for some
@ref{452,,SyntaxError}s.  But doctest uses the traceback header line to
distinguish exceptions from non-exceptions.  So in the rare case where you need
to test a @ref{452,,SyntaxError} that omits the traceback header, you will need to
manually add the traceback header line to your test example.
@end itemize

@geindex ^ (caret); marker


@itemize *

@item 
For some @ref{452,,SyntaxError}s, Python displays the character position of the
syntax error, using a @code{^} marker:

@example
>>> 1 1
  File "<stdin>", line 1
    1 1
      ^
SyntaxError: invalid syntax
@end example

Since the lines showing the position of the error come before the exception type
and detail, they are not checked by doctest.  For example, the following test
would pass, even though it puts the @code{^} marker in the wrong location:

@example
>>> 1 1
Traceback (most recent call last):
  File "<stdin>", line 1
    1 1
    ^
SyntaxError: invalid syntax
@end example
@end itemize
@anchor{library/doctest option-flags-and-directives}@anchor{3267}
@node Option Flags,Directives,What About Exceptions?,How It Works
@anchor{library/doctest doctest-options}@anchor{836}@anchor{library/doctest option-flags}@anchor{3268}
@subsubsection Option Flags


A number of option flags control various aspects of doctest's behavior.
Symbolic names for the flags are supplied as module constants, which can be
@ref{14d6,,bitwise ORed} together and passed to various functions.
The names can also be used in @ref{3260,,doctest directives},
and may be passed to the doctest command line interface via the @code{-o} option.


3.4 新版功能: The @code{-o} command line option.


The first group of options define test semantics, controlling aspects of how
doctest decides whether actual output matches an example's expected output:

@geindex DONT_ACCEPT_TRUE_FOR_1() (在 doctest 模块中)
@anchor{library/doctest doctest DONT_ACCEPT_TRUE_FOR_1}@anchor{3269}
@deffn {数据} doctest.DONT_ACCEPT_TRUE_FOR_1

By default, if an expected output block contains just @code{1}, an actual output
block containing just @code{1} or just @code{True} is considered to be a match, and
similarly for @code{0} versus @code{False}.  When @ref{3269,,DONT_ACCEPT_TRUE_FOR_1} is
specified, neither substitution is allowed.  The default behavior caters to that
Python changed the return type of many functions from integer to boolean;
doctests expecting "little integer" output still work in these cases.  This
option will probably go away, but not for several years.
@end deffn

@geindex <BLANKLINE>

@geindex DONT_ACCEPT_BLANKLINE() (在 doctest 模块中)
@anchor{library/doctest doctest DONT_ACCEPT_BLANKLINE}@anchor{326a}
@deffn {数据} doctest.DONT_ACCEPT_BLANKLINE

By default, if an expected output block contains a line containing only the
string @code{<BLANKLINE>}, then that line will match a blank line in the actual
output.  Because a genuinely blank line delimits the expected output, this is
the only way to communicate that a blank line is expected.  When
@ref{326a,,DONT_ACCEPT_BLANKLINE} is specified, this substitution is not allowed.
@end deffn

@geindex NORMALIZE_WHITESPACE() (在 doctest 模块中)
@anchor{library/doctest doctest NORMALIZE_WHITESPACE}@anchor{325f}
@deffn {数据} doctest.NORMALIZE_WHITESPACE

When specified, all sequences of whitespace (blanks and newlines) are treated as
equal.  Any sequence of whitespace within the expected output will match any
sequence of whitespace within the actual output. By default, whitespace must
match exactly. @ref{325f,,NORMALIZE_WHITESPACE} is especially useful when a line of
expected output is very long, and you want to wrap it across multiple lines in
your source.
@end deffn

@geindex ...; in doctests

@geindex ELLIPSIS() (在 doctest 模块中)
@anchor{library/doctest doctest ELLIPSIS}@anchor{dca}
@deffn {数据} doctest.ELLIPSIS

When specified, an ellipsis marker (@code{...}) in the expected output can match
any substring in the actual output.  This includes substrings that span line
boundaries, and empty substrings, so it's best to keep usage of this simple.
Complicated uses can lead to the same kinds of "oops, it matched too much!"
surprises that @code{.*} is prone to in regular expressions.
@end deffn

@geindex IGNORE_EXCEPTION_DETAIL() (在 doctest 模块中)
@anchor{library/doctest doctest IGNORE_EXCEPTION_DETAIL}@anchor{3266}
@deffn {数据} doctest.IGNORE_EXCEPTION_DETAIL

When specified, an example that expects an exception passes if an exception of
the expected type is raised, even if the exception detail does not match.  For
example, an example expecting @code{ValueError: 42} will pass if the actual
exception raised is @code{ValueError: 3*14}, but will fail, e.g., if
@ref{192,,TypeError} is raised.

It will also ignore the module name used in Python 3 doctest reports. Hence
both of these variations will work with the flag specified, regardless of
whether the test is run under Python 2.7 or Python 3.2 (or later versions):

@example
>>> raise CustomError('message')
Traceback (most recent call last):
CustomError: message

>>> raise CustomError('message')
Traceback (most recent call last):
my_module.CustomError: message
@end example

Note that @ref{dca,,ELLIPSIS} can also be used to ignore the
details of the exception message, but such a test may still fail based
on whether or not the module details are printed as part of the
exception name. Using @ref{3266,,IGNORE_EXCEPTION_DETAIL} and the details
from Python 2.3 is also the only clear way to write a doctest that doesn't
care about the exception detail yet continues to pass under Python 2.3 or
earlier (those releases do not support @ref{3260,,doctest directives} and ignore them as irrelevant comments). For example:

@example
>>> (1, 2)[3] = 'moo'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: object doesn't support item assignment
@end example

passes under Python 2.3 and later Python versions with the flag specified,
even though the detail
changed in Python 2.4 to say "does not" instead of "doesn't".


在 3.2 版更改: @ref{3266,,IGNORE_EXCEPTION_DETAIL} now also ignores any information relating
to the module containing the exception under test.

@end deffn

@geindex SKIP() (在 doctest 模块中)
@anchor{library/doctest doctest SKIP}@anchor{326b}
@deffn {数据} doctest.SKIP

When specified, do not run the example at all.  This can be useful in contexts
where doctest examples serve as both documentation and test cases, and an
example should be included for documentation purposes, but should not be
checked.  E.g., the example's output might be random; or the example might
depend on resources which would be unavailable to the test driver.

The SKIP flag can also be used for temporarily "commenting out" examples.
@end deffn

@geindex COMPARISON_FLAGS() (在 doctest 模块中)
@anchor{library/doctest doctest COMPARISON_FLAGS}@anchor{326c}
@deffn {数据} doctest.COMPARISON_FLAGS

A bitmask or'ing together all the comparison flags above.
@end deffn

The second group of options controls how test failures are reported:

@geindex REPORT_UDIFF() (在 doctest 模块中)
@anchor{library/doctest doctest REPORT_UDIFF}@anchor{dcb}
@deffn {数据} doctest.REPORT_UDIFF

When specified, failures that involve multi-line expected and actual outputs are
displayed using a unified diff.
@end deffn

@geindex REPORT_CDIFF() (在 doctest 模块中)
@anchor{library/doctest doctest REPORT_CDIFF}@anchor{dcc}
@deffn {数据} doctest.REPORT_CDIFF

When specified, failures that involve multi-line expected and actual outputs
will be displayed using a context diff.
@end deffn

@geindex REPORT_NDIFF() (在 doctest 模块中)
@anchor{library/doctest doctest REPORT_NDIFF}@anchor{dcd}
@deffn {数据} doctest.REPORT_NDIFF

When specified, differences are computed by @code{difflib.Differ}, using the same
algorithm as the popular @code{ndiff.py} utility. This is the only method that
marks differences within lines as well as across lines.  For example, if a line
of expected output contains digit @code{1} where actual output contains letter
@code{l}, a line is inserted with a caret marking the mismatching column positions.
@end deffn

@geindex REPORT_ONLY_FIRST_FAILURE() (在 doctest 模块中)
@anchor{library/doctest doctest REPORT_ONLY_FIRST_FAILURE}@anchor{326d}
@deffn {数据} doctest.REPORT_ONLY_FIRST_FAILURE

When specified, display the first failing example in each doctest, but suppress
output for all remaining examples.  This will prevent doctest from reporting
correct examples that break because of earlier failures; but it might also hide
incorrect examples that fail independently of the first failure.  When
@ref{326d,,REPORT_ONLY_FIRST_FAILURE} is specified, the remaining examples are
still run, and still count towards the total number of failures reported; only
the output is suppressed.
@end deffn

@geindex FAIL_FAST() (在 doctest 模块中)
@anchor{library/doctest doctest FAIL_FAST}@anchor{837}
@deffn {数据} doctest.FAIL_FAST

When specified, exit after the first failing example and don't attempt to run
the remaining examples. Thus, the number of failures reported will be at most
1.  This flag may be useful during debugging, since examples after the first
failure won't even produce debugging output.

The doctest command line accepts the option @code{-f} as a shorthand for @code{-o
FAIL_FAST}.


3.4 新版功能.

@end deffn

@geindex REPORTING_FLAGS() (在 doctest 模块中)
@anchor{library/doctest doctest REPORTING_FLAGS}@anchor{326e}
@deffn {数据} doctest.REPORTING_FLAGS

A bitmask or'ing together all the reporting flags above.
@end deffn

There is also a way to register new option flag names, though this isn't
useful unless you intend to extend @ref{67,,doctest} internals via subclassing:

@geindex register_optionflag() (在 doctest 模块中)
@anchor{library/doctest doctest register_optionflag}@anchor{326f}
@deffn {函数} doctest.register_optionflag (name)

Create a new option flag with a given name, and return the new flag's integer
value.  @ref{326f,,register_optionflag()} can be used when subclassing
@ref{3270,,OutputChecker} or @ref{3271,,DocTestRunner} to create new options that are
supported by your subclasses.  @ref{326f,,register_optionflag()} should always be
called using the following idiom:

@example
MY_FLAG = register_optionflag('MY_FLAG')
@end example
@end deffn

@geindex # (hash); in doctests
@geindex + (plus); in doctests
@geindex - (minus); in doctests

@node Directives,警告<2>,Option Flags,How It Works
@anchor{library/doctest directives}@anchor{3272}@anchor{library/doctest doctest-directives}@anchor{3260}
@subsubsection Directives


Doctest directives may be used to modify the @ref{836,,option flags} for an individual example.  Doctest directives are
special Python comments following an example's source code:

@example
@anchor{library/doctest grammar-token-directive}@anchor{3273}directive             ::= "#" "doctest:" directive_options
@anchor{library/doctest grammar-token-directive-options}@anchor{3274}directive_options     ::= directive_option ("," directive_option)\*
@anchor{library/doctest grammar-token-directive-option}@anchor{3275}directive_option      ::= on_or_off directive_option_name
@anchor{library/doctest grammar-token-on-or-off}@anchor{3276}on_or_off             ::= "+" \| "-"
@anchor{library/doctest grammar-token-directive-option-name}@anchor{3277}directive_option_name ::= "DONT_ACCEPT_BLANKLINE" \| "NORMALIZE_WHITESPACE" \| ...
@end example

Whitespace is not allowed between the @code{+} or @code{-} and the directive option
name.  The directive option name can be any of the option flag names explained
above.

An example's doctest directives modify doctest's behavior for that single
example.  Use @code{+} to enable the named behavior, or @code{-} to disable it.

For example, this test passes:

@example
>>> print(list(range(20))) 
[0,   1,  2,  3,  4,  5,  6,  7,  8,  9,
10,  11, 12, 13, 14, 15, 16, 17, 18, 19]
@end example

Without the directive it would fail, both because the actual output doesn't have
two blanks before the single-digit list elements, and because the actual output
is on a single line.  This test also passes, and also requires a directive to do
so:

@example
>>> print(list(range(20))) 
[0, 1, ..., 18, 19]
@end example

Multiple directives can be used on a single physical line, separated by
commas:

@example
>>> print(list(range(20))) 
[0,    1, ...,   18,    19]
@end example

If multiple directive comments are used for a single example, then they are
combined:

@example
>>> print(list(range(20))) 
...                        
[0,    1, ...,   18,    19]
@end example

As the previous example shows, you can add @code{...} lines to your example
containing only directives.  This can be useful when an example is too long for
a directive to comfortably fit on the same line:

@example
>>> print(list(range(5)) + list(range(10, 20)) + list(range(30, 40)))
... 
[0, ..., 4, 10, ..., 19, 30, ..., 39]
@end example

Note that since all options are disabled by default, and directives apply only
to the example they appear in, enabling options (via @code{+} in a directive) is
usually the only meaningful choice.  However, option flags can also be passed to
functions that run doctests, establishing different defaults.  In such cases,
disabling an option via @code{-} in a directive can be useful.

@node 警告<2>,,Directives,How It Works
@anchor{library/doctest doctest-warnings}@anchor{3278}@anchor{library/doctest warnings}@anchor{3279}
@subsubsection 警告


@ref{67,,doctest} is serious about requiring exact matches in expected output.  If
even a single character doesn't match, the test fails.  This will probably
surprise you a few times, as you learn exactly what Python does and doesn't
guarantee about output.  For example, when printing a set, Python doesn't
guarantee that the element is printed in any particular order, so a test like

@example
>>> foo()
@{"Hermione", "Harry"@}
@end example

is vulnerable!  One workaround is to do

@example
>>> foo() == @{"Hermione", "Harry"@}
True
@end example

instead.  Another is to do

@example
>>> d = sorted(foo())
>>> d
['Harry', 'Hermione']
@end example

@cartouche
@quotation 注解 
Before Python 3.6, when printing a dict, Python did not guarantee that
the key-value pairs was printed in any particular order.
@end quotation
@end cartouche

There are others, but you get the idea.

Another bad idea is to print things that embed an object address, like

@example
>>> id(1.0) # certain to fail some of the time
7948648
>>> class C: pass
>>> C()   # the default repr() for instances embeds an address
<__main__.C instance at 0x00AC18F0>
@end example

The @ref{dca,,ELLIPSIS} directive gives a nice approach for the last example:

@example
>>> C() 
<__main__.C instance at 0x...>
@end example

Floating-point numbers are also subject to small output variations across
platforms, because Python defers to the platform C library for float formatting,
and C libraries vary widely in quality here.

@example
>>> 1./7  # risky
0.14285714285714285
>>> print(1./7) # safer
0.142857142857
>>> print(round(1./7, 6)) # much safer
0.142857
@end example

Numbers of the form @code{I/2.**J} are safe across all platforms, and I often
contrive doctest examples to produce numbers of that form:

@example
>>> 3./4  # utterly safe
0.75
@end example

Simple fractions are also easier for people to understand, and that makes for
better documentation.

@node Basic API,Unittest API,How It Works,doctest --- 测试交互性的Python示例
@anchor{library/doctest basic-api}@anchor{327a}@anchor{library/doctest doctest-basic-api}@anchor{3255}
@subsubsection Basic API


The functions @ref{dc9,,testmod()} and @ref{3258,,testfile()} provide a simple interface to
doctest that should be sufficient for most basic uses.  For a less formal
introduction to these two functions, see sections @ref{3253,,简单用法：检查Docstrings中的示例}
and @ref{3256,,Simple Usage; Checking Examples in a Text File}.

@geindex testfile() (在 doctest 模块中)
@anchor{library/doctest doctest testfile}@anchor{3258}
@deffn {函数} doctest.testfile (filename, module_relative=True, name=None, package=None, globs=None, verbose=None, report=True, optionflags=0, extraglobs=None, raise_on_error=False, parser=DocTestParser(), encoding=None)

All arguments except @emph{filename} are optional, and should be specified in keyword
form.

Test examples in the file named @emph{filename}.  Return @code{(failure_count,
test_count)}.

Optional argument @emph{module_relative} specifies how the filename should be
interpreted:


@itemize *

@item 
If @emph{module_relative} is @code{True} (the default), then @emph{filename} specifies an
OS-independent module-relative path.  By default, this path is relative to the
calling module's directory; but if the @emph{package} argument is specified, then it
is relative to that package.  To ensure OS-independence, @emph{filename} should use
@code{/} characters to separate path segments, and may not be an absolute path
(i.e., it may not begin with @code{/}).

@item 
If @emph{module_relative} is @code{False}, then @emph{filename} specifies an OS-specific
path.  The path may be absolute or relative; relative paths are resolved with
respect to the current working directory.
@end itemize

Optional argument @emph{name} gives the name of the test; by default, or if @code{None},
@code{os.path.basename(filename)} is used.

Optional argument @emph{package} is a Python package or the name of a Python package
whose directory should be used as the base directory for a module-relative
filename.  If no package is specified, then the calling module's directory is
used as the base directory for module-relative filenames.  It is an error to
specify @emph{package} if @emph{module_relative} is @code{False}.

Optional argument @emph{globs} gives a dict to be used as the globals when executing
examples.  A new shallow copy of this dict is created for the doctest, so its
examples start with a clean slate. By default, or if @code{None}, a new empty dict
is used.

Optional argument @emph{extraglobs} gives a dict merged into the globals used to
execute examples.  This works like @ref{dc2,,dict.update()}:  if @emph{globs} and
@emph{extraglobs} have a common key, the associated value in @emph{extraglobs} appears in
the combined dict.  By default, or if @code{None}, no extra globals are used.  This
is an advanced feature that allows parameterization of doctests.  For example, a
doctest can be written for a base class, using a generic name for the class,
then reused to test any number of subclasses by passing an @emph{extraglobs} dict
mapping the generic name to the subclass to be tested.

Optional argument @emph{verbose} prints lots of stuff if true, and prints only
failures if false; by default, or if @code{None}, it's true if and only if @code{'-v'}
is in @code{sys.argv}.

Optional argument @emph{report} prints a summary at the end when true, else prints
nothing at the end.  In verbose mode, the summary is detailed, else the summary
is very brief (in fact, empty if all tests passed).

Optional argument @emph{optionflags} (default value 0) takes the
@ref{14d6,,bitwise OR} of option flags.
See section @ref{836,,Option Flags}.

Optional argument @emph{raise_on_error} defaults to false.  If true, an exception is
raised upon the first failure or unexpected exception in an example.  This
allows failures to be post-mortem debugged. Default behavior is to continue
running examples.

Optional argument @emph{parser} specifies a @ref{3261,,DocTestParser} (or subclass) that
should be used to extract tests from the files.  It defaults to a normal parser
(i.e., @code{DocTestParser()}).

Optional argument @emph{encoding} specifies an encoding that should be used to
convert the file to unicode.
@end deffn

@geindex testmod() (在 doctest 模块中)
@anchor{library/doctest doctest testmod}@anchor{dc9}
@deffn {函数} doctest.testmod (m=None, name=None, globs=None, verbose=None, report=True, optionflags=0, extraglobs=None, raise_on_error=False, exclude_empty=False)

All arguments are optional, and all except for @emph{m} should be specified in
keyword form.

Test examples in docstrings in functions and classes reachable from module @emph{m}
(or module @ref{1,,__main__} if @emph{m} is not supplied or is @code{None}), starting with
@code{m.__doc__}.

Also test examples reachable from dict @code{m.__test__}, if it exists and is not
@code{None}.  @code{m.__test__} maps names (strings) to functions, classes and
strings; function and class docstrings are searched for examples; strings are
searched directly, as if they were docstrings.

Only docstrings attached to objects belonging to module @emph{m} are searched.

Return @code{(failure_count, test_count)}.

Optional argument @emph{name} gives the name of the module; by default, or if
@code{None}, @code{m.__name__} is used.

Optional argument @emph{exclude_empty} defaults to false.  If true, objects for which
no doctests are found are excluded from consideration. The default is a backward
compatibility hack, so that code still using @code{doctest.master.summarize()} in
conjunction with @ref{dc9,,testmod()} continues to get output for objects with no
tests. The @emph{exclude_empty} argument to the newer @ref{327b,,DocTestFinder}
constructor defaults to true.

Optional arguments @emph{extraglobs}, @emph{verbose}, @emph{report}, @emph{optionflags},
@emph{raise_on_error}, and @emph{globs} are the same as for function @ref{3258,,testfile()}
above, except that @emph{globs} defaults to @code{m.__dict__}.
@end deffn

@geindex run_docstring_examples() (在 doctest 模块中)
@anchor{library/doctest doctest run_docstring_examples}@anchor{327c}
@deffn {函数} doctest.run_docstring_examples (f, globs, verbose=False, name="NoName", compileflags=None, optionflags=0)

Test examples associated with object @emph{f}; for example, @emph{f} may be a string,
a module, a function, or a class object.

A shallow copy of dictionary argument @emph{globs} is used for the execution context.

Optional argument @emph{name} is used in failure messages, and defaults to
@code{"NoName"}.

If optional argument @emph{verbose} is true, output is generated even if there are no
failures.  By default, output is generated only in case of an example failure.

Optional argument @emph{compileflags} gives the set of flags that should be used by
the Python compiler when running the examples.  By default, or if @code{None},
flags are deduced corresponding to the set of future features found in @emph{globs}.

Optional argument @emph{optionflags} works as for function @ref{3258,,testfile()} above.
@end deffn

@node Unittest API,Advanced API,Basic API,doctest --- 测试交互性的Python示例
@anchor{library/doctest doctest-unittest-api}@anchor{327d}@anchor{library/doctest unittest-api}@anchor{327e}
@subsubsection Unittest API


As your collection of doctest'ed modules grows, you'll want a way to run all
their doctests systematically.  @ref{67,,doctest} provides two functions that can
be used to create @ref{11b,,unittest} test suites from modules and text files
containing doctests.  To integrate with @ref{11b,,unittest} test discovery, include
a @code{load_tests()} function in your test module:

@example
import unittest
import doctest
import my_module_with_doctests

def load_tests(loader, tests, ignore):
    tests.addTests(doctest.DocTestSuite(my_module_with_doctests))
    return tests
@end example

There are two main functions for creating @ref{6c8,,unittest.TestSuite} instances
from text files and modules with doctests:

@geindex DocFileSuite() (在 doctest 模块中)
@anchor{library/doctest doctest DocFileSuite}@anchor{327f}
@deffn {函数} doctest.DocFileSuite (*paths, module_relative=True, package=None, setUp=None, tearDown=None, globs=None, optionflags=0, parser=DocTestParser(), encoding=None)

Convert doctest tests from one or more text files to a
@ref{6c8,,unittest.TestSuite}.

The returned @ref{6c8,,unittest.TestSuite} is to be run by the unittest framework
and runs the interactive examples in each file.  If an example in any file
fails, then the synthesized unit test fails, and a @code{failureException}
exception is raised showing the name of the file containing the test and a
(sometimes approximate) line number.

Pass one or more paths (as strings) to text files to be examined.

Options may be provided as keyword arguments:

Optional argument @emph{module_relative} specifies how the filenames in @emph{paths}
should be interpreted:


@itemize *

@item 
If @emph{module_relative} is @code{True} (the default), then each filename in
@emph{paths} specifies an OS-independent module-relative path.  By default, this
path is relative to the calling module's directory; but if the @emph{package}
argument is specified, then it is relative to that package.  To ensure
OS-independence, each filename should use @code{/} characters to separate path
segments, and may not be an absolute path (i.e., it may not begin with
@code{/}).

@item 
If @emph{module_relative} is @code{False}, then each filename in @emph{paths} specifies
an OS-specific path.  The path may be absolute or relative; relative paths
are resolved with respect to the current working directory.
@end itemize

Optional argument @emph{package} is a Python package or the name of a Python
package whose directory should be used as the base directory for
module-relative filenames in @emph{paths}.  If no package is specified, then the
calling module's directory is used as the base directory for module-relative
filenames.  It is an error to specify @emph{package} if @emph{module_relative} is
@code{False}.

Optional argument @emph{setUp} specifies a set-up function for the test suite.
This is called before running the tests in each file.  The @emph{setUp} function
will be passed a @ref{3280,,DocTest} object.  The setUp function can access the
test globals as the @emph{globs} attribute of the test passed.

Optional argument @emph{tearDown} specifies a tear-down function for the test
suite.  This is called after running the tests in each file.  The @emph{tearDown}
function will be passed a @ref{3280,,DocTest} object.  The setUp function can
access the test globals as the @emph{globs} attribute of the test passed.

Optional argument @emph{globs} is a dictionary containing the initial global
variables for the tests.  A new copy of this dictionary is created for each
test.  By default, @emph{globs} is a new empty dictionary.

Optional argument @emph{optionflags} specifies the default doctest options for the
tests, created by or-ing together individual option flags.  See section
@ref{836,,Option Flags}. See function @ref{3281,,set_unittest_reportflags()} below
for a better way to set reporting options.

Optional argument @emph{parser} specifies a @ref{3261,,DocTestParser} (or subclass)
that should be used to extract tests from the files.  It defaults to a normal
parser (i.e., @code{DocTestParser()}).

Optional argument @emph{encoding} specifies an encoding that should be used to
convert the file to unicode.

The global @code{__file__} is added to the globals provided to doctests loaded
from a text file using @ref{327f,,DocFileSuite()}.
@end deffn

@geindex DocTestSuite() (在 doctest 模块中)
@anchor{library/doctest doctest DocTestSuite}@anchor{6c7}
@deffn {函数} doctest.DocTestSuite (module=None, globs=None, extraglobs=None, test_finder=None, setUp=None, tearDown=None, checker=None)

Convert doctest tests for a module to a @ref{6c8,,unittest.TestSuite}.

The returned @ref{6c8,,unittest.TestSuite} is to be run by the unittest framework
and runs each doctest in the module.  If any of the doctests fail, then the
synthesized unit test fails, and a @code{failureException} exception is raised
showing the name of the file containing the test and a (sometimes approximate)
line number.

Optional argument @emph{module} provides the module to be tested.  It can be a module
object or a (possibly dotted) module name.  If not specified, the module calling
this function is used.

Optional argument @emph{globs} is a dictionary containing the initial global
variables for the tests.  A new copy of this dictionary is created for each
test.  By default, @emph{globs} is a new empty dictionary.

Optional argument @emph{extraglobs} specifies an extra set of global variables, which
is merged into @emph{globs}.  By default, no extra globals are used.

Optional argument @emph{test_finder} is the @ref{327b,,DocTestFinder} object (or a
drop-in replacement) that is used to extract doctests from the module.

Optional arguments @emph{setUp}, @emph{tearDown}, and @emph{optionflags} are the same as for
function @ref{327f,,DocFileSuite()} above.

This function uses the same search technique as @ref{dc9,,testmod()}.


在 3.5 版更改: @ref{6c7,,DocTestSuite()} returns an empty @ref{6c8,,unittest.TestSuite} if @emph{module}
contains no docstrings instead of raising @ref{1fb,,ValueError}.

@end deffn

Under the covers, @ref{6c7,,DocTestSuite()} creates a @ref{6c8,,unittest.TestSuite} out
of @code{doctest.DocTestCase} instances, and @code{DocTestCase} is a
subclass of @ref{8f9,,unittest.TestCase}. @code{DocTestCase} isn't documented
here (it's an internal detail), but studying its code can answer questions about
the exact details of @ref{11b,,unittest} integration.

Similarly, @ref{327f,,DocFileSuite()} creates a @ref{6c8,,unittest.TestSuite} out of
@code{doctest.DocFileCase} instances, and @code{DocFileCase} is a subclass
of @code{DocTestCase}.

So both ways of creating a @ref{6c8,,unittest.TestSuite} run instances of
@code{DocTestCase}.  This is important for a subtle reason: when you run
@ref{67,,doctest} functions yourself, you can control the @ref{67,,doctest} options in
use directly, by passing option flags to @ref{67,,doctest} functions.  However, if
you're writing a @ref{11b,,unittest} framework, @ref{11b,,unittest} ultimately controls
when and how tests get run.  The framework author typically wants to control
@ref{67,,doctest} reporting options (perhaps, e.g., specified by command line
options), but there's no way to pass options through @ref{11b,,unittest} to
@ref{67,,doctest} test runners.

For this reason, @ref{67,,doctest} also supports a notion of @ref{67,,doctest}
reporting flags specific to @ref{11b,,unittest} support, via this function:

@geindex set_unittest_reportflags() (在 doctest 模块中)
@anchor{library/doctest doctest set_unittest_reportflags}@anchor{3281}
@deffn {函数} doctest.set_unittest_reportflags (flags)

Set the @ref{67,,doctest} reporting flags to use.

Argument @emph{flags} takes the @ref{14d6,,bitwise OR} of option flags.  See
section @ref{836,,Option Flags}.  Only "reporting flags" can be used.

This is a module-global setting, and affects all future doctests run by module
@ref{11b,,unittest}:  the @code{runTest()} method of @code{DocTestCase} looks at
the option flags specified for the test case when the @code{DocTestCase}
instance was constructed.  If no reporting flags were specified (which is the
typical and expected case), @ref{67,,doctest}'s @ref{11b,,unittest} reporting flags are
@ref{14d6,,bitwise ORed} into the option flags, and the option flags
so augmented are passed to the @ref{3271,,DocTestRunner} instance created to
run the doctest.  If any reporting flags were specified when the
@code{DocTestCase} instance was constructed, @ref{67,,doctest}'s
@ref{11b,,unittest} reporting flags are ignored.

The value of the @ref{11b,,unittest} reporting flags in effect before the function
was called is returned by the function.
@end deffn

@node Advanced API,调试,Unittest API,doctest --- 测试交互性的Python示例
@anchor{library/doctest advanced-api}@anchor{3282}@anchor{library/doctest doctest-advanced-api}@anchor{3283}
@subsubsection Advanced API


The basic API is a simple wrapper that's intended to make doctest easy to use.
It is fairly flexible, and should meet most users' needs; however, if you
require more fine-grained control over testing, or wish to extend doctest's
capabilities, then you should use the advanced API.

The advanced API revolves around two container classes, which are used to store
the interactive examples extracted from doctest cases:


@itemize *

@item 
@ref{3284,,Example}: A single Python @ref{1b24,,statement}, paired with its expected
output.

@item 
@ref{3280,,DocTest}: A collection of @ref{3284,,Example}s, typically extracted
from a single docstring or text file.
@end itemize

Additional processing classes are defined to find, parse, and run, and check
doctest examples:


@itemize *

@item 
@ref{327b,,DocTestFinder}: Finds all docstrings in a given module, and uses a
@ref{3261,,DocTestParser} to create a @ref{3280,,DocTest} from every docstring that
contains interactive examples.

@item 
@ref{3261,,DocTestParser}: Creates a @ref{3280,,DocTest} object from a string (such
as an object's docstring).

@item 
@ref{3271,,DocTestRunner}: Executes the examples in a @ref{3280,,DocTest}, and uses
an @ref{3270,,OutputChecker} to verify their output.

@item 
@ref{3270,,OutputChecker}: Compares the actual output from a doctest example with
the expected output, and decides whether they match.
@end itemize

The relationships among these processing classes are summarized in the following
diagram:

@example
                            list of:
+------+                   +---------+
|module| --DocTestFinder-> | DocTest | --DocTestRunner-> results
+------+    |        ^     +---------+     |       ^    (printed)
            |        |     | Example |     |       |
            v        |     |   ...   |     v       |
           DocTestParser   | Example |   OutputChecker
                           +---------+
@end example

@menu
* DocTest 对象:: 
* Example Objects:: 
* DocTestFinder 对象:: 
* DocTestParser 对象:: 
* DocTestRunner 对象:: 
* OutputChecker 对象:: 

@end menu

@node DocTest 对象,Example Objects,,Advanced API
@anchor{library/doctest doctest-doctest}@anchor{3285}@anchor{library/doctest doctest-objects}@anchor{3286}
@subsubsection DocTest 对象


@geindex DocTest (doctest 中的类)
@anchor{library/doctest doctest DocTest}@anchor{3280}
@deffn {类} doctest.DocTest (examples, globs, name, filename, lineno, docstring)

A collection of doctest examples that should be run in a single namespace.  The
constructor arguments are used to initialize the attributes of the same names.

@ref{3280,,DocTest} defines the following attributes.  They are initialized by
the constructor, and should not be modified directly.

@geindex examples (doctest.DocTest 属性)
@anchor{library/doctest doctest DocTest examples}@anchor{3287}
@deffn {属性} examples

A list of @ref{3284,,Example} objects encoding the individual interactive Python
examples that should be run by this test.
@end deffn

@geindex globs (doctest.DocTest 属性)
@anchor{library/doctest doctest DocTest globs}@anchor{3288}
@deffn {属性} globs

The namespace (aka globals) that the examples should be run in. This is a
dictionary mapping names to values.  Any changes to the namespace made by the
examples (such as binding new variables) will be reflected in @ref{3288,,globs}
after the test is run.
@end deffn

@geindex name (doctest.DocTest 属性)
@anchor{library/doctest doctest DocTest name}@anchor{3289}
@deffn {属性} name

A string name identifying the @ref{3280,,DocTest}.  Typically, this is the name
of the object or file that the test was extracted from.
@end deffn

@geindex filename (doctest.DocTest 属性)
@anchor{library/doctest doctest DocTest filename}@anchor{328a}
@deffn {属性} filename

The name of the file that this @ref{3280,,DocTest} was extracted from; or
@code{None} if the filename is unknown, or if the @ref{3280,,DocTest} was not
extracted from a file.
@end deffn

@geindex lineno (doctest.DocTest 属性)
@anchor{library/doctest doctest DocTest lineno}@anchor{328b}
@deffn {属性} lineno

The line number within @ref{328a,,filename} where this @ref{3280,,DocTest} begins, or
@code{None} if the line number is unavailable.  This line number is zero-based
with respect to the beginning of the file.
@end deffn

@geindex docstring (doctest.DocTest 属性)
@anchor{library/doctest doctest DocTest docstring}@anchor{328c}
@deffn {属性} docstring

The string that the test was extracted from, or @code{None} if the string is
unavailable, or if the test was not extracted from a string.
@end deffn
@end deffn

@node Example Objects,DocTestFinder 对象,DocTest 对象,Advanced API
@anchor{library/doctest doctest-example}@anchor{328d}@anchor{library/doctest example-objects}@anchor{328e}
@subsubsection Example Objects


@geindex Example (doctest 中的类)
@anchor{library/doctest doctest Example}@anchor{3284}
@deffn {类} doctest.Example (source, want, exc_msg=None, lineno=0, indent=0, options=None)

A single interactive example, consisting of a Python statement and its expected
output.  The constructor arguments are used to initialize the attributes of
the same names.

@ref{3284,,Example} defines the following attributes.  They are initialized by
the constructor, and should not be modified directly.

@geindex source (doctest.Example 属性)
@anchor{library/doctest doctest Example source}@anchor{328f}
@deffn {属性} source

A string containing the example's source code.  This source code consists of a
single Python statement, and always ends with a newline; the constructor adds
a newline when necessary.
@end deffn

@geindex want (doctest.Example 属性)
@anchor{library/doctest doctest Example want}@anchor{3290}
@deffn {属性} want

The expected output from running the example's source code (either from
stdout, or a traceback in case of exception).  @ref{3290,,want} ends with a
newline unless no output is expected, in which case it's an empty string.  The
constructor adds a newline when necessary.
@end deffn

@geindex exc_msg (doctest.Example 属性)
@anchor{library/doctest doctest Example exc_msg}@anchor{3291}
@deffn {属性} exc_msg

The exception message generated by the example, if the example is expected to
generate an exception; or @code{None} if it is not expected to generate an
exception.  This exception message is compared against the return value of
@ref{3292,,traceback.format_exception_only()}.  @ref{3291,,exc_msg} ends with a newline
unless it's @code{None}.  The constructor adds a newline if needed.
@end deffn

@geindex lineno (doctest.Example 属性)
@anchor{library/doctest doctest Example lineno}@anchor{3293}
@deffn {属性} lineno

The line number within the string containing this example where the example
begins.  This line number is zero-based with respect to the beginning of the
containing string.
@end deffn

@geindex indent (doctest.Example 属性)
@anchor{library/doctest doctest Example indent}@anchor{3294}
@deffn {属性} indent

The example's indentation in the containing string, i.e., the number of space
characters that precede the example's first prompt.
@end deffn

@geindex options (doctest.Example 属性)
@anchor{library/doctest doctest Example options}@anchor{3295}
@deffn {属性} options

A dictionary mapping from option flags to @code{True} or @code{False}, which is used
to override default options for this example.  Any option flags not contained
in this dictionary are left at their default value (as specified by the
@ref{3271,,DocTestRunner}'s @code{optionflags}). By default, no options are set.
@end deffn
@end deffn

@node DocTestFinder 对象,DocTestParser 对象,Example Objects,Advanced API
@anchor{library/doctest doctest-doctestfinder}@anchor{3296}@anchor{library/doctest doctestfinder-objects}@anchor{3297}
@subsubsection DocTestFinder 对象


@geindex DocTestFinder (doctest 中的类)
@anchor{library/doctest doctest DocTestFinder}@anchor{327b}
@deffn {类} doctest.DocTestFinder (verbose=False, parser=DocTestParser(), recurse=True, exclude_empty=True)

A processing class used to extract the @ref{3280,,DocTest}s that are relevant to
a given object, from its docstring and the docstrings of its contained objects.
@ref{3280,,DocTest}s can be extracted from modules, classes, functions,
methods, staticmethods, classmethods, and properties.

The optional argument @emph{verbose} can be used to display the objects searched by
the finder.  It defaults to @code{False} (no output).

The optional argument @emph{parser} specifies the @ref{3261,,DocTestParser} object (or a
drop-in replacement) that is used to extract doctests from docstrings.

If the optional argument @emph{recurse} is false, then @ref{3298,,DocTestFinder.find()}
will only examine the given object, and not any contained objects.

If the optional argument @emph{exclude_empty} is false, then
@ref{3298,,DocTestFinder.find()} will include tests for objects with empty docstrings.

@ref{327b,,DocTestFinder} defines the following method:

@geindex find() (doctest.DocTestFinder 方法)
@anchor{library/doctest doctest DocTestFinder find}@anchor{3298}
@deffn {方法} find (obj[, name][, module][, globs][, extraglobs])

Return a list of the @ref{3280,,DocTest}s that are defined by @emph{obj}'s
docstring, or by any of its contained objects' docstrings.

The optional argument @emph{name} specifies the object's name; this name will be
used to construct names for the returned @ref{3280,,DocTest}s.  If @emph{name} is
not specified, then @code{obj.__name__} is used.

The optional parameter @emph{module} is the module that contains the given object.
If the module is not specified or is @code{None}, then the test finder will attempt
to automatically determine the correct module.  The object's module is used:


@itemize *

@item 
As a default namespace, if @emph{globs} is not specified.

@item 
To prevent the DocTestFinder from extracting DocTests from objects that are
imported from other modules.  (Contained objects with modules other than
@emph{module} are ignored.)

@item 
To find the name of the file containing the object.

@item 
To help find the line number of the object within its file.
@end itemize

If @emph{module} is @code{False}, no attempt to find the module will be made.  This is
obscure, of use mostly in testing doctest itself: if @emph{module} is @code{False}, or
is @code{None} but cannot be found automatically, then all objects are considered
to belong to the (non-existent) module, so all contained objects will
(recursively) be searched for doctests.

The globals for each @ref{3280,,DocTest} is formed by combining @emph{globs} and
@emph{extraglobs} (bindings in @emph{extraglobs} override bindings in @emph{globs}).  A new
shallow copy of the globals dictionary is created for each @ref{3280,,DocTest}.
If @emph{globs} is not specified, then it defaults to the module's @emph{__dict__}, if
specified, or @code{@{@}} otherwise.  If @emph{extraglobs} is not specified, then it
defaults to @code{@{@}}.
@end deffn
@end deffn

@node DocTestParser 对象,DocTestRunner 对象,DocTestFinder 对象,Advanced API
@anchor{library/doctest doctest-doctestparser}@anchor{3299}@anchor{library/doctest doctestparser-objects}@anchor{329a}
@subsubsection DocTestParser 对象


@geindex DocTestParser (doctest 中的类)
@anchor{library/doctest doctest DocTestParser}@anchor{3261}
@deffn {类} doctest.DocTestParser

A processing class used to extract interactive examples from a string, and use
them to create a @ref{3280,,DocTest} object.

@ref{3261,,DocTestParser} defines the following methods:

@geindex get_doctest() (doctest.DocTestParser 方法)
@anchor{library/doctest doctest DocTestParser get_doctest}@anchor{329b}
@deffn {方法} get_doctest (string, globs, name, filename, lineno)

Extract all doctest examples from the given string, and collect them into a
@ref{3280,,DocTest} object.

@emph{globs}, @emph{name}, @emph{filename}, and @emph{lineno} are attributes for the new
@ref{3280,,DocTest} object.  See the documentation for @ref{3280,,DocTest} for more
information.
@end deffn

@geindex get_examples() (doctest.DocTestParser 方法)
@anchor{library/doctest doctest DocTestParser get_examples}@anchor{329c}
@deffn {方法} get_examples (string, name='<string>')

Extract all doctest examples from the given string, and return them as a list
of @ref{3284,,Example} objects.  Line numbers are 0-based.  The optional argument
@emph{name} is a name identifying this string, and is only used for error messages.
@end deffn

@geindex parse() (doctest.DocTestParser 方法)
@anchor{library/doctest doctest DocTestParser parse}@anchor{329d}
@deffn {方法} parse (string, name='<string>')

Divide the given string into examples and intervening text, and return them as
a list of alternating @ref{3284,,Example}s and strings. Line numbers for the
@ref{3284,,Example}s are 0-based.  The optional argument @emph{name} is a name
identifying this string, and is only used for error messages.
@end deffn
@end deffn

@node DocTestRunner 对象,OutputChecker 对象,DocTestParser 对象,Advanced API
@anchor{library/doctest doctest-doctestrunner}@anchor{329e}@anchor{library/doctest doctestrunner-objects}@anchor{329f}
@subsubsection DocTestRunner 对象


@geindex DocTestRunner (doctest 中的类)
@anchor{library/doctest doctest DocTestRunner}@anchor{3271}
@deffn {类} doctest.DocTestRunner (checker=None, verbose=None, optionflags=0)

A processing class used to execute and verify the interactive examples in a
@ref{3280,,DocTest}.

The comparison between expected outputs and actual outputs is done by an
@ref{3270,,OutputChecker}.  This comparison may be customized with a number of
option flags; see section @ref{836,,Option Flags} for more information.  If the
option flags are insufficient, then the comparison may also be customized by
passing a subclass of @ref{3270,,OutputChecker} to the constructor.

The test runner's display output can be controlled in two ways. First, an output
function can be passed to @code{TestRunner.run()}; this function will be called
with strings that should be displayed.  It defaults to @code{sys.stdout.write}.  If
capturing the output is not sufficient, then the display output can be also
customized by subclassing DocTestRunner, and overriding the methods
@ref{32a0,,report_start()}, @ref{32a1,,report_success()},
@ref{32a2,,report_unexpected_exception()}, and @ref{32a3,,report_failure()}.

The optional keyword argument @emph{checker} specifies the @ref{3270,,OutputChecker}
object (or drop-in replacement) that should be used to compare the expected
outputs to the actual outputs of doctest examples.

The optional keyword argument @emph{verbose} controls the @ref{3271,,DocTestRunner}'s
verbosity.  If @emph{verbose} is @code{True}, then information is printed about each
example, as it is run.  If @emph{verbose} is @code{False}, then only failures are
printed.  If @emph{verbose} is unspecified, or @code{None}, then verbose output is used
iff the command-line switch @code{-v} is used.

The optional keyword argument @emph{optionflags} can be used to control how the test
runner compares expected output to actual output, and how it displays failures.
For more information, see section @ref{836,,Option Flags}.

@ref{3261,,DocTestParser} defines the following methods:

@geindex report_start() (doctest.DocTestRunner 方法)
@anchor{library/doctest doctest DocTestRunner report_start}@anchor{32a0}
@deffn {方法} report_start (out, test, example)

Report that the test runner is about to process the given example. This method
is provided to allow subclasses of @ref{3271,,DocTestRunner} to customize their
output; it should not be called directly.

@emph{example} is the example about to be processed.  @emph{test} is the test
@emph{containing example}.  @emph{out} is the output function that was passed to
@ref{32a4,,DocTestRunner.run()}.
@end deffn

@geindex report_success() (doctest.DocTestRunner 方法)
@anchor{library/doctest doctest DocTestRunner report_success}@anchor{32a1}
@deffn {方法} report_success (out, test, example, got)

Report that the given example ran successfully.  This method is provided to
allow subclasses of @ref{3271,,DocTestRunner} to customize their output; it
should not be called directly.

@emph{example} is the example about to be processed.  @emph{got} is the actual output
from the example.  @emph{test} is the test containing @emph{example}.  @emph{out} is the
output function that was passed to @ref{32a4,,DocTestRunner.run()}.
@end deffn

@geindex report_failure() (doctest.DocTestRunner 方法)
@anchor{library/doctest doctest DocTestRunner report_failure}@anchor{32a3}
@deffn {方法} report_failure (out, test, example, got)

Report that the given example failed.  This method is provided to allow
subclasses of @ref{3271,,DocTestRunner} to customize their output; it should not
be called directly.

@emph{example} is the example about to be processed.  @emph{got} is the actual output
from the example.  @emph{test} is the test containing @emph{example}.  @emph{out} is the
output function that was passed to @ref{32a4,,DocTestRunner.run()}.
@end deffn

@geindex report_unexpected_exception() (doctest.DocTestRunner 方法)
@anchor{library/doctest doctest DocTestRunner report_unexpected_exception}@anchor{32a2}
@deffn {方法} report_unexpected_exception (out, test, example, exc_info)

Report that the given example raised an unexpected exception. This method is
provided to allow subclasses of @ref{3271,,DocTestRunner} to customize their
output; it should not be called directly.

@emph{example} is the example about to be processed. @emph{exc_info} is a tuple
containing information about the unexpected exception (as returned by
@ref{c58,,sys.exc_info()}). @emph{test} is the test containing @emph{example}.  @emph{out} is the
output function that was passed to @ref{32a4,,DocTestRunner.run()}.
@end deffn

@geindex run() (doctest.DocTestRunner 方法)
@anchor{library/doctest doctest DocTestRunner run}@anchor{32a4}
@deffn {方法} run (test, compileflags=None, out=None, clear_globs=True)

Run the examples in @emph{test} (a @ref{3280,,DocTest} object), and display the
results using the writer function @emph{out}.

The examples are run in the namespace @code{test.globs}.  If @emph{clear_globs} is
true (the default), then this namespace will be cleared after the test runs,
to help with garbage collection. If you would like to examine the namespace
after the test completes, then use @emph{clear_globs=False}.

@emph{compileflags} gives the set of flags that should be used by the Python
compiler when running the examples.  If not specified, then it will default to
the set of future-import flags that apply to @emph{globs}.

The output of each example is checked using the @ref{3271,,DocTestRunner}'s
output checker, and the results are formatted by the
@code{DocTestRunner.report_*()} methods.
@end deffn

@geindex summarize() (doctest.DocTestRunner 方法)
@anchor{library/doctest doctest DocTestRunner summarize}@anchor{32a5}
@deffn {方法} summarize (verbose=None)

Print a summary of all the test cases that have been run by this DocTestRunner,
and return a @ref{a9e,,named tuple} @code{TestResults(failed, attempted)}.

The optional @emph{verbose} argument controls how detailed the summary is.  If the
verbosity is not specified, then the @ref{3271,,DocTestRunner}'s verbosity is
used.
@end deffn
@end deffn

@node OutputChecker 对象,,DocTestRunner 对象,Advanced API
@anchor{library/doctest doctest-outputchecker}@anchor{32a6}@anchor{library/doctest outputchecker-objects}@anchor{32a7}
@subsubsection OutputChecker 对象


@geindex OutputChecker (doctest 中的类)
@anchor{library/doctest doctest OutputChecker}@anchor{3270}
@deffn {类} doctest.OutputChecker

A class used to check the whether the actual output from a doctest example
matches the expected output.  @ref{3270,,OutputChecker} defines two methods:
@ref{32a8,,check_output()}, which compares a given pair of outputs, and returns @code{True}
if they match; and @ref{32a9,,output_difference()}, which returns a string describing
the differences between two outputs.

@ref{3270,,OutputChecker} defines the following methods:

@geindex check_output() (doctest.OutputChecker 方法)
@anchor{library/doctest doctest OutputChecker check_output}@anchor{32a8}
@deffn {方法} check_output (want, got, optionflags)

Return @code{True} iff the actual output from an example (@emph{got}) matches the
expected output (@emph{want}).  These strings are always considered to match if
they are identical; but depending on what option flags the test runner is
using, several non-exact match types are also possible.  See section
@ref{836,,Option Flags} for more information about option flags.
@end deffn

@geindex output_difference() (doctest.OutputChecker 方法)
@anchor{library/doctest doctest OutputChecker output_difference}@anchor{32a9}
@deffn {方法} output_difference (example, got, optionflags)

Return a string describing the differences between the expected output for a
given example (@emph{example}) and the actual output (@emph{got}).  @emph{optionflags} is the
set of option flags used to compare @emph{want} and @emph{got}.
@end deffn
@end deffn

@node 调试,Soapbox,Advanced API,doctest --- 测试交互性的Python示例
@anchor{library/doctest debugging}@anchor{32aa}@anchor{library/doctest doctest-debugging}@anchor{32ab}
@subsubsection 调试


Doctest provides several mechanisms for debugging doctest examples:


@itemize *

@item 
Several functions convert doctests to executable Python programs, which can be
run under the Python debugger, @ref{c9,,pdb}.

@item 
The @ref{32ac,,DebugRunner} class is a subclass of @ref{3271,,DocTestRunner} that
raises an exception for the first failing example, containing information about
that example. This information can be used to perform post-mortem debugging on
the example.

@item 
The @ref{11b,,unittest} cases generated by @ref{6c7,,DocTestSuite()} support the
@ref{32ad,,debug()} method defined by @ref{8f9,,unittest.TestCase}.

@item 
You can add a call to @ref{3ba,,pdb.set_trace()} in a doctest example, and you'll
drop into the Python debugger when that line is executed.  Then you can inspect
current values of variables, and so on.  For example, suppose @code{a.py}
contains just this module docstring:

@example
"""
>>> def f(x):
...     g(x*2)
>>> def g(x):
...     print(x+3)
...     import pdb; pdb.set_trace()
>>> f(3)
9
"""
@end example

Then an interactive Python session may look like this:

@example
>>> import a, doctest
>>> doctest.testmod(a)
--Return--
> <doctest a[1]>(3)g()->None
-> import pdb; pdb.set_trace()
(Pdb) list
  1     def g(x):
  2         print(x+3)
  3  ->     import pdb; pdb.set_trace()
[EOF]
(Pdb) p x
6
(Pdb) step
--Return--
> <doctest a[0]>(2)f()->None
-> g(x*2)
(Pdb) list
  1     def f(x):
  2  ->     g(x*2)
[EOF]
(Pdb) p x
3
(Pdb) step
--Return--
> <doctest a[2]>(1)?()->None
-> f(3)
(Pdb) cont
(0, 3)
>>>
@end example
@end itemize

Functions that convert doctests to Python code, and possibly run the synthesized
code under the debugger:

@geindex script_from_examples() (在 doctest 模块中)
@anchor{library/doctest doctest script_from_examples}@anchor{32ae}
@deffn {函数} doctest.script_from_examples (s)

Convert text with examples to a script.

Argument @emph{s} is a string containing doctest examples.  The string is converted
to a Python script, where doctest examples in @emph{s} are converted to regular code,
and everything else is converted to Python comments.  The generated script is
returned as a string. For example,

@example
import doctest
print(doctest.script_from_examples(r"""
    Set x and y to 1 and 2.
    >>> x, y = 1, 2

    Print their sum:
    >>> print(x+y)
    3
"""))
@end example

displays:

@example
# Set x and y to 1 and 2.
x, y = 1, 2
#
# Print their sum:
print(x+y)
# Expected:
## 3
@end example

This function is used internally by other functions (see below), but can also be
useful when you want to transform an interactive Python session into a Python
script.
@end deffn

@geindex testsource() (在 doctest 模块中)
@anchor{library/doctest doctest testsource}@anchor{32af}
@deffn {函数} doctest.testsource (module, name)

Convert the doctest for an object to a script.

Argument @emph{module} is a module object, or dotted name of a module, containing the
object whose doctests are of interest.  Argument @emph{name} is the name (within the
module) of the object with the doctests of interest.  The result is a string,
containing the object's docstring converted to a Python script, as described for
@ref{32ae,,script_from_examples()} above.  For example, if module @code{a.py}
contains a top-level function @code{f()}, then

@example
import a, doctest
print(doctest.testsource(a, "a.f"))
@end example

prints a script version of function @code{f()}'s docstring, with doctests
converted to code, and the rest placed in comments.
@end deffn

@geindex debug() (在 doctest 模块中)
@anchor{library/doctest doctest debug}@anchor{32ad}
@deffn {函数} doctest.debug (module, name, pm=False)

Debug the doctests for an object.

The @emph{module} and @emph{name} arguments are the same as for function
@ref{32af,,testsource()} above.  The synthesized Python script for the named object's
docstring is written to a temporary file, and then that file is run under the
control of the Python debugger, @ref{c9,,pdb}.

A shallow copy of @code{module.__dict__} is used for both local and global
execution context.

Optional argument @emph{pm} controls whether post-mortem debugging is used.  If @emph{pm}
has a true value, the script file is run directly, and the debugger gets
involved only if the script terminates via raising an unhandled exception.  If
it does, then post-mortem debugging is invoked, via @ref{d3e,,pdb.post_mortem()},
passing the traceback object from the unhandled exception.  If @emph{pm} is not
specified, or is false, the script is run under the debugger from the start, via
passing an appropriate @ref{c3d,,exec()} call to @ref{32b0,,pdb.run()}.
@end deffn

@geindex debug_src() (在 doctest 模块中)
@anchor{library/doctest doctest debug_src}@anchor{32b1}
@deffn {函数} doctest.debug_src (src, pm=False, globs=None)

Debug the doctests in a string.

This is like function @ref{32ad,,debug()} above, except that a string containing
doctest examples is specified directly, via the @emph{src} argument.

Optional argument @emph{pm} has the same meaning as in function @ref{32ad,,debug()} above.

Optional argument @emph{globs} gives a dictionary to use as both local and global
execution context.  If not specified, or @code{None}, an empty dictionary is used.
If specified, a shallow copy of the dictionary is used.
@end deffn

The @ref{32ac,,DebugRunner} class, and the special exceptions it may raise, are of
most interest to testing framework authors, and will only be sketched here.  See
the source code, and especially @ref{32ac,,DebugRunner}'s docstring (which is a
doctest!) for more details:

@geindex DebugRunner (doctest 中的类)
@anchor{library/doctest doctest DebugRunner}@anchor{32ac}
@deffn {类} doctest.DebugRunner (checker=None, verbose=None, optionflags=0)

A subclass of @ref{3271,,DocTestRunner} that raises an exception as soon as a
failure is encountered.  If an unexpected exception occurs, an
@ref{32b2,,UnexpectedException} exception is raised, containing the test, the
example, and the original exception.  If the output doesn't match, then a
@ref{32b3,,DocTestFailure} exception is raised, containing the test, the example, and
the actual output.

For information about the constructor parameters and methods, see the
documentation for @ref{3271,,DocTestRunner} in section @ref{3283,,Advanced API}.
@end deffn

There are two exceptions that may be raised by @ref{32ac,,DebugRunner} instances:

@geindex DocTestFailure
@anchor{library/doctest doctest DocTestFailure}@anchor{32b3}
@deffn {例外} doctest.DocTestFailure (test, example, got)

An exception raised by @ref{3271,,DocTestRunner} to signal that a doctest example's
actual output did not match its expected output. The constructor arguments are
used to initialize the attributes of the same names.
@end deffn

@ref{32b3,,DocTestFailure} defines the following attributes:

@geindex test (doctest.DocTestFailure 属性)
@anchor{library/doctest doctest DocTestFailure test}@anchor{32b4}
@deffn {属性} DocTestFailure.test

The @ref{3280,,DocTest} object that was being run when the example failed.
@end deffn

@geindex example (doctest.DocTestFailure 属性)
@anchor{library/doctest doctest DocTestFailure example}@anchor{32b5}
@deffn {属性} DocTestFailure.example

The @ref{3284,,Example} that failed.
@end deffn

@geindex got (doctest.DocTestFailure 属性)
@anchor{library/doctest doctest DocTestFailure got}@anchor{32b6}
@deffn {属性} DocTestFailure.got

The example's actual output.
@end deffn

@geindex UnexpectedException
@anchor{library/doctest doctest UnexpectedException}@anchor{32b2}
@deffn {例外} doctest.UnexpectedException (test, example, exc_info)

An exception raised by @ref{3271,,DocTestRunner} to signal that a doctest
example raised an unexpected exception.  The constructor arguments are used
to initialize the attributes of the same names.
@end deffn

@ref{32b2,,UnexpectedException} defines the following attributes:

@geindex test (doctest.UnexpectedException 属性)
@anchor{library/doctest doctest UnexpectedException test}@anchor{32b7}
@deffn {属性} UnexpectedException.test

The @ref{3280,,DocTest} object that was being run when the example failed.
@end deffn

@geindex example (doctest.UnexpectedException 属性)
@anchor{library/doctest doctest UnexpectedException example}@anchor{32b8}
@deffn {属性} UnexpectedException.example

The @ref{3284,,Example} that failed.
@end deffn

@geindex exc_info (doctest.UnexpectedException 属性)
@anchor{library/doctest doctest UnexpectedException exc_info}@anchor{32b9}
@deffn {属性} UnexpectedException.exc_info

A tuple containing information about the unexpected exception, as returned by
@ref{c58,,sys.exc_info()}.
@end deffn

@node Soapbox,,调试,doctest --- 测试交互性的Python示例
@anchor{library/doctest doctest-soapbox}@anchor{32ba}@anchor{library/doctest soapbox}@anchor{32bb}
@subsubsection Soapbox


As mentioned in the introduction, @ref{67,,doctest} has grown to have three primary
uses:


@enumerate 

@item 
Checking examples in docstrings.

@item 
Regression testing.

@item 
Executable documentation / literate testing.
@end enumerate

These uses have different requirements, and it is important to distinguish them.
In particular, filling your docstrings with obscure test cases makes for bad
documentation.

When writing a docstring, choose docstring examples with care. There's an art to
this that needs to be learned---it may not be natural at first.  Examples should
add genuine value to the documentation.  A good example can often be worth many
words. If done with care, the examples will be invaluable for your users, and
will pay back the time it takes to collect them many times over as the years go
by and things change.  I'm still amazed at how often one of my @ref{67,,doctest}
examples stops working after a "harmless" change.

Doctest also makes an excellent tool for regression testing, especially if you
don't skimp on explanatory text.  By interleaving prose and examples, it becomes
much easier to keep track of what's actually being tested, and why.  When a test
fails, good prose can make it much easier to figure out what the problem is, and
how it should be fixed.  It's true that you could write extensive comments in
code-based testing, but few programmers do. Many have found that using doctest
approaches instead leads to much clearer tests.  Perhaps this is simply because
doctest makes writing prose a little easier than writing code, while writing
comments in code is a little harder.  I think it goes deeper than just that:
the natural attitude when writing a doctest-based test is that you want to
explain the fine points of your software, and illustrate them with examples.
This in turn naturally leads to test files that start with the simplest
features, and logically progress to complications and edge cases.  A coherent
narrative is the result, instead of a collection of isolated functions that test
isolated bits of functionality seemingly at random.  It's a different attitude,
and produces different results, blurring the distinction between testing and
explaining.

Regression testing is best confined to dedicated objects or files.  There are
several options for organizing tests:


@itemize *

@item 
Write text files containing test cases as interactive examples, and test the
files using @ref{3258,,testfile()} or @ref{327f,,DocFileSuite()}.  This is recommended,
although is easiest to do for new projects, designed from the start to use
doctest.

@item 
Define functions named @code{_regrtest_topic} that consist of single docstrings,
containing test cases for the named topics.  These functions can be included in
the same file as the module, or separated out into a separate test file.

@item 
Define a @code{__test__} dictionary mapping from regression test topics to
docstrings containing test cases.
@end itemize

When you have placed your tests in a module, the module can itself be the test
runner.  When a test fails, you can arrange for your test runner to re-run only
the failing doctest while you debug the problem.  Here is a minimal example of
such a test runner:

@example
if __name__ == '__main__':
    import doctest
    flags = doctest.REPORT_NDIFF|doctest.FAIL_FAST
    if len(sys.argv) > 1:
        name = sys.argv[1]
        if name in globals():
            obj = globals()[name]
        else:
            obj = __test__[name]
        doctest.run_docstring_examples(obj, globals(), name=name,
                                       optionflags=flags)
    else:
        fail, total = doctest.testmod(optionflags=flags)
        print("@{@} failures out of @{@} tests".format(fail, total))
@end example

@subsubheading 备注


@node unittest --- 单元测试框架,unittest mock --- 模拟对象库,doctest --- 测试交互性的Python示例,开发工具
@anchor{library/unittest doc}@anchor{32bc}@anchor{library/unittest module-unittest}@anchor{11b}@anchor{library/unittest unittest-unit-testing-framework}@anchor{32bd}
@subsection @code{unittest} --- 单元测试框架


@geindex unittest (模块)

@strong{源代码：} Lib/unittest/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/unittest/__init__.py}


__________________________________________________________________


（如果你已经对测试的概念比较熟悉了，你可能想直接跳转到这一部分 @ref{32be,,断言方法}。）

@ref{11b,,unittest} 单元测试框架是受到 JUnit 的启发，与其他语言中的主流单元测试框架有着相似的风格。其支持测试自动化，配置共享和关机代码测试。支持将测试样例聚合到测试集中，并将测试与报告框架独立。

为了实现这些，@ref{11b,,unittest} 通过面向对象的方式支持了一些重要的概念。


@table @asis

@item 测试脚手架

@emph{test fixture} 表示为了开展一项或多项测试所需要进行的准备工作，以及所有相关的清理操作。举个例子，这可能包含创建临时或代理的数据库、目录，再或者启动一个服务器进程。

@item 测试用例

一个测试用例是一个独立的测试单元。它检查输入特定的数据时的响应。 @ref{11b,,unittest} 提供一个基类： @ref{8f9,,TestCase} ，用于新建测试用例。

@item 测试套件

@emph{test suite} 是一系列的测试用例，或测试套件，或两者皆有。它用于归档需要一起执行的测试。

@item 测试运行器（test runner）

@emph{test runner} 是一个用于执行和输出测试结果的组件。这个运行器可能使用图形接口、文本接口，或返回一个特定的值表示运行测试的结果。
@end table


@subsubheading 参见



@table @asis

@item @ref{67,,doctest} --- 文档测试模块

另一个风格完全不同的测试模块。

@item Simple Smalltalk Testing: With Patterns@footnote{https://web.archive.org/web/20150315073817/http://www.xprogramming.com/testfram.htm}

Kent Beck's original paper on testing frameworks using the pattern shared
by @ref{11b,,unittest}.

@item pytest@footnote{https://docs.pytest.org/}

Third-party unittest framework with a lighter-weight syntax for writing
tests.  For example, @code{assert func(10) == 42}.

@item The Python Testing Tools Taxonomy@footnote{https://wiki.python.org/moin/PythonTestingToolsTaxonomy}

An extensive list of Python testing tools including functional testing
frameworks and mock object libraries.

@item Testing in Python Mailing List@footnote{http://lists.idyll.org/listinfo/testing-in-python}

A special-interest-group for discussion of testing, and testing tools,
in Python.
@end table

The script @code{Tools/unittestgui/unittestgui.py} in the Python source distribution is
a GUI tool for test discovery and execution.  This is intended largely for ease of use
for those new to unit testing.  For production environments it is
recommended that tests be driven by a continuous integration system such as
Buildbot@footnote{https://buildbot.net/}, Jenkins@footnote{https://jenkins.io/}
or  Hudson@footnote{http://hudson-ci.org/}.


@menu
* 基本实例:: 
* 命令行界面: 命令行界面<5>. 
* 探索性测试:: 
* 组织你的测试代码:: 
* 复用已有的测试代码:: 
* 跳过测试与预计的失败:: 
* Distinguishing test iterations using subtests:: 
* 类与函数:: 
* Class and Module Fixtures:: 
* Signal Handling:: 

@end menu

@node 基本实例,命令行界面<5>,,unittest --- 单元测试框架
@anchor{library/unittest basic-example}@anchor{32bf}@anchor{library/unittest unittest-minimal-example}@anchor{32c0}
@subsubsection 基本实例


@ref{11b,,unittest} 模块提供了一系列创建和运行测试的工具。这一段落演示了这些工具的一小部分，但也足以满足大部分用户的需求。

这是一段简短的代码，来测试三种字符串方法:

@example
import unittest

class TestStringMethods(unittest.TestCase):

    def test_upper(self):
        self.assertEqual('foo'.upper(), 'FOO')

    def test_isupper(self):
        self.assertTrue('FOO'.isupper())
        self.assertFalse('Foo'.isupper())

    def test_split(self):
        s = 'hello world'
        self.assertEqual(s.split(), ['hello', 'world'])
        # check that s.split fails when the separator is not a string
        with self.assertRaises(TypeError):
            s.split(2)

if __name__ == '__main__':
    unittest.main()
@end example

继承 @ref{8f9,,unittest.TestCase} 就创建了一个测试样例。上述三个独立的测试是三个类的方法，这些方法的命名都以 @code{test} 开头。 这个命名约定告诉测试运行者类的哪些方法表示测试。

每个测试的关键是：调用 @ref{bae,,assertEqual()} 来检查预期的输出； 调用 @ref{bad,,assertTrue()} 或 @ref{cc0,,assertFalse()} 来验证一个条件；调用 @ref{ab5,,assertRaises()} 来验证抛出了一个特定的异常。使用这些方法而不是 @ref{dff,,assert} 语句是为了让测试运行者能聚合所有的测试结果并产生结果报告。

通过 @ref{cc4,,setUp()} 和 @ref{cc5,,tearDown()} 方法，可以设置测试开始前与完成后需要执行的指令。 在  @ref{32c1,,组织你的测试代码} 中，对此有更为详细的描述。

最后的代码块中，演示了运行测试的一个简单的方法。 @ref{8fc,,unittest.main()} 提供了一个测试脚本的命令行接口。当在命令行运行该测试脚本，上文的脚本生成如以下格式的输出:

@example
...
----------------------------------------------------------------------
Ran 3 tests in 0.000s

OK
@end example

在调用测试脚本时添加 @code{-v} 参数使 @ref{8fc,,unittest.main()} 显示更为详细的信息，生成如以下形式的输出:

@example
test_isupper (__main__.TestStringMethods) ... ok
test_split (__main__.TestStringMethods) ... ok
test_upper (__main__.TestStringMethods) ... ok

----------------------------------------------------------------------
Ran 3 tests in 0.001s

OK
@end example

以上例子演示了 @ref{11b,,unittest} 中最常用的、足够满足许多日常测试需求的特性。文档的剩余部分详述该框架的完整特性。

@node 命令行界面<5>,探索性测试,基本实例,unittest --- 单元测试框架
@anchor{library/unittest command-line-interface}@anchor{32c2}@anchor{library/unittest unittest-command-line-interface}@anchor{32c3}
@subsubsection 命令行界面


unittest 模块可以通过命令行运行模块、类和独立测试方法的测试:

@example
python -m unittest test_module1 test_module2
python -m unittest test_module.TestClass
python -m unittest test_module.TestClass.test_method
@end example

你可以传入模块名、类或方法名或他们的任意组合。

同样的，测试模块可以通过文件路径指定:

@example
python -m unittest tests/test_something.py
@end example

这样就可以使用 shell 的文件名补全指定测试模块。所指定的文件仍需要可以被作为模块导入。路径通过去除 '.py' 、把分隔符转换为 '.' 转换为模块名。若你需要执行不能被作为模块导入的测试文件，你需要直接执行该测试文件。

在运行测试时，你可以通过添加 -v 参数获取更详细（更多的冗余）的信息。

@example
python -m unittest -v test_module
@end example

当运行时不包含参数，开始 @ref{32c4,,探索性测试}

@example
python -m unittest
@end example

用于获取命令行选项列表：

@example
python -m unittest -h
@end example


在 3.2 版更改: 在早期版本中，只支持运行独立的测试方法，而不支持模块和类。


@menu
* 命令行选项: 命令行选项<5>. 

@end menu

@node 命令行选项<5>,,,命令行界面<5>
@anchor{library/unittest command-line-options}@anchor{32c5}
@subsubsection 命令行选项


@code{unittest} supports these command-line options:

@geindex unittest command line option; -b
@geindex unittest command line option; --buffer
@anchor{library/unittest cmdoption-unittest-b}@anchor{cbc}
@deffn {程序选项} @w{-}b, @w{-}@w{-}buffer

在测试运行时，标准输出流与标准错误流会被放入缓冲区。成功的测试的运行时输出会被丢弃；测试不通过时，测试运行中的输出会正常显示，错误会被加入到测试失败信息。
@end deffn

@geindex unittest command line option; -c
@geindex unittest command line option; --catch
@anchor{library/unittest cmdoption-unittest-c}@anchor{cbd}
@deffn {程序选项} @w{-}c, @w{-}@w{-}catch

当测试正在运行时， @code{Control-C} 会等待当前测试完成，并在完成后报告已执行的测试的结果。当再次按下 @code{Control-C} 时，引发平常的 @ref{197,,KeyboardInterrupt} 异常。

See @ref{32c6,,Signal Handling} for the functions that provide this functionality.
@end deffn

@geindex unittest command line option; -f
@geindex unittest command line option; --failfast
@anchor{library/unittest cmdoption-unittest-f}@anchor{cbf}
@deffn {程序选项} @w{-}f, @w{-}@w{-}failfast

当出现第一个错误或者失败时，停止运行测试。
@end deffn

@geindex unittest command line option; -k
@anchor{library/unittest cmdoption-unittest-k}@anchor{32c7}
@deffn {程序选项} @w{-}k

只运行匹配模式或子串的测试方法和类。可以多次使用这个选项，以便包含匹配子串的所有测试用例。

包含通配符（*）的模式使用 @ref{1c0f,,fnmatch.fnmatchcase()} 对测试名称进行匹配。另外，该匹配是大小写敏感的。

模式对测试加载器导入的测试方法全名进行匹配。

例如，@code{-k foo} 可以匹配到 @code{foo_tests.SomeTest.test_something}  和 @code{bar_tests.SomeTest.test_foo} ，但是不能匹配到 @code{bar_tests.FooTest.test_something} 。
@end deffn

@geindex unittest command line option; --locals
@anchor{library/unittest cmdoption-unittest-locals}@anchor{32c8}
@deffn {程序选项} @w{-}@w{-}locals

在回溯中显示局部变量。
@end deffn


3.2 新版功能: 添加命令行选项 @code{-b}, @code{-c} 和 @code{-f} 。



3.5 新版功能: 命令行选项 @code{--locals} 。



3.7 新版功能: 命令行选项 @code{-k} 。


命令行亦可用于探索性测试，以运行一个项目的所有测试或其子集。

@node 探索性测试,组织你的测试代码,命令行界面<5>,unittest --- 单元测试框架
@anchor{library/unittest test-discovery}@anchor{32c9}@anchor{library/unittest unittest-test-discovery}@anchor{32c4}
@subsubsection 探索性测试



3.2 新版功能.


Unittest支持简单的测试搜索。若需要使用探索性测试，所有的测试文件必须是 @ref{1211,,modules} 或 @ref{121e,,packages} （包括 @ref{144c,,namespace packages} )并可从项目根目录导入（即它们的文件名必须是有效的 @ref{136a,,identifiers} ）。

探索性测试在 @ref{8fe,,TestLoader.discover()} 中实现，但也可以通过命令行使用。它在命令行中的基本用法如下：

@example
cd project_directory
python -m unittest discover
@end example

@cartouche
@quotation 注解 
方便起见， @code{python -m unittest} 与 @code{python -m unittest discover} 等价。如果你需要向探索性测试传入参数，必须显式地使用 @code{discover} 子命令。
@end quotation
@end cartouche

@code{discover} 有以下选项：

@geindex unittest-discover command line option; -v
@geindex unittest-discover command line option; --verbose
@anchor{library/unittest cmdoption-unittest-discover-v}@anchor{32ca}
@deffn {程序选项} @w{-}v, @w{-}@w{-}verbose

更详细地输出结果。
@end deffn

@geindex unittest-discover command line option; -s
@geindex unittest-discover command line option; --start-directory directory
@anchor{library/unittest cmdoption-unittest-discover-s}@anchor{32cb}
@deffn {程序选项} @w{-}s, @w{-}@w{-}start@w{-}directory directory

开始进行搜索的目录(默认值为当前目录 @code{.} )。
@end deffn

@geindex unittest-discover command line option; -p
@geindex unittest-discover command line option; --pattern pattern
@anchor{library/unittest cmdoption-unittest-discover-p}@anchor{32cc}
@deffn {程序选项} @w{-}p, @w{-}@w{-}pattern pattern

用于匹配测试文件的模式（默认为 @code{test*.py} ）。
@end deffn

@geindex unittest-discover command line option; -t
@geindex unittest-discover command line option; --top-level-directory directory
@anchor{library/unittest cmdoption-unittest-discover-t}@anchor{32cd}
@deffn {程序选项} @w{-}t, @w{-}@w{-}top@w{-}level@w{-}directory directory

指定项目的最上层目录（通常为开始时所在目录）。
@end deffn

@ref{32cb,,-s} ，@ref{32cc,,-p} 和 @ref{32cd,,-t} 选项可以按顺序作为位置参数传入。以下两条命令是等价的：

@example
python -m unittest discover -s project_directory -p "*_test.py"
python -m unittest discover project_directory "*_test.py"
@end example

正如可以传入路径那样，传入一个包名作为起始目录也是可行的，如 @code{myproject.subpackage.test} 。你提供的包名会被导入，它在文件系统中的位置会被作为起始目录。

@cartouche
@quotation 警告 
探索性测试通过导入测试对测试进行加载。在找到所有你指定的开始目录下的所有测试文件后，它把路径转换为包名并进行导入。如 @code{foo/bar/baz.py} 会被导入为 @code{foo.bar.baz} 。

如果你有一个全局安装的包，并尝试对这个包的副本进行探索性测试，可能会从错误的地方开始导入。如果出现这种情况，测试会输出警告并退出。

如果你使用包名而不是路径作为开始目录，搜索时会假定它导入的是你想要的目录，所以你不会收到警告。
@end quotation
@end cartouche

测试模块和包可以通过 @ref{32ce,,load_tests protocol} 自定义测试的加载和搜索。


在 3.4 版更改: 探索性测试支持命名空间包（ @ref{144c,,namespace packages} ）。


@node 组织你的测试代码,复用已有的测试代码,探索性测试,unittest --- 单元测试框架
@anchor{library/unittest organizing-test-code}@anchor{32cf}@anchor{library/unittest organizing-tests}@anchor{32c1}
@subsubsection 组织你的测试代码


单元测试的构建单位是 @emph{test cases} ：独立的、包含执行条件与正确性检查的方案。在 @ref{11b,,unittest} 中，测试用例表示为 @ref{8f9,,unittest.TestCase} 的实例。通过编写 @ref{8f9,,TestCase} 的子类或使用 @ref{32d0,,FunctionTestCase} 编写你自己的测试用例。

一个 @ref{8f9,,TestCase} 实例的测试代码必须是完全自含的，因此它可以独立运行，或与其它任意组合任意数量的测试用例一起运行。

@ref{8f9,,TestCase} 的最简单的子类需要实现一个测试方法（例如一个命名以 @code{test} 开头的方法）以执行特定的测试代码：

@example
import unittest

class DefaultWidgetSizeTestCase(unittest.TestCase):
    def test_default_widget_size(self):
        widget = Widget('The widget')
        self.assertEqual(widget.size(), (50, 50))
@end example

可以看到，为了进行测试，我们使用了基类 @ref{8f9,,TestCase} 提供的其中一个 @code{assert*()} 方法。若测试不通过，将会引发一个带有说明信息的异常，并且 @ref{11b,,unittest} 会将这个测试用例标记为测试不通过。任何其它类型的异常将会被当做错误处理。

可能同时存在多个前置操作相同的测试，我们可以把测试的前置操作从测试代码中拆解出来，并实现测试前置方法 @ref{cc4,,setUp()} 。在运行测试时，测试框架会自动地为每个单独测试调用前置方法。

@example
import unittest

class WidgetTestCase(unittest.TestCase):
    def setUp(self):
        self.widget = Widget('The widget')

    def test_default_widget_size(self):
        self.assertEqual(self.widget.size(), (50,50),
                         'incorrect default size')

    def test_widget_resize(self):
        self.widget.resize(100,150)
        self.assertEqual(self.widget.size(), (100,150),
                         'wrong size after resize')
@end example

@cartouche
@quotation 注解 
多个测试运行的顺序由内置字符串排序方法对测试名进行排序的结果决定。
@end quotation
@end cartouche

在测试运行时，若 @ref{cc4,,setUp()} 方法引发异常，测试框架会认为测试发生了错误，因此测试方法不会被运行。

相似的，我们提供了一个 @ref{cc5,,tearDown()} 方法在测试方法运行后进行清理工作。

@example
import unittest

class WidgetTestCase(unittest.TestCase):
    def setUp(self):
        self.widget = Widget('The widget')

    def tearDown(self):
        self.widget.dispose()
@end example

若 @ref{cc4,,setUp()} 成功运行，无论测试方法是否成功，都会运行 @ref{cc5,,tearDown()} 。

这样的一个测试代码运行的环境被称为 @emph{test fixture} 。一个新的 TestCase 实例作为一个测试脚手架，用于运行各个独立的测试方法。在运行每个测试时，@ref{cc4,,setUp()} 、@ref{cc5,,tearDown()} 和 @code{__init__()} 会被调用一次。

It is recommended that you use TestCase implementations to group tests together
according to the features they test.  @ref{11b,,unittest} provides a mechanism for
this: the @emph{test suite}, represented by @ref{11b,,unittest}'s
@ref{6c8,,TestSuite} class.  In most cases, calling @ref{8fc,,unittest.main()} will do
the right thing and collect all the module's test cases for you and execute
them.

然而，如果你需要自定义你的测试套件的话，你可以参考以下方法组织你的测试：

@example
def suite():
    suite = unittest.TestSuite()
    suite.addTest(WidgetTestCase('test_default_widget_size'))
    suite.addTest(WidgetTestCase('test_widget_resize'))
    return suite

if __name__ == '__main__':
    runner = unittest.TextTestRunner()
    runner.run(suite())
@end example

You can place the definitions of test cases and test suites in the same modules
as the code they are to test (such as @code{widget.py}), but there are several
advantages to placing the test code in a separate module, such as
@code{test_widget.py}:


@itemize *

@item 
The test module can be run standalone from the command line.

@item 
The test code can more easily be separated from shipped code.

@item 
There is less temptation to change test code to fit the code it tests without
a good reason.

@item 
Test code should be modified much less frequently than the code it tests.

@item 
Tested code can be refactored more easily.

@item 
Tests for modules written in C must be in separate modules anyway, so why not
be consistent?

@item 
If the testing strategy changes, there is no need to change the source code.
@end itemize

@node 复用已有的测试代码,跳过测试与预计的失败,组织你的测试代码,unittest --- 单元测试框架
@anchor{library/unittest legacy-unit-tests}@anchor{32d1}@anchor{library/unittest re-using-old-test-code}@anchor{32d2}
@subsubsection 复用已有的测试代码


一些用户希望直接使用 @ref{11b,,unittest} 运行已有的测试代码，而不需要把已有的每个测试函数转化为一个 @ref{8f9,,TestCase} 的子类。

因此， @ref{11b,,unittest} 提供 @ref{32d0,,FunctionTestCase} 类。这个 @ref{8f9,,TestCase} 的子类可用于打包已有的测试函数，并支持设置前置与后置函数。

假定有一个测试函数：

@example
def testSomething():
    something = makeSomething()
    assert something.name is not None
    # ...
@end example

可以创建等价的测试用例如下，其中前置和后置方法是可选的。

@example
testcase = unittest.FunctionTestCase(testSomething,
                                     setUp=makeSomethingDB,
                                     tearDown=deleteSomethingDB)
@end example

@cartouche
@quotation 注解 
Even though @ref{32d0,,FunctionTestCase} can be used to quickly convert an
existing test base over to a @ref{11b,,unittest}-based system, this approach is
not recommended.  Taking the time to set up proper @ref{8f9,,TestCase}
subclasses will make future test refactorings infinitely easier.
@end quotation
@end cartouche

In some cases, the existing tests may have been written using the @ref{67,,doctest}
module.  If so, @ref{67,,doctest} provides a @code{DocTestSuite} class that can
automatically build @ref{6c8,,unittest.TestSuite} instances from the existing
@ref{67,,doctest}-based tests.

@node 跳过测试与预计的失败,Distinguishing test iterations using subtests,复用已有的测试代码,unittest --- 单元测试框架
@anchor{library/unittest skipping-tests-and-expected-failures}@anchor{32d3}@anchor{library/unittest unittest-skipping}@anchor{32d4}
@subsubsection 跳过测试与预计的失败



3.1 新版功能.


Unittest supports skipping individual test methods and even whole classes of
tests.  In addition, it supports marking a test as an "expected failure," a test
that is broken and will fail, but shouldn't be counted as a failure on a
@ref{aba,,TestResult}.

Skipping a test is simply a matter of using the @ref{f0f,,skip()} @ref{283,,decorator}
or one of its conditional variants, calling @ref{32d5,,TestCase.skipTest()} within a
@ref{cc4,,setUp()} or test method, or raising @ref{8fd,,SkipTest} directly.

跳过测试的基本用法如下:

@example
class MyTestCase(unittest.TestCase):

    @@unittest.skip("demonstrating skipping")
    def test_nothing(self):
        self.fail("shouldn't happen")

    @@unittest.skipIf(mylib.__version__ < (1, 3),
                     "not supported in this library version")
    def test_format(self):
        # Tests that work for only a certain version of the library.
        pass

    @@unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
    def test_windows_support(self):
        # windows specific testing code
        pass

    def test_maybe_skipped(self):
        if not external_resource_available():
            self.skipTest("external resource not available")
        # test code that depends on the external resource
        pass
@end example

在啰嗦模式下运行以上测试例子时，程序输出如下：

@example
test_format (__main__.MyTestCase) ... skipped 'not supported in this library version'
test_nothing (__main__.MyTestCase) ... skipped 'demonstrating skipping'
test_maybe_skipped (__main__.MyTestCase) ... skipped 'external resource not available'
test_windows_support (__main__.MyTestCase) ... skipped 'requires Windows'

----------------------------------------------------------------------
Ran 4 tests in 0.005s

OK (skipped=4)
@end example

跳过测试类的写法跟跳过测试方法的写法相似:

@example
@@unittest.skip("showing class skipping")
class MySkippedTestCase(unittest.TestCase):
    def test_not_run(self):
        pass
@end example

@ref{cc4,,TestCase.setUp()}  也可以跳过测试。可以用于所需资源不可用的情况下跳过接下来的测试。

使用 @ref{32d6,,expectedFailure()} 装饰器表明这个测试预计失败。:

@example
class ExpectedFailureTestCase(unittest.TestCase):
    @@unittest.expectedFailure
    def test_fail(self):
        self.assertEqual(1, 0, "broken")
@end example

It's easy to roll your own skipping decorators by making a decorator that calls
@ref{f0f,,skip()} on the test when it wants it to be skipped.  This decorator skips
the test unless the passed object has a certain attribute:

@example
def skipUnlessHasattr(obj, attr):
    if hasattr(obj, attr):
        return lambda func: func
    return unittest.skip("@{!r@} doesn't have @{!r@}".format(obj, attr))
@end example

The following decorators and exception implement test skipping and expected failures:

@geindex skip() (在 unittest 模块中)
@anchor{library/unittest unittest skip}@anchor{f0f}
@deffn {函数} @@unittest.skip (reason)

跳过被此装饰器装饰的测试。 @emph{reason}  为测试被跳过的原因。
@end deffn

@geindex skipIf() (在 unittest 模块中)
@anchor{library/unittest unittest skipIf}@anchor{32d7}
@deffn {函数} @@unittest.skipIf (condition, reason)

当 @emph{condition} 为真时，跳过被装饰的测试。
@end deffn

@geindex skipUnless() (在 unittest 模块中)
@anchor{library/unittest unittest skipUnless}@anchor{32d8}
@deffn {函数} @@unittest.skipUnless (condition, reason)

跳过被装饰的测试，除非 @emph{condition} 为真。
@end deffn

@geindex expectedFailure() (在 unittest 模块中)
@anchor{library/unittest unittest expectedFailure}@anchor{32d6}
@deffn {函数} @@unittest.expectedFailure

把测试标记为预计失败。如果测试不通过，会被认为测试成功；如果测试通过了，则被认为是测试失败。
@end deffn

@geindex SkipTest
@anchor{library/unittest unittest SkipTest}@anchor{8fd}
@deffn {例外} unittest.SkipTest (reason)

引发此异常以跳过一个测试。

通常来说，你可以使用 @ref{32d5,,TestCase.skipTest()} 或其中一个跳过测试的装饰器实现跳过测试的功能，而不是直接引发此异常。
@end deffn

被跳过的测试的 @ref{cc4,,setUp()}  和 @ref{cc5,,tearDown()} 不会被运行。被跳过的类的 @ref{24c,,setUpClass()} 和 @ref{cc2,,tearDownClass()} 不会被运行。被跳过的模组的 @code{setUpModule()} 和 @code{tearDownModule()} 不会被运行。

@node Distinguishing test iterations using subtests,类与函数,跳过测试与预计的失败,unittest --- 单元测试框架
@anchor{library/unittest distinguishing-test-iterations-using-subtests}@anchor{32d9}@anchor{library/unittest subtests}@anchor{8fb}
@subsubsection Distinguishing test iterations using subtests



3.4 新版功能.


When there are very small differences among your tests, for
instance some parameters, unittest allows you to distinguish them inside
the body of a test method using the @ref{8fa,,subTest()} context manager.

例如，以下测试:

@example
class NumbersTest(unittest.TestCase):

    def test_even(self):
        """
        Test that numbers between 0 and 5 are all even.
        """
        for i in range(0, 6):
            with self.subTest(i=i):
                self.assertEqual(i % 2, 0)
@end example

可以得到以下输出:

@example
======================================================================
FAIL: test_even (__main__.NumbersTest) (i=1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 32, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0

======================================================================
FAIL: test_even (__main__.NumbersTest) (i=3)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 32, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0

======================================================================
FAIL: test_even (__main__.NumbersTest) (i=5)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 32, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0
@end example

Without using a subtest, execution would stop after the first failure,
and the error would be less easy to diagnose because the value of @code{i}
wouldn't be displayed:

@example
======================================================================
FAIL: test_even (__main__.NumbersTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 32, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0
@end example

@node 类与函数,Class and Module Fixtures,Distinguishing test iterations using subtests,unittest --- 单元测试框架
@anchor{library/unittest classes-and-functions}@anchor{32da}@anchor{library/unittest unittest-contents}@anchor{32db}
@subsubsection 类与函数


本节深入介绍了 @ref{11b,,unittest} 的 API。

@menu
* 测试用例:: 
* Grouping tests:: 
* Loading and running tests:: 

@end menu

@node 测试用例,Grouping tests,,类与函数
@anchor{library/unittest test-cases}@anchor{32dc}@anchor{library/unittest testcase-objects}@anchor{32dd}
@subsubsection 测试用例


@geindex TestCase (unittest 中的类)
@anchor{library/unittest unittest TestCase}@anchor{8f9}
@deffn {类} unittest.TestCase (methodName='runTest')

Instances of the @ref{8f9,,TestCase} class represent the logical test units
in the @ref{11b,,unittest} universe.  This class is intended to be used as a base
class, with specific tests being implemented by concrete subclasses.  This class
implements the interface needed by the test runner to allow it to drive the
tests, and methods that the test code can use to check for and report various
kinds of failure.

Each instance of @ref{8f9,,TestCase} will run a single base method: the method
named @emph{methodName}.
In most uses of @ref{8f9,,TestCase}, you will neither change
the @emph{methodName} nor reimplement the default @code{runTest()} method.


在 3.2 版更改: @ref{8f9,,TestCase} can be instantiated successfully without providing a
@emph{methodName}. This makes it easier to experiment with @ref{8f9,,TestCase}
from the interactive interpreter.


@ref{8f9,,TestCase} instances provide three groups of methods: one group used
to run the test, another used by the test implementation to check conditions
and report failures, and some inquiry methods allowing information about the
test itself to be gathered.

Methods in the first group (running the test) are:

@geindex setUp() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase setUp}@anchor{cc4}
@deffn {方法} setUp ()

Method called to prepare the test fixture.  This is called immediately
before calling the test method; other than @ref{fc1,,AssertionError} or @ref{8fd,,SkipTest},
any exception raised by this method will be considered an error rather than
a test failure. The default implementation does nothing.
@end deffn

@geindex tearDown() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase tearDown}@anchor{cc5}
@deffn {方法} tearDown ()

Method called immediately after the test method has been called and the
result recorded.  This is called even if the test method raised an
exception, so the implementation in subclasses may need to be particularly
careful about checking internal state.  Any exception, other than
@ref{fc1,,AssertionError} or @ref{8fd,,SkipTest}, raised by this method will be
considered an additional error rather than a test failure (thus increasing
the total number of reported errors). This method will only be called if
the @ref{cc4,,setUp()} succeeds, regardless of the outcome of the test method.
The default implementation does nothing.
@end deffn

@geindex setUpClass() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase setUpClass}@anchor{24c}
@deffn {方法} setUpClass ()

A class method called before tests in an individual class are run.
@code{setUpClass} is called with the class as the only argument
and must be decorated as a @ref{1d8,,classmethod()}:

@example
@@classmethod
def setUpClass(cls):
    ...
@end example

查看 @ref{32de,,Class and Module Fixtures} 获取更详细的说明。


3.2 新版功能.

@end deffn

@geindex tearDownClass() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase tearDownClass}@anchor{cc2}
@deffn {方法} tearDownClass ()

A class method called after tests in an individual class have run.
@code{tearDownClass} is called with the class as the only argument
and must be decorated as a @ref{1d8,,classmethod()}:

@example
@@classmethod
def tearDownClass(cls):
    ...
@end example

查看 @ref{32de,,Class and Module Fixtures} 获取更详细的说明。


3.2 新版功能.

@end deffn

@geindex run() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase run}@anchor{ab9}
@deffn {方法} run (result=None)

Run the test, collecting the result into the @ref{aba,,TestResult} object
passed as @emph{result}.  If @emph{result} is omitted or @code{None}, a temporary
result object is created (by calling the @ref{32df,,defaultTestResult()}
method) and used. The result object is returned to @ref{ab9,,run()}'s
caller.

The same effect may be had by simply calling the @ref{8f9,,TestCase}
instance.


在 3.3 版更改: Previous versions of @code{run} did not return the result. Neither did
calling an instance.

@end deffn

@geindex skipTest() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase skipTest}@anchor{32d5}
@deffn {方法} skipTest (reason)

Calling this during a test method or @ref{cc4,,setUp()} skips the current
test.  See @ref{32d4,,跳过测试与预计的失败} for more information.


3.1 新版功能.

@end deffn

@geindex subTest() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase subTest}@anchor{8fa}
@deffn {方法} subTest (msg=None, **params)

Return a context manager which executes the enclosed code block as a
subtest.  @emph{msg} and @emph{params} are optional, arbitrary values which are
displayed whenever a subtest fails, allowing you to identify them
clearly.

A test case can contain any number of subtest declarations, and
they can be arbitrarily nested.

查看 @ref{8fb,,Distinguishing test iterations using subtests} 获取更详细的信息。


3.4 新版功能.

@end deffn

@geindex debug() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase debug}@anchor{fba}
@deffn {方法} debug ()

Run the test without collecting the result.  This allows exceptions raised
by the test to be propagated to the caller, and can be used to support
running tests under a debugger.
@end deffn
@anchor{library/unittest assert-methods}@anchor{32be}
The @ref{8f9,,TestCase} class provides several assert methods to check for and
report failures.  The following table lists the most commonly used methods
(see the tables below for more assert methods):


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} 
@headitem

Method

@tab

Checks that

@tab

New in

@item

@ref{bae,,assertEqual(a@comma{} b)}

@tab

@code{a == b}

@tab

@item

@ref{baf,,assertNotEqual(a@comma{} b)}

@tab

@code{a != b}

@tab

@item

@ref{bad,,assertTrue(x)}

@tab

@code{bool(x) is True}

@tab

@item

@ref{cc0,,assertFalse(x)}

@tab

@code{bool(x) is False}

@tab

@item

@ref{cc8,,assertIs(a@comma{} b)}

@tab

@code{a is b}

@tab

3.1

@item

@ref{cc9,,assertIsNot(a@comma{} b)}

@tab

@code{a is not b}

@tab

3.1

@item

@ref{cc6,,assertIsNone(x)}

@tab

@code{x is None}

@tab

3.1

@item

@ref{cc7,,assertIsNotNone(x)}

@tab

@code{x is not None}

@tab

3.1

@item

@ref{cd1,,assertIn(a@comma{} b)}

@tab

@code{a in b}

@tab

3.1

@item

@ref{cd2,,assertNotIn(a@comma{} b)}

@tab

@code{a not in b}

@tab

3.1

@item

@ref{cca,,assertIsInstance(a@comma{} b)}

@tab

@code{isinstance(a, b)}

@tab

3.2

@item

@ref{ccb,,assertNotIsInstance(a@comma{} b)}

@tab

@code{not isinstance(a, b)}

@tab

3.2

@end multitable


All the assert methods accept a @emph{msg} argument that, if specified, is used
as the error message on failure (see also @ref{cc1,,longMessage}).
Note that the @emph{msg} keyword argument can be passed to @ref{ab5,,assertRaises()},
@ref{ab6,,assertRaisesRegex()}, @ref{ab7,,assertWarns()}, @ref{ab8,,assertWarnsRegex()}
only when they are used as a context manager.

@geindex assertEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertEqual}@anchor{bae}
@deffn {方法} assertEqual (first, second, msg=None)

Test that @emph{first} and @emph{second} are equal.  If the values do not
compare equal, the test will fail.

In addition, if @emph{first} and @emph{second} are the exact same type and one of
list, tuple, dict, set, frozenset or str or any type that a subclass
registers with @ref{cda,,addTypeEqualityFunc()} the type-specific equality
function will be called in order to generate a more useful default
error message (see also the @ref{32e0,,list of type-specific methods}).


在 3.1 版更改: Added the automatic calling of type-specific equality function.



在 3.2 版更改: @ref{cd0,,assertMultiLineEqual()} added as the default type equality
function for comparing strings.

@end deffn

@geindex assertNotEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertNotEqual}@anchor{baf}
@deffn {方法} assertNotEqual (first, second, msg=None)

Test that @emph{first} and @emph{second} are not equal.  If the values do
compare equal, the test will fail.
@end deffn

@geindex assertTrue() (unittest.TestCase 方法)
@geindex assertFalse() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertTrue}@anchor{bad}
@deffn {方法} assertTrue (expr, msg=None)
@anchor{library/unittest unittest TestCase assertFalse}@anchor{cc0}
@deffnx {方法} assertFalse (expr, msg=None)

Test that @emph{expr} is true (or false).

Note that this is equivalent to @code{bool(expr) is True} and not to @code{expr
is True} (use @code{assertIs(expr, True)} for the latter).  This method
should also be avoided when more specific methods are available (e.g.
@code{assertEqual(a, b)} instead of @code{assertTrue(a == b)}), because they
provide a better error message in case of failure.
@end deffn

@geindex assertIs() (unittest.TestCase 方法)
@geindex assertIsNot() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertIs}@anchor{cc8}
@deffn {方法} assertIs (first, second, msg=None)
@anchor{library/unittest unittest TestCase assertIsNot}@anchor{cc9}
@deffnx {方法} assertIsNot (first, second, msg=None)

Test that @emph{first} and @emph{second} evaluate (or don't evaluate) to the
same object.


3.1 新版功能.

@end deffn

@geindex assertIsNone() (unittest.TestCase 方法)
@geindex assertIsNotNone() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertIsNone}@anchor{cc6}
@deffn {方法} assertIsNone (expr, msg=None)
@anchor{library/unittest unittest TestCase assertIsNotNone}@anchor{cc7}
@deffnx {方法} assertIsNotNone (expr, msg=None)

Test that @emph{expr} is (or is not) @code{None}.


3.1 新版功能.

@end deffn

@geindex assertIn() (unittest.TestCase 方法)
@geindex assertNotIn() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertIn}@anchor{cd1}
@deffn {方法} assertIn (member, container, msg=None)
@anchor{library/unittest unittest TestCase assertNotIn}@anchor{cd2}
@deffnx {方法} assertNotIn (member, container, msg=None)

Test that @emph{member} is (or is not) in @emph{container}.


3.1 新版功能.

@end deffn

@geindex assertIsInstance() (unittest.TestCase 方法)
@geindex assertNotIsInstance() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertIsInstance}@anchor{cca}
@deffn {方法} assertIsInstance (obj, cls, msg=None)
@anchor{library/unittest unittest TestCase assertNotIsInstance}@anchor{ccb}
@deffnx {方法} assertNotIsInstance (obj, cls, msg=None)

Test that @emph{obj} is (or is not) an instance of @emph{cls} (which can be a
class or a tuple of classes, as supported by @ref{449,,isinstance()}).
To check for the exact type, use @ref{cc8,,assertIs(type(obj)@comma{} cls)}.


3.2 新版功能.

@end deffn

It is also possible to check the production of exceptions, warnings, and
log messages using the following methods:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} 
@headitem

Method

@tab

Checks that

@tab

New in

@item

@ref{ab5,,assertRaises(exc@comma{} fun@comma{} *args@comma{} **kwds)}

@tab

@code{fun(*args, **kwds)} raises @emph{exc}

@tab

@item

@ref{ab6,,assertRaisesRegex(exc@comma{} r@comma{} fun@comma{} *args@comma{} **kwds)}

@tab

@code{fun(*args, **kwds)} raises @emph{exc}
and the message matches regex @emph{r}

@tab

3.1

@item

@ref{ab7,,assertWarns(warn@comma{} fun@comma{} *args@comma{} **kwds)}

@tab

@code{fun(*args, **kwds)} raises @emph{warn}

@tab

3.2

@item

@ref{ab8,,assertWarnsRegex(warn@comma{} r@comma{} fun@comma{} *args@comma{} **kwds)}

@tab

@code{fun(*args, **kwds)} raises @emph{warn}
and the message matches regex @emph{r}

@tab

3.2

@item

@ref{8ff,,assertLogs(logger@comma{} level)}

@tab

The @code{with} block logs on @emph{logger}
with minimum @emph{level}

@tab

3.4

@end multitable


@geindex assertRaises() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertRaises}@anchor{ab5}
@deffn {方法} assertRaises (exception, callable, *args, **kwds)

@deffnx {方法} assertRaises (exception, *, msg=None)

Test that an exception is raised when @emph{callable} is called with any
positional or keyword arguments that are also passed to
@ref{ab5,,assertRaises()}.  The test passes if @emph{exception} is raised, is an
error if another exception is raised, or fails if no exception is raised.
To catch any of a group of exceptions, a tuple containing the exception
classes may be passed as @emph{exception}.

If only the @emph{exception} and possibly the @emph{msg} arguments are given,
return a context manager so that the code under test can be written
inline rather than as a function:

@example
with self.assertRaises(SomeException):
    do_something()
@end example

When used as a context manager, @ref{ab5,,assertRaises()} accepts the
additional keyword argument @emph{msg}.

The context manager will store the caught exception object in its
@code{exception} attribute.  This can be useful if the intention
is to perform additional checks on the exception raised:

@example
with self.assertRaises(SomeException) as cm:
    do_something()

the_exception = cm.exception
self.assertEqual(the_exception.error_code, 3)
@end example


在 3.1 版更改: Added the ability to use @ref{ab5,,assertRaises()} as a context manager.



在 3.2 版更改: Added the @code{exception} attribute.



在 3.3 版更改: Added the @emph{msg} keyword argument when used as a context manager.

@end deffn

@geindex assertRaisesRegex() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertRaisesRegex}@anchor{ab6}
@deffn {方法} assertRaisesRegex (exception, regex, callable, *args, **kwds)

@deffnx {方法} assertRaisesRegex (exception, regex, *, msg=None)

Like @ref{ab5,,assertRaises()} but also tests that @emph{regex} matches
on the string representation of the raised exception.  @emph{regex} may be
a regular expression object or a string containing a regular expression
suitable for use by @ref{bab,,re.search()}.  Examples:

@example
self.assertRaisesRegex(ValueError, "invalid literal for.*XYZ'$",
                       int, 'XYZ')
@end example

或者：

@example
with self.assertRaisesRegex(ValueError, 'literal'):
   int('XYZ')
@end example


3.1 新版功能: Added under the name @code{assertRaisesRegexp}.



在 3.2 版更改: Renamed to @ref{ab6,,assertRaisesRegex()}.



在 3.3 版更改: Added the @emph{msg} keyword argument when used as a context manager.

@end deffn

@geindex assertWarns() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertWarns}@anchor{ab7}
@deffn {方法} assertWarns (warning, callable, *args, **kwds)

@deffnx {方法} assertWarns (warning, *, msg=None)

Test that a warning is triggered when @emph{callable} is called with any
positional or keyword arguments that are also passed to
@ref{ab7,,assertWarns()}.  The test passes if @emph{warning} is triggered and
fails if it isn't.  Any exception is an error.
To catch any of a group of warnings, a tuple containing the warning
classes may be passed as @emph{warnings}.

If only the @emph{warning} and possibly the @emph{msg} arguments are given,
return a context manager so that the code under test can be written
inline rather than as a function:

@example
with self.assertWarns(SomeWarning):
    do_something()
@end example

When used as a context manager, @ref{ab7,,assertWarns()} accepts the
additional keyword argument @emph{msg}.

The context manager will store the caught warning object in its
@code{warning} attribute, and the source line which triggered the
warnings in the @code{filename} and @code{lineno} attributes.
This can be useful if the intention is to perform additional checks
on the warning caught:

@example
with self.assertWarns(SomeWarning) as cm:
    do_something()

self.assertIn('myfile.py', cm.filename)
self.assertEqual(320, cm.lineno)
@end example

This method works regardless of the warning filters in place when it
is called.


3.2 新版功能.



在 3.3 版更改: Added the @emph{msg} keyword argument when used as a context manager.

@end deffn

@geindex assertWarnsRegex() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertWarnsRegex}@anchor{ab8}
@deffn {方法} assertWarnsRegex (warning, regex, callable, *args, **kwds)

@deffnx {方法} assertWarnsRegex (warning, regex, *, msg=None)

Like @ref{ab7,,assertWarns()} but also tests that @emph{regex} matches on the
message of the triggered warning.  @emph{regex} may be a regular expression
object or a string containing a regular expression suitable for use
by @ref{bab,,re.search()}.  Example:

@example
self.assertWarnsRegex(DeprecationWarning,
                      r'legacy_function\(\) is deprecated',
                      legacy_function, 'XYZ')
@end example

或者：

@example
with self.assertWarnsRegex(RuntimeWarning, 'unsafe frobnicating'):
    frobnicate('/etc/passwd')
@end example


3.2 新版功能.



在 3.3 版更改: Added the @emph{msg} keyword argument when used as a context manager.

@end deffn

@geindex assertLogs() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertLogs}@anchor{8ff}
@deffn {方法} assertLogs (logger=None, level=None)

A context manager to test that at least one message is logged on
the @emph{logger} or one of its children, with at least the given
@emph{level}.

If given, @emph{logger} should be a @ref{39f,,logging.Logger} object or a
@ref{329,,str} giving the name of a logger.  The default is the root
logger, which will catch all messages.

If given, @emph{level} should be either a numeric logging level or
its string equivalent (for example either @code{"ERROR"} or
@code{logging.ERROR}).  The default is @code{logging.INFO}.

The test passes if at least one message emitted inside the @code{with}
block matches the @emph{logger} and @emph{level} conditions, otherwise it fails.

The object returned by the context manager is a recording helper
which keeps tracks of the matching log messages.  It has two
attributes:

@geindex records (unittest.TestCase 属性)
@anchor{library/unittest unittest TestCase records}@anchor{32e1}
@deffn {属性} records

A list of @ref{900,,logging.LogRecord} objects of the matching
log messages.
@end deffn

@geindex output (unittest.TestCase 属性)
@anchor{library/unittest unittest TestCase output}@anchor{32e2}
@deffn {属性} output

A list of @ref{329,,str} objects with the formatted output of
matching messages.
@end deffn

示例:

@example
with self.assertLogs('foo', level='INFO') as cm:
   logging.getLogger('foo').info('first message')
   logging.getLogger('foo.bar').error('second message')
self.assertEqual(cm.output, ['INFO:foo:first message',
                             'ERROR:foo.bar:second message'])
@end example


3.4 新版功能.

@end deffn

There are also other methods used to perform more specific checks, such as:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} 
@headitem

Method

@tab

Checks that

@tab

New in

@item

@ref{bb0,,assertAlmostEqual(a@comma{} b)}

@tab

@code{round(a-b, 7) == 0}

@tab

@item

@ref{bb1,,assertNotAlmostEqual(a@comma{} b)}

@tab

@code{round(a-b, 7) != 0}

@tab

@item

@ref{ccc,,assertGreater(a@comma{} b)}

@tab

@code{a > b}

@tab

3.1

@item

@ref{ccd,,assertGreaterEqual(a@comma{} b)}

@tab

@code{a >= b}

@tab

3.1

@item

@ref{cce,,assertLess(a@comma{} b)}

@tab

@code{a < b}

@tab

3.1

@item

@ref{ccf,,assertLessEqual(a@comma{} b)}

@tab

@code{a <= b}

@tab

3.1

@item

@ref{baa,,assertRegex(s@comma{} r)}

@tab

@code{r.search(s)}

@tab

3.1

@item

@ref{32e3,,assertNotRegex(s@comma{} r)}

@tab

@code{not r.search(s)}

@tab

3.2

@item

@ref{ba8,,assertCountEqual(a@comma{} b)}

@tab

@emph{a} and @emph{b} have the same
elements in the same number,
regardless of their order.

@tab

3.2

@end multitable


@geindex assertAlmostEqual() (unittest.TestCase 方法)
@geindex assertNotAlmostEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertAlmostEqual}@anchor{bb0}
@deffn {方法} assertAlmostEqual (first, second, places=7, msg=None, delta=None)
@anchor{library/unittest unittest TestCase assertNotAlmostEqual}@anchor{bb1}
@deffnx {方法} assertNotAlmostEqual (first, second, places=7, msg=None, delta=None)

Test that @emph{first} and @emph{second} are approximately (or not approximately)
equal by computing the difference, rounding to the given number of
decimal @emph{places} (default 7), and comparing to zero.  Note that these
methods round the values to the given number of @emph{decimal places} (i.e.
like the @ref{c66,,round()} function) and not @emph{significant digits}.

If @emph{delta} is supplied instead of @emph{places} then the difference
between @emph{first} and @emph{second} must be less or equal to (or greater than) @emph{delta}.

Supplying both @emph{delta} and @emph{places} raises a @ref{192,,TypeError}.


在 3.2 版更改: @ref{bb0,,assertAlmostEqual()} automatically considers almost equal objects
that compare equal.  @ref{bb1,,assertNotAlmostEqual()} automatically fails
if the objects compare equal.  Added the @emph{delta} keyword argument.

@end deffn

@geindex assertGreater() (unittest.TestCase 方法)
@geindex assertGreaterEqual() (unittest.TestCase 方法)
@geindex assertLess() (unittest.TestCase 方法)
@geindex assertLessEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertGreater}@anchor{ccc}
@deffn {方法} assertGreater (first, second, msg=None)
@anchor{library/unittest unittest TestCase assertGreaterEqual}@anchor{ccd}
@deffnx {方法} assertGreaterEqual (first, second, msg=None)
@anchor{library/unittest unittest TestCase assertLess}@anchor{cce}
@deffnx {方法} assertLess (first, second, msg=None)
@anchor{library/unittest unittest TestCase assertLessEqual}@anchor{ccf}
@deffnx {方法} assertLessEqual (first, second, msg=None)

Test that @emph{first} is respectively >, >=, < or <= than @emph{second} depending
on the method name.  If not, the test will fail:

@example
>>> self.assertGreaterEqual(3, 4)
AssertionError: "3" unexpectedly not greater than or equal to "4"
@end example


3.1 新版功能.

@end deffn

@geindex assertRegex() (unittest.TestCase 方法)
@geindex assertNotRegex() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertRegex}@anchor{baa}
@deffn {方法} assertRegex (text, regex, msg=None)
@anchor{library/unittest unittest TestCase assertNotRegex}@anchor{32e3}
@deffnx {方法} assertNotRegex (text, regex, msg=None)

Test that a @emph{regex} search matches (or does not match) @emph{text}.  In case
of failure, the error message will include the pattern and the @emph{text} (or
the pattern and the part of @emph{text} that unexpectedly matched).  @emph{regex}
may be a regular expression object or a string containing a regular
expression suitable for use by @ref{bab,,re.search()}.


3.1 新版功能: Added under the name @code{assertRegexpMatches}.



在 3.2 版更改: The method @code{assertRegexpMatches()} has been renamed to
@ref{baa,,assertRegex()}.



3.2 新版功能: @ref{32e3,,assertNotRegex()}



3.5 新版功能: The name @code{assertNotRegexpMatches} is a deprecated alias
for @ref{32e3,,assertNotRegex()}.

@end deffn

@geindex assertCountEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertCountEqual}@anchor{ba8}
@deffn {方法} assertCountEqual (first, second, msg=None)

Test that sequence @emph{first} contains the same elements as @emph{second},
regardless of their order. When they don't, an error message listing the
differences between the sequences will be generated.

Duplicate elements are @emph{not} ignored when comparing @emph{first} and
@emph{second}. It verifies whether each element has the same count in both
sequences. Equivalent to:
@code{assertEqual(Counter(list(first)), Counter(list(second)))}
but works with sequences of unhashable objects as well.


3.2 新版功能.

@end deffn
@anchor{library/unittest type-specific-methods}@anchor{32e0}
The @ref{bae,,assertEqual()} method dispatches the equality check for objects of
the same type to different type-specific methods.  These methods are already
implemented for most of the built-in types, but it's also possible to
register new methods using @ref{cda,,addTypeEqualityFunc()}:

@geindex addTypeEqualityFunc() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase addTypeEqualityFunc}@anchor{cda}
@deffn {方法} addTypeEqualityFunc (typeobj, function)

Registers a type-specific method called by @ref{bae,,assertEqual()} to check
if two objects of exactly the same @emph{typeobj} (not subclasses) compare
equal.  @emph{function} must take two positional arguments and a third msg=None
keyword argument just as @ref{bae,,assertEqual()} does.  It must raise
@ref{32e4,,self.failureException(msg)} when inequality
between the first two parameters is detected -- possibly providing useful
information and explaining the inequalities in details in the error
message.


3.1 新版功能.

@end deffn

The list of type-specific methods automatically used by
@ref{bae,,assertEqual()} are summarized in the following table.  Note
that it's usually not necessary to invoke these methods directly.


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} 
@headitem

Method

@tab

Used to compare

@tab

New in

@item

@ref{cd0,,assertMultiLineEqual(a@comma{} b)}

@tab

strings

@tab

3.1

@item

@ref{cd6,,assertSequenceEqual(a@comma{} b)}

@tab

sequences

@tab

3.1

@item

@ref{cd4,,assertListEqual(a@comma{} b)}

@tab

lists

@tab

3.1

@item

@ref{cd5,,assertTupleEqual(a@comma{} b)}

@tab

tuples

@tab

3.1

@item

@ref{cd3,,assertSetEqual(a@comma{} b)}

@tab

sets or frozensets

@tab

3.1

@item

@ref{cd7,,assertDictEqual(a@comma{} b)}

@tab

dicts

@tab

3.1

@end multitable


@geindex assertMultiLineEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertMultiLineEqual}@anchor{cd0}
@deffn {方法} assertMultiLineEqual (first, second, msg=None)

Test that the multiline string @emph{first} is equal to the string @emph{second}.
When not equal a diff of the two strings highlighting the differences
will be included in the error message. This method is used by default
when comparing strings with @ref{bae,,assertEqual()}.


3.1 新版功能.

@end deffn

@geindex assertSequenceEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertSequenceEqual}@anchor{cd6}
@deffn {方法} assertSequenceEqual (first, second, msg=None, seq_type=None)

Tests that two sequences are equal.  If a @emph{seq_type} is supplied, both
@emph{first} and @emph{second} must be instances of @emph{seq_type} or a failure will
be raised.  If the sequences are different an error message is
constructed that shows the difference between the two.

This method is not called directly by @ref{bae,,assertEqual()}, but
it's used to implement @ref{cd4,,assertListEqual()} and
@ref{cd5,,assertTupleEqual()}.


3.1 新版功能.

@end deffn

@geindex assertListEqual() (unittest.TestCase 方法)
@geindex assertTupleEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertListEqual}@anchor{cd4}
@deffn {方法} assertListEqual (first, second, msg=None)
@anchor{library/unittest unittest TestCase assertTupleEqual}@anchor{cd5}
@deffnx {方法} assertTupleEqual (first, second, msg=None)

Tests that two lists or tuples are equal.  If not, an error message is
constructed that shows only the differences between the two.  An error
is also raised if either of the parameters are of the wrong type.
These methods are used by default when comparing lists or tuples with
@ref{bae,,assertEqual()}.


3.1 新版功能.

@end deffn

@geindex assertSetEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertSetEqual}@anchor{cd3}
@deffn {方法} assertSetEqual (first, second, msg=None)

Tests that two sets are equal.  If not, an error message is constructed
that lists the differences between the sets.  This method is used by
default when comparing sets or frozensets with @ref{bae,,assertEqual()}.

Fails if either of @emph{first} or @emph{second} does not have a @code{set.difference()}
method.


3.1 新版功能.

@end deffn

@geindex assertDictEqual() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase assertDictEqual}@anchor{cd7}
@deffn {方法} assertDictEqual (first, second, msg=None)

Test that two dictionaries are equal.  If not, an error message is
constructed that shows the differences in the dictionaries. This
method will be used by default to compare dictionaries in
calls to @ref{bae,,assertEqual()}.


3.1 新版功能.

@end deffn
@anchor{library/unittest other-methods-and-attrs}@anchor{32e5}
Finally the @ref{8f9,,TestCase} provides the following methods and attributes:

@geindex fail() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase fail}@anchor{32e6}
@deffn {方法} fail (msg=None)

Signals a test failure unconditionally, with @emph{msg} or @code{None} for
the error message.
@end deffn

@geindex failureException (unittest.TestCase 属性)
@anchor{library/unittest unittest TestCase failureException}@anchor{32e4}
@deffn {属性} failureException

This class attribute gives the exception raised by the test method.  If a
test framework needs to use a specialized exception, possibly to carry
additional information, it must subclass this exception in order to "play
fair" with the framework.  The initial value of this attribute is
@ref{fc1,,AssertionError}.
@end deffn

@geindex longMessage (unittest.TestCase 属性)
@anchor{library/unittest unittest TestCase longMessage}@anchor{cc1}
@deffn {属性} longMessage

This class attribute determines what happens when a custom failure message
is passed as the msg argument to an assertXYY call that fails.
@code{True} is the default value. In this case, the custom message is appended
to the end of the standard failure message.
When set to @code{False}, the custom message replaces the standard message.

The class setting can be overridden in individual test methods by assigning
an instance attribute, self.longMessage, to @code{True} or @code{False} before
calling the assert methods.

The class setting gets reset before each test call.


3.1 新版功能.

@end deffn

@geindex maxDiff (unittest.TestCase 属性)
@anchor{library/unittest unittest TestCase maxDiff}@anchor{ba9}
@deffn {属性} maxDiff

This attribute controls the maximum length of diffs output by assert
methods that report diffs on failure. It defaults to 80*8 characters.
Assert methods affected by this attribute are
@ref{cd6,,assertSequenceEqual()} (including all the sequence comparison
methods that delegate to it), @ref{cd7,,assertDictEqual()} and
@ref{cd0,,assertMultiLineEqual()}.

Setting @code{maxDiff} to @code{None} means that there is no maximum length of
diffs.


3.2 新版功能.

@end deffn

Testing frameworks can use the following methods to collect information on
the test:

@geindex countTestCases() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase countTestCases}@anchor{32e7}
@deffn {方法} countTestCases ()

Return the number of tests represented by this test object.  For
@ref{8f9,,TestCase} instances, this will always be @code{1}.
@end deffn

@geindex defaultTestResult() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase defaultTestResult}@anchor{32df}
@deffn {方法} defaultTestResult ()

Return an instance of the test result class that should be used for this
test case class (if no other result instance is provided to the
@ref{ab9,,run()} method).

For @ref{8f9,,TestCase} instances, this will always be an instance of
@ref{aba,,TestResult}; subclasses of @ref{8f9,,TestCase} should override this
as necessary.
@end deffn

@geindex id() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase id}@anchor{32e8}
@deffn {方法} id ()

Return a string identifying the specific test case.  This is usually the
full name of the test method, including the module and class name.
@end deffn

@geindex shortDescription() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase shortDescription}@anchor{32e9}
@deffn {方法} shortDescription ()

Returns a description of the test, or @code{None} if no description
has been provided.  The default implementation of this method
returns the first line of the test method's docstring, if available,
or @code{None}.


在 3.1 版更改: In 3.1 this was changed to add the test name to the short description
even in the presence of a docstring.  This caused compatibility issues
with unittest extensions and adding the test name was moved to the
@ref{32ea,,TextTestResult} in Python 3.2.

@end deffn

@geindex addCleanup() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase addCleanup}@anchor{2a2}
@deffn {方法} addCleanup (function, *args, **kwargs)

Add a function to be called after @ref{cc5,,tearDown()} to cleanup resources
used during the test. Functions will be called in reverse order to the
order they are added (@abbr{LIFO}).  They
are called with any arguments and keyword arguments passed into
@ref{2a2,,addCleanup()} when they are added.

If @ref{cc4,,setUp()} fails, meaning that @ref{cc5,,tearDown()} is not called,
then any cleanup functions added will still be called.


3.1 新版功能.

@end deffn

@geindex doCleanups() (unittest.TestCase 方法)
@anchor{library/unittest unittest TestCase doCleanups}@anchor{cc3}
@deffn {方法} doCleanups ()

This method is called unconditionally after @ref{cc5,,tearDown()}, or
after @ref{cc4,,setUp()} if @ref{cc4,,setUp()} raises an exception.

It is responsible for calling all the cleanup functions added by
@ref{2a2,,addCleanup()}. If you need cleanup functions to be called
@emph{prior} to @ref{cc5,,tearDown()} then you can call @ref{cc3,,doCleanups()}
yourself.

@ref{cc3,,doCleanups()} pops methods off the stack of cleanup
functions one at a time, so it can be called at any time.


3.1 新版功能.

@end deffn

@geindex addClassCleanup() (unittest.TestCase 类方法)
@anchor{library/unittest unittest TestCase addClassCleanup}@anchor{24b}
@deffn {方法} classmethod addClassCleanup (function, /, *args, **kwargs)

Add a function to be called after @ref{cc2,,tearDownClass()} to cleanup
resources used during the test class. Functions will be called in reverse
order to the order they are added (@abbr{LIFO}).
They are called with any arguments and keyword arguments passed into
@ref{24b,,addClassCleanup()} when they are added.

If @ref{24c,,setUpClass()} fails, meaning that @ref{cc2,,tearDownClass()} is not
called, then any cleanup functions added will still be called.


3.8 新版功能.

@end deffn

@geindex doClassCleanups() (unittest.TestCase 类方法)
@anchor{library/unittest unittest TestCase doClassCleanups}@anchor{32eb}
@deffn {方法} classmethod doClassCleanups ()

This method is called unconditionally after @ref{cc2,,tearDownClass()}, or
after @ref{24c,,setUpClass()} if @ref{24c,,setUpClass()} raises an exception.

It is responsible for calling all the cleanup functions added by
@code{addCleanupClass()}. If you need cleanup functions to be called
@emph{prior} to @ref{cc2,,tearDownClass()} then you can call
@code{doCleanupsClass()} yourself.

@code{doCleanupsClass()} pops methods off the stack of cleanup
functions one at a time, so it can be called at any time.


3.8 新版功能.

@end deffn
@end deffn

@geindex IsolatedAsyncioTestCase (unittest 中的类)
@anchor{library/unittest unittest IsolatedAsyncioTestCase}@anchor{24d}
@deffn {类} unittest.IsolatedAsyncioTestCase (methodName='runTest')

This class provides an API similar to @ref{8f9,,TestCase} and also accepts
coroutines as test functions.


3.8 新版功能.


@geindex asyncSetUp() (unittest.IsolatedAsyncioTestCase 方法)
@anchor{library/unittest unittest IsolatedAsyncioTestCase asyncSetUp}@anchor{32ec}
@deffn {方法} coroutine asyncSetUp ()

Method called to prepare the test fixture. This is called after @code{setUp()}.
This is called immediately before calling the test method; other than
@ref{fc1,,AssertionError} or @ref{8fd,,SkipTest}, any exception raised by this method
will be considered an error rather than a test failure. The default implementation
does nothing.
@end deffn

@geindex asyncTearDown() (unittest.IsolatedAsyncioTestCase 方法)
@anchor{library/unittest unittest IsolatedAsyncioTestCase asyncTearDown}@anchor{32ed}
@deffn {方法} coroutine asyncTearDown ()

Method called immediately after the test method has been called and the
result recorded.  This is called before @code{tearDown()}. This is called even if
the test method raised an exception, so the implementation in subclasses may need
to be particularly careful about checking internal state.  Any exception, other than
@ref{fc1,,AssertionError} or @ref{8fd,,SkipTest}, raised by this method will be
considered an additional error rather than a test failure (thus increasing
the total number of reported errors). This method will only be called if
the @ref{32ec,,asyncSetUp()} succeeds, regardless of the outcome of the test method.
The default implementation does nothing.
@end deffn

@geindex addAsyncCleanup() (unittest.IsolatedAsyncioTestCase 方法)
@anchor{library/unittest unittest IsolatedAsyncioTestCase addAsyncCleanup}@anchor{32ee}
@deffn {方法} addAsyncCleanup (function, /, *args, **kwargs)

This method accepts a coroutine that can be used as a cleanup function.
@end deffn

@geindex run() (unittest.IsolatedAsyncioTestCase 方法)
@anchor{library/unittest unittest IsolatedAsyncioTestCase run}@anchor{32ef}
@deffn {方法} run (result=None)

Sets up a new event loop to run the test, collecting the result into
the @ref{aba,,TestResult} object passed as @emph{result}.  If @emph{result} is
omitted or @code{None}, a temporary result object is created (by calling
the @code{defaultTestResult()} method) and used. The result object is
returned to @ref{32ef,,run()}'s caller. At the end of the test all the tasks
in the event loop are cancelled.
@end deffn

An example illustrating the order:

@example
from unittest import IsolatedAsyncioTestCase

events = []


class Test(IsolatedAsyncioTestCase):


    def setUp(self):
        events.append("setUp")

    async def asyncSetUp(self):
        self._async_connection = await AsyncConnection()
        events.append("asyncSetUp")

    async def test_response(self):
        events.append("test_response")
        response = await self._async_connection.get("https://example.com")
        self.assertEqual(response.status_code, 200)
        self.addAsyncCleanup(self.on_cleanup)

    def tearDown(self):
        events.append("tearDown")

    async def asyncTearDown(self):
        await self._async_connection.close()
        events.append("asyncTearDown")

    async def on_cleanup(self):
        events.append("cleanup")

if __name__ == "__main__":
    unittest.main()
@end example

After running the test, @code{events} would contain @code{["setUp", "asyncSetUp", "test_response", "asyncTearDown", "tearDown", "cleanup"]}.
@end deffn

@geindex FunctionTestCase (unittest 中的类)
@anchor{library/unittest unittest FunctionTestCase}@anchor{32d0}
@deffn {类} unittest.FunctionTestCase (testFunc, setUp=None, tearDown=None, description=None)

This class implements the portion of the @ref{8f9,,TestCase} interface which
allows the test runner to drive the test, but does not provide the methods
which test code can use to check and report errors.  This is used to create
test cases using legacy test code, allowing it to be integrated into a
@ref{11b,,unittest}-based test framework.
@end deffn

@menu
* Deprecated aliases:: 

@end menu

@node Deprecated aliases,,,测试用例
@anchor{library/unittest deprecated-aliases}@anchor{bb2}@anchor{library/unittest id1}@anchor{32f0}
@subsubsection Deprecated aliases


For historical reasons, some of the @ref{8f9,,TestCase} methods had one or more
aliases that are now deprecated.  The following table lists the correct names
along with their deprecated aliases:

@quotation


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

方法名

@tab

Deprecated alias

@tab

Deprecated alias

@item

@ref{bae,,assertEqual()}

@tab

failUnlessEqual

@tab

assertEquals

@item

@ref{baf,,assertNotEqual()}

@tab

failIfEqual

@tab

assertNotEquals

@item

@ref{bad,,assertTrue()}

@tab

failUnless

@tab

assert_

@item

@ref{cc0,,assertFalse()}

@tab

failIf

@tab

@item

@ref{ab5,,assertRaises()}

@tab

failUnlessRaises

@tab

@item

@ref{bb0,,assertAlmostEqual()}

@tab

failUnlessAlmostEqual

@tab

assertAlmostEquals

@item

@ref{bb1,,assertNotAlmostEqual()}

@tab

failIfAlmostEqual

@tab

assertNotAlmostEquals

@item

@ref{baa,,assertRegex()}

@tab

@tab

assertRegexpMatches

@item

@ref{32e3,,assertNotRegex()}

@tab

@tab

assertNotRegexpMatches

@item

@ref{ab6,,assertRaisesRegex()}

@tab

@tab

assertRaisesRegexp

@end multitable



3.1 版后已移除: The fail* aliases listed in the second column have been deprecated.



3.2 版后已移除: The assert* aliases listed in the third column have been deprecated.



3.2 版后已移除: @code{assertRegexpMatches} and @code{assertRaisesRegexp} have been renamed to
@ref{baa,,assertRegex()} and @ref{ab6,,assertRaisesRegex()}.



3.5 版后已移除: The @code{assertNotRegexpMatches} name is deprecated in favor of @ref{32e3,,assertNotRegex()}.

@end quotation

@node Grouping tests,Loading and running tests,测试用例,类与函数
@anchor{library/unittest grouping-tests}@anchor{32f1}@anchor{library/unittest testsuite-objects}@anchor{32f2}
@subsubsection Grouping tests


@geindex TestSuite (unittest 中的类)
@anchor{library/unittest unittest TestSuite}@anchor{6c8}
@deffn {类} unittest.TestSuite (tests=())

This class represents an aggregation of individual test cases and test suites.
The class presents the interface needed by the test runner to allow it to be run
as any other test case.  Running a @ref{6c8,,TestSuite} instance is the same as
iterating over the suite, running each test individually.

If @emph{tests} is given, it must be an iterable of individual test cases or other
test suites that will be used to build the suite initially. Additional methods
are provided to add test cases and suites to the collection later on.

@ref{6c8,,TestSuite} objects behave much like @ref{8f9,,TestCase} objects, except
they do not actually implement a test.  Instead, they are used to aggregate
tests into groups of tests that should be run together. Some additional
methods are available to add tests to @ref{6c8,,TestSuite} instances:

@geindex addTest() (unittest.TestSuite 方法)
@anchor{library/unittest unittest TestSuite addTest}@anchor{32f3}
@deffn {方法} addTest (test)

Add a @ref{8f9,,TestCase} or @ref{6c8,,TestSuite} to the suite.
@end deffn

@geindex addTests() (unittest.TestSuite 方法)
@anchor{library/unittest unittest TestSuite addTests}@anchor{32f4}
@deffn {方法} addTests (tests)

Add all the tests from an iterable of @ref{8f9,,TestCase} and @ref{6c8,,TestSuite}
instances to this test suite.

This is equivalent to iterating over @emph{tests}, calling @ref{32f3,,addTest()} for
each element.
@end deffn

@ref{6c8,,TestSuite} shares the following methods with @ref{8f9,,TestCase}:

@geindex run() (unittest.TestSuite 方法)
@anchor{library/unittest unittest TestSuite run}@anchor{32f5}
@deffn {方法} run (result)

Run the tests associated with this suite, collecting the result into the
test result object passed as @emph{result}.  Note that unlike
@ref{ab9,,TestCase.run()}, @ref{32f5,,TestSuite.run()} requires the result object to
be passed in.
@end deffn

@geindex debug() (unittest.TestSuite 方法)
@anchor{library/unittest unittest TestSuite debug}@anchor{32f6}
@deffn {方法} debug ()

Run the tests associated with this suite without collecting the
result. This allows exceptions raised by the test to be propagated to the
caller and can be used to support running tests under a debugger.
@end deffn

@geindex countTestCases() (unittest.TestSuite 方法)
@anchor{library/unittest unittest TestSuite countTestCases}@anchor{32f7}
@deffn {方法} countTestCases ()

Return the number of tests represented by this test object, including all
individual tests and sub-suites.
@end deffn

@geindex __iter__() (unittest.TestSuite 方法)
@anchor{library/unittest unittest TestSuite __iter__}@anchor{95c}
@deffn {方法} __iter__ ()

Tests grouped by a @ref{6c8,,TestSuite} are always accessed by iteration.
Subclasses can lazily provide tests by overriding @ref{95c,,__iter__()}. Note
that this method may be called several times on a single suite (for
example when counting tests or comparing for equality) so the tests
returned by repeated iterations before @ref{32f5,,TestSuite.run()} must be the
same for each call iteration. After @ref{32f5,,TestSuite.run()}, callers should
not rely on the tests returned by this method unless the caller uses a
subclass that overrides @code{TestSuite._removeTestAtIndex()} to preserve
test references.


在 3.2 版更改: In earlier versions the @ref{6c8,,TestSuite} accessed tests directly rather
than through iteration, so overriding @ref{95c,,__iter__()} wasn't sufficient
for providing tests.



在 3.4 版更改: In earlier versions the @ref{6c8,,TestSuite} held references to each
@ref{8f9,,TestCase} after @ref{32f5,,TestSuite.run()}. Subclasses can restore
that behavior by overriding @code{TestSuite._removeTestAtIndex()}.

@end deffn

In the typical usage of a @ref{6c8,,TestSuite} object, the @ref{32f5,,run()} method
is invoked by a @code{TestRunner} rather than by the end-user test harness.
@end deffn

@node Loading and running tests,,Grouping tests,类与函数
@anchor{library/unittest loading-and-running-tests}@anchor{32f8}
@subsubsection Loading and running tests


@geindex TestLoader (unittest 中的类)
@anchor{library/unittest unittest TestLoader}@anchor{77c}
@deffn {类} unittest.TestLoader

The @ref{77c,,TestLoader} class is used to create test suites from classes and
modules.  Normally, there is no need to create an instance of this class; the
@ref{11b,,unittest} module provides an instance that can be shared as
@ref{32f9,,unittest.defaultTestLoader}.  Using a subclass or instance, however,
allows customization of some configurable properties.

@ref{77c,,TestLoader} objects have the following attributes:

@geindex errors (unittest.TestLoader 属性)
@anchor{library/unittest unittest TestLoader errors}@anchor{77b}
@deffn {属性} errors

A list of the non-fatal errors encountered while loading tests. Not reset
by the loader at any point. Fatal errors are signalled by the relevant
a method raising an exception to the caller. Non-fatal errors are also
indicated by a synthetic test that will raise the original error when
run.


3.5 新版功能.

@end deffn

@ref{77c,,TestLoader} objects have the following methods:

@geindex loadTestsFromTestCase() (unittest.TestLoader 方法)
@anchor{library/unittest unittest TestLoader loadTestsFromTestCase}@anchor{32fa}
@deffn {方法} loadTestsFromTestCase (testCaseClass)

Return a suite of all test cases contained in the @ref{8f9,,TestCase}-derived
@code{testCaseClass}.

A test case instance is created for each method named by
@ref{32fb,,getTestCaseNames()}. By default these are the method names
beginning with @code{test}. If @ref{32fb,,getTestCaseNames()} returns no
methods, but the @code{runTest()} method is implemented, a single test
case is created for that method instead.
@end deffn

@geindex loadTestsFromModule() (unittest.TestLoader 方法)
@anchor{library/unittest unittest TestLoader loadTestsFromModule}@anchor{77a}
@deffn {方法} loadTestsFromModule (module, pattern=None)

Return a suite of all test cases contained in the given module. This
method searches @emph{module} for classes derived from @ref{8f9,,TestCase} and
creates an instance of the class for each test method defined for the
class.

@cartouche
@quotation 注解 
While using a hierarchy of @ref{8f9,,TestCase}-derived classes can be
convenient in sharing fixtures and helper functions, defining test
methods on base classes that are not intended to be instantiated
directly does not play well with this method.  Doing so, however, can
be useful when the fixtures are different and defined in subclasses.
@end quotation
@end cartouche

If a module provides a @code{load_tests} function it will be called to
load the tests. This allows modules to customize test loading.
This is the @ref{32ce,,load_tests protocol}.  The @emph{pattern} argument is passed as
the third argument to @code{load_tests}.


在 3.2 版更改: Support for @code{load_tests} added.



在 3.5 版更改: The undocumented and unofficial @emph{use_load_tests} default argument is
deprecated and ignored, although it is still accepted for backward
compatibility.  The method also now accepts a keyword-only argument
@emph{pattern} which is passed to @code{load_tests} as the third argument.

@end deffn

@geindex loadTestsFromName() (unittest.TestLoader 方法)
@anchor{library/unittest unittest TestLoader loadTestsFromName}@anchor{cd8}
@deffn {方法} loadTestsFromName (name, module=None)

Return a suite of all test cases given a string specifier.

The specifier @emph{name} is a "dotted name" that may resolve either to a
module, a test case class, a test method within a test case class, a
@ref{6c8,,TestSuite} instance, or a callable object which returns a
@ref{8f9,,TestCase} or @ref{6c8,,TestSuite} instance.  These checks are
applied in the order listed here; that is, a method on a possible test
case class will be picked up as "a test method within a test case class",
rather than "a callable object".

For example, if you have a module @code{SampleTests} containing a
@ref{8f9,,TestCase}-derived class @code{SampleTestCase} with three test
methods (@code{test_one()}, @code{test_two()}, and @code{test_three()}), the
specifier @code{'SampleTests.SampleTestCase'} would cause this method to
return a suite which will run all three test methods. Using the specifier
@code{'SampleTests.SampleTestCase.test_two'} would cause it to return a test
suite which will run only the @code{test_two()} test method. The specifier
can refer to modules and packages which have not been imported; they will
be imported as a side-effect.

The method optionally resolves @emph{name} relative to the given @emph{module}.


在 3.5 版更改: If an @ref{32d,,ImportError} or @ref{393,,AttributeError} occurs while traversing
@emph{name} then a synthetic test that raises that error when run will be
returned. These errors are included in the errors accumulated by
self.errors.

@end deffn

@geindex loadTestsFromNames() (unittest.TestLoader 方法)
@anchor{library/unittest unittest TestLoader loadTestsFromNames}@anchor{32fc}
@deffn {方法} loadTestsFromNames (names, module=None)

Similar to @ref{cd8,,loadTestsFromName()}, but takes a sequence of names rather
than a single name.  The return value is a test suite which supports all
the tests defined for each name.
@end deffn

@geindex getTestCaseNames() (unittest.TestLoader 方法)
@anchor{library/unittest unittest TestLoader getTestCaseNames}@anchor{32fb}
@deffn {方法} getTestCaseNames (testCaseClass)

Return a sorted sequence of method names found within @emph{testCaseClass};
this should be a subclass of @ref{8f9,,TestCase}.
@end deffn

@geindex discover() (unittest.TestLoader 方法)
@anchor{library/unittest unittest TestLoader discover}@anchor{8fe}
@deffn {方法} discover (start_dir, pattern='test*.py', top_level_dir=None)

Find all the test modules by recursing into subdirectories from the
specified start directory, and return a TestSuite object containing them.
Only test files that match @emph{pattern} will be loaded. (Using shell style
pattern matching.) Only module names that are importable (i.e. are valid
Python identifiers) will be loaded.

All test modules must be importable from the top level of the project. If
the start directory is not the top level directory then the top level
directory must be specified separately.

If importing a module fails, for example due to a syntax error, then
this will be recorded as a single error and discovery will continue.  If
the import failure is due to @ref{8fd,,SkipTest} being raised, it will be
recorded as a skip instead of an error.

If a package (a directory containing a file named @code{__init__.py}) is
found, the package will be checked for a @code{load_tests} function. If this
exists then it will be called
@code{package.load_tests(loader, tests, pattern)}. Test discovery takes care
to ensure that a package is only checked for tests once during an
invocation, even if the load_tests function itself calls
@code{loader.discover}.

If @code{load_tests} exists then discovery does @emph{not} recurse into the
package, @code{load_tests} is responsible for loading all tests in the
package.

The pattern is deliberately not stored as a loader attribute so that
packages can continue discovery themselves. @emph{top_level_dir} is stored so
@code{load_tests} does not need to pass this argument in to
@code{loader.discover()}.

@emph{start_dir} can be a dotted module name as well as a directory.


3.2 新版功能.



在 3.4 版更改: Modules that raise @ref{8fd,,SkipTest} on import are recorded as skips,
  not errors.
Discovery works for @ref{144c,,namespace packages}.
Paths are sorted before being imported so that execution order is
  the same even if the underlying file system's ordering is not
  dependent on file name.



在 3.5 版更改: Found packages are now checked for @code{load_tests} regardless of
whether their path matches @emph{pattern}, because it is impossible for
a package name to match the default pattern.

@end deffn

The following attributes of a @ref{77c,,TestLoader} can be configured either by
subclassing or assignment on an instance:

@geindex testMethodPrefix (unittest.TestLoader 属性)
@anchor{library/unittest unittest TestLoader testMethodPrefix}@anchor{32fd}
@deffn {属性} testMethodPrefix

String giving the prefix of method names which will be interpreted as test
methods.  The default value is @code{'test'}.

This affects @ref{32fb,,getTestCaseNames()} and all the @code{loadTestsFrom*()}
methods.
@end deffn

@geindex sortTestMethodsUsing (unittest.TestLoader 属性)
@anchor{library/unittest unittest TestLoader sortTestMethodsUsing}@anchor{32fe}
@deffn {属性} sortTestMethodsUsing

Function to be used to compare method names when sorting them in
@ref{32fb,,getTestCaseNames()} and all the @code{loadTestsFrom*()} methods.
@end deffn

@geindex suiteClass (unittest.TestLoader 属性)
@anchor{library/unittest unittest TestLoader suiteClass}@anchor{cd9}
@deffn {属性} suiteClass

Callable object that constructs a test suite from a list of tests. No
methods on the resulting object are needed.  The default value is the
@ref{6c8,,TestSuite} class.

This affects all the @code{loadTestsFrom*()} methods.
@end deffn

@geindex testNamePatterns (unittest.TestLoader 属性)
@anchor{library/unittest unittest TestLoader testNamePatterns}@anchor{32ff}
@deffn {属性} testNamePatterns

List of Unix shell-style wildcard test name patterns that test methods
have to match to be included in test suites (see @code{-v} option).

If this attribute is not @code{None} (the default), all test methods to be
included in test suites must match one of the patterns in this list.
Note that matches are always performed using @ref{1c0f,,fnmatch.fnmatchcase()},
so unlike patterns passed to the @code{-v} option, simple substring patterns
will have to be converted using @code{*} wildcards.

This affects all the @code{loadTestsFrom*()} methods.


3.7 新版功能.

@end deffn
@end deffn

@geindex TestResult (unittest 中的类)
@anchor{library/unittest unittest TestResult}@anchor{aba}
@deffn {类} unittest.TestResult

This class is used to compile information about which tests have succeeded
and which have failed.

A @ref{aba,,TestResult} object stores the results of a set of tests.  The
@ref{8f9,,TestCase} and @ref{6c8,,TestSuite} classes ensure that results are
properly recorded; test authors do not need to worry about recording the
outcome of tests.

Testing frameworks built on top of @ref{11b,,unittest} may want access to the
@ref{aba,,TestResult} object generated by running a set of tests for reporting
purposes; a @ref{aba,,TestResult} instance is returned by the
@code{TestRunner.run()} method for this purpose.

@ref{aba,,TestResult} instances have the following attributes that will be of
interest when inspecting the results of running a set of tests:

@geindex errors (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult errors}@anchor{3300}
@deffn {属性} errors

A list containing 2-tuples of @ref{8f9,,TestCase} instances and strings
holding formatted tracebacks. Each tuple represents a test which raised an
unexpected exception.
@end deffn

@geindex failures (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult failures}@anchor{3301}
@deffn {属性} failures

A list containing 2-tuples of @ref{8f9,,TestCase} instances and strings
holding formatted tracebacks. Each tuple represents a test where a failure
was explicitly signalled using the @code{TestCase.assert*()} methods.
@end deffn

@geindex skipped (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult skipped}@anchor{3302}
@deffn {属性} skipped

A list containing 2-tuples of @ref{8f9,,TestCase} instances and strings
holding the reason for skipping the test.


3.1 新版功能.

@end deffn

@geindex expectedFailures (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult expectedFailures}@anchor{3303}
@deffn {属性} expectedFailures

A list containing 2-tuples of @ref{8f9,,TestCase} instances and strings
holding formatted tracebacks.  Each tuple represents an expected failure
of the test case.
@end deffn

@geindex unexpectedSuccesses (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult unexpectedSuccesses}@anchor{3304}
@deffn {属性} unexpectedSuccesses

A list containing @ref{8f9,,TestCase} instances that were marked as expected
failures, but succeeded.
@end deffn

@geindex shouldStop (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult shouldStop}@anchor{3305}
@deffn {属性} shouldStop

Set to @code{True} when the execution of tests should stop by @ref{3306,,stop()}.
@end deffn

@geindex testsRun (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult testsRun}@anchor{3307}
@deffn {属性} testsRun

The total number of tests run so far.
@end deffn

@geindex buffer (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult buffer}@anchor{3308}
@deffn {属性} buffer

If set to true, @code{sys.stdout} and @code{sys.stderr} will be buffered in between
@ref{3309,,startTest()} and @ref{330a,,stopTest()} being called. Collected output will
only be echoed onto the real @code{sys.stdout} and @code{sys.stderr} if the test
fails or errors. Any output is also attached to the failure / error message.


3.2 新版功能.

@end deffn

@geindex failfast (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult failfast}@anchor{330b}
@deffn {属性} failfast

If set to true @ref{3306,,stop()} will be called on the first failure or error,
halting the test run.


3.2 新版功能.

@end deffn

@geindex tb_locals (unittest.TestResult 属性)
@anchor{library/unittest unittest TestResult tb_locals}@anchor{330c}
@deffn {属性} tb_locals

If set to true then local variables will be shown in tracebacks.


3.5 新版功能.

@end deffn

@geindex wasSuccessful() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult wasSuccessful}@anchor{330d}
@deffn {方法} wasSuccessful ()

Return @code{True} if all tests run so far have passed, otherwise returns
@code{False}.


在 3.4 版更改: Returns @code{False} if there were any @ref{3304,,unexpectedSuccesses}
from tests marked with the @ref{32d6,,expectedFailure()} decorator.

@end deffn

@geindex stop() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult stop}@anchor{3306}
@deffn {方法} stop ()

This method can be called to signal that the set of tests being run should
be aborted by setting the @ref{3305,,shouldStop} attribute to @code{True}.
@code{TestRunner} objects should respect this flag and return without
running any additional tests.

For example, this feature is used by the @ref{330e,,TextTestRunner} class to
stop the test framework when the user signals an interrupt from the
keyboard.  Interactive tools which provide @code{TestRunner}
implementations can use this in a similar manner.
@end deffn

The following methods of the @ref{aba,,TestResult} class are used to maintain
the internal data structures, and may be extended in subclasses to support
additional reporting requirements.  This is particularly useful in building
tools which support interactive reporting while tests are being run.

@geindex startTest() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult startTest}@anchor{3309}
@deffn {方法} startTest (test)

Called when the test case @emph{test} is about to be run.
@end deffn

@geindex stopTest() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult stopTest}@anchor{330a}
@deffn {方法} stopTest (test)

Called after the test case @emph{test} has been executed, regardless of the
outcome.
@end deffn

@geindex startTestRun() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult startTestRun}@anchor{cdc}
@deffn {方法} startTestRun ()

Called once before any tests are executed.


3.1 新版功能.

@end deffn

@geindex stopTestRun() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult stopTestRun}@anchor{cdd}
@deffn {方法} stopTestRun ()

Called once after all tests are executed.


3.1 新版功能.

@end deffn

@geindex addError() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult addError}@anchor{330f}
@deffn {方法} addError (test, err)

Called when the test case @emph{test} raises an unexpected exception. @emph{err} is a
tuple of the form returned by @ref{c58,,sys.exc_info()}: @code{(type, value,
traceback)}.

The default implementation appends a tuple @code{(test, formatted_err)} to
the instance's @ref{3300,,errors} attribute, where @emph{formatted_err} is a
formatted traceback derived from @emph{err}.
@end deffn

@geindex addFailure() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult addFailure}@anchor{3310}
@deffn {方法} addFailure (test, err)

Called when the test case @emph{test} signals a failure. @emph{err} is a tuple of
the form returned by @ref{c58,,sys.exc_info()}: @code{(type, value, traceback)}.

The default implementation appends a tuple @code{(test, formatted_err)} to
the instance's @ref{3301,,failures} attribute, where @emph{formatted_err} is a
formatted traceback derived from @emph{err}.
@end deffn

@geindex addSuccess() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult addSuccess}@anchor{3311}
@deffn {方法} addSuccess (test)

Called when the test case @emph{test} succeeds.

The default implementation does nothing.
@end deffn

@geindex addSkip() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult addSkip}@anchor{3312}
@deffn {方法} addSkip (test, reason)

Called when the test case @emph{test} is skipped.  @emph{reason} is the reason the
test gave for skipping.

The default implementation appends a tuple @code{(test, reason)} to the
instance's @ref{3302,,skipped} attribute.
@end deffn

@geindex addExpectedFailure() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult addExpectedFailure}@anchor{3313}
@deffn {方法} addExpectedFailure (test, err)

Called when the test case @emph{test} fails, but was marked with the
@ref{32d6,,expectedFailure()} decorator.

The default implementation appends a tuple @code{(test, formatted_err)} to
the instance's @ref{3303,,expectedFailures} attribute, where @emph{formatted_err}
is a formatted traceback derived from @emph{err}.
@end deffn

@geindex addUnexpectedSuccess() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult addUnexpectedSuccess}@anchor{3314}
@deffn {方法} addUnexpectedSuccess (test)

Called when the test case @emph{test} was marked with the
@ref{32d6,,expectedFailure()} decorator, but succeeded.

The default implementation appends the test to the instance's
@ref{3304,,unexpectedSuccesses} attribute.
@end deffn

@geindex addSubTest() (unittest.TestResult 方法)
@anchor{library/unittest unittest TestResult addSubTest}@anchor{3315}
@deffn {方法} addSubTest (test, subtest, outcome)

Called when a subtest finishes.  @emph{test} is the test case
corresponding to the test method.  @emph{subtest} is a custom
@ref{8f9,,TestCase} instance describing the subtest.

If @emph{outcome} is @ref{157,,None}, the subtest succeeded.  Otherwise,
it failed with an exception where @emph{outcome} is a tuple of the form
returned by @ref{c58,,sys.exc_info()}: @code{(type, value, traceback)}.

The default implementation does nothing when the outcome is a
success, and records subtest failures as normal failures.


3.4 新版功能.

@end deffn
@end deffn

@geindex TextTestResult (unittest 中的类)
@anchor{library/unittest unittest TextTestResult}@anchor{32ea}
@deffn {类} unittest.TextTestResult (stream, descriptions, verbosity)

A concrete implementation of @ref{aba,,TestResult} used by the
@ref{330e,,TextTestRunner}.


3.2 新版功能: This class was previously named @code{_TextTestResult}. The old name still
exists as an alias but is deprecated.

@end deffn

@geindex defaultTestLoader() (在 unittest 模块中)
@anchor{library/unittest unittest defaultTestLoader}@anchor{32f9}
@deffn {数据} unittest.defaultTestLoader

Instance of the @ref{77c,,TestLoader} class intended to be shared.  If no
customization of the @ref{77c,,TestLoader} is needed, this instance can be used
instead of repeatedly creating new instances.
@end deffn

@geindex TextTestRunner (unittest 中的类)
@anchor{library/unittest unittest TextTestRunner}@anchor{330e}
@deffn {类} unittest.TextTestRunner (stream=None, descriptions=True, verbosity=1, failfast=False, buffer=False, resultclass=None, warnings=None, *, tb_locals=False)

A basic test runner implementation that outputs results to a stream. If @emph{stream}
is @code{None}, the default, @ref{308,,sys.stderr} is used as the output stream. This class
has a few configurable parameters, but is essentially very simple.  Graphical
applications which run test suites should provide alternate implementations. Such
implementations should accept @code{**kwargs} as the interface to construct runners
changes when features are added to unittest.

By default this runner shows @ref{278,,DeprecationWarning},
@ref{279,,PendingDeprecationWarning}, @ref{4ca,,ResourceWarning} and
@ref{5d3,,ImportWarning} even if they are @ref{3316,,ignored by default}. Deprecation warnings caused by @ref{bb2,,deprecated unittest methods} are also special-cased and, when the warning
filters are @code{'default'} or @code{'always'}, they will appear only once
per-module, in order to avoid too many warning messages.  This behavior can
be overridden using Python's @code{-Wd} or @code{-Wa} options
(see @ref{12e1,,Warning control}) and leaving
@emph{warnings} to @code{None}.


在 3.2 版更改: Added the @code{warnings} argument.



在 3.2 版更改: The default stream is set to @ref{308,,sys.stderr} at instantiation time rather
than import time.



在 3.5 版更改: Added the tb_locals parameter.


@geindex _makeResult() (unittest.TextTestRunner 方法)
@anchor{library/unittest unittest TextTestRunner _makeResult}@anchor{3317}
@deffn {方法} _makeResult ()

This method returns the instance of @code{TestResult} used by @ref{3318,,run()}.
It is not intended to be called directly, but can be overridden in
subclasses to provide a custom @code{TestResult}.

@code{_makeResult()} instantiates the class or callable passed in the
@code{TextTestRunner} constructor as the @code{resultclass} argument. It
defaults to @ref{32ea,,TextTestResult} if no @code{resultclass} is provided.
The result class is instantiated with the following arguments:

@example
stream, descriptions, verbosity
@end example
@end deffn

@geindex run() (unittest.TextTestRunner 方法)
@anchor{library/unittest unittest TextTestRunner run}@anchor{3318}
@deffn {方法} run (test)

This method is the main public interface to the @code{TextTestRunner}. This
method takes a @ref{6c8,,TestSuite} or @ref{8f9,,TestCase} instance. A
@ref{aba,,TestResult} is created by calling
@ref{3317,,_makeResult()} and the test(s) are run and the
results printed to stdout.
@end deffn
@end deffn

@geindex main() (在 unittest 模块中)
@anchor{library/unittest unittest main}@anchor{8fc}
@deffn {函数} unittest.main (module='__main__', defaultTest=None, argv=None, testRunner=None, testLoader=unittest.defaultTestLoader, exit=True, verbosity=1, failfast=None, catchbreak=None, buffer=None, warnings=None)

A command-line program that loads a set of tests from @emph{module} and runs them;
this is primarily for making test modules conveniently executable.
The simplest use for this function is to include the following line at the
end of a test script:

@example
if __name__ == '__main__':
    unittest.main()
@end example

You can run tests with more detailed information by passing in the verbosity
argument:

@example
if __name__ == '__main__':
    unittest.main(verbosity=2)
@end example

The @emph{defaultTest} argument is either the name of a single test or an
iterable of test names to run if no test names are specified via @emph{argv}.  If
not specified or @code{None} and no test names are provided via @emph{argv}, all
tests found in @emph{module} are run.

The @emph{argv} argument can be a list of options passed to the program, with the
first element being the program name.  If not specified or @code{None},
the values of @ref{bf4,,sys.argv} are used.

The @emph{testRunner} argument can either be a test runner class or an already
created instance of it. By default @code{main} calls @ref{cdb,,sys.exit()} with
an exit code indicating success or failure of the tests run.

The @emph{testLoader} argument has to be a @ref{77c,,TestLoader} instance,
and defaults to @ref{32f9,,defaultTestLoader}.

@code{main} supports being used from the interactive interpreter by passing in the
argument @code{exit=False}. This displays the result on standard output without
calling @ref{cdb,,sys.exit()}:

@example
>>> from unittest import main
>>> main(module='test_module', exit=False)
@end example

The @emph{failfast}, @emph{catchbreak} and @emph{buffer} parameters have the same
effect as the same-name @ref{32c5,,command-line options}.

The @emph{warnings} argument specifies the @ref{12e2,,warning filter}
that should be used while running the tests.  If it's not specified, it will
remain @code{None} if a @code{-W} option is passed to @code{python}
(see @ref{12e1,,Warning control}),
otherwise it will be set to @code{'default'}.

Calling @code{main} actually returns an instance of the @code{TestProgram} class.
This stores the result of the tests run as the @code{result} attribute.


在 3.1 版更改: The @emph{exit} parameter was added.



在 3.2 版更改: The @emph{verbosity}, @emph{failfast}, @emph{catchbreak}, @emph{buffer}
and @emph{warnings} parameters were added.



在 3.4 版更改: The @emph{defaultTest} parameter was changed to also accept an iterable of
test names.

@end deffn

@menu
* load_tests Protocol:: 

@end menu

@node load_tests Protocol,,,Loading and running tests
@anchor{library/unittest load-tests-protocol}@anchor{32ce}
@subsubsection load_tests Protocol



3.2 新版功能.


Modules or packages can customize how tests are loaded from them during normal
test runs or test discovery by implementing a function called @code{load_tests}.

If a test module defines @code{load_tests} it will be called by
@ref{77a,,TestLoader.loadTestsFromModule()} with the following arguments:

@example
load_tests(loader, standard_tests, pattern)
@end example

where @emph{pattern} is passed straight through from @code{loadTestsFromModule}.  It
defaults to @code{None}.

It should return a @ref{6c8,,TestSuite}.

@emph{loader} is the instance of @ref{77c,,TestLoader} doing the loading.
@emph{standard_tests} are the tests that would be loaded by default from the
module. It is common for test modules to only want to add or remove tests
from the standard set of tests.
The third argument is used when loading packages as part of test discovery.

A typical @code{load_tests} function that loads tests from a specific set of
@ref{8f9,,TestCase} classes may look like:

@example
test_cases = (TestCase1, TestCase2, TestCase3)

def load_tests(loader, tests, pattern):
    suite = TestSuite()
    for test_class in test_cases:
        tests = loader.loadTestsFromTestCase(test_class)
        suite.addTests(tests)
    return suite
@end example

If discovery is started in a directory containing a package, either from the
command line or by calling @ref{8fe,,TestLoader.discover()}, then the package
@code{__init__.py} will be checked for @code{load_tests}.  If that function does
not exist, discovery will recurse into the package as though it were just
another directory.  Otherwise, discovery of the package's tests will be left up
to @code{load_tests} which is called with the following arguments:

@example
load_tests(loader, standard_tests, pattern)
@end example

This should return a @ref{6c8,,TestSuite} representing all the tests
from the package. (@code{standard_tests} will only contain tests
collected from @code{__init__.py}.)

Because the pattern is passed into @code{load_tests} the package is free to
continue (and potentially modify) test discovery. A 'do nothing'
@code{load_tests} function for a test package would look like:

@example
def load_tests(loader, standard_tests, pattern):
    # top level directory cached on loader instance
    this_dir = os.path.dirname(__file__)
    package_tests = loader.discover(start_dir=this_dir, pattern=pattern)
    standard_tests.addTests(package_tests)
    return standard_tests
@end example


在 3.5 版更改: Discovery no longer checks package names for matching @emph{pattern} due to the
impossibility of package names matching the default pattern.


@node Class and Module Fixtures,Signal Handling,类与函数,unittest --- 单元测试框架
@anchor{library/unittest class-and-module-fixtures}@anchor{32de}
@subsubsection Class and Module Fixtures


Class and module level fixtures are implemented in @ref{6c8,,TestSuite}. When
the test suite encounters a test from a new class then @code{tearDownClass()}
from the previous class (if there is one) is called, followed by
@code{setUpClass()} from the new class.

Similarly if a test is from a different module from the previous test then
@code{tearDownModule} from the previous module is run, followed by
@code{setUpModule} from the new module.

After all the tests have run the final @code{tearDownClass} and
@code{tearDownModule} are run.

Note that shared fixtures do not play well with [potential] features like test
parallelization and they break test isolation. They should be used with care.

The default ordering of tests created by the unittest test loaders is to group
all tests from the same modules and classes together. This will lead to
@code{setUpClass} / @code{setUpModule} (etc) being called exactly once per class and
module. If you randomize the order, so that tests from different modules and
classes are adjacent to each other, then these shared fixture functions may be
called multiple times in a single test run.

Shared fixtures are not intended to work with suites with non-standard
ordering. A @code{BaseTestSuite} still exists for frameworks that don't want to
support shared fixtures.

If there are any exceptions raised during one of the shared fixture functions
the test is reported as an error. Because there is no corresponding test
instance an @code{_ErrorHolder} object (that has the same interface as a
@ref{8f9,,TestCase}) is created to represent the error. If you are just using
the standard unittest test runner then this detail doesn't matter, but if you
are a framework author it may be relevant.

@menu
* setUpClass and tearDownClass:: 
* setUpModule and tearDownModule:: 

@end menu

@node setUpClass and tearDownClass,setUpModule and tearDownModule,,Class and Module Fixtures
@anchor{library/unittest setupclass-and-teardownclass}@anchor{3319}
@subsubsection setUpClass and tearDownClass


These must be implemented as class methods:

@example
import unittest

class Test(unittest.TestCase):
    @@classmethod
    def setUpClass(cls):
        cls._connection = createExpensiveConnectionObject()

    @@classmethod
    def tearDownClass(cls):
        cls._connection.destroy()
@end example

If you want the @code{setUpClass} and @code{tearDownClass} on base classes called
then you must call up to them yourself. The implementations in
@ref{8f9,,TestCase} are empty.

If an exception is raised during a @code{setUpClass} then the tests in the class
are not run and the @code{tearDownClass} is not run. Skipped classes will not
have @code{setUpClass} or @code{tearDownClass} run. If the exception is a
@ref{8fd,,SkipTest} exception then the class will be reported as having been skipped
instead of as an error.

@node setUpModule and tearDownModule,,setUpClass and tearDownClass,Class and Module Fixtures
@anchor{library/unittest setupmodule-and-teardownmodule}@anchor{331a}
@subsubsection setUpModule and tearDownModule


These should be implemented as functions:

@example
def setUpModule():
    createConnection()

def tearDownModule():
    closeConnection()
@end example

If an exception is raised in a @code{setUpModule} then none of the tests in the
module will be run and the @code{tearDownModule} will not be run. If the exception is a
@ref{8fd,,SkipTest} exception then the module will be reported as having been skipped
instead of as an error.

To add cleanup code that must be run even in the case of an exception, use
@code{addModuleCleanup}:

@geindex addModuleCleanup() (在 unittest 模块中)
@anchor{library/unittest unittest addModuleCleanup}@anchor{24a}
@deffn {函数} unittest.addModuleCleanup (function, /, *args, **kwargs)

Add a function to be called after @code{tearDownModule()} to cleanup
resources used during the test class. Functions will be called in reverse
order to the order they are added (@abbr{LIFO}).
They are called with any arguments and keyword arguments passed into
@ref{24a,,addModuleCleanup()} when they are added.

If @code{setUpModule()} fails, meaning that @code{tearDownModule()} is not
called, then any cleanup functions added will still be called.


3.8 新版功能.

@end deffn

@geindex doModuleCleanups() (在 unittest 模块中)
@anchor{library/unittest unittest doModuleCleanups}@anchor{331b}
@deffn {函数} unittest.doModuleCleanups ()

This function is called unconditionally after @code{tearDownModule()}, or
after @code{setUpModule()} if @code{setUpModule()} raises an exception.

It is responsible for calling all the cleanup functions added by
@code{addCleanupModule()}. If you need cleanup functions to be called
@emph{prior} to @code{tearDownModule()} then you can call
@ref{331b,,doModuleCleanups()} yourself.

@ref{331b,,doModuleCleanups()} pops methods off the stack of cleanup
functions one at a time, so it can be called at any time.


3.8 新版功能.

@end deffn

@node Signal Handling,,Class and Module Fixtures,unittest --- 单元测试框架
@anchor{library/unittest signal-handling}@anchor{32c6}
@subsubsection Signal Handling



3.2 新版功能.


The @ref{cbd,,-c/--catch} command-line option to unittest,
along with the @code{catchbreak} parameter to @ref{8fc,,unittest.main()}, provide
more friendly handling of control-C during a test run. With catch break
behavior enabled control-C will allow the currently running test to complete,
and the test run will then end and report all the results so far. A second
control-c will raise a @ref{197,,KeyboardInterrupt} in the usual way.

The control-c handling signal handler attempts to remain compatible with code or
tests that install their own @ref{2458,,signal.SIGINT} handler. If the @code{unittest}
handler is called but @emph{isn't} the installed @ref{2458,,signal.SIGINT} handler,
i.e. it has been replaced by the system under test and delegated to, then it
calls the default handler. This will normally be the expected behavior by code
that replaces an installed handler and delegates to it. For individual tests
that need @code{unittest} control-c handling disabled the @ref{cbe,,removeHandler()}
decorator can be used.

There are a few utility functions for framework authors to enable control-c
handling functionality within test frameworks.

@geindex installHandler() (在 unittest 模块中)
@anchor{library/unittest unittest installHandler}@anchor{331c}
@deffn {函数} unittest.installHandler ()

Install the control-c handler. When a @ref{2458,,signal.SIGINT} is received
(usually in response to the user pressing control-c) all registered results
have @ref{3306,,stop()} called.
@end deffn

@geindex registerResult() (在 unittest 模块中)
@anchor{library/unittest unittest registerResult}@anchor{331d}
@deffn {函数} unittest.registerResult (result)

Register a @ref{aba,,TestResult} object for control-c handling. Registering a
result stores a weak reference to it, so it doesn't prevent the result from
being garbage collected.

Registering a @ref{aba,,TestResult} object has no side-effects if control-c
handling is not enabled, so test frameworks can unconditionally register
all results they create independently of whether or not handling is enabled.
@end deffn

@geindex removeResult() (在 unittest 模块中)
@anchor{library/unittest unittest removeResult}@anchor{331e}
@deffn {函数} unittest.removeResult (result)

Remove a registered result. Once a result has been removed then
@ref{3306,,stop()} will no longer be called on that result object in
response to a control-c.
@end deffn

@geindex removeHandler() (在 unittest 模块中)
@anchor{library/unittest unittest removeHandler}@anchor{cbe}
@deffn {函数} unittest.removeHandler (function=None)

When called without arguments this function removes the control-c handler
if it has been installed. This function can also be used as a test decorator
to temporarily remove the handler while the test is being executed:

@example
@@unittest.removeHandler
def test_signal_handling(self):
    ...
@end example
@end deffn

@node unittest mock --- 模拟对象库,unittest mock 上手指南,unittest --- 单元测试框架,开发工具
@anchor{library/unittest mock doc}@anchor{331f}@anchor{library/unittest mock module-unittest mock}@anchor{11c}@anchor{library/unittest mock unittest-mock-mock-object-library}@anchor{3320}
@subsection @code{unittest.mock} --- 模拟对象库


@geindex unittest.mock (模块)


3.3 新版功能.


@strong{源代码：} Lib/unittest/mock.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/unittest/mock.py}


__________________________________________________________________


@ref{11c,,unittest.mock} 是一个用于测试的Python库。它允许使用模拟对象来替换受测系统的部分，并对它们如何已经被使用进行断言。

@ref{11c,,unittest.mock} 提供了一个核心类 @ref{249,,Mock} 用于消除了在整个测试套件中创建大量存根(stub)的需求。创建后，就可以断言调用了哪些方法/属性及其参数。还可以以常规方式指定返回值并设置所需的属性。

此外，mock 提供了用于修补测试范围内模块和类级别属性的 @ref{782,,patch()} 装饰器，和用于创建独特对象的 @ref{402,,sentinel} 。 阅读 @ref{3321,,quick guide} 中的案例了解如何使用 @ref{249,,Mock} ，@ref{77f,,MagicMock} 和 @ref{782,,patch()} 。

Mock 是为 @ref{11b,,unittest} 而设计，且简单易用。模拟基于 'action -> assertion' 模式，而不是许多模拟框架所使用的 'record -> replay'模式。

在 Python 的早期版本要单独使用 @ref{11c,,unittest.mock} ，在 PyPI 获取 mock@footnote{https://pypi.org/project/mock}

@menu
* 快速上手:: 
* Mock 类:: 
* The patchers:: 
* MagicMock and magic method support:: 
* Helpers:: 

@end menu

@node 快速上手,Mock 类,,unittest mock --- 模拟对象库
@anchor{library/unittest mock quick-guide}@anchor{3321}
@subsubsection 快速上手


@c class ProductionClass:
@c     def method(self, a, b, c):
@c         pass
@c 
@c class SomeClass:
@c     @staticmethod
@c     def static_method(args):
@c         return args
@c 
@c     @classmethod
@c     def class_method(cls, args):
@c         return args

当您访问对象时， @ref{249,,Mock} 和 @ref{77f,,MagicMock} 将创建所有属性和方法，并保存他们在使用时的细节。你可以通过配置，指定返回值或者限制可访问属性，然后断言他们如何被调用。

@example
>>> from unittest.mock import MagicMock
>>> thing = ProductionClass()
>>> thing.method = MagicMock(return_value=3)
>>> thing.method(3, 4, 5, key='value')
3
>>> thing.method.assert_called_with(3, 4, 5, key='value')
@end example

通过 @code{side_effect} 设置副作用(side effects) ，可以是一个 mock 被调用是抛出的异常

@example
>>> mock = Mock(side_effect=KeyError('foo'))
>>> mock()
Traceback (most recent call last):
 ...
KeyError: 'foo'
@end example

@example
>>> values = @{'a': 1, 'b': 2, 'c': 3@}
>>> def side_effect(arg):
...     return values[arg]
...
>>> mock.side_effect = side_effect
>>> mock('a'), mock('b'), mock('c')
(1, 2, 3)
>>> mock.side_effect = [5, 4, 3, 2, 1]
>>> mock(), mock(), mock()
(5, 4, 3)
@end example

Mock 还可以通过其他方法配置和控制其行为。例如 mock 可以通过设置 @emph{spec} 参数来从一个对象中获取其规格(specification)。如果访问 mock 的属性或方法不在 spec 中，会报 @ref{393,,AttributeError} 错误。

使用 @ref{782,,patch()} 装饰去/上下文管理器，可以更方便地测试一个模块下的类或对象。你指定的对象会在测试过程中替换成 mock （或者其他对象），测试结束后恢复。

@example
>>> from unittest.mock import patch
>>> @@patch('module.ClassName2')
... @@patch('module.ClassName1')
... def test(MockClass1, MockClass2):
...     module.ClassName1()
...     module.ClassName2()
...     assert MockClass1 is module.ClassName1
...     assert MockClass2 is module.ClassName2
...     assert MockClass1.called
...     assert MockClass2.called
...
>>> test()
@end example

@cartouche
@quotation 注解 
当你嵌套 patch 装饰器时，mock 将以执行顺序传递给装饰器函数（@emph{Python} 装饰器正常顺序）。由于从下至上，因此在上面的示例中，首先 mock 传入的 @code{module.ClassName1} 。

在查找对象的名称空间中修补对象使用 @ref{782,,patch()} 。使用起来很简单，阅读 @ref{3322,,在哪里打补丁} 来快速上手。
@end quotation
@end cartouche

@ref{782,,patch()} 也可以 with 语句中使用上下文管理。

@example
>>> with patch.object(ProductionClass, 'method', return_value=None) as mock_method:
...     thing = ProductionClass()
...     thing.method(1, 2, 3)
...
>>> mock_method.assert_called_once_with(1, 2, 3)
@end example

还有一个 @ref{f5f,,patch.dict()} 用于在一定范围内设置字典中的值，并在测试结束时将字典恢复为其原始状态：

@example
>>> foo = @{'key': 'value'@}
>>> original = foo.copy()
>>> with patch.dict(foo, @{'newkey': 'newvalue'@}, clear=True):
...     assert foo == @{'newkey': 'newvalue'@}
...
>>> assert foo == original
@end example

Mock支持 Python @ref{3323,,魔术方法} 。使用模式方法最简单的方式是使用 @ref{77f,,MagicMock} class. 。它可以做如下事情：

@example
>>> mock = MagicMock()
>>> mock.__str__.return_value = 'foobarbaz'
>>> str(mock)
'foobarbaz'
>>> mock.__str__.assert_called_with()
@end example

Mock 能指定函数（或其他 Mock 实例）为魔术方法，它们将被适当地调用。  @ref{77f,,MagicMock} 是预先创建了所有魔术方法（所有有用的方法） 的 Mock 。

下面是一个使用了普通 Mock 类的魔术方法的例子

@example
>>> mock = Mock()
>>> mock.__str__ = Mock(return_value='wheeeeee')
>>> str(mock)
'wheeeeee'
@end example

使用 @ref{3324,,auto-speccing} 可以保证测试中的模拟对象与要替换的对象具有相同的api 。在 patch  中可以通过 @emph{autospec} 参数实现自动推断，或者使用 @ref{ed8,,create_autospec()} 函数。自动推断会创建一个与要替换对象相同的属相和方法的模拟对象，并且任何函数和方法（包括构造函数）都具有与真实对象相同的调用签名。

这么做是为了因确保不当地使用 mock 导致与生产代码相同的失败：

@example
>>> from unittest.mock import create_autospec
>>> def function(a, b, c):
...     pass
...
>>> mock_function = create_autospec(function, return_value='fishy')
>>> mock_function(1, 2, 3)
'fishy'
>>> mock_function.assert_called_once_with(1, 2, 3)
>>> mock_function('wrong arguments')
Traceback (most recent call last):
 ...
TypeError: <lambda>() takes exactly 3 arguments (1 given)
@end example

在类中使用 @ref{ed8,,create_autospec()} 时，会复制 @code{__init__} 的签名，另外在可调用对象上使用时，会复制 @code{__call__} 的签名。

@node Mock 类,The patchers,快速上手,unittest mock --- 模拟对象库
@anchor{library/unittest mock the-mock-class}@anchor{3325}
@subsubsection Mock 类


@c import asyncio
@c import inspect
@c import unittest
@c from unittest.mock import sentinel, DEFAULT, ANY
@c from unittest.mock import patch, call, Mock, MagicMock, PropertyMock, AsyncMock
@c from unittest.mock import mock_open

@ref{249,,Mock} 是一个可以灵活的替换存根 (stubs) 的对象，可以测试所有代码。 Mock 是可调用的，在访问其属性时创建一个新的 mock @footnote{@w{(1)} 
The only exceptions are magic methods and attributes (those that have
leading and trailing double underscores). Mock doesn't create these but
instead raises an @ref{393,,AttributeError}. This is because the interpreter
will often implicitly request these methods, and gets @emph{very} confused to
get a new Mock object when it expects a magic method. If you need magic
method support see @ref{3323,,magic methods}.
} 。访问相同的属性只会返回相同的 mock 。 Mock 保存调用记录，可以通过断言获悉代码的调用。

@ref{77f,,MagicMock} 是  @ref{249,,Mock} 的子类，它有所有预创建且可使用的魔术方法。在需要模拟不可调用对象时，可以使用 @ref{3326,,NonCallableMock}  和 @ref{3327,,NonCallableMagicMock}

@ref{782,,patch()} 装饰器使得用 @ref{249,,Mock} 对象临时替换特定模块中的类非常方便。 默认情况下 @ref{782,,patch()} 将为你创建一个 @ref{77f,,MagicMock}。 你可以使用 @ref{782,,patch()} 的 @emph{new_callable} 参数指定替代 @ref{249,,Mock} 的类。

@geindex Mock (unittest.mock 中的类)
@anchor{library/unittest mock unittest mock Mock}@anchor{249}
@deffn {类} unittest.mock.Mock (spec=None, side_effect=None, return_value=DEFAULT, wraps=None, name=None, spec_set=None, unsafe=False, **kwargs)

创建一个新的  @ref{249,,Mock} 对象。通过可选参数指定 @ref{249,,Mock} 对象的行为：


@itemize *

@item 
@emph{spec}: This can be either a list of strings or an existing object (a
class or instance) that acts as the specification for the mock object. If
you pass in an object then a list of strings is formed by calling dir on
the object (excluding unsupported magic attributes and methods).
Accessing any attribute not in this list will raise an @ref{393,,AttributeError}.

If @emph{spec} is an object (rather than a list of strings) then
@ref{e03,,__class__} returns the class of the spec object. This
allows mocks to pass @ref{449,,isinstance()} tests.

@item 
@emph{spec_set}: A stricter variant of @emph{spec}. If used, attempting to @emph{set}
or get an attribute on the mock that isn't on the object passed as
@emph{spec_set} will raise an @ref{393,,AttributeError}.

@item 
@emph{side_effect}: A function to be called whenever the Mock is called. See
the @ref{3328,,side_effect} attribute. Useful for raising exceptions or
dynamically changing return values. The function is called with the same
arguments as the mock, and unless it returns @ref{3329,,DEFAULT}, the return
value of this function is used as the return value.

Alternatively @emph{side_effect} can be an exception class or instance. In
this case the exception will be raised when the mock is called.

If @emph{side_effect} is an iterable then each call to the mock will return
the next value from the iterable.

A @emph{side_effect} can be cleared by setting it to @code{None}.

@item 
@emph{return_value}: The value returned when the mock is called. By default
this is a new Mock (created on first access). See the
@ref{332a,,return_value} attribute.

@item 
@emph{unsafe}: By default if any attribute starts with @emph{assert} or
@emph{assret} will raise an @ref{393,,AttributeError}. Passing @code{unsafe=True}
will allow access to these attributes.


3.5 新版功能.


@item 
@emph{wraps}: Item for the mock object to wrap. If @emph{wraps} is not @code{None} then
calling the Mock will pass the call through to the wrapped object
(returning the real result). Attribute access on the mock will return a
Mock object that wraps the corresponding attribute of the wrapped
object (so attempting to access an attribute that doesn't exist will
raise an @ref{393,,AttributeError}).

If the mock has an explicit @emph{return_value} set then calls are not passed
to the wrapped object and the @emph{return_value} is returned instead.

@item 
@emph{name}: If the mock has a name then it will be used in the repr of the
mock. This can be useful for debugging. The name is propagated to child
mocks.
@end itemize

Mocks can also be called with arbitrary keyword arguments. These will be
used to set attributes on the mock after it is created. See the
@ref{332b,,configure_mock()} method for details.

@geindex assert_called() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock assert_called}@anchor{5a3}
@deffn {方法} assert_called ()

Assert that the mock was called at least once.

@example
>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called()
@end example


3.6 新版功能.

@end deffn

@geindex assert_called_once() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock assert_called_once}@anchor{5a4}
@deffn {方法} assert_called_once ()

Assert that the mock was called exactly once.

@example
>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_once()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_once()
Traceback (most recent call last):
...
AssertionError: Expected 'method' to have been called once. Called 2 times.
@end example


3.6 新版功能.

@end deffn

@geindex assert_called_with() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock assert_called_with}@anchor{f90}
@deffn {方法} assert_called_with (*args, **kwargs)

This method is a convenient way of asserting that the last call has been
made in a particular way:

@example
>>> mock = Mock()
>>> mock.method(1, 2, 3, test='wow')
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_with(1, 2, 3, test='wow')
@end example
@end deffn

@geindex assert_called_once_with() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock assert_called_once_with}@anchor{332c}
@deffn {方法} assert_called_once_with (*args, **kwargs)

Assert that the mock was called exactly once and that that call was
with the specified arguments.

@example
>>> mock = Mock(return_value=None)
>>> mock('foo', bar='baz')
>>> mock.assert_called_once_with('foo', bar='baz')
>>> mock('other', bar='values')
>>> mock.assert_called_once_with('other', bar='values')
Traceback (most recent call last):
  ...
AssertionError: Expected 'mock' to be called once. Called 2 times.
@end example
@end deffn

@geindex assert_any_call() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock assert_any_call}@anchor{332d}
@deffn {方法} assert_any_call (*args, **kwargs)

assert the mock has been called with the specified arguments.

The assert passes if the mock has @emph{ever} been called, unlike
@ref{f90,,assert_called_with()} and @ref{332c,,assert_called_once_with()} that
only pass if the call is the most recent one, and in the case of
@ref{332c,,assert_called_once_with()} it must also be the only call.

@example
>>> mock = Mock(return_value=None)
>>> mock(1, 2, arg='thing')
>>> mock('some', 'thing', 'else')
>>> mock.assert_any_call(1, 2, arg='thing')
@end example
@end deffn

@geindex assert_has_calls() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock assert_has_calls}@anchor{332e}
@deffn {方法} assert_has_calls (calls, any_order=False)

assert the mock has been called with the specified calls.
The @ref{332f,,mock_calls} list is checked for the calls.

If @emph{any_order} is false then the calls must be
sequential. There can be extra calls before or after the
specified calls.

If @emph{any_order} is true then the calls can be in any order, but
they must all appear in @ref{332f,,mock_calls}.

@example
>>> mock = Mock(return_value=None)
>>> mock(1)
>>> mock(2)
>>> mock(3)
>>> mock(4)
>>> calls = [call(2), call(3)]
>>> mock.assert_has_calls(calls)
>>> calls = [call(4), call(2), call(3)]
>>> mock.assert_has_calls(calls, any_order=True)
@end example
@end deffn

@geindex assert_not_called() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock assert_not_called}@anchor{77e}
@deffn {方法} assert_not_called ()

Assert the mock was never called.

@example
>>> m = Mock()
>>> m.hello.assert_not_called()
>>> obj = m.hello()
>>> m.hello.assert_not_called()
Traceback (most recent call last):
  ...
AssertionError: Expected 'hello' to not have been called. Called 1 times.
@end example


3.5 新版功能.

@end deffn

@geindex reset_mock() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock reset_mock}@anchor{5a5}
@deffn {方法} reset_mock (*, return_value=False, side_effect=False)

The reset_mock method resets all the call attributes on a mock object:

@example
>>> mock = Mock(return_value=None)
>>> mock('hello')
>>> mock.called
True
>>> mock.reset_mock()
>>> mock.called
False
@end example


在 3.6 版更改: Added two keyword only argument to the reset_mock function.


This can be useful where you want to make a series of assertions that
reuse the same object. Note that @ref{5a5,,reset_mock()} @emph{doesn't} clear the
return value, @ref{3328,,side_effect} or any child attributes you have
set using normal assignment by default. In case you want to reset
@emph{return_value} or @ref{3328,,side_effect}, then pass the corresponding
parameter as @code{True}. Child mocks and the return value mock
(if any) are reset as well.

@cartouche
@quotation 注解 
@emph{return_value}, and @ref{3328,,side_effect} are keyword only
argument.
@end quotation
@end cartouche
@end deffn

@geindex mock_add_spec() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock mock_add_spec}@anchor{3330}
@deffn {方法} mock_add_spec (spec, spec_set=False)

Add a spec to a mock. @emph{spec} can either be an object or a
list of strings. Only attributes on the @emph{spec} can be fetched as
attributes from the mock.

If @emph{spec_set} is true then only attributes on the spec can be set.
@end deffn

@geindex attach_mock() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock attach_mock}@anchor{3331}
@deffn {方法} attach_mock (mock, attribute)

Attach a mock as an attribute of this one, replacing its name and
parent. Calls to the attached mock will be recorded in the
@ref{3332,,method_calls} and @ref{332f,,mock_calls} attributes of this one.
@end deffn

@geindex configure_mock() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock configure_mock}@anchor{332b}
@deffn {方法} configure_mock (**kwargs)

Set attributes on the mock through keyword arguments.

Attributes plus return values and side effects can be set on child
mocks using standard dot notation and unpacking a dictionary in the
method call:

@example
>>> mock = Mock()
>>> attrs = @{'method.return_value': 3, 'other.side_effect': KeyError@}
>>> mock.configure_mock(**attrs)
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
  ...
KeyError
@end example

The same thing can be achieved in the constructor call to mocks:

@example
>>> attrs = @{'method.return_value': 3, 'other.side_effect': KeyError@}
>>> mock = Mock(some_attribute='eggs', **attrs)
>>> mock.some_attribute
'eggs'
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
  ...
KeyError
@end example

@ref{332b,,configure_mock()} exists to make it easier to do configuration
after the mock has been created.
@end deffn

@geindex __dir__() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock __dir__}@anchor{3333}
@deffn {方法} __dir__ ()

@ref{249,,Mock} objects limit the results of @code{dir(some_mock)} to useful results.
For mocks with a @emph{spec} this includes all the permitted attributes
for the mock.

See @ref{3334,,FILTER_DIR} for what this filtering does, and how to
switch it off.
@end deffn

@geindex _get_child_mock() (unittest.mock.Mock 方法)
@anchor{library/unittest mock unittest mock Mock _get_child_mock}@anchor{3335}
@deffn {方法} _get_child_mock (**kw)

Create the child mocks for attributes and return value.
By default child mocks will be the same type as the parent.
Subclasses of Mock may want to override this to customize the way
child mocks are made.

For non-callable mocks the callable variant will be used (rather than
any custom subclass).
@end deffn

@geindex called (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock called}@anchor{3336}
@deffn {属性} called

A boolean representing whether or not the mock object has been called:

@example
>>> mock = Mock(return_value=None)
>>> mock.called
False
>>> mock()
>>> mock.called
True
@end example
@end deffn

@geindex call_count (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock call_count}@anchor{3337}
@deffn {属性} call_count

An integer telling you how many times the mock object has been called:

@example
>>> mock = Mock(return_value=None)
>>> mock.call_count
0
>>> mock()
>>> mock()
>>> mock.call_count
2
@end example
@end deffn

@geindex return_value (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock return_value}@anchor{332a}
@deffn {属性} return_value

Set this to configure the value returned by calling the mock:

@example
>>> mock = Mock()
>>> mock.return_value = 'fish'
>>> mock()
'fish'
@end example

The default return value is a mock object and you can configure it in
the normal way:

@example
>>> mock = Mock()
>>> mock.return_value.attribute = sentinel.Attribute
>>> mock.return_value()
<Mock name='mock()()' id='...'>
>>> mock.return_value.assert_called_with()
@end example

@ref{332a,,return_value} can also be set in the constructor:

@example
>>> mock = Mock(return_value=3)
>>> mock.return_value
3
>>> mock()
3
@end example
@end deffn

@geindex side_effect (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock side_effect}@anchor{3328}
@deffn {属性} side_effect

This can either be a function to be called when the mock is called,
an iterable or an exception (class or instance) to be raised.

If you pass in a function it will be called with same arguments as the
mock and unless the function returns the @ref{3329,,DEFAULT} singleton the
call to the mock will then return whatever the function returns. If the
function returns @ref{3329,,DEFAULT} then the mock will return its normal
value (from the @ref{332a,,return_value}).

If you pass in an iterable, it is used to retrieve an iterator which
must yield a value on every call.  This value can either be an exception
instance to be raised, or a value to be returned from the call to the
mock (@ref{3329,,DEFAULT} handling is identical to the function case).

An example of a mock that raises an exception (to test exception
handling of an API):

@example
>>> mock = Mock()
>>> mock.side_effect = Exception('Boom!')
>>> mock()
Traceback (most recent call last):
  ...
Exception: Boom!
@end example

Using @ref{3328,,side_effect} to return a sequence of values:

@example
>>> mock = Mock()
>>> mock.side_effect = [3, 2, 1]
>>> mock(), mock(), mock()
(3, 2, 1)
@end example

Using a callable:

@example
>>> mock = Mock(return_value=3)
>>> def side_effect(*args, **kwargs):
...     return DEFAULT
...
>>> mock.side_effect = side_effect
>>> mock()
3
@end example

@ref{3328,,side_effect} can be set in the constructor. Here's an example that
adds one to the value the mock is called with and returns it:

@example
>>> side_effect = lambda value: value + 1
>>> mock = Mock(side_effect=side_effect)
>>> mock(3)
4
>>> mock(-8)
-7
@end example

Setting @ref{3328,,side_effect} to @code{None} clears it:

@example
>>> m = Mock(side_effect=KeyError, return_value=3)
>>> m()
Traceback (most recent call last):
 ...
KeyError
>>> m.side_effect = None
>>> m()
3
@end example
@end deffn

@geindex call_args (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock call_args}@anchor{eb3}
@deffn {属性} call_args

This is either @code{None} (if the mock hasn't been called), or the
arguments that the mock was last called with. This will be in the
form of a tuple: the first member, which can also be accessed through
the @code{args} property, is any ordered arguments the mock was
called with (or an empty tuple) and the second member, which can
also be accessed through the @code{kwargs} property, is any keyword
arguments (or an empty dictionary).

@example
>>> mock = Mock(return_value=None)
>>> print(mock.call_args)
None
>>> mock()
>>> mock.call_args
call()
>>> mock.call_args == ()
True
>>> mock(3, 4)
>>> mock.call_args
call(3, 4)
>>> mock.call_args == ((3, 4),)
True
>>> mock.call_args.args
(3, 4)
>>> mock.call_args.kwargs
@{@}
>>> mock(3, 4, 5, key='fish', next='w00t!')
>>> mock.call_args
call(3, 4, 5, key='fish', next='w00t!')
>>> mock.call_args.args
(3, 4, 5)
>>> mock.call_args.kwargs
@{'key': 'fish', 'next': 'w00t!'@}
@end example

@ref{eb3,,call_args}, along with members of the lists @ref{3338,,call_args_list},
@ref{3332,,method_calls} and @ref{332f,,mock_calls} are @ref{f09,,call} objects.
These are tuples, so they can be unpacked to get at the individual
arguments and make more complex assertions. See
@ref{3339,,calls as tuples}.


在 3.8 版更改: Added @code{args} and @code{kwargs} properties.

@end deffn

@geindex call_args_list (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock call_args_list}@anchor{3338}
@deffn {属性} call_args_list

This is a list of all the calls made to the mock object in sequence
(so the length of the list is the number of times it has been
called). Before any calls have been made it is an empty list. The
@ref{f09,,call} object can be used for conveniently constructing lists of
calls to compare with @ref{3338,,call_args_list}.

@example
>>> mock = Mock(return_value=None)
>>> mock()
>>> mock(3, 4)
>>> mock(key='fish', next='w00t!')
>>> mock.call_args_list
[call(), call(3, 4), call(key='fish', next='w00t!')]
>>> expected = [(), ((3, 4),), (@{'key': 'fish', 'next': 'w00t!'@},)]
>>> mock.call_args_list == expected
True
@end example

Members of @ref{3338,,call_args_list} are @ref{f09,,call} objects. These can be
unpacked as tuples to get at the individual arguments. See
@ref{3339,,calls as tuples}.
@end deffn

@geindex method_calls (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock method_calls}@anchor{3332}
@deffn {属性} method_calls

As well as tracking calls to themselves, mocks also track calls to
methods and attributes, and @emph{their} methods and attributes:

@example
>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.property.method.attribute()
<Mock name='mock.property.method.attribute()' id='...'>
>>> mock.method_calls
[call.method(), call.property.method.attribute()]
@end example

Members of @ref{3332,,method_calls} are @ref{f09,,call} objects. These can be
unpacked as tuples to get at the individual arguments. See
@ref{3339,,calls as tuples}.
@end deffn

@geindex mock_calls (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock mock_calls}@anchor{332f}
@deffn {属性} mock_calls

@ref{332f,,mock_calls} records @emph{all} calls to the mock object, its methods,
magic methods @emph{and} return value mocks.

@example
>>> mock = MagicMock()
>>> result = mock(1, 2, 3)
>>> mock.first(a=3)
<MagicMock name='mock.first()' id='...'>
>>> mock.second()
<MagicMock name='mock.second()' id='...'>
>>> int(mock)
1
>>> result(1)
<MagicMock name='mock()()' id='...'>
>>> expected = [call(1, 2, 3), call.first(a=3), call.second(),
... call.__int__(), call()(1)]
>>> mock.mock_calls == expected
True
@end example

Members of @ref{332f,,mock_calls} are @ref{f09,,call} objects. These can be
unpacked as tuples to get at the individual arguments. See
@ref{3339,,calls as tuples}.

@cartouche
@quotation 注解 
The way @ref{332f,,mock_calls} are recorded means that where nested
calls are made, the parameters of ancestor calls are not recorded
and so will always compare equal:

@example
>>> mock = MagicMock()
>>> mock.top(a=3).bottom()
<MagicMock name='mock.top().bottom()' id='...'>
>>> mock.mock_calls
[call.top(a=3), call.top().bottom()]
>>> mock.mock_calls[-1] == call.top(a=-1).bottom()
True
@end example
@end quotation
@end cartouche
@end deffn

@geindex __class__ (unittest.mock.Mock 属性)
@anchor{library/unittest mock unittest mock Mock __class__}@anchor{333a}
@deffn {属性} __class__

Normally the @ref{333a,,__class__} attribute of an object will return its type.
For a mock object with a @code{spec}, @code{__class__} returns the spec class
instead. This allows mock objects to pass @ref{449,,isinstance()} tests for the
object they are replacing / masquerading as:

@example
>>> mock = Mock(spec=3)
>>> isinstance(mock, int)
True
@end example

@ref{333a,,__class__} is assignable to, this allows a mock to pass an
@ref{449,,isinstance()} check without forcing you to use a spec:

@example
>>> mock = Mock()
>>> mock.__class__ = dict
>>> isinstance(mock, dict)
True
@end example
@end deffn
@end deffn

@geindex NonCallableMock (unittest.mock 中的类)
@anchor{library/unittest mock unittest mock NonCallableMock}@anchor{3326}
@deffn {类} unittest.mock.NonCallableMock (spec=None, wraps=None, name=None, spec_set=None, **kwargs)

A non-callable version of @ref{249,,Mock}. The constructor parameters have the same
meaning of @ref{249,,Mock}, with the exception of @emph{return_value} and @emph{side_effect}
which have no meaning on a non-callable mock.
@end deffn

Mock objects that use a class or an instance as a @code{spec} or
@code{spec_set} are able to pass @ref{449,,isinstance()} tests:

@example
>>> mock = Mock(spec=SomeClass)
>>> isinstance(mock, SomeClass)
True
>>> mock = Mock(spec_set=SomeClass())
>>> isinstance(mock, SomeClass)
True
@end example

The @ref{249,,Mock} classes have support for mocking magic methods. See @ref{3323,,magic methods} for the full details.

The mock classes and the @ref{782,,patch()} decorators all take arbitrary keyword
arguments for configuration. For the @ref{782,,patch()} decorators the keywords are
passed to the constructor of the mock being created. The keyword arguments
are for configuring attributes of the mock:

@example
>>> m = MagicMock(attribute=3, other='fish')
>>> m.attribute
3
>>> m.other
'fish'
@end example

The return value and side effect of child mocks can be set in the same way,
using dotted notation. As you can't use dotted names directly in a call you
have to create a dictionary and unpack it using @code{**}:

@example
>>> attrs = @{'method.return_value': 3, 'other.side_effect': KeyError@}
>>> mock = Mock(some_attribute='eggs', **attrs)
>>> mock.some_attribute
'eggs'
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
  ...
KeyError
@end example

A callable mock which was created with a @emph{spec} (or a @emph{spec_set}) will
introspect the specification object's signature when matching calls to
the mock.  Therefore, it can match the actual call's arguments regardless
of whether they were passed positionally or by name:

@example
>>> def f(a, b, c): pass
...
>>> mock = Mock(spec=f)
>>> mock(1, 2, c=3)
<Mock name='mock()' id='140161580456576'>
>>> mock.assert_called_with(1, 2, 3)
>>> mock.assert_called_with(a=1, b=2, c=3)
@end example

This applies to @ref{f90,,assert_called_with()},
@ref{332c,,assert_called_once_with()}, @ref{332e,,assert_has_calls()} and
@ref{332d,,assert_any_call()}.  When @ref{3324,,Autospeccing}, it will also
apply to method calls on the mock object.

@quotation


在 3.4 版更改: Added signature introspection on specced and autospecced mock objects.

@end quotation

@geindex PropertyMock (unittest.mock 中的类)
@anchor{library/unittest mock unittest mock PropertyMock}@anchor{333b}
@deffn {类} unittest.mock.PropertyMock (*args, **kwargs)

A mock intended to be used as a property, or other descriptor, on a class.
@ref{333b,,PropertyMock} provides @ref{13d3,,__get__()} and @ref{13d7,,__set__()} methods
so you can specify a return value when it is fetched.

Fetching a @ref{333b,,PropertyMock} instance from an object calls the mock, with
no args. Setting it calls the mock with the value being set.

@example
>>> class Foo:
...     @@property
...     def foo(self):
...         return 'something'
...     @@foo.setter
...     def foo(self, value):
...         pass
...
>>> with patch('__main__.Foo.foo', new_callable=PropertyMock) as mock_foo:
...     mock_foo.return_value = 'mockity-mock'
...     this_foo = Foo()
...     print(this_foo.foo)
...     this_foo.foo = 6
...
mockity-mock
>>> mock_foo.mock_calls
[call(), call(6)]
@end example
@end deffn

Because of the way mock attributes are stored you can't directly attach a
@ref{333b,,PropertyMock} to a mock object. Instead you can attach it to the mock type
object:

@example
>>> m = MagicMock()
>>> p = PropertyMock(return_value=3)
>>> type(m).foo = p
>>> m.foo
3
>>> p.assert_called_once_with()
@end example

@geindex AsyncMock (unittest.mock 中的类)
@anchor{library/unittest mock unittest mock AsyncMock}@anchor{248}
@deffn {类} unittest.mock.AsyncMock (spec=None, side_effect=None, return_value=DEFAULT, wraps=None, name=None, spec_set=None, unsafe=False, **kwargs)

An asynchronous version of @ref{249,,Mock}. The @ref{248,,AsyncMock} object will
behave so the object is recognized as an async function, and the result of a
call is an awaitable.

@example
>>> mock = AsyncMock()
>>> asyncio.iscoroutinefunction(mock)
True
>>> inspect.isawaitable(mock())  
True
@end example

The result of @code{mock()} is an async function which will have the outcome
of @code{side_effect} or @code{return_value} after it has been awaited:


@itemize -

@item 
if @code{side_effect} is a function, the async function will return the
result of that function,

@item 
if @code{side_effect} is an exception, the async function will raise the
exception,

@item 
if @code{side_effect} is an iterable, the async function will return the
next value of the iterable, however, if the sequence of result is
exhausted, @code{StopAsyncIteration} is raised immediately,

@item 
if @code{side_effect} is not defined, the async function will return the
value defined by @code{return_value}, hence, by default, the async function
returns a new @ref{248,,AsyncMock} object.
@end itemize

Setting the @emph{spec} of a @ref{249,,Mock} or @ref{77f,,MagicMock} to an async function
will result in a coroutine object being returned after calling.

@example
>>> async def async_func(): pass
...
>>> mock = MagicMock(async_func)
>>> mock
<MagicMock spec='function' id='...'>
>>> mock()  
<coroutine object AsyncMockMixin._mock_call at ...>
@end example

Setting the @emph{spec} of a @ref{249,,Mock}, @ref{77f,,MagicMock}, or @ref{248,,AsyncMock}
to a class with asynchronous and synchronous functions will automatically
detect the synchronous functions and set them as @ref{77f,,MagicMock} (if the
parent mock is @ref{248,,AsyncMock} or @ref{77f,,MagicMock}) or @ref{249,,Mock} (if
the parent mock is @ref{249,,Mock}). All asynchronous functions will be
@ref{248,,AsyncMock}.

@example
>>> class ExampleClass:
...     def sync_foo():
...         pass
...     async def async_foo():
...         pass
...
>>> a_mock = AsyncMock(ExampleClass)
>>> a_mock.sync_foo
<MagicMock name='mock.sync_foo' id='...'>
>>> a_mock.async_foo
<AsyncMock name='mock.async_foo' id='...'>
>>> mock = Mock(ExampleClass)
>>> mock.sync_foo
<Mock name='mock.sync_foo' id='...'>
>>> mock.async_foo
<AsyncMock name='mock.async_foo' id='...'>
@end example


3.8 新版功能.


@geindex assert_awaited() (unittest.mock.AsyncMock 方法)
@anchor{library/unittest mock unittest mock AsyncMock assert_awaited}@anchor{333c}
@deffn {方法} assert_awaited ()

Assert that the mock was awaited at least once. Note that this is separate
from the object having been called, the @code{await} keyword must be used:

@example
>>> mock = AsyncMock()
>>> async def main(coroutine_mock):
...     await coroutine_mock
...
>>> coroutine_mock = mock()
>>> mock.called
True
>>> mock.assert_awaited()
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited.
>>> asyncio.run(main(coroutine_mock))
>>> mock.assert_awaited()
@end example
@end deffn

@geindex assert_awaited_once() (unittest.mock.AsyncMock 方法)
@anchor{library/unittest mock unittest mock AsyncMock assert_awaited_once}@anchor{333d}
@deffn {方法} assert_awaited_once ()

Assert that the mock was awaited exactly once.

@example
>>> mock = AsyncMock()
>>> async def main():
...     await mock()
...
>>> asyncio.run(main())
>>> mock.assert_awaited_once()
>>> asyncio.run(main())
>>> mock.method.assert_awaited_once()
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited once. Awaited 2 times.
@end example
@end deffn

@geindex assert_awaited_with() (unittest.mock.AsyncMock 方法)
@anchor{library/unittest mock unittest mock AsyncMock assert_awaited_with}@anchor{333e}
@deffn {方法} assert_awaited_with (*args, **kwargs)

Assert that the last await was with the specified arguments.

@example
>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
...     await mock(*args, **kwargs)
...
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_with('foo', bar='bar')
>>> mock.assert_awaited_with('other')
Traceback (most recent call last):
...
AssertionError: expected call not found.
Expected: mock('other')
Actual: mock('foo', bar='bar')
@end example
@end deffn

@geindex assert_awaited_once_with() (unittest.mock.AsyncMock 方法)
@anchor{library/unittest mock unittest mock AsyncMock assert_awaited_once_with}@anchor{333f}
@deffn {方法} assert_awaited_once_with (*args, **kwargs)

Assert that the mock was awaited exactly once and with the specified
arguments.

@example
>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
...     await mock(*args, **kwargs)
...
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_once_with('foo', bar='bar')
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_once_with('foo', bar='bar')
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited once. Awaited 2 times.
@end example
@end deffn

@geindex assert_any_await() (unittest.mock.AsyncMock 方法)
@anchor{library/unittest mock unittest mock AsyncMock assert_any_await}@anchor{3340}
@deffn {方法} assert_any_await (*args, **kwargs)

Assert the mock has ever been awaited with the specified arguments.

@example
>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
...     await mock(*args, **kwargs)
...
>>> asyncio.run(main('foo', bar='bar'))
>>> asyncio.run(main('hello'))
>>> mock.assert_any_await('foo', bar='bar')
>>> mock.assert_any_await('other')
Traceback (most recent call last):
...
AssertionError: mock('other') await not found
@end example
@end deffn

@geindex assert_has_awaits() (unittest.mock.AsyncMock 方法)
@anchor{library/unittest mock unittest mock AsyncMock assert_has_awaits}@anchor{3341}
@deffn {方法} assert_has_awaits (calls, any_order=False)

Assert the mock has been awaited with the specified calls.
The @ref{eb2,,await_args_list} list is checked for the awaits.

If @emph{any_order} is false then the awaits must be
sequential. There can be extra calls before or after the
specified awaits.

If @emph{any_order} is true then the awaits can be in any order, but
they must all appear in @ref{eb2,,await_args_list}.

@example
>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
...     await mock(*args, **kwargs)
...
>>> calls = [call("foo"), call("bar")]
>>> mock.assert_has_awaits(calls)
Traceback (most recent call last):
...
AssertionError: Awaits not found.
Expected: [call('foo'), call('bar')]
Actual: []
>>> asyncio.run(main('foo'))
>>> asyncio.run(main('bar'))
>>> mock.assert_has_awaits(calls)
@end example
@end deffn

@geindex assert_not_awaited() (unittest.mock.AsyncMock 方法)
@anchor{library/unittest mock unittest mock AsyncMock assert_not_awaited}@anchor{3342}
@deffn {方法} assert_not_awaited ()

Assert that the mock was never awaited.

@example
>>> mock = AsyncMock()
>>> mock.assert_not_awaited()
@end example
@end deffn

@geindex reset_mock() (unittest.mock.AsyncMock 方法)
@anchor{library/unittest mock unittest mock AsyncMock reset_mock}@anchor{3343}
@deffn {方法} reset_mock (*args, **kwargs)

See @ref{5a5,,Mock.reset_mock()}. Also sets @ref{3344,,await_count} to 0,
@ref{3345,,await_args} to None, and clears the @ref{eb2,,await_args_list}.
@end deffn

@geindex await_count (unittest.mock.AsyncMock 属性)
@anchor{library/unittest mock unittest mock AsyncMock await_count}@anchor{3344}
@deffn {属性} await_count

An integer keeping track of how many times the mock object has been awaited.

@example
>>> mock = AsyncMock()
>>> async def main():
...     await mock()
...
>>> asyncio.run(main())
>>> mock.await_count
1
>>> asyncio.run(main())
>>> mock.await_count
2
@end example
@end deffn

@geindex await_args (unittest.mock.AsyncMock 属性)
@anchor{library/unittest mock unittest mock AsyncMock await_args}@anchor{3345}
@deffn {属性} await_args

This is either @code{None} (if the mock hasn’t been awaited), or the arguments that
the mock was last awaited with. Functions the same as @ref{eb3,,Mock.call_args}.

@example
>>> mock = AsyncMock()
>>> async def main(*args):
...     await mock(*args)
...
>>> mock.await_args
>>> asyncio.run(main('foo'))
>>> mock.await_args
call('foo')
>>> asyncio.run(main('bar'))
>>> mock.await_args
call('bar')
@end example
@end deffn

@geindex await_args_list (unittest.mock.AsyncMock 属性)
@anchor{library/unittest mock unittest mock AsyncMock await_args_list}@anchor{eb2}
@deffn {属性} await_args_list

This is a list of all the awaits made to the mock object in sequence (so the
length of the list is the number of times it has been awaited). Before any
awaits have been made it is an empty list.

@example
>>> mock = AsyncMock()
>>> async def main(*args):
...     await mock(*args)
...
>>> mock.await_args_list
[]
>>> asyncio.run(main('foo'))
>>> mock.await_args_list
[call('foo')]
>>> asyncio.run(main('bar'))
>>> mock.await_args_list
[call('foo'), call('bar')]
@end example
@end deffn
@end deffn

@menu
* Calling:: 
* Deleting Attributes:: 
* Mock names and the name attribute:: 
* Attaching Mocks as Attributes:: 

@end menu

@node Calling,Deleting Attributes,,Mock 类
@anchor{library/unittest mock calling}@anchor{3346}
@subsubsection Calling


Mock objects are callable. The call will return the value set as the
@ref{332a,,return_value} attribute. The default return value is a new Mock
object; it is created the first time the return value is accessed (either
explicitly or by calling the Mock) - but it is stored and the same one
returned each time.

Calls made to the object will be recorded in the attributes
like @ref{eb3,,call_args} and @ref{3338,,call_args_list}.

If @ref{3328,,side_effect} is set then it will be called after the call has
been recorded, so if @code{side_effect} raises an exception the call is still
recorded.

The simplest way to make a mock raise an exception when called is to make
@ref{3328,,side_effect} an exception class or instance:

@example
>>> m = MagicMock(side_effect=IndexError)
>>> m(1, 2, 3)
Traceback (most recent call last):
  ...
IndexError
>>> m.mock_calls
[call(1, 2, 3)]
>>> m.side_effect = KeyError('Bang!')
>>> m('two', 'three', 'four')
Traceback (most recent call last):
  ...
KeyError: 'Bang!'
>>> m.mock_calls
[call(1, 2, 3), call('two', 'three', 'four')]
@end example

If @code{side_effect} is a function then whatever that function returns is what
calls to the mock return. The @code{side_effect} function is called with the
same arguments as the mock. This allows you to vary the return value of the
call dynamically, based on the input:

@example
>>> def side_effect(value):
...     return value + 1
...
>>> m = MagicMock(side_effect=side_effect)
>>> m(1)
2
>>> m(2)
3
>>> m.mock_calls
[call(1), call(2)]
@end example

If you want the mock to still return the default return value (a new mock), or
any set return value, then there are two ways of doing this. Either return
@code{mock.return_value} from inside @code{side_effect}, or return @ref{3329,,DEFAULT}:

@example
>>> m = MagicMock()
>>> def side_effect(*args, **kwargs):
...     return m.return_value
...
>>> m.side_effect = side_effect
>>> m.return_value = 3
>>> m()
3
>>> def side_effect(*args, **kwargs):
...     return DEFAULT
...
>>> m.side_effect = side_effect
>>> m()
3
@end example

To remove a @code{side_effect}, and return to the default behaviour, set the
@code{side_effect} to @code{None}:

@example
>>> m = MagicMock(return_value=6)
>>> def side_effect(*args, **kwargs):
...     return 3
...
>>> m.side_effect = side_effect
>>> m()
3
>>> m.side_effect = None
>>> m()
6
@end example

The @code{side_effect} can also be any iterable object. Repeated calls to the mock
will return values from the iterable (until the iterable is exhausted and
a @ref{480,,StopIteration} is raised):

@example
>>> m = MagicMock(side_effect=[1, 2, 3])
>>> m()
1
>>> m()
2
>>> m()
3
>>> m()
Traceback (most recent call last):
  ...
StopIteration
@end example

If any members of the iterable are exceptions they will be raised instead of
returned:

@example
>>> iterable = (33, ValueError, 66)
>>> m = MagicMock(side_effect=iterable)
>>> m()
33
>>> m()
Traceback (most recent call last):
 ...
ValueError
>>> m()
66
@end example

@node Deleting Attributes,Mock names and the name attribute,Calling,Mock 类
@anchor{library/unittest mock deleting-attributes}@anchor{3347}@anchor{library/unittest mock id2}@anchor{3348}
@subsubsection Deleting Attributes


Mock objects create attributes on demand. This allows them to pretend to be
objects of any type.

You may want a mock object to return @code{False} to a @ref{442,,hasattr()} call, or raise an
@ref{393,,AttributeError} when an attribute is fetched. You can do this by providing
an object as a @code{spec} for a mock, but that isn't always convenient.

You "block" attributes by deleting them. Once deleted, accessing an attribute
will raise an @ref{393,,AttributeError}.

@example
>>> mock = MagicMock()
>>> hasattr(mock, 'm')
True
>>> del mock.m
>>> hasattr(mock, 'm')
False
>>> del mock.f
>>> mock.f
Traceback (most recent call last):
    ...
AttributeError: f
@end example

@node Mock names and the name attribute,Attaching Mocks as Attributes,Deleting Attributes,Mock 类
@anchor{library/unittest mock mock-names-and-the-name-attribute}@anchor{3349}
@subsubsection Mock names and the name attribute


Since "name" is an argument to the @ref{249,,Mock} constructor, if you want your
mock object to have a "name" attribute you can't just pass it in at creation
time. There are two alternatives. One option is to use
@ref{332b,,configure_mock()}:

@example
>>> mock = MagicMock()
>>> mock.configure_mock(name='my_name')
>>> mock.name
'my_name'
@end example

A simpler option is to simply set the "name" attribute after mock creation:

@example
>>> mock = MagicMock()
>>> mock.name = "foo"
@end example

@node Attaching Mocks as Attributes,,Mock names and the name attribute,Mock 类
@anchor{library/unittest mock attaching-mocks-as-attributes}@anchor{334a}
@subsubsection Attaching Mocks as Attributes


When you attach a mock as an attribute of another mock (or as the return
value) it becomes a "child" of that mock. Calls to the child are recorded in
the @ref{3332,,method_calls} and @ref{332f,,mock_calls} attributes of the
parent. This is useful for configuring child mocks and then attaching them to
the parent, or for attaching mocks to a parent that records all calls to the
children and allows you to make assertions about the order of calls between
mocks:

@example
>>> parent = MagicMock()
>>> child1 = MagicMock(return_value=None)
>>> child2 = MagicMock(return_value=None)
>>> parent.child1 = child1
>>> parent.child2 = child2
>>> child1(1)
>>> child2(2)
>>> parent.mock_calls
[call.child1(1), call.child2(2)]
@end example

The exception to this is if the mock has a name. This allows you to prevent
the "parenting" if for some reason you don't want it to happen.

@example
>>> mock = MagicMock()
>>> not_a_child = MagicMock(name='not-a-child')
>>> mock.attribute = not_a_child
>>> mock.attribute()
<MagicMock name='not-a-child()' id='...'>
>>> mock.mock_calls
[]
@end example

Mocks created for you by @ref{782,,patch()} are automatically given names. To
attach mocks that have names to a parent you use the @ref{3331,,attach_mock()}
method:

@example
>>> thing1 = object()
>>> thing2 = object()
>>> parent = MagicMock()
>>> with patch('__main__.thing1', return_value=None) as child1:
...     with patch('__main__.thing2', return_value=None) as child2:
...         parent.attach_mock(child1, 'child1')
...         parent.attach_mock(child2, 'child2')
...         child1('one')
...         child2('two')
...
>>> parent.mock_calls
[call.child1('one'), call.child2('two')]
@end example

@node The patchers,MagicMock and magic method support,Mock 类,unittest mock --- 模拟对象库
@anchor{library/unittest mock the-patchers}@anchor{334b}
@subsubsection The patchers


The patch decorators are used for patching objects only within the scope of
the function they decorate. They automatically handle the unpatching for you,
even if exceptions are raised. All of these functions can also be used in with
statements or as class decorators.

@menu
* patch:: 
* patch.object: patch object. 
* patch.dict: patch dict. 
* patch.multiple: patch multiple. 
* patch methods; start and stop: patch methods start and stop. 
* patch builtins:: 
* TEST_PREFIX:: 
* Nesting Patch Decorators:: 
* Where to patch:: 
* Patching Descriptors and Proxy Objects:: 

@end menu

@node patch,patch object,,The patchers
@anchor{library/unittest mock patch}@anchor{334c}
@subsubsection patch


@cartouche
@quotation 注解 
@ref{782,,patch()} is straightforward to use. The key is to do the patching in the
right namespace. See the section @ref{334d,,where to patch}.
@end quotation
@end cartouche

@geindex patch() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock patch}@anchor{782}
@deffn {函数} unittest.mock.patch (target, new=DEFAULT, spec=None, create=False, spec_set=None, autospec=None, new_callable=None, **kwargs)

@ref{782,,patch()} acts as a function decorator, class decorator or a context
manager. Inside the body of the function or with statement, the @emph{target}
is patched with a @emph{new} object. When the function/with statement exits
the patch is undone.

If @emph{new} is omitted, then the target is replaced with an
@ref{248,,AsyncMock} if the patched object is an async function or
a @ref{77f,,MagicMock} otherwise.
If @ref{782,,patch()} is used as a decorator and @emph{new} is
omitted, the created mock is passed in as an extra argument to the
decorated function. If @ref{782,,patch()} is used as a context manager the created
mock is returned by the context manager.

@emph{target} should be a string in the form @code{'package.module.ClassName'}. The
@emph{target} is imported and the specified object replaced with the @emph{new}
object, so the @emph{target} must be importable from the environment you are
calling @ref{782,,patch()} from. The target is imported when the decorated function
is executed, not at decoration time.

The @emph{spec} and @emph{spec_set} keyword arguments are passed to the @ref{77f,,MagicMock}
if patch is creating one for you.

In addition you can pass @code{spec=True} or @code{spec_set=True}, which causes
patch to pass in the object being mocked as the spec/spec_set object.

@emph{new_callable} allows you to specify a different class, or callable object,
that will be called to create the @emph{new} object. By default @ref{248,,AsyncMock}
is used for async functions and @ref{77f,,MagicMock} for the rest.

A more powerful form of @emph{spec} is @emph{autospec}. If you set @code{autospec=True}
then the mock will be created with a spec from the object being replaced.
All attributes of the mock will also have the spec of the corresponding
attribute of the object being replaced. Methods and functions being mocked
will have their arguments checked and will raise a @ref{192,,TypeError} if they are
called with the wrong signature. For mocks
replacing a class, their return value (the 'instance') will have the same
spec as the class. See the @ref{ed8,,create_autospec()} function and
@ref{3324,,Autospeccing}.

Instead of @code{autospec=True} you can pass @code{autospec=some_object} to use an
arbitrary object as the spec instead of the one being replaced.

By default @ref{782,,patch()} will fail to replace attributes that don't exist.
If you pass in @code{create=True}, and the attribute doesn't exist, patch will
create the attribute for you when the patched function is called, and delete
it again after the patched function has exited. This is useful for writing
tests against attributes that your production code creates at runtime. It is
off by default because it can be dangerous. With it switched on you can
write passing tests against APIs that don't actually exist!

@cartouche
@quotation 注解 

在 3.5 版更改: If you are patching builtins in a module then you don't
need to pass @code{create=True}, it will be added by default.

@end quotation
@end cartouche

Patch can be used as a @code{TestCase} class decorator. It works by
decorating each test method in the class. This reduces the boilerplate
code when your test methods share a common patchings set. @ref{782,,patch()} finds
tests by looking for method names that start with @code{patch.TEST_PREFIX}.
By default this is @code{'test'}, which matches the way @ref{11b,,unittest} finds tests.
You can specify an alternative prefix by setting @code{patch.TEST_PREFIX}.

Patch can be used as a context manager, with the with statement. Here the
patching applies to the indented block after the with statement. If you
use "as" then the patched object will be bound to the name after the
"as"; very useful if @ref{782,,patch()} is creating a mock object for you.

@ref{782,,patch()} takes arbitrary keyword arguments. These will be passed to
the @ref{249,,Mock} (or @emph{new_callable}) on construction.

@code{patch.dict(...)}, @code{patch.multiple(...)} and @code{patch.object(...)} are
available for alternate use-cases.
@end deffn

@ref{782,,patch()} as function decorator, creating the mock for you and passing it into
the decorated function:

@example
>>> @@patch('__main__.SomeClass')
... def function(normal_argument, mock_class):
...     print(mock_class is SomeClass)
...
>>> function(None)
True
@end example

Patching a class replaces the class with a @ref{77f,,MagicMock} @emph{instance}. If the
class is instantiated in the code under test then it will be the
@ref{332a,,return_value} of the mock that will be used.

If the class is instantiated multiple times you could use
@ref{3328,,side_effect} to return a new mock each time. Alternatively you
can set the @emph{return_value} to be anything you want.

To configure return values on methods of @emph{instances} on the patched class
you must do this on the @code{return_value}. For example:

@example
>>> class Class:
...     def method(self):
...         pass
...
>>> with patch('__main__.Class') as MockClass:
...     instance = MockClass.return_value
...     instance.method.return_value = 'foo'
...     assert Class() is instance
...     assert Class().method() == 'foo'
...
@end example

If you use @emph{spec} or @emph{spec_set} and @ref{782,,patch()} is replacing a @emph{class}, then the
return value of the created mock will have the same spec.

@example
>>> Original = Class
>>> patcher = patch('__main__.Class', spec=True)
>>> MockClass = patcher.start()
>>> instance = MockClass()
>>> assert isinstance(instance, Original)
>>> patcher.stop()
@end example

The @emph{new_callable} argument is useful where you want to use an alternative
class to the default @ref{77f,,MagicMock} for the created mock. For example, if
you wanted a @ref{3326,,NonCallableMock} to be used:

@example
>>> thing = object()
>>> with patch('__main__.thing', new_callable=NonCallableMock) as mock_thing:
...     assert thing is mock_thing
...     thing()
...
Traceback (most recent call last):
  ...
TypeError: 'NonCallableMock' object is not callable
@end example

Another use case might be to replace an object with an @ref{827,,io.StringIO} instance:

@example
>>> from io import StringIO
>>> def foo():
...     print('Something')
...
>>> @@patch('sys.stdout', new_callable=StringIO)
... def test(mock_stdout):
...     foo()
...     assert mock_stdout.getvalue() == 'Something\n'
...
>>> test()
@end example

When @ref{782,,patch()} is creating a mock for you, it is common that the first thing
you need to do is to configure the mock. Some of that configuration can be done
in the call to patch. Any arbitrary keywords you pass into the call will be
used to set attributes on the created mock:

@example
>>> patcher = patch('__main__.thing', first='one', second='two')
>>> mock_thing = patcher.start()
>>> mock_thing.first
'one'
>>> mock_thing.second
'two'
@end example

As well as attributes on the created mock attributes, like the
@ref{332a,,return_value} and @ref{3328,,side_effect}, of child mocks can
also be configured. These aren't syntactically valid to pass in directly as
keyword arguments, but a dictionary with these as keys can still be expanded
into a @ref{782,,patch()} call using @code{**}:

@example
>>> config = @{'method.return_value': 3, 'other.side_effect': KeyError@}
>>> patcher = patch('__main__.thing', **config)
>>> mock_thing = patcher.start()
>>> mock_thing.method()
3
>>> mock_thing.other()
Traceback (most recent call last):
  ...
KeyError
@end example

By default, attempting to patch a function in a module (or a method or an
attribute in a class) that does not exist will fail with @ref{393,,AttributeError}:

@example
>>> @@patch('sys.non_existing_attribute', 42)
... def test():
...     assert sys.non_existing_attribute == 42
...
>>> test()
Traceback (most recent call last):
  ...
AttributeError: <module 'sys' (built-in)> does not have the attribute 'non_existing'
@end example

but adding @code{create=True} in the call to @ref{782,,patch()} will make the previous example
work as expected:

@example
>>> @@patch('sys.non_existing_attribute', 42, create=True)
... def test(mock_stdout):
...     assert sys.non_existing_attribute == 42
...
>>> test()
@end example


在 3.8 版更改: @ref{782,,patch()} now returns an @ref{248,,AsyncMock} if the target is an async function.


@node patch object,patch dict,patch,The patchers
@anchor{library/unittest mock patch-object}@anchor{334e}
@subsubsection patch.object


@geindex patch.object() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock patch object}@anchor{eee}
@deffn {函数} patch.object (target, attribute, new=DEFAULT, spec=None, create=False, spec_set=None, autospec=None, new_callable=None, **kwargs)

patch the named member (@emph{attribute}) on an object (@emph{target}) with a mock
object.

@ref{eee,,patch.object()} can be used as a decorator, class decorator or a context
manager. Arguments @emph{new}, @emph{spec}, @emph{create}, @emph{spec_set}, @emph{autospec} and
@emph{new_callable} have the same meaning as for @ref{782,,patch()}. Like @ref{782,,patch()},
@ref{eee,,patch.object()} takes arbitrary keyword arguments for configuring the mock
object it creates.

When used as a class decorator @ref{eee,,patch.object()} honours @code{patch.TEST_PREFIX}
for choosing which methods to wrap.
@end deffn

You can either call @ref{eee,,patch.object()} with three arguments or two arguments. The
three argument form takes the object to be patched, the attribute name and the
object to replace the attribute with.

When calling with the two argument form you omit the replacement object, and a
mock is created for you and passed in as an extra argument to the decorated
function:

@example
>>> @@patch.object(SomeClass, 'class_method')
... def test(mock_method):
...     SomeClass.class_method(3)
...     mock_method.assert_called_with(3)
...
>>> test()
@end example

@emph{spec}, @emph{create} and the other arguments to @ref{eee,,patch.object()} have the same
meaning as they do for @ref{782,,patch()}.

@node patch dict,patch multiple,patch object,The patchers
@anchor{library/unittest mock patch-dict}@anchor{334f}
@subsubsection patch.dict


@geindex patch.dict() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock patch dict}@anchor{f5f}
@deffn {函数} patch.dict (in_dict, values=(), clear=False, **kwargs)

Patch a dictionary, or dictionary like object, and restore the dictionary
to its original state after the test.

@emph{in_dict} can be a dictionary or a mapping like container. If it is a
mapping then it must at least support getting, setting and deleting items
plus iterating over keys.

@emph{in_dict} can also be a string specifying the name of the dictionary, which
will then be fetched by importing it.

@emph{values} can be a dictionary of values to set in the dictionary. @emph{values}
can also be an iterable of @code{(key, value)} pairs.

If @emph{clear} is true then the dictionary will be cleared before the new
values are set.

@ref{f5f,,patch.dict()} can also be called with arbitrary keyword arguments to set
values in the dictionary.


在 3.8 版更改: @ref{f5f,,patch.dict()} now returns the patched dictionary when used as a context
manager.

@end deffn

@ref{f5f,,patch.dict()} can be used as a context manager, decorator or class
decorator:

@example
>>> foo = @{@}
>>> @@patch.dict(foo, @{'newkey': 'newvalue'@})
... def test():
...     assert foo == @{'newkey': 'newvalue'@}
>>> test()
>>> assert foo == @{@}
@end example

When used as a class decorator @ref{f5f,,patch.dict()} honours
@code{patch.TEST_PREFIX} (default to @code{'test'}) for choosing which methods to wrap:

@example
>>> import os
>>> import unittest
>>> from unittest.mock import patch
>>> @@patch.dict('os.environ', @{'newkey': 'newvalue'@})
... class TestSample(unittest.TestCase):
...     def test_sample(self):
...         self.assertEqual(os.environ['newkey'], 'newvalue')
@end example

If you want to use a different prefix for your test, you can inform the
patchers of the different prefix by setting @code{patch.TEST_PREFIX}. For
more details about how to change the value of see @ref{3350,,TEST_PREFIX}.

@ref{f5f,,patch.dict()} can be used to add members to a dictionary, or simply let a test
change a dictionary, and ensure the dictionary is restored when the test
ends.

@example
>>> foo = @{@}
>>> with patch.dict(foo, @{'newkey': 'newvalue'@}) as patched_foo:
...     assert foo == @{'newkey': 'newvalue'@}
...     assert patched_foo == @{'newkey': 'newvalue'@}
...     # You can add, update or delete keys of foo (or patched_foo, it's the same dict)
...     patched_foo['spam'] = 'eggs'
...
>>> assert foo == @{@}
>>> assert patched_foo == @{@}
@end example

@example
>>> import os
>>> with patch.dict('os.environ', @{'newkey': 'newvalue'@}):
...     print(os.environ['newkey'])
...
newvalue
>>> assert 'newkey' not in os.environ
@end example

Keywords can be used in the @ref{f5f,,patch.dict()} call to set values in the dictionary:

@example
>>> mymodule = MagicMock()
>>> mymodule.function.return_value = 'fish'
>>> with patch.dict('sys.modules', mymodule=mymodule):
...     import mymodule
...     mymodule.function('some', 'args')
...
'fish'
@end example

@ref{f5f,,patch.dict()} can be used with dictionary like objects that aren't actually
dictionaries. At the very minimum they must support item getting, setting,
deleting and either iteration or membership test. This corresponds to the
magic methods @ref{27f,,__getitem__()}, @ref{c5b,,__setitem__()}, @ref{c5c,,__delitem__()} and either
@ref{509,,__iter__()} or @ref{d21,,__contains__()}.

@example
>>> class Container:
...     def __init__(self):
...         self.values = @{@}
...     def __getitem__(self, name):
...         return self.values[name]
...     def __setitem__(self, name, value):
...         self.values[name] = value
...     def __delitem__(self, name):
...         del self.values[name]
...     def __iter__(self):
...         return iter(self.values)
...
>>> thing = Container()
>>> thing['one'] = 1
>>> with patch.dict(thing, one=2, two=3):
...     assert thing['one'] == 2
...     assert thing['two'] == 3
...
>>> assert thing['one'] == 1
>>> assert list(thing) == ['one']
@end example

@node patch multiple,patch methods start and stop,patch dict,The patchers
@anchor{library/unittest mock patch-multiple}@anchor{3351}
@subsubsection patch.multiple


@geindex patch.multiple() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock patch multiple}@anchor{3352}
@deffn {函数} patch.multiple (target, spec=None, create=False, spec_set=None, autospec=None, new_callable=None, **kwargs)

Perform multiple patches in a single call. It takes the object to be
patched (either as an object or a string to fetch the object by importing)
and keyword arguments for the patches:

@example
with patch.multiple(settings, FIRST_PATCH='one', SECOND_PATCH='two'):
    ...
@end example

Use @ref{3329,,DEFAULT} as the value if you want @ref{3352,,patch.multiple()} to create
mocks for you. In this case the created mocks are passed into a decorated
function by keyword, and a dictionary is returned when @ref{3352,,patch.multiple()} is
used as a context manager.

@ref{3352,,patch.multiple()} can be used as a decorator, class decorator or a context
manager. The arguments @emph{spec}, @emph{spec_set}, @emph{create}, @emph{autospec} and
@emph{new_callable} have the same meaning as for @ref{782,,patch()}. These arguments will
be applied to @emph{all} patches done by @ref{3352,,patch.multiple()}.

When used as a class decorator @ref{3352,,patch.multiple()} honours @code{patch.TEST_PREFIX}
for choosing which methods to wrap.
@end deffn

If you want @ref{3352,,patch.multiple()} to create mocks for you, then you can use
@ref{3329,,DEFAULT} as the value. If you use @ref{3352,,patch.multiple()} as a decorator
then the created mocks are passed into the decorated function by keyword.

@example
>>> thing = object()
>>> other = object()

>>> @@patch.multiple('__main__', thing=DEFAULT, other=DEFAULT)
... def test_function(thing, other):
...     assert isinstance(thing, MagicMock)
...     assert isinstance(other, MagicMock)
...
>>> test_function()
@end example

@ref{3352,,patch.multiple()} can be nested with other @code{patch} decorators, but put arguments
passed by keyword @emph{after} any of the standard arguments created by @ref{782,,patch()}:

@example
>>> @@patch('sys.exit')
... @@patch.multiple('__main__', thing=DEFAULT, other=DEFAULT)
... def test_function(mock_exit, other, thing):
...     assert 'other' in repr(other)
...     assert 'thing' in repr(thing)
...     assert 'exit' in repr(mock_exit)
...
>>> test_function()
@end example

If @ref{3352,,patch.multiple()} is used as a context manager, the value returned by the
context manager is a dictionary where created mocks are keyed by name:

@example
>>> with patch.multiple('__main__', thing=DEFAULT, other=DEFAULT) as values:
...     assert 'other' in repr(values['other'])
...     assert 'thing' in repr(values['thing'])
...     assert values['thing'] is thing
...     assert values['other'] is other
...
@end example

@node patch methods start and stop,patch builtins,patch multiple,The patchers
@anchor{library/unittest mock patch-methods-start-and-stop}@anchor{3353}@anchor{library/unittest mock start-and-stop}@anchor{3354}
@subsubsection patch methods: start and stop


All the patchers have @code{start()} and @code{stop()} methods. These make it simpler to do
patching in @code{setUp} methods or where you want to do multiple patches without
nesting decorators or with statements.

To use them call @ref{782,,patch()}, @ref{eee,,patch.object()} or @ref{f5f,,patch.dict()} as
normal and keep a reference to the returned @code{patcher} object. You can then
call @code{start()} to put the patch in place and @code{stop()} to undo it.

If you are using @ref{782,,patch()} to create a mock for you then it will be returned by
the call to @code{patcher.start}.

@example
>>> patcher = patch('package.module.ClassName')
>>> from package import module
>>> original = module.ClassName
>>> new_mock = patcher.start()
>>> assert module.ClassName is not original
>>> assert module.ClassName is new_mock
>>> patcher.stop()
>>> assert module.ClassName is original
>>> assert module.ClassName is not new_mock
@end example

A typical use case for this might be for doing multiple patches in the @code{setUp}
method of a @code{TestCase}:

@example
>>> class MyTest(unittest.TestCase):
...     def setUp(self):
...         self.patcher1 = patch('package.module.Class1')
...         self.patcher2 = patch('package.module.Class2')
...         self.MockClass1 = self.patcher1.start()
...         self.MockClass2 = self.patcher2.start()
...
...     def tearDown(self):
...         self.patcher1.stop()
...         self.patcher2.stop()
...
...     def test_something(self):
...         assert package.module.Class1 is self.MockClass1
...         assert package.module.Class2 is self.MockClass2
...
>>> MyTest('test_something').run()
@end example

@cartouche
@quotation 警告 
If you use this technique you must ensure that the patching is "undone" by
calling @code{stop}. This can be fiddlier than you might think, because if an
exception is raised in the @code{setUp} then @code{tearDown} is not called.
@ref{2a2,,unittest.TestCase.addCleanup()} makes this easier:

@example
>>> class MyTest(unittest.TestCase):
...     def setUp(self):
...         patcher = patch('package.module.Class')
...         self.MockClass = patcher.start()
...         self.addCleanup(patcher.stop)
...
...     def test_something(self):
...         assert package.module.Class is self.MockClass
...
@end example

As an added bonus you no longer need to keep a reference to the @code{patcher}
object.
@end quotation
@end cartouche

It is also possible to stop all patches which have been started by using
@ref{3355,,patch.stopall()}.

@geindex patch.stopall() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock patch stopall}@anchor{3355}
@deffn {函数} patch.stopall ()

Stop all active patches. Only stops patches started with @code{start}.
@end deffn

@node patch builtins,TEST_PREFIX,patch methods start and stop,The patchers
@anchor{library/unittest mock id4}@anchor{3356}@anchor{library/unittest mock patch-builtins}@anchor{3357}
@subsubsection patch builtins


You can patch any builtins within a module. The following example patches
builtin @ref{13be,,ord()}:

@example
>>> @@patch('__main__.ord')
... def test(mock_ord):
...     mock_ord.return_value = 101
...     print(ord('c'))
...
>>> test()
101
@end example

@node TEST_PREFIX,Nesting Patch Decorators,patch builtins,The patchers
@anchor{library/unittest mock id5}@anchor{3358}@anchor{library/unittest mock test-prefix}@anchor{3350}
@subsubsection TEST_PREFIX


All of the patchers can be used as class decorators. When used in this way
they wrap every test method on the class. The patchers recognise methods that
start with @code{'test'} as being test methods. This is the same way that the
@ref{77c,,unittest.TestLoader} finds test methods by default.

It is possible that you want to use a different prefix for your tests. You can
inform the patchers of the different prefix by setting @code{patch.TEST_PREFIX}:

@example
>>> patch.TEST_PREFIX = 'foo'
>>> value = 3
>>>
>>> @@patch('__main__.value', 'not three')
... class Thing:
...     def foo_one(self):
...         print(value)
...     def foo_two(self):
...         print(value)
...
>>>
>>> Thing().foo_one()
not three
>>> Thing().foo_two()
not three
>>> value
3
@end example

@node Nesting Patch Decorators,Where to patch,TEST_PREFIX,The patchers
@anchor{library/unittest mock nesting-patch-decorators}@anchor{3359}
@subsubsection Nesting Patch Decorators


If you want to perform multiple patches then you can simply stack up the
decorators.

You can stack up multiple patch decorators using this pattern:

@example
>>> @@patch.object(SomeClass, 'class_method')
... @@patch.object(SomeClass, 'static_method')
... def test(mock1, mock2):
...     assert SomeClass.static_method is mock1
...     assert SomeClass.class_method is mock2
...     SomeClass.static_method('foo')
...     SomeClass.class_method('bar')
...     return mock1, mock2
...
>>> mock1, mock2 = test()
>>> mock1.assert_called_once_with('foo')
>>> mock2.assert_called_once_with('bar')
@end example

Note that the decorators are applied from the bottom upwards. This is the
standard way that Python applies decorators. The order of the created mocks
passed into your test function matches this order.

@node Where to patch,Patching Descriptors and Proxy Objects,Nesting Patch Decorators,The patchers
@anchor{library/unittest mock id6}@anchor{334d}@anchor{library/unittest mock where-to-patch}@anchor{3322}
@subsubsection Where to patch


@ref{782,,patch()} works by (temporarily) changing the object that a @emph{name} points to with
another one. There can be many names pointing to any individual object, so
for patching to work you must ensure that you patch the name used by the system
under test.

The basic principle is that you patch where an object is @emph{looked up}, which
is not necessarily the same place as where it is defined. A couple of
examples will help to clarify this.

Imagine we have a project that we want to test with the following structure:

@example
a.py
    -> Defines SomeClass

b.py
    -> from a import SomeClass
    -> some_function instantiates SomeClass
@end example

Now we want to test @code{some_function} but we want to mock out @code{SomeClass} using
@ref{782,,patch()}. The problem is that when we import module b, which we will have to
do then it imports @code{SomeClass} from module a. If we use @ref{782,,patch()} to mock out
@code{a.SomeClass} then it will have no effect on our test; module b already has a
reference to the @emph{real} @code{SomeClass} and it looks like our patching had no
effect.

The key is to patch out @code{SomeClass} where it is used (or where it is looked up).
In this case @code{some_function} will actually look up @code{SomeClass} in module b,
where we have imported it. The patching should look like:

@example
@@patch('b.SomeClass')
@end example

However, consider the alternative scenario where instead of @code{from a import
SomeClass} module b does @code{import a} and @code{some_function} uses @code{a.SomeClass}. Both
of these import forms are common. In this case the class we want to patch is
being looked up in the module and so we have to patch @code{a.SomeClass} instead:

@example
@@patch('a.SomeClass')
@end example

@node Patching Descriptors and Proxy Objects,,Where to patch,The patchers
@anchor{library/unittest mock patching-descriptors-and-proxy-objects}@anchor{335a}
@subsubsection Patching Descriptors and Proxy Objects


Both @ref{334c,,patch} and @ref{334e,,patch.object} correctly patch and restore descriptors: class
methods, static methods and properties. You should patch these on the @emph{class}
rather than an instance. They also work with @emph{some} objects
that proxy attribute access, like the django settings object@footnote{http://www.voidspace.org.uk/python/weblog/arch_d7_2010_12_04.shtml#e1198}.

@node MagicMock and magic method support,Helpers,The patchers,unittest mock --- 模拟对象库
@anchor{library/unittest mock magicmock-and-magic-method-support}@anchor{335b}
@subsubsection MagicMock and magic method support


@menu
* Mocking Magic Methods:: 
* Magic Mock:: 

@end menu

@node Mocking Magic Methods,Magic Mock,,MagicMock and magic method support
@anchor{library/unittest mock magic-methods}@anchor{3323}@anchor{library/unittest mock mocking-magic-methods}@anchor{335c}
@subsubsection Mocking Magic Methods


@ref{249,,Mock} supports mocking the Python protocol methods, also known as
"magic methods". This allows mock objects to replace containers or other
objects that implement Python protocols.

Because magic methods are looked up differently from normal methods @footnote{@w{(2)} 
Magic methods @emph{should} be looked up on the class rather than the
instance. Different versions of Python are inconsistent about applying this
rule. The supported protocol methods should work with all supported versions
of Python.
}, this
support has been specially implemented. This means that only specific magic
methods are supported. The supported list includes @emph{almost} all of them. If
there are any missing that you need please let us know.

You mock magic methods by setting the method you are interested in to a function
or a mock instance. If you are using a function then it @emph{must} take @code{self} as
the first argument @footnote{@w{(3)} 
The function is basically hooked up to the class, but each @code{Mock}
instance is kept isolated from the others.
}.

@example
>>> def __str__(self):
...     return 'fooble'
...
>>> mock = Mock()
>>> mock.__str__ = __str__
>>> str(mock)
'fooble'
@end example

@example
>>> mock = Mock()
>>> mock.__str__ = Mock()
>>> mock.__str__.return_value = 'fooble'
>>> str(mock)
'fooble'
@end example

@example
>>> mock = Mock()
>>> mock.__iter__ = Mock(return_value=iter([]))
>>> list(mock)
[]
@end example

One use case for this is for mocking objects used as context managers in a
@ref{6e3,,with} statement:

@example
>>> mock = Mock()
>>> mock.__enter__ = Mock(return_value='foo')
>>> mock.__exit__ = Mock(return_value=False)
>>> with mock as m:
...     assert m == 'foo'
...
>>> mock.__enter__.assert_called_with()
>>> mock.__exit__.assert_called_with(None, None, None)
@end example

Calls to magic methods do not appear in @ref{3332,,method_calls}, but they
are recorded in @ref{332f,,mock_calls}.

@cartouche
@quotation 注解 
If you use the @emph{spec} keyword argument to create a mock then attempting to
set a magic method that isn't in the spec will raise an @ref{393,,AttributeError}.
@end quotation
@end cartouche

The full list of supported magic methods is:


@itemize *

@item 
@code{__hash__}, @code{__sizeof__}, @code{__repr__} and @code{__str__}

@item 
@code{__dir__}, @code{__format__} and @code{__subclasses__}

@item 
@code{__round__}, @code{__floor__}, @code{__trunc__} and @code{__ceil__}

@item 
Comparisons: @code{__lt__}, @code{__gt__}, @code{__le__}, @code{__ge__},
@code{__eq__} and @code{__ne__}

@item 
Container methods: @code{__getitem__}, @code{__setitem__}, @code{__delitem__},
@code{__contains__}, @code{__len__}, @code{__iter__}, @code{__reversed__}
and @code{__missing__}

@item 
Context manager: @code{__enter__}, @code{__exit__}, @code{__aenter__} and @code{__aexit__}

@item 
Unary numeric methods: @code{__neg__}, @code{__pos__} and @code{__invert__}

@item 
The numeric methods (including right hand and in-place variants):
@code{__add__}, @code{__sub__}, @code{__mul__}, @code{__matmul__}, @code{__div__}, @code{__truediv__},
@code{__floordiv__}, @code{__mod__}, @code{__divmod__}, @code{__lshift__},
@code{__rshift__}, @code{__and__}, @code{__xor__}, @code{__or__}, and @code{__pow__}

@item 
Numeric conversion methods: @code{__complex__}, @code{__int__}, @code{__float__}
and @code{__index__}

@item 
Descriptor methods: @code{__get__}, @code{__set__} and @code{__delete__}

@item 
Pickling: @code{__reduce__}, @code{__reduce_ex__}, @code{__getinitargs__},
@code{__getnewargs__}, @code{__getstate__} and @code{__setstate__}

@item 
File system path representation: @code{__fspath__}

@item 
Asynchronous iteration methods: @code{__aiter__} and @code{__anext__}
@end itemize


在 3.8 版更改: Added support for @ref{4e6,,os.PathLike.__fspath__()}.



在 3.8 版更改: Added support for @code{__aenter__}, @code{__aexit__}, @code{__aiter__} and @code{__anext__}.


The following methods exist but are @emph{not} supported as they are either in use
by mock, can't be set dynamically, or can cause problems:


@itemize *

@item 
@code{__getattr__}, @code{__setattr__}, @code{__init__} and @code{__new__}

@item 
@code{__prepare__}, @code{__instancecheck__}, @code{__subclasscheck__}, @code{__del__}
@end itemize

@node Magic Mock,,Mocking Magic Methods,MagicMock and magic method support
@anchor{library/unittest mock magic-mock}@anchor{335d}
@subsubsection Magic Mock


There are two @code{MagicMock} variants: @ref{77f,,MagicMock} and @ref{3327,,NonCallableMagicMock}.

@geindex MagicMock (unittest.mock 中的类)
@anchor{library/unittest mock unittest mock MagicMock}@anchor{77f}
@deffn {类} unittest.mock.MagicMock (*args, **kw)

@code{MagicMock} is a subclass of @ref{249,,Mock} with default implementations
of most of the magic methods. You can use @code{MagicMock} without having to
configure the magic methods yourself.

The constructor parameters have the same meaning as for @ref{249,,Mock}.

If you use the @emph{spec} or @emph{spec_set} arguments then @emph{only} magic methods
that exist in the spec will be created.
@end deffn

@geindex NonCallableMagicMock (unittest.mock 中的类)
@anchor{library/unittest mock unittest mock NonCallableMagicMock}@anchor{3327}
@deffn {类} unittest.mock.NonCallableMagicMock (*args, **kw)

A non-callable version of @ref{77f,,MagicMock}.

The constructor parameters have the same meaning as for
@ref{77f,,MagicMock}, with the exception of @emph{return_value} and
@emph{side_effect} which have no meaning on a non-callable mock.
@end deffn

The magic methods are setup with @ref{77f,,MagicMock} objects, so you can configure them
and use them in the usual way:

@example
>>> mock = MagicMock()
>>> mock[3] = 'fish'
>>> mock.__setitem__.assert_called_with(3, 'fish')
>>> mock.__getitem__.return_value = 'result'
>>> mock[2]
'result'
@end example

By default many of the protocol methods are required to return objects of a
specific type. These methods are preconfigured with a default return value, so
that they can be used without you having to do anything if you aren't interested
in the return value. You can still @emph{set} the return value manually if you want
to change the default.

Methods and their defaults:


@itemize *

@item 
@code{__lt__}: @code{NotImplemented}

@item 
@code{__gt__}: @code{NotImplemented}

@item 
@code{__le__}: @code{NotImplemented}

@item 
@code{__ge__}: @code{NotImplemented}

@item 
@code{__int__}: @code{1}

@item 
@code{__contains__}: @code{False}

@item 
@code{__len__}: @code{0}

@item 
@code{__iter__}: @code{iter([])}

@item 
@code{__exit__}: @code{False}

@item 
@code{__aexit__}: @code{False}

@item 
@code{__complex__}: @code{1j}

@item 
@code{__float__}: @code{1.0}

@item 
@code{__bool__}: @code{True}

@item 
@code{__index__}: @code{1}

@item 
@code{__hash__}: default hash for the mock

@item 
@code{__str__}: default str for the mock

@item 
@code{__sizeof__}: default sizeof for the mock
@end itemize

例如:

@example
>>> mock = MagicMock()
>>> int(mock)
1
>>> len(mock)
0
>>> list(mock)
[]
>>> object() in mock
False
@end example

The two equality methods, @ref{338,,__eq__()} and @ref{e4f,,__ne__()}, are special.
They do the default equality comparison on identity, using the
@ref{3328,,side_effect} attribute, unless you change their return value to
return something else:

@example
>>> MagicMock() == 3
False
>>> MagicMock() != 3
True
>>> mock = MagicMock()
>>> mock.__eq__.return_value = True
>>> mock == 3
True
@end example

The return value of @code{MagicMock.__iter__()} can be any iterable object and isn't
required to be an iterator:

@example
>>> mock = MagicMock()
>>> mock.__iter__.return_value = ['a', 'b', 'c']
>>> list(mock)
['a', 'b', 'c']
>>> list(mock)
['a', 'b', 'c']
@end example

If the return value @emph{is} an iterator, then iterating over it once will consume
it and subsequent iterations will result in an empty list:

@example
>>> mock.__iter__.return_value = iter(['a', 'b', 'c'])
>>> list(mock)
['a', 'b', 'c']
>>> list(mock)
[]
@end example

@code{MagicMock} has all of the supported magic methods configured except for some
of the obscure and obsolete ones. You can still set these up if you want.

Magic methods that are supported but not setup by default in @code{MagicMock} are:


@itemize *

@item 
@code{__subclasses__}

@item 
@code{__dir__}

@item 
@code{__format__}

@item 
@code{__get__}, @code{__set__} and @code{__delete__}

@item 
@code{__reversed__} and @code{__missing__}

@item 
@code{__reduce__}, @code{__reduce_ex__}, @code{__getinitargs__}, @code{__getnewargs__},
@code{__getstate__} and @code{__setstate__}

@item 
@code{__getformat__} and @code{__setformat__}
@end itemize

@node Helpers,,MagicMock and magic method support,unittest mock --- 模拟对象库
@anchor{library/unittest mock helpers}@anchor{335e}
@subsubsection Helpers


@menu
* sentinel:: 
* DEFAULT:: 
* call:: 
* create_autospec:: 
* ANY:: 
* FILTER_DIR:: 
* mock_open:: 
* Autospeccing:: 
* Sealing mocks:: 

@end menu

@node sentinel,DEFAULT,,Helpers
@anchor{library/unittest mock sentinel}@anchor{335f}
@subsubsection sentinel


@geindex sentinel() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock sentinel}@anchor{402}
@deffn {数据} unittest.mock.sentinel

The @code{sentinel} object provides a convenient way of providing unique
objects for your tests.

Attributes are created on demand when you access them by name. Accessing
the same attribute will always return the same object. The objects
returned have a sensible repr so that test failure messages are readable.


在 3.7 版更改: The @code{sentinel} attributes now preserve their identity when they are
@ref{26,,copied} or @ref{ca,,pickled}.

@end deffn

Sometimes when testing you need to test that a specific object is passed as an
argument to another method, or returned. It can be common to create named
sentinel objects to test this. @ref{402,,sentinel} provides a convenient way of
creating and testing the identity of objects like this.

In this example we monkey patch @code{method} to return @code{sentinel.some_object}:

@example
>>> real = ProductionClass()
>>> real.method = Mock(name="method")
>>> real.method.return_value = sentinel.some_object
>>> result = real.method()
>>> assert result is sentinel.some_object
>>> sentinel.some_object
sentinel.some_object
@end example

@node DEFAULT,call,sentinel,Helpers
@anchor{library/unittest mock default}@anchor{3360}
@subsubsection DEFAULT


@geindex DEFAULT() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock DEFAULT}@anchor{3329}
@deffn {数据} unittest.mock.DEFAULT

The @ref{3329,,DEFAULT} object is a pre-created sentinel (actually
@code{sentinel.DEFAULT}). It can be used by @ref{3328,,side_effect}
functions to indicate that the normal return value should be used.
@end deffn

@node call,create_autospec,DEFAULT,Helpers
@anchor{library/unittest mock call}@anchor{3361}
@subsubsection call


@geindex call() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock call}@anchor{f09}
@deffn {函数} unittest.mock.call (*args, **kwargs)

@ref{f09,,call()} is a helper object for making simpler assertions, for comparing with
@ref{eb3,,call_args}, @ref{3338,,call_args_list},
@ref{332f,,mock_calls} and @ref{3332,,method_calls}. @ref{f09,,call()} can also be
used with @ref{332e,,assert_has_calls()}.

@example
>>> m = MagicMock(return_value=None)
>>> m(1, 2, a='foo', b='bar')
>>> m()
>>> m.call_args_list == [call(1, 2, a='foo', b='bar'), call()]
True
@end example
@end deffn

@geindex call_list() (unittest.mock.call 方法)
@anchor{library/unittest mock unittest mock call call_list}@anchor{3362}
@deffn {方法} call.call_list ()

For a call object that represents multiple calls, @ref{3362,,call_list()}
returns a list of all the intermediate calls as well as the
final call.
@end deffn

@code{call_list} is particularly useful for making assertions on "chained calls". A
chained call is multiple calls on a single line of code. This results in
multiple entries in @ref{332f,,mock_calls} on a mock. Manually constructing
the sequence of calls can be tedious.

@ref{3362,,call_list()} can construct the sequence of calls from the same
chained call:

@example
>>> m = MagicMock()
>>> m(1).method(arg='foo').other('bar')(2.0)
<MagicMock name='mock().method().other()()' id='...'>
>>> kall = call(1).method(arg='foo').other('bar')(2.0)
>>> kall.call_list()
[call(1),
 call().method(arg='foo'),
 call().method().other('bar'),
 call().method().other()(2.0)]
>>> m.mock_calls == kall.call_list()
True
@end example
@anchor{library/unittest mock calls-as-tuples}@anchor{3339}
A @code{call} object is either a tuple of (positional args, keyword args) or
(name, positional args, keyword args) depending on how it was constructed. When
you construct them yourself this isn't particularly interesting, but the @code{call}
objects that are in the @ref{eb3,,Mock.call_args}, @ref{3338,,Mock.call_args_list} and
@ref{332f,,Mock.mock_calls} attributes can be introspected to get at the individual
arguments they contain.

The @code{call} objects in @ref{eb3,,Mock.call_args} and @ref{3338,,Mock.call_args_list}
are two-tuples of (positional args, keyword args) whereas the @code{call} objects
in @ref{332f,,Mock.mock_calls}, along with ones you construct yourself, are
three-tuples of (name, positional args, keyword args).

You can use their "tupleness" to pull out the individual arguments for more
complex introspection and assertions. The positional arguments are a tuple
(an empty tuple if there are no positional arguments) and the keyword
arguments are a dictionary:

@example
>>> m = MagicMock(return_value=None)
>>> m(1, 2, 3, arg='one', arg2='two')
>>> kall = m.call_args
>>> kall.args
(1, 2, 3)
>>> kall.kwargs
@{'arg': 'one', 'arg2': 'two'@}
>>> kall.args is kall[0]
True
>>> kall.kwargs is kall[1]
True
@end example

@example
>>> m = MagicMock()
>>> m.foo(4, 5, 6, arg='two', arg2='three')
<MagicMock name='mock.foo()' id='...'>
>>> kall = m.mock_calls[0]
>>> name, args, kwargs = kall
>>> name
'foo'
>>> args
(4, 5, 6)
>>> kwargs
@{'arg': 'two', 'arg2': 'three'@}
>>> name is m.mock_calls[0][0]
True
@end example

@node create_autospec,ANY,call,Helpers
@anchor{library/unittest mock create-autospec}@anchor{3363}
@subsubsection create_autospec


@geindex create_autospec() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock create_autospec}@anchor{ed8}
@deffn {函数} unittest.mock.create_autospec (spec, spec_set=False, instance=False, **kwargs)

Create a mock object using another object as a spec. Attributes on the
mock will use the corresponding attribute on the @emph{spec} object as their
spec.

Functions or methods being mocked will have their arguments checked to
ensure that they are called with the correct signature.

If @emph{spec_set} is @code{True} then attempting to set attributes that don't exist
on the spec object will raise an @ref{393,,AttributeError}.

If a class is used as a spec then the return value of the mock (the
instance of the class) will have the same spec. You can use a class as the
spec for an instance object by passing @code{instance=True}. The returned mock
will only be callable if instances of the mock are callable.

@ref{ed8,,create_autospec()} also takes arbitrary keyword arguments that are passed to
the constructor of the created mock.
@end deffn

See @ref{3324,,Autospeccing} for examples of how to use auto-speccing with
@ref{ed8,,create_autospec()} and the @emph{autospec} argument to @ref{782,,patch()}.


在 3.8 版更改: @ref{ed8,,create_autospec()} now returns an @ref{248,,AsyncMock} if the target is
an async function.


@node ANY,FILTER_DIR,create_autospec,Helpers
@anchor{library/unittest mock any}@anchor{3364}
@subsubsection ANY


@geindex ANY() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock ANY}@anchor{3365}
@deffn {数据} unittest.mock.ANY
@end deffn

Sometimes you may need to make assertions about @emph{some} of the arguments in a
call to mock, but either not care about some of the arguments or want to pull
them individually out of @ref{eb3,,call_args} and make more complex
assertions on them.

To ignore certain arguments you can pass in objects that compare equal to
@emph{everything}. Calls to @ref{f90,,assert_called_with()} and
@ref{332c,,assert_called_once_with()} will then succeed no matter what was
passed in.

@example
>>> mock = Mock(return_value=None)
>>> mock('foo', bar=object())
>>> mock.assert_called_once_with('foo', bar=ANY)
@end example

@ref{3365,,ANY} can also be used in comparisons with call lists like
@ref{332f,,mock_calls}:

@example
>>> m = MagicMock(return_value=None)
>>> m(1)
>>> m(1, 2)
>>> m(object())
>>> m.mock_calls == [call(1), call(1, 2), ANY]
True
@end example

@node FILTER_DIR,mock_open,ANY,Helpers
@anchor{library/unittest mock filter-dir}@anchor{3366}
@subsubsection FILTER_DIR


@geindex FILTER_DIR() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock FILTER_DIR}@anchor{3334}
@deffn {数据} unittest.mock.FILTER_DIR
@end deffn

@ref{3334,,FILTER_DIR} is a module level variable that controls the way mock objects
respond to @ref{d2c,,dir()} (only for Python 2.6 or more recent). The default is @code{True},
which uses the filtering described below, to only show useful members. If you
dislike this filtering, or need to switch it off for diagnostic purposes, then
set @code{mock.FILTER_DIR = False}.

With filtering on, @code{dir(some_mock)} shows only useful attributes and will
include any dynamically created attributes that wouldn't normally be shown.
If the mock was created with a @emph{spec} (or @emph{autospec} of course) then all the
attributes from the original are shown, even if they haven't been accessed
yet:

@example
>>> dir(Mock())
['assert_any_call',
 'assert_called',
 'assert_called_once',
 'assert_called_once_with',
 'assert_called_with',
 'assert_has_calls',
 'assert_not_called',
 'attach_mock',
 ...
>>> from urllib import request
>>> dir(Mock(spec=request))
['AbstractBasicAuthHandler',
 'AbstractDigestAuthHandler',
 'AbstractHTTPHandler',
 'BaseHandler',
 ...
@end example

Many of the not-very-useful (private to @ref{249,,Mock} rather than the thing being
mocked) underscore and double underscore prefixed attributes have been
filtered from the result of calling @ref{d2c,,dir()} on a @ref{249,,Mock}. If you dislike this
behaviour you can switch it off by setting the module level switch
@ref{3334,,FILTER_DIR}:

@example
>>> from unittest import mock
>>> mock.FILTER_DIR = False
>>> dir(mock.Mock())
['_NonCallableMock__get_return_value',
 '_NonCallableMock__get_side_effect',
 '_NonCallableMock__return_value_doc',
 '_NonCallableMock__set_return_value',
 '_NonCallableMock__set_side_effect',
 '__call__',
 '__class__',
 ...
@end example

Alternatively you can just use @code{vars(my_mock)} (instance members) and
@code{dir(type(my_mock))} (type members) to bypass the filtering irrespective of
@code{mock.FILTER_DIR}.

@node mock_open,Autospeccing,FILTER_DIR,Helpers
@anchor{library/unittest mock mock-open}@anchor{3367}
@subsubsection mock_open


@geindex mock_open() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock mock_open}@anchor{f57}
@deffn {函数} unittest.mock.mock_open (mock=None, read_data=None)

A helper function to create a mock to replace the use of @ref{4ea,,open()}. It works
for @ref{4ea,,open()} called directly or used as a context manager.

The @emph{mock} argument is the mock object to configure. If @code{None} (the
default) then a @ref{77f,,MagicMock} will be created for you, with the API limited
to methods or attributes available on standard file handles.

@emph{read_data} is a string for the @code{read()},
@ref{169c,,readline()}, and @ref{1725,,readlines()} methods
of the file handle to return.  Calls to those methods will take data from
@emph{read_data} until it is depleted.  The mock of these methods is pretty
simplistic: every time the @emph{mock} is called, the @emph{read_data} is rewound to
the start.  If you need more control over the data that you are feeding to
the tested code you will need to customize this mock for yourself.  When that
is insufficient, one of the in-memory filesystem packages on PyPI@footnote{https://pypi.org} can offer a realistic filesystem for testing.


在 3.4 版更改: Added @ref{169c,,readline()} and @ref{1725,,readlines()} support.
The mock of @code{read()} changed to consume @emph{read_data} rather
than returning it on each call.



在 3.5 版更改: @emph{read_data} is now reset on each call to the @emph{mock}.



在 3.8 版更改: Added @ref{509,,__iter__()} to implementation so that iteration (such as in for
loops) correctly consumes @emph{read_data}.

@end deffn

Using @ref{4ea,,open()} as a context manager is a great way to ensure your file handles
are closed properly and is becoming common:

@example
with open('/some/path', 'w') as f:
    f.write('something')
@end example

The issue is that even if you mock out the call to @ref{4ea,,open()} it is the
@emph{returned object} that is used as a context manager (and has @ref{c8e,,__enter__()} and
@ref{c8f,,__exit__()} called).

Mocking context managers with a @ref{77f,,MagicMock} is common enough and fiddly
enough that a helper function is useful.

@example
>>> m = mock_open()
>>> with patch('__main__.open', m):
...     with open('foo', 'w') as h:
...         h.write('some stuff')
...
>>> m.mock_calls
[call('foo', 'w'),
 call().__enter__(),
 call().write('some stuff'),
 call().__exit__(None, None, None)]
>>> m.assert_called_once_with('foo', 'w')
>>> handle = m()
>>> handle.write.assert_called_once_with('some stuff')
@end example

And for reading files:

@example
>>> with patch('__main__.open', mock_open(read_data='bibble')) as m:
...     with open('foo') as h:
...         result = h.read()
...
>>> m.assert_called_once_with('foo')
>>> assert result == 'bibble'
@end example

@node Autospeccing,Sealing mocks,mock_open,Helpers
@anchor{library/unittest mock auto-speccing}@anchor{3324}@anchor{library/unittest mock autospeccing}@anchor{3368}
@subsubsection Autospeccing


Autospeccing is based on the existing @code{spec} feature of mock. It limits the
api of mocks to the api of an original object (the spec), but it is recursive
(implemented lazily) so that attributes of mocks only have the same api as
the attributes of the spec. In addition mocked functions / methods have the
same call signature as the original so they raise a @ref{192,,TypeError} if they are
called incorrectly.

Before I explain how auto-speccing works, here's why it is needed.

@ref{249,,Mock} is a very powerful and flexible object, but it suffers from two flaws
when used to mock out objects from a system under test. One of these flaws is
specific to the @ref{249,,Mock} api and the other is a more general problem with using
mock objects.

First the problem specific to @ref{249,,Mock}. @ref{249,,Mock} has two assert methods that are
extremely handy: @ref{f90,,assert_called_with()} and
@ref{332c,,assert_called_once_with()}.

@example
>>> mock = Mock(name='Thing', return_value=None)
>>> mock(1, 2, 3)
>>> mock.assert_called_once_with(1, 2, 3)
>>> mock(1, 2, 3)
>>> mock.assert_called_once_with(1, 2, 3)
Traceback (most recent call last):
 ...
AssertionError: Expected 'mock' to be called once. Called 2 times.
@end example

Because mocks auto-create attributes on demand, and allow you to call them
with arbitrary arguments, if you misspell one of these assert methods then
your assertion is gone:

@example
>>> mock = Mock(name='Thing', return_value=None)
>>> mock(1, 2, 3)
>>> mock.assret_called_once_with(4, 5, 6)
@end example

Your tests can pass silently and incorrectly because of the typo.

The second issue is more general to mocking. If you refactor some of your
code, rename members and so on, any tests for code that is still using the
@emph{old api} but uses mocks instead of the real objects will still pass. This
means your tests can all pass even though your code is broken.

Note that this is another reason why you need integration tests as well as
unit tests. Testing everything in isolation is all fine and dandy, but if you
don't test how your units are "wired together" there is still lots of room
for bugs that tests might have caught.

@code{mock} already provides a feature to help with this, called speccing. If you
use a class or instance as the @code{spec} for a mock then you can only access
attributes on the mock that exist on the real class:

@example
>>> from urllib import request
>>> mock = Mock(spec=request.Request)
>>> mock.assret_called_with
Traceback (most recent call last):
 ...
AttributeError: Mock object has no attribute 'assret_called_with'
@end example

The spec only applies to the mock itself, so we still have the same issue
with any methods on the mock:

@example
>>> mock.has_data()
<mock.Mock object at 0x...>
>>> mock.has_data.assret_called_with()
@end example

Auto-speccing solves this problem. You can either pass @code{autospec=True} to
@ref{782,,patch()} / @ref{eee,,patch.object()} or use the @ref{ed8,,create_autospec()} function to create a
mock with a spec. If you use the @code{autospec=True} argument to @ref{782,,patch()} then the
object that is being replaced will be used as the spec object. Because the
speccing is done "lazily" (the spec is created as attributes on the mock are
accessed) you can use it with very complex or deeply nested objects (like
modules that import modules that import modules) without a big performance
hit.

Here's an example of it in use:

@example
>>> from urllib import request
>>> patcher = patch('__main__.request', autospec=True)
>>> mock_request = patcher.start()
>>> request is mock_request
True
>>> mock_request.Request
<MagicMock name='request.Request' spec='Request' id='...'>
@end example

You can see that @code{request.Request} has a spec. @code{request.Request} takes two
arguments in the constructor (one of which is @emph{self}). Here's what happens if
we try to call it incorrectly:

@example
>>> req = request.Request()
Traceback (most recent call last):
 ...
TypeError: <lambda>() takes at least 2 arguments (1 given)
@end example

The spec also applies to instantiated classes (i.e. the return value of
specced mocks):

@example
>>> req = request.Request('foo')
>>> req
<NonCallableMagicMock name='request.Request()' spec='Request' id='...'>
@end example

@code{Request} objects are not callable, so the return value of instantiating our
mocked out @code{request.Request} is a non-callable mock. With the spec in place
any typos in our asserts will raise the correct error:

@example
>>> req.add_header('spam', 'eggs')
<MagicMock name='request.Request().add_header()' id='...'>
>>> req.add_header.assret_called_with
Traceback (most recent call last):
 ...
AttributeError: Mock object has no attribute 'assret_called_with'
>>> req.add_header.assert_called_with('spam', 'eggs')
@end example

In many cases you will just be able to add @code{autospec=True} to your existing
@ref{782,,patch()} calls and then be protected against bugs due to typos and api
changes.

As well as using @emph{autospec} through @ref{782,,patch()} there is a
@ref{ed8,,create_autospec()} for creating autospecced mocks directly:

@example
>>> from urllib import request
>>> mock_request = create_autospec(request)
>>> mock_request.Request('foo', 'bar')
<NonCallableMagicMock name='mock.Request()' spec='Request' id='...'>
@end example

This isn't without caveats and limitations however, which is why it is not
the default behaviour. In order to know what attributes are available on the
spec object, autospec has to introspect (access attributes) the spec. As you
traverse attributes on the mock a corresponding traversal of the original
object is happening under the hood. If any of your specced objects have
properties or descriptors that can trigger code execution then you may not be
able to use autospec. On the other hand it is much better to design your
objects so that introspection is safe @footnote{@w{(4)} 
This only applies to classes or already instantiated objects. Calling
a mocked class to create a mock instance @emph{does not} create a real instance.
It is only attribute lookups - along with calls to @ref{d2c,,dir()} - that are done.
}.

A more serious problem is that it is common for instance attributes to be
created in the @ref{d57,,__init__()} method and not to exist on the class at all.
@emph{autospec} can't know about any dynamically created attributes and restricts
the api to visible attributes.

@example
>>> class Something:
...   def __init__(self):
...     self.a = 33
...
>>> with patch('__main__.Something', autospec=True):
...   thing = Something()
...   thing.a
...
Traceback (most recent call last):
  ...
AttributeError: Mock object has no attribute 'a'
@end example

There are a few different ways of resolving this problem. The easiest, but
not necessarily the least annoying, way is to simply set the required
attributes on the mock after creation. Just because @emph{autospec} doesn't allow
you to fetch attributes that don't exist on the spec it doesn't prevent you
setting them:

@example
>>> with patch('__main__.Something', autospec=True):
...   thing = Something()
...   thing.a = 33
...
@end example

There is a more aggressive version of both @emph{spec} and @emph{autospec} that @emph{does}
prevent you setting non-existent attributes. This is useful if you want to
ensure your code only @emph{sets} valid attributes too, but obviously it prevents
this particular scenario:

@example
>>> with patch('__main__.Something', autospec=True, spec_set=True):
...   thing = Something()
...   thing.a = 33
...
Traceback (most recent call last):
 ...
AttributeError: Mock object has no attribute 'a'
@end example

Probably the best way of solving the problem is to add class attributes as
default values for instance members initialised in @ref{d57,,__init__()}. Note that if
you are only setting default attributes in @ref{d57,,__init__()} then providing them via
class attributes (shared between instances of course) is faster too. e.g.

@example
class Something:
    a = 33
@end example

This brings up another issue. It is relatively common to provide a default
value of @code{None} for members that will later be an object of a different type.
@code{None} would be useless as a spec because it wouldn't let you access @emph{any}
attributes or methods on it. As @code{None} is @emph{never} going to be useful as a
spec, and probably indicates a member that will normally of some other type,
autospec doesn't use a spec for members that are set to @code{None}. These will
just be ordinary mocks (well - MagicMocks):

@example
>>> class Something:
...     member = None
...
>>> mock = create_autospec(Something)
>>> mock.member.foo.bar.baz()
<MagicMock name='mock.member.foo.bar.baz()' id='...'>
@end example

If modifying your production classes to add defaults isn't to your liking
then there are more options. One of these is simply to use an instance as the
spec rather than the class. The other is to create a subclass of the
production class and add the defaults to the subclass without affecting the
production class. Both of these require you to use an alternative object as
the spec. Thankfully @ref{782,,patch()} supports this - you can simply pass the
alternative object as the @emph{autospec} argument:

@example
>>> class Something:
...   def __init__(self):
...     self.a = 33
...
>>> class SomethingForTest(Something):
...   a = 33
...
>>> p = patch('__main__.Something', autospec=SomethingForTest)
>>> mock = p.start()
>>> mock.a
<NonCallableMagicMock name='Something.a' spec='int' id='...'>
@end example

@node Sealing mocks,,Autospeccing,Helpers
@anchor{library/unittest mock sealing-mocks}@anchor{3369}
@subsubsection Sealing mocks


@c from unittest.mock import seal

@geindex seal() (在 unittest.mock 模块中)
@anchor{library/unittest mock unittest mock seal}@anchor{403}
@deffn {函数} unittest.mock.seal (mock)

Seal will disable the automatic creation of mocks when accessing an attribute of
the mock being sealed or any of its attributes that are already mocks recursively.

If a mock instance with a name or a spec is assigned to an attribute
it won't be considered in the sealing chain. This allows one to prevent seal from
fixing part of the mock object.

@example
>>> mock = Mock()
>>> mock.submock.attribute1 = 2
>>> mock.not_submock = mock.Mock(name="sample_name")
>>> seal(mock)
>>> mock.new_attribute  # This will raise AttributeError.
>>> mock.submock.attribute2  # This will raise AttributeError.
>>> mock.not_submock.attribute2  # This won't raise.
@end example


3.7 新版功能.

@end deffn

@node unittest mock 上手指南,2to3 - 自动将 Python 2 代码转为 Python 3 代码,unittest mock --- 模拟对象库,开发工具
@anchor{library/unittest mock-examples doc}@anchor{336a}@anchor{library/unittest mock-examples unittest-mock-getting-started}@anchor{336b}
@subsection @code{unittest.mock} 上手指南



3.3 新版功能.

@anchor{library/unittest mock-examples getting-started}@anchor{336c}
@c import asyncio
@c import unittest
@c from unittest.mock import Mock, MagicMock, AsyncMock, patch, call, sentinel
@c 
@c class SomeClass:
@c     attribute = 'this is a doctest'
@c 
@c     @staticmethod
@c     def static_method():
@c         pass

@menu
* 使用 mock:: 
* Patch Decorators:: 
* Further Examples:: 

@end menu

@node 使用 mock,Patch Decorators,,unittest mock 上手指南
@anchor{library/unittest mock-examples using-mock}@anchor{336d}
@subsubsection 使用 mock


@menu
* 模拟方法调用:: 
* 对象上的方法调用的 mock:: 
* Mocking Classes:: 
* Naming your mocks:: 
* Tracking all Calls:: 
* Setting Return Values and Attributes:: 
* Raising exceptions with mocks:: 
* Side effect functions and iterables:: 
* Mocking asynchronous iterators:: 
* Mocking asynchronous context manager:: 
* Creating a Mock from an Existing Object:: 

@end menu

@node 模拟方法调用,对象上的方法调用的 mock,,使用 mock
@anchor{library/unittest mock-examples mock-patching-methods}@anchor{336e}
@subsubsection 模拟方法调用


使用 @ref{249,,Mock} 的常见场景：


@itemize *

@item 
模拟函数调用

@item 
记录“对象上的方法调用”
@end itemize

你可能需要替换一个对象上的方法，用于确认此方法被系统中的其他部分调用过，并且调用时使用了正确的参数。

@example
>>> real = SomeClass()
>>> real.method = MagicMock(name='method')
>>> real.method(3, 4, 5, key='value')
<MagicMock name='method()' id='...'>
@end example

使用了 mock（本例中的 @code{real.method}）之后，它有方法和属性可以让你针对它是被如何使用的下断言。

@cartouche
@quotation 注解 
在多数示例中，@ref{249,,Mock} 与 @ref{77f,,MagicMock} 两个类可以相互替换，而 @code{MagicMock} 是一个更适用的类，通常情况下，使用它就可以了。
@end quotation
@end cartouche

如果 mock 被调用，它的 @ref{3336,,called} 属性就会变成 @code{True}，更重要的是，我们可以使用 @ref{f90,,assert_called_with()} 或者 @ref{332c,,assert_called_once_with()} 方法来确认它在被调用时使用了正确的参数。

在如下的测试示例中，验证对于 @code{ProductionClass().method} 的调用会导致 @code{something} 的调用。

@example
>>> class ProductionClass:
...     def method(self):
...         self.something(1, 2, 3)
...     def something(self, a, b, c):
...         pass
...
>>> real = ProductionClass()
>>> real.something = MagicMock()
>>> real.method()
>>> real.something.assert_called_once_with(1, 2, 3)
@end example

@node 对象上的方法调用的 mock,Mocking Classes,模拟方法调用,使用 mock
@anchor{library/unittest mock-examples mock-for-method-calls-on-an-object}@anchor{336f}
@subsubsection 对象上的方法调用的 mock


In the last example we patched a method directly on an object to check that it
was called correctly. Another common use case is to pass an object into a
method (or some part of the system under test) and then check that it is used
in the correct way.

The simple @code{ProductionClass} below has a @code{closer} method. If it is called with
an object then it calls @code{close} on it.

@example
>>> class ProductionClass:
...     def closer(self, something):
...         something.close()
...
@end example

So to test it we need to pass in an object with a @code{close} method and check
that it was called correctly.

@example
>>> real = ProductionClass()
>>> mock = Mock()
>>> real.closer(mock)
>>> mock.close.assert_called_with()
@end example

We don't have to do any work to provide the 'close' method on our mock.
Accessing close creates it. So, if 'close' hasn't already been called then
accessing it in the test will create it, but @ref{f90,,assert_called_with()}
will raise a failure exception.

@node Mocking Classes,Naming your mocks,对象上的方法调用的 mock,使用 mock
@anchor{library/unittest mock-examples mocking-classes}@anchor{3370}
@subsubsection Mocking Classes


A common use case is to mock out classes instantiated by your code under test.
When you patch a class, then that class is replaced with a mock. Instances
are created by @emph{calling the class}. This means you access the "mock instance"
by looking at the return value of the mocked class.

In the example below we have a function @code{some_function} that instantiates @code{Foo}
and calls a method on it. The call to @ref{782,,patch()} replaces the class @code{Foo} with a
mock. The @code{Foo} instance is the result of calling the mock, so it is configured
by modifying the mock @ref{332a,,return_value}.

@example
>>> def some_function():
...     instance = module.Foo()
...     return instance.method()
...
>>> with patch('module.Foo') as mock:
...     instance = mock.return_value
...     instance.method.return_value = 'the result'
...     result = some_function()
...     assert result == 'the result'
@end example

@node Naming your mocks,Tracking all Calls,Mocking Classes,使用 mock
@anchor{library/unittest mock-examples naming-your-mocks}@anchor{3371}
@subsubsection Naming your mocks


It can be useful to give your mocks a name. The name is shown in the repr of
the mock and can be helpful when the mock appears in test failure messages. The
name is also propagated to attributes or methods of the mock:

@example
>>> mock = MagicMock(name='foo')
>>> mock
<MagicMock name='foo' id='...'>
>>> mock.method
<MagicMock name='foo.method' id='...'>
@end example

@node Tracking all Calls,Setting Return Values and Attributes,Naming your mocks,使用 mock
@anchor{library/unittest mock-examples tracking-all-calls}@anchor{3372}
@subsubsection Tracking all Calls


Often you want to track more than a single call to a method. The
@ref{332f,,mock_calls} attribute records all calls
to child attributes of the mock - and also to their children.

@example
>>> mock = MagicMock()
>>> mock.method()
<MagicMock name='mock.method()' id='...'>
>>> mock.attribute.method(10, x=53)
<MagicMock name='mock.attribute.method()' id='...'>
>>> mock.mock_calls
[call.method(), call.attribute.method(10, x=53)]
@end example

If you make an assertion about @code{mock_calls} and any unexpected methods
have been called, then the assertion will fail. This is useful because as well
as asserting that the calls you expected have been made, you are also checking
that they were made in the right order and with no additional calls:

You use the @ref{f09,,call} object to construct lists for comparing with
@code{mock_calls}:

@example
>>> expected = [call.method(), call.attribute.method(10, x=53)]
>>> mock.mock_calls == expected
True
@end example

However, parameters to calls that return mocks are not recorded, which means it is not
possible to track nested calls where the parameters used to create ancestors are important:

@example
>>> m = Mock()
>>> m.factory(important=True).deliver()
<Mock name='mock.factory().deliver()' id='...'>
>>> m.mock_calls[-1] == call.factory(important=False).deliver()
True
@end example

@node Setting Return Values and Attributes,Raising exceptions with mocks,Tracking all Calls,使用 mock
@anchor{library/unittest mock-examples setting-return-values-and-attributes}@anchor{3373}
@subsubsection Setting Return Values and Attributes


Setting the return values on a mock object is trivially easy:

@example
>>> mock = Mock()
>>> mock.return_value = 3
>>> mock()
3
@end example

Of course you can do the same for methods on the mock:

@example
>>> mock = Mock()
>>> mock.method.return_value = 3
>>> mock.method()
3
@end example

The return value can also be set in the constructor:

@example
>>> mock = Mock(return_value=3)
>>> mock()
3
@end example

If you need an attribute setting on your mock, just do it:

@example
>>> mock = Mock()
>>> mock.x = 3
>>> mock.x
3
@end example

Sometimes you want to mock up a more complex situation, like for example
@code{mock.connection.cursor().execute("SELECT 1")}. If we wanted this call to
return a list, then we have to configure the result of the nested call.

We can use @ref{f09,,call} to construct the set of calls in a "chained call" like
this for easy assertion afterwards:

@example
>>> mock = Mock()
>>> cursor = mock.connection.cursor.return_value
>>> cursor.execute.return_value = ['foo']
>>> mock.connection.cursor().execute("SELECT 1")
['foo']
>>> expected = call.connection.cursor().execute("SELECT 1").call_list()
>>> mock.mock_calls
[call.connection.cursor(), call.connection.cursor().execute('SELECT 1')]
>>> mock.mock_calls == expected
True
@end example

It is the call to @code{.call_list()} that turns our call object into a list of
calls representing the chained calls.

@node Raising exceptions with mocks,Side effect functions and iterables,Setting Return Values and Attributes,使用 mock
@anchor{library/unittest mock-examples raising-exceptions-with-mocks}@anchor{3374}
@subsubsection Raising exceptions with mocks


A useful attribute is @ref{3328,,side_effect}. If you set this to an
exception class or instance then the exception will be raised when the mock
is called.

@example
>>> mock = Mock(side_effect=Exception('Boom!'))
>>> mock()
Traceback (most recent call last):
  ...
Exception: Boom!
@end example

@node Side effect functions and iterables,Mocking asynchronous iterators,Raising exceptions with mocks,使用 mock
@anchor{library/unittest mock-examples side-effect-functions-and-iterables}@anchor{3375}
@subsubsection Side effect functions and iterables


@code{side_effect} can also be set to a function or an iterable. The use case for
@code{side_effect} as an iterable is where your mock is going to be called several
times, and you want each call to return a different value. When you set
@code{side_effect} to an iterable every call to the mock returns the next value
from the iterable:

@example
>>> mock = MagicMock(side_effect=[4, 5, 6])
>>> mock()
4
>>> mock()
5
>>> mock()
6
@end example

For more advanced use cases, like dynamically varying the return values
depending on what the mock is called with, @code{side_effect} can be a function.
The function will be called with the same arguments as the mock. Whatever the
function returns is what the call returns:

@example
>>> vals = @{(1, 2): 1, (2, 3): 2@}
>>> def side_effect(*args):
...     return vals[args]
...
>>> mock = MagicMock(side_effect=side_effect)
>>> mock(1, 2)
1
>>> mock(2, 3)
2
@end example

@node Mocking asynchronous iterators,Mocking asynchronous context manager,Side effect functions and iterables,使用 mock
@anchor{library/unittest mock-examples mocking-asynchronous-iterators}@anchor{3376}
@subsubsection Mocking asynchronous iterators


Since Python 3.8, @code{AsyncMock} and @code{MagicMock} have support to mock
@ref{640,,异步迭代器} through @code{__aiter__}. The @ref{332a,,return_value}
attribute of @code{__aiter__} can be used to set the return values to be used for
iteration.

@example
>>> mock = MagicMock()  # AsyncMock also works here
>>> mock.__aiter__.return_value = [1, 2, 3]
>>> async def main():
...     return [i async for i in mock]
...
>>> asyncio.run(main())
[1, 2, 3]
@end example

@node Mocking asynchronous context manager,Creating a Mock from an Existing Object,Mocking asynchronous iterators,使用 mock
@anchor{library/unittest mock-examples mocking-asynchronous-context-manager}@anchor{3377}
@subsubsection Mocking asynchronous context manager


Since Python 3.8, @code{AsyncMock} and @code{MagicMock} have support to mock
@ref{142e,,异步上下文管理器} through @code{__aenter__} and @code{__aexit__}.
By default, @code{__aenter__} and @code{__aexit__} are @code{AsyncMock} instances that
return an async function.

@example
>>> class AsyncContextManager:
...     async def __aenter__(self):
...         return self
...     async def __aexit__(self, exc_type, exc, tb):
...         pass
...
>>> mock_instance = MagicMock(AsyncContextManager())  # AsyncMock also works here
>>> async def main():
...     async with mock_instance as result:
...         pass
...
>>> asyncio.run(main())
>>> mock_instance.__aenter__.assert_awaited_once()
>>> mock_instance.__aexit__.assert_awaited_once()
@end example

@node Creating a Mock from an Existing Object,,Mocking asynchronous context manager,使用 mock
@anchor{library/unittest mock-examples creating-a-mock-from-an-existing-object}@anchor{3378}
@subsubsection Creating a Mock from an Existing Object


One problem with over use of mocking is that it couples your tests to the
implementation of your mocks rather than your real code. Suppose you have a
class that implements @code{some_method}. In a test for another class, you
provide a mock of this object that @emph{also} provides @code{some_method}. If later
you refactor the first class, so that it no longer has @code{some_method} - then
your tests will continue to pass even though your code is now broken!

@ref{249,,Mock} allows you to provide an object as a specification for the mock,
using the @emph{spec} keyword argument. Accessing methods / attributes on the
mock that don't exist on your specification object will immediately raise an
attribute error. If you change the implementation of your specification, then
tests that use that class will start failing immediately without you having to
instantiate the class in those tests.

@example
>>> mock = Mock(spec=SomeClass)
>>> mock.old_method()
Traceback (most recent call last):
   ...
AttributeError: object has no attribute 'old_method'
@end example

Using a specification also enables a smarter matching of calls made to the
mock, regardless of whether some parameters were passed as positional or
named arguments:

@example
>>> def f(a, b, c): pass
...
>>> mock = Mock(spec=f)
>>> mock(1, 2, 3)
<Mock name='mock()' id='140161580456576'>
>>> mock.assert_called_with(a=1, b=2, c=3)
@end example

If you want this smarter matching to also work with method calls on the mock,
you can use @ref{3324,,auto-speccing}.

If you want a stronger form of specification that prevents the setting
of arbitrary attributes as well as the getting of them then you can use
@emph{spec_set} instead of @emph{spec}.

@node Patch Decorators,Further Examples,使用 mock,unittest mock 上手指南
@anchor{library/unittest mock-examples patch-decorators}@anchor{3379}
@subsubsection Patch Decorators


@cartouche
@quotation 注解 
在查找对象的名称空间中修补对象使用 @ref{782,,patch()} 。使用起来很简单，阅读 @ref{3322,,在哪里打补丁} 来快速上手。
@end quotation
@end cartouche

A common need in tests is to patch a class attribute or a module attribute,
for example patching a builtin or patching a class in a module to test that it
is instantiated. Modules and classes are effectively global, so patching on
them has to be undone after the test or the patch will persist into other
tests and cause hard to diagnose problems.

mock provides three convenient decorators for this: @ref{782,,patch()}, @ref{eee,,patch.object()} and
@ref{f5f,,patch.dict()}. @code{patch} takes a single string, of the form
@code{package.module.Class.attribute} to specify the attribute you are patching. It
also optionally takes a value that you want the attribute (or class or
whatever) to be replaced with. 'patch.object' takes an object and the name of
the attribute you would like patched, plus optionally the value to patch it
with.

@code{patch.object}:

@example
>>> original = SomeClass.attribute
>>> @@patch.object(SomeClass, 'attribute', sentinel.attribute)
... def test():
...     assert SomeClass.attribute == sentinel.attribute
...
>>> test()
>>> assert SomeClass.attribute == original

>>> @@patch('package.module.attribute', sentinel.attribute)
... def test():
...     from package.module import attribute
...     assert attribute is sentinel.attribute
...
>>> test()
@end example

If you are patching a module (including @ref{13,,builtins}) then use @ref{782,,patch()}
instead of @ref{eee,,patch.object()}:

@example
>>> mock = MagicMock(return_value=sentinel.file_handle)
>>> with patch('builtins.open', mock):
...     handle = open('filename', 'r')
...
>>> mock.assert_called_with('filename', 'r')
>>> assert handle == sentinel.file_handle, "incorrect file handle returned"
@end example

The module name can be 'dotted', in the form @code{package.module} if needed:

@example
>>> @@patch('package.module.ClassName.attribute', sentinel.attribute)
... def test():
...     from package.module import ClassName
...     assert ClassName.attribute == sentinel.attribute
...
>>> test()
@end example

A nice pattern is to actually decorate test methods themselves:

@example
>>> class MyTest(unittest.TestCase):
...     @@patch.object(SomeClass, 'attribute', sentinel.attribute)
...     def test_something(self):
...         self.assertEqual(SomeClass.attribute, sentinel.attribute)
...
>>> original = SomeClass.attribute
>>> MyTest('test_something').test_something()
>>> assert SomeClass.attribute == original
@end example

If you want to patch with a Mock, you can use @ref{782,,patch()} with only one argument
(or @ref{eee,,patch.object()} with two arguments). The mock will be created for you and
passed into the test function / method:

@example
>>> class MyTest(unittest.TestCase):
...     @@patch.object(SomeClass, 'static_method')
...     def test_something(self, mock_method):
...         SomeClass.static_method()
...         mock_method.assert_called_with()
...
>>> MyTest('test_something').test_something()
@end example

You can stack up multiple patch decorators using this pattern:

@example
>>> class MyTest(unittest.TestCase):
...     @@patch('package.module.ClassName1')
...     @@patch('package.module.ClassName2')
...     def test_something(self, MockClass2, MockClass1):
...         self.assertIs(package.module.ClassName1, MockClass1)
...         self.assertIs(package.module.ClassName2, MockClass2)
...
>>> MyTest('test_something').test_something()
@end example

When you nest patch decorators the mocks are passed in to the decorated
function in the same order they applied (the normal @emph{Python} order that
decorators are applied). This means from the bottom up, so in the example
above the mock for @code{test_module.ClassName2} is passed in first.

还有一个 @ref{f5f,,patch.dict()} 用于在一定范围内设置字典中的值，并在测试结束时将字典恢复为其原始状态：

@example
>>> foo = @{'key': 'value'@}
>>> original = foo.copy()
>>> with patch.dict(foo, @{'newkey': 'newvalue'@}, clear=True):
...     assert foo == @{'newkey': 'newvalue'@}
...
>>> assert foo == original
@end example

@code{patch}, @code{patch.object} and @code{patch.dict} can all be used as context managers.

Where you use @ref{782,,patch()} to create a mock for you, you can get a reference to the
mock using the "as" form of the with statement:

@example
>>> class ProductionClass:
...     def method(self):
...         pass
...
>>> with patch.object(ProductionClass, 'method') as mock_method:
...     mock_method.return_value = None
...     real = ProductionClass()
...     real.method(1, 2, 3)
...
>>> mock_method.assert_called_with(1, 2, 3)
@end example

As an alternative @code{patch}, @code{patch.object} and @code{patch.dict} can be used as
class decorators. When used in this way it is the same as applying the
decorator individually to every method whose name starts with "test".

@node Further Examples,,Patch Decorators,unittest mock 上手指南
@anchor{library/unittest mock-examples further-examples}@anchor{337a}@anchor{library/unittest mock-examples id1}@anchor{337b}
@subsubsection Further Examples


Here are some more examples for some slightly more advanced scenarios.

@menu
* Mocking chained calls:: 
* Partial mocking:: 
* Mocking a Generator Method:: 
* Applying the same patch to every test method:: 
* Mocking Unbound Methods:: 
* Checking multiple calls with mock:: 
* Coping with mutable arguments:: 
* Nesting Patches:: 
* Mocking a dictionary with MagicMock:: 
* Mock subclasses and their attributes:: 
* Mocking imports with patch.dict: Mocking imports with patch dict. 
* Tracking order of calls and less verbose call assertions:: 
* More complex argument matching:: 

@end menu

@node Mocking chained calls,Partial mocking,,Further Examples
@anchor{library/unittest mock-examples mocking-chained-calls}@anchor{337c}
@subsubsection Mocking chained calls


Mocking chained calls is actually straightforward with mock once you
understand the @ref{332a,,return_value} attribute. When a mock is called for
the first time, or you fetch its @code{return_value} before it has been called, a
new @ref{249,,Mock} is created.

This means that you can see how the object returned from a call to a mocked
object has been used by interrogating the @code{return_value} mock:

@example
>>> mock = Mock()
>>> mock().foo(a=2, b=3)
<Mock name='mock().foo()' id='...'>
>>> mock.return_value.foo.assert_called_with(a=2, b=3)
@end example

From here it is a simple step to configure and then make assertions about
chained calls. Of course another alternative is writing your code in a more
testable way in the first place...

So, suppose we have some code that looks a little bit like this:

@example
>>> class Something:
...     def __init__(self):
...         self.backend = BackendProvider()
...     def method(self):
...         response = self.backend.get_endpoint('foobar').create_call('spam', 'eggs').start_call()
...         # more code
@end example

Assuming that @code{BackendProvider} is already well tested, how do we test
@code{method()}? Specifically, we want to test that the code section @code{# more
code} uses the response object in the correct way.

As this chain of calls is made from an instance attribute we can monkey patch
the @code{backend} attribute on a @code{Something} instance. In this particular case
we are only interested in the return value from the final call to
@code{start_call} so we don't have much configuration to do. Let's assume the
object it returns is 'file-like', so we'll ensure that our response object
uses the builtin @ref{4ea,,open()} as its @code{spec}.

To do this we create a mock instance as our mock backend and create a mock
response object for it. To set the response as the return value for that final
@code{start_call} we could do this:

@example
mock_backend.get_endpoint.return_value.create_call.return_value.start_call.return_value = mock_response
@end example

We can do that in a slightly nicer way using the @ref{332b,,configure_mock()}
method to directly set the return value for us:

@example
>>> something = Something()
>>> mock_response = Mock(spec=open)
>>> mock_backend = Mock()
>>> config = @{'get_endpoint.return_value.create_call.return_value.start_call.return_value': mock_response@}
>>> mock_backend.configure_mock(**config)
@end example

With these we monkey patch the "mock backend" in place and can make the real
call:

@example
>>> something.backend = mock_backend
>>> something.method()
@end example

Using @ref{332f,,mock_calls} we can check the chained call with a single
assert. A chained call is several calls in one line of code, so there will be
several entries in @code{mock_calls}. We can use @ref{3362,,call.call_list()} to create
this list of calls for us:

@example
>>> chained = call.get_endpoint('foobar').create_call('spam', 'eggs').start_call()
>>> call_list = chained.call_list()
>>> assert mock_backend.mock_calls == call_list
@end example

@node Partial mocking,Mocking a Generator Method,Mocking chained calls,Further Examples
@anchor{library/unittest mock-examples partial-mocking}@anchor{337d}
@subsubsection Partial mocking


In some tests I wanted to mock out a call to @ref{183d,,datetime.date.today()}
to return a known date, but I didn't want to prevent the code under test from
creating new date objects. Unfortunately @ref{193,,datetime.date} is written in C, and
so I couldn't just monkey-patch out the static @code{date.today()} method.

I found a simple way of doing this that involved effectively wrapping the date
class with a mock, but passing through calls to the constructor to the real
class (and returning real instances).

The @ref{782,,patch decorator} is used here to
mock out the @code{date} class in the module under test. The @code{side_effect}
attribute on the mock date class is then set to a lambda function that returns
a real date. When the mock date class is called a real date will be
constructed and returned by @code{side_effect}.

@example
>>> from datetime import date
>>> with patch('mymodule.date') as mock_date:
...     mock_date.today.return_value = date(2010, 10, 8)
...     mock_date.side_effect = lambda *args, **kw: date(*args, **kw)
...
...     assert mymodule.date.today() == date(2010, 10, 8)
...     assert mymodule.date(2009, 6, 8) == date(2009, 6, 8)
@end example

Note that we don't patch @ref{193,,datetime.date} globally, we patch @code{date} in the
module that @emph{uses} it. See @ref{3322,,where to patch}.

When @code{date.today()} is called a known date is returned, but calls to the
@code{date(...)} constructor still return normal dates. Without this you can find
yourself having to calculate an expected result using exactly the same
algorithm as the code under test, which is a classic testing anti-pattern.

Calls to the date constructor are recorded in the @code{mock_date} attributes
(@code{call_count} and friends) which may also be useful for your tests.

An alternative way of dealing with mocking dates, or other builtin classes,
is discussed in this blog entry@footnote{https://williambert.online/2011/07/how-to-unit-testing-in-django-with-mocking-and-patching/}.

@node Mocking a Generator Method,Applying the same patch to every test method,Partial mocking,Further Examples
@anchor{library/unittest mock-examples mocking-a-generator-method}@anchor{337e}
@subsubsection Mocking a Generator Method


A Python generator is a function or method that uses the @ref{18f,,yield} statement
to return a series of values when iterated over @footnote{@w{(1)} 
There are also generator expressions and more @uref{http://www.dabeaz.com/coroutines/index.html,advanced uses} of generators, but we aren't
concerned about them here. A very good introduction to generators and how
powerful they are is: @uref{http://www.dabeaz.com/generators/,Generator Tricks for Systems Programmers}.
}.

A generator method / function is called to return the generator object. It is
the generator object that is then iterated over. The protocol method for
iteration is @ref{15c1,,__iter__()}, so we can
mock this using a @ref{77f,,MagicMock}.

Here's an example class with an "iter" method implemented as a generator:

@example
>>> class Foo:
...     def iter(self):
...         for i in [1, 2, 3]:
...             yield i
...
>>> foo = Foo()
>>> list(foo.iter())
[1, 2, 3]
@end example

How would we mock this class, and in particular its "iter" method?

To configure the values returned from the iteration (implicit in the call to
@ref{262,,list}), we need to configure the object returned by the call to @code{foo.iter()}.

@example
>>> mock_foo = MagicMock()
>>> mock_foo.iter.return_value = iter([1, 2, 3])
>>> list(mock_foo.iter())
[1, 2, 3]
@end example

@node Applying the same patch to every test method,Mocking Unbound Methods,Mocking a Generator Method,Further Examples
@anchor{library/unittest mock-examples applying-the-same-patch-to-every-test-method}@anchor{337f}
@subsubsection Applying the same patch to every test method


If you want several patches in place for multiple test methods the obvious way
is to apply the patch decorators to every method. This can feel like unnecessary
repetition. For Python 2.6 or more recent you can use @ref{782,,patch()} (in all its
various forms) as a class decorator. This applies the patches to all test
methods on the class. A test method is identified by methods whose names start
with @code{test}:

@example
>>> @@patch('mymodule.SomeClass')
... class MyTest(unittest.TestCase):
...
...     def test_one(self, MockSomeClass):
...         self.assertIs(mymodule.SomeClass, MockSomeClass)
...
...     def test_two(self, MockSomeClass):
...         self.assertIs(mymodule.SomeClass, MockSomeClass)
...
...     def not_a_test(self):
...         return 'something'
...
>>> MyTest('test_one').test_one()
>>> MyTest('test_two').test_two()
>>> MyTest('test_two').not_a_test()
'something'
@end example

An alternative way of managing patches is to use the @ref{3354,,patch methods; start and stop}.
These allow you to move the patching into your @code{setUp} and @code{tearDown} methods.

@example
>>> class MyTest(unittest.TestCase):
...     def setUp(self):
...         self.patcher = patch('mymodule.foo')
...         self.mock_foo = self.patcher.start()
...
...     def test_foo(self):
...         self.assertIs(mymodule.foo, self.mock_foo)
...
...     def tearDown(self):
...         self.patcher.stop()
...
>>> MyTest('test_foo').run()
@end example

If you use this technique you must ensure that the patching is "undone" by
calling @code{stop}. This can be fiddlier than you might think, because if an
exception is raised in the setUp then tearDown is not called.
@ref{2a2,,unittest.TestCase.addCleanup()} makes this easier:

@example
>>> class MyTest(unittest.TestCase):
...     def setUp(self):
...         patcher = patch('mymodule.foo')
...         self.addCleanup(patcher.stop)
...         self.mock_foo = patcher.start()
...
...     def test_foo(self):
...         self.assertIs(mymodule.foo, self.mock_foo)
...
>>> MyTest('test_foo').run()
@end example

@node Mocking Unbound Methods,Checking multiple calls with mock,Applying the same patch to every test method,Further Examples
@anchor{library/unittest mock-examples mocking-unbound-methods}@anchor{3380}
@subsubsection Mocking Unbound Methods


Whilst writing tests today I needed to patch an @emph{unbound method} (patching the
method on the class rather than on the instance). I needed self to be passed
in as the first argument because I want to make asserts about which objects
were calling this particular method. The issue is that you can't patch with a
mock for this, because if you replace an unbound method with a mock it doesn't
become a bound method when fetched from the instance, and so it doesn't get
self passed in. The workaround is to patch the unbound method with a real
function instead. The @ref{782,,patch()} decorator makes it so simple to
patch out methods with a mock that having to create a real function becomes a
nuisance.

If you pass @code{autospec=True} to patch then it does the patching with a
@emph{real} function object. This function object has the same signature as the one
it is replacing, but delegates to a mock under the hood. You still get your
mock auto-created in exactly the same way as before. What it means though, is
that if you use it to patch out an unbound method on a class the mocked
function will be turned into a bound method if it is fetched from an instance.
It will have @code{self} passed in as the first argument, which is exactly what I
wanted:

@example
>>> class Foo:
...   def foo(self):
...     pass
...
>>> with patch.object(Foo, 'foo', autospec=True) as mock_foo:
...   mock_foo.return_value = 'foo'
...   foo = Foo()
...   foo.foo()
...
'foo'
>>> mock_foo.assert_called_once_with(foo)
@end example

If we don't use @code{autospec=True} then the unbound method is patched out
with a Mock instance instead, and isn't called with @code{self}.

@node Checking multiple calls with mock,Coping with mutable arguments,Mocking Unbound Methods,Further Examples
@anchor{library/unittest mock-examples checking-multiple-calls-with-mock}@anchor{3381}
@subsubsection Checking multiple calls with mock


mock has a nice API for making assertions about how your mock objects are used.

@example
>>> mock = Mock()
>>> mock.foo_bar.return_value = None
>>> mock.foo_bar('baz', spam='eggs')
>>> mock.foo_bar.assert_called_with('baz', spam='eggs')
@end example

If your mock is only being called once you can use the
@code{assert_called_once_with()} method that also asserts that the
@code{call_count} is one.

@example
>>> mock.foo_bar.assert_called_once_with('baz', spam='eggs')
>>> mock.foo_bar()
>>> mock.foo_bar.assert_called_once_with('baz', spam='eggs')
Traceback (most recent call last):
    ...
AssertionError: Expected to be called once. Called 2 times.
@end example

Both @code{assert_called_with} and @code{assert_called_once_with} make assertions about
the @emph{most recent} call. If your mock is going to be called several times, and
you want to make assertions about @emph{all} those calls you can use
@ref{3338,,call_args_list}:

@example
>>> mock = Mock(return_value=None)
>>> mock(1, 2, 3)
>>> mock(4, 5, 6)
>>> mock()
>>> mock.call_args_list
[call(1, 2, 3), call(4, 5, 6), call()]
@end example

The @ref{f09,,call} helper makes it easy to make assertions about these calls. You
can build up a list of expected calls and compare it to @code{call_args_list}. This
looks remarkably similar to the repr of the @code{call_args_list}:

@example
>>> expected = [call(1, 2, 3), call(4, 5, 6), call()]
>>> mock.call_args_list == expected
True
@end example

@node Coping with mutable arguments,Nesting Patches,Checking multiple calls with mock,Further Examples
@anchor{library/unittest mock-examples coping-with-mutable-arguments}@anchor{3382}
@subsubsection Coping with mutable arguments


Another situation is rare, but can bite you, is when your mock is called with
mutable arguments. @code{call_args} and @code{call_args_list} store @emph{references} to the
arguments. If the arguments are mutated by the code under test then you can no
longer make assertions about what the values were when the mock was called.

Here's some example code that shows the problem. Imagine the following functions
defined in 'mymodule':

@example
def frob(val):
    pass

def grob(val):
    "First frob and then clear val"
    frob(val)
    val.clear()
@end example

When we try to test that @code{grob} calls @code{frob} with the correct argument look
what happens:

@example
>>> with patch('mymodule.frob') as mock_frob:
...     val = @{6@}
...     mymodule.grob(val)
...
>>> val
set()
>>> mock_frob.assert_called_with(@{6@})
Traceback (most recent call last):
    ...
AssertionError: Expected: ((@{6@},), @{@})
Called with: ((set(),), @{@})
@end example

One possibility would be for mock to copy the arguments you pass in. This
could then cause problems if you do assertions that rely on object identity
for equality.

Here's one solution that uses the @code{side_effect}
functionality. If you provide a @code{side_effect} function for a mock then
@code{side_effect} will be called with the same args as the mock. This gives us an
opportunity to copy the arguments and store them for later assertions. In this
example I'm using @emph{another} mock to store the arguments so that I can use the
mock methods for doing the assertion. Again a helper function sets this up for
me.

@example
>>> from copy import deepcopy
>>> from unittest.mock import Mock, patch, DEFAULT
>>> def copy_call_args(mock):
...     new_mock = Mock()
...     def side_effect(*args, **kwargs):
...         args = deepcopy(args)
...         kwargs = deepcopy(kwargs)
...         new_mock(*args, **kwargs)
...         return DEFAULT
...     mock.side_effect = side_effect
...     return new_mock
...
>>> with patch('mymodule.frob') as mock_frob:
...     new_mock = copy_call_args(mock_frob)
...     val = @{6@}
...     mymodule.grob(val)
...
>>> new_mock.assert_called_with(@{6@})
>>> new_mock.call_args
call(@{6@})
@end example

@code{copy_call_args} is called with the mock that will be called. It returns a new
mock that we do the assertion on. The @code{side_effect} function makes a copy of
the args and calls our @code{new_mock} with the copy.

@cartouche
@quotation 注解 
If your mock is only going to be used once there is an easier way of
checking arguments at the point they are called. You can simply do the
checking inside a @code{side_effect} function.

@example
>>> def side_effect(arg):
...     assert arg == @{6@}
...
>>> mock = Mock(side_effect=side_effect)
>>> mock(@{6@})
>>> mock(set())
Traceback (most recent call last):
    ...
AssertionError
@end example
@end quotation
@end cartouche

An alternative approach is to create a subclass of @ref{249,,Mock} or
@ref{77f,,MagicMock} that copies (using @ref{3c4,,copy.deepcopy()}) the arguments.
Here's an example implementation:

@example
>>> from copy import deepcopy
>>> class CopyingMock(MagicMock):
...     def __call__(self, /, *args, **kwargs):
...         args = deepcopy(args)
...         kwargs = deepcopy(kwargs)
...         return super(CopyingMock, self).__call__(*args, **kwargs)
...
>>> c = CopyingMock(return_value=None)
>>> arg = set()
>>> c(arg)
>>> arg.add(1)
>>> c.assert_called_with(set())
>>> c.assert_called_with(arg)
Traceback (most recent call last):
    ...
AssertionError: Expected call: mock(@{1@})
Actual call: mock(set())
>>> c.foo
<CopyingMock name='mock.foo' id='...'>
@end example

When you subclass @code{Mock} or @code{MagicMock} all dynamically created attributes,
and the @code{return_value} will use your subclass automatically. That means all
children of a @code{CopyingMock} will also have the type @code{CopyingMock}.

@node Nesting Patches,Mocking a dictionary with MagicMock,Coping with mutable arguments,Further Examples
@anchor{library/unittest mock-examples nesting-patches}@anchor{3383}
@subsubsection Nesting Patches


Using patch as a context manager is nice, but if you do multiple patches you
can end up with nested with statements indenting further and further to the
right:

@example
>>> class MyTest(unittest.TestCase):
...
...     def test_foo(self):
...         with patch('mymodule.Foo') as mock_foo:
...             with patch('mymodule.Bar') as mock_bar:
...                 with patch('mymodule.Spam') as mock_spam:
...                     assert mymodule.Foo is mock_foo
...                     assert mymodule.Bar is mock_bar
...                     assert mymodule.Spam is mock_spam
...
>>> original = mymodule.Foo
>>> MyTest('test_foo').test_foo()
>>> assert mymodule.Foo is original
@end example

With unittest @code{cleanup} functions and the @ref{3354,,patch methods; start and stop} we can
achieve the same effect without the nested indentation. A simple helper
method, @code{create_patch}, puts the patch in place and returns the created mock
for us:

@example
>>> class MyTest(unittest.TestCase):
...
...     def create_patch(self, name):
...         patcher = patch(name)
...         thing = patcher.start()
...         self.addCleanup(patcher.stop)
...         return thing
...
...     def test_foo(self):
...         mock_foo = self.create_patch('mymodule.Foo')
...         mock_bar = self.create_patch('mymodule.Bar')
...         mock_spam = self.create_patch('mymodule.Spam')
...
...         assert mymodule.Foo is mock_foo
...         assert mymodule.Bar is mock_bar
...         assert mymodule.Spam is mock_spam
...
>>> original = mymodule.Foo
>>> MyTest('test_foo').run()
>>> assert mymodule.Foo is original
@end example

@node Mocking a dictionary with MagicMock,Mock subclasses and their attributes,Nesting Patches,Further Examples
@anchor{library/unittest mock-examples mocking-a-dictionary-with-magicmock}@anchor{3384}
@subsubsection Mocking a dictionary with MagicMock


You may want to mock a dictionary, or other container object, recording all
access to it whilst having it still behave like a dictionary.

We can do this with @ref{77f,,MagicMock}, which will behave like a dictionary,
and using @ref{3328,,side_effect} to delegate dictionary access to a real
underlying dictionary that is under our control.

When the @ref{27f,,__getitem__()} and @ref{c5b,,__setitem__()} methods of our @code{MagicMock} are called
(normal dictionary access) then @code{side_effect} is called with the key (and in
the case of @code{__setitem__} the value too). We can also control what is returned.

After the @code{MagicMock} has been used we can use attributes like
@ref{3338,,call_args_list} to assert about how the dictionary was used:

@example
>>> my_dict = @{'a': 1, 'b': 2, 'c': 3@}
>>> def getitem(name):
...      return my_dict[name]
...
>>> def setitem(name, val):
...     my_dict[name] = val
...
>>> mock = MagicMock()
>>> mock.__getitem__.side_effect = getitem
>>> mock.__setitem__.side_effect = setitem
@end example

@cartouche
@quotation 注解 
An alternative to using @code{MagicMock} is to use @code{Mock} and @emph{only} provide
the magic methods you specifically want:

@example
>>> mock = Mock()
>>> mock.__getitem__ = Mock(side_effect=getitem)
>>> mock.__setitem__ = Mock(side_effect=setitem)
@end example

A @emph{third} option is to use @code{MagicMock} but passing in @code{dict} as the @emph{spec}
(or @emph{spec_set}) argument so that the @code{MagicMock} created only has
dictionary magic methods available:

@example
>>> mock = MagicMock(spec_set=dict)
>>> mock.__getitem__.side_effect = getitem
>>> mock.__setitem__.side_effect = setitem
@end example
@end quotation
@end cartouche

With these side effect functions in place, the @code{mock} will behave like a normal
dictionary but recording the access. It even raises a @ref{2c7,,KeyError} if you try
to access a key that doesn't exist.

@example
>>> mock['a']
1
>>> mock['c']
3
>>> mock['d']
Traceback (most recent call last):
    ...
KeyError: 'd'
>>> mock['b'] = 'fish'
>>> mock['d'] = 'eggs'
>>> mock['b']
'fish'
>>> mock['d']
'eggs'
@end example

After it has been used you can make assertions about the access using the normal
mock methods and attributes:

@example
>>> mock.__getitem__.call_args_list
[call('a'), call('c'), call('d'), call('b'), call('d')]
>>> mock.__setitem__.call_args_list
[call('b', 'fish'), call('d', 'eggs')]
>>> my_dict
@{'a': 1, 'b': 'fish', 'c': 3, 'd': 'eggs'@}
@end example

@node Mock subclasses and their attributes,Mocking imports with patch dict,Mocking a dictionary with MagicMock,Further Examples
@anchor{library/unittest mock-examples mock-subclasses-and-their-attributes}@anchor{3385}
@subsubsection Mock subclasses and their attributes


There are various reasons why you might want to subclass @ref{249,,Mock}. One
reason might be to add helper methods. Here's a silly example:

@example
>>> class MyMock(MagicMock):
...     def has_been_called(self):
...         return self.called
...
>>> mymock = MyMock(return_value=None)
>>> mymock
<MyMock id='...'>
>>> mymock.has_been_called()
False
>>> mymock()
>>> mymock.has_been_called()
True
@end example

The standard behaviour for @code{Mock} instances is that attributes and the return
value mocks are of the same type as the mock they are accessed on. This ensures
that @code{Mock} attributes are @code{Mocks} and @code{MagicMock} attributes are @code{MagicMocks}
@footnote{@w{(2)} 
An exception to this rule are the non-callable mocks. Attributes use the
callable variant because otherwise non-callable mocks couldn't have callable
methods.
}. So if you're subclassing to add helper methods then they'll also be
available on the attributes and return value mock of instances of your
subclass.

@example
>>> mymock.foo
<MyMock name='mock.foo' id='...'>
>>> mymock.foo.has_been_called()
False
>>> mymock.foo()
<MyMock name='mock.foo()' id='...'>
>>> mymock.foo.has_been_called()
True
@end example

Sometimes this is inconvenient. For example, one user@footnote{https://code.google.com/archive/p/mock/issues/105} is subclassing mock to
created a Twisted adaptor@footnote{https://twistedmatrix.com/documents/11.0.0/api/twisted.python.components.html}.
Having this applied to attributes too actually causes errors.

@code{Mock} (in all its flavours) uses a method called @code{_get_child_mock} to create
these "sub-mocks" for attributes and return values. You can prevent your
subclass being used for attributes by overriding this method. The signature is
that it takes arbitrary keyword arguments (@code{**kwargs}) which are then passed
onto the mock constructor:

@example
>>> class Subclass(MagicMock):
...     def _get_child_mock(self, /, **kwargs):
...         return MagicMock(**kwargs)
...
>>> mymock = Subclass()
>>> mymock.foo
<MagicMock name='mock.foo' id='...'>
>>> assert isinstance(mymock, Subclass)
>>> assert not isinstance(mymock.foo, Subclass)
>>> assert not isinstance(mymock(), Subclass)
@end example

@node Mocking imports with patch dict,Tracking order of calls and less verbose call assertions,Mock subclasses and their attributes,Further Examples
@anchor{library/unittest mock-examples mocking-imports-with-patch-dict}@anchor{3386}
@subsubsection Mocking imports with patch.dict


One situation where mocking can be hard is where you have a local import inside
a function. These are harder to mock because they aren't using an object from
the module namespace that we can patch out.

Generally local imports are to be avoided. They are sometimes done to prevent
circular dependencies, for which there is @emph{usually} a much better way to solve
the problem (refactor the code) or to prevent "up front costs" by delaying the
import. This can also be solved in better ways than an unconditional local
import (store the module as a class or module attribute and only do the import
on first use).

That aside there is a way to use @code{mock} to affect the results of an import.
Importing fetches an @emph{object} from the @ref{eb5,,sys.modules} dictionary. Note that it
fetches an @emph{object}, which need not be a module. Importing a module for the
first time results in a module object being put in @cite{sys.modules}, so usually
when you import something you get a module back. This need not be the case
however.

This means you can use @ref{f5f,,patch.dict()} to @emph{temporarily} put a mock in place
in @ref{eb5,,sys.modules}. Any imports whilst this patch is active will fetch the mock.
When the patch is complete (the decorated function exits, the with statement
body is complete or @code{patcher.stop()} is called) then whatever was there
previously will be restored safely.

Here's an example that mocks out the 'fooble' module.

@example
>>> import sys
>>> mock = Mock()
>>> with patch.dict('sys.modules', @{'fooble': mock@}):
...    import fooble
...    fooble.blob()
...
<Mock name='mock.blob()' id='...'>
>>> assert 'fooble' not in sys.modules
>>> mock.blob.assert_called_once_with()
@end example

As you can see the @code{import fooble} succeeds, but on exit there is no 'fooble'
left in @ref{eb5,,sys.modules}.

This also works for the @code{from module import name} form:

@example
>>> mock = Mock()
>>> with patch.dict('sys.modules', @{'fooble': mock@}):
...    from fooble import blob
...    blob.blip()
...
<Mock name='mock.blob.blip()' id='...'>
>>> mock.blob.blip.assert_called_once_with()
@end example

With slightly more work you can also mock package imports:

@example
>>> mock = Mock()
>>> modules = @{'package': mock, 'package.module': mock.module@}
>>> with patch.dict('sys.modules', modules):
...    from package.module import fooble
...    fooble()
...
<Mock name='mock.module.fooble()' id='...'>
>>> mock.module.fooble.assert_called_once_with()
@end example

@node Tracking order of calls and less verbose call assertions,More complex argument matching,Mocking imports with patch dict,Further Examples
@anchor{library/unittest mock-examples tracking-order-of-calls-and-less-verbose-call-assertions}@anchor{3387}
@subsubsection Tracking order of calls and less verbose call assertions


The @ref{249,,Mock} class allows you to track the @emph{order} of method calls on
your mock objects through the @ref{3332,,method_calls} attribute. This
doesn't allow you to track the order of calls between separate mock objects,
however we can use @ref{332f,,mock_calls} to achieve the same effect.

Because mocks track calls to child mocks in @code{mock_calls}, and accessing an
arbitrary attribute of a mock creates a child mock, we can create our separate
mocks from a parent one. Calls to those child mock will then all be recorded,
in order, in the @code{mock_calls} of the parent:

@example
>>> manager = Mock()
>>> mock_foo = manager.foo
>>> mock_bar = manager.bar
@end example

@example
>>> mock_foo.something()
<Mock name='mock.foo.something()' id='...'>
>>> mock_bar.other.thing()
<Mock name='mock.bar.other.thing()' id='...'>
@end example

@example
>>> manager.mock_calls
[call.foo.something(), call.bar.other.thing()]
@end example

We can then assert about the calls, including the order, by comparing with
the @code{mock_calls} attribute on the manager mock:

@example
>>> expected_calls = [call.foo.something(), call.bar.other.thing()]
>>> manager.mock_calls == expected_calls
True
@end example

If @code{patch} is creating, and putting in place, your mocks then you can attach
them to a manager mock using the @ref{3331,,attach_mock()} method. After
attaching calls will be recorded in @code{mock_calls} of the manager.

@example
>>> manager = MagicMock()
>>> with patch('mymodule.Class1') as MockClass1:
...     with patch('mymodule.Class2') as MockClass2:
...         manager.attach_mock(MockClass1, 'MockClass1')
...         manager.attach_mock(MockClass2, 'MockClass2')
...         MockClass1().foo()
...         MockClass2().bar()
<MagicMock name='mock.MockClass1().foo()' id='...'>
<MagicMock name='mock.MockClass2().bar()' id='...'>
>>> manager.mock_calls
[call.MockClass1(),
call.MockClass1().foo(),
call.MockClass2(),
call.MockClass2().bar()]
@end example

If many calls have been made, but you're only interested in a particular
sequence of them then an alternative is to use the
@ref{332e,,assert_has_calls()} method. This takes a list of calls (constructed
with the @ref{f09,,call} object). If that sequence of calls are in
@ref{332f,,mock_calls} then the assert succeeds.

@example
>>> m = MagicMock()
>>> m().foo().bar().baz()
<MagicMock name='mock().foo().bar().baz()' id='...'>
>>> m.one().two().three()
<MagicMock name='mock.one().two().three()' id='...'>
>>> calls = call.one().two().three().call_list()
>>> m.assert_has_calls(calls)
@end example

Even though the chained call @code{m.one().two().three()} aren't the only calls that
have been made to the mock, the assert still succeeds.

Sometimes a mock may have several calls made to it, and you are only interested
in asserting about @emph{some} of those calls. You may not even care about the
order. In this case you can pass @code{any_order=True} to @code{assert_has_calls}:

@example
>>> m = MagicMock()
>>> m(1), m.two(2, 3), m.seven(7), m.fifty('50')
(...)
>>> calls = [call.fifty('50'), call(1), call.seven(7)]
>>> m.assert_has_calls(calls, any_order=True)
@end example

@node More complex argument matching,,Tracking order of calls and less verbose call assertions,Further Examples
@anchor{library/unittest mock-examples more-complex-argument-matching}@anchor{3388}
@subsubsection More complex argument matching


Using the same basic concept as @ref{3365,,ANY} we can implement matchers to do more
complex assertions on objects used as arguments to mocks.

Suppose we expect some object to be passed to a mock that by default
compares equal based on object identity (which is the Python default for user
defined classes). To use @ref{f90,,assert_called_with()} we would need to pass
in the exact same object. If we are only interested in some of the attributes
of this object then we can create a matcher that will check these attributes
for us.

You can see in this example how a 'standard' call to @code{assert_called_with} isn't
sufficient:

@example
>>> class Foo:
...     def __init__(self, a, b):
...         self.a, self.b = a, b
...
>>> mock = Mock(return_value=None)
>>> mock(Foo(1, 2))
>>> mock.assert_called_with(Foo(1, 2))
Traceback (most recent call last):
    ...
AssertionError: Expected: call(<__main__.Foo object at 0x...>)
Actual call: call(<__main__.Foo object at 0x...>)
@end example

A comparison function for our @code{Foo} class might look something like this:

@example
>>> def compare(self, other):
...     if not type(self) == type(other):
...         return False
...     if self.a != other.a:
...         return False
...     if self.b != other.b:
...         return False
...     return True
...
@end example

And a matcher object that can use comparison functions like this for its
equality operation would look something like this:

@example
>>> class Matcher:
...     def __init__(self, compare, some_obj):
...         self.compare = compare
...         self.some_obj = some_obj
...     def __eq__(self, other):
...         return self.compare(self.some_obj, other)
...
@end example

Putting all this together:

@example
>>> match_foo = Matcher(compare, Foo(1, 2))
>>> mock.assert_called_with(match_foo)
@end example

The @code{Matcher} is instantiated with our compare function and the @code{Foo} object
we want to compare against. In @code{assert_called_with} the @code{Matcher} equality
method will be called, which compares the object the mock was called with
against the one we created our matcher with. If they match then
@code{assert_called_with} passes, and if they don't an @ref{fc1,,AssertionError} is raised:

@example
>>> match_wrong = Matcher(compare, Foo(3, 4))
>>> mock.assert_called_with(match_wrong)
Traceback (most recent call last):
    ...
AssertionError: Expected: ((<Matcher object at 0x...>,), @{@})
Called with: ((<Foo object at 0x...>,), @{@})
@end example

With a bit of tweaking you could have the comparison function raise the
@ref{fc1,,AssertionError} directly and provide a more useful failure message.

As of version 1.5, the Python testing library PyHamcrest@footnote{https://pyhamcrest.readthedocs.io/} provides similar functionality,
that may be useful here, in the form of its equality matcher
(hamcrest.library.integration.match_equality@footnote{https://pyhamcrest.readthedocs.io/en/release-1.8/integration/#module-hamcrest.library.integration.match_equality}).

@node 2to3 - 自动将 Python 2 代码转为 Python 3 代码,test --- Python回归测试包,unittest mock 上手指南,开发工具
@anchor{library/2to3 doc}@anchor{3389}@anchor{library/2to3 to3-automated-python-2-to-3-code-translation}@anchor{338a}@anchor{library/2to3 to3-reference}@anchor{c6f}
@subsection 2to3 - 自动将 Python 2 代码转为 Python 3 代码


2to3 是一个 Python 程序，它可以用来读取 Python 2.x 版本的代码，并使用一系列的 @emph{修复器} 来将其转换为合法的 Python 3.x 代码。标准库中已经包含了丰富的修复器，这足以处理绝大多数代码。不过 2to3 的支持库 @ref{a7,,lib2to3} 是一个很灵活通用的库，所以你也可以为 2to3 编写你自己的修复器。@ref{a7,,lib2to3} 也可以用在那些需要自动处理 Python 代码的应用中。

@menu
* 使用 2to3:: 
* 修复器:: 
* lib2to3 —— 2to3 支持库:: 

@end menu

@node 使用 2to3,修复器,,2to3 - 自动将 Python 2 代码转为 Python 3 代码
@anchor{library/2to3 to3-using}@anchor{338b}@anchor{library/2to3 using-2to3}@anchor{338c}
@subsubsection 使用 2to3


2to3 通常会作为脚本和 Python 解释器一起安装，你可以在 Python 根目录的 @code{Tools/scripts} 文件夹下找到它。

2to3 的基本调用参数是一个需要转换的文件或目录列表。对于目录，会递归地寻找其中的 Python 源码。

这里有一个 Python 2.x 的源码文件，@code{example.py}：

@example
def greet(name):
    print "Hello, @{0@}!".format(name)
print "What's your name?"
name = raw_input()
greet(name)
@end example

它可以在命令行中使用 2to3 转换成 Python 3.x 版本的代码：

@example
$ 2to3 example.py
@end example

这个命令会打印出和源文件的区别。通过传入 @code{-w} 参数，2to3 也可以把需要的修改写回到原文件中（除非传入了 @code{-n} 参数，否则会为原始文件创建一个副本）：

@example
$ 2to3 -w example.py
@end example

在转换完成后，@code{example.py} 看起来像是这样：

@example
def greet(name):
    print("Hello, @{0@}!".format(name))
print("What's your name?")
name = input()
greet(name)
@end example

注释和缩进都会在转换过程中保持不变。

默认情况下，2to3 会执行 @ref{338d,,预定义修复器} 的集合。使用 @code{-l} 参数可以列出所有可用的修复器。使用 @code{-f} 参数可以明确指定需要使用的修复器集合。而使用 @code{-x} 参数则可以明确指定不使用的修复器。下面的例子会只使用 @code{imports} 和 @code{has_key} 修复器运行：

@example
$ 2to3 -f imports -f has_key example.py
@end example

这个命令会执行除了 @code{apply} 之外的所有修复器：

@example
$ 2to3 -x apply example.py
@end example

有一些修复器是需要 @emph{显式指定} 的，它们默认不会执行，必须在命令行中列出才会执行。比如下面的例子，除了默认的修复器以外，还会执行 @code{idioms} 修复器：

@example
$ 2to3 -f all -f idioms example.py
@end example

注意这里使用 @code{all} 来启用所有默认的修复器。

有些情况下 2to3 会找到源码中有一些需要修改，但是无法自动处理的代码。在这种情况下，2to3 会在差异处下面打印一个警告信息。你应该定位到相应的代码并对其进行修改，以使其兼容 Python 3.x。

2to3 也可以重构 doctests。使用 @code{-d} 开启这个模式。需要注意*只有* doctests 会被重构。这种模式下不需要文件是合法的 Python 代码。举例来说，reST 文档中类似 doctests 的示例也可以使用这个选项进行重构。

@code{-v} 选项可以输出更多转换程序的详细信息。

由于某些 print 语句可被解读为函数调用或是语句，2to3 并不是总能读取包含 print 函数的文件。当 2to3 检测到存在 @code{from __future__ import print_function} 编译器指令时，会修改其内部语法将 @ref{880,,print()} 解读为函数。这一变动也可以使用 @code{-p} 选项手动开启。使用 @code{-p} 来为已经转换过 print 语句的代码运行修复器。

@code{-o} 或 @code{--output-dir} 选项可以指定将转换后的文件写入其他目录中。由于这种情况下不会覆写原始文件，所以创建副本文件毫无意义，因此也需要使用 @code{-n} 选项来禁用创建副本。


3.2.3 新版功能: 增加了 @code{-o} 选项。


@code{-W} 或 @code{--write-unchanged-files} 选项用来告诉 2to3 始终需要输出文件，即使没有任何改动。这在使用 @code{-o} 参数时十分有用，这样就可以将整个 Python 源码包完整地转换到另一个目录。这个选项隐含了 @code{-w} 选项，否则等于没有作用。


3.2.3 新版功能: 增加了 @code{-W} 选项。


@code{--add-suffix} 选项接受一个字符串，用来作为后缀附加在输出文件名后面的后面。由于写入的文件名与原始文件不同，所以没有必要创建副本，因此 @code{-n} 选项也是必要的。举个例子：

@example
$ 2to3 -n -W --add-suffix=3 example.py
@end example

这样会把转换后的文件写入 @code{example.py3} 文件。


3.2.3 新版功能: 增加了 @code{--add-suffix} 选项。


将整个项目从一个目录转换到另一个目录可以用这样的命令：

@example
$ 2to3 --output-dir=python3-version/mycode -W -n python2-version/mycode
@end example

@node 修复器,lib2to3 —— 2to3 支持库,使用 2to3,2to3 - 自动将 Python 2 代码转为 Python 3 代码
@anchor{library/2to3 fixers}@anchor{338e}@anchor{library/2to3 to3-fixers}@anchor{338d}
@subsubsection 修复器


转换代码的每一个步骤都封装在修复器中。可以使用 @code{2to3 -l} 来列出可用的修复器。@ref{338b,,之前已经提到}，每个修复器都可以独立地打开或是关闭。下面会对各个修复器做更详细的描述。

@geindex apply (2to3 fixer)
@anchor{library/2to3 2to3fixer-apply}@anchor{338f}
@deffn {2to3fixer} apply

移除对 @code{apply()} 的使用，举例来说，@code{apply(function, *args, **kwargs)} 会被转换成 @code{function(*args, **kwargs)}。
@end deffn

@geindex asserts (2to3 fixer)
@anchor{library/2to3 2to3fixer-asserts}@anchor{3390}
@deffn {2to3fixer} asserts

将已弃用的 @ref{11b,,unittest} 方法替换为正确的。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

从

@tab

到

@item

@code{failUnlessEqual(a, b)}

@tab

@ref{bae,,assertEqual(a@comma{} b)}

@item

@code{assertEquals(a, b)}

@tab

@ref{bae,,assertEqual(a@comma{} b)}

@item

@code{failIfEqual(a, b)}

@tab

@ref{baf,,assertNotEqual(a@comma{} b)}

@item

@code{assertNotEquals(a, b)}

@tab

@ref{baf,,assertNotEqual(a@comma{} b)}

@item

@code{failUnless(a)}

@tab

@ref{bad,,assertTrue(a)}

@item

@code{assert_(a)}

@tab

@ref{bad,,assertTrue(a)}

@item

@code{failIf(a)}

@tab

@ref{cc0,,assertFalse(a)}

@item

@code{failUnlessRaises(exc, cal)}

@tab

@ref{ab5,,assertRaises(exc@comma{} cal)}

@item

@code{failUnlessAlmostEqual(a, b)}

@tab

@ref{bb0,,assertAlmostEqual(a@comma{} b)}

@item

@code{assertAlmostEquals(a, b)}

@tab

@ref{bb0,,assertAlmostEqual(a@comma{} b)}

@item

@code{failIfAlmostEqual(a, b)}

@tab

@ref{bb1,,assertNotAlmostEqual(a@comma{} b)}

@item

@code{assertNotAlmostEquals(a, b)}

@tab

@ref{bb1,,assertNotAlmostEqual(a@comma{} b)}

@end multitable

@end deffn

@geindex basestring (2to3 fixer)
@anchor{library/2to3 2to3fixer-basestring}@anchor{3391}
@deffn {2to3fixer} basestring

将 @code{basestring} 转换为 @ref{329,,str}。
@end deffn

@geindex buffer (2to3 fixer)
@anchor{library/2to3 2to3fixer-buffer}@anchor{3392}
@deffn {2to3fixer} buffer

将 @code{buffer} 转换为 @ref{25c,,memoryview}。这个修复器是可选的，因为 @ref{25c,,memoryview} API 和 @code{buffer} 很相似，但不完全一样。
@end deffn

@geindex dict (2to3 fixer)
@anchor{library/2to3 2to3fixer-dict}@anchor{3393}
@deffn {2to3fixer} dict

修复字典迭代方法。@code{dict.iteritems()} 会转换成 @ref{c24,,dict.items()}，@code{dict.iterkeys()} 会转换成 @ref{c23,,dict.keys()}，@code{dict.itervalues()} 会转换成 @ref{c25,,dict.values()}。类似的，@code{dict.viewitems()}，@code{dict.viewkeys()} 和 @code{dict.viewvalues()} 会分别转换成 @ref{c24,,dict.items()}，@ref{c23,,dict.keys()} 和 @ref{c25,,dict.values()}。另外也会将原有的 @ref{c24,,dict.items()}，@ref{c23,,dict.keys()} 和  @ref{c25,,dict.values()} 方法调用用 @ref{262,,list} 包装一层。
@end deffn

@geindex except (2to3 fixer)
@anchor{library/2to3 2to3fixer-except}@anchor{3394}
@deffn {2to3fixer} except

将 @code{except X, T} 转换为 @code{except X as T}。
@end deffn

@geindex exec (2to3 fixer)
@anchor{library/2to3 2to3fixer-exec}@anchor{3395}
@deffn {2to3fixer} exec

将 @code{exec} 语句转换为 @ref{c3d,,exec()} 函数调用。
@end deffn

@geindex execfile (2to3 fixer)
@anchor{library/2to3 2to3fixer-execfile}@anchor{fb6}
@deffn {2to3fixer} execfile

移除 @code{execfile()} 的使用。@code{execfile()} 的实参会使用 @ref{4ea,,open()}，@ref{1b4,,compile()} 和 @ref{c3d,,exec()} 包装。
@end deffn

@geindex exitfunc (2to3 fixer)
@anchor{library/2to3 2to3fixer-exitfunc}@anchor{3396}
@deffn {2to3fixer} exitfunc

将对 @code{sys.exitfunc} 的赋值改为使用 @ref{c,,atexit} 模块代替。
@end deffn

@geindex filter (2to3 fixer)
@anchor{library/2to3 2to3fixer-filter}@anchor{3397}
@deffn {2to3fixer} filter

将 @ref{c27,,filter()} 函数用 @ref{262,,list} 包装一层。
@end deffn

@geindex funcattrs (2to3 fixer)
@anchor{library/2to3 2to3fixer-funcattrs}@anchor{3398}
@deffn {2to3fixer} funcattrs

修复已经重命名的函数属性。比如 @code{my_function.func_closure} 会被转换为 @code{my_function.__closure__}。
@end deffn

@geindex future (2to3 fixer)
@anchor{library/2to3 2to3fixer-future}@anchor{3399}
@deffn {2to3fixer} future

移除 @code{from __future__ import new_feature} 语句。
@end deffn

@geindex getcwdu (2to3 fixer)
@anchor{library/2to3 2to3fixer-getcwdu}@anchor{339a}
@deffn {2to3fixer} getcwdu

将 @code{os.getcwdu()} 重命名为 @ref{f6f,,os.getcwd()}。
@end deffn

@geindex has_key (2to3 fixer)
@anchor{library/2to3 2to3fixer-has_key}@anchor{339b}
@deffn {2to3fixer} has_key

将 @code{dict.has_key(key)} 转换为 @code{key in dict}。
@end deffn

@geindex idioms (2to3 fixer)
@anchor{library/2to3 2to3fixer-idioms}@anchor{339c}
@deffn {2to3fixer} idioms

这是一个可选的修复器，会进行多种转换，将 Python 代码变成更加常见的写法。类似 @code{type(x) is SomeClass} 和 @code{type(x) == SomeClass} 的类型对比会被转换成 @code{isinstance(x, SomeClass)}。@code{while 1} 转换成 @code{while True}。这个修复器还会在合适的地方使用 @ref{43e,,sorted()} 函数。举个例子，这样的代码块：

@example
L = list(some_iterable)
L.sort()
@end example

会被转换为：

@example
L = sorted(some_iterable)
@end example
@end deffn

@geindex import (2to3 fixer)
@anchor{library/2to3 2to3fixer-import}@anchor{339d}
@deffn {2to3fixer} import

检测 sibling imports，并将其转换成相对 import。
@end deffn

@geindex imports (2to3 fixer)
@anchor{library/2to3 2to3fixer-imports}@anchor{339e}
@deffn {2to3fixer} imports

处理标准库模块的重命名。
@end deffn

@geindex imports2 (2to3 fixer)
@anchor{library/2to3 2to3fixer-imports2}@anchor{339f}
@deffn {2to3fixer} imports2

处理标准库中其他模块的重命名。这个修复器由于一些技术上的限制，因此和 @ref{339e,,imports} 拆分开了。
@end deffn

@geindex input (2to3 fixer)
@anchor{library/2to3 2to3fixer-input}@anchor{33a0}
@deffn {2to3fixer} input

将 @code{input(prompt)} 转换为 @code{eval(input(prompt))}。
@end deffn

@geindex intern (2to3 fixer)
@anchor{library/2to3 2to3fixer-intern}@anchor{33a1}
@deffn {2to3fixer} intern

将 @code{intern()} 转换为 @ref{c67,,sys.intern()}。
@end deffn

@geindex isinstance (2to3 fixer)
@anchor{library/2to3 2to3fixer-isinstance}@anchor{33a2}
@deffn {2to3fixer} isinstance

修复 @ref{449,,isinstance()} 函数第二个实参中重复的类型。举例来说，@code{isinstance(x, (int, int))} 会转换为 @code{isinstance(x, int)}, @code{isinstance(x, (int, float, int))} 会转换为 @code{isinstance(x, (int, float))}。
@end deffn

@geindex itertools_imports (2to3 fixer)
@anchor{library/2to3 2to3fixer-itertools_imports}@anchor{33a3}
@deffn {2to3fixer} itertools_imports

移除 @code{itertools.ifilter()}，@code{itertools.izip()} 以及 @code{itertools.imap()} 的 import。对 @code{itertools.ifilterfalse()} 的 import 也会替换成 @ref{1584,,itertools.filterfalse()}。
@end deffn

@geindex itertools (2to3 fixer)
@anchor{library/2to3 2to3fixer-itertools}@anchor{33a4}
@deffn {2to3fixer} itertools

修改 @code{itertools.ifilter()}，@code{itertools.izip()} 和 @code{itertools.imap()} 的调用为对应的内建实现。@code{itertools.ifilterfalse()} 会替换成 @ref{1584,,itertools.filterfalse()}。
@end deffn

@geindex long (2to3 fixer)
@anchor{library/2to3 2to3fixer-long}@anchor{33a5}
@deffn {2to3fixer} long

将 @code{long} 重命名为 @ref{184,,int}。
@end deffn

@geindex map (2to3 fixer)
@anchor{library/2to3 2to3fixer-map}@anchor{33a6}
@deffn {2to3fixer} map

用 @ref{262,,list} 包装 @ref{c26,,map()}。同时也会将 @code{map(None, x)} 替换为 @code{list(x)}。使用 @code{from future_builtins import map} 禁用这个修复器。
@end deffn

@geindex metaclass (2to3 fixer)
@anchor{library/2to3 2to3fixer-metaclass}@anchor{33a7}
@deffn {2to3fixer} metaclass

将老的元类语法（类体中的 @code{__metaclass__ = Meta}）替换为新的（@code{class X(metaclass=Meta)}）。
@end deffn

@geindex methodattrs (2to3 fixer)
@anchor{library/2to3 2to3fixer-methodattrs}@anchor{33a8}
@deffn {2to3fixer} methodattrs

修复老的方法属性名。例如 @code{meth.im_func} 会被转换为 @code{meth.__func__}。
@end deffn

@geindex ne (2to3 fixer)
@anchor{library/2to3 2to3fixer-ne}@anchor{33a9}
@deffn {2to3fixer} ne

转换老的不等语法，将 @code{<>} 转为 @code{!=}。
@end deffn

@geindex next (2to3 fixer)
@anchor{library/2to3 2to3fixer-next}@anchor{33aa}
@deffn {2to3fixer} next

将迭代器的 @code{next()} 方法调用转为 @ref{67c,,next()} 函数。也会将 @ref{67c,,next()} 方法重命名为 @ref{c5d,,__next__()}。
@end deffn

@geindex nonzero (2to3 fixer)
@anchor{library/2to3 2to3fixer-nonzero}@anchor{33ab}
@deffn {2to3fixer} nonzero

将 @code{__nonzero__()} 转换为 @ref{c61,,__bool__()}。
@end deffn

@geindex numliterals (2to3 fixer)
@anchor{library/2to3 2to3fixer-numliterals}@anchor{33ac}
@deffn {2to3fixer} numliterals

将八进制字面量转为新的语法。
@end deffn

@geindex operator (2to3 fixer)
@anchor{library/2to3 2to3fixer-operator}@anchor{33ad}
@deffn {2to3fixer} operator

将 @ref{c2,,operator} 模块中的许多方法调用转为其他的等效函数调用。如果有需要，会添加适当的 @code{import} 语句，比如 @code{import collections.abc}。有以下转换映射：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

从

@tab

到

@item

@code{operator.isCallable(obj)}

@tab

@code{callable(obj)}

@item

@code{operator.sequenceIncludes(obj)}

@tab

@code{operator.contains(obj)}

@item

@code{operator.isSequenceType(obj)}

@tab

@code{isinstance(obj, collections.abc.Sequence)}

@item

@code{operator.isMappingType(obj)}

@tab

@code{isinstance(obj, collections.abc.Mapping)}

@item

@code{operator.isNumberType(obj)}

@tab

@code{isinstance(obj, numbers.Number)}

@item

@code{operator.repeat(obj, n)}

@tab

@code{operator.mul(obj, n)}

@item

@code{operator.irepeat(obj, n)}

@tab

@code{operator.imul(obj, n)}

@end multitable

@end deffn

@geindex paren (2to3 fixer)
@anchor{library/2to3 2to3fixer-paren}@anchor{33ae}
@deffn {2to3fixer} paren

在列表生成式中增加必须的括号。例如将 @code{[x for x in 1, 2]} 转换为 @code{[x for x in (1, 2)]}。
@end deffn

@geindex print (2to3 fixer)
@anchor{library/2to3 2to3fixer-print}@anchor{33af}
@deffn {2to3fixer} print

将 @code{print} 语句转换为 @ref{880,,print()} 函数。
@end deffn

@geindex raise (2to3 fixer)
@anchor{library/2to3 2to3fixer-raise}@anchor{33b0}
@deffn {2to3fixer} raise

将 @code{raise E, V} 转换为 @code{raise E(V)}，将 @code{raise E, V, T} 转换为 @code{raise E(V).with_traceback(T)}。如果 @code{E} 是元组，这样的转换是不正确的，因为用元组代替异常的做法在 3.0 中已经移除了。
@end deffn

@geindex raw_input (2to3 fixer)
@anchor{library/2to3 2to3fixer-raw_input}@anchor{33b1}
@deffn {2to3fixer} raw_input

将 @code{raw_input()} 转换为 @ref{c64,,input()}。
@end deffn

@geindex reduce (2to3 fixer)
@anchor{library/2to3 2to3fixer-reduce}@anchor{33b2}
@deffn {2to3fixer} reduce

将 @code{reduce()} 转换为 @ref{c68,,functools.reduce()}。
@end deffn

@geindex reload (2to3 fixer)
@anchor{library/2to3 2to3fixer-reload}@anchor{fc6}
@deffn {2to3fixer} reload

将 @code{reload()} 转换为 @ref{391,,importlib.reload()}。
@end deffn

@geindex renames (2to3 fixer)
@anchor{library/2to3 2to3fixer-renames}@anchor{33b3}
@deffn {2to3fixer} renames

将 @code{sys.maxint} 转换为 @ref{b3c,,sys.maxsize}。
@end deffn

@geindex repr (2to3 fixer)
@anchor{library/2to3 2to3fixer-repr}@anchor{33b4}
@deffn {2to3fixer} repr

将反引号 repr 表达式替换为 @ref{7c6,,repr()} 函数。
@end deffn

@geindex set_literal (2to3 fixer)
@anchor{library/2to3 2to3fixer-set_literal}@anchor{33b5}
@deffn {2to3fixer} set_literal

将 @ref{b68,,set} 构造函数替换为 set literals 写法。这个修复器是可选的。
@end deffn

@geindex standarderror (2to3 fixer)
@anchor{library/2to3 2to3fixer-standarderror}@anchor{33b6}
@deffn {2to3fixer} standarderror

将 @code{StandardError} 重命名为 @ref{1a9,,Exception}。
@end deffn

@geindex sys_exc (2to3 fixer)
@anchor{library/2to3 2to3fixer-sys_exc}@anchor{33b7}
@deffn {2to3fixer} sys_exc

将弃用的 @code{sys.exc_value}，@code{sys.exc_type}，@code{sys.exc_traceback} 替换为 @ref{c58,,sys.exc_info()} 的用法。
@end deffn

@geindex throw (2to3 fixer)
@anchor{library/2to3 2to3fixer-throw}@anchor{33b8}
@deffn {2to3fixer} throw

修复生成器的 @code{throw()} 方法的 API 变更。
@end deffn

@geindex tuple_params (2to3 fixer)
@anchor{library/2to3 2to3fixer-tuple_params}@anchor{33b9}
@deffn {2to3fixer} tuple_params

移除隐式的元组参数解包。这个修复器会插入临时变量。
@end deffn

@geindex types (2to3 fixer)
@anchor{library/2to3 2to3fixer-types}@anchor{33ba}
@deffn {2to3fixer} types

修复 @ref{603,,type} 模块中一些成员的移除引起的代码问题。
@end deffn

@geindex unicode (2to3 fixer)
@anchor{library/2to3 2to3fixer-unicode}@anchor{33bb}
@deffn {2to3fixer} unicode

将 @code{unicode} 重命名为 @ref{329,,str}。
@end deffn

@geindex urllib (2to3 fixer)
@anchor{library/2to3 2to3fixer-urllib}@anchor{33bc}
@deffn {2to3fixer} urllib

将 @ref{11d,,urllib} 和 @code{urllib2} 重命名为 @ref{11d,,urllib} 包。
@end deffn

@geindex ws_comma (2to3 fixer)
@anchor{library/2to3 2to3fixer-ws_comma}@anchor{33bd}
@deffn {2to3fixer} ws_comma

移除逗号分隔的元素之间多余的空白。这个修复器是可选的。
@end deffn

@geindex xrange (2to3 fixer)
@anchor{library/2to3 2to3fixer-xrange}@anchor{33be}
@deffn {2to3fixer} xrange

将 @code{xrange()} 重命名为 @ref{9b8,,range()}，并用 @ref{262,,list} 包装原有的 @ref{9b8,,range()}。
@end deffn

@geindex xreadlines (2to3 fixer)
@anchor{library/2to3 2to3fixer-xreadlines}@anchor{33bf}
@deffn {2to3fixer} xreadlines

将 @code{for x in file.xreadlines()} 转换为 @code{for x in file}。
@end deffn

@geindex zip (2to3 fixer)
@anchor{library/2to3 2to3fixer-zip}@anchor{33c0}
@deffn {2to3fixer} zip

用 @ref{262,,list} 包装 @ref{c2b,,zip()}。如果使用了 @code{from future_builtins import zip} 的话会禁用。
@end deffn

@node lib2to3 —— 2to3 支持库,,修复器,2to3 - 自动将 Python 2 代码转为 Python 3 代码
@anchor{library/2to3 lib2to3-2to3-s-library}@anchor{33c1}@anchor{library/2to3 module-lib2to3}@anchor{a7}
@subsubsection @code{lib2to3} —— 2to3 支持库


@geindex lib2to3 (模块)

@strong{源代码：} Lib/lib2to3/@footnote{https://github.com/python/cpython/tree/3.8/Lib/lib2to3/}


__________________________________________________________________


@cartouche
@quotation 注解 
@ref{a7,,lib2to3} API 并不稳定，并可能在未来大幅修改。
@end quotation
@end cartouche

@c XXX What is the public interface anyway?

@node test --- Python回归测试包,test support --- Utilities for the Python test suite,2to3 - 自动将 Python 2 代码转为 Python 3 代码,开发工具
@anchor{library/test doc}@anchor{33c2}@anchor{library/test module-test}@anchor{105}@anchor{library/test test-regression-tests-package-for-python}@anchor{33c3}
@subsection @code{test} ---  Python回归测试包


@geindex test (模块)

@cartouche
@quotation 注解 
The @ref{105,,test} package is meant for internal use by Python only. It is
documented for the benefit of the core developers of Python. Any use of
this package outside of Python's standard library is discouraged as code
mentioned here can change or be removed without notice between releases of
Python.
@end quotation
@end cartouche


__________________________________________________________________


The @ref{105,,test} package contains all regression tests for Python as well as the
modules @ref{106,,test.support} and @code{test.regrtest}.
@ref{106,,test.support} is used to enhance your tests while
@code{test.regrtest} drives the testing suite.

Each module in the @ref{105,,test} package whose name starts with @code{test_} is a
testing suite for a specific module or feature. All new tests should be written
using the @ref{11b,,unittest} or @ref{67,,doctest} module.  Some older tests are
written using a "traditional" testing style that compares output printed to
@code{sys.stdout}; this style of test is considered deprecated.


@subsubheading 参见



@table @asis

@item 模块 @ref{11b,,unittest}

编写 PyUnit 回归测试.

@item @ref{67,,doctest} --- 文档测试模块

Tests embedded in documentation strings.
@end table


@menu
* Writing Unit Tests for the test package:: 
* Running tests using the command-line interface:: 

@end menu

@node Writing Unit Tests for the test package,Running tests using the command-line interface,,test --- Python回归测试包
@anchor{library/test writing-tests}@anchor{33c4}@anchor{library/test writing-unit-tests-for-the-test-package}@anchor{33c5}
@subsubsection Writing Unit Tests for the @code{test} package


It is preferred that tests that use the @ref{11b,,unittest} module follow a few
guidelines. One is to name the test module by starting it with @code{test_} and end
it with the name of the module being tested. The test methods in the test module
should start with @code{test_} and end with a description of what the method is
testing. This is needed so that the methods are recognized by the test driver as
test methods. Also, no documentation string for the method should be included. A
comment (such as @code{# Tests function returns only True or False}) should be used
to provide documentation for test methods. This is done because documentation
strings get printed out if they exist and thus what test is being run is not
stated.

A basic boilerplate is often used:

@example
import unittest
from test import support

class MyTestCase1(unittest.TestCase):

    # Only use setUp() and tearDown() if necessary

    def setUp(self):
        ... code to execute in preparation for tests ...

    def tearDown(self):
        ... code to execute to clean up after tests ...

    def test_feature_one(self):
        # Test feature one.
        ... testing code ...

    def test_feature_two(self):
        # Test feature two.
        ... testing code ...

    ... more test methods ...

class MyTestCase2(unittest.TestCase):
    ... same structure as MyTestCase1 ...

... more test classes ...

if __name__ == '__main__':
    unittest.main()
@end example

This code pattern allows the testing suite to be run by @code{test.regrtest},
on its own as a script that supports the @ref{11b,,unittest} CLI, or via the
@code{python -m unittest} CLI.

The goal for regression testing is to try to break code. This leads to a few
guidelines to be followed:


@itemize *

@item 
The testing suite should exercise all classes, functions, and constants. This
includes not just the external API that is to be presented to the outside
world but also "private" code.

@item 
Whitebox testing (examining the code being tested when the tests are being
written) is preferred. Blackbox testing (testing only the published user
interface) is not complete enough to make sure all boundary and edge cases
are tested.

@item 
Make sure all possible values are tested including invalid ones. This makes
sure that not only all valid values are acceptable but also that improper
values are handled correctly.

@item 
Exhaust as many code paths as possible. Test where branching occurs and thus
tailor input to make sure as many different paths through the code are taken.

@item 
Add an explicit test for any bugs discovered for the tested code. This will
make sure that the error does not crop up again if the code is changed in the
future.

@item 
Make sure to clean up after your tests (such as close and remove all temporary
files).

@item 
If a test is dependent on a specific condition of the operating system then
verify the condition already exists before attempting the test.

@item 
Import as few modules as possible and do it as soon as possible. This
minimizes external dependencies of tests and also minimizes possible anomalous
behavior from side-effects of importing a module.

@item 
Try to maximize code reuse. On occasion, tests will vary by something as small
as what type of input is used. Minimize code duplication by subclassing a
basic test class with a class that specifies the input:

@example
class TestFuncAcceptsSequencesMixin:

    func = mySuperWhammyFunction

    def test_func(self):
        self.func(self.arg)

class AcceptLists(TestFuncAcceptsSequencesMixin, unittest.TestCase):
    arg = [1, 2, 3]

class AcceptStrings(TestFuncAcceptsSequencesMixin, unittest.TestCase):
    arg = 'abc'

class AcceptTuples(TestFuncAcceptsSequencesMixin, unittest.TestCase):
    arg = (1, 2, 3)
@end example

When using this pattern, remember that all classes that inherit from
@ref{8f9,,unittest.TestCase} are run as tests.  The @code{Mixin} class in the example above
does not have any data and so can't be run by itself, thus it does not
inherit from @ref{8f9,,unittest.TestCase}.
@end itemize


@subsubheading 参见



@table @asis

@item Test Driven Development

A book by Kent Beck on writing tests before code.
@end table


@node Running tests using the command-line interface,,Writing Unit Tests for the test package,test --- Python回归测试包
@anchor{library/test regrtest}@anchor{927}@anchor{library/test running-tests-using-the-command-line-interface}@anchor{33c6}
@subsubsection Running tests using the command-line interface


The @ref{105,,test} package can be run as a script to drive Python's regression
test suite, thanks to the @ref{330,,-m} option: @code{python -m test}. Under
the hood, it uses @code{test.regrtest}; the call @code{python -m
test.regrtest} used in previous Python versions still works.  Running the
script by itself automatically starts running all regression tests in the
@ref{105,,test} package. It does this by finding all modules in the package whose
name starts with @code{test_}, importing them, and executing the function
@code{test_main()} if present or loading the tests via
unittest.TestLoader.loadTestsFromModule if @code{test_main} does not exist.  The
names of tests to execute may also be passed to the script. Specifying a single
regression test (@code{python -m test test_spam}) will minimize output and
only print whether the test passed or failed.

Running @ref{105,,test} directly allows what resources are available for
tests to use to be set. You do this by using the @code{-u} command-line
option. Specifying @code{all} as the value for the @code{-u} option enables all
possible resources: @code{python -m test -uall}.
If all but one resource is desired (a more common case), a
comma-separated list of resources that are not desired may be listed after
@code{all}. The command @code{python -m test -uall,-audio,-largefile}
will run @ref{105,,test} with all resources except the @code{audio} and
@code{largefile} resources. For a list of all resources and more command-line
options, run @code{python -m test -h}.

Some other ways to execute the regression tests depend on what platform the
tests are being executed on. On Unix, you can run @code{make test} at the
top-level directory where Python was built. On Windows,
executing @code{rt.bat} from your @code{PCbuild} directory will run all
regression tests.

@node test support --- Utilities for the Python test suite,test support script_helper --- Utilities for the Python execution tests,test --- Python回归测试包,开发工具
@anchor{library/test module-test support}@anchor{106}@anchor{library/test test-support-utilities-for-the-python-test-suite}@anchor{33c7}
@subsection @code{test.support} --- Utilities for the Python test suite


@geindex test.support (模块)

The @ref{106,,test.support} module provides support for Python's regression
test suite.

@cartouche
@quotation 注解 
@ref{106,,test.support} is not a public module.  It is documented here to help
Python developers write tests.  The API of this module is subject to change
without backwards compatibility concerns between releases.
@end quotation
@end cartouche

This module defines the following exceptions:

@geindex TestFailed
@anchor{library/test test support TestFailed}@anchor{33c8}
@deffn {例外} test.support.TestFailed

Exception to be raised when a test fails. This is deprecated in favor of
@ref{11b,,unittest}-based tests and @ref{8f9,,unittest.TestCase}'s assertion
methods.
@end deffn

@geindex ResourceDenied
@anchor{library/test test support ResourceDenied}@anchor{33c9}
@deffn {例外} test.support.ResourceDenied

Subclass of @ref{8fd,,unittest.SkipTest}. Raised when a resource (such as a
network connection) is not available. Raised by the @ref{33ca,,requires()}
function.
@end deffn

The @ref{106,,test.support} module defines the following constants:

@geindex verbose() (在 test.support 模块中)
@anchor{library/test test support verbose}@anchor{33cb}
@deffn {数据} test.support.verbose

@code{True} when verbose output is enabled. Should be checked when more
detailed information is desired about a running test. @emph{verbose} is set by
@code{test.regrtest}.
@end deffn

@geindex is_jython() (在 test.support 模块中)
@anchor{library/test test support is_jython}@anchor{33cc}
@deffn {数据} test.support.is_jython

@code{True} if the running interpreter is Jython.
@end deffn

@geindex is_android() (在 test.support 模块中)
@anchor{library/test test support is_android}@anchor{33cd}
@deffn {数据} test.support.is_android

@code{True} if the system is Android.
@end deffn

@geindex unix_shell() (在 test.support 模块中)
@anchor{library/test test support unix_shell}@anchor{33ce}
@deffn {数据} test.support.unix_shell

Path for shell if not on Windows; otherwise @code{None}.
@end deffn

@geindex FS_NONASCII() (在 test.support 模块中)
@anchor{library/test test support FS_NONASCII}@anchor{33cf}
@deffn {数据} test.support.FS_NONASCII

A non-ASCII character encodable by @ref{4e9,,os.fsencode()}.
@end deffn

@geindex TESTFN() (在 test.support 模块中)
@anchor{library/test test support TESTFN}@anchor{33d0}
@deffn {数据} test.support.TESTFN

Set to a name that is safe to use as the name of a temporary file.  Any
temporary file that is created should be closed and unlinked (removed).
@end deffn

@geindex TESTFN_UNICODE() (在 test.support 模块中)
@anchor{library/test test support TESTFN_UNICODE}@anchor{33d1}
@deffn {数据} test.support.TESTFN_UNICODE

Set to a non-ASCII name for a temporary file.
@end deffn

@geindex TESTFN_ENCODING() (在 test.support 模块中)
@anchor{library/test test support TESTFN_ENCODING}@anchor{33d2}
@deffn {数据} test.support.TESTFN_ENCODING

Set to @ref{4f0,,sys.getfilesystemencoding()}.
@end deffn

@geindex TESTFN_UNENCODABLE() (在 test.support 模块中)
@anchor{library/test test support TESTFN_UNENCODABLE}@anchor{33d3}
@deffn {数据} test.support.TESTFN_UNENCODABLE

Set to a filename (str type) that should not be able to be encoded by file
system encoding in strict mode.  It may be @code{None} if it's not possible to
generate such a filename.
@end deffn

@geindex TESTFN_UNDECODABLE() (在 test.support 模块中)
@anchor{library/test test support TESTFN_UNDECODABLE}@anchor{33d4}
@deffn {数据} test.support.TESTFN_UNDECODABLE

Set to a filename (bytes type) that should not be able to be decoded by
file system encoding in strict mode.  It may be @code{None} if it's not
possible to generate such a filename.
@end deffn

@geindex TESTFN_NONASCII() (在 test.support 模块中)
@anchor{library/test test support TESTFN_NONASCII}@anchor{33d5}
@deffn {数据} test.support.TESTFN_NONASCII

Set to a filename containing the @ref{33cf,,FS_NONASCII} character.
@end deffn

@geindex IPV6_ENABLED() (在 test.support 模块中)
@anchor{library/test test support IPV6_ENABLED}@anchor{33d6}
@deffn {数据} test.support.IPV6_ENABLED

Set to @code{True} if IPV6 is enabled on this host, @code{False} otherwise.
@end deffn

@geindex SAVEDCWD() (在 test.support 模块中)
@anchor{library/test test support SAVEDCWD}@anchor{33d7}
@deffn {数据} test.support.SAVEDCWD

Set to @ref{f6f,,os.getcwd()}.
@end deffn

@geindex PGO() (在 test.support 模块中)
@anchor{library/test test support PGO}@anchor{33d8}
@deffn {数据} test.support.PGO

Set when tests can be skipped when they are not useful for PGO.
@end deffn

@geindex PIPE_MAX_SIZE() (在 test.support 模块中)
@anchor{library/test test support PIPE_MAX_SIZE}@anchor{33d9}
@deffn {数据} test.support.PIPE_MAX_SIZE

A constant that is likely larger than the underlying OS pipe buffer size,
to make writes blocking.
@end deffn

@geindex SOCK_MAX_SIZE() (在 test.support 模块中)
@anchor{library/test test support SOCK_MAX_SIZE}@anchor{33da}
@deffn {数据} test.support.SOCK_MAX_SIZE

A constant that is likely larger than the underlying OS socket buffer size,
to make writes blocking.
@end deffn

@geindex TEST_SUPPORT_DIR() (在 test.support 模块中)
@anchor{library/test test support TEST_SUPPORT_DIR}@anchor{33db}
@deffn {数据} test.support.TEST_SUPPORT_DIR

Set to the top level directory that contains @ref{106,,test.support}.
@end deffn

@geindex TEST_HOME_DIR() (在 test.support 模块中)
@anchor{library/test test support TEST_HOME_DIR}@anchor{33dc}
@deffn {数据} test.support.TEST_HOME_DIR

Set to the top level directory for the test package.
@end deffn

@geindex TEST_DATA_DIR() (在 test.support 模块中)
@anchor{library/test test support TEST_DATA_DIR}@anchor{33dd}
@deffn {数据} test.support.TEST_DATA_DIR

Set to the @code{data} directory within the test package.
@end deffn

@geindex MAX_Py_ssize_t() (在 test.support 模块中)
@anchor{library/test test support MAX_Py_ssize_t}@anchor{33de}
@deffn {数据} test.support.MAX_Py_ssize_t

Set to @ref{b3c,,sys.maxsize} for big memory tests.
@end deffn

@geindex max_memuse() (在 test.support 模块中)
@anchor{library/test test support max_memuse}@anchor{33df}
@deffn {数据} test.support.max_memuse

Set by @ref{33e0,,set_memlimit()} as the memory limit for big memory tests.
Limited by @ref{33de,,MAX_Py_ssize_t}.
@end deffn

@geindex real_max_memuse() (在 test.support 模块中)
@anchor{library/test test support real_max_memuse}@anchor{33e1}
@deffn {数据} test.support.real_max_memuse

Set by @ref{33e0,,set_memlimit()} as the memory limit for big memory tests.  Not
limited by @ref{33de,,MAX_Py_ssize_t}.
@end deffn

@geindex MISSING_C_DOCSTRINGS() (在 test.support 模块中)
@anchor{library/test test support MISSING_C_DOCSTRINGS}@anchor{33e2}
@deffn {数据} test.support.MISSING_C_DOCSTRINGS

Return @code{True} if running on CPython, not on Windows, and configuration
not set with @code{WITH_DOC_STRINGS}.
@end deffn

@geindex HAVE_DOCSTRINGS() (在 test.support 模块中)
@anchor{library/test test support HAVE_DOCSTRINGS}@anchor{33e3}
@deffn {数据} test.support.HAVE_DOCSTRINGS

Check for presence of docstrings.
@end deffn

@geindex TEST_HTTP_URL() (在 test.support 模块中)
@anchor{library/test test support TEST_HTTP_URL}@anchor{33e4}
@deffn {数据} test.support.TEST_HTTP_URL

Define the URL of a dedicated HTTP server for the network tests.
@end deffn

@geindex ALWAYS_EQ() (在 test.support 模块中)
@anchor{library/test test support ALWAYS_EQ}@anchor{33e5}
@deffn {数据} test.support.ALWAYS_EQ

Object that is equal to anything.  Used to test mixed type comparison.
@end deffn

@geindex LARGEST() (在 test.support 模块中)
@anchor{library/test test support LARGEST}@anchor{33e6}
@deffn {数据} test.support.LARGEST

Object that is greater than anything (except itself).
Used to test mixed type comparison.
@end deffn

@geindex SMALLEST() (在 test.support 模块中)
@anchor{library/test test support SMALLEST}@anchor{33e7}
@deffn {数据} test.support.SMALLEST

Object that is less than anything (except itself).
Used to test mixed type comparison.
@end deffn

The @ref{106,,test.support} module defines the following functions:

@geindex forget() (在 test.support 模块中)
@anchor{library/test test support forget}@anchor{33e8}
@deffn {函数} test.support.forget (module_name)

Remove the module named @emph{module_name} from @code{sys.modules} and delete any
byte-compiled files of the module.
@end deffn

@geindex unload() (在 test.support 模块中)
@anchor{library/test test support unload}@anchor{33e9}
@deffn {函数} test.support.unload (name)

Delete @emph{name} from @code{sys.modules}.
@end deffn

@geindex unlink() (在 test.support 模块中)
@anchor{library/test test support unlink}@anchor{33ea}
@deffn {函数} test.support.unlink (filename)

Call @ref{a37,,os.unlink()} on @emph{filename}.  On Windows platforms, this is
wrapped with a wait loop that checks for the existence fo the file.
@end deffn

@geindex rmdir() (在 test.support 模块中)
@anchor{library/test test support rmdir}@anchor{33eb}
@deffn {函数} test.support.rmdir (filename)

Call @ref{a35,,os.rmdir()} on @emph{filename}.  On Windows platforms, this is
wrapped with a wait loop that checks for the existence of the file.
@end deffn

@geindex rmtree() (在 test.support 模块中)
@anchor{library/test test support rmtree}@anchor{33ec}
@deffn {函数} test.support.rmtree (path)

Call @ref{21c,,shutil.rmtree()} on @emph{path} or call @ref{1f2,,os.lstat()} and
@ref{a35,,os.rmdir()} to remove a path and its contents.  On Windows platforms,
this is wrapped with a wait loop that checks for the existence of the files.
@end deffn

@geindex make_legacy_pyc() (在 test.support 模块中)
@anchor{library/test test support make_legacy_pyc}@anchor{33ed}
@deffn {函数} test.support.make_legacy_pyc (source)

Move a 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147}/
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} pyc file to its legacy pyc location and return the file
system path to the legacy pyc file.  The @emph{source} value is the file system
path to the source file.  It does not need to exist, however the PEP
3147/488 pyc file must exist.
@end deffn

@geindex is_resource_enabled() (在 test.support 模块中)
@anchor{library/test test support is_resource_enabled}@anchor{33ee}
@deffn {函数} test.support.is_resource_enabled (resource)

Return @code{True} if @emph{resource} is enabled and available. The list of
available resources is only set when @code{test.regrtest} is executing the
tests.
@end deffn

@geindex python_is_optimized() (在 test.support 模块中)
@anchor{library/test test support python_is_optimized}@anchor{33ef}
@deffn {函数} test.support.python_is_optimized ()

Return @code{True} if Python was not built with @code{-O0} or @code{-Og}.
@end deffn

@geindex with_pymalloc() (在 test.support 模块中)
@anchor{library/test test support with_pymalloc}@anchor{33f0}
@deffn {函数} test.support.with_pymalloc ()

Return @code{_testcapi.WITH_PYMALLOC}.
@end deffn

@geindex requires() (在 test.support 模块中)
@anchor{library/test test support requires}@anchor{33ca}
@deffn {函数} test.support.requires (resource, msg=None)

Raise @ref{33c9,,ResourceDenied} if @emph{resource} is not available. @emph{msg} is the
argument to @ref{33c9,,ResourceDenied} if it is raised. Always returns
@code{True} if called by a function whose @code{__name__} is @code{'__main__'}.
Used when tests are executed by @code{test.regrtest}.
@end deffn

@geindex system_must_validate_cert() (在 test.support 模块中)
@anchor{library/test test support system_must_validate_cert}@anchor{33f1}
@deffn {函数} test.support.system_must_validate_cert (f)

Raise @ref{8fd,,unittest.SkipTest} on TLS certification validation failures.
@end deffn

@geindex sortdict() (在 test.support 模块中)
@anchor{library/test test support sortdict}@anchor{33f2}
@deffn {函数} test.support.sortdict (dict)

Return a repr of @emph{dict} with keys sorted.
@end deffn

@geindex findfile() (在 test.support 模块中)
@anchor{library/test test support findfile}@anchor{33f3}
@deffn {函数} test.support.findfile (filename, subdir=None)

Return the path to the file named @emph{filename}. If no match is found
@emph{filename} is returned. This does not equal a failure since it could be the
path to the file.

Setting @emph{subdir} indicates a relative path to use to find the file
rather than looking directly in the path directories.
@end deffn

@geindex create_empty_file() (在 test.support 模块中)
@anchor{library/test test support create_empty_file}@anchor{33f4}
@deffn {函数} test.support.create_empty_file (filename)

Create an empty file with @emph{filename}.  If it already exists, truncate it.
@end deffn

@geindex fd_count() (在 test.support 模块中)
@anchor{library/test test support fd_count}@anchor{33f5}
@deffn {函数} test.support.fd_count ()

Count the number of open file descriptors.
@end deffn

@geindex match_test() (在 test.support 模块中)
@anchor{library/test test support match_test}@anchor{33f6}
@deffn {函数} test.support.match_test (test)

Match @emph{test} to patterns set in @ref{33f7,,set_match_tests()}.
@end deffn

@geindex set_match_tests() (在 test.support 模块中)
@anchor{library/test test support set_match_tests}@anchor{33f7}
@deffn {函数} test.support.set_match_tests (patterns)

Define match test with regular expression @emph{patterns}.
@end deffn

@geindex run_unittest() (在 test.support 模块中)
@anchor{library/test test support run_unittest}@anchor{fd6}
@deffn {函数} test.support.run_unittest (*classes)

Execute @ref{8f9,,unittest.TestCase} subclasses passed to the function. The
function scans the classes for methods starting with the prefix @code{test_}
and executes the tests individually.

It is also legal to pass strings as parameters; these should be keys in
@code{sys.modules}. Each associated module will be scanned by
@code{unittest.TestLoader.loadTestsFromModule()}. This is usually seen in the
following @code{test_main()} function:

@example
def test_main():
    support.run_unittest(__name__)
@end example

This will run all tests defined in the named module.
@end deffn

@geindex run_doctest() (在 test.support 模块中)
@anchor{library/test test support run_doctest}@anchor{33f8}
@deffn {函数} test.support.run_doctest (module, verbosity=None, optionflags=0)

Run @ref{dc9,,doctest.testmod()} on the given @emph{module}.  Return
@code{(failure_count, test_count)}.

If @emph{verbosity} is @code{None}, @ref{dc9,,doctest.testmod()} is run with verbosity
set to @ref{33cb,,verbose}.  Otherwise, it is run with verbosity set to
@code{None}.  @emph{optionflags} is passed as @code{optionflags} to
@ref{dc9,,doctest.testmod()}.
@end deffn

@geindex setswitchinterval() (在 test.support 模块中)
@anchor{library/test test support setswitchinterval}@anchor{33f9}
@deffn {函数} test.support.setswitchinterval (interval)

Set the @ref{be4,,sys.setswitchinterval()} to the given @emph{interval}.  Defines
a minimum interval for Android systems to prevent the system from hanging.
@end deffn

@geindex check_impl_detail() (在 test.support 模块中)
@anchor{library/test test support check_impl_detail}@anchor{33fa}
@deffn {函数} test.support.check_impl_detail (**guards)

Use this check to guard CPython's implementation-specific tests or to
run them only on the implementations guarded by the arguments:

@example
check_impl_detail()               # Only on CPython (default).
check_impl_detail(jython=True)    # Only on Jython.
check_impl_detail(cpython=False)  # Everywhere except CPython.
@end example
@end deffn

@geindex check_warnings() (在 test.support 模块中)
@anchor{library/test test support check_warnings}@anchor{33fb}
@deffn {函数} test.support.check_warnings (*filters, quiet=True)

A convenience wrapper for @ref{33fc,,warnings.catch_warnings()} that makes it
easier to test that a warning was correctly raised.  It is approximately
equivalent to calling @code{warnings.catch_warnings(record=True)} with
@ref{33fd,,warnings.simplefilter()} set to @code{always} and with the option to
automatically validate the results that are recorded.

@code{check_warnings} accepts 2-tuples of the form @code{("message regexp",
WarningCategory)} as positional arguments. If one or more @emph{filters} are
provided, or if the optional keyword argument @emph{quiet} is @code{False},
it checks to make sure the warnings are as expected:  each specified filter
must match at least one of the warnings raised by the enclosed code or the
test fails, and if any warnings are raised that do not match any of the
specified filters the test fails.  To disable the first of these checks,
set @emph{quiet} to @code{True}.

If no arguments are specified, it defaults to:

@example
check_warnings(("", Warning), quiet=True)
@end example

In this case all warnings are caught and no errors are raised.

On entry to the context manager, a @code{WarningRecorder} instance is
returned. The underlying warnings list from
@ref{33fc,,catch_warnings()} is available via the recorder object's
@ref{126,,warnings} attribute.  As a convenience, the attributes of the object
representing the most recent warning can also be accessed directly through
the recorder object (see example below).  If no warning has been raised,
then any of the attributes that would otherwise be expected on an object
representing a warning will return @code{None}.

The recorder object also has a @code{reset()} method, which clears the
warnings list.

The context manager is designed to be used like this:

@example
with check_warnings(("assertion is always true", SyntaxWarning),
                    ("", UserWarning)):
    exec('assert(False, "Hey!")')
    warnings.warn(UserWarning("Hide me!"))
@end example

In this case if either warning was not raised, or some other warning was
raised, @ref{33fb,,check_warnings()} would raise an error.

When a test needs to look more deeply into the warnings, rather than
just checking whether or not they occurred, code like this can be used:

@example
with check_warnings(quiet=True) as w:
    warnings.warn("foo")
    assert str(w.args[0]) == "foo"
    warnings.warn("bar")
    assert str(w.args[0]) == "bar"
    assert str(w.warnings[0].args[0]) == "foo"
    assert str(w.warnings[1].args[0]) == "bar"
    w.reset()
    assert len(w.warnings) == 0
@end example

Here all warnings will be caught, and the test code tests the captured
warnings directly.


在 3.2 版更改: New optional arguments @emph{filters} and @emph{quiet}.

@end deffn

@geindex check_no_resource_warning() (在 test.support 模块中)
@anchor{library/test test support check_no_resource_warning}@anchor{33fe}
@deffn {函数} test.support.check_no_resource_warning (testcase)

Context manager to check that no @ref{4ca,,ResourceWarning} was raised.  You
must remove the object which may emit @ref{4ca,,ResourceWarning} before the
end of the context manager.
@end deffn

@geindex set_memlimit() (在 test.support 模块中)
@anchor{library/test test support set_memlimit}@anchor{33e0}
@deffn {函数} test.support.set_memlimit (limit)

Set the values for @ref{33df,,max_memuse} and @ref{33e1,,real_max_memuse} for big
memory tests.
@end deffn

@geindex record_original_stdout() (在 test.support 模块中)
@anchor{library/test test support record_original_stdout}@anchor{33ff}
@deffn {函数} test.support.record_original_stdout (stdout)

Store the value from @emph{stdout}.  It is meant to hold the stdout at the
time the regrtest began.
@end deffn

@geindex get_original_stdout() (在 test.support 模块中)
@anchor{library/test test support get_original_stdout}@anchor{3400}
@deffn {函数} test.support.get_original_stdout ()

Return the original stdout set by @ref{33ff,,record_original_stdout()} or
@code{sys.stdout} if it's not set.
@end deffn

@geindex strip_python_strerr() (在 test.support 模块中)
@anchor{library/test test support strip_python_strerr}@anchor{3401}
@deffn {函数} test.support.strip_python_strerr (stderr)

Strip the @emph{stderr} of a Python process from potential debug output
emitted by the interpreter.  This will typically be run on the result of
@ref{23ee,,subprocess.Popen.communicate()}.
@end deffn

@geindex args_from_interpreter_flags() (在 test.support 模块中)
@anchor{library/test test support args_from_interpreter_flags}@anchor{3402}
@deffn {函数} test.support.args_from_interpreter_flags ()

Return a list of command line arguments reproducing the current settings
in @code{sys.flags} and @code{sys.warnoptions}.
@end deffn

@geindex optim_args_from_interpreter_flags() (在 test.support 模块中)
@anchor{library/test test support optim_args_from_interpreter_flags}@anchor{3403}
@deffn {函数} test.support.optim_args_from_interpreter_flags ()

Return a list of command line arguments reproducing the current
optimization settings in @code{sys.flags}.
@end deffn

@geindex captured_stdin() (在 test.support 模块中)
@geindex captured_stdout() (在 test.support 模块中)
@geindex captured_stderr() (在 test.support 模块中)
@anchor{library/test test support captured_stdin}@anchor{3404}
@deffn {函数} test.support.captured_stdin ()
@anchor{library/test test support captured_stdout}@anchor{3405}
@deffnx {函数} test.support.captured_stdout ()
@anchor{library/test test support captured_stderr}@anchor{f62}
@deffnx {函数} test.support.captured_stderr ()

A context managers that temporarily replaces the named stream with
@ref{827,,io.StringIO} object.

Example use with output streams:

@example
with captured_stdout() as stdout, captured_stderr() as stderr:
    print("hello")
    print("error", file=sys.stderr)
assert stdout.getvalue() == "hello\n"
assert stderr.getvalue() == "error\n"
@end example

Example use with input stream:

@example
with captured_stdin() as stdin:
    stdin.write('hello\n')
    stdin.seek(0)
    # call test code that consumes from sys.stdin
    captured = input()
self.assertEqual(captured, "hello")
@end example
@end deffn

@geindex temp_dir() (在 test.support 模块中)
@anchor{library/test test support temp_dir}@anchor{3406}
@deffn {函数} test.support.temp_dir (path=None, quiet=False)

A context manager that creates a temporary directory at @emph{path} and
yields the directory.

If @emph{path} is @code{None}, the temporary directory is created using
@ref{1bfb,,tempfile.mkdtemp()}.  If @emph{quiet} is @code{False}, the context manager
raises an exception on error.  Otherwise, if @emph{path} is specified and
cannot be created, only a warning is issued.
@end deffn

@geindex change_cwd() (在 test.support 模块中)
@anchor{library/test test support change_cwd}@anchor{3407}
@deffn {函数} test.support.change_cwd (path, quiet=False)

A context manager that temporarily changes the current working
directory to @emph{path} and yields the directory.

If @emph{quiet} is @code{False}, the context manager raises an exception
on error.  Otherwise, it issues only a warning and keeps the current
working directory the same.
@end deffn

@geindex temp_cwd() (在 test.support 模块中)
@anchor{library/test test support temp_cwd}@anchor{3408}
@deffn {函数} test.support.temp_cwd (name='tempcwd', quiet=False)

A context manager that temporarily creates a new directory and
changes the current working directory (CWD).

The context manager creates a temporary directory in the current
directory with name @emph{name} before temporarily changing the current
working directory.  If @emph{name} is @code{None}, the temporary directory is
created using @ref{1bfb,,tempfile.mkdtemp()}.

If @emph{quiet} is @code{False} and it is not possible to create or change
the CWD, an error is raised.  Otherwise, only a warning is raised
and the original CWD is used.
@end deffn

@geindex temp_umask() (在 test.support 模块中)
@anchor{library/test test support temp_umask}@anchor{3409}
@deffn {函数} test.support.temp_umask (umask)

A context manager that temporarily sets the process umask.
@end deffn

@geindex transient_internet() (在 test.support 模块中)
@anchor{library/test test support transient_internet}@anchor{340a}
@deffn {函数} test.support.transient_internet (resource_name, *, timeout=30.0, errnos=())

A context manager that raises @ref{33c9,,ResourceDenied} when various issues
with the internet connection manifest themselves as exceptions.
@end deffn

@geindex disable_faulthandler() (在 test.support 模块中)
@anchor{library/test test support disable_faulthandler}@anchor{340b}
@deffn {函数} test.support.disable_faulthandler ()

A context manager that replaces @code{sys.stderr} with @code{sys.__stderr__}.
@end deffn

@geindex gc_collect() (在 test.support 模块中)
@anchor{library/test test support gc_collect}@anchor{340c}
@deffn {函数} test.support.gc_collect ()

Force as many objects as possible to be collected.  This is needed because
timely deallocation is not guaranteed by the garbage collector.  This means
that @code{__del__} methods may be called later than expected and weakrefs
may remain alive for longer than expected.
@end deffn

@geindex disable_gc() (在 test.support 模块中)
@anchor{library/test test support disable_gc}@anchor{340d}
@deffn {函数} test.support.disable_gc ()

A context manager that disables the garbage collector upon entry and
reenables it upon exit.
@end deffn

@geindex swap_attr() (在 test.support 模块中)
@anchor{library/test test support swap_attr}@anchor{340e}
@deffn {函数} test.support.swap_attr (obj, attr, new_val)

Context manager to swap out an attribute with a new object.

用法:

@example
with swap_attr(obj, "attr", 5):
    ...
@end example

This will set @code{obj.attr} to 5 for the duration of the @code{with} block,
restoring the old value at the end of the block.  If @code{attr} doesn't
exist on @code{obj}, it will be created and then deleted at the end of the
block.

The old value (or @code{None} if it doesn't exist) will be assigned to the
target of the "as" clause, if there is one.
@end deffn

@geindex swap_item() (在 test.support 模块中)
@anchor{library/test test support swap_item}@anchor{340f}
@deffn {函数} test.support.swap_item (obj, attr, new_val)

Context manager to swap out an item with a new object.

用法:

@example
with swap_item(obj, "item", 5):
    ...
@end example

This will set @code{obj["item"]} to 5 for the duration of the @code{with} block,
restoring the old value at the end of the block. If @code{item} doesn't
exist on @code{obj}, it will be created and then deleted at the end of the
block.

The old value (or @code{None} if it doesn't exist) will be assigned to the
target of the "as" clause, if there is one.
@end deffn

@geindex wait_threads_exit() (在 test.support 模块中)
@anchor{library/test test support wait_threads_exit}@anchor{3410}
@deffn {函数} test.support.wait_threads_exit (timeout=60.0)

Context manager to wait until all threads created in the @code{with} statement
exit.
@end deffn

@geindex start_threads() (在 test.support 模块中)
@anchor{library/test test support start_threads}@anchor{3411}
@deffn {函数} test.support.start_threads (threads, unlock=None)

Context manager to start @emph{threads}.  It attempts to join the threads upon
exit.
@end deffn

@geindex calcobjsize() (在 test.support 模块中)
@anchor{library/test test support calcobjsize}@anchor{3412}
@deffn {函数} test.support.calcobjsize (fmt)

Return @ref{17a5,,struct.calcsize()} for @code{nP@{fmt@}0n} or, if @code{gettotalrefcount}
exists, @code{2PnP@{fmt@}0P}.
@end deffn

@geindex calcvobjsize() (在 test.support 模块中)
@anchor{library/test test support calcvobjsize}@anchor{3413}
@deffn {函数} test.support.calcvobjsize (fmt)

Return @ref{17a5,,struct.calcsize()} for @code{nPn@{fmt@}0n} or, if @code{gettotalrefcount}
exists, @code{2PnPn@{fmt@}0P}.
@end deffn

@geindex checksizeof() (在 test.support 模块中)
@anchor{library/test test support checksizeof}@anchor{3414}
@deffn {函数} test.support.checksizeof (test, o, size)

For testcase @emph{test}, assert that the @code{sys.getsizeof} for @emph{o} plus the GC
header size equals @emph{size}.
@end deffn

@geindex can_symlink() (在 test.support 模块中)
@anchor{library/test test support can_symlink}@anchor{3415}
@deffn {函数} test.support.can_symlink ()

Return @code{True} if the OS supports symbolic links, @code{False}
otherwise.
@end deffn

@geindex can_xattr() (在 test.support 模块中)
@anchor{library/test test support can_xattr}@anchor{3416}
@deffn {函数} test.support.can_xattr ()

Return @code{True} if the OS supports xattr, @code{False}
otherwise.
@end deffn

@geindex skip_unless_symlink() (在 test.support 模块中)
@anchor{library/test test support skip_unless_symlink}@anchor{3417}
@deffn {函数} @@test.support.skip_unless_symlink

A decorator for running tests that require support for symbolic links.
@end deffn

@geindex skip_unless_xattr() (在 test.support 模块中)
@anchor{library/test test support skip_unless_xattr}@anchor{3418}
@deffn {函数} @@test.support.skip_unless_xattr

A decorator for running tests that require support for xattr.
@end deffn

@geindex skip_unless_bind_unix_socket() (在 test.support 模块中)
@anchor{library/test test support skip_unless_bind_unix_socket}@anchor{3419}
@deffn {函数} @@test.support.skip_unless_bind_unix_socket

A decorator for running tests that require a functional bind() for Unix
sockets.
@end deffn

@geindex anticipate_failure() (在 test.support 模块中)
@anchor{library/test test support anticipate_failure}@anchor{341a}
@deffn {函数} @@test.support.anticipate_failure (condition)

A decorator to conditionally mark tests with
@ref{32d6,,unittest.expectedFailure()}. Any use of this decorator should
have an associated comment identifying the relevant tracker issue.
@end deffn

@geindex run_with_locale() (在 test.support 模块中)
@anchor{library/test test support run_with_locale}@anchor{341b}
@deffn {函数} @@test.support.run_with_locale (catstr, *locales)

A decorator for running a function in a different locale, correctly
resetting it after it has finished.  @emph{catstr} is the locale category as
a string (for example @code{"LC_ALL"}).  The @emph{locales} passed will be tried
sequentially, and the first valid locale will be used.
@end deffn

@geindex run_with_tz() (在 test.support 模块中)
@anchor{library/test test support run_with_tz}@anchor{341c}
@deffn {函数} @@test.support.run_with_tz (tz)

A decorator for running a function in a specific timezone, correctly
resetting it after it has finished.
@end deffn

@geindex requires_freebsd_version() (在 test.support 模块中)
@anchor{library/test test support requires_freebsd_version}@anchor{341d}
@deffn {函数} @@test.support.requires_freebsd_version (*min_version)

Decorator for the minimum version when running test on FreeBSD.  If the
FreeBSD version is less than the minimum, raise @ref{8fd,,unittest.SkipTest}.
@end deffn

@geindex requires_linux_version() (在 test.support 模块中)
@anchor{library/test test support requires_linux_version}@anchor{341e}
@deffn {函数} @@test.support.requires_linux_version (*min_version)

Decorator for the minimum version when running test on Linux.  If the
Linux version is less than the minimum, raise @ref{8fd,,unittest.SkipTest}.
@end deffn

@geindex requires_mac_version() (在 test.support 模块中)
@anchor{library/test test support requires_mac_version}@anchor{341f}
@deffn {函数} @@test.support.requires_mac_version (*min_version)

Decorator for the minimum version when running test on Mac OS X.  If the
MAC OS X version is less than the minimum, raise @ref{8fd,,unittest.SkipTest}.
@end deffn

@geindex requires_IEEE_754() (在 test.support 模块中)
@anchor{library/test test support requires_IEEE_754}@anchor{3420}
@deffn {函数} @@test.support.requires_IEEE_754

Decorator for skipping tests on non-IEEE 754 platforms.
@end deffn

@geindex requires_zlib() (在 test.support 模块中)
@anchor{library/test test support requires_zlib}@anchor{3421}
@deffn {函数} @@test.support.requires_zlib

Decorator for skipping tests if @ref{144,,zlib} doesn't exist.
@end deffn

@geindex requires_gzip() (在 test.support 模块中)
@anchor{library/test test support requires_gzip}@anchor{3422}
@deffn {函数} @@test.support.requires_gzip

Decorator for skipping tests if @ref{8c,,gzip} doesn't exist.
@end deffn

@geindex requires_bz2() (在 test.support 模块中)
@anchor{library/test test support requires_bz2}@anchor{3423}
@deffn {函数} @@test.support.requires_bz2

Decorator for skipping tests if @ref{14,,bz2} doesn't exist.
@end deffn

@geindex requires_lzma() (在 test.support 模块中)
@anchor{library/test test support requires_lzma}@anchor{3424}
@deffn {函数} @@test.support.requires_lzma

Decorator for skipping tests if @ref{ad,,lzma} doesn't exist.
@end deffn

@geindex requires_resource() (在 test.support 模块中)
@anchor{library/test test support requires_resource}@anchor{3425}
@deffn {函数} @@test.support.requires_resource (resource)

Decorator for skipping tests if @emph{resource} is not available.
@end deffn

@geindex requires_docstrings() (在 test.support 模块中)
@anchor{library/test test support requires_docstrings}@anchor{3426}
@deffn {函数} @@test.support.requires_docstrings

Decorator for only running the test if @ref{33e3,,HAVE_DOCSTRINGS}.
@end deffn

@geindex cpython_only() (在 test.support 模块中)
@anchor{library/test test support cpython_only}@anchor{3427}
@deffn {函数} @@test.support.cpython_only (test)

Decorator for tests only applicable to CPython.
@end deffn

@geindex impl_detail() (在 test.support 模块中)
@anchor{library/test test support impl_detail}@anchor{3428}
@deffn {函数} @@test.support.impl_detail (msg=None, **guards)

Decorator for invoking @ref{33fa,,check_impl_detail()} on @emph{guards}.  If that
returns @code{False}, then uses @emph{msg} as the reason for skipping the test.
@end deffn

@geindex no_tracing() (在 test.support 模块中)
@anchor{library/test test support no_tracing}@anchor{3429}
@deffn {函数} @@test.support.no_tracing (func)

Decorator to temporarily turn off tracing for the duration of the test.
@end deffn

@geindex refcount_test() (在 test.support 模块中)
@anchor{library/test test support refcount_test}@anchor{342a}
@deffn {函数} @@test.support.refcount_test (test)

Decorator for tests which involve reference counting.  The decorator does
not run the test if it is not run by CPython.  Any trace function is unset
for the duration of the test to prevent unexpected refcounts caused by
the trace function.
@end deffn

@geindex reap_threads() (在 test.support 模块中)
@anchor{library/test test support reap_threads}@anchor{342b}
@deffn {函数} @@test.support.reap_threads (func)

Decorator to ensure the threads are cleaned up even if the test fails.
@end deffn

@geindex bigmemtest() (在 test.support 模块中)
@anchor{library/test test support bigmemtest}@anchor{342c}
@deffn {函数} @@test.support.bigmemtest (size, memuse, dry_run=True)

Decorator for bigmem tests.

@emph{size} is a requested size for the test (in arbitrary, test-interpreted
units.)  @emph{memuse} is the number of bytes per unit for the test, or a good
estimate of it.  For example, a test that needs two byte buffers, of 4 GiB
each, could be decorated with @code{@@bigmemtest(size=_4G, memuse=2)}.

The @emph{size} argument is normally passed to the decorated test method as an
extra argument.  If @emph{dry_run} is @code{True}, the value passed to the test
method may be less than the requested value.  If @emph{dry_run} is @code{False}, it
means the test doesn't support dummy runs when @code{-M} is not specified.
@end deffn

@geindex bigaddrspacetest() (在 test.support 模块中)
@anchor{library/test test support bigaddrspacetest}@anchor{342d}
@deffn {函数} @@test.support.bigaddrspacetest (f)

Decorator for tests that fill the address space.  @emph{f} is the function to
wrap.
@end deffn

@geindex make_bad_fd() (在 test.support 模块中)
@anchor{library/test test support make_bad_fd}@anchor{342e}
@deffn {函数} test.support.make_bad_fd ()

Create an invalid file descriptor by opening and closing a temporary file,
and returning its descriptor.
@end deffn

@geindex check_syntax_error() (在 test.support 模块中)
@anchor{library/test test support check_syntax_error}@anchor{342f}
@deffn {函数} test.support.check_syntax_error (testcase, statement, errtext='@w{'}, *, lineno=None, offset=None)

Test for syntax errors in @emph{statement} by attempting to compile @emph{statement}.
@emph{testcase} is the @ref{11b,,unittest} instance for the test.  @emph{errtext} is the
regular expression which should match the string representation of the
raised @ref{452,,SyntaxError}.  If @emph{lineno} is not @code{None}, compares to
the line of the exception.  If @emph{offset} is not @code{None}, compares to
the offset of the exception.
@end deffn

@geindex check_syntax_warning() (在 test.support 模块中)
@anchor{library/test test support check_syntax_warning}@anchor{f94}
@deffn {函数} test.support.check_syntax_warning (testcase, statement, errtext='@w{'}, *, lineno=1, offset=None)

Test for syntax warning in @emph{statement} by attempting to compile @emph{statement}.
Test also that the @ref{191,,SyntaxWarning} is emitted only once, and that it
will be converted to a @ref{452,,SyntaxError} when turned into error.
@emph{testcase} is the @ref{11b,,unittest} instance for the test.  @emph{errtext} is the
regular expression which should match the string representation of the
emitted @ref{191,,SyntaxWarning} and raised @ref{452,,SyntaxError}.  If @emph{lineno}
is not @code{None}, compares to the line of the warning and exception.
If @emph{offset} is not @code{None}, compares to the offset of the exception.


3.8 新版功能.

@end deffn

@geindex open_urlresource() (在 test.support 模块中)
@anchor{library/test test support open_urlresource}@anchor{3430}
@deffn {函数} test.support.open_urlresource (url, *args, **kw)

Open @emph{url}.  If open fails, raises @ref{33c8,,TestFailed}.
@end deffn

@geindex import_module() (在 test.support 模块中)
@anchor{library/test test support import_module}@anchor{3431}
@deffn {函数} test.support.import_module (name, deprecated=False, *, required_on())

This function imports and returns the named module. Unlike a normal
import, this function raises @ref{8fd,,unittest.SkipTest} if the module
cannot be imported.

Module and package deprecation messages are suppressed during this import
if @emph{deprecated} is @code{True}.  If a module is required on a platform but
optional for others, set @emph{required_on} to an iterable of platform prefixes
which will be compared against @ref{2b1,,sys.platform}.


3.1 新版功能.

@end deffn

@geindex import_fresh_module() (在 test.support 模块中)
@anchor{library/test test support import_fresh_module}@anchor{3432}
@deffn {函数} test.support.import_fresh_module (name, fresh=(), blocked=(), deprecated=False)

This function imports and returns a fresh copy of the named Python module
by removing the named module from @code{sys.modules} before doing the import.
Note that unlike @code{reload()}, the original module is not affected by
this operation.

@emph{fresh} is an iterable of additional module names that are also removed
from the @code{sys.modules} cache before doing the import.

@emph{blocked} is an iterable of module names that are replaced with @code{None}
in the module cache during the import to ensure that attempts to import
them raise @ref{32d,,ImportError}.

The named module and any modules named in the @emph{fresh} and @emph{blocked}
parameters are saved before starting the import and then reinserted into
@code{sys.modules} when the fresh import is complete.

Module and package deprecation messages are suppressed during this import
if @emph{deprecated} is @code{True}.

This function will raise @ref{32d,,ImportError} if the named module cannot be
imported.

Example use:

@example
# Get copies of the warnings module for testing without affecting the
# version being used by the rest of the test suite. One copy uses the
# C implementation, the other is forced to use the pure Python fallback
# implementation
py_warnings = import_fresh_module('warnings', blocked=['_warnings'])
c_warnings = import_fresh_module('warnings', fresh=['_warnings'])
@end example


3.1 新版功能.

@end deffn

@geindex modules_setup() (在 test.support 模块中)
@anchor{library/test test support modules_setup}@anchor{3433}
@deffn {函数} test.support.modules_setup ()

Return a copy of @ref{eb5,,sys.modules}.
@end deffn

@geindex modules_cleanup() (在 test.support 模块中)
@anchor{library/test test support modules_cleanup}@anchor{3434}
@deffn {函数} test.support.modules_cleanup (oldmodules)

Remove modules except for @emph{oldmodules} and @code{encodings} in order to
preserve internal cache.
@end deffn

@geindex threading_setup() (在 test.support 模块中)
@anchor{library/test test support threading_setup}@anchor{3435}
@deffn {函数} test.support.threading_setup ()

Return current thread count and copy of dangling threads.
@end deffn

@geindex threading_cleanup() (在 test.support 模块中)
@anchor{library/test test support threading_cleanup}@anchor{3436}
@deffn {函数} test.support.threading_cleanup (*original_values)

Cleanup up threads not specified in @emph{original_values}.  Designed to emit
a warning if a test leaves running threads in the background.
@end deffn

@geindex join_thread() (在 test.support 模块中)
@anchor{library/test test support join_thread}@anchor{3437}
@deffn {函数} test.support.join_thread (thread, timeout=30.0)

Join a @emph{thread} within @emph{timeout}.  Raise an @ref{fc1,,AssertionError} if thread
is still alive after @emph{timeout} seconds.
@end deffn

@geindex reap_children() (在 test.support 模块中)
@anchor{library/test test support reap_children}@anchor{3438}
@deffn {函数} test.support.reap_children ()

Use this at the end of @code{test_main} whenever sub-processes are started.
This will help ensure that no extra children (zombies) stick around to
hog resources and create problems when looking for refleaks.
@end deffn

@geindex get_attribute() (在 test.support 模块中)
@anchor{library/test test support get_attribute}@anchor{3439}
@deffn {函数} test.support.get_attribute (obj, name)

Get an attribute, raising @ref{8fd,,unittest.SkipTest} if @ref{393,,AttributeError}
is raised.
@end deffn

@geindex bind_port() (在 test.support 模块中)
@anchor{library/test test support bind_port}@anchor{343a}
@deffn {函数} test.support.bind_port (sock, host=HOST)

Bind the socket to a free port and return the port number.  Relies on
ephemeral ports in order to ensure we are using an unbound port.  This is
important as many tests may be running simultaneously, especially in a
buildbot environment.  This method raises an exception if the
@code{sock.family} is @ref{2545,,AF_INET} and @code{sock.type} is
@ref{c83,,SOCK_STREAM}, and the socket has
@code{SO_REUSEADDR} or @code{SO_REUSEPORT} set on it.
Tests should never set these socket options for TCP/IP sockets.
The only case for setting these options is testing multicasting via
multiple UDP sockets.

Additionally, if the @code{SO_EXCLUSIVEADDRUSE} socket option is
available (i.e. on Windows), it will be set on the socket.  This will
prevent anyone else from binding to our host/port for the duration of the
test.
@end deffn

@geindex bind_unix_socket() (在 test.support 模块中)
@anchor{library/test test support bind_unix_socket}@anchor{343b}
@deffn {函数} test.support.bind_unix_socket (sock, addr)

Bind a unix socket, raising @ref{8fd,,unittest.SkipTest} if
@ref{5fa,,PermissionError} is raised.
@end deffn

@geindex catch_threading_exception() (在 test.support 模块中)
@anchor{library/test test support catch_threading_exception}@anchor{f32}
@deffn {函数} test.support.catch_threading_exception ()

Context manager catching @ref{234,,threading.Thread} exception using
@ref{231,,threading.excepthook()}.

Attributes set when an exception is catched:


@itemize *

@item 
@code{exc_type}

@item 
@code{exc_value}

@item 
@code{exc_traceback}

@item 
@code{thread}
@end itemize

See @ref{231,,threading.excepthook()} documentation.

These attributes are deleted at the context manager exit.

用法:

@example
with support.catch_threading_exception() as cm:
    # code spawning a thread which raises an exception
    ...

    # check the thread exception, use cm attributes:
    # exc_type, exc_value, exc_traceback, thread
    ...

# exc_type, exc_value, exc_traceback, thread attributes of cm no longer
# exists at this point
# (to avoid reference cycles)
@end example


3.8 新版功能.

@end deffn

@geindex catch_unraisable_exception() (在 test.support 模块中)
@anchor{library/test test support catch_unraisable_exception}@anchor{f41}
@deffn {函数} test.support.catch_unraisable_exception ()

Context manager catching unraisable exception using
@ref{22d,,sys.unraisablehook()}.

Storing the exception value (@code{cm.unraisable.exc_value}) creates a
reference cycle. The reference cycle is broken explicitly when the context
manager exits.

Storing the object (@code{cm.unraisable.object}) can resurrect it if it is set
to an object which is being finalized. Exiting the context manager clears
the stored object.

用法:

@example
with support.catch_unraisable_exception() as cm:
    # code creating an "unraisable exception"
    ...

    # check the unraisable exception: use cm.unraisable
    ...

# cm.unraisable attribute no longer exists at this point
# (to break a reference cycle)
@end example


3.8 新版功能.

@end deffn

@geindex find_unused_port() (在 test.support 模块中)
@anchor{library/test test support find_unused_port}@anchor{343c}
@deffn {函数} test.support.find_unused_port (family=socket.AF_INET, socktype=socket.SOCK_STREAM)

Returns an unused port that should be suitable for binding.  This is
achieved by creating a temporary socket with the same family and type as
the @code{sock} parameter (default is @ref{2545,,AF_INET},
@ref{c83,,SOCK_STREAM}),
and binding it to the specified host address (defaults to @code{0.0.0.0})
with the port set to 0, eliciting an unused ephemeral port from the OS.
The temporary socket is then closed and deleted, and the ephemeral port is
returned.

Either this method or @ref{343a,,bind_port()} should be used for any tests
where a server socket needs to be bound to a particular port for the
duration of the test.
Which one to use depends on whether the calling code is creating a Python
socket, or if an unused port needs to be provided in a constructor
or passed to an external program (i.e. the @code{-accept} argument to
openssl's s_server mode).  Always prefer @ref{343a,,bind_port()} over
@ref{343c,,find_unused_port()} where possible.  Using a hard coded port is
discouraged since it can make multiple instances of the test impossible to
run simultaneously, which is a problem for buildbots.
@end deffn

@geindex load_package_tests() (在 test.support 模块中)
@anchor{library/test test support load_package_tests}@anchor{343d}
@deffn {函数} test.support.load_package_tests (pkg_dir, loader, standard_tests, pattern)

Generic implementation of the @ref{11b,,unittest} @code{load_tests} protocol for
use in test packages.  @emph{pkg_dir} is the root directory of the package;
@emph{loader}, @emph{standard_tests}, and @emph{pattern} are the arguments expected by
@code{load_tests}.  In simple cases, the test package's @code{__init__.py}
can be the following:

@example
import os
from test.support import load_package_tests

def load_tests(*args):
    return load_package_tests(os.path.dirname(__file__), *args)
@end example
@end deffn

@geindex fs_is_case_insensitive() (在 test.support 模块中)
@anchor{library/test test support fs_is_case_insensitive}@anchor{343e}
@deffn {函数} test.support.fs_is_case_insensitive (directory)

Return @code{True} if the file system for @emph{directory} is case-insensitive.
@end deffn

@geindex detect_api_mismatch() (在 test.support 模块中)
@anchor{library/test test support detect_api_mismatch}@anchor{343f}
@deffn {函数} test.support.detect_api_mismatch (ref_api, other_api, *, ignore=())

Returns the set of attributes, functions or methods of @emph{ref_api} not
found on @emph{other_api}, except for a defined list of items to be
ignored in this check specified in @emph{ignore}.

By default this skips private attributes beginning with '_' but
includes all magic methods, i.e. those starting and ending in '__'.


3.5 新版功能.

@end deffn

@geindex patch() (在 test.support 模块中)
@anchor{library/test test support patch}@anchor{3440}
@deffn {函数} test.support.patch (test_instance, object_to_patch, attr_name, new_value)

Override @emph{object_to_patch.attr_name} with @emph{new_value}.  Also add
cleanup procedure to @emph{test_instance} to restore @emph{object_to_patch} for
@emph{attr_name}.  The @emph{attr_name} should be a valid attribute for
@emph{object_to_patch}.
@end deffn

@geindex run_in_subinterp() (在 test.support 模块中)
@anchor{library/test test support run_in_subinterp}@anchor{3441}
@deffn {函数} test.support.run_in_subinterp (code)

Run @emph{code} in subinterpreter.  Raise @ref{8fd,,unittest.SkipTest} if
@ref{114,,tracemalloc} is enabled.
@end deffn

@geindex check_free_after_iterating() (在 test.support 模块中)
@anchor{library/test test support check_free_after_iterating}@anchor{3442}
@deffn {函数} test.support.check_free_after_iterating (test, iter, cls, args=())

Assert that @emph{iter} is deallocated after iterating.
@end deffn

@geindex missing_compiler_executable() (在 test.support 模块中)
@anchor{library/test test support missing_compiler_executable}@anchor{3443}
@deffn {函数} test.support.missing_compiler_executable (cmd_names=[])

Check for the existence of the compiler executables whose names are listed
in @emph{cmd_names} or all the compiler executables when @emph{cmd_names} is empty
and return the first missing executable or @code{None} when none is found
missing.
@end deffn

@geindex check__all__() (在 test.support 模块中)
@anchor{library/test test support check__all__}@anchor{3444}
@deffn {函数} test.support.check__all__ (test_case, module, name_of_module=None, extra=(), blacklist=())

Assert that the @code{__all__} variable of @emph{module} contains all public names.

The module's public names (its API) are detected automatically
based on whether they match the public name convention and were defined in
@emph{module}.

The @emph{name_of_module} argument can specify (as a string or tuple thereof) what
module(s) an API could be defined in order to be detected as a public
API. One case for this is when @emph{module} imports part of its public API from
other modules, possibly a C backend (like @code{csv} and its @code{_csv}).

The @emph{extra} argument can be a set of names that wouldn't otherwise be automatically
detected as "public", like objects without a proper @code{__module__}
attribute. If provided, it will be added to the automatically detected ones.

The @emph{blacklist} argument can be a set of names that must not be treated as part of
the public API even though their names indicate otherwise.

Example use:

@example
import bar
import foo
import unittest
from test import support

class MiscTestCase(unittest.TestCase):
    def test__all__(self):
        support.check__all__(self, foo)

class OtherTestCase(unittest.TestCase):
    def test__all__(self):
        extra = @{'BAR_CONST', 'FOO_CONST'@}
        blacklist = @{'baz'@}  # Undocumented name.
        # bar imports part of its API from _bar.
        support.check__all__(self, bar, ('bar', '_bar'),
                             extra=extra, blacklist=blacklist)
@end example


3.6 新版功能.

@end deffn

The @ref{106,,test.support} module defines the following classes:

@geindex TransientResource (test.support 中的类)
@anchor{library/test test support TransientResource}@anchor{3445}
@deffn {类} test.support.TransientResource (exc, **kwargs)

Instances are a context manager that raises @ref{33c9,,ResourceDenied} if the
specified exception type is raised.  Any keyword arguments are treated as
attribute/value pairs to be compared against any exception raised within the
@ref{6e3,,with} statement.  Only if all pairs match properly against
attributes on the exception is @ref{33c9,,ResourceDenied} raised.
@end deffn

@geindex EnvironmentVarGuard (test.support 中的类)
@anchor{library/test test support EnvironmentVarGuard}@anchor{3446}
@deffn {类} test.support.EnvironmentVarGuard

Class used to temporarily set or unset environment variables.  Instances can
be used as a context manager and have a complete dictionary interface for
querying/modifying the underlying @code{os.environ}. After exit from the
context manager all changes to environment variables done through this
instance will be rolled back.


在 3.1 版更改: Added dictionary interface.

@end deffn

@geindex set() (test.support.EnvironmentVarGuard 方法)
@anchor{library/test test support EnvironmentVarGuard set}@anchor{3447}
@deffn {方法} EnvironmentVarGuard.set (envvar, value)

Temporarily set the environment variable @code{envvar} to the value of
@code{value}.
@end deffn

@geindex unset() (test.support.EnvironmentVarGuard 方法)
@anchor{library/test test support EnvironmentVarGuard unset}@anchor{3448}
@deffn {方法} EnvironmentVarGuard.unset (envvar)

Temporarily unset the environment variable @code{envvar}.
@end deffn

@geindex SuppressCrashReport (test.support 中的类)
@anchor{library/test test support SuppressCrashReport}@anchor{3449}
@deffn {类} test.support.SuppressCrashReport

A context manager used to try to prevent crash dialog popups on tests that
are expected to crash a subprocess.

On Windows, it disables Windows Error Reporting dialogs using
SetErrorMode@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/ms680621.aspx}.

On UNIX, @ref{344a,,resource.setrlimit()} is used to set
@ref{344b,,resource.RLIMIT_CORE}'s soft limit to 0 to prevent coredump file
creation.

On both platforms, the old value is restored by @ref{c8f,,__exit__()}.
@end deffn

@geindex CleanImport (test.support 中的类)
@anchor{library/test test support CleanImport}@anchor{344c}
@deffn {类} test.support.CleanImport (*module_names)

A context manager to force import to return a new module reference.  This
is useful for testing module-level behaviors, such as the emission of a
DeprecationWarning on import.  Example usage:

@example
with CleanImport('foo'):
    importlib.import_module('foo')  # New reference.
@end example
@end deffn

@geindex DirsOnSysPath (test.support 中的类)
@anchor{library/test test support DirsOnSysPath}@anchor{344d}
@deffn {类} test.support.DirsOnSysPath (*paths)

A context manager to temporarily add directories to sys.path.

This makes a copy of @ref{482,,sys.path}, appends any directories given
as positional arguments, then reverts @ref{482,,sys.path} to the copied
settings when the context ends.

Note that @emph{all} @ref{482,,sys.path} modifications in the body of the
context manager, including replacement of the object,
will be reverted at the end of the block.
@end deffn

@geindex SaveSignals (test.support 中的类)
@anchor{library/test test support SaveSignals}@anchor{344e}
@deffn {类} test.support.SaveSignals

Class to save and restore signal handlers registered by the Python signal
handler.
@end deffn

@geindex Matcher (test.support 中的类)
@anchor{library/test test support Matcher}@anchor{344f}
@deffn {类} test.support.Matcher

@geindex matches() (test.support.Matcher 方法)
@anchor{library/test test support Matcher matches}@anchor{3450}
@deffn {方法} matches (self, d, **kwargs)

Try to match a single dict with the supplied arguments.
@end deffn

@geindex match_value() (test.support.Matcher 方法)
@anchor{library/test test support Matcher match_value}@anchor{3451}
@deffn {方法} match_value (self, k, dv, v)

Try to match a single stored value (@emph{dv}) with a supplied value (@emph{v}).
@end deffn
@end deffn

@geindex WarningsRecorder (test.support 中的类)
@anchor{library/test test support WarningsRecorder}@anchor{3452}
@deffn {类} test.support.WarningsRecorder

Class used to record warnings for unit tests. See documentation of
@ref{33fb,,check_warnings()} above for more details.
@end deffn

@geindex BasicTestRunner (test.support 中的类)
@anchor{library/test test support BasicTestRunner}@anchor{3453}
@deffn {类} test.support.BasicTestRunner

@geindex run() (test.support.BasicTestRunner 方法)
@anchor{library/test test support BasicTestRunner run}@anchor{3454}
@deffn {方法} run (test)

Run @emph{test} and return the result.
@end deffn
@end deffn

@geindex TestHandler (test.support 中的类)
@anchor{library/test test support TestHandler}@anchor{3455}
@deffn {类} test.support.TestHandler (logging.handlers.BufferingHandler)

Class for logging support.
@end deffn

@geindex FakePath (test.support 中的类)
@anchor{library/test test support FakePath}@anchor{3456}
@deffn {类} test.support.FakePath (path)

Simple @ref{363,,path-like object}.  It implements the @code{__fspath__()}
method which just returns the @emph{path} argument.  If @emph{path} is an exception,
it will be raised in @code{__fspath__()}.
@end deffn

@node test support script_helper --- Utilities for the Python execution tests,,test support --- Utilities for the Python test suite,开发工具
@anchor{library/test module-test support script_helper}@anchor{107}@anchor{library/test test-support-script-helper-utilities-for-the-python-execution-tests}@anchor{3457}
@subsection @code{test.support.script_helper} --- Utilities for the Python execution tests


@geindex test.support.script_helper (模块)

The @ref{107,,test.support.script_helper} module provides support for Python's
script execution tests.

@geindex interpreter_requires_environment() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper interpreter_requires_environment}@anchor{3458}
@deffn {函数} test.support.script_helper.interpreter_requires_environment ()

Return @code{True} if @code{sys.executable interpreter} requires environment
variables in order to be able to run at all.

This is designed to be used with @code{@@unittest.skipIf()} to annotate tests
that need to use an @code{assert_python*()} function to launch an isolated
mode (@code{-I}) or no environment mode (@code{-E}) sub-interpreter process.

A normal build & test does not run into this situation but it can happen
when trying to run the standard library test suite from an interpreter that
doesn't have an obvious home with Python's current home finding logic.

Setting 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} is one way to get most of the testsuite to run
in that situation.  
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} or 
@geindex PYTHONUSERSITE
@geindex 环境变量; PYTHONUSERSITE
@code{PYTHONUSERSITE} are
other common environment variables that might impact whether or not the
interpreter can start.
@end deffn

@geindex run_python_until_end() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper run_python_until_end}@anchor{3459}
@deffn {函数} test.support.script_helper.run_python_until_end (*args, **env_vars)

Set up the environment based on @emph{env_vars} for running the interpreter
in a subprocess.  The values can include @code{__isolated}, @code{__cleanenv},
@code{__cwd}, and @code{TERM}.
@end deffn

@geindex assert_python_ok() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper assert_python_ok}@anchor{345a}
@deffn {函数} test.support.script_helper.assert_python_ok (*args, **env_vars)

Assert that running the interpreter with @emph{args} and optional environment
variables @emph{env_vars} succeeds (@code{rc == 0}) and return a @code{(return code,
stdout, stderr)} tuple.

If the @code{__cleanenv} keyword is set, @emph{env_vars} is used as a fresh
environment.

Python is started in isolated mode (command line option @code{-I}),
except if the @code{__isolated} keyword is set to @code{False}.
@end deffn

@geindex assert_python_failure() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper assert_python_failure}@anchor{345b}
@deffn {函数} test.support.script_helper.assert_python_failure (*args, **env_vars)

Assert that running the interpreter with @emph{args} and optional environment
variables @emph{env_vars} fails (@code{rc != 0}) and return a @code{(return code,
stdout, stderr)} tuple.

See @ref{345a,,assert_python_ok()} for more options.
@end deffn

@geindex spawn_python() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper spawn_python}@anchor{345c}
@deffn {函数} test.support.script_helper.spawn_python (*args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **kw)

Run a Python subprocess with the given arguments.

@emph{kw} is extra keyword args to pass to @ref{2b9,,subprocess.Popen()}. Returns a
@ref{2b9,,subprocess.Popen} object.
@end deffn

@geindex kill_python() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper kill_python}@anchor{345d}
@deffn {函数} test.support.script_helper.kill_python (p)

Run the given @ref{2b9,,subprocess.Popen} process until completion and return
stdout.
@end deffn

@geindex make_script() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper make_script}@anchor{345e}
@deffn {函数} test.support.script_helper.make_script (script_dir, script_basename, source, omit_suffix=False)

Create script containing @emph{source} in path @emph{script_dir} and @emph{script_basename}.
If @emph{omit_suffix} is @code{False}, append @code{.py} to the name.  Return the full
script path.
@end deffn

@geindex make_zip_script() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper make_zip_script}@anchor{345f}
@deffn {函数} test.support.script_helper.make_zip_script (zip_dir, zip_basename, script_name, name_in_zip=None)

Create zip file at @emph{zip_dir} and @emph{zip_basename} with extension @code{zip} which
contains the files in @emph{script_name}. @emph{name_in_zip} is the archive name.
Return a tuple containing @code{(full path, full path of archive name)}.
@end deffn

@geindex make_pkg() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper make_pkg}@anchor{3460}
@deffn {函数} test.support.script_helper.make_pkg (pkg_dir, init_source='@w{'})

Create a directory named @emph{pkg_dir} containing an @code{__init__} file with
@emph{init_source} as its contents.
@end deffn

@geindex make_zip_pkg() (在 test.support.script_helper 模块中)
@anchor{library/test test support script_helper make_zip_pkg}@anchor{3461}
@deffn {函数} test.support.script_helper.make_zip_pkg (zip_dir, zip_basename, pkg_name, script_basename, source, depth=1, compiled=False)

Create a zip package directory with a path of @emph{zip_dir} and @emph{zip_basename}
containing an empty @code{__init__} file and a file @emph{script_basename}
containing the @emph{source}.  If @emph{compiled} is @code{True}, both source files will
be compiled and added to the zip package.  Return a tuple of the full zip
path and the archive name for the zip file.
@end deffn

另请参看 Python 开发模式: @ref{155,,-X} @code{dev} 选项以及 
@geindex PYTHONDEVMODE
@geindex 环境变量; PYTHONDEVMODE
@ref{325,,PYTHONDEVMODE} 环境变量。

@node 调试和分析,软件打包和分发,开发工具,Python 标准库
@anchor{library/debug doc}@anchor{3462}@anchor{library/debug debugging-and-profiling}@anchor{3463}
@section 调试和分析


这些库可以帮助你进行 Python 开发：调试器使你能够逐步执行代码，分析堆栈帧并设置中断点等等，性能分析器可以运行代码并为你提供执行时间的详细数据，使你能够找出你的程序中的瓶颈。 审计事件提供运行时行为的可见性，如果没有此工具则需要进行侵入式调试或修补。
@anchor{library/audit_events audit-events}@anchor{3464}
@geindex audit events

@menu
* 审计事件表:: 
* bdb: bdb --- Debugger framework. Debugger framework
* faulthandler: faulthandler --- Dump the Python traceback. Dump the Python traceback
* pdb: pdb --- Python的调试器. Python的调试器
* Python Profilers 分析器:: 
* timeit: timeit --- 测量小代码片段的执行时间. 测量小代码片段的执行时间
* trace: trace --- Trace or track Python statement execution. Trace or track Python statement execution
* tracemalloc: tracemalloc --- 跟踪内存分配. 跟踪内存分配

@end menu

@node 审计事件表,bdb --- Debugger framework,,调试和分析
@anchor{library/audit_events doc}@anchor{3465}@anchor{library/audit_events audit-events-table}@anchor{3466}
@subsection 审计事件表


下表包含了在整个 CPython 运行时和标准库中由 @ref{eb7,,sys.audit()} 或 @ref{ec5,,PySys_Audit()} 调用引发的所有事件。这些调用是在 3.8.0 或更高版本中添加的。

请参阅 @ref{3467,,sys.addaudithook()} 和 @ref{3468,,PySys_AddAuditHook()} 了解有关处理这些事件的详细信息。

@strong{CPython implementation detail:} 此表是根据 CPython 文档生成的，可能无法表示其他实现所引发的事件。 请参阅你的运行时专属的文档了解实际引发的事件。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} 
@headitem

Audit event

@tab

Arguments

@tab

References

@item

array.__new__

@tab

@code{typecode}, @code{initializer}

@tab

@ref{44b,,[1]}

@item

builtins.breakpoint

@tab

@code{breakpointhook}

@tab

@ref{2f2,,[1]}

@item

builtins.input

@tab

@code{prompt}

@tab

@ref{c64,,[1]}

@item

builtins.input/result

@tab

@code{result}

@tab

@ref{c64,,[1]}

@item

code.__new__

@tab

@code{code}, @code{filename}, @code{name}, @code{argcount}, @code{posonlyargcount}, @code{kwonlyargcount}, @code{nlocals}, @code{stacksize}, @code{flags}

@tab

@ref{3469,,[1]}

@item

compile

@tab

@code{source}, @code{filename}

@tab

@ref{1b4,,[1]}

@item

cpython.PyInterpreterState_Clear

@tab



@tab

@ref{346a,,[1]}

@item

cpython.PyInterpreterState_New

@tab



@tab

@ref{346b,,[1]}

@item

cpython._PySys_ClearAuditHooks

@tab



@tab

@ref{5c4,,[1]}

@item

cpython.run_command

@tab

@code{command}

@tab

@ref{119f,,[1]}

@item

cpython.run_file

@tab

@code{filename}

@tab

@ref{346c,,[1]}

@item

cpython.run_interactivehook

@tab

@code{hook}

@tab

@ref{8de,,[1]}

@item

cpython.run_module

@tab

@code{module-name}

@tab

@ref{330,,[1]}

@item

cpython.run_startup

@tab

@code{filename}

@tab

@ref{346d,,[1]}

@item

cpython.run_stdin

@tab



@tab

@ref{346e,,[1]}

@item

ctypes.addressof

@tab

@code{obj}

@tab

@ref{22b6,,[1]}

@item

ctypes.call_function

@tab

@code{func_pointer}, @code{arguments}

@tab

@ref{346f,,[1]}

@item

ctypes.cdata

@tab

@code{address}

@tab

@ref{22c8,,[1]}

@item

ctypes.cdata/buffer

@tab

@code{pointer}, @code{size}, @code{offset}

@tab

@ref{22c6,,[1]}@ref{22c7,,[2]}

@item

ctypes.create_string_buffer

@tab

@code{init}, @code{size}

@tab

@ref{2268,,[1]}

@item

ctypes.create_unicode_buffer

@tab

@code{init}, @code{size}

@tab

@ref{f3c,,[1]}

@item

ctypes.dlopen

@tab

@code{name}

@tab

@ref{22a8,,[1]}

@item

ctypes.dlsym

@tab

@code{library}, @code{name}

@tab

@ref{22a8,,[1]}

@item

ctypes.dlsym/handle

@tab

@code{handle}, @code{name}

@tab

@ref{22a8,,[1]}

@item

ctypes.get_errno

@tab



@tab

@ref{22a2,,[1]}

@item

ctypes.get_last_error

@tab



@tab

@ref{22a4,,[1]}

@item

ctypes.seh_exception

@tab

@code{code}

@tab

@ref{22ab,,[1]}

@item

ctypes.set_errno

@tab

@code{errno}

@tab

@ref{22a3,,[1]}

@item

ctypes.set_last_error

@tab

@code{error}

@tab

@ref{22a5,,[1]}

@item

ctypes.string_at

@tab

@code{address}, @code{size}

@tab

@ref{22bf,,[1]}

@item

ctypes.wstring_at

@tab

@code{address}, @code{size}

@tab

@ref{22c1,,[1]}

@item

ensurepip.bootstrap

@tab

@code{root}

@tab

@ref{3470,,[1]}

@item

exec

@tab

@code{code_object}

@tab

@ref{b89,,[1]}@ref{c3d,,[2]}

@item

fcntl.fcntl

@tab

@code{fd}, @code{cmd}, @code{arg}

@tab

@ref{2639,,[1]}

@item

fcntl.flock

@tab

@code{fd}, @code{operation}

@tab

@ref{3471,,[1]}

@item

fcntl.ioctl

@tab

@code{fd}, @code{request}, @code{arg}

@tab

@ref{dd7,,[1]}

@item

fcntl.lockf

@tab

@code{fd}, @code{cmd}, @code{len}, @code{start}, @code{whence}

@tab

@ref{d4b,,[1]}

@item

ftplib.connect

@tab

@code{self}, @code{host}, @code{port}

@tab

@ref{2cb7,,[1]}

@item

ftplib.sendcmd

@tab

@code{self}, @code{cmd}

@tab

@ref{2cbb,,[1]}@ref{2cbc,,[2]}

@item

glob.glob

@tab

@code{pathname}, @code{recursive}

@tab

@ref{5c1,,[1]}@ref{5c2,,[2]}

@item

imaplib.open

@tab

@code{self}, @code{host}, @code{port}

@tab

@ref{2d07,,[1]}

@item

imaplib.send

@tab

@code{self}, @code{data}

@tab

@ref{2d0a,,[1]}

@item

import

@tab

@code{module}, @code{filename}, @code{sys.path}, @code{sys.meta_path}, @code{sys.path_hooks}

@tab

@ref{c16,,[1]}

@item

mmap.__new__

@tab

@code{fileno}, @code{length}, @code{access}, @code{offset}

@tab

@ref{1ec,,[1]}

@item

msvcrt.get_osfhandle

@tab

@code{fd}

@tab

@ref{3472,,[1]}

@item

msvcrt.locking

@tab

@code{fd}, @code{mode}, @code{nbytes}

@tab

@ref{3473,,[1]}

@item

msvcrt.open_osfhandle

@tab

@code{handle}, @code{flags}

@tab

@ref{3474,,[1]}

@item

nntplib.connect

@tab

@code{self}, @code{host}, @code{port}

@tab

@ref{a27,,[1]}@ref{b9e,,[2]}

@item

nntplib.putline

@tab

@code{self}, @code{line}

@tab

@ref{a27,,[1]}@ref{b9e,,[2]}

@item

open

@tab

@code{file}, @code{mode}, @code{flags}

@tab

@ref{4ea,,[1]}@ref{654,,[2]}@ref{65f,,[3]}

@item

os.add_dll_directory

@tab

@code{path}

@tab

@ref{1c2,,[1]}

@item

os.chdir

@tab

@code{path}

@tab

@ref{a3a,,[1]}@ref{655,,[2]}

@item

os.chflags

@tab

@code{path}, @code{flags}

@tab

@ref{a2d,,[1]}@ref{1ee3,,[2]}

@item

os.chmod

@tab

@code{path}, @code{mode}, @code{dir_fd}

@tab

@ref{a2e,,[1]}@ref{656,,[2]}@ref{fbc,,[3]}

@item

os.chown

@tab

@code{path}, @code{uid}, @code{gid}, @code{dir_fd}

@tab

@ref{a2f,,[1]}@ref{657,,[2]}@ref{1ee4,,[3]}

@item

os.exec

@tab

@code{path}, @code{args}, @code{env}

@tab

@ref{1f20,,[1]}

@item

os.fork

@tab



@tab

@ref{95b,,[1]}

@item

os.forkpty

@tab



@tab

@ref{1f38,,[1]}

@item

os.getxattr

@tab

@code{path}, @code{attribute}

@tab

@ref{a46,,[1]}

@item

os.kill

@tab

@code{pid}, @code{sig}

@tab

@ref{cec,,[1]}

@item

os.killpg

@tab

@code{pgid}, @code{sig}

@tab

@ref{ebe,,[1]}

@item

os.link

@tab

@code{src}, @code{dst}, @code{src_dir_fd}, @code{dst_dir_fd}

@tab

@ref{a30,,[1]}

@item

os.listdir

@tab

@code{path}

@tab

@ref{a3c,,[1]}

@item

os.listxattr

@tab

@code{path}

@tab

@ref{a47,,[1]}

@item

os.lockf

@tab

@code{fd}, @code{cmd}, @code{len}

@tab

@ref{a55,,[1]}

@item

os.mkdir

@tab

@code{path}, @code{mode}, @code{dir_fd}

@tab

@ref{3b5,,[1]}@ref{a31,,[2]}

@item

os.posix_spawn

@tab

@code{path}, @code{argv}, @code{env}

@tab

@ref{257,,[1]}@ref{fa8,,[2]}

@item

os.putenv

@tab

@code{key}, @code{value}

@tab

@ref{1e7c,,[1]}

@item

os.remove

@tab

@code{path}, @code{dir_fd}

@tab

@ref{a32,,[1]}@ref{1eeb,,[2]}@ref{a37,,[3]}

@item

os.removexattr

@tab

@code{path}, @code{attribute}

@tab

@ref{a48,,[1]}

@item

os.rename

@tab

@code{src}, @code{dst}, @code{src_dir_fd}, @code{dst_dir_fd}

@tab

@ref{a33,,[1]}@ref{1eec,,[2]}@ref{a34,,[3]}

@item

os.rmdir

@tab

@code{path}, @code{dir_fd}

@tab

@ref{a35,,[1]}

@item

os.scandir

@tab

@code{path}

@tab

@ref{25f,,[1]}

@item

os.setxattr

@tab

@code{path}, @code{attribute}, @code{value}, @code{flags}

@tab

@ref{a49,,[1]}

@item

os.spawn

@tab

@code{mode}, @code{path}, @code{args}, @code{env}

@tab

@ref{1edc,,[1]}

@item

os.startfile

@tab

@code{path}, @code{operation}

@tab

@ref{1f4c,,[1]}

@item

os.symlink

@tab

@code{src}, @code{dst}, @code{dir_fd}

@tab

@ref{a36,,[1]}

@item

os.system

@tab

@code{command}

@tab

@ref{dba,,[1]}

@item

os.truncate

@tab

@code{fd}, @code{length}

@tab

@ref{65c,,[1]}@ref{71e,,[2]}

@item

os.unsetenv

@tab

@code{key}

@tab

@ref{d3c,,[1]}

@item

os.utime

@tab

@code{path}, @code{times}, @code{ns}, @code{dir_fd}

@tab

@ref{a38,,[1]}

@item

pdb.Pdb

@tab



@tab

@ref{567,,[1]}

@item

pickle.find_class

@tab

@code{module}, @code{name}

@tab

@ref{1c53,,[1]}

@item

poplib.connect

@tab

@code{self}, @code{host}, @code{port}

@tab

@ref{2cd2,,[1]}@ref{bba,,[2]}

@item

poplib.putline

@tab

@code{self}, @code{line}

@tab

@ref{2cd2,,[1]}@ref{3475,,[2]}

@item

pty.spawn

@tab

@code{argv}

@tab

@ref{892,,[1]}

@item

resource.prlimit

@tab

@code{pid}, @code{resource}, @code{limits}

@tab

@ref{899,,[1]}

@item

resource.setrlimit

@tab

@code{resource}, @code{limits}

@tab

@ref{344a,,[1]}

@item

shutil.chown

@tab

@code{path}, @code{user}, @code{group}

@tab

@ref{a71,,[1]}

@item

shutil.copyfile

@tab

@code{src}, @code{dst}

@tab

@ref{259,,[1]}@ref{25a,,[2]}@ref{258,,[3]}

@item

shutil.copymode

@tab

@code{src}, @code{dst}

@tab

@ref{259,,[1]}@ref{1c1a,,[2]}

@item

shutil.copystat

@tab

@code{src}, @code{dst}

@tab

@ref{25a,,[1]}@ref{a72,,[2]}

@item

shutil.copytree

@tab

@code{src}, @code{dst}

@tab

@ref{21a,,[1]}

@item

shutil.make_archive

@tab

@code{base_name}, @code{format}, @code{root_dir}, @code{base_dir}

@tab

@ref{21b,,[1]}

@item

shutil.move

@tab

@code{src}, @code{dst}

@tab

@ref{25b,,[1]}

@item

shutil.rmtree

@tab

@code{path}

@tab

@ref{21c,,[1]}

@item

shutil.unpack_archive

@tab

@code{filename}, @code{extract_dir}, @code{format}

@tab

@ref{b90,,[1]}

@item

signal.pthread_kill

@tab

@code{thread_id}, @code{signalnum}

@tab

@ref{a75,,[1]}

@item

smtplib.connect

@tab

@code{self}, @code{host}, @code{port}

@tab

@ref{2d50,,[1]}

@item

smtplib.send

@tab

@code{self}, @code{data}

@tab

@ref{a7c,,[1]}

@item

socket.__new__

@tab

@code{self}, @code{family}, @code{type}, @code{protocol}

@tab

@ref{66e,,[1]}

@item

socket.bind

@tab

@code{self}, @code{address}

@tab

@ref{2633,,[1]}

@item

socket.connect

@tab

@code{self}, @code{address}

@tab

@ref{670,,[1]}@ref{2635,,[2]}

@item

socket.getaddrinfo

@tab

@code{host}, @code{port}, @code{family}, @code{type}, @code{protocol}

@tab

@ref{2559,,[1]}

@item

socket.gethostbyaddr

@tab

@code{ip_address}

@tab

@ref{260c,,[1]}

@item

socket.gethostbyname

@tab

@code{hostname}

@tab

@ref{262a,,[1]}@ref{260b,,[2]}

@item

socket.gethostname

@tab



@tab

@ref{1e9b,,[1]}

@item

socket.getnameinfo

@tab

@code{sockaddr}

@tab

@ref{255a,,[1]}

@item

socket.getservbyname

@tab

@code{servicename}, @code{protocolname}

@tab

@ref{262c,,[1]}

@item

socket.getservbyport

@tab

@code{port}, @code{protocolname}

@tab

@ref{262d,,[1]}

@item

socket.sendmsg

@tab

@code{self}, @code{address}

@tab

@ref{676,,[1]}

@item

socket.sendto

@tab

@code{self}, @code{address}

@tab

@ref{677,,[1]}

@item

socket.sethostname

@tab

@code{name}

@tab

@ref{a82,,[1]}

@item

sqlite3.connect

@tab

@code{database}

@tab

@ref{3d2,,[1]}

@item

subprocess.Popen

@tab

@code{executable}, @code{args}, @code{cwd}, @code{env}

@tab

@ref{2b9,,[1]}

@item

sys._current_frames

@tab



@tab

@ref{d94,,[1]}

@item

sys._getframe

@tab



@tab

@ref{e5d,,[1]}

@item

sys.addaudithook

@tab



@tab

@ref{3468,,[1]}@ref{3467,,[2]}

@item

sys.excepthook

@tab

@code{hook}, @code{type}, @code{value}, @code{traceback}

@tab

@ref{e5c,,[1]}

@item

sys.set_asyncgen_hooks_finalizer

@tab



@tab

@ref{eb8,,[1]}

@item

sys.set_asyncgen_hooks_firstiter

@tab



@tab

@ref{eb8,,[1]}

@item

sys.setprofile

@tab



@tab

@ref{e36,,[1]}

@item

sys.settrace

@tab



@tab

@ref{e37,,[1]}

@item

sys.unraisablehook

@tab

@code{hook}, @code{unraisable}

@tab

@ref{22d,,[1]}

@item

syslog.closelog

@tab



@tab

@ref{3476,,[1]}

@item

syslog.openlog

@tab

@code{ident}, @code{logoption}, @code{facility}

@tab

@ref{3477,,[1]}

@item

syslog.setlogmask

@tab

@code{maskpri}

@tab

@ref{3478,,[1]}

@item

syslog.syslog

@tab

@code{priority}, @code{message}

@tab

@ref{3479,,[1]}

@item

telnetlib.Telnet.open

@tab

@code{self}, @code{host}, @code{port}

@tab

@ref{2d7d,,[1]}

@item

telnetlib.Telnet.write

@tab

@code{self}, @code{buffer}

@tab

@ref{2d8d,,[1]}

@item

tempfile.mkdtemp

@tab

@code{fullpath}

@tab

@ref{bc1,,[1]}@ref{1bfb,,[2]}

@item

tempfile.mkstemp

@tab

@code{fullpath}

@tab

@ref{d42,,[1]}@ref{1bf9,,[2]}@ref{1bfa,,[3]}

@item

urllib.Request

@tab

@code{fullurl}, @code{data}, @code{headers}, @code{method}

@tab

@ref{786,,[1]}

@item

webbrowser.open

@tab

@code{url}

@tab

@ref{2b6d,,[1]}

@item

winreg.ConnectRegistry

@tab

@code{computer_name}, @code{key}

@tab

@ref{347a,,[1]}

@item

winreg.CreateKey

@tab

@code{key}, @code{sub_key}, @code{access}

@tab

@ref{347b,,[1]}@ref{347c,,[2]}

@item

winreg.DeleteKey

@tab

@code{key}, @code{sub_key}, @code{access}

@tab

@ref{347d,,[1]}@ref{347e,,[2]}

@item

winreg.DeleteValue

@tab

@code{key}, @code{value}

@tab

@ref{347f,,[1]}

@item

winreg.DisableReflectionKey

@tab

@code{key}

@tab

@ref{3480,,[1]}

@item

winreg.EnableReflectionKey

@tab

@code{key}

@tab

@ref{3481,,[1]}

@item

winreg.EnumKey

@tab

@code{key}, @code{index}

@tab

@ref{3482,,[1]}

@item

winreg.EnumValue

@tab

@code{key}, @code{index}

@tab

@ref{3483,,[1]}

@item

winreg.ExpandEnvironmentStrings

@tab

@code{str}

@tab

@ref{3484,,[1]}

@item

winreg.LoadKey

@tab

@code{key}, @code{sub_key}, @code{file_name}

@tab

@ref{3485,,[1]}

@item

winreg.OpenKey

@tab

@code{key}, @code{sub_key}, @code{access}

@tab

@ref{3486,,[1]}

@item

winreg.OpenKey/result

@tab

@code{key}

@tab

@ref{347b,,[1]}@ref{347c,,[2]}@ref{3486,,[3]}

@item

winreg.PyHKEY.Detach

@tab

@code{key}

@tab

@ref{3487,,[1]}

@item

winreg.QueryInfoKey

@tab

@code{key}

@tab

@ref{3488,,[1]}

@item

winreg.QueryReflectionKey

@tab

@code{key}

@tab

@ref{3489,,[1]}

@item

winreg.QueryValue

@tab

@code{key}, @code{sub_key}, @code{value_name}

@tab

@ref{348a,,[1]}@ref{348b,,[2]}

@item

winreg.SaveKey

@tab

@code{key}, @code{file_name}

@tab

@ref{348c,,[1]}

@item

winreg.SetValue

@tab

@code{key}, @code{sub_key}, @code{type}, @code{value}

@tab

@ref{348d,,[1]}@ref{348e,,[2]}

@end multitable


@node bdb --- Debugger framework,faulthandler --- Dump the Python traceback,审计事件表,调试和分析
@anchor{library/bdb doc}@anchor{348f}@anchor{library/bdb bdb-debugger-framework}@anchor{3490}@anchor{library/bdb module-bdb}@anchor{f}
@subsection @code{bdb} --- Debugger framework


@geindex bdb (模块)

@strong{Source code:} Lib/bdb.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/bdb.py}


__________________________________________________________________


The @ref{f,,bdb} module handles basic debugger functions, like setting breakpoints
or managing execution via the debugger.

定义了以下异常：

@geindex BdbQuit
@anchor{library/bdb bdb BdbQuit}@anchor{3491}
@deffn {例外} bdb.BdbQuit

Exception raised by the @ref{c91,,Bdb} class for quitting the debugger.
@end deffn

The @ref{f,,bdb} module also defines two classes:

@geindex Breakpoint (bdb 中的类)
@anchor{library/bdb bdb Breakpoint}@anchor{3492}
@deffn {类} bdb.Breakpoint (self, file, line, temporary=0, cond=None, funcname=None)

This class implements temporary breakpoints, ignore counts, disabling and
(re-)enabling, and conditionals.

Breakpoints are indexed by number through a list called @code{bpbynumber}
and by @code{(file, line)} pairs through @code{bplist}.  The former points to a
single instance of class @ref{3492,,Breakpoint}.  The latter points to a list of
such instances since there may be more than one breakpoint per line.

When creating a breakpoint, its associated filename should be in canonical
form.  If a @emph{funcname} is defined, a breakpoint hit will be counted when the
first line of that function is executed.  A conditional breakpoint always
counts a hit.

@ref{3492,,Breakpoint} instances have the following methods:

@geindex deleteMe() (bdb.Breakpoint 方法)
@anchor{library/bdb bdb Breakpoint deleteMe}@anchor{3493}
@deffn {方法} deleteMe ()

Delete the breakpoint from the list associated to a file/line.  If it is
the last breakpoint in that position, it also deletes the entry for the
file/line.
@end deffn

@geindex enable() (bdb.Breakpoint 方法)
@anchor{library/bdb bdb Breakpoint enable}@anchor{3494}
@deffn {方法} enable ()

Mark the breakpoint as enabled.
@end deffn

@geindex disable() (bdb.Breakpoint 方法)
@anchor{library/bdb bdb Breakpoint disable}@anchor{3495}
@deffn {方法} disable ()

Mark the breakpoint as disabled.
@end deffn

@geindex bpformat() (bdb.Breakpoint 方法)
@anchor{library/bdb bdb Breakpoint bpformat}@anchor{3496}
@deffn {方法} bpformat ()

Return a string with all the information about the breakpoint, nicely
formatted:


@itemize *

@item 
The breakpoint number.

@item 
If it is temporary or not.

@item 
Its file,line position.

@item 
The condition that causes a break.

@item 
If it must be ignored the next N times.

@item 
The breakpoint hit count.
@end itemize


3.2 新版功能.

@end deffn

@geindex bpprint() (bdb.Breakpoint 方法)
@anchor{library/bdb bdb Breakpoint bpprint}@anchor{3497}
@deffn {方法} bpprint (out=None)

Print the output of @ref{3496,,bpformat()} to the file @emph{out}, or if it is
@code{None}, to standard output.
@end deffn
@end deffn

@geindex Bdb (bdb 中的类)
@anchor{library/bdb bdb Bdb}@anchor{c91}
@deffn {类} bdb.Bdb (skip=None)

The @ref{c91,,Bdb} class acts as a generic Python debugger base class.

This class takes care of the details of the trace facility; a derived class
should implement user interaction.  The standard debugger class
(@ref{567,,pdb.Pdb}) is an example.

The @emph{skip} argument, if given, must be an iterable of glob-style
module name patterns.  The debugger will not step into frames that
originate in a module that matches one of these patterns. Whether a
frame is considered to originate in a certain module is determined
by the @code{__name__} in the frame globals.


3.1 新版功能: @emph{skip} 参数。


The following methods of @ref{c91,,Bdb} normally don't need to be overridden.

@geindex canonic() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb canonic}@anchor{3498}
@deffn {方法} canonic (filename)

Auxiliary method for getting a filename in a canonical form, that is, as a
case-normalized (on case-insensitive filesystems) absolute path, stripped
of surrounding angle brackets.
@end deffn

@geindex reset() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb reset}@anchor{3499}
@deffn {方法} reset ()

Set the @code{botframe}, @code{stopframe}, @code{returnframe} and
@code{quitting} attributes with values ready to start debugging.
@end deffn

@geindex trace_dispatch() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb trace_dispatch}@anchor{349a}
@deffn {方法} trace_dispatch (frame, event, arg)

This function is installed as the trace function of debugged frames.  Its
return value is the new trace function (in most cases, that is, itself).

The default implementation decides how to dispatch a frame, depending on
the type of event (passed as a string) that is about to be executed.
@emph{event} can be one of the following:


@itemize *

@item 
@code{"line"}: A new line of code is going to be executed.

@item 
@code{"call"}: A function is about to be called, or another code block
entered.

@item 
@code{"return"}: A function or other code block is about to return.

@item 
@code{"exception"}: An exception has occurred.

@item 
@code{"c_call"}: A C function is about to be called.

@item 
@code{"c_return"}: A C function has returned.

@item 
@code{"c_exception"}: A C function has raised an exception.
@end itemize

For the Python events, specialized functions (see below) are called.  For
the C events, no action is taken.

The @emph{arg} parameter depends on the previous event.

See the documentation for @ref{e37,,sys.settrace()} for more information on the
trace function.  For more information on code and frame objects, refer to
@ref{13b8,,标准类型层级结构}.
@end deffn

@geindex dispatch_line() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb dispatch_line}@anchor{349b}
@deffn {方法} dispatch_line (frame)

If the debugger should stop on the current line, invoke the
@ref{349c,,user_line()} method (which should be overridden in subclasses).
Raise a @ref{3491,,BdbQuit} exception if the @code{Bdb.quitting} flag is set
(which can be set from @ref{349c,,user_line()}).  Return a reference to the
@ref{349a,,trace_dispatch()} method for further tracing in that scope.
@end deffn

@geindex dispatch_call() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb dispatch_call}@anchor{349d}
@deffn {方法} dispatch_call (frame, arg)

If the debugger should stop on this function call, invoke the
@ref{349e,,user_call()} method (which should be overridden in subclasses).
Raise a @ref{3491,,BdbQuit} exception if the @code{Bdb.quitting} flag is set
(which can be set from @ref{349e,,user_call()}).  Return a reference to the
@ref{349a,,trace_dispatch()} method for further tracing in that scope.
@end deffn

@geindex dispatch_return() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb dispatch_return}@anchor{349f}
@deffn {方法} dispatch_return (frame, arg)

If the debugger should stop on this function return, invoke the
@ref{34a0,,user_return()} method (which should be overridden in subclasses).
Raise a @ref{3491,,BdbQuit} exception if the @code{Bdb.quitting} flag is set
(which can be set from @ref{34a0,,user_return()}).  Return a reference to the
@ref{349a,,trace_dispatch()} method for further tracing in that scope.
@end deffn

@geindex dispatch_exception() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb dispatch_exception}@anchor{34a1}
@deffn {方法} dispatch_exception (frame, arg)

If the debugger should stop at this exception, invokes the
@ref{34a2,,user_exception()} method (which should be overridden in subclasses).
Raise a @ref{3491,,BdbQuit} exception if the @code{Bdb.quitting} flag is set
(which can be set from @ref{34a2,,user_exception()}).  Return a reference to the
@ref{349a,,trace_dispatch()} method for further tracing in that scope.
@end deffn

Normally derived classes don't override the following methods, but they may
if they want to redefine the definition of stopping and breakpoints.

@geindex stop_here() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb stop_here}@anchor{34a3}
@deffn {方法} stop_here (frame)

This method checks if the @emph{frame} is somewhere below @code{botframe} in
the call stack.  @code{botframe} is the frame in which debugging started.
@end deffn

@geindex break_here() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb break_here}@anchor{34a4}
@deffn {方法} break_here (frame)

This method checks if there is a breakpoint in the filename and line
belonging to @emph{frame} or, at least, in the current function.  If the
breakpoint is a temporary one, this method deletes it.
@end deffn

@geindex break_anywhere() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb break_anywhere}@anchor{34a5}
@deffn {方法} break_anywhere (frame)

This method checks if there is a breakpoint in the filename of the current
frame.
@end deffn

Derived classes should override these methods to gain control over debugger
operation.

@geindex user_call() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb user_call}@anchor{349e}
@deffn {方法} user_call (frame, argument_list)

This method is called from @ref{349d,,dispatch_call()} when there is the
possibility that a break might be necessary anywhere inside the called
function.
@end deffn

@geindex user_line() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb user_line}@anchor{349c}
@deffn {方法} user_line (frame)

This method is called from @ref{349b,,dispatch_line()} when either
@ref{34a3,,stop_here()} or @ref{34a4,,break_here()} yields @code{True}.
@end deffn

@geindex user_return() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb user_return}@anchor{34a0}
@deffn {方法} user_return (frame, return_value)

This method is called from @ref{349f,,dispatch_return()} when @ref{34a3,,stop_here()}
yields @code{True}.
@end deffn

@geindex user_exception() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb user_exception}@anchor{34a2}
@deffn {方法} user_exception (frame, exc_info)

This method is called from @ref{34a1,,dispatch_exception()} when
@ref{34a3,,stop_here()} yields @code{True}.
@end deffn

@geindex do_clear() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb do_clear}@anchor{34a6}
@deffn {方法} do_clear (arg)

Handle how a breakpoint must be removed when it is a temporary one.

This method must be implemented by derived classes.
@end deffn

Derived classes and clients can call the following methods to affect the
stepping state.

@geindex set_step() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb set_step}@anchor{34a7}
@deffn {方法} set_step ()

Stop after one line of code.
@end deffn

@geindex set_next() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb set_next}@anchor{34a8}
@deffn {方法} set_next (frame)

Stop on the next line in or below the given frame.
@end deffn

@geindex set_return() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb set_return}@anchor{34a9}
@deffn {方法} set_return (frame)

Stop when returning from the given frame.
@end deffn

@geindex set_until() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb set_until}@anchor{34aa}
@deffn {方法} set_until (frame)

Stop when the line with the line no greater than the current one is
reached or when returning from current frame.
@end deffn

@geindex set_trace() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb set_trace}@anchor{34ab}
@deffn {方法} set_trace ([frame])

Start debugging from @emph{frame}.  If @emph{frame} is not specified, debugging
starts from caller's frame.
@end deffn

@geindex set_continue() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb set_continue}@anchor{34ac}
@deffn {方法} set_continue ()

Stop only at breakpoints or when finished.  If there are no breakpoints,
set the system trace function to @code{None}.
@end deffn

@geindex set_quit() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb set_quit}@anchor{34ad}
@deffn {方法} set_quit ()

Set the @code{quitting} attribute to @code{True}.  This raises @ref{3491,,BdbQuit} in
the next call to one of the @code{dispatch_*()} methods.
@end deffn

Derived classes and clients can call the following methods to manipulate
breakpoints.  These methods return a string containing an error message if
something went wrong, or @code{None} if all is well.

@geindex set_break() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb set_break}@anchor{34ae}
@deffn {方法} set_break (filename, lineno, temporary=0, cond, funcname)

Set a new breakpoint.  If the @emph{lineno} line doesn't exist for the
@emph{filename} passed as argument, return an error message.  The @emph{filename}
should be in canonical form, as described in the @ref{3498,,canonic()} method.
@end deffn

@geindex clear_break() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb clear_break}@anchor{34af}
@deffn {方法} clear_break (filename, lineno)

Delete the breakpoints in @emph{filename} and @emph{lineno}.  If none were set, an
error message is returned.
@end deffn

@geindex clear_bpbynumber() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb clear_bpbynumber}@anchor{34b0}
@deffn {方法} clear_bpbynumber (arg)

Delete the breakpoint which has the index @emph{arg} in the
@code{Breakpoint.bpbynumber}.  If @emph{arg} is not numeric or out of range,
return an error message.
@end deffn

@geindex clear_all_file_breaks() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb clear_all_file_breaks}@anchor{34b1}
@deffn {方法} clear_all_file_breaks (filename)

Delete all breakpoints in @emph{filename}.  If none were set, an error message
is returned.
@end deffn

@geindex clear_all_breaks() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb clear_all_breaks}@anchor{34b2}
@deffn {方法} clear_all_breaks ()

Delete all existing breakpoints.
@end deffn

@geindex get_bpbynumber() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb get_bpbynumber}@anchor{34b3}
@deffn {方法} get_bpbynumber (arg)

Return a breakpoint specified by the given number.  If @emph{arg} is a string,
it will be converted to a number.  If @emph{arg} is a non-numeric string, if
the given breakpoint never existed or has been deleted, a
@ref{1fb,,ValueError} is raised.


3.2 新版功能.

@end deffn

@geindex get_break() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb get_break}@anchor{34b4}
@deffn {方法} get_break (filename, lineno)

Check if there is a breakpoint for @emph{lineno} of @emph{filename}.
@end deffn

@geindex get_breaks() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb get_breaks}@anchor{34b5}
@deffn {方法} get_breaks (filename, lineno)

Return all breakpoints for @emph{lineno} in @emph{filename}, or an empty list if
none are set.
@end deffn

@geindex get_file_breaks() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb get_file_breaks}@anchor{34b6}
@deffn {方法} get_file_breaks (filename)

Return all breakpoints in @emph{filename}, or an empty list if none are set.
@end deffn

@geindex get_all_breaks() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb get_all_breaks}@anchor{34b7}
@deffn {方法} get_all_breaks ()

Return all breakpoints that are set.
@end deffn

Derived classes and clients can call the following methods to get a data
structure representing a stack trace.

@geindex get_stack() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb get_stack}@anchor{34b8}
@deffn {方法} get_stack (f, t)

Get a list of records for a frame and all higher (calling) and lower
frames, and the size of the higher part.
@end deffn

@geindex format_stack_entry() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb format_stack_entry}@anchor{34b9}
@deffn {方法} format_stack_entry (frame_lineno, lprefix=': ')

Return a string with information about a stack entry, identified by a
@code{(frame, lineno)} tuple:


@itemize *

@item 
The canonical form of the filename which contains the frame.

@item 
The function name, or @code{"<lambda>"}.

@item 
The input arguments.

@item 
The return value.

@item 
The line of code (if it exists).
@end itemize
@end deffn

The following two methods can be called by clients to use a debugger to debug
a @ref{1b24,,statement}, given as a string.

@geindex run() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb run}@anchor{34ba}
@deffn {方法} run (cmd, globals=None, locals=None)

Debug a statement executed via the @ref{c3d,,exec()} function.  @emph{globals}
defaults to @code{__main__.__dict__}, @emph{locals} defaults to @emph{globals}.
@end deffn

@geindex runeval() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb runeval}@anchor{34bb}
@deffn {方法} runeval (expr, globals=None, locals=None)

Debug an expression executed via the @ref{b89,,eval()} function.  @emph{globals} and
@emph{locals} have the same meaning as in @ref{34ba,,run()}.
@end deffn

@geindex runctx() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb runctx}@anchor{34bc}
@deffn {方法} runctx (cmd, globals, locals)

For backwards compatibility.  Calls the @ref{34ba,,run()} method.
@end deffn

@geindex runcall() (bdb.Bdb 方法)
@anchor{library/bdb bdb Bdb runcall}@anchor{29f}
@deffn {方法} runcall (func, *args, **kwds)

Debug a single function call, and return its result.
@end deffn
@end deffn

Finally, the module defines the following functions:

@geindex checkfuncname() (在 bdb 模块中)
@anchor{library/bdb bdb checkfuncname}@anchor{34bd}
@deffn {函数} bdb.checkfuncname (b, frame)

Check whether we should break here, depending on the way the breakpoint @emph{b}
was set.

If it was set via line number, it checks if @code{b.line} is the same as the one
in the frame also passed as argument.  If the breakpoint was set via function
name, we have to check we are in the right frame (the right function) and if
we are in its first executable line.
@end deffn

@geindex effective() (在 bdb 模块中)
@anchor{library/bdb bdb effective}@anchor{34be}
@deffn {函数} bdb.effective (file, line, frame)

Determine if there is an effective (active) breakpoint at this line of code.
Return a tuple of the breakpoint and a boolean that indicates if it is ok
to delete a temporary breakpoint.  Return @code{(None, None)} if there is no
matching breakpoint.
@end deffn

@geindex set_trace() (在 bdb 模块中)
@anchor{library/bdb bdb set_trace}@anchor{34bf}
@deffn {函数} bdb.set_trace ()

Start debugging with a @ref{c91,,Bdb} instance from caller's frame.
@end deffn

@node faulthandler --- Dump the Python traceback,pdb --- Python的调试器,bdb --- Debugger framework,调试和分析
@anchor{library/faulthandler doc}@anchor{34c0}@anchor{library/faulthandler faulthandler-dump-the-python-traceback}@anchor{34c1}@anchor{library/faulthandler module-faulthandler}@anchor{7d}
@subsection @code{faulthandler} --- Dump the Python traceback


@geindex faulthandler (模块)


3.3 新版功能.



__________________________________________________________________


This module contains functions to dump Python tracebacks explicitly, on a fault,
after a timeout, or on a user signal. Call @ref{543,,faulthandler.enable()} to
install fault handlers for the @code{SIGSEGV}, @code{SIGFPE},
@code{SIGABRT}, @code{SIGBUS}, and @code{SIGILL} signals. You can also
enable them at startup by setting the 
@geindex PYTHONFAULTHANDLER
@geindex 环境变量; PYTHONFAULTHANDLER
@ref{9c2,,PYTHONFAULTHANDLER} environment
variable or by using the @ref{155,,-X} @code{faulthandler} command line option.

The fault handler is compatible with system fault handlers like Apport or the
Windows fault handler. The module uses an alternative stack for signal handlers
if the @code{sigaltstack()} function is available. This allows it to dump the
traceback even on a stack overflow.

The fault handler is called on catastrophic cases and therefore can only use
signal-safe functions (e.g. it cannot allocate memory on the heap). Because of
this limitation traceback dumping is minimal compared to normal Python
tracebacks:


@itemize *

@item 
Only ASCII is supported. The @code{backslashreplace} error handler is used on
encoding.

@item 
Each string is limited to 500 characters.

@item 
Only the filename, the function name and the line number are
displayed. (no source code)

@item 
It is limited to 100 frames and 100 threads.

@item 
The order is reversed: the most recent call is shown first.
@end itemize

By default, the Python traceback is written to @ref{308,,sys.stderr}. To see
tracebacks, applications must be run in the terminal. A log file can
alternatively be passed to @ref{543,,faulthandler.enable()}.

The module is implemented in C, so tracebacks can be dumped on a crash or when
Python is deadlocked.

@menu
* Dumping the traceback:: 
* Fault handler state:: 
* Dumping the tracebacks after a timeout:: 
* Dumping the traceback on a user signal:: 
* Issue with file descriptors:: 
* 示例: 示例<15>. 

@end menu

@node Dumping the traceback,Fault handler state,,faulthandler --- Dump the Python traceback
@anchor{library/faulthandler dumping-the-traceback}@anchor{34c2}
@subsubsection Dumping the traceback


@geindex dump_traceback() (在 faulthandler 模块中)
@anchor{library/faulthandler faulthandler dump_traceback}@anchor{6d2}
@deffn {函数} faulthandler.dump_traceback (file=sys.stderr, all_threads=True)

Dump the tracebacks of all threads into @emph{file}. If @emph{all_threads} is
@code{False}, dump only the current thread.


在 3.5 版更改: Added support for passing file descriptor to this function.

@end deffn

@node Fault handler state,Dumping the tracebacks after a timeout,Dumping the traceback,faulthandler --- Dump the Python traceback
@anchor{library/faulthandler fault-handler-state}@anchor{34c3}
@subsubsection Fault handler state


@geindex enable() (在 faulthandler 模块中)
@anchor{library/faulthandler faulthandler enable}@anchor{543}
@deffn {函数} faulthandler.enable (file=sys.stderr, all_threads=True)

Enable the fault handler: install handlers for the @code{SIGSEGV},
@code{SIGFPE}, @code{SIGABRT}, @code{SIGBUS} and @code{SIGILL}
signals to dump the Python traceback. If @emph{all_threads} is @code{True},
produce tracebacks for every running thread. Otherwise, dump only the current
thread.

The @emph{file} must be kept open until the fault handler is disabled: see
@ref{34c4,,issue with file descriptors}.


在 3.5 版更改: Added support for passing file descriptor to this function.



在 3.6 版更改: On Windows, a handler for Windows exception is also installed.

@end deffn

@geindex disable() (在 faulthandler 模块中)
@anchor{library/faulthandler faulthandler disable}@anchor{34c5}
@deffn {函数} faulthandler.disable ()

Disable the fault handler: uninstall the signal handlers installed by
@ref{543,,enable()}.
@end deffn

@geindex is_enabled() (在 faulthandler 模块中)
@anchor{library/faulthandler faulthandler is_enabled}@anchor{34c6}
@deffn {函数} faulthandler.is_enabled ()

Check if the fault handler is enabled.
@end deffn

@node Dumping the tracebacks after a timeout,Dumping the traceback on a user signal,Fault handler state,faulthandler --- Dump the Python traceback
@anchor{library/faulthandler dumping-the-tracebacks-after-a-timeout}@anchor{34c7}
@subsubsection Dumping the tracebacks after a timeout


@geindex dump_traceback_later() (在 faulthandler 模块中)
@anchor{library/faulthandler faulthandler dump_traceback_later}@anchor{6d3}
@deffn {函数} faulthandler.dump_traceback_later (timeout, repeat=False, file=sys.stderr, exit=False)

Dump the tracebacks of all threads, after a timeout of @emph{timeout} seconds, or
every @emph{timeout} seconds if @emph{repeat} is @code{True}.  If @emph{exit} is @code{True}, call
@code{_exit()} with status=1 after dumping the tracebacks.  (Note
@code{_exit()} exits the process immediately, which means it doesn't do any
cleanup like flushing file buffers.) If the function is called twice, the new
call replaces previous parameters and resets the timeout. The timer has a
sub-second resolution.

The @emph{file} must be kept open until the traceback is dumped or
@ref{34c8,,cancel_dump_traceback_later()} is called: see @ref{34c4,,issue with file descriptors}.

This function is implemented using a watchdog thread.


在 3.7 版更改: This function is now always available.



在 3.5 版更改: Added support for passing file descriptor to this function.

@end deffn

@geindex cancel_dump_traceback_later() (在 faulthandler 模块中)
@anchor{library/faulthandler faulthandler cancel_dump_traceback_later}@anchor{34c8}
@deffn {函数} faulthandler.cancel_dump_traceback_later ()

Cancel the last call to @ref{6d3,,dump_traceback_later()}.
@end deffn

@node Dumping the traceback on a user signal,Issue with file descriptors,Dumping the tracebacks after a timeout,faulthandler --- Dump the Python traceback
@anchor{library/faulthandler dumping-the-traceback-on-a-user-signal}@anchor{34c9}
@subsubsection Dumping the traceback on a user signal


@geindex register() (在 faulthandler 模块中)
@anchor{library/faulthandler faulthandler register}@anchor{6d1}
@deffn {函数} faulthandler.register (signum, file=sys.stderr, all_threads=True, chain=False)

Register a user signal: install a handler for the @emph{signum} signal to dump
the traceback of all threads, or of the current thread if @emph{all_threads} is
@code{False}, into @emph{file}. Call the previous handler if chain is @code{True}.

The @emph{file} must be kept open until the signal is unregistered by
@ref{34ca,,unregister()}: see @ref{34c4,,issue with file descriptors}.

Not available on Windows.


在 3.5 版更改: Added support for passing file descriptor to this function.

@end deffn

@geindex unregister() (在 faulthandler 模块中)
@anchor{library/faulthandler faulthandler unregister}@anchor{34ca}
@deffn {函数} faulthandler.unregister (signum)

Unregister a user signal: uninstall the handler of the @emph{signum} signal
installed by @ref{6d1,,register()}. Return @code{True} if the signal was registered,
@code{False} otherwise.

Not available on Windows.
@end deffn

@node Issue with file descriptors,示例<15>,Dumping the traceback on a user signal,faulthandler --- Dump the Python traceback
@anchor{library/faulthandler faulthandler-fd}@anchor{34c4}@anchor{library/faulthandler issue-with-file-descriptors}@anchor{34cb}
@subsubsection Issue with file descriptors


@ref{543,,enable()}, @ref{6d3,,dump_traceback_later()} and @ref{6d1,,register()} keep the
file descriptor of their @emph{file} argument. If the file is closed and its file
descriptor is reused by a new file, or if @ref{3b6,,os.dup2()} is used to replace
the file descriptor, the traceback will be written into a different file. Call
these functions again each time that the file is replaced.

@node 示例<15>,,Issue with file descriptors,faulthandler --- Dump the Python traceback
@anchor{library/faulthandler example}@anchor{34cc}
@subsubsection 示例


Example of a segmentation fault on Linux with and without enabling the fault
handler:

@example
$ python3 -c "import ctypes; ctypes.string_at(0)"
Segmentation fault

$ python3 -q -X faulthandler
>>> import ctypes
>>> ctypes.string_at(0)
Fatal Python error: Segmentation fault

Current thread 0x00007fb899f39700 (most recent call first):
  File "/home/python/cpython/Lib/ctypes/__init__.py", line 486 in string_at
  File "<stdin>", line 1 in <module>
Segmentation fault
@end example

@node pdb --- Python的调试器,Python Profilers 分析器,faulthandler --- Dump the Python traceback,调试和分析
@anchor{library/pdb doc}@anchor{34cd}@anchor{library/pdb debugger}@anchor{34ce}@anchor{library/pdb module-pdb}@anchor{c9}@anchor{library/pdb pdb-the-python-debugger}@anchor{34cf}
@subsection @code{pdb} --- Python的调试器


@geindex pdb (模块)

@strong{源代码：} Lib/pdb.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pdb.py}

@geindex debugging


__________________________________________________________________


@ref{c9,,pdb} 模块定义了一个交互式源代码调试器，用于 Python 程序。它支持在源码行间设置（有条件的）断点和单步执行，检视堆栈帧，列出源码列表，以及在任何堆栈帧的上下文中运行任意 Python 代码。它还支持事后调试，可以在程序控制下调用。

@geindex Pdb (class in pdb)
@geindex 模块; bdb
@geindex 模块; cmd

调试器是可扩展的——调试器实际被定义为 @ref{567,,Pdb} 类。该类目前没有文档，但通过阅读源码很容易理解它。扩展接口使用了 @ref{f,,bdb} 和 @ref{1a,,cmd} 模块。

调试器的提示符是 @code{(Pdb)}。在调试器的控制下运行程序的典型用法是:

@example
>>> import pdb
>>> import mymodule
>>> pdb.run('mymodule.test()')
> <string>(0)?()
(Pdb) continue
> <string>(1)?()
(Pdb) continue
NameError: 'spam'
> <string>(1)?()
(Pdb)
@end example


在 3.3 版更改: 由 @ref{de,,readline} 模块实现的 Tab 补全可用于补全本模块的命令和命令的参数，例如，@code{p} 命令的参数可补全为当前的全局变量和局部变量。


也可以将 @code{pdb.py} 作为脚本调用来调试其他脚本。例如:

@example
python3 -m pdb myscript.py
@end example

当作为脚本调用时，如果要调试的程序异常退出，pdb 调试将自动进入事后调试。事后调试之后（或程序正常退出之后），pdb 将重新启动程序。自动重启会保留 pdb 的状态（如断点），在大多数情况下，这比在退出程序的同时退出调试器更加实用。


3.2 新版功能: @code{pdb.py} 现在接受 @code{-c} 选项，可以执行命令，这与将该命令写入 @code{.pdbrc} 文件相同，请参阅 @ref{34d0,,调试器命令}。



3.7 新版功能: @code{pdb.py} 现在接受 @code{-m} 选项，该选项用于执行一个模块，类似于 @code{python3 -m}。与脚本相同，调试器将暂停在待执行模块第一行前。


从正在运行的程序进入调试器的典型用法是插入

@example
import pdb; pdb.set_trace()
@end example

到你想进入调试器的位置。然后就可以单步执行上述语句之后的代码，要关闭调试器继续运行，请使用 @ref{34d1,,continue} 命令。


3.7 新版功能: 内置函数 @ref{2f2,,breakpoint()}，当以默认参数调用它时，可以用来代替 @code{import pdb; pdb.set_trace()}。


检查已崩溃程序的典型用法是:

@example
>>> import pdb
>>> import mymodule
>>> mymodule.test()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "./mymodule.py", line 4, in test
    test2()
  File "./mymodule.py", line 3, in test2
    print(spam)
NameError: spam
>>> pdb.pm()
> ./mymodule.py(3)test2()
-> print(spam)
(Pdb)
@end example

本模块定义了下列函数，每个函数进入调试器的方式略有不同：

@geindex run() (在 pdb 模块中)
@anchor{library/pdb pdb run}@anchor{32b0}
@deffn {函数} pdb.run (statement, globals=None, locals=None)

在调试器控制范围内执行 @emph{statement} （以字符串或代码对象的形式提供）。调试器提示符会在执行代码前出现，你可以设置断点并键入 @ref{34d1,,continue}，也可以使用 @ref{34d2,,step} 或 @ref{34d3,,next} 逐步执行语句（上述所有命令在后文有说明）。可选参数 @emph{globals} 和 @emph{locals} 指定代码执行环境，默认时使用 @ref{1,,__main__} 模块的字典。（请参阅内置函数 @ref{c3d,,exec()} 或 @ref{b89,,eval()} 的说明。）
@end deffn

@geindex runeval() (在 pdb 模块中)
@anchor{library/pdb pdb runeval}@anchor{34d4}
@deffn {函数} pdb.runeval (expression, globals=None, locals=None)

在调试器控制范围内执行 @emph{expression} （以字符串或代码对象的形式提供）。@ref{34d4,,runeval()} 返回时将返回表达式的值。本函数在其他方面与 @ref{32b0,,run()} 类似。
@end deffn

@geindex runcall() (在 pdb 模块中)
@anchor{library/pdb pdb runcall}@anchor{34d5}
@deffn {函数} pdb.runcall (function, *args, **kwds)

使用给定的参数调用 @emph{function} （以函数或方法对象的形式提供，不能是字符串）。@ref{34d5,,runcall()} 返回的是所调用函数的返回值。调试器提示符将在进入函数后立即出现。
@end deffn

@geindex set_trace() (在 pdb 模块中)
@anchor{library/pdb pdb set_trace}@anchor{3ba}
@deffn {函数} pdb.set_trace (*, header=None)

在调用本函数的堆栈帧处进入调试器。用于硬编码一个断点到程序中的固定点处，即使该代码不在调试状态（如断言失败时）。如果传入 @emph{header}，它将在调试开始前被打印到控制台。


在 3.7 版更改: 仅关键字参数 @emph{header}。

@end deffn

@geindex post_mortem() (在 pdb 模块中)
@anchor{library/pdb pdb post_mortem}@anchor{d3e}
@deffn {函数} pdb.post_mortem (traceback=None)

进入 @emph{traceback} 对象的事后调试。如果没有给定 @emph{traceback}，默认使用当前正在处理的异常之一（默认时，必须存在正在处理的异常）。
@end deffn

@geindex pm() (在 pdb 模块中)
@anchor{library/pdb pdb pm}@anchor{34d6}
@deffn {函数} pdb.pm ()

在 @ref{34d7,,sys.last_traceback} 中查找 traceback，并进入其事后调试。
@end deffn

@code{run*} 函数和 @ref{3ba,,set_trace()} 都是别名，用于实例化 @ref{567,,Pdb} 类和调用同名方法。如果要使用其他功能，则必须自己执行以下操作：

@geindex Pdb (pdb 中的类)
@anchor{library/pdb pdb Pdb}@anchor{567}
@deffn {类} pdb.Pdb (completekey='tab', stdin=None, stdout=None, skip=None, nosigint=False, readrc=True)

@ref{567,,Pdb} 是调试器类。

@emph{completekey}、@emph{stdin} 和 @emph{stdout} 参数都会传递给底层的 @ref{30d9,,cmd.Cmd} 类，请参考相应的描述。

如果给出 @emph{skip} 参数，则它必须是一个迭代器，可以迭代出 glob-style 样式的模块名称。如果遇到匹配上述样式的模块，调试器将不会进入来自该模块的堆栈帧。 @footnote{@w{(1)} 
一个帧是否会被认为源自特定模块是由帧全局变量 @code{__name__} 来决定的。
}

默认情况下，当发出 @code{continue} 命令时，Pdb 将为 SIGINT 信号设置一个处理程序（SIGINT 信号是用户在控制台按 @code{Ctrl-C} 时发出的）。这使用户可以按 @code{Ctrl-C} 再次进入调试器。如果希望 Pdb 不要修改 SIGINT 处理程序，请将 @emph{nosigint} 设置为 true。

@emph{readrc} 参数默认为 true，它控制 Pdb 是否从文件系统加载 .pdbrc 文件。

启用跟踪且带有 @emph{skip} 参数的调用示范:

@example
import pdb; pdb.Pdb(skip=['django.*']).set_trace()
@end example

引发一个 @ref{12d0,,审计事件} @code{pdb.Pdb}，没有附带参数。


3.1 新版功能: @emph{skip} 参数。



3.2 新版功能: @emph{nosigint} 参数。在这之前，Pdb 不为 SIGINT 设置处理程序。



在 3.6 版更改: @emph{readrc} 参数。


@geindex run() (pdb.Pdb 方法)
@geindex runeval() (pdb.Pdb 方法)
@geindex runcall() (pdb.Pdb 方法)
@geindex set_trace() (pdb.Pdb 方法)
@anchor{library/pdb pdb Pdb run}@anchor{34d8}
@deffn {方法} run (statement, globals=None, locals=None)
@anchor{library/pdb pdb Pdb runeval}@anchor{34d9}
@deffnx {方法} runeval (expression, globals=None, locals=None)
@anchor{library/pdb pdb Pdb runcall}@anchor{34da}
@deffnx {方法} runcall (function, *args, **kwds)
@anchor{library/pdb pdb Pdb set_trace}@anchor{34db}
@deffnx {方法} set_trace ()

请参阅上文解释同名函数的文档。
@end deffn
@end deffn

@menu
* 调试器命令:: 

@end menu

@node 调试器命令,,,pdb --- Python的调试器
@anchor{library/pdb debugger-commands}@anchor{34d0}@anchor{library/pdb id2}@anchor{34dc}
@subsubsection 调试器命令


下方列出的是调试器可接受的命令。如下所示，大多数命令可以缩写为一个或两个字母。如 @code{h(elp)} 表示可以输入 @code{h} 或 @code{help} 来输入帮助命令（但不能输入 @code{he} 或 @code{hel}，也不能是 @code{H} 或 @code{Help} 或 @code{HELP}）。命令的参数必须用空格（空格符或制表符）分隔。在命令语法中，可选参数括在方括号 (@code{[]}) 中，使用时请勿输入方括号。命令语法中的选择项由竖线 (@code{|}) 分隔。

输入一个空白行将重复最后输入的命令。例外：如果最后一个命令是 @ref{34dd,,list} 命令，则会列出接下来的 11 行。

调试器无法识别的命令将被认为是 Python 语句，并在正在调试的程序的上下文中执行。Python 语句也可以用感叹号 (@code{!}) 作为前缀。这是检查正在调试的程序的强大方法，甚至可以修改变量或调用函数。当此类语句发生异常，将打印异常名称，但调试器的状态不会改变。

调试器支持 @ref{34de,,别名}。别名可以有参数，使得调试器对被检查的上下文有一定程度的适应性。

在一行中可以输入多个命令，以 @code{;;} 分隔。（不能使用单个 @code{;}，因为它用于分隔传递给 Python 解释器的一行中的多条语句。）切分命令很无脑，总是在第一个 @code{;;} 对处将输入切分开，即使它位于带引号的字符串之中。

@geindex .pdbrc; file
@geindex debugger; configuration; file

如果文件 @code{.pdbrc} 存在于用户主目录或当前目录中，则将其读入并执行，等同于在调试器提示符下键入该文件。这对于别名很有用。若两个文件都存在则首先读取主目录中的文件，且本地文件可以覆盖其中定义的别名。


在 3.2 版更改: @code{.pdbrc} 现在可以包含继续调试的命令，如 @ref{34d1,,continue} 或 @ref{34d3,,next}。文件中的这些命令以前是无效的。


@geindex help (pdb command)
@anchor{library/pdb pdbcommand-help}@anchor{34df}
@deffn {Pdbcommand} h(elp) [command]

不带参数时，显示可用的命令列表。参数为 @emph{command} 时，打印有关该命令的帮助。@code{help pdb} 显示完整文档（即 @ref{c9,,pdb} 模块的文档字符串）。由于 @emph{command} 参数必须是标识符，因此要获取 @code{!} 的帮助必须输入 @code{help exec}。
@end deffn

@geindex where (pdb command)
@anchor{library/pdb pdbcommand-where}@anchor{34e0}
@deffn {Pdbcommand} w(here)

打印堆栈回溯，最新一帧在底部。有一个箭头指向当前帧，该帧决定了大多数命令的上下文。
@end deffn

@geindex down (pdb command)
@anchor{library/pdb pdbcommand-down}@anchor{34e1}
@deffn {Pdbcommand} d(own) [count]

在堆栈回溯中，将当前帧向下移动 @emph{count} 级（默认为 1 级，移向更新的帧）。
@end deffn

@geindex up (pdb command)
@anchor{library/pdb pdbcommand-up}@anchor{34e2}
@deffn {Pdbcommand} u(p) [count]

在堆栈回溯中，将当前帧向上移动 @emph{count} 级（默认为 1 级，移向更老的帧）。
@end deffn

@geindex break (pdb command)
@anchor{library/pdb pdbcommand-break}@anchor{34e3}
@deffn {Pdbcommand} b(reak) [([filename:]lineno | function) [, condition]]

如果带有 @emph{lineno} 参数，则在当前文件相应行处设置一个断点。如果带有 @emph{function} 参数，则在该函数的第一条可执行语句处设置一个断点。行号可以加上文件名和冒号作为前缀，以在另一个文件（可能是尚未加载的文件）中设置一个断点。另一个文件将在 @ref{482,,sys.path} 范围内搜索。请注意，每个断点都分配有一个编号，其他所有断点命令都引用该编号。

如果第二个参数存在，它应该是一个表达式，且它的计算值为 true 时断点才起作用。

如果不带参数执行，将列出所有中断，包括每个断点、命中该断点的次数、当前的忽略次数以及关联的条件（如果有）。
@end deffn

@geindex tbreak (pdb command)
@anchor{library/pdb pdbcommand-tbreak}@anchor{34e4}
@deffn {Pdbcommand} tbreak [([filename:]lineno | function) [, condition]]

临时断点，在第一次命中时会自动删除。它的参数与 @ref{34e3,,break} 相同。
@end deffn

@geindex clear (pdb command)
@anchor{library/pdb pdbcommand-clear}@anchor{34e5}
@deffn {Pdbcommand} cl(ear) [filename:lineno | bpnumber [bpnumber ...]]

如果参数是 @emph{filename:lineno}，则清除此行上的所有断点。如果参数是空格分隔的断点编号列表，则清除这些断点。如果不带参数，则清除所有断点（但会先提示确认）。
@end deffn

@geindex disable (pdb command)
@anchor{library/pdb pdbcommand-disable}@anchor{34e6}
@deffn {Pdbcommand} disable [bpnumber [bpnumber ...]]

禁用断点，断点以空格分隔的断点编号列表给出。禁用断点表示它不会导致程序停止执行，但是与清除断点不同，禁用的断点将保留在断点列表中并且可以（重新）启用。
@end deffn

@geindex enable (pdb command)
@anchor{library/pdb pdbcommand-enable}@anchor{34e7}
@deffn {Pdbcommand} enable [bpnumber [bpnumber ...]]

启用指定的断点。
@end deffn

@geindex ignore (pdb command)
@anchor{library/pdb pdbcommand-ignore}@anchor{34e8}
@deffn {Pdbcommand} ignore bpnumber [count]

为指定的断点编号设置忽略次数。如果省略 count，则忽略次数将设置为 0。忽略次数为 0 时断点将变为活动状态。如果为非零值，在每次达到断点，且断点未禁用，且关联条件计算值为 true 的情况下，该忽略次数会递减。
@end deffn

@geindex condition (pdb command)
@anchor{library/pdb pdbcommand-condition}@anchor{34e9}
@deffn {Pdbcommand} condition bpnumber [condition]

为断点设置一个新 @emph{condition}，它是一个表达式，且它的计算值为 true 时断点才起作用。如果没有给出 @emph{condition}，则删除现有条件，也就是将断点设为无条件。
@end deffn

@geindex commands (pdb command)
@anchor{library/pdb pdbcommand-commands}@anchor{34ea}
@deffn {Pdbcommand} commands [bpnumber]

为编号是 @emph{bpnumber} 的断点指定一系列命令。命令内容将显示在后续的几行中。输入仅包含 @code{end} 的行来结束命令列表。举个例子:

@example
(Pdb) commands 1
(com) p some_variable
(com) end
(Pdb)
@end example

要删除断点上的所有命令，请输入 @code{commands} 并立即以 @code{end} 结尾，也就是不指定任何命令。

如果不带 @emph{bpnumber} 参数，@code{commands} 作用于最后一个被设置的断点。

可以使用断点命令来重新启动程序。只需使用 @ref{34d1,,continue} 或 @ref{34d2,,step} 命令或其他可以恢复运行的命令。

如果指定了某个继续运行程序的命令（目前包括 @ref{34d1,,continue}, @ref{34d2,,step}, @ref{34d3,,next}, @ref{34eb,,return}, @ref{34ec,,jump}, @ref{34ed,,quit} 及它们的缩写）将终止命令列表（就像该命令后紧跟着 end）。因为在任何时候继续运行下去（即使是简单的 next 或 step），都可能会遇到另一个断点，该断点可能具有自己的命令列表，这导致要执行的列表含糊不清。

如果在命令列表中加入 'silent' 命令，那么在该断点处停下时就不会打印常规信息。如果希望断点打印特定信息后继续运行，这可能是理想的。如果没有其他命令来打印一些信息，则看不到已达到断点的迹象。
@end deffn

@geindex step (pdb command)
@anchor{library/pdb pdbcommand-step}@anchor{34d2}
@deffn {Pdbcommand} s(tep)

执行当前行，在第一个可以停止的位置（在调用的函数中或在当前函数的下一行）停下。
@end deffn

@geindex next (pdb command)
@anchor{library/pdb pdbcommand-next}@anchor{34d3}
@deffn {Pdbcommand} n(ext)

继续运行，直到运行到当前函数的下一行，或当前函数返回为止。（ @ref{34d3,,next} 和 @ref{34d2,,step} 之间的区别在于，@ref{34d2,,step} 进入被调用函数内部并停止，而 @ref{34d3,,next} （几乎）全速运行被调用函数，仅在当前函数的下一行停止。）
@end deffn

@geindex until (pdb command)
@anchor{library/pdb pdbcommand-until}@anchor{34ee}
@deffn {Pdbcommand} unt(il) [lineno]

如果不带参数，则继续运行，直到行号比当前行大时停止。

如果带有行号，则继续运行，直到行号大于或等于该行号时停止。在这两种情况下，当前帧返回时也将停止。


在 3.2 版更改: 允许明确给定行号。

@end deffn

@geindex return (pdb command)
@anchor{library/pdb pdbcommand-return}@anchor{34eb}
@deffn {Pdbcommand} r(eturn)

继续运行，直到当前函数返回。
@end deffn

@geindex continue (pdb command)
@anchor{library/pdb pdbcommand-continue}@anchor{34d1}
@deffn {Pdbcommand} c(ont(inue))

继续运行，仅在遇到断点时停止。
@end deffn

@geindex jump (pdb command)
@anchor{library/pdb pdbcommand-jump}@anchor{34ec}
@deffn {Pdbcommand} j(ump) lineno

设置即将运行的下一行。仅可用于堆栈最底部的帧。它可以往回跳来再次运行代码，也可以往前跳来跳过不想运行的代码。

需要注意的是，不是所有的跳转都是允许的 -- 例如，不能跳转到 @ref{c29,,for} 循环的中间或跳出 @ref{182,,finally} 子句。
@end deffn

@geindex list (pdb command)
@anchor{library/pdb pdbcommand-list}@anchor{34dd}
@deffn {Pdbcommand} l(ist) [first[, last]]

列出当前文件的源代码。如果不带参数，则列出当前行周围的 11 行，或继续前一个列表。如果用 @code{.} 作为参数，则列出当前行周围的 11 行。如果带有一个参数，则列出那一行周围的 11 行。如果带有两个参数，则列出所给的范围中的代码；如果第二个参数小于第一个参数，则将其解释为列出行数的计数。

当前帧中的当前行用 @code{->} 标记。如果正在调试异常，且最早抛出或传递该异常的行不是当前行，则那一行用 @code{>>} 标记。


3.2 新版功能: @code{>>} 标记。

@end deffn

@geindex ll (pdb command)
@anchor{library/pdb pdbcommand-ll}@anchor{34ef}
@deffn {Pdbcommand} ll | longlist

列出当前函数或帧的所有源代码。相关行的标记与 @ref{34dd,,list} 相同。


3.2 新版功能.

@end deffn

@geindex args (pdb command)
@anchor{library/pdb pdbcommand-args}@anchor{34f0}
@deffn {Pdbcommand} a(rgs)

打印当前函数的参数列表。
@end deffn

@geindex p (pdb command)
@anchor{library/pdb pdbcommand-p}@anchor{881}
@deffn {Pdbcommand} p expression

在当前上下文中运行 @emph{expression} 并打印它的值。

@cartouche
@quotation 注解 
@code{print()} 也可以使用，但它不是一个调试器命令 --- 它执行 Python @ref{880,,print()} 函数。
@end quotation
@end cartouche
@end deffn

@geindex pp (pdb command)
@anchor{library/pdb pdbcommand-pp}@anchor{34f1}
@deffn {Pdbcommand} pp expression

与 @ref{881,,p} 命令类似，但表达式的值使用 @ref{d2,,pprint} 模块美观地打印。
@end deffn

@geindex whatis (pdb command)
@anchor{library/pdb pdbcommand-whatis}@anchor{34f2}
@deffn {Pdbcommand} whatis expression

打印 @emph{expression} 的类型。
@end deffn

@geindex source (pdb command)
@anchor{library/pdb pdbcommand-source}@anchor{34f3}
@deffn {Pdbcommand} source expression

尝试获取给定对象的源代码并显示出来。


3.2 新版功能.

@end deffn

@geindex display (pdb command)
@anchor{library/pdb pdbcommand-display}@anchor{34f4}
@deffn {Pdbcommand} display [expression]

如果表达式的值发生改变则显示它的值，每次将停止执行当前帧。

不带表达式则列出当前帧的所有显示表达式。


3.2 新版功能.

@end deffn

@geindex undisplay (pdb command)
@anchor{library/pdb pdbcommand-undisplay}@anchor{34f5}
@deffn {Pdbcommand} undisplay [expression]

不再显示当前帧中的表达式。 不带表达式则清除当前帧的所有显示表达式。


3.2 新版功能.

@end deffn

@geindex interact (pdb command)
@anchor{library/pdb pdbcommand-interact}@anchor{34f6}
@deffn {Pdbcommand} interact

启动一个交互式解释器（使用 @ref{1b,,code} 模块），它的全局命名空间将包含当前作用域中的所有（全局和局部）名称。


3.2 新版功能.

@end deffn
@anchor{library/pdb debugger-aliases}@anchor{34de}
@geindex alias (pdb command)
@anchor{library/pdb pdbcommand-alias}@anchor{34f7}
@deffn {Pdbcommand} alias [name [command]]

创建一个标识为 @emph{name} 的别名来执行 @emph{command}。 执行的命令 @emph{不可} 加上引号。 可替换形参可通过 @code{%1}, @code{%2} 等来标示，而 @code{%*} 会被所有形参所替换。 如果没有给出命令，则会显示 @emph{name} 的当前别名。 如果没有给出参数，则会列出所有别名。

别名允许嵌套并可包含能在 pdb 提示符下合法输入的任何内容。 请注意内部 pdb 命令 @emph{可以} 被别名所覆盖。 这样的命令将被隐藏直到别名被移除。 别名会递归地应用到命令行的第一个单词；行内的其他单词不会受影响。

作为示例，这里列出了两个有用的别名（特别适合放在 @code{.pdbrc} 文件中）:

@example
# Print instance variables (usage "pi classInst")
alias pi for k in %1.__dict__.keys(): print("%1.",k,"=",%1.__dict__[k])
# Print instance variables in self
alias ps pi self
@end example
@end deffn

@geindex unalias (pdb command)
@anchor{library/pdb pdbcommand-unalias}@anchor{34f8}
@deffn {Pdbcommand} unalias name

删除指定的别名。
@end deffn

@geindex ! (pdb command)
@anchor{library/pdb pdbcommand-!}@anchor{34f9}
@deffn {Pdbcommand} ! statement

在当前堆栈帧的上下文中执行 (单行) @emph{statement}。 感叹号可以被省略，除非语句的第一个单词与调试器命令重名。 要设置全局变量，你可以在同一行上为赋值命令添加前缀的 @ref{11d8,,global} 语句，例如:

@example
(Pdb) global list_options; list_options = ['-l']
(Pdb)
@end example
@end deffn

@geindex run (pdb command)
@geindex restart (pdb command)
@anchor{library/pdb pdbcommand-run}@anchor{34fa}
@deffn {Pdbcommand} run [args ...]
@anchor{library/pdb pdbcommand-restart}@anchor{34fb}
@deffnx {Pdbcommand} restart [args ...]

重启被调试的 Python 程序。 如果提供了参数，它会用 @ref{e8,,shlex} 来拆分且拆分结果将被用作新的 @ref{bf4,,sys.argv}。 历史、中断点、动作和调试器选项将被保留。 @ref{34fb,,restart} 是 @ref{34fa,,run} 的一个别名。
@end deffn

@geindex quit (pdb command)
@anchor{library/pdb pdbcommand-quit}@anchor{34ed}
@deffn {Pdbcommand} q(uit)

退出调试器。 被执行的程序将被中止。
@end deffn

@geindex debug (pdb command)
@anchor{library/pdb pdbcommand-debug}@anchor{34fc}
@deffn {Pdbcommand} debug code

进入一个对代码参数执行步进的递归调试器（该参数是在当前环境中执行的任意表达式或语句）。
@end deffn

@geindex retval (pdb command)
@anchor{library/pdb pdbcommand-retval}@anchor{34fd}
@deffn {Pdbcommand} retval

打印函数最后一次返回的返回值。
@end deffn

@subsubheading 备注


@node Python Profilers 分析器,timeit --- 测量小代码片段的执行时间,pdb --- Python的调试器,调试和分析
@anchor{library/profile doc}@anchor{34fe}@anchor{library/profile profile}@anchor{34ff}@anchor{library/profile the-python-profilers}@anchor{3500}
@subsection Python Profilers 分析器


@strong{源代码：} Lib/profile.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/profile.py} 和 Lib/pstats.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pstats.py}


__________________________________________________________________


@menu
* profile分析器简介:: 
* 实时用户手册:: 
* profile 和 cProfile 模块参考:: 
* Stats 类:: 
* 什么是确定性性能分析？:: 
* 局限性:: 
* 准确估量:: 
* 使用自定义计时器:: 

@end menu

@node profile分析器简介,实时用户手册,,Python Profilers 分析器
@anchor{library/profile introduction-to-the-profilers}@anchor{3501}@anchor{library/profile profiler-introduction}@anchor{3502}
@subsubsection profile分析器简介


@geindex deterministic profiling
@geindex profiling@comma{} deterministic

@ref{28,,cProfile} 和 @ref{d3,,profile} 提供了 Python 程序的 @emph{确定性性能分析} 。 @emph{profile} 是一组统计数据，描述程序的各个部分执行的频率和时间。这些统计数据可以通过 @ref{d4,,pstats} 模块格式化为报表。

Python 标准库提供了同一分析接口的两种不同实现：


@enumerate 

@item 
对于大多数用户，建议使用 @ref{28,,cProfile} ；这是一个 C 扩展插件，因为其合理的运行开销，所以适合于分析长时间运行的程序。该插件基于 @code{lsprof} ，由 Brett Rosen 和 Ted Chaotter 贡献。

@item 
@ref{d3,,profile} 是一个纯 Python 模块（@ref{28,,cProfile} 就是模拟其接口的 C 语言实现），但它会显著增加配置程序的开销。如果你正在尝试以某种方式扩展分析器，则使用此模块可能会更容易完成任务。该模块最初由 Jim Roskind  设计和编写。
@end enumerate

@cartouche
@quotation 注解 
profiler 分析器模块被设计为给指定的程序提供执行概要文件，而不是用于基准测试目的（ @ref{10b,,timeit} 才是用于此目标的，它能获得合理准确的结果）。这特别适用于将 Python 代码与 C 代码进行基准测试：分析器为Python 代码引入开销，但不会为 C级别的函数引入开销，因此 C 代码似乎比任何Python 代码都更快。
@end quotation
@end cartouche

@node 实时用户手册,profile 和 cProfile 模块参考,profile分析器简介,Python Profilers 分析器
@anchor{library/profile instant-user-s-manual}@anchor{3503}@anchor{library/profile profile-instant}@anchor{3504}
@subsubsection 实时用户手册


本节是为 “不想阅读手册” 的用户提供的。它提供了非常简短的概述，并允许用户快速对现有应用程序执行评测。

要分析采用单个参数的函数，可以执行以下操作：

@example
import cProfile
import re
cProfile.run('re.compile("foo|bar")')
@end example

（如果 @ref{28,,cProfile} 在您的系统上不可用，请使用 @ref{d3,,profile} 。）

上述操作将运行 @ref{444,,re.compile()} 并打印分析结果，如下所示：

@example
      197 function calls (192 primitive calls) in 0.002 seconds

Ordered by: standard name

ncalls  tottime  percall  cumtime  percall filename:lineno(function)
     1    0.000    0.000    0.001    0.001 <string>:1(<module>)
     1    0.000    0.000    0.001    0.001 re.py:212(compile)
     1    0.000    0.000    0.001    0.001 re.py:268(_compile)
     1    0.000    0.000    0.000    0.000 sre_compile.py:172(_compile_charset)
     1    0.000    0.000    0.000    0.000 sre_compile.py:201(_optimize_charset)
     4    0.000    0.000    0.000    0.000 sre_compile.py:25(_identityfunction)
   3/1    0.000    0.000    0.000    0.000 sre_compile.py:33(_compile)
@end example

第一行显示监听了197个调用。在这些调用中，有192个是 @emph{原始的} ，这意味着调用不是通过递归引发的。下一行: @code{Ordered by: standard name} ，表示最右边列中的文本字符串用于对输出进行排序。列标题包括：


@table @asis

@item ncalls

调用次数

@item tottime

在指定函数中消耗的总时间（不包括调用子函数的时间）

@item percall

是 @code{tottime} 除以 @code{ncalls} 的商

@item cumtime

指定的函数及其所有子函数（从调用到退出）消耗的累积时间。这个数字对于递归函数来说是准确的。

@item percall

是 @code{cumtime} 除以原始调用（次数）的商（即：函数运行一次的平均时间）

@item filename:lineno(function)

提供相应数据的每个函数
@end table

如果第一列中有两个数字（例如3/1），则表示函数递归。第二个值是原始调用次数，第一个是调用的总次数。请注意，当函数不递归时，这两个值是相同的，并且只打印单个数字。

profile 运行结束时，打印输出不是必须的。也可以通过为 @code{run()} 函数指定文件名，将结果保存到文件中：

@example
import cProfile
import re
cProfile.run('re.compile("foo|bar")', 'restats')
@end example

@ref{3505,,pstats.Stats} 类从文件中读取 profile 结果，并以各种方式对其进行格式化。

@ref{28,,cProfile} 和 @ref{d3,,profile} 文件也可以作为脚本调用，以分析另一个脚本。例如：

@example
python -m cProfile [-o output_file] [-s sort_order] (-m module | myscript.py)
@end example

@code{-o} 将profile 结果写入文件而不是标准输出

@code{-s} 指定 @ref{3506,,sort_stats()} 排序值之一以对输出进行排序。这仅适用于未提供 @code{-o} 的情况

@code{-m} 指定要分析的是模块而不是脚本。

@quotation


3.7 新版功能: @ref{28,,cProfile} 添加 @code{-m} 选项



3.8 新版功能: @ref{d3,,profile} 添加 @code{-m} 选项

@end quotation

The @ref{d4,,pstats} module's @ref{3505,,Stats} class has a variety of methods
for manipulating and printing the data saved into a profile results file:

@example
import pstats
from pstats import SortKey
p = pstats.Stats('restats')
p.strip_dirs().sort_stats(-1).print_stats()
@end example

The @ref{3507,,strip_dirs()} method removed the extraneous path from all
the module names. The @ref{3506,,sort_stats()} method sorted all the
entries according to the standard module/line/name string that is printed. The
@ref{3508,,print_stats()} method printed out all the statistics.  You
might try the following sort calls:

@example
p.sort_stats(SortKey.NAME)
p.print_stats()
@end example

The first call will actually sort the list by function name, and the second call
will print out the statistics.  The following are some interesting calls to
experiment with:

@example
p.sort_stats(SortKey.CUMULATIVE).print_stats(10)
@end example

This sorts the profile by cumulative time in a function, and then only prints
the ten most significant lines.  If you want to understand what algorithms are
taking time, the above line is what you would use.

If you were looking to see what functions were looping a lot, and taking a lot
of time, you would do:

@example
p.sort_stats(SortKey.TIME).print_stats(10)
@end example

to sort according to time spent within each function, and then print the
statistics for the top ten functions.

你也可以尝试：

@example
p.sort_stats(SortKey.FILENAME).print_stats('__init__')
@end example

This will sort all the statistics by file name, and then print out statistics
for only the class init methods (since they are spelled with @code{__init__} in
them).  As one final example, you could try:

@example
p.sort_stats(SortKey.TIME, SortKey.CUMULATIVE).print_stats(.5, 'init')
@end example

This line sorts statistics with a primary key of time, and a secondary key of
cumulative time, and then prints out some of the statistics. To be specific, the
list is first culled down to 50% (re: @code{.5}) of its original size, then only
lines containing @code{init} are maintained, and that sub-sub-list is printed.

If you wondered what functions called the above functions, you could now (@code{p}
is still sorted according to the last criteria) do:

@example
p.print_callers(.5, 'init')
@end example

and you would get a list of callers for each of the listed functions.

If you want more functionality, you're going to have to read the manual, or
guess what the following functions do:

@example
p.print_callees()
p.add('restats')
@end example

Invoked as a script, the @ref{d4,,pstats} module is a statistics browser for
reading and examining profile dumps.  It has a simple line-oriented interface
(implemented using @ref{1a,,cmd}) and interactive help.

@node profile 和 cProfile 模块参考,Stats 类,实时用户手册,Python Profilers 分析器
@anchor{library/profile module-cProfile}@anchor{28}@anchor{library/profile profile-and-cprofile-module-reference}@anchor{3509}
@subsubsection @code{profile} 和 @code{cProfile} 模块参考


@geindex cProfile (模块)
@anchor{library/profile module-profile}@anchor{d3}
@geindex profile (模块)

@ref{d3,,profile} 和 @ref{28,,cProfile} 模块都提供下列函数：

@geindex run() (在 profile 模块中)
@anchor{library/profile profile run}@anchor{350a}
@deffn {函数} profile.run (command, filename=None, sort=-1)

This function takes a single argument that can be passed to the @ref{c3d,,exec()}
function, and an optional file name.  In all cases this routine executes:

@example
exec(command, __main__.__dict__, __main__.__dict__)
@end example

and gathers profiling statistics from the execution. If no file name is
present, then this function automatically creates a @ref{3505,,Stats}
instance and prints a simple profiling report. If the sort value is specified,
it is passed to this @ref{3505,,Stats} instance to control how the
results are sorted.
@end deffn

@geindex runctx() (在 profile 模块中)
@anchor{library/profile profile runctx}@anchor{350b}
@deffn {函数} profile.runctx (command, globals, locals, filename=None, sort=-1)

This function is similar to @ref{350a,,run()}, with added arguments to supply the
globals and locals dictionaries for the @emph{command} string. This routine
executes:

@example
exec(command, globals, locals)
@end example

and gathers profiling statistics as in the @ref{350a,,run()} function above.
@end deffn

@geindex Profile (profile 中的类)
@anchor{library/profile profile Profile}@anchor{1bb}
@deffn {类} profile.Profile (timer=None, timeunit=0.0, subcalls=True, builtins=True)

This class is normally only used if more precise control over profiling is
needed than what the @code{cProfile.run()} function provides.

A custom timer can be supplied for measuring how long code takes to run via
the @emph{timer} argument. This must be a function that returns a single number
representing the current time. If the number is an integer, the @emph{timeunit}
specifies a multiplier that specifies the duration of each unit of time. For
example, if the timer returns times measured in thousands of seconds, the
time unit would be @code{.001}.

Directly using the @ref{1bb,,Profile} class allows formatting profile results
without writing the profile data to a file:

@example
import cProfile, pstats, io
from pstats import SortKey
pr = cProfile.Profile()
pr.enable()
# ... do something ...
pr.disable()
s = io.StringIO()
sortby = SortKey.CUMULATIVE
ps = pstats.Stats(pr, stream=s).sort_stats(sortby)
ps.print_stats()
print(s.getvalue())
@end example

The @ref{1bb,,Profile} class can also be used as a context manager (supported
only in @ref{28,,cProfile} module. see @ref{1420,,上下文管理器类型}):

@example
import cProfile

with cProfile.Profile() as pr:
    # ... do something ...

pr.print_stats()
@end example


在 3.8 版更改: 添加了上下文管理器支持。


@geindex enable() (profile.Profile 方法)
@anchor{library/profile profile Profile enable}@anchor{350c}
@deffn {方法} enable ()

开始收集分析数据。仅在 @ref{28,,cProfile} 可用。
@end deffn

@geindex disable() (profile.Profile 方法)
@anchor{library/profile profile Profile disable}@anchor{350d}
@deffn {方法} disable ()

停止收集分析数据。仅在 @ref{28,,cProfile} 可用。
@end deffn

@geindex create_stats() (profile.Profile 方法)
@anchor{library/profile profile Profile create_stats}@anchor{350e}
@deffn {方法} create_stats ()

停止收集分析数据，并在内部将结果记录为当前 profile。
@end deffn

@geindex print_stats() (profile.Profile 方法)
@anchor{library/profile profile Profile print_stats}@anchor{350f}
@deffn {方法} print_stats (sort=-1)

Create a @ref{3505,,Stats} object based on the current
profile and print the results to stdout.
@end deffn

@geindex dump_stats() (profile.Profile 方法)
@anchor{library/profile profile Profile dump_stats}@anchor{3510}
@deffn {方法} dump_stats (filename)

将当前profile 的结果写入 @emph{filename} 。
@end deffn

@geindex run() (profile.Profile 方法)
@anchor{library/profile profile Profile run}@anchor{3511}
@deffn {方法} run (cmd)

Profile the cmd via @ref{c3d,,exec()}.
@end deffn

@geindex runctx() (profile.Profile 方法)
@anchor{library/profile profile Profile runctx}@anchor{3512}
@deffn {方法} runctx (cmd, globals, locals)

Profile the cmd via @ref{c3d,,exec()} with the specified global and
local environment.
@end deffn

@geindex runcall() (profile.Profile 方法)
@anchor{library/profile profile Profile runcall}@anchor{29e}
@deffn {方法} runcall (func, *args, **kwargs)

Profile @code{func(*args, **kwargs)}
@end deffn
@end deffn

Note that profiling will only work if the called command/function actually
returns.  If the interpreter is terminated (e.g. via a @ref{cdb,,sys.exit()} call
during the called command/function execution) no profiling results will be
printed.

@node Stats 类,什么是确定性性能分析？,profile 和 cProfile 模块参考,Python Profilers 分析器
@anchor{library/profile profile-stats}@anchor{3513}@anchor{library/profile the-stats-class}@anchor{3514}
@subsubsection @code{Stats} 类


Analysis of the profiler data is done using the @ref{3505,,Stats} class.
@anchor{library/profile module-pstats}@anchor{d4}
@geindex pstats (模块)

@geindex Stats (pstats 中的类)
@anchor{library/profile pstats Stats}@anchor{3505}
@deffn {类} pstats.Stats (*filenames or profile, stream=sys.stdout)

This class constructor creates an instance of a "statistics object" from a
@emph{filename} (or list of filenames) or from a @code{Profile} instance. Output
will be printed to the stream specified by @emph{stream}.

The file selected by the above constructor must have been created by the
corresponding version of @ref{d3,,profile} or @ref{28,,cProfile}.  To be specific,
there is @emph{no} file compatibility guaranteed with future versions of this
profiler, and there is no compatibility with files produced by other
profilers, or the same profiler run on a different operating system.  If
several files are provided, all the statistics for identical functions will
be coalesced, so that an overall view of several processes can be considered
in a single report.  If additional files need to be combined with data in an
existing @ref{3505,,Stats} object, the @ref{3515,,add()} method
can be used.

Instead of reading the profile data from a file, a @code{cProfile.Profile}
or @ref{1bb,,profile.Profile} object can be used as the profile data source.

@ref{3505,,Stats} 对象有以下方法:

@geindex strip_dirs() (pstats.Stats 方法)
@anchor{library/profile pstats Stats strip_dirs}@anchor{3507}
@deffn {方法} strip_dirs ()

This method for the @ref{3505,,Stats} class removes all leading path
information from file names.  It is very useful in reducing the size of
the printout to fit within (close to) 80 columns.  This method modifies
the object, and the stripped information is lost.  After performing a
strip operation, the object is considered to have its entries in a
"random" order, as it was just after object initialization and loading.
If @ref{3507,,strip_dirs()} causes two function names to be
indistinguishable (they are on the same line of the same filename, and
have the same function name), then the statistics for these two entries
are accumulated into a single entry.
@end deffn

@geindex add() (pstats.Stats 方法)
@anchor{library/profile pstats Stats add}@anchor{3515}
@deffn {方法} add (*filenames)

This method of the @ref{3505,,Stats} class accumulates additional profiling
information into the current profiling object.  Its arguments should refer
to filenames created by the corresponding version of @ref{350a,,profile.run()}
or @code{cProfile.run()}. Statistics for identically named (re: file, line,
name) functions are automatically accumulated into single function
statistics.
@end deffn

@geindex dump_stats() (pstats.Stats 方法)
@anchor{library/profile pstats Stats dump_stats}@anchor{3516}
@deffn {方法} dump_stats (filename)

Save the data loaded into the @ref{3505,,Stats} object to a file named
@emph{filename}.  The file is created if it does not exist, and is overwritten
if it already exists.  This is equivalent to the method of the same name
on the @ref{1bb,,profile.Profile} and @code{cProfile.Profile} classes.
@end deffn

@geindex sort_stats() (pstats.Stats 方法)
@anchor{library/profile pstats Stats sort_stats}@anchor{3506}
@deffn {方法} sort_stats (*keys)

This method modifies the @ref{3505,,Stats} object by sorting it according to
the supplied criteria.  The argument can be either a string or a SortKey
enum identifying the basis of a sort (example: @code{'time'}, @code{'name'},
@code{SortKey.TIME} or @code{SortKey.NAME}). The SortKey enums argument have
advantage over the string argument in that it is more robust and less
error prone.

When more than one key is provided, then additional keys are used as
secondary criteria when there is equality in all keys selected before
them.  For example, @code{sort_stats(SortKey.NAME, SortKey.FILE)} will sort
all the entries according to their function name, and resolve all ties
(identical function names) by sorting by file name.

For the string argument, abbreviations can be used for any key names, as
long as the abbreviation is unambiguous.

The following are the valid string and SortKey:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

有效字符串参数

@tab

有效枚举参数

@tab

含义

@item

@code{'calls'}

@tab

SortKey.CALLS

@tab

调用次数

@item

@code{'cumulative'}

@tab

SortKey.CUMULATIVE

@tab

累积时间

@item

@code{'cumtime'}

@tab

N/A

@tab

累积时间

@item

@code{'file'}

@tab

N/A

@tab

文件名

@item

@code{'filename'}

@tab

SortKey.FILENAME

@tab

文件名

@item

@code{'module'}

@tab

N/A

@tab

文件名

@item

@code{'ncalls'}

@tab

N/A

@tab

调用次数

@item

@code{'pcalls'}

@tab

SortKey.PCALLS

@tab

原始调用计数

@item

@code{'line'}

@tab

SortKey.LINE

@tab

行号

@item

@code{'name'}

@tab

SortKey.NAME

@tab

函数名称

@item

@code{'nfl'}

@tab

SortKey.NFL

@tab

名称/文件/行

@item

@code{'stdname'}

@tab

SortKey.STDNAME

@tab

标准名称

@item

@code{'time'}

@tab

SortKey.TIME

@tab

内部时间

@item

@code{'tottime'}

@tab

N/A

@tab

内部时间

@end multitable


Note that all sorts on statistics are in descending order (placing most
time consuming items first), where as name, file, and line number searches
are in ascending order (alphabetical). The subtle distinction between
@code{SortKey.NFL} and @code{SortKey.STDNAME} is that the standard name is a
sort of the name as printed, which means that the embedded line numbers
get compared in an odd way.  For example, lines 3, 20, and 40 would (if
the file names were the same) appear in the string order 20, 3 and 40.
In contrast, @code{SortKey.NFL} does a numeric compare of the line numbers.
In fact, @code{sort_stats(SortKey.NFL)} is the same as
@code{sort_stats(SortKey.NAME, SortKey.FILENAME, SortKey.LINE)}.

For backward-compatibility reasons, the numeric arguments @code{-1}, @code{0},
@code{1}, and @code{2} are permitted.  They are interpreted as @code{'stdname'},
@code{'calls'}, @code{'time'}, and @code{'cumulative'} respectively.  If this old
style format (numeric) is used, only one sort key (the numeric key) will
be used, and additional arguments will be silently ignored.

@c For compatibility with the old profiler.


3.7 新版功能: Added the SortKey enum.

@end deffn

@geindex reverse_order() (pstats.Stats 方法)
@anchor{library/profile pstats Stats reverse_order}@anchor{3517}
@deffn {方法} reverse_order ()

This method for the @ref{3505,,Stats} class reverses the ordering of the
basic list within the object.  Note that by default ascending vs
descending order is properly selected based on the sort key of choice.

@c This method is provided primarily for compatibility with the old
@c profiler.
@end deffn

@geindex print_stats() (pstats.Stats 方法)
@anchor{library/profile pstats Stats print_stats}@anchor{3508}
@deffn {方法} print_stats (*restrictions)

This method for the @ref{3505,,Stats} class prints out a report as described
in the @ref{350a,,profile.run()} definition.

The order of the printing is based on the last
@ref{3506,,sort_stats()} operation done on the object (subject to
caveats in @ref{3515,,add()} and
@ref{3507,,strip_dirs()}).

The arguments provided (if any) can be used to limit the list down to the
significant entries.  Initially, the list is taken to be the complete set
of profiled functions.  Each restriction is either an integer (to select a
count of lines), or a decimal fraction between 0.0 and 1.0 inclusive (to
select a percentage of lines), or a string that will interpreted as a
regular expression (to pattern match the standard name that is printed).
If several restrictions are provided, then they are applied sequentially.
For example:

@example
print_stats(.1, 'foo:')
@end example

would first limit the printing to first 10% of list, and then only print
functions that were part of filename @code{.*foo:}.  In contrast, the
command:

@example
print_stats('foo:', .1)
@end example

would limit the list to all functions having file names @code{.*foo:},
and then proceed to only print the first 10% of them.
@end deffn

@geindex print_callers() (pstats.Stats 方法)
@anchor{library/profile pstats Stats print_callers}@anchor{3518}
@deffn {方法} print_callers (*restrictions)

This method for the @ref{3505,,Stats} class prints a list of all functions
that called each function in the profiled database.  The ordering is
identical to that provided by @ref{3508,,print_stats()}, and the
definition of the restricting argument is also identical.  Each caller is
reported on its own line.  The format differs slightly depending on the
profiler that produced the stats:


@itemize *

@item 
With @ref{d3,,profile}, a number is shown in parentheses after each caller
to show how many times this specific call was made.  For convenience, a
second non-parenthesized number repeats the cumulative time spent in the
function at the right.

@item 
With @ref{28,,cProfile}, each caller is preceded by three numbers: the
number of times this specific call was made, and the total and
cumulative times spent in the current function while it was invoked by
this specific caller.
@end itemize
@end deffn

@geindex print_callees() (pstats.Stats 方法)
@anchor{library/profile pstats Stats print_callees}@anchor{3519}
@deffn {方法} print_callees (*restrictions)

This method for the @ref{3505,,Stats} class prints a list of all function
that were called by the indicated function.  Aside from this reversal of
direction of calls (re: called vs was called by), the arguments and
ordering are identical to the @ref{3518,,print_callers()} method.
@end deffn
@end deffn

@node 什么是确定性性能分析？,局限性,Stats 类,Python Profilers 分析器
@anchor{library/profile deterministic-profiling}@anchor{351a}@anchor{library/profile what-is-deterministic-profiling}@anchor{351b}
@subsubsection 什么是确定性性能分析？


@emph{确定性性能分析} 旨在反映这样一个事实：即所有 @emph{函数调用} 、 @emph{函数返回} 和 @emph{异常} 事件都被监控，并且对这些事件之间的间隔（在此期间用户的代码正在执行）进行精确计时。相反，统计分析（不是由该模块完成）随机采样有效指令指针，并推断时间花费在哪里。后一种技术传统上涉及较少的开销（因为代码不需要检测），但只提供了时间花在哪里的相对指示。

在Python中，由于在执行过程中总有一个活动的解释器，因此执行确定性评测不需要插入指令的代码。Python 自动为每个事件提供一个:dfn:@cite{钩子} （可选回调）。此外，Python 的解释特性往往会给执行增加太多开销，以至于在典型的应用程序中，确定性分析往往只会增加很小的处理开销。结果是，确定性分析并没有那么代价高昂，但是它提供了有关 Python 程序执行的大量运行时统计信息。

调用计数统计信息可用于识别代码中的错误（意外计数），并识别可能的内联扩展点（高频调用）。内部时间统计可用于识别应仔细优化的 "热循环" 。累积时间统计可用于识别算法选择上的高级别错误。请注意，该分析器中对累积时间的异常处理，允许直接比较算法的递归实现与迭代实现的统计信息。

@node 局限性,准确估量,什么是确定性性能分析？,Python Profilers 分析器
@anchor{library/profile limitations}@anchor{351c}@anchor{library/profile profile-limitations}@anchor{351d}
@subsubsection 局限性


一个限制是关于时间信息的准确性。确定性性能分析存在一个涉及精度的基本问题。最明显的限制是，底层的 "时钟" 周期大约为0.001秒（通常）。因此，没有什么测量会比底层时钟更精确。如果进行了足够的测量，那么 "误差" 将趋于平均。不幸的是，删除第一个错误会导致第二个错误来源。

第二个问题是，从调度事件到分析器调用获取时间函数实际 @emph{获取} 时钟状态，这需要 "一段时间" 。类似地，从获取时钟值（然后保存）开始，直到再次执行用户代码为止，退出分析器事件句柄时也存在一定的延迟。因此，多次调用单个函数或调用多个函数通常会累积此错误。尽管这种方式的误差通常小于时钟的精度（小于一个时钟周期），但它 @emph{可以} 累积并变得非常可观。

与开销较低的 @ref{28,,cProfile} 相比， @ref{d3,,profile} 的问题更为严重。出于这个原因， @ref{d3,,profile} 提供了一种针对指定平台的自我校准方法，以便可以在很大程度上（平均地）消除此误差。  校准后，结果将更准确（在最小二乘意义上），但它有时会产生负数（当调用计数异常低，且概率之神对您不利时：-）。因此 @emph{不要} 对产生的负数感到惊慌。它们应该只在你手工校准分析器的情况下才会出现，实际上结果比没有校准的情况要好。

@node 准确估量,使用自定义计时器,局限性,Python Profilers 分析器
@anchor{library/profile calibration}@anchor{351e}@anchor{library/profile profile-calibration}@anchor{351f}
@subsubsection 准确估量


@ref{d3,,profile} 模块的 profiler 会从每个事件处理时间中减去一个常量，以补偿调用 time 函数和存储结果的开销。默认情况下，常数为0。对于特定的平台，可用以下程序获得更好修正常数（ @ref{351d,,局限性} ）。

@example
import profile
pr = profile.Profile()
for i in range(5):
    print(pr.calibrate(10000))
@end example

The method executes the number of Python calls given by the argument, directly
and again under the profiler, measuring the time for both. It then computes the
hidden overhead per profiler event, and returns that as a float.  For example,
on a 1.8Ghz Intel Core i5 running Mac OS X, and using Python's time.process_time() as
the timer, the magical number is about 4.04e-6.

The object of this exercise is to get a fairly consistent result. If your
computer is @emph{very} fast, or your timer function has poor resolution, you might
have to pass 100000, or even 1000000, to get consistent results.

当你有一个一致的答案时，有三种方法可以使用：

@example
import profile

# 1. Apply computed bias to all Profile instances created hereafter.
profile.Profile.bias = your_computed_bias

# 2. Apply computed bias to a specific Profile instance.
pr = profile.Profile()
pr.bias = your_computed_bias

# 3. Specify computed bias in instance constructor.
pr = profile.Profile(bias=your_computed_bias)
@end example

If you have a choice, you are better off choosing a smaller constant, and then
your results will "less often" show up as negative in profile statistics.

@node 使用自定义计时器,,准确估量,Python Profilers 分析器
@anchor{library/profile profile-timers}@anchor{3520}@anchor{library/profile using-a-custom-timer}@anchor{3521}
@subsubsection 使用自定义计时器


If you want to change how current time is determined (for example, to force use
of wall-clock time or elapsed process time), pass the timing function you want
to the @code{Profile} class constructor:

@example
pr = profile.Profile(your_time_func)
@end example

The resulting profiler will then call @code{your_time_func}. Depending on whether
you are using @ref{1bb,,profile.Profile} or @code{cProfile.Profile},
@code{your_time_func}'s return value will be interpreted differently:


@table @asis

@item @ref{1bb,,profile.Profile}

@code{your_time_func} should return a single number, or a list of numbers whose
sum is the current time (like what @ref{a57,,os.times()} returns).  If the
function returns a single time number, or the list of returned numbers has
length 2, then you will get an especially fast version of the dispatch
routine.

Be warned that you should calibrate the profiler class for the timer function
that you choose (see @ref{351f,,准确估量}).  For most machines, a timer
that returns a lone integer value will provide the best results in terms of
low overhead during profiling.  (@ref{a57,,os.times()} is @emph{pretty} bad, as it
returns a tuple of floating point values).  If you want to substitute a
better timer in the cleanest fashion, derive a class and hardwire a
replacement dispatch method that best handles your timer call, along with the
appropriate calibration constant.

@item @code{cProfile.Profile}

@code{your_time_func} should return a single number.  If it returns integers,
you can also invoke the class constructor with a second argument specifying
the real duration of one unit of time.  For example, if
@code{your_integer_time_func} returns times measured in thousands of seconds,
you would construct the @code{Profile} instance as follows:

@example
pr = cProfile.Profile(your_integer_time_func, 0.001)
@end example

As the @code{cProfile.Profile} class cannot be calibrated, custom timer
functions should be used with care and should be as fast as possible.  For
the best results with a custom timer, it might be necessary to hard-code it
in the C source of the internal @code{_lsprof} module.
@end table

Python 3.3 adds several new functions in @ref{10a,,time} that can be used to make
precise measurements of process or wall-clock time. For example, see
@ref{2aa,,time.perf_counter()}.

@node timeit --- 测量小代码片段的执行时间,trace --- Trace or track Python statement execution,Python Profilers 分析器,调试和分析
@anchor{library/timeit doc}@anchor{3522}@anchor{library/timeit module-timeit}@anchor{10b}@anchor{library/timeit timeit-measure-execution-time-of-small-code-snippets}@anchor{3523}
@subsection @code{timeit} --- 测量小代码片段的执行时间


@geindex timeit (模块)

@strong{源码：} Lib/timeit.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/timeit.py}

@geindex Benchmarking
@geindex Performance


__________________________________________________________________


该模块提供了一种简单的方法来计算一小段 Python 代码的耗时。它有 @ref{3524,,命令行界面} 以及一个 @ref{3525,,可调用} 方法。它避免了许多用于测量执行时间的常见陷阱。另见 Tim Peters 对 O'Reilly 出版的 @emph{Python Cookbook} 中“算法”章节的介绍。

@menu
* 基本示例: 基本示例<2>. 
* Python 接口:: 
* 命令行界面: 命令行界面<6>. 
* 例子: 例子<25>. 

@end menu

@node 基本示例<2>,Python 接口,,timeit --- 测量小代码片段的执行时间
@anchor{library/timeit basic-examples}@anchor{3526}
@subsubsection 基本示例


以下示例显示了如何使用 @ref{3524,,命令行界面} 来比较三个不同的表达式：

@example
$ python3 -m timeit '"-".join(str(n) for n in range(100))'
10000 loops, best of 5: 30.2 usec per loop
$ python3 -m timeit '"-".join([str(n) for n in range(100)])'
10000 loops, best of 5: 27.5 usec per loop
$ python3 -m timeit '"-".join(map(str, range(100)))'
10000 loops, best of 5: 23.2 usec per loop
@end example

这可以通过 @ref{3525,,Python 接口} 实现

@example
>>> import timeit
>>> timeit.timeit('"-".join(str(n) for n in range(100))', number=10000)
0.3018611848820001
>>> timeit.timeit('"-".join([str(n) for n in range(100)])', number=10000)
0.2727368790656328
>>> timeit.timeit('"-".join(map(str, range(100)))', number=10000)
0.23702679807320237
@end example

从 @ref{3525,,Python 接口} 还可以传出一个可调用对象:

@example
>>> timeit.timeit(lambda: "-".join(map(str, range(100))), number=10000)
0.19665591977536678
@end example

但请注意 @ref{76b,,timeit()} 仅在使用命令行界面时会自动确定重复次数。 在 @ref{3527,,例子} 一节你可以找到更多的进阶示例。

@node Python 接口,命令行界面<6>,基本示例<2>,timeit --- 测量小代码片段的执行时间
@anchor{library/timeit id1}@anchor{3528}@anchor{library/timeit python-interface}@anchor{3525}
@subsubsection Python 接口


该模块定义了三个便利函数和一个公共类：

@geindex timeit() (在 timeit 模块中)
@anchor{library/timeit timeit timeit}@anchor{76b}
@deffn {函数} timeit.timeit (stmt='pass', setup='pass', timer=<default timer>, number=1000000, globals=None)

使用给定语句、 @emph{setup} 代码和 @emph{timer} 函数创建一个 @ref{3529,,Timer} 实例，并执行 @emph{number} 次其 @ref{597,,timeit()} 方法。可选的 @emph{globals} 参数指定用于执行代码的命名空间。


在 3.5 版更改: 添加可选参数 @emph{globals} 。

@end deffn

@geindex repeat() (在 timeit 模块中)
@anchor{library/timeit timeit repeat}@anchor{352a}
@deffn {函数} timeit.repeat (stmt='pass', setup='pass', timer=<default timer>, repeat=5, number=1000000, globals=None)

使用给定语句、 @emph{setup} 代码和 @emph{timer} 函数创建一个 @ref{3529,,Timer} 实例，并使用给定的 @emph{repeat} 计数和 @emph{number} 执行运行其 @ref{352b,,repeat()} 方法。可选的 @emph{globals} 参数指定用于执行代码的命名空间。


在 3.5 版更改: 添加可选参数 @emph{globals} 。



在 3.7 版更改: @emph{repeat} 的默认值由 3 更改为 5 。

@end deffn

@geindex default_timer() (在 timeit 模块中)
@anchor{library/timeit timeit default_timer}@anchor{352c}
@deffn {函数} timeit.default_timer ()

默认的计时器，总是 @ref{2aa,,time.perf_counter()} 。


在 3.3 版更改: @ref{2aa,,time.perf_counter()} 现在是默认计时器。

@end deffn

@geindex Timer (timeit 中的类)
@anchor{library/timeit timeit Timer}@anchor{3529}
@deffn {类} timeit.Timer (stmt='pass', setup='pass', timer=<timer function>, globals=None)

用于小代码片段的计数执行速度的类。

构造函数接受一个将计时的语句、一个用于设置的附加语句和一个定时器函数。两个语句都默认为 @code{'pass'} ；计时器函数与平台有关（请参阅模块文档字符串）。 @emph{stmt} 和 @emph{setup} 也可能包含多个以 @code{;} 或换行符分隔的语句，只要它们不包含多行字符串文字即可。该语句默认在 timeit 的命名空间内执行；可以通过将命名空间传递给 @emph{globals} 来控制此行为。

要测量第一个语句的执行时间，请使用 @ref{597,,timeit()} 方法。 @ref{352b,,repeat()} 和 @ref{596,,autorange()} 方法是方便的方法来调用 @ref{597,,timeit()} 多次。

@emph{setup} 的执行时间从总体计时执行中排除。

@emph{stmt} 和 @emph{setup} 参数也可以使用不带参数的可调用对象。这将在一个计时器函数中嵌入对它们的调用，然后由 @ref{597,,timeit()} 执行。请注意，由于额外的函数调用，在这种情况下，计时开销会略大一些。


在 3.5 版更改: 添加可选参数 @emph{globals} 。


@geindex timeit() (timeit.Timer 方法)
@anchor{library/timeit timeit Timer timeit}@anchor{597}
@deffn {方法} timeit (number=1000000)

执行 @emph{number} 次主要语句。这将执行一次 setup 语句，然后返回执行主语句多次所需的时间，以秒为单位测量为浮点数。参数是通过循环的次数，默认为一百万。要使用的主语句、 setup 语句和 timer 函数将传递给构造函数。

@cartouche
@quotation 注解 
默认情况下， @ref{597,,timeit()} 暂时关闭 @ref{129e,,garbage collection} 。这种方法的优点在于它使独立时序更具可比性。缺点是GC可能是所测量功能性能的重要组成部分。如果是这样，可以在 @emph{setup} 字符串中的第一个语句重新启用GC。例如:

@example
timeit.Timer('for i in range(10): oct(i)', 'gc.enable()').timeit()
@end example
@end quotation
@end cartouche
@end deffn

@geindex autorange() (timeit.Timer 方法)
@anchor{library/timeit timeit Timer autorange}@anchor{596}
@deffn {方法} autorange (callback=None)

自动决定调用多少次 @ref{597,,timeit()} 。

这是一个便利函数，它反复调用 @ref{597,,timeit()} ，以便总时间 >= 0.2 秒，返回最终（循环次数，循环所用的时间）。它调用 @ref{597,,timeit()} 的次数以序列 1, 2, 5, 10, 20, 50, ... 递增，直到所用的时间至少为0.2秒。

如果给出 @emph{callback} 并且不是 @code{None} ，则在每次试验后将使用两个参数调用它： @code{callback(number, time_taken)} 。


3.6 新版功能.

@end deffn

@geindex repeat() (timeit.Timer 方法)
@anchor{library/timeit timeit Timer repeat}@anchor{352b}
@deffn {方法} repeat (repeat=5, number=1000000)

调用 @ref{597,,timeit()} 几次。

这是一个方便的函数，它反复调用 @ref{597,,timeit()} ，返回结果列表。第一个参数指定调用 @ref{597,,timeit()} 的次数。第二个参数指定 @ref{597,,timeit()} 的 @emph{number} 参数。

@cartouche
@quotation 注解 
从结果向量计算并报告平均值和标准差这些是很诱人的。但是，这不是很有用。在典型情况下，最低值给出了机器运行给定代码段的速度的下限；结果向量中较高的值通常不是由Python的速度变化引起的，而是由于其他过程干扰你的计时准确性。所以结果的 @ref{803,,min()} 可能是你应该感兴趣的唯一数字。之后，你应该看看整个向量并应用常识而不是统计。
@end quotation
@end cartouche


在 3.7 版更改: @emph{repeat} 的默认值由 3 更改为 5 。

@end deffn

@geindex print_exc() (timeit.Timer 方法)
@anchor{library/timeit timeit Timer print_exc}@anchor{352d}
@deffn {方法} print_exc (file=None)

帮助程序从计时代码中打印回溯。

典型使用:

@example
t = Timer(...)       # outside the try/except
try:
    t.timeit(...)    # or t.repeat(...)
except Exception:
    t.print_exc()
@end example

与标准回溯相比，优势在于将显示已编译模板中的源行。可选的 @emph{file} 参数指向发送回溯的位置；它默认为 @ref{308,,sys.stderr} 。
@end deffn
@end deffn

@node 命令行界面<6>,例子<25>,Python 接口,timeit --- 测量小代码片段的执行时间
@anchor{library/timeit command-line-interface}@anchor{352e}@anchor{library/timeit timeit-command-line-interface}@anchor{3524}
@subsubsection 命令行界面


从命令行调用程序时，使用以下表单:

@example
python -m timeit [-n N] [-r N] [-u U] [-s S] [-h] [statement ...]
@end example

如果了解以下选项：

@geindex timeit command line option; -n N
@geindex timeit command line option; --number=N
@anchor{library/timeit cmdoption-timeit-n}@anchor{352f}
@deffn {程序选项} @w{-}n N, @w{-}@w{-}number=N

执行 '语句' 多少次
@end deffn

@geindex timeit command line option; -r N
@geindex timeit command line option; --repeat=N
@anchor{library/timeit cmdoption-timeit-r}@anchor{3530}
@deffn {程序选项} @w{-}r N, @w{-}@w{-}repeat=N

重复计时器的次数（默认为5）
@end deffn

@geindex timeit command line option; -s S
@geindex timeit command line option; --setup=S
@anchor{library/timeit cmdoption-timeit-s}@anchor{3531}
@deffn {程序选项} @w{-}s S, @w{-}@w{-}setup=S

最初要执行一次的语句（默认为 @code{pass} ）
@end deffn

@geindex timeit command line option; -p
@geindex timeit command line option; --process
@anchor{library/timeit cmdoption-timeit-p}@anchor{3532}
@deffn {程序选项} @w{-}p, @w{-}@w{-}process

测量进程时间，而不是 wallclock 时间，使用 @ref{2ab,,time.process_time()} 而不是 @ref{2aa,,time.perf_counter()} ，这是默认值


3.3 新版功能.

@end deffn

@geindex timeit command line option; -u
@geindex timeit command line option; --unit=U
@anchor{library/timeit cmdoption-timeit-u}@anchor{3533}
@deffn {程序选项} @w{-}u, @w{-}@w{-}unit=U

@quotation

指定定时器输出的时间单位；可以选择 nsec，usec，msec或sec
@end quotation


3.5 新版功能.

@end deffn

@geindex timeit command line option; -v
@geindex timeit command line option; --verbose
@anchor{library/timeit cmdoption-timeit-v}@anchor{3534}
@deffn {程序选项} @w{-}v, @w{-}@w{-}verbose

打印原始计时结果；重复更多位数精度
@end deffn

@geindex timeit command line option; -h
@geindex timeit command line option; --help
@anchor{library/timeit cmdoption-timeit-h}@anchor{3535}
@deffn {程序选项} @w{-}h, @w{-}@w{-}help

打印一条简短的使用信息并退出
@end deffn

可以通过将每一行指定为单独的语句参数来给出多行语句；通过在引号中包含参数并使用前导空格可以缩进行。多个 @ref{3531,,-s} 选项的处理方式相似。

如果未给出 @ref{352f,,-n}，则会通过尝试按序列 1, 2, 5, 10, 20, 50, ... 递增的数值来计算合适的循环次数，直到总计时间至少为 0.2 秒。

@ref{352c,,default_timer()} 测量可能受到在同一台机器上运行的其他程序的影响，因此在需要精确计时时最好的做法是重复几次计时并使用最佳时间。 @ref{3530,,-r} 选项对此有利；在大多数情况下，默认的 5 次重复可能就足够了。 你可以使用 @ref{2ab,,time.process_time()} 来测量CPU时间。

@cartouche
@quotation 注解 
执行 pass 语句会产生一定的基线开销。这里的代码不会试图隐藏它，但你应该知道它。可以通过不带参数调用程序来测量基线开销，并且Python版本之间可能会有所不同。
@end quotation
@end cartouche

@node 例子<25>,,命令行界面<6>,timeit --- 测量小代码片段的执行时间
@anchor{library/timeit examples}@anchor{3536}@anchor{library/timeit timeit-examples}@anchor{3527}
@subsubsection 例子


可以提供一个在开头只执行一次的 setup 语句：

@example
$ python -m timeit -s 'text = "sample string"; char = "g"'  'char in text'
5000000 loops, best of 5: 0.0877 usec per loop
$ python -m timeit -s 'text = "sample string"; char = "g"'  'text.find(char)'
1000000 loops, best of 5: 0.342 usec per loop
@end example

@example
>>> import timeit
>>> timeit.timeit('char in text', setup='text = "sample string"; char = "g"')
0.41440500499993504
>>> timeit.timeit('text.find(char)', setup='text = "sample string"; char = "g"')
1.7246671520006203
@end example

使用 @ref{3529,,Timer} 类及其方法可以完成同样的操作:

@example
>>> import timeit
>>> t = timeit.Timer('char in text', setup='text = "sample string"; char = "g"')
>>> t.timeit()
0.3955516149999312
>>> t.repeat()
[0.40183617287970225, 0.37027556854118704, 0.38344867356679524, 0.3712595970846668, 0.37866875250654886]
@end example

以下示例显示如何计算包含多行的表达式。 在这里我们对比使用 @ref{442,,hasattr()} 与 @ref{d6b,,try}/@ref{b37,,except} 的开销来测试缺失与提供对象属性:

@example
$ python -m timeit 'try:' '  str.__bool__' 'except AttributeError:' '  pass'
20000 loops, best of 5: 15.7 usec per loop
$ python -m timeit 'if hasattr(str, "__bool__"): pass'
50000 loops, best of 5: 4.26 usec per loop

$ python -m timeit 'try:' '  int.__bool__' 'except AttributeError:' '  pass'
200000 loops, best of 5: 1.43 usec per loop
$ python -m timeit 'if hasattr(int, "__bool__"): pass'
100000 loops, best of 5: 2.23 usec per loop
@end example

@example
>>> import timeit
>>> # attribute is missing
>>> s = """\
... try:
...     str.__bool__
... except AttributeError:
...     pass
... """
>>> timeit.timeit(stmt=s, number=100000)
0.9138244460009446
>>> s = "if hasattr(str, '__bool__'): pass"
>>> timeit.timeit(stmt=s, number=100000)
0.5829014980008651
>>>
>>> # attribute is present
>>> s = """\
... try:
...     int.__bool__
... except AttributeError:
...     pass
... """
>>> timeit.timeit(stmt=s, number=100000)
0.04215312199994514
>>> s = "if hasattr(int, '__bool__'): pass"
>>> timeit.timeit(stmt=s, number=100000)
0.08588060699912603
@end example

要让 @ref{10b,,timeit} 模块访问你定义的函数，你可以传递一个包含 import 语句的 @emph{setup} 参数:

@example
def test():
    """Stupid test function"""
    L = [i for i in range(100)]

if __name__ == '__main__':
    import timeit
    print(timeit.timeit("test()", setup="from __main__ import test"))
@end example

另一种选择是将 @ref{157b,,globals()} 传递给 @emph{globals} 参数，这将导致代码在当前的全局命名空间中执行。这比单独指定 import 更方便

@example
def f(x):
    return x**2
def g(x):
    return x**4
def h(x):
    return x**8

import timeit
print(timeit.timeit('[func(42) for func in (f,g,h)]', globals=globals()))
@end example

@node trace --- Trace or track Python statement execution,tracemalloc --- 跟踪内存分配,timeit --- 测量小代码片段的执行时间,调试和分析
@anchor{library/trace doc}@anchor{3537}@anchor{library/trace module-trace}@anchor{112}@anchor{library/trace trace-trace-or-track-python-statement-execution}@anchor{3538}
@subsection @code{trace} --- Trace or track Python statement execution


@geindex trace (模块)

@strong{Source code:} Lib/trace.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/trace.py}


__________________________________________________________________


The @ref{112,,trace} module allows you to trace program execution, generate
annotated statement coverage listings, print caller/callee relationships and
list functions executed during a program run.  It can be used in another program
or from the command line.


@subsubheading 参见



@table @asis

@item Coverage.py@footnote{https://coverage.readthedocs.io/}

A popular third-party coverage tool that provides HTML
output along with advanced features such as branch coverage.
@end table


@menu
* Command-Line Usage:: 
* 编程接口:: 

@end menu

@node Command-Line Usage,编程接口,,trace --- Trace or track Python statement execution
@anchor{library/trace command-line-usage}@anchor{3539}@anchor{library/trace trace-cli}@anchor{353a}
@subsubsection Command-Line Usage


The @ref{112,,trace} module can be invoked from the command line.  It can be as
simple as

@example
python -m trace --count -C . somefile.py ...
@end example

The above will execute @code{somefile.py} and generate annotated listings of
all Python modules imported during the execution into the current directory.

@geindex trace command line option; --help
@anchor{library/trace cmdoption-trace-help}@anchor{353b}
@deffn {程序选项} @w{-}@w{-}help

Display usage and exit.
@end deffn

@geindex trace command line option; --version
@anchor{library/trace cmdoption-trace-version}@anchor{353c}
@deffn {程序选项} @w{-}@w{-}version

Display the version of the module and exit.
@end deffn


3.8 新版功能: Added @code{--module} option that allows to run an executable module.


@menu
* Main options:: 
* Modifiers:: 
* Filters:: 

@end menu

@node Main options,Modifiers,,Command-Line Usage
@anchor{library/trace main-options}@anchor{353d}
@subsubsection Main options


At least one of the following options must be specified when invoking
@ref{112,,trace}.  The @ref{353e,,--listfuncs} option is mutually exclusive with
the @ref{353f,,--trace} and @ref{3540,,--count} options. When
@ref{353e,,--listfuncs} is provided, neither @ref{3540,,--count} nor
@ref{353f,,--trace} are accepted, and vice versa.

@geindex trace command line option; -c
@geindex trace command line option; --count
@anchor{library/trace cmdoption-trace-c}@anchor{3540}
@deffn {程序选项} @w{-}c, @w{-}@w{-}count

Produce a set of annotated listing files upon program completion that shows
how many times each statement was executed.  See also
@ref{3541,,--coverdir}, @ref{3542,,--file} and
@ref{3543,,--no-report} below.
@end deffn

@geindex trace command line option; -t
@geindex trace command line option; --trace
@anchor{library/trace cmdoption-trace-t}@anchor{353f}
@deffn {程序选项} @w{-}t, @w{-}@w{-}trace

Display lines as they are executed.
@end deffn

@geindex trace command line option; -l
@geindex trace command line option; --listfuncs
@anchor{library/trace cmdoption-trace-l}@anchor{353e}
@deffn {程序选项} @w{-}l, @w{-}@w{-}listfuncs

Display the functions executed by running the program.
@end deffn

@geindex trace command line option; -r
@geindex trace command line option; --report
@anchor{library/trace cmdoption-trace-r}@anchor{3544}
@deffn {程序选项} @w{-}r, @w{-}@w{-}report

Produce an annotated list from an earlier program run that used the
@ref{3540,,--count} and @ref{3542,,--file} option.  This does not
execute any code.
@end deffn

@geindex trace command line option; -T
@geindex trace command line option; --trackcalls
@anchor{library/trace cmdoption-trace-trackcalls}@anchor{3545}
@deffn {程序选项} @w{-}T, @w{-}@w{-}trackcalls

Display the calling relationships exposed by running the program.
@end deffn

@node Modifiers,Filters,Main options,Command-Line Usage
@anchor{library/trace modifiers}@anchor{3546}
@subsubsection Modifiers


@geindex trace command line option; -f
@geindex trace command line option; --file=<file>
@anchor{library/trace cmdoption-trace-f}@anchor{3542}
@deffn {程序选项} @w{-}f, @w{-}@w{-}file=<file>

Name of a file to accumulate counts over several tracing runs.  Should be
used with the @ref{3540,,--count} option.
@end deffn

@geindex trace command line option; -C
@geindex trace command line option; --coverdir=<dir>
@anchor{library/trace cmdoption-trace-coverdir}@anchor{3541}
@deffn {程序选项} @w{-}C, @w{-}@w{-}coverdir=<dir>

Directory where the report files go.  The coverage report for
@code{package.module} is written to file @code{@emph{dir}/@emph{package}/@emph{module}.cover}.
@end deffn

@geindex trace command line option; -m
@geindex trace command line option; --missing
@anchor{library/trace cmdoption-trace-m}@anchor{3547}
@deffn {程序选项} @w{-}m, @w{-}@w{-}missing

When generating annotated listings, mark lines which were not executed with
@code{>>>>>>}.
@end deffn

@geindex trace command line option; -s
@geindex trace command line option; --summary
@anchor{library/trace cmdoption-trace-s}@anchor{3548}
@deffn {程序选项} @w{-}s, @w{-}@w{-}summary

When using @ref{3540,,--count} or @ref{3544,,--report}, write a brief
summary to stdout for each file processed.
@end deffn

@geindex trace command line option; -R
@geindex trace command line option; --no-report
@anchor{library/trace cmdoption-trace-no-report}@anchor{3543}
@deffn {程序选项} @w{-}R, @w{-}@w{-}no@w{-}report

Do not generate annotated listings.  This is useful if you intend to make
several runs with @ref{3540,,--count}, and then produce a single set of
annotated listings at the end.
@end deffn

@geindex trace command line option; -g
@geindex trace command line option; --timing
@anchor{library/trace cmdoption-trace-g}@anchor{3549}
@deffn {程序选项} @w{-}g, @w{-}@w{-}timing

Prefix each line with the time since the program started.  Only used while
tracing.
@end deffn

@node Filters,,Modifiers,Command-Line Usage
@anchor{library/trace filters}@anchor{354a}
@subsubsection Filters


These options may be repeated multiple times.

@geindex trace command line option; --ignore-module=<mod>
@anchor{library/trace cmdoption-trace-ignore-module}@anchor{354b}
@deffn {程序选项} @w{-}@w{-}ignore@w{-}module=<mod>

Ignore each of the given module names and its submodules (if it is a
package).  The argument can be a list of names separated by a comma.
@end deffn

@geindex trace command line option; --ignore-dir=<dir>
@anchor{library/trace cmdoption-trace-ignore-dir}@anchor{354c}
@deffn {程序选项} @w{-}@w{-}ignore@w{-}dir=<dir>

Ignore all modules and packages in the named directory and subdirectories.
The argument can be a list of directories separated by @ref{12eb,,os.pathsep}.
@end deffn

@node 编程接口,,Command-Line Usage,trace --- Trace or track Python statement execution
@anchor{library/trace programmatic-interface}@anchor{354d}@anchor{library/trace trace-api}@anchor{354e}
@subsubsection 编程接口


@geindex Trace (trace 中的类)
@anchor{library/trace trace Trace}@anchor{354f}
@deffn {类} trace.Trace (count=1, trace=1, countfuncs=0, countcallers=0, ignoremods=(), ignoredirs=(), infile=None, outfile=None, timing=False)

Create an object to trace execution of a single statement or expression.  All
parameters are optional.  @emph{count} enables counting of line numbers.  @emph{trace}
enables line execution tracing.  @emph{countfuncs} enables listing of the
functions called during the run.  @emph{countcallers} enables call relationship
tracking.  @emph{ignoremods} is a list of modules or packages to ignore.
@emph{ignoredirs} is a list of directories whose modules or packages should be
ignored.  @emph{infile} is the name of the file from which to read stored count
information.  @emph{outfile} is the name of the file in which to write updated
count information.  @emph{timing} enables a timestamp relative to when tracing was
started to be displayed.

@quotation

@geindex run() (trace.Trace 方法)
@anchor{library/trace trace Trace run}@anchor{3550}
@deffn {方法} run (cmd)

Execute the command and gather statistics from the execution with
the current tracing parameters.  @emph{cmd} must be a string or code object,
suitable for passing into @ref{c3d,,exec()}.
@end deffn

@geindex runctx() (trace.Trace 方法)
@anchor{library/trace trace Trace runctx}@anchor{3551}
@deffn {方法} runctx (cmd, globals=None, locals=None)

Execute the command and gather statistics from the execution with the
current tracing parameters, in the defined global and local
environments.  If not defined, @emph{globals} and @emph{locals} default to empty
dictionaries.
@end deffn

@geindex runfunc() (trace.Trace 方法)
@anchor{library/trace trace Trace runfunc}@anchor{2a0}
@deffn {方法} runfunc (func, *args, **kwds)

Call @emph{func} with the given arguments under control of the @ref{354f,,Trace}
object with the current tracing parameters.
@end deffn

@geindex results() (trace.Trace 方法)
@anchor{library/trace trace Trace results}@anchor{3552}
@deffn {方法} results ()

Return a @ref{3553,,CoverageResults} object that contains the cumulative
results of all previous calls to @code{run}, @code{runctx} and @code{runfunc}
for the given @ref{354f,,Trace} instance.  Does not reset the accumulated
trace results.
@end deffn
@end quotation
@end deffn

@geindex CoverageResults (trace 中的类)
@anchor{library/trace trace CoverageResults}@anchor{3553}
@deffn {类} trace.CoverageResults

A container for coverage results, created by @ref{3552,,Trace.results()}.  Should
not be created directly by the user.

@quotation

@geindex update() (trace.CoverageResults 方法)
@anchor{library/trace trace CoverageResults update}@anchor{3554}
@deffn {方法} update (other)

Merge in data from another @ref{3553,,CoverageResults} object.
@end deffn

@geindex write_results() (trace.CoverageResults 方法)
@anchor{library/trace trace CoverageResults write_results}@anchor{3555}
@deffn {方法} write_results (show_missing=True, summary=False, coverdir=None)

Write coverage results.  Set @emph{show_missing} to show lines that had no
hits.  Set @emph{summary} to include in the output the coverage summary per
module.  @emph{coverdir} specifies the directory into which the coverage
result files will be output.  If @code{None}, the results for each source
file are placed in its directory.
@end deffn
@end quotation
@end deffn

A simple example demonstrating the use of the programmatic interface:

@example
import sys
import trace

# create a Trace object, telling it what to ignore, and whether to
# do tracing or line-counting or both.
tracer = trace.Trace(
    ignoredirs=[sys.prefix, sys.exec_prefix],
    trace=0,
    count=1)

# run the new command using the given tracer
tracer.run('main()')

# make a report, placing output in the current directory
r = tracer.results()
r.write_results(show_missing=True, coverdir=".")
@end example

@node tracemalloc --- 跟踪内存分配,,trace --- Trace or track Python statement execution,调试和分析
@anchor{library/tracemalloc doc}@anchor{3556}@anchor{library/tracemalloc module-tracemalloc}@anchor{114}@anchor{library/tracemalloc tracemalloc-trace-memory-allocations}@anchor{3557}
@subsection @code{tracemalloc} --- 跟踪内存分配


@geindex tracemalloc (模块)


3.4 新版功能.


@strong{源代码：} Lib/tracemalloc.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tracemalloc.py}


__________________________________________________________________


The tracemalloc module is a debug tool to trace memory blocks allocated by
Python. It provides the following information:


@itemize *

@item 
Traceback where an object was allocated

@item 
Statistics on allocated memory blocks per filename and per line number:
total size, number and average size of allocated memory blocks

@item 
Compute the differences between two snapshots to detect memory leaks
@end itemize

To trace most memory blocks allocated by Python, the module should be started
as early as possible by setting the 
@geindex PYTHONTRACEMALLOC
@geindex 环境变量; PYTHONTRACEMALLOC
@ref{12f1,,PYTHONTRACEMALLOC} environment
variable to @code{1}, or by using @ref{155,,-X} @code{tracemalloc} command line
option. The @ref{12e5,,tracemalloc.start()} function can be called at runtime to
start tracing Python memory allocations.

By default, a trace of an allocated memory block only stores the most recent
frame (1 frame). To store 25 frames at startup: set the
@geindex PYTHONTRACEMALLOC
@geindex 环境变量; PYTHONTRACEMALLOC
@ref{12f1,,PYTHONTRACEMALLOC} environment variable to @code{25}, or use the
@ref{155,,-X} @code{tracemalloc=25} command line option.

@menu
* 例子: 例子<26>. 
* API:: 

@end menu

@node 例子<26>,API,,tracemalloc --- 跟踪内存分配
@anchor{library/tracemalloc examples}@anchor{3558}
@subsubsection 例子


@menu
* 显示前10项:: 
* 计算差异:: 
* Get the traceback of a memory block:: 
* Pretty top:: 

@end menu

@node 显示前10项,计算差异,,例子<26>
@anchor{library/tracemalloc display-the-top-10}@anchor{3559}
@subsubsection 显示前10项


显示内存分配最多的10个文件：

@example
import tracemalloc

tracemalloc.start()

# ... run your application ...

snapshot = tracemalloc.take_snapshot()
top_stats = snapshot.statistics('lineno')

print("[ Top 10 ]")
for stat in top_stats[:10]:
    print(stat)
@end example

Python测试套件的输出示例：

@example
[ Top 10 ]
<frozen importlib._bootstrap>:716: size=4855 KiB, count=39328, average=126 B
<frozen importlib._bootstrap>:284: size=521 KiB, count=3199, average=167 B
/usr/lib/python3.4/collections/__init__.py:368: size=244 KiB, count=2315, average=108 B
/usr/lib/python3.4/unittest/case.py:381: size=185 KiB, count=779, average=243 B
/usr/lib/python3.4/unittest/case.py:402: size=154 KiB, count=378, average=416 B
/usr/lib/python3.4/abc.py:133: size=88.7 KiB, count=347, average=262 B
<frozen importlib._bootstrap>:1446: size=70.4 KiB, count=911, average=79 B
<frozen importlib._bootstrap>:1454: size=52.0 KiB, count=25, average=2131 B
<string>:5: size=49.7 KiB, count=148, average=344 B
/usr/lib/python3.4/sysconfig.py:411: size=48.0 KiB, count=1, average=48.0 KiB
@end example

We can see that Python loaded @code{4855 KiB} data (bytecode and constants) from
modules and that the @ref{1e,,collections} module allocated @code{244 KiB} to build
@ref{1b6,,namedtuple} types.

See @ref{355a,,Snapshot.statistics()} for more options.

@node 计算差异,Get the traceback of a memory block,显示前10项,例子<26>
@anchor{library/tracemalloc compute-differences}@anchor{355b}
@subsubsection 计算差异


获取两个快照并显示差异：

@example
import tracemalloc
tracemalloc.start()
# ... start your application ...

snapshot1 = tracemalloc.take_snapshot()
# ... call the function leaking memory ...
snapshot2 = tracemalloc.take_snapshot()

top_stats = snapshot2.compare_to(snapshot1, 'lineno')

print("[ Top 10 differences ]")
for stat in top_stats[:10]:
    print(stat)
@end example

Example of output before/after running some tests of the Python test suite:

@example
[ Top 10 differences ]
<frozen importlib._bootstrap>:716: size=8173 KiB (+4428 KiB), count=71332 (+39369), average=117 B
/usr/lib/python3.4/linecache.py:127: size=940 KiB (+940 KiB), count=8106 (+8106), average=119 B
/usr/lib/python3.4/unittest/case.py:571: size=298 KiB (+298 KiB), count=589 (+589), average=519 B
<frozen importlib._bootstrap>:284: size=1005 KiB (+166 KiB), count=7423 (+1526), average=139 B
/usr/lib/python3.4/mimetypes.py:217: size=112 KiB (+112 KiB), count=1334 (+1334), average=86 B
/usr/lib/python3.4/http/server.py:848: size=96.0 KiB (+96.0 KiB), count=1 (+1), average=96.0 KiB
/usr/lib/python3.4/inspect.py:1465: size=83.5 KiB (+83.5 KiB), count=109 (+109), average=784 B
/usr/lib/python3.4/unittest/mock.py:491: size=77.7 KiB (+77.7 KiB), count=143 (+143), average=557 B
/usr/lib/python3.4/urllib/parse.py:476: size=71.8 KiB (+71.8 KiB), count=969 (+969), average=76 B
/usr/lib/python3.4/contextlib.py:38: size=67.2 KiB (+67.2 KiB), count=126 (+126), average=546 B
@end example

We can see that Python has loaded @code{8173 KiB} of module data (bytecode and
constants), and that this is @code{4428 KiB} more than had been loaded before the
tests, when the previous snapshot was taken. Similarly, the @ref{a8,,linecache}
module has cached @code{940 KiB} of Python source code to format tracebacks, all
of it since the previous snapshot.

If the system has little free memory, snapshots can be written on disk using
the @ref{355c,,Snapshot.dump()} method to analyze the snapshot offline. Then use the
@ref{355d,,Snapshot.load()} method reload the snapshot.

@node Get the traceback of a memory block,Pretty top,计算差异,例子<26>
@anchor{library/tracemalloc get-the-traceback-of-a-memory-block}@anchor{355e}
@subsubsection Get the traceback of a memory block


Code to display the traceback of the biggest memory block:

@example
import tracemalloc

# Store 25 frames
tracemalloc.start(25)

# ... run your application ...

snapshot = tracemalloc.take_snapshot()
top_stats = snapshot.statistics('traceback')

# pick the biggest memory block
stat = top_stats[0]
print("%s memory blocks: %.1f KiB" % (stat.count, stat.size / 1024))
for line in stat.traceback.format():
    print(line)
@end example

Example of output of the Python test suite (traceback limited to 25 frames):

@example
903 memory blocks: 870.1 KiB
  File "<frozen importlib._bootstrap>", line 716
  File "<frozen importlib._bootstrap>", line 1036
  File "<frozen importlib._bootstrap>", line 934
  File "<frozen importlib._bootstrap>", line 1068
  File "<frozen importlib._bootstrap>", line 619
  File "<frozen importlib._bootstrap>", line 1581
  File "<frozen importlib._bootstrap>", line 1614
  File "/usr/lib/python3.4/doctest.py", line 101
    import pdb
  File "<frozen importlib._bootstrap>", line 284
  File "<frozen importlib._bootstrap>", line 938
  File "<frozen importlib._bootstrap>", line 1068
  File "<frozen importlib._bootstrap>", line 619
  File "<frozen importlib._bootstrap>", line 1581
  File "<frozen importlib._bootstrap>", line 1614
  File "/usr/lib/python3.4/test/support/__init__.py", line 1728
    import doctest
  File "/usr/lib/python3.4/test/test_pickletools.py", line 21
    support.run_doctest(pickletools)
  File "/usr/lib/python3.4/test/regrtest.py", line 1276
    test_runner()
  File "/usr/lib/python3.4/test/regrtest.py", line 976
    display_failure=not verbose)
  File "/usr/lib/python3.4/test/regrtest.py", line 761
    match_tests=ns.match_tests)
  File "/usr/lib/python3.4/test/regrtest.py", line 1563
    main()
  File "/usr/lib/python3.4/test/__main__.py", line 3
    regrtest.main_in_temp_cwd()
  File "/usr/lib/python3.4/runpy.py", line 73
    exec(code, run_globals)
  File "/usr/lib/python3.4/runpy.py", line 160
    "__main__", fname, loader, pkg_name)
@end example

We can see that the most memory was allocated in the @ref{9b,,importlib} module to
load data (bytecode and constants) from modules: @code{870.1 KiB}. The traceback is
where the @ref{9b,,importlib} loaded data most recently: on the @code{import pdb}
line of the @ref{67,,doctest} module. The traceback may change if a new module is
loaded.

@node Pretty top,,Get the traceback of a memory block,例子<26>
@anchor{library/tracemalloc pretty-top}@anchor{355f}
@subsubsection Pretty top


Code to display the 10 lines allocating the most memory with a pretty output,
ignoring @code{<frozen importlib._bootstrap>} and @code{<unknown>} files:

@example
import linecache
import os
import tracemalloc

def display_top(snapshot, key_type='lineno', limit=10):
    snapshot = snapshot.filter_traces((
        tracemalloc.Filter(False, "<frozen importlib._bootstrap>"),
        tracemalloc.Filter(False, "<unknown>"),
    ))
    top_stats = snapshot.statistics(key_type)

    print("Top %s lines" % limit)
    for index, stat in enumerate(top_stats[:limit], 1):
        frame = stat.traceback[0]
        print("#%s: %s:%s: %.1f KiB"
              % (index, frame.filename, frame.lineno, stat.size / 1024))
        line = linecache.getline(frame.filename, frame.lineno).strip()
        if line:
            print('    %s' % line)

    other = top_stats[limit:]
    if other:
        size = sum(stat.size for stat in other)
        print("%s other: %.1f KiB" % (len(other), size / 1024))
    total = sum(stat.size for stat in top_stats)
    print("Total allocated size: %.1f KiB" % (total / 1024))

tracemalloc.start()

# ... run your application ...

snapshot = tracemalloc.take_snapshot()
display_top(snapshot)
@end example

Python测试套件的输出示例：

@example
Top 10 lines
#1: Lib/base64.py:414: 419.8 KiB
    _b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
#2: Lib/base64.py:306: 419.8 KiB
    _a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
#3: collections/__init__.py:368: 293.6 KiB
    exec(class_definition, namespace)
#4: Lib/abc.py:133: 115.2 KiB
    cls = super().__new__(mcls, name, bases, namespace)
#5: unittest/case.py:574: 103.1 KiB
    testMethod()
#6: Lib/linecache.py:127: 95.4 KiB
    lines = fp.readlines()
#7: urllib/parse.py:476: 71.8 KiB
    for a in _hexdig for b in _hexdig@}
#8: <string>:5: 62.0 KiB
#9: Lib/_weakrefset.py:37: 60.0 KiB
    self.data = set()
#10: Lib/base64.py:142: 59.8 KiB
    _b32tab2 = [a + b for a in _b32tab for b in _b32tab]
6220 other: 3602.8 KiB
Total allocated size: 5303.1 KiB
@end example

See @ref{355a,,Snapshot.statistics()} for more options.

@node API,,例子<26>,tracemalloc --- 跟踪内存分配
@anchor{library/tracemalloc api}@anchor{3560}
@subsubsection API


@menu
* 函数: 函数<9>. 
* 域过滤器:: 
* 过滤器:: 
* Frame:: 
* 快照:: 
* 统计:: 
* StatisticDiff:: 
* 跟踪:: 
* 回溯: 回溯<4>. 

@end menu

@node 函数<9>,域过滤器,,API
@anchor{library/tracemalloc functions}@anchor{3561}
@subsubsection 函数


@geindex clear_traces() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc clear_traces}@anchor{3562}
@deffn {函数} tracemalloc.clear_traces ()

Clear traces of memory blocks allocated by Python.

See also @ref{3563,,stop()}.
@end deffn

@geindex get_object_traceback() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc get_object_traceback}@anchor{10f9}
@deffn {函数} tracemalloc.get_object_traceback (obj)

Get the traceback where the Python object @emph{obj} was allocated.
Return a @ref{3f7,,Traceback} instance, or @code{None} if the @ref{114,,tracemalloc}
module is not tracing memory allocations or did not trace the allocation of
the object.

See also @ref{3564,,gc.get_referrers()} and @ref{3565,,sys.getsizeof()} functions.
@end deffn

@geindex get_traceback_limit() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc get_traceback_limit}@anchor{3566}
@deffn {函数} tracemalloc.get_traceback_limit ()

Get the maximum number of frames stored in the traceback of a trace.

The @ref{114,,tracemalloc} module must be tracing memory allocations to
get the limit, otherwise an exception is raised.

The limit is set by the @ref{12e5,,start()} function.
@end deffn

@geindex get_traced_memory() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc get_traced_memory}@anchor{3567}
@deffn {函数} tracemalloc.get_traced_memory ()

Get the current size and peak size of memory blocks traced by the
@ref{114,,tracemalloc} module as a tuple: @code{(current: int, peak: int)}.
@end deffn

@geindex get_tracemalloc_memory() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc get_tracemalloc_memory}@anchor{3568}
@deffn {函数} tracemalloc.get_tracemalloc_memory ()

Get the memory usage in bytes of the @ref{114,,tracemalloc} module used to store
traces of memory blocks.
Return an @ref{184,,int}.
@end deffn

@geindex is_tracing() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc is_tracing}@anchor{3569}
@deffn {函数} tracemalloc.is_tracing ()

@code{True} if the @ref{114,,tracemalloc} module is tracing Python memory
allocations, @code{False} otherwise.

See also @ref{12e5,,start()} and @ref{3563,,stop()} functions.
@end deffn

@geindex start() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc start}@anchor{12e5}
@deffn {函数} tracemalloc.start (nframe: int=1)

Start tracing Python memory allocations: install hooks on Python memory
allocators. Collected tracebacks of traces will be limited to @emph{nframe}
frames. By default, a trace of a memory block only stores the most recent
frame: the limit is @code{1}. @emph{nframe} must be greater or equal to @code{1}.

Storing more than @code{1} frame is only useful to compute statistics grouped
by @code{'traceback'} or to compute cumulative statistics: see the
@ref{356a,,Snapshot.compare_to()} and @ref{355a,,Snapshot.statistics()} methods.

Storing more frames increases the memory and CPU overhead of the
@ref{114,,tracemalloc} module. Use the @ref{3568,,get_tracemalloc_memory()} function
to measure how much memory is used by the @ref{114,,tracemalloc} module.

The 
@geindex PYTHONTRACEMALLOC
@geindex 环境变量; PYTHONTRACEMALLOC
@ref{12f1,,PYTHONTRACEMALLOC} environment variable
(@code{PYTHONTRACEMALLOC=NFRAME}) and the @ref{155,,-X} @code{tracemalloc=NFRAME}
command line option can be used to start tracing at startup.

See also @ref{3563,,stop()}, @ref{3569,,is_tracing()} and @ref{3566,,get_traceback_limit()}
functions.
@end deffn

@geindex stop() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc stop}@anchor{3563}
@deffn {函数} tracemalloc.stop ()

Stop tracing Python memory allocations: uninstall hooks on Python memory
allocators. Also clears all previously collected traces of memory blocks
allocated by Python.

Call @ref{356b,,take_snapshot()} function to take a snapshot of traces before
clearing them.

See also @ref{12e5,,start()}, @ref{3569,,is_tracing()} and @ref{3562,,clear_traces()}
functions.
@end deffn

@geindex take_snapshot() (在 tracemalloc 模块中)
@anchor{library/tracemalloc tracemalloc take_snapshot}@anchor{356b}
@deffn {函数} tracemalloc.take_snapshot ()

Take a snapshot of traces of memory blocks allocated by Python. Return a new
@ref{356c,,Snapshot} instance.

The snapshot does not include memory blocks allocated before the
@ref{114,,tracemalloc} module started to trace memory allocations.

Tracebacks of traces are limited to @ref{3566,,get_traceback_limit()} frames. Use
the @emph{nframe} parameter of the @ref{12e5,,start()} function to store more frames.

The @ref{114,,tracemalloc} module must be tracing memory allocations to take a
snapshot, see the @ref{12e5,,start()} function.

See also the @ref{10f9,,get_object_traceback()} function.
@end deffn

@node 域过滤器,过滤器,函数<9>,API
@anchor{library/tracemalloc domainfilter}@anchor{356d}
@subsubsection 域过滤器


@geindex DomainFilter (tracemalloc 中的类)
@anchor{library/tracemalloc tracemalloc DomainFilter}@anchor{59b}
@deffn {类} tracemalloc.DomainFilter (inclusive: bool, domain: int)

Filter traces of memory blocks by their address space (domain).


3.6 新版功能.


@geindex inclusive (tracemalloc.DomainFilter 属性)
@anchor{library/tracemalloc tracemalloc DomainFilter inclusive}@anchor{356e}
@deffn {属性} inclusive

If @emph{inclusive} is @code{True} (include), match memory blocks allocated
in the address space @ref{356f,,domain}.

If @emph{inclusive} is @code{False} (exclude), match memory blocks not allocated
in the address space @ref{356f,,domain}.
@end deffn

@geindex domain (tracemalloc.DomainFilter 属性)
@anchor{library/tracemalloc tracemalloc DomainFilter domain}@anchor{356f}
@deffn {属性} domain

Address space of a memory block (@code{int}). Read-only property.
@end deffn
@end deffn

@node 过滤器,Frame,域过滤器,API
@anchor{library/tracemalloc filter}@anchor{3570}
@subsubsection 过滤器


@geindex Filter (tracemalloc 中的类)
@anchor{library/tracemalloc tracemalloc Filter}@anchor{3571}
@deffn {类} tracemalloc.Filter (inclusive: bool, filename_pattern: str, lineno: int=None, all_frames: bool=False, domain: int=None)

对内存块的跟踪进行筛选。

See the @ref{1c09,,fnmatch.fnmatch()} function for the syntax of
@emph{filename_pattern}. The @code{'.pyc'} file extension is
replaced with @code{'.py'}.

示例：


@itemize *

@item 
@code{Filter(True, subprocess.__file__)} only includes traces of the
@ref{f9,,subprocess} module

@item 
@code{Filter(False, tracemalloc.__file__)} excludes traces of the
@ref{114,,tracemalloc} module

@item 
@code{Filter(False, "<unknown>")} excludes empty tracebacks
@end itemize


在 3.5 版更改: The @code{'.pyo'} file extension is no longer replaced with @code{'.py'}.



在 3.6 版更改: Added the @ref{3572,,domain} attribute.


@geindex domain (tracemalloc.Filter 属性)
@anchor{library/tracemalloc tracemalloc Filter domain}@anchor{3572}
@deffn {属性} domain

Address space of a memory block (@code{int} or @code{None}).

tracemalloc uses the domain @code{0} to trace memory allocations made by
Python. C extensions can use other domains to trace other resources.
@end deffn

@geindex inclusive (tracemalloc.Filter 属性)
@anchor{library/tracemalloc tracemalloc Filter inclusive}@anchor{3573}
@deffn {属性} inclusive

If @emph{inclusive} is @code{True} (include), only match memory blocks allocated
in a file with a name matching @ref{3574,,filename_pattern} at line number
@ref{3575,,lineno}.

If @emph{inclusive} is @code{False} (exclude), ignore memory blocks allocated in
a file with a name matching @ref{3574,,filename_pattern} at line number
@ref{3575,,lineno}.
@end deffn

@geindex lineno (tracemalloc.Filter 属性)
@anchor{library/tracemalloc tracemalloc Filter lineno}@anchor{3575}
@deffn {属性} lineno

Line number (@code{int}) of the filter. If @emph{lineno} is @code{None}, the filter
matches any line number.
@end deffn

@geindex filename_pattern (tracemalloc.Filter 属性)
@anchor{library/tracemalloc tracemalloc Filter filename_pattern}@anchor{3574}
@deffn {属性} filename_pattern

Filename pattern of the filter (@code{str}). Read-only property.
@end deffn

@geindex all_frames (tracemalloc.Filter 属性)
@anchor{library/tracemalloc tracemalloc Filter all_frames}@anchor{3576}
@deffn {属性} all_frames

If @emph{all_frames} is @code{True}, all frames of the traceback are checked. If
@emph{all_frames} is @code{False}, only the most recent frame is checked.

This attribute has no effect if the traceback limit is @code{1}.  See the
@ref{3566,,get_traceback_limit()} function and @ref{3577,,Snapshot.traceback_limit}
attribute.
@end deffn
@end deffn

@node Frame,快照,过滤器,API
@anchor{library/tracemalloc frame}@anchor{3578}
@subsubsection Frame


@geindex Frame (tracemalloc 中的类)
@anchor{library/tracemalloc tracemalloc Frame}@anchor{3579}
@deffn {类} tracemalloc.Frame

Frame of a traceback.

The @ref{3f7,,Traceback} class is a sequence of @ref{3579,,Frame} instances.

@geindex filename (tracemalloc.Frame 属性)
@anchor{library/tracemalloc tracemalloc Frame filename}@anchor{357a}
@deffn {属性} filename

文件名（@code{字符串}）
@end deffn

@geindex lineno (tracemalloc.Frame 属性)
@anchor{library/tracemalloc tracemalloc Frame lineno}@anchor{357b}
@deffn {属性} lineno

行号（@code{整形}）
@end deffn
@end deffn

@node 快照,统计,Frame,API
@anchor{library/tracemalloc snapshot}@anchor{357c}
@subsubsection 快照


@geindex Snapshot (tracemalloc 中的类)
@anchor{library/tracemalloc tracemalloc Snapshot}@anchor{356c}
@deffn {类} tracemalloc.Snapshot

Snapshot of traces of memory blocks allocated by Python.

The @ref{356b,,take_snapshot()} function creates a snapshot instance.

@geindex compare_to() (tracemalloc.Snapshot 方法)
@anchor{library/tracemalloc tracemalloc Snapshot compare_to}@anchor{356a}
@deffn {方法} compare_to (old_snapshot: Snapshot, key_type: str, cumulative: bool=False)

Compute the differences with an old snapshot. Get statistics as a sorted
list of @ref{357d,,StatisticDiff} instances grouped by @emph{key_type}.

See the @ref{355a,,Snapshot.statistics()} method for @emph{key_type} and @emph{cumulative}
parameters.

The result is sorted from the biggest to the smallest by: absolute value
of @ref{357e,,StatisticDiff.size_diff}, @ref{357f,,StatisticDiff.size}, absolute
value of @ref{3580,,StatisticDiff.count_diff}, @ref{3581,,Statistic.count} and
then by @ref{3582,,StatisticDiff.traceback}.
@end deffn

@geindex dump() (tracemalloc.Snapshot 方法)
@anchor{library/tracemalloc tracemalloc Snapshot dump}@anchor{355c}
@deffn {方法} dump (filename)

将快照写入文件

使用 @ref{355d,,load()} 重载快照。
@end deffn

@geindex filter_traces() (tracemalloc.Snapshot 方法)
@anchor{library/tracemalloc tracemalloc Snapshot filter_traces}@anchor{3583}
@deffn {方法} filter_traces (filters)

Create a new @ref{356c,,Snapshot} instance with a filtered @ref{3584,,traces}
sequence, @emph{filters} is a list of @ref{59b,,DomainFilter} and
@ref{3571,,Filter} instances.  If @emph{filters} is an empty list, return a new
@ref{356c,,Snapshot} instance with a copy of the traces.

All inclusive filters are applied at once, a trace is ignored if no
inclusive filters match it. A trace is ignored if at least one exclusive
filter matches it.


在 3.6 版更改: @ref{59b,,DomainFilter} instances are now also accepted in @emph{filters}.

@end deffn

@geindex load() (tracemalloc.Snapshot 类方法)
@anchor{library/tracemalloc tracemalloc Snapshot load}@anchor{355d}
@deffn {方法} classmethod load (filename)

从文件载入快照。

另见 @ref{355c,,dump()}.
@end deffn

@geindex statistics() (tracemalloc.Snapshot 方法)
@anchor{library/tracemalloc tracemalloc Snapshot statistics}@anchor{355a}
@deffn {方法} statistics (key_type: str, cumulative: bool=False)

获取 @ref{3585,,Statistic} 信息列表，按 @emph{key_type} 分组排序：


@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

key_type

@tab

描述

@item

@code{'filename'}

@tab

文件名

@item

@code{'lineno'}

@tab

文件名和行号

@item

@code{'traceback'}

@tab

回溯

@end multitable


If @emph{cumulative} is @code{True}, cumulate size and count of memory blocks of
all frames of the traceback of a trace, not only the most recent frame.
The cumulative mode can only be used with @emph{key_type} equals to
@code{'filename'} and @code{'lineno'}.

The result is sorted from the biggest to the smallest by:
@ref{3586,,Statistic.size}, @ref{3581,,Statistic.count} and then by
@ref{3587,,Statistic.traceback}.
@end deffn

@geindex traceback_limit (tracemalloc.Snapshot 属性)
@anchor{library/tracemalloc tracemalloc Snapshot traceback_limit}@anchor{3577}
@deffn {属性} traceback_limit

Maximum number of frames stored in the traceback of @ref{3584,,traces}:
result of the @ref{3566,,get_traceback_limit()} when the snapshot was taken.
@end deffn

@geindex traces (tracemalloc.Snapshot 属性)
@anchor{library/tracemalloc tracemalloc Snapshot traces}@anchor{3584}
@deffn {属性} traces

Traces of all memory blocks allocated by Python: sequence of
@ref{3588,,Trace} instances.

The sequence has an undefined order. Use the @ref{355a,,Snapshot.statistics()}
method to get a sorted list of statistics.
@end deffn
@end deffn

@node 统计,StatisticDiff,快照,API
@anchor{library/tracemalloc statistic}@anchor{3589}
@subsubsection 统计


@geindex Statistic (tracemalloc 中的类)
@anchor{library/tracemalloc tracemalloc Statistic}@anchor{3585}
@deffn {类} tracemalloc.Statistic

统计内存分配

@ref{355a,,Snapshot.statistics()} 返回 @ref{3585,,Statistic} 实例的列表。.

参见 @ref{357d,,StatisticDiff} 类。

@geindex count (tracemalloc.Statistic 属性)
@anchor{library/tracemalloc tracemalloc Statistic count}@anchor{3581}
@deffn {属性} count

内存块数（@code{整形}）。
@end deffn

@geindex size (tracemalloc.Statistic 属性)
@anchor{library/tracemalloc tracemalloc Statistic size}@anchor{3586}
@deffn {属性} size

Total size of memory blocks in bytes (@code{int}).
@end deffn

@geindex traceback (tracemalloc.Statistic 属性)
@anchor{library/tracemalloc tracemalloc Statistic traceback}@anchor{3587}
@deffn {属性} traceback

Traceback where the memory block was allocated, @ref{3f7,,Traceback}
instance.
@end deffn
@end deffn

@node StatisticDiff,跟踪,统计,API
@anchor{library/tracemalloc statisticdiff}@anchor{358a}
@subsubsection StatisticDiff


@geindex StatisticDiff (tracemalloc 中的类)
@anchor{library/tracemalloc tracemalloc StatisticDiff}@anchor{357d}
@deffn {类} tracemalloc.StatisticDiff

Statistic difference on memory allocations between an old and a new
@ref{356c,,Snapshot} instance.

@ref{356a,,Snapshot.compare_to()} returns a list of @ref{357d,,StatisticDiff}
instances. See also the @ref{3585,,Statistic} class.

@geindex count (tracemalloc.StatisticDiff 属性)
@anchor{library/tracemalloc tracemalloc StatisticDiff count}@anchor{358b}
@deffn {属性} count

Number of memory blocks in the new snapshot (@code{int}): @code{0} if
the memory blocks have been released in the new snapshot.
@end deffn

@geindex count_diff (tracemalloc.StatisticDiff 属性)
@anchor{library/tracemalloc tracemalloc StatisticDiff count_diff}@anchor{3580}
@deffn {属性} count_diff

Difference of number of memory blocks between the old and the new
snapshots (@code{int}): @code{0} if the memory blocks have been allocated in
the new snapshot.
@end deffn

@geindex size (tracemalloc.StatisticDiff 属性)
@anchor{library/tracemalloc tracemalloc StatisticDiff size}@anchor{357f}
@deffn {属性} size

Total size of memory blocks in bytes in the new snapshot (@code{int}):
@code{0} if the memory blocks have been released in the new snapshot.
@end deffn

@geindex size_diff (tracemalloc.StatisticDiff 属性)
@anchor{library/tracemalloc tracemalloc StatisticDiff size_diff}@anchor{357e}
@deffn {属性} size_diff

Difference of total size of memory blocks in bytes between the old and
the new snapshots (@code{int}): @code{0} if the memory blocks have been
allocated in the new snapshot.
@end deffn

@geindex traceback (tracemalloc.StatisticDiff 属性)
@anchor{library/tracemalloc tracemalloc StatisticDiff traceback}@anchor{3582}
@deffn {属性} traceback

Traceback where the memory blocks were allocated, @ref{3f7,,Traceback}
instance.
@end deffn
@end deffn

@node 跟踪,回溯<4>,StatisticDiff,API
@anchor{library/tracemalloc trace}@anchor{358c}
@subsubsection 跟踪


@geindex Trace (tracemalloc 中的类)
@anchor{library/tracemalloc tracemalloc Trace}@anchor{3588}
@deffn {类} tracemalloc.Trace

Trace of a memory block.

The @ref{3584,,Snapshot.traces} attribute is a sequence of @ref{3588,,Trace}
instances.


在 3.6 版更改: Added the @ref{358d,,domain} attribute.


@geindex domain (tracemalloc.Trace 属性)
@anchor{library/tracemalloc tracemalloc Trace domain}@anchor{358d}
@deffn {属性} domain

Address space of a memory block (@code{int}). Read-only property.

tracemalloc uses the domain @code{0} to trace memory allocations made by
Python. C extensions can use other domains to trace other resources.
@end deffn

@geindex size (tracemalloc.Trace 属性)
@anchor{library/tracemalloc tracemalloc Trace size}@anchor{358e}
@deffn {属性} size

Size of the memory block in bytes (@code{int}).
@end deffn

@geindex traceback (tracemalloc.Trace 属性)
@anchor{library/tracemalloc tracemalloc Trace traceback}@anchor{358f}
@deffn {属性} traceback

Traceback where the memory block was allocated, @ref{3f7,,Traceback}
instance.
@end deffn
@end deffn

@node 回溯<4>,,跟踪,API
@anchor{library/tracemalloc traceback}@anchor{3590}
@subsubsection 回溯


@geindex Traceback (tracemalloc 中的类)
@anchor{library/tracemalloc tracemalloc Traceback}@anchor{3f7}
@deffn {类} tracemalloc.Traceback

Sequence of @ref{3579,,Frame} instances sorted from the oldest frame to the
most recent frame.

A traceback contains at least @code{1} frame. If the @code{tracemalloc} module
failed to get a frame, the filename @code{"<unknown>"} at line number @code{0} is
used.

When a snapshot is taken, tracebacks of traces are limited to
@ref{3566,,get_traceback_limit()} frames. See the @ref{356b,,take_snapshot()} function.

The @ref{358f,,Trace.traceback} attribute is an instance of @ref{3f7,,Traceback}
instance.


在 3.7 版更改: Frames are now sorted from the oldest to the most recent, instead of most recent to oldest.


@geindex format() (tracemalloc.Traceback 方法)
@anchor{library/tracemalloc tracemalloc Traceback format}@anchor{3f8}
@deffn {方法} format (limit=None, most_recent_first=False)

Format the traceback as a list of lines with newlines. Use the
@ref{a8,,linecache} module to retrieve lines from the source code.
If @emph{limit} is set, format the @emph{limit} most recent frames if @emph{limit}
is positive. Otherwise, format the @code{abs(limit)} oldest frames.
If @emph{most_recent_first} is @code{True}, the order of the formatted frames
is reversed, returning the most recent frame first instead of last.

Similar to the @ref{3591,,traceback.format_tb()} function, except that
@ref{3f8,,format()} does not include newlines.

示例:

@example
print("Traceback (most recent call first):")
for line in traceback:
    print(line)
@end example

输出:

@example
Traceback (most recent call first):
  File "test.py", line 9
    obj = Object()
  File "test.py", line 12
    tb = tracemalloc.get_object_traceback(f())
@end example
@end deffn
@end deffn

@node 软件打包和分发,Python运行时服务,调试和分析,Python 标准库
@anchor{library/distribution doc}@anchor{3592}@anchor{library/distribution software-packaging-and-distribution}@anchor{3593}
@section 软件打包和分发


这些库可帮助你发布和安装 Python 软件。 虽然这些模块设计为与`Python 包索引 <@indicateurl{https://pypi.org}>`__结合使用，但它们也可以与本地索引服务器一起使用，或者根本不使用任何索引服务器。

@menu
* distutils: distutils --- 构建和安装 Python 模块. 构建和安装 Python 模块
* ensurepip: ensurepip --- Bootstrapping the pip installer. Bootstrapping the pip installer
* venv: venv --- 创建虚拟环境. 创建虚拟环境
* zipapp: zipapp --- Manage executable Python zip archives. Manage executable Python zip archives

@end menu

@node distutils --- 构建和安装 Python 模块,ensurepip --- Bootstrapping the pip installer,,软件打包和分发
@anchor{library/distutils doc}@anchor{3594}@anchor{library/distutils distutils-building-and-installing-python-modules}@anchor{3595}@anchor{library/distutils module-distutils}@anchor{39}
@subsection @code{distutils} --- 构建和安装 Python 模块


@geindex distutils (模块)


__________________________________________________________________


@ref{39,,distutils} 包为将待构建和安装的额外的模块，打包成 Python 安装包提供支持。新模块既可以是百分百的纯 Python，也可以是用 C 写的扩展模块，或者可以是一组包含了同时用 Python 和 C 编码的 Python 包。

大多数 Python 用户 @emph{不会} 想要直接使用这个包，而是使用 Python 包官方维护的跨版本工具。特别地， setuptools@footnote{https://setuptools.readthedocs.io/en/latest/} 是一个对于 @ref{39,,distutils} 的增强选项，它能提供：


@itemize *

@item 
对声明项目依赖的支持

@item 
额外的用于配置哪些文件包含在源代码发布中的机制（包括与版本控制系统集成需要的插件）

@item 
生成项目“进入点”的能力，进入点可用作应用插件系统的基础

@item 
自动在安装时间生成 Windows 命令行可执行文件的能力，而不是需要预编译它们

@item 
跨所有受支持的 Python 版本上的一致的表现
@end itemize

推荐的  pip@footnote{https://pip.pypa.io/} 安装器用 @code{setuptools} 运行所有的 @code{setup.py} 脚本，即使脚本本身只引了 @code{distutils} 包。参考 Python Packaging User Guide@footnote{https://packaging.python.org}  获得更多信息。

为了打包工具的作者和用户能更好理解当前的打包和分发系统，遗留的基于 @ref{39,,distutils} 的用户文档和 API 参考保持可用：


@itemize *

@item 
@ref{7f1,,安装Python模块（旧版）}

@item 
@ref{7f2,,分发 Python 模块（遗留版本）}
@end itemize

@node ensurepip --- Bootstrapping the pip installer,venv --- 创建虚拟环境,distutils --- 构建和安装 Python 模块,软件打包和分发
@anchor{library/ensurepip doc}@anchor{3596}@anchor{library/ensurepip ensurepip-bootstrapping-the-pip-installer}@anchor{3597}@anchor{library/ensurepip module-ensurepip}@anchor{7a}
@subsection @code{ensurepip} --- Bootstrapping the @code{pip} installer


@geindex ensurepip (模块)


3.4 新版功能.



__________________________________________________________________


The @ref{7a,,ensurepip} package provides support for bootstrapping the @code{pip}
installer into an existing Python installation or virtual environment. This
bootstrapping approach reflects the fact that @code{pip} is an independent
project with its own release cycle, and the latest available stable version
is bundled with maintenance and feature releases of the CPython reference
interpreter.

In most cases, end users of Python shouldn't need to invoke this module
directly (as @code{pip} should be bootstrapped by default), but it may be
needed if installing @code{pip} was skipped when installing Python (or
when creating a virtual environment) or after explicitly uninstalling
@code{pip}.

@cartouche
@quotation 注解 
This module @emph{does not} access the internet. All of the components
needed to bootstrap @code{pip} are included as internal parts of the
package.
@end quotation
@end cartouche


@subsubheading 参见



@table @asis

@item @ref{7ef,,安装 Python 模块}

The end user guide for installing Python packages

@geindex Python 提高建议; PEP 453

@item PEP 453@footnote{https://www.python.org/dev/peps/pep-0453}: Explicit bootstrapping of pip in Python installations

The original rationale and specification for this module.
@end table


@menu
* Command line interface:: 
* Module API:: 

@end menu

@node Command line interface,Module API,,ensurepip --- Bootstrapping the pip installer
@anchor{library/ensurepip command-line-interface}@anchor{3598}
@subsubsection Command line interface


The command line interface is invoked using the interpreter's @code{-m} switch.

The simplest possible invocation is:

@example
python -m ensurepip
@end example

This invocation will install @code{pip} if it is not already installed,
but otherwise does nothing. To ensure the installed version of @code{pip}
is at least as recent as the one bundled with @code{ensurepip}, pass the
@code{--upgrade} option:

@example
python -m ensurepip --upgrade
@end example

By default, @code{pip} is installed into the current virtual environment
(if one is active) or into the system site packages (if there is no
active virtual environment). The installation location can be controlled
through two additional command line options:


@itemize *

@item 
@code{--root <dir>}: Installs @code{pip} relative to the given root directory
rather than the root of the currently active virtual environment (if any)
or the default root for the current Python installation.

@item 
@code{--user}: Installs @code{pip} into the user site packages directory rather
than globally for the current Python installation (this option is not
permitted inside an active virtual environment).
@end itemize

By default, the scripts @code{pipX} and @code{pipX.Y} will be installed (where
X.Y stands for the version of Python used to invoke @code{ensurepip}). The
scripts installed can be controlled through two additional command line
options:


@itemize *

@item 
@code{--altinstall}: if an alternate installation is requested, the @code{pipX}
script will @emph{not} be installed.

@item 
@code{--default-pip}: if a "default pip" installation is requested, the
@code{pip} script will be installed in addition to the two regular scripts.
@end itemize

Providing both of the script selection options will trigger an exception.

@node Module API,,Command line interface,ensurepip --- Bootstrapping the pip installer
@anchor{library/ensurepip module-api}@anchor{3599}
@subsubsection Module API


@ref{7a,,ensurepip} exposes two functions for programmatic use:

@geindex version() (在 ensurepip 模块中)
@anchor{library/ensurepip ensurepip version}@anchor{359a}
@deffn {函数} ensurepip.version ()

Returns a string specifying the bundled version of pip that will be
installed when bootstrapping an environment.
@end deffn

@geindex bootstrap() (在 ensurepip 模块中)
@anchor{library/ensurepip ensurepip bootstrap}@anchor{3470}
@deffn {函数} ensurepip.bootstrap (root=None, upgrade=False, user=False, altinstall=False, default_pip=False, verbosity=0)

Bootstraps @code{pip} into the current or designated environment.

@emph{root} specifies an alternative root directory to install relative to.
If @emph{root} is @code{None}, then installation uses the default install location
for the current environment.

@emph{upgrade} indicates whether or not to upgrade an existing installation
of an earlier version of @code{pip} to the bundled version.

@emph{user} indicates whether to use the user scheme rather than installing
globally.

By default, the scripts @code{pipX} and @code{pipX.Y} will be installed (where
X.Y stands for the current version of Python).

If @emph{altinstall} is set, then @code{pipX} will @emph{not} be installed.

If @emph{default_pip} is set, then @code{pip} will be installed in addition to
the two regular scripts.

Setting both @emph{altinstall} and @emph{default_pip} will trigger
@ref{1fb,,ValueError}.

@emph{verbosity} controls the level of output to @ref{307,,sys.stdout} from the
bootstrapping operation.

Raises an @ref{12d0,,auditing event} @code{ensurepip.bootstrap} with argument @code{root}.

@cartouche
@quotation 注解 
The bootstrapping process has side effects on both @code{sys.path} and
@code{os.environ}. Invoking the command line interface in a subprocess
instead allows these side effects to be avoided.
@end quotation
@end cartouche

@cartouche
@quotation 注解 
The bootstrapping process may install additional modules required by
@code{pip}, but other software should not assume those dependencies will
always be present by default (as the dependencies may be removed in a
future version of @code{pip}).
@end quotation
@end cartouche
@end deffn

@node venv --- 创建虚拟环境,zipapp --- Manage executable Python zip archives,ensurepip --- Bootstrapping the pip installer,软件打包和分发
@anchor{library/venv doc}@anchor{359b}@anchor{library/venv module-venv}@anchor{125}@anchor{library/venv venv-creation-of-virtual-environments}@anchor{359c}
@subsection @code{venv} --- 创建虚拟环境


@geindex venv (模块)


3.3 新版功能.


@strong{源码：} Lib/venv/@footnote{https://github.com/python/cpython/tree/3.8/Lib/venv/}

@geindex Environments; virtual


__________________________________________________________________


@ref{125,,venv} 模块支持使用自己的站点目录创建轻量级“虚拟环境”，可选择与系统站点目录隔离。每个虚拟环境都有自己的 Python 二进制文件（与用于创建此环境的二进制文件的版本相匹配），并且可以在其站点目录中拥有自己独立的已安装 Python 软件包集。

有关 Python 虚拟环境的更多信息，请参阅 
@geindex Python 提高建议; PEP 405
PEP 405@footnote{https://www.python.org/dev/peps/pep-0405} 。


@subsubheading 参见


Python Packaging User Guide: Creating and using virtual environments@footnote{https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/#creating-a-virtual-environment}


@menu
* 创建虚拟环境: 创建虚拟环境<2>. 
* API: API<2>. 
* 一个扩展 EnvBuilder 的例子:: 

@end menu

@node 创建虚拟环境<2>,API<2>,,venv --- 创建虚拟环境
@anchor{library/venv creating-virtual-environments}@anchor{359d}
@subsubsection 创建虚拟环境


通过执行 @code{venv} 指令来创建一个 @ref{359e,,虚拟环境}:

@example
python3 -m venv /path/to/new/virtual/environment
@end example

Running this command creates the target directory (creating any parent
directories that don't exist already) and places a @code{pyvenv.cfg} file in it
with a @code{home} key pointing to the Python installation from which the command
was run (a common name for the target directory is @code{.venv}).  It also creates
a @code{bin} (or @code{Scripts} on Windows) subdirectory containing a copy/symlink
of the Python binary/binaries (as appropriate for the platform or arguments
used at environment creation time). It also creates an (initially empty)
@code{lib/pythonX.Y/site-packages} subdirectory (on Windows, this is
@code{Lib\site-packages}). If an existing directory is specified, it will be
re-used.


3.6 版后已移除: @code{pyvenv} 是 Python 3.3 和 3.4 中创建虚拟环境的推荐工具，不过 在 Python 3.6 中已弃用@footnote{https://docs.python.org/dev/whatsnew/3.6.html#deprecated-features}。



在 3.5 版更改: 现在推荐使用 @code{venv} 来创建虚拟环境。


On Windows, invoke the @code{venv} command as follows:

@example
c:\>c:\Python35\python -m venv c:\path\to\myenv
@end example

Alternatively, if you configured the @code{PATH} and @code{PATHEXT} variables for
your @ref{2d9,,Python installation}:

@example
c:\>python -m venv c:\path\to\myenv
@end example

The command, if run with @code{-h}, will show the available options:

@example
usage: venv [-h] [--system-site-packages] [--symlinks | --copies] [--clear]
            [--upgrade] [--without-pip] [--prompt PROMPT]
            ENV_DIR [ENV_DIR ...]

Creates virtual Python environments in one or more target directories.

positional arguments:
  ENV_DIR               A directory to create the environment in.

optional arguments:
  -h, --help            show this help message and exit
  --system-site-packages
                        Give the virtual environment access to the system
                        site-packages dir.
  --symlinks            Try to use symlinks rather than copies, when symlinks
                        are not the default for the platform.
  --copies              Try to use copies rather than symlinks, even when
                        symlinks are the default for the platform.
  --clear               Delete the contents of the environment directory if it
                        already exists, before environment creation.
  --upgrade             Upgrade the environment directory to use this version
                        of Python, assuming Python has been upgraded in-place.
  --without-pip         Skips installing or upgrading pip in the virtual
                        environment (pip is bootstrapped by default)
  --prompt PROMPT       Provides an alternative prompt prefix for this
                        environment.

Once an environment has been created, you may wish to activate it, e.g. by
sourcing an activate script in its bin directory.
@end example


在 3.4 版更改: Installs pip by default, added the @code{--without-pip}  and @code{--copies}
options



在 3.4 版更改: In earlier versions, if the target directory already existed, an error was
raised, unless the @code{--clear} or @code{--upgrade} option was provided.


@cartouche
@quotation 注解 
While symlinks are supported on Windows, they are not recommended. Of
particular note is that double-clicking @code{python.exe} in File Explorer
will resolve the symlink eagerly and ignore the virtual environment.
@end quotation
@end cartouche

@cartouche
@quotation 注解 
On Microsoft Windows, it may be required to enable the @code{Activate.ps1}
script by setting the execution policy for the user. You can do this by
issuing the following PowerShell command:

PS C:> Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

See About Execution Policies@footnote{https://go.microsoft.com/fwlink/?LinkID=135170}
for more information.
@end quotation
@end cartouche

The created @code{pyvenv.cfg} file also includes the
@code{include-system-site-packages} key, set to @code{true} if @code{venv} is
run with the @code{--system-site-packages} option, @code{false} otherwise.

Unless the @code{--without-pip} option is given, @ref{7a,,ensurepip} will be
invoked to bootstrap @code{pip} into the virtual environment.

Multiple paths can be given to @code{venv}, in which case an identical virtual
environment will be created, according to the given options, at each provided
path.

Once a virtual environment has been created, it can be "activated" using a
script in the virtual environment's binary directory. The invocation of the
script is platform-specific (@cite{<venv>} must be replaced by the path of the
directory containing the virtual environment):


@multitable {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

平台

@tab

Shell

@tab

用于激活虚拟环境的命令

@item

POSIX

@tab

bash/zsh

@tab

$ source <venv>/bin/activate

@item

@tab

fish

@tab

$ . <venv>/bin/activate.fish

@item

@tab

csh/tcsh

@tab

$ source <venv>/bin/activate.csh

@item

@tab

PowerShell Core

@tab

$ <venv>/bin/Activate.ps1

@item

Windows

@tab

cmd.exe

@tab

C:\> <venv>\Scripts\activate.bat

@item

@tab

PowerShell

@tab

PS C:\> <venv>\Scripts\Activate.ps1

@end multitable


You don't specifically @emph{need} to activate an environment; activation just
prepends the virtual environment's binary directory to your path, so that
"python" invokes the virtual environment's Python interpreter and you can run
installed scripts without having to use their full path. However, all scripts
installed in a virtual environment should be runnable without activating it,
and run with the virtual environment's Python automatically.

You can deactivate a virtual environment by typing "deactivate" in your shell.
The exact mechanism is platform-specific and is an internal implementation
detail (typically a script or shell function will be used).


3.4 新版功能: @code{fish} and @code{csh} activation scripts.



3.8 新版功能: PowerShell activation scripts installed under POSIX for PowerShell Core
support.

@anchor{library/venv venv-def}@anchor{359e}
@cartouche
@quotation 注解 
A virtual environment is a Python environment such that the Python
interpreter, libraries and scripts installed into it are isolated from those
installed in other virtual environments, and (by default) any libraries
installed in a "system" Python, i.e., one which is installed as part of your
operating system.

A virtual environment is a directory tree which contains Python executable
files and other files which indicate that it is a virtual environment.

Common installation tools such as setuptools@footnote{https://pypi.org/project/setuptools/} and pip@footnote{https://pypi.org/project/pip/} work as
expected with virtual environments. In other words, when a virtual
environment is active, they install Python packages into the virtual
environment without needing to be told to do so explicitly.

When a virtual environment is active (i.e., the virtual environment's Python
interpreter is running), the attributes @ref{359f,,sys.prefix} and
@ref{35a0,,sys.exec_prefix} point to the base directory of the virtual
environment, whereas @ref{2fe1,,sys.base_prefix} and
@ref{35a1,,sys.base_exec_prefix} point to the non-virtual environment Python
installation which was used to create the virtual environment. If a virtual
environment is not active, then @ref{359f,,sys.prefix} is the same as
@ref{2fe1,,sys.base_prefix} and @ref{35a0,,sys.exec_prefix} is the same as
@ref{35a1,,sys.base_exec_prefix} (they all point to a non-virtual environment
Python installation).

When a virtual environment is active, any options that change the
installation path will be ignored from all @ref{39,,distutils} configuration
files to prevent projects being inadvertently installed outside of the
virtual environment.

When working in a command shell, users can make a virtual environment active
by running an @code{activate} script in the virtual environment's executables
directory (the precise filename and command to use the file is
shell-dependent), which prepends the virtual environment's directory for
executables to the @code{PATH} environment variable for the running shell. There
should be no need in other circumstances to activate a virtual
environment; scripts installed into virtual environments have a "shebang"
line which points to the virtual environment's Python interpreter. This means
that the script will run with that interpreter regardless of the value of
@code{PATH}. On Windows, "shebang" line processing is supported if you have the
Python Launcher for Windows installed (this was added to Python in 3.3 - see
@geindex Python 提高建议; PEP 397
PEP 397@footnote{https://www.python.org/dev/peps/pep-0397} for more details). Thus, double-clicking an installed script in a
Windows Explorer window should run the script with the correct interpreter
without there needing to be any reference to its virtual environment in
@code{PATH}.
@end quotation
@end cartouche

@node API<2>,一个扩展 EnvBuilder 的例子,创建虚拟环境<2>,venv --- 创建虚拟环境
@anchor{library/venv api}@anchor{35a2}@anchor{library/venv venv-api}@anchor{7ec}
@subsubsection API


The high-level method described above makes use of a simple API which provides
mechanisms for third-party virtual environment creators to customize environment
creation according to their needs, the @ref{902,,EnvBuilder} class.

@geindex EnvBuilder (venv 中的类)
@anchor{library/venv venv EnvBuilder}@anchor{902}
@deffn {类} venv.EnvBuilder (system_site_packages=False, clear=False, symlinks=False, upgrade=False, with_pip=False, prompt=None)

The @ref{902,,EnvBuilder} class accepts the following keyword arguments on
instantiation:


@itemize *

@item 
@code{system_site_packages} -- a Boolean value indicating that the system Python
site-packages should be available to the environment (defaults to @code{False}).

@item 
@code{clear} -- a Boolean value which, if true, will delete the contents of
any existing target directory, before creating the environment.

@item 
@code{symlinks} -- a Boolean value indicating whether to attempt to symlink the
Python binary rather than copying.

@item 
@code{upgrade} -- a Boolean value which, if true, will upgrade an existing
environment with the running Python - for use when that Python has been
upgraded in-place (defaults to @code{False}).

@item 
@code{with_pip} -- a Boolean value which, if true, ensures pip is
installed in the virtual environment. This uses @ref{7a,,ensurepip} with
the @code{--default-pip} option.

@item 
@code{prompt} -- a String to be used after virtual environment is activated
(defaults to @code{None} which means directory name of the environment would
be used).
@end itemize


在 3.4 版更改: Added the @code{with_pip} parameter



3.6 新版功能: Added the @code{prompt} parameter


Creators of third-party virtual environment tools will be free to use the
provided @ref{902,,EnvBuilder} class as a base class.

The returned env-builder is an object which has a method, @code{create}:

@geindex create() (venv.EnvBuilder 方法)
@anchor{library/venv venv EnvBuilder create}@anchor{35a3}
@deffn {方法} create (env_dir)

Create a virtual environment by specifying the target directory
(absolute or relative to the current directory) which is to contain the
virtual environment.  The @code{create} method will either create the
environment in the specified directory, or raise an appropriate
exception.

The @code{create} method of the @ref{902,,EnvBuilder} class illustrates the
hooks available for subclass customization:

@example
def create(self, env_dir):
    """
    Create a virtualized Python environment in a directory.
    env_dir is the target directory to create an environment in.
    """
    env_dir = os.path.abspath(env_dir)
    context = self.ensure_directories(env_dir)
    self.create_configuration(context)
    self.setup_python(context)
    self.setup_scripts(context)
    self.post_setup(context)
@end example

Each of the methods @ref{35a4,,ensure_directories()},
@ref{35a5,,create_configuration()}, @ref{35a6,,setup_python()},
@ref{35a7,,setup_scripts()} and @ref{35a8,,post_setup()} can be overridden.
@end deffn

@geindex ensure_directories() (venv.EnvBuilder 方法)
@anchor{library/venv venv EnvBuilder ensure_directories}@anchor{35a4}
@deffn {方法} ensure_directories (env_dir)

Creates the environment directory and all necessary directories, and
returns a context object.  This is just a holder for attributes (such as
paths), for use by the other methods. The directories are allowed to
exist already, as long as either @code{clear} or @code{upgrade} were
specified to allow operating on an existing environment directory.
@end deffn

@geindex create_configuration() (venv.EnvBuilder 方法)
@anchor{library/venv venv EnvBuilder create_configuration}@anchor{35a5}
@deffn {方法} create_configuration (context)

Creates the @code{pyvenv.cfg} configuration file in the environment.
@end deffn

@geindex setup_python() (venv.EnvBuilder 方法)
@anchor{library/venv venv EnvBuilder setup_python}@anchor{35a6}
@deffn {方法} setup_python (context)

Creates a copy or symlink to the Python executable in the environment.
On POSIX systems, if a specific executable @code{python3.x} was used,
symlinks to @code{python} and @code{python3} will be created pointing to that
executable, unless files with those names already exist.
@end deffn

@geindex setup_scripts() (venv.EnvBuilder 方法)
@anchor{library/venv venv EnvBuilder setup_scripts}@anchor{35a7}
@deffn {方法} setup_scripts (context)

Installs activation scripts appropriate to the platform into the virtual
environment.
@end deffn

@geindex post_setup() (venv.EnvBuilder 方法)
@anchor{library/venv venv EnvBuilder post_setup}@anchor{35a8}
@deffn {方法} post_setup (context)

A placeholder method which can be overridden in third party
implementations to pre-install packages in the virtual environment or
perform other post-creation steps.
@end deffn


在 3.7.2 版更改: Windows now uses redirector scripts for @code{python[w].exe} instead of
copying the actual binaries. In 3.7.2 only @ref{35a6,,setup_python()} does
nothing unless running from a build in the source tree.



在 3.7.3 版更改: Windows copies the redirector scripts as part of @ref{35a6,,setup_python()}
instead of @ref{35a7,,setup_scripts()}. This was not the case in 3.7.2.
When using symlinks, the original executables will be linked.


In addition, @ref{902,,EnvBuilder} provides this utility method that can be
called from @ref{35a7,,setup_scripts()} or @ref{35a8,,post_setup()} in subclasses to
assist in installing custom scripts into the virtual environment.

@geindex install_scripts() (venv.EnvBuilder 方法)
@anchor{library/venv venv EnvBuilder install_scripts}@anchor{35a9}
@deffn {方法} install_scripts (context, path)

@emph{path} is the path to a directory that should contain subdirectories
"common", "posix", "nt", each containing scripts destined for the bin
directory in the environment.  The contents of "common" and the
directory corresponding to @ref{1e76,,os.name} are copied after some text
replacement of placeholders:


@itemize *

@item 
@code{__VENV_DIR__} is replaced with the absolute path of the environment
directory.

@item 
@code{__VENV_NAME__} is replaced with the environment name (final path
segment of environment directory).

@item 
@code{__VENV_PROMPT__} is replaced with the prompt (the environment
name surrounded by parentheses and with a following space)

@item 
@code{__VENV_BIN_NAME__} is replaced with the name of the bin directory
(either @code{bin} or @code{Scripts}).

@item 
@code{__VENV_PYTHON__} is replaced with the absolute path of the
environment's executable.
@end itemize

The directories are allowed to exist (for when an existing environment
is being upgraded).
@end deffn
@end deffn

有一个方便实用的模块级别的函数:

@geindex create() (在 venv 模块中)
@anchor{library/venv venv create}@anchor{903}
@deffn {函数} venv.create (env_dir, system_site_packages=False, clear=False, symlinks=False, with_pip=False, prompt=None)

通过关键词参数来创建一个 @ref{902,,EnvBuilder}，并且使用 @emph{env_dir} 参数来调用它的 @ref{35a3,,create()} 方法。


3.3 新版功能.



在 3.4 版更改: Added the @code{with_pip} parameter



在 3.6 版更改: Added the @code{prompt} parameter

@end deffn

@node 一个扩展 EnvBuilder 的例子,,API<2>,venv --- 创建虚拟环境
@anchor{library/venv an-example-of-extending-envbuilder}@anchor{35aa}
@subsubsection 一个扩展 @code{EnvBuilder} 的例子


下面的脚本展示了如何通过实现一个子类来扩展 @ref{902,,EnvBuilder}。这个子类会安装 setuptotols 和 pip 的到被创建的虚拟环境中。

@example
import os
import os.path
from subprocess import Popen, PIPE
import sys
from threading import Thread
from urllib.parse import urlparse
from urllib.request import urlretrieve
import venv

class ExtendedEnvBuilder(venv.EnvBuilder):
    """
    This builder installs setuptools and pip so that you can pip or
    easy_install other packages into the created virtual environment.

    :param nodist: If true, setuptools and pip are not installed into the
                   created virtual environment.
    :param nopip: If true, pip is not installed into the created
                  virtual environment.
    :param progress: If setuptools or pip are installed, the progress of the
                     installation can be monitored by passing a progress
                     callable. If specified, it is called with two
                     arguments: a string indicating some progress, and a
                     context indicating where the string is coming from.
                     The context argument can have one of three values:
                     'main', indicating that it is called from virtualize()
                     itself, and 'stdout' and 'stderr', which are obtained
                     by reading lines from the output streams of a subprocess
                     which is used to install the app.

                     If a callable is not specified, default progress
                     information is output to sys.stderr.
    """

    def __init__(self, *args, **kwargs):
        self.nodist = kwargs.pop('nodist', False)
        self.nopip = kwargs.pop('nopip', False)
        self.progress = kwargs.pop('progress', None)
        self.verbose = kwargs.pop('verbose', False)
        super().__init__(*args, **kwargs)

    def post_setup(self, context):
        """
        Set up any packages which need to be pre-installed into the
        virtual environment being created.

        :param context: The information for the virtual environment
                        creation request being processed.
        """
        os.environ['VIRTUAL_ENV'] = context.env_dir
        if not self.nodist:
            self.install_setuptools(context)
        # Can't install pip without setuptools
        if not self.nopip and not self.nodist:
            self.install_pip(context)

    def reader(self, stream, context):
        """
        Read lines from a subprocess' output stream and either pass to a progress
        callable (if specified) or write progress information to sys.stderr.
        """
        progress = self.progress
        while True:
            s = stream.readline()
            if not s:
                break
            if progress is not None:
                progress(s, context)
            else:
                if not self.verbose:
                    sys.stderr.write('.')
                else:
                    sys.stderr.write(s.decode('utf-8'))
                sys.stderr.flush()
        stream.close()

    def install_script(self, context, name, url):
        _, _, path, _, _, _ = urlparse(url)
        fn = os.path.split(path)[-1]
        binpath = context.bin_path
        distpath = os.path.join(binpath, fn)
        # Download script into the virtual environment's binaries folder
        urlretrieve(url, distpath)
        progress = self.progress
        if self.verbose:
            term = '\n'
        else:
            term = '@w{'}
        if progress is not None:
            progress('Installing %s ...%s' % (name, term), 'main')
        else:
            sys.stderr.write('Installing %s ...%s' % (name, term))
            sys.stderr.flush()
        # Install in the virtual environment
        args = [context.env_exe, fn]
        p = Popen(args, stdout=PIPE, stderr=PIPE, cwd=binpath)
        t1 = Thread(target=self.reader, args=(p.stdout, 'stdout'))
        t1.start()
        t2 = Thread(target=self.reader, args=(p.stderr, 'stderr'))
        t2.start()
        p.wait()
        t1.join()
        t2.join()
        if progress is not None:
            progress('done.', 'main')
        else:
            sys.stderr.write('done.\n')
        # Clean up - no longer needed
        os.unlink(distpath)

    def install_setuptools(self, context):
        """
        Install setuptools in the virtual environment.

        :param context: The information for the virtual environment
                        creation request being processed.
        """
        url = 'https://bitbucket.org/pypa/setuptools/downloads/ez_setup.py'
        self.install_script(context, 'setuptools', url)
        # clear up the setuptools archive which gets downloaded
        pred = lambda o: o.startswith('setuptools-') and o.endswith('.tar.gz')
        files = filter(pred, os.listdir(context.bin_path))
        for f in files:
            f = os.path.join(context.bin_path, f)
            os.unlink(f)

    def install_pip(self, context):
        """
        Install pip in the virtual environment.

        :param context: The information for the virtual environment
                        creation request being processed.
        """
        url = 'https://raw.github.com/pypa/pip/master/contrib/get-pip.py'
        self.install_script(context, 'pip', url)

def main(args=None):
    compatible = True
    if sys.version_info < (3, 3):
        compatible = False
    elif not hasattr(sys, 'base_prefix'):
        compatible = False
    if not compatible:
        raise ValueError('This script is only for use with '
                         'Python 3.3 or later')
    else:
        import argparse

        parser = argparse.ArgumentParser(prog=__name__,
                                         description='Creates virtual Python '
                                                     'environments in one or '
                                                     'more target '
                                                     'directories.')
        parser.add_argument('dirs', metavar='ENV_DIR', nargs='+',
                            help='A directory in which to create the
                                 'virtual environment.')
        parser.add_argument('--no-setuptools', default=False,
                            action='store_true', dest='nodist',
                            help="Don't install setuptools or pip in the "
                                 "virtual environment.")
        parser.add_argument('--no-pip', default=False,
                            action='store_true', dest='nopip',
                            help="Don't install pip in the virtual "
                                 "environment.")
        parser.add_argument('--system-site-packages', default=False,
                            action='store_true', dest='system_site',
                            help='Give the virtual environment access to the '
                                 'system site-packages dir.')
        if os.name == 'nt':
            use_symlinks = False
        else:
            use_symlinks = True
        parser.add_argument('--symlinks', default=use_symlinks,
                            action='store_true', dest='symlinks',
                            help='Try to use symlinks rather than copies, '
                                 'when symlinks are not the default for '
                                 'the platform.')
        parser.add_argument('--clear', default=False, action='store_true',
                            dest='clear', help='Delete the contents of the '
                                               'virtual environment '
                                               'directory if it already '
                                               'exists, before virtual '
                                               'environment creation.')
        parser.add_argument('--upgrade', default=False, action='store_true',
                            dest='upgrade', help='Upgrade the virtual '
                                                 'environment directory to '
                                                 'use this version of '
                                                 'Python, assuming Python '
                                                 'has been upgraded '
                                                 'in-place.')
        parser.add_argument('--verbose', default=False, action='store_true',
                            dest='verbose', help='Display the output '
                                               'from the scripts which '
                                               'install setuptools and pip.')
        options = parser.parse_args(args)
        if options.upgrade and options.clear:
            raise ValueError('you cannot supply --upgrade and --clear together.')
        builder = ExtendedEnvBuilder(system_site_packages=options.system_site,
                                       clear=options.clear,
                                       symlinks=options.symlinks,
                                       upgrade=options.upgrade,
                                       nodist=options.nodist,
                                       nopip=options.nopip,
                                       verbose=options.verbose)
        for d in options.dirs:
            builder.create(d)

if __name__ == '__main__':
    rc = 1
    try:
        main()
        rc = 0
    except Exception as e:
        print('Error: %s' % e, file=sys.stderr)
    sys.exit(rc)
@end example

这个脚本同样可以 在线下载@footnote{https://gist.github.com/vsajip/4673395}。

@node zipapp --- Manage executable Python zip archives,,venv --- 创建虚拟环境,软件打包和分发
@anchor{library/zipapp doc}@anchor{35ab}@anchor{library/zipapp module-zipapp}@anchor{141}@anchor{library/zipapp pip}@anchor{35ac}@anchor{library/zipapp zipapp-manage-executable-python-zip-archives}@anchor{35ad}
@subsection @code{zipapp} --- Manage executable Python zip archives


@geindex zipapp (模块)


3.5 新版功能.


@strong{Source code:} Lib/zipapp.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/zipapp.py}

@geindex Executable Zip Files


__________________________________________________________________


This module provides tools to manage the creation of zip files containing
Python code, which can be  @ref{12cf,,executed directly by the Python interpreter}.  The module provides both a
@ref{35ae,,命令行界面} and a @ref{35af,,Python API}.

@menu
* Basic Example:: 
* 命令行界面: 命令行界面<7>. 
* Python API:: 
* 例子: 例子<27>. 
* Specifying the Interpreter:: 
* Creating Standalone Applications with zipapp:: 
* The Python Zip Application Archive Format:: 

@end menu

@node Basic Example,命令行界面<7>,,zipapp --- Manage executable Python zip archives
@anchor{library/zipapp basic-example}@anchor{35b0}
@subsubsection Basic Example


The following example shows how the @ref{35ae,,命令行界面}
can be used to create an executable archive from a directory containing
Python code.  When run, the archive will execute the @code{main} function from
the module @code{myapp} in the archive.

@example
$ python -m zipapp myapp -m "myapp:main"
$ python myapp.pyz
<output from myapp>
@end example

@node 命令行界面<7>,Python API,Basic Example,zipapp --- Manage executable Python zip archives
@anchor{library/zipapp command-line-interface}@anchor{35b1}@anchor{library/zipapp zipapp-command-line-interface}@anchor{35ae}
@subsubsection 命令行界面


When called as a program from the command line, the following form is used:

@example
$ python -m zipapp source [options]
@end example

If @emph{source} is a directory, this will create an archive from the contents of
@emph{source}.  If @emph{source} is a file, it should be an archive, and it will be
copied to the target archive (or the contents of its shebang line will be
displayed if the --info option is specified).

The following options are understood:

@geindex zipapp command line option; -o <output>
@geindex zipapp command line option; --output=<output>
@anchor{library/zipapp cmdoption-zipapp-o}@anchor{35b2}
@deffn {程序选项} @w{-}o <output>, @w{-}@w{-}output=<output>

Write the output to a file named @emph{output}.  If this option is not specified,
the output filename will be the same as the input @emph{source}, with the
extension @code{.pyz} added.  If an explicit filename is given, it is used as
is (so a @code{.pyz} extension should be included if required).

An output filename must be specified if the @emph{source} is an archive (and in
that case, @emph{output} must not be the same as @emph{source}).
@end deffn

@geindex zipapp command line option; -p <interpreter>
@geindex zipapp command line option; --python=<interpreter>
@anchor{library/zipapp cmdoption-zipapp-p}@anchor{35b3}
@deffn {程序选项} @w{-}p <interpreter>, @w{-}@w{-}python=<interpreter>

Add a @code{#!} line to the archive specifying @emph{interpreter} as the command
to run.  Also, on POSIX, make the archive executable.  The default is to
write no @code{#!} line, and not make the file executable.
@end deffn

@geindex zipapp command line option; -m <mainfn>
@geindex zipapp command line option; --main=<mainfn>
@anchor{library/zipapp cmdoption-zipapp-m}@anchor{35b4}
@deffn {程序选项} @w{-}m <mainfn>, @w{-}@w{-}main=<mainfn>

Write a @code{__main__.py} file to the archive that executes @emph{mainfn}.  The
@emph{mainfn} argument should have the form "pkg.mod:fn", where "pkg.mod" is a
package/module in the archive, and "fn" is a callable in the given module.
The @code{__main__.py} file will execute that callable.

@ref{35b4,,--main} cannot be specified when copying an archive.
@end deffn

@geindex zipapp command line option; -c
@geindex zipapp command line option; --compress
@anchor{library/zipapp cmdoption-zipapp-c}@anchor{35b5}
@deffn {程序选项} @w{-}c, @w{-}@w{-}compress

Compress files with the deflate method, reducing the size of the output
file. By default, files are stored uncompressed in the archive.

@ref{35b5,,--compress} has no effect when copying an archive.


3.7 新版功能.

@end deffn

@geindex zipapp command line option; --info
@anchor{library/zipapp cmdoption-zipapp-info}@anchor{35b6}
@deffn {程序选项} @w{-}@w{-}info

Display the interpreter embedded in the archive, for diagnostic purposes.  In
this case, any other options are ignored and SOURCE must be an archive, not a
directory.
@end deffn

@geindex zipapp command line option; -h
@geindex zipapp command line option; --help
@anchor{library/zipapp cmdoption-zipapp-h}@anchor{35b7}
@deffn {程序选项} @w{-}h, @w{-}@w{-}help

Print a short usage message and exit.
@end deffn

@node Python API,例子<27>,命令行界面<7>,zipapp --- Manage executable Python zip archives
@anchor{library/zipapp python-api}@anchor{35b8}@anchor{library/zipapp zipapp-python-api}@anchor{35af}
@subsubsection Python API


The module defines two convenience functions:

@geindex create_archive() (在 zipapp 模块中)
@anchor{library/zipapp zipapp create_archive}@anchor{415}
@deffn {函数} zipapp.create_archive (source, target=None, interpreter=None, main=None, filter=None, compressed=False)

Create an application archive from @emph{source}.  The source can be any
of the following:


@itemize *

@item 
The name of a directory, or a @ref{363,,path-like object} referring
to a directory, in which case a new application archive will be
created from the content of that directory.

@item 
The name of an existing application archive file, or a @ref{363,,path-like object}
referring to such a file, in which case the file is copied to
the target (modifying it to reflect the value given for the @emph{interpreter}
argument).  The file name should include the @code{.pyz} extension, if required.

@item 
A file object open for reading in bytes mode.  The content of the
file should be an application archive, and the file object is
assumed to be positioned at the start of the archive.
@end itemize

The @emph{target} argument determines where the resulting archive will be
written:


@itemize *

@item 
If it is the name of a file, or a @ref{363,,path-like object},
the archive will be written to that file.

@item 
If it is an open file object, the archive will be written to that
file object, which must be open for writing in bytes mode.

@item 
If the target is omitted (or @code{None}), the source must be a directory
and the target will be a file with the same name as the source, with
a @code{.pyz} extension added.
@end itemize

The @emph{interpreter} argument specifies the name of the Python
interpreter with which the archive will be executed.  It is written as
a "shebang" line at the start of the archive.  On POSIX, this will be
interpreted by the OS, and on Windows it will be handled by the Python
launcher.  Omitting the @emph{interpreter} results in no shebang line being
written.  If an interpreter is specified, and the target is a
filename, the executable bit of the target file will be set.

The @emph{main} argument specifies the name of a callable which will be
used as the main program for the archive.  It can only be specified if
the source is a directory, and the source does not already contain a
@code{__main__.py} file.  The @emph{main} argument should take the form
"pkg.module:callable" and the archive will be run by importing
"pkg.module" and executing the given callable with no arguments.  It
is an error to omit @emph{main} if the source is a directory and does not
contain a @code{__main__.py} file, as otherwise the resulting archive
would not be executable.

The optional @emph{filter} argument specifies a callback function that
is passed a Path object representing the path to the file being added
(relative to the source directory).  It should return @code{True} if the
file is to be added.

The optional @emph{compressed} argument determines whether files are
compressed.  If set to @code{True}, files in the archive are compressed
with the deflate method; otherwise, files are stored uncompressed.
This argument has no effect when copying an existing archive.

If a file object is specified for @emph{source} or @emph{target}, it is the
caller's responsibility to close it after calling create_archive.

When copying an existing archive, file objects supplied only need
@code{read} and @code{readline}, or @code{write} methods.  When creating an
archive from a directory, if the target is a file object it will be
passed to the @code{zipfile.ZipFile} class, and must supply the methods
needed by that class.


3.7 新版功能: Added the @emph{filter} and @emph{compressed} arguments.

@end deffn

@geindex get_interpreter() (在 zipapp 模块中)
@anchor{library/zipapp zipapp get_interpreter}@anchor{35b9}
@deffn {函数} zipapp.get_interpreter (archive)

Return the interpreter specified in the @code{#!} line at the start of the
archive.  If there is no @code{#!} line, return @ref{157,,None}.
The @emph{archive} argument can be a filename or a file-like object open
for reading in bytes mode.  It is assumed to be at the start of the archive.
@end deffn

@node 例子<27>,Specifying the Interpreter,Python API,zipapp --- Manage executable Python zip archives
@anchor{library/zipapp examples}@anchor{35ba}@anchor{library/zipapp zipapp-examples}@anchor{35bb}
@subsubsection 例子


Pack up a directory into an archive, and run it.

@example
$ python -m zipapp myapp
$ python myapp.pyz
<output from myapp>
@end example

The same can be done using the @ref{415,,create_archive()} function:

@example
>>> import zipapp
>>> zipapp.create_archive('myapp', 'myapp.pyz')
@end example

To make the application directly executable on POSIX, specify an interpreter
to use.

@example
$ python -m zipapp myapp -p "/usr/bin/env python"
$ ./myapp.pyz
<output from myapp>
@end example

To replace the shebang line on an existing archive, create a modified archive
using the @ref{415,,create_archive()} function:

@example
>>> import zipapp
>>> zipapp.create_archive('old_archive.pyz', 'new_archive.pyz', '/usr/bin/python3')
@end example

To update the file in place, do the replacement in memory using a @code{BytesIO}
object, and then overwrite the source afterwards.  Note that there is a risk
when overwriting a file in place that an error will result in the loss of
the original file.  This code does not protect against such errors, but
production code should do so.  Also, this method will only work if the archive
fits in memory:

@example
>>> import zipapp
>>> import io
>>> temp = io.BytesIO()
>>> zipapp.create_archive('myapp.pyz', temp, '/usr/bin/python2')
>>> with open('myapp.pyz', 'wb') as f:
>>>     f.write(temp.getvalue())
@end example

@node Specifying the Interpreter,Creating Standalone Applications with zipapp,例子<27>,zipapp --- Manage executable Python zip archives
@anchor{library/zipapp specifying-the-interpreter}@anchor{35bc}@anchor{library/zipapp zipapp-specifying-the-interpreter}@anchor{35bd}
@subsubsection Specifying the Interpreter


Note that if you specify an interpreter and then distribute your application
archive, you need to ensure that the interpreter used is portable.  The Python
launcher for Windows supports most common forms of POSIX @code{#!} line, but there
are other issues to consider:


@itemize *

@item 
If you use "/usr/bin/env python" (or other forms of the "python" command,
such as "/usr/bin/python"), you need to consider that your users may have
either Python 2 or Python 3 as their default, and write your code to work
under both versions.

@item 
If you use an explicit version, for example "/usr/bin/env python3" your
application will not work for users who do not have that version.  (This
may be what you want if you have not made your code Python 2 compatible).

@item 
There is no way to say "python X.Y or later", so be careful of using an
exact version like "/usr/bin/env python3.4" as you will need to change your
shebang line for users of Python 3.5, for example.
@end itemize

Typically, you should use an "/usr/bin/env python2" or "/usr/bin/env python3",
depending on whether your code is written for Python 2 or 3.

@node Creating Standalone Applications with zipapp,The Python Zip Application Archive Format,Specifying the Interpreter,zipapp --- Manage executable Python zip archives
@anchor{library/zipapp creating-standalone-applications-with-zipapp}@anchor{35be}
@subsubsection Creating Standalone Applications with zipapp


Using the @ref{141,,zipapp} module, it is possible to create self-contained Python
programs, which can be distributed to end users who only need to have a
suitable version of Python installed on their system.  The key to doing this
is to bundle all of the application's dependencies into the archive, along
with the application code.

The steps to create a standalone archive are as follows:


@enumerate 

@item 
Create your application in a directory as normal, so you have a @code{myapp}
directory containing a @code{__main__.py} file, and any supporting application
code.

@item 
Install all of your application's dependencies into the @code{myapp} directory,
using pip:

@example
$ python -m pip install -r requirements.txt --target myapp
@end example

(this assumes you have your project requirements in a @code{requirements.txt}
file - if not, you can just list the dependencies manually on the pip command
line).

@item 
Optionally, delete the @code{.dist-info} directories created by pip in the
@code{myapp} directory. These hold metadata for pip to manage the packages, and
as you won't be making any further use of pip they aren't required -
although it won't do any harm if you leave them.

@item 
Package the application using:

@example
$ python -m zipapp -p "interpreter" myapp
@end example
@end enumerate

This will produce a standalone executable, which can be run on any machine with
the appropriate interpreter available. See @ref{35bd,,Specifying the Interpreter}
for details. It can be shipped to users as a single file.

On Unix, the @code{myapp.pyz} file is executable as it stands.  You can rename the
file to remove the @code{.pyz} extension if you prefer a "plain" command name.  On
Windows, the @code{myapp.pyz[w]} file is executable by virtue of the fact that
the Python interpreter registers the @code{.pyz} and @code{.pyzw} file extensions
when installed.

@menu
* Making a Windows executable:: 
* Caveats:: 

@end menu

@node Making a Windows executable,Caveats,,Creating Standalone Applications with zipapp
@anchor{library/zipapp making-a-windows-executable}@anchor{35bf}
@subsubsection Making a Windows executable


On Windows, registration of the @code{.pyz} extension is optional, and
furthermore, there are certain places that don't recognise registered
extensions "transparently" (the simplest example is that
@code{subprocess.run(['myapp'])} won't find your application - you need to
explicitly specify the extension).

On Windows, therefore, it is often preferable to create an executable from the
zipapp.  This is relatively easy, although it does require a C compiler.  The
basic approach relies on the fact that zipfiles can have arbitrary data
prepended, and Windows exe files can have arbitrary data appended.  So by
creating a suitable launcher and tacking the @code{.pyz} file onto the end of it,
you end up with a single-file executable that runs your application.

A suitable launcher can be as simple as the following:

@example
#define Py_LIMITED_API 1
#include "Python.h"

#define WIN32_LEAN_AND_MEAN
#include <windows.h>

#ifdef WINDOWS
int WINAPI wWinMain(
    HINSTANCE hInstance,      /* handle to current instance */
    HINSTANCE hPrevInstance,  /* handle to previous instance */
    LPWSTR lpCmdLine,         /* pointer to command line */
    int nCmdShow              /* show state of window */
)
#else
int wmain()
#endif
@{
    wchar_t **myargv = _alloca((__argc + 1) * sizeof(wchar_t*));
    myargv[0] = __wargv[0];
    memcpy(myargv + 1, __wargv, __argc * sizeof(wchar_t *));
    return Py_Main(__argc+1, myargv);
@}
@end example

If you define the @code{WINDOWS} preprocessor symbol, this will generate a
GUI executable, and without it, a console executable.

To compile the executable, you can either just use the standard MSVC
command line tools, or you can take advantage of the fact that distutils
knows how to compile Python source:

@example
>>> from distutils.ccompiler import new_compiler
>>> import distutils.sysconfig
>>> import sys
>>> import os
>>> from pathlib import Path

>>> def compile(src):
>>>     src = Path(src)
>>>     cc = new_compiler()
>>>     exe = src.stem
>>>     cc.add_include_dir(distutils.sysconfig.get_python_inc())
>>>     cc.add_library_dir(os.path.join(sys.base_exec_prefix, 'libs'))
>>>     # First the CLI executable
>>>     objs = cc.compile([str(src)])
>>>     cc.link_executable(objs, exe)
>>>     # Now the GUI executable
>>>     cc.define_macro('WINDOWS')
>>>     objs = cc.compile([str(src)])
>>>     cc.link_executable(objs, exe + 'w')

>>> if __name__ == "__main__":
>>>     compile("zastub.c")
@end example

The resulting launcher uses the "Limited ABI", so it will run unchanged with
any version of Python 3.x.  All it needs is for Python (@code{python3.dll}) to be
on the user's @code{PATH}.

For a fully standalone distribution, you can distribute the launcher with your
application appended, bundled with the Python "embedded" distribution.  This
will run on any PC with the appropriate architecture (32 bit or 64 bit).

@node Caveats,,Making a Windows executable,Creating Standalone Applications with zipapp
@anchor{library/zipapp caveats}@anchor{35c0}
@subsubsection Caveats


There are some limitations to the process of bundling your application into
a single file.  In most, if not all, cases they can be addressed without
needing major changes to your application.


@enumerate 

@item 
If your application depends on a package that includes a C extension, that
package cannot be run from a zip file (this is an OS limitation, as executable
code must be present in the filesystem for the OS loader to load it). In this
case, you can exclude that dependency from the zipfile, and either require
your users to have it installed, or ship it alongside your zipfile and add code
to your @code{__main__.py} to include the directory containing the unzipped
module in @code{sys.path}. In this case, you will need to make sure to ship
appropriate binaries for your target architecture(s) (and potentially pick the
correct version to add to @code{sys.path} at runtime, based on the user's machine).

@item 
If you are shipping a Windows executable as described above, you either need to
ensure that your users have @code{python3.dll} on their PATH (which is not the
default behaviour of the installer) or you should bundle your application with
the embedded distribution.

@item 
The suggested launcher above uses the Python embedding API.  This means that in
your application, @code{sys.executable} will be your application, and @emph{not} a
conventional Python interpreter.  Your code and its dependencies need to be
prepared for this possibility.  For example, if your application uses the
@ref{b7,,multiprocessing} module, it will need to call
@ref{2364,,multiprocessing.set_executable()} to let the module know where to find the
standard Python interpreter.
@end enumerate

@node The Python Zip Application Archive Format,,Creating Standalone Applications with zipapp,zipapp --- Manage executable Python zip archives
@anchor{library/zipapp the-python-zip-application-archive-format}@anchor{35c1}
@subsubsection The Python Zip Application Archive Format


Python has been able to execute zip files which contain a @code{__main__.py} file
since version 2.6.  In order to be executed by Python, an application archive
simply has to be a standard zip file containing a @code{__main__.py} file which
will be run as the entry point for the application.  As usual for any Python
script, the parent of the script (in this case the zip file) will be placed on
@ref{482,,sys.path} and thus further modules can be imported from the zip file.

The zip file format allows arbitrary data to be prepended to a zip file.  The
zip application format uses this ability to prepend a standard POSIX "shebang"
line to the file (@code{#!/path/to/interpreter}).

Formally, the Python zip application format is therefore:


@enumerate 

@item 
An optional shebang line, containing the characters @code{b'#!'} followed by an
interpreter name, and then a newline (@code{b'\n'}) character.  The interpreter
name can be anything acceptable to the OS "shebang" processing, or the Python
launcher on Windows.  The interpreter should be encoded in UTF-8 on Windows,
and in @ref{4f0,,sys.getfilesystemencoding()} on POSIX.

@item 
Standard zipfile data, as generated by the @ref{142,,zipfile} module.  The
zipfile content @emph{must} include a file called @code{__main__.py} (which must be
in the "root" of the zipfile - i.e., it cannot be in a subdirectory).  The
zipfile data can be compressed or uncompressed.
@end enumerate

If an application archive has a shebang line, it may have the executable bit set
on POSIX systems, to allow it to be executed directly.

There is no requirement that the tools in this module are used to create
application archives - the module is a convenience, but archives in the above
format created by any means are acceptable to Python.

@node Python运行时服务,自定义 Python 解释器,软件打包和分发,Python 标准库
@anchor{library/python doc}@anchor{35c2}@anchor{library/python python}@anchor{35c3}@anchor{library/python python-runtime-services}@anchor{35c4}
@section Python运行时服务


本章里描述的模块提供了和Python解释器及其环境交互相关的广泛服务。以下是综述：

@menu
* sys: sys --- 系统相关的参数和函数. 系统相关的参数和函数
* sysconfig: sysconfig --- Provide access to Python's configuration information. Provide access to Python's configuration information
* builtins: builtins --- 内建对象. 内建对象
* __main__: __main__ --- 顶层脚本环境. 顶层脚本环境
* warnings: warnings --- Warning control. Warning control
* dataclasses: dataclasses --- 数据类. 数据类
* contextlib: contextlib --- 为 with语句上下文提供的工具. 为 with语句上下文提供的工具
* abc: abc --- 抽象基类. 抽象基类
* atexit: atexit --- 退出处理器. 退出处理器
* traceback: traceback --- 打印或检索堆栈回溯. 打印或检索堆栈回溯
* __future__: __future__ --- Future 语句定义. Future 语句定义
* gc: gc --- 垃圾回收器接口. 垃圾回收器接口
* inspect: inspect --- 检查对象. 检查对象
* site —— 指定域的配置钩子:: 

@end menu

@node sys --- 系统相关的参数和函数,sysconfig --- Provide access to Python's configuration information,,Python运行时服务
@anchor{library/sys doc}@anchor{35c5}@anchor{library/sys module-sys}@anchor{fd}@anchor{library/sys sys-system-specific-parameters-and-functions}@anchor{35c6}
@subsection @code{sys} --- 系统相关的参数和函数


@geindex sys (模块)


__________________________________________________________________


该模块提供了一些变量和函数。这些变量可能被解释器使用，也可能由解释器提供。这些函数会影响解释器。本模块总是可用的。

@geindex abiflags() (在 sys 模块中)
@anchor{library/sys sys abiflags}@anchor{264}
@deffn {数据} sys.abiflags

在POSIX系统上，以标准的 @code{configure} 脚本构建的 Python 中，这个变量会包含 
@geindex Python 提高建议; PEP 3149
PEP 3149@footnote{https://www.python.org/dev/peps/pep-3149} 中定义的ABI标签。


在 3.8 版更改: 默认的 flags 变为了空字符串（用于 pymalloc 的 @code{m} 旗标已经移除）



3.2 新版功能.

@end deffn

@geindex addaudithook() (在 sys 模块中)
@anchor{library/sys sys addaudithook}@anchor{3467}
@deffn {函数} sys.addaudithook (hook)

将可调用的 @emph{hook} 附加到当前解释器的活动的审核钩子列表中。

通过 @ref{eb7,,sys.audit()} 函数引发审计事件时，将按照加入钩子的先后顺序调用每个钩子，调用时将带有事件名称和参数元组。首先调用由 @ref{3468,,PySys_AddAuditHook()} 添加的静态钩子，然后调用添加到当前解释器中的钩子。

引发一个 @ref{12d0,,审计事件} @code{sys.addaudithook}，没有附带参数。


3.8 新版功能.



在 3.8.1 版更改: 派生自 @ref{1a9,,Exception} （而非 @ref{2ba,,RuntimeError} ）的异常不会被抑制。


@strong{CPython implementation detail:} 启用跟踪时（参阅 @ref{e37,,settrace()} ），仅当可调用对象（钩子）的 @code{__cantrace__} 成员设置为 true 时，才会跟踪该钩子。否则，跟踪功能将跳过该钩子。
@end deffn

@geindex argv() (在 sys 模块中)
@anchor{library/sys sys argv}@anchor{bf4}
@deffn {数据} sys.argv

一个列表，其中包含了被传递给 Python 脚本的命令行参数。 @code{argv[0]} 为脚本的名称（是否是完整的路径名取决于操作系统）。如果是通过 Python 解释器的命令行参数 @ref{119f,,-c} 来执行的， @code{argv[0]} 会被设置成字符串 @code{'-c'} 。如果没有脚本名被传递给 Python 解释器， @code{argv[0]} 为空字符串。

为了遍历标准输入，或者通过命令行传递的文件列表，参照 @ref{80,,fileinput} 模块

@cartouche
@quotation 注解 
在 Unix 上，系统传递的命令行参数是字节类型的。Python 使用文件系统编码和 "surrogateescape" 错误处理程序对它们进行解码。当需要原始字节时，可以通过 @code{[os.fsencode(arg) for arg in sys.argv]} 来获取。
@end quotation
@end cartouche
@end deffn
@anchor{library/sys auditing}@anchor{12d0}
@geindex audit() (在 sys 模块中)
@anchor{library/sys sys audit}@anchor{eb7}
@deffn {函数} sys.audit (event, *args)

@geindex auditing

利用某些活动的钩子引发审计事件。事件名称是一个字符串，用于标记事件及其关联的架构（即参数的数量和类型）。给定事件的架构应视作公开且稳定的 API，并且不应在版本之间进行修改。

任何钩子抛出第一个异常时，此函数也将抛出该异常。通常不应处理这些错误，而应尽快终止该进程。

钩子程序由 @ref{3467,,sys.addaudithook()} 或 @ref{3468,,PySys_AddAuditHook()} 函数添加。

与本函数相等效的原生函数是 @ref{ec5,,PySys_Audit()}，应尽量使用原生函数。

参阅 @ref{3464,,审计事件表} 以获取 CPython 定义的所有审计事件。


3.8 新版功能.

@end deffn

@geindex base_exec_prefix() (在 sys 模块中)
@anchor{library/sys sys base_exec_prefix}@anchor{35a1}
@deffn {数据} sys.base_exec_prefix

在 @code{site.py} 运行之前， Python 启动的时候被设置为跟 @ref{35a0,,exec_prefix} 同样的值。如果不是运行在 @ref{359e,,虚拟环境} 中，两个值会保持相同；如果 @code{site.py} 发现处于一个虚拟环境中， @ref{359f,,prefix} 和 @ref{35a0,,exec_prefix} 将会指向虚拟环境。然而 @ref{2fe1,,base_prefix} 和 @ref{35a1,,base_exec_prefix} 将仍然会指向基础的 Python 环境（用来创建虚拟环境的 Python 环境）


3.3 新版功能.

@end deffn

@geindex base_prefix() (在 sys 模块中)
@anchor{library/sys sys base_prefix}@anchor{2fe1}
@deffn {数据} sys.base_prefix

在 @code{site.py} 运行之前， Python 启动的时候被设置为跟 @ref{359f,,prefix} 同样的值。如果不是运行在 @ref{359e,,虚拟环境} 中, 两个值会保持相同；如果 @code{site.py} 发现处于一个虚拟环境中， @ref{359f,,prefix} 和 @ref{35a0,,exec_prefix} 将会指向虚拟环境。然而 @ref{2fe1,,base_prefix} 和 @ref{35a1,,base_exec_prefix} 将仍然会指向基础的 Python 环境（用来创建虚拟环境的 Python 环境）


3.3 新版功能.

@end deffn

@geindex byteorder() (在 sys 模块中)
@anchor{library/sys sys byteorder}@anchor{15b9}
@deffn {数据} sys.byteorder

本地字节顺序的指示符。在大端序（最高有效位优先）操作系统上值为 @code{'big'} ，在小端序（最低有效位优先）操作系统上为 @code{'little'} 。
@end deffn

@geindex builtin_module_names() (在 sys 模块中)
@anchor{library/sys sys builtin_module_names}@anchor{35c7}
@deffn {数据} sys.builtin_module_names

一个元素为字符串的元组。包含了所有的被编译进 Python 解释器的模块。（这个信息无法通过其他的办法获取， @code{modules.keys()} 只包括被导入过的模块。）
@end deffn

@geindex call_tracing() (在 sys 模块中)
@anchor{library/sys sys call_tracing}@anchor{35c8}
@deffn {函数} sys.call_tracing (func, args)

在启用跟踪时调用 @code{func(*args)}  来保存跟踪状态，然后恢复跟踪状态。这将从检查点的调试器调用，以便递归地调试其他的一些代码。
@end deffn

@geindex copyright() (在 sys 模块中)
@anchor{library/sys sys copyright}@anchor{35c9}
@deffn {数据} sys.copyright

一个字符串，包含了 Python 解释器有关的版权信息
@end deffn

@geindex _clear_type_cache() (在 sys 模块中)
@anchor{library/sys sys _clear_type_cache}@anchor{35ca}
@deffn {函数} sys._clear_type_cache ()

清除内部的类型缓存。类型缓存是为了加速查找方法和属性的。在调试引用泄漏的时候调用这个函数 @emph{只会} 清除不必要的引用。

这个函数应该只在内部为了一些特定的目的使用。
@end deffn

@geindex _current_frames() (在 sys 模块中)
@anchor{library/sys sys _current_frames}@anchor{d94}
@deffn {函数} sys._current_frames ()

返回一个字典，存放着每个线程的标识符与（调用本函数时）该线程栈顶的帧（当前活动的帧）之间的映射。注意 @ref{113,,traceback} 模块中的函数可以在给定某一帧的情况下构建调用堆栈。

这对于调试死锁最有用：本函数不需要死锁线程的配合，并且只要这些线程的调用栈保持死锁，它们就是冻结的。在调用本代码来检查栈顶的帧的那一刻，非死锁线程返回的帧可能与该线程当前活动的帧没有任何关系。

这个函数应该只在内部为了一些特定的目的使用。

引发一个 @ref{12d0,,审计事件} @code{sys._current_frames}，没有附带参数。
@end deffn

@geindex breakpointhook() (在 sys 模块中)
@anchor{library/sys sys breakpointhook}@anchor{30c}
@deffn {函数} sys.breakpointhook ()

本钩子函数由内建函数 @ref{2f2,,breakpoint()} 调用。默认情况下，它将进入 @ref{c9,,pdb} 调试器，但可以将其改为任何其他函数，以选择使用哪个调试器。

该函数的特征取决于其调用的函数。例如，默认绑定（即 @code{pdb.set_trace()} ）不要求提供参数，但可以将绑定换成要求提供附加参数（位置参数/关键字参数）的函数。内建函数 @code{breakpoint()} 直接将其 @code{*args} 和 @code{**kws} 传入。@code{breakpointhooks()} 返回的所有内容都会从 @code{breakpoint()} 返回。

默认的实现首先会查询环境变量 
@geindex PYTHONBREAKPOINT
@geindex 环境变量; PYTHONBREAKPOINT
@ref{30d,,PYTHONBREAKPOINT}。如果将该变量设置为 @code{"0"}，则本函数立即返回，表示在断点处无操作。如果未设置该环境变量或将其设置为空字符串，则调用 @code{pdb.set_trace()}。否则，此变量应指定要运行的函数，指定函数时应使用 Python 的点导入命名法，如 @code{package.subpackage.module.function}。这种情况下将导入 @code{package.subpackage.module}，且导入的模块必须有一个名为 @code{function()} 的可调用对象。该可调用对象会运行，@code{*args} 和 @code{**kws} 会传入，且无论 @code{function()} 返回什么，@code{sys.breakpointhook()} 都将返回到內建函数 @ref{2f2,,breakpoint()}。

注意，如果在导入 
@geindex PYTHONBREAKPOINT
@geindex 环境变量; PYTHONBREAKPOINT
@ref{30d,,PYTHONBREAKPOINT} 指定的可调用对象时出错，则将报告一个 @ref{2c0,,RuntimeWarning} 并忽略断点。

另请注意，如果以编程方式覆盖 @code{sys.breakpointhook()}，则 @emph{不会} 查询 
@geindex PYTHONBREAKPOINT
@geindex 环境变量; PYTHONBREAKPOINT
@ref{30d,,PYTHONBREAKPOINT}。


3.7 新版功能.

@end deffn

@geindex _debugmallocstats() (在 sys 模块中)
@anchor{library/sys sys _debugmallocstats}@anchor{35cb}
@deffn {函数} sys._debugmallocstats ()

将有关 CPython 内存分配器状态的底层的信息打印至 stderr。

如果 Python 被配置为 --with-pydebug，本方法还将执行一些开销较大的内部一致性检查。


3.3 新版功能.


@strong{CPython implementation detail:} 本函数仅限 CPython。此处没有定义确切的输出格式，且可能会更改。
@end deffn

@geindex dllhandle() (在 sys 模块中)
@anchor{library/sys sys dllhandle}@anchor{35cc}
@deffn {数据} sys.dllhandle

指向 Python DLL 句柄的整数。

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex displayhook() (在 sys 模块中)
@anchor{library/sys sys displayhook}@anchor{e58}
@deffn {函数} sys.displayhook (value)

如果 @emph{value} 不是 @code{None}，则本函数会将 @code{repr(value)} 打印至 @code{sys.stdout}，并将 @emph{value} 保存在 @code{builtins._} 中。如果 @code{repr(value)} 无法用 @code{sys.stdout.errors} 错误回调方法（可能较为“严格”）编码为 @code{sys.stdout.encoding}，请用 @code{'backslashreplace'} 错误回调方法将其编码为 @code{sys.stdout.encoding}。

在交互式 Python 会话中运行 @ref{35cd,,expression} 产生结果后，将在结果上调用 @code{sys.displayhook}。若要自定义这些 value 的显示，可以将 @code{sys.displayhook} 指定为另一个单参数函数。

伪代码:

@example
def displayhook(value):
    if value is None:
        return
    # Set '_' to None to avoid recursion
    builtins._ = None
    text = repr(value)
    try:
        sys.stdout.write(text)
    except UnicodeEncodeError:
        bytes = text.encode(sys.stdout.encoding, 'backslashreplace')
        if hasattr(sys.stdout, 'buffer'):
            sys.stdout.buffer.write(bytes)
        else:
            text = bytes.decode(sys.stdout.encoding, 'strict')
            sys.stdout.write(text)
    sys.stdout.write("\n")
    builtins._ = value
@end example


在 3.2 版更改: 在发生 @ref{1fc,,UnicodeEncodeError} 时使用 @code{'backslashreplace'} 错误回调方法。

@end deffn

@geindex dont_write_bytecode() (在 sys 模块中)
@anchor{library/sys sys dont_write_bytecode}@anchor{35ce}
@deffn {数据} sys.dont_write_bytecode

如果该值为 true，则 Python 在导入源码模块时将不会尝试写入 @code{.pyc} 文件。该值会被初始化为 @code{True} 或 @code{False}，依据是 @ref{d31,,-B} 命令行选项和 
@geindex PYTHONDONTWRITEBYTECODE
@geindex 环境变量; PYTHONDONTWRITEBYTECODE
@ref{d32,,PYTHONDONTWRITEBYTECODE} 环境变量，可以自行设置该值，来控制是否生成字节码文件。
@end deffn

@geindex pycache_prefix() (在 sys 模块中)
@anchor{library/sys sys pycache_prefix}@anchor{156}
@deffn {数据} sys.pycache_prefix

如果将该选项设为某个目录（不是 @code{None} ），Python 会将字节码缓存文件 @code{.pyc} 写入到以该目录为根的并行目录树中（并从中读取），而不是在源码树中的 @code{__pycache__} 目录下读写。源码树中所有的 @code{__pycache__} 目录都将被忽略，并将在 pycache prefix 内写入新的 @cite{.pyc} 文件。因此，如果使用 @ref{21,,compileall} 作为预构建步骤，则必须确保预构建时使用的 pycache prefix （如果有）与将来运行的时候相同。

相对路径将解释为相对于当前工作目录。

该值的初值设置，依据 @ref{155,,-X} @code{pycache_prefix=PATH} 命令行选项或 
@geindex PYTHONPYCACHEPREFIX
@geindex 环境变量; PYTHONPYCACHEPREFIX
@ref{154,,PYTHONPYCACHEPREFIX} 环境变量的值（命令行优先）。如果两者均未设置，则为 @code{None}。


3.8 新版功能.

@end deffn

@geindex excepthook() (在 sys 模块中)
@anchor{library/sys sys excepthook}@anchor{e5c}
@deffn {函数} sys.excepthook (type, value, traceback)

本函数会将所给的回溯和异常输出到 @code{sys.stderr} 中。

当抛出一个异常，且未被捕获时，解释器将调用 @code{sys.excepthook} 并带有三个参数：异常类、异常实例和一个回溯对象。在交互式会话中，这会在控制权返回到提示符之前发生。在 Python 程序中，这会在程序退出之前发生。如果要自定义此类顶级异常的处理过程，可以将另一个 3 个参数的函数赋给 @code{sys.excepthook}。

引发一个 @ref{12d0,,审计事件} @code{sys.excepthook}，附带参数 @code{hook}, @code{type}, @code{value}, @code{traceback}。


@subsubheading 参见


@ref{22d,,sys.unraisablehook()} 函数处理无法抛出的异常，@ref{231,,threading.excepthook()} 函数处理 @ref{232,,threading.Thread.run()} 抛出的异常。

@end deffn

@geindex __breakpointhook__() (在 sys 模块中)
@geindex __displayhook__() (在 sys 模块中)
@geindex __excepthook__() (在 sys 模块中)
@geindex __unraisablehook__() (在 sys 模块中)
@anchor{library/sys sys __breakpointhook__}@anchor{35cf}
@deffn {数据} sys.__breakpointhook__
@anchor{library/sys sys __displayhook__}@anchor{35d0}
@deffnx {数据} sys.__displayhook__
@anchor{library/sys sys __excepthook__}@anchor{35d1}
@deffnx {数据} sys.__excepthook__
@anchor{library/sys sys __unraisablehook__}@anchor{35d2}
@deffnx {数据} sys.__unraisablehook__

程序开始时，这些对象存有 @code{breakpointhook}、@code{displayhook}、@code{excepthook} 和 @code{unraisablehook} 的初始值。保存它们是为了可以在 @code{breakpointhook}、@code{displayhook} 和 @code{excepthook}、@code{unraisablehook} 被破坏或被替换时恢复它们。


3.7 新版功能: __breakpointhook__



3.8 新版功能: __unraisablehook__

@end deffn

@geindex exc_info() (在 sys 模块中)
@anchor{library/sys sys exc_info}@anchor{c58}
@deffn {函数} sys.exc_info ()

本函数返回的元组包含三个值，它们给出当前正在处理的异常的信息。返回的信息仅限于当前线程和当前堆栈帧。如果当前堆栈帧没有正在处理的异常，则信息将从调用的下级堆栈帧或上级调用者等位置获取，依此类推，直到找到正在处理异常的堆栈帧为止。此处的“处理异常”被定义为“执行 except 子句”。任何堆栈帧都只能访问当前正在处理的异常的信息。

@geindex 对象; traceback

如果整个堆栈都没有正在处理的异常，则返回包含三个 @code{None} 值的元组。否则返回值为 @code{(type, value, traceback)}。它们的含义是：@emph{type} 是正在处理的异常类型（它是 @ref{1a8,,BaseException} 的子类）；@emph{value} 是异常实例（异常类型的实例）；@emph{traceback} 是一个 @ref{32f,,回溯对象}，该对象封装了最初发生异常时的调用堆栈。
@end deffn

@geindex exec_prefix() (在 sys 模块中)
@anchor{library/sys sys exec_prefix}@anchor{35a0}
@deffn {数据} sys.exec_prefix

一个字符串，给出特定域的目录前缀，该目录中安装了与平台相关的 Python 文件，默认也是 @code{'/usr/local'}。该目录前缀可以在构建时使用 @code{configure} 脚本的 @code{--exec-prefix} 参数进行设置。具体而言，所有配置文件（如 @code{pyconfig.h} 头文件）都安装在目录 @code{@emph{exec_prefix}/lib/python@emph{X.Y}/config} 中，共享库模块安装在 @code{@emph{exec_prefix}/lib/python@emph{X.Y}/lib-dynload} 中，其中 @emph{X.Y} 是 Python 的版本号，如 @code{3.2}。

@cartouche
@quotation 注解 
如果在一个 @ref{359e,,虚拟环境} 中，那么该值将在 @code{site.py} 中被修改，指向虚拟环境。Python 安装位置仍然可以用 @ref{35a1,,base_exec_prefix} 来获取。
@end quotation
@end cartouche
@end deffn

@geindex executable() (在 sys 模块中)
@anchor{library/sys sys executable}@anchor{274}
@deffn {数据} sys.executable

一个字符串，提供 Python 解释器的可执行二进制文件的绝对路径，仅在部分系统中此值有意义。如果 Python 无法获取其可执行文件的真实路径，则 @ref{274,,sys.executable} 将为空字符串或 @code{None}。
@end deffn

@geindex exit() (在 sys 模块中)
@anchor{library/sys sys exit}@anchor{cdb}
@deffn {函数} sys.exit ([arg])

从Python中退出。实现方式是抛出一个 @ref{5f7,,SystemExit} 异常。异常抛出后 @ref{d6b,,try} 声明的 finally 分支语句的清除动作将被出发。此动作有可能打断更外层的退出尝试。

可选参数 @emph{arg} 可以是表示退出状态的整数（默认为 0），也可以是其他类型的对象。如果它是整数，则 shell 等将 0 视为“成功终止”，非零值视为“异常终止”。大多数系统要求该值的范围是 0--127，否则会产生不确定的结果。某些系统为退出代码约定了特定的含义，但通常尚不完善；Unix 程序通常用 2 表示命令行语法错误，用 1 表示所有其他类型的错误。传入其他类型的对象，如果传入 @code{None} 等同于传入 0，如果传入其他对象则将其打印至 @ref{308,,stderr}，且退出代码为 1。特别地，@code{sys.exit("some error message")} 可以在发生错误时快速退出程序。

由于 @ref{15a7,,exit()} 最终“只是”抛出一个异常，因此当从主线程调用时，只会从进程退出；而异常不会因此被打断。


在 3.6 版更改: 在 Python 解释器捕获 @ref{5f7,,SystemExit} 后，如果在清理中发生错误（如清除标准流中的缓冲数据时出错），则退出状态码将变为 120。

@end deffn

@geindex flags() (在 sys 模块中)
@anchor{library/sys sys flags}@anchor{b35}
@deffn {数据} sys.flags

@ref{a9e,,具名元组} @emph{flags} 含有命令行标志的状态。这些属性是只读的。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

attribute -- 属性

@tab

标志

@item

@code{debug}

@tab

@ref{12d8,,-d}

@item

@ref{a0,,inspect}

@tab

@ref{e18,,-i}

@item

@code{interactive}

@tab

@ref{e18,,-i}

@item

@code{isolated}

@tab

@ref{f99,,-I}

@item

@code{optimize}

@tab

@ref{685,,-O} 或 @ref{686,,-OO}

@item

@ref{35ce,,dont_write_bytecode}

@tab

@ref{d31,,-B}

@item

@code{no_user_site}

@tab

@ref{d0e,,-s}

@item

@code{no_site}

@tab

@ref{b1d,,-S}

@item

@code{ignore_environment}

@tab

@ref{f9a,,-E}

@item

@code{verbose}

@tab

@ref{d81,,-v}

@item

@code{bytes_warning}

@tab

@ref{40d,,-b}

@item

@code{quiet}

@tab

@ref{12db,,-q}

@item

@code{hash_randomization}

@tab

@ref{1027,,-R}

@item

@code{dev_mode}

@tab

@ref{155,,-X} @code{dev}

@item

@code{utf8_mode}

@tab

@ref{155,,-X} @code{utf8}

@end multitable



在 3.2 版更改: 为新的 @ref{12db,,-q} 标志添加了 @code{quiet} 属性



3.2.3 新版功能: @code{hash_randomization} 属性



在 3.3 版更改: 删除了过时的 @code{division_warning} 属性



在 3.4 版更改: 为 @ref{f99,,-I} @code{isolated} 标志添加了 @code{isolated} 属性。



在 3.7 版更改: Added @code{dev_mode} attribute for the new @ref{155,,-X} @code{dev} flag
and @code{utf8_mode} attribute for the new  @ref{155,,-X} @code{utf8} flag.

@end deffn

@geindex float_info() (在 sys 模块中)
@anchor{library/sys sys float_info}@anchor{f51}
@deffn {数据} sys.float_info

一个 @ref{a9e,,具名元组}，存有浮点型的相关信息。它包含的是关于精度和内部表示的底层信息。这些值与标准头文件 @code{float.h} 中为 C 语言定义的各种浮点常量对应，详情请参阅 1999 ISO/IEC C 标准 @ref{35d3,,[C99]} 的 5.2.4.2.2 节，'Characteristics of floating types（浮点型的特性）'。


@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

attribute -- 属性

@tab

float.h 宏

@tab

说明

@item

@code{epsilon}

@tab

DBL_EPSILON

@tab

大于 1.0 的最小值和 1.0 之间的差，表示为浮点数

@item

@code{dig}

@tab

DBL_DIG

@tab

浮点数可以真实表示的最大十进制数字；见下文

@item

@code{mant_dig}

@tab

DBL_MANT_DIG

@tab

浮点数精度：@code{radix} 基数下的浮点数有效位数

@item

@ref{804,,max}

@tab

DBL_MAX

@tab

最大可表示的正有限浮点数

@item

@code{max_exp}

@tab

DBL_MAX_EXP

@tab

使得 @code{radix**(e-1)} 是可表示的浮点数（非无穷）的最大整数 @emph{e}

@item

@code{max_10_exp}

@tab

DBL_MAX_10_EXP

@tab

使得 @code{10**e} 在可表示的浮点数（非无穷）范围内的最大整数 @emph{e}

@item

@ref{803,,min}

@tab

DBL_MIN

@tab

可表示的最小正 @emph{规格化} 浮点数

@item

@code{min_exp}

@tab

DBL_MIN_EXP

@tab

使得 @code{radix**(e-1)} 是规格化浮点数的最小整数 @emph{e}

@item

@code{min_10_exp}

@tab

DBL_MIN_10_EXP

@tab

使得 @code{10**e} 是规格化浮点数的最小整数 @emph{e}

@item

@code{radix}

@tab

FLT_RADIX

@tab

指数表示法中采用的基数

@item

@code{rounds}

@tab

FLT_ROUNDS

@tab

整数常数，表示算术运算中的舍入方式。它反映了解释器启动时系统的 FLT_ROUNDS 宏的值。关于可能的值及其含义的说明，请参阅 C99 标准 5.2.4.2.2 节。

@end multitable


关于 @code{sys.float_info.dig} 属性的进一步说明。如果 @code{s} 是表示十进制数的字符串，而该数最多有 @code{sys.float_info.dig} 位有效数字，则将 @code{s} 转换为 float 再转回去将恢复原先相同十进制值的字符串:

@example
>>> import sys
>>> sys.float_info.dig
15
>>> s = '3.14159265358979'    # decimal string with 15 significant digits
>>> format(float(s), '.15g')  # convert to float and back -> same value
'3.14159265358979'
@end example

但是对于超过 @code{sys.float_info.dig} 位有效数字的字符串，转换前后并非总是相同:

@example
>>> s = '9876543211234567'    # 16 significant digits is too many!
>>> format(float(s), '.16g')  # conversion changes value
'9876543211234568'
@end example
@end deffn

@geindex float_repr_style() (在 sys 模块中)
@anchor{library/sys sys float_repr_style}@anchor{c89}
@deffn {数据} sys.float_repr_style

一个字符串，反映 @ref{7c6,,repr()} 函数在浮点数上的行为。如果该字符串是 @code{'short'}，那么对于（非无穷的）浮点数 @code{x}，@code{repr(x)} 将会生成一个短字符串，满足 @code{float(repr(x)) == x} 的特性。这是 Python 3.1 及更高版本中的常见行为。否则 @code{float_repr_style} 的值将是 @code{'legacy'}，此时 @code{repr(x)} 的行为方式将与 Python 3.1 之前的版本相同。


3.1 新版功能.

@end deffn

@geindex getallocatedblocks() (在 sys 模块中)
@anchor{library/sys sys getallocatedblocks}@anchor{8dc}
@deffn {函数} sys.getallocatedblocks ()

返回解释器当前已分配的内存块数，无论它们大小如何。本函数主要用于跟踪和调试内存泄漏。因为解释器有内部缓存，所以不同调用之间结果会变化。可能需要调用 @ref{35ca,,_clear_type_cache()} 和 @ref{22e,,gc.collect()} 使结果更容易预测。

如果当前 Python 构建或实现无法合理地计算此信息，允许 @ref{8dc,,getallocatedblocks()} 返回 0。


3.4 新版功能.

@end deffn

@geindex getandroidapilevel() (在 sys 模块中)
@anchor{library/sys sys getandroidapilevel}@anchor{3e9}
@deffn {函数} sys.getandroidapilevel ()

返回一个整数，表示 Android 构建时 API 版本。

@ref{12f5,,可用性}：Android。


3.7 新版功能.

@end deffn

@geindex getcheckinterval() (在 sys 模块中)
@anchor{library/sys sys getcheckinterval}@anchor{e01}
@deffn {函数} sys.getcheckinterval ()

Return the interpreter's "check interval"; see @ref{35d4,,setcheckinterval()}.


3.2 版后已移除: Use @ref{35d5,,getswitchinterval()} instead.

@end deffn

@geindex getdefaultencoding() (在 sys 模块中)
@anchor{library/sys sys getdefaultencoding}@anchor{35d6}
@deffn {函数} sys.getdefaultencoding ()

返回当前 Unicode 实现所使用的默认字符串编码名称。
@end deffn

@geindex getdlopenflags() (在 sys 模块中)
@anchor{library/sys sys getdlopenflags}@anchor{e47}
@deffn {函数} sys.getdlopenflags ()

返回当前 @code{dlopen()} 调用所使用的标志位的值。标志值对应的符号名称可以在 @ref{c4,,os} 模块中找到（形如 @code{RTLD_xxx} 的常量，如 @ref{a5a,,os.RTLD_LAZY} ）。

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex getfilesystemencoding() (在 sys 模块中)
@anchor{library/sys sys getfilesystemencoding}@anchor{4f0}
@deffn {函数} sys.getfilesystemencoding ()

返回编码名称，该编码用于在 Unicode 文件名和 bytes 文件名之间转换。为获得最佳兼容性，任何时候都应使用 str 表示文件名，尽管用字节来表示文件名也是支持的。函数如果需要接受或返回文件名，它应支持 str 或 bytes，并在内部将其转换为系统首选的表示形式。

该编码始终是 ASCII 兼容的。

应使用 @ref{4e9,,os.fsencode()} 和 @ref{4e8,,os.fsdecode()} 来保证所采用的编码和错误模式都是正确的。


@itemize *

@item 
在UTF-8模式下，任何平台上的编码均为 @code{utf-8} 。

@item 
在macOS上，编码为 @code{'utf-8'}。

@item 
在Unix上，编码是语言环境编码。

@item 
在Windows上取决于用户配置，编码可能是 @code{'utf-8'} 或 @code{'mbcs'}。

@item 
在Android上，编码为 @code{'utf-8'}。

@item 
在VxWorks上，编码为 @code{'utf-8'}。
@end itemize


在 3.2 版更改: @ref{4f0,,getfilesystemencoding()} 的结果将不再有可能是 @code{None}。



在 3.6 版更改: Windows 不再保证会返回 @code{'mbcs'}。详情请参阅 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529} 和 @ref{4f2,,_enablelegacywindowsfsencoding()}。



在 3.7 版更改: 在UTF-8模式下返回 'utf-8' 。

@end deffn

@geindex getfilesystemencodeerrors() (在 sys 模块中)
@anchor{library/sys sys getfilesystemencodeerrors}@anchor{58f}
@deffn {函数} sys.getfilesystemencodeerrors ()

返回错误回调函数的名称，该错误回调函数将在 Unicode 文件名和 bytes 文件名转换时生效。编码的名称是由 @ref{4f0,,getfilesystemencoding()} 返回的。

应使用 @ref{4e9,,os.fsencode()} 和 @ref{4e8,,os.fsdecode()} 来保证所采用的编码和错误模式都是正确的。


3.6 新版功能.

@end deffn

@geindex getrefcount() (在 sys 模块中)
@anchor{library/sys sys getrefcount}@anchor{35d7}
@deffn {函数} sys.getrefcount (object)

返回 @emph{object} 的引用计数。返回的计数通常比预期的多一，因为它包括了作为 @ref{35d7,,getrefcount()} 参数的这一次（临时）引用。
@end deffn

@geindex getrecursionlimit() (在 sys 模块中)
@anchor{library/sys sys getrecursionlimit}@anchor{e73}
@deffn {函数} sys.getrecursionlimit ()

返回当前的递归限制值，即 Python 解释器堆栈的最大深度。此限制可防止无限递归导致的 C 堆栈溢出和 Python 崩溃。该值可以通过 @ref{e74,,setrecursionlimit()} 设置。
@end deffn

@geindex getsizeof() (在 sys 模块中)
@anchor{library/sys sys getsizeof}@anchor{3565}
@deffn {函数} sys.getsizeof (object[, default])

返回对象的大小（以字节为单位）。该对象可以是任何类型。所有内建对象返回的结果都是正确的，但对于第三方扩展不一定正确，因为这与具体实现有关。

只计算直接分配给对象的内存消耗，不计算它所引用的对象的内存消耗。

对象不提供计算大小的方法时，如果有给出 @emph{default} 则返回它，否则抛出 @ref{192,,TypeError} 异常。

如果对象由垃圾回收器管理，则 @ref{3565,,getsizeof()} 将调用对象的 @code{__sizeof__} 方法，并在上层添加额外的垃圾回收器。

可以参考 recursive sizeof recipe@footnote{https://code.activestate.com/recipes/577504} 中的示例，关于递归调用 @ref{3565,,getsizeof()} 来得到各个容器及其所有内容物的大小。
@end deffn

@geindex getswitchinterval() (在 sys 模块中)
@anchor{library/sys sys getswitchinterval}@anchor{35d5}
@deffn {函数} sys.getswitchinterval ()

返回解释器的“线程切换间隔时间”，请参阅 @ref{be4,,setswitchinterval()}。


3.2 新版功能.

@end deffn

@geindex _getframe() (在 sys 模块中)
@anchor{library/sys sys _getframe}@anchor{e5d}
@deffn {函数} sys._getframe ([depth])

返回来自调用栈的一个帧对象。如果传入可选整数 @emph{depth}，则返回从栈顶往下相应调用层数的帧对象。如果该数比调用栈更深，则抛出 @ref{1fb,,ValueError}。@emph{depth} 的默认值是 0，返回调用栈顶部的帧。

引发一个 @ref{12d0,,审计事件} @code{sys._getframe}，没有附带参数。

@strong{CPython implementation detail:} 这个函数应该只在内部为了一些特定的目的使用。不保证它在所有 Python 实现中都存在。
@end deffn

@geindex getprofile() (在 sys 模块中)
@anchor{library/sys sys getprofile}@anchor{d40}
@deffn {函数} sys.getprofile ()

@geindex profile function
@geindex profiler

返回由 @ref{e36,,setprofile()} 设置的性能分析函数
@end deffn

@geindex gettrace() (在 sys 模块中)
@anchor{library/sys sys gettrace}@anchor{d41}
@deffn {函数} sys.gettrace ()

@geindex trace function
@geindex debugger

返回由 @ref{e37,,settrace()} 设置的跟踪函数。

@strong{CPython implementation detail:} @ref{d41,,gettrace()} 函数仅用于实现调试器，性能分析器，打包工具等。它的行为是实现平台的一部分，而不是语言定义的一部分，因此并非在所有 Python 实现中都可用。
@end deffn

@geindex getwindowsversion() (在 sys 模块中)
@anchor{library/sys sys getwindowsversion}@anchor{590}
@deffn {函数} sys.getwindowsversion ()

返回一个具名元组，描述当前正在运行的 Windows 版本。元素名称包括 @emph{major}, @emph{minor}, @emph{build}, @emph{platform}, @emph{service_pack}, @emph{service_pack_minor}, @emph{service_pack_major}, @emph{suite_mask}, @emph{product_type} 和 @emph{platform_version}。@emph{service_pack} 包含一个字符串，@emph{platform_version} 包含一个三元组，其他所有值都是整数。元素也可以通过名称来访问，所以 @code{sys.getwindowsversion()[0]} 与 @code{sys.getwindowsversion().major} 是等效的。为保持与旧版本的兼容性，只有前 5 个元素可以用索引检索。

@emph{platform} 将会是 @code{2 (VER_PLATFORM_WIN32_NT)}。

@emph{product_type} 可能是以下值之一：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{1 (VER_NT_WORKSTATION)}

@tab

系统是工作站。

@item

@code{2 (VER_NT_DOMAIN_CONTROLLER)}

@tab

系统是域控制器。

@item

@code{3 (VER_NT_SERVER)}

@tab

系统是服务器，但不是域控制器。

@end multitable


本函数包装了 Win32 @code{GetVersionEx()} 函数，参阅 Microsoft 文档有关 @code{OSVERSIONINFOEX()} 的内容可获取这些字段的更多信息。

@emph{platform_version} 返回的是当前操作系统真实准确的主要版本、次要版本和内部版本号，不是为该进程模拟的版本。它旨在用于记录日志，不用于检测功能。

@ref{12f5,,可用性}: Windows。


在 3.2 版更改: 更改为具名元组，添加 @emph{service_pack_minor}, @emph{service_pack_major}, @emph{suite_mask} 和 @emph{product_type}。



在 3.6 版更改: 添加了 @emph{platform_version}

@end deffn

@geindex get_asyncgen_hooks() (在 sys 模块中)
@anchor{library/sys sys get_asyncgen_hooks}@anchor{35d8}
@deffn {函数} sys.get_asyncgen_hooks ()

返回一个 @emph{asyncgen_hooks} 对象，该对象类似于 @ref{1b6,,namedtuple}，形式为 @cite{(firstiter@comma{} finalizer)}，其中 @emph{firstiter} 和 @emph{finalizer} 为 @code{None} 或函数，函数以 @ref{35d9,,异步生成器迭代器} 作为参数，并用于在事件循环中干预异步生成器的终结。


3.6 新版功能: 详情请参阅 
@geindex Python 提高建议; PEP 525
PEP 525@footnote{https://www.python.org/dev/peps/pep-0525}。


@cartouche
@quotation 注解 
本函数已添加至暂定软件包（详情请参阅 
@geindex Python 提高建议; PEP 411
PEP 411@footnote{https://www.python.org/dev/peps/pep-0411} ）。
@end quotation
@end cartouche
@end deffn

@geindex get_coroutine_origin_tracking_depth() (在 sys 模块中)
@anchor{library/sys sys get_coroutine_origin_tracking_depth}@anchor{3ea}
@deffn {函数} sys.get_coroutine_origin_tracking_depth ()

获取由 @ref{3eb,,set_coroutine_origin_tracking_depth()} 设置的协程来源的追踪深度。


3.7 新版功能.


@cartouche
@quotation 注解 
本函数已添加至暂定软件包（详情请参阅 
@geindex Python 提高建议; PEP 411
PEP 411@footnote{https://www.python.org/dev/peps/pep-0411} ）。仅将其用于调试目的。
@end quotation
@end cartouche
@end deffn

@geindex hash_info() (在 sys 模块中)
@anchor{library/sys sys hash_info}@anchor{91b}
@deffn {数据} sys.hash_info

一个 @ref{a9e,,具名元组}，给出数字类型的哈希的实现参数。关于数字类型的哈希的详情请参阅 @ref{15bf,,数字类型的哈希运算}。


@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

attribute -- 属性

@tab

说明

@item

@code{width}

@tab

用于哈希值的位宽度

@item

@code{modulus}

@tab

用于数字散列方案的素数模数P。

@item

@code{inf}

@tab

为正无穷大返回的哈希值

@item

@code{nan}

@tab

为nan返回的哈希值

@item

@code{imag}

@tab

用于复数虚部的乘数

@item

@code{algorithm}

@tab

字符串、字节和内存视图的哈希算法的名称

@item

@code{hash_bits}

@tab

哈希算法的内部输出大小。

@item

@code{seed_bits}

@tab

散列算法的种子密钥的大小

@end multitable



3.2 新版功能.



在 3.4 版更改: 添加了 @emph{algorithm}, @emph{hash_bits} 和 @emph{seed_bits}

@end deffn

@geindex hexversion() (在 sys 模块中)
@anchor{library/sys sys hexversion}@anchor{35da}
@deffn {数据} sys.hexversion

编码为单个整数的版本号。该整数会确保每个版本都自增，其中适当包括了未发布版本。举例来说，要测试 Python 解释器的版本不低于 1.5.2，请使用:

@example
if sys.hexversion >= 0x010502F0:
    # use some advanced feature
    ...
else:
    # use an alternative implementation or warn the user
    ...
@end example

之所以称它为 @code{hexversion}，是因为只有将它传入内置函数 @ref{c5f,,hex()} 后，其结果才看起来有意义。也可以使用 @ref{a9e,,具名元组} @ref{b13,,sys.version_info}，它对相同信息有着更人性化的编码。

关于 @code{hexversion} 的更多信息可以在 @ref{35db,,API 和 ABI 版本管理} 中找到。
@end deffn

@geindex implementation() (在 sys 模块中)
@anchor{library/sys sys implementation}@anchor{9a4}
@deffn {数据} sys.implementation

一个对象，该对象包含当前运行的 Python 解释器的实现信息。所有 Python 实现中都必须存在下列属性。

@emph{name} 是当前实现的标识符，如 @code{'cpython'}。实际的字符串由 Python 实现定义，但保证是小写字母。

@emph{version} 是一个具名元组，格式与 @ref{b13,,sys.version_info} 相同。它表示 Python @emph{实现} 的版本。 另一个（由 @code{sys.version_info} 表示）是当前解释器遵循的相应 Python @emph{语言} 的版本，两者具有不同的含义。 例如，对于 PyPy 1.8，@code{sys.implementation.version} 可能是 @code{sys.version_info(1, 8, 0, 'final', 0)}，而 @code{sys.version_info} 则是 @code{sys.version_info(2, 7, 2, 'final', 0)}。对于 CPython 而言两个值是相同的，因为它是参考实现。

@emph{hexversion} 是十六进制的实现版本，类似于 @ref{35da,,sys.hexversion}。

@emph{cache_tag} 是导入机制使用的标记，用于已缓存模块的文件名。按照惯例，它将由实现的名称和版本组成，如 @code{'cpython-33'}。但如果合适，Python 实现可以使用其他值。如果 @code{cache_tag} 被置为 @code{None}，表示模块缓存已禁用。

@ref{9a4,,sys.implementation} 可能包含相应 Python 实现的其他属性。这些非标准属性必须以下划线开头，此处不详细阐述。无论其内容如何，@ref{9a4,,sys.implementation} 在解释器运行期间或不同实现版本之间都不会更改。（但是不同 Python 语言版本间可能会不同。）详情请参阅 
@geindex Python 提高建议; PEP 421
PEP 421@footnote{https://www.python.org/dev/peps/pep-0421}。


3.3 新版功能.


@cartouche
@quotation 注解 
新的必要属性的添加必须经过常规的 PEP 过程。详情请参阅 
@geindex Python 提高建议; PEP 421
PEP 421@footnote{https://www.python.org/dev/peps/pep-0421}。
@end quotation
@end cartouche
@end deffn

@geindex int_info() (在 sys 模块中)
@anchor{library/sys sys int_info}@anchor{c1a}
@deffn {数据} sys.int_info

一个 @ref{a9e,,具名元组}，包含 Python 内部整数表示形式的信息。这些属性是只读的。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性

@tab

说明

@item

@code{bits_per_digit}

@tab

每个数字占有的位数。Python 内部将整数存储在基底 @code{2**int_info.bits_per_digit}

@item

@code{sizeof_digit}

@tab

用于表示数字的C类型的字节大小

@end multitable



3.1 新版功能.

@end deffn

@geindex __interactivehook__() (在 sys 模块中)
@anchor{library/sys sys __interactivehook__}@anchor{8de}
@deffn {数据} sys.__interactivehook__

When this attribute exists, its value is automatically called (with no
arguments) when the interpreter is launched in @ref{8dd,,interactive mode}.  This is done after the 
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP} file is
read, so that you can set this hook there.  The @ref{eb,,site} module
@ref{8e0,,sets this}.

引发一个 @ref{12d0,,审计事件} @code{cpython.run_interactivehook}，附带参数 @code{hook}。


3.4 新版功能.

@end deffn

@geindex intern() (在 sys 模块中)
@anchor{library/sys sys intern}@anchor{c67}
@deffn {函数} sys.intern (string)

Enter @emph{string} in the table of "interned" strings and return the interned string
-- which is @emph{string} itself or a copy. Interning strings is useful to gain a
little performance on dictionary lookup -- if the keys in a dictionary are
interned, and the lookup key is interned, the key comparisons (after hashing)
can be done by a pointer compare instead of a string compare.  Normally, the
names used in Python programs are automatically interned, and the dictionaries
used to hold module, class or instance attributes have interned keys.

Interned strings are not immortal; you must keep a reference to the return
value of @ref{c67,,intern()} around to benefit from it.
@end deffn

@geindex is_finalizing() (在 sys 模块中)
@anchor{library/sys sys is_finalizing}@anchor{75c}
@deffn {函数} sys.is_finalizing ()

Return @ref{494,,True} if the Python interpreter is
@ref{75d,,shutting down}, @ref{380,,False} otherwise.


3.5 新版功能.

@end deffn

@geindex last_type() (在 sys 模块中)
@geindex last_value() (在 sys 模块中)
@geindex last_traceback() (在 sys 模块中)
@anchor{library/sys sys last_type}@anchor{c53}
@deffn {数据} sys.last_type
@anchor{library/sys sys last_value}@anchor{35dc}
@deffnx {数据} sys.last_value
@anchor{library/sys sys last_traceback}@anchor{34d7}
@deffnx {数据} sys.last_traceback

These three variables are not always defined; they are set when an exception is
not handled and the interpreter prints an error message and a stack traceback.
Their intended use is to allow an interactive user to import a debugger module
and engage in post-mortem debugging without having to re-execute the command
that caused the error.  (Typical use is @code{import pdb; pdb.pm()} to enter the
post-mortem debugger; see @ref{c9,,pdb} module for
more information.)

The meaning of the variables is the same as that of the return values from
@ref{c58,,exc_info()} above.
@end deffn

@geindex maxsize() (在 sys 模块中)
@anchor{library/sys sys maxsize}@anchor{b3c}
@deffn {数据} sys.maxsize

An integer giving the maximum value a variable of type @code{Py_ssize_t} can
take.  It's usually @code{2**31 - 1} on a 32-bit platform and @code{2**63 - 1} on a
64-bit platform.
@end deffn

@geindex maxunicode() (在 sys 模块中)
@anchor{library/sys sys maxunicode}@anchor{985}
@deffn {数据} sys.maxunicode

An integer giving the value of the largest Unicode code point,
i.e. @code{1114111} (@code{0x10FFFF} in hexadecimal).


在 3.3 版更改: Before 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393}, @code{sys.maxunicode} used to be either @code{0xFFFF}
or @code{0x10FFFF}, depending on the configuration option that specified
whether Unicode characters were stored as UCS-2 or UCS-4.

@end deffn

@geindex meta_path() (在 sys 模块中)
@anchor{library/sys sys meta_path}@anchor{5e1}
@deffn {数据} sys.meta_path

A list of @ref{9ab,,meta path finder} objects that have their
@ref{45d,,find_spec()} methods called to see if one
of the objects can find the module to be imported. The
@ref{45d,,find_spec()} method is called with at
least the absolute name of the module being imported. If the module to be
imported is contained in a package, then the parent package's @ref{1223,,__path__}
attribute is passed in as a second argument. The method returns a
@ref{35dd,,module spec}, or @code{None} if the module cannot be found.


@subsubheading 参见



@table @asis

@item @ref{9ad,,importlib.abc.MetaPathFinder}

The abstract base class defining the interface of finder objects on
@ref{5e1,,meta_path}.

@item @ref{145e,,importlib.machinery.ModuleSpec}

The concrete class which
@ref{45d,,find_spec()} should return
instances of.
@end table



在 3.4 版更改: @ref{35dd,,Module specs} were introduced in Python 3.4, by
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}. Earlier versions of Python looked for a method called
@ref{45c,,find_module()}.
This is still called as a fallback if a @ref{5e1,,meta_path} entry doesn't
have a @ref{45d,,find_spec()} method.

@end deffn

@geindex modules() (在 sys 模块中)
@anchor{library/sys sys modules}@anchor{eb5}
@deffn {数据} sys.modules

This is a dictionary that maps module names to modules which have already been
loaded.  This can be manipulated to force reloading of modules and other tricks.
However, replacing the dictionary will not necessarily work as expected and
deleting essential items from the dictionary may cause Python to fail.
@end deffn

@geindex path() (在 sys 模块中)
@anchor{library/sys sys path}@anchor{482}
@deffn {数据} sys.path

@geindex module; search; path

A list of strings that specifies the search path for modules. Initialized from
the environment variable 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH}, plus an installation-dependent
default.

As initialized upon program startup, the first item of this list, @code{path[0]},
is the directory containing the script that was used to invoke the Python
interpreter.  If the script directory is not available (e.g.  if the interpreter
is invoked interactively or if the script is read from standard input),
@code{path[0]} is the empty string, which directs Python to search modules in the
current directory first.  Notice that the script directory is inserted @emph{before}
the entries inserted as a result of 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH}.

A program is free to modify this list for its own purposes.  Only strings
and bytes should be added to @ref{482,,sys.path}; all other data types are
ignored during import.


@subsubheading 参见


Module @ref{eb,,site} This describes how to use .pth files to extend
@ref{482,,sys.path}.

@end deffn

@geindex path_hooks() (在 sys 模块中)
@anchor{library/sys sys path_hooks}@anchor{956}
@deffn {数据} sys.path_hooks

A list of callables that take a path argument to try to create a
@ref{1452,,finder} for the path. If a finder can be created, it is to be
returned by the callable, else raise @ref{32d,,ImportError}.

Originally specified in 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}.
@end deffn

@geindex path_importer_cache() (在 sys 模块中)
@anchor{library/sys sys path_importer_cache}@anchor{498}
@deffn {数据} sys.path_importer_cache

A dictionary acting as a cache for @ref{1452,,finder} objects. The keys are
paths that have been passed to @ref{956,,sys.path_hooks} and the values are
the finders that are found. If a path is a valid file system path but no
finder is found on @ref{956,,sys.path_hooks} then @code{None} is
stored.

Originally specified in 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}.


在 3.3 版更改: @code{None} is stored instead of @ref{9b5,,imp.NullImporter} when no finder
is found.

@end deffn

@geindex platform() (在 sys 模块中)
@anchor{library/sys sys platform}@anchor{2b1}
@deffn {数据} sys.platform

This string contains a platform identifier that can be used to append
platform-specific components to @ref{482,,sys.path}, for instance.

For Unix systems, except on Linux and AIX, this is the lowercased OS name as
returned by @code{uname -s} with the first part of the version as returned by
@code{uname -r} appended, e.g. @code{'sunos5'} or @code{'freebsd8'}, @emph{at the time
when Python was built}.  Unless you want to test for a specific system
version, it is therefore recommended to use the following idiom:

@example
if sys.platform.startswith('freebsd'):
    # FreeBSD-specific code here...
elif sys.platform.startswith('linux'):
    # Linux-specific code here...
elif sys.platform.startswith('aix'):
    # AIX-specific code here...
@end example

对于其他系统，值是：


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

系统

@tab

@code{平台} 值

@item

AIX

@tab

@code{'aix'}

@item

Linux

@tab

@code{'linux'}

@item

Windows

@tab

@code{'win32'}

@item

Windows/Cygwin

@tab

@code{'cygwin'}

@item

macOS

@tab

@code{'darwin'}

@end multitable



在 3.3 版更改: On Linux, @ref{2b1,,sys.platform} doesn't contain the major version anymore.
It is always @code{'linux'}, instead of @code{'linux2'} or @code{'linux3'}.  Since
older Python versions include the version number, it is recommended to
always use the @code{startswith} idiom presented above.



在 3.8 版更改: On AIX, @ref{2b1,,sys.platform} doesn't contain the major version anymore.
It is always @code{'aix'}, instead of @code{'aix5'} or @code{'aix7'}.  Since
older Python versions include the version number, it is recommended to
always use the @code{startswith} idiom presented above.



@subsubheading 参见


@ref{1e76,,os.name} has a coarser granularity.  @ref{a58,,os.uname()} gives
system-dependent version information.

@ref{ce,,platform} 模块对系统的标识有更详细的检查。

@end deffn

@geindex prefix() (在 sys 模块中)
@anchor{library/sys sys prefix}@anchor{359f}
@deffn {数据} sys.prefix

A string giving the site-specific directory prefix where the platform
independent Python files are installed; by default, this is the string
@code{'/usr/local'}.  This can be set at build time with the @code{--prefix}
argument to the @code{configure} script.  The main collection of Python
library modules is installed in the directory @code{@emph{prefix}/lib/python@emph{X.Y}}
while the platform independent header files (all except @code{pyconfig.h}) are
stored in @code{@emph{prefix}/include/python@emph{X.Y}}, where @emph{X.Y} is the version
number of Python, for example @code{3.2}.

@cartouche
@quotation 注解 
If a @ref{359e,,virtual environment} is in effect, this
value will be changed in @code{site.py} to point to the virtual
environment. The value for the Python installation will still be
available, via @ref{2fe1,,base_prefix}.
@end quotation
@end cartouche
@end deffn

@geindex ps1() (在 sys 模块中)
@geindex ps2() (在 sys 模块中)
@anchor{library/sys sys ps1}@anchor{12ec}
@deffn {数据} sys.ps1
@anchor{library/sys sys ps2}@anchor{12ed}
@deffnx {数据} sys.ps2

@geindex interpreter prompts
@geindex prompts@comma{} interpreter
@geindex >>>; interpreter prompt
@geindex ...; interpreter prompt

Strings specifying the primary and secondary prompt of the interpreter.  These
are only defined if the interpreter is in interactive mode.  Their initial
values in this case are @code{'>>> '} and @code{'... '}.  If a non-string object is
assigned to either variable, its @ref{329,,str()} is re-evaluated each time the
interpreter prepares to read a new interactive command; this can be used to
implement a dynamic prompt.
@end deffn

@geindex setcheckinterval() (在 sys 模块中)
@anchor{library/sys sys setcheckinterval}@anchor{35d4}
@deffn {函数} sys.setcheckinterval (interval)

Set the interpreter's "check interval".  This integer value determines how often
the interpreter checks for periodic things such as thread switches and signal
handlers.  The default is @code{100}, meaning the check is performed every 100
Python virtual instructions. Setting it to a larger value may increase
performance for programs using threads.  Setting it to a value @code{<=} 0 checks
every virtual instruction, maximizing responsiveness as well as overhead.


3.2 版后已移除: This function doesn't have an effect anymore, as the internal logic for
thread switching and asynchronous tasks has been rewritten.  Use
@ref{be4,,setswitchinterval()} instead.

@end deffn

@geindex setdlopenflags() (在 sys 模块中)
@anchor{library/sys sys setdlopenflags}@anchor{a61}
@deffn {函数} sys.setdlopenflags (n)

Set the flags used by the interpreter for @code{dlopen()} calls, such as when
the interpreter loads extension modules.  Among other things, this will enable a
lazy resolving of symbols when importing a module, if called as
@code{sys.setdlopenflags(0)}.  To share symbols across extension modules, call as
@code{sys.setdlopenflags(os.RTLD_GLOBAL)}.  Symbolic names for the flag values
can be found in the @ref{c4,,os} module (@code{RTLD_xxx} constants, e.g.
@ref{a5a,,os.RTLD_LAZY}).

@ref{12f5,,可用性}: Unix。
@end deffn

@geindex setprofile() (在 sys 模块中)
@anchor{library/sys sys setprofile}@anchor{e36}
@deffn {函数} sys.setprofile (profilefunc)

@geindex profile function
@geindex profiler

设置系统的性能分析函数，该函数使得在 Py​​thon 中能够实现一个 Python 源代码性能分析器。关于 Python Profiler 的更多信息请参阅 @ref{34ff,,Python Profilers 分析器} 章节。性能分析函数的调用方式类似于系统的跟踪函数（参阅 @ref{e37,,settrace()} ），但它是通过不同的事件调用的，例如，不是每执行一行代码就调用它一次（仅在调用某函数和从某函数返回时才会调用性能分析函数，但即使某函数发生异常也会算作返回事件）。该函数是特定于线程的，但是性能分析器无法得知线程之间的上下文切换，因此在存在多个线程的情况下使用它是没有意义的。另外，因为它的返回值不会被用到，所以可以简单地返回 @code{None}。性能分析函数中的错误将导致其自身被解除设置。

性能分析函数应接收三个参数：@emph{frame}、@emph{event} 和 @emph{arg}。@emph{frame} 是当前的堆栈帧。@emph{event} 是一个字符串：@code{'call'}、@code{'return'}、@code{'c_call'}、@code{'c_return'} 或 @code{'c_exception'}。@emph{arg} 取决于事件类型。

引发一个 @ref{12d0,,审计事件} @code{sys.setprofile}，不附带任何参数。

这些事件具有以下含义：


@table @asis

@item @code{'call'}

A function is called (or some other code block entered).  The
profile function is called; @emph{arg} is @code{None}.

@item @code{'return'}

A function (or other code block) is about to return.  The profile
function is called; @emph{arg} is the value that will be returned, or @code{None}
if the event is caused by an exception being raised.

@item @code{'c_call'}

A C function is about to be called.  This may be an extension function or
a built-in.  @emph{arg} is the C function object.

@item @code{'c_return'}

A C function has returned. @emph{arg} is the C function object.

@item @code{'c_exception'}

A C function has raised an exception.  @emph{arg} is the C function object.
@end table
@end deffn

@geindex setrecursionlimit() (在 sys 模块中)
@anchor{library/sys sys setrecursionlimit}@anchor{e74}
@deffn {函数} sys.setrecursionlimit (limit)

Set the maximum depth of the Python interpreter stack to @emph{limit}.  This limit
prevents infinite recursion from causing an overflow of the C stack and crashing
Python.

The highest possible limit is platform-dependent.  A user may need to set the
limit higher when they have a program that requires deep recursion and a platform
that supports a higher limit.  This should be done with care, because a too-high
limit can lead to a crash.

If the new limit is too low at the current recursion depth, a
@ref{62e,,RecursionError} exception is raised.


在 3.5.1 版更改: A @ref{62e,,RecursionError} exception is now raised if the new limit is too
low at the current recursion depth.

@end deffn

@geindex setswitchinterval() (在 sys 模块中)
@anchor{library/sys sys setswitchinterval}@anchor{be4}
@deffn {函数} sys.setswitchinterval (interval)

设置解释器的线程切换间隔时间（单位为秒）。该浮点数决定了“时间片”的理想持续时间，时间片将分配给同时运行的 Python 线程。请注意，实际值可能更高，尤其是使用了运行时间长的内部函数或方法时。同时，在时间间隔末尾调度哪个线程是操作系统的决定。解释器没有自己的调度程序。


3.2 新版功能.

@end deffn

@geindex settrace() (在 sys 模块中)
@anchor{library/sys sys settrace}@anchor{e37}
@deffn {函数} sys.settrace (tracefunc)

@geindex trace function
@geindex debugger

Set the system's trace function, which allows you to implement a Python
source code debugger in Python.  The function is thread-specific; for a
debugger to support multiple threads, it must register a trace function using
@ref{e37,,settrace()} for each thread being debugged or use @ref{22ed,,threading.settrace()}.

Trace functions should have three arguments: @emph{frame}, @emph{event}, and
@emph{arg}. @emph{frame} is the current stack frame.  @emph{event} is a string: @code{'call'},
@code{'line'}, @code{'return'}, @code{'exception'} or @code{'opcode'}.  @emph{arg} depends on
the event type.

The trace function is invoked (with @emph{event} set to @code{'call'}) whenever a new
local scope is entered; it should return a reference to a local trace
function to be used for the new scope, or @code{None} if the scope shouldn't be
traced.

The local trace function should return a reference to itself (or to another
function for further tracing in that scope), or @code{None} to turn off tracing
in that scope.

If there is any error occurred in the trace function, it will be unset, just
like @code{settrace(None)} is called.

这些事件具有以下含义：


@table @asis

@item @code{'call'}

A function is called (or some other code block entered).  The
global trace function is called; @emph{arg} is @code{None}; the return value
specifies the local trace function.

@item @code{'line'}

The interpreter is about to execute a new line of code or re-execute the
condition of a loop.  The local trace function is called; @emph{arg} is
@code{None}; the return value specifies the new local trace function.  See
@code{Objects/lnotab_notes.txt} for a detailed explanation of how this
works.
Per-line events may be disabled for a frame by setting
@code{f_trace_lines} to @ref{380,,False} on that frame.

@item @code{'return'}

A function (or other code block) is about to return.  The local trace
function is called; @emph{arg} is the value that will be returned, or @code{None}
if the event is caused by an exception being raised.  The trace function's
return value is ignored.

@item @code{'exception'}

An exception has occurred.  The local trace function is called; @emph{arg} is a
tuple @code{(exception, value, traceback)}; the return value specifies the
new local trace function.

@item @code{'opcode'}

The interpreter is about to execute a new opcode (see @ref{38,,dis} for
opcode details).  The local trace function is called; @emph{arg} is
@code{None}; the return value specifies the new local trace function.
Per-opcode events are not emitted by default: they must be explicitly
requested by setting @code{f_trace_opcodes} to @ref{494,,True} on the
frame.
@end table

Note that as an exception is propagated down the chain of callers, an
@code{'exception'} event is generated at each level.

For more fine-grained usage, it's possible to set a trace function by
assigning @code{frame.f_trace = tracefunc} explicitly, rather than relying on
it being set indirectly via the return value from an already installed
trace function. This is also required for activating the trace function on
the current frame, which @ref{e37,,settrace()} doesn't do. Note that in order
for this to work, a global tracing function must have been installed
with @ref{e37,,settrace()} in order to enable the runtime tracing machinery,
but it doesn't need to be the same tracing function (e.g. it could be a
low overhead tracing function that simply returns @code{None} to disable
itself immediately on each frame).

For more information on code and frame objects, refer to @ref{13b8,,标准类型层级结构}.

Raises an @ref{12d0,,auditing event} @code{sys.settrace} with no arguments.

@strong{CPython implementation detail:} The @ref{e37,,settrace()} function is intended only for implementing debuggers,
profilers, coverage tools and the like.  Its behavior is part of the
implementation platform, rather than part of the language definition, and
thus may not be available in all Python implementations.


在 3.7 版更改: @code{'opcode'} event type added; @code{f_trace_lines} and
@code{f_trace_opcodes} attributes added to frames

@end deffn

@geindex set_asyncgen_hooks() (在 sys 模块中)
@anchor{library/sys sys set_asyncgen_hooks}@anchor{eb8}
@deffn {函数} sys.set_asyncgen_hooks (firstiter, finalizer)

Accepts two optional keyword arguments which are callables that accept an
@ref{35d9,,asynchronous generator iterator} as an argument. The @emph{firstiter}
callable will be called when an asynchronous generator is iterated for the
first time. The @emph{finalizer} will be called when an asynchronous generator
is about to be garbage collected.

Raises an @ref{12d0,,auditing event} @code{sys.set_asyncgen_hooks_firstiter} with no arguments.

Raises an @ref{12d0,,auditing event} @code{sys.set_asyncgen_hooks_finalizer} with no arguments.

Two auditing events are raised because the underlying API consists of two
calls, each of which must raise its own event.


3.6 新版功能: See 
@geindex Python 提高建议; PEP 525
PEP 525@footnote{https://www.python.org/dev/peps/pep-0525} for more details, and for a reference example of a
@emph{finalizer} method see the implementation of
@code{asyncio.Loop.shutdown_asyncgens} in
Lib/asyncio/base_events.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/asyncio/base_events.py}


@cartouche
@quotation 注解 
本函数已添加至暂定软件包（详情请参阅 
@geindex Python 提高建议; PEP 411
PEP 411@footnote{https://www.python.org/dev/peps/pep-0411} ）。
@end quotation
@end cartouche
@end deffn

@geindex set_coroutine_origin_tracking_depth() (在 sys 模块中)
@anchor{library/sys sys set_coroutine_origin_tracking_depth}@anchor{3eb}
@deffn {函数} sys.set_coroutine_origin_tracking_depth (depth)

Allows enabling or disabling coroutine origin tracking. When
enabled, the @code{cr_origin} attribute on coroutine objects will
contain a tuple of (filename, line number, function name) tuples
describing the traceback where the coroutine object was created,
with the most recent call first. When disabled, @code{cr_origin} will
be None.

To enable, pass a @emph{depth} value greater than zero; this sets the
number of frames whose information will be captured. To disable,
pass set @emph{depth} to zero.

This setting is thread-specific.


3.7 新版功能.


@cartouche
@quotation 注解 
本函数已添加至暂定软件包（详情请参阅 
@geindex Python 提高建议; PEP 411
PEP 411@footnote{https://www.python.org/dev/peps/pep-0411} ）。仅将其用于调试目的。
@end quotation
@end cartouche
@end deffn

@geindex _enablelegacywindowsfsencoding() (在 sys 模块中)
@anchor{library/sys sys _enablelegacywindowsfsencoding}@anchor{4f2}
@deffn {函数} sys._enablelegacywindowsfsencoding ()

Changes the default filesystem encoding and errors mode to 'mbcs' and
'replace' respectively, for consistency with versions of Python prior to 3.6.

This is equivalent to defining the 
@geindex PYTHONLEGACYWINDOWSFSENCODING
@geindex 环境变量; PYTHONLEGACYWINDOWSFSENCODING
@ref{4f1,,PYTHONLEGACYWINDOWSFSENCODING}
environment variable before launching Python.

@ref{12f5,,可用性}: Windows。


3.6 新版功能: 有关更多详细信息，请参阅 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529}。

@end deffn

@geindex stdin() (在 sys 模块中)
@geindex stdout() (在 sys 模块中)
@geindex stderr() (在 sys 模块中)
@anchor{library/sys sys stdin}@anchor{306}
@deffn {数据} sys.stdin
@anchor{library/sys sys stdout}@anchor{307}
@deffnx {数据} sys.stdout
@anchor{library/sys sys stderr}@anchor{308}
@deffnx {数据} sys.stderr

@ref{b3b,,File objects} used by the interpreter for standard
input, output and errors:


@itemize *

@item 
@code{stdin} is used for all interactive input (including calls to
@ref{c64,,input()});

@item 
@code{stdout} is used for the output of @ref{880,,print()} and @ref{35cd,,expression}
statements and for the prompts of @ref{c64,,input()};

@item 
The interpreter's own prompts and its error messages go to @code{stderr}.
@end itemize

These streams are regular @ref{1239,,text files} like those
returned by the @ref{4ea,,open()} function.  Their parameters are chosen as
follows:


@itemize *

@item 
The character encoding is platform-dependent.  Non-Windows
platforms use the locale encoding (see
@ref{39d,,locale.getpreferredencoding()}).

On Windows, UTF-8 is used for the console device.  Non-character
devices such as disk files and pipes use the system locale
encoding (i.e. the ANSI codepage).  Non-console character
devices such as NUL (i.e. where @code{isatty()} returns @code{True}) use the
value of the console input and output codepages at startup,
respectively for stdin and stdout/stderr. This defaults to the
system locale encoding if the process is not initially attached
to a console.

The special behaviour of the console can be overridden
by setting the environment variable PYTHONLEGACYWINDOWSSTDIO
before starting Python. In that case, the console codepages are
used as for any other character device.

Under all platforms, you can override the character encoding by
setting the 
@geindex PYTHONIOENCODING
@geindex 环境变量; PYTHONIOENCODING
@ref{929,,PYTHONIOENCODING} environment variable before
starting Python or by using the new @ref{155,,-X} @code{utf8} command
line option and 
@geindex PYTHONUTF8
@geindex 环境变量; PYTHONUTF8
@ref{30a,,PYTHONUTF8} environment variable.  However,
for the Windows console, this only applies when
@geindex PYTHONLEGACYWINDOWSSTDIO
@geindex 环境变量; PYTHONLEGACYWINDOWSSTDIO
@ref{4f4,,PYTHONLEGACYWINDOWSSTDIO} is also set.

@item 
When interactive, @code{stdout} and @code{stderr} streams are line-buffered.
Otherwise, they are block-buffered like regular text files.  You can
override this value with the @ref{12de,,-u} command-line option.
@end itemize

@cartouche
@quotation 注解 
To write or read binary data from/to the standard streams, use the
underlying binary @ref{c33,,buffer} object.  For example, to
write bytes to @ref{307,,stdout}, use @code{sys.stdout.buffer.write(b'abc')}.

However, if you are writing a library (and do not control in which
context its code will be executed), be aware that the standard streams
may be replaced with file-like objects like @ref{827,,io.StringIO} which
do not support the @code{buffer} attribute.
@end quotation
@end cartouche
@end deffn

@geindex __stdin__() (在 sys 模块中)
@geindex __stdout__() (在 sys 模块中)
@geindex __stderr__() (在 sys 模块中)
@anchor{library/sys sys __stdin__}@anchor{35de}
@deffn {数据} sys.__stdin__
@anchor{library/sys sys __stdout__}@anchor{1c2f}
@deffnx {数据} sys.__stdout__
@anchor{library/sys sys __stderr__}@anchor{35df}
@deffnx {数据} sys.__stderr__

These objects contain the original values of @code{stdin}, @code{stderr} and
@code{stdout} at the start of the program.  They are used during finalization,
and could be useful to print to the actual standard stream no matter if the
@code{sys.std*} object has been redirected.

It can also be used to restore the actual files to known working file objects
in case they have been overwritten with a broken object.  However, the
preferred way to do this is to explicitly save the previous stream before
replacing it, and restore the saved object.

@cartouche
@quotation 注解 
Under some conditions @code{stdin}, @code{stdout} and @code{stderr} as well as the
original values @code{__stdin__}, @code{__stdout__} and @code{__stderr__} can be
@code{None}. It is usually the case for Windows GUI apps that aren't connected
to a console and Python apps started with @code{pythonw}.
@end quotation
@end cartouche
@end deffn

@geindex thread_info() (在 sys 模块中)
@anchor{library/sys sys thread_info}@anchor{a9d}
@deffn {数据} sys.thread_info

A @ref{a9e,,named tuple} holding information about the thread
implementation.


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性

@tab

说明

@item

@code{name}

@tab

线程实现的名称：

@quotation


@itemize *

@item 
@code{'nt'}: Windows 线程

@item 
@code{'pthread'}: POSIX 线程

@item 
@code{'solaris'}: Solaris 线程
@end itemize
@end quotation

@item

@code{lock}

@tab

锁实现的名称：

@quotation


@itemize *

@item 
@code{'semaphore'}: 锁使用信号量

@item 
@code{'mutex+cond'}: 锁使用互斥和条件变量

@item 
@code{None} 如果此信息未知
@end itemize
@end quotation

@item

@ref{5ce,,version}

@tab

线程库的名称和版本。它是一个字符串，如果此信息未知，则为 @code{None} 。

@end multitable



3.3 新版功能.

@end deffn

@geindex tracebacklimit() (在 sys 模块中)
@anchor{library/sys sys tracebacklimit}@anchor{35e0}
@deffn {数据} sys.tracebacklimit

When this variable is set to an integer value, it determines the maximum number
of levels of traceback information printed when an unhandled exception occurs.
The default is @code{1000}.  When set to @code{0} or less, all traceback information
is suppressed and only the exception type and value are printed.
@end deffn

@geindex unraisablehook() (在 sys 模块中)
@anchor{library/sys sys unraisablehook}@anchor{22d}
@deffn {函数} sys.unraisablehook (unraisable, /)

Handle an unraisable exception.

Called when an exception has occurred but there is no way for Python to
handle it. For example, when a destructor raises an exception or during
garbage collection (@ref{22e,,gc.collect()}).

The @emph{unraisable} argument has the following attributes:


@itemize *

@item 
@emph{exc_type}: 异常类型

@item 
@emph{exc_value}: 异常值，可以是 @code{None}.

@item 
@emph{exc_traceback}: 异常回溯，可以是 @code{None}.

@item 
@emph{err_msg}: 错误信息，可以是 @code{None}.

@item 
@emph{object}: 导致异常的对象，可以为 @code{None}.
@end itemize

The default hook formats @emph{err_msg} and @emph{object} as:
@code{f'@{err_msg@}: @{object!r@}'}; use "Exception ignored in" error message
if @emph{err_msg} is @code{None}.

@ref{22d,,sys.unraisablehook()} can be overridden to control how unraisable
exceptions are handled.

使用定制钩子存放 @emph{exc_value} 可能会创建引用循环。 它应当在不再需要异常时被显式地清空以打破引用循环。

Storing @emph{object} using a custom hook can resurrect it if it is set to an
object which is being finalized. Avoid storing @emph{object} after the custom
hook completes to avoid resurrecting objects.

See also @ref{e5c,,excepthook()} which handles uncaught exceptions.


Raise an auditing event @code{sys.unraisablehook} with arguments
@code{hook}, @code{unraisable} when an exception that cannot be handled occurs.
The @code{unraisable} object is the same as what will be passed to the hook.
If no hook has been set, @code{hook} may be @code{None}.



3.8 新版功能.

@end deffn

@geindex version() (在 sys 模块中)
@anchor{library/sys sys version}@anchor{5ce}
@deffn {数据} sys.version

A string containing the version number of the Python interpreter plus additional
information on the build number and compiler used.  This string is displayed
when the interactive interpreter is started.  Do not extract version information
out of it, rather, use @ref{b13,,version_info} and the functions provided by the
@ref{ce,,platform} module.
@end deffn

@geindex api_version() (在 sys 模块中)
@anchor{library/sys sys api_version}@anchor{35e1}
@deffn {数据} sys.api_version

这个解释器的 C API 版本。当你在调试 Python及期扩展模板的版本冲突这个功能非常有用。
@end deffn

@geindex version_info() (在 sys 模块中)
@anchor{library/sys sys version_info}@anchor{b13}
@deffn {数据} sys.version_info

A tuple containing the five components of the version number: @emph{major}, @emph{minor},
@emph{micro}, @emph{releaselevel}, and @emph{serial}.  All values except @emph{releaselevel} are
integers; the release level is @code{'alpha'}, @code{'beta'}, @code{'candidate'}, or
@code{'final'}.  The @code{version_info} value corresponding to the Python version 2.0
is @code{(2, 0, 0, 'final', 0)}.  The components can also be accessed by name,
so @code{sys.version_info[0]} is equivalent to @code{sys.version_info.major}
and so on.


在 3.1 版更改: Added named component attributes.

@end deffn

@geindex warnoptions() (在 sys 模块中)
@anchor{library/sys sys warnoptions}@anchor{40e}
@deffn {数据} sys.warnoptions

This is an implementation detail of the warnings framework; do not modify this
value.  Refer to the @ref{126,,warnings} module for more information on the warnings
framework.
@end deffn

@geindex winver() (在 sys 模块中)
@anchor{library/sys sys winver}@anchor{35e2}
@deffn {数据} sys.winver

The version number used to form registry keys on Windows platforms. This is
stored as string resource 1000 in the Python DLL.  The value is normally the
first three characters of @ref{5ce,,version}.  It is provided in the @ref{fd,,sys}
module for informational purposes; modifying this value has no effect on the
registry keys used by Python.

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex _xoptions() (在 sys 模块中)
@anchor{library/sys sys _xoptions}@anchor{12e7}
@deffn {数据} sys._xoptions

A dictionary of the various implementation-specific flags passed through
the @ref{155,,-X} command-line option.  Option names are either mapped to
their values, if given explicitly, or to @ref{494,,True}.  Example:

@example
$ ./python -Xa=b -Xc
Python 3.2a3+ (py3k, Oct 16 2010, 20:14:50)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys._xoptions
@{'a': 'b', 'c': True@}
@end example

@strong{CPython implementation detail:} This is a CPython-specific way of accessing options passed through
@ref{155,,-X}.  Other implementations may export them through other
means, or not at all.


3.2 新版功能.

@end deffn

@subsubheading Citations


@anchor{library/sys c99}@anchor{35d3}@w{(C99)} 
ISO/IEC 9899:1999.  "Programming languages -- C."  A public draft of this standard is available at @indicateurl{http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf}.

@node sysconfig --- Provide access to Python's configuration information,builtins --- 内建对象,sys --- 系统相关的参数和函数,Python运行时服务
@anchor{library/sysconfig doc}@anchor{35e3}@anchor{library/sysconfig module-sysconfig}@anchor{fe}@anchor{library/sysconfig sysconfig-provide-access-to-python-s-configuration-information}@anchor{35e4}
@subsection @code{sysconfig} --- Provide access to Python's configuration information


@geindex sysconfig (模块)


3.2 新版功能.


@strong{源代码：} Lib/sysconfig.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/sysconfig.py}

@geindex configuration information


__________________________________________________________________


The @ref{fe,,sysconfig} module provides access to Python's configuration
information like the list of installation paths and the configuration variables
relevant for the current platform.

@menu
* 配置变量:: 
* 安装路径:: 
* 其他功能: 其他功能<3>. 
* Using sysconfig as a script:: 

@end menu

@node 配置变量,安装路径,,sysconfig --- Provide access to Python's configuration information
@anchor{library/sysconfig configuration-variables}@anchor{35e5}
@subsubsection 配置变量


A Python distribution contains a @code{Makefile} and a @code{pyconfig.h}
header file that are necessary to build both the Python binary itself and
third-party C extensions compiled using @ref{39,,distutils}.

@ref{fe,,sysconfig} puts all variables found in these files in a dictionary that
can be accessed using @ref{95f,,get_config_vars()} or @ref{95e,,get_config_var()}.

Notice that on Windows, it's a much smaller set.

@geindex get_config_vars() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_config_vars}@anchor{95f}
@deffn {函数} sysconfig.get_config_vars (*args)

With no arguments, return a dictionary of all configuration variables
relevant for the current platform.

With arguments, return a list of values that result from looking up each
argument in the configuration variable dictionary.

For each argument, if the value is not found, return @code{None}.
@end deffn

@geindex get_config_var() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_config_var}@anchor{95e}
@deffn {函数} sysconfig.get_config_var (name)

Return the value of a single variable @emph{name}. Equivalent to
@code{get_config_vars().get(name)}.

If @emph{name} is not found, return @code{None}.
@end deffn

用法示例:

@example
>>> import sysconfig
>>> sysconfig.get_config_var('Py_ENABLE_SHARED')
0
>>> sysconfig.get_config_var('LIBDIR')
'/usr/local/lib'
>>> sysconfig.get_config_vars('AR', 'CXX')
['ar', 'g++']
@end example

@node 安装路径,其他功能<3>,配置变量,sysconfig --- Provide access to Python's configuration information
@anchor{library/sysconfig installation-paths}@anchor{35e6}
@subsubsection 安装路径


Python uses an installation scheme that differs depending on the platform and on
the installation options.  These schemes are stored in @ref{fe,,sysconfig} under
unique identifiers based on the value returned by @ref{1e76,,os.name}.

Every new component that is installed using @ref{39,,distutils} or a
Distutils-based system will follow the same scheme to copy its file in the right
places.

Python currently supports seven schemes:


@itemize -

@item 
@emph{posix_prefix}: scheme for POSIX platforms like Linux or Mac OS X.  This is
the default scheme used when Python or a component is installed.

@item 
@emph{posix_home}: scheme for POSIX platforms used when a @emph{home} option is used
upon installation.  This scheme is used when a component is installed through
Distutils with a specific home prefix.

@item 
@emph{posix_user}: scheme for POSIX platforms used when a component is installed
through Distutils and the @emph{user} option is used.  This scheme defines paths
located under the user home directory.

@item 
@emph{nt}: scheme for NT platforms like Windows.

@item 
@emph{nt_user}: scheme for NT platforms, when the @emph{user} option is used.
@end itemize

Each scheme is itself composed of a series of paths and each path has a unique
identifier.  Python currently uses eight paths:


@itemize -

@item 
@emph{stdlib}: directory containing the standard Python library files that are not
platform-specific.

@item 
@emph{platstdlib}: directory containing the standard Python library files that are
platform-specific.

@item 
@emph{platlib}: directory for site-specific, platform-specific files.

@item 
@emph{purelib}: directory for site-specific, non-platform-specific files.

@item 
@emph{include}: directory for non-platform-specific header files.

@item 
@emph{platinclude}: directory for platform-specific header files.

@item 
@emph{scripts}: directory for script files.

@item 
@emph{data}: directory for data files.
@end itemize

@ref{fe,,sysconfig} provides some functions to determine these paths.

@geindex get_scheme_names() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_scheme_names}@anchor{35e7}
@deffn {函数} sysconfig.get_scheme_names ()

Return a tuple containing all schemes currently supported in
@ref{fe,,sysconfig}.
@end deffn

@geindex get_path_names() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_path_names}@anchor{35e8}
@deffn {函数} sysconfig.get_path_names ()

Return a tuple containing all path names currently supported in
@ref{fe,,sysconfig}.
@end deffn

@geindex get_path() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_path}@anchor{cb7}
@deffn {函数} sysconfig.get_path (name[, scheme[, vars[, expand]]])

Return an installation path corresponding to the path @emph{name}, from the
install scheme named @emph{scheme}.

@emph{name} has to be a value from the list returned by @ref{35e8,,get_path_names()}.

@ref{fe,,sysconfig} stores installation paths corresponding to each path name,
for each platform, with variables to be expanded.  For instance the @emph{stdlib}
path for the @emph{nt} scheme is: @code{@{base@}/Lib}.

@ref{cb7,,get_path()} will use the variables returned by @ref{95f,,get_config_vars()}
to expand the path.  All variables have default values for each platform so
one may call this function and get the default value.

If @emph{scheme} is provided, it must be a value from the list returned by
@ref{35e7,,get_scheme_names()}.  Otherwise, the default scheme for the current
platform is used.

If @emph{vars} is provided, it must be a dictionary of variables that will update
the dictionary return by @ref{95f,,get_config_vars()}.

If @emph{expand} is set to @code{False}, the path will not be expanded using the
variables.

If @emph{name} is not found, return @code{None}.
@end deffn

@geindex get_paths() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_paths}@anchor{bd2}
@deffn {函数} sysconfig.get_paths ([scheme[, vars[, expand]]])

Return a dictionary containing all installation paths corresponding to an
installation scheme. See @ref{cb7,,get_path()} for more information.

If @emph{scheme} is not provided, will use the default scheme for the current
platform.

If @emph{vars} is provided, it must be a dictionary of variables that will
update the dictionary used to expand the paths.

If @emph{expand} is set to false, the paths will not be expanded.

If @emph{scheme} is not an existing scheme, @ref{bd2,,get_paths()} will raise a
@ref{2c7,,KeyError}.
@end deffn

@node 其他功能<3>,Using sysconfig as a script,安装路径,sysconfig --- Provide access to Python's configuration information
@anchor{library/sysconfig other-functions}@anchor{35e9}
@subsubsection 其他功能


@geindex get_python_version() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_python_version}@anchor{bd1}
@deffn {函数} sysconfig.get_python_version ()

Return the @code{MAJOR.MINOR} Python version number as a string.  Similar to
@code{'%d.%d' % sys.version_info[:2]}.
@end deffn

@geindex get_platform() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_platform}@anchor{bd0}
@deffn {函数} sysconfig.get_platform ()

Return a string that identifies the current platform.

This is used mainly to distinguish platform-specific build directories and
platform-specific built distributions.  Typically includes the OS name and
version and the architecture (as supplied by 'os.uname()'), although the
exact information included depends on the OS; e.g., on Linux, the kernel
version isn't particularly important.

返回值的示例：


@itemize -

@item 
linux-i586

@item 
linux-alpha (?)

@item 
solaris-2.6-sun4u
@end itemize

Windows将返回以下之一：


@itemize -

@item 
win-amd64 (在 AMD64, aka x86_64, Intel64, 和 EM64T上的64位 Windows )

@item 
win32 (all others - specifically, sys.platform is returned)
@end itemize

Mac OS X 返回：


@itemize -

@item 
macosx-10.6-ppc

@item 
macosx-10.4-ppc64

@item 
macosx-10.3-i386

@item 
macosx-10.4-fat
@end itemize

对于其他非-POSIX 平台， 目前只是返回 @ref{2b1,,sys.platform} 。
@end deffn

@geindex is_python_build() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig is_python_build}@anchor{cb8}
@deffn {函数} sysconfig.is_python_build ()

Return @code{True} if the running Python interpreter was built from source and
is being run from its built location, and not from a location resulting from
e.g. running @code{make install} or installing via a binary installer.
@end deffn

@geindex parse_config_h() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig parse_config_h}@anchor{35ea}
@deffn {函数} sysconfig.parse_config_h (fp[, vars])

Parse a @code{config.h}-style file.

@emph{fp} is a file-like object pointing to the @code{config.h}-like file.

A dictionary containing name/value pairs is returned.  If an optional
dictionary is passed in as the second argument, it is used instead of a new
dictionary, and updated with the values read in the file.
@end deffn

@geindex get_config_h_filename() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_config_h_filename}@anchor{35eb}
@deffn {函数} sysconfig.get_config_h_filename ()

返回  @code{pyconfig.h} 的目录
@end deffn

@geindex get_makefile_filename() (在 sysconfig 模块中)
@anchor{library/sysconfig sysconfig get_makefile_filename}@anchor{35ec}
@deffn {函数} sysconfig.get_makefile_filename ()

返回 @code{Makefile} 的目录
@end deffn

@node Using sysconfig as a script,,其他功能<3>,sysconfig --- Provide access to Python's configuration information
@anchor{library/sysconfig using-sysconfig-as-a-script}@anchor{35ed}
@subsubsection Using @code{sysconfig} as a script


You can use @ref{fe,,sysconfig} as a script with Python's @emph{-m} option:

@example
$ python -m sysconfig
Platform: "macosx-10.4-i386"
Python version: "3.2"
Current installation scheme: "posix_prefix"

Paths:
        data = "/usr/local"
        include = "/Users/tarek/Dev/svn.python.org/py3k/Include"
        platinclude = "."
        platlib = "/usr/local/lib/python3.2/site-packages"
        platstdlib = "/usr/local/lib/python3.2"
        purelib = "/usr/local/lib/python3.2/site-packages"
        scripts = "/usr/local/bin"
        stdlib = "/usr/local/lib/python3.2"

Variables:
        AC_APPLE_UNIVERSAL_BUILD = "0"
        AIX_GENUINE_CPLUSPLUS = "0"
        AR = "ar"
        ARFLAGS = "rc"
        ...
@end example

This call will print in the standard output the information returned by
@ref{bd0,,get_platform()}, @ref{bd1,,get_python_version()}, @ref{cb7,,get_path()} and
@ref{95f,,get_config_vars()}.

@node builtins --- 内建对象,__main__ --- 顶层脚本环境,sysconfig --- Provide access to Python's configuration information,Python运行时服务
@anchor{library/builtins doc}@anchor{35ee}@anchor{library/builtins builtins-built-in-objects}@anchor{35ef}@anchor{library/builtins module-builtins}@anchor{13}
@subsection @code{builtins} --- 内建对象


@geindex builtins (模块)


__________________________________________________________________


该模块提供对Python的所有“内置”标识符的直接访问；例如，@code{builtins.open} 是内置函数的全名 @ref{4ea,,open()} 。请参阅 @ref{bec,,内置函数} 和 @ref{15a3,,内置常量} 的文档。

大多数应用程序通常不会显式访问此模块，但在提供与内置值同名的对象的模块中可能很有用，但其中还需要内置该名称。例如，在一个想要实现 @ref{4ea,,open()} 函数的模块中，它包装了内置的 @ref{4ea,,open()} ，这个模块可以直接使用:

@example
import builtins

def open(path):
    f = builtins.open(path, 'r')
    return UpperCaser(f)

class UpperCaser:
    '@w{'}'Wrapper around a file that converts output to upper-case.'@w{'}'

    def __init__(self, f):
        self._f = f

    def read(self, count=-1):
        return self._f.read(count).upper()

    # ...
@end example

作为一个实现细节，大多数模块都将名称 @code{__builtins__} 作为其全局变量的一部分提供。 @code{__builtins__} 的值通常是这个模块或者这个模块的值 @ref{4f6,,__dict__} 属性。由于这是一个实现细节，因此Python的替代实现可能不会使用它。

@node __main__ --- 顶层脚本环境,warnings --- Warning control,builtins --- 内建对象,Python运行时服务
@anchor{library/__main__ doc}@anchor{35f0}@anchor{library/__main__ main-top-level-script-environment}@anchor{35f1}@anchor{library/__main__ module-__main__}@anchor{1}
@subsection @code{__main__} --- 顶层脚本环境


@geindex __main__ (模块)


__________________________________________________________________


@code{'__main__'} 是顶层代码执行的作用域的名称。模块的 __name__ 在通过标准输入、脚本文件或是交互式命令读入的时候会等于 @code{'__main__'}。

模块可以通过检查自己的 @code{__name__} 来得知是否运行在 main 作用域中，这使得模块可以在作为脚本或是通过 @code{python -m} 运行时条件性地执行一些代码，而在被 import 时不会执行。

@example
if __name__ == "__main__":
    # execute only if run as a script
    main()
@end example

对软件包来说，通过加入 @code{__main__.py} 模块可以达到同样的效果，当使用 @code{-m} 运行模块时，其中的代码会被执行。

@node warnings --- Warning control,dataclasses --- 数据类,__main__ --- 顶层脚本环境,Python运行时服务
@anchor{library/warnings doc}@anchor{35f2}@anchor{library/warnings module-warnings}@anchor{126}@anchor{library/warnings warnings-warning-control}@anchor{35f3}
@subsection @code{warnings} --- Warning control


@geindex warnings (模块)

@strong{源代码：} Lib/warnings.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/warnings.py}

@geindex warnings


__________________________________________________________________


Warning messages are typically issued in situations where it is useful to alert
the user of some condition in a program, where that condition (normally) doesn't
warrant raising an exception and terminating the program.  For example, one
might want to issue a warning when a program uses an obsolete module.

Python programmers issue warnings by calling the @ref{e51,,warn()} function defined
in this module.  (C programmers use @ref{daa,,PyErr_WarnEx()}; see
@ref{35f4,,异常处理} for details).

Warning messages are normally written to @ref{308,,sys.stderr}, but their disposition
can be changed flexibly, from ignoring all warnings to turning them into
exceptions.  The disposition of warnings can vary based on the @ref{16ae,,warning category}, the text of the warning message, and the source location where it
is issued.  Repetitions of a particular warning for the same source location are
typically suppressed.

There are two stages in warning control: first, each time a warning is issued, a
determination is made whether a message should be issued or not; next, if a
message is to be issued, it is formatted and printed using a user-settable hook.

The determination whether to issue a warning message is controlled by the
@ref{12e2,,warning filter}, which is a sequence of matching rules and actions. Rules can be
added to the filter by calling @ref{e00,,filterwarnings()} and reset to its default
state by calling @ref{35f5,,resetwarnings()}.

The printing of warning messages is done by calling @ref{35f6,,showwarning()}, which
may be overridden; the default implementation of this function formats the
message by calling @ref{f83,,formatwarning()}, which is also available for use by
custom implementations.


@subsubheading 参见


@ref{2068,,logging.captureWarnings()} allows you to handle all warnings with
the standard logging infrastructure.


@menu
* 警告类别:: 
* The Warnings Filter:: 
* 暂时禁止警告:: 
* 测试警告:: 
* Updating Code For New Versions of Dependencies:: 
* Available Functions:: 
* Available Context Managers:: 

@end menu

@node 警告类别,The Warnings Filter,,warnings --- Warning control
@anchor{library/warnings id1}@anchor{35f7}@anchor{library/warnings warning-categories}@anchor{16ae}
@subsubsection 警告类别


There are a number of built-in exceptions that represent warning categories.
This categorization is useful to be able to filter out groups of warnings.

While these are technically
@ref{16ac,,built-in exceptions}, they are
documented here, because conceptually they belong to the warnings mechanism.

User code can define additional warning categories by subclassing one of the
standard warning categories.  A warning category must always be a subclass of
the @ref{16af,,Warning} class.

The following warnings category classes are currently defined:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Class

@tab

描述

@item

@ref{16af,,Warning}

@tab

This is the base class of all warning
category classes.  It is a subclass of
@ref{1a9,,Exception}.

@item

@ref{16b0,,UserWarning}

@tab

The default category for @ref{e51,,warn()}.

@item

@ref{278,,DeprecationWarning}

@tab

Base category for warnings about deprecated
features when those warnings are intended for
other Python developers (ignored by default,
unless triggered by code in @code{__main__}).

@item

@ref{191,,SyntaxWarning}

@tab

Base category for warnings about dubious
syntactic features.

@item

@ref{2c0,,RuntimeWarning}

@tab

Base category for warnings about dubious
runtime features.

@item

@ref{31e,,FutureWarning}

@tab

Base category for warnings about deprecated
features when those warnings are intended for
end users of applications that are written in
Python.

@item

@ref{279,,PendingDeprecationWarning}

@tab

Base category for warnings about features
that will be deprecated in the future
(ignored by default).

@item

@ref{5d3,,ImportWarning}

@tab

Base category for warnings triggered during
the process of importing a module (ignored by
default).

@item

@ref{d80,,UnicodeWarning}

@tab

Base category for warnings related to
Unicode.

@item

@ref{4b0,,BytesWarning}

@tab

Base category for warnings related to
@ref{32a,,bytes} and @ref{32b,,bytearray}.

@item

@ref{4ca,,ResourceWarning}

@tab

Base category for warnings related to
resource usage.

@end multitable



在 3.7 版更改: Previously @ref{278,,DeprecationWarning} and @ref{31e,,FutureWarning} were
distinguished based on whether a feature was being removed entirely or
changing its behaviour. They are now distinguished based on their
intended audience and the way they're handled by the default warnings
filters.


@node The Warnings Filter,暂时禁止警告,警告类别,warnings --- Warning control
@anchor{library/warnings the-warnings-filter}@anchor{35f8}@anchor{library/warnings warning-filter}@anchor{12e2}
@subsubsection The Warnings Filter


The warnings filter controls whether warnings are ignored, displayed, or turned
into errors (raising an exception).

Conceptually, the warnings filter maintains an ordered list of filter
specifications; any specific warning is matched against each filter
specification in the list in turn until a match is found; the filter determines
the disposition of the match.  Each entry is a tuple of the form (@emph{action},
@emph{message}, @emph{category}, @emph{module}, @emph{lineno}), where:


@itemize *

@item 
@emph{action} is one of the following strings:


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

处置

@item

@code{"default"}

@tab

为发出警告的每个位置（模块+行号）打印第一个匹配警告

@item

@code{"error"}

@tab

将匹配警告转换为异常

@item

@code{"ignore"}

@tab

从不打印匹配的警告

@item

@code{"always"}

@tab

总是打印匹配的警告

@item

@code{"module"}

@tab

为发出警告的每个模块打印第一次匹配警告（无论行号如何）

@item

@code{"once"}

@tab

无论位置如何，仅打印第一次出现的匹配警告

@end multitable


@item 
@emph{message} is a string containing a regular expression that the start of
the warning message must match.  The expression is compiled to always be
case-insensitive.

@item 
@emph{category} is a class (a subclass of @ref{16af,,Warning}) of which the warning
category must be a subclass in order to match.

@item 
@emph{module} is a string containing a regular expression that the module name must
match.  The expression is compiled to be case-sensitive.

@item 
@emph{lineno} is an integer that the line number where the warning occurred must
match, or @code{0} to match all line numbers.
@end itemize

Since the @ref{16af,,Warning} class is derived from the built-in @ref{1a9,,Exception}
class, to turn a warning into an error we simply raise @code{category(message)}.

If a warning is reported and doesn't match any registered filter then the
"default" action is applied (hence its name).

@menu
* Describing Warning Filters:: 
* 默认警告过滤器:: 
* Overriding the default filter:: 

@end menu

@node Describing Warning Filters,默认警告过滤器,,The Warnings Filter
@anchor{library/warnings describing-warning-filters}@anchor{12e3}@anchor{library/warnings id2}@anchor{35f9}
@subsubsection Describing Warning Filters


The warnings filter is initialized by @ref{40f,,-W} options passed to the Python
interpreter command line and the 
@geindex PYTHONWARNINGS
@geindex 环境变量; PYTHONWARNINGS
@ref{410,,PYTHONWARNINGS} environment variable.
The interpreter saves the arguments for all supplied entries without
interpretation in @ref{40e,,sys.warnoptions}; the @ref{126,,warnings} module parses these
when it is first imported (invalid options are ignored, after printing a
message to @ref{308,,sys.stderr}).

Individual warnings filters are specified as a sequence of fields separated by
colons:

@example
action:message:category:module:line
@end example

The meaning of each of these fields is as described in @ref{12e2,,The Warnings Filter}.
When listing multiple filters on a single line (as for
@geindex PYTHONWARNINGS
@geindex 环境变量; PYTHONWARNINGS
@ref{410,,PYTHONWARNINGS}), the individual filters are separated by commas and
the filters listed later take precedence over those listed before them (as
they're applied left-to-right, and the most recently applied filters take
precedence over earlier ones).

Commonly used warning filters apply to either all warnings, warnings in a
particular category, or warnings raised by particular modules or packages.
Some examples:

@example
default                      # Show all warnings (even those ignored by default)
ignore                       # Ignore all warnings
error                        # Convert all warnings to errors
error::ResourceWarning       # Treat ResourceWarning messages as errors
default::DeprecationWarning  # Show DeprecationWarning messages
ignore,default:::mymodule    # Only report warnings triggered by "mymodule"
error:::mymodule[.*]         # Convert warnings to errors in "mymodule"
                             # and any subpackages of "mymodule"
@end example

@node 默认警告过滤器,Overriding the default filter,Describing Warning Filters,The Warnings Filter
@anchor{library/warnings default-warning-filter}@anchor{35fa}@anchor{library/warnings id3}@anchor{35fb}
@subsubsection 默认警告过滤器


By default, Python installs several warning filters, which can be overridden by
the @ref{40f,,-W} command-line option, the 
@geindex PYTHONWARNINGS
@geindex 环境变量; PYTHONWARNINGS
@ref{410,,PYTHONWARNINGS} environment
variable and calls to @ref{e00,,filterwarnings()}.

In regular release builds, the default warning filter has the following entries
(in order of precedence):

@example
default::DeprecationWarning:__main__
ignore::DeprecationWarning
ignore::PendingDeprecationWarning
ignore::ImportWarning
ignore::ResourceWarning
@end example

In debug builds, the list of default warning filters is empty.


在 3.2 版更改: @ref{278,,DeprecationWarning} is now ignored by default in addition to
@ref{279,,PendingDeprecationWarning}.



在 3.7 版更改: @ref{278,,DeprecationWarning} is once again shown by default when triggered
directly by code in @code{__main__}.



在 3.7 版更改: @ref{4b0,,BytesWarning} no longer appears in the default filter list and is
instead configured via @ref{40e,,sys.warnoptions} when @ref{40d,,-b} is specified
twice.


@node Overriding the default filter,,默认警告过滤器,The Warnings Filter
@anchor{library/warnings overriding-the-default-filter}@anchor{35fc}@anchor{library/warnings warning-disable}@anchor{35fd}
@subsubsection Overriding the default filter


Developers of applications written in Python may wish to hide @emph{all} Python level
warnings from their users by default, and only display them when running tests
or otherwise working on the application. The @ref{40e,,sys.warnoptions} attribute
used to pass filter configurations to the interpreter can be used as a marker to
indicate whether or not warnings should be disabled:

@example
import sys

if not sys.warnoptions:
    import warnings
    warnings.simplefilter("ignore")
@end example

Developers of test runners for Python code are advised to instead ensure that
@emph{all} warnings are displayed by default for the code under test, using code
like:

@example
import sys

if not sys.warnoptions:
    import os, warnings
    warnings.simplefilter("default") # Change the filter in this process
    os.environ["PYTHONWARNINGS"] = "default" # Also affect subprocesses
@end example

Finally, developers of interactive shells that run user code in a namespace
other than @code{__main__} are advised to ensure that @ref{278,,DeprecationWarning}
messages are made visible by default, using code like the following (where
@code{user_ns} is the module used to execute code entered interactively):

@example
import warnings
warnings.filterwarnings("default", category=DeprecationWarning,
                                   module=user_ns.get("__name__"))
@end example

@node 暂时禁止警告,测试警告,The Warnings Filter,warnings --- Warning control
@anchor{library/warnings temporarily-suppressing-warnings}@anchor{35fe}@anchor{library/warnings warning-suppress}@anchor{35ff}
@subsubsection 暂时禁止警告


If you are using code that you know will raise a warning, such as a deprecated
function, but do not want to see the warning (even when warnings have been
explicitly configured via the command line), then it is possible to suppress
the warning using the @ref{33fc,,catch_warnings} context manager:

@example
import warnings

def fxn():
    warnings.warn("deprecated", DeprecationWarning)

with warnings.catch_warnings():
    warnings.simplefilter("ignore")
    fxn()
@end example

While within the context manager all warnings will simply be ignored. This
allows you to use known-deprecated code without having to see the warning while
not suppressing the warning for other code that might not be aware of its use
of deprecated code.  Note: this can only be guaranteed in a single-threaded
application. If two or more threads use the @ref{33fc,,catch_warnings} context
manager at the same time, the behavior is undefined.

@node 测试警告,Updating Code For New Versions of Dependencies,暂时禁止警告,warnings --- Warning control
@anchor{library/warnings testing-warnings}@anchor{3600}@anchor{library/warnings warning-testing}@anchor{3601}
@subsubsection 测试警告


To test warnings raised by code, use the @ref{33fc,,catch_warnings} context
manager. With it you can temporarily mutate the warnings filter to facilitate
your testing. For instance, do the following to capture all raised warnings to
check:

@example
import warnings

def fxn():
    warnings.warn("deprecated", DeprecationWarning)

with warnings.catch_warnings(record=True) as w:
    # Cause all warnings to always be triggered.
    warnings.simplefilter("always")
    # Trigger a warning.
    fxn()
    # Verify some things
    assert len(w) == 1
    assert issubclass(w[-1].category, DeprecationWarning)
    assert "deprecated" in str(w[-1].message)
@end example

One can also cause all warnings to be exceptions by using @code{error} instead of
@code{always}. One thing to be aware of is that if a warning has already been
raised because of a @code{once}/@code{default} rule, then no matter what filters are
set the warning will not be seen again unless the warnings registry related to
the warning has been cleared.

Once the context manager exits, the warnings filter is restored to its state
when the context was entered. This prevents tests from changing the warnings
filter in unexpected ways between tests and leading to indeterminate test
results. The @ref{35f6,,showwarning()} function in the module is also restored to
its original value.  Note: this can only be guaranteed in a single-threaded
application. If two or more threads use the @ref{33fc,,catch_warnings} context
manager at the same time, the behavior is undefined.

When testing multiple operations that raise the same kind of warning, it
is important to test them in a manner that confirms each operation is raising
a new warning (e.g. set warnings to be raised as exceptions and check the
operations raise exceptions, check that the length of the warning list
continues to increase after each operation, or else delete the previous
entries from the warnings list before each new operation).

@node Updating Code For New Versions of Dependencies,Available Functions,测试警告,warnings --- Warning control
@anchor{library/warnings updating-code-for-new-versions-of-dependencies}@anchor{3602}@anchor{library/warnings warning-ignored}@anchor{3316}
@subsubsection Updating Code For New Versions of Dependencies


Warning categories that are primarily of interest to Python developers (rather
than end users of applications written in Python) are ignored by default.

Notably, this "ignored by default" list includes @ref{278,,DeprecationWarning}
(for every module except @code{__main__}), which means developers should make sure
to test their code with typically ignored warnings made visible in order to
receive timely notifications of future breaking API changes (whether in the
standard library or third party packages).

In the ideal case, the code will have a suitable test suite, and the test runner
will take care of implicitly enabling all warnings when running tests
(the test runner provided by the @ref{11b,,unittest} module does this).

In less ideal cases, applications can be checked for use of deprecated
interfaces by passing @ref{40f,,-Wd} to the Python interpreter (this is
shorthand for @code{-W default}) or setting @code{PYTHONWARNINGS=default} in
the environment. This enables default handling for all warnings, including those
that are ignored by default. To change what action is taken for encountered
warnings you can change what argument is passed to @ref{40f,,-W} (e.g.
@code{-W error}). See the @ref{40f,,-W} flag for more details on what is
possible.

@node Available Functions,Available Context Managers,Updating Code For New Versions of Dependencies,warnings --- Warning control
@anchor{library/warnings available-functions}@anchor{3603}@anchor{library/warnings warning-functions}@anchor{3604}
@subsubsection Available Functions


@geindex warn() (在 warnings 模块中)
@anchor{library/warnings warnings warn}@anchor{e51}
@deffn {函数} warnings.warn (message, category=None, stacklevel=1, source=None)

Issue a warning, or maybe ignore it or raise an exception.  The @emph{category}
argument, if given, must be a @ref{16ae,,warning category class}; it
defaults to @ref{16b0,,UserWarning}.  Alternatively, @emph{message} can be a @ref{16af,,Warning} instance,
in which case @emph{category} will be ignored and @code{message.__class__} will be used.
In this case, the message text will be @code{str(message)}. This function raises an
exception if the particular warning issued is changed into an error by the
@ref{12e2,,warnings filter}.  The @emph{stacklevel} argument can be used by wrapper
functions written in Python, like this:

@example
def deprecation(message):
    warnings.warn(message, DeprecationWarning, stacklevel=2)
@end example

This makes the warning refer to @code{deprecation()}'s caller, rather than to the
source of @code{deprecation()} itself (since the latter would defeat the purpose
of the warning message).

@emph{source}, if supplied, is the destroyed object which emitted a
@ref{4ca,,ResourceWarning}.


在 3.6 版更改: Added @emph{source} parameter.

@end deffn

@geindex warn_explicit() (在 warnings 模块中)
@anchor{library/warnings warnings warn_explicit}@anchor{5ab}
@deffn {函数} warnings.warn_explicit (message, category, filename, lineno, module=None, registry=None, module_globals=None, source=None)

This is a low-level interface to the functionality of @ref{e51,,warn()}, passing in
explicitly the message, category, filename and line number, and optionally the
module name and the registry (which should be the @code{__warningregistry__}
dictionary of the module).  The module name defaults to the filename with
@code{.py} stripped; if no registry is passed, the warning is never suppressed.
@emph{message} must be a string and @emph{category} a subclass of @ref{16af,,Warning} or
@emph{message} may be a @ref{16af,,Warning} instance, in which case @emph{category} will be
ignored.

@emph{module_globals}, if supplied, should be the global namespace in use by the code
for which the warning is issued.  (This argument is used to support displaying
source for modules found in zipfiles or other non-filesystem import
sources).

@emph{source}, if supplied, is the destroyed object which emitted a
@ref{4ca,,ResourceWarning}.


在 3.6 版更改: Add the @emph{source} parameter.

@end deffn

@geindex showwarning() (在 warnings 模块中)
@anchor{library/warnings warnings showwarning}@anchor{35f6}
@deffn {函数} warnings.showwarning (message, category, filename, lineno, file=None, line=None)

Write a warning to a file.  The default implementation calls
@code{formatwarning(message, category, filename, lineno, line)} and writes the
resulting string to @emph{file}, which defaults to @ref{308,,sys.stderr}.  You may replace
this function with any callable by assigning to @code{warnings.showwarning}.
@emph{line} is a line of source code to be included in the warning
message; if @emph{line} is not supplied, @ref{35f6,,showwarning()} will
try to read the line specified by @emph{filename} and @emph{lineno}.
@end deffn

@geindex formatwarning() (在 warnings 模块中)
@anchor{library/warnings warnings formatwarning}@anchor{f83}
@deffn {函数} warnings.formatwarning (message, category, filename, lineno, line=None)

Format a warning the standard way.  This returns a string which may contain
embedded newlines and ends in a newline.  @emph{line} is a line of source code to
be included in the warning message; if @emph{line} is not supplied,
@ref{f83,,formatwarning()} will try to read the line specified by @emph{filename} and
@emph{lineno}.
@end deffn

@geindex filterwarnings() (在 warnings 模块中)
@anchor{library/warnings warnings filterwarnings}@anchor{e00}
@deffn {函数} warnings.filterwarnings (action, message='@w{'}, category=Warning, module='@w{'}, lineno=0, append=False)

Insert an entry into the list of @ref{12e2,,warnings filter specifications}.  The entry is inserted at the front by default; if
@emph{append} is true, it is inserted at the end.  This checks the types of the
arguments, compiles the @emph{message} and @emph{module} regular expressions, and
inserts them as a tuple in the list of warnings filters.  Entries closer to
the front of the list override entries later in the list, if both match a
particular warning.  Omitted arguments default to a value that matches
everything.
@end deffn

@geindex simplefilter() (在 warnings 模块中)
@anchor{library/warnings warnings simplefilter}@anchor{33fd}
@deffn {函数} warnings.simplefilter (action, category=Warning, lineno=0, append=False)

Insert a simple entry into the list of @ref{12e2,,warnings filter specifications}.  The meaning of the function parameters is as for
@ref{e00,,filterwarnings()}, but regular expressions are not needed as the filter
inserted always matches any message in any module as long as the category and
line number match.
@end deffn

@geindex resetwarnings() (在 warnings 模块中)
@anchor{library/warnings warnings resetwarnings}@anchor{35f5}
@deffn {函数} warnings.resetwarnings ()

Reset the warnings filter.  This discards the effect of all previous calls to
@ref{e00,,filterwarnings()}, including that of the @ref{40f,,-W} command line options
and calls to @ref{33fd,,simplefilter()}.
@end deffn

@node Available Context Managers,,Available Functions,warnings --- Warning control
@anchor{library/warnings available-context-managers}@anchor{3605}
@subsubsection Available Context Managers


@geindex catch_warnings (warnings 中的类)
@anchor{library/warnings warnings catch_warnings}@anchor{33fc}
@deffn {类} warnings.catch_warnings (*, record=False, module=None)

A context manager that copies and, upon exit, restores the warnings filter
and the @ref{35f6,,showwarning()} function.
If the @emph{record} argument is @ref{380,,False} (the default) the context manager
returns @ref{157,,None} on entry. If @emph{record} is @ref{494,,True}, a list is
returned that is progressively populated with objects as seen by a custom
@ref{35f6,,showwarning()} function (which also suppresses output to @code{sys.stdout}).
Each object in the list has attributes with the same names as the arguments to
@ref{35f6,,showwarning()}.

The @emph{module} argument takes a module that will be used instead of the
module returned when you import @ref{126,,warnings} whose filter will be
protected. This argument exists primarily for testing the @ref{126,,warnings}
module itself.

@cartouche
@quotation 注解 
The @ref{33fc,,catch_warnings} manager works by replacing and
then later restoring the module's
@ref{35f6,,showwarning()} function and internal list of filter
specifications.  This means the context manager is modifying
global state and therefore is not thread-safe.
@end quotation
@end cartouche
@end deffn

@node dataclasses --- 数据类,contextlib --- 为 with语句上下文提供的工具,warnings --- Warning control,Python运行时服务
@anchor{library/dataclasses doc}@anchor{3606}@anchor{library/dataclasses dataclasses-data-classes}@anchor{3607}@anchor{library/dataclasses module-dataclasses}@anchor{30}
@subsection @code{dataclasses} --- 数据类


@geindex dataclasses (模块)

@strong{源码：} Lib/dataclasses.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/dataclasses.py}


__________________________________________________________________


这个模块提供了一个装饰器和一些函数，用于自动添加生成的 @ref{3608,,special method}s ，例如 @ref{d57,,__init__()} 和 @ref{337,,__repr__()} 到用户定义的类。 它最初描述于 
@geindex Python 提高建议; PEP 557
PEP 557@footnote{https://www.python.org/dev/peps/pep-0557} 。

在这些生成的方法中使用的成员变量使用 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} 类型注释定义。例如这段代码:

@example
from dataclasses import dataclass

@@dataclass
class InventoryItem:
    """Class for keeping track of an item in inventory."""
    name: str
    unit_price: float
    quantity_on_hand: int = 0

    def total_cost(self) -> float:
        return self.unit_price * self.quantity_on_hand
@end example

除其他事情外，将添加 @ref{d57,,__init__()} ，其看起来像:

@example
def __init__(self, name: str, unit_price: float, quantity_on_hand: int=0):
    self.name = name
    self.unit_price = unit_price
    self.quantity_on_hand = quantity_on_hand
@end example

请注意，此方法会自动添加到类中：它不会在上面显示的 @code{InventoryItem} 定义中直接指定。


3.7 新版功能.


@menu
* 模块级装饰器、类和函数:: 
* 初始化后处理:: 
* 类变量:: 
* 仅初始化变量:: 
* 冻结的实例:: 
* 继承: 继承<2>. 
* 默认工厂函数:: 
* 可变的默认值:: 
* 异常: 异常<17>. 

@end menu

@node 模块级装饰器、类和函数,初始化后处理,,dataclasses --- 数据类
@anchor{library/dataclasses module-level-decorators-classes-and-functions}@anchor{3609}
@subsubsection 模块级装饰器、类和函数


@geindex dataclass() (在 dataclasses 模块中)
@anchor{library/dataclasses dataclasses dataclass}@anchor{336}
@deffn {函数} @@dataclasses.dataclass (*, init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)

这个函数是 @ref{283,,decorator} ，用于将生成的 @ref{3608,,special method} 添加到类中，如下所述。

@ref{336,,dataclass()} 装饰器检查类以找到 @code{field}。 @code{field} 被定义为具有 @ref{61a,,类型标注} 的类变量。除了下面描述的两个例外，在 @ref{336,,dataclass()} 中没有任何内容检查变量标注中指定的类型。

所有生成的方法中的字段顺序是它们在类定义中出现的顺序。

@ref{336,,dataclass()} 装饰器将向类中添加各种“dunder”方法，如下所述。如果类中已存在任何添加的方法，则行为取决于参数，如下所述。装饰器返回被调用的同一个类；没有创建新类。

如果 @ref{336,,dataclass()} 仅用作没有参数的简单装饰器，它就像它具有此签名中记录的默认值一样。也就是说，这三种 @ref{336,,dataclass()} 用法是等价的:

@example
@@dataclass
class C:
    ...

@@dataclass()
class C:
    ...

@@dataclass(init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)
class C:
   ...
@end example

@ref{336,,dataclass()} 的参数有：


@itemize -

@item 
@code{init}: 如果为真值（默认），将生成一个 @code{__ init__()} 方法。

如果类已定义 @code{__ init__()} ，则忽略此参数。

@item 
@code{repr} ：如果为真值（默认），将生成一个 @ref{337,,__repr__()} 方法。 生成的 repr 字符串将具有类名以及每个字段的名称和 repr ，按照它们在类中定义的顺序。不包括标记为从 repr 中排除的字段。 例如：@code{InventoryItem(name='widget', unit_price=3.0, quantity_on_hand=10)}。

如果类已定义 @ref{337,,__repr__()} ，则忽略此参数。

@item 
@code{eq} ：如果为true（默认值），将生成 @ref{338,,__eq__()} 方法。此方法将类作为其字段的元组按顺序比较。比较中的两个实例必须是相同的类型。

如果类已定义 @ref{338,,__eq__()} ，则忽略此参数。

@item 
@code{order} ：如果为真值（默认为 @code{False} ），则 @ref{c2d,,__lt__()} 、 @code{__ le__()} 、 @ref{c9a,,__gt__()} 和 @ref{c9b,,__ge__()} 方法将生成。 这将类作为其字段的元组按顺序比较。比较中的两个实例必须是相同的类型。如果 @code{order} 为真值并且 @code{eq} 为假值 ，则引发 @ref{1fb,,ValueError} 。

如果类已经定义了 @ref{c2d,,__lt__()} 、 @ref{c99,,__le__()} 、 @ref{c9a,,__gt__()} 或者 @ref{c9b,,__ge__()} 中的任意一个，将引发 @ref{192,,TypeError} 。

@item 
@code{unsafe_hash} ：如果为 @code{False} （默认值），则根据 @code{eq} 和 @code{frozen} 的设置方式生成 @ref{339,,__hash__()} 方法。

@ref{339,,__hash__()} 由内置的 @ref{9be,,hash()} 使用，当对象被添加到散列集合（如字典和集合）时。有一个 @ref{339,,__hash__()} 意味着类的实例是不可变的。可变性是一个复杂的属性，取决于程序员的意图， @ref{338,,__eq__()} 的存在性和行为，以及 @ref{336,,dataclass()} 装饰器中 @code{eq} 和 @code{frozen} 标志的值。

默认情况下， @ref{336,,dataclass()} 不会隐式添加 @ref{339,,__hash__()} 方法，除非这样做是安全的。 它也不会添加或更改现有的明确定义的 @ref{339,,__hash__()} 方法。 设置类属性 @code{__hash__ = None} 对 Python 具有特定含义，如 @ref{339,,__hash__()} 文档中所述。

如果 @ref{339,,__hash__()} 没有显式定义，或者它被设置为 @code{None} ，那么 @ref{336,,dataclass()} @emph{可以} 添加一个隐式 @ref{339,,__hash__()} 方法。虽然不推荐，但你可以强制 @ref{336,,dataclass()} 用 @code{unsafe_hash=True} 创建一个 @ref{339,,__hash__()} 方法。 如果你的类在逻辑上是不可变的但实际仍然可变，则可能就是这种情况。这是一个特殊的用例，应该仔细考虑。

以下是隐式创建 @ref{339,,__hash__()} 方法的规则。请注意，你不能在数据类中都使用显式的 @ref{339,,__hash__()} 方法并设置 @code{unsafe_hash=True} ；这将导致 @ref{192,,TypeError} 。

如果 @code{eq} 和 @code{frozen} 都是 true，默认情况下 @ref{336,,dataclass()} 将为你生成一个 @ref{339,,__hash__()} 方法。如果 @code{eq} 为 true 且 @code{frozen} 为 false ，则 @ref{339,,__hash__()} 将被设置为 @code{None} ，标记它不可用（因为它是可变的）。如果 @code{eq} 为 false ，则 @ref{339,,__hash__()} 将保持不变，这意味着将使用超类的 @ref{339,,__hash__()} 方法（如果超类是 @ref{2b0,,object} ，这意味着它将回到基于id的hash）。

@item 
@code{frozen}: 如为真值 (默认值为 @code{False})，则对字段赋值将会产生异常。 这模拟了只读的冻结实例。 如果在类中定义了 @ref{e25,,__setattr__()} 或 @ref{13c8,,__delattr__()} 则将会引发 @ref{192,,TypeError}。 参见下文的讨论。
@end itemize

@code{field}s 可以选择使用普通的 Python 语法指定默认值:

@example
@@dataclass
class C:
    a: int       # 'a' has no default value
    b: int = 0   # assign a default value for 'b'
@end example

在这个例子中， @code{a} 和 @code{b} 都将包含在添加的 @ref{d57,,__init__()} 方法中，它们将被定义为:

@example
def __init__(self, a: int, b: int = 0):
@end example

如果没有默认值的字段跟在具有默认值的字段后，将引发 @ref{192,,TypeError} 。当这发生在单个类中时，或者作为类继承的结果时，都是如此。
@end deffn

@geindex field() (在 dataclasses 模块中)
@anchor{library/dataclasses dataclasses field}@anchor{f8f}
@deffn {函数} dataclasses.field (*, default=MISSING, default_factory=MISSING, repr=True, hash=None, init=True, compare=True, metadata=None)

对于常见和简单的用例，不需要其他功能。但是，有些数据类功能需要额外的每字段信息。为了满足这种对附加信息的需求，你可以通过调用提供的 @ref{f8f,,field()} 函数来替换默认字段值。例如:

@example
@@dataclass
class C:
    mylist: List[int] = field(default_factory=list)

c = C()
c.mylist += [1, 2, 3]
@end example

如上所示， @code{MISSING} 值是一个 sentinel 对象，用于检测是否提供了 @code{default} 和 @code{default_factory} 参数。 使用此 sentinel 是因为 @code{None} 是 @code{default} 的有效值。没有代码应该直接使用 @code{MISSING} 值。

@ref{f8f,,field()} 参数有：


@itemize -

@item 
@code{default} ：如果提供，这将是该字段的默认值。这是必需的，因为 @ref{f8f,,field()} 调用本身会替换一般的默认值。

@item 
@code{default_factory} ：如果提供，它必须是一个零参数可调用对象，当该字段需要一个默认值时，它将被调用。除了其他目的之外，这可以用于指定具有可变默认值的字段，如下所述。 同时指定 @code{default} 和 @code{default_factory} 将产生错误。

@item 
@code{init} ：如果为true（默认值），则该字段作为参数包含在生成的 @ref{d57,,__init__()} 方法中。

@item 
@code{repr} ：如果为true（默认值），则该字段包含在生成的 @ref{337,,__repr__()} 方法返回的字符串中。

@item 
@code{compare} ：如果为true（默认值），则该字段包含在生成的相等性和比较方法中（ @ref{338,,__eq__()} ， @ref{c9a,,__gt__()} 等等）。

@item 
@code{hash} ：这可以是布尔值或 @code{None} 。如果为true，则此字段包含在生成的 @ref{339,,__hash__()} 方法中。如果为 @code{None} （默认值），请使用 @code{compare} 的值，这通常是预期的行为。如果字段用于比较，则应在 hash 中考虑该字段。不鼓励将此值设置为 @code{None} 以外的任何值。

设置 @code{hash=False} 但 @code{compare=True} 的一个可能原因是，如果一个计算 hash 的代价很高的字段是检验等价性需要的，但还有其他字段可以计算类型的 hash 。 即使从 hash 中排除某个字段，它仍将用于比较。

@item 
@code{metadata} ：这可以是映射或 None 。 None 被视为一个空的字典。这个值包含在 @code{MappingProxyType()} 中，使其成为只读，并暴露在 @ref{360a,,Field} 对象上。数据类根本不使用它，它是作为第三方扩展机制提供的。多个第三方可以各自拥有自己的键值，以用作元数据中的命名空间。
@end itemize

如果通过调用 @ref{f8f,,field()} 指定字段的默认值，则该字段的类属性将替换为指定的 @code{default} 值。如果没有提供 @code{default} ，那么将删除类属性。目的是在 @ref{336,,dataclass()} 装饰器运行之后，类属性将包含字段的默认值，就像指定了默认值一样。例如，之后:

@example
@@dataclass
class C:
    x: int
    y: int = field(repr=False)
    z: int = field(repr=False, default=10)
    t: int = 20
@end example

类属性 @code{C.z} 将是 @code{10} ，类属性 @code{C.t} 将是 @code{20}，类属性 @code{C.x} 和 @code{C.y} 将不设置。
@end deffn

@geindex Field (dataclasses 中的类)
@anchor{library/dataclasses dataclasses Field}@anchor{360a}
@deffn {类} dataclasses.Field

@ref{360a,,Field} 对象描述每个定义的字段。这些对象在内部创建，并由 @ref{360b,,fields()} 模块级方法返回（见下文）。用户永远不应该直接实例化 @ref{360a,,Field} 对象。 其有文档的属性是：

@quotation


@itemize -

@item 
@code{name} ：字段的名字。

@item 
@code{type} ：字段的类型。

@item 
@code{default} 、 @code{default_factory} 、 @code{init} 、 @code{repr} 、 @code{hash} 、 @code{compare} 以及 @code{metadata} 与具有和 @ref{f8f,,field()} 声明中相同的意义和值。
@end itemize
@end quotation

可能存在其他属性，但它们是私有的，不能被审查或依赖。
@end deffn

@geindex fields() (在 dataclasses 模块中)
@anchor{library/dataclasses dataclasses fields}@anchor{360b}
@deffn {函数} dataclasses.fields (class_or_instance)

返回 @ref{360a,,Field} 对象的元组，用于定义此数据类的字段。 接受数据类或数据类的实例。如果没有传递一个数据类或实例将引发 @ref{192,,TypeError} 。 不返回 @code{ClassVar} 或 @code{InitVar} 的伪字段。
@end deffn

@geindex asdict() (在 dataclasses 模块中)
@anchor{library/dataclasses dataclasses asdict}@anchor{360c}
@deffn {函数} dataclasses.asdict (instance, *, dict_factory=dict)

将数据类 @code{instance} 转换为字典（使用工厂函数 @code{dict_factory} ）。每个数据类都转换为其字段的字典，如 @code{name: value} 对。数据类、字典、列表和元组被递归。例如:

@example
@@dataclass
class Point:
     x: int
     y: int

@@dataclass
class C:
     mylist: List[Point]

p = Point(10, 20)
assert asdict(p) == @{'x': 10, 'y': 20@}

c = C([Point(0, 0), Point(10, 4)])
assert asdict(c) == @{'mylist': [@{'x': 0, 'y': 0@}, @{'x': 10, 'y': 4@}]@}
@end example

引发 @ref{192,,TypeError} 如果 @code{instance} 不是数据类实例。
@end deffn

@geindex astuple() (在 dataclasses 模块中)
@anchor{library/dataclasses dataclasses astuple}@anchor{360d}
@deffn {函数} dataclasses.astuple (instance, *, tuple_factory=tuple)

将数据类 @code{instance} 转换为元组（通过使用工厂函数 @code{tuple_factory} ）。每个数据类都转换为其字段值的元组。数据类、字典、列表和元组被递归。

继续前一个例子:

@example
assert astuple(p) == (10, 20)
assert astuple(c) == ([(0, 0), (10, 4)],)
@end example

引发 @ref{192,,TypeError} 如果 @code{instance} 不是数据类实例。
@end deffn

@geindex make_dataclass() (在 dataclasses 模块中)
@anchor{library/dataclasses dataclasses make_dataclass}@anchor{360e}
@deffn {函数} dataclasses.make_dataclass (cls_name, fields, *, bases=(), namespace=None, init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)

创建一个名为 @code{cls_name} 的新数据类，字段为 @code{fields} 中定义的字段，基类为 @code{bases} 中给出的基类，并使用 @code{namespace} 中给出的命名空间进行初始化。 @code{fields} 是一个可迭代的元素，每个元素都是 @code{name} 、 @code{(name, type)} 或 @code{(name, type, Field)} 。 如果只提供`@w{`}name`@w{`} ， @code{type} 为 @code{typing.Any} 。 @code{init} 、 @code{repr} 、 @code{eq} 、 @code{order} 、 @code{unsafe_hash} 和 @code{frozen} 的值与它们在  @ref{336,,dataclass()} 中的含义相同。

此函数不是严格要求的，因为用于任何创建带有 @code{__annotations__} 的新类的 Python 机制都可以应用 @ref{336,,dataclass()} 函数将该类转换为数据类。提供此功能是为了方便。例如:

@example
C = make_dataclass('C',
                   [('x', int),
                     'y',
                    ('z', int, field(default=5))],
                   namespace=@{'add_one': lambda self: self.x + 1@})
@end example

等价于

@example
@@dataclass
class C:
    x: int
    y: 'typing.Any'
    z: int = 5

    def add_one(self):
        return self.x + 1
@end example
@end deffn

@geindex replace() (在 dataclasses 模块中)
@anchor{library/dataclasses dataclasses replace}@anchor{f3d}
@deffn {函数} dataclasses.replace (instance, **changes)

创建一个 @code{instance} 相同类型的新对象，用 @code{changes} 中的值替换字段。如果 @code{instance} 不是数据类，则引发 @ref{192,,TypeError} 。如果 @code{changes} 中的值没有指定字段，则引发 @ref{192,,TypeError} 。

新返回的对象通过调用数据类的 @ref{d57,,__init__()} 方法创建。这确保了如果存在 @code{__post_init__()} ，其也被调用。

如果存在没有默认值的仅初始化变量，必须在调用 @ref{f3d,,replace()} 时指定，以便它们可以传递给 @ref{d57,,__init__()} 和 @code{__post_init__()} 。

@code{changes} 包含任何定义为 @code{init=False} 的字段是错误的。在这种情况下会引发 @ref{1fb,,ValueError} 。

提前提醒 @code{init=False} 字段在调用 @ref{f3d,,replace()} 时的工作方式。如果它们完全被初始化的话，它们不是从源对象复制的，而是在 @code{__post_init__()} 中初始化。估计 @code{init=False} 字段很少能被正确地使用。如果使用它们，那么使用备用类构造函数或者可能是处理实例复制的自定义 @code{replace()} （或类似命名的）方法可能是明智的。
@end deffn

@geindex is_dataclass() (在 dataclasses 模块中)
@anchor{library/dataclasses dataclasses is_dataclass}@anchor{360f}
@deffn {函数} dataclasses.is_dataclass (class_or_instance)

如果其形参为 dataclass 或其实例则返回 @code{True}，否则返回 @code{False}。

如果你需要知道一个类是否是一个数据类的实例（而不是一个数据类本身），那么再添加一个 @code{not isinstance(obj, type)} 检查:

@example
def is_dataclass_instance(obj):
    return is_dataclass(obj) and not isinstance(obj, type)
@end example
@end deffn

@node 初始化后处理,类变量,模块级装饰器、类和函数,dataclasses --- 数据类
@anchor{library/dataclasses post-init-processing}@anchor{3610}
@subsubsection 初始化后处理


生成的 @ref{d57,,__init__()} 代码将调用一个名为 @code{__post_init__()} 的方法，如果在类上已经定义了 @code{__post_init__()} 。它通常被称为 @code{self.__post_init__()} 。但是，如果定义了任何 @code{InitVar} 字段，它们也将按照它们在类中定义的顺序传递给 @code{__post_init__()} 。 如果没有 @code{__ init__()} 方法生成，那么 @code{__post_init__()} 将不会被自动调用。

在其他用途中，这允许初始化依赖于一个或多个其他字段的字段值。例如:

@example
@@dataclass
class C:
    a: float
    b: float
    c: float = field(init=False)

    def __post_init__(self):
        self.c = self.a + self.b
@end example

有关将参数传递给 @code{__post_init__()} 的方法，请参阅下面有关仅初始化变量的段落。另请参阅关于 @ref{f3d,,replace()} 处理 @code{init=False} 字段的警告。

@node 类变量,仅初始化变量,初始化后处理,dataclasses --- 数据类
@anchor{library/dataclasses class-variables}@anchor{3611}
@subsubsection 类变量


两个地方 @ref{336,,dataclass()} 实际检查字段类型的之一是确定字段是否是如 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526} 所定义的类变量。它通过检查字段的类型是否为 @code{typing.ClassVar} 来完成此操作。如果一个字段是一个 @code{ClassVar} ，它将被排除在考虑范围之外，并被数据类机制忽略。这样的 @code{ClassVar} 伪字段不会由模块级的 @ref{360b,,fields()} 函数返回。

@node 仅初始化变量,冻结的实例,类变量,dataclasses --- 数据类
@anchor{library/dataclasses init-only-variables}@anchor{3612}
@subsubsection 仅初始化变量


另一个 @ref{336,,dataclass()} 检查类型注解地方是为了确定一个字段是否是一个仅初始化变量。它通过查看字段的类型是否为 @code{dataclasses.InitVar} 类型来实现。如果一个字段是一个 @code{InitVar} ，它被认为是一个称为仅初始化字段的伪字段。因为它不是一个真正的字段，所以它不会被模块级的 @ref{360b,,fields()} 函数返回。仅初始化字段作为参数添加到生成的 @ref{d57,,__init__()} 方法中，并传递给可选的 @code{__post_init__()} 方法。数据类不会使用它们。

例如，假设一个字段将从数据库初始化，如果在创建类时未提供其值:

@example
@@dataclass
class C:
    i: int
    j: int = None
    database: InitVar[DatabaseType] = None

    def __post_init__(self, database):
        if self.j is None and database is not None:
            self.j = database.lookup('j')

c = C(10, database=my_database)
@end example

在这种情况下， @ref{360b,,fields()} 将返回 @code{i} 和 @code{j} 的 @ref{360a,,Field} 对象，但不包括 @code{database} 。

@node 冻结的实例,继承<2>,仅初始化变量,dataclasses --- 数据类
@anchor{library/dataclasses frozen-instances}@anchor{3613}
@subsubsection 冻结的实例


无法创建真正不可变的 Python 对象。但是，通过将 @code{frozen=True} 传递给 @ref{336,,dataclass()} 装饰器，你可以模拟不变性。在这种情况下，数据类将向类添加 @ref{e25,,__setattr__()} 和 @ref{13c8,,__delattr__()} 方法。 些方法在调用时会引发 @ref{3614,,FrozenInstanceError} 。

使用 @code{frozen=True} 时会有很小的性能损失： @code{__ init__()} 不能使用简单的赋值来初始化字段，并必须使用 @code{object.__ setattr__()} 。

@node 继承<2>,默认工厂函数,冻结的实例,dataclasses --- 数据类
@anchor{library/dataclasses inheritance}@anchor{3615}
@subsubsection 继承


当数组由 @ref{336,,dataclass()} 装饰器创建时，它会查看反向 MRO 中的所有类的基类（即从 @ref{2b0,,object} 开始 ），并且对于它找到的每个数据类， 将该基类中的字段添加到字段的有序映射中。添加完所有基类字段后，它会将自己的字段添加到有序映射中。所有生成的方法都将使用这种组合的，计算的有序字段映射。由于字段是按插入顺序排列的，因此派生类会重载基类。一个例子:

@example
@@dataclass
class Base:
    x: Any = 15.0
    y: int = 0

@@dataclass
class C(Base):
    z: int = 10
    x: int = 15
@end example

最后的字段列表依次是 @code{x} 、 @code{y} 、 @code{z} 。 @code{x} 的最终类型是 @code{int} ，如类 @code{C} 中所指定的那样。

为 @code{C} 生成的 @ref{d57,,__init__()} 方法看起来像:

@example
def __init__(self, x: int = 15, y: int = 0, z: int = 10):
@end example

@node 默认工厂函数,可变的默认值,继承<2>,dataclasses --- 数据类
@anchor{library/dataclasses default-factory-functions}@anchor{3616}
@subsubsection 默认工厂函数


@quotation

如果一个 @ref{f8f,,field()} 指定了一个 @code{default_factory} ，当需要该字段的默认值时，将使用零参数调用它。例如，要创建列表的新实例，请使用:

@example
mylist: list = field(default_factory=list)
@end example

如果一个字段被排除在 @ref{d57,,__init__()} 之外（使用 @code{init=False} ）并且字段也指定 @code{default_factory} ，则默认的工厂函数将始终从生成的 @code{__ init__()} 函数调用。发生这种情况是因为没有其他方法可以为字段提供初始值。
@end quotation

@node 可变的默认值,异常<17>,默认工厂函数,dataclasses --- 数据类
@anchor{library/dataclasses mutable-default-values}@anchor{3617}
@subsubsection 可变的默认值


@quotation

Python 在类属性中存储默认成员变量值。思考这个例子，不使用数据类:

@example
class C:
    x = []
    def add(self, element):
        self.x.append(element)

o1 = C()
o2 = C()
o1.add(1)
o2.add(2)
assert o1.x == [1, 2]
assert o1.x is o2.x
@end example

请注意，类 @code{C} 的两个实例共享相同的类变量 @code{x} ，如预期的那样。

使用数据类， @emph{如果} 此代码有效:

@example
@@dataclass
class D:
    x: List = []
    def add(self, element):
        self.x += element
@end example

它生成的代码类似于:

@example
class D:
    x = []
    def __init__(self, x=x):
        self.x = x
    def add(self, element):
        self.x += element

assert D().x is D().x
@end example

这与使用类 @code{C} 的原始示例具有相同的问题。也就是说，在创建类实例时没有为 @code{x} 指定值的类 @code{D} 的两个实例将共享相同的 @code{x} 副本。由于数据类只使用普通的 Python 类创建，因此它们也会共享此行为。数据类没有通用的方法来检测这种情况。相反，如果数据类检测到类型为 @code{list} 、 @code{dict} 或 @code{set} 的默认参数，则会引发 @ref{192,,TypeError} 。这是一个部分解决方案，但它可以防止许多常见错误。

使用默认工厂函数是一种创建可变类型新实例的方法，并将其作为字段的默认值:

@example
@@dataclass
class D:
    x: list = field(default_factory=list)

assert D().x is not D().x
@end example
@end quotation

@node 异常<17>,,可变的默认值,dataclasses --- 数据类
@anchor{library/dataclasses exceptions}@anchor{3618}
@subsubsection 异常


@geindex FrozenInstanceError
@anchor{library/dataclasses dataclasses FrozenInstanceError}@anchor{3614}
@deffn {例外} dataclasses.FrozenInstanceError

在使用 @code{frozen=True} 定义的数据类上调用隐式定义的 @ref{e25,,__setattr__()} 或 @ref{13c8,,__delattr__()} 时引发。
@end deffn

@node contextlib --- 为 with语句上下文提供的工具,abc --- 抽象基类,dataclasses --- 数据类,Python运行时服务
@anchor{library/contextlib doc}@anchor{3619}@anchor{library/contextlib contextlib-utilities-for-with-statement-contexts}@anchor{361a}@anchor{library/contextlib module-contextlib}@anchor{24}
@subsection @code{contextlib} --- 为 @code{with}语句上下文提供的工具


@geindex contextlib (模块)

@strong{源代码} Lib/contextlib.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/contextlib.py}


__________________________________________________________________


此模块为涉及 @ref{6e3,,with} 语句的常见任务提供了实用的程序。更多信息请参见 @ref{1420,,上下文管理器类型} 和 @ref{141e,,with 语句上下文管理器}。

@menu
* 工具:: 
* 例子和配方: 例子和配方<2>. 
* Single use@comma{} reusable and reentrant context managers: Single use reusable and reentrant context managers. 

@end menu

@node 工具,例子和配方<2>,,contextlib --- 为 with语句上下文提供的工具
@anchor{library/contextlib utilities}@anchor{361b}
@subsubsection 工具


提供的函数和类：

@geindex AbstractContextManager (contextlib 中的类)
@anchor{library/contextlib contextlib AbstractContextManager}@anchor{52e}
@deffn {类} contextlib.AbstractContextManager

一个为实现了 @ref{1430,,object.__aenter__()} 与 @ref{1431,,object.__aexit__()} 的类提供的 @ref{b2c,,abstract base class}。 为 @ref{1430,,object.__aenter__()} 提供的一个默认实现是返回 @code{self} 而 @ref{1431,,object.__aexit__()} 是一个默认返回 @code{None} 的抽象方法。 参见 @ref{142e,,异步上下文管理器} 的定义。


3.6 新版功能.

@end deffn

@geindex AbstractAsyncContextManager (contextlib 中的类)
@anchor{library/contextlib contextlib AbstractAsyncContextManager}@anchor{371}
@deffn {类} contextlib.AbstractAsyncContextManager

一个为实现了 @ref{1430,,object.__aenter__()} 与 @ref{1431,,object.__aexit__()} 的类提供的 @ref{b2c,,abstract base class}。 为 @ref{1430,,object.__aenter__()} 提供的一个默认实现是返回 @code{self} 而 @ref{1431,,object.__aexit__()} 是一个默认返回 @code{None} 的抽象方法。 参见 @ref{142e,,异步上下文管理器} 的定义。


3.7 新版功能.

@end deffn

@geindex contextmanager() (在 contextlib 模块中)
@anchor{library/contextlib contextlib contextmanager}@anchor{b77}
@deffn {函数} @@contextlib.contextmanager

这个函数是一个 @ref{283,,decorator} ，它可以定义一个支持 @ref{6e3,,with} 语句上下文的工厂函数， 而不需要创建一个类或区 @ref{c8e,,__enter__()} 与 @ref{c8f,,__exit__()} 方法。

尽管许多对象原生支持使用 with 语句，但有些需要被管理的资源并不是上下文管理器，并且没有实现 @code{close()} 方法而不能使用 @code{contextlib.closing} 。

下面是一个抽象的示例，展示如何确保正确的资源管理：

@example
from contextlib import contextmanager

@@contextmanager
def managed_resource(*args, **kwds):
    # Code to acquire resource, e.g.:
    resource = acquire_resource(*args, **kwds)
    try:
        yield resource
    finally:
        # Code to release resource, e.g.:
        release_resource(resource)

>>> with managed_resource(timeout=3600) as resource:
...     # Resource is released at the end of this block,
...     # even if code in the block raises an exception
@end example

被装饰的函数在被调用时，必须返回一个 @ref{99c,,generator}-iterator。这个迭代器必须只 yield 一个值出来，这个值会被用在 @ref{6e3,,with} 语句中，绑定到 @code{as} 后面的变量，如果给定了的话。

当生成器发生 yield 时，嵌套在 @ref{6e3,,with} 语句中的语句体会被执行。 语句体执行完毕离开之后，该生成器将被恢复执行。 如果在该语句体中发生了未处理的异常，则该异常会在生成器发生 yield 时重新被引发。 因此，你可以使用 @ref{d6b,,try}...@ref{b37,,except}...@ref{182,,finally} 语句来捕获该异常（如果有的话），或确保进行了一些清理。 如果仅出于记录日志或执行某些操作（而非完全抑制异常）的目的捕获了异常，生成器必须重新引发该异常。 否则生成器的上下文管理器将向 @code{with} 语句指示该异常已经被处理，程序将立即在 @code{with} 语句之后恢复并继续执行。

@ref{b77,,contextmanager()} 使用 @ref{b76,,ContextDecorator} 因此它创建的上下文管理器不仅可以用在 @ref{6e3,,with} 语句中，还可以用作一个装饰器。当它用作一个装饰器时，每一次函数调用时都会隐式创建一个新的生成器实例（这使得 @ref{b77,,contextmanager()} 创建的上下文管理器满足了支持多次调用以用作装饰器的需求，而非“一次性”的上下文管理器）。


在 3.2 版更改: @ref{b76,,ContextDecorator} 的使用。

@end deffn

@geindex asynccontextmanager() (在 contextlib 模块中)
@anchor{library/contextlib contextlib asynccontextmanager}@anchor{370}
@deffn {函数} @@contextlib.asynccontextmanager

Similar to @ref{b77,,contextmanager()}, but creates an
@ref{142e,,asynchronous context manager}.

This function is a @ref{283,,decorator} that can be used to define a factory
function for @ref{63d,,async with} statement asynchronous context managers,
without needing to create a class or separate @ref{1430,,__aenter__()} and
@ref{1431,,__aexit__()} methods. It must be applied to an @ref{149c,,asynchronous generator} function.

A simple example:

@example
from contextlib import asynccontextmanager

@@asynccontextmanager
async def get_connection():
    conn = await acquire_db_connection()
    try:
        yield conn
    finally:
        await release_db_connection(conn)

async def get_all_users():
    async with get_connection() as conn:
        return conn.query('SELECT ...')
@end example


3.7 新版功能.

@end deffn

@geindex closing() (在 contextlib 模块中)
@anchor{library/contextlib contextlib closing}@anchor{361c}
@deffn {函数} contextlib.closing (thing)

Return a context manager that closes @emph{thing} upon completion of the block.  This
is basically equivalent to:

@example
from contextlib import contextmanager

@@contextmanager
def closing(thing):
    try:
        yield thing
    finally:
        thing.close()
@end example

And lets you write code like this:

@example
from contextlib import closing
from urllib.request import urlopen

with closing(urlopen('http://www.python.org')) as page:
    for line in page:
        print(line)
@end example

without needing to explicitly close @code{page}.  Even if an error occurs,
@code{page.close()} will be called when the @ref{6e3,,with} block is exited.
@end deffn
@anchor{library/contextlib simplifying-support-for-single-optional-context-managers}@anchor{361d}
@geindex nullcontext() (在 contextlib 模块中)
@anchor{library/contextlib contextlib nullcontext}@anchor{36e}
@deffn {函数} contextlib.nullcontext (enter_result=None)

Return a context manager that returns @emph{enter_result} from @code{__enter__}, but
otherwise does nothing. It is intended to be used as a stand-in for an
optional context manager, for example:

@example
def myfunction(arg, ignore_exceptions=False):
    if ignore_exceptions:
        # Use suppress to ignore all exceptions.
        cm = contextlib.suppress(Exception)
    else:
        # Do not ignore any exceptions, cm has no effect.
        cm = contextlib.nullcontext()
    with cm:
        # Do something
@end example

An example using @emph{enter_result}:

@example
def process_file(file_or_path):
    if isinstance(file_or_path, str):
        # If string, open file
        cm = open(file_or_path)
    else:
        # Caller is responsible for closing file
        cm = nullcontext(file_or_path)

    with cm as file:
        # Perform processing on the file
@end example


3.7 新版功能.

@end deffn

@geindex suppress() (在 contextlib 模块中)
@anchor{library/contextlib contextlib suppress}@anchor{826}
@deffn {函数} contextlib.suppress (*exceptions)

Return a context manager that suppresses any of the specified exceptions
if they occur in the body of a with statement and then resumes execution
with the first statement following the end of the with statement.

As with any other mechanism that completely suppresses exceptions, this
context manager should be used only to cover very specific errors where
silently continuing with program execution is known to be the right
thing to do.

例如

@example
from contextlib import suppress

with suppress(FileNotFoundError):
    os.remove('somefile.tmp')

with suppress(FileNotFoundError):
    os.remove('someotherfile.tmp')
@end example

This code is equivalent to:

@example
try:
    os.remove('somefile.tmp')
except FileNotFoundError:
    pass

try:
    os.remove('someotherfile.tmp')
except FileNotFoundError:
    pass
@end example

This context manager is @ref{361e,,reentrant}.


3.4 新版功能.

@end deffn

@geindex redirect_stdout() (在 contextlib 模块中)
@anchor{library/contextlib contextlib redirect_stdout}@anchor{6bc}
@deffn {函数} contextlib.redirect_stdout (new_target)

Context manager for temporarily redirecting @ref{307,,sys.stdout} to
another file or file-like object.

This tool adds flexibility to existing functions or classes whose output
is hardwired to stdout.

For example, the output of @ref{56d,,help()} normally is sent to @emph{sys.stdout}.
You can capture that output in a string by redirecting the output to an
@ref{827,,io.StringIO} object:

@example
f = io.StringIO()
with redirect_stdout(f):
    help(pow)
s = f.getvalue()
@end example

To send the output of @ref{56d,,help()} to a file on disk, redirect the output
to a regular file:

@example
with open('help.txt', 'w') as f:
    with redirect_stdout(f):
        help(pow)
@end example

To send the output of @ref{56d,,help()} to @emph{sys.stderr}:

@example
with redirect_stdout(sys.stderr):
    help(pow)
@end example

Note that the global side effect on @ref{307,,sys.stdout} means that this
context manager is not suitable for use in library code and most threaded
applications. It also has no effect on the output of subprocesses.
However, it is still a useful approach for many utility scripts.

This context manager is @ref{361e,,reentrant}.


3.4 新版功能.

@end deffn

@geindex redirect_stderr() (在 contextlib 模块中)
@anchor{library/contextlib contextlib redirect_stderr}@anchor{6bb}
@deffn {函数} contextlib.redirect_stderr (new_target)

Similar to @ref{6bc,,redirect_stdout()} but redirecting
@ref{308,,sys.stderr} to another file or file-like object.

This context manager is @ref{361e,,reentrant}.


3.5 新版功能.

@end deffn

@geindex ContextDecorator (contextlib 中的类)
@anchor{library/contextlib contextlib ContextDecorator}@anchor{b76}
@deffn {类} contextlib.ContextDecorator

A base class that enables a context manager to also be used as a decorator.

Context managers inheriting from @code{ContextDecorator} have to implement
@code{__enter__} and @code{__exit__} as normal. @code{__exit__} retains its optional
exception handling even when used as a decorator.

@code{ContextDecorator} is used by @ref{b77,,contextmanager()}, so you get this
functionality automatically.

@code{ContextDecorator} 的示例:

@example
from contextlib import ContextDecorator

class mycontext(ContextDecorator):
    def __enter__(self):
        print('Starting')
        return self

    def __exit__(self, *exc):
        print('Finishing')
        return False

>>> @@mycontext()
... def function():
...     print('The bit in the middle')
...
>>> function()
Starting
The bit in the middle
Finishing

>>> with mycontext():
...     print('The bit in the middle')
...
Starting
The bit in the middle
Finishing
@end example

This change is just syntactic sugar for any construct of the following form:

@example
def f():
    with cm():
        # Do stuff
@end example

@code{ContextDecorator} lets you instead write:

@example
@@cm()
def f():
    # Do stuff
@end example

It makes it clear that the @code{cm} applies to the whole function, rather than
just a piece of it (and saving an indentation level is nice, too).

Existing context managers that already have a base class can be extended by
using @code{ContextDecorator} as a mixin class:

@example
from contextlib import ContextDecorator

class mycontext(ContextBaseClass, ContextDecorator):
    def __enter__(self):
        return self

    def __exit__(self, *exc):
        return False
@end example

@cartouche
@quotation 注解 
As the decorated function must be able to be called multiple times, the
underlying context manager must support use in multiple @ref{6e3,,with}
statements. If this is not the case, then the original construct with the
explicit @code{with} statement inside the function should be used.
@end quotation
@end cartouche


3.2 新版功能.

@end deffn

@geindex ExitStack (contextlib 中的类)
@anchor{library/contextlib contextlib ExitStack}@anchor{36f}
@deffn {类} contextlib.ExitStack

A context manager that is designed to make it easy to programmatically
combine other context managers and cleanup functions, especially those
that are optional or otherwise driven by input data.

For example, a set of files may easily be handled in a single with
statement as follows:

@example
with ExitStack() as stack:
    files = [stack.enter_context(open(fname)) for fname in filenames]
    # All opened files will automatically be closed at the end of
    # the with statement, even if attempts to open files later
    # in the list raise an exception
@end example

Each instance maintains a stack of registered callbacks that are called in
reverse order when the instance is closed (either explicitly or implicitly
at the end of a @ref{6e3,,with} statement). Note that callbacks are @emph{not}
invoked implicitly when the context stack instance is garbage collected.

This stack model is used so that context managers that acquire their
resources in their @code{__init__} method (such as file objects) can be
handled correctly.

Since registered callbacks are invoked in the reverse order of
registration, this ends up behaving as if multiple nested @ref{6e3,,with}
statements had been used with the registered set of callbacks. This even
extends to exception handling - if an inner callback suppresses or replaces
an exception, then outer callbacks will be passed arguments based on that
updated state.

This is a relatively low level API that takes care of the details of
correctly unwinding the stack of exit callbacks. It provides a suitable
foundation for higher level context managers that manipulate the exit
stack in application specific ways.


3.3 新版功能.


@geindex enter_context() (contextlib.ExitStack 方法)
@anchor{library/contextlib contextlib ExitStack enter_context}@anchor{361f}
@deffn {方法} enter_context (cm)

Enters a new context manager and adds its @ref{c8f,,__exit__()} method to
the callback stack. The return value is the result of the context
manager's own @ref{c8e,,__enter__()} method.

These context managers may suppress exceptions just as they normally
would if used directly as part of a @ref{6e3,,with} statement.
@end deffn

@geindex push() (contextlib.ExitStack 方法)
@anchor{library/contextlib contextlib ExitStack push}@anchor{3620}
@deffn {方法} push (exit)

Adds a context manager's @ref{c8f,,__exit__()} method to the callback stack.

As @code{__enter__} is @emph{not} invoked, this method can be used to cover
part of an @ref{c8e,,__enter__()} implementation with a context manager's own
@ref{c8f,,__exit__()} method.

If passed an object that is not a context manager, this method assumes
it is a callback with the same signature as a context manager's
@ref{c8f,,__exit__()} method and adds it directly to the callback stack.

By returning true values, these callbacks can suppress exceptions the
same way context manager @ref{c8f,,__exit__()} methods can.

The passed in object is returned from the function, allowing this
method to be used as a function decorator.
@end deffn

@geindex callback() (contextlib.ExitStack 方法)
@anchor{library/contextlib contextlib ExitStack callback}@anchor{2a5}
@deffn {方法} callback (callback, *args, **kwds)

Accepts an arbitrary callback function and arguments and adds it to
the callback stack.

Unlike the other methods, callbacks added this way cannot suppress
exceptions (as they are never passed the exception details).

The passed in callback is returned from the function, allowing this
method to be used as a function decorator.
@end deffn

@geindex pop_all() (contextlib.ExitStack 方法)
@anchor{library/contextlib contextlib ExitStack pop_all}@anchor{3621}
@deffn {方法} pop_all ()

Transfers the callback stack to a fresh @ref{36f,,ExitStack} instance
and returns it. No callbacks are invoked by this operation - instead,
they will now be invoked when the new stack is closed (either
explicitly or implicitly at the end of a @ref{6e3,,with} statement).

For example, a group of files can be opened as an "all or nothing"
operation as follows:

@example
with ExitStack() as stack:
    files = [stack.enter_context(open(fname)) for fname in filenames]
    # Hold onto the close method, but don't call it yet.
    close_files = stack.pop_all().close
    # If opening any file fails, all previously opened files will be
    # closed automatically. If all files are opened successfully,
    # they will remain open even after the with statement ends.
    # close_files() can then be invoked explicitly to close them all.
@end example
@end deffn

@geindex close() (contextlib.ExitStack 方法)
@anchor{library/contextlib contextlib ExitStack close}@anchor{3622}
@deffn {方法} close ()

Immediately unwinds the callback stack, invoking callbacks in the
reverse order of registration. For any context managers and exit
callbacks registered, the arguments passed in will indicate that no
exception occurred.
@end deffn
@end deffn

@geindex AsyncExitStack (contextlib 中的类)
@anchor{library/contextlib contextlib AsyncExitStack}@anchor{372}
@deffn {类} contextlib.AsyncExitStack

An @ref{142e,,asynchronous context manager}, similar
to @ref{36f,,ExitStack}, that supports combining both synchronous and
asynchronous context managers, as well as having coroutines for
cleanup logic.

The @code{close()} method is not implemented, @ref{3623,,aclose()} must be used
instead.

@geindex enter_async_context() (contextlib.AsyncExitStack 方法)
@anchor{library/contextlib contextlib AsyncExitStack enter_async_context}@anchor{3624}
@deffn {方法} enter_async_context (cm)

Similar to @code{enter_context()} but expects an asynchronous context
manager.
@end deffn

@geindex push_async_exit() (contextlib.AsyncExitStack 方法)
@anchor{library/contextlib contextlib AsyncExitStack push_async_exit}@anchor{3625}
@deffn {方法} push_async_exit (exit)

Similar to @code{push()} but expects either an asynchronous context manager
or a coroutine function.
@end deffn

@geindex push_async_callback() (contextlib.AsyncExitStack 方法)
@anchor{library/contextlib contextlib AsyncExitStack push_async_callback}@anchor{2a6}
@deffn {方法} push_async_callback (callback, *args, **kwds)

Similar to @code{callback()} but expects a coroutine function.
@end deffn

@geindex aclose() (contextlib.AsyncExitStack 方法)
@anchor{library/contextlib contextlib AsyncExitStack aclose}@anchor{3623}
@deffn {方法} aclose ()

Similar to @code{close()} but properly handles awaitables.
@end deffn

Continuing the example for @ref{370,,asynccontextmanager()}:

@example
async with AsyncExitStack() as stack:
    connections = [await stack.enter_async_context(get_connection())
        for i in range(5)]
    # All opened connections will automatically be released at the end of
    # the async with statement, even if attempts to open a connection
    # later in the list raise an exception.
@end example


3.7 新版功能.

@end deffn

@node 例子和配方<2>,Single use reusable and reentrant context managers,工具,contextlib --- 为 with语句上下文提供的工具
@anchor{library/contextlib examples-and-recipes}@anchor{3626}
@subsubsection 例子和配方


This section describes some examples and recipes for making effective use of
the tools provided by @ref{24,,contextlib}.

@menu
* Supporting a variable number of context managers:: 
* Catching exceptions from __enter__ methods:: 
* Cleaning up in an __enter__ implementation:: 
* Replacing any use of try-finally and flag variables:: 
* Using a context manager as a function decorator:: 

@end menu

@node Supporting a variable number of context managers,Catching exceptions from __enter__ methods,,例子和配方<2>
@anchor{library/contextlib supporting-a-variable-number-of-context-managers}@anchor{3627}
@subsubsection Supporting a variable number of context managers


The primary use case for @ref{36f,,ExitStack} is the one given in the class
documentation: supporting a variable number of context managers and other
cleanup operations in a single @ref{6e3,,with} statement. The variability
may come from the number of context managers needed being driven by user
input (such as opening a user specified collection of files), or from
some of the context managers being optional:

@example
with ExitStack() as stack:
    for resource in resources:
        stack.enter_context(resource)
    if need_special_resource():
        special = acquire_special_resource()
        stack.callback(release_special_resource, special)
    # Perform operations that use the acquired resources
@end example

As shown, @ref{36f,,ExitStack} also makes it quite easy to use @ref{6e3,,with}
statements to manage arbitrary resources that don't natively support the
context management protocol.

@node Catching exceptions from __enter__ methods,Cleaning up in an __enter__ implementation,Supporting a variable number of context managers,例子和配方<2>
@anchor{library/contextlib catching-exceptions-from-enter-methods}@anchor{3628}
@subsubsection Catching exceptions from @code{__enter__} methods


It is occasionally desirable to catch exceptions from an @code{__enter__}
method implementation, @emph{without} inadvertently catching exceptions from
the @ref{6e3,,with} statement body or the context manager's @code{__exit__}
method. By using @ref{36f,,ExitStack} the steps in the context management
protocol can be separated slightly in order to allow this:

@example
stack = ExitStack()
try:
    x = stack.enter_context(cm)
except Exception:
    # handle __enter__ exception
else:
    with stack:
        # Handle normal case
@end example

Actually needing to do this is likely to indicate that the underlying API
should be providing a direct resource management interface for use with
@ref{d6b,,try}/@ref{b37,,except}/@ref{182,,finally} statements, but not
all APIs are well designed in that regard. When a context manager is the
only resource management API provided, then @ref{36f,,ExitStack} can make it
easier to handle various situations that can't be handled directly in a
@ref{6e3,,with} statement.

@node Cleaning up in an __enter__ implementation,Replacing any use of try-finally and flag variables,Catching exceptions from __enter__ methods,例子和配方<2>
@anchor{library/contextlib cleaning-up-in-an-enter-implementation}@anchor{3629}
@subsubsection Cleaning up in an @code{__enter__} implementation


As noted in the documentation of @ref{3620,,ExitStack.push()}, this
method can be useful in cleaning up an already allocated resource if later
steps in the @ref{c8e,,__enter__()} implementation fail.

Here's an example of doing this for a context manager that accepts resource
acquisition and release functions, along with an optional validation function,
and maps them to the context management protocol:

@example
from contextlib import contextmanager, AbstractContextManager, ExitStack

class ResourceManager(AbstractContextManager):

    def __init__(self, acquire_resource, release_resource, check_resource_ok=None):
        self.acquire_resource = acquire_resource
        self.release_resource = release_resource
        if check_resource_ok is None:
            def check_resource_ok(resource):
                return True
        self.check_resource_ok = check_resource_ok

    @@contextmanager
    def _cleanup_on_error(self):
        with ExitStack() as stack:
            stack.push(self)
            yield
            # The validation check passed and didn't raise an exception
            # Accordingly, we want to keep the resource, and pass it
            # back to our caller
            stack.pop_all()

    def __enter__(self):
        resource = self.acquire_resource()
        with self._cleanup_on_error():
            if not self.check_resource_ok(resource):
                msg = "Failed validation for @{!r@}"
                raise RuntimeError(msg.format(resource))
        return resource

    def __exit__(self, *exc_details):
        # We don't need to duplicate any of our resource release logic
        self.release_resource()
@end example

@node Replacing any use of try-finally and flag variables,Using a context manager as a function decorator,Cleaning up in an __enter__ implementation,例子和配方<2>
@anchor{library/contextlib replacing-any-use-of-try-finally-and-flag-variables}@anchor{362a}
@subsubsection Replacing any use of @code{try-finally} and flag variables


A pattern you will sometimes see is a @code{try-finally} statement with a flag
variable to indicate whether or not the body of the @code{finally} clause should
be executed. In its simplest form (that can't already be handled just by
using an @code{except} clause instead), it looks something like this:

@example
cleanup_needed = True
try:
    result = perform_operation()
    if result:
        cleanup_needed = False
finally:
    if cleanup_needed:
        cleanup_resources()
@end example

As with any @code{try} statement based code, this can cause problems for
development and review, because the setup code and the cleanup code can end
up being separated by arbitrarily long sections of code.

@ref{36f,,ExitStack} makes it possible to instead register a callback for
execution at the end of a @code{with} statement, and then later decide to skip
executing that callback:

@example
from contextlib import ExitStack

with ExitStack() as stack:
    stack.callback(cleanup_resources)
    result = perform_operation()
    if result:
        stack.pop_all()
@end example

This allows the intended cleanup up behaviour to be made explicit up front,
rather than requiring a separate flag variable.

If a particular application uses this pattern a lot, it can be simplified
even further by means of a small helper class:

@example
from contextlib import ExitStack

class Callback(ExitStack):
    def __init__(self, callback, /, *args, **kwds):
        super(Callback, self).__init__()
        self.callback(callback, *args, **kwds)

    def cancel(self):
        self.pop_all()

with Callback(cleanup_resources) as cb:
    result = perform_operation()
    if result:
        cb.cancel()
@end example

If the resource cleanup isn't already neatly bundled into a standalone
function, then it is still possible to use the decorator form of
@ref{2a5,,ExitStack.callback()} to declare the resource cleanup in
advance:

@example
from contextlib import ExitStack

with ExitStack() as stack:
    @@stack.callback
    def cleanup_resources():
        ...
    result = perform_operation()
    if result:
        stack.pop_all()
@end example

Due to the way the decorator protocol works, a callback function
declared this way cannot take any parameters. Instead, any resources to
be released must be accessed as closure variables.

@node Using a context manager as a function decorator,,Replacing any use of try-finally and flag variables,例子和配方<2>
@anchor{library/contextlib using-a-context-manager-as-a-function-decorator}@anchor{362b}
@subsubsection Using a context manager as a function decorator


@ref{b76,,ContextDecorator} makes it possible to use a context manager in
both an ordinary @code{with} statement and also as a function decorator.

For example, it is sometimes useful to wrap functions or groups of statements
with a logger that can track the time of entry and time of exit.  Rather than
writing both a function decorator and a context manager for the task,
inheriting from @ref{b76,,ContextDecorator} provides both capabilities in a
single definition:

@example
from contextlib import ContextDecorator
import logging

logging.basicConfig(level=logging.INFO)

class track_entry_and_exit(ContextDecorator):
    def __init__(self, name):
        self.name = name

    def __enter__(self):
        logging.info('Entering: %s', self.name)

    def __exit__(self, exc_type, exc, exc_tb):
        logging.info('Exiting: %s', self.name)
@end example

Instances of this class can be used as both a context manager:

@example
with track_entry_and_exit('widget loader'):
    print('Some time consuming activity goes here')
    load_widget()
@end example

And also as a function decorator:

@example
@@track_entry_and_exit('widget loader')
def activity():
    print('Some time consuming activity goes here')
    load_widget()
@end example

Note that there is one additional limitation when using context managers
as function decorators: there's no way to access the return value of
@ref{c8e,,__enter__()}. If that value is needed, then it is still necessary to use
an explicit @code{with} statement.


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 343

@item PEP 343@footnote{https://www.python.org/dev/peps/pep-0343} - "with" 语句

Python @ref{6e3,,with} 语句的规范描述、背景和示例。
@end table


@node Single use reusable and reentrant context managers,,例子和配方<2>,contextlib --- 为 with语句上下文提供的工具
@anchor{library/contextlib single-use-reusable-and-reentrant-cms}@anchor{828}@anchor{library/contextlib single-use-reusable-and-reentrant-context-managers}@anchor{362c}
@subsubsection Single use, reusable and reentrant context managers


Most context managers are written in a way that means they can only be
used effectively in a @ref{6e3,,with} statement once. These single use
context managers must be created afresh each time they're used -
attempting to use them a second time will trigger an exception or
otherwise not work correctly.

This common limitation means that it is generally advisable to create
context managers directly in the header of the @ref{6e3,,with} statement
where they are used (as shown in all of the usage examples above).

Files are an example of effectively single use context managers, since
the first @ref{6e3,,with} statement will close the file, preventing any
further IO operations using that file object.

Context managers created using @ref{b77,,contextmanager()} are also single use
context managers, and will complain about the underlying generator failing
to yield if an attempt is made to use them a second time:

@example
>>> from contextlib import contextmanager
>>> @@contextmanager
... def singleuse():
...     print("Before")
...     yield
...     print("After")
...
>>> cm = singleuse()
>>> with cm:
...     pass
...
Before
After
>>> with cm:
...     pass
...
Traceback (most recent call last):
    ...
RuntimeError: generator didn't yield
@end example

@menu
* Reentrant context managers:: 
* Reusable context managers:: 

@end menu

@node Reentrant context managers,Reusable context managers,,Single use reusable and reentrant context managers
@anchor{library/contextlib reentrant-cms}@anchor{361e}@anchor{library/contextlib reentrant-context-managers}@anchor{362d}
@subsubsection Reentrant context managers


More sophisticated context managers may be "reentrant". These context
managers can not only be used in multiple @ref{6e3,,with} statements,
but may also be used @emph{inside} a @code{with} statement that is already
using the same context manager.

@ref{be8,,threading.RLock} is an example of a reentrant context manager, as are
@ref{826,,suppress()} and @ref{6bc,,redirect_stdout()}. Here's a very simple example of
reentrant use:

@example
>>> from contextlib import redirect_stdout
>>> from io import StringIO
>>> stream = StringIO()
>>> write_to_stream = redirect_stdout(stream)
>>> with write_to_stream:
...     print("This is written to the stream rather than stdout")
...     with write_to_stream:
...         print("This is also written to the stream")
...
>>> print("This is written directly to stdout")
This is written directly to stdout
>>> print(stream.getvalue())
This is written to the stream rather than stdout
This is also written to the stream
@end example

Real world examples of reentrancy are more likely to involve multiple
functions calling each other and hence be far more complicated than this
example.

Note also that being reentrant is @emph{not} the same thing as being thread safe.
@ref{6bc,,redirect_stdout()}, for example, is definitely not thread safe, as it
makes a global modification to the system state by binding @ref{307,,sys.stdout}
to a different stream.

@node Reusable context managers,,Reentrant context managers,Single use reusable and reentrant context managers
@anchor{library/contextlib reusable-cms}@anchor{362e}@anchor{library/contextlib reusable-context-managers}@anchor{362f}
@subsubsection Reusable context managers


Distinct from both single use and reentrant context managers are "reusable"
context managers (or, to be completely explicit, "reusable, but not
reentrant" context managers, since reentrant context managers are also
reusable). These context managers support being used multiple times, but
will fail (or otherwise not work correctly) if the specific context manager
instance has already been used in a containing with statement.

@ref{2300,,threading.Lock} is an example of a reusable, but not reentrant,
context manager (for a reentrant lock, it is necessary to use
@ref{be8,,threading.RLock} instead).

Another example of a reusable, but not reentrant, context manager is
@ref{36f,,ExitStack}, as it invokes @emph{all} currently registered callbacks
when leaving any with statement, regardless of where those callbacks
were added:

@example
>>> from contextlib import ExitStack
>>> stack = ExitStack()
>>> with stack:
...     stack.callback(print, "Callback: from first context")
...     print("Leaving first context")
...
Leaving first context
Callback: from first context
>>> with stack:
...     stack.callback(print, "Callback: from second context")
...     print("Leaving second context")
...
Leaving second context
Callback: from second context
>>> with stack:
...     stack.callback(print, "Callback: from outer context")
...     with stack:
...         stack.callback(print, "Callback: from inner context")
...         print("Leaving inner context")
...     print("Leaving outer context")
...
Leaving inner context
Callback: from inner context
Callback: from outer context
Leaving outer context
@end example

As the output from the example shows, reusing a single stack object across
multiple with statements works correctly, but attempting to nest them
will cause the stack to be cleared at the end of the innermost with
statement, which is unlikely to be desirable behaviour.

Using separate @ref{36f,,ExitStack} instances instead of reusing a single
instance avoids that problem:

@example
>>> from contextlib import ExitStack
>>> with ExitStack() as outer_stack:
...     outer_stack.callback(print, "Callback: from outer context")
...     with ExitStack() as inner_stack:
...         inner_stack.callback(print, "Callback: from inner context")
...         print("Leaving inner context")
...     print("Leaving outer context")
...
Leaving inner context
Callback: from inner context
Leaving outer context
Callback: from outer context
@end example

@node abc --- 抽象基类,atexit --- 退出处理器,contextlib --- 为 with语句上下文提供的工具,Python运行时服务
@anchor{library/abc doc}@anchor{3630}@anchor{library/abc abc-abstract-base-classes}@anchor{3631}@anchor{library/abc module-abc}@anchor{4}
@subsection @code{abc} --- 抽象基类


@geindex abc (模块)

@c much of the content adapted from docstrings

@strong{源代码：} Lib/abc.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/abc.py}


__________________________________________________________________


该模块提供了在 Python 中定义 @ref{b2c,,抽象基类} (ABC) 的组件，在 
@geindex Python 提高建议; PEP 3119
PEP 3119@footnote{https://www.python.org/dev/peps/pep-3119} 中已有概述。查看 PEP 文档了解为什么需要在 Python 中增加这个模块。（也可查看 
@geindex Python 提高建议; PEP 3141
PEP 3141@footnote{https://www.python.org/dev/peps/pep-3141} 以及 @ref{c1,,numbers} 模块了解基于 ABC 的数字类型继承关系。）

@ref{1e,,collections} 模块中有一些派生自 ABC 的具体类；当然这些类还可以进一步被派生。此外，@ref{1f,,collections.abc} 子模块中有一些 ABC 可被用于测试一个类或实例是否提供特定的接口，例如它是否可哈希或它是否为映射等。

该模块提供了一个元类 @ref{813,,ABCMeta}，可以用来定义抽象类，另外还提供一个工具类 @ref{812,,ABC}，可以用它以继承的方式定义抽象基类。

@geindex ABC (abc 中的类)
@anchor{library/abc abc ABC}@anchor{812}
@deffn {类} abc.ABC

一个使用 @ref{813,,ABCMeta} 作为元类的工具类。抽象基类可以通过从 @ref{812,,ABC} 派生来简单地创建，这就避免了在某些情况下会令人混淆的元类用法，例如：

@example
from abc import ABC

class MyABC(ABC):
    pass
@end example

注意 @ref{812,,ABC} 的类型仍然是 @ref{813,,ABCMeta}，因此继承 @ref{812,,ABC} 仍然需要关注元类使用中的注意事项，比如可能会导致元类冲突的多重继承。当然你也可以直接使用 @ref{813,,ABCMeta} 作为元类来定义抽象基类，例如：

@example
from abc import ABCMeta

class MyABC(metaclass=ABCMeta):
    pass
@end example


3.4 新版功能.

@end deffn

@geindex ABCMeta (abc 中的类)
@anchor{library/abc abc ABCMeta}@anchor{813}
@deffn {类} abc.ABCMeta

用于定义抽象基类（ABC）的元类。

使用该元类以创建抽象基类。抽象基类可以像 mix-in 类一样直接被子类继承。你也可以将不相关的具体类（包括内建类）和抽象基类注册为“抽象子类” —— 这些类以及它们的子类会被内建函数 @ref{44a,,issubclass()} 识别为对应的抽象基类的子类，但是该抽象基类不会出现在其 MRO（Method Resolution Order，方法解析顺序）中，抽象基类中实现的方法也不可调用（即使通过 @ref{4dc,,super()} 调用也不行）。@footnote{@w{(1)} 
C++ 程序员需要注意：Python 中虚基类的概念和 C++ 中的并不相同。
}

使用 @ref{813,,ABCMeta} 作为元类创建的类含有如下方法：

@geindex register() (abc.ABCMeta 方法)
@anchor{library/abc abc ABCMeta register}@anchor{9cb}
@deffn {方法} register (subclass)

将“子类”注册为该抽象基类的“抽象子类”，例如：

@example
from abc import ABC

class MyABC(ABC):
    pass

MyABC.register(tuple)

assert issubclass(tuple, MyABC)
assert isinstance((), MyABC)
@end example


在 3.3 版更改: 返回注册的子类，使其能够作为类装饰器。



在 3.4 版更改: 你可以使用 @ref{811,,get_cache_token()} 函数来检测对 @ref{9cb,,register()} 的调用。

@end deffn

你也可以在虚基类中重载这个方法。

@geindex __subclasshook__() (abc.ABCMeta 方法)
@anchor{library/abc abc ABCMeta __subclasshook__}@anchor{3632}
@deffn {方法} __subclasshook__ (subclass)

（必须定义为类方法。）

检查 @emph{subclass} 是否是该抽象基类的子类。也就是说对于那些你希望定义为该抽象基类的子类的类，你不用对每个类都调用 @ref{9cb,,register()} 方法了，而是可以直接自定义 @code{issubclass} 的行为。（这个类方法是在抽象基类的 @code{__subclasscheck__()} 方法中调用的。）

该方法必须返回 @code{True}, @code{False} 或是 @code{NotImplemented}。如果返回 @code{True}，@emph{subclass} 就会被认为是这个抽象基类的子类。如果返回 @code{False}，无论正常情况是否应该认为是其子类，统一视为不是。如果返回 @code{NotImplemented}，子类检查会按照正常机制继续执行。

@c XXX explain the "usual mechanism"
@end deffn

为了对这些概念做一演示，请看以下定义 ABC 的示例：

@example
class Foo:
    def __getitem__(self, index):
        ...
    def __len__(self):
        ...
    def get_iterator(self):
        return iter(self)

class MyIterable(ABC):

    @@abstractmethod
    def __iter__(self):
        while False:
            yield None

    def get_iterator(self):
        return self.__iter__()

    @@classmethod
    def __subclasshook__(cls, C):
        if cls is MyIterable:
            if any("__iter__" in B.__dict__ for B in C.__mro__):
                return True
        return NotImplemented

MyIterable.register(Foo)
@end example

ABC @code{MyIterable} 定义了标准的迭代方法 @ref{15c2,,__iter__()} 作为一个抽象方法。这里给出的实现仍可在子类中被调用。@code{get_iterator()} 方法也是 @code{MyIterable} 抽象基类的一部分，但它并非必须被非抽象派生类所重载。

这里定义的 @ref{3632,,__subclasshook__()} 类方法指明了任何在其 @ref{4f6,,__dict__} (或在其通过 @ref{159d,,__mro__} 列表访问的基类) 中具有 @ref{15c2,,__iter__()} 方法的类也都会被视为 @code{MyIterable}。

最后，末尾行使得 @code{Foo} 成为 @code{MyIterable} 的一个虚子类，即使它没有定义 @ref{15c2,,__iter__()} 方法（它使用了以 @ref{dc4,,__len__()} 和 @ref{27f,,__getitem__()} 术语定义的旧式可迭代对象协议）。 请注意这将不会使 @code{get_iterator} 成为 @code{Foo} 的一个可用方法，它是被另外提供的。
@end deffn

此外，@ref{4,,abc} 模块还提供了这些装饰器：

@geindex abstractmethod() (在 abc 模块中)
@anchor{library/abc abc abstractmethod}@anchor{9c8}
@deffn {函数} @@abc.abstractmethod

用于声明抽象方法的装饰器。

使用此装饰器要求类的元类是 @ref{813,,ABCMeta} 或是从该类派生。一个具有派生自 @ref{813,,ABCMeta} 的元类的类不可以被实例化，除非它全部的抽象方法和特征属性均已被重载。抽象方法可通过任何普通的“super”调用机制来调用。 @ref{9c8,,abstractmethod()} 可被用于声明特性属性和描述器的抽象方法。

不支持动态添加抽象方法到一个类，或试图在方法或类被创建后修改其抽象状态等操作。 @ref{9c8,,abstractmethod()} 只会影响使用常规继承所派生的子类；通过 ABC 的 @code{register()} 方法注册的“虚子类”不会受到影响。

当 @ref{9c8,,abstractmethod()} 与其他方法描述符配合应用时，它应当被应用为最内层的装饰器，如以下用法示例所示:

@example
class C(ABC):
    @@abstractmethod
    def my_abstract_method(self, ...):
        ...
    @@classmethod
    @@abstractmethod
    def my_abstract_classmethod(cls, ...):
        ...
    @@staticmethod
    @@abstractmethod
    def my_abstract_staticmethod(...):
        ...

    @@property
    @@abstractmethod
    def my_abstract_property(self):
        ...
    @@my_abstract_property.setter
    @@abstractmethod
    def my_abstract_property(self, val):
        ...

    @@abstractmethod
    def _get_x(self):
        ...
    @@abstractmethod
    def _set_x(self, val):
        ...
    x = property(_get_x, _set_x)
@end example

为了能正确地与抽象基类机制实现互操作，描述符必须使用 @code{__isabstractmethod__} 将自身标识为抽象的。 通常，如果被用于组成描述符的任何方法都是抽象的则此属性应当为 @code{True}。 例如，Python 的内置 @ref{1d7,,property} 所做的就等价于:

@example
class Descriptor:
    ...
    @@property
    def __isabstractmethod__(self):
        return any(getattr(f, '__isabstractmethod__', False) for
                   f in (self._fget, self._fset, self._fdel))
@end example

@cartouche
@quotation 注解 
不同于 Java 抽象方法，这些抽象方法可能具有一个实现。 这个实现可在重载它的类上通过 @ref{4dc,,super()} 机制来调用。 这在使用协作多重继承的框架中可以被用作超调用的一个端点。
@end quotation
@end cartouche
@end deffn

@ref{4,,abc} 模块还支持下列旧式装饰器:

@geindex abstractclassmethod() (在 abc 模块中)
@anchor{library/abc abc abstractclassmethod}@anchor{9c9}
@deffn {函数} @@abc.abstractclassmethod


3.2 新版功能.



3.3 版后已移除: 现在可以让 @ref{1d8,,classmethod} 配合 @ref{9c8,,abstractmethod()} 使用，使得此装饰器变得冗余。


内置 @ref{1d8,,classmethod()} 的子类，指明一个抽象类方法。 在其他情况下它都类似于 @ref{9c8,,abstractmethod()}。

这个特殊情况已被弃用，因为现在 @ref{1d8,,classmethod()} 当将装饰器应用于抽象方法时它会被正确地标识为抽象的:

@example
class C(ABC):
    @@classmethod
    @@abstractmethod
    def my_abstract_classmethod(cls, ...):
        ...
@end example
@end deffn

@geindex abstractstaticmethod() (在 abc 模块中)
@anchor{library/abc abc abstractstaticmethod}@anchor{9ca}
@deffn {函数} @@abc.abstractstaticmethod


3.2 新版功能.



3.3 版后已移除: 现在可以让 @ref{1d9,,staticmethod} 配合 @ref{9c8,,abstractmethod()} 使用，使得此装饰器变得冗余。


内置 @ref{1d9,,staticmethod()} 的子类，指明一个抽象静态方法。 在其他方面它都类似于 @ref{9c8,,abstractmethod()}。

这个特殊情况已被弃用，因为现在当 @ref{1d9,,staticmethod()} 装饰器应用于抽象方法时它会被正确地标识为抽象的:

@example
class C(ABC):
    @@staticmethod
    @@abstractmethod
    def my_abstract_staticmethod(...):
        ...
@end example
@end deffn

@geindex abstractproperty() (在 abc 模块中)
@anchor{library/abc abc abstractproperty}@anchor{9c7}
@deffn {函数} @@abc.abstractproperty


3.3 版后已移除: 现在可以让 @ref{1d7,,property}, @code{property.getter()}, @code{property.setter()} 和 @code{property.deleter()} 配合 @ref{9c8,,abstractmethod()} 使用，使得此装饰器变得冗余。


内置 @ref{1d7,,property()} 的子类，指明一个抽象特性属性。

这个特例已被弃用，因为现在当 @ref{1d7,,property()} 装饰器应用于抽象方法时它会被正确地标识为抽象的:

@example
class C(ABC):
    @@property
    @@abstractmethod
    def my_abstract_property(self):
        ...
@end example

上面的例子定义了一个只读特征属性；你也可以通过适当地将一个或多个下层方法标记为抽象的来定义可读写的抽象特征属性:

@example
class C(ABC):
    @@property
    def x(self):
        ...

    @@x.setter
    @@abstractmethod
    def x(self, val):
        ...
@end example

如果只有某些组件是抽象的，则只需更新那些组件即可在子类中创建具体的特征属性:

@example
class D(C):
    @@C.x.setter
    def x(self, val):
        ...
@end example
@end deffn

@ref{4,,abc} 模块还提供了这些函数：

@geindex get_cache_token() (在 abc 模块中)
@anchor{library/abc abc get_cache_token}@anchor{811}
@deffn {函数} abc.get_cache_token ()

返回当前抽象基类的缓存令牌

此令牌是一个不透明对象（支持相等性测试），用于为虚子类标识抽象基类缓存的当前版本。 此令牌会在任何 ABC 上每次调用 @ref{9cb,,ABCMeta.register()} 时发生更改。


3.4 新版功能.

@end deffn

@subsubheading 备注


@node atexit --- 退出处理器,traceback --- 打印或检索堆栈回溯,abc --- 抽象基类,Python运行时服务
@anchor{library/atexit doc}@anchor{3633}@anchor{library/atexit atexit-exit-handlers}@anchor{3634}@anchor{library/atexit module-atexit}@anchor{c}
@subsection @code{atexit} --- 退出处理器


@geindex atexit (模块)


__________________________________________________________________


@ref{c,,atexit} 模块定义了清理函数的注册和反注册函数. 被注册的函数会在解释器正常终止时执行. @ref{c,,atexit} 会按照注册顺序的*逆序*执行; 如果你注册了 @code{A}, @code{B} 和 @code{C}, 那么在解释器终止时会依序执行 @code{C}, @code{B}, @code{A}.

@strong{注意:} 通过该模块注册的函数, 在程序被未被 Python 捕获的信号杀死时并不会执行, 在检测到 Python 内部致命错误以及调用了 @ref{16a3,,os._exit()} 时也不会执行.


在 3.7 版更改: 当配合 C-API 子解释器使用时，已注册函数是它们所注册解释器中的局部对象。


@geindex register() (在 atexit 模块中)
@anchor{library/atexit atexit register}@anchor{e7e}
@deffn {函数} atexit.register (func, *args, **kwargs)

将 @emph{func} 注册为终止时执行的函数.  任何传给 @emph{func} 的可选的参数都应当作为参数传给 @ref{e7e,,register()}.  可以多次注册同样的函数及参数.

在正常的程序终止时 (举例来说, 当调用了 @ref{cdb,,sys.exit()} 或是主模块的执行完成时), 所有注册过的函数都会以后进先出的顺序执行. 这样做是假定更底层的模块通常会比高层模块更早引入, 因此需要更晚清理.

如果在 exit 处理程序执行期间引发了异常，将会打印回溯信息 (除非引发的是 @ref{5f7,,SystemExit}) 并且异常信息会被保存。 在所有 exit 处理程序获得运行机会之后，所引发的最后一个异常会被重新引发。

这个函数返回 @emph{func} 对象，可以把它当作装饰器使用。
@end deffn

@geindex unregister() (在 atexit 模块中)
@anchor{library/atexit atexit unregister}@anchor{3635}
@deffn {函数} atexit.unregister (func)

从解释器关闭前要运行的函数列表中移除 @emph{func}。 在调用 @ref{3635,,unregister()} 之后，当解释器关闭时会确保 @emph{func} 不会被调用，即使它被多次注册。 如果 @emph{func} 之前没有被注册，@ref{3635,,unregister()} 会静默地不做任何操作。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{de,,readline}

使用 @ref{c,,atexit} 读写 @ref{de,,readline} 历史文件的有用的例子。
@end table


@menu
* atexit 示例:: 

@end menu

@node atexit 示例,,,atexit --- 退出处理器
@anchor{library/atexit atexit-example}@anchor{3636}@anchor{library/atexit id1}@anchor{3637}
@subsubsection @code{atexit} 示例


以下简单例子演示了一个模块在被导入时如何从文件初始化一个计数器，并在程序终结时自动保存计数器的更新值，此操作不依赖于应用在终结时对此模块进行显式调用。:

@example
try:
    with open("counterfile") as infile:
        _count = int(infile.read())
except FileNotFoundError:
    _count = 0

def incrcounter(n):
    global _count
    _count = _count + n

def savecounter():
    with open("counterfile", "w") as outfile:
        outfile.write("%d" % _count)

import atexit
atexit.register(savecounter)
@end example

位置和关键字参数也可传入 @ref{e7e,,register()} 以便传递给被调用的已注册函数:

@example
def goodbye(name, adjective):
    print('Goodbye, %s, it was %s to meet you.' % (name, adjective))

import atexit
atexit.register(goodbye, 'Donny', 'nice')

# or:
atexit.register(goodbye, adjective='nice', name='Donny')
@end example

作为 @ref{283,,decorator}: 使用:

@example
import atexit

@@atexit.register
def goodbye():
    print("You are now leaving the Python sector.")
@end example

只有在函数不需要任何参数调用时才能工作.

@node traceback --- 打印或检索堆栈回溯,__future__ --- Future 语句定义,atexit --- 退出处理器,Python运行时服务
@anchor{library/traceback doc}@anchor{3638}@anchor{library/traceback module-traceback}@anchor{113}@anchor{library/traceback traceback-print-or-retrieve-a-stack-traceback}@anchor{3639}
@subsection @code{traceback} --- 打印或检索堆栈回溯


@geindex traceback (模块)

@strong{源代码：} Lib/traceback.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/traceback.py}


__________________________________________________________________


该模块提供了一个标准接口来提取、格式化和打印 Python 程序的堆栈跟踪结果。它完全模仿Python 解释器在打印堆栈跟踪结果时的行为。当您想要在程序控制下打印堆栈跟踪结果时，例如在“封装”解释器时，这是非常有用的。

@geindex 对象; traceback

这个模块使用 traceback 对象 —— 这是存储在 @ref{34d7,,sys.last_traceback} 中的对象类型变量，并作为 @ref{c58,,sys.exc_info()} 的第三项被返回。

这个模块定义了以下函数：

@geindex print_tb() (在 traceback 模块中)
@anchor{library/traceback traceback print_tb}@anchor{773}
@deffn {函数} traceback.print_tb (tb, limit=None, file=None)

Print up to @emph{limit} stack trace entries from traceback object @emph{tb} (starting
from the caller's frame) if @emph{limit} is positive.  Otherwise, print the last
@code{abs(limit)} entries.  If @emph{limit} is omitted or @code{None}, all entries are
printed.  If @emph{file} is omitted or @code{None}, the output goes to
@code{sys.stderr}; otherwise it should be an open file or file-like object to
receive the output.


在 3.5 版更改: Added negative @emph{limit} support.

@end deffn

@geindex print_exception() (在 traceback 模块中)
@anchor{library/traceback traceback print_exception}@anchor{2047}
@deffn {函数} traceback.print_exception (etype, value, tb, limit=None, file=None, chain=True)

打印回溯对象 @emph{tb} 到 @emph{file} 的异常信息和整个堆栈回溯。这和 @ref{773,,print_tb()} 比有以下方面不同：


@itemize *

@item 
如果 @emph{tb} 不为 @code{None}，它将打印头部 @code{Traceback (most recent call last):}

@item 
it prints the exception @emph{etype} and @emph{value} after the stack trace
@end itemize

@geindex ^ (caret); marker


@itemize *

@item 
if @emph{type(value)} is @ref{452,,SyntaxError} and @emph{value} has the appropriate
format, it prints the line where the syntax error occurred with a caret
indicating the approximate position of the error.
@end itemize

The optional @emph{limit} argument has the same meaning as for @ref{773,,print_tb()}.
If @emph{chain} is true (the default), then chained exceptions (the
@code{__cause__} or @code{__context__} attributes of the exception) will be
printed as well, like the interpreter itself does when printing an unhandled
exception.


在 3.5 版更改: The @emph{etype} argument is ignored and inferred from the type of @emph{value}.

@end deffn

@geindex print_exc() (在 traceback 模块中)
@anchor{library/traceback traceback print_exc}@anchor{363a}
@deffn {函数} traceback.print_exc (limit=None, file=None, chain=True)

This is a shorthand for @code{print_exception(*sys.exc_info(), limit, file,
chain)}.
@end deffn

@geindex print_last() (在 traceback 模块中)
@anchor{library/traceback traceback print_last}@anchor{363b}
@deffn {函数} traceback.print_last (limit=None, file=None, chain=True)

This is a shorthand for @code{print_exception(sys.last_type, sys.last_value,
sys.last_traceback, limit, file, chain)}.  In general it will work only
after an exception has reached an interactive prompt (see
@ref{c53,,sys.last_type}).
@end deffn

@geindex print_stack() (在 traceback 模块中)
@anchor{library/traceback traceback print_stack}@anchor{774}
@deffn {函数} traceback.print_stack (f=None, limit=None, file=None)

Print up to @emph{limit} stack trace entries (starting from the invocation
point) if @emph{limit} is positive.  Otherwise, print the last @code{abs(limit)}
entries.  If @emph{limit} is omitted or @code{None}, all entries are printed.
The optional @emph{f} argument can be used to specify an alternate stack frame
to start.  The optional @emph{file} argument has the same meaning as for
@ref{773,,print_tb()}.


在 3.5 版更改: Added negative @emph{limit} support.

@end deffn

@geindex extract_tb() (在 traceback 模块中)
@anchor{library/traceback traceback extract_tb}@anchor{363c}
@deffn {函数} traceback.extract_tb (tb, limit=None)

Return a @ref{771,,StackSummary} object representing a list of "pre-processed"
stack trace entries extracted from the traceback object @emph{tb}.  It is useful
for alternate formatting of stack traces.  The optional @emph{limit} argument has
the same meaning as for @ref{773,,print_tb()}.  A "pre-processed" stack trace
entry is a @ref{772,,FrameSummary} object containing attributes
@code{filename}, @code{lineno},
@code{name}, and @code{line} representing the
information that is usually printed for a stack trace.  The
@code{line} is a string with leading and trailing
whitespace stripped; if the source is not available it is @code{None}.
@end deffn

@geindex extract_stack() (在 traceback 模块中)
@anchor{library/traceback traceback extract_stack}@anchor{363d}
@deffn {函数} traceback.extract_stack (f=None, limit=None)

Extract the raw traceback from the current stack frame.  The return value has
the same format as for @ref{363c,,extract_tb()}.  The optional @emph{f} and @emph{limit}
arguments have the same meaning as for @ref{774,,print_stack()}.
@end deffn

@geindex format_list() (在 traceback 模块中)
@anchor{library/traceback traceback format_list}@anchor{363e}
@deffn {函数} traceback.format_list (extracted_list)

Given a list of tuples or @ref{772,,FrameSummary} objects as returned by
@ref{363c,,extract_tb()} or @ref{363d,,extract_stack()}, return a list of strings ready
for printing.  Each string in the resulting list corresponds to the item with
the same index in the argument list.  Each string ends in a newline; the
strings may contain internal newlines as well, for those items whose source
text line is not @code{None}.
@end deffn

@geindex format_exception_only() (在 traceback 模块中)
@anchor{library/traceback traceback format_exception_only}@anchor{3292}
@deffn {函数} traceback.format_exception_only (etype, value)

Format the exception part of a traceback.  The arguments are the exception
type and value such as given by @code{sys.last_type} and @code{sys.last_value}.
The return value is a list of strings, each ending in a newline.  Normally,
the list contains a single string; however, for @ref{452,,SyntaxError}
exceptions, it contains several lines that (when printed) display detailed
information about where the syntax error occurred.  The message indicating
which exception occurred is the always last string in the list.
@end deffn

@geindex format_exception() (在 traceback 模块中)
@anchor{library/traceback traceback format_exception}@anchor{363f}
@deffn {函数} traceback.format_exception (etype, value, tb, limit=None, chain=True)

Format a stack trace and the exception information.  The arguments  have the
same meaning as the corresponding arguments to @ref{2047,,print_exception()}.  The
return value is a list of strings, each ending in a newline and some
containing internal newlines.  When these lines are concatenated and printed,
exactly the same text is printed as does @ref{2047,,print_exception()}.


在 3.5 版更改: The @emph{etype} argument is ignored and inferred from the type of @emph{value}.

@end deffn

@geindex format_exc() (在 traceback 模块中)
@anchor{library/traceback traceback format_exc}@anchor{3640}
@deffn {函数} traceback.format_exc (limit=None, chain=True)

This is like @code{print_exc(limit)} but returns a string instead of printing to
a file.
@end deffn

@geindex format_tb() (在 traceback 模块中)
@anchor{library/traceback traceback format_tb}@anchor{3591}
@deffn {函数} traceback.format_tb (tb, limit=None)

A shorthand for @code{format_list(extract_tb(tb, limit))}.
@end deffn

@geindex format_stack() (在 traceback 模块中)
@anchor{library/traceback traceback format_stack}@anchor{3641}
@deffn {函数} traceback.format_stack (f=None, limit=None)

A shorthand for @code{format_list(extract_stack(f, limit))}.
@end deffn

@geindex clear_frames() (在 traceback 模块中)
@anchor{library/traceback traceback clear_frames}@anchor{8eb}
@deffn {函数} traceback.clear_frames (tb)

Clears the local variables of all the stack frames in a traceback @emph{tb}
by calling the @code{clear()} method of each frame object.


3.4 新版功能.

@end deffn

@geindex walk_stack() (在 traceback 模块中)
@anchor{library/traceback traceback walk_stack}@anchor{76e}
@deffn {函数} traceback.walk_stack (f)

Walk a stack following @code{f.f_back} from the given frame, yielding the frame
and line number for each frame. If @emph{f} is @code{None}, the current stack is
used. This helper is used with @ref{3642,,StackSummary.extract()}.


3.5 新版功能.

@end deffn

@geindex walk_tb() (在 traceback 模块中)
@anchor{library/traceback traceback walk_tb}@anchor{76f}
@deffn {函数} traceback.walk_tb (tb)

Walk a traceback following @code{tb_next} yielding the frame and line number
for each frame. This helper is used with @ref{3642,,StackSummary.extract()}.


3.5 新版功能.

@end deffn

The module also defines the following classes:

@menu
* TracebackException Objects:: 
* StackSummary Objects:: 
* FrameSummary Objects:: 
* Traceback Examples:: 

@end menu

@node TracebackException Objects,StackSummary Objects,,traceback --- 打印或检索堆栈回溯
@anchor{library/traceback tracebackexception-objects}@anchor{3643}
@subsubsection @code{TracebackException} Objects



3.5 新版功能.


@ref{770,,TracebackException} objects are created from actual exceptions to
capture data for later printing in a lightweight fashion.

@geindex TracebackException (traceback 中的类)
@anchor{library/traceback traceback TracebackException}@anchor{770}
@deffn {类} traceback.TracebackException (exc_type, exc_value, exc_traceback, *, limit=None, lookup_lines=True, capture_locals=False)

Capture an exception for later rendering. @emph{limit}, @emph{lookup_lines} and
@emph{capture_locals} are as for the @ref{771,,StackSummary} class.

Note that when locals are captured, they are also shown in the traceback.

@geindex __cause__ (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException __cause__}@anchor{3644}
@deffn {属性} __cause__

A @ref{770,,TracebackException} of the original @code{__cause__}.
@end deffn

@geindex __context__ (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException __context__}@anchor{3645}
@deffn {属性} __context__

A @ref{770,,TracebackException} of the original @code{__context__}.
@end deffn

@geindex __suppress_context__ (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException __suppress_context__}@anchor{3646}
@deffn {属性} __suppress_context__

The @code{__suppress_context__} value from the original exception.
@end deffn

@geindex stack (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException stack}@anchor{3647}
@deffn {属性} stack

A @ref{771,,StackSummary} representing the traceback.
@end deffn

@geindex exc_type (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException exc_type}@anchor{3648}
@deffn {属性} exc_type

The class of the original traceback.
@end deffn

@geindex filename (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException filename}@anchor{3649}
@deffn {属性} filename

For syntax errors - the file name where the error occurred.
@end deffn

@geindex lineno (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException lineno}@anchor{364a}
@deffn {属性} lineno

For syntax errors - the line number where the error occurred.
@end deffn

@geindex text (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException text}@anchor{364b}
@deffn {属性} text

For syntax errors - the text where the error occurred.
@end deffn

@geindex offset (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException offset}@anchor{364c}
@deffn {属性} offset

For syntax errors - the offset into the text where the error occurred.
@end deffn

@geindex msg (traceback.TracebackException 属性)
@anchor{library/traceback traceback TracebackException msg}@anchor{364d}
@deffn {属性} msg

For syntax errors - the compiler error message.
@end deffn

@geindex from_exception() (traceback.TracebackException 类方法)
@anchor{library/traceback traceback TracebackException from_exception}@anchor{364e}
@deffn {方法} classmethod from_exception (exc, *, limit=None, lookup_lines=True, capture_locals=False)

Capture an exception for later rendering. @emph{limit}, @emph{lookup_lines} and
@emph{capture_locals} are as for the @ref{771,,StackSummary} class.

Note that when locals are captured, they are also shown in the traceback.
@end deffn

@geindex format() (traceback.TracebackException 方法)
@anchor{library/traceback traceback TracebackException format}@anchor{364f}
@deffn {方法} format (*, chain=True)

Format the exception.

If @emph{chain} is not @code{True}, @code{__cause__} and @code{__context__} will not
be formatted.

The return value is a generator of strings, each ending in a newline and
some containing internal newlines. @ref{2047,,print_exception()}
is a wrapper around this method which just prints the lines to a file.

The message indicating which exception occurred is always the last
string in the output.
@end deffn

@geindex format_exception_only() (traceback.TracebackException 方法)
@anchor{library/traceback traceback TracebackException format_exception_only}@anchor{3650}
@deffn {方法} format_exception_only ()

Format the exception part of the traceback.

The return value is a generator of strings, each ending in a newline.

Normally, the generator emits a single string; however, for
@ref{452,,SyntaxError} exceptions, it emits several lines that (when
printed) display detailed information about where the syntax
error occurred.

The message indicating which exception occurred is always the last
string in the output.
@end deffn
@end deffn

@node StackSummary Objects,FrameSummary Objects,TracebackException Objects,traceback --- 打印或检索堆栈回溯
@anchor{library/traceback stacksummary-objects}@anchor{3651}
@subsubsection @code{StackSummary} Objects



3.5 新版功能.


@ref{771,,StackSummary} objects represent a call stack ready for formatting.

@geindex StackSummary (traceback 中的类)
@anchor{library/traceback traceback StackSummary}@anchor{771}
@deffn {类} traceback.StackSummary

@geindex extract() (traceback.StackSummary 类方法)
@anchor{library/traceback traceback StackSummary extract}@anchor{3642}
@deffn {方法} classmethod extract (frame_gen, *, limit=None, lookup_lines=True, capture_locals=False)

Construct a @ref{771,,StackSummary} object from a frame generator (such as
is returned by @ref{76e,,walk_stack()} or
@ref{76f,,walk_tb()}).

If @emph{limit} is supplied, only this many frames are taken from @emph{frame_gen}.
If @emph{lookup_lines} is @code{False}, the returned @ref{772,,FrameSummary}
objects will not have read their lines in yet, making the cost of
creating the @ref{771,,StackSummary} cheaper (which may be valuable if it
may not actually get formatted). If @emph{capture_locals} is @code{True} the
local variables in each @ref{772,,FrameSummary} are captured as object
representations.
@end deffn

@geindex from_list() (traceback.StackSummary 类方法)
@anchor{library/traceback traceback StackSummary from_list}@anchor{3652}
@deffn {方法} classmethod from_list (a_list)

Construct a @ref{771,,StackSummary} object from a supplied list of
@ref{772,,FrameSummary} objects or old-style list of tuples.  Each tuple
should be a 4-tuple with filename, lineno, name, line as the elements.
@end deffn

@geindex format() (traceback.StackSummary 方法)
@anchor{library/traceback traceback StackSummary format}@anchor{3653}
@deffn {方法} format ()

Returns a list of strings ready for printing.  Each string in the
resulting list corresponds to a single frame from the stack.
Each string ends in a newline; the strings may contain internal
newlines as well, for those items with source text lines.

For long sequences of the same frame and line, the first few
repetitions are shown, followed by a summary line stating the exact
number of further repetitions.


在 3.6 版更改: Long sequences of repeated frames are now abbreviated.

@end deffn
@end deffn

@node FrameSummary Objects,Traceback Examples,StackSummary Objects,traceback --- 打印或检索堆栈回溯
@anchor{library/traceback framesummary-objects}@anchor{3654}
@subsubsection @code{FrameSummary} Objects



3.5 新版功能.


@ref{772,,FrameSummary} objects represent a single frame in a traceback.

@geindex FrameSummary (traceback 中的类)
@anchor{library/traceback traceback FrameSummary}@anchor{772}
@deffn {类} traceback.FrameSummary (filename, lineno, name, lookup_line=True, locals=None, line=None)

Represent a single frame in the traceback or stack that is being formatted
or printed. It may optionally have a stringified version of the frames
locals included in it. If @emph{lookup_line} is @code{False}, the source code is not
looked up until the @ref{772,,FrameSummary} has the @code{line}
attribute accessed (which also happens when casting it to a tuple).
@code{line} may be directly provided, and will prevent line
lookups happening at all. @emph{locals} is an optional local variable
dictionary, and if supplied the variable representations are stored in the
summary for later display.
@end deffn

@node Traceback Examples,,FrameSummary Objects,traceback --- 打印或检索堆栈回溯
@anchor{library/traceback traceback-example}@anchor{3655}@anchor{library/traceback traceback-examples}@anchor{3656}
@subsubsection Traceback Examples


This simple example implements a basic read-eval-print loop, similar to (but
less useful than) the standard Python interactive interpreter loop.  For a more
complete implementation of the interpreter loop, refer to the @ref{1b,,code}
module.

@example
import sys, traceback

def run_user_code(envdir):
    source = input(">>> ")
    try:
        exec(source, envdir)
    except Exception:
        print("Exception in user code:")
        print("-"*60)
        traceback.print_exc(file=sys.stdout)
        print("-"*60)

envdir = @{@}
while True:
    run_user_code(envdir)
@end example

The following example demonstrates the different ways to print and format the
exception and traceback:

@example
import sys, traceback

def lumberjack():
    bright_side_of_death()

def bright_side_of_death():
    return tuple()[0]

try:
    lumberjack()
except IndexError:
    exc_type, exc_value, exc_traceback = sys.exc_info()
    print("*** print_tb:")
    traceback.print_tb(exc_traceback, limit=1, file=sys.stdout)
    print("*** print_exception:")
    # exc_type below is ignored on 3.5 and later
    traceback.print_exception(exc_type, exc_value, exc_traceback,
                              limit=2, file=sys.stdout)
    print("*** print_exc:")
    traceback.print_exc(limit=2, file=sys.stdout)
    print("*** format_exc, first and last line:")
    formatted_lines = traceback.format_exc().splitlines()
    print(formatted_lines[0])
    print(formatted_lines[-1])
    print("*** format_exception:")
    # exc_type below is ignored on 3.5 and later
    print(repr(traceback.format_exception(exc_type, exc_value,
                                          exc_traceback)))
    print("*** extract_tb:")
    print(repr(traceback.extract_tb(exc_traceback)))
    print("*** format_tb:")
    print(repr(traceback.format_tb(exc_traceback)))
    print("*** tb_lineno:", exc_traceback.tb_lineno)
@end example

The output for the example would look similar to this:

@example
*** print_tb:
  File "<doctest...>", line 10, in <module>
    lumberjack()
*** print_exception:
Traceback (most recent call last):
  File "<doctest...>", line 10, in <module>
    lumberjack()
  File "<doctest...>", line 4, in lumberjack
    bright_side_of_death()
IndexError: tuple index out of range
*** print_exc:
Traceback (most recent call last):
  File "<doctest...>", line 10, in <module>
    lumberjack()
  File "<doctest...>", line 4, in lumberjack
    bright_side_of_death()
IndexError: tuple index out of range
*** format_exc, first and last line:
Traceback (most recent call last):
IndexError: tuple index out of range
*** format_exception:
['Traceback (most recent call last):\n',
 '  File "<doctest...>", line 10, in <module>\n    lumberjack()\n',
 '  File "<doctest...>", line 4, in lumberjack\n    bright_side_of_death()\n',
 '  File "<doctest...>", line 7, in bright_side_of_death\n    return tuple()[0]\n',
 'IndexError: tuple index out of range\n']
*** extract_tb:
[<FrameSummary file <doctest...>, line 10 in <module>>,
 <FrameSummary file <doctest...>, line 4 in lumberjack>,
 <FrameSummary file <doctest...>, line 7 in bright_side_of_death>]
*** format_tb:
['  File "<doctest...>", line 10, in <module>\n    lumberjack()\n',
 '  File "<doctest...>", line 4, in lumberjack\n    bright_side_of_death()\n',
 '  File "<doctest...>", line 7, in bright_side_of_death\n    return tuple()[0]\n']
*** tb_lineno: 10
@end example

The following example shows the different ways to print and format the stack:

@example
>>> import traceback
>>> def another_function():
...     lumberstack()
...
>>> def lumberstack():
...     traceback.print_stack()
...     print(repr(traceback.extract_stack()))
...     print(repr(traceback.format_stack()))
...
>>> another_function()
  File "<doctest>", line 10, in <module>
    another_function()
  File "<doctest>", line 3, in another_function
    lumberstack()
  File "<doctest>", line 6, in lumberstack
    traceback.print_stack()
[('<doctest>', 10, '<module>', 'another_function()'),
 ('<doctest>', 3, 'another_function', 'lumberstack()'),
 ('<doctest>', 7, 'lumberstack', 'print(repr(traceback.extract_stack()))')]
['  File "<doctest>", line 10, in <module>\n    another_function()\n',
 '  File "<doctest>", line 3, in another_function\n    lumberstack()\n',
 '  File "<doctest>", line 8, in lumberstack\n    print(repr(traceback.format_stack()))\n']
@end example

This last example demonstrates the final few formatting functions:

@example
>>> import traceback
>>> traceback.format_list([('spam.py', 3, '<module>', 'spam.eggs()'),
...                        ('eggs.py', 42, 'eggs', 'return "bacon"')])
['  File "spam.py", line 3, in <module>\n    spam.eggs()\n',
 '  File "eggs.py", line 42, in eggs\n    return "bacon"\n']
>>> an_error = IndexError('tuple index out of range')
>>> traceback.format_exception_only(type(an_error), an_error)
['IndexError: tuple index out of range\n']
@end example

@node __future__ --- Future 语句定义,gc --- 垃圾回收器接口,traceback --- 打印或检索堆栈回溯,Python运行时服务
@anchor{library/__future__ doc}@anchor{3657}@anchor{library/__future__ future-future-statement-definitions}@anchor{3658}@anchor{library/__future__ module-__future__}@anchor{0}
@subsection @code{__future__} --- Future 语句定义


@geindex __future__ (模块)

@strong{源代码：} Lib/__future__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/__future__.py}


__________________________________________________________________


@ref{0,,__future__} 是一个真正的模块，这主要有 3 个原因：


@itemize *

@item 
避免混淆已有的分析 import 语句并查找 import 的模块的工具。

@item 
确保 @ref{1526,,future 语句} 在 2.1 之前的版本运行时至少能抛出 runtime 异常（import @ref{0,,__future__} 会失败，因为 2.1 版本之前没有这个模块）。

@item 
当引入不兼容的修改时，可以记录其引入的时间以及强制使用的时间。这是一种可执行的文档，并且可以通过 import @ref{0,,__future__} 来做程序性的检查。
@end itemize

@code{__future__.py} 中的每一条语句都是以下格式的：

@example
FeatureName = _Feature(OptionalRelease, MandatoryRelease,
                       CompilerFlag)
@end example

通常 @emph{OptionalRelease} 要比 @emph{MandatoryRelease} 小，并且都是和 @ref{b13,,sys.version_info} 格式一致的 5 元素元组。

@example
(PY_MAJOR_VERSION, # the 2 in 2.1.0a3; an int
 PY_MINOR_VERSION, # the 1; an int
 PY_MICRO_VERSION, # the 0; an int
 PY_RELEASE_LEVEL, # "alpha", "beta", "candidate" or "final"; string
 PY_RELEASE_SERIAL # the 3; an int
)
@end example

@emph{OptionalRelease} 记录了一个特性首次发布时的 Python 版本。

在 @emph{MandatoryRelases} 还没有发布时，@emph{MandatoryRelease} 表示该特性会变成语言的一部分的预测时间。

其他情况下，@emph{MandatoryRelease} 用来记录这个特性是何时成为语言的一部分的。从该版本往后，使用该特性将不需要 future 语句，不过很多人还是会加上对应的 import。

@emph{MandatoryRelease} 也可能是 @code{None}, 表示这个特性已经被撤销。

@code{_Feature} 类的实例有两个对应的方法，@code{getOptionalRelease()} 和 @code{getMandatoryRelease()}。

@emph{CompilerFlag} 是一个（位）标记，对于动态编译的代码，需要将这个标记作为第四个参数传入内建函数 @ref{1b4,,compile()} 中以开启对应的特性。这个标记存储在 @code{_Feature} 类实例的 @code{compiler_flag} 属性中。

@ref{0,,__future__} 中不会删除特性的描述。从 Python 2.1 中首次加入以来，通过这种方式引入了以下特性：


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

特性

@tab

可选版本

@tab

强制加入版本

@tab

效果

@item

nested_scopes

@tab

2.1.0b1

@tab

2.2

@tab

@geindex Python 提高建议; PEP 227
PEP 227@footnote{https://www.python.org/dev/peps/pep-0227}: @emph{静态嵌套作用域}

@item

generators

@tab

2.2.0a1

@tab

2.3

@tab

@geindex Python 提高建议; PEP 255
PEP 255@footnote{https://www.python.org/dev/peps/pep-0255}: @emph{简单生成器}

@item

division

@tab

2.2.0a2

@tab

3.0

@tab

@geindex Python 提高建议; PEP 238
PEP 238@footnote{https://www.python.org/dev/peps/pep-0238}: @emph{修改除法运算符}

@item

absolute_import

@tab

2.5.0a1

@tab

3.0

@tab

@geindex Python 提高建议; PEP 328
PEP 328@footnote{https://www.python.org/dev/peps/pep-0328}: @emph{导入：多行与绝对/相对}

@item

with_statement

@tab

2.5.0a1

@tab

2.6

@tab

@geindex Python 提高建议; PEP 343
PEP 343@footnote{https://www.python.org/dev/peps/pep-0343}: * "with" 语句*

@item

print_function

@tab

2.6.0a2

@tab

3.0

@tab

@geindex Python 提高建议; PEP 3105
PEP 3105@footnote{https://www.python.org/dev/peps/pep-3105}: @emph{print 改为函数}

@item

unicode_literals

@tab

2.6.0a2

@tab

3.0

@tab

@geindex Python 提高建议; PEP 3112
PEP 3112@footnote{https://www.python.org/dev/peps/pep-3112}: @emph{Python 3000 中的字节字面值}

@item

generator_stop

@tab

3.5.0b1

@tab

3.7

@tab

@geindex Python 提高建议; PEP 479
PEP 479@footnote{https://www.python.org/dev/peps/pep-0479}: @emph{在生成器中处理 StopIteration}

@item

annotations

@tab

3.7.0b1

@tab

4.0

@tab

@geindex Python 提高建议; PEP 563
PEP 563@footnote{https://www.python.org/dev/peps/pep-0563}:
@emph{Postponed evaluation of annotations}

@end multitable


@c XXX Adding a new entry?  Remember to update simple_stmts.rst, too.


@subsubheading 参见



@table @asis

@item @ref{1526,,future 语句}

编译器怎样处理 future import。
@end table


@node gc --- 垃圾回收器接口,inspect --- 检查对象,__future__ --- Future 语句定义,Python运行时服务
@anchor{library/gc doc}@anchor{3659}@anchor{library/gc gc-garbage-collector-interface}@anchor{365a}@anchor{library/gc module-gc}@anchor{86}
@subsection @code{gc} --- 垃圾回收器接口


@geindex gc (模块)


__________________________________________________________________


此模块提供可选的垃圾回收器的接口，提供的功能包括：关闭收集器、调整收集频率、设置调试选项。它同时提供对回收器找到但是无法释放的不可达对象的访问。由于 Python 使用了带有引用计数的回收器，如果你确定你的程序不会产生循环引用，你可以关闭回收器。可以通过调用 @code{gc.disable()} 关闭自动垃圾回收。若要调试一个存在内存泄漏的程序，调用 @code{gc.set_debug(gc.DEBUG_LEAK)} ；需要注意的是，它包含 @code{gc.DEBUG_SAVEALL} ，使得被垃圾回收的对象会被存放在 gc.garbage 中以待检查。

@ref{86,,gc} 模块提供下列函数：

@geindex enable() (在 gc 模块中)
@anchor{library/gc gc enable}@anchor{365b}
@deffn {函数} gc.enable ()

启用自动垃圾回收
@end deffn

@geindex disable() (在 gc 模块中)
@anchor{library/gc gc disable}@anchor{365c}
@deffn {函数} gc.disable ()

停用自动垃圾回收
@end deffn

@geindex isenabled() (在 gc 模块中)
@anchor{library/gc gc isenabled}@anchor{365d}
@deffn {函数} gc.isenabled ()

如果启用了自动回收则返回 @code{True}。
@end deffn

@geindex collect() (在 gc 模块中)
@anchor{library/gc gc collect}@anchor{22e}
@deffn {函数} gc.collect (generation=2)

若被调用时不包含参数，则启动完全的垃圾回收。可选的参数 @emph{generation} 可以是一个整数，指明需要回收哪一代（从 0 到 2 ）的垃圾。当参数 @emph{generation} 无效时，会引发 @ref{1fb,,ValueError} 异常。返回发现的不可达对象的数目。

每当运行完整收集或最高代 (2) 收集时，为多个内置类型所维护的空闲列表会被清空。 由于特定类型特别是 @ref{187,,float} 的实现，在某些空闲列表中并非所有项都会被释放。
@end deffn

@geindex set_debug() (在 gc 模块中)
@anchor{library/gc gc set_debug}@anchor{365e}
@deffn {函数} gc.set_debug (flags)

设置垃圾回收器的调试标识位。调试信息会被写入 @code{sys.stderr} 。此文档末尾列出了各个标志位及其含义；可以使用位操作对多个标志位进行设置以控制调试器。
@end deffn

@geindex get_debug() (在 gc 模块中)
@anchor{library/gc gc get_debug}@anchor{365f}
@deffn {函数} gc.get_debug ()

返回当前调试标识位。
@end deffn

@geindex get_objects() (在 gc 模块中)
@anchor{library/gc gc get_objects}@anchor{1cd}
@deffn {函数} gc.get_objects (generation=None)

返回一个收集器所跟踪的所有对象的列表，所返回的列表除外。 如果 @emph{generation} 不为 None，则只返回收集器所跟踪的属于该生成的对象。


在 3.8 版更改: 新的 @emph{generation} 形参。

@end deffn

@geindex get_stats() (在 gc 模块中)
@anchor{library/gc gc get_stats}@anchor{848}
@deffn {函数} gc.get_stats ()

返回一个包含三个字典对象的列表，每个字典分别包含对应代的从解释器开始运行的垃圾回收统计数据。字典的键的数目在将来可能发生改变，目前每个字典包含以下内容：


@itemize *

@item 
@code{collections} 是该代被回收的次数；

@item 
@code{collected} 是该代中被回收的对象总数；

@item 
@code{uncollectable} 是在这一代中被发现无法收集的对象总数 （因此被移动到 @ref{b39,,garbage} 列表中）。
@end itemize


3.4 新版功能.

@end deffn

@geindex set_threshold() (在 gc 模块中)
@anchor{library/gc gc set_threshold}@anchor{3660}
@deffn {函数} gc.set_threshold (threshold0[, threshold1[, threshold2]])

设置垃圾回收阈值（收集频率）。 将 @emph{threshold0} 设为零会禁用回收。

垃圾回收器把所有对象分类为三代，取决于对象幸存于多少次垃圾回收。新创建的对象会被放在最年轻代（第 @code{0} 代）。如果一个对象幸存于一次垃圾回收，则该对象会被放入下一代。第 @code{2} 代是最老的一代，因此这一代的对象幸存于垃圾回收后，仍会留在第 @code{2} 代。为了判定何时需要进行垃圾回收，垃圾回收器会跟踪上一次回收后，分配和释放的对象的数目。当分配对象的数量减去释放对象的数量大于阈值 @emph{threshold0} 时，回收器开始进行垃圾回收。起初只有第 @code{0} 代会被检查。当上一次第 @code{1} 代被检查后，第 @code{0} 代被检查的次数多于阈值 @emph{threshold1} 时，第 @code{1} 代也会被检查。相似的， @emph{threshold2} 设置了触发第 @code{2} 代被垃圾回收的第 @code{1} 代被垃圾回收的次数。
@end deffn

@geindex get_count() (在 gc 模块中)
@anchor{library/gc gc get_count}@anchor{3661}
@deffn {函数} gc.get_count ()

将当前回收计数以形为 @code{(count0, count1, count2)} 的元组返回。
@end deffn

@geindex get_threshold() (在 gc 模块中)
@anchor{library/gc gc get_threshold}@anchor{3662}
@deffn {函数} gc.get_threshold ()

将当前回收阈值以形为 @code{(threshold0, threshold1, threshold2)} 的元组返回。
@end deffn

@geindex get_referrers() (在 gc 模块中)
@anchor{library/gc gc get_referrers}@anchor{3564}
@deffn {函数} gc.get_referrers (*objs)

返回直接引用任意一个 @emph{ojbs} 的对象列表。这个函数只定位支持垃圾回收的容器；引用了其它对象但不支持垃圾回收的扩展类型不会被找到。

需要注意的是，已经解除对 @emph{objs} 引用的对象，但仍存在于循环引用中未被回收时，仍然会被作为引用者出现在返回的列表当中。若要获取当前正在引用 @emph{objs} 的对象，需要调用 @ref{22e,,collect()} 然后再调用 @ref{3564,,get_referrers()} 。

在使用 @ref{3564,,get_referrers()} 返回的对象时必须要小心，因为其中一些对象可能仍在构造中因此处于暂时的无效状态。不要把 @ref{3564,,get_referrers()} 用于调试以外的其它目的。
@end deffn

@geindex get_referents() (在 gc 模块中)
@anchor{library/gc gc get_referents}@anchor{3663}
@deffn {函数} gc.get_referents (*objs)

返回被任意一个参数中的对象直接引用的对象的列表。返回的被引用对象是被参数中的对象的C语言级别方法（若存在） @ref{3664,,tp_traverse} 访问到的对象，可能不是所有的实际直接可达对象。只有支持垃圾回收的对象支持 @ref{3664,,tp_traverse}  方法，并且此方法只会在需要访问涉及循环引用的对象时使用。因此，可以有以下例子：一个整数对其中一个参数是直接可达的，这个整数有可能出现或不出现在返回的结果列表当中。
@end deffn

@geindex is_tracked() (在 gc 模块中)
@anchor{library/gc gc is_tracked}@anchor{c9c}
@deffn {函数} gc.is_tracked (obj)

当对象正在被垃圾回收器监控时返回 @code{True} ，否则返回 @code{False} 。一般来说，原子类的实例不会被监控，而非原子类（如容器、用户自定义的对象）会被监控。然而，会有一些特定类型的优化以便减少垃圾回收器在简单实例（如只含有原子性的键和值的字典）上的消耗。

@example
>>> gc.is_tracked(0)
False
>>> gc.is_tracked("a")
False
>>> gc.is_tracked([])
True
>>> gc.is_tracked(@{@})
False
>>> gc.is_tracked(@{"a": 1@})
False
>>> gc.is_tracked(@{"a": []@})
True
@end example


3.1 新版功能.

@end deffn

@geindex freeze() (在 gc 模块中)
@anchor{library/gc gc freeze}@anchor{384}
@deffn {函数} gc.freeze ()

冻结 gc 所跟踪的所有对象 —— 将它们移至永久代并忽略所有未来的集合。 这可以在 POSIX fork() 调用之前使用以便令对写入复制保持友好或加速收集。 并且在 POSIX fork() 调用之前的收集也可以释放页面以供未来分配，这也可能导致写入时复制，因此建议在主进程中禁用 gc 并在 fork 之前冻结，而在子进程中启用 gc。


3.7 新版功能.

@end deffn

@geindex unfreeze() (在 gc 模块中)
@anchor{library/gc gc unfreeze}@anchor{385}
@deffn {函数} gc.unfreeze ()

解冻永久代中的对象，并将它们放回到年老代中。


3.7 新版功能.

@end deffn

@geindex get_freeze_count() (在 gc 模块中)
@anchor{library/gc gc get_freeze_count}@anchor{386}
@deffn {函数} gc.get_freeze_count ()

返回永久代中的对象数量。


3.7 新版功能.

@end deffn

提供以下变量仅供只读访问（你可以修改但不应该重绑定它们）：

@geindex garbage() (在 gc 模块中)
@anchor{library/gc gc garbage}@anchor{b39}
@deffn {数据} gc.garbage

一个回收器发现不可达而又无法被释放的对象（不可回收对象）列表。 从 Python 3.4 开始，该列表在大多数时候都应该是空的，除非使用了含有非 @code{NULL} @code{tp_del} 空位的 C 扩展类型的实例。

如果设置了 @ref{3665,,DEBUG_SAVEALL} ，则所有不可访问对象将被添加至该列表而不会被释放。


在 3.2 版更改: 当 @ref{75d,,interpreter shutdown} 即解释器关闭时，若此列表非空，会产生 @ref{4ca,,ResourceWarning} ，即资源警告，在默认情况下此警告不会被提醒。如果设置了 @ref{b3a,,DEBUG_UNCOLLECTABLE} ，所有无法被回收的对象会被打印。



在 3.4 版更改: 根据 
@geindex Python 提高建议; PEP 442
PEP 442@footnote{https://www.python.org/dev/peps/pep-0442} ，带有 @ref{919,,__del__()} 方法的对象最终不再会进入 @ref{b39,,gc.garbage} 。

@end deffn

@geindex callbacks() (在 gc 模块中)
@anchor{library/gc gc callbacks}@anchor{a05}
@deffn {数据} gc.callbacks

在垃圾回收器开始前和完成后会被调用的一系列回调函数。这些回调函数在被调用时使用两个参数： @emph{phase} 和 @emph{info} 。

@emph{phase} 可为以下两值之一：

@quotation

"start": 垃圾回收即将开始。

"stop": 垃圾回收已结束。
@end quotation

@emph{info} is a dict providing more information for the callback.  The following
keys are currently defined:

@quotation

"generation"（代） ：正在被回收的最久远的一代。

"collected"（已回收的 ）: 当*phase* 为 "stop" 时，被成功回收的对象的数目。

"uncollectable"（不可回收的）: 当 @emph{phase} 为 "stop" 时，不能被回收并被放入 @ref{b39,,garbage} 的对象的数目。
@end quotation

应用程序可以把他们自己的回调函数加入此列表。主要的使用场景有：

@quotation

统计垃圾回收的数据，如：不同代的回收频率、回收所花费的时间。

使应用程序可以识别和清理他们自己的在 @ref{b39,,garbage} 中的不可回收类型的对象。
@end quotation


3.3 新版功能.

@end deffn

以下常量被用于 @ref{365e,,set_debug()} ：

@geindex DEBUG_STATS() (在 gc 模块中)
@anchor{library/gc gc DEBUG_STATS}@anchor{3666}
@deffn {数据} gc.DEBUG_STATS

在回收完成后打印统计信息。当回收频率设置较高时，这些信息会比较有用。
@end deffn

@geindex DEBUG_COLLECTABLE() (在 gc 模块中)
@anchor{library/gc gc DEBUG_COLLECTABLE}@anchor{3667}
@deffn {数据} gc.DEBUG_COLLECTABLE

当发现可回收对象时打印信息。
@end deffn

@geindex DEBUG_UNCOLLECTABLE() (在 gc 模块中)
@anchor{library/gc gc DEBUG_UNCOLLECTABLE}@anchor{b3a}
@deffn {数据} gc.DEBUG_UNCOLLECTABLE

打印找到的不可回收对象的信息（指不能被回收器回收的不可达对象）。这些对象会被添加到 @code{garbage} 列表中。


在 3.2 版更改: 当 @ref{75d,,interpreter shutdown} 时，即解释器关闭时，若 @ref{b39,,garbage} 列表中存在对象，这些对象也会被打印输出。

@end deffn

@geindex DEBUG_SAVEALL() (在 gc 模块中)
@anchor{library/gc gc DEBUG_SAVEALL}@anchor{3665}
@deffn {数据} gc.DEBUG_SAVEALL

设置后，所有回收器找到的不可达对象会被添加进 @emph{garbage} 而不是直接被释放。这在调试一个内存泄漏的程序时会很有用。
@end deffn

@geindex DEBUG_LEAK() (在 gc 模块中)
@anchor{library/gc gc DEBUG_LEAK}@anchor{3668}
@deffn {数据} gc.DEBUG_LEAK

调试内存泄漏的程序时，使回收器打印信息的调试标识位。（等价于 @code{DEBUG_COLLECTABLE | DEBUG_UNCOLLECTABLE | DEBUG_SAVEALL} ）。
@end deffn

@node inspect --- 检查对象,site —— 指定域的配置钩子,gc --- 垃圾回收器接口,Python运行时服务
@anchor{library/inspect doc}@anchor{3669}@anchor{library/inspect inspect-inspect-live-objects}@anchor{366a}@anchor{library/inspect module-inspect}@anchor{a0}
@subsection @code{inspect} --- 检查对象


@geindex inspect (模块)

@strong{源代码:} Lib/inspect.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/inspect.py}


__________________________________________________________________


@ref{a0,,inspect} 模块提供了一些有用的函数帮助获取对象的信息，例如模块、类、方法、函数、回溯、帧对象以及代码对象。例如它可以帮助你检查类的内容，获取某个方法的源代码，取得并格式化某个函数的参数列表，或者获取你需要显示的回溯的详细信息。

该模块提供了4种主要的功能：类型检查、获取源代码、检查类与函数、检查解释器的调用堆栈。

@menu
* 类型和成员:: 
* Retrieving source code:: 
* Introspecting callables with the Signature object:: 
* 类与函数: 类与函数<2>. 
* The interpreter stack:: 
* Fetching attributes statically:: 
* Current State of Generators and Coroutines:: 
* Code Objects Bit Flags:: 
* 命令行界面: 命令行界面<8>. 

@end menu

@node 类型和成员,Retrieving source code,,inspect --- 检查对象
@anchor{library/inspect inspect-types}@anchor{366b}@anchor{library/inspect types-and-members}@anchor{366c}
@subsubsection 类型和成员


@ref{366d,,getmembers()} 函数获取对象的成员，例如类或模块。函数名以"is"开始的函数主要作为 @ref{366d,,getmembers()} 的第2个参数使用。它们也可用于判定某对象是否有如下的特殊属性:

@c this function name is too big to fit in the ascii-art table below


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

类型

@tab

属性

@tab

描述

@item

module

@tab

__doc__

@tab

文档字符串

@item

@tab

__file__

@tab

文件名(内置模块没有文件名)

@item

class -- 类

@tab

__doc__

@tab

文档字符串

@item

@tab

__name__

@tab

类定义时所使用的名称

@item

@tab

__qualname__

@tab

qualified name -- 限定名称

@item

@tab

__module__

@tab

该类型被定义时所在的模块的名称

@item

method 方法

@tab

__doc__

@tab

文档字符串

@item

@tab

__name__

@tab

该方法定义时所使用的名称

@item

@tab

__qualname__

@tab

qualified name -- 限定名称

@item

@tab

__func__

@tab

实现该方法的函数对象

@item

@tab

__self__

@tab

该方法被绑定的实例，若没有绑定则为 @code{None}

@item

@tab

__module__

@tab

name of module in which
this method was defined

@item

function -- 函数

@tab

__doc__

@tab

文档字符串

@item

@tab

__name__

@tab

用于定义此函数的名称

@item

@tab

__qualname__

@tab

qualified name -- 限定名称

@item

@tab

__code__

@tab

包含已编译函数的代码对象 @ref{60f,,bytecode}

@item

@tab

__defaults__

@tab

tuple of any default
values for positional or
keyword parameters

@item

@tab

__kwdefaults__

@tab

mapping of any default
values for keyword-only
parameters

@item

@tab

__globals__

@tab

global namespace in which
this function was defined

@item

@tab

__annotations__

@tab

mapping of parameters
names to annotations;
@code{"return"} key is
reserved for return
annotations.

@item

@tab

__module__

@tab

name of module in which
this function was defined

@item

回溯

@tab

tb_frame

@tab

此级别的框架对象

@item

@tab

tb_lasti

@tab

index of last attempted
instruction in bytecode

@item

@tab

tb_lineno

@tab

current line number in
Python source code

@item

@tab

tb_next

@tab

next inner traceback
object (called by this
level)

@item

框架

@tab

f_back

@tab

next outer frame object
(this frame's caller)

@item

@tab

f_builtins

@tab

builtins namespace seen
by this frame

@item

@tab

f_code

@tab

code object being
executed in this frame

@item

@tab

f_globals

@tab

global namespace seen by
this frame

@item

@tab

f_lasti

@tab

index of last attempted
instruction in bytecode

@item

@tab

f_lineno

@tab

current line number in
Python source code

@item

@tab

f_locals

@tab

local namespace seen by
this frame

@item

@tab

f_trace

@tab

tracing function for this
frame, or @code{None}

@item

code

@tab

co_argcount

@tab

number of arguments (not
including keyword only
arguments, * or **
args)

@item

@tab

co_code

@tab

原始编译字节码的字符串

@item

@tab

co_cellvars

@tab

单元变量名称的元组(通过包含作用域引用)

@item

@tab

co_consts

@tab

字节码中使用的常量元组

@item

@tab

co_filename

@tab

创建此代码对象的文件的名称

@item

@tab

co_firstlineno

@tab

number of first line in
Python source code

@item

@tab

co_flags

@tab

bitmap of @code{CO_*} flags,
read more @ref{366e,,here}

@item

@tab

co_lnotab

@tab

编码的行号到字节码索引的映射

@item

@tab

co_freevars

@tab

tuple of names of free
variables (referenced via
a function's closure)

@item

@tab

co_posonlyargcount

@tab

number of positional only
arguments

@item

@tab

co_kwonlyargcount

@tab

number of keyword only
arguments (not including
** arg)

@item

@tab

co_name

@tab

定义此代码对象的名称

@item

@tab

co_names

@tab

局部变量名称的元组

@item

@tab

co_nlocals

@tab

局部变量的数量

@item

@tab

co_stacksize

@tab

需要虚拟机堆栈空间

@item

@tab

co_varnames

@tab

参数名和局部变量的元组

@item

generator -- 生成器

@tab

__name__

@tab

名称

@item

@tab

__qualname__

@tab

qualified name -- 限定名称

@item

@tab

gi_frame

@tab

框架

@item

@tab

gi_running

@tab

生成器在运行吗？

@item

@tab

gi_code

@tab

code

@item

@tab

gi_yieldfrom

@tab

object being iterated by
@code{yield from}, or
@code{None}

@item

coroutine -- 协程

@tab

__name__

@tab

名称

@item

@tab

__qualname__

@tab

qualified name -- 限定名称

@item

@tab

cr_await

@tab

object being awaited on,
or @code{None}

@item

@tab

cr_frame

@tab

框架

@item

@tab

cr_running

@tab

is the coroutine running?

@item

@tab

cr_code

@tab

code

@item

@tab

cr_origin

@tab

where coroutine was
created, or @code{None}. See
@ref{3eb,,sys.set_coroutine_origin_tracking_depth()}

@item

builtin

@tab

__doc__

@tab

文档字符串

@item

@tab

__name__

@tab

此函数或方法的原始名称

@item

@tab

__qualname__

@tab

qualified name -- 限定名称

@item

@tab

__self__

@tab

instance to which a
method is bound, or
@code{None}

@end multitable



在 3.5 版更改: Add @code{__qualname__} and @code{gi_yieldfrom} attributes to generators.

The @code{__name__} attribute of generators is now set from the function
name, instead of the code name, and it can now be modified.



在 3.7 版更改: Add @code{cr_origin} attribute to coroutines.


@geindex getmembers() (在 inspect 模块中)
@anchor{library/inspect inspect getmembers}@anchor{366d}
@deffn {函数} inspect.getmembers (object[, predicate])

Return all the members of an object in a list of @code{(name, value)}
pairs sorted by name. If the optional @emph{predicate} argument—which will be
called with the @code{value} object of each member—is supplied, only members
for which the predicate returns a true value are included.

@cartouche
@quotation 注解 
@ref{366d,,getmembers()} will only return class attributes defined in the
metaclass when the argument is a class and those attributes have been
listed in the metaclass' custom @ref{314,,__dir__()}.
@end quotation
@end cartouche
@end deffn

@geindex getmodulename() (在 inspect 模块中)
@anchor{library/inspect inspect getmodulename}@anchor{5ed}
@deffn {函数} inspect.getmodulename (path)

Return the name of the module named by the file @emph{path}, without including the
names of enclosing packages. The file extension is checked against all of
the entries in @ref{366f,,importlib.machinery.all_suffixes()}. If it matches,
the final path component is returned with the extension removed.
Otherwise, @code{None} is returned.

Note that this function @emph{only} returns a meaningful name for actual
Python modules - paths that potentially refer to Python packages will
still return @code{None}.


在 3.3 版更改: The function is based directly on @ref{9b,,importlib}.

@end deffn

@geindex ismodule() (在 inspect 模块中)
@anchor{library/inspect inspect ismodule}@anchor{3670}
@deffn {函数} inspect.ismodule (object)

Return @code{True} if the object is a module.
@end deffn

@geindex isclass() (在 inspect 模块中)
@anchor{library/inspect inspect isclass}@anchor{3671}
@deffn {函数} inspect.isclass (object)

Return @code{True} if the object is a class, whether built-in or created in Python
code.
@end deffn

@geindex ismethod() (在 inspect 模块中)
@anchor{library/inspect inspect ismethod}@anchor{3672}
@deffn {函数} inspect.ismethod (object)

Return @code{True} if the object is a bound method written in Python.
@end deffn

@geindex isfunction() (在 inspect 模块中)
@anchor{library/inspect inspect isfunction}@anchor{3673}
@deffn {函数} inspect.isfunction (object)

Return @code{True} if the object is a Python function, which includes functions
created by a @ref{3674,,lambda} expression.
@end deffn

@geindex isgeneratorfunction() (在 inspect 模块中)
@anchor{library/inspect inspect isgeneratorfunction}@anchor{fb1}
@deffn {函数} inspect.isgeneratorfunction (object)

Return @code{True} if the object is a Python generator function.


在 3.8 版更改: Functions wrapped in @ref{7c2,,functools.partial()} now return @code{True} if the
wrapped function is a Python generator function.

@end deffn

@geindex isgenerator() (在 inspect 模块中)
@anchor{library/inspect inspect isgenerator}@anchor{3675}
@deffn {函数} inspect.isgenerator (object)

Return @code{True} if the object is a generator.
@end deffn

@geindex iscoroutinefunction() (在 inspect 模块中)
@anchor{library/inspect inspect iscoroutinefunction}@anchor{6f2}
@deffn {函数} inspect.iscoroutinefunction (object)

Return @code{True} if the object is a @ref{639,,coroutine function}
(a function defined with an @ref{284,,async def} syntax).


3.5 新版功能.



在 3.8 版更改: Functions wrapped in @ref{7c2,,functools.partial()} now return @code{True} if the
wrapped function is a @ref{639,,coroutine function}.

@end deffn

@geindex iscoroutine() (在 inspect 模块中)
@anchor{library/inspect inspect iscoroutine}@anchor{6f1}
@deffn {函数} inspect.iscoroutine (object)

Return @code{True} if the object is a @ref{1a6,,coroutine} created by an
@ref{284,,async def} function.


3.5 新版功能.

@end deffn

@geindex isawaitable() (在 inspect 模块中)
@anchor{library/inspect inspect isawaitable}@anchor{6f3}
@deffn {函数} inspect.isawaitable (object)

Return @code{True} if the object can be used in @ref{1a3,,await} expression.

Can also be used to distinguish generator-based coroutines from regular
generators:

@example
def gen():
    yield
@@types.coroutine
def gen_coro():
    yield

assert not isawaitable(gen())
assert isawaitable(gen_coro())
@end example


3.5 新版功能.

@end deffn

@geindex isasyncgenfunction() (在 inspect 模块中)
@anchor{library/inspect inspect isasyncgenfunction}@anchor{fb2}
@deffn {函数} inspect.isasyncgenfunction (object)

Return @code{True} if the object is an @ref{149c,,asynchronous generator} function,
for example:

@example
>>> async def agen():
...     yield 1
...
>>> inspect.isasyncgenfunction(agen)
True
@end example


3.6 新版功能.



在 3.8 版更改: Functions wrapped in @ref{7c2,,functools.partial()} now return @code{True} if the
wrapped function is a @ref{149c,,asynchronous generator} function.

@end deffn

@geindex isasyncgen() (在 inspect 模块中)
@anchor{library/inspect inspect isasyncgen}@anchor{3676}
@deffn {函数} inspect.isasyncgen (object)

Return @code{True} if the object is an @ref{35d9,,asynchronous generator iterator}
created by an @ref{149c,,asynchronous generator} function.


3.6 新版功能.

@end deffn

@geindex istraceback() (在 inspect 模块中)
@anchor{library/inspect inspect istraceback}@anchor{3677}
@deffn {函数} inspect.istraceback (object)

Return @code{True} if the object is a traceback.
@end deffn

@geindex isframe() (在 inspect 模块中)
@anchor{library/inspect inspect isframe}@anchor{3678}
@deffn {函数} inspect.isframe (object)

Return @code{True} if the object is a frame.
@end deffn

@geindex iscode() (在 inspect 模块中)
@anchor{library/inspect inspect iscode}@anchor{3679}
@deffn {函数} inspect.iscode (object)

Return @code{True} if the object is a code.
@end deffn

@geindex isbuiltin() (在 inspect 模块中)
@anchor{library/inspect inspect isbuiltin}@anchor{367a}
@deffn {函数} inspect.isbuiltin (object)

Return @code{True} if the object is a built-in function or a bound built-in method.
@end deffn

@geindex isroutine() (在 inspect 模块中)
@anchor{library/inspect inspect isroutine}@anchor{367b}
@deffn {函数} inspect.isroutine (object)

Return @code{True} if the object is a user-defined or built-in function or method.
@end deffn

@geindex isabstract() (在 inspect 模块中)
@anchor{library/inspect inspect isabstract}@anchor{367c}
@deffn {函数} inspect.isabstract (object)

Return @code{True} if the object is an abstract base class.
@end deffn

@geindex ismethoddescriptor() (在 inspect 模块中)
@anchor{library/inspect inspect ismethoddescriptor}@anchor{367d}
@deffn {函数} inspect.ismethoddescriptor (object)

Return @code{True} if the object is a method descriptor, but not if
@ref{3672,,ismethod()}, @ref{3671,,isclass()}, @ref{3673,,isfunction()} or @ref{367a,,isbuiltin()}
are true.

This, for example, is true of @code{int.__add__}.  An object passing this test
has a @ref{13d3,,__get__()} method but not a @ref{13d7,,__set__()}
method, but beyond that the set of attributes varies.  A
@ref{c60,,__name__} attribute is usually
sensible, and @code{__doc__} often is.

Methods implemented via descriptors that also pass one of the other tests
return @code{False} from the @ref{367d,,ismethoddescriptor()} test, simply because the
other tests promise more -- you can, e.g., count on having the
@code{__func__} attribute (etc) when an object passes @ref{3672,,ismethod()}.
@end deffn

@geindex isdatadescriptor() (在 inspect 模块中)
@anchor{library/inspect inspect isdatadescriptor}@anchor{367e}
@deffn {函数} inspect.isdatadescriptor (object)

Return @code{True} if the object is a data descriptor.

Data descriptors have a @ref{13d7,,__set__} or a @ref{13d8,,__delete__} method.
Examples are properties (defined in Python), getsets, and members.  The
latter two are defined in C and there are more specific tests available for
those types, which is robust across Python implementations.  Typically, data
descriptors will also have @ref{c60,,__name__} and @code{__doc__} attributes
(properties, getsets, and members have both of these attributes), but this is
not guaranteed.
@end deffn

@geindex isgetsetdescriptor() (在 inspect 模块中)
@anchor{library/inspect inspect isgetsetdescriptor}@anchor{367f}
@deffn {函数} inspect.isgetsetdescriptor (object)

Return @code{True} if the object is a getset descriptor.

@strong{CPython implementation detail:} getsets are attributes defined in extension modules via
@ref{421,,PyGetSetDef} structures.  For Python implementations without such
types, this method will always return @code{False}.
@end deffn

@geindex ismemberdescriptor() (在 inspect 模块中)
@anchor{library/inspect inspect ismemberdescriptor}@anchor{3680}
@deffn {函数} inspect.ismemberdescriptor (object)

Return @code{True} if the object is a member descriptor.

@strong{CPython implementation detail:} Member descriptors are attributes defined in extension modules via
@ref{420,,PyMemberDef} structures.  For Python implementations without such
types, this method will always return @code{False}.
@end deffn

@node Retrieving source code,Introspecting callables with the Signature object,类型和成员,inspect --- 检查对象
@anchor{library/inspect inspect-source}@anchor{3681}@anchor{library/inspect retrieving-source-code}@anchor{3682}
@subsubsection Retrieving source code


@geindex getdoc() (在 inspect 模块中)
@anchor{library/inspect inspect getdoc}@anchor{1d6}
@deffn {函数} inspect.getdoc (object)

Get the documentation string for an object, cleaned up with @ref{3683,,cleandoc()}.
If the documentation string for an object is not provided and the object is
a class, a method, a property or a descriptor, retrieve the documentation
string from the inheritance hierarchy.


在 3.5 版更改: Documentation strings are now inherited if not overridden.

@end deffn

@geindex getcomments() (在 inspect 模块中)
@anchor{library/inspect inspect getcomments}@anchor{3250}
@deffn {函数} inspect.getcomments (object)

Return in a single string any lines of comments immediately preceding the
object's source code (for a class, function, or method), or at the top of the
Python source file (if the object is a module).  If the object's source code
is unavailable, return @code{None}.  This could happen if the object has been
defined in C or the interactive shell.
@end deffn

@geindex getfile() (在 inspect 模块中)
@anchor{library/inspect inspect getfile}@anchor{1036}
@deffn {函数} inspect.getfile (object)

Return the name of the (text or binary) file in which an object was defined.
This will fail with a @ref{192,,TypeError} if the object is a built-in module,
class, or function.
@end deffn

@geindex getmodule() (在 inspect 模块中)
@anchor{library/inspect inspect getmodule}@anchor{eb4}
@deffn {函数} inspect.getmodule (object)

Try to guess which module an object was defined in.
@end deffn

@geindex getsourcefile() (在 inspect 模块中)
@anchor{library/inspect inspect getsourcefile}@anchor{3684}
@deffn {函数} inspect.getsourcefile (object)

Return the name of the Python source file in which an object was defined.  This
will fail with a @ref{192,,TypeError} if the object is a built-in module, class, or
function.
@end deffn

@geindex getsourcelines() (在 inspect 模块中)
@anchor{library/inspect inspect getsourcelines}@anchor{3685}
@deffn {函数} inspect.getsourcelines (object)

Return a list of source lines and starting line number for an object. The
argument may be a module, class, method, function, traceback, frame, or code
object.  The source code is returned as a list of the lines corresponding to the
object and the line number indicates where in the original source file the first
line of code was found.  An @ref{1d3,,OSError} is raised if the source code cannot
be retrieved.


在 3.3 版更改: @ref{1d3,,OSError} is raised instead of @ref{98c,,IOError}, now an alias of the
former.

@end deffn

@geindex getsource() (在 inspect 模块中)
@anchor{library/inspect inspect getsource}@anchor{115d}
@deffn {函数} inspect.getsource (object)

Return the text of the source code for an object. The argument may be a module,
class, method, function, traceback, frame, or code object.  The source code is
returned as a single string.  An @ref{1d3,,OSError} is raised if the source code
cannot be retrieved.


在 3.3 版更改: @ref{1d3,,OSError} is raised instead of @ref{98c,,IOError}, now an alias of the
former.

@end deffn

@geindex cleandoc() (在 inspect 模块中)
@anchor{library/inspect inspect cleandoc}@anchor{3683}
@deffn {函数} inspect.cleandoc (doc)

Clean up indentation from docstrings that are indented to line up with blocks
of code.

All leading whitespace is removed from the first line.  Any leading whitespace
that can be uniformly removed from the second line onwards is removed.  Empty
lines at the beginning and end are subsequently removed.  Also, all tabs are
expanded to spaces.
@end deffn

@node Introspecting callables with the Signature object,类与函数<2>,Retrieving source code,inspect --- 检查对象
@anchor{library/inspect inspect-signature-object}@anchor{3686}@anchor{library/inspect introspecting-callables-with-the-signature-object}@anchor{3687}
@subsubsection Introspecting callables with the Signature object



3.3 新版功能.


The Signature object represents the call signature of a callable object and its
return annotation.  To retrieve a Signature object, use the @ref{556,,signature()}
function.

@geindex signature() (在 inspect 模块中)
@anchor{library/inspect inspect signature}@anchor{556}
@deffn {函数} inspect.signature (callable, *, follow_wrapped=True)

Return a @ref{6ed,,Signature} object for the given @code{callable}:

@example
>>> from inspect import signature
>>> def foo(a, *, b:int, **kwargs):
...     pass

>>> sig = signature(foo)

>>> str(sig)
'(a, *, b:int, **kwargs)'

>>> str(sig.parameters['b'])
'b:int'

>>> sig.parameters['b'].annotation
<class 'int'>
@end example

Accepts a wide range of Python callables, from plain functions and classes to
@ref{7c2,,functools.partial()} objects.

Raises @ref{1fb,,ValueError} if no signature can be provided, and
@ref{192,,TypeError} if that type of object is not supported.

A slash(/) in the signature of a function denotes that the parameters prior
to it are positional-only. For more info, see
@ref{158b,,the FAQ entry on positional-only parameters}.


3.5 新版功能: @code{follow_wrapped} parameter. Pass @code{False} to get a signature of
@code{callable} specifically (@code{callable.__wrapped__} will not be used to
unwrap decorated callables.)


@cartouche
@quotation 注解 
Some callables may not be introspectable in certain implementations of
Python.  For example, in CPython, some built-in functions defined in
C provide no metadata about their arguments.
@end quotation
@end cartouche
@end deffn

@geindex Signature (inspect 中的类)
@anchor{library/inspect inspect Signature}@anchor{6ed}
@deffn {类} inspect.Signature (parameters=None, *, return_annotation=Signature.empty)

A Signature object represents the call signature of a function and its return
annotation.  For each parameter accepted by the function it stores a
@ref{6ee,,Parameter} object in its @ref{3688,,parameters} collection.

The optional @emph{parameters} argument is a sequence of @ref{6ee,,Parameter}
objects, which is validated to check that there are no parameters with
duplicate names, and that the parameters are in the right order, i.e.
positional-only first, then positional-or-keyword, and that parameters with
defaults follow parameters without defaults.

The optional @emph{return_annotation} argument, can be an arbitrary Python object,
is the "return" annotation of the callable.

Signature objects are @emph{immutable}.  Use @ref{3689,,Signature.replace()} to make a
modified copy.


在 3.5 版更改: Signature objects are picklable and hashable.


@geindex empty (inspect.Signature 属性)
@anchor{library/inspect inspect Signature empty}@anchor{368a}
@deffn {属性} empty

A special class-level marker to specify absence of a return annotation.
@end deffn

@geindex parameters (inspect.Signature 属性)
@anchor{library/inspect inspect Signature parameters}@anchor{3688}
@deffn {属性} parameters

An ordered mapping of parameters' names to the corresponding
@ref{6ee,,Parameter} objects.  Parameters appear in strict definition
order, including keyword-only parameters.


在 3.7 版更改: Python only explicitly guaranteed that it preserved the declaration
order of keyword-only parameters as of version 3.7, although in practice
this order had always been preserved in Python 3.

@end deffn

@geindex return_annotation (inspect.Signature 属性)
@anchor{library/inspect inspect Signature return_annotation}@anchor{368b}
@deffn {属性} return_annotation

The "return" annotation for the callable.  If the callable has no "return"
annotation, this attribute is set to @ref{368a,,Signature.empty}.
@end deffn

@geindex bind() (inspect.Signature 方法)
@anchor{library/inspect inspect Signature bind}@anchor{368c}
@deffn {方法} bind (*args, **kwargs)

Create a mapping from positional and keyword arguments to parameters.
Returns @ref{9a2,,BoundArguments} if @code{*args} and @code{**kwargs} match the
signature, or raises a @ref{192,,TypeError}.
@end deffn

@geindex bind_partial() (inspect.Signature 方法)
@anchor{library/inspect inspect Signature bind_partial}@anchor{368d}
@deffn {方法} bind_partial (*args, **kwargs)

Works the same way as @ref{368c,,Signature.bind()}, but allows the omission of
some required arguments (mimics @ref{7c2,,functools.partial()} behavior.)
Returns @ref{9a2,,BoundArguments}, or raises a @ref{192,,TypeError} if the
passed arguments do not match the signature.
@end deffn

@geindex replace() (inspect.Signature 方法)
@anchor{library/inspect inspect Signature replace}@anchor{3689}
@deffn {方法} replace (*[, parameters][, return_annotation])

Create a new Signature instance based on the instance replace was invoked
on.  It is possible to pass different @code{parameters} and/or
@code{return_annotation} to override the corresponding properties of the base
signature.  To remove return_annotation from the copied Signature, pass in
@ref{368a,,Signature.empty}.

@example
>>> def test(a, b):
...     pass
>>> sig = signature(test)
>>> new_sig = sig.replace(return_annotation="new return anno")
>>> str(new_sig)
"(a, b) -> 'new return anno'"
@end example
@end deffn

@geindex from_callable() (inspect.Signature 类方法)
@anchor{library/inspect inspect Signature from_callable}@anchor{6f0}
@deffn {方法} classmethod from_callable (obj, *, follow_wrapped=True)

Return a @ref{6ed,,Signature} (or its subclass) object for a given callable
@code{obj}.  Pass @code{follow_wrapped=False} to get a signature of @code{obj}
without unwrapping its @code{__wrapped__} chain.

This method simplifies subclassing of @ref{6ed,,Signature}:

@example
class MySignature(Signature):
    pass
sig = MySignature.from_callable(min)
assert isinstance(sig, MySignature)
@end example


3.5 新版功能.

@end deffn
@end deffn

@geindex Parameter (inspect 中的类)
@anchor{library/inspect inspect Parameter}@anchor{6ee}
@deffn {类} inspect.Parameter (name, kind, *, default=Parameter.empty, annotation=Parameter.empty)

Parameter objects are @emph{immutable}.  Instead of modifying a Parameter object,
you can use @ref{368e,,Parameter.replace()} to create a modified copy.


在 3.5 版更改: Parameter objects are picklable and hashable.


@geindex empty (inspect.Parameter 属性)
@anchor{library/inspect inspect Parameter empty}@anchor{368f}
@deffn {属性} empty

A special class-level marker to specify absence of default values and
annotations.
@end deffn

@geindex name (inspect.Parameter 属性)
@anchor{library/inspect inspect Parameter name}@anchor{3690}
@deffn {属性} name

The name of the parameter as a string.  The name must be a valid
Python identifier.

@strong{CPython implementation detail:} CPython generates implicit parameter names of the form @code{.0} on the
code objects used to implement comprehensions and generator
expressions.


在 3.6 版更改: These parameter names are exposed by this module as names like
@code{implicit0}.

@end deffn

@geindex default (inspect.Parameter 属性)
@anchor{library/inspect inspect Parameter default}@anchor{3691}
@deffn {属性} default

The default value for the parameter.  If the parameter has no default
value, this attribute is set to @ref{368f,,Parameter.empty}.
@end deffn

@geindex annotation (inspect.Parameter 属性)
@anchor{library/inspect inspect Parameter annotation}@anchor{3692}
@deffn {属性} annotation

The annotation for the parameter.  If the parameter has no annotation,
this attribute is set to @ref{368f,,Parameter.empty}.
@end deffn

@geindex kind (inspect.Parameter 属性)
@anchor{library/inspect inspect Parameter kind}@anchor{3693}
@deffn {属性} kind

Describes how argument values are bound to the parameter.  Possible values
(accessible via @ref{6ee,,Parameter}, like @code{Parameter.KEYWORD_ONLY}):


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

名称

@tab

含义

@item

@emph{POSITIONAL_ONLY}

@tab

Value must be supplied as a positional
argument. Positional only parameters are
those which appear before a @code{/} entry (if
present) in a Python function definition.

@item

@emph{POSITIONAL_OR_KEYWORD}

@tab

Value may be supplied as either a keyword or
positional argument (this is the standard
binding behaviour for functions implemented
in Python.)

@item

@emph{VAR_POSITIONAL}

@tab

A tuple of positional arguments that aren't
bound to any other parameter. This
corresponds to a @code{*args} parameter in a
Python function definition.

@item

@emph{KEYWORD_ONLY}

@tab

Value must be supplied as a keyword argument.
Keyword only parameters are those which
appear after a @code{*} or @code{*args} entry in a
Python function definition.

@item

@emph{VAR_KEYWORD}

@tab

A dict of keyword arguments that aren't bound
to any other parameter. This corresponds to a
@code{**kwargs} parameter in a Python function
definition.

@end multitable


Example: print all keyword-only arguments without default values:

@example
>>> def foo(a, b, *, c, d=10):
...     pass

>>> sig = signature(foo)
>>> for param in sig.parameters.values():
...     if (param.kind == param.KEYWORD_ONLY and
...                        param.default is param.empty):
...         print('Parameter:', param)
Parameter: c
@end example
@end deffn

@geindex description (inspect.Parameter.kind 属性)
@anchor{library/inspect inspect Parameter kind description}@anchor{3694}
@deffn {属性} kind.description

Describes a enum value of Parameter.kind.


3.8 新版功能.


Example: print all descriptions of arguments:

@example
>>> def foo(a, b, *, c, d=10):
...     pass

>>> sig = signature(foo)
>>> for param in sig.parameters.values():
...     print(param.kind.description)
positional or keyword
positional or keyword
keyword-only
keyword-only
@end example
@end deffn

@geindex replace() (inspect.Parameter 方法)
@anchor{library/inspect inspect Parameter replace}@anchor{368e}
@deffn {方法} replace (*[, name][, kind][, default][, annotation])

@quotation

Create a new Parameter instance based on the instance replaced was invoked
on.  To override a @ref{6ee,,Parameter} attribute, pass the corresponding
argument.  To remove a default value or/and an annotation from a
Parameter, pass @ref{368f,,Parameter.empty}.

@example
>>> from inspect import Parameter
>>> param = Parameter('foo', Parameter.KEYWORD_ONLY, default=42)
>>> str(param)
'foo=42'

>>> str(param.replace()) # Will create a shallow copy of 'param'
'foo=42'

>>> str(param.replace(default=Parameter.empty, annotation='spam'))
"foo:'spam'"
@end example
@end quotation


在 3.4 版更改: In Python 3.3 Parameter objects were allowed to have @code{name} set
to @code{None} if their @code{kind} was set to @code{POSITIONAL_ONLY}.
This is no longer permitted.

@end deffn
@end deffn

@geindex BoundArguments (inspect 中的类)
@anchor{library/inspect inspect BoundArguments}@anchor{9a2}
@deffn {类} inspect.BoundArguments

Result of a @ref{368c,,Signature.bind()} or @ref{368d,,Signature.bind_partial()} call.
Holds the mapping of arguments to the function's parameters.

@geindex arguments (inspect.BoundArguments 属性)
@anchor{library/inspect inspect BoundArguments arguments}@anchor{3695}
@deffn {属性} arguments

An ordered, mutable mapping (@ref{1b9,,collections.OrderedDict}) of
parameters' names to arguments' values.  Contains only explicitly bound
arguments.  Changes in @ref{3695,,arguments} will reflect in @ref{3696,,args} and
@ref{3697,,kwargs}.

Should be used in conjunction with @ref{3688,,Signature.parameters} for any
argument processing purposes.

@cartouche
@quotation 注解 
Arguments for which @ref{368c,,Signature.bind()} or
@ref{368d,,Signature.bind_partial()} relied on a default value are skipped.
However, if needed, use @ref{6ef,,BoundArguments.apply_defaults()} to add
them.
@end quotation
@end cartouche
@end deffn

@geindex args (inspect.BoundArguments 属性)
@anchor{library/inspect inspect BoundArguments args}@anchor{3696}
@deffn {属性} args

A tuple of positional arguments values.  Dynamically computed from the
@ref{3695,,arguments} attribute.
@end deffn

@geindex kwargs (inspect.BoundArguments 属性)
@anchor{library/inspect inspect BoundArguments kwargs}@anchor{3697}
@deffn {属性} kwargs

A dict of keyword arguments values.  Dynamically computed from the
@ref{3695,,arguments} attribute.
@end deffn

@geindex signature (inspect.BoundArguments 属性)
@anchor{library/inspect inspect BoundArguments signature}@anchor{3698}
@deffn {属性} signature

A reference to the parent @ref{6ed,,Signature} object.
@end deffn

@geindex apply_defaults() (inspect.BoundArguments 方法)
@anchor{library/inspect inspect BoundArguments apply_defaults}@anchor{6ef}
@deffn {方法} apply_defaults ()

Set default values for missing arguments.

For variable-positional arguments (@code{*args}) the default is an
empty tuple.

For variable-keyword arguments (@code{**kwargs}) the default is an
empty dict.

@example
>>> def foo(a, b='ham', *args): pass
>>> ba = inspect.signature(foo).bind('spam')
>>> ba.apply_defaults()
>>> ba.arguments
OrderedDict([('a', 'spam'), ('b', 'ham'), ('args', ())])
@end example


3.5 新版功能.

@end deffn

The @ref{3696,,args} and @ref{3697,,kwargs} properties can be used to invoke
functions:

@example
def test(a, *, b):
    ...

sig = signature(test)
ba = sig.bind(10, b=20)
test(*ba.args, **ba.kwargs)
@end example
@end deffn


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 362

@item PEP 362@footnote{https://www.python.org/dev/peps/pep-0362} - Function Signature Object.

The detailed specification, implementation details and examples.
@end table


@node 类与函数<2>,The interpreter stack,Introspecting callables with the Signature object,inspect --- 检查对象
@anchor{library/inspect classes-and-functions}@anchor{3699}@anchor{library/inspect inspect-classes-functions}@anchor{369a}
@subsubsection 类与函数


@geindex getclasstree() (在 inspect 模块中)
@anchor{library/inspect inspect getclasstree}@anchor{369b}
@deffn {函数} inspect.getclasstree (classes, unique=False)

Arrange the given list of classes into a hierarchy of nested lists. Where a
nested list appears, it contains classes derived from the class whose entry
immediately precedes the list.  Each entry is a 2-tuple containing a class and a
tuple of its base classes.  If the @emph{unique} argument is true, exactly one entry
appears in the returned structure for each class in the given list.  Otherwise,
classes using multiple inheritance and their descendants will appear multiple
times.
@end deffn

@geindex getargspec() (在 inspect 模块中)
@anchor{library/inspect inspect getargspec}@anchor{557}
@deffn {函数} inspect.getargspec (func)

Get the names and default values of a Python function's parameters. A
@ref{a9e,,named tuple} @code{ArgSpec(args, varargs, keywords, defaults)} is
returned. @emph{args} is a list of the parameter names. @emph{varargs} and @emph{keywords}
are the names of the @code{*} and @code{**} parameters or @code{None}. @emph{defaults} is a
tuple of default argument values or @code{None} if there are no default
arguments; if this tuple has @emph{n} elements, they correspond to the last
@emph{n} elements listed in @emph{args}.


3.0 版后已移除: Use @ref{558,,getfullargspec()} for an updated API that is usually a drop-in
replacement, but also correctly handles function annotations and
keyword-only parameters.

Alternatively, use @ref{556,,signature()} and
@ref{3686,,Signature Object}, which provide a
more structured introspection API for callables.

@end deffn

@geindex getfullargspec() (在 inspect 模块中)
@anchor{library/inspect inspect getfullargspec}@anchor{558}
@deffn {函数} inspect.getfullargspec (func)

Get the names and default values of a Python function's parameters.  A
@ref{a9e,,named tuple} is returned:

@code{FullArgSpec(args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults,
annotations)}

@emph{args} is a list of the positional parameter names.
@emph{varargs} is the name of the @code{*} parameter or @code{None} if arbitrary
positional arguments are not accepted.
@emph{varkw} is the name of the @code{**} parameter or @code{None} if arbitrary
keyword arguments are not accepted.
@emph{defaults} is an @emph{n}-tuple of default argument values corresponding to the
last @emph{n} positional parameters, or @code{None} if there are no such defaults
defined.
@emph{kwonlyargs} is a list of keyword-only parameter names in declaration order.
@emph{kwonlydefaults} is a dictionary mapping parameter names from @emph{kwonlyargs}
to the default values used if no argument is supplied.
@emph{annotations} is a dictionary mapping parameter names to annotations.
The special key @code{"return"} is used to report the function return value
annotation (if any).

Note that @ref{556,,signature()} and
@ref{3686,,Signature Object} provide the recommended
API for callable introspection, and support additional behaviours (like
positional-only arguments) that are sometimes encountered in extension module
APIs. This function is retained primarily for use in code that needs to
maintain compatibility with the Python 2 @code{inspect} module API.


在 3.4 版更改: This function is now based on @ref{556,,signature()}, but still ignores
@code{__wrapped__} attributes and includes the already bound first
parameter in the signature output for bound methods.



在 3.6 版更改: This method was previously documented as deprecated in favour of
@ref{556,,signature()} in Python 3.5, but that decision has been reversed
in order to restore a clearly supported standard interface for
single-source Python 2/3 code migrating away from the legacy
@ref{557,,getargspec()} API.



在 3.7 版更改: Python only explicitly guaranteed that it preserved the declaration
order of keyword-only parameters as of version 3.7, although in practice
this order had always been preserved in Python 3.

@end deffn

@geindex getargvalues() (在 inspect 模块中)
@anchor{library/inspect inspect getargvalues}@anchor{7b2}
@deffn {函数} inspect.getargvalues (frame)

Get information about arguments passed into a particular frame.  A
@ref{a9e,,named tuple} @code{ArgInfo(args, varargs, keywords, locals)} is
returned. @emph{args} is a list of the argument names.  @emph{varargs} and @emph{keywords}
are the names of the @code{*} and @code{**} arguments or @code{None}.  @emph{locals} is the
locals dictionary of the given frame.

@cartouche
@quotation 注解 
This function was inadvertently marked as deprecated in Python 3.5.
@end quotation
@end cartouche
@end deffn

@geindex formatargspec() (在 inspect 模块中)
@anchor{library/inspect inspect formatargspec}@anchor{7b1}
@deffn {函数} inspect.formatargspec (args[, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, annotations[, formatarg, formatvarargs, formatvarkw, formatvalue, formatreturns, formatannotations]])

Format a pretty argument spec from the values returned by
@ref{558,,getfullargspec()}.

The first seven arguments are (@code{args}, @code{varargs}, @code{varkw},
@code{defaults}, @code{kwonlyargs}, @code{kwonlydefaults}, @code{annotations}).

The other six arguments are functions that are called to turn argument names,
@code{*} argument name, @code{**} argument name, default values, return annotation
and individual annotations into strings, respectively.

例如:

@example
>>> from inspect import formatargspec, getfullargspec
>>> def f(a: int, b: float):
...     pass
...
>>> formatargspec(*getfullargspec(f))
'(a: int, b: float)'
@end example


3.5 版后已移除: Use @ref{556,,signature()} and
@ref{3686,,Signature Object}, which provide a
better introspecting API for callables.

@end deffn

@geindex formatargvalues() (在 inspect 模块中)
@anchor{library/inspect inspect formatargvalues}@anchor{7b3}
@deffn {函数} inspect.formatargvalues (args[, varargs, varkw, locals, formatarg, formatvarargs, formatvarkw, formatvalue])

Format a pretty argument spec from the four values returned by
@ref{7b2,,getargvalues()}.  The format* arguments are the corresponding optional
formatting functions that are called to turn names and values into strings.

@cartouche
@quotation 注解 
This function was inadvertently marked as deprecated in Python 3.5.
@end quotation
@end cartouche
@end deffn

@geindex getmro() (在 inspect 模块中)
@anchor{library/inspect inspect getmro}@anchor{369c}
@deffn {函数} inspect.getmro (cls)

Return a tuple of class cls's base classes, including cls, in method resolution
order.  No class appears more than once in this tuple. Note that the method
resolution order depends on cls's type.  Unless a very peculiar user-defined
metatype is in use, cls will be the first element of the tuple.
@end deffn

@geindex getcallargs() (在 inspect 模块中)
@anchor{library/inspect inspect getcallargs}@anchor{7b0}
@deffn {函数} inspect.getcallargs (func, /, *args, **kwds)

Bind the @emph{args} and @emph{kwds} to the argument names of the Python function or
method @emph{func}, as if it was called with them. For bound methods, bind also the
first argument (typically named @code{self}) to the associated instance. A dict
is returned, mapping the argument names (including the names of the @code{*} and
@code{**} arguments, if any) to their values from @emph{args} and @emph{kwds}. In case of
invoking @emph{func} incorrectly, i.e. whenever @code{func(*args, **kwds)} would raise
an exception because of incompatible signature, an exception of the same type
and the same or similar message is raised. For example:

@example
>>> from inspect import getcallargs
>>> def f(a, b=1, *pos, **named):
...     pass
>>> getcallargs(f, 1, 2, 3) == @{'a': 1, 'named': @{@}, 'b': 2, 'pos': (3,)@}
True
>>> getcallargs(f, a=2, x=4) == @{'a': 2, 'named': @{'x': 4@}, 'b': 1, 'pos': ()@}
True
>>> getcallargs(f)
Traceback (most recent call last):
...
TypeError: f() missing 1 required positional argument: 'a'
@end example


3.2 新版功能.



3.5 版后已移除: Use @ref{368c,,Signature.bind()} and @ref{368d,,Signature.bind_partial()} instead.

@end deffn

@geindex getclosurevars() (在 inspect 模块中)
@anchor{library/inspect inspect getclosurevars}@anchor{a14}
@deffn {函数} inspect.getclosurevars (func)

Get the mapping of external name references in a Python function or
method @emph{func} to their current values. A
@ref{a9e,,named tuple} @code{ClosureVars(nonlocals, globals, builtins, unbound)}
is returned. @emph{nonlocals} maps referenced names to lexical closure
variables, @emph{globals} to the function's module globals and @emph{builtins} to
the builtins visible from the function body. @emph{unbound} is the set of names
referenced in the function that could not be resolved at all given the
current module globals and builtins.

@ref{192,,TypeError} is raised if @emph{func} is not a Python function or method.


3.3 新版功能.

@end deffn

@geindex unwrap() (在 inspect 模块中)
@anchor{library/inspect inspect unwrap}@anchor{863}
@deffn {函数} inspect.unwrap (func, *, stop=None)

Get the object wrapped by @emph{func}. It follows the chain of @code{__wrapped__}
attributes returning the last object in the chain.

@emph{stop} is an optional callback accepting an object in the wrapper chain
as its sole argument that allows the unwrapping to be terminated early if
the callback returns a true value. If the callback never returns a true
value, the last object in the chain is returned as usual. For example,
@ref{556,,signature()} uses this to stop unwrapping if any object in the
chain has a @code{__signature__} attribute defined.

@ref{1fb,,ValueError} is raised if a cycle is encountered.


3.4 新版功能.

@end deffn

@node The interpreter stack,Fetching attributes statically,类与函数<2>,inspect --- 检查对象
@anchor{library/inspect inspect-stack}@anchor{369d}@anchor{library/inspect the-interpreter-stack}@anchor{369e}
@subsubsection The interpreter stack


When the following functions return "frame records," each record is a
@ref{a9e,,named tuple}
@code{FrameInfo(frame, filename, lineno, function, code_context, index)}.
The tuple contains the frame object, the filename, the line number of the
current line,
the function name, a list of lines of context from the source code, and the
index of the current line within that list.


在 3.5 版更改: Return a named tuple instead of a tuple.


@cartouche
@quotation 注解 
Keeping references to frame objects, as found in the first element of the frame
records these functions return, can cause your program to create reference
cycles.  Once a reference cycle has been created, the lifespan of all objects
which can be accessed from the objects which form the cycle can become much
longer even if Python's optional cycle detector is enabled.  If such cycles must
be created, it is important to ensure they are explicitly broken to avoid the
delayed destruction of objects and increased memory consumption which occurs.

Though the cycle detector will catch these, destruction of the frames (and local
variables) can be made deterministic by removing the cycle in a
@ref{182,,finally} clause.  This is also important if the cycle detector was
disabled when Python was compiled or using @ref{365c,,gc.disable()}.  For example:

@example
def handle_stackframe_without_leak():
    frame = inspect.currentframe()
    try:
        # do something with the frame
    finally:
        del frame
@end example

If you want to keep the frame around (for example to print a traceback
later), you can also break reference cycles by using the
@ref{805,,frame.clear()} method.
@end quotation
@end cartouche

The optional @emph{context} argument supported by most of these functions specifies
the number of lines of context to return, which are centered around the current
line.

@geindex getframeinfo() (在 inspect 模块中)
@anchor{library/inspect inspect getframeinfo}@anchor{369f}
@deffn {函数} inspect.getframeinfo (frame, context=1)

Get information about a frame or traceback object.  A @ref{a9e,,named tuple}
@code{Traceback(filename, lineno, function, code_context, index)} is returned.
@end deffn

@geindex getouterframes() (在 inspect 模块中)
@anchor{library/inspect inspect getouterframes}@anchor{6f8}
@deffn {函数} inspect.getouterframes (frame, context=1)

Get a list of frame records for a frame and all outer frames.  These frames
represent the calls that lead to the creation of @emph{frame}. The first entry in the
returned list represents @emph{frame}; the last entry represents the outermost call
on @emph{frame}'s stack.


在 3.5 版更改: A list of @ref{a9e,,named tuples}
@code{FrameInfo(frame, filename, lineno, function, code_context, index)}
is returned.

@end deffn

@geindex getinnerframes() (在 inspect 模块中)
@anchor{library/inspect inspect getinnerframes}@anchor{6f9}
@deffn {函数} inspect.getinnerframes (traceback, context=1)

Get a list of frame records for a traceback's frame and all inner frames.  These
frames represent calls made as a consequence of @emph{frame}.  The first entry in the
list represents @emph{traceback}; the last entry represents where the exception was
raised.


在 3.5 版更改: A list of @ref{a9e,,named tuples}
@code{FrameInfo(frame, filename, lineno, function, code_context, index)}
is returned.

@end deffn

@geindex currentframe() (在 inspect 模块中)
@anchor{library/inspect inspect currentframe}@anchor{36a0}
@deffn {函数} inspect.currentframe ()

Return the frame object for the caller's stack frame.

@strong{CPython implementation detail:} This function relies on Python stack frame support in the interpreter,
which isn't guaranteed to exist in all implementations of Python.  If
running in an implementation without Python stack frame support this
function returns @code{None}.
@end deffn

@geindex stack() (在 inspect 模块中)
@anchor{library/inspect inspect stack}@anchor{6f6}
@deffn {函数} inspect.stack (context=1)

Return a list of frame records for the caller's stack.  The first entry in the
returned list represents the caller; the last entry represents the outermost
call on the stack.


在 3.5 版更改: A list of @ref{a9e,,named tuples}
@code{FrameInfo(frame, filename, lineno, function, code_context, index)}
is returned.

@end deffn

@geindex trace() (在 inspect 模块中)
@anchor{library/inspect inspect trace}@anchor{6f7}
@deffn {函数} inspect.trace (context=1)

Return a list of frame records for the stack between the current frame and the
frame in which an exception currently being handled was raised in.  The first
entry in the list represents the caller; the last entry represents where the
exception was raised.


在 3.5 版更改: A list of @ref{a9e,,named tuples}
@code{FrameInfo(frame, filename, lineno, function, code_context, index)}
is returned.

@end deffn

@node Fetching attributes statically,Current State of Generators and Coroutines,The interpreter stack,inspect --- 检查对象
@anchor{library/inspect fetching-attributes-statically}@anchor{36a1}
@subsubsection Fetching attributes statically


Both @ref{443,,getattr()} and @ref{442,,hasattr()} can trigger code execution when
fetching or checking for the existence of attributes. Descriptors, like
properties, will be invoked and @ref{313,,__getattr__()} and @ref{441,,__getattribute__()}
may be called.

For cases where you want passive introspection, like documentation tools, this
can be inconvenient. @ref{bc4,,getattr_static()} has the same signature as @ref{443,,getattr()}
but avoids executing code when it fetches attributes.

@geindex getattr_static() (在 inspect 模块中)
@anchor{library/inspect inspect getattr_static}@anchor{bc4}
@deffn {函数} inspect.getattr_static (obj, attr, default=None)

Retrieve attributes without triggering dynamic lookup via the
descriptor protocol, @ref{313,,__getattr__()} or @ref{441,,__getattribute__()}.

Note: this function may not be able to retrieve all attributes
that getattr can fetch (like dynamically created attributes)
and may find attributes that getattr can't (like descriptors
that raise AttributeError). It can also return descriptors objects
instead of instance members.

If the instance @ref{4f6,,__dict__} is shadowed by another member (for
example a property) then this function will be unable to find instance
members.


3.2 新版功能.

@end deffn

@ref{bc4,,getattr_static()} does not resolve descriptors, for example slot descriptors or
getset descriptors on objects implemented in C. The descriptor object
is returned instead of the underlying attribute.

You can handle these with code like the following. Note that
for arbitrary getset descriptors invoking these may trigger
code execution:

@example
# example code for resolving the builtin descriptor types
class _foo:
    __slots__ = ['foo']

slot_descriptor = type(_foo.foo)
getset_descriptor = type(type(open(__file__)).name)
wrapper_descriptor = type(str.__dict__['__add__'])
descriptor_types = (slot_descriptor, getset_descriptor, wrapper_descriptor)

result = getattr_static(some_object, 'foo')
if type(result) in descriptor_types:
    try:
        result = result.__get__()
    except AttributeError:
        # descriptors can raise AttributeError to
        # indicate there is no underlying value
        # in which case the descriptor itself will
        # have to do
        pass
@end example

@node Current State of Generators and Coroutines,Code Objects Bit Flags,Fetching attributes statically,inspect --- 检查对象
@anchor{library/inspect current-state-of-generators-and-coroutines}@anchor{36a2}
@subsubsection Current State of Generators and Coroutines


When implementing coroutine schedulers and for other advanced uses of
generators, it is useful to determine whether a generator is currently
executing, is waiting to start or resume or execution, or has already
terminated. @ref{bc3,,getgeneratorstate()} allows the current state of a
generator to be determined easily.

@geindex getgeneratorstate() (在 inspect 模块中)
@anchor{library/inspect inspect getgeneratorstate}@anchor{bc3}
@deffn {函数} inspect.getgeneratorstate (generator)

Get current state of a generator-iterator.


@table @asis

@item Possible states are:


@itemize *

@item 
GEN_CREATED: Waiting to start execution.

@item 
GEN_RUNNING: Currently being executed by the interpreter.

@item 
GEN_SUSPENDED: Currently suspended at a yield expression.

@item 
GEN_CLOSED: Execution has completed.
@end itemize
@end table


3.2 新版功能.

@end deffn

@geindex getcoroutinestate() (在 inspect 模块中)
@anchor{library/inspect inspect getcoroutinestate}@anchor{6f5}
@deffn {函数} inspect.getcoroutinestate (coroutine)

Get current state of a coroutine object.  The function is intended to be
used with coroutine objects created by @ref{284,,async def} functions, but
will accept any coroutine-like object that has @code{cr_running} and
@code{cr_frame} attributes.


@table @asis

@item Possible states are:


@itemize *

@item 
CORO_CREATED: Waiting to start execution.

@item 
CORO_RUNNING: Currently being executed by the interpreter.

@item 
CORO_SUSPENDED: Currently suspended at an await expression.

@item 
CORO_CLOSED: Execution has completed.
@end itemize
@end table


3.5 新版功能.

@end deffn

The current internal state of the generator can also be queried. This is
mostly useful for testing purposes, to ensure that internal state is being
updated as expected:

@geindex getgeneratorlocals() (在 inspect 模块中)
@anchor{library/inspect inspect getgeneratorlocals}@anchor{a15}
@deffn {函数} inspect.getgeneratorlocals (generator)

Get the mapping of live local variables in @emph{generator} to their current
values.  A dictionary is returned that maps from variable names to values.
This is the equivalent of calling @ref{44f,,locals()} in the body of the
generator, and all the same caveats apply.

If @emph{generator} is a @ref{99c,,generator} with no currently associated frame,
then an empty dictionary is returned.  @ref{192,,TypeError} is raised if
@emph{generator} is not a Python generator object.

@strong{CPython implementation detail:} This function relies on the generator exposing a Python stack frame
for introspection, which isn't guaranteed to be the case in all
implementations of Python. In such cases, this function will always
return an empty dictionary.


3.3 新版功能.

@end deffn

@geindex getcoroutinelocals() (在 inspect 模块中)
@anchor{library/inspect inspect getcoroutinelocals}@anchor{6f4}
@deffn {函数} inspect.getcoroutinelocals (coroutine)

This function is analogous to @ref{a15,,getgeneratorlocals()}, but
works for coroutine objects created by @ref{284,,async def} functions.


3.5 新版功能.

@end deffn

@node Code Objects Bit Flags,命令行界面<8>,Current State of Generators and Coroutines,inspect --- 检查对象
@anchor{library/inspect code-objects-bit-flags}@anchor{36a3}@anchor{library/inspect inspect-module-co-flags}@anchor{366e}
@subsubsection Code Objects Bit Flags


Python code objects have a @code{co_flags} attribute, which is a bitmap of
the following flags:

@geindex CO_OPTIMIZED() (在 inspect 模块中)
@anchor{library/inspect inspect CO_OPTIMIZED}@anchor{36a4}
@deffn {数据} inspect.CO_OPTIMIZED

The code object is optimized, using fast locals.
@end deffn

@geindex CO_NEWLOCALS() (在 inspect 模块中)
@anchor{library/inspect inspect CO_NEWLOCALS}@anchor{36a5}
@deffn {数据} inspect.CO_NEWLOCALS

If set, a new dict will be created for the frame's @code{f_locals} when
the code object is executed.
@end deffn

@geindex CO_VARARGS() (在 inspect 模块中)
@anchor{library/inspect inspect CO_VARARGS}@anchor{36a6}
@deffn {数据} inspect.CO_VARARGS

The code object has a variable positional parameter (@code{*args}-like).
@end deffn

@geindex CO_VARKEYWORDS() (在 inspect 模块中)
@anchor{library/inspect inspect CO_VARKEYWORDS}@anchor{36a7}
@deffn {数据} inspect.CO_VARKEYWORDS

The code object has a variable keyword parameter (@code{**kwargs}-like).
@end deffn

@geindex CO_NESTED() (在 inspect 模块中)
@anchor{library/inspect inspect CO_NESTED}@anchor{36a8}
@deffn {数据} inspect.CO_NESTED

The flag is set when the code object is a nested function.
@end deffn

@geindex CO_GENERATOR() (在 inspect 模块中)
@anchor{library/inspect inspect CO_GENERATOR}@anchor{36a9}
@deffn {数据} inspect.CO_GENERATOR

The flag is set when the code object is a generator function, i.e.
a generator object is returned when the code object is executed.
@end deffn

@geindex CO_NOFREE() (在 inspect 模块中)
@anchor{library/inspect inspect CO_NOFREE}@anchor{36aa}
@deffn {数据} inspect.CO_NOFREE

The flag is set if there are no free or cell variables.
@end deffn

@geindex CO_COROUTINE() (在 inspect 模块中)
@anchor{library/inspect inspect CO_COROUTINE}@anchor{36ab}
@deffn {数据} inspect.CO_COROUTINE

The flag is set when the code object is a coroutine function.
When the code object is executed it returns a coroutine object.
See 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} for more details.


3.5 新版功能.

@end deffn

@geindex CO_ITERABLE_COROUTINE() (在 inspect 模块中)
@anchor{library/inspect inspect CO_ITERABLE_COROUTINE}@anchor{36ac}
@deffn {数据} inspect.CO_ITERABLE_COROUTINE

The flag is used to transform generators into generator-based
coroutines.  Generator objects with this flag can be used in
@code{await} expression, and can @code{yield from} coroutine objects.
See 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} for more details.


3.5 新版功能.

@end deffn

@geindex CO_ASYNC_GENERATOR() (在 inspect 模块中)
@anchor{library/inspect inspect CO_ASYNC_GENERATOR}@anchor{36ad}
@deffn {数据} inspect.CO_ASYNC_GENERATOR

The flag is set when the code object is an asynchronous generator
function.  When the code object is executed it returns an
asynchronous generator object.  See 
@geindex Python 提高建议; PEP 525
PEP 525@footnote{https://www.python.org/dev/peps/pep-0525} for more details.


3.6 新版功能.

@end deffn

@cartouche
@quotation 注解 
The flags are specific to CPython, and may not be defined in other
Python implementations.  Furthermore, the flags are an implementation
detail, and can be removed or deprecated in future Python releases.
It's recommended to use public APIs from the @ref{a0,,inspect} module
for any introspection needs.
@end quotation
@end cartouche

@node 命令行界面<8>,,Code Objects Bit Flags,inspect --- 检查对象
@anchor{library/inspect command-line-interface}@anchor{36ae}@anchor{library/inspect inspect-module-cli}@anchor{862}
@subsubsection 命令行界面


The @ref{a0,,inspect} module also provides a basic introspection capability
from the command line.

By default, accepts the name of a module and prints the source of that
module. A class or function within the module can be printed instead by
appended a colon and the qualified name of the target object.

@geindex inspect command line option; --details
@anchor{library/inspect cmdoption-inspect-details}@anchor{36af}
@deffn {程序选项} @w{-}@w{-}details

Print information about the specified object rather than the source code
@end deffn

@node site —— 指定域的配置钩子,,inspect --- 检查对象,Python运行时服务
@anchor{library/site doc}@anchor{36b0}@anchor{library/site module-site}@anchor{eb}@anchor{library/site site-site-specific-configuration-hook}@anchor{36b1}
@subsection @code{site} —— 指定域的配置钩子


@geindex site (模块)

@strong{源代码:} Lib/site.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/site.py}


__________________________________________________________________


@strong{这个模块将在初始化时被自动导入。} 此自动导入可以通过使用解释器的 @ref{b1d,,-S} 选项来屏蔽。

@geindex module; search; path

导入此模块将会附加域特定的路径到模块搜索路径并且添加一些内建对象，除非使用了 @ref{b1d,,-S} 选项。在此例中，模块可以被安全地导入，而不会对模块搜索路径和内建对象有自动的修改或添加。要明确地触发通常域特定的添加，调用函数 @ref{12dd,,site.main()}。


在 3.3 版更改: 即便使用了 @ref{b1d,,-S}，也会导入此模块用于触发路径操纵。


@geindex site-packages; directory

It starts by constructing up to four directories from a head and a tail part.
For the head part, it uses @code{sys.prefix} and @code{sys.exec_prefix}; empty heads
are skipped.  For the tail part, it uses the empty string and then
@code{lib/site-packages} (on Windows) or
@code{lib/python@emph{X.Y}/site-packages} (on Unix and Macintosh).  For each
of the distinct head-tail combinations, it sees if it refers to an existing
directory, and if so, adds it to @code{sys.path} and also inspects the newly
added path for configuration files.


在 3.5 版更改: Support for the "site-python" directory has been removed.


如果名为 "pyvenv.cfg" 的文件存在于 sys.executable 之上的一个目录中，则 sys.prefix 和 sys.exec_prefix 将被设置为该目录，并且还会检查 site-packages （ sys.base_prefix 和 sys.base_exec_prefix 始终是 Python 安装的 "真实" 前缀）。 如果 "pyvenv.cfg" （引导程序配置文件）包含设置为非 "true"（不区分大小写）的 "include-system-site-packages" 键，则不会在系统级前缀中搜索 site-packages；反之则会。

@geindex # (hash); comment
@geindex 语句; import

一个路径配置文件是具有 @code{@emph{name}.pth} 命名格式的文件，并且存在上面提到的四个目录之一中；它的内容是要添加到 @code{sys.path} 中的额外项目（每行一个）。不存在的项目不会添加到 @code{sys.path}，并且不会检查项目指向的是目录还是文件。项目不会被添加到 @code{sys.path} 超过一次。空行和由 @code{#} 起始的行会被跳过。以 @code{import} 开始的行（跟着空格或 TAB）会被执行。

@cartouche
@quotation 注解 
每次启动 Python，在 @code{.pth} 文件中的可执行行都将会被运行，而不管特定的模块实际上是否需要被使用。 因此，其影响应降至最低。可执行行的主要预期目的是使相关模块可导入（加载第三方导入钩子，调整 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 等）。如果它发生了，任何其他的初始化都应当在模块实际导入之前完成。将代码块限制为一行是一种有意采取的措施，不鼓励在此处放置更复杂的内容。
@end quotation
@end cartouche

@geindex package
@geindex path; configuration; file

例如，假设 @code{sys.prefix} 和 @code{sys.exec_prefix} 已经被设置为 @code{/usr/local}。 Python X.Y 的库之后被安装为 @code{/usr/local/lib/python@emph{X.Y}}。假设有一个拥有三个孙目录 @code{foo}, @code{bar} 和 @code{spam} 的子目录 @code{/usr/local/lib/python@emph{X.Y}/site-packages}，并且有两个路径配置文件 @code{foot.pth} 和 @code{bar.pth}。假定 @code{foo.pth} 内容如下:

@example
# foo package configuration

foo
bar
bletch
@end example

并且 @code{bar.pth} 包含:

@example
# bar package configuration

bar
@end example

则下面特定版目录将以如下顺序被添加到 @code{sys.path}。

@example
/usr/local/lib/pythonX.Y/site-packages/bar
/usr/local/lib/pythonX.Y/site-packages/foo
@end example

Note that @code{bletch} is omitted because it doesn't exist; the @code{bar}
directory precedes the @code{foo} directory because @code{bar.pth} comes
alphabetically before @code{foo.pth}; and @code{spam} is omitted because it is
not mentioned in either path configuration file.

@geindex 模块; sitecustomize

After these path manipulations, an attempt is made to import a module named
@code{sitecustomize}, which can perform arbitrary site-specific customizations.
It is typically created by a system administrator in the site-packages
directory.  If this import fails with an @ref{32d,,ImportError} or its subclass
exception, and the exception's @code{name} attribute equals to @code{'sitecustomize'},
it is silently ignored.  If Python is started without output streams available, as
with @code{pythonw.exe} on Windows (which is used by default to start IDLE),
attempted output from @code{sitecustomize} is ignored.  Any other exception
causes a silent and perhaps mysterious failure of the process.

@geindex 模块; usercustomize

After this, an attempt is made to import a module named @code{usercustomize},
which can perform arbitrary user-specific customizations, if
@ref{36b2,,ENABLE_USER_SITE} is true.  This file is intended to be created in the
user site-packages directory (see below), which is part of @code{sys.path} unless
disabled by @ref{d0e,,-s}.  If this import fails with an @ref{32d,,ImportError} or
its subclass exception, and the exception's @code{name} attribute equals to
@code{'usercustomize'}, it is silently ignored.

Note that for some non-Unix systems, @code{sys.prefix} and @code{sys.exec_prefix} are
empty, and the path manipulations are skipped; however the import of
@code{sitecustomize} and @code{usercustomize} is still attempted.

@menu
* Readline configuration:: 
* 模块内容: 模块内容<7>. 
* 命令行界面: 命令行界面<9>. 

@end menu

@node Readline configuration,模块内容<7>,,site —— 指定域的配置钩子
@anchor{library/site readline-configuration}@anchor{36b3}@anchor{library/site rlcompleter-config}@anchor{8e0}
@subsubsection Readline configuration


On systems that support @ref{de,,readline}, this module will also import and
configure the @ref{e1,,rlcompleter} module, if Python is started in
@ref{8dd,,interactive mode} and without the @ref{b1d,,-S} option.
The default behavior is enable tab-completion and to use
@code{~/.python_history} as the history save file.  To disable it, delete (or
override) the @ref{8de,,sys.__interactivehook__} attribute in your
@code{sitecustomize} or @code{usercustomize} module or your
@geindex PYTHONSTARTUP
@geindex 环境变量; PYTHONSTARTUP
@ref{8df,,PYTHONSTARTUP} file.


在 3.4 版更改: Activation of rlcompleter and history was made automatic.


@node 模块内容<7>,命令行界面<9>,Readline configuration,site —— 指定域的配置钩子
@anchor{library/site module-contents}@anchor{36b4}
@subsubsection 模块内容


@geindex PREFIXES() (在 site 模块中)
@anchor{library/site site PREFIXES}@anchor{36b5}
@deffn {数据} site.PREFIXES

A list of prefixes for site-packages directories.
@end deffn

@geindex ENABLE_USER_SITE() (在 site 模块中)
@anchor{library/site site ENABLE_USER_SITE}@anchor{36b2}
@deffn {数据} site.ENABLE_USER_SITE

Flag showing the status of the user site-packages directory.  @code{True} means
that it is enabled and was added to @code{sys.path}.  @code{False} means that it
was disabled by user request (with @ref{d0e,,-s} or
@geindex PYTHONNOUSERSITE
@geindex 环境变量; PYTHONNOUSERSITE
@ref{d0f,,PYTHONNOUSERSITE}).  @code{None} means it was disabled for security
reasons (mismatch between user or group id and effective id) or by an
administrator.
@end deffn

@geindex USER_SITE() (在 site 模块中)
@anchor{library/site site USER_SITE}@anchor{12dc}
@deffn {数据} site.USER_SITE

Path to the user site-packages for the running Python.  Can be @code{None} if
@ref{bce,,getusersitepackages()} hasn't been called yet.  Default value is
@code{~/.local/lib/python@emph{X.Y}/site-packages} for UNIX and non-framework Mac
OS X builds, @code{~/Library/Python/@emph{X.Y}/lib/python/site-packages} for Mac
framework builds, and @code{@emph{%APPDATA%}\Python\Python@emph{XY}\site-packages}
on Windows.  This directory is a site directory, which means that
@code{.pth} files in it will be processed.
@end deffn

@geindex USER_BASE() (在 site 模块中)
@anchor{library/site site USER_BASE}@anchor{12ee}
@deffn {数据} site.USER_BASE

Path to the base directory for the user site-packages.  Can be @code{None} if
@ref{bcd,,getuserbase()} hasn't been called yet.  Default value is
@code{~/.local} for UNIX and Mac OS X non-framework builds,
@code{~/Library/Python/@emph{X.Y}} for Mac framework builds, and
@code{@emph{%APPDATA%}\Python} for Windows.  This value is used by Distutils to
compute the installation directories for scripts, data files, Python modules,
etc. for the @ref{12ef,,user installation scheme}.
See also 
@geindex PYTHONUSERBASE
@geindex 环境变量; PYTHONUSERBASE
@ref{d0d,,PYTHONUSERBASE}.
@end deffn

@geindex main() (在 site 模块中)
@anchor{library/site site main}@anchor{12dd}
@deffn {函数} site.main ()

Adds all the standard site-specific directories to the module search
path.  This function is called automatically when this module is imported,
unless the Python interpreter was started with the @ref{b1d,,-S} flag.


在 3.3 版更改: This function used to be called unconditionally.

@end deffn

@geindex addsitedir() (在 site 模块中)
@anchor{library/site site addsitedir}@anchor{36b6}
@deffn {函数} site.addsitedir (sitedir, known_paths=None)

Add a directory to sys.path and process its @code{.pth} files.  Typically
used in @code{sitecustomize} or @code{usercustomize} (see above).
@end deffn

@geindex getsitepackages() (在 site 模块中)
@anchor{library/site site getsitepackages}@anchor{bcc}
@deffn {函数} site.getsitepackages ()

Return a list containing all global site-packages directories.


3.2 新版功能.

@end deffn

@geindex getuserbase() (在 site 模块中)
@anchor{library/site site getuserbase}@anchor{bcd}
@deffn {函数} site.getuserbase ()

Return the path of the user base directory, @ref{12ee,,USER_BASE}.  If it is not
initialized yet, this function will also set it, respecting
@geindex PYTHONUSERBASE
@geindex 环境变量; PYTHONUSERBASE
@ref{d0d,,PYTHONUSERBASE}.


3.2 新版功能.

@end deffn

@geindex getusersitepackages() (在 site 模块中)
@anchor{library/site site getusersitepackages}@anchor{bce}
@deffn {函数} site.getusersitepackages ()

Return the path of the user-specific site-packages directory,
@ref{12dc,,USER_SITE}.  If it is not initialized yet, this function will also set
it, respecting 
@geindex PYTHONNOUSERSITE
@geindex 环境变量; PYTHONNOUSERSITE
@ref{d0f,,PYTHONNOUSERSITE} and @ref{12ee,,USER_BASE}.


3.2 新版功能.

@end deffn

@node 命令行界面<9>,,模块内容<7>,site —— 指定域的配置钩子
@anchor{library/site command-line-interface}@anchor{36b7}@anchor{library/site site-commandline}@anchor{36b8}
@subsubsection 命令行界面


The @ref{eb,,site} module also provides a way to get the user directories from the
command line:

@example
$ python3 -m site --user-site
/home/user/.local/lib/python3.3/site-packages
@end example

If it is called without arguments, it will print the contents of
@ref{482,,sys.path} on the standard output, followed by the value of
@ref{12ee,,USER_BASE} and whether the directory exists, then the same thing for
@ref{12dc,,USER_SITE}, and finally the value of @ref{36b2,,ENABLE_USER_SITE}.

@geindex site command line option; --user-base
@anchor{library/site cmdoption-site-user-base}@anchor{36b9}
@deffn {程序选项} @w{-}@w{-}user@w{-}base

Print the path to the user base directory.
@end deffn

@geindex site command line option; --user-site
@anchor{library/site cmdoption-site-user-site}@anchor{36ba}
@deffn {程序选项} @w{-}@w{-}user@w{-}site

Print the path to the user site-packages directory.
@end deffn

If both options are given, user base and user site will be printed (always in
this order), separated by @ref{12eb,,os.pathsep}.

If any option is given, the script will exit with one of these values: @code{0} if
the user site-packages directory is enabled, @code{1} if it was disabled by the
user, @code{2} if it is disabled for security reasons or by an administrator, and a
value greater than 2 if there is an error.


@subsubheading 参见


@geindex Python 提高建议; PEP 370
PEP 370@footnote{https://www.python.org/dev/peps/pep-0370} -- 分用户的 site-packages 目录


@node 自定义 Python 解释器,导入模块,Python运行时服务,Python 标准库
@anchor{library/custominterp doc}@anchor{36bb}@anchor{library/custominterp custom-python-interpreters}@anchor{36bc}@anchor{library/custominterp custominterp}@anchor{36bd}
@section 自定义 Python 解释器


本章中描述的模块允许编写类似于 Python 的交互式解释器的接口。 如果你想要一个支持附加一些特殊功能到 Python 语言的 Python 解释器，你应该看看 @ref{1b,,code} 模块。 （ @ref{1d,,codeop} 模块是低层级的，用于支持编译可能不完整的 Python 代码块。）

本章描述的完整模块列表如下：

@menu
* code: code --- 解释器基类. 解释器基类
* codeop: codeop --- 编译Python代码. 编译Python代码

@end menu

@node code --- 解释器基类,codeop --- 编译Python代码,,自定义 Python 解释器
@anchor{library/code doc}@anchor{36be}@anchor{library/code code-interpreter-base-classes}@anchor{36bf}@anchor{library/code module-code}@anchor{1b}
@subsection @code{code} --- 解释器基类


@geindex code (模块)

@strong{源代码：} Lib/code.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/code.py}


__________________________________________________________________


@code{code} 模块提供了在 Python 中实现 read-eval-print 循环的功能。它包含两个类和一些快捷功能，可用于构建提供交互式解释器的应用程序。

@geindex InteractiveInterpreter (code 中的类)
@anchor{library/code code InteractiveInterpreter}@anchor{36c0}
@deffn {类} code.InteractiveInterpreter (locals=None)

这个类处理解析器和解释器状态（用户命名空间的）；它不处理缓冲器、终端提示区或着输入文件名（文件名总是显示地传递）。可选的 @emph{locals} 参数指定一个字典，字典里面包含将在此类执行的代码；它默认创建新的字典，其键 @code{'__name__'} 设置为 @code{'__console__'} ，键 @code{'__doc__'} 设置为 @code{None} 。
@end deffn

@geindex InteractiveConsole (code 中的类)
@anchor{library/code code InteractiveConsole}@anchor{1796}
@deffn {类} code.InteractiveConsole (locals=None, filename="<console>")

尽可能模拟交互式 Python 解释器的行为。此类建立在 @ref{36c0,,InteractiveInterpreter} 的基础上，使用熟悉的 @code{sys.ps1} 和 @code{sys.ps2} 作为输入提示符，并有输入缓冲。
@end deffn

@geindex interact() (在 code 模块中)
@anchor{library/code code interact}@anchor{36c1}
@deffn {函数} code.interact (banner=None, readfunc=None, local=None, exitmsg=None)

运行一个 read-eval-print 循环的便捷函数。这会创建一个新的 @ref{1796,,InteractiveConsole} 实例。如果提供了 @emph{readfunc} ，会设置为 @ref{36c2,,InteractiveConsole.raw_input()} 方法。如果提供了 @emph{local} ，则将其传递给 @ref{1796,,InteractiveConsole} 的构造函数，以用作解释器循环的默认命名空间。然后，如果提供了 @emph{banner} 和 @emph{exitmsg} ，实例的 @ref{36c1,,interact()} 方法会以此为标题和退出消息。控制台对象在使用后将被丢弃。


在 3.6 版更改: 加入 @emph{exitmsg} 参数。

@end deffn

@geindex compile_command() (在 code 模块中)
@anchor{library/code code compile_command}@anchor{36c3}
@deffn {函数} code.compile_command (source, filename="<input>", symbol="single")

这个函数主要用来模拟 Python 解释器的主循环（即 read-eval-print 循环）。难点的部分是当用户输入不完整命令时，判断能否通过之后的输入来完成（要么成为完整的命令，要么语法错误）。该函数  @emph{几乎} 和实际的解释器主循环的判断是相同的。

@emph{source} 是源字符串；@emph{filename} 是可选的用作读取源的文件名，默认为 @code{'<input>'}；@emph{symbol} 是可选的语法开启符号，应为 @code{'single'} (默认), @code{'eval'} 或 @code{'exec'}。

如果命令完整且有效则返回一个代码对象 (等价于 @code{compile(source, filename, symbol)})；如果命令不完整则返回 @code{None}；如果命令完整但包含语法错误则会引发 @ref{452,,SyntaxError} 或 @ref{95a,,OverflowError} 而如果命令包含无效字面值则将引发 @ref{1fb,,ValueError}。
@end deffn

@menu
* 交互解释器对象:: 
* 交互式控制台对象:: 

@end menu

@node 交互解释器对象,交互式控制台对象,,code --- 解释器基类
@anchor{library/code interactive-interpreter-objects}@anchor{36c4}@anchor{library/code interpreter-objects}@anchor{36c5}
@subsubsection 交互解释器对象


@geindex runsource() (code.InteractiveInterpreter 方法)
@anchor{library/code code InteractiveInterpreter runsource}@anchor{36c6}
@deffn {方法} InteractiveInterpreter.runsource (source, filename="<input>", symbol="single")

在解释器中编译并运行一段源码。 所用参数与 @ref{36c3,,compile_command()} 一样；@emph{filename} 的默认值为 @code{'<input>'}，@emph{symbol} 则为 @code{'single'}。 可能发生以下情况之一：


@itemize *

@item 
输入不正确；@ref{36c3,,compile_command()} 引发了一个异常 (@ref{452,,SyntaxError} 或 @ref{95a,,OverflowError})。 将通过调用 @ref{36c7,,showsyntaxerror()} 方法打印语法回溯信息。 @ref{36c6,,runsource()} 返回 @code{False}。

@item 
输入不完整，需要更多输入；函数 @ref{36c3,,compile_command()} 返回 @code{None} 。方法 @ref{36c6,,runsource()} 返回 @code{True} 。

@item 
输入完整；@ref{36c3,,compile_command()} 返回了一个代码对象。 将通过调用 @ref{36c8,,runcode()} 执行代码（该方法也会处理运行时异常，@ref{5f7,,SystemExit} 除外）。 @ref{36c6,,runsource()} 返回 @code{False}。
@end itemize

该返回值用于决定使用 @code{sys.ps1} 还是 @code{sys.ps2} 来作为下一行的输入提示符。
@end deffn

@geindex runcode() (code.InteractiveInterpreter 方法)
@anchor{library/code code InteractiveInterpreter runcode}@anchor{36c8}
@deffn {方法} InteractiveInterpreter.runcode (code)

执行一个代码对象。当发生异常时，调用 @ref{6a1,,showtraceback()} 来显示回溯。除 @ref{5f7,,SystemExit} （允许传播）以外的所有异常都会被捕获。

有关 @ref{197,,KeyboardInterrupt} 的说明，该异常可能发生于此代码的其他位置，并且并不总能被捕获。 调用者应当准备好处理它。
@end deffn

@geindex showsyntaxerror() (code.InteractiveInterpreter 方法)
@anchor{library/code code InteractiveInterpreter showsyntaxerror}@anchor{36c7}
@deffn {方法} InteractiveInterpreter.showsyntaxerror (filename=None)

显示刚发生的语法错误。 这不会显示堆栈回溯因为语法错误并无此种信息。 如果给出了 @emph{filename}，它会被放入异常来替代 Python 解析器所提供的默认文件名，因为它在从一个字符串读取时总是会使用 @code{'<string>'}。 输出将由 @ref{36c9,,write()} 方法来写入。
@end deffn

@geindex showtraceback() (code.InteractiveInterpreter 方法)
@anchor{library/code code InteractiveInterpreter showtraceback}@anchor{6a1}
@deffn {方法} InteractiveInterpreter.showtraceback ()

显示刚发生的异常。 我们移除了第一个堆栈条目因为它从属于解释器对象的实现。 输出将由 @ref{36c9,,write()} 方法来写入。


在 3.5 版更改: 将显示完整的链式回溯，而不只是主回溯。

@end deffn

@geindex write() (code.InteractiveInterpreter 方法)
@anchor{library/code code InteractiveInterpreter write}@anchor{36c9}
@deffn {方法} InteractiveInterpreter.write (data)

将一个字符串写入到标准错误流 (@code{sys.stderr})。 所有派生类都应重载此方法以提供必要的正确输出处理。
@end deffn

@node 交互式控制台对象,,交互解释器对象,code --- 解释器基类
@anchor{library/code console-objects}@anchor{36ca}@anchor{library/code interactive-console-objects}@anchor{36cb}
@subsubsection 交互式控制台对象


@ref{1796,,InteractiveConsole} 类是 @ref{36c0,,InteractiveInterpreter} 的子类，因此它提供了解释器对象的所有方法，还有以下的额外方法。

@geindex interact() (code.InteractiveConsole 方法)
@anchor{library/code code InteractiveConsole interact}@anchor{36cc}
@deffn {方法} InteractiveConsole.interact (banner=None, exitmsg=None)

近似地模拟交互式 Python 终端。 可选的 @emph{banner} 参数指定要在第一次交互前打印的条幅；默认情况下会类似于标准 Python 解释器所打印的内容，并附上外加圆括号的终端对象类名（这样就不会与真正的解释器混淆 —— 因为确实太像了！）

可选的 @emph{exitmsg} 参数指定要在退出时打印的退出消息。 传入空字符串可以屏蔽退出消息。 如果 @emph{exitmsg} 未给出或为 @code{None}，则将打印默认消息。


在 3.4 版更改: 要禁止打印任何条幅消息，请传递一个空字符串。



在 3.6 版更改: 退出时打印退出消息。

@end deffn

@geindex push() (code.InteractiveConsole 方法)
@anchor{library/code code InteractiveConsole push}@anchor{36cd}
@deffn {方法} InteractiveConsole.push (line)

将一行源文本推入解释器。 行内容不应带有末尾换行符；它可以有内部换行符。 行内容会被添加到一个缓冲区并且会调用解释器的 @code{runsource()} 方法，附带缓冲区内容的拼接结果作为源文本。 如果显示命令已执行或不合法，缓冲区将被重置；否则，则命令尚未结束，缓冲区将在添加行后保持原样。 如果要求更多输入则返回值为 @code{True}，如果行已按某种方式被处理则返回值为 @code{False} (这与 @code{runsource()} 相同)。
@end deffn

@geindex resetbuffer() (code.InteractiveConsole 方法)
@anchor{library/code code InteractiveConsole resetbuffer}@anchor{36ce}
@deffn {方法} InteractiveConsole.resetbuffer ()

从输入缓冲区中删除所有未处理的内容。
@end deffn

@geindex raw_input() (code.InteractiveConsole 方法)
@anchor{library/code code InteractiveConsole raw_input}@anchor{36c2}
@deffn {方法} InteractiveConsole.raw_input (prompt="")

输出提示并读取一行。返回的行不包含末尾的换行符。当用户输入 EOF 键序列时，会引发 @ref{c65,,EOFError} 异常。默认实现是从 @code{sys.stdin} 读取；子类可以用其他实现代替。
@end deffn

@node codeop --- 编译Python代码,,code --- 解释器基类,自定义 Python 解释器
@anchor{library/codeop doc}@anchor{36cf}@anchor{library/codeop codeop-compile-python-code}@anchor{36d0}@anchor{library/codeop module-codeop}@anchor{1d}
@subsection @code{codeop} --- 编译Python代码


@geindex codeop (模块)

@strong{源代码：} Lib/codeop.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/codeop.py}


__________________________________________________________________


@ref{1d,,codeop} 模块提供了可以模拟Python读取-执行-打印循环的实用程序，就像在 @ref{1b,,code} 模块中一样。因此，您可能不希望直接使用该模块；如果你想在程序中包含这样一个循环，你可能需要使用 @ref{1b,,code} 模块。

这个任务有两个部分:


@enumerate 

@item 
能够判断一行输入是否完成了一个Python语句：简而言之，告诉我们是否要打印 '@code{>>>}' 或 '@code{...}'。

@item 
记住用户已输入了哪些 future 语句，这样后续的输入可以在这些语句被启用的状态下被编译。
@end enumerate

@ref{1d,,codeop} 模块提供了分别以及同时执行这两个部分的方式。

只执行前一部分：

@geindex compile_command() (在 codeop 模块中)
@anchor{library/codeop codeop compile_command}@anchor{36d1}
@deffn {函数} codeop.compile_command (source, filename="<input>", symbol="single")

尝试编译 @emph{source}，这应当是一个 Python 代码字符串，并且在 @emph{source} 是有效的 Python 代码时返回一个代码对象。 在此情况下，代码对象的 filename 属性将为 @emph{filename}，其默认值为 @code{'<input>'}。 如果 @emph{source} @emph{不是} 有效的 Python 代码而是有效的 Python 代码的一个前缀时将返回 @code{None}。

如果 @emph{source} 存在问题，将引发异常。 如果存在无效的 Python 语法将引发 @ref{452,,SyntaxError}，而如果存在无效的字面值则将引发 @ref{95a,,OverflowError} 或 @ref{1fb,,ValueError}。

@emph{symbol} 参数确定 @emph{source} 是作为一条语句 (对应默认值 @code{'single'})，作为一系列语句 (@code{'exec'}) 还是作为一个 @ref{35cd,,expression} (@code{'eval'}) 进行编译。 任何其他值都将导致引发 @ref{1fb,,ValueError}。

@cartouche
@quotation 注解 
解析器有可能（但很不常见）会在到达源码结尾之前停止解析并成功输出结果；在这种情况下，末尾的符号可能会被忽略而不是引发错误。 例如，一个反斜杠加两个换行符之后可以跟随任何无意义的符号。 一旦解析器 API 得到改进将修正这个问题。
@end quotation
@end cartouche
@end deffn

@geindex Compile (codeop 中的类)
@anchor{library/codeop codeop Compile}@anchor{36d2}
@deffn {类} codeop.Compile

这个类的实例具有 @ref{13c5,,__call__()} 方法，其签名与内置函数 @ref{1b4,,compile()} 相似，区别在于如果该实例编译了包含 @ref{0,,__future__} 语句的程序文本，则实例会‘记住’并使用已生效的语句编译所有后续程序文本。
@end deffn

@geindex CommandCompiler (codeop 中的类)
@anchor{library/codeop codeop CommandCompiler}@anchor{36d3}
@deffn {类} codeop.CommandCompiler

这个类的实例具有 @ref{13c5,,__call__()} 方法，其签名与 @ref{36d1,,compile_command()} 相似；区别在于如果该实例编译了包含 @code{__future__} 语句的程序文本，则实例会‘记住’并使用已生效的语句编译编译所有后续程序文本。
@end deffn

@node 导入模块,Python 语言服务,自定义 Python 解释器,Python 标准库
@anchor{library/modules doc}@anchor{36d4}@anchor{library/modules importing-modules}@anchor{36d5}@anchor{library/modules modules}@anchor{36d6}
@section 导入模块


本章中介绍的模块提供了导入其他Python模块和挂钩以自定义导入过程的新方法。

本章描述的完整模块列表如下：

@menu
* zipimport: zipimport --- 从 Zip 存档中导入模块. 从 Zip 存档中导入模块
* pkgutil: pkgutil --- 包扩展工具. 包扩展工具
* modulefinder: modulefinder --- 查找脚本使用的模块. 查找脚本使用的模块
* runpy: runpy --- Locating and executing Python modules. Locating and executing Python modules
* importlib: importlib --- import 的实现. import 的实现
* Using importlib.metadata: Using importlib metadata. 

@end menu

@node zipimport --- 从 Zip 存档中导入模块,pkgutil --- 包扩展工具,,导入模块
@anchor{library/zipimport doc}@anchor{36d7}@anchor{library/zipimport module-zipimport}@anchor{143}@anchor{library/zipimport zipimport-import-modules-from-zip-archives}@anchor{36d8}
@subsection @code{zipimport} --- 从 Zip 存档中导入模块


@geindex zipimport (模块)

@strong{源代码：} Lib/zipimport.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/zipimport.py}


__________________________________________________________________


此模块添加了从 ZIP 格式档案中导入 Python 模块（ @code{*.py} ， @code{*.pyc} ）和包的能力。通常不需要明确地使用 @ref{143,,zipimport} 模块，内置的 @ref{c16,,import} 机制会自动将此模块用于 ZIP 档案路径的 @ref{482,,sys.path} 项目上。

通常， @ref{482,,sys.path} 是字符串的目录名称列表。此模块同样允许 @ref{482,,sys.path} 的一项成为命名 ZIP 文件档案的字符串。 ZIP 档案可以容纳子目录结构去支持包的导入，并且可以将归档文件中的路径指定为仅从子目录导入。比如说，路径 @code{example.zip/lib/} 将只会从档案中的 @code{lib/} 子目录导入。

任何文件都可以存在于 ZIP档案之中，但是只有 @code{.py} 和 @code{.pyc} 文件是能够导入的。不允许导入 ZIP 中的动态模组（ @code{.pyd} ， @code{.so} ）。请注意，如果档案中只包含 @code{.py} 文件， Python不会尝试通过添加对应的 @code{.pyc} 文件修改档案，意思是如果 ZIP 档案不包含 @code{.pyc} 文件，导入或许会变慢。


在 3.8 版更改: 以前，不支持带有档案注释的 ZIP 档案。



@subsubheading 参见



@table @asis

@item PKZIP Application Note@footnote{https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT}

Phil Katz 编写的 ZIP 文件格式文档，此格式和使用的算法的创建者。

@geindex Python 提高建议; PEP 273

@item PEP 273@footnote{https://www.python.org/dev/peps/pep-0273} -  从ZIP压缩包导入模块

由 James C. Ahlstrom 编写，他也提供了实现。 Python 2.3 遵循 
@geindex Python 提高建议; PEP 273
PEP 273@footnote{https://www.python.org/dev/peps/pep-0273} 的规范，但是使用 Just van Rossum 编写的使用了 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} 中描述的导入钩的实现。

@geindex Python 提高建议; PEP 302

@item PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} - 新导入钩

PEP 添加导入钩来有助于模块运作。
@end table


此模块定义了一个异常：

@geindex ZipImportError
@anchor{library/zipimport zipimport ZipImportError}@anchor{36d9}
@deffn {例外} zipimport.ZipImportError

异常由 zipimporter 对象引发。这是 @ref{32d,,ImportError} 的子类，因此，也可以捕获为 @ref{32d,,ImportError} 。
@end deffn

@menu
* zipimporter 对象:: 
* 例子: 例子<28>. 

@end menu

@node zipimporter 对象,例子<28>,,zipimport --- 从 Zip 存档中导入模块
@anchor{library/zipimport id1}@anchor{36da}@anchor{library/zipimport zipimporter-objects}@anchor{36db}
@subsubsection zipimporter 对象


@ref{36dc,,zipimporter} 是用于导入 ZIP 文件的类。

@geindex zipimporter (zipimport 中的类)
@anchor{library/zipimport zipimport zipimporter}@anchor{36dc}
@deffn {类} zipimport.zipimporter (archivepath)

创建新的 zipimporter 实例。 @emph{archivepath} 必须是指向 ZIP 文件的路径，或者 ZIP 文件中的特定路径。例如， @code{foo/bar.zip/lib} 的 @emph{archivepath} 将在 ZIP 文件 @code{foo/bar.zip} 中的 @code{lib} 目录中查找模块（只要它存在）。

如果 @emph{archivepath} 没有指向一个有效的 ZIP 档案，引发 @ref{36d9,,ZipImportError} 。

@geindex find_module() (zipimport.zipimporter 方法)
@anchor{library/zipimport zipimport zipimporter find_module}@anchor{36dd}
@deffn {方法} find_module (fullname[, path])

搜索由 @emph{fullname} 指定的模块。 @emph{fullname} 必须是完全合格的（点分的）模块名。它返回 zipimporter 实例本身如果模块被找到，或者返回 @ref{157,,None} 如果没找到指定模块。可选的 @emph{path} 被忽略，这是为了与导入器协议兼容。
@end deffn

@geindex get_code() (zipimport.zipimporter 方法)
@anchor{library/zipimport zipimport zipimporter get_code}@anchor{36de}
@deffn {方法} get_code (fullname)

返回指定模块的代码对象。如果不能找到模块会引发 @ref{36d9,,ZipImportError} 错误。
@end deffn

@geindex get_data() (zipimport.zipimporter 方法)
@anchor{library/zipimport zipimport zipimporter get_data}@anchor{104d}
@deffn {方法} get_data (pathname)

返回与 @emph{pathname} 相关联的数据。如果不能找到文件则引发 @ref{1d3,,OSError} 错误。


在 3.3 版更改: 曾经是 @ref{98c,,IOError} 被引发而不是 @ref{1d3,,OSError} 。

@end deffn

@geindex get_filename() (zipimport.zipimporter 方法)
@anchor{library/zipimport zipimport zipimporter get_filename}@anchor{36df}
@deffn {方法} get_filename (fullname)

如果导入了指定的模块 @code{__file__} ，则返回为该模块设置的值。如果未找到模块则引发 @ref{36d9,,ZipImportError} 错误。


3.1 新版功能.

@end deffn

@geindex get_source() (zipimport.zipimporter 方法)
@anchor{library/zipimport zipimport zipimporter get_source}@anchor{36e0}
@deffn {方法} get_source (fullname)

返回指定模块的源代码。如果没有找到模块则引发 @ref{36d9,,ZipImportError} ，如果档案包含模块但是没有源代码，返回 @ref{157,,None} 。
@end deffn

@geindex is_package() (zipimport.zipimporter 方法)
@anchor{library/zipimport zipimport zipimporter is_package}@anchor{36e1}
@deffn {方法} is_package (fullname)

如果由 @emph{fullname} 指定的模块是一个包则返回 @code{True} 。如果不能找到模块则引发 @ref{36d9,,ZipImportError} 错误。
@end deffn

@geindex load_module() (zipimport.zipimporter 方法)
@anchor{library/zipimport zipimport zipimporter load_module}@anchor{36e2}
@deffn {方法} load_module (fullname)

加载由 @emph{fullname} 指定的模块。 @emph{fullname} 必须是完全限定的（点分的）模块名。它返回已加载模块，或者当找不到模块时引发 @ref{36d9,,ZipImportError} 错误。
@end deffn

@geindex archive (zipimport.zipimporter 属性)
@anchor{library/zipimport zipimport zipimporter archive}@anchor{36e3}
@deffn {属性} archive

导入器关联的 ZIP 文件的文件名，没有可能的子路径。
@end deffn

@geindex prefix (zipimport.zipimporter 属性)
@anchor{library/zipimport zipimport zipimporter prefix}@anchor{36e4}
@deffn {属性} prefix

ZIP 文件中搜索的模块的子路径。这是一个指向 ZIP 文件根目录的 zipimporter 对象的空字符串。
@end deffn

当与斜杠结合使用时， @ref{36e3,,archive} 和 @ref{36e4,,prefix} 属性等价于赋予 @ref{36dc,,zipimporter} 构造器的原始 @emph{archivepath} 参数。
@end deffn

@node 例子<28>,,zipimporter 对象,zipimport --- 从 Zip 存档中导入模块
@anchor{library/zipimport examples}@anchor{36e5}@anchor{library/zipimport zipimport-examples}@anchor{36e6}
@subsubsection 例子


这是一个从 ZIP 档案中导入模块的例子 - 请注意 @ref{143,,zipimport} 模块不需要明确地使用。

@example
$ unzip -l example.zip
Archive:  example.zip
  Length     Date   Time    Name
 --------    ----   ----    ----
     8467  11-26-02 22:30   jwzthreading.py
 --------                   -------
     8467                   1 file
$ ./python
Python 2.3 (#1, Aug 1 2003, 19:54:32)
>>> import sys
>>> sys.path.insert(0, 'example.zip')  # Add .zip file to front of path
>>> import jwzthreading
>>> jwzthreading.__file__
'example.zip/jwzthreading.py'
@end example

@node pkgutil --- 包扩展工具,modulefinder --- 查找脚本使用的模块,zipimport --- 从 Zip 存档中导入模块,导入模块
@anchor{library/pkgutil doc}@anchor{36e7}@anchor{library/pkgutil module-pkgutil}@anchor{cd}@anchor{library/pkgutil pkgutil-package-extension-utility}@anchor{36e8}
@subsection @code{pkgutil} --- 包扩展工具


@geindex pkgutil (模块)

@strong{源代码:} Lib/pkgutil.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pkgutil.py}


__________________________________________________________________


该模块为导入系统提供了工具，尤其是在包支持方面。

@geindex ModuleInfo (pkgutil 中的类)
@anchor{library/pkgutil pkgutil ModuleInfo}@anchor{608}
@deffn {类} pkgutil.ModuleInfo (module_finder, name, ispkg)

一个包含模块信息的简短摘要的命名元组。


3.6 新版功能.

@end deffn

@geindex extend_path() (在 pkgutil 模块中)
@anchor{library/pkgutil pkgutil extend_path}@anchor{36e9}
@deffn {函数} pkgutil.extend_path (path, name)

Extend the search path for the modules which comprise a package.  Intended
use is to place the following code in a package's @code{__init__.py}:

@example
from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)
@end example

This will add to the package's @code{__path__} all subdirectories of directories
on @code{sys.path} named after the package.  This is useful if one wants to
distribute different parts of a single logical package as multiple
directories.

It also looks for @code{*.pkg} files beginning where @code{*} matches the
@emph{name} argument.  This feature is similar to @code{*.pth} files (see the
@ref{eb,,site} module for more information), except that it doesn't special-case
lines starting with @code{import}.  A @code{*.pkg} file is trusted at face
value: apart from checking for duplicates, all entries found in a
@code{*.pkg} file are added to the path, regardless of whether they exist
on the filesystem.  (This is a feature.)

If the input path is not a list (as is the case for frozen packages) it is
returned unchanged.  The input path is not modified; an extended copy is
returned.  Items are only appended to the copy at the end.

It is assumed that @ref{482,,sys.path} is a sequence.  Items of @ref{482,,sys.path}
that are not strings referring to existing directories are ignored. Unicode
items on @ref{482,,sys.path} that cause errors when used as filenames may cause
this function to raise an exception (in line with @ref{1f8,,os.path.isdir()}
behavior).
@end deffn

@geindex ImpImporter (pkgutil 中的类)
@anchor{library/pkgutil pkgutil ImpImporter}@anchor{36ea}
@deffn {类} pkgutil.ImpImporter (dirname=None)

@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} Finder that wraps Python's "classic" import algorithm.

If @emph{dirname} is a string, a 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} finder is created that searches that
directory.  If @emph{dirname} is @code{None}, a 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} finder is created that
searches the current @ref{482,,sys.path}, plus any modules that are frozen or
built-in.

Note that @ref{36ea,,ImpImporter} does not currently support being used by
placement on @ref{5e1,,sys.meta_path}.


3.3 版后已移除: This emulation is no longer needed, as the standard import mechanism
is now fully 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} compliant and available in @ref{9b,,importlib}.

@end deffn

@geindex ImpLoader (pkgutil 中的类)
@anchor{library/pkgutil pkgutil ImpLoader}@anchor{36eb}
@deffn {类} pkgutil.ImpLoader (fullname, file, filename, etc)

@ref{1453,,Loader} that wraps Python's "classic" import algorithm.


3.3 版后已移除: This emulation is no longer needed, as the standard import mechanism
is now fully 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} compliant and available in @ref{9b,,importlib}.

@end deffn

@geindex find_loader() (在 pkgutil 模块中)
@anchor{library/pkgutil pkgutil find_loader}@anchor{36ec}
@deffn {函数} pkgutil.find_loader (fullname)

Retrieve a module @ref{1453,,loader} for the given @emph{fullname}.

This is a backwards compatibility wrapper around
@ref{932,,importlib.util.find_spec()} that converts most failures to
@ref{32d,,ImportError} and only returns the loader rather than the full
@code{ModuleSpec}.


在 3.3 版更改: Updated to be based directly on @ref{9b,,importlib} rather than relying
on the package internal 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} import emulation.



在 3.4 版更改: Updated to be based on 
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}

@end deffn

@geindex get_importer() (在 pkgutil 模块中)
@anchor{library/pkgutil pkgutil get_importer}@anchor{36ed}
@deffn {函数} pkgutil.get_importer (path_item)

Retrieve a @ref{1452,,finder} for the given @emph{path_item}.

The returned finder is cached in @ref{498,,sys.path_importer_cache} if it was
newly created by a path hook.

The cache (or part of it) can be cleared manually if a rescan of
@ref{956,,sys.path_hooks} is necessary.


在 3.3 版更改: Updated to be based directly on @ref{9b,,importlib} rather than relying
on the package internal 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} import emulation.

@end deffn

@geindex get_loader() (在 pkgutil 模块中)
@anchor{library/pkgutil pkgutil get_loader}@anchor{36ee}
@deffn {函数} pkgutil.get_loader (module_or_name)

Get a @ref{1453,,loader} object for @emph{module_or_name}.

If the module or package is accessible via the normal import mechanism, a
wrapper around the relevant part of that machinery is returned.  Returns
@code{None} if the module cannot be found or imported.  If the named module is
not already imported, its containing package (if any) is imported, in order
to establish the package @code{__path__}.


在 3.3 版更改: Updated to be based directly on @ref{9b,,importlib} rather than relying
on the package internal 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} import emulation.



在 3.4 版更改: Updated to be based on 
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}

@end deffn

@geindex iter_importers() (在 pkgutil 模块中)
@anchor{library/pkgutil pkgutil iter_importers}@anchor{b0d}
@deffn {函数} pkgutil.iter_importers (fullname='@w{'})

Yield @ref{1452,,finder} objects for the given module name.

If fullname contains a '.', the finders will be for the package
containing fullname, otherwise they will be all registered top level
finders (i.e. those on both sys.meta_path and sys.path_hooks).

If the named module is in a package, that package is imported as a side
effect of invoking this function.

If no module name is specified, all top level finders are produced.


在 3.3 版更改: Updated to be based directly on @ref{9b,,importlib} rather than relying
on the package internal 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} import emulation.

@end deffn

@geindex iter_modules() (在 pkgutil 模块中)
@anchor{library/pkgutil pkgutil iter_modules}@anchor{607}
@deffn {函数} pkgutil.iter_modules (path=None, prefix='@w{'})

Yields @ref{608,,ModuleInfo} for all submodules on @emph{path}, or, if
@emph{path} is @code{None}, all top-level modules on @code{sys.path}.

@emph{path} should be either @code{None} or a list of paths to look for modules in.

@emph{prefix} is a string to output on the front of every module name on output.

@cartouche
@quotation 注解 
Only works for a @ref{1452,,finder} which defines an @code{iter_modules()}
method. This interface is non-standard, so the module also provides
implementations for @ref{9b0,,importlib.machinery.FileFinder} and
@ref{36dc,,zipimport.zipimporter}.
@end quotation
@end cartouche


在 3.3 版更改: Updated to be based directly on @ref{9b,,importlib} rather than relying
on the package internal 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} import emulation.

@end deffn

@geindex walk_packages() (在 pkgutil 模块中)
@anchor{library/pkgutil pkgutil walk_packages}@anchor{485}
@deffn {函数} pkgutil.walk_packages (path=None, prefix='@w{'}, onerror=None)

Yields @ref{608,,ModuleInfo} for all modules recursively on
@emph{path}, or, if @emph{path} is @code{None}, all accessible modules.

@emph{path} should be either @code{None} or a list of paths to look for modules in.

@emph{prefix} is a string to output on the front of every module name on output.

Note that this function must import all @emph{packages} (@emph{not} all modules!) on
the given @emph{path}, in order to access the @code{__path__} attribute to find
submodules.

@emph{onerror} is a function which gets called with one argument (the name of the
package which was being imported) if any exception occurs while trying to
import a package.  If no @emph{onerror} function is supplied, @ref{32d,,ImportError}s
are caught and ignored, while all other exceptions are propagated,
terminating the search.

示例:

@example
# list all modules python can access
walk_packages()

# list all submodules of ctypes
walk_packages(ctypes.__path__, ctypes.__name__ + '.')
@end example

@cartouche
@quotation 注解 
Only works for a @ref{1452,,finder} which defines an @code{iter_modules()}
method. This interface is non-standard, so the module also provides
implementations for @ref{9b0,,importlib.machinery.FileFinder} and
@ref{36dc,,zipimport.zipimporter}.
@end quotation
@end cartouche


在 3.3 版更改: Updated to be based directly on @ref{9b,,importlib} rather than relying
on the package internal 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} import emulation.

@end deffn

@geindex get_data() (在 pkgutil 模块中)
@anchor{library/pkgutil pkgutil get_data}@anchor{36ef}
@deffn {函数} pkgutil.get_data (package, resource)

从包中获取一个资源。

This is a wrapper for the @ref{1453,,loader}
@ref{36f0,,get_data} API.  The
@emph{package} argument should be the name of a package, in standard module format
(@code{foo.bar}).  The @emph{resource} argument should be in the form of a relative
filename, using @code{/} as the path separator.  The parent directory name
@code{..} is not allowed, and nor is a rooted name (starting with a @code{/}).

The function returns a binary string that is the contents of the specified
resource.

For packages located in the filesystem, which have already been imported,
this is the rough equivalent of:

@example
d = os.path.dirname(sys.modules[package].__file__)
data = open(os.path.join(d, resource), 'rb').read()
@end example

If the package cannot be located or loaded, or it uses a @ref{1453,,loader}
which does not support @ref{36f0,,get_data},
then @code{None} is returned.  In particular, the @ref{1453,,loader} for
@ref{144c,,namespace packages} does not support
@ref{36f0,,get_data}.
@end deffn

@node modulefinder --- 查找脚本使用的模块,runpy --- Locating and executing Python modules,pkgutil --- 包扩展工具,导入模块
@anchor{library/modulefinder doc}@anchor{36f1}@anchor{library/modulefinder module-modulefinder}@anchor{b4}@anchor{library/modulefinder modulefinder-find-modules-used-by-a-script}@anchor{36f2}
@subsection @code{modulefinder} --- 查找脚本使用的模块


@geindex modulefinder (模块)

@strong{源码：} Lib/modulefinder.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/modulefinder.py}


__________________________________________________________________


该模块提供了一个 @ref{f71,,ModuleFinder} 类，可用于确定脚本导入的模块集。 @code{modulefinder.py} 也可以作为脚本运行，给出 Python 脚本的文件名作为参数，之后将打印导入模块的报告。

@geindex AddPackagePath() (在 modulefinder 模块中)
@anchor{library/modulefinder modulefinder AddPackagePath}@anchor{36f3}
@deffn {函数} modulefinder.AddPackagePath (pkg_name, path)

记录名为 @emph{pkg_name} 的包可以在指定的 @emph{path} 中找到。
@end deffn

@geindex ReplacePackage() (在 modulefinder 模块中)
@anchor{library/modulefinder modulefinder ReplacePackage}@anchor{36f4}
@deffn {函数} modulefinder.ReplacePackage (oldname, newname)

允许指定名为 @emph{oldname} 的模块实际上是名为 @emph{newname} 的包。
@end deffn

@geindex ModuleFinder (modulefinder 中的类)
@anchor{library/modulefinder modulefinder ModuleFinder}@anchor{f71}
@deffn {类} modulefinder.ModuleFinder (path=None, debug=0, excludes=[], replace_paths=[])

该类提供 @ref{36f5,,run_script()} 和 @ref{36f6,,report()} 方法，用于确定脚本导入的模块集。 @emph{path} 可以是搜索模块的目录列表；如果没有指定，则使用 @code{sys.path} 。  @emph{debug} 设置调试级别；更高的值使类打印调试消息，关于它正在做什么。 @emph{excludes} 是要从分析中排除的模块名称列表。 @emph{replace_paths} 是将在模块路径中替换的 @code{(oldpath, newpath)} 元组的列表。

@geindex report() (modulefinder.ModuleFinder 方法)
@anchor{library/modulefinder modulefinder ModuleFinder report}@anchor{36f6}
@deffn {方法} report ()

将报告打印到标准输出，列出脚本导入的模块及其路径，以及缺少或似乎缺失的模块。
@end deffn

@geindex run_script() (modulefinder.ModuleFinder 方法)
@anchor{library/modulefinder modulefinder ModuleFinder run_script}@anchor{36f5}
@deffn {方法} run_script (pathname)

分析 @emph{pathname} 文件的内容，该文件必须包含 Python 代码。
@end deffn

@geindex modules (modulefinder.ModuleFinder 属性)
@anchor{library/modulefinder modulefinder ModuleFinder modules}@anchor{36f7}
@deffn {属性} modules

一个将模块名称映射到模块的字典。 请参阅 @ref{36f8,,ModuleFinder 的示例用法}。
@end deffn
@end deffn

@menu
* ModuleFinder 的示例用法:: 

@end menu

@node ModuleFinder 的示例用法,,,modulefinder --- 查找脚本使用的模块
@anchor{library/modulefinder example-usage-of-modulefinder}@anchor{36f9}@anchor{library/modulefinder modulefinder-example}@anchor{36f8}
@subsubsection @code{ModuleFinder} 的示例用法


稍后将分析的脚本（bacon.py）:

@example
import re, itertools

try:
    import baconhameggs
except ImportError:
    pass

try:
    import guido.python.ham
except ImportError:
    pass
@end example

将输出 bacon.py 报告的脚本:

@example
from modulefinder import ModuleFinder

finder = ModuleFinder()
finder.run_script('bacon.py')

print('Loaded modules:')
for name, mod in finder.modules.items():
    print('%s: ' % name, end='@w{'})
    print(','.join(list(mod.globalnames.keys())[:3]))

print('-'*50)
print('Modules not imported:')
print('\n'.join(finder.badmodules.keys()))
@end example

输出样例（可能因架构而异）:

@example
Loaded modules:
_types:
copyreg:  _inverted_registry,_slotnames,__all__
sre_compile:  isstring,_sre,_optimize_unicode
_sre:
sre_constants:  REPEAT_ONE,makedict,AT_END_LINE
sys:
re:  __module__,finditer,_expand
itertools:
__main__:  re,itertools,baconhameggs
sre_parse:  _PATTERNENDERS,SRE_FLAG_UNICODE
array:
types:  __module__,IntType,TypeType
---------------------------------------------------
Modules not imported:
guido.python.ham
baconhameggs
@end example

@node runpy --- Locating and executing Python modules,importlib --- import 的实现,modulefinder --- 查找脚本使用的模块,导入模块
@anchor{library/runpy doc}@anchor{36fa}@anchor{library/runpy module-runpy}@anchor{e2}@anchor{library/runpy runpy-locating-and-executing-python-modules}@anchor{36fb}
@subsection @code{runpy} --- Locating and executing Python modules


@geindex runpy (模块)

@strong{Source code:} Lib/runpy.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/runpy.py}


__________________________________________________________________


The @ref{e2,,runpy} module is used to locate and run Python modules without
importing them first. Its main use is to implement the @ref{330,,-m} command
line switch that allows scripts to be located using the Python module
namespace rather than the filesystem.

Note that this is @emph{not} a sandbox module - all code is executed in the
current process, and any side effects (such as cached imports of other
modules) will remain in place after the functions have returned.

Furthermore, any functions and classes defined by the executed code are not
guaranteed to work correctly after a @ref{e2,,runpy} function has returned.
If that limitation is not acceptable for a given use case, @ref{9b,,importlib}
is likely to be a more suitable choice than this module.

The @ref{e2,,runpy} module provides two functions:

@geindex run_module() (在 runpy 模块中)
@anchor{library/runpy runpy run_module}@anchor{12d1}
@deffn {函数} runpy.run_module (mod_name, init_globals=None, run_name=None, alter_sys=False)

@geindex 模块; __main__

Execute the code of the specified module and return the resulting module
globals dictionary. The module's code is first located using the standard
import mechanism (refer to 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} for details) and then executed in a
fresh module namespace.

The @emph{mod_name} argument should be an absolute module name.
If the module name refers to a package rather than a normal
module, then that package is imported and the @code{__main__} submodule within
that package is then executed and the resulting module globals dictionary
returned.

The optional dictionary argument @emph{init_globals} may be used to pre-populate
the module's globals dictionary before the code is executed. The supplied
dictionary will not be modified. If any of the special global variables
below are defined in the supplied dictionary, those definitions are
overridden by @ref{12d1,,run_module()}.

The special global variables @code{__name__}, @code{__spec__}, @code{__file__},
@code{__cached__}, @code{__loader__} and @code{__package__} are set in the globals
dictionary before the module code is executed (Note that this is a
minimal set of variables - other variables may be set implicitly as an
interpreter implementation detail).

@code{__name__} is set to @emph{run_name} if this optional argument is not
@ref{157,,None}, to @code{mod_name + '.__main__'} if the named module is a
package and to the @emph{mod_name} argument otherwise.

@code{__spec__} will be set appropriately for the @emph{actually} imported
module (that is, @code{__spec__.name} will always be @emph{mod_name} or
@code{mod_name + '.__main__}, never @emph{run_name}).

@code{__file__}, @code{__cached__}, @code{__loader__} and @code{__package__} are
@ref{145a,,set as normal} based on the module spec.

If the argument @emph{alter_sys} is supplied and evaluates to @ref{494,,True},
then @code{sys.argv[0]} is updated with the value of @code{__file__} and
@code{sys.modules[__name__]} is updated with a temporary module object for the
module being executed. Both @code{sys.argv[0]} and @code{sys.modules[__name__]}
are restored to their original values before the function returns.

Note that this manipulation of @ref{fd,,sys} is not thread-safe. Other threads
may see the partially initialised module, as well as the altered list of
arguments. It is recommended that the @ref{fd,,sys} module be left alone when
invoking this function from threaded code.


@subsubheading 参见


The @ref{330,,-m} option offering equivalent functionality from the
command line.



在 3.1 版更改: Added ability to execute packages by looking for a @code{__main__} submodule.



在 3.2 版更改: Added @code{__cached__} global variable (see 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147}).



在 3.4 版更改: Updated to take advantage of the module spec feature added by
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}. This allows @code{__cached__} to be set correctly for modules
run this way, as well as ensuring the real module name is always
accessible as @code{__spec__.name}.

@end deffn

@geindex run_path() (在 runpy 模块中)
@anchor{library/runpy runpy run_path}@anchor{caa}
@deffn {函数} runpy.run_path (file_path, init_globals=None, run_name=None)

@geindex 模块; __main__

Execute the code at the named filesystem location and return the resulting
module globals dictionary. As with a script name supplied to the CPython
command line, the supplied path may refer to a Python source file, a
compiled bytecode file or a valid sys.path entry containing a @code{__main__}
module (e.g. a zipfile containing a top-level @code{__main__.py} file).

For a simple script, the specified code is simply executed in a fresh
module namespace. For a valid sys.path entry (typically a zipfile or
directory), the entry is first added to the beginning of @code{sys.path}. The
function then looks for and executes a @ref{1,,__main__} module using the
updated path. Note that there is no special protection against invoking
an existing @ref{1,,__main__} entry located elsewhere on @code{sys.path} if
there is no such module at the specified location.

The optional dictionary argument @emph{init_globals} may be used to pre-populate
the module's globals dictionary before the code is executed. The supplied
dictionary will not be modified. If any of the special global variables
below are defined in the supplied dictionary, those definitions are
overridden by @ref{caa,,run_path()}.

The special global variables @code{__name__}, @code{__spec__}, @code{__file__},
@code{__cached__}, @code{__loader__} and @code{__package__} are set in the globals
dictionary before the module code is executed (Note that this is a
minimal set of variables - other variables may be set implicitly as an
interpreter implementation detail).

@code{__name__} is set to @emph{run_name} if this optional argument is not
@ref{157,,None} and to @code{'<run_path>'} otherwise.

If the supplied path directly references a script file (whether as source
or as precompiled byte code), then @code{__file__} will be set to the
supplied path, and @code{__spec__}, @code{__cached__}, @code{__loader__} and
@code{__package__} will all be set to @ref{157,,None}.

If the supplied path is a reference to a valid sys.path entry, then
@code{__spec__} will be set appropriately for the imported @code{__main__}
module (that is, @code{__spec__.name} will always be @code{__main__}).
@code{__file__}, @code{__cached__}, @code{__loader__} and @code{__package__} will be
@ref{145a,,set as normal} based on the module spec.

A number of alterations are also made to the @ref{fd,,sys} module. Firstly,
@code{sys.path} may be altered as described above. @code{sys.argv[0]} is updated
with the value of @code{file_path} and @code{sys.modules[__name__]} is updated
with a temporary module object for the module being executed. All
modifications to items in @ref{fd,,sys} are reverted before the function
returns.

Note that, unlike @ref{12d1,,run_module()}, the alterations made to @ref{fd,,sys}
are not optional in this function as these adjustments are essential to
allowing the execution of sys.path entries. As the thread-safety
limitations still apply, use of this function in threaded code should be
either serialised with the import lock or delegated to a separate process.


@subsubheading 参见


@ref{12cf,,接口选项} for equivalent functionality on the
command line (@code{python path/to/script}).



3.2 新版功能.



在 3.4 版更改: Updated to take advantage of the module spec feature added by
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}. This allows @code{__cached__} to be set correctly in the
case where @code{__main__} is imported from a valid sys.path entry rather
than being executed directly.

@end deffn


@subsubheading 参见



@table @asis

@geindex Python 提高建议; PEP 338

@item PEP 338@footnote{https://www.python.org/dev/peps/pep-0338} -- 将模块作为脚本执行

PEP 由 Nick Coghlan 撰写并实现。

@geindex Python 提高建议; PEP 366

@item PEP 366@footnote{https://www.python.org/dev/peps/pep-0366} -- Main module explicit relative imports

PEP 由 Nick Coghlan 撰写并实现。

@geindex Python 提高建议; PEP 451

@item PEP 451@footnote{https://www.python.org/dev/peps/pep-0451} -- A ModuleSpec Type for the Import System

PEP written and implemented by Eric Snow
@end table

@ref{f39,,命令行与环境} - CPython command line details

The @ref{b0c,,importlib.import_module()} function


@node importlib --- import 的实现,Using importlib metadata,runpy --- Locating and executing Python modules,导入模块
@anchor{library/importlib doc}@anchor{36fc}@anchor{library/importlib importlib-the-implementation-of-import}@anchor{36fd}@anchor{library/importlib module-importlib}@anchor{9b}
@subsection @code{importlib} --- @code{import} 的实现


@geindex importlib (模块)


3.1 新版功能.


@strong{源代码} Lib/importlib/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/importlib/__init__.py}


__________________________________________________________________


@menu
* 概述: 概述<13>. 
* 函数: 函数<10>. 
* importlib.abc —— 关于导入的抽象基类: importlib abc —— 关于导入的抽象基类. 
* importlib.resources: importlib resources -- 资源. 资源
* importlib.machinery: importlib machinery -- Importers and path hooks. Importers and path hooks
* importlib.util: importlib util -- Utility code for importers. Utility code for importers
* 例子: 例子<29>. 

@end menu

@node 概述<13>,函数<10>,,importlib --- import 的实现
@anchor{library/importlib introduction}@anchor{36fe}
@subsubsection 概述


@ref{9b,,importlib} 包的目的有两个。 第一个目的是在 Python 源代码中提供 @ref{c16,,import} 语句的实现（并且因此而扩展 @ref{60b,,__import__()} 函数）。 这提供了一个可移植到任何 Python 解释器的 @code{import} 实现。 相比使用 Python 以外的编程语言实现方式，这一实现更加易于理解。

第二个目的是实现 @ref{c16,,import} 的部分被公开在这个包中，使得用户更容易创建他们自己的自定义对象 (通常被称为 @ref{1454,,importer}) 来参与到导入过程中。


@subsubheading 参见



@table @asis

@item @ref{c16,,import 语句}

@ref{c16,,import} 语句的语言参考

@item 包规格说明@footnote{https://www.python.org/doc/essays/packages/}

包的初始规范。自从编写这个文档开始，一些语义已经发生改变了（比如基于 @ref{eb5,,sys.modules} 中 @code{None} 的重定向）。

@item @ref{9a8,,__import__()} 函数

@ref{c16,,import} 语句是这个函数的语法糖。

@geindex Python 提高建议; PEP 235

@item PEP 235@footnote{https://www.python.org/dev/peps/pep-0235}

在忽略大小写的平台上进行导入

@geindex Python 提高建议; PEP 263

@item PEP 263@footnote{https://www.python.org/dev/peps/pep-0263}

定义 Python 源代码编码

@geindex Python 提高建议; PEP 302

@item PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}

新导入钩子

@geindex Python 提高建议; PEP 328

@item PEP 328@footnote{https://www.python.org/dev/peps/pep-0328}

导入：多行和绝对/相对

@geindex Python 提高建议; PEP 366

@item PEP 366@footnote{https://www.python.org/dev/peps/pep-0366}

主模块显式相对导入

@geindex Python 提高建议; PEP 420

@item PEP 420@footnote{https://www.python.org/dev/peps/pep-0420}

隐式命名空间包

@geindex Python 提高建议; PEP 451

@item PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}

导入系统的一个模块规范类型

@geindex Python 提高建议; PEP 488

@item PEP 488@footnote{https://www.python.org/dev/peps/pep-0488}

消除PYO文件

@geindex Python 提高建议; PEP 489

@item PEP 489@footnote{https://www.python.org/dev/peps/pep-0489}

多阶段扩展模块初始化

@geindex Python 提高建议; PEP 552

@item PEP 552@footnote{https://www.python.org/dev/peps/pep-0552}

确定性的 pyc 文件

@geindex Python 提高建议; PEP 3120

@item PEP 3120@footnote{https://www.python.org/dev/peps/pep-3120}

使用 UTF-8 作为默认的源编码

@geindex Python 提高建议; PEP 3147

@item PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147}

PYC 仓库目录
@end table


@node 函数<10>,importlib abc —— 关于导入的抽象基类,概述<13>,importlib --- import 的实现
@anchor{library/importlib functions}@anchor{36ff}
@subsubsection 函数


@geindex __import__() (在 importlib 模块中)
@anchor{library/importlib importlib __import__}@anchor{9a8}
@deffn {函数} importlib.__import__ (name, globals=None, locals=None, fromlist=(), level=0)

内置 @ref{60b,,__import__()} 函数的实现。

@cartouche
@quotation 注解 
程序式地导入模块应该使用 @ref{b0c,,import_module()} 而不是这个函数。
@end quotation
@end cartouche
@end deffn

@geindex import_module() (在 importlib 模块中)
@anchor{library/importlib importlib import_module}@anchor{b0c}
@deffn {函数} importlib.import_module (name, package=None)

导入一个模块。参数 @emph{name} 指定了以绝对或相对导入方式导入什么模块 (比如要么像这样 @code{pkg.mod} 或者这样 @code{..mod})。如果参数 name 使用相对导入的方式来指定，那么那个参数 @emph{packages} 必须设置为那个包名，这个包名作为解析这个包名的锚点 (比如  @code{import_module('..mod', 'pkg.subpkg')} 将会导入 @code{pkg.mod})。

@ref{b0c,,import_module()} 函数是一个对 @ref{9a8,,importlib.__import__()} 进行简化的包装器。 这意味着该函数的所有主义都来自于 @ref{9a8,,importlib.__import__()}。 这两个函数之间最重要的不同点在于 @ref{b0c,,import_module()} 返回指定的包或模块 (例如 @code{pkg.mod})，而 @ref{60b,,__import__()} 返回最高层级的包或模块 (例如 @code{pkg})。

如果动态导入一个自从解释器开始执行以来被创建的模块（即创建了一个 Python 源代码文件），为了让导入系统知道这个新模块，可能需要调用 @ref{497,,invalidate_caches()}。


在 3.3 版更改: 父包会被自动导入。

@end deffn

@geindex find_loader() (在 importlib 模块中)
@anchor{library/importlib importlib find_loader}@anchor{931}
@deffn {函数} importlib.find_loader (name, path=None)

查找一个模块的加载器，可选择地在指定的 @emph{path} 里面。如果这个模块是在 @ref{eb5,,sys.modules}，那么返回 @code{sys.modules[name].__loader__} (除非这个加载器是 @code{None} 或者是没有被设置， 在这样的情况下，会引起 @ref{1fb,,ValueError} 异常）。 否则使用 @ref{5e1,,sys.meta_path} 的一次搜索就结束。如果未发现加载器，则返回 @code{None}。

点状的名称没有使得它父包或模块隐式地导入，因为它需要加载它们并且可能不需要。为了适当地导入一个子模块，需要导入子模块的所有父包并且使用正确的参数提供给 @emph{path}。


3.3 新版功能.



在 3.4 版更改: 如果没有设置 @code{__loader__}，会引起 @ref{1fb,,ValueError} 异常，就像属性设置为 @code{None} 的时候一样。



3.4 版后已移除: 使用 @ref{932,,importlib.util.find_spec()} 来代替。

@end deffn

@geindex invalidate_caches() (在 importlib 模块中)
@anchor{library/importlib importlib invalidate_caches}@anchor{497}
@deffn {函数} importlib.invalidate_caches ()

使查找器存储在 @ref{5e1,,sys.meta_path} 中的内部缓存无效。如果一个查找器实现了 @code{invalidate_caches()}，那么它会被调用来执行那个无效过程。 如果创建/安装任何模块，同时正在运行的程序是为了保证所有的查找器知道新模块的存在，那么应该调用这个函数。


3.3 新版功能.

@end deffn

@geindex reload() (在 importlib 模块中)
@anchor{library/importlib importlib reload}@anchor{391}
@deffn {函数} importlib.reload (module)

重新加载之前导入的 @emph{module}。那个参数必须是一个模块对象，所以它之前必须已经成功导入了。这样做是有用的，如果使用外部编辑器编已经辑过了那个模块的源代码文件并且想在退出 Python 解释器之前试验这个新版本的模块。函数的返回值是那个模块对象（如果重新导入导致一个不同的对象放置在 @ref{eb5,,sys.modules} 中，那么那个模块对象是有可能会不同）。

当执行 @ref{391,,reload()} 的时候：


@itemize *

@item 
Python 模块的代码会被重新编译并且那个模块级的代码被重新执行，通过重新使用一开始加载那个模块的 @ref{1453,,loader}，定义一个新的绑定在那个模块字典中的名称的对象集合。扩展模块的`@w{`}init`@w{`}函数不会被调用第二次。

@item 
与Python中的所有的其它对象一样，旧的对象只有在它们的引用计数为0之后才会被回收。

@item 
模块命名空间中的名称重新指向任何新的或更改后的对象。

@item 
其他旧对象的引用（例如那个模块的外部名称）不会被重新绑定到引用的新对象的，并且如果有需要，必须在出现的每个命名空间中进行更新。
@end itemize

有一些其他注意事项：

当一个模块被重新加载的时候，它的字典（包含了那个模块的全区变量）会被保留。名称的重新定义会覆盖旧的定义，所以通常来说这不是问题。如果一个新模块没有定义在旧版本模块中定义的名称，则将保留旧版本中的定义。这一特性可用于作为那个模块的优点，如果它维护一个全局表或者对象的缓存 —— 使用 @ref{d6b,,try} 语句，就可以测试表的存在并且跳过它的初始化，如果有需要的话:

@example
try:
    cache
except NameError:
    cache = @{@}
@end example

重新加载内置的或者动态加载模块，通常来说不是很有用处。不推荐重新加载"@ref{fd,,sys}，@ref{1,,__main__}，@ref{13,,builtins} 和其它关键模块。在很多例子中，扩展模块并不是设计为不止一次的初始化，并且当重新加载时，可能会以任意方式失败。

如果一个模块使用 @ref{c3e,,from} ... @ref{c16,,import} ... 导入的对象来自另外一个模块，给其它模块调用 @ref{391,,reload()} 不会重新定义来自这个模块的对象 —— 解决这个问题的一种方式是重新执行 @code{from} 语句，另一种方式是使用 @code{import} 和限定名称(@emph{module.name})来代替。

如果一个模块创建一个类的实例，重新加载定义那个类的模块不影响那些实例的方法定义———它们继续使用旧类中的定义。对于子类来说同样是正确的。


3.4 新版功能.



在 3.7 版更改: 当重新加载的那个模块缺少 @code{ModuleSpec} 的时候，会引起 @ref{392,,ModuleNotFoundError} 异常。

@end deffn

@node importlib abc —— 关于导入的抽象基类,importlib resources -- 资源,函数<10>,importlib --- import 的实现
@anchor{library/importlib importlib-abc-abstract-base-classes-related-to-import}@anchor{3700}@anchor{library/importlib module-importlib abc}@anchor{9c}
@subsubsection @code{importlib.abc} —— 关于导入的抽象基类


@geindex importlib.abc (模块)

@strong{源代码：} Lib/importlib/abc.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/importlib/abc.py}


__________________________________________________________________


The @ref{9c,,importlib.abc} module contains all of the core abstract base classes
used by @ref{c16,,import}. Some subclasses of the core abstract base classes
are also provided to help in implementing the core ABCs.

ABC 类的层次结构：

@example
object
 +-- Finder (deprecated)
 |    +-- MetaPathFinder
 |    +-- PathEntryFinder
 +-- Loader
      +-- ResourceLoader --------+
      +-- InspectLoader          |
           +-- ExecutionLoader --+
                                 +-- FileLoader
                                 +-- SourceLoader
@end example

@geindex Finder (importlib.abc 中的类)
@anchor{library/importlib importlib abc Finder}@anchor{9af}
@deffn {类} importlib.abc.Finder

代表 @ref{1452,,finder} 的一个抽象基类


3.3 版后已移除: 使用 @ref{9ad,,MetaPathFinder} 或 @ref{9ae,,PathEntryFinder} 来代替。


@geindex find_module() (importlib.abc.Finder 方法)
@anchor{library/importlib importlib abc Finder find_module}@anchor{3701}
@deffn {方法} abstractmethod find_module (fullname, path=None)

为指定的模块查找 @ref{1453,,loader} 定义的抽象方法。本来是在 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} 指定的，这个方法是在 @ref{5e1,,sys.meta_path} 和基于路径的导入子系统中使用。


在 3.4 版更改: 当被调用的时候，返回 @code{None} 而不是引发 @ref{609,,NotImplementedError}。

@end deffn
@end deffn

@geindex MetaPathFinder (importlib.abc 中的类)
@anchor{library/importlib importlib abc MetaPathFinder}@anchor{9ad}
@deffn {类} importlib.abc.MetaPathFinder

代表 @ref{9ab,,meta path finder} 的一个抽象基类。 为了保持兼容性，这是 @ref{9af,,Finder} 的一个子类。


3.3 新版功能.


@geindex find_spec() (importlib.abc.MetaPathFinder 方法)
@anchor{library/importlib importlib abc MetaPathFinder find_spec}@anchor{45d}
@deffn {方法} find_spec (fullname, path, target=None)

An abstract method for finding a @ref{35dd,,spec} for
the specified module.  If this is a top-level import, @emph{path} will
be @code{None}.  Otherwise, this is a search for a subpackage or
module and @emph{path} will be the value of @ref{1223,,__path__} from the
parent package. If a spec cannot be found, @code{None} is returned.
When passed in, @code{target} is a module object that the finder may
use to make a more educated guess about what spec to return.
@ref{3702,,importlib.util.spec_from_loader()} may be useful for implementing
concrete @code{MetaPathFinders}.


3.4 新版功能.

@end deffn

@geindex find_module() (importlib.abc.MetaPathFinder 方法)
@anchor{library/importlib importlib abc MetaPathFinder find_module}@anchor{45c}
@deffn {方法} find_module (fullname, path)

一个用于查找指定的模块中 @ref{1453,,loader} 的遗留方法。如果这是最高层级的导入，@emph{path} 的值将会是 @code{None}。否则，这是一个查找子包或者模块的方法，并且 @emph{path} 的值将会是来自父包的 @ref{1223,,__path__} 的值。如果未发现加载器，返回 @code{None}。

如果定义了 @ref{45d,,find_spec()} 方法，则提供了向后兼容的功能。


在 3.4 版更改: 当调用这个方法的时候返回 @code{None} 而不是引发 @ref{609,,NotImplementedError}。 可以使用 @ref{45d,,find_spec()} 来提供功能。



3.4 版后已移除: 使用 @ref{45d,,find_spec()} 来代替。

@end deffn

@geindex invalidate_caches() (importlib.abc.MetaPathFinder 方法)
@anchor{library/importlib importlib abc MetaPathFinder invalidate_caches}@anchor{3703}
@deffn {方法} invalidate_caches ()

当被调用的时候，一个可选的方法应该将查找器使用的任何内部缓存进行无效。将在 @ref{5e1,,sys.meta_path} 上的所有查找器的缓存进行无效的时候，这个函数被 @ref{497,,importlib.invalidate_caches()} 所使用。


在 3.4 版更改: 当方法被调用的时候，方法返回是 @code{None} 而不是 @code{NotImplemented} 。

@end deffn
@end deffn

@geindex PathEntryFinder (importlib.abc 中的类)
@anchor{library/importlib importlib abc PathEntryFinder}@anchor{9ae}
@deffn {类} importlib.abc.PathEntryFinder

@ref{9ac,,path entry finder} 的一个抽象基类。尽管这个基类和 @ref{9ad,,MetaPathFinder} 有一些相似之处，但是 @code{PathEntryFinder} 只在由 @code{PathFinder} 提供的基于路径导入子系统中使用。这个抽象类是 @ref{1452,,Finder} 的一个子类，仅仅是因为兼容性的原因。


3.3 新版功能.


@geindex find_spec() (importlib.abc.PathEntryFinder 方法)
@anchor{library/importlib importlib abc PathEntryFinder find_spec}@anchor{45f}
@deffn {方法} find_spec (fullname, target=None)

An abstract method for finding a @ref{35dd,,spec} for
the specified module.  The finder will search for the module only
within the @ref{1468,,path entry} to which it is assigned.  If a spec
cannot be found, @code{None} is returned.  When passed in, @code{target}
is a module object that the finder may use to make a more educated
guess about what spec to return. @ref{3702,,importlib.util.spec_from_loader()}
may be useful for implementing concrete @code{PathEntryFinders}.


3.4 新版功能.

@end deffn

@geindex find_loader() (importlib.abc.PathEntryFinder 方法)
@anchor{library/importlib importlib abc PathEntryFinder find_loader}@anchor{45e}
@deffn {方法} find_loader (fullname)

一个用于在模块中查找一个 @ref{1453,,loader} 的遗留方法。 返回一个 @code{(loader, portion)} 的2元组，@code{portion} 是一个贡献给命名空间包部分的文件系统位置的序列。 加载器可能是 @code{None}，同时正在指定的 @code{portion} 表示的是贡献给命名空间包的文件系统位置。@code{portion} 可以使用一个空列表来表示加载器不是命名空间包的一部分。 如果 @code{loader} 是 @code{None} 并且 @code{portion} 是一个空列表，那么命名空间包中无加载器或者文件系统位置可查找到（即在那个模块中未能找到任何东西）。

如果定义了 @ref{45f,,find_spec()} ，则提供了向后兼容的功能。


在 3.4 版更改: 返回 @code{(None, [])} 而不是引发 @ref{609,,NotImplementedError}。 当可于提供相应的功能的时候，使用 @ref{45f,,find_spec()}。



3.4 版后已移除: 使用 @ref{45f,,find_spec()} 来代替。

@end deffn

@geindex find_module() (importlib.abc.PathEntryFinder 方法)
@anchor{library/importlib importlib abc PathEntryFinder find_module}@anchor{935}
@deffn {方法} find_module (fullname)

@code{Finder.find_module`的具体实现，该方法等价于`@w{`}self.find_loader(fullname)[0]`()}。


3.4 版后已移除: 使用 @ref{45f,,find_spec()} 来代替。

@end deffn

@geindex invalidate_caches() (importlib.abc.PathEntryFinder 方法)
@anchor{library/importlib importlib abc PathEntryFinder invalidate_caches}@anchor{3704}
@deffn {方法} invalidate_caches ()

当被调用的时候，一个可选的方法应该将查找器使用的任何内部缓存进行无效。当将所有缓存的查找器的缓存进行无效的时候，该函数被  @code{PathFinder.invalidate_caches()} 使用。
@end deffn
@end deffn

@geindex Loader (importlib.abc 中的类)
@anchor{library/importlib importlib abc Loader}@anchor{7bc}
@deffn {类} importlib.abc.Loader

@ref{1453,,loader} 的抽象基类。 关于一个加载器的实际定义请查看 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}。

加载器想要支持资源读取应该实现一个由 @ref{33b,,importlib.abc.ResourceReader} 指定的`@w{`}get_resource_reader(fullname)`@w{`} 方法。


在 3.7 版更改: 引入了可选的 @code{get_resource_reader()} 方法。


@geindex create_module() (importlib.abc.Loader 方法)
@anchor{library/importlib importlib abc Loader create_module}@anchor{54f}
@deffn {方法} create_module (spec)

当导入一个模块的时候，一个返回将要使用的那个模块对象的方法。这个方法可能返回 @code{None} ，这暗示着应该发生默认的模块创建语义。"


3.4 新版功能.



在 3.5 版更改: 从 Python 3.6 开始，当定义了 @ref{5df,,exec_module()} 的时候，这个方法将不会是可选的。

@end deffn

@geindex exec_module() (importlib.abc.Loader 方法)
@anchor{library/importlib importlib abc Loader exec_module}@anchor{5df}
@deffn {方法} exec_module (module)

当一个模块被导入或重新加载时，一个抽象方法在它自己的命名空间中执行那个模块。当调用 @code{exec_module()} 的时候，那个模块应该已经被初始化 了。当这个方法存在时，必须定义 @ref{54f,,create_module()} 。


3.4 新版功能.



在 3.6 版更改: @ref{54f,,create_module()} 也必须被定义。

@end deffn

@geindex load_module() (importlib.abc.Loader 方法)
@anchor{library/importlib importlib abc Loader load_module}@anchor{5de}
@deffn {方法} load_module (fullname)

用于加载一个模块的传统方法。如果这个模块不能被导入，将引起 @ref{32d,,ImportError} 异常，否则返回那个被加载的模块。

如果请求的模块已经存在 @ref{eb5,,sys.modules}，应该使用并且重新加载那个模块。 否则加载器应该是创建一个新的模块并且在任何家过程开始之前将这个新模块插入到 @ref{eb5,,sys.modules} 中，来阻止递归导入。 如果加载器插入了一个模块并且加载失败了，加载器必须从 @ref{eb5,,sys.modules} 中将这个模块移除。在加载器开始执行之前，已经在 @ref{eb5,,sys.modules} 中的模块应该被忽略 (查看 @ref{93c,,importlib.util.module_for_loader()})。

加载器应该在模块上面设置几个属性。（要知道当重新加载一个模块的时候，那些属性某部分可以改变）：


@itemize -

@item 

@table @asis

@item @ref{d0b,,__name__}

模块的名字
@end table

@item 

@table @asis

@item @ref{13c7,,__file__}

模块数据存储的路径(不是为了内置的模块而设置)
@end table

@item 

@table @asis

@item @ref{b2b,,__cached__}

被存储或应该被存储的模块的编译版本的路径（当这个属性不恰当的时候不设置）。
@end table

@item 

@table @asis

@item @ref{1223,,__path__}

指定在一个包中搜索路径的一个字符串列表。这个属性不在模块上面进行设置。
@end table

@item 

@table @asis

@item @ref{94f,,__package__}

模块/包的父包。如果这个模块是最上层的，那么它是一个为空字符串的值。 @ref{93c,,importlib.util.module_for_loader()} 装饰器可以处理 @ref{94f,,__package__} 的细节。
@end table

@item 

@table @asis

@item @ref{950,,__loader__}

用来加载那个模块的加载器。 @ref{93c,,importlib.util.module_for_loader()} 装饰器可以处理 @ref{94f,,__package__} 的细节。
@end table
@end itemize

当 @ref{5df,,exec_module()} 可用的时候，那么则提供了向后兼容的功能。


在 3.4 版更改: 当这个方法被调用的时候，触发 @ref{32d,,ImportError} 异常而不是 @ref{609,,NotImplementedError}。当 @ref{5df,,exec_module()} 可用的时候，使用它的功能。



3.4 版后已移除: 加载模块推荐的使用的 API 是 @ref{5df,,exec_module()} (和 @ref{54f,,create_module()})。 加载器应该实现它而不是 load_module()。 当 exec_module() 被实现的时候，导入机制关心的是 load_module() 所有其他的责任。

@end deffn

@geindex module_repr() (importlib.abc.Loader 方法)
@anchor{library/importlib importlib abc Loader module_repr}@anchor{93b}
@deffn {方法} module_repr (module)

一个遗留方法，在实现时计算并返回给定模块的 repr，作为字符串。 模块类型的默认 repr() 将根据需要使用此方法的结果。


3.3 新版功能.



在 3.4 版更改: 是可选的方法而不是一个抽象方法。



3.4 版后已移除: 现在导入机制会自动地关注这个方法。

@end deffn
@end deffn

@geindex ResourceReader (importlib.abc 中的类)
@anchor{library/importlib importlib abc ResourceReader}@anchor{33b}
@deffn {类} importlib.abc.ResourceReader

提供读取 @emph{resources} 能力的一个 @ref{b2c,,abstract base class} 。

从这个 ABC 的视角出发，@emph{resource} 指一个包附带的二进制文件。常见的如在包的  @code{__init__.py} 文件旁的数据文件。这个类存在的目的是为了将对数据文件的访问进行抽象，这样包就和其数据文件的存储方式无关了。不论这些文件是存放在一个 zip 文件里还是直接在文件系统内。

对于该类中的任一方法，@emph{resource} 参数的值都需要是一个在概念上表示文件名称的 @ref{363,,path-like object}。 这意味着任何子目录的路径都不该出现在 @emph{resouce} 参数值内。 因为对于阅读器而言，包的位置就代表着「目录」。 因此目录和文件名就分别对应于包和资源。 这也是该类的实例都需要和一个包直接关联（而不是潜在指代很多包或者一整个模块）的原因。

想支持资源读取的加载器需要提供一个返回实现了此 ABC 的接口的 @code{get_resource_reader(fullname)} 方法。如果通过全名指定的模块不是一个包，这个方法应该返回 @ref{157,,None}。 当指定的模块是一个包时，应该只返回一个与这个抽象类ABC兼容的对象。


3.7 新版功能.


@geindex open_resource() (importlib.abc.ResourceReader 方法)
@anchor{library/importlib importlib abc ResourceReader open_resource}@anchor{3705}
@deffn {方法} abstractmethod open_resource (resource)

返回一个打开的 @ref{1bfc,,file-like object} 用于 @emph{resource} 的二进制读取。

如果无法找到资源，将会引发 @ref{7ba,,FileNotFoundError}。
@end deffn

@geindex resource_path() (importlib.abc.ResourceReader 方法)
@anchor{library/importlib importlib abc ResourceReader resource_path}@anchor{3706}
@deffn {方法} abstractmethod resource_path (resource)

返回 @emph{resource} 的文件系统路径。

如果资源并不实际存在于文件系统中，将会引发 @ref{7ba,,FileNotFoundError}。
@end deffn

@geindex is_resource() (importlib.abc.ResourceReader 方法)
@anchor{library/importlib importlib abc ResourceReader is_resource}@anchor{3707}
@deffn {方法} abstractmethod is_resource (name)

如果*name* 被视作资源，则返回True。如果*name*不存在，则引发 @ref{7ba,,FileNotFoundError} 异常。
@end deffn

@geindex contents() (importlib.abc.ResourceReader 方法)
@anchor{library/importlib importlib abc ResourceReader contents}@anchor{fcd}
@deffn {方法} abstractmethod contents ()

反回由字符串组成的 @ref{ba5,,iterable}，表示这个包的所有内容。 请注意并不要求迭代器返回的所有名称都是实际的资源，例如返回 @ref{3707,,is_resource()} 为假值的名称也是可接受的。

允许非资源名字被返回是为了允许存储的一个包和它的资源的方式是已知先验的并且非资源名字会有用的情况。比如，允许返回子目录名字，目的是当得知包和资源存储在文件系统上面的时候，能够直接使用子目录的名字。

这个抽象方法返回了一个不包含任何内容的可迭代对象。
@end deffn
@end deffn

@geindex ResourceLoader (importlib.abc 中的类)
@anchor{library/importlib importlib abc ResourceLoader}@anchor{460}
@deffn {类} importlib.abc.ResourceLoader

一个 @ref{1453,,loader} 的抽象基类，它实现了可选的 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} 协议用于从存储后端加载任意资源。


3.7 版后已移除: 由于要支持使用 @ref{33b,,importlib.abc.ResourceReader}  类来加载资源，这个 ABC 已经被弃用了。


@geindex get_data() (importlib.abc.ResourceLoader 方法)
@anchor{library/importlib importlib abc ResourceLoader get_data}@anchor{36f0}
@deffn {方法} abstractmethod get_data (path)

一个用于返回位于 @emph{path} 的字节数据的抽象方法。有一个允许存储任意数据的类文件存储后端的加载器能够实现这个抽象方法来直接访问这些被存储的数据。如果不能够找到 @emph{path}，则会引发 @ref{1d3,,OSError} 异常。@emph{path} 被希望使用一个模块的 @code{__file} 属性或来自一个包的 @ref{1223,,__path__} 来构建。


在 3.4 版更改: 引发 @ref{1d3,,OSError} 异常而不是 @ref{609,,NotImplementedError} 异常。

@end deffn
@end deffn

@geindex InspectLoader (importlib.abc 中的类)
@anchor{library/importlib importlib abc InspectLoader}@anchor{85a}
@deffn {类} importlib.abc.InspectLoader

一个实现加载器检查模块可选的 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} 协议的 @ref{1453,,loader} 的抽象基类。

@geindex get_code() (importlib.abc.InspectLoader 方法)
@anchor{library/importlib importlib abc InspectLoader get_code}@anchor{85b}
@deffn {方法} get_code (fullname)

返回一个模块的代码对象，或如果模块没有一个代码对象（例如，对于内置的模块来说，这会是这种情况），则为 @code{None}。 如果加载器不能找到请求的模块，则引发 @ref{32d,,ImportError} 异常。

@cartouche
@quotation 注解 
当这个方法有一个默认的实现的时候，出于性能方面的考虑，如果有可能的话，建议覆盖它。
@end quotation
@end cartouche

@geindex universal newlines; importlib.abc.InspectLoader.get_source method


在 3.4 版更改: 不再抽象并且提供一个具体的实现。

@end deffn

@geindex get_source() (importlib.abc.InspectLoader 方法)
@anchor{library/importlib importlib abc InspectLoader get_source}@anchor{85f}
@deffn {方法} abstractmethod get_source (fullname)

一个返回模块源的抽象方法。使用 @ref{5ef,,universal newlines} 作为文本字符串被返回，将所有可识别行分割符翻译成 @code{'\n'} 字符。 如果没有可用的源（例如，一个内置模块），则返回 @code{None}。 如果加载器不能找到指定的模块，则引发 @ref{32d,,ImportError} 异常。


在 3.4 版更改: 引发 @ref{32d,,ImportError} 而不是 @ref{609,,NotImplementedError}。

@end deffn

@geindex is_package() (importlib.abc.InspectLoader 方法)
@anchor{library/importlib importlib abc InspectLoader is_package}@anchor{3708}
@deffn {方法} is_package (fullname)

一个抽象方法，如果这个模块是一个包则返回真值，否则返回假值。 如果 @ref{1453,,loader} 不能找到这个模块，则引发 @ref{32d,,ImportError}。


在 3.4 版更改: 引发 @ref{32d,,ImportError} 而不是 @ref{609,,NotImplementedError}。

@end deffn

@geindex source_to_code() (importlib.abc.InspectLoader 静态方法)
@anchor{library/importlib importlib abc InspectLoader source_to_code}@anchor{6e9}
@deffn {方法} static source_to_code (data, path='<string>')

创建一个来自Python源码的代码对象。

参数 @emph{data} 可以是任意 @ref{1b4,,compile()} 函数支持的类型（例如字符串或字节串）。 参数 @emph{path} 应该是源代码来源的路径，这可能是一个抽象概念（例如位于一个 zip 文件中）。

在有后续代码对象的情况下，可以在一个模块中通过运行`@w{`}exec(code, module.__dict__)`@w{`}来执行它。


3.4 新版功能.



在 3.5 版更改: 使得这个方法变成静态的。

@end deffn

@geindex exec_module() (importlib.abc.InspectLoader 方法)
@anchor{library/importlib importlib abc InspectLoader exec_module}@anchor{939}
@deffn {方法} exec_module (module)

@ref{5df,,Loader.exec_module()} 的实现。


3.4 新版功能.

@end deffn

@geindex load_module() (importlib.abc.InspectLoader 方法)
@anchor{library/importlib importlib abc InspectLoader load_module}@anchor{936}
@deffn {方法} load_module (fullname)

@ref{5de,,Loader.load_module()} 的实现。


3.4 版后已移除: 使用 @ref{939,,exec_module()} 来代替。

@end deffn
@end deffn

@geindex ExecutionLoader (importlib.abc 中的类)
@anchor{library/importlib importlib abc ExecutionLoader}@anchor{3709}
@deffn {类} importlib.abc.ExecutionLoader

一个继承自 @ref{85a,,InspectLoader} 的抽象基类，当被实现时，帮助一个模块作为脚本来执行。 这个抽象基类表示可选的 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} 协议。

@geindex get_filename() (importlib.abc.ExecutionLoader 方法)
@anchor{library/importlib importlib abc ExecutionLoader get_filename}@anchor{370a}
@deffn {方法} abstractmethod get_filename (fullname)

一个用来为指定模块返回 @ref{13c7,,__file__} 的值的抽象方法。如果无路径可用，则引发 @ref{32d,,ImportError}。

如果源代码可用，那么这个方法返回源文件的路径，不管是否是用来加载模块的字节码。


在 3.4 版更改: 引发 @ref{32d,,ImportError} 而不是 @ref{609,,NotImplementedError}。

@end deffn
@end deffn

@geindex FileLoader (importlib.abc 中的类)
@anchor{library/importlib importlib abc FileLoader}@anchor{9b1}
@deffn {类} importlib.abc.FileLoader (fullname, path)

一个继承自 @ref{460,,ResourceLoader} 和 @ref{3709,,ExecutionLoader}，提供 @ref{36f0,,ResourceLoader.get_data()} 和 @ref{370a,,ExecutionLoader.get_filename()} 具体实现的抽象基类。

参数*fullname*是加载器要处理的模块的完全解析的名字。参数*path*是模块文件的路径。


3.3 新版功能.


@geindex name (importlib.abc.FileLoader 属性)
@anchor{library/importlib importlib abc FileLoader name}@anchor{370b}
@deffn {属性} name

加载器可以处理的模块的名字。
@end deffn

@geindex path (importlib.abc.FileLoader 属性)
@anchor{library/importlib importlib abc FileLoader path}@anchor{370c}
@deffn {属性} path

模块的文件路径
@end deffn

@geindex load_module() (importlib.abc.FileLoader 方法)
@anchor{library/importlib importlib abc FileLoader load_module}@anchor{937}
@deffn {方法} load_module (fullname)

调用super的`@w{`}load_module()`@w{`}。


3.4 版后已移除: 使用 @ref{5df,,Loader.exec_module()} 来代替。

@end deffn

@geindex get_filename() (importlib.abc.FileLoader 方法)
@anchor{library/importlib importlib abc FileLoader get_filename}@anchor{370d}
@deffn {方法} abstractmethod get_filename (fullname)

返回 @ref{370c,,path}。
@end deffn

@geindex get_data() (importlib.abc.FileLoader 方法)
@anchor{library/importlib importlib abc FileLoader get_data}@anchor{370e}
@deffn {方法} abstractmethod get_data (path)

读取 @emph{path} 作为二进制文件并且返回来自它的字节数据。
@end deffn
@end deffn

@geindex SourceLoader (importlib.abc 中的类)
@anchor{library/importlib importlib abc SourceLoader}@anchor{370f}
@deffn {类} importlib.abc.SourceLoader

一个用于实现源文件（和可选地字节码）加载的抽象基类。这个类继承自 @ref{460,,ResourceLoader} 和 @ref{3709,,ExecutionLoader}，需要实现：


@itemize *

@item 
@ref{36f0,,ResourceLoader.get_data()}

@item 

@table @asis

@item @ref{370a,,ExecutionLoader.get_filename()}

应该是只返回源文件的路径；不支持无源加载。
@end table
@end itemize

由这个类定义的抽象方法用来添加可选的字节码文件支持。不实现这些可选的方法（或导致它们引发 @ref{609,,NotImplementedError} 异常）导致这个加载器只能与源代码一起工作。 实现这些方法允许加载器能与源 @emph{和} 字节码文件一起工作。不允许只提供字节码的 @emph{无源式} 加载。字节码文件是通过移除 Python 编译器的解析步骤来加速加载的优化，并且因此没有开放出字节码专用的 API。

@geindex path_stats() (importlib.abc.SourceLoader 方法)
@anchor{library/importlib importlib abc SourceLoader path_stats}@anchor{ae7}
@deffn {方法} path_stats (path)

返回一个包含关于指定路径的元数据的 @ref{1b8,,dict} 的可选的抽象方法。 支持的字典键有：


@itemize -

@item 
@code{'mtime'} (必选项): 一个表示源码修改时间的整数或浮点数；

@item 
@code{'size'} (可选项)：源码的字节大小。
@end itemize

字典中任何其他键会被忽略，以允许将来的扩展。 如果不能处理该路径，则会引发 @ref{1d3,,OSError}。


3.3 新版功能.



在 3.4 版更改: 引发 @ref{1d3,,OSError} 而不是 @ref{846,,NotImplemented}。

@end deffn

@geindex path_mtime() (importlib.abc.SourceLoader 方法)
@anchor{library/importlib importlib abc SourceLoader path_mtime}@anchor{ae6}
@deffn {方法} path_mtime (path)

返回指定文件路径修改时间的可选的抽象方法。


3.3 版后已移除: 在有了 @ref{ae7,,path_stats()} 的情况下，这个方法被弃用了。 没必要去实现它了，但是为了兼容性，它依然处于可用状态。 如果文件路径不能被处理，则引发 @ref{1d3,,OSError} 异常。



在 3.4 版更改: 引发 @ref{1d3,,OSError} 而不是 @ref{846,,NotImplemented}。

@end deffn

@geindex set_data() (importlib.abc.SourceLoader 方法)
@anchor{library/importlib importlib abc SourceLoader set_data}@anchor{3710}
@deffn {方法} set_data (path, data)

往一个文件路径写入指定字节的的可选的抽象方法。任何中间不存在的目录不会被自动创建。

由于路径是只读的，当写入的路径产生错误时（@ref{21dd,,errno.EACCES}/@ref{5fa,,PermissionError}），不会传播异常。


在 3.4 版更改: 当被调用时，不再引起 @ref{609,,NotImplementedError} 异常。

@end deffn

@geindex get_code() (importlib.abc.SourceLoader 方法)
@anchor{library/importlib importlib abc SourceLoader get_code}@anchor{3711}
@deffn {方法} get_code (fullname)

@ref{85b,,InspectLoader.get_code()} 的具体实现。
@end deffn

@geindex exec_module() (importlib.abc.SourceLoader 方法)
@anchor{library/importlib importlib abc SourceLoader exec_module}@anchor{93a}
@deffn {方法} exec_module (module)

@ref{5df,,Loader.exec_module()} 的具体实现。


3.4 新版功能.

@end deffn

@geindex load_module() (importlib.abc.SourceLoader 方法)
@anchor{library/importlib importlib abc SourceLoader load_module}@anchor{938}
@deffn {方法} load_module (fullname)

Concrete implementation of @ref{5de,,Loader.load_module()}.


3.4 版后已移除: 使用 @ref{93a,,exec_module()} 来代替。

@end deffn

@geindex get_source() (importlib.abc.SourceLoader 方法)
@anchor{library/importlib importlib abc SourceLoader get_source}@anchor{953}
@deffn {方法} get_source (fullname)

@ref{85f,,InspectLoader.get_source()} 的具体实现。
@end deffn

@geindex is_package() (importlib.abc.SourceLoader 方法)
@anchor{library/importlib importlib abc SourceLoader is_package}@anchor{3712}
@deffn {方法} is_package (fullname)

@ref{3708,,InspectLoader.is_package()} 的具体实现。一个模块被确定为一个包的条件是：它的文件路径（由 @ref{370a,,ExecutionLoader.get_filename()} 提供）当文件扩展名被移除时是一个命名为 @code{__init__} 的文件，@strong{并且} 这个模块名字本身不是以`@w{`}__init__`@w{`}结束。
@end deffn
@end deffn

@node importlib resources -- 资源,importlib machinery -- Importers and path hooks,importlib abc —— 关于导入的抽象基类,importlib --- import 的实现
@anchor{library/importlib importlib-resources-resources}@anchor{3713}@anchor{library/importlib module-importlib resources}@anchor{9e}
@subsubsection @code{importlib.resources} -- 资源


@geindex importlib.resources (模块)

@strong{源码：} Lib/importlib/resources.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/importlib/resources.py}


__________________________________________________________________



3.7 新版功能.


这个模块使得Python的导入系统提供了访问*包*内的*资源*的功能。如果能够导入一个包，那么就能够访问那个包里面的资源。资源可以以二进制或文本模式方式被打开或读取。

资源非常类似于目录内部的文件，要牢记的是这仅仅是一个比喻。资源和包不是与文件系统上的物理文件和目录一样存在着。

@cartouche
@quotation 注解 
This module provides functionality similar to pkg_resources@footnote{https://setuptools.readthedocs.io/en/latest/pkg_resources.html} Basic Resource Access@footnote{http://setuptools.readthedocs.io/en/latest/pkg_resources.html#basic-resource-access}
without the performance overhead of that package.  This makes reading
resources included in packages easier, with more stable and consistent
semantics.

The standalone backport of this module provides more information
on using importlib.resources@footnote{http://importlib-resources.readthedocs.io/en/latest/using.html} and
migrating from pkg_resources to importlib.resources@footnote{http://importlib-resources.readthedocs.io/en/latest/migration.html}.
@end quotation
@end cartouche

加载器想要支持资源读取应该实现一个由 @ref{33b,,importlib.abc.ResourceReader} 指定的`@w{`}get_resource_reader(fullname)`@w{`} 方法。

The following types are defined.

@geindex Package() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources Package}@anchor{3714}
@deffn {数据} importlib.resources.Package

The @code{Package} type is defined as @code{Union[str, ModuleType]}.  This means
that where the function describes accepting a @code{Package}, you can pass in
either a string or a module.  Module objects must have a resolvable
@code{__spec__.submodule_search_locations} that is not @code{None}.
@end deffn

@geindex Resource() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources Resource}@anchor{3715}
@deffn {数据} importlib.resources.Resource

This type describes the resource names passed into the various functions
in this package.  This is defined as @code{Union[str, os.PathLike]}.
@end deffn

The following functions are available.

@geindex open_binary() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources open_binary}@anchor{3716}
@deffn {函数} importlib.resources.open_binary (package, resource)

Open for binary reading the @emph{resource} within @emph{package}.

@emph{package} is either a name or a module object which conforms to the
@code{Package} requirements.  @emph{resource} is the name of the resource to open
within @emph{package}; it may not contain path separators and it may not have
sub-resources (i.e. it cannot be a directory).  This function returns a
@code{typing.BinaryIO} instance, a binary I/O stream open for reading.
@end deffn

@geindex open_text() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources open_text}@anchor{3717}
@deffn {函数} importlib.resources.open_text (package, resource, encoding='utf-8', errors='strict')

Open for text reading the @emph{resource} within @emph{package}.  By default, the
resource is opened for reading as UTF-8.

@emph{package} is either a name or a module object which conforms to the
@code{Package} requirements.  @emph{resource} is the name of the resource to open
within @emph{package}; it may not contain path separators and it may not have
sub-resources (i.e. it cannot be a directory).  @emph{encoding} and @emph{errors}
have the same meaning as with built-in @ref{4ea,,open()}.

This function returns a @code{typing.TextIO} instance, a text I/O stream open
for reading.
@end deffn

@geindex read_binary() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources read_binary}@anchor{3718}
@deffn {函数} importlib.resources.read_binary (package, resource)

Read and return the contents of the @emph{resource} within @emph{package} as
@code{bytes}.

@emph{package} is either a name or a module object which conforms to the
@code{Package} requirements.  @emph{resource} is the name of the resource to open
within @emph{package}; it may not contain path separators and it may not have
sub-resources (i.e. it cannot be a directory).  This function returns the
contents of the resource as @ref{32a,,bytes}.
@end deffn

@geindex read_text() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources read_text}@anchor{3719}
@deffn {函数} importlib.resources.read_text (package, resource, encoding='utf-8', errors='strict')

Read and return the contents of @emph{resource} within @emph{package} as a @code{str}.
By default, the contents are read as strict UTF-8.

@emph{package} is either a name or a module object which conforms to the
@code{Package} requirements.  @emph{resource} is the name of the resource to open
within @emph{package}; it may not contain path separators and it may not have
sub-resources (i.e. it cannot be a directory).  @emph{encoding} and @emph{errors}
have the same meaning as with built-in @ref{4ea,,open()}.  This function
returns the contents of the resource as @ref{329,,str}.
@end deffn

@geindex path() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources path}@anchor{371a}
@deffn {函数} importlib.resources.path (package, resource)

Return the path to the @emph{resource} as an actual file system path.  This
function returns a context manager for use in a @ref{6e3,,with} statement.
The context manager provides a @ref{201,,pathlib.Path} object.

Exiting the context manager cleans up any temporary file created when the
resource needs to be extracted from e.g. a zip file.

@emph{package} is either a name or a module object which conforms to the
@code{Package} requirements.  @emph{resource} is the name of the resource to open
within @emph{package}; it may not contain path separators and it may not have
sub-resources (i.e. it cannot be a directory).
@end deffn

@geindex is_resource() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources is_resource}@anchor{371b}
@deffn {函数} importlib.resources.is_resource (package, name)

Return @code{True} if there is a resource named @emph{name} in the package,
otherwise @code{False}.  Remember that directories are @emph{not} resources!
@emph{package} is either a name or a module object which conforms to the
@code{Package} requirements.
@end deffn

@geindex contents() (在 importlib.resources 模块中)
@anchor{library/importlib importlib resources contents}@anchor{fcc}
@deffn {函数} importlib.resources.contents (package)

Return an iterable over the named items within the package.  The iterable
returns @ref{329,,str} resources (e.g. files) and non-resources
(e.g. directories).  The iterable does not recurse into subdirectories.

@emph{package} is either a name or a module object which conforms to the
@code{Package} requirements.
@end deffn

@node importlib machinery -- Importers and path hooks,importlib util -- Utility code for importers,importlib resources -- 资源,importlib --- import 的实现
@anchor{library/importlib importlib-machinery-importers-and-path-hooks}@anchor{371c}@anchor{library/importlib module-importlib machinery}@anchor{9d}
@subsubsection @code{importlib.machinery} -- Importers and path hooks


@geindex importlib.machinery (模块)

@strong{Source code:} Lib/importlib/machinery.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/importlib/machinery.py}


__________________________________________________________________


This module contains the various objects that help @ref{c16,,import}
find and load modules.

@geindex SOURCE_SUFFIXES() (在 importlib.machinery 模块中)
@anchor{library/importlib importlib machinery SOURCE_SUFFIXES}@anchor{371d}
@deffn {属性} importlib.machinery.SOURCE_SUFFIXES

A list of strings representing the recognized file suffixes for source
modules.


3.3 新版功能.

@end deffn

@geindex DEBUG_BYTECODE_SUFFIXES() (在 importlib.machinery 模块中)
@anchor{library/importlib importlib machinery DEBUG_BYTECODE_SUFFIXES}@anchor{371e}
@deffn {属性} importlib.machinery.DEBUG_BYTECODE_SUFFIXES

A list of strings representing the file suffixes for non-optimized bytecode
modules.


3.3 新版功能.



3.5 版后已移除: Use @ref{371f,,BYTECODE_SUFFIXES} instead.

@end deffn

@geindex OPTIMIZED_BYTECODE_SUFFIXES() (在 importlib.machinery 模块中)
@anchor{library/importlib importlib machinery OPTIMIZED_BYTECODE_SUFFIXES}@anchor{3720}
@deffn {属性} importlib.machinery.OPTIMIZED_BYTECODE_SUFFIXES

A list of strings representing the file suffixes for optimized bytecode
modules.


3.3 新版功能.



3.5 版后已移除: Use @ref{371f,,BYTECODE_SUFFIXES} instead.

@end deffn

@geindex BYTECODE_SUFFIXES() (在 importlib.machinery 模块中)
@anchor{library/importlib importlib machinery BYTECODE_SUFFIXES}@anchor{371f}
@deffn {属性} importlib.machinery.BYTECODE_SUFFIXES

A list of strings representing the recognized file suffixes for bytecode
modules (including the leading dot).


3.3 新版功能.



在 3.5 版更改: The value is no longer dependent on @code{__debug__}.

@end deffn

@geindex EXTENSION_SUFFIXES() (在 importlib.machinery 模块中)
@anchor{library/importlib importlib machinery EXTENSION_SUFFIXES}@anchor{3721}
@deffn {属性} importlib.machinery.EXTENSION_SUFFIXES

A list of strings representing the recognized file suffixes for
extension modules.


3.3 新版功能.

@end deffn

@geindex all_suffixes() (在 importlib.machinery 模块中)
@anchor{library/importlib importlib machinery all_suffixes}@anchor{366f}
@deffn {函数} importlib.machinery.all_suffixes ()

Returns a combined list of strings representing all file suffixes for
modules recognized by the standard import machinery. This is a
helper for code which simply needs to know if a filesystem path
potentially refers to a module without needing any details on the kind
of module (for example, @ref{5ed,,inspect.getmodulename()}).


3.3 新版功能.

@end deffn

@geindex BuiltinImporter (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery BuiltinImporter}@anchor{550}
@deffn {类} importlib.machinery.BuiltinImporter

An @ref{1454,,importer} for built-in modules. All known built-in modules are
listed in @ref{35c7,,sys.builtin_module_names}. This class implements the
@ref{9ad,,importlib.abc.MetaPathFinder} and
@ref{85a,,importlib.abc.InspectLoader} ABCs.

Only class methods are defined by this class to alleviate the need for
instantiation.


在 3.5 版更改: As part of 
@geindex Python 提高建议; PEP 489
PEP 489@footnote{https://www.python.org/dev/peps/pep-0489}, the builtin importer now implements
@code{Loader.create_module()} and @code{Loader.exec_module()}

@end deffn

@geindex FrozenImporter (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery FrozenImporter}@anchor{951}
@deffn {类} importlib.machinery.FrozenImporter

An @ref{1454,,importer} for frozen modules. This class implements the
@ref{9ad,,importlib.abc.MetaPathFinder} and
@ref{85a,,importlib.abc.InspectLoader} ABCs.

Only class methods are defined by this class to alleviate the need for
instantiation.


在 3.4 版更改: Gained @code{create_module()} and @code{exec_module()}
methods.

@end deffn

@geindex WindowsRegistryFinder (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery WindowsRegistryFinder}@anchor{5e0}
@deffn {类} importlib.machinery.WindowsRegistryFinder

@ref{1452,,Finder} for modules declared in the Windows registry.  This class
implements the @ref{9ad,,importlib.abc.MetaPathFinder} ABC.

Only class methods are defined by this class to alleviate the need for
instantiation.


3.3 新版功能.



3.6 版后已移除: Use @ref{eb,,site} configuration instead. Future versions of Python may
not enable this finder by default.

@end deffn

@geindex PathFinder (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery PathFinder}@anchor{955}
@deffn {类} importlib.machinery.PathFinder

A @ref{1452,,Finder} for @ref{482,,sys.path} and package @code{__path__} attributes.
This class implements the @ref{9ad,,importlib.abc.MetaPathFinder} ABC.

Only class methods are defined by this class to alleviate the need for
instantiation.

@geindex find_spec() (importlib.machinery.PathFinder 类方法)
@anchor{library/importlib importlib machinery PathFinder find_spec}@anchor{934}
@deffn {方法} classmethod find_spec (fullname, path=None, target=None)

Class method that attempts to find a @ref{35dd,,spec}
for the module specified by @emph{fullname} on @ref{482,,sys.path} or, if
defined, on @emph{path}. For each path entry that is searched,
@ref{498,,sys.path_importer_cache} is checked. If a non-false object
is found then it is used as the @ref{9ac,,path entry finder} to look
for the module being searched for. If no entry is found in
@ref{498,,sys.path_importer_cache}, then @ref{956,,sys.path_hooks} is
searched for a finder for the path entry and, if found, is stored
in @ref{498,,sys.path_importer_cache} along with being queried about
the module. If no finder is ever found then @code{None} is both
stored in the cache and returned.


3.4 新版功能.



在 3.5 版更改: If the current working directory -- represented by an empty string --
is no longer valid then @code{None} is returned but no value is cached
in @ref{498,,sys.path_importer_cache}.

@end deffn

@geindex find_module() (importlib.machinery.PathFinder 类方法)
@anchor{library/importlib importlib machinery PathFinder find_module}@anchor{933}
@deffn {方法} classmethod find_module (fullname, path=None)

A legacy wrapper around @ref{934,,find_spec()}.


3.4 版后已移除: 使用 @ref{934,,find_spec()} 来代替。

@end deffn

@geindex invalidate_caches() (importlib.machinery.PathFinder 类方法)
@anchor{library/importlib importlib machinery PathFinder invalidate_caches}@anchor{496}
@deffn {方法} classmethod invalidate_caches ()

Calls @ref{3704,,importlib.abc.PathEntryFinder.invalidate_caches()} on all
finders stored in @ref{498,,sys.path_importer_cache} that define the method.
Otherwise entries in @ref{498,,sys.path_importer_cache} set to @code{None} are
deleted.


在 3.7 版更改: Entries of @code{None} in @ref{498,,sys.path_importer_cache} are deleted.

@end deffn


在 3.4 版更改: Calls objects in @ref{956,,sys.path_hooks} with the current working
directory for @code{'@w{'}} (i.e. the empty string).

@end deffn

@geindex FileFinder (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery FileFinder}@anchor{9b0}
@deffn {类} importlib.machinery.FileFinder (path, *loader_details)

A concrete implementation of @ref{9ae,,importlib.abc.PathEntryFinder} which
caches results from the file system.

The @emph{path} argument is the directory for which the finder is in charge of
searching.

The @emph{loader_details} argument is a variable number of 2-item tuples each
containing a loader and a sequence of file suffixes the loader recognizes.
The loaders are expected to be callables which accept two arguments of
the module's name and the path to the file found.

The finder will cache the directory contents as necessary, making stat calls
for each module search to verify the cache is not outdated. Because cache
staleness relies upon the granularity of the operating system's state
information of the file system, there is a potential race condition of
searching for a module, creating a new file, and then searching for the
module the new file represents. If the operations happen fast enough to fit
within the granularity of stat calls, then the module search will fail. To
prevent this from happening, when you create a module dynamically, make sure
to call @ref{497,,importlib.invalidate_caches()}.


3.3 新版功能.


@geindex path (importlib.machinery.FileFinder 属性)
@anchor{library/importlib importlib machinery FileFinder path}@anchor{3722}
@deffn {属性} path

The path the finder will search in.
@end deffn

@geindex find_spec() (importlib.machinery.FileFinder 方法)
@anchor{library/importlib importlib machinery FileFinder find_spec}@anchor{7bb}
@deffn {方法} find_spec (fullname, target=None)

Attempt to find the spec to handle @emph{fullname} within @ref{3722,,path}.


3.4 新版功能.

@end deffn

@geindex find_loader() (importlib.machinery.FileFinder 方法)
@anchor{library/importlib importlib machinery FileFinder find_loader}@anchor{3723}
@deffn {方法} find_loader (fullname)

Attempt to find the loader to handle @emph{fullname} within @ref{3722,,path}.
@end deffn

@geindex invalidate_caches() (importlib.machinery.FileFinder 方法)
@anchor{library/importlib importlib machinery FileFinder invalidate_caches}@anchor{3724}
@deffn {方法} invalidate_caches ()

Clear out the internal cache.
@end deffn

@geindex path_hook() (importlib.machinery.FileFinder 类方法)
@anchor{library/importlib importlib machinery FileFinder path_hook}@anchor{3725}
@deffn {方法} classmethod path_hook (*loader_details)

A class method which returns a closure for use on @ref{956,,sys.path_hooks}.
An instance of @ref{9b0,,FileFinder} is returned by the closure using the
path argument given to the closure directly and @emph{loader_details}
indirectly.

If the argument to the closure is not an existing directory,
@ref{32d,,ImportError} is raised.
@end deffn
@end deffn

@geindex SourceFileLoader (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery SourceFileLoader}@anchor{9b2}
@deffn {类} importlib.machinery.SourceFileLoader (fullname, path)

A concrete implementation of @ref{370f,,importlib.abc.SourceLoader} by
subclassing @ref{9b1,,importlib.abc.FileLoader} and providing some concrete
implementations of other methods.


3.3 新版功能.


@geindex name (importlib.machinery.SourceFileLoader 属性)
@anchor{library/importlib importlib machinery SourceFileLoader name}@anchor{3726}
@deffn {属性} name

The name of the module that this loader will handle.
@end deffn

@geindex path (importlib.machinery.SourceFileLoader 属性)
@anchor{library/importlib importlib machinery SourceFileLoader path}@anchor{3727}
@deffn {属性} path

The path to the source file.
@end deffn

@geindex is_package() (importlib.machinery.SourceFileLoader 方法)
@anchor{library/importlib importlib machinery SourceFileLoader is_package}@anchor{3728}
@deffn {方法} is_package (fullname)

Return @code{True} if @ref{3727,,path} appears to be for a package.
@end deffn

@geindex path_stats() (importlib.machinery.SourceFileLoader 方法)
@anchor{library/importlib importlib machinery SourceFileLoader path_stats}@anchor{3729}
@deffn {方法} path_stats (path)

Concrete implementation of @ref{ae7,,importlib.abc.SourceLoader.path_stats()}.
@end deffn

@geindex set_data() (importlib.machinery.SourceFileLoader 方法)
@anchor{library/importlib importlib machinery SourceFileLoader set_data}@anchor{372a}
@deffn {方法} set_data (path, data)

Concrete implementation of @ref{3710,,importlib.abc.SourceLoader.set_data()}.
@end deffn

@geindex load_module() (importlib.machinery.SourceFileLoader 方法)
@anchor{library/importlib importlib machinery SourceFileLoader load_module}@anchor{5dc}
@deffn {方法} load_module (name=None)

Concrete implementation of @ref{5de,,importlib.abc.Loader.load_module()} where
specifying the name of the module to load is optional.


3.6 版后已移除: Use @ref{5df,,importlib.abc.Loader.exec_module()} instead.

@end deffn
@end deffn

@geindex SourcelessFileLoader (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery SourcelessFileLoader}@anchor{9b3}
@deffn {类} importlib.machinery.SourcelessFileLoader (fullname, path)

A concrete implementation of @ref{9b1,,importlib.abc.FileLoader} which can
import bytecode files (i.e. no source code files exist).

Please note that direct use of bytecode files (and thus not source code
files) inhibits your modules from being usable by all Python
implementations or new versions of Python which change the bytecode
format.


3.3 新版功能.


@geindex name (importlib.machinery.SourcelessFileLoader 属性)
@anchor{library/importlib importlib machinery SourcelessFileLoader name}@anchor{372b}
@deffn {属性} name

The name of the module the loader will handle.
@end deffn

@geindex path (importlib.machinery.SourcelessFileLoader 属性)
@anchor{library/importlib importlib machinery SourcelessFileLoader path}@anchor{372c}
@deffn {属性} path

The path to the bytecode file.
@end deffn

@geindex is_package() (importlib.machinery.SourcelessFileLoader 方法)
@anchor{library/importlib importlib machinery SourcelessFileLoader is_package}@anchor{372d}
@deffn {方法} is_package (fullname)

Determines if the module is a package based on @ref{372c,,path}.
@end deffn

@geindex get_code() (importlib.machinery.SourcelessFileLoader 方法)
@anchor{library/importlib importlib machinery SourcelessFileLoader get_code}@anchor{372e}
@deffn {方法} get_code (fullname)

Returns the code object for @ref{372b,,name} created from @ref{372c,,path}.
@end deffn

@geindex get_source() (importlib.machinery.SourcelessFileLoader 方法)
@anchor{library/importlib importlib machinery SourcelessFileLoader get_source}@anchor{372f}
@deffn {方法} get_source (fullname)

Returns @code{None} as bytecode files have no source when this loader is
used.
@end deffn

@geindex load_module() (importlib.machinery.SourcelessFileLoader 方法)
@anchor{library/importlib importlib machinery SourcelessFileLoader load_module}@anchor{5dd}
@deffn {方法} load_module (name=None)
@end deffn

Concrete implementation of @ref{5de,,importlib.abc.Loader.load_module()} where
specifying the name of the module to load is optional.


3.6 版后已移除: Use @ref{5df,,importlib.abc.Loader.exec_module()} instead.

@end deffn

@geindex ExtensionFileLoader (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery ExtensionFileLoader}@anchor{551}
@deffn {类} importlib.machinery.ExtensionFileLoader (fullname, path)

A concrete implementation of @ref{3709,,importlib.abc.ExecutionLoader} for
extension modules.

The @emph{fullname} argument specifies the name of the module the loader is to
support. The @emph{path} argument is the path to the extension module's file.


3.3 新版功能.


@geindex name (importlib.machinery.ExtensionFileLoader 属性)
@anchor{library/importlib importlib machinery ExtensionFileLoader name}@anchor{3730}
@deffn {属性} name

Name of the module the loader supports.
@end deffn

@geindex path (importlib.machinery.ExtensionFileLoader 属性)
@anchor{library/importlib importlib machinery ExtensionFileLoader path}@anchor{3731}
@deffn {属性} path

Path to the extension module.
@end deffn

@geindex create_module() (importlib.machinery.ExtensionFileLoader 方法)
@anchor{library/importlib importlib machinery ExtensionFileLoader create_module}@anchor{3732}
@deffn {方法} create_module (spec)

Creates the module object from the given specification in accordance
with 
@geindex Python 提高建议; PEP 489
PEP 489@footnote{https://www.python.org/dev/peps/pep-0489}.


3.5 新版功能.

@end deffn

@geindex exec_module() (importlib.machinery.ExtensionFileLoader 方法)
@anchor{library/importlib importlib machinery ExtensionFileLoader exec_module}@anchor{3733}
@deffn {方法} exec_module (module)

Initializes the given module object in accordance with 
@geindex Python 提高建议; PEP 489
PEP 489@footnote{https://www.python.org/dev/peps/pep-0489}.


3.5 新版功能.

@end deffn

@geindex is_package() (importlib.machinery.ExtensionFileLoader 方法)
@anchor{library/importlib importlib machinery ExtensionFileLoader is_package}@anchor{3734}
@deffn {方法} is_package (fullname)

Returns @code{True} if the file path points to a package's @code{__init__}
module based on @ref{3721,,EXTENSION_SUFFIXES}.
@end deffn

@geindex get_code() (importlib.machinery.ExtensionFileLoader 方法)
@anchor{library/importlib importlib machinery ExtensionFileLoader get_code}@anchor{3735}
@deffn {方法} get_code (fullname)

Returns @code{None} as extension modules lack a code object.
@end deffn

@geindex get_source() (importlib.machinery.ExtensionFileLoader 方法)
@anchor{library/importlib importlib machinery ExtensionFileLoader get_source}@anchor{3736}
@deffn {方法} get_source (fullname)

Returns @code{None} as extension modules do not have source code.
@end deffn

@geindex get_filename() (importlib.machinery.ExtensionFileLoader 方法)
@anchor{library/importlib importlib machinery ExtensionFileLoader get_filename}@anchor{860}
@deffn {方法} get_filename (fullname)

返回 @ref{3731,,path}。


3.4 新版功能.

@end deffn
@end deffn

@geindex ModuleSpec (importlib.machinery 中的类)
@anchor{library/importlib importlib machinery ModuleSpec}@anchor{145e}
@deffn {类} importlib.machinery.ModuleSpec (name, loader, *, origin=None, loader_state=None, is_package=None)

A specification for a module's import-system-related state.  This is
typically exposed as the module's @code{__spec__} attribute.  In the
descriptions below, the names in parentheses give the corresponding
attribute available directly on the module object.
E.g. @code{module.__spec__.origin == module.__file__}.  Note however that
while the @emph{values} are usually equivalent, they can differ since there is
no synchronization between the two objects.  Thus it is possible to update
the module's @code{__path__} at runtime, and this will not be automatically
reflected in @code{__spec__.submodule_search_locations}.


3.4 新版功能.


@geindex name (importlib.machinery.ModuleSpec 属性)
@anchor{library/importlib importlib machinery ModuleSpec name}@anchor{3737}
@deffn {属性} name
@end deffn

(@code{__name__})

A string for the fully-qualified name of the module.

@geindex loader (importlib.machinery.ModuleSpec 属性)
@anchor{library/importlib importlib machinery ModuleSpec loader}@anchor{3738}
@deffn {属性} loader
@end deffn

(@code{__loader__})

The loader to use for loading.  For namespace packages this should be
set to @code{None}.

@geindex origin (importlib.machinery.ModuleSpec 属性)
@anchor{library/importlib importlib machinery ModuleSpec origin}@anchor{3739}
@deffn {属性} origin
@end deffn

(@code{__file__})

Name of the place from which the module is loaded, e.g. "builtin" for
built-in modules and the filename for modules loaded from source.
Normally "origin" should be set, but it may be @code{None} (the default)
which indicates it is unspecified (e.g. for namespace packages).

@geindex submodule_search_locations (importlib.machinery.ModuleSpec 属性)
@anchor{library/importlib importlib machinery ModuleSpec submodule_search_locations}@anchor{373a}
@deffn {属性} submodule_search_locations
@end deffn

(@code{__path__})

List of strings for where to find submodules, if a package (@code{None}
otherwise).

@geindex loader_state (importlib.machinery.ModuleSpec 属性)
@anchor{library/importlib importlib machinery ModuleSpec loader_state}@anchor{373b}
@deffn {属性} loader_state
@end deffn

Container of extra module-specific data for use during loading (or
@code{None}).

@geindex cached (importlib.machinery.ModuleSpec 属性)
@anchor{library/importlib importlib machinery ModuleSpec cached}@anchor{373c}
@deffn {属性} cached
@end deffn

(@code{__cached__})

String for where the compiled module should be stored (or @code{None}).

@geindex parent (importlib.machinery.ModuleSpec 属性)
@anchor{library/importlib importlib machinery ModuleSpec parent}@anchor{373d}
@deffn {属性} parent
@end deffn

(@code{__package__})

(Read-only) Fully-qualified name of the package to which the module
belongs as a submodule (or @code{None}).

@geindex has_location (importlib.machinery.ModuleSpec 属性)
@anchor{library/importlib importlib machinery ModuleSpec has_location}@anchor{373e}
@deffn {属性} has_location
@end deffn

Boolean indicating whether or not the module's "origin"
attribute refers to a loadable location.
@end deffn

@node importlib util -- Utility code for importers,例子<29>,importlib machinery -- Importers and path hooks,importlib --- import 的实现
@anchor{library/importlib importlib-util-utility-code-for-importers}@anchor{373f}@anchor{library/importlib module-importlib util}@anchor{9f}
@subsubsection @code{importlib.util} -- Utility code for importers


@geindex importlib.util (模块)

@strong{Source code:} Lib/importlib/util.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/importlib/util.py}


__________________________________________________________________


This module contains the various objects that help in the construction of
an @ref{1454,,importer}.

@geindex MAGIC_NUMBER() (在 importlib.util 模块中)
@anchor{library/importlib importlib util MAGIC_NUMBER}@anchor{85c}
@deffn {属性} importlib.util.MAGIC_NUMBER

The bytes which represent the bytecode version number. If you need help with
loading/writing bytecode then consider @ref{370f,,importlib.abc.SourceLoader}.


3.4 新版功能.

@end deffn

@geindex cache_from_source() (在 importlib.util 模块中)
@anchor{library/importlib importlib util cache_from_source}@anchor{552}
@deffn {函数} importlib.util.cache_from_source (path, debug_override=None, *, optimization=None)

Return the 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147}/
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} path to the byte-compiled file associated
with the source @emph{path}.  For example, if @emph{path} is @code{/foo/bar/baz.py} the return
value would be @code{/foo/bar/__pycache__/baz.cpython-32.pyc} for Python 3.2.
The @code{cpython-32} string comes from the current magic tag (see
@code{get_tag()}; if @code{sys.implementation.cache_tag} is not defined then
@ref{609,,NotImplementedError} will be raised).

The @emph{optimization} parameter is used to specify the optimization level of the
bytecode file. An empty string represents no optimization, so
@code{/foo/bar/baz.py} with an @emph{optimization} of @code{'@w{'}} will result in a
bytecode path of @code{/foo/bar/__pycache__/baz.cpython-32.pyc}. @code{None} causes
the interpreter's optimization level to be used. Any other value's string
representation is used, so @code{/foo/bar/baz.py} with an @emph{optimization} of
@code{2} will lead to the bytecode path of
@code{/foo/bar/__pycache__/baz.cpython-32.opt-2.pyc}. The string representation
of @emph{optimization} can only be alphanumeric, else @ref{1fb,,ValueError} is raised.

The @emph{debug_override} parameter is deprecated and can be used to override
the system's value for @code{__debug__}. A @code{True} value is the equivalent of
setting @emph{optimization} to the empty string. A @code{False} value is the same as
setting @emph{optimization} to @code{1}. If both @emph{debug_override} an @emph{optimization}
are not @code{None} then @ref{192,,TypeError} is raised.


3.4 新版功能.



在 3.5 版更改: The @emph{optimization} parameter was added and the @emph{debug_override} parameter
was deprecated.



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex source_from_cache() (在 importlib.util 模块中)
@anchor{library/importlib importlib util source_from_cache}@anchor{553}
@deffn {函数} importlib.util.source_from_cache (path)

Given the @emph{path} to a 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} file name, return the associated source code
file path.  For example, if @emph{path} is
@code{/foo/bar/__pycache__/baz.cpython-32.pyc} the returned path would be
@code{/foo/bar/baz.py}.  @emph{path} need not exist, however if it does not conform
to 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} or 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} format, a @ref{1fb,,ValueError} is raised. If
@code{sys.implementation.cache_tag} is not defined,
@ref{609,,NotImplementedError} is raised.


3.4 新版功能.



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex decode_source() (在 importlib.util 模块中)
@anchor{library/importlib importlib util decode_source}@anchor{85e}
@deffn {函数} importlib.util.decode_source (source_bytes)

Decode the given bytes representing source code and return it as a string
with universal newlines (as required by
@ref{85f,,importlib.abc.InspectLoader.get_source()}).


3.4 新版功能.

@end deffn

@geindex resolve_name() (在 importlib.util 模块中)
@anchor{library/importlib importlib util resolve_name}@anchor{3740}
@deffn {函数} importlib.util.resolve_name (name, package)

Resolve a relative module name to an absolute one.

If  @strong{name} has no leading dots, then @strong{name} is simply returned. This
allows for usage such as
@code{importlib.util.resolve_name('sys', __package__)} without doing a
check to see if the @strong{package} argument is needed.

@ref{1fb,,ValueError} is raised if @strong{name} is a relative module name but
package is a false value (e.g. @code{None} or the empty string).
@ref{1fb,,ValueError} is also raised a relative name would escape its containing
package (e.g. requesting @code{..bacon} from within the @code{spam} package).


3.3 新版功能.

@end deffn

@geindex find_spec() (在 importlib.util 模块中)
@anchor{library/importlib importlib util find_spec}@anchor{932}
@deffn {函数} importlib.util.find_spec (name, package=None)

Find the @ref{35dd,,spec} for a module, optionally relative to
the specified @strong{package} name. If the module is in @ref{eb5,,sys.modules},
then @code{sys.modules[name].__spec__} is returned (unless the spec would be
@code{None} or is not set, in which case @ref{1fb,,ValueError} is raised).
Otherwise a search using @ref{5e1,,sys.meta_path} is done. @code{None} is
returned if no spec is found.

If @strong{name} is for a submodule (contains a dot), the parent module is
automatically imported.

@strong{name} and @strong{package} work the same as for @code{import_module()}.


3.4 新版功能.



在 3.7 版更改: Raises @ref{392,,ModuleNotFoundError} instead of @ref{393,,AttributeError} if
@strong{package} is in fact not a package (i.e. lacks a @ref{1223,,__path__}
attribute).

@end deffn

@geindex module_from_spec() (在 importlib.util 模块中)
@anchor{library/importlib importlib util module_from_spec}@anchor{6ea}
@deffn {函数} importlib.util.module_from_spec (spec)

Create a new module based on @strong{spec} and
@ref{54f,,spec.loader.create_module}.

If @ref{54f,,spec.loader.create_module}
does not return @code{None}, then any pre-existing attributes will not be reset.
Also, no @ref{393,,AttributeError} will be raised if triggered while accessing
@strong{spec} or setting an attribute on the module.

This function is preferred over using @ref{6eb,,types.ModuleType} to create a
new module as @strong{spec} is used to set as many import-controlled attributes on
the module as possible.


3.5 新版功能.

@end deffn

@geindex module_for_loader() (在 importlib.util 模块中)
@anchor{library/importlib importlib util module_for_loader}@anchor{93c}
@deffn {函数} @@importlib.util.module_for_loader

A @ref{283,,decorator} for @ref{5de,,importlib.abc.Loader.load_module()}
to handle selecting the proper
module object to load with. The decorated method is expected to have a call
signature taking two positional arguments
(e.g. @code{load_module(self, module)}) for which the second argument
will be the module @strong{object} to be used by the loader.
Note that the decorator will not work on static methods because of the
assumption of two arguments.

The decorated method will take in the @strong{name} of the module to be loaded
as expected for a @ref{1453,,loader}. If the module is not found in
@ref{eb5,,sys.modules} then a new one is constructed. Regardless of where the
module came from, @ref{950,,__loader__} set to @strong{self} and @ref{94f,,__package__}
is set based on what @ref{3708,,importlib.abc.InspectLoader.is_package()} returns
(if available). These attributes are set unconditionally to support
reloading.

If an exception is raised by the decorated method and a module was added to
@ref{eb5,,sys.modules}, then the module will be removed to prevent a partially
initialized module from being in left in @ref{eb5,,sys.modules}. If the module
was already in @ref{eb5,,sys.modules} then it is left alone.


在 3.3 版更改: @ref{950,,__loader__} and @ref{94f,,__package__} are automatically set
(when possible).



在 3.4 版更改: Set @ref{d0b,,__name__}, @ref{950,,__loader__} @ref{94f,,__package__}
unconditionally to support reloading.



3.4 版后已移除: The import machinery now directly performs all the functionality
provided by this function.

@end deffn

@geindex set_loader() (在 importlib.util 模块中)
@anchor{library/importlib importlib util set_loader}@anchor{93d}
@deffn {函数} @@importlib.util.set_loader

A @ref{283,,decorator} for @ref{5de,,importlib.abc.Loader.load_module()}
to set the @ref{950,,__loader__}
attribute on the returned module. If the attribute is already set the
decorator does nothing. It is assumed that the first positional argument to
the wrapped method (i.e. @code{self}) is what @ref{950,,__loader__} should be set
to.


在 3.4 版更改: Set @code{__loader__} if set to @code{None}, as if the attribute does not
exist.



3.4 版后已移除: The import machinery takes care of this automatically.

@end deffn

@geindex set_package() (在 importlib.util 模块中)
@anchor{library/importlib importlib util set_package}@anchor{93e}
@deffn {函数} @@importlib.util.set_package

A @ref{283,,decorator} for @ref{5de,,importlib.abc.Loader.load_module()} to set the
@ref{94f,,__package__} attribute on the returned module. If @ref{94f,,__package__}
is set and has a value other than @code{None} it will not be changed.


3.4 版后已移除: The import machinery takes care of this automatically.

@end deffn

@geindex spec_from_loader() (在 importlib.util 模块中)
@anchor{library/importlib importlib util spec_from_loader}@anchor{3702}
@deffn {函数} importlib.util.spec_from_loader (name, loader, *, origin=None, is_package=None)

A factory function for creating a @code{ModuleSpec} instance based
on a loader.  The parameters have the same meaning as they do for
ModuleSpec.  The function uses available @ref{1453,,loader} APIs, such as
@code{InspectLoader.is_package()}, to fill in any missing
information on the spec.


3.4 新版功能.

@end deffn

@geindex spec_from_file_location() (在 importlib.util 模块中)
@anchor{library/importlib importlib util spec_from_file_location}@anchor{554}
@deffn {函数} importlib.util.spec_from_file_location (name, location, *, loader=None, submodule_search_locations=None)

A factory function for creating a @code{ModuleSpec} instance based
on the path to a file.  Missing information will be filled in on the
spec by making use of loader APIs and by the implication that the
module will be file-based.


3.4 新版功能.



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex source_hash() (在 importlib.util 模块中)
@anchor{library/importlib importlib util source_hash}@anchor{3741}
@deffn {函数} importlib.util.source_hash (source_bytes)

Return the hash of @emph{source_bytes} as bytes. A hash-based @code{.pyc} file embeds
the @ref{3741,,source_hash()} of the corresponding source file's contents in its
header.


3.7 新版功能.

@end deffn

@geindex LazyLoader (importlib.util 中的类)
@anchor{library/importlib importlib util LazyLoader}@anchor{54e}
@deffn {类} importlib.util.LazyLoader (loader)

A class which postpones the execution of the loader of a module until the
module has an attribute accessed.

This class @strong{only} works with loaders that define
@ref{5df,,exec_module()} as control over what module type
is used for the module is required. For those same reasons, the loader's
@ref{54f,,create_module()} method must return @code{None} or a
type for which its @code{__class__} attribute can be mutated along with not
using @ref{3742,,slots}. Finally, modules which substitute the object
placed into @ref{eb5,,sys.modules} will not work as there is no way to properly
replace the module references throughout the interpreter safely;
@ref{1fb,,ValueError} is raised if such a substitution is detected.

@cartouche
@quotation 注解 
For projects where startup time is critical, this class allows for
potentially minimizing the cost of loading a module if it is never used.
For projects where startup time is not essential then use of this class is
@strong{heavily} discouraged due to error messages created during loading being
postponed and thus occurring out of context.
@end quotation
@end cartouche


3.5 新版功能.



在 3.6 版更改: Began calling @ref{54f,,create_module()}, removing the
compatibility warning for @ref{550,,importlib.machinery.BuiltinImporter} and
@ref{551,,importlib.machinery.ExtensionFileLoader}.


@geindex factory() (importlib.util.LazyLoader 类方法)
@anchor{library/importlib importlib util LazyLoader factory}@anchor{3743}
@deffn {方法} classmethod factory (loader)

A static method which returns a callable that creates a lazy loader. This
is meant to be used in situations where the loader is passed by class
instead of by instance.

@example
suffixes = importlib.machinery.SOURCE_SUFFIXES
loader = importlib.machinery.SourceFileLoader
lazy_loader = importlib.util.LazyLoader.factory(loader)
finder = importlib.machinery.FileFinder(path, (lazy_loader, suffixes))
@end example
@end deffn
@end deffn

@node 例子<29>,,importlib util -- Utility code for importers,importlib --- import 的实现
@anchor{library/importlib examples}@anchor{3744}@anchor{library/importlib importlib-examples}@anchor{3745}
@subsubsection 例子


@menu
* Importing programmatically:: 
* Checking if a module can be imported:: 
* Importing a source file directly:: 
* Setting up an importer:: 
* Approximating importlib.import_module(): Approximating importlib import_module. 

@end menu

@node Importing programmatically,Checking if a module can be imported,,例子<29>
@anchor{library/importlib importing-programmatically}@anchor{3746}
@subsubsection Importing programmatically


To programmatically import a module, use @ref{b0c,,importlib.import_module()}.

@example
import importlib

itertools = importlib.import_module('itertools')
@end example

@node Checking if a module can be imported,Importing a source file directly,Importing programmatically,例子<29>
@anchor{library/importlib checking-if-a-module-can-be-imported}@anchor{3747}
@subsubsection Checking if a module can be imported


If you need to find out if a module can be imported without actually doing the
import, then you should use @ref{932,,importlib.util.find_spec()}.

@example
import importlib.util
import sys

# For illustrative purposes.
name = 'itertools'

if name in sys.modules:
    print(f"@{name!r@} already in sys.modules")
elif (spec := importlib.util.find_spec(name)) is not None:
    # If you chose to perform the actual import ...
    module = importlib.util.module_from_spec(spec)
    sys.modules[name] = module
    spec.loader.exec_module(module)
    print(f"@{name!r@} has been imported")
else:
    print(f"can't find the @{name!r@} module")
@end example

@node Importing a source file directly,Setting up an importer,Checking if a module can be imported,例子<29>
@anchor{library/importlib importing-a-source-file-directly}@anchor{3748}
@subsubsection Importing a source file directly


To import a Python source file directly, use the following recipe
(Python 3.5 and newer only):

@example
import importlib.util
import sys

# For illustrative purposes.
import tokenize
file_path = tokenize.__file__
module_name = tokenize.__name__

spec = importlib.util.spec_from_file_location(module_name, file_path)
module = importlib.util.module_from_spec(spec)
sys.modules[module_name] = module
spec.loader.exec_module(module)
@end example

@node Setting up an importer,Approximating importlib import_module,Importing a source file directly,例子<29>
@anchor{library/importlib setting-up-an-importer}@anchor{3749}
@subsubsection Setting up an importer


For deep customizations of import, you typically want to implement an
@ref{1454,,importer}. This means managing both the @ref{1452,,finder} and @ref{1453,,loader}
side of things. For finders there are two flavours to choose from depending on
your needs: a @ref{9ab,,meta path finder} or a @ref{9ac,,path entry finder}. The
former is what you would put on @ref{5e1,,sys.meta_path} while the latter is what
you create using a @ref{146a,,path entry hook} on @ref{956,,sys.path_hooks} which works
with @ref{482,,sys.path} entries to potentially create a finder. This example will
show you how to register your own importers so that import will use them (for
creating an importer for yourself, read the documentation for the appropriate
classes defined within this package):

@example
import importlib.machinery
import sys

# For illustrative purposes only.
SpamMetaPathFinder = importlib.machinery.PathFinder
SpamPathEntryFinder = importlib.machinery.FileFinder
loader_details = (importlib.machinery.SourceFileLoader,
                  importlib.machinery.SOURCE_SUFFIXES)

# Setting up a meta path finder.
# Make sure to put the finder in the proper location in the list in terms of
# priority.
sys.meta_path.append(SpamMetaPathFinder)

# Setting up a path entry finder.
# Make sure to put the path hook in the proper location in the list in terms
# of priority.
sys.path_hooks.append(SpamPathEntryFinder.path_hook(loader_details))
@end example

@node Approximating importlib import_module,,Setting up an importer,例子<29>
@anchor{library/importlib approximating-importlib-import-module}@anchor{374a}
@subsubsection Approximating @code{importlib.import_module()}


Import itself is implemented in Python code, making it possible to
expose most of the import machinery through importlib. The following
helps illustrate the various APIs that importlib exposes by providing an
approximate implementation of
@ref{b0c,,importlib.import_module()} (Python 3.4 and newer for the importlib usage,
Python 3.6 and newer for other parts of the code).

@example
import importlib.util
import sys

def import_module(name, package=None):
    """An approximate implementation of import."""
    absolute_name = importlib.util.resolve_name(name, package)
    try:
        return sys.modules[absolute_name]
    except KeyError:
        pass

    path = None
    if '.' in absolute_name:
        parent_name, _, child_name = absolute_name.rpartition('.')
        parent_module = import_module(parent_name)
        path = parent_module.__spec__.submodule_search_locations
    for finder in sys.meta_path:
        spec = finder.find_spec(absolute_name, path)
        if spec is not None:
            break
    else:
        msg = f'No module named @{absolute_name!r@}'
        raise ModuleNotFoundError(msg, name=absolute_name)
    module = importlib.util.module_from_spec(spec)
    sys.modules[absolute_name] = module
    spec.loader.exec_module(module)
    if path is not None:
        setattr(parent_module, child_name, module)
    return module
@end example

@node Using importlib metadata,,importlib --- import 的实现,导入模块
@anchor{library/importlib metadata doc}@anchor{374b}@anchor{library/importlib metadata using}@anchor{374c}@anchor{library/importlib metadata using-importlib-metadata}@anchor{374d}
@subsection Using importlib.metadata


@cartouche
@quotation 注解 
This functionality is provisional and may deviate from the usual
version semantics of the standard library.
@end quotation
@end cartouche

@code{importlib.metadata} is a library that provides for access to installed
package metadata.  Built in part on Python's import system, this library
intends to replace similar functionality in the entry point API@footnote{https://setuptools.readthedocs.io/en/latest/pkg_resources.html#entry-points} and metadata API@footnote{https://setuptools.readthedocs.io/en/latest/pkg_resources.html#metadata-api} of @code{pkg_resources}.  Along with
@code{importlib.resources} in Python 3.7 and newer@footnote{https://docs.python.org/3/library/importlib.html#module-importlib.resources} (backported as importlib_resources@footnote{https://importlib-resources.readthedocs.io/en/latest/index.html} for older versions of
Python), this can eliminate the need to use the older and less efficient
@code{pkg_resources} package.

By "installed package" we generally mean a third-party package installed into
Python's @code{site-packages} directory via tools such as pip@footnote{https://pypi.org/project/pip/}.  Specifically,
it means a package with either a discoverable @code{dist-info} or @code{egg-info}
directory, and metadata defined by PEP 566@footnote{https://www.python.org/dev/peps/pep-0566/} or its older specifications.
By default, package metadata can live on the file system or in zip archives on
@code{sys.path}.  Through an extension mechanism, the metadata can live almost
anywhere.

@menu
* 概述: 概述<14>. 
* 功能性 API: 功能性 API<2>. 
* Distributions:: 
* Extending the search algorithm:: 

@end menu

@node 概述<14>,功能性 API<2>,,Using importlib metadata
@anchor{library/importlib metadata overview}@anchor{374e}
@subsubsection 概述


Let's say you wanted to get the version string for a package you've installed
using @code{pip}.  We start by creating a virtual environment and installing
something into it:

@example
$ python3 -m venv example
$ source example/bin/activate
(example) $ pip install wheel
@end example

You can get the version string for @code{wheel} by running the following:

@example
(example) $ python
>>> from importlib.metadata import version  
>>> version('wheel')  
'0.32.3'
@end example

You can also get the set of entry points keyed by group, such as
@code{console_scripts}, @code{distutils.commands} and others.  Each group contains a
sequence of @ref{374f,,EntryPoint} objects.

You can get the @ref{3750,,metadata for a distribution}:

@example
>>> list(metadata('wheel'))  
['Metadata-Version', 'Name', 'Version', 'Summary', 'Home-page', 'Author', 'Author-email', 'Maintainer', 'Maintainer-email', 'License', 'Project-URL', 'Project-URL', 'Project-URL', 'Keywords', 'Platform', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Classifier', 'Requires-Python', 'Provides-Extra', 'Requires-Dist', 'Requires-Dist']
@end example

You can also get a @ref{3751,,distribution's version number}, list its
@ref{3752,,constituent files}, and get a list of the distribution's
@ref{3753,,Distribution requirements}.

@node 功能性 API<2>,Distributions,概述<14>,Using importlib metadata
@anchor{library/importlib metadata functional-api}@anchor{3754}
@subsubsection 功能性 API


This package provides the following functionality via its public API.

@menu
* Entry points:: 
* Distribution metadata:: 
* Distribution versions:: 
* Distribution files:: 
* Distribution requirements:: 

@end menu

@node Entry points,Distribution metadata,,功能性 API<2>
@anchor{library/importlib metadata entry-points}@anchor{374f}@anchor{library/importlib metadata id1}@anchor{3755}
@subsubsection Entry points


The @code{entry_points()} function returns a dictionary of all entry points,
keyed by group.  Entry points are represented by @code{EntryPoint} instances;
each @code{EntryPoint} has a @code{.name}, @code{.group}, and @code{.value} attributes and
a @code{.load()} method to resolve the value.

@example
>>> eps = entry_points()  
>>> list(eps)  
['console_scripts', 'distutils.commands', 'distutils.setup_keywords', 'egg_info.writers', 'setuptools.installation']
>>> scripts = eps['console_scripts']  
>>> wheel = [ep for ep in scripts if ep.name == 'wheel'][0]  
>>> wheel  
EntryPoint(name='wheel', value='wheel.cli:main', group='console_scripts')
>>> main = wheel.load()  
>>> main  
<function main at 0x103528488>
@end example

The @code{group} and @code{name} are arbitrary values defined by the package author
and usually a client will wish to resolve all entry points for a particular
group.  Read the setuptools docs@footnote{https://setuptools.readthedocs.io/en/latest/setuptools.html#dynamic-discovery-of-services-and-plugins}
for more information on entrypoints, their definition, and usage.

@node Distribution metadata,Distribution versions,Entry points,功能性 API<2>
@anchor{library/importlib metadata distribution-metadata}@anchor{3756}@anchor{library/importlib metadata metadata}@anchor{3750}
@subsubsection Distribution metadata


Every distribution includes some metadata, which you can extract using the
@code{metadata()} function:

@example
>>> wheel_metadata = metadata('wheel')  
@end example

The keys of the returned data structure @footnote{@w{(1)} 
Technically, the returned distribution metadata object is an
@uref{https://docs.python.org/3/library/email.message.html#email.message.EmailMessage,email.message.Message}
instance, but this is an implementation detail, and not part of the
stable API.  You should only use dictionary-like methods and syntax
to access the metadata contents.
} name the metadata keywords, and
their values are returned unparsed from the distribution metadata:

@example
>>> wheel_metadata['Requires-Python']  
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'
@end example

@node Distribution versions,Distribution files,Distribution metadata,功能性 API<2>
@anchor{library/importlib metadata distribution-versions}@anchor{3757}@anchor{library/importlib metadata version}@anchor{3751}
@subsubsection Distribution versions


The @code{version()} function is the quickest way to get a distribution's version
number, as a string:

@example
>>> version('wheel')  
'0.32.3'
@end example

@node Distribution files,Distribution requirements,Distribution versions,功能性 API<2>
@anchor{library/importlib metadata distribution-files}@anchor{3758}@anchor{library/importlib metadata files}@anchor{3752}
@subsubsection Distribution files


You can also get the full set of files contained within a distribution.  The
@code{files()} function takes a distribution package name and returns all of the
files installed by this distribution.  Each file object returned is a
@code{PackagePath}, a pathlib.Path@footnote{https://docs.python.org/3/library/pathlib.html#pathlib.Path} derived object with additional @code{dist},
@code{size}, and @code{hash} properties as indicated by the metadata.  For example:

@example
>>> util = [p for p in files('wheel') if 'util.py' in str(p)][0]  
>>> util  
PackagePath('wheel/util.py')
>>> util.size  
859
>>> util.dist  
<importlib.metadata._hooks.PathDistribution object at 0x101e0cef0>
>>> util.hash  
<FileHash mode: sha256 value: bYkw5oMccfazVCoYQwKkkemoVyMAFoR34mmKBx8R1NI>
@end example

Once you have the file, you can also read its contents:

@example
>>> print(util.read_text())  
import base64
import sys
...
def as_bytes(s):
    if isinstance(s, text_type):
        return s.encode('utf-8')
    return s
@end example

In the case where the metadata file listing files
(RECORD or SOURCES.txt) is missing, @code{files()} will
return @code{None}. The caller may wish to wrap calls to
@code{files()} in always_iterable@footnote{https://more-itertools.readthedocs.io/en/stable/api.html#more_itertools.always_iterable}
or otherwise guard against this condition if the target
distribution is not known to have the metadata present.

@node Distribution requirements,,Distribution files,功能性 API<2>
@anchor{library/importlib metadata distribution-requirements}@anchor{3759}@anchor{library/importlib metadata requirements}@anchor{3753}
@subsubsection Distribution requirements


To get the full set of requirements for a distribution, use the @code{requires()}
function:

@example
>>> requires('wheel')  
["pytest (>=3.0.0) ; extra == 'test'", "pytest-cov ; extra == 'test'"]
@end example

@node Distributions,Extending the search algorithm,功能性 API<2>,Using importlib metadata
@anchor{library/importlib metadata distributions}@anchor{375a}
@subsubsection Distributions


While the above API is the most common and convenient usage, you can get all
of that information from the @code{Distribution} class.  A @code{Distribution} is an
abstract object that represents the metadata for a Python package.  You can
get the @code{Distribution} instance:

@example
>>> from importlib.metadata import distribution  
>>> dist = distribution('wheel')  
@end example

Thus, an alternative way to get the version number is through the
@code{Distribution} instance:

@example
>>> dist.version  
'0.32.3'
@end example

There are all kinds of additional metadata available on the @code{Distribution}
instance:

@example
>>> d.metadata['Requires-Python']  
'>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*'
>>> d.metadata['License']  
'MIT'
@end example

The full set of available metadata is not described here.  See PEP 566@footnote{https://www.python.org/dev/peps/pep-0566/} for additional details.

@node Extending the search algorithm,,Distributions,Using importlib metadata
@anchor{library/importlib metadata extending-the-search-algorithm}@anchor{375b}
@subsubsection Extending the search algorithm


Because package metadata is not available through @code{sys.path} searches, or
package loaders directly, the metadata for a package is found through import
system finders@footnote{https://docs.python.org/3/reference/import.html#finders-and-loaders}.  To find a distribution package's metadata,
@code{importlib.metadata} queries the list of meta path finders@footnote{https://docs.python.org/3/glossary.html#term-meta-path-finder} on
sys.meta_path@footnote{https://docs.python.org/3/library/sys.html#sys.meta_path}.

The default @code{PathFinder} for Python includes a hook that calls into
@code{importlib.metadata.MetadataPathFinder} for finding distributions
loaded from typical file-system-based paths.

The abstract class @ref{9ad,,importlib.abc.MetaPathFinder} defines the
interface expected of finders by Python's import system.
@code{importlib.metadata} extends this protocol by looking for an optional
@code{find_distributions} callable on the finders from
@code{sys.meta_path} and presents this extended interface as the
@code{DistributionFinder} abstract base class, which defines this abstract
method:

@example
@@abc.abstractmethod
def find_distributions(context=DistributionFinder.Context()):
    """Return an iterable of all Distribution instances capable of
    loading the metadata for packages for the indicated `@w{`}context`@w{`}.
    """
@end example

The @code{DistributionFinder.Context} object provides @code{.path} and @code{.name}
properties indicating the path to search and names to match and may
supply other relevant context.

What this means in practice is that to support finding distribution package
metadata in locations other than the file system, subclass
@code{Distribution} and implement the abstract methods. Then from
a custom finder, return instances of this derived @code{Distribution} in the
@code{find_distributions()} method.

@subsubheading 备注


@node Python 语言服务,杂项服务,导入模块,Python 标准库
@anchor{library/language doc}@anchor{375c}@anchor{library/language language}@anchor{375d}@anchor{library/language python-language-services}@anchor{375e}
@section Python 语言服务


Python 提供了许多模块来帮助使用 Python 语言。 这些模块支持标记化、解析、语法分析、字节码反汇编以及各种其他工具。

这些模块包括：

@menu
* parser: parser --- 访问 Python 解析树. 访问 Python 解析树
* ast: ast --- 抽象语法树. 抽象语法树
* symtable: symtable --- Access to the compiler's symbol tables. Access to the compiler's symbol tables
* symbol: symbol --- 与 Python 解析树一起使用的常量. 与 Python 解析树一起使用的常量
* token: token --- 与Python解析树一起使用的常量. 与Python解析树一起使用的常量
* keyword: keyword --- 检验Python关键字. 检验Python关键字
* tokenize: tokenize --- 对 Python 代码使用的标记解析器. 对 Python 代码使用的标记解析器
* tabnanny: tabnanny --- 模糊缩进检测. 模糊缩进检测
* pyclbr: pyclbr --- Python module browser support. Python module browser support
* py_compile: py_compile --- Compile Python source files. Compile Python source files
* compileall: compileall --- Byte-compile Python libraries. Byte-compile Python libraries
* dis: dis --- Python 字节码反汇编器. Python 字节码反汇编器
* pickletools: pickletools --- pickle 开发者工具集. pickle 开发者工具集

@end menu

@node parser --- 访问 Python 解析树,ast --- 抽象语法树,,Python 语言服务
@anchor{library/parser doc}@anchor{375f}@anchor{library/parser module-parser}@anchor{c7}@anchor{library/parser parser-access-python-parse-trees}@anchor{3760}
@subsection @code{parser} --- 访问 Python 解析树


@geindex parser (模块)

@c Copyright 1995 Virginia Polytechnic Institute and State University and Fred
@c L. Drake, Jr.  This copyright notice must be distributed on all copies, but
@c this document otherwise may be distributed as part of the Python
@c distribution.  No fee may be charged for this document in any representation,
@c either on paper or electronically.  This restriction does not affect other
@c elements in a distributed package in any way.

@geindex parsing; Python source code


__________________________________________________________________


The @ref{c7,,parser} module provides an interface to Python's internal parser and
byte-code compiler.  The primary purpose for this interface is to allow Python
code to edit the parse tree of a Python expression and create executable code
from this.  This is better than trying to parse and modify an arbitrary Python
code fragment as a string because parsing is performed in a manner identical to
the code forming the application.  It is also faster.

@cartouche
@quotation 注解 
From Python 2.5 onward, it's much more convenient to cut in at the Abstract
Syntax Tree (AST) generation and compilation stage, using the @ref{8,,ast}
module.
@end quotation
@end cartouche

There are a few things to note about this module which are important to making
use of the data structures created.  This is not a tutorial on editing the parse
trees for Python code, but some examples of using the @ref{c7,,parser} module are
presented.

Most importantly, a good understanding of the Python grammar processed by the
internal parser is required.  For full information on the language syntax, refer
to @ref{1190,,Python语言参考}.  The parser
itself is created from a grammar specification defined in the file
@code{Grammar/Grammar} in the standard Python distribution.  The parse trees
stored in the ST objects created by this module are the actual output from the
internal parser when created by the @ref{3761,,expr()} or @ref{3762,,suite()} functions,
described below.  The ST objects created by @ref{3763,,sequence2st()} faithfully
simulate those structures.  Be aware that the values of the sequences which are
considered "correct" will vary from one version of Python to another as the
formal grammar for the language is revised.  However, transporting code from one
Python version to another as source text will always allow correct parse trees
to be created in the target version, with the only restriction being that
migrating to an older version of the interpreter will not support more recent
language constructs.  The parse trees are not typically compatible from one
version to another, though source code has usually been forward-compatible within
a major release series.

Each element of the sequences returned by @ref{3764,,st2list()} or @ref{3765,,st2tuple()}
has a simple form.  Sequences representing non-terminal elements in the grammar
always have a length greater than one.  The first element is an integer which
identifies a production in the grammar.  These integers are given symbolic names
in the C header file @code{Include/graminit.h} and the Python module
@ref{fb,,symbol}.  Each additional element of the sequence represents a component
of the production as recognized in the input string: these are always sequences
which have the same form as the parent.  An important aspect of this structure
which should be noted is that keywords used to identify the parent node type,
such as the keyword @ref{de0,,if} in an @code{if_stmt}, are included in the
node tree without any special treatment.  For example, the @code{if} keyword
is represented by the tuple @code{(1, 'if')}, where @code{1} is the numeric value
associated with all @code{NAME} tokens, including variable and function names
defined by the user.  In an alternate form returned when line number information
is requested, the same token might be represented as @code{(1, 'if', 12)}, where
the @code{12} represents the line number at which the terminal symbol was found.

Terminal elements are represented in much the same way, but without any child
elements and the addition of the source text which was identified.  The example
of the @ref{de0,,if} keyword above is representative.  The various types of
terminal symbols are defined in the C header file @code{Include/token.h} and
the Python module @ref{110,,token}.

The ST objects are not required to support the functionality of this module,
but are provided for three purposes: to allow an application to amortize the
cost of processing complex parse trees, to provide a parse tree representation
which conserves memory space when compared to the Python list or tuple
representation, and to ease the creation of additional modules in C which
manipulate parse trees.  A simple "wrapper" class may be created in Python to
hide the use of ST objects.

The @ref{c7,,parser} module defines functions for a few distinct purposes.  The
most important purposes are to create ST objects and to convert ST objects to
other representations such as parse trees and compiled code objects, but there
are also functions which serve to query the type of parse tree represented by an
ST object.


@subsubheading 参见



@table @asis

@item 模块 @ref{fb,,symbol}

代表解析树内部节点的有用常量。

@item 模块 @ref{110,,token}

代表解析树叶子节点和测试节点值的函数的有用常量。
@end table


@menu
* 创建 ST 对象:: 
* 转换 ST 对象:: 
* Queries on ST Objects:: 
* 异常和错误处理:: 
* ST 对象:: 
* 示例; compile() 的模拟: 示例 compile 的模拟. 

@end menu

@node 创建 ST 对象,转换 ST 对象,,parser --- 访问 Python 解析树
@anchor{library/parser creating-st-objects}@anchor{3766}@anchor{library/parser creating-sts}@anchor{3767}
@subsubsection 创建 ST 对象


ST objects may be created from source code or from a parse tree. When creating
an ST object from source, different functions are used to create the @code{'eval'}
and @code{'exec'} forms.

@geindex expr() (在 parser 模块中)
@anchor{library/parser parser expr}@anchor{3761}
@deffn {函数} parser.expr (source)

The @ref{3761,,expr()} function parses the parameter @emph{source} as if it were an input
to @code{compile(source, 'file.py', 'eval')}.  If the parse succeeds, an ST object
is created to hold the internal parse tree representation, otherwise an
appropriate exception is raised.
@end deffn

@geindex suite() (在 parser 模块中)
@anchor{library/parser parser suite}@anchor{3762}
@deffn {函数} parser.suite (source)

The @ref{3762,,suite()} function parses the parameter @emph{source} as if it were an input
to @code{compile(source, 'file.py', 'exec')}.  If the parse succeeds, an ST object
is created to hold the internal parse tree representation, otherwise an
appropriate exception is raised.
@end deffn

@geindex sequence2st() (在 parser 模块中)
@anchor{library/parser parser sequence2st}@anchor{3763}
@deffn {函数} parser.sequence2st (sequence)

This function accepts a parse tree represented as a sequence and builds an
internal representation if possible.  If it can validate that the tree conforms
to the Python grammar and all nodes are valid node types in the host version of
Python, an ST object is created from the internal representation and returned
to the called.  If there is a problem creating the internal representation, or
if the tree cannot be validated, a @ref{3768,,ParserError} exception is raised.  An
ST object created this way should not be assumed to compile correctly; normal
exceptions raised by compilation may still be initiated when the ST object is
passed to @ref{3769,,compilest()}.  This may indicate problems not related to syntax
(such as a @ref{f9f,,MemoryError} exception), but may also be due to constructs such
as the result of parsing @code{del f(0)}, which escapes the Python parser but is
checked by the bytecode compiler.

Sequences representing terminal tokens may be represented as either two-element
lists of the form @code{(1, 'name')} or as three-element lists of the form @code{(1,
'name', 56)}.  If the third element is present, it is assumed to be a valid
line number.  The line number may be specified for any subset of the terminal
symbols in the input tree.
@end deffn

@geindex tuple2st() (在 parser 模块中)
@anchor{library/parser parser tuple2st}@anchor{376a}
@deffn {函数} parser.tuple2st (sequence)

This is the same function as @ref{3763,,sequence2st()}.  This entry point is
maintained for backward compatibility.
@end deffn

@node 转换 ST 对象,Queries on ST Objects,创建 ST 对象,parser --- 访问 Python 解析树
@anchor{library/parser converting-st-objects}@anchor{376b}@anchor{library/parser converting-sts}@anchor{376c}
@subsubsection 转换 ST 对象


ST objects, regardless of the input used to create them, may be converted to
parse trees represented as list- or tuple- trees, or may be compiled into
executable code objects.  Parse trees may be extracted with or without line
numbering information.

@geindex st2list() (在 parser 模块中)
@anchor{library/parser parser st2list}@anchor{3764}
@deffn {函数} parser.st2list (st, line_info=False, col_info=False)

This function accepts an ST object from the caller in @emph{st} and returns a
Python list representing the equivalent parse tree.  The resulting list
representation can be used for inspection or the creation of a new parse tree in
list form.  This function does not fail so long as memory is available to build
the list representation.  If the parse tree will only be used for inspection,
@ref{3765,,st2tuple()} should be used instead to reduce memory consumption and
fragmentation.  When the list representation is required, this function is
significantly faster than retrieving a tuple representation and converting that
to nested lists.

If @emph{line_info} is true, line number information will be included for all
terminal tokens as a third element of the list representing the token.  Note
that the line number provided specifies the line on which the token @emph{ends}.
This information is omitted if the flag is false or omitted.
@end deffn

@geindex st2tuple() (在 parser 模块中)
@anchor{library/parser parser st2tuple}@anchor{3765}
@deffn {函数} parser.st2tuple (st, line_info=False, col_info=False)

This function accepts an ST object from the caller in @emph{st} and returns a
Python tuple representing the equivalent parse tree.  Other than returning a
tuple instead of a list, this function is identical to @ref{3764,,st2list()}.

If @emph{line_info} is true, line number information will be included for all
terminal tokens as a third element of the list representing the token.  This
information is omitted if the flag is false or omitted.
@end deffn

@geindex compilest() (在 parser 模块中)
@anchor{library/parser parser compilest}@anchor{3769}
@deffn {函数} parser.compilest (st, filename='<syntax-tree>')

@geindex 內置函数; exec
@geindex 內置函数; eval

The Python byte compiler can be invoked on an ST object to produce code objects
which can be used as part of a call to the built-in @ref{c3d,,exec()} or @ref{b89,,eval()}
functions. This function provides the interface to the compiler, passing the
internal parse tree from @emph{st} to the parser, using the source file name
specified by the @emph{filename} parameter. The default value supplied for @emph{filename}
indicates that the source was an ST object.

Compiling an ST object may result in exceptions related to compilation; an
example would be a @ref{452,,SyntaxError} caused by the parse tree for @code{del f(0)}:
this statement is considered legal within the formal grammar for Python but is
not a legal language construct.  The @ref{452,,SyntaxError} raised for this
condition is actually generated by the Python byte-compiler normally, which is
why it can be raised at this point by the @ref{c7,,parser} module.  Most causes of
compilation failure can be diagnosed programmatically by inspection of the parse
tree.
@end deffn

@node Queries on ST Objects,异常和错误处理,转换 ST 对象,parser --- 访问 Python 解析树
@anchor{library/parser queries-on-st-objects}@anchor{376d}@anchor{library/parser querying-sts}@anchor{376e}
@subsubsection Queries on ST Objects


Two functions are provided which allow an application to determine if an ST was
created as an expression or a suite.  Neither of these functions can be used to
determine if an ST was created from source code via @ref{3761,,expr()} or
@ref{3762,,suite()} or from a parse tree via @ref{3763,,sequence2st()}.

@geindex isexpr() (在 parser 模块中)
@anchor{library/parser parser isexpr}@anchor{376f}
@deffn {函数} parser.isexpr (st)

@geindex 內置函数; compile

When @emph{st} represents an @code{'eval'} form, this function returns @code{True}, otherwise
it returns @code{False}.  This is useful, since code objects normally cannot be queried
for this information using existing built-in functions.  Note that the code
objects created by @ref{3769,,compilest()} cannot be queried like this either, and
are identical to those created by the built-in @ref{1b4,,compile()} function.
@end deffn

@geindex issuite() (在 parser 模块中)
@anchor{library/parser parser issuite}@anchor{3770}
@deffn {函数} parser.issuite (st)

This function mirrors @ref{376f,,isexpr()} in that it reports whether an ST object
represents an @code{'exec'} form, commonly known as a "suite."  It is not safe to
assume that this function is equivalent to @code{not isexpr(st)}, as additional
syntactic fragments may be supported in the future.
@end deffn

@node 异常和错误处理,ST 对象,Queries on ST Objects,parser --- 访问 Python 解析树
@anchor{library/parser exceptions-and-error-handling}@anchor{3771}@anchor{library/parser st-errors}@anchor{3772}
@subsubsection 异常和错误处理


The parser module defines a single exception, but may also pass other built-in
exceptions from other portions of the Python runtime environment.  See each
function for information about the exceptions it can raise.

@geindex ParserError
@anchor{library/parser parser ParserError}@anchor{3768}
@deffn {例外} parser.ParserError

Exception raised when a failure occurs within the parser module.  This is
generally produced for validation failures rather than the built-in
@ref{452,,SyntaxError} raised during normal parsing. The exception argument is
either a string describing the reason of the failure or a tuple containing a
sequence causing the failure from a parse tree passed to @ref{3763,,sequence2st()}
and an explanatory string.  Calls to @ref{3763,,sequence2st()} need to be able to
handle either type of exception, while calls to other functions in the module
will only need to be aware of the simple string values.
@end deffn

Note that the functions @ref{3769,,compilest()}, @ref{3761,,expr()}, and @ref{3762,,suite()} may
raise exceptions which are normally raised by the parsing and compilation
process.  These include the built in exceptions @ref{f9f,,MemoryError},
@ref{95a,,OverflowError}, @ref{452,,SyntaxError}, and @ref{5f6,,SystemError}.  In these
cases, these exceptions carry all the meaning normally associated with them.
Refer to the descriptions of each function for detailed information.

@node ST 对象,示例 compile 的模拟,异常和错误处理,parser --- 访问 Python 解析树
@anchor{library/parser id1}@anchor{3773}@anchor{library/parser st-objects}@anchor{3774}
@subsubsection ST 对象


Ordered and equality comparisons are supported between ST objects. Pickling of
ST objects (using the @ref{ca,,pickle} module) is also supported.

@geindex STType() (在 parser 模块中)
@anchor{library/parser parser STType}@anchor{3775}
@deffn {数据} parser.STType

The type of the objects returned by @ref{3761,,expr()}, @ref{3762,,suite()} and
@ref{3763,,sequence2st()}.
@end deffn

ST 对象具有以下方法:

@geindex compile() (parser.ST 方法)
@anchor{library/parser parser ST compile}@anchor{3776}
@deffn {方法} ST.compile (filename='<syntax-tree>')

和 @code{compilest(st, filename)} 相同.
@end deffn

@geindex isexpr() (parser.ST 方法)
@anchor{library/parser parser ST isexpr}@anchor{3777}
@deffn {方法} ST.isexpr ()

和  @code{isexpr(st)} 相同。
@end deffn

@geindex issuite() (parser.ST 方法)
@anchor{library/parser parser ST issuite}@anchor{3778}
@deffn {方法} ST.issuite ()

和 @code{issuite(st)} 相同。
@end deffn

@geindex tolist() (parser.ST 方法)
@anchor{library/parser parser ST tolist}@anchor{3779}
@deffn {方法} ST.tolist (line_info=False, col_info=False)

和 @code{st2list(st, line_info, col_info)} 相同。
@end deffn

@geindex totuple() (parser.ST 方法)
@anchor{library/parser parser ST totuple}@anchor{377a}
@deffn {方法} ST.totuple (line_info=False, col_info=False)

和 @code{st2tuple(st, line_info, col_info)} 相同。
@end deffn

@node 示例 compile 的模拟,,ST 对象,parser --- 访问 Python 解析树
@anchor{library/parser example-emulation-of-compile}@anchor{377b}
@subsubsection 示例: @code{compile()} 的模拟


While many useful operations may take place between parsing and bytecode
generation, the simplest operation is to do nothing.  For this purpose, using
the @ref{c7,,parser} module to produce an intermediate data structure is equivalent
to the code

@example
>>> code = compile('a + 5', 'file.py', 'eval')
>>> a = 5
>>> eval(code)
10
@end example

The equivalent operation using the @ref{c7,,parser} module is somewhat longer, and
allows the intermediate internal parse tree to be retained as an ST object:

@example
>>> import parser
>>> st = parser.expr('a + 5')
>>> code = st.compile('file.py')
>>> a = 5
>>> eval(code)
10
@end example

An application which needs both ST and code objects can package this code into
readily available functions:

@example
import parser

def load_suite(source_string):
    st = parser.suite(source_string)
    return st, st.compile()

def load_expression(source_string):
    st = parser.expr(source_string)
    return st, st.compile()
@end example

@node ast --- 抽象语法树,symtable --- Access to the compiler's symbol tables,parser --- 访问 Python 解析树,Python 语言服务
@anchor{library/ast doc}@anchor{377c}@anchor{library/ast ast-abstract-syntax-trees}@anchor{377d}@anchor{library/ast module-ast}@anchor{8}
@subsection @code{ast} --- 抽象语法树


@geindex ast (模块)

@strong{源代码：} Lib/ast.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/ast.py}


__________________________________________________________________


@ref{8,,ast} 模块帮助 Python 程序处理 Python 语法的抽象语法树。抽象语法或许会随着 Python 的更新发布而改变；该模块能够帮助理解当前语法在编程层面的样貌。

抽象语法树可通过将 @code{ast.PyCF_ONLY_AST} 作为旗标传递给 @ref{1b4,,compile()} 内置函数来生成，或是使用此模块中提供的 @ref{1a1,,parse()} 辅助函数。返回结果将是一个对象树，，其中的类都继承自 @ref{377e,,ast.AST}。抽象语法树可被内置的 @ref{1b4,,compile()} 函数编译为一个 Python 代码对象。

@menu
* 节点类:: 
* 抽象文法:: 
* ast 中的辅助函数:: 

@end menu

@node 节点类,抽象文法,,ast --- 抽象语法树
@anchor{library/ast node-classes}@anchor{377f}
@subsubsection 节点类


@geindex AST (ast 中的类)
@anchor{library/ast ast AST}@anchor{377e}
@deffn {类} ast.AST

这是所有 AST 节点类的基类。实际上，这些节点类派生自 @code{Parser/Python.asdl} 文件，其中定义的语法树示例 @ref{3780,,如下}。它们在 C 语言模块 @code{_ast} 中定义，并被导出至 @ref{8,,ast} 模块。

抽象语法定义的每个左侧符号(比方说，  @code{ast.stmt} 或者 @code{ast.expr})定义了一个类。另外，在抽象语法定义的右侧，对每一个构造器也定义了一个类；这些类继承自树左侧的类。比如，@code{ast.BinOp} 继承自 @code{ast.expr}。对于多分支产生式(也就是"和规则")，树右侧的类是抽象的；只有特定构造器结点的实例能被构造。

@geindex ? (question mark); in AST grammar

@geindex * (asterisk); in AST grammar

@geindex _fields (ast.AST 属性)
@anchor{library/ast ast AST _fields}@anchor{3781}
@deffn {属性} _fields

每个具体类都有个属性 @ref{3781,,_fields}, 用来给出所有子节点的名字。

每个具体类的实例对它每个子节点都有一个属性，对应类型如文法中所定义。比如，@code{ast.BinOp} 的实例有个属性 @code{left}，类型是 @code{ast.expr}.

如果这些属性在文法中标记为可选（使用问号），对应值可能会是 @code{None}。如果这些属性有零或多个（用星号标记），对应值会用Python的列表来表示。所有可能的属性必须在用 @ref{1b4,,compile()} 编译得到AST时给出，且是有效的值。
@end deffn

@geindex lineno (ast.AST 属性)
@geindex col_offset (ast.AST 属性)
@geindex end_lineno (ast.AST 属性)
@geindex end_col_offset (ast.AST 属性)
@anchor{library/ast ast AST lineno}@anchor{3782}
@deffn {属性} lineno
@anchor{library/ast ast AST col_offset}@anchor{3783}
@deffnx {属性} col_offset
@anchor{library/ast ast AST end_lineno}@anchor{3784}
@deffnx {属性} end_lineno
@anchor{library/ast ast AST end_col_offset}@anchor{3785}
@deffnx {属性} end_col_offset

Instances of @code{ast.expr} and @code{ast.stmt} subclasses have
@ref{3782,,lineno}, @ref{3783,,col_offset}, @ref{3782,,lineno}, and @ref{3783,,col_offset}
attributes.  The @ref{3782,,lineno} and @ref{3784,,end_lineno} are the first and
last line numbers of source text span (1-indexed so the first line is line 1)
and the @ref{3783,,col_offset} and @ref{3785,,end_col_offset} are the corresponding
UTF-8 byte offsets of the first and last tokens that generated the node.
The UTF-8 offset is recorded because the parser uses UTF-8 internally.

Note that the end positions are not required by the compiler and are
therefore optional. The end offset is @emph{after} the last symbol, for example
one can get the source segment of a one-line expression node using
@code{source_line[node.col_offset : node.end_col_offset]}.
@end deffn

一个类的构造器 @code{ast.T} 像下面这样parse它的参数。


@itemize *

@item 
如果有位置参数，它们必须和 @code{T._fields} 中的元素一样多；他们会像这些名字的属性一样被赋值。

@item 
如果有关键字参数，它们必须被设为和给定值同名的属性。
@end itemize

比方说，要创建和填充节点 @code{ast.UnaryOp}，你得用

@example
node = ast.UnaryOp()
node.op = ast.USub()
node.operand = ast.Constant()
node.operand.value = 5
node.operand.lineno = 0
node.operand.col_offset = 0
node.lineno = 0
node.col_offset = 0
@end example

或者更紧凑点

@example
node = ast.UnaryOp(ast.USub(), ast.Constant(5, lineno=0, col_offset=0),
                   lineno=0, col_offset=0)
@end example
@end deffn


在 3.8 版更改: Class @code{ast.Constant} is now used for all constants.



3.8 版后已移除: Old classes @code{ast.Num}, @code{ast.Str}, @code{ast.Bytes},
@code{ast.NameConstant} and @code{ast.Ellipsis} are still available,
but they will be removed in future Python releases.  In the meanwhile,
instantiating them will return an instance of a different class.


@node 抽象文法,ast 中的辅助函数,节点类,ast --- 抽象语法树
@anchor{library/ast abstract-grammar}@anchor{3780}@anchor{library/ast id1}@anchor{3786}
@subsubsection 抽象文法


抽象文法目前定义如下

@example
-- ASDL's 5 builtin types are:
-- identifier, int, string, object, constant

module Python
@{
    mod = Module(stmt* body, type_ignore *type_ignores)
        | Interactive(stmt* body)
        | Expression(expr body)
        | FunctionType(expr* argtypes, expr returns)

        -- not really an actual node but useful in Jython's typesystem.
        | Suite(stmt* body)

    stmt = FunctionDef(identifier name, arguments args,
                       stmt* body, expr* decorator_list, expr? returns,
                       string? type_comment)
          | AsyncFunctionDef(identifier name, arguments args,
                             stmt* body, expr* decorator_list, expr? returns,
                             string? type_comment)

          | ClassDef(identifier name,
             expr* bases,
             keyword* keywords,
             stmt* body,
             expr* decorator_list)
          | Return(expr? value)

          | Delete(expr* targets)
          | Assign(expr* targets, expr value, string? type_comment)
          | AugAssign(expr target, operator op, expr value)
          -- 'simple' indicates that we annotate simple name without parens
          | AnnAssign(expr target, expr annotation, expr? value, int simple)

          -- use 'orelse' because else is a keyword in target languages
          | For(expr target, expr iter, stmt* body, stmt* orelse, string? type_comment)
          | AsyncFor(expr target, expr iter, stmt* body, stmt* orelse, string? type_comment)
          | While(expr test, stmt* body, stmt* orelse)
          | If(expr test, stmt* body, stmt* orelse)
          | With(withitem* items, stmt* body, string? type_comment)
          | AsyncWith(withitem* items, stmt* body, string? type_comment)

          | Raise(expr? exc, expr? cause)
          | Try(stmt* body, excepthandler* handlers, stmt* orelse, stmt* finalbody)
          | Assert(expr test, expr? msg)

          | Import(alias* names)
          | ImportFrom(identifier? module, alias* names, int? level)

          | Global(identifier* names)
          | Nonlocal(identifier* names)
          | Expr(expr value)
          | Pass | Break | Continue

          -- XXX Jython will be different
          -- col_offset is the byte offset in the utf8 string the parser uses
          attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

          -- BoolOp() can use left & right?
    expr = BoolOp(boolop op, expr* values)
         | NamedExpr(expr target, expr value)
         | BinOp(expr left, operator op, expr right)
         | UnaryOp(unaryop op, expr operand)
         | Lambda(arguments args, expr body)
         | IfExp(expr test, expr body, expr orelse)
         | Dict(expr* keys, expr* values)
         | Set(expr* elts)
         | ListComp(expr elt, comprehension* generators)
         | SetComp(expr elt, comprehension* generators)
         | DictComp(expr key, expr value, comprehension* generators)
         | GeneratorExp(expr elt, comprehension* generators)
         -- the grammar constrains where yield expressions can occur
         | Await(expr value)
         | Yield(expr? value)
         | YieldFrom(expr value)
         -- need sequences for compare to distinguish between
         -- x < 4 < 3 and (x < 4) < 3
         | Compare(expr left, cmpop* ops, expr* comparators)
         | Call(expr func, expr* args, keyword* keywords)
         | FormattedValue(expr value, int? conversion, expr? format_spec)
         | JoinedStr(expr* values)
         | Constant(constant value, string? kind)

         -- the following expression can appear in assignment context
         | Attribute(expr value, identifier attr, expr_context ctx)
         | Subscript(expr value, slice slice, expr_context ctx)
         | Starred(expr value, expr_context ctx)
         | Name(identifier id, expr_context ctx)
         | List(expr* elts, expr_context ctx)
         | Tuple(expr* elts, expr_context ctx)

          -- col_offset is the byte offset in the utf8 string the parser uses
          attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

    expr_context = Load | Store | Del | AugLoad | AugStore | Param

    slice = Slice(expr? lower, expr? upper, expr? step)
          | ExtSlice(slice* dims)
          | Index(expr value)

    boolop = And | Or

    operator = Add | Sub | Mult | MatMult | Div | Mod | Pow | LShift
                 | RShift | BitOr | BitXor | BitAnd | FloorDiv

    unaryop = Invert | Not | UAdd | USub

    cmpop = Eq | NotEq | Lt | LtE | Gt | GtE | Is | IsNot | In | NotIn

    comprehension = (expr target, expr iter, expr* ifs, int is_async)

    excepthandler = ExceptHandler(expr? type, identifier? name, stmt* body)
                    attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

    arguments = (arg* posonlyargs, arg* args, arg? vararg, arg* kwonlyargs,
                 expr* kw_defaults, arg? kwarg, expr* defaults)

    arg = (identifier arg, expr? annotation, string? type_comment)
           attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)

    -- keyword arguments supplied to call (NULL identifier for **kwargs)
    keyword = (identifier? arg, expr value)

    -- import name with optional 'as' alias.
    alias = (identifier name, identifier? asname)

    withitem = (expr context_expr, expr? optional_vars)

    type_ignore = TypeIgnore(int lineno, string tag)
@}
@end example

@node ast 中的辅助函数,,抽象文法,ast --- 抽象语法树
@anchor{library/ast ast-helpers}@anchor{3787}
@subsubsection @code{ast} 中的辅助函数


除了节点类， @ref{8,,ast} 模块里为遍历抽象语法树定义了这些工具函数和类:

@geindex parse() (在 ast 模块中)
@anchor{library/ast ast parse}@anchor{1a1}
@deffn {函数} ast.parse (source, filename='<unknown>', mode='exec', *, type_comments=False, feature_version=None)

把源码解析为AST节点。和 @code{compile(source, filename, mode,ast.PyCF_ONLY_AST)} 等价。

If @code{type_comments=True} is given, the parser is modified to check
and return type comments as specified by 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} and 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526}.
This is equivalent to adding @code{ast.PyCF_TYPE_COMMENTS} to the
flags passed to @ref{1b4,,compile()}.  This will report syntax errors
for misplaced type comments.  Without this flag, type comments will
be ignored, and the @code{type_comment} field on selected AST nodes
will always be @code{None}.  In addition, the locations of @code{# type:
ignore} comments will be returned as the @code{type_ignores}
attribute of @code{Module} (otherwise it is always an empty list).

In addition, if @code{mode} is @code{'func_type'}, the input syntax is
modified to correspond to 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} "signature type comments",
e.g. @code{(str, int) -> List[str]}.

Also, setting @code{feature_version} to a tuple @code{(major, minor)}
will attempt to parse using that Python version's grammar.
Currently @code{major} must equal to @code{3}.  For example, setting
@code{feature_version=(3, 4)} will allow the use of @code{async} and
@code{await} as variable names.  The lowest supported version is
@code{(3, 4)}; the highest is @code{sys.version_info[0:2]}.

@cartouche
@quotation 警告 
足够复杂或是巨大的字符串可能导致Python解释器的崩溃，因为Python的AST编译器是有栈深限制的。
@end quotation
@end cartouche


在 3.8 版更改: Added @code{type_comments}, @code{mode='func_type'} and @code{feature_version}.

@end deffn

@geindex literal_eval() (在 ast 模块中)
@anchor{library/ast ast literal_eval}@anchor{4a0}
@deffn {函数} ast.literal_eval (node_or_string)

对表达式节点以及包含Python字面量或容器的字符串进行安全的求值。传入的字符串或者节点里可能只包含下列的Python字面量结构: 字符串，字节对象(bytes)，数值，元组，列表，字典，集合，布尔值和 @code{None}。

This can be used for safely evaluating strings containing Python values from
untrusted sources without the need to parse the values oneself.  It is not
capable of evaluating arbitrarily complex expressions, for example involving
operators or indexing.

@cartouche
@quotation 警告 
足够复杂或是巨大的字符串可能导致Python解释器的崩溃，因为Python的AST编译器是有栈深限制的。
@end quotation
@end cartouche


在 3.2 版更改: 目前支持字节和集合。

@end deffn

@geindex get_docstring() (在 ast 模块中)
@anchor{library/ast ast get_docstring}@anchor{fe8}
@deffn {函数} ast.get_docstring (node, clean=True)

Return the docstring of the given @emph{node} (which must be a
@code{FunctionDef}, @code{AsyncFunctionDef}, @code{ClassDef},
or @code{Module} node), or @code{None} if it has no docstring.
If @emph{clean} is true, clean up the docstring's indentation with
@ref{3683,,inspect.cleandoc()}.


在 3.5 版更改: 目前支持 @code{AsyncFunctionDef}

@end deffn

@geindex get_source_segment() (在 ast 模块中)
@anchor{library/ast ast get_source_segment}@anchor{1a0}
@deffn {函数} ast.get_source_segment (source, node, *, padded=False)

Get source code segment of the @emph{source} that generated @emph{node}.
If some location information (@code{lineno}, @code{end_lineno},
@code{col_offset}, or @code{end_col_offset}) is missing, return @code{None}.

If @emph{padded} is @code{True}, the first line of a multi-line statement will
be padded with spaces to match its original position.


3.8 新版功能.

@end deffn

@geindex fix_missing_locations() (在 ast 模块中)
@anchor{library/ast ast fix_missing_locations}@anchor{3788}
@deffn {函数} ast.fix_missing_locations (node)

When you compile a node tree with @ref{1b4,,compile()}, the compiler expects
@code{lineno} and @code{col_offset} attributes for every node that supports
them.  This is rather tedious to fill in for generated nodes, so this helper
adds these attributes recursively where not already set, by setting them to
the values of the parent node.  It works recursively starting at @emph{node}.
@end deffn

@geindex increment_lineno() (在 ast 模块中)
@anchor{library/ast ast increment_lineno}@anchor{3789}
@deffn {函数} ast.increment_lineno (node, n=1)

Increment the line number and end line number of each node in the tree
starting at @emph{node} by @emph{n}. This is useful to "move code" to a different
location in a file.
@end deffn

@geindex copy_location() (在 ast 模块中)
@anchor{library/ast ast copy_location}@anchor{378a}
@deffn {函数} ast.copy_location (new_node, old_node)

Copy source location (@code{lineno}, @code{col_offset}, @code{end_lineno},
and @code{end_col_offset}) from @emph{old_node} to @emph{new_node} if possible,
and return @emph{new_node}.
@end deffn

@geindex iter_fields() (在 ast 模块中)
@anchor{library/ast ast iter_fields}@anchor{378b}
@deffn {函数} ast.iter_fields (node)

Yield a tuple of @code{(fieldname, value)} for each field in @code{node._fields}
that is present on @emph{node}.
@end deffn

@geindex iter_child_nodes() (在 ast 模块中)
@anchor{library/ast ast iter_child_nodes}@anchor{378c}
@deffn {函数} ast.iter_child_nodes (node)

Yield all direct child nodes of @emph{node}, that is, all fields that are nodes
and all items of fields that are lists of nodes.
@end deffn

@geindex walk() (在 ast 模块中)
@anchor{library/ast ast walk}@anchor{378d}
@deffn {函数} ast.walk (node)

Recursively yield all descendant nodes in the tree starting at @emph{node}
(including @emph{node} itself), in no specified order.  This is useful if you only
want to modify nodes in place and don't care about the context.
@end deffn

@geindex NodeVisitor (ast 中的类)
@anchor{library/ast ast NodeVisitor}@anchor{281}
@deffn {类} ast.NodeVisitor

A node visitor base class that walks the abstract syntax tree and calls a
visitor function for every node found.  This function may return a value
which is forwarded by the @ref{378e,,visit()} method.

This class is meant to be subclassed, with the subclass adding visitor
methods.

@geindex visit() (ast.NodeVisitor 方法)
@anchor{library/ast ast NodeVisitor visit}@anchor{378e}
@deffn {方法} visit (node)

Visit a node.  The default implementation calls the method called
@code{self.visit_@emph{classname}} where @emph{classname} is the name of the node
class, or @ref{378f,,generic_visit()} if that method doesn't exist.
@end deffn

@geindex generic_visit() (ast.NodeVisitor 方法)
@anchor{library/ast ast NodeVisitor generic_visit}@anchor{378f}
@deffn {方法} generic_visit (node)

This visitor calls @ref{378e,,visit()} on all children of the node.

Note that child nodes of nodes that have a custom visitor method won't be
visited unless the visitor calls @ref{378f,,generic_visit()} or visits them
itself.
@end deffn

Don't use the @ref{281,,NodeVisitor} if you want to apply changes to nodes
during traversal.  For this a special visitor exists
(@ref{3790,,NodeTransformer}) that allows modifications.


3.8 版后已移除: Methods @code{visit_Num()}, @code{visit_Str()}, @code{visit_Bytes()},
@code{visit_NameConstant()} and @code{visit_Ellipsis()} are deprecated
now and will not be called in future Python versions.  Add the
@code{visit_Constant()} method to handle all constant nodes.

@end deffn

@geindex NodeTransformer (ast 中的类)
@anchor{library/ast ast NodeTransformer}@anchor{3790}
@deffn {类} ast.NodeTransformer

子类 @ref{281,,NodeVisitor}  用于遍历抽象语法树，并允许修改节点。

@ref{3790,,NodeTransformer} 将遍历抽象语法树并使用visitor方法的返回值去替换或移除旧节点。如果visitor方法的返回值为 @code{None} , 则该节点将从其位置移除，否则将替换为返回值。当返回值是原始节点时，无需替换。

如下是一个转换器示例，它将所有出现的名称 (@code{foo}) 重写为 @code{data['foo']}:

@example
class RewriteName(NodeTransformer):

    def visit_Name(self, node):
        return Subscript(
            value=Name(id='data', ctx=Load()),
            slice=Index(value=Constant(value=node.id)),
            ctx=node.ctx
        )
@end example

请记住，如果您正在操作的节点具有子节点，则必须先转换其子节点或为该节点调用 @code{generic_visit()}  方法。

对于属于语句集合（适用于所有语句节点）的节点，访问者还可以返回节点列表而不仅仅是单个节点。

If @ref{3790,,NodeTransformer} introduces new nodes (that weren't part of
original tree) without giving them location information (such as
@code{lineno}), @ref{3788,,fix_missing_locations()} should be called with
the new sub-tree to recalculate the location information:

@example
tree = ast.parse('foo', mode='eval')
new_tree = fix_missing_locations(RewriteName().visit(tree))
@end example

通常你可以像这样使用转换器:

@example
node = YourTransformer().visit(node)
@end example
@end deffn

@geindex dump() (在 ast 模块中)
@anchor{library/ast ast dump}@anchor{f1e}
@deffn {函数} ast.dump (node, annotate_fields=True, include_attributes=False)

Return a formatted dump of the tree in @emph{node}.  This is mainly useful for
debugging purposes.  If @emph{annotate_fields} is true (by default),
the returned string will show the names and the values for fields.
If @emph{annotate_fields} is false, the result string will be more compact by
omitting unambiguous field names.  Attributes such as line
numbers and column offsets are not dumped by default.  If this is wanted,
@emph{include_attributes} can be set to true.
@end deffn


@subsubheading 参见


Green Tree Snakes@footnote{https://greentreesnakes.readthedocs.io/}, an external documentation resource, has good
details on working with Python ASTs.


@node symtable --- Access to the compiler's symbol tables,symbol --- 与 Python 解析树一起使用的常量,ast --- 抽象语法树,Python 语言服务
@anchor{library/symtable doc}@anchor{3791}@anchor{library/symtable module-symtable}@anchor{fc}@anchor{library/symtable symtable-access-to-the-compiler-s-symbol-tables}@anchor{3792}
@subsection @code{symtable} --- Access to the compiler's symbol tables


@geindex symtable (模块)

@strong{Source code:} Lib/symtable.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/symtable.py}


__________________________________________________________________


Symbol tables are generated by the compiler from AST just before bytecode is
generated.  The symbol table is responsible for calculating the scope of every
identifier in the code.  @ref{fc,,symtable} provides an interface to examine these
tables.

@menu
* Generating Symbol Tables:: 
* Examining Symbol Tables:: 

@end menu

@node Generating Symbol Tables,Examining Symbol Tables,,symtable --- Access to the compiler's symbol tables
@anchor{library/symtable generating-symbol-tables}@anchor{3793}
@subsubsection Generating Symbol Tables


@geindex symtable() (在 symtable 模块中)
@anchor{library/symtable symtable symtable}@anchor{f56}
@deffn {函数} symtable.symtable (code, filename, compile_type)

Return the toplevel @ref{3794,,SymbolTable} for the Python source @emph{code}.
@emph{filename} is the name of the file containing the code.  @emph{compile_type} is
like the @emph{mode} argument to @ref{1b4,,compile()}.
@end deffn

@node Examining Symbol Tables,,Generating Symbol Tables,symtable --- Access to the compiler's symbol tables
@anchor{library/symtable examining-symbol-tables}@anchor{3795}
@subsubsection Examining Symbol Tables


@geindex SymbolTable (symtable 中的类)
@anchor{library/symtable symtable SymbolTable}@anchor{3794}
@deffn {类} symtable.SymbolTable

A namespace table for a block.  The constructor is not public.

@geindex get_type() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable get_type}@anchor{3796}
@deffn {方法} get_type ()

Return the type of the symbol table.  Possible values are @code{'class'},
@code{'module'}, and @code{'function'}.
@end deffn

@geindex get_id() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable get_id}@anchor{3797}
@deffn {方法} get_id ()

Return the table's identifier.
@end deffn

@geindex get_name() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable get_name}@anchor{3798}
@deffn {方法} get_name ()

Return the table's name.  This is the name of the class if the table is
for a class, the name of the function if the table is for a function, or
@code{'top'} if the table is global (@ref{3796,,get_type()} returns @code{'module'}).
@end deffn

@geindex get_lineno() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable get_lineno}@anchor{3799}
@deffn {方法} get_lineno ()

Return the number of the first line in the block this table represents.
@end deffn

@geindex is_optimized() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable is_optimized}@anchor{379a}
@deffn {方法} is_optimized ()

Return @code{True} if the locals in this table can be optimized.
@end deffn

@geindex is_nested() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable is_nested}@anchor{379b}
@deffn {方法} is_nested ()

Return @code{True} if the block is a nested class or function.
@end deffn

@geindex has_children() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable has_children}@anchor{379c}
@deffn {方法} has_children ()

Return @code{True} if the block has nested namespaces within it.  These can
be obtained with @ref{379d,,get_children()}.
@end deffn

@geindex has_exec() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable has_exec}@anchor{379e}
@deffn {方法} has_exec ()

Return @code{True} if the block uses @code{exec}.
@end deffn

@geindex get_identifiers() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable get_identifiers}@anchor{379f}
@deffn {方法} get_identifiers ()

Return a list of names of symbols in this table.
@end deffn

@geindex lookup() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable lookup}@anchor{37a0}
@deffn {方法} lookup (name)

Lookup @emph{name} in the table and return a @ref{37a1,,Symbol} instance.
@end deffn

@geindex get_symbols() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable get_symbols}@anchor{37a2}
@deffn {方法} get_symbols ()

Return a list of @ref{37a1,,Symbol} instances for names in the table.
@end deffn

@geindex get_children() (symtable.SymbolTable 方法)
@anchor{library/symtable symtable SymbolTable get_children}@anchor{379d}
@deffn {方法} get_children ()

Return a list of the nested symbol tables.
@end deffn
@end deffn

@geindex Function (symtable 中的类)
@anchor{library/symtable symtable Function}@anchor{37a3}
@deffn {类} symtable.Function

A namespace for a function or method.  This class inherits
@ref{3794,,SymbolTable}.

@geindex get_parameters() (symtable.Function 方法)
@anchor{library/symtable symtable Function get_parameters}@anchor{37a4}
@deffn {方法} get_parameters ()

Return a tuple containing names of parameters to this function.
@end deffn

@geindex get_locals() (symtable.Function 方法)
@anchor{library/symtable symtable Function get_locals}@anchor{37a5}
@deffn {方法} get_locals ()

Return a tuple containing names of locals in this function.
@end deffn

@geindex get_globals() (symtable.Function 方法)
@anchor{library/symtable symtable Function get_globals}@anchor{37a6}
@deffn {方法} get_globals ()

Return a tuple containing names of globals in this function.
@end deffn

@geindex get_nonlocals() (symtable.Function 方法)
@anchor{library/symtable symtable Function get_nonlocals}@anchor{37a7}
@deffn {方法} get_nonlocals ()

Return a tuple containing names of nonlocals in this function.
@end deffn

@geindex get_frees() (symtable.Function 方法)
@anchor{library/symtable symtable Function get_frees}@anchor{37a8}
@deffn {方法} get_frees ()

Return a tuple containing names of free variables in this function.
@end deffn
@end deffn

@geindex Class (symtable 中的类)
@anchor{library/symtable symtable Class}@anchor{37a9}
@deffn {类} symtable.Class

A namespace of a class.  This class inherits @ref{3794,,SymbolTable}.

@geindex get_methods() (symtable.Class 方法)
@anchor{library/symtable symtable Class get_methods}@anchor{37aa}
@deffn {方法} get_methods ()

Return a tuple containing the names of methods declared in the class.
@end deffn
@end deffn

@geindex Symbol (symtable 中的类)
@anchor{library/symtable symtable Symbol}@anchor{37a1}
@deffn {类} symtable.Symbol

An entry in a @ref{3794,,SymbolTable} corresponding to an identifier in the
source.  The constructor is not public.

@geindex get_name() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol get_name}@anchor{37ab}
@deffn {方法} get_name ()

Return the symbol's name.
@end deffn

@geindex is_referenced() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_referenced}@anchor{37ac}
@deffn {方法} is_referenced ()

Return @code{True} if the symbol is used in its block.
@end deffn

@geindex is_imported() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_imported}@anchor{37ad}
@deffn {方法} is_imported ()

Return @code{True} if the symbol is created from an import statement.
@end deffn

@geindex is_parameter() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_parameter}@anchor{37ae}
@deffn {方法} is_parameter ()

Return @code{True} if the symbol is a parameter.
@end deffn

@geindex is_global() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_global}@anchor{37af}
@deffn {方法} is_global ()

Return @code{True} if the symbol is global.
@end deffn

@geindex is_nonlocal() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_nonlocal}@anchor{f9e}
@deffn {方法} is_nonlocal ()

Return @code{True} if the symbol is nonlocal.
@end deffn

@geindex is_declared_global() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_declared_global}@anchor{caf}
@deffn {方法} is_declared_global ()

Return @code{True} if the symbol is declared global with a global statement.
@end deffn

@geindex is_local() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_local}@anchor{37b0}
@deffn {方法} is_local ()

Return @code{True} if the symbol is local to its block.
@end deffn

@geindex is_free() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_free}@anchor{37b1}
@deffn {方法} is_free ()

Return @code{True} if the symbol is referenced in its block, but not assigned
to.
@end deffn

@geindex is_assigned() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_assigned}@anchor{37b2}
@deffn {方法} is_assigned ()

Return @code{True} if the symbol is assigned to in its block.
@end deffn

@geindex is_namespace() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol is_namespace}@anchor{37b3}
@deffn {方法} is_namespace ()

Return @code{True} if name binding introduces new namespace.

If the name is used as the target of a function or class statement, this
will be true.

例如

@example
>>> table = symtable.symtable("def some_func(): pass", "string", "exec")
>>> table.lookup("some_func").is_namespace()
True
@end example

Note that a single name can be bound to multiple objects.  If the result
is @code{True}, the name may also be bound to other objects, like an int or
list, that does not introduce a new namespace.
@end deffn

@geindex get_namespaces() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol get_namespaces}@anchor{37b4}
@deffn {方法} get_namespaces ()

Return a list of namespaces bound to this name.
@end deffn

@geindex get_namespace() (symtable.Symbol 方法)
@anchor{library/symtable symtable Symbol get_namespace}@anchor{37b5}
@deffn {方法} get_namespace ()

Return the namespace bound to this name.  If more than one namespace is
bound, @ref{1fb,,ValueError} is raised.
@end deffn
@end deffn

@node symbol --- 与 Python 解析树一起使用的常量,token --- 与Python解析树一起使用的常量,symtable --- Access to the compiler's symbol tables,Python 语言服务
@anchor{library/symbol doc}@anchor{37b6}@anchor{library/symbol module-symbol}@anchor{fb}@anchor{library/symbol symbol-constants-used-with-python-parse-trees}@anchor{37b7}
@subsection @code{symbol} --- 与 Python 解析树一起使用的常量


@geindex symbol (模块)

@strong{源代码:} Lib/symbol.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/symbol.py}


__________________________________________________________________


此模块提供用于表示解析树内部节点数值的常量。 与大多数 Python 不同，这些常量使用小写字符名称。 请参阅 Python 发行版中的 @code{Grammar/Grammar} 文件来获取该语言语法上下文中对这些名称的定义。 这些名称所映射的特定数字值可能会在 Python 版本之间更改。

此模块还提供了一个额外的数据对象:

@geindex sym_name() (在 symbol 模块中)
@anchor{library/symbol symbol sym_name}@anchor{37b8}
@deffn {数据} symbol.sym_name

将此模块中定义的常量的数值映射回名称字符串的字典，允许生成更加人类可读的解析树表示。
@end deffn

@node token --- 与Python解析树一起使用的常量,keyword --- 检验Python关键字,symbol --- 与 Python 解析树一起使用的常量,Python 语言服务
@anchor{library/token doc}@anchor{37b9}@anchor{library/token module-token}@anchor{110}@anchor{library/token token-constants-used-with-python-parse-trees}@anchor{37ba}
@subsection @code{token} --- 与Python解析树一起使用的常量


@geindex token (模块)

@strong{源码：} Lib/token.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/token.py}


__________________________________________________________________


此模块提供表示解析树（终端令牌）的叶节点的数值的常量。 请参阅 Python 发行版中的文件 @code{Grammar/Grammar} ，以获取语言语法上下文中名称的定义。 名称映射到的特定数值可能会在 Python 版本之间更改。

该模块还提供从数字代码到名称和一些函数的映射。 这些函数镜像了 Python C 头文件中的定义。

@geindex tok_name() (在 token 模块中)
@anchor{library/token token tok_name}@anchor{37bb}
@deffn {数据} token.tok_name

将此模块中定义的常量的数值映射回名称字符串的字典，允许生成更加人类可读的解析树表示。
@end deffn

@geindex ISTERMINAL() (在 token 模块中)
@anchor{library/token token ISTERMINAL}@anchor{37bc}
@deffn {函数} token.ISTERMINAL (x)

对终端标记值返回 @code{True}。
@end deffn

@geindex ISNONTERMINAL() (在 token 模块中)
@anchor{library/token token ISNONTERMINAL}@anchor{37bd}
@deffn {函数} token.ISNONTERMINAL (x)

对非终端标记值返回 @code{True}。
@end deffn

@geindex ISEOF() (在 token 模块中)
@anchor{library/token token ISEOF}@anchor{37be}
@deffn {函数} token.ISEOF (x)

如果 @emph{x} 是表示输入结束的标记则返回 @code{True}。
@end deffn

标记常量是：

@c Auto-generated by Tools/scripts/generate_token.py

@geindex ENDMARKER() (在 token 模块中)
@anchor{library/token token ENDMARKER}@anchor{37bf}
@deffn {数据} token.ENDMARKER
@end deffn

@geindex NAME() (在 token 模块中)
@anchor{library/token token NAME}@anchor{37c0}
@deffn {数据} token.NAME
@end deffn

@geindex NUMBER() (在 token 模块中)
@anchor{library/token token NUMBER}@anchor{37c1}
@deffn {数据} token.NUMBER
@end deffn

@geindex STRING() (在 token 模块中)
@anchor{library/token token STRING}@anchor{37c2}
@deffn {数据} token.STRING
@end deffn

@geindex NEWLINE() (在 token 模块中)
@anchor{library/token token NEWLINE}@anchor{37c3}
@deffn {数据} token.NEWLINE
@end deffn

@geindex INDENT() (在 token 模块中)
@anchor{library/token token INDENT}@anchor{37c4}
@deffn {数据} token.INDENT
@end deffn

@geindex DEDENT() (在 token 模块中)
@anchor{library/token token DEDENT}@anchor{37c5}
@deffn {数据} token.DEDENT
@end deffn

@geindex LPAR() (在 token 模块中)
@anchor{library/token token LPAR}@anchor{37c6}
@deffn {数据} token.LPAR

Token value for @code{"("}.
@end deffn

@geindex RPAR() (在 token 模块中)
@anchor{library/token token RPAR}@anchor{37c7}
@deffn {数据} token.RPAR

Token value for @code{")"}.
@end deffn

@geindex LSQB() (在 token 模块中)
@anchor{library/token token LSQB}@anchor{37c8}
@deffn {数据} token.LSQB

Token value for @code{"["}.
@end deffn

@geindex RSQB() (在 token 模块中)
@anchor{library/token token RSQB}@anchor{37c9}
@deffn {数据} token.RSQB

Token value for @code{"]"}.
@end deffn

@geindex COLON() (在 token 模块中)
@anchor{library/token token COLON}@anchor{37ca}
@deffn {数据} token.COLON

Token value for @code{":"}.
@end deffn

@geindex COMMA() (在 token 模块中)
@anchor{library/token token COMMA}@anchor{37cb}
@deffn {数据} token.COMMA

Token value for @code{","}.
@end deffn

@geindex SEMI() (在 token 模块中)
@anchor{library/token token SEMI}@anchor{37cc}
@deffn {数据} token.SEMI

Token value for @code{";"}.
@end deffn

@geindex PLUS() (在 token 模块中)
@anchor{library/token token PLUS}@anchor{37cd}
@deffn {数据} token.PLUS

Token value for @code{"+"}.
@end deffn

@geindex MINUS() (在 token 模块中)
@anchor{library/token token MINUS}@anchor{37ce}
@deffn {数据} token.MINUS

Token value for @code{"-"}.
@end deffn

@geindex STAR() (在 token 模块中)
@anchor{library/token token STAR}@anchor{37cf}
@deffn {数据} token.STAR

Token value for @code{"*"}.
@end deffn

@geindex SLASH() (在 token 模块中)
@anchor{library/token token SLASH}@anchor{37d0}
@deffn {数据} token.SLASH

Token value for @code{"/"}.
@end deffn

@geindex VBAR() (在 token 模块中)
@anchor{library/token token VBAR}@anchor{37d1}
@deffn {数据} token.VBAR

Token value for @code{"|"}.
@end deffn

@geindex AMPER() (在 token 模块中)
@anchor{library/token token AMPER}@anchor{37d2}
@deffn {数据} token.AMPER

Token value for @code{"&"}.
@end deffn

@geindex LESS() (在 token 模块中)
@anchor{library/token token LESS}@anchor{37d3}
@deffn {数据} token.LESS

Token value for @code{"<"}.
@end deffn

@geindex GREATER() (在 token 模块中)
@anchor{library/token token GREATER}@anchor{37d4}
@deffn {数据} token.GREATER

Token value for @code{">"}.
@end deffn

@geindex EQUAL() (在 token 模块中)
@anchor{library/token token EQUAL}@anchor{37d5}
@deffn {数据} token.EQUAL

Token value for @code{"="}.
@end deffn

@geindex DOT() (在 token 模块中)
@anchor{library/token token DOT}@anchor{37d6}
@deffn {数据} token.DOT

Token value for @code{"."}.
@end deffn

@geindex PERCENT() (在 token 模块中)
@anchor{library/token token PERCENT}@anchor{37d7}
@deffn {数据} token.PERCENT

Token value for @code{"%"}.
@end deffn

@geindex LBRACE() (在 token 模块中)
@anchor{library/token token LBRACE}@anchor{37d8}
@deffn {数据} token.LBRACE

Token value for @code{"@{"}.
@end deffn

@geindex RBRACE() (在 token 模块中)
@anchor{library/token token RBRACE}@anchor{37d9}
@deffn {数据} token.RBRACE

Token value for @code{"@}"}.
@end deffn

@geindex EQEQUAL() (在 token 模块中)
@anchor{library/token token EQEQUAL}@anchor{37da}
@deffn {数据} token.EQEQUAL

Token value for @code{"=="}.
@end deffn

@geindex NOTEQUAL() (在 token 模块中)
@anchor{library/token token NOTEQUAL}@anchor{37db}
@deffn {数据} token.NOTEQUAL

Token value for @code{"!="}.
@end deffn

@geindex LESSEQUAL() (在 token 模块中)
@anchor{library/token token LESSEQUAL}@anchor{37dc}
@deffn {数据} token.LESSEQUAL

Token value for @code{"<="}.
@end deffn

@geindex GREATEREQUAL() (在 token 模块中)
@anchor{library/token token GREATEREQUAL}@anchor{37dd}
@deffn {数据} token.GREATEREQUAL

Token value for @code{">="}.
@end deffn

@geindex TILDE() (在 token 模块中)
@anchor{library/token token TILDE}@anchor{37de}
@deffn {数据} token.TILDE

Token value for @code{"~"}.
@end deffn

@geindex CIRCUMFLEX() (在 token 模块中)
@anchor{library/token token CIRCUMFLEX}@anchor{37df}
@deffn {数据} token.CIRCUMFLEX

Token value for @code{"^"}.
@end deffn

@geindex LEFTSHIFT() (在 token 模块中)
@anchor{library/token token LEFTSHIFT}@anchor{37e0}
@deffn {数据} token.LEFTSHIFT

Token value for @code{"<<"}.
@end deffn

@geindex RIGHTSHIFT() (在 token 模块中)
@anchor{library/token token RIGHTSHIFT}@anchor{37e1}
@deffn {数据} token.RIGHTSHIFT

Token value for @code{">>"}.
@end deffn

@geindex DOUBLESTAR() (在 token 模块中)
@anchor{library/token token DOUBLESTAR}@anchor{37e2}
@deffn {数据} token.DOUBLESTAR

Token value for @code{"**"}.
@end deffn

@geindex PLUSEQUAL() (在 token 模块中)
@anchor{library/token token PLUSEQUAL}@anchor{37e3}
@deffn {数据} token.PLUSEQUAL

Token value for @code{"+="}.
@end deffn

@geindex MINEQUAL() (在 token 模块中)
@anchor{library/token token MINEQUAL}@anchor{37e4}
@deffn {数据} token.MINEQUAL

Token value for @code{"-="}.
@end deffn

@geindex STAREQUAL() (在 token 模块中)
@anchor{library/token token STAREQUAL}@anchor{37e5}
@deffn {数据} token.STAREQUAL

Token value for @code{"*="}.
@end deffn

@geindex SLASHEQUAL() (在 token 模块中)
@anchor{library/token token SLASHEQUAL}@anchor{37e6}
@deffn {数据} token.SLASHEQUAL

Token value for @code{"/="}.
@end deffn

@geindex PERCENTEQUAL() (在 token 模块中)
@anchor{library/token token PERCENTEQUAL}@anchor{37e7}
@deffn {数据} token.PERCENTEQUAL

Token value for @code{"%="}.
@end deffn

@geindex AMPEREQUAL() (在 token 模块中)
@anchor{library/token token AMPEREQUAL}@anchor{37e8}
@deffn {数据} token.AMPEREQUAL

Token value for @code{"&="}.
@end deffn

@geindex VBAREQUAL() (在 token 模块中)
@anchor{library/token token VBAREQUAL}@anchor{37e9}
@deffn {数据} token.VBAREQUAL

Token value for @code{"|="}.
@end deffn

@geindex CIRCUMFLEXEQUAL() (在 token 模块中)
@anchor{library/token token CIRCUMFLEXEQUAL}@anchor{37ea}
@deffn {数据} token.CIRCUMFLEXEQUAL

Token value for @code{"^="}.
@end deffn

@geindex LEFTSHIFTEQUAL() (在 token 模块中)
@anchor{library/token token LEFTSHIFTEQUAL}@anchor{37eb}
@deffn {数据} token.LEFTSHIFTEQUAL

Token value for @code{"<<="}.
@end deffn

@geindex RIGHTSHIFTEQUAL() (在 token 模块中)
@anchor{library/token token RIGHTSHIFTEQUAL}@anchor{37ec}
@deffn {数据} token.RIGHTSHIFTEQUAL

Token value for @code{">>="}.
@end deffn

@geindex DOUBLESTAREQUAL() (在 token 模块中)
@anchor{library/token token DOUBLESTAREQUAL}@anchor{37ed}
@deffn {数据} token.DOUBLESTAREQUAL

Token value for @code{"**="}.
@end deffn

@geindex DOUBLESLASH() (在 token 模块中)
@anchor{library/token token DOUBLESLASH}@anchor{37ee}
@deffn {数据} token.DOUBLESLASH

Token value for @code{"//"}.
@end deffn

@geindex DOUBLESLASHEQUAL() (在 token 模块中)
@anchor{library/token token DOUBLESLASHEQUAL}@anchor{37ef}
@deffn {数据} token.DOUBLESLASHEQUAL

Token value for @code{"//="}.
@end deffn

@geindex AT() (在 token 模块中)
@anchor{library/token token AT}@anchor{37f0}
@deffn {数据} token.AT

Token value for @code{"@@"}.
@end deffn

@geindex ATEQUAL() (在 token 模块中)
@anchor{library/token token ATEQUAL}@anchor{37f1}
@deffn {数据} token.ATEQUAL

Token value for @code{"@@="}.
@end deffn

@geindex RARROW() (在 token 模块中)
@anchor{library/token token RARROW}@anchor{37f2}
@deffn {数据} token.RARROW

Token value for @code{"->"}.
@end deffn

@geindex ELLIPSIS() (在 token 模块中)
@anchor{library/token token ELLIPSIS}@anchor{37f3}
@deffn {数据} token.ELLIPSIS

Token value for @code{"..."}.
@end deffn

@geindex COLONEQUAL() (在 token 模块中)
@anchor{library/token token COLONEQUAL}@anchor{37f4}
@deffn {数据} token.COLONEQUAL

Token value for @code{":="}.
@end deffn

@geindex OP() (在 token 模块中)
@anchor{library/token token OP}@anchor{37f5}
@deffn {数据} token.OP
@end deffn

@geindex AWAIT() (在 token 模块中)
@anchor{library/token token AWAIT}@anchor{37f6}
@deffn {数据} token.AWAIT
@end deffn

@geindex ASYNC() (在 token 模块中)
@anchor{library/token token ASYNC}@anchor{37f7}
@deffn {数据} token.ASYNC
@end deffn

@geindex TYPE_IGNORE() (在 token 模块中)
@anchor{library/token token TYPE_IGNORE}@anchor{37f8}
@deffn {数据} token.TYPE_IGNORE
@end deffn

@geindex TYPE_COMMENT() (在 token 模块中)
@anchor{library/token token TYPE_COMMENT}@anchor{37f9}
@deffn {数据} token.TYPE_COMMENT
@end deffn

@geindex ERRORTOKEN() (在 token 模块中)
@anchor{library/token token ERRORTOKEN}@anchor{37fa}
@deffn {数据} token.ERRORTOKEN
@end deffn

@geindex N_TOKENS() (在 token 模块中)
@anchor{library/token token N_TOKENS}@anchor{37fb}
@deffn {数据} token.N_TOKENS
@end deffn

@geindex NT_OFFSET() (在 token 模块中)
@anchor{library/token token NT_OFFSET}@anchor{37fc}
@deffn {数据} token.NT_OFFSET
@end deffn

C 标记生成器不使用以下标记类型值，但 @ref{111,,tokenize} 模块需要这些标记类型值。

@geindex COMMENT() (在 token 模块中)
@anchor{library/token token COMMENT}@anchor{37fd}
@deffn {数据} token.COMMENT

标记值用于表示注释。
@end deffn

@geindex NL() (在 token 模块中)
@anchor{library/token token NL}@anchor{37fe}
@deffn {数据} token.NL

标记值用于表示非终止换行符。 @ref{37c3,,NEWLINE} 标记表示 Python 代码逻辑行的结束；当在多条物理线路上继续执行逻辑代码行时，会生成 @code{NL} 标记。
@end deffn

@geindex ENCODING() (在 token 模块中)
@anchor{library/token token ENCODING}@anchor{37ff}
@deffn {数据} token.ENCODING

指示用于将源字节解码为文本的编码的标记值。 @ref{c54,,tokenize.tokenize()} 返回的第一个标记将始终是一个 @code{ENCODING} 标记。
@end deffn

@geindex TYPE_COMMENT() (在 token 模块中)

@deffn {数据} token.TYPE_COMMENT

Token value indicating that a type comment was recognized.  Such
tokens are only produced when @ref{1a1,,ast.parse()} is invoked with
@code{type_comments=True}.
@end deffn


在 3.5 版更改: 补充 @ref{37f6,,AWAIT} 和 @ref{37f7,,ASYNC} 标记。



在 3.7 版更改: 补充 @ref{37fd,,COMMENT} 、 @ref{37fe,,NL} 和 @ref{37ff,,ENCODING} 标记。



在 3.7 版更改: 移除 @ref{37f6,,AWAIT} 和 @ref{37f7,,ASYNC} 标记。 "async" 和 "await" 现在被标记为 @ref{37c0,,NAME} 标记。



在 3.8 版更改: Added @ref{37f9,,TYPE_COMMENT}, @ref{37f8,,TYPE_IGNORE}, @ref{37f4,,COLONEQUAL}.
Added @ref{37f6,,AWAIT} and @ref{37f7,,ASYNC} tokens back (they're needed
to support parsing older Python versions for @ref{1a1,,ast.parse()} with
@code{feature_version} set to 6 or lower).


@node keyword --- 检验Python关键字,tokenize --- 对 Python 代码使用的标记解析器,token --- 与Python解析树一起使用的常量,Python 语言服务
@anchor{library/keyword doc}@anchor{3800}@anchor{library/keyword keyword-testing-for-python-keywords}@anchor{3801}@anchor{library/keyword module-keyword}@anchor{a6}
@subsection @code{keyword} --- 检验Python关键字


@geindex keyword (模块)

@strong{源码：} Lib/keyword.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/keyword.py}


__________________________________________________________________


此模块允许 Python 程序确定某个字符串是否为 @ref{1372,,关键字}。

@geindex iskeyword() (在 keyword 模块中)
@anchor{library/keyword keyword iskeyword}@anchor{15e5}
@deffn {函数} keyword.iskeyword (s)

如果 @emph{s} 是一个 Python @ref{1372,,关键字} 则返回 @code{True}。
@end deffn

@geindex kwlist() (在 keyword 模块中)
@anchor{library/keyword keyword kwlist}@anchor{3802}
@deffn {数据} keyword.kwlist

包含解释器定义的所有 @ref{1372,,关键字} 的序列。 如果所定义的任何关键字仅在特定 @ref{0,,__future__} 语句生效时被激活，它们也将被包含在内。
@end deffn

@node tokenize --- 对 Python 代码使用的标记解析器,tabnanny --- 模糊缩进检测,keyword --- 检验Python关键字,Python 语言服务
@anchor{library/tokenize doc}@anchor{3803}@anchor{library/tokenize module-tokenize}@anchor{111}@anchor{library/tokenize tokenize-tokenizer-for-python-source}@anchor{3804}
@subsection @code{tokenize} --- 对 Python 代码使用的标记解析器


@geindex tokenize (模块)

@strong{源码：} Lib/tokenize.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tokenize.py}


__________________________________________________________________


The @ref{111,,tokenize} module provides a lexical scanner for Python source code,
implemented in Python.  The scanner in this module returns comments as tokens
as well, making it useful for implementing "pretty-printers", including
colorizers for on-screen displays.

为了简化标记流的处理，所有的 @ref{13af,,运算符} 和 @ref{13b0,,定界符} 以及 @ref{15a4,,Ellipsis} 返回时都会打上通用的 @ref{37f5,,OP} 标记。 可以通过 @ref{c54,,tokenize.tokenize()} 返回的 @ref{a9e,,named tuple} 对象的 @code{exact_type} 属性来获得确切的标记类型。

@menu
* 对输入进行解析标记:: 
* Command-Line Usage: Command-Line Usage<2>. 
* 例子: 例子<30>. 

@end menu

@node 对输入进行解析标记,Command-Line Usage<2>,,tokenize --- 对 Python 代码使用的标记解析器
@anchor{library/tokenize tokenizing-input}@anchor{3805}
@subsubsection 对输入进行解析标记


主要的入口是一个 @ref{99c,,generator}:

@geindex tokenize() (在 tokenize 模块中)
@anchor{library/tokenize tokenize tokenize}@anchor{c54}
@deffn {函数} tokenize.tokenize (readline)

生成器 @ref{c54,,tokenize()} 需要一个 @emph{readline} 参数，这个参数必须是一个可调用对象，且能提供与文件对象的 @ref{169c,,io.IOBase.readline()} 方法相同的接口。每次调用这个函数都要 返回字节类型输入的一行数据。

The generator produces 5-tuples with these members: the token type; the
token string; a 2-tuple @code{(srow, scol)} of ints specifying the row and
column where the token begins in the source; a 2-tuple @code{(erow, ecol)} of
ints specifying the row and column where the token ends in the source; and
the line on which the token was found. The line passed (the last tuple item)
is the @emph{physical} line.  The 5 tuple is returned as a @ref{a9e,,named tuple}
with the field names:
@code{type string start end line}.

The returned @ref{a9e,,named tuple} has an additional property named
@code{exact_type} that contains the exact operator type for
@ref{37f5,,OP} tokens.  For all other token types @code{exact_type}
equals the named tuple @code{type} field.


在 3.1 版更改: Added support for named tuples.



在 3.3 版更改: Added support for @code{exact_type}.


@ref{c54,,tokenize()} determines the source encoding of the file by looking for a
UTF-8 BOM or encoding cookie, according to 
@geindex Python 提高建议; PEP 263
PEP 263@footnote{https://www.python.org/dev/peps/pep-0263}.
@end deffn

@geindex generate_tokens() (在 tokenize 模块中)
@anchor{library/tokenize tokenize generate_tokens}@anchor{fc8}
@deffn {函数} tokenize.generate_tokens (readline)

Tokenize a source reading unicode strings instead of bytes.

Like @ref{c54,,tokenize()}, the @emph{readline} argument is a callable returning
a single line of input. However, @ref{fc8,,generate_tokens()} expects @emph{readline}
to return a str object rather than bytes.

The result is an iterator yielding named tuples, exactly like
@ref{c54,,tokenize()}. It does not yield an @ref{37ff,,ENCODING} token.
@end deffn

All constants from the @ref{110,,token} module are also exported from
@ref{111,,tokenize}.

Another function is provided to reverse the tokenization process. This is
useful for creating tools that tokenize a script, modify the token stream, and
write back the modified script.

@geindex untokenize() (在 tokenize 模块中)
@anchor{library/tokenize tokenize untokenize}@anchor{3806}
@deffn {函数} tokenize.untokenize (iterable)

Converts tokens back into Python source code.  The @emph{iterable} must return
sequences with at least two elements, the token type and the token string.
Any additional sequence elements are ignored.

The reconstructed script is returned as a single string.  The result is
guaranteed to tokenize back to match the input so that the conversion is
lossless and round-trips are assured.  The guarantee applies only to the
token type and token string as the spacing between tokens (column
positions) may change.

It returns bytes, encoded using the @ref{37ff,,ENCODING} token, which
is the first token sequence output by @ref{c54,,tokenize()}. If there is no
encoding token in the input, it returns a str instead.
@end deffn

@ref{c54,,tokenize()} needs to detect the encoding of source files it tokenizes. The
function it uses to do this is available:

@geindex detect_encoding() (在 tokenize 模块中)
@anchor{library/tokenize tokenize detect_encoding}@anchor{1c13}
@deffn {函数} tokenize.detect_encoding (readline)

The @ref{1c13,,detect_encoding()} function is used to detect the encoding that
should be used to decode a Python source file. It requires one argument,
readline, in the same way as the @ref{c54,,tokenize()} generator.

It will call readline a maximum of twice, and return the encoding used
(as a string) and a list of any lines (not decoded from bytes) it has read
in.

It detects the encoding from the presence of a UTF-8 BOM or an encoding
cookie as specified in 
@geindex Python 提高建议; PEP 263
PEP 263@footnote{https://www.python.org/dev/peps/pep-0263}. If both a BOM and a cookie are present,
but disagree, a @ref{452,,SyntaxError} will be raised. Note that if the BOM is found,
@code{'utf-8-sig'} will be returned as an encoding.

If no encoding is specified, then the default of @code{'utf-8'} will be
returned.

Use @ref{1c12,,open()} to open Python source files: it uses
@ref{1c13,,detect_encoding()} to detect the file encoding.
@end deffn

@geindex open() (在 tokenize 模块中)
@anchor{library/tokenize tokenize open}@anchor{1c12}
@deffn {函数} tokenize.open (filename)

Open a file in read only mode using the encoding detected by
@ref{1c13,,detect_encoding()}.


3.2 新版功能.

@end deffn

@geindex TokenError
@anchor{library/tokenize tokenize TokenError}@anchor{3807}
@deffn {例外} tokenize.TokenError

Raised when either a docstring or expression that may be split over several
lines is not completed anywhere in the file, for example:

@example
"""Beginning of
docstring
@end example

或者：

@example
[1,
 2,
 3
@end example
@end deffn

Note that unclosed single-quoted strings do not cause an error to be
raised. They are tokenized as @ref{37fa,,ERRORTOKEN}, followed by the
tokenization of their contents.

@node Command-Line Usage<2>,例子<30>,对输入进行解析标记,tokenize --- 对 Python 代码使用的标记解析器
@anchor{library/tokenize command-line-usage}@anchor{3808}@anchor{library/tokenize tokenize-cli}@anchor{3809}
@subsubsection Command-Line Usage



3.3 新版功能.


The @ref{111,,tokenize} module can be executed as a script from the command line.
It is as simple as:

@example
python -m tokenize [-e] [filename.py]
@end example

The following options are accepted:

@geindex tokenize command line option; -h
@geindex tokenize command line option; --help
@anchor{library/tokenize cmdoption-tokenize-h}@anchor{380a}
@deffn {程序选项} @w{-}h, @w{-}@w{-}help

show this help message and exit
@end deffn

@geindex tokenize command line option; -e
@geindex tokenize command line option; --exact
@anchor{library/tokenize cmdoption-tokenize-e}@anchor{380b}
@deffn {程序选项} @w{-}e, @w{-}@w{-}exact

display token names using the exact type
@end deffn

If @code{filename.py} is specified its contents are tokenized to stdout.
Otherwise, tokenization is performed on stdin.

@node 例子<30>,,Command-Line Usage<2>,tokenize --- 对 Python 代码使用的标记解析器
@anchor{library/tokenize examples}@anchor{380c}
@subsubsection 例子


Example of a script rewriter that transforms float literals into Decimal
objects:

@example
from tokenize import tokenize, untokenize, NUMBER, STRING, NAME, OP
from io import BytesIO

def decistmt(s):
    """Substitute Decimals for floats in a string of statements.

    >>> from decimal import Decimal
    >>> s = 'print(+21.3e-5*-.1234/81.7)'
    >>> decistmt(s)
    "print (+Decimal ('21.3e-5')*-Decimal ('.1234')/Decimal ('81.7'))"

    The format of the exponent is inherited from the platform C library.
    Known cases are "e-007" (Windows) and "e-07" (not Windows).  Since
    we're only showing 12 digits, and the 13th isn't close to 5, the
    rest of the output should be platform-independent.

    >>> exec(s)  #doctest: +ELLIPSIS
    -3.21716034272e-0...7

    Output from calculations with Decimal should be identical across all
    platforms.

    >>> exec(decistmt(s))
    -3.217160342717258261933904529E-7
    """
    result = []
    g = tokenize(BytesIO(s.encode('utf-8')).readline)  # tokenize the string
    for toknum, tokval, _, _, _ in g:
        if toknum == NUMBER and '.' in tokval:  # replace NUMBER tokens
            result.extend([
                (NAME, 'Decimal'),
                (OP, '('),
                (STRING, repr(tokval)),
                (OP, ')')
            ])
        else:
            result.append((toknum, tokval))
    return untokenize(result).decode('utf-8')
@end example

Example of tokenizing from the command line.  The script:

@example
def say_hello():
    print("Hello, World!")

say_hello()
@end example

will be tokenized to the following output where the first column is the range
of the line/column coordinates where the token is found, the second column is
the name of the token, and the final column is the value of the token (if any)

@example
$ python -m tokenize hello.py
0,0-0,0:            ENCODING       'utf-8'
1,0-1,3:            NAME           'def'
1,4-1,13:           NAME           'say_hello'
1,13-1,14:          OP             '('
1,14-1,15:          OP             ')'
1,15-1,16:          OP             ':'
1,16-1,17:          NEWLINE        '\n'
2,0-2,4:            INDENT         '    '
2,4-2,9:            NAME           'print'
2,9-2,10:           OP             '('
2,10-2,25:          STRING         '"Hello, World!"'
2,25-2,26:          OP             ')'
2,26-2,27:          NEWLINE        '\n'
3,0-3,1:            NL             '\n'
4,0-4,0:            DEDENT         '@w{'}
4,0-4,9:            NAME           'say_hello'
4,9-4,10:           OP             '('
4,10-4,11:          OP             ')'
4,11-4,12:          NEWLINE        '\n'
5,0-5,0:            ENDMARKER      '@w{'}
@end example

The exact token type names can be displayed using the @ref{380b,,-e} option:

@example
$ python -m tokenize -e hello.py
0,0-0,0:            ENCODING       'utf-8'
1,0-1,3:            NAME           'def'
1,4-1,13:           NAME           'say_hello'
1,13-1,14:          LPAR           '('
1,14-1,15:          RPAR           ')'
1,15-1,16:          COLON          ':'
1,16-1,17:          NEWLINE        '\n'
2,0-2,4:            INDENT         '    '
2,4-2,9:            NAME           'print'
2,9-2,10:           LPAR           '('
2,10-2,25:          STRING         '"Hello, World!"'
2,25-2,26:          RPAR           ')'
2,26-2,27:          NEWLINE        '\n'
3,0-3,1:            NL             '\n'
4,0-4,0:            DEDENT         '@w{'}
4,0-4,9:            NAME           'say_hello'
4,9-4,10:           LPAR           '('
4,10-4,11:          RPAR           ')'
4,11-4,12:          NEWLINE        '\n'
5,0-5,0:            ENDMARKER      '@w{'}
@end example

Example of tokenizing a file programmatically, reading unicode
strings instead of bytes with @ref{fc8,,generate_tokens()}:

@example
import tokenize

with tokenize.open('hello.py') as f:
    tokens = tokenize.generate_tokens(f.readline)
    for token in tokens:
        print(token)
@end example

或者通过 @ref{c54,,tokenize()} 直接读取字节数据:

@example
import tokenize

with open('hello.py', 'rb') as f:
    tokens = tokenize.tokenize(f.readline)
    for token in tokens:
        print(token)
@end example

@node tabnanny --- 模糊缩进检测,pyclbr --- Python module browser support,tokenize --- 对 Python 代码使用的标记解析器,Python 语言服务
@anchor{library/tabnanny doc}@anchor{380d}@anchor{library/tabnanny module-tabnanny}@anchor{100}@anchor{library/tabnanny tabnanny-detection-of-ambiguous-indentation}@anchor{380e}
@subsection @code{tabnanny} --- 模糊缩进检测


@geindex tabnanny (模块)

@c rudimentary documentation based on module comments

@strong{源代码:} Lib/tabnanny.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tabnanny.py}


__________________________________________________________________


目前，该模块旨在作为脚本调用。但是可以使用下面描述的 @ref{380f,,check()} 函数将其导入IDE。

@cartouche
@quotation 注解 
此模块提供的API可能会在将来的版本中更改；此类更改可能无法向后兼容。
@end quotation
@end cartouche

@geindex check() (在 tabnanny 模块中)
@anchor{library/tabnanny tabnanny check}@anchor{380f}
@deffn {函数} tabnanny.check (file_or_dir)

如果 @emph{file_or_dir} 是目录而非符号链接，则递归地在名为 @emph{file_or_dir} 的目录树中下行，沿途检查所有 @code{.py} 文件。 如果 @emph{file_or_dir} 是一个普通 Python 源文件，将检查其中的空格相关问题。 诊断消息将使用 @ref{880,,print()} 函数写入到标准输出。
@end deffn

@geindex verbose() (在 tabnanny 模块中)
@anchor{library/tabnanny tabnanny verbose}@anchor{3810}
@deffn {数据} tabnanny.verbose

此旗标指明是否打印详细消息。 如果作为脚本调用则是通过 @code{-v} 选项来增加。
@end deffn

@geindex filename_only() (在 tabnanny 模块中)
@anchor{library/tabnanny tabnanny filename_only}@anchor{3811}
@deffn {数据} tabnanny.filename_only

此旗标指明是否只打印包含空格相关问题文件的文件名。 如果作为脚本调用则是通过 @code{-q} 选项来设为真值。
@end deffn

@geindex NannyNag
@anchor{library/tabnanny tabnanny NannyNag}@anchor{3812}
@deffn {例外} tabnanny.NannyNag

如果检测到模糊缩进则由 @ref{3813,,process_tokens()} 引发。 在 @ref{380f,,check()} 中捕获并处理。
@end deffn

@geindex process_tokens() (在 tabnanny 模块中)
@anchor{library/tabnanny tabnanny process_tokens}@anchor{3813}
@deffn {函数} tabnanny.process_tokens (tokens)

此函数由 @ref{380f,,check()} 用来处理由 @ref{111,,tokenize} 模块所生成的标记。
@end deffn

@c XXX document errprint, format_witnesses, Whitespace, check_equal, indents,
@c reset_globals


@subsubheading 参见



@table @asis

@item 模块 @ref{111,,tokenize}

用于Python源代码的词法扫描程序。
@end table


@node pyclbr --- Python module browser support,py_compile --- Compile Python source files,tabnanny --- 模糊缩进检测,Python 语言服务
@anchor{library/pyclbr doc}@anchor{3814}@anchor{library/pyclbr module-pyclbr}@anchor{d8}@anchor{library/pyclbr pyclbr-python-module-browser-support}@anchor{3815}
@subsection @code{pyclbr} --- Python module browser support


@geindex pyclbr (模块)

@strong{Source code:} Lib/pyclbr.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pyclbr.py}


__________________________________________________________________


The @ref{d8,,pyclbr} module provides limited information about the
functions, classes, and methods defined in a Python-coded module.  The
information is sufficient to implement a module browser.  The
information is extracted from the Python source code rather than by
importing the module, so this module is safe to use with untrusted code.
This restriction makes it impossible to use this module with modules not
implemented in Python, including all standard and optional extension
modules.

@geindex readmodule() (在 pyclbr 模块中)
@anchor{library/pyclbr pyclbr readmodule}@anchor{10fc}
@deffn {函数} pyclbr.readmodule (module, path=None)

Return a dictionary mapping module-level class names to class
descriptors.  If possible, descriptors for imported base classes are
included.  Parameter @emph{module} is a string with the name of the module
to read; it may be the name of a module within a package.  If given,
@emph{path} is a sequence of directory paths prepended to @code{sys.path},
which is used to locate the module source code.

This function is the original interface and is only kept for back
compatibility.  It returns a filtered version of the following.
@end deffn

@geindex readmodule_ex() (在 pyclbr 模块中)
@anchor{library/pyclbr pyclbr readmodule_ex}@anchor{10fd}
@deffn {函数} pyclbr.readmodule_ex (module, path=None)

Return a dictionary-based tree containing a function or class
descriptors for each function and class defined in the module with a
@code{def} or @code{class} statement.  The returned dictionary maps
module-level function and class names to their descriptors.  Nested
objects are entered into the children dictionary of their parent.  As
with readmodule, @emph{module} names the module to be read and @emph{path} is
prepended to sys.path.  If the module being read is a package, the
returned dictionary has a key @code{'__path__'} whose value is a list
containing the package search path.
@end deffn


3.7 新版功能: Descriptors for nested definitions.  They are accessed through the
new children attribute.  Each has a new parent attribute.


The descriptors returned by these functions are instances of
Function and Class classes.  Users are not expected to create instances
of these classes.

@menu
* 函数对象:: 
* 类对象: 类对象<2>. 

@end menu

@node 函数对象,类对象<2>,,pyclbr --- Python module browser support
@anchor{library/pyclbr function-objects}@anchor{3816}@anchor{library/pyclbr pyclbr-function-objects}@anchor{3817}
@subsubsection 函数对象


Class @code{Function} instances describe functions defined by def
statements.  They have the following attributes:

@geindex file (pyclbr.Function 属性)
@anchor{library/pyclbr pyclbr Function file}@anchor{3818}
@deffn {属性} Function.file

Name of the file in which the function is defined.
@end deffn

@geindex module (pyclbr.Function 属性)
@anchor{library/pyclbr pyclbr Function module}@anchor{3819}
@deffn {属性} Function.module

The name of the module defining the function described.
@end deffn

@geindex name (pyclbr.Function 属性)
@anchor{library/pyclbr pyclbr Function name}@anchor{381a}
@deffn {属性} Function.name

The name of the function.
@end deffn

@geindex lineno (pyclbr.Function 属性)
@anchor{library/pyclbr pyclbr Function lineno}@anchor{381b}
@deffn {属性} Function.lineno

The line number in the file where the definition starts.
@end deffn

@geindex parent (pyclbr.Function 属性)
@anchor{library/pyclbr pyclbr Function parent}@anchor{381c}
@deffn {属性} Function.parent

For top-level functions, None.  For nested functions, the parent.


3.7 新版功能.

@end deffn

@geindex children (pyclbr.Function 属性)
@anchor{library/pyclbr pyclbr Function children}@anchor{381d}
@deffn {属性} Function.children

A dictionary mapping names to descriptors for nested functions and
classes.


3.7 新版功能.

@end deffn

@node 类对象<2>,,函数对象,pyclbr --- Python module browser support
@anchor{library/pyclbr class-objects}@anchor{381e}@anchor{library/pyclbr pyclbr-class-objects}@anchor{381f}
@subsubsection 类对象


Class @code{Class} instances describe classes defined by class
statements.  They have the same attributes as Functions and two more.

@geindex file (pyclbr.Class 属性)
@anchor{library/pyclbr pyclbr Class file}@anchor{3820}
@deffn {属性} Class.file

Name of the file in which the class is defined.
@end deffn

@geindex module (pyclbr.Class 属性)
@anchor{library/pyclbr pyclbr Class module}@anchor{3821}
@deffn {属性} Class.module

The name of the module defining the class described.
@end deffn

@geindex name (pyclbr.Class 属性)
@anchor{library/pyclbr pyclbr Class name}@anchor{3822}
@deffn {属性} Class.name

The name of the class.
@end deffn

@geindex lineno (pyclbr.Class 属性)
@anchor{library/pyclbr pyclbr Class lineno}@anchor{3823}
@deffn {属性} Class.lineno

The line number in the file where the definition starts.
@end deffn

@geindex parent (pyclbr.Class 属性)
@anchor{library/pyclbr pyclbr Class parent}@anchor{3824}
@deffn {属性} Class.parent

For top-level classes, None.  For nested classes, the parent.


3.7 新版功能.

@end deffn

@geindex children (pyclbr.Class 属性)
@anchor{library/pyclbr pyclbr Class children}@anchor{3825}
@deffn {属性} Class.children

A dictionary mapping names to descriptors for nested functions and
classes.


3.7 新版功能.

@end deffn

@geindex super (pyclbr.Class 属性)
@anchor{library/pyclbr pyclbr Class super}@anchor{3826}
@deffn {属性} Class.super

A list of @code{Class} objects which describe the immediate base
classes of the class being described.  Classes which are named as
superclasses but which are not discoverable by @ref{10fd,,readmodule_ex()}
are listed as a string with the class name instead of as
@code{Class} objects.
@end deffn

@geindex methods (pyclbr.Class 属性)
@anchor{library/pyclbr pyclbr Class methods}@anchor{3827}
@deffn {属性} Class.methods

A dictionary mapping method names to line numbers.  This can be
derived from the newer children dictionary, but remains for
back-compatibility.
@end deffn

@node py_compile --- Compile Python source files,compileall --- Byte-compile Python libraries,pyclbr --- Python module browser support,Python 语言服务
@anchor{library/py_compile doc}@anchor{3828}@anchor{library/py_compile module-py_compile}@anchor{d7}@anchor{library/py_compile py-compile-compile-python-source-files}@anchor{3829}
@subsection @code{py_compile} --- Compile Python source files


@geindex py_compile (模块)

@c documentation based on module docstrings

@strong{Source code:} Lib/py_compile.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/py_compile.py}

@geindex file; byte-code


__________________________________________________________________


The @ref{d7,,py_compile} module provides a function to generate a byte-code file
from a source file, and another function used when the module source file is
invoked as a script.

Though not often needed, this function can be useful when installing modules for
shared use, especially if some of the users may not have permission to write the
byte-code cache files in the directory containing the source code.

@geindex PyCompileError
@anchor{library/py_compile py_compile PyCompileError}@anchor{382a}
@deffn {例外} py_compile.PyCompileError

Exception raised when an error occurs while attempting to compile the file.
@end deffn

@geindex compile() (在 py_compile 模块中)
@anchor{library/py_compile py_compile compile}@anchor{215}
@deffn {函数} py_compile.compile (file, cfile=None, dfile=None, doraise=False, optimize=-1, invalidation_mode=PycInvalidationMode.TIMESTAMP, quiet=0)

Compile a source file to byte-code and write out the byte-code cache file.
The source code is loaded from the file named @emph{file}.  The byte-code is
written to @emph{cfile}, which defaults to the 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147}/
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488} path, ending
in @code{.pyc}.
For example, if @emph{file} is @code{/foo/bar/baz.py} @emph{cfile} will default to
@code{/foo/bar/__pycache__/baz.cpython-32.pyc} for Python 3.2.  If @emph{dfile} is
specified, it is used as the name of the source file in error messages when
instead of @emph{file}.  If @emph{doraise} is true, a @ref{382a,,PyCompileError} is raised
when an error is encountered while compiling @emph{file}. If @emph{doraise} is false
(the default), an error string is written to @code{sys.stderr}, but no exception
is raised.  This function returns the path to byte-compiled file, i.e.
whatever @emph{cfile} value was used.

The @emph{doraise} and @emph{quiet} arguments determine how errors are handled while
compiling file. If @emph{quiet} is 0 or 1, and @emph{doraise} is false, the default
behaviour is enabled: an error string is written to @code{sys.stderr}, and the
function returns @code{None} instead of a path. If @emph{doraise} is true,
a @ref{382a,,PyCompileError} is raised instead. However if @emph{quiet} is 2,
no message is written, and @emph{doraise} has no effect.

If the path that @emph{cfile} becomes (either explicitly specified or computed)
is a symlink or non-regular file, @ref{952,,FileExistsError} will be raised.
This is to act as a warning that import will turn those paths into regular
files if it is allowed to write byte-compiled files to those paths. This is
a side-effect of import using file renaming to place the final byte-compiled
file into place to prevent concurrent file writing issues.

@emph{optimize} controls the optimization level and is passed to the built-in
@ref{1b4,,compile()} function.  The default of @code{-1} selects the optimization
level of the current interpreter.

@emph{invalidation_mode} should be a member of the @ref{382b,,PycInvalidationMode}
enum and controls how the generated bytecode cache is invalidated at
runtime.  The default is @ref{382c,,PycInvalidationMode.CHECKED_HASH} if
the 
@geindex SOURCE_DATE_EPOCH
@geindex 环境变量; SOURCE_DATE_EPOCH
@code{SOURCE_DATE_EPOCH} environment variable is set, otherwise
the default is @ref{382d,,PycInvalidationMode.TIMESTAMP}.


在 3.2 版更改: Changed default value of @emph{cfile} to be 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147}-compliant.  Previous
default was @emph{file} + @code{'c'} (@code{'o'} if optimization was enabled).
Also added the @emph{optimize} parameter.



在 3.4 版更改: Changed code to use @ref{9b,,importlib} for the byte-code cache file writing.
This means file creation/writing semantics now match what @ref{9b,,importlib}
does, e.g. permissions, write-and-move semantics, etc. Also added the
caveat that @ref{952,,FileExistsError} is raised if @emph{cfile} is a symlink or
non-regular file.



在 3.7 版更改: The @emph{invalidation_mode} parameter was added as specified in 
@geindex Python 提高建议; PEP 552
PEP 552@footnote{https://www.python.org/dev/peps/pep-0552}.
If the 
@geindex SOURCE_DATE_EPOCH
@geindex 环境变量; SOURCE_DATE_EPOCH
@code{SOURCE_DATE_EPOCH} environment variable is set,
@emph{invalidation_mode} will be forced to
@ref{382c,,PycInvalidationMode.CHECKED_HASH}.



在 3.7.2 版更改: The 
@geindex SOURCE_DATE_EPOCH
@geindex 环境变量; SOURCE_DATE_EPOCH
@code{SOURCE_DATE_EPOCH} environment variable no longer
overrides the value of the @emph{invalidation_mode} argument, and determines
its default value instead.



在 3.8 版更改: The @emph{quiet} parameter was added.

@end deffn

@geindex PycInvalidationMode (py_compile 中的类)
@anchor{library/py_compile py_compile PycInvalidationMode}@anchor{382b}
@deffn {类} py_compile.PycInvalidationMode

A enumeration of possible methods the interpreter can use to determine
whether a bytecode file is up to date with a source file. The @code{.pyc} file
indicates the desired invalidation mode in its header. See
@ref{322,,已缓存字节码的失效} for more information on how Python invalidates
@code{.pyc} files at runtime.


3.7 新版功能.


@geindex TIMESTAMP (py_compile.PycInvalidationMode 属性)
@anchor{library/py_compile py_compile PycInvalidationMode TIMESTAMP}@anchor{382d}
@deffn {属性} TIMESTAMP

The @code{.pyc} file includes the timestamp and size of the source file,
which Python will compare against the metadata of the source file at
runtime to determine if the @code{.pyc} file needs to be regenerated.
@end deffn

@geindex CHECKED_HASH (py_compile.PycInvalidationMode 属性)
@anchor{library/py_compile py_compile PycInvalidationMode CHECKED_HASH}@anchor{382c}
@deffn {属性} CHECKED_HASH

The @code{.pyc} file includes a hash of the source file content, which Python
will compare against the source at runtime to determine if the @code{.pyc}
file needs to be regenerated.
@end deffn

@geindex UNCHECKED_HASH (py_compile.PycInvalidationMode 属性)
@anchor{library/py_compile py_compile PycInvalidationMode UNCHECKED_HASH}@anchor{382e}
@deffn {属性} UNCHECKED_HASH

Like @ref{382c,,CHECKED_HASH}, the @code{.pyc} file includes a hash of the source
file content. However, Python will at runtime assume the @code{.pyc} file is
up to date and not validate the @code{.pyc} against the source file at all.

This option is useful when the @code{.pycs} are kept up to date by some
system external to Python like a build system.
@end deffn
@end deffn

@geindex main() (在 py_compile 模块中)
@anchor{library/py_compile py_compile main}@anchor{382f}
@deffn {函数} py_compile.main (args=None)

Compile several source files.  The files named in @emph{args} (or on the command
line, if @emph{args} is @code{None}) are compiled and the resulting byte-code is
cached in the normal manner.  This function does not search a directory
structure to locate source files; it only compiles files named explicitly.
If @code{'-'} is the only parameter in args, the list of files is taken from
standard input.


在 3.2 版更改: Added support for @code{'-'}.

@end deffn

When this module is run as a script, the @ref{382f,,main()} is used to compile all the
files named on the command line.  The exit status is nonzero if one of the files
could not be compiled.


@subsubheading 参见



@table @asis

@item Module @ref{21,,compileall}

Utilities to compile all Python source files in a directory tree.
@end table


@node compileall --- Byte-compile Python libraries,dis --- Python 字节码反汇编器,py_compile --- Compile Python source files,Python 语言服务
@anchor{library/compileall doc}@anchor{3830}@anchor{library/compileall compileall-byte-compile-python-libraries}@anchor{3831}@anchor{library/compileall module-compileall}@anchor{21}
@subsection @code{compileall} --- Byte-compile Python libraries


@geindex compileall (模块)

@strong{Source code:} Lib/compileall.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/compileall.py}


__________________________________________________________________


This module provides some utility functions to support installing Python
libraries.  These functions compile Python source files in a directory tree.
This module can be used to create the cached byte-code files at library
installation time, which makes them available for use even by users who don't
have write permission to the library directories.

@menu
* Command-line use:: 
* Public functions:: 

@end menu

@node Command-line use,Public functions,,compileall --- Byte-compile Python libraries
@anchor{library/compileall command-line-use}@anchor{3832}
@subsubsection Command-line use


This module can work as a script (using @code{python -m compileall}) to
compile Python sources.

@geindex compileall command line option; directory ...
@geindex compileall command line option; file ...
@anchor{library/compileall cmdoption-compileall-arg-directory}@anchor{3833}
@deffn {程序选项} directory ...
@anchor{library/compileall cmdoption-compileall-arg-file}@anchor{3834}
@deffnx {程序选项} file ...

Positional arguments are files to compile or directories that contain
source files, traversed recursively.  If no argument is given, behave as if
the command line was @code{-l <directories from sys.path>}.
@end deffn

@geindex compileall command line option; -l
@anchor{library/compileall cmdoption-compileall-l}@anchor{3835}
@deffn {程序选项} @w{-}l

Do not recurse into subdirectories, only compile source code files directly
contained in the named or implied directories.
@end deffn

@geindex compileall command line option; -f
@anchor{library/compileall cmdoption-compileall-f}@anchor{3836}
@deffn {程序选项} @w{-}f

Force rebuild even if timestamps are up-to-date.
@end deffn

@geindex compileall command line option; -q
@anchor{library/compileall cmdoption-compileall-q}@anchor{3837}
@deffn {程序选项} @w{-}q

Do not print the list of files compiled. If passed once, error messages will
still be printed. If passed twice (@code{-qq}), all output is suppressed.
@end deffn

@geindex compileall command line option; -d destdir
@anchor{library/compileall cmdoption-compileall-d}@anchor{3838}
@deffn {程序选项} @w{-}d destdir

Directory prepended to the path to each file being compiled.  This will
appear in compilation time tracebacks, and is also compiled in to the
byte-code file, where it will be used in tracebacks and other messages in
cases where the source file does not exist at the time the byte-code file is
executed.
@end deffn

@geindex compileall command line option; -x regex
@anchor{library/compileall cmdoption-compileall-x}@anchor{3839}
@deffn {程序选项} @w{-}x regex

regex is used to search the full path to each file considered for
compilation, and if the regex produces a match, the file is skipped.
@end deffn

@geindex compileall command line option; -i list
@anchor{library/compileall cmdoption-compileall-i}@anchor{383a}
@deffn {程序选项} @w{-}i list

Read the file @code{list} and add each line that it contains to the list of
files and directories to compile.  If @code{list} is @code{-}, read lines from
@code{stdin}.
@end deffn

@geindex compileall command line option; -b
@anchor{library/compileall cmdoption-compileall-b}@anchor{383b}
@deffn {程序选项} @w{-}b

Write the byte-code files to their legacy locations and names, which may
overwrite byte-code files created by another version of Python.  The default
is to write files to their 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} locations and names, which allows
byte-code files from multiple versions of Python to coexist.
@end deffn

@geindex compileall command line option; -r
@anchor{library/compileall cmdoption-compileall-r}@anchor{383c}
@deffn {程序选项} @w{-}r

Control the maximum recursion level for subdirectories.
If this is given, then @code{-l} option will not be taken into account.
@code{python -m compileall <directory> -r 0} is equivalent to
@code{python -m compileall <directory> -l}.
@end deffn

@geindex compileall command line option; -j N
@anchor{library/compileall cmdoption-compileall-j}@anchor{383d}
@deffn {程序选项} @w{-}j N

Use @emph{N} workers to compile the files within the given directory.
If @code{0} is used, then the result of @ref{879,,os.cpu_count()}
will be used.
@end deffn

@geindex compileall command line option; --invalidation-mode [timestamp|checked-hash|unchecked-hash]
@anchor{library/compileall cmdoption-compileall-invalidation-mode}@anchor{383e}
@deffn {程序选项} @w{-}@w{-}invalidation@w{-}mode [timestamp|checked@w{-}hash|unchecked@w{-}hash]

Control how the generated byte-code files are invalidated at runtime.
The @code{timestamp} value, means that @code{.pyc} files with the source timestamp
and size embedded will be generated. The @code{checked-hash} and
@code{unchecked-hash} values cause hash-based pycs to be generated. Hash-based
pycs embed a hash of the source file contents rather than a timestamp. See
@ref{322,,已缓存字节码的失效} for more information on how Python validates
bytecode cache files at runtime.
The default is @code{timestamp} if the 
@geindex SOURCE_DATE_EPOCH
@geindex 环境变量; SOURCE_DATE_EPOCH
@code{SOURCE_DATE_EPOCH} environment
variable is not set, and @code{checked-hash} if the @code{SOURCE_DATE_EPOCH}
environment variable is set.
@end deffn


在 3.2 版更改: Added the @code{-i}, @code{-b} and @code{-h} options.



在 3.5 版更改: Added the  @code{-j}, @code{-r}, and @code{-qq} options.  @code{-q} option
was changed to a multilevel value.  @code{-b} will always produce a
byte-code file ending in @code{.pyc}, never @code{.pyo}.



在 3.7 版更改: Added the @code{--invalidation-mode} option.


There is no command-line option to control the optimization level used by the
@ref{1b4,,compile()} function, because the Python interpreter itself already
provides the option: @code{python -O -m compileall}.

Similarly, the @ref{1b4,,compile()} function respects the @ref{156,,sys.pycache_prefix}
setting. The generated bytecode cache will only be useful if @ref{1b4,,compile()} is
run with the same @ref{156,,sys.pycache_prefix} (if any) that will be used at
runtime.

@node Public functions,,Command-line use,compileall --- Byte-compile Python libraries
@anchor{library/compileall public-functions}@anchor{383f}
@subsubsection Public functions


@geindex compile_dir() (在 compileall 模块中)
@anchor{library/compileall compileall compile_dir}@anchor{36b}
@deffn {函数} compileall.compile_dir (dir, maxlevels=10, ddir=None, force=False, rx=None, quiet=0, legacy=False, optimize=-1, workers=1, invalidation_mode=None)

Recursively descend the directory tree named by @emph{dir}, compiling all @code{.py}
files along the way. Return a true value if all the files compiled successfully,
and a false value otherwise.

The @emph{maxlevels} parameter is used to limit the depth of the recursion; it
defaults to @code{10}.

If @emph{ddir} is given, it is prepended to the path to each file being compiled
for use in compilation time tracebacks, and is also compiled in to the
byte-code file, where it will be used in tracebacks and other messages in
cases where the source file does not exist at the time the byte-code file is
executed.

If @emph{force} is true, modules are re-compiled even if the timestamps are up to
date.

If @emph{rx} is given, its search method is called on the complete path to each
file considered for compilation, and if it returns a true value, the file
is skipped.

If @emph{quiet} is @code{False} or @code{0} (the default), the filenames and other
information are printed to standard out. Set to @code{1}, only errors are
printed. Set to @code{2}, all output is suppressed.

If @emph{legacy} is true, byte-code files are written to their legacy locations
and names, which may overwrite byte-code files created by another version of
Python.  The default is to write files to their 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} locations and
names, which allows byte-code files from multiple versions of Python to
coexist.

@emph{optimize} specifies the optimization level for the compiler.  It is passed to
the built-in @ref{1b4,,compile()} function.

The argument @emph{workers} specifies how many workers are used to
compile files in parallel. The default is to not use multiple workers.
If the platform can't use multiple workers and @emph{workers} argument is given,
then sequential compilation will be used as a fallback.  If @emph{workers}
is 0, the number of cores in the system is used.  If @emph{workers} is
lower than @code{0}, a @ref{1fb,,ValueError} will be raised.

@emph{invalidation_mode} should be a member of the
@ref{382b,,py_compile.PycInvalidationMode} enum and controls how the generated
pycs are invalidated at runtime.


在 3.2 版更改: Added the @emph{legacy} and @emph{optimize} parameter.



在 3.5 版更改: Added the @emph{workers} parameter.



在 3.5 版更改: @emph{quiet} parameter was changed to a multilevel value.



在 3.5 版更改: The @emph{legacy} parameter only writes out @code{.pyc} files, not @code{.pyo} files
no matter what the value of @emph{optimize} is.



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。



在 3.7 版更改: The @emph{invalidation_mode} parameter was added.



在 3.7.2 版更改: The @emph{invalidation_mode} parameter's default value is updated to None.



在 3.8 版更改: Setting @emph{workers} to 0 now chooses the optimal number of cores.

@end deffn

@geindex compile_file() (在 compileall 模块中)
@anchor{library/compileall compileall compile_file}@anchor{6b5}
@deffn {函数} compileall.compile_file (fullname, ddir=None, force=False, rx=None, quiet=0, legacy=False, optimize=-1, invalidation_mode=None)

Compile the file with path @emph{fullname}. Return a true value if the file
compiled successfully, and a false value otherwise.

If @emph{ddir} is given, it is prepended to the path to the file being compiled
for use in compilation time tracebacks, and is also compiled in to the
byte-code file, where it will be used in tracebacks and other messages in
cases where the source file does not exist at the time the byte-code file is
executed.

If @emph{rx} is given, its search method is passed the full path name to the
file being compiled, and if it returns a true value, the file is not
compiled and @code{True} is returned.

If @emph{quiet} is @code{False} or @code{0} (the default), the filenames and other
information are printed to standard out. Set to @code{1}, only errors are
printed. Set to @code{2}, all output is suppressed.

If @emph{legacy} is true, byte-code files are written to their legacy locations
and names, which may overwrite byte-code files created by another version of
Python.  The default is to write files to their 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} locations and
names, which allows byte-code files from multiple versions of Python to
coexist.

@emph{optimize} specifies the optimization level for the compiler.  It is passed to
the built-in @ref{1b4,,compile()} function.

@emph{invalidation_mode} should be a member of the
@ref{382b,,py_compile.PycInvalidationMode} enum and controls how the generated
pycs are invalidated at runtime.


3.2 新版功能.



在 3.5 版更改: @emph{quiet} parameter was changed to a multilevel value.



在 3.5 版更改: The @emph{legacy} parameter only writes out @code{.pyc} files, not @code{.pyo} files
no matter what the value of @emph{optimize} is.



在 3.7 版更改: The @emph{invalidation_mode} parameter was added.



在 3.7.2 版更改: The @emph{invalidation_mode} parameter's default value is updated to None.

@end deffn

@geindex compile_path() (在 compileall 模块中)
@anchor{library/compileall compileall compile_path}@anchor{6b6}
@deffn {函数} compileall.compile_path (skip_curdir=True, maxlevels=0, force=False, quiet=0, legacy=False, optimize=-1, invalidation_mode=None)

Byte-compile all the @code{.py} files found along @code{sys.path}. Return a
true value if all the files compiled successfully, and a false value otherwise.

If @emph{skip_curdir} is true (the default), the current directory is not included
in the search.  All other parameters are passed to the @ref{36b,,compile_dir()}
function.  Note that unlike the other compile functions, @code{maxlevels}
defaults to @code{0}.


在 3.2 版更改: Added the @emph{legacy} and @emph{optimize} parameter.



在 3.5 版更改: @emph{quiet} parameter was changed to a multilevel value.



在 3.5 版更改: The @emph{legacy} parameter only writes out @code{.pyc} files, not @code{.pyo} files
no matter what the value of @emph{optimize} is.



在 3.7 版更改: The @emph{invalidation_mode} parameter was added.



在 3.7.2 版更改: The @emph{invalidation_mode} parameter's default value is updated to None.

@end deffn

To force a recompile of all the @code{.py} files in the @code{Lib/}
subdirectory and all its subdirectories:

@example
import compileall

compileall.compile_dir('Lib/', force=True)

# Perform same compilation, excluding files in .svn directories.
import re
compileall.compile_dir('Lib/', rx=re.compile(r'[/\\][.]svn'), force=True)

# pathlib.Path objects can also be used.
import pathlib
compileall.compile_dir(pathlib.Path('Lib/'), force=True)
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{d7,,py_compile}

Byte-compile a single source file.
@end table


@node dis --- Python 字节码反汇编器,pickletools --- pickle 开发者工具集,compileall --- Byte-compile Python libraries,Python 语言服务
@anchor{library/dis doc}@anchor{3840}@anchor{library/dis dis-disassembler-for-python-bytecode}@anchor{3841}@anchor{library/dis module-dis}@anchor{38}
@subsection @code{dis} --- Python 字节码反汇编器


@geindex dis (模块)

@strong{Source code:} Lib/dis.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/dis.py}


__________________________________________________________________


@ref{38,,dis} 模块通过反汇编支持CPython的 @ref{60f,,bytecode} 分析。该模块作为输入的 CPython 字节码在文件 @code{Include/opcode.h} 中定义，并由编译器和解释器使用。

@strong{CPython implementation detail:} 字节码是 CPython 解释器的实现细节。不保证不会在Python版本之间添加、删除或更改字节码。不应考虑将此模块的跨 Python VM 或 Python 版本的使用。


在 3.6 版更改: 每条指令使用2个字节。以前字节数因指令而异。


示例：给出函数 @code{myfunc()}:

@example
def myfunc(alist):
    return len(alist)
@end example

可以使用以下命令显示 @code{myfunc()} 的反汇编

@example
>>> dis.dis(myfunc)
  2           0 LOAD_GLOBAL              0 (len)
              2 LOAD_FAST                0 (alist)
              4 CALL_FUNCTION            1
              6 RETURN_VALUE
@end example

("2" 是行号)。

@menu
* 字节码分析:: 
* 分析函数:: 
* Python字节码说明:: 
* 操作码集合:: 

@end menu

@node 字节码分析,分析函数,,dis --- Python 字节码反汇编器
@anchor{library/dis bytecode-analysis}@anchor{3842}
@subsubsection 字节码分析



3.4 新版功能.


字节码分析 API 允许将 Python 代码片段包装在 @ref{831,,Bytecode} 对象中，以便轻松访问已编译代码的详细信息。

@geindex Bytecode (dis 中的类)
@anchor{library/dis dis Bytecode}@anchor{831}
@deffn {类} dis.Bytecode (x, *, first_line=None, current_offset=None)

分析的字节码对应于函数、生成器、异步生成器、协程、方法、源代码字符串或代码对象（由 @ref{1b4,,compile()} 返回）。

这是下面列出的许多函数的便利包装，最值得注意的是 @ref{830,,get_instructions()} ，迭代于 @ref{831,,Bytecode} 的实例产生字节码操作 @ref{82f,,Instruction} 的实例。

如果 @emph{first_line} 不是 @code{None} ，则表示应该为反汇编代码中的第一个源代码行报告的行号。否则，源行信息（如果有的话）直接来自反汇编的代码对象。

如果 @emph{current_offset} 不是 @code{None} ，则它指的是反汇编代码中的指令偏移量。设置它意味着 @ref{832,,dis()} 将针对指定的操作码显示“当前指令”标记。

@geindex from_traceback() (dis.Bytecode 类方法)
@anchor{library/dis dis Bytecode from_traceback}@anchor{833}
@deffn {方法} classmethod from_traceback (tb)

从给定回溯构造一个 @ref{831,,Bytecode} 实例，将设置 @emph{current_offset} 为异常负责的指令。
@end deffn

@geindex Bytecode.codeobj() (在 dis 模块中)
@anchor{library/dis dis Bytecode codeobj}@anchor{3843}
@deffn {数据} codeobj

已编译的代码对象。
@end deffn

@geindex Bytecode.first_line() (在 dis 模块中)
@anchor{library/dis dis Bytecode first_line}@anchor{3844}
@deffn {数据} first_line

代码对象的第一个源代码行（如果可用）
@end deffn

@geindex dis() (dis.Bytecode 方法)
@anchor{library/dis dis Bytecode dis}@anchor{832}
@deffn {方法} dis ()

返回字节码操作的格式化视图（与 @ref{37c,,dis.dis()} 打印相同，但作为多行字符串返回）。
@end deffn

@geindex info() (dis.Bytecode 方法)
@anchor{library/dis dis Bytecode info}@anchor{3845}
@deffn {方法} info ()

返回带有关于代码对象的详细信息的格式化多行字符串，如 @ref{bc7,,code_info()} 。
@end deffn


在 3.7 版更改: 现在可以处理协程和异步生成器对象。

@end deffn

示例:

@example
>>> bytecode = dis.Bytecode(myfunc)
>>> for instr in bytecode:
...     print(instr.opname)
...
LOAD_GLOBAL
LOAD_FAST
CALL_FUNCTION
RETURN_VALUE
@end example

@node 分析函数,Python字节码说明,字节码分析,dis --- Python 字节码反汇编器
@anchor{library/dis analysis-functions}@anchor{3846}
@subsubsection 分析函数


@ref{38,,dis} 模块还定义了以下分析函数，它们将输入直接转换为所需的输出。如果只执行单个操作，它们可能很有用，因此中间分析对象没用：

@geindex code_info() (在 dis 模块中)
@anchor{library/dis dis code_info}@anchor{bc7}
@deffn {函数} dis.code_info (x)

返回格式化的多行字符串，其包含详细代码对象信息的用于被提供的函数、生成器、异步生成器、协程、方法、源代码字符串或代码对象。

请注意，代码信息字符串的确切内容是高度依赖于实现的，它们可能会在Python VM或Python版本中任意更改。


3.2 新版功能.



在 3.7 版更改: 现在可以处理协程和异步生成器对象。

@end deffn

@geindex show_code() (在 dis 模块中)
@anchor{library/dis dis show_code}@anchor{82c}
@deffn {函数} dis.show_code (x, *, file=None)

将提供的函数、方法。源代码字符串或代码对象的详细代码对象信息打印到 @emph{file} （如果未指定 @emph{file} ，则为 @code{sys.stdout} ）。

这是 @code{print(code_info(x), file=file)} 的便捷简写，用于在解释器提示符下进行交互式探索。


3.2 新版功能.



在 3.4 版更改: 添加 @emph{file} 形参。

@end deffn

@geindex dis() (在 dis 模块中)
@anchor{library/dis dis dis}@anchor{37c}
@deffn {函数} dis.dis (x=None, *, file=None, depth=None)

反汇编 @emph{x} 对象。 @emph{x} 可以表示模块、类、方法、函数、生成器、异步生成器、协程、代码对象、源代码字符串或原始字节码的字节序列。对于模块，它会反汇编所有功能。对于一个类，它反汇编所有方法（包括类和静态方法）。对于代码对象或原始字节码序列，它每字节码指令打印一行。它还递归地反汇编嵌套代码对象（推导式代码，生成器表达式和嵌套函数，以及用于构建嵌套类的代码）。在被反汇编之前，首先使用 @ref{1b4,,compile()} 内置函数将字符串编译为代码对象。如果未提供任何对象，则此函数会反汇编最后一次回溯。

如果提供的话，反汇编将作为文本写入提供的 @emph{file} 参数，否则写入 @code{sys.stdout} 。

递归的最大深度受 @emph{depth} 限制，除非它是 @code{None} 。 @code{depth=0} 表示没有递归。


在 3.4 版更改: 添加 @emph{file} 形参。



在 3.7 版更改: 实现了递归反汇编并添加了 @emph{depth} 参数。



在 3.7 版更改: 现在可以处理协程和异步生成器对象。

@end deffn

@geindex distb() (在 dis 模块中)
@anchor{library/dis dis distb}@anchor{82d}
@deffn {函数} dis.distb (tb=None, *, file=None)

如果没有传递，则使用最后一个回溯来反汇编回溯的堆栈顶部函数。 指示了导致异常的指令。

如果提供的话，反汇编将作为文本写入提供的 @emph{file} 参数，否则写入 @code{sys.stdout} 。


在 3.4 版更改: 添加 @emph{file} 形参。

@end deffn

@geindex disassemble() (在 dis 模块中)
@geindex disco() (在 dis 模块中)
@anchor{library/dis dis disassemble}@anchor{82e}
@deffn {函数} dis.disassemble (code, lasti=-1, *, file=None)
@anchor{library/dis dis disco}@anchor{3847}
@deffnx {函数} dis.disco (code, lasti=-1, *, file=None)

反汇编代码对象，如果提供了 @emph{lasti} ，则指示最后一条指令。输出分为以下几列：


@enumerate 

@item 
行号，用于每行的第一条指令

@item 
当前指令，表示为 @code{-->} ，

@item 
一个标记的指令，用 @code{>>} 表示，

@item 
指令的地址，

@item 
操作码名称，

@item 
操作参数，和

@item 
括号中参数的解释。
@end enumerate

参数解释识别本地和全局变量名称、常量值、分支目标和比较运算符。

如果提供的话，反汇编将作为文本写入提供的 @emph{file} 参数，否则写入 @code{sys.stdout} 。


在 3.4 版更改: 添加 @emph{file} 形参。

@end deffn

@geindex get_instructions() (在 dis 模块中)
@anchor{library/dis dis get_instructions}@anchor{830}
@deffn {函数} dis.get_instructions (x, *, first_line=None)

在所提供的函数、方法、源代码字符串或代码对象中的指令上返回一个迭代器。

迭代器生成一系列 @ref{82f,,Instruction} ，命名为元组，提供所提供代码中每个操作的详细信息。

如果 @emph{first_line} 不是 @code{None} ，则表示应该为反汇编代码中的第一个源代码行报告的行号。否则，源行信息（如果有的话）直接来自反汇编的代码对象。


3.4 新版功能.

@end deffn

@geindex findlinestarts() (在 dis 模块中)
@anchor{library/dis dis findlinestarts}@anchor{3848}
@deffn {函数} dis.findlinestarts (code)

此生成器函数使用代码对象 @emph{code} 的 @code{co_firstlineno} 和 @code{co_lnotab} 属性来查找源代码中行开头的偏移量。它们生成为 @code{(offset, lineno)} 对。请参阅 objects/lnotab_notes.txt@footnote{https://github.com/python/cpython/tree/3.8/objects/lnotab_notes.txt} ，了解 @code{co_lnotab} 格式以及如何解码它。


在 3.6 版更改: 行号可能会减少。 以前，他们总是在增加。

@end deffn

@geindex findlabels() (在 dis 模块中)
@anchor{library/dis dis findlabels}@anchor{3849}
@deffn {函数} dis.findlabels (code)

检测作为跳转目标的原始编译后字节码字符串 @emph{code} 中的所有偏移量，并返回这些偏移量的列表。
@end deffn

@geindex stack_effect() (在 dis 模块中)
@anchor{library/dis dis stack_effect}@anchor{834}
@deffn {函数} dis.stack_effect (opcode, oparg=None, *, jump=None)

使用参数 @emph{oparg} 计算 @emph{opcode} 的堆栈效果。

如果代码有一个跳转目标并且 @emph{jump} 是 @code{True} ，则 @code{drag_effect()} 将返回跳转的堆栈效果。如果 @emph{jump} 是 @code{False} ，它将返回不跳跃的堆栈效果。如果 @emph{jump} 是 @code{None} （默认值），它将返回两种情况的最大堆栈效果。


3.4 新版功能.



在 3.8 版更改: 添加 @emph{jump} 参数。

@end deffn

@node Python字节码说明,操作码集合,分析函数,dis --- Python 字节码反汇编器
@anchor{library/dis bytecodes}@anchor{384a}@anchor{library/dis python-bytecode-instructions}@anchor{384b}
@subsubsection Python字节码说明


@ref{830,,get_instructions()} 函数和 @ref{831,,Bytecode} 类提供字节码指令的详细信息的 @ref{82f,,Instruction} 实例：

@geindex Instruction (dis 中的类)
@anchor{library/dis dis Instruction}@anchor{82f}
@deffn {类} dis.Instruction

字节码操作的详细信息

@geindex Instruction.opcode() (在 dis 模块中)
@anchor{library/dis dis Instruction opcode}@anchor{384c}
@deffn {数据} opcode

操作的数字代码，对应于下面列出的操作码值和 @ref{384d,,操作码集合} 中的字节码值。
@end deffn

@geindex Instruction.opname() (在 dis 模块中)
@anchor{library/dis dis Instruction opname}@anchor{384e}
@deffn {数据} opname

人类可读的操作名称
@end deffn

@geindex Instruction.arg() (在 dis 模块中)
@anchor{library/dis dis Instruction arg}@anchor{384f}
@deffn {数据} arg

操作的数字参数（如果有的话），否则为 @code{None}
@end deffn

@geindex Instruction.argval() (在 dis 模块中)
@anchor{library/dis dis Instruction argval}@anchor{3850}
@deffn {数据} argval

已解析的 arg 值（如果已知），否则与 arg 相同
@end deffn

@geindex Instruction.argrepr() (在 dis 模块中)
@anchor{library/dis dis Instruction argrepr}@anchor{3851}
@deffn {数据} argrepr

人类可读的操作参数描述
@end deffn

@geindex Instruction.offset() (在 dis 模块中)
@anchor{library/dis dis Instruction offset}@anchor{3852}
@deffn {数据} offset

在字节码序列中启动操作索引
@end deffn

@geindex Instruction.starts_line() (在 dis 模块中)
@anchor{library/dis dis Instruction starts_line}@anchor{3853}
@deffn {数据} starts_line

行由此操作码（如果有）启动，否则为 @code{None}
@end deffn

@geindex Instruction.is_jump_target() (在 dis 模块中)
@anchor{library/dis dis Instruction is_jump_target}@anchor{3854}
@deffn {数据} is_jump_target

如果其他代码跳到这里，则为 @code{True} ，否则为 @code{False}
@end deffn


3.4 新版功能.

@end deffn

Python编译器当前生成以下字节码指令。

@strong{一般指令}

@geindex NOP (opcode)
@anchor{library/dis opcode-NOP}@anchor{3855}
@deffn {Opcode} NOP

什么都不做。 用作字节码优化器的占位符。
@end deffn

@geindex POP_TOP (opcode)
@anchor{library/dis opcode-POP_TOP}@anchor{3856}
@deffn {Opcode} POP_TOP

删除堆栈顶部（TOS）项。
@end deffn

@geindex ROT_TWO (opcode)
@anchor{library/dis opcode-ROT_TWO}@anchor{3857}
@deffn {Opcode} ROT_TWO

交换两个最顶层的堆栈项。
@end deffn

@geindex ROT_THREE (opcode)
@anchor{library/dis opcode-ROT_THREE}@anchor{3858}
@deffn {Opcode} ROT_THREE

将第二个和第三个堆栈项向上提升一个位置，顶项移动到位置三。
@end deffn

@geindex ROT_FOUR (opcode)
@anchor{library/dis opcode-ROT_FOUR}@anchor{2dc}
@deffn {Opcode} ROT_FOUR

将第二个，第三个和第四个堆栈项向上提升一个位置，将顶项移动到第四个位置。


3.8 新版功能.

@end deffn

@geindex DUP_TOP (opcode)
@anchor{library/dis opcode-DUP_TOP}@anchor{3859}
@deffn {Opcode} DUP_TOP

复制堆栈顶部的引用。


3.2 新版功能.

@end deffn

@geindex DUP_TOP_TWO (opcode)
@anchor{library/dis opcode-DUP_TOP_TWO}@anchor{385a}
@deffn {Opcode} DUP_TOP_TWO

复制堆栈顶部的两个引用，使它们保持相同的顺序。


3.2 新版功能.

@end deffn

@strong{一元操作}

一元操作获取堆栈顶部元素，应用操作，并将结果推回堆栈。

@geindex UNARY_POSITIVE (opcode)
@anchor{library/dis opcode-UNARY_POSITIVE}@anchor{385b}
@deffn {Opcode} UNARY_POSITIVE

实现 @code{TOS = +TOS} 。
@end deffn

@geindex UNARY_NEGATIVE (opcode)
@anchor{library/dis opcode-UNARY_NEGATIVE}@anchor{385c}
@deffn {Opcode} UNARY_NEGATIVE

实现 @code{TOS = -TOS} 。
@end deffn

@geindex UNARY_NOT (opcode)
@anchor{library/dis opcode-UNARY_NOT}@anchor{385d}
@deffn {Opcode} UNARY_NOT

实现 @code{TOS = not TOS} 。
@end deffn

@geindex UNARY_INVERT (opcode)
@anchor{library/dis opcode-UNARY_INVERT}@anchor{385e}
@deffn {Opcode} UNARY_INVERT

实现 @code{TOS = ~TOS} 。
@end deffn

@geindex GET_ITER (opcode)
@anchor{library/dis opcode-GET_ITER}@anchor{385f}
@deffn {Opcode} GET_ITER

实现 @code{TOS = iter(TOS)} 。
@end deffn

@geindex GET_YIELD_FROM_ITER (opcode)
@anchor{library/dis opcode-GET_YIELD_FROM_ITER}@anchor{3860}
@deffn {Opcode} GET_YIELD_FROM_ITER

如果 @code{TOS} 是一个 @ref{451,,generator iterator} 或 @ref{1a6,,coroutine} 对象则保持原样。否则实现 @code{TOS = iter(TOS)} 。


3.5 新版功能.

@end deffn

@strong{二元操作}

二元操作从堆栈中删除堆栈顶部（TOS）和第二个最顶层堆栈项（TOS1）。 它们执行操作，并将结果放回堆栈。

@geindex BINARY_POWER (opcode)
@anchor{library/dis opcode-BINARY_POWER}@anchor{3861}
@deffn {Opcode} BINARY_POWER

实现 @code{TOS = TOS1 ** TOS} 。
@end deffn

@geindex BINARY_MULTIPLY (opcode)
@anchor{library/dis opcode-BINARY_MULTIPLY}@anchor{3862}
@deffn {Opcode} BINARY_MULTIPLY

实现 @code{TOS = TOS1 * TOS} 。
@end deffn

@geindex BINARY_MATRIX_MULTIPLY (opcode)
@anchor{library/dis opcode-BINARY_MATRIX_MULTIPLY}@anchor{3863}
@deffn {Opcode} BINARY_MATRIX_MULTIPLY

实现 @code{TOS = TOS1 @@ TOS} 。


3.5 新版功能.

@end deffn

@geindex BINARY_FLOOR_DIVIDE (opcode)
@anchor{library/dis opcode-BINARY_FLOOR_DIVIDE}@anchor{3864}
@deffn {Opcode} BINARY_FLOOR_DIVIDE

实现 @code{TOS = TOS1 // TOS}。
@end deffn

@geindex BINARY_TRUE_DIVIDE (opcode)
@anchor{library/dis opcode-BINARY_TRUE_DIVIDE}@anchor{3865}
@deffn {Opcode} BINARY_TRUE_DIVIDE

实现 @code{TOS = TOS1 / TOS} 。
@end deffn

@geindex BINARY_MODULO (opcode)
@anchor{library/dis opcode-BINARY_MODULO}@anchor{3866}
@deffn {Opcode} BINARY_MODULO

实现 @code{TOS = TOS1 % TOS} 。
@end deffn

@geindex BINARY_ADD (opcode)
@anchor{library/dis opcode-BINARY_ADD}@anchor{3867}
@deffn {Opcode} BINARY_ADD

实现 @code{TOS = TOS1 + TOS} 。
@end deffn

@geindex BINARY_SUBTRACT (opcode)
@anchor{library/dis opcode-BINARY_SUBTRACT}@anchor{3868}
@deffn {Opcode} BINARY_SUBTRACT

实现 @code{TOS = TOS1 - TOS} 。
@end deffn

@geindex BINARY_SUBSCR (opcode)
@anchor{library/dis opcode-BINARY_SUBSCR}@anchor{3869}
@deffn {Opcode} BINARY_SUBSCR

实现 @code{TOS = TOS1[TOS]} 。
@end deffn

@geindex BINARY_LSHIFT (opcode)
@anchor{library/dis opcode-BINARY_LSHIFT}@anchor{386a}
@deffn {Opcode} BINARY_LSHIFT

实现 @code{TOS = TOS1 << TOS} 。
@end deffn

@geindex BINARY_RSHIFT (opcode)
@anchor{library/dis opcode-BINARY_RSHIFT}@anchor{386b}
@deffn {Opcode} BINARY_RSHIFT

实现 @code{TOS = TOS1 >> TOS} 。
@end deffn

@geindex BINARY_AND (opcode)
@anchor{library/dis opcode-BINARY_AND}@anchor{386c}
@deffn {Opcode} BINARY_AND

实现 @code{TOS = TOS1 & TOS} 。
@end deffn

@geindex BINARY_XOR (opcode)
@anchor{library/dis opcode-BINARY_XOR}@anchor{386d}
@deffn {Opcode} BINARY_XOR

实现 @code{TOS = TOS1 ^ TOS} 。
@end deffn

@geindex BINARY_OR (opcode)
@anchor{library/dis opcode-BINARY_OR}@anchor{386e}
@deffn {Opcode} BINARY_OR

实现 @code{TOS = TOS1 | TOS} 。
@end deffn

@strong{就地操作}

就地操作就像二元操作，因为它们删除了TOS和TOS1，并将结果推回到堆栈上，但是当TOS1支持它时，操作就地完成，并且产生的TOS可能是（但不一定） 原来的TOS1。

@geindex INPLACE_POWER (opcode)
@anchor{library/dis opcode-INPLACE_POWER}@anchor{386f}
@deffn {Opcode} INPLACE_POWER

就地实现 @code{TOS = TOS1 ** TOS} 。
@end deffn

@geindex INPLACE_MULTIPLY (opcode)
@anchor{library/dis opcode-INPLACE_MULTIPLY}@anchor{3870}
@deffn {Opcode} INPLACE_MULTIPLY

就地实现 @code{TOS = TOS1 * TOS} 。
@end deffn

@geindex INPLACE_MATRIX_MULTIPLY (opcode)
@anchor{library/dis opcode-INPLACE_MATRIX_MULTIPLY}@anchor{3871}
@deffn {Opcode} INPLACE_MATRIX_MULTIPLY

就地实现 @code{TOS = TOS1 @@ TOS} 。


3.5 新版功能.

@end deffn

@geindex INPLACE_FLOOR_DIVIDE (opcode)
@anchor{library/dis opcode-INPLACE_FLOOR_DIVIDE}@anchor{3872}
@deffn {Opcode} INPLACE_FLOOR_DIVIDE

就地实现 @code{TOS = TOS1 // TOS} 。
@end deffn

@geindex INPLACE_TRUE_DIVIDE (opcode)
@anchor{library/dis opcode-INPLACE_TRUE_DIVIDE}@anchor{3873}
@deffn {Opcode} INPLACE_TRUE_DIVIDE

就地实现 @code{TOS = TOS1 / TOS} 。
@end deffn

@geindex INPLACE_MODULO (opcode)
@anchor{library/dis opcode-INPLACE_MODULO}@anchor{3874}
@deffn {Opcode} INPLACE_MODULO

就地实现 @code{TOS = TOS1 % TOS} 。
@end deffn

@geindex INPLACE_ADD (opcode)
@anchor{library/dis opcode-INPLACE_ADD}@anchor{3875}
@deffn {Opcode} INPLACE_ADD

就地实现 @code{TOS = TOS1 + TOS} 。
@end deffn

@geindex INPLACE_SUBTRACT (opcode)
@anchor{library/dis opcode-INPLACE_SUBTRACT}@anchor{3876}
@deffn {Opcode} INPLACE_SUBTRACT

就地实现 @code{TOS = TOS1 - TOS} 。
@end deffn

@geindex INPLACE_LSHIFT (opcode)
@anchor{library/dis opcode-INPLACE_LSHIFT}@anchor{3877}
@deffn {Opcode} INPLACE_LSHIFT

就地实现 @code{TOS = TOS1 << TOS} 。
@end deffn

@geindex INPLACE_RSHIFT (opcode)
@anchor{library/dis opcode-INPLACE_RSHIFT}@anchor{3878}
@deffn {Opcode} INPLACE_RSHIFT

就地实现 @code{TOS = TOS1 >> TOS} 。
@end deffn

@geindex INPLACE_AND (opcode)
@anchor{library/dis opcode-INPLACE_AND}@anchor{3879}
@deffn {Opcode} INPLACE_AND

就地实现 @code{TOS = TOS1 & TOS} 。
@end deffn

@geindex INPLACE_XOR (opcode)
@anchor{library/dis opcode-INPLACE_XOR}@anchor{387a}
@deffn {Opcode} INPLACE_XOR

就地实现 @code{TOS = TOS1 ^ TOS} 。
@end deffn

@geindex INPLACE_OR (opcode)
@anchor{library/dis opcode-INPLACE_OR}@anchor{387b}
@deffn {Opcode} INPLACE_OR

就地实现 @code{TOS = TOS1 | TOS} 。
@end deffn

@geindex STORE_SUBSCR (opcode)
@anchor{library/dis opcode-STORE_SUBSCR}@anchor{387c}
@deffn {Opcode} STORE_SUBSCR

实现 @code{TOS1[TOS] = TOS2} 。
@end deffn

@geindex DELETE_SUBSCR (opcode)
@anchor{library/dis opcode-DELETE_SUBSCR}@anchor{387d}
@deffn {Opcode} DELETE_SUBSCR

实现 @code{del TOS1[TOS]} 。
@end deffn

@strong{协程操作码}

@geindex GET_AWAITABLE (opcode)
@anchor{library/dis opcode-GET_AWAITABLE}@anchor{387e}
@deffn {Opcode} GET_AWAITABLE

实现 @code{TOS = get_awaitable(TOS)} ，其中 @code{get_awaitable(o)} 返回 @code{o} 如果 @code{o} 是一个有 CO_ITERABLE_COROUTINE 标志的协程对象或生成器对象，否则解析 @code{o.__await__} 。


3.5 新版功能.

@end deffn

@geindex GET_AITER (opcode)
@anchor{library/dis opcode-GET_AITER}@anchor{387f}
@deffn {Opcode} GET_AITER

实现 @code{TOS = TOS.__aiter__()} 。


3.5 新版功能.



在 3.7 版更改: 已经不再支持从 @code{__aiter__} 返回可等待对象。

@end deffn

@geindex GET_ANEXT (opcode)
@anchor{library/dis opcode-GET_ANEXT}@anchor{3880}
@deffn {Opcode} GET_ANEXT

实现 @code{PUSH(get_awaitable(TOS.__anext__()))} 。参见 @code{GET_AWAITABLE} 获取更多 @code{get_awaitable} 的细节


3.5 新版功能.

@end deffn

@geindex END_ASYNC_FOR (opcode)
@anchor{library/dis opcode-END_ASYNC_FOR}@anchor{2e2}
@deffn {Opcode} END_ASYNC_FOR

终止一个 @ref{2e3,,async for}  循环。处理等待下一个项目时引发的异常。如果 TOS 是 @ref{fa5,,StopAsyncIteration}， 从堆栈弹出7个值，并使用后三个恢复异常状态。否则，使用堆栈中的三个值重新引发异常。从块堆栈中删除异常处理程序块。


3.8 新版功能.

@end deffn

@geindex BEFORE_ASYNC_WITH (opcode)
@anchor{library/dis opcode-BEFORE_ASYNC_WITH}@anchor{3881}
@deffn {Opcode} BEFORE_ASYNC_WITH

从栈顶对象解析 @code{__aenter__} 和 @code{__aexit__} 。将 @code{__aexit__} 和 @code{__aenter__()} 的结果推入堆栈。


3.5 新版功能.

@end deffn

@geindex SETUP_ASYNC_WITH (opcode)
@anchor{library/dis opcode-SETUP_ASYNC_WITH}@anchor{3882}
@deffn {Opcode} SETUP_ASYNC_WITH

创建一个新的帧对象。


3.5 新版功能.

@end deffn

@strong{其他操作码}

@geindex PRINT_EXPR (opcode)
@anchor{library/dis opcode-PRINT_EXPR}@anchor{3883}
@deffn {Opcode} PRINT_EXPR

实现交互模式的表达式语句。TOS从堆栈中被移除并打印。在非交互模式下，表达式语句以 @ref{3856,,POP_TOP} 终止。
@end deffn

@geindex SET_ADD (opcode)
@anchor{library/dis opcode-SET_ADD}@anchor{3884}
@deffn {Opcode} SET_ADD (i)

调用 @code{set.add(TOS1[-i], TOS)} 。 用于实现集合推导。
@end deffn

@geindex LIST_APPEND (opcode)
@anchor{library/dis opcode-LIST_APPEND}@anchor{3885}
@deffn {Opcode} LIST_APPEND (i)

调用 @code{list.append(TOS[-i], TOS)} 。 用于实现列表推导。
@end deffn

@geindex MAP_ADD (opcode)
@anchor{library/dis opcode-MAP_ADD}@anchor{2e4}
@deffn {Opcode} MAP_ADD (i)

调用 @code{dict.__setitem__(TOS1[-i], TOS1, TOS)} 。 用于实现字典推导。


3.1 新版功能.



在 3.8 版更改: 映射值为 TOS ，映射键为 TOS1 。之前，它们被颠倒了。

@end deffn

对于所有 @ref{3884,,SET_ADD} 、 @ref{3885,,LIST_APPEND} 和 @ref{2e4,,MAP_ADD} 指令，当弹出添加的值或键值对时，容器对象保留在堆栈上，以便它可用于循环的进一步迭代。

@geindex RETURN_VALUE (opcode)
@anchor{library/dis opcode-RETURN_VALUE}@anchor{3886}
@deffn {Opcode} RETURN_VALUE

返回 TOS 到函数的调用者。
@end deffn

@geindex YIELD_VALUE (opcode)
@anchor{library/dis opcode-YIELD_VALUE}@anchor{3887}
@deffn {Opcode} YIELD_VALUE

弹出 TOS 并从一个 @ref{99c,,generator} 生成它。
@end deffn

@geindex YIELD_FROM (opcode)
@anchor{library/dis opcode-YIELD_FROM}@anchor{3888}
@deffn {Opcode} YIELD_FROM

弹出 TOS 并将其委托给它作为 @ref{99c,,generator} 的子迭代器。


3.3 新版功能.

@end deffn

@geindex SETUP_ANNOTATIONS (opcode)
@anchor{library/dis opcode-SETUP_ANNOTATIONS}@anchor{619}
@deffn {Opcode} SETUP_ANNOTATIONS

检查 @code{__annotations__} 是否在 @code{locals()} 中定义，如果没有，它被设置为空 @code{dict} 。只有在类或模块体静态地包含 @ref{61a,,variable annotations} 时才会发出此操作码。


3.6 新版功能.

@end deffn

@geindex IMPORT_STAR (opcode)
@anchor{library/dis opcode-IMPORT_STAR}@anchor{3889}
@deffn {Opcode} IMPORT_STAR

将所有不以 @code{'_'} 开头的符号直接从模块 TOS 加载到局部命名空间。加载所有名称后弹出该模块。这个操作码实现了 @code{from module import *} 。
@end deffn

@geindex POP_BLOCK (opcode)
@anchor{library/dis opcode-POP_BLOCK}@anchor{388a}
@deffn {Opcode} POP_BLOCK

从块堆栈中删除一个块。有一块堆栈，每帧用于表示 @ref{d6b,,try} 语句等。
@end deffn

@geindex POP_EXCEPT (opcode)
@anchor{library/dis opcode-POP_EXCEPT}@anchor{388b}
@deffn {Opcode} POP_EXCEPT

从块堆栈中删除一个块。 弹出的块必须是异常处理程序块，在进入 except 处理程序时隐式创建。除了从帧堆栈弹出无关值之外，最后三个弹出值还用于恢复异常状态。
@end deffn

@geindex POP_FINALLY (opcode)
@anchor{library/dis opcode-POP_FINALLY}@anchor{2df}
@deffn {Opcode} POP_FINALLY (preserve_tos)

清除值堆栈和块堆栈。如果 @emph{preserve_tos} 不是 @code{0} ，则在执行其他堆栈操作后，首先从堆栈中弹出 TOS 并将其推入堆栈：


@itemize *

@item 
如果TOS是 @code{NULL} 或整数（由 @ref{2dd,,BEGIN_FINALLY} 或 @ref{2de,,CALL_FINALLY} 推入），它将从堆栈中弹出。

@item 
如果TOS是异常类型（在引发异常时被推入），则从堆栈中弹出6个值，最后三个弹出值用于恢复异常状态。从块堆栈中删除异常处理程序块。
@end itemize

它类似于 @ref{2e0,,END_FINALLY} ，但不会更改字节码计数器也不会引发异常。用于在 @ref{182,,finally} 块中实现 @ref{2db,,break} 、 @ref{181,,continue} 和 @ref{190,,return} 。


3.8 新版功能.

@end deffn

@geindex BEGIN_FINALLY (opcode)
@anchor{library/dis opcode-BEGIN_FINALLY}@anchor{2dd}
@deffn {Opcode} BEGIN_FINALLY

将 @code{NULL} 推入堆栈以便在以下操作中使用 @ref{2e0,,END_FINALLY} 、 @ref{2df,,POP_FINALLY} 、 @ref{2e1,,WITH_CLEANUP_START} 和 @ref{388c,,WITH_CLEANUP_FINISH} 。开始 @ref{182,,finally} 块。


3.8 新版功能.

@end deffn

@geindex END_FINALLY (opcode)
@anchor{library/dis opcode-END_FINALLY}@anchor{2e0}
@deffn {Opcode} END_FINALLY

终止 @ref{182,,finally} 子句。解释器回溯是否有必须重新抛出异常的情况或根据 TOS 的值继续执行。


@itemize *

@item 
如果 TOS 是 @code{NULL} （由 @ref{2dd,,BEGIN_FINALLY} 推入）继续下一条指令。 TOS 被弹出。

@item 
如果 TO S是一个整数（由 @ref{2de,,CALL_FINALLY} 推入），则将字节码计数器设置为 TOS 。 TOS 被弹出。

@item 
如果TOS是异常类型（在引发异常时被推送），则从堆栈中弹出 6 个值，前三个弹出值用于重新引发异常，最后三个弹出值用于恢复异常状态。从块堆栈中删除异常处理程序块。
@end itemize
@end deffn

@geindex LOAD_BUILD_CLASS (opcode)
@anchor{library/dis opcode-LOAD_BUILD_CLASS}@anchor{388d}
@deffn {Opcode} LOAD_BUILD_CLASS

将 @code{builtins .__ build_class__()} 推到堆栈上。它之后被 @ref{614,,CALL_FUNCTION} 调用来构造一个类。
@end deffn

@geindex SETUP_WITH (opcode)
@anchor{library/dis opcode-SETUP_WITH}@anchor{388e}
@deffn {Opcode} SETUP_WITH (delta)

此操作码在 with 块开始之前执行多个操作。首先，它从上下文管理器加载 @ref{c8f,,__exit__()} 并将其推入到堆栈以供以后被 @ref{2e1,,WITH_CLEANUP_START} 使用。然后，调用 @code{__enter__()} ，并推入指向 @emph{delta} 的 finally 块。最后，调用 @code{__enter__()} 方法的结果被压入堆栈。一个操作码将忽略它（ @ref{3856,,POP_TOP} ），或将其存储在一个或多个变量（ @ref{388f,,STORE_FAST} 、 @ref{3890,,STORE_NAME} 或 @ref{3891,,UNPACK_SEQUENCE} ）中。


3.2 新版功能.

@end deffn

@geindex WITH_CLEANUP_START (opcode)
@anchor{library/dis opcode-WITH_CLEANUP_START}@anchor{2e1}
@deffn {Opcode} WITH_CLEANUP_START

当 @ref{6e3,,with} 语句块退出时，开始清理堆栈。

在堆栈的顶部是 @code{NULL} （由 @ref{2dd,,BEGIN_FINALLY} 推送）或者如果在 with 块中引发了异常，则推送 6 个值。下面是上下文管理器 @ref{c8f,,__exit__()} 或 @ref{1431,,__aexit__()} 绑定方法。

如果TOS是 @code{NULL} ，则调用 @code{SECOND(None, None, None)} ，从堆栈中删除函数，离开 TOS ，并将 @code{None} 推送到堆栈。 否则调用 @code{SEVENTH(TOP, SECOND, THIRD)} ，将堆栈的底部3值向下移动，用 @code{NULL} 替换空位并推入 TOS 。最后拖入调用的结果。
@end deffn

@geindex WITH_CLEANUP_FINISH (opcode)
@anchor{library/dis opcode-WITH_CLEANUP_FINISH}@anchor{388c}
@deffn {Opcode} WITH_CLEANUP_FINISH

当 @ref{6e3,,with} 语句块退出时，完成清理堆栈。

TOS 是 @ref{2e1,,WITH_CLEANUP_START} 推送的 @code{__exit__()} 或 @code{__aexit__()} 函数的结果。 SECOND是 @code{None} 或异常类型（引发异常时推入的）。

从堆栈中弹出两个值。如果 SECOND 不为 None 并且 TOS 为 true ，则展开 EXCEPT_HANDLER 块，该块是在捕获异常时创建的，并将 @code{NULL} 推入堆栈。
@end deffn

以下所有操作码均使用其参数。

@geindex STORE_NAME (opcode)
@anchor{library/dis opcode-STORE_NAME}@anchor{3890}
@deffn {Opcode} STORE_NAME (namei)

实现 @code{name = TOS}。 @emph{namei} 是 @emph{name} 在代码对象的 @code{co_names} 属性中的索引。 在可能的情况下，编译器会尝试使用 @ref{388f,,STORE_FAST} 或 @ref{3892,,STORE_GLOBAL}。
@end deffn

@geindex DELETE_NAME (opcode)
@anchor{library/dis opcode-DELETE_NAME}@anchor{3893}
@deffn {Opcode} DELETE_NAME (namei)

实现 @code{del name} ，其中 @emph{namei} 是代码对象的 @code{co_names} 属性的索引。
@end deffn

@geindex UNPACK_SEQUENCE (opcode)
@anchor{library/dis opcode-UNPACK_SEQUENCE}@anchor{3891}
@deffn {Opcode} UNPACK_SEQUENCE (count)

将 TOS 解包为 @emph{count} 个单独的值，它们将按从右至左的顺序被放入堆栈。
@end deffn

@geindex UNPACK_EX (opcode)
@anchor{library/dis opcode-UNPACK_EX}@anchor{3894}
@deffn {Opcode} UNPACK_EX (counts)

实现使用带星号的目标进行赋值：将 TOS 中的可迭代对象解包为单独的值，其中值的总数可以小于可迭代对象中的项数：新值之一将是由所有剩余项构成的列表。

@emph{counts} 的低字节是列表值之前的值的数量，@emph{counts} 中的高字节则是之后的值的数量。 结果值会按从右至左的顺序入栈。
@end deffn

@geindex STORE_ATTR (opcode)
@anchor{library/dis opcode-STORE_ATTR}@anchor{3895}
@deffn {Opcode} STORE_ATTR (namei)

实现 @code{TOS.name = TOS1}，其中 @emph{namei} 是 name 在 @code{co_names} 中的索引号。
@end deffn

@geindex DELETE_ATTR (opcode)
@anchor{library/dis opcode-DELETE_ATTR}@anchor{3896}
@deffn {Opcode} DELETE_ATTR (namei)

实现 @code{del TOS.name}，使用 @emph{namei} 作为 @code{co_names} 中的索引号。
@end deffn

@geindex STORE_GLOBAL (opcode)
@anchor{library/dis opcode-STORE_GLOBAL}@anchor{3892}
@deffn {Opcode} STORE_GLOBAL (namei)

类似于 @ref{3890,,STORE_NAME} 但会将 name 存储为全局变量。
@end deffn

@geindex DELETE_GLOBAL (opcode)
@anchor{library/dis opcode-DELETE_GLOBAL}@anchor{3897}
@deffn {Opcode} DELETE_GLOBAL (namei)

类似于 @ref{3893,,DELETE_NAME} 但会删除一个全局变量。
@end deffn

@geindex LOAD_CONST (opcode)
@anchor{library/dis opcode-LOAD_CONST}@anchor{3898}
@deffn {Opcode} LOAD_CONST (consti)

将 @code{co_consts[consti]} 推入栈顶。
@end deffn

@geindex LOAD_NAME (opcode)
@anchor{library/dis opcode-LOAD_NAME}@anchor{3899}
@deffn {Opcode} LOAD_NAME (namei)

将与 @code{co_names[namei]} 相关联的值推入栈顶。
@end deffn

@geindex BUILD_TUPLE (opcode)
@anchor{library/dis opcode-BUILD_TUPLE}@anchor{389a}
@deffn {Opcode} BUILD_TUPLE (count)

创建一个使用了来自栈的 @emph{count} 个项的元组，并将结果元组推入栈顶。
@end deffn

@geindex BUILD_LIST (opcode)
@anchor{library/dis opcode-BUILD_LIST}@anchor{389b}
@deffn {Opcode} BUILD_LIST (count)

类似于 @ref{389a,,BUILD_TUPLE} 但会创建一个列表。
@end deffn

@geindex BUILD_SET (opcode)
@anchor{library/dis opcode-BUILD_SET}@anchor{389c}
@deffn {Opcode} BUILD_SET (count)

类似于 @ref{389a,,BUILD_TUPLE} 但会创建一个集合。
@end deffn

@geindex BUILD_MAP (opcode)
@anchor{library/dis opcode-BUILD_MAP}@anchor{389d}
@deffn {Opcode} BUILD_MAP (count)

将一个新字典对象推入栈顶。 弹出 @code{2 * count} 项使得字典包含 @emph{count} 个条目: @code{@{..., TOS3: TOS2, TOS1: TOS@}}。


在 3.5 版更改: 字典是根据栈中的项创建而不是创建一个预设大小包含 @emph{count} 项的空字典。

@end deffn

@geindex BUILD_CONST_KEY_MAP (opcode)
@anchor{library/dis opcode-BUILD_CONST_KEY_MAP}@anchor{612}
@deffn {Opcode} BUILD_CONST_KEY_MAP (count)

@ref{389d,,BUILD_MAP} 版本专用于常量键。 弹出的栈顶元素包含一个由键构成的元组，然后从 @code{TOS1} 开始从构建字典的值中弹出 @emph{count} 个值。


3.6 新版功能.

@end deffn

@geindex BUILD_STRING (opcode)
@anchor{library/dis opcode-BUILD_STRING}@anchor{611}
@deffn {Opcode} BUILD_STRING (count)

拼接 @emph{count} 个来自栈的字符串并将结果字符串推入栈顶。


3.6 新版功能.

@end deffn

@geindex BUILD_TUPLE_UNPACK (opcode)
@anchor{library/dis opcode-BUILD_TUPLE_UNPACK}@anchor{389e}
@deffn {Opcode} BUILD_TUPLE_UNPACK (count)

从栈中弹出 @emph{count} 个可迭代对象，将它们合并为单个元组，并将结果推入栈顶。 实现可迭代对象解包为元组形式 @code{(*x, *y, *z)}。


3.5 新版功能.

@end deffn

@geindex BUILD_TUPLE_UNPACK_WITH_CALL (opcode)
@anchor{library/dis opcode-BUILD_TUPLE_UNPACK_WITH_CALL}@anchor{618}
@deffn {Opcode} BUILD_TUPLE_UNPACK_WITH_CALL (count)

这类似于 @ref{389e,,BUILD_TUPLE_UNPACK} 但专用于 @code{f(*x, *y, *z)} 调用语法。 栈中 @code{count + 1} 位置上的项应当是相应的可调用对象 @code{f}。


3.6 新版功能.

@end deffn

@geindex BUILD_LIST_UNPACK (opcode)
@anchor{library/dis opcode-BUILD_LIST_UNPACK}@anchor{389f}
@deffn {Opcode} BUILD_LIST_UNPACK (count)

这类似于 @ref{389e,,BUILD_TUPLE_UNPACK} 但会将一个列表而非元组推入栈顶。 实现可迭代对象解包为列表形式 @code{[*x, *y, *z]}。


3.5 新版功能.

@end deffn

@geindex BUILD_SET_UNPACK (opcode)
@anchor{library/dis opcode-BUILD_SET_UNPACK}@anchor{38a0}
@deffn {Opcode} BUILD_SET_UNPACK (count)

这类似于 @ref{389e,,BUILD_TUPLE_UNPACK} 但会将一个集合而非元组推入栈顶。 实现可迭代对象解包为集合形式 @code{@{*x, *y, *z@}}。


3.5 新版功能.

@end deffn

@geindex BUILD_MAP_UNPACK (opcode)
@anchor{library/dis opcode-BUILD_MAP_UNPACK}@anchor{38a1}
@deffn {Opcode} BUILD_MAP_UNPACK (count)

从栈中弹出 @emph{count} 个映射对象，将它们合并为单个字典，并将结果推入栈顶。 实现字典解包为字典形式 @code{@{**x, **y, **z@}}。


3.5 新版功能.

@end deffn

@geindex BUILD_MAP_UNPACK_WITH_CALL (opcode)
@anchor{library/dis opcode-BUILD_MAP_UNPACK_WITH_CALL}@anchor{616}
@deffn {Opcode} BUILD_MAP_UNPACK_WITH_CALL (count)

这类似于 @ref{38a1,,BUILD_MAP_UNPACK} 但专用于 @code{f(**x, **y, **z)} 调用语法。 栈中 @code{count + 2} 位置上的项应当是相应的可调用对象 @code{f}。


3.5 新版功能.



在 3.6 版更改: 可迭代对象的位置的确定方式是将操作码参数加 2 而不是将其编码到参数的第二个字节。

@end deffn

@geindex LOAD_ATTR (opcode)
@anchor{library/dis opcode-LOAD_ATTR}@anchor{38a2}
@deffn {Opcode} LOAD_ATTR (namei)

将 TOS 替换为 @code{getattr(TOS, co_names[namei])}。
@end deffn

@geindex COMPARE_OP (opcode)
@anchor{library/dis opcode-COMPARE_OP}@anchor{38a3}
@deffn {Opcode} COMPARE_OP (opname)

执行布尔运算操作。 操作名称可在 @code{cmp_op[opname]} 中找到。
@end deffn

@geindex IMPORT_NAME (opcode)
@anchor{library/dis opcode-IMPORT_NAME}@anchor{38a4}
@deffn {Opcode} IMPORT_NAME (namei)

导入模块 @code{co_names[namei]}。 会弹出 TOS 和 TOS1 以提供 @emph{fromlist} 和 @emph{level} 参数给 @ref{60b,,__import__()}。 模块对象会被推入栈顶。 当前命名空间不受影响：对于一条标准 import 语句，会执行后续的 @ref{388f,,STORE_FAST} 指令来修改命名空间。
@end deffn

@geindex IMPORT_FROM (opcode)
@anchor{library/dis opcode-IMPORT_FROM}@anchor{38a5}
@deffn {Opcode} IMPORT_FROM (namei)

从在 TOS 内找到的模块中加载属性 @code{co_names[namei]}。 结果对象会被推入栈顶，以便由后续的 @ref{388f,,STORE_FAST} 指令来保存。
@end deffn

@geindex JUMP_FORWARD (opcode)
@anchor{library/dis opcode-JUMP_FORWARD}@anchor{38a6}
@deffn {Opcode} JUMP_FORWARD (delta)

将字节码计数器的值增加 @emph{delta}。
@end deffn

@geindex POP_JUMP_IF_TRUE (opcode)
@anchor{library/dis opcode-POP_JUMP_IF_TRUE}@anchor{38a7}
@deffn {Opcode} POP_JUMP_IF_TRUE (target)

如果 TOS 为真值，则将字节码计数器的值设为 @emph{target}。 TOS 会被弹出。


3.1 新版功能.

@end deffn

@geindex POP_JUMP_IF_FALSE (opcode)
@anchor{library/dis opcode-POP_JUMP_IF_FALSE}@anchor{38a8}
@deffn {Opcode} POP_JUMP_IF_FALSE (target)

如果 TOS 为假值，则将字节码计数器的值设为 @emph{target}。 TOS 会被弹出。


3.1 新版功能.

@end deffn

@geindex JUMP_IF_TRUE_OR_POP (opcode)
@anchor{library/dis opcode-JUMP_IF_TRUE_OR_POP}@anchor{38a9}
@deffn {Opcode} JUMP_IF_TRUE_OR_POP (target)

如果 TOS 为真值，则将字节码计数器的值设为 @emph{target} 并将 TOS 留在栈顶。 否则（如 TOS 为假值），TOS 会被弹出。


3.1 新版功能.

@end deffn

@geindex JUMP_IF_FALSE_OR_POP (opcode)
@anchor{library/dis opcode-JUMP_IF_FALSE_OR_POP}@anchor{38aa}
@deffn {Opcode} JUMP_IF_FALSE_OR_POP (target)

如果 TOS 为假值，则将字节码计数器的值设为 @emph{target} 并将 TOS 留在栈顶。 否则（如 TOS 为假值），TOS 会被弹出。


3.1 新版功能.

@end deffn

@geindex JUMP_ABSOLUTE (opcode)
@anchor{library/dis opcode-JUMP_ABSOLUTE}@anchor{38ab}
@deffn {Opcode} JUMP_ABSOLUTE (target)

将字节码计数器的值设为 @emph{target}。
@end deffn

@geindex FOR_ITER (opcode)
@anchor{library/dis opcode-FOR_ITER}@anchor{38ac}
@deffn {Opcode} FOR_ITER (delta)

TOS 是一个 @ref{fce,,iterator}。 可调用它的 @ref{c5d,,__next__()} 方法。 如果产生了一个新值，则将其推入栈顶（将迭代器留在其下方）。 如果迭代器提示已耗尽则 TOS 会被弹出，并将字节码计数器的值增加 @emph{delta}。
@end deffn

@geindex LOAD_GLOBAL (opcode)
@anchor{library/dis opcode-LOAD_GLOBAL}@anchor{38ad}
@deffn {Opcode} LOAD_GLOBAL (namei)

加载名称为 @code{co_names[namei]} 的全局对象推入栈顶。
@end deffn

@geindex SETUP_FINALLY (opcode)
@anchor{library/dis opcode-SETUP_FINALLY}@anchor{38ae}
@deffn {Opcode} SETUP_FINALLY (delta)

将一个来自 try-finally 或 try-except 子句的 try 代码块推入代码块栈顶。 相对 finally 代码块或第一个 except 代码块 @emph{delta} 个点数。
@end deffn

@geindex CALL_FINALLY (opcode)
@anchor{library/dis opcode-CALL_FINALLY}@anchor{2de}
@deffn {Opcode} CALL_FINALLY (delta)

将下一条指令的地址推入栈顶并将字节码计数器的值增加 @emph{delta}。 用于将 finally 代码块作为一个“子例程”调用。


3.8 新版功能.

@end deffn

@geindex LOAD_FAST (opcode)
@anchor{library/dis opcode-LOAD_FAST}@anchor{38af}
@deffn {Opcode} LOAD_FAST (var_num)

将指向局部对象 @code{co_varnames[var_num]} 的引用推入栈顶。
@end deffn

@geindex STORE_FAST (opcode)
@anchor{library/dis opcode-STORE_FAST}@anchor{388f}
@deffn {Opcode} STORE_FAST (var_num)

将 TOS 存放到局部对象 @code{co_varnames[var_num]}。
@end deffn

@geindex DELETE_FAST (opcode)
@anchor{library/dis opcode-DELETE_FAST}@anchor{38b0}
@deffn {Opcode} DELETE_FAST (var_num)

移除局部对象 @code{co_varnames[var_num]}。
@end deffn

@geindex LOAD_CLOSURE (opcode)
@anchor{library/dis opcode-LOAD_CLOSURE}@anchor{38b1}
@deffn {Opcode} LOAD_CLOSURE (i)

将一个包含在单元的第 @emph{i} 个空位中的对单元的引用推入栈顶并释放可用的存储空间。 如果 @emph{i} 小于 @emph{co_cellvars} 的长度则变量的名称为 @code{co_cellvars[i]}。 否则为 @code{co_freevars[i - len(co_cellvars)]}。
@end deffn

@geindex LOAD_DEREF (opcode)
@anchor{library/dis opcode-LOAD_DEREF}@anchor{38b2}
@deffn {Opcode} LOAD_DEREF (i)

加载包含在单元的第 @emph{i} 个空位中的单元并释放可用的存储空间。 将一个对单元所包含对象的引用推入栈顶。
@end deffn

@geindex LOAD_CLASSDEREF (opcode)
@anchor{library/dis opcode-LOAD_CLASSDEREF}@anchor{928}
@deffn {Opcode} LOAD_CLASSDEREF (i)

类似于 @ref{38b2,,LOAD_DEREF} 但在查询单元之前会首先检查局部对象字典。 这被用于加载类语句体中的自由变量。


3.4 新版功能.

@end deffn

@geindex STORE_DEREF (opcode)
@anchor{library/dis opcode-STORE_DEREF}@anchor{38b3}
@deffn {Opcode} STORE_DEREF (i)

将 TOS 存放到包含在单元的第 @emph{i} 个空位中的单元内并释放可用存储空间。
@end deffn

@geindex DELETE_DEREF (opcode)
@anchor{library/dis opcode-DELETE_DEREF}@anchor{38b4}
@deffn {Opcode} DELETE_DEREF (i)

清空包含在单元的第 @emph{i} 个空位中的单元并释放可用存储空间。 被用于 @ref{1202,,del} 语句。


3.2 新版功能.

@end deffn

@geindex RAISE_VARARGS (opcode)
@anchor{library/dis opcode-RAISE_VARARGS}@anchor{38b5}
@deffn {Opcode} RAISE_VARARGS (argc)

使用 @code{raise} 语句的 3 种形式之一引发异常，具体形式取决于 @emph{argc} 的值：


@itemize *

@item 
0: @code{raise} (重新引发之前的异常)

@item 
1: @code{raise TOS} (在 @code{TOS} 上引发异常实例或类型)

@item 
2: @code{raise TOS1 from TOS} (在 @code{TOS1} 上引发异常实例或类型并将 @code{__cause__} 设为 @code{TOS})
@end itemize
@end deffn

@geindex CALL_FUNCTION (opcode)
@anchor{library/dis opcode-CALL_FUNCTION}@anchor{614}
@deffn {Opcode} CALL_FUNCTION (argc)

调用一个可调用对象并传入位置参数。 @emph{argc} 指明位置参数的数量。 栈顶包含位置参数，其中最右边的参数在最顶端。 在参数之下是一个待调用的可调用对象。 @code{CALL_FUNCTION} 会从栈中弹出所有参数以及可调用对象，附带这些参数调用该可调用对象，并将可调用对象所返回的返回值推入栈顶。


在 3.6 版更改: 此操作码仅用于附带位置参数的调用。

@end deffn

@geindex CALL_FUNCTION_KW (opcode)
@anchor{library/dis opcode-CALL_FUNCTION_KW}@anchor{615}
@deffn {Opcode} CALL_FUNCTION_KW (argc)

调用一个可调用对象并传入位置参数（如果有的话）和关键字参数。 @emph{argc} 指明位置参数和关键字参数的总数量。 栈顶元素包含一个关键字参数名称的元组。 在元组之下是根据元组排序的关键字参数。 在关键字参数之下是位置参数，其中最右边的参数在最顶端。 在参数之下是一个待调用的可调用对象。 @code{CALL_FUNCTION_KW} 会从栈中弹出所有参数以及可调用对象，附带这些参数调用该可调用对象，并将可调用对象所返回的返回值推入栈顶。


在 3.6 版更改: 关键字参数会被打包为一个元组而非字典，@emph{argc} 指明参数的总数量。

@end deffn

@geindex CALL_FUNCTION_EX (opcode)
@anchor{library/dis opcode-CALL_FUNCTION_EX}@anchor{617}
@deffn {Opcode} CALL_FUNCTION_EX (flags)

调用一个可调用对象并附带位置参数和关键字参数变量集合。 如果设置了 @emph{flags} 的最低位，则栈顶包含一个由额外关键字参数组成的映射对象。 在该对象之下是一个包含位置参数的可迭代对象和一个待调用的可调用对象。 @ref{616,,BUILD_MAP_UNPACK_WITH_CALL} 和 @ref{618,,BUILD_TUPLE_UNPACK_WITH_CALL} 可用于合并多个映射对象和包含参数的可迭代对象。  在该可调用对象被调用之前，映射对象和可迭代对象会被分别“解包”并将它们的内容分别作为关键字参数和位置参数传入。 @code{CALL_FUNCTION_EX} 会从栈中弹出所有参数以及可调用对象，附带这些参数调用该可调用对象，并将可调用对象所返回的返回值推入栈顶。


3.6 新版功能.

@end deffn

@geindex LOAD_METHOD (opcode)
@anchor{library/dis opcode-LOAD_METHOD}@anchor{4a8}
@deffn {Opcode} LOAD_METHOD (namei)

从 TOS 对象加载一个名为 @code{co_names[namei]} 的方法。 TOS 将被弹出。 此字节码可区分两种情况：如果 TOS 有一个名称正确的方法，字节码会将未绑定方法和 TOS 推入栈顶。 TOS 将在调用未绑定方法时被用作 @ref{4a9,,CALL_METHOD} 的第一个参数 (@code{self})。 否则会将 @code{NULL} 和属性查找所返回的对象推入栈顶。


3.7 新版功能.

@end deffn

@geindex CALL_METHOD (opcode)
@anchor{library/dis opcode-CALL_METHOD}@anchor{4a9}
@deffn {Opcode} CALL_METHOD (argc)

调用一个方法。 @emph{argc} 是位置参数的数量。 关键字参数不受支持。 此操作码被设计用于配合 @ref{4a8,,LOAD_METHOD} 使用。 位置参数放在栈顶。 在它们之下放在栈中的是由 @ref{4a8,,LOAD_METHOD} 所描述的两个条目（或者是 @code{self} 和一个未绑定方法对象，或者是 @code{NULL} 和一个任意可调用对象）。 它们会被全部弹出并将返回值推入栈顶。


3.7 新版功能.

@end deffn

@geindex MAKE_FUNCTION (opcode)
@anchor{library/dis opcode-MAKE_FUNCTION}@anchor{613}
@deffn {Opcode} MAKE_FUNCTION (flags)

将一个新函数对象推入栈顶。 从底端到顶端，如果参数带有指定的旗标值则所使用的栈必须由这些值组成。


@itemize *

@item 
@code{0x01} 一个默认值的元组，用于按位置排序的仅限位置形参以及位置或关键字形参

@item 
@code{0x02} 一个仅限关键字形参的默认值的字典

@item 
@code{0x04} 是一个标注字典

@item 
@code{0x08} 一个包含用于自由变量的单元的元组，生成一个闭包

@item 
与函数相关联的代码 (在 TOS1)

@item 
函数的 @ref{13c2,,qualified name} (在 TOS)
@end itemize
@end deffn

@geindex BUILD_SLICE (opcode)
@anchor{library/dis opcode-BUILD_SLICE}@anchor{38b6}
@deffn {Opcode} BUILD_SLICE (argc)

@geindex 內置函数; slice

将一个切片对象推入栈顶。 @emph{argc} 必须为 2 或 3。 如果为 2，则推入 @code{slice(TOS1, TOS)}；如果为 3，则推入 @code{slice(TOS2, TOS1, TOS)}。 请参阅 @ref{dfd,,slice()} 内置函数了解详细信息。
@end deffn

@geindex EXTENDED_ARG (opcode)
@anchor{library/dis opcode-EXTENDED_ARG}@anchor{38b7}
@deffn {Opcode} EXTENDED_ARG (ext)

为任意带有大到无法放入默认的单字节的参数的操作码添加前缀。 @emph{ext} 存放一个附加字节作为参数中的高比特位。 对于每个操作码，最多允许三个 @code{EXTENDED_ARG} 前缀，构成两字节到三字节的参数。
@end deffn

@geindex FORMAT_VALUE (opcode)
@anchor{library/dis opcode-FORMAT_VALUE}@anchor{610}
@deffn {Opcode} FORMAT_VALUE (flags)

用于实现格式化字面值字符串（f-字符串）。 从栈中弹出一个可选的 @emph{fmt_spec}，然后是一个必须的 @emph{value}。 @emph{flags} 的解读方式如下：


@itemize *

@item 
@code{(flags & 0x03) == 0x00}: @emph{value} 按原样格式化。

@item 
@code{(flags & 0x03) == 0x01}: 在格式化 @emph{value} 之前调用其 @ref{329,,str()}。

@item 
@code{(flags & 0x03) == 0x02}: 在格式化 @emph{value} 之前调用其 @ref{7c6,,repr()}。

@item 
@code{(flags & 0x03) == 0x03}: 在格式化 @emph{value} 之前调用其 @ref{d45,,ascii()}。

@item 
@code{(flags & 0x04) == 0x04}: 从栈中弹出 @emph{fmt_spec} 并使用它，否则使用空的 @emph{fmt_spec}。
@end itemize

使用 @code{PyObject_Format()} 执行格式化。 结果会被推入栈顶。


3.6 新版功能.

@end deffn

@geindex HAVE_ARGUMENT (opcode)
@anchor{library/dis opcode-HAVE_ARGUMENT}@anchor{38b8}
@deffn {Opcode} HAVE_ARGUMENT

这不是一个真正的操作码。 它用于标明使用参数和不使用参数的操作码 (分别为 @code{< HAVE_ARGUMENT} 和 @code{>= HAVE_ARGUMENT}) 之间的分隔线。


在 3.6 版更改: 现在每条指令都带有参数，但操作码 @code{< HAVE_ARGUMENT} 会忽略它。 之前仅限操作码 @code{>= HAVE_ARGUMENT} 带有参数。

@end deffn

@node 操作码集合,,Python字节码说明,dis --- Python 字节码反汇编器
@anchor{library/dis id1}@anchor{38b9}@anchor{library/dis opcode-collections}@anchor{384d}
@subsubsection 操作码集合


提供这些集合用于字节码指令的自动内省：

@geindex opname() (在 dis 模块中)
@anchor{library/dis dis opname}@anchor{38ba}
@deffn {数据} dis.opname

操作名称的序列，可使用字节码来索引。
@end deffn

@geindex opmap() (在 dis 模块中)
@anchor{library/dis dis opmap}@anchor{38bb}
@deffn {数据} dis.opmap

映射操作名称到字节码的字典
@end deffn

@geindex cmp_op() (在 dis 模块中)
@anchor{library/dis dis cmp_op}@anchor{38bc}
@deffn {数据} dis.cmp_op

所有比较操作名称的序列。
@end deffn

@geindex hasconst() (在 dis 模块中)
@anchor{library/dis dis hasconst}@anchor{38bd}
@deffn {数据} dis.hasconst

访问常量的字节码序列。
@end deffn

@geindex hasfree() (在 dis 模块中)
@anchor{library/dis dis hasfree}@anchor{38be}
@deffn {数据} dis.hasfree

访问自由变量的字节码序列（请注意这里所说的‘自由’是指在当前作用域中被内部作用域所引用的名称，或在外部作用域中被此作用域所引用的名称。 它 @emph{并不} 包括对全局或内置作用域的引用）。
@end deffn

@geindex hasname() (在 dis 模块中)
@anchor{library/dis dis hasname}@anchor{38bf}
@deffn {数据} dis.hasname

按名称访问属性的字节码序列。
@end deffn

@geindex hasjrel() (在 dis 模块中)
@anchor{library/dis dis hasjrel}@anchor{38c0}
@deffn {数据} dis.hasjrel

具有相对跳转目标的字节码序列。
@end deffn

@geindex hasjabs() (在 dis 模块中)
@anchor{library/dis dis hasjabs}@anchor{38c1}
@deffn {数据} dis.hasjabs

具有绝对跳转目标的字节码序列。
@end deffn

@geindex haslocal() (在 dis 模块中)
@anchor{library/dis dis haslocal}@anchor{38c2}
@deffn {数据} dis.haslocal

访问局部变量的字节码序列。
@end deffn

@geindex hascompare() (在 dis 模块中)
@anchor{library/dis dis hascompare}@anchor{38c3}
@deffn {数据} dis.hascompare

布尔运算的字节码序列。
@end deffn

@node pickletools --- pickle 开发者工具集,,dis --- Python 字节码反汇编器,Python 语言服务
@anchor{library/pickletools doc}@anchor{38c4}@anchor{library/pickletools module-pickletools}@anchor{cb}@anchor{library/pickletools pickletools-tools-for-pickle-developers}@anchor{38c5}
@subsection @code{pickletools} --- pickle 开发者工具集


@geindex pickletools (模块)

@strong{源代码:} Lib/pickletools.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pickletools.py}


__________________________________________________________________


此模块包含与 @ref{ca,,pickle} 模块内部细节有关的多个常量，一些关于具体实现的详细注释，以及一些能够分析封存数据的有用函数。 此模块的内容对需要操作 @ref{ca,,pickle} 的 Python 核心开发者来说很有用处；@ref{ca,,pickle} 的一般用户则可能会感觉 @ref{cb,,pickletools} 模块与他们无关。

@menu
* 命令行语法: 命令行语法<2>. 
* 编程接口: 编程接口<2>. 

@end menu

@node 命令行语法<2>,编程接口<2>,,pickletools --- pickle 开发者工具集
@anchor{library/pickletools command-line-usage}@anchor{38c6}
@subsubsection 命令行语法



3.2 新版功能.


当从命令行发起调用时，@code{python -m pickletools} 将对一个或更多 pickle 文件的内容进行拆解。 请注意如果你查看 pickle 中保存的 Python 对象而非 pickle 格式的细节，你可能需要改用 @code{-m pickle}。 但是，当你想检查的 pickle 文件来自某个不受信任的源时，@code{-m pickletools} 是更安全的选择，因为它不会执行 pickle 字节码。

例如，对于一个封存在文件 @code{x.pickle} 中的元组 @code{(1, 2)}:

@example
$ python -m pickle x.pickle
(1, 2)

$ python -m pickletools x.pickle
    0: \x80 PROTO      3
    2: K    BININT1    1
    4: K    BININT1    2
    6: \x86 TUPLE2
    7: q    BINPUT     0
    9: .    STOP
highest protocol among opcodes = 2
@end example

@menu
* 命令行选项: 命令行选项<6>. 

@end menu

@node 命令行选项<6>,,,命令行语法<2>
@anchor{library/pickletools command-line-options}@anchor{38c7}
@subsubsection 命令行选项


@geindex pickletools command line option; -a
@geindex pickletools command line option; --annotate
@anchor{library/pickletools cmdoption-pickletools-a}@anchor{38c8}
@deffn {程序选项} @w{-}a, @w{-}@w{-}annotate

使用简短的操作码描述来标注每一行。
@end deffn

@geindex pickletools command line option; -o
@geindex pickletools command line option; --output=<file>
@anchor{library/pickletools cmdoption-pickletools-o}@anchor{38c9}
@deffn {程序选项} @w{-}o, @w{-}@w{-}output=<file>

输出应当写入到的文件名称。
@end deffn

@geindex pickletools command line option; -l
@geindex pickletools command line option; --indentlevel=<num>
@anchor{library/pickletools cmdoption-pickletools-l}@anchor{38ca}
@deffn {程序选项} @w{-}l, @w{-}@w{-}indentlevel=<num>

一个新的 MARK 层级所需缩进的空格数。
@end deffn

@geindex pickletools command line option; -m
@geindex pickletools command line option; --memo
@anchor{library/pickletools cmdoption-pickletools-m}@anchor{38cb}
@deffn {程序选项} @w{-}m, @w{-}@w{-}memo

当反汇编多个对象时，保留各个反汇编的备忘记录。
@end deffn

@geindex pickletools command line option; -p
@geindex pickletools command line option; --preamble=<preamble>
@anchor{library/pickletools cmdoption-pickletools-p}@anchor{38cc}
@deffn {程序选项} @w{-}p, @w{-}@w{-}preamble=<preamble>

当指定一个以上的 pickle 文件时，在每次反汇编之前打印给定的前言。
@end deffn

@node 编程接口<2>,,命令行语法<2>,pickletools --- pickle 开发者工具集
@anchor{library/pickletools programmatic-interface}@anchor{38cd}
@subsubsection 编程接口


@geindex dis() (在 pickletools 模块中)
@anchor{library/pickletools pickletools dis}@anchor{56b}
@deffn {函数} pickletools.dis (pickle, out=None, memo=None, indentlevel=4, annotate=0)

将 pickle 的符号化反汇编数据输出到文件类对象 @emph{out}，默认为 @code{sys.stdout}。 @emph{pickle} 可以是一个字符串或一个文件类对象。 @emph{memo} 可以是一个将被用作 pickle 的备忘记录的 Python 字典；它可被用来对由同一封存器创建的多个封存对象执行反汇编。 由 @code{MARK} 操作码指明的每个连续级别将会缩进 @emph{indentlevel} 个空格。 如果为 @emph{annotate} 指定了一个非零值，则输出中的每个操作码将以一个简短描述来标注。 @emph{annotate} 的值会被用作标注所应开始的列的提示。


3.2 新版功能: @emph{annotate} 参数。

@end deffn

@geindex genops() (在 pickletools 模块中)
@anchor{library/pickletools pickletools genops}@anchor{38ce}
@deffn {函数} pickletools.genops (pickle)

提供包含 pickle 中所有操作码的 @ref{fce,,iterator}，返回一个 @code{(opcode, arg, pos)} 三元组的序列。 @emph{opcode} 是 @code{OpcodeInfo} 类的一个实例；@emph{arg} 是 Python 对象形式的 opcode 参数的已解码值；@emph{pos} 是 opcode 所在的位置。 @emph{pickle} 可以是一个字符串或一个文件类对象。
@end deffn

@geindex optimize() (在 pickletools 模块中)
@anchor{library/pickletools pickletools optimize}@anchor{1c51}
@deffn {函数} pickletools.optimize (picklestring)

在消除未使用的 @code{PUT} 操作码之后返回一个新的等效 pickle 字符串。 优化后的 pickle 将更为简短，耗费更为的传输时间，要求更少的存储空间并能更高效地解封。
@end deffn

@node 杂项服务,Windows系统相关模块,Python 语言服务,Python 标准库
@anchor{library/misc doc}@anchor{38cf}@anchor{library/misc misc}@anchor{38d0}@anchor{library/misc miscellaneous-services}@anchor{38d1}
@section 杂项服务


本章中介绍的模块提供了所有 Python 版本中提供的各种杂项服务。 这是一个概述：

@menu
* formatter: formatter --- 通用格式化输出. 通用格式化输出

@end menu

@node formatter --- 通用格式化输出,,,杂项服务
@anchor{library/formatter doc}@anchor{38d2}@anchor{library/formatter formatter-generic-output-formatting}@anchor{38d3}@anchor{library/formatter module-formatter}@anchor{82}
@subsection @code{formatter} --- 通用格式化输出


@geindex formatter (模块)


3.4 版后已移除: 因为被使用的次数很少，此格式化模块已经被弃用了。



__________________________________________________________________


This module supports two interface definitions, each with multiple
implementations: The @emph{formatter} interface, and the @emph{writer} interface which is
required by the formatter interface.

Formatter objects transform an abstract flow of formatting events into specific
output events on writer objects.  Formatters manage several stack structures to
allow various properties of a writer object to be changed and restored; writers
need not be able to handle relative changes nor any sort of "change back"
operation.  Specific writer properties which may be controlled via formatter
objects are horizontal alignment, font, and left margin indentations.  A
mechanism is provided which supports providing arbitrary, non-exclusive style
settings to a writer as well.  Additional interfaces facilitate formatting
events which are not reversible, such as paragraph separation.

Writer objects encapsulate device interfaces.  Abstract devices, such as file
formats, are supported as well as physical devices.  The provided
implementations all work with abstract devices.  The interface makes available
mechanisms for setting the properties which formatter objects manage and
inserting data into the output.

@menu
* The Formatter Interface:: 
* Formatter Implementations:: 
* The Writer Interface:: 
* Writer Implementations:: 

@end menu

@node The Formatter Interface,Formatter Implementations,,formatter --- 通用格式化输出
@anchor{library/formatter formatter-interface}@anchor{38d4}@anchor{library/formatter the-formatter-interface}@anchor{38d5}
@subsubsection The Formatter Interface


Interfaces to create formatters are dependent on the specific formatter class
being instantiated.  The interfaces described below are the required interfaces
which all formatters must support once initialized.

One data element is defined at the module level:

@geindex AS_IS() (在 formatter 模块中)
@anchor{library/formatter formatter AS_IS}@anchor{38d6}
@deffn {数据} formatter.AS_IS

Value which can be used in the font specification passed to the @code{push_font()}
method described below, or as the new value to any other @code{push_property()}
method.  Pushing the @code{AS_IS} value allows the corresponding @code{pop_property()}
method to be called without having to track whether the property was changed.
@end deffn

The following attributes are defined for formatter instance objects:

@geindex writer (formatter.formatter 属性)
@anchor{library/formatter formatter formatter writer}@anchor{38d7}
@deffn {属性} formatter.writer

The writer instance with which the formatter interacts.
@end deffn

@geindex end_paragraph() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter end_paragraph}@anchor{38d8}
@deffn {方法} formatter.end_paragraph (blanklines)

Close any open paragraphs and insert at least @emph{blanklines} before the next
paragraph.
@end deffn

@geindex add_line_break() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter add_line_break}@anchor{38d9}
@deffn {方法} formatter.add_line_break ()

Add a hard line break if one does not already exist.  This does not break the
logical paragraph.
@end deffn

@geindex add_hor_rule() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter add_hor_rule}@anchor{38da}
@deffn {方法} formatter.add_hor_rule (*args, **kw)

Insert a horizontal rule in the output.  A hard break is inserted if there is
data in the current paragraph, but the logical paragraph is not broken.  The
arguments and keywords are passed on to the writer's @code{send_line_break()}
method.
@end deffn

@geindex add_flowing_data() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter add_flowing_data}@anchor{38db}
@deffn {方法} formatter.add_flowing_data (data)

Provide data which should be formatted with collapsed whitespace. Whitespace
from preceding and successive calls to @ref{38db,,add_flowing_data()} is considered as
well when the whitespace collapse is performed.  The data which is passed to
this method is expected to be word-wrapped by the output device.  Note that any
word-wrapping still must be performed by the writer object due to the need to
rely on device and font information.
@end deffn

@geindex add_literal_data() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter add_literal_data}@anchor{38dc}
@deffn {方法} formatter.add_literal_data (data)

Provide data which should be passed to the writer unchanged. Whitespace,
including newline and tab characters, are considered legal in the value of
@emph{data}.
@end deffn

@geindex add_label_data() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter add_label_data}@anchor{38dd}
@deffn {方法} formatter.add_label_data (format, counter)

Insert a label which should be placed to the left of the current left margin.
This should be used for constructing bulleted or numbered lists.  If the
@emph{format} value is a string, it is interpreted as a format specification for
@emph{counter}, which should be an integer. The result of this formatting becomes the
value of the label; if @emph{format} is not a string it is used as the label value
directly. The label value is passed as the only argument to the writer's
@code{send_label_data()} method.  Interpretation of non-string label values is
dependent on the associated writer.

Format specifications are strings which, in combination with a counter value,
are used to compute label values.  Each character in the format string is copied
to the label value, with some characters recognized to indicate a transform on
the counter value.  Specifically, the character @code{'1'} represents the counter
value formatter as an Arabic number, the characters @code{'A'} and @code{'a'}
represent alphabetic representations of the counter value in upper and lower
case, respectively, and @code{'I'} and @code{'i'} represent the counter value in Roman
numerals, in upper and lower case.  Note that the alphabetic and roman
transforms require that the counter value be greater than zero.
@end deffn

@geindex flush_softspace() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter flush_softspace}@anchor{38de}
@deffn {方法} formatter.flush_softspace ()

Send any pending whitespace buffered from a previous call to
@ref{38db,,add_flowing_data()} to the associated writer object.  This should be called
before any direct manipulation of the writer object.
@end deffn

@geindex push_alignment() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter push_alignment}@anchor{38df}
@deffn {方法} formatter.push_alignment (align)

Push a new alignment setting onto the alignment stack.  This may be
@ref{38d6,,AS_IS} if no change is desired.  If the alignment value is changed from
the previous setting, the writer's @code{new_alignment()} method is called with
the @emph{align} value.
@end deffn

@geindex pop_alignment() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter pop_alignment}@anchor{38e0}
@deffn {方法} formatter.pop_alignment ()

Restore the previous alignment.
@end deffn

@geindex push_font() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter push_font}@anchor{38e1}
@deffn {方法} formatter.push_font ((size, italic, bold, teletype))

Change some or all font properties of the writer object.  Properties which are
not set to @ref{38d6,,AS_IS} are set to the values passed in while others are
maintained at their current settings.  The writer's @code{new_font()} method is
called with the fully resolved font specification.
@end deffn

@geindex pop_font() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter pop_font}@anchor{38e2}
@deffn {方法} formatter.pop_font ()

Restore the previous font.
@end deffn

@geindex push_margin() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter push_margin}@anchor{38e3}
@deffn {方法} formatter.push_margin (margin)

Increase the number of left margin indentations by one, associating the logical
tag @emph{margin} with the new indentation.  The initial margin level is @code{0}.
Changed values of the logical tag must be true values; false values other than
@ref{38d6,,AS_IS} are not sufficient to change the margin.
@end deffn

@geindex pop_margin() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter pop_margin}@anchor{38e4}
@deffn {方法} formatter.pop_margin ()

Restore the previous margin.
@end deffn

@geindex push_style() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter push_style}@anchor{38e5}
@deffn {方法} formatter.push_style (*styles)

Push any number of arbitrary style specifications.  All styles are pushed onto
the styles stack in order.  A tuple representing the entire stack, including
@ref{38d6,,AS_IS} values, is passed to the writer's @code{new_styles()} method.
@end deffn

@geindex pop_style() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter pop_style}@anchor{38e6}
@deffn {方法} formatter.pop_style (n=1)

Pop the last @emph{n} style specifications passed to @ref{38e5,,push_style()}.  A tuple
representing the revised stack, including @ref{38d6,,AS_IS} values, is passed to
the writer's @code{new_styles()} method.
@end deffn

@geindex set_spacing() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter set_spacing}@anchor{38e7}
@deffn {方法} formatter.set_spacing (spacing)

Set the spacing style for the writer.
@end deffn

@geindex assert_line_data() (formatter.formatter 方法)
@anchor{library/formatter formatter formatter assert_line_data}@anchor{38e8}
@deffn {方法} formatter.assert_line_data (flag=1)

Inform the formatter that data has been added to the current paragraph
out-of-band.  This should be used when the writer has been manipulated
directly.  The optional @emph{flag} argument can be set to false if the writer
manipulations produced a hard line break at the end of the output.
@end deffn

@node Formatter Implementations,The Writer Interface,The Formatter Interface,formatter --- 通用格式化输出
@anchor{library/formatter formatter-implementations}@anchor{38e9}@anchor{library/formatter formatter-impls}@anchor{38ea}
@subsubsection Formatter Implementations


Two implementations of formatter objects are provided by this module. Most
applications may use one of these classes without modification or subclassing.

@geindex NullFormatter (formatter 中的类)
@anchor{library/formatter formatter NullFormatter}@anchor{38eb}
@deffn {类} formatter.NullFormatter (writer=None)

A formatter which does nothing.  If @emph{writer} is omitted, a @ref{38ec,,NullWriter}
instance is created.  No methods of the writer are called by
@ref{38eb,,NullFormatter} instances.  Implementations should inherit from this
class if implementing a writer interface but don't need to inherit any
implementation.
@end deffn

@geindex AbstractFormatter (formatter 中的类)
@anchor{library/formatter formatter AbstractFormatter}@anchor{38ed}
@deffn {类} formatter.AbstractFormatter (writer)

The standard formatter.  This implementation has demonstrated wide applicability
to many writers, and may be used directly in most circumstances.  It has been
used to implement a full-featured World Wide Web browser.
@end deffn

@node The Writer Interface,Writer Implementations,Formatter Implementations,formatter --- 通用格式化输出
@anchor{library/formatter the-writer-interface}@anchor{38ee}@anchor{library/formatter writer-interface}@anchor{38ef}
@subsubsection The Writer Interface


Interfaces to create writers are dependent on the specific writer class being
instantiated.  The interfaces described below are the required interfaces which
all writers must support once initialized. Note that while most applications can
use the @ref{38ed,,AbstractFormatter} class as a formatter, the writer must
typically be provided by the application.

@geindex flush() (formatter.writer 方法)
@anchor{library/formatter formatter writer flush}@anchor{38f0}
@deffn {方法} writer.flush ()

Flush any buffered output or device control events.
@end deffn

@geindex new_alignment() (formatter.writer 方法)
@anchor{library/formatter formatter writer new_alignment}@anchor{38f1}
@deffn {方法} writer.new_alignment (align)

Set the alignment style.  The @emph{align} value can be any object, but by convention
is a string or @code{None}, where @code{None} indicates that the writer's "preferred"
alignment should be used. Conventional @emph{align} values are @code{'left'},
@code{'center'}, @code{'right'}, and @code{'justify'}.
@end deffn

@geindex new_font() (formatter.writer 方法)
@anchor{library/formatter formatter writer new_font}@anchor{38f2}
@deffn {方法} writer.new_font (font)

Set the font style.  The value of @emph{font} will be @code{None}, indicating that the
device's default font should be used, or a tuple of the form @code{(size,
italic, bold, teletype)}.  Size will be a string indicating the size of
font that should be used; specific strings and their interpretation must be
defined by the application.  The @emph{italic}, @emph{bold}, and @emph{teletype} values are
Boolean values specifying which of those font attributes should be used.
@end deffn

@geindex new_margin() (formatter.writer 方法)
@anchor{library/formatter formatter writer new_margin}@anchor{38f3}
@deffn {方法} writer.new_margin (margin, level)

Set the margin level to the integer @emph{level} and the logical tag to @emph{margin}.
Interpretation of the logical tag is at the writer's discretion; the only
restriction on the value of the logical tag is that it not be a false value for
non-zero values of @emph{level}.
@end deffn

@geindex new_spacing() (formatter.writer 方法)
@anchor{library/formatter formatter writer new_spacing}@anchor{38f4}
@deffn {方法} writer.new_spacing (spacing)

Set the spacing style to @emph{spacing}.
@end deffn

@geindex new_styles() (formatter.writer 方法)
@anchor{library/formatter formatter writer new_styles}@anchor{38f5}
@deffn {方法} writer.new_styles (styles)

Set additional styles.  The @emph{styles} value is a tuple of arbitrary values; the
value @ref{38d6,,AS_IS} should be ignored.  The @emph{styles} tuple may be interpreted
either as a set or as a stack depending on the requirements of the application
and writer implementation.
@end deffn

@geindex send_line_break() (formatter.writer 方法)
@anchor{library/formatter formatter writer send_line_break}@anchor{38f6}
@deffn {方法} writer.send_line_break ()

Break the current line.
@end deffn

@geindex send_paragraph() (formatter.writer 方法)
@anchor{library/formatter formatter writer send_paragraph}@anchor{38f7}
@deffn {方法} writer.send_paragraph (blankline)

Produce a paragraph separation of at least @emph{blankline} blank lines, or the
equivalent.  The @emph{blankline} value will be an integer.  Note that the
implementation will receive a call to @ref{38f6,,send_line_break()} before this call
if a line break is needed;  this method should not include ending the last line
of the paragraph. It is only responsible for vertical spacing between
paragraphs.
@end deffn

@geindex send_hor_rule() (formatter.writer 方法)
@anchor{library/formatter formatter writer send_hor_rule}@anchor{38f8}
@deffn {方法} writer.send_hor_rule (*args, **kw)

Display a horizontal rule on the output device.  The arguments to this method
are entirely application- and writer-specific, and should be interpreted with
care.  The method implementation may assume that a line break has already been
issued via @ref{38f6,,send_line_break()}.
@end deffn

@geindex send_flowing_data() (formatter.writer 方法)
@anchor{library/formatter formatter writer send_flowing_data}@anchor{38f9}
@deffn {方法} writer.send_flowing_data (data)

Output character data which may be word-wrapped and re-flowed as needed.  Within
any sequence of calls to this method, the writer may assume that spans of
multiple whitespace characters have been collapsed to single space characters.
@end deffn

@geindex send_literal_data() (formatter.writer 方法)
@anchor{library/formatter formatter writer send_literal_data}@anchor{38fa}
@deffn {方法} writer.send_literal_data (data)

Output character data which has already been formatted for display.  Generally,
this should be interpreted to mean that line breaks indicated by newline
characters should be preserved and no new line breaks should be introduced.  The
data may contain embedded newline and tab characters, unlike data provided to
the @code{send_formatted_data()} interface.
@end deffn

@geindex send_label_data() (formatter.writer 方法)
@anchor{library/formatter formatter writer send_label_data}@anchor{38fb}
@deffn {方法} writer.send_label_data (data)

Set @emph{data} to the left of the current left margin, if possible. The value of
@emph{data} is not restricted; treatment of non-string values is entirely
application- and writer-dependent.  This method will only be called at the
beginning of a line.
@end deffn

@node Writer Implementations,,The Writer Interface,formatter --- 通用格式化输出
@anchor{library/formatter writer-implementations}@anchor{38fc}@anchor{library/formatter writer-impls}@anchor{38fd}
@subsubsection Writer Implementations


Three implementations of the writer object interface are provided as examples by
this module.  Most applications will need to derive new writer classes from the
@ref{38ec,,NullWriter} class.

@geindex NullWriter (formatter 中的类)
@anchor{library/formatter formatter NullWriter}@anchor{38ec}
@deffn {类} formatter.NullWriter

A writer which only provides the interface definition; no actions are taken on
any methods.  This should be the base class for all writers which do not need to
inherit any implementation methods.
@end deffn

@geindex AbstractWriter (formatter 中的类)
@anchor{library/formatter formatter AbstractWriter}@anchor{38fe}
@deffn {类} formatter.AbstractWriter

A writer which can be used in debugging formatters, but not much else.  Each
method simply announces itself by printing its name and arguments on standard
output.
@end deffn

@geindex DumbWriter (formatter 中的类)
@anchor{library/formatter formatter DumbWriter}@anchor{38ff}
@deffn {类} formatter.DumbWriter (file=None, maxcol=72)

Simple writer class which writes output on the @ref{b3b,,file object} passed
in as @emph{file} or, if @emph{file} is omitted, on standard output.  The output is
simply word-wrapped to the number of columns specified by @emph{maxcol}.  This
class is suitable for reflowing a sequence of paragraphs.
@end deffn

@node Windows系统相关模块,Unix 专有服务,杂项服务,Python 标准库
@anchor{library/windows doc}@anchor{3900}@anchor{library/windows ms-windows-specific-services}@anchor{3901}@anchor{library/windows mswin-specific-services}@anchor{132c}
@section Windows系统相关模块


本章节叙述的模块只在 Windows 平台上可用。

@menu
* msilib: msilib --- Read and write Microsoft Installer files. Read and write Microsoft Installer files
* msvcrt: msvcrt --- 来自 MS VC++ 运行时的有用例程. 来自 MS VC++ 运行时的有用例程
* winreg: winreg --- Windows 注册表访问. Windows 注册表访问
* winsound: winsound --- Sound-playing interface for Windows. Sound-playing interface for Windows

@end menu

@node msilib --- Read and write Microsoft Installer files,msvcrt --- 来自 MS VC++ 运行时的有用例程,,Windows系统相关模块
@anchor{library/msilib doc}@anchor{3902}@anchor{library/msilib module-msilib}@anchor{b5}@anchor{library/msilib msilib-read-and-write-microsoft-installer-files}@anchor{3903}
@subsection @code{msilib} --- Read and write Microsoft Installer files


@geindex msilib (模块)

@strong{Source code:} Lib/msilib/__init__.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/msilib/__init__.py}

@geindex msi


__________________________________________________________________


The @ref{b5,,msilib} supports the creation of Microsoft Installer (@code{.msi}) files.
Because these files often contain an embedded "cabinet" file (@code{.cab}), it also
exposes an API to create CAB files. Support for reading @code{.cab} files is
currently not implemented; read support for the @code{.msi} database is possible.

This package aims to provide complete access to all tables in an @code{.msi} file,
therefore, it is a fairly low-level API. Two primary applications of this
package are the @ref{39,,distutils} command @code{bdist_msi}, and the creation of
Python installer package itself (although that currently uses a different
version of @code{msilib}).

The package contents can be roughly split into four parts: low-level CAB
routines, low-level MSI routines, higher-level MSI routines, and standard table
structures.

@geindex FCICreate() (在 msilib 模块中)
@anchor{library/msilib msilib FCICreate}@anchor{3904}
@deffn {函数} msilib.FCICreate (cabname, files)

Create a new CAB file named @emph{cabname}. @emph{files} must be a list of tuples, each
containing the name of the file on disk, and the name of the file inside the CAB
file.

The files are added to the CAB file in the order they appear in the list. All
files are added into a single CAB file, using the MSZIP compression algorithm.

Callbacks to Python for the various steps of MSI creation are currently not
exposed.
@end deffn

@geindex UuidCreate() (在 msilib 模块中)
@anchor{library/msilib msilib UuidCreate}@anchor{3905}
@deffn {函数} msilib.UuidCreate ()

Return the string representation of a new unique identifier. This wraps the
Windows API functions @code{UuidCreate()} and @code{UuidToString()}.
@end deffn

@geindex OpenDatabase() (在 msilib 模块中)
@anchor{library/msilib msilib OpenDatabase}@anchor{e9d}
@deffn {函数} msilib.OpenDatabase (path, persist)

Return a new database object by calling MsiOpenDatabase.   @emph{path} is the file
name of the MSI file; @emph{persist} can be one of the constants
@code{MSIDBOPEN_CREATEDIRECT}, @code{MSIDBOPEN_CREATE}, @code{MSIDBOPEN_DIRECT},
@code{MSIDBOPEN_READONLY}, or @code{MSIDBOPEN_TRANSACT}, and may include the flag
@code{MSIDBOPEN_PATCHFILE}. See the Microsoft documentation for the meaning of
these flags; depending on the flags, an existing database is opened, or a new
one created.
@end deffn

@geindex CreateRecord() (在 msilib 模块中)
@anchor{library/msilib msilib CreateRecord}@anchor{3906}
@deffn {函数} msilib.CreateRecord (count)

Return a new record object by calling @code{MSICreateRecord()}. @emph{count} is the
number of fields of the record.
@end deffn

@geindex init_database() (在 msilib 模块中)
@anchor{library/msilib msilib init_database}@anchor{e9e}
@deffn {函数} msilib.init_database (name, schema, ProductName, ProductCode, ProductVersion, Manufacturer)

Create and return a new database @emph{name}, initialize it with @emph{schema}, and set
the properties @emph{ProductName}, @emph{ProductCode}, @emph{ProductVersion}, and
@emph{Manufacturer}.

@emph{schema} must be a module object containing @code{tables} and
@code{_Validation_records} attributes; typically, @ref{3907,,msilib.schema} should be
used.

The database will contain just the schema and the validation records when this
function returns.
@end deffn

@geindex add_data() (在 msilib 模块中)
@anchor{library/msilib msilib add_data}@anchor{3908}
@deffn {函数} msilib.add_data (database, table, records)

Add all @emph{records} to the table named @emph{table} in @emph{database}.

The @emph{table} argument must be one of the predefined tables in the MSI schema,
e.g. @code{'Feature'}, @code{'File'}, @code{'Component'}, @code{'Dialog'}, @code{'Control'},
etc.

@emph{records} should be a list of tuples, each one containing all fields of a
record according to the schema of the table.  For optional fields,
@code{None} can be passed.

Field values can be ints, strings, or instances of the Binary class.
@end deffn

@geindex Binary (msilib 中的类)
@anchor{library/msilib msilib Binary}@anchor{3909}
@deffn {类} msilib.Binary (filename)

Represents entries in the Binary table; inserting such an object using
@ref{3908,,add_data()} reads the file named @emph{filename} into the table.
@end deffn

@geindex add_tables() (在 msilib 模块中)
@anchor{library/msilib msilib add_tables}@anchor{390a}
@deffn {函数} msilib.add_tables (database, module)

Add all table content from @emph{module} to @emph{database}. @emph{module} must contain an
attribute @emph{tables} listing all tables for which content should be added, and one
attribute per table that has the actual content.

This is typically used to install the sequence tables.
@end deffn

@geindex add_stream() (在 msilib 模块中)
@anchor{library/msilib msilib add_stream}@anchor{390b}
@deffn {函数} msilib.add_stream (database, name, path)

Add the file @emph{path} into the @code{_Stream} table of @emph{database}, with the stream
name @emph{name}.
@end deffn

@geindex gen_uuid() (在 msilib 模块中)
@anchor{library/msilib msilib gen_uuid}@anchor{390c}
@deffn {函数} msilib.gen_uuid ()

Return a new UUID, in the format that MSI typically requires (i.e. in curly
braces, and with all hexdigits in upper-case).
@end deffn


@subsubheading 参见


FCICreate@footnote{https://msdn.microsoft.com/en-us/library/bb432265.aspx}
UuidCreate@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa379205.aspx}
UuidToString@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa379352.aspx}


@menu
* Database Objects:: 
* View Objects:: 
* Summary Information Objects:: 
* Record Objects:: 
* Errors:: 
* CAB Objects:: 
* Directory Objects:: 
* 相关特性: 相关特性<3>. 
* GUI classes:: 
* Precomputed tables:: 

@end menu

@node Database Objects,View Objects,,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib database-objects}@anchor{390d}@anchor{library/msilib id1}@anchor{390e}
@subsubsection Database Objects


@geindex OpenView() (msilib.Database 方法)
@anchor{library/msilib msilib Database OpenView}@anchor{e9f}
@deffn {方法} Database.OpenView (sql)

Return a view object, by calling @code{MSIDatabaseOpenView()}. @emph{sql} is the SQL
statement to execute.
@end deffn

@geindex Commit() (msilib.Database 方法)
@anchor{library/msilib msilib Database Commit}@anchor{390f}
@deffn {方法} Database.Commit ()

Commit the changes pending in the current transaction, by calling
@code{MSIDatabaseCommit()}.
@end deffn

@geindex GetSummaryInformation() (msilib.Database 方法)
@anchor{library/msilib msilib Database GetSummaryInformation}@anchor{3910}
@deffn {方法} Database.GetSummaryInformation (count)

Return a new summary information object, by calling
@code{MsiGetSummaryInformation()}.  @emph{count} is the maximum number of updated
values.
@end deffn

@geindex Close() (msilib.Database 方法)
@anchor{library/msilib msilib Database Close}@anchor{3a6}
@deffn {方法} Database.Close ()

Close the database object, through @code{MsiCloseHandle()}.


3.7 新版功能.

@end deffn


@subsubheading 参见


MSIDatabaseOpenView@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370082.aspx}
MSIDatabaseCommit@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370075.aspx}
MSIGetSummaryInformation@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370301.aspx}
MsiCloseHandle@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370067.aspx}


@node View Objects,Summary Information Objects,Database Objects,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib id2}@anchor{3911}@anchor{library/msilib view-objects}@anchor{3912}
@subsubsection View Objects


@geindex Execute() (msilib.View 方法)
@anchor{library/msilib msilib View Execute}@anchor{3913}
@deffn {方法} View.Execute (params)

Execute the SQL query of the view, through @code{MSIViewExecute()}. If
@emph{params} is not @code{None}, it is a record describing actual values of the
parameter tokens in the query.
@end deffn

@geindex GetColumnInfo() (msilib.View 方法)
@anchor{library/msilib msilib View GetColumnInfo}@anchor{3914}
@deffn {方法} View.GetColumnInfo (kind)

Return a record describing the columns of the view, through calling
@code{MsiViewGetColumnInfo()}. @emph{kind} can be either @code{MSICOLINFO_NAMES} or
@code{MSICOLINFO_TYPES}.
@end deffn

@geindex Fetch() (msilib.View 方法)
@anchor{library/msilib msilib View Fetch}@anchor{3915}
@deffn {方法} View.Fetch ()

Return a result record of the query, through calling @code{MsiViewFetch()}.
@end deffn

@geindex Modify() (msilib.View 方法)
@anchor{library/msilib msilib View Modify}@anchor{3916}
@deffn {方法} View.Modify (kind, data)

Modify the view, by calling @code{MsiViewModify()}. @emph{kind} can be one of
@code{MSIMODIFY_SEEK}, @code{MSIMODIFY_REFRESH}, @code{MSIMODIFY_INSERT},
@code{MSIMODIFY_UPDATE}, @code{MSIMODIFY_ASSIGN}, @code{MSIMODIFY_REPLACE},
@code{MSIMODIFY_MERGE}, @code{MSIMODIFY_DELETE}, @code{MSIMODIFY_INSERT_TEMPORARY},
@code{MSIMODIFY_VALIDATE}, @code{MSIMODIFY_VALIDATE_NEW},
@code{MSIMODIFY_VALIDATE_FIELD}, or @code{MSIMODIFY_VALIDATE_DELETE}.

@emph{data} must be a record describing the new data.
@end deffn

@geindex Close() (msilib.View 方法)
@anchor{library/msilib msilib View Close}@anchor{3917}
@deffn {方法} View.Close ()

Close the view, through @code{MsiViewClose()}.
@end deffn


@subsubheading 参见


MsiViewExecute@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370513.aspx}
MSIViewGetColumnInfo@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370516.aspx}
MsiViewFetch@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370514.aspx}
MsiViewModify@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370519.aspx}
MsiViewClose@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370510.aspx}


@node Summary Information Objects,Record Objects,View Objects,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib summary-information-objects}@anchor{3918}@anchor{library/msilib summary-objects}@anchor{3919}
@subsubsection Summary Information Objects


@geindex GetProperty() (msilib.SummaryInformation 方法)
@anchor{library/msilib msilib SummaryInformation GetProperty}@anchor{f53}
@deffn {方法} SummaryInformation.GetProperty (field)

Return a property of the summary, through @code{MsiSummaryInfoGetProperty()}.
@emph{field} is the name of the property, and can be one of the constants
@code{PID_CODEPAGE}, @code{PID_TITLE}, @code{PID_SUBJECT}, @code{PID_AUTHOR},
@code{PID_KEYWORDS}, @code{PID_COMMENTS}, @code{PID_TEMPLATE}, @code{PID_LASTAUTHOR},
@code{PID_REVNUMBER}, @code{PID_LASTPRINTED}, @code{PID_CREATE_DTM},
@code{PID_LASTSAVE_DTM}, @code{PID_PAGECOUNT}, @code{PID_WORDCOUNT}, @code{PID_CHARCOUNT},
@code{PID_APPNAME}, or @code{PID_SECURITY}.
@end deffn

@geindex GetPropertyCount() (msilib.SummaryInformation 方法)
@anchor{library/msilib msilib SummaryInformation GetPropertyCount}@anchor{391a}
@deffn {方法} SummaryInformation.GetPropertyCount ()

Return the number of summary properties, through
@code{MsiSummaryInfoGetPropertyCount()}.
@end deffn

@geindex SetProperty() (msilib.SummaryInformation 方法)
@anchor{library/msilib msilib SummaryInformation SetProperty}@anchor{391b}
@deffn {方法} SummaryInformation.SetProperty (field, value)

Set a property through @code{MsiSummaryInfoSetProperty()}. @emph{field} can have the
same values as in @ref{f53,,GetProperty()}, @emph{value} is the new value of the property.
Possible value types are integer and string.
@end deffn

@geindex Persist() (msilib.SummaryInformation 方法)
@anchor{library/msilib msilib SummaryInformation Persist}@anchor{391c}
@deffn {方法} SummaryInformation.Persist ()

Write the modified properties to the summary information stream, using
@code{MsiSummaryInfoPersist()}.
@end deffn


@subsubheading 参见


MsiSummaryInfoGetProperty@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370409.aspx}
MsiSummaryInfoGetPropertyCount@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370488.aspx}
MsiSummaryInfoSetProperty@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370491.aspx}
MsiSummaryInfoPersist@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370490.aspx}


@node Record Objects,Errors,Summary Information Objects,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib id3}@anchor{391d}@anchor{library/msilib record-objects}@anchor{391e}
@subsubsection Record Objects


@geindex GetFieldCount() (msilib.Record 方法)
@anchor{library/msilib msilib Record GetFieldCount}@anchor{391f}
@deffn {方法} Record.GetFieldCount ()

Return the number of fields of the record, through
@code{MsiRecordGetFieldCount()}.
@end deffn

@geindex GetInteger() (msilib.Record 方法)
@anchor{library/msilib msilib Record GetInteger}@anchor{3920}
@deffn {方法} Record.GetInteger (field)

Return the value of @emph{field} as an integer where possible.  @emph{field} must
be an integer.
@end deffn

@geindex GetString() (msilib.Record 方法)
@anchor{library/msilib msilib Record GetString}@anchor{3921}
@deffn {方法} Record.GetString (field)

Return the value of @emph{field} as a string where possible.  @emph{field} must
be an integer.
@end deffn

@geindex SetString() (msilib.Record 方法)
@anchor{library/msilib msilib Record SetString}@anchor{3922}
@deffn {方法} Record.SetString (field, value)

Set @emph{field} to @emph{value} through @code{MsiRecordSetString()}. @emph{field} must be an
integer; @emph{value} a string.
@end deffn

@geindex SetStream() (msilib.Record 方法)
@anchor{library/msilib msilib Record SetStream}@anchor{3923}
@deffn {方法} Record.SetStream (field, value)

Set @emph{field} to the contents of the file named @emph{value}, through
@code{MsiRecordSetStream()}. @emph{field} must be an integer; @emph{value} a string.
@end deffn

@geindex SetInteger() (msilib.Record 方法)
@anchor{library/msilib msilib Record SetInteger}@anchor{3924}
@deffn {方法} Record.SetInteger (field, value)

Set @emph{field} to @emph{value} through @code{MsiRecordSetInteger()}. Both @emph{field} and
@emph{value} must be an integer.
@end deffn

@geindex ClearData() (msilib.Record 方法)
@anchor{library/msilib msilib Record ClearData}@anchor{3925}
@deffn {方法} Record.ClearData ()

Set all fields of the record to 0, through @code{MsiRecordClearData()}.
@end deffn


@subsubheading 参见


MsiRecordGetFieldCount@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370366.aspx}
MsiRecordSetString@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370373.aspx}
MsiRecordSetStream@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370372.aspx}
MsiRecordSetInteger@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370371.aspx}
MsiRecordClearData@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370364.aspx}


@node Errors,CAB Objects,Record Objects,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib errors}@anchor{3926}@anchor{library/msilib msi-errors}@anchor{3927}
@subsubsection Errors


All wrappers around MSI functions raise @code{MSIError}; the string inside the
exception will contain more detail.

@node CAB Objects,Directory Objects,Errors,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib cab}@anchor{3928}@anchor{library/msilib cab-objects}@anchor{3929}
@subsubsection CAB Objects


@geindex CAB (msilib 中的类)
@anchor{library/msilib msilib CAB}@anchor{392a}
@deffn {类} msilib.CAB (name)

The class @ref{392a,,CAB} represents a CAB file. During MSI construction, files
will be added simultaneously to the @code{Files} table, and to a CAB file. Then,
when all files have been added, the CAB file can be written, then added to the
MSI file.

@emph{name} is the name of the CAB file in the MSI file.

@geindex append() (msilib.CAB 方法)
@anchor{library/msilib msilib CAB append}@anchor{392b}
@deffn {方法} append (full, file, logical)

Add the file with the pathname @emph{full} to the CAB file, under the name
@emph{logical}.  If there is already a file named @emph{logical}, a new file name is
created.

Return the index of the file in the CAB file, and the new name of the file
inside the CAB file.
@end deffn

@geindex commit() (msilib.CAB 方法)
@anchor{library/msilib msilib CAB commit}@anchor{392c}
@deffn {方法} commit (database)

Generate a CAB file, add it as a stream to the MSI file, put it into the
@code{Media} table, and remove the generated file from the disk.
@end deffn
@end deffn

@node Directory Objects,相关特性<3>,CAB Objects,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib directory-objects}@anchor{392d}@anchor{library/msilib msi-directory}@anchor{392e}
@subsubsection Directory Objects


@geindex Directory (msilib 中的类)
@anchor{library/msilib msilib Directory}@anchor{392f}
@deffn {类} msilib.Directory (database, cab, basedir, physical, logical, default[, componentflags])

Create a new directory in the Directory table. There is a current component at
each point in time for the directory, which is either explicitly created through
@ref{f54,,start_component()}, or implicitly when files are added for the first time.
Files are added into the current component, and into the cab file.  To create a
directory, a base directory object needs to be specified (can be @code{None}), the
path to the physical directory, and a logical directory name.  @emph{default}
specifies the DefaultDir slot in the directory table. @emph{componentflags} specifies
the default flags that new components get.

@geindex start_component() (msilib.Directory 方法)
@anchor{library/msilib msilib Directory start_component}@anchor{f54}
@deffn {方法} start_component (component=None, feature=None, flags=None, keyfile=None, uuid=None)

Add an entry to the Component table, and make this component the current
component for this directory. If no component name is given, the directory
name is used. If no @emph{feature} is given, the current feature is used. If no
@emph{flags} are given, the directory's default flags are used. If no @emph{keyfile}
is given, the KeyPath is left null in the Component table.
@end deffn

@geindex add_file() (msilib.Directory 方法)
@anchor{library/msilib msilib Directory add_file}@anchor{3930}
@deffn {方法} add_file (file, src=None, version=None, language=None)

Add a file to the current component of the directory, starting a new one
if there is no current component. By default, the file name in the source
and the file table will be identical. If the @emph{src} file is specified, it
is interpreted relative to the current directory. Optionally, a @emph{version}
and a @emph{language} can be specified for the entry in the File table.
@end deffn

@geindex glob() (msilib.Directory 方法)
@anchor{library/msilib msilib Directory glob}@anchor{3931}
@deffn {方法} glob (pattern, exclude=None)

Add a list of files to the current component as specified in the glob
pattern.  Individual files can be excluded in the @emph{exclude} list.
@end deffn

@geindex remove_pyc() (msilib.Directory 方法)
@anchor{library/msilib msilib Directory remove_pyc}@anchor{3932}
@deffn {方法} remove_pyc ()

Remove @code{.pyc} files on uninstall.
@end deffn
@end deffn


@subsubheading 参见


Directory Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368295.aspx}
File Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368596.aspx}
Component Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368007.aspx}
FeatureComponents Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368579.aspx}


@node 相关特性<3>,GUI classes,Directory Objects,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib features}@anchor{3933}@anchor{library/msilib id4}@anchor{3934}
@subsubsection 相关特性


@geindex Feature (msilib 中的类)
@anchor{library/msilib msilib Feature}@anchor{3935}
@deffn {类} msilib.Feature (db, id, title, desc, display, level=1, parent=None, directory=None, attributes=0)

Add a new record to the @code{Feature} table, using the values @emph{id}, @emph{parent.id},
@emph{title}, @emph{desc}, @emph{display}, @emph{level}, @emph{directory}, and @emph{attributes}. The
resulting feature object can be passed to the @code{start_component()} method of
@ref{392f,,Directory}.

@geindex set_current() (msilib.Feature 方法)
@anchor{library/msilib msilib Feature set_current}@anchor{3936}
@deffn {方法} set_current ()

Make this feature the current feature of @ref{b5,,msilib}. New components are
automatically added to the default feature, unless a feature is explicitly
specified.
@end deffn
@end deffn


@subsubheading 参见


Feature Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368585.aspx}


@node GUI classes,Precomputed tables,相关特性<3>,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib gui-classes}@anchor{3937}@anchor{library/msilib msi-gui}@anchor{3938}
@subsubsection GUI classes


@ref{b5,,msilib} provides several classes that wrap the GUI tables in an MSI
database. However, no standard user interface is provided; use
@ref{41,,bdist_msi} to create MSI files with a user-interface
for installing Python packages.

@geindex Control (msilib 中的类)
@anchor{library/msilib msilib Control}@anchor{3939}
@deffn {类} msilib.Control (dlg, name)

Base class of the dialog controls. @emph{dlg} is the dialog object the control
belongs to, and @emph{name} is the control's name.

@geindex event() (msilib.Control 方法)
@anchor{library/msilib msilib Control event}@anchor{393a}
@deffn {方法} event (event, argument, condition=1, ordering=None)

Make an entry into the @code{ControlEvent} table for this control.
@end deffn

@geindex mapping() (msilib.Control 方法)
@anchor{library/msilib msilib Control mapping}@anchor{393b}
@deffn {方法} mapping (event, attribute)

Make an entry into the @code{EventMapping} table for this control.
@end deffn

@geindex condition() (msilib.Control 方法)
@anchor{library/msilib msilib Control condition}@anchor{393c}
@deffn {方法} condition (action, condition)

Make an entry into the @code{ControlCondition} table for this control.
@end deffn
@end deffn

@geindex RadioButtonGroup (msilib 中的类)
@anchor{library/msilib msilib RadioButtonGroup}@anchor{393d}
@deffn {类} msilib.RadioButtonGroup (dlg, name, property)

Create a radio button control named @emph{name}. @emph{property} is the installer property
that gets set when a radio button is selected.

@geindex add() (msilib.RadioButtonGroup 方法)
@anchor{library/msilib msilib RadioButtonGroup add}@anchor{393e}
@deffn {方法} add (name, x, y, width, height, text, value=None)

Add a radio button named @emph{name} to the group, at the coordinates @emph{x}, @emph{y},
@emph{width}, @emph{height}, and with the label @emph{text}. If @emph{value} is @code{None}, it
defaults to @emph{name}.
@end deffn
@end deffn

@geindex Dialog (msilib 中的类)
@anchor{library/msilib msilib Dialog}@anchor{393f}
@deffn {类} msilib.Dialog (db, name, x, y, w, h, attr, title, first, default, cancel)

Return a new @ref{393f,,Dialog} object. An entry in the @code{Dialog} table is made,
with the specified coordinates, dialog attributes, title, name of the first,
default, and cancel controls.

@geindex control() (msilib.Dialog 方法)
@anchor{library/msilib msilib Dialog control}@anchor{3940}
@deffn {方法} control (name, type, x, y, width, height, attributes, property, text, control_next, help)

Return a new @ref{3939,,Control} object. An entry in the @code{Control} table is
made with the specified parameters.

This is a generic method; for specific types, specialized methods are
provided.
@end deffn

@geindex text() (msilib.Dialog 方法)
@anchor{library/msilib msilib Dialog text}@anchor{3941}
@deffn {方法} text (name, x, y, width, height, attributes, text)

Add and return a @code{Text} control.
@end deffn

@geindex bitmap() (msilib.Dialog 方法)
@anchor{library/msilib msilib Dialog bitmap}@anchor{3942}
@deffn {方法} bitmap (name, x, y, width, height, text)

Add and return a @code{Bitmap} control.
@end deffn

@geindex line() (msilib.Dialog 方法)
@anchor{library/msilib msilib Dialog line}@anchor{3943}
@deffn {方法} line (name, x, y, width, height)

Add and return a @code{Line} control.
@end deffn

@geindex pushbutton() (msilib.Dialog 方法)
@anchor{library/msilib msilib Dialog pushbutton}@anchor{3944}
@deffn {方法} pushbutton (name, x, y, width, height, attributes, text, next_control)

Add and return a @code{PushButton} control.
@end deffn

@geindex radiogroup() (msilib.Dialog 方法)
@anchor{library/msilib msilib Dialog radiogroup}@anchor{3945}
@deffn {方法} radiogroup (name, x, y, width, height, attributes, property, text, next_control)

Add and return a @code{RadioButtonGroup} control.
@end deffn

@geindex checkbox() (msilib.Dialog 方法)
@anchor{library/msilib msilib Dialog checkbox}@anchor{3946}
@deffn {方法} checkbox (name, x, y, width, height, attributes, property, text, next_control)

Add and return a @code{CheckBox} control.
@end deffn
@end deffn


@subsubheading 参见


Dialog Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368286.aspx}
Control Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368044.aspx}
Control Types@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368039.aspx}
ControlCondition Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368035.aspx}
ControlEvent Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368037.aspx}
EventMapping Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa368559.aspx}
RadioButton Table@footnote{https://msdn.microsoft.com/en-us/library/windows/desktop/aa370962.aspx}


@node Precomputed tables,,GUI classes,msilib --- Read and write Microsoft Installer files
@anchor{library/msilib msi-tables}@anchor{3947}@anchor{library/msilib precomputed-tables}@anchor{3948}
@subsubsection Precomputed tables


@ref{b5,,msilib} provides a few subpackages that contain only schema and table
definitions. Currently, these definitions are based on MSI version 2.0.

@geindex schema() (在 msilib 模块中)
@anchor{library/msilib msilib schema}@anchor{3907}
@deffn {数据} msilib.schema

This is the standard MSI schema for MSI 2.0, with the @emph{tables} variable
providing a list of table definitions, and @emph{_Validation_records} providing the
data for MSI validation.
@end deffn

@geindex sequence() (在 msilib 模块中)
@anchor{library/msilib msilib sequence}@anchor{3949}
@deffn {数据} msilib.sequence

This module contains table contents for the standard sequence tables:
@emph{AdminExecuteSequence}, @emph{AdminUISequence}, @emph{AdvtExecuteSequence},
@emph{InstallExecuteSequence}, and @emph{InstallUISequence}.
@end deffn

@geindex text() (在 msilib 模块中)
@anchor{library/msilib msilib text}@anchor{394a}
@deffn {数据} msilib.text

This module contains definitions for the UIText and ActionText tables, for the
standard installer actions.
@end deffn

@node msvcrt --- 来自 MS VC++ 运行时的有用例程,winreg --- Windows 注册表访问,msilib --- Read and write Microsoft Installer files,Windows系统相关模块
@anchor{library/msvcrt doc}@anchor{394b}@anchor{library/msvcrt module-msvcrt}@anchor{b6}@anchor{library/msvcrt msvcrt-useful-routines-from-the-ms-vc-runtime}@anchor{394c}
@subsection @code{msvcrt} --- 来自 MS VC++ 运行时的有用例程


@geindex msvcrt (模块)


__________________________________________________________________


这些函数提供了对 Windows 平台上一些有用功能的访问。一些更高级别的模块使用这些函数来构建其服务的 Windows 实现。 例如， @ref{88,,getpass} 模块在实现 @ref{88,,getpass()} 函数时使用了这些函数。

关于这些函数的更多信息可以在平台 API 文档中找到。

该模块实现了控制台 I/O API 的普通和宽字符变体。普通的 API 只处理ASCII字符，国际化应用受限。应该尽可能地使用宽字符 API 。


在 3.3 版更改: Operations in this module now raise @ref{1d3,,OSError} where @ref{98c,,IOError}
was raised.


@menu
* File Operations:: 
* Console I/O:: 
* Other Functions:: 

@end menu

@node File Operations,Console I/O,,msvcrt --- 来自 MS VC++ 运行时的有用例程
@anchor{library/msvcrt file-operations}@anchor{394d}@anchor{library/msvcrt msvcrt-files}@anchor{394e}
@subsubsection File Operations


@geindex locking() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt locking}@anchor{3473}
@deffn {函数} msvcrt.locking (fd, mode, nbytes)

Lock part of a file based on file descriptor @emph{fd} from the C runtime.  Raises
@ref{1d3,,OSError} on failure.  The locked region of the file extends from the
current file position for @emph{nbytes} bytes, and may continue beyond the end of the
file.  @emph{mode} must be one of the @code{LK_*} constants listed below. Multiple
regions in a file may be locked at the same time, but may not overlap.  Adjacent
regions are not merged; they must be unlocked individually.

Raises an @ref{12d0,,auditing event} @code{msvcrt.locking} with arguments @code{fd}, @code{mode}, @code{nbytes}.
@end deffn

@geindex LK_LOCK() (在 msvcrt 模块中)
@geindex LK_RLCK() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt LK_LOCK}@anchor{394f}
@deffn {数据} msvcrt.LK_LOCK
@anchor{library/msvcrt msvcrt LK_RLCK}@anchor{3950}
@deffnx {数据} msvcrt.LK_RLCK

Locks the specified bytes. If the bytes cannot be locked, the program
immediately tries again after 1 second.  If, after 10 attempts, the bytes cannot
be locked, @ref{1d3,,OSError} is raised.
@end deffn

@geindex LK_NBLCK() (在 msvcrt 模块中)
@geindex LK_NBRLCK() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt LK_NBLCK}@anchor{3951}
@deffn {数据} msvcrt.LK_NBLCK
@anchor{library/msvcrt msvcrt LK_NBRLCK}@anchor{3952}
@deffnx {数据} msvcrt.LK_NBRLCK

Locks the specified bytes. If the bytes cannot be locked, @ref{1d3,,OSError} is
raised.
@end deffn

@geindex LK_UNLCK() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt LK_UNLCK}@anchor{3953}
@deffn {数据} msvcrt.LK_UNLCK

Unlocks the specified bytes, which must have been previously locked.
@end deffn

@geindex setmode() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt setmode}@anchor{3954}
@deffn {函数} msvcrt.setmode (fd, flags)

Set the line-end translation mode for the file descriptor @emph{fd}. To set it to
text mode, @emph{flags} should be @ref{1ebe,,os.O_TEXT}; for binary, it should be
@ref{1eaf,,os.O_BINARY}.
@end deffn

@geindex open_osfhandle() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt open_osfhandle}@anchor{3474}
@deffn {函数} msvcrt.open_osfhandle (handle, flags)

Create a C runtime file descriptor from the file handle @emph{handle}.  The @emph{flags}
parameter should be a bitwise OR of @ref{1eb1,,os.O_APPEND}, @ref{1ead,,os.O_RDONLY},
and @ref{1ebe,,os.O_TEXT}.  The returned file descriptor may be used as a parameter
to @ref{13c9,,os.fdopen()} to create a file object.

Raises an @ref{12d0,,auditing event} @code{msvcrt.open_osfhandle} with arguments @code{handle}, @code{flags}.
@end deffn

@geindex get_osfhandle() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt get_osfhandle}@anchor{3472}
@deffn {函数} msvcrt.get_osfhandle (fd)

Return the file handle for the file descriptor @emph{fd}.  Raises @ref{1d3,,OSError} if
@emph{fd} is not recognized.

Raises an @ref{12d0,,auditing event} @code{msvcrt.get_osfhandle} with argument @code{fd}.
@end deffn

@node Console I/O,Other Functions,File Operations,msvcrt --- 来自 MS VC++ 运行时的有用例程
@anchor{library/msvcrt console-i-o}@anchor{3955}@anchor{library/msvcrt msvcrt-console}@anchor{3956}
@subsubsection Console I/O


@geindex kbhit() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt kbhit}@anchor{3957}
@deffn {函数} msvcrt.kbhit ()

Return @code{True} if a keypress is waiting to be read.
@end deffn

@geindex getch() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt getch}@anchor{3958}
@deffn {函数} msvcrt.getch ()

Read a keypress and return the resulting character as a byte string.
Nothing is echoed to the console.  This call will block if a keypress
is not already available, but will not wait for @code{Enter} to be
pressed. If the pressed key was a special function key, this will
return @code{'\000'} or @code{'\xe0'}; the next call will return the keycode.
The @code{Control-C} keypress cannot be read with this function.
@end deffn

@geindex getwch() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt getwch}@anchor{3959}
@deffn {函数} msvcrt.getwch ()

Wide char variant of @ref{3958,,getch()}, returning a Unicode value.
@end deffn

@geindex getche() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt getche}@anchor{395a}
@deffn {函数} msvcrt.getche ()

Similar to @ref{3958,,getch()}, but the keypress will be echoed if it  represents a
printable character.
@end deffn

@geindex getwche() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt getwche}@anchor{395b}
@deffn {函数} msvcrt.getwche ()

Wide char variant of @ref{395a,,getche()}, returning a Unicode value.
@end deffn

@geindex putch() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt putch}@anchor{395c}
@deffn {函数} msvcrt.putch (char)

Print the byte string @emph{char} to the console without buffering.
@end deffn

@geindex putwch() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt putwch}@anchor{395d}
@deffn {函数} msvcrt.putwch (unicode_char)

Wide char variant of @ref{395c,,putch()}, accepting a Unicode value.
@end deffn

@geindex ungetch() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt ungetch}@anchor{395e}
@deffn {函数} msvcrt.ungetch (char)

Cause the byte string @emph{char} to be "pushed back" into the console buffer;
it will be the next character read by @ref{3958,,getch()} or @ref{395a,,getche()}.
@end deffn

@geindex ungetwch() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt ungetwch}@anchor{395f}
@deffn {函数} msvcrt.ungetwch (unicode_char)

Wide char variant of @ref{395e,,ungetch()}, accepting a Unicode value.
@end deffn

@node Other Functions,,Console I/O,msvcrt --- 来自 MS VC++ 运行时的有用例程
@anchor{library/msvcrt msvcrt-other}@anchor{3960}@anchor{library/msvcrt other-functions}@anchor{3961}
@subsubsection Other Functions


@geindex heapmin() (在 msvcrt 模块中)
@anchor{library/msvcrt msvcrt heapmin}@anchor{3962}
@deffn {函数} msvcrt.heapmin ()

Force the @code{malloc()} heap to clean itself up and return unused blocks to
the operating system.  On failure, this raises @ref{1d3,,OSError}.
@end deffn

@node winreg --- Windows 注册表访问,winsound --- Sound-playing interface for Windows,msvcrt --- 来自 MS VC++ 运行时的有用例程,Windows系统相关模块
@anchor{library/winreg doc}@anchor{3963}@anchor{library/winreg module-winreg}@anchor{12a}@anchor{library/winreg winreg-windows-registry-access}@anchor{3964}
@subsection @code{winreg} --- Windows 注册表访问


@geindex winreg (模块)


__________________________________________________________________


这些函数将 Windows 注册表 API 暴露给 Python。为了确保即便程序员忽略了显式关闭句柄，该句柄依然能够正确关闭，它使用了一个 @ref{3965,,handle 对象} 而不是整数来作为注册表句柄。
@anchor{library/winreg exception-changed}@anchor{3966}

在 3.3 版更改: 该模块中的几个函数被用于引发 @ref{98e,,WindowsError}，该异常现在是 @ref{1d3,,OSError} 的别名。


@menu
* 函数: 函数<11>. 
* 常量: 常量<10>. 
* Registry Handle Objects:: 

@end menu

@node 函数<11>,常量<10>,,winreg --- Windows 注册表访问
@anchor{library/winreg functions}@anchor{3967}@anchor{library/winreg id1}@anchor{3968}
@subsubsection 函数


该模块提供了下列函数：

@geindex CloseKey() (在 winreg 模块中)
@anchor{library/winreg winreg CloseKey}@anchor{3969}
@deffn {函数} winreg.CloseKey (hkey)

关闭之前打开的注册表键。参数 @emph{hkey} 指之前打开的键。

@cartouche
@quotation 注解 
如果没有使用该方法关闭 @emph{hkey} (或者通过 @ref{396a,,hkey.Close()})，在对象 @emph{hkey} 被 Python 销毁时会将其关闭。
@end quotation
@end cartouche
@end deffn

@geindex ConnectRegistry() (在 winreg 模块中)
@anchor{library/winreg winreg ConnectRegistry}@anchor{347a}
@deffn {函数} winreg.ConnectRegistry (computer_name, key)

建立到另一台计算上上的预定义注册表句柄的连接，并返回一个 @ref{3965,,handle 对象}.

@emph{computer_name} 是远程计算机的名称，以 @code{r"\\computername"} 的形式。如果是 @code{None} ，将会使用本地计算机。

@emph{key} 是所连接到的预定义句柄。

返回值是所开打键的句柄。如果函数失败，则引发一个 @ref{1d3,,OSError} 异常。

引发一个 @ref{12d0,,审计事件} @code{winreg.ConnectRegistry}，附带参数 @code{computer_name}, @code{key}。


在 3.3 版更改: 参考 @ref{3966,,上文}。

@end deffn

@geindex CreateKey() (在 winreg 模块中)
@anchor{library/winreg winreg CreateKey}@anchor{347b}
@deffn {函数} winreg.CreateKey (key, sub_key)

创建或打开特定的键，返回一个 @ref{3965,,handle 对象}。

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{sub_key} 是用于命名该方法所打开或创建的键的字符串。

如果 @emph{key} 是预定义键之一，@emph{sub_key} 可能会是 @code{None}。该情况下，返回的句柄就是传入函数的句柄。

如果键已经存在，则该函数打开已经存在的该键。

返回值是所开打键的句柄。如果函数失败，则引发一个 @ref{1d3,,OSError} 异常。

引发一个 @ref{12d0,,审计事件} @code{winreg.CreateKey}，附带参数 @code{key}, @code{sub_key}, @code{access}。

引发一个 @ref{12d0,,审计事件} @code{winreg.OpenKey/result}，附带参数 @code{key}。


在 3.3 版更改: 参考 @ref{3966,,上文}。

@end deffn

@geindex CreateKeyEx() (在 winreg 模块中)
@anchor{library/winreg winreg CreateKeyEx}@anchor{347c}
@deffn {函数} winreg.CreateKeyEx (key, sub_key, reserved=0, access=KEY_WRITE)

创建或打开特定的键，返回一个 @ref{3965,,handle 对象}。

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{sub_key} 是用于命名该方法所打开或创建的键的字符串。

@emph{reserved} 是一个保留的证书，必须是零。默认值为零。

@emph{access} 为一个整数，用于给键的预期安全访问指定访问掩码。默认值为 @ref{396c,,KEY_WRITE}。 参阅 @ref{396d,,Access Rights}  了解其它允许值。

如果 @emph{key} 是预定义键之一，@emph{sub_key} 可能会是 @code{None}。该情况下，返回的句柄就是传入函数的句柄。

如果键已经存在，则该函数打开已经存在的该键。

返回值是所开打键的句柄。如果函数失败，则引发一个 @ref{1d3,,OSError} 异常。

引发一个 @ref{12d0,,审计事件} @code{winreg.CreateKey}，附带参数 @code{key}, @code{sub_key}, @code{access}。

引发一个 @ref{12d0,,审计事件} @code{winreg.OpenKey/result}，附带参数 @code{key}。


3.2 新版功能.



在 3.3 版更改: 参考 @ref{3966,,上文}。

@end deffn

@geindex DeleteKey() (在 winreg 模块中)
@anchor{library/winreg winreg DeleteKey}@anchor{347d}
@deffn {函数} winreg.DeleteKey (key, sub_key)

删除指定的键。

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{sub_key} 这个字符串必须是由 @emph{key} 参数所指定键的一个子项。该值项不可以是 @code{None}，同时键也不可以有子项。

@emph{该方法不能删除带有子项的键。}

如果方法成功，则整个键，包括其所有值项都会被移除。如果方法失败，则引发一个 @ref{1d3,,OSError} 异常。

引发一个 @ref{12d0,,审计事件} @code{winreg.DeleteKey}，附带参数 @code{key}, @code{sub_key}, @code{access}。


在 3.3 版更改: 参考 @ref{3966,,上文}。

@end deffn

@geindex DeleteKeyEx() (在 winreg 模块中)
@anchor{library/winreg winreg DeleteKeyEx}@anchor{347e}
@deffn {函数} winreg.DeleteKeyEx (key, sub_key, access=KEY_WOW64_64KEY, reserved=0)

删除指定的键。

@cartouche
@quotation 注解 
函数 @ref{347e,,DeleteKeyEx()} 通过 RegDeleteKeyEx 这个 Windows API 函数实现，该函数为 Windows 的64位版本专属。 参阅 RegDeleteKeyEx 文档@footnote{https://msdn.microsoft.com/en-us/library/ms724847%28VS.85%29.aspx}。
@end quotation
@end cartouche

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{sub_key} 这个字符串必须是由 @emph{key} 参数所指定键的一个子项。该值项不可以是 @code{None}，同时键也不可以有子项。

@emph{reserved} 是一个保留的证书，必须是零。默认值为零。

@emph{access} 为一个整数，用于给键的预期安全访问指定访问掩码。默认值为常量 @code{_WOW64_64KEY} 。参阅 @ref{396d,,Access Rights}  了解其它允许值。

@emph{该方法不能删除带有子项的键。}

如果方法成功，则整个键，包括其所有值项都会被移除。如果方法失败，则引发一个 @ref{1d3,,OSError} 异常。

在不支持的 Windows 版本之上，将会引发 @ref{609,,NotImplementedError} 异常。

引发一个 @ref{12d0,,审计事件} @code{winreg.DeleteKey}，附带参数 @code{key}, @code{sub_key}, @code{access}。


3.2 新版功能.



在 3.3 版更改: 参考 @ref{3966,,上文}。

@end deffn

@geindex DeleteValue() (在 winreg 模块中)
@anchor{library/winreg winreg DeleteValue}@anchor{347f}
@deffn {函数} winreg.DeleteValue (key, value)

从某个注册键中删除一个命名值项。

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{value} 为标识所要删除值项的字符串。

引发一个 @ref{12d0,,审计事件} @code{winreg.DeleteValue}，附带参数 @code{key}, @code{value}。
@end deffn

@geindex EnumKey() (在 winreg 模块中)
@anchor{library/winreg winreg EnumKey}@anchor{3482}
@deffn {函数} winreg.EnumKey (key, index)

列举某个已经打开注册表键的子项，并返回一个字符串。

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{index} 为一个整数，用于标识所获取键的索引。

每次调用该函数都会获取一个子项的名字。通常它会被反复调用，直到引发 @ref{1d3,,OSError} 异常，这说明已经没有更多的可用值了。

引发一个 @ref{12d0,,审计事件} @code{winreg.EnumKey}，附带参数 @code{key}, @code{index}。


在 3.3 版更改: 参考 @ref{3966,,上文}。

@end deffn

@geindex EnumValue() (在 winreg 模块中)
@anchor{library/winreg winreg EnumValue}@anchor{3483}
@deffn {函数} winreg.EnumValue (key, index)

列举某个已经打开注册表键的值项，并返回一个元组。

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{index} 为一个整数，用于标识要获取值项的索引。

每次调用该函数都会获取一个子项的名字。通常它会被反复调用，直到引发 @ref{1d3,,OSError} 异常，这说明已经没有更多的可用值了。

结果为3元素的元组。


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

含义

@item

@code{0}

@tab

用于标识值项名称的字符串。

@item

@code{1}

@tab

保存值项数据的对象，其类型取决于背后的注册表类型。

@item

@code{2}

@tab

标识值项数据类型的整数。（请查阅 @ref{348e,,SetValueEx()} 文档中的表格）

@end multitable


引发一个 @ref{12d0,,审计事件} @code{winreg.EnumValue}，附带参数 @code{key}, @code{index}。


在 3.3 版更改: 参考 @ref{3966,,上文}。

@end deffn

@geindex % (percent); environment variables expansion (Windows)

@geindex ExpandEnvironmentStrings() (在 winreg 模块中)
@anchor{library/winreg winreg ExpandEnvironmentStrings}@anchor{3484}
@deffn {函数} winreg.ExpandEnvironmentStrings (str)

Expands environment variable placeholders @code{%NAME%} in strings like
@ref{396e,,REG_EXPAND_SZ}:

@example
>>> ExpandEnvironmentStrings('%windir%')
'C:\\Windows'
@end example

引发一个 @ref{12d0,,审计事件} @code{winreg.ExpandEnvironmentStrings}，附带参数 @code{str}。
@end deffn

@geindex FlushKey() (在 winreg 模块中)
@anchor{library/winreg winreg FlushKey}@anchor{396f}
@deffn {函数} winreg.FlushKey (key)

将某个键的所有属性写入注册表。

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

It is not necessary to call @ref{396f,,FlushKey()} to change a key. Registry changes are
flushed to disk by the registry using its lazy flusher.  Registry changes are
also flushed to disk at system shutdown.  Unlike @ref{3969,,CloseKey()}, the
@ref{396f,,FlushKey()} method returns only when all the data has been written to the
registry. An application should only call @ref{396f,,FlushKey()} if it requires
absolute certainty that registry changes are on disk.

@cartouche
@quotation 注解 
If you don't know whether a @ref{396f,,FlushKey()} call is required, it probably
isn't.
@end quotation
@end cartouche
@end deffn

@geindex LoadKey() (在 winreg 模块中)
@anchor{library/winreg winreg LoadKey}@anchor{3485}
@deffn {函数} winreg.LoadKey (key, sub_key, file_name)

Creates a subkey under the specified key and stores registration information
from a specified file into that subkey.

@emph{key} is a handle returned by @ref{347a,,ConnectRegistry()} or one of the constants
@ref{3970,,HKEY_USERS} or @ref{3971,,HKEY_LOCAL_MACHINE}.

@emph{sub_key} is a string that identifies the subkey to load.

@emph{file_name} is the name of the file to load registry data from. This file must
have been created with the @ref{348c,,SaveKey()} function. Under the file allocation
table (FAT) file system, the filename may not have an extension.

A call to @ref{3485,,LoadKey()} fails if the calling process does not have the
@code{SE_RESTORE_PRIVILEGE} privilege.  Note that privileges are different
from permissions -- see the RegLoadKey documentation@footnote{https://msdn.microsoft.com/en-us/library/ms724889%28v=VS.85%29.aspx} for
more details.

If @emph{key} is a handle returned by @ref{347a,,ConnectRegistry()}, then the path
specified in @emph{file_name} is relative to the remote computer.

引发一个 @ref{12d0,,审计事件} @code{winreg.LoadKey}，附带参数 @code{key}, @code{sub_key}, @code{file_name}。
@end deffn

@geindex OpenKey() (在 winreg 模块中)
@geindex OpenKeyEx() (在 winreg 模块中)
@anchor{library/winreg winreg OpenKey}@anchor{3486}
@deffn {函数} winreg.OpenKey (key, sub_key, reserved=0, access=KEY_READ)
@anchor{library/winreg winreg OpenKeyEx}@anchor{3972}
@deffnx {函数} winreg.OpenKeyEx (key, sub_key, reserved=0, access=KEY_READ)

Opens the specified key, returning a @ref{3965,,handle object}.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{sub_key} is a string that identifies the sub_key to open.

@emph{reserved} is a reserved integer, and must be zero.  The default is zero.

@emph{access} is an integer that specifies an access mask that describes the desired
security access for the key.  Default is @ref{3973,,KEY_READ}.  See @ref{396d,,Access Rights} for other allowed values.

The result is a new handle to the specified key.

If the function fails, @ref{1d3,,OSError} is raised.

引发一个 @ref{12d0,,审计事件} @code{winreg.OpenKey}，附带参数 @code{key}, @code{sub_key}, @code{access}。

引发一个 @ref{12d0,,审计事件} @code{winreg.OpenKey/result}，附带参数 @code{key}。


在 3.2 版更改: Allow the use of named arguments.



在 3.3 版更改: 参考 @ref{3966,,上文}。

@end deffn

@geindex QueryInfoKey() (在 winreg 模块中)
@anchor{library/winreg winreg QueryInfoKey}@anchor{3488}
@deffn {函数} winreg.QueryInfoKey (key)

Returns information about a key, as a tuple.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

结果为3元素的元组。


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

含义

@item

@code{0}

@tab

An integer giving the number of sub keys
this key has.

@item

@code{1}

@tab

An integer giving the number of values this
key has.

@item

@code{2}

@tab

An integer giving when the key was last
modified (if available) as 100's of
nanoseconds since Jan 1, 1601.

@end multitable


引发一个 @ref{12d0,,审计事件} @code{winreg.QueryInfoKey}，附带参数 @code{key}。
@end deffn

@geindex QueryValue() (在 winreg 模块中)
@anchor{library/winreg winreg QueryValue}@anchor{348a}
@deffn {函数} winreg.QueryValue (key, sub_key)

Retrieves the unnamed value for a key, as a string.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{sub_key} is a string that holds the name of the subkey with which the value is
associated.  If this parameter is @code{None} or empty, the function retrieves the
value set by the @ref{348d,,SetValue()} method for the key identified by @emph{key}.

Values in the registry have name, type, and data components. This method
retrieves the data for a key's first value that has a @code{NULL} name. But the
underlying API call doesn't return the type, so always use
@ref{348b,,QueryValueEx()} if possible.

引发一个 @ref{12d0,,审计事件} @code{winreg.QueryValue}，附带参数 @code{key}, @code{sub_key}, @code{value_name}。
@end deffn

@geindex QueryValueEx() (在 winreg 模块中)
@anchor{library/winreg winreg QueryValueEx}@anchor{348b}
@deffn {函数} winreg.QueryValueEx (key, value_name)

Retrieves the type and data for a specified value name associated with
an open registry key.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{value_name} is a string indicating the value to query.

The result is a tuple of 2 items:


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

含义

@item

@code{0}

@tab

The value of the registry item.

@item

@code{1}

@tab

An integer giving the registry type for
this value (see table in docs for
@ref{348e,,SetValueEx()})

@end multitable


引发一个 @ref{12d0,,审计事件} @code{winreg.QueryValue}，附带参数 @code{key}, @code{sub_key}, @code{value_name}。
@end deffn

@geindex SaveKey() (在 winreg 模块中)
@anchor{library/winreg winreg SaveKey}@anchor{348c}
@deffn {函数} winreg.SaveKey (key, file_name)

Saves the specified key, and all its subkeys to the specified file.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{file_name} is the name of the file to save registry data to.  This file
cannot already exist. If this filename includes an extension, it cannot be
used on file allocation table (FAT) file systems by the @ref{3485,,LoadKey()}
method.

If @emph{key} represents a key on a remote computer, the path described by
@emph{file_name} is relative to the remote computer. The caller of this method must
possess the @code{SeBackupPrivilege} security privilege.  Note that
privileges are different than permissions -- see the
Conflicts Between User Rights and Permissions documentation@footnote{https://msdn.microsoft.com/en-us/library/ms724878%28v=VS.85%29.aspx}
for more details.

This function passes @code{NULL} for @emph{security_attributes} to the API.

引发一个 @ref{12d0,,审计事件} @code{winreg.SaveKey}，附带参数 @code{key}, @code{file_name}。
@end deffn

@geindex SetValue() (在 winreg 模块中)
@anchor{library/winreg winreg SetValue}@anchor{348d}
@deffn {函数} winreg.SetValue (key, sub_key, type, value)

Associates a value with a specified key.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{sub_key} is a string that names the subkey with which the value is associated.

@emph{type} is an integer that specifies the type of the data. Currently this must be
@ref{3974,,REG_SZ}, meaning only strings are supported.  Use the @ref{348e,,SetValueEx()}
function for support for other data types.

@emph{value} is a string that specifies the new value.

If the key specified by the @emph{sub_key} parameter does not exist, the SetValue
function creates it.

Value lengths are limited by available memory. Long values (more than 2048
bytes) should be stored as files with the filenames stored in the configuration
registry.  This helps the registry perform efficiently.

The key identified by the @emph{key} parameter must have been opened with
@ref{3975,,KEY_SET_VALUE} access.

引发一个 @ref{12d0,,审计事件} @code{winreg.SetValue}，附带参数 @code{key}, @code{sub_key}, @code{type}, @code{value}。
@end deffn

@geindex SetValueEx() (在 winreg 模块中)
@anchor{library/winreg winreg SetValueEx}@anchor{348e}
@deffn {函数} winreg.SetValueEx (key, value_name, reserved, type, value)

Stores data in the value field of an open registry key.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

@emph{value_name} is a string that names the subkey with which the value is
associated.

@emph{reserved} can be anything -- zero is always passed to the API.

@emph{type} is an integer that specifies the type of the data. See
@ref{3976,,Value Types} for the available types.

@emph{value} is a string that specifies the new value.

This method can also set additional value and type information for the specified
key.  The key identified by the key parameter must have been opened with
@ref{3975,,KEY_SET_VALUE} access.

To open the key, use the @ref{347b,,CreateKey()} or @ref{3486,,OpenKey()} methods.

Value lengths are limited by available memory. Long values (more than 2048
bytes) should be stored as files with the filenames stored in the configuration
registry.  This helps the registry perform efficiently.

引发一个 @ref{12d0,,审计事件} @code{winreg.SetValue}，附带参数 @code{key}, @code{sub_key}, @code{type}, @code{value}。
@end deffn

@geindex DisableReflectionKey() (在 winreg 模块中)
@anchor{library/winreg winreg DisableReflectionKey}@anchor{3480}
@deffn {函数} winreg.DisableReflectionKey (key)

Disables registry reflection for 32-bit processes running on a 64-bit
operating system.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

Will generally raise @ref{609,,NotImplementedError} if executed on a 32-bit operating
system.

If the key is not on the reflection list, the function succeeds but has no
effect.  Disabling reflection for a key does not affect reflection of any
subkeys.

引发一个 @ref{12d0,,审计事件} @code{winreg.DisableReflectionKey}，附带参数 @code{key}。
@end deffn

@geindex EnableReflectionKey() (在 winreg 模块中)
@anchor{library/winreg winreg EnableReflectionKey}@anchor{3481}
@deffn {函数} winreg.EnableReflectionKey (key)

Restores registry reflection for the specified disabled key.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

Will generally raise @ref{609,,NotImplementedError} if executed on a 32-bit operating
system.

Restoring reflection for a key does not affect reflection of any subkeys.

引发一个 @ref{12d0,,审计事件} @code{winreg.EnableReflectionKey}，附带参数 @code{key}。
@end deffn

@geindex QueryReflectionKey() (在 winreg 模块中)
@anchor{library/winreg winreg QueryReflectionKey}@anchor{3489}
@deffn {函数} winreg.QueryReflectionKey (key)

Determines the reflection state for the specified key.

@emph{key} 为某个已经打开的键，或者预定义的 @ref{396b,,HKEY_* 常量} 之一。

Returns @code{True} if reflection is disabled.

Will generally raise @ref{609,,NotImplementedError} if executed on a 32-bit
operating system.

引发一个 @ref{12d0,,审计事件} @code{winreg.QueryReflectionKey}，附带参数 @code{key}。
@end deffn

@node 常量<10>,Registry Handle Objects,函数<11>,winreg --- Windows 注册表访问
@anchor{library/winreg constants}@anchor{3977}@anchor{library/winreg id2}@anchor{3978}
@subsubsection 常量


The following constants are defined for use in many @code{_winreg} functions.

@menu
* HKEY_* Constants:: 
* Access Rights:: 
* Value Types:: 

@end menu

@node HKEY_* Constants,Access Rights,,常量<10>
@anchor{library/winreg hkey-constants}@anchor{396b}@anchor{library/winreg id3}@anchor{3979}
@subsubsection HKEY_* Constants


@geindex HKEY_CLASSES_ROOT() (在 winreg 模块中)
@anchor{library/winreg winreg HKEY_CLASSES_ROOT}@anchor{397a}
@deffn {数据} winreg.HKEY_CLASSES_ROOT

Registry entries subordinate to this key define types (or classes) of
documents and the properties associated with those types. Shell and
COM applications use the information stored under this key.
@end deffn

@geindex HKEY_CURRENT_USER() (在 winreg 模块中)
@anchor{library/winreg winreg HKEY_CURRENT_USER}@anchor{397b}
@deffn {数据} winreg.HKEY_CURRENT_USER

Registry entries subordinate to this key define the preferences of
the current user. These preferences include the settings of
environment variables, data about program groups, colors, printers,
network connections, and application preferences.
@end deffn

@geindex HKEY_LOCAL_MACHINE() (在 winreg 模块中)
@anchor{library/winreg winreg HKEY_LOCAL_MACHINE}@anchor{3971}
@deffn {数据} winreg.HKEY_LOCAL_MACHINE

Registry entries subordinate to this key define the physical state
of the computer, including data about the bus type, system memory,
and installed hardware and software.
@end deffn

@geindex HKEY_USERS() (在 winreg 模块中)
@anchor{library/winreg winreg HKEY_USERS}@anchor{3970}
@deffn {数据} winreg.HKEY_USERS

Registry entries subordinate to this key define the default user
configuration for new users on the local computer and the user
configuration for the current user.
@end deffn

@geindex HKEY_PERFORMANCE_DATA() (在 winreg 模块中)
@anchor{library/winreg winreg HKEY_PERFORMANCE_DATA}@anchor{397c}
@deffn {数据} winreg.HKEY_PERFORMANCE_DATA

Registry entries subordinate to this key allow you to access
performance data. The data is not actually stored in the registry;
the registry functions cause the system to collect the data from
its source.
@end deffn

@geindex HKEY_CURRENT_CONFIG() (在 winreg 模块中)
@anchor{library/winreg winreg HKEY_CURRENT_CONFIG}@anchor{397d}
@deffn {数据} winreg.HKEY_CURRENT_CONFIG

Contains information about the current hardware profile of the
local computer system.
@end deffn

@geindex HKEY_DYN_DATA() (在 winreg 模块中)
@anchor{library/winreg winreg HKEY_DYN_DATA}@anchor{397e}
@deffn {数据} winreg.HKEY_DYN_DATA

This key is not used in versions of Windows after 98.
@end deffn

@node Access Rights,Value Types,HKEY_* Constants,常量<10>
@anchor{library/winreg access-rights}@anchor{396d}@anchor{library/winreg id4}@anchor{397f}
@subsubsection Access Rights


For more information, see Registry Key Security and Access@footnote{https://msdn.microsoft.com/en-us/library/ms724878%28v=VS.85%29.aspx}.

@geindex KEY_ALL_ACCESS() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_ALL_ACCESS}@anchor{3980}
@deffn {数据} winreg.KEY_ALL_ACCESS

Combines the STANDARD_RIGHTS_REQUIRED, @ref{3981,,KEY_QUERY_VALUE},
@ref{3975,,KEY_SET_VALUE}, @ref{3982,,KEY_CREATE_SUB_KEY},
@ref{3983,,KEY_ENUMERATE_SUB_KEYS}, @ref{3984,,KEY_NOTIFY},
and @ref{3985,,KEY_CREATE_LINK} access rights.
@end deffn

@geindex KEY_WRITE() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_WRITE}@anchor{396c}
@deffn {数据} winreg.KEY_WRITE

Combines the STANDARD_RIGHTS_WRITE, @ref{3975,,KEY_SET_VALUE}, and
@ref{3982,,KEY_CREATE_SUB_KEY} access rights.
@end deffn

@geindex KEY_READ() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_READ}@anchor{3973}
@deffn {数据} winreg.KEY_READ

Combines the STANDARD_RIGHTS_READ, @ref{3981,,KEY_QUERY_VALUE},
@ref{3983,,KEY_ENUMERATE_SUB_KEYS}, and @ref{3984,,KEY_NOTIFY} values.
@end deffn

@geindex KEY_EXECUTE() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_EXECUTE}@anchor{3986}
@deffn {数据} winreg.KEY_EXECUTE

Equivalent to @ref{3973,,KEY_READ}.
@end deffn

@geindex KEY_QUERY_VALUE() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_QUERY_VALUE}@anchor{3981}
@deffn {数据} winreg.KEY_QUERY_VALUE

Required to query the values of a registry key.
@end deffn

@geindex KEY_SET_VALUE() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_SET_VALUE}@anchor{3975}
@deffn {数据} winreg.KEY_SET_VALUE

Required to create, delete, or set a registry value.
@end deffn

@geindex KEY_CREATE_SUB_KEY() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_CREATE_SUB_KEY}@anchor{3982}
@deffn {数据} winreg.KEY_CREATE_SUB_KEY

Required to create a subkey of a registry key.
@end deffn

@geindex KEY_ENUMERATE_SUB_KEYS() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_ENUMERATE_SUB_KEYS}@anchor{3983}
@deffn {数据} winreg.KEY_ENUMERATE_SUB_KEYS

Required to enumerate the subkeys of a registry key.
@end deffn

@geindex KEY_NOTIFY() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_NOTIFY}@anchor{3984}
@deffn {数据} winreg.KEY_NOTIFY

Required to request change notifications for a registry key or for
subkeys of a registry key.
@end deffn

@geindex KEY_CREATE_LINK() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_CREATE_LINK}@anchor{3985}
@deffn {数据} winreg.KEY_CREATE_LINK

Reserved for system use.
@end deffn

@menu
* 64-bit Specific:: 

@end menu

@node 64-bit Specific,,,Access Rights
@anchor{library/winreg bit-access-rights}@anchor{3987}@anchor{library/winreg bit-specific}@anchor{3988}
@subsubsection 64-bit Specific


For more information, see Accessing an Alternate Registry View@footnote{https://msdn.microsoft.com/en-us/library/aa384129(v=VS.85).aspx}.

@geindex KEY_WOW64_64KEY() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_WOW64_64KEY}@anchor{3989}
@deffn {数据} winreg.KEY_WOW64_64KEY

Indicates that an application on 64-bit Windows should operate on
the 64-bit registry view.
@end deffn

@geindex KEY_WOW64_32KEY() (在 winreg 模块中)
@anchor{library/winreg winreg KEY_WOW64_32KEY}@anchor{398a}
@deffn {数据} winreg.KEY_WOW64_32KEY

Indicates that an application on 64-bit Windows should operate on
the 32-bit registry view.
@end deffn

@node Value Types,,Access Rights,常量<10>
@anchor{library/winreg id5}@anchor{398b}@anchor{library/winreg value-types}@anchor{3976}
@subsubsection Value Types


For more information, see Registry Value Types@footnote{https://msdn.microsoft.com/en-us/library/ms724884%28v=VS.85%29.aspx}.

@geindex REG_BINARY() (在 winreg 模块中)
@anchor{library/winreg winreg REG_BINARY}@anchor{398c}
@deffn {数据} winreg.REG_BINARY

Binary data in any form.
@end deffn

@geindex REG_DWORD() (在 winreg 模块中)
@anchor{library/winreg winreg REG_DWORD}@anchor{398d}
@deffn {数据} winreg.REG_DWORD

32-bit number.
@end deffn

@geindex REG_DWORD_LITTLE_ENDIAN() (在 winreg 模块中)
@anchor{library/winreg winreg REG_DWORD_LITTLE_ENDIAN}@anchor{398e}
@deffn {数据} winreg.REG_DWORD_LITTLE_ENDIAN

A 32-bit number in little-endian format. Equivalent to @ref{398d,,REG_DWORD}.
@end deffn

@geindex REG_DWORD_BIG_ENDIAN() (在 winreg 模块中)
@anchor{library/winreg winreg REG_DWORD_BIG_ENDIAN}@anchor{398f}
@deffn {数据} winreg.REG_DWORD_BIG_ENDIAN

A 32-bit number in big-endian format.
@end deffn

@geindex REG_EXPAND_SZ() (在 winreg 模块中)
@anchor{library/winreg winreg REG_EXPAND_SZ}@anchor{396e}
@deffn {数据} winreg.REG_EXPAND_SZ

Null-terminated string containing references to environment
variables (@code{%PATH%}).
@end deffn

@geindex REG_LINK() (在 winreg 模块中)
@anchor{library/winreg winreg REG_LINK}@anchor{3990}
@deffn {数据} winreg.REG_LINK

A Unicode symbolic link.
@end deffn

@geindex REG_MULTI_SZ() (在 winreg 模块中)
@anchor{library/winreg winreg REG_MULTI_SZ}@anchor{f12}
@deffn {数据} winreg.REG_MULTI_SZ

A sequence of null-terminated strings, terminated by two null characters.
(Python handles this termination automatically.)
@end deffn

@geindex REG_NONE() (在 winreg 模块中)
@anchor{library/winreg winreg REG_NONE}@anchor{3991}
@deffn {数据} winreg.REG_NONE

No defined value type.
@end deffn

@geindex REG_QWORD() (在 winreg 模块中)
@anchor{library/winreg winreg REG_QWORD}@anchor{5ad}
@deffn {数据} winreg.REG_QWORD

A 64-bit number.


3.6 新版功能.

@end deffn

@geindex REG_QWORD_LITTLE_ENDIAN() (在 winreg 模块中)
@anchor{library/winreg winreg REG_QWORD_LITTLE_ENDIAN}@anchor{3992}
@deffn {数据} winreg.REG_QWORD_LITTLE_ENDIAN

A 64-bit number in little-endian format. Equivalent to @ref{5ad,,REG_QWORD}.


3.6 新版功能.

@end deffn

@geindex REG_RESOURCE_LIST() (在 winreg 模块中)
@anchor{library/winreg winreg REG_RESOURCE_LIST}@anchor{3993}
@deffn {数据} winreg.REG_RESOURCE_LIST

A device-driver resource list.
@end deffn

@geindex REG_FULL_RESOURCE_DESCRIPTOR() (在 winreg 模块中)
@anchor{library/winreg winreg REG_FULL_RESOURCE_DESCRIPTOR}@anchor{3994}
@deffn {数据} winreg.REG_FULL_RESOURCE_DESCRIPTOR

A hardware setting.
@end deffn

@geindex REG_RESOURCE_REQUIREMENTS_LIST() (在 winreg 模块中)
@anchor{library/winreg winreg REG_RESOURCE_REQUIREMENTS_LIST}@anchor{3995}
@deffn {数据} winreg.REG_RESOURCE_REQUIREMENTS_LIST

A hardware resource list.
@end deffn

@geindex REG_SZ() (在 winreg 模块中)
@anchor{library/winreg winreg REG_SZ}@anchor{3974}
@deffn {数据} winreg.REG_SZ

A null-terminated string.
@end deffn

@node Registry Handle Objects,,常量<10>,winreg --- Windows 注册表访问
@anchor{library/winreg handle-object}@anchor{3965}@anchor{library/winreg registry-handle-objects}@anchor{3996}
@subsubsection Registry Handle Objects


This object wraps a Windows HKEY object, automatically closing it when the
object is destroyed.  To guarantee cleanup, you can call either the
@ref{396a,,Close()} method on the object, or the @ref{3969,,CloseKey()} function.

All registry functions in this module return one of these objects.

All registry functions in this module which accept a handle object also accept
an integer, however, use of the handle object is encouraged.

Handle objects provide semantics for @ref{c61,,__bool__()} -- thus

@example
if handle:
    print("Yes")
@end example

will print @code{Yes} if the handle is currently valid (has not been closed or
detached).

The object also support comparison semantics, so handle objects will compare
true if they both reference the same underlying Windows handle value.

Handle objects can be converted to an integer (e.g., using the built-in
@ref{184,,int()} function), in which case the underlying Windows handle value is
returned.  You can also use the @ref{3487,,Detach()} method to return the
integer handle, and also disconnect the Windows handle from the handle object.

@geindex Close() (winreg.PyHKEY 方法)
@anchor{library/winreg winreg PyHKEY Close}@anchor{396a}
@deffn {方法} PyHKEY.Close ()

Closes the underlying Windows handle.

If the handle is already closed, no error is raised.
@end deffn

@geindex Detach() (winreg.PyHKEY 方法)
@anchor{library/winreg winreg PyHKEY Detach}@anchor{3487}
@deffn {方法} PyHKEY.Detach ()

Detaches the Windows handle from the handle object.

The result is an integer that holds the value of the handle before it is
detached.  If the handle is already detached or closed, this will return
zero.

After calling this function, the handle is effectively invalidated, but the
handle is not closed.  You would call this function when you need the
underlying Win32 handle to exist beyond the lifetime of the handle object.

引发一个 @ref{12d0,,审计事件} @code{winreg.PyHKEY.Detach}，附带参数 @code{key}。
@end deffn

@geindex __enter__() (winreg.PyHKEY 方法)
@geindex __exit__() (winreg.PyHKEY 方法)
@anchor{library/winreg winreg PyHKEY __enter__}@anchor{3997}
@deffn {方法} PyHKEY.__enter__ ()
@anchor{library/winreg winreg PyHKEY __exit__}@anchor{3998}
@deffnx {方法} PyHKEY.__exit__ (*exc_info)

The HKEY object implements @ref{c8e,,__enter__()} and
@ref{c8f,,__exit__()} and thus supports the context protocol for the
@ref{6e3,,with} statement:

@example
with OpenKey(HKEY_LOCAL_MACHINE, "foo") as key:
    ...  # work with key
@end example

will automatically close @emph{key} when control leaves the @ref{6e3,,with} block.
@end deffn

@node winsound --- Sound-playing interface for Windows,,winreg --- Windows 注册表访问,Windows系统相关模块
@anchor{library/winsound doc}@anchor{3999}@anchor{library/winsound module-winsound}@anchor{12b}@anchor{library/winsound winsound-sound-playing-interface-for-windows}@anchor{399a}
@subsection @code{winsound} --- Sound-playing interface for Windows


@geindex winsound (模块)


__________________________________________________________________


The @ref{12b,,winsound} module provides access to the basic sound-playing machinery
provided by Windows platforms.  It includes functions and several constants.

@geindex Beep() (在 winsound 模块中)
@anchor{library/winsound winsound Beep}@anchor{5af}
@deffn {函数} winsound.Beep (frequency, duration)

Beep the PC's speaker. The @emph{frequency} parameter specifies frequency, in hertz,
of the sound, and must be in the range 37 through 32,767. The @emph{duration}
parameter specifies the number of milliseconds the sound should last.  If the
system is not able to beep the speaker, @ref{2ba,,RuntimeError} is raised.
@end deffn

@geindex PlaySound() (在 winsound 模块中)
@anchor{library/winsound winsound PlaySound}@anchor{5b1}
@deffn {函数} winsound.PlaySound (sound, flags)

Call the underlying @code{PlaySound()} function from the Platform API.  The
@emph{sound} parameter may be a filename, a system sound alias, audio data as a
@ref{5e3,,bytes-like object}, or @code{None}.  Its
interpretation depends on the value of @emph{flags}, which can be a bitwise ORed
combination of the constants described below. If the @emph{sound} parameter is
@code{None}, any currently playing waveform sound is stopped. If the system
indicates an error, @ref{2ba,,RuntimeError} is raised.
@end deffn

@geindex MessageBeep() (在 winsound 模块中)
@anchor{library/winsound winsound MessageBeep}@anchor{5b0}
@deffn {函数} winsound.MessageBeep (type=MB_OK)

Call the underlying @code{MessageBeep()} function from the Platform API.  This
plays a sound as specified in the registry.  The @emph{type} argument specifies which
sound to play; possible values are @code{-1}, @code{MB_ICONASTERISK},
@code{MB_ICONEXCLAMATION}, @code{MB_ICONHAND}, @code{MB_ICONQUESTION}, and @code{MB_OK}, all
described below.  The value @code{-1} produces a "simple beep"; this is the final
fallback if a sound cannot be played otherwise.  If the system indicates an
error, @ref{2ba,,RuntimeError} is raised.
@end deffn

@geindex SND_FILENAME() (在 winsound 模块中)
@anchor{library/winsound winsound SND_FILENAME}@anchor{399b}
@deffn {数据} winsound.SND_FILENAME

The @emph{sound} parameter is the name of a WAV file. Do not use with
@ref{399c,,SND_ALIAS}.
@end deffn

@geindex SND_ALIAS() (在 winsound 模块中)
@anchor{library/winsound winsound SND_ALIAS}@anchor{399c}
@deffn {数据} winsound.SND_ALIAS

The @emph{sound} parameter is a sound association name from the registry.  If the
registry contains no such name, play the system default sound unless
@ref{399d,,SND_NODEFAULT} is also specified. If no default sound is registered,
raise @ref{2ba,,RuntimeError}. Do not use with @ref{399b,,SND_FILENAME}.

All Win32 systems support at least the following; most systems support many
more:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

@ref{5b1,,PlaySound()} @emph{name}

@tab

Corresponding Control Panel Sound name

@item

@code{'SystemAsterisk'}

@tab

Asterisk

@item

@code{'SystemExclamation'}

@tab

Exclamation

@item

@code{'SystemExit'}

@tab

Exit Windows

@item

@code{'SystemHand'}

@tab

Critical Stop

@item

@code{'SystemQuestion'}

@tab

Question

@end multitable


例如

@example
import winsound
# Play Windows exit sound.
winsound.PlaySound("SystemExit", winsound.SND_ALIAS)

# Probably play Windows default sound, if any is registered (because
# "*" probably isn't the registered name of any sound).
winsound.PlaySound("*", winsound.SND_ALIAS)
@end example
@end deffn

@geindex SND_LOOP() (在 winsound 模块中)
@anchor{library/winsound winsound SND_LOOP}@anchor{399e}
@deffn {数据} winsound.SND_LOOP

Play the sound repeatedly.  The @ref{399f,,SND_ASYNC} flag must also be used to
avoid blocking.  Cannot be used with @ref{39a0,,SND_MEMORY}.
@end deffn

@geindex SND_MEMORY() (在 winsound 模块中)
@anchor{library/winsound winsound SND_MEMORY}@anchor{39a0}
@deffn {数据} winsound.SND_MEMORY

The @emph{sound} parameter to @ref{5b1,,PlaySound()} is a memory image of a WAV file, as a
@ref{5e3,,bytes-like object}.

@cartouche
@quotation 注解 
This module does not support playing from a memory image asynchronously, so a
combination of this flag and @ref{399f,,SND_ASYNC} will raise @ref{2ba,,RuntimeError}.
@end quotation
@end cartouche
@end deffn

@geindex SND_PURGE() (在 winsound 模块中)
@anchor{library/winsound winsound SND_PURGE}@anchor{39a1}
@deffn {数据} winsound.SND_PURGE

Stop playing all instances of the specified sound.

@cartouche
@quotation 注解 
This flag is not supported on modern Windows platforms.
@end quotation
@end cartouche
@end deffn

@geindex SND_ASYNC() (在 winsound 模块中)
@anchor{library/winsound winsound SND_ASYNC}@anchor{399f}
@deffn {数据} winsound.SND_ASYNC

Return immediately, allowing sounds to play asynchronously.
@end deffn

@geindex SND_NODEFAULT() (在 winsound 模块中)
@anchor{library/winsound winsound SND_NODEFAULT}@anchor{399d}
@deffn {数据} winsound.SND_NODEFAULT

If the specified sound cannot be found, do not play the system default sound.
@end deffn

@geindex SND_NOSTOP() (在 winsound 模块中)
@anchor{library/winsound winsound SND_NOSTOP}@anchor{39a2}
@deffn {数据} winsound.SND_NOSTOP

Do not interrupt sounds currently playing.
@end deffn

@geindex SND_NOWAIT() (在 winsound 模块中)
@anchor{library/winsound winsound SND_NOWAIT}@anchor{39a3}
@deffn {数据} winsound.SND_NOWAIT

Return immediately if the sound driver is busy.

@cartouche
@quotation 注解 
This flag is not supported on modern Windows platforms.
@end quotation
@end cartouche
@end deffn

@geindex MB_ICONASTERISK() (在 winsound 模块中)
@anchor{library/winsound winsound MB_ICONASTERISK}@anchor{39a4}
@deffn {数据} winsound.MB_ICONASTERISK

Play the @code{SystemDefault} sound.
@end deffn

@geindex MB_ICONEXCLAMATION() (在 winsound 模块中)
@anchor{library/winsound winsound MB_ICONEXCLAMATION}@anchor{39a5}
@deffn {数据} winsound.MB_ICONEXCLAMATION

Play the @code{SystemExclamation} sound.
@end deffn

@geindex MB_ICONHAND() (在 winsound 模块中)
@anchor{library/winsound winsound MB_ICONHAND}@anchor{39a6}
@deffn {数据} winsound.MB_ICONHAND

Play the @code{SystemHand} sound.
@end deffn

@geindex MB_ICONQUESTION() (在 winsound 模块中)
@anchor{library/winsound winsound MB_ICONQUESTION}@anchor{39a7}
@deffn {数据} winsound.MB_ICONQUESTION

Play the @code{SystemQuestion} sound.
@end deffn

@geindex MB_OK() (在 winsound 模块中)
@anchor{library/winsound winsound MB_OK}@anchor{39a8}
@deffn {数据} winsound.MB_OK

Play the @code{SystemDefault} sound.
@end deffn

@node Unix 专有服务,被取代的模块,Windows系统相关模块,Python 标准库
@anchor{library/unix doc}@anchor{39a9}@anchor{library/unix unix}@anchor{39aa}@anchor{library/unix unix-specific-services}@anchor{39ab}
@section Unix 专有服务


本章描述的模块提供了 Unix 操作系统独有特性的接口，在某些情况下也适用于它的某些或许多衍生版。 以下为模块概览：

@menu
* posix: posix --- 最常见的 POSIX 系统调用. 最常见的 POSIX 系统调用
* pwd: pwd --- 用户密码数据库. 用户密码数据库
* spwd: spwd --- The shadow password database. The shadow password database
* grp: grp --- 组数据库. 组数据库
* crypt: crypt --- Function to check Unix passwords. Function to check Unix passwords
* termios: termios --- POSIX 风格的 tty 控制. POSIX 风格的 tty 控制
* tty: tty --- 终端控制功能. 终端控制功能
* pty: pty --- 伪终端工具. 伪终端工具
* fcntl: fcntl --- The fcntl and ioctl system calls. The fcntl and ioctl system calls
* pipes: pipes --- 终端管道接口. 终端管道接口
* resource: resource --- Resource usage information. Resource usage information
* nis: nis --- Sun 的 NIS 黄页 接口. Sun 的 NIS (黄页) 接口
* Unix syslog 库例程:: 

@end menu

@node posix --- 最常见的 POSIX 系统调用,pwd --- 用户密码数据库,,Unix 专有服务
@anchor{library/posix doc}@anchor{39ac}@anchor{library/posix module-posix}@anchor{d1}@anchor{library/posix posix-the-most-common-posix-system-calls}@anchor{39ad}
@subsection @code{posix} --- 最常见的 POSIX 系统调用


@geindex posix (模块)


__________________________________________________________________


此模块提供了对基于 C 标准和 POSIX 标准（一种稍加修改的 Unix 接口）进行标准化的系统功能的访问。

@geindex 模块; os

@strong{请勿直接导入此模块。} 而应导入 @ref{c4,,os} 模块，它提供了此接口的 @emph{可移植} 版本。 在 Unix 上，@ref{c4,,os} 模块提供了 @ref{d1,,posix} 接口的一个超集。 在非 Unix 操作系统上 @ref{d1,,posix} 模块将不可用，但会通过 @ref{c4,,os} 接口提供它的一个可用子集。 一旦导入了 @ref{c4,,os}，用它替代 @ref{d1,,posix} 时就 @emph{没有} 性能惩罚。 此外，@ref{c4,,os} 还提供了一些附加功能，例如在 @code{os.environ} 中的某个条目被修改时会自动调用 @ref{1e7c,,putenv()}。

错误将作为异常被报告；对于类型错误会给出普通异常，而系统调用所报告的异常则会引发 @ref{1d3,,OSError}。

@menu
* 大文件支持:: 
* 重要的模块内容:: 

@end menu

@node 大文件支持,重要的模块内容,,posix --- 最常见的 POSIX 系统调用
@anchor{library/posix large-file-support}@anchor{39ae}@anchor{library/posix posix-large-files}@anchor{39af}
@subsubsection 大文件支持


@geindex large files
@geindex file; large files

某些操作系统（包括 AIX, HP-UX, Irix 和 Solaris）可对 @code{int} 和 @code{long} 为 32 位值的 C 编程模型提供大于 2 GiB 的文件的支持。 这在通常情况下是以将相关数据长度和偏移类型定义为 64 位值的方式来实现的。 这样的文件有时被称为 @emph{大文件}。

Python 中的大文件支持会在 @code{off_t} 的大小超过 @code{long} 且 @code{long long} 至少与 @code{off_t} 一样大时被启用。 要启用此模式可能必须在启用特定编译旗标的情况下执行 Python 配置和编译。 例如，在最近几个版本的 Irix 中默认启用了大文件支持，但在 Solaris 2.6 和 2.7 中你还需要执行这样的操作:

@example
CFLAGS="`getconf LFS_CFLAGS`" OPT="-g -O2 $CFLAGS" \
        ./configure
@end example

在支持大文件的 Linux 系统中，可以这样做:

@example
CFLAGS='-D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64' OPT="-g -O2 $CFLAGS" \
        ./configure
@end example

@node 重要的模块内容,,大文件支持,posix --- 最常见的 POSIX 系统调用
@anchor{library/posix notable-module-contents}@anchor{39b0}@anchor{library/posix posix-contents}@anchor{39b1}
@subsubsection 重要的模块内容


除了 @ref{c4,,os} 模块文档已说明的许多函数，@ref{d1,,posix} 还定义了下列数据项:

@geindex environ() (在 posix 模块中)
@anchor{library/posix posix environ}@anchor{39b2}
@deffn {数据} posix.environ

一个表示解释器启动时间点的字符串环境的字典。 键和值的类型在Unix 上为 bytes 而在 Windows 上为 str。 例如，@code{environ[b'HOME']} (Windows 上的 @code{environ['HOME']}) 是你的家目录的路径名，等价于 C 中的 @code{getenv("HOME")}。

修改此字典不会影响由 @ref{1e8f,,execv()}, @ref{2a9,,popen()} 或 @ref{dba,,system()} 所传入的字符串环境；如果你需要修改环境，请将 @code{environ} 传给 @ref{a3b,,execve()} 或者为 @ref{dba,,system()} 或 @ref{2a9,,popen()} 的命令字符串添加变量赋值和 export 语句。


在 3.2 版更改: 在 Unix 上，键和值为 bytes 类型。


@cartouche
@quotation 注解 
@ref{c4,,os} 模块提供了对 @code{environ} 的替代实现，它会在被修改时更新环境。 还要注意更新 @ref{b30,,os.environ} 将导致此字典失效。 推荐使用这个 @ref{c4,,os} 模块版本而不是直接访问 @ref{d1,,posix} 模块。
@end quotation
@end cartouche
@end deffn

@node pwd --- 用户密码数据库,spwd --- The shadow password database,posix --- 最常见的 POSIX 系统调用,Unix 专有服务
@anchor{library/pwd doc}@anchor{39b3}@anchor{library/pwd module-pwd}@anchor{d6}@anchor{library/pwd pwd-the-password-database}@anchor{39b4}
@subsection @code{pwd} --- 用户密码数据库


@geindex pwd (模块)


__________________________________________________________________


此模块可以访问 Unix 用户账户名及密码数据库，在所有 Unix 版本上均可使用。

密码数据库中的条目以元组对象返回，属性对应 @code{passwd} 中的结构（属性如下所示，可参考 @code{<pwd.h>}）：


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

属性

@tab

含义

@item

0

@tab

@code{pw_name}

@tab

登录名

@item

1

@tab

@code{pw_passwd}

@tab

密码，可能已经加密

@item

2

@tab

@code{pw_uid}

@tab

用户 ID 数值

@item

3

@tab

@code{pw_gid}

@tab

组 ID 数值

@item

4

@tab

@code{pw_gecos}

@tab

用户名或备注

@item

5

@tab

@code{pw_dir}

@tab

用户主目录

@item

6

@tab

@code{pw_shell}

@tab

用户的命令解释器

@end multitable


其中 uid 和 gid 是整数，其他是字符串，如果找不到对应的项目，抛出 @ref{2c7,,KeyError} 异常。

@cartouche
@quotation 注解 
@geindex 模块; crypt

传统的 Unix 系统中，@code{pw_passwd} 的值通常使用 DES 导出的算法加密（参阅 @ref{29,,crypt} 模块）。不过现在的 unix 系统使用 @emph{影子密码} 系统。在这些 unix 上，@emph{pw_passwd} 只包含星号（@code{'*'}）或字母（@code{'x'}），而加密的密码存储在文件 @code{/etc/shadow} 中，此文件不是全局可读的。在 @emph{pw_passwd} 中是否包含有用信息是系统相关的。如果可以访问到加密的密码，就需要使用 @ref{f1,,spwd} 模块了。
@end quotation
@end cartouche

本模块定义如下内容：

@geindex getpwuid() (在 pwd 模块中)
@anchor{library/pwd pwd getpwuid}@anchor{faa}
@deffn {函数} pwd.getpwuid (uid)

给定用户的数值 ID，返回密码数据库的对应项目。
@end deffn

@geindex getpwnam() (在 pwd 模块中)
@anchor{library/pwd pwd getpwnam}@anchor{fbd}
@deffn {函数} pwd.getpwnam (name)

给定用户名，返回密码数据库的对应项目。
@end deffn

@geindex getpwall() (在 pwd 模块中)
@anchor{library/pwd pwd getpwall}@anchor{39b5}
@deffn {函数} pwd.getpwall ()

返回密码数据库中所有项目的列表，顺序不是固定的。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{8b,,grp}

针对用户组数据库的接口，与本模块类似。

@item 模块 @ref{f1,,spwd}

针对影子密码数据库的接口，与本模块类似。
@end table


@node spwd --- The shadow password database,grp --- 组数据库,pwd --- 用户密码数据库,Unix 专有服务
@anchor{library/spwd doc}@anchor{39b6}@anchor{library/spwd module-spwd}@anchor{f1}@anchor{library/spwd spwd-the-shadow-password-database}@anchor{39b7}
@subsection @code{spwd} --- The shadow password database


@geindex spwd (模块)


__________________________________________________________________


This module provides access to the Unix shadow password database. It is
available on various Unix versions.

You must have enough privileges to access the shadow password database (this
usually means you have to be root).

Shadow password database entries are reported as a tuple-like object, whose
attributes correspond to the members of the @code{spwd} structure (Attribute field
below, see @code{<shadow.h>}):


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

属性

@tab

含义

@item

0

@tab

@code{sp_namp}

@tab

登录名

@item

1

@tab

@code{sp_pwdp}

@tab

Encrypted password

@item

2

@tab

@code{sp_lstchg}

@tab

Date of last change

@item

3

@tab

@code{sp_min}

@tab

Minimal number of days between
changes

@item

4

@tab

@code{sp_max}

@tab

Maximum number of days between
changes

@item

5

@tab

@code{sp_warn}

@tab

Number of days before password
expires to warn user about it

@item

6

@tab

@code{sp_inact}

@tab

Number of days after password
expires until account is
disabled

@item

7

@tab

@code{sp_expire}

@tab

Number of days since 1970-01-01
when account expires

@item

8

@tab

@code{sp_flag}

@tab

Reserved

@end multitable


The sp_namp and sp_pwdp items are strings, all others are integers.
@ref{2c7,,KeyError} is raised if the entry asked for cannot be found.

定义了以下函数：

@geindex getspnam() (在 spwd 模块中)
@anchor{library/spwd spwd getspnam}@anchor{5f9}
@deffn {函数} spwd.getspnam (name)

Return the shadow password database entry for the given user name.


在 3.6 版更改: Raises a @ref{5fa,,PermissionError} instead of @ref{2c7,,KeyError} if the user
doesn't have privileges.

@end deffn

@geindex getspall() (在 spwd 模块中)
@anchor{library/spwd spwd getspall}@anchor{39b8}
@deffn {函数} spwd.getspall ()

Return a list of all available shadow password database entries, in arbitrary
order.
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{8b,,grp}

针对用户组数据库的接口，与本模块类似。

@item 模块 @ref{d6,,pwd}

An interface to the normal password database, similar to this.
@end table


@node grp --- 组数据库,crypt --- Function to check Unix passwords,spwd --- The shadow password database,Unix 专有服务
@anchor{library/grp doc}@anchor{39b9}@anchor{library/grp grp-the-group-database}@anchor{39ba}@anchor{library/grp module-grp}@anchor{8b}
@subsection @code{grp} --- 组数据库


@geindex grp (模块)


__________________________________________________________________


该模块提供对Unix组数据库的访问。 它在所有Unix版本上都可用。

组数据库条目被报告为类似元组的对象，其属性对应于 @code{group} 结构的成员（下面的属性字段，请参见 @code{<pwd.h>} ）：


@multitable {xxxxxxxxx} {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

属性

@tab

含义

@item

0

@tab

gr_name

@tab

组名

@item

1

@tab

gr_passwd

@tab

（加密的）组密码； 通常为空

@item

2

@tab

gr_gid

@tab

数字组ID

@item

3

@tab

gr_mem

@tab

组内所有成员的用户名

@end multitable


gid 是整数，名称和密码是字符串，成员列表是字符串列表。 （注意，大多数用户未根据密码数据库显式列为所属组的成员。请检查两个数据库以获取完整的成员资格信息。还要注意，以 @code{+} 或 @code{-} 开头的 @code{gr_name} 可能是 YP/NIS 引用，可能无法通过 @ref{fbe,,getgrnam()} 或 @ref{5da,,getgrgid()} 访问。）

本模块定义如下内容：

@geindex getgrgid() (在 grp 模块中)
@anchor{library/grp grp getgrgid}@anchor{5da}
@deffn {函数} grp.getgrgid (gid)

返回给定数字组 ID 的组数据库条目。 如果请求的条目无法找到则会引发 @ref{2c7,,KeyError}。


3.6 版后已移除: 从 Python 3.6 开始，弃用对 @ref{5da,,getgrgid()} 中的 float 或 string 等非 integer 参数的支持。

@end deffn

@geindex getgrnam() (在 grp 模块中)
@anchor{library/grp grp getgrnam}@anchor{fbe}
@deffn {函数} grp.getgrnam (name)

返回给定组名的组数据库条目。 如果找不到要求的条目，则会引发 @ref{2c7,,KeyError} 错误。
@end deffn

@geindex getgrall() (在 grp 模块中)
@anchor{library/grp grp getgrall}@anchor{39bb}
@deffn {函数} grp.getgrall ()

以任意顺序返回所有可用组条目的列表。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{d6,,pwd}

用户数据库的接口，与此类似。

@item 模块 @ref{f1,,spwd}

针对影子密码数据库的接口，与本模块类似。
@end table


@node crypt --- Function to check Unix passwords,termios --- POSIX 风格的 tty 控制,grp --- 组数据库,Unix 专有服务
@anchor{library/crypt doc}@anchor{39bc}@anchor{library/crypt crypt-function-to-check-unix-passwords}@anchor{39bd}@anchor{library/crypt module-crypt}@anchor{29}
@subsection @code{crypt} --- Function to check Unix passwords


@geindex crypt (模块)

@strong{Source code:} Lib/crypt.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/crypt.py}

@geindex crypt(3)
@geindex cipher; DES


__________________________________________________________________


This module implements an interface to the @code{crypt(3)} routine, which is
a one-way hash function based upon a modified DES algorithm; see the Unix man
page for further details.  Possible uses include storing hashed passwords
so you can check passwords without storing the actual password, or attempting
to crack Unix passwords with a dictionary.

@geindex crypt(3)

Notice that the behavior of this module depends on the actual implementation  of
the @code{crypt(3)} routine in the running system.  Therefore, any
extensions available on the current implementation will also  be available on
this module.

@ref{12f5,,Availability}: Unix. Not available on VxWorks.

@menu
* Hashing Methods:: 
* Module Attributes:: 
* 模块函数: 模块函数<2>. 
* 例子: 例子<31>. 

@end menu

@node Hashing Methods,Module Attributes,,crypt --- Function to check Unix passwords
@anchor{library/crypt hashing-methods}@anchor{39be}
@subsubsection Hashing Methods



3.3 新版功能.


The @ref{29,,crypt} module defines the list of hashing methods (not all methods
are available on all platforms):

@geindex METHOD_SHA512() (在 crypt 模块中)
@anchor{library/crypt crypt METHOD_SHA512}@anchor{39bf}
@deffn {数据} crypt.METHOD_SHA512

A Modular Crypt Format method with 16 character salt and 86 character
hash based on the SHA-512 hash function.  This is the strongest method.
@end deffn

@geindex METHOD_SHA256() (在 crypt 模块中)
@anchor{library/crypt crypt METHOD_SHA256}@anchor{39c0}
@deffn {数据} crypt.METHOD_SHA256

Another Modular Crypt Format method with 16 character salt and 43
character hash based on the SHA-256 hash function.
@end deffn

@geindex METHOD_BLOWFISH() (在 crypt 模块中)
@anchor{library/crypt crypt METHOD_BLOWFISH}@anchor{39c1}
@deffn {数据} crypt.METHOD_BLOWFISH

Another Modular Crypt Format method with 22 character salt and 31
character hash based on the Blowfish cipher.


3.7 新版功能.

@end deffn

@geindex METHOD_MD5() (在 crypt 模块中)
@anchor{library/crypt crypt METHOD_MD5}@anchor{39c2}
@deffn {数据} crypt.METHOD_MD5

Another Modular Crypt Format method with 8 character salt and 22
character hash based on the MD5 hash function.
@end deffn

@geindex METHOD_CRYPT() (在 crypt 模块中)
@anchor{library/crypt crypt METHOD_CRYPT}@anchor{604}
@deffn {数据} crypt.METHOD_CRYPT

The traditional method with a 2 character salt and 13 characters of
hash.  This is the weakest method.
@end deffn

@node Module Attributes,模块函数<2>,Hashing Methods,crypt --- Function to check Unix passwords
@anchor{library/crypt module-attributes}@anchor{39c3}
@subsubsection Module Attributes



3.3 新版功能.


@geindex methods() (在 crypt 模块中)
@anchor{library/crypt crypt methods}@anchor{39c4}
@deffn {属性} crypt.methods

A list of available password hashing algorithms, as
@code{crypt.METHOD_*} objects.  This list is sorted from strongest to
weakest.
@end deffn

@node 模块函数<2>,例子<31>,Module Attributes,crypt --- Function to check Unix passwords
@anchor{library/crypt module-functions}@anchor{39c5}
@subsubsection 模块函数


The @ref{29,,crypt} module defines the following functions:

@geindex crypt() (在 crypt 模块中)
@anchor{library/crypt crypt crypt}@anchor{39c6}
@deffn {函数} crypt.crypt (word, salt=None)

@emph{word} will usually be a user's password as typed at a prompt or  in a graphical
interface.  The optional @emph{salt} is either a string as returned from
@ref{375,,mksalt()}, one of the @code{crypt.METHOD_*} values (though not all
may be available on all platforms), or a full encrypted password
including salt, as returned by this function.  If @emph{salt} is not
provided, the strongest method will be used (as returned by
@ref{39c4,,methods()}).

Checking a password is usually done by passing the plain-text password
as @emph{word} and the full results of a previous @ref{29,,crypt()} call,
which should be the same as the results of this call.

@emph{salt} (either a random 2 or 16 character string, possibly prefixed with
@code{$digit$} to indicate the method) which will be used to perturb the
encryption algorithm.  The characters in @emph{salt} must be in the set
@code{[./a-zA-Z0-9]}, with the exception of Modular Crypt Format which
prefixes a @code{$digit$}.

Returns the hashed password as a string, which will be composed of
characters from the same alphabet as the salt.

@geindex crypt(3)

Since a few @code{crypt(3)} extensions allow different values, with
different sizes in the @emph{salt}, it is recommended to use  the full crypted
password as salt when checking for a password.


在 3.3 版更改: Accept @code{crypt.METHOD_*} values in addition to strings for @emph{salt}.

@end deffn

@geindex mksalt() (在 crypt 模块中)
@anchor{library/crypt crypt mksalt}@anchor{375}
@deffn {函数} crypt.mksalt (method=None, *, rounds=None)

Return a randomly generated salt of the specified method.  If no
@emph{method} is given, the strongest method available as returned by
@ref{39c4,,methods()} is used.

The return value is a string suitable for passing as the @emph{salt} argument
to @ref{29,,crypt()}.

@emph{rounds} specifies the number of rounds for @code{METHOD_SHA256},
@code{METHOD_SHA512} and @code{METHOD_BLOWFISH}.
For @code{METHOD_SHA256} and @code{METHOD_SHA512} it must be an integer between
@code{1000} and @code{999_999_999}, the default is @code{5000}.  For
@code{METHOD_BLOWFISH} it must be a power of two between @code{16} (2@w{^4})
and @code{2_147_483_648} (2@w{^31}), the default is @code{4096}
(2@w{^12}).


3.3 新版功能.



在 3.7 版更改: Added the @emph{rounds} parameter.

@end deffn

@node 例子<31>,,模块函数<2>,crypt --- Function to check Unix passwords
@anchor{library/crypt examples}@anchor{39c7}
@subsubsection 例子


A simple example illustrating typical use (a constant-time comparison
operation is needed to limit exposure to timing attacks.
@ref{a07,,hmac.compare_digest()} is suitable for this purpose):

@example
import pwd
import crypt
import getpass
from hmac import compare_digest as compare_hash

def login():
    username = input('Python login: ')
    cryptedpasswd = pwd.getpwnam(username)[1]
    if cryptedpasswd:
        if cryptedpasswd == 'x' or cryptedpasswd == '*':
            raise ValueError('no support for shadow passwords')
        cleartext = getpass.getpass()
        return compare_hash(crypt.crypt(cleartext, cryptedpasswd), cryptedpasswd)
    else:
        return True
@end example

To generate a hash of a password using the strongest available method and
check it against the original:

@example
import crypt
from hmac import compare_digest as compare_hash

hashed = crypt.crypt(plaintext)
if not compare_hash(hashed, crypt.crypt(plaintext, hashed)):
    raise ValueError("hashed version doesn't validate against original")
@end example

@node termios --- POSIX 风格的 tty 控制,tty --- 终端控制功能,crypt --- Function to check Unix passwords,Unix 专有服务
@anchor{library/termios doc}@anchor{39c8}@anchor{library/termios module-termios}@anchor{104}@anchor{library/termios termios-posix-style-tty-control}@anchor{39c9}
@subsection @code{termios} --- POSIX 风格的 tty 控制


@geindex termios (模块)

@geindex POSIX; I/O control
@geindex tty; I/O control


__________________________________________________________________


此模块提供了针对tty I/O 控制的 POSIX 调用的接口。 有关此类调用的完整描述，请参阅 @code{termios(3)} Unix 指南页。 它仅在当安装时配置了支持 POSIX @emph{termios} 风格的 tty I/O 控制的 Unix 版本上可用。

此模块中的所有函数均接受一个文件描述符 @emph{fd} 作为第一个参数。 这可以是一个整数形式的文件描述符，例如 @code{sys.stdin.fileno()} 所返回的对象，或是一个 @ref{b3b,,file object}，例如 @code{sys.stdin} 本身。

这个模块还定义了与此处所提供的函数一起使用的所有必要的常量；这些常量与它们在 C 中的对应常量同名。 请参考你的系统文档了解有关如何使用这些终端控制接口的更多信息。

这个模块定义了以下函数：

@geindex tcgetattr() (在 termios 模块中)
@anchor{library/termios termios tcgetattr}@anchor{39ca}
@deffn {函数} termios.tcgetattr (fd)

对于文件描述符 @emph{fd} 返回一个包含 tty 属性的列表，形式如下: @code{[iflag, oflag, cflag, lflag, ispeed, ospeed, cc]}，其中 @emph{cc} 为一个包含 tty 特殊字符的列表（每一项都是长度为 1 的字符串，索引号为 @code{VMIN} 和 @code{VTIME} 的项除外，这些字段如有定义则应为整数）。 对旗标和速度以及 @emph{cc} 数组中索引的解读必须使用在 @ref{104,,termios} 模块中定义的符号常量来完成。
@end deffn

@geindex tcsetattr() (在 termios 模块中)
@anchor{library/termios termios tcsetattr}@anchor{39cb}
@deffn {函数} termios.tcsetattr (fd, when, attributes)

根据 @emph{attributes} 列表设置文件描述符 @emph{fd} 的 tty 属性，该列表即 @ref{39ca,,tcgetattr()} 所返回的对象。 @emph{when} 参数确定何时改变属性: @code{TCSANOW} 表示立即改变，@code{TCSADRAIN} 表示在传输所有队列输出后再改变，或 @code{TCSAFLUSH} 表示在传输所有队列输出并丢失所有队列输入后再改变。
@end deffn

@geindex tcsendbreak() (在 termios 模块中)
@anchor{library/termios termios tcsendbreak}@anchor{39cc}
@deffn {函数} termios.tcsendbreak (fd, duration)

在文件描述符 @emph{fd} 上发送一个中断。 @emph{duration} 为零表示发送时长为 0.25--0.5 秒的中断；@emph{duration} 非零值的含义取决于具体系统。
@end deffn

@geindex tcdrain() (在 termios 模块中)
@anchor{library/termios termios tcdrain}@anchor{39cd}
@deffn {函数} termios.tcdrain (fd)

进入等待状态直到写入文件描述符 @emph{fd} 的所有输出都传送完毕。
@end deffn

@geindex tcflush() (在 termios 模块中)
@anchor{library/termios termios tcflush}@anchor{39ce}
@deffn {函数} termios.tcflush (fd, queue)

在文件描述符 @emph{fd} 上丢弃队列数据。 @emph{queue} 选择器指定哪个队列: @code{TCIFLUSH} 表示输入队列，@code{TCOFLUSH} 表示输出队列，或 @code{TCIOFLUSH} 表示两个队列同时。
@end deffn

@geindex tcflow() (在 termios 模块中)
@anchor{library/termios termios tcflow}@anchor{39cf}
@deffn {函数} termios.tcflow (fd, action)

在文件描述符 @emph{fd} 上挂起一战恢复输入或输出。 @emph{action} 参数可以为 @code{TCOOFF} 表示挂起输出，@code{TCOON} 表示重启输出，@code{TCIOFF} 表示挂起输入，或 @code{TCION} 表示重启输入。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{115,,tty}

针对常用终端控制操作的便捷函数。
@end table


@menu
* 示例: 示例<16>. 

@end menu

@node 示例<16>,,,termios --- POSIX 风格的 tty 控制
@anchor{library/termios example}@anchor{39d0}@anchor{library/termios termios-example}@anchor{39d1}
@subsubsection 示例


这个函数可提示输入密码并且关闭回显。 请注意其采取的技巧是使用一个单独的 @ref{39ca,,tcgetattr()} 调用和一个 @ref{d6b,,try} ... @ref{182,,finally} 语句来确保旧的 tty 属性无论在何种情况下都会被原样保存:

@example
def getpass(prompt="Password: "):
    import termios, sys
    fd = sys.stdin.fileno()
    old = termios.tcgetattr(fd)
    new = termios.tcgetattr(fd)
    new[3] = new[3] & ~termios.ECHO          # lflags
    try:
        termios.tcsetattr(fd, termios.TCSADRAIN, new)
        passwd = input(prompt)
    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, old)
    return passwd
@end example

@node tty --- 终端控制功能,pty --- 伪终端工具,termios --- POSIX 风格的 tty 控制,Unix 专有服务
@anchor{library/tty doc}@anchor{39d2}@anchor{library/tty module-tty}@anchor{115}@anchor{library/tty tty-terminal-control-functions}@anchor{39d3}
@subsection @code{tty} --- 终端控制功能


@geindex tty (模块)

@strong{Source code:} Lib/tty.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/tty.py}


__________________________________________________________________


@ref{115,,tty} 模块定义了将 tty 放入 cbreak 和 raw 模式的函数。

因为它需要 @ref{104,,termios} 模块，所以只能在 Unix 上运行。

@ref{115,,tty} 模块定义了以下函数：

@geindex setraw() (在 tty 模块中)
@anchor{library/tty tty setraw}@anchor{39d4}
@deffn {函数} tty.setraw (fd, when=termios.TCSAFLUSH)

将文件描述符 @emph{fd} 的模式更改为 raw 。如果 @emph{when} 被省略，则默认为 @code{termios.TCSAFLUSH} ，并传递给 @ref{39cb,,termios.tcsetattr()} 。
@end deffn

@geindex setcbreak() (在 tty 模块中)
@anchor{library/tty tty setcbreak}@anchor{39d5}
@deffn {函数} tty.setcbreak (fd, when=termios.TCSAFLUSH)

将文件描述符 @emph{fd} 的模式更改为 cbreak 。如果 @emph{when} 被省略，则默认为 @code{termios.TCSAFLUSH} ，并传递给 @ref{39cb,,termios.tcsetattr()} 。
@end deffn


@subsubheading 参见



@table @asis

@item 模块 @ref{104,,termios}

低级终端控制接口。
@end table


@node pty --- 伪终端工具,fcntl --- The fcntl and ioctl system calls,tty --- 终端控制功能,Unix 专有服务
@anchor{library/pty doc}@anchor{39d6}@anchor{library/pty module-pty}@anchor{d5}@anchor{library/pty pty-pseudo-terminal-utilities}@anchor{39d7}
@subsection @code{pty} --- 伪终端工具


@geindex pty (模块)

@strong{源代码:} Lib/pty.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pty.py}


__________________________________________________________________


@ref{d5,,pty} 模块定义了一些处理“伪终端”概念的操作：启动另一个进程并能以程序方式在其控制终端中进行读写。

由于伪终端处理高度依赖于具体平台，因此此功能只有针对 Linux 的代码。 （Linux 代码也可在其他平台上工作，但是未经测试。）

@ref{d5,,pty} 模块定义了下列函数:

@geindex fork() (在 pty 模块中)
@anchor{library/pty pty fork}@anchor{39d8}
@deffn {函数} pty.fork ()

分叉。 将子进程的控制终端连接到一个伪终端。 返回值为 @code{(pid, fd)}。 请注意子进程获得 @emph{pid} 0 而 @emph{fd} 为 @emph{invalid}。 父进程返回值为子进程的 @emph{pid} 而 @emph{fd} 为一个连接到子进程的控制终端（并同时连接到子进程的标准输入和输出）的文件描述符。
@end deffn

@geindex openpty() (在 pty 模块中)
@anchor{library/pty pty openpty}@anchor{39d9}
@deffn {函数} pty.openpty ()

打开一个新的伪终端对，如果可能将使用 @ref{1ec4,,os.openpty()}，或是针对通用 Unix 系统的模拟代码。 返回一个文件描述符对 @code{(master, slave)}，分别表示主从两端。
@end deffn

@geindex spawn() (在 pty 模块中)
@anchor{library/pty pty spawn}@anchor{892}
@deffn {函数} pty.spawn (argv[, master_read[, stdin_read]])

生成一个进程，并将其控制终端连接到当前进程的标准 io。 这常被用来应对坚持要从控制终端读取数据的程序。 在 pty 背后生成的进程预期最后将被终止，而且当它被终止时 @emph{spawn} 将会返回。

会向 @emph{master_read} 和 @emph{stdin_read} 函数传入一个文件描述符供它们读取，并且它们总是应当返回一个字节串。 为了强制 spawn 在子进程退出之前返回所以应当抛出 @ref{1d3,,OSError}。

两个函数的默认实现在每次函数被调用时将读取并返回至多 1024 个字节。 会向 @emph{master_read} 回调传入伪终端的主文件描述符以从子进程读取输出，而向 @emph{stdin_read} 传入文件描述符 0 以从父进程的标准输入读取数据。

从两个回调返回空字节串会被解读为文件结束 (EOF) 条件，在此之后回调将不再被调用。 如果 @emph{stdin_read} 发出 EOF 信号则控制终端就不能再与父进程或子进程进行通信。 除非子进程将不带任何输入就退出，否则随后 @emph{spawn} 将一直循环下去。 如果 @emph{master_read} 发出 EOF 信号则会有相同的行为结果（至少是在 Linux 上）。

如果两个回调都发出 EOF 信号则 @emph{spawn} 可能将永不返回，除非在你的平台上当传入三个空列表时 @emph{select} 会抛出一个错误。 这是一个程序缺陷，相关文档见 问题 26228@footnote{https://bugs.python.org/issue26228}。

引发一个 @ref{12d0,,审计事件} @code{pty.spawn}，附带参数 @code{argv}。


在 3.4 版更改: @ref{892,,spawn()} 现在会从子进程的 @ref{667,,os.waitpid()} 返回状态值。

@end deffn

@menu
* 示例: 示例<17>. 

@end menu

@node 示例<17>,,,pty --- 伪终端工具
@anchor{library/pty example}@anchor{39da}
@subsubsection 示例


以下程序的作用类似于 Unix 命令 @code{script(1)}，它使用一个伪终端来记录一个 "typescript" 里终端进程的所有输入和输出:

@example
import argparse
import os
import pty
import sys
import time

parser = argparse.ArgumentParser()
parser.add_argument('-a', dest='append', action='store_true')
parser.add_argument('-p', dest='use_python', action='store_true')
parser.add_argument('filename', nargs='?', default='typescript')
options = parser.parse_args()

shell = sys.executable if options.use_python else os.environ.get('SHELL', 'sh')
filename = options.filename
mode = 'ab' if options.append else 'wb'

with open(filename, mode) as script:
    def read(fd):
        data = os.read(fd, 1024)
        script.write(data)
        return data

    print('Script started, file is', filename)
    script.write(('Script started on %s\n' % time.asctime()).encode())

    pty.spawn(shell, read)

    script.write(('Script done on %s\n' % time.asctime()).encode())
    print('Script done, file is', filename)
@end example

@node fcntl --- The fcntl and ioctl system calls,pipes --- 终端管道接口,pty --- 伪终端工具,Unix 专有服务
@anchor{library/fcntl doc}@anchor{39db}@anchor{library/fcntl fcntl-the-fcntl-and-ioctl-system-calls}@anchor{39dc}@anchor{library/fcntl module-fcntl}@anchor{7e}
@subsection @code{fcntl} --- The @code{fcntl} and @code{ioctl} system calls


@geindex fcntl (模块)

@geindex UNIX; file control
@geindex UNIX; I/O control


__________________________________________________________________


This module performs file control and I/O control on file descriptors. It is an
interface to the @code{fcntl()} and @code{ioctl()} Unix routines.  For a
complete description of these calls, see @code{fcntl(2)} and
@code{ioctl(2)} Unix manual pages.

All functions in this module take a file descriptor @emph{fd} as their first
argument.  This can be an integer file descriptor, such as returned by
@code{sys.stdin.fileno()}, or an @ref{1db,,io.IOBase} object, such as @code{sys.stdin}
itself, which provides a @ref{1ea0,,fileno()} that returns a genuine file
descriptor.


在 3.3 版更改: Operations in this module used to raise an @ref{98c,,IOError} where they now
raise an @ref{1d3,,OSError}.



在 3.8 版更改: The fcntl module now contains @code{F_ADD_SEALS}, @code{F_GET_SEALS}, and
@code{F_SEAL_*} constants for sealing of @ref{1f0,,os.memfd_create()} file
descriptors.


这个模块定义了以下函数：

@geindex fcntl() (在 fcntl 模块中)
@anchor{library/fcntl fcntl fcntl}@anchor{2639}
@deffn {函数} fcntl.fcntl (fd, cmd, arg=0)

Perform the operation @emph{cmd} on file descriptor @emph{fd} (file objects providing
a @ref{1ea0,,fileno()} method are accepted as well).  The values used
for @emph{cmd} are operating system dependent, and are available as constants
in the @ref{7e,,fcntl} module, using the same names as used in the relevant C
header files. The argument @emph{arg} can either be an integer value, or a
@ref{32a,,bytes} object. With an integer value, the return value of this
function is the integer return value of the C @code{fcntl()} call.  When
the argument is bytes it represents a binary structure, e.g. created by
@ref{c04,,struct.pack()}. The binary data is copied to a buffer whose address is
passed to the C @code{fcntl()} call.  The return value after a successful
call is the contents of the buffer, converted to a @ref{32a,,bytes} object.
The length of the returned object will be the same as the length of the
@emph{arg} argument. This is limited to 1024 bytes. If the information returned
in the buffer by the operating system is larger than 1024 bytes, this is
most likely to result in a segmentation violation or a more subtle data
corruption.

If the @code{fcntl()} fails, an @ref{1d3,,OSError} is raised.

Raises an @ref{12d0,,auditing event} @code{fcntl.fcntl} with arguments @code{fd}, @code{cmd}, @code{arg}.
@end deffn

@geindex ioctl() (在 fcntl 模块中)
@anchor{library/fcntl fcntl ioctl}@anchor{dd7}
@deffn {函数} fcntl.ioctl (fd, request, arg=0, mutate_flag=True)

This function is identical to the @ref{2639,,fcntl()} function, except
that the argument handling is even more complicated.

The @emph{request} parameter is limited to values that can fit in 32-bits.
Additional constants of interest for use as the @emph{request} argument can be
found in the @ref{104,,termios} module, under the same names as used in
the relevant C header files.

The parameter @emph{arg} can be one of an integer, an object supporting the
read-only buffer interface (like @ref{32a,,bytes}) or an object supporting
the read-write buffer interface (like @ref{32b,,bytearray}).

In all but the last case, behaviour is as for the @ref{2639,,fcntl()}
function.

If a mutable buffer is passed, then the behaviour is determined by the value of
the @emph{mutate_flag} parameter.

If it is false, the buffer's mutability is ignored and behaviour is as for a
read-only buffer, except that the 1024 byte limit mentioned above is avoided --
so long as the buffer you pass is at least as long as what the operating system
wants to put there, things should work.

If @emph{mutate_flag} is true (the default), then the buffer is (in effect) passed
to the underlying @ref{dd7,,ioctl()} system call, the latter's return code is
passed back to the calling Python, and the buffer's new contents reflect the
action of the @ref{dd7,,ioctl()}.  This is a slight simplification, because if the
supplied buffer is less than 1024 bytes long it is first copied into a static
buffer 1024 bytes long which is then passed to @ref{dd7,,ioctl()} and copied back
into the supplied buffer.

If the @code{ioctl()} fails, an @ref{1d3,,OSError} exception is raised.

举个例子：

@example
>>> import array, fcntl, struct, termios, os
>>> os.getpgrp()
13341
>>> struct.unpack('h', fcntl.ioctl(0, termios.TIOCGPGRP, "  "))[0]
13341
>>> buf = array.array('h', [0])
>>> fcntl.ioctl(0, termios.TIOCGPGRP, buf, 1)
0
>>> buf
array('h', [13341])
@end example

Raises an @ref{12d0,,auditing event} @code{fcntl.ioctl} with arguments @code{fd}, @code{request}, @code{arg}.
@end deffn

@geindex flock() (在 fcntl 模块中)
@anchor{library/fcntl fcntl flock}@anchor{3471}
@deffn {函数} fcntl.flock (fd, operation)

Perform the lock operation @emph{operation} on file descriptor @emph{fd} (file objects providing
a @ref{1ea0,,fileno()} method are accepted as well). See the Unix manual
@code{flock(2)} for details.  (On some systems, this function is emulated
using @code{fcntl()}.)

If the @code{flock()} fails, an @ref{1d3,,OSError} exception is raised.

Raises an @ref{12d0,,auditing event} @code{fcntl.flock} with arguments @code{fd}, @code{operation}.
@end deffn

@geindex lockf() (在 fcntl 模块中)
@anchor{library/fcntl fcntl lockf}@anchor{d4b}
@deffn {函数} fcntl.lockf (fd, cmd, len=0, start=0, whence=0)

This is essentially a wrapper around the @ref{2639,,fcntl()} locking calls.
@emph{fd} is the file descriptor (file objects providing a @ref{1ea0,,fileno()}
method are accepted as well) of the file to lock or unlock, and @emph{cmd}
is one of the following values:


@itemize *

@item 
@code{LOCK_UN} -- unlock

@item 
@code{LOCK_SH} -- acquire a shared lock

@item 
@code{LOCK_EX} -- acquire an exclusive lock
@end itemize

When @emph{cmd} is @code{LOCK_SH} or @code{LOCK_EX}, it can also be
bitwise ORed with @code{LOCK_NB} to avoid blocking on lock acquisition.
If @code{LOCK_NB} is used and the lock cannot be acquired, an
@ref{1d3,,OSError} will be raised and the exception will have an @emph{errno}
attribute set to @code{EACCES} or @code{EAGAIN} (depending on the
operating system; for portability, check for both values).  On at least some
systems, @code{LOCK_EX} can only be used if the file descriptor refers to a
file opened for writing.

@emph{len} is the number of bytes to lock, @emph{start} is the byte offset at
which the lock starts, relative to @emph{whence}, and @emph{whence} is as with
@ref{1d2d,,io.IOBase.seek()}, specifically:


@itemize *

@item 
@code{0} -- relative to the start of the file (@ref{d8d,,os.SEEK_SET})

@item 
@code{1} -- relative to the current buffer position (@ref{d8e,,os.SEEK_CUR})

@item 
@code{2} -- relative to the end of the file (@ref{d8f,,os.SEEK_END})
@end itemize

The default for @emph{start} is 0, which means to start at the beginning of the file.
The default for @emph{len} is 0 which means to lock to the end of the file.  The
default for @emph{whence} is also 0.

Raises an @ref{12d0,,auditing event} @code{fcntl.lockf} with arguments @code{fd}, @code{cmd}, @code{len}, @code{start}, @code{whence}.
@end deffn

Examples (all on a SVR4 compliant system):

@example
import struct, fcntl, os

f = open(...)
rv = fcntl.fcntl(f, fcntl.F_SETFL, os.O_NDELAY)

lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 0, 0, 0)
rv = fcntl.fcntl(f, fcntl.F_SETLKW, lockdata)
@end example

Note that in the first example the return value variable @emph{rv} will hold an
integer value; in the second example it will hold a @ref{32a,,bytes} object.  The
structure lay-out for the @emph{lockdata} variable is system dependent --- therefore
using the @ref{3471,,flock()} call may be better.


@subsubheading 参见



@table @asis

@item 模块 @ref{c4,,os}

If the locking flags @ref{d90,,O_SHLOCK} and @ref{d91,,O_EXLOCK} are
present in the @ref{c4,,os} module (on BSD only), the @ref{65f,,os.open()}
function provides an alternative to the @ref{d4b,,lockf()} and @ref{3471,,flock()}
functions.
@end table


@node pipes --- 终端管道接口,resource --- Resource usage information,fcntl --- The fcntl and ioctl system calls,Unix 专有服务
@anchor{library/pipes doc}@anchor{39dd}@anchor{library/pipes module-pipes}@anchor{cc}@anchor{library/pipes pipes-interface-to-shell-pipelines}@anchor{39de}
@subsection @code{pipes} --- 终端管道接口


@geindex pipes (模块)

@strong{源代码：} Lib/pipes.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/pipes.py}


__________________________________________________________________


@ref{cc,,pipes} 定义了一个类用来抽象 @emph{pipeline} 的概念 --- 将数据从一个文件转到另一文件的转换器序列。

由于模块使用了 @code{/bin/sh} 命令行，因此要求有 POSIX 或兼容 @ref{dba,,os.system()} 和 @ref{2a9,,os.popen()} 的终端程序。

@ref{cc,,pipes} 模块定义了以下的类:

@geindex Template (pipes 中的类)
@anchor{library/pipes pipes Template}@anchor{39df}
@deffn {类} pipes.Template

对管道的抽象。
@end deffn

示例:

@example
>>> import pipes
>>> t = pipes.Template()
>>> t.append('tr a-z A-Z', '--')
>>> f = t.open('pipefile', 'w')
>>> f.write('hello world')
>>> f.close()
>>> open('pipefile').read()
'HELLO WORLD'
@end example

@menu
* 模板对象:: 

@end menu

@node 模板对象,,,pipes --- 终端管道接口
@anchor{library/pipes id1}@anchor{39e0}@anchor{library/pipes template-objects}@anchor{39e1}
@subsubsection 模板对象


模板对象有以下方法:

@geindex reset() (pipes.Template 方法)
@anchor{library/pipes pipes Template reset}@anchor{39e2}
@deffn {方法} Template.reset ()

将一个管道模板恢复为初始状态。
@end deffn

@geindex clone() (pipes.Template 方法)
@anchor{library/pipes pipes Template clone}@anchor{39e3}
@deffn {方法} Template.clone ()

返回一个新的等价的管道模板。
@end deffn

@geindex debug() (pipes.Template 方法)
@anchor{library/pipes pipes Template debug}@anchor{39e4}
@deffn {方法} Template.debug (flag)

如果 @emph{flag} 为真值，则启用调试。 否则禁用调试。 当启用调试时，要执行的命令会被打印出来，并且会给予终端 @code{set -x} 命令以输出更详细的信息。
@end deffn

@geindex append() (pipes.Template 方法)
@anchor{library/pipes pipes Template append}@anchor{39e5}
@deffn {方法} Template.append (cmd, kind)

在末尾添加一个新的动作。 @emph{cmd} 变量必须为一个有效的 bourne 终端命令。 @emph{kind} 变量由两个字母组成。

第一个字母可以为 @code{'-'} (这表示命令将读取其标准输入), @code{'f'} (这表示命令将读取在命令行中给定的文件) 或 @code{'.'} (这表示命令将不读取输入，因而必须放在前面。)

类似地，第二个字母可以为 @code{'-'} (这表示命令将写入到标准输出), @code{'f'} (这表示命令将写入在命令行中给定的文件) 或 @code{'.'} (这表示命令将不执行写入，因而必须放在末尾。)
@end deffn

@geindex prepend() (pipes.Template 方法)
@anchor{library/pipes pipes Template prepend}@anchor{39e6}
@deffn {方法} Template.prepend (cmd, kind)

在开头添加一个新的动作。 请参阅 @ref{39e5,,append()} 获取相应参数的说明。
@end deffn

@geindex open() (pipes.Template 方法)
@anchor{library/pipes pipes Template open}@anchor{39e7}
@deffn {方法} Template.open (file, mode)

返回一个文件类对象，打开到 @emph{file}，但是将从管道读取或写入。 请注意只能给出 @code{'r'}, @code{'w'} 中的一个。
@end deffn

@geindex copy() (pipes.Template 方法)
@anchor{library/pipes pipes Template copy}@anchor{39e8}
@deffn {方法} Template.copy (infile, outfile)

通过管道将 @emph{infile} 拷贝到 @emph{outfile}。
@end deffn

@node resource --- Resource usage information,nis --- Sun 的 NIS 黄页 接口,pipes --- 终端管道接口,Unix 专有服务
@anchor{library/resource doc}@anchor{39e9}@anchor{library/resource module-resource}@anchor{e0}@anchor{library/resource resource-resource-usage-information}@anchor{39ea}
@subsection @code{resource} --- Resource usage information


@geindex resource (模块)


__________________________________________________________________


This module provides basic mechanisms for measuring and controlling system
resources utilized by a program.

Symbolic constants are used to specify particular system resources and to
request usage information about either the current process or its children.

An @ref{1d3,,OSError} is raised on syscall failure.

@geindex error
@anchor{library/resource resource error}@anchor{39eb}
@deffn {例外} resource.error

一个被弃用的 @ref{1d3,,OSError} 的别名。


在 3.3 版更改: 根据 
@geindex Python 提高建议; PEP 3151
PEP 3151@footnote{https://www.python.org/dev/peps/pep-3151}，这个类是 @ref{1d3,,OSError} 的别名。

@end deffn

@menu
* Resource Limits:: 
* Resource Usage:: 

@end menu

@node Resource Limits,Resource Usage,,resource --- Resource usage information
@anchor{library/resource resource-limits}@anchor{39ec}
@subsubsection Resource Limits


Resources usage can be limited using the @ref{344a,,setrlimit()} function described
below. Each resource is controlled by a pair of limits: a soft limit and a hard
limit. The soft limit is the current limit, and may be lowered or raised by a
process over time. The soft limit can never exceed the hard limit. The hard
limit can be lowered to any value greater than the soft limit, but not raised.
(Only processes with the effective UID of the super-user can raise a hard
limit.)

The specific resources that can be limited are system dependent. They are
described in the @code{getrlimit(2)} man page.  The resources listed below
are supported when the underlying operating system supports them; resources
which cannot be checked or controlled by the operating system are not defined in
this module for those platforms.

@geindex RLIM_INFINITY() (在 resource 模块中)
@anchor{library/resource resource RLIM_INFINITY}@anchor{39ed}
@deffn {数据} resource.RLIM_INFINITY

Constant used to represent the limit for an unlimited resource.
@end deffn

@geindex getrlimit() (在 resource 模块中)
@anchor{library/resource resource getrlimit}@anchor{39ee}
@deffn {函数} resource.getrlimit (resource)

Returns a tuple @code{(soft, hard)} with the current soft and hard limits of
@emph{resource}. Raises @ref{1fb,,ValueError} if an invalid resource is specified, or
@ref{39eb,,error} if the underlying system call fails unexpectedly.
@end deffn

@geindex setrlimit() (在 resource 模块中)
@anchor{library/resource resource setrlimit}@anchor{344a}
@deffn {函数} resource.setrlimit (resource, limits)

Sets new limits of consumption of @emph{resource}. The @emph{limits} argument must be a
tuple @code{(soft, hard)} of two integers describing the new limits. A value of
@ref{39ed,,RLIM_INFINITY} can be used to request a limit that is
unlimited.

Raises @ref{1fb,,ValueError} if an invalid resource is specified, if the new soft
limit exceeds the hard limit, or if a process tries to raise its hard limit.
Specifying a limit of @ref{39ed,,RLIM_INFINITY} when the hard or
system limit for that resource is not unlimited will result in a
@ref{1fb,,ValueError}.  A process with the effective UID of super-user can
request any valid limit value, including unlimited, but @ref{1fb,,ValueError}
will still be raised if the requested limit exceeds the system imposed
limit.

@code{setrlimit} may also raise @ref{39eb,,error} if the underlying system call
fails.

VxWorks only supports setting @ref{39ef,,RLIMIT_NOFILE}.

Raises an @ref{12d0,,auditing event} @code{resource.setrlimit} with arguments @code{resource}, @code{limits}.
@end deffn

@geindex prlimit() (在 resource 模块中)
@anchor{library/resource resource prlimit}@anchor{899}
@deffn {函数} resource.prlimit (pid, resource[, limits])

Combines @ref{344a,,setrlimit()} and @ref{39ee,,getrlimit()} in one function and
supports to get and set the resources limits of an arbitrary process. If
@emph{pid} is 0, then the call applies to the current process. @emph{resource} and
@emph{limits} have the same meaning as in @ref{344a,,setrlimit()}, except that
@emph{limits} is optional.

When @emph{limits} is not given the function returns the @emph{resource} limit of the
process @emph{pid}. When @emph{limits} is given the @emph{resource} limit of the process is
set and the former resource limit is returned.

Raises @ref{995,,ProcessLookupError} when @emph{pid} can't be found and
@ref{5fa,,PermissionError} when the user doesn't have @code{CAP_SYS_RESOURCE} for
the process.

Raises an @ref{12d0,,auditing event} @code{resource.prlimit} with arguments @code{pid}, @code{resource}, @code{limits}.

@ref{12f5,,Availability}: Linux 2.6.36 or later with glibc 2.13 or later.


3.4 新版功能.

@end deffn

These symbols define resources whose consumption can be controlled using the
@ref{344a,,setrlimit()} and @ref{39ee,,getrlimit()} functions described below. The values of
these symbols are exactly the constants used by C programs.

The Unix man page for @code{getrlimit(2)} lists the available resources.
Note that not all systems use the same symbol or same value to denote the same
resource.  This module does not attempt to mask platform differences --- symbols
not defined for a platform will not be available from this module on that
platform.

@geindex RLIMIT_CORE() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_CORE}@anchor{344b}
@deffn {数据} resource.RLIMIT_CORE

The maximum size (in bytes) of a core file that the current process can create.
This may result in the creation of a partial core file if a larger core would be
required to contain the entire process image.
@end deffn

@geindex RLIMIT_CPU() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_CPU}@anchor{39f0}
@deffn {数据} resource.RLIMIT_CPU

The maximum amount of processor time (in seconds) that a process can use. If
this limit is exceeded, a @code{SIGXCPU} signal is sent to the process. (See
the @ref{ea,,signal} module documentation for information about how to catch this
signal and do something useful, e.g. flush open files to disk.)
@end deffn

@geindex RLIMIT_FSIZE() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_FSIZE}@anchor{39f1}
@deffn {数据} resource.RLIMIT_FSIZE

The maximum size of a file which the process may create.
@end deffn

@geindex RLIMIT_DATA() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_DATA}@anchor{39f2}
@deffn {数据} resource.RLIMIT_DATA

The maximum size (in bytes) of the process's heap.
@end deffn

@geindex RLIMIT_STACK() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_STACK}@anchor{39f3}
@deffn {数据} resource.RLIMIT_STACK

The maximum size (in bytes) of the call stack for the current process.  This only
affects the stack of the main thread in a multi-threaded process.
@end deffn

@geindex RLIMIT_RSS() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_RSS}@anchor{39f4}
@deffn {数据} resource.RLIMIT_RSS

The maximum resident set size that should be made available to the process.
@end deffn

@geindex RLIMIT_NPROC() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_NPROC}@anchor{39f5}
@deffn {数据} resource.RLIMIT_NPROC

The maximum number of processes the current process may create.
@end deffn

@geindex RLIMIT_NOFILE() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_NOFILE}@anchor{39ef}
@deffn {数据} resource.RLIMIT_NOFILE

The maximum number of open file descriptors for the current process.
@end deffn

@geindex RLIMIT_OFILE() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_OFILE}@anchor{39f6}
@deffn {数据} resource.RLIMIT_OFILE

The BSD name for @ref{39ef,,RLIMIT_NOFILE}.
@end deffn

@geindex RLIMIT_MEMLOCK() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_MEMLOCK}@anchor{39f7}
@deffn {数据} resource.RLIMIT_MEMLOCK

The maximum address space which may be locked in memory.
@end deffn

@geindex RLIMIT_VMEM() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_VMEM}@anchor{39f8}
@deffn {数据} resource.RLIMIT_VMEM

The largest area of mapped memory which the process may occupy.
@end deffn

@geindex RLIMIT_AS() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_AS}@anchor{39f9}
@deffn {数据} resource.RLIMIT_AS

The maximum area (in bytes) of address space which may be taken by the process.
@end deffn

@geindex RLIMIT_MSGQUEUE() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_MSGQUEUE}@anchor{89a}
@deffn {数据} resource.RLIMIT_MSGQUEUE

The number of bytes that can be allocated for POSIX message queues.

@ref{12f5,,Availability}: Linux 2.6.8 or later.


3.4 新版功能.

@end deffn

@geindex RLIMIT_NICE() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_NICE}@anchor{89b}
@deffn {数据} resource.RLIMIT_NICE

The ceiling for the process's nice level (calculated as 20 - rlim_cur).

@ref{12f5,,Availability}: Linux 2.6.12 or later.


3.4 新版功能.

@end deffn

@geindex RLIMIT_RTPRIO() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_RTPRIO}@anchor{89c}
@deffn {数据} resource.RLIMIT_RTPRIO

The ceiling of the real-time priority.

@ref{12f5,,Availability}: Linux 2.6.12 or later.


3.4 新版功能.

@end deffn

@geindex RLIMIT_RTTIME() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_RTTIME}@anchor{89d}
@deffn {数据} resource.RLIMIT_RTTIME

The time limit (in microseconds) on CPU time that a process can spend
under real-time scheduling without making a blocking syscall.

@ref{12f5,,Availability}: Linux 2.6.25 or later.


3.4 新版功能.

@end deffn

@geindex RLIMIT_SIGPENDING() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_SIGPENDING}@anchor{89e}
@deffn {数据} resource.RLIMIT_SIGPENDING

The number of signals which the process may queue.

@ref{12f5,,Availability}: Linux 2.6.8 or later.


3.4 新版功能.

@end deffn

@geindex RLIMIT_SBSIZE() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_SBSIZE}@anchor{89f}
@deffn {数据} resource.RLIMIT_SBSIZE

The maximum size (in bytes) of socket buffer usage for this user.
This limits the amount of network memory, and hence the amount of mbufs,
that this user may hold at any time.

@ref{12f5,,Availability}: FreeBSD 9 or later.


3.4 新版功能.

@end deffn

@geindex RLIMIT_SWAP() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_SWAP}@anchor{8a0}
@deffn {数据} resource.RLIMIT_SWAP

The maximum size (in bytes) of the swap space that may be reserved or
used by all of this user id's processes.
This limit is enforced only if bit 1 of the vm.overcommit sysctl is set.
Please see @code{tuning(7)} for a complete description of this sysctl.

@ref{12f5,,Availability}: FreeBSD 9 or later.


3.4 新版功能.

@end deffn

@geindex RLIMIT_NPTS() (在 resource 模块中)
@anchor{library/resource resource RLIMIT_NPTS}@anchor{8a1}
@deffn {数据} resource.RLIMIT_NPTS

The maximum number of pseudo-terminals created by this user id.

@ref{12f5,,Availability}: FreeBSD 9 or later.


3.4 新版功能.

@end deffn

@node Resource Usage,,Resource Limits,resource --- Resource usage information
@anchor{library/resource resource-usage}@anchor{39fa}
@subsubsection Resource Usage


These functions are used to retrieve resource usage information:

@geindex getrusage() (在 resource 模块中)
@anchor{library/resource resource getrusage}@anchor{d92}
@deffn {函数} resource.getrusage (who)

This function returns an object that describes the resources consumed by either
the current process or its children, as specified by the @emph{who} parameter.  The
@emph{who} parameter should be specified using one of the @code{RUSAGE_*}
constants described below.

A simple example:

@example
from resource import *
import time

# a non CPU-bound task
time.sleep(3)
print(getrusage(RUSAGE_SELF))

# a CPU-bound task
for i in range(10 ** 8):
   _ = 1 + 1
print(getrusage(RUSAGE_SELF))
@end example

The fields of the return value each describe how a particular system resource
has been used, e.g. amount of time spent running is user mode or number of times
the process was swapped out of main memory. Some values are dependent on the
clock tick internal, e.g. the amount of memory the process is using.

For backward compatibility, the return value is also accessible as a tuple of 16
elements.

The fields @code{ru_utime} and @code{ru_stime} of the return value are
floating point values representing the amount of time spent executing in user
mode and the amount of time spent executing in system mode, respectively. The
remaining values are integers. Consult the @code{getrusage(2)} man page for
detailed information about these values. A brief summary is presented here:


@multitable {xxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

索引

@tab

域

@tab

Resource

@item

@code{0}

@tab

@code{ru_utime}

@tab

time in user mode (float seconds)

@item

@code{1}

@tab

@code{ru_stime}

@tab

time in system mode (float seconds)

@item

@code{2}

@tab

@code{ru_maxrss}

@tab

maximum resident set size

@item

@code{3}

@tab

@code{ru_ixrss}

@tab

shared memory size

@item

@code{4}

@tab

@code{ru_idrss}

@tab

unshared memory size

@item

@code{5}

@tab

@code{ru_isrss}

@tab

unshared stack size

@item

@code{6}

@tab

@code{ru_minflt}

@tab

page faults not requiring I/O

@item

@code{7}

@tab

@code{ru_majflt}

@tab

page faults requiring I/O

@item

@code{8}

@tab

@code{ru_nswap}

@tab

number of swap outs

@item

@code{9}

@tab

@code{ru_inblock}

@tab

block input operations

@item

@code{10}

@tab

@code{ru_oublock}

@tab

block output operations

@item

@code{11}

@tab

@code{ru_msgsnd}

@tab

messages sent

@item

@code{12}

@tab

@code{ru_msgrcv}

@tab

messages received

@item

@code{13}

@tab

@code{ru_nsignals}

@tab

signals received

@item

@code{14}

@tab

@code{ru_nvcsw}

@tab

voluntary context switches

@item

@code{15}

@tab

@code{ru_nivcsw}

@tab

involuntary context switches

@end multitable


This function will raise a @ref{1fb,,ValueError} if an invalid @emph{who} parameter is
specified. It may also raise @ref{39eb,,error} exception in unusual circumstances.
@end deffn

@geindex getpagesize() (在 resource 模块中)
@anchor{library/resource resource getpagesize}@anchor{39fb}
@deffn {函数} resource.getpagesize ()

Returns the number of bytes in a system page. (This need not be the same as the
hardware page size.)
@end deffn

The following @code{RUSAGE_*} symbols are passed to the @ref{d92,,getrusage()}
function to specify which processes information should be provided for.

@geindex RUSAGE_SELF() (在 resource 模块中)
@anchor{library/resource resource RUSAGE_SELF}@anchor{39fc}
@deffn {数据} resource.RUSAGE_SELF

Pass to @ref{d92,,getrusage()} to request resources consumed by the calling
process, which is the sum of resources used by all threads in the process.
@end deffn

@geindex RUSAGE_CHILDREN() (在 resource 模块中)
@anchor{library/resource resource RUSAGE_CHILDREN}@anchor{39fd}
@deffn {数据} resource.RUSAGE_CHILDREN

Pass to @ref{d92,,getrusage()} to request resources consumed by child processes
of the calling process which have been terminated and waited for.
@end deffn

@geindex RUSAGE_BOTH() (在 resource 模块中)
@anchor{library/resource resource RUSAGE_BOTH}@anchor{39fe}
@deffn {数据} resource.RUSAGE_BOTH

Pass to @ref{d92,,getrusage()} to request resources consumed by both the current
process and child processes.  May not be available on all systems.
@end deffn

@geindex RUSAGE_THREAD() (在 resource 模块中)
@anchor{library/resource resource RUSAGE_THREAD}@anchor{39ff}
@deffn {数据} resource.RUSAGE_THREAD

Pass to @ref{d92,,getrusage()} to request resources consumed by the current
thread.  May not be available on all systems.


3.2 新版功能.

@end deffn

@node nis --- Sun 的 NIS 黄页 接口,Unix syslog 库例程,resource --- Resource usage information,Unix 专有服务
@anchor{library/nis doc}@anchor{3a00}@anchor{library/nis module-nis}@anchor{bf}@anchor{library/nis nis-interface-to-sun-s-nis-yellow-pages}@anchor{3a01}
@subsection @code{nis} --- Sun 的 NIS (黄页) 接口


@geindex nis (模块)


__________________________________________________________________


@ref{bf,,nis} 模块提供了对 NIS 库的轻量级包装，适用于多个主机的集中管理。

因为 NIS 仅存在于 Unix 系统，此模块仅在 Unix 上可用。

@ref{bf,,nis} 模块定义了以下函数：

@geindex match() (在 nis 模块中)
@anchor{library/nis nis match}@anchor{d8b}
@deffn {函数} nis.match (key, mapname, domain=default_domain)

返回 @emph{key} 在映射 @emph{mapname} 中的匹配结果，如无结果则会引发错误 (@ref{3a02,,nis.error})。 两个参数都应为字符串，@emph{key} 定长 8 个比特。 返回值为任意字节数组（可包含 @code{NULL} 和其他特殊值）。

请注意如果 @emph{mapname} 是另一名称的别名则会先检查别名。

@emph{domain} 参数可允许重载用于查找的 NIS 域。 如果未指定，则会在默认 NIS 域中查找。
@end deffn

@geindex cat() (在 nis 模块中)
@anchor{library/nis nis cat}@anchor{3a03}
@deffn {函数} nis.cat (mapname, domain=default_domain)

返回一个字典，其元素为 @emph{key} 到 @emph{value} 的映射使得 @code{match(key, mapname)==value}。 请注意字典的键和值均为任意字节数组。

请注意如果 @emph{mapname} 是另一名称的别名则会先检查别名。

@emph{domain} 参数可允许重载用于查找的 NIS 域。 如果未指定，则会在默认 NIS 域中查找。
@end deffn

@geindex maps() (在 nis 模块中)
@anchor{library/nis nis maps}@anchor{d8c}
@deffn {函数} nis.maps (domain=default_domain)

返回全部可用映射的列表。

@emph{domain} 参数可允许重载用于查找的 NIS 域。 如果未指定，则会在默认 NIS 域中查找。
@end deffn

@geindex get_default_domain() (在 nis 模块中)
@anchor{library/nis nis get_default_domain}@anchor{3a04}
@deffn {函数} nis.get_default_domain ()

返回系统默认的 NIS 域。
@end deffn

@ref{bf,,nis} 模块定义了以下异常：

@geindex error
@anchor{library/nis nis error}@anchor{3a02}
@deffn {例外} nis.error

当 NIS 函数返回一个错误码时引发的异常。
@end deffn

@node Unix syslog 库例程,,nis --- Sun 的 NIS 黄页 接口,Unix 专有服务
@anchor{library/syslog doc}@anchor{3a05}@anchor{library/syslog module-syslog}@anchor{ff}@anchor{library/syslog syslog-unix-syslog-library-routines}@anchor{3a06}
@subsection Unix syslog 库例程


@geindex syslog (模块)


__________________________________________________________________


此模块提供一个接口到Unix @code{syslog} 日常库. 参考 Unix 手册页关于 @code{syslog} 设施的详细描述.

此模块包装了系统的 @code{syslog} 例程族。 一个能与 syslog 服务器对话的纯 Python 库则以 @ref{ac,,logging.handlers} 模块中 @code{SysLogHandler} 类的形式提供。

这个模块定义了以下函数：

@geindex syslog() (在 syslog 模块中)
@anchor{library/syslog syslog syslog}@anchor{3479}
@deffn {函数} syslog.syslog (message)

@deffnx {函数} syslog.syslog (priority, message)

将字符串 @emph{message} 发送到系统日志记录器。 如有必要会添加末尾换行符。 每条消息都带有一个由 @emph{facility} 和 @emph{level} 组成的优先级标价签。 可选的 @emph{priority} 参数默认值为 @code{LOG_INFO}，它确定消息的优先级。 如果未在 @emph{priority} 中使用逻辑或 (@code{LOG_INFO | LOG_USER}) 对 facility 进行编码，则会使用在 @ref{3477,,openlog()} 调用中所给定的值。

如果 @ref{3477,,openlog()} 未在对 @ref{ff,,syslog()} 的调用之前被调用，则将不带参数地调用 @code{openlog()}。

引发 @ref{12d0,,审计事件} @code{syslog.syslog} 使用参数 @code{priority}, @code{message}.
@end deffn

@geindex openlog() (在 syslog 模块中)
@anchor{library/syslog syslog openlog}@anchor{3477}
@deffn {函数} syslog.openlog ([ident[, logoption[, facility]]])

后续 @ref{ff,,syslog()} 调用的日志选项可以通过调用 @ref{3477,,openlog()} 来设置。 如果日志当前未打开则 @ref{ff,,syslog()} 将不带参数地调用 @ref{3477,,openlog()}。

可选的 @emph{ident} 关键字参数是在每条消息前添加的字符串，默认为 @code{sys.argv[0]} 去除打头的路径部分。 可选的 @emph{logoption} 关键字参数（默认为 0）是一个位字段 -- 请参见下文了解可能的组合值。 可选的 @emph{facility} 关键字参数 (默认为 @code{LOG_USER}) 为没有显式编码 facility 的消息设置默认的 facility。

引发 @ref{12d0,,审计事件} @code{syslog.openlog} 使用参数 @code{ident}, @code{logoption}, @code{facility}.


在 3.2 版更改: 在之前的版本中，不允许关键字参数，并且要求必须有 @emph{ident}。 @emph{ident} 的默认值依赖于系统库，它往往为 @code{python} 而不是 Python 程序文件的实际名称。

@end deffn

@geindex closelog() (在 syslog 模块中)
@anchor{library/syslog syslog closelog}@anchor{3476}
@deffn {函数} syslog.closelog ()

重置日志模块值并且调用系统库 @code{closelog()}.

这使得此模块在初始导入时行为固定。 例如，@ref{3477,,openlog()} 将在首次调用 @ref{ff,,syslog()} 时被调用（如果 @ref{3477,,openlog()} 还未被调用过），并且 @emph{ident} 和其他 @ref{3477,,openlog()} 形参会被重置为默认值。

引发一个 @ref{12d0,,审计事件} @code{syslog.closelog} 不附带任何参数。
@end deffn

@geindex setlogmask() (在 syslog 模块中)
@anchor{library/syslog syslog setlogmask}@anchor{3478}
@deffn {函数} syslog.setlogmask (maskpri)

将优先级掩码设为 @emph{maskpri} 并返回之前的掩码值。 调用 @ref{ff,,syslog()} 并附带未在 @emph{maskpri} 中设置的优先级将会被忽略。 默认设置为记录所有优先级。 函数 @code{LOG_MASK(pri)} 可计算单个优先级 @emph{pri} 的掩码。 函数 @code{LOG_UPTO(pri)} 可计算包括 @emph{pri} 在内的所有优先级的掩码。

引发一个 @ref{12d0,,审计事件} @code{syslog.setlogmask} 附带参数 @code{maskpri}。
@end deffn

此莫款定义了一下常量:


@table @asis

@item 优先级级别 (高到低):

@code{LOG_EMERG}, @code{LOG_ALERT}, @code{LOG_CRIT}, @code{LOG_ERR},
@code{LOG_WARNING}, @code{LOG_NOTICE}, @code{LOG_INFO},
@code{LOG_DEBUG}.

@item 设施:

@code{LOG_KERN}, @code{LOG_USER}, @code{LOG_MAIL}, @code{LOG_DAEMON}, @code{LOG_AUTH}, @code{LOG_LPR}, @code{LOG_NEWS}, @code{LOG_UUCP}, @code{LOG_CRON}, @code{LOG_SYSLOG}, @code{LOG_LOCAL0} to @code{LOG_LOCAL7}，如果 @code{<syslog.h>} 中有定义则还有 @code{LOG_AUTHPRIV}。

@item 日志选项:

@code{LOG_PID}, @code{LOG_CONS}, @code{LOG_NDELAY}，如果 @code{<syslog.h>} 中有定义则还有 @code{LOG_ODELAY}, @code{LOG_NOWAIT} 以及 @code{LOG_PERROR}。
@end table

@menu
* 例子: 例子<32>. 

@end menu

@node 例子<32>,,,Unix syslog 库例程
@anchor{library/syslog examples}@anchor{3a07}
@subsubsection 例子


@menu
* 简单示例:: 

@end menu

@node 简单示例,,,例子<32>
@anchor{library/syslog simple-example}@anchor{3a08}
@subsubsection 简单示例


一个简单的示例集:

@example
import syslog

syslog.syslog('Processing started')
if error:
    syslog.syslog(syslog.LOG_ERR, 'Processing started')
@end example

一个设置多种日志选项的示例，其中有在日志消息中包含进程 ID，以及将消息写入用于邮件日志记录的目标设施等:

@example
syslog.openlog(logoption=syslog.LOG_PID, facility=syslog.LOG_MAIL)
syslog.syslog('E-mail processing initiated...')
@end example

@node 被取代的模块,未创建文档的模块,Unix 专有服务,Python 标准库
@anchor{library/superseded doc}@anchor{3a09}@anchor{library/superseded superseded}@anchor{3a0a}@anchor{library/superseded superseded-modules}@anchor{3a0b}
@section 被取代的模块


本章中描述的模块均已弃用，仅保留用于向后兼容。 它们已经被其他模块所取代。

@menu
* optparse: optparse --- 解析器的命令行选项. 解析器的命令行选项
* imp: imp --- Access the import internals. Access the import internals

@end menu

@node optparse --- 解析器的命令行选项,imp --- Access the import internals,,被取代的模块
@anchor{library/optparse doc}@anchor{3a0c}@anchor{library/optparse module-optparse}@anchor{c3}@anchor{library/optparse optparse-parser-for-command-line-options}@anchor{3a0d}
@subsection @code{optparse} --- 解析器的命令行选项


@geindex optparse (模块)

@strong{源代码：} Lib/optparse.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/optparse.py}


3.2 版后已移除: The @ref{c3,,optparse} module is deprecated and will not be developed further;
development will continue with the @ref{6,,argparse} module.



__________________________________________________________________


@ref{c3,,optparse} is a more convenient, flexible, and powerful library for parsing
command-line options than the old @ref{87,,getopt} module.  @ref{c3,,optparse} uses a
more declarative style of command-line parsing: you create an instance of
@ref{3a0e,,OptionParser}, populate it with options, and parse the command
line. @ref{c3,,optparse} allows users to specify options in the conventional
GNU/POSIX syntax, and additionally generates usage and help messages for you.

Here's an example of using @ref{c3,,optparse} in a simple script:

@example
from optparse import OptionParser
...
parser = OptionParser()
parser.add_option("-f", "--file", dest="filename",
                  help="write report to FILE", metavar="FILE")
parser.add_option("-q", "--quiet",
                  action="store_false", dest="verbose", default=True,
                  help="don't print status messages to stdout")

(options, args) = parser.parse_args()
@end example

With these few lines of code, users of your script can now do the "usual thing"
on the command-line, for example:

@example
<yourscript> --file=outfile -q
@end example

As it parses the command line, @ref{c3,,optparse} sets attributes of the
@code{options} object returned by @code{parse_args()} based on user-supplied
command-line values.  When @code{parse_args()} returns from parsing this command
line, @code{options.filename} will be @code{"outfile"} and @code{options.verbose} will be
@code{False}.  @ref{c3,,optparse} supports both long and short options, allows short
options to be merged together, and allows options to be associated with their
arguments in a variety of ways.  Thus, the following command lines are all
equivalent to the above example:

@example
<yourscript> -f outfile --quiet
<yourscript> --quiet --file outfile
<yourscript> -q -foutfile
<yourscript> -qfoutfile
@end example

Additionally, users can run one of

@example
<yourscript> -h
<yourscript> --help
@end example

and @ref{c3,,optparse} will print out a brief summary of your script's options:

@example
Usage: <yourscript> [options]

Options:
  -h, --help            show this help message and exit
  -f FILE, --file=FILE  write report to FILE
  -q, --quiet           don't print status messages to stdout
@end example

where the value of @emph{yourscript} is determined at runtime (normally from
@code{sys.argv[0]}).

@menu
* 背景:: 
* 教程: 教程<2>. 
* 参考指南:: 
* Option Callbacks:: 
* Extending optparse:: 

@end menu

@node 背景,教程<2>,,optparse --- 解析器的命令行选项
@anchor{library/optparse background}@anchor{3a0f}@anchor{library/optparse optparse-background}@anchor{3a10}
@subsubsection 背景


@ref{c3,,optparse} was explicitly designed to encourage the creation of programs
with straightforward, conventional command-line interfaces.  To that end, it
supports only the most common command-line syntax and semantics conventionally
used under Unix.  If you are unfamiliar with these conventions, read this
section to acquaint yourself with them.

@menu
* 术语:: 
* What are options for?:: 
* 位置位置:: 

@end menu

@node 术语,What are options for?,,背景
@anchor{library/optparse optparse-terminology}@anchor{3a11}@anchor{library/optparse terminology}@anchor{3a12}
@subsubsection 术语



@table @asis

@item argument -- 参数

a string entered on the command-line, and passed by the shell to @code{execl()}
or @code{execv()}.  In Python, arguments are elements of @code{sys.argv[1:]}
(@code{sys.argv[0]} is the name of the program being executed).  Unix shells
also use the term "word".

It is occasionally desirable to substitute an argument list other than
@code{sys.argv[1:]}, so you should read "argument" as "an element of
@code{sys.argv[1:]}, or of some other list provided as a substitute for
@code{sys.argv[1:]}".

@item 选项

an argument used to supply extra information to guide or customize the
execution of a program.  There are many different syntaxes for options; the
traditional Unix syntax is a hyphen ("-") followed by a single letter,
e.g. @code{-x} or @code{-F}.  Also, traditional Unix syntax allows multiple
options to be merged into a single argument, e.g. @code{-x -F} is equivalent
to @code{-xF}.  The GNU project introduced @code{--} followed by a series of
hyphen-separated words, e.g. @code{--file} or @code{--dry-run}.  These are the
only two option syntaxes provided by @ref{c3,,optparse}.

Some other option syntaxes that the world has seen include:


@itemize *

@item 
a hyphen followed by a few letters, e.g. @code{-pf} (this is @emph{not} the same
as multiple options merged into a single argument)

@item 
a hyphen followed by a whole word, e.g. @code{-file} (this is technically
equivalent to the previous syntax, but they aren't usually seen in the same
program)

@item 
a plus sign followed by a single letter, or a few letters, or a word, e.g.
@code{+f}, @code{+rgb}

@item 
a slash followed by a letter, or a few letters, or a word, e.g. @code{/f},
@code{/file}
@end itemize

These option syntaxes are not supported by @ref{c3,,optparse}, and they never
will be.  This is deliberate: the first three are non-standard on any
environment, and the last only makes sense if you're exclusively targeting
VMS, MS-DOS, and/or Windows.

@item 可选参数:

an argument that follows an option, is closely associated with that option,
and is consumed from the argument list when that option is. With
@ref{c3,,optparse}, option arguments may either be in a separate argument from
their option:

@example
-f foo
--file foo
@end example

or included in the same argument:

@example
-ffoo
--file=foo
@end example

Typically, a given option either takes an argument or it doesn't. Lots of
people want an "optional option arguments" feature, meaning that some options
will take an argument if they see it, and won't if they don't.  This is
somewhat controversial, because it makes parsing ambiguous: if @code{-a} takes
an optional argument and @code{-b} is another option entirely, how do we
interpret @code{-ab}?  Because of this ambiguity, @ref{c3,,optparse} does not
support this feature.

@item positional argument -- 位置参数

something leftover in the argument list after options have been parsed, i.e.
after options and their arguments have been parsed and removed from the
argument list.

@item 必选选项

an option that must be supplied on the command-line; note that the phrase
"required option" is self-contradictory in English.  @ref{c3,,optparse} doesn't
prevent you from implementing required options, but doesn't give you much
help at it either.
@end table

For example, consider this hypothetical command-line:

@example
prog -v --report report.txt foo bar
@end example

@code{-v} and @code{--report} are both options.  Assuming that @code{--report}
takes one argument, @code{report.txt} is an option argument.  @code{foo} and
@code{bar} are positional arguments.

@node What are options for?,位置位置,术语,背景
@anchor{library/optparse optparse-what-options-for}@anchor{3a13}@anchor{library/optparse what-are-options-for}@anchor{3a14}
@subsubsection What are options for?


Options are used to provide extra information to tune or customize the execution
of a program.  In case it wasn't clear, options are usually @emph{optional}.  A
program should be able to run just fine with no options whatsoever.  (Pick a
random program from the Unix or GNU toolsets.  Can it run without any options at
all and still make sense?  The main exceptions are @code{find}, @code{tar}, and
@code{dd}---all of which are mutant oddballs that have been rightly criticized
for their non-standard syntax and confusing interfaces.)

Lots of people want their programs to have "required options".  Think about it.
If it's required, then it's @emph{not optional}!  If there is a piece of information
that your program absolutely requires in order to run successfully, that's what
positional arguments are for.

As an example of good command-line interface design, consider the humble @code{cp}
utility, for copying files.  It doesn't make much sense to try to copy files
without supplying a destination and at least one source. Hence, @code{cp} fails if
you run it with no arguments.  However, it has a flexible, useful syntax that
does not require any options at all:

@example
cp SOURCE DEST
cp SOURCE ... DEST-DIR
@end example

You can get pretty far with just that.  Most @code{cp} implementations provide a
bunch of options to tweak exactly how the files are copied: you can preserve
mode and modification time, avoid following symlinks, ask before clobbering
existing files, etc.  But none of this distracts from the core mission of
@code{cp}, which is to copy either one file to another, or several files to another
directory.

@node 位置位置,,What are options for?,背景
@anchor{library/optparse optparse-what-positional-arguments-for}@anchor{3a15}@anchor{library/optparse what-are-positional-arguments-for}@anchor{3a16}
@subsubsection 位置位置


Positional arguments are for those pieces of information that your program
absolutely, positively requires to run.

A good user interface should have as few absolute requirements as possible.  If
your program requires 17 distinct pieces of information in order to run
successfully, it doesn't much matter @emph{how} you get that information from the
user---most people will give up and walk away before they successfully run the
program.  This applies whether the user interface is a command-line, a
configuration file, or a GUI: if you make that many demands on your users, most
of them will simply give up.

In short, try to minimize the amount of information that users are absolutely
required to supply---use sensible defaults whenever possible.  Of course, you
also want to make your programs reasonably flexible.  That's what options are
for.  Again, it doesn't matter if they are entries in a config file, widgets in
the "Preferences" dialog of a GUI, or command-line options---the more options
you implement, the more flexible your program is, and the more complicated its
implementation becomes.  Too much flexibility has drawbacks as well, of course;
too many options can overwhelm users and make your code much harder to maintain.

@node 教程<2>,参考指南,背景,optparse --- 解析器的命令行选项
@anchor{library/optparse optparse-tutorial}@anchor{3a17}@anchor{library/optparse tutorial}@anchor{3a18}
@subsubsection 教程


While @ref{c3,,optparse} is quite flexible and powerful, it's also straightforward
to use in most cases.  This section covers the code patterns that are common to
any @ref{c3,,optparse}-based program.

First, you need to import the OptionParser class; then, early in the main
program, create an OptionParser instance:

@example
from optparse import OptionParser
...
parser = OptionParser()
@end example

Then you can start defining options.  The basic syntax is:

@example
parser.add_option(opt_str, ...,
                  attr=value, ...)
@end example

Each option has one or more option strings, such as @code{-f} or @code{--file},
and several option attributes that tell @ref{c3,,optparse} what to expect and what
to do when it encounters that option on the command line.

Typically, each option will have one short option string and one long option
string, e.g.:

@example
parser.add_option("-f", "--file", ...)
@end example

You're free to define as many short option strings and as many long option
strings as you like (including zero), as long as there is at least one option
string overall.

The option strings passed to @ref{200b,,OptionParser.add_option()} are effectively
labels for the
option defined by that call.  For brevity, we will frequently refer to
@emph{encountering an option} on the command line; in reality, @ref{c3,,optparse}
encounters @emph{option strings} and looks up options from them.

Once all of your options are defined, instruct @ref{c3,,optparse} to parse your
program's command line:

@example
(options, args) = parser.parse_args()
@end example

(If you like, you can pass a custom argument list to @code{parse_args()}, but
that's rarely necessary: by default it uses @code{sys.argv[1:]}.)

@code{parse_args()} 返回两个值：


@itemize *

@item 
@code{options}, an object containing values for all of your options---e.g. if
@code{--file} takes a single string argument, then @code{options.file} will be the
filename supplied by the user, or @code{None} if the user did not supply that
option

@item 
@code{args}, the list of positional arguments leftover after parsing options
@end itemize

This tutorial section only covers the four most important option attributes:
@ref{3a19,,action}, @ref{3a1a,,type}, @ref{3a1b,,dest}
(destination), and @ref{3a1c,,help}. Of these, @ref{3a19,,action} is the
most fundamental.

@menu
* Understanding option actions:: 
* The store action:: 
* Handling boolean (flag) options: Handling boolean flag options. 
* Other actions:: 
* 默认值: 默认值<2>. 
* Generating help:: 
* Printing a version string:: 
* How optparse handles errors:: 
* Putting it all together:: 

@end menu

@node Understanding option actions,The store action,,教程<2>
@anchor{library/optparse optparse-understanding-option-actions}@anchor{3a1d}@anchor{library/optparse understanding-option-actions}@anchor{3a1e}
@subsubsection Understanding option actions


Actions tell @ref{c3,,optparse} what to do when it encounters an option on the
command line.  There is a fixed set of actions hard-coded into @ref{c3,,optparse};
adding new actions is an advanced topic covered in section
@ref{3a1f,,Extending optparse}.  Most actions tell @ref{c3,,optparse} to store
a value in some variable---for example, take a string from the command line and
store it in an attribute of @code{options}.

If you don't specify an option action, @ref{c3,,optparse} defaults to @code{store}.

@node The store action,Handling boolean flag options,Understanding option actions,教程<2>
@anchor{library/optparse optparse-store-action}@anchor{3a20}@anchor{library/optparse the-store-action}@anchor{3a21}
@subsubsection The store action


The most common option action is @code{store}, which tells @ref{c3,,optparse} to take
the next argument (or the remainder of the current argument), ensure that it is
of the correct type, and store it to your chosen destination.

例如

@example
parser.add_option("-f", "--file",
                  action="store", type="string", dest="filename")
@end example

Now let's make up a fake command line and ask @ref{c3,,optparse} to parse it:

@example
args = ["-f", "foo.txt"]
(options, args) = parser.parse_args(args)
@end example

When @ref{c3,,optparse} sees the option string @code{-f}, it consumes the next
argument, @code{foo.txt}, and stores it in @code{options.filename}.  So, after this
call to @code{parse_args()}, @code{options.filename} is @code{"foo.txt"}.

Some other option types supported by @ref{c3,,optparse} are @code{int} and @code{float}.
Here's an option that expects an integer argument:

@example
parser.add_option("-n", type="int", dest="num")
@end example

Note that this option has no long option string, which is perfectly acceptable.
Also, there's no explicit action, since the default is @code{store}.

Let's parse another fake command-line.  This time, we'll jam the option argument
right up against the option: since @code{-n42} (one argument) is equivalent to
@code{-n 42} (two arguments), the code

@example
(options, args) = parser.parse_args(["-n42"])
print(options.num)
@end example

will print @code{42}.

If you don't specify a type, @ref{c3,,optparse} assumes @code{string}.  Combined with
the fact that the default action is @code{store}, that means our first example can
be a lot shorter:

@example
parser.add_option("-f", "--file", dest="filename")
@end example

If you don't supply a destination, @ref{c3,,optparse} figures out a sensible
default from the option strings: if the first long option string is
@code{--foo-bar}, then the default destination is @code{foo_bar}.  If there are no
long option strings, @ref{c3,,optparse} looks at the first short option string: the
default destination for @code{-f} is @code{f}.

@ref{c3,,optparse} also includes the built-in @code{complex} type.  Adding
types is covered in section @ref{3a1f,,Extending optparse}.

@node Handling boolean flag options,Other actions,The store action,教程<2>
@anchor{library/optparse handling-boolean-flag-options}@anchor{3a22}@anchor{library/optparse optparse-handling-boolean-options}@anchor{3a23}
@subsubsection Handling boolean (flag) options


Flag options---set a variable to true or false when a particular option is
seen---are quite common.  @ref{c3,,optparse} supports them with two separate actions,
@code{store_true} and @code{store_false}.  For example, you might have a @code{verbose}
flag that is turned on with @code{-v} and off with @code{-q}:

@example
parser.add_option("-v", action="store_true", dest="verbose")
parser.add_option("-q", action="store_false", dest="verbose")
@end example

Here we have two different options with the same destination, which is perfectly
OK.  (It just means you have to be a bit careful when setting default
values---see below.)

When @ref{c3,,optparse} encounters @code{-v} on the command line, it sets
@code{options.verbose} to @code{True}; when it encounters @code{-q},
@code{options.verbose} is set to @code{False}.

@node Other actions,默认值<2>,Handling boolean flag options,教程<2>
@anchor{library/optparse optparse-other-actions}@anchor{3a24}@anchor{library/optparse other-actions}@anchor{3a25}
@subsubsection Other actions


Some other actions supported by @ref{c3,,optparse} are:


@table @asis

@item @code{"store_const"}

store a constant value

@item @code{"append"}

append this option's argument to a list

@item @code{"count"}

increment a counter by one

@item @code{"callback"}

调用指定函数
@end table

These are covered in section @ref{3a26,,参考指南},
and section @ref{3a27,,Option Callbacks}.

@node 默认值<2>,Generating help,Other actions,教程<2>
@anchor{library/optparse default-values}@anchor{3a28}@anchor{library/optparse optparse-default-values}@anchor{3a29}
@subsubsection 默认值


All of the above examples involve setting some variable (the "destination") when
certain command-line options are seen.  What happens if those options are never
seen?  Since we didn't supply any defaults, they are all set to @code{None}.  This
is usually fine, but sometimes you want more control.  @ref{c3,,optparse} lets you
supply a default value for each destination, which is assigned before the
command line is parsed.

First, consider the verbose/quiet example.  If we want @ref{c3,,optparse} to set
@code{verbose} to @code{True} unless @code{-q} is seen, then we can do this:

@example
parser.add_option("-v", action="store_true", dest="verbose", default=True)
parser.add_option("-q", action="store_false", dest="verbose")
@end example

Since default values apply to the @emph{destination} rather than to any particular
option, and these two options happen to have the same destination, this is
exactly equivalent:

@example
parser.add_option("-v", action="store_true", dest="verbose")
parser.add_option("-q", action="store_false", dest="verbose", default=True)
@end example

考虑一下：

@example
parser.add_option("-v", action="store_true", dest="verbose", default=False)
parser.add_option("-q", action="store_false", dest="verbose", default=True)
@end example

Again, the default value for @code{verbose} will be @code{True}: the last default
value supplied for any particular destination is the one that counts.

A clearer way to specify default values is the @code{set_defaults()} method of
OptionParser, which you can call at any time before calling @code{parse_args()}:

@example
parser.set_defaults(verbose=True)
parser.add_option(...)
(options, args) = parser.parse_args()
@end example

As before, the last value specified for a given option destination is the one
that counts.  For clarity, try to use one method or the other of setting default
values, not both.

@node Generating help,Printing a version string,默认值<2>,教程<2>
@anchor{library/optparse generating-help}@anchor{3a2a}@anchor{library/optparse optparse-generating-help}@anchor{3a2b}
@subsubsection Generating help


@ref{c3,,optparse}'s ability to generate help and usage text automatically is
useful for creating user-friendly command-line interfaces.  All you have to do
is supply a @ref{3a1c,,help} value for each option, and optionally a short
usage message for your whole program.  Here's an OptionParser populated with
user-friendly (documented) options:

@example
usage = "usage: %prog [options] arg1 arg2"
parser = OptionParser(usage=usage)
parser.add_option("-v", "--verbose",
                  action="store_true", dest="verbose", default=True,
                  help="make lots of noise [default]")
parser.add_option("-q", "--quiet",
                  action="store_false", dest="verbose",
                  help="be vewwy quiet (I'm hunting wabbits)")
parser.add_option("-f", "--filename",
                  metavar="FILE", help="write output to FILE")
parser.add_option("-m", "--mode",
                  default="intermediate",
                  help="interaction mode: novice, intermediate, "
                       "or expert [default: %default]")
@end example

If @ref{c3,,optparse} encounters either @code{-h} or @code{--help} on the
command-line, or if you just call @code{parser.print_help()}, it prints the
following to standard output:

@example
Usage: <yourscript> [options] arg1 arg2

Options:
  -h, --help            show this help message and exit
  -v, --verbose         make lots of noise [default]
  -q, --quiet           be vewwy quiet (I'm hunting wabbits)
  -f FILE, --filename=FILE
                        write output to FILE
  -m MODE, --mode=MODE  interaction mode: novice, intermediate, or
                        expert [default: intermediate]
@end example

(If the help output is triggered by a help option, @ref{c3,,optparse} exits after
printing the help text.)

There's a lot going on here to help @ref{c3,,optparse} generate the best possible
help message:


@itemize *

@item 
the script defines its own usage message:

@example
usage = "usage: %prog [options] arg1 arg2"
@end example

@ref{c3,,optparse} expands @code{%prog} in the usage string to the name of the
current program, i.e. @code{os.path.basename(sys.argv[0])}.  The expanded string
is then printed before the detailed option help.

If you don't supply a usage string, @ref{c3,,optparse} uses a bland but sensible
default: @code{"Usage: %prog [options]"}, which is fine if your script doesn't
take any positional arguments.

@item 
every option defines a help string, and doesn't worry about
line-wrapping---@ref{c3,,optparse} takes care of wrapping lines and making
the help output look good.

@item 
options that take a value indicate this fact in their automatically-generated
help message, e.g. for the "mode" option:

@example
-m MODE, --mode=MODE
@end example

Here, "MODE" is called the meta-variable: it stands for the argument that the
user is expected to supply to @code{-m}/@code{--mode}.  By default,
@ref{c3,,optparse} converts the destination variable name to uppercase and uses
that for the meta-variable.  Sometimes, that's not what you want---for
example, the @code{--filename} option explicitly sets @code{metavar="FILE"},
resulting in this automatically-generated option description:

@example
-f FILE, --filename=FILE
@end example

This is important for more than just saving space, though: the manually
written help text uses the meta-variable @code{FILE} to clue the user in that
there's a connection between the semi-formal syntax @code{-f FILE} and the informal
semantic description "write output to FILE". This is a simple but effective
way to make your help text a lot clearer and more useful for end users.

@item 
options that have a default value can include @code{%default} in the help
string---@ref{c3,,optparse} will replace it with @ref{329,,str()} of the option's
default value.  If an option has no default value (or the default value is
@code{None}), @code{%default} expands to @code{none}.
@end itemize

@menu
* Grouping Options:: 

@end menu

@node Grouping Options,,,Generating help
@anchor{library/optparse grouping-options}@anchor{3a2c}
@subsubsection Grouping Options


When dealing with many options, it is convenient to group these options for
better help output.  An @ref{3a0e,,OptionParser} can contain several option groups,
each of which can contain several options.

An option group is obtained using the class @ref{3a2d,,OptionGroup}:

@geindex OptionGroup (optparse 中的类)
@anchor{library/optparse optparse OptionGroup}@anchor{3a2d}
@deffn {类} optparse.OptionGroup (parser, title, description=None)

where


@itemize *

@item 
parser is the @ref{3a0e,,OptionParser} instance the group will be inserted in
to

@item 
title is the group title

@item 
description, optional, is a long description of the group
@end itemize
@end deffn

@ref{3a2d,,OptionGroup} inherits from @code{OptionContainer} (like
@ref{3a0e,,OptionParser}) and so the @code{add_option()} method can be used to add
an option to the group.

Once all the options are declared, using the @ref{3a0e,,OptionParser} method
@code{add_option_group()} the group is added to the previously defined parser.

Continuing with the parser defined in the previous section, adding an
@ref{3a2d,,OptionGroup} to a parser is easy:

@example
group = OptionGroup(parser, "Dangerous Options",
                    "Caution: use these options at your own risk.  "
                    "It is believed that some of them bite.")
group.add_option("-g", action="store_true", help="Group option.")
parser.add_option_group(group)
@end example

This would result in the following help output:

@example
Usage: <yourscript> [options] arg1 arg2

Options:
  -h, --help            show this help message and exit
  -v, --verbose         make lots of noise [default]
  -q, --quiet           be vewwy quiet (I'm hunting wabbits)
  -f FILE, --filename=FILE
                        write output to FILE
  -m MODE, --mode=MODE  interaction mode: novice, intermediate, or
                        expert [default: intermediate]

  Dangerous Options:
    Caution: use these options at your own risk.  It is believed that some
    of them bite.

    -g                  Group option.
@end example

A bit more complete example might involve using more than one group: still
extending the previous example:

@example
group = OptionGroup(parser, "Dangerous Options",
                    "Caution: use these options at your own risk.  "
                    "It is believed that some of them bite.")
group.add_option("-g", action="store_true", help="Group option.")
parser.add_option_group(group)

group = OptionGroup(parser, "Debug Options")
group.add_option("-d", "--debug", action="store_true",
                 help="Print debug information")
group.add_option("-s", "--sql", action="store_true",
                 help="Print all SQL statements executed")
group.add_option("-e", action="store_true", help="Print every action done")
parser.add_option_group(group)
@end example

that results in the following output:

@example
Usage: <yourscript> [options] arg1 arg2

Options:
  -h, --help            show this help message and exit
  -v, --verbose         make lots of noise [default]
  -q, --quiet           be vewwy quiet (I'm hunting wabbits)
  -f FILE, --filename=FILE
                        write output to FILE
  -m MODE, --mode=MODE  interaction mode: novice, intermediate, or expert
                        [default: intermediate]

  Dangerous Options:
    Caution: use these options at your own risk.  It is believed that some
    of them bite.

    -g                  Group option.

  Debug Options:
    -d, --debug         Print debug information
    -s, --sql           Print all SQL statements executed
    -e                  Print every action done
@end example

Another interesting method, in particular when working programmatically with
option groups is:

@geindex get_option_group() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser get_option_group}@anchor{3a2e}
@deffn {方法} OptionParser.get_option_group (opt_str)

Return the @ref{3a2d,,OptionGroup} to which the short or long option
string @emph{opt_str} (e.g. @code{'-o'} or @code{'--option'}) belongs. If
there's no such @ref{3a2d,,OptionGroup}, return @code{None}.
@end deffn

@node Printing a version string,How optparse handles errors,Generating help,教程<2>
@anchor{library/optparse optparse-printing-version-string}@anchor{3a2f}@anchor{library/optparse printing-a-version-string}@anchor{3a30}
@subsubsection Printing a version string


Similar to the brief usage string, @ref{c3,,optparse} can also print a version
string for your program.  You have to supply the string as the @code{version}
argument to OptionParser:

@example
parser = OptionParser(usage="%prog [-f] [-q]", version="%prog 1.0")
@end example

@code{%prog} is expanded just like it is in @code{usage}.  Apart from that,
@code{version} can contain anything you like.  When you supply it, @ref{c3,,optparse}
automatically adds a @code{--version} option to your parser. If it encounters
this option on the command line, it expands your @code{version} string (by
replacing @code{%prog}), prints it to stdout, and exits.

For example, if your script is called @code{/usr/bin/foo}:

@example
$ /usr/bin/foo --version
foo 1.0
@end example

The following two methods can be used to print and get the @code{version} string:

@geindex print_version() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser print_version}@anchor{3a31}
@deffn {方法} OptionParser.print_version (file=None)

Print the version message for the current program (@code{self.version}) to
@emph{file} (default stdout).  As with @ref{3a32,,print_usage()}, any occurrence
of @code{%prog} in @code{self.version} is replaced with the name of the current
program.  Does nothing if @code{self.version} is empty or undefined.
@end deffn

@geindex get_version() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser get_version}@anchor{3a33}
@deffn {方法} OptionParser.get_version ()

Same as @ref{3a31,,print_version()} but returns the version string instead of
printing it.
@end deffn

@node How optparse handles errors,Putting it all together,Printing a version string,教程<2>
@anchor{library/optparse how-optparse-handles-errors}@anchor{3a34}@anchor{library/optparse optparse-how-optparse-handles-errors}@anchor{3a35}
@subsubsection How @code{optparse} handles errors


There are two broad classes of errors that @ref{c3,,optparse} has to worry about:
programmer errors and user errors.  Programmer errors are usually erroneous
calls to @ref{200b,,OptionParser.add_option()}, e.g. invalid option strings, unknown
option attributes, missing option attributes, etc.  These are dealt with in the
usual way: raise an exception (either @code{optparse.OptionError} or
@ref{192,,TypeError}) and let the program crash.

Handling user errors is much more important, since they are guaranteed to happen
no matter how stable your code is.  @ref{c3,,optparse} can automatically detect
some user errors, such as bad option arguments (passing @code{-n 4x} where
@code{-n} takes an integer argument), missing arguments (@code{-n} at the end
of the command line, where @code{-n} takes an argument of any type).  Also,
you can call @code{OptionParser.error()} to signal an application-defined error
condition:

@example
(options, args) = parser.parse_args()
...
if options.a and options.b:
    parser.error("options -a and -b are mutually exclusive")
@end example

In either case, @ref{c3,,optparse} handles the error the same way: it prints the
program's usage message and an error message to standard error and exits with
error status 2.

Consider the first example above, where the user passes @code{4x} to an option
that takes an integer:

@example
$ /usr/bin/foo -n 4x
Usage: foo [options]

foo: error: option -n: invalid integer value: '4x'
@end example

Or, where the user fails to pass a value at all:

@example
$ /usr/bin/foo -n
Usage: foo [options]

foo: error: -n option requires an argument
@end example

@ref{c3,,optparse}-generated error messages take care always to mention the
option involved in the error; be sure to do the same when calling
@code{OptionParser.error()} from your application code.

If @ref{c3,,optparse}'s default error-handling behaviour does not suit your needs,
you'll need to subclass OptionParser and override its @code{exit()}
and/or @code{error()} methods.

@node Putting it all together,,How optparse handles errors,教程<2>
@anchor{library/optparse optparse-putting-it-all-together}@anchor{3a36}@anchor{library/optparse putting-it-all-together}@anchor{3a37}
@subsubsection Putting it all together


Here's what @ref{c3,,optparse}-based scripts usually look like:

@example
from optparse import OptionParser
...
def main():
    usage = "usage: %prog [options] arg"
    parser = OptionParser(usage)
    parser.add_option("-f", "--file", dest="filename",
                      help="read data from FILENAME")
    parser.add_option("-v", "--verbose",
                      action="store_true", dest="verbose")
    parser.add_option("-q", "--quiet",
                      action="store_false", dest="verbose")
    ...
    (options, args) = parser.parse_args()
    if len(args) != 1:
        parser.error("incorrect number of arguments")
    if options.verbose:
        print("reading %s..." % options.filename)
    ...

if __name__ == "__main__":
    main()
@end example

@node 参考指南,Option Callbacks,教程<2>,optparse --- 解析器的命令行选项
@anchor{library/optparse optparse-reference-guide}@anchor{3a26}@anchor{library/optparse reference-guide}@anchor{3a38}
@subsubsection 参考指南


@menu
* 创建解析器:: 
* 填充解析器:: 
* 定义选项:: 
* Option attributes:: 
* Standard option actions:: 
* Standard option types:: 
* 解析参数: 解析参数<2>. 
* Querying and manipulating your option parser:: 
* Conflicts between options:: 
* 清理: 清理<2>. 
* Other methods:: 

@end menu

@node 创建解析器,填充解析器,,参考指南
@anchor{library/optparse creating-the-parser}@anchor{3a39}@anchor{library/optparse optparse-creating-parser}@anchor{3a3a}
@subsubsection 创建解析器


The first step in using @ref{c3,,optparse} is to create an OptionParser instance.

@geindex OptionParser (optparse 中的类)
@anchor{library/optparse optparse OptionParser}@anchor{3a0e}
@deffn {类} optparse.OptionParser (...)

The OptionParser constructor has no required arguments, but a number of
optional keyword arguments.  You should always pass them as keyword
arguments, i.e. do not rely on the order in which the arguments are declared.


@table @asis

@item @code{usage} (默认: @code{"%prog [options]"})

The usage summary to print when your program is run incorrectly or with a
help option.  When @ref{c3,,optparse} prints the usage string, it expands
@code{%prog} to @code{os.path.basename(sys.argv[0])} (or to @code{prog} if you
passed that keyword argument).  To suppress a usage message, pass the
special value @code{optparse.SUPPRESS_USAGE}.

@item @code{option_list} (默认: @code{[]})

A list of Option objects to populate the parser with.  The options in
@code{option_list} are added after any options in @code{standard_option_list} (a
class attribute that may be set by OptionParser subclasses), but before
any version or help options. Deprecated; use @ref{200b,,add_option()} after
creating the parser instead.

@item @code{option_class} (默认: optparse.Option)

Class to use when adding options to the parser in @ref{200b,,add_option()}.

@item @code{version} (默认: @code{None})

A version string to print when the user supplies a version option. If you
supply a true value for @code{version}, @ref{c3,,optparse} automatically adds a
version option with the single option string @code{--version}.  The
substring @code{%prog} is expanded the same as for @code{usage}.

@item @code{conflict_handler} (默认: @code{"error"})

Specifies what to do when options with conflicting option strings are
added to the parser; see section
@ref{3a3b,,Conflicts between options}.

@item @code{description} (默认: @code{None})

A paragraph of text giving a brief overview of your program.
@ref{c3,,optparse} reformats this paragraph to fit the current terminal width
and prints it when the user requests help (after @code{usage}, but before the
list of options).

@item @code{formatter} (default: a new @code{IndentedHelpFormatter})

An instance of optparse.HelpFormatter that will be used for printing help
text.  @ref{c3,,optparse} provides two concrete classes for this purpose:
IndentedHelpFormatter and TitledHelpFormatter.

@item @code{add_help_option} (默认: @code{True})

If true, @ref{c3,,optparse} will add a help option (with option strings @code{-h}
and @code{--help}) to the parser.

@item @code{prog}

The string to use when expanding @code{%prog} in @code{usage} and @code{version}
instead of @code{os.path.basename(sys.argv[0])}.

@item @code{epilog} (默认: @code{None})

A paragraph of help text to print after the option help.
@end table
@end deffn

@node 填充解析器,定义选项,创建解析器,参考指南
@anchor{library/optparse optparse-populating-parser}@anchor{3a3c}@anchor{library/optparse populating-the-parser}@anchor{3a3d}
@subsubsection 填充解析器


There are several ways to populate the parser with options.  The preferred way
is by using @ref{200b,,OptionParser.add_option()}, as shown in section
@ref{3a17,,教程}.  @code{add_option()} can be called in one of two ways:


@itemize *

@item 
pass it an Option instance (as returned by @code{make_option()})

@item 
pass it any combination of positional and keyword arguments that are
acceptable to @code{make_option()} (i.e., to the Option constructor), and it
will create the Option instance for you
@end itemize

The other alternative is to pass a list of pre-constructed Option instances to
the OptionParser constructor, as in:

@example
option_list = [
    make_option("-f", "--filename",
                action="store", type="string", dest="filename"),
    make_option("-q", "--quiet",
                action="store_false", dest="verbose"),
    ]
parser = OptionParser(option_list=option_list)
@end example

(@code{make_option()} is a factory function for creating Option instances;
currently it is an alias for the Option constructor.  A future version of
@ref{c3,,optparse} may split Option into several classes, and @code{make_option()}
will pick the right class to instantiate.  Do not instantiate Option directly.)

@node 定义选项,Option attributes,填充解析器,参考指南
@anchor{library/optparse defining-options}@anchor{3a3e}@anchor{library/optparse optparse-defining-options}@anchor{3a3f}
@subsubsection 定义选项


Each Option instance represents a set of synonymous command-line option strings,
e.g. @code{-f} and @code{--file}.  You can specify any number of short or
long option strings, but you must specify at least one overall option string.

The canonical way to create an @code{Option} instance is with the
@code{add_option()} method of @ref{3a0e,,OptionParser}.

@geindex add_option() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser add_option}@anchor{200b}
@deffn {方法} OptionParser.add_option (option)

@deffnx {方法} OptionParser.add_option (*opt_str, attr=value, ...)

To define an option with only a short option string:

@example
parser.add_option("-f", attr=value, ...)
@end example

And to define an option with only a long option string:

@example
parser.add_option("--foo", attr=value, ...)
@end example

The keyword arguments define attributes of the new Option object.  The most
important option attribute is @ref{3a19,,action}, and it largely
determines which other attributes are relevant or required.  If you pass
irrelevant option attributes, or fail to pass required ones, @ref{c3,,optparse}
raises an @code{OptionError} exception explaining your mistake.

An option's @emph{action} determines what @ref{c3,,optparse} does when it encounters
this option on the command-line.  The standard option actions hard-coded into
@ref{c3,,optparse} are:


@table @asis

@item @code{"store"}

存储此选项的参数（默认）

@item @code{"store_const"}

store a constant value

@item @code{"store_true"}

store @code{True}

@item @code{"store_false"}

store @code{False}

@item @code{"append"}

append this option's argument to a list

@item @code{"append_const"}

将常量值附加到列表

@item @code{"count"}

increment a counter by one

@item @code{"callback"}

调用指定函数

@item @code{"help"}

打印用法消息，包括所有选项和文档
@end table

(If you don't supply an action, the default is @code{"store"}.  For this action,
you may also supply @ref{3a1a,,type} and @ref{3a1b,,dest} option
attributes; see @ref{3a40,,Standard option actions}.)
@end deffn

As you can see, most actions involve storing or updating a value somewhere.
@ref{c3,,optparse} always creates a special object for this, conventionally called
@code{options} (it happens to be an instance of @code{optparse.Values}).  Option
arguments (and various other values) are stored as attributes of this object,
according to the @ref{3a1b,,dest} (destination) option attribute.

For example, when you call

@example
parser.parse_args()
@end example

one of the first things @ref{c3,,optparse} does is create the @code{options} object:

@example
options = Values()
@end example

If one of the options in this parser is defined with

@example
parser.add_option("-f", "--file", action="store", type="string", dest="filename")
@end example

and the command-line being parsed includes any of the following:

@example
-ffoo
-f foo
--file=foo
--file foo
@end example

then @ref{c3,,optparse}, on seeing this option, will do the equivalent of

@example
options.filename = "foo"
@end example

The @ref{3a1a,,type} and @ref{3a1b,,dest} option attributes are almost
as important as @ref{3a19,,action}, but @ref{3a19,,action} is the only
one that makes sense for @emph{all} options.

@node Option attributes,Standard option actions,定义选项,参考指南
@anchor{library/optparse option-attributes}@anchor{3a41}@anchor{library/optparse optparse-option-attributes}@anchor{3a42}
@subsubsection Option attributes


The following option attributes may be passed as keyword arguments to
@ref{200b,,OptionParser.add_option()}.  If you pass an option attribute that is not
relevant to a particular option, or fail to pass a required option attribute,
@ref{c3,,optparse} raises @code{OptionError}.

@geindex action (optparse.Option 属性)
@anchor{library/optparse optparse Option action}@anchor{3a19}
@deffn {属性} Option.action

(默认: @code{"store"})

Determines @ref{c3,,optparse}'s behaviour when this option is seen on the
command line; the available options are documented @ref{3a40,,here}.
@end deffn

@geindex type (optparse.Option 属性)
@anchor{library/optparse optparse Option type}@anchor{3a1a}
@deffn {属性} Option.type

(默认: @code{"string"})

The argument type expected by this option (e.g., @code{"string"} or @code{"int"});
the available option types are documented @ref{3a43,,here}.
@end deffn

@geindex dest (optparse.Option 属性)
@anchor{library/optparse optparse Option dest}@anchor{3a1b}
@deffn {属性} Option.dest

(default: derived from option strings)

If the option's action implies writing or modifying a value somewhere, this
tells @ref{c3,,optparse} where to write it: @ref{3a1b,,dest} names an
attribute of the @code{options} object that @ref{c3,,optparse} builds as it parses
the command line.
@end deffn

@geindex default (optparse.Option 属性)
@anchor{library/optparse optparse Option default}@anchor{3a44}
@deffn {属性} Option.default

The value to use for this option's destination if the option is not seen on
the command line.  See also @ref{3a45,,OptionParser.set_defaults()}.
@end deffn

@geindex nargs (optparse.Option 属性)
@anchor{library/optparse optparse Option nargs}@anchor{3a46}
@deffn {属性} Option.nargs

(默认: 1)

How many arguments of type @ref{3a1a,,type} should be consumed when this
option is seen.  If > 1, @ref{c3,,optparse} will store a tuple of values to
@ref{3a1b,,dest}.
@end deffn

@geindex const (optparse.Option 属性)
@anchor{library/optparse optparse Option const}@anchor{3a47}
@deffn {属性} Option.const

For actions that store a constant value, the constant value to store.
@end deffn

@geindex choices (optparse.Option 属性)
@anchor{library/optparse optparse Option choices}@anchor{3a48}
@deffn {属性} Option.choices

For options of type @code{"choice"}, the list of strings the user may choose
from.
@end deffn

@geindex callback (optparse.Option 属性)
@anchor{library/optparse optparse Option callback}@anchor{3a49}
@deffn {属性} Option.callback

For options with action @code{"callback"}, the callable to call when this option
is seen.  See section @ref{3a27,,Option Callbacks} for detail on the
arguments passed to the callable.
@end deffn

@geindex callback_args (optparse.Option 属性)
@geindex callback_kwargs (optparse.Option 属性)
@anchor{library/optparse optparse Option callback_args}@anchor{3a4a}
@deffn {属性} Option.callback_args
@anchor{library/optparse optparse Option callback_kwargs}@anchor{3a4b}
@deffnx {属性} Option.callback_kwargs

Additional positional and keyword arguments to pass to @code{callback} after the
four standard callback arguments.
@end deffn

@geindex help (optparse.Option 属性)
@anchor{library/optparse optparse Option help}@anchor{3a1c}
@deffn {属性} Option.help

Help text to print for this option when listing all available options after
the user supplies a @ref{3a1c,,help} option (such as @code{--help}).  If
no help text is supplied, the option will be listed without help text.  To
hide this option, use the special value @code{optparse.SUPPRESS_HELP}.
@end deffn

@geindex metavar (optparse.Option 属性)
@anchor{library/optparse optparse Option metavar}@anchor{3a4c}
@deffn {属性} Option.metavar

(default: derived from option strings)

Stand-in for the option argument(s) to use when printing help text.  See
section @ref{3a17,,教程} for an example.
@end deffn

@node Standard option actions,Standard option types,Option attributes,参考指南
@anchor{library/optparse optparse-standard-option-actions}@anchor{3a40}@anchor{library/optparse standard-option-actions}@anchor{3a4d}
@subsubsection Standard option actions


The various option actions all have slightly different requirements and effects.
Most actions have several relevant option attributes which you may specify to
guide @ref{c3,,optparse}'s behaviour; a few have required attributes, which you
must specify for any option using that action.


@itemize *

@item 
@code{"store"} [relevant: @ref{3a1a,,type}, @ref{3a1b,,dest},
@ref{3a46,,nargs}, @ref{3a48,,choices}]

The option must be followed by an argument, which is converted to a value
according to @ref{3a1a,,type} and stored in @ref{3a1b,,dest}.  If
@ref{3a46,,nargs} > 1, multiple arguments will be consumed from the
command line; all will be converted according to @ref{3a1a,,type} and
stored to @ref{3a1b,,dest} as a tuple.  See the
@ref{3a43,,Standard option types} section.

If @ref{3a48,,choices} is supplied (a list or tuple of strings), the type
defaults to @code{"choice"}.

If @ref{3a1a,,type} is not supplied, it defaults to @code{"string"}.

If @ref{3a1b,,dest} is not supplied, @ref{c3,,optparse} derives a destination
from the first long option string (e.g., @code{--foo-bar} implies
@code{foo_bar}). If there are no long option strings, @ref{c3,,optparse} derives a
destination from the first short option string (e.g., @code{-f} implies @code{f}).

示例:

@example
parser.add_option("-f")
parser.add_option("-p", type="float", nargs=3, dest="point")
@end example

As it parses the command line

@example
-f foo.txt -p 1 -3.5 4 -fbar.txt
@end example

@ref{c3,,optparse} will set

@example
options.f = "foo.txt"
options.point = (1.0, -3.5, 4.0)
options.f = "bar.txt"
@end example

@item 
@code{"store_const"} [required: @ref{3a47,,const}; relevant:
@ref{3a1b,,dest}]

The value @ref{3a47,,const} is stored in @ref{3a1b,,dest}.

示例:

@example
parser.add_option("-q", "--quiet",
                  action="store_const", const=0, dest="verbose")
parser.add_option("-v", "--verbose",
                  action="store_const", const=1, dest="verbose")
parser.add_option("--noisy",
                  action="store_const", const=2, dest="verbose")
@end example

If @code{--noisy} is seen, @ref{c3,,optparse} will set

@example
options.verbose = 2
@end example

@item 
@code{"store_true"} [relevant: @ref{3a1b,,dest}]

A special case of @code{"store_const"} that stores @code{True} to
@ref{3a1b,,dest}.

@item 
@code{"store_false"} [relevant: @ref{3a1b,,dest}]

Like @code{"store_true"}, but stores @code{False}.

示例:

@example
parser.add_option("--clobber", action="store_true", dest="clobber")
parser.add_option("--no-clobber", action="store_false", dest="clobber")
@end example

@item 
@code{"append"} [relevant: @ref{3a1a,,type}, @ref{3a1b,,dest},
@ref{3a46,,nargs}, @ref{3a48,,choices}]

The option must be followed by an argument, which is appended to the list in
@ref{3a1b,,dest}.  If no default value for @ref{3a1b,,dest} is
supplied, an empty list is automatically created when @ref{c3,,optparse} first
encounters this option on the command-line.  If @ref{3a46,,nargs} > 1,
multiple arguments are consumed, and a tuple of length @ref{3a46,,nargs}
is appended to @ref{3a1b,,dest}.

The defaults for @ref{3a1a,,type} and @ref{3a1b,,dest} are the same as
for the @code{"store"} action.

示例:

@example
parser.add_option("-t", "--tracks", action="append", type="int")
@end example

If @code{-t3} is seen on the command-line, @ref{c3,,optparse} does the equivalent
of:

@example
options.tracks = []
options.tracks.append(int("3"))
@end example

If, a little later on, @code{--tracks=4} is seen, it does:

@example
options.tracks.append(int("4"))
@end example

The @code{append} action calls the @code{append} method on the current value of the
option.  This means that any default value specified must have an @code{append}
method.  It also means that if the default value is non-empty, the default
elements will be present in the parsed value for the option, with any values
from the command line appended after those default values:

@example
>>> parser.add_option("--files", action="append", default=['~/.mypkg/defaults'])
>>> opts, args = parser.parse_args(['--files', 'overrides.mypkg'])
>>> opts.files
['~/.mypkg/defaults', 'overrides.mypkg']
@end example

@item 
@code{"append_const"} [required: @ref{3a47,,const}; relevant:
@ref{3a1b,,dest}]

Like @code{"store_const"}, but the value @ref{3a47,,const} is appended to
@ref{3a1b,,dest}; as with @code{"append"}, @ref{3a1b,,dest} defaults to
@code{None}, and an empty list is automatically created the first time the option
is encountered.

@item 
@code{"count"} [relevant: @ref{3a1b,,dest}]

Increment the integer stored at @ref{3a1b,,dest}.  If no default value is
supplied, @ref{3a1b,,dest} is set to zero before being incremented the
first time.

示例:

@example
parser.add_option("-v", action="count", dest="verbosity")
@end example

The first time @code{-v} is seen on the command line, @ref{c3,,optparse} does the
equivalent of:

@example
options.verbosity = 0
options.verbosity += 1
@end example

Every subsequent occurrence of @code{-v} results in

@example
options.verbosity += 1
@end example

@item 
@code{"callback"} [required: @ref{3a49,,callback}; relevant:
@ref{3a1a,,type}, @ref{3a46,,nargs}, @ref{3a4a,,callback_args},
@ref{3a4b,,callback_kwargs}]

Call the function specified by @ref{3a49,,callback}, which is called as

@example
func(option, opt_str, value, parser, *args, **kwargs)
@end example

See section @ref{3a27,,Option Callbacks} for more detail.

@item 
@code{"help"}

Prints a complete help message for all the options in the current option
parser.  The help message is constructed from the @code{usage} string passed to
OptionParser's constructor and the @ref{3a1c,,help} string passed to every
option.

If no @ref{3a1c,,help} string is supplied for an option, it will still be
listed in the help message.  To omit an option entirely, use the special value
@code{optparse.SUPPRESS_HELP}.

@ref{c3,,optparse} automatically adds a @ref{3a1c,,help} option to all
OptionParsers, so you do not normally need to create one.

示例:

@example
from optparse import OptionParser, SUPPRESS_HELP

# usually, a help option is added automatically, but that can
# be suppressed using the add_help_option argument
parser = OptionParser(add_help_option=False)

parser.add_option("-h", "--help", action="help")
parser.add_option("-v", action="store_true", dest="verbose",
                  help="Be moderately verbose")
parser.add_option("--file", dest="filename",
                  help="Input file to read data from")
parser.add_option("--secret", help=SUPPRESS_HELP)
@end example

If @ref{c3,,optparse} sees either @code{-h} or @code{--help} on the command line,
it will print something like the following help message to stdout (assuming
@code{sys.argv[0]} is @code{"foo.py"}):

@example
Usage: foo.py [options]

Options:
  -h, --help        Show this help message and exit
  -v                Be moderately verbose
  --file=FILENAME   Input file to read data from
@end example

After printing the help message, @ref{c3,,optparse} terminates your process with
@code{sys.exit(0)}.

@item 
@code{"version"}

Prints the version number supplied to the OptionParser to stdout and exits.
The version number is actually formatted and printed by the
@code{print_version()} method of OptionParser.  Generally only relevant if the
@code{version} argument is supplied to the OptionParser constructor.  As with
@ref{3a1c,,help} options, you will rarely create @code{version} options,
since @ref{c3,,optparse} automatically adds them when needed.
@end itemize

@node Standard option types,解析参数<2>,Standard option actions,参考指南
@anchor{library/optparse optparse-standard-option-types}@anchor{3a43}@anchor{library/optparse standard-option-types}@anchor{3a4e}
@subsubsection Standard option types


@ref{c3,,optparse} has five built-in option types: @code{"string"}, @code{"int"},
@code{"choice"}, @code{"float"} and @code{"complex"}.  If you need to add new
option types, see section @ref{3a1f,,Extending optparse}.

Arguments to string options are not checked or converted in any way: the text on
the command line is stored in the destination (or passed to the callback) as-is.

Integer arguments (type @code{"int"}) are parsed as follows:


@itemize *

@item 
if the number starts with @code{0x}, it is parsed as a hexadecimal number

@item 
if the number starts with @code{0}, it is parsed as an octal number

@item 
if the number starts with @code{0b}, it is parsed as a binary number

@item 
otherwise, the number is parsed as a decimal number
@end itemize

The conversion is done by calling @ref{184,,int()} with the appropriate base (2, 8,
10, or 16).  If this fails, so will @ref{c3,,optparse}, although with a more useful
error message.

@code{"float"} and @code{"complex"} option arguments are converted directly with
@ref{187,,float()} and @ref{189,,complex()}, with similar error-handling.

@code{"choice"} options are a subtype of @code{"string"} options.  The
@ref{3a48,,choices} option attribute (a sequence of strings) defines the
set of allowed option arguments.  @code{optparse.check_choice()} compares
user-supplied option arguments against this master list and raises
@code{OptionValueError} if an invalid string is given.

@node 解析参数<2>,Querying and manipulating your option parser,Standard option types,参考指南
@anchor{library/optparse optparse-parsing-arguments}@anchor{3a4f}@anchor{library/optparse parsing-arguments}@anchor{3a50}
@subsubsection 解析参数


The whole point of creating and populating an OptionParser is to call its
@code{parse_args()} method:

@example
(options, args) = parser.parse_args(args=None, values=None)
@end example

输入参数的位置


@table @asis

@item @code{args}

the list of arguments to process (default: @code{sys.argv[1:]})

@item @code{values}

an @code{optparse.Values} object to store option arguments in (default: a
new instance of @code{Values}) -- if you give an existing object, the
option defaults will not be initialized on it
@end table

and the return values are


@table @asis

@item @code{options}

the same object that was passed in as @code{values}, or the optparse.Values
instance created by @ref{c3,,optparse}

@item @code{args}

the leftover positional arguments after all options have been processed
@end table

The most common usage is to supply neither keyword argument.  If you supply
@code{values}, it will be modified with repeated @ref{1575,,setattr()} calls (roughly one
for every option argument stored to an option destination) and returned by
@code{parse_args()}.

If @code{parse_args()} encounters any errors in the argument list, it calls the
OptionParser's @code{error()} method with an appropriate end-user error message.
This ultimately terminates your process with an exit status of 2 (the
traditional Unix exit status for command-line errors).

@node Querying and manipulating your option parser,Conflicts between options,解析参数<2>,参考指南
@anchor{library/optparse optparse-querying-manipulating-option-parser}@anchor{3a51}@anchor{library/optparse querying-and-manipulating-your-option-parser}@anchor{3a52}
@subsubsection Querying and manipulating your option parser


The default behavior of the option parser can be customized slightly, and you
can also poke around your option parser and see what's there.  OptionParser
provides several methods to help you out:

@geindex disable_interspersed_args() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser disable_interspersed_args}@anchor{200c}
@deffn {方法} OptionParser.disable_interspersed_args ()

Set parsing to stop on the first non-option.  For example, if @code{-a} and
@code{-b} are both simple options that take no arguments, @ref{c3,,optparse}
normally accepts this syntax:

@example
prog -a arg1 -b arg2
@end example

and treats it as equivalent to

@example
prog -a -b arg1 arg2
@end example

To disable this feature, call @ref{200c,,disable_interspersed_args()}.  This
restores traditional Unix syntax, where option parsing stops with the first
non-option argument.

Use this if you have a command processor which runs another command which has
options of its own and you want to make sure these options don't get
confused.  For example, each command might have a different set of options.
@end deffn

@geindex enable_interspersed_args() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser enable_interspersed_args}@anchor{3a53}
@deffn {方法} OptionParser.enable_interspersed_args ()

Set parsing to not stop on the first non-option, allowing interspersing
switches with command arguments.  This is the default behavior.
@end deffn

@geindex get_option() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser get_option}@anchor{3a54}
@deffn {方法} OptionParser.get_option (opt_str)

Returns the Option instance with the option string @emph{opt_str}, or @code{None} if
no options have that option string.
@end deffn

@geindex has_option() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser has_option}@anchor{3a55}
@deffn {方法} OptionParser.has_option (opt_str)

Return @code{True} if the OptionParser has an option with option string @emph{opt_str}
(e.g., @code{-q} or @code{--verbose}).
@end deffn

@geindex remove_option() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser remove_option}@anchor{3a56}
@deffn {方法} OptionParser.remove_option (opt_str)

If the @ref{3a0e,,OptionParser} has an option corresponding to @emph{opt_str}, that
option is removed.  If that option provided any other option strings, all of
those option strings become invalid. If @emph{opt_str} does not occur in any
option belonging to this @ref{3a0e,,OptionParser}, raises @ref{1fb,,ValueError}.
@end deffn

@node Conflicts between options,清理<2>,Querying and manipulating your option parser,参考指南
@anchor{library/optparse conflicts-between-options}@anchor{3a57}@anchor{library/optparse optparse-conflicts-between-options}@anchor{3a3b}
@subsubsection Conflicts between options


If you're not careful, it's easy to define options with conflicting option
strings:

@example
parser.add_option("-n", "--dry-run", ...)
...
parser.add_option("-n", "--noisy", ...)
@end example

(This is particularly true if you've defined your own OptionParser subclass with
some standard options.)

Every time you add an option, @ref{c3,,optparse} checks for conflicts with existing
options.  If it finds any, it invokes the current conflict-handling mechanism.
You can set the conflict-handling mechanism either in the constructor:

@example
parser = OptionParser(..., conflict_handler=handler)
@end example

or with a separate call:

@example
parser.set_conflict_handler(handler)
@end example

The available conflict handlers are:

@quotation


@table @asis

@item @code{"error"} (默认)

assume option conflicts are a programming error and raise
@code{OptionConflictError}

@item @code{"resolve"}

resolve option conflicts intelligently (see below)
@end table
@end quotation

As an example, let's define an @ref{3a0e,,OptionParser} that resolves conflicts
intelligently and add conflicting options to it:

@example
parser = OptionParser(conflict_handler="resolve")
parser.add_option("-n", "--dry-run", ..., help="do no harm")
parser.add_option("-n", "--noisy", ..., help="be noisy")
@end example

At this point, @ref{c3,,optparse} detects that a previously-added option is already
using the @code{-n} option string.  Since @code{conflict_handler} is @code{"resolve"},
it resolves the situation by removing @code{-n} from the earlier option's list of
option strings.  Now @code{--dry-run} is the only way for the user to activate
that option.  If the user asks for help, the help message will reflect that:

@example
Options:
  --dry-run     do no harm
  ...
  -n, --noisy   be noisy
@end example

It's possible to whittle away the option strings for a previously-added option
until there are none left, and the user has no way of invoking that option from
the command-line.  In that case, @ref{c3,,optparse} removes that option completely,
so it doesn't show up in help text or anywhere else. Carrying on with our
existing OptionParser:

@example
parser.add_option("--dry-run", ..., help="new dry-run option")
@end example

At this point, the original @code{-n}/@code{--dry-run} option is no longer
accessible, so @ref{c3,,optparse} removes it, leaving this help text:

@example
Options:
  ...
  -n, --noisy   be noisy
  --dry-run     new dry-run option
@end example

@node 清理<2>,Other methods,Conflicts between options,参考指南
@anchor{library/optparse cleanup}@anchor{3a58}@anchor{library/optparse optparse-cleanup}@anchor{3a59}
@subsubsection 清理


OptionParser instances have several cyclic references.  This should not be a
problem for Python's garbage collector, but you may wish to break the cyclic
references explicitly by calling @code{destroy()} on your
OptionParser once you are done with it.  This is particularly useful in
long-running applications where large object graphs are reachable from your
OptionParser.

@node Other methods,,清理<2>,参考指南
@anchor{library/optparse optparse-other-methods}@anchor{3a5a}@anchor{library/optparse other-methods}@anchor{3a5b}
@subsubsection Other methods


OptionParser supports several other public methods:

@geindex set_usage() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser set_usage}@anchor{3a5c}
@deffn {方法} OptionParser.set_usage (usage)

Set the usage string according to the rules described above for the @code{usage}
constructor keyword argument.  Passing @code{None} sets the default usage
string; use @code{optparse.SUPPRESS_USAGE} to suppress a usage message.
@end deffn

@geindex print_usage() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser print_usage}@anchor{3a32}
@deffn {方法} OptionParser.print_usage (file=None)

Print the usage message for the current program (@code{self.usage}) to @emph{file}
(default stdout).  Any occurrence of the string @code{%prog} in @code{self.usage}
is replaced with the name of the current program.  Does nothing if
@code{self.usage} is empty or not defined.
@end deffn

@geindex get_usage() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser get_usage}@anchor{3a5d}
@deffn {方法} OptionParser.get_usage ()

Same as @ref{3a32,,print_usage()} but returns the usage string instead of
printing it.
@end deffn

@geindex set_defaults() (optparse.OptionParser 方法)
@anchor{library/optparse optparse OptionParser set_defaults}@anchor{3a45}
@deffn {方法} OptionParser.set_defaults (dest=value, ...)

Set default values for several option destinations at once.  Using
@ref{3a45,,set_defaults()} is the preferred way to set default values for options,
since multiple options can share the same destination.  For example, if
several "mode" options all set the same destination, any one of them can set
the default, and the last one wins:

@example
parser.add_option("--advanced", action="store_const",
                  dest="mode", const="advanced",
                  default="novice")    # overridden below
parser.add_option("--novice", action="store_const",
                  dest="mode", const="novice",
                  default="advanced")  # overrides above setting
@end example

To avoid this confusion, use @ref{3a45,,set_defaults()}:

@example
parser.set_defaults(mode="advanced")
parser.add_option("--advanced", action="store_const",
                  dest="mode", const="advanced")
parser.add_option("--novice", action="store_const",
                  dest="mode", const="novice")
@end example
@end deffn

@node Option Callbacks,Extending optparse,参考指南,optparse --- 解析器的命令行选项
@anchor{library/optparse option-callbacks}@anchor{3a5e}@anchor{library/optparse optparse-option-callbacks}@anchor{3a27}
@subsubsection Option Callbacks


When @ref{c3,,optparse}'s built-in actions and types aren't quite enough for your
needs, you have two choices: extend @ref{c3,,optparse} or define a callback option.
Extending @ref{c3,,optparse} is more general, but overkill for a lot of simple
cases.  Quite often a simple callback is all you need.

There are two steps to defining a callback option:


@itemize *

@item 
define the option itself using the @code{"callback"} action

@item 
write the callback; this is a function (or method) that takes at least four
arguments, as described below
@end itemize

@menu
* Defining a callback option:: 
* How callbacks are called:: 
* Raising errors in a callback:: 
* Callback example 1; trivial callback: Callback example 1 trivial callback. 
* Callback example 2; check option order: Callback example 2 check option order. 
* Callback example 3; check option order (generalized): Callback example 3 check option order generalized. 
* Callback example 4; check arbitrary condition: Callback example 4 check arbitrary condition. 
* Callback example 5; fixed arguments: Callback example 5 fixed arguments. 
* Callback example 6; variable arguments: Callback example 6 variable arguments. 

@end menu

@node Defining a callback option,How callbacks are called,,Option Callbacks
@anchor{library/optparse defining-a-callback-option}@anchor{3a5f}@anchor{library/optparse optparse-defining-callback-option}@anchor{3a60}
@subsubsection Defining a callback option


As always, the easiest way to define a callback option is by using the
@ref{200b,,OptionParser.add_option()} method.  Apart from @ref{3a19,,action}, the
only option attribute you must specify is @code{callback}, the function to call:

@example
parser.add_option("-c", action="callback", callback=my_callback)
@end example

@code{callback} is a function (or other callable object), so you must have already
defined @code{my_callback()} when you create this callback option. In this simple
case, @ref{c3,,optparse} doesn't even know if @code{-c} takes any arguments,
which usually means that the option takes no arguments---the mere presence of
@code{-c} on the command-line is all it needs to know.  In some
circumstances, though, you might want your callback to consume an arbitrary
number of command-line arguments.  This is where writing callbacks gets tricky;
it's covered later in this section.

@ref{c3,,optparse} always passes four particular arguments to your callback, and it
will only pass additional arguments if you specify them via
@ref{3a4a,,callback_args} and @ref{3a4b,,callback_kwargs}.  Thus, the
minimal callback function signature is:

@example
def my_callback(option, opt, value, parser):
@end example

The four arguments to a callback are described below.

There are several other option attributes that you can supply when you define a
callback option:


@table @asis

@item @ref{3a1a,,type}

has its usual meaning: as with the @code{"store"} or @code{"append"} actions, it
instructs @ref{c3,,optparse} to consume one argument and convert it to
@ref{3a1a,,type}.  Rather than storing the converted value(s) anywhere,
though, @ref{c3,,optparse} passes it to your callback function.

@item @ref{3a46,,nargs}

also has its usual meaning: if it is supplied and > 1, @ref{c3,,optparse} will
consume @ref{3a46,,nargs} arguments, each of which must be convertible to
@ref{3a1a,,type}.  It then passes a tuple of converted values to your
callback.

@item @ref{3a4a,,callback_args}

a tuple of extra positional arguments to pass to the callback

@item @ref{3a4b,,callback_kwargs}

a dictionary of extra keyword arguments to pass to the callback
@end table

@node How callbacks are called,Raising errors in a callback,Defining a callback option,Option Callbacks
@anchor{library/optparse how-callbacks-are-called}@anchor{3a61}@anchor{library/optparse optparse-how-callbacks-called}@anchor{3a62}
@subsubsection How callbacks are called


All callbacks are called as follows:

@example
func(option, opt_str, value, parser, *args, **kwargs)
@end example

where


@table @asis

@item @code{option}

is the Option instance that's calling the callback

@item @code{opt_str}

is the option string seen on the command-line that's triggering the callback.
(If an abbreviated long option was used, @code{opt_str} will be the full,
canonical option string---e.g. if the user puts @code{--foo} on the
command-line as an abbreviation for @code{--foobar}, then @code{opt_str} will be
@code{"--foobar"}.)

@item @code{value}

is the argument to this option seen on the command-line.  @ref{c3,,optparse} will
only expect an argument if @ref{3a1a,,type} is set; the type of @code{value} will be
the type implied by the option's type.  If @ref{3a1a,,type} for this option is
@code{None} (no argument expected), then @code{value} will be @code{None}.  If @ref{3a46,,nargs}
> 1, @code{value} will be a tuple of values of the appropriate type.

@item @code{parser}

is the OptionParser instance driving the whole thing, mainly useful because
you can access some other interesting data through its instance attributes:


@table @asis

@item @code{parser.largs}

the current list of leftover arguments, ie. arguments that have been
consumed but are neither options nor option arguments. Feel free to modify
@code{parser.largs}, e.g. by adding more arguments to it.  (This list will
become @code{args}, the second return value of @code{parse_args()}.)

@item @code{parser.rargs}

the current list of remaining arguments, ie. with @code{opt_str} and
@code{value} (if applicable) removed, and only the arguments following them
still there.  Feel free to modify @code{parser.rargs}, e.g. by consuming more
arguments.

@item @code{parser.values}

the object where option values are by default stored (an instance of
optparse.OptionValues).  This lets callbacks use the same mechanism as the
rest of @ref{c3,,optparse} for storing option values; you don't need to mess
around with globals or closures.  You can also access or modify the
value(s) of any options already encountered on the command-line.
@end table

@item @code{args}

is a tuple of arbitrary positional arguments supplied via the
@ref{3a4a,,callback_args} option attribute.

@item @code{kwargs}

is a dictionary of arbitrary keyword arguments supplied via
@ref{3a4b,,callback_kwargs}.
@end table

@node Raising errors in a callback,Callback example 1 trivial callback,How callbacks are called,Option Callbacks
@anchor{library/optparse optparse-raising-errors-in-callback}@anchor{3a63}@anchor{library/optparse raising-errors-in-a-callback}@anchor{3a64}
@subsubsection Raising errors in a callback


The callback function should raise @code{OptionValueError} if there are any
problems with the option or its argument(s).  @ref{c3,,optparse} catches this and
terminates the program, printing the error message you supply to stderr.  Your
message should be clear, concise, accurate, and mention the option at fault.
Otherwise, the user will have a hard time figuring out what they did wrong.

@node Callback example 1 trivial callback,Callback example 2 check option order,Raising errors in a callback,Option Callbacks
@anchor{library/optparse callback-example-1-trivial-callback}@anchor{3a65}@anchor{library/optparse optparse-callback-example-1}@anchor{3a66}
@subsubsection Callback example 1: trivial callback


Here's an example of a callback option that takes no arguments, and simply
records that the option was seen:

@example
def record_foo_seen(option, opt_str, value, parser):
    parser.values.saw_foo = True

parser.add_option("--foo", action="callback", callback=record_foo_seen)
@end example

Of course, you could do that with the @code{"store_true"} action.

@node Callback example 2 check option order,Callback example 3 check option order generalized,Callback example 1 trivial callback,Option Callbacks
@anchor{library/optparse callback-example-2-check-option-order}@anchor{3a67}@anchor{library/optparse optparse-callback-example-2}@anchor{3a68}
@subsubsection Callback example 2: check option order


Here's a slightly more interesting example: record the fact that @code{-a} is
seen, but blow up if it comes after @code{-b} in the command-line.

@example
def check_order(option, opt_str, value, parser):
    if parser.values.b:
        raise OptionValueError("can't use -a after -b")
    parser.values.a = 1
...
parser.add_option("-a", action="callback", callback=check_order)
parser.add_option("-b", action="store_true", dest="b")
@end example

@node Callback example 3 check option order generalized,Callback example 4 check arbitrary condition,Callback example 2 check option order,Option Callbacks
@anchor{library/optparse callback-example-3-check-option-order-generalized}@anchor{3a69}@anchor{library/optparse optparse-callback-example-3}@anchor{3a6a}
@subsubsection Callback example 3: check option order (generalized)


If you want to re-use this callback for several similar options (set a flag, but
blow up if @code{-b} has already been seen), it needs a bit of work: the error
message and the flag that it sets must be generalized.

@example
def check_order(option, opt_str, value, parser):
    if parser.values.b:
        raise OptionValueError("can't use %s after -b" % opt_str)
    setattr(parser.values, option.dest, 1)
...
parser.add_option("-a", action="callback", callback=check_order, dest='a')
parser.add_option("-b", action="store_true", dest="b")
parser.add_option("-c", action="callback", callback=check_order, dest='c')
@end example

@node Callback example 4 check arbitrary condition,Callback example 5 fixed arguments,Callback example 3 check option order generalized,Option Callbacks
@anchor{library/optparse callback-example-4-check-arbitrary-condition}@anchor{3a6b}@anchor{library/optparse optparse-callback-example-4}@anchor{3a6c}
@subsubsection Callback example 4: check arbitrary condition


Of course, you could put any condition in there---you're not limited to checking
the values of already-defined options.  For example, if you have options that
should not be called when the moon is full, all you have to do is this:

@example
def check_moon(option, opt_str, value, parser):
    if is_moon_full():
        raise OptionValueError("%s option invalid when moon is full"
                               % opt_str)
    setattr(parser.values, option.dest, 1)
...
parser.add_option("--foo",
                  action="callback", callback=check_moon, dest="foo")
@end example

(The definition of @code{is_moon_full()} is left as an exercise for the reader.)

@node Callback example 5 fixed arguments,Callback example 6 variable arguments,Callback example 4 check arbitrary condition,Option Callbacks
@anchor{library/optparse callback-example-5-fixed-arguments}@anchor{3a6d}@anchor{library/optparse optparse-callback-example-5}@anchor{3a6e}
@subsubsection Callback example 5: fixed arguments


Things get slightly more interesting when you define callback options that take
a fixed number of arguments.  Specifying that a callback option takes arguments
is similar to defining a @code{"store"} or @code{"append"} option: if you define
@ref{3a1a,,type}, then the option takes one argument that must be
convertible to that type; if you further define @ref{3a46,,nargs}, then the
option takes @ref{3a46,,nargs} arguments.

Here's an example that just emulates the standard @code{"store"} action:

@example
def store_value(option, opt_str, value, parser):
    setattr(parser.values, option.dest, value)
...
parser.add_option("--foo",
                  action="callback", callback=store_value,
                  type="int", nargs=3, dest="foo")
@end example

Note that @ref{c3,,optparse} takes care of consuming 3 arguments and converting
them to integers for you; all you have to do is store them.  (Or whatever;
obviously you don't need a callback for this example.)

@node Callback example 6 variable arguments,,Callback example 5 fixed arguments,Option Callbacks
@anchor{library/optparse callback-example-6-variable-arguments}@anchor{3a6f}@anchor{library/optparse optparse-callback-example-6}@anchor{3a70}
@subsubsection Callback example 6: variable arguments


Things get hairy when you want an option to take a variable number of arguments.
For this case, you must write a callback, as @ref{c3,,optparse} doesn't provide any
built-in capabilities for it.  And you have to deal with certain intricacies of
conventional Unix command-line parsing that @ref{c3,,optparse} normally handles for
you.  In particular, callbacks should implement the conventional rules for bare
@code{--} and @code{-} arguments:


@itemize *

@item 
either @code{--} or @code{-} can be option arguments

@item 
bare @code{--} (if not the argument to some option): halt command-line
processing and discard the @code{--}

@item 
bare @code{-} (if not the argument to some option): halt command-line
processing but keep the @code{-} (append it to @code{parser.largs})
@end itemize

If you want an option that takes a variable number of arguments, there are
several subtle, tricky issues to worry about.  The exact implementation you
choose will be based on which trade-offs you're willing to make for your
application (which is why @ref{c3,,optparse} doesn't support this sort of thing
directly).

Nevertheless, here's a stab at a callback for an option with variable
arguments:

@example
def vararg_callback(option, opt_str, value, parser):
    assert value is None
    value = []

    def floatable(str):
        try:
            float(str)
            return True
        except ValueError:
            return False

    for arg in parser.rargs:
        # stop on --foo like options
        if arg[:2] == "--" and len(arg) > 2:
            break
        # stop on -a, but not on -3 or -3.0
        if arg[:1] == "-" and len(arg) > 1 and not floatable(arg):
            break
        value.append(arg)

    del parser.rargs[:len(value)]
    setattr(parser.values, option.dest, value)

...
parser.add_option("-c", "--callback", dest="vararg_attr",
                  action="callback", callback=vararg_callback)
@end example

@node Extending optparse,,Option Callbacks,optparse --- 解析器的命令行选项
@anchor{library/optparse extending-optparse}@anchor{3a71}@anchor{library/optparse optparse-extending-optparse}@anchor{3a1f}
@subsubsection Extending @code{optparse}


Since the two major controlling factors in how @ref{c3,,optparse} interprets
command-line options are the action and type of each option, the most likely
direction of extension is to add new actions and new types.

@menu
* Adding new types:: 
* Adding new actions:: 

@end menu

@node Adding new types,Adding new actions,,Extending optparse
@anchor{library/optparse adding-new-types}@anchor{3a72}@anchor{library/optparse optparse-adding-new-types}@anchor{3a73}
@subsubsection Adding new types


To add new types, you need to define your own subclass of @ref{c3,,optparse}'s
@code{Option} class.  This class has a couple of attributes that define
@ref{c3,,optparse}'s types: @ref{3a74,,TYPES} and @ref{3a75,,TYPE_CHECKER}.

@geindex TYPES (optparse.Option 属性)
@anchor{library/optparse optparse Option TYPES}@anchor{3a74}
@deffn {属性} Option.TYPES

A tuple of type names; in your subclass, simply define a new tuple
@ref{3a74,,TYPES} that builds on the standard one.
@end deffn

@geindex TYPE_CHECKER (optparse.Option 属性)
@anchor{library/optparse optparse Option TYPE_CHECKER}@anchor{3a75}
@deffn {属性} Option.TYPE_CHECKER

A dictionary mapping type names to type-checking functions.  A type-checking
function has the following signature:

@example
def check_mytype(option, opt, value)
@end example

where @code{option} is an @code{Option} instance, @code{opt} is an option string
(e.g., @code{-f}), and @code{value} is the string from the command line that must
be checked and converted to your desired type.  @code{check_mytype()} should
return an object of the hypothetical type @code{mytype}.  The value returned by
a type-checking function will wind up in the OptionValues instance returned
by @code{OptionParser.parse_args()}, or be passed to a callback as the
@code{value} parameter.

Your type-checking function should raise @code{OptionValueError} if it
encounters any problems.  @code{OptionValueError} takes a single string
argument, which is passed as-is to @ref{3a0e,,OptionParser}'s @code{error()}
method, which in turn prepends the program name and the string @code{"error:"}
and prints everything to stderr before terminating the process.
@end deffn

Here's a silly example that demonstrates adding a @code{"complex"} option type to
parse Python-style complex numbers on the command line.  (This is even sillier
than it used to be, because @ref{c3,,optparse} 1.3 added built-in support for
complex numbers, but never mind.)

First, the necessary imports:

@example
from copy import copy
from optparse import Option, OptionValueError
@end example

You need to define your type-checker first, since it's referred to later (in the
@ref{3a75,,TYPE_CHECKER} class attribute of your Option subclass):

@example
def check_complex(option, opt, value):
    try:
        return complex(value)
    except ValueError:
        raise OptionValueError(
            "option %s: invalid complex value: %r" % (opt, value))
@end example

Finally, the Option subclass:

@example
class MyOption (Option):
    TYPES = Option.TYPES + ("complex",)
    TYPE_CHECKER = copy(Option.TYPE_CHECKER)
    TYPE_CHECKER["complex"] = check_complex
@end example

(If we didn't make a @ref{26,,copy()} of @ref{3a75,,Option.TYPE_CHECKER}, we would end
up modifying the @ref{3a75,,TYPE_CHECKER} attribute of @ref{c3,,optparse}'s
Option class.  This being Python, nothing stops you from doing that except good
manners and common sense.)

That's it!  Now you can write a script that uses the new option type just like
any other @ref{c3,,optparse}-based script, except you have to instruct your
OptionParser to use MyOption instead of Option:

@example
parser = OptionParser(option_class=MyOption)
parser.add_option("-c", type="complex")
@end example

Alternately, you can build your own option list and pass it to OptionParser; if
you don't use @code{add_option()} in the above way, you don't need to tell
OptionParser which option class to use:

@example
option_list = [MyOption("-c", action="store", type="complex", dest="c")]
parser = OptionParser(option_list=option_list)
@end example

@node Adding new actions,,Adding new types,Extending optparse
@anchor{library/optparse adding-new-actions}@anchor{3a76}@anchor{library/optparse optparse-adding-new-actions}@anchor{3a77}
@subsubsection Adding new actions


Adding new actions is a bit trickier, because you have to understand that
@ref{c3,,optparse} has a couple of classifications for actions:


@table @asis

@item "store" actions

actions that result in @ref{c3,,optparse} storing a value to an attribute of the
current OptionValues instance; these options require a @ref{3a1b,,dest}
attribute to be supplied to the Option constructor.

@item "typed" actions

actions that take a value from the command line and expect it to be of a
certain type; or rather, a string that can be converted to a certain type.
These options require a @ref{3a1a,,type} attribute to the Option
constructor.
@end table

These are overlapping sets: some default "store" actions are @code{"store"},
@code{"store_const"}, @code{"append"}, and @code{"count"}, while the default "typed"
actions are @code{"store"}, @code{"append"}, and @code{"callback"}.

When you add an action, you need to categorize it by listing it in at least one
of the following class attributes of Option (all are lists of strings):

@geindex ACTIONS (optparse.Option 属性)
@anchor{library/optparse optparse Option ACTIONS}@anchor{3a78}
@deffn {属性} Option.ACTIONS

All actions must be listed in ACTIONS.
@end deffn

@geindex STORE_ACTIONS (optparse.Option 属性)
@anchor{library/optparse optparse Option STORE_ACTIONS}@anchor{3a79}
@deffn {属性} Option.STORE_ACTIONS

"store" actions are additionally listed here.
@end deffn

@geindex TYPED_ACTIONS (optparse.Option 属性)
@anchor{library/optparse optparse Option TYPED_ACTIONS}@anchor{3a7a}
@deffn {属性} Option.TYPED_ACTIONS

"typed" actions are additionally listed here.
@end deffn

@geindex ALWAYS_TYPED_ACTIONS (optparse.Option 属性)
@anchor{library/optparse optparse Option ALWAYS_TYPED_ACTIONS}@anchor{3a7b}
@deffn {属性} Option.ALWAYS_TYPED_ACTIONS

Actions that always take a type (i.e. whose options always take a value) are
additionally listed here.  The only effect of this is that @ref{c3,,optparse}
assigns the default type, @code{"string"}, to options with no explicit type
whose action is listed in @ref{3a7b,,ALWAYS_TYPED_ACTIONS}.
@end deffn

In order to actually implement your new action, you must override Option's
@code{take_action()} method and add a case that recognizes your action.

For example, let's add an @code{"extend"} action.  This is similar to the standard
@code{"append"} action, but instead of taking a single value from the command-line
and appending it to an existing list, @code{"extend"} will take multiple values in
a single comma-delimited string, and extend an existing list with them.  That
is, if @code{--names} is an @code{"extend"} option of type @code{"string"}, the command
line

@example
--names=foo,bar --names blah --names ding,dong
@end example

would result in a list

@example
["foo", "bar", "blah", "ding", "dong"]
@end example

Again we define a subclass of Option:

@example
class MyOption(Option):

    ACTIONS = Option.ACTIONS + ("extend",)
    STORE_ACTIONS = Option.STORE_ACTIONS + ("extend",)
    TYPED_ACTIONS = Option.TYPED_ACTIONS + ("extend",)
    ALWAYS_TYPED_ACTIONS = Option.ALWAYS_TYPED_ACTIONS + ("extend",)

    def take_action(self, action, dest, opt, value, values, parser):
        if action == "extend":
            lvalue = value.split(",")
            values.ensure_value(dest, []).extend(lvalue)
        else:
            Option.take_action(
                self, action, dest, opt, value, values, parser)
@end example

Features of note:


@itemize *

@item 
@code{"extend"} both expects a value on the command-line and stores that value
somewhere, so it goes in both @ref{3a79,,STORE_ACTIONS} and
@ref{3a7a,,TYPED_ACTIONS}.

@item 
to ensure that @ref{c3,,optparse} assigns the default type of @code{"string"} to
@code{"extend"} actions, we put the @code{"extend"} action in
@ref{3a7b,,ALWAYS_TYPED_ACTIONS} as well.

@item 
@code{MyOption.take_action()} implements just this one new action, and passes
control back to @code{Option.take_action()} for the standard @ref{c3,,optparse}
actions.

@item 
@code{values} is an instance of the optparse_parser.Values class, which provides
the very useful @code{ensure_value()} method. @code{ensure_value()} is
essentially @ref{443,,getattr()} with a safety valve; it is called as

@example
values.ensure_value(attr, value)
@end example

If the @code{attr} attribute of @code{values} doesn't exist or is @code{None}, then
ensure_value() first sets it to @code{value}, and then returns 'value. This is
very handy for actions like @code{"extend"}, @code{"append"}, and @code{"count"}, all
of which accumulate data in a variable and expect that variable to be of a
certain type (a list for the first two, an integer for the latter).  Using
@code{ensure_value()} means that scripts using your action don't have to worry
about setting a default value for the option destinations in question; they
can just leave the default as @code{None} and @code{ensure_value()} will take care of
getting it right when it's needed.
@end itemize

@node imp --- Access the import internals,,optparse --- 解析器的命令行选项,被取代的模块
@anchor{library/imp doc}@anchor{3a7c}@anchor{library/imp imp-access-the-import-internals}@anchor{3a7d}@anchor{library/imp module-imp}@anchor{9a}
@subsection @code{imp} --- Access the import internals


@geindex imp (模块)

@strong{Source code:} Lib/imp.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/imp.py}


3.4 版后已移除: The @ref{9a,,imp} module is deprecated in favor of @ref{9b,,importlib}.


@geindex 语句; import


__________________________________________________________________


This module provides an interface to the mechanisms used to implement the
@ref{c16,,import} statement.  It defines the following constants and functions:

@geindex get_magic() (在 imp 模块中)
@anchor{library/imp imp get_magic}@anchor{85d}
@deffn {函数} imp.get_magic ()

@geindex file; byte-code

Return the magic string value used to recognize byte-compiled code files
(@code{.pyc} files).  (This value may be different for each Python version.)


3.4 版后已移除: Use @ref{85c,,importlib.util.MAGIC_NUMBER} instead.

@end deffn

@geindex get_suffixes() (在 imp 模块中)
@anchor{library/imp imp get_suffixes}@anchor{3a7e}
@deffn {函数} imp.get_suffixes ()

Return a list of 3-element tuples, each describing a particular type of
module. Each triple has the form @code{(suffix, mode, type)}, where @emph{suffix} is
a string to be appended to the module name to form the filename to search
for, @emph{mode} is the mode string to pass to the built-in @ref{4ea,,open()} function
to open the file (this can be @code{'r'} for text files or @code{'rb'} for binary
files), and @emph{type} is the file type, which has one of the values
@ref{3a7f,,PY_SOURCE}, @ref{3a80,,PY_COMPILED}, or @ref{3a81,,C_EXTENSION}, described
below.


3.3 版后已移除: Use the constants defined on @ref{9d,,importlib.machinery} instead.

@end deffn

@geindex find_module() (在 imp 模块中)
@anchor{library/imp imp find_module}@anchor{3a82}
@deffn {函数} imp.find_module (name[, path])

Try to find the module @emph{name}.  If @emph{path} is omitted or @code{None}, the list of
directory names given by @code{sys.path} is searched, but first a few special
places are searched: the function tries to find a built-in module with the
given name (@ref{3a83,,C_BUILTIN}), then a frozen module (@ref{3a84,,PY_FROZEN}),
and on some systems some other places are looked in as well (on Windows, it
looks in the registry which may point to a specific file).

Otherwise, @emph{path} must be a list of directory names; each directory is
searched for files with any of the suffixes returned by @ref{3a7e,,get_suffixes()}
above.  Invalid names in the list are silently ignored (but all list items
must be strings).

If search is successful, the return value is a 3-element tuple @code{(file,
pathname, description)}:

@emph{file} is an open @ref{b3b,,file object} positioned at the beginning, @emph{pathname}
is the pathname of the file found, and @emph{description} is a 3-element tuple as
contained in the list returned by @ref{3a7e,,get_suffixes()} describing the kind of
module found.

If the module is built-in or frozen then @emph{file} and @emph{pathname} are both @code{None}
and the @emph{description} tuple contains empty strings for its suffix and mode;
the module type is indicated as given in parentheses above.  If the search
is unsuccessful, @ref{32d,,ImportError} is raised.  Other exceptions indicate
problems with the arguments or environment.

If the module is a package, @emph{file} is @code{None}, @emph{pathname} is the package
path and the last item in the @emph{description} tuple is @ref{3a85,,PKG_DIRECTORY}.

This function does not handle hierarchical module names (names containing
dots).  In order to find @emph{P.M}, that is, submodule @emph{M} of package @emph{P}, use
@ref{3a82,,find_module()} and @ref{3a86,,load_module()} to find and load package @emph{P}, and
then use @ref{3a82,,find_module()} with the @emph{path} argument set to @code{P.__path__}.
When @emph{P} itself has a dotted name, apply this recipe recursively.


3.3 版后已移除: Use @ref{932,,importlib.util.find_spec()} instead unless Python 3.3
compatibility is required, in which case use
@ref{931,,importlib.find_loader()}. For example usage of the former case,
see the @ref{3745,,例子} section of the @ref{9b,,importlib}
documentation.

@end deffn

@geindex load_module() (在 imp 模块中)
@anchor{library/imp imp load_module}@anchor{3a86}
@deffn {函数} imp.load_module (name, file, pathname, description)

Load a module that was previously found by @ref{3a82,,find_module()} (or by an
otherwise conducted search yielding compatible results).  This function does
more than importing the module: if the module was already imported, it will
reload the module!  The @emph{name} argument indicates the full
module name (including the package name, if this is a submodule of a
package).  The @emph{file} argument is an open file, and @emph{pathname} is the
corresponding file name; these can be @code{None} and @code{'@w{'}}, respectively, when
the module is a package or not being loaded from a file.  The @emph{description}
argument is a tuple, as would be returned by @ref{3a7e,,get_suffixes()}, describing
what kind of module must be loaded.

If the load is successful, the return value is the module object; otherwise,
an exception (usually @ref{32d,,ImportError}) is raised.

@strong{Important:} the caller is responsible for closing the @emph{file} argument, if
it was not @code{None}, even when an exception is raised.  This is best done
using a @ref{d6b,,try} ... @ref{182,,finally} statement.


3.3 版后已移除: If previously used in conjunction with @ref{3a82,,imp.find_module()} then
consider using @ref{b0c,,importlib.import_module()}, otherwise use the loader
returned by the replacement you chose for @ref{3a82,,imp.find_module()}. If you
called @ref{3a86,,imp.load_module()} and related functions directly with file
path arguments then use a combination of
@ref{554,,importlib.util.spec_from_file_location()} and
@ref{6ea,,importlib.util.module_from_spec()}. See the @ref{3745,,例子}
section of the @ref{9b,,importlib} documentation for details of the various
approaches.

@end deffn

@geindex new_module() (在 imp 模块中)
@anchor{library/imp imp new_module}@anchor{3a87}
@deffn {函数} imp.new_module (name)

Return a new empty module object called @emph{name}.  This object is @emph{not} inserted
in @code{sys.modules}.


3.4 版后已移除: Use @ref{6ea,,importlib.util.module_from_spec()} instead.

@end deffn

@geindex reload() (在 imp 模块中)
@anchor{library/imp imp reload}@anchor{c69}
@deffn {函数} imp.reload (module)

Reload a previously imported @emph{module}.  The argument must be a module object, so
it must have been successfully imported before.  This is useful if you have
edited the module source file using an external editor and want to try out the
new version without leaving the Python interpreter.  The return value is the
module object (the same as the @emph{module} argument).

When @code{reload(module)} is executed:


@itemize *

@item 
Python modules' code is recompiled and the module-level code reexecuted,
defining a new set of objects which are bound to names in the module's
dictionary.  The @code{init} function of extension modules is not called a second
time.

@item 
与Python中的所有的其它对象一样，旧的对象只有在它们的引用计数为0之后才会被回收。

@item 
模块命名空间中的名称重新指向任何新的或更改后的对象。

@item 
其他旧对象的引用（例如那个模块的外部名称）不会被重新绑定到引用的新对象的，并且如果有需要，必须在出现的每个命名空间中进行更新。
@end itemize

有一些其他注意事项：

当一个模块被重新加载的时候，它的字典（包含了那个模块的全区变量）会被保留。名称的重新定义会覆盖旧的定义，所以通常来说这不是问题。如果一个新模块没有定义在旧版本模块中定义的名称，则将保留旧版本中的定义。这一特性可用于作为那个模块的优点，如果它维护一个全局表或者对象的缓存 —— 使用 @ref{d6b,,try} 语句，就可以测试表的存在并且跳过它的初始化，如果有需要的话:

@example
try:
    cache
except NameError:
    cache = @{@}
@end example

It is legal though generally not very useful to reload built-in or dynamically
loaded modules, except for @ref{fd,,sys}, @ref{1,,__main__} and @ref{13,,builtins}.
In many cases, however, extension modules are not designed to be initialized
more than once, and may fail in arbitrary ways when reloaded.

If a module imports objects from another module using @ref{c3e,,from} ...
@ref{c16,,import} ..., calling @ref{c69,,reload()} for the other module does not
redefine the objects imported from it --- one way around this is to re-execute
the @code{from} statement, another is to use @code{import} and qualified
names (@emph{module}.*name*) instead.

如果一个模块创建一个类的实例，重新加载定义那个类的模块不影响那些实例的方法定义———它们继续使用旧类中的定义。对于子类来说同样是正确的。


在 3.3 版更改: Relies on both @code{__name__} and @code{__loader__} being defined on the module
being reloaded instead of just @code{__name__}.



3.4 版后已移除: Use @ref{391,,importlib.reload()} instead.

@end deffn

The following functions are conveniences for handling 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} byte-compiled
file paths.


3.2 新版功能.


@geindex cache_from_source() (在 imp 模块中)
@anchor{library/imp imp cache_from_source}@anchor{3a88}
@deffn {函数} imp.cache_from_source (path, debug_override=None)

Return the 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} path to the byte-compiled file associated with the
source @emph{path}.  For example, if @emph{path} is @code{/foo/bar/baz.py} the return
value would be @code{/foo/bar/__pycache__/baz.cpython-32.pyc} for Python 3.2.
The @code{cpython-32} string comes from the current magic tag (see
@ref{3a89,,get_tag()}; if @code{sys.implementation.cache_tag} is not defined then
@ref{609,,NotImplementedError} will be raised). By passing in @code{True} or
@code{False} for @emph{debug_override} you can override the system's value for
@code{__debug__}, leading to optimized bytecode.

@emph{path} need not exist.


在 3.3 版更改: If @code{sys.implementation.cache_tag} is @code{None}, then
@ref{609,,NotImplementedError} is raised.



3.4 版后已移除: Use @ref{552,,importlib.util.cache_from_source()} instead.



在 3.5 版更改: The @emph{debug_override} parameter no longer creates a @code{.pyo} file.

@end deffn

@geindex source_from_cache() (在 imp 模块中)
@anchor{library/imp imp source_from_cache}@anchor{3a8a}
@deffn {函数} imp.source_from_cache (path)

Given the @emph{path} to a 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} file name, return the associated source code
file path.  For example, if @emph{path} is
@code{/foo/bar/__pycache__/baz.cpython-32.pyc} the returned path would be
@code{/foo/bar/baz.py}.  @emph{path} need not exist, however if it does not conform
to 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} format, a @ref{1fb,,ValueError} is raised. If
@code{sys.implementation.cache_tag} is not defined,
@ref{609,,NotImplementedError} is raised.


在 3.3 版更改: Raise @ref{609,,NotImplementedError} when
@code{sys.implementation.cache_tag} is not defined.



3.4 版后已移除: Use @ref{553,,importlib.util.source_from_cache()} instead.

@end deffn

@geindex get_tag() (在 imp 模块中)
@anchor{library/imp imp get_tag}@anchor{3a89}
@deffn {函数} imp.get_tag ()

Return the 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} magic tag string matching this version of Python's
magic number, as returned by @ref{85d,,get_magic()}.


3.4 版后已移除: Use @code{sys.implementation.cache_tag} directly starting
in Python 3.3.

@end deffn

The following functions help interact with the import system's internal
locking mechanism.  Locking semantics of imports are an implementation
detail which may vary from release to release.  However, Python ensures
that circular imports work without any deadlocks.

@geindex lock_held() (在 imp 模块中)
@anchor{library/imp imp lock_held}@anchor{3a8b}
@deffn {函数} imp.lock_held ()

Return @code{True} if the global import lock is currently held, else
@code{False}. On platforms without threads, always return @code{False}.

On platforms with threads, a thread executing an import first holds a
global import lock, then sets up a per-module lock for the rest of the
import.  This blocks other threads from importing the same module until
the original import completes, preventing other threads from seeing
incomplete module objects constructed by the original thread.  An
exception is made for circular imports, which by construction have to
expose an incomplete module object at some point.


在 3.3 版更改: The locking scheme has changed to per-module locks for
the most part.  A global import lock is kept for some critical tasks,
such as initializing the per-module locks.



3.4 版后已移除.

@end deffn

@geindex acquire_lock() (在 imp 模块中)
@anchor{library/imp imp acquire_lock}@anchor{3a8c}
@deffn {函数} imp.acquire_lock ()

Acquire the interpreter's global import lock for the current thread.
This lock should be used by import hooks to ensure thread-safety when
importing modules.

Once a thread has acquired the import lock, the same thread may acquire it
again without blocking; the thread must release it once for each time it has
acquired it.

On platforms without threads, this function does nothing.


在 3.3 版更改: The locking scheme has changed to per-module locks for
the most part.  A global import lock is kept for some critical tasks,
such as initializing the per-module locks.



3.4 版后已移除.

@end deffn

@geindex release_lock() (在 imp 模块中)
@anchor{library/imp imp release_lock}@anchor{3a8d}
@deffn {函数} imp.release_lock ()

Release the interpreter's global import lock. On platforms without
threads, this function does nothing.


在 3.3 版更改: The locking scheme has changed to per-module locks for
the most part.  A global import lock is kept for some critical tasks,
such as initializing the per-module locks.



3.4 版后已移除.

@end deffn

The following constants with integer values, defined in this module, are used
to indicate the search result of @ref{3a82,,find_module()}.

@geindex PY_SOURCE() (在 imp 模块中)
@anchor{library/imp imp PY_SOURCE}@anchor{3a7f}
@deffn {数据} imp.PY_SOURCE

The module was found as a source file.


3.3 版后已移除.

@end deffn

@geindex PY_COMPILED() (在 imp 模块中)
@anchor{library/imp imp PY_COMPILED}@anchor{3a80}
@deffn {数据} imp.PY_COMPILED

The module was found as a compiled code object file.


3.3 版后已移除.

@end deffn

@geindex C_EXTENSION() (在 imp 模块中)
@anchor{library/imp imp C_EXTENSION}@anchor{3a81}
@deffn {数据} imp.C_EXTENSION

The module was found as dynamically loadable shared library.


3.3 版后已移除.

@end deffn

@geindex PKG_DIRECTORY() (在 imp 模块中)
@anchor{library/imp imp PKG_DIRECTORY}@anchor{3a85}
@deffn {数据} imp.PKG_DIRECTORY

The module was found as a package directory.


3.3 版后已移除.

@end deffn

@geindex C_BUILTIN() (在 imp 模块中)
@anchor{library/imp imp C_BUILTIN}@anchor{3a83}
@deffn {数据} imp.C_BUILTIN

The module was found as a built-in module.


3.3 版后已移除.

@end deffn

@geindex PY_FROZEN() (在 imp 模块中)
@anchor{library/imp imp PY_FROZEN}@anchor{3a84}
@deffn {数据} imp.PY_FROZEN

The module was found as a frozen module.


3.3 版后已移除.

@end deffn

@geindex NullImporter (imp 中的类)
@anchor{library/imp imp NullImporter}@anchor{9b5}
@deffn {类} imp.NullImporter (path_string)

The @ref{9b5,,NullImporter} type is a 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302} import hook that handles
non-directory path strings by failing to find any modules.  Calling this type
with an existing directory or empty string raises @ref{32d,,ImportError}.
Otherwise, a @ref{9b5,,NullImporter} instance is returned.

Instances have only one method:

@geindex find_module() (imp.NullImporter 方法)
@anchor{library/imp imp NullImporter find_module}@anchor{3a8e}
@deffn {方法} find_module (fullname[, path])

This method always returns @code{None}, indicating that the requested module could
not be found.
@end deffn


在 3.3 版更改: @code{None} is inserted into @code{sys.path_importer_cache} instead of an
instance of @ref{9b5,,NullImporter}.



3.4 版后已移除: Insert @code{None} into @code{sys.path_importer_cache} instead.

@end deffn

@menu
* 例子: 例子<33>. 

@end menu

@node 例子<33>,,,imp --- Access the import internals
@anchor{library/imp examples}@anchor{3a8f}@anchor{library/imp examples-imp}@anchor{3a90}
@subsubsection 例子


The following function emulates what was the standard import statement up to
Python 1.4 (no hierarchical module names).  (This @emph{implementation} wouldn't work
in that version, since @ref{3a82,,find_module()} has been extended and
@ref{3a86,,load_module()} has been added in 1.4.)

@example
import imp
import sys

def __import__(name, globals=None, locals=None, fromlist=None):
    # Fast path: see if the module has already been imported.
    try:
        return sys.modules[name]
    except KeyError:
        pass

    # If any of the following calls raises an exception,
    # there's a problem we can't handle -- let the caller handle it.

    fp, pathname, description = imp.find_module(name)

    try:
        return imp.load_module(name, fp, pathname, description)
    finally:
        # Since we may exit via an exception, close fp explicitly.
        if fp:
            fp.close()
@end example

@node 未创建文档的模块,,被取代的模块,Python 标准库
@anchor{library/undoc doc}@anchor{3a91}@anchor{library/undoc undoc}@anchor{3a92}@anchor{library/undoc undocumented-modules}@anchor{3a93}
@section 未创建文档的模块


以下是目前未创建文档模块的速览列表，但其它们应创建文档。 欢迎为他们提供文档！ （通过电子邮件发送到 @email{docs@@python.org} ）

本章的想法和原内容取自 Fredrik Lundh 的帖子；本章的具体内容已经大幅修改。

@menu
* 平台特定模块:: 

@end menu

@node 平台特定模块,,,未创建文档的模块
@anchor{library/undoc platform-specific-modules}@anchor{3a94}
@subsection 平台特定模块


这些模块用于实现 @ref{c5,,os.path} 模块，除此之外没有文档。几乎没有必要创建这些文档。


@table @asis

@item @code{ntpath}

--- 在 Win32 和 Win64 平台上实现 @ref{c5,,os.path} 。

@item @code{posixpath}

--- 在 POSIX 上实现 @ref{c5,,os.path} 。
@end table

@node 扩展和嵌入 Python 解释器,Python/C API 参考手册,Python 标准库,Top
@anchor{extending/index doc}@anchor{3a95}@anchor{extending/index extending-and-embedding-the-python-interpreter}@anchor{3a96}@anchor{extending/index extending-index}@anchor{1191}
@chapter 扩展和嵌入 Python 解释器


本文档描述了如何使用 C 或 C++ 编写模块以使用新模块来扩展 Python 解释器的功能。 这些模块不仅可以定义新的函数，还可以定义新的对象类型及其方法。 该文档还描述了如何将 Python 解释器嵌入到另一个应用程序中，以用作扩展语言。 最后，它展示了如何编译和链接扩展模块，以便它们可以动态地（在运行时）加载到解释器中，如果底层操作系统支持此特性的话。

本文档假设你具备有关 Python 的基本知识。有关该语言的非正式介绍，请参阅 @ref{118e,,Python 教程} 。 @ref{1190,,Python语言参考} 给出了更正式的语言定义。 @ref{118f,,Python 标准库} 包含现有的对象类型、函数和模块（内置和用 Python 编写）的文档，使语言具有广泛的应用范围。

关于整个 Python/C API 的详细介绍，请参阅独立的 @ref{1192,,Python/C API 参考手册} 。

@menu
* 推荐的第三方工具:: 
* 不使用第三方工具创建扩展:: 
* 在更大的应用程序中嵌入 CPython 运行时:: 

@end menu

@node 推荐的第三方工具,不使用第三方工具创建扩展,,扩展和嵌入 Python 解释器
@anchor{extending/index recommended-third-party-tools}@anchor{3a97}
@section 推荐的第三方工具


本指南仅介绍了作为此 CPython 版本的一部分提供的创建扩展的基本工具。 第三方工具，如 Cython@footnote{http://cython.org/} 、 cffi@footnote{https://cffi.readthedocs.io} 、 SWIG@footnote{http://www.swig.org} 和 Numba@footnote{https://numba.pydata.org/} 提供了更简单和更复杂的方法来为 Python 创建 C 和 C ++ 扩展。


@subsubheading 参见



@table @asis

@item Python Packaging User Guide: Binary Extensions@footnote{https://packaging.python.org/guides/packaging-binary-extensions/}

“ Python Packaging User Guide ”不仅涵盖了几个简化二进制扩展创建的可用工具，还讨论了为什么首先创建扩展模块的各种原因。
@end table


@node 不使用第三方工具创建扩展,在更大的应用程序中嵌入 CPython 运行时,推荐的第三方工具,扩展和嵌入 Python 解释器
@anchor{extending/index creating-extensions-without-third-party-tools}@anchor{3a98}
@section 不使用第三方工具创建扩展


本指南的这一部分包括在没有第三方工具帮助的情况下创建 C 和 C ++ 扩展。它主要用于这些工具的创建者，而不是建议你创建自己的 C 扩展的方法。

@menu
* 使用 C 或 C++ 扩展 Python:: 
* 自定义扩展类型：教程:: 
* 定义扩展类型：已分类主题:: 
* 构建C/C++扩展:: 
* 在Windows平台编译C和C++扩展:: 

@end menu

@node 使用 C 或 C++ 扩展 Python,自定义扩展类型：教程,,不使用第三方工具创建扩展
@anchor{extending/extending doc}@anchor{3a99}@anchor{extending/extending extending-intro}@anchor{3a9a}@anchor{extending/extending extending-python-with-c-or-c}@anchor{3a9b}
@subsection 使用 C 或 C++ 扩展 Python


如果你会用 C，添加新的 Python 内置模块会很简单。以下两件不能用 Python 直接做的事，可以通过 @emph{extension modules} 来实现：实现新的内置对象类型；调用 C 的库函数和系统调用。

为了支持扩展，Python API（应用程序编程接口）定义了一系列函数、宏和变量，可以访问 Python 运行时系统的大部分内容。Python 的 API 可以通过在一个 C 源文件中引用 @code{"Python.h"} 头文件来使用。

扩展模块的编写方式取决与你的目的以及系统设置；下面章节会详细介绍。

@cartouche
@quotation 注解 
C扩展接口特指CPython，扩展模块无法在其他Python实现上工作。在大多数情况下，应该避免写C扩展，来保持可移植性。举个例子，如果你的用例调用了C库或系统调用，你应该考虑使用 @ref{2b,,ctypes} 模块或 cffi@footnote{https://cffi.readthedocs.io/} 库，而不是自己写C代码。这些模块允许你写Python代码来接口C代码，而且可移植性更好。不知为何编译失败了。
@end quotation
@end cartouche

@menu
* 一个简单的例子:: 
* 关于错误和异常:: 
* 回到例子:: 
* 模块方法表和初始化函数:: 
* 编译和链接:: 
* 在C中调用Python函数:: 
* 提取扩展函数的参数:: 
* 给扩展函数的关键字参数:: 
* 构造任意值:: 
* 引用计数:: 
* 在C++中编写扩展:: 
* 给扩展模块提供C API:: 

@end menu

@node 一个简单的例子,关于错误和异常,,使用 C 或 C++ 扩展 Python
@anchor{extending/extending a-simple-example}@anchor{3a9c}@anchor{extending/extending extending-simpleexample}@anchor{3a9d}
@subsubsection 一个简单的例子


让我们创建一个扩展模块 @code{spam} (Monty Python 粉丝最喜欢的食物...) 并且想要创建对应 C 库函数 @code{system()} @footnote{@w{(1)} 
这个函数的接口已经在标准模块 @ref{c4,,os} 里了，这里作为一个简单而直接的例子。
} 的 Python 接口。 这个函数接受一个以 null 结尾的字符串参数并返回一个整数。 我们希望可以在 Python 中以如下方式调用此函数:

@example
>>> import spam
>>> status = spam.system("ls -l")
@end example

首先创建一个 @code{spammodule.c} 文件。（传统上，如果一个模块叫 @code{spam}，则对应实现它的 C 文件叫 @code{spammodule.c}；如果这个模块名字非常长，比如 @code{spammify}，则这个模块的文件可以直接叫 @code{spammify.c}。）

文件中开始的两行是：

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>
@end example

这会导入 Python API（如果你喜欢，你可以在这里添加描述模块目标和版权信息的注释)。

@cartouche
@quotation 注解 
由于 Python 可能会定义一些能在某些系统上影响标准头文件的预处理器定义，因此在包含任何标准头文件之前，你 @emph{必须} 先包含 @code{Python.h}。

推荐总是在 @code{Python.h} 前定义 @code{PY_SSIZE_T_CLEAN} 。查看 @ref{3a9e,,提取扩展函数的参数} 来了解这个宏的更多内容。
@end quotation
@end cartouche

所有用户可见的符号都定义自爱 @code{Python.h} 中，并拥有前缀 @code{Py} 或 @code{PY} ，除了那些已经定义在i包准头文件的。为了方便，以及为了让Python解释器应用广泛， @code{"Python.h"} 也包含了少量标准头文件： @code{<stdio.h>} ， @code{<string.h>} ， @code{<errno.h>} ，和 @code{<stdlib.h>} 。如果后面的头文件在你的系统上不存在，还会直接声明函数 @code{malloc()} ， @code{free()} 和 @code{realloc()} 。

下面添加C函数到扩展模块，当调用 @code{spam.system(string)} 时会做出响应，(我们稍后会看到调用)：

@example
static PyObject *
spam_system(PyObject *self, PyObject *args)
@{
    const char *command;
    int sts;

    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;
    sts = system(command);
    return PyLong_FromLong(sts);
@}
@end example

有个直接翻译参数列表的方法(举个例子，单独的 @code{"ls -l"} )到要传递给C函数的参数。C函数总是有两个参数，通常名字是 @emph{self} 和 @emph{args} 。

对模块级函数， @emph{self} 参数指向模块对象；对于对象实例则指向方法。

@emph{args} 参数是指向一个 Python 的 tuple 对象的指针，其中包含参数。 每个 tuple 项对应一个调用参数。 这些参数也全都是 Python 对象 --- 要在我们的 C 函数中使用它们就需要先将其转换为 C 值。 Python API 中的函数 @ref{26a,,PyArg_ParseTuple()} 会检查参数类型并将其转换为 C 值。 它使用模板字符串确定需要的参数类型以及存储被转换的值的 C 变量类型。 细节将稍后说明。

@ref{26a,,PyArg_ParseTuple()} 在所有参数都有正确类型且组成部分按顺序放在传递进来的地址里时，返回真(非零)。其在传入无效参数时返回假(零)。在后续例子里，还会抛出特定异常，使得调用的函数可以理解返回 @code{NULL} (也就是例子里所见)。

@node 关于错误和异常,回到例子,一个简单的例子,使用 C 或 C++ 扩展 Python
@anchor{extending/extending extending-errors}@anchor{3a9f}@anchor{extending/extending intermezzo-errors-and-exceptions}@anchor{3aa0}
@subsubsection 关于错误和异常


在 Python 解释器中有一个重要的惯例：当一个函数出错时，它应当设置异常条件并返回错误值（通常为 @code{NULL} 指针）。 异常存储于解释器内部的静态全局变量中；如此变量为 @code{NULL} 表示未发生异常。 还有第二个全局变量用于保存异常的“关联值”（即 @ref{c3b,,raise} 的第二个参数）。 第三个变量包含 Python 代码产生错误情况下的栈回溯信息。 这三个变量是 Python 中 @ref{c58,,sys.exc_info()} 的结果在 C 中的对应物（请参阅 Python 库参考的 @ref{fd,,sys} 模块部分）。 了解它们对于理解错误的传递方式是非常重要的。

Python API中定义了一些函数来设置这些变量。

最常用的就是 @ref{3aa1,,PyErr_SetString()}。 其参数是异常对象和 C 字符串。 异常对象一般是像 @code{PyExc_ZeroDivisionError} 这样的预定义对象。 C 字符串指明异常原因，并被转换为一个 Python 字符串对象存储为异常的“关联值”。

另一个有用的函数是 @ref{3aa2,,PyErr_SetFromErrno()} ，仅接受一个异常对象，异常描述包含在全局变量 @code{errno} 中。最通用的函数还是 @ref{3aa3,,PyErr_SetObject()} ，包含两个参数，分别为异常对象和异常描述。你不需要使用 @ref{265,,Py_INCREF()} 来增加传递到其他函数的参数对象的引用计数。

你可以通过 @ref{3aa4,,PyErr_Occurred()} 在不造成破坏的情况下检测是否设置了异常。 这将返回当前异常对象，或者如果未发生异常则返回 @code{NULL}。 你通常不需要调用 @ref{3aa4,,PyErr_Occurred()} 来查看函数调用中是否发生了错误，因为你应该能从返回值中看出来。

当一个函数 @emph{f} 调用另一个函数 @emph{g} 时检测到后者出错了，@emph{f} 应当自己返回一个错误值 (通常为 @code{NULL} 或 @code{-1})。 它 @emph{不应该} 调用某个 @code{PyErr_*()} 函数 --- 这类函数已经被 @emph{g} 调用过了。 @emph{f} 的调用者随后也应当返回一个错误来提示 @emph{它的} 调用者，同样 @emph{不应该} 调用 @code{PyErr_*()}，依此类推 --- 错误的最详细原因已经由首先检测到它的函数报告了。 一旦这个错误到达 Python 解释器的主循环，它会中止当前执行的 Python 代码并尝试找出由 Python 程序员所指定的异常处理程序。

（在某些情况下，当模块确实能够通过调用其它 @code{PyErr_*()} 函数给出更加详细的错误消息，并且在这些情况是可以这样做的。 但是按照一般规则，这是不必要的，并可能导致有关错误原因的信息丢失：大多数操作会由于种种原因而失败。）

想要忽略由一个失败的函数调用所设置的异常，异常条件必须通过调用 @ref{965,,PyErr_Clear()} 显式地被清除。 C 代码应当调用 @ref{965,,PyErr_Clear()} 的唯一情况是如果它不想将错误传给解释器而是想完全由自己来处理它（可能是尝试其他方法，或是假装没有出错）。

每次失败的 @code{malloc()} 调用必须转换为一个异常。 @code{malloc()} (或 @code{realloc()} )的直接调用者必须调用 @ref{3aa5,,PyErr_NoMemory()} 来返回错误来提示。所有对象创建函数(例如 @ref{3aa6,,PyLong_FromLong()} )已经这么做了，所以这个提示仅用于直接调用 @code{malloc()} 的情况。

还要注意的是，除了 @ref{26a,,PyArg_ParseTuple()} 等重要的例外，返回整数状态码的函数通常都是返回正值或零来表示成功，而以 @code{-1} 表示失败，如同 Unix 系统调用一样。

最后，当你返回一个错误指示器时要注意清理垃圾（通过为你已经创建的对象执行 @ref{268,,Py_XDECREF()} 或 @ref{266,,Py_DECREF()} 调用）！

选择引发哪个异常完全取决于你的喜好。 所有内置的 Python 异常都有对应的预声明 C 对象，例如 @code{PyExc_ZeroDivisionError}，你可以直接使用它们。 当然，你应当明智地选择异常 --- 不要使用 @code{PyExc_TypeError} 来表示一个文件无法被打开 (那大概应该用 @code{PyExc_IOError})。 如果参数列表有问题，@ref{26a,,PyArg_ParseTuple()} 函数通常会引发 @code{PyExc_TypeError}。 如果你想要一个参数的值必须处于特定范围之内或必须满足其他条件，则适宜使用 @code{PyExc_ValueError}。

你也可以为你的模块定义一个唯一的新异常。需要在文件前部声明一个静态对象变量，如:

@example
static PyObject *SpamError;
@end example

并且在你的模块的初始化函数 (@code{PyInit_spam()}) 中使用一个异常对象来初始化:

@example
PyMODINIT_FUNC
PyInit_spam(void)
@{
    PyObject *m;

    m = PyModule_Create(&spammodule);
    if (m == NULL)
        return NULL;

    SpamError = PyErr_NewException("spam.error", NULL, NULL);
    Py_XINCREF(SpamError);
    if (PyModule_AddObject(m, "error", SpamError) < 0) @{
        Py_XDECREF(SpamError);
        Py_CLEAR(SpamError);
        Py_DECREF(m);
        return NULL;
    @}

    return m;
@}
@end example

注意异常对象的Python名字是 @code{spam.error} 。而 @ref{bf9,,PyErr_NewException()} 函数可以创建一个类，其基类为 @ref{1a9,,Exception} (除非是另一个类传入以替换 @code{NULL} )， 细节参见 @ref{1242,,内置异常} 。

同样注意的是创建类保存了 @code{SpamError} 的一个引用，这是有意的。为了防止被垃圾回收掉，否则 @code{SpamError} 随时会成为野指针。

一会讨论 @code{PyMODINIT_FUNC} 作为函数返回类型的用法。

@code{spam.error} 异常可以在扩展模块中抛出，通过 @ref{3aa1,,PyErr_SetString()} 函数调用，如下：

@example
static PyObject *
spam_system(PyObject *self, PyObject *args)
@{
    const char *command;
    int sts;

    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;
    sts = system(command);
    if (sts < 0) @{
        PyErr_SetString(SpamError, "System command failed");
        return NULL;
    @}
    return PyLong_FromLong(sts);
@}
@end example

@node 回到例子,模块方法表和初始化函数,关于错误和异常,使用 C 或 C++ 扩展 Python
@anchor{extending/extending back-to-the-example}@anchor{3aa7}@anchor{extending/extending backtoexample}@anchor{3aa8}
@subsubsection 回到例子


回到前面的例子，你应该明白下面的代码:

@example
if (!PyArg_ParseTuple(args, "s", &command))
    return NULL;
@end example

如果在参数列表中检测到错误，它将返回 @code{NULL} (该值是返回对象指针的函数所使用的错误提示)，这取决于 @ref{26a,,PyArg_ParseTuple()} 设置的异常。 在其他情况下参数的字符串值会被拷贝到局部变量 @code{command}。 这是一个指针赋值并且你不应该修改它所指向的字符串 (因此在标准 C 中，变量 @code{command} 应当被正确地声明为 @code{const char *command})。

下一个语句使用UNIX系统函数 @code{system()} ，传递给他的参数是刚才从 @ref{26a,,PyArg_ParseTuple()} 取出的:

@example
sts = system(command);
@end example

我们的 @code{spam.system()} 函数必须返回 @code{sts} 的值作为Python对象。这通过使用函数 @ref{3aa6,,PyLong_FromLong()} 来实现。

@example
return PyLong_FromLong(sts);
@end example

在这种情况下，会返回一个整数对象，(这个对象会在Python堆里面管理)。

如果你的C函数没有有用的返回值(返回 @code{void} 的函数)，则必须返回 @code{None} 。(你可以用  @code{Py_RETUN_NONE} 宏来完成):

@example
Py_INCREF(Py_None);
return Py_None;
@end example

@ref{3aa9,,Py_None} 是特殊 Python 对象 @code{None} 所对应的 C 名称。 它是一个真正的 Python 对象而不是 @code{NULL} 指针，如我们所见，后者在大多数上下文中都意味着“错误”。

@node 模块方法表和初始化函数,编译和链接,回到例子,使用 C 或 C++ 扩展 Python
@anchor{extending/extending methodtable}@anchor{3aaa}@anchor{extending/extending the-module-s-method-table-and-initialization-function}@anchor{3aab}
@subsubsection 模块方法表和初始化函数


为了展示 @code{spam_system()} 如何被Python程序调用。把函数声明为可以被Python调用，需要先定义一个方法表 "method table" 。

@example
static PyMethodDef SpamMethods[] = @{
    ...
    @{"system",  spam_system, METH_VARARGS,
     "Execute a shell command."@},
    ...
    @{NULL, NULL, 0, NULL@}        /* Sentinel */
@};
@end example

注意第三个参数 ( @code{METH_VARARGS} ) ，这个标志指定会使用C的调用惯例。可选值有  @code{METH_VARARGS} 、 @code{METH_VARARGS | METH_KEYWORDS} 。值 @code{0} 代表使用 @ref{26a,,PyArg_ParseTuple()} 的陈旧变量。

如果单独使用 @code{METH_VARARGS} ，函数会等待Python传来tuple格式的参数，并最终使用  @ref{26a,,PyArg_ParseTuple()} 进行解析。

@code{METH_KEYWORDS} 值表示接受关键字参数。这种情况下C函数需要接受第三个 @code{PyObject *}  对象，表示字典参数，使用 @ref{5c5,,PyArg_ParseTupleAndKeywords()} 来解析出参数。

这个方法表必须被模块定义结构所引用。

@example
static struct PyModuleDef spammodule = @{
    PyModuleDef_HEAD_INIT,
    "spam",   /* name of module */
    spam_doc, /* module documentation, may be NULL */
    -1,       /* size of per-interpreter state of the module,
                 or -1 if the module keeps state in global variables. */
    SpamMethods
@};
@end example

这个结构体必须传递给解释器的模块初始化函数。初始化函数必须命名为 @code{PyInit_name()} ，其中 @emph{name} 是模块的名字，并应该定义为非 @code{static} ，且在模块文件里：

@example
PyMODINIT_FUNC
PyInit_spam(void)
@{
    return PyModule_Create(&spammodule);
@}
@end example

注意 PyMODINIT_FUNC 声明了函数作为 @code{PyObject *} 返回类型，声明任何平台的链接生命，以及给C++生命函数的 @code{extern "C"} 。

当 Python 程序首次导入 @code{spam} 模块时， @code{PyInit_spam()} 会被调用。 （有关嵌入 Python 的注释参见下文。） 它将调用 @ref{3aac,,PyModule_Create()}，该函数会返回一个模块对象，并基于在模块定义中找到的表将内置函数对象插入到新创建的模块中（该表是一个 @ref{e14,,PyMethodDef} 结构体的数组）。 @ref{3aac,,PyModule_Create()} 返回一个指向它所创建的模块对象的指针。 它可能会因程度严重的特定错误而中止，或者在模块无法成功初始化时返回 @code{NULL}。 初始化函数必须返回模块对象给其调用者，这样它就可以被插入到 @code{sys.modules} 中。

当嵌入Python时， @code{PyInit_spam()} 函数不会被自动调用，除非放在 @code{PyImport_Inittab} 表里。要添加模块到初始化表，使用 @ref{3aad,,PyImport_AppendInittab()} ，可选的跟着一个模块的导入。

@example
int
main(int argc, char *argv[])
@{
    wchar_t *program = Py_DecodeLocale(argv[0], NULL);
    if (program == NULL) @{
        fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
        exit(1);
    @}

    /* Add a built-in module, before Py_Initialize */
    if (PyImport_AppendInittab("spam", PyInit_spam) == -1) @{
        fprintf(stderr, "Error: could not extend in-built modules table\n");
        exit(1);
    @}

    /* Pass argv[0] to the Python interpreter */
    Py_SetProgramName(program);

    /* Initialize the Python interpreter.  Required.
       If this step fails, it will be a fatal error. */
    Py_Initialize();

    /* Optionally import the module; alternatively,
       import can be deferred until the embedded script
       imports it. */
    pmodule = PyImport_ImportModule("spam");
    if (!pmodule) @{
        PyErr_Print();
        fprintf(stderr, "Error: could not import module 'spam'\n");
    @}

    ...

    PyMem_RawFree(program);
    return 0;
@}
@end example

@cartouche
@quotation 注解 
要从 @code{sys.modules} 删除实体或导入已编译模块到一个进程里的多个解释器(或使用 @code{fork()} 而没用 @code{exec()} )会在一些扩展模块上产生错误。扩展模块作者可以在初始化内部数据结构时给出警告。
@end quotation
@end cartouche

更多关于模块的现实的例子包含在Python源码包的 @code{Modules/xxmodule.c} 中。这些文件可以用作你的代码模板，或者学习。脚本 modulator.py 包含在源码发行版或Windows安装中，提供了一个简单的GUI，用来声明需要实现的函数和对象，并且可以生成供填入的模板。脚本在 Tools/modulator/ 目录。查看README以了解用法。

@cartouche
@quotation 注解 
不像我们的 @code{spam} 例子， @code{xxmodule} 使用了 @emph{多阶段初始化} (Python3.5开始引入)， @code{PyInit_spam} 会返回一个 PyModuleDef 结构体，然后创建的模块放到导入机制。细节参考 
@geindex Python 提高建议; PEP 489
PEP 489@footnote{https://www.python.org/dev/peps/pep-0489} 的多阶段初始化。
@end quotation
@end cartouche

@node 编译和链接,在C中调用Python函数,模块方法表和初始化函数,使用 C 或 C++ 扩展 Python
@anchor{extending/extending compilation}@anchor{3aae}@anchor{extending/extending compilation-and-linkage}@anchor{3aaf}
@subsubsection 编译和链接


在你能使用你的新写的扩展之前，你还需要做两件事情：使用 Python 系统来编译和链接。如果你使用动态加载，这取决于你使用的操作系统的动态加载机制；更多信息请参考编译扩展模块的章节（ @ref{3ab0,,构建C/C++扩展} 章节），以及在 Windows 上编译需要的额外信息（ @ref{1332,,在Windows平台编译C和C++扩展} 章节）。

如果你不使用动态加载，或者想要让模块永久性的作为Python解释器的一部分，就必须修改配置设置，并重新构建解释器。幸运的是在Unix上很简单，只需要把你的文件 ( @code{spammodule.c} 为例) 放在解压缩源码发行包的 @code{Modules/} 目录下，添加一行到 @code{Modules/Setup.local} 来描述你的文件：

@example
spam spammodule.o
@end example

然后在顶层目录运行 @code{make} 来重新构建解释器。你也可以在 @code{Modules/} 子目录使用 @code{make}，但是你必须先重建 @code{Makefile} 文件，然后运行 '@code{make} Makefile' 命令。（你每次修改 @code{Setup} 文件都需要这样操作。）

如果你的模块需要额外的链接，这些内容可以列出在配置文件里，举个实例：

@example
spam spammodule.o -lX11
@end example

@node 在C中调用Python函数,提取扩展函数的参数,编译和链接,使用 C 或 C++ 扩展 Python
@anchor{extending/extending calling-python-functions-from-c}@anchor{3ab1}@anchor{extending/extending callingpython}@anchor{3ab2}
@subsubsection 在C中调用Python函数


迄今为止，我们一直把注意力集中于让Python调用C函数，其实反过来也很有用，就是用C调用Python函数。这在回调函数中尤其有用。如果一个C接口使用回调，那么就要实现这个回调机制。

幸运的是，Python解释器是比较方便回调的，并给标准Python函数提供了标准接口。(这里就不再详述解析Python字符串作为输入的方式，如果有兴趣可以参考 @code{Python/pythonmain.c} 中的 @ref{119f,,-c} 命令行代码。)

调用Python函数很简单，首先Python程序要传递Python函数对象。应该提供个函数(或其他接口)来实现。当调用这个函数时，用全局变量保存Python函数对象的指针，还要调用 (@ref{265,,Py_INCREF()}) 来增加引用计数，当然不用全局变量也没什么关系。举个例子，如下函数可能是模块定义的一部分：

@example
static PyObject *my_callback = NULL;

static PyObject *
my_set_callback(PyObject *dummy, PyObject *args)
@{
    PyObject *result = NULL;
    PyObject *temp;

    if (PyArg_ParseTuple(args, "O:set_callback", &temp)) @{
        if (!PyCallable_Check(temp)) @{
            PyErr_SetString(PyExc_TypeError, "parameter must be callable");
            return NULL;
        @}
        Py_XINCREF(temp);         /* Add a reference to new callback */
        Py_XDECREF(my_callback);  /* Dispose of previous callback */
        my_callback = temp;       /* Remember new callback */
        /* Boilerplate to return "None" */
        Py_INCREF(Py_None);
        result = Py_None;
    @}
    return result;
@}
@end example

这个函数必须使用 @ref{e41,,METH_VARARGS} 标志注册到解释器，这在 @ref{3aaa,,模块方法表和初始化函数} 章节会描述。 @ref{26a,,PyArg_ParseTuple()} 函数及其参数的文档在 @ref{3a9e,,提取扩展函数的参数} 。

@ref{267,,Py_XINCREF()} 和 @ref{268,,Py_XDECREF()} 这两个宏可增加/减少一个对象的引用计数，并且当存在 @code{NULL} 指针时仍可保证安全 (但请注意在这个上下文中 @emph{temp} 将不为  @code{NULL})。 更多相关信息请参考 @ref{3ab3,,引用计数} 章节。

@geindex PyObject_CallObject()

随后，当要调用此函数时，你将调用 C 函数 @ref{3ab4,,PyObject_CallObject()}。 该函数有两个参数，它们都属于指针，指向任意 Python 对象：即 Python 函数，及其参数列表。 参数列表必须总是一个元组对象，其长度即参数的个数量。 要不带参数地调用 Python 函数，则传入 @code{NULL} 或一个空元组；要带一个参数调用它，则传入一个单元组。 @ref{2ce,,Py_BuildValue()} 会在其格式字符串包含一对圆括号内的零个或多个格式代码时返回一个元组。 例如:

@example
int arg;
PyObject *arglist;
PyObject *result;
...
arg = 123;
...
/* Time to call the callback */
arglist = Py_BuildValue("(i)", arg);
result = PyObject_CallObject(my_callback, arglist);
Py_DECREF(arglist);
@end example

@ref{3ab4,,PyObject_CallObject()} 返回Python对象指针，这也是Python函数的返回值。 @ref{3ab4,,PyObject_CallObject()} 是一个对其参数 "引用计数无关" 的函数。例子中新的元组创建用于参数列表，并且在  @ref{3ab4,,PyObject_CallObject()} 之后立即使用了 @ref{266,,Py_DECREF()} 。

@code{PyEval_CallObject()} 的返回值总是“新”的：要么是一个新建的对象；要么是已有对象，但增加了引用计数。所以除非你想把结果保存在全局变量中，你需要对这个值使用 @ref{266,,Py_DECREF()}，即使你对里面的内容（特别！）不感兴趣。

但是在你这么做之前，很重要的一点是检查返回值不是 @code{NULL}。 如果是的话，Python 函数会终止并引发异常。 如果调用 @ref{3ab4,,PyObject_CallObject()} 的 C 代码是在 Python 中发起调用的，它应当立即返回一个错误来告知其 Python 调用者，以便解释器能打印栈回溯信息，或者让调用方 Python 代码能处理该异常。 如果这无法做到或不合本意，则应当通过调用 @ref{965,,PyErr_Clear()} 来清除异常。 例如:

@example
if (result == NULL)
    return NULL; /* Pass error back */
...use result...
Py_DECREF(result);
@end example

依赖于具体的回调函数，你还要提供一个参数列表到 @code{PyEval_CallObject()} 。在某些情况下参数列表是由Python程序提供的，通过接口再传到回调函数对象。这样就可以不改变形式直接传递。另外一些时候你要构造一个新的元组来传递参数。最简单的方法就是 @ref{2ce,,Py_BuildValue()} 函数构造tuple。举个例子，你要传递一个事件代码时可以用如下代码:

@example
PyObject *arglist;
...
arglist = Py_BuildValue("(l)", eventcode);
result = PyObject_CallObject(my_callback, arglist);
Py_DECREF(arglist);
if (result == NULL)
    return NULL; /* Pass error back */
/* Here maybe use the result */
Py_DECREF(result);
@end example

注意 @code{Py_DECREF(arglist)} 所在处会立即调用，在错误检查之前。当然还要注意一些常规的错误，比如 @ref{2ce,,Py_BuildValue()} 可能会遭遇内存不足等等。

当你调用函数时还需要注意，用关键字参数调用 @ref{3ab5,,PyObject_Call()} ，需要支持普通参数和关键字参数。有如如上例子中，我们使用 @ref{2ce,,Py_BuildValue()} 来构造字典。

@example
PyObject *dict;
...
dict = Py_BuildValue("@{s:i@}", "name", val);
result = PyObject_Call(my_callback, NULL, dict);
Py_DECREF(dict);
if (result == NULL)
    return NULL; /* Pass error back */
/* Here maybe use the result */
Py_DECREF(result);
@end example

@node 提取扩展函数的参数,给扩展函数的关键字参数,在C中调用Python函数,使用 C 或 C++ 扩展 Python
@anchor{extending/extending extracting-parameters-in-extension-functions}@anchor{3ab6}@anchor{extending/extending parsetuple}@anchor{3a9e}
@subsubsection 提取扩展函数的参数


@geindex PyArg_ParseTuple()

函数 @ref{26a,,PyArg_ParseTuple()} 的声明如下：

@example
int PyArg_ParseTuple(PyObject *arg, const char *format, ...);
@end example

参数 @emph{arg} 必须是一个元组对象，包含从 Python 传递给 C 函数的参数列表。@emph{format} 参数必须是一个格式字符串，语法请参考 Python C/API 手册中的 @ref{2d0,,解析参数并构建值变量}。剩余参数是各个变量的地址，类型要与格式字符串对应。

注意 @ref{26a,,PyArg_ParseTuple()} 会检测他需要的Python参数类型，却无法检测传递给他的C变量地址，如果这里出错了，可能会在内存中随机写入东西，小心。

注意任何由调用者提供的 Python 对象引用是 @emph{借来的} 引用；不要递减它们的引用计数！

一些调用的例子：

@example
#define PY_SSIZE_T_CLEAN  /* Make "s#" use Py_ssize_t rather than int. */
#include <Python.h>
@end example

@example
int ok;
int i, j;
long k, l;
const char *s;
Py_ssize_t size;

ok = PyArg_ParseTuple(args, ""); /* No arguments */
    /* Python call: f() */
@end example

@example
ok = PyArg_ParseTuple(args, "s", &s); /* A string */
    /* Possible Python call: f('whoops!') */
@end example

@example
ok = PyArg_ParseTuple(args, "lls", &k, &l, &s); /* Two longs and a string */
    /* Possible Python call: f(1, 2, 'three') */
@end example

@example
ok = PyArg_ParseTuple(args, "(ii)s#", &i, &j, &s, &size);
    /* A pair of ints and a string, whose size is also returned */
    /* Possible Python call: f((1, 2), 'three') */
@end example

@example
@{
    const char *file;
    const char *mode = "r";
    int bufsize = 0;
    ok = PyArg_ParseTuple(args, "s|si", &file, &mode, &bufsize);
    /* A string, and optionally another string and an integer */
    /* Possible Python calls:
       f('spam')
       f('spam', 'w')
       f('spam', 'wb', 100000) */
@}
@end example

@example
@{
    int left, top, right, bottom, h, v;
    ok = PyArg_ParseTuple(args, "((ii)(ii))(ii)",
             &left, &top, &right, &bottom, &h, &v);
    /* A rectangle and a point */
    /* Possible Python call:
       f(((0, 0), (400, 300)), (10, 10)) */
@}
@end example

@example
@{
    Py_complex c;
    ok = PyArg_ParseTuple(args, "D:myfunction", &c);
    /* a complex, also providing a function name for errors */
    /* Possible Python call: myfunction(1+2j) */
@}
@end example

@node 给扩展函数的关键字参数,构造任意值,提取扩展函数的参数,使用 C 或 C++ 扩展 Python
@anchor{extending/extending keyword-parameters-for-extension-functions}@anchor{3ab7}@anchor{extending/extending parsetupleandkeywords}@anchor{3ab8}
@subsubsection 给扩展函数的关键字参数


@geindex PyArg_ParseTupleAndKeywords()

函数 @ref{5c5,,PyArg_ParseTupleAndKeywords()} 声明如下：

@example
int PyArg_ParseTupleAndKeywords(PyObject *arg, PyObject *kwdict,
                                const char *format, char *kwlist[], ...);
@end example

@emph{arg} 与 @emph{format} 形参与 @ref{26a,,PyArg_ParseTuple()} 函数所定义的一致。 @emph{kwdict} 形参是作为第三个参数从 Python 运行时接收的关键字字典。 @emph{kwlist} 形参是以 @code{NULL} 结尾的字符串列表，它被用来标识形参；名称从左至右与来自 @emph{format} 的类型信息相匹配。 如果执行成功，@ref{5c5,,PyArg_ParseTupleAndKeywords()} 会返回真值，否则返回假值并引发一个适当的异常。

@cartouche
@quotation 注解 
嵌套的元组在使用关键字参数时无法生效，不在 @emph{kwlist} 中的关键字参数会导致 @ref{192,,TypeError} 异常。
@end quotation
@end cartouche

@geindex Philbrick@comma{} Geoff

如下例子是使用关键字参数的例子模块，作者是 Geoff Philbrick (@email{philbrick@@hks.com}):

@example
#define PY_SSIZE_T_CLEAN  /* Make "s#" use Py_ssize_t rather than int. */
#include <Python.h>

static PyObject *
keywdarg_parrot(PyObject *self, PyObject *args, PyObject *keywds)
@{
    int voltage;
    const char *state = "a stiff";
    const char *action = "voom";
    const char *type = "Norwegian Blue";

    static char *kwlist[] = @{"voltage", "state", "action", "type", NULL@};

    if (!PyArg_ParseTupleAndKeywords(args, keywds, "i|sss", kwlist,
                                     &voltage, &state, &action, &type))
        return NULL;

    printf("-- This parrot wouldn't %s if you put %i Volts through it.\n",
           action, voltage);
    printf("-- Lovely plumage, the %s -- It's %s!\n", type, state);

    Py_RETURN_NONE;
@}

static PyMethodDef keywdarg_methods[] = @{
    /* The cast of the function is necessary since PyCFunction values
     * only take two PyObject* parameters, and keywdarg_parrot() takes
     * three.
     */
    @{"parrot", (PyCFunction)(void(*)(void))keywdarg_parrot, METH_VARARGS | METH_KEYWORDS,
     "Print a lovely skit to standard output."@},
    @{NULL, NULL, 0, NULL@}   /* sentinel */
@};

static struct PyModuleDef keywdargmodule = @{
    PyModuleDef_HEAD_INIT,
    "keywdarg",
    NULL,
    -1,
    keywdarg_methods
@};

PyMODINIT_FUNC
PyInit_keywdarg(void)
@{
    return PyModule_Create(&keywdargmodule);
@}
@end example

@node 构造任意值,引用计数,给扩展函数的关键字参数,使用 C 或 C++ 扩展 Python
@anchor{extending/extending building-arbitrary-values}@anchor{3ab9}@anchor{extending/extending buildvalue}@anchor{3aba}
@subsubsection 构造任意值


这个函数与 @ref{26a,,PyArg_ParseTuple()} 很相似，声明如下：

@example
PyObject *Py_BuildValue(const char *format, ...);
@end example

接受一个格式字符串，与 @ref{26a,,PyArg_ParseTuple()} 相同，但是参数必须是原变量的地址指针(输入给函数，而非输出)。最终返回一个Python对象适合于返回C函数调用给Python代码。

一个与 @ref{26a,,PyArg_ParseTuple()} 的不同是，后面可能需要的要求返回一个元组(Python参数里诶包总是在内部描述为元组)，比如用于传递给其他Python函数以参数。 @ref{2ce,,Py_BuildValue()} 并不总是生成元组，在多于1个格式字符串时会生成元组，而如果格式字符串为空则返回 @code{None} ，一个参数则直接返回该参数的对象。如果要求强制生成一个长度为0的元组，或包含一个元素的元组，需要在格式字符串中加上括号。

例子(左侧是调用，右侧是Python值结果)：

@example
Py_BuildValue("")                        None
Py_BuildValue("i", 123)                  123
Py_BuildValue("iii", 123, 456, 789)      (123, 456, 789)
Py_BuildValue("s", "hello")              'hello'
Py_BuildValue("y", "hello")              b'hello'
Py_BuildValue("ss", "hello", "world")    ('hello', 'world')
Py_BuildValue("s#", "hello", 4)          'hell'
Py_BuildValue("y#", "hello", 4)          b'hell'
Py_BuildValue("()")                      ()
Py_BuildValue("(i)", 123)                (123,)
Py_BuildValue("(ii)", 123, 456)          (123, 456)
Py_BuildValue("(i,i)", 123, 456)         (123, 456)
Py_BuildValue("[i,i]", 123, 456)         [123, 456]
Py_BuildValue("@{s:i,s:i@}",
              "abc", 123, "def", 456)    @{'abc': 123, 'def': 456@}
Py_BuildValue("((ii)(ii)) (ii)",
              1, 2, 3, 4, 5, 6)          (((1, 2), (3, 4)), (5, 6))
@end example

@node 引用计数,在C++中编写扩展,构造任意值,使用 C 或 C++ 扩展 Python
@anchor{extending/extending refcounts}@anchor{3ab3}@anchor{extending/extending reference-counts}@anchor{3abb}
@subsubsection 引用计数


在C/C++语言中，程序员负责动态分配和回收堆heap当中的内存。在C里，通过函数 @code{malloc()} 和 @code{free()} 来完成。在C++里是操作 @code{new} 和 @code{delete} 来实现相同的功能。

每个由 @code{malloc()} 分配的内存块，最终都要由 @code{free()} 退回到可用内存池里面去。而调用 @code{free()} 的时机非常重要，如果一个内存块忘了 @code{free()} 则会导致内存泄漏，这块内存在程序结束前将无法重新使用。这叫做 @emph{内存泄漏} 。而如果对同一内存块 @code{free()} 了以后，另外一个指针再次访问，则再次使用 @code{malloc()} 复用这块内存会导致冲突。这叫做 @emph{野指针} 。等同于使用未初始化的数据，core dump，错误结果，神秘的崩溃等。

内存泄露往往发生在一些并不常见的代码流程上面。比如一个函数申请了内存以后，做了些计算，然后释放内存块。现在一些对函数的修改可能增加对计算的测试并检测错误条件，然后过早的从函数返回了。这很容易忘记在退出前释放内存，特别是后期修改的代码。这种内存泄漏，一旦引入，通常很长时间都难以检测到，错误退出被调用的频度较低，而现代电脑又有非常巨大的虚拟内存，所以泄漏仅在长期运行或频繁调用泄漏函数时才会变得明显。因此，有必要避免内存泄漏，通过代码规范会策略来最小化此类错误。

Python通过 @code{malloc()} 和 @code{free()} 包含大量的内存分配和释放，同样需要避免内存泄漏和野指针。他选择的方法就是 @emph{引用计数} 。其原理比较简单：每个对象都包含一个计数器，计数器的增减与对象引用的增减直接相关，当引用计数为0时，表示对象已经没有存在的意义了，对象就可以删除了。

另一个叫法是 @emph{自动垃圾回收} 。(有时引用计数也被看作是垃圾回收策略，于是这里的"自动"用以区分两者)。自动垃圾回收的优点是用户不需要明确的调用 @code{free()} 。(另一个优点是改善速度或内存使用，然而这并不难)。缺点是对C，没有可移植的自动垃圾回收器，而引用计数则可以可移植的实现(只要 @code{malloc()} 和 @code{free()} 函数是可用的，这也是C标准担保的)。也许以后有一天会出现可移植的自动垃圾回收器，但在此前我们必须与引用计数一起工作。

Python使用传统的引用计数实现，也提供了循环监测器，用以检测引用循环。这使得应用无需担心直接或间接的创建了循环引用，这是引用计数垃圾收集的一个弱点。引用循环是对象(可能直接)的引用了本身，所以循环中的每个对象的引用计数都不是0。典型的引用计数实现无法回收处于引用循环中的对象，或者被循环所引用的对象，哪怕没有循环以外的引用了。

循环探测器可以检测垃圾循环并回收。 @ref{86,,gc} 模块提供了方法运行探测器 ( @ref{22e,,collect()} 函数) ，而且可以在运行时配置禁用探测器。循环探测器被当作可选组件，默认是包含的，也可以在构建时禁用，在Unix平台(包括Mac OS X)使用 @code{--without-cycle-gc} 选项到 @code{configure} 脚本。如果循环探测器被禁用， @ref{86,,gc} 模块就不可用了。

@menu
* Python中的引用计数:: 
* 拥有规则:: 
* 危险的薄冰:: 
* NULL指针:: 

@end menu

@node Python中的引用计数,拥有规则,,引用计数
@anchor{extending/extending refcountsinpython}@anchor{3abc}@anchor{extending/extending reference-counting-in-python}@anchor{3abd}
@subsubsection Python中的引用计数


有两个宏 @code{Py_INCREF(x)} 和 @code{Py_DECREF(x)} ，会处理引用计数的增减。 @ref{266,,Py_DECREF()} 也会在引用计数到达0时释放对象。为了灵活，并不会直接调用 @code{free()} ，而是通过对象的 @emph{类型对象} 的函数指针来调用。为了这个目的(或其他的)，每个对象同时包含一个指向自身类型对象的指针。

最大的问题依旧：何时使用 @code{Py_INCREF(x)} 和 @code{Py_DECREF(x)} ？我们首先引入一些概念。没有人"拥有"一个对象，你可以 @emph{拥有一个引用} 到一个对象。一个对象的引用计数定义为拥有引用的数量。引用的拥有者有责任调用 @ref{266,,Py_DECREF()} ，在引用不再需要时。引用的拥有关系可以被传递。有三种办法来处置拥有的引用：传递、存储、调用 @ref{266,,Py_DECREF()} 。忘记处置一个拥有的引用会导致内存泄漏。

还可以 @emph{借用} @footnote{@w{(2)} 
术语"借用"一个引用是不完全正确的：拥有者仍然有引用的拷贝。
} 一个对象的引用。借用的引用不应该调用 @ref{266,,Py_DECREF()} 。借用者必须确保不能持有对象超过拥有者借出的时间。在拥有者处置对象后使用借用的引用是有风险的，应该完全避免 @footnote{@w{(3)} 
检查引用计数至少为1 @strong{没有用} ，引用计数本身可以在已经释放的内存里，并有可能被其他对象所用。
} 。

借用相对于引用的优点是你无需担心整条路径上代码的引用，或者说，通过借用你无需担心内存泄漏的风险。借用的缺点是一些看起来正确代码上的借用可能会在拥有者处置后使用对象。

借用可以变为拥有引用，通过调用 @ref{265,,Py_INCREF()} 。这不会影响已经借出的拥有者的状态。这回创建一个新的拥有引用，并给予完全的拥有者责任(新的拥有者必须恰当的处置引用，就像之前的拥有者那样)。

@node 拥有规则,危险的薄冰,Python中的引用计数,引用计数
@anchor{extending/extending ownership-rules}@anchor{3abe}@anchor{extending/extending ownershiprules}@anchor{3abf}
@subsubsection 拥有规则


当一个对象引用传递进出一个函数时，函数的接口应该指定拥有关系的传递是否包含引用。

大多数函数返回一个对象的引用，并传递引用拥有关系。通常，所有创建对象的函数，例如 @ref{3aa6,,PyLong_FromLong()} 和 @ref{2ce,,Py_BuildValue()} ，会传递拥有关系给接收者。即便是对象不是真正新的，你仍然可以获得对象的新引用。一个实例是 @ref{3aa6,,PyLong_FromLong()} 维护了一个流行值的缓存，并可以返回已缓存项目的新引用。

很多另一个对象提取对象的函数，也会传递引用关系，例如 @ref{3ac0,,PyObject_GetAttrString()} 。这里的情况不够清晰，一些不太常用的例程是例外的 @ref{3ac1,,PyTuple_GetItem()} ， @ref{3ac2,,PyList_GetItem()} ， @ref{3ac3,,PyDict_GetItem()} ， @ref{3ac4,,PyDict_GetItemString()} 都是返回从元组、列表、字典里借用的引用。

函数 @ref{3ac5,,PyImport_AddModule()} 也会返回借用的引用，哪怕可能会返回创建的对象：这个可能因为一个拥有的引用对象是存储在 @code{sys.modules} 里。

当你传递一个对象引用到另一个函数时，通常函数是借用出去的。如果需要存储，就使用 @ref{265,,Py_INCREF()} 来变成独立的拥有者。这个规则有两个重要的例外： @ref{3ac6,,PyTuple_SetItem()} 和 @ref{3ac7,,PyList_SetItem()} 。这些函数接受传递来的引用关系，哪怕会失败！(注意 @ref{3ac8,,PyDict_SetItem()} 及其同类不会接受引用关系，他们是"正常的")。

当一个C函数被Python调用时，会从调用方传来的参数借用引用。调用者拥有对象的引用，所以借用的引用生命周期可以保证到函数返回。只要当借用的引用需要存储或传递时，就必须转换为拥有的引用，通过调用 @ref{265,,Py_INCREF()} 。

Python调用从C函数返回的对象引用时必须是拥有的引用---拥有关系被从函数传递给调用者。

@node 危险的薄冰,NULL指针,拥有规则,引用计数
@anchor{extending/extending thin-ice}@anchor{3ac9}@anchor{extending/extending thinice}@anchor{3aca}
@subsubsection 危险的薄冰


有少数情况下，借用的引用看起来无害，但却可能导致问题。这通常是因为解释器的隐式调用，并可能导致引用拥有者处置这个引用。

首先需要特别注意的情况是使用 @ref{266,,Py_DECREF()} 到一个无关对象，而这个对象的引用是借用自一个列表的元素。举个实例：

@example
void
bug(PyObject *list)
@{
    PyObject *item = PyList_GetItem(list, 0);

    PyList_SetItem(list, 1, PyLong_FromLong(0L));
    PyObject_Print(item, stdout, 0); /* BUG! */
@}
@end example

这个函数首先借用一个引用 @code{list[0]} ，然后替换 @code{list[1]} 为值 @code{0} ，最后打印借用的引用。看起来无害是吧，但却不是。

我们跟着控制流进入 @ref{3ac7,,PyList_SetItem()} 。列表拥有者引用了其所有成员，所以当成员1被替换时，就必须处置原来的成员1。现在假设原来的成员1是用户定义类的实例，且假设这个类定义了 @ref{919,,__del__()} 方法。如果这个类实例的引用计数是1，那么处置动作就会调用 @ref{919,,__del__()} 方法。

既然是Python写的， @ref{919,,__del__()} 方法可以执行任意Python代码。是否可能在 @code{bug()} 的 @code{item} 废止引用呢，是的。假设列表传递到 @code{bug()} 会被 @ref{919,,__del__()} 方法所访问，就可以执行一个语句来实现 @code{del list[0]} ，然后假设这是最后一个对对象的引用，就需要释放内存，从而使得 @code{item} 无效化。

解决方法是，当你知道了问题的根源，就容易了：临时增加引用计数。正确版本的函数代码如下：

@example
void
no_bug(PyObject *list)
@{
    PyObject *item = PyList_GetItem(list, 0);

    Py_INCREF(item);
    PyList_SetItem(list, 1, PyLong_FromLong(0L));
    PyObject_Print(item, stdout, 0);
    Py_DECREF(item);
@}
@end example

这是个真实的故事。一个旧版本的Python包含了这个bug的变种，而一些人花费了大量时间在C调试器上去寻找为什么 @ref{919,,__del__()} 方法会失败。

这个问题的第二种情况是借用的引用涉及线程的变种。通常，Python解释器里多个线程无法进入对方的路径，因为有个全局锁保护着Python整个对象空间。但可以使用宏 @ref{3acb,,Py_BEGIN_ALLOW_THREADS} 来临时释放这个锁，重新获取锁用 @ref{2b5,,Py_END_ALLOW_THREADS} 。这通常围绕在阻塞I/O调用外，使得其他线程可以在等待I/O期间使用处理器。显然，如下函数会跟之前那个有一样的问题：

@example
void
bug(PyObject *list)
@{
    PyObject *item = PyList_GetItem(list, 0);
    Py_BEGIN_ALLOW_THREADS
    ...some blocking I/O call...
    Py_END_ALLOW_THREADS
    PyObject_Print(item, stdout, 0); /* BUG! */
@}
@end example

@node NULL指针,,危险的薄冰,引用计数
@anchor{extending/extending null-pointers}@anchor{3acc}@anchor{extending/extending nullpointers}@anchor{3acd}
@subsubsection NULL指针


通常，接受对象引用作为参数的函数不希望你传给它们 @code{NULL} 指针，并且当你这样做时将会转储核心（或在以后导致核心转储）。 返回对象引用的函数通常只在要指明发生了异常时才返回 @code{NULL}。 不检测 @code{NULL} 参数的原因在于这些函数经常要将它们所接收的对象传给其他函数 --- 如果每个函数都检测 @code{NULL}，将会导致大量的冗余检测而使代码运行得更缓慢。

更好的做法是仅在“源头”上检测 @code{NULL}，即在接收到一个可能为 @code{NULL} 的指针，例如来自 @code{malloc()} 或是一个可能引发异常的函数的时候。

@ref{265,,Py_INCREF()} 和 @ref{266,,Py_DECREF()} 等宏不会检测 @code{NULL} 指针 --- 但是，它们的变种 @ref{267,,Py_XINCREF()} 和 @ref{268,,Py_XDECREF()} 则会检测。

用于检测特定对象类型的宏 (@code{Pytype_Check()}) 不会检测 @code{NULL} 指针 --- 同样地，有大量代码会连续调用这些宏来测试一个对象是否为几种不同预期类型之一，这将会生成冗余的测试。 不存在带有 @code{NULL} 检测的变体。

C 函数调用机制会保证传给 C 函数的参数 (本示例中为 @code{args}) 绝不会为 @code{NULL} --- 实际上它会保证其总是为一个元组 @footnote{@w{(4)} 
当你使用 "旧式" 风格调用约定时，这些保证不成立，尽管这依旧存在于很多旧代码中。
}。

任何时候将 @code{NULL} 指针“泄露”给 Python 用户都会是个严重的错误。

@c Frank Stajano:
@c A pedagogically buggy example, along the lines of the previous listing, would
@c be helpful here -- showing in more concrete terms what sort of actions could
@c cause the problem. I can't very well imagine it from the description.

@node 在C++中编写扩展,给扩展模块提供C API,引用计数,使用 C 或 C++ 扩展 Python
@anchor{extending/extending cplusplus}@anchor{3ace}@anchor{extending/extending writing-extensions-in-c}@anchor{3acf}
@subsubsection 在C++中编写扩展


还可以在C++中编写扩展模块，只是有些限制。如果主程序(Python解释器)是使用C编译器来编译和链接的，全局或静态对象的构造器就不能使用。而如果是C++编译器来链接的就没有这个问题。函数会被Python解释器调用(通常就是模块初始化函数)必须声明为 @code{extern "C"} 。而是否在 @code{extern "C" @{...@}} 里包含Python头文件则不是那么重要，因为如果定义了符号 @code{__cplusplus} 则已经是这么声明的了(所有现代C++编译器都会定义这个符号)。

@node 给扩展模块提供C API,,在C++中编写扩展,使用 C 或 C++ 扩展 Python
@anchor{extending/extending providing-a-c-api-for-an-extension-module}@anchor{3ad0}@anchor{extending/extending using-capsules}@anchor{cea}
@subsubsection 给扩展模块提供C API


很多扩展模块提供了新的函数和类型供Python使用，但有时扩展模块里的代码也可以被其他扩展模块使用。例如，一个扩展模块可以实现一个类型 "collection" 看起来是没有顺序的。就像是Python列表类型，拥有C API允许扩展模块来创建和维护列表，这个新的集合类型可以有一堆C函数用于给其他扩展模块直接使用。

开始看起来很简单：只需要编写函数(无需声明为 @code{static} )，提供恰当的头文件，以及C API的文档。实际上在所有扩展模块都是静态链接到Python解释器时也是可以正常工作的。当模块以共享库链接时，一个模块中的符号定义对另一个模块不可见。可见的细节依赖于操作系统，一些系统的Python解释器使用全局命名空间(例如Windows)，有些则在链接时需要一个严格的已导入符号列表(一个例子是AIX)，或者提供可选的不同策略(如Unix系列)。即便是符号是全局可见的，你要调用的模块也可能尚未加载。

可移植性需要不能对符号可见性做任何假设。这意味着扩展模块里的所有符号都应该声明为 @code{static} ，除了模块的初始化函数，来避免与其他扩展模块的命名冲突(在段落 @ref{3aaa,,模块方法表和初始化函数} 中讨论) 。这意味着符号应该 @emph{必须} 通过其他导出方式来供其他扩展模块访问。

Python提供了一个特别的机制来传递C级别信息(指针)，从一个扩展模块到另一个：Capsules。一个Capsule是一个Python数据类型，会保存指针( @code{void *} )。Capsule只能通过其C API来创建和访问，但可以像其他Python对象一样的传递。通常，我们可以指定一个扩展模块命名空间的名字。其他扩展模块可以导入这个模块，获取这个名字的值，然后从Capsule获取指针。

Capsule可以用多种方式导出C API给扩展模块。每个函数可以用自己的Capsule，或者所有C API指针可以存储在一个数组里，数组地址再发布给Capsule。存储和获取指针也可以用多种方式，供客户端模块使用。

无论你选择哪个方法，正确地为你的 Capsule 命名都很重要。 函数 @ref{3ad1,,PyCapsule_New()} 接受一个名称形参 (@code{const char *})；允许你传入一个 @code{NULL} 作为名称，但我们强烈建议你指定一个名称。 正确地命名的 Capsule 提供了一定程序的运行时类型安全；没有可行的方式能区分两个未命名的 Capsule。

通常来说，Capsule用于暴露C API，其名字应该遵循如下规范：

@example
modulename.attributename
@end example

便利函数 @ref{3ad2,,PyCapsule_Import()} 可以方便的载入通过Capsule提供的C API，仅在Capsule的名字匹配时。这个行为为C API用户提供了高度的确定性来载入正确的C API。

如下例子展示了将大部分负担交由导出模块作者的方法，适用于常用的库模块。其会存储所有C API指针(例子里只有一个)在 @code{void} 指针的数组里，并使其值变为Capsule。对应的模块头文件提供了宏来管理导入模块和获取C API指针；客户端模块只需要在访问C API前调用这个宏即可。

导出的模块修改自 @code{spam} 模块，来自 @ref{3a9d,,一个简单的例子} 段落。函数 @code{spam.system()} 不会直接调用C库函数 @code{system()} ，但一个函数 @code{PySpam_System()} 会负责调用，当然现实中会更复杂些(例如添加 "spam" 到每个命令)。函数 @code{PySpam_System()} 也会导出给其他扩展模块。

函数 @code{PySpam_System()} 是个纯C函数，声明 @code{static} 就像其他地方那样:

@example
static int
PySpam_System(const char *command)
@{
    return system(command);
@}
@end example

函数 @code{spam_system()} 按照如下方式修改:

@example
static PyObject *
spam_system(PyObject *self, PyObject *args)
@{
    const char *command;
    int sts;

    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;
    sts = PySpam_System(command);
    return PyLong_FromLong(sts);
@}
@end example

在模块开头，在此行后:

@example
#include <Python.h>
@end example

添加另外两行:

@example
#define SPAM_MODULE
#include "spammodule.h"
@end example

@code{#define} 用于告知头文件需要包含给导出的模块，而不是客户端模块。最终，模块的初始化函数必须负责初始化C API指针数组:

@example
PyMODINIT_FUNC
PyInit_spam(void)
@{
    PyObject *m;
    static void *PySpam_API[PySpam_API_pointers];
    PyObject *c_api_object;

    m = PyModule_Create(&spammodule);
    if (m == NULL)
        return NULL;

    /* Initialize the C API pointer array */
    PySpam_API[PySpam_System_NUM] = (void *)PySpam_System;

    /* Create a Capsule containing the API pointer array's address */
    c_api_object = PyCapsule_New((void *)PySpam_API, "spam._C_API", NULL);

    if (PyModule_AddObject(m, "_C_API", c_api_object) < 0) @{
        Py_XDECREF(c_api_object);
        Py_DECREF(m);
        return NULL;
    @}

    return m;
@}
@end example

注意 @code{PySpam_API} 声明为 @code{static} ；此外指针数组会在 @code{PyInit_spam()} 结束后消失!

头文件 @code{spammodule.h} 里的一堆工作，看起来如下所示:

@example
#ifndef Py_SPAMMODULE_H
#define Py_SPAMMODULE_H
#ifdef __cplusplus
extern "C" @{
#endif

/* Header file for spammodule */

/* C API functions */
#define PySpam_System_NUM 0
#define PySpam_System_RETURN int
#define PySpam_System_PROTO (const char *command)

/* Total number of C API pointers */
#define PySpam_API_pointers 1


#ifdef SPAM_MODULE
/* This section is used when compiling spammodule.c */

static PySpam_System_RETURN PySpam_System PySpam_System_PROTO;

#else
/* This section is used in modules that use spammodule's API */

static void **PySpam_API;

#define PySpam_System \
 (*(PySpam_System_RETURN (*)PySpam_System_PROTO) PySpam_API[PySpam_System_NUM])

/* Return -1 on error, 0 on success.
 * PyCapsule_Import will set an exception if there's an error.
 */
static int
import_spam(void)
@{
    PySpam_API = (void **)PyCapsule_Import("spam._C_API", 0);
    return (PySpam_API != NULL) ? 0 : -1;
@}

#endif

#ifdef __cplusplus
@}
#endif

#endif /* !defined(Py_SPAMMODULE_H) */
@end example

客户端模块必须在其初始化函数里按顺序调用函数 @code{import_spam()} (或其他宏)才能访问函数 @code{PySpam_System()} 。

@example
PyMODINIT_FUNC
PyInit_client(void)
@{
    PyObject *m;

    m = PyModule_Create(&clientmodule);
    if (m == NULL)
        return NULL;
    if (import_spam() < 0)
        return NULL;
    /* additional initialization can happen here */
    return m;
@}
@end example

这种方法的主要缺点是，文件 @code{spammodule.h} 过于复杂。当然，对每个要导出的函数，基本结构是相似的，所以只需要学习一次。

最后需要提醒的是Capsule提供了额外的功能，用于存储在Capsule里的指针的内存分配和释放。细节参考 Python/C API参考手册的章节 @ref{3ad3,,胶囊} 和Capsule的实现(在Python源码发行包的 @code{Include/pycapsule.h} 和 @code{Objects/pycapsule.c} )。

@subsubheading 备注


@node 自定义扩展类型：教程,定义扩展类型：已分类主题,使用 C 或 C++ 扩展 Python,不使用第三方工具创建扩展
@anchor{extending/newtypes_tutorial doc}@anchor{3ad4}@anchor{extending/newtypes_tutorial defining-extension-types-tutorial}@anchor{3ad5}@anchor{extending/newtypes_tutorial defining-new-types}@anchor{3ad6}
@subsection 自定义扩展类型：教程


Python 允许编写 C 扩展模块定义可以从 Python 代码中操纵的新类型，这很像内置的 @ref{329,,str} 和 @ref{262,,list} 类型。所有扩展类型的代码都遵循一个模式，但是在您开始之前，您需要了解一些细节。这份文件是对这个主题介绍。

@menu
* 基础:: 
* Adding data and methods to the Basic example:: 
* Providing finer control over data attributes:: 
* Supporting cyclic garbage collection:: 
* Subclassing other types:: 

@end menu

@node 基础,Adding data and methods to the Basic example,,自定义扩展类型：教程
@anchor{extending/newtypes_tutorial dnt-basics}@anchor{3ad7}@anchor{extending/newtypes_tutorial the-basics}@anchor{3ad8}
@subsubsection 基础


@ref{13ce,,CPython} 运行时将所有 Python 对象都视为类型 @ref{4b5,,PyObject*} 的变量，即所有 Python 对象的"基础类型"。 @ref{4b5,,PyObject} 结构体本身包含了对象的 @ref{3ad9,,reference count} 和对象的"类型对象"。 类型对象确定解释器需要调用哪些 (C) 函数，例如一个属性查询一个对象，一个方法调用，或者与另一个对象相乘。 这些 C 函数被称为“类型方法”。

所以，如果你想要定义新的扩展类型，需要创建新的类型对象。

这类事情只能用例子解释，这里用一个最小化但完整的的模块，定义了新的类型叫做 @code{Custom} 在C扩展模块 @code{custom} 里。

@cartouche
@quotation 注解 
这里展示的方法是定义 @emph{static} 扩展类型的传统方法。可以适合大部分用途。C API也可以定义在堆上分配的扩展类型，使用 @ref{2d1,,PyType_FromSpec()} 函数，但不在本入门里讨论。
@end quotation
@end cartouche

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>

typedef struct @{
    PyObject_HEAD
    /* Type-specific fields go here. */
@} CustomObject;

static PyTypeObject CustomType = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom.Custom",
    .tp_doc = "Custom objects",
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT,
    .tp_new = PyType_GenericNew,
@};

static PyModuleDef custommodule = @{
    PyModuleDef_HEAD_INIT,
    .m_name = "custom",
    .m_doc = "Example module that creates an extension type.",
    .m_size = -1,
@};

PyMODINIT_FUNC
PyInit_custom(void)
@{
    PyObject *m;
    if (PyType_Ready(&CustomType) < 0)
        return NULL;

    m = PyModule_Create(&custommodule);
    if (m == NULL)
        return NULL;

    Py_INCREF(&CustomType);
    if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) @{
        Py_DECREF(&CustomType);
        Py_DECREF(m);
        return NULL;
    @}

    return m;
@}
@end example

这部分很容易理解，这是为了跟上一章能对接上。这个文件定义了三件事：


@enumerate 

@item 
@code{Custom} 类的对象 @strong{object} 包含了： @code{CustomObject} 结构，这会为每个 @code{Custom} 实例分配一次。

@item 
@code{Custom} @strong{type} 的行为：这是 @code{CustomType} 结构体，其定义了一堆标识和函数指针，会指向解释器里请求的操作。

@item 
初始化 @code{custom} 模块： @code{PyInit_custom} 函数和对应的 @code{custommodule} 结构体。
@end enumerate

结构的第一块是

@example
typedef struct @{
    PyObject_HEAD
@} CustomObject;
@end example

这就是一个自定义对象所包含的。 @code{PyObject_HEAD} 是强制要求必须在每个对象结构体之前，用以定义一个类型为 @ref{4b5,,PyObject} 的字段叫 @code{ob_base} ，包含了一个指针指向类型对象和一个引用计数(这可以用宏 @ref{3ada,,Py_REFCNT} 和 @ref{3adb,,Py_TYPE} 来区分)。用宏来抽象，使得附加字段可以用调试构建。

@cartouche
@quotation 注解 
注意在宏 @ref{c6b,,PyObject_HEAD} 后没有分号。意外添加分号会导致编译器提示出错。
@end quotation
@end cartouche

当然，对象除了在 @code{PyObject_HEAD} 存储数据外，还有额外数据；例如，如下定义了标准的Python浮点数:

@example
typedef struct @{
    PyObject_HEAD
    double ob_fval;
@} PyFloatObject;
@end example

第二个位是类型对象的定义:

@example
static PyTypeObject CustomType = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom.Custom",
    .tp_doc = "Custom objects",
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT,
    .tp_new = PyType_GenericNew,
@};
@end example

@cartouche
@quotation 注解 
推荐使用如上C99风格的初始化，以避免列出所有的 @ref{2d6,,PyTypeObject} 字段，其中很多是你不需要关心的，这样也可以避免关注字段的定义顺序。
@end quotation
@end cartouche

在 @code{object.h} 中实际定义的 @ref{2d6,,PyTypeObject} 具有比如上定义更多的 @ref{3adc,,字段}。 剩余的字段会由 C 编译器用零来填充，通常的做法是不显式地指定它们，除非你确实需要它们。

我们先挑选一部分，每次一个字段:

@example
PyVarObject_HEAD_INIT(NULL, 0)
@end example

这一行是强制的样板，用以初始化如上提到的 @code{ob_base} 字段:

@example
.tp_name = "custom.Custom",
@end example

我们的类型的名称。 这将出现在我们的对象的默认文本表示形式和某些错误消息中，例如:

@example
>>> "" + custom.Custom()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can only concatenate str (not "custom.Custom") to str
@end example

Note that the name is a dotted name that includes both the module name and the
name of the type within the module. The module in this case is @code{custom} and
the type is @code{Custom}, so we set the type name to @code{custom.Custom}.
Using the real dotted import path is important to make your type compatible
with the @ref{d9,,pydoc} and @ref{ca,,pickle} modules.

@example
.tp_basicsize = sizeof(CustomObject),
.tp_itemsize = 0,
@end example

This is so that Python knows how much memory to allocate when creating
new @code{Custom} instances.  @ref{3add,,tp_itemsize} is
only used for variable-sized objects and should otherwise be zero.

@cartouche
@quotation 注解 
If you want your type to be subclassable from Python, and your type has the same
@ref{3ade,,tp_basicsize} as its base type, you may have problems with multiple
inheritance.  A Python subclass of your type will have to list your type first
in its @ref{e02,,__bases__}, or else it will not be able to call your type's
@ref{883,,__new__()} method without getting an error.  You can avoid this problem by
ensuring that your type has a larger value for @ref{3ade,,tp_basicsize} than its
base type does.  Most of the time, this will be true anyway, because either your
base type will be @ref{2b0,,object}, or else you will be adding data members to
your base type, and therefore increasing its size.
@end quotation
@end cartouche

We set the class flags to @ref{3adf,,Py_TPFLAGS_DEFAULT}.

@example
.tp_flags = Py_TPFLAGS_DEFAULT,
@end example

All types should include this constant in their flags.  It enables all of the
members defined until at least Python 3.3.  If you need further members,
you will need to OR the corresponding flags.

We provide a doc string for the type in @ref{3ae0,,tp_doc}.

@example
.tp_doc = "Custom objects",
@end example

To enable object creation, we have to provide a @ref{3ae1,,tp_new}
handler.  This is the equivalent of the Python method @ref{883,,__new__()}, but
has to be specified explicitly.  In this case, we can just use the default
implementation provided by the API function @ref{3ae2,,PyType_GenericNew()}.

@example
.tp_new = PyType_GenericNew,
@end example

Everything else in the file should be familiar, except for some code in
@code{PyInit_custom()}:

@example
if (PyType_Ready(&CustomType) < 0)
    return;
@end example

This initializes the @code{Custom} type, filling in a number of members
to the appropriate default values, including @code{ob_type} that we initially
set to @code{NULL}.

@example
Py_INCREF(&CustomType);
if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) @{
    Py_DECREF(&CustomType);
    Py_DECREF(m);
    return NULL;
@}
@end example

This adds the type to the module dictionary.  This allows us to create
@code{Custom} instances by calling the @code{Custom} class:

@example
>>> import custom
>>> mycustom = custom.Custom()
@end example

That's it!  All that remains is to build it; put the above code in a file called
@code{custom.c} and:

@example
from distutils.core import setup, Extension
setup(name="custom", version="1.0",
      ext_modules=[Extension("custom", ["custom.c"])])
@end example

in a file called @code{setup.py}; then typing

@example
$ python setup.py build
@end example

at a shell should produce a file @code{custom.so} in a subdirectory; move to
that directory and fire up Python --- you should be able to @code{import custom} and
play around with Custom objects.

That wasn't so hard, was it?

Of course, the current Custom type is pretty uninteresting. It has no data and
doesn't do anything. It can't even be subclassed.

@cartouche
@quotation 注解 
While this documentation showcases the standard @ref{39,,distutils} module
for building C extensions, it is recommended in real-world use cases to
use the newer and better-maintained @code{setuptools} library.  Documentation
on how to do this is out of scope for this document and can be found in
the Python Packaging User's Guide@footnote{https://packaging.python.org/tutorials/distributing-packages/}.
@end quotation
@end cartouche

@node Adding data and methods to the Basic example,Providing finer control over data attributes,基础,自定义扩展类型：教程
@anchor{extending/newtypes_tutorial adding-data-and-methods-to-the-basic-example}@anchor{3ae3}
@subsubsection Adding data and methods to the Basic example


Let's extend the basic example to add some data and methods.  Let's also make
the type usable as a base class. We'll create a new module, @code{custom2} that
adds these capabilities:

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include "structmember.h"

typedef struct @{
    PyObject_HEAD
    PyObject *first; /* first name */
    PyObject *last;  /* last name */
    int number;
@} CustomObject;

static void
Custom_dealloc(CustomObject *self)
@{
    Py_XDECREF(self->first);
    Py_XDECREF(self->last);
    Py_TYPE(self)->tp_free((PyObject *) self);
@}

static PyObject *
Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
@{
    CustomObject *self;
    self = (CustomObject *) type->tp_alloc(type, 0);
    if (self != NULL) @{
        self->first = PyUnicode_FromString("");
        if (self->first == NULL) @{
            Py_DECREF(self);
            return NULL;
        @}
        self->last = PyUnicode_FromString("");
        if (self->last == NULL) @{
            Py_DECREF(self);
            return NULL;
        @}
        self->number = 0;
    @}
    return (PyObject *) self;
@}

static int
Custom_init(CustomObject *self, PyObject *args, PyObject *kwds)
@{
    static char *kwlist[] = @{"first", "last", "number", NULL@};
    PyObject *first = NULL, *last = NULL, *tmp;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) @{
        tmp = self->first;
        Py_INCREF(first);
        self->first = first;
        Py_XDECREF(tmp);
    @}
    if (last) @{
        tmp = self->last;
        Py_INCREF(last);
        self->last = last;
        Py_XDECREF(tmp);
    @}
    return 0;
@}

static PyMemberDef Custom_members[] = @{
    @{"first", T_OBJECT_EX, offsetof(CustomObject, first), 0,
     "first name"@},
    @{"last", T_OBJECT_EX, offsetof(CustomObject, last), 0,
     "last name"@},
    @{"number", T_INT, offsetof(CustomObject, number), 0,
     "custom number"@},
    @{NULL@}  /* Sentinel */
@};

static PyObject *
Custom_name(CustomObject *self, PyObject *Py_UNUSED(ignored))
@{
    if (self->first == NULL) @{
        PyErr_SetString(PyExc_AttributeError, "first");
        return NULL;
    @}
    if (self->last == NULL) @{
        PyErr_SetString(PyExc_AttributeError, "last");
        return NULL;
    @}
    return PyUnicode_FromFormat("%S %S", self->first, self->last);
@}

static PyMethodDef Custom_methods[] = @{
    @{"name", (PyCFunction) Custom_name, METH_NOARGS,
     "Return the name, combining the first and last name"
    @},
    @{NULL@}  /* Sentinel */
@};

static PyTypeObject CustomType = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom2.Custom",
    .tp_doc = "Custom objects",
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    .tp_new = Custom_new,
    .tp_init = (initproc) Custom_init,
    .tp_dealloc = (destructor) Custom_dealloc,
    .tp_members = Custom_members,
    .tp_methods = Custom_methods,
@};

static PyModuleDef custommodule = @{
    PyModuleDef_HEAD_INIT,
    .m_name = "custom2",
    .m_doc = "Example module that creates an extension type.",
    .m_size = -1,
@};

PyMODINIT_FUNC
PyInit_custom2(void)
@{
    PyObject *m;
    if (PyType_Ready(&CustomType) < 0)
        return NULL;

    m = PyModule_Create(&custommodule);
    if (m == NULL)
        return NULL;

    Py_INCREF(&CustomType);
    if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) @{
        Py_DECREF(&CustomType);
        Py_DECREF(m);
        return NULL;
    @}

    return m;
@}
@end example

This version of the module has a number of changes.

We've added an extra include:

@example
#include <structmember.h>
@end example

This include provides declarations that we use to handle attributes, as
described a bit later.

The  @code{Custom} type now has three data attributes in its C struct,
@emph{first}, @emph{last}, and @emph{number}.  The @emph{first} and @emph{last} variables are Python
strings containing first and last names.  The @emph{number} attribute is a C integer.

The object structure is updated accordingly:

@example
typedef struct @{
    PyObject_HEAD
    PyObject *first; /* first name */
    PyObject *last;  /* last name */
    int number;
@} CustomObject;
@end example

Because we now have data to manage, we have to be more careful about object
allocation and deallocation.  At a minimum, we need a deallocation method:

@example
static void
Custom_dealloc(CustomObject *self)
@{
    Py_XDECREF(self->first);
    Py_XDECREF(self->last);
    Py_TYPE(self)->tp_free((PyObject *) self);
@}
@end example

which is assigned to the @ref{3ae4,,tp_dealloc} member:

@example
.tp_dealloc = (destructor) Custom_dealloc,
@end example

This method first clears the reference counts of the two Python attributes.
@ref{268,,Py_XDECREF()} correctly handles the case where its argument is
@code{NULL} (which might happen here if @code{tp_new} failed midway).  It then
calls the @ref{3ae5,,tp_free} member of the object's type
(computed by @code{Py_TYPE(self)}) to free the object's memory.  Note that
the object's type might not be @code{CustomType}, because the object may
be an instance of a subclass.

@cartouche
@quotation 注解 
The explicit cast to @code{destructor} above is needed because we defined
@code{Custom_dealloc} to take a @code{CustomObject *} argument, but the @code{tp_dealloc}
function pointer expects to receive a @code{PyObject *} argument.  Otherwise,
the compiler will emit a warning.  This is object-oriented polymorphism,
in C!
@end quotation
@end cartouche

We want to make sure that the first and last names are initialized to empty
strings, so we provide a @code{tp_new} implementation:

@example
static PyObject *
Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
@{
    CustomObject *self;
    self = (CustomObject *) type->tp_alloc(type, 0);
    if (self != NULL) @{
        self->first = PyUnicode_FromString("");
        if (self->first == NULL) @{
            Py_DECREF(self);
            return NULL;
        @}
        self->last = PyUnicode_FromString("");
        if (self->last == NULL) @{
            Py_DECREF(self);
            return NULL;
        @}
        self->number = 0;
    @}
    return (PyObject *) self;
@}
@end example

and install it in the @ref{3ae1,,tp_new} member:

@example
.tp_new = Custom_new,
@end example

The @code{tp_new} handler is responsible for creating (as opposed to initializing)
objects of the type.  It is exposed in Python as the @ref{883,,__new__()} method.
It is not required to define a @code{tp_new} member, and indeed many extension
types will simply reuse @ref{3ae2,,PyType_GenericNew()} as done in the first
version of the @code{Custom} type above.  In this case, we use the @code{tp_new}
handler to initialize the @code{first} and @code{last} attributes to non-@code{NULL}
default values.

@code{tp_new} is passed the type being instantiated (not necessarily @code{CustomType},
if a subclass is instantiated) and any arguments passed when the type was
called, and is expected to return the instance created.  @code{tp_new} handlers
always accept positional and keyword arguments, but they often ignore the
arguments, leaving the argument handling to initializer (a.k.a. @code{tp_init}
in C or @code{__init__} in Python) methods.

@cartouche
@quotation 注解 
@code{tp_new} shouldn't call @code{tp_init} explicitly, as the interpreter
will do it itself.
@end quotation
@end cartouche

The @code{tp_new} implementation calls the @ref{3ae6,,tp_alloc}
slot to allocate memory:

@example
self = (CustomObject *) type->tp_alloc(type, 0);
@end example

Since memory allocation may fail, we must check the @ref{3ae6,,tp_alloc}
result against @code{NULL} before proceeding.

@cartouche
@quotation 注解 
We didn't fill the @ref{3ae6,,tp_alloc} slot ourselves. Rather
@ref{3ae7,,PyType_Ready()} fills it for us by inheriting it from our base class,
which is @ref{2b0,,object} by default.  Most types use the default allocation
strategy.
@end quotation
@end cartouche

@cartouche
@quotation 注解 
If you are creating a co-operative @ref{3ae1,,tp_new} (one
that calls a base type's @ref{3ae1,,tp_new} or @ref{883,,__new__()}),
you must @emph{not} try to determine what method to call using method resolution
order at runtime.  Always statically determine what type you are going to
call, and call its @ref{3ae1,,tp_new} directly, or via
@code{type->tp_base->tp_new}.  If you do not do this, Python subclasses of your
type that also inherit from other Python-defined classes may not work correctly.
(Specifically, you may not be able to create instances of such subclasses
without getting a @ref{192,,TypeError}.)
@end quotation
@end cartouche

We also define an initialization function which accepts arguments to provide
initial values for our instance:

@example
static int
Custom_init(CustomObject *self, PyObject *args, PyObject *kwds)
@{
    static char *kwlist[] = @{"first", "last", "number", NULL@};
    PyObject *first = NULL, *last = NULL, *tmp;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) @{
        tmp = self->first;
        Py_INCREF(first);
        self->first = first;
        Py_XDECREF(tmp);
    @}
    if (last) @{
        tmp = self->last;
        Py_INCREF(last);
        self->last = last;
        Py_XDECREF(tmp);
    @}
    return 0;
@}
@end example

by filling the @ref{3ae8,,tp_init} slot.

@example
.tp_init = (initproc) Custom_init,
@end example

The @ref{3ae8,,tp_init} slot is exposed in Python as the
@ref{d57,,__init__()} method.  It is used to initialize an object after it's
created.  Initializers always accept positional and keyword arguments,
and they should return either @code{0} on success or @code{-1} on error.

Unlike the @code{tp_new} handler, there is no guarantee that @code{tp_init}
is called at all (for example, the @ref{ca,,pickle} module by default
doesn't call @ref{d57,,__init__()} on unpickled instances).  It can also be
called multiple times.  Anyone can call the @ref{d57,,__init__()} method on
our objects.  For this reason, we have to be extra careful when assigning
the new attribute values.  We might be tempted, for example to assign the
@code{first} member like this:

@example
if (first) @{
    Py_XDECREF(self->first);
    Py_INCREF(first);
    self->first = first;
@}
@end example

But this would be risky.  Our type doesn't restrict the type of the
@code{first} member, so it could be any kind of object.  It could have a
destructor that causes code to be executed that tries to access the
@code{first} member; or that destructor could release the
@ref{500,,Global interpreter Lock} and let arbitrary code run in other
threads that accesses and modifies our object.

To be paranoid and protect ourselves against this possibility, we almost
always reassign members before decrementing their reference counts.  When
don't we have to do this?


@itemize *

@item 
when we absolutely know that the reference count is greater than 1;

@item 
when we know that deallocation of the object @footnote{@w{(1)} 
This is true when we know that the object is a basic type, like a string or a
float.
} will neither release
the @ref{be3,,GIL} nor cause any calls back into our type's code;

@item 
when decrementing a reference count in a @ref{3ae4,,tp_dealloc}
handler on a type which doesn't support cyclic garbage collection @footnote{@w{(2)} 
We relied on this in the @ref{3ae4,,tp_dealloc} handler
in this example, because our type doesn't support garbage collection.
}.
@end itemize

We want to expose our instance variables as attributes. There are a
number of ways to do that. The simplest way is to define member definitions:

@example
static PyMemberDef Custom_members[] = @{
    @{"first", T_OBJECT_EX, offsetof(CustomObject, first), 0,
     "first name"@},
    @{"last", T_OBJECT_EX, offsetof(CustomObject, last), 0,
     "last name"@},
    @{"number", T_INT, offsetof(CustomObject, number), 0,
     "custom number"@},
    @{NULL@}  /* Sentinel */
@};
@end example

and put the definitions in the @ref{3ae9,,tp_members} slot:

@example
.tp_members = Custom_members,
@end example

Each member definition has a member name, type, offset, access flags and
documentation string.  See the @ref{3aea,,泛型属性管理} section
below for details.

A disadvantage of this approach is that it doesn't provide a way to restrict the
types of objects that can be assigned to the Python attributes.  We expect the
first and last names to be strings, but any Python objects can be assigned.
Further, the attributes can be deleted, setting the C pointers to @code{NULL}.  Even
though we can make sure the members are initialized to non-@code{NULL} values, the
members can be set to @code{NULL} if the attributes are deleted.

We define a single method, @code{Custom.name()}, that outputs the objects name as the
concatenation of the first and last names.

@example
static PyObject *
Custom_name(CustomObject *self, PyObject *Py_UNUSED(ignored))
@{
    if (self->first == NULL) @{
        PyErr_SetString(PyExc_AttributeError, "first");
        return NULL;
    @}
    if (self->last == NULL) @{
        PyErr_SetString(PyExc_AttributeError, "last");
        return NULL;
    @}
    return PyUnicode_FromFormat("%S %S", self->first, self->last);
@}
@end example

The method is implemented as a C function that takes a @code{Custom} (or
@code{Custom} subclass) instance as the first argument.  Methods always take an
instance as the first argument. Methods often take positional and keyword
arguments as well, but in this case we don't take any and don't need to accept
a positional argument tuple or keyword argument dictionary. This method is
equivalent to the Python method:

@example
def name(self):
    return "%s %s" % (self.first, self.last)
@end example

Note that we have to check for the possibility that our @code{first} and
@code{last} members are @code{NULL}.  This is because they can be deleted, in which
case they are set to @code{NULL}.  It would be better to prevent deletion of these
attributes and to restrict the attribute values to be strings.  We'll see how to
do that in the next section.

Now that we've defined the method, we need to create an array of method
definitions:

@example
static PyMethodDef Custom_methods[] = @{
    @{"name", (PyCFunction) Custom_name, METH_NOARGS,
     "Return the name, combining the first and last name"
    @},
    @{NULL@}  /* Sentinel */
@};
@end example

(note that we used the @ref{e11,,METH_NOARGS} flag to indicate that the method
is expecting no arguments other than @emph{self})

and assign it to the @ref{3aeb,,tp_methods} slot:

@example
.tp_methods = Custom_methods,
@end example

Finally, we'll make our type usable as a base class for subclassing.  We've
written our methods carefully so far so that they don't make any assumptions
about the type of the object being created or used, so all we need to do is
to add the @ref{3aec,,Py_TPFLAGS_BASETYPE} to our class flag definition:

@example
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
@end example

We rename @code{PyInit_custom()} to @code{PyInit_custom2()}, update the
module name in the @ref{3aed,,PyModuleDef} struct, and update the full class
name in the @ref{2d6,,PyTypeObject} struct.

Finally, we update our @code{setup.py} file to build the new module:

@example
from distutils.core import setup, Extension
setup(name="custom", version="1.0",
      ext_modules=[
         Extension("custom", ["custom.c"]),
         Extension("custom2", ["custom2.c"]),
         ])
@end example

@node Providing finer control over data attributes,Supporting cyclic garbage collection,Adding data and methods to the Basic example,自定义扩展类型：教程
@anchor{extending/newtypes_tutorial providing-finer-control-over-data-attributes}@anchor{3aee}
@subsubsection Providing finer control over data attributes


In this section, we'll provide finer control over how the @code{first} and
@code{last} attributes are set in the @code{Custom} example. In the previous
version of our module, the instance variables @code{first} and @code{last}
could be set to non-string values or even deleted. We want to make sure that
these attributes always contain strings.

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include "structmember.h"

typedef struct @{
    PyObject_HEAD
    PyObject *first; /* first name */
    PyObject *last;  /* last name */
    int number;
@} CustomObject;

static void
Custom_dealloc(CustomObject *self)
@{
    Py_XDECREF(self->first);
    Py_XDECREF(self->last);
    Py_TYPE(self)->tp_free((PyObject *) self);
@}

static PyObject *
Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
@{
    CustomObject *self;
    self = (CustomObject *) type->tp_alloc(type, 0);
    if (self != NULL) @{
        self->first = PyUnicode_FromString("");
        if (self->first == NULL) @{
            Py_DECREF(self);
            return NULL;
        @}
        self->last = PyUnicode_FromString("");
        if (self->last == NULL) @{
            Py_DECREF(self);
            return NULL;
        @}
        self->number = 0;
    @}
    return (PyObject *) self;
@}

static int
Custom_init(CustomObject *self, PyObject *args, PyObject *kwds)
@{
    static char *kwlist[] = @{"first", "last", "number", NULL@};
    PyObject *first = NULL, *last = NULL, *tmp;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|UUi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) @{
        tmp = self->first;
        Py_INCREF(first);
        self->first = first;
        Py_DECREF(tmp);
    @}
    if (last) @{
        tmp = self->last;
        Py_INCREF(last);
        self->last = last;
        Py_DECREF(tmp);
    @}
    return 0;
@}

static PyMemberDef Custom_members[] = @{
    @{"number", T_INT, offsetof(CustomObject, number), 0,
     "custom number"@},
    @{NULL@}  /* Sentinel */
@};

static PyObject *
Custom_getfirst(CustomObject *self, void *closure)
@{
    Py_INCREF(self->first);
    return self->first;
@}

static int
Custom_setfirst(CustomObject *self, PyObject *value, void *closure)
@{
    PyObject *tmp;
    if (value == NULL) @{
        PyErr_SetString(PyExc_TypeError, "Cannot delete the first attribute");
        return -1;
    @}
    if (!PyUnicode_Check(value)) @{
        PyErr_SetString(PyExc_TypeError,
                        "The first attribute value must be a string");
        return -1;
    @}
    tmp = self->first;
    Py_INCREF(value);
    self->first = value;
    Py_DECREF(tmp);
    return 0;
@}

static PyObject *
Custom_getlast(CustomObject *self, void *closure)
@{
    Py_INCREF(self->last);
    return self->last;
@}

static int
Custom_setlast(CustomObject *self, PyObject *value, void *closure)
@{
    PyObject *tmp;
    if (value == NULL) @{
        PyErr_SetString(PyExc_TypeError, "Cannot delete the last attribute");
        return -1;
    @}
    if (!PyUnicode_Check(value)) @{
        PyErr_SetString(PyExc_TypeError,
                        "The last attribute value must be a string");
        return -1;
    @}
    tmp = self->last;
    Py_INCREF(value);
    self->last = value;
    Py_DECREF(tmp);
    return 0;
@}

static PyGetSetDef Custom_getsetters[] = @{
    @{"first", (getter) Custom_getfirst, (setter) Custom_setfirst,
     "first name", NULL@},
    @{"last", (getter) Custom_getlast, (setter) Custom_setlast,
     "last name", NULL@},
    @{NULL@}  /* Sentinel */
@};

static PyObject *
Custom_name(CustomObject *self, PyObject *Py_UNUSED(ignored))
@{
    return PyUnicode_FromFormat("%S %S", self->first, self->last);
@}

static PyMethodDef Custom_methods[] = @{
    @{"name", (PyCFunction) Custom_name, METH_NOARGS,
     "Return the name, combining the first and last name"
    @},
    @{NULL@}  /* Sentinel */
@};

static PyTypeObject CustomType = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom3.Custom",
    .tp_doc = "Custom objects",
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    .tp_new = Custom_new,
    .tp_init = (initproc) Custom_init,
    .tp_dealloc = (destructor) Custom_dealloc,
    .tp_members = Custom_members,
    .tp_methods = Custom_methods,
    .tp_getset = Custom_getsetters,
@};

static PyModuleDef custommodule = @{
    PyModuleDef_HEAD_INIT,
    .m_name = "custom3",
    .m_doc = "Example module that creates an extension type.",
    .m_size = -1,
@};

PyMODINIT_FUNC
PyInit_custom3(void)
@{
    PyObject *m;
    if (PyType_Ready(&CustomType) < 0)
        return NULL;

    m = PyModule_Create(&custommodule);
    if (m == NULL)
        return NULL;

    Py_INCREF(&CustomType);
    if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) @{
        Py_DECREF(&CustomType);
        Py_DECREF(m);
        return NULL;
    @}

    return m;
@}
@end example

To provide greater control, over the @code{first} and @code{last} attributes,
we'll use custom getter and setter functions.  Here are the functions for
getting and setting the @code{first} attribute:

@example
static PyObject *
Custom_getfirst(CustomObject *self, void *closure)
@{
    Py_INCREF(self->first);
    return self->first;
@}

static int
Custom_setfirst(CustomObject *self, PyObject *value, void *closure)
@{
    PyObject *tmp;
    if (value == NULL) @{
        PyErr_SetString(PyExc_TypeError, "Cannot delete the first attribute");
        return -1;
    @}
    if (!PyUnicode_Check(value)) @{
        PyErr_SetString(PyExc_TypeError,
                        "The first attribute value must be a string");
        return -1;
    @}
    tmp = self->first;
    Py_INCREF(value);
    self->first = value;
    Py_DECREF(tmp);
    return 0;
@}
@end example

The getter function is passed a @code{Custom} object and a "closure", which is
a void pointer.  In this case, the closure is ignored.  (The closure supports an
advanced usage in which definition data is passed to the getter and setter. This
could, for example, be used to allow a single set of getter and setter functions
that decide the attribute to get or set based on data in the closure.)

The setter function is passed the @code{Custom} object, the new value, and the
closure.  The new value may be @code{NULL}, in which case the attribute is being
deleted.  In our setter, we raise an error if the attribute is deleted or if its
new value is not a string.

We create an array of @ref{421,,PyGetSetDef} structures:

@example
static PyGetSetDef Custom_getsetters[] = @{
    @{"first", (getter) Custom_getfirst, (setter) Custom_setfirst,
     "first name", NULL@},
    @{"last", (getter) Custom_getlast, (setter) Custom_setlast,
     "last name", NULL@},
    @{NULL@}  /* Sentinel */
@};
@end example

and register it in the @ref{3aef,,tp_getset} slot:

@example
.tp_getset = Custom_getsetters,
@end example

The last item in a @ref{421,,PyGetSetDef} structure is the "closure" mentioned
above.  In this case, we aren't using a closure, so we just pass @code{NULL}.

We also remove the member definitions for these attributes:

@example
static PyMemberDef Custom_members[] = @{
    @{"number", T_INT, offsetof(CustomObject, number), 0,
     "custom number"@},
    @{NULL@}  /* Sentinel */
@};
@end example

We also need to update the @ref{3ae8,,tp_init} handler to only
allow strings @footnote{@w{(3)} 
We now know that the first and last members are strings, so perhaps we
could be less careful about decrementing their reference counts, however,
we accept instances of string subclasses.  Even though deallocating normal
strings won't call back into our objects, we can't guarantee that deallocating
an instance of a string subclass won't call back into our objects.
} to be passed:

@example
static int
Custom_init(CustomObject *self, PyObject *args, PyObject *kwds)
@{
    static char *kwlist[] = @{"first", "last", "number", NULL@};
    PyObject *first = NULL, *last = NULL, *tmp;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|UUi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) @{
        tmp = self->first;
        Py_INCREF(first);
        self->first = first;
        Py_DECREF(tmp);
    @}
    if (last) @{
        tmp = self->last;
        Py_INCREF(last);
        self->last = last;
        Py_DECREF(tmp);
    @}
    return 0;
@}
@end example

With these changes, we can assure that the @code{first} and @code{last} members are
never @code{NULL} so we can remove checks for @code{NULL} values in almost all cases.
This means that most of the @ref{268,,Py_XDECREF()} calls can be converted to
@ref{266,,Py_DECREF()} calls.  The only place we can't change these calls is in
the @code{tp_dealloc} implementation, where there is the possibility that the
initialization of these members failed in @code{tp_new}.

We also rename the module initialization function and module name in the
initialization function, as we did before, and we add an extra definition to the
@code{setup.py} file.

@node Supporting cyclic garbage collection,Subclassing other types,Providing finer control over data attributes,自定义扩展类型：教程
@anchor{extending/newtypes_tutorial supporting-cyclic-garbage-collection}@anchor{3af0}
@subsubsection Supporting cyclic garbage collection


Python has a @ref{129e,,cyclic garbage collector (GC)} that
can identify unneeded objects even when their reference counts are not zero.
This can happen when objects are involved in cycles.  For example, consider:

@example
>>> l = []
>>> l.append(l)
>>> del l
@end example

In this example, we create a list that contains itself. When we delete it, it
still has a reference from itself. Its reference count doesn't drop to zero.
Fortunately, Python's cyclic garbage collector will eventually figure out that
the list is garbage and free it.

In the second version of the @code{Custom} example, we allowed any kind of
object to be stored in the @code{first} or @code{last} attributes @footnote{@w{(4)} 
Also, even with our attributes restricted to strings instances, the user
could pass arbitrary @ref{329,,str} subclasses and therefore still create
reference cycles.
}.
Besides, in the second and third versions, we allowed subclassing
@code{Custom}, and subclasses may add arbitrary attributes.  For any of
those two reasons, @code{Custom} objects can participate in cycles:

@example
>>> import custom3
>>> class Derived(custom3.Custom): pass
...
>>> n = Derived()
>>> n.some_attribute = n
@end example

To allow a @code{Custom} instance participating in a reference cycle to
be properly detected and collected by the cyclic GC, our @code{Custom} type
needs to fill two additional slots and to enable a flag that enables these slots:

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include "structmember.h"

typedef struct @{
    PyObject_HEAD
    PyObject *first; /* first name */
    PyObject *last;  /* last name */
    int number;
@} CustomObject;

static int
Custom_traverse(CustomObject *self, visitproc visit, void *arg)
@{
    Py_VISIT(self->first);
    Py_VISIT(self->last);
    return 0;
@}

static int
Custom_clear(CustomObject *self)
@{
    Py_CLEAR(self->first);
    Py_CLEAR(self->last);
    return 0;
@}

static void
Custom_dealloc(CustomObject *self)
@{
    PyObject_GC_UnTrack(self);
    Custom_clear(self);
    Py_TYPE(self)->tp_free((PyObject *) self);
@}

static PyObject *
Custom_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
@{
    CustomObject *self;
    self = (CustomObject *) type->tp_alloc(type, 0);
    if (self != NULL) @{
        self->first = PyUnicode_FromString("");
        if (self->first == NULL) @{
            Py_DECREF(self);
            return NULL;
        @}
        self->last = PyUnicode_FromString("");
        if (self->last == NULL) @{
            Py_DECREF(self);
            return NULL;
        @}
        self->number = 0;
    @}
    return (PyObject *) self;
@}

static int
Custom_init(CustomObject *self, PyObject *args, PyObject *kwds)
@{
    static char *kwlist[] = @{"first", "last", "number", NULL@};
    PyObject *first = NULL, *last = NULL, *tmp;

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|UUi", kwlist,
                                     &first, &last,
                                     &self->number))
        return -1;

    if (first) @{
        tmp = self->first;
        Py_INCREF(first);
        self->first = first;
        Py_DECREF(tmp);
    @}
    if (last) @{
        tmp = self->last;
        Py_INCREF(last);
        self->last = last;
        Py_DECREF(tmp);
    @}
    return 0;
@}

static PyMemberDef Custom_members[] = @{
    @{"number", T_INT, offsetof(CustomObject, number), 0,
     "custom number"@},
    @{NULL@}  /* Sentinel */
@};

static PyObject *
Custom_getfirst(CustomObject *self, void *closure)
@{
    Py_INCREF(self->first);
    return self->first;
@}

static int
Custom_setfirst(CustomObject *self, PyObject *value, void *closure)
@{
    if (value == NULL) @{
        PyErr_SetString(PyExc_TypeError, "Cannot delete the first attribute");
        return -1;
    @}
    if (!PyUnicode_Check(value)) @{
        PyErr_SetString(PyExc_TypeError,
                        "The first attribute value must be a string");
        return -1;
    @}
    Py_INCREF(value);
    Py_CLEAR(self->first);
    self->first = value;
    return 0;
@}

static PyObject *
Custom_getlast(CustomObject *self, void *closure)
@{
    Py_INCREF(self->last);
    return self->last;
@}

static int
Custom_setlast(CustomObject *self, PyObject *value, void *closure)
@{
    if (value == NULL) @{
        PyErr_SetString(PyExc_TypeError, "Cannot delete the last attribute");
        return -1;
    @}
    if (!PyUnicode_Check(value)) @{
        PyErr_SetString(PyExc_TypeError,
                        "The last attribute value must be a string");
        return -1;
    @}
    Py_INCREF(value);
    Py_CLEAR(self->last);
    self->last = value;
    return 0;
@}

static PyGetSetDef Custom_getsetters[] = @{
    @{"first", (getter) Custom_getfirst, (setter) Custom_setfirst,
     "first name", NULL@},
    @{"last", (getter) Custom_getlast, (setter) Custom_setlast,
     "last name", NULL@},
    @{NULL@}  /* Sentinel */
@};

static PyObject *
Custom_name(CustomObject *self, PyObject *Py_UNUSED(ignored))
@{
    return PyUnicode_FromFormat("%S %S", self->first, self->last);
@}

static PyMethodDef Custom_methods[] = @{
    @{"name", (PyCFunction) Custom_name, METH_NOARGS,
     "Return the name, combining the first and last name"
    @},
    @{NULL@}  /* Sentinel */
@};

static PyTypeObject CustomType = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "custom4.Custom",
    .tp_doc = "Custom objects",
    .tp_basicsize = sizeof(CustomObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
    .tp_new = Custom_new,
    .tp_init = (initproc) Custom_init,
    .tp_dealloc = (destructor) Custom_dealloc,
    .tp_traverse = (traverseproc) Custom_traverse,
    .tp_clear = (inquiry) Custom_clear,
    .tp_members = Custom_members,
    .tp_methods = Custom_methods,
    .tp_getset = Custom_getsetters,
@};

static PyModuleDef custommodule = @{
    PyModuleDef_HEAD_INIT,
    .m_name = "custom4",
    .m_doc = "Example module that creates an extension type.",
    .m_size = -1,
@};

PyMODINIT_FUNC
PyInit_custom4(void)
@{
    PyObject *m;
    if (PyType_Ready(&CustomType) < 0)
        return NULL;

    m = PyModule_Create(&custommodule);
    if (m == NULL)
        return NULL;

    Py_INCREF(&CustomType);
    if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) @{
        Py_DECREF(&CustomType);
        Py_DECREF(m);
        return NULL;
    @}

    return m;
@}
@end example

First, the traversal method lets the cyclic GC know about subobjects that could
participate in cycles:

@example
static int
Custom_traverse(CustomObject *self, visitproc visit, void *arg)
@{
    int vret;
    if (self->first) @{
        vret = visit(self->first, arg);
        if (vret != 0)
            return vret;
    @}
    if (self->last) @{
        vret = visit(self->last, arg);
        if (vret != 0)
            return vret;
    @}
    return 0;
@}
@end example

For each subobject that can participate in cycles, we need to call the
@code{visit()} function, which is passed to the traversal method. The
@code{visit()} function takes as arguments the subobject and the extra argument
@emph{arg} passed to the traversal method.  It returns an integer value that must be
returned if it is non-zero.

Python provides a @ref{3af1,,Py_VISIT()} macro that automates calling visit
functions.  With @ref{3af1,,Py_VISIT()}, we can minimize the amount of boilerplate
in @code{Custom_traverse}:

@example
static int
Custom_traverse(CustomObject *self, visitproc visit, void *arg)
@{
    Py_VISIT(self->first);
    Py_VISIT(self->last);
    return 0;
@}
@end example

@cartouche
@quotation 注解 
The @ref{3664,,tp_traverse} implementation must name its
arguments exactly @emph{visit} and @emph{arg} in order to use @ref{3af1,,Py_VISIT()}.
@end quotation
@end cartouche

Second, we need to provide a method for clearing any subobjects that can
participate in cycles:

@example
static int
Custom_clear(CustomObject *self)
@{
    Py_CLEAR(self->first);
    Py_CLEAR(self->last);
    return 0;
@}
@end example

Notice the use of the @ref{3af2,,Py_CLEAR()} macro.  It is the recommended and safe
way to clear data attributes of arbitrary types while decrementing
their reference counts.  If you were to call @ref{268,,Py_XDECREF()} instead
on the attribute before setting it to @code{NULL}, there is a possibility
that the attribute's destructor would call back into code that reads the
attribute again (@emph{especially} if there is a reference cycle).

@cartouche
@quotation 注解 
You could emulate @ref{3af2,,Py_CLEAR()} by writing:

@example
PyObject *tmp;
tmp = self->first;
self->first = NULL;
Py_XDECREF(tmp);
@end example

Nevertheless, it is much easier and less error-prone to always
use @ref{3af2,,Py_CLEAR()} when deleting an attribute.  Don't
try to micro-optimize at the expense of robustness!
@end quotation
@end cartouche

The deallocator @code{Custom_dealloc} may call arbitrary code when clearing
attributes.  It means the circular GC can be triggered inside the function.
Since the GC assumes reference count is not zero, we need to untrack the object
from the GC by calling @ref{e3e,,PyObject_GC_UnTrack()} before clearing members.
Here is our reimplemented deallocator using @ref{e3e,,PyObject_GC_UnTrack()}
and @code{Custom_clear}:

@example
static void
Custom_dealloc(CustomObject *self)
@{
    PyObject_GC_UnTrack(self);
    Custom_clear(self);
    Py_TYPE(self)->tp_free((PyObject *) self);
@}
@end example

Finally, we add the @ref{3af3,,Py_TPFLAGS_HAVE_GC} flag to the class flags:

@example
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
@end example

That's pretty much it.  If we had written custom @ref{3ae6,,tp_alloc} or
@ref{3ae5,,tp_free} handlers, we'd need to modify them for cyclic
garbage collection.  Most extensions will use the versions automatically provided.

@node Subclassing other types,,Supporting cyclic garbage collection,自定义扩展类型：教程
@anchor{extending/newtypes_tutorial subclassing-other-types}@anchor{3af4}
@subsubsection Subclassing other types


It is possible to create new extension types that are derived from existing
types. It is easiest to inherit from the built in types, since an extension can
easily use the @ref{2d6,,PyTypeObject} it needs. It can be difficult to share
these @ref{2d6,,PyTypeObject} structures between extension modules.

In this example we will create a @code{SubList} type that inherits from the
built-in @ref{262,,list} type. The new type will be completely compatible with
regular lists, but will have an additional @code{increment()} method that
increases an internal counter:

@example
>>> import sublist
>>> s = sublist.SubList(range(3))
>>> s.extend(s)
>>> print(len(s))
6
>>> print(s.increment())
1
>>> print(s.increment())
2
@end example

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>

typedef struct @{
    PyListObject list;
    int state;
@} SubListObject;

static PyObject *
SubList_increment(SubListObject *self, PyObject *unused)
@{
    self->state++;
    return PyLong_FromLong(self->state);
@}

static PyMethodDef SubList_methods[] = @{
    @{"increment", (PyCFunction) SubList_increment, METH_NOARGS,
     PyDoc_STR("increment state counter")@},
    @{NULL@},
@};

static int
SubList_init(SubListObject *self, PyObject *args, PyObject *kwds)
@{
    if (PyList_Type.tp_init((PyObject *) self, args, kwds) < 0)
        return -1;
    self->state = 0;
    return 0;
@}

static PyTypeObject SubListType = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "sublist.SubList",
    .tp_doc = "SubList objects",
    .tp_basicsize = sizeof(SubListObject),
    .tp_itemsize = 0,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
    .tp_init = (initproc) SubList_init,
    .tp_methods = SubList_methods,
@};

static PyModuleDef sublistmodule = @{
    PyModuleDef_HEAD_INIT,
    .m_name = "sublist",
    .m_doc = "Example module that creates an extension type.",
    .m_size = -1,
@};

PyMODINIT_FUNC
PyInit_sublist(void)
@{
    PyObject *m;
    SubListType.tp_base = &PyList_Type;
    if (PyType_Ready(&SubListType) < 0)
        return NULL;

    m = PyModule_Create(&sublistmodule);
    if (m == NULL)
        return NULL;

    Py_INCREF(&SubListType);
    if (PyModule_AddObject(m, "SubList", (PyObject *) &SubListType) < 0) @{
        Py_DECREF(&SubListType);
        Py_DECREF(m);
        return NULL;
    @}

    return m;
@}
@end example

As you can see, the source code closely resembles the @code{Custom} examples in
previous sections. We will break down the main differences between them.

@example
typedef struct @{
    PyListObject list;
    int state;
@} SubListObject;
@end example

The primary difference for derived type objects is that the base type's
object structure must be the first value.  The base type will already include
the @ref{c6b,,PyObject_HEAD()} at the beginning of its structure.

When a Python object is a @code{SubList} instance, its @code{PyObject *} pointer
can be safely cast to both @code{PyListObject *} and @code{SubListObject *}:

@example
static int
SubList_init(SubListObject *self, PyObject *args, PyObject *kwds)
@{
    if (PyList_Type.tp_init((PyObject *) self, args, kwds) < 0)
        return -1;
    self->state = 0;
    return 0;
@}
@end example

We see above how to call through to the @code{__init__} method of the base
type.

This pattern is important when writing a type with custom
@ref{3ae1,,tp_new} and @ref{3ae4,,tp_dealloc}
members.  The @ref{3ae1,,tp_new} handler should not actually
create the memory for the object with its @ref{3ae6,,tp_alloc},
but let the base class handle it by calling its own @ref{3ae1,,tp_new}.

The @ref{2d6,,PyTypeObject} struct supports a @ref{3af5,,tp_base}
specifying the type's concrete base class.  Due to cross-platform compiler
issues, you can't fill that field directly with a reference to
@ref{3af6,,PyList_Type}; it should be done later in the module initialization
function:

@example
PyMODINIT_FUNC
PyInit_sublist(void)
@{
    PyObject* m;
    SubListType.tp_base = &PyList_Type;
    if (PyType_Ready(&SubListType) < 0)
        return NULL;

    m = PyModule_Create(&sublistmodule);
    if (m == NULL)
        return NULL;

    Py_INCREF(&SubListType);
    if (PyModule_AddObject(m, "SubList", (PyObject *) &SubListType) < 0) @{
        Py_DECREF(&SubListType);
        Py_DECREF(m);
        return NULL;
    @}

    return m;
@}
@end example

Before calling @ref{3ae7,,PyType_Ready()}, the type structure must have the
@ref{3af5,,tp_base} slot filled in.  When we are deriving an
existing type, it is not necessary to fill out the @ref{3ae6,,tp_alloc}
slot with @ref{3ae2,,PyType_GenericNew()} -- the allocation function from the base
type will be inherited.

After that, calling @ref{3ae7,,PyType_Ready()} and adding the type object to the
module is the same as with the basic @code{Custom} examples.

@subsubheading 备注


@node 定义扩展类型：已分类主题,构建C/C++扩展,自定义扩展类型：教程,不使用第三方工具创建扩展
@anchor{extending/newtypes doc}@anchor{3af7}@anchor{extending/newtypes defining-extension-types-assorted-topics}@anchor{3af8}@anchor{extending/newtypes new-types-topics}@anchor{3af9}
@subsection 定义扩展类型：已分类主题

@anchor{extending/newtypes dnt-type-methods}@anchor{3afa}
本章节目标是提供一个各种你可以实现的类型方法及其功能的简短介绍。

这是C类型 @ref{2d6,,PyTypeObject} 的定义，省略了只用于调试构建的字段:

@example
typedef struct _typeobject @{
    PyObject_VAR_HEAD
    const char *tp_name; /* For printing, in format "<module>.<name>" */
    Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */

    /* Methods to implement standard operations */

    destructor tp_dealloc;
    Py_ssize_t tp_vectorcall_offset;
    getattrfunc tp_getattr;
    setattrfunc tp_setattr;
    PyAsyncMethods *tp_as_async; /* formerly known as tp_compare (Python 2)
                                    or tp_reserved (Python 3) */
    reprfunc tp_repr;

    /* Method suites for standard classes */

    PyNumberMethods *tp_as_number;
    PySequenceMethods *tp_as_sequence;
    PyMappingMethods *tp_as_mapping;

    /* More standard operations (here for binary compatibility) */

    hashfunc tp_hash;
    ternaryfunc tp_call;
    reprfunc tp_str;
    getattrofunc tp_getattro;
    setattrofunc tp_setattro;

    /* Functions to access object as input/output buffer */
    PyBufferProcs *tp_as_buffer;

    /* Flags to define presence of optional/expanded features */
    unsigned long tp_flags;

    const char *tp_doc; /* Documentation string */

    /* call function for all accessible objects */
    traverseproc tp_traverse;

    /* delete references to contained objects */
    inquiry tp_clear;

    /* rich comparisons */
    richcmpfunc tp_richcompare;

    /* weak reference enabler */
    Py_ssize_t tp_weaklistoffset;

    /* Iterators */
    getiterfunc tp_iter;
    iternextfunc tp_iternext;

    /* Attribute descriptor and subclassing stuff */
    struct PyMethodDef *tp_methods;
    struct PyMemberDef *tp_members;
    struct PyGetSetDef *tp_getset;
    struct _typeobject *tp_base;
    PyObject *tp_dict;
    descrgetfunc tp_descr_get;
    descrsetfunc tp_descr_set;
    Py_ssize_t tp_dictoffset;
    initproc tp_init;
    allocfunc tp_alloc;
    newfunc tp_new;
    freefunc tp_free; /* Low-level free-memory routine */
    inquiry tp_is_gc; /* For PyObject_IS_GC */
    PyObject *tp_bases;
    PyObject *tp_mro; /* method resolution order */
    PyObject *tp_cache;
    PyObject *tp_subclasses;
    PyObject *tp_weaklist;
    destructor tp_del;

    /* Type attribute cache version tag. Added in version 2.6 */
    unsigned int tp_version_tag;

    destructor tp_finalize;

@} PyTypeObject;
@end example

这里有 @emph{很多} 方法。但是不要太担心，如果你要定义一个类型，通常只需要实现少量的方法。

正如你猜到的一样，我们正要一步一步详细介绍各种处理程序。因为有大量的历史包袱影响字段的排序，所以我们不会根据它们在结构体里定义的顺序讲解。通常非常容易找到一个包含你需要的字段的例子，然后改变值去适应你新的类型。

@example
const char *tp_name; /* For printing */
@end example

类型的名字 - 上一章提到过的，会出现在很多地方，几乎全部都是为了诊断目的。尝试选择一个好名字，对于诊断很有帮助。

@example
Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */
@end example

这些字段告诉运行时在创造这个类型的新对象时需要分配多少内存。Python为了可变长度的结构（想下：字符串，元组）有些内置支持，这是 @ref{3add,,tp_itemsize} 字段存在的原由。这部分稍后解释。

@example
const char *tp_doc;
@end example

这里你可以放置一段字符串（或者它的地址），当你想在Python脚本引用 @code{obj.__doc__} 时返回这段文档字符串。

现在我们来看一下基本类型方法 - 大多数扩展类型将实现的方法。

@menu
* 终结和内存释放:: 
* 对象展示:: 
* Attribute Management:: 
* Object Comparison:: 
* Abstract Protocol Support:: 
* Weak Reference Support:: 
* 更多建议:: 

@end menu

@node 终结和内存释放,对象展示,,定义扩展类型：已分类主题
@anchor{extending/newtypes finalization-and-de-allocation}@anchor{3afb}
@subsubsection 终结和内存释放


@geindex object; deallocation
@geindex deallocation@comma{} object
@geindex object; finalization
@geindex finalization@comma{} of objects

@example
destructor tp_dealloc;
@end example

当您的类型实例的引用计数减少为零并且Python解释器想要回收它时，将调用此函数。如果你的类型有内存可供释放或执行其他清理，你可以把它放在这里。 对象本身也需要在这里释放。 以下是此函数的示例：

@example
static void
newdatatype_dealloc(newdatatypeobject *obj)
@{
    free(obj->obj_UnderlyingDatatypePtr);
    Py_TYPE(obj)->tp_free(obj);
@}
@end example

@geindex PyErr_Fetch()
@geindex PyErr_Restore()

One important requirement of the deallocator function is that it leaves any
pending exceptions alone.  This is important since deallocators are frequently
called as the interpreter unwinds the Python stack; when the stack is unwound
due to an exception (rather than normal returns), nothing is done to protect the
deallocators from seeing that an exception has already been set.  Any actions
which a deallocator performs which may cause additional Python code to be
executed may detect that an exception has been set.  This can lead to misleading
errors from the interpreter.  The proper way to protect against this is to save
a pending exception before performing the unsafe action, and restoring it when
done.  This can be done using the @ref{964,,PyErr_Fetch()} and
@ref{3afc,,PyErr_Restore()} functions:

@example
static void
my_dealloc(PyObject *obj)
@{
    MyObject *self = (MyObject *) obj;
    PyObject *cbresult;

    if (self->my_callback != NULL) @{
        PyObject *err_type, *err_value, *err_traceback;

        /* This saves the current exception state */
        PyErr_Fetch(&err_type, &err_value, &err_traceback);

        cbresult = PyObject_CallObject(self->my_callback, NULL);
        if (cbresult == NULL)
            PyErr_WriteUnraisable(self->my_callback);
        else
            Py_DECREF(cbresult);

        /* This restores the saved exception state */
        PyErr_Restore(err_type, err_value, err_traceback);

        Py_DECREF(self->my_callback);
    @}
    Py_TYPE(obj)->tp_free((PyObject*)self);
@}
@end example

@cartouche
@quotation 注解 
There are limitations to what you can safely do in a deallocator function.
First, if your type supports garbage collection (using @ref{3664,,tp_traverse}
and/or @ref{3afd,,tp_clear}), some of the object's members can have been
cleared or finalized by the time @ref{3ae4,,tp_dealloc} is called.  Second, in
@ref{3ae4,,tp_dealloc}, your object is in an unstable state: its reference
count is equal to zero.  Any call to a non-trivial object or API (as in the
example above) might end up calling @ref{3ae4,,tp_dealloc} again, causing a
double free and a crash.

从 Python 3.4 开始，推荐不要在 @ref{3ae4,,tp_dealloc} 放复杂的终结代码，而是使用新的 @ref{2d7,,tp_finalize} 类型方法。


@subsubheading 参见


@geindex Python 提高建议; PEP 442
PEP 442@footnote{https://www.python.org/dev/peps/pep-0442} 解释了新的终结方案。

@end quotation
@end cartouche

@geindex string; object representation
@geindex 內置函数; repr

@node 对象展示,Attribute Management,终结和内存释放,定义扩展类型：已分类主题
@anchor{extending/newtypes object-presentation}@anchor{3afe}
@subsubsection 对象展示


在 Python 中，有两种方式可以生成对象的文本表示: @ref{7c6,,repr()} 函数和 @ref{329,,str()} 函数。 (@ref{880,,print()} 函数会直接调用 @ref{329,,str()}。) 这些处理程序都是可选的。

@example
reprfunc tp_repr;
reprfunc tp_str;
@end example

@ref{3aff,,tp_repr} 处理程序应该返回一个字符串对象，其中包含调用它的实例的表示形式。 下面是一个简单的例子:

@example
static PyObject *
newdatatype_repr(newdatatypeobject * obj)
@{
    return PyUnicode_FromFormat("Repr-ified_newdatatype@{@{size:%d@}@}",
                                obj->obj_UnderlyingDatatypePtr->size);
@}
@end example

如果没有指定 @ref{3aff,,tp_repr} 处理程序，解释器将提供一个使用 @ref{3b00,,tp_name} 的表示形式以及对象的惟一标识值。

The @ref{3b01,,tp_str} handler is to @ref{329,,str()} what the @ref{3aff,,tp_repr} handler
described above is to @ref{7c6,,repr()}; that is, it is called when Python code calls
@ref{329,,str()} on an instance of your object.  Its implementation is very similar
to the @ref{3aff,,tp_repr} function, but the resulting string is intended for human
consumption.  If @ref{3b01,,tp_str} is not specified, the @ref{3aff,,tp_repr} handler is
used instead.

下面是一个简单的例子:

@example
static PyObject *
newdatatype_str(newdatatypeobject * obj)
@{
    return PyUnicode_FromFormat("Stringified_newdatatype@{@{size:%d@}@}",
                                obj->obj_UnderlyingDatatypePtr->size);
@}
@end example

@node Attribute Management,Object Comparison,对象展示,定义扩展类型：已分类主题
@anchor{extending/newtypes attribute-management}@anchor{3b02}
@subsubsection Attribute Management


For every object which can support attributes, the corresponding type must
provide the functions that control how the attributes are resolved.  There needs
to be a function which can retrieve attributes (if any are defined), and another
to set attributes (if setting attributes is allowed).  Removing an attribute is
a special case, for which the new value passed to the handler is @code{NULL}.

Python supports two pairs of attribute handlers; a type that supports attributes
only needs to implement the functions for one pair.  The difference is that one
pair takes the name of the attribute as a @code{char*}, while the other
accepts a @ref{4b5,,PyObject*}.  Each type can use whichever pair makes more
sense for the implementation's convenience.

@example
getattrfunc  tp_getattr;        /* char * version */
setattrfunc  tp_setattr;
/* ... */
getattrofunc tp_getattro;       /* PyObject * version */
setattrofunc tp_setattro;
@end example

If accessing attributes of an object is always a simple operation (this will be
explained shortly), there are generic implementations which can be used to
provide the @ref{4b5,,PyObject*} version of the attribute management functions.
The actual need for type-specific attribute handlers almost completely
disappeared starting with Python 2.2, though there are many examples which have
not been updated to use some of the new generic mechanism that is available.

@menu
* 泛型属性管理:: 
* Type-specific Attribute Management:: 

@end menu

@node 泛型属性管理,Type-specific Attribute Management,,Attribute Management
@anchor{extending/newtypes generic-attribute-management}@anchor{3aea}@anchor{extending/newtypes id1}@anchor{3b03}
@subsubsection 泛型属性管理


Most extension types only use @emph{simple} attributes.  So, what makes the
attributes simple?  There are only a couple of conditions that must be met:


@enumerate 

@item 
The name of the attributes must be known when @ref{3ae7,,PyType_Ready()} is
called.

@item 
不需要特殊的处理来记录属性是否被查找或设置，也不需要根据值采取操作。
@end enumerate

请注意，此列表不对属性的值、值的计算时间或相关数据的存储方式施加任何限制。

When @ref{3ae7,,PyType_Ready()} is called, it uses three tables referenced by the
type object to create @ref{159e,,descriptor}s which are placed in the dictionary of the
type object.  Each descriptor controls access to one attribute of the instance
object.  Each of the tables is optional; if all three are @code{NULL}, instances of
the type will only have attributes that are inherited from their base type, and
should leave the @ref{3b04,,tp_getattro} and @ref{3b05,,tp_setattro} fields @code{NULL} as
well, allowing the base type to handle attributes.

表被声明为object::类型的三个字段:

@example
struct PyMethodDef *tp_methods;
struct PyMemberDef *tp_members;
struct PyGetSetDef *tp_getset;
@end example

If @ref{3aeb,,tp_methods} is not @code{NULL}, it must refer to an array of
@ref{e14,,PyMethodDef} structures.  Each entry in the table is an instance of this
structure:

@example
typedef struct PyMethodDef @{
    const char  *ml_name;       /* method name */
    PyCFunction  ml_meth;       /* implementation function */
    int          ml_flags;      /* flags */
    const char  *ml_doc;        /* docstring */
@} PyMethodDef;
@end example

One entry should be defined for each method provided by the type; no entries are
needed for methods inherited from a base type.  One additional entry is needed
at the end; it is a sentinel that marks the end of the array.  The
@code{ml_name} field of the sentinel must be @code{NULL}.

The second table is used to define attributes which map directly to data stored
in the instance.  A variety of primitive C types are supported, and access may
be read-only or read-write.  The structures in the table are defined as:

@example
typedef struct PyMemberDef @{
    const char *name;
    int         type;
    int         offset;
    int         flags;
    const char *doc;
@} PyMemberDef;
@end example

For each entry in the table, a @ref{159e,,descriptor} will be constructed and added to the
type which will be able to extract a value from the instance structure.  The
@ref{603,,type} field should contain one of the type codes defined in the
@code{structmember.h} header; the value will be used to determine how to
convert Python values to and from C values.  The @code{flags} field is used to
store flags which control how the attribute can be accessed.

以下标志常量定义在:file: ' structmember.h ';它们可以使用bitwise-OR组合。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

常数

@tab

含义

@item

@code{READONLY}

@tab

没有可写的

@item

@code{READ_RESTRICTED}

@tab

Not readable in restricted mode.

@item

@code{WRITE_RESTRICTED}

@tab

Not writable in restricted mode.

@item

@code{RESTRICTED}

@tab

在受限模式下不可读，也不可写。

@end multitable


@geindex READONLY
@geindex READ_RESTRICTED
@geindex WRITE_RESTRICTED
@geindex RESTRICTED

An interesting advantage of using the @ref{3ae9,,tp_members} table to build
descriptors that are used at runtime is that any attribute defined this way can
have an associated doc string simply by providing the text in the table.  An
application can use the introspection API to retrieve the descriptor from the
class object, and get the doc string using its @code{__doc__} attribute.

As with the @ref{3aeb,,tp_methods} table, a sentinel entry with a @code{name} value
of @code{NULL} is required.

@c XXX Descriptors need to be explained in more detail somewhere, but not here.
@c 
@c Descriptor objects have two handler functions which correspond to the
@c \member{tp_getattro} and \member{tp_setattro} handlers.  The
@c \method{__get__()} handler is a function which is passed the descriptor,
@c instance, and type objects, and returns the value of the attribute, or it
@c returns \NULL{} and sets an exception.  The \method{__set__()} handler is
@c passed the descriptor, instance, type, and new value;

@node Type-specific Attribute Management,,泛型属性管理,Attribute Management
@anchor{extending/newtypes type-specific-attribute-management}@anchor{3b06}
@subsubsection Type-specific Attribute Management


For simplicity, only the @code{char*} version will be demonstrated here; the
type of the name parameter is the only difference between the @code{char*}
and @ref{4b5,,PyObject*} flavors of the interface. This example effectively does
the same thing as the generic example above, but does not use the generic
support added in Python 2.2.  It explains how the handler functions are
called, so that if you do need to extend their functionality, you'll understand
what needs to be done.

The @ref{3b07,,tp_getattr} handler is called when the object requires an attribute
look-up.  It is called in the same situations where the @ref{313,,__getattr__()}
method of a class would be called.

Here is an example:

@example
static PyObject *
newdatatype_getattr(newdatatypeobject *obj, char *name)
@{
    if (strcmp(name, "data") == 0)
    @{
        return PyLong_FromLong(obj->data);
    @}

    PyErr_Format(PyExc_AttributeError,
                 "'%.50s' object has no attribute '%.400s'",
                 tp->tp_name, name);
    return NULL;
@}
@end example

The @ref{3b08,,tp_setattr} handler is called when the @ref{e25,,__setattr__()} or
@ref{13c8,,__delattr__()} method of a class instance would be called.  When an
attribute should be deleted, the third parameter will be @code{NULL}.  Here is an
example that simply raises an exception; if this were really all you wanted, the
@ref{3b08,,tp_setattr} handler should be set to @code{NULL}.

@example
static int
newdatatype_setattr(newdatatypeobject *obj, char *name, PyObject *v)
@{
    PyErr_Format(PyExc_RuntimeError, "Read-only attribute: %s", name);
    return -1;
@}
@end example

@node Object Comparison,Abstract Protocol Support,Attribute Management,定义扩展类型：已分类主题
@anchor{extending/newtypes object-comparison}@anchor{3b09}
@subsubsection Object Comparison


@example
richcmpfunc tp_richcompare;
@end example

The @ref{3b0a,,tp_richcompare} handler is called when comparisons are needed.  It is
analogous to the @ref{13d0,,rich comparison methods}, like
@ref{c2d,,__lt__()}, and also called by @ref{3b0b,,PyObject_RichCompare()} and
@ref{ed6,,PyObject_RichCompareBool()}.

This function is called with two Python objects and the operator as arguments,
where the operator is one of @code{Py_EQ}, @code{Py_NE}, @code{Py_LE}, @code{Py_GT},
@code{Py_LT} or @code{Py_GT}.  It should compare the two objects with respect to the
specified operator and return @code{Py_True} or @code{Py_False} if the comparison is
successful, @code{Py_NotImplemented} to indicate that comparison is not
implemented and the other object's comparison method should be tried, or @code{NULL}
if an exception was set.

Here is a sample implementation, for a datatype that is considered equal if the
size of an internal pointer is equal:

@example
static PyObject *
newdatatype_richcmp(PyObject *obj1, PyObject *obj2, int op)
@{
    PyObject *result;
    int c, size1, size2;

    /* code to make sure that both arguments are of type
       newdatatype omitted */

    size1 = obj1->obj_UnderlyingDatatypePtr->size;
    size2 = obj2->obj_UnderlyingDatatypePtr->size;

    switch (op) @{
    case Py_LT: c = size1 <  size2; break;
    case Py_LE: c = size1 <= size2; break;
    case Py_EQ: c = size1 == size2; break;
    case Py_NE: c = size1 != size2; break;
    case Py_GT: c = size1 >  size2; break;
    case Py_GE: c = size1 >= size2; break;
    @}
    result = c ? Py_True : Py_False;
    Py_INCREF(result);
    return result;
 @}
@end example

@node Abstract Protocol Support,Weak Reference Support,Object Comparison,定义扩展类型：已分类主题
@anchor{extending/newtypes abstract-protocol-support}@anchor{3b0c}
@subsubsection Abstract Protocol Support


Python supports a variety of @emph{abstract} 'protocols;' the specific interfaces
provided to use these interfaces are documented in @ref{3b0d,,抽象对象层}.

A number of these abstract interfaces were defined early in the development of
the Python implementation.  In particular, the number, mapping, and sequence
protocols have been part of Python since the beginning.  Other protocols have
been added over time.  For protocols which depend on several handler routines
from the type implementation, the older protocols have been defined as optional
blocks of handlers referenced by the type object.  For newer protocols there are
additional slots in the main type object, with a flag bit being set to indicate
that the slots are present and should be checked by the interpreter.  (The flag
bit does not indicate that the slot values are non-@code{NULL}. The flag may be set
to indicate the presence of a slot, but a slot may still be unfilled.)

@example
PyNumberMethods   *tp_as_number;
PySequenceMethods *tp_as_sequence;
PyMappingMethods  *tp_as_mapping;
@end example

If you wish your object to be able to act like a number, a sequence, or a
mapping object, then you place the address of a structure that implements the C
type @ref{d7a,,PyNumberMethods}, @ref{3b0e,,PySequenceMethods}, or
@ref{3b0f,,PyMappingMethods}, respectively. It is up to you to fill in this
structure with appropriate values. You can find examples of the use of each of
these in the @code{Objects} directory of the Python source distribution.

@example
hashfunc tp_hash;
@end example

This function, if you choose to provide it, should return a hash number for an
instance of your data type. Here is a simple example:

@example
static Py_hash_t
newdatatype_hash(newdatatypeobject *obj)
@{
    Py_hash_t result;
    result = obj->some_size + 32767 * obj->some_number;
    if (result == -1)
       result = -2;
    return result;
@}
@end example

@code{Py_hash_t} is a signed integer type with a platform-varying width.
Returning @code{-1} from @ref{3b10,,tp_hash} indicates an error,
which is why you should be careful to avoid returning it when hash computation
is successful, as seen above.

@example
ternaryfunc tp_call;
@end example

This function is called when an instance of your data type is "called", for
example, if @code{obj1} is an instance of your data type and the Python script
contains @code{obj1('hello')}, the @ref{3b11,,tp_call} handler is invoked.

This function takes three arguments:


@enumerate 

@item 
@emph{self} is the instance of the data type which is the subject of the call.
If the call is @code{obj1('hello')}, then @emph{self} is @code{obj1}.

@item 
@emph{args} is a tuple containing the arguments to the call.  You can use
@ref{26a,,PyArg_ParseTuple()} to extract the arguments.

@item 
@emph{kwds} is a dictionary of keyword arguments that were passed. If this is
non-@code{NULL} and you support keyword arguments, use
@ref{5c5,,PyArg_ParseTupleAndKeywords()} to extract the arguments.  If you
do not want to support keyword arguments and this is non-@code{NULL}, raise a
@ref{192,,TypeError} with a message saying that keyword arguments are not supported.
@end enumerate

Here is a toy @code{tp_call} implementation:

@example
static PyObject *
newdatatype_call(newdatatypeobject *self, PyObject *args, PyObject *kwds)
@{
    PyObject *result;
    const char *arg1;
    const char *arg2;
    const char *arg3;

    if (!PyArg_ParseTuple(args, "sss:call", &arg1, &arg2, &arg3)) @{
        return NULL;
    @}
    result = PyUnicode_FromFormat(
        "Returning -- value: [%d] arg1: [%s] arg2: [%s] arg3: [%s]\n",
        obj->obj_UnderlyingDatatypePtr->size,
        arg1, arg2, arg3);
    return result;
@}
@end example

@example
/* Iterators */
getiterfunc tp_iter;
iternextfunc tp_iternext;
@end example

These functions provide support for the iterator protocol.  Both handlers
take exactly one parameter, the instance for which they are being called,
and return a new reference.  In the case of an error, they should set an
exception and return @code{NULL}.  @ref{e29,,tp_iter} corresponds
to the Python @ref{509,,__iter__()} method, while @ref{e2a,,tp_iternext}
corresponds to the Python @ref{c5d,,__next__()} method.

Any @ref{ba5,,iterable} object must implement the @ref{e29,,tp_iter}
handler, which must return an @ref{fce,,iterator} object.  Here the same guidelines
apply as for Python classes:


@itemize *

@item 
For collections (such as lists and tuples) which can support multiple
independent iterators, a new iterator should be created and returned by
each call to @ref{e29,,tp_iter}.

@item 
Objects which can only be iterated over once (usually due to side effects of
iteration, such as file objects) can implement @ref{e29,,tp_iter}
by returning a new reference to themselves -- and should also therefore
implement the @ref{e2a,,tp_iternext}  handler.
@end itemize

Any @ref{fce,,iterator} object should implement both @ref{e29,,tp_iter}
and @ref{e2a,,tp_iternext}.  An iterator's
@ref{e29,,tp_iter} handler should return a new reference
to the iterator.  Its @ref{e2a,,tp_iternext} handler should
return a new reference to the next object in the iteration, if there is one.
If the iteration has reached the end, @ref{e2a,,tp_iternext}
may return @code{NULL} without setting an exception, or it may set
@ref{480,,StopIteration} @emph{in addition} to returning @code{NULL}; avoiding
the exception can yield slightly better performance.  If an actual error
occurs, @ref{e2a,,tp_iternext} should always set an exception
and return @code{NULL}.

@node Weak Reference Support,更多建议,Abstract Protocol Support,定义扩展类型：已分类主题
@anchor{extending/newtypes weak-reference-support}@anchor{3b12}@anchor{extending/newtypes weakref-support}@anchor{1924}
@subsubsection Weak Reference Support


One of the goals of Python's weak reference implementation is to allow any type
to participate in the weak reference mechanism without incurring the overhead on
performance-critical objects (such as numbers).


@subsubheading 参见


Documentation for the @ref{128,,weakref} module.


For an object to be weakly referencable, the extension type must do two things:


@enumerate 

@item 
Include a @ref{4b5,,PyObject*} field in the C object structure dedicated to
the weak reference mechanism.  The object's constructor should leave it
@code{NULL} (which is automatic when using the default
@ref{3ae6,,tp_alloc}).

@item 
Set the @ref{3b13,,tp_weaklistoffset} type member
to the offset of the aforementioned field in the C object structure,
so that the interpreter knows how to access and modify that field.
@end enumerate

Concretely, here is how a trivial object structure would be augmented
with the required field:

@example
typedef struct @{
    PyObject_HEAD
    PyObject *weakreflist;  /* List of weak references */
@} TrivialObject;
@end example

And the corresponding member in the statically-declared type object:

@example
static PyTypeObject TrivialType = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    /* ... other members omitted for brevity ... */
    .tp_weaklistoffset = offsetof(TrivialObject, weakreflist),
@};
@end example

The only further addition is that @code{tp_dealloc} needs to clear any weak
references (by calling @code{PyObject_ClearWeakRefs()}) if the field is
non-@code{NULL}:

@example
static void
Trivial_dealloc(TrivialObject *self)
@{
    /* Clear weakrefs first before calling any destructors */
    if (self->weakreflist != NULL)
        PyObject_ClearWeakRefs((PyObject *) self);
    /* ... remainder of destruction code omitted for brevity ... */
    Py_TYPE(self)->tp_free((PyObject *) self);
@}
@end example

@node 更多建议,,Weak Reference Support,定义扩展类型：已分类主题
@anchor{extending/newtypes more-suggestions}@anchor{3b14}
@subsubsection 更多建议


In order to learn how to implement any specific method for your new data type,
get the @ref{13ce,,CPython} source code.  Go to the @code{Objects} directory,
then search the C source files for @code{tp_} plus the function you want
(for example, @code{tp_richcompare}).  You will find examples of the function
you want to implement.

When you need to verify that an object is a concrete instance of the type you
are implementing, use the @ref{3b15,,PyObject_TypeCheck()} function.  A sample of
its use might be something like the following:

@example
if (!PyObject_TypeCheck(some_object, &MyType)) @{
    PyErr_SetString(PyExc_TypeError, "arg #1 not a mything");
    return NULL;
@}
@end example


@subsubheading 参见



@table @asis

@item 下载CPython源代码版本。

@indicateurl{https://www.python.org/downloads/source/}

@item GitHub上开发CPython源代码的CPython项目。

@indicateurl{https://github.com/python/cpython}
@end table


@node 构建C/C++扩展,在Windows平台编译C和C++扩展,定义扩展类型：已分类主题,不使用第三方工具创建扩展
@anchor{extending/building doc}@anchor{3b16}@anchor{extending/building building}@anchor{3ab0}@anchor{extending/building building-c-and-c-extensions}@anchor{3b17}
@subsection 构建C/C++扩展


一个CPython的C扩展是一个共享库(例如一个Linux上的 @code{.so} ，或者Windows上的 @code{.pyd} )，其会导出一个 @emph{初始化函数} 。

为了可导入，共享库必须在 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 中有效，且必须命名遵循模块名字，通过适当的扩展。当使用distutils时，会自动生成正确的文件名。

初始化函数的声明如下：

@geindex PyInit_modulename (C 函数)
@anchor{extending/building c PyInit_modulename}@anchor{3b18}
@deffn {C 函数} PyObject* PyInit_modulename (void)
@end deffn

该函数返回完整初始化过的模块，或一个 @ref{3aed,,PyModuleDef} 实例。查看 @ref{3b19,,Initializing C modules} 了解更多细节。

对于仅有ASCII编码的模块名，函数必须是 @code{PyInit_<modulename>} ，将 @code{<modulename>} 替换为模块的名字。当使用 @ref{3b1a,,Multi-phase initialization} 时，允许使用非ASCII编码的模块名。此时初始化函数的名字是 @code{PyInitU_<modulename>} ，而 @code{<modulename>} 需要用Python的 @emph{punycode} 编码，连字号需替换为下划线。在Python里:

@example
def initfunc_name(name):
    try:
        suffix = b'_' + name.encode('ascii')
    except UnicodeEncodeError:
        suffix = b'U_' + name.encode('punycode').replace(b'-', b'_')
    return b'PyInit' + suffix
@end example

可以在一个动态库里导出多个模块，通过定义多个初始化函数。而导入他们需要符号链接或自定义导入器，因为缺省时只有对应了文件名的函数才会被发现。查看 @emph{"一个库里的多模块"} 章节，在 
@geindex Python 提高建议; PEP 489
PEP 489@footnote{https://www.python.org/dev/peps/pep-0489} 了解更多细节。

@menu
* 使用distutils构建C和C++扩展:: 
* 发布你的扩展模块:: 

@end menu

@node 使用distutils构建C和C++扩展,发布你的扩展模块,,构建C/C++扩展
@anchor{extending/building building-c-and-c-extensions-with-distutils}@anchor{3b1b}
@subsubsection 使用distutils构建C和C++扩展


扩展模块可以用distutils来构建，这是Python自带的。distutils也支持创建二进制包，用户无需编译器而distutils就能安装扩展。

一个distutils包包含了一个驱动脚本 @code{setup.py} 。这是个纯Python文件，大多数时候也很简单，看起来如下：

@example
from distutils.core import setup, Extension

module1 = Extension('demo',
                    sources = ['demo.c'])

setup (name = 'PackageName',
       version = '1.0',
       description = 'This is a demo package',
       ext_modules = [module1])
@end example

通过文件 @code{setup.py} ，和文件 @code{demo.c} ，运行如下

@example
python setup.py build
@end example

这会编译 @code{demo.c} ，然后产生一个扩展模块叫做 @code{demo} 在目录 @code{build} 里。依赖于系统，模块文件会放在某个子目录形如 @code{build/lib.system} ，名字可能是 @code{demo.so} 或 @code{demo.pyd} 。

在文件 @code{setup.py} 里，所有动作的入口通过 @code{setup} 函数。该函数可以接受可变数量个关键字参数，上面的例子只使用了一个子集。特别需要注意的例子指定了构建包的元信息，以及指定了包内容。通常一个包会包括多个模块，就像Python的源码模块、文档、子包等。请参数distutils的文档，在 @ref{7f2,,分发 Python 模块（遗留版本）} 来了解更多distutils的特性；本章节只解释构建扩展模块的部分。

通常预计算参数给 @code{setup()} ，想要更好的结构化驱动脚本。有如如上例子函数 @ref{3b1c,,setup()} 的 @code{ext_modules} 参数是一列扩展模块，每个是一个 @code{Extension} 类的实例。例子中的实例定义了扩展命名为 @code{demo} ，从单一源码文件构建 @code{demo.c} 。

更多时候，构建一个扩展会复杂的多，需要额外的预处理器定义和库。如下例子展示了这些。

@example
from distutils.core import setup, Extension

module1 = Extension('demo',
                    define_macros = [('MAJOR_VERSION', '1'),
                                     ('MINOR_VERSION', '0')],
                    include_dirs = ['/usr/local/include'],
                    libraries = ['tcl83'],
                    library_dirs = ['/usr/local/lib'],
                    sources = ['demo.c'])

setup (name = 'PackageName',
       version = '1.0',
       description = 'This is a demo package',
       author = 'Martin v. Loewis',
       author_email = 'martin@@v.loewis.de',
       url = 'https://docs.python.org/extending/building',
       long_description = '@w{'}'
This is really just a demo package.
'@w{'}',
       ext_modules = [module1])
@end example

例子中函数 @ref{3b1c,,setup()} 在调用时额外传递了元信息，是推荐发布包构建时的内容。对于这个扩展，其指定了预处理器定义，include目录，库目录，库。依赖于编译器，distutils还会用其他方式传递信息给编译器。例如在Unix上，结果是如下编译命令

@example
gcc -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -fPIC -DMAJOR_VERSION=1 -DMINOR_VERSION=0 -I/usr/local/include -I/usr/local/include/python2.2 -c demo.c -o build/temp.linux-i686-2.2/demo.o

gcc -shared build/temp.linux-i686-2.2/demo.o -L/usr/local/lib -ltcl83 -o build/lib.linux-i686-2.2/demo.so
@end example

这些行代码仅用于展示目的；distutils用户应该相信distutils能正确调用。

@node 发布你的扩展模块,,使用distutils构建C和C++扩展,构建C/C++扩展
@anchor{extending/building distributing}@anchor{3b1d}@anchor{extending/building distributing-your-extension-modules}@anchor{3b1e}
@subsubsection 发布你的扩展模块


当一个扩展已经成功地被构建时，有三种方式来使用它。

最终用户通常想要安装模块，可以这么运行

@example
python setup.py install
@end example

模块维护者应该制作源码包；要实现可以运行

@example
python setup.py sdist
@end example

有些情况下，需要在源码发布包里包含额外的文件；这通过 @code{MANIFEST.in} 文件实现，查看 @ref{3b1f,,Specifying the files to distribute} 了解细节。

如果源码发行包被成功地构建，维护者还可以创建二进制发行包。 取决于具体平台，以下命令中的一个可以用来完成此任务

@example
python setup.py bdist_wininst
python setup.py bdist_rpm
python setup.py bdist_dumb
@end example

@node 在Windows平台编译C和C++扩展,,构建C/C++扩展,不使用第三方工具创建扩展
@anchor{extending/windows doc}@anchor{3b20}@anchor{extending/windows building-c-and-c-extensions-on-windows}@anchor{3b21}@anchor{extending/windows building-on-windows}@anchor{1332}
@subsection 在Windows平台编译C和C++扩展


这一章简要介绍了如何使用 Microsoft Visual C++ 创建 Python 的 Windows 扩展模块，然后再提供有关其工作机理的详细背景信息。 这些说明材料同时适用于 Windows 程序员学习构建 Python 扩展以及 Unix 程序员学习如何生成在 Unix 和 Windows 上均能成功构建的软件。

鼓励模块作者使用 distutils 方式来构建扩展模块，而不使用本节所描述的方式。 你仍将需要使用 C 编译器来构建 Python；通常为 Microsoft Visual C++。

@cartouche
@quotation 注解 
这一章提及了多个包括已编码 Python 版本号的文件名。 这些文件名以显示为 @code{XY} 的版本号来代表；在实践中，@code{'X'} 将为你所使用的 Python 发布版的主版本号而 @code{'Y'} 将为次版本号。 例如，如果你所使用的是 Python 2.2.1，@code{XY} 将为 @code{22}。
@end quotation
@end cartouche

@menu
* 菜谱式说明:: 
* Unix 和 Windows 之间的差异:: 
* DLL 的实际使用:: 

@end menu

@node 菜谱式说明,Unix 和 Windows 之间的差异,,在Windows平台编译C和C++扩展
@anchor{extending/windows a-cookbook-approach}@anchor{3b22}@anchor{extending/windows win-cookbook}@anchor{3b23}
@subsubsection 菜谱式说明


在 Windows 和 Unix 上构建扩展模块都有两种方式：使用 @ref{39,,distutils} 包来控制构建过程，或者全手动操作。 distutils 方式适用于大多数扩展；使用 @ref{39,,distutils} 构建和打包扩展模块的文档见 @ref{7f2,,分发 Python 模块（遗留版本）}。 如果你发现你确实需要手动操作，那么研究一下 winsound@footnote{https://github.com/python/cpython/tree/3.8/PCbuild/winsound.vcxproj} 标准库模块的项目文件可能会很有帮助。

@node Unix 和 Windows 之间的差异,DLL 的实际使用,菜谱式说明,在Windows平台编译C和C++扩展
@anchor{extending/windows differences-between-unix-and-windows}@anchor{3b24}@anchor{extending/windows dynamic-linking}@anchor{3b25}
@subsubsection Unix 和 Windows 之间的差异


Unix 和 Windows 对于代码的运行时加载使用了完全不同的范式。 在你尝试构建可动态加载的模块之前，要先了解你所用系统是如何工作的。

在 Unix 中，一个共享对象 (@code{.so}) 文件中包含将由程序来使用的代码，也包含在程序中可被找到的函数名称和数据。 当文件被合并到程序中时，对在文件代码中这些函数和数据的全部引用都会被改为指向程序中函数和数据在内存中所放置的实际位置。 这基本上是一个链接操作。

在 Windows 中，一个动态链接库 (@code{.dll}) 文件中没有悬挂的引用。 而是通过一个查找表执行对函数或数据的访问。 因此在运行时 DLL 代码不必在运行时进行修改；相反地，代码已经使用了 DLL 的查找表，并且在运行时查找表会被修改以指向特定的函数和数据。

在 Unix 中，只存在一种库文件 (@code{.a})，它包含来自多个对象文件 (@code{.o}) 的代码。 在创建共享对象文件 (@code{.so}) 的链接阶段，链接器可能会发现它不知道某个标识符是在哪里定义的。 链接器将在各个库的对象文件中查找它；如果找到了它，链接器将会包括来自该对象文件的所有代码。

在 Windows 中，存在两种库类型，静态库和导入库 (扩展名都是 @code{.lib})。 静态库类似于 Unix 的 @code{.a} 文件；它包含在必要时可被包括的代码。 导入库基本上仅用于让链接器能确保特定标识符是合法的，并且将在 DLL 被加载时出现于程序中。 这样链接器可使用来自导入库的信息构建查找表以便使用未包括在 DLL 中的标识符。 当一个应用程序或  DLL 被链接时，可能会生成一个导入库，它将需要被用于应用程序或 DLL 中未来所有依赖于这些符号的 DLL。

假设你正在编译两个动态加载模块 B 和 C，它们应当共享另一个代码块 A。 在 Unix 上，你 @emph{不应} 将 @code{A.a} 传给链接器作为 @code{B.so} 和 @code{C.so}；那会导致它被包括两次，这样 B 和 C 将分别拥有它们自己的副本。 在 Windows 上，编译 @code{A.dll} 将同时编译 @code{A.lib}。 你 @emph{应当} 将 @code{A.lib} 传给链接器用于 B 和 C。 @code{A.lib} 并不包含代码；它只包含将在运行时被用于访问 A 的代码的信息。

在 Windows 上，使用导入库有点像是使用 @code{import spam}；它让你可以访问 spam 中的名称，但并不会创建一个单独副本。 在 Unix 上，链接到一个库更像是 @code{from spam import *}；它会创建一个单独副本。

@node DLL 的实际使用,,Unix 和 Windows 之间的差异,在Windows平台编译C和C++扩展
@anchor{extending/windows using-dlls-in-practice}@anchor{3b26}@anchor{extending/windows win-dlls}@anchor{3b27}
@subsubsection DLL 的实际使用


Windows 版 Python 是用 Microsoft Visual C++ 编译的；使用其他编译器可能行也可能不行（但 Borland 看来是可以的）。 这一节的剩余部分只适用于 MSVC++。

当在 Windows 中创建 DLL 时，你必须将 @code{pythonXY.lib} 传给链接器。 要编译两个 DLL，spam 和 ni (会使用 spam 中找到的 C 函数)，你应当使用以下命令:

@example
cl /LD /I/python/include spam.c ../libs/pythonXY.lib
cl /LD /I/python/include ni.c spam.lib ../libs/pythonXY.lib
@end example

第一个命令创建了三个文件: @code{spam.obj}, @code{spam.dll} 和 @code{spam.lib}。 @code{Spam.dll} 不包含任何 Python 函数 (例如 @ref{26a,,PyArg_ParseTuple()})，但它通过 @code{pythonXY.lib} 可以知道如何找到所需的 Python 代码。

第二条命令创建了 @code{ni.dll} (以及 @code{.obj} 和 @code{.lib})，它知道如何从 spam 以及 Python 可执行文件中找到所需的函数。

不是每个标识符都会被导出到查找表。 如果你想要任何其他模块（包括 Python）都能看到你的标识符，你必须写上 @code{_declspec(dllexport)}，就如在 @code{void _declspec(dllexport) initspam(void)} 或 @code{PyObject _declspec(dllexport) *NiGetSpamData(void)} 中一样。

Developer Studio 将加入大量你并不真正需要的导入库，使你的可执行文件大小增加 100K。 要摆脱它们，请使用项目设置对话框的链接选项卡指定 @emph{忽略默认库}。 将正确的 @code{msvcrtxx.lib} 添加到库列表中。

@node 在更大的应用程序中嵌入 CPython 运行时,,不使用第三方工具创建扩展,扩展和嵌入 Python 解释器
@anchor{extending/index embedding-the-cpython-runtime-in-a-larger-application}@anchor{3b28}
@section 在更大的应用程序中嵌入 CPython 运行时


有时，不是要创建在 Python 解释器中作为主应用程序运行的扩展，而是希望将 CPython 运行时嵌入到更大的应用程序中。 本节介绍了成功完成此操作所涉及的一些细节。

@menu
* 在其它应用程序嵌入 Python:: 

@end menu

@node 在其它应用程序嵌入 Python,,,在更大的应用程序中嵌入 CPython 运行时
@anchor{extending/embedding doc}@anchor{3b29}@anchor{extending/embedding embedding}@anchor{3b2a}@anchor{extending/embedding embedding-python-in-another-application}@anchor{3b2b}
@subsection 在其它应用程序嵌入 Python


The previous chapters discussed how to extend Python, that is, how to extend the
functionality of Python by attaching a library of C functions to it.  It is also
possible to do it the other way around: enrich your C/C++ application by
embedding Python in it.  Embedding provides your application with the ability to
implement some of the functionality of your application in Python rather than C
or C++. This can be used for many purposes; one example would be to allow users
to tailor the application to their needs by writing some scripts in Python.  You
can also use it yourself if some of the functionality can be written in Python
more easily.

Embedding Python is similar to extending it, but not quite.  The difference is
that when you extend Python, the main program of the application is still the
Python interpreter, while if you embed Python, the main program may have nothing
to do with Python --- instead, some parts of the application occasionally call
the Python interpreter to run some Python code.

So if you are embedding Python, you are providing your own main program.  One of
the things this main program has to do is initialize the Python interpreter.  At
the very least, you have to call the function @ref{433,,Py_Initialize()}.  There are
optional calls to pass command line arguments to Python.  Then later you can
call the interpreter from any part of the application.

There are several different ways to call the interpreter: you can pass a string
containing Python statements to @ref{3b2c,,PyRun_SimpleString()}, or you can pass a
stdio file pointer and a file name (for identification in error messages only)
to @ref{3b2d,,PyRun_SimpleFile()}.  You can also call the lower-level operations
described in the previous chapters to construct and use Python objects.


@subsubheading 参见



@table @asis

@item @ref{1192,,Python/C API 参考手册}

The details of Python's C interface are given in this manual. A great deal of
necessary information can be found here.
@end table


@menu
* Very High Level Embedding:: 
* Beyond Very High Level Embedding; An overview: Beyond Very High Level Embedding An overview. 
* 纯嵌入:: 
* Extending Embedded Python:: 
* 在 C++ 中嵌入 Python:: 
* 在类 Unix 系统中编译和链接:: 

@end menu

@node Very High Level Embedding,Beyond Very High Level Embedding An overview,,在其它应用程序嵌入 Python
@anchor{extending/embedding high-level-embedding}@anchor{3b2e}@anchor{extending/embedding very-high-level-embedding}@anchor{3b2f}
@subsubsection Very High Level Embedding


The simplest form of embedding Python is the use of the very high level
interface. This interface is intended to execute a Python script without needing
to interact with the application directly. This can for example be used to
perform some operation on a file.

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>

int
main(int argc, char *argv[])
@{
    wchar_t *program = Py_DecodeLocale(argv[0], NULL);
    if (program == NULL) @{
        fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
        exit(1);
    @}
    Py_SetProgramName(program);  /* optional but recommended */
    Py_Initialize();
    PyRun_SimpleString("from time import time,ctime\n"
                       "print('Today is', ctime(time()))\n");
    if (Py_FinalizeEx() < 0) @{
        exit(120);
    @}
    PyMem_RawFree(program);
    return 0;
@}
@end example

The @ref{f18,,Py_SetProgramName()} function should be called before
@ref{433,,Py_Initialize()} to inform the interpreter about paths to Python run-time
libraries.  Next, the Python interpreter is initialized with
@ref{433,,Py_Initialize()}, followed by the execution of a hard-coded Python script
that prints the date and time.  Afterwards, the @ref{5c4,,Py_FinalizeEx()} call shuts
the interpreter down, followed by the end of the program.  In a real program,
you may want to get the Python script from another source, perhaps a text-editor
routine, a file, or a database.  Getting the Python code from a file can better
be done by using the @ref{3b2d,,PyRun_SimpleFile()} function, which saves you the
trouble of allocating memory space and loading the file contents.

@node Beyond Very High Level Embedding An overview,纯嵌入,Very High Level Embedding,在其它应用程序嵌入 Python
@anchor{extending/embedding beyond-very-high-level-embedding-an-overview}@anchor{3b30}@anchor{extending/embedding lower-level-embedding}@anchor{3b31}
@subsubsection Beyond Very High Level Embedding: An overview


The high level interface gives you the ability to execute arbitrary pieces of
Python code from your application, but exchanging data values is quite
cumbersome to say the least. If you want that, you should use lower level calls.
At the cost of having to write more C code, you can achieve almost anything.

It should be noted that extending Python and embedding Python is quite the same
activity, despite the different intent. Most topics discussed in the previous
chapters are still valid. To show this, consider what the extension code from
Python to C really does:


@enumerate 

@item 
转换 Python 的数据值到 C,

@item 
Perform a function call to a C routine using the converted values, and

@item 
Convert the data values from the call from C to Python.
@end enumerate

When embedding Python, the interface code does:


@enumerate 

@item 
转换 C 的数据值到 Python,

@item 
Perform a function call to a Python interface routine using the converted
values, and

@item 
Convert the data values from the call from Python to C.
@end enumerate

As you can see, the data conversion steps are simply swapped to accommodate the
different direction of the cross-language transfer. The only difference is the
routine that you call between both data conversions. When extending, you call a
C routine, when embedding, you call a Python routine.

This chapter will not discuss how to convert data from Python to C and vice
versa.  Also, proper use of references and dealing with errors is assumed to be
understood.  Since these aspects do not differ from extending the interpreter,
you can refer to earlier chapters for the required information.

@node 纯嵌入,Extending Embedded Python,Beyond Very High Level Embedding An overview,在其它应用程序嵌入 Python
@anchor{extending/embedding id1}@anchor{3b32}@anchor{extending/embedding pure-embedding}@anchor{3b33}
@subsubsection 纯嵌入


The first program aims to execute a function in a Python script. Like in the
section about the very high level interface, the Python interpreter does not
directly interact with the application (but that will change in the next
section).

The code to run a function defined in a Python script is:

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>

int
main(int argc, char *argv[])
@{
    PyObject *pName, *pModule, *pFunc;
    PyObject *pArgs, *pValue;
    int i;

    if (argc < 3) @{
        fprintf(stderr,"Usage: call pythonfile funcname [args]\n");
        return 1;
    @}

    Py_Initialize();
    pName = PyUnicode_DecodeFSDefault(argv[1]);
    /* Error checking of pName left out */

    pModule = PyImport_Import(pName);
    Py_DECREF(pName);

    if (pModule != NULL) @{
        pFunc = PyObject_GetAttrString(pModule, argv[2]);
        /* pFunc is a new reference */

        if (pFunc && PyCallable_Check(pFunc)) @{
            pArgs = PyTuple_New(argc - 3);
            for (i = 0; i < argc - 3; ++i) @{
                pValue = PyLong_FromLong(atoi(argv[i + 3]));
                if (!pValue) @{
                    Py_DECREF(pArgs);
                    Py_DECREF(pModule);
                    fprintf(stderr, "Cannot convert argument\n");
                    return 1;
                @}
                /* pValue reference stolen here: */
                PyTuple_SetItem(pArgs, i, pValue);
            @}
            pValue = PyObject_CallObject(pFunc, pArgs);
            Py_DECREF(pArgs);
            if (pValue != NULL) @{
                printf("Result of call: %ld\n", PyLong_AsLong(pValue));
                Py_DECREF(pValue);
            @}
            else @{
                Py_DECREF(pFunc);
                Py_DECREF(pModule);
                PyErr_Print();
                fprintf(stderr,"Call failed\n");
                return 1;
            @}
        @}
        else @{
            if (PyErr_Occurred())
                PyErr_Print();
            fprintf(stderr, "Cannot find function \"%s\"\n", argv[2]);
        @}
        Py_XDECREF(pFunc);
        Py_DECREF(pModule);
    @}
    else @{
        PyErr_Print();
        fprintf(stderr, "Failed to load \"%s\"\n", argv[1]);
        return 1;
    @}
    if (Py_FinalizeEx() < 0) @{
        return 120;
    @}
    return 0;
@}
@end example

This code loads a Python script using @code{argv[1]}, and calls the function named
in @code{argv[2]}.  Its integer arguments are the other values of the @code{argv}
array.  If you @ref{3b34,,compile and link} this program (let's call
the finished executable @code{call}), and use it to execute a Python
script, such as:

@example
def multiply(a,b):
    print("Will compute", a, "times", b)
    c = 0
    for i in range(0, a):
        c = c + b
    return c
@end example

然后结果应该是:

@example
$ call multiply multiply 3 2
Will compute 3 times 2
Result of call: 6
@end example

Although the program is quite large for its functionality, most of the code is
for data conversion between Python and C, and for error reporting.  The
interesting part with respect to embedding Python starts with

@example
Py_Initialize();
pName = PyUnicode_DecodeFSDefault(argv[1]);
/* Error checking of pName left out */
pModule = PyImport_Import(pName);
@end example

After initializing the interpreter, the script is loaded using
@ref{d58,,PyImport_Import()}.  This routine needs a Python string as its argument,
which is constructed using the @ref{3b35,,PyUnicode_FromString()} data conversion
routine.

@example
pFunc = PyObject_GetAttrString(pModule, argv[2]);
/* pFunc is a new reference */

if (pFunc && PyCallable_Check(pFunc)) @{
    ...
@}
Py_XDECREF(pFunc);
@end example

Once the script is loaded, the name we're looking for is retrieved using
@ref{3ac0,,PyObject_GetAttrString()}.  If the name exists, and the object returned is
callable, you can safely assume that it is a function.  The program then
proceeds by constructing a tuple of arguments as normal.  The call to the Python
function is then made with:

@example
pValue = PyObject_CallObject(pFunc, pArgs);
@end example

Upon return of the function, @code{pValue} is either @code{NULL} or it contains a
reference to the return value of the function.  Be sure to release the reference
after examining the value.

@node Extending Embedded Python,在 C++ 中嵌入 Python,纯嵌入,在其它应用程序嵌入 Python
@anchor{extending/embedding extending-embedded-python}@anchor{3b36}@anchor{extending/embedding extending-with-embedding}@anchor{3b37}
@subsubsection Extending Embedded Python


Until now, the embedded Python interpreter had no access to functionality from
the application itself.  The Python API allows this by extending the embedded
interpreter.  That is, the embedded interpreter gets extended with routines
provided by the application. While it sounds complex, it is not so bad.  Simply
forget for a while that the application starts the Python interpreter.  Instead,
consider the application to be a set of subroutines, and write some glue code
that gives Python access to those routines, just like you would write a normal
Python extension.  For example:

@example
static int numargs=0;

/* Return the number of arguments of the application command line */
static PyObject*
emb_numargs(PyObject *self, PyObject *args)
@{
    if(!PyArg_ParseTuple(args, ":numargs"))
        return NULL;
    return PyLong_FromLong(numargs);
@}

static PyMethodDef EmbMethods[] = @{
    @{"numargs", emb_numargs, METH_VARARGS,
     "Return the number of arguments received by the process."@},
    @{NULL, NULL, 0, NULL@}
@};

static PyModuleDef EmbModule = @{
    PyModuleDef_HEAD_INIT, "emb", NULL, -1, EmbMethods,
    NULL, NULL, NULL, NULL
@};

static PyObject*
PyInit_emb(void)
@{
    return PyModule_Create(&EmbModule);
@}
@end example

Insert the above code just above the @code{main()} function. Also, insert the
following two statements before the call to @ref{433,,Py_Initialize()}:

@example
numargs = argc;
PyImport_AppendInittab("emb", &PyInit_emb);
@end example

These two lines initialize the @code{numargs} variable, and make the
@code{emb.numargs()} function accessible to the embedded Python interpreter.
With these extensions, the Python script can do things like

@example
import emb
print("Number of arguments", emb.numargs())
@end example

In a real application, the methods will expose an API of the application to
Python.

@c TODO: threads, code examples do not really behave well if errors happen
@c (what to watch out for)

@node 在 C++ 中嵌入 Python,在类 Unix 系统中编译和链接,Extending Embedded Python,在其它应用程序嵌入 Python
@anchor{extending/embedding embedding-python-in-c}@anchor{3b38}@anchor{extending/embedding embeddingincplusplus}@anchor{3b39}
@subsubsection 在 C++ 中嵌入 Python


It is also possible to embed Python in a C++ program; precisely how this is done
will depend on the details of the C++ system used; in general you will need to
write the main program in C++, and use the C++ compiler to compile and link your
program.  There is no need to recompile Python itself using C++.

@node 在类 Unix 系统中编译和链接,,在 C++ 中嵌入 Python,在其它应用程序嵌入 Python
@anchor{extending/embedding compiling}@anchor{3b34}@anchor{extending/embedding compiling-and-linking-under-unix-like-systems}@anchor{3b3a}
@subsubsection 在类 Unix 系统中编译和链接


It is not necessarily trivial to find the right flags to pass to your
compiler (and linker) in order to embed the Python interpreter into your
application, particularly because Python needs to load library modules
implemented as C dynamic extensions (@code{.so} files) linked against
it.

To find out the required compiler and linker flags, you can execute the
@code{python@emph{X.Y}-config} script which is generated as part of the
installation process (a @code{python3-config} script may also be
available).  This script has several options, of which the following will
be directly useful to you:


@itemize *

@item 
@code{pythonX.Y-config --cflags} will give you the recommended flags when
compiling:

@example
$ /opt/bin/python3.4-config --cflags
-I/opt/include/python3.4m -I/opt/include/python3.4m -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes
@end example

@item 
@code{pythonX.Y-config --ldflags} will give you the recommended flags when
linking:

@example
$ /opt/bin/python3.4-config --ldflags
-L/opt/lib/python3.4/config-3.4m -lpthread -ldl -lutil -lm -lpython3.4m -Xlinker -export-dynamic
@end example
@end itemize

@cartouche
@quotation 注解 
To avoid confusion between several Python installations (and especially
between the system Python and your own compiled Python), it is recommended
that you use the absolute path to @code{python@emph{X.Y}-config}, as in the above
example.
@end quotation
@end cartouche

If this procedure doesn't work for you (it is not guaranteed to work for
all Unix-like platforms; however, we welcome @ref{3b3b,,bug reports})
you will have to read your system's documentation about dynamic linking and/or
examine Python's @code{Makefile} (use @ref{35ec,,sysconfig.get_makefile_filename()}
to find its location) and compilation
options.  In this case, the @ref{fe,,sysconfig} module is a useful tool to
programmatically extract the configuration values that you will want to
combine together.  For example:

@example
>>> import sysconfig
>>> sysconfig.get_config_var('LIBS')
'-lpthread -ldl  -lutil'
>>> sysconfig.get_config_var('LINKFORSHARED')
'-Xlinker -export-dynamic'
@end example

@c XXX similar documentation for Windows missing

@node Python/C API 参考手册,分发 Python 模块,扩展和嵌入 Python 解释器,Top
@anchor{c-api/index doc}@anchor{3b3c}@anchor{c-api/index c-api-index}@anchor{1192}@anchor{c-api/index python-c-api-reference-manual}@anchor{3b3d}
@chapter Python/C API 参考手册


本手册描述了希望编写扩展模块并将 Python 解释器嵌入其应用程序中的 C 和 C++ 程序员可用的 API。同时可以参阅 @ref{1191,,扩展和嵌入 Python 解释器} ，其中描述了扩展编写的一般原则，但没有详细描述 API 函数。

@menu
* 概述: 概述<15>. 
* 稳定的应用程序二进制接口:: 
* The Very High Level Layer:: 
* 引用计数: 引用计数<3>. 
* 异常处理:: 
* 工具: 工具<2>. 
* 抽象对象层:: 
* 具体的对象层:: 
* Initialization@comma{} Finalization@comma{} and Threads: Initialization Finalization and Threads. 
* Python初始化配置:: 
* 内存管理:: 
* 对象实现支持:: 
* API 和 ABI 版本管理:: 

@end menu

@node 概述<15>,稳定的应用程序二进制接口,,Python/C API 参考手册
@anchor{c-api/intro doc}@anchor{3b3e}@anchor{c-api/intro api-intro}@anchor{3b3f}@anchor{c-api/intro introduction}@anchor{3b40}
@section 概述


Python 的应用编程接口（API）使得 C 和 C++ 程序员可以在多个层级上访问 Python 解释器。该 API 在 C++ 中同样可用，但为简化描述，通常将其称为 Python/C API。使用 Python/C API 有两个基本的理由。第一个理由是为了特定目的而编写 @emph{扩展模块}；它们是扩展 Python 解释器功能的 C 模块。这可能是最常见的使用场景。第二个理由是将 Python 用作更大规模应用的组件；这种技巧通常被称为在一个应用中 @emph{embedding} Python。

编写扩展模块的过程相对来说更易于理解，可以通过“菜谱”的形式分步骤介绍。使用某些工具可在一定程度上自动化这一过程。虽然人们在其他应用中嵌入 Python 的做法早已有之，但嵌入 Python 的过程没有编写扩展模块那样方便直观。

许多 API 函数在你嵌入或是扩展 Python 这两种场景下都能发挥作用；此外，大多数嵌入 Python 的应用程序也需要提供自定义扩展，因此在尝试在实际应用中嵌入 Python 之前先熟悉编写扩展应该会是个好主意。

@menu
* 代码标准:: 
* 包含文件:: 
* 有用的宏:: 
* 对象、类型和引用计数:: 
* 异常: 异常<18>. 
* 嵌入Python: 嵌入Python<2>. 
* 调试构建:: 

@end menu

@node 代码标准,包含文件,,概述<15>
@anchor{c-api/intro coding-standards}@anchor{3b41}
@subsection 代码标准


如果你想要编写可包含于 CPython 的 C 代码，你 @strong{必须} 遵循在 
@geindex Python 提高建议; PEP 7
PEP 7@footnote{https://www.python.org/dev/peps/pep-0007} 中定义的指导原则和标准。这些指导原则适用于任何你所要扩展的 Python 版本。在编写你自己的第三方扩展模块时可以不必遵循这些规范，除非你准备在日后向 Python 贡献这些模块。

@node 包含文件,有用的宏,代码标准,概述<15>
@anchor{c-api/intro api-includes}@anchor{3b42}@anchor{c-api/intro include-files}@anchor{3b43}
@subsection 包含文件


使用 Python/C API 所需要的全部函数、类型和宏定义可通过下面这行语句包含到你的代码之中：

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>
@end example

这意味着包含以下标准头文件：@code{<stdio.h>}，@code{<string.h>}，@code{<errno.h>}，@code{<limits.h>}，@code{<assert.h>} 和 @code{<stdlib.h>}（如果可用）。

@cartouche
@quotation 注解 
由于 Python 可能会定义一些能在某些系统上影响标准头文件的预处理器定义，因此在包含任何标准头文件之前，你 @emph{必须} 先包含 @code{Python.h}。

It is recommended to always define @code{PY_SSIZE_T_CLEAN} before including
@code{Python.h}.  See @ref{2d0,,解析参数并构建值变量} for a description of this macro.
@end quotation
@end cartouche

Python.h 所定义的全部用户可见名称（由包含的标准头文件所定义的除外）都带有前缀 @code{Py} 或者 @code{_Py}。以 @code{_Py} 打头的名称是供 Python 实现内部使用的，不应被扩展编写者使用。结构成员名称没有保留前缀。

@cartouche
@quotation 注解 
User code should never define names that begin with @code{Py} or @code{_Py}. This
confuses the reader, and jeopardizes the portability of the user code to
future Python versions, which may define additional names beginning with one
of these prefixes.
@end quotation
@end cartouche

头文件通常会与 Python 一起安装。在 Unix 上，它们位于以下目录：@code{@emph{prefix}/include/pythonversion/} 和 @code{@emph{exec_prefix}/include/pythonversion/}，其中 
@geindex prefix
@geindex 环境变量; prefix
@code{prefix} 和 
@geindex exec_prefix
@geindex 环境变量; exec_prefix
@code{exec_prefix} 是由向 Python 的 @code{configure} 脚本传入的对应形参所定义，而 @emph{version} 则为 @code{'%d.%d' % sys.version_info[:2]}。在 Windows 上，头文件安装于 @code{@emph{prefix}/include}，其中 
@geindex prefix
@geindex 环境变量; prefix
@code{prefix} 是向安装程序指定的安装目录。

要包含头文件，请将两个目录（如果不同）都放到你所用编译器的包含搜索路径中。请 @emph{不要} 将父目录放入搜索路径然后使用 @code{#include <pythonX.Y/Python.h>}；这将使得多平台编译不可用，因为 
@geindex prefix
@geindex 环境变量; prefix
@code{prefix} 下平台无关的头文件需要包含来自 
@geindex exec_prefix
@geindex 环境变量; exec_prefix
@code{exec_prefix} 下特定平台的头文件。

C++ users should note that although the API is defined entirely using C, the
header files properly declare the entry points to be @code{extern "C"}. As a result,
there is no need to do anything special to use the API from C++.

@node 有用的宏,对象、类型和引用计数,包含文件,概述<15>
@anchor{c-api/intro useful-macros}@anchor{3b44}
@subsection 有用的宏


Python 头文件中定义了一些有用的宏。许多是在靠近它们被使用的地方定义的（例如 @ref{dcf,,Py_RETURN_NONE}）。其他更为通用的则定义在这里。这里所显示的并不是一个完整的列表。

@geindex Py_UNREACHABLE (C 宏)
@anchor{c-api/intro c Py_UNREACHABLE}@anchor{41b}
@deffn {C 宏} Py_UNREACHABLE ()

这个可以在你有一个不打算被触及的代码路径时使用。例如，当一个 @code{switch} 语句中所有可能的值都已被 @code{case} 子句覆盖了，就可将其用在 @code{default:} 子句中。当你非常想在某个位置放一个 @code{assert(0)} 或 @code{abort()} 调用时也可以用这个。


3.7 新版功能.

@end deffn

@geindex Py_ABS (C 宏)
@anchor{c-api/intro c Py_ABS}@anchor{3b45}
@deffn {C 宏} Py_ABS (x)

返回 @code{x} 的绝对值。


3.3 新版功能.

@end deffn

@geindex Py_MIN (C 宏)
@anchor{c-api/intro c Py_MIN}@anchor{3b46}
@deffn {C 宏} Py_MIN (x, y)

返回 @code{x} 和 @code{y} 当中的最小值。


3.3 新版功能.

@end deffn

@geindex Py_MAX (C 宏)
@anchor{c-api/intro c Py_MAX}@anchor{3b47}
@deffn {C 宏} Py_MAX (x, y)

返回 @code{x} 和 @code{y} 当中的最大值。


3.3 新版功能.

@end deffn

@geindex Py_STRINGIFY (C 宏)
@anchor{c-api/intro c Py_STRINGIFY}@anchor{3b48}
@deffn {C 宏} Py_STRINGIFY (x)

将 @code{x} 转换为 C 字符串。例如 @code{Py_STRINGIFY(123)} 返回 @code{"123"}。


3.4 新版功能.

@end deffn

@geindex Py_MEMBER_SIZE (C 宏)
@anchor{c-api/intro c Py_MEMBER_SIZE}@anchor{3b49}
@deffn {C 宏} Py_MEMBER_SIZE (type, member)

返回结构 (@code{type}) @code{member} 的大小，以字节表示。


3.6 新版功能.

@end deffn

@geindex Py_CHARMASK (C 宏)
@anchor{c-api/intro c Py_CHARMASK}@anchor{3b4a}
@deffn {C 宏} Py_CHARMASK (c)

参数必须为 [-128, 127] 或 [0, 255] 范围内的字符或整数类型。这个宏将 @code{c} 强制转换为 @code{unsigned char} 返回。
@end deffn

@geindex Py_GETENV (C 宏)
@anchor{c-api/intro c Py_GETENV}@anchor{3b4b}
@deffn {C 宏} Py_GETENV (s)

Like @code{getenv(s)}, but returns @code{NULL} if @ref{f9a,,-E} was passed on the
command line (i.e. if @code{Py_IgnoreEnvironmentFlag} is set).
@end deffn

@geindex Py_UNUSED (C 宏)
@anchor{c-api/intro c Py_UNUSED}@anchor{3b4c}
@deffn {C 宏} Py_UNUSED (arg)

Use this for unused arguments in a function definition to silence compiler
warnings. Example: @code{int func(int a, int Py_UNUSED(b)) @{ return a; @}}.


3.4 新版功能.

@end deffn

@geindex Py_DEPRECATED (C 宏)
@anchor{c-api/intro c Py_DEPRECATED}@anchor{3b4d}
@deffn {C 宏} Py_DEPRECATED (version)

Use this for deprecated declarations.  The macro must be placed before the
symbol name.

示例:

@example
Py_DEPRECATED(3.8) PyAPI_FUNC(int) Py_OldFunction(void);
@end example


在 3.8 版更改: MSVC support was added.

@end deffn

@geindex PyDoc_STRVAR (C 宏)
@anchor{c-api/intro c PyDoc_STRVAR}@anchor{ebb}
@deffn {C 宏} PyDoc_STRVAR (name, str)

Creates a variable with name @code{name} that can be used in docstrings.
If Python is built without docstrings, the value will be empty.

Use @ref{ebb,,PyDoc_STRVAR} for docstrings to support building
Python without docstrings, as specified in 
@geindex Python 提高建议; PEP 7
PEP 7@footnote{https://www.python.org/dev/peps/pep-0007}.

示例:

@example
PyDoc_STRVAR(pop_doc, "Remove and return the rightmost element.");

static PyMethodDef deque_methods[] = @{
    // ...
    @{"pop", (PyCFunction)deque_pop, METH_NOARGS, pop_doc@},
    // ...
@}
@end example
@end deffn

@geindex PyDoc_STR (C 宏)
@anchor{c-api/intro c PyDoc_STR}@anchor{3b4e}
@deffn {C 宏} PyDoc_STR (str)

Creates a docstring for the given input string or an empty string
if docstrings are disabled.

Use @ref{3b4e,,PyDoc_STR} in specifying docstrings to support
building Python without docstrings, as specified in 
@geindex Python 提高建议; PEP 7
PEP 7@footnote{https://www.python.org/dev/peps/pep-0007}.

示例:

@example
static PyMethodDef pysqlite_row_methods[] = @{
    @{"keys", (PyCFunction)pysqlite_row_keys, METH_NOARGS,
        PyDoc_STR("Returns the keys of the row.")@},
    @{NULL, NULL@}
@};
@end example
@end deffn

@node 对象、类型和引用计数,异常<18>,有用的宏,概述<15>
@anchor{c-api/intro api-objects}@anchor{3b4f}@anchor{c-api/intro objects-types-and-reference-counts}@anchor{3b50}
@subsection 对象、类型和引用计数


@geindex 对象; type

大多数 Python/C API 函数都有一个或多个参数以及一个 @ref{4b5,,PyObject*} 类型的返回值。此类型是一个指针，指向表示一个任意 Python 对象的不透明数据类型。由于在大多数情况下（例如赋值、作用域规则和参数传递） Python 语言都会以同样的方式处理所有 Python 对象类型，因此它们由一个单独的 C 类型来表示是很适宜的。几乎所有 Python 对象都生存在堆上：你绝不会声明一个 @ref{4b5,,PyObject} 类型的自动或静态变量，只有 @ref{4b5,,PyObject*} 类型的指针变量可以被声明。唯一的例外是 type 对象；由于此种对象永远不能被释放，所以它们通常是静态 @ref{2d6,,PyTypeObject} 对象。

所有 Python 对象（甚至 Python 整数）都有一个 @emph{type} 和一个 @emph{reference count}。对象的类型确定它是什么类型的对象（例如整数、列表或用户定义函数；还有更多，如 @ref{13b8,,标准类型层级结构} 中所述）。对于每个众所周知的类型，都有一个宏来检查对象是否属于该类型；例如，当（且仅当） @emph{a} 所指的对象是 Python 列表时 @code{PyList_Check(a)} 为真。

@menu
* 引用计数: 引用计数<2>. 
* 类型:: 

@end menu

@node 引用计数<2>,类型,,对象、类型和引用计数
@anchor{c-api/intro api-refcounts}@anchor{3b51}@anchor{c-api/intro reference-counts}@anchor{3b52}
@subsubsection 引用计数


The reference count is important because today's computers have a  finite (and
often severely limited) memory size; it counts how many  different places there
are that have a reference to an object.  Such a  place could be another object,
or a global (or static) C variable, or  a local variable in some C function.
When an object's reference count  becomes zero, the object is deallocated.  If
it contains references to  other objects, their reference count is decremented.
Those other  objects may be deallocated in turn, if this decrement makes their
reference count become zero, and so on.  (There's an obvious problem  with
objects that reference each other here; for now, the solution is  "don't do
that.")

@geindex Py_INCREF()
@geindex Py_DECREF()

Reference counts are always manipulated explicitly.  The normal way is  to use
the macro @ref{265,,Py_INCREF()} to increment an object's reference count by one,
and @ref{266,,Py_DECREF()} to decrement it by   one.  The @ref{266,,Py_DECREF()} macro
is considerably more complex than the incref one, since it must check whether
the reference count becomes zero and then cause the object's deallocator to be
called. The deallocator is a function pointer contained in the object's type
structure.  The type-specific deallocator takes care of decrementing the
reference counts for other objects contained in the object if this is a compound
object type, such as a list, as well as performing any additional finalization
that's needed.  There's no chance that the reference count can overflow; at
least as many bits are used to hold the reference count as there are distinct
memory locations in virtual memory (assuming @code{sizeof(Py_ssize_t) >= sizeof(void*)}).
Thus, the reference count increment is a simple operation.

It is not necessary to increment an object's reference count for every  local
variable that contains a pointer to an object.  In theory, the  object's
reference count goes up by one when the variable is made to  point to it and it
goes down by one when the variable goes out of  scope.  However, these two
cancel each other out, so at the end the  reference count hasn't changed.  The
only real reason to use the  reference count is to prevent the object from being
deallocated as  long as our variable is pointing to it.  If we know that there
is at  least one other reference to the object that lives at least as long as
our variable, there is no need to increment the reference count  temporarily.
An important situation where this arises is in objects  that are passed as
arguments to C functions in an extension module  that are called from Python;
the call mechanism guarantees to hold a  reference to every argument for the
duration of the call.

However, a common pitfall is to extract an object from a list and hold on to it
for a while without incrementing its reference count. Some other operation might
conceivably remove the object from the list, decrementing its reference count
and possibly deallocating it. The real danger is that innocent-looking
operations may invoke arbitrary Python code which could do this; there is a code
path which allows control to flow back to the user from a @ref{266,,Py_DECREF()}, so
almost any operation is potentially dangerous.

A safe approach is to always use the generic operations (functions  whose name
begins with @code{PyObject_}, @code{PyNumber_}, @code{PySequence_} or @code{PyMapping_}).
These operations always increment the reference count of the object they return.
This leaves the caller with the responsibility to call @ref{266,,Py_DECREF()} when
they are done with the result; this soon becomes second nature.

@menu
* Reference Count Details:: 

@end menu

@node Reference Count Details,,,引用计数<2>
@anchor{c-api/intro api-refcountdetails}@anchor{3b53}@anchor{c-api/intro reference-count-details}@anchor{3b54}
@subsubsection Reference Count Details


The reference count behavior of functions in the Python/C API is best  explained
in terms of @emph{ownership of references}.  Ownership pertains to references, never
to objects (objects are not owned: they are always shared).  "Owning a
reference" means being responsible for calling Py_DECREF on it when the
reference is no longer needed.  Ownership can also be transferred, meaning that
the code that receives ownership of the reference then becomes responsible for
eventually decref'ing it by calling @ref{266,,Py_DECREF()} or @ref{268,,Py_XDECREF()}
when it's no longer needed---or passing on this responsibility (usually to its
caller). When a function passes ownership of a reference on to its caller, the
caller is said to receive a @emph{new} reference.  When no ownership is transferred,
the caller is said to @emph{borrow} the reference. Nothing needs to be done for a
borrowed reference.

Conversely, when a calling function passes in a reference to an  object, there
are two possibilities: the function @emph{steals} a  reference to the object, or it
does not.  @emph{Stealing a reference} means that when you pass a reference to a
function, that function assumes that it now owns that reference, and you are not
responsible for it any longer.

@geindex PyList_SetItem()
@geindex PyTuple_SetItem()

Few functions steal references; the two notable exceptions are
@ref{3ac7,,PyList_SetItem()} and @ref{3ac6,,PyTuple_SetItem()}, which  steal a reference
to the item (but not to the tuple or list into which the item is put!).  These
functions were designed to steal a reference because of a common idiom for
populating a tuple or list with newly created objects; for example, the code to
create the tuple @code{(1, 2, "three")} could look like this (forgetting about
error handling for the moment; a better way to code this is shown below):

@example
PyObject *t;

t = PyTuple_New(3);
PyTuple_SetItem(t, 0, PyLong_FromLong(1L));
PyTuple_SetItem(t, 1, PyLong_FromLong(2L));
PyTuple_SetItem(t, 2, PyUnicode_FromString("three"));
@end example

Here, @ref{3aa6,,PyLong_FromLong()} returns a new reference which is immediately
stolen by @ref{3ac6,,PyTuple_SetItem()}.  When you want to keep using an object
although the reference to it will be stolen, use @ref{265,,Py_INCREF()} to grab
another reference before calling the reference-stealing function.

Incidentally, @ref{3ac6,,PyTuple_SetItem()} is the @emph{only} way to set tuple items;
@ref{fe2,,PySequence_SetItem()} and @ref{3b55,,PyObject_SetItem()} refuse to do this
since tuples are an immutable data type.  You should only use
@ref{3ac6,,PyTuple_SetItem()} for tuples that you are creating yourself.

Equivalent code for populating a list can be written using @ref{3b56,,PyList_New()}
and @ref{3ac7,,PyList_SetItem()}.

However, in practice, you will rarely use these ways of creating and populating
a tuple or list.  There's a generic function, @ref{2ce,,Py_BuildValue()}, that can
create most common objects from C values, directed by a @emph{format string}.
For example, the above two blocks of code could be replaced by the following
(which also takes care of the error checking):

@example
PyObject *tuple, *list;

tuple = Py_BuildValue("(iis)", 1, 2, "three");
list = Py_BuildValue("[iis]", 1, 2, "three");
@end example

It is much more common to use @ref{3b55,,PyObject_SetItem()} and friends with items
whose references you are only borrowing, like arguments that were passed in to
the function you are writing.  In that case, their behaviour regarding reference
counts is much saner, since you don't have to increment a reference count so you
can give a reference away ("have it be stolen").  For example, this function
sets all items of a list (actually, any mutable sequence) to a given item:

@example
int
set_all(PyObject *target, PyObject *item)
@{
    Py_ssize_t i, n;

    n = PyObject_Length(target);
    if (n < 0)
        return -1;
    for (i = 0; i < n; i++) @{
        PyObject *index = PyLong_FromSsize_t(i);
        if (!index)
            return -1;
        if (PyObject_SetItem(target, index, item) < 0) @{
            Py_DECREF(index);
            return -1;
        @}
        Py_DECREF(index);
    @}
    return 0;
@}
@end example

@geindex set_all()

The situation is slightly different for function return values.   While passing
a reference to most functions does not change your  ownership responsibilities
for that reference, many functions that  return a reference to an object give
you ownership of the reference. The reason is simple: in many cases, the
returned object is created  on the fly, and the reference you get is the only
reference to the  object.  Therefore, the generic functions that return object
references, like @ref{3b57,,PyObject_GetItem()} and  @ref{fe1,,PySequence_GetItem()},
always return a new reference (the caller becomes the owner of the reference).

It is important to realize that whether you own a reference returned  by a
function depends on which function you call only --- @emph{the plumage} (the type of
the object passed as an argument to the function) @emph{doesn't enter into it!}
Thus, if you  extract an item from a list using @ref{3ac2,,PyList_GetItem()}, you
don't own the reference --- but if you obtain the same item from the same list
using @ref{fe1,,PySequence_GetItem()} (which happens to take exactly the same
arguments), you do own a reference to the returned object.

@geindex PyList_GetItem()
@geindex PySequence_GetItem()

Here is an example of how you could write a function that computes the sum of
the items in a list of integers; once using  @ref{3ac2,,PyList_GetItem()}, and once
using @ref{fe1,,PySequence_GetItem()}.

@example
long
sum_list(PyObject *list)
@{
    Py_ssize_t i, n;
    long total = 0, value;
    PyObject *item;

    n = PyList_Size(list);
    if (n < 0)
        return -1; /* Not a list */
    for (i = 0; i < n; i++) @{
        item = PyList_GetItem(list, i); /* Can't fail */
        if (!PyLong_Check(item)) continue; /* Skip non-integers */
        value = PyLong_AsLong(item);
        if (value == -1 && PyErr_Occurred())
            /* Integer too big to fit in a C long, bail out */
            return -1;
        total += value;
    @}
    return total;
@}
@end example

@geindex sum_list()

@example
long
sum_sequence(PyObject *sequence)
@{
    Py_ssize_t i, n;
    long total = 0, value;
    PyObject *item;
    n = PySequence_Length(sequence);
    if (n < 0)
        return -1; /* Has no length */
    for (i = 0; i < n; i++) @{
        item = PySequence_GetItem(sequence, i);
        if (item == NULL)
            return -1; /* Not a sequence, or other failure */
        if (PyLong_Check(item)) @{
            value = PyLong_AsLong(item);
            Py_DECREF(item);
            if (value == -1 && PyErr_Occurred())
                /* Integer too big to fit in a C long, bail out */
                return -1;
            total += value;
        @}
        else @{
            Py_DECREF(item); /* Discard reference ownership */
        @}
    @}
    return total;
@}
@end example

@geindex sum_sequence()

@node 类型,,引用计数<2>,对象、类型和引用计数
@anchor{c-api/intro api-types}@anchor{3b58}@anchor{c-api/intro types}@anchor{3b59}
@subsubsection 类型


There are few other data types that play a significant role in  the Python/C
API; most are simple C types such as @code{int},  @code{long},
@code{double} and @code{char*}.  A few structure types  are used to
describe static tables used to list the functions exported  by a module or the
data attributes of a new object type, and another is used to describe the value
of a complex number.  These will  be discussed together with the functions that
use them.

@node 异常<18>,嵌入Python<2>,对象、类型和引用计数,概述<15>
@anchor{c-api/intro api-exceptions}@anchor{3b5a}@anchor{c-api/intro exceptions}@anchor{3b5b}
@subsection 异常


Python程序员只需要处理特定需要处理的错误异常；未处理的异常会自动传递给调用者，然后传递给调用者的调用者，依此类推，直到他们到达顶级解释器，在那里将它们报告给用户并伴随堆栈回溯。

@geindex PyErr_Occurred()

For C programmers, however, error checking always has to be explicit.  All
functions in the Python/C API can raise exceptions, unless an explicit claim is
made otherwise in a function's documentation.  In general, when a function
encounters an error, it sets an exception, discards any object references that
it owns, and returns an error indicator.  If not documented otherwise, this
indicator is either @code{NULL} or @code{-1}, depending on the function's return type.
A few functions return a Boolean true/false result, with false indicating an
error.  Very few functions return no explicit error indicator or have an
ambiguous return value, and require explicit testing for errors with
@ref{3aa4,,PyErr_Occurred()}.  These exceptions are always explicitly documented.

@geindex PyErr_SetString()
@geindex PyErr_Clear()

Exception state is maintained in per-thread storage (this is  equivalent to
using global storage in an unthreaded application).  A  thread can be in one of
two states: an exception has occurred, or not. The function
@ref{3aa4,,PyErr_Occurred()} can be used to check for this: it returns a borrowed
reference to the exception type object when an exception has occurred, and
@code{NULL} otherwise.  There are a number of functions to set the exception state:
@ref{3aa1,,PyErr_SetString()} is the most common (though not the most general)
function to set the exception state, and @ref{965,,PyErr_Clear()} clears the
exception state.

The full exception state consists of three objects (all of which can  be
@code{NULL}): the exception type, the corresponding exception  value, and the
traceback.  These have the same meanings as the Python result of
@code{sys.exc_info()}; however, they are not the same: the Python objects represent
the last exception being handled by a Python  @ref{d6b,,try} ...
@ref{b37,,except} statement, while the C level exception state only exists while
an exception is being passed on between C functions until it reaches the Python
bytecode interpreter's  main loop, which takes care of transferring it to
@code{sys.exc_info()} and friends.

@geindex exc_info() (in module sys)

Note that starting with Python 1.5, the preferred, thread-safe way to access the
exception state from Python code is to call the function @ref{c58,,sys.exc_info()},
which returns the per-thread exception state for Python code.  Also, the
semantics of both ways to access the exception state have changed so that a
function which catches an exception will save and restore its thread's exception
state so as to preserve the exception state of its caller.  This prevents common
bugs in exception handling code caused by an innocent-looking function
overwriting the exception being handled; it also reduces the often unwanted
lifetime extension for objects that are referenced by the stack frames in the
traceback.

As a general principle, a function that calls another function to  perform some
task should check whether the called function raised an  exception, and if so,
pass the exception state on to its caller.  It  should discard any object
references that it owns, and return an  error indicator, but it should @emph{not} set
another exception --- that would overwrite the exception that was just raised,
and lose important information about the exact cause of the error.

@geindex sum_sequence()

A simple example of detecting exceptions and passing them on is shown in the
@code{sum_sequence()} example above.  It so happens that this example doesn't
need to clean up any owned references when it detects an error.  The following
example function shows some error cleanup.  First, to remind you why you like
Python, we show the equivalent Python code:

@example
def incr_item(dict, key):
    try:
        item = dict[key]
    except KeyError:
        item = 0
    dict[key] = item + 1
@end example

@geindex incr_item()

Here is the corresponding C code, in all its glory:

@example
int
incr_item(PyObject *dict, PyObject *key)
@{
    /* Objects all initialized to NULL for Py_XDECREF */
    PyObject *item = NULL, *const_one = NULL, *incremented_item = NULL;
    int rv = -1; /* Return value initialized to -1 (failure) */

    item = PyObject_GetItem(dict, key);
    if (item == NULL) @{
        /* Handle KeyError only: */
        if (!PyErr_ExceptionMatches(PyExc_KeyError))
            goto error;

        /* Clear the error and use zero: */
        PyErr_Clear();
        item = PyLong_FromLong(0L);
        if (item == NULL)
            goto error;
    @}
    const_one = PyLong_FromLong(1L);
    if (const_one == NULL)
        goto error;

    incremented_item = PyNumber_Add(item, const_one);
    if (incremented_item == NULL)
        goto error;

    if (PyObject_SetItem(dict, key, incremented_item) < 0)
        goto error;
    rv = 0; /* Success */
    /* Continue with cleanup code */

 error:
    /* Cleanup code, shared by success and failure path */

    /* Use Py_XDECREF() to ignore NULL references */
    Py_XDECREF(item);
    Py_XDECREF(const_one);
    Py_XDECREF(incremented_item);

    return rv; /* -1 for error, 0 for success */
@}
@end example

@geindex incr_item()

@geindex PyErr_ExceptionMatches()
@geindex PyErr_Clear()
@geindex Py_XDECREF()

This example represents an endorsed use of the @code{goto} statement  in C!
It illustrates the use of @ref{3b5c,,PyErr_ExceptionMatches()} and
@ref{965,,PyErr_Clear()} to handle specific exceptions, and the use of
@ref{268,,Py_XDECREF()} to dispose of owned references that may be @code{NULL} (note the
@code{'X'} in the name; @ref{266,,Py_DECREF()} would crash when confronted with a
@code{NULL} reference).  It is important that the variables used to hold owned
references are initialized to @code{NULL} for this to work; likewise, the proposed
return value is initialized to @code{-1} (failure) and only set to success after
the final call made is successful.

@node 嵌入Python<2>,调试构建,异常<18>,概述<15>
@anchor{c-api/intro api-embedding}@anchor{3b5d}@anchor{c-api/intro embedding-python}@anchor{3b5e}
@subsection 嵌入Python


The one important task that only embedders (as opposed to extension writers) of
the Python interpreter have to worry about is the initialization, and possibly
the finalization, of the Python interpreter.  Most functionality of the
interpreter can only be used after the interpreter has been initialized.

@geindex Py_Initialize()
@geindex 模块; builtins
@geindex 模块; __main__
@geindex 模块; sys
@geindex module; search; path
@geindex path (in module sys)

The basic initialization function is @ref{433,,Py_Initialize()}. This initializes
the table of loaded modules, and creates the fundamental modules
@ref{13,,builtins}, @ref{1,,__main__}, and @ref{fd,,sys}.  It also
initializes the module search path (@code{sys.path}).

@geindex PySys_SetArgvEx()

@ref{433,,Py_Initialize()} does not set the "script argument list"  (@code{sys.argv}).
If this variable is needed by Python code that will be executed later, it must
be set explicitly with a call to  @code{PySys_SetArgvEx(argc, argv, updatepath)}
after the call to @ref{433,,Py_Initialize()}.

On most systems (in particular, on Unix and Windows, although the details are
slightly different), @ref{433,,Py_Initialize()} calculates the module search path
based upon its best guess for the location of the standard Python interpreter
executable, assuming that the Python library is found in a fixed location
relative to the Python interpreter executable.  In particular, it looks for a
directory named @code{lib/python@emph{X.Y}} relative to the parent directory
where the executable named @code{python} is found on the shell command search
path (the environment variable 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH}).

For instance, if the Python executable is found in
@code{/usr/local/bin/python}, it will assume that the libraries are in
@code{/usr/local/lib/python@emph{X.Y}}.  (In fact, this particular path is also
the "fallback" location, used when no executable file named @code{python} is
found along 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH}.)  The user can override this behavior by setting the
environment variable 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME}, or insert additional directories in
front of the standard path by setting 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH}.

@geindex Py_SetProgramName()
@geindex Py_GetPath()
@geindex Py_GetPrefix()
@geindex Py_GetExecPrefix()
@geindex Py_GetProgramFullPath()

The embedding application can steer the search by calling
@code{Py_SetProgramName(file)} @emph{before} calling  @ref{433,,Py_Initialize()}.  Note that
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} still overrides this and 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} is still
inserted in front of the standard path.  An application that requires total
control has to provide its own implementation of @ref{3b5f,,Py_GetPath()},
@ref{3b60,,Py_GetPrefix()}, @ref{3b61,,Py_GetExecPrefix()}, and
@ref{275,,Py_GetProgramFullPath()} (all defined in @code{Modules/getpath.c}).

@geindex Py_IsInitialized()

Sometimes, it is desirable to "uninitialize" Python.  For instance,  the
application may want to start over (make another call to
@ref{433,,Py_Initialize()}) or the application is simply done with its  use of
Python and wants to free memory allocated by Python.  This can be accomplished
by calling @ref{5c4,,Py_FinalizeEx()}.  The function @ref{3b62,,Py_IsInitialized()} returns
true if Python is currently in the initialized state.  More information about
these functions is given in a later chapter. Notice that @ref{5c4,,Py_FinalizeEx()}
does @emph{not} free all memory allocated by the Python interpreter, e.g. memory
allocated by extension modules currently cannot be released.

@node 调试构建,,嵌入Python<2>,概述<15>
@anchor{c-api/intro api-debugging}@anchor{3b63}@anchor{c-api/intro debugging-builds}@anchor{3b64}
@subsection 调试构建


Python can be built with several macros to enable extra checks of the
interpreter and extension modules.  These checks tend to add a large amount of
overhead to the runtime so they are not enabled by default.

A full list of the various types of debugging builds is in the file
@code{Misc/SpecialBuilds.txt} in the Python source distribution. Builds are
available that support tracing of reference counts, debugging the memory
allocator, or low-level profiling of the main interpreter loop.  Only the most
frequently-used builds will be described in the remainder of this section.

Compiling the interpreter with the @code{Py_DEBUG} macro defined produces
what is generally meant by "a debug build" of Python. @code{Py_DEBUG} is
enabled in the Unix build by adding @code{--with-pydebug} to the
@code{./configure} command.  It is also implied by the presence of the
not-Python-specific @code{_DEBUG} macro.  When @code{Py_DEBUG} is enabled
in the Unix build, compiler optimization is disabled.

除了前面描述的引用计数调试之外，还执行以下额外检查：


@itemize *

@item 
额外检查将添加到对象分配器。

@item 
额外的检查将添加到解析器和编译器中。

@item 
Downcasts from wide types to narrow types are checked for loss of information.

@item 
许多断言被添加到字典和集合实现中。另外，集合对象包含 @code{test_c_api()} 方法。

@item 
添加输入参数的完整性检查到框架创建中。

@item 
使用已知的无效模式初始化整型的存储，以捕获对未初始化数字的引用。

@item 
添加底层跟踪和额外的异常检查到虚拟机的运行时中。

@item 
Extra checks are added to the memory arena implementation.

@item 
添加额外调试到线程模块。
@end itemize

这里可能没有提到的额外的检查。

Defining @code{Py_TRACE_REFS} enables reference tracing.  When defined, a
circular doubly linked list of active objects is maintained by adding two extra
fields to every @ref{4b5,,PyObject}.  Total allocations are tracked as well.  Upon
exit, all existing references are printed.  (In interactive mode this happens
after every statement run by the interpreter.)  Implied by @code{Py_DEBUG}.

有关更多详细信息，请参阅Python源代码中的 @code{Misc/SpecialBuilds.txt} 。

@node 稳定的应用程序二进制接口,The Very High Level Layer,概述<15>,Python/C API 参考手册
@anchor{c-api/stable doc}@anchor{3b65}@anchor{c-api/stable stable}@anchor{3b66}@anchor{c-api/stable stable-application-binary-interface}@anchor{3b67}
@section 稳定的应用程序二进制接口


传统上，Python的C API将随每个版本而变化。大多数更改都与源代码兼容，通常只添加API，而不是更改现有API或删除API（尽管某些接口会首先弃用然后再删除）。

不幸的是，API兼容性没有扩展到二进制兼容性（ABI）。原因主要是结构定义的演变，在这里添加新字段或更改字段类型可能不会破坏API，但可能会破坏ABI。因此，每个Python版本都需要重新编译扩展模块（即使在未使用任何受影响的接口的情况下，Unix上也可能会出现异常）。此外，在Windows上，扩展模块与特定的pythonXY.dll链接，需要重新编译才能与新的pythonXY.dll链接。

从Python3.2起，已经声明了一个API的子集，以确保稳定的ABI。如果使用此API（也被称为“受限API”）的扩展模块需要定义`@w{`}Py_LIMITED_API`@w{`}。许多解释器细节将从扩展模块中隐藏;  反过来，在任何3.x版本（x>=2）上构建的模块都不需要重新编译

在某些情况下，需要添加新函数来扩展稳定版 ABI。希望使用这些新 API 的扩展模块需要将 @code{Py_LIMITED_API} 设置为他们想要支持的最低 Python 版本的 @code{PY_VERSION_HEX} 值（例如： Python 3.3 为 @code{0x03030000}）（参见 @ref{35db,,API 和 ABI 版本管理}）。此类模块将适用于所有后续 Python版本，但无法在旧版本上加载（因为缺少符号）。

从Python 3.2开始，受限API可用的函数集记录在 
@geindex Python 提高建议; PEP 384
PEP 384@footnote{https://www.python.org/dev/peps/pep-0384} 。在C API文档中，不属于受限API的API元素标记为 “不属于受限API” 。

@node The Very High Level Layer,引用计数<3>,稳定的应用程序二进制接口,Python/C API 参考手册
@anchor{c-api/veryhigh doc}@anchor{3b68}@anchor{c-api/veryhigh the-very-high-level-layer}@anchor{3b69}@anchor{c-api/veryhigh veryhigh}@anchor{3b6a}
@section The Very High Level Layer


The functions in this chapter will let you execute Python source code given in a
file or a buffer, but they will not let you interact in a more detailed way with
the interpreter.

Several of these functions accept a start symbol from the grammar as a
parameter.  The available start symbols are @code{Py_eval_input},
@code{Py_file_input}, and @code{Py_single_input}.  These are described
following the functions which accept them as parameters.

Note also that several of these functions take @code{FILE*} parameters.  One
particular issue which needs to be handled carefully is that the @code{FILE}
structure for different C libraries can be different and incompatible.  Under
Windows (at least), it is possible for dynamically linked extensions to actually
use different libraries, so care should be taken that @code{FILE*} parameters
are only passed to these functions if it is certain that they were created by
the same library that the Python runtime is using.

@geindex Py_Main (C 函数)
@anchor{c-api/veryhigh c Py_Main}@anchor{4b2}
@deffn {C 函数} int Py_Main (int@w{ }argc, wchar_t@w{ }**argv)

The main program for the standard interpreter.  This is made available for
programs which embed Python.  The @emph{argc} and @emph{argv} parameters should be
prepared exactly as those which are passed to a C program's @code{main()}
function (converted to wchar_t according to the user's locale).  It is
important to note that the argument list may be modified (but the contents of
the strings pointed to by the argument list are not). The return value will
be @code{0} if the interpreter exits normally (i.e., without an exception),
@code{1} if the interpreter exits due to an exception, or @code{2} if the parameter
list does not represent a valid Python command line.

Note that if an otherwise unhandled @ref{5f7,,SystemExit} is raised, this
function will not return @code{1}, but exit the process, as long as
@code{Py_InspectFlag} is not set.
@end deffn

@geindex Py_BytesMain (C 函数)
@anchor{c-api/veryhigh c Py_BytesMain}@anchor{176}
@deffn {C 函数} int Py_BytesMain (int@w{ }argc, char@w{ }**argv)

Similar to @ref{4b2,,Py_Main()} but @emph{argv} is an array of bytes strings.


3.8 新版功能.

@end deffn

@geindex PyRun_AnyFile (C 函数)
@anchor{c-api/veryhigh c PyRun_AnyFile}@anchor{3b6b}
@deffn {C 函数} int PyRun_AnyFile (FILE@w{ }*fp, const char@w{ }*filename)

This is a simplified interface to @ref{3b6c,,PyRun_AnyFileExFlags()} below, leaving
@emph{closeit} set to @code{0} and @emph{flags} set to @code{NULL}.
@end deffn

@geindex PyRun_AnyFileFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_AnyFileFlags}@anchor{3b6d}
@deffn {C 函数} int PyRun_AnyFileFlags (FILE@w{ }*fp, const char@w{ }*filename, PyCompilerFlags@w{ }*flags)

This is a simplified interface to @ref{3b6c,,PyRun_AnyFileExFlags()} below, leaving
the @emph{closeit} argument set to @code{0}.
@end deffn

@geindex PyRun_AnyFileEx (C 函数)
@anchor{c-api/veryhigh c PyRun_AnyFileEx}@anchor{3b6e}
@deffn {C 函数} int PyRun_AnyFileEx (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }closeit)

This is a simplified interface to @ref{3b6c,,PyRun_AnyFileExFlags()} below, leaving
the @emph{flags} argument set to @code{NULL}.
@end deffn

@geindex PyRun_AnyFileExFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_AnyFileExFlags}@anchor{3b6c}
@deffn {C 函数} int PyRun_AnyFileExFlags (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }closeit, PyCompilerFlags@w{ }*flags)

If @emph{fp} refers to a file associated with an interactive device (console or
terminal input or Unix pseudo-terminal), return the value of
@ref{3b6f,,PyRun_InteractiveLoop()}, otherwise return the result of
@ref{3b2d,,PyRun_SimpleFile()}.  @emph{filename} is decoded from the filesystem
encoding (@ref{4f0,,sys.getfilesystemencoding()}).  If @emph{filename} is @code{NULL}, this
function uses @code{"???"} as the filename.
@end deffn

@geindex PyRun_SimpleString (C 函数)
@anchor{c-api/veryhigh c PyRun_SimpleString}@anchor{3b2c}
@deffn {C 函数} int PyRun_SimpleString (const char@w{ }*command)

This is a simplified interface to @ref{3b70,,PyRun_SimpleStringFlags()} below,
leaving the @ref{2cc,,PyCompilerFlags}* argument set to @code{NULL}.
@end deffn

@geindex PyRun_SimpleStringFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_SimpleStringFlags}@anchor{3b70}
@deffn {C 函数} int PyRun_SimpleStringFlags (const char@w{ }*command, PyCompilerFlags@w{ }*flags)

Executes the Python source code from @emph{command} in the @ref{1,,__main__} module
according to the @emph{flags} argument. If @ref{1,,__main__} does not already exist, it
is created.  Returns @code{0} on success or @code{-1} if an exception was raised.  If
there was an error, there is no way to get the exception information. For the
meaning of @emph{flags}, see below.

Note that if an otherwise unhandled @ref{5f7,,SystemExit} is raised, this
function will not return @code{-1}, but exit the process, as long as
@code{Py_InspectFlag} is not set.
@end deffn

@geindex PyRun_SimpleFile (C 函数)
@anchor{c-api/veryhigh c PyRun_SimpleFile}@anchor{3b2d}
@deffn {C 函数} int PyRun_SimpleFile (FILE@w{ }*fp, const char@w{ }*filename)

This is a simplified interface to @ref{fa2,,PyRun_SimpleFileExFlags()} below,
leaving @emph{closeit} set to @code{0} and @emph{flags} set to @code{NULL}.
@end deffn

@geindex PyRun_SimpleFileEx (C 函数)
@anchor{c-api/veryhigh c PyRun_SimpleFileEx}@anchor{3b71}
@deffn {C 函数} int PyRun_SimpleFileEx (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }closeit)

This is a simplified interface to @ref{fa2,,PyRun_SimpleFileExFlags()} below,
leaving @emph{flags} set to @code{NULL}.
@end deffn

@geindex PyRun_SimpleFileExFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_SimpleFileExFlags}@anchor{fa2}
@deffn {C 函数} int PyRun_SimpleFileExFlags (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }closeit, PyCompilerFlags@w{ }*flags)

Similar to @ref{3b70,,PyRun_SimpleStringFlags()}, but the Python source code is read
from @emph{fp} instead of an in-memory string. @emph{filename} should be the name of
the file, it is decoded from the filesystem encoding
(@ref{4f0,,sys.getfilesystemencoding()}).  If @emph{closeit} is true, the file is
closed before PyRun_SimpleFileExFlags returns.

@cartouche
@quotation 注解 
On Windows, @emph{fp} should be opened as binary mode (e.g. @code{fopen(filename, "rb")}.
Otherwise, Python may not handle script file with LF line ending correctly.
@end quotation
@end cartouche
@end deffn

@geindex PyRun_InteractiveOne (C 函数)
@anchor{c-api/veryhigh c PyRun_InteractiveOne}@anchor{3b72}
@deffn {C 函数} int PyRun_InteractiveOne (FILE@w{ }*fp, const char@w{ }*filename)

This is a simplified interface to @ref{3b73,,PyRun_InteractiveOneFlags()} below,
leaving @emph{flags} set to @code{NULL}.
@end deffn

@geindex PyRun_InteractiveOneFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_InteractiveOneFlags}@anchor{3b73}
@deffn {C 函数} int PyRun_InteractiveOneFlags (FILE@w{ }*fp, const char@w{ }*filename, PyCompilerFlags@w{ }*flags)

Read and execute a single statement from a file associated with an
interactive device according to the @emph{flags} argument.  The user will be
prompted using @code{sys.ps1} and @code{sys.ps2}.  @emph{filename} is decoded from the
filesystem encoding (@ref{4f0,,sys.getfilesystemencoding()}).

Returns @code{0} when the input was
executed successfully, @code{-1} if there was an exception, or an error code
from the @code{errcode.h} include file distributed as part of Python if
there was a parse error.  (Note that @code{errcode.h} is not included by
@code{Python.h}, so must be included specifically if needed.)
@end deffn

@geindex PyRun_InteractiveLoop (C 函数)
@anchor{c-api/veryhigh c PyRun_InteractiveLoop}@anchor{3b6f}
@deffn {C 函数} int PyRun_InteractiveLoop (FILE@w{ }*fp, const char@w{ }*filename)

This is a simplified interface to @ref{3b74,,PyRun_InteractiveLoopFlags()} below,
leaving @emph{flags} set to @code{NULL}.
@end deffn

@geindex PyRun_InteractiveLoopFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_InteractiveLoopFlags}@anchor{3b74}
@deffn {C 函数} int PyRun_InteractiveLoopFlags (FILE@w{ }*fp, const char@w{ }*filename, PyCompilerFlags@w{ }*flags)

Read and execute statements from a file associated with an interactive device
until EOF is reached.  The user will be prompted using @code{sys.ps1} and
@code{sys.ps2}.  @emph{filename} is decoded from the filesystem encoding
(@ref{4f0,,sys.getfilesystemencoding()}).  Returns @code{0} at EOF or a negative
number upon failure.
@end deffn

@geindex PyOS_InputHook (C 变量)
@anchor{c-api/veryhigh c PyOS_InputHook}@anchor{3b75}
@deffn {C 变量} int (*PyOS_InputHook) (void)

Can be set to point to a function with the prototype
@code{int func(void)}.  The function will be called when Python's
interpreter prompt is about to become idle and wait for user input
from the terminal.  The return value is ignored.  Overriding this
hook can be used to integrate the interpreter's prompt with other
event loops, as done in the @code{Modules/_tkinter.c} in the
Python source code.
@end deffn

@geindex PyOS_ReadlineFunctionPointer (C 变量)
@anchor{c-api/veryhigh c PyOS_ReadlineFunctionPointer}@anchor{966}
@deffn {C 变量} char* (*PyOS_ReadlineFunctionPointer) (FILE@w{ }*, FILE@w{ }*, const char@w{ }*)

Can be set to point to a function with the prototype
@code{char *func(FILE *stdin, FILE *stdout, char *prompt)},
overriding the default function used to read a single line of input
at the interpreter's prompt.  The function is expected to output
the string @emph{prompt} if it's not @code{NULL}, and then read a line of
input from the provided standard input file, returning the
resulting string.  For example, The @ref{de,,readline} module sets
this hook to provide line-editing and tab-completion features.

The result must be a string allocated by @ref{967,,PyMem_RawMalloc()} or
@ref{968,,PyMem_RawRealloc()}, or @code{NULL} if an error occurred.


在 3.4 版更改: The result must be allocated by @ref{967,,PyMem_RawMalloc()} or
@ref{968,,PyMem_RawRealloc()}, instead of being allocated by
@ref{4ff,,PyMem_Malloc()} or @ref{969,,PyMem_Realloc()}.

@end deffn

@geindex PyParser_SimpleParseString (C 函数)
@anchor{c-api/veryhigh c PyParser_SimpleParseString}@anchor{3b76}
@deffn {C 函数} struct _node* PyParser_SimpleParseString (const char@w{ }*str, int@w{ }start)

This is a simplified interface to
@ref{3b77,,PyParser_SimpleParseStringFlagsFilename()} below, leaving  @emph{filename} set
to @code{NULL} and @emph{flags} set to @code{0}.
@end deffn

@geindex PyParser_SimpleParseStringFlags (C 函数)
@anchor{c-api/veryhigh c PyParser_SimpleParseStringFlags}@anchor{3b78}
@deffn {C 函数} struct _node* PyParser_SimpleParseStringFlags (const char@w{ }*str, int@w{ }start, int@w{ }flags)

This is a simplified interface to
@ref{3b77,,PyParser_SimpleParseStringFlagsFilename()} below, leaving  @emph{filename} set
to @code{NULL}.
@end deffn

@geindex PyParser_SimpleParseStringFlagsFilename (C 函数)
@anchor{c-api/veryhigh c PyParser_SimpleParseStringFlagsFilename}@anchor{3b77}
@deffn {C 函数} struct _node* PyParser_SimpleParseStringFlagsFilename (const char@w{ }*str, const char@w{ }*filename, int@w{ }start, int@w{ }flags)

Parse Python source code from @emph{str} using the start token @emph{start} according to
the @emph{flags} argument.  The result can be used to create a code object which can
be evaluated efficiently. This is useful if a code fragment must be evaluated
many times. @emph{filename} is decoded from the filesystem encoding
(@ref{4f0,,sys.getfilesystemencoding()}).
@end deffn

@geindex PyParser_SimpleParseFile (C 函数)
@anchor{c-api/veryhigh c PyParser_SimpleParseFile}@anchor{3b79}
@deffn {C 函数} struct _node* PyParser_SimpleParseFile (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }start)

This is a simplified interface to @ref{3b7a,,PyParser_SimpleParseFileFlags()} below,
leaving @emph{flags} set to @code{0}.
@end deffn

@geindex PyParser_SimpleParseFileFlags (C 函数)
@anchor{c-api/veryhigh c PyParser_SimpleParseFileFlags}@anchor{3b7a}
@deffn {C 函数} struct _node* PyParser_SimpleParseFileFlags (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }start, int@w{ }flags)

Similar to @ref{3b77,,PyParser_SimpleParseStringFlagsFilename()}, but the Python
source code is read from @emph{fp} instead of an in-memory string.
@end deffn

@geindex PyRun_String (C 函数)
@anchor{c-api/veryhigh c PyRun_String}@anchor{f43}
@deffn {C 函数} PyObject* PyRun_String (const char@w{ }*str, int@w{ }start, PyObject@w{ }*globals, PyObject@w{ }*locals)
@emph{Return value: New reference.}
This is a simplified interface to @ref{3b7b,,PyRun_StringFlags()} below, leaving
@emph{flags} set to @code{NULL}.
@end deffn

@geindex PyRun_StringFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_StringFlags}@anchor{3b7b}
@deffn {C 函数} PyObject* PyRun_StringFlags (const char@w{ }*str, int@w{ }start, PyObject@w{ }*globals, PyObject@w{ }*locals, PyCompilerFlags@w{ }*flags)
@emph{Return value: New reference.}
Execute Python source code from @emph{str} in the context specified by the
objects @emph{globals} and @emph{locals} with the compiler flags specified by
@emph{flags}.  @emph{globals} must be a dictionary; @emph{locals} can be any object
that implements the mapping protocol.  The parameter @emph{start} specifies
the start token that should be used to parse the source code.

Returns the result of executing the code as a Python object, or @code{NULL} if an
exception was raised.
@end deffn

@geindex PyRun_File (C 函数)
@anchor{c-api/veryhigh c PyRun_File}@anchor{3b7c}
@deffn {C 函数} PyObject* PyRun_File (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }start, PyObject@w{ }*globals, PyObject@w{ }*locals)
@emph{Return value: New reference.}
This is a simplified interface to @ref{3b7d,,PyRun_FileExFlags()} below, leaving
@emph{closeit} set to @code{0} and @emph{flags} set to @code{NULL}.
@end deffn

@geindex PyRun_FileEx (C 函数)
@anchor{c-api/veryhigh c PyRun_FileEx}@anchor{3b7e}
@deffn {C 函数} PyObject* PyRun_FileEx (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }start, PyObject@w{ }*globals, PyObject@w{ }*locals, int@w{ }closeit)
@emph{Return value: New reference.}
This is a simplified interface to @ref{3b7d,,PyRun_FileExFlags()} below, leaving
@emph{flags} set to @code{NULL}.
@end deffn

@geindex PyRun_FileFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_FileFlags}@anchor{3b7f}
@deffn {C 函数} PyObject* PyRun_FileFlags (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }start, PyObject@w{ }*globals, PyObject@w{ }*locals, PyCompilerFlags@w{ }*flags)
@emph{Return value: New reference.}
This is a simplified interface to @ref{3b7d,,PyRun_FileExFlags()} below, leaving
@emph{closeit} set to @code{0}.
@end deffn

@geindex PyRun_FileExFlags (C 函数)
@anchor{c-api/veryhigh c PyRun_FileExFlags}@anchor{3b7d}
@deffn {C 函数} PyObject* PyRun_FileExFlags (FILE@w{ }*fp, const char@w{ }*filename, int@w{ }start, PyObject@w{ }*globals, PyObject@w{ }*locals, int@w{ }closeit, PyCompilerFlags@w{ }*flags)
@emph{Return value: New reference.}
Similar to @ref{3b7b,,PyRun_StringFlags()}, but the Python source code is read from
@emph{fp} instead of an in-memory string. @emph{filename} should be the name of the file,
it is decoded from the filesystem encoding (@ref{4f0,,sys.getfilesystemencoding()}).
If @emph{closeit} is true, the file is closed before @ref{3b7d,,PyRun_FileExFlags()}
returns.
@end deffn

@geindex Py_CompileString (C 函数)
@anchor{c-api/veryhigh c Py_CompileString}@anchor{3b80}
@deffn {C 函数} PyObject* Py_CompileString (const char@w{ }*str, const char@w{ }*filename, int@w{ }start)
@emph{Return value: New reference.}
This is a simplified interface to @ref{3b81,,Py_CompileStringFlags()} below, leaving
@emph{flags} set to @code{NULL}.
@end deffn

@geindex Py_CompileStringFlags (C 函数)
@anchor{c-api/veryhigh c Py_CompileStringFlags}@anchor{3b81}
@deffn {C 函数} PyObject* Py_CompileStringFlags (const char@w{ }*str, const char@w{ }*filename, int@w{ }start, PyCompilerFlags@w{ }*flags)
@emph{Return value: New reference.}
This is a simplified interface to @ref{3b82,,Py_CompileStringExFlags()} below, with
@emph{optimize} set to @code{-1}.
@end deffn

@geindex Py_CompileStringObject (C 函数)
@anchor{c-api/veryhigh c Py_CompileStringObject}@anchor{3b83}
@deffn {C 函数} PyObject* Py_CompileStringObject (const char@w{ }*str, PyObject@w{ }*filename, int@w{ }start, PyCompilerFlags@w{ }*flags, int@w{ }optimize)
@emph{Return value: New reference.}
Parse and compile the Python source code in @emph{str}, returning the resulting code
object.  The start token is given by @emph{start}; this can be used to constrain the
code which can be compiled and should be @code{Py_eval_input},
@code{Py_file_input}, or @code{Py_single_input}.  The filename specified by
@emph{filename} is used to construct the code object and may appear in tracebacks or
@ref{452,,SyntaxError} exception messages.  This returns @code{NULL} if the code
cannot be parsed or compiled.

The integer @emph{optimize} specifies the optimization level of the compiler; a
value of @code{-1} selects the optimization level of the interpreter as given by
@ref{685,,-O} options.  Explicit levels are @code{0} (no optimization;
@code{__debug__} is true), @code{1} (asserts are removed, @code{__debug__} is false)
or @code{2} (docstrings are removed too).


3.4 新版功能.

@end deffn

@geindex Py_CompileStringExFlags (C 函数)
@anchor{c-api/veryhigh c Py_CompileStringExFlags}@anchor{3b82}
@deffn {C 函数} PyObject* Py_CompileStringExFlags (const char@w{ }*str, const char@w{ }*filename, int@w{ }start, PyCompilerFlags@w{ }*flags, int@w{ }optimize)
@emph{Return value: New reference.}
Like @ref{3b83,,Py_CompileStringObject()}, but @emph{filename} is a byte string
decoded from the filesystem encoding (@ref{4e8,,os.fsdecode()}).


3.2 新版功能.

@end deffn

@geindex PyEval_EvalCode (C 函数)
@anchor{c-api/veryhigh c PyEval_EvalCode}@anchor{3b84}
@deffn {C 函数} PyObject* PyEval_EvalCode (PyObject@w{ }*co, PyObject@w{ }*globals, PyObject@w{ }*locals)
@emph{Return value: New reference.}
This is a simplified interface to @ref{3b85,,PyEval_EvalCodeEx()}, with just
the code object, and global and local variables.  The other arguments are
set to @code{NULL}.
@end deffn

@geindex PyEval_EvalCodeEx (C 函数)
@anchor{c-api/veryhigh c PyEval_EvalCodeEx}@anchor{3b85}
@deffn {C 函数} PyObject* PyEval_EvalCodeEx (PyObject@w{ }*co, PyObject@w{ }*globals, PyObject@w{ }*locals, PyObject *const@w{ }*args, int@w{ }argcount, PyObject *const@w{ }*kws, int@w{ }kwcount, PyObject *const@w{ }*defs, int@w{ }defcount, PyObject@w{ }*kwdefs, PyObject@w{ }*closure)
@emph{Return value: New reference.}
Evaluate a precompiled code object, given a particular environment for its
evaluation.  This environment consists of a dictionary of global variables,
a mapping object of local variables, arrays of arguments, keywords and
defaults, a dictionary of default values for @ref{2ac,,keyword-only} arguments and a closure tuple of cells.
@end deffn

@geindex PyFrameObject (C 类型)
@anchor{c-api/veryhigh c PyFrameObject}@anchor{96b}
@deffn {C 类型} PyFrameObject

The C structure of the objects used to describe frame objects. The
fields of this type are subject to change at any time.
@end deffn

@geindex PyEval_EvalFrame (C 函数)
@anchor{c-api/veryhigh c PyEval_EvalFrame}@anchor{3b86}
@deffn {C 函数} PyObject* PyEval_EvalFrame (PyFrameObject@w{ }*f)
@emph{Return value: New reference.}
Evaluate an execution frame.  This is a simplified interface to
@ref{961,,PyEval_EvalFrameEx()}, for backward compatibility.
@end deffn

@geindex PyEval_EvalFrameEx (C 函数)
@anchor{c-api/veryhigh c PyEval_EvalFrameEx}@anchor{961}
@deffn {C 函数} PyObject* PyEval_EvalFrameEx (PyFrameObject@w{ }*f, int@w{ }throwflag)
@emph{Return value: New reference.}
This is the main, unvarnished function of Python interpretation.  The code
object associated with the execution frame @emph{f} is executed, interpreting
bytecode and executing calls as needed.  The additional @emph{throwflag}
parameter can mostly be ignored - if true, then it causes an exception
to immediately be thrown; this is used for the @ref{1429,,throw()}
methods of generator objects.


在 3.4 版更改: This function now includes a debug assertion to help ensure that it
does not silently discard an active exception.

@end deffn

@geindex PyEval_MergeCompilerFlags (C 函数)
@anchor{c-api/veryhigh c PyEval_MergeCompilerFlags}@anchor{3b87}
@deffn {C 函数} int PyEval_MergeCompilerFlags (PyCompilerFlags@w{ }*cf)

This function changes the flags of the current evaluation frame, and returns
true on success, false on failure.
@end deffn

@geindex Py_eval_input (C 变量)
@anchor{c-api/veryhigh c Py_eval_input}@anchor{3b88}
@deffn {C 变量} int Py_eval_input

@geindex Py_CompileString()

The start symbol from the Python grammar for isolated expressions; for use with
@ref{3b80,,Py_CompileString()}.
@end deffn

@geindex Py_file_input (C 变量)
@anchor{c-api/veryhigh c Py_file_input}@anchor{3b89}
@deffn {C 变量} int Py_file_input

@geindex Py_CompileString()

The start symbol from the Python grammar for sequences of statements as read
from a file or other source; for use with @ref{3b80,,Py_CompileString()}.  This is
the symbol to use when compiling arbitrarily long Python source code.
@end deffn

@geindex Py_single_input (C 变量)
@anchor{c-api/veryhigh c Py_single_input}@anchor{3b8a}
@deffn {C 变量} int Py_single_input

@geindex Py_CompileString()

The start symbol from the Python grammar for a single statement; for use with
@ref{3b80,,Py_CompileString()}. This is the symbol used for the interactive
interpreter loop.
@end deffn

@geindex PyCompilerFlags (C 类型)
@anchor{c-api/veryhigh c PyCompilerFlags}@anchor{2cc}
@deffn {C 类型} struct PyCompilerFlags

This is the structure used to hold compiler flags.  In cases where code is only
being compiled, it is passed as @code{int flags}, and in cases where code is being
executed, it is passed as @code{PyCompilerFlags *flags}.  In this case, @code{from
__future__ import} can modify @emph{flags}.

Whenever @code{PyCompilerFlags *flags} is @code{NULL}, @code{cf_flags} is treated as
equal to @code{0}, and any modification due to @code{from __future__ import} is
discarded.

@geindex PyCompilerFlags.cf_flags (C 成员)
@anchor{c-api/veryhigh c PyCompilerFlags cf_flags}@anchor{3b8b}
@deffn {C 成员} int cf_flags

Compiler flags.
@end deffn

@geindex PyCompilerFlags.cf_feature_version (C 成员)
@anchor{c-api/veryhigh c PyCompilerFlags cf_feature_version}@anchor{3b8c}
@deffn {C 成员} int cf_feature_version

@emph{cf_feature_version} is the minor Python version. It should be
initialized to @code{PY_MINOR_VERSION}.

The field is ignored by default, it is used if and only if
@code{PyCF_ONLY_AST} flag is set in @emph{cf_flags}.
@end deffn


在 3.8 版更改: Added @emph{cf_feature_version} field.

@end deffn

@geindex CO_FUTURE_DIVISION (C 变量)
@anchor{c-api/veryhigh c CO_FUTURE_DIVISION}@anchor{3b8d}
@deffn {C 变量} int CO_FUTURE_DIVISION

This bit can be set in @emph{flags} to cause division operator @code{/} to be
interpreted as "true division" according to 
@geindex Python 提高建议; PEP 238
PEP 238@footnote{https://www.python.org/dev/peps/pep-0238}.
@end deffn

@node 引用计数<3>,异常处理,The Very High Level Layer,Python/C API 参考手册
@anchor{c-api/refcounting doc}@anchor{3b8e}@anchor{c-api/refcounting countingrefs}@anchor{3b8f}@anchor{c-api/refcounting reference-counting}@anchor{3b90}
@section 引用计数


本节介绍的宏被用于管理 Python 对象的引用计数。

@geindex Py_INCREF (C 函数)
@anchor{c-api/refcounting c Py_INCREF}@anchor{265}
@deffn {C 函数} void Py_INCREF (PyObject@w{ }*o)

增加对象 @emph{o} 的引用计数。 对象必须不为 @code{NULL}；如果你不确定它不为 @code{NULL}，可使用 @ref{267,,Py_XINCREF()}。
@end deffn

@geindex Py_XINCREF (C 函数)
@anchor{c-api/refcounting c Py_XINCREF}@anchor{267}
@deffn {C 函数} void Py_XINCREF (PyObject@w{ }*o)

增加对象 @emph{o} 的引用计数。 对象可以为 @code{NULL}，在此情况下该宏不产生任何效果。
@end deffn

@geindex Py_DECREF (C 函数)
@anchor{c-api/refcounting c Py_DECREF}@anchor{266}
@deffn {C 函数} void Py_DECREF (PyObject@w{ }*o)

减少对象 @emph{o} 的引用计数。 对象必须不为 @code{NULL}；如果你不确定它不为 @code{NULL}，可使用 @ref{268,,Py_XDECREF()}。 如果引用计数降为零，将发起调用对象所属类型的释放函数 (它必须不为 @code{NULL})。

@cartouche
@quotation 警告 
释放函数可导致任意 Python 代码被发起调用（例如当一个带有 @ref{919,,__del__()} 方法的类实例被释放时就是如此）。 虽然此类代码中的异常不会被传播，但被执行的代码能够自由访问所有 Python 全局变量。 这意味着任何可通过全局变量获取的对象在  @ref{266,,Py_DECREF()} 被发起调用之前都应当处于完好状态。 例如，从一个列表中删除对象的代码应当将被删除对象的引用拷贝到一个临时变量中，更新列表数据结构，然后再为临时变量调用 @ref{266,,Py_DECREF()}。
@end quotation
@end cartouche
@end deffn

@geindex Py_XDECREF (C 函数)
@anchor{c-api/refcounting c Py_XDECREF}@anchor{268}
@deffn {C 函数} void Py_XDECREF (PyObject@w{ }*o)

减少对象 @emph{o} 的引用计数。 对象可以为 @code{NULL}，在此情况下该宏不产生任何效果；在其他情况下其效果与 @ref{266,,Py_DECREF()} 相同，并会应用同样的警告。
@end deffn

@geindex Py_CLEAR (C 函数)
@anchor{c-api/refcounting c Py_CLEAR}@anchor{3af2}
@deffn {C 函数} void Py_CLEAR (PyObject@w{ }*o)

减少对象 @emph{o} 的引用计数。 对象可以为 @code{NULL}，在此情况下该宏不产生任何效果；在其他情况下其效果与 @ref{266,,Py_DECREF()} 相同，区别在于其参数也会被设为 @code{NULL}。 针对 @ref{266,,Py_DECREF()} 的警告不适用于所传递的对象，因为该宏会细心地使用一个临时变量并在减少其引用计数之前将参数设为 @code{NULL}。

每当要减少在垃圾回收期间可能会被遍历的对象的引用计数时，使用该宏是一个好主意。
@end deffn

以下函数适用于 Python 的运行时动态嵌入: @code{Py_IncRef(PyObject *o)}, @code{Py_DecRef(PyObject *o)}。 它们分别只是 @ref{267,,Py_XINCREF()} 和 @ref{268,,Py_XDECREF()} 的简单导出函数版本。

以下函数或宏仅可在解释器核心内部使用: @code{_Py_Dealloc()}, @code{_Py_ForgetReference()}, @code{_Py_NewReference()} 以及全局变量 @code{_Py_RefTotal}。

@node 异常处理,工具<2>,引用计数<3>,Python/C API 参考手册
@anchor{c-api/exceptions doc}@anchor{3b91}@anchor{c-api/exceptions exception-handling}@anchor{3b92}@anchor{c-api/exceptions exceptionhandling}@anchor{35f4}
@section 异常处理


The functions described in this chapter will let you handle and raise Python
exceptions.  It is important to understand some of the basics of Python
exception handling.  It works somewhat like the POSIX @code{errno} variable:
there is a global indicator (per thread) of the last error that occurred.  Most
C API functions don't clear this on success, but will set it to indicate the
cause of the error on failure.  Most C API functions also return an error
indicator, usually @code{NULL} if they are supposed to return a pointer, or @code{-1}
if they return an integer (exception: the @code{PyArg_*()} functions
return @code{1} for success and @code{0} for failure).

Concretely, the error indicator consists of three object pointers: the
exception's type, the exception's value, and the traceback object.  Any
of those pointers can be @code{NULL} if non-set (although some combinations are
forbidden, for example you can't have a non-@code{NULL} traceback if the exception
type is @code{NULL}).

When a function must fail because some function it called failed, it generally
doesn't set the error indicator; the function it called already set it.  It is
responsible for either handling the error and clearing the exception or
returning after cleaning up any resources it holds (such as object references or
memory allocations); it should @emph{not} continue normally if it is not prepared to
handle the error.  If returning due to an error, it is important to indicate to
the caller that an error has been set.  If the error is not handled or carefully
propagated, additional calls into the Python/C API may not behave as intended
and may fail in mysterious ways.

@cartouche
@quotation 注解 
The error indicator is @strong{not} the result of @ref{c58,,sys.exc_info()}.
The former corresponds to an exception that is not yet caught (and is
therefore still propagating), while the latter returns an exception after
it is caught (and has therefore stopped propagating).
@end quotation
@end cartouche

@menu
* Printing and clearing:: 
* 抛出异常: 抛出异常<2>. 
* Issuing warnings:: 
* Querying the error indicator:: 
* Signal Handling: Signal Handling<2>. 
* Exception Classes:: 
* Exception Objects:: 
* Unicode Exception Objects:: 
* 递归控制:: 
* 标准异常:: 
* 标准警告类别:: 

@end menu

@node Printing and clearing,抛出异常<2>,,异常处理
@anchor{c-api/exceptions printing-and-clearing}@anchor{3b93}
@subsection Printing and clearing


@geindex PyErr_Clear (C 函数)
@anchor{c-api/exceptions c PyErr_Clear}@anchor{965}
@deffn {C 函数} void PyErr_Clear ()

Clear the error indicator.  If the error indicator is not set, there is no
effect.
@end deffn

@geindex PyErr_PrintEx (C 函数)
@anchor{c-api/exceptions c PyErr_PrintEx}@anchor{3b94}
@deffn {C 函数} void PyErr_PrintEx (int@w{ }set_sys_last_vars)

Print a standard traceback to @code{sys.stderr} and clear the error indicator.
@strong{Unless} the error is a @code{SystemExit}, in that case no traceback is
printed and the Python process will exit with the error code specified by
the @code{SystemExit} instance.

Call this function @strong{only} when the error indicator is set.  Otherwise it
will cause a fatal error!

If @emph{set_sys_last_vars} is nonzero, the variables @ref{c53,,sys.last_type},
@ref{35dc,,sys.last_value} and @ref{34d7,,sys.last_traceback} will be set to the
type, value and traceback of the printed exception, respectively.
@end deffn

@geindex PyErr_Print (C 函数)
@anchor{c-api/exceptions c PyErr_Print}@anchor{e97}
@deffn {C 函数} void PyErr_Print ()

Alias for @code{PyErr_PrintEx(1)}.
@end deffn

@geindex PyErr_WriteUnraisable (C 函数)
@anchor{c-api/exceptions c PyErr_WriteUnraisable}@anchor{f4e}
@deffn {C 函数} void PyErr_WriteUnraisable (PyObject@w{ }*obj)

Call @ref{22d,,sys.unraisablehook()} using the current exception and @emph{obj}
argument.

This utility function prints a warning message to @code{sys.stderr} when an
exception has been set but it is impossible for the interpreter to actually
raise the exception.  It is used, for example, when an exception occurs in an
@ref{919,,__del__()} method.

The function is called with a single argument @emph{obj} that identifies the context
in which the unraisable exception occurred. If possible,
the repr of @emph{obj} will be printed in the warning message.

An exception must be set when calling this function.
@end deffn

@node 抛出异常<2>,Issuing warnings,Printing and clearing,异常处理
@anchor{c-api/exceptions raising-exceptions}@anchor{3b95}
@subsection 抛出异常


These functions help you set the current thread's error indicator.
For convenience, some of these functions will always return a
@code{NULL} pointer for use in a @code{return} statement.

@geindex PyErr_SetString (C 函数)
@anchor{c-api/exceptions c PyErr_SetString}@anchor{3aa1}
@deffn {C 函数} void PyErr_SetString (PyObject@w{ }*type, const char@w{ }*message)

This is the most common way to set the error indicator.  The first argument
specifies the exception type; it is normally one of the standard exceptions,
e.g. @code{PyExc_RuntimeError}.  You need not increment its reference count.
The second argument is an error message; it is decoded from @code{'utf-8}'.
@end deffn

@geindex PyErr_SetObject (C 函数)
@anchor{c-api/exceptions c PyErr_SetObject}@anchor{3aa3}
@deffn {C 函数} void PyErr_SetObject (PyObject@w{ }*type, PyObject@w{ }*value)

This function is similar to @ref{3aa1,,PyErr_SetString()} but lets you specify an
arbitrary Python object for the "value" of the exception.
@end deffn

@geindex PyErr_Format (C 函数)
@anchor{c-api/exceptions c PyErr_Format}@anchor{7a4}
@deffn {C 函数} PyObject* PyErr_Format (PyObject@w{ }*exception, const char@w{ }*format, ...)
@emph{Return value: Always NULL.}
This function sets the error indicator and returns @code{NULL}.  @emph{exception}
should be a Python exception class.  The @emph{format} and subsequent
parameters help format the error message; they have the same meaning and
values as in @ref{7c5,,PyUnicode_FromFormat()}. @emph{format} is an ASCII-encoded
string.
@end deffn

@geindex PyErr_FormatV (C 函数)
@anchor{c-api/exceptions c PyErr_FormatV}@anchor{7a3}
@deffn {C 函数} PyObject* PyErr_FormatV (PyObject@w{ }*exception, const char@w{ }*format, va_list@w{ }vargs)
@emph{Return value: Always NULL.}
Same as @ref{7a4,,PyErr_Format()}, but taking a @code{va_list} argument rather
than a variable number of arguments.


3.5 新版功能.

@end deffn

@geindex PyErr_SetNone (C 函数)
@anchor{c-api/exceptions c PyErr_SetNone}@anchor{3b96}
@deffn {C 函数} void PyErr_SetNone (PyObject@w{ }*type)

This is a shorthand for @code{PyErr_SetObject(type, Py_None)}.
@end deffn

@geindex PyErr_BadArgument (C 函数)
@anchor{c-api/exceptions c PyErr_BadArgument}@anchor{3b97}
@deffn {C 函数} int PyErr_BadArgument ()

This is a shorthand for @code{PyErr_SetString(PyExc_TypeError, message)}, where
@emph{message} indicates that a built-in operation was invoked with an illegal
argument.  It is mostly for internal use.
@end deffn

@geindex PyErr_NoMemory (C 函数)
@anchor{c-api/exceptions c PyErr_NoMemory}@anchor{3aa5}
@deffn {C 函数} PyObject* PyErr_NoMemory ()
@emph{Return value: Always NULL.}
This is a shorthand for @code{PyErr_SetNone(PyExc_MemoryError)}; it returns @code{NULL}
so an object allocation function can write @code{return PyErr_NoMemory();} when it
runs out of memory.
@end deffn

@geindex PyErr_SetFromErrno (C 函数)
@anchor{c-api/exceptions c PyErr_SetFromErrno}@anchor{3aa2}
@deffn {C 函数} PyObject* PyErr_SetFromErrno (PyObject@w{ }*type)
@emph{Return value: Always NULL.}
@geindex strerror()

This is a convenience function to raise an exception when a C library function
has returned an error and set the C variable @code{errno}.  It constructs a
tuple object whose first item is the integer @code{errno} value and whose
second item is the corresponding error message (gotten from @code{strerror()}),
and then calls @code{PyErr_SetObject(type, object)}.  On Unix, when the
@code{errno} value is @code{EINTR}, indicating an interrupted system call,
this calls @ref{3b98,,PyErr_CheckSignals()}, and if that set the error indicator,
leaves it set to that.  The function always returns @code{NULL}, so a wrapper
function around a system call can write @code{return PyErr_SetFromErrno(type);}
when the system call returns an error.
@end deffn

@geindex PyErr_SetFromErrnoWithFilenameObject (C 函数)
@anchor{c-api/exceptions c PyErr_SetFromErrnoWithFilenameObject}@anchor{3b99}
@deffn {C 函数} PyObject* PyErr_SetFromErrnoWithFilenameObject (PyObject@w{ }*type, PyObject@w{ }*filenameObject)
@emph{Return value: Always NULL.}
Similar to @ref{3aa2,,PyErr_SetFromErrno()}, with the additional behavior that if
@emph{filenameObject} is not @code{NULL}, it is passed to the constructor of @emph{type} as
a third parameter.  In the case of @ref{1d3,,OSError} exception,
this is used to define the @code{filename} attribute of the
exception instance.
@end deffn

@geindex PyErr_SetFromErrnoWithFilenameObjects (C 函数)
@anchor{c-api/exceptions c PyErr_SetFromErrnoWithFilenameObjects}@anchor{3b9a}
@deffn {C 函数} PyObject* PyErr_SetFromErrnoWithFilenameObjects (PyObject@w{ }*type, PyObject@w{ }*filenameObject, PyObject@w{ }*filenameObject2)
@emph{Return value: Always NULL.}
Similar to @ref{3b99,,PyErr_SetFromErrnoWithFilenameObject()}, but takes a second
filename object, for raising errors when a function that takes two filenames
fails.


3.4 新版功能.

@end deffn

@geindex PyErr_SetFromErrnoWithFilename (C 函数)
@anchor{c-api/exceptions c PyErr_SetFromErrnoWithFilename}@anchor{3b9b}
@deffn {C 函数} PyObject* PyErr_SetFromErrnoWithFilename (PyObject@w{ }*type, const char@w{ }*filename)
@emph{Return value: Always NULL.}
Similar to @ref{3b99,,PyErr_SetFromErrnoWithFilenameObject()}, but the filename
is given as a C string.  @emph{filename} is decoded from the filesystem encoding
(@ref{4e8,,os.fsdecode()}).
@end deffn

@geindex PyErr_SetFromWindowsErr (C 函数)
@anchor{c-api/exceptions c PyErr_SetFromWindowsErr}@anchor{3b9c}
@deffn {C 函数} PyObject* PyErr_SetFromWindowsErr (int@w{ }ierr)
@emph{Return value: Always NULL.}
This is a convenience function to raise @ref{98e,,WindowsError}. If called with
@emph{ierr} of @code{0}, the error code returned by a call to @code{GetLastError()}
is used instead.  It calls the Win32 function @code{FormatMessage()} to retrieve
the Windows description of error code given by @emph{ierr} or @code{GetLastError()},
then it constructs a tuple object whose first item is the @emph{ierr} value and whose
second item is the corresponding error message (gotten from
@code{FormatMessage()}), and then calls @code{PyErr_SetObject(PyExc_WindowsError,
object)}. This function always returns @code{NULL}.

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex PyErr_SetExcFromWindowsErr (C 函数)
@anchor{c-api/exceptions c PyErr_SetExcFromWindowsErr}@anchor{3b9d}
@deffn {C 函数} PyObject* PyErr_SetExcFromWindowsErr (PyObject@w{ }*type, int@w{ }ierr)
@emph{Return value: Always NULL.}
Similar to @ref{3b9c,,PyErr_SetFromWindowsErr()}, with an additional parameter
specifying the exception type to be raised.

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex PyErr_SetFromWindowsErrWithFilename (C 函数)
@anchor{c-api/exceptions c PyErr_SetFromWindowsErrWithFilename}@anchor{3b9e}
@deffn {C 函数} PyObject* PyErr_SetFromWindowsErrWithFilename (int@w{ }ierr, const char@w{ }*filename)
@emph{Return value: Always NULL.}
Similar to @code{PyErr_SetFromWindowsErrWithFilenameObject()}, but the
filename is given as a C string.  @emph{filename} is decoded from the filesystem
encoding (@ref{4e8,,os.fsdecode()}).

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex PyErr_SetExcFromWindowsErrWithFilenameObject (C 函数)
@anchor{c-api/exceptions c PyErr_SetExcFromWindowsErrWithFilenameObject}@anchor{3b9f}
@deffn {C 函数} PyObject* PyErr_SetExcFromWindowsErrWithFilenameObject (PyObject@w{ }*type, int@w{ }ierr, PyObject@w{ }*filename)
@emph{Return value: Always NULL.}
Similar to @code{PyErr_SetFromWindowsErrWithFilenameObject()}, with an
additional parameter specifying the exception type to be raised.

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex PyErr_SetExcFromWindowsErrWithFilenameObjects (C 函数)
@anchor{c-api/exceptions c PyErr_SetExcFromWindowsErrWithFilenameObjects}@anchor{3ba0}
@deffn {C 函数} PyObject* PyErr_SetExcFromWindowsErrWithFilenameObjects (PyObject@w{ }*type, int@w{ }ierr, PyObject@w{ }*filename, PyObject@w{ }*filename2)
@emph{Return value: Always NULL.}
Similar to @ref{3b9f,,PyErr_SetExcFromWindowsErrWithFilenameObject()},
but accepts a second filename object.

@ref{12f5,,可用性}: Windows。


3.4 新版功能.

@end deffn

@geindex PyErr_SetExcFromWindowsErrWithFilename (C 函数)
@anchor{c-api/exceptions c PyErr_SetExcFromWindowsErrWithFilename}@anchor{3ba1}
@deffn {C 函数} PyObject* PyErr_SetExcFromWindowsErrWithFilename (PyObject@w{ }*type, int@w{ }ierr, const char@w{ }*filename)
@emph{Return value: Always NULL.}
Similar to @ref{3b9e,,PyErr_SetFromWindowsErrWithFilename()}, with an additional
parameter specifying the exception type to be raised.

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex PyErr_SetImportError (C 函数)
@anchor{c-api/exceptions c PyErr_SetImportError}@anchor{5f3}
@deffn {C 函数} PyObject* PyErr_SetImportError (PyObject@w{ }*msg, PyObject@w{ }*name, PyObject@w{ }*path)
@emph{Return value: Always NULL.}
This is a convenience function to raise @ref{32d,,ImportError}. @emph{msg} will be
set as the exception's message string. @emph{name} and @emph{path}, both of which can
be @code{NULL}, will be set as the @ref{32d,,ImportError}'s respective @code{name}
and @code{path} attributes.


3.3 新版功能.

@end deffn

@geindex PyErr_SyntaxLocationObject (C 函数)
@anchor{c-api/exceptions c PyErr_SyntaxLocationObject}@anchor{3ba2}
@deffn {C 函数} void PyErr_SyntaxLocationObject (PyObject@w{ }*filename, int@w{ }lineno, int@w{ }col_offset)

Set file, line, and offset information for the current exception.  If the
current exception is not a @ref{452,,SyntaxError}, then it sets additional
attributes, which make the exception printing subsystem think the exception
is a @ref{452,,SyntaxError}.


3.4 新版功能.

@end deffn

@geindex PyErr_SyntaxLocationEx (C 函数)
@anchor{c-api/exceptions c PyErr_SyntaxLocationEx}@anchor{3ba3}
@deffn {C 函数} void PyErr_SyntaxLocationEx (const char@w{ }*filename, int@w{ }lineno, int@w{ }col_offset)

Like @ref{3ba2,,PyErr_SyntaxLocationObject()}, but @emph{filename} is a byte string
decoded from the filesystem encoding (@ref{4e8,,os.fsdecode()}).


3.2 新版功能.

@end deffn

@geindex PyErr_SyntaxLocation (C 函数)
@anchor{c-api/exceptions c PyErr_SyntaxLocation}@anchor{3ba4}
@deffn {C 函数} void PyErr_SyntaxLocation (const char@w{ }*filename, int@w{ }lineno)

Like @ref{3ba3,,PyErr_SyntaxLocationEx()}, but the col_offset parameter is
omitted.
@end deffn

@geindex PyErr_BadInternalCall (C 函数)
@anchor{c-api/exceptions c PyErr_BadInternalCall}@anchor{3ba5}
@deffn {C 函数} void PyErr_BadInternalCall ()

This is a shorthand for @code{PyErr_SetString(PyExc_SystemError, message)},
where @emph{message} indicates that an internal operation (e.g. a Python/C API
function) was invoked with an illegal argument.  It is mostly for internal
use.
@end deffn

@node Issuing warnings,Querying the error indicator,抛出异常<2>,异常处理
@anchor{c-api/exceptions issuing-warnings}@anchor{3ba6}
@subsection Issuing warnings


Use these functions to issue warnings from C code.  They mirror similar
functions exported by the Python @ref{126,,warnings} module.  They normally
print a warning message to @emph{sys.stderr}; however, it is
also possible that the user has specified that warnings are to be turned into
errors, and in that case they will raise an exception.  It is also possible that
the functions raise an exception because of a problem with the warning machinery.
The return value is @code{0} if no exception is raised, or @code{-1} if an exception
is raised.  (It is not possible to determine whether a warning message is
actually printed, nor what the reason is for the exception; this is
intentional.)  If an exception is raised, the caller should do its normal
exception handling (for example, @ref{266,,Py_DECREF()} owned references and return
an error value).

@geindex PyErr_WarnEx (C 函数)
@anchor{c-api/exceptions c PyErr_WarnEx}@anchor{daa}
@deffn {C 函数} int PyErr_WarnEx (PyObject@w{ }*category, const char@w{ }*message, Py_ssize_t@w{ }stack_level)

Issue a warning message.  The @emph{category} argument is a warning category (see
below) or @code{NULL}; the @emph{message} argument is a UTF-8 encoded string.  @emph{stack_level} is a
positive number giving a number of stack frames; the warning will be issued from
the  currently executing line of code in that stack frame.  A @emph{stack_level} of 1
is the function calling @ref{daa,,PyErr_WarnEx()}, 2 is  the function above that,
and so forth.

Warning categories must be subclasses of @code{PyExc_Warning};
@code{PyExc_Warning} is a subclass of @code{PyExc_Exception};
the default warning category is @code{PyExc_RuntimeWarning}. The standard
Python warning categories are available as global variables whose names are
enumerated at @ref{3ba7,,标准警告类别}.

For information about warning control, see the documentation for the
@ref{126,,warnings} module and the @ref{40f,,-W} option in the command line
documentation.  There is no C API for warning control.
@end deffn

@geindex PyErr_SetImportErrorSubclass (C 函数)
@anchor{c-api/exceptions c PyErr_SetImportErrorSubclass}@anchor{5c6}
@deffn {C 函数} PyObject* PyErr_SetImportErrorSubclass (PyObject@w{ }*exception, PyObject@w{ }*msg, PyObject@w{ }*name, PyObject@w{ }*path)
@emph{Return value: Always NULL.}
Much like @ref{5f3,,PyErr_SetImportError()} but this function allows for
specifying a subclass of @ref{32d,,ImportError} to raise.


3.6 新版功能.

@end deffn

@geindex PyErr_WarnExplicitObject (C 函数)
@anchor{c-api/exceptions c PyErr_WarnExplicitObject}@anchor{3ba8}
@deffn {C 函数} int PyErr_WarnExplicitObject (PyObject@w{ }*category, PyObject@w{ }*message, PyObject@w{ }*filename, int@w{ }lineno, PyObject@w{ }*module, PyObject@w{ }*registry)

Issue a warning message with explicit control over all warning attributes.  This
is a straightforward wrapper around the Python function
@ref{5ab,,warnings.warn_explicit()}, see there for more information.  The @emph{module}
and @emph{registry} arguments may be set to @code{NULL} to get the default effect
described there.


3.4 新版功能.

@end deffn

@geindex PyErr_WarnExplicit (C 函数)
@anchor{c-api/exceptions c PyErr_WarnExplicit}@anchor{3ba9}
@deffn {C 函数} int PyErr_WarnExplicit (PyObject@w{ }*category, const char@w{ }*message, const char@w{ }*filename, int@w{ }lineno, const char@w{ }*module, PyObject@w{ }*registry)

Similar to @ref{3ba8,,PyErr_WarnExplicitObject()} except that @emph{message} and
@emph{module} are UTF-8 encoded strings, and @emph{filename} is decoded from the
filesystem encoding (@ref{4e8,,os.fsdecode()}).
@end deffn

@geindex PyErr_WarnFormat (C 函数)
@anchor{c-api/exceptions c PyErr_WarnFormat}@anchor{3baa}
@deffn {C 函数} int PyErr_WarnFormat (PyObject@w{ }*category, Py_ssize_t@w{ }stack_level, const char@w{ }*format, ...)

Function similar to @ref{daa,,PyErr_WarnEx()}, but use
@ref{7c5,,PyUnicode_FromFormat()} to format the warning message.  @emph{format} is
an ASCII-encoded string.


3.2 新版功能.

@end deffn

@geindex PyErr_ResourceWarning (C 函数)
@anchor{c-api/exceptions c PyErr_ResourceWarning}@anchor{5c7}
@deffn {C 函数} int PyErr_ResourceWarning (PyObject@w{ }*source, Py_ssize_t@w{ }stack_level, const char@w{ }*format, ...)

Function similar to @ref{3baa,,PyErr_WarnFormat()}, but @emph{category} is
@ref{4ca,,ResourceWarning} and it passes @emph{source} to @code{warnings.WarningMessage()}.


3.6 新版功能.

@end deffn

@node Querying the error indicator,Signal Handling<2>,Issuing warnings,异常处理
@anchor{c-api/exceptions querying-the-error-indicator}@anchor{3bab}
@subsection Querying the error indicator


@geindex PyErr_Occurred (C 函数)
@anchor{c-api/exceptions c PyErr_Occurred}@anchor{3aa4}
@deffn {C 函数} PyObject* PyErr_Occurred ()
@emph{Return value: Borrowed reference.}
Test whether the error indicator is set.  If set, return the exception @emph{type}
(the first argument to the last call to one of the @code{PyErr_Set*()}
functions or to @ref{3afc,,PyErr_Restore()}).  If not set, return @code{NULL}.  You do not
own a reference to the return value, so you do not need to @ref{266,,Py_DECREF()}
it.

@cartouche
@quotation 注解 
Do not compare the return value to a specific exception; use
@ref{3b5c,,PyErr_ExceptionMatches()} instead, shown below.  (The comparison could
easily fail since the exception may be an instance instead of a class, in the
case of a class exception, or it may be a subclass of the expected exception.)
@end quotation
@end cartouche
@end deffn

@geindex PyErr_ExceptionMatches (C 函数)
@anchor{c-api/exceptions c PyErr_ExceptionMatches}@anchor{3b5c}
@deffn {C 函数} int PyErr_ExceptionMatches (PyObject@w{ }*exc)

Equivalent to @code{PyErr_GivenExceptionMatches(PyErr_Occurred(), exc)}.  This
should only be called when an exception is actually set; a memory access
violation will occur if no exception has been raised.
@end deffn

@geindex PyErr_GivenExceptionMatches (C 函数)
@anchor{c-api/exceptions c PyErr_GivenExceptionMatches}@anchor{3bac}
@deffn {C 函数} int PyErr_GivenExceptionMatches (PyObject@w{ }*given, PyObject@w{ }*exc)

Return true if the @emph{given} exception matches the exception type in @emph{exc}.  If
@emph{exc} is a class object, this also returns true when @emph{given} is an instance
of a subclass.  If @emph{exc} is a tuple, all exception types in the tuple (and
recursively in subtuples) are searched for a match.
@end deffn

@geindex PyErr_Fetch (C 函数)
@anchor{c-api/exceptions c PyErr_Fetch}@anchor{964}
@deffn {C 函数} void PyErr_Fetch (PyObject@w{ }**ptype, PyObject@w{ }**pvalue, PyObject@w{ }**ptraceback)

Retrieve the error indicator into three variables whose addresses are passed.
If the error indicator is not set, set all three variables to @code{NULL}.  If it is
set, it will be cleared and you own a reference to each object retrieved.  The
value and traceback object may be @code{NULL} even when the type object is not.

@cartouche
@quotation 注解 
This function is normally only used by code that needs to catch exceptions or
by code that needs to save and restore the error indicator temporarily, e.g.:

@example
@{
   PyObject *type, *value, *traceback;
   PyErr_Fetch(&type, &value, &traceback);

   /* ... code that might produce other errors ... */

   PyErr_Restore(type, value, traceback);
@}
@end example
@end quotation
@end cartouche
@end deffn

@geindex PyErr_Restore (C 函数)
@anchor{c-api/exceptions c PyErr_Restore}@anchor{3afc}
@deffn {C 函数} void PyErr_Restore (PyObject@w{ }*type, PyObject@w{ }*value, PyObject@w{ }*traceback)

Set  the error indicator from the three objects.  If the error indicator is
already set, it is cleared first.  If the objects are @code{NULL}, the error
indicator is cleared.  Do not pass a @code{NULL} type and non-@code{NULL} value or
traceback.  The exception type should be a class.  Do not pass an invalid
exception type or value. (Violating these rules will cause subtle problems
later.)  This call takes away a reference to each object: you must own a
reference to each object before the call and after the call you no longer own
these references.  (If you don't understand this, don't use this function.  I
warned you.)

@cartouche
@quotation 注解 
This function is normally only used by code that needs to save and restore the
error indicator temporarily.  Use @ref{964,,PyErr_Fetch()} to save the current
error indicator.
@end quotation
@end cartouche
@end deffn

@geindex PyErr_NormalizeException (C 函数)
@anchor{c-api/exceptions c PyErr_NormalizeException}@anchor{f4f}
@deffn {C 函数} void PyErr_NormalizeException (PyObject**exc, PyObject**val, PyObject**tb)

Under certain circumstances, the values returned by @ref{964,,PyErr_Fetch()} below
can be "unnormalized", meaning that @code{*exc} is a class object but @code{*val} is
not an instance of the  same class.  This function can be used to instantiate
the class in that case.  If the values are already normalized, nothing happens.
The delayed normalization is implemented to improve performance.

@cartouche
@quotation 注解 
This function @emph{does not} implicitly set the @code{__traceback__}
attribute on the exception value. If setting the traceback
appropriately is desired, the following additional snippet is needed:

@example
if (tb != NULL) @{
  PyException_SetTraceback(val, tb);
@}
@end example
@end quotation
@end cartouche
@end deffn

@geindex PyErr_GetExcInfo (C 函数)
@anchor{c-api/exceptions c PyErr_GetExcInfo}@anchor{3bad}
@deffn {C 函数} void PyErr_GetExcInfo (PyObject@w{ }**ptype, PyObject@w{ }**pvalue, PyObject@w{ }**ptraceback)

Retrieve the exception info, as known from @code{sys.exc_info()}.  This refers
to an exception that was @emph{already caught}, not to an exception that was
freshly raised.  Returns new references for the three objects, any of which
may be @code{NULL}.  Does not modify the exception info state.

@cartouche
@quotation 注解 
This function is not normally used by code that wants to handle exceptions.
Rather, it can be used when code needs to save and restore the exception
state temporarily.  Use @ref{3bae,,PyErr_SetExcInfo()} to restore or clear the
exception state.
@end quotation
@end cartouche


3.3 新版功能.

@end deffn

@geindex PyErr_SetExcInfo (C 函数)
@anchor{c-api/exceptions c PyErr_SetExcInfo}@anchor{3bae}
@deffn {C 函数} void PyErr_SetExcInfo (PyObject@w{ }*type, PyObject@w{ }*value, PyObject@w{ }*traceback)

Set the exception info, as known from @code{sys.exc_info()}.  This refers
to an exception that was @emph{already caught}, not to an exception that was
freshly raised.  This function steals the references of the arguments.
To clear the exception state, pass @code{NULL} for all three arguments.
For general rules about the three arguments, see @ref{3afc,,PyErr_Restore()}.

@cartouche
@quotation 注解 
This function is not normally used by code that wants to handle exceptions.
Rather, it can be used when code needs to save and restore the exception
state temporarily.  Use @ref{3bad,,PyErr_GetExcInfo()} to read the exception
state.
@end quotation
@end cartouche


3.3 新版功能.

@end deffn

@node Signal Handling<2>,Exception Classes,Querying the error indicator,异常处理
@anchor{c-api/exceptions signal-handling}@anchor{3baf}
@subsection Signal Handling


@geindex PyErr_CheckSignals (C 函数)
@anchor{c-api/exceptions c PyErr_CheckSignals}@anchor{3b98}
@deffn {C 函数} int PyErr_CheckSignals ()

@geindex 模块; signal
@geindex SIGINT
@geindex KeyboardInterrupt (built-in exception)

This function interacts with Python's signal handling.  It checks whether a
signal has been sent to the processes and if so, invokes the corresponding
signal handler.  If the @ref{ea,,signal} module is supported, this can invoke a
signal handler written in Python.  In all cases, the default effect for
@code{SIGINT} is to raise the  @ref{197,,KeyboardInterrupt} exception.  If an
exception is raised the error indicator is set and the function returns @code{-1};
otherwise the function returns @code{0}.  The error indicator may or may not be
cleared if it was previously set.
@end deffn

@geindex PyErr_SetInterrupt (C 函数)
@anchor{c-api/exceptions c PyErr_SetInterrupt}@anchor{3bb0}
@deffn {C 函数} void PyErr_SetInterrupt ()

@geindex SIGINT
@geindex KeyboardInterrupt (built-in exception)

Simulate the effect of a @code{SIGINT} signal arriving. The next time
@ref{3b98,,PyErr_CheckSignals()} is called,  the Python signal handler for
@code{SIGINT} will be called.

If @code{SIGINT} isn't handled by Python (it was set to
@ref{2459,,signal.SIG_DFL} or @ref{245a,,signal.SIG_IGN}), this function does
nothing.
@end deffn

@geindex PySignal_SetWakeupFd (C 函数)
@anchor{c-api/exceptions c PySignal_SetWakeupFd}@anchor{d3f}
@deffn {C 函数} int PySignal_SetWakeupFd (int@w{ }fd)

This utility function specifies a file descriptor to which the signal number
is written as a single byte whenever a signal is received. @emph{fd} must be
non-blocking. It returns the previous such file descriptor.

The value @code{-1} disables the feature; this is the initial state.
This is equivalent to @ref{3c6,,signal.set_wakeup_fd()} in Python, but without any
error checking.  @emph{fd} should be a valid file descriptor.  The function should
only be called from the main thread.


在 3.5 版更改: On Windows, the function now also supports socket handles.

@end deffn

@node Exception Classes,Exception Objects,Signal Handling<2>,异常处理
@anchor{c-api/exceptions exception-classes}@anchor{3bb1}
@subsection Exception Classes


@geindex PyErr_NewException (C 函数)
@anchor{c-api/exceptions c PyErr_NewException}@anchor{bf9}
@deffn {C 函数} PyObject* PyErr_NewException (const char@w{ }*name, PyObject@w{ }*base, PyObject@w{ }*dict)
@emph{Return value: New reference.}
This utility function creates and returns a new exception class. The @emph{name}
argument must be the name of the new exception, a C string of the form
@code{module.classname}.  The @emph{base} and @emph{dict} arguments are normally @code{NULL}.
This creates a class object derived from @ref{1a9,,Exception} (accessible in C as
@code{PyExc_Exception}).

The @code{__module__} attribute of the new class is set to the first part (up
to the last dot) of the @emph{name} argument, and the class name is set to the last
part (after the last dot).  The @emph{base} argument can be used to specify alternate
base classes; it can either be only one class or a tuple of classes. The @emph{dict}
argument can be used to specify a dictionary of class variables and methods.
@end deffn

@geindex PyErr_NewExceptionWithDoc (C 函数)
@anchor{c-api/exceptions c PyErr_NewExceptionWithDoc}@anchor{bf8}
@deffn {C 函数} PyObject* PyErr_NewExceptionWithDoc (const char@w{ }*name, const char@w{ }*doc, PyObject@w{ }*base, PyObject@w{ }*dict)
@emph{Return value: New reference.}
Same as @ref{bf9,,PyErr_NewException()}, except that the new exception class can
easily be given a docstring: If @emph{doc} is non-@code{NULL}, it will be used as the
docstring for the exception class.


3.2 新版功能.

@end deffn

@node Exception Objects,Unicode Exception Objects,Exception Classes,异常处理
@anchor{c-api/exceptions exception-objects}@anchor{3bb2}
@subsection Exception Objects


@geindex PyException_GetTraceback (C 函数)
@anchor{c-api/exceptions c PyException_GetTraceback}@anchor{3bb3}
@deffn {C 函数} PyObject* PyException_GetTraceback (PyObject@w{ }*ex)
@emph{Return value: New reference.}
Return the traceback associated with the exception as a new reference, as
accessible from Python through @code{__traceback__}.  If there is no
traceback associated, this returns @code{NULL}.
@end deffn

@geindex PyException_SetTraceback (C 函数)
@anchor{c-api/exceptions c PyException_SetTraceback}@anchor{f50}
@deffn {C 函数} int PyException_SetTraceback (PyObject@w{ }*ex, PyObject@w{ }*tb)

Set the traceback associated with the exception to @emph{tb}.  Use @code{Py_None} to
clear it.
@end deffn

@geindex PyException_GetContext (C 函数)
@anchor{c-api/exceptions c PyException_GetContext}@anchor{3bb4}
@deffn {C 函数} PyObject* PyException_GetContext (PyObject@w{ }*ex)
@emph{Return value: New reference.}
Return the context (another exception instance during whose handling @emph{ex} was
raised) associated with the exception as a new reference, as accessible from
Python through @code{__context__}.  If there is no context associated, this
returns @code{NULL}.
@end deffn

@geindex PyException_SetContext (C 函数)
@anchor{c-api/exceptions c PyException_SetContext}@anchor{3bb5}
@deffn {C 函数} void PyException_SetContext (PyObject@w{ }*ex, PyObject@w{ }*ctx)

Set the context associated with the exception to @emph{ctx}.  Use @code{NULL} to clear
it.  There is no type check to make sure that @emph{ctx} is an exception instance.
This steals a reference to @emph{ctx}.
@end deffn

@geindex PyException_GetCause (C 函数)
@anchor{c-api/exceptions c PyException_GetCause}@anchor{3bb6}
@deffn {C 函数} PyObject* PyException_GetCause (PyObject@w{ }*ex)
@emph{Return value: New reference.}
Return the cause (either an exception instance, or @ref{157,,None},
set by @code{raise ... from ...}) associated with the exception as a new
reference, as accessible from Python through @code{__cause__}.
@end deffn

@geindex PyException_SetCause (C 函数)
@anchor{c-api/exceptions c PyException_SetCause}@anchor{3bb7}
@deffn {C 函数} void PyException_SetCause (PyObject@w{ }*ex, PyObject@w{ }*cause)

Set the cause associated with the exception to @emph{cause}.  Use @code{NULL} to clear
it.  There is no type check to make sure that @emph{cause} is either an exception
instance or @ref{157,,None}.  This steals a reference to @emph{cause}.

@code{__suppress_context__} is implicitly set to @code{True} by this function.
@end deffn

@node Unicode Exception Objects,递归控制,Exception Objects,异常处理
@anchor{c-api/exceptions unicode-exception-objects}@anchor{3bb8}@anchor{c-api/exceptions unicodeexceptions}@anchor{3bb9}
@subsection Unicode Exception Objects


The following functions are used to create and modify Unicode exceptions from C.

@geindex PyUnicodeDecodeError_Create (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_Create}@anchor{3bba}
@deffn {C 函数} PyObject* PyUnicodeDecodeError_Create (const char@w{ }*encoding, const char@w{ }*object, Py_ssize_t@w{ }length, Py_ssize_t@w{ }start, Py_ssize_t@w{ }end, const char@w{ }*reason)
@emph{Return value: New reference.}
Create a @ref{1fd,,UnicodeDecodeError} object with the attributes @emph{encoding},
@emph{object}, @emph{length}, @emph{start}, @emph{end} and @emph{reason}. @emph{encoding} and @emph{reason} are
UTF-8 encoded strings.
@end deffn

@geindex PyUnicodeEncodeError_Create (C 函数)
@anchor{c-api/exceptions c PyUnicodeEncodeError_Create}@anchor{3bbb}
@deffn {C 函数} PyObject* PyUnicodeEncodeError_Create (const char@w{ }*encoding, const Py_UNICODE@w{ }*object, Py_ssize_t@w{ }length, Py_ssize_t@w{ }start, Py_ssize_t@w{ }end, const char@w{ }*reason)
@emph{Return value: New reference.}
Create a @ref{1fc,,UnicodeEncodeError} object with the attributes @emph{encoding},
@emph{object}, @emph{length}, @emph{start}, @emph{end} and @emph{reason}. @emph{encoding} and @emph{reason} are
UTF-8 encoded strings.
@end deffn

@geindex PyUnicodeTranslateError_Create (C 函数)
@anchor{c-api/exceptions c PyUnicodeTranslateError_Create}@anchor{3bbc}
@deffn {C 函数} PyObject* PyUnicodeTranslateError_Create (const Py_UNICODE@w{ }*object, Py_ssize_t@w{ }length, Py_ssize_t@w{ }start, Py_ssize_t@w{ }end, const char@w{ }*reason)
@emph{Return value: New reference.}
Create a @ref{16aa,,UnicodeTranslateError} object with the attributes @emph{object},
@emph{length}, @emph{start}, @emph{end} and @emph{reason}. @emph{reason} is a UTF-8 encoded string.
@end deffn

@geindex PyUnicodeDecodeError_GetEncoding (C 函数)
@geindex PyUnicodeEncodeError_GetEncoding (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_GetEncoding}@anchor{3bbd}
@deffn {C 函数} PyObject* PyUnicodeDecodeError_GetEncoding (PyObject@w{ }*exc)
@anchor{c-api/exceptions c PyUnicodeEncodeError_GetEncoding}@anchor{3bbe}
@deffnx {C 函数} PyObject* PyUnicodeEncodeError_GetEncoding (PyObject@w{ }*exc)
@emph{Return value: New reference.}
Return the @emph{encoding} attribute of the given exception object.
@end deffn

@geindex PyUnicodeDecodeError_GetObject (C 函数)
@geindex PyUnicodeEncodeError_GetObject (C 函数)
@geindex PyUnicodeTranslateError_GetObject (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_GetObject}@anchor{3bbf}
@deffn {C 函数} PyObject* PyUnicodeDecodeError_GetObject (PyObject@w{ }*exc)
@anchor{c-api/exceptions c PyUnicodeEncodeError_GetObject}@anchor{3bc0}
@deffnx {C 函数} PyObject* PyUnicodeEncodeError_GetObject (PyObject@w{ }*exc)
@anchor{c-api/exceptions c PyUnicodeTranslateError_GetObject}@anchor{3bc1}
@deffnx {C 函数} PyObject* PyUnicodeTranslateError_GetObject (PyObject@w{ }*exc)
@emph{Return value: New reference.}
Return the @emph{object} attribute of the given exception object.
@end deffn

@geindex PyUnicodeDecodeError_GetStart (C 函数)
@geindex PyUnicodeEncodeError_GetStart (C 函数)
@geindex PyUnicodeTranslateError_GetStart (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_GetStart}@anchor{3bc2}
@deffn {C 函数} int PyUnicodeDecodeError_GetStart (PyObject@w{ }*exc, Py_ssize_t@w{ }*start)
@anchor{c-api/exceptions c PyUnicodeEncodeError_GetStart}@anchor{3bc3}
@deffnx {C 函数} int PyUnicodeEncodeError_GetStart (PyObject@w{ }*exc, Py_ssize_t@w{ }*start)
@anchor{c-api/exceptions c PyUnicodeTranslateError_GetStart}@anchor{3bc4}
@deffnx {C 函数} int PyUnicodeTranslateError_GetStart (PyObject@w{ }*exc, Py_ssize_t@w{ }*start)

Get the @emph{start} attribute of the given exception object and place it into
@emph{*start}.  @emph{start} must not be @code{NULL}.  Return @code{0} on success, @code{-1} on
failure.
@end deffn

@geindex PyUnicodeDecodeError_SetStart (C 函数)
@geindex PyUnicodeEncodeError_SetStart (C 函数)
@geindex PyUnicodeTranslateError_SetStart (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_SetStart}@anchor{3bc5}
@deffn {C 函数} int PyUnicodeDecodeError_SetStart (PyObject@w{ }*exc, Py_ssize_t@w{ }start)
@anchor{c-api/exceptions c PyUnicodeEncodeError_SetStart}@anchor{3bc6}
@deffnx {C 函数} int PyUnicodeEncodeError_SetStart (PyObject@w{ }*exc, Py_ssize_t@w{ }start)
@anchor{c-api/exceptions c PyUnicodeTranslateError_SetStart}@anchor{3bc7}
@deffnx {C 函数} int PyUnicodeTranslateError_SetStart (PyObject@w{ }*exc, Py_ssize_t@w{ }start)

Set the @emph{start} attribute of the given exception object to @emph{start}.  Return
@code{0} on success, @code{-1} on failure.
@end deffn

@geindex PyUnicodeDecodeError_GetEnd (C 函数)
@geindex PyUnicodeEncodeError_GetEnd (C 函数)
@geindex PyUnicodeTranslateError_GetEnd (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_GetEnd}@anchor{3bc8}
@deffn {C 函数} int PyUnicodeDecodeError_GetEnd (PyObject@w{ }*exc, Py_ssize_t@w{ }*end)
@anchor{c-api/exceptions c PyUnicodeEncodeError_GetEnd}@anchor{3bc9}
@deffnx {C 函数} int PyUnicodeEncodeError_GetEnd (PyObject@w{ }*exc, Py_ssize_t@w{ }*end)
@anchor{c-api/exceptions c PyUnicodeTranslateError_GetEnd}@anchor{3bca}
@deffnx {C 函数} int PyUnicodeTranslateError_GetEnd (PyObject@w{ }*exc, Py_ssize_t@w{ }*end)

Get the @emph{end} attribute of the given exception object and place it into
@emph{*end}.  @emph{end} must not be @code{NULL}.  Return @code{0} on success, @code{-1} on
failure.
@end deffn

@geindex PyUnicodeDecodeError_SetEnd (C 函数)
@geindex PyUnicodeEncodeError_SetEnd (C 函数)
@geindex PyUnicodeTranslateError_SetEnd (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_SetEnd}@anchor{3bcb}
@deffn {C 函数} int PyUnicodeDecodeError_SetEnd (PyObject@w{ }*exc, Py_ssize_t@w{ }end)
@anchor{c-api/exceptions c PyUnicodeEncodeError_SetEnd}@anchor{3bcc}
@deffnx {C 函数} int PyUnicodeEncodeError_SetEnd (PyObject@w{ }*exc, Py_ssize_t@w{ }end)
@anchor{c-api/exceptions c PyUnicodeTranslateError_SetEnd}@anchor{3bcd}
@deffnx {C 函数} int PyUnicodeTranslateError_SetEnd (PyObject@w{ }*exc, Py_ssize_t@w{ }end)

Set the @emph{end} attribute of the given exception object to @emph{end}.  Return @code{0}
on success, @code{-1} on failure.
@end deffn

@geindex PyUnicodeDecodeError_GetReason (C 函数)
@geindex PyUnicodeEncodeError_GetReason (C 函数)
@geindex PyUnicodeTranslateError_GetReason (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_GetReason}@anchor{3bce}
@deffn {C 函数} PyObject* PyUnicodeDecodeError_GetReason (PyObject@w{ }*exc)
@anchor{c-api/exceptions c PyUnicodeEncodeError_GetReason}@anchor{3bcf}
@deffnx {C 函数} PyObject* PyUnicodeEncodeError_GetReason (PyObject@w{ }*exc)
@anchor{c-api/exceptions c PyUnicodeTranslateError_GetReason}@anchor{3bd0}
@deffnx {C 函数} PyObject* PyUnicodeTranslateError_GetReason (PyObject@w{ }*exc)
@emph{Return value: New reference.}
Return the @emph{reason} attribute of the given exception object.
@end deffn

@geindex PyUnicodeDecodeError_SetReason (C 函数)
@geindex PyUnicodeEncodeError_SetReason (C 函数)
@geindex PyUnicodeTranslateError_SetReason (C 函数)
@anchor{c-api/exceptions c PyUnicodeDecodeError_SetReason}@anchor{3bd1}
@deffn {C 函数} int PyUnicodeDecodeError_SetReason (PyObject@w{ }*exc, const char@w{ }*reason)
@anchor{c-api/exceptions c PyUnicodeEncodeError_SetReason}@anchor{3bd2}
@deffnx {C 函数} int PyUnicodeEncodeError_SetReason (PyObject@w{ }*exc, const char@w{ }*reason)
@anchor{c-api/exceptions c PyUnicodeTranslateError_SetReason}@anchor{3bd3}
@deffnx {C 函数} int PyUnicodeTranslateError_SetReason (PyObject@w{ }*exc, const char@w{ }*reason)

Set the @emph{reason} attribute of the given exception object to @emph{reason}.  Return
@code{0} on success, @code{-1} on failure.
@end deffn

@node 递归控制,标准异常,Unicode Exception Objects,异常处理
@anchor{c-api/exceptions recursion-control}@anchor{3bd4}
@subsection 递归控制


These two functions provide a way to perform safe recursive calls at the C
level, both in the core and in extension modules.  They are needed if the
recursive code does not necessarily invoke Python code (which tracks its
recursion depth automatically).

@geindex Py_EnterRecursiveCall (C 函数)
@anchor{c-api/exceptions c Py_EnterRecursiveCall}@anchor{3bd5}
@deffn {C 函数} int Py_EnterRecursiveCall (const char@w{ }*where)

Marks a point where a recursive C-level call is about to be performed.

If @code{USE_STACKCHECK} is defined, this function checks if the OS
stack overflowed using @ref{3bd6,,PyOS_CheckStack()}.  In this is the case, it
sets a @ref{f9f,,MemoryError} and returns a nonzero value.

The function then checks if the recursion limit is reached.  If this is the
case, a @ref{62e,,RecursionError} is set and a nonzero value is returned.
Otherwise, zero is returned.

@emph{where} should be a string such as @code{" in instance check"} to be
concatenated to the @ref{62e,,RecursionError} message caused by the recursion
depth limit.
@end deffn

@geindex Py_LeaveRecursiveCall (C 函数)
@anchor{c-api/exceptions c Py_LeaveRecursiveCall}@anchor{3bd7}
@deffn {C 函数} void Py_LeaveRecursiveCall ()

Ends a @ref{3bd5,,Py_EnterRecursiveCall()}.  Must be called once for each
@emph{successful} invocation of @ref{3bd5,,Py_EnterRecursiveCall()}.
@end deffn

Properly implementing @ref{3aff,,tp_repr} for container types requires
special recursion handling.  In addition to protecting the stack,
@ref{3aff,,tp_repr} also needs to track objects to prevent cycles.  The
following two functions facilitate this functionality.  Effectively,
these are the C equivalent to @ref{b69,,reprlib.recursive_repr()}.

@geindex Py_ReprEnter (C 函数)
@anchor{c-api/exceptions c Py_ReprEnter}@anchor{3bd8}
@deffn {C 函数} int Py_ReprEnter (PyObject@w{ }*object)

Called at the beginning of the @ref{3aff,,tp_repr} implementation to
detect cycles.

If the object has already been processed, the function returns a
positive integer.  In that case the @ref{3aff,,tp_repr} implementation
should return a string object indicating a cycle.  As examples,
@ref{1b8,,dict} objects return @code{@{...@}} and @ref{262,,list} objects
return @code{[...]}.

The function will return a negative integer if the recursion limit
is reached.  In that case the @ref{3aff,,tp_repr} implementation should
typically return @code{NULL}.

Otherwise, the function returns zero and the @ref{3aff,,tp_repr}
implementation can continue normally.
@end deffn

@geindex Py_ReprLeave (C 函数)
@anchor{c-api/exceptions c Py_ReprLeave}@anchor{3bd9}
@deffn {C 函数} void Py_ReprLeave (PyObject@w{ }*object)

Ends a @ref{3bd8,,Py_ReprEnter()}.  Must be called once for each
invocation of @ref{3bd8,,Py_ReprEnter()} that returns zero.
@end deffn

@node 标准异常,标准警告类别,递归控制,异常处理
@anchor{c-api/exceptions standard-exceptions}@anchor{3bda}@anchor{c-api/exceptions standardexceptions}@anchor{3bdb}
@subsection 标准异常


All standard Python exceptions are available as global variables whose names are
@code{PyExc_} followed by the Python exception name.  These have the type
@ref{4b5,,PyObject*}; they are all class objects.  For completeness, here are all
the variables:

@geindex PyExc_BaseException
@geindex PyExc_Exception
@geindex PyExc_ArithmeticError
@geindex PyExc_AssertionError
@geindex PyExc_AttributeError
@geindex PyExc_BlockingIOError
@geindex PyExc_BrokenPipeError
@geindex PyExc_BufferError
@geindex PyExc_ChildProcessError
@geindex PyExc_ConnectionAbortedError
@geindex PyExc_ConnectionError
@geindex PyExc_ConnectionRefusedError
@geindex PyExc_ConnectionResetError
@geindex PyExc_EOFError
@geindex PyExc_FileExistsError
@geindex PyExc_FileNotFoundError
@geindex PyExc_FloatingPointError
@geindex PyExc_GeneratorExit
@geindex PyExc_ImportError
@geindex PyExc_IndentationError
@geindex PyExc_IndexError
@geindex PyExc_InterruptedError
@geindex PyExc_IsADirectoryError
@geindex PyExc_KeyError
@geindex PyExc_KeyboardInterrupt
@geindex PyExc_LookupError
@geindex PyExc_MemoryError
@geindex PyExc_ModuleNotFoundError
@geindex PyExc_NameError
@geindex PyExc_NotADirectoryError
@geindex PyExc_NotImplementedError
@geindex PyExc_OSError
@geindex PyExc_OverflowError
@geindex PyExc_PermissionError
@geindex PyExc_ProcessLookupError
@geindex PyExc_RecursionError
@geindex PyExc_ReferenceError
@geindex PyExc_RuntimeError
@geindex PyExc_StopAsyncIteration
@geindex PyExc_StopIteration
@geindex PyExc_SyntaxError
@geindex PyExc_SystemError
@geindex PyExc_SystemExit
@geindex PyExc_TabError
@geindex PyExc_TimeoutError
@geindex PyExc_TypeError
@geindex PyExc_UnboundLocalError
@geindex PyExc_UnicodeDecodeError
@geindex PyExc_UnicodeEncodeError
@geindex PyExc_UnicodeError
@geindex PyExc_UnicodeTranslateError
@geindex PyExc_ValueError
@geindex PyExc_ZeroDivisionError


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx} 
@headitem

C 名称

@tab

Python 名称

@tab

注释

@item

@code{PyExc_BaseException}

@tab

@ref{1a8,,BaseException}

@tab

(1)

@item

@code{PyExc_Exception}

@tab

@ref{1a9,,Exception}

@tab

(1)

@item

@code{PyExc_ArithmeticError}

@tab

@ref{1697,,ArithmeticError}

@tab

(1)

@item

@code{PyExc_AssertionError}

@tab

@ref{fc1,,AssertionError}

@tab

@item

@code{PyExc_AttributeError}

@tab

@ref{393,,AttributeError}

@tab

@item

@code{PyExc_BlockingIOError}

@tab

@ref{991,,BlockingIOError}

@tab

@item

@code{PyExc_BrokenPipeError}

@tab

@ref{997,,BrokenPipeError}

@tab

@item

@code{PyExc_BufferError}

@tab

@ref{1699,,BufferError}

@tab

@item

@code{PyExc_ChildProcessError}

@tab

@ref{992,,ChildProcessError}

@tab

@item

@code{PyExc_ConnectionAbortedError}

@tab

@ref{998,,ConnectionAbortedError}

@tab

@item

@code{PyExc_ConnectionError}

@tab

@ref{6e0,,ConnectionError}

@tab

@item

@code{PyExc_ConnectionRefusedError}

@tab

@ref{999,,ConnectionRefusedError}

@tab

@item

@code{PyExc_ConnectionResetError}

@tab

@ref{99a,,ConnectionResetError}

@tab

@item

@code{PyExc_EOFError}

@tab

@ref{c65,,EOFError}

@tab

@item

@code{PyExc_FileExistsError}

@tab

@ref{952,,FileExistsError}

@tab

@item

@code{PyExc_FileNotFoundError}

@tab

@ref{7ba,,FileNotFoundError}

@tab

@item

@code{PyExc_FloatingPointError}

@tab

@ref{1698,,FloatingPointError}

@tab

@item

@code{PyExc_GeneratorExit}

@tab

@ref{d2b,,GeneratorExit}

@tab

@item

@code{PyExc_ImportError}

@tab

@ref{32d,,ImportError}

@tab

@item

@code{PyExc_IndentationError}

@tab

@ref{e71,,IndentationError}

@tab

@item

@code{PyExc_IndexError}

@tab

@ref{e6e,,IndexError}

@tab

@item

@code{PyExc_InterruptedError}

@tab

@ref{653,,InterruptedError}

@tab

@item

@code{PyExc_IsADirectoryError}

@tab

@ref{993,,IsADirectoryError}

@tab

@item

@code{PyExc_KeyError}

@tab

@ref{2c7,,KeyError}

@tab

@item

@code{PyExc_KeyboardInterrupt}

@tab

@ref{197,,KeyboardInterrupt}

@tab

@item

@code{PyExc_LookupError}

@tab

@ref{15f6,,LookupError}

@tab

(1)

@item

@code{PyExc_MemoryError}

@tab

@ref{f9f,,MemoryError}

@tab

@item

@code{PyExc_ModuleNotFoundError}

@tab

@ref{392,,ModuleNotFoundError}

@tab

@item

@code{PyExc_NameError}

@tab

@ref{d74,,NameError}

@tab

@item

@code{PyExc_NotADirectoryError}

@tab

@ref{994,,NotADirectoryError}

@tab

@item

@code{PyExc_NotImplementedError}

@tab

@ref{609,,NotImplementedError}

@tab

@item

@code{PyExc_OSError}

@tab

@ref{1d3,,OSError}

@tab

(1)

@item

@code{PyExc_OverflowError}

@tab

@ref{95a,,OverflowError}

@tab

@item

@code{PyExc_PermissionError}

@tab

@ref{5fa,,PermissionError}

@tab

@item

@code{PyExc_ProcessLookupError}

@tab

@ref{995,,ProcessLookupError}

@tab

@item

@code{PyExc_RecursionError}

@tab

@ref{62e,,RecursionError}

@tab

@item

@code{PyExc_ReferenceError}

@tab

@ref{e46,,ReferenceError}

@tab

(2)

@item

@code{PyExc_RuntimeError}

@tab

@ref{2ba,,RuntimeError}

@tab

@item

@code{PyExc_StopAsyncIteration}

@tab

@ref{fa5,,StopAsyncIteration}

@tab

@item

@code{PyExc_StopIteration}

@tab

@ref{480,,StopIteration}

@tab

@item

@code{PyExc_SyntaxError}

@tab

@ref{452,,SyntaxError}

@tab

@item

@code{PyExc_SystemError}

@tab

@ref{5f6,,SystemError}

@tab

@item

@code{PyExc_SystemExit}

@tab

@ref{5f7,,SystemExit}

@tab

@item

@code{PyExc_TabError}

@tab

@ref{e70,,TabError}

@tab

@item

@code{PyExc_TimeoutError}

@tab

@ref{996,,TimeoutError}

@tab

@item

@code{PyExc_TypeError}

@tab

@ref{192,,TypeError}

@tab

@item

@code{PyExc_UnboundLocalError}

@tab

@ref{e6f,,UnboundLocalError}

@tab

@item

@code{PyExc_UnicodeDecodeError}

@tab

@ref{1fd,,UnicodeDecodeError}

@tab

@item

@code{PyExc_UnicodeEncodeError}

@tab

@ref{1fc,,UnicodeEncodeError}

@tab

@item

@code{PyExc_UnicodeError}

@tab

@ref{c34,,UnicodeError}

@tab

@item

@code{PyExc_UnicodeTranslateError}

@tab

@ref{16aa,,UnicodeTranslateError}

@tab

@item

@code{PyExc_ValueError}

@tab

@ref{1fb,,ValueError}

@tab

@item

@code{PyExc_ZeroDivisionError}

@tab

@ref{1241,,ZeroDivisionError}

@tab

@end multitable



3.3 新版功能: @code{PyExc_BlockingIOError}, @code{PyExc_BrokenPipeError}, @code{PyExc_ChildProcessError}, @code{PyExc_ConnectionError}, @code{PyExc_ConnectionAbortedError}, @code{PyExc_ConnectionRefusedError}, @code{PyExc_ConnectionResetError}, @code{PyExc_FileExistsError}, @code{PyExc_FileNotFoundError}, @code{PyExc_InterruptedError}, @code{PyExc_IsADirectoryError}, @code{PyExc_NotADirectoryError}, @code{PyExc_PermissionError}, @code{PyExc_ProcessLookupError} and @code{PyExc_TimeoutError} 介绍如下 
@geindex Python 提高建议; PEP 3151
PEP 3151@footnote{https://www.python.org/dev/peps/pep-3151}.



3.5 新版功能: @code{PyExc_StopAsyncIteration} 和 @code{PyExc_RecursionError}.



3.6 新版功能: @code{PyExc_ModuleNotFoundError}.


这些是兼容性别名 @code{PyExc_OSError}:

@geindex PyExc_EnvironmentError
@geindex PyExc_IOError
@geindex PyExc_WindowsError


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx} 
@headitem

C 名称

@tab

注释

@item

@code{PyExc_EnvironmentError}

@tab

@item

@code{PyExc_IOError}

@tab

@item

@code{PyExc_WindowsError}

@tab

(3)

@end multitable



在 3.3 版更改: 这些别名曾经是单独的异常类型。


注释:


@enumerate 

@item 
这是其他标准异常的基类。

@item 
Only defined on Windows; protect code that uses this by testing that the
preprocessor macro @code{MS_WINDOWS} is defined.
@end enumerate

@node 标准警告类别,,标准异常,异常处理
@anchor{c-api/exceptions standard-warning-categories}@anchor{3bdc}@anchor{c-api/exceptions standardwarningcategories}@anchor{3ba7}
@subsection 标准警告类别


All standard Python warning categories are available as global variables whose
names are @code{PyExc_} followed by the Python exception name. These have the type
@ref{4b5,,PyObject*}; they are all class objects. For completeness, here are all
the variables:

@geindex PyExc_Warning
@geindex PyExc_BytesWarning
@geindex PyExc_DeprecationWarning
@geindex PyExc_FutureWarning
@geindex PyExc_ImportWarning
@geindex PyExc_PendingDeprecationWarning
@geindex PyExc_ResourceWarning
@geindex PyExc_RuntimeWarning
@geindex PyExc_SyntaxWarning
@geindex PyExc_UnicodeWarning
@geindex PyExc_UserWarning


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx} 
@headitem

C 名称

@tab

Python 名称

@tab

注释

@item

@code{PyExc_Warning}

@tab

@ref{16af,,Warning}

@tab

(1)

@item

@code{PyExc_BytesWarning}

@tab

@ref{4b0,,BytesWarning}

@tab

@item

@code{PyExc_DeprecationWarning}

@tab

@ref{278,,DeprecationWarning}

@tab

@item

@code{PyExc_FutureWarning}

@tab

@ref{31e,,FutureWarning}

@tab

@item

@code{PyExc_ImportWarning}

@tab

@ref{5d3,,ImportWarning}

@tab

@item

@code{PyExc_PendingDeprecationWarning}

@tab

@ref{279,,PendingDeprecationWarning}

@tab

@item

@code{PyExc_ResourceWarning}

@tab

@ref{4ca,,ResourceWarning}

@tab

@item

@code{PyExc_RuntimeWarning}

@tab

@ref{2c0,,RuntimeWarning}

@tab

@item

@code{PyExc_SyntaxWarning}

@tab

@ref{191,,SyntaxWarning}

@tab

@item

@code{PyExc_UnicodeWarning}

@tab

@ref{d80,,UnicodeWarning}

@tab

@item

@code{PyExc_UserWarning}

@tab

@ref{16b0,,UserWarning}

@tab

@end multitable



3.2 新版功能: @code{PyExc_ResourceWarning}.


注释:


@enumerate 

@item 
这是其他标准警告类别的基类。
@end enumerate

@node 工具<2>,抽象对象层,异常处理,Python/C API 参考手册
@anchor{c-api/utilities doc}@anchor{3bdd}@anchor{c-api/utilities id1}@anchor{3bde}@anchor{c-api/utilities utilities}@anchor{3bdf}
@section 工具


本章中的函数执行各种实用工具任务，包括帮助 C 代码提升跨平台可移植性，在 C 中使用 Python 模块，以及解析函数参数并根据 C 中的值构建 Python 中的值等等。

@menu
* 操作系统实用程序:: 
* 系统功能:: 
* 过程控制:: 
* 导入模块: 导入模块<2>. 
* 数据 marshal 操作支持:: 
* 解析参数并构建值变量:: 
* 字符串转换与格式化:: 
* 反射:: 
* 编解码器注册与支持功能:: 

@end menu

@node 操作系统实用程序,系统功能,,工具<2>
@anchor{c-api/sys doc}@anchor{3be0}@anchor{c-api/sys operating-system-utilities}@anchor{3be1}@anchor{c-api/sys os}@anchor{3be2}
@subsection 操作系统实用程序


@geindex PyOS_FSPath (C 函数)
@anchor{c-api/sys c PyOS_FSPath}@anchor{5c8}
@deffn {C 函数} PyObject* PyOS_FSPath (PyObject@w{ }*path)
@emph{Return value: New reference.}
Return the file system representation for @emph{path}. If the object is a
@ref{329,,str} or @ref{32a,,bytes} object, then its reference count is
incremented. If the object implements the @ref{4e5,,os.PathLike} interface,
then @ref{4e6,,__fspath__()} is returned as long as it is a
@ref{329,,str} or @ref{32a,,bytes} object. Otherwise @ref{192,,TypeError} is raised
and @code{NULL} is returned.


3.6 新版功能.

@end deffn

@geindex Py_FdIsInteractive (C 函数)
@anchor{c-api/sys c Py_FdIsInteractive}@anchor{3be3}
@deffn {C 函数} int Py_FdIsInteractive (FILE@w{ }*fp, const char@w{ }*filename)

Return true (nonzero) if the standard I/O file @emph{fp} with name @emph{filename} is
deemed interactive.  This is the case for files for which @code{isatty(fileno(fp))}
is true.  If the global flag @ref{3be4,,Py_InteractiveFlag} is true, this function
also returns true if the @emph{filename} pointer is @code{NULL} or if the name is equal to
one of the strings @code{'<stdin>'} or @code{'???'}.
@end deffn

@geindex PyOS_BeforeFork (C 函数)
@anchor{c-api/sys c PyOS_BeforeFork}@anchor{42c}
@deffn {C 函数} void PyOS_BeforeFork ()

Function to prepare some internal state before a process fork.  This
should be called before calling @code{fork()} or any similar function
that clones the current process.
Only available on systems where @code{fork()} is defined.

@cartouche
@quotation 警告 
The C @code{fork()} call should only be made from the
@ref{3be5,,"main" thread} (of the
@ref{3be6,,"main" interpreter}).  The same is
true for @code{PyOS_BeforeFork()}.
@end quotation
@end cartouche


3.7 新版功能.

@end deffn

@geindex PyOS_AfterFork_Parent (C 函数)
@anchor{c-api/sys c PyOS_AfterFork_Parent}@anchor{42d}
@deffn {C 函数} void PyOS_AfterFork_Parent ()

Function to update some internal state after a process fork.  This
should be called from the parent process after calling @code{fork()}
or any similar function that clones the current process, regardless
of whether process cloning was successful.
Only available on systems where @code{fork()} is defined.

@cartouche
@quotation 警告 
The C @code{fork()} call should only be made from the
@ref{3be5,,"main" thread} (of the
@ref{3be6,,"main" interpreter}).  The same is
true for @code{PyOS_AfterFork_Parent()}.
@end quotation
@end cartouche


3.7 新版功能.

@end deffn

@geindex PyOS_AfterFork_Child (C 函数)
@anchor{c-api/sys c PyOS_AfterFork_Child}@anchor{2cd}
@deffn {C 函数} void PyOS_AfterFork_Child ()

Function to update internal interpreter state after a process fork.
This must be called from the child process after calling @code{fork()},
or any similar function that clones the current process, if there is
any chance the process will call back into the Python interpreter.
Only available on systems where @code{fork()} is defined.

@cartouche
@quotation 警告 
The C @code{fork()} call should only be made from the
@ref{3be5,,"main" thread} (of the
@ref{3be6,,"main" interpreter}).  The same is
true for @code{PyOS_AfterFork_Child()}.
@end quotation
@end cartouche


3.7 新版功能.



@subsubheading 参见


@ref{3ae,,os.register_at_fork()} allows registering custom Python functions
to be called by @ref{42c,,PyOS_BeforeFork()},
@ref{42d,,PyOS_AfterFork_Parent()} and  @ref{2cd,,PyOS_AfterFork_Child()}.

@end deffn

@geindex PyOS_AfterFork (C 函数)
@anchor{c-api/sys c PyOS_AfterFork}@anchor{42b}
@deffn {C 函数} void PyOS_AfterFork ()

Function to update some internal state after a process fork; this should be
called in the new process if the Python interpreter will continue to be used.
If a new executable is loaded into the new process, this function does not need
to be called.


3.7 版后已移除: This function is superseded by @ref{2cd,,PyOS_AfterFork_Child()}.

@end deffn

@geindex PyOS_CheckStack (C 函数)
@anchor{c-api/sys c PyOS_CheckStack}@anchor{3bd6}
@deffn {C 函数} int PyOS_CheckStack ()

Return true when the interpreter runs out of stack space.  This is a reliable
check, but is only available when @code{USE_STACKCHECK} is defined (currently
on Windows using the Microsoft Visual C++ compiler).  @code{USE_STACKCHECK}
will be defined automatically; you should never change the definition in your
own code.
@end deffn

@geindex PyOS_getsig (C 函数)
@anchor{c-api/sys c PyOS_getsig}@anchor{3be7}
@deffn {C 函数} PyOS_sighandler_t PyOS_getsig (int@w{ }i)

Return the current signal handler for signal @emph{i}.  This is a thin wrapper around
either @code{sigaction()} or @code{signal()}.  Do not call those functions
directly! @code{PyOS_sighandler_t} is a typedef alias for @code{void
(*)(int)}.
@end deffn

@geindex PyOS_setsig (C 函数)
@anchor{c-api/sys c PyOS_setsig}@anchor{3be8}
@deffn {C 函数} PyOS_sighandler_t PyOS_setsig (int@w{ }i, PyOS_sighandler_t@w{ }h)

Set the signal handler for signal @emph{i} to be @emph{h}; return the old signal handler.
This is a thin wrapper around either @code{sigaction()} or @code{signal()}.  Do
not call those functions directly!  @code{PyOS_sighandler_t} is a typedef
alias for @code{void (*)(int)}.
@end deffn

@geindex Py_DecodeLocale (C 函数)
@anchor{c-api/sys c Py_DecodeLocale}@anchor{436}
@deffn {C 函数} wchar_t* Py_DecodeLocale (const char*@w{ }arg, size_t@w{ }*size)

Decode a byte string from the locale encoding with the @ref{17dd,,surrogateescape error handler}: undecodable bytes are decoded as
characters in range U+DC80..U+DCFF. If a byte sequence can be decoded as a
surrogate character, escape the bytes using the surrogateescape error
handler instead of decoding them.

Encoding, highest priority to lowest priority:


@itemize *

@item 
@code{UTF-8} on macOS, Android, and VxWorks;

@item 
@code{UTF-8} on Windows if @ref{3be9,,Py_LegacyWindowsFSEncodingFlag} is zero;

@item 
@code{UTF-8} if the Python UTF-8 mode is enabled;

@item 
@code{ASCII} if the @code{LC_CTYPE} locale is @code{"C"},
@code{nl_langinfo(CODESET)} returns the @code{ASCII} encoding (or an alias),
and @code{mbstowcs()} and @code{wcstombs()} functions uses the
@code{ISO-8859-1} encoding.

@item 
the current locale encoding.
@end itemize

Return a pointer to a newly allocated wide character string, use
@ref{3bea,,PyMem_RawFree()} to free the memory. If size is not @code{NULL}, write
the number of wide characters excluding the null character into @code{*size}

Return @code{NULL} on decoding error or memory allocation error. If @emph{size} is
not @code{NULL}, @code{*size} is set to @code{(size_t)-1} on memory error or set to
@code{(size_t)-2} on decoding error.

Decoding errors should never happen, unless there is a bug in the C
library.

Use the @ref{437,,Py_EncodeLocale()} function to encode the character string
back to a byte string.


@subsubheading 参见


The @ref{3beb,,PyUnicode_DecodeFSDefaultAndSize()} and
@ref{438,,PyUnicode_DecodeLocaleAndSize()} functions.



3.5 新版功能.



在 3.7 版更改: The function now uses the UTF-8 encoding in the UTF-8 mode.



在 3.8 版更改: The function now uses the UTF-8 encoding on Windows if
@ref{3be9,,Py_LegacyWindowsFSEncodingFlag} is zero;

@end deffn

@geindex Py_EncodeLocale (C 函数)
@anchor{c-api/sys c Py_EncodeLocale}@anchor{437}
@deffn {C 函数} char* Py_EncodeLocale (const wchar_t@w{ }*text, size_t@w{ }*error_pos)

Encode a wide character string to the locale encoding with the
@ref{17dd,,surrogateescape error handler}: surrogate characters
in the range U+DC80..U+DCFF are converted to bytes 0x80..0xFF.

Encoding, highest priority to lowest priority:


@itemize *

@item 
@code{UTF-8} on macOS, Android, and VxWorks;

@item 
@code{UTF-8} on Windows if @ref{3be9,,Py_LegacyWindowsFSEncodingFlag} is zero;

@item 
@code{UTF-8} if the Python UTF-8 mode is enabled;

@item 
@code{ASCII} if the @code{LC_CTYPE} locale is @code{"C"},
@code{nl_langinfo(CODESET)} returns the @code{ASCII} encoding (or an alias),
and @code{mbstowcs()} and @code{wcstombs()} functions uses the
@code{ISO-8859-1} encoding.

@item 
the current locale encoding.
@end itemize

The function uses the UTF-8 encoding in the Python UTF-8 mode.

Return a pointer to a newly allocated byte string, use @ref{da2,,PyMem_Free()}
to free the memory. Return @code{NULL} on encoding error or memory allocation
error

If error_pos is not @code{NULL}, @code{*error_pos} is set to @code{(size_t)-1} on
success,  or set to the index of the invalid character on encoding error.

Use the @ref{436,,Py_DecodeLocale()} function to decode the bytes string back
to a wide character string.


@subsubheading 参见


The @ref{fde,,PyUnicode_EncodeFSDefault()} and
@ref{439,,PyUnicode_EncodeLocale()} functions.



3.5 新版功能.



在 3.7 版更改: The function now uses the UTF-8 encoding in the UTF-8 mode.



在 3.8 版更改: The function now uses the UTF-8 encoding on Windows if
@ref{3be9,,Py_LegacyWindowsFSEncodingFlag} is zero;

@end deffn

@node 系统功能,过程控制,操作系统实用程序,工具<2>
@anchor{c-api/sys system-functions}@anchor{3bec}@anchor{c-api/sys systemfunctions}@anchor{3bed}
@subsection 系统功能


These are utility functions that make functionality from the @ref{fd,,sys} module
accessible to C code.  They all work with the current interpreter thread's
@ref{fd,,sys} module's dict, which is contained in the internal thread state structure.

@geindex PySys_GetObject (C 函数)
@anchor{c-api/sys c PySys_GetObject}@anchor{3bee}
@deffn {C 函数} PyObject *PySys_GetObject (const char@w{ }*name)
@emph{Return value: Borrowed reference.}
Return the object @emph{name} from the @ref{fd,,sys} module or @code{NULL} if it does
not exist, without setting an exception.
@end deffn

@geindex PySys_SetObject (C 函数)
@anchor{c-api/sys c PySys_SetObject}@anchor{3bef}
@deffn {C 函数} int PySys_SetObject (const char@w{ }*name, PyObject@w{ }*v)

Set @emph{name} in the @ref{fd,,sys} module to @emph{v} unless @emph{v} is @code{NULL}, in which
case @emph{name} is deleted from the sys module. Returns @code{0} on success, @code{-1}
on error.
@end deffn

@geindex PySys_ResetWarnOptions (C 函数)
@anchor{c-api/sys c PySys_ResetWarnOptions}@anchor{3bf0}
@deffn {C 函数} void PySys_ResetWarnOptions ()

Reset @ref{40e,,sys.warnoptions} to an empty list. This function may be
called prior to @ref{433,,Py_Initialize()}.
@end deffn

@geindex PySys_AddWarnOption (C 函数)
@anchor{c-api/sys c PySys_AddWarnOption}@anchor{4ae}
@deffn {C 函数} void PySys_AddWarnOption (const wchar_t@w{ }*s)

Append @emph{s} to @ref{40e,,sys.warnoptions}. This function must be called prior
to @ref{433,,Py_Initialize()} in order to affect the warnings filter list.
@end deffn

@geindex PySys_AddWarnOptionUnicode (C 函数)
@anchor{c-api/sys c PySys_AddWarnOptionUnicode}@anchor{4ad}
@deffn {C 函数} void PySys_AddWarnOptionUnicode (PyObject@w{ }*unicode)

Append @emph{unicode} to @ref{40e,,sys.warnoptions}.

Note: this function is not currently usable from outside the CPython
implementation, as it must be called prior to the implicit import of
@ref{126,,warnings} in @ref{433,,Py_Initialize()} to be effective, but can't be
called until enough of the runtime has been initialized to permit the
creation of Unicode objects.
@end deffn

@geindex PySys_SetPath (C 函数)
@anchor{c-api/sys c PySys_SetPath}@anchor{3bf1}
@deffn {C 函数} void PySys_SetPath (const wchar_t@w{ }*path)

Set @ref{482,,sys.path} to a list object of paths found in @emph{path} which should
be a list of paths separated with the platform's search path delimiter
(@code{:} on Unix, @code{;} on Windows).
@end deffn

@geindex PySys_WriteStdout (C 函数)
@anchor{c-api/sys c PySys_WriteStdout}@anchor{3bf2}
@deffn {C 函数} void PySys_WriteStdout (const char@w{ }*format, ...)

Write the output string described by @emph{format} to @ref{307,,sys.stdout}.  No
exceptions are raised, even if truncation occurs (see below).

@emph{format} should limit the total size of the formatted output string to
1000 bytes or less -- after 1000 bytes, the output string is truncated.
In particular, this means that no unrestricted "%s" formats should occur;
these should be limited using "%.<N>s" where <N> is a decimal number
calculated so that <N> plus the maximum size of other formatted text does not
exceed 1000 bytes.  Also watch out for "%f", which can print hundreds of
digits for very large numbers.

If a problem occurs, or @ref{307,,sys.stdout} is unset, the formatted message
is written to the real (C level) @emph{stdout}.
@end deffn

@geindex PySys_WriteStderr (C 函数)
@anchor{c-api/sys c PySys_WriteStderr}@anchor{3bf3}
@deffn {C 函数} void PySys_WriteStderr (const char@w{ }*format, ...)

As @ref{3bf2,,PySys_WriteStdout()}, but write to @ref{308,,sys.stderr} or @emph{stderr}
instead.
@end deffn

@geindex PySys_FormatStdout (C 函数)
@anchor{c-api/sys c PySys_FormatStdout}@anchor{3bf4}
@deffn {C 函数} void PySys_FormatStdout (const char@w{ }*format, ...)

Function similar to PySys_WriteStdout() but format the message using
@ref{3bf5,,PyUnicode_FromFormatV()} and don't truncate the message to an
arbitrary length.


3.2 新版功能.

@end deffn

@geindex PySys_FormatStderr (C 函数)
@anchor{c-api/sys c PySys_FormatStderr}@anchor{3bf6}
@deffn {C 函数} void PySys_FormatStderr (const char@w{ }*format, ...)

As @ref{3bf4,,PySys_FormatStdout()}, but write to @ref{308,,sys.stderr} or @emph{stderr}
instead.


3.2 新版功能.

@end deffn

@geindex PySys_AddXOption (C 函数)
@anchor{c-api/sys c PySys_AddXOption}@anchor{3bf7}
@deffn {C 函数} void PySys_AddXOption (const wchar_t@w{ }*s)

Parse @emph{s} as a set of @ref{155,,-X} options and add them to the current
options mapping as returned by @ref{3bf8,,PySys_GetXOptions()}. This function
may be called prior to @ref{433,,Py_Initialize()}.


3.2 新版功能.

@end deffn

@geindex PySys_GetXOptions (C 函数)
@anchor{c-api/sys c PySys_GetXOptions}@anchor{3bf8}
@deffn {C 函数} PyObject *PySys_GetXOptions ()
@emph{Return value: Borrowed reference.}
Return the current dictionary of @ref{155,,-X} options, similarly to
@ref{12e7,,sys._xoptions}.  On error, @code{NULL} is returned and an exception is
set.


3.2 新版功能.

@end deffn

@geindex PySys_Audit (C 函数)
@anchor{c-api/sys c PySys_Audit}@anchor{ec5}
@deffn {C 函数} int PySys_Audit (const char@w{ }*event, const char@w{ }*format, ...)

Raise an auditing event with any active hooks. Return zero for success
and non-zero with an exception set on failure.

If any hooks have been added, @emph{format} and other arguments will be used
to construct a tuple to pass. Apart from @code{N}, the same format characters
as used in @ref{2ce,,Py_BuildValue()} are available. If the built value is not
a tuple, it will be added into a single-element tuple. (The @code{N} format
option consumes a reference, but since there is no way to know whether
arguments to this function will be consumed, using it may cause reference
leaks.)

Note that @code{#} format characters should always be treated as
@code{Py_ssize_t}, regardless of whether @code{PY_SSIZE_T_CLEAN} was defined.

@ref{eb7,,sys.audit()} performs the same function from Python code.


3.8 新版功能.



在 3.8.2 版更改: Require @code{Py_ssize_t} for @code{#} format characters. Previously, an
unavoidable deprecation warning was raised.

@end deffn

@geindex PySys_AddAuditHook (C 函数)
@anchor{c-api/sys c PySys_AddAuditHook}@anchor{3468}
@deffn {C 函数} int PySys_AddAuditHook (Py_AuditHookFunction@w{ }hook, void@w{ }*userData)

Append the callable @emph{hook} to the list of active auditing hooks.
Return zero for success
and non-zero on failure. If the runtime has been initialized, also set an
error on failure. Hooks added through this API are called for all
interpreters created by the runtime.

@emph{userData} 指针会被传入钩子函数。 因于钩子函数可能由不同的运行时调用，该指针不应直接指向 Python 状态。

This function is safe to call before @ref{433,,Py_Initialize()}. When called
after runtime initialization, existing audit hooks are notified and may
silently abort the operation by raising an error subclassed from
@ref{1a9,,Exception} (other errors will not be silenced).

The hook function is of type @code{int (*)(const char *event, PyObject
*args, void *userData)}, where @emph{args} is guaranteed to be a
@ref{3bf9,,PyTupleObject}. The hook function is always called with the GIL
held by the Python interpreter that raised the event.

See 
@geindex Python 提高建议; PEP 578
PEP 578@footnote{https://www.python.org/dev/peps/pep-0578} for a detailed description of auditing.  Functions in the
runtime and standard library that raise events are listed in the
@ref{3464,,audit events table}.
Details are in each function's documentation.

引发一个 @ref{12d0,,审计事件} @code{sys.addaudithook}，没有附带参数。


3.8 新版功能.

@end deffn

@node 过程控制,导入模块<2>,系统功能,工具<2>
@anchor{c-api/sys process-control}@anchor{3bfa}@anchor{c-api/sys processcontrol}@anchor{3bfb}
@subsection 过程控制


@geindex Py_FatalError (C 函数)
@anchor{c-api/sys c Py_FatalError}@anchor{f19}
@deffn {C 函数} void Py_FatalError (const char@w{ }*message)

@geindex abort()

Print a fatal error message and kill the process.  No cleanup is performed.
This function should only be invoked when a condition is detected that would
make it dangerous to continue using the Python interpreter; e.g., when the
object administration appears to be corrupted.  On Unix, the standard C library
function @code{abort()} is called which will attempt to produce a @code{core}
file.
@end deffn

@geindex Py_Exit (C 函数)
@anchor{c-api/sys c Py_Exit}@anchor{60d}
@deffn {C 函数} void Py_Exit (int@w{ }status)

@geindex Py_FinalizeEx()
@geindex exit()

Exit the current process.  This calls @ref{5c4,,Py_FinalizeEx()} and then calls the
standard C library function @code{exit(status)}.  If @ref{5c4,,Py_FinalizeEx()}
indicates an error, the exit status is set to 120.


在 3.6 版更改: Errors from finalization no longer ignored.

@end deffn

@geindex Py_AtExit (C 函数)
@anchor{c-api/sys c Py_AtExit}@anchor{3bfc}
@deffn {C 函数} int Py_AtExit (void (*func)())

@geindex Py_FinalizeEx()
@geindex cleanup functions

Register a cleanup function to be called by @ref{5c4,,Py_FinalizeEx()}.  The cleanup
function will be called with no arguments and should return no value.  At most
32 cleanup functions can be registered.  When the registration is successful,
@ref{3bfc,,Py_AtExit()} returns @code{0}; on failure, it returns @code{-1}.  The cleanup
function registered last is called first. Each cleanup function will be called
at most once.  Since Python's internal finalization will have completed before
the cleanup function, no Python APIs should be called by @emph{func}.
@end deffn

@node 导入模块<2>,数据 marshal 操作支持,过程控制,工具<2>
@anchor{c-api/import doc}@anchor{3bfd}@anchor{c-api/import importing}@anchor{3bfe}@anchor{c-api/import importing-modules}@anchor{3bff}
@subsection 导入模块


@geindex PyImport_ImportModule (C 函数)
@anchor{c-api/import c PyImport_ImportModule}@anchor{c6c}
@deffn {C 函数} PyObject* PyImport_ImportModule (const char@w{ }*name)
@emph{Return value: New reference.}
@geindex package variable; __all__
@geindex __all__ (package variable)
@geindex modules (in module sys)

This is a simplified interface to @ref{b1a,,PyImport_ImportModuleEx()} below,
leaving the @emph{globals} and @emph{locals} arguments set to @code{NULL} and @emph{level} set
to 0.  When the @emph{name}
argument contains a dot (when it specifies a submodule of a package), the
@emph{fromlist} argument is set to the list @code{['*']} so that the return value is the
named module rather than the top-level package containing it as would otherwise
be the case.  (Unfortunately, this has an additional side effect when @emph{name} in
fact specifies a subpackage instead of a submodule: the submodules specified in
the package's @code{__all__} variable are  loaded.)  Return a new reference to the
imported module, or @code{NULL} with an exception set on failure.  A failing
import of a module doesn't leave the module in @ref{eb5,,sys.modules}.

该函数总是使用绝对路径导入。
@end deffn

@geindex PyImport_ImportModuleNoBlock (C 函数)
@anchor{c-api/import c PyImport_ImportModuleNoBlock}@anchor{9bb}
@deffn {C 函数} PyObject* PyImport_ImportModuleNoBlock (const char@w{ }*name)
@emph{Return value: New reference.}
该函数是 @ref{c6c,,PyImport_ImportModule()} 的一个被遗弃的别名。


在 3.3 版更改: This function used to fail immediately when the import lock was held
by another thread.  In Python 3.3 though, the locking scheme switched
to per-module locks for most purposes, so this function's special
behaviour isn't needed anymore.

@end deffn

@geindex PyImport_ImportModuleEx (C 函数)
@anchor{c-api/import c PyImport_ImportModuleEx}@anchor{b1a}
@deffn {C 函数} PyObject* PyImport_ImportModuleEx (const char@w{ }*name, PyObject@w{ }*globals, PyObject@w{ }*locals, PyObject@w{ }*fromlist)
@emph{Return value: New reference.}
@geindex 內置函数; __import__

Import a module.  This is best described by referring to the built-in Python
function @ref{60b,,__import__()}.

The return value is a new reference to the imported module or top-level
package, or @code{NULL} with an exception set on failure.  Like for
@ref{60b,,__import__()}, the return value when a submodule of a package was
requested is normally the top-level package, unless a non-empty @emph{fromlist}
was given.

Failing imports remove incomplete module objects, like with
@ref{c6c,,PyImport_ImportModule()}.
@end deffn

@geindex PyImport_ImportModuleLevelObject (C 函数)
@anchor{c-api/import c PyImport_ImportModuleLevelObject}@anchor{3c00}
@deffn {C 函数} PyObject* PyImport_ImportModuleLevelObject (PyObject@w{ }*name, PyObject@w{ }*globals, PyObject@w{ }*locals, PyObject@w{ }*fromlist, int@w{ }level)
@emph{Return value: New reference.}
Import a module.  This is best described by referring to the built-in Python
function @ref{60b,,__import__()}, as the standard @ref{60b,,__import__()} function calls
this function directly.

The return value is a new reference to the imported module or top-level package,
or @code{NULL} with an exception set on failure.  Like for @ref{60b,,__import__()},
the return value when a submodule of a package was requested is normally the
top-level package, unless a non-empty @emph{fromlist} was given.


3.3 新版功能.

@end deffn

@geindex PyImport_ImportModuleLevel (C 函数)
@anchor{c-api/import c PyImport_ImportModuleLevel}@anchor{b19}
@deffn {C 函数} PyObject* PyImport_ImportModuleLevel (const char@w{ }*name, PyObject@w{ }*globals, PyObject@w{ }*locals, PyObject@w{ }*fromlist, int@w{ }level)
@emph{Return value: New reference.}
Similar to @ref{3c00,,PyImport_ImportModuleLevelObject()}, but the name is a
UTF-8 encoded string instead of a Unicode object.


在 3.3 版更改: Negative values for @emph{level} are no longer accepted.

@end deffn

@geindex PyImport_Import (C 函数)
@anchor{c-api/import c PyImport_Import}@anchor{d58}
@deffn {C 函数} PyObject* PyImport_Import (PyObject@w{ }*name)
@emph{Return value: New reference.}
This is a higher-level interface that calls the current "import hook
function" (with an explicit @emph{level} of 0, meaning absolute import).  It
invokes the @ref{60b,,__import__()} function from the @code{__builtins__} of the
current globals.  This means that the import is done using whatever import
hooks are installed in the current environment.

该函数总是使用绝对路径导入。
@end deffn

@geindex PyImport_ReloadModule (C 函数)
@anchor{c-api/import c PyImport_ReloadModule}@anchor{3c01}
@deffn {C 函数} PyObject* PyImport_ReloadModule (PyObject@w{ }*m)
@emph{Return value: New reference.}
Reload a module.  Return a new reference to the reloaded module, or @code{NULL} with
an exception set on failure (the module still exists in this case).
@end deffn

@geindex PyImport_AddModuleObject (C 函数)
@anchor{c-api/import c PyImport_AddModuleObject}@anchor{3c02}
@deffn {C 函数} PyObject* PyImport_AddModuleObject (PyObject@w{ }*name)
@emph{Return value: Borrowed reference.}
Return the module object corresponding to a module name.  The @emph{name} argument
may be of the form @code{package.module}. First check the modules dictionary if
there's one there, and if not, create a new one and insert it in the modules
dictionary. Return @code{NULL} with an exception set on failure.

@cartouche
@quotation 注解 
This function does not load or import the module; if the module wasn't already
loaded, you will get an empty module object. Use @ref{c6c,,PyImport_ImportModule()}
or one of its variants to import a module.  Package structures implied by a
dotted name for @emph{name} are not created if not already present.
@end quotation
@end cartouche


3.3 新版功能.

@end deffn

@geindex PyImport_AddModule (C 函数)
@anchor{c-api/import c PyImport_AddModule}@anchor{3ac5}
@deffn {C 函数} PyObject* PyImport_AddModule (const char@w{ }*name)
@emph{Return value: Borrowed reference.}
Similar to @ref{3c02,,PyImport_AddModuleObject()}, but the name is a UTF-8
encoded string instead of a Unicode object.
@end deffn

@geindex PyImport_ExecCodeModule (C 函数)
@anchor{c-api/import c PyImport_ExecCodeModule}@anchor{3c03}
@deffn {C 函数} PyObject* PyImport_ExecCodeModule (const char@w{ }*name, PyObject@w{ }*co)
@emph{Return value: New reference.}
@geindex 內置函数; compile

Given a module name (possibly of the form @code{package.module}) and a code object
read from a Python bytecode file or obtained from the built-in function
@ref{1b4,,compile()}, load the module.  Return a new reference to the module object,
or @code{NULL} with an exception set if an error occurred.  @emph{name}
is removed from @ref{eb5,,sys.modules} in error cases, even if @emph{name} was already
in @ref{eb5,,sys.modules} on entry to @ref{3c03,,PyImport_ExecCodeModule()}.  Leaving
incompletely initialized modules in @ref{eb5,,sys.modules} is dangerous, as imports of
such modules have no way to know that the module object is an unknown (and
probably damaged with respect to the module author's intents) state.

The module's @ref{1460,,__spec__} and @ref{950,,__loader__} will be set, if
not set already, with the appropriate values.  The spec's loader will
be set to the module's @code{__loader__} (if set) and to an instance of
@code{SourceFileLoader} otherwise.

The module's @ref{13c7,,__file__} attribute will be set to the code object's
@code{co_filename}.  If applicable, @ref{b2b,,__cached__} will also
be set.

This function will reload the module if it was already imported.  See
@ref{3c01,,PyImport_ReloadModule()} for the intended way to reload a module.

If @emph{name} points to a dotted name of the form @code{package.module}, any package
structures not already created will still not be created.

See also @ref{3c04,,PyImport_ExecCodeModuleEx()} and
@ref{3c05,,PyImport_ExecCodeModuleWithPathnames()}.
@end deffn

@geindex PyImport_ExecCodeModuleEx (C 函数)
@anchor{c-api/import c PyImport_ExecCodeModuleEx}@anchor{3c04}
@deffn {C 函数} PyObject* PyImport_ExecCodeModuleEx (const char@w{ }*name, PyObject@w{ }*co, const char@w{ }*pathname)
@emph{Return value: New reference.}
Like @ref{3c03,,PyImport_ExecCodeModule()}, but the @ref{13c7,,__file__} attribute of
the module object is set to @emph{pathname} if it is non-@code{NULL}.

参见 @ref{3c05,,PyImport_ExecCodeModuleWithPathnames()}。
@end deffn

@geindex PyImport_ExecCodeModuleObject (C 函数)
@anchor{c-api/import c PyImport_ExecCodeModuleObject}@anchor{3c06}
@deffn {C 函数} PyObject* PyImport_ExecCodeModuleObject (PyObject@w{ }*name, PyObject@w{ }*co, PyObject@w{ }*pathname, PyObject@w{ }*cpathname)
@emph{Return value: New reference.}
Like @ref{3c04,,PyImport_ExecCodeModuleEx()}, but the @ref{b2b,,__cached__}
attribute of the module object is set to @emph{cpathname} if it is
non-@code{NULL}.  Of the three functions, this is the preferred one to use.


3.3 新版功能.

@end deffn

@geindex PyImport_ExecCodeModuleWithPathnames (C 函数)
@anchor{c-api/import c PyImport_ExecCodeModuleWithPathnames}@anchor{3c05}
@deffn {C 函数} PyObject* PyImport_ExecCodeModuleWithPathnames (const char@w{ }*name, PyObject@w{ }*co, const char@w{ }*pathname, const char@w{ }*cpathname)
@emph{Return value: New reference.}
Like @ref{3c06,,PyImport_ExecCodeModuleObject()}, but @emph{name}, @emph{pathname} and
@emph{cpathname} are UTF-8 encoded strings. Attempts are also made to figure out
what the value for @emph{pathname} should be from @emph{cpathname} if the former is
set to @code{NULL}.


3.2 新版功能.



在 3.3 版更改: Uses @ref{3a8a,,imp.source_from_cache()} in calculating the source path if
only the bytecode path is provided.

@end deffn

@geindex PyImport_GetMagicNumber (C 函数)
@anchor{c-api/import c PyImport_GetMagicNumber}@anchor{b18}
@deffn {C 函数} long PyImport_GetMagicNumber ()

Return the magic number for Python bytecode files (a.k.a. @code{.pyc} file).
The magic number should be present in the first four bytes of the bytecode
file, in little-endian byte order. Returns @code{-1} on error.


在 3.3 版更改: 失败时返回值 @code{-1}。

@end deffn

@geindex PyImport_GetMagicTag (C 函数)
@anchor{c-api/import c PyImport_GetMagicTag}@anchor{3c07}
@deffn {C 函数} const char * PyImport_GetMagicTag ()

Return the magic tag string for 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} format Python bytecode file
names.  Keep in mind that the value at @code{sys.implementation.cache_tag} is
authoritative and should be used instead of this function.


3.2 新版功能.

@end deffn

@geindex PyImport_GetModuleDict (C 函数)
@anchor{c-api/import c PyImport_GetModuleDict}@anchor{3c08}
@deffn {C 函数} PyObject* PyImport_GetModuleDict ()
@emph{Return value: Borrowed reference.}
Return the dictionary used for the module administration (a.k.a.
@code{sys.modules}).  Note that this is a per-interpreter variable.
@end deffn

@geindex PyImport_GetModule (C 函数)
@anchor{c-api/import c PyImport_GetModule}@anchor{419}
@deffn {C 函数} PyObject* PyImport_GetModule (PyObject@w{ }*name)
@emph{Return value: New reference.}
Return the already imported module with the given name.  If the
module has not been imported yet then returns @code{NULL} but does not set
an error.  Returns @code{NULL} and sets an error if the lookup failed.


3.7 新版功能.

@end deffn

@geindex PyImport_GetImporter (C 函数)
@anchor{c-api/import c PyImport_GetImporter}@anchor{3c09}
@deffn {C 函数} PyObject* PyImport_GetImporter (PyObject@w{ }*path)
@emph{Return value: New reference.}
Return a finder object for a @ref{482,,sys.path}/@code{pkg.__path__} item
@emph{path}, possibly by fetching it from the @ref{498,,sys.path_importer_cache}
dict.  If it wasn't yet cached, traverse @ref{956,,sys.path_hooks} until a hook
is found that can handle the path item.  Return @code{None} if no hook could;
this tells our caller that the @ref{1458,,path based finder} could not find a
finder for this path item. Cache the result in @ref{498,,sys.path_importer_cache}.
Return a new reference to the finder object.
@end deffn

@geindex _PyImport_Init (C 函数)
@anchor{c-api/import c _PyImport_Init}@anchor{3c0a}
@deffn {C 函数} void _PyImport_Init ()

Initialize the import mechanism.  For internal use only.
@end deffn

@geindex PyImport_Cleanup (C 函数)
@anchor{c-api/import c PyImport_Cleanup}@anchor{3c0b}
@deffn {C 函数} void PyImport_Cleanup ()

Empty the module table.  For internal use only.
@end deffn

@geindex _PyImport_Fini (C 函数)
@anchor{c-api/import c _PyImport_Fini}@anchor{3c0c}
@deffn {C 函数} void _PyImport_Fini ()

Finalize the import mechanism.  For internal use only.
@end deffn

@geindex PyImport_ImportFrozenModuleObject (C 函数)
@anchor{c-api/import c PyImport_ImportFrozenModuleObject}@anchor{3c0d}
@deffn {C 函数} int PyImport_ImportFrozenModuleObject (PyObject@w{ }*name)
@emph{Return value: New reference.}
Load a frozen module named @emph{name}.  Return @code{1} for success, @code{0} if the
module is not found, and @code{-1} with an exception set if the initialization
failed.  To access the imported module on a successful load, use
@ref{c6c,,PyImport_ImportModule()}.  (Note the misnomer --- this function would
reload the module if it was already imported.)


3.3 新版功能.



在 3.4 版更改: The @code{__file__} attribute is no longer set on the module.

@end deffn

@geindex PyImport_ImportFrozenModule (C 函数)
@anchor{c-api/import c PyImport_ImportFrozenModule}@anchor{3c0e}
@deffn {C 函数} int PyImport_ImportFrozenModule (const char@w{ }*name)

Similar to @ref{3c0d,,PyImport_ImportFrozenModuleObject()}, but the name is a
UTF-8 encoded string instead of a Unicode object.
@end deffn

@geindex _frozen (C 类型)
@anchor{c-api/import c _frozen}@anchor{3c0f}
@deffn {C 类型} struct _frozen

@geindex freeze utility

This is the structure type definition for frozen module descriptors, as
generated by the @code{freeze} utility (see @code{Tools/freeze/} in the
Python source distribution).  Its definition, found in @code{Include/import.h},
is:

@example
struct _frozen @{
    const char *name;
    const unsigned char *code;
    int size;
@};
@end example
@end deffn

@geindex PyImport_FrozenModules (C 变量)
@anchor{c-api/import c PyImport_FrozenModules}@anchor{2292}
@deffn {C 变量} const struct _frozen* PyImport_FrozenModules

This pointer is initialized to point to an array of @code{struct _frozen}
records, terminated by one whose members are all @code{NULL} or zero.  When a frozen
module is imported, it is searched in this table.  Third-party code could play
tricks with this to provide a dynamically created collection of frozen modules.
@end deffn

@geindex PyImport_AppendInittab (C 函数)
@anchor{c-api/import c PyImport_AppendInittab}@anchor{3aad}
@deffn {C 函数} int PyImport_AppendInittab (const char@w{ }*name, PyObject* (*initfunc)(void))

Add a single module to the existing table of built-in modules.  This is a
convenience wrapper around @ref{3c10,,PyImport_ExtendInittab()}, returning @code{-1} if
the table could not be extended.  The new module can be imported by the name
@emph{name}, and uses the function @emph{initfunc} as the initialization function called
on the first attempted import.  This should be called before
@ref{433,,Py_Initialize()}.
@end deffn

@geindex _inittab (C 类型)
@anchor{c-api/import c _inittab}@anchor{3c11}
@deffn {C 类型} struct _inittab

Structure describing a single entry in the list of built-in modules.  Each of
these structures gives the name and initialization function for a module built
into the interpreter.  The name is an ASCII encoded string.  Programs which
embed Python may use an array of these structures in conjunction with
@ref{3c10,,PyImport_ExtendInittab()} to provide additional built-in modules.
The structure is defined in @code{Include/import.h} as:

@example
struct _inittab @{
    const char *name;           /* ASCII encoded string */
    PyObject* (*initfunc)(void);
@};
@end example
@end deffn

@geindex PyImport_ExtendInittab (C 函数)
@anchor{c-api/import c PyImport_ExtendInittab}@anchor{3c10}
@deffn {C 函数} int PyImport_ExtendInittab (struct _inittab@w{ }*newtab)

Add a collection of modules to the table of built-in modules.  The @emph{newtab}
array must end with a sentinel entry which contains @code{NULL} for the @code{name}
field; failure to provide the sentinel value can result in a memory fault.
Returns @code{0} on success or @code{-1} if insufficient memory could be allocated to
extend the internal table.  In the event of failure, no modules are added to the
internal table.  This should be called before @ref{433,,Py_Initialize()}.
@end deffn

@node 数据 marshal 操作支持,解析参数并构建值变量,导入模块<2>,工具<2>
@anchor{c-api/marshal doc}@anchor{3c12}@anchor{c-api/marshal data-marshalling-support}@anchor{3c13}@anchor{c-api/marshal marshalling-utils}@anchor{3c14}
@subsection 数据 marshal 操作支持


这些例程允许 C 代码处理与 @ref{b0,,marshal} 模块所用相同数据格式的序列化对象。 其中有些函数可用来将数据写入这种序列化格式，另一些函数则可用来读取并恢复数据。 用于存储 marshal 数据的文件必须以二进制模式打开。

数字值在存储时会将最低位字节放在开头。

此模块支持两种数据格式版本：第 0 版为历史版本，第 1 版本会在文件和 marshal 反序列化中共享固化的字符串。 第 2 版本会对浮点数使用二进制格式。 @code{Py_MARSHAL_VERSION} 指明了当前文件的格式（当前取值为 2）。

@geindex PyMarshal_WriteLongToFile (C 函数)
@anchor{c-api/marshal c PyMarshal_WriteLongToFile}@anchor{3c15}
@deffn {C 函数} void PyMarshal_WriteLongToFile (long@w{ }value, FILE@w{ }*file, int@w{ }version)

将一个 @code{long} 整数 @emph{value} 以 marshal 格式写入 @emph{file}。 这将只写入 @emph{value} 最低的 32 位；无论本机 @code{long} 类型的长度如何。 @emph{version} 指明文件格式的版本。
@end deffn

@geindex PyMarshal_WriteObjectToFile (C 函数)
@anchor{c-api/marshal c PyMarshal_WriteObjectToFile}@anchor{3c16}
@deffn {C 函数} void PyMarshal_WriteObjectToFile (PyObject@w{ }*value, FILE@w{ }*file, int@w{ }version)

将一个 Python 对象 @emph{value} 以 marshal 格式写入 @emph{file}。 @emph{version} 指明文件格式的版本。
@end deffn

@geindex PyMarshal_WriteObjectToString (C 函数)
@anchor{c-api/marshal c PyMarshal_WriteObjectToString}@anchor{3c17}
@deffn {C 函数} PyObject* PyMarshal_WriteObjectToString (PyObject@w{ }*value, int@w{ }version)
@emph{Return value: New reference.}
返回一个包含 @emph{value} 的 marshal 表示形式的字节串对象。 @emph{version} 指明文件格式的版本。
@end deffn

以下函数允许读取并恢复存储为 marshal 格式的值。

@geindex PyMarshal_ReadLongFromFile (C 函数)
@anchor{c-api/marshal c PyMarshal_ReadLongFromFile}@anchor{3c18}
@deffn {C 函数} long PyMarshal_ReadLongFromFile (FILE@w{ }*file)

从打开用于读取的 @code{FILE*} 的对应数据流返回一个 C @code{long}。 使用此函数只能读取 32 位的值，无论本机 @code{long} 类型的长度如何。

发生错误时，将设置适当的异常 (@ref{c65,,EOFError}) 并返回 @code{-1}。
@end deffn

@geindex PyMarshal_ReadShortFromFile (C 函数)
@anchor{c-api/marshal c PyMarshal_ReadShortFromFile}@anchor{3c19}
@deffn {C 函数} int PyMarshal_ReadShortFromFile (FILE@w{ }*file)

从打开用于读取的 @code{FILE*} 的对应数据流返回一个 C @code{short}。 使用此函数只能读取 16 位的值，无论本机 @code{short} 的长度如何。

发生错误时，将设置适当的异常 (@ref{c65,,EOFError}) 并返回 @code{-1}。
@end deffn

@geindex PyMarshal_ReadObjectFromFile (C 函数)
@anchor{c-api/marshal c PyMarshal_ReadObjectFromFile}@anchor{3c1a}
@deffn {C 函数} PyObject* PyMarshal_ReadObjectFromFile (FILE@w{ }*file)
@emph{Return value: New reference.}
从打开用于读取的 @code{FILE*} 的对应数据流返回一个 Python 对象。

发生错误时，将设置适当的异常 (@ref{c65,,EOFError}, @ref{1fb,,ValueError} 或 @ref{192,,TypeError}) 并返回 @code{NULL}。
@end deffn

@geindex PyMarshal_ReadLastObjectFromFile (C 函数)
@anchor{c-api/marshal c PyMarshal_ReadLastObjectFromFile}@anchor{3c1b}
@deffn {C 函数} PyObject* PyMarshal_ReadLastObjectFromFile (FILE@w{ }*file)
@emph{Return value: New reference.}
从打开用于读取的 @code{FILE*} 的对应数据流返回一个 Python 对象。 不同于 @ref{3c1a,,PyMarshal_ReadObjectFromFile()}，此函数假定将不再从该文件读取更多的对象，允许其将文件数据积极地载入内存，以便反序列化过程可以在内存中的数据上操作而不是每次从文件读取一个字节。 只有当你确定不会再从文件读取任何内容时方可使用此方式。

发生错误时，将设置适当的异常 (@ref{c65,,EOFError}, @ref{1fb,,ValueError} 或 @ref{192,,TypeError}) 并返回 @code{NULL}。
@end deffn

@geindex PyMarshal_ReadObjectFromString (C 函数)
@anchor{c-api/marshal c PyMarshal_ReadObjectFromString}@anchor{3c1c}
@deffn {C 函数} PyObject* PyMarshal_ReadObjectFromString (const char@w{ }*data, Py_ssize_t@w{ }len)
@emph{Return value: New reference.}
从包含指向 @emph{data} 的 @emph{len} 个字节的字节缓冲区对应的数据流返回一个 Python 对象。

发生错误时，将设置适当的异常 (@ref{c65,,EOFError}, @ref{1fb,,ValueError} 或 @ref{192,,TypeError}) 并返回 @code{NULL}。
@end deffn

@node 解析参数并构建值变量,字符串转换与格式化,数据 marshal 操作支持,工具<2>
@anchor{c-api/arg doc}@anchor{3c1d}@anchor{c-api/arg arg-parsing}@anchor{2d0}@anchor{c-api/arg parsing-arguments-and-building-values}@anchor{3c1e}
@subsection 解析参数并构建值变量


在创建你自己的扩展函数和方法时，这些函数是有用的。其它的信息和样例见 @ref{1191,,扩展和嵌入 Python 解释器} 。

这些函数描述的前三个，@ref{26a,,PyArg_ParseTuple()}，@ref{5c5,,PyArg_ParseTupleAndKeywords()}，以及 @ref{ef4,,PyArg_Parse()}，它们都使用 @emph{格式化字符串} 来将函数期待的参数告知函数。这些函数都使用相同语法规则的格式化字符串。

@menu
* 解析参数: 解析参数<3>. 
* 创建变量:: 

@end menu

@node 解析参数<3>,创建变量,,解析参数并构建值变量
@anchor{c-api/arg parsing-arguments}@anchor{3c1f}
@subsubsection 解析参数


一个格式化字符串包含 0 或者更多的格式单元。一个格式单元用来描述一个 Python 对象；它通常是一个字符或者由括号括起来的格式单元序列。除了少数例外，一个非括号序列的格式单元通常对应这些函数的具有单一地址的参数。在接下来的描述中，双引号内的表达式是格式单元；圆括号 () 内的是对应这个格式单元的 Python 对象类型；方括号 [] 内的是传递的 C 变量(变量集)类型。

@menu
* 字符串和缓存区:: 
* 数字: 数字<2>. 
* 其他对象:: 
* API 函数:: 

@end menu

@node 字符串和缓存区,数字<2>,,解析参数<3>
@anchor{c-api/arg strings-and-buffers}@anchor{3c20}
@subsubsection 字符串和缓存区


这些格式允许将对象按照连续的内存块形式进行访问。你没必要提供返回的 unicode 字符或者字节区的原始数据存储。

一般的，当一个表达式设置一个指针指向一个缓冲区，这个缓冲区可以被相应的 Python 对象管理，并且这个缓冲区共享这个对象的生存周期。你不需要人为的释放任何内存空间。除了这些 @code{es}, @code{es#}, @code{et} and @code{et#}.

然而，当一个 @ref{b14,,Py_buffer} 结构被赋值，其包含的缓冲区被锁住，所以调用者在随后使用这个缓冲区，即使在 @ref{3acb,,Py_BEGIN_ALLOW_THREADS} 块中，可以避免可变数据因为调整大小或者被销毁所带来的风险。因此，@strong{你不得不调用} @ref{d4d,,PyBuffer_Release()} 在你结束数据的处理时(或者在之前任何中断事件中)

除非另有说明，缓冲区是不会以空终止的。

某些格式需要只读的 @ref{5e3,,bytes-like object}，并设置指针而不是缓冲区结构。 他们通过检查对象的 @ref{3c21,,PyBufferProcs.bf_releasebuffer} 字段是否为 @code{NULL} 来发挥作用，该字段不允许为 @ref{32b,,bytearray} 这样的可变对象。

@cartouche
@quotation 注解 
所有 @code{#} 表达式的变式(@code{s#}，@code{y#}，等等)，长度参数的类型(整型或者 @code{Py_ssize_t})在包含 @code{Python.h} 头文件之前由 @code{PY_SSIZE_T_CLEAN} 宏的定义控制。如果这个宏被定义，长度是一个 @code{Py_ssize_t} Python 元大小类型而不是一个 @code{int} 整型。在未来的 Python 版本中将会改变，只支持 @code{Py_ssize_t} 而放弃支持 @code{int} 整型。最好一直定义 @code{PY_SSIZE_T_CLEAN} 这个宏。
@end quotation
@end cartouche


@table @asis

@item @code{s} (@ref{329,,str}) [const char *]

将一个 Unicode 对象转换成一个指向字符串的 C 指针。一个指针指向一个已经存在的字符串，这个字符串存储的是传如的字符指针变量。C 字符串是已空结束的。Python 字符串不能包含嵌入的无效的代码点；如果由，一个 @ref{1fb,,ValueError} 异常会被引发。Unicode 对象被转化成 @code{'utf-8'} 编码的 C 字符串。如果转换失败，一个 @ref{c34,,UnicodeError} 异常被引发。

@cartouche
@quotation 注解 
这个表达式不接受 @ref{5e3,,bytes-like objects}。如果你想接受文件系统路径并将它们转化成 C 字符串，建议使用 @code{O&} 表达式配合 @ref{5c9,,PyUnicode_FSConverter()} 作为 @emph{转化函数}。
@end quotation
@end cartouche


在 3.5 版更改: 以前，当 Python 字符串中遇到了嵌入的 null 代码点会引发 @ref{192,,TypeError} 。


@item @code{s*} (@ref{329,,str} or @ref{5e3,,bytes-like object}) [Py_buffer]

这个表达式既接受 Unicode 对象也接受类字节类型对象。它为由调用者提供的 @ref{b14,,Py_buffer} 结构赋值。这里结果的 C 字符串可能包含嵌入的 NUL 字节。Unicode 对象通过 @code{'utf-8'} 编码转化成 C 字符串。

@item @code{s#} (@ref{329,,str}, 只读 @ref{5e3,,bytes-like object}) [const char *, int or @code{Py_ssize_t}]

像 @code{s*}，除了它不接受易变的对象。结果存储在两个 C 变量中，第一个是指向 C 字符串的指针，第二个是它的长度。字符串可能包含嵌入的 null 字节。Unicode 对象都被通过 @code{'utf-8'} 编码转化成 C 字符串。

@item @code{z} (@ref{329,,str} or @code{None}) [const char *]

与 @code{s} 类似，但 Python 对象也可能为 @code{None}，在这种情况下，C 指针设置为 @code{NULL}。

@item @code{z*} (@ref{329,,str}, @ref{5e3,,bytes-like object} or @code{None}) [Py_buffer]

与 @code{s*} 类似，但 Python 对象也可能为 @code{None}，在这种情况下，@ref{b14,,Py_buffer} 结构的 @code{buf} 成员设置为 @code{NULL}。

@item @code{z#} (@ref{329,,str}, 只读 @ref{5e3,,bytes-like object} 或 @code{None}) [const char *, int 或 @code{Py_ssize_t}]

与 @code{s#} 类似，但 Python 对象也可能为 @code{None}，在这种情况下，C 指针设置为 @code{NULL}。

@item @code{y} (read-only @ref{5e3,,bytes-like object}) [const char *]

这个表达式将一个类字节类型对象转化成一个指向字符串的 C 指针；它不接受 Unicode 对象。字节缓存区必须不包含嵌入的 null 字节；如果包含了 null 字节，会引发一个 @ref{1fb,,ValueError} 异常。


在 3.5 版更改: 以前，当字节缓冲区中遇到了嵌入的 null 字节会引发 @ref{192,,TypeError} 。


@item @code{y*} (@ref{5e3,,bytes-like object}) [Py_buffer]

@code{s*} 的变式，不接受 Unicode 对象，只接受类字节类型变量。@strong{这是接受二进制数据的推荐方法。}

@item @code{y#} (只读 @ref{5e3,,bytes-like object}) [const char *, int 或 @code{Py_ssize_t}]

@code{s#} 的变式，不接受 Unicode 对象，只接受类字节类型变量。

@item @code{S} (@ref{32a,,bytes}) [PyBytesObject *]

要求 Python 对象是一个 @ref{32a,,bytes} 类型对象，没有尝试任何的转换。如果不是一个字节类型对象会引发 @ref{192,,TypeError} 异常。C 变量也可能声明为 @ref{4b5,,PyObject*} 类型。

@item @code{Y} (@ref{32b,,bytearray}) [PyByteArrayObject *]

要求 Python 对象是一个 @ref{32b,,bytearray} 类型对象，没有尝试任何的转换。如果不是一个 @ref{32b,,bytearray} 类型对象会引发 @ref{192,,TypeError} 异常。C 变量也可能声明为 @ref{4b5,,PyObject*} 类型。

@item @code{u} (@ref{329,,str}) [const Py_UNICODE *]

将一个 Python Unicode 对象转化成指向一个以空终止的 Unicode 字符缓冲区的指针。你必须传入一个 @ref{ae9,,Py_UNICODE} 指针变量的地址，存储了一个指向已经存在的 Unicode 缓冲区的指针。请注意一个 @ref{ae9,,Py_UNICODE} 类型的字符宽度取决于编译选项(16 位或者 32 位)。Python 字符串必须不能包含嵌入的 null 代码点；如果有，引发一个 @ref{1fb,,ValueError} 异常。


在 3.5 版更改: 以前，当 Python 字符串中遇到了嵌入的 null 代码点会引发 @ref{192,,TypeError} 。



Deprecated since version 3.3, will be removed in version 4.0: 这是旧版样式 @ref{ae9,,Py_UNICODE} API; 请迁移至 @ref{432,,PyUnicode_AsWideCharString()}.


@item @code{u#} (@ref{329,,str}) [const Py_UNICODE *, int 或 @code{Py_ssize_t}]

@code{u} 的变式，存储两个 C 变量，第一个指针指向一个 Unicode 数据缓存区，第二个是它的长度。它允许 null 代码点。


Deprecated since version 3.3, will be removed in version 4.0: 这是旧版样式 @ref{ae9,,Py_UNICODE} API; 请迁移至 @ref{432,,PyUnicode_AsWideCharString()}.


@item @code{Z} (@ref{329,,str} 或 @code{None}) [const Py_UNICODE *]

与 @code{u} 类似，但 Python 对象也可能为 @code{None}，在这种情况下 @ref{ae9,,Py_UNICODE} 指针设置为 @code{NULL}。


Deprecated since version 3.3, will be removed in version 4.0: 这是旧版样式 @ref{ae9,,Py_UNICODE} API; 请迁移至 @ref{432,,PyUnicode_AsWideCharString()}.


@item @code{Z#} (@ref{329,,str} 或 @code{None}) [const Py_UNICODE *, int 或 @code{Py_ssize_t}]

与 @code{u#} 类似，但 Python 对象也可能为 @code{None}，在这种情况下 @ref{ae9,,Py_UNICODE} 指针设置为 @code{NULL}。


Deprecated since version 3.3, will be removed in version 4.0: 这是旧版样式 @ref{ae9,,Py_UNICODE} API; 请迁移至 @ref{432,,PyUnicode_AsWideCharString()}.


@item @code{U} (@ref{329,,str}) [PyObject *]

要求 Python 对象是一个 Unicode 对象，没有尝试任何的转换。如果不是一个 Unicode 对象会引发 @ref{192,,TypeError} 异常。C 变量也可能声明为 @ref{4b5,,PyObject*} 类型。

@item @code{w*} (可读写 @ref{5e3,,bytes-like object}) [Py_buffer]

这个表达式接受任何实现可读写缓存区接口的对象。它为调用者提供的 @ref{b14,,Py_buffer} 结构赋值。缓冲区可能存在嵌入的 null 字节。当缓冲区使用完后调用者需要调用 @ref{d4d,,PyBuffer_Release()}。

@item @code{es} (@ref{329,,str}) [const char *encoding, char **buffer]

@code{s} 的变式，它将编码后的 Unicode 字符存入字符缓冲区。它只处理没有嵌 NUL 字节的已编码数据。

此格式需要两个参数。 第一个仅用作输入，并且必须是 @code{const char*}，该名称将编码的名称指向 NUL 终止字符串或"NULL"，在这种情况下，使用 @code{'utf-8'} 编码。如果 Python 不知道命名编码，则引发异常。 第二个参数必须为 @code{char**} 它引用的指针的值将设置为包含参数文本内容的缓冲区。文本将以第一个参数指定的编码进行编码。

@ref{26a,,PyArg_ParseTuple()} 会分配一个足够大小的缓冲区，将编码后的数据拷贝进这个缓冲区并且设置 @emph{*buffer} 引用这个新分配的内存空间。调用者有责任在使用后调用 @ref{da2,,PyMem_Free()} 去释放已经分配的缓冲区。

@item @code{et} (@ref{329,,str}, @ref{32a,,bytes} or @ref{32b,,bytearray}) [const char *encoding, char **buffer]

和 @code{es} 相同，除了不用重编码传入的字符串对象。相反，它假设传入的参数是编码后的字符串类型。

@item @code{es#} (@ref{329,,str}) [const char *encoding, char **buffer, int 或 @code{Py_ssize_t} *buffer_length]

@code{s#} 的变式，它将已编码的 Unicode 字符存入字符缓冲区。不像 @code{es} 表达式，它允许传入的数据包含 NUL 字符。

它需要三个参数。 第一个仅用作输入，并且必须为 @code{const char*}，该对象指向一个编码格式名称，形式为以 NUL 结束的字符串或 @code{NULL}，在后一种情况下将使用 @code{'utf-8'} 编码格式。 如果编码格式名称无法被 Python 识别则会引发异常。 第二个参数必须为 @code{char**}；它所引用的指针的值将被设为包含参数文本内容的缓冲区。 文本将以第一个参数所指定的编码格式进行编码。 第三个参数必须是指向一个整数的指针；所引用的整数将被设为输出缓冲区中的字节数。

有两种操作方式：

如果 @emph{*buffer} 指向 @code{NULL} 指针，则函数将分配所需大小的缓冲区，将编码的数据复制到此缓冲区，并设置 @emph{*buffer} 以引用新分配的存储。 呼叫者负责调用 @ref{da2,,PyMem_Free()} 以在使用后释放分配的缓冲区。

如果 @emph{*buffer} 指向非 @code{NULL} 指针（已分配的缓冲区），则 @ref{26a,,PyArg_ParseTuple()} 将使用此位置作为缓冲区，并将 @emph{*buffer_length} 的初始值解释为缓冲区大小。 然后，它将将编码的数据复制到缓冲区，并终止它。 如果缓冲区不够大，将设置一个 @ref{1fb,,ValueError}。

在这两个例子中，@emph{*buffer_length} 被设置为编码后结尾不为 NUL 的数据的长度。

@item @code{et#} (@ref{329,,str}, @ref{32a,,bytes} 或 @ref{32b,,bytearray}) [const char *encoding, char **buffer, int 或 @code{Py_ssize_t} *buffer_length]

和 @code{es#} 相同，除了不用重编码传入的字符串对象。相反，它假设传入的参数是编码后的字符串类型。
@end table

@node 数字<2>,其他对象,字符串和缓存区,解析参数<3>
@anchor{c-api/arg numbers}@anchor{3c22}
@subsubsection 数字



@table @asis

@item @code{b} (@ref{184,,int}) [unsigned char]

将一个非负的 Python 整型转化成一个无符号的微整型，存储在一个 C @code{unsigned char} 类型中。

@item @code{B} (@ref{184,,int}) [unsigned char]

将一个 Python 整型转化成一个微整型并不检查溢出问题，存储在一个 C @code{unsigned char} 类型中。

@item @code{h} (@ref{184,,int}) [short int]

将一个 Python 整型转化成一个 C @code{short int} 短整型。

@item @code{H} (@ref{184,,int}) [unsigned short int]

将一个 Python 整型转化成一个 C @code{unsigned short int} 无符号短整型，并不检查溢出问题。

@item @code{i} (@ref{184,,int}) [int]

将一个 Python 整型转化成一个 C @code{int} 整型。

@item @code{I} (@ref{184,,int}) [unsigned int]

将一个 Python 整型转化成一个 C @code{unsigned int} 无符号整型，并不检查溢出问题。

@item @code{l} (@ref{184,,int}) [long int]

将一个 Python 整型转化成一个 C @code{long int} 长整型。

@item @code{k} (@ref{184,,int}) [unsigned long]

将一个Python整型转化成一个C @code{unsigned long int} 无符号长整型，并不检查溢出问题。

@item @code{L} (@ref{184,,int}) [long long]

将一个 Python 整型转化成一个 C @code{long long} 长长整型。

@item @code{K} (@ref{184,,int}) [unsigned long long]

将一个 Python 整型转化成一个 C @code{unsigned long long} 无符号长长整型，并不检查溢出问题。

@item @code{n} (@ref{184,,int}) [Py_ssize_t]

将一个 Python 整型转化成一个 C @code{Py_ssize_t} Python 元大小类型。

@item @code{c} (@ref{32a,,bytes} 或者 @ref{32b,,bytearray} 长度为 1) [char]

将一个 Python 字节类型，如一个长度为 1 的 @ref{32a,,bytes} 或者 @ref{32b,,bytearray} 对象，转化成一个 C @code{char} 字符类型。


在 3.3 版更改: 允许 @ref{32b,,bytearray} 类型的对象。


@item @code{C} (@ref{329,,str} 长度为 1) [int]

将一个 Python 字符，如一个长度为 1 的 @ref{329,,str} 字符串对象，转化成一个 C @code{int} 整型类型。

@item @code{f} (@ref{187,,float}) [float]

将一个 Python 浮点数转化成一个 C @code{float} 浮点数。

@item @code{d} (@ref{187,,float}) [double]

将一个Python浮点数转化成一个C @code{double} 双精度浮点数。

@item @code{D} (@ref{189,,complex}) [Py_complex]

将一个 Python 复数类型转化成一个 C @ref{3c23,,Py_complex} Python 复数类型。
@end table

@node 其他对象,API 函数,数字<2>,解析参数<3>
@anchor{c-api/arg other-objects}@anchor{3c24}
@subsubsection 其他对象



@table @asis

@item @code{O} (object) [PyObject *]

将 Python 对象（不进行任何转换）存储在 C 对象指针中。 因此，C 程序接收已传递的实际对象。 对象的引用计数不会增加。 存储的指针不是 @code{NULL}。

@item @code{O!} (object) [@emph{typeobject}, PyObject *]

将一个 Python 对象存入一个 C 指针。和 @code{O} 类似，但是需要两个 C 参数：第一个是 Python 类型对象的地址，第二个是存储对象指针的 C 变量( @ref{4b5,,PyObject*} 变量)的地址。如果 Python 对象类型不对，会抛出 @ref{192,,TypeError} 异常。
@end table
@anchor{c-api/arg o-ampersand}@anchor{3c25}

@table @asis

@item @code{O&} (object) [@emph{converter}, @emph{anything}]

通过一个 @emph{converter} 函数将一个 Python 对象转换成一个 C 变量。这需要两个参数：第一个是一个函数，第二个是一个 C 变量的地址(任意类型的)，转化为 @code{void *} 类型。@emph{converter} 函数像这样被调用：

@example
status = converter(object, address);
@end example

@emph{object*是待转化的Python对象并且 *address} 是传入 @ref{ef4,,PyArg_Parse*()} 函数的 @code{void*} 类型参数。返回的 @emph{status} 是1代表转换成功，0代表转换失败。当转换失败，@emph{converter*函数会引发一个异常并且不会修改 *address} 的内容。

如果 @emph{converter} 返回 @code{Py_CLEANUP_SUPPORTED}，则如果参数解析最终失败，它可能会再次调用该函数，从而使转换器有机会释放已分配的任何内存。在第二个调用中，@emph{object} 参数将为 @code{NULL};因此，该参数将为 @code{NULL};因此，该参数将为 @code{NULL}，因此，该参数将为 @code{NULL`@w{`}（如果值）为 `@w{`}NULL} @emph{address} 的值与原始呼叫中的值相同。


在 3.1 版更改: @code{Py_CLEANUP_SUPPORTED} 被添加。


@item @code{p} (@ref{183,,bool}) [int]

测试传入的值是否为真(一个布尔判断)并且将结果转化为相对应的 C true/false 整型值。如果表达式为真置 @code{1}，假则置 @code{0}。它接受任何合法的 Python 值。参见 @ref{157c,,逻辑值检测} 获取更多关于 Python 如何测试值为真的信息。


3.3 新版功能.


@item @code{(items)} (@ref{478,,tuple}) [@emph{matching-items}]

对象必须是 Python 序列，它的长度是 @emph{items} 中格式单元的数量。C 参数必须对应 @emph{items} 中每一个独立的格式单元。序列中的格式单元可能有嵌套。
@end table

传递 "long" 整型(整型的值超过了平台的 @code{LONG_MAX} 限制)是可能的，然而没有进行适当的范围检测——当接收字段太小而接收不到值时，最重要的位被静默地截断(实际上，C 语言会在语义继承的基础上强制类型转换——期望的值可能会发生变化)。

格式化字符串中还有一些其他的字符具有特殊的涵义。这些可能并不嵌套在圆括号中。它们是：


@table @asis

@item @code{|}

表明在 Python 参数列表中剩下的参数都是可选的。C 变量对应的可选参数需要初始化为默认值——当一个可选参数没有指定时， @ref{26a,,PyArg_ParseTuple()}  不能访问相应的 C 变量(变量集)的内容。

@item @code{$}

@ref{5c5,,PyArg_ParseTupleAndKeywords()} only：表明在 Python 参数列表中剩下的参数都是强制关键字参数。当前，所有强制关键字参数都必须也是可选参数，所以格式化字符串中  @code{|} 必须一直在 @code{$} 前面。


3.3 新版功能.


@item @code{:}

格式单元的列表结束标志；冒号后的字符串被用来作为错误消息中的函数名(@ref{26a,,PyArg_ParseTuple()} 函数引发的“关联值”异常)。

@item @code{;}

格式单元的列表结束标志；分号后的字符串被用来作为错误消息取代默认的错误消息。 @code{:} 和 @code{;} 相互排斥。
@end table

注意任何由调用者提供的 Python 对象引用是 @emph{借来的} 引用；不要递减它们的引用计数！

传递给这些函数的附加参数必须是由格式化字符串确定的变量的地址；这些都是用来存储输入元组的值。有一些情况，如上面的格式单元列表中所描述的，这些参数作为输入值使用；在这种情况下，它们应该匹配指定的相应的格式单元。

为了转换成功，@emph{arg} 对象必须匹配格式并且格式必须用尽。成功的话，@ref{ef4,,PyArg_Parse*()} 函数返回 true，反之它们返回 false 并且引发一个合适的异常。当 @ref{ef4,,PyArg_Parse*()} 函数因为某一个格式单元转化失败而失败时，对应的以及后续的格式单元地址内的变量都不会被使用。

@node API 函数,,其他对象,解析参数<3>
@anchor{c-api/arg api-functions}@anchor{3c26}
@subsubsection API 函数


@geindex PyArg_ParseTuple (C 函数)
@anchor{c-api/arg c PyArg_ParseTuple}@anchor{26a}
@deffn {C 函数} int PyArg_ParseTuple (PyObject@w{ }*args, const char@w{ }*format, ...)

解析一个函数的参数，表达式中的参数按参数位置顺序存入局部变量中。成功返回 true；失败返回 false 并且引发相应的异常。
@end deffn

@geindex PyArg_VaParse (C 函数)
@anchor{c-api/arg c PyArg_VaParse}@anchor{3c27}
@deffn {C 函数} int PyArg_VaParse (PyObject@w{ }*args, const char@w{ }*format, va_list@w{ }vargs)

和 @ref{26a,,PyArg_ParseTuple()} 相同，然而它接受一个 va_list 类型的参数而不是可变数量的参数集。
@end deffn

@geindex PyArg_ParseTupleAndKeywords (C 函数)
@anchor{c-api/arg c PyArg_ParseTupleAndKeywords}@anchor{5c5}
@deffn {C 函数} int PyArg_ParseTupleAndKeywords (PyObject@w{ }*args, PyObject@w{ }*kw, const char@w{ }*format, char@w{ }*keywords[], ...)

分析将位置参数和关键字参数同时转换为局部变量的函数的参数。 @emph{keywords} 参数是关键字参数名称的 @code{NULL} 终止数组。 空名称表示 @ref{2a7,,positional-only parameters}。成功时返回 true;发生故障时，它将返回 false 并引发相应的异常。


在 3.6 版更改: 添加了 @ref{2a7,,positional-only parameters} 的支持。

@end deffn

@geindex PyArg_VaParseTupleAndKeywords (C 函数)
@anchor{c-api/arg c PyArg_VaParseTupleAndKeywords}@anchor{dd3}
@deffn {C 函数} int PyArg_VaParseTupleAndKeywords (PyObject@w{ }*args, PyObject@w{ }*kw, const char@w{ }*format, char@w{ }*keywords[], va_list@w{ }vargs)

和 @ref{5c5,,PyArg_ParseTupleAndKeywords()} 相同，然而它接受一个va_list类型的参数而不是可变数量的参数集。
@end deffn

@geindex PyArg_ValidateKeywordArguments (C 函数)
@anchor{c-api/arg c PyArg_ValidateKeywordArguments}@anchor{3c28}
@deffn {C 函数} int PyArg_ValidateKeywordArguments (PyObject@w{ }*)

确保字典中的关键字参数都是字符串。这个函数只被使用于 @ref{5c5,,PyArg_ParseTupleAndKeywords()} 不被使用的情况下，后者已经不再做这样的检查。


3.2 新版功能.

@end deffn

@c XXX deprecated, will be removed

@geindex PyArg_Parse (C 函数)
@anchor{c-api/arg c PyArg_Parse}@anchor{ef4}
@deffn {C 函数} int PyArg_Parse (PyObject@w{ }*args, const char@w{ }*format, ...)

函数被用来析构“旧类型”函数的参数列表——这些函数使用的 @code{METH_OLDARGS} 参数解析方法已从 Python 3 中移除。这不被推荐用于新代码的参数解析，并且在标准解释器中的大多数代码已被修改，已不再用于该目的。它仍然方便于分解其他元组，然而可能因为这个目的被继续使用。
@end deffn

@geindex PyArg_UnpackTuple (C 函数)
@anchor{c-api/arg c PyArg_UnpackTuple}@anchor{e3f}
@deffn {C 函数} int PyArg_UnpackTuple (PyObject@w{ }*args, const char@w{ }*name, Py_ssize_t@w{ }min, Py_ssize_t@w{ }max, ...)

一个不使用格式化字符串指定参数类型的简单形式的参数检索。使用这种方法来检索参数的函数应该在函数或者方法表中声明 @ref{e41,,METH_VARARGS}。包含实际参数的元组应该以 @emph{args} 形式被传入；它必须是一个实际的元组。元组的长度必须至少是 @emph{min} 并且不超过 @emph{max}； @emph{min} 和 @emph{max} 可能相同。额外的参数必须传递给函数，每一个参数必须是一个指向 @ref{4b5,,PyObject*} 类型变量的指针；它们将被赋值为 @emph{args} 的值；它们将包含借来的引用。不在 @emph{args} 里面的可选参数不会被赋值；由调用者完成初始化。函数成功则返回 true 并且如果 @emph{args} 不是元组或者包含错误数量的元素则返回 false；如果失败了会引发一个异常。

这是一个使用此函数的示例，取自 @code{_weakref} 帮助模块用来弱化引用的源代码：

@example
static PyObject *
weakref_ref(PyObject *self, PyObject *args)
@{
    PyObject *object;
    PyObject *callback = NULL;
    PyObject *result = NULL;

    if (PyArg_UnpackTuple(args, "ref", 1, 2, &object, &callback)) @{
        result = PyWeakref_NewRef(object, callback);
    @}
    return result;
@}
@end example

这个例子中调用 @ref{e3f,,PyArg_UnpackTuple()} 完全等价于调用 @ref{26a,,PyArg_ParseTuple()}:

@example
PyArg_ParseTuple(args, "O|O:ref", &object, &callback)
@end example
@end deffn

@node 创建变量,,解析参数<3>,解析参数并构建值变量
@anchor{c-api/arg building-values}@anchor{3c29}
@subsubsection 创建变量


@geindex Py_BuildValue (C 函数)
@anchor{c-api/arg c Py_BuildValue}@anchor{2ce}
@deffn {C 函数} PyObject* Py_BuildValue (const char@w{ }*format, ...)
@emph{Return value: New reference.}
基于类似于 @ref{ef4,,PyArg_Parse*()} 函数系列和一系列值的格式字符串创建新值。 在出现错误时返回值或 @code{NULL};如果返回 @code{NULL}，将引发异常。

@ref{2ce,,Py_BuildValue()} 并不一直创建一个元组。只有当它的格式化字符串包含两个或更多的格式单元才会创建一个元组。如果格式化字符串是空，它返回 @code{None}；如果它包含一个格式单元，它返回由格式单元描述的的任一对象。用圆括号包裹格式化字符串可以强制它返回一个大小为 0 或者 1 的元组。

当内存缓存区的数据以参数形式传递用来构建对象时，如 @code{s} 和 @code{s#} 格式单元，会拷贝需要的数据。调用者提供的缓冲区从来都不会被由 @ref{2ce,,Py_BuildValue()} 创建的对象来引用。换句话说，如果你的代码调用 @code{malloc()} 并且将分配的内存空间传递给 @ref{2ce,,Py_BuildValue()}，你的代码就有责任在 @ref{2ce,,Py_BuildValue()} 返回时调用 @code{free()} 。

在下面的描述中，双引号的表达式使格式单元；圆括号 () 内的是格式单元将要返回的 Python 对象类型；方括号 [] 内的是传递的 C 变量(变量集)的类型。

字符例如空格，制表符，冒号和逗号在格式化字符串中会被忽略(但是不包括格式单元，如 @code{s#})。这可以使很长的格式化字符串具有更好的可读性。


@table @asis

@item @code{s} (@ref{329,,str} 或 @code{None}) [const char *]

使用 @code{'utf-8'} 编码将空终止的 C 字符串转换为 Python @ref{329,,str} 对象。如果 C 字符串指针为 @code{NULL}，则使用 @code{None}。

@item @code{s#} (@ref{329,,str} 或 @code{None}) [const char *, int 或 @code{Py_ssize_t}]

使用 @code{'utf-8'} 编码将 C 字符串及其长度转换为 Python @ref{329,,str} 对象。如果 C 字符串指针为 @code{NULL}，则长度将被忽略，并返回 @code{None}。

@item @code{y} (@ref{32a,,bytes}) [const char *]

这将 C 字符串转换为 Python @ref{32a,,bytes} 对象。 如果 C 字符串指针为 @code{NULL}，则返回 @code{None}。

@item @code{y#} (@ref{32a,,bytes}) [const char *, int 或 @code{Py_ssize_t}]

这会将 C 字符串及其长度转换为一个 Python 对象。 如果该 C 字符串指针为 @code{NULL}，则返回 @code{None}。

@item @code{z} (@ref{329,,str} or @code{None}) [const char *]

和 @code{s} 一样。

@item @code{z#} (@ref{329,,str} 或 @code{None}) [const char *, int 或 @code{Py_ssize_t}]

和 @code{s#} 一样。

@item @code{u} (@ref{329,,str}) [const wchar_t *]

将空终止的 @code{wchar_t} 的 Unicode （UTF-16 或 UCS-4） 数据缓冲区转换为 Python Unicode 对象。 如果 Unicode 缓冲区指针为 @code{NULL}，则返回 @code{None}。

@item @code{u#} (@ref{329,,str}) [const wchar_t *, int 或 @code{Py_ssize_t}]

将 Unicode （UTF-16 或 UCS-4） 数据缓冲区及其长度转换为 Python Unicode 对象。  如果 Unicode 缓冲区指针为 @code{NULL}，则长度将被忽略，并返回 @code{None}。

@item @code{U} (@ref{329,,str} 或 @code{None}) [const char *]

和 @code{s} 一样。

@item @code{U#} (@ref{329,,str} 或 @code{None}) [const char *, int 或 @code{Py_ssize_t}]

和 @code{s#} 一样。

@item @code{i} (@ref{184,,int}) [int]

将一个 C @code{int} 整型转化成 Python 整型对象。

@item @code{b} (@ref{184,,int}) [char]

将一个 C @code{char} 字符型转化成 Python 整型对象。

@item @code{h} (@ref{184,,int}) [short int]

将一个 C @code{short int} 短整型转化成 Python 整型对象。

@item @code{l} (@ref{184,,int}) [long int]

将一个 C @code{long int} 长整型转化成 Python 整型对象。

@item @code{B} (@ref{184,,int}) [unsigned char]

将一个 C @code{unsigned char} 无符号字符型转化成 Python 整型对象。

@item @code{H} (@ref{184,,int}) [unsigned short int]

将一个 C @code{unsigned long} 无符号短整型转化成 Python 整型对象。

@item @code{I} (@ref{184,,int}) [unsigned int]

将一个 C @code{unsigned long} 无符号整型转化成 Python 整型对象。

@item @code{k} (@ref{184,,int}) [unsigned long]

将一个 C @code{unsigned long} 无符号长整型转化成 Python 整型对象。

@item @code{L} (@ref{184,,int}) [long long]

将一个 C @code{long long} 长长整形转化成 Python 整形对象。

@item @code{K} (@ref{184,,int}) [unsigned long long]

将一个 C @code{unsigned long long} 无符号长长整型转化成 Python 整型对象。

@item @code{n} (@ref{184,,int}) [Py_ssize_t]

将一个 C @code{Py_ssize_t} 类型转化为 Python 整型。

@item @code{c} (@ref{32a,,bytes} 长度为1 ) [char]

将一个 C @code{int} 整型代表的字符转化为 Python @ref{32a,,bytes} 长度为 1 的字节对象。

@item @code{C} (@ref{329,,str} 长度为 1) [int]

将一个 C @code{int} 整型代表的字符转化为 Python @ref{329,,str} 长度为 1 的字符串对象。

@item @code{d} (@ref{187,,float}) [double]

将一个 C @code{double} 双精度浮点数转化为 Python 浮点数类型数字。

@item @code{f} (@ref{187,,float}) [float]

将一个 C @code{float} 单精度浮点数转化为 Python 浮点数类型数字。

@item @code{D} (@ref{189,,complex}) [Py_complex *]

将一个 C @ref{3c23,,Py_complex} 类型的结构转化为 Python 复数类型。

@item @code{O} (object) [PyObject *]

将 Python 对象传递不变（其引用计数除外，该计数由 1 递增）。 如果传入的对象是 @code{NULL} 指针，则假定这是由于生成参数的调用发现错误并设置异常而引起的。因此，@ref{2ce,,Py_BuildValue()} 将返回 @code{NULL}，但不会引发异常。 如果尚未引发异常，则设置 @ref{5f6,,SystemError}。

@item @code{S} (object) [PyObject *]

和 @code{O} 相同。

@item @code{N} (object) [PyObject *]

和 @code{O} 相同，然而它并不增加对象的引用计数。当通过调用参数列表中的对象构造器创建对象时很实用。

@item @code{O&} (object) [@emph{converter}, @emph{anything}]

通过 @emph{converter} 函数将 @emph{anything} 转换为 Python 对象。 该函数以 @emph{anything} （应与 @code{void *} 兼容）作为其参数，应返回 "new" Python 对象，如果发生错误，则应返回 @code{NULL}。

@item @code{(items)} (@ref{478,,tuple}) [@emph{matching-items}]

将一个 C 变量序列转换成 Python 元组并保持相同的元素数量。

@item @code{[items]} (@ref{262,,list}) [@emph{相关的元素}]

将一个 C 变量序列转换成 Python 列表并保持相同的元素数量。

@item @code{@{items@}} (@ref{1b8,,dict}) [@emph{相关的元素}]

将一个C变量序列转换成 Python 字典。每一对连续的 C 变量对作为一个元素插入字典中，分别作为关键字和值。
@end table

如果格式字符串中出现错误，则设置 @ref{5f6,,SystemError} 异常并返回 @code{NULL}。
@end deffn

@geindex Py_VaBuildValue (C 函数)
@anchor{c-api/arg c Py_VaBuildValue}@anchor{3c2a}
@deffn {C 函数} PyObject* Py_VaBuildValue (const char@w{ }*format, va_list@w{ }vargs)
@emph{Return value: New reference.}
和 @ref{2ce,,Py_BuildValue()} 相同，然而它接受一个 va_list 类型的参数而不是可变数量的参数集。
@end deffn

@node 字符串转换与格式化,反射,解析参数并构建值变量,工具<2>
@anchor{c-api/conversion doc}@anchor{3c2b}@anchor{c-api/conversion string-conversion}@anchor{3c2c}@anchor{c-api/conversion string-conversion-and-formatting}@anchor{3c2d}
@subsection 字符串转换与格式化


用于数字转换和格式化字符串输出的函数

@geindex PyOS_snprintf (C 函数)
@anchor{c-api/conversion c PyOS_snprintf}@anchor{e42}
@deffn {C 函数} int PyOS_snprintf (char@w{ }*str, size_t@w{ }size, const char@w{ }*format, ...)

根据格式字符串 @emph{format} 和额外参数，输出不超过 @emph{size} 字节到 @emph{str} 。请参见Unix手册页 @code{snprintf(2)} 。
@end deffn

@geindex PyOS_vsnprintf (C 函数)
@anchor{c-api/conversion c PyOS_vsnprintf}@anchor{e43}
@deffn {C 函数} int PyOS_vsnprintf (char@w{ }*str, size_t@w{ }size, const char@w{ }*format, va_list@w{ }va)

根据格式字符串 @emph{format} 和 变量参数列表 @emph{va} ，不能输出超过 @emph{size} 字节到 @emph{str} 。请参见Unix手册页 @code{vsnprintf(2)} 。
@end deffn

@ref{e42,,PyOS_snprintf()} 和 @ref{e43,,PyOS_vsnprintf()} 包装 C 标准库函数 @code{snprintf()} 和 @code{vsnprintf()} 。它们的目的是保证在极端情况下的一致行为，而标准 C 的函数则不然。

包装器确保 @emph{str*[*size}-1] 在返回时始终是 @code{'\0'} 。它们从不写入超过 @emph{size} 字节（包括结尾的 @code{'\0'} ）到字符串。两函数都需要满足 @code{str != NULL} , @code{size > 0} 和 @code{format != NULL} 。

如果平台没有 @code{vsnprintf()} 而且缓冲区大小需要避免截断超出 @emph{size} 512 字节以上，Python 会以一个 @ref{f19,,Py_FatalError()} 来中止。

这些函数的返回值（ @emph{rv} ）应按照以下规则被解释：


@itemize *

@item 
当 @code{0 <= rv < size} ，输出转换成功而且 @emph{rv} 个字符被写入 @emph{str} （不包含末尾 @emph{str*[*rv}] 的 @code{'\0'} 字节）

@item 
当 @code{rv >= size} ，输出转换被截断并且成功需要一个带有 @code{rv + 1} 字节的缓冲区。在这种情况下， @emph{str*[*size}-1] 的值是 @code{'\0'} 。

@item 
当 @code{rv < 0} ，会发生一些不好的事情。 在这种情况下， @emph{str*[*size}-1] 的值也是 @code{'\0'} ， 但是 @emph{str} 的其余部分未被定义。错误的确切原因取决于底层平台。
@end itemize

以下函数提供与语言环境无关的字符串到数字转换。

@geindex PyOS_string_to_double (C 函数)
@anchor{c-api/conversion c PyOS_string_to_double}@anchor{c1c}
@deffn {C 函数} double PyOS_string_to_double (const char@w{ }*s, char@w{ }**endptr, PyObject@w{ }*overflow_exception)

将字符串 @code{s} 转换为 @code{double} 类型，失败时引发Python异常。接受的字符串的集合对应于被 Python 的 @ref{187,,float()} 构造函数接受的字符串的集合，除了 @code{s} 必须没有前导或尾随空格。转换必须独立于当前的区域。

如果 @code{endptr} 是 @code{NULL} ，转换整个字符串。引发 @ref{1fb,,ValueError} 并且 返回 @code{-1.0} 如果字符串不是浮点数的有效的表达方式。

如果 @code{endptr} 不是 @code{NULL} ，尽可能多的转换字符串并将 @code{*endptr} 设置为指向第一个未转换的字符。如果字符串的初始段不是浮点数的有效的表达方式，将 @code{*endptr} 设置为指向字符串的开头，引发 ValueError 异常，并且返回 @code{-1.0} 。

如果 @code{s} 表示一个太大而不能存储在一个浮点数中的值（比方说， @code{"1e500"} 在许多平台上是一个字符串）然后如果 @code{overflow_exception} 是 @code{NULL} 返回 @code{Py_HUGE_VAL} （用适当的符号）并且不设置任何异常。 在其他方面， @code{overflow_exception} 必须指向一个 Python 异常对象；引发异常并返回 @code{-1.0} 。在这两种情况下，设置 @code{*endptr} 指向转换值之后的第一个字符。

如果在转换期间发生任何其他错误（比如一个内存不足的错误），设置适当的 Python 异常并且返回 @code{-1.0} 。


3.1 新版功能.

@end deffn

@geindex PyOS_double_to_string (C 函数)
@anchor{c-api/conversion c PyOS_double_to_string}@anchor{3c2e}
@deffn {C 函数} char* PyOS_double_to_string (double@w{ }val, char@w{ }format_code, int@w{ }precision, int@w{ }flags, int@w{ }*ptype)

转换 @code{double} @emph{val} 为一个使用 @emph{format_code}， @emph{precision} 和 @emph{flags} 的字符串

@emph{格式码} 必须是以下其中之一, @code{'e'}, @code{'E'}, @code{'f'}, @code{'F'}, @code{'g'}, @code{'G'} 或者 @code{'r'}。对于 @code{'r'} , 提供的 @emph{精度} 必须是0。@code{'r'} 格式码指定了标准函数 @ref{7c6,,repr()} 格式。

@emph{flags} 可以为零或者其他值 @code{Py_DTSF_SIGN}, @code{Py_DTSF_ADD_DOT_0} 或 @code{Py_DTSF_ALT} 或其组合：


@itemize *

@item 
@code{Py_DTSF_SIGN} 表示总是在返回的字符串前附加一个符号字符，即使 @emph{val} 为非负数。

@item 
@code{Py_DTSF_ADD_DOT_0} 表示确保返回的字符串看起来不像是一个整数。

@item 
@code{Py_DTSF_ALT} 表示应用 "替代的" 格式化规则。 相关细节请参阅 @ref{e42,,PyOS_snprintf()} @code{'#'} 定义文档。
@end itemize

如果 @emph{ptype} 不为 @code{NULL}，则它指向的值将被设为 @code{Py_DTST_FINITE}, @code{Py_DTST_INFINITE} 或 @code{Py_DTST_NAN} 中的一个，分别表示 @emph{val} 是一个有限数字、无限数字或非数字。

返回值是一个指向包含转换后字符串的 @emph{buffer} 的指针，如果转换失败则为 @code{NULL}。 调用方要负责调用 @ref{da2,,PyMem_Free()} 来释放返回的字符串。


3.1 新版功能.

@end deffn

@geindex PyOS_stricmp (C 函数)
@anchor{c-api/conversion c PyOS_stricmp}@anchor{3c2f}
@deffn {C 函数} int PyOS_stricmp (const char@w{ }*s1, const char@w{ }*s2)

字符串不区分大小写。该函数几乎与 @code{strcmp()} 的工作方式相同，只是它忽略了大小写。
@end deffn

@geindex PyOS_strnicmp (C 函数)
@anchor{c-api/conversion c PyOS_strnicmp}@anchor{3c30}
@deffn {C 函数} int PyOS_strnicmp (const char@w{ }*s1, const char@w{ }*s2, Py_ssize_t @w{ }size)

字符串不区分大小写。该函数几乎与 @code{strncmp()} 的工作方式相同，只是它忽略了大小写。
@end deffn

@node 反射,编解码器注册与支持功能,字符串转换与格式化,工具<2>
@anchor{c-api/reflection doc}@anchor{3c31}@anchor{c-api/reflection id1}@anchor{3c32}@anchor{c-api/reflection reflection}@anchor{3c33}
@subsection 反射


@geindex PyEval_GetBuiltins (C 函数)
@anchor{c-api/reflection c PyEval_GetBuiltins}@anchor{3c34}
@deffn {C 函数} PyObject* PyEval_GetBuiltins ()
@emph{Return value: Borrowed reference.}
返回当前执行帧中内置函数的字典，如果当前没有帧正在执行，则返回线程状态的解释器。
@end deffn

@geindex PyEval_GetLocals (C 函数)
@anchor{c-api/reflection c PyEval_GetLocals}@anchor{3c35}
@deffn {C 函数} PyObject* PyEval_GetLocals ()
@emph{Return value: Borrowed reference.}
返回当前执行帧中局部变量的字典，如果没有当前执行的帧则返回 @code{NULL}。
@end deffn

@geindex PyEval_GetGlobals (C 函数)
@anchor{c-api/reflection c PyEval_GetGlobals}@anchor{3c36}
@deffn {C 函数} PyObject* PyEval_GetGlobals ()
@emph{Return value: Borrowed reference.}
返回当前执行帧中全局变量的字典，如果没有当前执行的帧则返回 @code{NULL}。
@end deffn

@geindex PyEval_GetFrame (C 函数)
@anchor{c-api/reflection c PyEval_GetFrame}@anchor{3c37}
@deffn {C 函数} PyFrameObject* PyEval_GetFrame ()
@emph{Return value: Borrowed reference.}
返回当前线程状态的帧，如果没有当前执行的帧则返回 @code{NULL}。
@end deffn

@geindex PyFrame_GetLineNumber (C 函数)
@anchor{c-api/reflection c PyFrame_GetLineNumber}@anchor{ce4}
@deffn {C 函数} int PyFrame_GetLineNumber (PyFrameObject@w{ }*frame)

返回 @emph{frame} 当前正在执行的行号。
@end deffn

@geindex PyEval_GetFuncName (C 函数)
@anchor{c-api/reflection c PyEval_GetFuncName}@anchor{3c38}
@deffn {C 函数} const char* PyEval_GetFuncName (PyObject@w{ }*func)

如果 @emph{func} 是函数、类或实例对象，则返回它的名称，否则返回 @emph{func} 的类型的名称。
@end deffn

@geindex PyEval_GetFuncDesc (C 函数)
@anchor{c-api/reflection c PyEval_GetFuncDesc}@anchor{3c39}
@deffn {C 函数} const char* PyEval_GetFuncDesc (PyObject@w{ }*func)

根据 @emph{func} 的类型返回描述字符串。 返回值包括函数和方法的 "()", " constructor", " instance" 和 " object"。 与 @ref{3c38,,PyEval_GetFuncName()} 的结果连接，结果将是 @emph{func} 的描述。
@end deffn

@node 编解码器注册与支持功能,,反射,工具<2>
@anchor{c-api/codec doc}@anchor{3c3a}@anchor{c-api/codec codec-registry}@anchor{5e9}@anchor{c-api/codec codec-registry-and-support-functions}@anchor{3c3b}
@subsection 编解码器注册与支持功能


@geindex PyCodec_Register (C 函数)
@anchor{c-api/codec c PyCodec_Register}@anchor{3c3c}
@deffn {C 函数} int PyCodec_Register (PyObject@w{ }*search_function)

注册一个新的编解码器搜索函数。

作为副作用，其尝试加载 @code{encodings} 包，如果尚未完成，请确保它始终位于搜索函数列表的第一位。
@end deffn

@geindex PyCodec_KnownEncoding (C 函数)
@anchor{c-api/codec c PyCodec_KnownEncoding}@anchor{3c3d}
@deffn {C 函数} int PyCodec_KnownEncoding (const char@w{ }*encoding)

根据注册的给定 @emph{encoding} 的编解码器是否已存在而返回 @code{1} 或 @code{0}。此函数总能成功。
@end deffn

@geindex PyCodec_Encode (C 函数)
@anchor{c-api/codec c PyCodec_Encode}@anchor{3c3e}
@deffn {C 函数} PyObject* PyCodec_Encode (PyObject@w{ }*object, const char@w{ }*encoding, const char@w{ }*errors)
@emph{Return value: New reference.}
泛型编解码器基本编码 API。

@emph{object} 使用由 @emph{errors} 所定义的错误处理方法传递给定 @emph{encoding} 的编码器函数。 @emph{errors} 可以为 @code{NULL} 表示使用为编码器所定义的默认方法。 如果找不到编码器则会引发 @ref{15f6,,LookupError}。
@end deffn

@geindex PyCodec_Decode (C 函数)
@anchor{c-api/codec c PyCodec_Decode}@anchor{3c3f}
@deffn {C 函数} PyObject* PyCodec_Decode (PyObject@w{ }*object, const char@w{ }*encoding, const char@w{ }*errors)
@emph{Return value: New reference.}
泛型编解码器基本解码 API。

@emph{object} 使用由 @emph{errors} 所定义的错误处理方法传递给定 @emph{encoding} 的解码器函数。 @emph{errors} 可以为 @code{NULL} 表示使用为编解码器所定义的默认方法。 如果找不到编解码器则会引发 @ref{15f6,,LookupError}。
@end deffn

@menu
* Codec 查找API:: 
* 用于Unicode编码错误处理程序的注册表API:: 

@end menu

@node Codec 查找API,用于Unicode编码错误处理程序的注册表API,,编解码器注册与支持功能
@anchor{c-api/codec codec-lookup-api}@anchor{3c40}
@subsubsection Codec 查找API


在下列函数中，@emph{encoding} 字符串会被查找并转换为小写字母形式，这使得通过此机制查找编码格式实际上对大小写不敏感。 如果未找到任何编解码器，则将设置 @ref{2c7,,KeyError} 并返回 @code{NULL}。

@geindex PyCodec_Encoder (C 函数)
@anchor{c-api/codec c PyCodec_Encoder}@anchor{3c41}
@deffn {C 函数} PyObject* PyCodec_Encoder (const char@w{ }*encoding)
@emph{Return value: New reference.}
为给定的 @emph{encoding} 获取一个编码器函数。
@end deffn

@geindex PyCodec_Decoder (C 函数)
@anchor{c-api/codec c PyCodec_Decoder}@anchor{3c42}
@deffn {C 函数} PyObject* PyCodec_Decoder (const char@w{ }*encoding)
@emph{Return value: New reference.}
为给定的 @emph{encoding} 获取一个解码器函数。
@end deffn

@geindex PyCodec_IncrementalEncoder (C 函数)
@anchor{c-api/codec c PyCodec_IncrementalEncoder}@anchor{3c43}
@deffn {C 函数} PyObject* PyCodec_IncrementalEncoder (const char@w{ }*encoding, const char@w{ }*errors)
@emph{Return value: New reference.}
为给定的 @emph{encoding} 获取一个 @ref{17c1,,IncrementalEncoder} 对象。
@end deffn

@geindex PyCodec_IncrementalDecoder (C 函数)
@anchor{c-api/codec c PyCodec_IncrementalDecoder}@anchor{3c44}
@deffn {C 函数} PyObject* PyCodec_IncrementalDecoder (const char@w{ }*encoding, const char@w{ }*errors)
@emph{Return value: New reference.}
为给定的 @emph{encoding} 获取一个 @ref{17c2,,IncrementalDecoder} 对象。
@end deffn

@geindex PyCodec_StreamReader (C 函数)
@anchor{c-api/codec c PyCodec_StreamReader}@anchor{3c45}
@deffn {C 函数} PyObject* PyCodec_StreamReader (const char@w{ }*encoding, PyObject@w{ }*stream, const char@w{ }*errors)
@emph{Return value: New reference.}
为给定的 @emph{encoding} 获取一个 @ref{17c6,,StreamReader} 工厂函数。
@end deffn

@geindex PyCodec_StreamWriter (C 函数)
@anchor{c-api/codec c PyCodec_StreamWriter}@anchor{3c46}
@deffn {C 函数} PyObject* PyCodec_StreamWriter (const char@w{ }*encoding, PyObject@w{ }*stream, const char@w{ }*errors)
@emph{Return value: New reference.}
为给定的 @emph{encoding} 获取一个 @ref{17c5,,StreamWriter} 工厂函数。
@end deffn

@node 用于Unicode编码错误处理程序的注册表API,,Codec 查找API,编解码器注册与支持功能
@anchor{c-api/codec registry-api-for-unicode-encoding-error-handlers}@anchor{3c47}
@subsubsection 用于Unicode编码错误处理程序的注册表API


@geindex PyCodec_RegisterError (C 函数)
@anchor{c-api/codec c PyCodec_RegisterError}@anchor{3c48}
@deffn {C 函数} int PyCodec_RegisterError (const char@w{ }*name, PyObject@w{ }*error)

在给定的 @emph{name} 之下注册错误处理回调函数 @emph{error}。 该回调函数将在一个编解码器遇到无法编码的字符/无法解码的字节数据并且 @emph{name} 被指定为 encode/decode 函数调用的 error 形参时由该编解码器来调用。

该回调函数会接受一个 @ref{1fc,,UnicodeEncodeError}, @ref{1fd,,UnicodeDecodeError} 或 @ref{16aa,,UnicodeTranslateError} 的实例作为单独参数，其中包含关于有问题字符或字节序列及其在原始序列的偏移量信息（请参阅 @ref{3bb9,,Unicode Exception Objects} 了解提取此信息的函数详情）。 该回调函数必须引发给定的异常，或者返回一个包含有问题序列及相应替换序列的二元组，以及一个表示偏移量的整数，该整数指明应在什么位置上恢复编码/解码操作。

成功则返回`@w{`}0`@w{`} ，失败则返回`@w{`}-1`@w{`}
@end deffn

@geindex PyCodec_LookupError (C 函数)
@anchor{c-api/codec c PyCodec_LookupError}@anchor{3c49}
@deffn {C 函数} PyObject* PyCodec_LookupError (const char@w{ }*name)
@emph{Return value: New reference.}
查找在 @emph{name} 之下注册的错误处理回调函数。 作为特例还可以传入 @code{NULL}，在此情况下将返回针对 "strict" 的错误处理回调函数。
@end deffn

@geindex PyCodec_StrictErrors (C 函数)
@anchor{c-api/codec c PyCodec_StrictErrors}@anchor{3c4a}
@deffn {C 函数} PyObject* PyCodec_StrictErrors (PyObject@w{ }*exc)
@emph{Return value: Always NULL.}
引发 @emph{exc} 作为异常。
@end deffn

@geindex PyCodec_IgnoreErrors (C 函数)
@anchor{c-api/codec c PyCodec_IgnoreErrors}@anchor{3c4b}
@deffn {C 函数} PyObject* PyCodec_IgnoreErrors (PyObject@w{ }*exc)
@emph{Return value: New reference.}
忽略 unicode 错误，跳过错误的输入。
@end deffn

@geindex PyCodec_ReplaceErrors (C 函数)
@anchor{c-api/codec c PyCodec_ReplaceErrors}@anchor{3c4c}
@deffn {C 函数} PyObject* PyCodec_ReplaceErrors (PyObject@w{ }*exc)
@emph{Return value: New reference.}
使用 @code{?} 或 @code{U+FFFD} 替换 unicode 编码错误。
@end deffn

@geindex PyCodec_XMLCharRefReplaceErrors (C 函数)
@anchor{c-api/codec c PyCodec_XMLCharRefReplaceErrors}@anchor{3c4d}
@deffn {C 函数} PyObject* PyCodec_XMLCharRefReplaceErrors (PyObject@w{ }*exc)
@emph{Return value: New reference.}
使用 XML 字符引用替换 unicode 编码错误。
@end deffn

@geindex PyCodec_BackslashReplaceErrors (C 函数)
@anchor{c-api/codec c PyCodec_BackslashReplaceErrors}@anchor{3c4e}
@deffn {C 函数} PyObject* PyCodec_BackslashReplaceErrors (PyObject@w{ }*exc)
@emph{Return value: New reference.}
使用反斜杠转义符 (@code{\x}, @code{\u} 和 @code{\U}) 替换 unicode 编码错误。
@end deffn

@geindex PyCodec_NameReplaceErrors (C 函数)
@anchor{c-api/codec c PyCodec_NameReplaceErrors}@anchor{7a2}
@deffn {C 函数} PyObject* PyCodec_NameReplaceErrors (PyObject@w{ }*exc)
@emph{Return value: New reference.}
使用 @code{\N@{...@}} 转义符替换 unicode 编码错误。


3.5 新版功能.

@end deffn

@node 抽象对象层,具体的对象层,工具<2>,Python/C API 参考手册
@anchor{c-api/abstract doc}@anchor{3c4f}@anchor{c-api/abstract abstract}@anchor{3b0d}@anchor{c-api/abstract abstract-objects-layer}@anchor{3c50}
@section 抽象对象层


本章中的函数与 Python对象交互，无论其类型，或具有广泛类的对象类型（例如，所有数值类型，或所有序列类型）。当使用对象类型并不适用时，他们会产生一个 Python 异常。

这些函数是不可能用于未正确初始化的对象的，如一个列表对象被 @ref{3b56,,PyList_New()} 创建，但其中的项目没有被设置为一些非`@w{`}NULL`@w{`}的值。

@menu
* 对象协议:: 
* 数字协议:: 
* 序列协议:: 
* 映射协议:: 
* 迭代器协议:: 
* 缓冲协议:: 
* 旧缓冲协议:: 

@end menu

@node 对象协议,数字协议,,抽象对象层
@anchor{c-api/object doc}@anchor{3c51}@anchor{c-api/object object}@anchor{3c52}@anchor{c-api/object object-protocol}@anchor{3c53}
@subsection 对象协议


@geindex Py_NotImplemented (C 变量)
@anchor{c-api/object c Py_NotImplemented}@anchor{3c54}
@deffn {C 变量} PyObject* Py_NotImplemented

The @code{NotImplemented} singleton, used to signal that an operation is
not implemented for the given type combination.
@end deffn

@geindex Py_RETURN_NOTIMPLEMENTED (C 宏)
@anchor{c-api/object c Py_RETURN_NOTIMPLEMENTED}@anchor{3c55}
@deffn {C 宏} Py_RETURN_NOTIMPLEMENTED

Properly handle returning @ref{3c54,,Py_NotImplemented} from within a C
function (that is, increment the reference count of NotImplemented and
return it).
@end deffn

@geindex PyObject_Print (C 函数)
@anchor{c-api/object c PyObject_Print}@anchor{fdf}
@deffn {C 函数} int PyObject_Print (PyObject@w{ }*o, FILE@w{ }*fp, int@w{ }flags)

Print an object @emph{o}, on file @emph{fp}.  Returns @code{-1} on error.  The flags argument
is used to enable certain printing options.  The only option currently supported
is @code{Py_PRINT_RAW}; if given, the @ref{329,,str()} of the object is written
instead of the @ref{7c6,,repr()}.
@end deffn

@geindex PyObject_HasAttr (C 函数)
@anchor{c-api/object c PyObject_HasAttr}@anchor{3c56}
@deffn {C 函数} int PyObject_HasAttr (PyObject@w{ }*o, PyObject@w{ }*attr_name)

Returns @code{1} if @emph{o} has the attribute @emph{attr_name}, and @code{0} otherwise.  This
is equivalent to the Python expression @code{hasattr(o, attr_name)}.  This function
always succeeds.

Note that exceptions which occur while calling @ref{313,,__getattr__()} and
@ref{441,,__getattribute__()} methods will get suppressed.
To get error reporting use @ref{3c57,,PyObject_GetAttr()} instead.
@end deffn

@geindex PyObject_HasAttrString (C 函数)
@anchor{c-api/object c PyObject_HasAttrString}@anchor{3c58}
@deffn {C 函数} int PyObject_HasAttrString (PyObject@w{ }*o, const char@w{ }*attr_name)

Returns @code{1} if @emph{o} has the attribute @emph{attr_name}, and @code{0} otherwise.  This
is equivalent to the Python expression @code{hasattr(o, attr_name)}.  This function
always succeeds.

Note that exceptions which occur while calling @ref{313,,__getattr__()} and
@ref{441,,__getattribute__()} methods and creating a temporary string object
will get suppressed.
To get error reporting use @ref{3ac0,,PyObject_GetAttrString()} instead.
@end deffn

@geindex PyObject_GetAttr (C 函数)
@anchor{c-api/object c PyObject_GetAttr}@anchor{3c57}
@deffn {C 函数} PyObject* PyObject_GetAttr (PyObject@w{ }*o, PyObject@w{ }*attr_name)
@emph{Return value: New reference.}
Retrieve an attribute named @emph{attr_name} from object @emph{o}. Returns the attribute
value on success, or @code{NULL} on failure.  This is the equivalent of the Python
expression @code{o.attr_name}.
@end deffn

@geindex PyObject_GetAttrString (C 函数)
@anchor{c-api/object c PyObject_GetAttrString}@anchor{3ac0}
@deffn {C 函数} PyObject* PyObject_GetAttrString (PyObject@w{ }*o, const char@w{ }*attr_name)
@emph{Return value: New reference.}
Retrieve an attribute named @emph{attr_name} from object @emph{o}. Returns the attribute
value on success, or @code{NULL} on failure. This is the equivalent of the Python
expression @code{o.attr_name}.
@end deffn

@geindex PyObject_GenericGetAttr (C 函数)
@anchor{c-api/object c PyObject_GenericGetAttr}@anchor{3c59}
@deffn {C 函数} PyObject* PyObject_GenericGetAttr (PyObject@w{ }*o, PyObject@w{ }*name)
@emph{Return value: New reference.}
Generic attribute getter function that is meant to be put into a type
object's @code{tp_getattro} slot.  It looks for a descriptor in the dictionary
of classes in the object's MRO as well as an attribute in the object's
@ref{4f6,,__dict__} (if present).  As outlined in @ref{4e3,,实现描述器},
data descriptors take preference over instance attributes, while non-data
descriptors don't.  Otherwise, an @ref{393,,AttributeError} is raised.
@end deffn

@geindex PyObject_SetAttr (C 函数)
@anchor{c-api/object c PyObject_SetAttr}@anchor{3c5a}
@deffn {C 函数} int PyObject_SetAttr (PyObject@w{ }*o, PyObject@w{ }*attr_name, PyObject@w{ }*v)

Set the value of the attribute named @emph{attr_name}, for object @emph{o}, to the value
@emph{v}. Raise an exception and return @code{-1} on failure;
return @code{0} on success.  This is the equivalent of the Python statement
@code{o.attr_name = v}.

If @emph{v} is @code{NULL}, the attribute is deleted, however this feature is
deprecated in favour of using @ref{3c5b,,PyObject_DelAttr()}.
@end deffn

@geindex PyObject_SetAttrString (C 函数)
@anchor{c-api/object c PyObject_SetAttrString}@anchor{3c5c}
@deffn {C 函数} int PyObject_SetAttrString (PyObject@w{ }*o, const char@w{ }*attr_name, PyObject@w{ }*v)

Set the value of the attribute named @emph{attr_name}, for object @emph{o}, to the value
@emph{v}. Raise an exception and return @code{-1} on failure;
return @code{0} on success.  This is the equivalent of the Python statement
@code{o.attr_name = v}.

If @emph{v} is @code{NULL}, the attribute is deleted, however this feature is
deprecated in favour of using @ref{3c5d,,PyObject_DelAttrString()}.
@end deffn

@geindex PyObject_GenericSetAttr (C 函数)
@anchor{c-api/object c PyObject_GenericSetAttr}@anchor{3c5e}
@deffn {C 函数} int PyObject_GenericSetAttr (PyObject@w{ }*o, PyObject@w{ }*name, PyObject@w{ }*value)

Generic attribute setter and deleter function that is meant
to be put into a type object's @ref{3b05,,tp_setattro}
slot.  It looks for a data descriptor in the
dictionary of classes in the object's MRO, and if found it takes preference
over setting or deleting the attribute in the instance dictionary. Otherwise, the
attribute is set or deleted in the object's @ref{4f6,,__dict__} (if present).
On success, @code{0} is returned, otherwise an @ref{393,,AttributeError}
is raised and @code{-1} is returned.
@end deffn

@geindex PyObject_DelAttr (C 函数)
@anchor{c-api/object c PyObject_DelAttr}@anchor{3c5b}
@deffn {C 函数} int PyObject_DelAttr (PyObject@w{ }*o, PyObject@w{ }*attr_name)

Delete attribute named @emph{attr_name}, for object @emph{o}. Returns @code{-1} on failure.
This is the equivalent of the Python statement @code{del o.attr_name}.
@end deffn

@geindex PyObject_DelAttrString (C 函数)
@anchor{c-api/object c PyObject_DelAttrString}@anchor{3c5d}
@deffn {C 函数} int PyObject_DelAttrString (PyObject@w{ }*o, const char@w{ }*attr_name)

Delete attribute named @emph{attr_name}, for object @emph{o}. Returns @code{-1} on failure.
This is the equivalent of the Python statement @code{del o.attr_name}.
@end deffn

@geindex PyObject_GenericGetDict (C 函数)
@anchor{c-api/object c PyObject_GenericGetDict}@anchor{3c5f}
@deffn {C 函数} PyObject* PyObject_GenericGetDict (PyObject@w{ }*o, void@w{ }*context)
@emph{Return value: New reference.}
A generic implementation for the getter of a @code{__dict__} descriptor. It
creates the dictionary if necessary.


3.3 新版功能.

@end deffn

@geindex PyObject_GenericSetDict (C 函数)
@anchor{c-api/object c PyObject_GenericSetDict}@anchor{3c60}
@deffn {C 函数} int PyObject_GenericSetDict (PyObject@w{ }*o, PyObject@w{ }*value, void@w{ }*context)

A generic implementation for the setter of a @code{__dict__} descriptor. This
implementation does not allow the dictionary to be deleted.


3.3 新版功能.

@end deffn

@geindex PyObject_RichCompare (C 函数)
@anchor{c-api/object c PyObject_RichCompare}@anchor{3b0b}
@deffn {C 函数} PyObject* PyObject_RichCompare (PyObject@w{ }*o1, PyObject@w{ }*o2, int@w{ }opid)
@emph{Return value: New reference.}
Compare the values of @emph{o1} and @emph{o2} using the operation specified by @emph{opid},
which must be one of @code{Py_LT}, @code{Py_LE}, @code{Py_EQ},
@code{Py_NE}, @code{Py_GT}, or @code{Py_GE}, corresponding to @code{<},
@code{<=}, @code{==}, @code{!=}, @code{>}, or @code{>=} respectively. This is the equivalent of
the Python expression @code{o1 op o2}, where @code{op} is the operator corresponding
to @emph{opid}. Returns the value of the comparison on success, or @code{NULL} on failure.
@end deffn

@geindex PyObject_RichCompareBool (C 函数)
@anchor{c-api/object c PyObject_RichCompareBool}@anchor{ed6}
@deffn {C 函数} int PyObject_RichCompareBool (PyObject@w{ }*o1, PyObject@w{ }*o2, int@w{ }opid)

Compare the values of @emph{o1} and @emph{o2} using the operation specified by @emph{opid},
which must be one of @code{Py_LT}, @code{Py_LE}, @code{Py_EQ},
@code{Py_NE}, @code{Py_GT}, or @code{Py_GE}, corresponding to @code{<},
@code{<=}, @code{==}, @code{!=}, @code{>}, or @code{>=} respectively. Returns @code{-1} on error,
@code{0} if the result is false, @code{1} otherwise. This is the equivalent of the
Python expression @code{o1 op o2}, where @code{op} is the operator corresponding to
@emph{opid}.
@end deffn

@cartouche
@quotation 注解 
If @emph{o1} and @emph{o2} are the same object, @ref{ed6,,PyObject_RichCompareBool()}
will always return @code{1} for @code{Py_EQ} and @code{0} for @code{Py_NE}.
@end quotation
@end cartouche

@geindex PyObject_Repr (C 函数)
@anchor{c-api/object c PyObject_Repr}@anchor{962}
@deffn {C 函数} PyObject* PyObject_Repr (PyObject@w{ }*o)
@emph{Return value: New reference.}
@geindex 內置函数; repr

Compute a string representation of object @emph{o}.  Returns the string
representation on success, @code{NULL} on failure.  This is the equivalent of the
Python expression @code{repr(o)}.  Called by the @ref{7c6,,repr()} built-in function.


在 3.4 版更改: This function now includes a debug assertion to help ensure that it
does not silently discard an active exception.

@end deffn

@geindex PyObject_ASCII (C 函数)
@anchor{c-api/object c PyObject_ASCII}@anchor{3c61}
@deffn {C 函数} PyObject* PyObject_ASCII (PyObject@w{ }*o)
@emph{Return value: New reference.}
@geindex 內置函数; ascii

As @ref{962,,PyObject_Repr()}, compute a string representation of object @emph{o}, but
escape the non-ASCII characters in the string returned by
@ref{962,,PyObject_Repr()} with @code{\x}, @code{\u} or @code{\U} escapes.  This generates
a string similar to that returned by @ref{962,,PyObject_Repr()} in Python 2.
Called by the @ref{d45,,ascii()} built-in function.

@geindex string; PyObject_Str (C function)
@end deffn

@geindex PyObject_Str (C 函数)
@anchor{c-api/object c PyObject_Str}@anchor{963}
@deffn {C 函数} PyObject* PyObject_Str (PyObject@w{ }*o)
@emph{Return value: New reference.}
Compute a string representation of object @emph{o}.  Returns the string
representation on success, @code{NULL} on failure.  This is the equivalent of the
Python expression @code{str(o)}.  Called by the @ref{329,,str()} built-in function
and, therefore, by the @ref{880,,print()} function.


在 3.4 版更改: This function now includes a debug assertion to help ensure that it
does not silently discard an active exception.

@end deffn

@geindex PyObject_Bytes (C 函数)
@anchor{c-api/object c PyObject_Bytes}@anchor{3c62}
@deffn {C 函数} PyObject* PyObject_Bytes (PyObject@w{ }*o)
@emph{Return value: New reference.}
@geindex 內置函数; bytes

Compute a bytes representation of object @emph{o}.  @code{NULL} is returned on
failure and a bytes object on success.  This is equivalent to the Python
expression @code{bytes(o)}, when @emph{o} is not an integer.  Unlike @code{bytes(o)},
a TypeError is raised when @emph{o} is an integer instead of a zero-initialized
bytes object.
@end deffn

@geindex PyObject_IsSubclass (C 函数)
@anchor{c-api/object c PyObject_IsSubclass}@anchor{798}
@deffn {C 函数} int PyObject_IsSubclass (PyObject@w{ }*derived, PyObject@w{ }*cls)

Return @code{1} if the class @emph{derived} is identical to or derived from the class
@emph{cls}, otherwise return @code{0}.  In case of an error, return @code{-1}.

If @emph{cls} is a tuple, the check will be done against every entry in @emph{cls}.
The result will be @code{1} when at least one of the checks returns @code{1},
otherwise it will be @code{0}.

If @emph{cls} has a @ref{13e9,,__subclasscheck__()} method, it will be called to
determine the subclass status as described in 
@geindex Python 提高建议; PEP 3119
PEP 3119@footnote{https://www.python.org/dev/peps/pep-3119}.  Otherwise,
@emph{derived} is a subclass of @emph{cls} if it is a direct or indirect subclass,
i.e. contained in @code{cls.__mro__}.

Normally only class objects, i.e. instances of @ref{603,,type} or a derived
class, are considered classes.  However, objects can override this by having
a @code{__bases__} attribute (which must be a tuple of base classes).
@end deffn

@geindex PyObject_IsInstance (C 函数)
@anchor{c-api/object c PyObject_IsInstance}@anchor{797}
@deffn {C 函数} int PyObject_IsInstance (PyObject@w{ }*inst, PyObject@w{ }*cls)

Return @code{1} if @emph{inst} is an instance of the class @emph{cls} or a subclass of
@emph{cls}, or @code{0} if not.  On error, returns @code{-1} and sets an exception.

If @emph{cls} is a tuple, the check will be done against every entry in @emph{cls}.
The result will be @code{1} when at least one of the checks returns @code{1},
otherwise it will be @code{0}.

If @emph{cls} has a @ref{13e8,,__instancecheck__()} method, it will be called to
determine the subclass status as described in 
@geindex Python 提高建议; PEP 3119
PEP 3119@footnote{https://www.python.org/dev/peps/pep-3119}.  Otherwise, @emph{inst}
is an instance of @emph{cls} if its class is a subclass of @emph{cls}.

An instance @emph{inst} can override what is considered its class by having a
@code{__class__} attribute.

An object @emph{cls} can override if it is considered a class, and what its base
classes are, by having a @code{__bases__} attribute (which must be a tuple
of base classes).
@end deffn

@geindex PyCallable_Check (C 函数)
@anchor{c-api/object c PyCallable_Check}@anchor{3c63}
@deffn {C 函数} int PyCallable_Check (PyObject@w{ }*o)

Determine if the object @emph{o} is callable.  Return @code{1} if the object is callable
and @code{0} otherwise.  This function always succeeds.
@end deffn

@geindex PyObject_Call (C 函数)
@anchor{c-api/object c PyObject_Call}@anchor{3ab5}
@deffn {C 函数} PyObject* PyObject_Call (PyObject@w{ }*callable, PyObject@w{ }*args, PyObject@w{ }*kwargs)
@emph{Return value: New reference.}
Call a callable Python object @emph{callable}, with arguments given by the
tuple @emph{args}, and named arguments given by the dictionary @emph{kwargs}.

@emph{args} must not be @code{NULL}, use an empty tuple if no arguments are needed.
If no named arguments are needed, @emph{kwargs} can be @code{NULL}.

Return the result of the call on success, or raise an exception and return
@code{NULL} on failure.

This is the equivalent of the Python expression:
@code{callable(*args, **kwargs)}.
@end deffn

@geindex PyObject_CallObject (C 函数)
@anchor{c-api/object c PyObject_CallObject}@anchor{3ab4}
@deffn {C 函数} PyObject* PyObject_CallObject (PyObject@w{ }*callable, PyObject@w{ }*args)
@emph{Return value: New reference.}
Call a callable Python object @emph{callable}, with arguments given by the
tuple @emph{args}.  If no arguments are needed, then @emph{args} can be @code{NULL}.

Return the result of the call on success, or raise an exception and return
@code{NULL} on failure.

This is the equivalent of the Python expression: @code{callable(*args)}.
@end deffn

@geindex PyObject_CallFunction (C 函数)
@anchor{c-api/object c PyObject_CallFunction}@anchor{2cf}
@deffn {C 函数} PyObject* PyObject_CallFunction (PyObject@w{ }*callable, const char@w{ }*format, ...)
@emph{Return value: New reference.}
Call a callable Python object @emph{callable}, with a variable number of C arguments.
The C arguments are described using a @ref{2ce,,Py_BuildValue()} style format
string.  The format can be @code{NULL}, indicating that no arguments are provided.

Return the result of the call on success, or raise an exception and return
@code{NULL} on failure.

This is the equivalent of the Python expression: @code{callable(*args)}.

Note that if you only pass @ref{4b5,,PyObject *} args,
@ref{3c64,,PyObject_CallFunctionObjArgs()} is a faster alternative.


在 3.4 版更改: The type of @emph{format} was changed from @code{char *}.

@end deffn

@geindex PyObject_CallMethod (C 函数)
@anchor{c-api/object c PyObject_CallMethod}@anchor{3c65}
@deffn {C 函数} PyObject* PyObject_CallMethod (PyObject@w{ }*obj, const char@w{ }*name, const char@w{ }*format, ...)
@emph{Return value: New reference.}
Call the method named @emph{name} of object @emph{obj} with a variable number of C
arguments.  The C arguments are described by a @ref{2ce,,Py_BuildValue()} format
string that should  produce a tuple.

The format can be @code{NULL}, indicating that no arguments are provided.

Return the result of the call on success, or raise an exception and return
@code{NULL} on failure.

This is the equivalent of the Python expression:
@code{obj.name(arg1, arg2, ...)}.

Note that if you only pass @ref{4b5,,PyObject *} args,
@ref{f69,,PyObject_CallMethodObjArgs()} is a faster alternative.


在 3.4 版更改: The types of @emph{name} and @emph{format} were changed from @code{char *}.

@end deffn

@geindex PyObject_CallFunctionObjArgs (C 函数)
@anchor{c-api/object c PyObject_CallFunctionObjArgs}@anchor{3c64}
@deffn {C 函数} PyObject* PyObject_CallFunctionObjArgs (PyObject@w{ }*callable, ..., NULL)
@emph{Return value: New reference.}
Call a callable Python object @emph{callable}, with a variable number of
@ref{4b5,,PyObject*} arguments.  The arguments are provided as a variable number
of parameters followed by @code{NULL}.

Return the result of the call on success, or raise an exception and return
@code{NULL} on failure.

This is the equivalent of the Python expression:
@code{callable(arg1, arg2, ...)}.
@end deffn

@geindex PyObject_CallMethodObjArgs (C 函数)
@anchor{c-api/object c PyObject_CallMethodObjArgs}@anchor{f69}
@deffn {C 函数} PyObject* PyObject_CallMethodObjArgs (PyObject@w{ }*obj, PyObject@w{ }*name, ..., NULL)
@emph{Return value: New reference.}
Calls a method of the Python object @emph{obj}, where the name of the method is given as a
Python string object in @emph{name}.  It is called with a variable number of
@ref{4b5,,PyObject*} arguments.  The arguments are provided as a variable number
of parameters followed by @code{NULL}.

Return the result of the call on success, or raise an exception and return
@code{NULL} on failure.
@end deffn

@geindex _PyObject_Vectorcall (C 函数)
@anchor{c-api/object c _PyObject_Vectorcall}@anchor{3c66}
@deffn {C 函数} PyObject* _PyObject_Vectorcall (PyObject@w{ }*callable, PyObject *const@w{ }*args, size_t@w{ }nargsf, PyObject@w{ }*kwnames)

Call a callable Python object @emph{callable}, using
@ref{3c67,,vectorcall} if possible.

@emph{args} is a C array with the positional arguments.

@emph{nargsf} is the number of positional arguments plus optionally the flag
@code{PY_VECTORCALL_ARGUMENTS_OFFSET} (see below).
To get actual number of arguments, use
@ref{3c68,,PyVectorcall_NARGS(nargsf)}.

@emph{kwnames} can be either @code{NULL} (no keyword arguments) or a tuple of keyword
names. In the latter case, the values of the keyword arguments are stored
in @emph{args} after the positional arguments.
The number of keyword arguments does not influence @emph{nargsf}.

@emph{kwnames} must contain only objects of type @code{str} (not a subclass),
and all keys must be unique.

Return the result of the call on success, or raise an exception and return
@code{NULL} on failure.

This uses the vectorcall protocol if the callable supports it;
otherwise, the arguments are converted to use
@ref{3b11,,tp_call}.

@cartouche
@quotation 注解 
This function is provisional and expected to become public in Python 3.9,
with a different name and, possibly, changed semantics.
If you use the function, plan for updating your code for Python 3.9.
@end quotation
@end cartouche


3.8 新版功能.

@end deffn

@geindex PY_VECTORCALL_ARGUMENTS_OFFSET (C 变量)
@anchor{c-api/object c PY_VECTORCALL_ARGUMENTS_OFFSET}@anchor{3c69}
@deffn {C 变量} PY_VECTORCALL_ARGUMENTS_OFFSET

If set in a vectorcall @emph{nargsf} argument, the callee is allowed to
temporarily change @code{args[-1]}. In other words, @emph{args} points to
argument 1 (not 0) in the allocated vector.
The callee must restore the value of @code{args[-1]} before returning.

Whenever they can do so cheaply (without additional allocation), callers
are encouraged to use @code{PY_VECTORCALL_ARGUMENTS_OFFSET}.
Doing so will allow callables such as bound methods to make their onward
calls (which include a prepended @emph{self} argument) cheaply.


3.8 新版功能.

@end deffn

@geindex PyVectorcall_NARGS (C 函数)
@anchor{c-api/object c PyVectorcall_NARGS}@anchor{3c68}
@deffn {C 函数} Py_ssize_t PyVectorcall_NARGS (size_t@w{ }nargsf)

Given a vectorcall @emph{nargsf} argument, return the actual number of
arguments.
Currently equivalent to @code{nargsf & ~PY_VECTORCALL_ARGUMENTS_OFFSET}.


3.8 新版功能.

@end deffn

@geindex _PyObject_FastCallDict (C 函数)
@anchor{c-api/object c _PyObject_FastCallDict}@anchor{3c6a}
@deffn {C 函数} PyObject* _PyObject_FastCallDict (PyObject@w{ }*callable, PyObject *const@w{ }*args, size_t@w{ }nargsf, PyObject@w{ }*kwdict)

Same as @ref{3c66,,_PyObject_Vectorcall()} except that the keyword arguments
are passed as a dictionary in @emph{kwdict}. This may be @code{NULL} if there
are no keyword arguments.

For callables supporting @ref{3c67,,vectorcall},
the arguments are internally converted to the vectorcall convention.
Therefore, this function adds some overhead compared to
@ref{3c66,,_PyObject_Vectorcall()}.
It should only be used if the caller already has a dictionary ready to use.

@cartouche
@quotation 注解 
This function is provisional and expected to become public in Python 3.9,
with a different name and, possibly, changed semantics.
If you use the function, plan for updating your code for Python 3.9.
@end quotation
@end cartouche


3.8 新版功能.

@end deffn

@geindex PyObject_Hash (C 函数)
@anchor{c-api/object c PyObject_Hash}@anchor{3c6b}
@deffn {C 函数} Py_hash_t PyObject_Hash (PyObject@w{ }*o)

@geindex 內置函数; hash

Compute and return the hash value of an object @emph{o}.  On failure, return @code{-1}.
This is the equivalent of the Python expression @code{hash(o)}.


在 3.2 版更改: The return type is now Py_hash_t.  This is a signed integer the same size
as Py_ssize_t.

@end deffn

@geindex PyObject_HashNotImplemented (C 函数)
@anchor{c-api/object c PyObject_HashNotImplemented}@anchor{d2a}
@deffn {C 函数} Py_hash_t PyObject_HashNotImplemented (PyObject@w{ }*o)

Set a @ref{192,,TypeError} indicating that @code{type(o)} is not hashable and return @code{-1}.
This function receives special treatment when stored in a @code{tp_hash} slot,
allowing a type to explicitly indicate to the interpreter that it is not
hashable.
@end deffn

@geindex PyObject_IsTrue (C 函数)
@anchor{c-api/object c PyObject_IsTrue}@anchor{3c6c}
@deffn {C 函数} int PyObject_IsTrue (PyObject@w{ }*o)

Returns @code{1} if the object @emph{o} is considered to be true, and @code{0} otherwise.
This is equivalent to the Python expression @code{not not o}.  On failure, return
@code{-1}.
@end deffn

@geindex PyObject_Not (C 函数)
@anchor{c-api/object c PyObject_Not}@anchor{3c6d}
@deffn {C 函数} int PyObject_Not (PyObject@w{ }*o)

Returns @code{0} if the object @emph{o} is considered to be true, and @code{1} otherwise.
This is equivalent to the Python expression @code{not o}.  On failure, return
@code{-1}.
@end deffn

@geindex PyObject_Type (C 函数)
@anchor{c-api/object c PyObject_Type}@anchor{3c6e}
@deffn {C 函数} PyObject* PyObject_Type (PyObject@w{ }*o)
@emph{Return value: New reference.}
@geindex 內置函数; type

When @emph{o} is non-@code{NULL}, returns a type object corresponding to the object type
of object @emph{o}. On failure, raises @ref{5f6,,SystemError} and returns @code{NULL}.  This
is equivalent to the Python expression @code{type(o)}. This function increments the
reference count of the return value. There's really no reason to use this
function instead of the common expression @code{o->ob_type}, which returns a
pointer of type @ref{2d6,,PyTypeObject*}, except when the incremented reference
count is needed.
@end deffn

@geindex PyObject_TypeCheck (C 函数)
@anchor{c-api/object c PyObject_TypeCheck}@anchor{3b15}
@deffn {C 函数} int PyObject_TypeCheck (PyObject@w{ }*o, PyTypeObject@w{ }*type)

Return true if the object @emph{o} is of type @emph{type} or a subtype of @emph{type}.  Both
parameters must be non-@code{NULL}.
@end deffn

@geindex PyObject_Size (C 函数)
@geindex PyObject_Length (C 函数)
@anchor{c-api/object c PyObject_Size}@anchor{3c6f}
@deffn {C 函数} Py_ssize_t PyObject_Size (PyObject@w{ }*o)
@anchor{c-api/object c PyObject_Length}@anchor{3c70}
@deffnx {C 函数} Py_ssize_t PyObject_Length (PyObject@w{ }*o)

@geindex 內置函数; len

Return the length of object @emph{o}.  If the object @emph{o} provides either the sequence
and mapping protocols, the sequence length is returned.  On error, @code{-1} is
returned.  This is the equivalent to the Python expression @code{len(o)}.
@end deffn

@geindex PyObject_LengthHint (C 函数)
@anchor{c-api/object c PyObject_LengthHint}@anchor{922}
@deffn {C 函数} Py_ssize_t PyObject_LengthHint (PyObject@w{ }*o, Py_ssize_t@w{ }default)

Return an estimated length for the object @emph{o}. First try to return its
actual length, then an estimate using @ref{806,,__length_hint__()}, and
finally return the default value. On error return @code{-1}. This is the
equivalent to the Python expression @code{operator.length_hint(o, default)}.


3.4 新版功能.

@end deffn

@geindex PyObject_GetItem (C 函数)
@anchor{c-api/object c PyObject_GetItem}@anchor{3b57}
@deffn {C 函数} PyObject* PyObject_GetItem (PyObject@w{ }*o, PyObject@w{ }*key)
@emph{Return value: New reference.}
Return element of @emph{o} corresponding to the object @emph{key} or @code{NULL} on failure.
This is the equivalent of the Python expression @code{o[key]}.
@end deffn

@geindex PyObject_SetItem (C 函数)
@anchor{c-api/object c PyObject_SetItem}@anchor{3b55}
@deffn {C 函数} int PyObject_SetItem (PyObject@w{ }*o, PyObject@w{ }*key, PyObject@w{ }*v)

Map the object @emph{key} to the value @emph{v}.  Raise an exception and
return @code{-1} on failure; return @code{0} on success.  This is the
equivalent of the Python statement @code{o[key] = v}.  This function @emph{does
not} steal a reference to @emph{v}.
@end deffn

@geindex PyObject_DelItem (C 函数)
@anchor{c-api/object c PyObject_DelItem}@anchor{3c71}
@deffn {C 函数} int PyObject_DelItem (PyObject@w{ }*o, PyObject@w{ }*key)

Remove the mapping for the object @emph{key} from the object @emph{o}.  Return @code{-1}
on failure.  This is equivalent to the Python statement @code{del o[key]}.
@end deffn

@geindex PyObject_Dir (C 函数)
@anchor{c-api/object c PyObject_Dir}@anchor{3c72}
@deffn {C 函数} PyObject* PyObject_Dir (PyObject@w{ }*o)
@emph{Return value: New reference.}
This is equivalent to the Python expression @code{dir(o)}, returning a (possibly
empty) list of strings appropriate for the object argument, or @code{NULL} if there
was an error.  If the argument is @code{NULL}, this is like the Python @code{dir()},
returning the names of the current locals; in this case, if no execution frame
is active then @code{NULL} is returned but @ref{3aa4,,PyErr_Occurred()} will return false.
@end deffn

@geindex PyObject_GetIter (C 函数)
@anchor{c-api/object c PyObject_GetIter}@anchor{3c73}
@deffn {C 函数} PyObject* PyObject_GetIter (PyObject@w{ }*o)
@emph{Return value: New reference.}
This is equivalent to the Python expression @code{iter(o)}. It returns a new
iterator for the object argument, or the object  itself if the object is already
an iterator.  Raises @ref{192,,TypeError} and returns @code{NULL} if the object cannot be
iterated.
@end deffn

@node 数字协议,序列协议,对象协议,抽象对象层
@anchor{c-api/number doc}@anchor{3c74}@anchor{c-api/number number}@anchor{3c75}@anchor{c-api/number number-protocol}@anchor{3c76}
@subsection 数字协议


@geindex PyNumber_Check (C 函数)
@anchor{c-api/number c PyNumber_Check}@anchor{26b}
@deffn {C 函数} int PyNumber_Check (PyObject@w{ }*o)

如果对象 @emph{o} 提供数字的协议，返回真 @code{1}，否则返回假。这个函数不会调用失败。


在 3.8 版更改: 如果 @emph{o} 是一个索引整数则返回 @code{1}。

@end deffn

@geindex PyNumber_Add (C 函数)
@anchor{c-api/number c PyNumber_Add}@anchor{3c77}
@deffn {C 函数} PyObject* PyNumber_Add (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of adding @emph{o1} and @emph{o2}, or @code{NULL} on failure.  This is the
equivalent of the Python expression @code{o1 + o2}.
@end deffn

@geindex PyNumber_Subtract (C 函数)
@anchor{c-api/number c PyNumber_Subtract}@anchor{3c78}
@deffn {C 函数} PyObject* PyNumber_Subtract (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of subtracting @emph{o2} from @emph{o1}, or @code{NULL} on failure.  This is
the equivalent of the Python expression @code{o1 - o2}.
@end deffn

@geindex PyNumber_Multiply (C 函数)
@anchor{c-api/number c PyNumber_Multiply}@anchor{3c79}
@deffn {C 函数} PyObject* PyNumber_Multiply (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of multiplying @emph{o1} and @emph{o2}, or @code{NULL} on failure.  This is
the equivalent of the Python expression @code{o1 * o2}.
@end deffn

@geindex PyNumber_MatrixMultiply (C 函数)
@anchor{c-api/number c PyNumber_MatrixMultiply}@anchor{7a8}
@deffn {C 函数} PyObject* PyNumber_MatrixMultiply (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of matrix multiplication on @emph{o1} and @emph{o2}, or @code{NULL} on
failure.  This is the equivalent of the Python expression @code{o1 @@ o2}.


3.5 新版功能.

@end deffn

@geindex PyNumber_FloorDivide (C 函数)
@anchor{c-api/number c PyNumber_FloorDivide}@anchor{3c7a}
@deffn {C 函数} PyObject* PyNumber_FloorDivide (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Return the floor of @emph{o1} divided by @emph{o2}, or @code{NULL} on failure.  This is
equivalent to the "classic" division of integers.
@end deffn

@geindex PyNumber_TrueDivide (C 函数)
@anchor{c-api/number c PyNumber_TrueDivide}@anchor{3c7b}
@deffn {C 函数} PyObject* PyNumber_TrueDivide (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Return a reasonable approximation for the mathematical value of @emph{o1} divided by
@emph{o2}, or @code{NULL} on failure.  The return value is "approximate" because binary
floating point numbers are approximate; it is not possible to represent all real
numbers in base two.  This function can return a floating point value when
passed two integers.
@end deffn

@geindex PyNumber_Remainder (C 函数)
@anchor{c-api/number c PyNumber_Remainder}@anchor{3c7c}
@deffn {C 函数} PyObject* PyNumber_Remainder (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the remainder of dividing @emph{o1} by @emph{o2}, or @code{NULL} on failure.  This is
the equivalent of the Python expression @code{o1 % o2}.
@end deffn

@geindex PyNumber_Divmod (C 函数)
@anchor{c-api/number c PyNumber_Divmod}@anchor{3c7d}
@deffn {C 函数} PyObject* PyNumber_Divmod (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
@geindex 內置函数; divmod

See the built-in function @ref{152,,divmod()}. Returns @code{NULL} on failure.  This is
the equivalent of the Python expression @code{divmod(o1, o2)}.
@end deffn

@geindex PyNumber_Power (C 函数)
@anchor{c-api/number c PyNumber_Power}@anchor{3c7e}
@deffn {C 函数} PyObject* PyNumber_Power (PyObject@w{ }*o1, PyObject@w{ }*o2, PyObject@w{ }*o3)
@emph{Return value: New reference.}
@geindex 內置函数; pow

See the built-in function @ref{19a,,pow()}. Returns @code{NULL} on failure.  This is the
equivalent of the Python expression @code{pow(o1, o2, o3)}, where @emph{o3} is optional.
If @emph{o3} is to be ignored, pass @ref{3aa9,,Py_None} in its place (passing @code{NULL} for
@emph{o3} would cause an illegal memory access).
@end deffn

@geindex PyNumber_Negative (C 函数)
@anchor{c-api/number c PyNumber_Negative}@anchor{3c7f}
@deffn {C 函数} PyObject* PyNumber_Negative (PyObject@w{ }*o)
@emph{Return value: New reference.}
Returns the negation of @emph{o} on success, or @code{NULL} on failure. This is the
equivalent of the Python expression @code{-o}.
@end deffn

@geindex PyNumber_Positive (C 函数)
@anchor{c-api/number c PyNumber_Positive}@anchor{3c80}
@deffn {C 函数} PyObject* PyNumber_Positive (PyObject@w{ }*o)
@emph{Return value: New reference.}
Returns @emph{o} on success, or @code{NULL} on failure.  This is the equivalent of the
Python expression @code{+o}.
@end deffn

@geindex PyNumber_Absolute (C 函数)
@anchor{c-api/number c PyNumber_Absolute}@anchor{3c81}
@deffn {C 函数} PyObject* PyNumber_Absolute (PyObject@w{ }*o)
@emph{Return value: New reference.}
@geindex 內置函数; abs

Returns the absolute value of @emph{o}, or @code{NULL} on failure.  This is the equivalent
of the Python expression @code{abs(o)}.
@end deffn

@geindex PyNumber_Invert (C 函数)
@anchor{c-api/number c PyNumber_Invert}@anchor{3c82}
@deffn {C 函数} PyObject* PyNumber_Invert (PyObject@w{ }*o)
@emph{Return value: New reference.}
Returns the bitwise negation of @emph{o} on success, or @code{NULL} on failure.  This is
the equivalent of the Python expression @code{~o}.
@end deffn

@geindex PyNumber_Lshift (C 函数)
@anchor{c-api/number c PyNumber_Lshift}@anchor{3c83}
@deffn {C 函数} PyObject* PyNumber_Lshift (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of left shifting @emph{o1} by @emph{o2} on success, or @code{NULL} on
failure.  This is the equivalent of the Python expression @code{o1 << o2}.
@end deffn

@geindex PyNumber_Rshift (C 函数)
@anchor{c-api/number c PyNumber_Rshift}@anchor{3c84}
@deffn {C 函数} PyObject* PyNumber_Rshift (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of right shifting @emph{o1} by @emph{o2} on success, or @code{NULL} on
failure.  This is the equivalent of the Python expression @code{o1 >> o2}.
@end deffn

@geindex PyNumber_And (C 函数)
@anchor{c-api/number c PyNumber_And}@anchor{3c85}
@deffn {C 函数} PyObject* PyNumber_And (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the "bitwise and" of @emph{o1} and @emph{o2} on success and @code{NULL} on failure.
This is the equivalent of the Python expression @code{o1 & o2}.
@end deffn

@geindex PyNumber_Xor (C 函数)
@anchor{c-api/number c PyNumber_Xor}@anchor{3c86}
@deffn {C 函数} PyObject* PyNumber_Xor (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the "bitwise exclusive or" of @emph{o1} by @emph{o2} on success, or @code{NULL} on
failure.  This is the equivalent of the Python expression @code{o1 ^ o2}.
@end deffn

@geindex PyNumber_Or (C 函数)
@anchor{c-api/number c PyNumber_Or}@anchor{3c87}
@deffn {C 函数} PyObject* PyNumber_Or (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the "bitwise or" of @emph{o1} and @emph{o2} on success, or @code{NULL} on failure.
This is the equivalent of the Python expression @code{o1 | o2}.
@end deffn

@geindex PyNumber_InPlaceAdd (C 函数)
@anchor{c-api/number c PyNumber_InPlaceAdd}@anchor{3c88}
@deffn {C 函数} PyObject* PyNumber_InPlaceAdd (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of adding @emph{o1} and @emph{o2}, or @code{NULL} on failure.  The operation
is done @emph{in-place} when @emph{o1} supports it.  This is the equivalent of the Python
statement @code{o1 += o2}.
@end deffn

@geindex PyNumber_InPlaceSubtract (C 函数)
@anchor{c-api/number c PyNumber_InPlaceSubtract}@anchor{3c89}
@deffn {C 函数} PyObject* PyNumber_InPlaceSubtract (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of subtracting @emph{o2} from @emph{o1}, or @code{NULL} on failure.  The
operation is done @emph{in-place} when @emph{o1} supports it.  This is the equivalent of
the Python statement @code{o1 -= o2}.
@end deffn

@geindex PyNumber_InPlaceMultiply (C 函数)
@anchor{c-api/number c PyNumber_InPlaceMultiply}@anchor{3c8a}
@deffn {C 函数} PyObject* PyNumber_InPlaceMultiply (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of multiplying @emph{o1} and @emph{o2}, or @code{NULL} on failure.  The
operation is done @emph{in-place} when @emph{o1} supports it.  This is the equivalent of
the Python statement @code{o1 *= o2}.
@end deffn

@geindex PyNumber_InPlaceMatrixMultiply (C 函数)
@anchor{c-api/number c PyNumber_InPlaceMatrixMultiply}@anchor{7a9}
@deffn {C 函数} PyObject* PyNumber_InPlaceMatrixMultiply (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of matrix multiplication on @emph{o1} and @emph{o2}, or @code{NULL} on
failure.  The operation is done @emph{in-place} when @emph{o1} supports it.  This is
the equivalent of the Python statement @code{o1 @@= o2}.


3.5 新版功能.

@end deffn

@geindex PyNumber_InPlaceFloorDivide (C 函数)
@anchor{c-api/number c PyNumber_InPlaceFloorDivide}@anchor{3c8b}
@deffn {C 函数} PyObject* PyNumber_InPlaceFloorDivide (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the mathematical floor of dividing @emph{o1} by @emph{o2}, or @code{NULL} on failure.
The operation is done @emph{in-place} when @emph{o1} supports it.  This is the equivalent
of the Python statement @code{o1 //= o2}.
@end deffn

@geindex PyNumber_InPlaceTrueDivide (C 函数)
@anchor{c-api/number c PyNumber_InPlaceTrueDivide}@anchor{3c8c}
@deffn {C 函数} PyObject* PyNumber_InPlaceTrueDivide (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Return a reasonable approximation for the mathematical value of @emph{o1} divided by
@emph{o2}, or @code{NULL} on failure.  The return value is "approximate" because binary
floating point numbers are approximate; it is not possible to represent all real
numbers in base two.  This function can return a floating point value when
passed two integers.  The operation is done @emph{in-place} when @emph{o1} supports it.
@end deffn

@geindex PyNumber_InPlaceRemainder (C 函数)
@anchor{c-api/number c PyNumber_InPlaceRemainder}@anchor{3c8d}
@deffn {C 函数} PyObject* PyNumber_InPlaceRemainder (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the remainder of dividing @emph{o1} by @emph{o2}, or @code{NULL} on failure.  The
operation is done @emph{in-place} when @emph{o1} supports it.  This is the equivalent of
the Python statement @code{o1 %= o2}.
@end deffn

@geindex PyNumber_InPlacePower (C 函数)
@anchor{c-api/number c PyNumber_InPlacePower}@anchor{3c8e}
@deffn {C 函数} PyObject* PyNumber_InPlacePower (PyObject@w{ }*o1, PyObject@w{ }*o2, PyObject@w{ }*o3)
@emph{Return value: New reference.}
@geindex 內置函数; pow

See the built-in function @ref{19a,,pow()}. Returns @code{NULL} on failure.  The operation
is done @emph{in-place} when @emph{o1} supports it.  This is the equivalent of the Python
statement @code{o1 **= o2} when o3 is @ref{3aa9,,Py_None}, or an in-place variant of
@code{pow(o1, o2, o3)} otherwise. If @emph{o3} is to be ignored, pass @ref{3aa9,,Py_None}
in its place (passing @code{NULL} for @emph{o3} would cause an illegal memory access).
@end deffn

@geindex PyNumber_InPlaceLshift (C 函数)
@anchor{c-api/number c PyNumber_InPlaceLshift}@anchor{3c8f}
@deffn {C 函数} PyObject* PyNumber_InPlaceLshift (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of left shifting @emph{o1} by @emph{o2} on success, or @code{NULL} on
failure.  The operation is done @emph{in-place} when @emph{o1} supports it.  This is the
equivalent of the Python statement @code{o1 <<= o2}.
@end deffn

@geindex PyNumber_InPlaceRshift (C 函数)
@anchor{c-api/number c PyNumber_InPlaceRshift}@anchor{3c90}
@deffn {C 函数} PyObject* PyNumber_InPlaceRshift (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the result of right shifting @emph{o1} by @emph{o2} on success, or @code{NULL} on
failure.  The operation is done @emph{in-place} when @emph{o1} supports it.  This is the
equivalent of the Python statement @code{o1 >>= o2}.
@end deffn

@geindex PyNumber_InPlaceAnd (C 函数)
@anchor{c-api/number c PyNumber_InPlaceAnd}@anchor{3c91}
@deffn {C 函数} PyObject* PyNumber_InPlaceAnd (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the "bitwise and" of @emph{o1} and @emph{o2} on success and @code{NULL} on failure. The
operation is done @emph{in-place} when @emph{o1} supports it.  This is the equivalent of
the Python statement @code{o1 &= o2}.
@end deffn

@geindex PyNumber_InPlaceXor (C 函数)
@anchor{c-api/number c PyNumber_InPlaceXor}@anchor{3c92}
@deffn {C 函数} PyObject* PyNumber_InPlaceXor (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the "bitwise exclusive or" of @emph{o1} by @emph{o2} on success, or @code{NULL} on
failure.  The operation is done @emph{in-place} when @emph{o1} supports it.  This is the
equivalent of the Python statement @code{o1 ^= o2}.
@end deffn

@geindex PyNumber_InPlaceOr (C 函数)
@anchor{c-api/number c PyNumber_InPlaceOr}@anchor{3c93}
@deffn {C 函数} PyObject* PyNumber_InPlaceOr (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
Returns the "bitwise or" of @emph{o1} and @emph{o2} on success, or @code{NULL} on failure.  The
operation is done @emph{in-place} when @emph{o1} supports it.  This is the equivalent of
the Python statement @code{o1 |= o2}.
@end deffn

@geindex PyNumber_Long (C 函数)
@anchor{c-api/number c PyNumber_Long}@anchor{26c}
@deffn {C 函数} PyObject* PyNumber_Long (PyObject@w{ }*o)
@emph{Return value: New reference.}
@geindex 內置函数; int

Returns the @emph{o} converted to an integer object on success, or @code{NULL} on
failure.  This is the equivalent of the Python expression @code{int(o)}.
@end deffn

@geindex PyNumber_Float (C 函数)
@anchor{c-api/number c PyNumber_Float}@anchor{26d}
@deffn {C 函数} PyObject* PyNumber_Float (PyObject@w{ }*o)
@emph{Return value: New reference.}
@geindex 內置函数; float

Returns the @emph{o} converted to a float object on success, or @code{NULL} on failure.
This is the equivalent of the Python expression @code{float(o)}.
@end deffn

@geindex PyNumber_Index (C 函数)
@anchor{c-api/number c PyNumber_Index}@anchor{3c94}
@deffn {C 函数} PyObject* PyNumber_Index (PyObject@w{ }*o)
@emph{Return value: New reference.}
Returns the @emph{o} converted to a Python int on success or @code{NULL} with a
@ref{192,,TypeError} exception raised on failure.
@end deffn

@geindex PyNumber_ToBase (C 函数)
@anchor{c-api/number c PyNumber_ToBase}@anchor{ec7}
@deffn {C 函数} PyObject* PyNumber_ToBase (PyObject@w{ }*n, int@w{ }base)
@emph{Return value: New reference.}
返回整数 @emph{n} 转换成以 @emph{base} 为基数的字符串后的结果。这个 @emph{base} 参数必须是 2，8，10 或者 16 。对于基数 2，8，或 16 ，返回的字符串将分别加上基数标识 @code{'0b'}, @code{'0o'}, or @code{'0x'}。如果 @emph{n} 不是 Python 中的整数 @emph{int} 类型，就先通过 @ref{3c94,,PyNumber_Index()} 将它转换成整数类型。
@end deffn

@geindex PyNumber_AsSsize_t (C 函数)
@anchor{c-api/number c PyNumber_AsSsize_t}@anchor{3c95}
@deffn {C 函数} Py_ssize_t PyNumber_AsSsize_t (PyObject@w{ }*o, PyObject@w{ }*exc)

如果 @emph{o} 是一个整数类型的解释型，返回 @emph{o} 转换成一个 Py_ssize_t 值项后的结果。如果调用失败，返回 @code{-1} 并引发异常。

If @emph{o} can be converted to a Python int but the attempt to
convert to a Py_ssize_t value would raise an @ref{95a,,OverflowError}, then the
@emph{exc} argument is the type of exception that will be raised (usually
@ref{e6e,,IndexError} or @ref{95a,,OverflowError}).  If @emph{exc} is @code{NULL}, then the
exception is cleared and the value is clipped to @code{PY_SSIZE_T_MIN} for a negative
integer or @code{PY_SSIZE_T_MAX} for a positive integer.
@end deffn

@geindex PyIndex_Check (C 函数)
@anchor{c-api/number c PyIndex_Check}@anchor{fa4}
@deffn {C 函数} int PyIndex_Check (PyObject@w{ }*o)

如果 @emph{o} 是一个索引整数（存有 nb_index 位置并有 tp_as_number 填入其中）则返回 @code{1}，否则返回 @code{0} 。这个函数不会调用失败。
@end deffn

@node 序列协议,映射协议,数字协议,抽象对象层
@anchor{c-api/sequence doc}@anchor{3c96}@anchor{c-api/sequence sequence}@anchor{3c97}@anchor{c-api/sequence sequence-protocol}@anchor{3c98}
@subsection 序列协议


@geindex PySequence_Check (C 函数)
@anchor{c-api/sequence c PySequence_Check}@anchor{3c99}
@deffn {C 函数} int PySequence_Check (PyObject@w{ }*o)

如果对象提供序列协议，函数返回 @code{1}，否则返回 @code{0}。 请注意它将为具有 @ref{27f,,__getitem__()} 方法的 Python 类返回 @code{1}，除非它们是 @ref{1b8,,dict} 的子类，因为在一般情况下无法确定它所支持键类型。 此函数总是会成功执行。
@end deffn

@geindex PySequence_Size (C 函数)
@geindex PySequence_Length (C 函数)
@anchor{c-api/sequence c PySequence_Size}@anchor{fe0}
@deffn {C 函数} Py_ssize_t PySequence_Size (PyObject@w{ }*o)
@anchor{c-api/sequence c PySequence_Length}@anchor{3c9a}
@deffnx {C 函数} Py_ssize_t PySequence_Length (PyObject@w{ }*o)

@geindex 內置函数; len

成功时返回序列中*o*的对象数,失败时返回`@w{`}-1`@w{`}. 相当于Python的`@w{`}len(o)`@w{`}表达式.
@end deffn

@geindex PySequence_Concat (C 函数)
@anchor{c-api/sequence c PySequence_Concat}@anchor{3c9b}
@deffn {C 函数} PyObject* PySequence_Concat (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
成功时返回 @emph{o1} 和 @emph{o2} 的拼接，失败时返回 @code{NULL}。 这等价于 Python 表达式 @code{o1 + o2}。
@end deffn

@geindex PySequence_Repeat (C 函数)
@anchor{c-api/sequence c PySequence_Repeat}@anchor{3c9c}
@deffn {C 函数} PyObject* PySequence_Repeat (PyObject@w{ }*o, Py_ssize_t@w{ }count)
@emph{Return value: New reference.}
返回序列对象 @emph{o} 重复 @emph{count} 次的结果，失败时返回 @code{NULL}。 这等价于 Python 表达式 @code{o * count}。
@end deffn

@geindex PySequence_InPlaceConcat (C 函数)
@anchor{c-api/sequence c PySequence_InPlaceConcat}@anchor{3c9d}
@deffn {C 函数} PyObject* PySequence_InPlaceConcat (PyObject@w{ }*o1, PyObject@w{ }*o2)
@emph{Return value: New reference.}
成功时返回 @emph{o1} 和 @emph{o2} 的拼接，失败时返回 @code{NULL}。 在 @emph{o1} 支持的情况下操作将 @emph{原地} 完成。 这等价于 Python 表达式 @code{o1 += o2}。
@end deffn

@geindex PySequence_InPlaceRepeat (C 函数)
@anchor{c-api/sequence c PySequence_InPlaceRepeat}@anchor{3c9e}
@deffn {C 函数} PyObject* PySequence_InPlaceRepeat (PyObject@w{ }*o, Py_ssize_t@w{ }count)
@emph{Return value: New reference.}
Return the result of repeating sequence object返回序列对象 @emph{o} 重复 @emph{count} 次的结果，失败时返回 @code{NULL}。 在 @emph{o} 支持的情况下该操作会 @emph{原地} 完成。 这等价于 Python 表达式 @code{o *= count}。
@end deffn

@geindex PySequence_GetItem (C 函数)
@anchor{c-api/sequence c PySequence_GetItem}@anchor{fe1}
@deffn {C 函数} PyObject* PySequence_GetItem (PyObject@w{ }*o, Py_ssize_t@w{ }i)
@emph{Return value: New reference.}
返回 @emph{o} 中的第 @emph{i} 号元素，失败时返回 @code{NULL}。 这等价于 Python 表达式 @code{o[i]}。
@end deffn

@geindex PySequence_GetSlice (C 函数)
@anchor{c-api/sequence c PySequence_GetSlice}@anchor{3c9f}
@deffn {C 函数} PyObject* PySequence_GetSlice (PyObject@w{ }*o, Py_ssize_t@w{ }i1, Py_ssize_t@w{ }i2)
@emph{Return value: New reference.}
返回序列对象 @emph{o} 的 @emph{i1} 到 @emph{i2} 的切片，失败时返回 @code{NULL}。 这等价于 Python 表达式 @code{o[i1:i2]}。
@end deffn

@geindex PySequence_SetItem (C 函数)
@anchor{c-api/sequence c PySequence_SetItem}@anchor{fe2}
@deffn {C 函数} int PySequence_SetItem (PyObject@w{ }*o, Py_ssize_t@w{ }i, PyObject@w{ }*v)

将对象 @emph{v} 赋值给 @emph{o} 的第 @emph{i} 号元素。 失败时会引发异常并返回 @code{-1}；成功时返回 @code{0}。 这相当于 Python 语句 @code{o[i] = v}。 此函数 @emph{不会} 改变对 @emph{v} 的引用。

如果 @emph{v} 为 @code{NULL}，元素将被删除，但是此特性已被弃用，应当改用 @ref{fe3,,PySequence_DelItem()}。
@end deffn

@geindex PySequence_DelItem (C 函数)
@anchor{c-api/sequence c PySequence_DelItem}@anchor{fe3}
@deffn {C 函数} int PySequence_DelItem (PyObject@w{ }*o, Py_ssize_t@w{ }i)

删除对象 @emph{o} 的第 @emph{i} 号元素。 失败时返回 @code{-1}。 这相当于 Python 语句 @code{del o[i]}。
@end deffn

@geindex PySequence_SetSlice (C 函数)
@anchor{c-api/sequence c PySequence_SetSlice}@anchor{3ca0}
@deffn {C 函数} int PySequence_SetSlice (PyObject@w{ }*o, Py_ssize_t@w{ }i1, Py_ssize_t@w{ }i2, PyObject@w{ }*v)

将序列对象 @emph{v} 赋值给序列对象 @emph{o} 的从 @emph{i1} 到 @emph{i2} 切片。 这相当于 Python 语句 @code{o[i1:i2] = v}。
@end deffn

@geindex PySequence_DelSlice (C 函数)
@anchor{c-api/sequence c PySequence_DelSlice}@anchor{3ca1}
@deffn {C 函数} int PySequence_DelSlice (PyObject@w{ }*o, Py_ssize_t@w{ }i1, Py_ssize_t@w{ }i2)

删除序列对象 @emph{o} 的从 @emph{i1} 到 @emph{i2} 的切片。 失败时返回 @code{-1}。 这相当于 Python 语句 @code{del o[i1:i2]}。
@end deffn

@geindex PySequence_Count (C 函数)
@anchor{c-api/sequence c PySequence_Count}@anchor{3ca2}
@deffn {C 函数} Py_ssize_t PySequence_Count (PyObject@w{ }*o, PyObject@w{ }*value)

返回 @emph{value} 在 @emph{o} 中出现的次数，即返回使得 @code{o[key] == value} 的键的数量。 失败时返回 @code{-1}。 这相当于 Python 表达式 @code{o.count(value)}。
@end deffn

@geindex PySequence_Contains (C 函数)
@anchor{c-api/sequence c PySequence_Contains}@anchor{3ca3}
@deffn {C 函数} int PySequence_Contains (PyObject@w{ }*o, PyObject@w{ }*value)

确定 @emph{o} 是否包含 @emph{value}。 如果 @emph{o} 中的某一项等于 @emph{value}，则返回 @code{1}，否则返回 @code{0}。 出错时，返回 @code{-1}。 这相当于 Python 表达式 @code{value in o}。
@end deffn

@geindex PySequence_Index (C 函数)
@anchor{c-api/sequence c PySequence_Index}@anchor{3ca4}
@deffn {C 函数} Py_ssize_t PySequence_Index (PyObject@w{ }*o, PyObject@w{ }*value)

返回第一个索引*i*,其中 @code{o[i] == value}.出错时,返回 @code{-1}.相当于Python的`@w{`}o.index(value)`@w{`}表达式.
@end deffn

@geindex PySequence_List (C 函数)
@anchor{c-api/sequence c PySequence_List}@anchor{3ca5}
@deffn {C 函数} PyObject* PySequence_List (PyObject@w{ }*o)
@emph{Return value: New reference.}
返回一个列表对象，其内容与序列或可迭代对象 @emph{o} 相同，失败时返回 @code{NULL}。 返回的列表保证是一个新对象。 这等价于 Python 表达式 @code{list(o)}。
@end deffn

@geindex PySequence_Tuple (C 函数)
@anchor{c-api/sequence c PySequence_Tuple}@anchor{3ca6}
@deffn {C 函数} PyObject* PySequence_Tuple (PyObject@w{ }*o)
@emph{Return value: New reference.}
@geindex 內置函数; tuple

返回一个元组对象，其内容与序列或可迭代对象 @emph{o} 相同，失败时返回 @code{NULL}。 如果 @emph{o} 为元组，则将返回一个新的引用，在其他情况下将使用适当的内容构造一个元组。 这等价于 Python 表达式 @code{tuple(o)}。
@end deffn

@geindex PySequence_Fast (C 函数)
@anchor{c-api/sequence c PySequence_Fast}@anchor{3ca7}
@deffn {C 函数} PyObject* PySequence_Fast (PyObject@w{ }*o, const char@w{ }*m)
@emph{Return value: New reference.}
将序列或可迭代对象 @emph{o} 作为其他 @code{PySequence_Fast*} 函数族可用的对象返回。 如果该对象不是序列或可迭代对象，则会引发 @ref{192,,TypeError} 并将 @emph{m} 作为消息文本。 失败时返回 @code{NULL}。

@code{PySequence_Fast*} 函数之所以这样命名，是因为它们会假定 @emph{o} 是一个 @ref{3bf9,,PyTupleObject} 或 @ref{3ca8,,PyListObject} 并直接访问 @emph{o} 的数据字段。

作为 CPython 的实现细节，如果 @emph{o} 已经是一个序列或列表，它将被直接返回。
@end deffn

@geindex PySequence_Fast_GET_SIZE (C 函数)
@anchor{c-api/sequence c PySequence_Fast_GET_SIZE}@anchor{3ca9}
@deffn {C 函数} Py_ssize_t PySequence_Fast_GET_SIZE (PyObject@w{ }*o)

在 @emph{o} 由 @ref{3ca7,,PySequence_Fast()} 返回且 @emph{o} 不为 @code{NULL} 的情况下返回 @emph{o} 的长度。 也可以通过在 @emph{o} 上调用 @ref{fe0,,PySequence_Size()} 来获取大小，但是 @ref{3ca9,,PySequence_Fast_GET_SIZE()} 速度更快，因为它可以假定 @emph{o} 为列表或元组。
@end deffn

@geindex PySequence_Fast_GET_ITEM (C 函数)
@anchor{c-api/sequence c PySequence_Fast_GET_ITEM}@anchor{3caa}
@deffn {C 函数} PyObject* PySequence_Fast_GET_ITEM (PyObject@w{ }*o, Py_ssize_t@w{ }i)
@emph{Return value: Borrowed reference.}
在 @emph{o} 由 @ref{3ca7,,PySequence_Fast()} 返回且 @emph{o} 不 @code{NULL}，并且 @emph{i} d在索引范围内的情况下返回 @emph{o} 的第 @emph{i} 号元素。
@end deffn

@geindex PySequence_Fast_ITEMS (C 函数)
@anchor{c-api/sequence c PySequence_Fast_ITEMS}@anchor{3cab}
@deffn {C 函数} PyObject** PySequence_Fast_ITEMS (PyObject@w{ }*o)

返回 PyObject 指针的底层数组。 假设 @emph{o} 由 @ref{3ca7,,PySequence_Fast()} 返回且 @emph{o} 不为 @code{NULL}。

请注意,如果列表调整大小,重新分配可能会重新定位items数组.因此,仅在序列无法更改的上下文中使用基础数组指针.
@end deffn

@geindex PySequence_ITEM (C 函数)
@anchor{c-api/sequence c PySequence_ITEM}@anchor{3cac}
@deffn {C 函数} PyObject* PySequence_ITEM (PyObject@w{ }*o, Py_ssize_t@w{ }i)
@emph{Return value: New reference.}
返回 @emph{o} 的第 @emph{i} 个元素或在失败时返回 @code{NULL}。 此形式比 @ref{fe1,,PySequence_GetItem()} 理馔，但不会检查 @emph{o} 上的 @ref{3c99,,PySequence_Check()} 是否为真值，也不会对负序号进行调整。
@end deffn

@node 映射协议,迭代器协议,序列协议,抽象对象层
@anchor{c-api/mapping doc}@anchor{3cad}@anchor{c-api/mapping mapping}@anchor{3cae}@anchor{c-api/mapping mapping-protocol}@anchor{3caf}
@subsection 映射协议


参见 @ref{3b57,,PyObject_GetItem()}、@ref{3b55,,PyObject_SetItem()} 与 @ref{3c71,,PyObject_DelItem()}。

@geindex PyMapping_Check (C 函数)
@anchor{c-api/mapping c PyMapping_Check}@anchor{3cb0}
@deffn {C 函数} int PyMapping_Check (PyObject@w{ }*o)

如果对象提供映射协议或支持切片则返回 @code{1}，否则返回 @code{0}。 请注意它将为具有 @ref{27f,,__getitem__()} 方法的 Python 类返回 @code{1}，因为在一般情况下无法确定它所支持的键类型。 此函数总是会成功执行。
@end deffn

@geindex PyMapping_Size (C 函数)
@geindex PyMapping_Length (C 函数)
@anchor{c-api/mapping c PyMapping_Size}@anchor{fe4}
@deffn {C 函数} Py_ssize_t PyMapping_Size (PyObject@w{ }*o)
@anchor{c-api/mapping c PyMapping_Length}@anchor{3cb1}
@deffnx {C 函数} Py_ssize_t PyMapping_Length (PyObject@w{ }*o)

@geindex 內置函数; len

成功时返回对象 @emph{o} 中键的数量，失败时返回 @code{-1}。 这相当于 Python 表达式 @code{len(o)}。
@end deffn

@geindex PyMapping_GetItemString (C 函数)
@anchor{c-api/mapping c PyMapping_GetItemString}@anchor{3cb2}
@deffn {C 函数} PyObject* PyMapping_GetItemString (PyObject@w{ }*o, const char@w{ }*key)
@emph{Return value: New reference.}
返回 @emph{o} 中对应于字符串 @emph{key} 的元素，或者失败时返回 @code{NULL}。 这相当于 Python 表达式 @code{o[key]}。 另请参见 also @ref{3b57,,PyObject_GetItem()}。
@end deffn

@geindex PyMapping_SetItemString (C 函数)
@anchor{c-api/mapping c PyMapping_SetItemString}@anchor{3cb3}
@deffn {C 函数} int PyMapping_SetItemString (PyObject@w{ }*o, const char@w{ }*key, PyObject@w{ }*v)

在对象 @emph{o} 中将字符串 @emph{key} 映射到值 @emph{v}。 失败时返回 @code{-1}。 这相当于 Python 语句 @code{o[key] = v}。 另请参见 @ref{3b55,,PyObject_SetItem()}。 此函数 @emph{不会} 增加对 @emph{v} 的引用。
@end deffn

@geindex PyMapping_DelItem (C 函数)
@anchor{c-api/mapping c PyMapping_DelItem}@anchor{3cb4}
@deffn {C 函数} int PyMapping_DelItem (PyObject@w{ }*o, PyObject@w{ }*key)

从对象 @emph{o} 中移除对象 @emph{key} 的映射。 失败时返回 @code{-1}。 这相当于 Python 语句 @code{del o[key]}。 这是 @ref{3c71,,PyObject_DelItem()} 的一个别名。
@end deffn

@geindex PyMapping_DelItemString (C 函数)
@anchor{c-api/mapping c PyMapping_DelItemString}@anchor{3cb5}
@deffn {C 函数} int PyMapping_DelItemString (PyObject@w{ }*o, const char@w{ }*key)

从对象 @emph{o} 中移除字符串 @emph{key} 的映射。 失败时返回 @code{-1}。 这相当于 Python 语句 @code{del o[key]}。
@end deffn

@geindex PyMapping_HasKey (C 函数)
@anchor{c-api/mapping c PyMapping_HasKey}@anchor{3cb6}
@deffn {C 函数} int PyMapping_HasKey (PyObject@w{ }*o, PyObject@w{ }*key)

如果映射对象具有键 @emph{key} 则返回 @code{1}，否则返回 @code{0}。 这相当于 Python 表达式 @code{key in o}。 此函数总是会成功执行。

请注意在调用 @ref{27f,,__getitem__()} 方法期间发生的异常将会被屏蔽。 要获取错误报告请改用 @ref{3b57,,PyObject_GetItem()}。
@end deffn

@geindex PyMapping_HasKeyString (C 函数)
@anchor{c-api/mapping c PyMapping_HasKeyString}@anchor{3cb7}
@deffn {C 函数} int PyMapping_HasKeyString (PyObject@w{ }*o, const char@w{ }*key)

如果映射对象具有键 @emph{key} 则返回 @code{1}，否则返回 @code{0}。 这相当于 Python 表达式 @code{key in o}。 此函数总是会成功执行。

请注意在调用 @ref{27f,,__getitem__()} 方法期间发生的异常将会被屏蔽。 要获取错误报告请改用 @ref{3cb2,,PyMapping_GetItemString()}。
@end deffn

@geindex PyMapping_Keys (C 函数)
@anchor{c-api/mapping c PyMapping_Keys}@anchor{426}
@deffn {C 函数} PyObject* PyMapping_Keys (PyObject@w{ }*o)
@emph{Return value: New reference.}
成功时，返回对象 @emph{o} 中的键的列表。 失败时，返回 @code{NULL}。


在 3.7 版更改: 在之前版本中，此函数返回一个列表或元组。

@end deffn

@geindex PyMapping_Values (C 函数)
@anchor{c-api/mapping c PyMapping_Values}@anchor{427}
@deffn {C 函数} PyObject* PyMapping_Values (PyObject@w{ }*o)
@emph{Return value: New reference.}
成功时，返回对象 @emph{o} 中的值的列表。 失败时，返回 @code{NULL}。


在 3.7 版更改: 在之前版本中，此函数返回一个列表或元组。

@end deffn

@geindex PyMapping_Items (C 函数)
@anchor{c-api/mapping c PyMapping_Items}@anchor{428}
@deffn {C 函数} PyObject* PyMapping_Items (PyObject@w{ }*o)
@emph{Return value: New reference.}
成功时，返回对象 @emph{o} 中条目的列表，其中每个条目是一个包含键值对的元组。 失败时，返回 @code{NULL}。


在 3.7 版更改: 在之前版本中，此函数返回一个列表或元组。

@end deffn

@node 迭代器协议,缓冲协议,映射协议,抽象对象层
@anchor{c-api/iter doc}@anchor{3cb8}@anchor{c-api/iter iterator}@anchor{3cb9}@anchor{c-api/iter iterator-protocol}@anchor{3cba}
@subsection 迭代器协议


迭代器有两个函数。

@geindex PyIter_Check (C 函数)
@anchor{c-api/iter c PyIter_Check}@anchor{fa3}
@deffn {C 函数} int PyIter_Check (PyObject@w{ }*o)

返回 true ， 如果对象 @emph{o} 支持迭代器协议的话。
@end deffn

@geindex PyIter_Next (C 函数)
@anchor{c-api/iter c PyIter_Next}@anchor{3cbb}
@deffn {C 函数} PyObject* PyIter_Next (PyObject@w{ }*o)
@emph{Return value: New reference.}
返回迭代 @emph{o} 的下一个值。 对象必须是一个迭代器（这应由调用者来判断）。 如果没有余下的值，则返回 @code{NULL} 并且不设置异常。 如果在获取条目时发生了错误，则返回 @code{NULL} 并且传递异常。
@end deffn

要为迭代器编写一个一个循环，C代码应该看起来像这样

@example
PyObject *iterator = PyObject_GetIter(obj);
PyObject *item;

if (iterator == NULL) @{
    /* propagate error */
@}

while ((item = PyIter_Next(iterator))) @{
    /* do something with item */
    ...
    /* release reference when done */
    Py_DECREF(item);
@}

Py_DECREF(iterator);

if (PyErr_Occurred()) @{
    /* propagate error */
@}
else @{
    /* continue doing useful work */
@}
@end example

@geindex buffer protocol
@geindex buffer interface; (see buffer protocol)
@geindex buffer object; (see buffer protocol)

@node 缓冲协议,旧缓冲协议,迭代器协议,抽象对象层
@anchor{c-api/buffer doc}@anchor{3cbc}@anchor{c-api/buffer buffer-protocol}@anchor{3cbd}@anchor{c-api/buffer bufferobjects}@anchor{15d6}
@subsection 缓冲协议


在 Python 中可使用一些对象来包装对底层内存数组或称 @emph{缓冲} 的访问。此类对象包括内置的 @ref{32a,,bytes} 和 @ref{32b,,bytearray} 以及一些如 @ref{44b,,array.array} 这样的扩展类型。第三方库也可能会为了特殊的目的而定义它们自己的类型，例如用于图像处理和数值分析等。

虽然这些类型中的每一种都有自己的语义，但它们具有由可能较大的内存缓冲区支持的共同特征。 在某些情况下，希望直接访问该缓冲区而无需中间复制。

Python 以 @ref{15d6,,缓冲协议} 的形式在 C 层级上提供这样的功能。 此协议包括两个方面:

@geindex PyBufferProcs


@itemize -

@item 
在生产者这一方面，该类型的协议可以导出一个“缓冲区接口”，允许公开它的底层缓冲区信息。该接口的描述信息在 @ref{3cbe,,Buffer Object Structures} 一节中；

@item 
在消费者一侧，有几种方法可用于获得指向对象的原始底层数据的指针（例如一个方法的形参）。
@end itemize

一些简单的对象例如 @ref{32a,,bytes} 和 @ref{32b,,bytearray} 会以面向字节的形式公开它们的底层缓冲区。 也可能会用其他形式；例如 @ref{44b,,array.array} 所公开的元素可以是多字节值。

缓冲区接口的消费者的一个例子是文件对象的 @ref{584,,write()} 方法：任何可以输出为一系列字节流的对象可以被写入文件。然而 @code{write()} 方法只需要对于传入对象的只读权限，其他的方法，如 @ref{1f8b,,readinto()} 需要参数内容的写入权限。缓冲区接口使得对象可以选择性地允许或拒绝读写或只读缓冲区的导出。

对于缓冲接口的消费者而言，有两种方式来获取一个目的对象的缓冲：


@itemize *

@item 
使用正确的参数来调用 @ref{d1e,,PyObject_GetBuffer()} 函数；

@item 
调用 @ref{26a,,PyArg_ParseTuple()} (或其同级对象之一) 并传入 @code{y*}, @code{w*} or @code{s*} @ref{2d0,,格式代码} 中的一个。
@end itemize

在这两种情况下，当不再需要缓冲区时必须调用 @ref{d4d,,PyBuffer_Release()} 。如果此操作失败，可能会导致各种问题，例如资源泄漏。

@menu
* 缓冲区结构:: 
* Buffer request types:: 
* 复杂数组:: 
* Buffer-related functions:: 

@end menu

@node 缓冲区结构,Buffer request types,,缓冲协议
@anchor{c-api/buffer buffer-structure}@anchor{3cbf}@anchor{c-api/buffer id1}@anchor{3cc0}
@subsubsection 缓冲区结构


缓冲区结构(或者简单地称为“buffers”)对于将二进制数据从另一个对象公开给 Python 程序员非常有用。它们还可以用作零拷贝切片机制。使用它们引用内存块的能力，可以很容易地将任何数据公开给 Python 程序员。内存可以是 C 扩展中的一个大的常量数组，也可以是在传递到操作系统库之前用于操作的原始内存块，或者可以用来传递本机内存格式的结构化数据。

与 Python 解释器公开的大多部数据类型不同，缓冲区不是 @ref{4b5,,PyObject} 指针而是简单的 C 结构。 这使得它们可以非常简单地创建和复制。 当需要为缓冲区加上泛型包装器时，可以创建一个 @ref{3cc1,,内存视图} 对象。

有关如何编写并导出对象的简短说明，请参阅 @ref{3cbe,,缓冲区对象结构}。 要获取缓冲区对象，请参阅 @ref{d1e,,PyObject_GetBuffer()}。

@geindex Py_buffer (C 类型)
@anchor{c-api/buffer c Py_buffer}@anchor{b14}
@deffn {C 类型} Py_buffer

@geindex Py_buffer.buf (C 成员)
@anchor{c-api/buffer c Py_buffer buf}@anchor{3cc2}
@deffn {C 成员} void *buf

指向由缓冲区字段描述的逻辑结构开始的指针。 这可以是导出程序底层物理内存块中的任何位置。 例如，使用负的 @ref{3cc3,,strides} 值可能指向内存块的末尾。

对于 @ref{164e,,contiguous} ，‘邻接’数组，值指向内存块的开头。
@end deffn

@geindex Py_buffer.obj (C 成员)
@anchor{c-api/buffer c Py_buffer obj}@anchor{3cc4}
@deffn {C 成员} void *obj

对导出对象的新引用。 该引用归使用者所有，并由 @ref{d4d,,PyBuffer_Release()} 自动递减并设置为 @code{NULL}。 该字段等于任何标准 C-API 函数的返回值。

作为一种特殊情况，对于由 @ref{3cc5,,PyMemoryView_FromBuffer()} 或 @ref{3cc6,,PyBuffer_FillInfo()} 包装的 @emph{temporary} 缓冲区，此字段为 @code{NULL}。 通常，导出对象不得使用此方案。
@end deffn

@geindex Py_buffer.len (C 成员)
@anchor{c-api/buffer c Py_buffer len}@anchor{3cc7}
@deffn {C 成员} Py_ssize_t len

@code{product(shape) * itemsize}。对于连续数组，这是基础内存块的长度。对于非连续数组，如果逻辑结构复制到连续表示形式，则该长度将具有该长度。

仅当缓冲区是通过保证连续性的请求获取时，才访问 @code{((char *)buf)[0] up to ((char *)buf)[len-1]} 时才有效。在大多数情况下，此类请求将为 @ref{3cc8,,PyBUF_SIMPLE} 或 @ref{3cc9,,PyBUF_WRITABLE}。
@end deffn

@geindex Py_buffer.readonly (C 成员)
@anchor{c-api/buffer c Py_buffer readonly}@anchor{3cca}
@deffn {C 成员} int readonly

缓冲区是否为只读的指示器。此字段由 @ref{3cc9,,PyBUF_WRITABLE} 标志控制。
@end deffn

@geindex Py_buffer.itemsize (C 成员)
@anchor{c-api/buffer c Py_buffer itemsize}@anchor{3ccb}
@deffn {C 成员} Py_ssize_t itemsize

单个元素的项大小（以字节为单位）。与 @ref{17a5,,struct.calcsize()} 调用非 @code{NULL} @ref{3ccc,,format} 的值相同。

重要例外：如果使用者请求的缓冲区没有 @ref{3ccd,,PyBUF_FORMAT} 标志，@ref{3ccc,,format} 将设置为 @code{NULL}，但 @ref{3ccb,,itemsize} 仍具有原始格式的值。

如果 @ref{3cce,,shape} 存在，则相等的 @code{product(shape) * itemsize == len} 仍然存在，使用者可以使用 @ref{3ccb,,itemsize} 来导航缓冲区。

如果 @ref{3cce,,shape} 是 @code{NULL}，因为结果为 @ref{3cc8,,PyBUF_SIMPLE} 或 @ref{3cc9,,PyBUF_WRITABLE} 请求，则使用者必须忽略 @ref{3ccb,,itemsize}，并假设 @code{itemsize == 1}。
@end deffn

@geindex Py_buffer.format (C 成员)
@anchor{c-api/buffer c Py_buffer format}@anchor{3ccc}
@deffn {C 成员} const char *format

在 @ref{f8,,struct} 模块样式语法中 @emph{NUL} 字符串，描述单个项的内容。如果这是 @code{NULL}，则假定为`@w{`}"B"`@w{`} (无符号字节) 。

此字段由 @ref{3ccd,,PyBUF_FORMAT} 标志控制。
@end deffn

@geindex Py_buffer.ndim (C 成员)
@anchor{c-api/buffer c Py_buffer ndim}@anchor{3ccf}
@deffn {C 成员} int ndim

The number of dimensions the memory represents as an n-dimensional array.
If it is @code{0}, @ref{3cc2,,buf} points to a single item representing
a scalar. In this case, @ref{3cce,,shape}, @ref{3cc3,,strides}
and @ref{3cd0,,suboffsets} MUST be @code{NULL}.

The macro @code{PyBUF_MAX_NDIM} limits the maximum number of dimensions
to 64. Exporters MUST respect this limit, consumers of multi-dimensional
buffers SHOULD be able to handle up to @code{PyBUF_MAX_NDIM} dimensions.
@end deffn

@geindex Py_buffer.shape (C 成员)
@anchor{c-api/buffer c Py_buffer shape}@anchor{3cce}
@deffn {C 成员} Py_ssize_t *shape

An array of @code{Py_ssize_t} of length @ref{3ccf,,ndim}
indicating the shape of the memory as an n-dimensional array. Note that
@code{shape[0] * ... * shape[ndim-1] * itemsize} MUST be equal to
@ref{3cc7,,len}.

Shape values are restricted to @code{shape[n] >= 0}. The case
@code{shape[n] == 0} requires special attention. See @ref{3cd1,,complex arrays}
for further information.

The shape array is read-only for the consumer.
@end deffn

@geindex Py_buffer.strides (C 成员)
@anchor{c-api/buffer c Py_buffer strides}@anchor{3cc3}
@deffn {C 成员} Py_ssize_t *strides

An array of @code{Py_ssize_t} of length @ref{3ccf,,ndim}
giving the number of bytes to skip to get to a new element in each
dimension.

Stride values can be any integer. For regular arrays, strides are
usually positive, but a consumer MUST be able to handle the case
@code{strides[n] <= 0}. See @ref{3cd1,,complex arrays} for further information.

The strides array is read-only for the consumer.
@end deffn

@geindex Py_buffer.suboffsets (C 成员)
@anchor{c-api/buffer c Py_buffer suboffsets}@anchor{3cd0}
@deffn {C 成员} Py_ssize_t *suboffsets

An array of @code{Py_ssize_t} of length @ref{3ccf,,ndim}.
If @code{suboffsets[n] >= 0}, the values stored along the nth dimension are
pointers and the suboffset value dictates how many bytes to add to each
pointer after de-referencing. A suboffset value that is negative
indicates that no de-referencing should occur (striding in a contiguous
memory block).

If all suboffsets are negative (i.e. no de-referencing is needed), then
this field must be @code{NULL} (the default value).

This type of array representation is used by the Python Imaging Library
(PIL). See @ref{3cd1,,complex arrays} for further information how to access elements
of such an array.

The suboffsets array is read-only for the consumer.
@end deffn

@geindex Py_buffer.internal (C 成员)
@anchor{c-api/buffer c Py_buffer internal}@anchor{3cd2}
@deffn {C 成员} void *internal

This is for use internally by the exporting object. For example, this
might be re-cast as an integer by the exporter and used to store flags
about whether or not the shape, strides, and suboffsets arrays must be
freed when the buffer is released. The consumer MUST NOT alter this
value.
@end deffn
@end deffn

@node Buffer request types,复杂数组,缓冲区结构,缓冲协议
@anchor{c-api/buffer buffer-request-types}@anchor{3cd3}@anchor{c-api/buffer id2}@anchor{3cd4}
@subsubsection Buffer request types


Buffers are usually obtained by sending a buffer request to an exporting
object via @ref{d1e,,PyObject_GetBuffer()}. Since the complexity of the logical
structure of the memory can vary drastically, the consumer uses the @emph{flags}
argument to specify the exact buffer type it can handle.

All @ref{b14,,Py_buffer} fields are unambiguously defined by the request
type.

@menu
* request-independent fields:: 
* readonly@comma{} format: readonly format. 
* shape@comma{} strides@comma{} suboffsets: shape strides suboffsets. 
* 连续性的请求:: 
* 复合请求:: 

@end menu

@node request-independent fields,readonly format,,Buffer request types
@anchor{c-api/buffer request-independent-fields}@anchor{3cd5}
@subsubsection request-independent fields


The following fields are not influenced by @emph{flags} and must always be filled in
with the correct values: @ref{3cc4,,obj}, @ref{3cc2,,buf},
@ref{3cc7,,len}, @ref{3ccb,,itemsize}, @ref{3ccf,,ndim}.

@node readonly format,shape strides suboffsets,request-independent fields,Buffer request types
@anchor{c-api/buffer readonly-format}@anchor{3cd6}
@subsubsection readonly, format


@quotation

@geindex PyBUF_WRITABLE (C 宏)
@anchor{c-api/buffer c PyBUF_WRITABLE}@anchor{3cc9}
@deffn {C 宏} PyBUF_WRITABLE

Controls the @ref{3cca,,readonly} field. If set, the exporter
MUST provide a writable buffer or else report failure. Otherwise, the
exporter MAY provide either a read-only or writable buffer, but the choice
MUST be consistent for all consumers.
@end deffn

@geindex PyBUF_FORMAT (C 宏)
@anchor{c-api/buffer c PyBUF_FORMAT}@anchor{3ccd}
@deffn {C 宏} PyBUF_FORMAT

Controls the @ref{3ccc,,format} field. If set, this field MUST
be filled in correctly. Otherwise, this field MUST be @code{NULL}.
@end deffn
@end quotation

@ref{3cc9,,PyBUF_WRITABLE} can be |'d to any of the flags in the next section.
Since @ref{3cc8,,PyBUF_SIMPLE} is defined as 0, @ref{3cc9,,PyBUF_WRITABLE}
can be used as a stand-alone flag to request a simple writable buffer.

@ref{3ccd,,PyBUF_FORMAT} can be |'d to any of the flags except @ref{3cc8,,PyBUF_SIMPLE}.
The latter already implies format @code{B} (unsigned bytes).

@node shape strides suboffsets,连续性的请求,readonly format,Buffer request types
@anchor{c-api/buffer shape-strides-suboffsets}@anchor{3cd7}
@subsubsection shape, strides, suboffsets


The flags that control the logical structure of the memory are listed
in decreasing order of complexity. Note that each flag contains all bits
of the flags below it.


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxxx} 
@headitem

请求

@tab

形状

@tab

步幅

@tab

子偏移量

@item

@geindex PyBUF_INDIRECT (C 宏)
@anchor{c-api/buffer c PyBUF_INDIRECT}@anchor{3cd8}
@deffn {C 宏} PyBUF_INDIRECT
@end deffn

@tab

是

@tab

是

@tab

如果需要的话

@item

@geindex PyBUF_STRIDES (C 宏)
@anchor{c-api/buffer c PyBUF_STRIDES}@anchor{3cd9}
@deffn {C 宏} PyBUF_STRIDES
@end deffn

@tab

是

@tab

是

@tab

NULL

@item

@geindex PyBUF_ND (C 宏)
@anchor{c-api/buffer c PyBUF_ND}@anchor{3cda}
@deffn {C 宏} PyBUF_ND
@end deffn

@tab

是

@tab

NULL

@tab

NULL

@item

@geindex PyBUF_SIMPLE (C 宏)
@anchor{c-api/buffer c PyBUF_SIMPLE}@anchor{3cc8}
@deffn {C 宏} PyBUF_SIMPLE
@end deffn

@tab

NULL

@tab

NULL

@tab

NULL

@end multitable


@geindex contiguous
@geindex C-contiguous
@geindex Fortran contiguous

@node 连续性的请求,复合请求,shape strides suboffsets,Buffer request types
@anchor{c-api/buffer contiguity-requests}@anchor{3cdb}
@subsubsection 连续性的请求


C or Fortran @ref{164e,,contiguity} can be explicitly requested,
with and without stride information. Without stride information, the buffer
must be C-contiguous.


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxxx} {xxxxxxxxxx} 
@headitem

请求

@tab

形状

@tab

步幅

@tab

子偏移量

@tab

邻接

@item

@geindex PyBUF_C_CONTIGUOUS (C 宏)
@anchor{c-api/buffer c PyBUF_C_CONTIGUOUS}@anchor{3cdc}
@deffn {C 宏} PyBUF_C_CONTIGUOUS
@end deffn

@tab

是

@tab

是

@tab

NULL

@tab

C

@item

@geindex PyBUF_F_CONTIGUOUS (C 宏)
@anchor{c-api/buffer c PyBUF_F_CONTIGUOUS}@anchor{3cdd}
@deffn {C 宏} PyBUF_F_CONTIGUOUS
@end deffn

@tab

是

@tab

是

@tab

NULL

@tab

F

@item

@geindex PyBUF_ANY_CONTIGUOUS (C 宏)
@anchor{c-api/buffer c PyBUF_ANY_CONTIGUOUS}@anchor{3cde}
@deffn {C 宏} PyBUF_ANY_CONTIGUOUS
@end deffn

@tab

是

@tab

是

@tab

NULL

@tab

C 或 F

@item

@geindex PyBUF_ND (C 宏)

@deffn {C 宏} PyBUF_ND
@end deffn

@tab

是

@tab

NULL

@tab

NULL

@tab

C

@end multitable


@node 复合请求,,连续性的请求,Buffer request types
@anchor{c-api/buffer compound-requests}@anchor{3cdf}
@subsubsection 复合请求


所有可能的请求都由上一节中某些标志的组合完全定义。为方便起见，缓冲区协议提供常用的组合作为单个标志。

In the following table @emph{U} stands for undefined contiguity. The consumer would
have to call @ref{3ce0,,PyBuffer_IsContiguous()} to determine contiguity.


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} {xxxxxxxxxxx} {xxxxxxxxxxxxxx} {xxxxxxxxxx} {xxxxxxxxxxxx} {xxxxxxxxxx} 
@headitem

请求

@tab

形状

@tab

步幅

@tab

子偏移量

@tab

邻接

@tab

只读

@tab

format

@item

@geindex PyBUF_FULL (C 宏)
@anchor{c-api/buffer c PyBUF_FULL}@anchor{3ce1}
@deffn {C 宏} PyBUF_FULL
@end deffn

@tab

是

@tab

是

@tab

如果需要的话

@tab

U

@tab

0

@tab

是

@item

@geindex PyBUF_FULL_RO (C 宏)
@anchor{c-api/buffer c PyBUF_FULL_RO}@anchor{3ce2}
@deffn {C 宏} PyBUF_FULL_RO
@end deffn

@tab

是

@tab

是

@tab

如果需要的话

@tab

U

@tab

1 或 0

@tab

是

@item

@geindex PyBUF_RECORDS (C 宏)
@anchor{c-api/buffer c PyBUF_RECORDS}@anchor{3ce3}
@deffn {C 宏} PyBUF_RECORDS
@end deffn

@tab

是

@tab

是

@tab

NULL

@tab

U

@tab

0

@tab

是

@item

@geindex PyBUF_RECORDS_RO (C 宏)
@anchor{c-api/buffer c PyBUF_RECORDS_RO}@anchor{3ce4}
@deffn {C 宏} PyBUF_RECORDS_RO
@end deffn

@tab

是

@tab

是

@tab

NULL

@tab

U

@tab

1 或 0

@tab

是

@item

@geindex PyBUF_STRIDED (C 宏)
@anchor{c-api/buffer c PyBUF_STRIDED}@anchor{3ce5}
@deffn {C 宏} PyBUF_STRIDED
@end deffn

@tab

是

@tab

是

@tab

NULL

@tab

U

@tab

0

@tab

NULL

@item

@geindex PyBUF_STRIDED_RO (C 宏)
@anchor{c-api/buffer c PyBUF_STRIDED_RO}@anchor{3ce6}
@deffn {C 宏} PyBUF_STRIDED_RO
@end deffn

@tab

是

@tab

是

@tab

NULL

@tab

U

@tab

1 或 0

@tab

NULL

@item

@geindex PyBUF_CONTIG (C 宏)
@anchor{c-api/buffer c PyBUF_CONTIG}@anchor{3ce7}
@deffn {C 宏} PyBUF_CONTIG
@end deffn

@tab

是

@tab

NULL

@tab

NULL

@tab

C

@tab

0

@tab

NULL

@item

@geindex PyBUF_CONTIG_RO (C 宏)
@anchor{c-api/buffer c PyBUF_CONTIG_RO}@anchor{3ce8}
@deffn {C 宏} PyBUF_CONTIG_RO
@end deffn

@tab

是

@tab

NULL

@tab

NULL

@tab

C

@tab

1 或 0

@tab

NULL

@end multitable


@node 复杂数组,Buffer-related functions,Buffer request types,缓冲协议
@anchor{c-api/buffer complex-arrays}@anchor{3cd1}
@subsubsection 复杂数组


@menu
* NumPy-style; shape and strides: NumPy-style shape and strides. 
* PIL-style; shape@comma{} strides and suboffsets: PIL-style shape strides and suboffsets. 

@end menu

@node NumPy-style shape and strides,PIL-style shape strides and suboffsets,,复杂数组
@anchor{c-api/buffer numpy-style-shape-and-strides}@anchor{3ce9}
@subsubsection NumPy-style: shape and strides


The logical structure of NumPy-style arrays is defined by @ref{3ccb,,itemsize},
@ref{3ccf,,ndim}, @ref{3cce,,shape} and @ref{3cc3,,strides}.

If @code{ndim == 0}, the memory location pointed to by @ref{3cc2,,buf} is
interpreted as a scalar of size @ref{3ccb,,itemsize}. In that case,
both @ref{3cce,,shape} and @ref{3cc3,,strides} are @code{NULL}.

If @ref{3cc3,,strides} is @code{NULL}, the array is interpreted as
a standard n-dimensional C-array. Otherwise, the consumer must access an
n-dimensional array as follows:

@example
ptr = (char *)buf + indices[0] * strides[0] + ... + indices[n-1] * strides[n-1];
item = *((typeof(item) *)ptr);
@end example

As noted above, @ref{3cc2,,buf} can point to any location within
the actual memory block. An exporter can check the validity of a buffer with
this function:

@example
def verify_structure(memlen, itemsize, ndim, shape, strides, offset):
    """Verify that the parameters represent a valid array within
       the bounds of the allocated memory:
           char *mem: start of the physical memory block
           memlen: length of the physical memory block
           offset: (char *)buf - mem
    """
    if offset % itemsize:
        return False
    if offset < 0 or offset+itemsize > memlen:
        return False
    if any(v % itemsize for v in strides):
        return False

    if ndim <= 0:
        return ndim == 0 and not shape and not strides
    if 0 in shape:
        return True

    imin = sum(strides[j]*(shape[j]-1) for j in range(ndim)
               if strides[j] <= 0)
    imax = sum(strides[j]*(shape[j]-1) for j in range(ndim)
               if strides[j] > 0)

    return 0 <= offset+imin and offset+imax+itemsize <= memlen
@end example

@node PIL-style shape strides and suboffsets,,NumPy-style shape and strides,复杂数组
@anchor{c-api/buffer pil-style-shape-strides-and-suboffsets}@anchor{3cea}
@subsubsection PIL-style: shape, strides and suboffsets


In addition to the regular items, PIL-style arrays can contain pointers
that must be followed in order to get to the next element in a dimension.
For example, the regular three-dimensional C-array @code{char v[2][2][3]} can
also be viewed as an array of 2 pointers to 2 two-dimensional arrays:
@code{char (*v[2])[2][3]}. In suboffsets representation, those two pointers
can be embedded at the start of @ref{3cc2,,buf}, pointing
to two @code{char x[2][3]} arrays that can be located anywhere in memory.

Here is a function that returns a pointer to the element in an N-D array
pointed to by an N-dimensional index when there are both non-@code{NULL} strides
and suboffsets:

@example
void *get_item_pointer(int ndim, void *buf, Py_ssize_t *strides,
                       Py_ssize_t *suboffsets, Py_ssize_t *indices) @{
    char *pointer = (char*)buf;
    int i;
    for (i = 0; i < ndim; i++) @{
        pointer += strides[i] * indices[i];
        if (suboffsets[i] >=0 ) @{
            pointer = *((char**)pointer) + suboffsets[i];
        @}
    @}
    return (void*)pointer;
@}
@end example

@node Buffer-related functions,,复杂数组,缓冲协议
@anchor{c-api/buffer buffer-related-functions}@anchor{3ceb}
@subsubsection Buffer-related functions


@geindex PyObject_CheckBuffer (C 函数)
@anchor{c-api/buffer c PyObject_CheckBuffer}@anchor{3cec}
@deffn {C 函数} int PyObject_CheckBuffer (PyObject@w{ }*obj)

Return @code{1} if @emph{obj} supports the buffer interface otherwise @code{0}.  When @code{1} is
returned, it doesn't guarantee that @ref{d1e,,PyObject_GetBuffer()} will
succeed.  This function always succeeds.
@end deffn

@geindex PyObject_GetBuffer (C 函数)
@anchor{c-api/buffer c PyObject_GetBuffer}@anchor{d1e}
@deffn {C 函数} int PyObject_GetBuffer (PyObject@w{ }*exporter, Py_buffer@w{ }*view, int@w{ }flags)

Send a request to @emph{exporter} to fill in @emph{view} as specified by  @emph{flags}.
If the exporter cannot provide a buffer of the exact type, it MUST raise
@code{PyExc_BufferError}, set @code{view->obj} to @code{NULL} and
return @code{-1}.

On success, fill in @emph{view}, set @code{view->obj} to a new reference
to @emph{exporter} and return 0. In the case of chained buffer providers
that redirect requests to a single object, @code{view->obj} MAY
refer to this object instead of @emph{exporter} (See @ref{3cbe,,Buffer Object Structures}).

Successful calls to @ref{d1e,,PyObject_GetBuffer()} must be paired with calls
to @ref{d4d,,PyBuffer_Release()}, similar to @code{malloc()} and @code{free()}.
Thus, after the consumer is done with the buffer, @ref{d4d,,PyBuffer_Release()}
must be called exactly once.
@end deffn

@geindex PyBuffer_Release (C 函数)
@anchor{c-api/buffer c PyBuffer_Release}@anchor{d4d}
@deffn {C 函数} void PyBuffer_Release (Py_buffer@w{ }*view)

Release the buffer @emph{view} and decrement the reference count for
@code{view->obj}. This function MUST be called when the buffer
is no longer being used, otherwise reference leaks may occur.

It is an error to call this function on a buffer that was not obtained via
@ref{d1e,,PyObject_GetBuffer()}.
@end deffn

@geindex PyBuffer_SizeFromFormat (C 函数)
@anchor{c-api/buffer c PyBuffer_SizeFromFormat}@anchor{3ced}
@deffn {C 函数} Py_ssize_t PyBuffer_SizeFromFormat (const char@w{ }*)

Return the implied @ref{3ccb,,itemsize} from @ref{3ccc,,format}.
This function is not yet implemented.
@end deffn

@geindex PyBuffer_IsContiguous (C 函数)
@anchor{c-api/buffer c PyBuffer_IsContiguous}@anchor{3ce0}
@deffn {C 函数} int PyBuffer_IsContiguous (Py_buffer@w{ }*view, char@w{ }order)

Return @code{1} if the memory defined by the @emph{view} is C-style (@emph{order} is
@code{'C'}) or Fortran-style (@emph{order} is @code{'F'}) @ref{164e,,contiguous} or either one
(@emph{order} is @code{'A'}).  Return @code{0} otherwise.  This function always succeeds.
@end deffn

@geindex PyBuffer_GetPointer (C 函数)
@anchor{c-api/buffer c PyBuffer_GetPointer}@anchor{3cee}
@deffn {C 函数} void* PyBuffer_GetPointer (Py_buffer@w{ }*view, Py_ssize_t@w{ }*indices)

Get the memory area pointed to by the @emph{indices} inside the given @emph{view}.
@emph{indices} must point to an array of @code{view->ndim} indices.
@end deffn

@geindex PyBuffer_FromContiguous (C 函数)
@anchor{c-api/buffer c PyBuffer_FromContiguous}@anchor{3cef}
@deffn {C 函数} int PyBuffer_FromContiguous (Py_buffer@w{ }*view, void@w{ }*buf, Py_ssize_t@w{ }len, char@w{ }fort)

Copy contiguous @emph{len} bytes from @emph{buf} to @emph{view}.
@emph{fort} can be @code{'C'} or @code{'F'} (for C-style or Fortran-style ordering).
@code{0} is returned on success, @code{-1} on error.
@end deffn

@geindex PyBuffer_ToContiguous (C 函数)
@anchor{c-api/buffer c PyBuffer_ToContiguous}@anchor{3cf0}
@deffn {C 函数} int PyBuffer_ToContiguous (void@w{ }*buf, Py_buffer@w{ }*src, Py_ssize_t@w{ }len, char@w{ }order)

Copy @emph{len} bytes from @emph{src} to its contiguous representation in @emph{buf}.
@emph{order} can be @code{'C'} or @code{'F'} or @code{'A'} (for C-style or Fortran-style
ordering or either one). @code{0} is returned on success, @code{-1} on error.

This function fails if @emph{len} != @emph{src->len}.
@end deffn

@geindex PyBuffer_FillContiguousStrides (C 函数)
@anchor{c-api/buffer c PyBuffer_FillContiguousStrides}@anchor{3cf1}
@deffn {C 函数} void PyBuffer_FillContiguousStrides (int@w{ }ndims, Py_ssize_t@w{ }*shape, Py_ssize_t@w{ }*strides, int@w{ }itemsize, char@w{ }order)

Fill the @emph{strides} array with byte-strides of a @ref{164e,,contiguous} (C-style if
@emph{order} is @code{'C'} or Fortran-style if @emph{order} is @code{'F'}) array of the
given shape with the given number of bytes per element.
@end deffn

@geindex PyBuffer_FillInfo (C 函数)
@anchor{c-api/buffer c PyBuffer_FillInfo}@anchor{3cc6}
@deffn {C 函数} int PyBuffer_FillInfo (Py_buffer@w{ }*view, PyObject@w{ }*exporter, void@w{ }*buf, Py_ssize_t@w{ }len, int@w{ }readonly, int@w{ }flags)

Handle buffer requests for an exporter that wants to expose @emph{buf} of size @emph{len}
with writability set according to @emph{readonly}. @emph{buf} is interpreted as a sequence
of unsigned bytes.

The @emph{flags} argument indicates the request type. This function always fills in
@emph{view} as specified by flags, unless @emph{buf} has been designated as read-only
and @ref{3cc9,,PyBUF_WRITABLE} is set in @emph{flags}.

On success, set @code{view->obj} to a new reference to @emph{exporter} and
return 0. Otherwise, raise @code{PyExc_BufferError}, set
@code{view->obj} to @code{NULL} and return @code{-1};

如果此函数用作 @ref{3cbe,,getbufferproc} 的一部分，则 @emph{exporter} 必须设置为导出对象，并且必须在未修改的情况下传递 @emph{flags}。否则，@emph{exporter} 必须是 @code{NULL}。
@end deffn

@node 旧缓冲协议,,缓冲协议,抽象对象层
@anchor{c-api/objbuffer doc}@anchor{3cf2}@anchor{c-api/objbuffer old-buffer-protocol}@anchor{3cf3}
@subsection 旧缓冲协议



3.0 版后已移除.


这些函数是 Python 2 中“旧缓冲协议”API 的组成部分。 在 Python 3 中，此协议已不复存在，但这些函数仍然被公开以便移植 2.x 的代码。 它们被用作 @ref{15d6,,新缓冲协议} 的兼容性包装器，但它们并不会在缓冲被导出时向你提供对所获资源的生命周期控制。

因此，推荐你调用 @ref{d1e,,PyObject_GetBuffer()} (或者配合 @ref{26a,,PyArg_ParseTuple()} 函数族使用 @code{y*} 或 @code{w*} @ref{2d0,,格式码}) 来获取一个对象的缓冲视图，并在缓冲视图可被释放时调用 @ref{d4d,,PyBuffer_Release()}。

@geindex PyObject_AsCharBuffer (C 函数)
@anchor{c-api/objbuffer c PyObject_AsCharBuffer}@anchor{3cf4}
@deffn {C 函数} int PyObject_AsCharBuffer (PyObject@w{ }*obj, const char@w{ }**buffer, Py_ssize_t@w{ }*buffer_len)

返回一个指向可用作基于字符的输入的只读内存地址的指针。 @emph{obj} 参数必须支持单段字符缓冲接口。 成功时返回 @code{0}，将 @emph{buffer} 设为内存地址并将 @emph{buffer_len} 设为缓冲区长度。 出错时返回 @code{-1} 并设置一个 @ref{192,,TypeError}。
@end deffn

@geindex PyObject_AsReadBuffer (C 函数)
@anchor{c-api/objbuffer c PyObject_AsReadBuffer}@anchor{3cf5}
@deffn {C 函数} int PyObject_AsReadBuffer (PyObject@w{ }*obj, const void@w{ }**buffer, Py_ssize_t@w{ }*buffer_len)

返回一个指向包含任意数据的只读内存地址的指针。 @emph{obj} 参数必须支持单段可读缓冲接口。 成功时返回 @code{0}，将 @emph{buffer} 设为内存地址并将 @emph{buffer_len} 设为缓冲区长度。 出错时返回 @code{-1} 并设置一个 @ref{192,,TypeError}。
@end deffn

@geindex PyObject_CheckReadBuffer (C 函数)
@anchor{c-api/objbuffer c PyObject_CheckReadBuffer}@anchor{3cf6}
@deffn {C 函数} int PyObject_CheckReadBuffer (PyObject@w{ }*o)

如果 @emph{o} 支持单段可读缓冲接口则返回 @code{1}。 否则返回 @code{0}。 此函数总是会成功执行。

请注意此函数会尝试获取并释放一个缓冲区，并且在调用对应函数期间发生的异常会被屏蔽。 要获取错误报告则应改用 @ref{d1e,,PyObject_GetBuffer()}。
@end deffn

@geindex PyObject_AsWriteBuffer (C 函数)
@anchor{c-api/objbuffer c PyObject_AsWriteBuffer}@anchor{3cf7}
@deffn {C 函数} int PyObject_AsWriteBuffer (PyObject@w{ }*obj, void@w{ }**buffer, Py_ssize_t@w{ }*buffer_len)

返回一个指向可写内存地址的指针。 @emph{obj} 必须支持单段字符缓冲接口。 成功时返回 @code{0}，将 @emph{buffer} 设为内存地址并将 @emph{buffer_len} 设为缓冲区长度。 出错时返回 @code{-1} 并设置一个 @ref{192,,TypeError}。
@end deffn

@node 具体的对象层,Initialization Finalization and Threads,抽象对象层,Python/C API 参考手册
@anchor{c-api/concrete doc}@anchor{3cf8}@anchor{c-api/concrete concrete}@anchor{3cf9}@anchor{c-api/concrete concrete-objects-layer}@anchor{3cfa}
@section 具体的对象层


本章中的函数特定于某些 Python 对象类型。 将错误类型的对象传递给它们并不是一个好主意；如果您从 Python 程序接收到一个对象，但不确定它是否具有正确的类型，则必须首先执行类型检查；例如，要检查对象是否为字典，请使用 @ref{3cfb,,PyDict_Check()}。 本章的结构类似于 Python 对象类型的“家族树”。

@cartouche
@quotation 警告 
虽然本章所描述的函数会仔细检查传入对象的类型，但是其中许多函数不会检查传入的对象是否为 @code{NULL}。 允许传入 @code{NULL} 可能导致内存访问冲突和解释器的立即终止。
@end quotation
@end cartouche

@menu
* 基本对象:: 
* 数值对象:: 
* 序列对象:: 
* 容器对象:: 
* 函数对象: 函数对象<2>. 
* 其他对象: 其他对象<2>. 

@end menu

@node 基本对象,数值对象,,具体的对象层
@anchor{c-api/concrete fundamental}@anchor{3cfc}@anchor{c-api/concrete fundamental-objects}@anchor{3cfd}
@subsection 基本对象


本节描述Python类型对象和单一实例对象 象None。

@menu
* 类型对象: 类型对象<2>. 
* None 对象:: 

@end menu

@node 类型对象<2>,None 对象,,基本对象
@anchor{c-api/type doc}@anchor{3cfe}@anchor{c-api/type type-objects}@anchor{3cff}@anchor{c-api/type typeobjects}@anchor{3d00}
@subsubsection 类型对象


@geindex 对象; type

@geindex PyTypeObject (C 类型)
@anchor{c-api/type c PyTypeObject}@anchor{2d6}
@deffn {C 类型} PyTypeObject

对象的 C 结构用于描述 built-in 类型。
@end deffn

@geindex PyType_Type (C 变量)
@anchor{c-api/type c PyType_Type}@anchor{3d01}
@deffn {C 变量} PyObject* PyType_Type

这是属于 type 对象的 type object，它在 Python 层面和 @ref{603,,type} 是相同的对象。
@end deffn

@geindex PyType_Check (C 函数)
@anchor{c-api/type c PyType_Check}@anchor{3d02}
@deffn {C 函数} int PyType_Check (PyObject@w{ }*o)

如果对象 @emph{o} 是一个类型对象，包括继承于标准类型对象的类型实例，返回真。在其它所有情况下返回假。
@end deffn

@geindex PyType_CheckExact (C 函数)
@anchor{c-api/type c PyType_CheckExact}@anchor{3d03}
@deffn {C 函数} int PyType_CheckExact (PyObject@w{ }*o)

如果对象 @emph{o} 是一个类型对象，但不是标准类型对象的子类型时，返回真。在其它所有情况下返回假。
@end deffn

@geindex PyType_ClearCache (C 函数)
@anchor{c-api/type c PyType_ClearCache}@anchor{3d04}
@deffn {C 函数} unsigned int PyType_ClearCache ()

Clear the internal lookup cache. Return the current version tag.
@end deffn

@geindex PyType_GetFlags (C 函数)
@anchor{c-api/type c PyType_GetFlags}@anchor{3d05}
@deffn {C 函数} unsigned long PyType_GetFlags (PyTypeObject*@w{ }type)

Return the @ref{3d06,,tp_flags} member of @emph{type}. This function is primarily
meant for use with @cite{Py_LIMITED_API}; the individual flag bits are
guaranteed to be stable across Python releases, but access to
@ref{3d06,,tp_flags} itself is not part of the limited API.


3.2 新版功能.



在 3.4 版更改: The return type is now @code{unsigned long} rather than @code{long}.

@end deffn

@geindex PyType_Modified (C 函数)
@anchor{c-api/type c PyType_Modified}@anchor{3d07}
@deffn {C 函数} void PyType_Modified (PyTypeObject@w{ }*type)

Invalidate the internal lookup cache for the type and all of its
subtypes.  This function must be called after any manual
modification of the attributes or base classes of the type.
@end deffn

@geindex PyType_HasFeature (C 函数)
@anchor{c-api/type c PyType_HasFeature}@anchor{3d08}
@deffn {C 函数} int PyType_HasFeature (PyTypeObject@w{ }*o, int@w{ }feature)

Return true if the type object @emph{o} sets the feature @emph{feature}.  Type features
are denoted by single bit flags.
@end deffn

@geindex PyType_IS_GC (C 函数)
@anchor{c-api/type c PyType_IS_GC}@anchor{3d09}
@deffn {C 函数} int PyType_IS_GC (PyTypeObject@w{ }*o)

Return true if the type object includes support for the cycle detector; this
tests the type flag @ref{3af3,,Py_TPFLAGS_HAVE_GC}.
@end deffn

@geindex PyType_IsSubtype (C 函数)
@anchor{c-api/type c PyType_IsSubtype}@anchor{3d0a}
@deffn {C 函数} int PyType_IsSubtype (PyTypeObject@w{ }*a, PyTypeObject@w{ }*b)

Return true if @emph{a} is a subtype of @emph{b}.

This function only checks for actual subtypes, which means that
@ref{13e9,,__subclasscheck__()} is not called on @emph{b}.  Call
@ref{798,,PyObject_IsSubclass()} to do the same check that @ref{44a,,issubclass()}
would do.
@end deffn

@geindex PyType_GenericAlloc (C 函数)
@anchor{c-api/type c PyType_GenericAlloc}@anchor{270}
@deffn {C 函数} PyObject* PyType_GenericAlloc (PyTypeObject@w{ }*type, Py_ssize_t@w{ }nitems)
@emph{Return value: New reference.}
Generic handler for the @ref{3ae6,,tp_alloc} slot of a type object.  Use
Python's default memory allocation mechanism to allocate a new instance and
initialize all its contents to @code{NULL}.
@end deffn

@geindex PyType_GenericNew (C 函数)
@anchor{c-api/type c PyType_GenericNew}@anchor{3ae2}
@deffn {C 函数} PyObject* PyType_GenericNew (PyTypeObject@w{ }*type, PyObject@w{ }*args, PyObject@w{ }*kwds)
@emph{Return value: New reference.}
Generic handler for the @ref{3ae1,,tp_new} slot of a type object.  Create a
new instance using the type's @ref{3ae6,,tp_alloc} slot.
@end deffn

@geindex PyType_Ready (C 函数)
@anchor{c-api/type c PyType_Ready}@anchor{3ae7}
@deffn {C 函数} int PyType_Ready (PyTypeObject@w{ }*type)

Finalize a type object.  This should be called on all type objects to finish
their initialization.  This function is responsible for adding inherited slots
from a type's base class.  Return @code{0} on success, or return @code{-1} and sets an
exception on error.
@end deffn

@geindex PyType_GetSlot (C 函数)
@anchor{c-api/type c PyType_GetSlot}@anchor{91e}
@deffn {C 函数} void* PyType_GetSlot (PyTypeObject@w{ }*type, int@w{ }slot)

Return the function pointer stored in the given slot. If the
result is @code{NULL}, this indicates that either the slot is @code{NULL},
or that the function was called with invalid parameters.
Callers will typically cast the result pointer into the appropriate
function type.

See @code{PyType_Slot.slot} for possible values of the @emph{slot} argument.

An exception is raised if @emph{type} is not a heap type.


3.4 新版功能.

@end deffn

@menu
* Creating Heap-Allocated Types:: 

@end menu

@node Creating Heap-Allocated Types,,,类型对象<2>
@anchor{c-api/type creating-heap-allocated-types}@anchor{3d0b}
@subsubsection Creating Heap-Allocated Types


The following functions and structs are used to create
@ref{3d0c,,heap types}.

@geindex PyType_FromSpecWithBases (C 函数)
@anchor{c-api/type c PyType_FromSpecWithBases}@anchor{3d0d}
@deffn {C 函数} PyObject* PyType_FromSpecWithBases (PyType_Spec@w{ }*spec, PyObject@w{ }*bases)
@emph{Return value: New reference.}
Creates and returns a heap type object from the @emph{spec}
(@ref{3d0e,,Py_TPFLAGS_HEAPTYPE}).

If @emph{bases} is a tuple, the created heap type contains all types contained
in it as base types.

If @emph{bases} is @code{NULL}, the @emph{Py_tp_base} slot is used instead.
If that also is @code{NULL}, the new type derives from @ref{2b0,,object}.

This function calls @ref{3ae7,,PyType_Ready()} on the new type.


3.3 新版功能.

@end deffn

@geindex PyType_FromSpec (C 函数)
@anchor{c-api/type c PyType_FromSpec}@anchor{2d1}
@deffn {C 函数} PyObject* PyType_FromSpec (PyType_Spec@w{ }*spec)
@emph{Return value: New reference.}
Equivalent to @code{PyType_FromSpecWithBases(spec, NULL)}.
@end deffn

@geindex PyType_Spec (C 类型)
@anchor{c-api/type c PyType_Spec}@anchor{3d0f}
@deffn {C 类型} PyType_Spec

Structure defining a type's behavior.

@geindex PyType_Spec.PyType_Spec.name (C 成员)
@anchor{c-api/type c PyType_Spec PyType_Spec name}@anchor{3d10}
@deffn {C 成员} const char* PyType_Spec.name

Name of the type, used to set @ref{3b00,,PyTypeObject.tp_name}.
@end deffn

@geindex PyType_Spec.PyType_Spec.basicsize (C 成员)
@anchor{c-api/type c PyType_Spec PyType_Spec basicsize}@anchor{3d11}
@deffn {C 成员} int PyType_Spec.basicsize
@end deffn

@geindex PyType_Spec.PyType_Spec.itemsize (C 成员)
@anchor{c-api/type c PyType_Spec PyType_Spec itemsize}@anchor{3d12}
@deffn {C 成员} int PyType_Spec.itemsize

Size of the instance in bytes, used to set
@ref{3ade,,PyTypeObject.tp_basicsize} and
@ref{3add,,PyTypeObject.tp_itemsize}.
@end deffn

@geindex PyType_Spec.PyType_Spec.flags (C 成员)
@anchor{c-api/type c PyType_Spec PyType_Spec flags}@anchor{3d13}
@deffn {C 成员} int PyType_Spec.flags

Type flags, used to set @ref{3d06,,PyTypeObject.tp_flags}.

If the @code{Py_TPFLAGS_HEAPTYPE} flag is not set,
@ref{3d0d,,PyType_FromSpecWithBases()} sets it automatically.
@end deffn

@geindex PyType_Spec.PyType_Spec.slots (C 成员)
@anchor{c-api/type c PyType_Spec PyType_Spec slots}@anchor{3d14}
@deffn {C 成员} PyType_Slot *PyType_Spec.slots

Array of @ref{3d15,,PyType_Slot} structures.
Terminated by the special slot value @code{@{0, NULL@}}.
@end deffn
@end deffn

@geindex PyType_Slot (C 类型)
@anchor{c-api/type c PyType_Slot}@anchor{3d15}
@deffn {C 类型} PyType_Slot

Structure defining optional functionality of a type, containing a slot ID
and a value pointer.

@geindex PyType_Slot.PyType_Slot.slot (C 成员)
@anchor{c-api/type c PyType_Slot PyType_Slot slot}@anchor{3d16}
@deffn {C 成员} int PyType_Slot.slot

A slot ID.

Slot IDs are named like the field names of the structures
@ref{2d6,,PyTypeObject}, @ref{d7a,,PyNumberMethods},
@ref{3b0e,,PySequenceMethods}, @ref{3b0f,,PyMappingMethods} and
@ref{3d17,,PyAsyncMethods} with an added @code{Py_} prefix.
For example, use:


@itemize *

@item 
@code{Py_tp_dealloc} to set @ref{3ae4,,PyTypeObject.tp_dealloc}

@item 
@code{Py_nb_add} to set @ref{3d18,,PyNumberMethods.nb_add}

@item 
@code{Py_sq_length} to set @ref{3d19,,PySequenceMethods.sq_length}
@end itemize

The following fields cannot be set using @ref{3d0f,,PyType_Spec} and @ref{3d15,,PyType_Slot}:


@itemize *

@item 
@ref{3d1a,,tp_dict}

@item 
@ref{3d1b,,tp_mro}

@item 
@ref{3d1c,,tp_cache}

@item 
@ref{3d1d,,tp_subclasses}

@item 
@ref{3d1e,,tp_weaklist}

@item 
@code{tp_print}

@item 
@ref{3b13,,tp_weaklistoffset}

@item 
@ref{3d1f,,tp_dictoffset}

@item 
@ref{3d20,,bf_getbuffer}

@item 
@ref{3c21,,bf_releasebuffer}
@end itemize

Setting @code{Py_tp_bases} may be problematic on some platforms.
To avoid issues, use the @emph{bases} argument of
@code{PyType_FromSpecWithBases()} instead.
@end deffn

@geindex PyType_Slot.PyType_Slot.pfunc (C 成员)
@anchor{c-api/type c PyType_Slot PyType_Slot pfunc}@anchor{3d21}
@deffn {C 成员} void *PyType_Slot.pfunc

The desired value of the slot. In most cases, this is a pointer
to a function.

May not be @code{NULL}.
@end deffn
@end deffn

@node None 对象,,类型对象<2>,基本对象
@anchor{c-api/none doc}@anchor{3d22}@anchor{c-api/none noneobject}@anchor{3d23}@anchor{c-api/none the-none-object}@anchor{3d24}
@subsubsection @code{None} 对象


@geindex 对象; None

请注意， @code{None} 的 @ref{2d6,,PyTypeObject} 不会直接在 Python / C API 中公开。 由于 @code{None} 是单例，测试对象标识（在C中使用 @code{==} ）就足够了。 由于同样的原因，没有 @code{PyNone_Check()} 函数。

@geindex Py_None (C 变量)
@anchor{c-api/none c Py_None}@anchor{3aa9}
@deffn {C 变量} PyObject* Py_None

Python @code{None} 对象，表示缺乏值。 这个对象没有方法。 它需要像引用计数一样处理任何其他对象。
@end deffn

@geindex Py_RETURN_NONE (C 宏)
@anchor{c-api/none c Py_RETURN_NONE}@anchor{dcf}
@deffn {C 宏} Py_RETURN_NONE

正确处理来自C函数内的 @ref{3aa9,,Py_None} 返回（也就是说，增加 @code{None} 的引用计数并返回它。）
@end deffn

@node 数值对象,序列对象,基本对象,具体的对象层
@anchor{c-api/concrete numeric-objects}@anchor{3d25}@anchor{c-api/concrete numericobjects}@anchor{3d26}
@subsection 数值对象


@geindex 对象; numeric

@menu
* 整数型对象:: 
* 布尔对象:: 
* 浮点数对象:: 
* 复数对象:: 

@end menu

@node 整数型对象,布尔对象,,数值对象
@anchor{c-api/long doc}@anchor{3d27}@anchor{c-api/long integer-objects}@anchor{3d28}@anchor{c-api/long longobjects}@anchor{3d29}
@subsubsection 整数型对象


@geindex 对象; long integer
@geindex 对象; integer

所有整数都使用以任意大小的长整数对象表示。

在出错时，大多数 @code{PyLong_As*} API返回 @code{(返回值类型)-1} ，无法与一般的数字区分开来。请使用 @ref{3aa4,,PyErr_Occurred()} 来区分。

@geindex PyLongObject (C 类型)
@anchor{c-api/long c PyLongObject}@anchor{3d2a}
@deffn {C 类型} PyLongObject

表示 Python 整数对象的 @ref{4b5,,PyObject} 子类型。
@end deffn

@geindex PyLong_Type (C 变量)
@anchor{c-api/long c PyLong_Type}@anchor{3d2b}
@deffn {C 变量} PyTypeObject PyLong_Type

这个 @ref{2d6,,PyTypeObject} 的实例表示 Python 的整数类型。与Python层中的 @ref{184,,int} 相同。
@end deffn

@geindex PyLong_Check (C 函数)
@anchor{c-api/long c PyLong_Check}@anchor{3d2c}
@deffn {C 函数} int PyLong_Check (PyObject@w{ }*p)

如果参数是 @ref{3d2a,,PyLongObject} 或 @ref{3d2a,,PyLongObject} 的子类型，返回 true 。
@end deffn

@geindex PyLong_CheckExact (C 函数)
@anchor{c-api/long c PyLong_CheckExact}@anchor{3d2d}
@deffn {C 函数} int PyLong_CheckExact (PyObject@w{ }*p)

如果参数是 @ref{3d2a,,PyLongObject} 但不是 @ref{3d2a,,PyLongObject} 的子类型，返回 true。
@end deffn

@geindex PyLong_FromLong (C 函数)
@anchor{c-api/long c PyLong_FromLong}@anchor{3aa6}
@deffn {C 函数} PyObject* PyLong_FromLong (long@w{ }v)
@emph{Return value: New reference.}
由 @emph{v} 返回一个新的 @ref{3d2a,,PyLongObject} 对象，失败时返回 @code{NULL} 。

The current implementation keeps an array of integer objects for all integers
between @code{-5} and @code{256}, when you create an int in that range you actually
just get back a reference to the existing object. So it should be possible to
change the value of @code{1}.  I suspect the behaviour of Python in this case is
undefined. :-)
@end deffn

@geindex PyLong_FromUnsignedLong (C 函数)
@anchor{c-api/long c PyLong_FromUnsignedLong}@anchor{3d2e}
@deffn {C 函数} PyObject* PyLong_FromUnsignedLong (unsigned long@w{ }v)
@emph{Return value: New reference.}
由 C @code{unsigned long} 类型返回一个新的 @ref{3d2a,,PyLongObject} 对象，失败时返回 @code{NULL} 。
@end deffn

@geindex PyLong_FromSsize_t (C 函数)
@anchor{c-api/long c PyLong_FromSsize_t}@anchor{3d2f}
@deffn {C 函数} PyObject* PyLong_FromSsize_t (Py_ssize_t@w{ }v)
@emph{Return value: New reference.}
从 C @code{Py_ssize_t} 类型返回一个新的 @ref{3d2a,,PyLongObject} 对象，如果失败则返回`@w{`}NULL`@w{`}。
@end deffn

@geindex PyLong_FromSize_t (C 函数)
@anchor{c-api/long c PyLong_FromSize_t}@anchor{3d30}
@deffn {C 函数} PyObject* PyLong_FromSize_t (size_t@w{ }v)
@emph{Return value: New reference.}
从 C @code{size_t} 返回一个新的 @ref{3d2a,,PyLongObject} 对象，如果失败则返回`@w{`}NULL`@w{`}。
@end deffn

@geindex PyLong_FromLongLong (C 函数)
@anchor{c-api/long c PyLong_FromLongLong}@anchor{3d31}
@deffn {C 函数} PyObject* PyLong_FromLongLong (long long@w{ }v)
@emph{Return value: New reference.}
从 C @code{long long} 返回一个新的 @ref{3d2a,,PyLongObject} 对象，失败时返回`@w{`}NULL`@w{`}。
@end deffn

@geindex PyLong_FromUnsignedLongLong (C 函数)
@anchor{c-api/long c PyLong_FromUnsignedLongLong}@anchor{3d32}
@deffn {C 函数} PyObject* PyLong_FromUnsignedLongLong (unsigned long long@w{ }v)
@emph{Return value: New reference.}
从 C @code{unsigned long long} 返回一个新的 @ref{3d2a,,PyLongObject} 对象，失败时返回`@w{`}NULL`@w{`}。
@end deffn

@geindex PyLong_FromDouble (C 函数)
@anchor{c-api/long c PyLong_FromDouble}@anchor{3d33}
@deffn {C 函数} PyObject* PyLong_FromDouble (double@w{ }v)
@emph{Return value: New reference.}
从 @emph{v} 的整数部分返回一个新的 @ref{3d2a,,PyLongObject} 对象，如果失败则返回`@w{`}NULL`@w{`}。
@end deffn

@geindex PyLong_FromString (C 函数)
@anchor{c-api/long c PyLong_FromString}@anchor{3d34}
@deffn {C 函数} PyObject* PyLong_FromString (const char@w{ }*str, char@w{ }**pend, int@w{ }base)
@emph{Return value: New reference.}
根据 @emph{str} 字符串值返回一个新的 @ref{3d2a,,PyLongObject} ，@emph{base} 指定基数。如果 @emph{pend} 不是 @code{NULL} ， @emph{/*pend} 将指向 @emph{str} 中表示这个数字部分的后面的第一个字符。如果 @emph{base} 是 @code{0} ， @emph{str} 将使用 @ref{1398,,整型数字面值} 定义来解释；在这种情况下，一个非零的十进制数中的前导零会引发一个 @ref{1fb,,ValueError} 。如果 @emph{base} 不是 @code{0} ，它必须在 @code{2} 和` @cite{36`} 之间，包括2和36。基数说明符后以及数字之间的前导空格、单下划线将被忽略。如果没有数字，将引发 @ref{1fb,,ValueError}。
@end deffn

@geindex PyLong_FromUnicode (C 函数)
@anchor{c-api/long c PyLong_FromUnicode}@anchor{3d35}
@deffn {C 函数} PyObject* PyLong_FromUnicode (Py_UNICODE@w{ }*u, Py_ssize_t@w{ }length, int@w{ }base)
@emph{Return value: New reference.}
Convert a sequence of Unicode digits to a Python integer value.


Deprecated since version 3.3, will be removed in version 3.10: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{3d36,,PyLong_FromUnicodeObject()}.

@end deffn

@geindex PyLong_FromUnicodeObject (C 函数)
@anchor{c-api/long c PyLong_FromUnicodeObject}@anchor{3d36}
@deffn {C 函数} PyObject* PyLong_FromUnicodeObject (PyObject@w{ }*u, int@w{ }base)
@emph{Return value: New reference.}
Convert a sequence of Unicode digits in the string @emph{u} to a Python integer
value.


3.3 新版功能.

@end deffn

@geindex PyLong_FromVoidPtr (C 函数)
@anchor{c-api/long c PyLong_FromVoidPtr}@anchor{3d37}
@deffn {C 函数} PyObject* PyLong_FromVoidPtr (void@w{ }*p)
@emph{Return value: New reference.}
Create a Python integer from the pointer @emph{p}. The pointer value can be
retrieved from the resulting value using @ref{3d38,,PyLong_AsVoidPtr()}.
@end deffn

@c XXX alias PyLong_AS_LONG (for now)

@geindex PyLong_AsLong (C 函数)
@anchor{c-api/long c PyLong_AsLong}@anchor{269}
@deffn {C 函数} long PyLong_AsLong (PyObject@w{ }*obj)

@geindex LONG_MAX
@geindex OverflowError (built-in exception)

Return a C @code{long} representation of @emph{obj}.  If @emph{obj} is not an
instance of @ref{3d2a,,PyLongObject}, first call its @ref{18a,,__index__()} or
@ref{18b,,__int__()} method (if present) to convert it to a
@ref{3d2a,,PyLongObject}.

Raise @ref{95a,,OverflowError} if the value of @emph{obj} is out of range for a
@code{long}.

Returns @code{-1} on error.  Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.


在 3.8 版更改: 如果可用将使用 @ref{18a,,__index__()}。



3.8 版后已移除: Using @ref{18b,,__int__()} is deprecated.

@end deffn

@geindex PyLong_AsLongAndOverflow (C 函数)
@anchor{c-api/long c PyLong_AsLongAndOverflow}@anchor{bf6}
@deffn {C 函数} long PyLong_AsLongAndOverflow (PyObject@w{ }*obj, int@w{ }*overflow)

Return a C @code{long} representation of @emph{obj}.  If @emph{obj} is not an
instance of @ref{3d2a,,PyLongObject}, first call its @ref{18a,,__index__()} or
@ref{18b,,__int__()} method (if present) to convert it to a
@ref{3d2a,,PyLongObject}.

If the value of @emph{obj} is greater than @code{LONG_MAX} or less than
@code{LONG_MIN}, set @emph{*overflow} to @code{1} or @code{-1}, respectively, and
return @code{-1}; otherwise, set @emph{*overflow} to @code{0}.  If any other exception
occurs set @emph{*overflow} to @code{0} and return @code{-1} as usual.

Returns @code{-1} on error.  Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.


在 3.8 版更改: 如果可用将使用 @ref{18a,,__index__()}。



3.8 版后已移除: Using @ref{18b,,__int__()} is deprecated.

@end deffn

@geindex PyLong_AsLongLong (C 函数)
@anchor{c-api/long c PyLong_AsLongLong}@anchor{3d39}
@deffn {C 函数} long long PyLong_AsLongLong (PyObject@w{ }*obj)

@geindex OverflowError (built-in exception)

Return a C @code{long long} representation of @emph{obj}.  If @emph{obj} is not an
instance of @ref{3d2a,,PyLongObject}, first call its @ref{18a,,__index__()} or
@ref{18b,,__int__()} method (if present) to convert it to a
@ref{3d2a,,PyLongObject}.

Raise @ref{95a,,OverflowError} if the value of @emph{obj} is out of range for a
@code{long long}.

Returns @code{-1} on error.  Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.


在 3.8 版更改: 如果可用将使用 @ref{18a,,__index__()}。



3.8 版后已移除: Using @ref{18b,,__int__()} is deprecated.

@end deffn

@geindex PyLong_AsLongLongAndOverflow (C 函数)
@anchor{c-api/long c PyLong_AsLongLongAndOverflow}@anchor{bf5}
@deffn {C 函数} long long PyLong_AsLongLongAndOverflow (PyObject@w{ }*obj, int@w{ }*overflow)

Return a C @code{long long} representation of @emph{obj}.  If @emph{obj} is not an
instance of @ref{3d2a,,PyLongObject}, first call its @ref{18a,,__index__()} or
@ref{18b,,__int__()} method (if present) to convert it to a
@ref{3d2a,,PyLongObject}.

If the value of @emph{obj} is greater than @code{PY_LLONG_MAX} or less than
@code{PY_LLONG_MIN}, set @emph{*overflow} to @code{1} or @code{-1}, respectively,
and return @code{-1}; otherwise, set @emph{*overflow} to @code{0}.  If any other
exception occurs set @emph{*overflow} to @code{0} and return @code{-1} as usual.

Returns @code{-1} on error.  Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.


3.2 新版功能.



在 3.8 版更改: 如果可用将使用 @ref{18a,,__index__()}。



3.8 版后已移除: Using @ref{18b,,__int__()} is deprecated.

@end deffn

@geindex PyLong_AsSsize_t (C 函数)
@anchor{c-api/long c PyLong_AsSsize_t}@anchor{3d3a}
@deffn {C 函数} Py_ssize_t PyLong_AsSsize_t (PyObject@w{ }*pylong)

@geindex PY_SSIZE_T_MAX
@geindex OverflowError (built-in exception)

Return a C @code{Py_ssize_t} representation of @emph{pylong}.  @emph{pylong} must
be an instance of @ref{3d2a,,PyLongObject}.

Raise @ref{95a,,OverflowError} if the value of @emph{pylong} is out of range for a
@code{Py_ssize_t}.

Returns @code{-1} on error.  Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.
@end deffn

@geindex PyLong_AsUnsignedLong (C 函数)
@anchor{c-api/long c PyLong_AsUnsignedLong}@anchor{3d3b}
@deffn {C 函数} unsigned long PyLong_AsUnsignedLong (PyObject@w{ }*pylong)

@geindex ULONG_MAX
@geindex OverflowError (built-in exception)

Return a C @code{unsigned long} representation of @emph{pylong}.  @emph{pylong}
must be an instance of @ref{3d2a,,PyLongObject}.

Raise @ref{95a,,OverflowError} if the value of @emph{pylong} is out of range for a
@code{unsigned long}.

Returns @code{(unsigned long)-1} on error.
Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.
@end deffn

@geindex PyLong_AsSize_t (C 函数)
@anchor{c-api/long c PyLong_AsSize_t}@anchor{3d3c}
@deffn {C 函数} size_t PyLong_AsSize_t (PyObject@w{ }*pylong)

@geindex SIZE_MAX
@geindex OverflowError (built-in exception)

Return a C @code{size_t} representation of @emph{pylong}.  @emph{pylong} must be
an instance of @ref{3d2a,,PyLongObject}.

Raise @ref{95a,,OverflowError} if the value of @emph{pylong} is out of range for a
@code{size_t}.

Returns @code{(size_t)-1} on error.
Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.
@end deffn

@geindex PyLong_AsUnsignedLongLong (C 函数)
@anchor{c-api/long c PyLong_AsUnsignedLongLong}@anchor{c1b}
@deffn {C 函数} unsigned long long PyLong_AsUnsignedLongLong (PyObject@w{ }*pylong)

@geindex OverflowError (built-in exception)

Return a C @code{unsigned long long} representation of @emph{pylong}.  @emph{pylong}
must be an instance of @ref{3d2a,,PyLongObject}.

Raise @ref{95a,,OverflowError} if the value of @emph{pylong} is out of range for an
@code{unsigned long long}.

Returns @code{(unsigned long long)-1} on error.
Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.


在 3.1 版更改: A negative @emph{pylong} now raises @ref{95a,,OverflowError}, not @ref{192,,TypeError}.

@end deffn

@geindex PyLong_AsUnsignedLongMask (C 函数)
@anchor{c-api/long c PyLong_AsUnsignedLongMask}@anchor{3d3d}
@deffn {C 函数} unsigned long PyLong_AsUnsignedLongMask (PyObject@w{ }*obj)

Return a C @code{unsigned long} representation of @emph{obj}.  If @emph{obj}
is not an instance of @ref{3d2a,,PyLongObject}, first call its
@ref{18a,,__index__()} or @ref{18b,,__int__()} method (if present) to convert
it to a @ref{3d2a,,PyLongObject}.

If the value of @emph{obj} is out of range for an @code{unsigned long},
return the reduction of that value modulo @code{ULONG_MAX + 1}.

Returns @code{(unsigned long)-1} on error.  Use @ref{3aa4,,PyErr_Occurred()} to
disambiguate.


在 3.8 版更改: 如果可用将使用 @ref{18a,,__index__()}。



3.8 版后已移除: Using @ref{18b,,__int__()} is deprecated.

@end deffn

@geindex PyLong_AsUnsignedLongLongMask (C 函数)
@anchor{c-api/long c PyLong_AsUnsignedLongLongMask}@anchor{f49}
@deffn {C 函数} unsigned long long PyLong_AsUnsignedLongLongMask (PyObject@w{ }*obj)

Return a C @code{unsigned long long} representation of @emph{obj}.  If @emph{obj}
is not an instance of @ref{3d2a,,PyLongObject}, first call its
@ref{18a,,__index__()} or @ref{18b,,__int__()} method (if present) to convert
it to a @ref{3d2a,,PyLongObject}.

If the value of @emph{obj} is out of range for an @code{unsigned long long},
return the reduction of that value modulo @code{PY_ULLONG_MAX + 1}.

Returns @code{(unsigned long long)-1} on error.  Use @ref{3aa4,,PyErr_Occurred()}
to disambiguate.


在 3.8 版更改: 如果可用将使用 @ref{18a,,__index__()}。



3.8 版后已移除: Using @ref{18b,,__int__()} is deprecated.

@end deffn

@geindex PyLong_AsDouble (C 函数)
@anchor{c-api/long c PyLong_AsDouble}@anchor{3d3e}
@deffn {C 函数} double PyLong_AsDouble (PyObject@w{ }*pylong)

Return a C @code{double} representation of @emph{pylong}.  @emph{pylong} must be
an instance of @ref{3d2a,,PyLongObject}.

Raise @ref{95a,,OverflowError} if the value of @emph{pylong} is out of range for a
@code{double}.

Returns @code{-1.0} on error.  Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.
@end deffn

@geindex PyLong_AsVoidPtr (C 函数)
@anchor{c-api/long c PyLong_AsVoidPtr}@anchor{3d38}
@deffn {C 函数} void* PyLong_AsVoidPtr (PyObject@w{ }*pylong)

Convert a Python integer @emph{pylong} to a C @code{void} pointer.
If @emph{pylong} cannot be converted, an @ref{95a,,OverflowError} will be raised.  This
is only assured to produce a usable @code{void} pointer for values created
with @ref{3d37,,PyLong_FromVoidPtr()}.

Returns @code{NULL} on error.  Use @ref{3aa4,,PyErr_Occurred()} to disambiguate.
@end deffn

@node 布尔对象,浮点数对象,整数型对象,数值对象
@anchor{c-api/bool doc}@anchor{3d3f}@anchor{c-api/bool boolean-objects}@anchor{3d40}@anchor{c-api/bool boolobjects}@anchor{3d41}
@subsubsection 布尔对象


Python 中的布尔值是作为整数的子类实现的。只有 @code{Py_False} 和 @code{Py_True} 两个布尔值。因此，正常的创建和删除功能不适用于布尔值。但是，下列宏可用。

@geindex PyBool_Check (C 函数)
@anchor{c-api/bool c PyBool_Check}@anchor{3d42}
@deffn {C 函数} int PyBool_Check (PyObject@w{ }*o)

如果 @emph{o} 是 @code{PyBool_Type} 类型，则返回true。
@end deffn

@geindex Py_False (C 变量)
@anchor{c-api/bool c Py_False}@anchor{3d43}
@deffn {C 变量} PyObject* Py_False

Python的`@w{`}False`@w{`}对象。该对象没有任何方法。它应该象其它使用引用计数管理的对象一样使用。
@end deffn

@geindex Py_True (C 变量)
@anchor{c-api/bool c Py_True}@anchor{3d44}
@deffn {C 变量} PyObject* Py_True

Python的`@w{`}True`@w{`}对象。该对象没有任何方法。它应该象其它使用引用计数管理的对象一样使用。
@end deffn

@geindex Py_RETURN_FALSE (C 宏)
@anchor{c-api/bool c Py_RETURN_FALSE}@anchor{dd1}
@deffn {C 宏} Py_RETURN_FALSE

从函数返回 @code{Py_False} 时，需要增加它的引用计数。
@end deffn

@geindex Py_RETURN_TRUE (C 宏)
@anchor{c-api/bool c Py_RETURN_TRUE}@anchor{dd0}
@deffn {C 宏} Py_RETURN_TRUE

从函数返回 @code{Py_True} 时，需要增加它的引用计数。
@end deffn

@geindex PyBool_FromLong (C 函数)
@anchor{c-api/bool c PyBool_FromLong}@anchor{3d45}
@deffn {C 函数} PyObject* PyBool_FromLong (long@w{ }v)
@emph{Return value: New reference.}
根据 @emph{v} 的实际值，返回一个 @code{Py_True} 或者 @code{Py_False} 的新引用。
@end deffn

@node 浮点数对象,复数对象,布尔对象,数值对象
@anchor{c-api/float doc}@anchor{3d46}@anchor{c-api/float floating-point-objects}@anchor{3d47}@anchor{c-api/float floatobjects}@anchor{3d48}
@subsubsection 浮点数对象


@geindex 对象; floating point

@geindex PyFloatObject (C 类型)
@anchor{c-api/float c PyFloatObject}@anchor{3d49}
@deffn {C 类型} PyFloatObject

这个C类型 @ref{4b5,,PyObject} 的子类型代表一个Python浮点数对象。
@end deffn

@geindex PyFloat_Type (C 变量)
@anchor{c-api/float c PyFloat_Type}@anchor{3d4a}
@deffn {C 变量} PyTypeObject PyFloat_Type

这是个属于C类型 @ref{2d6,,PyTypeObject} 的代表Python浮点类型的实例。在Python层面的类型 @ref{187,,float} 是同一个对象。
@end deffn

@geindex PyFloat_Check (C 函数)
@anchor{c-api/float c PyFloat_Check}@anchor{3d4b}
@deffn {C 函数} int PyFloat_Check (PyObject@w{ }*p)

当他的参数是一个C类型 @ref{3d49,,PyFloatObject} 或者是C类型 @ref{3d49,,PyFloatObject} 的子类型时，返回真。
@end deffn

@geindex PyFloat_CheckExact (C 函数)
@anchor{c-api/float c PyFloat_CheckExact}@anchor{3d4c}
@deffn {C 函数} int PyFloat_CheckExact (PyObject@w{ }*p)

当他的参数是一个C类型 @ref{3d49,,PyFloatObject} 但不是C类型 @ref{3d49,,PyFloatObject} 的子类型时，返回真。
@end deffn

@geindex PyFloat_FromString (C 函数)
@anchor{c-api/float c PyFloat_FromString}@anchor{3d4d}
@deffn {C 函数} PyObject* PyFloat_FromString (PyObject@w{ }*str)
@emph{Return value: New reference.}
根据字符串 @emph{str} 的值创建一个 @ref{3d49,,PyFloatObject}，失败时返回 @code{NULL}。
@end deffn

@geindex PyFloat_FromDouble (C 函数)
@anchor{c-api/float c PyFloat_FromDouble}@anchor{3d4e}
@deffn {C 函数} PyObject* PyFloat_FromDouble (double@w{ }v)
@emph{Return value: New reference.}
根据 @emph{v} 创建一个 @ref{3d49,,PyFloatObject} 对象，失败时返回 @code{NULL}。
@end deffn

@geindex PyFloat_AsDouble (C 函数)
@anchor{c-api/float c PyFloat_AsDouble}@anchor{26e}
@deffn {C 函数} double PyFloat_AsDouble (PyObject@w{ }*pyfloat)

返回一个 C @code{double} 代表 @emph{pyfloat} 的内容。 如果 @emph{pyfloat} 不是一个 Python 浮点数对象但是具有 @ref{18c,,__float__()} 方法，此方法将首先被调用，将 @emph{pyfloat} 转换成一个数点数。 如果 @code{__float__()} 未定义则将回退至 @ref{18a,,__index__()}。 如果失败，此方法将返回 @code{-1.0}，因此开发者应当调用 @ref{3aa4,,PyErr_Occurred()} 来检查错误。


在 3.8 版更改: 如果可用将使用 @ref{18a,,__index__()}。

@end deffn

@geindex PyFloat_AS_DOUBLE (C 函数)
@anchor{c-api/float c PyFloat_AS_DOUBLE}@anchor{3d4f}
@deffn {C 函数} double PyFloat_AS_DOUBLE (PyObject@w{ }*pyfloat)

返回一个 @emph{pyfloat} 内容的 C @code{double} 表示，但没有错误检查。
@end deffn

@geindex PyFloat_GetInfo (C 函数)
@anchor{c-api/float c PyFloat_GetInfo}@anchor{d50}
@deffn {C 函数} PyObject* PyFloat_GetInfo (void)
@emph{Return value: New reference.}
返回一个 structseq 实例，其中包含有关 float 的精度、最小值和最大值的信息。 它是头文件 @code{float.h} 的一个简单包装。
@end deffn

@geindex PyFloat_GetMax (C 函数)
@anchor{c-api/float c PyFloat_GetMax}@anchor{d4e}
@deffn {C 函数} double PyFloat_GetMax ()

返回最大可表示的有限浮点数 @emph{DBL_MAX} 为 C @code{double} 。
@end deffn

@geindex PyFloat_GetMin (C 函数)
@anchor{c-api/float c PyFloat_GetMin}@anchor{d4f}
@deffn {C 函数} double PyFloat_GetMin ()

返回最小可表示归一化正浮点数 @emph{DBL_MIN} 为 C @code{double} 。
@end deffn

@geindex PyFloat_ClearFreeList (C 函数)
@anchor{c-api/float c PyFloat_ClearFreeList}@anchor{3d50}
@deffn {C 函数} int PyFloat_ClearFreeList ()

清空浮点数释放列表。 返回无法释放的项目数。
@end deffn

@node 复数对象,,浮点数对象,数值对象
@anchor{c-api/complex doc}@anchor{3d51}@anchor{c-api/complex complex-number-objects}@anchor{3d52}@anchor{c-api/complex complexobjects}@anchor{3d53}
@subsubsection 复数对象


@geindex 对象; complex number

从C API看，Python的复数对象由两个不同的部分实现：一个是在Python程序使用的Python对象，另外的是一个代表真正复数值的C结构体。API提供了函数共同操作两者。

@menu
* 表示复数的C结构体:: 
* 表示复数的Python对象:: 

@end menu

@node 表示复数的C结构体,表示复数的Python对象,,复数对象
@anchor{c-api/complex complex-numbers-as-c-structures}@anchor{3d54}
@subsubsection 表示复数的C结构体


需要注意的是接受这些结构体的作为参数并当做结果返回的函数，都是传递“值”而不是引用指针。此规则适用于整个API。

@geindex Py_complex (C 类型)
@anchor{c-api/complex c Py_complex}@anchor{3c23}
@deffn {C 类型} Py_complex

这是一个对应Python复数对象的值部分的C结构体。绝大部分处理复数对象的函数都用这类型的结构体作为输入或者输出值，它可近似地定义为：

@example
typedef struct @{
   double real;
   double imag;
@} Py_complex;
@end example
@end deffn

@geindex _Py_c_sum (C 函数)
@anchor{c-api/complex c _Py_c_sum}@anchor{3d55}
@deffn {C 函数} Py_complex _Py_c_sum (Py_complex@w{ }left, Py_complex@w{ }right)

返回两个复数的和，用 C 类型 @ref{3c23,,Py_complex} 表示。
@end deffn

@geindex _Py_c_diff (C 函数)
@anchor{c-api/complex c _Py_c_diff}@anchor{3d56}
@deffn {C 函数} Py_complex _Py_c_diff (Py_complex@w{ }left, Py_complex@w{ }right)

返回两个复数的差，用 C 类型 @ref{3c23,,Py_complex} 表示。
@end deffn

@geindex _Py_c_neg (C 函数)
@anchor{c-api/complex c _Py_c_neg}@anchor{3d57}
@deffn {C 函数} Py_complex _Py_c_neg (Py_complex@w{ }complex)

返回复数 @emph{complex} 的负值，用 C 类型 @ref{3c23,,Py_complex} 表示。
@end deffn

@geindex _Py_c_prod (C 函数)
@anchor{c-api/complex c _Py_c_prod}@anchor{3d58}
@deffn {C 函数} Py_complex _Py_c_prod (Py_complex@w{ }left, Py_complex@w{ }right)

返回两个复数的乘积，用 C 类型 @ref{3c23,,Py_complex} 表示。
@end deffn

@geindex _Py_c_quot (C 函数)
@anchor{c-api/complex c _Py_c_quot}@anchor{3d59}
@deffn {C 函数} Py_complex _Py_c_quot (Py_complex@w{ }dividend, Py_complex@w{ }divisor)

返回两个复数的商，用 C 类型 @ref{3c23,,Py_complex} 表示。

如果 @emph{divisor} 为空，这个方法返回零并设置 @code{errno} 为 @code{EDOM}。
@end deffn

@geindex _Py_c_pow (C 函数)
@anchor{c-api/complex c _Py_c_pow}@anchor{3d5a}
@deffn {C 函数} Py_complex _Py_c_pow (Py_complex@w{ }num, Py_complex@w{ }exp)

返回 @emph{num} 的 @emph{exp} 次幂，用 C 类型 @ref{3c23,,Py_complex} 表示。

如果 @emph{num} 为空且 @emph{exp} 不是正实数，这个方法返回零并设置 @code{errno} 为 @code{EDOM}。
@end deffn

@node 表示复数的Python对象,,表示复数的C结构体,复数对象
@anchor{c-api/complex complex-numbers-as-python-objects}@anchor{3d5b}
@subsubsection 表示复数的Python对象


@geindex PyComplexObject (C 类型)
@anchor{c-api/complex c PyComplexObject}@anchor{3d5c}
@deffn {C 类型} PyComplexObject

这个C类型 @ref{4b5,,PyObject} 的子类型代表一个 Python 复数对象。
@end deffn

@geindex PyComplex_Type (C 变量)
@anchor{c-api/complex c PyComplex_Type}@anchor{3d5d}
@deffn {C 变量} PyTypeObject PyComplex_Type

这是个属于 @ref{2d6,,PyTypeObject} 的代表Python复数类型的实例。在Python层面的类型 @ref{189,,complex} 是同一个对象。
@end deffn

@geindex PyComplex_Check (C 函数)
@anchor{c-api/complex c PyComplex_Check}@anchor{3d5e}
@deffn {C 函数} int PyComplex_Check (PyObject@w{ }*p)

如果它的变量是一个C类型 @ref{3d5c,,PyComplexObject} 或者是C类型 @ref{3d5c,,PyComplexObject} 的子类型，返回真。
@end deffn

@geindex PyComplex_CheckExact (C 函数)
@anchor{c-api/complex c PyComplex_CheckExact}@anchor{3d5f}
@deffn {C 函数} int PyComplex_CheckExact (PyObject@w{ }*p)

如果它的参数是一个C类型 @ref{3d5c,,PyComplexObject} 但不是C类型 @ref{3d5c,,PyComplexObject} 的子类型，返回真。
@end deffn

@geindex PyComplex_FromCComplex (C 函数)
@anchor{c-api/complex c PyComplex_FromCComplex}@anchor{3d60}
@deffn {C 函数} PyObject* PyComplex_FromCComplex (Py_complex@w{ }v)
@emph{Return value: New reference.}
根据C类型 @ref{3c23,,Py_complex} 的值生成一个新的Python复数对象。
@end deffn

@geindex PyComplex_FromDoubles (C 函数)
@anchor{c-api/complex c PyComplex_FromDoubles}@anchor{3d61}
@deffn {C 函数} PyObject* PyComplex_FromDoubles (double@w{ }real, double@w{ }imag)
@emph{Return value: New reference.}
根据 @emph{real} 和 @emph{imag} 返回一个新的C类型 @ref{3d5c,,PyComplexObject} 对象。
@end deffn

@geindex PyComplex_RealAsDouble (C 函数)
@anchor{c-api/complex c PyComplex_RealAsDouble}@anchor{3d62}
@deffn {C 函数} double PyComplex_RealAsDouble (PyObject@w{ }*op)

以C类型 @code{double} 返回 @emph{op} 的实部。
@end deffn

@geindex PyComplex_ImagAsDouble (C 函数)
@anchor{c-api/complex c PyComplex_ImagAsDouble}@anchor{3d63}
@deffn {C 函数} double PyComplex_ImagAsDouble (PyObject@w{ }*op)

以C类型 @code{double} 返回 @emph{op} 的虚部。
@end deffn

@geindex PyComplex_AsCComplex (C 函数)
@anchor{c-api/complex c PyComplex_AsCComplex}@anchor{d51}
@deffn {C 函数} Py_complex PyComplex_AsCComplex (PyObject@w{ }*op)

返回复数 @emph{op} 的C类型 @ref{3c23,,Py_complex} 值。

如果 @emph{op} 不是一个 Python 复数对象，但是具有 @ref{18d,,__complex__()} 方法，此方法将首先被调用，将 @emph{op} 转换为一个 Python 复数对象。 如果 @code{__complex__()} 未定义则将回退至 @ref{18c,,__float__()}，如果 @code{__float__()} 未定义则将回退至 @ref{18a,,__index__()}。 如果失败，此方法将返回 @code{-1.0} 作为实数值。


在 3.8 版更改: 如果可用将使用 @ref{18a,,__index__()}。

@end deffn

@node 序列对象,容器对象,数值对象,具体的对象层
@anchor{c-api/concrete sequence-objects}@anchor{3d64}@anchor{c-api/concrete sequenceobjects}@anchor{3d65}
@subsection 序列对象


@geindex 对象; sequence

序列对象的一般操作在前一章中讨论过;本节介绍Python语言固有的特定类型的序列对象。

@c XXX sort out unicode, str, bytes and bytearray

@menu
* bytes 对象: bytes 对象<2>. 
* 字节数组对象:: 
* Unicode Objects and Codecs:: 
* 元组对象:: 
* Struct Sequence Objects:: 
* 列表对象:: 

@end menu

@node bytes 对象<2>,字节数组对象,,序列对象
@anchor{c-api/bytes doc}@anchor{3d66}@anchor{c-api/bytes bytes-objects}@anchor{3d67}@anchor{c-api/bytes bytesobjects}@anchor{3d68}
@subsubsection bytes 对象


当期望带一个字节串形参但却带一个非字节串形参被调用时，这些函数会引发 @ref{192,,TypeError}。

@geindex 对象; bytes

@geindex PyBytesObject (C 类型)
@anchor{c-api/bytes c PyBytesObject}@anchor{d17}
@deffn {C 类型} PyBytesObject

这种 @ref{4b5,,PyObject} 的子类型表示一个 Python 字节对象。
@end deffn

@geindex PyBytes_Type (C 变量)
@anchor{c-api/bytes c PyBytes_Type}@anchor{3d69}
@deffn {C 变量} PyTypeObject PyBytes_Type

@ref{2d6,,PyTypeObject} 的实例代表一个 Python 字节类型，在 Python 层面它与 @ref{32a,,bytes} 是相同的对象。
@end deffn

@geindex PyBytes_Check (C 函数)
@anchor{c-api/bytes c PyBytes_Check}@anchor{d18}
@deffn {C 函数} int PyBytes_Check (PyObject@w{ }*o)

如果对象 @emph{o} 是字节对象或字节类型的子类型的实例，则返回 true。
@end deffn

@geindex PyBytes_CheckExact (C 函数)
@anchor{c-api/bytes c PyBytes_CheckExact}@anchor{3d6a}
@deffn {C 函数} int PyBytes_CheckExact (PyObject@w{ }*o)

如果对象 @emph{o} 是字节对象，但不是字节类型子类型的实例，则返回 true。
@end deffn

@geindex PyBytes_FromString (C 函数)
@anchor{c-api/bytes c PyBytes_FromString}@anchor{3d6b}
@deffn {C 函数} PyObject* PyBytes_FromString (const char@w{ }*v)
@emph{Return value: New reference.}
成功时返回一个以字符串 @emph{v} 的副本为值的新字节串对象，失败时返回 @code{NULL}。 形参 @emph{v} 不可为 @code{NULL}；它不会被检查。
@end deffn

@geindex PyBytes_FromStringAndSize (C 函数)
@anchor{c-api/bytes c PyBytes_FromStringAndSize}@anchor{d19}
@deffn {C 函数} PyObject* PyBytes_FromStringAndSize (const char@w{ }*v, Py_ssize_t@w{ }len)
@emph{Return value: New reference.}
成功时返回一个以字符串 @emph{v} 的副本为值且长度为 @emph{len} 的新字节串对象，失败时返回 @code{NULL}。 如果 @emph{v} 为 @code{NULL}，则不初始化字节串对象的内容。
@end deffn

@geindex PyBytes_FromFormat (C 函数)
@anchor{c-api/bytes c PyBytes_FromFormat}@anchor{f9c}
@deffn {C 函数} PyObject* PyBytes_FromFormat (const char@w{ }*format, ...)
@emph{Return value: New reference.}
接受一个 C @code{printf()} 风格的 @emph{format} 字符串和可变数量的参数，计算结果 Python 字节串对象的大小并返回参数值经格式化后的字节串对象。 可变数量的参数必须均为 C 类型并且必须恰好与 @emph{format} 字符串中的格式字符相对应。 允许使用下列格式字符串:

@c % XXX: This should be exactly the same as the table in PyErr_Format.

@c % One should just refer to the other.

@c % XXX: The descriptions for %zd and %zu are wrong, but the truth is complicated

@c % because not all compilers support the %z width modifier -- we fake it

@c % when necessary via interpolating PY_FORMAT_SIZE_T.


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

格式字符

@tab

类型

@tab

注释

@item

@code{%%}

@tab

@emph{不适用}

@tab

文字%字符。

@item

@code{%c}

@tab

int

@tab

一个字节，被表示为一个 C 语言的整型

@item

@code{%d}

@tab

int

@tab

相当于 @code{printf("%d")}. @footnote{@w{(1)} 
对于整数说明符（d，u，ld，lu，zd，zu，i，x）：当给出精度时，0 转换标志是有效的。
}

@item

@code{%u}

@tab

unsigned int

@tab

相当于 @code{printf("%u")}. @footnote{@w{(1)} 
对于整数说明符（d，u，ld，lu，zd，zu，i，x）：当给出精度时，0 转换标志是有效的。
}

@item

@code{%ld}

@tab

长整型

@tab

相当于 @code{printf("%ld")}. @footnote{@w{(1)} 
对于整数说明符（d，u，ld，lu，zd，zu，i，x）：当给出精度时，0 转换标志是有效的。
}

@item

@code{%lu}

@tab

unsigned long

@tab

相当于 @code{printf("%lu")}. @footnote{@w{(1)} 
对于整数说明符（d，u，ld，lu，zd，zu，i，x）：当给出精度时，0 转换标志是有效的。
}

@item

@code{%zd}

@tab

Py_ssize_t

@tab

相当于 @code{printf("%zd")}. @footnote{@w{(1)} 
对于整数说明符（d，u，ld，lu，zd，zu，i，x）：当给出精度时，0 转换标志是有效的。
}

@item

@code{%zu}

@tab

size_t

@tab

相当于 @code{printf("%zu")}. @footnote{@w{(1)} 
对于整数说明符（d，u，ld，lu，zd，zu，i，x）：当给出精度时，0 转换标志是有效的。
}

@item

@code{%i}

@tab

int

@tab

相当于 @code{printf("%i")}. @footnote{@w{(1)} 
对于整数说明符（d，u，ld，lu，zd，zu，i，x）：当给出精度时，0 转换标志是有效的。
}

@item

@code{%x}

@tab

int

@tab

相当于 @code{printf("%x")}. @footnote{@w{(1)} 
对于整数说明符（d，u，ld，lu，zd，zu，i，x）：当给出精度时，0 转换标志是有效的。
}

@item

@code{%s}

@tab

const char*

@tab

以 null 为终止符的 C 字符数组。

@item

@code{%p}

@tab

const void*

@tab

一个 C 指针的十六进制表示形式。 基本等价于 @code{printf("%p")} 但它会确保以字面值 @code{0x} 开头，不论系统平台上 @code{printf} 的输出是什么。

@end multitable


无法识别的格式字符会导致将格式字符串的其余所有内容原样复制到结果对象，并丢弃所有多余的参数。
@end deffn

@geindex PyBytes_FromFormatV (C 函数)
@anchor{c-api/bytes c PyBytes_FromFormatV}@anchor{3d6c}
@deffn {C 函数} PyObject* PyBytes_FromFormatV (const char@w{ }*format, va_list@w{ }vargs)
@emph{Return value: New reference.}
与 @ref{f9c,,PyBytes_FromFormat()} 完全相同，除了它需要两个参数。
@end deffn

@geindex PyBytes_FromObject (C 函数)
@anchor{c-api/bytes c PyBytes_FromObject}@anchor{3d6d}
@deffn {C 函数} PyObject* PyBytes_FromObject (PyObject@w{ }*o)
@emph{Return value: New reference.}
返回字节表示实现缓冲区协议的对象*o*。
@end deffn

@geindex PyBytes_Size (C 函数)
@anchor{c-api/bytes c PyBytes_Size}@anchor{3d6e}
@deffn {C 函数} Py_ssize_t PyBytes_Size (PyObject@w{ }*o)

返回字节对象*o*中字节的长度。
@end deffn

@geindex PyBytes_GET_SIZE (C 函数)
@anchor{c-api/bytes c PyBytes_GET_SIZE}@anchor{3d6f}
@deffn {C 函数} Py_ssize_t PyBytes_GET_SIZE (PyObject@w{ }*o)

宏版本的 @ref{3d6e,,PyBytes_Size()} 但是不带错误检测。
@end deffn

@geindex PyBytes_AsString (C 函数)
@anchor{c-api/bytes c PyBytes_AsString}@anchor{3d70}
@deffn {C 函数} char* PyBytes_AsString (PyObject@w{ }*o)

返回对应 @emph{o} 的内容的指针。 该指针指向 @emph{o} 的内部缓冲区，其中包含 @code{len(o) + 1} 个字节。 缓冲区的最后一个字节总是为空，不论是否存在其他空字节。 该数据不可通过任何形式来修改，除非是刚使用 @code{PyBytes_FromStringAndSize(NULL, size)} 创建该对象。 它不可被撤销分配。 如果 @emph{o} 根本不是一个字节串对象，则 @ref{3d70,,PyBytes_AsString()} 将返回 @code{NULL} 并引发 @ref{192,,TypeError}。
@end deffn

@geindex PyBytes_AS_STRING (C 函数)
@anchor{c-api/bytes c PyBytes_AS_STRING}@anchor{3d71}
@deffn {C 函数} char* PyBytes_AS_STRING (PyObject@w{ }*string)

宏版本的 @ref{3d70,,PyBytes_AsString()} 但是不带错误检测。
@end deffn

@geindex PyBytes_AsStringAndSize (C 函数)
@anchor{c-api/bytes c PyBytes_AsStringAndSize}@anchor{3d72}
@deffn {C 函数} int PyBytes_AsStringAndSize (PyObject@w{ }*obj, char@w{ }**buffer, Py_ssize_t@w{ }*length)

通过输出变量 @emph{buffer} 和 @emph{length} 返回以 null 为终止符的对象 @emph{obj} 的内容。

如果 @emph{length} 为 @code{NULL}，字节串对象就不包含嵌入的空字节；如果包含，则该函数将返回 @code{-1} 并引发 @ref{1fb,,ValueError}。

该缓冲区指向 @emph{obj} 的内部缓冲，它的末尾包含一个额外的空字节（不算在 @emph{length} 当中）。 该数据不可通过任何方式来修改，除非是刚使用 @code{PyBytes_FromStringAndSize(NULL, size)} 创建该对象。 它不可被撤销分配。 如果 @emph{obj} 根本不是一个字节串对象，则 @ref{3d72,,PyBytes_AsStringAndSize()} 将返回 @code{-1} 并引发 @ref{192,,TypeError}。


在 3.5 版更改: 以前，当字节串对象中出现嵌入的空字节时将引发 @ref{192,,TypeError}。

@end deffn

@geindex PyBytes_Concat (C 函数)
@anchor{c-api/bytes c PyBytes_Concat}@anchor{3d73}
@deffn {C 函数} void PyBytes_Concat (PyObject@w{ }**bytes, PyObject@w{ }*newpart)

在 @emph{*bytes} 中创建新的字节串对象，其中包含添加到 @emph{bytes} 的 @emph{newpart} 的内容；调用者将获得新的引用。 对 @emph{bytes} 原值的引用将被收回。 如果无法创建新对象，对 @emph{bytes} 的旧引用仍将被丢弃且 @emph{*bytes} 的值将被设为 @code{NULL}；并将设置适当的异常。
@end deffn

@geindex PyBytes_ConcatAndDel (C 函数)
@anchor{c-api/bytes c PyBytes_ConcatAndDel}@anchor{3d74}
@deffn {C 函数} void PyBytes_ConcatAndDel (PyObject@w{ }**bytes, PyObject@w{ }*newpart)

在 @emph{*bytes} 中创建新的字节串对象，其中包含添加到 @emph{bytes} 的 @emph{newpart} 的内容。 此版本会减少 @emph{newpart} 的引用计数。
@end deffn

@geindex _PyBytes_Resize (C 函数)
@anchor{c-api/bytes c _PyBytes_Resize}@anchor{fdd}
@deffn {C 函数} int _PyBytes_Resize (PyObject@w{ }**bytes, Py_ssize_t@w{ }newsize)

改变字节串大小的一种方式，即使其为“不可变对象”。 此方式仅用于创建全新的字节串对象；如果字节串在代码的其他部分已知则不可使用此方式。 如果输入字节串对象的引用计数不为一则调用此函数将报错。 传入一个现有字节串对象的地址作为 lvalue（它可能会被写入），并传入希望的新大小。 当成功时，@emph{*bytes} 将存放改变大小后的字节串对象并返回 @code{0}；@emph{*bytes} 中的地址可能与其输入值不同。 如果重新分配失败，则 @emph{*bytes} 上的原字节串对象将被撤销分配，@emph{*bytes} 会被设为 @code{NULL}，同时设置 @ref{f9f,,MemoryError} 并返回 @code{-1}。
@end deffn

@node 字节数组对象,Unicode Objects and Codecs,bytes 对象<2>,序列对象
@anchor{c-api/bytearray doc}@anchor{3d75}@anchor{c-api/bytearray byte-array-objects}@anchor{3d76}@anchor{c-api/bytearray bytearrayobjects}@anchor{3d77}
@subsubsection 字节数组对象


@geindex 对象; bytearray

@geindex PyByteArrayObject (C 类型)
@anchor{c-api/bytearray c PyByteArrayObject}@anchor{3d78}
@deffn {C 类型} PyByteArrayObject

这个 @ref{4b5,,PyObject} 的子类型表示一个 Python 字节数组对象。
@end deffn

@geindex PyByteArray_Type (C 变量)
@anchor{c-api/bytearray c PyByteArray_Type}@anchor{3d79}
@deffn {C 变量} PyTypeObject PyByteArray_Type

Python bytearray 类型表示为 @ref{2d6,,PyTypeObject} 的实例；这与Python层面的 @ref{32b,,bytearray} 是相同的对象。
@end deffn

@menu
* 类型检查宏:: 
* 直接 API 函数:: 
* 宏:: 

@end menu

@node 类型检查宏,直接 API 函数,,字节数组对象
@anchor{c-api/bytearray type-check-macros}@anchor{3d7a}
@subsubsection 类型检查宏


@geindex PyByteArray_Check (C 函数)
@anchor{c-api/bytearray c PyByteArray_Check}@anchor{3d7b}
@deffn {C 函数} int PyByteArray_Check (PyObject@w{ }*o)

当对象 @emph{o} 是一个字节数组对象而且是一个字节数组类型的子类型实例时，返回真。
@end deffn

@geindex PyByteArray_CheckExact (C 函数)
@anchor{c-api/bytearray c PyByteArray_CheckExact}@anchor{3d7c}
@deffn {C 函数} int PyByteArray_CheckExact (PyObject@w{ }*o)

当对象 @emph{o} 是一个字节数组对象，但不是一个字节数组类型的子类型实例时，返回真。
@end deffn

@node 直接 API 函数,宏,类型检查宏,字节数组对象
@anchor{c-api/bytearray direct-api-functions}@anchor{3d7d}
@subsubsection 直接 API 函数


@geindex PyByteArray_FromObject (C 函数)
@anchor{c-api/bytearray c PyByteArray_FromObject}@anchor{d1a}
@deffn {C 函数} PyObject* PyByteArray_FromObject (PyObject@w{ }*o)
@emph{Return value: New reference.}
根据任何实现了 @ref{15d6,,缓冲区协议} 的对象 @emph{o}，返回一个新的字节数组对象。

@c XXX expand about the buffer protocol, at least somewhere
@end deffn

@geindex PyByteArray_FromStringAndSize (C 函数)
@anchor{c-api/bytearray c PyByteArray_FromStringAndSize}@anchor{d1b}
@deffn {C 函数} PyObject* PyByteArray_FromStringAndSize (const char@w{ }*string, Py_ssize_t@w{ }len)
@emph{Return value: New reference.}
根据 @emph{string} 及其长度 @emph{len} 创建一个新的 bytearray 对象。 当失败时返回 @code{NULL}。
@end deffn

@geindex PyByteArray_Concat (C 函数)
@anchor{c-api/bytearray c PyByteArray_Concat}@anchor{3d7e}
@deffn {C 函数} PyObject* PyByteArray_Concat (PyObject@w{ }*a, PyObject@w{ }*b)
@emph{Return value: New reference.}
连接字节数组 @emph{a} 和 @emph{b} 并返回一个带有结果的新的字节数组。
@end deffn

@geindex PyByteArray_Size (C 函数)
@anchor{c-api/bytearray c PyByteArray_Size}@anchor{3d7f}
@deffn {C 函数} Py_ssize_t PyByteArray_Size (PyObject@w{ }*bytearray)

在检查 @code{NULL} 指针后返回 @emph{bytearray} 的大小。
@end deffn

@geindex PyByteArray_AsString (C 函数)
@anchor{c-api/bytearray c PyByteArray_AsString}@anchor{3d80}
@deffn {C 函数} char* PyByteArray_AsString (PyObject@w{ }*bytearray)

在检查 @code{NULL} 指针后返回将 @emph{bytearray} 返回为一个字符数组。 返回的数组总是会附加一个额外的空字节。
@end deffn

@geindex PyByteArray_Resize (C 函数)
@anchor{c-api/bytearray c PyByteArray_Resize}@anchor{3d81}
@deffn {C 函数} int PyByteArray_Resize (PyObject@w{ }*bytearray, Py_ssize_t@w{ }len)

将 @emph{bytearray} 的内部缓冲区的大小调整为 @emph{len}。
@end deffn

@node 宏,,直接 API 函数,字节数组对象
@anchor{c-api/bytearray macros}@anchor{3d82}
@subsubsection 宏


这些宏减低安全性以换取性能，它们不检查指针。

@geindex PyByteArray_AS_STRING (C 函数)
@anchor{c-api/bytearray c PyByteArray_AS_STRING}@anchor{3d83}
@deffn {C 函数} char* PyByteArray_AS_STRING (PyObject@w{ }*bytearray)

C函数 @ref{3d80,,PyByteArray_AsString()} 的宏版本。
@end deffn

@geindex PyByteArray_GET_SIZE (C 函数)
@anchor{c-api/bytearray c PyByteArray_GET_SIZE}@anchor{3d84}
@deffn {C 函数} Py_ssize_t PyByteArray_GET_SIZE (PyObject@w{ }*bytearray)

C函数 @ref{3d7f,,PyByteArray_Size()} 的宏版本。
@end deffn

@node Unicode Objects and Codecs,元组对象,字节数组对象,序列对象
@anchor{c-api/unicode doc}@anchor{b15}@anchor{c-api/unicode unicode-objects-and-codecs}@anchor{3d85}@anchor{c-api/unicode unicodeobjects}@anchor{3d86}
@subsubsection Unicode Objects and Codecs


@menu
* Unicode对象:: 
* Built-in Codecs:: 
* Methods and Slot Functions:: 

@end menu

@node Unicode对象,Built-in Codecs,,Unicode Objects and Codecs
@anchor{c-api/unicode unicode-objects}@anchor{3d87}
@subsubsection Unicode对象


Since the implementation of 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393} in Python 3.3, Unicode objects internally
use a variety of representations, in order to allow handling the complete range
of Unicode characters while staying memory efficient.  There are special cases
for strings where all code points are below 128, 256, or 65536; otherwise, code
points must be below 1114112 (which is the full Unicode range).

@ref{ae9,,Py_UNICODE*} and UTF-8 representations are created on demand and cached
in the Unicode object.  The @ref{ae9,,Py_UNICODE*} representation is deprecated
and inefficient; it should be avoided in performance- or memory-sensitive
situations.

Due to the transition between the old APIs and the new APIs, Unicode objects
can internally be in two states depending on how they were created:


@itemize *

@item 
"canonical" Unicode objects are all objects created by a non-deprecated
Unicode API.  They use the most efficient representation allowed by the
implementation.

@item 
"legacy" Unicode objects have been created through one of the deprecated
APIs (typically @ref{aea,,PyUnicode_FromUnicode()}) and only bear the
@ref{ae9,,Py_UNICODE*} representation; you will have to call
@ref{ad1,,PyUnicode_READY()} on them before calling any other API.
@end itemize

@menu
* Unicode类型:: 
* Unicode字符属性:: 
* Creating and accessing Unicode strings:: 
* Deprecated Py_UNICODE APIs:: 
* Locale Encoding:: 
* File System Encoding:: 
* wchar_t Support:: 

@end menu

@node Unicode类型,Unicode字符属性,,Unicode对象
@anchor{c-api/unicode unicode-type}@anchor{3d88}
@subsubsection Unicode类型


These are the basic Unicode object types used for the Unicode implementation in
Python:

@geindex Py_UCS4 (C 类型)
@geindex Py_UCS2 (C 类型)
@geindex Py_UCS1 (C 类型)
@anchor{c-api/unicode c Py_UCS4}@anchor{ace}
@deffn {C 类型} Py_UCS4
@anchor{c-api/unicode c Py_UCS2}@anchor{acd}
@deffnx {C 类型} Py_UCS2
@anchor{c-api/unicode c Py_UCS1}@anchor{acc}
@deffnx {C 类型} Py_UCS1

These types are typedefs for unsigned integer types wide enough to contain
characters of 32 bits, 16 bits and 8 bits, respectively.  When dealing with
single Unicode characters, use @ref{ace,,Py_UCS4}.


3.3 新版功能.

@end deffn

@geindex Py_UNICODE (C 类型)
@anchor{c-api/unicode c Py_UNICODE}@anchor{ae9}
@deffn {C 类型} Py_UNICODE

This is a typedef of @code{wchar_t}, which is a 16-bit type or 32-bit type
depending on the platform.


在 3.3 版更改: In previous versions, this was a 16-bit type or a 32-bit type depending on
whether you selected a "narrow" or "wide" Unicode version of Python at
build time.

@end deffn

@geindex PyASCIIObject (C 类型)
@geindex PyCompactUnicodeObject (C 类型)
@geindex PyUnicodeObject (C 类型)
@anchor{c-api/unicode c PyASCIIObject}@anchor{acf}
@deffn {C 类型} PyASCIIObject
@anchor{c-api/unicode c PyCompactUnicodeObject}@anchor{ad0}
@deffnx {C 类型} PyCompactUnicodeObject
@anchor{c-api/unicode c PyUnicodeObject}@anchor{3d89}
@deffnx {C 类型} PyUnicodeObject

These subtypes of @ref{4b5,,PyObject} represent a Python Unicode object.  In
almost all cases, they shouldn't be used directly, since all API functions
that deal with Unicode objects take and return @ref{4b5,,PyObject} pointers.


3.3 新版功能.

@end deffn

@geindex PyUnicode_Type (C 变量)
@anchor{c-api/unicode c PyUnicode_Type}@anchor{3d8a}
@deffn {C 变量} PyTypeObject PyUnicode_Type

This instance of @ref{2d6,,PyTypeObject} represents the Python Unicode type.  It
is exposed to Python code as @code{str}.
@end deffn

The following APIs are really C macros and can be used to do fast checks and to
access internal read-only data of Unicode objects:

@geindex PyUnicode_Check (C 函数)
@anchor{c-api/unicode c PyUnicode_Check}@anchor{3d8b}
@deffn {C 函数} int PyUnicode_Check (PyObject@w{ }*o)

Return true if the object @emph{o} is a Unicode object or an instance of a Unicode
subtype.
@end deffn

@geindex PyUnicode_CheckExact (C 函数)
@anchor{c-api/unicode c PyUnicode_CheckExact}@anchor{3d8c}
@deffn {C 函数} int PyUnicode_CheckExact (PyObject@w{ }*o)

Return true if the object @emph{o} is a Unicode object, but not an instance of a
subtype.
@end deffn

@geindex PyUnicode_READY (C 函数)
@anchor{c-api/unicode c PyUnicode_READY}@anchor{ad1}
@deffn {C 函数} int PyUnicode_READY (PyObject@w{ }*o)

Ensure the string object @emph{o} is in the "canonical" representation.  This is
required before using any of the access macros described below.

@c XXX expand on when it is not required

Returns @code{0} on success and @code{-1} with an exception set on failure, which in
particular happens if memory allocation fails.


3.3 新版功能.

@end deffn

@geindex PyUnicode_GET_LENGTH (C 函数)
@anchor{c-api/unicode c PyUnicode_GET_LENGTH}@anchor{ac7}
@deffn {C 函数} Py_ssize_t PyUnicode_GET_LENGTH (PyObject@w{ }*o)

Return the length of the Unicode string, in code points.  @emph{o} has to be a
Unicode object in the "canonical" representation (not checked).


3.3 新版功能.

@end deffn

@geindex PyUnicode_1BYTE_DATA (C 函数)
@geindex PyUnicode_2BYTE_DATA (C 函数)
@geindex PyUnicode_4BYTE_DATA (C 函数)
@anchor{c-api/unicode c PyUnicode_1BYTE_DATA}@anchor{ad6}
@deffn {C 函数} Py_UCS1* PyUnicode_1BYTE_DATA (PyObject@w{ }*o)
@anchor{c-api/unicode c PyUnicode_2BYTE_DATA}@anchor{ad7}
@deffnx {C 函数} Py_UCS2* PyUnicode_2BYTE_DATA (PyObject@w{ }*o)
@anchor{c-api/unicode c PyUnicode_4BYTE_DATA}@anchor{ad8}
@deffnx {C 函数} Py_UCS4* PyUnicode_4BYTE_DATA (PyObject@w{ }*o)

Return a pointer to the canonical representation cast to UCS1, UCS2 or UCS4
integer types for direct character access.  No checks are performed if the
canonical representation has the correct character size; use
@ref{ad9,,PyUnicode_KIND()} to select the right macro.  Make sure
@ref{ad1,,PyUnicode_READY()} has been called before accessing this.


3.3 新版功能.

@end deffn

@geindex PyUnicode_WCHAR_KIND (C 宏)
@geindex PyUnicode_1BYTE_KIND (C 宏)
@geindex PyUnicode_2BYTE_KIND (C 宏)
@geindex PyUnicode_4BYTE_KIND (C 宏)
@anchor{c-api/unicode c PyUnicode_WCHAR_KIND}@anchor{ada}
@deffn {C 宏} PyUnicode_WCHAR_KIND
@anchor{c-api/unicode c PyUnicode_1BYTE_KIND}@anchor{adb}
@deffnx {C 宏} PyUnicode_1BYTE_KIND
@anchor{c-api/unicode c PyUnicode_2BYTE_KIND}@anchor{adc}
@deffnx {C 宏} PyUnicode_2BYTE_KIND
@anchor{c-api/unicode c PyUnicode_4BYTE_KIND}@anchor{add}
@deffnx {C 宏} PyUnicode_4BYTE_KIND

Return values of the @ref{ad9,,PyUnicode_KIND()} macro.


3.3 新版功能.

@end deffn

@geindex PyUnicode_KIND (C 函数)
@anchor{c-api/unicode c PyUnicode_KIND}@anchor{ad9}
@deffn {C 函数} int PyUnicode_KIND (PyObject@w{ }*o)

Return one of the PyUnicode kind constants (see above) that indicate how many
bytes per character this Unicode object uses to store its data.  @emph{o} has to
be a Unicode object in the "canonical" representation (not checked).

@c XXX document "0" return value?


3.3 新版功能.

@end deffn

@geindex PyUnicode_DATA (C 函数)
@anchor{c-api/unicode c PyUnicode_DATA}@anchor{ad5}
@deffn {C 函数} void* PyUnicode_DATA (PyObject@w{ }*o)

Return a void pointer to the raw Unicode buffer.  @emph{o} has to be a Unicode
object in the "canonical" representation (not checked).


3.3 新版功能.

@end deffn

@geindex PyUnicode_WRITE (C 函数)
@anchor{c-api/unicode c PyUnicode_WRITE}@anchor{ae0}
@deffn {C 函数} void PyUnicode_WRITE (int@w{ }kind, void@w{ }*data, Py_ssize_t@w{ }index, Py_UCS4@w{ }value)

Write into a canonical representation @emph{data} (as obtained with
@ref{ad5,,PyUnicode_DATA()}).  This macro does not do any sanity checks and is
intended for usage in loops.  The caller should cache the @emph{kind} value and
@emph{data} pointer as obtained from other macro calls.  @emph{index} is the index in
the string (starts at 0) and @emph{value} is the new code point value which should
be written to that location.


3.3 新版功能.

@end deffn

@geindex PyUnicode_READ (C 函数)
@anchor{c-api/unicode c PyUnicode_READ}@anchor{ade}
@deffn {C 函数} Py_UCS4 PyUnicode_READ (int@w{ }kind, void@w{ }*data, Py_ssize_t@w{ }index)

Read a code point from a canonical representation @emph{data} (as obtained with
@ref{ad5,,PyUnicode_DATA()}).  No checks or ready calls are performed.


3.3 新版功能.

@end deffn

@geindex PyUnicode_READ_CHAR (C 函数)
@anchor{c-api/unicode c PyUnicode_READ_CHAR}@anchor{adf}
@deffn {C 函数} Py_UCS4 PyUnicode_READ_CHAR (PyObject@w{ }*o, Py_ssize_t@w{ }index)

Read a character from a Unicode object @emph{o}, which must be in the "canonical"
representation.  This is less efficient than @ref{ade,,PyUnicode_READ()} if you
do multiple consecutive reads.


3.3 新版功能.

@end deffn

@geindex PyUnicode_MAX_CHAR_VALUE (C 函数)
@anchor{c-api/unicode c PyUnicode_MAX_CHAR_VALUE}@anchor{ae1}
@deffn {C 函数} PyUnicode_MAX_CHAR_VALUE (PyObject@w{ }*o)

Return the maximum code point that is suitable for creating another string
based on @emph{o}, which must be in the "canonical" representation.  This is
always an approximation but more efficient than iterating over the string.


3.3 新版功能.

@end deffn

@geindex PyUnicode_ClearFreeList (C 函数)
@anchor{c-api/unicode c PyUnicode_ClearFreeList}@anchor{3d8d}
@deffn {C 函数} int PyUnicode_ClearFreeList ()

清空释放列表。 返回所释放的条目数。
@end deffn

@geindex PyUnicode_GET_SIZE (C 函数)
@anchor{c-api/unicode c PyUnicode_GET_SIZE}@anchor{af0}
@deffn {C 函数} Py_ssize_t PyUnicode_GET_SIZE (PyObject@w{ }*o)

Return the size of the deprecated @ref{ae9,,Py_UNICODE} representation, in
code units (this includes surrogate pairs as 2 units).  @emph{o} has to be a
Unicode object (not checked).


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Unicode API, please migrate to using
@ref{ac7,,PyUnicode_GET_LENGTH()}.

@end deffn

@geindex PyUnicode_GET_DATA_SIZE (C 函数)
@anchor{c-api/unicode c PyUnicode_GET_DATA_SIZE}@anchor{af2}
@deffn {C 函数} Py_ssize_t PyUnicode_GET_DATA_SIZE (PyObject@w{ }*o)

Return the size of the deprecated @ref{ae9,,Py_UNICODE} representation in
bytes.  @emph{o} has to be a Unicode object (not checked).


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Unicode API, please migrate to using
@ref{ac7,,PyUnicode_GET_LENGTH()}.

@end deffn

@geindex PyUnicode_AS_UNICODE (C 函数)
@geindex PyUnicode_AS_DATA (C 函数)
@anchor{c-api/unicode c PyUnicode_AS_UNICODE}@anchor{aec}
@deffn {C 函数} Py_UNICODE* PyUnicode_AS_UNICODE (PyObject@w{ }*o)
@anchor{c-api/unicode c PyUnicode_AS_DATA}@anchor{aef}
@deffnx {C 函数} const char* PyUnicode_AS_DATA (PyObject@w{ }*o)

Return a pointer to a @ref{ae9,,Py_UNICODE} representation of the object.  The
returned buffer is always terminated with an extra null code point.  It
may also contain embedded null code points, which would cause the string
to be truncated when used in most C functions.  The @code{AS_DATA} form
casts the pointer to @code{const char *}.  The @emph{o} argument has to be
a Unicode object (not checked).


在 3.3 版更改: This macro is now inefficient -- because in many cases the
@ref{ae9,,Py_UNICODE} representation does not exist and needs to be created
-- and can fail (return @code{NULL} with an exception set).  Try to port the
code to use the new @code{PyUnicode_nBYTE_DATA()} macros or use
@ref{ae0,,PyUnicode_WRITE()} or @ref{ade,,PyUnicode_READ()}.



Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style Unicode API, please migrate to using the
@code{PyUnicode_nBYTE_DATA()} family of macros.

@end deffn

@node Unicode字符属性,Creating and accessing Unicode strings,Unicode类型,Unicode对象
@anchor{c-api/unicode unicode-character-properties}@anchor{3d8e}
@subsubsection Unicode字符属性


Unicode provides many different character properties. The most often needed ones
are available through these macros which are mapped to C functions depending on
the Python configuration.

@geindex Py_UNICODE_ISSPACE (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISSPACE}@anchor{3d8f}
@deffn {C 函数} int Py_UNICODE_ISSPACE (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is a whitespace character.
@end deffn

@geindex Py_UNICODE_ISLOWER (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISLOWER}@anchor{3d90}
@deffn {C 函数} int Py_UNICODE_ISLOWER (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is a lowercase character.
@end deffn

@geindex Py_UNICODE_ISUPPER (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISUPPER}@anchor{3d91}
@deffn {C 函数} int Py_UNICODE_ISUPPER (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is an uppercase character.
@end deffn

@geindex Py_UNICODE_ISTITLE (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISTITLE}@anchor{3d92}
@deffn {C 函数} int Py_UNICODE_ISTITLE (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is a titlecase character.
@end deffn

@geindex Py_UNICODE_ISLINEBREAK (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISLINEBREAK}@anchor{3d93}
@deffn {C 函数} int Py_UNICODE_ISLINEBREAK (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is a linebreak character.
@end deffn

@geindex Py_UNICODE_ISDECIMAL (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISDECIMAL}@anchor{3d94}
@deffn {C 函数} int Py_UNICODE_ISDECIMAL (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is a decimal character.
@end deffn

@geindex Py_UNICODE_ISDIGIT (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISDIGIT}@anchor{3d95}
@deffn {C 函数} int Py_UNICODE_ISDIGIT (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is a digit character.
@end deffn

@geindex Py_UNICODE_ISNUMERIC (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISNUMERIC}@anchor{3d96}
@deffn {C 函数} int Py_UNICODE_ISNUMERIC (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is a numeric character.
@end deffn

@geindex Py_UNICODE_ISALPHA (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISALPHA}@anchor{3d97}
@deffn {C 函数} int Py_UNICODE_ISALPHA (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is an alphabetic character.
@end deffn

@geindex Py_UNICODE_ISALNUM (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISALNUM}@anchor{3d98}
@deffn {C 函数} int Py_UNICODE_ISALNUM (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is an alphanumeric character.
@end deffn

@geindex Py_UNICODE_ISPRINTABLE (C 函数)
@anchor{c-api/unicode c Py_UNICODE_ISPRINTABLE}@anchor{3d99}
@deffn {C 函数} int Py_UNICODE_ISPRINTABLE (Py_UNICODE@w{ }ch)

Return @code{1} or @code{0} depending on whether @emph{ch} is a printable character.
Nonprintable characters are those characters defined in the Unicode character
database as "Other" or "Separator", excepting the ASCII space (0x20) which is
considered printable.  (Note that printable characters in this context are
those which should not be escaped when @ref{7c6,,repr()} is invoked on a string.
It has no bearing on the handling of strings written to @ref{307,,sys.stdout} or
@ref{308,,sys.stderr}.)
@end deffn

These APIs can be used for fast direct character conversions:

@geindex Py_UNICODE_TOLOWER (C 函数)
@anchor{c-api/unicode c Py_UNICODE_TOLOWER}@anchor{3d9a}
@deffn {C 函数} Py_UNICODE Py_UNICODE_TOLOWER (Py_UNICODE@w{ }ch)

Return the character @emph{ch} converted to lower case.


3.3 版后已移除: This function uses simple case mappings.

@end deffn

@geindex Py_UNICODE_TOUPPER (C 函数)
@anchor{c-api/unicode c Py_UNICODE_TOUPPER}@anchor{3d9b}
@deffn {C 函数} Py_UNICODE Py_UNICODE_TOUPPER (Py_UNICODE@w{ }ch)

Return the character @emph{ch} converted to upper case.


3.3 版后已移除: This function uses simple case mappings.

@end deffn

@geindex Py_UNICODE_TOTITLE (C 函数)
@anchor{c-api/unicode c Py_UNICODE_TOTITLE}@anchor{3d9c}
@deffn {C 函数} Py_UNICODE Py_UNICODE_TOTITLE (Py_UNICODE@w{ }ch)

Return the character @emph{ch} converted to title case.


3.3 版后已移除: This function uses simple case mappings.

@end deffn

@geindex Py_UNICODE_TODECIMAL (C 函数)
@anchor{c-api/unicode c Py_UNICODE_TODECIMAL}@anchor{3d9d}
@deffn {C 函数} int Py_UNICODE_TODECIMAL (Py_UNICODE@w{ }ch)

Return the character @emph{ch} converted to a decimal positive integer.  Return
@code{-1} if this is not possible.  This macro does not raise exceptions.
@end deffn

@geindex Py_UNICODE_TODIGIT (C 函数)
@anchor{c-api/unicode c Py_UNICODE_TODIGIT}@anchor{3d9e}
@deffn {C 函数} int Py_UNICODE_TODIGIT (Py_UNICODE@w{ }ch)

Return the character @emph{ch} converted to a single digit integer. Return @code{-1} if
this is not possible.  This macro does not raise exceptions.
@end deffn

@geindex Py_UNICODE_TONUMERIC (C 函数)
@anchor{c-api/unicode c Py_UNICODE_TONUMERIC}@anchor{3d9f}
@deffn {C 函数} double Py_UNICODE_TONUMERIC (Py_UNICODE@w{ }ch)

Return the character @emph{ch} converted to a double. Return @code{-1.0} if this is not
possible.  This macro does not raise exceptions.
@end deffn

These APIs can be used to work with surrogates:

@geindex Py_UNICODE_IS_SURROGATE (C 宏)
@anchor{c-api/unicode c Py_UNICODE_IS_SURROGATE}@anchor{3da0}
@deffn {C 宏} Py_UNICODE_IS_SURROGATE (ch)

Check if @emph{ch} is a surrogate (@code{0xD800 <= ch <= 0xDFFF}).
@end deffn

@geindex Py_UNICODE_IS_HIGH_SURROGATE (C 宏)
@anchor{c-api/unicode c Py_UNICODE_IS_HIGH_SURROGATE}@anchor{3da1}
@deffn {C 宏} Py_UNICODE_IS_HIGH_SURROGATE (ch)

Check if @emph{ch} is a high surrogate (@code{0xD800 <= ch <= 0xDBFF}).
@end deffn

@geindex Py_UNICODE_IS_LOW_SURROGATE (C 宏)
@anchor{c-api/unicode c Py_UNICODE_IS_LOW_SURROGATE}@anchor{3da2}
@deffn {C 宏} Py_UNICODE_IS_LOW_SURROGATE (ch)

Check if @emph{ch} is a low surrogate (@code{0xDC00 <= ch <= 0xDFFF}).
@end deffn

@geindex Py_UNICODE_JOIN_SURROGATES (C 宏)
@anchor{c-api/unicode c Py_UNICODE_JOIN_SURROGATES}@anchor{3da3}
@deffn {C 宏} Py_UNICODE_JOIN_SURROGATES (high, low)

Join two surrogate characters and return a single Py_UCS4 value.
@emph{high} and @emph{low} are respectively the leading and trailing surrogates in a
surrogate pair.
@end deffn

@node Creating and accessing Unicode strings,Deprecated Py_UNICODE APIs,Unicode字符属性,Unicode对象
@anchor{c-api/unicode creating-and-accessing-unicode-strings}@anchor{3da4}
@subsubsection Creating and accessing Unicode strings


To create Unicode objects and access their basic sequence properties, use these
APIs:

@geindex PyUnicode_New (C 函数)
@anchor{c-api/unicode c PyUnicode_New}@anchor{ac8}
@deffn {C 函数} PyObject* PyUnicode_New (Py_ssize_t@w{ }size, Py_UCS4@w{ }maxchar)
@emph{Return value: New reference.}
Create a new Unicode object.  @emph{maxchar} should be the true maximum code point
to be placed in the string.  As an approximation, it can be rounded up to the
nearest value in the sequence 127, 255, 65535, 1114111.

This is the recommended way to allocate a new Unicode object.  Objects
created using this function are not resizable.


3.3 新版功能.

@end deffn

@geindex PyUnicode_FromKindAndData (C 函数)
@anchor{c-api/unicode c PyUnicode_FromKindAndData}@anchor{ad2}
@deffn {C 函数} PyObject* PyUnicode_FromKindAndData (int@w{ }kind, const void@w{ }*buffer, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
Create a new Unicode object with the given @emph{kind} (possible values are
@ref{adb,,PyUnicode_1BYTE_KIND} etc., as returned by
@ref{ad9,,PyUnicode_KIND()}).  The @emph{buffer} must point to an array of @emph{size}
units of 1, 2 or 4 bytes per character, as given by the kind.


3.3 新版功能.

@end deffn

@geindex PyUnicode_FromStringAndSize (C 函数)
@anchor{c-api/unicode c PyUnicode_FromStringAndSize}@anchor{3da5}
@deffn {C 函数} PyObject* PyUnicode_FromStringAndSize (const char@w{ }*u, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
Create a Unicode object from the char buffer @emph{u}.  The bytes will be
interpreted as being UTF-8 encoded.  The buffer is copied into the new
object. If the buffer is not @code{NULL}, the return value might be a shared
object, i.e. modification of the data is not allowed.

If @emph{u} is @code{NULL}, this function behaves like @ref{aea,,PyUnicode_FromUnicode()}
with the buffer set to @code{NULL}.  This usage is deprecated in favor of
@ref{ac8,,PyUnicode_New()}.
@end deffn

@geindex PyUnicode_FromString (C 函数)
@anchor{c-api/unicode c PyUnicode_FromString}@anchor{3b35}
@deffn {C 函数} PyObject *PyUnicode_FromString (const char@w{ }*u)
@emph{Return value: New reference.}
Create a Unicode object from a UTF-8 encoded null-terminated char buffer
@emph{u}.
@end deffn

@geindex PyUnicode_FromFormat (C 函数)
@anchor{c-api/unicode c PyUnicode_FromFormat}@anchor{7c5}
@deffn {C 函数} PyObject* PyUnicode_FromFormat (const char@w{ }*format, ...)
@emph{Return value: New reference.}
Take a C @code{printf()}-style @emph{format} string and a variable number of
arguments, calculate the size of the resulting Python Unicode string and return
a string with the values formatted into it.  The variable arguments must be C
types and must correspond exactly to the format characters in the @emph{format}
ASCII-encoded string. The following format characters are allowed:

@c % This should be exactly the same as the table in PyErr_Format.

@c % The descriptions for %zd and %zu are wrong, but the truth is complicated

@c % because not all compilers support the %z width modifier -- we fake it

@c % when necessary via interpolating PY_FORMAT_SIZE_T.

@c % Similar comments apply to the %ll width modifier and


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

格式字符

@tab

类型

@tab

注释

@item

@code{%%}

@tab

@emph{不适用}

@tab

文字%字符。

@item

@code{%c}

@tab

int

@tab

单个字符，表示为C 语言的整型。

@item

@code{%d}

@tab

int

@tab

相当于 @code{printf("%d")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%u}

@tab

unsigned int

@tab

相当于 @code{printf("%u")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%ld}

@tab

长整型

@tab

相当于 @code{printf("%ld")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%li}

@tab

长整型

@tab

相当于 @code{printf("%li")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%lu}

@tab

unsigned long

@tab

相当于 @code{printf("%lu")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%lld}

@tab

long long

@tab

相当于 @code{printf("%lld")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%lli}

@tab

long long

@tab

相当于 @code{printf("%lli")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%llu}

@tab

unsigned long long

@tab

相当于 @code{printf("%llu")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%zd}

@tab

Py_ssize_t

@tab

相当于 @code{printf("%zd")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%zi}

@tab

Py_ssize_t

@tab

相当于 @code{printf("%zi")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%zu}

@tab

size_t

@tab

相当于 @code{printf("%zu")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%i}

@tab

int

@tab

相当于 @code{printf("%i")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%x}

@tab

int

@tab

相当于 @code{printf("%x")}. @footnote{@w{(1)} 
For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd, zi,
zu, i, x): the 0-conversion flag has effect even when a precision is given.
}

@item

@code{%s}

@tab

const char*

@tab

以 null 为终止符的 C 字符数组。

@item

@code{%p}

@tab

const void*

@tab

一个 C 指针的十六进制表示形式。 基本等价于 @code{printf("%p")} 但它会确保以字面值 @code{0x} 开头，不论系统平台上 @code{printf} 的输出是什么。

@item

@code{%A}

@tab

PyObject*

@tab

@ref{d45,,ascii()} 调用的结果。

@item

@code{%U}

@tab

PyObject*

@tab

A Unicode object.

@item

@code{%V}

@tab

PyObject*,
const char*

@tab

A Unicode object (which may be
@code{NULL}) and a null-terminated
C character array as a second
parameter (which will be used,
if the first parameter is
@code{NULL}).

@item

@code{%S}

@tab

PyObject*

@tab

The result of calling
@ref{963,,PyObject_Str()}.

@item

@code{%R}

@tab

PyObject*

@tab

The result of calling
@ref{962,,PyObject_Repr()}.

@end multitable


An unrecognized format character causes all the rest of the format string to be
copied as-is to the result string, and any extra arguments discarded.

@cartouche
@quotation 注解 
The width formatter unit is number of characters rather than bytes.
The precision formatter unit is number of bytes for @code{"%s"} and
@code{"%V"} (if the @code{PyObject*} argument is @code{NULL}), and a number of
characters for @code{"%A"}, @code{"%U"}, @code{"%S"}, @code{"%R"} and @code{"%V"}
(if the @code{PyObject*} argument is not @code{NULL}).
@end quotation
@end cartouche


在 3.2 版更改: Support for @code{"%lld"} and @code{"%llu"} added.



在 3.3 版更改: Support for @code{"%li"}, @code{"%lli"} and @code{"%zi"} added.



在 3.4 版更改: Support width and precision formatter for @code{"%s"}, @code{"%A"}, @code{"%U"},
@code{"%V"}, @code{"%S"}, @code{"%R"} added.

@end deffn

@geindex PyUnicode_FromFormatV (C 函数)
@anchor{c-api/unicode c PyUnicode_FromFormatV}@anchor{3bf5}
@deffn {C 函数} PyObject* PyUnicode_FromFormatV (const char@w{ }*format, va_list@w{ }vargs)
@emph{Return value: New reference.}
Identical to @ref{7c5,,PyUnicode_FromFormat()} except that it takes exactly two
arguments.
@end deffn

@geindex PyUnicode_FromEncodedObject (C 函数)
@anchor{c-api/unicode c PyUnicode_FromEncodedObject}@anchor{3da6}
@deffn {C 函数} PyObject* PyUnicode_FromEncodedObject (PyObject@w{ }*obj, const char@w{ }*encoding, const char@w{ }*errors)
@emph{Return value: New reference.}
Decode an encoded object @emph{obj} to a Unicode object.

@ref{32a,,bytes}, @ref{32b,,bytearray} and other
@ref{5e3,,bytes-like objects}
are decoded according to the given @emph{encoding} and using the error handling
defined by @emph{errors}. Both can be @code{NULL} to have the interface use the default
values (see @ref{3da7,,Built-in Codecs} for details).

All other objects, including Unicode objects, cause a @ref{192,,TypeError} to be
set.

The API returns @code{NULL} if there was an error.  The caller is responsible for
decref'ing the returned objects.
@end deffn

@geindex PyUnicode_GetLength (C 函数)
@anchor{c-api/unicode c PyUnicode_GetLength}@anchor{ac6}
@deffn {C 函数} Py_ssize_t PyUnicode_GetLength (PyObject@w{ }*unicode)

Return the length of the Unicode object, in code points.


3.3 新版功能.

@end deffn

@geindex PyUnicode_CopyCharacters (C 函数)
@anchor{c-api/unicode c PyUnicode_CopyCharacters}@anchor{ac5}
@deffn {C 函数} Py_ssize_t PyUnicode_CopyCharacters (PyObject@w{ }*to, Py_ssize_t@w{ }to_start, PyObject@w{ }*from, Py_ssize_t@w{ }from_start, Py_ssize_t@w{ }how_many)

Copy characters from one Unicode object into another.  This function performs
character conversion when necessary and falls back to @code{memcpy()} if
possible.  Returns @code{-1} and sets an exception on error, otherwise returns
the number of copied characters.


3.3 新版功能.

@end deffn

@geindex PyUnicode_Fill (C 函数)
@anchor{c-api/unicode c PyUnicode_Fill}@anchor{af6}
@deffn {C 函数} Py_ssize_t PyUnicode_Fill (PyObject@w{ }*unicode, Py_ssize_t@w{ }start, Py_ssize_t@w{ }length, Py_UCS4@w{ }fill_char)

Fill a string with a character: write @emph{fill_char} into
@code{unicode[start:start+length]}.

Fail if @emph{fill_char} is bigger than the string maximum character, or if the
string has more than 1 reference.

Return the number of written character, or return @code{-1} and raise an
exception on error.


3.3 新版功能.

@end deffn

@geindex PyUnicode_WriteChar (C 函数)
@anchor{c-api/unicode c PyUnicode_WriteChar}@anchor{acb}
@deffn {C 函数} int PyUnicode_WriteChar (PyObject@w{ }*unicode, Py_ssize_t@w{ }index, Py_UCS4@w{ }character)

Write a character to a string.  The string must have been created through
@ref{ac8,,PyUnicode_New()}.  Since Unicode strings are supposed to be immutable,
the string must not be shared, or have been hashed yet.

This function checks that @emph{unicode} is a Unicode object, that the index is
not out of bounds, and that the object can be modified safely (i.e. that it
its reference count is one).


3.3 新版功能.

@end deffn

@geindex PyUnicode_ReadChar (C 函数)
@anchor{c-api/unicode c PyUnicode_ReadChar}@anchor{aca}
@deffn {C 函数} Py_UCS4 PyUnicode_ReadChar (PyObject@w{ }*unicode, Py_ssize_t@w{ }index)

Read a character from a string.  This function checks that @emph{unicode} is a
Unicode object and the index is not out of bounds, in contrast to the macro
version @ref{adf,,PyUnicode_READ_CHAR()}.


3.3 新版功能.

@end deffn

@geindex PyUnicode_Substring (C 函数)
@anchor{c-api/unicode c PyUnicode_Substring}@anchor{ac9}
@deffn {C 函数} PyObject* PyUnicode_Substring (PyObject@w{ }*str, Py_ssize_t@w{ }start, Py_ssize_t@w{ }end)
@emph{Return value: New reference.}
Return a substring of @emph{str}, from character index @emph{start} (included) to
character index @emph{end} (excluded).  Negative indices are not supported.


3.3 新版功能.

@end deffn

@geindex PyUnicode_AsUCS4 (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUCS4}@anchor{ad3}
@deffn {C 函数} Py_UCS4* PyUnicode_AsUCS4 (PyObject@w{ }*u, Py_UCS4@w{ }*buffer, Py_ssize_t@w{ }buflen, int@w{ }copy_null)

Copy the string @emph{u} into a UCS4 buffer, including a null character, if
@emph{copy_null} is set.  Returns @code{NULL} and sets an exception on error (in
particular, a @ref{5f6,,SystemError} if @emph{buflen} is smaller than the length of
@emph{u}).  @emph{buffer} is returned on success.


3.3 新版功能.

@end deffn

@geindex PyUnicode_AsUCS4Copy (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUCS4Copy}@anchor{ad4}
@deffn {C 函数} Py_UCS4* PyUnicode_AsUCS4Copy (PyObject@w{ }*u)

Copy the string @emph{u} into a new UCS4 buffer that is allocated using
@ref{4ff,,PyMem_Malloc()}.  If this fails, @code{NULL} is returned with a
@ref{f9f,,MemoryError} set.  The returned buffer always has an extra
null code point appended.


3.3 新版功能.

@end deffn

@node Deprecated Py_UNICODE APIs,Locale Encoding,Creating and accessing Unicode strings,Unicode对象
@anchor{c-api/unicode deprecated-py-unicode-apis}@anchor{3da8}
@subsubsection Deprecated Py_UNICODE APIs



Deprecated since version 3.3, will be removed in version 4.0.


These API functions are deprecated with the implementation of 
@geindex Python 提高建议; PEP 393
PEP 393@footnote{https://www.python.org/dev/peps/pep-0393}.
Extension modules can continue using them, as they will not be removed in Python
3.x, but need to be aware that their use can now cause performance and memory hits.

@geindex PyUnicode_FromUnicode (C 函数)
@anchor{c-api/unicode c PyUnicode_FromUnicode}@anchor{aea}
@deffn {C 函数} PyObject* PyUnicode_FromUnicode (const Py_UNICODE@w{ }*u, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
Create a Unicode object from the Py_UNICODE buffer @emph{u} of the given size. @emph{u}
may be @code{NULL} which causes the contents to be undefined. It is the user's
responsibility to fill in the needed data.  The buffer is copied into the new
object.

If the buffer is not @code{NULL}, the return value might be a shared object.
Therefore, modification of the resulting Unicode object is only allowed when
@emph{u} is @code{NULL}.

If the buffer is @code{NULL}, @ref{ad1,,PyUnicode_READY()} must be called once the
string content has been filled before using any of the access macros such as
@ref{ad9,,PyUnicode_KIND()}.

Please migrate to using @ref{ad2,,PyUnicode_FromKindAndData()},
@ref{aeb,,PyUnicode_FromWideChar()} or @ref{ac8,,PyUnicode_New()}.
@end deffn

@geindex PyUnicode_AsUnicode (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUnicode}@anchor{aed}
@deffn {C 函数} Py_UNICODE* PyUnicode_AsUnicode (PyObject@w{ }*unicode)

Return a read-only pointer to the Unicode object's internal
@ref{ae9,,Py_UNICODE} buffer, or @code{NULL} on error. This will create the
@ref{ae9,,Py_UNICODE*} representation of the object if it is not yet
available. The buffer is always terminated with an extra null code point.
Note that the resulting @ref{ae9,,Py_UNICODE} string may also contain
embedded null code points, which would cause the string to be truncated when
used in most C functions.

Please migrate to using @ref{ad3,,PyUnicode_AsUCS4()},
@ref{fe5,,PyUnicode_AsWideChar()}, @ref{aca,,PyUnicode_ReadChar()} or similar new
APIs.


Deprecated since version 3.3, will be removed in version 3.10.

@end deffn

@geindex PyUnicode_TransformDecimalToASCII (C 函数)
@anchor{c-api/unicode c PyUnicode_TransformDecimalToASCII}@anchor{b08}
@deffn {C 函数} PyObject* PyUnicode_TransformDecimalToASCII (Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
Create a Unicode object by replacing all decimal digits in
@ref{ae9,,Py_UNICODE} buffer of the given @emph{size} by ASCII digits 0--9
according to their decimal value.  Return @code{NULL} if an exception occurs.
@end deffn

@geindex PyUnicode_AsUnicodeAndSize (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUnicodeAndSize}@anchor{aee}
@deffn {C 函数} Py_UNICODE* PyUnicode_AsUnicodeAndSize (PyObject@w{ }*unicode, Py_ssize_t@w{ }*size)

Like @ref{aed,,PyUnicode_AsUnicode()}, but also saves the @ref{ae9,,Py_UNICODE()}
array length (excluding the extra null terminator) in @emph{size}.
Note that the resulting @ref{ae9,,Py_UNICODE*} string
may contain embedded null code points, which would cause the string to be
truncated when used in most C functions.


3.3 新版功能.

@end deffn

@geindex PyUnicode_AsUnicodeCopy (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUnicodeCopy}@anchor{af3}
@deffn {C 函数} Py_UNICODE* PyUnicode_AsUnicodeCopy (PyObject@w{ }*unicode)

Create a copy of a Unicode string ending with a null code point. Return @code{NULL}
and raise a @ref{f9f,,MemoryError} exception on memory allocation failure,
otherwise return a new allocated buffer (use @ref{da2,,PyMem_Free()} to free
the buffer). Note that the resulting @ref{ae9,,Py_UNICODE*} string may
contain embedded null code points, which would cause the string to be
truncated when used in most C functions.


3.2 新版功能.


Please migrate to using @ref{ad4,,PyUnicode_AsUCS4Copy()} or similar new APIs.
@end deffn

@geindex PyUnicode_GetSize (C 函数)
@anchor{c-api/unicode c PyUnicode_GetSize}@anchor{af1}
@deffn {C 函数} Py_ssize_t PyUnicode_GetSize (PyObject@w{ }*unicode)

Return the size of the deprecated @ref{ae9,,Py_UNICODE} representation, in
code units (this includes surrogate pairs as 2 units).

Please migrate to using @ref{ac6,,PyUnicode_GetLength()}.
@end deffn

@geindex PyUnicode_FromObject (C 函数)
@anchor{c-api/unicode c PyUnicode_FromObject}@anchor{3da9}
@deffn {C 函数} PyObject* PyUnicode_FromObject (PyObject@w{ }*obj)
@emph{Return value: New reference.}
Copy an instance of a Unicode subtype to a new true Unicode object if
necessary. If @emph{obj} is already a true Unicode object (not a subtype),
return the reference with incremented refcount.

Objects other than Unicode or its subtypes will cause a @ref{192,,TypeError}.
@end deffn

@node Locale Encoding,File System Encoding,Deprecated Py_UNICODE APIs,Unicode对象
@anchor{c-api/unicode locale-encoding}@anchor{3daa}
@subsubsection Locale Encoding


The current locale encoding can be used to decode text from the operating
system.

@geindex PyUnicode_DecodeLocaleAndSize (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeLocaleAndSize}@anchor{438}
@deffn {C 函数} PyObject* PyUnicode_DecodeLocaleAndSize (const char@w{ }*str, Py_ssize_t@w{ }len, const char@w{ }*errors)
@emph{Return value: New reference.}
Decode a string from UTF-8 on Android and VxWorks, or from the current
locale encoding on other platforms. The supported
error handlers are @code{"strict"} and @code{"surrogateescape"}
(
@geindex Python 提高建议; PEP 383
PEP 383@footnote{https://www.python.org/dev/peps/pep-0383}). The decoder uses @code{"strict"} error handler if
@emph{errors} is @code{NULL}.  @emph{str} must end with a null character but
cannot contain embedded null characters.

Use @ref{3beb,,PyUnicode_DecodeFSDefaultAndSize()} to decode a string from
@code{Py_FileSystemDefaultEncoding} (the locale encoding read at
Python startup).

This function ignores the Python UTF-8 mode.


@subsubheading 参见


The @ref{436,,Py_DecodeLocale()} function.



3.3 新版功能.



在 3.7 版更改: The function now also uses the current locale encoding for the
@code{surrogateescape} error handler, except on Android. Previously, @ref{436,,Py_DecodeLocale()}
was used for the @code{surrogateescape}, and the current locale encoding was
used for @code{strict}.

@end deffn

@geindex PyUnicode_DecodeLocale (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeLocale}@anchor{3dab}
@deffn {C 函数} PyObject* PyUnicode_DecodeLocale (const char@w{ }*str, const char@w{ }*errors)
@emph{Return value: New reference.}
Similar to @ref{438,,PyUnicode_DecodeLocaleAndSize()}, but compute the string
length using @code{strlen()}.


3.3 新版功能.

@end deffn

@geindex PyUnicode_EncodeLocale (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeLocale}@anchor{439}
@deffn {C 函数} PyObject* PyUnicode_EncodeLocale (PyObject@w{ }*unicode, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode a Unicode object to UTF-8 on Android and VxWorks, or to the current
locale encoding on other platforms. The
supported error handlers are @code{"strict"} and @code{"surrogateescape"}
(
@geindex Python 提高建议; PEP 383
PEP 383@footnote{https://www.python.org/dev/peps/pep-0383}). The encoder uses @code{"strict"} error handler if
@emph{errors} is @code{NULL}. Return a @ref{32a,,bytes} object. @emph{unicode} cannot
contain embedded null characters.

Use @ref{fde,,PyUnicode_EncodeFSDefault()} to encode a string to
@code{Py_FileSystemDefaultEncoding} (the locale encoding read at
Python startup).

This function ignores the Python UTF-8 mode.


@subsubheading 参见


The @ref{437,,Py_EncodeLocale()} function.



3.3 新版功能.



在 3.7 版更改: The function now also uses the current locale encoding for the
@code{surrogateescape} error handler, except on Android. Previously,
@ref{437,,Py_EncodeLocale()}
was used for the @code{surrogateescape}, and the current locale encoding was
used for @code{strict}.

@end deffn

@node File System Encoding,wchar_t Support,Locale Encoding,Unicode对象
@anchor{c-api/unicode file-system-encoding}@anchor{3dac}
@subsubsection File System Encoding


To encode and decode file names and other environment strings,
@code{Py_FileSystemDefaultEncoding} should be used as the encoding, and
@code{Py_FileSystemDefaultEncodeErrors} should be used as the error handler
(
@geindex Python 提高建议; PEP 383
PEP 383@footnote{https://www.python.org/dev/peps/pep-0383} and 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529}). To encode file names to @ref{32a,,bytes} during
argument parsing, the @code{"O&"} converter should be used, passing
@ref{5c9,,PyUnicode_FSConverter()} as the conversion function:

@geindex PyUnicode_FSConverter (C 函数)
@anchor{c-api/unicode c PyUnicode_FSConverter}@anchor{5c9}
@deffn {C 函数} int PyUnicode_FSConverter (PyObject*@w{ }obj, void*@w{ }result)

ParseTuple converter: encode @ref{329,,str} objects -- obtained directly or
through the @ref{4e5,,os.PathLike} interface -- to @ref{32a,,bytes} using
@ref{fde,,PyUnicode_EncodeFSDefault()}; @ref{32a,,bytes} objects are output as-is.
@emph{result} must be a @ref{d17,,PyBytesObject*} which must be released when it is
no longer used.


3.1 新版功能.



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

To decode file names to @ref{329,,str} during argument parsing, the @code{"O&"}
converter should be used, passing @ref{5ca,,PyUnicode_FSDecoder()} as the
conversion function:

@geindex PyUnicode_FSDecoder (C 函数)
@anchor{c-api/unicode c PyUnicode_FSDecoder}@anchor{5ca}
@deffn {C 函数} int PyUnicode_FSDecoder (PyObject*@w{ }obj, void*@w{ }result)

ParseTuple converter: decode @ref{32a,,bytes} objects -- obtained either
directly or indirectly through the @ref{4e5,,os.PathLike} interface -- to
@ref{329,,str} using @ref{3beb,,PyUnicode_DecodeFSDefaultAndSize()}; @ref{329,,str}
objects are output as-is. @emph{result} must be a @ref{3d89,,PyUnicodeObject*} which
must be released when it is no longer used.


3.2 新版功能.



在 3.6 版更改: 接受一个 @ref{363,,path-like object}。

@end deffn

@geindex PyUnicode_DecodeFSDefaultAndSize (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeFSDefaultAndSize}@anchor{3beb}
@deffn {C 函数} PyObject* PyUnicode_DecodeFSDefaultAndSize (const char@w{ }*s, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
Decode a string using @code{Py_FileSystemDefaultEncoding} and the
@code{Py_FileSystemDefaultEncodeErrors} error handler.

If @code{Py_FileSystemDefaultEncoding} is not set, fall back to the
locale encoding.

@code{Py_FileSystemDefaultEncoding} is initialized at startup from the
locale encoding and cannot be modified later. If you need to decode a string
from the current locale encoding, use
@ref{438,,PyUnicode_DecodeLocaleAndSize()}.


@subsubheading 参见


The @ref{436,,Py_DecodeLocale()} function.



在 3.6 版更改: Use @code{Py_FileSystemDefaultEncodeErrors} error handler.

@end deffn

@geindex PyUnicode_DecodeFSDefault (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeFSDefault}@anchor{3dad}
@deffn {C 函数} PyObject* PyUnicode_DecodeFSDefault (const char@w{ }*s)
@emph{Return value: New reference.}
Decode a null-terminated string using @code{Py_FileSystemDefaultEncoding}
and the @code{Py_FileSystemDefaultEncodeErrors} error handler.

If @code{Py_FileSystemDefaultEncoding} is not set, fall back to the
locale encoding.

Use @ref{3beb,,PyUnicode_DecodeFSDefaultAndSize()} if you know the string length.


在 3.6 版更改: Use @code{Py_FileSystemDefaultEncodeErrors} error handler.

@end deffn

@geindex PyUnicode_EncodeFSDefault (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeFSDefault}@anchor{fde}
@deffn {C 函数} PyObject* PyUnicode_EncodeFSDefault (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Encode a Unicode object to @code{Py_FileSystemDefaultEncoding} with the
@code{Py_FileSystemDefaultEncodeErrors} error handler, and return
@ref{32a,,bytes}. Note that the resulting @ref{32a,,bytes} object may contain
null bytes.

If @code{Py_FileSystemDefaultEncoding} is not set, fall back to the
locale encoding.

@code{Py_FileSystemDefaultEncoding} is initialized at startup from the
locale encoding and cannot be modified later. If you need to encode a string
to the current locale encoding, use @ref{439,,PyUnicode_EncodeLocale()}.


@subsubheading 参见


The @ref{437,,Py_EncodeLocale()} function.



3.2 新版功能.



在 3.6 版更改: Use @code{Py_FileSystemDefaultEncodeErrors} error handler.

@end deffn

@node wchar_t Support,,File System Encoding,Unicode对象
@anchor{c-api/unicode wchar-t-support}@anchor{3dae}
@subsubsection wchar_t Support


@code{wchar_t} support for platforms which support it:

@geindex PyUnicode_FromWideChar (C 函数)
@anchor{c-api/unicode c PyUnicode_FromWideChar}@anchor{aeb}
@deffn {C 函数} PyObject* PyUnicode_FromWideChar (const wchar_t@w{ }*w, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
Create a Unicode object from the @code{wchar_t} buffer @emph{w} of the given @emph{size}.
Passing @code{-1} as the @emph{size} indicates that the function must itself compute the length,
using wcslen.
Return @code{NULL} on failure.
@end deffn

@geindex PyUnicode_AsWideChar (C 函数)
@anchor{c-api/unicode c PyUnicode_AsWideChar}@anchor{fe5}
@deffn {C 函数} Py_ssize_t PyUnicode_AsWideChar (PyObject@w{ }*unicode, wchar_t@w{ }*w, Py_ssize_t@w{ }size)

Copy the Unicode object contents into the @code{wchar_t} buffer @emph{w}.  At most
@emph{size} @code{wchar_t} characters are copied (excluding a possibly trailing
null termination character).  Return the number of @code{wchar_t} characters
copied or @code{-1} in case of an error.  Note that the resulting @code{wchar_t*}
string may or may not be null-terminated.  It is the responsibility of the caller
to make sure that the @code{wchar_t*} string is null-terminated in case this is
required by the application. Also, note that the @code{wchar_t*} string
might contain null characters, which would cause the string to be truncated
when used with most C functions.
@end deffn

@geindex PyUnicode_AsWideCharString (C 函数)
@anchor{c-api/unicode c PyUnicode_AsWideCharString}@anchor{432}
@deffn {C 函数} wchar_t* PyUnicode_AsWideCharString (PyObject@w{ }*unicode, Py_ssize_t@w{ }*size)

Convert the Unicode object to a wide character string. The output string
always ends with a null character. If @emph{size} is not @code{NULL}, write the number
of wide characters (excluding the trailing null termination character) into
@emph{*size}. Note that the resulting @code{wchar_t} string might contain
null characters, which would cause the string to be truncated when used with
most C functions. If @emph{size} is @code{NULL} and the @code{wchar_t*} string
contains null characters a @ref{1fb,,ValueError} is raised.

Returns a buffer allocated by @code{PyMem_Alloc()} (use
@ref{da2,,PyMem_Free()} to free it) on success. On error, returns @code{NULL}
and @emph{*size} is undefined. Raises a @ref{f9f,,MemoryError} if memory allocation
is failed.


3.2 新版功能.



在 3.7 版更改: Raises a @ref{1fb,,ValueError} if @emph{size} is @code{NULL} and the @code{wchar_t*}
string contains null characters.

@end deffn

@node Built-in Codecs,Methods and Slot Functions,Unicode对象,Unicode Objects and Codecs
@anchor{c-api/unicode built-in-codecs}@anchor{3daf}@anchor{c-api/unicode builtincodecs}@anchor{3da7}
@subsubsection Built-in Codecs


Python provides a set of built-in codecs which are written in C for speed. All of
these codecs are directly usable via the following functions.

Many of the following APIs take two arguments encoding and errors, and they
have the same semantics as the ones of the built-in @ref{329,,str()} string object
constructor.

Setting encoding to @code{NULL} causes the default encoding to be used
which is ASCII.  The file system calls should use
@ref{5c9,,PyUnicode_FSConverter()} for encoding file names. This uses the
variable @code{Py_FileSystemDefaultEncoding} internally. This
variable should be treated as read-only: on some systems, it will be a
pointer to a static string, on others, it will change at run-time
(such as when the application invokes setlocale).

Error handling is set by errors which may also be set to @code{NULL} meaning to use
the default handling defined for the codec.  Default error handling for all
built-in codecs is "strict" (@ref{1fb,,ValueError} is raised).

The codecs all use a similar interface.  Only deviation from the following
generic ones are documented for simplicity.

@menu
* Generic Codecs:: 
* UTF-8 Codecs:: 
* UTF-32 Codecs:: 
* UTF-16 Codecs:: 
* UTF-7 Codecs:: 
* Unicode-Escape Codecs:: 
* Raw-Unicode-Escape Codecs:: 
* Latin-1 Codecs:: 
* ASCII Codecs:: 
* Character Map Codecs:: 
* MBCS codecs for Windows:: 
* Methods & Slots:: 

@end menu

@node Generic Codecs,UTF-8 Codecs,,Built-in Codecs
@anchor{c-api/unicode generic-codecs}@anchor{3db0}
@subsubsection Generic Codecs


These are the generic codec APIs:

@geindex PyUnicode_Decode (C 函数)
@anchor{c-api/unicode c PyUnicode_Decode}@anchor{f02}
@deffn {C 函数} PyObject* PyUnicode_Decode (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*encoding, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the encoded string @emph{s}.
@emph{encoding} and @emph{errors} have the same meaning as the parameters of the same name
in the @ref{329,,str()} built-in function.  The codec to be used is looked up
using the Python codec registry.  Return @code{NULL} if an exception was raised by
the codec.
@end deffn

@geindex PyUnicode_AsEncodedString (C 函数)
@anchor{c-api/unicode c PyUnicode_AsEncodedString}@anchor{3db1}
@deffn {C 函数} PyObject* PyUnicode_AsEncodedString (PyObject@w{ }*unicode, const char@w{ }*encoding, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode a Unicode object and return the result as Python bytes object.
@emph{encoding} and @emph{errors} have the same meaning as the parameters of the same
name in the Unicode @ref{c30,,encode()} method. The codec to be used is looked up
using the Python codec registry. Return @code{NULL} if an exception was raised by
the codec.
@end deffn

@geindex PyUnicode_Encode (C 函数)
@anchor{c-api/unicode c PyUnicode_Encode}@anchor{af7}
@deffn {C 函数} PyObject* PyUnicode_Encode (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*encoding, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer @emph{s} of the given @emph{size} and return a Python
bytes object.  @emph{encoding} and @emph{errors} have the same meaning as the
parameters of the same name in the Unicode @ref{c30,,encode()} method.  The codec
to be used is looked up using the Python codec registry.  Return @code{NULL} if an
exception was raised by the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node UTF-8 Codecs,UTF-32 Codecs,Generic Codecs,Built-in Codecs
@anchor{c-api/unicode utf-8-codecs}@anchor{3db2}
@subsubsection UTF-8 Codecs


These are the UTF-8 codec APIs:

@geindex PyUnicode_DecodeUTF8 (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUTF8}@anchor{3db3}
@deffn {C 函数} PyObject* PyUnicode_DecodeUTF8 (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the UTF-8 encoded string
@emph{s}. Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_DecodeUTF8Stateful (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUTF8Stateful}@anchor{3db4}
@deffn {C 函数} PyObject* PyUnicode_DecodeUTF8Stateful (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, Py_ssize_t@w{ }*consumed)
@emph{Return value: New reference.}
If @emph{consumed} is @code{NULL}, behave like @ref{3db3,,PyUnicode_DecodeUTF8()}. If
@emph{consumed} is not @code{NULL}, trailing incomplete UTF-8 byte sequences will not be
treated as an error. Those bytes will not be decoded and the number of bytes
that have been decoded will be stored in @emph{consumed}.
@end deffn

@geindex PyUnicode_AsUTF8String (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUTF8String}@anchor{afa}
@deffn {C 函数} PyObject* PyUnicode_AsUTF8String (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Encode a Unicode object using UTF-8 and return the result as Python bytes
object.  Error handling is "strict".  Return @code{NULL} if an exception was
raised by the codec.
@end deffn

@geindex PyUnicode_AsUTF8AndSize (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUTF8AndSize}@anchor{424}
@deffn {C 函数} const char* PyUnicode_AsUTF8AndSize (PyObject@w{ }*unicode, Py_ssize_t@w{ }*size)

Return a pointer to the UTF-8 encoding of the Unicode object, and
store the size of the encoded representation (in bytes) in @emph{size}.  The
@emph{size} argument can be @code{NULL}; in this case no size will be stored.  The
returned buffer always has an extra null byte appended (not included in
@emph{size}), regardless of whether there are any other null code points.

In the case of an error, @code{NULL} is returned with an exception set and no
@emph{size} is stored.

This caches the UTF-8 representation of the string in the Unicode object, and
subsequent calls will return a pointer to the same buffer.  The caller is not
responsible for deallocating the buffer.


3.3 新版功能.



在 3.7 版更改: The return type is now @code{const char *} rather of @code{char *}.

@end deffn

@geindex PyUnicode_AsUTF8 (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUTF8}@anchor{425}
@deffn {C 函数} const char* PyUnicode_AsUTF8 (PyObject@w{ }*unicode)

As @ref{424,,PyUnicode_AsUTF8AndSize()}, but does not store the size.


3.3 新版功能.



在 3.7 版更改: The return type is now @code{const char *} rather of @code{char *}.

@end deffn

@geindex PyUnicode_EncodeUTF8 (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeUTF8}@anchor{af9}
@deffn {C 函数} PyObject* PyUnicode_EncodeUTF8 (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer @emph{s} of the given @emph{size} using UTF-8 and
return a Python bytes object.  Return @code{NULL} if an exception was raised by
the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{afa,,PyUnicode_AsUTF8String()}, @ref{424,,PyUnicode_AsUTF8AndSize()} or
@ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node UTF-32 Codecs,UTF-16 Codecs,UTF-8 Codecs,Built-in Codecs
@anchor{c-api/unicode utf-32-codecs}@anchor{3db5}
@subsubsection UTF-32 Codecs


These are the UTF-32 codec APIs:

@geindex PyUnicode_DecodeUTF32 (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUTF32}@anchor{3db6}
@deffn {C 函数} PyObject* PyUnicode_DecodeUTF32 (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, int@w{ }*byteorder)
@emph{Return value: New reference.}
Decode @emph{size} bytes from a UTF-32 encoded buffer string and return the
corresponding Unicode object.  @emph{errors} (if non-@code{NULL}) defines the error
handling. It defaults to "strict".

If @emph{byteorder} is non-@code{NULL}, the decoder starts decoding using the given byte
order:

@example
*byteorder == -1: little endian
*byteorder == 0:  native order
*byteorder == 1:  big endian
@end example

If @code{*byteorder} is zero, and the first four bytes of the input data are a
byte order mark (BOM), the decoder switches to this byte order and the BOM is
not copied into the resulting Unicode string.  If @code{*byteorder} is @code{-1} or
@code{1}, any byte order mark is copied to the output.

After completion, @emph{*byteorder} is set to the current byte order at the end
of input data.

If @emph{byteorder} is @code{NULL}, the codec starts in native order mode.

Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_DecodeUTF32Stateful (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUTF32Stateful}@anchor{3db7}
@deffn {C 函数} PyObject* PyUnicode_DecodeUTF32Stateful (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, int@w{ }*byteorder, Py_ssize_t@w{ }*consumed)
@emph{Return value: New reference.}
If @emph{consumed} is @code{NULL}, behave like @ref{3db6,,PyUnicode_DecodeUTF32()}. If
@emph{consumed} is not @code{NULL}, @ref{3db7,,PyUnicode_DecodeUTF32Stateful()} will not treat
trailing incomplete UTF-32 byte sequences (such as a number of bytes not divisible
by four) as an error. Those bytes will not be decoded and the number of bytes
that have been decoded will be stored in @emph{consumed}.
@end deffn

@geindex PyUnicode_AsUTF32String (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUTF32String}@anchor{3db8}
@deffn {C 函数} PyObject* PyUnicode_AsUTF32String (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Return a Python byte string using the UTF-32 encoding in native byte
order. The string always starts with a BOM mark.  Error handling is "strict".
Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_EncodeUTF32 (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeUTF32}@anchor{afb}
@deffn {C 函数} PyObject* PyUnicode_EncodeUTF32 (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, int@w{ }byteorder)
@emph{Return value: New reference.}
Return a Python bytes object holding the UTF-32 encoded value of the Unicode
data in @emph{s}.  Output is written according to the following byte order:

@example
byteorder == -1: little endian
byteorder == 0:  native byte order (writes a BOM mark)
byteorder == 1:  big endian
@end example

If byteorder is @code{0}, the output string will always start with the Unicode BOM
mark (U+FEFF). In the other two modes, no BOM mark is prepended.

If @code{Py_UNICODE_WIDE} is not defined, surrogate pairs will be output
as a single code point.

Return @code{NULL} if an exception was raised by the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{3db8,,PyUnicode_AsUTF32String()} or @ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node UTF-16 Codecs,UTF-7 Codecs,UTF-32 Codecs,Built-in Codecs
@anchor{c-api/unicode utf-16-codecs}@anchor{3db9}
@subsubsection UTF-16 Codecs


These are the UTF-16 codec APIs:

@geindex PyUnicode_DecodeUTF16 (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUTF16}@anchor{3dba}
@deffn {C 函数} PyObject* PyUnicode_DecodeUTF16 (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, int@w{ }*byteorder)
@emph{Return value: New reference.}
Decode @emph{size} bytes from a UTF-16 encoded buffer string and return the
corresponding Unicode object.  @emph{errors} (if non-@code{NULL}) defines the error
handling. It defaults to "strict".

If @emph{byteorder} is non-@code{NULL}, the decoder starts decoding using the given byte
order:

@example
*byteorder == -1: little endian
*byteorder == 0:  native order
*byteorder == 1:  big endian
@end example

If @code{*byteorder} is zero, and the first two bytes of the input data are a
byte order mark (BOM), the decoder switches to this byte order and the BOM is
not copied into the resulting Unicode string.  If @code{*byteorder} is @code{-1} or
@code{1}, any byte order mark is copied to the output (where it will result in
either a @code{\ufeff} or a @code{\ufffe} character).

After completion, @emph{*byteorder} is set to the current byte order at the end
of input data.

If @emph{byteorder} is @code{NULL}, the codec starts in native order mode.

Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_DecodeUTF16Stateful (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUTF16Stateful}@anchor{3dbb}
@deffn {C 函数} PyObject* PyUnicode_DecodeUTF16Stateful (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, int@w{ }*byteorder, Py_ssize_t@w{ }*consumed)
@emph{Return value: New reference.}
If @emph{consumed} is @code{NULL}, behave like @ref{3dba,,PyUnicode_DecodeUTF16()}. If
@emph{consumed} is not @code{NULL}, @ref{3dbb,,PyUnicode_DecodeUTF16Stateful()} will not treat
trailing incomplete UTF-16 byte sequences (such as an odd number of bytes or a
split surrogate pair) as an error. Those bytes will not be decoded and the
number of bytes that have been decoded will be stored in @emph{consumed}.
@end deffn

@geindex PyUnicode_AsUTF16String (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUTF16String}@anchor{3dbc}
@deffn {C 函数} PyObject* PyUnicode_AsUTF16String (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Return a Python byte string using the UTF-16 encoding in native byte
order. The string always starts with a BOM mark.  Error handling is "strict".
Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_EncodeUTF16 (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeUTF16}@anchor{afc}
@deffn {C 函数} PyObject* PyUnicode_EncodeUTF16 (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, int@w{ }byteorder)
@emph{Return value: New reference.}
Return a Python bytes object holding the UTF-16 encoded value of the Unicode
data in @emph{s}.  Output is written according to the following byte order:

@example
byteorder == -1: little endian
byteorder == 0:  native byte order (writes a BOM mark)
byteorder == 1:  big endian
@end example

If byteorder is @code{0}, the output string will always start with the Unicode BOM
mark (U+FEFF). In the other two modes, no BOM mark is prepended.

If @code{Py_UNICODE_WIDE} is defined, a single @ref{ae9,,Py_UNICODE} value may get
represented as a surrogate pair. If it is not defined, each @ref{ae9,,Py_UNICODE}
values is interpreted as a UCS-2 character.

Return @code{NULL} if an exception was raised by the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{3dbc,,PyUnicode_AsUTF16String()} or @ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node UTF-7 Codecs,Unicode-Escape Codecs,UTF-16 Codecs,Built-in Codecs
@anchor{c-api/unicode utf-7-codecs}@anchor{3dbd}
@subsubsection UTF-7 Codecs


These are the UTF-7 codec APIs:

@geindex PyUnicode_DecodeUTF7 (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUTF7}@anchor{3dbe}
@deffn {C 函数} PyObject* PyUnicode_DecodeUTF7 (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the UTF-7 encoded string
@emph{s}.  Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_DecodeUTF7Stateful (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUTF7Stateful}@anchor{3dbf}
@deffn {C 函数} PyObject* PyUnicode_DecodeUTF7Stateful (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, Py_ssize_t@w{ }*consumed)
@emph{Return value: New reference.}
If @emph{consumed} is @code{NULL}, behave like @ref{3dbe,,PyUnicode_DecodeUTF7()}.  If
@emph{consumed} is not @code{NULL}, trailing incomplete UTF-7 base-64 sections will not
be treated as an error.  Those bytes will not be decoded and the number of
bytes that have been decoded will be stored in @emph{consumed}.
@end deffn

@geindex PyUnicode_EncodeUTF7 (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeUTF7}@anchor{af8}
@deffn {C 函数} PyObject* PyUnicode_EncodeUTF7 (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, int@w{ }base64SetO, int@w{ }base64WhiteSpace, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer of the given size using UTF-7 and
return a Python bytes object.  Return @code{NULL} if an exception was raised by
the codec.

If @emph{base64SetO} is nonzero, "Set O" (punctuation that has no otherwise
special meaning) will be encoded in base-64.  If @emph{base64WhiteSpace} is
nonzero, whitespace will be encoded in base-64.  Both are set to zero for the
Python "utf-7" codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node Unicode-Escape Codecs,Raw-Unicode-Escape Codecs,UTF-7 Codecs,Built-in Codecs
@anchor{c-api/unicode unicode-escape-codecs}@anchor{3dc0}
@subsubsection Unicode-Escape Codecs


These are the "Unicode Escape" codec APIs:

@geindex PyUnicode_DecodeUnicodeEscape (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeUnicodeEscape}@anchor{3dc1}
@deffn {C 函数} PyObject* PyUnicode_DecodeUnicodeEscape (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the Unicode-Escape encoded
string @emph{s}.  Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_AsUnicodeEscapeString (C 函数)
@anchor{c-api/unicode c PyUnicode_AsUnicodeEscapeString}@anchor{afd}
@deffn {C 函数} PyObject* PyUnicode_AsUnicodeEscapeString (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Encode a Unicode object using Unicode-Escape and return the result as a
bytes object.  Error handling is "strict".  Return @code{NULL} if an exception was
raised by the codec.
@end deffn

@geindex PyUnicode_EncodeUnicodeEscape (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeUnicodeEscape}@anchor{3dc2}
@deffn {C 函数} PyObject* PyUnicode_EncodeUnicodeEscape (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer of the given @emph{size} using Unicode-Escape and
return a bytes object.  Return @code{NULL} if an exception was raised by the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{afd,,PyUnicode_AsUnicodeEscapeString()}.

@end deffn

@node Raw-Unicode-Escape Codecs,Latin-1 Codecs,Unicode-Escape Codecs,Built-in Codecs
@anchor{c-api/unicode raw-unicode-escape-codecs}@anchor{3dc3}
@subsubsection Raw-Unicode-Escape Codecs


These are the "Raw Unicode Escape" codec APIs:

@geindex PyUnicode_DecodeRawUnicodeEscape (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeRawUnicodeEscape}@anchor{3dc4}
@deffn {C 函数} PyObject* PyUnicode_DecodeRawUnicodeEscape (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the Raw-Unicode-Escape
encoded string @emph{s}.  Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_AsRawUnicodeEscapeString (C 函数)
@anchor{c-api/unicode c PyUnicode_AsRawUnicodeEscapeString}@anchor{afe}
@deffn {C 函数} PyObject* PyUnicode_AsRawUnicodeEscapeString (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Encode a Unicode object using Raw-Unicode-Escape and return the result as
a bytes object.  Error handling is "strict".  Return @code{NULL} if an exception
was raised by the codec.
@end deffn

@geindex PyUnicode_EncodeRawUnicodeEscape (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeRawUnicodeEscape}@anchor{3dc5}
@deffn {C 函数} PyObject* PyUnicode_EncodeRawUnicodeEscape (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer of the given @emph{size} using Raw-Unicode-Escape
and return a bytes object.  Return @code{NULL} if an exception was raised by the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{afe,,PyUnicode_AsRawUnicodeEscapeString()} or
@ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node Latin-1 Codecs,ASCII Codecs,Raw-Unicode-Escape Codecs,Built-in Codecs
@anchor{c-api/unicode latin-1-codecs}@anchor{3dc6}
@subsubsection Latin-1 Codecs


These are the Latin-1 codec APIs: Latin-1 corresponds to the first 256 Unicode
ordinals and only these are accepted by the codecs during encoding.

@geindex PyUnicode_DecodeLatin1 (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeLatin1}@anchor{3dc7}
@deffn {C 函数} PyObject* PyUnicode_DecodeLatin1 (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the Latin-1 encoded string
@emph{s}.  Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_AsLatin1String (C 函数)
@anchor{c-api/unicode c PyUnicode_AsLatin1String}@anchor{b00}
@deffn {C 函数} PyObject* PyUnicode_AsLatin1String (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Encode a Unicode object using Latin-1 and return the result as Python bytes
object.  Error handling is "strict".  Return @code{NULL} if an exception was
raised by the codec.
@end deffn

@geindex PyUnicode_EncodeLatin1 (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeLatin1}@anchor{aff}
@deffn {C 函数} PyObject* PyUnicode_EncodeLatin1 (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer of the given @emph{size} using Latin-1 and
return a Python bytes object.  Return @code{NULL} if an exception was raised by
the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{b00,,PyUnicode_AsLatin1String()} or
@ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node ASCII Codecs,Character Map Codecs,Latin-1 Codecs,Built-in Codecs
@anchor{c-api/unicode ascii-codecs}@anchor{3dc8}
@subsubsection ASCII Codecs


These are the ASCII codec APIs.  Only 7-bit ASCII data is accepted. All other
codes generate errors.

@geindex PyUnicode_DecodeASCII (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeASCII}@anchor{3dc9}
@deffn {C 函数} PyObject* PyUnicode_DecodeASCII (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the ASCII encoded string
@emph{s}.  Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_AsASCIIString (C 函数)
@anchor{c-api/unicode c PyUnicode_AsASCIIString}@anchor{b02}
@deffn {C 函数} PyObject* PyUnicode_AsASCIIString (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Encode a Unicode object using ASCII and return the result as Python bytes
object.  Error handling is "strict".  Return @code{NULL} if an exception was
raised by the codec.
@end deffn

@geindex PyUnicode_EncodeASCII (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeASCII}@anchor{b01}
@deffn {C 函数} PyObject* PyUnicode_EncodeASCII (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer of the given @emph{size} using ASCII and
return a Python bytes object.  Return @code{NULL} if an exception was raised by
the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{b02,,PyUnicode_AsASCIIString()} or
@ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node Character Map Codecs,MBCS codecs for Windows,ASCII Codecs,Built-in Codecs
@anchor{c-api/unicode character-map-codecs}@anchor{3dca}
@subsubsection Character Map Codecs


This codec is special in that it can be used to implement many different codecs
(and this is in fact what was done to obtain most of the standard codecs
included in the @code{encodings} package). The codec uses mapping to encode and
decode characters.  The mapping objects provided must support the
@ref{27f,,__getitem__()} mapping interface; dictionaries and sequences work well.

These are the mapping codec APIs:

@geindex PyUnicode_DecodeCharmap (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeCharmap}@anchor{3dcb}
@deffn {C 函数} PyObject* PyUnicode_DecodeCharmap (const char@w{ }*data, Py_ssize_t@w{ }size, PyObject@w{ }*mapping, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the encoded string @emph{s}
using the given @emph{mapping} object.  Return @code{NULL} if an exception was raised
by the codec.

If @emph{mapping} is @code{NULL}, Latin-1 decoding will be applied.  Else
@emph{mapping} must map bytes ordinals (integers in the range from 0 to 255)
to Unicode strings, integers (which are then interpreted as Unicode
ordinals) or @code{None}.  Unmapped data bytes -- ones which cause a
@ref{15f6,,LookupError}, as well as ones which get mapped to @code{None},
@code{0xFFFE} or @code{'\ufffe'}, are treated as undefined mappings and cause
an error.
@end deffn

@geindex PyUnicode_AsCharmapString (C 函数)
@anchor{c-api/unicode c PyUnicode_AsCharmapString}@anchor{3dcc}
@deffn {C 函数} PyObject* PyUnicode_AsCharmapString (PyObject@w{ }*unicode, PyObject@w{ }*mapping)
@emph{Return value: New reference.}
Encode a Unicode object using the given @emph{mapping} object and return the
result as a bytes object.  Error handling is "strict".  Return @code{NULL} if an
exception was raised by the codec.

The @emph{mapping} object must map Unicode ordinal integers to bytes objects,
integers in the range from 0 to 255 or @code{None}.  Unmapped character
ordinals (ones which cause a @ref{15f6,,LookupError}) as well as mapped to
@code{None} are treated as "undefined mapping" and cause an error.
@end deffn

@geindex PyUnicode_EncodeCharmap (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeCharmap}@anchor{b03}
@deffn {C 函数} PyObject* PyUnicode_EncodeCharmap (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, PyObject@w{ }*mapping, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer of the given @emph{size} using the given
@emph{mapping} object and return the result as a bytes object.  Return @code{NULL} if
an exception was raised by the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{3dcc,,PyUnicode_AsCharmapString()} or
@ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

The following codec API is special in that maps Unicode to Unicode.

@geindex PyUnicode_Translate (C 函数)
@anchor{c-api/unicode c PyUnicode_Translate}@anchor{3dcd}
@deffn {C 函数} PyObject* PyUnicode_Translate (PyObject@w{ }*unicode, PyObject@w{ }*mapping, const char@w{ }*errors)
@emph{Return value: New reference.}
Translate a Unicode object using the given @emph{mapping} object and return the
resulting Unicode object.  Return @code{NULL} if an exception was raised by the
codec.

The @emph{mapping} object must map Unicode ordinal integers to Unicode strings,
integers (which are then interpreted as Unicode ordinals) or @code{None}
(causing deletion of the character).  Unmapped character ordinals (ones
which cause a @ref{15f6,,LookupError}) are left untouched and are copied as-is.
@end deffn

@geindex PyUnicode_TranslateCharmap (C 函数)
@anchor{c-api/unicode c PyUnicode_TranslateCharmap}@anchor{b04}
@deffn {C 函数} PyObject* PyUnicode_TranslateCharmap (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, PyObject@w{ }*mapping, const char@w{ }*errors)
@emph{Return value: New reference.}
Translate a @ref{ae9,,Py_UNICODE} buffer of the given @emph{size} by applying a
character @emph{mapping} table to it and return the resulting Unicode object.
Return @code{NULL} when an exception was raised by the codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{3dcd,,PyUnicode_Translate()}. or @ref{5e9,,generic codec based API}

@end deffn

@node MBCS codecs for Windows,Methods & Slots,Character Map Codecs,Built-in Codecs
@anchor{c-api/unicode mbcs-codecs-for-windows}@anchor{3dce}
@subsubsection MBCS codecs for Windows


These are the MBCS codec APIs. They are currently only available on Windows and
use the Win32 MBCS converters to implement the conversions.  Note that MBCS (or
DBCS) is a class of encodings, not just one.  The target encoding is defined by
the user settings on the machine running the codec.

@geindex PyUnicode_DecodeMBCS (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeMBCS}@anchor{3dcf}
@deffn {C 函数} PyObject* PyUnicode_DecodeMBCS (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Create a Unicode object by decoding @emph{size} bytes of the MBCS encoded string @emph{s}.
Return @code{NULL} if an exception was raised by the codec.
@end deffn

@geindex PyUnicode_DecodeMBCSStateful (C 函数)
@anchor{c-api/unicode c PyUnicode_DecodeMBCSStateful}@anchor{3dd0}
@deffn {C 函数} PyObject* PyUnicode_DecodeMBCSStateful (const char@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors, Py_ssize_t@w{ }*consumed)
@emph{Return value: New reference.}
If @emph{consumed} is @code{NULL}, behave like @ref{3dcf,,PyUnicode_DecodeMBCS()}. If
@emph{consumed} is not @code{NULL}, @ref{3dd0,,PyUnicode_DecodeMBCSStateful()} will not decode
trailing lead byte and the number of bytes that have been decoded will be stored
in @emph{consumed}.
@end deffn

@geindex PyUnicode_AsMBCSString (C 函数)
@anchor{c-api/unicode c PyUnicode_AsMBCSString}@anchor{b06}
@deffn {C 函数} PyObject* PyUnicode_AsMBCSString (PyObject@w{ }*unicode)
@emph{Return value: New reference.}
Encode a Unicode object using MBCS and return the result as Python bytes
object.  Error handling is "strict".  Return @code{NULL} if an exception was
raised by the codec.
@end deffn

@geindex PyUnicode_EncodeCodePage (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeCodePage}@anchor{b07}
@deffn {C 函数} PyObject* PyUnicode_EncodeCodePage (int@w{ }code_page, PyObject@w{ }*unicode, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode the Unicode object using the specified code page and return a Python
bytes object.  Return @code{NULL} if an exception was raised by the codec. Use
@code{CP_ACP} code page to get the MBCS encoder.


3.3 新版功能.

@end deffn

@geindex PyUnicode_EncodeMBCS (C 函数)
@anchor{c-api/unicode c PyUnicode_EncodeMBCS}@anchor{b05}
@deffn {C 函数} PyObject* PyUnicode_EncodeMBCS (const Py_UNICODE@w{ }*s, Py_ssize_t@w{ }size, const char@w{ }*errors)
@emph{Return value: New reference.}
Encode the @ref{ae9,,Py_UNICODE} buffer of the given @emph{size} using MBCS and return
a Python bytes object.  Return @code{NULL} if an exception was raised by the
codec.


Deprecated since version 3.3, will be removed in version 4.0: Part of the old-style @ref{ae9,,Py_UNICODE} API; please migrate to using
@ref{b06,,PyUnicode_AsMBCSString()}, @ref{b07,,PyUnicode_EncodeCodePage()} or
@ref{3db1,,PyUnicode_AsEncodedString()}.

@end deffn

@node Methods & Slots,,MBCS codecs for Windows,Built-in Codecs
@anchor{c-api/unicode methods-slots}@anchor{3dd1}
@subsubsection Methods & Slots


@node Methods and Slot Functions,,Built-in Codecs,Unicode Objects and Codecs
@anchor{c-api/unicode methods-and-slot-functions}@anchor{3dd2}@anchor{c-api/unicode unicodemethodsandslots}@anchor{3dd3}
@subsubsection Methods and Slot Functions


The following APIs are capable of handling Unicode objects and strings on input
(we refer to them as strings in the descriptions) and return Unicode objects or
integers as appropriate.

They all return @code{NULL} or @code{-1} if an exception occurs.

@geindex PyUnicode_Concat (C 函数)
@anchor{c-api/unicode c PyUnicode_Concat}@anchor{b16}
@deffn {C 函数} PyObject* PyUnicode_Concat (PyObject@w{ }*left, PyObject@w{ }*right)
@emph{Return value: New reference.}
Concat two strings giving a new Unicode string.
@end deffn

@geindex PyUnicode_Split (C 函数)
@anchor{c-api/unicode c PyUnicode_Split}@anchor{3dd4}
@deffn {C 函数} PyObject* PyUnicode_Split (PyObject@w{ }*s, PyObject@w{ }*sep, Py_ssize_t@w{ }maxsplit)
@emph{Return value: New reference.}
Split a string giving a list of Unicode strings.  If @emph{sep} is @code{NULL}, splitting
will be done at all whitespace substrings.  Otherwise, splits occur at the given
separator.  At most @emph{maxsplit} splits will be done.  If negative, no limit is
set.  Separators are not included in the resulting list.
@end deffn

@geindex PyUnicode_Splitlines (C 函数)
@anchor{c-api/unicode c PyUnicode_Splitlines}@anchor{3dd5}
@deffn {C 函数} PyObject* PyUnicode_Splitlines (PyObject@w{ }*s, int@w{ }keepend)
@emph{Return value: New reference.}
Split a Unicode string at line breaks, returning a list of Unicode strings.
CRLF is considered to be one line break.  If @emph{keepend} is @code{0}, the Line break
characters are not included in the resulting strings.
@end deffn

@geindex PyUnicode_Translate (C 函数)

@deffn {C 函数} PyObject* PyUnicode_Translate (PyObject@w{ }*str, PyObject@w{ }*table, const char@w{ }*errors)

Translate a string by applying a character mapping table to it and return the
resulting Unicode object.

The mapping table must map Unicode ordinal integers to Unicode ordinal integers
or @code{None} (causing deletion of the character).

Mapping tables need only provide the @ref{27f,,__getitem__()} interface; dictionaries
and sequences work well.  Unmapped character ordinals (ones which cause a
@ref{15f6,,LookupError}) are left untouched and are copied as-is.

@emph{errors} has the usual meaning for codecs. It may be @code{NULL} which indicates to
use the default error handling.
@end deffn

@geindex PyUnicode_Join (C 函数)
@anchor{c-api/unicode c PyUnicode_Join}@anchor{b17}
@deffn {C 函数} PyObject* PyUnicode_Join (PyObject@w{ }*separator, PyObject@w{ }*seq)
@emph{Return value: New reference.}
Join a sequence of strings using the given @emph{separator} and return the resulting
Unicode string.
@end deffn

@geindex PyUnicode_Tailmatch (C 函数)
@anchor{c-api/unicode c PyUnicode_Tailmatch}@anchor{af5}
@deffn {C 函数} Py_ssize_t PyUnicode_Tailmatch (PyObject@w{ }*str, PyObject@w{ }*substr, Py_ssize_t@w{ }start, Py_ssize_t@w{ }end, int@w{ }direction)

Return @code{1} if @emph{substr} matches @code{str[start:end]} at the given tail end
(@emph{direction} == @code{-1} means to do a prefix match, @emph{direction} == @code{1} a suffix match),
@code{0} otherwise. Return @code{-1} if an error occurred.
@end deffn

@geindex PyUnicode_Find (C 函数)
@anchor{c-api/unicode c PyUnicode_Find}@anchor{3dd6}
@deffn {C 函数} Py_ssize_t PyUnicode_Find (PyObject@w{ }*str, PyObject@w{ }*substr, Py_ssize_t@w{ }start, Py_ssize_t@w{ }end, int@w{ }direction)

Return the first position of @emph{substr} in @code{str[start:end]} using the given
@emph{direction} (@emph{direction} == @code{1} means to do a forward search, @emph{direction} == @code{-1} a
backward search).  The return value is the index of the first match; a value of
@code{-1} indicates that no match was found, and @code{-2} indicates that an error
occurred and an exception has been set.
@end deffn

@geindex PyUnicode_FindChar (C 函数)
@anchor{c-api/unicode c PyUnicode_FindChar}@anchor{43a}
@deffn {C 函数} Py_ssize_t PyUnicode_FindChar (PyObject@w{ }*str, Py_UCS4@w{ }ch, Py_ssize_t@w{ }start, Py_ssize_t@w{ }end, int@w{ }direction)

Return the first position of the character @emph{ch} in @code{str[start:end]} using
the given @emph{direction} (@emph{direction} == @code{1} means to do a forward search,
@emph{direction} == @code{-1} a backward search).  The return value is the index of the
first match; a value of @code{-1} indicates that no match was found, and @code{-2}
indicates that an error occurred and an exception has been set.


3.3 新版功能.



在 3.7 版更改: @emph{start} and @emph{end} are now adjusted to behave like @code{str[start:end]}.

@end deffn

@geindex PyUnicode_Count (C 函数)
@anchor{c-api/unicode c PyUnicode_Count}@anchor{3dd7}
@deffn {C 函数} Py_ssize_t PyUnicode_Count (PyObject@w{ }*str, PyObject@w{ }*substr, Py_ssize_t@w{ }start, Py_ssize_t@w{ }end)

Return the number of non-overlapping occurrences of @emph{substr} in
@code{str[start:end]}.  Return @code{-1} if an error occurred.
@end deffn

@geindex PyUnicode_Replace (C 函数)
@anchor{c-api/unicode c PyUnicode_Replace}@anchor{3dd8}
@deffn {C 函数} PyObject* PyUnicode_Replace (PyObject@w{ }*str, PyObject@w{ }*substr, PyObject@w{ }*replstr, Py_ssize_t@w{ }maxcount)
@emph{Return value: New reference.}
Replace at most @emph{maxcount} occurrences of @emph{substr} in @emph{str} with @emph{replstr} and
return the resulting Unicode object. @emph{maxcount} == @code{-1} means replace all
occurrences.
@end deffn

@geindex PyUnicode_Compare (C 函数)
@anchor{c-api/unicode c PyUnicode_Compare}@anchor{af4}
@deffn {C 函数} int PyUnicode_Compare (PyObject@w{ }*left, PyObject@w{ }*right)

Compare two strings and return @code{-1}, @code{0}, @code{1} for less than, equal, and greater than,
respectively.

This function returns @code{-1} upon failure, so one should call
@ref{3aa4,,PyErr_Occurred()} to check for errors.
@end deffn

@geindex PyUnicode_CompareWithASCIIString (C 函数)
@anchor{c-api/unicode c PyUnicode_CompareWithASCIIString}@anchor{bf7}
@deffn {C 函数} int PyUnicode_CompareWithASCIIString (PyObject@w{ }*uni, const char@w{ }*string)

Compare a Unicode object, @emph{uni}, with @emph{string} and return @code{-1}, @code{0}, @code{1} for less
than, equal, and greater than, respectively. It is best to pass only
ASCII-encoded strings, but the function interprets the input string as
ISO-8859-1 if it contains non-ASCII characters.

This function does not raise exceptions.
@end deffn

@geindex PyUnicode_RichCompare (C 函数)
@anchor{c-api/unicode c PyUnicode_RichCompare}@anchor{3dd9}
@deffn {C 函数} PyObject* PyUnicode_RichCompare (PyObject@w{ }*left, PyObject@w{ }*right, int@w{ }op)
@emph{Return value: New reference.}
Rich compare two Unicode strings and return one of the following:


@itemize *

@item 
@code{NULL} in case an exception was raised

@item 
@code{Py_True} or @code{Py_False} for successful comparisons

@item 
@code{Py_NotImplemented} in case the type combination is unknown
@end itemize

Possible values for @emph{op} are @code{Py_GT}, @code{Py_GE}, @code{Py_EQ},
@code{Py_NE}, @code{Py_LT}, and @code{Py_LE}.
@end deffn

@geindex PyUnicode_Format (C 函数)
@anchor{c-api/unicode c PyUnicode_Format}@anchor{3dda}
@deffn {C 函数} PyObject* PyUnicode_Format (PyObject@w{ }*format, PyObject@w{ }*args)
@emph{Return value: New reference.}
Return a new string object from @emph{format} and @emph{args}; this is analogous to
@code{format % args}.
@end deffn

@geindex PyUnicode_Contains (C 函数)
@anchor{c-api/unicode c PyUnicode_Contains}@anchor{3ddb}
@deffn {C 函数} int PyUnicode_Contains (PyObject@w{ }*container, PyObject@w{ }*element)

Check whether @emph{element} is contained in @emph{container} and return true or false
accordingly.

@emph{element} has to coerce to a one element Unicode string. @code{-1} is returned
if there was an error.
@end deffn

@geindex PyUnicode_InternInPlace (C 函数)
@anchor{c-api/unicode c PyUnicode_InternInPlace}@anchor{3ddc}
@deffn {C 函数} void PyUnicode_InternInPlace (PyObject@w{ }**string)

Intern the argument @emph{*string} in place.  The argument must be the address of a
pointer variable pointing to a Python Unicode string object.  If there is an
existing interned string that is the same as @emph{*string}, it sets @emph{*string} to
it (decrementing the reference count of the old string object and incrementing
the reference count of the interned string object), otherwise it leaves
@emph{*string} alone and interns it (incrementing its reference count).
(Clarification: even though there is a lot of talk about reference counts, think
of this function as reference-count-neutral; you own the object after the call
if and only if you owned it before the call.)
@end deffn

@geindex PyUnicode_InternFromString (C 函数)
@anchor{c-api/unicode c PyUnicode_InternFromString}@anchor{3ddd}
@deffn {C 函数} PyObject* PyUnicode_InternFromString (const char@w{ }*v)
@emph{Return value: New reference.}
A combination of @ref{3b35,,PyUnicode_FromString()} and
@ref{3ddc,,PyUnicode_InternInPlace()}, returning either a new Unicode string
object that has been interned, or a new ("owned") reference to an earlier
interned string object with the same value.
@end deffn

@node 元组对象,Struct Sequence Objects,Unicode Objects and Codecs,序列对象
@anchor{c-api/tuple doc}@anchor{3dde}@anchor{c-api/tuple tuple-objects}@anchor{3ddf}@anchor{c-api/tuple tupleobjects}@anchor{3de0}
@subsubsection 元组对象


@geindex 对象; tuple

@geindex PyTupleObject (C 类型)
@anchor{c-api/tuple c PyTupleObject}@anchor{3bf9}
@deffn {C 类型} PyTupleObject

这个 @ref{4b5,,PyObject} 的子类型代表一个 Python 的元组对象。
@end deffn

@geindex PyTuple_Type (C 变量)
@anchor{c-api/tuple c PyTuple_Type}@anchor{3de1}
@deffn {C 变量} PyTypeObject PyTuple_Type

@ref{2d6,,PyTypeObject} 的实例代表一个 Python 元组类型，这与 Python 层面的 @ref{478,,tuple} 是相同的对象。
@end deffn

@geindex PyTuple_Check (C 函数)
@anchor{c-api/tuple c PyTuple_Check}@anchor{3de2}
@deffn {C 函数} int PyTuple_Check (PyObject@w{ }*p)

如果 @emph{p} 是一个元组对象或者元组类型的子类型的实例，则返回真值。
@end deffn

@geindex PyTuple_CheckExact (C 函数)
@anchor{c-api/tuple c PyTuple_CheckExact}@anchor{3de3}
@deffn {C 函数} int PyTuple_CheckExact (PyObject@w{ }*p)

如果 @emph{p} 是一个元组对象，而不是一个元组子类型的实例，则返回真值。
@end deffn

@geindex PyTuple_New (C 函数)
@anchor{c-api/tuple c PyTuple_New}@anchor{3de4}
@deffn {C 函数} PyObject* PyTuple_New (Py_ssize_t@w{ }len)
@emph{Return value: New reference.}
Return a new tuple object of size @emph{len}, or @code{NULL} on failure.
@end deffn

@geindex PyTuple_Pack (C 函数)
@anchor{c-api/tuple c PyTuple_Pack}@anchor{3de5}
@deffn {C 函数} PyObject* PyTuple_Pack (Py_ssize_t@w{ }n, ...)
@emph{Return value: New reference.}
Return a new tuple object of size @emph{n}, or @code{NULL} on failure. The tuple values
are initialized to the subsequent @emph{n} C arguments pointing to Python objects.
@code{PyTuple_Pack(2, a, b)} is equivalent to @code{Py_BuildValue("(OO)", a, b)}.
@end deffn

@geindex PyTuple_Size (C 函数)
@anchor{c-api/tuple c PyTuple_Size}@anchor{3de6}
@deffn {C 函数} Py_ssize_t PyTuple_Size (PyObject@w{ }*p)

Take a pointer to a tuple object, and return the size of that tuple.
@end deffn

@geindex PyTuple_GET_SIZE (C 函数)
@anchor{c-api/tuple c PyTuple_GET_SIZE}@anchor{3de7}
@deffn {C 函数} Py_ssize_t PyTuple_GET_SIZE (PyObject@w{ }*p)

Return the size of the tuple @emph{p}, which must be non-@code{NULL} and point to a tuple;
no error checking is performed.
@end deffn

@geindex PyTuple_GetItem (C 函数)
@anchor{c-api/tuple c PyTuple_GetItem}@anchor{3ac1}
@deffn {C 函数} PyObject* PyTuple_GetItem (PyObject@w{ }*p, Py_ssize_t@w{ }pos)
@emph{Return value: Borrowed reference.}
Return the object at position @emph{pos} in the tuple pointed to by @emph{p}.  If @emph{pos} is
out of bounds, return @code{NULL} and set an @ref{e6e,,IndexError} exception.
@end deffn

@geindex PyTuple_GET_ITEM (C 函数)
@anchor{c-api/tuple c PyTuple_GET_ITEM}@anchor{3de8}
@deffn {C 函数} PyObject* PyTuple_GET_ITEM (PyObject@w{ }*p, Py_ssize_t@w{ }pos)
@emph{Return value: Borrowed reference.}
Like @ref{3ac1,,PyTuple_GetItem()}, but does no checking of its arguments.
@end deffn

@geindex PyTuple_GetSlice (C 函数)
@anchor{c-api/tuple c PyTuple_GetSlice}@anchor{3de9}
@deffn {C 函数} PyObject* PyTuple_GetSlice (PyObject@w{ }*p, Py_ssize_t@w{ }low, Py_ssize_t@w{ }high)
@emph{Return value: New reference.}
Return the slice of the tuple pointed to by @emph{p} between @emph{low} and @emph{high},
or @code{NULL} on failure.  This is the equivalent of the Python expression
@code{p[low:high]}.  Indexing from the end of the list is not supported.
@end deffn

@geindex PyTuple_SetItem (C 函数)
@anchor{c-api/tuple c PyTuple_SetItem}@anchor{3ac6}
@deffn {C 函数} int PyTuple_SetItem (PyObject@w{ }*p, Py_ssize_t@w{ }pos, PyObject@w{ }*o)

Insert a reference to object @emph{o} at position @emph{pos} of the tuple pointed to by
@emph{p}.  Return @code{0} on success.  If @emph{pos} is out of bounds, return @code{-1}
and set an @ref{e6e,,IndexError} exception.

@cartouche
@quotation 注解 
This function "steals" a reference to @emph{o} and discards a reference to
an item already in the tuple at the affected position.
@end quotation
@end cartouche
@end deffn

@geindex PyTuple_SET_ITEM (C 函数)
@anchor{c-api/tuple c PyTuple_SET_ITEM}@anchor{3dea}
@deffn {C 函数} void PyTuple_SET_ITEM (PyObject@w{ }*p, Py_ssize_t@w{ }pos, PyObject@w{ }*o)

Like @ref{3ac6,,PyTuple_SetItem()}, but does no error checking, and should @emph{only} be
used to fill in brand new tuples.

@cartouche
@quotation 注解 
This macro "steals" a reference to @emph{o}, and, unlike
@ref{3ac6,,PyTuple_SetItem()}, does @emph{not} discard a reference to any item that
is being replaced; any reference in the tuple at position @emph{pos} will be
leaked.
@end quotation
@end cartouche
@end deffn

@geindex _PyTuple_Resize (C 函数)
@anchor{c-api/tuple c _PyTuple_Resize}@anchor{e44}
@deffn {C 函数} int _PyTuple_Resize (PyObject@w{ }**p, Py_ssize_t@w{ }newsize)

Can be used to resize a tuple.  @emph{newsize} will be the new length of the tuple.
Because tuples are @emph{supposed} to be immutable, this should only be used if there
is only one reference to the object.  Do @emph{not} use this if the tuple may already
be known to some other part of the code.  The tuple will always grow or shrink
at the end.  Think of this as destroying the old tuple and creating a new one,
only more efficiently.  Returns @code{0} on success. Client code should never
assume that the resulting value of @code{*p} will be the same as before calling
this function. If the object referenced by @code{*p} is replaced, the original
@code{*p} is destroyed.  On failure, returns @code{-1} and sets @code{*p} to @code{NULL}, and
raises @ref{f9f,,MemoryError} or @ref{5f6,,SystemError}.
@end deffn

@geindex PyTuple_ClearFreeList (C 函数)
@anchor{c-api/tuple c PyTuple_ClearFreeList}@anchor{3deb}
@deffn {C 函数} int PyTuple_ClearFreeList ()

清空释放列表。 返回所释放的条目数。
@end deffn

@node Struct Sequence Objects,列表对象,元组对象,序列对象
@anchor{c-api/tuple struct-sequence-objects}@anchor{3dec}
@subsubsection Struct Sequence Objects


Struct sequence objects are the C equivalent of @ref{1b6,,namedtuple()}
objects, i.e. a sequence whose items can also be accessed through attributes.
To create a struct sequence, you first have to create a specific struct sequence
type.

@geindex PyStructSequence_NewType (C 函数)
@anchor{c-api/tuple c PyStructSequence_NewType}@anchor{3ded}
@deffn {C 函数} PyTypeObject* PyStructSequence_NewType (PyStructSequence_Desc@w{ }*desc)
@emph{Return value: New reference.}
Create a new struct sequence type from the data in @emph{desc}, described below. Instances
of the resulting type can be created with @ref{3dee,,PyStructSequence_New()}.
@end deffn

@geindex PyStructSequence_InitType (C 函数)
@anchor{c-api/tuple c PyStructSequence_InitType}@anchor{921}
@deffn {C 函数} void PyStructSequence_InitType (PyTypeObject@w{ }*type, PyStructSequence_Desc@w{ }*desc)

Initializes a struct sequence type @emph{type} from @emph{desc} in place.
@end deffn

@geindex PyStructSequence_InitType2 (C 函数)
@anchor{c-api/tuple c PyStructSequence_InitType2}@anchor{920}
@deffn {C 函数} int PyStructSequence_InitType2 (PyTypeObject@w{ }*type, PyStructSequence_Desc@w{ }*desc)

The same as @code{PyStructSequence_InitType}, but returns @code{0} on success and @code{-1} on
failure.


3.4 新版功能.

@end deffn

@geindex PyStructSequence_Desc (C 类型)
@anchor{c-api/tuple c PyStructSequence_Desc}@anchor{423}
@deffn {C 类型} PyStructSequence_Desc

包含要创建的结构序列类型的元信息。


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

C 类型

@tab

含义

@item

@code{name}

@tab

@code{const char *}

@tab

结构序列类型的名称

@item

@code{doc}

@tab

@code{const char *}

@tab

pointer to docstring for the type
or @code{NULL} to omit

@item

@code{fields}

@tab

@code{PyStructSequence_Field *}

@tab

pointer to @code{NULL}-terminated array
with field names of the new type

@item

@code{n_in_sequence}

@tab

@code{int}

@tab

number of fields visible to the
Python side (if used as tuple)

@end multitable

@end deffn

@geindex PyStructSequence_Field (C 类型)
@anchor{c-api/tuple c PyStructSequence_Field}@anchor{422}
@deffn {C 类型} PyStructSequence_Field

Describes a field of a struct sequence. As a struct sequence is modeled as a
tuple, all fields are typed as @ref{4b5,,PyObject*}.  The index in the
@code{fields} array of the @ref{423,,PyStructSequence_Desc} determines which
field of the struct sequence is described.


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

C 类型

@tab

含义

@item

@code{name}

@tab

@code{const char *}

@tab

name for the field or @code{NULL} to end
the list of named fields, set to
@ref{3def,,PyStructSequence_UnnamedField}
to leave unnamed

@item

@code{doc}

@tab

@code{const char *}

@tab

field docstring or @code{NULL} to omit

@end multitable

@end deffn

@geindex PyStructSequence_UnnamedField (C 变量)
@anchor{c-api/tuple c PyStructSequence_UnnamedField}@anchor{3def}
@deffn {C 变量} char* PyStructSequence_UnnamedField

Special value for a field name to leave it unnamed.
@end deffn

@geindex PyStructSequence_New (C 函数)
@anchor{c-api/tuple c PyStructSequence_New}@anchor{3dee}
@deffn {C 函数} PyObject* PyStructSequence_New (PyTypeObject@w{ }*type)
@emph{Return value: New reference.}
Creates an instance of @emph{type}, which must have been created with
@ref{3ded,,PyStructSequence_NewType()}.
@end deffn

@geindex PyStructSequence_GetItem (C 函数)
@anchor{c-api/tuple c PyStructSequence_GetItem}@anchor{3df0}
@deffn {C 函数} PyObject* PyStructSequence_GetItem (PyObject@w{ }*p, Py_ssize_t@w{ }pos)
@emph{Return value: Borrowed reference.}
Return the object at position @emph{pos} in the struct sequence pointed to by @emph{p}.
No bounds checking is performed.
@end deffn

@geindex PyStructSequence_GET_ITEM (C 函数)
@anchor{c-api/tuple c PyStructSequence_GET_ITEM}@anchor{3df1}
@deffn {C 函数} PyObject* PyStructSequence_GET_ITEM (PyObject@w{ }*p, Py_ssize_t@w{ }pos)
@emph{Return value: Borrowed reference.}
Macro equivalent of @ref{3df0,,PyStructSequence_GetItem()}.
@end deffn

@geindex PyStructSequence_SetItem (C 函数)
@anchor{c-api/tuple c PyStructSequence_SetItem}@anchor{3df2}
@deffn {C 函数} void PyStructSequence_SetItem (PyObject@w{ }*p, Py_ssize_t@w{ }pos, PyObject@w{ }*o)

Sets the field at index @emph{pos} of the struct sequence @emph{p} to value @emph{o}.  Like
@ref{3dea,,PyTuple_SET_ITEM()}, this should only be used to fill in brand new
instances.

@cartouche
@quotation 注解 
This function "steals" a reference to @emph{o}.
@end quotation
@end cartouche
@end deffn

@geindex PyStructSequence_SET_ITEM (C 函数)
@anchor{c-api/tuple c PyStructSequence_SET_ITEM}@anchor{3df3}
@deffn {C 函数} void PyStructSequence_SET_ITEM (PyObject@w{ }*p, Py_ssize_t@w{ }*pos, PyObject@w{ }*o)

Macro equivalent of @ref{3df2,,PyStructSequence_SetItem()}.

@cartouche
@quotation 注解 
This function "steals" a reference to @emph{o}.
@end quotation
@end cartouche
@end deffn

@node 列表对象,,Struct Sequence Objects,序列对象
@anchor{c-api/list doc}@anchor{3df4}@anchor{c-api/list list-objects}@anchor{3df5}@anchor{c-api/list listobjects}@anchor{3df6}
@subsubsection 列表对象


@geindex 对象; list

@geindex PyListObject (C 类型)
@anchor{c-api/list c PyListObject}@anchor{3ca8}
@deffn {C 类型} PyListObject

这个C类型 @ref{4b5,,PyObject} 的子类型代表一个Python列表对象。
@end deffn

@geindex PyList_Type (C 变量)
@anchor{c-api/list c PyList_Type}@anchor{3af6}
@deffn {C 变量} PyTypeObject PyList_Type

这是个属于 @ref{2d6,,PyTypeObject} 的代表Python列表类型的实例。在Python层面和类型 @ref{262,,list} 是同一个对象。
@end deffn

@geindex PyList_Check (C 函数)
@anchor{c-api/list c PyList_Check}@anchor{3df7}
@deffn {C 函数} int PyList_Check (PyObject@w{ }*p)

如果 @emph{p} 是一个列表对象或者是一个列表类型的子类型实例时，返回真。
@end deffn

@geindex PyList_CheckExact (C 函数)
@anchor{c-api/list c PyList_CheckExact}@anchor{3df8}
@deffn {C 函数} int PyList_CheckExact (PyObject@w{ }*p)

当 @emph{p} 是一个列表对象，但是不是列表类型的子类型实例时，返回真。
@end deffn

@geindex PyList_New (C 函数)
@anchor{c-api/list c PyList_New}@anchor{3b56}
@deffn {C 函数} PyObject* PyList_New (Py_ssize_t@w{ }len)
@emph{Return value: New reference.}
成功时返回一个长度为 @emph{len} 的新列表，失败时返回 @code{NULL}。

@cartouche
@quotation 注解 
当 @emph{len} 大于零时，被返回的列表对象项目被设成 @code{NULL}。因此你不能用类似C函数 @ref{fe2,,PySequence_SetItem()} 的抽象API或者用C函数 @ref{3ac7,,PyList_SetItem()} 将所有项目设置成真实对象前对Python代码公开这个对象。
@end quotation
@end cartouche
@end deffn

@geindex PyList_Size (C 函数)
@anchor{c-api/list c PyList_Size}@anchor{d77}
@deffn {C 函数} Py_ssize_t PyList_Size (PyObject@w{ }*list)

@geindex 內置函数; len

返回 @emph{list} 中列表对象的长度；这等于在列表对象调用 @code{len(list)} 。
@end deffn

@geindex PyList_GET_SIZE (C 函数)
@anchor{c-api/list c PyList_GET_SIZE}@anchor{3df9}
@deffn {C 函数} Py_ssize_t PyList_GET_SIZE (PyObject@w{ }*list)

宏版本的C函数 @ref{d77,,PyList_Size()} ，没有错误检测。
@end deffn

@geindex PyList_GetItem (C 函数)
@anchor{c-api/list c PyList_GetItem}@anchor{3ac2}
@deffn {C 函数} PyObject* PyList_GetItem (PyObject@w{ }*list, Py_ssize_t@w{ }index)
@emph{Return value: Borrowed reference.}
返回 @emph{list} 所指向列表中 @emph{index} 位置上的对象。 位置值必须为非负数；不支持从列表末尾进行索引。 如果 @emph{index} 超出边界 (<0 or >=len(list))，则返回 @code{NULL} 并设置 @ref{e6e,,IndexError} 异常。
@end deffn

@geindex PyList_GET_ITEM (C 函数)
@anchor{c-api/list c PyList_GET_ITEM}@anchor{3dfa}
@deffn {C 函数} PyObject* PyList_GET_ITEM (PyObject@w{ }*list, Py_ssize_t@w{ }i)
@emph{Return value: Borrowed reference.}
宏版本的C函数 @ref{3ac2,,PyList_GetItem()} ，没有错误检测。
@end deffn

@geindex PyList_SetItem (C 函数)
@anchor{c-api/list c PyList_SetItem}@anchor{3ac7}
@deffn {C 函数} int PyList_SetItem (PyObject@w{ }*list, Py_ssize_t@w{ }index, PyObject@w{ }*item)

将列表中索引为 @emph{index} 的项设为 @emph{item}。 成功时返回 @code{0}。 如果 @emph{index} 超出范围则返回 @code{-1} 并设定 @ref{e6e,,IndexError} 异常。

@cartouche
@quotation 注解 
此函数会“偷走”一个对 @emph{item} 的引用并丢弃一个对列表中受影响位置上的已有条目的引用。
@end quotation
@end cartouche
@end deffn

@geindex PyList_SET_ITEM (C 函数)
@anchor{c-api/list c PyList_SET_ITEM}@anchor{3dfb}
@deffn {C 函数} void PyList_SET_ITEM (PyObject@w{ }*list, Py_ssize_t@w{ }i, PyObject@w{ }*o)

不带错误检测的宏版本 @ref{3ac7,,PyList_SetItem()}。 这通常只被用于新列表中之前没有内容的位置进行填充。

@cartouche
@quotation 注解 
该宏会“偷走”一个对 @emph{item} 的引用，但与 @ref{3ac7,,PyList_SetItem()} 不同的是它 @emph{不会} 丢弃对任何被替换条目的引用；在 @emph{list} 的 @emph{i} 位置上的任何引用都将被泄露。
@end quotation
@end cartouche
@end deffn

@geindex PyList_Insert (C 函数)
@anchor{c-api/list c PyList_Insert}@anchor{3dfc}
@deffn {C 函数} int PyList_Insert (PyObject@w{ }*list, Py_ssize_t@w{ }index, PyObject@w{ }*item)

将条目 @emph{item} 插入到列表 @emph{list} 索引号 @emph{index} 之前的位置。 如果成功将返回 @code{0}；如果不成功则返回 @code{-1} 并设置一个异常。 相当于 @code{list.insert(index, item)}。
@end deffn

@geindex PyList_Append (C 函数)
@anchor{c-api/list c PyList_Append}@anchor{3dfd}
@deffn {C 函数} int PyList_Append (PyObject@w{ }*list, PyObject@w{ }*item)

将对象 @emph{item} 添加到列表 @emph{list} 的末尾。 如果成功将返回 @code{0}；如果不成功则返回 @code{-1} 并设置一个异常。 相当于 @code{list.append(item)}。
@end deffn

@geindex PyList_GetSlice (C 函数)
@anchor{c-api/list c PyList_GetSlice}@anchor{3dfe}
@deffn {C 函数} PyObject* PyList_GetSlice (PyObject@w{ }*list, Py_ssize_t@w{ }low, Py_ssize_t@w{ }high)
@emph{Return value: New reference.}
返回一个对象列表，包含 @emph{list} 当中位于 @emph{low} 和 @emph{high} @emph{之间} 的对象。 如果不成功则返回 @code{NULL} 并设置异常。 相当于 @code{list[low:high]}。 不支持从列表末尾进行索引。
@end deffn

@geindex PyList_SetSlice (C 函数)
@anchor{c-api/list c PyList_SetSlice}@anchor{3dff}
@deffn {C 函数} int PyList_SetSlice (PyObject@w{ }*list, Py_ssize_t@w{ }low, Py_ssize_t@w{ }high, PyObject@w{ }*itemlist)

将 @emph{list} 当中 @emph{low} 与 @emph{high} 之间的切片设为 @emph{itemlist} 的内容。 相当于 @code{list[low:high] = itemlist}。 @emph{itemlist} 可以为 @code{NULL}，表示赋值为一个空列表（删除切片）。 成功时返回 @code{0}，失败时返回 @code{-1}。 这里不支持从列表末尾进行索引。
@end deffn

@geindex PyList_Sort (C 函数)
@anchor{c-api/list c PyList_Sort}@anchor{3e00}
@deffn {C 函数} int PyList_Sort (PyObject@w{ }*list)

对 @emph{list} 中的条目进行原地排序。 成功时返回 @code{0}，失败时返回 @code{-1}。 这等价于 @code{list.sort()}。
@end deffn

@geindex PyList_Reverse (C 函数)
@anchor{c-api/list c PyList_Reverse}@anchor{3e01}
@deffn {C 函数} int PyList_Reverse (PyObject@w{ }*list)

对 @emph{list} 中的条目进行原地反转。 成功时返回 @code{0}，失败时返回 @code{-1}。 这等价于 @code{list.reverse()}。
@end deffn

@geindex PyList_AsTuple (C 函数)
@anchor{c-api/list c PyList_AsTuple}@anchor{3e02}
@deffn {C 函数} PyObject* PyList_AsTuple (PyObject@w{ }*list)
@emph{Return value: New reference.}
@geindex 內置函数; tuple

返回一个新的元组对象，其中包含 @emph{list} 的内容；等价于 @code{tuple(list)}。
@end deffn

@geindex PyList_ClearFreeList (C 函数)
@anchor{c-api/list c PyList_ClearFreeList}@anchor{3e03}
@deffn {C 函数} int PyList_ClearFreeList ()

清空释放列表。 返回所释放的条目数。


3.3 新版功能.

@end deffn

@node 容器对象,函数对象<2>,序列对象,具体的对象层
@anchor{c-api/concrete container-objects}@anchor{3e04}@anchor{c-api/concrete mapobjects}@anchor{3e05}
@subsection 容器对象


@geindex 对象; mapping

@menu
* 字典对象:: 
* 集合对象:: 

@end menu

@node 字典对象,集合对象,,容器对象
@anchor{c-api/dict doc}@anchor{3e06}@anchor{c-api/dict dictionary-objects}@anchor{3e07}@anchor{c-api/dict dictobjects}@anchor{3e08}
@subsubsection 字典对象


@geindex 对象; dictionary

@geindex PyDictObject (C 类型)
@anchor{c-api/dict c PyDictObject}@anchor{3e09}
@deffn {C 类型} PyDictObject

这个 @ref{4b5,,PyObject} 的子类型代表一个Python字典对象。
@end deffn

@geindex PyDict_Type (C 变量)
@anchor{c-api/dict c PyDict_Type}@anchor{3e0a}
@deffn {C 变量} PyTypeObject PyDict_Type

Python字典类型表示为 @ref{2d6,,PyTypeObject} 的实例。这与Python层面的 @ref{1b8,,dict} 是相同的对象。
@end deffn

@geindex PyDict_Check (C 函数)
@anchor{c-api/dict c PyDict_Check}@anchor{3cfb}
@deffn {C 函数} int PyDict_Check (PyObject@w{ }*p)

如果 @emph{p} 是字典对象或者字典类型的子类型的实例，则返回真。
@end deffn

@geindex PyDict_CheckExact (C 函数)
@anchor{c-api/dict c PyDict_CheckExact}@anchor{3e0b}
@deffn {C 函数} int PyDict_CheckExact (PyObject@w{ }*p)

如果 @emph{p} 是字典对象但不是字典类型的子类型的实例，则返回真。
@end deffn

@geindex PyDict_New (C 函数)
@anchor{c-api/dict c PyDict_New}@anchor{3e0c}
@deffn {C 函数} PyObject* PyDict_New ()
@emph{Return value: New reference.}
返回一个新的空字典，失败时返回 @code{NULL}。
@end deffn

@geindex PyDictProxy_New (C 函数)
@anchor{c-api/dict c PyDictProxy_New}@anchor{3e0d}
@deffn {C 函数} PyObject* PyDictProxy_New (PyObject@w{ }*mapping)
@emph{Return value: New reference.}
返回 @ref{ab1,,types.MappingProxyType} 对象，用于强制执行只读行为的映射。这通常用于创建视图以防止修改非动态类类型的字典。
@end deffn

@geindex PyDict_Clear (C 函数)
@anchor{c-api/dict c PyDict_Clear}@anchor{3e0e}
@deffn {C 函数} void PyDict_Clear (PyObject@w{ }*p)

清空现有字典的所有键值对。
@end deffn

@geindex PyDict_Contains (C 函数)
@anchor{c-api/dict c PyDict_Contains}@anchor{3e0f}
@deffn {C 函数} int PyDict_Contains (PyObject@w{ }*p, PyObject@w{ }*key)

确定 @emph{key} 是否包含在字典 @emph{p} 中。如果 @emph{key} 匹配上 @emph{p} 的某一项，则返回 @code{1} ，否则返回 @code{0} 。返回 @code{-1} 表示出错。这等同于Python表达式 @code{key in p} 。
@end deffn

@geindex PyDict_Copy (C 函数)
@anchor{c-api/dict c PyDict_Copy}@anchor{3e10}
@deffn {C 函数} PyObject* PyDict_Copy (PyObject@w{ }*p)
@emph{Return value: New reference.}
返回与 @emph{p} 包含相同键值对的新字典。
@end deffn

@geindex PyDict_SetItem (C 函数)
@anchor{c-api/dict c PyDict_SetItem}@anchor{3ac8}
@deffn {C 函数} int PyDict_SetItem (PyObject@w{ }*p, PyObject@w{ }*key, PyObject@w{ }*val)

使用 @emph{key} 作为键将 @emph{val} 插入字典 @emph{p}。 @emph{key} 必须为 @ref{13c0,,hashable}；如果不是，则将引发 @ref{192,,TypeError}。 成功时返回 @code{0}，失败时返回 @code{-1}。 此函数 @emph{不会} 附带对 @emph{val} 的引用。
@end deffn

@geindex PyDict_SetItemString (C 函数)
@anchor{c-api/dict c PyDict_SetItemString}@anchor{3e11}
@deffn {C 函数} int PyDict_SetItemString (PyObject@w{ }*p, const char@w{ }*key, PyObject@w{ }*val)

@geindex PyUnicode_FromString()

使用 @emph{key} 作为键将 @emph{val} 插入到字典 @emph{p}。 @emph{key} 应当为 @code{const char*}。 键对象是使用 @code{PyUnicode_FromString(key)} 创建的。 成功时返回 @code{0}，失败时返回 @code{-1}。 此函数 @emph{不会} 附带对 @emph{val} 的引用。
@end deffn

@geindex PyDict_DelItem (C 函数)
@anchor{c-api/dict c PyDict_DelItem}@anchor{3e12}
@deffn {C 函数} int PyDict_DelItem (PyObject@w{ }*p, PyObject@w{ }*key)

使用键 @emph{key} 删除字典 @emph{p} 中的条目。 @emph{key} 必须是可哈希的；如果不是，则抛出 @ref{192,,TypeError} 异常。成功时返回 @code{0} ，失败时返回 @code{-1} 。
@end deffn

@geindex PyDict_DelItemString (C 函数)
@anchor{c-api/dict c PyDict_DelItemString}@anchor{3e13}
@deffn {C 函数} int PyDict_DelItemString (PyObject@w{ }*p, const char@w{ }*key)

删除字典 @emph{p} 中由字符串 @emph{key} 作为键的条目。成功时返回 @code{0} ，失败时返回 @code{-1}。
@end deffn

@geindex PyDict_GetItem (C 函数)
@anchor{c-api/dict c PyDict_GetItem}@anchor{3ac3}
@deffn {C 函数} PyObject* PyDict_GetItem (PyObject@w{ }*p, PyObject@w{ }*key)
@emph{Return value: Borrowed reference.}
从字典 @emph{p} 中返回以 @emph{key} 为键的对象。 如果键名 @emph{key} 不存在但 @emph{没有} 设置一个异常则返回 @code{NULL}。

需要注意的是，调用 @ref{339,,__hash__()} 和 @ref{338,,__eq__()} 方法产生的异常不会被抛出。改用 @ref{3e14,,PyDict_GetItemWithError()} 获得错误报告。
@end deffn

@geindex PyDict_GetItemWithError (C 函数)
@anchor{c-api/dict c PyDict_GetItemWithError}@anchor{3e14}
@deffn {C 函数} PyObject* PyDict_GetItemWithError (PyObject@w{ }*p, PyObject@w{ }*key)
@emph{Return value: Borrowed reference.}
@ref{3ac3,,PyDict_GetItem()} 的变种，它不会屏蔽异常。 当异常发生时将返回 @code{NULL} @strong{并且} 设置一个异常。 如果键不存在则返回 @code{NULL} @strong{并且不会} 设置一个异常。
@end deffn

@geindex PyDict_GetItemString (C 函数)
@anchor{c-api/dict c PyDict_GetItemString}@anchor{3ac4}
@deffn {C 函数} PyObject* PyDict_GetItemString (PyObject@w{ }*p, const char@w{ }*key)
@emph{Return value: Borrowed reference.}
这与 @ref{3ac3,,PyDict_GetItem()} 一样，但是 @emph{key} 需要指定一个 @code{const char*} ，而不是 @ref{4b5,,PyObject*} 。

需要注意的是，调用 @ref{339,,__hash__()} 、 @ref{338,,__eq__()} 方法和创建一个临时的字符串对象时产生的异常不会被抛出。改用 @ref{3e14,,PyDict_GetItemWithError()} 获得错误报告。
@end deffn

@geindex PyDict_SetDefault (C 函数)
@anchor{c-api/dict c PyDict_SetDefault}@anchor{3e15}
@deffn {C 函数} PyObject* PyDict_SetDefault (PyObject@w{ }*p, PyObject@w{ }*key, PyObject@w{ }*defaultobj)
@emph{Return value: Borrowed reference.}
这跟Python层面的 @ref{9b9,,dict.setdefault()} 一样。如果键 @emph{key} 存在，它返回在字典 @emph{p} 里面对应的值。如果键不存在，它会和值 @emph{defaultobj} 一起插入并返回 @emph{defaultobj} 。这个函数只计算 @emph{key} 的哈希函数一次，而不是在查找和插入时分别计算它。


3.4 新版功能.

@end deffn

@geindex PyDict_Items (C 函数)
@anchor{c-api/dict c PyDict_Items}@anchor{3e16}
@deffn {C 函数} PyObject* PyDict_Items (PyObject@w{ }*p)
@emph{Return value: New reference.}
返回一个包含字典中所有键值项的 @ref{3ca8,,PyListObject}。
@end deffn

@geindex PyDict_Keys (C 函数)
@anchor{c-api/dict c PyDict_Keys}@anchor{3e17}
@deffn {C 函数} PyObject* PyDict_Keys (PyObject@w{ }*p)
@emph{Return value: New reference.}
返回一个包含字典中所有键(keys)的 @ref{3ca8,,PyListObject}。
@end deffn

@geindex PyDict_Values (C 函数)
@anchor{c-api/dict c PyDict_Values}@anchor{3e18}
@deffn {C 函数} PyObject* PyDict_Values (PyObject@w{ }*p)
@emph{Return value: New reference.}
返回一个包含字典中所有值(values)的 @ref{3ca8,,PyListObject}。
@end deffn

@geindex PyDict_Size (C 函数)
@anchor{c-api/dict c PyDict_Size}@anchor{3e19}
@deffn {C 函数} Py_ssize_t PyDict_Size (PyObject@w{ }*p)

@geindex 內置函数; len

返回字典中项目数，等价于对字典 @emph{p} 使用 @code{len(p)}。
@end deffn

@geindex PyDict_Next (C 函数)
@anchor{c-api/dict c PyDict_Next}@anchor{3e1a}
@deffn {C 函数} int PyDict_Next (PyObject@w{ }*p, Py_ssize_t@w{ }*ppos, PyObject@w{ }**pkey, PyObject@w{ }**pvalue)

迭代字典 @emph{p} 中的所有键值对。 在第一次调用此函数开始迭代之前，由 @emph{ppos} 所引用的 @code{Py_ssize_t} 必须初始化为 @code{0}；该函数将为字典中的每个键值对返回真值，一旦所有键值对报告完毕则返回假值。 形参 @emph{pkey} 和 @emph{pvalue} 应当指向 @ref{4b5,,PyObject*} 变量，它们将分别使用每个键和值来填充，或者也可以为 @code{NULL}。 通过它们返回的任何引用都是暂借的。 @emph{ppos} 在迭代期间不应被更改。 它的值表示内部字典结构中的偏移量，并且由于结构是稀疏的，因此偏移量并不连续。

例如

@example
PyObject *key, *value;
Py_ssize_t pos = 0;

while (PyDict_Next(self->dict, &pos, &key, &value)) @{
    /* do something interesting with the values... */
    ...
@}
@end example

字典 @emph{p} 不应该在遍历期间发生改变。在遍历字典时，改变键中的值是安全的，但仅限于键的集合不发生改变。例如:

@example
PyObject *key, *value;
Py_ssize_t pos = 0;

while (PyDict_Next(self->dict, &pos, &key, &value)) @{
    long i = PyLong_AsLong(value);
    if (i == -1 && PyErr_Occurred()) @{
        return -1;
    @}
    PyObject *o = PyLong_FromLong(i + 1);
    if (o == NULL)
        return -1;
    if (PyDict_SetItem(self->dict, key, o) < 0) @{
        Py_DECREF(o);
        return -1;
    @}
    Py_DECREF(o);
@}
@end example
@end deffn

@geindex PyDict_Merge (C 函数)
@anchor{c-api/dict c PyDict_Merge}@anchor{3e1b}
@deffn {C 函数} int PyDict_Merge (PyObject@w{ }*a, PyObject@w{ }*b, int@w{ }override)

对映射对象 @emph{b} 进行迭代，将键值对添加到字典 @emph{a}。 @emph{b} 可以是一个字典，或任何支持 @ref{426,,PyMapping_Keys()} 和 @ref{3b57,,PyObject_GetItem()} 的对象。 如果 @emph{override} 为真值，则如果在 @emph{b} 中找到相同的键则 @emph{a} 中已存在的相应键值对将被替换，否则如果在 @emph{a} 中没有相同的键则只是添加键值对。 当成功时返回 @code{0} 或者当引发异常时返回 @code{-1}。
@end deffn

@geindex PyDict_Update (C 函数)
@anchor{c-api/dict c PyDict_Update}@anchor{3e1c}
@deffn {C 函数} int PyDict_Update (PyObject@w{ }*a, PyObject@w{ }*b)

这与 C 中的 @code{PyDict_Merge(a, b, 1)} 一样，也类似于 Python 中的 @code{a.update(b)}，差别在于 @ref{3e1c,,PyDict_Update()} 在第二个参数没有 "keys" 属性时不会回退到迭代键值对的序列。 当成功时返回 @code{0} 或者当引发异常时返回 @code{-1}。
@end deffn

@geindex PyDict_MergeFromSeq2 (C 函数)
@anchor{c-api/dict c PyDict_MergeFromSeq2}@anchor{3e1d}
@deffn {C 函数} int PyDict_MergeFromSeq2 (PyObject@w{ }*a, PyObject@w{ }*seq2, int@w{ }override)

将 @emph{seq2} 中的键值对更新或合并到字典 @emph{a}。 @emph{seq2} 必须为产生长度为 2 的用作键值对的元素的可迭代对象。 当存在重复的键时，如果 @emph{override} 真值则最后出现的键胜出。 当成功时返回 @code{0} 或者当引发异常时返回 @code{-1}。 等价的 Python 代码（返回值除外）:

@example
def PyDict_MergeFromSeq2(a, seq2, override):
    for key, value in seq2:
        if override or key not in a:
            a[key] = value
@end example
@end deffn

@geindex PyDict_ClearFreeList (C 函数)
@anchor{c-api/dict c PyDict_ClearFreeList}@anchor{3e1e}
@deffn {C 函数} int PyDict_ClearFreeList ()

清空释放列表。 返回所释放的条目数。


3.3 新版功能.

@end deffn

@node 集合对象,,字典对象,容器对象
@anchor{c-api/set doc}@anchor{3e1f}@anchor{c-api/set set-objects}@anchor{3e20}@anchor{c-api/set setobjects}@anchor{3e21}
@subsubsection 集合对象


@geindex 对象; set
@geindex 对象; frozenset

这一章节详细介绍了 @ref{b68,,set} 和 @ref{be7,,frozenset} 对象的公共 API。 任何未在下面列出的功能最好是使用抽象对象协议 (包括 @ref{3c65,,PyObject_CallMethod()}, @ref{ed6,,PyObject_RichCompareBool()}, @ref{3c6b,,PyObject_Hash()}, @ref{962,,PyObject_Repr()}, @ref{3c6c,,PyObject_IsTrue()}, @ref{fdf,,PyObject_Print()} 以及 @ref{3c73,,PyObject_GetIter()}) 或者抽象数字协议 (包括 @ref{3c85,,PyNumber_And()}, @ref{3c78,,PyNumber_Subtract()}, @ref{3c87,,PyNumber_Or()}, @ref{3c86,,PyNumber_Xor()}, @ref{3c91,,PyNumber_InPlaceAnd()}, @ref{3c89,,PyNumber_InPlaceSubtract()}, @ref{3c93,,PyNumber_InPlaceOr()} 以及 @ref{3c92,,PyNumber_InPlaceXor()}) 来访问。

@geindex PySetObject (C 类型)
@anchor{c-api/set c PySetObject}@anchor{3e22}
@deffn {C 类型} PySetObject

这个 @ref{4b5,,PyObject} 的子类型被用来保存 @ref{b68,,set} 和 @ref{be7,,frozenset} 对象的内部数据。 它类似于 @ref{3e09,,PyDictObject}，因为对于小尺寸集合来说它是固定大小的（很像元组的存储方式），并且对于中等和大尺寸集合来说它将指向单独的可变大小的内存块（很像列表的存储方式）。 此结构体的字段不应被视为公有并且可能发生改变。 所有访问应当通过已写入文档的 API 来进行，而不可通过操纵结构体中的值。
@end deffn

@geindex PySet_Type (C 变量)
@anchor{c-api/set c PySet_Type}@anchor{3e23}
@deffn {C 变量} PyTypeObject PySet_Type

这是一个 @ref{2d6,,PyTypeObject} 实例，表示 Python @ref{b68,,set} 类型。
@end deffn

@geindex PyFrozenSet_Type (C 变量)
@anchor{c-api/set c PyFrozenSet_Type}@anchor{3e24}
@deffn {C 变量} PyTypeObject PyFrozenSet_Type

这是一个 @ref{2d6,,PyTypeObject} 实例，表示 Python @ref{be7,,frozenset} 类型。
@end deffn

下列类型检查宏适用于指向任意 Python 对象的指针。 类似地，这些构造函数也适用于任意可迭代的 Python 对象。

@geindex PySet_Check (C 函数)
@anchor{c-api/set c PySet_Check}@anchor{3e25}
@deffn {C 函数} int PySet_Check (PyObject@w{ }*p)

如果 @emph{p} 是一个 @ref{b68,,set} 对象或者是其子类型的实例则返回真值。
@end deffn

@geindex PyFrozenSet_Check (C 函数)
@anchor{c-api/set c PyFrozenSet_Check}@anchor{3e26}
@deffn {C 函数} int PyFrozenSet_Check (PyObject@w{ }*p)

如果 @emph{p} 是一个 @ref{be7,,frozenset} 对象或者是其子类型的实例则返回真值。
@end deffn

@geindex PyAnySet_Check (C 函数)
@anchor{c-api/set c PyAnySet_Check}@anchor{3e27}
@deffn {C 函数} int PyAnySet_Check (PyObject@w{ }*p)

如果 @emph{p} 是一个 @ref{b68,,set} 对象、@ref{be7,,frozenset} 对象或者是其子类型的实例则返回真值。
@end deffn

@geindex PyAnySet_CheckExact (C 函数)
@anchor{c-api/set c PyAnySet_CheckExact}@anchor{3e28}
@deffn {C 函数} int PyAnySet_CheckExact (PyObject@w{ }*p)

如果 @emph{p} 是一个 @ref{b68,,set} 对象或 @ref{be7,,frozenset} 对象但不是其子类型的实例则返回真值。
@end deffn

@geindex PyFrozenSet_CheckExact (C 函数)
@anchor{c-api/set c PyFrozenSet_CheckExact}@anchor{3e29}
@deffn {C 函数} int PyFrozenSet_CheckExact (PyObject@w{ }*p)

如果 @emph{p} 是一个 @ref{be7,,frozenset} 对象但不是其子类型的实例则返回真值。
@end deffn

@geindex PySet_New (C 函数)
@anchor{c-api/set c PySet_New}@anchor{da4}
@deffn {C 函数} PyObject* PySet_New (PyObject@w{ }*iterable)
@emph{Return value: New reference.}
返回一个新的 @ref{b68,,set}，其中包含 @emph{iterable} 所返回的对象。 @emph{iterable} 可以为 @code{NULL} 表示创建一个新的空集合。 成功时返回新的集合，失败时返回 @code{NULL}。 如果 @emph{iterable} 实际上不是可迭代对象则引发 @ref{192,,TypeError}。 该构造器也适用于拷贝集合 (@code{c=set(s)})。
@end deffn

@geindex PyFrozenSet_New (C 函数)
@anchor{c-api/set c PyFrozenSet_New}@anchor{da5}
@deffn {C 函数} PyObject* PyFrozenSet_New (PyObject@w{ }*iterable)
@emph{Return value: New reference.}
返回一个新的 @ref{be7,,frozenset}，其中包含 @emph{iterable} 所返回的对象。 @emph{iterable} 可以为 @code{NULL} 表示创建一个新的空冻结集合。 成功时返回新的冻结集合，失败时返回 @code{NULL}。 如果 @emph{iterable} 实际上不是可迭代对象则引发 @ref{192,,TypeError}。
@end deffn

下列函数和宏适用于 @ref{b68,,set} 或 @ref{be7,,frozenset} 的实例或是其子类型的实例。

@geindex PySet_Size (C 函数)
@anchor{c-api/set c PySet_Size}@anchor{da9}
@deffn {C 函数} Py_ssize_t PySet_Size (PyObject@w{ }*anyset)

@geindex 內置函数; len

返回 @ref{b68,,set} 或 @ref{be7,,frozenset} 对象的长度。 等价于 @code{len(anyset)}。 如果 @emph{anyset} 不是 @ref{b68,,set}, @ref{be7,,frozenset} 或其子类型的实例则会引发 @code{PyExc_SystemError}。
@end deffn

@geindex PySet_GET_SIZE (C 函数)
@anchor{c-api/set c PySet_GET_SIZE}@anchor{3e2a}
@deffn {C 函数} Py_ssize_t PySet_GET_SIZE (PyObject@w{ }*anyset)

宏版本的 @ref{da9,,PySet_Size()}，不带错误检测。
@end deffn

@geindex PySet_Contains (C 函数)
@anchor{c-api/set c PySet_Contains}@anchor{da8}
@deffn {C 函数} int PySet_Contains (PyObject@w{ }*anyset, PyObject@w{ }*key)

如果找到返回 @code{1}，如果未找到返回 @code{0}，如果遇到错误则返回 @code{-1}。 不同于 Python @ref{d21,,__contains__()} 方法，此函数不会自动将不可哈希的集合转换为临时的冻结集合。 如果 @emph{key} 为不可哈希对象则会引发 @ref{192,,TypeError}。 如果 @emph{anyset} 不是 @ref{b68,,set}, @ref{be7,,frozenset} 或其子类型的实例则会引发 @code{PyExc_SystemError}。
@end deffn

@geindex PySet_Add (C 函数)
@anchor{c-api/set c PySet_Add}@anchor{da6}
@deffn {C 函数} int PySet_Add (PyObject@w{ }*set, PyObject@w{ }*key)

添加 @emph{key} 到一个 @ref{b68,,set} 实例。 也可用于 @ref{be7,,frozenset} 实例（类似于 @ref{3ac6,,PyTuple_SetItem()}，它可被用来为全新冻结集合在公开给其他代码之前填充全新的值）。 成功时返回 @code{0}，失败时返回 @code{-1}。 如果 @emph{key} 为不可哈希对象则会引发 @ref{192,,TypeError}。 如果没有增长空间则会引发 @ref{f9f,,MemoryError}。 如果 @emph{set} 不是 @ref{b68,,set} 或其子类型的实例则会引发 @ref{5f6,,SystemError}。
@end deffn

下列函数适用于 @ref{b68,,set} 或其子类型的实例，但不可用于 @ref{be7,,frozenset} 或其子类型的实例。

@geindex PySet_Discard (C 函数)
@anchor{c-api/set c PySet_Discard}@anchor{da7}
@deffn {C 函数} int PySet_Discard (PyObject@w{ }*set, PyObject@w{ }*key)

如果找到并移除返回 @code{1}，如果未找到（无操作）返回 @code{0}，如果遇到错误则返回 @code{-1}。 对于不存在的键不会引发 @ref{2c7,,KeyError}。 如果 @emph{key} 为不可哈希对象则会引发 @ref{192,,TypeError}。 不同于 Python @code{discard()} 方法，此函数不会自动将不可哈希的集合转换为临时的冻结集合。 如果 @emph{set} 不是 @ref{b68,,set} 或其子类型的实例则会引发 @code{PyExc_SystemError}。
@end deffn

@geindex PySet_Pop (C 函数)
@anchor{c-api/set c PySet_Pop}@anchor{3e2b}
@deffn {C 函数} PyObject* PySet_Pop (PyObject@w{ }*set)
@emph{Return value: New reference.}
返回 @emph{set} 中任意对象的新引用，并从 @emph{set} 中移除该对象。 失败时返回 @code{NULL}。 如果集合为空则会引发 @ref{2c7,,KeyError}。 如果 @emph{set} 不是 @ref{b68,,set} 或其子类型的实例则会引发 @ref{5f6,,SystemError}。
@end deffn

@geindex PySet_Clear (C 函数)
@anchor{c-api/set c PySet_Clear}@anchor{3e2c}
@deffn {C 函数} int PySet_Clear (PyObject@w{ }*set)

清空现有字典的所有键值对。
@end deffn

@geindex PySet_ClearFreeList (C 函数)
@anchor{c-api/set c PySet_ClearFreeList}@anchor{3e2d}
@deffn {C 函数} int PySet_ClearFreeList ()

清空释放列表。 返回所释放的条目数。


3.3 新版功能.

@end deffn

@node 函数对象<2>,其他对象<2>,容器对象,具体的对象层
@anchor{c-api/concrete function-objects}@anchor{3e2e}@anchor{c-api/concrete otherobjects}@anchor{3e2f}
@subsection 函数对象


@menu
* 函数对象: 函数对象<3>. 
* 实例方法对象:: 
* 方法对象: 方法对象<2>. 
* Cell 对象:: 
* 代码对象: 代码对象<2>. 

@end menu

@node 函数对象<3>,实例方法对象,,函数对象<2>
@anchor{c-api/function doc}@anchor{3e30}@anchor{c-api/function function-objects}@anchor{3e31}@anchor{c-api/function id1}@anchor{3e32}
@subsubsection 函数对象


@geindex 对象; function

有一些特定于 Python 函数的函数。

@geindex PyFunctionObject (C 类型)
@anchor{c-api/function c PyFunctionObject}@anchor{3e33}
@deffn {C 类型} PyFunctionObject

用于函数的 C 结构体。
@end deffn

@geindex PyFunction_Type (C 变量)
@anchor{c-api/function c PyFunction_Type}@anchor{3e34}
@deffn {C 变量} PyTypeObject PyFunction_Type

@geindex MethodType (in module types)

这是一个 @ref{2d6,,PyTypeObject} 实例并表示 Python 函数类型。 它作为 @code{types.FunctionType} 向 Python 程序员公开。
@end deffn

@geindex PyFunction_Check (C 函数)
@anchor{c-api/function c PyFunction_Check}@anchor{3e35}
@deffn {C 函数} int PyFunction_Check (PyObject@w{ }*o)

如果 @emph{o} 是函数对象 (类型为 @ref{3e34,,PyFunction_Type}) 则返回真值。 形参必须不为 @code{NULL}。
@end deffn

@geindex PyFunction_New (C 函数)
@anchor{c-api/function c PyFunction_New}@anchor{3e36}
@deffn {C 函数} PyObject* PyFunction_New (PyObject@w{ }*code, PyObject@w{ }*globals)
@emph{Return value: New reference.}
返回与代码对象 @emph{code} 关联的新函数对象。 @emph{globals} 必须是一个字典，该函数可以访问全局变量。

从代码对象中提取函数的文档字符串和名称。 @emph{__module__} 会从 @emph{globals} 中提取。 参数 defaults, annotations 和 closure 设为 @code{NULL}。 @emph{__qualname__} 设为与函数名称相同的值。
@end deffn

@geindex PyFunction_NewWithQualName (C 函数)
@anchor{c-api/function c PyFunction_NewWithQualName}@anchor{3e37}
@deffn {C 函数} PyObject* PyFunction_NewWithQualName (PyObject@w{ }*code, PyObject@w{ }*globals, PyObject@w{ }*qualname)
@emph{Return value: New reference.}
类似 @ref{3e36,,PyFunction_New()}，但还允许设置函数对象的 @code{__qualname__} 属性。 @emph{qualname} 应当是 unicode 对象或 @code{NULL}；如果是 @code{NULL} 则 @code{__qualname__} 属性设为与其 @code{__name__} 属性相同的值。


3.3 新版功能.

@end deffn

@geindex PyFunction_GetCode (C 函数)
@anchor{c-api/function c PyFunction_GetCode}@anchor{3e38}
@deffn {C 函数} PyObject* PyFunction_GetCode (PyObject@w{ }*op)
@emph{Return value: Borrowed reference.}
返回与函数对象 @emph{op} 关联的代码对象。
@end deffn

@geindex PyFunction_GetGlobals (C 函数)
@anchor{c-api/function c PyFunction_GetGlobals}@anchor{3e39}
@deffn {C 函数} PyObject* PyFunction_GetGlobals (PyObject@w{ }*op)
@emph{Return value: Borrowed reference.}
返回与函数对象*op*相关联的全局字典。
@end deffn

@geindex PyFunction_GetModule (C 函数)
@anchor{c-api/function c PyFunction_GetModule}@anchor{3e3a}
@deffn {C 函数} PyObject* PyFunction_GetModule (PyObject@w{ }*op)
@emph{Return value: Borrowed reference.}
返回函数对象 @emph{op} 的 @emph{__module__} 属性，通常为一个包含了模块名称的字符串，但可以通过 Python 代码设为返回其他任意对象。
@end deffn

@geindex PyFunction_GetDefaults (C 函数)
@anchor{c-api/function c PyFunction_GetDefaults}@anchor{3e3b}
@deffn {C 函数} PyObject* PyFunction_GetDefaults (PyObject@w{ }*op)
@emph{Return value: Borrowed reference.}
返回函数对象 @emph{op} 的参数默认值。 这可以是一个参数元组或 @code{NULL}。
@end deffn

@geindex PyFunction_SetDefaults (C 函数)
@anchor{c-api/function c PyFunction_SetDefaults}@anchor{3e3c}
@deffn {C 函数} int PyFunction_SetDefaults (PyObject@w{ }*op, PyObject@w{ }*defaults)

为函数对象 @emph{op} 设置参数默认值。 @emph{defaults} 必须为 @code{Py_None} 或一个元组。

失败时引发 @ref{5f6,,SystemError} 异常并返回 @code{-1} 。
@end deffn

@geindex PyFunction_GetClosure (C 函数)
@anchor{c-api/function c PyFunction_GetClosure}@anchor{3e3d}
@deffn {C 函数} PyObject* PyFunction_GetClosure (PyObject@w{ }*op)
@emph{Return value: Borrowed reference.}
返回关联到函数对象 @emph{op} 的闭包。 这可以是 @code{NULL} 或 cell 对象的元组。
@end deffn

@geindex PyFunction_SetClosure (C 函数)
@anchor{c-api/function c PyFunction_SetClosure}@anchor{3e3e}
@deffn {C 函数} int PyFunction_SetClosure (PyObject@w{ }*op, PyObject@w{ }*closure)

设置关联到函数对象 @emph{op} 的闭包。 @emph{closure} 必须为 @code{Py_None} 或 cell 对象的元组。

失败时引发 @ref{5f6,,SystemError} 异常并返回 @code{-1} 。
@end deffn

@geindex PyFunction_GetAnnotations (C 函数)
@anchor{c-api/function c PyFunction_GetAnnotations}@anchor{3e3f}
@deffn {C 函数} PyObject *PyFunction_GetAnnotations (PyObject@w{ }*op)
@emph{Return value: Borrowed reference.}
返回函数对象 @emph{op} 的标注。 这可以是一个可变字典或 @code{NULL}。
@end deffn

@geindex PyFunction_SetAnnotations (C 函数)
@anchor{c-api/function c PyFunction_SetAnnotations}@anchor{3e40}
@deffn {C 函数} int PyFunction_SetAnnotations (PyObject@w{ }*op, PyObject@w{ }*annotations)

设置函数对象 @emph{op} 的标注。 @emph{annotations} 必须为一个字典或 @code{Py_None}。

失败时引发 @ref{5f6,,SystemError} 异常并返回 @code{-1} 。
@end deffn

@node 实例方法对象,方法对象<2>,函数对象<3>,函数对象<2>
@anchor{c-api/method doc}@anchor{3e41}@anchor{c-api/method instance-method-objects}@anchor{3e42}@anchor{c-api/method instancemethod-objects}@anchor{3e43}
@subsubsection 实例方法对象


@geindex 对象; instancemethod

实例方法是 @ref{dd4,,PyCFunction} 的包装器，也是将 @ref{dd4,,PyCFunction} 绑定到类对象的一种新方式。 它替代了原先的调用 @code{PyMethod_New(func, NULL, class)}。

@geindex PyInstanceMethod_Type (C 变量)
@anchor{c-api/method c PyInstanceMethod_Type}@anchor{3e44}
@deffn {C 变量} PyTypeObject PyInstanceMethod_Type

这个 @ref{2d6,,PyTypeObject} 实例代表 Python 实例方法类型。 它并不对 Python 程序公开。
@end deffn

@geindex PyInstanceMethod_Check (C 函数)
@anchor{c-api/method c PyInstanceMethod_Check}@anchor{3e45}
@deffn {C 函数} int PyInstanceMethod_Check (PyObject@w{ }*o)

如果 @emph{o} 是实例方法对象 (类型为 @ref{3e44,,PyInstanceMethod_Type}) 则返回真值。 形参必须不为 @code{NULL}。
@end deffn

@geindex PyInstanceMethod_New (C 函数)
@anchor{c-api/method c PyInstanceMethod_New}@anchor{3e46}
@deffn {C 函数} PyObject* PyInstanceMethod_New (PyObject@w{ }*func)
@emph{Return value: New reference.}
返回一个新的实例方法对象，@emph{func} 应为任意可调用对象，@emph{func} 将在实例方法被调用时作为函数被调用。
@end deffn

@geindex PyInstanceMethod_Function (C 函数)
@anchor{c-api/method c PyInstanceMethod_Function}@anchor{3e47}
@deffn {C 函数} PyObject* PyInstanceMethod_Function (PyObject@w{ }*im)
@emph{Return value: Borrowed reference.}
返回关联到实例方法 @emph{im} 的函数对象。
@end deffn

@geindex PyInstanceMethod_GET_FUNCTION (C 函数)
@anchor{c-api/method c PyInstanceMethod_GET_FUNCTION}@anchor{3e48}
@deffn {C 函数} PyObject* PyInstanceMethod_GET_FUNCTION (PyObject@w{ }*im)
@emph{Return value: Borrowed reference.}
宏版本的 @ref{3e47,,PyInstanceMethod_Function()}，略去了错误检测。
@end deffn

@node 方法对象<2>,Cell 对象,实例方法对象,函数对象<2>
@anchor{c-api/method id1}@anchor{3e49}@anchor{c-api/method method-objects}@anchor{3e4a}
@subsubsection 方法对象


@geindex 对象; method

方法是绑定的函数对象。 方法总是会被绑定到一个用户自定义类的实例。 未绑定方法（绑定到一个类的方法）已不再可用。

@geindex PyMethod_Type (C 变量)
@anchor{c-api/method c PyMethod_Type}@anchor{3e4b}
@deffn {C 变量} PyTypeObject PyMethod_Type

@geindex MethodType (in module types)

这个 @ref{2d6,,PyTypeObject} 实例代表 Python 方法类型。 它作为 @code{types.MethodType} 向 Python 程序公开。
@end deffn

@geindex PyMethod_Check (C 函数)
@anchor{c-api/method c PyMethod_Check}@anchor{3e4c}
@deffn {C 函数} int PyMethod_Check (PyObject@w{ }*o)

如果 @emph{o} 是方法对象 (类型为 @ref{3e4b,,PyMethod_Type}) 则返回真值。 形参必须不为 @code{NULL}。
@end deffn

@geindex PyMethod_New (C 函数)
@anchor{c-api/method c PyMethod_New}@anchor{3e4d}
@deffn {C 函数} PyObject* PyMethod_New (PyObject@w{ }*func, PyObject@w{ }*self)
@emph{Return value: New reference.}
返回一个新的方法对象，@emph{func} 应为任意可调用对象，@emph{self} 为该方法应绑定的实例。 在方法被调用时 @emph{func} 将作为函数被调用。 @emph{self} 必须不为 @code{NULL}。
@end deffn

@geindex PyMethod_Function (C 函数)
@anchor{c-api/method c PyMethod_Function}@anchor{3e4e}
@deffn {C 函数} PyObject* PyMethod_Function (PyObject@w{ }*meth)
@emph{Return value: Borrowed reference.}
返回关联到方法 @emph{meth} 的函数对象。
@end deffn

@geindex PyMethod_GET_FUNCTION (C 函数)
@anchor{c-api/method c PyMethod_GET_FUNCTION}@anchor{3e4f}
@deffn {C 函数} PyObject* PyMethod_GET_FUNCTION (PyObject@w{ }*meth)
@emph{Return value: Borrowed reference.}
宏版本的 @ref{3e4e,,PyMethod_Function()}，略去了错误检测。
@end deffn

@geindex PyMethod_Self (C 函数)
@anchor{c-api/method c PyMethod_Self}@anchor{3e50}
@deffn {C 函数} PyObject* PyMethod_Self (PyObject@w{ }*meth)
@emph{Return value: Borrowed reference.}
返回关联到方法 @emph{meth} 的实例。
@end deffn

@geindex PyMethod_GET_SELF (C 函数)
@anchor{c-api/method c PyMethod_GET_SELF}@anchor{3e51}
@deffn {C 函数} PyObject* PyMethod_GET_SELF (PyObject@w{ }*meth)
@emph{Return value: Borrowed reference.}
宏版本的 @ref{3e50,,PyMethod_Self()}，略去了错误检测。
@end deffn

@geindex PyMethod_ClearFreeList (C 函数)
@anchor{c-api/method c PyMethod_ClearFreeList}@anchor{3e52}
@deffn {C 函数} int PyMethod_ClearFreeList ()

清空释放列表。 返回所释放的条目数。
@end deffn

@node Cell 对象,代码对象<2>,方法对象<2>,函数对象<2>
@anchor{c-api/cell doc}@anchor{3e53}@anchor{c-api/cell cell-objects}@anchor{3e54}@anchor{c-api/cell id1}@anchor{3e55}
@subsubsection Cell 对象


“Cell”对象用于实现由多个作用域引用的变量。 对于每个这样的变量，一个“Cell”对象为了存储该值而被创建；引用该值的每个堆栈框架的局部变量包含同样使用该变量的对外部作用域的“Cell”引用。 访问该值时，将使用“Cell”中包含的值而不是单元格对象本身。 这种对“Cell”对象的非关联化的引用需要支持生成的字节码；访问时不会自动非关联化这些内容。 “Cell”对象在其他地方可能不太有用。

@geindex PyCellObject (C 类型)
@anchor{c-api/cell c PyCellObject}@anchor{3e56}
@deffn {C 类型} PyCellObject

用于Cell对象的C结构体。
@end deffn

@geindex PyCell_Type (C 变量)
@anchor{c-api/cell c PyCell_Type}@anchor{3e57}
@deffn {C 变量} PyTypeObject PyCell_Type

与 Cell 对象对应的类型对​​象。
@end deffn

@geindex PyCell_Check (C 函数)
@anchor{c-api/cell c PyCell_Check}@anchor{3e58}
@deffn {C 函数} int PyCell_Check (ob)

如果 @emph{ob} 是一个 cell 对象则返回真值；@emph{ob} 必须不为 @code{NULL}。
@end deffn

@geindex PyCell_New (C 函数)
@anchor{c-api/cell c PyCell_New}@anchor{3e59}
@deffn {C 函数} PyObject* PyCell_New (PyObject@w{ }*ob)
@emph{Return value: New reference.}
创建并返回一个包含值 @emph{ob} 的新 cell 对象。形参可以为 @code{NULL}。
@end deffn

@geindex PyCell_Get (C 函数)
@anchor{c-api/cell c PyCell_Get}@anchor{3e5a}
@deffn {C 函数} PyObject* PyCell_Get (PyObject@w{ }*cell)
@emph{Return value: New reference.}
返回 cell 对象 @emph{cell} 的内容。
@end deffn

@geindex PyCell_GET (C 函数)
@anchor{c-api/cell c PyCell_GET}@anchor{3e5b}
@deffn {C 函数} PyObject* PyCell_GET (PyObject@w{ }*cell)
@emph{Return value: Borrowed reference.}
返回 cell 对象 @emph{cell} 的内容，但是不检测 @emph{cell} 是否非 @code{NULL} 并且为一个 cell 对象。
@end deffn

@geindex PyCell_Set (C 函数)
@anchor{c-api/cell c PyCell_Set}@anchor{3e5c}
@deffn {C 函数} int PyCell_Set (PyObject@w{ }*cell, PyObject@w{ }*value)

将 cell 对象 @emph{cell} 的内容设为 @emph{value}。 这将释放任何对 cell 对象当前内容的引用。 @emph{value} 可以为 @code{NULL}。 @emph{cell} 必须为非 @code{NULL}；如果它不是一个 cell 对象则将返回 @code{-1}。 如果设置成功则将返回 @code{0}。
@end deffn

@geindex PyCell_SET (C 函数)
@anchor{c-api/cell c PyCell_SET}@anchor{3e5d}
@deffn {C 函数} void PyCell_SET (PyObject@w{ }*cell, PyObject@w{ }*value)

将 cell 对象 @emph{cell} 的值设为 @emph{value}。 不会调整引用计数，并且不会进行检测以保证安全；@emph{cell} 必须为非 @code{NULL} 并且为一个 cell 对象。
@end deffn
@anchor{c-api/code codeobjects}@anchor{3e5e}
@geindex object; code
@geindex code object

@node 代码对象<2>,,Cell 对象,函数对象<2>
@anchor{c-api/code doc}@anchor{3e5f}@anchor{c-api/code code-objects}@anchor{3e60}
@subsubsection 代码对象


代码对象是 CPython 实现的低级细节。 每个代表一块尚未绑定到函数中的可执行代码。

@geindex PyCodeObject (C 类型)
@anchor{c-api/code c PyCodeObject}@anchor{3e61}
@deffn {C 类型} PyCodeObject

用于描述代码对象的对象的 C 结构。 此类型字段可随时更改。
@end deffn

@geindex PyCode_Type (C 变量)
@anchor{c-api/code c PyCode_Type}@anchor{3e62}
@deffn {C 变量} PyTypeObject PyCode_Type

这是一个 @ref{2d6,,PyTypeObject} 实例，其表示Python的 @ref{1b,,code} 类型。
@end deffn

@geindex PyCode_Check (C 函数)
@anchor{c-api/code c PyCode_Check}@anchor{3e63}
@deffn {C 函数} int PyCode_Check (PyObject@w{ }*co)

如果 @emph{co} 是一个 @ref{1b,,code} 对象则返回 true。
@end deffn

@geindex PyCode_GetNumFree (C 函数)
@anchor{c-api/code c PyCode_GetNumFree}@anchor{3e64}
@deffn {C 函数} int PyCode_GetNumFree (PyCodeObject@w{ }*co)

返回 @emph{co} 中的自由变量数。
@end deffn

@geindex PyCode_New (C 函数)
@anchor{c-api/code c PyCode_New}@anchor{272}
@deffn {C 函数} PyCodeObject* PyCode_New (int@w{ }argcount, int@w{ }kwonlyargcount, int@w{ }nlocals, int@w{ }stacksize, int@w{ }flags, PyObject@w{ }*code, PyObject@w{ }*consts, PyObject@w{ }*names, PyObject@w{ }*varnames, PyObject@w{ }*freevars, PyObject@w{ }*cellvars, PyObject@w{ }*filename, PyObject@w{ }*name, int@w{ }firstlineno, PyObject@w{ }*lnotab)
@emph{Return value: New reference.}
返回一个新的代码对象。 如果你需要一个虚拟代码对象来创建一个代码帧，请使用 @ref{ce3,,PyCode_NewEmpty()}。 调用 @ref{272,,PyCode_New()} 直接可以绑定到准确的 Python 版本，因为字节码的定义经常变化。
@end deffn

@geindex PyCode_NewWithPosOnlyArgs (C 函数)
@anchor{c-api/code c PyCode_NewWithPosOnlyArgs}@anchor{271}
@deffn {C 函数} PyCodeObject* PyCode_NewWithPosOnlyArgs (int@w{ }argcount, int@w{ }posonlyargcount, int@w{ }kwonlyargcount, int@w{ }nlocals, int@w{ }stacksize, int@w{ }flags, PyObject@w{ }*code, PyObject@w{ }*consts, PyObject@w{ }*names, PyObject@w{ }*varnames, PyObject@w{ }*freevars, PyObject@w{ }*cellvars, PyObject@w{ }*filename, PyObject@w{ }*name, int@w{ }firstlineno, PyObject@w{ }*lnotab)
@emph{Return value: New reference.}
类似于 @ref{272,,PyCode_New()}，但带有一个额外的 "posonlyargcount" 用于仅限位置参数。


3.8 新版功能.

@end deffn

@geindex PyCode_NewEmpty (C 函数)
@anchor{c-api/code c PyCode_NewEmpty}@anchor{ce3}
@deffn {C 函数} PyCodeObject* PyCode_NewEmpty (const char@w{ }*filename, const char@w{ }*funcname, int@w{ }firstlineno)
@emph{Return value: New reference.}
返回具有指定文件名、函数名和第一行号的新空代码对象。 对于 @ref{c3d,,exec()} 或 @ref{b89,,eval()} 生成的代码对象是非法的。
@end deffn

@node 其他对象<2>,,函数对象<2>,具体的对象层
@anchor{c-api/concrete other-objects}@anchor{3e65}
@subsection 其他对象


@menu
* 文件对象:: 
* 模块对象:: 
* 迭代器对象:: 
* 描述符对象:: 
* 切片对象:: 
* Ellipsis 对象:: 
* MemoryView 对象:: 
* 弱引用对象: 弱引用对象<2>. 
* 胶囊: 胶囊<2>. 
* 生成器对象:: 
* 协程对象: 协程对象<2>. 
* 上下文变量对象:: 
* DateTime 对象: DateTime 对象<2>. 

@end menu

@node 文件对象,模块对象,,其他对象<2>
@anchor{c-api/file doc}@anchor{3e66}@anchor{c-api/file file-objects}@anchor{3e67}@anchor{c-api/file fileobjects}@anchor{3e68}
@subsubsection 文件对象


@geindex 对象; file

这些 API 是内置文件对象的 Python 2 C API 的最小仿真，它过去依赖于C标准库的缓冲 I/O（ @code{FILE*} ）支持。 在Python 3中，文件和流使用新的 @ref{a1,,io} 模块，该模块在操作系统的低级无缓冲 I/O 上定义了几个层。 下面描述的函数是针对这些新API的便捷 C 包装器，主要用于解释器中的内部错误报告；建议第三方代码访问 @ref{a1,,io} API。

@geindex PyFile_FromFd (C 函数)
@anchor{c-api/file c PyFile_FromFd}@anchor{3e69}
@deffn {C 函数} PyFile_FromFd (int@w{ }fd, const char@w{ }*name, const char@w{ }*mode, int@w{ }buffering, const char@w{ }*encoding, const char@w{ }*errors, const char@w{ }*newline, int@w{ }closefd)
@emph{Return value: New reference.}
根据已打开文件 @emph{fd} 的文件描述符创建一个 Python 文件对象。 参数 @emph{name}, @emph{encoding}, @emph{errors} 和 @emph{newline} 可以为 @code{NULL} 表示使用默认值；@emph{buffering} 可以为 @emph{-1} 表示使用默认值。 @emph{name} 会被忽略仅保留用于向下兼容。 失败时返回 @code{NULL}。 有关参数的更全面描述，请参阅 @ref{654,,io.open()} 函数的文档。

@cartouche
@quotation 警告 
由于Python流具有自己的缓冲层，因此将它们与 OS 级文件描述符混合会产生各种问题（例如数据的意外排序）。
@end quotation
@end cartouche


在 3.2 版更改: 忽略 @emph{name} 属性。

@end deffn

@geindex PyObject_AsFileDescriptor (C 函数)
@anchor{c-api/file c PyObject_AsFileDescriptor}@anchor{3e6a}
@deffn {C 函数} int PyObject_AsFileDescriptor (PyObject@w{ }*p)

将与 @emph{p} 关联的文件描述器返回为 @code{int} 。 如果对象是整数，则返回其值。 如果没有，则调用对象的 @ref{1ea0,,fileno()} 方法（如果存在）; 该方法必须返回一个整数，该整数作为文件描述器值返回。 设置异常并在失败时返回 @code{-1}。
@end deffn

@geindex PyFile_GetLine (C 函数)
@anchor{c-api/file c PyFile_GetLine}@anchor{3e6b}
@deffn {C 函数} PyObject* PyFile_GetLine (PyObject@w{ }*p, int@w{ }n)
@emph{Return value: New reference.}
@geindex EOFError (built-in exception)

等价于 @code{p.readline([n])} ，这个函数从对象 @emph{p} 中读取一行。 @emph{p} 可以是文件对象或具有 @ref{169c,,readline()} 方法的任何对象。 如果 @emph{n} 是 @code{0} ，则无论该行的长度如何，都会读取一行。 如果 @emph{n} 大于`@w{`}0`@w{`}，则从文件中读取不超过 @emph{n} 个字节；可以返回行的一部分。 在这两种情况下，如果立即到达文件末尾，则返回空字符串。 但是，如果 @emph{n} 小于 @code{0} ，则无论长度如何都会读取一行，但是如果立即到达文件末尾，则引发 @ref{c65,,EOFError}。
@end deffn

@geindex PyFile_SetOpenCodeHook (C 函数)
@anchor{c-api/file c PyFile_SetOpenCodeHook}@anchor{1f7d}
@deffn {C 函数} int PyFile_SetOpenCodeHook (Py_OpenCodeHookFunction@w{ }handler)

重载 @ref{eb1,,io.open_code()} 的正常行为，将其形参通过所提供的处理程序来传递。

处理程序是一个类型为 @code{PyObject *(*)(PyObject *path, void *userData)} 的函数，其中 @emph{path} 确保为 @ref{3d89,,PyUnicodeObject}。

@emph{userData} 指针会被传入钩子函数。 因于钩子函数可能由不同的运行时调用，该指针不应直接指向 Python 状态。

鉴于这个钩子专门在导入期间使用的，请避免在新模块执行期间进行导入操作，除非已知它们为冻结状态或者是在 @code{sys.modules} 中可用。

一旦钩子被设定，它就不能被移除或替换，之后对 @ref{1f7d,,PyFile_SetOpenCodeHook()} 的调用也将失败，如果解释器已经被初始化，函数将返回 -1 并设置一个异常。

此函数可以安全地在 @ref{433,,Py_Initialize()} 之前调用。


3.8 新版功能.

@end deffn

@geindex PyFile_WriteObject (C 函数)
@anchor{c-api/file c PyFile_WriteObject}@anchor{3e6c}
@deffn {C 函数} int PyFile_WriteObject (PyObject@w{ }*obj, PyObject@w{ }*p, int@w{ }flags)

@geindex Py_PRINT_RAW

将对象 @emph{obj} 写入文件对象 @emph{p} 。 @emph{flags} 唯一支持的标志是 @code{Py_PRINT_RAW}；如果给定，则写入对象的 @ref{329,,str()} 而不是 @ref{7c6,,repr()}。成功时返回 @code{0}，失败时返回 @code{-1}。 将设置适当的例外。
@end deffn

@geindex PyFile_WriteString (C 函数)
@anchor{c-api/file c PyFile_WriteString}@anchor{3e6d}
@deffn {C 函数} int PyFile_WriteString (const char@w{ }*s, PyObject@w{ }*p)

将字符串 @emph{s} 写入文件对象 @emph{p}。 成功返回 @code{0} 失败返回 @code{-1}；将设定相应的异常。
@end deffn

@node 模块对象,迭代器对象,文件对象,其他对象<2>
@anchor{c-api/module doc}@anchor{3e6e}@anchor{c-api/module module-objects}@anchor{3e6f}@anchor{c-api/module moduleobjects}@anchor{3e70}
@subsubsection 模块对象


@geindex 对象; module

@geindex PyModule_Type (C 变量)
@anchor{c-api/module c PyModule_Type}@anchor{3e71}
@deffn {C 变量} PyTypeObject PyModule_Type

@geindex ModuleType (in module types)

This instance of @ref{2d6,,PyTypeObject} represents the Python module type.  This
is exposed to Python programs as @code{types.ModuleType}.
@end deffn

@geindex PyModule_Check (C 函数)
@anchor{c-api/module c PyModule_Check}@anchor{3e72}
@deffn {C 函数} int PyModule_Check (PyObject@w{ }*p)

Return true if @emph{p} is a module object, or a subtype of a module object.
@end deffn

@geindex PyModule_CheckExact (C 函数)
@anchor{c-api/module c PyModule_CheckExact}@anchor{3e73}
@deffn {C 函数} int PyModule_CheckExact (PyObject@w{ }*p)

Return true if @emph{p} is a module object, but not a subtype of
@ref{3e71,,PyModule_Type}.
@end deffn

@geindex PyModule_NewObject (C 函数)
@anchor{c-api/module c PyModule_NewObject}@anchor{3e74}
@deffn {C 函数} PyObject* PyModule_NewObject (PyObject@w{ }*name)
@emph{Return value: New reference.}
@geindex __name__ (module attribute)
@geindex __doc__ (module attribute)
@geindex __file__ (module attribute)
@geindex __package__ (module attribute)
@geindex __loader__ (module attribute)

Return a new module object with the @ref{d0b,,__name__} attribute set to @emph{name}.
The module's @ref{d0b,,__name__}, @code{__doc__}, @ref{94f,,__package__}, and
@ref{950,,__loader__} attributes are filled in (all but @ref{d0b,,__name__} are set
to @code{None}); the caller is responsible for providing a @ref{13c7,,__file__}
attribute.


3.3 新版功能.



在 3.4 版更改: @ref{94f,,__package__} and @ref{950,,__loader__} are set to @code{None}.

@end deffn

@geindex PyModule_New (C 函数)
@anchor{c-api/module c PyModule_New}@anchor{3e75}
@deffn {C 函数} PyObject* PyModule_New (const char@w{ }*name)
@emph{Return value: New reference.}
Similar to @ref{3e74,,PyModule_NewObject()}, but the name is a UTF-8 encoded
string instead of a Unicode object.
@end deffn

@geindex PyModule_GetDict (C 函数)
@anchor{c-api/module c PyModule_GetDict}@anchor{3e76}
@deffn {C 函数} PyObject* PyModule_GetDict (PyObject@w{ }*module)
@emph{Return value: Borrowed reference.}
@geindex __dict__ (module attribute)

Return the dictionary object that implements @emph{module}'s namespace; this object
is the same as the @ref{4f6,,__dict__} attribute of the module object.
If @emph{module} is not a module object (or a subtype of a module object),
@ref{5f6,,SystemError} is raised and @code{NULL} is returned.

It is recommended extensions use other @code{PyModule_*()} and
@code{PyObject_*()} functions rather than directly manipulate a module's
@ref{4f6,,__dict__}.
@end deffn

@geindex PyModule_GetNameObject (C 函数)
@anchor{c-api/module c PyModule_GetNameObject}@anchor{3e77}
@deffn {C 函数} PyObject* PyModule_GetNameObject (PyObject@w{ }*module)
@emph{Return value: New reference.}
@geindex __name__ (module attribute)
@geindex SystemError (built-in exception)

Return @emph{module}'s @ref{d0b,,__name__} value.  If the module does not provide one,
or if it is not a string, @ref{5f6,,SystemError} is raised and @code{NULL} is returned.


3.3 新版功能.

@end deffn

@geindex PyModule_GetName (C 函数)
@anchor{c-api/module c PyModule_GetName}@anchor{3e78}
@deffn {C 函数} const char* PyModule_GetName (PyObject@w{ }*module)

Similar to @ref{3e77,,PyModule_GetNameObject()} but return the name encoded to
@code{'utf-8'}.
@end deffn

@geindex PyModule_GetState (C 函数)
@anchor{c-api/module c PyModule_GetState}@anchor{3e79}
@deffn {C 函数} void* PyModule_GetState (PyObject@w{ }*module)

Return the "state" of the module, that is, a pointer to the block of memory
allocated at module creation time, or @code{NULL}.  See
@ref{3e7a,,PyModuleDef.m_size}.
@end deffn

@geindex PyModule_GetDef (C 函数)
@anchor{c-api/module c PyModule_GetDef}@anchor{3e7b}
@deffn {C 函数} PyModuleDef* PyModule_GetDef (PyObject@w{ }*module)

Return a pointer to the @ref{3aed,,PyModuleDef} struct from which the module was
created, or @code{NULL} if the module wasn't created from a definition.
@end deffn

@geindex PyModule_GetFilenameObject (C 函数)
@anchor{c-api/module c PyModule_GetFilenameObject}@anchor{3e7c}
@deffn {C 函数} PyObject* PyModule_GetFilenameObject (PyObject@w{ }*module)
@emph{Return value: New reference.}
@geindex __file__ (module attribute)
@geindex SystemError (built-in exception)

Return the name of the file from which @emph{module} was loaded using @emph{module}'s
@ref{13c7,,__file__} attribute.  If this is not defined, or if it is not a
unicode string, raise @ref{5f6,,SystemError} and return @code{NULL}; otherwise return
a reference to a Unicode object.


3.2 新版功能.

@end deffn

@geindex PyModule_GetFilename (C 函数)
@anchor{c-api/module c PyModule_GetFilename}@anchor{3e7d}
@deffn {C 函数} const char* PyModule_GetFilename (PyObject@w{ }*module)

Similar to @ref{3e7c,,PyModule_GetFilenameObject()} but return the filename
encoded to 'utf-8'.


3.2 版后已移除: @ref{3e7d,,PyModule_GetFilename()} raises @code{UnicodeEncodeError} on
unencodable filenames, use @ref{3e7c,,PyModule_GetFilenameObject()} instead.

@end deffn

@menu
* Initializing C modules:: 
* Module lookup:: 

@end menu

@node Initializing C modules,Module lookup,,模块对象
@anchor{c-api/module initializing-c-modules}@anchor{3e7e}@anchor{c-api/module initializing-modules}@anchor{3b19}
@subsubsection Initializing C modules


Modules objects are usually created from extension modules (shared libraries
which export an initialization function), or compiled-in modules
(where the initialization function is added using @ref{3aad,,PyImport_AppendInittab()}).
See @ref{3ab0,,构建C/C++扩展} or @ref{3b37,,Extending Embedded Python} for details.

The initialization function can either pass a module definition instance
to @ref{3aac,,PyModule_Create()}, and return the resulting module object,
or request "multi-phase initialization" by returning the definition struct itself.

@geindex PyModuleDef (C 类型)
@anchor{c-api/module c PyModuleDef}@anchor{3aed}
@deffn {C 类型} PyModuleDef

The module definition struct, which holds all information needed to create
a module object. There is usually only one statically initialized variable
of this type for each module.

@geindex PyModuleDef.m_base (C 成员)
@anchor{c-api/module c PyModuleDef m_base}@anchor{3e7f}
@deffn {C 成员} PyModuleDef_Base m_base

Always initialize this member to @code{PyModuleDef_HEAD_INIT}.
@end deffn

@geindex PyModuleDef.m_name (C 成员)
@anchor{c-api/module c PyModuleDef m_name}@anchor{3e80}
@deffn {C 成员} const char *m_name

Name for the new module.
@end deffn

@geindex PyModuleDef.m_doc (C 成员)
@anchor{c-api/module c PyModuleDef m_doc}@anchor{3e81}
@deffn {C 成员} const char *m_doc

Docstring for the module; usually a docstring variable created with
@ref{ebb,,PyDoc_STRVAR} is used.
@end deffn

@geindex PyModuleDef.m_size (C 成员)
@anchor{c-api/module c PyModuleDef m_size}@anchor{3e7a}
@deffn {C 成员} Py_ssize_t m_size

Module state may be kept in a per-module memory area that can be
retrieved with @ref{3e79,,PyModule_GetState()}, rather than in static globals.
This makes modules safe for use in multiple sub-interpreters.

This memory area is allocated based on @emph{m_size} on module creation,
and freed when the module object is deallocated, after the
@code{m_free} function has been called, if present.

Setting @code{m_size} to @code{-1} means that the module does not support
sub-interpreters, because it has global state.

Setting it to a non-negative value means that the module can be
re-initialized and specifies the additional amount of memory it requires
for its state. Non-negative @code{m_size} is required for multi-phase
initialization.

See 
@geindex Python 提高建议; PEP 3121
PEP 3121@footnote{https://www.python.org/dev/peps/pep-3121} for more details.
@end deffn

@geindex PyModuleDef.m_methods (C 成员)
@anchor{c-api/module c PyModuleDef m_methods}@anchor{3e82}
@deffn {C 成员} PyMethodDef* m_methods

A pointer to a table of module-level functions, described by
@ref{e14,,PyMethodDef} values.  Can be @code{NULL} if no functions are present.
@end deffn

@geindex PyModuleDef.m_slots (C 成员)
@anchor{c-api/module c PyModuleDef m_slots}@anchor{3e83}
@deffn {C 成员} PyModuleDef_Slot* m_slots

An array of slot definitions for multi-phase initialization, terminated by
a @code{@{0, NULL@}} entry.
When using single-phase initialization, @emph{m_slots} must be @code{NULL}.


在 3.5 版更改: Prior to version 3.5, this member was always set to @code{NULL},
and was defined as:

@quotation

@geindex PyModuleDef.m_reload (C 成员)
@anchor{c-api/module c PyModuleDef m_reload}@anchor{3e84}
@deffn {C 成员} inquiry m_reload
@end deffn
@end quotation

@end deffn

@geindex PyModuleDef.m_traverse (C 成员)
@anchor{c-api/module c PyModuleDef m_traverse}@anchor{3e85}
@deffn {C 成员} traverseproc m_traverse

A traversal function to call during GC traversal of the module object, or
@code{NULL} if not needed. This function may be called before module state
is allocated (@ref{3e79,,PyModule_GetState()} may return @cite{NULL}),
and before the @ref{3e86,,Py_mod_exec} function is executed.
@end deffn

@geindex PyModuleDef.m_clear (C 成员)
@anchor{c-api/module c PyModuleDef m_clear}@anchor{3e87}
@deffn {C 成员} inquiry m_clear

A clear function to call during GC clearing of the module object, or
@code{NULL} if not needed. This function may be called before module state
is allocated (@ref{3e79,,PyModule_GetState()} may return @cite{NULL}),
and before the @ref{3e86,,Py_mod_exec} function is executed.
@end deffn

@geindex PyModuleDef.m_free (C 成员)
@anchor{c-api/module c PyModuleDef m_free}@anchor{3e88}
@deffn {C 成员} freefunc m_free

A function to call during deallocation of the module object, or @code{NULL} if
not needed. This function may be called before module state
is allocated (@ref{3e79,,PyModule_GetState()} may return @cite{NULL}),
and before the @ref{3e86,,Py_mod_exec} function is executed.
@end deffn
@end deffn

@menu
* Single-phase initialization:: 
* Multi-phase initialization:: 
* Low-level module creation functions:: 
* Support functions:: 

@end menu

@node Single-phase initialization,Multi-phase initialization,,Initializing C modules
@anchor{c-api/module single-phase-initialization}@anchor{3e89}
@subsubsection Single-phase initialization


The module initialization function may create and return the module object
directly. This is referred to as "single-phase initialization", and uses one
of the following two module creation functions:

@geindex PyModule_Create (C 函数)
@anchor{c-api/module c PyModule_Create}@anchor{3aac}
@deffn {C 函数} PyObject* PyModule_Create (PyModuleDef@w{ }*def)
@emph{Return value: New reference.}
Create a new module object, given the definition in @emph{def}.  This behaves
like @ref{3e8a,,PyModule_Create2()} with @emph{module_api_version} set to
@code{PYTHON_API_VERSION}.
@end deffn

@geindex PyModule_Create2 (C 函数)
@anchor{c-api/module c PyModule_Create2}@anchor{3e8a}
@deffn {C 函数} PyObject* PyModule_Create2 (PyModuleDef@w{ }*def, int@w{ }module_api_version)
@emph{Return value: New reference.}
Create a new module object, given the definition in @emph{def}, assuming the
API version @emph{module_api_version}.  If that version does not match the version
of the running interpreter, a @ref{2c0,,RuntimeWarning} is emitted.

@cartouche
@quotation 注解 
Most uses of this function should be using @ref{3aac,,PyModule_Create()}
instead; only use this if you are sure you need it.
@end quotation
@end cartouche
@end deffn

Before it is returned from in the initialization function, the resulting module
object is typically populated using functions like @ref{f0d,,PyModule_AddObject()}.

@node Multi-phase initialization,Low-level module creation functions,Single-phase initialization,Initializing C modules
@anchor{c-api/module id1}@anchor{3e8b}@anchor{c-api/module multi-phase-initialization}@anchor{3b1a}
@subsubsection Multi-phase initialization


An alternate way to specify extensions is to request "multi-phase initialization".
Extension modules created this way behave more like Python modules: the
initialization is split between the @emph{creation phase}, when the module object
is created, and the @emph{execution phase}, when it is populated.
The distinction is similar to the @ref{883,,__new__()} and @ref{d57,,__init__()} methods
of classes.

Unlike modules created using single-phase initialization, these modules are not
singletons: if the @emph{sys.modules} entry is removed and the module is re-imported,
a new module object is created, and the old module is subject to normal garbage
collection -- as with Python modules.
By default, multiple modules created from the same definition should be
independent: changes to one should not affect the others.
This means that all state should be specific to the module object (using e.g.
using @ref{3e79,,PyModule_GetState()}), or its contents (such as the module's
@code{__dict__} or individual classes created with @ref{2d1,,PyType_FromSpec()}).

All modules created using multi-phase initialization are expected to support
@ref{3be6,,sub-interpreters}. Making sure multiple modules
are independent is typically enough to achieve this.

To request multi-phase initialization, the initialization function
(PyInit_modulename) returns a @ref{3aed,,PyModuleDef} instance with non-empty
@ref{3e83,,m_slots}. Before it is returned, the @code{PyModuleDef}
instance must be initialized with the following function:

@geindex PyModuleDef_Init (C 函数)
@anchor{c-api/module c PyModuleDef_Init}@anchor{3e8c}
@deffn {C 函数} PyObject* PyModuleDef_Init (PyModuleDef@w{ }*def)
@emph{Return value: Borrowed reference.}
Ensures a module definition is a properly initialized Python object that
correctly reports its type and reference count.

Returns @emph{def} cast to @code{PyObject*}, or @code{NULL} if an error occurred.


3.5 新版功能.

@end deffn

The @emph{m_slots} member of the module definition must point to an array of
@code{PyModuleDef_Slot} structures:

@geindex PyModuleDef_Slot (C 类型)
@anchor{c-api/module c PyModuleDef_Slot}@anchor{3e8d}
@deffn {C 类型} PyModuleDef_Slot

@geindex PyModuleDef_Slot.slot (C 成员)
@anchor{c-api/module c PyModuleDef_Slot slot}@anchor{3e8e}
@deffn {C 成员} int slot

A slot ID, chosen from the available values explained below.
@end deffn

@geindex PyModuleDef_Slot.value (C 成员)
@anchor{c-api/module c PyModuleDef_Slot value}@anchor{3e8f}
@deffn {C 成员} void* value

Value of the slot, whose meaning depends on the slot ID.
@end deffn


3.5 新版功能.

@end deffn

The @emph{m_slots} array must be terminated by a slot with id 0.

The available slot types are:

@geindex Py_mod_create (C 变量)
@anchor{c-api/module c Py_mod_create}@anchor{3e90}
@deffn {C 变量} Py_mod_create

Specifies a function that is called to create the module object itself.
The @emph{value} pointer of this slot must point to a function of the signature:

@geindex create_module (C 函数)
@anchor{c-api/module c create_module}@anchor{3e91}
@deffn {C 函数} PyObject* create_module (PyObject@w{ }*spec, PyModuleDef@w{ }*def)
@end deffn

The function receives a @ref{145e,,ModuleSpec}
instance, as defined in 
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}, and the module definition.
It should return a new module object, or set an error
and return @code{NULL}.

This function should be kept minimal. In particular, it should not
call arbitrary Python code, as trying to import the same module again may
result in an infinite loop.

Multiple @code{Py_mod_create} slots may not be specified in one module
definition.

If @code{Py_mod_create} is not specified, the import machinery will create
a normal module object using @ref{3e75,,PyModule_New()}. The name is taken from
@emph{spec}, not the definition, to allow extension modules to dynamically adjust
to their place in the module hierarchy and be imported under different
names through symlinks, all while sharing a single module definition.

There is no requirement for the returned object to be an instance of
@ref{3e71,,PyModule_Type}. Any type can be used, as long as it supports
setting and getting import-related attributes.
However, only @code{PyModule_Type} instances may be returned if the
@code{PyModuleDef} has non-@code{NULL} @code{m_traverse}, @code{m_clear},
@code{m_free}; non-zero @code{m_size}; or slots other than @code{Py_mod_create}.
@end deffn

@geindex Py_mod_exec (C 变量)
@anchor{c-api/module c Py_mod_exec}@anchor{3e86}
@deffn {C 变量} Py_mod_exec

Specifies a function that is called to @emph{execute} the module.
This is equivalent to executing the code of a Python module: typically,
this function adds classes and constants to the module.
The signature of the function is:

@geindex exec_module (C 函数)
@anchor{c-api/module c exec_module}@anchor{3e92}
@deffn {C 函数} int exec_module (PyObject*@w{ }module)
@end deffn

If multiple @code{Py_mod_exec} slots are specified, they are processed in the
order they appear in the @emph{m_slots} array.
@end deffn

See 
@geindex Python 提高建议; PEP 489
PEP 489@footnote{https://www.python.org/dev/peps/pep-0489} for more details on multi-phase initialization.

@node Low-level module creation functions,Support functions,Multi-phase initialization,Initializing C modules
@anchor{c-api/module low-level-module-creation-functions}@anchor{3e93}
@subsubsection Low-level module creation functions


The following functions are called under the hood when using multi-phase
initialization. They can be used directly, for example when creating module
objects dynamically. Note that both @code{PyModule_FromDefAndSpec} and
@code{PyModule_ExecDef} must be called to fully initialize a module.

@geindex PyModule_FromDefAndSpec (C 函数)
@anchor{c-api/module c PyModule_FromDefAndSpec}@anchor{7a5}
@deffn {C 函数} PyObject * PyModule_FromDefAndSpec (PyModuleDef@w{ }*def, PyObject@w{ }*spec)
@emph{Return value: New reference.}
Create a new module object, given the definition in @emph{module} and the
ModuleSpec @emph{spec}.  This behaves like @ref{7a6,,PyModule_FromDefAndSpec2()}
with @emph{module_api_version} set to @code{PYTHON_API_VERSION}.


3.5 新版功能.

@end deffn

@geindex PyModule_FromDefAndSpec2 (C 函数)
@anchor{c-api/module c PyModule_FromDefAndSpec2}@anchor{7a6}
@deffn {C 函数} PyObject * PyModule_FromDefAndSpec2 (PyModuleDef@w{ }*def, PyObject@w{ }*spec, int@w{ }module_api_version)
@emph{Return value: New reference.}
Create a new module object, given the definition in @emph{module} and the
ModuleSpec @emph{spec}, assuming the API version @emph{module_api_version}.
If that version does not match the version of the running interpreter,
a @ref{2c0,,RuntimeWarning} is emitted.

@cartouche
@quotation 注解 
Most uses of this function should be using @ref{7a5,,PyModule_FromDefAndSpec()}
instead; only use this if you are sure you need it.
@end quotation
@end cartouche


3.5 新版功能.

@end deffn

@geindex PyModule_ExecDef (C 函数)
@anchor{c-api/module c PyModule_ExecDef}@anchor{7a7}
@deffn {C 函数} int PyModule_ExecDef (PyObject@w{ }*module, PyModuleDef@w{ }*def)

Process any execution slots (@ref{3e86,,Py_mod_exec}) given in @emph{def}.


3.5 新版功能.

@end deffn

@geindex PyModule_SetDocString (C 函数)
@anchor{c-api/module c PyModule_SetDocString}@anchor{3e94}
@deffn {C 函数} int PyModule_SetDocString (PyObject@w{ }*module, const char@w{ }*docstring)

Set the docstring for @emph{module} to @emph{docstring}.
This function is called automatically when creating a module from
@code{PyModuleDef}, using either @code{PyModule_Create} or
@code{PyModule_FromDefAndSpec}.


3.5 新版功能.

@end deffn

@geindex PyModule_AddFunctions (C 函数)
@anchor{c-api/module c PyModule_AddFunctions}@anchor{3e95}
@deffn {C 函数} int PyModule_AddFunctions (PyObject@w{ }*module, PyMethodDef@w{ }*functions)

Add the functions from the @code{NULL} terminated @emph{functions} array to @emph{module}.
Refer to the @ref{e14,,PyMethodDef} documentation for details on individual
entries (due to the lack of a shared module namespace, module level
"functions" implemented in C typically receive the module as their first
parameter, making them similar to instance methods on Python classes).
This function is called automatically when creating a module from
@code{PyModuleDef}, using either @code{PyModule_Create} or
@code{PyModule_FromDefAndSpec}.


3.5 新版功能.

@end deffn

@node Support functions,,Low-level module creation functions,Initializing C modules
@anchor{c-api/module support-functions}@anchor{3e96}
@subsubsection Support functions


The module initialization function (if using single phase initialization) or
a function called from a module execution slot (if using multi-phase
initialization), can use the following functions to help initialize the module
state:

@geindex PyModule_AddObject (C 函数)
@anchor{c-api/module c PyModule_AddObject}@anchor{f0d}
@deffn {C 函数} int PyModule_AddObject (PyObject@w{ }*module, const char@w{ }*name, PyObject@w{ }*value)

Add an object to @emph{module} as @emph{name}.  This is a convenience function which can
be used from the module's initialization function.  This steals a reference to
@emph{value} on success.  Return @code{-1} on error, @code{0} on success.

@cartouche
@quotation 注解 
Unlike other functions that steal references, @code{PyModule_AddObject()} only
decrements the reference count of @emph{value} @strong{on success}.

This means that its return value must be checked, and calling code must
@ref{266,,Py_DECREF()} @emph{value} manually on error. Example usage:

@example
Py_INCREF(spam);
if (PyModule_AddObject(module, "spam", spam) < 0) @{
    Py_DECREF(module);
    Py_DECREF(spam);
    return NULL;
@}
@end example
@end quotation
@end cartouche
@end deffn

@geindex PyModule_AddIntConstant (C 函数)
@anchor{c-api/module c PyModule_AddIntConstant}@anchor{3e97}
@deffn {C 函数} int PyModule_AddIntConstant (PyObject@w{ }*module, const char@w{ }*name, long@w{ }value)

Add an integer constant to @emph{module} as @emph{name}.  This convenience function can be
used from the module's initialization function. Return @code{-1} on error, @code{0} on
success.
@end deffn

@geindex PyModule_AddStringConstant (C 函数)
@anchor{c-api/module c PyModule_AddStringConstant}@anchor{3e98}
@deffn {C 函数} int PyModule_AddStringConstant (PyObject@w{ }*module, const char@w{ }*name, const char@w{ }*value)

Add a string constant to @emph{module} as @emph{name}.  This convenience function can be
used from the module's initialization function.  The string @emph{value} must be
@code{NULL}-terminated.  Return @code{-1} on error, @code{0} on success.
@end deffn

@geindex PyModule_AddIntMacro (C 函数)
@anchor{c-api/module c PyModule_AddIntMacro}@anchor{3e99}
@deffn {C 函数} int PyModule_AddIntMacro (PyObject@w{ }*module, macro)

Add an int constant to @emph{module}. The name and the value are taken from
@emph{macro}. For example @code{PyModule_AddIntMacro(module, AF_INET)} adds the int
constant @emph{AF_INET} with the value of @emph{AF_INET} to @emph{module}.
Return @code{-1} on error, @code{0} on success.
@end deffn

@geindex PyModule_AddStringMacro (C 函数)
@anchor{c-api/module c PyModule_AddStringMacro}@anchor{d52}
@deffn {C 函数} int PyModule_AddStringMacro (PyObject@w{ }*module, macro)

Add a string constant to @emph{module}.
@end deffn

@node Module lookup,,Initializing C modules,模块对象
@anchor{c-api/module module-lookup}@anchor{3e9a}
@subsubsection Module lookup


Single-phase initialization creates singleton modules that can be looked up
in the context of the current interpreter. This allows the module object to be
retrieved later with only a reference to the module definition.

These functions will not work on modules created using multi-phase initialization,
since multiple such modules can be created from a single definition.

@geindex PyState_FindModule (C 函数)
@anchor{c-api/module c PyState_FindModule}@anchor{3e9b}
@deffn {C 函数} PyObject* PyState_FindModule (PyModuleDef@w{ }*def)
@emph{Return value: Borrowed reference.}
Returns the module object that was created from @emph{def} for the current interpreter.
This method requires that the module object has been attached to the interpreter state with
@ref{3e9c,,PyState_AddModule()} beforehand. In case the corresponding module object is not
found or has not been attached to the interpreter state yet, it returns @code{NULL}.
@end deffn

@geindex PyState_AddModule (C 函数)
@anchor{c-api/module c PyState_AddModule}@anchor{3e9c}
@deffn {C 函数} int PyState_AddModule (PyObject@w{ }*module, PyModuleDef@w{ }*def)

Attaches the module object passed to the function to the interpreter state. This allows
the module object to be accessible via @ref{3e9b,,PyState_FindModule()}.

Only effective on modules created using single-phase initialization.

Python calls @code{PyState_AddModule} automatically after importing a module,
so it is unnecessary (but harmless) to call it from module initialization
code. An explicit call is needed only if the module's own init code
subsequently calls @code{PyState_FindModule}.
The function is mainly intended for implementing alternative import
mechanisms (either by calling it directly, or by referring to its
implementation for details of the required state updates).

Return 0 on success or -1 on failure.


3.3 新版功能.

@end deffn

@geindex PyState_RemoveModule (C 函数)
@anchor{c-api/module c PyState_RemoveModule}@anchor{3e9d}
@deffn {C 函数} int PyState_RemoveModule (PyModuleDef@w{ }*def)

Removes the module object created from @emph{def} from the interpreter state.
Return 0 on success or -1 on failure.


3.3 新版功能.

@end deffn

@node 迭代器对象,描述符对象,模块对象,其他对象<2>
@anchor{c-api/iterator doc}@anchor{3e9e}@anchor{c-api/iterator id1}@anchor{3e9f}@anchor{c-api/iterator iterator-objects}@anchor{3ea0}
@subsubsection 迭代器对象


Python 提供了两个通用迭代器对象。 第一个是序列迭代器，它使用支持 @ref{27f,,__getitem__()} 方法的任意序列。 第二个使用可调用对象和一个 sentinel 值，为序列中的每个项调用可调用对象，并在返回 sentinel 值时结束迭代。

@geindex PySeqIter_Type (C 变量)
@anchor{c-api/iterator c PySeqIter_Type}@anchor{3ea1}
@deffn {C 变量} PyTypeObject PySeqIter_Type

@ref{3ea2,,PySeqIter_New()} 返回迭代器对象的类型对象和内置序列类型内置函数 @ref{d20,,iter()} 的单参数形式。
@end deffn

@geindex PySeqIter_Check (C 函数)
@anchor{c-api/iterator c PySeqIter_Check}@anchor{3ea3}
@deffn {C 函数} int PySeqIter_Check (op)

如果 @emph{op} 的类型为 @ref{3ea1,,PySeqIter_Type} 则返回 true。
@end deffn

@geindex PySeqIter_New (C 函数)
@anchor{c-api/iterator c PySeqIter_New}@anchor{3ea2}
@deffn {C 函数} PyObject* PySeqIter_New (PyObject@w{ }*seq)
@emph{Return value: New reference.}
返回一个与常规序列对象一起使用的迭代器 @emph{seq}。 当序列订阅操作引发 @ref{e6e,,IndexError} 时，迭代结束。
@end deffn

@geindex PyCallIter_Type (C 变量)
@anchor{c-api/iterator c PyCallIter_Type}@anchor{3ea4}
@deffn {C 变量} PyTypeObject PyCallIter_Type

由函数 @ref{3ea5,,PyCallIter_New()} 和 @ref{d20,,iter()} 内置函数的双参数形式返回的迭代器对象类型对象。
@end deffn

@geindex PyCallIter_Check (C 函数)
@anchor{c-api/iterator c PyCallIter_Check}@anchor{3ea6}
@deffn {C 函数} int PyCallIter_Check (op)

如果 @emph{op} 的类型为 @ref{3ea4,,PyCallIter_Type} 则返回 true。
@end deffn

@geindex PyCallIter_New (C 函数)
@anchor{c-api/iterator c PyCallIter_New}@anchor{3ea5}
@deffn {C 函数} PyObject* PyCallIter_New (PyObject@w{ }*callable, PyObject@w{ }*sentinel)
@emph{Return value: New reference.}
返回一个新的迭代器。 第一个参数 @emph{callable} 可以是任何可以在没有参数的情况下调用的 Python 可调用对象；每次调用都应该返回迭代中的下一个项目。 当 @emph{callable} 返回等于 @emph{sentinel} 的值时，迭代将终止。
@end deffn

@node 描述符对象,切片对象,迭代器对象,其他对象<2>
@anchor{c-api/descriptor doc}@anchor{3ea7}@anchor{c-api/descriptor descriptor-objects}@anchor{3ea8}@anchor{c-api/descriptor id1}@anchor{3ea9}
@subsubsection 描述符对象


“描述符”是描述对象的某些属性的对象。它们存在于类型对象的字典中。

@c XXX document these!

@geindex PyProperty_Type (C 变量)
@anchor{c-api/descriptor c PyProperty_Type}@anchor{3eaa}
@deffn {C 变量} PyTypeObject PyProperty_Type

内建描述符类型的类型对象。
@end deffn

@geindex PyDescr_NewGetSet (C 函数)
@anchor{c-api/descriptor c PyDescr_NewGetSet}@anchor{3eab}
@deffn {C 函数} PyObject* PyDescr_NewGetSet (PyTypeObject@w{ }*type, struct PyGetSetDef@w{ }*getset)
@emph{Return value: New reference.}
@end deffn

@geindex PyDescr_NewMember (C 函数)
@anchor{c-api/descriptor c PyDescr_NewMember}@anchor{3eac}
@deffn {C 函数} PyObject* PyDescr_NewMember (PyTypeObject@w{ }*type, struct PyMemberDef@w{ }*meth)
@emph{Return value: New reference.}
@end deffn

@geindex PyDescr_NewMethod (C 函数)
@anchor{c-api/descriptor c PyDescr_NewMethod}@anchor{ec6}
@deffn {C 函数} PyObject* PyDescr_NewMethod (PyTypeObject@w{ }*type, struct PyMethodDef@w{ }*meth)
@emph{Return value: New reference.}
@end deffn

@geindex PyDescr_NewWrapper (C 函数)
@anchor{c-api/descriptor c PyDescr_NewWrapper}@anchor{3ead}
@deffn {C 函数} PyObject* PyDescr_NewWrapper (PyTypeObject@w{ }*type, struct wrapperbase@w{ }*wrapper, void@w{ }*wrapped)
@emph{Return value: New reference.}
@end deffn

@geindex PyDescr_NewClassMethod (C 函数)
@anchor{c-api/descriptor c PyDescr_NewClassMethod}@anchor{3eae}
@deffn {C 函数} PyObject* PyDescr_NewClassMethod (PyTypeObject@w{ }*type, PyMethodDef@w{ }*method)
@emph{Return value: New reference.}
@end deffn

@geindex PyDescr_IsData (C 函数)
@anchor{c-api/descriptor c PyDescr_IsData}@anchor{3eaf}
@deffn {C 函数} int PyDescr_IsData (PyObject@w{ }*descr)

如果描述符对象 @emph{descr} 描述数据属性，则返回true；如果描述方法，则返回false。 @emph{descr} 必须是描述符对象；没有错误检查。
@end deffn

@geindex PyWrapper_New (C 函数)
@anchor{c-api/descriptor c PyWrapper_New}@anchor{3eb0}
@deffn {C 函数} PyObject* PyWrapper_New (PyObject@w{ }*, PyObject@w{ }*)
@emph{Return value: New reference.}
@end deffn

@node 切片对象,Ellipsis 对象,描述符对象,其他对象<2>
@anchor{c-api/slice doc}@anchor{3eb1}@anchor{c-api/slice id1}@anchor{3eb2}@anchor{c-api/slice slice-objects}@anchor{3eb3}
@subsubsection 切片对象


@geindex PySlice_Type (C 变量)
@anchor{c-api/slice c PySlice_Type}@anchor{3eb4}
@deffn {C 变量} PyTypeObject PySlice_Type

切片对象的类型对象。 它与 Python 层面的 @ref{dfd,,slice} 是相同的对象。
@end deffn

@geindex PySlice_Check (C 函数)
@anchor{c-api/slice c PySlice_Check}@anchor{3eb5}
@deffn {C 函数} int PySlice_Check (PyObject@w{ }*ob)

如果 @emph{ob} 是一个 slice 对象则返回真值；@emph{ob} 必须不为 @code{NULL}。
@end deffn

@geindex PySlice_New (C 函数)
@anchor{c-api/slice c PySlice_New}@anchor{3eb6}
@deffn {C 函数} PyObject* PySlice_New (PyObject@w{ }*start, PyObject@w{ }*stop, PyObject@w{ }*step)
@emph{Return value: New reference.}
返回一个具有给定值的新 slice 对象。 @emph{start}, @emph{stop} 和 @emph{step} 形参会被用作 slice 对象相应名称的属性的值。 这些值中的任何一个都可以为 @code{NULL}，在这种情况下将使用 @code{None} 作为对应属性的值。 如果新对象无法被分配则返回 @code{NULL}。
@end deffn

@geindex PySlice_GetIndices (C 函数)
@anchor{c-api/slice c PySlice_GetIndices}@anchor{3eb7}
@deffn {C 函数} int PySlice_GetIndices (PyObject@w{ }*slice, Py_ssize_t@w{ }length, Py_ssize_t@w{ }*start, Py_ssize_t@w{ }*stop, Py_ssize_t@w{ }*step)

从 slice 对象 @emph{slice} 提取 start, stop 和 step 索引号，将序列长度视为 @emph{length}。 大于 @emph{length} 的序列号将被当作错误。

成功时返回 @code{0}，出错时返回 @code{-1} 并且不设置异常（除非某个序列号不为 @ref{157,,None} 且无法被转换为整数，在这种情况下会返回 @code{-1} 并且设置一个异常）。

你可能不会打算使用此函数。


在 3.2 版更改: 之前 @emph{slice} 形参的形参类型是 @code{PySliceObject*}。

@end deffn

@geindex PySlice_GetIndicesEx (C 函数)
@anchor{c-api/slice c PySlice_GetIndicesEx}@anchor{472}
@deffn {C 函数} int PySlice_GetIndicesEx (PyObject@w{ }*slice, Py_ssize_t@w{ }length, Py_ssize_t@w{ }*start, Py_ssize_t@w{ }*stop, Py_ssize_t@w{ }*step, Py_ssize_t@w{ }*slicelength)

@ref{3eb7,,PySlice_GetIndices()} 的可用替代。 从 slice 对象 @emph{slice} 提取 start, stop 和 step 索引号，将序列长度视为 @emph{length}，并将切片的长度保存在 @emph{slicelength} 中，超出范围的索引号会以与普通切片一致的方式进行剪切。

成功时返回 @code{0}，出错时返回 @code{-1} 并且不设置异常。

@cartouche
@quotation 注解 
此函数对于可变大小序列来说是不安全的。 对它的调用应被替换为 @ref{429,,PySlice_Unpack()} 和 @ref{42a,,PySlice_AdjustIndices()} 的组合，其中

@example
if (PySlice_GetIndicesEx(slice, length, &start, &stop, &step, &slicelength) < 0) @{
    // return error
@}
@end example

会被替换为

@example
if (PySlice_Unpack(slice, &start, &stop, &step) < 0) @{
    // return error
@}
slicelength = PySlice_AdjustIndices(length, &start, &stop, step);
@end example
@end quotation
@end cartouche


在 3.2 版更改: 之前 @emph{slice} 形参的形参类型是 @code{PySliceObject*}。



在 3.6.1 版更改: 如果 @code{Py_LIMITED_API} 未设置或设置为 @code{0x03050400} 与 @code{0x03060000} 之前的值（不包含边界）或 @code{0x03060100} 或更大则 @code{PySlice_GetIndicesEx()} 会被实现为一个使用 @code{PySlice_Unpack()} 和 @code{PySlice_AdjustIndices()} 的宏。 参数 @emph{start}, @emph{stop} 和 @emph{step} 会被多被求值。



3.6.1 版后已移除: 如果 @code{Py_LIMITED_API} 设置为小于 @code{0x03050400} 或 @code{0x03060000} 与 @code{0x03060100} 之间的值（不包括边界）则 @code{PySlice_GetIndicesEx()} 为已弃用的函数。

@end deffn

@geindex PySlice_Unpack (C 函数)
@anchor{c-api/slice c PySlice_Unpack}@anchor{429}
@deffn {C 函数} int PySlice_Unpack (PyObject@w{ }*slice, Py_ssize_t@w{ }*start, Py_ssize_t@w{ }*stop, Py_ssize_t@w{ }*step)

从切片对象中将 start, stop 和 step 数据成员提取为 C 整数。 会静默地将大于 @code{PY_SSIZE_T_MAX} 的值减小为 @code{PY_SSIZE_T_MAX}，静默地将小于 @code{PY_SSIZE_T_MIN} 的 start 和 stop 值增大为 @code{PY_SSIZE_T_MIN}，并静默地将小于 @code{-PY_SSIZE_T_MAX} 的 step 值增大为 @code{-PY_SSIZE_T_MAX}。

出错时返回 @code{-1}，成功时返回 @code{0}。


3.6.1 新版功能.

@end deffn

@geindex PySlice_AdjustIndices (C 函数)
@anchor{c-api/slice c PySlice_AdjustIndices}@anchor{42a}
@deffn {C 函数} Py_ssize_t PySlice_AdjustIndices (Py_ssize_t@w{ }length, Py_ssize_t@w{ }*start, Py_ssize_t@w{ }*stop, Py_ssize_t@w{ }step)

将 start/end 切片索引号根据指定的序列长度进行调整。 超出范围的索引号会以与普通切片一致的方式进行剪切。

返回切片的长度。 此操作总是会成功。 不会调用 Python 代码。


3.6.1 新版功能.

@end deffn

@node Ellipsis 对象,MemoryView 对象,切片对象,其他对象<2>
@anchor{c-api/slice ellipsis-object}@anchor{3eb8}
@subsubsection Ellipsis 对象


@geindex Py_Ellipsis (C 变量)
@anchor{c-api/slice c Py_Ellipsis}@anchor{3eb9}
@deffn {C 变量} PyObject *Py_Ellipsis

Python 的 @code{Ellipsis} 对象。 该对象没有任何方法。 它必须以与任何其他对象一样的方式遵循引用计数。 它与 @ref{3aa9,,Py_None} 一样是单例对象。
@end deffn
@anchor{c-api/memoryview memoryview-objects}@anchor{3cc1}
@geindex 对象; memoryview

@node MemoryView 对象,弱引用对象<2>,Ellipsis 对象,其他对象<2>
@anchor{c-api/memoryview doc}@anchor{3eba}@anchor{c-api/memoryview id1}@anchor{3ebb}
@subsubsection MemoryView 对象


一个 @ref{25c,,memoryview} 对象C级别的 @ref{15d6,,缓冲区接口} 暴露为一个可以像任何其他对象一样传递的 Python 对象。

@geindex PyMemoryView_FromObject (C 函数)
@anchor{c-api/memoryview c PyMemoryView_FromObject}@anchor{3ebc}
@deffn {C 函数} PyObject *PyMemoryView_FromObject (PyObject@w{ }*obj)
@emph{Return value: New reference.}
从提供缓冲区接口的对象创建 memoryview 对象。 如果 @emph{obj} 支持可写缓冲区导出，则 memoryview 对象将可以被读/写，否则它可能是只读的，也可以是导出器自行决定的读/写。
@end deffn

@geindex PyMemoryView_FromMemory (C 函数)
@anchor{c-api/memoryview c PyMemoryView_FromMemory}@anchor{ac4}
@deffn {C 函数} PyObject *PyMemoryView_FromMemory (char@w{ }*mem, Py_ssize_t@w{ }size, int@w{ }flags)
@emph{Return value: New reference.}
使用 @emph{mem} 作为底层缓冲区创建一个 memoryview 对象。 @emph{flags} 可以是 @code{PyBUF_READ} 或者 @code{PyBUF_WRITE} 之一.


3.3 新版功能.

@end deffn

@geindex PyMemoryView_FromBuffer (C 函数)
@anchor{c-api/memoryview c PyMemoryView_FromBuffer}@anchor{3cc5}
@deffn {C 函数} PyObject *PyMemoryView_FromBuffer (Py_buffer@w{ }*view)
@emph{Return value: New reference.}
创建一个包含给定缓冲区结构 @emph{view} 的 memoryview 对象。 对于简单的字节缓冲区，@ref{ac4,,PyMemoryView_FromMemory()} 是首选函数。
@end deffn

@geindex PyMemoryView_GetContiguous (C 函数)
@anchor{c-api/memoryview c PyMemoryView_GetContiguous}@anchor{3ebd}
@deffn {C 函数} PyObject *PyMemoryView_GetContiguous (PyObject@w{ }*obj, int@w{ }buffertype, char@w{ }order)
@emph{Return value: New reference.}
从定义缓冲区接口的对象创建一个 memoryview 对象 @ref{164e,,contiguous} 内存块（在 'C' 或 'F'ortran @emph{order} 中）。 如果内存是连续的，则 memoryview 对象指向原始内存。 否则，复制并且 memoryview 指向新的 bytes 对象。
@end deffn

@geindex PyMemoryView_Check (C 函数)
@anchor{c-api/memoryview c PyMemoryView_Check}@anchor{3ebe}
@deffn {C 函数} int PyMemoryView_Check (PyObject@w{ }*obj)

如果对象 @emph{obj} 是 memoryview 对象，则返回 true 。 目前不允许创建 @ref{25c,,memoryview} 的子类。
@end deffn

@geindex PyMemoryView_GET_BUFFER (C 函数)
@anchor{c-api/memoryview c PyMemoryView_GET_BUFFER}@anchor{3ebf}
@deffn {C 函数} Py_buffer *PyMemoryView_GET_BUFFER (PyObject@w{ }*mview)

返回指向 memoryview 的导出缓冲区私有副本的指针。 @emph{mview} @strong{必须} 是一个 memoryview 实例；这个宏不检查它的类型，你必须自己检查，否则你将面临崩溃风险。
@end deffn

@geindex PyMemoryView_GET_BASE (C 函数)
@anchor{c-api/memoryview c PyMemoryView_GET_BASE}@anchor{3ec0}
@deffn {C 函数} Py_buffer *PyMemoryView_GET_BASE (PyObject@w{ }*mview)

返回 memoryview 所基于的导出对象的指针，或者如果 memoryview 已由函数 @ref{ac4,,PyMemoryView_FromMemory()} 或 @ref{3cc5,,PyMemoryView_FromBuffer()} 创建则返回 @code{NULL}。 @emph{mview} @strong{必须} 是一个 memoryview 实例。
@end deffn

@node 弱引用对象<2>,胶囊<2>,MemoryView 对象,其他对象<2>
@anchor{c-api/weakref doc}@anchor{3ec1}@anchor{c-api/weakref weak-reference-objects}@anchor{3ec2}@anchor{c-api/weakref weakrefobjects}@anchor{3ec3}
@subsubsection 弱引用对象


Python 支持 “弱引用” 作为一类对象。具体来说，有两种直接实现弱引用的对象。第一种就是简单的引用对象，第二种尽可能地作用为一个原对象的代理。

@geindex PyWeakref_Check (C 函数)
@anchor{c-api/weakref c PyWeakref_Check}@anchor{3ec4}
@deffn {C 函数} int PyWeakref_Check (ob)

如果 “ob” 是一个引用或者一个代理对象，则返回 true。
@end deffn

@geindex PyWeakref_CheckRef (C 函数)
@anchor{c-api/weakref c PyWeakref_CheckRef}@anchor{3ec5}
@deffn {C 函数} int PyWeakref_CheckRef (ob)

如果 “ob” 是一个引用，则返回 true。
@end deffn

@geindex PyWeakref_CheckProxy (C 函数)
@anchor{c-api/weakref c PyWeakref_CheckProxy}@anchor{3ec6}
@deffn {C 函数} int PyWeakref_CheckProxy (ob)

如果 “ob” 是一个代理对象，则返回 true。
@end deffn

@geindex PyWeakref_NewRef (C 函数)
@anchor{c-api/weakref c PyWeakref_NewRef}@anchor{3ec7}
@deffn {C 函数} PyObject* PyWeakref_NewRef (PyObject@w{ }*ob, PyObject@w{ }*callback)
@emph{Return value: New reference.}
返回对象 @emph{ob} 的一个弱引用对象。 该函数总是会返回一个新的引用，但不保证创建一个新的对象；它有可能返回一个现有的引用对象。 第二个形参 @emph{callback} 为一个可调用对象，它会在 @emph{ob} 被作为垃圾回收时接收通知；它应该接受一个单独形参，即弱引用对象本身。 @emph{callback} 也可以为 @code{None} 或 @code{NULL}。 如果 @emph{ob} 不是一个弱引用对象，或者如果 @emph{callback} 不是可调用对象，@code{None} 或 @code{NULL}，该函数将返回 @code{NULL} 并且引发 @ref{192,,TypeError}。
@end deffn

@geindex PyWeakref_NewProxy (C 函数)
@anchor{c-api/weakref c PyWeakref_NewProxy}@anchor{3ec8}
@deffn {C 函数} PyObject* PyWeakref_NewProxy (PyObject@w{ }*ob, PyObject@w{ }*callback)
@emph{Return value: New reference.}
返回对象 @emph{ob} 的一个弱引用代理对象。 该函数将总是返回一个新的引用，但不保证创建一个新的对象；它有可能返回一个现有的代理对象。 第二个形参 @emph{callback} 为一个可调用对象，它会在 @emph{ob} 被作为垃圾回收时接收通知；它应该接受一个单独形参，即弱引用对象本身。 @emph{callback} 也可以为 @code{None} 或 @code{NULL}。 如果 @emph{ob} 不是一个弱引用对象，或者如果 @emph{callback} 不是可调用对象，@code{None} 或 @code{NULL}，该函数将返回 @code{NULL} 并且引发 @ref{192,,TypeError}。
@end deffn

@geindex PyWeakref_GetObject (C 函数)
@anchor{c-api/weakref c PyWeakref_GetObject}@anchor{3ec9}
@deffn {C 函数} PyObject* PyWeakref_GetObject (PyObject@w{ }*ref)
@emph{Return value: Borrowed reference.}
返回弱引用对象 ref 的被引用对象。如果被引用对象不再存在，则返回 @code{Py_None}。

@cartouche
@quotation 注解 
该函数返回被引用对象的一个**借来的引用**。这意味着除非你很清楚在你使用期间这个对象不可能被销毁，否则你应该始终对该对象调用 @ref{265,,Py_INCREF()}。
@end quotation
@end cartouche
@end deffn

@geindex PyWeakref_GET_OBJECT (C 函数)
@anchor{c-api/weakref c PyWeakref_GET_OBJECT}@anchor{3eca}
@deffn {C 函数} PyObject* PyWeakref_GET_OBJECT (PyObject@w{ }*ref)
@emph{Return value: Borrowed reference.}
类似 @ref{3ec9,,PyWeakref_GetObject()}，但实现为一个不做类型检查的宏。
@end deffn

@node 胶囊<2>,生成器对象,弱引用对象<2>,其他对象<2>
@anchor{c-api/capsule doc}@anchor{3ecb}@anchor{c-api/capsule capsules}@anchor{3ad3}@anchor{c-api/capsule id1}@anchor{3ecc}
@subsubsection 胶囊


@geindex 对象; Capsule

有关使用这些对象的更多信息请参阅 @ref{cea,,给扩展模块提供C API}。


3.1 新版功能.


@geindex PyCapsule (C 类型)
@anchor{c-api/capsule c PyCapsule}@anchor{c00}
@deffn {C 类型} PyCapsule

这个 @ref{4b5,,PyObject} 的子类型代表着一个任意值，当需要通过 Python 代码将任意值（以 @code{void*} 指针的形式）从 C 扩展模块传递给其他 C 代码时非常有用。它通常用于将指向一个模块中定义的 C 语言函数指针传递给其他模块，以便可以从那里调用它们。这允许通过正常的模块导入机制访问动态加载的模块中的 C API。
@end deffn

@geindex PyCapsule_Destructor (C 类型)
@anchor{c-api/capsule c PyCapsule_Destructor}@anchor{3ecd}
@deffn {C 类型} PyCapsule_Destructor

这种类型的一个析构器返回一个胶囊，定义如下：

@example
typedef void (*PyCapsule_Destructor)(PyObject *);
@end example

参阅 @ref{3ad1,,PyCapsule_New()} 来获取 PyCapsule_Destructor 返回值的语义。
@end deffn

@geindex PyCapsule_CheckExact (C 函数)
@anchor{c-api/capsule c PyCapsule_CheckExact}@anchor{3ece}
@deffn {C 函数} int PyCapsule_CheckExact (PyObject@w{ }*p)

如果参数是一个 @ref{c00,,PyCapsule} 则返回 True
@end deffn

@geindex PyCapsule_New (C 函数)
@anchor{c-api/capsule c PyCapsule_New}@anchor{3ad1}
@deffn {C 函数} PyObject* PyCapsule_New (void@w{ }*pointer, const char@w{ }*name, PyCapsule_Destructor@w{ }destructor)
@emph{Return value: New reference.}
Create a @ref{c00,,PyCapsule} encapsulating the @emph{pointer}.  The @emph{pointer}
argument may not be @code{NULL}.

On failure, set an exception and return @code{NULL}.

The @emph{name} string may either be @code{NULL} or a pointer to a valid C string.  If
non-@code{NULL}, this string must outlive the capsule.  (Though it is permitted to
free it inside the @emph{destructor}.)

If the @emph{destructor} argument is not @code{NULL}, it will be called with the
capsule as its argument when it is destroyed.

If this capsule will be stored as an attribute of a module, the @emph{name} should
be specified as @code{modulename.attributename}.  This will enable other modules
to import the capsule using @ref{3ad2,,PyCapsule_Import()}.
@end deffn

@geindex PyCapsule_GetPointer (C 函数)
@anchor{c-api/capsule c PyCapsule_GetPointer}@anchor{3ecf}
@deffn {C 函数} void* PyCapsule_GetPointer (PyObject@w{ }*capsule, const char@w{ }*name)

Retrieve the @emph{pointer} stored in the capsule.  On failure, set an exception
and return @code{NULL}.

The @emph{name} parameter must compare exactly to the name stored in the capsule.
If the name stored in the capsule is @code{NULL}, the @emph{name} passed in must also
be @code{NULL}.  Python uses the C function @code{strcmp()} to compare capsule
names.
@end deffn

@geindex PyCapsule_GetDestructor (C 函数)
@anchor{c-api/capsule c PyCapsule_GetDestructor}@anchor{3ed0}
@deffn {C 函数} PyCapsule_Destructor PyCapsule_GetDestructor (PyObject@w{ }*capsule)

Return the current destructor stored in the capsule.  On failure, set an
exception and return @code{NULL}.

It is legal for a capsule to have a @code{NULL} destructor.  This makes a @code{NULL}
return code somewhat ambiguous; use @ref{ce9,,PyCapsule_IsValid()} or
@ref{3aa4,,PyErr_Occurred()} to disambiguate.
@end deffn

@geindex PyCapsule_GetContext (C 函数)
@anchor{c-api/capsule c PyCapsule_GetContext}@anchor{3ed1}
@deffn {C 函数} void* PyCapsule_GetContext (PyObject@w{ }*capsule)

Return the current context stored in the capsule.  On failure, set an
exception and return @code{NULL}.

It is legal for a capsule to have a @code{NULL} context.  This makes a @code{NULL}
return code somewhat ambiguous; use @ref{ce9,,PyCapsule_IsValid()} or
@ref{3aa4,,PyErr_Occurred()} to disambiguate.
@end deffn

@geindex PyCapsule_GetName (C 函数)
@anchor{c-api/capsule c PyCapsule_GetName}@anchor{3ed2}
@deffn {C 函数} const char* PyCapsule_GetName (PyObject@w{ }*capsule)

Return the current name stored in the capsule.  On failure, set an exception
and return @code{NULL}.

It is legal for a capsule to have a @code{NULL} name.  This makes a @code{NULL} return
code somewhat ambiguous; use @ref{ce9,,PyCapsule_IsValid()} or
@ref{3aa4,,PyErr_Occurred()} to disambiguate.
@end deffn

@geindex PyCapsule_Import (C 函数)
@anchor{c-api/capsule c PyCapsule_Import}@anchor{3ad2}
@deffn {C 函数} void* PyCapsule_Import (const char@w{ }*name, int@w{ }no_block)

Import a pointer to a C object from a capsule attribute in a module.  The
@emph{name} parameter should specify the full name to the attribute, as in
@code{module.attribute}.  The @emph{name} stored in the capsule must match this
string exactly.  If @emph{no_block} is true, import the module without blocking
(using @ref{9bb,,PyImport_ImportModuleNoBlock()}).  If @emph{no_block} is false,
import the module conventionally (using @ref{c6c,,PyImport_ImportModule()}).

Return the capsule's internal @emph{pointer} on success.  On failure, set an
exception and return @code{NULL}.
@end deffn

@geindex PyCapsule_IsValid (C 函数)
@anchor{c-api/capsule c PyCapsule_IsValid}@anchor{ce9}
@deffn {C 函数} int PyCapsule_IsValid (PyObject@w{ }*capsule, const char@w{ }*name)

Determines whether or not @emph{capsule} is a valid capsule.  A valid capsule is
non-@code{NULL}, passes @ref{3ece,,PyCapsule_CheckExact()}, has a non-@code{NULL} pointer
stored in it, and its internal name matches the @emph{name} parameter.  (See
@ref{3ecf,,PyCapsule_GetPointer()} for information on how capsule names are
compared.)

In other words, if @ref{ce9,,PyCapsule_IsValid()} returns a true value, calls to
any of the accessors (any function starting with @code{PyCapsule_Get()}) are
guaranteed to succeed.

Return a nonzero value if the object is valid and matches the name passed in.
Return @code{0} otherwise.  This function will not fail.
@end deffn

@geindex PyCapsule_SetContext (C 函数)
@anchor{c-api/capsule c PyCapsule_SetContext}@anchor{3ed3}
@deffn {C 函数} int PyCapsule_SetContext (PyObject@w{ }*capsule, void@w{ }*context)

Set the context pointer inside @emph{capsule} to @emph{context}.

Return @code{0} on success.  Return nonzero and set an exception on failure.
@end deffn

@geindex PyCapsule_SetDestructor (C 函数)
@anchor{c-api/capsule c PyCapsule_SetDestructor}@anchor{3ed4}
@deffn {C 函数} int PyCapsule_SetDestructor (PyObject@w{ }*capsule, PyCapsule_Destructor@w{ }destructor)

Set the destructor inside @emph{capsule} to @emph{destructor}.

Return @code{0} on success.  Return nonzero and set an exception on failure.
@end deffn

@geindex PyCapsule_SetName (C 函数)
@anchor{c-api/capsule c PyCapsule_SetName}@anchor{3ed5}
@deffn {C 函数} int PyCapsule_SetName (PyObject@w{ }*capsule, const char@w{ }*name)

Set the name inside @emph{capsule} to @emph{name}.  If non-@code{NULL}, the name must
outlive the capsule.  If the previous @emph{name} stored in the capsule was not
@code{NULL}, no attempt is made to free it.

Return @code{0} on success.  Return nonzero and set an exception on failure.
@end deffn

@geindex PyCapsule_SetPointer (C 函数)
@anchor{c-api/capsule c PyCapsule_SetPointer}@anchor{3ed6}
@deffn {C 函数} int PyCapsule_SetPointer (PyObject@w{ }*capsule, void@w{ }*pointer)

Set the void pointer inside @emph{capsule} to @emph{pointer}.  The pointer may not be
@code{NULL}.

Return @code{0} on success.  Return nonzero and set an exception on failure.
@end deffn

@node 生成器对象,协程对象<2>,胶囊<2>,其他对象<2>
@anchor{c-api/gen doc}@anchor{3ed7}@anchor{c-api/gen gen-objects}@anchor{3ed8}@anchor{c-api/gen generator-objects}@anchor{3ed9}
@subsubsection 生成器对象


生成器对象是Python用来实现生成器迭代器的对象。它们通常通过迭代产生值的函数来创建，而不是显式调用 @ref{3eda,,PyGen_New()} 或 @ref{3edb,,PyGen_NewWithQualName()}。

@geindex PyGenObject (C 类型)
@anchor{c-api/gen c PyGenObject}@anchor{3edc}
@deffn {C 类型} PyGenObject

用于生成器对象的C结构体。
@end deffn

@geindex PyGen_Type (C 变量)
@anchor{c-api/gen c PyGen_Type}@anchor{3edd}
@deffn {C 变量} PyTypeObject PyGen_Type

与生成器对象对应的类型对​​象。
@end deffn

@geindex PyGen_Check (C 函数)
@anchor{c-api/gen c PyGen_Check}@anchor{3ede}
@deffn {C 函数} int PyGen_Check (PyObject@w{ }*ob)

如果 @emph{ob} 是一个生成器对象则返回真值；@emph{ob} 必须不为 @code{NULL}。
@end deffn

@geindex PyGen_CheckExact (C 函数)
@anchor{c-api/gen c PyGen_CheckExact}@anchor{3edf}
@deffn {C 函数} int PyGen_CheckExact (PyObject@w{ }*ob)

如果 @emph{ob} 的类型为 @ref{3edd,,PyGen_Type} 则返回真值；@emph{ob} 必须不为 @code{NULL}。
@end deffn

@geindex PyGen_New (C 函数)
@anchor{c-api/gen c PyGen_New}@anchor{3eda}
@deffn {C 函数} PyObject* PyGen_New (PyFrameObject@w{ }*frame)
@emph{Return value: New reference.}
基于 @emph{frame} 对象创建并返回一个新的生成器对象。 此函数会取走一个对 @emph{frame} 的引用。 参数必须不为 @code{NULL}。
@end deffn

@geindex PyGen_NewWithQualName (C 函数)
@anchor{c-api/gen c PyGen_NewWithQualName}@anchor{3edb}
@deffn {C 函数} PyObject* PyGen_NewWithQualName (PyFrameObject@w{ }*frame, PyObject@w{ }*name, PyObject@w{ }*qualname)
@emph{Return value: New reference.}
基于 @emph{frame} 对象创建并返回一个新的生成器对象，其中 @code{__name__} 和 @code{__qualname__} 设为 @emph{name} 和 @emph{qualname}。 此函数会取走一个对 @emph{frame} 的引用。 @emph{frame} 参数必须不为 @code{NULL}。
@end deffn

@node 协程对象<2>,上下文变量对象,生成器对象,其他对象<2>
@anchor{c-api/coro doc}@anchor{3ee0}@anchor{c-api/coro coro-objects}@anchor{7c7}@anchor{c-api/coro coroutine-objects}@anchor{3ee1}
@subsubsection 协程对象



3.5 新版功能.


协程对象是使用 @code{async} 关键字声明的函数返回的。

@geindex PyCoroObject (C 类型)
@anchor{c-api/coro c PyCoroObject}@anchor{3ee2}
@deffn {C 类型} PyCoroObject

用于协程对象的C结构体。
@end deffn

@geindex PyCoro_Type (C 变量)
@anchor{c-api/coro c PyCoro_Type}@anchor{3ee3}
@deffn {C 变量} PyTypeObject PyCoro_Type

与协程对象对应的类型对​​象。
@end deffn

@geindex PyCoro_CheckExact (C 函数)
@anchor{c-api/coro c PyCoro_CheckExact}@anchor{3ee4}
@deffn {C 函数} int PyCoro_CheckExact (PyObject@w{ }*ob)

如果 @emph{ob} 的类型是 @ref{3ee3,,PyCoro_Type} 则返回真值；@emph{ob} 必须不为 @code{NULL}。
@end deffn

@geindex PyCoro_New (C 函数)
@anchor{c-api/coro c PyCoro_New}@anchor{3ee5}
@deffn {C 函数} PyObject* PyCoro_New (PyFrameObject@w{ }*frame, PyObject@w{ }*name, PyObject@w{ }*qualname)
@emph{Return value: New reference.}
基于 @emph{frame} 对象创建并返回一个新的协程对象，其中 @code{__name__} 和 @code{__qualname__} 设为 @emph{name} 和 @emph{qualname}。 此函数会取得一个对 @emph{frame} 的引用。 @emph{frame} 参数必须不为 @code{NULL}。
@end deffn

@node 上下文变量对象,DateTime 对象<2>,协程对象<2>,其他对象<2>
@anchor{c-api/contextvars doc}@anchor{3ee6}@anchor{c-api/contextvars context-variables-objects}@anchor{3ee7}@anchor{c-api/contextvars contextvarsobjects}@anchor{334}
@subsubsection 上下文变量对象

@anchor{c-api/contextvars contextvarsobjects-pointertype-change}@anchor{4b4}

@cartouche
@quotation 注解 在 3.7.1 版更改: 
在 Python 3.7.1 中，所有上下文变量 C API 的签名被 @strong{更改} 为使用 @ref{4b5,,PyObject} 指针而不是 @ref{3ee8,,PyContext}, @ref{3ee9,,PyContextVar} 以及 @ref{3eea,,PyContextToken}，例如:

@example
// in 3.7.0:
PyContext *PyContext_New(void);

// in 3.7.1+:
PyObject *PyContext_New(void);
@end example

详情请参阅:issue: ' 34762 '。
@end quotation
@end cartouche



3.7 新版功能.


本节深入介绍了 @ref{25,,contextvars} 模块的公用 C API。

@geindex PyContext (C 类型)
@anchor{c-api/contextvars c PyContext}@anchor{3ee8}
@deffn {C 类型} PyContext

用于表示 @ref{246c,,contextvars.Context} 对象的 C 结构体。
@end deffn

@geindex PyContextVar (C 类型)
@anchor{c-api/contextvars c PyContextVar}@anchor{3ee9}
@deffn {C 类型} PyContextVar

用于表示 @ref{246a,,contextvars.ContextVar} 对象的 C 结构体。
@end deffn

@geindex PyContextToken (C 类型)
@anchor{c-api/contextvars c PyContextToken}@anchor{3eea}
@deffn {C 类型} PyContextToken

用于表示 @code{contextvars.Token} 对象的 C 结构体。
@end deffn

@geindex PyContext_Type (C 变量)
@anchor{c-api/contextvars c PyContext_Type}@anchor{3eeb}
@deffn {C 变量} PyTypeObject PyContext_Type

表示 @emph{context} 类型的类型对象。
@end deffn

@geindex PyContextVar_Type (C 变量)
@anchor{c-api/contextvars c PyContextVar_Type}@anchor{3eec}
@deffn {C 变量} PyTypeObject PyContextVar_Type

表示 @emph{context variable} 类型的类型对象。
@end deffn

@geindex PyContextToken_Type (C 变量)
@anchor{c-api/contextvars c PyContextToken_Type}@anchor{3eed}
@deffn {C 变量} PyTypeObject PyContextToken_Type

表示 @emph{context variable token} 类型的类型对象。
@end deffn

类型检查宏：

@geindex PyContext_CheckExact (C 函数)
@anchor{c-api/contextvars c PyContext_CheckExact}@anchor{3eee}
@deffn {C 函数} int PyContext_CheckExact (PyObject@w{ }*o)

如果 @emph{o} 的类型为 @ref{3eeb,,PyContext_Type} 则返回真值。 @emph{o} 必须不为 @code{NULL}。 此函数总是会成功执行。
@end deffn

@geindex PyContextVar_CheckExact (C 函数)
@anchor{c-api/contextvars c PyContextVar_CheckExact}@anchor{3eef}
@deffn {C 函数} int PyContextVar_CheckExact (PyObject@w{ }*o)

如果 @emph{o} 的类型为 @ref{3eec,,PyContextVar_Type} 则返回真值。 @emph{o} 必须不为 @code{NULL}。 此函数总是会成功执行。
@end deffn

@geindex PyContextToken_CheckExact (C 函数)
@anchor{c-api/contextvars c PyContextToken_CheckExact}@anchor{3ef0}
@deffn {C 函数} int PyContextToken_CheckExact (PyObject@w{ }*o)

如果 @emph{o} 的类型为 @ref{3eed,,PyContextToken_Type} 则返回真值。 @emph{o} 必须不为 @code{NULL}。 此函数总是会成功执行。
@end deffn

上下文对象管理函数:

@geindex PyContext_New (C 函数)
@anchor{c-api/contextvars c PyContext_New}@anchor{3ef1}
@deffn {C 函数} PyObject *PyContext_New (void)
@emph{Return value: New reference.}
创建一个新的空上下文对象。 如果发生错误则返回 @code{NULL}。
@end deffn

@geindex PyContext_Copy (C 函数)
@anchor{c-api/contextvars c PyContext_Copy}@anchor{3ef2}
@deffn {C 函数} PyObject *PyContext_Copy (PyObject@w{ }*ctx)
@emph{Return value: New reference.}
创建所传入的 @emph{ctx} 上下文对象的浅拷贝。 如果发生错误则返回 @code{NULL}。
@end deffn

@geindex PyContext_CopyCurrent (C 函数)
@anchor{c-api/contextvars c PyContext_CopyCurrent}@anchor{3ef3}
@deffn {C 函数} PyObject *PyContext_CopyCurrent (void)
@emph{Return value: New reference.}
创建当前线程上下文的浅拷贝。 如果发生错误则返回 @code{NULL}。
@end deffn

@geindex PyContext_Enter (C 函数)
@anchor{c-api/contextvars c PyContext_Enter}@anchor{3ef4}
@deffn {C 函数} int PyContext_Enter (PyObject@w{ }*ctx)

将 @emph{ctx} 设为当前线程的当前上下文。 成功时返回 @code{0}，出错时返回 @code{-1}。
@end deffn

@geindex PyContext_Exit (C 函数)
@anchor{c-api/contextvars c PyContext_Exit}@anchor{3ef5}
@deffn {C 函数} int PyContext_Exit (PyObject@w{ }*ctx)

取消激活 @emph{ctx} 上下文并将之前的上下文恢复为当前线程的当前上下文。 成功时返回 @code{0}，出错时返回 @code{-1}。
@end deffn

@geindex PyContext_ClearFreeList (C 函数)
@anchor{c-api/contextvars c PyContext_ClearFreeList}@anchor{3ef6}
@deffn {C 函数} int PyContext_ClearFreeList ()

Clear the context variable free list. Return the total number of
freed items.  This function always succeeds.
@end deffn

上下文变量函数:

@geindex PyContextVar_New (C 函数)
@anchor{c-api/contextvars c PyContextVar_New}@anchor{3ef7}
@deffn {C 函数} PyObject *PyContextVar_New (const char@w{ }*name, PyObject@w{ }*def)
@emph{Return value: New reference.}
创建一个新的' ' ContextVar' '对象。形参*name*用于自我检查和调试目的。可选形参*def*为上下文变量指定默认值。如果发生错误，这个函数返回' ' NULL ' '。
@end deffn

@geindex PyContextVar_Get (C 函数)
@anchor{c-api/contextvars c PyContextVar_Get}@anchor{3ef8}
@deffn {C 函数} int PyContextVar_Get (PyObject@w{ }*var, PyObject@w{ }*default_value, PyObject@w{ }**value)

获取上下文变量的值。如果在查找过程中发生错误，返回' ' -1 ' '，如果没有发生错误，无论是否找到值，都返回' ' 0 ' '，

如果找到上下文变量，@emph{value} 将是指向它的指针。 如果上下文变量 @emph{没有} 找到，@emph{value} 将指向：


@itemize -

@item 
@emph{default_value}，如果非`@w{`}NULL`@w{`};

@item 
@emph{var} 的默认值，如果不是 @code{NULL}；

@item 
@code{NULL}
@end itemize

如果找到该值，函数将创建对它的新引用。
@end deffn

@geindex PyContextVar_Set (C 函数)
@anchor{c-api/contextvars c PyContextVar_Set}@anchor{3ef9}
@deffn {C 函数} PyObject *PyContextVar_Set (PyObject@w{ }*var, PyObject@w{ }*value)
@emph{Return value: New reference.}
在当前上下文中将 @emph{var} 的值设为 @emph{value}。 返回指向 @ref{4b5,,PyObject} 对象的指针，如果发生错误则返回 @code{NULL}。
@end deffn

@geindex PyContextVar_Reset (C 函数)
@anchor{c-api/contextvars c PyContextVar_Reset}@anchor{3efa}
@deffn {C 函数} int PyContextVar_Reset (PyObject@w{ }*var, PyObject@w{ }*token)

将上下文变量 @emph{var} 的状态重置为它在返回 @emph{token} 的 @ref{3ef9,,PyContextVar_Set()} 被调用之前的状态。 此函数成功时返回 @code{0}，出错时返回 @code{-1}。
@end deffn

@node DateTime 对象<2>,,上下文变量对象,其他对象<2>
@anchor{c-api/datetime doc}@anchor{3efb}@anchor{c-api/datetime datetime-objects}@anchor{3efc}@anchor{c-api/datetime datetimeobjects}@anchor{3efd}
@subsubsection DateTime 对象


@ref{31,,datetime} 模块提供了各种日期和时间对象。 在使用任何这些函数之前，必须在你的源码中包含头文件 @code{datetime.h} (请注意此文件并未包含在 @code{Python.h} 中)，并且宏 @code{PyDateTime_IMPORT} 必须被发起调用，通常是作为模块初始化函数的一部分。 这个宏会将指向特定 C 结构的指针放入一个静态变量 @code{PyDateTimeAPI} 中，它会由下面的宏来使用。

宏访问UTC单例:

@geindex PyDateTime_TimeZone_UTC (C 变量)
@anchor{c-api/datetime c PyDateTime_TimeZone_UTC}@anchor{430}
@deffn {C 变量} PyObject* PyDateTime_TimeZone_UTC

返回表示 UTC 的时区单例，与 @ref{187f,,datetime.timezone.utc} 为同一对象。


3.7 新版功能.

@end deffn

类型检查宏：

@geindex PyDate_Check (C 函数)
@anchor{c-api/datetime c PyDate_Check}@anchor{3efe}
@deffn {C 函数} int PyDate_Check (PyObject@w{ }*ob)

如果 @emph{ob} 为 @code{PyDateTime_DateType} 类型或 @code{PyDateTime_DateType} 的某个子类型则返回真值。 @emph{ob} 不能为 @code{NULL}。
@end deffn

@geindex PyDate_CheckExact (C 函数)
@anchor{c-api/datetime c PyDate_CheckExact}@anchor{3eff}
@deffn {C 函数} int PyDate_CheckExact (PyObject@w{ }*ob)

如果 @emph{ob} 为 @code{PyDateTime_DateType} 类型则返回真值。 @emph{ob} 不能为 @code{NULL}。
@end deffn

@geindex PyDateTime_Check (C 函数)
@anchor{c-api/datetime c PyDateTime_Check}@anchor{3f00}
@deffn {C 函数} int PyDateTime_Check (PyObject@w{ }*ob)

如果 @emph{ob} 为 @code{PyDateTime_DateTimeType} 类型或 @code{PyDateTime_DateTimeType} 的某个子类型则返回真值。 @emph{ob} 不能为 @code{NULL}。
@end deffn

@geindex PyDateTime_CheckExact (C 函数)
@anchor{c-api/datetime c PyDateTime_CheckExact}@anchor{3f01}
@deffn {C 函数} int PyDateTime_CheckExact (PyObject@w{ }*ob)

如果 @emph{ob} 为 @code{PyDateTime_DateTimeType} 类型则返回真值。 @emph{ob} 不能为 @code{NULL}。
@end deffn

@geindex PyTime_Check (C 函数)
@anchor{c-api/datetime c PyTime_Check}@anchor{3f02}
@deffn {C 函数} int PyTime_Check (PyObject@w{ }*ob)

如果 @emph{ob} 的类型是 @code{PyDateTime_TimeType} 或是 @code{PyDateTime_TimeType} 的子类型则返回真值。 @emph{ob} 必须不为 @code{NULL}。
@end deffn

@geindex PyTime_CheckExact (C 函数)
@anchor{c-api/datetime c PyTime_CheckExact}@anchor{3f03}
@deffn {C 函数} int PyTime_CheckExact (PyObject@w{ }*ob)

如果 @emph{ob} 的类型是 @code{PyDateTime_TimeType} 则返回真值。 @emph{ob} 必须不为 @code{NULL}。
@end deffn

@geindex PyDelta_Check (C 函数)
@anchor{c-api/datetime c PyDelta_Check}@anchor{3f04}
@deffn {C 函数} int PyDelta_Check (PyObject@w{ }*ob)

如果 @emph{ob} 为 @code{PyDateTime_DeltaType} 类型或 @code{PyDateTime_DeltaType} 的某个子类型则返回真值。 @emph{ob} 不能为 @code{NULL}。
@end deffn

@geindex PyDelta_CheckExact (C 函数)
@anchor{c-api/datetime c PyDelta_CheckExact}@anchor{3f05}
@deffn {C 函数} int PyDelta_CheckExact (PyObject@w{ }*ob)

如果 @emph{ob} 为 @code{PyDateTime_DeltaType} 类型则返回真值。 @emph{ob} 不能为 @code{NULL}。
@end deffn

@geindex PyTZInfo_Check (C 函数)
@anchor{c-api/datetime c PyTZInfo_Check}@anchor{3f06}
@deffn {C 函数} int PyTZInfo_Check (PyObject@w{ }*ob)

如果 @emph{ob} 为 @code{PyDateTime_TZInfoType} 类型或 @code{PyDateTime_TZInfoType} 的某个子类型则返回真值。 @emph{ob} 必须不为 @code{NULL}。
@end deffn

@geindex PyTZInfo_CheckExact (C 函数)
@anchor{c-api/datetime c PyTZInfo_CheckExact}@anchor{3f07}
@deffn {C 函数} int PyTZInfo_CheckExact (PyObject@w{ }*ob)

如果 @emph{ob} 的类型是 @code{PyDateTime_TZInfoType} 则返回真值。 @emph{ob} 不能为 @code{NULL}。
@end deffn

用于创建对象的宏：

@geindex PyDate_FromDate (C 函数)
@anchor{c-api/datetime c PyDate_FromDate}@anchor{3f08}
@deffn {C 函数} PyObject* PyDate_FromDate (int@w{ }year, int@w{ }month, int@w{ }day)
@emph{Return value: New reference.}
返回指定年、月、日的 @ref{193,,datetime.date} 对象。
@end deffn

@geindex PyDateTime_FromDateAndTime (C 函数)
@anchor{c-api/datetime c PyDateTime_FromDateAndTime}@anchor{3f09}
@deffn {C 函数} PyObject* PyDateTime_FromDateAndTime (int@w{ }year, int@w{ }month, int@w{ }day, int@w{ }hour, int@w{ }minute, int@w{ }second, int@w{ }usecond)
@emph{Return value: New reference.}
返回具有指定 year, month, day, hour, minute, second 和 microsecond 属性的 @ref{194,,datetime.datetime} 对象。
@end deffn

@geindex PyDateTime_FromDateAndTimeAndFold (C 函数)
@anchor{c-api/datetime c PyDateTime_FromDateAndTimeAndFold}@anchor{3f0a}
@deffn {C 函数} PyObject* PyDateTime_FromDateAndTimeAndFold (int@w{ }year, int@w{ }month, int@w{ }day, int@w{ }hour, int@w{ }minute, int@w{ }second, int@w{ }usecond, int@w{ }fold)
@emph{Return value: New reference.}
返回具有指定 year, month, day, hour, minute, second, microsecond 和 fold 属性的 @ref{194,,datetime.datetime} 对象。


3.6 新版功能.

@end deffn

@geindex PyTime_FromTime (C 函数)
@anchor{c-api/datetime c PyTime_FromTime}@anchor{3f0b}
@deffn {C 函数} PyObject* PyTime_FromTime (int@w{ }hour, int@w{ }minute, int@w{ }second, int@w{ }usecond)
@emph{Return value: New reference.}
返回具有指定 hour, minute, second and microsecond 属性的 @ref{4ed,,datetime.time} 对象。
@end deffn

@geindex PyTime_FromTimeAndFold (C 函数)
@anchor{c-api/datetime c PyTime_FromTimeAndFold}@anchor{3f0c}
@deffn {C 函数} PyObject* PyTime_FromTimeAndFold (int@w{ }hour, int@w{ }minute, int@w{ }second, int@w{ }usecond, int@w{ }fold)
@emph{Return value: New reference.}
返回具有指定 hour, minute, second, microsecond 和 fold 属性的 @ref{4ed,,datetime.time} 对象。


3.6 新版功能.

@end deffn

@geindex PyDelta_FromDSU (C 函数)
@anchor{c-api/datetime c PyDelta_FromDSU}@anchor{3f0d}
@deffn {C 函数} PyObject* PyDelta_FromDSU (int@w{ }days, int@w{ }seconds, int@w{ }useconds)
@emph{Return value: New reference.}
返回代表给定天、秒和微秒数的 @ref{195,,datetime.timedelta} 对象。 将执行正规化操作以使最终的微秒和秒数处在 @ref{195,,datetime.timedelta} 对象的文档指明的区间之内。
@end deffn

@geindex PyTimeZone_FromOffset (C 函数)
@anchor{c-api/datetime c PyTimeZone_FromOffset}@anchor{42e}
@deffn {C 函数} PyObject* PyTimeZone_FromOffset (PyDateTime_DeltaType*@w{ }offset)
@emph{Return value: New reference.}
返回一个 @ref{9fb,,datetime.timezone} 对象，该对象具有以 @emph{offset} 参数表示 的未命名固定时差。


3.7 新版功能.

@end deffn

@geindex PyTimeZone_FromOffsetAndName (C 函数)
@anchor{c-api/datetime c PyTimeZone_FromOffsetAndName}@anchor{42f}
@deffn {C 函数} PyObject* PyTimeZone_FromOffsetAndName (PyDateTime_DeltaType*@w{ }offset, PyUnicode*@w{ }name)
@emph{Return value: New reference.}
返回一个 @ref{9fb,,datetime.timezone} 对象，该对象具有以 @emph{offset} 参数表示的固定时差和时区名称 @emph{name}。


3.7 新版功能.

@end deffn

一些用来从 date 对象中提取字段的宏。 参数必须是 @code{PyDateTime_Date} 包括其子类 (例如 @code{PyDateTime_DateTime}) 的实例。 参数必须不为 @code{NULL}，并且类型不被会检查:

@geindex PyDateTime_GET_YEAR (C 函数)
@anchor{c-api/datetime c PyDateTime_GET_YEAR}@anchor{3f0e}
@deffn {C 函数} int PyDateTime_GET_YEAR (PyDateTime_Date@w{ }*o)

以正整数的形式返回年份值。
@end deffn

@geindex PyDateTime_GET_MONTH (C 函数)
@anchor{c-api/datetime c PyDateTime_GET_MONTH}@anchor{3f0f}
@deffn {C 函数} int PyDateTime_GET_MONTH (PyDateTime_Date@w{ }*o)

返回月，从0到12的整数。
@end deffn

@geindex PyDateTime_GET_DAY (C 函数)
@anchor{c-api/datetime c PyDateTime_GET_DAY}@anchor{3f10}
@deffn {C 函数} int PyDateTime_GET_DAY (PyDateTime_Date@w{ }*o)

返回日期，从0到31的整数。
@end deffn

一些用来从 datetime 对象中提取字段的宏。 参数必须是 @code{PyDateTime_DateTime} 包括其子类的实例。 参数必须不为 @code{NULL}，并且类型不会被检查:

@geindex PyDateTime_DATE_GET_HOUR (C 函数)
@anchor{c-api/datetime c PyDateTime_DATE_GET_HOUR}@anchor{3f11}
@deffn {C 函数} int PyDateTime_DATE_GET_HOUR (PyDateTime_DateTime@w{ }*o)

返回小时，从0到23的整数。
@end deffn

@geindex PyDateTime_DATE_GET_MINUTE (C 函数)
@anchor{c-api/datetime c PyDateTime_DATE_GET_MINUTE}@anchor{3f12}
@deffn {C 函数} int PyDateTime_DATE_GET_MINUTE (PyDateTime_DateTime@w{ }*o)

返回分钟，从0到59的整数。
@end deffn

@geindex PyDateTime_DATE_GET_SECOND (C 函数)
@anchor{c-api/datetime c PyDateTime_DATE_GET_SECOND}@anchor{3f13}
@deffn {C 函数} int PyDateTime_DATE_GET_SECOND (PyDateTime_DateTime@w{ }*o)

返回秒，从0到59的整数。
@end deffn

@geindex PyDateTime_DATE_GET_MICROSECOND (C 函数)
@anchor{c-api/datetime c PyDateTime_DATE_GET_MICROSECOND}@anchor{3f14}
@deffn {C 函数} int PyDateTime_DATE_GET_MICROSECOND (PyDateTime_DateTime@w{ }*o)

返回微秒，从0到999999的整数。
@end deffn

一些用来从 time 对象中提取字段的宏。 参数必须是 @code{PyDateTime_Time} 包括其子类的实例。 参数必须不为 @code{NULL}，并且类型不会被检查:

@geindex PyDateTime_TIME_GET_HOUR (C 函数)
@anchor{c-api/datetime c PyDateTime_TIME_GET_HOUR}@anchor{3f15}
@deffn {C 函数} int PyDateTime_TIME_GET_HOUR (PyDateTime_Time@w{ }*o)

返回小时，从0到23的整数。
@end deffn

@geindex PyDateTime_TIME_GET_MINUTE (C 函数)
@anchor{c-api/datetime c PyDateTime_TIME_GET_MINUTE}@anchor{3f16}
@deffn {C 函数} int PyDateTime_TIME_GET_MINUTE (PyDateTime_Time@w{ }*o)

返回分钟，从0到59的整数。
@end deffn

@geindex PyDateTime_TIME_GET_SECOND (C 函数)
@anchor{c-api/datetime c PyDateTime_TIME_GET_SECOND}@anchor{3f17}
@deffn {C 函数} int PyDateTime_TIME_GET_SECOND (PyDateTime_Time@w{ }*o)

返回秒，从0到59的整数。
@end deffn

@geindex PyDateTime_TIME_GET_MICROSECOND (C 函数)
@anchor{c-api/datetime c PyDateTime_TIME_GET_MICROSECOND}@anchor{3f18}
@deffn {C 函数} int PyDateTime_TIME_GET_MICROSECOND (PyDateTime_Time@w{ }*o)

返回微秒，从0到999999的整数。
@end deffn

一些用来从 timedelta 对象中提取字段的宏。 参数必须是 @code{PyDateTime_Delta} 包括其子类的实例。 参数必须不为 @code{NULL}，并且类型不会被检查:

@geindex PyDateTime_DELTA_GET_DAYS (C 函数)
@anchor{c-api/datetime c PyDateTime_DELTA_GET_DAYS}@anchor{3f19}
@deffn {C 函数} int PyDateTime_DELTA_GET_DAYS (PyDateTime_Delta@w{ }*o)

返回天数，从-999999999到999999999的整数。


3.3 新版功能.

@end deffn

@geindex PyDateTime_DELTA_GET_SECONDS (C 函数)
@anchor{c-api/datetime c PyDateTime_DELTA_GET_SECONDS}@anchor{3f1a}
@deffn {C 函数} int PyDateTime_DELTA_GET_SECONDS (PyDateTime_Delta@w{ }*o)

返回秒数，从0到86399的整数。


3.3 新版功能.

@end deffn

@geindex PyDateTime_DELTA_GET_MICROSECONDS (C 函数)
@anchor{c-api/datetime c PyDateTime_DELTA_GET_MICROSECONDS}@anchor{3f1b}
@deffn {C 函数} int PyDateTime_DELTA_GET_MICROSECONDS (PyDateTime_Delta@w{ }*o)

返回微秒数，从0到999999的整数。


3.3 新版功能.

@end deffn

一些便于模块实现 DB API 的宏:

@geindex PyDateTime_FromTimestamp (C 函数)
@anchor{c-api/datetime c PyDateTime_FromTimestamp}@anchor{3f1c}
@deffn {C 函数} PyObject* PyDateTime_FromTimestamp (PyObject@w{ }*args)
@emph{Return value: New reference.}
创建并返回一个给定元组参数的新 @ref{194,,datetime.datetime} 对象，适合传给 @ref{101e,,datetime.datetime.fromtimestamp()}。
@end deffn

@geindex PyDate_FromTimestamp (C 函数)
@anchor{c-api/datetime c PyDate_FromTimestamp}@anchor{f7c}
@deffn {C 函数} PyObject* PyDate_FromTimestamp (PyObject@w{ }*args)
@emph{Return value: New reference.}
创建并返回一个给定元组参数的新 @ref{193,,datetime.date} 对象，适合传给 @ref{183e,,datetime.date.fromtimestamp()}。
@end deffn

@node Initialization Finalization and Threads,Python初始化配置,具体的对象层,Python/C API 参考手册
@anchor{c-api/init doc}@anchor{3f1d}@anchor{c-api/init initialization}@anchor{3f1e}@anchor{c-api/init initialization-finalization-and-threads}@anchor{3f1f}
@section Initialization, Finalization, and Threads


请参阅 @ref{17d,,Python 初始化配置} 。

@menu
* 在Python初始化之前:: 
* 全局配置变量:: 
* Initializing and finalizing the interpreter:: 
* Process-wide parameters:: 
* Thread State and the Global Interpreter Lock:: 
* Sub-interpreter support:: 
* 异步通知:: 
* 分析和跟踪:: 
* 高级调试器支持:: 
* Thread Local Storage Support:: 

@end menu

@node 在Python初始化之前,全局配置变量,,Initialization Finalization and Threads
@anchor{c-api/init before-python-initialization}@anchor{3f20}@anchor{c-api/init pre-init-safe}@anchor{434}
@subsection 在Python初始化之前


In an application embedding  Python, the @ref{433,,Py_Initialize()} function must
be called before using any other Python/C API functions; with the exception of
a few functions and the @ref{3f21,,global configuration variables}.

在初始化Python之前，可以安全地调用以下函数：


@itemize *

@item 
配置函数：


@itemize *

@item 
@ref{3aad,,PyImport_AppendInittab()}

@item 
@ref{3c10,,PyImport_ExtendInittab()}

@item 
@code{PyInitFrozenExtensions()}

@item 
@ref{3f22,,PyMem_SetAllocator()}

@item 
@ref{504,,PyMem_SetupDebugHooks()}

@item 
@ref{3f23,,PyObject_SetArenaAllocator()}

@item 
@ref{273,,Py_SetPath()}

@item 
@ref{f18,,Py_SetProgramName()}

@item 
@ref{f17,,Py_SetPythonHome()}

@item 
@ref{91f,,Py_SetStandardStreamEncoding()}

@item 
@ref{4ae,,PySys_AddWarnOption()}

@item 
@ref{3bf7,,PySys_AddXOption()}

@item 
@ref{3bf0,,PySys_ResetWarnOptions()}
@end itemize

@item 
信息函数：


@itemize *

@item 
@ref{3b62,,Py_IsInitialized()}

@item 
@ref{3f24,,PyMem_GetAllocator()}

@item 
@ref{3f25,,PyObject_GetArenaAllocator()}

@item 
@ref{d93,,Py_GetBuildInfo()}

@item 
@ref{3f26,,Py_GetCompiler()}

@item 
@ref{3f27,,Py_GetCopyright()}

@item 
@ref{3f28,,Py_GetPlatform()}

@item 
@ref{3f29,,Py_GetVersion()}
@end itemize

@item 
工具


@itemize *

@item 
@ref{436,,Py_DecodeLocale()}
@end itemize

@item 
内存分配器：


@itemize *

@item 
@ref{967,,PyMem_RawMalloc()}

@item 
@ref{968,,PyMem_RawRealloc()}

@item 
@ref{79f,,PyMem_RawCalloc()}

@item 
@ref{3bea,,PyMem_RawFree()}
@end itemize
@end itemize

@cartouche
@quotation 注解 
以下函数 @strong{不应该} 在 @ref{433,,Py_Initialize()}: @ref{437,,Py_EncodeLocale()}, @ref{3b5f,,Py_GetPath()}, @ref{3b60,,Py_GetPrefix()}, @ref{3b61,,Py_GetExecPrefix()}, @ref{275,,Py_GetProgramFullPath()}, @ref{3f2a,,Py_GetPythonHome()}, @ref{276,,Py_GetProgramName()} 和 @ref{c0b,,PyEval_InitThreads()} 前调用。
@end quotation
@end cartouche

@node 全局配置变量,Initializing and finalizing the interpreter,在Python初始化之前,Initialization Finalization and Threads
@anchor{c-api/init global-conf-vars}@anchor{3f21}@anchor{c-api/init global-configuration-variables}@anchor{3f2b}
@subsection 全局配置变量


Python has variables for the global configuration to control different features
and options. By default, these flags are controlled by @ref{12cf,,command line options}.

When a flag is set by an option, the value of the flag is the number of times
that the option was set. For example, @code{-b} sets @ref{4af,,Py_BytesWarningFlag}
to 1 and @code{-bb} sets @ref{4af,,Py_BytesWarningFlag} to 2.

@geindex Py_BytesWarningFlag (C 变量)
@anchor{c-api/init c Py_BytesWarningFlag}@anchor{4af}
@deffn {C 变量} Py_BytesWarningFlag

Issue a warning when comparing @ref{32a,,bytes} or @ref{32b,,bytearray} with
@ref{329,,str} or @ref{32a,,bytes} with @ref{184,,int}.  Issue an error if greater
or equal to @code{2}.

由 @ref{40d,,-b} 选项设置。
@end deffn

@geindex Py_DebugFlag (C 变量)
@anchor{c-api/init c Py_DebugFlag}@anchor{3f2c}
@deffn {C 变量} Py_DebugFlag

Turn on parser debugging output (for expert only, depending on compilation
options).

Set by the @ref{12d8,,-d} option and the 
@geindex PYTHONDEBUG
@geindex 环境变量; PYTHONDEBUG
@ref{12d9,,PYTHONDEBUG} environment
variable.
@end deffn

@geindex Py_DontWriteBytecodeFlag (C 变量)
@anchor{c-api/init c Py_DontWriteBytecodeFlag}@anchor{3f2d}
@deffn {C 变量} Py_DontWriteBytecodeFlag

If set to non-zero, Python won't try to write @code{.pyc} files on the
import of source modules.

Set by the @ref{d31,,-B} option and the 
@geindex PYTHONDONTWRITEBYTECODE
@geindex 环境变量; PYTHONDONTWRITEBYTECODE
@ref{d32,,PYTHONDONTWRITEBYTECODE}
environment variable.
@end deffn

@geindex Py_FrozenFlag (C 变量)
@anchor{c-api/init c Py_FrozenFlag}@anchor{3f2e}
@deffn {C 变量} Py_FrozenFlag

Suppress error messages when calculating the module search path in
@ref{3b5f,,Py_GetPath()}.

Private flag used by @code{_freeze_importlib} and @code{frozenmain} programs.
@end deffn

@geindex Py_HashRandomizationFlag (C 变量)
@anchor{c-api/init c Py_HashRandomizationFlag}@anchor{3f2f}
@deffn {C 变量} Py_HashRandomizationFlag

Set to @code{1} if the 
@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED} environment variable is set to
a non-empty string.

If the flag is non-zero, read the 
@geindex PYTHONHASHSEED
@geindex 环境变量; PYTHONHASHSEED
@ref{9bf,,PYTHONHASHSEED} environment
variable to initialize the secret hash seed.
@end deffn

@geindex Py_IgnoreEnvironmentFlag (C 变量)
@anchor{c-api/init c Py_IgnoreEnvironmentFlag}@anchor{4b3}
@deffn {C 变量} Py_IgnoreEnvironmentFlag

忽略所有 
@geindex PYTHON*
@geindex 环境变量; PYTHON*
@code{PYTHON*} 环境变量，例如可能已设置的 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} 和 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME}。

由 @ref{f9a,,-E}  和 @ref{f99,,-I} 选项设置。
@end deffn

@geindex Py_InspectFlag (C 变量)
@anchor{c-api/init c Py_InspectFlag}@anchor{3f30}
@deffn {C 变量} Py_InspectFlag

When a script is passed as first argument or the @ref{119f,,-c} option is used,
enter interactive mode after executing the script or the command, even when
@ref{306,,sys.stdin} does not appear to be a terminal.

Set by the @ref{e18,,-i} option and the 
@geindex PYTHONINSPECT
@geindex 环境变量; PYTHONINSPECT
@ref{e17,,PYTHONINSPECT} environment
variable.
@end deffn

@geindex Py_InteractiveFlag (C 变量)
@anchor{c-api/init c Py_InteractiveFlag}@anchor{3be4}
@deffn {C 变量} Py_InteractiveFlag

由 @ref{e18,,-i} 选项设置。
@end deffn

@geindex Py_IsolatedFlag (C 变量)
@anchor{c-api/init c Py_IsolatedFlag}@anchor{3f31}
@deffn {C 变量} Py_IsolatedFlag

Run Python in isolated mode. In isolated mode @ref{482,,sys.path} contains
neither the script's directory nor the user's site-packages directory.

由 @ref{f99,,-I} 选项设置。


3.4 新版功能.

@end deffn

@geindex Py_LegacyWindowsFSEncodingFlag (C 变量)
@anchor{c-api/init c Py_LegacyWindowsFSEncodingFlag}@anchor{3be9}
@deffn {C 变量} Py_LegacyWindowsFSEncodingFlag

If the flag is non-zero, use the @code{mbcs} encoding instead of the UTF-8
encoding for the filesystem encoding.

Set to @code{1} if the 
@geindex PYTHONLEGACYWINDOWSFSENCODING
@geindex 环境变量; PYTHONLEGACYWINDOWSFSENCODING
@ref{4f1,,PYTHONLEGACYWINDOWSFSENCODING} environment
variable is set to a non-empty string.

有关更多详细信息，请参阅 
@geindex Python 提高建议; PEP 529
PEP 529@footnote{https://www.python.org/dev/peps/pep-0529}。

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex Py_LegacyWindowsStdioFlag (C 变量)
@anchor{c-api/init c Py_LegacyWindowsStdioFlag}@anchor{3f32}
@deffn {C 变量} Py_LegacyWindowsStdioFlag

If the flag is non-zero, use @ref{c9d,,io.FileIO} instead of
@code{WindowsConsoleIO} for @ref{fd,,sys} standard streams.

Set to @code{1} if the 
@geindex PYTHONLEGACYWINDOWSSTDIO
@geindex 环境变量; PYTHONLEGACYWINDOWSSTDIO
@ref{4f4,,PYTHONLEGACYWINDOWSSTDIO} environment
variable is set to a non-empty string.

有关更多详细信息，请参阅 
@geindex Python 提高建议; PEP 528
PEP 528@footnote{https://www.python.org/dev/peps/pep-0528}。

@ref{12f5,,可用性}: Windows。
@end deffn

@geindex Py_NoSiteFlag (C 变量)
@anchor{c-api/init c Py_NoSiteFlag}@anchor{3f33}
@deffn {C 变量} Py_NoSiteFlag

禁用 @ref{eb,,site} 的导入及其所附带的基于站点对 @ref{482,,sys.path} 的操作。 如果 @ref{eb,,site} 会在稍后被显式地导入也会禁用这些操作 (如果你希望触发它们则应调用 @ref{12dd,,site.main()})。

由 @ref{b1d,,-S} 选项设置。
@end deffn

@geindex Py_NoUserSiteDirectory (C 变量)
@anchor{c-api/init c Py_NoUserSiteDirectory}@anchor{3f34}
@deffn {C 变量} Py_NoUserSiteDirectory

不要将 @ref{12dc,,用户 site-packages 目录} 添加到 @ref{482,,sys.path}。

Set by the @ref{d0e,,-s} and @ref{f99,,-I} options, and the
@geindex PYTHONNOUSERSITE
@geindex 环境变量; PYTHONNOUSERSITE
@ref{d0f,,PYTHONNOUSERSITE} environment variable.
@end deffn

@geindex Py_OptimizeFlag (C 变量)
@anchor{c-api/init c Py_OptimizeFlag}@anchor{2291}
@deffn {C 变量} Py_OptimizeFlag

Set by the @ref{685,,-O} option and the 
@geindex PYTHONOPTIMIZE
@geindex 环境变量; PYTHONOPTIMIZE
@ref{12da,,PYTHONOPTIMIZE} environment
variable.
@end deffn

@geindex Py_QuietFlag (C 变量)
@anchor{c-api/init c Py_QuietFlag}@anchor{3f35}
@deffn {C 变量} Py_QuietFlag

即使在交互模式下也不显示版权和版本信息。

由 @ref{12db,,-q} 选项设置。


3.2 新版功能.

@end deffn

@geindex Py_UnbufferedStdioFlag (C 变量)
@anchor{c-api/init c Py_UnbufferedStdioFlag}@anchor{3f36}
@deffn {C 变量} Py_UnbufferedStdioFlag

Force the stdout and stderr streams to be unbuffered.

Set by the @ref{12de,,-u} option and the 
@geindex PYTHONUNBUFFERED
@geindex 环境变量; PYTHONUNBUFFERED
@ref{12df,,PYTHONUNBUFFERED}
environment variable.
@end deffn

@geindex Py_VerboseFlag (C 变量)
@anchor{c-api/init c Py_VerboseFlag}@anchor{3f37}
@deffn {C 变量} Py_VerboseFlag

Print a message each time a module is initialized, showing the place
(filename or built-in module) from which it is loaded.  If greater or equal
to @code{2}, print a message for each file that is checked for when
searching for a module. Also provides information on module cleanup at exit.

Set by the @ref{d81,,-v} option and the 
@geindex PYTHONVERBOSE
@geindex 环境变量; PYTHONVERBOSE
@ref{12e0,,PYTHONVERBOSE} environment
variable.
@end deffn

@node Initializing and finalizing the interpreter,Process-wide parameters,全局配置变量,Initialization Finalization and Threads
@anchor{c-api/init initializing-and-finalizing-the-interpreter}@anchor{3f38}
@subsection Initializing and finalizing the interpreter


@geindex Py_Initialize (C 函数)
@anchor{c-api/init c Py_Initialize}@anchor{433}
@deffn {C 函数} void Py_Initialize ()

@geindex Py_SetProgramName()
@geindex PyEval_InitThreads()
@geindex modules (in module sys)
@geindex path (in module sys)
@geindex 模块; builtins
@geindex 模块; __main__
@geindex 模块; sys
@geindex module; search; path
@geindex PySys_SetArgv()
@geindex PySys_SetArgvEx()
@geindex Py_FinalizeEx()

Initialize the Python interpreter.  In an application embedding  Python,
this should be called before using any other Python/C API functions; see
@ref{434,,Before Python Initialization} for the few exceptions.

This initializes
the table of loaded modules (@code{sys.modules}), and creates the fundamental
modules @ref{13,,builtins}, @ref{1,,__main__} and @ref{fd,,sys}.  It also initializes
the module search path (@code{sys.path}). It does not set @code{sys.argv}; use
@ref{bf3,,PySys_SetArgvEx()} for that.  This is a no-op when called for a second time
(without calling @ref{5c4,,Py_FinalizeEx()} first).  There is no return value; it is a
fatal error if the initialization fails.

@cartouche
@quotation 注解 
On Windows, changes the console mode from @code{O_TEXT} to @code{O_BINARY}, which will
also affect non-Python uses of the console using the C Runtime.
@end quotation
@end cartouche
@end deffn

@geindex Py_InitializeEx (C 函数)
@anchor{c-api/init c Py_InitializeEx}@anchor{3f39}
@deffn {C 函数} void Py_InitializeEx (int@w{ }initsigs)

This function works like @ref{433,,Py_Initialize()} if @emph{initsigs} is @code{1}. If
@emph{initsigs} is @code{0}, it skips initialization registration of signal handlers, which
might be useful when Python is embedded.
@end deffn

@geindex Py_IsInitialized (C 函数)
@anchor{c-api/init c Py_IsInitialized}@anchor{3b62}
@deffn {C 函数} int Py_IsInitialized ()

Return true (nonzero) when the Python interpreter has been initialized, false
(zero) if not.  After @ref{5c4,,Py_FinalizeEx()} is called, this returns false until
@ref{433,,Py_Initialize()} is called again.
@end deffn

@geindex Py_FinalizeEx (C 函数)
@anchor{c-api/init c Py_FinalizeEx}@anchor{5c4}
@deffn {C 函数} int Py_FinalizeEx ()

Undo all initializations made by @ref{433,,Py_Initialize()} and subsequent use of
Python/C API functions, and destroy all sub-interpreters (see
@ref{3f3a,,Py_NewInterpreter()} below) that were created and not yet destroyed since
the last call to @ref{433,,Py_Initialize()}.  Ideally, this frees all memory
allocated by the Python interpreter.  This is a no-op when called for a second
time (without calling @ref{433,,Py_Initialize()} again first).  Normally the
return value is @code{0}.  If there were errors during finalization
(flushing buffered data), @code{-1} is returned.

This function is provided for a number of reasons.  An embedding application
might want to restart Python without having to restart the application itself.
An application that has loaded the Python interpreter from a dynamically
loadable library (or DLL) might want to free all memory allocated by Python
before unloading the DLL. During a hunt for memory leaks in an application a
developer might want to free all memory allocated by Python before exiting from
the application.

@strong{Bugs and caveats:} The destruction of modules and objects in modules is done
in random order; this may cause destructors (@ref{919,,__del__()} methods) to fail
when they depend on other objects (even functions) or modules.  Dynamically
loaded extension modules loaded by Python are not unloaded.  Small amounts of
memory allocated by the Python interpreter may not be freed (if you find a leak,
please report it).  Memory tied up in circular references between objects is not
freed.  Some memory allocated by extension modules may not be freed.  Some
extensions may not work properly if their initialization routine is called more
than once; this can happen if an application calls @ref{433,,Py_Initialize()} and
@ref{5c4,,Py_FinalizeEx()} more than once.

Raises an @ref{12d0,,auditing event} @code{cpython._PySys_ClearAuditHooks} with no arguments.


3.6 新版功能.

@end deffn

@geindex Py_Finalize (C 函数)
@anchor{c-api/init c Py_Finalize}@anchor{ce6}
@deffn {C 函数} void Py_Finalize ()

This is a backwards-compatible version of @ref{5c4,,Py_FinalizeEx()} that
disregards the return value.
@end deffn

@node Process-wide parameters,Thread State and the Global Interpreter Lock,Initializing and finalizing the interpreter,Initialization Finalization and Threads
@anchor{c-api/init process-wide-parameters}@anchor{3f3b}
@subsection Process-wide parameters


@geindex Py_SetStandardStreamEncoding (C 函数)
@anchor{c-api/init c Py_SetStandardStreamEncoding}@anchor{91f}
@deffn {C 函数} int Py_SetStandardStreamEncoding (const char@w{ }*encoding, const char@w{ }*errors)

@geindex Py_Initialize()
@geindex main()
@geindex stdin; stdout; sdterr

This function should be called before @ref{433,,Py_Initialize()}, if it is
called at all. It specifies which encoding and error handling to use
with standard IO, with the same meanings as in @ref{c30,,str.encode()}.

It overrides 
@geindex PYTHONIOENCODING
@geindex 环境变量; PYTHONIOENCODING
@ref{929,,PYTHONIOENCODING} values, and allows embedding code
to control IO encoding when the environment variable does not work.

@emph{encoding} and/or @emph{errors} may be @code{NULL} to use
@geindex PYTHONIOENCODING
@geindex 环境变量; PYTHONIOENCODING
@ref{929,,PYTHONIOENCODING} and/or default values (depending on other
settings).

Note that @ref{308,,sys.stderr} always uses the "backslashreplace" error
handler, regardless of this (or any other) setting.

If @ref{5c4,,Py_FinalizeEx()} is called, this function will need to be called
again in order to affect subsequent calls to @ref{433,,Py_Initialize()}.

Returns @code{0} if successful, a nonzero value on error (e.g. calling after the
interpreter has already been initialized).


3.4 新版功能.

@end deffn

@geindex Py_SetProgramName (C 函数)
@anchor{c-api/init c Py_SetProgramName}@anchor{f18}
@deffn {C 函数} void Py_SetProgramName (const wchar_t@w{ }*name)

@geindex Py_Initialize()
@geindex main()
@geindex Py_GetPath()

This function should be called before @ref{433,,Py_Initialize()} is called for
the first time, if it is called at all.  It tells the interpreter the value
of the @code{argv[0]} argument to the @code{main()} function of the program
(converted to wide characters).
This is used by @ref{3b5f,,Py_GetPath()} and some other functions below to find
the Python run-time libraries relative to the interpreter executable.  The
default value is @code{'python'}.  The argument should point to a
zero-terminated wide character string in static storage whose contents will not
change for the duration of the program's execution.  No code in the Python
interpreter will change the contents of this storage.

Use @ref{436,,Py_DecodeLocale()} to decode a bytes string to get a
@code{wchar_*} string.
@end deffn

@geindex Py_GetProgramName (C 函数)
@anchor{c-api/init c Py_GetProgramName}@anchor{276}
@deffn {C 函数} wchar* Py_GetProgramName ()

@geindex Py_SetProgramName()

Return the program name set with @ref{f18,,Py_SetProgramName()}, or the default.
The returned string points into static storage; the caller should not modify its
value.
@end deffn

@geindex Py_GetPrefix (C 函数)
@anchor{c-api/init c Py_GetPrefix}@anchor{3b60}
@deffn {C 函数} wchar_t* Py_GetPrefix ()

Return the @emph{prefix} for installed platform-independent files. This is derived
through a number of complicated rules from the program name set with
@ref{f18,,Py_SetProgramName()} and some environment variables; for example, if the
program name is @code{'/usr/local/bin/python'}, the prefix is @code{'/usr/local'}. The
returned string points into static storage; the caller should not modify its
value.  This corresponds to the @code{prefix} variable in the top-level
@code{Makefile} and the @code{--prefix} argument to the @code{configure}
script at build time.  The value is available to Python code as @code{sys.prefix}.
It is only useful on Unix.  See also the next function.
@end deffn

@geindex Py_GetExecPrefix (C 函数)
@anchor{c-api/init c Py_GetExecPrefix}@anchor{3b61}
@deffn {C 函数} wchar_t* Py_GetExecPrefix ()

Return the @emph{exec-prefix} for installed platform-@emph{dependent} files.  This is
derived through a number of complicated rules from the program name set with
@ref{f18,,Py_SetProgramName()} and some environment variables; for example, if the
program name is @code{'/usr/local/bin/python'}, the exec-prefix is
@code{'/usr/local'}.  The returned string points into static storage; the caller
should not modify its value.  This corresponds to the @code{exec_prefix}
variable in the top-level @code{Makefile} and the @code{--exec-prefix}
argument to the @code{configure} script at build  time.  The value is
available to Python code as @code{sys.exec_prefix}.  It is only useful on Unix.

Background: The exec-prefix differs from the prefix when platform dependent
files (such as executables and shared libraries) are installed in a different
directory tree.  In a typical installation, platform dependent files may be
installed in the @code{/usr/local/plat} subtree while platform independent may
be installed in @code{/usr/local}.

Generally speaking, a platform is a combination of hardware and software
families, e.g.  Sparc machines running the Solaris 2.x operating system are
considered the same platform, but Intel machines running Solaris 2.x are another
platform, and Intel machines running Linux are yet another platform.  Different
major revisions of the same operating system generally also form different
platforms.  Non-Unix operating systems are a different story; the installation
strategies on those systems are so different that the prefix and exec-prefix are
meaningless, and set to the empty string. Note that compiled Python bytecode
files are platform independent (but not independent from the Python version by
which they were compiled!).

System administrators will know how to configure the @code{mount} or
@code{automount} programs to share @code{/usr/local} between platforms
while having @code{/usr/local/plat} be a different filesystem for each
platform.
@end deffn

@geindex Py_GetProgramFullPath (C 函数)
@anchor{c-api/init c Py_GetProgramFullPath}@anchor{275}
@deffn {C 函数} wchar_t* Py_GetProgramFullPath ()

@geindex Py_SetProgramName()
@geindex executable (in module sys)

Return the full program name of the Python executable; this is  computed as a
side-effect of deriving the default module search path  from the program name
(set by @ref{f18,,Py_SetProgramName()} above). The returned string points into
static storage; the caller should not modify its value.  The value is available
to Python code as @code{sys.executable}.
@end deffn

@geindex Py_GetPath (C 函数)
@anchor{c-api/init c Py_GetPath}@anchor{3b5f}
@deffn {C 函数} wchar_t* Py_GetPath ()

@geindex module; search; path
@geindex path (in module sys)
@geindex Py_SetPath()

Return the default module search path; this is computed from the program name
(set by @ref{f18,,Py_SetProgramName()} above) and some environment variables.
The returned string consists of a series of directory names separated by a
platform dependent delimiter character.  The delimiter character is @code{':'}
on Unix and Mac OS X, @code{';'} on Windows.  The returned string points into
static storage; the caller should not modify its value.  The list
@ref{482,,sys.path} is initialized with this value on interpreter startup; it
can be (and usually is) modified later to change the search path for loading
modules.

@c XXX should give the exact rules
@end deffn

@geindex Py_SetPath (C 函数)
@anchor{c-api/init c Py_SetPath}@anchor{273}
@deffn {C 函数} void Py_SetPath (const wchar_t@w{ }*)

@geindex module; search; path
@geindex path (in module sys)
@geindex Py_GetPath()

Set the default module search path.  If this function is called before
@ref{433,,Py_Initialize()}, then @ref{3b5f,,Py_GetPath()} won't attempt to compute a
default search path but uses the one provided instead.  This is useful if
Python is embedded by an application that has full knowledge of the location
of all modules.  The path components should be separated by the platform
dependent delimiter character, which is @code{':'} on Unix and Mac OS X, @code{';'}
on Windows.

This also causes @ref{274,,sys.executable} to be set to the program
full path (see @ref{275,,Py_GetProgramFullPath()}) and for @ref{359f,,sys.prefix} and
@ref{35a0,,sys.exec_prefix} to be empty.  It is up to the caller to modify these
if required after calling @ref{433,,Py_Initialize()}.

Use @ref{436,,Py_DecodeLocale()} to decode a bytes string to get a
@code{wchar_*} string.

The path argument is copied internally, so the caller may free it after the
call completes.


在 3.8 版更改: The program full path is now used for @ref{274,,sys.executable}, instead
of the program name.

@end deffn

@geindex Py_GetVersion (C 函数)
@anchor{c-api/init c Py_GetVersion}@anchor{3f29}
@deffn {C 函数} const char* Py_GetVersion ()

Return the version of this Python interpreter.  This is a string that looks
something like

@example
"3.0a5+ (py3k:63103M, May 12 2008, 00:53:55) \n[GCC 4.2.3]"
@end example

@geindex version (in module sys)

The first word (up to the first space character) is the current Python version;
the first three characters are the major and minor version separated by a
period.  The returned string points into static storage; the caller should not
modify its value.  The value is available to Python code as @ref{5ce,,sys.version}.
@end deffn

@geindex Py_GetPlatform (C 函数)
@anchor{c-api/init c Py_GetPlatform}@anchor{3f28}
@deffn {C 函数} const char* Py_GetPlatform ()

@geindex platform (in module sys)

Return the platform identifier for the current platform.  On Unix, this is
formed from the "official" name of the operating system, converted to lower
case, followed by the major revision number; e.g., for Solaris 2.x, which is
also known as SunOS 5.x, the value is @code{'sunos5'}.  On Mac OS X, it is
@code{'darwin'}.  On Windows, it is @code{'win'}.  The returned string points into
static storage; the caller should not modify its value.  The value is available
to Python code as @code{sys.platform}.
@end deffn

@geindex Py_GetCopyright (C 函数)
@anchor{c-api/init c Py_GetCopyright}@anchor{3f27}
@deffn {C 函数} const char* Py_GetCopyright ()

Return the official copyright string for the current Python version, for example

@code{'Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam'}

@geindex copyright (in module sys)

The returned string points into static storage; the caller should not modify its
value.  The value is available to Python code as @code{sys.copyright}.
@end deffn

@geindex Py_GetCompiler (C 函数)
@anchor{c-api/init c Py_GetCompiler}@anchor{3f26}
@deffn {C 函数} const char* Py_GetCompiler ()

Return an indication of the compiler used to build the current Python version,
in square brackets, for example:

@example
"[GCC 2.7.2.2]"
@end example

@geindex version (in module sys)

The returned string points into static storage; the caller should not modify its
value.  The value is available to Python code as part of the variable
@code{sys.version}.
@end deffn

@geindex Py_GetBuildInfo (C 函数)
@anchor{c-api/init c Py_GetBuildInfo}@anchor{d93}
@deffn {C 函数} const char* Py_GetBuildInfo ()

Return information about the sequence number and build date and time  of the
current Python interpreter instance, for example

@example
"#67, Aug  1 1997, 22:34:28"
@end example

@geindex version (in module sys)

The returned string points into static storage; the caller should not modify its
value.  The value is available to Python code as part of the variable
@code{sys.version}.
@end deffn

@geindex PySys_SetArgvEx (C 函数)
@anchor{c-api/init c PySys_SetArgvEx}@anchor{bf3}
@deffn {C 函数} void PySys_SetArgvEx (int@w{ }argc, wchar_t@w{ }**argv, int@w{ }updatepath)

@geindex main()
@geindex Py_FatalError()
@geindex argv (in module sys)

Set @ref{bf4,,sys.argv} based on @emph{argc} and @emph{argv}.  These parameters are
similar to those passed to the program's @code{main()} function with the
difference that the first entry should refer to the script file to be
executed rather than the executable hosting the Python interpreter.  If there
isn't a script that will be run, the first entry in @emph{argv} can be an empty
string.  If this function fails to initialize @ref{bf4,,sys.argv}, a fatal
condition is signalled using @ref{f19,,Py_FatalError()}.

If @emph{updatepath} is zero, this is all the function does.  If @emph{updatepath}
is non-zero, the function also modifies @ref{482,,sys.path} according to the
following algorithm:


@itemize -

@item 
If the name of an existing script is passed in @code{argv[0]}, the absolute
path of the directory where the script is located is prepended to
@ref{482,,sys.path}.

@item 
Otherwise (that is, if @emph{argc} is @code{0} or @code{argv[0]} doesn't point
to an existing file name), an empty string is prepended to
@ref{482,,sys.path}, which is the same as prepending the current working
directory (@code{"."}).
@end itemize

Use @ref{436,,Py_DecodeLocale()} to decode a bytes string to get a
@code{wchar_*} string.

@cartouche
@quotation 注解 
It is recommended that applications embedding the Python interpreter
for purposes other than executing a single script pass @code{0} as @emph{updatepath},
and update @ref{482,,sys.path} themselves if desired.
See CVE-2008-5983@footnote{https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983}.

On versions before 3.1.3, you can achieve the same effect by manually
popping the first @ref{482,,sys.path} element after having called
@ref{ce5,,PySys_SetArgv()}, for example using:

@example
PyRun_SimpleString("import sys; sys.path.pop(0)\n");
@end example
@end quotation
@end cartouche


3.1.3 新版功能.


@c XXX impl. doesn't seem consistent in allowing ``0``/``NULL`` for the params;
@c check w/ Guido.
@end deffn

@geindex PySys_SetArgv (C 函数)
@anchor{c-api/init c PySys_SetArgv}@anchor{ce5}
@deffn {C 函数} void PySys_SetArgv (int@w{ }argc, wchar_t@w{ }**argv)

This function works like @ref{bf3,,PySys_SetArgvEx()} with @emph{updatepath} set
to @code{1} unless the @code{python} interpreter was started with the
@ref{f99,,-I}.

Use @ref{436,,Py_DecodeLocale()} to decode a bytes string to get a
@code{wchar_*} string.


在 3.4 版更改: The @emph{updatepath} value depends on @ref{f99,,-I}.

@end deffn

@geindex Py_SetPythonHome (C 函数)
@anchor{c-api/init c Py_SetPythonHome}@anchor{f17}
@deffn {C 函数} void Py_SetPythonHome (const wchar_t@w{ }*home)

Set the default "home" directory, that is, the location of the standard
Python libraries.  See 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} for the meaning of the
argument string.

The argument should point to a zero-terminated character string in static
storage whose contents will not change for the duration of the program's
execution.  No code in the Python interpreter will change the contents of
this storage.

Use @ref{436,,Py_DecodeLocale()} to decode a bytes string to get a
@code{wchar_*} string.
@end deffn

@geindex Py_GetPythonHome (C 函数)
@anchor{c-api/init c Py_GetPythonHome}@anchor{3f2a}
@deffn {C 函数} w_char* Py_GetPythonHome ()

Return the default "home", that is, the value set by a previous call to
@ref{f17,,Py_SetPythonHome()}, or the value of the 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME}
environment variable if it is set.
@end deffn

@node Thread State and the Global Interpreter Lock,Sub-interpreter support,Process-wide parameters,Initialization Finalization and Threads
@anchor{c-api/init thread-state-and-the-global-interpreter-lock}@anchor{3f3c}@anchor{c-api/init threads}@anchor{3f3d}
@subsection Thread State and the Global Interpreter Lock


@geindex global interpreter lock
@geindex interpreter lock
@geindex lock@comma{} interpreter

The Python interpreter is not fully thread-safe.  In order to support
multi-threaded Python programs, there's a global lock, called the @ref{500,,global interpreter lock} or @ref{be3,,GIL}, that must be held by the current thread before
it can safely access Python objects. Without the lock, even the simplest
operations could cause problems in a multi-threaded program: for example, when
two threads simultaneously increment the reference count of the same object, the
reference count could end up being incremented only once instead of twice.

@geindex setswitchinterval() (in module sys)

Therefore, the rule exists that only the thread that has acquired the
@ref{be3,,GIL} may operate on Python objects or call Python/C API functions.
In order to emulate concurrency of execution, the interpreter regularly
tries to switch threads (see @ref{be4,,sys.setswitchinterval()}).  The lock is also
released around potentially blocking I/O operations like reading or writing
a file, so that other Python threads can run in the meantime.

@geindex PyThreadState
@geindex PyThreadState

The Python interpreter keeps some thread-specific bookkeeping information
inside a data structure called @ref{3f3e,,PyThreadState}.  There's also one
global variable pointing to the current @ref{3f3e,,PyThreadState}: it can
be retrieved using @ref{3f3f,,PyThreadState_Get()}.

@menu
* Releasing the GIL from extension code:: 
* 非Python创建的线程:: 
* Cautions about fork(): Cautions about fork. 
* 高阶 API:: 
* Low-level API:: 

@end menu

@node Releasing the GIL from extension code,非Python创建的线程,,Thread State and the Global Interpreter Lock
@anchor{c-api/init releasing-the-gil-from-extension-code}@anchor{3f40}
@subsubsection Releasing the GIL from extension code


Most extension code manipulating the @ref{be3,,GIL} has the following simple
structure:

@example
Save the thread state in a local variable.
Release the global interpreter lock.
... Do some blocking I/O operation ...
Reacquire the global interpreter lock.
Restore the thread state from the local variable.
@end example

This is so common that a pair of macros exists to simplify it:

@example
Py_BEGIN_ALLOW_THREADS
... Do some blocking I/O operation ...
Py_END_ALLOW_THREADS
@end example

@geindex Py_BEGIN_ALLOW_THREADS
@geindex Py_END_ALLOW_THREADS

The @ref{3acb,,Py_BEGIN_ALLOW_THREADS} macro opens a new block and declares a
hidden local variable; the @ref{2b5,,Py_END_ALLOW_THREADS} macro closes the
block.

The block above expands to the following code:

@example
PyThreadState *_save;

_save = PyEval_SaveThread();
... Do some blocking I/O operation ...
PyEval_RestoreThread(_save);
@end example

@geindex PyEval_RestoreThread()
@geindex PyEval_SaveThread()

Here is how these functions work: the global interpreter lock is used to protect the pointer to the
current thread state.  When releasing the lock and saving the thread state,
the current thread state pointer must be retrieved before the lock is released
(since another thread could immediately acquire the lock and store its own thread
state in the global variable). Conversely, when acquiring the lock and restoring
the thread state, the lock must be acquired before storing the thread state
pointer.

@cartouche
@quotation 注解 
Calling system I/O functions is the most common use case for releasing
the GIL, but it can also be useful before calling long-running computations
which don't need access to Python objects, such as compression or
cryptographic functions operating over memory buffers.  For example, the
standard @ref{144,,zlib} and @ref{8d,,hashlib} modules release the GIL when
compressing or hashing data.
@end quotation
@end cartouche

@node 非Python创建的线程,Cautions about fork,Releasing the GIL from extension code,Thread State and the Global Interpreter Lock
@anchor{c-api/init gilstate}@anchor{3f41}@anchor{c-api/init non-python-created-threads}@anchor{3f42}
@subsubsection 非Python创建的线程


When threads are created using the dedicated Python APIs (such as the
@ref{109,,threading} module), a thread state is automatically associated to them
and the code showed above is therefore correct.  However, when threads are
created from C (for example by a third-party library with its own thread
management), they don't hold the GIL, nor is there a thread state structure
for them.

If you need to call Python code from these threads (often this will be part
of a callback API provided by the aforementioned third-party library),
you must first register these threads with the interpreter by
creating a thread state data structure, then acquiring the GIL, and finally
storing their thread state pointer, before you can start using the Python/C
API.  When you are done, you should reset the thread state pointer, release
the GIL, and finally free the thread state data structure.

The @ref{2b6,,PyGILState_Ensure()} and @ref{3f43,,PyGILState_Release()} functions do
all of the above automatically.  The typical idiom for calling into Python
from a C thread is:

@example
PyGILState_STATE gstate;
gstate = PyGILState_Ensure();

/* Perform Python actions here. */
result = CallSomeFunction();
/* evaluate result or handle exception */

/* Release the thread. No Python API allowed beyond this point. */
PyGILState_Release(gstate);
@end example

Note that the @code{PyGILState_*()} functions assume there is only one global
interpreter (created automatically by @ref{433,,Py_Initialize()}).  Python
supports the creation of additional interpreters (using
@ref{3f3a,,Py_NewInterpreter()}), but mixing multiple interpreters and the
@code{PyGILState_*()} API is unsupported.

@node Cautions about fork,高阶 API,非Python创建的线程,Thread State and the Global Interpreter Lock
@anchor{c-api/init cautions-about-fork}@anchor{3f44}@anchor{c-api/init fork-and-threads}@anchor{3be5}
@subsubsection Cautions about fork()


Another important thing to note about threads is their behaviour in the face
of the C @code{fork()} call. On most systems with @code{fork()}, after a
process forks only the thread that issued the fork will exist.  This has a
concrete impact both on how locks must be handled and on all stored state
in CPython's runtime.

The fact that only the "current" thread remains
means any locks held by other threads will never be released. Python solves
this for @ref{95b,,os.fork()} by acquiring the locks it uses internally before
the fork, and releasing them afterwards. In addition, it resets any
@ref{22fd,,锁对象} in the child. When extending or embedding Python, there
is no way to inform Python of additional (non-Python) locks that need to be
acquired before or reset after a fork. OS facilities such as
@code{pthread_atfork()} would need to be used to accomplish the same thing.
Additionally, when extending or embedding Python, calling @code{fork()}
directly rather than through @ref{95b,,os.fork()} (and returning to or calling
into Python) may result in a deadlock by one of Python's internal locks
being held by a thread that is defunct after the fork.
@ref{2cd,,PyOS_AfterFork_Child()} tries to reset the necessary locks, but is not
always able to.

The fact that all other threads go away also means that CPython's
runtime state there must be cleaned up properly, which @ref{95b,,os.fork()}
does.  This means finalizing all other @ref{3f3e,,PyThreadState} objects
belonging to the current interpreter and all other
@ref{2c2,,PyInterpreterState} objects.  Due to this and the special
nature of the @ref{3be6,,"main" interpreter},
@code{fork()} should only be called in that interpreter's "main"
thread, where the CPython global runtime was originally initialized.
The only exception is if @code{exec()} will be called immediately
after.

@node 高阶 API,Low-level API,Cautions about fork,Thread State and the Global Interpreter Lock
@anchor{c-api/init high-level-api}@anchor{3f45}
@subsubsection 高阶 API


These are the most commonly used types and functions when writing C extension
code, or when embedding the Python interpreter:

@geindex PyInterpreterState (C 类型)
@anchor{c-api/init c PyInterpreterState}@anchor{2c2}
@deffn {C 类型} PyInterpreterState

This data structure represents the state shared by a number of cooperating
threads.  Threads belonging to the same interpreter share their module
administration and a few other internal items. There are no public members in
this structure.

Threads belonging to different interpreters initially share nothing, except
process state like available memory, open file descriptors and such.  The global
interpreter lock is also shared by all threads, regardless of to which
interpreter they belong.
@end deffn

@geindex PyThreadState (C 类型)
@anchor{c-api/init c PyThreadState}@anchor{3f3e}
@deffn {C 类型} PyThreadState

This data structure represents the state of a single thread.  The only public
data member is @ref{2c2,,PyInterpreterState *}@code{interp}, which points to
this thread's interpreter state.
@end deffn

@geindex PyEval_InitThreads (C 函数)
@anchor{c-api/init c PyEval_InitThreads}@anchor{c0b}
@deffn {C 函数} void PyEval_InitThreads ()

@geindex PyEval_AcquireThread()
@geindex PyEval_ReleaseThread()
@geindex PyEval_SaveThread()
@geindex PyEval_RestoreThread()

Initialize and acquire the global interpreter lock.  It should be called in the
main thread before creating a second thread or engaging in any other thread
operations such as @code{PyEval_ReleaseThread(tstate)}. It is not needed before
calling @ref{c0a,,PyEval_SaveThread()} or @ref{2b4,,PyEval_RestoreThread()}.

This is a no-op when called for a second time.


在 3.7 版更改: This function is now called by @ref{433,,Py_Initialize()}, so you don't
have to call it yourself anymore.



在 3.2 版更改: This function cannot be called before @ref{433,,Py_Initialize()} anymore.


@geindex 模块; _thread
@end deffn

@geindex PyEval_ThreadsInitialized (C 函数)
@anchor{c-api/init c PyEval_ThreadsInitialized}@anchor{dd2}
@deffn {C 函数} int PyEval_ThreadsInitialized ()

Returns a non-zero value if @ref{c0b,,PyEval_InitThreads()} has been called.  This
function can be called without holding the GIL, and therefore can be used to
avoid calls to the locking API when running single-threaded.


在 3.7 版更改: The @ref{be3,,GIL} is now initialized by @ref{433,,Py_Initialize()}.

@end deffn

@geindex PyEval_SaveThread (C 函数)
@anchor{c-api/init c PyEval_SaveThread}@anchor{c0a}
@deffn {C 函数} PyThreadState* PyEval_SaveThread ()

Release the global interpreter lock (if it has been created) and reset the
thread state to @code{NULL}, returning the previous thread state (which is not
@code{NULL}).  If the lock has been created, the current thread must have
acquired it.
@end deffn

@geindex PyEval_RestoreThread (C 函数)
@anchor{c-api/init c PyEval_RestoreThread}@anchor{2b4}
@deffn {C 函数} void PyEval_RestoreThread (PyThreadState@w{ }*tstate)

Acquire the global interpreter lock (if it has been created) and set the
thread state to @emph{tstate}, which must not be @code{NULL}.  If the lock has been
created, the current thread must not have acquired it, otherwise deadlock
ensues.

@cartouche
@quotation 注解 
Calling this function from a thread when the runtime is finalizing
will terminate the thread, even if the thread was not created by Python.
You can use @code{_Py_IsFinalizing()} or @ref{75c,,sys.is_finalizing()} to
check if the interpreter is in process of being finalized before calling
this function to avoid unwanted termination.
@end quotation
@end cartouche
@end deffn

@geindex PyThreadState_Get (C 函数)
@anchor{c-api/init c PyThreadState_Get}@anchor{3f3f}
@deffn {C 函数} PyThreadState* PyThreadState_Get ()

Return the current thread state.  The global interpreter lock must be held.
When the current thread state is @code{NULL}, this issues a fatal error (so that
the caller needn't check for @code{NULL}).
@end deffn

@geindex PyThreadState_Swap (C 函数)
@anchor{c-api/init c PyThreadState_Swap}@anchor{3f46}
@deffn {C 函数} PyThreadState* PyThreadState_Swap (PyThreadState@w{ }*tstate)

Swap the current thread state with the thread state given by the argument
@emph{tstate}, which may be @code{NULL}.  The global interpreter lock must be held
and is not released.
@end deffn

The following functions use thread-local storage, and are not compatible
with sub-interpreters:

@geindex PyGILState_Ensure (C 函数)
@anchor{c-api/init c PyGILState_Ensure}@anchor{2b6}
@deffn {C 函数} PyGILState_STATE PyGILState_Ensure ()

Ensure that the current thread is ready to call the Python C API regardless
of the current state of Python, or of the global interpreter lock. This may
be called as many times as desired by a thread as long as each call is
matched with a call to @ref{3f43,,PyGILState_Release()}. In general, other
thread-related APIs may be used between @ref{2b6,,PyGILState_Ensure()} and
@ref{3f43,,PyGILState_Release()} calls as long as the thread state is restored to
its previous state before the Release().  For example, normal usage of the
@ref{3acb,,Py_BEGIN_ALLOW_THREADS} and @ref{2b5,,Py_END_ALLOW_THREADS} macros is
acceptable.

The return value is an opaque "handle" to the thread state when
@ref{2b6,,PyGILState_Ensure()} was called, and must be passed to
@ref{3f43,,PyGILState_Release()} to ensure Python is left in the same state. Even
though recursive calls are allowed, these handles @emph{cannot} be shared - each
unique call to @ref{2b6,,PyGILState_Ensure()} must save the handle for its call
to @ref{3f43,,PyGILState_Release()}.

When the function returns, the current thread will hold the GIL and be able
to call arbitrary Python code.  Failure is a fatal error.

@cartouche
@quotation 注解 
Calling this function from a thread when the runtime is finalizing
will terminate the thread, even if the thread was not created by Python.
You can use @code{_Py_IsFinalizing()} or @ref{75c,,sys.is_finalizing()} to
check if the interpreter is in process of being finalized before calling
this function to avoid unwanted termination.
@end quotation
@end cartouche
@end deffn

@geindex PyGILState_Release (C 函数)
@anchor{c-api/init c PyGILState_Release}@anchor{3f43}
@deffn {C 函数} void PyGILState_Release (PyGILState_STATE)

Release any resources previously acquired.  After this call, Python's state will
be the same as it was prior to the corresponding @ref{2b6,,PyGILState_Ensure()} call
(but generally this state will be unknown to the caller, hence the use of the
GILState API).

Every call to @ref{2b6,,PyGILState_Ensure()} must be matched by a call to
@ref{3f43,,PyGILState_Release()} on the same thread.
@end deffn

@geindex PyGILState_GetThisThreadState (C 函数)
@anchor{c-api/init c PyGILState_GetThisThreadState}@anchor{3f47}
@deffn {C 函数} PyThreadState* PyGILState_GetThisThreadState ()

Get the current thread state for this thread.  May return @code{NULL} if no
GILState API has been used on the current thread.  Note that the main thread
always has such a thread-state, even if no auto-thread-state call has been
made on the main thread.  This is mainly a helper/diagnostic function.
@end deffn

@geindex PyGILState_Check (C 函数)
@anchor{c-api/init c PyGILState_Check}@anchor{3f48}
@deffn {C 函数} int PyGILState_Check ()

Return @code{1} if the current thread is holding the GIL and @code{0} otherwise.
This function can be called from any thread at any time.
Only if it has had its Python thread state initialized and currently is
holding the GIL will it return @code{1}.
This is mainly a helper/diagnostic function.  It can be useful
for example in callback contexts or memory allocation functions when
knowing that the GIL is locked can allow the caller to perform sensitive
actions or otherwise behave differently.


3.4 新版功能.

@end deffn

The following macros are normally used without a trailing semicolon; look for
example usage in the Python source distribution.

@geindex Py_BEGIN_ALLOW_THREADS (C 宏)
@anchor{c-api/init c Py_BEGIN_ALLOW_THREADS}@anchor{3acb}
@deffn {C 宏} Py_BEGIN_ALLOW_THREADS

This macro expands to @code{@{ PyThreadState *_save; _save = PyEval_SaveThread();}.
Note that it contains an opening brace; it must be matched with a following
@ref{2b5,,Py_END_ALLOW_THREADS} macro.  See above for further discussion of this
macro.
@end deffn

@geindex Py_END_ALLOW_THREADS (C 宏)
@anchor{c-api/init c Py_END_ALLOW_THREADS}@anchor{2b5}
@deffn {C 宏} Py_END_ALLOW_THREADS

This macro expands to @code{PyEval_RestoreThread(_save); @}}. Note that it contains
a closing brace; it must be matched with an earlier
@ref{3acb,,Py_BEGIN_ALLOW_THREADS} macro.  See above for further discussion of
this macro.
@end deffn

@geindex Py_BLOCK_THREADS (C 宏)
@anchor{c-api/init c Py_BLOCK_THREADS}@anchor{3f49}
@deffn {C 宏} Py_BLOCK_THREADS

This macro expands to @code{PyEval_RestoreThread(_save);}: it is equivalent to
@ref{2b5,,Py_END_ALLOW_THREADS} without the closing brace.
@end deffn

@geindex Py_UNBLOCK_THREADS (C 宏)
@anchor{c-api/init c Py_UNBLOCK_THREADS}@anchor{3f4a}
@deffn {C 宏} Py_UNBLOCK_THREADS

This macro expands to @code{_save = PyEval_SaveThread();}: it is equivalent to
@ref{3acb,,Py_BEGIN_ALLOW_THREADS} without the opening brace and variable
declaration.
@end deffn

@node Low-level API,,高阶 API,Thread State and the Global Interpreter Lock
@anchor{c-api/init low-level-api}@anchor{3f4b}
@subsubsection Low-level API


All of the following functions must be called after @ref{433,,Py_Initialize()}.


在 3.7 版更改: @ref{433,,Py_Initialize()} now initializes the @ref{be3,,GIL}.


@geindex PyInterpreterState_New (C 函数)
@anchor{c-api/init c PyInterpreterState_New}@anchor{346b}
@deffn {C 函数} PyInterpreterState* PyInterpreterState_New ()

Create a new interpreter state object.  The global interpreter lock need not
be held, but may be held if it is necessary to serialize calls to this
function.

Raises an @ref{12d0,,auditing event} @code{cpython.PyInterpreterState_New} with no arguments.
@end deffn

@geindex PyInterpreterState_Clear (C 函数)
@anchor{c-api/init c PyInterpreterState_Clear}@anchor{346a}
@deffn {C 函数} void PyInterpreterState_Clear (PyInterpreterState@w{ }*interp)

Reset all information in an interpreter state object.  The global interpreter
lock must be held.

Raises an @ref{12d0,,auditing event} @code{cpython.PyInterpreterState_Clear} with no arguments.
@end deffn

@geindex PyInterpreterState_Delete (C 函数)
@anchor{c-api/init c PyInterpreterState_Delete}@anchor{3f4c}
@deffn {C 函数} void PyInterpreterState_Delete (PyInterpreterState@w{ }*interp)

Destroy an interpreter state object.  The global interpreter lock need not be
held.  The interpreter state must have been reset with a previous call to
@ref{346a,,PyInterpreterState_Clear()}.
@end deffn

@geindex PyThreadState_New (C 函数)
@anchor{c-api/init c PyThreadState_New}@anchor{3f4d}
@deffn {C 函数} PyThreadState* PyThreadState_New (PyInterpreterState@w{ }*interp)

Create a new thread state object belonging to the given interpreter object.
The global interpreter lock need not be held, but may be held if it is
necessary to serialize calls to this function.
@end deffn

@geindex PyThreadState_Clear (C 函数)
@anchor{c-api/init c PyThreadState_Clear}@anchor{eae}
@deffn {C 函数} void PyThreadState_Clear (PyThreadState@w{ }*tstate)

Reset all information in a thread state object.  The global interpreter lock
must be held.
@end deffn

@geindex PyThreadState_Delete (C 函数)
@anchor{c-api/init c PyThreadState_Delete}@anchor{3f4e}
@deffn {C 函数} void PyThreadState_Delete (PyThreadState@w{ }*tstate)

Destroy a thread state object.  The global interpreter lock need not be held.
The thread state must have been reset with a previous call to
@ref{eae,,PyThreadState_Clear()}.
@end deffn

@geindex PyInterpreterState_GetID (C 函数)
@anchor{c-api/init c PyInterpreterState_GetID}@anchor{435}
@deffn {C 函数} PY_INT64_T PyInterpreterState_GetID (PyInterpreterState@w{ }*interp)

Return the interpreter's unique ID.  If there was any error in doing
so then @code{-1} is returned and an error is set.


3.7 新版功能.

@end deffn

@geindex PyInterpreterState_GetDict (C 函数)
@anchor{c-api/init c PyInterpreterState_GetDict}@anchor{3f4f}
@deffn {C 函数} PyObject* PyInterpreterState_GetDict (PyInterpreterState@w{ }*interp)

Return a dictionary in which interpreter-specific data may be stored.
If this function returns @code{NULL} then no exception has been raised and
the caller should assume no interpreter-specific dict is available.

This is not a replacement for @ref{3e79,,PyModule_GetState()}, which
extensions should use to store interpreter-specific state information.


3.8 新版功能.

@end deffn

@geindex PyThreadState_GetDict (C 函数)
@anchor{c-api/init c PyThreadState_GetDict}@anchor{3f50}
@deffn {C 函数} PyObject* PyThreadState_GetDict ()
@emph{Return value: Borrowed reference.}
Return a dictionary in which extensions can store thread-specific state
information.  Each extension should use a unique key to use to store state in
the dictionary.  It is okay to call this function when no current thread state
is available. If this function returns @code{NULL}, no exception has been raised and
the caller should assume no current thread state is available.
@end deffn

@geindex PyThreadState_SetAsyncExc (C 函数)
@anchor{c-api/init c PyThreadState_SetAsyncExc}@anchor{431}
@deffn {C 函数} int PyThreadState_SetAsyncExc (unsigned long@w{ }id, PyObject@w{ }*exc)

Asynchronously raise an exception in a thread. The @emph{id} argument is the thread
id of the target thread; @emph{exc} is the exception object to be raised. This
function does not steal any references to @emph{exc}. To prevent naive misuse, you
must write your own C extension to call this.  Must be called with the GIL held.
Returns the number of thread states modified; this is normally one, but will be
zero if the thread id isn't found.  If @emph{exc} is @code{NULL}, the pending
exception (if any) for the thread is cleared. This raises no exceptions.


在 3.7 版更改: The type of the @emph{id} parameter changed from @code{long} to
@code{unsigned long}.

@end deffn

@geindex PyEval_AcquireThread (C 函数)
@anchor{c-api/init c PyEval_AcquireThread}@anchor{2b3}
@deffn {C 函数} void PyEval_AcquireThread (PyThreadState@w{ }*tstate)

Acquire the global interpreter lock and set the current thread state to
@emph{tstate}, which should not be @code{NULL}.  The lock must have been created earlier.
If this thread already has the lock, deadlock ensues.

@cartouche
@quotation 注解 
Calling this function from a thread when the runtime is finalizing
will terminate the thread, even if the thread was not created by Python.
You can use @code{_Py_IsFinalizing()} or @ref{75c,,sys.is_finalizing()} to
check if the interpreter is in process of being finalized before calling
this function to avoid unwanted termination.
@end quotation
@end cartouche


在 3.8 版更改: Updated to be consistent with @ref{2b4,,PyEval_RestoreThread()},
@ref{2b5,,Py_END_ALLOW_THREADS()}, and @ref{2b6,,PyGILState_Ensure()},
and terminate the current thread if called while the interpreter is finalizing.


@ref{2b4,,PyEval_RestoreThread()} is a higher-level function which is always
available (even when threads have not been initialized).
@end deffn

@geindex PyEval_ReleaseThread (C 函数)
@anchor{c-api/init c PyEval_ReleaseThread}@anchor{3f51}
@deffn {C 函数} void PyEval_ReleaseThread (PyThreadState@w{ }*tstate)

Reset the current thread state to @code{NULL} and release the global interpreter
lock.  The lock must have been created earlier and must be held by the current
thread.  The @emph{tstate} argument, which must not be @code{NULL}, is only used to check
that it represents the current thread state --- if it isn't, a fatal error is
reported.

@ref{c0a,,PyEval_SaveThread()} is a higher-level function which is always
available (even when threads have not been initialized).
@end deffn

@geindex PyEval_AcquireLock (C 函数)
@anchor{c-api/init c PyEval_AcquireLock}@anchor{2b2}
@deffn {C 函数} void PyEval_AcquireLock ()

Acquire the global interpreter lock.  The lock must have been created earlier.
If this thread already has the lock, a deadlock ensues.


3.2 版后已移除: This function does not update the current thread state.  Please use
@ref{2b4,,PyEval_RestoreThread()} or @ref{2b3,,PyEval_AcquireThread()}
instead.


@cartouche
@quotation 注解 
Calling this function from a thread when the runtime is finalizing
will terminate the thread, even if the thread was not created by Python.
You can use @code{_Py_IsFinalizing()} or @ref{75c,,sys.is_finalizing()} to
check if the interpreter is in process of being finalized before calling
this function to avoid unwanted termination.
@end quotation
@end cartouche


在 3.8 版更改: Updated to be consistent with @ref{2b4,,PyEval_RestoreThread()},
@ref{2b5,,Py_END_ALLOW_THREADS()}, and @ref{2b6,,PyGILState_Ensure()},
and terminate the current thread if called while the interpreter is finalizing.

@end deffn

@geindex PyEval_ReleaseLock (C 函数)
@anchor{c-api/init c PyEval_ReleaseLock}@anchor{c09}
@deffn {C 函数} void PyEval_ReleaseLock ()

Release the global interpreter lock.  The lock must have been created earlier.


3.2 版后已移除: This function does not update the current thread state.  Please use
@ref{c0a,,PyEval_SaveThread()} or @ref{3f51,,PyEval_ReleaseThread()}
instead.

@end deffn

@node Sub-interpreter support,异步通知,Thread State and the Global Interpreter Lock,Initialization Finalization and Threads
@anchor{c-api/init id1}@anchor{3f52}@anchor{c-api/init sub-interpreter-support}@anchor{3be6}
@subsection Sub-interpreter support


While in most uses, you will only embed a single Python interpreter, there
are cases where you need to create several independent interpreters in the
same process and perhaps even in the same thread. Sub-interpreters allow
you to do that.

The "main" interpreter is the first one created when the runtime initializes.
It is usually the only Python interpreter in a process.  Unlike sub-interpreters,
the main interpreter has unique process-global responsibilities like signal
handling.  It is also responsible for execution during runtime initialization and
is usually the active interpreter during runtime finalization.  The
@ref{3f53,,PyInterpreterState_Main()} function returns a pointer to its state.

You can switch between sub-interpreters using the @ref{3f46,,PyThreadState_Swap()}
function. You can create and destroy them using the following functions:

@geindex Py_NewInterpreter (C 函数)
@anchor{c-api/init c Py_NewInterpreter}@anchor{3f3a}
@deffn {C 函数} PyThreadState* Py_NewInterpreter ()

@geindex 模块; builtins
@geindex 模块; __main__
@geindex 模块; sys
@geindex stdout (in module sys)
@geindex stderr (in module sys)
@geindex stdin (in module sys)

Create a new sub-interpreter.  This is an (almost) totally separate environment
for the execution of Python code.  In particular, the new interpreter has
separate, independent versions of all imported modules, including the
fundamental modules @ref{13,,builtins}, @ref{1,,__main__} and @ref{fd,,sys}.  The
table of loaded modules (@code{sys.modules}) and the module search path
(@code{sys.path}) are also separate.  The new environment has no @code{sys.argv}
variable.  It has new standard I/O stream file objects @code{sys.stdin},
@code{sys.stdout} and @code{sys.stderr} (however these refer to the same underlying
file descriptors).

The return value points to the first thread state created in the new
sub-interpreter.  This thread state is made in the current thread state.
Note that no actual thread is created; see the discussion of thread states
below.  If creation of the new interpreter is unsuccessful, @code{NULL} is
returned; no exception is set since the exception state is stored in the
current thread state and there may not be a current thread state.  (Like all
other Python/C API functions, the global interpreter lock must be held before
calling this function and is still held when it returns; however, unlike most
other Python/C API functions, there needn't be a current thread state on
entry.)

@geindex Py_FinalizeEx()
@geindex Py_Initialize()

Extension modules are shared between (sub-)interpreters as follows:


@itemize *

@item 
For modules using multi-phase initialization,
e.g. @ref{7a5,,PyModule_FromDefAndSpec()}, a separate module object is
created and initialized for each interpreter.
Only C-level static and global variables are shared between these
module objects.

@item 
For modules using single-phase initialization,
e.g. @ref{3aac,,PyModule_Create()}, the first time a particular extension
is imported, it is initialized normally, and a (shallow) copy of its
module's dictionary is squirreled away.
When the same extension is imported by another (sub-)interpreter, a new
module is initialized and filled with the contents of this copy; the
extension's @code{init} function is not called.
Objects in the module's dictionary thus end up shared across
(sub-)interpreters, which might cause unwanted behavior (see
@ref{3f54,,Bugs and caveats} below).

Note that this is different from what happens when an extension is
imported after the interpreter has been completely re-initialized by
calling @ref{5c4,,Py_FinalizeEx()} and @ref{433,,Py_Initialize()}; in that
case, the extension's @code{initmodule} function @emph{is} called again.
As with multi-phase initialization, this means that only C-level static
and global variables are shared between these modules.
@end itemize

@geindex close() (in module os)
@end deffn

@geindex Py_EndInterpreter (C 函数)
@anchor{c-api/init c Py_EndInterpreter}@anchor{3f55}
@deffn {C 函数} void Py_EndInterpreter (PyThreadState@w{ }*tstate)

@geindex Py_FinalizeEx()

Destroy the (sub-)interpreter represented by the given thread state. The given
thread state must be the current thread state.  See the discussion of thread
states below.  When the call returns, the current thread state is @code{NULL}.  All
thread states associated with this interpreter are destroyed.  (The global
interpreter lock must be held before calling this function and is still held
when it returns.)  @ref{5c4,,Py_FinalizeEx()} will destroy all sub-interpreters that
haven't been explicitly destroyed at that point.
@end deffn

@menu
* 错误和警告:: 

@end menu

@node 错误和警告,,,Sub-interpreter support
@anchor{c-api/init bugs-and-caveats}@anchor{3f54}
@subsubsection 错误和警告


Because sub-interpreters (and the main interpreter) are part of the same
process, the insulation between them isn't perfect --- for example, using
low-level file operations like  @ref{3ca,,os.close()} they can
(accidentally or maliciously) affect each other's open files.  Because of the
way extensions are shared between (sub-)interpreters, some extensions may not
work properly; this is especially likely when using single-phase initialization
or (static) global variables.
It is possible to insert objects created in one sub-interpreter into
a namespace of another (sub-)interpreter; this should be avoided if possible.

Special care should be taken to avoid sharing user-defined functions,
methods, instances or classes between sub-interpreters, since import
operations executed by such objects may affect the wrong (sub-)interpreter's
dictionary of loaded modules. It is equally important to avoid sharing
objects from which the above are reachable.

Also note that combining this functionality with @code{PyGILState_*()} APIs
is delicate, because these APIs assume a bijection between Python thread states
and OS-level threads, an assumption broken by the presence of sub-interpreters.
It is highly recommended that you don't switch sub-interpreters between a pair
of matching @ref{2b6,,PyGILState_Ensure()} and @ref{3f43,,PyGILState_Release()} calls.
Furthermore, extensions (such as @ref{2b,,ctypes}) using these APIs to allow calling
of Python code from non-Python created threads will probably be broken when using
sub-interpreters.

@node 异步通知,分析和跟踪,Sub-interpreter support,Initialization Finalization and Threads
@anchor{c-api/init asynchronous-notifications}@anchor{3f56}
@subsection 异步通知


A mechanism is provided to make asynchronous notifications to the main
interpreter thread.  These notifications take the form of a function
pointer and a void pointer argument.

@geindex Py_AddPendingCall (C 函数)
@anchor{c-api/init c Py_AddPendingCall}@anchor{ce2}
@deffn {C 函数} int Py_AddPendingCall (int (*func)(void *), void@w{ }*arg)

@geindex Py_AddPendingCall()

Schedule a function to be called from the main interpreter thread.  On
success, @code{0} is returned and @emph{func} is queued for being called in the
main thread.  On failure, @code{-1} is returned without setting any exception.

When successfully queued, @emph{func} will be @emph{eventually} called from the
main interpreter thread with the argument @emph{arg}.  It will be called
asynchronously with respect to normally running Python code, but with
both these conditions met:


@itemize *

@item 
on a @ref{60f,,bytecode} boundary;

@item 
with the main thread holding the @ref{500,,global interpreter lock}
(@emph{func} can therefore use the full C API).
@end itemize

@emph{func} must return @code{0} on success, or @code{-1} on failure with an exception
set.  @emph{func} won't be interrupted to perform another asynchronous
notification recursively, but it can still be interrupted to switch
threads if the global interpreter lock is released.

This function doesn't need a current thread state to run, and it doesn't
need the global interpreter lock.

@cartouche
@quotation 警告 
This is a low-level function, only useful for very special cases.
There is no guarantee that @emph{func} will be called as quick as
possible.  If the main thread is busy executing a system call,
@emph{func} won't be called before the system call returns.  This
function is generally @strong{not} suitable for calling Python code from
arbitrary C threads.  Instead, use the @ref{3f41,,PyGILState API}.
@end quotation
@end cartouche


3.1 新版功能.

@end deffn

@node 分析和跟踪,高级调试器支持,异步通知,Initialization Finalization and Threads
@anchor{c-api/init profiling}@anchor{3f57}@anchor{c-api/init profiling-and-tracing}@anchor{3f58}
@subsection 分析和跟踪


The Python interpreter provides some low-level support for attaching profiling
and execution tracing facilities.  These are used for profiling, debugging, and
coverage analysis tools.

This C interface allows the profiling or tracing code to avoid the overhead of
calling through Python-level callable objects, making a direct C function call
instead.  The essential attributes of the facility have not changed; the
interface allows trace functions to be installed per-thread, and the basic
events reported to the trace function are the same as had been reported to the
Python-level trace functions in previous versions.

@geindex Py_tracefunc (C 类型)
@anchor{c-api/init c Py_tracefunc}@anchor{3f59}
@deffn {C 类型} int (*Py_tracefunc) (PyObject@w{ }*obj, PyFrameObject@w{ }*frame, int@w{ }what, PyObject@w{ }*arg)

The type of the trace function registered using @ref{e34,,PyEval_SetProfile()} and
@ref{e35,,PyEval_SetTrace()}. The first parameter is the object passed to the
registration function as @emph{obj}, @emph{frame} is the frame object to which the event
pertains, @emph{what} is one of the constants @code{PyTrace_CALL},
@code{PyTrace_EXCEPTION}, @code{PyTrace_LINE}, @code{PyTrace_RETURN},
@code{PyTrace_C_CALL}, @code{PyTrace_C_EXCEPTION}, @code{PyTrace_C_RETURN},
or @code{PyTrace_OPCODE}, and @emph{arg} depends on the value of @emph{what}:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

@emph{what} 的值

@tab

@emph{arg} 的含义

@item

@code{PyTrace_CALL}

@tab

总是 @ref{3aa9,,Py_None}.

@item

@code{PyTrace_EXCEPTION}

@tab

@ref{c58,,sys.exc_info()} 返回的异常信息。

@item

@code{PyTrace_LINE}

@tab

总是 @ref{3aa9,,Py_None}.

@item

@code{PyTrace_RETURN}

@tab

Value being returned to the caller,
or @code{NULL} if caused by an exception.

@item

@code{PyTrace_C_CALL}

@tab

正在调用函数对象。

@item

@code{PyTrace_C_EXCEPTION}

@tab

正在调用函数对象。

@item

@code{PyTrace_C_RETURN}

@tab

正在调用函数对象。

@item

@code{PyTrace_OPCODE}

@tab

总是 @ref{3aa9,,Py_None}.

@end multitable

@end deffn

@geindex PyTrace_CALL (C 变量)
@anchor{c-api/init c PyTrace_CALL}@anchor{3f5a}
@deffn {C 变量} int PyTrace_CALL

The value of the @emph{what} parameter to a @ref{3f59,,Py_tracefunc} function when a new
call to a function or method is being reported, or a new entry into a generator.
Note that the creation of the iterator for a generator function is not reported
as there is no control transfer to the Python bytecode in the corresponding
frame.
@end deffn

@geindex PyTrace_EXCEPTION (C 变量)
@anchor{c-api/init c PyTrace_EXCEPTION}@anchor{3f5b}
@deffn {C 变量} int PyTrace_EXCEPTION

The value of the @emph{what} parameter to a @ref{3f59,,Py_tracefunc} function when an
exception has been raised.  The callback function is called with this value for
@emph{what} when after any bytecode is processed after which the exception becomes
set within the frame being executed.  The effect of this is that as exception
propagation causes the Python stack to unwind, the callback is called upon
return to each frame as the exception propagates.  Only trace functions receives
these events; they are not needed by the profiler.
@end deffn

@geindex PyTrace_LINE (C 变量)
@anchor{c-api/init c PyTrace_LINE}@anchor{3f5c}
@deffn {C 变量} int PyTrace_LINE

The value passed as the @emph{what} parameter to a @ref{3f59,,Py_tracefunc} function
(but not a profiling function) when a line-number event is being reported.
It may be disabled for a frame by setting @code{f_trace_lines} to @emph{0} on that frame.
@end deffn

@geindex PyTrace_RETURN (C 变量)
@anchor{c-api/init c PyTrace_RETURN}@anchor{3f5d}
@deffn {C 变量} int PyTrace_RETURN

The value for the @emph{what} parameter to @ref{3f59,,Py_tracefunc} functions when a
call is about to return.
@end deffn

@geindex PyTrace_C_CALL (C 变量)
@anchor{c-api/init c PyTrace_C_CALL}@anchor{3f5e}
@deffn {C 变量} int PyTrace_C_CALL

The value for the @emph{what} parameter to @ref{3f59,,Py_tracefunc} functions when a C
function is about to be called.
@end deffn

@geindex PyTrace_C_EXCEPTION (C 变量)
@anchor{c-api/init c PyTrace_C_EXCEPTION}@anchor{3f5f}
@deffn {C 变量} int PyTrace_C_EXCEPTION

The value for the @emph{what} parameter to @ref{3f59,,Py_tracefunc} functions when a C
function has raised an exception.
@end deffn

@geindex PyTrace_C_RETURN (C 变量)
@anchor{c-api/init c PyTrace_C_RETURN}@anchor{3f60}
@deffn {C 变量} int PyTrace_C_RETURN

The value for the @emph{what} parameter to @ref{3f59,,Py_tracefunc} functions when a C
function has returned.
@end deffn

@geindex PyTrace_OPCODE (C 变量)
@anchor{c-api/init c PyTrace_OPCODE}@anchor{3f61}
@deffn {C 变量} int PyTrace_OPCODE

The value for the @emph{what} parameter to @ref{3f59,,Py_tracefunc} functions (but not
profiling functions) when a new opcode is about to be executed.  This event is
not emitted by default: it must be explicitly requested by setting
@code{f_trace_opcodes} to @emph{1} on the frame.
@end deffn

@geindex PyEval_SetProfile (C 函数)
@anchor{c-api/init c PyEval_SetProfile}@anchor{e34}
@deffn {C 函数} void PyEval_SetProfile (Py_tracefunc@w{ }func, PyObject@w{ }*obj)

Set the profiler function to @emph{func}.  The @emph{obj} parameter is passed to the
function as its first parameter, and may be any Python object, or @code{NULL}.  If
the profile function needs to maintain state, using a different value for @emph{obj}
for each thread provides a convenient and thread-safe place to store it.  The
profile function is called for all monitored events except @code{PyTrace_LINE}
@code{PyTrace_OPCODE} and @code{PyTrace_EXCEPTION}.
@end deffn

@geindex PyEval_SetTrace (C 函数)
@anchor{c-api/init c PyEval_SetTrace}@anchor{e35}
@deffn {C 函数} void PyEval_SetTrace (Py_tracefunc@w{ }func, PyObject@w{ }*obj)

Set the tracing function to @emph{func}.  This is similar to
@ref{e34,,PyEval_SetProfile()}, except the tracing function does receive line-number
events and per-opcode events, but does not receive any event related to C function
objects being called.  Any trace function registered using @ref{e35,,PyEval_SetTrace()}
will not receive @code{PyTrace_C_CALL}, @code{PyTrace_C_EXCEPTION} or
@code{PyTrace_C_RETURN} as a value for the @emph{what} parameter.
@end deffn

@node 高级调试器支持,Thread Local Storage Support,分析和跟踪,Initialization Finalization and Threads
@anchor{c-api/init advanced-debugger-support}@anchor{3f62}@anchor{c-api/init advanced-debugging}@anchor{3f63}
@subsection 高级调试器支持


These functions are only intended to be used by advanced debugging tools.

@geindex PyInterpreterState_Head (C 函数)
@anchor{c-api/init c PyInterpreterState_Head}@anchor{e38}
@deffn {C 函数} PyInterpreterState* PyInterpreterState_Head ()

Return the interpreter state object at the head of the list of all such objects.
@end deffn

@geindex PyInterpreterState_Main (C 函数)
@anchor{c-api/init c PyInterpreterState_Main}@anchor{3f53}
@deffn {C 函数} PyInterpreterState* PyInterpreterState_Main ()

Return the main interpreter state object.
@end deffn

@geindex PyInterpreterState_Next (C 函数)
@anchor{c-api/init c PyInterpreterState_Next}@anchor{e39}
@deffn {C 函数} PyInterpreterState* PyInterpreterState_Next (PyInterpreterState@w{ }*interp)

Return the next interpreter state object after @emph{interp} from the list of all
such objects.
@end deffn

@geindex PyInterpreterState_ThreadHead (C 函数)
@anchor{c-api/init c PyInterpreterState_ThreadHead}@anchor{e3a}
@deffn {C 函数} PyThreadState * PyInterpreterState_ThreadHead (PyInterpreterState@w{ }*interp)

Return the pointer to the first @ref{3f3e,,PyThreadState} object in the list of
threads associated with the interpreter @emph{interp}.
@end deffn

@geindex PyThreadState_Next (C 函数)
@anchor{c-api/init c PyThreadState_Next}@anchor{e3b}
@deffn {C 函数} PyThreadState* PyThreadState_Next (PyThreadState@w{ }*tstate)

Return the next thread state object after @emph{tstate} from the list of all such
objects belonging to the same @ref{2c2,,PyInterpreterState} object.
@end deffn

@node Thread Local Storage Support,,高级调试器支持,Initialization Finalization and Threads
@anchor{c-api/init thread-local-storage}@anchor{3f64}@anchor{c-api/init thread-local-storage-support}@anchor{3f65}
@subsection Thread Local Storage Support


The Python interpreter provides low-level support for thread-local storage
(TLS) which wraps the underlying native TLS implementation to support the
Python-level thread local storage API (@ref{228e,,threading.local}).  The
CPython C level APIs are similar to those offered by pthreads and Windows:
use a thread key and functions to associate a @code{void*} value per
thread.

The GIL does @emph{not} need to be held when calling these functions; they supply
their own locking.

Note that @code{Python.h} does not include the declaration of the TLS APIs,
you need to include @code{pythread.h} to use thread-local storage.

@cartouche
@quotation 注解 
None of these API functions handle memory management on behalf of the
@code{void*} values.  You need to allocate and deallocate them yourself.
If the @code{void*} values happen to be @ref{4b5,,PyObject*}, these
functions don't do refcount operations on them either.
@end quotation
@end cartouche

@menu
* Thread Specific Storage (TSS) API: Thread Specific Storage TSS API. 
* Thread Local Storage (TLS) API: Thread Local Storage TLS API. 

@end menu

@node Thread Specific Storage TSS API,Thread Local Storage TLS API,,Thread Local Storage Support
@anchor{c-api/init thread-specific-storage-api}@anchor{310}@anchor{c-api/init thread-specific-storage-tss-api}@anchor{3f66}
@subsubsection Thread Specific Storage (TSS) API


TSS API is introduced to supersede the use of the existing TLS API within the
CPython interpreter.  This API uses a new type @ref{311,,Py_tss_t} instead of
@code{int} to represent thread keys.


3.7 新版功能.



@subsubheading 参见


"A New C-API for Thread-Local Storage in CPython" (
@geindex Python 提高建议; PEP 539
PEP 539@footnote{https://www.python.org/dev/peps/pep-0539})


@geindex Py_tss_t (C 类型)
@anchor{c-api/init c Py_tss_t}@anchor{311}
@deffn {C 类型} Py_tss_t

This data structure represents the state of a thread key, the definition of
which may depend on the underlying TLS implementation, and it has an
internal field representing the key's initialization state.  There are no
public members in this structure.

When @ref{3b66,,Py_LIMITED_API} is not defined, static allocation of
this type by @ref{3f67,,Py_tss_NEEDS_INIT} is allowed.
@end deffn

@geindex Py_tss_NEEDS_INIT (C 宏)
@anchor{c-api/init c Py_tss_NEEDS_INIT}@anchor{3f67}
@deffn {C 宏} Py_tss_NEEDS_INIT

This macro expands to the initializer for @ref{311,,Py_tss_t} variables.
Note that this macro won't be defined with @ref{3b66,,Py_LIMITED_API}.
@end deffn

@menu
* Dynamic Allocation:: 
* 方法: 方法<4>. 

@end menu

@node Dynamic Allocation,方法<4>,,Thread Specific Storage TSS API
@anchor{c-api/init dynamic-allocation}@anchor{3f68}
@subsubsection Dynamic Allocation


Dynamic allocation of the @ref{311,,Py_tss_t}, required in extension modules
built with @ref{3b66,,Py_LIMITED_API}, where static allocation of this type
is not possible due to its implementation being opaque at build time.

@geindex PyThread_tss_alloc (C 函数)
@anchor{c-api/init c PyThread_tss_alloc}@anchor{3f69}
@deffn {C 函数} Py_tss_t* PyThread_tss_alloc ()

Return a value which is the same state as a value initialized with
@ref{3f67,,Py_tss_NEEDS_INIT}, or @code{NULL} in the case of dynamic allocation
failure.
@end deffn

@geindex PyThread_tss_free (C 函数)
@anchor{c-api/init c PyThread_tss_free}@anchor{3f6a}
@deffn {C 函数} void PyThread_tss_free (Py_tss_t@w{ }*key)

Free the given @emph{key} allocated by @ref{3f69,,PyThread_tss_alloc()}, after
first calling @ref{3f6b,,PyThread_tss_delete()} to ensure any associated
thread locals have been unassigned. This is a no-op if the @emph{key}
argument is @cite{NULL}.

@cartouche
@quotation 注解 
A freed key becomes a dangling pointer, you should reset the key to
@cite{NULL}.
@end quotation
@end cartouche
@end deffn

@node 方法<4>,,Dynamic Allocation,Thread Specific Storage TSS API
@anchor{c-api/init methods}@anchor{3f6c}
@subsubsection 方法


The parameter @emph{key} of these functions must not be @code{NULL}.  Moreover, the
behaviors of @ref{3f6d,,PyThread_tss_set()} and @ref{3f6e,,PyThread_tss_get()} are
undefined if the given @ref{311,,Py_tss_t} has not been initialized by
@ref{3f6f,,PyThread_tss_create()}.

@geindex PyThread_tss_is_created (C 函数)
@anchor{c-api/init c PyThread_tss_is_created}@anchor{3f70}
@deffn {C 函数} int PyThread_tss_is_created (Py_tss_t@w{ }*key)

Return a non-zero value if the given @ref{311,,Py_tss_t} has been initialized
by @ref{3f6f,,PyThread_tss_create()}.
@end deffn

@geindex PyThread_tss_create (C 函数)
@anchor{c-api/init c PyThread_tss_create}@anchor{3f6f}
@deffn {C 函数} int PyThread_tss_create (Py_tss_t@w{ }*key)

Return a zero value on successful initialization of a TSS key.  The behavior
is undefined if the value pointed to by the @emph{key} argument is not
initialized by @ref{3f67,,Py_tss_NEEDS_INIT}.  This function can be called
repeatedly on the same key -- calling it on an already initialized key is a
no-op and immediately returns success.
@end deffn

@geindex PyThread_tss_delete (C 函数)
@anchor{c-api/init c PyThread_tss_delete}@anchor{3f6b}
@deffn {C 函数} void PyThread_tss_delete (Py_tss_t@w{ }*key)

Destroy a TSS key to forget the values associated with the key across all
threads, and change the key's initialization state to uninitialized.  A
destroyed key is able to be initialized again by
@ref{3f6f,,PyThread_tss_create()}. This function can be called repeatedly on
the same key -- calling it on an already destroyed key is a no-op.
@end deffn

@geindex PyThread_tss_set (C 函数)
@anchor{c-api/init c PyThread_tss_set}@anchor{3f6d}
@deffn {C 函数} int PyThread_tss_set (Py_tss_t@w{ }*key, void@w{ }*value)

Return a zero value to indicate successfully associating a @code{void*}
value with a TSS key in the current thread.  Each thread has a distinct
mapping of the key to a @code{void*} value.
@end deffn

@geindex PyThread_tss_get (C 函数)
@anchor{c-api/init c PyThread_tss_get}@anchor{3f6e}
@deffn {C 函数} void* PyThread_tss_get (Py_tss_t@w{ }*key)

Return the @code{void*} value associated with a TSS key in the current
thread.  This returns @code{NULL} if no value is associated with the key in the
current thread.
@end deffn

@node Thread Local Storage TLS API,,Thread Specific Storage TSS API,Thread Local Storage Support
@anchor{c-api/init thread-local-storage-api}@anchor{30f}@anchor{c-api/init thread-local-storage-tls-api}@anchor{3f71}
@subsubsection Thread Local Storage (TLS) API



3.7 版后已移除: This API is superseded by
@ref{310,,Thread Specific Storage (TSS) API}.


@cartouche
@quotation 注解 
This version of the API does not support platforms where the native TLS key
is defined in a way that cannot be safely cast to @code{int}.  On such platforms,
@ref{3f72,,PyThread_create_key()} will return immediately with a failure status,
and the other TLS functions will all be no-ops on such platforms.
@end quotation
@end cartouche

由于上面提到的兼容性问题，不应在新代码中使用此版本的API。

@geindex PyThread_create_key (C 函数)
@anchor{c-api/init c PyThread_create_key}@anchor{3f72}
@deffn {C 函数} int PyThread_create_key ()
@end deffn

@geindex PyThread_delete_key (C 函数)
@anchor{c-api/init c PyThread_delete_key}@anchor{3f73}
@deffn {C 函数} void PyThread_delete_key (int@w{ }key)
@end deffn

@geindex PyThread_set_key_value (C 函数)
@anchor{c-api/init c PyThread_set_key_value}@anchor{96a}
@deffn {C 函数} int PyThread_set_key_value (int@w{ }key, void@w{ }*value)
@end deffn

@geindex PyThread_get_key_value (C 函数)
@anchor{c-api/init c PyThread_get_key_value}@anchor{3f74}
@deffn {C 函数} void* PyThread_get_key_value (int@w{ }key)
@end deffn

@geindex PyThread_delete_key_value (C 函数)
@anchor{c-api/init c PyThread_delete_key_value}@anchor{3f75}
@deffn {C 函数} void PyThread_delete_key_value (int@w{ }key)
@end deffn

@geindex PyThread_ReInitTLS (C 函数)
@anchor{c-api/init c PyThread_ReInitTLS}@anchor{3f76}
@deffn {C 函数} void PyThread_ReInitTLS ()
@end deffn

@node Python初始化配置,内存管理,Initialization Finalization and Threads,Python/C API 参考手册
@anchor{c-api/init_config doc}@anchor{3f77}@anchor{c-api/init_config init-config}@anchor{17d}@anchor{c-api/init_config python-initialization-configuration}@anchor{3f78}
@section Python初始化配置



3.8 新版功能.


结构


@itemize *

@item 
@ref{15f,,PyConfig}

@item 
@ref{160,,PyPreConfig}

@item 
@ref{161,,PyStatus}

@item 
@ref{162,,PyWideStringList}
@end itemize

函数


@itemize *

@item 
@ref{163,,PyConfig_Clear()}

@item 
@ref{164,,PyConfig_InitIsolatedConfig()}

@item 
@ref{165,,PyConfig_InitPythonConfig()}

@item 
@ref{166,,PyConfig_Read()}

@item 
@ref{167,,PyConfig_SetArgv()}

@item 
@ref{168,,PyConfig_SetBytesArgv()}

@item 
@ref{169,,PyConfig_SetBytesString()}

@item 
@ref{16a,,PyConfig_SetString()}

@item 
@ref{3f79,,PyConfig_SetWideStringList()}

@item 
@ref{16b,,PyPreConfig_InitIsolatedConfig()}

@item 
@ref{16c,,PyPreConfig_InitPythonConfig()}

@item 
@ref{16d,,PyStatus_Error()}

@item 
@ref{16e,,PyStatus_Exception()}

@item 
@ref{16f,,PyStatus_Exit()}

@item 
@ref{170,,PyStatus_IsError()}

@item 
@ref{171,,PyStatus_IsExit()}

@item 
@ref{172,,PyStatus_NoMemory()}

@item 
@ref{173,,PyStatus_Ok()}

@item 
@ref{174,,PyWideStringList_Append()}

@item 
@ref{175,,PyWideStringList_Insert()}

@item 
@ref{177,,Py_ExitStatusException()}

@item 
@ref{178,,Py_InitializeFromConfig()}

@item 
@ref{179,,Py_PreInitialize()}

@item 
@ref{17a,,Py_PreInitializeFromArgs()}

@item 
@ref{17b,,Py_PreInitializeFromBytesArgs()}

@item 
@ref{17c,,Py_RunMain()}
@end itemize

The preconfiguration (@code{PyPreConfig} type) is stored in
@code{_PyRuntime.preconfig} and the configuration (@code{PyConfig} type) is stored in
@code{PyInterpreterState.config}.

See also @ref{3f1e,,Initialization@comma{} Finalization@comma{} and Threads}.


@subsubheading 参见


@geindex Python 提高建议; PEP 587
PEP 587@footnote{https://www.python.org/dev/peps/pep-0587} "Python 初始化配置".


@menu
* PyWideStringList:: 
* PyStatus:: 
* PyPreConfig:: 
* Preinitialization with PyPreConfig:: 
* PyConfig:: 
* Initialization with PyConfig:: 
* Isolated Configuration:: 
* Python Configuration:: 
* 路径配置:: 
* Py_RunMain(): Py_RunMain. 
* Multi-Phase Initialization Private Provisional API:: 

@end menu

@node PyWideStringList,PyStatus,,Python初始化配置
@anchor{c-api/init_config pywidestringlist}@anchor{3f7a}
@subsection PyWideStringList


@geindex PyWideStringList (C 类型)
@anchor{c-api/init_config c PyWideStringList}@anchor{162}
@deffn {C 类型} PyWideStringList

List of @code{wchar_t*} strings.

If @emph{length} is non-zero, @emph{items} must be non-@code{NULL} and all strings must be
non-@code{NULL}.

方法

@geindex PyWideStringList_Append (C 函数)
@anchor{c-api/init_config c PyWideStringList_Append}@anchor{174}
@deffn {C 函数} PyStatus PyWideStringList_Append (PyWideStringList@w{ }*list, const wchar_t@w{ }*item)

Append @emph{item} to @emph{list}.

Python must be preinitialized to call this function.
@end deffn

@geindex PyWideStringList_Insert (C 函数)
@anchor{c-api/init_config c PyWideStringList_Insert}@anchor{175}
@deffn {C 函数} PyStatus PyWideStringList_Insert (PyWideStringList@w{ }*list, Py_ssize_t@w{ }index, const wchar_t@w{ }*item)

Insert @emph{item} into @emph{list} at @emph{index}.

If @emph{index} is greater than or equal to @emph{list} length, append @emph{item} to
@emph{list}.

@emph{index} must be greater than or equal to 0.

Python must be preinitialized to call this function.
@end deffn

Structure fields:

@geindex PyWideStringList.length (C 成员)
@anchor{c-api/init_config c PyWideStringList length}@anchor{3f7b}
@deffn {C 成员} Py_ssize_t length

List 长度。
@end deffn

@geindex PyWideStringList.items (C 成员)
@anchor{c-api/init_config c PyWideStringList items}@anchor{3f7c}
@deffn {C 成员} wchar_t** items

列表项目。
@end deffn
@end deffn

@node PyStatus,PyPreConfig,PyWideStringList,Python初始化配置
@anchor{c-api/init_config pystatus}@anchor{3f7d}
@subsection PyStatus


@geindex PyStatus (C 类型)
@anchor{c-api/init_config c PyStatus}@anchor{161}
@deffn {C 类型} PyStatus

Structure to store an initialization function status: success, error
or exit.

For an error, it can store the C function name which created the error.

Structure fields:

@geindex PyStatus.exitcode (C 成员)
@anchor{c-api/init_config c PyStatus exitcode}@anchor{3f7e}
@deffn {C 成员} int exitcode

Exit code. Argument passed to @code{exit()}.
@end deffn

@geindex PyStatus.err_msg (C 成员)
@anchor{c-api/init_config c PyStatus err_msg}@anchor{3f7f}
@deffn {C 成员} const char *err_msg

错误信息
@end deffn

@geindex PyStatus.func (C 成员)
@anchor{c-api/init_config c PyStatus func}@anchor{3f80}
@deffn {C 成员} const char *func

Name of the function which created an error, can be @code{NULL}.
@end deffn

Functions to create a status:

@geindex PyStatus_Ok (C 函数)
@anchor{c-api/init_config c PyStatus_Ok}@anchor{173}
@deffn {C 函数} PyStatus PyStatus_Ok (void)

完成。
@end deffn

@geindex PyStatus_Error (C 函数)
@anchor{c-api/init_config c PyStatus_Error}@anchor{16d}
@deffn {C 函数} PyStatus PyStatus_Error (const char@w{ }*err_msg)

Initialization error with a message.
@end deffn

@geindex PyStatus_NoMemory (C 函数)
@anchor{c-api/init_config c PyStatus_NoMemory}@anchor{172}
@deffn {C 函数} PyStatus PyStatus_NoMemory (void)

Memory allocation failure (out of memory).
@end deffn

@geindex PyStatus_Exit (C 函数)
@anchor{c-api/init_config c PyStatus_Exit}@anchor{16f}
@deffn {C 函数} PyStatus PyStatus_Exit (int@w{ }exitcode)

Exit Python with the specified exit code.
@end deffn

Functions to handle a status:

@geindex PyStatus_Exception (C 函数)
@anchor{c-api/init_config c PyStatus_Exception}@anchor{16e}
@deffn {C 函数} int PyStatus_Exception (PyStatus@w{ }status)

Is the status an error or an exit? If true, the exception must be
handled; by calling @ref{177,,Py_ExitStatusException()} for example.
@end deffn

@geindex PyStatus_IsError (C 函数)
@anchor{c-api/init_config c PyStatus_IsError}@anchor{170}
@deffn {C 函数} int PyStatus_IsError (PyStatus@w{ }status)

结果错误吗？
@end deffn

@geindex PyStatus_IsExit (C 函数)
@anchor{c-api/init_config c PyStatus_IsExit}@anchor{171}
@deffn {C 函数} int PyStatus_IsExit (PyStatus@w{ }status)

结果是否退出？
@end deffn

@geindex Py_ExitStatusException (C 函数)
@anchor{c-api/init_config c Py_ExitStatusException}@anchor{177}
@deffn {C 函数} void Py_ExitStatusException (PyStatus@w{ }status)

Call @code{exit(exitcode)} if @emph{status} is an exit. Print the error
message and exit with a non-zero exit code if @emph{status} is an error.  Must
only be called if @code{PyStatus_Exception(status)} is non-zero.
@end deffn
@end deffn

@cartouche
@quotation 注解 
Internally, Python uses macros which set @code{PyStatus.func},
whereas functions to create a status set @code{func} to @code{NULL}.
@end quotation
@end cartouche

示例:

@example
PyStatus alloc(void **ptr, size_t size)
@{
    *ptr = PyMem_RawMalloc(size);
    if (*ptr == NULL) @{
        return PyStatus_NoMemory();
    @}
    return PyStatus_Ok();
@}

int main(int argc, char **argv)
@{
    void *ptr;
    PyStatus status = alloc(&ptr, 16);
    if (PyStatus_Exception(status)) @{
        Py_ExitStatusException(status);
    @}
    PyMem_Free(ptr);
    return 0;
@}
@end example

@node PyPreConfig,Preinitialization with PyPreConfig,PyStatus,Python初始化配置
@anchor{c-api/init_config pypreconfig}@anchor{3f81}
@subsection PyPreConfig


@geindex PyPreConfig (C 类型)
@anchor{c-api/init_config c PyPreConfig}@anchor{160}
@deffn {C 类型} PyPreConfig

Structure used to preinitialize Python:


@itemize *

@item 
Set the Python memory allocator

@item 
Configure the LC_CTYPE locale

@item 
Set the UTF-8 mode
@end itemize

Function to initialize a preconfiguration:

@geindex PyPreConfig_InitPythonConfig (C 函数)
@anchor{c-api/init_config c PyPreConfig_InitPythonConfig}@anchor{16c}
@deffn {C 函数} void PyPreConfig_InitPythonConfig (PyPreConfig@w{ }*preconfig)

Initialize the preconfiguration with @ref{3f82,,Python Configuration}.
@end deffn

@geindex PyPreConfig_InitIsolatedConfig (C 函数)
@anchor{c-api/init_config c PyPreConfig_InitIsolatedConfig}@anchor{16b}
@deffn {C 函数} void PyPreConfig_InitIsolatedConfig (PyPreConfig@w{ }*preconfig)

Initialize the preconfiguration with @ref{3f83,,Isolated Configuration}.
@end deffn

Structure fields:

@geindex PyPreConfig.allocator (C 成员)
@anchor{c-api/init_config c PyPreConfig allocator}@anchor{3f84}
@deffn {C 成员} int allocator

Name of the memory allocator:


@itemize *

@item 
@code{PYMEM_ALLOCATOR_NOT_SET} (@code{0}): don't change memory allocators
(use defaults)

@item 
@code{PYMEM_ALLOCATOR_DEFAULT} (@code{1}): default memory allocators

@item 
@code{PYMEM_ALLOCATOR_DEBUG} (@code{2}): default memory allocators with
debug hooks

@item 
@code{PYMEM_ALLOCATOR_MALLOC} (@code{3}): force usage of @code{malloc()}

@item 
@code{PYMEM_ALLOCATOR_MALLOC_DEBUG} (@code{4}): force usage of
@code{malloc()} with debug hooks

@item 
@code{PYMEM_ALLOCATOR_PYMALLOC} (@code{5}): @ref{5bc,,Python pymalloc memory allocator}

@item 
@code{PYMEM_ALLOCATOR_PYMALLOC_DEBUG} (@code{6}): @ref{5bc,,Python pymalloc memory allocator} with debug hooks
@end itemize

@code{PYMEM_ALLOCATOR_PYMALLOC} and @code{PYMEM_ALLOCATOR_PYMALLOC_DEBUG}
are not supported if Python is configured using @code{--without-pymalloc}

See @ref{3f85,,Memory Management}.
@end deffn

@geindex PyPreConfig.configure_locale (C 成员)
@anchor{c-api/init_config c PyPreConfig configure_locale}@anchor{3f86}
@deffn {C 成员} int configure_locale

Set the LC_CTYPE locale to the user preferred locale? If equals to 0, set
@code{coerce_c_locale} and @code{coerce_c_locale_warn} to 0.
@end deffn

@geindex PyPreConfig.coerce_c_locale (C 成员)
@anchor{c-api/init_config c PyPreConfig coerce_c_locale}@anchor{3f87}
@deffn {C 成员} int coerce_c_locale

If equals to 2, coerce the C locale; if equals to 1, read the LC_CTYPE
locale to decide if it should be coerced.
@end deffn

@geindex PyPreConfig.coerce_c_locale_warn (C 成员)
@anchor{c-api/init_config c PyPreConfig coerce_c_locale_warn}@anchor{3f88}
@deffn {C 成员} int coerce_c_locale_warn

If non-zero, emit a warning if the C locale is coerced.
@end deffn

@geindex PyPreConfig.dev_mode (C 成员)
@anchor{c-api/init_config c PyPreConfig dev_mode}@anchor{3f89}
@deffn {C 成员} int dev_mode

参见 @ref{3f8a,,PyConfig.dev_mode}.
@end deffn

@geindex PyPreConfig.isolated (C 成员)
@anchor{c-api/init_config c PyPreConfig isolated}@anchor{3f8b}
@deffn {C 成员} int isolated

参见 @ref{3f8c,,PyConfig.isolated}.
@end deffn

@geindex PyPreConfig.legacy_windows_fs_encoding (C 成员)
@anchor{c-api/init_config c PyPreConfig legacy_windows_fs_encoding}@anchor{3f8d}
@deffn {C 成员} int legacy_windows_fs_encoding (Windows@w{ }only)

If non-zero, disable UTF-8 Mode, set the Python filesystem encoding to
@code{mbcs}, set the filesystem error handler to @code{replace}.

Only available on Windows. @code{#ifdef MS_WINDOWS} macro can be used for
Windows specific code.
@end deffn

@geindex PyPreConfig.parse_argv (C 成员)
@anchor{c-api/init_config c PyPreConfig parse_argv}@anchor{3f8e}
@deffn {C 成员} int parse_argv

If non-zero, @ref{17a,,Py_PreInitializeFromArgs()} and
@ref{17b,,Py_PreInitializeFromBytesArgs()} parse their @code{argv} argument the
same way the regular Python parses command line arguments: see
@ref{925,,Command Line Arguments}.
@end deffn

@geindex PyPreConfig.use_environment (C 成员)
@anchor{c-api/init_config c PyPreConfig use_environment}@anchor{3f8f}
@deffn {C 成员} int use_environment

参见 @ref{3f90,,PyConfig.use_environment}.
@end deffn

@geindex PyPreConfig.utf8_mode (C 成员)
@anchor{c-api/init_config c PyPreConfig utf8_mode}@anchor{3f91}
@deffn {C 成员} int utf8_mode

If non-zero, enable the UTF-8 mode.
@end deffn
@end deffn

@node Preinitialization with PyPreConfig,PyConfig,PyPreConfig,Python初始化配置
@anchor{c-api/init_config preinitialization-with-pypreconfig}@anchor{3f92}
@subsection Preinitialization with PyPreConfig


Functions to preinitialize Python:

@geindex Py_PreInitialize (C 函数)
@anchor{c-api/init_config c Py_PreInitialize}@anchor{179}
@deffn {C 函数} PyStatus Py_PreInitialize (const PyPreConfig@w{ }*preconfig)

Preinitialize Python from @emph{preconfig} preconfiguration.
@end deffn

@geindex Py_PreInitializeFromBytesArgs (C 函数)
@anchor{c-api/init_config c Py_PreInitializeFromBytesArgs}@anchor{17b}
@deffn {C 函数} PyStatus Py_PreInitializeFromBytesArgs (const PyPreConfig@w{ }*preconfig, int@w{ }argc, char * const@w{ }*argv)

Preinitialize Python from @emph{preconfig} preconfiguration and command line
arguments (bytes strings).
@end deffn

@geindex Py_PreInitializeFromArgs (C 函数)
@anchor{c-api/init_config c Py_PreInitializeFromArgs}@anchor{17a}
@deffn {C 函数} PyStatus Py_PreInitializeFromArgs (const PyPreConfig@w{ }*preconfig, int@w{ }argc, wchar_t * const *@w{ }argv)

Preinitialize Python from @emph{preconfig} preconfiguration and command line
arguments (wide strings).
@end deffn

The caller is responsible to handle exceptions (error or exit) using
@ref{16e,,PyStatus_Exception()} and @ref{177,,Py_ExitStatusException()}.

For @ref{3f82,,Python Configuration}
(@ref{16c,,PyPreConfig_InitPythonConfig()}), if Python is initialized with
command line arguments, the command line arguments must also be passed to
preinitialize Python, since they have an effect on the pre-configuration
like encodings. For example, the @ref{155,,-X utf8} command line option
enables the UTF-8 Mode.

@code{PyMem_SetAllocator()} can be called after @ref{179,,Py_PreInitialize()} and
before @ref{178,,Py_InitializeFromConfig()} to install a custom memory allocator.
It can be called before @ref{179,,Py_PreInitialize()} if
@ref{3f84,,PyPreConfig.allocator} is set to @code{PYMEM_ALLOCATOR_NOT_SET}.

Python memory allocation functions like @ref{967,,PyMem_RawMalloc()} must not be
used before Python preinitialization, whereas calling directly @code{malloc()} and
@code{free()} is always safe. @ref{436,,Py_DecodeLocale()} must not be called before
the preinitialization.

Example using the preinitialization to enable the UTF-8 Mode:

@example
PyStatus status;
PyPreConfig preconfig;
PyPreConfig_InitPythonConfig(&preconfig);

preconfig.utf8_mode = 1;

status = Py_PreInitialize(&preconfig);
if (PyStatus_Exception(status)) @{
    Py_ExitStatusException(status);
@}

/* at this point, Python will speak UTF-8 */

Py_Initialize();
/* ... use Python API here ... */
Py_Finalize();
@end example

@node PyConfig,Initialization with PyConfig,Preinitialization with PyPreConfig,Python初始化配置
@anchor{c-api/init_config pyconfig}@anchor{3f93}
@subsection PyConfig


@geindex PyConfig (C 类型)
@anchor{c-api/init_config c PyConfig}@anchor{15f}
@deffn {C 类型} PyConfig

Structure containing most parameters to configure Python.

Structure methods:

@geindex PyConfig_InitPythonConfig (C 函数)
@anchor{c-api/init_config c PyConfig_InitPythonConfig}@anchor{165}
@deffn {C 函数} void PyConfig_InitPythonConfig (PyConfig@w{ }*config)

Initialize configuration with @ref{3f82,,Python Configuration}.
@end deffn

@geindex PyConfig_InitIsolatedConfig (C 函数)
@anchor{c-api/init_config c PyConfig_InitIsolatedConfig}@anchor{164}
@deffn {C 函数} void PyConfig_InitIsolatedConfig (PyConfig@w{ }*config)

Initialize configuration with @ref{3f83,,Isolated Configuration}.
@end deffn

@geindex PyConfig_SetString (C 函数)
@anchor{c-api/init_config c PyConfig_SetString}@anchor{16a}
@deffn {C 函数} PyStatus PyConfig_SetString (PyConfig@w{ }*config, wchar_t * const@w{ }*config_str, const wchar_t@w{ }*str)

Copy the wide character string @emph{str} into @code{*config_str}.

Preinitialize Python if needed.
@end deffn

@geindex PyConfig_SetBytesString (C 函数)
@anchor{c-api/init_config c PyConfig_SetBytesString}@anchor{169}
@deffn {C 函数} PyStatus PyConfig_SetBytesString (PyConfig@w{ }*config, wchar_t * const@w{ }*config_str, const char@w{ }*str)

Decode @emph{str} using @code{Py_DecodeLocale()} and set the result into @code{*config_str}.

Preinitialize Python if needed.
@end deffn

@geindex PyConfig_SetArgv (C 函数)
@anchor{c-api/init_config c PyConfig_SetArgv}@anchor{167}
@deffn {C 函数} PyStatus PyConfig_SetArgv (PyConfig@w{ }*config, int@w{ }argc, wchar_t * const@w{ }*argv)

Set command line arguments from wide character strings.

Preinitialize Python if needed.
@end deffn

@geindex PyConfig_SetBytesArgv (C 函数)
@anchor{c-api/init_config c PyConfig_SetBytesArgv}@anchor{168}
@deffn {C 函数} PyStatus PyConfig_SetBytesArgv (PyConfig@w{ }*config, int@w{ }argc, char * const@w{ }*argv)

Set command line arguments: decode bytes using @ref{436,,Py_DecodeLocale()}.

Preinitialize Python if needed.
@end deffn

@geindex PyConfig_SetWideStringList (C 函数)
@anchor{c-api/init_config c PyConfig_SetWideStringList}@anchor{3f79}
@deffn {C 函数} PyStatus PyConfig_SetWideStringList (PyConfig@w{ }*config, PyWideStringList@w{ }*list, Py_ssize_t@w{ }length, wchar_t@w{ }**items)

Set the list of wide strings @emph{list} to @emph{length} and @emph{items}.

Preinitialize Python if needed.
@end deffn

@geindex PyConfig_Read (C 函数)
@anchor{c-api/init_config c PyConfig_Read}@anchor{166}
@deffn {C 函数} PyStatus PyConfig_Read (PyConfig@w{ }*config)

Read all Python configuration.

Fields which are already initialized are left unchanged.

Preinitialize Python if needed.
@end deffn

@geindex PyConfig_Clear (C 函数)
@anchor{c-api/init_config c PyConfig_Clear}@anchor{163}
@deffn {C 函数} void PyConfig_Clear (PyConfig@w{ }*config)

Release configuration memory.
@end deffn

Most @code{PyConfig} methods preinitialize Python if needed. In that case, the
Python preinitialization configuration in based on the @ref{15f,,PyConfig}.
If configuration fields which are in common with @ref{160,,PyPreConfig} are
tuned, they must be set before calling a @ref{15f,,PyConfig} method:


@itemize *

@item 
@ref{3f8a,,dev_mode}

@item 
@ref{3f8c,,isolated}

@item 
@ref{3f94,,parse_argv}

@item 
@ref{3f90,,use_environment}
@end itemize

Moreover, if @ref{167,,PyConfig_SetArgv()} or @ref{168,,PyConfig_SetBytesArgv()}
is used, this method must be called first, before other methods, since the
preinitialization configuration depends on command line arguments (if
@code{parse_argv} is non-zero).

The caller of these methods is responsible to handle exceptions (error or
exit) using @code{PyStatus_Exception()} and @code{Py_ExitStatusException()}.

Structure fields:

@geindex PyConfig.argv (C 成员)
@anchor{c-api/init_config c PyConfig argv}@anchor{3f95}
@deffn {C 成员} PyWideStringList argv

Command line arguments, @ref{bf4,,sys.argv}. See
@ref{3f94,,parse_argv} to parse @ref{3f95,,argv} the
same way the regular Python parses Python command line arguments. If
@ref{3f95,,argv} is empty, an empty string is added to ensure
that @ref{bf4,,sys.argv} always exists and is never empty.
@end deffn

@geindex PyConfig.base_exec_prefix (C 成员)
@anchor{c-api/init_config c PyConfig base_exec_prefix}@anchor{3f96}
@deffn {C 成员} wchar_t* base_exec_prefix

@ref{35a1,,sys.base_exec_prefix}.
@end deffn

@geindex PyConfig.base_executable (C 成员)
@anchor{c-api/init_config c PyConfig base_executable}@anchor{3f97}
@deffn {C 成员} wchar_t* base_executable

@code{sys._base_executable}: @code{__PYVENV_LAUNCHER__} environment
variable value, or copy of @ref{3f98,,PyConfig.executable}.
@end deffn

@geindex PyConfig.base_prefix (C 成员)
@anchor{c-api/init_config c PyConfig base_prefix}@anchor{3f99}
@deffn {C 成员} wchar_t* base_prefix

@ref{2fe1,,sys.base_prefix}.
@end deffn

@geindex PyConfig.buffered_stdio (C 成员)
@anchor{c-api/init_config c PyConfig buffered_stdio}@anchor{3f9a}
@deffn {C 成员} int buffered_stdio

If equals to 0, enable unbuffered mode, making the stdout and stderr
streams unbuffered.

stdin is always opened in buffered mode.
@end deffn

@geindex PyConfig.bytes_warning (C 成员)
@anchor{c-api/init_config c PyConfig bytes_warning}@anchor{3f9b}
@deffn {C 成员} int bytes_warning

If equals to 1, issue a warning when comparing @ref{32a,,bytes} or
@ref{32b,,bytearray} with @ref{329,,str}, or comparing @ref{32a,,bytes} with
@ref{184,,int}. If equal or greater to 2, raise a @ref{4b0,,BytesWarning}
exception.
@end deffn

@geindex PyConfig.check_hash_pycs_mode (C 成员)
@anchor{c-api/init_config c PyConfig check_hash_pycs_mode}@anchor{3f9c}
@deffn {C 成员} wchar_t* check_hash_pycs_mode

Control the validation behavior of hash-based @code{.pyc} files (see
@geindex Python 提高建议; PEP 552
PEP 552@footnote{https://www.python.org/dev/peps/pep-0552}): @ref{12d7,,--check-hash-based-pycs} command line option value.

Valid values: @code{always}, @code{never} and @code{default}.

默认值为: @code{default}.
@end deffn

@geindex PyConfig.configure_c_stdio (C 成员)
@anchor{c-api/init_config c PyConfig configure_c_stdio}@anchor{3f9d}
@deffn {C 成员} int configure_c_stdio

If non-zero, configure C standard streams (@code{stdio}, @code{stdout},
@code{stdout}). For example, set their mode to @code{O_BINARY} on Windows.
@end deffn

@geindex PyConfig.dev_mode (C 成员)
@anchor{c-api/init_config c PyConfig dev_mode}@anchor{3f8a}
@deffn {C 成员} int dev_mode

Development mode: see @ref{155,,-X dev}.
@end deffn

@geindex PyConfig.dump_refs (C 成员)
@anchor{c-api/init_config c PyConfig dump_refs}@anchor{3f9e}
@deffn {C 成员} int dump_refs

If non-zero, dump all objects which are still alive at exit.

Require a debug build of Python (@code{Py_REF_DEBUG} macro must be defined).
@end deffn

@geindex PyConfig.exec_prefix (C 成员)
@anchor{c-api/init_config c PyConfig exec_prefix}@anchor{3f9f}
@deffn {C 成员} wchar_t* exec_prefix

@ref{35a0,,sys.exec_prefix}.
@end deffn

@geindex PyConfig.executable (C 成员)
@anchor{c-api/init_config c PyConfig executable}@anchor{3f98}
@deffn {C 成员} wchar_t* executable

@ref{274,,sys.executable}.
@end deffn

@geindex PyConfig.faulthandler (C 成员)
@anchor{c-api/init_config c PyConfig faulthandler}@anchor{3fa0}
@deffn {C 成员} int faulthandler

If non-zero, call @ref{543,,faulthandler.enable()} at startup.
@end deffn

@geindex PyConfig.filesystem_encoding (C 成员)
@anchor{c-api/init_config c PyConfig filesystem_encoding}@anchor{3fa1}
@deffn {C 成员} wchar_t* filesystem_encoding

Filesystem encoding, @ref{4f0,,sys.getfilesystemencoding()}.
@end deffn

@geindex PyConfig.filesystem_errors (C 成员)
@anchor{c-api/init_config c PyConfig filesystem_errors}@anchor{3fa2}
@deffn {C 成员} wchar_t* filesystem_errors

Filesystem encoding errors, @ref{58f,,sys.getfilesystemencodeerrors()}.
@end deffn

@geindex PyConfig.hash_seed (C 成员)
@anchor{c-api/init_config c PyConfig hash_seed}@anchor{3fa3}
@deffn {C 成员} unsigned long hash_seed
@end deffn

@geindex PyConfig.use_hash_seed (C 成员)
@anchor{c-api/init_config c PyConfig use_hash_seed}@anchor{3fa4}
@deffn {C 成员} int use_hash_seed

Randomized hash function seed.

If @ref{3fa4,,use_hash_seed} is zero, a seed is chosen randomly
at Pythonstartup, and @ref{3fa3,,hash_seed} is ignored.
@end deffn

@geindex PyConfig.home (C 成员)
@anchor{c-api/init_config c PyConfig home}@anchor{3fa5}
@deffn {C 成员} wchar_t* home

Python home directory.

Initialized from 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} environment variable value by
default.
@end deffn

@geindex PyConfig.import_time (C 成员)
@anchor{c-api/init_config c PyConfig import_time}@anchor{3fa6}
@deffn {C 成员} int import_time

If non-zero, profile import time.
@end deffn

@geindex PyConfig.inspect (C 成员)
@anchor{c-api/init_config c PyConfig inspect}@anchor{3fa7}
@deffn {C 成员} int inspect

Enter interactive mode after executing a script or a command.
@end deffn

@geindex PyConfig.install_signal_handlers (C 成员)
@anchor{c-api/init_config c PyConfig install_signal_handlers}@anchor{3fa8}
@deffn {C 成员} int install_signal_handlers

Install signal handlers?
@end deffn

@geindex PyConfig.interactive (C 成员)
@anchor{c-api/init_config c PyConfig interactive}@anchor{3fa9}
@deffn {C 成员} int interactive

交互模式
@end deffn

@geindex PyConfig.isolated (C 成员)
@anchor{c-api/init_config c PyConfig isolated}@anchor{3f8c}
@deffn {C 成员} int isolated

If greater than 0, enable isolated mode:


@itemize *

@item 
@ref{482,,sys.path} contains neither the script's directory (computed from
@code{argv[0]} or the current directory) nor the user's site-packages
directory.

@item 
Python REPL doesn't import @ref{de,,readline} nor enable default readline
configuration on interactive prompts.

@item 
Set @ref{3f90,,use_environment} and
@ref{3faa,,user_site_directory} to 0.
@end itemize
@end deffn

@geindex PyConfig.legacy_windows_stdio (C 成员)
@anchor{c-api/init_config c PyConfig legacy_windows_stdio}@anchor{3fab}
@deffn {C 成员} int legacy_windows_stdio

If non-zero, use @ref{c9d,,io.FileIO} instead of
@code{io.WindowsConsoleIO} for @ref{306,,sys.stdin}, @ref{307,,sys.stdout}
and @ref{308,,sys.stderr}.

Only available on Windows. @code{#ifdef MS_WINDOWS} macro can be used for
Windows specific code.
@end deffn

@geindex PyConfig.malloc_stats (C 成员)
@anchor{c-api/init_config c PyConfig malloc_stats}@anchor{3fac}
@deffn {C 成员} int malloc_stats

If non-zero, dump statistics on @ref{5bc,,Python pymalloc memory allocator} at exit.

The option is ignored if Python is built using @code{--without-pymalloc}.
@end deffn

@geindex PyConfig.pythonpath_env (C 成员)
@anchor{c-api/init_config c PyConfig pythonpath_env}@anchor{3fad}
@deffn {C 成员} wchar_t* pythonpath_env

Module search paths as a string separated by @code{DELIM}
(@code{os.path.pathsep}).

Initialized from 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} environment variable value by
default.
@end deffn

@geindex PyConfig.module_search_paths (C 成员)
@anchor{c-api/init_config c PyConfig module_search_paths}@anchor{3fae}
@deffn {C 成员} PyWideStringList module_search_paths
@end deffn

@geindex PyConfig.module_search_paths_set (C 成员)
@anchor{c-api/init_config c PyConfig module_search_paths_set}@anchor{3faf}
@deffn {C 成员} int module_search_paths_set

@ref{482,,sys.path}. If @ref{3faf,,module_search_paths_set} is
equal to 0, the @ref{3fae,,module_search_paths} is overridden
by the function calculating the @ref{3fb0,,Path Configuration}.
@end deffn

@geindex PyConfig.optimization_level (C 成员)
@anchor{c-api/init_config c PyConfig optimization_level}@anchor{3fb1}
@deffn {C 成员} int optimization_level

Compilation optimization level:


@itemize *

@item 
0: Peephole optimizer (and @code{__debug__} is set to @code{True})

@item 
1: Remove assertions, set @code{__debug__} to @code{False}

@item 
2: Strip docstrings
@end itemize
@end deffn

@geindex PyConfig.parse_argv (C 成员)
@anchor{c-api/init_config c PyConfig parse_argv}@anchor{3f94}
@deffn {C 成员} int parse_argv

If non-zero, parse @ref{3f95,,argv} the same way the regular
Python command line arguments, and strip Python arguments from
@ref{3f95,,argv}: see @ref{925,,Command Line Arguments}.
@end deffn

@geindex PyConfig.parser_debug (C 成员)
@anchor{c-api/init_config c PyConfig parser_debug}@anchor{3fb2}
@deffn {C 成员} int parser_debug

If non-zero, turn on parser debugging output (for expert only, depending
on compilation options).
@end deffn

@geindex PyConfig.pathconfig_warnings (C 成员)
@anchor{c-api/init_config c PyConfig pathconfig_warnings}@anchor{3fb3}
@deffn {C 成员} int pathconfig_warnings

If equal to 0, suppress warnings when calculating the @ref{3fb0,,Path Configuration} (Unix only, Windows does not log any
warning). Otherwise, warnings are written into @code{stderr}.
@end deffn

@geindex PyConfig.prefix (C 成员)
@anchor{c-api/init_config c PyConfig prefix}@anchor{3fb4}
@deffn {C 成员} wchar_t* prefix

@ref{359f,,sys.prefix}.
@end deffn

@geindex PyConfig.program_name (C 成员)
@anchor{c-api/init_config c PyConfig program_name}@anchor{3fb5}
@deffn {C 成员} wchar_t* program_name

Program name. Used to initialize @ref{3f98,,executable}, and in
early error messages.
@end deffn

@geindex PyConfig.pycache_prefix (C 成员)
@anchor{c-api/init_config c PyConfig pycache_prefix}@anchor{3fb6}
@deffn {C 成员} wchar_t* pycache_prefix

@ref{156,,sys.pycache_prefix}: @code{.pyc} cache prefix.

If @code{NULL}, @ref{156,,sys.pycache_prefix} is set to @code{None}.
@end deffn

@geindex PyConfig.quiet (C 成员)
@anchor{c-api/init_config c PyConfig quiet}@anchor{3fb7}
@deffn {C 成员} int quiet

Quiet mode. For example, don't display the copyright and version messages
in interactive mode.
@end deffn

@geindex PyConfig.run_command (C 成员)
@anchor{c-api/init_config c PyConfig run_command}@anchor{3fb8}
@deffn {C 成员} wchar_t* run_command

@code{python3 -c COMMAND} argument. Used by @ref{17c,,Py_RunMain()}.
@end deffn

@geindex PyConfig.run_filename (C 成员)
@anchor{c-api/init_config c PyConfig run_filename}@anchor{3fb9}
@deffn {C 成员} wchar_t* run_filename

@code{python3 FILENAME} argument. Used by @ref{17c,,Py_RunMain()}.
@end deffn

@geindex PyConfig.run_module (C 成员)
@anchor{c-api/init_config c PyConfig run_module}@anchor{3fba}
@deffn {C 成员} wchar_t* run_module

@code{python3 -m MODULE} argument. Used by @ref{17c,,Py_RunMain()}.
@end deffn

@geindex PyConfig.show_alloc_count (C 成员)
@anchor{c-api/init_config c PyConfig show_alloc_count}@anchor{3fbb}
@deffn {C 成员} int show_alloc_count

Show allocation counts at exit?

Set to 1 by @ref{155,,-X showalloccount} command line option.

Need a special Python build with @code{COUNT_ALLOCS} macro defined.
@end deffn

@geindex PyConfig.show_ref_count (C 成员)
@anchor{c-api/init_config c PyConfig show_ref_count}@anchor{3fbc}
@deffn {C 成员} int show_ref_count

Show total reference count at exit?

Set to 1 by @ref{155,,-X showrefcount} command line option.

Need a debug build of Python (@code{Py_REF_DEBUG} macro must be defined).
@end deffn

@geindex PyConfig.site_import (C 成员)
@anchor{c-api/init_config c PyConfig site_import}@anchor{3fbd}
@deffn {C 成员} int site_import

Import the @ref{eb,,site} module at startup?
@end deffn

@geindex PyConfig.skip_source_first_line (C 成员)
@anchor{c-api/init_config c PyConfig skip_source_first_line}@anchor{3fbe}
@deffn {C 成员} int skip_source_first_line

Skip the first line of the source?
@end deffn

@geindex PyConfig.stdio_encoding (C 成员)
@anchor{c-api/init_config c PyConfig stdio_encoding}@anchor{3fbf}
@deffn {C 成员} wchar_t* stdio_encoding
@end deffn

@geindex PyConfig.stdio_errors (C 成员)
@anchor{c-api/init_config c PyConfig stdio_errors}@anchor{3fc0}
@deffn {C 成员} wchar_t* stdio_errors

Encoding and encoding errors of @ref{306,,sys.stdin}, @ref{307,,sys.stdout} and
@ref{308,,sys.stderr}.
@end deffn

@geindex PyConfig.tracemalloc (C 成员)
@anchor{c-api/init_config c PyConfig tracemalloc}@anchor{3fc1}
@deffn {C 成员} int tracemalloc

If non-zero, call @ref{12e5,,tracemalloc.start()} at startup.
@end deffn

@geindex PyConfig.use_environment (C 成员)
@anchor{c-api/init_config c PyConfig use_environment}@anchor{3f90}
@deffn {C 成员} int use_environment

If greater than 0, use @ref{12ea,,environment variables}.
@end deffn

@geindex PyConfig.user_site_directory (C 成员)
@anchor{c-api/init_config c PyConfig user_site_directory}@anchor{3faa}
@deffn {C 成员} int user_site_directory

If non-zero, add user site directory to @ref{482,,sys.path}.
@end deffn

@geindex PyConfig.verbose (C 成员)
@anchor{c-api/init_config c PyConfig verbose}@anchor{3fc2}
@deffn {C 成员} int verbose

If non-zero, enable verbose mode.
@end deffn

@geindex PyConfig.warnoptions (C 成员)
@anchor{c-api/init_config c PyConfig warnoptions}@anchor{3fc3}
@deffn {C 成员} PyWideStringList warnoptions

@ref{40e,,sys.warnoptions}: options of the @ref{126,,warnings} module to build
warnings filters: lowest to highest priority.

The @ref{126,,warnings} module adds @ref{40e,,sys.warnoptions} in the reverse
order: the last @ref{3fc3,,PyConfig.warnoptions} item becomes the first
item of @code{warnings.filters} which is checked first (highest
priority).
@end deffn

@geindex PyConfig.write_bytecode (C 成员)
@anchor{c-api/init_config c PyConfig write_bytecode}@anchor{3fc4}
@deffn {C 成员} int write_bytecode

If non-zero, write @code{.pyc} files.

@ref{35ce,,sys.dont_write_bytecode} is initialized to the inverted value of
@ref{3fc4,,write_bytecode}.
@end deffn

@geindex PyConfig.xoptions (C 成员)
@anchor{c-api/init_config c PyConfig xoptions}@anchor{3fc5}
@deffn {C 成员} PyWideStringList xoptions

@ref{12e7,,sys._xoptions}.
@end deffn
@end deffn

If @code{parse_argv} is non-zero, @code{argv} arguments are parsed the same
way the regular Python parses command line arguments, and Python
arguments are stripped from @code{argv}: see @ref{925,,Command Line Arguments}.

The @code{xoptions} options are parsed to set other options: see @ref{155,,-X}
option.

@node Initialization with PyConfig,Isolated Configuration,PyConfig,Python初始化配置
@anchor{c-api/init_config initialization-with-pyconfig}@anchor{3fc6}
@subsection Initialization with PyConfig


Function to initialize Python:

@geindex Py_InitializeFromConfig (C 函数)
@anchor{c-api/init_config c Py_InitializeFromConfig}@anchor{178}
@deffn {C 函数} PyStatus Py_InitializeFromConfig (const PyConfig@w{ }*config)

Initialize Python from @emph{config} configuration.
@end deffn

The caller is responsible to handle exceptions (error or exit) using
@ref{16e,,PyStatus_Exception()} and @ref{177,,Py_ExitStatusException()}.

If @code{PyImport_FrozenModules}, @code{PyImport_AppendInittab()} or
@code{PyImport_ExtendInittab()} are used, they must be set or called after Python
preinitialization and before the Python initialization.

Example setting the program name:

@example
void init_python(void)
@{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);

    /* Set the program name. Implicitly preinitialize Python. */
    status = PyConfig_SetString(&config, &config.program_name,
                                L"/path/to/my_program");
    if (PyStatus_Exception(status)) @{
        goto fail;
    @}

    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) @{
        goto fail;
    @}
    PyConfig_Clear(&config);
    return;

fail:
    PyConfig_Clear(&config);
    Py_ExitStatusException(status);
@}
@end example

More complete example modifying the default configuration, read the
configuration, and then override some parameters:

@example
PyStatus init_python(const char *program_name)
@{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);

    /* Set the program name before reading the configuration
       (decode byte string from the locale encoding).

       Implicitly preinitialize Python. */
    status = PyConfig_SetBytesString(&config, &config.program_name,
                                  program_name);
    if (PyStatus_Exception(status)) @{
        goto done;
    @}

    /* Read all configuration at once */
    status = PyConfig_Read(&config);
    if (PyStatus_Exception(status)) @{
        goto done;
    @}

    /* Append our custom search path to sys.path */
    status = PyWideStringList_Append(&config.module_search_paths,
                                     L"/path/to/more/modules");
    if (PyStatus_Exception(status)) @{
        goto done;
    @}

    /* Override executable computed by PyConfig_Read() */
    status = PyConfig_SetString(&config, &config.executable,
                                L"/path/to/my_executable");
    if (PyStatus_Exception(status)) @{
        goto done;
    @}

    status = Py_InitializeFromConfig(&config);

done:
    PyConfig_Clear(&config);
    return status;
@}
@end example

@node Isolated Configuration,Python Configuration,Initialization with PyConfig,Python初始化配置
@anchor{c-api/init_config init-isolated-conf}@anchor{3f83}@anchor{c-api/init_config isolated-configuration}@anchor{3fc7}
@subsection Isolated Configuration


@ref{16b,,PyPreConfig_InitIsolatedConfig()} and
@ref{164,,PyConfig_InitIsolatedConfig()} functions create a configuration to
isolate Python from the system. For example, to embed Python into an
application.

This configuration ignores global configuration variables, environments
variables, command line arguments (@ref{3f95,,PyConfig.argv} is not parsed)
and user site directory. The C standard streams (ex: @code{stdout}) and the
LC_CTYPE locale are left unchanged. Signal handlers are not installed.

Configuration files are still used with this configuration. Set the
@ref{3fb0,,Path Configuration} ("output fields") to ignore these
configuration files and avoid the function computing the default path
configuration.

@node Python Configuration,路径配置,Isolated Configuration,Python初始化配置
@anchor{c-api/init_config init-python-config}@anchor{3f82}@anchor{c-api/init_config python-configuration}@anchor{3fc8}
@subsection Python Configuration


@ref{16c,,PyPreConfig_InitPythonConfig()} and @ref{165,,PyConfig_InitPythonConfig()}
functions create a configuration to build a customized Python which behaves as
the regular Python.

Environments variables and command line arguments are used to configure
Python, whereas global configuration variables are ignored.

This function enables C locale coercion (
@geindex Python 提高建议; PEP 538
PEP 538@footnote{https://www.python.org/dev/peps/pep-0538}) and UTF-8 Mode
(
@geindex Python 提高建议; PEP 540
PEP 540@footnote{https://www.python.org/dev/peps/pep-0540}) depending on the LC_CTYPE locale, 
@geindex PYTHONUTF8
@geindex 环境变量; PYTHONUTF8
@ref{30a,,PYTHONUTF8} and
@geindex PYTHONCOERCECLOCALE
@geindex 环境变量; PYTHONCOERCECLOCALE
@ref{305,,PYTHONCOERCECLOCALE} environment variables.

Example of customized Python always running in isolated mode:

@example
int main(int argc, char **argv)
@{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);
    config.isolated = 1;

    /* Decode command line arguments.
       Implicitly preinitialize Python (in isolated mode). */
    status = PyConfig_SetBytesArgv(&config, argc, argv);
    if (PyStatus_Exception(status)) @{
        goto fail;
    @}

    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) @{
        goto fail;
    @}
    PyConfig_Clear(&config);

    return Py_RunMain();

fail:
    PyConfig_Clear(&config);
    if (PyStatus_IsExit(status)) @{
        return status.exitcode;
    @}
    /* Display the error message and exit the process with
       non-zero exit code */
    Py_ExitStatusException(status);
@}
@end example

@node 路径配置,Py_RunMain,Python Configuration,Python初始化配置
@anchor{c-api/init_config init-path-config}@anchor{3fb0}@anchor{c-api/init_config path-configuration}@anchor{3fc9}
@subsection 路径配置


@ref{15f,,PyConfig} contains multiple fields for the path configuration:


@itemize *

@item 
路径配置输入：


@itemize *

@item 
@ref{3fa5,,PyConfig.home}

@item 
@ref{3fb3,,PyConfig.pathconfig_warnings}

@item 
@ref{3fb5,,PyConfig.program_name}

@item 
@ref{3fad,,PyConfig.pythonpath_env}

@item 
current working directory: to get absolute paths

@item 
@code{PATH} environment variable to get the program full path
(from @ref{3fb5,,PyConfig.program_name})

@item 
@code{__PYVENV_LAUNCHER__} environment variable

@item 
(Windows only) Application paths in the registry under
"SoftwarePythonPythonCoreX.YPythonPath" of HKEY_CURRENT_USER and
HKEY_LOCAL_MACHINE (where X.Y is the Python version).
@end itemize

@item 
Path configuration output fields:


@itemize *

@item 
@ref{3f96,,PyConfig.base_exec_prefix}

@item 
@ref{3f97,,PyConfig.base_executable}

@item 
@ref{3f99,,PyConfig.base_prefix}

@item 
@ref{3f9f,,PyConfig.exec_prefix}

@item 
@ref{3f98,,PyConfig.executable}

@item 
@ref{3faf,,PyConfig.module_search_paths_set},
@ref{3fae,,PyConfig.module_search_paths}

@item 
@ref{3fb4,,PyConfig.prefix}
@end itemize
@end itemize

If at least one "output field" is not set, Python calculates the path
configuration to fill unset fields. If
@ref{3faf,,module_search_paths_set} is equal to 0,
@ref{3fae,,module_search_paths} is overridden and
@ref{3faf,,module_search_paths_set} is set to 1.

It is possible to completely ignore the function calculating the default
path configuration by setting explicitly all path configuration output
fields listed above. A string is considered as set even if it is non-empty.
@code{module_search_paths} is considered as set if
@code{module_search_paths_set} is set to 1. In this case, path
configuration input fields are ignored as well.

Set @ref{3fb3,,pathconfig_warnings} to 0 to suppress warnings when
calculating the path configuration (Unix only, Windows does not log any warning).

If @ref{3f99,,base_prefix} or @ref{3f96,,base_exec_prefix}
fields are not set, they inherit their value from @ref{3fb4,,prefix}
and @ref{3f9f,,exec_prefix} respectively.

@ref{17c,,Py_RunMain()} and @ref{4b2,,Py_Main()} modify @ref{482,,sys.path}:


@itemize *

@item 
If @ref{3fb9,,run_filename} is set and is a directory which contains a
@code{__main__.py} script, prepend @ref{3fb9,,run_filename} to
@ref{482,,sys.path}.

@item 
If @ref{3f8c,,isolated} is zero:


@itemize *

@item 
If @ref{3fba,,run_module} is set, prepend the current directory
to @ref{482,,sys.path}. Do nothing if the current directory cannot be read.

@item 
If @ref{3fb9,,run_filename} is set, prepend the directory of the
filename to @ref{482,,sys.path}.

@item 
Otherwise, prepend an empty string to @ref{482,,sys.path}.
@end itemize
@end itemize

If @ref{3fbd,,site_import} is non-zero, @ref{482,,sys.path} can be
modified by the @ref{eb,,site} module. If
@ref{3faa,,user_site_directory} is non-zero and the user's
site-package directory exists, the @ref{eb,,site} module appends the user's
site-package directory to @ref{482,,sys.path}.

The following configuration files are used by the path configuration:


@itemize *

@item 
@code{pyvenv.cfg}

@item 
@code{python._pth} (仅Windows)

@item 
@code{pybuilddir.txt} (仅Unix)
@end itemize

The @code{__PYVENV_LAUNCHER__} environment variable is used to set
@ref{3f97,,PyConfig.base_executable}

@node Py_RunMain,Multi-Phase Initialization Private Provisional API,路径配置,Python初始化配置
@anchor{c-api/init_config py-runmain}@anchor{3fca}
@subsection Py_RunMain()


@geindex Py_RunMain (C 函数)
@anchor{c-api/init_config c Py_RunMain}@anchor{17c}
@deffn {C 函数} int Py_RunMain (void)

Execute the command (@ref{3fb8,,PyConfig.run_command}), the script
(@ref{3fb9,,PyConfig.run_filename}) or the module
(@ref{3fba,,PyConfig.run_module}) specified on the command line or in the
configuration.

By default and when if @ref{e18,,-i} option is used, run the REPL.

Finally, finalizes Python and returns an exit status that can be passed to
the @code{exit()} function.
@end deffn

See @ref{3f82,,Python Configuration} for an example of
customized Python always running in isolated mode using
@ref{17c,,Py_RunMain()}.

@node Multi-Phase Initialization Private Provisional API,,Py_RunMain,Python初始化配置
@anchor{c-api/init_config multi-phase-initialization-private-provisional-api}@anchor{3fcb}
@subsection Multi-Phase Initialization Private Provisional API


This section is a private provisional API introducing multi-phase
initialization, the core feature of the 
@geindex Python 提高建议; PEP 432
PEP 432@footnote{https://www.python.org/dev/peps/pep-0432}:


@itemize *

@item 
"Core" initialization phase, "bare minimum Python":


@itemize *

@item 
Builtin types;

@item 
Builtin exceptions;

@item 
Builtin and frozen modules;

@item 
The @ref{fd,,sys} module is only partially initialized
(ex: @ref{482,,sys.path} doesn't exist yet).
@end itemize

@item 
"Main" initialization phase, Python is fully initialized:


@itemize *

@item 
Install and configure @ref{9b,,importlib};

@item 
Apply the @ref{3fb0,,Path Configuration};

@item 
Install signal handlers;

@item 
Finish @ref{fd,,sys} module initialization (ex: create @ref{307,,sys.stdout}
and @ref{482,,sys.path});

@item 
Enable optional features like @ref{7d,,faulthandler} and @ref{114,,tracemalloc};

@item 
Import the @ref{eb,,site} module;

@item 
等等.
@end itemize
@end itemize

Private provisional API:


@itemize *

@item 
@code{PyConfig._init_main}: if set to 0,
@ref{178,,Py_InitializeFromConfig()} stops at the "Core" initialization phase.
@end itemize

@geindex _Py_InitializeMain (C 函数)
@anchor{c-api/init_config c _Py_InitializeMain}@anchor{3fcc}
@deffn {C 函数} PyStatus _Py_InitializeMain (void)

Move to the "Main" initialization phase, finish the Python initialization.
@end deffn

No module is imported during the "Core" phase and the @code{importlib} module is
not configured: the @ref{3fb0,,Path Configuration} is only
applied during the "Main" phase. It may allow to customize Python in Python to
override or tune the @ref{3fb0,,Path Configuration}, maybe
install a custom @ref{5e1,,sys.meta_path} importer or an import hook, etc.

It may become possible to calculatin the @ref{3fb0,,Path Configuration} in Python, after the Core phase and before the Main phase,
which is one of the 
@geindex Python 提高建议; PEP 432
PEP 432@footnote{https://www.python.org/dev/peps/pep-0432} motivation.

The "Core" phase is not properly defined: what should be and what should
not be available at this phase is not specified yet. The API is marked
as private and provisional: the API can be modified or even be removed
anytime until a proper public API is designed.

Example running Python code between "Core" and "Main" initialization
phases:

@example
void init_python(void)
@{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);
    config._init_main = 0;

    /* ... customize 'config' configuration ... */

    status = Py_InitializeFromConfig(&config);
    PyConfig_Clear(&config);
    if (PyStatus_Exception(status)) @{
        Py_ExitStatusException(status);
    @}

    /* Use sys.stderr because sys.stdout is only created
       by _Py_InitializeMain() */
    int res = PyRun_SimpleString(
        "import sys; "
        "print('Run Python code before _Py_InitializeMain', "
               "file=sys.stderr)");
    if (res < 0) @{
        exit(1);
    @}

    /* ... put more configuration code here ... */

    status = _Py_InitializeMain();
    if (PyStatus_Exception(status)) @{
        Py_ExitStatusException(status);
    @}
@}
@end example

@node 内存管理,对象实现支持,Python初始化配置,Python/C API 参考手册
@anchor{c-api/memory doc}@anchor{3fcd}@anchor{c-api/memory memory}@anchor{3f85}@anchor{c-api/memory memory-management}@anchor{3fce}
@section 内存管理


@menu
* 概述: 概述<16>. 
* 原始内存接口:: 
* 内存接口:: 
* 对象分配器:: 
* 默认内存分配器:: 
* 自定义内存分配器:: 
* pymalloc 分配器:: 
* tracemalloc C API:: 
* 例子: 例子<34>. 

@end menu

@node 概述<16>,原始内存接口,,内存管理
@anchor{c-api/memory memoryoverview}@anchor{3fcf}@anchor{c-api/memory overview}@anchor{3fd0}
@subsection 概述


在 Python 中，内存管理涉及到一个包含所有 Python 对象和数据结构的私有堆（heap）。这个私有堆的管理由内部的 @emph{Python 内存管理器（Python memory manager）} 保证。Python 内存管理器有不同的组件来处理各种动态存储管理方面的问题，如共享、分割、预分配或缓存。

在最底层，一个原始内存分配器通过与操作系统的内存管理器交互，确保私有堆中有足够的空间来存储所有与 Python 相关的数据。在原始内存分配器的基础上，几个对象特定的分配器在同一堆上运行，并根据每种对象类型的特点实现不同的内存管理策略。例如，整数对象在堆内的管理方式不同于字符串、元组或字典，因为整数需要不同的存储需求和速度与空间的权衡。因此，Python 内存管理器将一些工作分配给对象特定分配器，但确保后者在私有堆的范围内运行。

Python 堆内存的管理是由解释器来执行，用户对它没有控制权，即使他们经常操作指向堆内内存块的对象指针，理解这一点十分重要。Python 对象和其他内部缓冲区的堆空间分配是由 Python 内存管理器按需通过本文档中列出的 Python/C API 函数进行的。

@geindex malloc()
@geindex calloc()
@geindex realloc()
@geindex free()

为了避免内存破坏，扩展的作者永远不应该试图用 C 库函数导出的函数来对 Python 对象进行操作，这些函数包括： @code{malloc()}, @code{calloc()}, @code{realloc()} 和 @code{free()}。这将导致 C 分配器和 Python 内存管理器之间的混用，引发严重后果，这是由于它们实现了不同的算法，并在不同的堆上操作。但是，我们可以安全地使用 C 库分配器为单独的目的分配和释放内存块，如下例所示：

@example
PyObject *res;
char *buf = (char *) malloc(BUFSIZ); /* for I/O */

if (buf == NULL)
    return PyErr_NoMemory();
...Do some I/O operation involving buf...
res = PyBytes_FromString(buf);
free(buf); /* malloc'ed */
return res;
@end example

在这个例子中，I/O 缓冲区的内存请求是由 C 库分配器处理的。Python 内存管理器只参与了分配作为结果返回的字节对象。

然而，在大多数情况下，建议专门从 Python 堆中分配内存，因为后者由 Python 内存管理器控制。例如，当解释器扩展了用 C 写的新对象类型时，就必须这样做。使用 Python 堆的另一个原因是希望*通知* Python 内存管理器关于扩展模块的内存需求。即使所请求的内存全部只用于内部的、高度特定的目的，将所有的内存请求交给 Python 内存管理器能让解释器对其内存占用的整体情况有更准确的了解。因此，在某些情况下，Python 内存管理器可能会触发或不触发适当的操作，如垃圾回收、内存压缩或其他预防性操作。请注意，通过使用前面例子中所示的 C 库分配器，为 I/O 缓冲区分配的内存会完全不受 Python 内存管理器管理。


@subsubheading 参见


环境变量 
@geindex PYTHONMALLOC
@geindex 环境变量; PYTHONMALLOC
@ref{4fd,,PYTHONMALLOC} 可被用来配置 Python 所使用的内存分配器。

环境变量 
@geindex PYTHONMALLOCSTATS
@geindex 环境变量; PYTHONMALLOCSTATS
@ref{10f5,,PYTHONMALLOCSTATS} 可以用来在每次创建和关闭新的 pymalloc 对象区域时打印 @ref{5bc,,pymalloc 内存分配器} 的统计数据。


@node 原始内存接口,内存接口,概述<16>,内存管理
@anchor{c-api/memory raw-memory-interface}@anchor{3fd1}
@subsection 原始内存接口


以下函数集封装了系统分配器。这些函数是线程安全的，不需要持有 @ref{500,,GIL}。

@ref{12f3,,default raw memory allocator} 使用这些函数：@code{malloc()}、 @code{calloc()}、 @code{realloc()} 和 @code{free()}；申请零字节时则调用 @code{malloc(1)`@w{`}（或 `@w{`}calloc(1, 1)}）


3.4 新版功能.


@geindex PyMem_RawMalloc (C 函数)
@anchor{c-api/memory c PyMem_RawMalloc}@anchor{967}
@deffn {C 函数} void* PyMem_RawMalloc (size_t@w{ }n)

分配 @emph{n} 个字节，并返回一个指向分配的内存的 @code{void*} 类型指针，如果请求失败，则返回 @code{NULL} 。

请求零字节可能返回一个独特的非 @code{NULL} 指针，就像调用了`@w{`}PyMem_RawMalloc(1)`@w{`} 一样。但是内存不会以任何方式被初始化。
@end deffn

@geindex PyMem_RawCalloc (C 函数)
@anchor{c-api/memory c PyMem_RawCalloc}@anchor{79f}
@deffn {C 函数} void* PyMem_RawCalloc (size_t@w{ }nelem, size_t@w{ }elsize)

分配 @emph{nelem} 个元素，每个元素的大小为 @emph{elsize} 字节，并返回指向分配的内存的 @code{void*/} 类型指针，如果请求失败，则返回`@w{`}NULL`@w{`}。内存被初始化为零。

请求零字节可能返回一个独特的非 @code{NULL} 指针，就像调用了`@w{`}PyMem_RawCalloc(1, 1)`@w{`} 一样。


3.5 新版功能.

@end deffn

@geindex PyMem_RawRealloc (C 函数)
@anchor{c-api/memory c PyMem_RawRealloc}@anchor{968}
@deffn {C 函数} void* PyMem_RawRealloc (void@w{ }*p, size_t@w{ }n)

将 @emph{p} 指向的内存块大小调整为 @emph{n} 字节。以新旧内存块大小中的最小值为准，其中内容保持不变，

如果*p*是`@w{`}NULL`@w{`}，则相当于调用 @code{PyMem_RawMalloc(n)} ；如果 @emph{n} 等于 0，则内存块大小会被调整，但不会被释放，返回非 @code{NULL} 指针。

除非 @emph{p} 是 @code{NULL} ，否则它必须是之前调用 @ref{967,,PyMem_RawMalloc()} 、 @ref{968,,PyMem_RawRealloc()} 或 @ref{79f,,PyMem_RawCalloc()} 所返回的。

如果请求失败，@ref{968,,PyMem_RawRealloc()} 返回 @code{NULL} ， @emph{p} 仍然是指向先前内存区域的有效指针。
@end deffn

@geindex PyMem_RawFree (C 函数)
@anchor{c-api/memory c PyMem_RawFree}@anchor{3bea}
@deffn {C 函数} void PyMem_RawFree (void@w{ }*p)

释放 @emph{p} 指向的内存块。除非 @emph{p} 是 @code{NULL} ，否则它必须是之前调用 @ref{967,,PyMem_RawMalloc()} 、 @ref{968,,PyMem_RawRealloc()} 或 @ref{79f,,PyMem_RawCalloc()} 所返回的指针。否则，或在 @code{PyMem_RawFree(p)} 之前已经调用过的情况下，未定义的行为会发生。

如果 @emph{p} 是 @code{NULL}, 那么什么操作也不会进行。
@end deffn

@node 内存接口,对象分配器,原始内存接口,内存管理
@anchor{c-api/memory memory-interface}@anchor{3fd2}@anchor{c-api/memory memoryinterface}@anchor{3fd3}
@subsection 内存接口


以下函数集，仿照 ANSI C 标准，并指定了请求零字节时的行为，可用于从Python堆分配和释放内存。

@ref{12f3,,默认内存分配器} 使用了 @ref{5bc,,pymalloc 内存分配器}.

@cartouche
@quotation 警告 
在使用这些函数时，必须持有 @ref{500,,全局解释器锁（GIL）} 。
@end quotation
@end cartouche


在 3.6 版更改: 现在默认的分配器是 pymalloc 而非系统的 @code{malloc()} 。


@geindex PyMem_Malloc (C 函数)
@anchor{c-api/memory c PyMem_Malloc}@anchor{4ff}
@deffn {C 函数} void* PyMem_Malloc (size_t@w{ }n)

分配 @emph{n} 个字节，并返回一个指向分配的内存的 @code{void*} 类型指针，如果请求失败，则返回 @code{NULL} 。

请求零字节可能返回一个独特的非 @code{NULL} 指针，就像调用了`@w{`}PyMem_Malloc(1)`@w{`} 一样。但是内存不会以任何方式被初始化。
@end deffn

@geindex PyMem_Calloc (C 函数)
@anchor{c-api/memory c PyMem_Calloc}@anchor{7a0}
@deffn {C 函数} void* PyMem_Calloc (size_t@w{ }nelem, size_t@w{ }elsize)

分配 @emph{nelem} 个元素，每个元素的大小为 @emph{elsize} 字节，并返回指向分配的内存的 @code{void*/} 类型指针，如果请求失败，则返回`@w{`}NULL`@w{`}。内存被初始化为零。

请求零字节可能返回一个独特的非 @code{NULL} 指针，就像调用了`@w{`}PyMem_Calloc(1, 1)`@w{`} 一样。


3.5 新版功能.

@end deffn

@geindex PyMem_Realloc (C 函数)
@anchor{c-api/memory c PyMem_Realloc}@anchor{969}
@deffn {C 函数} void* PyMem_Realloc (void@w{ }*p, size_t@w{ }n)

将 @emph{p} 指向的内存块大小调整为 @emph{n} 字节。以新旧内存块大小中的最小值为准，其中内容保持不变，

如果*p*是`@w{`}NULL`@w{`}，则相当于调用 @code{PyMem_Malloc(n)} ；如果 @emph{n} 等于 0，则内存块大小会被调整，但不会被释放，返回非 @code{NULL} 指针。

除非 @emph{p} 是 @code{NULL} ，否则它必须是之前调用 @ref{4ff,,PyMem_Malloc()} 、 @ref{969,,PyMem_Realloc()} 或 @ref{7a0,,PyMem_Calloc()} 所返回的。

如果请求失败，@ref{969,,PyMem_Realloc()} 返回 @code{NULL} ， @emph{p} 仍然是指向先前内存区域的有效指针。
@end deffn

@geindex PyMem_Free (C 函数)
@anchor{c-api/memory c PyMem_Free}@anchor{da2}
@deffn {C 函数} void PyMem_Free (void@w{ }*p)

释放 @emph{p} 指向的内存块。除非 @emph{p} 是 @code{NULL} ，否则它必须是之前调用 @ref{4ff,,PyMem_Malloc()} 、 @ref{969,,PyMem_Realloc()} 或 @ref{7a0,,PyMem_Calloc()} 所返回的指针。否则，或在 @code{PyMem_Free(p)} 之前已经调用过的情况下，未定义的行为会发生。

如果 @emph{p} 是 @code{NULL}, 那么什么操作也不会进行。
@end deffn

以下面向类型的宏为方便而提供。 注意 @emph{TYPE} 可以指任何 C 类型。

@geindex PyMem_New (C 函数)
@anchor{c-api/memory c PyMem_New}@anchor{3fd4}
@deffn {C 函数} TYPE* PyMem_New (TYPE, size_t@w{ }n)

与 @ref{4ff,,PyMem_Malloc()} 相同，但分配 @code{(n * sizeof(TYPE))} 字节的内存。返回一个转换为 @code{TYPE*} 的指针。内存不会以任何方式被初始化。
@end deffn

@geindex PyMem_Resize (C 函数)
@anchor{c-api/memory c PyMem_Resize}@anchor{3fd5}
@deffn {C 函数} TYPE* PyMem_Resize (void@w{ }*p, TYPE, size_t@w{ }n)

与 @ref{969,,PyMem_Realloc()} 相同，但内存块的大小被调整为 @code{(n * sizeof(TYPE))} 字节。返回一个转换为 @code{TYPE|*} 类型的指针。返回时， @emph{p} 是指向新内存区域的指针；如果失败，则返回 @code{NULL} 。

这是一个 C 预处理宏， @emph{p} 总是被重新赋值。请保存 @emph{p} 的原始值，以避免在处理错误时丢失内存。
@end deffn

@geindex PyMem_Del (C 函数)
@anchor{c-api/memory c PyMem_Del}@anchor{3fd6}
@deffn {C 函数} void PyMem_Del (void@w{ }*p)

与 @ref{da2,,PyMem_Free()} 相同
@end deffn

此外，我们还提供了以下宏集用于直接调用 Python 内存分配器，而不涉及上面列出的 C API 函数。但是请注意，使用它们并不能保证跨 Python 版本的二进制兼容性，因此在扩展模块被弃用。


@itemize *

@item 
@code{PyMem_MALLOC(size)}

@item 
@code{PyMem_NEW(type, size)}

@item 
@code{PyMem_REALLOC(ptr, size)}

@item 
@code{PyMem_RESIZE(ptr, type, size)}

@item 
@code{PyMem_FREE(ptr)}

@item 
@code{PyMem_DEL(ptr)}
@end itemize

@node 对象分配器,默认内存分配器,内存接口,内存管理
@anchor{c-api/memory object-allocators}@anchor{3fd7}
@subsection 对象分配器


以下函数集，仿照 ANSI C 标准，并指定了请求零字节时的行为，可用于从Python堆分配和释放内存。

@ref{12f3,,默认对象分配器} 使用 @ref{5bc,,pymalloc 内存分配器}.

@cartouche
@quotation 警告 
在使用这些函数时，必须持有 @ref{500,,全局解释器锁（GIL）} 。
@end quotation
@end cartouche

@geindex PyObject_Malloc (C 函数)
@anchor{c-api/memory c PyObject_Malloc}@anchor{502}
@deffn {C 函数} void* PyObject_Malloc (size_t@w{ }n)

分配 @emph{n} 个字节，并返回一个指向分配的内存的 @code{void*} 类型指针，如果请求失败，则返回 @code{NULL} 。

请求零字节可能返回一个独特的非 @code{NULL} 指针，就像调用了`@w{`}PyObject_Malloc(1)`@w{`} 一样。但是内存不会以任何方式被初始化。
@end deffn

@geindex PyObject_Calloc (C 函数)
@anchor{c-api/memory c PyObject_Calloc}@anchor{7a1}
@deffn {C 函数} void* PyObject_Calloc (size_t@w{ }nelem, size_t@w{ }elsize)

分配 @emph{nelem} 个元素，每个元素的大小为 @emph{elsize} 字节，并返回指向分配的内存的 @code{void*/} 类型指针，如果请求失败，则返回`@w{`}NULL`@w{`}。内存被初始化为零。

请求零字节可能返回一个独特的非 @code{NULL} 指针，就像调用了`@w{`}PyObject_Calloc(1, 1)`@w{`} 一样。


3.5 新版功能.

@end deffn

@geindex PyObject_Realloc (C 函数)
@anchor{c-api/memory c PyObject_Realloc}@anchor{da3}
@deffn {C 函数} void* PyObject_Realloc (void@w{ }*p, size_t@w{ }n)

将 @emph{p} 指向的内存块大小调整为 @emph{n} 字节。以新旧内存块大小中的最小值为准，其中内容保持不变，

如果*p*是`@w{`}NULL`@w{`}，则相当于调用 @code{PyObject_Malloc(n)} ；如果 @emph{n} 等于 0，则内存块大小会被调整，但不会被释放，返回非 @code{NULL} 指针。

除非 @emph{p} 是 @code{NULL} ，否则它必须是之前调用 @ref{502,,PyObject_Malloc()} 、 @ref{da3,,PyObject_Realloc()} 或 @ref{7a1,,PyObject_Calloc()} 所返回的。

如果请求失败，@ref{da3,,PyObject_Realloc()} 返回 @code{NULL} ， @emph{p} 仍然是指向先前内存区域的有效指针。
@end deffn

@geindex PyObject_Free (C 函数)
@anchor{c-api/memory c PyObject_Free}@anchor{4fe}
@deffn {C 函数} void PyObject_Free (void@w{ }*p)

释放 @emph{p} 指向的内存块。除非 @emph{p} 是 @code{NULL} ，否则它必须是之前调用 @ref{502,,PyObject_Malloc()} 、 @ref{da3,,PyObject_Realloc()} 或 @ref{7a1,,PyObject_Calloc()} 所返回的指针。否则，或在 @code{PyObject_Free(p)} 之前已经调用过的情况下，未定义的行为会发生。

如果 @emph{p} 是 @code{NULL}, 那么什么操作也不会进行。
@end deffn

@node 默认内存分配器,自定义内存分配器,对象分配器,内存管理
@anchor{c-api/memory default-memory-allocators}@anchor{12f3}@anchor{c-api/memory id1}@anchor{3fd8}
@subsection 默认内存分配器


默认内存分配器：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} 
@headitem

配置

@tab

名称

@tab

PyMem_RawMalloc

@tab

PyMem_Malloc

@tab

PyObject_Malloc

@item

发布版本

@tab

@code{"pymalloc"}

@tab

@code{malloc}

@tab

@code{pymalloc}

@tab

@code{pymalloc}

@item

调试构建

@tab

@code{"pymalloc_debug"}

@tab

@code{malloc} + debug

@tab

@code{pymalloc} + debug

@tab

@code{pymalloc} + debug

@item

没有 pymalloc 的发布版本

@tab

@code{"malloc"}

@tab

@code{malloc}

@tab

@code{malloc}

@tab

@code{malloc}

@item

没有 pymalloc 的调试构建

@tab

@code{"malloc_debug"}

@tab

@code{malloc} + debug

@tab

@code{malloc} + debug

@tab

@code{malloc} + debug

@end multitable


说明：


@itemize *

@item 
名称: 环境变量 
@geindex PYTHONMALLOC
@geindex 环境变量; PYTHONMALLOC
@ref{4fd,,PYTHONMALLOC} 的值

@item 
@code{malloc}: 来自 C 标准库的系统分配, C 函数 @code{malloc()}, @code{calloc()}, @code{realloc()} and @code{free()}

@item 
@code{pymalloc}: @ref{5bc,,pymalloc 内存分配器}

@item 
"+ debug": 带有 @ref{504,,PyMem_SetupDebugHooks()} 安装的调试钩子
@end itemize

@node 自定义内存分配器,pymalloc 分配器,默认内存分配器,内存管理
@anchor{c-api/memory customize-memory-allocators}@anchor{3fd9}
@subsection 自定义内存分配器



3.4 新版功能.


@geindex PyMemAllocatorEx (C 类型)
@anchor{c-api/memory c PyMemAllocatorEx}@anchor{7c4}
@deffn {C 类型} PyMemAllocatorEx

用于描述内存块分配器的结构体。包含四个字段：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

含义

@item

@code{void *ctx}

@tab

作为第一个参数传入的用户上下文

@item

@code{void* malloc(void *ctx, size_t size)}

@tab

分配一个内存块

@item

@code{void* calloc(void *ctx, size_t nelem, size_t elsize)}

@tab

分配一个初始化为 0 的内存块

@item

@code{void* realloc(void *ctx, void *ptr, size_t new_size)}

@tab

分配一个内存块或调整其大小

@item

@code{void free(void *ctx, void *ptr)}

@tab

释放一个内存块

@end multitable



在 3.5 版更改: The @code{PyMemAllocator} structure was renamed to
@ref{7c4,,PyMemAllocatorEx} and a new @code{calloc} field was added.

@end deffn

@geindex PyMemAllocatorDomain (C 类型)
@anchor{c-api/memory c PyMemAllocatorDomain}@anchor{3fda}
@deffn {C 类型} PyMemAllocatorDomain

用来识别分配器域的枚举类。域有：

@geindex PYMEM_DOMAIN_RAW (C 变量)
@anchor{c-api/memory c PYMEM_DOMAIN_RAW}@anchor{12f4}
@deffn {C 变量} PYMEM_DOMAIN_RAW

函数


@itemize *

@item 
@ref{967,,PyMem_RawMalloc()}

@item 
@ref{968,,PyMem_RawRealloc()}

@item 
@ref{79f,,PyMem_RawCalloc()}

@item 
@ref{3bea,,PyMem_RawFree()}
@end itemize
@end deffn

@geindex PYMEM_DOMAIN_MEM (C 变量)
@anchor{c-api/memory c PYMEM_DOMAIN_MEM}@anchor{503}
@deffn {C 变量} PYMEM_DOMAIN_MEM

函数


@itemize *

@item 
@ref{4ff,,PyMem_Malloc()},

@item 
@ref{969,,PyMem_Realloc()}

@item 
@ref{7a0,,PyMem_Calloc()}

@item 
@ref{da2,,PyMem_Free()}
@end itemize
@end deffn

@geindex PYMEM_DOMAIN_OBJ (C 变量)
@anchor{c-api/memory c PYMEM_DOMAIN_OBJ}@anchor{501}
@deffn {C 变量} PYMEM_DOMAIN_OBJ

函数


@itemize *

@item 
@ref{502,,PyObject_Malloc()}

@item 
@ref{da3,,PyObject_Realloc()}

@item 
@ref{7a1,,PyObject_Calloc()}

@item 
@ref{4fe,,PyObject_Free()}
@end itemize
@end deffn
@end deffn

@geindex PyMem_GetAllocator (C 函数)
@anchor{c-api/memory c PyMem_GetAllocator}@anchor{3f24}
@deffn {C 函数} void PyMem_GetAllocator (PyMemAllocatorDomain@w{ }domain, PyMemAllocatorEx@w{ }*allocator)

获取指定域的内存块分配器。
@end deffn

@geindex PyMem_SetAllocator (C 函数)
@anchor{c-api/memory c PyMem_SetAllocator}@anchor{3f22}
@deffn {C 函数} void PyMem_SetAllocator (PyMemAllocatorDomain@w{ }domain, PyMemAllocatorEx@w{ }*allocator)

设置指定域的内存块分配器。

当请求零字节时，新的分配器必须返回一个独特的非 @code{NULL} 指针。

对于 @ref{12f4,,PYMEM_DOMAIN_RAW} 域，分配器必须是线程安全的：当分配器被调用时，不持有 @ref{500,,全局解释器锁} 。

如果新的分配器不是钩子（不调用之前的分配器），必须调用 @ref{504,,PyMem_SetupDebugHooks()} 函数在新分配器上重新安装调试钩子。
@end deffn

@geindex PyMem_SetupDebugHooks (C 函数)
@anchor{c-api/memory c PyMem_SetupDebugHooks}@anchor{504}
@deffn {C 函数} void PyMem_SetupDebugHooks (void)

设置检测 Python 内存分配器函数中错误的钩子。

新分配的内存由字节 @code{0xCD} ( @code{CLEANBYTE} ) 填充，释放的内存由字节 @code{0xDD} ( @code{DEADBYTE} )填充。内存块被 "禁止字节" 包围（ @code{FORBIDDENBYTE} ：字节 @code{0xFD} ）。

运行时检查：


@itemize -

@item 
检测对 API 的违反，例如：对用 @ref{4ff,,PyMem_Malloc()} 分配的缓冲区调用 @ref{4fe,,PyObject_Free()} 。

@item 
检测缓冲区起始位置前的写入（缓冲区下溢）。

@item 
检测缓冲区终止位置后的写入（缓冲区溢出）。

@item 
检测当调用 @ref{501,,PYMEM_DOMAIN_OBJ} (如: @ref{502,,PyObject_Malloc()}) 和 @ref{503,,PYMEM_DOMAIN_MEM} (如: @ref{4ff,,PyMem_Malloc()}) 域的分配器函数时 @ref{500,,GIL} 已被保持。
@end itemize

在出错时，调试钩子使用 @ref{114,,tracemalloc} 模块来回溯内存块被分配的位置。只有当 @ref{114,,tracemalloc} 正在追踪 Python 内存分配，并且内存块被追踪时，才会显示回溯。

如果 Python 是在调试模式下编译的，这些钩子是 @ref{12f3,,installed by default} 。环境变量 
@geindex PYTHONMALLOC
@geindex 环境变量; PYTHONMALLOC
@ref{4fd,,PYTHONMALLOC} 可以用来在发布模式编译的 Python 上安装调试钩子。


在 3.6 版更改: 这个函数现在也适用于以 发布模式编译的 Python。在出错时，调试钩子现在使用 @ref{114,,tracemalloc} 来回溯内存块被分配的位置。调试钩子现在也检查当 @ref{501,,PYMEM_DOMAIN_OBJ} 和 @ref{503,,PYMEM_DOMAIN_MEM} 域的函数被调用时，全局解释器锁是否被持有。



在 3.8 版更改: 字节模式 @code{0xCB} (@code{CLEANBYTE})、 @code{0xDB} (@code{DEADBYTE}) 和 @code{0xFB} (@code{FORBIDDENBYTE}) 已被 @code{0xCD} 、 @code{0xDD} 和 @code{0xFD} 替代以使用与 Windows CRT 调试 @code{malloc()} 和 @code{free()} 相同的值。

@end deffn

@node pymalloc 分配器,tracemalloc C API,自定义内存分配器,内存管理
@anchor{c-api/memory pymalloc}@anchor{5bc}@anchor{c-api/memory the-pymalloc-allocator}@anchor{3fdb}
@subsection pymalloc 分配器


Python 有为具有短生命周期的小对象（小于或等于 512 字节）优化的 @emph{pymalloc} 分配器。它使用固定大小为 256 KiB 的称为 "arenas" 的内存映射。对于大于512字节的分配，它回到使用 @ref{967,,PyMem_RawMalloc()} 和 @ref{968,,PyMem_RawRealloc()} 。

@emph{pymalloc} 是 @ref{503,,PYMEM_DOMAIN_MEM} (例如: @ref{4ff,,PyMem_Malloc()}) 和 @ref{501,,PYMEM_DOMAIN_OBJ} (例如: @ref{502,,PyObject_Malloc()}) 域的 @ref{12f3,,默认分配器} 。

arena 分配器使用以下函数：


@itemize *

@item 
Windows 上的 @code{VirtualAlloc()} and @code{VirtualFree()} ,

@item 
@code{mmap()} 和 @code{munmap()} ，如果可用，

@item 
否则， @code{malloc()} 和 @code{free()} 。
@end itemize

@menu
* 自定义 pymalloc Arena 分配器:: 

@end menu

@node 自定义 pymalloc Arena 分配器,,,pymalloc 分配器
@anchor{c-api/memory customize-pymalloc-arena-allocator}@anchor{3fdc}
@subsubsection 自定义 pymalloc Arena 分配器



3.4 新版功能.


@geindex PyObjectArenaAllocator (C 类型)
@anchor{c-api/memory c PyObjectArenaAllocator}@anchor{3fdd}
@deffn {C 类型} PyObjectArenaAllocator

用来描述一个 arena 分配器的结构体。这个结构体有三个字段：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

含义

@item

@code{void *ctx}

@tab

作为第一个参数传入的用户上下文

@item

@code{void* alloc(void *ctx, size_t size)}

@tab

分配一块 size 字节的区域

@item

@code{void free(void *ctx, size_t size, void *ptr)}

@tab

释放一块区域

@end multitable

@end deffn

@geindex PyObject_GetArenaAllocator (C 函数)
@anchor{c-api/memory c PyObject_GetArenaAllocator}@anchor{3f25}
@deffn {C 函数} PyObject_GetArenaAllocator (PyObjectArenaAllocator@w{ }*allocator)

获取 arena 分配器
@end deffn

@geindex PyObject_SetArenaAllocator (C 函数)
@anchor{c-api/memory c PyObject_SetArenaAllocator}@anchor{3f23}
@deffn {C 函数} PyObject_SetArenaAllocator (PyObjectArenaAllocator@w{ }*allocator)

设置 arena 分配器
@end deffn

@node tracemalloc C API,例子<34>,pymalloc 分配器,内存管理
@anchor{c-api/memory tracemalloc-c-api}@anchor{3fde}
@subsection tracemalloc C API



3.7 新版功能.


@geindex PyTraceMalloc_Track (C 函数)
@anchor{c-api/memory c PyTraceMalloc_Track}@anchor{41c}
@deffn {C 函数} int PyTraceMalloc_Track (unsigned int@w{ }domain, uintptr_t@w{ }ptr, size_t@w{ }size)

在 @ref{114,,tracemalloc} 模块中跟踪一个已分配的内存块。

成功时返回 @code{0}，出错时返回 @code{-1} (无法分配内存来保存跟踪信息)。 如果禁用了 tracemalloc 则返回 @code{-2}。

如果内存块已被跟踪，则更新现有跟踪信息。
@end deffn

@geindex PyTraceMalloc_Untrack (C 函数)
@anchor{c-api/memory c PyTraceMalloc_Untrack}@anchor{41d}
@deffn {C 函数} int PyTraceMalloc_Untrack (unsigned int@w{ }domain, uintptr_t@w{ }ptr)

在 @ref{114,,tracemalloc} 模块中取消跟踪一个已分配的内存块。 如果内存块未被跟踪则不执行任何操作。

如果 tracemalloc 被禁用则返回 @code{-2}，否则返回 @code{0}。
@end deffn

@node 例子<34>,,tracemalloc C API,内存管理
@anchor{c-api/memory examples}@anchor{3fdf}@anchor{c-api/memory memoryexamples}@anchor{3fe0}
@subsection 例子


以下是来自 @ref{3fcf,,概述} 小节的示例，经过重写以使 I/O 缓冲区是通过使用第一个函数集从 Python 堆中分配的:

@example
PyObject *res;
char *buf = (char *) PyMem_Malloc(BUFSIZ); /* for I/O */

if (buf == NULL)
    return PyErr_NoMemory();
/* ...Do some I/O operation involving buf... */
res = PyBytes_FromString(buf);
PyMem_Free(buf); /* allocated with PyMem_Malloc */
return res;
@end example

使用面向类型函数集的相同代码:

@example
PyObject *res;
char *buf = PyMem_New(char, BUFSIZ); /* for I/O */

if (buf == NULL)
    return PyErr_NoMemory();
/* ...Do some I/O operation involving buf... */
res = PyBytes_FromString(buf);
PyMem_Del(buf); /* allocated with PyMem_New */
return res;
@end example

请注意在以上两个示例中，缓冲区总是通过归属于相同集的函数来操纵的。 事实上，对于一个给定的内存块必须使用相同的内存 API 族，以便使得混合不同分配器的风险减至最低。 以下代码序列包含两处错误，其中一个被标记为 @emph{fatal} 因为它混合了两种在不同堆上操作的不同分配器。

@example
char *buf1 = PyMem_New(char, BUFSIZ);
char *buf2 = (char *) malloc(BUFSIZ);
char *buf3 = (char *) PyMem_Malloc(BUFSIZ);
...
PyMem_Del(buf3);  /* Wrong -- should be PyMem_Free() */
free(buf2);       /* Right -- allocated via malloc() */
free(buf1);       /* Fatal -- should be PyMem_Del()  */
@end example

除了旨在处理来自 Python 堆的原始内存块的函数之外， Python 中的对象是通过 @ref{2d2,,PyObject_New()}, @ref{2d3,,PyObject_NewVar()} 和 @ref{e0f,,PyObject_Del()} 来分配和释放的。

这些将在有关如何在 C 中定义和实现新对象类型的下一章中讲解。

@node 对象实现支持,API 和 ABI 版本管理,内存管理,Python/C API 参考手册
@anchor{c-api/objimpl doc}@anchor{3fe1}@anchor{c-api/objimpl newtypes}@anchor{3fe2}@anchor{c-api/objimpl object-implementation-support}@anchor{3fe3}
@section 对象实现支持


本章描述了定义新对象类型时所使用的函数、类型和宏。

@menu
* 在堆上分配对象:: 
* Common Object Structures:: 
* 类型对象: 类型对象<3>. 
* Number Object Structures:: 
* Mapping Object Structures:: 
* Sequence Object Structures:: 
* Buffer Object Structures:: 
* Async Object Structures:: 
* Slot Type typedefs:: 
* 例子: 例子<35>. 
* 使对象类型支持循环垃圾回收:: 

@end menu

@node 在堆上分配对象,Common Object Structures,,对象实现支持
@anchor{c-api/allocation doc}@anchor{3fe4}@anchor{c-api/allocation allocating-objects}@anchor{3fe5}@anchor{c-api/allocation allocating-objects-on-the-heap}@anchor{3fe6}
@subsection 在堆上分配对象


@geindex _PyObject_New (C 函数)
@anchor{c-api/allocation c _PyObject_New}@anchor{3fe7}
@deffn {C 函数} PyObject* _PyObject_New (PyTypeObject@w{ }*type)
@emph{Return value: New reference.}
@end deffn

@geindex _PyObject_NewVar (C 函数)
@anchor{c-api/allocation c _PyObject_NewVar}@anchor{3fe8}
@deffn {C 函数} PyVarObject* _PyObject_NewVar (PyTypeObject@w{ }*type, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
@end deffn

@geindex PyObject_Init (C 函数)
@anchor{c-api/allocation c PyObject_Init}@anchor{26f}
@deffn {C 函数} PyObject* PyObject_Init (PyObject@w{ }*op, PyTypeObject@w{ }*type)
@emph{Return value: Borrowed reference.}
用它的类型和初始引用来初始化新分配对象 @emph{op}。返回已初始化对象。如果 @emph{type} 表明该对象参与循环垃圾检测器，则将其添加到检测器的观察对象集中。 对象的其他字段不受影响。
@end deffn

@geindex PyObject_InitVar (C 函数)
@anchor{c-api/allocation c PyObject_InitVar}@anchor{3fe9}
@deffn {C 函数} PyVarObject* PyObject_InitVar (PyVarObject@w{ }*op, PyTypeObject@w{ }*type, Py_ssize_t@w{ }size)
@emph{Return value: Borrowed reference.}
它的功能和 @ref{26f,,PyObject_Init()} 一样，并且会初始化变量大小对象的长度信息。
@end deffn

@geindex PyObject_New (C 函数)
@anchor{c-api/allocation c PyObject_New}@anchor{2d2}
@deffn {C 函数} TYPE* PyObject_New (TYPE, PyTypeObject@w{ }*type)
@emph{Return value: New reference.}
使用 C 结构类型 @emph{TYPE} 和 Python 类型对象 @emph{type} 分配一个新的 Python 对象。 未在该 Python 对象标头中定义的字段不会被初始化；对象的引用计数将为一。 内存分配大小由 type 对象的 @ref{3ade,,tp_basicsize} 字段来确定。
@end deffn

@geindex PyObject_NewVar (C 函数)
@anchor{c-api/allocation c PyObject_NewVar}@anchor{2d3}
@deffn {C 函数} TYPE* PyObject_NewVar (TYPE, PyTypeObject@w{ }*type, Py_ssize_t@w{ }size)
@emph{Return value: New reference.}
使用C的数据结构类型 @emph{TYPE} 和Python的类型对象 @emph{type} 分配一个新的Python对象。Python对象头文件中没有定义的字段不会被初始化。被分配的内存空间预留了 @emph{TYPE} 结构加 @emph{type} 对象中 @ref{3add,,tp_itemsize} 字段提供的 @emph{size} 字段的值。这对于实现类似元组这种能够在构造期决定自己大小的对象是很实用的。将字段的数组嵌入到相同的内存分配中可以减少内存分配的次数，这提高了内存分配的效率。
@end deffn

@geindex PyObject_Del (C 函数)
@anchor{c-api/allocation c PyObject_Del}@anchor{e0f}
@deffn {C 函数} void PyObject_Del (void@w{ }*op)

释放由 @ref{2d2,,PyObject_New()} 或者 @ref{2d3,,PyObject_NewVar()} 分配内存的对象。这通常由对象的type字段定义的 @ref{3ae4,,tp_dealloc} 处理函数来调用。调用这个函数以后op对象中的字段都不可以被访问，因为原分配的内存空间已不再是一个有效的Python对象。
@end deffn

@geindex _Py_NoneStruct (C 变量)
@anchor{c-api/allocation c _Py_NoneStruct}@anchor{3fea}
@deffn {C 变量} PyObject _Py_NoneStruct

这个对象是像 @code{None} 一样的 Python 对象。它可以使用 @ref{3aa9,,Py_None} 宏访问，该宏的拿到指向该对象的指针。
@end deffn


@subsubheading 参见



@table @asis

@item @ref{3aac,,PyModule_Create()}

分配内存和创建扩展模块
@end table


@node Common Object Structures,类型对象<3>,在堆上分配对象,对象实现支持
@anchor{c-api/structures doc}@anchor{3feb}@anchor{c-api/structures common-object-structures}@anchor{3fec}@anchor{c-api/structures common-structs}@anchor{3fed}
@subsection Common Object Structures


There are a large number of structures which are used in the definition of
object types for Python.  This section describes these structures and how they
are used.

All Python objects ultimately share a small number of fields at the beginning
of the object's representation in memory.  These are represented by the
@ref{4b5,,PyObject} and @ref{3fee,,PyVarObject} types, which are defined, in turn,
by the expansions of some macros also used, whether directly or indirectly, in
the definition of all other Python objects.

@geindex PyObject (C 类型)
@anchor{c-api/structures c PyObject}@anchor{4b5}
@deffn {C 类型} PyObject

All object types are extensions of this type.  This is a type which
contains the information Python needs to treat a pointer to an object as an
object.  In a normal "release" build, it contains only the object's
reference count and a pointer to the corresponding type object.
Nothing is actually declared to be a @ref{4b5,,PyObject}, but every pointer
to a Python object can be cast to a @ref{4b5,,PyObject*}.  Access to the
members must be done by using the macros @ref{3ada,,Py_REFCNT} and
@ref{3adb,,Py_TYPE}.
@end deffn

@geindex PyVarObject (C 类型)
@anchor{c-api/structures c PyVarObject}@anchor{3fee}
@deffn {C 类型} PyVarObject

This is an extension of @ref{4b5,,PyObject} that adds the @code{ob_size}
field.  This is only used for objects that have some notion of @emph{length}.
This type does not often appear in the Python/C API.
Access to the members must be done by using the macros
@ref{3ada,,Py_REFCNT}, @ref{3adb,,Py_TYPE}, and @ref{3fef,,Py_SIZE}.
@end deffn

@geindex PyObject_HEAD (C 宏)
@anchor{c-api/structures c PyObject_HEAD}@anchor{c6b}
@deffn {C 宏} PyObject_HEAD

This is a macro used when declaring new types which represent objects
without a varying length.  The PyObject_HEAD macro expands to:

@example
PyObject ob_base;
@end example

See documentation of @ref{4b5,,PyObject} above.
@end deffn

@geindex PyObject_VAR_HEAD (C 宏)
@anchor{c-api/structures c PyObject_VAR_HEAD}@anchor{3ff0}
@deffn {C 宏} PyObject_VAR_HEAD

This is a macro used when declaring new types which represent objects
with a length that varies from instance to instance.
The PyObject_VAR_HEAD macro expands to:

@example
PyVarObject ob_base;
@end example

See documentation of @ref{3fee,,PyVarObject} above.
@end deffn

@geindex Py_TYPE (C 宏)
@anchor{c-api/structures c Py_TYPE}@anchor{3adb}
@deffn {C 宏} Py_TYPE (o)

This macro is used to access the @code{ob_type} member of a Python object.
It expands to:

@example
(((PyObject*)(o))->ob_type)
@end example
@end deffn

@geindex Py_REFCNT (C 宏)
@anchor{c-api/structures c Py_REFCNT}@anchor{3ada}
@deffn {C 宏} Py_REFCNT (o)

This macro is used to access the @code{ob_refcnt} member of a Python
object.
It expands to:

@example
(((PyObject*)(o))->ob_refcnt)
@end example
@end deffn

@geindex Py_SIZE (C 宏)
@anchor{c-api/structures c Py_SIZE}@anchor{3fef}
@deffn {C 宏} Py_SIZE (o)

This macro is used to access the @code{ob_size} member of a Python object.
It expands to:

@example
(((PyVarObject*)(o))->ob_size)
@end example
@end deffn

@geindex PyObject_HEAD_INIT (C 宏)
@anchor{c-api/structures c PyObject_HEAD_INIT}@anchor{3ff1}
@deffn {C 宏} PyObject_HEAD_INIT (type)

This is a macro which expands to initialization values for a new
@ref{4b5,,PyObject} type.  This macro expands to:

@example
_PyObject_EXTRA_INIT
1, type,
@end example
@end deffn

@geindex PyVarObject_HEAD_INIT (C 宏)
@anchor{c-api/structures c PyVarObject_HEAD_INIT}@anchor{3ff2}
@deffn {C 宏} PyVarObject_HEAD_INIT (type, size)

This is a macro which expands to initialization values for a new
@ref{3fee,,PyVarObject} type, including the @code{ob_size} field.
This macro expands to:

@example
_PyObject_EXTRA_INIT
1, type, size,
@end example
@end deffn

@geindex PyCFunction (C 类型)
@anchor{c-api/structures c PyCFunction}@anchor{dd4}
@deffn {C 类型} PyCFunction

Type of the functions used to implement most Python callables in C.
Functions of this type take two @ref{4b5,,PyObject*} parameters and return
one such value.  If the return value is @code{NULL}, an exception shall have
been set.  If not @code{NULL}, the return value is interpreted as the return
value of the function as exposed in Python.  The function must return a new
reference.
@end deffn

@geindex PyCFunctionWithKeywords (C 类型)
@anchor{c-api/structures c PyCFunctionWithKeywords}@anchor{3ff3}
@deffn {C 类型} PyCFunctionWithKeywords

Type of the functions used to implement Python callables in C
with signature @code{METH_VARARGS | METH_KEYWORDS}.
@end deffn

@geindex _PyCFunctionFast (C 类型)
@anchor{c-api/structures c _PyCFunctionFast}@anchor{3ff4}
@deffn {C 类型} _PyCFunctionFast

Type of the functions used to implement Python callables in C
with signature @ref{f48,,METH_FASTCALL}.
@end deffn

@geindex _PyCFunctionFastWithKeywords (C 类型)
@anchor{c-api/structures c _PyCFunctionFastWithKeywords}@anchor{3ff5}
@deffn {C 类型} _PyCFunctionFastWithKeywords

Type of the functions used to implement Python callables in C
with signature @code{METH_FASTCALL | METH_KEYWORDS}.
@end deffn

@geindex PyMethodDef (C 类型)
@anchor{c-api/structures c PyMethodDef}@anchor{e14}
@deffn {C 类型} PyMethodDef

Structure used to describe a method of an extension type.  This structure has
four fields:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

C 类型

@tab

含义

@item

@code{ml_name}

@tab

const char *

@tab

name of the method

@item

@code{ml_meth}

@tab

PyCFunction

@tab

pointer to the C
implementation

@item

@code{ml_flags}

@tab

int

@tab

flag bits indicating how the
call should be constructed

@item

@code{ml_doc}

@tab

const char *

@tab

points to the contents of the
docstring

@end multitable

@end deffn

The @code{ml_meth} is a C function pointer.  The functions may be of different
types, but they always return @ref{4b5,,PyObject*}.  If the function is not of
the @ref{dd4,,PyCFunction}, the compiler will require a cast in the method table.
Even though @ref{dd4,,PyCFunction} defines the first parameter as
@ref{4b5,,PyObject*}, it is common that the method implementation uses the
specific C type of the @emph{self} object.

The @code{ml_flags} field is a bitfield which can include the following flags.
The individual flags indicate either a calling convention or a binding
convention.

There are four basic calling conventions for positional arguments
and two of them can be combined with @code{METH_KEYWORDS} to support
also keyword arguments.  So there are a total of 6 calling conventions:

@geindex METH_VARARGS (內置变量)
@anchor{c-api/structures METH_VARARGS}@anchor{e41}
@deffn {数据} METH_VARARGS

This is the typical calling convention, where the methods have the type
@ref{dd4,,PyCFunction}. The function expects two @ref{4b5,,PyObject*} values.
The first one is the @emph{self} object for methods; for module functions, it is
the module object.  The second parameter (often called @emph{args}) is a tuple
object representing all arguments. This parameter is typically processed
using @ref{26a,,PyArg_ParseTuple()} or @ref{e3f,,PyArg_UnpackTuple()}.
@end deffn


@deffn {数据} METH_VARARGS | METH_KEYWORDS

Methods with these flags must be of type @ref{3ff3,,PyCFunctionWithKeywords}.
The function expects three parameters: @emph{self}, @emph{args}, @emph{kwargs} where
@emph{kwargs} is a dictionary of all the keyword arguments or possibly @code{NULL}
if there are no keyword arguments.  The parameters are typically processed
using @ref{5c5,,PyArg_ParseTupleAndKeywords()}.
@end deffn

@geindex METH_FASTCALL (內置变量)
@anchor{c-api/structures METH_FASTCALL}@anchor{f48}
@deffn {数据} METH_FASTCALL

Fast calling convention supporting only positional arguments.
The methods have the type @ref{3ff4,,_PyCFunctionFast}.
The first parameter is @emph{self}, the second parameter is a C array
of @ref{4b5,,PyObject*} values indicating the arguments and the third
parameter is the number of arguments (the length of the array).

This is not part of the @ref{3b66,,limited API}.


3.7 新版功能.

@end deffn


@deffn {数据} METH_FASTCALL | METH_KEYWORDS

Extension of @ref{f48,,METH_FASTCALL} supporting also keyword arguments,
with methods of type @ref{3ff5,,_PyCFunctionFastWithKeywords}.
Keyword arguments are passed the same way as in the vectorcall protocol:
there is an additional fourth @ref{4b5,,PyObject*} parameter
which is a tuple representing the names of the keyword arguments
or possibly @code{NULL} if there are no keywords.  The values of the keyword
arguments are stored in the @emph{args} array, after the positional arguments.

This is not part of the @ref{3b66,,limited API}.


3.7 新版功能.

@end deffn

@geindex METH_NOARGS (內置变量)
@anchor{c-api/structures METH_NOARGS}@anchor{e11}
@deffn {数据} METH_NOARGS

Methods without parameters don't need to check whether arguments are given if
they are listed with the @ref{e11,,METH_NOARGS} flag.  They need to be of type
@ref{dd4,,PyCFunction}.  The first parameter is typically named @emph{self} and will
hold a reference to the module or object instance.  In all cases the second
parameter will be @code{NULL}.
@end deffn

@geindex METH_O (內置变量)
@anchor{c-api/structures METH_O}@anchor{e40}
@deffn {数据} METH_O

Methods with a single object argument can be listed with the @ref{e40,,METH_O}
flag, instead of invoking @ref{26a,,PyArg_ParseTuple()} with a @code{"O"} argument.
They have the type @ref{dd4,,PyCFunction}, with the @emph{self} parameter, and a
@ref{4b5,,PyObject*} parameter representing the single argument.
@end deffn

These two constants are not used to indicate the calling convention but the
binding when use with methods of classes.  These may not be used for functions
defined for modules.  At most one of these flags may be set for any given
method.

@geindex METH_CLASS (內置变量)
@anchor{c-api/structures METH_CLASS}@anchor{e12}
@deffn {数据} METH_CLASS

@geindex 內置函数; classmethod

The method will be passed the type object as the first parameter rather
than an instance of the type.  This is used to create @emph{class methods},
similar to what is created when using the @ref{1d8,,classmethod()} built-in
function.
@end deffn

@geindex METH_STATIC (內置变量)
@anchor{c-api/structures METH_STATIC}@anchor{e13}
@deffn {数据} METH_STATIC

@geindex 內置函数; staticmethod

The method will be passed @code{NULL} as the first parameter rather than an
instance of the type.  This is used to create @emph{static methods}, similar to
what is created when using the @ref{1d9,,staticmethod()} built-in function.
@end deffn

One other constant controls whether a method is loaded in place of another
definition with the same method name.

@geindex METH_COEXIST (內置变量)
@anchor{c-api/structures METH_COEXIST}@anchor{3ff6}
@deffn {数据} METH_COEXIST

The method will be loaded in place of existing definitions.  Without
@emph{METH_COEXIST}, the default is to skip repeated definitions.  Since slot
wrappers are loaded before the method table, the existence of a
@emph{sq_contains} slot, for example, would generate a wrapped method named
@ref{d21,,__contains__()} and preclude the loading of a corresponding
PyCFunction with the same name.  With the flag defined, the PyCFunction
will be loaded in place of the wrapper object and will co-exist with the
slot.  This is helpful because calls to PyCFunctions are optimized more
than wrapper object calls.
@end deffn

@geindex PyMemberDef (C 类型)
@anchor{c-api/structures c PyMemberDef}@anchor{420}
@deffn {C 类型} PyMemberDef

Structure which describes an attribute of a type which corresponds to a C
struct member.  Its fields are:


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

C 类型

@tab

含义

@item

@code{name}

@tab

const char *

@tab

name of the member

@item

@code{type}

@tab

int

@tab

the type of the member in the
C struct

@item

@code{offset}

@tab

Py_ssize_t

@tab

the offset in bytes that the
member is located on the
type's object struct

@item

@code{flags}

@tab

int

@tab

flag bits indicating if the
field should be read-only or
writable

@item

@code{doc}

@tab

const char *

@tab

points to the contents of the
docstring

@end multitable


@code{type} can be one of many @code{T_} macros corresponding to various C
types.  When the member is accessed in Python, it will be converted to the
equivalent Python type.


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} 
@headitem

Macro name

@tab

C 类型

@item

T_SHORT

@tab

short

@item

T_INT

@tab

int

@item

T_LONG

@tab

长整型

@item

T_FLOAT

@tab

float

@item

T_DOUBLE

@tab

double

@item

T_STRING

@tab

const char *

@item

T_OBJECT

@tab

PyObject *

@item

T_OBJECT_EX

@tab

PyObject *

@item

T_CHAR

@tab

char

@item

T_BYTE

@tab

char

@item

T_UBYTE

@tab

unsigned char

@item

T_UINT

@tab

unsigned int

@item

T_USHORT

@tab

unsigned short

@item

T_ULONG

@tab

unsigned long

@item

T_BOOL

@tab

char

@item

T_LONGLONG

@tab

long long

@item

T_ULONGLONG

@tab

unsigned long long

@item

T_PYSSIZET

@tab

Py_ssize_t

@end multitable


@code{T_OBJECT} and @code{T_OBJECT_EX} differ in that
@code{T_OBJECT} returns @code{None} if the member is @code{NULL} and
@code{T_OBJECT_EX} raises an @ref{393,,AttributeError}.  Try to use
@code{T_OBJECT_EX} over @code{T_OBJECT} because @code{T_OBJECT_EX}
handles use of the @ref{1202,,del} statement on that attribute more correctly
than @code{T_OBJECT}.

@code{flags} can be @code{0} for write and read access or @code{READONLY} for
read-only access.  Using @code{T_STRING} for @ref{603,,type} implies
@code{READONLY}.  @code{T_STRING} data is interpreted as UTF-8.
Only @code{T_OBJECT} and @code{T_OBJECT_EX}
members can be deleted.  (They are set to @code{NULL}).
@end deffn

@geindex PyGetSetDef (C 类型)
@anchor{c-api/structures c PyGetSetDef}@anchor{421}
@deffn {C 类型} PyGetSetDef

Structure to define property-like access for a type. See also description of
the @ref{3aef,,PyTypeObject.tp_getset} slot.


@multitable {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

域

@tab

C 类型

@tab

含义

@item

名称

@tab

const char *

@tab

attribute name

@item

get

@tab

getter

@tab

C Function to get the attribute

@item

set

@tab

setter

@tab

optional C function to set or
delete the attribute, if omitted
the attribute is readonly

@item

doc

@tab

const char *

@tab

optional docstring

@item

closure

@tab

void *

@tab

optional function pointer,
providing additional data for
getter and setter

@end multitable


The @code{get} function takes one @ref{4b5,,PyObject*} parameter (the
instance) and a function pointer (the associated @code{closure}):

@example
typedef PyObject *(*getter)(PyObject *, void *);
@end example

It should return a new reference on success or @code{NULL} with a set exception
on failure.

@code{set} functions take two @ref{4b5,,PyObject*} parameters (the instance and
the value to be set) and a function pointer (the associated @code{closure}):

@example
typedef int (*setter)(PyObject *, PyObject *, void *);
@end example

In case the attribute should be deleted the second parameter is @code{NULL}.
Should return @code{0} on success or @code{-1} with a set exception on failure.
@end deffn

@node 类型对象<3>,Number Object Structures,Common Object Structures,对象实现支持
@anchor{c-api/typeobj doc}@anchor{3ff7}@anchor{c-api/typeobj type-objects}@anchor{3ff8}@anchor{c-api/typeobj type-structs}@anchor{3adc}
@subsection 类型对象


Perhaps one of the most important structures of the Python object system is the
structure that defines a new type: the @ref{2d6,,PyTypeObject} structure.  Type
objects can be handled using any of the @code{PyObject_*()} or
@code{PyType_*()} functions, but do not offer much that's interesting to most
Python applications. These objects are fundamental to how objects behave, so
they are very important to the interpreter itself and to any extension module
that implements new types.

Type objects are fairly large compared to most of the standard types. The reason
for the size is that each type object stores a large number of values, mostly C
function pointers, each of which implements a small part of the type's
functionality.  The fields of the type object are examined in detail in this
section.  The fields will be described in the order in which they occur in the
structure.

In addition to the following quick reference, the @ref{3ff9,,例子}
section provides at-a-glance insight into the meaning and use of
@ref{2d6,,PyTypeObject}.

@menu
* 快速参考:: 
* PyTypeObject Definition:: 
* PyObject Slots:: 
* PyVarObject Slots:: 
* PyTypeObject Slots:: 
* Heap Types:: 

@end menu

@node 快速参考,PyTypeObject Definition,,类型对象<3>
@anchor{c-api/typeobj quick-reference}@anchor{3ffa}
@subsubsection 快速参考


@menu
* "tp 槽":: 
* sub-slots:: 
* slot typedefs:: 

@end menu

@node "tp 槽",sub-slots,,快速参考
@anchor{c-api/typeobj tp-slots}@anchor{3ffb}@anchor{c-api/typeobj tp-slots-table}@anchor{3ffc}
@subsubsection "tp 槽"



@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} {xxx} {xxx} {xxx} {xxx} 
@headitem

PyTypeObject 槽 @footnote{@w{(1)} 
A slot name in parentheses indicates it is (effectively) deprecated.
Names in angle brackets should be treated as read-only.
Names in square brackets are for internal use only.
"<R>" (as a prefix) means the field is required (must be non-@code{NULL}).
}

@tab

@ref{3ffd,,Type}

@tab

特殊方法/属性

@tab

信息 @footnote{@w{(2)} 
列：

@strong{"O"}:  set on @code{PyBaseObject_Type}

@strong{"T"}:  set on @ref{3d01,,PyType_Type}

@strong{"D"}:  default (if slot is set to @code{NULL})

@example
X - PyType_Ready sets this value if it is NULL
~ - PyType_Ready always sets this value (it should be NULL)
? - PyType_Ready may set this value depending on other slots

Also see the inheritance column ("I").
@end example

@strong{"I"}:  inheritance

@example
X - type slot is inherited via PyType_Ready if defined with a NULL value
% - the slots of the sub-struct are inherited individually
G - inherited, but only in combination with other slots; see the slot's description
? - it's complicated; see the slot's description
@end example

Note that some slots are effectively inherited through the normal
attribute lookup chain.
}

@tab

@tab

@tab

@item

O

@tab

T

@tab

D

@tab

I

@item

<R> @ref{3b00,,tp_name}

@tab

const char *

@tab

__name__

@tab

X

@tab

X

@tab

@tab

@item

@ref{3ade,,tp_basicsize}

@tab

Py_ssize_t

@tab

@tab

X

@tab

X

@tab

@tab

X

@item

@ref{3add,,tp_itemsize}

@tab

Py_ssize_t

@tab

@tab

@tab

X

@tab

@tab

X

@item

@ref{3ae4,,tp_dealloc}

@tab

@ref{3ffe,,destructor}

@tab

@tab

X

@tab

X

@tab

@tab

X

@item

@ref{3c67,,tp_vectorcall_offset}

@tab

Py_ssize_t

@tab

@tab

@tab

@tab

@tab

?

@item

(@ref{3b07,,tp_getattr})

@tab

@ref{3fff,,getattrfunc}

@tab

__getattribute__,
__getattr__

@tab

@tab

@tab

@tab

G

@item

(@ref{3b08,,tp_setattr})

@tab

@ref{4000,,setattrfunc}

@tab

__setattr__,
__delattr__

@tab

@tab

@tab

@tab

G

@item

@ref{4001,,tp_as_async}

@tab

@ref{3d17,,PyAsyncMethods} *

@tab

@ref{4002,,sub-slots}

@tab

@tab

@tab

@tab

%

@item

@ref{3aff,,tp_repr}

@tab

@ref{4003,,reprfunc}

@tab

__repr__

@tab

X

@tab

X

@tab

@tab

X

@item

@ref{4004,,tp_as_number}

@tab

@ref{d7a,,PyNumberMethods} *

@tab

@ref{4002,,sub-slots}

@tab

@tab

@tab

@tab

%

@item

@ref{4005,,tp_as_sequence}

@tab

@ref{3b0e,,PySequenceMethods} *

@tab

@ref{4002,,sub-slots}

@tab

@tab

@tab

@tab

%

@item

@ref{4006,,tp_as_mapping}

@tab

@ref{3b0f,,PyMappingMethods} *

@tab

@ref{4002,,sub-slots}

@tab

@tab

@tab

@tab

%

@item

@ref{3b10,,tp_hash}

@tab

@ref{4007,,hashfunc}

@tab

__hash__

@tab

X

@tab

@tab

@tab

G

@item

@ref{3b11,,tp_call}

@tab

@ref{4008,,ternaryfunc}

@tab

__call__

@tab

@tab

X

@tab

@tab

X

@item

@ref{3b01,,tp_str}

@tab

@ref{4003,,reprfunc}

@tab

__str__

@tab

X

@tab

@tab

@tab

X

@item

@ref{3b04,,tp_getattro}

@tab

@ref{4009,,getattrofunc}

@tab

__getattribute__,
__getattr__

@tab

X

@tab

X

@tab

@tab

G

@item

@ref{3b05,,tp_setattro}

@tab

@ref{400a,,setattrofunc}

@tab

__setattr__,
__delattr__

@tab

X

@tab

X

@tab

@tab

G

@item

@ref{400b,,tp_as_buffer}

@tab

@ref{400c,,PyBufferProcs} *

@tab

@tab

@tab

@tab

@tab

%

@item

@ref{3d06,,tp_flags}

@tab

unsigned long

@tab

@tab

X

@tab

X

@tab

@tab

?

@item

@ref{3ae0,,tp_doc}

@tab

const char *

@tab

__doc__

@tab

X

@tab

X

@tab

@tab

@item

@ref{3664,,tp_traverse}

@tab

@ref{400d,,traverseproc}

@tab

@tab

@tab

X

@tab

@tab

G

@item

@ref{3afd,,tp_clear}

@tab

@ref{400e,,inquiry}

@tab

@tab

@tab

X

@tab

@tab

G

@item

@ref{3b0a,,tp_richcompare}

@tab

@ref{400f,,richcmpfunc}

@tab

__lt__,
__le__,
__eq__,
__ne__,
__gt__,
__ge__

@tab

X

@tab

@tab

@tab

G

@item

@ref{3b13,,tp_weaklistoffset}

@tab

Py_ssize_t

@tab

@tab

@tab

X

@tab

@tab

?

@item

@ref{e29,,tp_iter}

@tab

@ref{4010,,getiterfunc}

@tab

__iter__

@tab

@tab

@tab

@tab

X

@item

@ref{e2a,,tp_iternext}

@tab

@ref{4011,,iternextfunc}

@tab

__next__

@tab

@tab

@tab

@tab

X

@item

@ref{3aeb,,tp_methods}

@tab

@ref{e14,,PyMethodDef} []

@tab

@tab

X

@tab

X

@tab

@tab

@item

@ref{3ae9,,tp_members}

@tab

@ref{420,,PyMemberDef} []

@tab

@tab

@tab

X

@tab

@tab

@item

@ref{3aef,,tp_getset}

@tab

@ref{421,,PyGetSetDef} []

@tab

@tab

X

@tab

X

@tab

@tab

@item

@ref{3af5,,tp_base}

@tab

@ref{2d6,,PyTypeObject} *

@tab

__base__

@tab

@tab

@tab

X

@tab

@item

@ref{3d1a,,tp_dict}

@tab

@ref{4b5,,PyObject} *

@tab

__dict__

@tab

@tab

@tab

?

@tab

@item

@ref{4012,,tp_descr_get}

@tab

@ref{4013,,descrgetfunc}

@tab

__get__

@tab

@tab

@tab

@tab

X

@item

@ref{4014,,tp_descr_set}

@tab

@ref{4015,,descrsetfunc}

@tab

__set__,
__delete__

@tab

@tab

@tab

@tab

X

@item

@ref{3d1f,,tp_dictoffset}

@tab

Py_ssize_t

@tab

@tab

@tab

X

@tab

@tab

?

@item

@ref{3ae8,,tp_init}

@tab

@ref{4016,,initproc}

@tab

__init__

@tab

X

@tab

X

@tab

@tab

X

@item

@ref{3ae6,,tp_alloc}

@tab

@ref{4017,,allocfunc}

@tab

@tab

X

@tab

@tab

?

@tab

?

@item

@ref{3ae1,,tp_new}

@tab

@ref{4018,,newfunc}

@tab

__new__

@tab

X

@tab

X

@tab

?

@tab

?

@item

@ref{3ae5,,tp_free}

@tab

@ref{4019,,freefunc}

@tab

@tab

X

@tab

X

@tab

?

@tab

?

@item

@ref{401a,,tp_is_gc}

@tab

@ref{400e,,inquiry}

@tab

@tab

@tab

X

@tab

@tab

X

@item

<@ref{401b,,tp_bases}>

@tab

@ref{4b5,,PyObject} *

@tab

__bases__

@tab

@tab

@tab

~

@tab

@item

<@ref{3d1b,,tp_mro}>

@tab

@ref{4b5,,PyObject} *

@tab

__mro__

@tab

@tab

@tab

~

@tab

@item

[@ref{3d1c,,tp_cache}]

@tab

@ref{4b5,,PyObject} *

@tab

@tab

@tab

@tab

@tab

@item

[@ref{3d1d,,tp_subclasses}]

@tab

@ref{4b5,,PyObject} *

@tab

__subclasses__

@tab

@tab

@tab

@tab

@item

[@ref{3d1e,,tp_weaklist}]

@tab

@ref{4b5,,PyObject} *

@tab

@tab

@tab

@tab

@tab

@item

(@ref{401c,,tp_del})

@tab

@ref{3ffe,,destructor}

@tab

@tab

@tab

@tab

@tab

@item

[@ref{401d,,tp_version_tag}]

@tab

unsigned int

@tab

@tab

@tab

@tab

@tab

@item

@ref{2d7,,tp_finalize}

@tab

@ref{3ffe,,destructor}

@tab

__del__

@tab

@tab

@tab

@tab

X

@end multitable


如果定义了 @code{COUNT_ALLOCS} ，则还存在以下（仅内部）字段：


@itemize *

@item 
@ref{401e,,tp_allocs}

@item 
@ref{401f,,tp_frees}

@item 
@ref{4020,,tp_maxalloc}

@item 
@ref{4021,,tp_prev}

@item 
@ref{4022,,tp_next}
@end itemize

@node sub-slots,slot typedefs,"tp 槽",快速参考
@anchor{c-api/typeobj id3}@anchor{4023}@anchor{c-api/typeobj sub-slots}@anchor{4002}
@subsubsection sub-slots



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} 
@headitem

槽

@tab

@ref{3ffd,,Type}

@tab

特殊方法

@item

@ref{4024,,am_await}

@tab

@ref{4025,,unaryfunc}

@tab

__await__

@item

@ref{4026,,am_aiter}

@tab

@ref{4025,,unaryfunc}

@tab

__aiter__

@item

@ref{4027,,am_anext}

@tab

@ref{4025,,unaryfunc}

@tab

__anext__

@item

@tab

@tab

@item

@ref{3d18,,nb_add}

@tab

@ref{4028,,binaryfunc}

@tab

__add__
__radd__

@item

@ref{4029,,nb_inplace_add}

@tab

@ref{4028,,binaryfunc}

@tab

__iadd__

@item

@ref{402a,,nb_subtract}

@tab

@ref{4028,,binaryfunc}

@tab

__sub__
__rsub__

@item

@ref{402b,,nb_inplace_subtract}

@tab

@ref{4028,,binaryfunc}

@tab

__sub__

@item

@ref{402c,,nb_multiply}

@tab

@ref{4028,,binaryfunc}

@tab

__mul__
__rmul__

@item

@ref{402d,,nb_inplace_multiply}

@tab

@ref{4028,,binaryfunc}

@tab

__mul__

@item

@ref{402e,,nb_remainder}

@tab

@ref{4028,,binaryfunc}

@tab

__mod__
__rmod__

@item

@ref{402f,,nb_inplace_remainder}

@tab

@ref{4028,,binaryfunc}

@tab

__mod__

@item

@ref{4030,,nb_divmod}

@tab

@ref{4028,,binaryfunc}

@tab

__divmod__
__rdivmod__

@item

@ref{4031,,nb_power}

@tab

@ref{4008,,ternaryfunc}

@tab

__pow__
__rpow__

@item

@ref{4032,,nb_inplace_power}

@tab

@ref{4008,,ternaryfunc}

@tab

__pow__

@item

@ref{4033,,nb_negative}

@tab

@ref{4025,,unaryfunc}

@tab

__neg__

@item

@ref{4034,,nb_positive}

@tab

@ref{4025,,unaryfunc}

@tab

__pos__

@item

@ref{4035,,nb_absolute}

@tab

@ref{4025,,unaryfunc}

@tab

__abs__

@item

@ref{4036,,nb_bool}

@tab

@ref{400e,,inquiry}

@tab

__bool__

@item

@ref{4037,,nb_invert}

@tab

@ref{4025,,unaryfunc}

@tab

__invert__

@item

@ref{4038,,nb_lshift}

@tab

@ref{4028,,binaryfunc}

@tab

__lshift__
__rlshift__

@item

@ref{4039,,nb_inplace_lshift}

@tab

@ref{4028,,binaryfunc}

@tab

__lshift__

@item

@ref{403a,,nb_rshift}

@tab

@ref{4028,,binaryfunc}

@tab

__rshift__
__rrshift__

@item

@ref{403b,,nb_inplace_rshift}

@tab

@ref{4028,,binaryfunc}

@tab

__rshift__

@item

@ref{403c,,nb_and}

@tab

@ref{4028,,binaryfunc}

@tab

__and__
__rand__

@item

@ref{403d,,nb_inplace_and}

@tab

@ref{4028,,binaryfunc}

@tab

__and__

@item

@ref{403e,,nb_xor}

@tab

@ref{4028,,binaryfunc}

@tab

__xor__
__rxor__

@item

@ref{403f,,nb_inplace_xor}

@tab

@ref{4028,,binaryfunc}

@tab

__xor__

@item

@ref{4040,,nb_or}

@tab

@ref{4028,,binaryfunc}

@tab

__or__
__ror__

@item

@ref{4041,,nb_inplace_or}

@tab

@ref{4028,,binaryfunc}

@tab

__or__

@item

@ref{4042,,nb_int}

@tab

@ref{4025,,unaryfunc}

@tab

__int__

@item

@ref{4043,,nb_reserved}

@tab

void *

@tab

@item

@ref{4044,,nb_float}

@tab

@ref{4025,,unaryfunc}

@tab

__float__

@item

@ref{4045,,nb_floor_divide}

@tab

@ref{4028,,binaryfunc}

@tab

__floordiv__

@item

@ref{4046,,nb_inplace_floor_divide}

@tab

@ref{4028,,binaryfunc}

@tab

__floordiv__

@item

@ref{4047,,nb_true_divide}

@tab

@ref{4028,,binaryfunc}

@tab

__truediv__

@item

@ref{4048,,nb_inplace_true_divide}

@tab

@ref{4028,,binaryfunc}

@tab

__truediv__

@item

@ref{4049,,nb_index}

@tab

@ref{4025,,unaryfunc}

@tab

__index__

@item

@ref{404a,,nb_matrix_multiply}

@tab

@ref{4028,,binaryfunc}

@tab

__matmul__
__rmatmul__

@item

@ref{404b,,nb_inplace_matrix_multiply}

@tab

@ref{4028,,binaryfunc}

@tab

__matmul__

@item

@tab

@tab

@item

@ref{404c,,mp_length}

@tab

@ref{404d,,lenfunc}

@tab

__len__

@item

@ref{404e,,mp_subscript}

@tab

@ref{4028,,binaryfunc}

@tab

__getitem__

@item

@ref{404f,,mp_ass_subscript}

@tab

@ref{4050,,objobjargproc}

@tab

__setitem__,
__delitem__

@item

@tab

@tab

@item

@ref{3d19,,sq_length}

@tab

@ref{404d,,lenfunc}

@tab

__len__

@item

@ref{4051,,sq_concat}

@tab

@ref{4028,,binaryfunc}

@tab

__add__

@item

@ref{4052,,sq_repeat}

@tab

@ref{4053,,ssizeargfunc}

@tab

__mul__

@item

@ref{4054,,sq_item}

@tab

@ref{4053,,ssizeargfunc}

@tab

__getitem__

@item

@ref{4055,,sq_ass_item}

@tab

@ref{4056,,ssizeobjargproc}

@tab

__setitem__
__delitem__

@item

@ref{4057,,sq_contains}

@tab

@ref{4058,,objobjproc}

@tab

__contains__

@item

@ref{4059,,sq_inplace_concat}

@tab

@ref{4028,,binaryfunc}

@tab

__iadd__

@item

@ref{405a,,sq_inplace_repeat}

@tab

@ref{4053,,ssizeargfunc}

@tab

__imul__

@item

@tab

@tab

@item

@ref{3d20,,bf_getbuffer}

@tab

@ref{405b,,getbufferproc()}

@tab

@item

@ref{3c21,,bf_releasebuffer}

@tab

@ref{405c,,releasebufferproc()}

@tab

@end multitable


@node slot typedefs,,sub-slots,快速参考
@anchor{c-api/typeobj slot-typedefs}@anchor{405d}@anchor{c-api/typeobj slot-typedefs-table}@anchor{3ffd}
@subsubsection slot typedefs



@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

typedef

@tab

参数类型

@tab

返回类型

@item

@ref{4017,,allocfunc}

@tab


@display
@ref{2d6,,PyTypeObject} *@w{ }
Py_ssize_t@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{3ffe,,destructor}

@tab

void *

@tab

void

@item

@ref{4019,,freefunc}

@tab

void *

@tab

void

@item

@ref{400d,,traverseproc}

@tab


@display
void *@w{ }
@ref{405e,,visitproc}@w{ }
void *@w{ }
@end display



@tab

int

@item

@ref{4018,,newfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{4016,,initproc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

int

@item

@ref{4003,,reprfunc}

@tab

@ref{4b5,,PyObject} *

@tab

@ref{4b5,,PyObject} *

@item

@ref{3fff,,getattrfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
const char *@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{4000,,setattrfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
const char *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

int

@item

@ref{4009,,getattrofunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{400a,,setattrofunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

int

@item

@ref{4013,,descrgetfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{4015,,descrsetfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

int

@item

@ref{4007,,hashfunc}

@tab

@ref{4b5,,PyObject} *

@tab

Py_hash_t

@item

@ref{400f,,richcmpfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
int@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{4010,,getiterfunc}

@tab

@ref{4b5,,PyObject} *

@tab

@ref{4b5,,PyObject} *

@item

@ref{4011,,iternextfunc}

@tab

@ref{4b5,,PyObject} *

@tab

@ref{4b5,,PyObject} *

@item

@ref{404d,,lenfunc}

@tab

@ref{4b5,,PyObject} *

@tab

Py_ssize_t

@item

@ref{405b,,getbufferproc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{b14,,Py_buffer} *@w{ }
int@w{ }
@end display



@tab

int

@item

@ref{405c,,releasebufferproc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{b14,,Py_buffer} *@w{ }
@end display



@tab

void

@item

@ref{400e,,inquiry}

@tab

void *

@tab

int

@item

@ref{4025,,unaryfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{4028,,binaryfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{4008,,ternaryfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{4053,,ssizeargfunc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
Py_ssize_t@w{ }
@end display



@tab

@ref{4b5,,PyObject} *

@item

@ref{4056,,ssizeobjargproc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
Py_ssize_t@w{ }
@end display



@tab

int

@item

@ref{4058,,objobjproc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

int

@item

@ref{4050,,objobjargproc}

@tab


@display
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@ref{4b5,,PyObject} *@w{ }
@end display



@tab

int

@end multitable


请参阅 @ref{405f,,Slot Type typedefs} 里有更多详细信息。

@node PyTypeObject Definition,PyObject Slots,快速参考,类型对象<3>
@anchor{c-api/typeobj pytypeobject-definition}@anchor{4060}
@subsubsection PyTypeObject Definition


The structure definition for @ref{2d6,,PyTypeObject} can be found in
@code{Include/object.h}.  For convenience of reference, this repeats the
definition found there:

@c XXX Drop this?

@example
typedef struct _typeobject @{
    PyObject_VAR_HEAD
    const char *tp_name; /* For printing, in format "<module>.<name>" */
    Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */

    /* Methods to implement standard operations */

    destructor tp_dealloc;
    Py_ssize_t tp_vectorcall_offset;
    getattrfunc tp_getattr;
    setattrfunc tp_setattr;
    PyAsyncMethods *tp_as_async; /* formerly known as tp_compare (Python 2)
                                    or tp_reserved (Python 3) */
    reprfunc tp_repr;

    /* Method suites for standard classes */

    PyNumberMethods *tp_as_number;
    PySequenceMethods *tp_as_sequence;
    PyMappingMethods *tp_as_mapping;

    /* More standard operations (here for binary compatibility) */

    hashfunc tp_hash;
    ternaryfunc tp_call;
    reprfunc tp_str;
    getattrofunc tp_getattro;
    setattrofunc tp_setattro;

    /* Functions to access object as input/output buffer */
    PyBufferProcs *tp_as_buffer;

    /* Flags to define presence of optional/expanded features */
    unsigned long tp_flags;

    const char *tp_doc; /* Documentation string */

    /* call function for all accessible objects */
    traverseproc tp_traverse;

    /* delete references to contained objects */
    inquiry tp_clear;

    /* rich comparisons */
    richcmpfunc tp_richcompare;

    /* weak reference enabler */
    Py_ssize_t tp_weaklistoffset;

    /* Iterators */
    getiterfunc tp_iter;
    iternextfunc tp_iternext;

    /* Attribute descriptor and subclassing stuff */
    struct PyMethodDef *tp_methods;
    struct PyMemberDef *tp_members;
    struct PyGetSetDef *tp_getset;
    struct _typeobject *tp_base;
    PyObject *tp_dict;
    descrgetfunc tp_descr_get;
    descrsetfunc tp_descr_set;
    Py_ssize_t tp_dictoffset;
    initproc tp_init;
    allocfunc tp_alloc;
    newfunc tp_new;
    freefunc tp_free; /* Low-level free-memory routine */
    inquiry tp_is_gc; /* For PyObject_IS_GC */
    PyObject *tp_bases;
    PyObject *tp_mro; /* method resolution order */
    PyObject *tp_cache;
    PyObject *tp_subclasses;
    PyObject *tp_weaklist;
    destructor tp_del;

    /* Type attribute cache version tag. Added in version 2.6 */
    unsigned int tp_version_tag;

    destructor tp_finalize;

@} PyTypeObject;
@end example

@node PyObject Slots,PyVarObject Slots,PyTypeObject Definition,类型对象<3>
@anchor{c-api/typeobj pyobject-slots}@anchor{4061}
@subsubsection PyObject Slots


The type object structure extends the @ref{3fee,,PyVarObject} structure. The
@code{ob_size} field is used for dynamic types (created by  @code{type_new()},
usually called from a class statement). Note that @ref{3d01,,PyType_Type} (the
metatype) initializes @ref{3add,,tp_itemsize}, which means that its instances (i.e.
type objects) @emph{must} have the @code{ob_size} field.

@geindex PyObject._ob_next (C 成员)
@geindex PyObject._ob_prev (C 成员)
@anchor{c-api/typeobj c PyObject _ob_next}@anchor{4062}
@deffn {C 成员} PyObject* PyObject._ob_next
@anchor{c-api/typeobj c PyObject _ob_prev}@anchor{4063}
@deffnx {C 成员} PyObject* PyObject._ob_prev

These fields are only present when the macro @code{Py_TRACE_REFS} is defined.
Their initialization to @code{NULL} is taken care of by the @code{PyObject_HEAD_INIT}
macro.  For statically allocated objects, these fields always remain @code{NULL}.
For dynamically allocated objects, these two fields are used to link the object
into a doubly-linked list of @emph{all} live objects on the heap.  This could be used
for various debugging purposes; currently the only use is to print the objects
that are still alive at the end of a run when the environment variable
@geindex PYTHONDUMPREFS
@geindex 环境变量; PYTHONDUMPREFS
@ref{159,,PYTHONDUMPREFS} is set.

@strong{Inheritance:}

These fields are not inherited by subtypes.
@end deffn

@geindex PyObject.ob_refcnt (C 成员)
@anchor{c-api/typeobj c PyObject ob_refcnt}@anchor{4064}
@deffn {C 成员} Py_ssize_t PyObject.ob_refcnt

This is the type object's reference count, initialized to @code{1} by the
@code{PyObject_HEAD_INIT} macro.  Note that for statically allocated type objects,
the type's instances (objects whose @code{ob_type} points back to the type) do
@emph{not} count as references.  But for dynamically allocated type objects, the
instances @emph{do} count as references.

@strong{Inheritance:}

This field is not inherited by subtypes.
@end deffn

@geindex PyObject.ob_type (C 成员)
@anchor{c-api/typeobj c PyObject ob_type}@anchor{4065}
@deffn {C 成员} PyTypeObject* PyObject.ob_type

This is the type's type, in other words its metatype.  It is initialized by the
argument to the @code{PyObject_HEAD_INIT} macro, and its value should normally be
@code{&PyType_Type}.  However, for dynamically loadable extension modules that must
be usable on Windows (at least), the compiler complains that this is not a valid
initializer.  Therefore, the convention is to pass @code{NULL} to the
@code{PyObject_HEAD_INIT} macro and to initialize this field explicitly at the
start of the module's initialization function, before doing anything else.  This
is typically done like this:

@example
Foo_Type.ob_type = &PyType_Type;
@end example

This should be done before any instances of the type are created.
@ref{3ae7,,PyType_Ready()} checks if @code{ob_type} is @code{NULL}, and if so,
initializes it to the @code{ob_type} field of the base class.
@ref{3ae7,,PyType_Ready()} will not change this field if it is non-zero.

@strong{Inheritance:}

This field is inherited by subtypes.
@end deffn

@node PyVarObject Slots,PyTypeObject Slots,PyObject Slots,类型对象<3>
@anchor{c-api/typeobj pyvarobject-slots}@anchor{4066}
@subsubsection PyVarObject Slots


@geindex PyVarObject.ob_size (C 成员)
@anchor{c-api/typeobj c PyVarObject ob_size}@anchor{4067}
@deffn {C 成员} Py_ssize_t PyVarObject.ob_size

For statically allocated type objects, this should be initialized to zero.  For
dynamically allocated type objects, this field has a special internal meaning.

@strong{Inheritance:}

This field is not inherited by subtypes.
@end deffn

@node PyTypeObject Slots,Heap Types,PyVarObject Slots,类型对象<3>
@anchor{c-api/typeobj pytypeobject-slots}@anchor{4068}
@subsubsection PyTypeObject Slots


Each slot has a section describing inheritance.  If @ref{3ae7,,PyType_Ready()}
may set a value when the field is set to @code{NULL} then there will also be
a "Default" section.  (Note that many fields set on @code{PyBaseObject_Type}
and @ref{3d01,,PyType_Type} effectively act as defaults.)

@geindex PyTypeObject.tp_name (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_name}@anchor{3b00}
@deffn {C 成员} const char* PyTypeObject.tp_name

Pointer to a NUL-terminated string containing the name of the type. For types
that are accessible as module globals, the string should be the full module
name, followed by a dot, followed by the type name; for built-in types, it
should be just the type name.  If the module is a submodule of a package, the
full package name is part of the full module name.  For example, a type named
@code{T} defined in module @code{M} in subpackage @code{Q} in package @code{P}
should have the @ref{3b00,,tp_name} initializer @code{"P.Q.M.T"}.

For dynamically allocated type objects, this should just be the type name, and
the module name explicitly stored in the type dict as the value for key
@code{'__module__'}.

For statically allocated type objects, the tp_name field should contain a dot.
Everything before the last dot is made accessible as the @code{__module__}
attribute, and everything after the last dot is made accessible as the
@ref{c60,,__name__} attribute.

If no dot is present, the entire @ref{3b00,,tp_name} field is made accessible as the
@ref{c60,,__name__} attribute, and the @code{__module__} attribute is undefined
(unless explicitly set in the dictionary, as explained above).  This means your
type will be impossible to pickle.  Additionally, it will not be listed in
module documentations created with pydoc.

This field must not be @code{NULL}.  It is the only required field
in @ref{2d6,,PyTypeObject()} (other than potentially
@ref{3add,,tp_itemsize}).

@strong{Inheritance:}

This field is not inherited by subtypes.
@end deffn

@geindex PyTypeObject.tp_basicsize (C 成员)
@geindex PyTypeObject.tp_itemsize (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_basicsize}@anchor{3ade}
@deffn {C 成员} Py_ssize_t PyTypeObject.tp_basicsize
@anchor{c-api/typeobj c PyTypeObject tp_itemsize}@anchor{3add}
@deffnx {C 成员} Py_ssize_t PyTypeObject.tp_itemsize

These fields allow calculating the size in bytes of instances of the type.

There are two kinds of types: types with fixed-length instances have a zero
@ref{3add,,tp_itemsize} field, types with variable-length instances have a non-zero
@ref{3add,,tp_itemsize} field.  For a type with fixed-length instances, all
instances have the same size, given in @ref{3ade,,tp_basicsize}.

For a type with variable-length instances, the instances must have an
@code{ob_size} field, and the instance size is @ref{3ade,,tp_basicsize} plus N
times @ref{3add,,tp_itemsize}, where N is the "length" of the object.  The value of
N is typically stored in the instance's @code{ob_size} field.  There are
exceptions:  for example, ints use a negative @code{ob_size} to indicate a
negative number, and N is @code{abs(ob_size)} there.  Also, the presence of an
@code{ob_size} field in the instance layout doesn't mean that the instance
structure is variable-length (for example, the structure for the list type has
fixed-length instances, yet those instances have a meaningful @code{ob_size}
field).

The basic size includes the fields in the instance declared by the macro
@ref{c6b,,PyObject_HEAD} or @ref{3ff0,,PyObject_VAR_HEAD} (whichever is used to
declare the instance struct) and this in turn includes the @code{_ob_prev} and
@code{_ob_next} fields if they are present.  This means that the only correct
way to get an initializer for the @ref{3ade,,tp_basicsize} is to use the
@code{sizeof} operator on the struct used to declare the instance layout.
The basic size does not include the GC header size.

A note about alignment: if the variable items require a particular alignment,
this should be taken care of by the value of @ref{3ade,,tp_basicsize}.  Example:
suppose a type implements an array of @code{double}. @ref{3add,,tp_itemsize} is
@code{sizeof(double)}. It is the programmer's responsibility that
@ref{3ade,,tp_basicsize} is a multiple of @code{sizeof(double)} (assuming this is the
alignment requirement for @code{double}).

For any type with variable-length instances, this field must not be @code{NULL}.

@strong{Inheritance:}

These fields are inherited separately by subtypes.  If the base type has a
non-zero @ref{3add,,tp_itemsize}, it is generally not safe to set
@ref{3add,,tp_itemsize} to a different non-zero value in a subtype (though this
depends on the implementation of the base type).
@end deffn

@geindex PyTypeObject.tp_dealloc (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_dealloc}@anchor{3ae4}
@deffn {C 成员} destructor PyTypeObject.tp_dealloc

A pointer to the instance destructor function.  This function must be defined
unless the type guarantees that its instances will never be deallocated (as is
the case for the singletons @code{None} and @code{Ellipsis}).  The function signature is:

@example
void tp_dealloc(PyObject *self);
@end example

The destructor function is called by the @ref{266,,Py_DECREF()} and
@ref{268,,Py_XDECREF()} macros when the new reference count is zero.  At this point,
the instance is still in existence, but there are no references to it.  The
destructor function should free all references which the instance owns, free all
memory buffers owned by the instance (using the freeing function corresponding
to the allocation function used to allocate the buffer), and call the type's
@ref{3ae5,,tp_free} function.  If the type is not subtypable
(doesn't have the @ref{3aec,,Py_TPFLAGS_BASETYPE} flag bit set), it is
permissible to call the object deallocator directly instead of via
@ref{3ae5,,tp_free}.  The object deallocator should be the one used to allocate the
instance; this is normally @ref{e0f,,PyObject_Del()} if the instance was allocated
using @ref{2d2,,PyObject_New()} or @code{PyObject_VarNew()}, or
@ref{e3c,,PyObject_GC_Del()} if the instance was allocated using
@ref{2d4,,PyObject_GC_New()} or @ref{2d5,,PyObject_GC_NewVar()}.

Finally, if the type is heap allocated (@ref{3d0e,,Py_TPFLAGS_HEAPTYPE}), the
deallocator should decrement the reference count for its type object after
calling the type deallocator. In order to avoid dangling pointers, the
recommended way to achieve this is:

@example
static void foo_dealloc(foo_object *self) @{
    PyTypeObject *tp = Py_TYPE(self);
    // free references and buffers here
    tp->tp_free(self);
    Py_DECREF(tp);
@}
@end example

@strong{Inheritance:}

This field is inherited by subtypes.
@end deffn

@geindex PyTypeObject.tp_vectorcall_offset (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_vectorcall_offset}@anchor{3c67}
@deffn {C 成员} Py_ssize_t PyTypeObject.tp_vectorcall_offset

An optional offset to a per-instance function that implements calling
the object using the @emph{vectorcall} protocol, a more efficient alternative
of the simpler @ref{3b11,,tp_call}.

This field is only used if the flag @ref{4069,,_Py_TPFLAGS_HAVE_VECTORCALL}
is set. If so, this must be a positive integer containing the offset in the
instance of a @ref{406a,,vectorcallfunc} pointer.
The signature is the same as for @ref{3c66,,_PyObject_Vectorcall()}:

@example
PyObject *vectorcallfunc(PyObject *callable, PyObject *const *args, size_t nargsf, PyObject *kwnames)
@end example

The @emph{vectorcallfunc} pointer may be zero, in which case the instance behaves
as if @ref{4069,,_Py_TPFLAGS_HAVE_VECTORCALL} was not set: calling the instance
falls back to @ref{3b11,,tp_call}.

Any class that sets @code{_Py_TPFLAGS_HAVE_VECTORCALL} must also set
@ref{3b11,,tp_call} and make sure its behaviour is consistent
with the @emph{vectorcallfunc} function.
This can be done by setting @emph{tp_call} to @code{PyVectorcall_Call}:

@geindex PyVectorcall_Call (C 函数)
@anchor{c-api/typeobj c PyVectorcall_Call}@anchor{406b}
@deffn {C 函数} PyObject *PyVectorcall_Call (PyObject@w{ }*callable, PyObject@w{ }*tuple, PyObject@w{ }*dict)

Call @emph{callable}'s @emph{vectorcallfunc} with positional and keyword
arguments given in a tuple and dict, respectively.

This function is intended to be used in the @code{tp_call} slot.
It does not fall back to @code{tp_call} and it currently does not check the
@code{_Py_TPFLAGS_HAVE_VECTORCALL} flag.
To call an object, use one of the @ref{3ab5,,PyObject_Call}
functions instead.
@end deffn

@cartouche
@quotation 注解 
It is not recommended for @ref{3d0c,,heap types} to implement
the vectorcall protocol.
When a user sets @code{__call__} in Python code, only @code{tp_call} is updated,
possibly making it inconsistent with the vectorcall function.
@end quotation
@end cartouche

@cartouche
@quotation 注解 
The semantics of the @code{tp_vectorcall_offset} slot are provisional and
expected to be finalized in Python 3.9.
If you use vectorcall, plan for updating your code for Python 3.9.
@end quotation
@end cartouche


在 3.8 版更改: This slot was used for print formatting in Python 2.x.
In Python 3.0 to 3.7, it was reserved and named @code{tp_print}.


@strong{Inheritance:}

This field is inherited by subtypes together with
@ref{3b11,,tp_call}: a subtype inherits
@ref{3c67,,tp_vectorcall_offset} from its base type when
the subtype’s @ref{3b11,,tp_call} is @code{NULL}.

Note that @ref{406c,,heap types} (including subclasses defined in Python) do not
inherit the @ref{4069,,_Py_TPFLAGS_HAVE_VECTORCALL} flag.
@end deffn

@geindex PyTypeObject.tp_getattr (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_getattr}@anchor{3b07}
@deffn {C 成员} getattrfunc PyTypeObject.tp_getattr

An optional pointer to the get-attribute-string function.

This field is deprecated.  When it is defined, it should point to a function
that acts the same as the @ref{3b04,,tp_getattro} function, but taking a C string
instead of a Python string object to give the attribute name.

@strong{Inheritance:}

Group: @code{tp_getattr}, @code{tp_getattro}

This field is inherited by subtypes together with @ref{3b04,,tp_getattro}: a subtype
inherits both @ref{3b07,,tp_getattr} and @ref{3b04,,tp_getattro} from its base type when
the subtype's @ref{3b07,,tp_getattr} and @ref{3b04,,tp_getattro} are both @code{NULL}.
@end deffn

@geindex PyTypeObject.tp_setattr (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_setattr}@anchor{3b08}
@deffn {C 成员} setattrfunc PyTypeObject.tp_setattr

An optional pointer to the function for setting and deleting attributes.

This field is deprecated.  When it is defined, it should point to a function
that acts the same as the @ref{3b05,,tp_setattro} function, but taking a C string
instead of a Python string object to give the attribute name.

@strong{Inheritance:}

Group: @code{tp_setattr}, @code{tp_setattro}

This field is inherited by subtypes together with @ref{3b05,,tp_setattro}: a subtype
inherits both @ref{3b08,,tp_setattr} and @ref{3b05,,tp_setattro} from its base type when
the subtype's @ref{3b08,,tp_setattr} and @ref{3b05,,tp_setattro} are both @code{NULL}.
@end deffn

@geindex PyTypeObject.tp_as_async (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_as_async}@anchor{4001}
@deffn {C 成员} PyAsyncMethods* PyTypeObject.tp_as_async

Pointer to an additional structure that contains fields relevant only to
objects which implement @ref{513,,awaitable} and @ref{63f,,asynchronous iterator}
protocols at the C-level.  See @ref{406d,,Async Object Structures} for details.


3.5 新版功能: Formerly known as @code{tp_compare} and @code{tp_reserved}.


@strong{Inheritance:}

The @ref{4001,,tp_as_async} field is not inherited,
but the contained fields are inherited individually.
@end deffn

@geindex PyTypeObject.tp_repr (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_repr}@anchor{3aff}
@deffn {C 成员} reprfunc PyTypeObject.tp_repr

@geindex 內置函数; repr

An optional pointer to a function that implements the built-in function
@ref{7c6,,repr()}.

The signature is the same as for @ref{962,,PyObject_Repr()}:

@example
PyObject *tp_repr(PyObject *self);
@end example

The function must return a string or a Unicode object.  Ideally,
this function should return a string that, when passed to
@ref{b89,,eval()}, given a suitable environment, returns an object with the
same value.  If this is not feasible, it should return a string starting with
@code{'<'} and ending with @code{'>'} from which both the type and the value of the
object can be deduced.

@strong{Inheritance:}

This field is inherited by subtypes.

@strong{Default:}

When this field is not set, a string of the form @code{<%s object at %p>} is
returned, where @code{%s} is replaced by the type name, and @code{%p} by the object's
memory address.
@end deffn

@geindex PyTypeObject.tp_as_number (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_as_number}@anchor{4004}
@deffn {C 成员} PyNumberMethods* PyTypeObject.tp_as_number

Pointer to an additional structure that contains fields relevant only to
objects which implement the number protocol.  These fields are documented in
@ref{406e,,Number Object Structures}.

@strong{Inheritance:}

The @ref{4004,,tp_as_number} field is not inherited, but the contained fields are
inherited individually.
@end deffn

@geindex PyTypeObject.tp_as_sequence (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_as_sequence}@anchor{4005}
@deffn {C 成员} PySequenceMethods* PyTypeObject.tp_as_sequence

Pointer to an additional structure that contains fields relevant only to
objects which implement the sequence protocol.  These fields are documented
in @ref{406f,,Sequence Object Structures}.

@strong{Inheritance:}

The @ref{4005,,tp_as_sequence} field is not inherited, but the contained fields
are inherited individually.
@end deffn

@geindex PyTypeObject.tp_as_mapping (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_as_mapping}@anchor{4006}
@deffn {C 成员} PyMappingMethods* PyTypeObject.tp_as_mapping

Pointer to an additional structure that contains fields relevant only to
objects which implement the mapping protocol.  These fields are documented in
@ref{4070,,Mapping Object Structures}.

@strong{Inheritance:}

The @ref{4006,,tp_as_mapping} field is not inherited, but the contained fields
are inherited individually.
@end deffn

@geindex PyTypeObject.tp_hash (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_hash}@anchor{3b10}
@deffn {C 成员} hashfunc PyTypeObject.tp_hash

@geindex 內置函数; hash

An optional pointer to a function that implements the built-in function
@ref{9be,,hash()}.

The signature is the same as for @ref{3c6b,,PyObject_Hash()}:

@example
Py_hash_t tp_hash(PyObject *);
@end example

The value @code{-1} should not be returned as a
normal return value; when an error occurs during the computation of the hash
value, the function should set an exception and return @code{-1}.

When this field is not set (@emph{and} @code{tp_richcompare} is not set),
an attempt to take the hash of the object raises @ref{192,,TypeError}.
This is the same as setting it to @ref{d2a,,PyObject_HashNotImplemented()}.

This field can be set explicitly to @ref{d2a,,PyObject_HashNotImplemented()} to
block inheritance of the hash method from a parent type. This is interpreted
as the equivalent of @code{__hash__ = None} at the Python level, causing
@code{isinstance(o, collections.Hashable)} to correctly return @code{False}. Note
that the converse is also true - setting @code{__hash__ = None} on a class at
the Python level will result in the @code{tp_hash} slot being set to
@ref{d2a,,PyObject_HashNotImplemented()}.

@strong{Inheritance:}

Group: @code{tp_hash}, @code{tp_richcompare}

This field is inherited by subtypes together with
@ref{3b0a,,tp_richcompare}: a subtype inherits both of
@ref{3b0a,,tp_richcompare} and @ref{3b10,,tp_hash}, when the subtype's
@ref{3b0a,,tp_richcompare} and @ref{3b10,,tp_hash} are both @code{NULL}.
@end deffn

@geindex PyTypeObject.tp_call (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_call}@anchor{3b11}
@deffn {C 成员} ternaryfunc PyTypeObject.tp_call

An optional pointer to a function that implements calling the object.  This
should be @code{NULL} if the object is not callable.  The signature is the same as
for @ref{3ab5,,PyObject_Call()}:

@example
PyObject *tp_call(PyObject *self, PyObject *args, PyObject *kwargs);
@end example

@strong{Inheritance:}

This field is inherited by subtypes.
@end deffn

@geindex PyTypeObject.tp_str (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_str}@anchor{3b01}
@deffn {C 成员} reprfunc PyTypeObject.tp_str

An optional pointer to a function that implements the built-in operation
@ref{329,,str()}.  (Note that @ref{329,,str} is a type now, and @ref{329,,str()} calls the
constructor for that type.  This constructor calls @ref{963,,PyObject_Str()} to do
the actual work, and @ref{963,,PyObject_Str()} will call this handler.)

The signature is the same as for @ref{963,,PyObject_Str()}:

@example
PyObject *tp_str(PyObject *self);
@end example

The function must return a string or a Unicode object.  It should be a "friendly" string
representation of the object, as this is the representation that will be used,
among other things, by the @ref{880,,print()} function.

@strong{Inheritance:}

This field is inherited by subtypes.

@strong{Default:}

When this field is not set, @ref{962,,PyObject_Repr()} is called to return a string
representation.
@end deffn

@geindex PyTypeObject.tp_getattro (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_getattro}@anchor{3b04}
@deffn {C 成员} getattrofunc PyTypeObject.tp_getattro

An optional pointer to the get-attribute function.

The signature is the same as for @ref{3c57,,PyObject_GetAttr()}:

@example
PyObject *tp_getattro(PyObject *self, PyObject *attr);
@end example

It is usually convenient to set this field to @ref{3c59,,PyObject_GenericGetAttr()},
which implements the normal way of looking for object attributes.

@strong{Inheritance:}

Group: @code{tp_getattr}, @code{tp_getattro}

This field is inherited by subtypes together with @ref{3b07,,tp_getattr}: a subtype
inherits both @ref{3b07,,tp_getattr} and @ref{3b04,,tp_getattro} from its base type when
the subtype's @ref{3b07,,tp_getattr} and @ref{3b04,,tp_getattro} are both @code{NULL}.

@strong{Default:}

@code{PyBaseObject_Type} uses @ref{3c59,,PyObject_GenericGetAttr()}.
@end deffn

@geindex PyTypeObject.tp_setattro (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_setattro}@anchor{3b05}
@deffn {C 成员} setattrofunc PyTypeObject.tp_setattro

An optional pointer to the function for setting and deleting attributes.

The signature is the same as for @ref{3c5a,,PyObject_SetAttr()}:

@example
PyObject *tp_setattro(PyObject *self, PyObject *attr, PyObject *value);
@end example

In addition, setting @emph{value} to @code{NULL} to delete an attribute must be
supported.  It is usually convenient to set this field to
@ref{3c5e,,PyObject_GenericSetAttr()}, which implements the normal
way of setting object attributes.

@strong{Inheritance:}

Group: @code{tp_setattr}, @code{tp_setattro}

This field is inherited by subtypes together with @ref{3b08,,tp_setattr}: a subtype
inherits both @ref{3b08,,tp_setattr} and @ref{3b05,,tp_setattro} from its base type when
the subtype's @ref{3b08,,tp_setattr} and @ref{3b05,,tp_setattro} are both @code{NULL}.

@strong{Default:}

@code{PyBaseObject_Type} uses @ref{3c5e,,PyObject_GenericSetAttr()}.
@end deffn

@geindex PyTypeObject.tp_as_buffer (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_as_buffer}@anchor{400b}
@deffn {C 成员} PyBufferProcs* PyTypeObject.tp_as_buffer

Pointer to an additional structure that contains fields relevant only to objects
which implement the buffer interface.  These fields are documented in
@ref{3cbe,,Buffer Object Structures}.

@strong{Inheritance:}

The @ref{400b,,tp_as_buffer} field is not inherited,
but the contained fields are inherited individually.
@end deffn

@geindex PyTypeObject.tp_flags (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_flags}@anchor{3d06}
@deffn {C 成员} unsigned long PyTypeObject.tp_flags

This field is a bit mask of various flags.  Some flags indicate variant
semantics for certain situations; others are used to indicate that certain
fields in the type object (or in the extension structures referenced via
@ref{4004,,tp_as_number}, @ref{4005,,tp_as_sequence}, @ref{4006,,tp_as_mapping}, and
@ref{400b,,tp_as_buffer}) that were historically not always present are valid; if
such a flag bit is clear, the type fields it guards must not be accessed and
must be considered to have a zero or @code{NULL} value instead.

@strong{Inheritance:}

Inheritance of this field is complicated.  Most flag bits are inherited
individually, i.e. if the base type has a flag bit set, the subtype inherits
this flag bit.  The flag bits that pertain to extension structures are strictly
inherited if the extension structure is inherited, i.e. the base type's value of
the flag bit is copied into the subtype together with a pointer to the extension
structure.  The @ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit is inherited together with
the @ref{3664,,tp_traverse} and @ref{3afd,,tp_clear} fields, i.e. if the
@ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit is clear in the subtype and the
@ref{3664,,tp_traverse} and @ref{3afd,,tp_clear} fields in the subtype exist and have
@code{NULL} values.

@c XXX are most flag bits *really* inherited individually?

@strong{Default:}

@code{PyBaseObject_Type} uses
@code{Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE}.

@strong{Bit Masks:}

The following bit masks are currently defined; these can be ORed together using
the @code{|} operator to form the value of the @ref{3d06,,tp_flags} field.  The macro
@ref{3d08,,PyType_HasFeature()} takes a type and a flags value, @emph{tp} and @emph{f}, and
checks whether @code{tp->tp_flags & f} is non-zero.

@geindex Py_TPFLAGS_HEAPTYPE (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_HEAPTYPE}@anchor{3d0e}
@deffn {数据} Py_TPFLAGS_HEAPTYPE

This bit is set when the type object itself is allocated on the heap, for
example, types created dynamically using @ref{2d1,,PyType_FromSpec()}.  In this
case, the @code{ob_type} field of its instances is considered a reference to
the type, and the type object is INCREF'ed when a new instance is created, and
DECREF'ed when an instance is destroyed (this does not apply to instances of
subtypes; only the type referenced by the instance's ob_type gets INCREF'ed or
DECREF'ed).

@strong{Inheritance:}

???
@end deffn

@geindex Py_TPFLAGS_BASETYPE (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_BASETYPE}@anchor{3aec}
@deffn {数据} Py_TPFLAGS_BASETYPE

This bit is set when the type can be used as the base type of another type.  If
this bit is clear, the type cannot be subtyped (similar to a "final" class in
Java).

@strong{Inheritance:}

???
@end deffn

@geindex Py_TPFLAGS_READY (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_READY}@anchor{4071}
@deffn {数据} Py_TPFLAGS_READY

This bit is set when the type object has been fully initialized by
@ref{3ae7,,PyType_Ready()}.

@strong{Inheritance:}

???
@end deffn

@geindex Py_TPFLAGS_READYING (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_READYING}@anchor{4072}
@deffn {数据} Py_TPFLAGS_READYING

This bit is set while @ref{3ae7,,PyType_Ready()} is in the process of initializing
the type object.

@strong{Inheritance:}

???
@end deffn

@geindex Py_TPFLAGS_HAVE_GC (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_HAVE_GC}@anchor{3af3}
@deffn {数据} Py_TPFLAGS_HAVE_GC

This bit is set when the object supports garbage collection.  If this bit
is set, instances must be created using @ref{2d4,,PyObject_GC_New()} and
destroyed using @ref{e3c,,PyObject_GC_Del()}.  More information in section
@ref{4073,,使对象类型支持循环垃圾回收}.  This bit also implies that the
GC-related fields @ref{3664,,tp_traverse} and @ref{3afd,,tp_clear} are present in
the type object.

@strong{Inheritance:}

Group: @ref{3af3,,Py_TPFLAGS_HAVE_GC}, @code{tp_traverse}, @code{tp_clear}

The @ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit is inherited
together with the @code{tp_traverse} and @code{tp_clear}
fields, i.e.  if the @ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit is
clear in the subtype and the @code{tp_traverse} and
@code{tp_clear} fields in the subtype exist and have @code{NULL}
values.
@end deffn

@geindex Py_TPFLAGS_DEFAULT (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_DEFAULT}@anchor{3adf}
@deffn {数据} Py_TPFLAGS_DEFAULT

This is a bitmask of all the bits that pertain to the existence of certain
fields in the type object and its extension structures. Currently, it includes
the following bits: @code{Py_TPFLAGS_HAVE_STACKLESS_EXTENSION},
@code{Py_TPFLAGS_HAVE_VERSION_TAG}.

@strong{Inheritance:}

???
@end deffn

@geindex Py_TPFLAGS_METHOD_DESCRIPTOR (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_METHOD_DESCRIPTOR}@anchor{4074}
@deffn {数据} Py_TPFLAGS_METHOD_DESCRIPTOR

This bit indicates that objects behave like unbound methods.

If this flag is set for @code{type(meth)}, then:


@itemize -

@item 
@code{meth.__get__(obj, cls)(*args, **kwds)} (with @code{obj} not None)
must be equivalent to @code{meth(obj, *args, **kwds)}.

@item 
@code{meth.__get__(None, cls)(*args, **kwds)}
must be equivalent to @code{meth(*args, **kwds)}.
@end itemize

This flag enables an optimization for typical method calls like
@code{obj.meth()}: it avoids creating a temporary "bound method" object for
@code{obj.meth}.


3.8 新版功能.


@strong{Inheritance:}

This flag is never inherited by heap types.
For extension types, it is inherited whenever
@ref{4012,,tp_descr_get} is inherited.
@end deffn

@c XXX Document more flags here?

@geindex Py_TPFLAGS_LONG_SUBCLASS (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_LONG_SUBCLASS}@anchor{4075}
@deffn {数据} Py_TPFLAGS_LONG_SUBCLASS
@end deffn

@geindex Py_TPFLAGS_LIST_SUBCLASS (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_LIST_SUBCLASS}@anchor{4076}
@deffn {数据} Py_TPFLAGS_LIST_SUBCLASS
@end deffn

@geindex Py_TPFLAGS_TUPLE_SUBCLASS (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_TUPLE_SUBCLASS}@anchor{4077}
@deffn {数据} Py_TPFLAGS_TUPLE_SUBCLASS
@end deffn

@geindex Py_TPFLAGS_BYTES_SUBCLASS (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_BYTES_SUBCLASS}@anchor{4078}
@deffn {数据} Py_TPFLAGS_BYTES_SUBCLASS
@end deffn

@geindex Py_TPFLAGS_UNICODE_SUBCLASS (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_UNICODE_SUBCLASS}@anchor{4079}
@deffn {数据} Py_TPFLAGS_UNICODE_SUBCLASS
@end deffn

@geindex Py_TPFLAGS_DICT_SUBCLASS (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_DICT_SUBCLASS}@anchor{407a}
@deffn {数据} Py_TPFLAGS_DICT_SUBCLASS
@end deffn

@geindex Py_TPFLAGS_BASE_EXC_SUBCLASS (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_BASE_EXC_SUBCLASS}@anchor{407b}
@deffn {数据} Py_TPFLAGS_BASE_EXC_SUBCLASS
@end deffn

@geindex Py_TPFLAGS_TYPE_SUBCLASS (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_TYPE_SUBCLASS}@anchor{407c}
@deffn {数据} Py_TPFLAGS_TYPE_SUBCLASS

These flags are used by functions such as
@ref{3d2c,,PyLong_Check()} to quickly determine if a type is a subclass
of a built-in type; such specific checks are faster than a generic
check, like @ref{797,,PyObject_IsInstance()}. Custom types that inherit
from built-ins should have their @ref{3d06,,tp_flags}
set appropriately, or the code that interacts with such types
will behave differently depending on what kind of check is used.
@end deffn

@geindex Py_TPFLAGS_HAVE_FINALIZE (內置变量)
@anchor{c-api/typeobj Py_TPFLAGS_HAVE_FINALIZE}@anchor{2d8}
@deffn {数据} Py_TPFLAGS_HAVE_FINALIZE

This bit is set when the @ref{2d7,,tp_finalize} slot is present in the
type structure.


3.4 新版功能.



3.8 版后已移除: This flag isn't necessary anymore, as the interpreter assumes the
@ref{2d7,,tp_finalize} slot is always present in the
type structure.

@end deffn

@geindex _Py_TPFLAGS_HAVE_VECTORCALL (內置变量)
@anchor{c-api/typeobj _Py_TPFLAGS_HAVE_VECTORCALL}@anchor{4069}
@deffn {数据} _Py_TPFLAGS_HAVE_VECTORCALL

This bit is set when the class implements the vectorcall protocol.
See @ref{3c67,,tp_vectorcall_offset} for details.

@strong{Inheritance:}

This bit is set on @emph{static} subtypes if @code{tp_flags} is not overridden:
a subtype inherits @code{_Py_TPFLAGS_HAVE_VECTORCALL} from its base type
when the subtype’s @ref{3b11,,tp_call} is @code{NULL}
and the subtype's @code{Py_TPFLAGS_HEAPTYPE} is not set.

@ref{406c,,Heap types} do not inherit @code{_Py_TPFLAGS_HAVE_VECTORCALL}.

@cartouche
@quotation 注解 
This flag is provisional and expected to become public in Python 3.9,
with a different name and, possibly, changed semantics.
If you use vectorcall, plan for updating your code for Python 3.9.
@end quotation
@end cartouche


3.8 新版功能.

@end deffn
@end deffn

@geindex PyTypeObject.tp_doc (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_doc}@anchor{3ae0}
@deffn {C 成员} const char* PyTypeObject.tp_doc

An optional pointer to a NUL-terminated C string giving the docstring for this
type object.  This is exposed as the @code{__doc__} attribute on the type and
instances of the type.

@strong{Inheritance:}

This field is @emph{not} inherited by subtypes.
@end deffn

@geindex PyTypeObject.tp_traverse (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_traverse}@anchor{3664}
@deffn {C 成员} traverseproc PyTypeObject.tp_traverse

An optional pointer to a traversal function for the garbage collector.  This is
only used if the @ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit is set.  The signature is:

@example
int tp_traverse(PyObject *self, visitproc visit, void *arg);
@end example

More information about Python's garbage collection scheme can be found
in section @ref{4073,,使对象类型支持循环垃圾回收}.

The @ref{3664,,tp_traverse} pointer is used by the garbage collector to detect
reference cycles. A typical implementation of a @ref{3664,,tp_traverse} function
simply calls @ref{3af1,,Py_VISIT()} on each of the instance's members that are Python
objects that the instance owns. For example, this is function @code{local_traverse()} from the
@ref{3,,_thread} extension module:

@example
static int
local_traverse(localobject *self, visitproc visit, void *arg)
@{
    Py_VISIT(self->args);
    Py_VISIT(self->kw);
    Py_VISIT(self->dict);
    return 0;
@}
@end example

Note that @ref{3af1,,Py_VISIT()} is called only on those members that can participate
in reference cycles.  Although there is also a @code{self->key} member, it can only
be @code{NULL} or a Python string and therefore cannot be part of a reference cycle.

On the other hand, even if you know a member can never be part of a cycle, as a
debugging aid you may want to visit it anyway just so the @ref{86,,gc} module's
@ref{3663,,get_referents()} function will include it.

@cartouche
@quotation 警告 
When implementing @ref{3664,,tp_traverse}, only the members
that the instance @emph{owns} (by having strong references to them) must be
visited. For instance, if an object supports weak references via the
@ref{3d1e,,tp_weaklist} slot, the pointer supporting
the linked list (what @emph{tp_weaklist} points to) must @strong{not} be
visited as the instance does not directly own the weak references to itself
(the weakreference list is there to support the weak reference machinery,
but the instance has no strong reference to the elements inside it, as they
are allowed to be removed even if the instance is still alive).
@end quotation
@end cartouche

Note that @ref{3af1,,Py_VISIT()} requires the @emph{visit} and @emph{arg} parameters to
@code{local_traverse()} to have these specific names; don't name them just
anything.

@strong{Inheritance:}

Group: @ref{3af3,,Py_TPFLAGS_HAVE_GC}, @code{tp_traverse}, @code{tp_clear}

This field is inherited by subtypes together with @ref{3afd,,tp_clear} and the
@ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit: the flag bit, @ref{3664,,tp_traverse}, and
@ref{3afd,,tp_clear} are all inherited from the base type if they are all zero in
the subtype.
@end deffn

@geindex PyTypeObject.tp_clear (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_clear}@anchor{3afd}
@deffn {C 成员} inquiry PyTypeObject.tp_clear

An optional pointer to a clear function for the garbage collector. This is only
used if the @ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit is set.  The signature is:

@example
int tp_clear(PyObject *);
@end example

The @ref{3afd,,tp_clear} member function is used to break reference cycles in cyclic
garbage detected by the garbage collector.  Taken together, all @ref{3afd,,tp_clear}
functions in the system must combine to break all reference cycles.  This is
subtle, and if in any doubt supply a @ref{3afd,,tp_clear} function.  For example,
the tuple type does not implement a @ref{3afd,,tp_clear} function, because it's
possible to prove that no reference cycle can be composed entirely of tuples.
Therefore the @ref{3afd,,tp_clear} functions of other types must be sufficient to
break any cycle containing a tuple.  This isn't immediately obvious, and there's
rarely a good reason to avoid implementing @ref{3afd,,tp_clear}.

Implementations of @ref{3afd,,tp_clear} should drop the instance's references to
those of its members that may be Python objects, and set its pointers to those
members to @code{NULL}, as in the following example:

@example
static int
local_clear(localobject *self)
@{
    Py_CLEAR(self->key);
    Py_CLEAR(self->args);
    Py_CLEAR(self->kw);
    Py_CLEAR(self->dict);
    return 0;
@}
@end example

The @ref{3af2,,Py_CLEAR()} macro should be used, because clearing references is
delicate:  the reference to the contained object must not be decremented until
after the pointer to the contained object is set to @code{NULL}.  This is because
decrementing the reference count may cause the contained object to become trash,
triggering a chain of reclamation activity that may include invoking arbitrary
Python code (due to finalizers, or weakref callbacks, associated with the
contained object). If it's possible for such code to reference @emph{self} again,
it's important that the pointer to the contained object be @code{NULL} at that time,
so that @emph{self} knows the contained object can no longer be used.  The
@ref{3af2,,Py_CLEAR()} macro performs the operations in a safe order.

Because the goal of @ref{3afd,,tp_clear} functions is to break reference cycles,
it's not necessary to clear contained objects like Python strings or Python
integers, which can't participate in reference cycles. On the other hand, it may
be convenient to clear all contained Python objects, and write the type's
@ref{3ae4,,tp_dealloc} function to invoke @ref{3afd,,tp_clear}.

More information about Python's garbage collection scheme can be found in
section @ref{4073,,使对象类型支持循环垃圾回收}.

@strong{Inheritance:}

Group: @ref{3af3,,Py_TPFLAGS_HAVE_GC}, @code{tp_traverse}, @code{tp_clear}

This field is inherited by subtypes together with @ref{3664,,tp_traverse} and the
@ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit: the flag bit, @ref{3664,,tp_traverse}, and
@ref{3afd,,tp_clear} are all inherited from the base type if they are all zero in
the subtype.
@end deffn

@geindex PyTypeObject.tp_richcompare (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_richcompare}@anchor{3b0a}
@deffn {C 成员} richcmpfunc PyTypeObject.tp_richcompare

An optional pointer to the rich comparison function, whose signature is:

@example
PyObject *tp_richcompare(PyObject *self, PyObject *other, int op);
@end example

The first parameter is guaranteed to be an instance of the type
that is defined by @ref{2d6,,PyTypeObject}.

The function should return the result of the comparison (usually @code{Py_True}
or @code{Py_False}).  If the comparison is undefined, it must return
@code{Py_NotImplemented}, if another error occurred it must return @code{NULL} and
set an exception condition.

The following constants are defined to be used as the third argument for
@ref{3b0a,,tp_richcompare} and for @ref{3b0b,,PyObject_RichCompare()}:


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} 
@headitem

常数

@tab

对照

@item

@code{Py_LT}

@tab

@code{<}

@item

@code{Py_LE}

@tab

@code{<=}

@item

@code{Py_EQ}

@tab

@code{==}

@item

@code{Py_NE}

@tab

@code{!=}

@item

@code{Py_GT}

@tab

@code{>}

@item

@code{Py_GE}

@tab

@code{>=}

@end multitable


定义以下宏是为了简化编写丰富的比较函数：

@geindex Py_RETURN_RICHCOMPARE (C 函数)
@anchor{c-api/typeobj c Py_RETURN_RICHCOMPARE}@anchor{41a}
@deffn {C 函数} PyObject *Py_RETURN_RICHCOMPARE (VAL_A, VAL_B, int@w{ }op)

Return @code{Py_True} or @code{Py_False} from the function, depending on the
result of a comparison.
VAL_A and VAL_B must be orderable by C comparison operators (for example,
they may be C ints or floats). The third argument specifies the requested
operation, as for @ref{3b0b,,PyObject_RichCompare()}.

The return value's reference count is properly incremented.

On error, sets an exception and returns @code{NULL} from the function.


3.7 新版功能.

@end deffn

@strong{Inheritance:}

Group: @code{tp_hash}, @code{tp_richcompare}

This field is inherited by subtypes together with @ref{3b10,,tp_hash}:
a subtype inherits @ref{3b0a,,tp_richcompare} and @ref{3b10,,tp_hash} when
the subtype's @ref{3b0a,,tp_richcompare} and @ref{3b10,,tp_hash} are both
@code{NULL}.

@strong{Default:}

@code{PyBaseObject_Type} provides a @code{tp_richcompare}
implementation, which may be inherited.  However, if only
@code{tp_hash} is defined, not even the inherited function is used
and instances of the type will not be able to participate in any
comparisons.
@end deffn

@geindex PyTypeObject.tp_weaklistoffset (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_weaklistoffset}@anchor{3b13}
@deffn {C 成员} Py_ssize_t PyTypeObject.tp_weaklistoffset

If the instances of this type are weakly referenceable, this field is greater
than zero and contains the offset in the instance structure of the weak
reference list head (ignoring the GC header, if present); this offset is used by
@code{PyObject_ClearWeakRefs()} and the @code{PyWeakref_*()} functions.  The
instance structure needs to include a field of type @ref{4b5,,PyObject*} which is
initialized to @code{NULL}.

Do not confuse this field with @ref{3d1e,,tp_weaklist}; that is the list head for
weak references to the type object itself.

@strong{Inheritance:}

This field is inherited by subtypes, but see the rules listed below. A subtype
may override this offset; this means that the subtype uses a different weak
reference list head than the base type.  Since the list head is always found via
@ref{3b13,,tp_weaklistoffset}, this should not be a problem.

When a type defined by a class statement has no @ref{e26,,__slots__} declaration,
and none of its base types are weakly referenceable, the type is made weakly
referenceable by adding a weak reference list head slot to the instance layout
and setting the @ref{3b13,,tp_weaklistoffset} of that slot's offset.

When a type's @code{__slots__} declaration contains a slot named
@code{__weakref__}, that slot becomes the weak reference list head for
instances of the type, and the slot's offset is stored in the type's
@ref{3b13,,tp_weaklistoffset}.

When a type's @code{__slots__} declaration does not contain a slot named
@code{__weakref__}, the type inherits its @ref{3b13,,tp_weaklistoffset} from its
base type.
@end deffn

@geindex PyTypeObject.tp_iter (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_iter}@anchor{e29}
@deffn {C 成员} getiterfunc PyTypeObject.tp_iter

An optional pointer to a function that returns an iterator for the object.  Its
presence normally signals that the instances of this type are iterable (although
sequences may be iterable without this function).

This function has the same signature as @ref{3c73,,PyObject_GetIter()}:

@example
PyObject *tp_iter(PyObject *self);
@end example

@strong{Inheritance:}

This field is inherited by subtypes.
@end deffn

@geindex PyTypeObject.tp_iternext (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_iternext}@anchor{e2a}
@deffn {C 成员} iternextfunc PyTypeObject.tp_iternext

An optional pointer to a function that returns the next item in an iterator.
The signature is:

@example
PyObject *tp_iternext(PyObject *self);
@end example

When the iterator is exhausted, it must return @code{NULL}; a @ref{480,,StopIteration}
exception may or may not be set.  When another error occurs, it must return
@code{NULL} too.  Its presence signals that the instances of this type are
iterators.

Iterator types should also define the @ref{e29,,tp_iter} function, and that
function should return the iterator instance itself (not a new iterator
instance).

This function has the same signature as @ref{3cbb,,PyIter_Next()}.

@strong{Inheritance:}

This field is inherited by subtypes.
@end deffn

@geindex PyTypeObject.tp_methods (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_methods}@anchor{3aeb}
@deffn {C 成员} struct PyMethodDef* PyTypeObject.tp_methods

An optional pointer to a static @code{NULL}-terminated array of @ref{e14,,PyMethodDef}
structures, declaring regular methods of this type.

For each entry in the array, an entry is added to the type's dictionary (see
@ref{3d1a,,tp_dict} below) containing a method descriptor.

@strong{Inheritance:}

This field is not inherited by subtypes (methods are inherited through a
different mechanism).
@end deffn

@geindex PyTypeObject.tp_members (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_members}@anchor{3ae9}
@deffn {C 成员} struct PyMemberDef* PyTypeObject.tp_members

An optional pointer to a static @code{NULL}-terminated array of @ref{420,,PyMemberDef}
structures, declaring regular data members (fields or slots) of instances of
this type.

For each entry in the array, an entry is added to the type's dictionary (see
@ref{3d1a,,tp_dict} below) containing a member descriptor.

@strong{Inheritance:}

This field is not inherited by subtypes (members are inherited through a
different mechanism).
@end deffn

@geindex PyTypeObject.tp_getset (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_getset}@anchor{3aef}
@deffn {C 成员} struct PyGetSetDef* PyTypeObject.tp_getset

An optional pointer to a static @code{NULL}-terminated array of @ref{421,,PyGetSetDef}
structures, declaring computed attributes of instances of this type.

For each entry in the array, an entry is added to the type's dictionary (see
@ref{3d1a,,tp_dict} below) containing a getset descriptor.

@strong{Inheritance:}

This field is not inherited by subtypes (computed attributes are inherited
through a different mechanism).
@end deffn

@geindex PyTypeObject.tp_base (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_base}@anchor{3af5}
@deffn {C 成员} PyTypeObject* PyTypeObject.tp_base

An optional pointer to a base type from which type properties are inherited.  At
this level, only single inheritance is supported; multiple inheritance require
dynamically creating a type object by calling the metatype.

@cartouche
@quotation 注解 
@c from Modules/xxmodule.c

Slot initialization is subject to the rules of initializing globals.
C99 requires the initializers to be "address constants".  Function
designators like @ref{3ae2,,PyType_GenericNew()}, with implicit conversion
to a pointer, are valid C99 address constants.

However, the unary '&' operator applied to a non-static variable
like @code{PyBaseObject_Type()} is not required to produce an address
constant.  Compilers may support this (gcc does), MSVC does not.
Both compilers are strictly standard conforming in this particular
behavior.

Consequently, @ref{3af5,,tp_base} should be set in
the extension module's init function.
@end quotation
@end cartouche

@strong{Inheritance:}

This field is not inherited by subtypes (obviously).

@strong{Default:}

This field defaults to @code{&PyBaseObject_Type} (which to Python
programmers is known as the type @ref{2b0,,object}).
@end deffn

@geindex PyTypeObject.tp_dict (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_dict}@anchor{3d1a}
@deffn {C 成员} PyObject* PyTypeObject.tp_dict

The type's dictionary is stored here by @ref{3ae7,,PyType_Ready()}.

This field should normally be initialized to @code{NULL} before PyType_Ready is
called; it may also be initialized to a dictionary containing initial attributes
for the type.  Once @ref{3ae7,,PyType_Ready()} has initialized the type, extra
attributes for the type may be added to this dictionary only if they don't
correspond to overloaded operations (like @ref{13ef,,__add__()}).

@strong{Inheritance:}

This field is not inherited by subtypes (though the attributes defined in here
are inherited through a different mechanism).

@strong{Default:}

If this field is @code{NULL}, @ref{3ae7,,PyType_Ready()} will assign a new
dictionary to it.

@cartouche
@quotation 警告 
It is not safe to use @ref{3ac8,,PyDict_SetItem()} on or otherwise modify
@ref{3d1a,,tp_dict} with the dictionary C-API.
@end quotation
@end cartouche
@end deffn

@geindex PyTypeObject.tp_descr_get (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_descr_get}@anchor{4012}
@deffn {C 成员} descrgetfunc PyTypeObject.tp_descr_get

An optional pointer to a "descriptor get" function.

The function signature is:

@example
PyObject * tp_descr_get(PyObject *self, PyObject *obj, PyObject *type);
@end example

@c XXX explain more?

@strong{Inheritance:}

This field is inherited by subtypes.
@end deffn

@geindex PyTypeObject.tp_descr_set (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_descr_set}@anchor{4014}
@deffn {C 成员} descrsetfunc PyTypeObject.tp_descr_set

An optional pointer to a function for setting and deleting
a descriptor's value.

The function signature is:

@example
int tp_descr_set(PyObject *self, PyObject *obj, PyObject *value);
@end example

The @emph{value} argument is set to @code{NULL} to delete the value.

@c XXX explain more?

@strong{Inheritance:}

This field is inherited by subtypes.
@end deffn

@geindex PyTypeObject.tp_dictoffset (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_dictoffset}@anchor{3d1f}
@deffn {C 成员} Py_ssize_t PyTypeObject.tp_dictoffset

If the instances of this type have a dictionary containing instance variables,
this field is non-zero and contains the offset in the instances of the type of
the instance variable dictionary; this offset is used by
@ref{3c59,,PyObject_GenericGetAttr()}.

Do not confuse this field with @ref{3d1a,,tp_dict}; that is the dictionary for
attributes of the type object itself.

If the value of this field is greater than zero, it specifies the offset from
the start of the instance structure.  If the value is less than zero, it
specifies the offset from the @emph{end} of the instance structure.  A negative
offset is more expensive to use, and should only be used when the instance
structure contains a variable-length part.  This is used for example to add an
instance variable dictionary to subtypes of @ref{329,,str} or @ref{478,,tuple}. Note
that the @ref{3ade,,tp_basicsize} field should account for the dictionary added to
the end in that case, even though the dictionary is not included in the basic
object layout.  On a system with a pointer size of 4 bytes,
@ref{3d1f,,tp_dictoffset} should be set to @code{-4} to indicate that the dictionary is
at the very end of the structure.

The real dictionary offset in an instance can be computed from a negative
@ref{3d1f,,tp_dictoffset} as follows:

@example
dictoffset = tp_basicsize + abs(ob_size)*tp_itemsize + tp_dictoffset
if dictoffset is not aligned on sizeof(void*):
    round up to sizeof(void*)
@end example

where @ref{3ade,,tp_basicsize}, @ref{3add,,tp_itemsize} and @ref{3d1f,,tp_dictoffset} are
taken from the type object, and @code{ob_size} is taken from the instance.  The
absolute value is taken because ints use the sign of @code{ob_size} to
store the sign of the number.  (There's never a need to do this calculation
yourself; it is done for you by @code{_PyObject_GetDictPtr()}.)

@strong{Inheritance:}

This field is inherited by subtypes, but see the rules listed below. A subtype
may override this offset; this means that the subtype instances store the
dictionary at a difference offset than the base type.  Since the dictionary is
always found via @ref{3d1f,,tp_dictoffset}, this should not be a problem.

When a type defined by a class statement has no @ref{e26,,__slots__} declaration,
and none of its base types has an instance variable dictionary, a dictionary
slot is added to the instance layout and the @ref{3d1f,,tp_dictoffset} is set to
that slot's offset.

When a type defined by a class statement has a @code{__slots__} declaration,
the type inherits its @ref{3d1f,,tp_dictoffset} from its base type.

(Adding a slot named @ref{4f6,,__dict__} to the @code{__slots__} declaration does
not have the expected effect, it just causes confusion.  Maybe this should be
added as a feature just like @code{__weakref__} though.)

@strong{Default:}

This slot has no default.  For static types, if the field is
@code{NULL} then no @code{__dict__} gets created for instances.
@end deffn

@geindex PyTypeObject.tp_init (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_init}@anchor{3ae8}
@deffn {C 成员} initproc PyTypeObject.tp_init

An optional pointer to an instance initialization function.

This function corresponds to the @ref{d57,,__init__()} method of classes.  Like
@ref{d57,,__init__()}, it is possible to create an instance without calling
@ref{d57,,__init__()}, and it is possible to reinitialize an instance by calling its
@ref{d57,,__init__()} method again.

The function signature is:

@example
int tp_init(PyObject *self, PyObject *args, PyObject *kwds);
@end example

The self argument is the instance to be initialized; the @emph{args} and @emph{kwds}
arguments represent positional and keyword arguments of the call to
@ref{d57,,__init__()}.

The @ref{3ae8,,tp_init} function, if not @code{NULL}, is called when an instance is
created normally by calling its type, after the type's @ref{3ae1,,tp_new} function
has returned an instance of the type.  If the @ref{3ae1,,tp_new} function returns an
instance of some other type that is not a subtype of the original type, no
@ref{3ae8,,tp_init} function is called; if @ref{3ae1,,tp_new} returns an instance of a
subtype of the original type, the subtype's @ref{3ae8,,tp_init} is called.

Returns @code{0} on success, @code{-1} and sets an exception on error.

@strong{Inheritance:}

This field is inherited by subtypes.

@strong{Default:}

For static types this field does not have a default.
@end deffn

@geindex PyTypeObject.tp_alloc (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_alloc}@anchor{3ae6}
@deffn {C 成员} allocfunc PyTypeObject.tp_alloc

An optional pointer to an instance allocation function.

The function signature is:

@example
PyObject *tp_alloc(PyTypeObject *self, Py_ssize_t nitems);
@end example

@strong{Inheritance:}

This field is inherited by static subtypes, but not by dynamic
subtypes (subtypes created by a class statement).

@strong{Default:}

For dynamic subtypes, this field is always set to
@ref{270,,PyType_GenericAlloc()}, to force a standard heap
allocation strategy.

For static subtypes, @code{PyBaseObject_Type} uses
@ref{270,,PyType_GenericAlloc()}.  That is the recommended value
for all statically defined types.
@end deffn

@geindex PyTypeObject.tp_new (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_new}@anchor{3ae1}
@deffn {C 成员} newfunc PyTypeObject.tp_new

An optional pointer to an instance creation function.

The function signature is:

@example
PyObject *tp_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds);
@end example

The subtype argument is the type of the object being created; the @emph{args} and
@emph{kwds} arguments represent positional and keyword arguments of the call to the
type.  Note that subtype doesn't have to equal the type whose @ref{3ae1,,tp_new}
function is called; it may be a subtype of that type (but not an unrelated
type).

The @ref{3ae1,,tp_new} function should call @code{subtype->tp_alloc(subtype, nitems)}
to allocate space for the object, and then do only as much further
initialization as is absolutely necessary.  Initialization that can safely be
ignored or repeated should be placed in the @ref{3ae8,,tp_init} handler.  A good
rule of thumb is that for immutable types, all initialization should take place
in @ref{3ae1,,tp_new}, while for mutable types, most initialization should be
deferred to @ref{3ae8,,tp_init}.

@strong{Inheritance:}

This field is inherited by subtypes, except it is not inherited by static types
whose @ref{3af5,,tp_base} is @code{NULL} or @code{&PyBaseObject_Type}.

@strong{Default:}

For static types this field has no default.  This means if the
slot is defined as @code{NULL}, the type cannot be called to create new
instances; presumably there is some other way to create
instances, like a factory function.
@end deffn

@geindex PyTypeObject.tp_free (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_free}@anchor{3ae5}
@deffn {C 成员} freefunc PyTypeObject.tp_free

An optional pointer to an instance deallocation function.  Its signature is:

@example
void tp_free(void *self);
@end example

An initializer that is compatible with this signature is @ref{4fe,,PyObject_Free()}.

@strong{Inheritance:}

This field is inherited by static subtypes, but not by dynamic
subtypes (subtypes created by a class statement)

@strong{Default:}

In dynamic subtypes, this field is set to a deallocator suitable to
match @ref{270,,PyType_GenericAlloc()} and the value of the
@ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit.

For static subtypes, @code{PyBaseObject_Type} uses PyObject_Del.
@end deffn

@geindex PyTypeObject.tp_is_gc (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_is_gc}@anchor{401a}
@deffn {C 成员} inquiry PyTypeObject.tp_is_gc

An optional pointer to a function called by the garbage collector.

The garbage collector needs to know whether a particular object is collectible
or not.  Normally, it is sufficient to look at the object's type's
@ref{3d06,,tp_flags} field, and check the @ref{3af3,,Py_TPFLAGS_HAVE_GC} flag bit.  But
some types have a mixture of statically and dynamically allocated instances, and
the statically allocated instances are not collectible.  Such types should
define this function; it should return @code{1} for a collectible instance, and
@code{0} for a non-collectible instance. The signature is:

@example
int tp_is_gc(PyObject *self);
@end example

(The only example of this are types themselves.  The metatype,
@ref{3d01,,PyType_Type}, defines this function to distinguish between statically
and dynamically allocated types.)

@strong{Inheritance:}

This field is inherited by subtypes.

@strong{Default:}

This slot has no default.  If this field is @code{NULL},
@ref{3af3,,Py_TPFLAGS_HAVE_GC} is used as the functional equivalent.
@end deffn

@geindex PyTypeObject.tp_bases (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_bases}@anchor{401b}
@deffn {C 成员} PyObject* PyTypeObject.tp_bases

Tuple of base types.

This is set for types created by a class statement.  It should be @code{NULL} for
statically defined types.

@strong{Inheritance:}

This field is not inherited.
@end deffn

@geindex PyTypeObject.tp_mro (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_mro}@anchor{3d1b}
@deffn {C 成员} PyObject* PyTypeObject.tp_mro

Tuple containing the expanded set of base types, starting with the type itself
and ending with @ref{2b0,,object}, in Method Resolution Order.

@strong{Inheritance:}

This field is not inherited; it is calculated fresh by
@ref{3ae7,,PyType_Ready()}.
@end deffn

@geindex PyTypeObject.tp_cache (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_cache}@anchor{3d1c}
@deffn {C 成员} PyObject* PyTypeObject.tp_cache

Unused.  Internal use only.

@strong{Inheritance:}

This field is not inherited.
@end deffn

@geindex PyTypeObject.tp_subclasses (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_subclasses}@anchor{3d1d}
@deffn {C 成员} PyObject* PyTypeObject.tp_subclasses

List of weak references to subclasses.  Internal use only.

@strong{Inheritance:}

This field is not inherited.
@end deffn

@geindex PyTypeObject.tp_weaklist (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_weaklist}@anchor{3d1e}
@deffn {C 成员} PyObject* PyTypeObject.tp_weaklist

Weak reference list head, for weak references to this type object.  Not
inherited.  Internal use only.

@strong{Inheritance:}

This field is not inherited.
@end deffn

@geindex PyTypeObject.tp_del (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_del}@anchor{401c}
@deffn {C 成员} destructor PyTypeObject.tp_del

This field is deprecated.  Use @ref{2d7,,tp_finalize} instead.
@end deffn

@geindex PyTypeObject.tp_version_tag (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_version_tag}@anchor{401d}
@deffn {C 成员} unsigned int PyTypeObject.tp_version_tag

Used to index into the method cache.  Internal use only.

@strong{Inheritance:}

This field is not inherited.
@end deffn

@geindex PyTypeObject.tp_finalize (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_finalize}@anchor{2d7}
@deffn {C 成员} destructor PyTypeObject.tp_finalize

An optional pointer to an instance finalization function.  Its signature is:

@example
void tp_finalize(PyObject *self);
@end example

If @ref{2d7,,tp_finalize} is set, the interpreter calls it once when
finalizing an instance.  It is called either from the garbage
collector (if the instance is part of an isolated reference cycle) or
just before the object is deallocated.  Either way, it is guaranteed
to be called before attempting to break reference cycles, ensuring
that it finds the object in a sane state.

@ref{2d7,,tp_finalize} should not mutate the current exception status;
therefore, a recommended way to write a non-trivial finalizer is:

@example
static void
local_finalize(PyObject *self)
@{
    PyObject *error_type, *error_value, *error_traceback;

    /* Save the current exception, if any. */
    PyErr_Fetch(&error_type, &error_value, &error_traceback);

    /* ... */

    /* Restore the saved exception. */
    PyErr_Restore(error_type, error_value, error_traceback);
@}
@end example

For this field to be taken into account (even through inheritance),
you must also set the @ref{2d8,,Py_TPFLAGS_HAVE_FINALIZE} flags bit.

@strong{Inheritance:}

This field is inherited by subtypes.


3.4 新版功能.



@subsubheading 参见


"Safe object finalization" (
@geindex Python 提高建议; PEP 442
PEP 442@footnote{https://www.python.org/dev/peps/pep-0442})

@end deffn

The remaining fields are only defined if the feature test macro
@code{COUNT_ALLOCS} is defined, and are for internal use only. They are
documented here for completeness.  None of these fields are inherited by
subtypes.

@geindex PyTypeObject.tp_allocs (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_allocs}@anchor{401e}
@deffn {C 成员} Py_ssize_t PyTypeObject.tp_allocs

Number of allocations.
@end deffn

@geindex PyTypeObject.tp_frees (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_frees}@anchor{401f}
@deffn {C 成员} Py_ssize_t PyTypeObject.tp_frees

Number of frees.
@end deffn

@geindex PyTypeObject.tp_maxalloc (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_maxalloc}@anchor{4020}
@deffn {C 成员} Py_ssize_t PyTypeObject.tp_maxalloc

Maximum simultaneously allocated objects.
@end deffn

@geindex PyTypeObject.tp_prev (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_prev}@anchor{4021}
@deffn {C 成员} PyTypeObject* PyTypeObject.tp_prev

Pointer to the previous type object with a non-zero @ref{401e,,tp_allocs} field.
@end deffn

@geindex PyTypeObject.tp_next (C 成员)
@anchor{c-api/typeobj c PyTypeObject tp_next}@anchor{4022}
@deffn {C 成员} PyTypeObject* PyTypeObject.tp_next

Pointer to the next type object with a non-zero @ref{401e,,tp_allocs} field.
@end deffn

Also, note that, in a garbage collected Python, @ref{3ae4,,tp_dealloc} may be called from
any Python thread, not just the thread which created the object (if the object
becomes part of a refcount cycle, that cycle might be collected by a garbage
collection on any thread).  This is not a problem for Python API calls, since
the thread on which tp_dealloc is called will own the Global Interpreter Lock
(GIL). However, if the object being destroyed in turn destroys objects from some
other C or C++ library, care should be taken to ensure that destroying those
objects on the thread which called tp_dealloc will not violate any assumptions
of the library.

@node Heap Types,,PyTypeObject Slots,类型对象<3>
@anchor{c-api/typeobj heap-types}@anchor{3d0c}@anchor{c-api/typeobj id4}@anchor{406c}
@subsubsection Heap Types


Traditionally, types defined in C code are @emph{static}, that is,
a static @ref{2d6,,PyTypeObject} structure is defined directly in code
and initialized using @ref{3ae7,,PyType_Ready()}.

This results in types that are limited relative to types defined in Python:


@itemize *

@item 
Static types are limited to one base, i.e. they cannot use multiple
inheritance.

@item 
Static type objects (but not necessarily their instances) are immutable.
It is not possible to add or modify the type object's attributes from Python.

@item 
Static type objects are shared across
@ref{3be6,,sub-interpreters}, so they should not
include any subinterpreter-specific state.
@end itemize

Also, since @ref{2d6,,PyTypeObject} is not part of the @ref{3b66,,stable ABI},
any extension modules using static types must be compiled for a specific
Python minor version.

An alternative to static types is @emph{heap-allocated types}, or @emph{heap types}
for short, which correspond closely to classes created by Python's
@code{class} statement.

This is done by filling a @ref{3d0f,,PyType_Spec} structure and calling
@ref{3d0d,,PyType_FromSpecWithBases()}.

@node Number Object Structures,Mapping Object Structures,类型对象<3>,对象实现支持
@anchor{c-api/typeobj number-object-structures}@anchor{407d}@anchor{c-api/typeobj number-structs}@anchor{406e}
@subsection Number Object Structures


@geindex PyNumberMethods (C 类型)
@anchor{c-api/typeobj c PyNumberMethods}@anchor{d7a}
@deffn {C 类型} PyNumberMethods

This structure holds pointers to the functions which an object uses to
implement the number protocol.  Each function is used by the function of
similar name documented in the @ref{3c75,,数字协议} section.

@c XXX Drop the definition?

Here is the structure definition:

@example
typedef struct @{
     binaryfunc nb_add;
     binaryfunc nb_subtract;
     binaryfunc nb_multiply;
     binaryfunc nb_remainder;
     binaryfunc nb_divmod;
     ternaryfunc nb_power;
     unaryfunc nb_negative;
     unaryfunc nb_positive;
     unaryfunc nb_absolute;
     inquiry nb_bool;
     unaryfunc nb_invert;
     binaryfunc nb_lshift;
     binaryfunc nb_rshift;
     binaryfunc nb_and;
     binaryfunc nb_xor;
     binaryfunc nb_or;
     unaryfunc nb_int;
     void *nb_reserved;
     unaryfunc nb_float;

     binaryfunc nb_inplace_add;
     binaryfunc nb_inplace_subtract;
     binaryfunc nb_inplace_multiply;
     binaryfunc nb_inplace_remainder;
     ternaryfunc nb_inplace_power;
     binaryfunc nb_inplace_lshift;
     binaryfunc nb_inplace_rshift;
     binaryfunc nb_inplace_and;
     binaryfunc nb_inplace_xor;
     binaryfunc nb_inplace_or;

     binaryfunc nb_floor_divide;
     binaryfunc nb_true_divide;
     binaryfunc nb_inplace_floor_divide;
     binaryfunc nb_inplace_true_divide;

     unaryfunc nb_index;

     binaryfunc nb_matrix_multiply;
     binaryfunc nb_inplace_matrix_multiply;
@} PyNumberMethods;
@end example

@cartouche
@quotation 注解 
Binary and ternary functions must check the type of all their operands,
and implement the necessary conversions (at least one of the operands is
an instance of the defined type).  If the operation is not defined for the
given operands, binary and ternary functions must return
@code{Py_NotImplemented}, if another error occurred they must return @code{NULL}
and set an exception.
@end quotation
@end cartouche

@cartouche
@quotation 注解 
The @code{nb_reserved} field should always be @code{NULL}.  It
was previously called @code{nb_long}, and was renamed in
Python 3.0.1.
@end quotation
@end cartouche
@end deffn

@geindex PyNumberMethods.nb_add (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_add}@anchor{3d18}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_add
@end deffn

@geindex PyNumberMethods.nb_subtract (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_subtract}@anchor{402a}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_subtract
@end deffn

@geindex PyNumberMethods.nb_multiply (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_multiply}@anchor{402c}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_multiply
@end deffn

@geindex PyNumberMethods.nb_remainder (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_remainder}@anchor{402e}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_remainder
@end deffn

@geindex PyNumberMethods.nb_divmod (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_divmod}@anchor{4030}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_divmod
@end deffn

@geindex PyNumberMethods.nb_power (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_power}@anchor{4031}
@deffn {C 成员} ternaryfunc PyNumberMethods.nb_power
@end deffn

@geindex PyNumberMethods.nb_negative (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_negative}@anchor{4033}
@deffn {C 成员} unaryfunc PyNumberMethods.nb_negative
@end deffn

@geindex PyNumberMethods.nb_positive (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_positive}@anchor{4034}
@deffn {C 成员} unaryfunc PyNumberMethods.nb_positive
@end deffn

@geindex PyNumberMethods.nb_absolute (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_absolute}@anchor{4035}
@deffn {C 成员} unaryfunc PyNumberMethods.nb_absolute
@end deffn

@geindex PyNumberMethods.nb_bool (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_bool}@anchor{4036}
@deffn {C 成员} inquiry PyNumberMethods.nb_bool
@end deffn

@geindex PyNumberMethods.nb_invert (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_invert}@anchor{4037}
@deffn {C 成员} unaryfunc PyNumberMethods.nb_invert
@end deffn

@geindex PyNumberMethods.nb_lshift (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_lshift}@anchor{4038}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_lshift
@end deffn

@geindex PyNumberMethods.nb_rshift (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_rshift}@anchor{403a}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_rshift
@end deffn

@geindex PyNumberMethods.nb_and (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_and}@anchor{403c}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_and
@end deffn

@geindex PyNumberMethods.nb_xor (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_xor}@anchor{403e}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_xor
@end deffn

@geindex PyNumberMethods.nb_or (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_or}@anchor{4040}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_or
@end deffn

@geindex PyNumberMethods.nb_int (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_int}@anchor{4042}
@deffn {C 成员} unaryfunc PyNumberMethods.nb_int
@end deffn

@geindex PyNumberMethods.nb_reserved (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_reserved}@anchor{4043}
@deffn {C 成员} void *PyNumberMethods.nb_reserved
@end deffn

@geindex PyNumberMethods.nb_float (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_float}@anchor{4044}
@deffn {C 成员} unaryfunc PyNumberMethods.nb_float
@end deffn

@geindex PyNumberMethods.nb_inplace_add (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_add}@anchor{4029}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_add
@end deffn

@geindex PyNumberMethods.nb_inplace_subtract (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_subtract}@anchor{402b}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_subtract
@end deffn

@geindex PyNumberMethods.nb_inplace_multiply (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_multiply}@anchor{402d}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_multiply
@end deffn

@geindex PyNumberMethods.nb_inplace_remainder (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_remainder}@anchor{402f}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_remainder
@end deffn

@geindex PyNumberMethods.nb_inplace_power (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_power}@anchor{4032}
@deffn {C 成员} ternaryfunc PyNumberMethods.nb_inplace_power
@end deffn

@geindex PyNumberMethods.nb_inplace_lshift (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_lshift}@anchor{4039}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_lshift
@end deffn

@geindex PyNumberMethods.nb_inplace_rshift (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_rshift}@anchor{403b}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_rshift
@end deffn

@geindex PyNumberMethods.nb_inplace_and (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_and}@anchor{403d}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_and
@end deffn

@geindex PyNumberMethods.nb_inplace_xor (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_xor}@anchor{403f}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_xor
@end deffn

@geindex PyNumberMethods.nb_inplace_or (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_or}@anchor{4041}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_or
@end deffn

@geindex PyNumberMethods.nb_floor_divide (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_floor_divide}@anchor{4045}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_floor_divide
@end deffn

@geindex PyNumberMethods.nb_true_divide (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_true_divide}@anchor{4047}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_true_divide
@end deffn

@geindex PyNumberMethods.nb_inplace_floor_divide (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_floor_divide}@anchor{4046}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_floor_divide
@end deffn

@geindex PyNumberMethods.nb_inplace_true_divide (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_true_divide}@anchor{4048}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_true_divide
@end deffn

@geindex PyNumberMethods.nb_index (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_index}@anchor{4049}
@deffn {C 成员} unaryfunc PyNumberMethods.nb_index
@end deffn

@geindex PyNumberMethods.nb_matrix_multiply (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_matrix_multiply}@anchor{404a}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_matrix_multiply
@end deffn

@geindex PyNumberMethods.nb_inplace_matrix_multiply (C 成员)
@anchor{c-api/typeobj c PyNumberMethods nb_inplace_matrix_multiply}@anchor{404b}
@deffn {C 成员} binaryfunc PyNumberMethods.nb_inplace_matrix_multiply
@end deffn

@node Mapping Object Structures,Sequence Object Structures,Number Object Structures,对象实现支持
@anchor{c-api/typeobj mapping-object-structures}@anchor{407e}@anchor{c-api/typeobj mapping-structs}@anchor{4070}
@subsection Mapping Object Structures


@geindex PyMappingMethods (C 类型)
@anchor{c-api/typeobj c PyMappingMethods}@anchor{3b0f}
@deffn {C 类型} PyMappingMethods

This structure holds pointers to the functions which an object uses to
implement the mapping protocol.  It has three members:
@end deffn

@geindex PyMappingMethods.mp_length (C 成员)
@anchor{c-api/typeobj c PyMappingMethods mp_length}@anchor{404c}
@deffn {C 成员} lenfunc PyMappingMethods.mp_length

This function is used by @ref{fe4,,PyMapping_Size()} and
@ref{3c6f,,PyObject_Size()}, and has the same signature.  This slot may be set to
@code{NULL} if the object has no defined length.
@end deffn

@geindex PyMappingMethods.mp_subscript (C 成员)
@anchor{c-api/typeobj c PyMappingMethods mp_subscript}@anchor{404e}
@deffn {C 成员} binaryfunc PyMappingMethods.mp_subscript

This function is used by @ref{3b57,,PyObject_GetItem()} and
@ref{3c9f,,PySequence_GetSlice()}, and has the same signature as
@code{PyObject_GetItem()}.  This slot must be filled for the
@ref{3cb0,,PyMapping_Check()} function to return @code{1}, it can be @code{NULL}
otherwise.
@end deffn

@geindex PyMappingMethods.mp_ass_subscript (C 成员)
@anchor{c-api/typeobj c PyMappingMethods mp_ass_subscript}@anchor{404f}
@deffn {C 成员} objobjargproc PyMappingMethods.mp_ass_subscript

This function is used by @ref{3b55,,PyObject_SetItem()},
@ref{3c71,,PyObject_DelItem()}, @code{PyObject_SetSlice()} and
@code{PyObject_DelSlice()}.  It has the same signature as
@code{PyObject_SetItem()}, but @emph{v} can also be set to @code{NULL} to delete
an item.  If this slot is @code{NULL}, the object does not support item
assignment and deletion.
@end deffn

@node Sequence Object Structures,Buffer Object Structures,Mapping Object Structures,对象实现支持
@anchor{c-api/typeobj sequence-object-structures}@anchor{407f}@anchor{c-api/typeobj sequence-structs}@anchor{406f}
@subsection Sequence Object Structures


@geindex PySequenceMethods (C 类型)
@anchor{c-api/typeobj c PySequenceMethods}@anchor{3b0e}
@deffn {C 类型} PySequenceMethods

This structure holds pointers to the functions which an object uses to
implement the sequence protocol.
@end deffn

@geindex PySequenceMethods.sq_length (C 成员)
@anchor{c-api/typeobj c PySequenceMethods sq_length}@anchor{3d19}
@deffn {C 成员} lenfunc PySequenceMethods.sq_length

This function is used by @ref{fe0,,PySequence_Size()} and
@ref{3c6f,,PyObject_Size()}, and has the same signature.  It is also used for
handling negative indices via the @ref{4054,,sq_item}
and the @ref{4055,,sq_ass_item} slots.
@end deffn

@geindex PySequenceMethods.sq_concat (C 成员)
@anchor{c-api/typeobj c PySequenceMethods sq_concat}@anchor{4051}
@deffn {C 成员} binaryfunc PySequenceMethods.sq_concat

This function is used by @ref{3c9b,,PySequence_Concat()} and has the same
signature.  It is also used by the @code{+} operator, after trying the numeric
addition via the @ref{3d18,,nb_add} slot.
@end deffn

@geindex PySequenceMethods.sq_repeat (C 成员)
@anchor{c-api/typeobj c PySequenceMethods sq_repeat}@anchor{4052}
@deffn {C 成员} ssizeargfunc PySequenceMethods.sq_repeat

This function is used by @ref{3c9c,,PySequence_Repeat()} and has the same
signature.  It is also used by the @code{*} operator, after trying numeric
multiplication via the @ref{402c,,nb_multiply} slot.
@end deffn

@geindex PySequenceMethods.sq_item (C 成员)
@anchor{c-api/typeobj c PySequenceMethods sq_item}@anchor{4054}
@deffn {C 成员} ssizeargfunc PySequenceMethods.sq_item

This function is used by @ref{fe1,,PySequence_GetItem()} and has the same
signature.  It is also used by @ref{3b57,,PyObject_GetItem()}, after trying
the subscription via the @ref{404e,,mp_subscript} slot.
This slot must be filled for the @ref{3c99,,PySequence_Check()}
function to return @code{1}, it can be @code{NULL} otherwise.

Negative indexes are handled as follows: if the @code{sq_length} slot is
filled, it is called and the sequence length is used to compute a positive
index which is passed to @code{sq_item}.  If @code{sq_length} is @code{NULL},
the index is passed as is to the function.
@end deffn

@geindex PySequenceMethods.sq_ass_item (C 成员)
@anchor{c-api/typeobj c PySequenceMethods sq_ass_item}@anchor{4055}
@deffn {C 成员} ssizeobjargproc PySequenceMethods.sq_ass_item

This function is used by @ref{fe2,,PySequence_SetItem()} and has the same
signature.  It is also used by @ref{3b55,,PyObject_SetItem()} and
@ref{3c71,,PyObject_DelItem()}, after trying the item assignment and deletion
via the @ref{404f,,mp_ass_subscript} slot.
This slot may be left to @code{NULL} if the object does not support
item assignment and deletion.
@end deffn

@geindex PySequenceMethods.sq_contains (C 成员)
@anchor{c-api/typeobj c PySequenceMethods sq_contains}@anchor{4057}
@deffn {C 成员} objobjproc PySequenceMethods.sq_contains

This function may be used by @ref{3ca3,,PySequence_Contains()} and has the same
signature.  This slot may be left to @code{NULL}, in this case
@code{PySequence_Contains()} simply traverses the sequence until it
finds a match.
@end deffn

@geindex PySequenceMethods.sq_inplace_concat (C 成员)
@anchor{c-api/typeobj c PySequenceMethods sq_inplace_concat}@anchor{4059}
@deffn {C 成员} binaryfunc PySequenceMethods.sq_inplace_concat

This function is used by @ref{3c9d,,PySequence_InPlaceConcat()} and has the same
signature.  It should modify its first operand, and return it.  This slot
may be left to @code{NULL}, in this case @code{PySequence_InPlaceConcat()}
will fall back to @ref{3c9b,,PySequence_Concat()}.  It is also used by the
augmented assignment @code{+=}, after trying numeric in-place addition
via the @ref{4029,,nb_inplace_add} slot.
@end deffn

@geindex PySequenceMethods.sq_inplace_repeat (C 成员)
@anchor{c-api/typeobj c PySequenceMethods sq_inplace_repeat}@anchor{405a}
@deffn {C 成员} ssizeargfunc PySequenceMethods.sq_inplace_repeat

This function is used by @ref{3c9e,,PySequence_InPlaceRepeat()} and has the same
signature.  It should modify its first operand, and return it.  This slot
may be left to @code{NULL}, in this case @code{PySequence_InPlaceRepeat()}
will fall back to @ref{3c9c,,PySequence_Repeat()}.  It is also used by the
augmented assignment @code{*=}, after trying numeric in-place multiplication
via the @ref{402d,,nb_inplace_multiply} slot.
@end deffn

@node Buffer Object Structures,Async Object Structures,Sequence Object Structures,对象实现支持
@anchor{c-api/typeobj buffer-object-structures}@anchor{4080}@anchor{c-api/typeobj buffer-structs}@anchor{3cbe}
@subsection Buffer Object Structures


@geindex PyBufferProcs (C 类型)
@anchor{c-api/typeobj c PyBufferProcs}@anchor{400c}
@deffn {C 类型} PyBufferProcs

This structure holds pointers to the functions required by the
@ref{15d6,,Buffer protocol}. The protocol defines how
an exporter object can expose its internal data to consumer objects.
@end deffn

@geindex PyBufferProcs.bf_getbuffer (C 成员)
@anchor{c-api/typeobj c PyBufferProcs bf_getbuffer}@anchor{3d20}
@deffn {C 成员} getbufferproc PyBufferProcs.bf_getbuffer

The signature of this function is:

@example
int (PyObject *exporter, Py_buffer *view, int flags);
@end example

Handle a request to @emph{exporter} to fill in @emph{view} as specified by @emph{flags}.
Except for point (3), an implementation of this function MUST take these
steps:


@enumerate 

@item 
Check if the request can be met. If not, raise @code{PyExc_BufferError},
set @code{view->obj} to @code{NULL} and return @code{-1}.

@item 
Fill in the requested fields.

@item 
Increment an internal counter for the number of exports.

@item 
Set @code{view->obj} to @emph{exporter} and increment @code{view->obj}.

@item 
Return @code{0}.
@end enumerate

If @emph{exporter} is part of a chain or tree of buffer providers, two main
schemes can be used:


@itemize *

@item 
Re-export: Each member of the tree acts as the exporting object and
sets @code{view->obj} to a new reference to itself.

@item 
Redirect: The buffer request is redirected to the root object of the
tree. Here, @code{view->obj} will be a new reference to the root
object.
@end itemize

The individual fields of @emph{view} are described in section
@ref{3cbf,,Buffer structure}, the rules how an exporter
must react to specific requests are in section
@ref{3cd3,,Buffer request types}.

All memory pointed to in the @ref{b14,,Py_buffer} structure belongs to
the exporter and must remain valid until there are no consumers left.
@ref{3ccc,,format}, @ref{3cce,,shape},
@ref{3cc3,,strides}, @ref{3cd0,,suboffsets}
and @ref{3cd2,,internal}
are read-only for the consumer.

@ref{3cc6,,PyBuffer_FillInfo()} provides an easy way of exposing a simple
bytes buffer while dealing correctly with all request types.

@ref{d1e,,PyObject_GetBuffer()} is the interface for the consumer that
wraps this function.
@end deffn

@geindex PyBufferProcs.bf_releasebuffer (C 成员)
@anchor{c-api/typeobj c PyBufferProcs bf_releasebuffer}@anchor{3c21}
@deffn {C 成员} releasebufferproc PyBufferProcs.bf_releasebuffer

The signature of this function is:

@example
void (PyObject *exporter, Py_buffer *view);
@end example

Handle a request to release the resources of the buffer. If no resources
need to be released, @ref{3c21,,PyBufferProcs.bf_releasebuffer} may be
@code{NULL}. Otherwise, a standard implementation of this function will take
these optional steps:


@enumerate 

@item 
Decrement an internal counter for the number of exports.

@item 
If the counter is @code{0}, free all memory associated with @emph{view}.
@end enumerate

The exporter MUST use the @ref{3cd2,,internal} field to keep
track of buffer-specific resources. This field is guaranteed to remain
constant, while a consumer MAY pass a copy of the original buffer as the
@emph{view} argument.

This function MUST NOT decrement @code{view->obj}, since that is
done automatically in @ref{d4d,,PyBuffer_Release()} (this scheme is
useful for breaking reference cycles).

@ref{d4d,,PyBuffer_Release()} is the interface for the consumer that
wraps this function.
@end deffn

@node Async Object Structures,Slot Type typedefs,Buffer Object Structures,对象实现支持
@anchor{c-api/typeobj async-object-structures}@anchor{4081}@anchor{c-api/typeobj async-structs}@anchor{406d}
@subsection Async Object Structures



3.5 新版功能.


@geindex PyAsyncMethods (C 类型)
@anchor{c-api/typeobj c PyAsyncMethods}@anchor{3d17}
@deffn {C 类型} PyAsyncMethods

This structure holds pointers to the functions required to implement
@ref{513,,awaitable} and @ref{63f,,asynchronous iterator} objects.

Here is the structure definition:

@example
typedef struct @{
    unaryfunc am_await;
    unaryfunc am_aiter;
    unaryfunc am_anext;
@} PyAsyncMethods;
@end example
@end deffn

@geindex PyAsyncMethods.am_await (C 成员)
@anchor{c-api/typeobj c PyAsyncMethods am_await}@anchor{4024}
@deffn {C 成员} unaryfunc PyAsyncMethods.am_await

The signature of this function is:

@example
PyObject *am_await(PyObject *self);
@end example

The returned object must be an iterator, i.e. @ref{fa3,,PyIter_Check()} must
return @code{1} for it.

This slot may be set to @code{NULL} if an object is not an @ref{513,,awaitable}.
@end deffn

@geindex PyAsyncMethods.am_aiter (C 成员)
@anchor{c-api/typeobj c PyAsyncMethods am_aiter}@anchor{4026}
@deffn {C 成员} unaryfunc PyAsyncMethods.am_aiter

The signature of this function is:

@example
PyObject *am_aiter(PyObject *self);
@end example

Must return an @ref{513,,awaitable} object.  See @ref{142d,,__anext__()} for details.

This slot may be set to @code{NULL} if an object does not implement
asynchronous iteration protocol.
@end deffn

@geindex PyAsyncMethods.am_anext (C 成员)
@anchor{c-api/typeobj c PyAsyncMethods am_anext}@anchor{4027}
@deffn {C 成员} unaryfunc PyAsyncMethods.am_anext

The signature of this function is:

@example
PyObject *am_anext(PyObject *self);
@end example

Must return an @ref{513,,awaitable} object.  See @ref{142d,,__anext__()} for details.
This slot may be set to @code{NULL}.
@end deffn

@node Slot Type typedefs,例子<35>,Async Object Structures,对象实现支持
@anchor{c-api/typeobj id5}@anchor{405f}@anchor{c-api/typeobj slot-type-typedefs}@anchor{4082}
@subsection Slot Type typedefs


@geindex allocfunc (C 类型)
@anchor{c-api/typeobj c allocfunc}@anchor{4017}
@deffn {C 类型} PyObject *(*allocfunc) (PyTypeObject@w{ }*cls, Py_ssize_t@w{ }nitems)

The purpose of this function is to separate memory allocation from memory
initialization.  It should return a pointer to a block of memory of adequate
length for the instance, suitably aligned, and initialized to zeros, but with
@code{ob_refcnt} set to @code{1} and @code{ob_type} set to the type argument.  If
the type's @ref{3add,,tp_itemsize} is non-zero, the object's @code{ob_size} field
should be initialized to @emph{nitems} and the length of the allocated memory block
should be @code{tp_basicsize + nitems*tp_itemsize}, rounded up to a multiple of
@code{sizeof(void*)}; otherwise, @emph{nitems} is not used and the length of the block
should be @ref{3ade,,tp_basicsize}.

This function should not do any other instance initialization, not even to
allocate additional memory; that should be done by @ref{3ae1,,tp_new}.
@end deffn

@geindex destructor (C 类型)
@anchor{c-api/typeobj c destructor}@anchor{3ffe}
@deffn {C 类型} void (*destructor) (PyObject@w{ }*)
@end deffn

@geindex vectorcallfunc (C 类型)
@anchor{c-api/typeobj c vectorcallfunc}@anchor{406a}
@deffn {C 类型} PyObject *(*vectorcallfunc) (PyObject@w{ }*callable, PyObject *const@w{ }*args, size_t@w{ }nargsf, PyObject@w{ }*kwnames)

See @ref{3c67,,tp_vectorcall_offset}.

Arguments to @code{vectorcallfunc} are the same as for @ref{3c66,,_PyObject_Vectorcall()}.


3.8 新版功能.

@end deffn

@geindex freefunc (C 类型)
@anchor{c-api/typeobj c freefunc}@anchor{4019}
@deffn {C 类型} void (*freefunc) (void@w{ }*)

See @ref{3ae5,,tp_free}.
@end deffn

@geindex newfunc (C 类型)
@anchor{c-api/typeobj c newfunc}@anchor{4018}
@deffn {C 类型} PyObject *(*newfunc) (PyObject@w{ }*, PyObject@w{ }*, PyObject@w{ }*)

See @ref{3ae1,,tp_new}.
@end deffn

@geindex initproc (C 类型)
@anchor{c-api/typeobj c initproc}@anchor{4016}
@deffn {C 类型} int (*initproc) (PyObject@w{ }*, PyObject@w{ }*, PyObject@w{ }*)

See @ref{3ae8,,tp_init}.
@end deffn

@geindex reprfunc (C 类型)
@anchor{c-api/typeobj c reprfunc}@anchor{4003}
@deffn {C 类型} PyObject *(*reprfunc) (PyObject@w{ }*)

See @ref{3aff,,tp_repr}.
@end deffn

@geindex getattrfunc (C 类型)
@anchor{c-api/typeobj c getattrfunc}@anchor{3fff}
@deffn {C 类型} PyObject *(*getattrfunc) (PyObject@w{ }*self, char@w{ }*attr)

Return the value of the named attribute for the object.
@end deffn

@geindex setattrfunc (C 类型)
@anchor{c-api/typeobj c setattrfunc}@anchor{4000}
@deffn {C 类型} int (*setattrfunc) (PyObject@w{ }*self, char@w{ }*attr, PyObject@w{ }*value)

Set the value of the named attribute for the object.
The value argument is set to @code{NULL} to delete the attribute.
@end deffn

@geindex getattrofunc (C 类型)
@anchor{c-api/typeobj c getattrofunc}@anchor{4009}
@deffn {C 类型} PyObject *(*getattrofunc) (PyObject@w{ }*self, PyObject@w{ }*attr)

Return the value of the named attribute for the object.

See @ref{3b04,,tp_getattro}.
@end deffn

@geindex setattrofunc (C 类型)
@anchor{c-api/typeobj c setattrofunc}@anchor{400a}
@deffn {C 类型} int (*setattrofunc) (PyObject@w{ }*self, PyObject@w{ }*attr, PyObject@w{ }*value)

Set the value of the named attribute for the object.
The value argument is set to @code{NULL} to delete the attribute.

See @ref{3b05,,tp_setattro}.
@end deffn

@geindex descrgetfunc (C 类型)
@anchor{c-api/typeobj c descrgetfunc}@anchor{4013}
@deffn {C 类型} PyObject *(*descrgetfunc) (PyObject@w{ }*, PyObject@w{ }*, PyObject@w{ }*)

See @code{tp_descrget}.
@end deffn

@geindex descrsetfunc (C 类型)
@anchor{c-api/typeobj c descrsetfunc}@anchor{4015}
@deffn {C 类型} int (*descrsetfunc) (PyObject@w{ }*, PyObject@w{ }*, PyObject@w{ }*)

See @code{tp_descrset}.
@end deffn

@geindex hashfunc (C 类型)
@anchor{c-api/typeobj c hashfunc}@anchor{4007}
@deffn {C 类型} Py_hash_t (*hashfunc) (PyObject@w{ }*)

See @ref{3b10,,tp_hash}.
@end deffn

@geindex richcmpfunc (C 类型)
@anchor{c-api/typeobj c richcmpfunc}@anchor{400f}
@deffn {C 类型} PyObject *(*richcmpfunc) (PyObject@w{ }*, PyObject@w{ }*, int)

See @ref{3b0a,,tp_richcompare}.
@end deffn

@geindex getiterfunc (C 类型)
@anchor{c-api/typeobj c getiterfunc}@anchor{4010}
@deffn {C 类型} PyObject *(*getiterfunc) (PyObject@w{ }*)

See @ref{e29,,tp_iter}.
@end deffn

@geindex iternextfunc (C 类型)
@anchor{c-api/typeobj c iternextfunc}@anchor{4011}
@deffn {C 类型} PyObject *(*iternextfunc) (PyObject@w{ }*)

See @ref{e2a,,tp_iternext}.
@end deffn

@geindex lenfunc (C 类型)
@anchor{c-api/typeobj c lenfunc}@anchor{404d}
@deffn {C 类型} Py_ssize_t (*lenfunc) (PyObject@w{ }*)
@end deffn

@geindex getbufferproc (C 类型)
@anchor{c-api/typeobj c getbufferproc}@anchor{405b}
@deffn {C 类型} int (*getbufferproc) (PyObject@w{ }*, Py_buffer@w{ }*, int)
@end deffn

@geindex releasebufferproc (C 类型)
@anchor{c-api/typeobj c releasebufferproc}@anchor{405c}
@deffn {C 类型} void (*releasebufferproc) (PyObject@w{ }*, Py_buffer@w{ }*)
@end deffn

@geindex unaryfunc (C 类型)
@anchor{c-api/typeobj c unaryfunc}@anchor{4025}
@deffn {C 类型} PyObject *(*unaryfunc) (PyObject@w{ }*)
@end deffn

@geindex binaryfunc (C 类型)
@anchor{c-api/typeobj c binaryfunc}@anchor{4028}
@deffn {C 类型} PyObject *(*binaryfunc) (PyObject@w{ }*, PyObject@w{ }*)
@end deffn

@geindex ternaryfunc (C 类型)
@anchor{c-api/typeobj c ternaryfunc}@anchor{4008}
@deffn {C 类型} PyObject *(*ternaryfunc) (PyObject@w{ }*, PyObject@w{ }*, PyObject@w{ }*)
@end deffn

@geindex ssizeargfunc (C 类型)
@anchor{c-api/typeobj c ssizeargfunc}@anchor{4053}
@deffn {C 类型} PyObject *(*ssizeargfunc) (PyObject@w{ }*, Py_ssize_t)
@end deffn

@geindex ssizeobjargproc (C 类型)
@anchor{c-api/typeobj c ssizeobjargproc}@anchor{4056}
@deffn {C 类型} int (*ssizeobjargproc) (PyObject@w{ }*, Py_ssize_t)
@end deffn

@geindex objobjproc (C 类型)
@anchor{c-api/typeobj c objobjproc}@anchor{4058}
@deffn {C 类型} int (*objobjproc) (PyObject@w{ }*, PyObject@w{ }*)
@end deffn

@geindex objobjargproc (C 类型)
@anchor{c-api/typeobj c objobjargproc}@anchor{4050}
@deffn {C 类型} int (*objobjargproc) (PyObject@w{ }*, PyObject@w{ }*, PyObject@w{ }*)
@end deffn

@node 例子<35>,使对象类型支持循环垃圾回收,Slot Type typedefs,对象实现支持
@anchor{c-api/typeobj examples}@anchor{4083}@anchor{c-api/typeobj typedef-examples}@anchor{3ff9}
@subsection 例子


The following are simple examples of Python type definitions.  They
include common usage you may encounter.  Some demonstrate tricky corner
cases.  For more examples, practical info, and a tutorial, see
@ref{3ad6,,自定义扩展类型：教程} and @ref{3af9,,定义扩展类型：已分类主题}.

A basic static type:

@example
typedef struct @{
    PyObject_HEAD
    const char *data;
@} MyObject;

static PyTypeObject MyObject_Type = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyObject",
    .tp_basicsize = sizeof(MyObject),
    .tp_doc = "My objects",
    .tp_new = myobj_new,
    .tp_dealloc = (destructor)myobj_dealloc,
    .tp_repr = (reprfunc)myobj_repr,
@};
@end example

You may also find older code (especially in the CPython code base)
with a more verbose initializer:

@example
static PyTypeObject MyObject_Type = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    "mymod.MyObject",               /* tp_name */
    sizeof(MyObject),               /* tp_basicsize */
    0,                              /* tp_itemsize */
    (destructor)myobj_dealloc,      /* tp_dealloc */
    0,                              /* tp_vectorcall_offset */
    0,                              /* tp_getattr */
    0,                              /* tp_setattr */
    0,                              /* tp_as_async */
    (reprfunc)myobj_repr,           /* tp_repr */
    0,                              /* tp_as_number */
    0,                              /* tp_as_sequence */
    0,                              /* tp_as_mapping */
    0,                              /* tp_hash */
    0,                              /* tp_call */
    0,                              /* tp_str */
    0,                              /* tp_getattro */
    0,                              /* tp_setattro */
    0,                              /* tp_as_buffer */
    0,                              /* tp_flags */
    "My objects",                   /* tp_doc */
    0,                              /* tp_traverse */
    0,                              /* tp_clear */
    0,                              /* tp_richcompare */
    0,                              /* tp_weaklistoffset */
    0,                              /* tp_iter */
    0,                              /* tp_iternext */
    0,                              /* tp_methods */
    0,                              /* tp_members */
    0,                              /* tp_getset */
    0,                              /* tp_base */
    0,                              /* tp_dict */
    0,                              /* tp_descr_get */
    0,                              /* tp_descr_set */
    0,                              /* tp_dictoffset */
    0,                              /* tp_init */
    0,                              /* tp_alloc */
    myobj_new,                      /* tp_new */
@};
@end example

A type that supports weakrefs, instance dicts, and hashing:

@example
typedef struct @{
    PyObject_HEAD
    const char *data;
    PyObject *inst_dict;
    PyObject *weakreflist;
@} MyObject;

static PyTypeObject MyObject_Type = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyObject",
    .tp_basicsize = sizeof(MyObject),
    .tp_doc = "My objects",
    .tp_weaklistoffset = offsetof(MyObject, weakreflist),
    .tp_dictoffset = offsetof(MyObject, inst_dict),
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
    .tp_new = myobj_new,
    .tp_traverse = (traverseproc)myobj_traverse,
    .tp_clear = (inquiry)myobj_clear,
    .tp_alloc = PyType_GenericNew,
    .tp_dealloc = (destructor)myobj_dealloc,
    .tp_repr = (reprfunc)myobj_repr,
    .tp_hash = (hashfunc)myobj_hash,
    .tp_richcompare = PyBaseObject_Type.tp_richcompare,
@};
@end example

A str subclass that cannot be subclassed and cannot be called
to create instances (e.g. uses a separate factory func):

@example
typedef struct @{
    PyUnicodeObject raw;
    char *extra;
@} MyStr;

static PyTypeObject MyStr_Type = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyStr",
    .tp_basicsize = sizeof(MyStr),
    .tp_base = NULL,  // set to &PyUnicode_Type in module init
    .tp_doc = "my custom str",
    .tp_flags = Py_TPFLAGS_DEFAULT,
    .tp_new = NULL,
    .tp_repr = (reprfunc)myobj_repr,
@};
@end example

The simplest static type (with fixed-length instances):

@example
typedef struct @{
    PyObject_HEAD
@} MyObject;

static PyTypeObject MyObject_Type = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyObject",
@};
@end example

The simplest static type (with variable-length instances):

@example
typedef struct @{
    PyObject_VAR_HEAD
    const char *data[1];
@} MyObject;

static PyTypeObject MyObject_Type = @{
    PyVarObject_HEAD_INIT(NULL, 0)
    .tp_name = "mymod.MyObject",
    .tp_basicsize = sizeof(MyObject) - sizeof(char *),
    .tp_itemsize = sizeof(char *),
@};
@end example

@node 使对象类型支持循环垃圾回收,,例子<35>,对象实现支持
@anchor{c-api/gcsupport doc}@anchor{4084}@anchor{c-api/gcsupport supporting-cycle-detection}@anchor{4073}@anchor{c-api/gcsupport supporting-cyclic-garbage-collection}@anchor{4085}
@subsection 使对象类型支持循环垃圾回收


Python 对循环引用的垃圾检测与回收需要“容器”对象类型的支持，此类型的容器对象中可能包含其它容器对象。不保存其它对象的引用的类型，或者只保存原子类型（如数字或字符串）的引用的类型，不需要显式提供垃圾回收的支持。

若要创建一个容器类，类型对象的 @ref{3d06,,tp_flags} 字段必须包含 @ref{3af3,,Py_TPFLAGS_HAVE_GC} 并提供一个 @ref{3664,,tp_traverse} 处理的实现。如果该类型的实例是可变的，还需要实现 @ref{3afd,,tp_clear} 。


@deffn {数据} Py_TPFLAGS_HAVE_GC

设置了此标志位的类型的对象必须符合此处记录的规则。为方便起见，下文把这些对象称为容器对象。
@end deffn

容器类型的构造函数必须符合两个规则：


@enumerate 

@item 
必须使用 @ref{2d4,,PyObject_GC_New()} 或 @ref{2d5,,PyObject_GC_NewVar()} 为这些对象分配内存。

@item 
初始化了所有可能包含其他容器的引用的字段后，它必须调用 @ref{e3d,,PyObject_GC_Track()} 。
@end enumerate

@geindex PyObject_GC_New (C 函数)
@anchor{c-api/gcsupport c PyObject_GC_New}@anchor{2d4}
@deffn {C 函数} TYPE* PyObject_GC_New (TYPE, PyTypeObject@w{ }*type)

类似于 @ref{2d2,,PyObject_New()} ，适用于设置了 @ref{3af3,,Py_TPFLAGS_HAVE_GC} 标签的容器对象。
@end deffn

@geindex PyObject_GC_NewVar (C 函数)
@anchor{c-api/gcsupport c PyObject_GC_NewVar}@anchor{2d5}
@deffn {C 函数} TYPE* PyObject_GC_NewVar (TYPE, PyTypeObject@w{ }*type, Py_ssize_t@w{ }size)

类似于 @ref{2d3,,PyObject_NewVar()} ，适用于设置了 @ref{3af3,,Py_TPFLAGS_HAVE_GC} 标签的容器对象。
@end deffn

@geindex PyObject_GC_Resize (C 函数)
@anchor{c-api/gcsupport c PyObject_GC_Resize}@anchor{4086}
@deffn {C 函数} TYPE* PyObject_GC_Resize (TYPE, PyVarObject@w{ }*op, Py_ssize_t@w{ }newsize)

为 @ref{2d3,,PyObject_NewVar()} 所分配对象重新调整大小。 返回调整大小后的对象或在失败时返回 @code{NULL}。 @emph{op} 必须尚未被垃圾回收器追踪。
@end deffn

@geindex PyObject_GC_Track (C 函数)
@anchor{c-api/gcsupport c PyObject_GC_Track}@anchor{e3d}
@deffn {C 函数} void PyObject_GC_Track (PyObject@w{ }*op)

把对象 @emph{op} 加入到垃圾回收器跟踪的容器对象中。对象在被回收器跟踪时必须保持有效的，因为回收器可能在任何时候开始运行。在 @ref{3664,,tp_traverse} 处理前的所有字段变为有效后，必须调用此函数，通常在靠近构造函数末尾的位置。
@end deffn

同样的，对象的释放器必须符合两个类似的规则：


@enumerate 

@item 
在引用其它容器的字段失效前，必须调用 @ref{e3e,,PyObject_GC_UnTrack()} 。

@item 
必须使用 @ref{e3c,,PyObject_GC_Del()} 释放对象的内存。
@end enumerate

@geindex PyObject_GC_Del (C 函数)
@anchor{c-api/gcsupport c PyObject_GC_Del}@anchor{e3c}
@deffn {C 函数} void PyObject_GC_Del (void@w{ }*op)

释放对象的内存，该对象初始化时由 @ref{2d4,,PyObject_GC_New()} 或 @ref{2d5,,PyObject_GC_NewVar()} 分配内存。
@end deffn

@geindex PyObject_GC_UnTrack (C 函数)
@anchor{c-api/gcsupport c PyObject_GC_UnTrack}@anchor{e3e}
@deffn {C 函数} void PyObject_GC_UnTrack (void@w{ }*op)

从回收器跟踪的容器对象集合中移除 @emph{op} 对象。 请注意可以在此对象上再次调用 @ref{e3d,,PyObject_GC_Track()} 以将其加回到被跟踪对象集合。 释放器 (@ref{3ae4,,tp_dealloc} 句柄) 应当在 @ref{3664,,tp_traverse} 句柄所使用的任何字段失效之前为对象调用此函数。
@end deffn


在 3.8 版更改: @code{_PyObject_GC_TRACK()} 和 @code{_PyObject_GC_UNTRACK()} 宏已从公有 C API 中移除。


@ref{3664,,tp_traverse} 处理接收以下类型的函数形参。

@geindex visitproc (C 类型)
@anchor{c-api/gcsupport c visitproc}@anchor{405e}
@deffn {C 类型} int (*visitproc) (PyObject@w{ }*object, void@w{ }*arg)

传给 @ref{3664,,tp_traverse} 处理的访问函数的类型。@emph{object} 是容器中需要被遍历的一个对象，第三个形参对应于 @ref{3664,,tp_traverse} 处理的 @emph{arg} 。Python核心使用多个访问者函数实现循环引用的垃圾检测，不需要用户自行实现访问者函数。
@end deffn

@ref{3664,,tp_traverse} 处理必须是以下类型：

@geindex traverseproc (C 类型)
@anchor{c-api/gcsupport c traverseproc}@anchor{400d}
@deffn {C 类型} int (*traverseproc) (PyObject@w{ }*self, visitproc@w{ }visit, void@w{ }*arg)

用于容器对象的遍历函数。 它的实现必须对 @emph{self} 所直接包含的每个对象调用 @emph{visit} 函数，@emph{visit} 的形参为所包含对象和传给处理程序的 @emph{arg} 值。 @emph{visit} 函数调用不可附带 @code{NULL} 对象作为参数。 如果 @emph{visit} 返回非零值，则该值应当被立即返回。
@end deffn

为了简化 @ref{3664,,tp_traverse} 处理的实现，Python提供了一个 @ref{3af1,,Py_VISIT()} 宏。若要使用这个宏，必须把 @ref{3664,,tp_traverse} 的参数命名为 @emph{visit} 和 @emph{arg} 。

@geindex Py_VISIT (C 函数)
@anchor{c-api/gcsupport c Py_VISIT}@anchor{3af1}
@deffn {C 函数} void Py_VISIT (PyObject@w{ }*o)

如果 @emph{o} 不为 @code{NULL}，则调用 @emph{visit} 回调函数，附带参数 @emph{o} 和 @emph{arg}。 如果 @emph{visit} 返回一个非零值，则返回该值。 使用此宏之后，@ref{3664,,tp_traverse} 处理程序的形式如下:

@example
static int
my_traverse(Noddy *self, visitproc visit, void *arg)
@{
    Py_VISIT(self->foo);
    Py_VISIT(self->bar);
    return 0;
@}
@end example
@end deffn

@ref{3afd,,tp_clear} 处理程序必须为 @ref{400e,,inquiry} 类型，如果对象不可变则为 @code{NULL}。

@geindex inquiry (C 类型)
@anchor{c-api/gcsupport c inquiry}@anchor{400e}
@deffn {C 类型} int (*inquiry) (PyObject@w{ }*self)

丢弃产生循环引用的引用。不可变对象不需要声明此方法，因为他们不可能直接产生循环引用。需要注意的是，对象在调用此方法后必须仍是有效的（不能对引用只调用 @ref{266,,Py_DECREF()} 方法）。当垃圾回收器检测到该对象在循环引用中时，此方法会被调用。
@end deffn

@node API 和 ABI 版本管理,,对象实现支持,Python/C API 参考手册
@anchor{c-api/apiabiversion doc}@anchor{4087}@anchor{c-api/apiabiversion api-and-abi-versioning}@anchor{4088}@anchor{c-api/apiabiversion apiabiversion}@anchor{35db}
@section API 和 ABI 版本管理


@code{PY_VERSION_HEX} 是Python的版本号的单一整数形式。

例如, 如果 "PY _ VERSION _ HEX" 设置为 "0x0304012", 则可以通过按以下方式将其视为32位数字来查找基础版本信息:

@quotation


@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

字节串

@tab

位数（大端字节序）

@tab

含义

@item

@code{1}

@tab

@code{1-8}

@tab

@code{PY_MAJOR_VERSION} （@code{3.4.1a2} 中的 @code{3} ）

@item

@code{2}

@tab

@code{9-16}

@tab

@code{PY_MINOR_VERSION} （@code{3.4.1a2} 中的 @code{4} ）

@item

@code{3}

@tab

@code{17-24}

@tab

@code{PY_MICRO_VERSION} （@code{3.4.1a2} 中的 @code{1} ）

@item

@code{4}

@tab

@code{25-28}

@tab

@code{PY_RELEASE_LEVEL} (@code{0xA} 是 alpha版本, @code{0xB} 是 beta版本, @code{0xC} 发布的候选版本并且 @code{0xF} 是最终版本)，在这个例子中这个版本是alpha版本。

@item

@tab

@code{29-32}

@tab

@code{PY_RELEASE_SERIAL} （ @code{3.4.1a2} 中的 @code{2} ，最终版本用0)

@end multitable

@end quotation

因此 @code{3.4.1a2} 的16进制版本号是 @code{0x030401a2} 。

所有提到的宏都定义在 Include/patchlevel.h@footnote{https://github.com/python/cpython/tree/3.8/Include/patchlevel.h}。

@node 分发 Python 模块,安装 Python 模块,Python/C API 参考手册,Top
@anchor{distributing/index doc}@anchor{4089}@anchor{distributing/index distributing-index}@anchor{7f0}@anchor{distributing/index distributing-python-modules}@anchor{408a}
@chapter 分发 Python 模块


@*电子邮箱: 
@email{distutils-sig@@python.org}


作为一个流行的开源开发项目，Python拥有一个活跃的贡献者和用户支持社区，这些社区也可以让他们的软件可供其他Python开发人员在开源许可条款下使用。

这允许Python用户有效地共享和协作，从其他人已经创建的解决方案中受益于常见（有时甚至是罕见的）问题，以及可以提供他们自己的解决方案。

本指南涵盖了分发部分的流程。有关安装其他Python项目的指南，请参阅 @ref{7ef,,安装指南}。

@cartouche
@quotation 注解 
对于企业和其他机构用户，请注意许多组织都有自己的政策来使用和贡献开源软件。在使用Python提供的分发和安装工具时，请考虑这些政策。
@end quotation
@end cartouche

@menu
* 关键术语:: 
* 开源许可与协作:: 
* 安装工具:: 
* 阅读Python包用户指南:: 
* 我该如何...？: 我该如何 ？. 

@end menu

@node 关键术语,开源许可与协作,,分发 Python 模块
@anchor{distributing/index key-terms}@anchor{408b}
@section 关键术语



@itemize *

@item 
Python Packaging Index@footnote{https://pypi.org} 是一个开源许可的软件包公共存储库，可供所有 Python 用户使用。

@item 
Python Packaging Authority@footnote{https://www.pypa.io/} 是负责标准打包工具以及相关元数据和文件格式标准维护与改进的开发人员和文档作者团队。 他们基于 GitHub@footnote{https://github.com/pypa} 和 Bitbucket@footnote{https://bitbucket.org/pypa/} 这两个平台维护着各种工具、文档和问题追踪系统。

@item 
@ref{39,,distutils} 是1998年首次添加到Python标准库的原始构建和分发系统。虽然直接使用 @ref{39,,distutils} 正在逐步淘汰，但它仍然为当前的打包和分发基础架构奠定了基础它不仅仍然是标准库的一部分，而且它的名称还以其他方式存在（例如用于协调Python包装标准开发的邮件列表的名称）。

@item 
setuptools@footnote{https://setuptools.readthedocs.io/en/latest/} （在很大程序上）是作为 @ref{39,,distutils} 的取代者，于 2004 年首次发布。它对未经修改的 @ref{39,,distutils} 工具最重要的补充是能够声明对其他包的依赖。目前它被推荐用来替代 @ref{39,,distutils}，其更新更为频繁，在更为多样的 Python 版本之上为最新的包标准提供持续支持。

@item 
wheel@footnote{https://wheel.readthedocs.io/} （在此上下文中）是一个将 @code{bdist_wheel} 命令添加到 @ref{39,,distutils}/setuptools@footnote{https://setuptools.readthedocs.io/en/latest/} 的项目。这产生了一个跨平台的二进制打包格式（称为“轮子”或“轮子文件”，并在 
@geindex Python 提高建议; PEP 427
PEP 427@footnote{https://www.python.org/dev/peps/pep-0427} 中定义），它允许在系统上安装Python库，甚至包括二进制扩展的库，而不需在本地进行构建。
@end itemize

@node 开源许可与协作,安装工具,关键术语,分发 Python 模块
@anchor{distributing/index open-source-licensing-and-collaboration}@anchor{408c}@anchor{distributing/index wheel}@anchor{408d}
@section 开源许可与协作


在世界上大多数地方，软件自动受版权保护。这意味着其他开发人员需要明确的权限来复制，使用，修改和重新分发软件。

开源许可是一种以相对一致的方式明确授予此类权限的方式，允许开发人员通过为各种问题免费提供通用解决方案来有效地共享和协作。这使得许多开发人员可以将更多时间用于关注他们特定情况相对独特的问题。

Python提供的分发工具旨在使开发人员选择开源时，可以合理地直接将其自己的贡献回馈到该公共软件池。

无论该软件是否作为开源软件发布，相同的分发工具也可用于在组织内分发软件。

@node 安装工具,阅读Python包用户指南,开源许可与协作,分发 Python 模块
@anchor{distributing/index installing-the-tools}@anchor{408e}
@section 安装工具


标准库不包括支持现代Python打包标准的构建工具，因为核心开发团队已经发现，即使在旧版本的Python上，使用一致工作的标准工具也很重要。

可以通过在命令行调用 @code{pip} 模块来安装当前推荐的构建和分发工具:

@example
python -m pip install setuptools wheel twine
@end example

@cartouche
@quotation 注解 
对于POSIX用户（包括Mac OS X和Linux用户），这些说明假定使用 @ref{12a7,,virtual environment} 。

对于Windows用户，这些说明假定在安装Python时选择了调整系统PATH环境变量的选项。
@end quotation
@end cartouche

Python打包指南包含有关 currently recommended tools@footnote{https://packaging.python.org/guides/tool-recommendations/#packaging-tool-recommendations} 的更多详细信息。

@geindex Python Package Index (PyPI)
@geindex PyPI; (see Python Package Index (PyPI))

@node 阅读Python包用户指南,我该如何 ？,安装工具,分发 Python 模块
@anchor{distributing/index publishing-python-packages}@anchor{408f}@anchor{distributing/index reading-the-python-packaging-user-guide}@anchor{4090}
@section 阅读Python包用户指南


“Python包装用户指南”介绍了创建和发布项目所涉及的各个关键步骤和元素：


@itemize *

@item 
项目的结构@footnote{https://packaging.python.org/tutorials/distributing-packages/}

@item 
项目的构建与打包@footnote{https://packaging.python.org/tutorials/distributing-packages/#packaging-your-project}

@item 
上传项目到 Python Packaging Index@footnote{https://packaging.python.org/tutorials/distributing-packages/#uploading-your-project-to-pypi}

@item 
The .pypirc file@footnote{https://packaging.python.org/specifications/pypirc/}
@end itemize

@node 我该如何 ？,,阅读Python包用户指南,分发 Python 模块
@anchor{distributing/index how-do-i}@anchor{4091}@anchor{distributing/index the-pypirc-file}@anchor{4092}
@section 我该如何...？


这是一些常见任务的快速解答或相关链接。

@menu
* ...为我的项目选择一个名字？: 为我的项目选择一个名字？. 
* ...创建和分发二进制扩展？: 创建和分发二进制扩展？. 

@end menu

@node 为我的项目选择一个名字？,创建和分发二进制扩展？,,我该如何 ？
@anchor{distributing/index choose-a-name-for-my-project}@anchor{4093}
@subsection ...为我的项目选择一个名字？


这不是一个简单的主题，但这里有一些提示：


@itemize *

@item 
检查Python Packaging Index以查看该名称是否已被使用

@item 
检查流行的托管网站如 GitHub，Bitbucket 等等，看是否已有一个该名称的项目

@item 
检查您正在考虑的名称在网络搜索中出现的内容

@item 
避免使用特别常见的单词，尤其是具有多重含义的单词，因为它们会使用户在搜索时难以找到您的软件
@end itemize

@node 创建和分发二进制扩展？,,为我的项目选择一个名字？,我该如何 ？
@anchor{distributing/index create-and-distribute-binary-extensions}@anchor{4094}
@subsection ...创建和分发二进制扩展？


这实际上是一个非常复杂的主题，根据您的目标，可以提供各种替代方案。有关更多信息和建议，请参阅Python打包指南。


@subsubheading 参见


Python 封装使用指南：二进制扩展@footnote{https://packaging.python.org/guides/packaging-binary-extensions/}


@c other topics:
@c 
@c Once the Development & Deployment part of PPUG is fleshed out, some of
@c those sections should be linked from new questions here (most notably,
@c we should have a question about avoiding depending on PyPI that links to
@c https://packaging.python.org/en/latest/mirrors/)

@node 安装 Python 模块,Python 常用指引,分发 Python 模块,Top
@anchor{installing/index doc}@anchor{4095}@anchor{installing/index installing-index}@anchor{7ef}@anchor{installing/index installing-python-modules}@anchor{4096}
@chapter 安装 Python 模块


@*电子邮箱: 
@email{distutils-sig@@python.org}


作为一个流行的开源开发项目，Python拥有一个活跃的贡献者和用户支持社区，这些社区也可以让他们的软件可供其他Python开发人员在开源许可条款下使用。

这允许Python用户有效地共享和协作，从其他人已经创建的解决方案中受益于常见（有时甚至是罕见的）问题，以及可以提供他们自己的解决方案。

本指南涵盖了分发部分的流程。有关安装其他Python项目的指南，请参阅 @ref{7f0,,安装指南}。

@cartouche
@quotation 注解 
对于企业和其他机构用户，请注意许多组织都有自己的政策来使用和贡献开源软件。在使用Python提供的分发和安装工具时，请考虑这些政策。
@end quotation
@end cartouche

@menu
* 关键术语: 关键术语<2>. 
* 基本使用: 基本使用<2>. 
* 我应如何 ...？: 我应如何 ？. 
* 常见的安装问题:: 

@end menu

@node 关键术语<2>,基本使用<2>,,安装 Python 模块
@anchor{installing/index key-terms}@anchor{4097}
@section 关键术语



@itemize *

@item 
@code{pip} 是首选的安装程序。从Python 3.4开始，它默认包含在Python二进制安装程序中。

@item 
@emph{virtual environment} 是一种半隔离的 Python 环境，允许为特定的应用安装各自的包，而不是安装到整个系统。

@item 
@code{venv} 是创建虚拟环境的标准工具，从 Python 3.3 开始成为 Python 的组成部分。 从 Python 3.4 开始，它会默认安装 @code{pip} 到所创建的全部虚拟环境。

@item 
@code{virtualenv} 是 @code{venv} 的第三方替代（及其前身）。 它允许在 Python 3.4 之前的版本中使用虚拟环境，那些版本或是完全不提供 @code{venv}，或是不会自动安装 @code{pip} 到所创建的虚拟环境。

@item 
Python Packaging Index@footnote{https://pypi.org} 是一个由 Python 用户向其他用户发布开源许可软件包的公共仓库。

@item 
Python Packaging Authority@footnote{https://www.pypa.io/} 是负责标准打包工具以及相关元数据和文件格式标准维护与改进的开发人员和文档作者团队。 他们基于 GitHub@footnote{https://github.com/pypa} 和 Bitbucket@footnote{https://bitbucket.org/pypa/} 这两个平台维护着各种工具、文档和问题追踪系统。

@item 
@code{distutils} 是最初的构建和分发系统，于 1998 年首次加入 Python 标准库。 虽然直接使用 @code{distutils} 的方式已被淘汰，它仍然是当前打包和分发架构的基础，而且它不仅仍然是标准库的一部分，这个名称还以其他方式存在（例如用于协调 Python 打包标准开发流程的邮件列表就以此命名）。
@end itemize


在 3.5 版更改: 现在推荐使用 @code{venv} 来创建虚拟环境。



@subsubheading 参见


Python 软件包用户指南：创建和使用虚拟环境@footnote{https://packaging.python.org/installing/#creating-virtual-environments}


@node 基本使用<2>,我应如何 ？,关键术语<2>,安装 Python 模块
@anchor{installing/index basic-usage}@anchor{4098}
@section 基本使用


标准打包工具完全是针对命令行使用方式来设计的。

以下命令将从 Python Packaging Index 安装一个模块的最新版本及其依赖项:

@example
python -m pip install SomePackage
@end example

@cartouche
@quotation 注解 
对于 POSIX 用户（包括 Mac OS X 和 Linux 用户）本指南中的示例假定使用了 @ref{12a7,,virtual environment}。

对于 Windows 用户，本指南中的示例假定在安装 Python 时选择了修改系统 PATH 环境变量。
@end quotation
@end cartouche

在命令行中指定一个准确或最小版本也是可以的。 当使用比较运算符例如 @code{>}, @code{<} 或其他某些可以被终端所解析的特殊字符时，包名称与版本号应当用双引号括起来:

@example
python -m pip install SomePackage==1.0.4    # specific version
python -m pip install "SomePackage>=1.0.4"  # minimum version
@end example

通常，如果一个匹配的模块已安装，尝试再次安装将不会有任何效果。 要升级现有模块必须显式地发出请求:

@example
python -m pip install --upgrade SomePackage
@end example

更多有关 @code{pip} 及其功能的信息和资源可以在 Python 软件包用户指南@footnote{https://packaging.python.org} 中找到。

虚拟环境的创建可使用 @ref{125,,venv} 模块来完成。 向已激活虚拟环境安装软件包可使用上文所介绍的命令。


@subsubheading 参见


Python 软件包用户指南：安装 Python 分发包@footnote{https://packaging.python.org/installing/}


@node 我应如何 ？,常见的安装问题,基本使用<2>,安装 Python 模块
@anchor{installing/index how-do-i}@anchor{4099}
@section 我应如何 ...？


这是一些常见任务的快速解答或相关链接。

@menu
* ... 在 Python 3.4 之前的 Python 版本中安装 pip ？: 在 Python 3 4 之前的 Python 版本中安装 pip ？. 
* ... 只为当前用户安装软件包？: 只为当前用户安装软件包？. 
* ... 安装科学计算类 Python 软件包？: 安装科学计算类 Python 软件包？. 
* ... 使用并行安装的多个 Python 版本？: 使用并行安装的多个 Python 版本？. 

@end menu

@node 在 Python 3 4 之前的 Python 版本中安装 pip ？,只为当前用户安装软件包？,,我应如何 ？
@anchor{installing/index install-pip-in-versions-of-python-prior-to-python-3-4}@anchor{409a}
@subsection ... 在 Python 3.4 之前的 Python 版本中安装 @code{pip} ？


Python 捆绑 @code{pip} 是从 Python 3.4 才开始的。 对于更早的版本，@code{pip} 需要“引导安装bootstrapped”，具体说明参见 Python 软件包用户指南。


@subsubheading 参见


Python 软件包用户指南：安装软件包的前提要求@footnote{https://packaging.python.org/installing/#requirements-for-installing-packages}


@c installing-per-user-installation:

@node 只为当前用户安装软件包？,安装科学计算类 Python 软件包？,在 Python 3 4 之前的 Python 版本中安装 pip ？,我应如何 ？
@anchor{installing/index install-packages-just-for-the-current-user}@anchor{409b}
@subsection ... 只为当前用户安装软件包？


将 @code{--user} 选项传入 @code{python -m pip install} 将只为当前用户而非为系统中的所有用户安装软件包。

@node 安装科学计算类 Python 软件包？,使用并行安装的多个 Python 版本？,只为当前用户安装软件包？,我应如何 ？
@anchor{installing/index install-scientific-python-packages}@anchor{409c}
@subsection ... 安装科学计算类 Python 软件包？


许多科学计算类 Python 软件包都有复杂的二进制编译文件依赖，直接使用 @code{pip} 安装目前并不太容易。 在当前情况下，通过 其他方式@footnote{https://packaging.python.org/science/} 而非尝试用 @code{pip} 安装这些软件包对用户来说通常会更容易。


@subsubheading 参见


Python 软件包用户指南：安装科学计算类软件包@footnote{https://packaging.python.org/science/}


@node 使用并行安装的多个 Python 版本？,,安装科学计算类 Python 软件包？,我应如何 ？
@anchor{installing/index work-with-multiple-versions-of-python-installed-in-parallel}@anchor{409d}
@subsection ... 使用并行安装的多个 Python 版本？


在 Linux, Mac OS X 以及其他 POSIX 系统中，使用带版本号的 Python 命令配合 @code{-m} 开关选项来运行特定版本的 @code{pip}:

@example
python2   -m pip install SomePackage  # default Python 2
python2.7 -m pip install SomePackage  # specifically Python 2.7
python3   -m pip install SomePackage  # default Python 3
python3.4 -m pip install SomePackage  # specifically Python 3.4
@end example

也可以使用带特定版本号的 @code{pip} 命令。

在 Windows 中，使用 @code{py} Python 启动器命令配合 @code{-m} 开关选项:

@example
py -2   -m pip install SomePackage  # default Python 2
py -2.7 -m pip install SomePackage  # specifically Python 2.7
py -3   -m pip install SomePackage  # default Python 3
py -3.4 -m pip install SomePackage  # specifically Python 3.4
@end example

@c other questions:
@c 
@c Once the Development & Deployment part of PPUG is fleshed out, some of
@c those sections should be linked from new questions here (most notably,
@c we should have a question about avoiding depending on PyPI that links to
@c https://packaging.python.org/en/latest/mirrors/)

@node 常见的安装问题,,我应如何 ？,安装 Python 模块
@anchor{installing/index common-installation-issues}@anchor{409e}
@section 常见的安装问题


@menu
* 在 Linux 的系统 Python 版本上安装:: 
* 未安装 pip:: 
* 安装二进制编译扩展:: 

@end menu

@node 在 Linux 的系统 Python 版本上安装,未安装 pip,,常见的安装问题
@anchor{installing/index installing-into-the-system-python-on-linux}@anchor{409f}
@subsection 在 Linux 的系统 Python 版本上安装


Linux 系统通常会将某个 Python 版本作为发行版的一部分包含在内。 将软件包安装到这个 Python 版本上需要系统 root 权限，并可能会干扰到系统包管理器和其他系统组件的运作，如果这些组件在使用 @code{pip} 时被意外升级的话。

在这样的系统上，通过 @code{pip} 安装软件包通常最好是使用虚拟环境或分用户安装。

@node 未安装 pip,安装二进制编译扩展,在 Linux 的系统 Python 版本上安装,常见的安装问题
@anchor{installing/index pip-not-installed}@anchor{40a0}
@subsection 未安装 pip


默认情况下可能未安装 @code{pip}，一种可选解决方案是:

@example
python -m ensurepip --default-pip
@end example

还有其他资源可用来 安装 pip@footnote{https://packaging.python.org/tutorials/installing-packages/#install-pip-setuptools-and-wheel}

@node 安装二进制编译扩展,,未安装 pip,常见的安装问题
@anchor{installing/index installing-binary-extensions}@anchor{40a1}
@subsection 安装二进制编译扩展


Python 通常非常依赖基于源代码的发布方式，也就是期望最终用户在安装过程中使用源码来编译生成扩展模块。

随着对二进制码 @code{wheel} 格式支持的引入，以及通过 Python Packaging Index 至少发布 Windows 和 Mac OS X 版的 wheel 文件，预计此问题将逐步得到解决，因为用户将能够更频繁地安装预编译扩展，而不再需要自己编译它们。

某些用来安装 科学计算类软件包@footnote{https://packaging.python.org/science/} 的解决方案对于尚未提供预编译 @code{wheel} 文件的那些扩展模块来说，也有助于用户在无需进行本机编译的情况下获取二进制码扩展模块。


@subsubheading 参见


Python 软件包用户指南：二进制码扩展@footnote{https://packaging.python.org/extensions/}


@node Python 常用指引,Python 常见问题,安装 Python 模块,Top
@anchor{howto/index doc}@anchor{40a2}@anchor{howto/index python-howtos}@anchor{40a3}
@chapter Python 常用指引


Python常用指引的形式来源于Linux文档项目的常用指引章节，是一系列独立、指定主题并尝试完全覆盖该主题的文章集合。致力于提供比Python库参考帮助更详尽的文档。

目前，提供了如下指引：

@menu
* 将 Python 2 代码迁移到 Python 3:: 
* 将扩展模块移植到 Python 3:: 
* 用 Python 进行 Curses 编程:: 
* 描述器使用指南:: 
* 函数式编程指引:: 
* 日志常用指引:: 
* 日志操作手册:: 
* 正则表达式HOWTO:: 
* 套接字编程指南:: 
* 排序指南:: 
* Unicode 指南:: 
* HOWTO 使用 urllib 包获取网络资源:: 
* Argparse 教程:: 
* ipaddress模块介绍:: 
* Argument Clinic How-To:: 
* 使用 DTrace 和 SystemTap 检测CPython:: 

@end menu

@node 将 Python 2 代码迁移到 Python 3,将扩展模块移植到 Python 3,,Python 常用指引
@anchor{howto/pyporting doc}@anchor{40a4}@anchor{howto/pyporting porting-python-2-code-to-python-3}@anchor{40a5}@anchor{howto/pyporting pyporting-howto}@anchor{c76}
@section 将 Python 2 代码迁移到 Python 3


@*作者: 
Brett Cannon


@subsubheading 摘要



Python 3 是 Python 的未来，但 Python 2 仍处于活跃使用阶段，最好让您的项目在两个主要版本的Python 上都可用。本指南旨在帮助您了解如何最好地同时支持 Python 2 和 3。

如果您希望迁移扩展模块而不是纯 Python 代码，请参阅 @ref{c70,,将扩展模块移植到 Python 3}。

如果你想了解核心 Python 开发者对于 Python 3 的出现有何看法，你可以阅读 Nick Coghlan 的 Python 3 Q & A@footnote{https://ncoghlan-devs-python-notes.readthedocs.io/en/latest/python3/questions_and_answers.html} 或 Brett Cannon 的 为什么要有 Python 3@footnote{https://snarky.ca/why-python-3-exists}.

有关迁移的帮助，您可以通过电子邮件向 python-porting@footnote{https://mail.python.org/mailman/listinfo/python-porting} 邮件列表发送问题。

@menu
* 简要说明:: 
* 详情:: 

@end menu

@node 简要说明,详情,,将 Python 2 代码迁移到 Python 3
@anchor{howto/pyporting the-short-explanation}@anchor{40a6}
@subsection 简要说明


To make your project be single-source Python 2/3 compatible, the basic steps
are:


@enumerate 

@item 
Only worry about supporting Python 2.7

@item 
确保有良好的测试覆盖率（可以用 coverage.py@footnote{https://pypi.org/project/coverage} 来完成此任务；用 @code{pip install coverage} 安装）

@item 
了解Python 2 和 3之间的区别

@item 
使用 Futurize@footnote{http://python-future.org/automatic_conversion.html} (或 Modernize@footnote{https://python-modernize.readthedocs.io/}) 升级你的代码 (例如. @code{pip install future})

@item 
Use Pylint@footnote{https://pypi.org/project/pylint} to help make sure you don't regress on your Python 3 support
(@code{pip install pylint})

@item 
Use caniusepython3@footnote{https://pypi.org/project/caniusepython3} to find out which of your dependencies are blocking your
use of Python 3 (@code{pip install caniusepython3})

@item 
Once your dependencies are no longer blocking you, use continuous integration
to make sure you stay compatible with Python 2 & 3 (tox@footnote{https://pypi.org/project/tox} can help test
against multiple versions of Python; @code{pip install tox})

@item 
Consider using optional static type checking to make sure your type usage
works in both Python 2 & 3 (e.g. use mypy@footnote{http://mypy-lang.org/} to check your typing under both
Python 2 & Python 3).
@end enumerate

@node 详情,,简要说明,将 Python 2 代码迁移到 Python 3
@anchor{howto/pyporting details}@anchor{40a7}
@subsection 详情


A key point about supporting Python 2 & 3 simultaneously is that you can start
@strong{today}! Even if your dependencies are not supporting Python 3 yet that does
not mean you can't modernize your code @strong{now} to support Python 3. Most changes
required to support Python 3 lead to cleaner code using newer practices even in
Python 2 code.

Another key point is that modernizing your Python 2 code to also support
Python 3 is largely automated for you. While you might have to make some API
decisions thanks to Python 3 clarifying text data versus binary data, the
lower-level work is now mostly done for you and thus can at least benefit from
the automated changes immediately.

Keep those key points in mind while you read on about the details of porting
your code to support Python 2 & 3 simultaneously.

@menu
* 删除对Python 2.6及更早版本的支持: 删除对Python 2 6及更早版本的支持. 
* Make sure you specify the proper version support in your setup.py file: Make sure you specify the proper version support in your setup py file. 
* 良好的测试覆盖率:: 
* 了解Python 2 和 3之间的区别:: 
* 更新代码:: 
* Prevent compatibility regressions:: 
* Check which dependencies block your transition:: 
* Update your setup.py file to denote Python 3 compatibility: Update your setup py file to denote Python 3 compatibility. 
* Use continuous integration to stay compatible:: 
* 考虑使用可选的静态类型检查:: 

@end menu

@node 删除对Python 2 6及更早版本的支持,Make sure you specify the proper version support in your setup py file,,详情
@anchor{howto/pyporting drop-support-for-python-2-6-and-older}@anchor{40a8}
@subsubsection 删除对Python 2.6及更早版本的支持


While you can make Python 2.5 work with Python 3, it is @strong{much} easier if you
only have to work with Python 2.7. If dropping Python 2.5 is not an
option then the six@footnote{https://pypi.org/project/six} project can help you support Python 2.5 & 3 simultaneously
(@code{pip install six}). Do realize, though, that nearly all the projects listed
in this HOWTO will not be available to you.

If you are able to skip Python 2.5 and older, then the required changes
to your code should continue to look and feel like idiomatic Python code. At
worst you will have to use a function instead of a method in some instances or
have to import a function instead of using a built-in one, but otherwise the
overall transformation should not feel foreign to you.

But you should aim for only supporting Python 2.7. Python 2.6 is no longer
freely supported and thus is not receiving bugfixes. This means @strong{you} will have
to work around any issues you come across with Python 2.6. There are also some
tools mentioned in this HOWTO which do not support Python 2.6 (e.g., Pylint@footnote{https://pypi.org/project/pylint}),
and this will become more commonplace as time goes on. It will simply be easier
for you if you only support the versions of Python that you have to support.

@node Make sure you specify the proper version support in your setup py file,良好的测试覆盖率,删除对Python 2 6及更早版本的支持,详情
@anchor{howto/pyporting make-sure-you-specify-the-proper-version-support-in-your-setup-py-file}@anchor{40a9}
@subsubsection Make sure you specify the proper version support in your @code{setup.py} file


In your @code{setup.py} file you should have the proper trove classifier@footnote{https://pypi.org/classifiers}
specifying what versions of Python you support. As your project does not support
Python 3 yet you should at least have
@code{Programming Language :: Python :: 2 :: Only} specified. Ideally you should
also specify each major/minor version of Python that you do support, e.g.
@code{Programming Language :: Python :: 2.7}.

@node 良好的测试覆盖率,了解Python 2 和 3之间的区别,Make sure you specify the proper version support in your setup py file,详情
@anchor{howto/pyporting have-good-test-coverage}@anchor{40aa}
@subsubsection 良好的测试覆盖率


Once you have your code supporting the oldest version of Python 2 you want it
to, you will want to make sure your test suite has good coverage. A good rule of
thumb is that if you want to be confident enough in your test suite that any
failures that appear after having tools rewrite your code are actual bugs in the
tools and not in your code. If you want a number to aim for, try to get over 80%
coverage (and don't feel bad if you find it hard to get better than 90%
coverage). If you don't already have a tool to measure test coverage then
coverage.py@footnote{https://pypi.org/project/coverage} is recommended.

@node 了解Python 2 和 3之间的区别,更新代码,良好的测试覆盖率,详情
@anchor{howto/pyporting learn-the-differences-between-python-2-3}@anchor{40ab}
@subsubsection 了解Python 2 和 3之间的区别


Once you have your code well-tested you are ready to begin porting your code to
Python 3! But to fully understand how your code is going to change and what
you want to look out for while you code, you will want to learn what changes
Python 3 makes in terms of Python 2. Typically the two best ways of doing that
is reading the @ref{149,,"What's New"} doc for each release of Python 3 and the
Porting to Python 3@footnote{http://python3porting.com/} book (which is free online). There is also a handy
cheat sheet@footnote{http://python-future.org/compatible_idioms.html} from the Python-Future project.

@node 更新代码,Prevent compatibility regressions,了解Python 2 和 3之间的区别,详情
@anchor{howto/pyporting update-your-code}@anchor{40ac}
@subsubsection 更新代码


Once you feel like you know what is different in Python 3 compared to Python 2,
it's time to update your code! You have a choice between two tools in porting
your code automatically: Futurize@footnote{http://python-future.org/automatic_conversion.html} and Modernize@footnote{https://python-modernize.readthedocs.io/}. Which tool you choose will
depend on how much like Python 3 you want your code to be. Futurize@footnote{http://python-future.org/automatic_conversion.html} does its
best to make Python 3 idioms and practices exist in Python 2, e.g. backporting
the @code{bytes} type from Python 3 so that you have semantic parity between the
major versions of Python. Modernize@footnote{https://python-modernize.readthedocs.io/},
on the other hand, is more conservative and targets a Python 2/3 subset of
Python, directly relying on six@footnote{https://pypi.org/project/six} to help provide compatibility. As Python 3 is
the future, it might be best to consider Futurize to begin adjusting to any new
practices that Python 3 introduces which you are not accustomed to yet.

Regardless of which tool you choose, they will update your code to run under
Python 3 while staying compatible with the version of Python 2 you started with.
Depending on how conservative you want to be, you may want to run the tool over
your test suite first and visually inspect the diff to make sure the
transformation is accurate. After you have transformed your test suite and
verified that all the tests still pass as expected, then you can transform your
application code knowing that any tests which fail is a translation failure.

Unfortunately the tools can't automate everything to make your code work under
Python 3 and so there are a handful of things you will need to update manually
to get full Python 3 support (which of these steps are necessary vary between
the tools). Read the documentation for the tool you choose to use to see what it
fixes by default and what it can do optionally to know what will (not) be fixed
for you and what you may have to fix on your own (e.g. using @code{io.open()} over
the built-in @code{open()} function is off by default in Modernize). Luckily,
though, there are only a couple of things to watch out for which can be
considered large issues that may be hard to debug if not watched for.

@menu
* 除法:: 
* 文本与二进制数据:: 
* Use feature detection instead of version detection:: 

@end menu

@node 除法,文本与二进制数据,,更新代码
@anchor{howto/pyporting division}@anchor{40ad}
@subsubsection 除法


In Python 3, @code{5 / 2 == 2.5} and not @code{2}; all division between @code{int} values
result in a @code{float}. This change has actually been planned since Python 2.2
which was released in 2002. Since then users have been encouraged to add
@code{from __future__ import division} to any and all files which use the @code{/} and
@code{//} operators or to be running the interpreter with the @code{-Q} flag. If you
have not been doing this then you will need to go through your code and do two
things:


@enumerate 

@item 
Add @code{from __future__ import division} to your files

@item 
Update any division operator as necessary to either use @code{//} to use floor
division or continue using @code{/} and expect a float
@end enumerate

The reason that @code{/} isn't simply translated to @code{//} automatically is that if
an object defines a @code{__truediv__} method but not @code{__floordiv__} then your
code would begin to fail (e.g. a user-defined class that uses @code{/} to
signify some operation but not @code{//} for the same thing or at all).

@node 文本与二进制数据,Use feature detection instead of version detection,除法,更新代码
@anchor{howto/pyporting text-versus-binary-data}@anchor{40ae}
@subsubsection 文本与二进制数据


In Python 2 you could use the @code{str} type for both text and binary data.
Unfortunately this confluence of two different concepts could lead to brittle
code which sometimes worked for either kind of data, sometimes not. It also
could lead to confusing APIs if people didn't explicitly state that something
that accepted @code{str} accepted either text or binary data instead of one
specific type. This complicated the situation especially for anyone supporting
multiple languages as APIs wouldn't bother explicitly supporting @code{unicode}
when they claimed text data support.

To make the distinction between text and binary data clearer and more
pronounced, Python 3 did what most languages created in the age of the internet
have done and made text and binary data distinct types that cannot blindly be
mixed together (Python predates widespread access to the internet). For any code
that deals only with text or only binary data, this separation doesn't pose an
issue. But for code that has to deal with both, it does mean you might have to
now care about when you are using text compared to binary data, which is why
this cannot be entirely automated.

To start, you will need to decide which APIs take text and which take binary
(it is @strong{highly} recommended you don't design APIs that can take both due to
the difficulty of keeping the code working; as stated earlier it is difficult to
do well). In Python 2 this means making sure the APIs that take text can work
with @code{unicode} and those that work with binary data work with the
@code{bytes} type from Python 3 (which is a subset of @code{str} in Python 2 and acts
as an alias for @code{bytes} type in Python 2). Usually the biggest issue is
realizing which methods exist on which types in Python 2 & 3 simultaneously
(for text that's @code{unicode} in Python 2 and @code{str} in Python 3, for binary
that's @code{str}/@code{bytes} in Python 2 and @code{bytes} in Python 3). The following
table lists the @strong{unique} methods of each data type across Python 2 & 3
(e.g., the @code{decode()} method is usable on the equivalent binary data type in
either Python 2 or 3, but it can't be used by the textual data type consistently
between Python 2 and 3 because @code{str} in Python 3 doesn't have the method). Do
note that as of Python 3.5 the @code{__mod__} method was added to the bytes type.


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxx} 
@item

@strong{文本数据}

@tab

@strong{二进制数据}

@item



@tab

decode

@item

encode

@tab

@item

format

@tab

@item

isdecimal

@tab

@item

isnumeric

@tab

@end multitable


Making the distinction easier to handle can be accomplished by encoding and
decoding between binary data and text at the edge of your code. This means that
when you receive text in binary data, you should immediately decode it. And if
your code needs to send text as binary data then encode it as late as possible.
This allows your code to work with only text internally and thus eliminates
having to keep track of what type of data you are working with.

The next issue is making sure you know whether the string literals in your code
represent text or binary data. You should add a @code{b} prefix to any
literal that presents binary data. For text you should add a @code{u} prefix to
the text literal. (there is a @ref{0,,__future__} import to force all unspecified
literals to be Unicode, but usage has shown it isn't as effective as adding a
@code{b} or @code{u} prefix to all literals explicitly)

As part of this dichotomy you also need to be careful about opening files.
Unless you have been working on Windows, there is a chance you have not always
bothered to add the @code{b} mode when opening a binary file (e.g., @code{rb} for
binary reading).  Under Python 3, binary files and text files are clearly
distinct and mutually incompatible; see the @ref{a1,,io} module for details.
Therefore, you @strong{must} make a decision of whether a file will be used for
binary access (allowing binary data to be read and/or written) or textual access
(allowing text data to be read and/or written). You should also use @ref{654,,io.open()}
for opening files instead of the built-in @ref{4ea,,open()} function as the @ref{a1,,io}
module is consistent from Python 2 to 3 while the built-in @ref{4ea,,open()} function
is not (in Python 3 it's actually @ref{654,,io.open()}). Do not bother with the
outdated practice of using @ref{12f8,,codecs.open()} as that's only necessary for
keeping compatibility with Python 2.5.

The constructors of both @code{str} and @code{bytes} have different semantics for the
same arguments between Python 2 & 3. Passing an integer to @code{bytes} in Python 2
will give you the string representation of the integer: @code{bytes(3) == '3'}.
But in Python 3, an integer argument to @code{bytes} will give you a bytes object
as long as the integer specified, filled with null bytes:
@code{bytes(3) == b'\x00\x00\x00'}. A similar worry is necessary when passing a
bytes object to @code{str}. In Python 2 you just get the bytes object back:
@code{str(b'3') == b'3'}. But in Python 3 you get the string representation of the
bytes object: @code{str(b'3') == "b'3'"}.

Finally, the indexing of binary data requires careful handling (slicing does
@strong{not} require any special handling). In Python 2,
@code{b'123'[1] == b'2'} while in Python 3 @code{b'123'[1] == 50}. Because binary data
is simply a collection of binary numbers, Python 3 returns the integer value for
the byte you index on. But in Python 2 because @code{bytes == str}, indexing
returns a one-item slice of bytes. The six@footnote{https://pypi.org/project/six} project has a function
named @code{six.indexbytes()} which will return an integer like in Python 3:
@code{six.indexbytes(b'123', 1)}.

To summarize:


@enumerate 

@item 
Decide which of your APIs take text and which take binary data

@item 
Make sure that your code that works with text also works with @code{unicode} and
code for binary data works with @code{bytes} in Python 2 (see the table above
for what methods you cannot use for each type)

@item 
Mark all binary literals with a @code{b} prefix, textual literals with a @code{u}
prefix

@item 
Decode binary data to text as soon as possible, encode text as binary data as
late as possible

@item 
Open files using @ref{654,,io.open()} and make sure to specify the @code{b} mode when
appropriate

@item 
Be careful when indexing into binary data
@end enumerate

@node Use feature detection instead of version detection,,文本与二进制数据,更新代码
@anchor{howto/pyporting use-feature-detection-instead-of-version-detection}@anchor{40af}
@subsubsection Use feature detection instead of version detection


Inevitably you will have code that has to choose what to do based on what
version of Python is running. The best way to do this is with feature detection
of whether the version of Python you're running under supports what you need.
If for some reason that doesn't work then you should make the version check be
against Python 2 and not Python 3. To help explain this, let's look at an
example.

Let's pretend that you need access to a feature of @ref{9b,,importlib} that
is available in Python's standard library since Python 3.3 and available for
Python 2 through importlib2@footnote{https://pypi.org/project/importlib2} on PyPI. You might be tempted to write code to
access e.g. the @ref{9c,,importlib.abc} module by doing the following:

@example
import sys

if sys.version_info[0] == 3:
    from importlib import abc
else:
    from importlib2 import abc
@end example

The problem with this code is what happens when Python 4 comes out? It would
be better to treat Python 2 as the exceptional case instead of Python 3 and
assume that future Python versions will be more compatible with Python 3 than
Python 2:

@example
import sys

if sys.version_info[0] > 2:
    from importlib import abc
else:
    from importlib2 import abc
@end example

The best solution, though, is to do no version detection at all and instead rely
on feature detection. That avoids any potential issues of getting the version
detection wrong and helps keep you future-compatible:

@example
try:
    from importlib import abc
except ImportError:
    from importlib2 import abc
@end example

@node Prevent compatibility regressions,Check which dependencies block your transition,更新代码,详情
@anchor{howto/pyporting prevent-compatibility-regressions}@anchor{40b0}
@subsubsection Prevent compatibility regressions


Once you have fully translated your code to be compatible with Python 3, you
will want to make sure your code doesn't regress and stop working under
Python 3. This is especially true if you have a dependency which is blocking you
from actually running under Python 3 at the moment.

To help with staying compatible, any new modules you create should have
at least the following block of code at the top of it:

@example
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
@end example

You can also run Python 2 with the @code{-3} flag to be warned about various
compatibility issues your code triggers during execution. If you turn warnings
into errors with @code{-Werror} then you can make sure that you don't accidentally
miss a warning.

You can also use the Pylint@footnote{https://pypi.org/project/pylint} project and its @code{--py3k} flag to lint your code
to receive warnings when your code begins to deviate from Python 3
compatibility. This also prevents you from having to run Modernize@footnote{https://python-modernize.readthedocs.io/} or Futurize@footnote{http://python-future.org/automatic_conversion.html}
over your code regularly to catch compatibility regressions. This does require
you only support Python 2.7 and Python 3.4 or newer as that is Pylint's
minimum Python version support.

@node Check which dependencies block your transition,Update your setup py file to denote Python 3 compatibility,Prevent compatibility regressions,详情
@anchor{howto/pyporting check-which-dependencies-block-your-transition}@anchor{40b1}
@subsubsection Check which dependencies block your transition


@strong{After} you have made your code compatible with Python 3 you should begin to
care about whether your dependencies have also been ported. The caniusepython3@footnote{https://pypi.org/project/caniusepython3}
project was created to help you determine which projects
-- directly or indirectly -- are blocking you from supporting Python 3. There
is both a command-line tool as well as a web interface at
@indicateurl{https://caniusepython3.com}.

The project also provides code which you can integrate into your test suite so
that you will have a failing test when you no longer have dependencies blocking
you from using Python 3. This allows you to avoid having to manually check your
dependencies and to be notified quickly when you can start running on Python 3.

@node Update your setup py file to denote Python 3 compatibility,Use continuous integration to stay compatible,Check which dependencies block your transition,详情
@anchor{howto/pyporting update-your-setup-py-file-to-denote-python-3-compatibility}@anchor{40b2}
@subsubsection Update your @code{setup.py} file to denote Python 3 compatibility


Once your code works under Python 3, you should update the classifiers in
your @code{setup.py} to contain @code{Programming Language :: Python :: 3} and to not
specify sole Python 2 support. This will tell anyone using your code that you
support Python 2 @strong{and} 3. Ideally you will also want to add classifiers for
each major/minor version of Python you now support.

@node Use continuous integration to stay compatible,考虑使用可选的静态类型检查,Update your setup py file to denote Python 3 compatibility,详情
@anchor{howto/pyporting use-continuous-integration-to-stay-compatible}@anchor{40b3}
@subsubsection Use continuous integration to stay compatible


Once you are able to fully run under Python 3 you will want to make sure your
code always works under both Python 2 & 3. Probably the best tool for running
your tests under multiple Python interpreters is tox@footnote{https://pypi.org/project/tox}. You can then integrate
tox with your continuous integration system so that you never accidentally break
Python 2 or 3 support.

You may also want to use the @code{-bb} flag with the Python 3 interpreter to
trigger an exception when you are comparing bytes to strings or bytes to an int
(the latter is available starting in Python 3.5). By default type-differing
comparisons simply return @code{False}, but if you made a mistake in your
separation of text/binary data handling or indexing on bytes you wouldn't easily
find the mistake. This flag will raise an exception when these kinds of
comparisons occur, making the mistake much easier to track down.

And that's mostly it! At this point your code base is compatible with both
Python 2 and 3 simultaneously. Your testing will also be set up so that you
don't accidentally break Python 2 or 3 compatibility regardless of which version
you typically run your tests under while developing.

@node 考虑使用可选的静态类型检查,,Use continuous integration to stay compatible,详情
@anchor{howto/pyporting consider-using-optional-static-type-checking}@anchor{40b4}
@subsubsection 考虑使用可选的静态类型检查


Another way to help port your code is to use a static type checker like
mypy@footnote{http://mypy-lang.org/} or pytype@footnote{https://github.com/google/pytype} on your code. These tools can be used to analyze your code as
if it's being run under Python 2, then you can run the tool a second time as if
your code is running under Python 3. By running a static type checker twice like
this you can discover if you're e.g. misusing binary data type in one version
of Python compared to another. If you add optional type hints to your code you
can also explicitly state whether your APIs use textual or binary data, helping
to make sure everything functions as expected in both versions of Python.

@node 将扩展模块移植到 Python 3,用 Python 进行 Curses 编程,将 Python 2 代码迁移到 Python 3,Python 常用指引
@anchor{howto/cporting doc}@anchor{40b5}@anchor{howto/cporting cporting-howto}@anchor{c70}@anchor{howto/cporting porting-extension-modules-to-python-3}@anchor{40b6}@anchor{howto/cporting why-python-3-exists}@anchor{40b7}
@section 将扩展模块移植到 Python 3


对于将扩展模块移植到 Python 3，我们推荐下列资源：


@itemize *

@item 
@emph{Supporting Python 3: An in-depth guide} 中的 Migrating C extensions@footnote{http://python3porting.com/cextensions.html} 这一章，这本书介绍了如何从 Python 2 迁移到 Python 3，包括指导读者如何移植扩展模块。

@item 
@emph{py3c} 项目中的 Porting guide@footnote{https://py3c.readthedocs.io/en/latest/guide.html} 提供了有关支持代码的指导性建议。

@item 
Cython@footnote{http://cython.org/} 和 CFFI@footnote{https://cffi.readthedocs.io/en/latest/} 库提供了对于 Python 的 C API 的抽象。 扩展大都需要进行重写以使用两者中的一个，然后就可以通过库来处理各种 Python 版本和实现之间的差异。
@end itemize

@node 用 Python 进行 Curses 编程,描述器使用指南,将扩展模块移植到 Python 3,Python 常用指引
@anchor{howto/curses doc}@anchor{40b8}@anchor{howto/curses cffi}@anchor{40b9}@anchor{howto/curses curses-howto}@anchor{20e9}@anchor{howto/curses curses-programming-with-python}@anchor{40ba}
@section 用 Python 进行 Curses 编程


@*作者: 
A.M. Kuchling, Eric S. Raymond


@*发布版本: 
2.04


@subsubheading 摘要



本文档介绍了如何使用 @ref{2c,,curses} 扩展模块控制文本模式的显示。

@menu
* curses 是什么？:: 
* 开始和结束curses应用程序:: 
* 窗口和面板:: 
* 显示文字:: 
* 用户输入:: 
* 更多的信息:: 

@end menu

@node curses 是什么？,开始和结束curses应用程序,,用 Python 进行 Curses 编程
@anchor{howto/curses what-is-curses}@anchor{40bb}
@subsection curses 是什么？


curses 库为基于文本的终端提供了独立于终端的屏幕绘制和键盘处理功能；这些终端包括 VT100，Linux 控制台以及各种程序提供的模拟终端。显示终端支持各种控制代码以执行常见的操作，例如移动光标，滚动屏幕和擦除区域。不同的终端使用相差很大的代码，并且往往有自己的小怪癖。

在普遍使用图形显示的世界中，人们可能会问“为什么自找要麻烦”？毕竟字符单元显示终端确实是一种过时的技术，但是在某些领域中，能够用它们做花哨的事情仍然很有价值。一个小众市场是在不运行 X server 的小型或嵌入式 Unix 上。另一个是在提供图形支持之前，可能需要运行的工具，例如操作系统安装程序和内核配置程序。

curses 库提供了相当基础的功能，为程序员提供了包含多个非重叠文本窗口的显示的抽象。窗口的内容可以通过多种方式更改---添加文本，擦除文本，更改其外观---以及curses库将确定需要向终端发送哪些控制代码以产生正确的输出。 curses并没有提供诸多用户界面概念，例如按钮，复选框或对话框。如果需要这些功能，请考虑用户界面库，例如 Urwid@footnote{https://pypi.org/project/urwid/} 。

curses 库最初是为BSD Unix 编写的。 后来 AT&T 的Unix System V 版本加入了许多增强功能和新功能。如今BSD curses已不再维护，被ncurses取代，ncurses是 AT&T 接口的开源实现。如果使用的是 Linux 或 FreeBSD 等开源Unix系统，则几乎肯定会使用ncurses。由于大多数当前的商业Unix版本都基于System V代码，因此这里描述的所有功能可能都可用。但是，某些专有Unix所带来的较早版本的curses可能无法支持所有功能。

Windows 版本的 Python 不包含 @ref{2c,,curses} 模块。提供了一个名为 UniCurses@footnote{https://pypi.org/project/UniCurses} 的移植版本。也可以尝试使用 Fredrik Lundh 编写 the Console module@footnote{http://effbot.org/zone/console-index.htm}，它使用了与curses不相同的API，但提供了可光标定位的文本输出，完全支持鼠标和键盘输入。

@menu
* Python 的 curses 模块:: 

@end menu

@node Python 的 curses 模块,,,curses 是什么？
@anchor{howto/curses the-python-curses-module}@anchor{40bc}
@subsubsection Python 的 curses 模块


此 Python 模块相当简单地封装了 curses 提供的 C 函数；如果你已经熟悉在 C 语言中使用 curses 编程，把这些知识转移的 Python 是非常容易的。最大的差异在于 Python 中的接口通过把不同的 C 函数合并来让事情变得更简单，比如 @code{addstr()}、@code{mvaddstr()} 和 @code{mvwaddstr()} 三个 C 函数被并入 @ref{20fd,,addstr()} 这一个方法。下文中会描述更多的细节。

本 HOWTO 是关于使用 curses 和 Python 编写文本模式程序的概述。它并不被设计为一个 curses API 的完整指南；如需完整指南，请参见 ncurses 的 Python 库指南章节和 ncurses 的 C 手册页。相对地，本 HOWTO 将会给你一些基本思路。

@node 开始和结束curses应用程序,窗口和面板,curses 是什么？,用 Python 进行 Curses 编程
@anchor{howto/curses starting-and-ending-a-curses-application}@anchor{40bd}
@subsection 开始和结束curses应用程序


在做任何事情之前，curses 必须先被初始化。可以通过调用函数 @ref{2103,,initscr()} 来实现，它将查明终端的类型，向终端发送任何必须的设置代码，并创建多种内部数据结构。如果此操作成功，@code{initscr()} 将会返回一个代表整个屏幕的窗口对象；它通常会遵循对应的 C 变量名被称作 @code{stdscr}：

@example
import curses
stdscr = curses.initscr()
@end example

使用 curses 的应用程序通常会关闭按键自动上屏，目的是读取按键并只在特定情况下展示它们。这需要调用函数 @ref{2121,,noecho()}：

@example
curses.noecho()
@end example

应用程序也会广泛地需要立即响应按键，而不需要按下回车键；这被称为 “cbreak” 模式，与通常的缓冲输入模式相对：

@example
curses.cbreak()
@end example

终端通常会以多字节转义序列的形式返回特殊按键，比如光标键和导航键比如 Page Up 键和 Home 键。尽管你可以编写你的程序来应对这些序列，curses 能够代替你做到这件事，返回一个特殊值比如 @code{curses.KEY_LEFT}。为了让 curses 做这项工作，你需要启用 keypad 模式：

@example
stdscr.keypad(True)
@end example

终止一个 curses 应用程序比建立一个容易得多，你只需要调用：

@example
curses.nocbreak()
stdscr.keypad(False)
curses.echo()
@end example

来还原对终端作出的 curses 友好设置。然后，调用函数 @ref{2100,,endwin()} 来将终端还原到它的原始操作模式：

@example
curses.endwin()
@end example

调试一个 curses 应用程序时常会发生，一个应用程序还未能还原终端到原本的状态就意外退出了，这会搅乱你的终端。在 Python 中这常常会发生在你的代码中有 bug 并引发了一个未捕获的异常。当你尝试输入时按键不会上屏，这使得使用终端变得困难。

在 Python 中你可以避免这些复杂问题并让调试变得更简单，只需要导入 @ref{2a1,,curses.wrapper()} 函数并像这样使用它：

@example
from curses import wrapper

def main(stdscr):
    # Clear screen
    stdscr.clear()

    # This raises ZeroDivisionError when i == 10.
    for i in range(0, 11):
        v = i-10
        stdscr.addstr(i, 0, '10 divided by @{@} is @{@}'.format(v, 10/v))

    stdscr.refresh()
    stdscr.getkey()

wrapper(main)
@end example

函数 @ref{2a1,,wrapper()} 接受一个可调用对象并首先进行上述初始化过程，在终端支持着色时还会初始化颜色。接着 @code{wrapper()} 运行你提供的可调用对象。当该可调用对象返回时，@code{wrapper()} 会还原终端到初始状态。该可调用对象会在 @ref{d6b,,try}...@ref{b37,,except} 这样的结构内被调用，当它捕获到异常时，会先还原终端再重新引发这个异常。所以你的终端不会因为异常而被留在一个搞笑的状态，你也可以正常阅读异常消息和回溯信息。

@node 窗口和面板,显示文字,开始和结束curses应用程序,用 Python 进行 Curses 编程
@anchor{howto/curses windows-and-pads}@anchor{40be}
@subsection 窗口和面板


窗口是 curses 中的基本抽象。一个窗口对象表示了屏幕上的一个矩形区域，并且提供方法来显示文本、擦除文本、允许用户输入字符串等等。

函数 @ref{2103,,initscr()} 返回的 @code{stdscr} 对象覆盖整个屏幕。许多程序可能只需要这一个窗口，但你可能希望把屏幕分割为多个更小的窗口，来分别重绘或者清楚它们。函数 @ref{211f,,newwin()} 根据给定的尺寸创建一个新窗口，并返回这个新的窗口对象：

@example
begin_x = 20; begin_y = 7
height = 5; width = 40
win = curses.newwin(height, width, begin_y, begin_x)
@end example

注意 curses 使用的坐标系统与寻常的不同。坐标始终是以 @emph{y,x} 的顺序传递，并且左上角是坐标 (0,0)。这打破了正常的坐标处理约定，即 @emph{x} 坐标在前。这是一个与其他计算机应用程序糟糕的差异，但这从 curses 最初被编写出来就已是它的一部分，现在想要修改它已为时已晚。

你的应用程序能够查明屏幕的尺寸，@code{curses.LINES} 和 @code{curses.COLS} 分别代表了 @emph{y} 和 @emph{x} 方向上的尺寸。合理的坐标应位于 @code{(0,0)} 到 @code{(curses.LINES - 1, curses.COLS - 1)} 范围内。

当你调用一个方法来显示或擦除文本时，效果并不会立即显示。相反，你必须调用窗口对象的 @ref{20fe,,refresh()} 方法来更新屏幕。

这是因为 curses 最初是为 300 波特的龟速终端连接编写的；在这些终端上，压制重绘屏幕的时间就非常重要。相对地，当你调用 @code{refresh()} 时，curses 会累积屏幕的修改并以效率最高的方式显示它们。打个比方，如果你的程序在一个窗口内显示一些文本然后清楚了这个窗口，那么这些原始文本不需要被发送，因为它们甚至不曾能被看见。

在实践中，显式地告诉 curses 来重绘一个窗口并不会太复杂化 curses 编程。大部分程序会显示一堆内容然后等待按键或者其他某些用户侧动作。你要做的事情就是，保证屏幕在暂停并等待用户输入前被重绘，只需要先调用 @code{stdscr.refresh()} 或者其他相关窗口的 @code{refresh()} 方法。

一个面板是一种特殊的窗口，它可以比实际的显示屏幕更大，并且能只显示它的一部分。创建面板需要指定面板的高度和宽度，但刷新一个面板需要给出屏幕坐标和面板的需要显示的局部。

@example
pad = curses.newpad(100, 100)
# These loops fill the pad with letters; addch() is
# explained in the next section
for y in range(0, 99):
    for x in range(0, 99):
        pad.addch(y,x, ord('a') + (x*x+y*y) % 26)

# Displays a section of the pad in the middle of the screen.
# (0,0) : coordinate of upper-left corner of pad area to display.
# (5,5) : coordinate of upper-left corner of window area to be filled
#         with pad content.
# (20, 75) : coordinate of lower-right corner of window area to be
#          : filled with pad content.
pad.refresh( 0,0, 5,5, 20,75)
@end example

此 @code{refresh()} 调用会在屏幕坐标 (5,5) 到坐标 (20,75) 的矩形范围内显示面板的一个部分，被显示的部分在面板上的坐标是 (0,0)。除了上述差异，面板与常规的窗口相同，也支持相同的方法。

如果你在屏幕上有多个窗口和面板，有一个更有效率的方法来更新窗口，避免每个部分单独更新时烦人的屏幕闪烁。@code{refresh()} 实际上做了两件事：


@enumerate 

@item 
调用每个窗口的  @ref{20fc,,noutrefresh()} 方法来更新一个表达屏幕期望状态的底层的数据结构。

@item 
调用函数 @ref{20fb,,doupdate()} 来改变物理屏幕来符合这个数据结构中记录的期望状态。
@end enumerate

你可以改为调用在多个窗口上 @code{noutrefresh()} 方法来更新该数据结构，然后调用函数 @code{doupdate()} 来更新屏幕。

@node 显示文字,用户输入,窗口和面板,用 Python 进行 Curses 编程
@anchor{howto/curses displaying-text}@anchor{40bf}
@subsection 显示文字


从一名 C 语言程序员的视角来看，curses 有时看起来就像是一堆略有差异的函数组成的扭曲迷宫。举个例子，@code{addstr()} 在 @code{stdscr} 窗口的当前光标位置显示一个字符串，而 @code{mvaddstr()} 则是先移动到一个给定的 y,x 坐标再显示字符串。@code{waddstr()} 与 @code{addstr()} 类似，但允许指定一个窗口而非默认的 @code{stdscr}。@code{mvwaddstr()} 允许同时指定一个窗口和一个坐标。

幸运的是，Python 接口隐藏了所有这些细节。@code{stdscr} 和其他任何窗口一样是一个窗口对象，并且诸如 @ref{20fd,,addstr()} 之类的方法接受多种参数形式。通常有四种形式。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

形式

@tab

描述

@item

@emph{str} 或 @emph{ch}

@tab

在当前位置显示字符串 @emph{str} 或字符 @emph{ch}

@item

@emph{str} 或 @emph{ch}, @emph{attr}

@tab

在当前位置使用 @emph{attr} 属性显示字符串 @emph{str} 或字符 @emph{ch}

@item

@emph{y}, @emph{x}, @emph{str} 或 @emph{ch}

@tab

移动到窗口内的 @emph{y,x} 位置，并显示 @emph{str} 或 @emph{ch}

@item

@emph{y}, @emph{x}, @emph{str} 或 @emph{ch}, @emph{attr}

@tab

移至窗口内的 @emph{y,x} 位置，并使用 @emph{attr} 属性显示 @emph{str} 或 @emph{ch}

@end multitable


属性允许以突出显示形态显示文本，比如加粗、下划线、反相或添加颜色。这些属性将来下一小节细说。

方法 @ref{20fd,,addstr()} 接受一个 Python 字符串或字节串作为用于显示的值。字节串的内容会被原样发送到终端。字符串会使用窗口的 @code{encoding} 属性值编码为字节，它默认为 @ref{39d,,locale.getpreferredencoding()} 返回的系统默认编码。

方法 @ref{213b,,addch()} 接受一个字符，可以是长度为 1 的字符串，长度为 1 的字节串或者一个整数。

对于特殊扩展字符有一些常量，这些常量是大于 255 的整数。比如，@code{ACS_PLMINUS} 是一个 “加减” 符号，@code{ACS_ULCORNER} 是一个框的左上角（方便绘制边界）。你也可以使用正确的 Unicode 字符。

窗口会记住上次操作之后光标所在位置，所以如果你忽略 @emph{y,x} 坐标，字符串和字符会出现在上次操作结束的位置。你也可以通过 @code{move(y,x)} 的方法来移动光标。因为一些终端始终会显示一个闪烁的光标，你可能会想要保证光标处于一些不会让人感到分心的位置。在看似随机的位置出现一个闪烁的光标会令人非常迷惑。

如果你的应用程序完全不需要一个闪烁的光标，你可以调用 @code{curs_set(False)} 来使它隐形。为与旧版本 curses 的兼容性的关系，有函数 @code{leaveok(bool)} 作为 @ref{20f5,,curs_set()} 的等价替换。如果 @emph{bool} 是真值，curses 库会尝试移除闪烁光标，并且你也不必担心它会留在一些奇怪的位置。

@menu
* 属性和颜色:: 

@end menu

@node 属性和颜色,,,显示文字
@anchor{howto/curses attributes-and-color}@anchor{40c0}
@subsubsection 属性和颜色


字符可以以不同的方式显示。基于文本的应用程序常常以反相显示状态行，一个文本查看器可能需要突出显示某些单词。为了支持这种用法，curses 允许你为屏幕上的每个单元指定一个属性值。

属性值是一个整数，它的每一个二进制位代表一个不同的属性。你可以尝试以多种不属性位组合来显示文本，但 curses 不保证所有的组合都是有效的，或者看上去有明显不同。这一点取决于用户终端的能力，所以最稳妥的方式是只采用最常见的有效属性，见下表。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

属性

@tab

描述

@item

@code{A_BLINK}

@tab

闪烁文字

@item

@code{A_BOLD}

@tab

超亮或粗体文字

@item

@code{A_DIM}

@tab

半明亮的文字

@item

@code{A_REVERSE}

@tab

反相显示文本

@item

@code{A_STANDOUT}

@tab

可用的最佳突出显示模式

@item

@code{A_UNDERLINE}

@tab

带下划线的文字

@end multitable


所以，为了在屏幕顶部显示一个反相的状态行，你可以这么编写：

@example
stdscr.addstr(0, 0, "Current mode: Typing mode",
              curses.A_REVERSE)
stdscr.refresh()
@end example

curses 库还支持在提供了颜色功能的终端上显示颜色的功能。最常见的提供颜色的终端很可能是 Linux 控制台，采用了 xterms 配色方案。

为了使用颜色，你必须在调用完函数 @ref{2103,,initscr()} 后尽快调用函数 @ref{212d,,start_color()}，来初始化默认颜色集 (@ref{2a1,,curses.wrapper()} 函数自动完成了这一点)。 当它完成后，如果使用中的终端支持显示颜色， @ref{210b,,has_colors()} 会返回真值。 （注意：curses 使用美式拼写 “color”，而不是英式／加拿大拼写 “colour”。如果你习惯了英式拼写，你需要避免自己在这些函数上拼写错误。）

curses 库维护一个有限数量的颜色对，包括一个前景（文本）色和一个背景色。你可以使用函数  @ref{20f3,,color_pair()} 获得一个颜色对对应的属性值。它可以通过按位或运算与其他属性，比如 @code{A_REVERSE} 组合。但再说明一遍，这种组合并不保证在所有终端上都有效。

一个样例，用 1 号颜色对显示一行文本：

@example
stdscr.addstr("Pretty text", curses.color_pair(1))
stdscr.refresh()
@end example

如前所述， 颜色对由前景色和背景色组成。  @code{init_pair(n, f, b)} 函数改变颜色对*n*的定义， 为前景色f和背景色b。 颜色对0硬连接到黑色上的白色，不能改变。

Colors are numbered, and @code{start_color()} initializes 8 basic
colors when it activates color mode.  They are: 0:black, 1:red,
2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and 7:white.  The @ref{2c,,curses}
module defines named constants for each of these colors:
@code{curses.COLOR_BLACK}, @code{curses.COLOR_RED}, and so forth.

Let's put all this together. To change color 1 to red text on a white
background, you would call:

@example
curses.init_pair(1, curses.COLOR_RED, curses.COLOR_WHITE)
@end example

When you change a color pair, any text already displayed using that color pair
will change to the new colors.  You can also display new text in this color
with:

@example
stdscr.addstr(0,0, "RED ALERT!", curses.color_pair(1))
@end example

Very fancy terminals can change the definitions of the actual colors to a given
RGB value.  This lets you change color 1, which is usually red, to purple or
blue or any other color you like.  Unfortunately, the Linux console doesn't
support this, so I'm unable to try it out, and can't provide any examples.  You
can check if your terminal can do this by calling
@ref{20ef,,can_change_color()}, which returns @code{True} if the capability is
there.  If you're lucky enough to have such a talented terminal, consult your
system's man pages for more information.

@node 用户输入,更多的信息,显示文字,用 Python 进行 Curses 编程
@anchor{howto/curses user-input}@anchor{40c1}
@subsection 用户输入


The C curses library offers only very simple input mechanisms. Python's
@ref{2c,,curses} module adds a basic text-input widget.  (Other libraries
such as Urwid@footnote{https://pypi.org/project/urwid/} have more extensive
collections of widgets.)

There are two methods for getting input from a window:


@itemize *

@item 
@ref{2107,,getch()} refreshes the screen and then waits for
the user to hit a key, displaying the key if @ref{20ff,,echo()} has been
called earlier.  You can optionally specify a coordinate to which
the cursor should be moved before pausing.

@item 
@ref{2154,,getkey()} does the same thing but converts the
integer to a string.  Individual characters are returned as
1-character strings, and special keys such as function keys return
longer strings containing a key name such as @code{KEY_UP} or @code{^G}.
@end itemize

It's possible to not wait for the user using the
@ref{216a,,nodelay()} window method. After @code{nodelay(True)},
@code{getch()} and @code{getkey()} for the window become
non-blocking. To signal that no input is ready, @code{getch()} returns
@code{curses.ERR} (a value of -1) and @code{getkey()} raises an exception.
There's also a @ref{210f,,halfdelay()} function, which can be used to (in
effect) set a timer on each @code{getch()}; if no input becomes
available within a specified delay (measured in tenths of a second),
curses raises an exception.

The @code{getch()} method returns an integer; if it's between 0 and 255, it
represents the ASCII code of the key pressed.  Values greater than 255 are
special keys such as Page Up, Home, or the cursor keys. You can compare the
value returned to constants such as @code{curses.KEY_PPAGE},
@code{curses.KEY_HOME}, or @code{curses.KEY_LEFT}.  The main loop of
your program may look something like this:

@example
while True:
    c = stdscr.getch()
    if c == ord('p'):
        PrintDocument()
    elif c == ord('q'):
        break  # Exit the while loop
    elif c == curses.KEY_HOME:
        x = y = 0
@end example

The @ref{2d,,curses.ascii} module supplies ASCII class membership functions that
take either integer or 1-character string arguments; these may be useful in
writing more readable tests for such loops.  It also supplies
conversion functions  that take either integer or 1-character-string arguments
and return the same type.  For example, @ref{219e,,curses.ascii.ctrl()} returns the
control character corresponding to its argument.

There's also a method to retrieve an entire string,
@ref{2157,,getstr()}.  It isn't used very often, because its
functionality is quite limited; the only editing keys available are
the backspace key and the Enter key, which terminates the string.  It
can optionally be limited to a fixed number of characters.

@example
curses.echo()            # Enable echoing of characters

# Get a 15-character string, with the cursor on the top line
s = stdscr.getstr(0,0, 15)
@end example

The @ref{2f,,curses.textpad} module supplies a text box that supports an
Emacs-like set of keybindings.  Various methods of the
@ref{2184,,Textbox} class support editing with input
validation and gathering the edit results either with or without
trailing spaces.  Here's an example:

@example
import curses
from curses.textpad import Textbox, rectangle

def main(stdscr):
    stdscr.addstr(0, 0, "Enter IM message: (hit Ctrl-G to send)")

    editwin = curses.newwin(5,30, 2,1)
    rectangle(stdscr, 1,0, 1+5+1, 1+30+1)
    stdscr.refresh()

    box = Textbox(editwin)

    # Let the user edit until Ctrl-G is struck.
    box.edit()

    # Get resulting contents
    message = box.gather()
@end example

See the library documentation on @ref{2f,,curses.textpad} for more details.

@node 更多的信息,,用户输入,用 Python 进行 Curses 编程
@anchor{howto/curses for-more-information}@anchor{40c2}
@subsection 更多的信息


This HOWTO doesn't cover some advanced topics, such as reading the
contents of the screen or capturing mouse events from an xterm
instance, but the Python library page for the @ref{2c,,curses} module is now
reasonably complete.  You should browse it next.

If you're in doubt about the detailed behavior of the curses
functions, consult the manual pages for your curses implementation,
whether it's ncurses or a proprietary Unix vendor's.  The manual pages
will document any quirks, and provide complete lists of all the
functions, attributes, and @code{ACS_*} characters available to
you.

Because the curses API is so large, some functions aren't supported in
the Python interface.  Often this isn't because they're difficult to
implement, but because no one has needed them yet.  Also, Python
doesn't yet support the menu library associated with ncurses.
Patches adding support for these would be welcome; see
the Python Developer's Guide@footnote{https://devguide.python.org/} to
learn more about submitting patches to Python.


@itemize *

@item 
Writing Programs with NCURSES@footnote{http://invisible-island.net/ncurses/ncurses-intro.html}:
a lengthy tutorial for C programmers.

@item 
ncurses 手册主页 <@indicateurl{https://linux.die.net/man/3/ncurses}>`_

@item 
ncurses 常见问题 <@indicateurl{http://invisible-island.net/ncurses/ncurses.faq.html}>`_

@item 
"Use curses... don't swear"@footnote{https://www.youtube.com/watch?v=eN1eZtjLEnU}:
video of a PyCon 2013 talk on controlling terminals using curses or Urwid.

@item 
"Console Applications with Urwid"@footnote{http://www.pyvideo.org/video/1568/console-applications-with-urwid}:
video of a PyCon CA 2012 talk demonstrating some applications written using
Urwid.
@end itemize

@node 描述器使用指南,函数式编程指引,用 Python 进行 Curses 编程,Python 常用指引
@anchor{howto/descriptor doc}@anchor{40c3}@anchor{howto/descriptor descriptor-howto-guide}@anchor{40c4}
@section 描述器使用指南


@*作者: 
Raymond Hettinger


@*联系方式: 
<python at rcn dot com>


@menu
* 摘要:: 
* 定义和简介:: 
* 描述器协议:: 
* 调用描述器: 调用描述器<2>. 
* 描述器示例:: 
* 属性:: 
* 函数和方法:: 
* 静态方法和类方法:: 

@end menu

@node 摘要,定义和简介,,描述器使用指南
@anchor{howto/descriptor abstract}@anchor{40c5}
@subsection 摘要


定义描述器，总结描述器协议，展示描述器被如何使用。测试一个自定义的描述器和若干 Python 内置的描述器，包括函数、属性、静态方法和类方法。通过给出一个纯 Python 的等价实现和例程，展示每个描述器如何工作。

学习描述器不仅能提供接触到更多工具集的途径，还能更深地理解 Python 工作的原理并更加体会到其设计的优雅性。

@node 定义和简介,描述器协议,摘要,描述器使用指南
@anchor{howto/descriptor definition-and-introduction}@anchor{40c6}
@subsection 定义和简介


一般地，一个描述器是一个包含 “绑定行为” 的对象，对其属性的访问被描述器协议中定义的方法覆盖。这些方法有：@ref{13d3,,__get__()}，@ref{13d7,,__set__()} 和 @ref{13d8,,__delete__()}。如果某个对象中定义了这些方法中的任意一个，那么这个对象就可以被称为一个描述器。

属性访问的默认行为是从一个对象的字典中获取、设置或删除属性。例如，@code{a.x} 的查找顺序会从 @code{a.__dict__['x']} 开始，然后是 @code{type(a).__dict__['x']}，接下来依次查找 @code{type(a)} 的基类，不包括元类。 如果找到的值是定义了某个描述器方法的对象，则 Python 可能会重载默认行为并转而发起调用描述器方法。这具体发生在优先级链的哪个环节则要根据所定义的描述器方法及其被调用的方式来决定。

描述器是一个强大而通用的协议。 它们是特征属性、方法静态方法、类方法和 @ref{4dc,,super()} 背后的实现机制。 它们在 Python 内部被广泛使用来实现自 2.2 版中引入的新式类。 描述器简化了底层的 C 代码并为 Python 的日常程序提供了一组灵活的新工具。

@node 描述器协议,调用描述器<2>,定义和简介,描述器使用指南
@anchor{howto/descriptor descriptor-protocol}@anchor{40c7}
@subsection 描述器协议


@code{descr.__get__(self, obj, type=None) -> value}

@code{descr.__set__(self, obj, value) -> None}

@code{descr.__delete__(self, obj) -> None}

以上就是全部。定义这些方法中的任何一个的对象被视为描述器，并在被作为属性时覆盖其默认行为。

如果一个对象定义了 @ref{13d7,,__set__()} 或 @ref{13d8,,__delete__()}，则它会被视为数据描述器。 仅定义了 @ref{13d3,,__get__()} 的描述器称为非数据描述器（它们通常被用于方法，但也可以有其他用途）。

数据和非数据描述器的不同之处在于，如何计算实例字典中条目的替代值。如果实例的字典具有与数据描述器同名的条目，则数据描述器优先。如果实例的字典具有与非数据描述器同名的条目，则该字典条目优先。

为了使数据描述器成为只读的，应该同时定义 @ref{13d3,,__get__()} 和 @ref{13d7,,__set__()} ，并在 @ref{13d7,,__set__()} 中引发 @ref{393,,AttributeError} 。用引发异常的占位符定义 @ref{13d7,,__set__()}  方法使其成为数据描述器。

@node 调用描述器<2>,描述器示例,描述器协议,描述器使用指南
@anchor{howto/descriptor invoking-descriptors}@anchor{40c8}
@subsection 调用描述器


描述器可以通过其方法名称直接调用。例如， @code{d.__get__(obj)} 。

或者，更常见的是在属性访问时自动调用描述器。例如，在中 @code{obj.d} 会在 @code{d} 的字典中查找 @code{obj} 。如果 @code{d} 定义了方法 @ref{13d3,,__get__()} ，则 @code{d.__get__(obj)} 根据下面列出的优先级规则进行调用。

调用的细节取决于 @code{obj} 是对象还是类。

对于对象来说，机制是 @ref{441,,object.__getattribute__()} 中将 @code{b.x} 转换为 @code{type(b).__dict__['x'].__get__(b, type(b))} 。这个实现通过一个优先级链完成，该优先级链赋予数据描述器优先于实例变量的优先级，实例变量优先于非数据描述器的优先级，并如果 @ref{313,,__getattr__()} 方法存在，为其分配最低的优先级。 完整的C实现可在 Objects/object.c@footnote{https://github.com/python/cpython/tree/3.8/Objects/object.c} 中的 @ref{3c59,,PyObject_GenericGetAttr()} 找到。

对于类来说，机制是 @code{type.__getattribute__()} 中将 @code{B.x} 转换为 @code{B.__dict__['x'].__get__(None, B)} 。在纯 Python中 ，它是这样的:

@example
def __getattribute__(self, key):
    "Emulate type_getattro() in Objects/typeobject.c"
    v = object.__getattribute__(self, key)
    if hasattr(v, '__get__'):
        return v.__get__(None, self)
    return v
@end example

要记住的重要点是：


@itemize *

@item 
描述器由 @ref{441,,__getattribute__()} 方法调用

@item 
重写 @ref{441,,__getattribute__()} 会阻止描述器的自动调用

@item 
@ref{441,,object.__getattribute__()} 和 @code{type.__getattribute__()} 会用不同的方式调用 @ref{13d3,,__get__()}.

@item 
数据描述器始终会覆盖实例字典。

@item 
非数据描述器会被实例字典覆盖。
@end itemize

The object returned by @code{super()} also has a custom @ref{441,,__getattribute__()}
method for invoking descriptors.  The attribute lookup @code{super(B, obj).m} searches
@code{obj.__class__.__mro__} for the base class @code{A} immediately following @code{B}
and then returns @code{A.__dict__['m'].__get__(obj, B)}.  If not a descriptor,
@code{m} is returned unchanged.  If not in the dictionary, @code{m} reverts to a
search using @ref{441,,object.__getattribute__()}.

这个实现的具体细节在 Objects/typeobject.c@footnote{https://github.com/python/cpython/tree/3.8/Objects/typeobject.c}. 的 @code{super_getattro()} 中，并且你还可以在 Guido's Tutorial@footnote{https://www.python.org/download/releases/2.2.3/descrintro/#cooperation} 中找到等价的纯 Python 实现。

以上展示的关于描述器机制的细节嵌入在 @ref{2b0,,object} ， @ref{603,,type} ， 和 @ref{4dc,,super()} 中的 @ref{441,,__getattribute__()} 。当类派生自类 @ref{2b0,,object} 或有提供类似功能的元类时，它们将继承此机制。同样，类可以通过重写 @ref{441,,__getattribute__()} 阻止描述器调用。

@node 描述器示例,属性,调用描述器<2>,描述器使用指南
@anchor{howto/descriptor descriptor-example}@anchor{40c9}
@subsection 描述器示例


以下代码创建一个类，其对象是数据描述器，该描述器为每个 get 或 set 打印一条消息。  覆盖 @ref{441,,__getattribute__()} 是可以对每个属性执行此操作的替代方法。但是，此描述器对于跟踪少数几个选定的属性很有用:

@example
class RevealAccess(object):
    """A data descriptor that sets and returns values
       normally and prints a message logging their access.
    """

    def __init__(self, initval=None, name='var'):
        self.val = initval
        self.name = name

    def __get__(self, obj, objtype):
        print('Retrieving', self.name)
        return self.val

    def __set__(self, obj, val):
        print('Updating', self.name)
        self.val = val

>>> class MyClass(object):
...     x = RevealAccess(10, 'var "x"')
...     y = 5
...
>>> m = MyClass()
>>> m.x
Retrieving var "x"
10
>>> m.x = 20
Updating var "x"
>>> m.x
Retrieving var "x"
20
>>> m.y
5
@end example

这个协议很简单，并提供了令人兴奋的可能性。有几种用例非常普遍，以至于它们被打包到单独的函数调用中。属性、绑定方法、静态方法和类方法均基于描述器协议。

@node 属性,函数和方法,描述器示例,描述器使用指南
@anchor{howto/descriptor properties}@anchor{40ca}
@subsection 属性


调用 @ref{1d7,,property()} 是构建数据描述器的简洁方式，该数据描述器在访问属性时触发函数调用。它的签名是:

@example
property(fget=None, fset=None, fdel=None, doc=None) -> property attribute
@end example

该文档显示了定义托管属性 @code{x} 的典型用法:

@example
class C(object):
    def getx(self): return self.__x
    def setx(self, value): self.__x = value
    def delx(self): del self.__x
    x = property(getx, setx, delx, "I'm the 'x' property.")
@end example

要了解 @ref{1d7,,property()} 如何根据描述器协议实现，这里是一个纯 Python 的等价实现如下:

@example
class Property(object):
    "Emulate PyProperty_Type() in Objects/descrobject.c"

    def __init__(self, fget=None, fset=None, fdel=None, doc=None):
        self.fget = fget
        self.fset = fset
        self.fdel = fdel
        if doc is None and fget is not None:
            doc = fget.__doc__
        self.__doc__ = doc

    def __get__(self, obj, objtype=None):
        if obj is None:
            return self
        if self.fget is None:
            raise AttributeError("unreadable attribute")
        return self.fget(obj)

    def __set__(self, obj, value):
        if self.fset is None:
            raise AttributeError("can't set attribute")
        self.fset(obj, value)

    def __delete__(self, obj):
        if self.fdel is None:
            raise AttributeError("can't delete attribute")
        self.fdel(obj)

    def getter(self, fget):
        return type(self)(fget, self.fset, self.fdel, self.__doc__)

    def setter(self, fset):
        return type(self)(self.fget, fset, self.fdel, self.__doc__)

    def deleter(self, fdel):
        return type(self)(self.fget, self.fset, fdel, self.__doc__)
@end example

这个内置的 @ref{1d7,,property()} 每当用户访问属性时生效，随后的变化需要一个方法的参与。

例如，一个电子表格类可以通过 @code{Cell('b10').value} 授予对单元格值的访问权限。对程序的后续改进要求每次访问都要重新计算单元格；但是，程序员不希望影响直接访问该属性的现有客户端代码。解决方案是将对 value 属性的访问包装在属性数据描述器中:

@example
class Cell(object):
    . . .
    def getvalue(self):
        "Recalculate the cell before returning value"
        self.recalc()
        return self._value
    value = property(getvalue)
@end example

@node 函数和方法,静态方法和类方法,属性,描述器使用指南
@anchor{howto/descriptor functions-and-methods}@anchor{40cb}
@subsection 函数和方法


Python 的面向对象功能是在基于函数的环境构建的。通过使用非数据描述器，这两方面完成了无缝融合。

类字典将方法存储为函数。在类定义中，方法是用 @ref{db7,,def} 或 @ref{c28,,lambda} 这两个创建函数的常用工具编写的。方法与常规函数的不同之处仅在于第一个参数是为对象实例保留的。按照 Python 约定，实例引用称为 @emph{self} ，但也可以称为 @emph{this} 或任何其他变量名称。

为了支持方法调用，函数包含 @ref{13d3,,__get__()} 方法用于在访问属性时将其绑定成方法。这意味着所有函数都是非数据描述器，当从对象调用它们时，它们返回绑定方法。在纯 Python 中，它的工作方式如下:

@example
class Function(object):
    . . .
    def __get__(self, obj, objtype=None):
        "Simulate func_descr_get() in Objects/funcobject.c"
        if obj is None:
            return self
        return types.MethodType(self, obj)
@end example

运行解释器显示了函数描述器在实践中的工作方式：

@example
>>> class D(object):
...     def f(self, x):
...         return x
...
>>> d = D()

# Access through the class dictionary does not invoke __get__.
# It just returns the underlying function object.
>>> D.__dict__['f']
<function D.f at 0x00C45070>

# Dotted access from a class calls __get__() which just returns
# the underlying function unchanged.
>>> D.f
<function D.f at 0x00C45070>

# The function has a __qualname__ attribute to support introspection
>>> D.f.__qualname__
'D.f'

# Dotted access from an instance calls __get__() which returns the
# function wrapped in a bound method object
>>> d.f
<bound method D.f of <__main__.D object at 0x00B18C90>>

# Internally, the bound method stores the underlying function,
# the bound instance, and the class of the bound instance.
>>> d.f.__func__
<function D.f at 0x1012e5ae8>
>>> d.f.__self__
<__main__.D object at 0x1012e1f98>
>>> d.f.__class__
<class 'method'>
@end example

@node 静态方法和类方法,,函数和方法,描述器使用指南
@anchor{howto/descriptor static-methods-and-class-methods}@anchor{40cc}
@subsection 静态方法和类方法


非数据描述器为把函数绑定为方法的通常模式提供了一种简单的机制。

概括地说，函数具有 @ref{13d3,,__get__()} 方法，以便在作为属性访问时可以将其转换为方法。非数据描述符将 @code{obj.f(*args)} 的调用转换为 @code{f(obj, *args)} 。调用 @cite{klass.f(*args)`} 因而变成 @code{f(*args)} 。

下表总结了绑定及其两个最有用的变体：

@quotation


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} 
@headitem

转换形式

@tab

通过对象调用

@tab

通过类调用

@item

function -- 函数

@tab

f(obj, *args)

@tab

f(*args)

@item

静态方法

@tab

f(*args)

@tab

f(*args)

@item

类方法

@tab

f(type(obj), *args)

@tab

f(klass, *args)

@end multitable

@end quotation

静态方法返回底层函数，不做任何更改。调用 @code{c.f} 或 @code{C.f} 等效于通过 @code{object.__getattribute__(c, "f")} 或 @code{object.__getattribute__(C, "f")} 查找。这样该函数就可以从对象或类中进行相同的访问。

适合于作为静态方法的是那些不引用 @code{self} 变量的方法。

例如，一个统计用的包可能包含一个实验数据的容器类。该容器类提供了用于计算数据的平均值，均值，中位数和其他描述性统计信息的常规方法。但是，可能有在概念上相关但不依赖于数据的函数。例如， @code{erf(x)} 是在统计中的便捷转换，但并不直接依赖于特定的数据集。可以从对象或类中调用它： @code{s.erf(1.5) --> .9332} 或 @code{Sample.erf(1.5) --> .9332}。

由于静态方法直接返回了底层的函数，因此示例调用是相同的：

@example
>>> class E(object):
...     def f(x):
...         print(x)
...     f = staticmethod(f)
...
>>> E.f(3)
3
>>> E().f(3)
3
@end example

使用非数据描述器，纯 Python 版本的 @ref{1d9,,staticmethod()} 如下所示：

@example
class StaticMethod(object):
    "Emulate PyStaticMethod_Type() in Objects/funcobject.c"

    def __init__(self, f):
        self.f = f

    def __get__(self, obj, objtype=None):
        return self.f
@end example

与静态方法不同，类方法在调用函数之前将类引用放在参数列表的最前。无论调用方是对象还是类，此格式相同：

@example
>>> class E(object):
...     def f(klass, x):
...         return klass.__name__, x
...     f = classmethod(f)
...
>>> print(E.f(3))
('E', 3)
>>> print(E().f(3))
('E', 3)
@end example

此行为适用于当函数仅需要使用类引用并且不关心任何底层数据时的情况。 类方法的一种用途是创建替代的类构造器。 在 Python 2.3 中，类方法 @ref{166d,,dict.fromkeys()} 会从键列表中创建一个新的字典。 纯 Python 的等价形式是:

@example
class Dict(object):
    . . .
    def fromkeys(klass, iterable, value=None):
        "Emulate dict_fromkeys() in Objects/dictobject.c"
        d = klass()
        for key in iterable:
            d[key] = value
        return d
    fromkeys = classmethod(fromkeys)
@end example

现在可以这样构造一个新的唯一键字典：

@example
>>> Dict.fromkeys('abracadabra')
@{'a': None, 'r': None, 'b': None, 'c': None, 'd': None@}
@end example

使用非数据描述符协议，纯 Python 版本的 @ref{1d8,,classmethod()} 如下：

@example
class ClassMethod(object):
    "Emulate PyClassMethod_Type() in Objects/funcobject.c"

    def __init__(self, f):
        self.f = f

    def __get__(self, obj, klass=None):
        if klass is None:
            klass = type(obj)
        def newfunc(*args):
            return self.f(klass, *args)
        return newfunc
@end example

@node 函数式编程指引,日志常用指引,描述器使用指南,Python 常用指引
@anchor{howto/functional doc}@anchor{40cd}@anchor{howto/functional functional-programming-howto}@anchor{40ce}
@section 函数式编程指引


@*作者: 
A. M. Kuchling


@*发布版本: 
0.32


本文档提供恰当的 Python 函数式编程范例，在函数式编程简单的介绍之后，将简单介绍Python中关于函数式编程的特性如 @ref{fce,,iterator} 和 @ref{99c,,generator} 以及相关库模块如 @ref{a3,,itertools} 和 @ref{85,,functools} 等。

@menu
* 概述: 概述<17>. 
* 迭代器: 迭代器<2>. 
* 生成器表达式和列表推导式:: 
* 生成器: 生成器<2>. 
* 内置函数: 内置函数<2>. 
* itertools 模块:: 
* functools 模块:: 
* 小函数和 lambda 表达式:: 
* 修订记录和致谢:: 
* 参考文献: 参考文献<2>. 

@end menu

@node 概述<17>,迭代器<2>,,函数式编程指引
@anchor{howto/functional introduction}@anchor{40cf}
@subsection 概述


本章介绍函数式编程的基本概念。如您仅想学习 Python 语言的特性，可跳过本章直接查看 @ref{40d0,,迭代器}.

编程语言支持通过以下几种方式来解构具体问题：


@itemize *

@item 
大多数的编程语言都是 @strong{过程式} 的，所谓程序就是一连串告诉计算机怎样处理程序输入的指令。C、Pascal 甚至 Unix shells 都是过程式语言。

@item 
在 @strong{声明式} 语言中，你编写一个用来描述待解决问题的说明，并且这个语言的具体实现会指明怎样高效的进行计算。 SQL 可能是你最熟悉的声明式语言了。 一个 SQL 查询语句描述了你想要检索的数据集，并且 SQL 引擎会决定是扫描整张表还是使用索引，应该先执行哪些子句等等。

@item 
@strong{面向对象} 程序会操作一组对象。 对象拥有内部状态，并能够以某种方式支持请求和修改这个内部状态的方法。Smalltalk 和 Java 都是面向对象的语言。 C++ 和 Python 支持面向对象编程，但并不强制使用面向对象特性。

@item 
@strong{函数式} 编程则将一个问题分解成一系列函数。 理想情况下，函数只接受输入并输出结果，对一个给定的输入也不会有影响输出的内部状态。 著名的函数式语言有 ML 家族（Standard ML，Ocaml 以及其他变种）和 Haskell。
@end itemize

一些语言的设计者选择强调一种特定的编程方式。 这通常会让以不同的方式来编写程序变得困难。其他多范式语言则支持几种不同的编程方式。Lisp，C++ 和 Python 都是多范式语言；使用这些语言，你可以编写主要为过程式，面向对象或者函数式的程序和函数库。在大型程序中，不同的部分可能会采用不同的方式编写；比如 GUI 可能是面向对象的而处理逻辑则是过程式或者函数式。

在函数式程序里，输入会流经一系列函数。每个函数接受输入并输出结果。函数式风格反对使用带有副作用的函数，这些副作用会修改内部状态，或者引起一些无法体现在函数的返回值中的变化。完全不产生副作用的函数被称作“纯函数”。消除副作用意味着不能使用随程序运行而更新的数据结构；每个函数的输出必须只依赖于输入。

一些语言对纯洁性要求非常严格，以至于没有像 @code{a=3} 或 @code{c = a + b} 这样的赋值表达式，但是完全消除副作用非常困难。 比如，显示在屏幕上或者写到磁盘文件中都是副作用。举个例子，在 Python 里，调用函数 @ref{880,,print()} 或者 @ref{67a,,time.sleep()} 并不会返回有用的结果；它们的用途只在于副作用，向屏幕发送一段文字或暂停一秒钟。

函数式风格的 Python 程序并不会极端到消除所有 I/O 或者赋值的程度；相反，他们会提供像函数式一样的接口，但会在内部使用非函数式的特性。比如，函数的实现仍然会使用局部变量，但不会修改全局变量或者有其他副作用。

函数式编程可以被认为是面向对象编程的对立面。对象就像是颗小胶囊，包裹着内部状态和随之而来的能让你修改这个内部状态的一组调用方法，以及由正确的状态变化所构成的程序。函数式编程希望尽可能地消除状态变化，只和流经函数的数据打交道。在 Python 里你可以把两种编程方式结合起来，在你的应用（电子邮件信息，事务处理）中编写接受和返回对象实例的函数。

函数式设计在工作中看起来是个奇怪的约束。为什么你要消除对象和副作用呢？不过函数式风格有其理论和实践上的优点：


@itemize *

@item 
形式证明。

@item 
模块化。

@item 
组合性。

@item 
易于调试和测试。
@end itemize

@menu
* 形式证明:: 
* 模块化:: 
* 易于调试和测试:: 
* 组合性:: 

@end menu

@node 形式证明,模块化,,概述<17>
@anchor{howto/functional formal-provability}@anchor{40d1}
@subsubsection 形式证明


一个理论上的优点是，构造数学证明来说明函数式程序是正确的相对更容易些。

很长时间，研究者们对寻找证明程序正确的数学方法都很感兴趣。这和通过大量输入来测试，并得出程序的输出基本正确，或者阅读一个程序的源代码然后得出代码看起来没问题不同；相反，这里的目标是一个严格的证明，证明程序对所有可能的输入都能给出正确的结果。

证明程序正确性所用到的技术是写出 @strong{不变量}，也就是对于输入数据和程序中的变量永远为真的特性。然后对每行代码，你说明这行代码执行前的不变量 X 和 Y 以及执行后稍有不同的不变量 X' 和 Y' 为真。如此一直到程序结束，这时候在程序的输出上，不变量应该会与期望的状态一致。

函数式编程之所以要消除赋值，是因为赋值在这个技术中难以处理；赋值可能会破坏赋值前为真的不变量，却并不产生任何可以传递下去的新的不变量。

不幸的是，证明程序的正确性很大程度上是经验性质的，而且和 Python 软件无关。即使是微不足道的程序都需要几页长的证明；一个中等复杂的程序的正确性证明会非常庞大，而且，极少甚至没有你日常所使用的程序（Python 解释器，XML 解析器，浏览器）的正确性能够被证明。即使你写出或者生成一个证明，验证证明也会是一个问题；里面可能出了差错，而你错误地相信你证明了程序的正确性。

@node 模块化,易于调试和测试,形式证明,概述<17>
@anchor{howto/functional modularity}@anchor{40d2}
@subsubsection 模块化


函数式编程的一个更实用的优点是，它强制你把问题分解成小的方面。因此程序会更加模块化。相对于一个进行了复杂变换的大型函数，一个小的函数更明确，更易于编写, 也更易于阅读和检查错误。

@node 易于调试和测试,组合性,模块化,概述<17>
@anchor{howto/functional ease-of-debugging-and-testing}@anchor{40d3}
@subsubsection 易于调试和测试


测试和调试函数式程序相对来说更容易。

调试很简单是因为函数通常都很小而且清晰明确。当程序无法工作的时候，每个函数都是一个可以检查数据是否正确的接入点。你可以通过查看中间输入和输出迅速找到出错的函数。

测试更容易是因为每个函数都是单元测试的潜在目标。在执行测试前，函数并不依赖于需要重现的系统状态；相反，你只需要给出正确的输入，然后检查输出是否和期望的结果一致。

@node 组合性,,易于调试和测试,概述<17>
@anchor{howto/functional composability}@anchor{40d4}
@subsubsection 组合性


当你编写函数式风格的程序时，你会写出很多带有不同输入和输出的函数。其中一些不可避免地会局限于特定的应用，但其他的却可以广泛的用在程序中。举例来说，一个接受文件夹目录返回所有文件夹中的 XML 文件的函数； 或是一个接受文件名，然后返回文件内容的函数，都可以应用在很多不同的场合。

久而久之你会形成一个个人工具库。通常你可以重新组织已有的函数来组成新的程序，然后为当前的工作写一些特殊的函数。

@node 迭代器<2>,生成器表达式和列表推导式,概述<17>,函数式编程指引
@anchor{howto/functional functional-howto-iterators}@anchor{40d0}@anchor{howto/functional iterators}@anchor{40d5}
@subsection 迭代器


我会从 Python 的一个语言特性， 编写函数式风格程序的重要基石开始说起：迭代器。

迭代器是一个表示数据流的对象；这个对象每次只返回一个元素。Python 迭代器必须支持 @ref{c5d,,__next__()} 方法；这个方法不接受参数，并总是返回数据流中的下一个元素。如果数据流中没有元素，@ref{c5d,,__next__()} 会抛出 @ref{480,,StopIteration} 异常。迭代器未必是有限的；完全有理由构造一个输出无限数据流的迭代器。

内置的 @ref{d20,,iter()} 函数接受任意对象并试图返回一个迭代器来输出对象的内容或元素，并会在对象不支持迭代的时候抛出 @ref{192,,TypeError} 异常。Python 有几种内置数据类型支持迭代，最常见的就是列表和字典。如果一个对象能生成迭代器，那么它就会被称作 @ref{ba5,,iterable}。

你可以手动试验迭代器的接口。

@example
>>> L = [1, 2, 3]
>>> it = iter(L)
>>> it  
<...iterator object at ...>
>>> it.__next__()  # same as next(it)
1
>>> next(it)
2
>>> next(it)
3
>>> next(it)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
>>>
@end example

Python 有不少要求使用可迭代的对象的地方，其中最重要的就是 @ref{c29,,for} 表达式。在表达式 @code{for X in Y}，Y 要么自身是一个迭代器，要么能够由 @ref{d20,,iter()} 创建一个迭代器。以下两种表达是等价的:

@example
for i in iter(obj):
    print(i)

for i in obj:
    print(i)
@end example

可以用 @ref{262,,list()} 或 @ref{478,,tuple()} 这样的构造函数把迭代器具体化成列表或元组:

@example
>>> L = [1, 2, 3]
>>> iterator = iter(L)
>>> t = tuple(iterator)
>>> t
(1, 2, 3)
@end example

序列的解压操作也支持迭代器：如果你知道一个迭代器能够返回 N 个元素，你可以把他们解压到有 N 个元素的元组:

@example
>>> L = [1, 2, 3]
>>> iterator = iter(L)
>>> a, b, c = iterator
>>> a, b, c
(1, 2, 3)
@end example

像 @ref{804,,max()} 和 @ref{803,,min()} 这样的内置函数可以接受单个迭代器参数，然后返回其中最大或者最小的元素。@code{"in"} 和 @code{"not in"} 操作也支持迭代器：如果能够在迭代器 iterator 返回的数据流中找到 X 的话，则`@w{`}X in iterator`@w{`} 为真。很显然，如果迭代器是无限的，这么做你就会遇到问题；@ref{804,,max()} 和 @ref{803,,min()} 永远也不会返回；如果元素 X 也不出现在数据流中，@code{"in"} 和 @code{"not in"} 操作同样也永远不会返回。

注意你只能在迭代器中顺序前进；没有获取前一个元素的方法，除非重置迭代器，或者重新复制一份。迭代器对象可以提供这些额外的功能，但迭代器协议只明确了 @ref{c5d,,__next__()} 方法。函数可能因此而耗尽迭代器的输出，如果你要对同样的数据流做不同的操作，你必须重新创建一个迭代器。

@menu
* 支持迭代器的数据类型:: 

@end menu

@node 支持迭代器的数据类型,,,迭代器<2>
@anchor{howto/functional data-types-that-support-iterators}@anchor{40d6}
@subsubsection 支持迭代器的数据类型


我们已经知道列表和元组支持迭代器。实际上，Python 中的任何序列类型，比如字符串，都自动支持创建迭代器。

对字典调用 @ref{d20,,iter()} 会返回一个遍历字典的键的迭代器:

@example
>>> m = @{'Jan': 1, 'Feb': 2, 'Mar': 3, 'Apr': 4, 'May': 5, 'Jun': 6,
...      'Jul': 7, 'Aug': 8, 'Sep': 9, 'Oct': 10, 'Nov': 11, 'Dec': 12@}
>>> for key in m:
...     print(key, m[key])
Jan 1
Feb 2
Mar 3
Apr 4
May 5
Jun 6
Jul 7
Aug 8
Sep 9
Oct 10
Nov 11
Dec 12
@end example

注意从 Python 3.7 开始，字典的遍历顺序一定和输入顺序一样。先前的版本并没有明确这一点，所以不同的实现可能不一致。

对字典使用 @ref{d20,,iter()} 总是会遍历键，但字典也有返回其他迭代器的方法。如果你只遍历值或者键/值对，你可以明确地调用 @ref{c25,,values()} 或 @ref{c24,,items()} 方法得到合适的迭代器。

@ref{1b8,,dict()} 构造函数可以接受一个迭代器，然后返回一个有限的 @code{(key, value)} 元组的数据流:

@example
>>> L = [('Italy', 'Rome'), ('France', 'Paris'), ('US', 'Washington DC')]
>>> dict(iter(L))
@{'Italy': 'Rome', 'France': 'Paris', 'US': 'Washington DC'@}
@end example

文件也可以通过调用 @ref{1b90,,readline()} 来遍历，直到穷尽文件中所有的行。这意味着你可以像这样读取文件中的每一行:

@example
for line in file:
    # do something for each line
    ...
@end example

集合可以从可遍历的对象获取内容，也可以让你遍历集合的元素:

@example
S = @{2, 3, 5, 7, 11, 13@}
for i in S:
    print(i)
@end example

@node 生成器表达式和列表推导式,生成器<2>,迭代器<2>,函数式编程指引
@anchor{howto/functional generator-expressions-and-list-comprehensions}@anchor{40d7}
@subsection 生成器表达式和列表推导式


迭代器的输出有两个很常见的使用方式，1) 对每一个元素执行操作，2) 选择一个符合条件的元素子集。比如，给定一个字符串列表，你可能想去掉每个字符串尾部的空白字符，或是选出所有包含给定子串的字符串。

列表推导式和生成器表达时（简写："listcomps" 和 "genexps"）让这些操作更加简明，这个形式借鉴自函数式程序语言 Haskell（@indicateurl{https://www.haskell.org/}）。你可以用以下代码去掉一个字符串流中的所有空白字符:

@example
line_list = ['  line 1\n', 'line 2  \n', ...]

# Generator expression -- returns iterator
stripped_iter = (line.strip() for line in line_list)

# List comprehension -- returns list
stripped_list = [line.strip() for line in line_list]
@end example

你可以加上条件语句 @code{"if"} 来选取特定的元素:

@example
stripped_list = [line.strip() for line in line_list
                 if line != ""]
@end example

通过列表推导式，你会获得一个 Python 列表；@code{stripped_list} 就是一个包含所有结果行的列表，并不是迭代器。 生成器表达式会返回一个迭代器，它在必要的时候计算结果，避免一次性生成所有的值。 这意味着，如果迭代器返回一个无限数据流或者大量的数据，列表推导式就不太好用了。 这种情况下生成器表达式会更受青睐。

生成器表达式两边使用圆括号 ("()") ，而列表推导式则使用方括号 ("[]")。生成器表达式的形式为:

@example
( expression for expr in sequence1
             if condition1
             for expr2 in sequence2
             if condition2
             for expr3 in sequence3 ...
             if condition3
             for exprN in sequenceN
             if conditionN )
@end example

再次说明，列表推导式只有两边的括号不一样（方括号而不是圆括号）。

这些生成用于输出的元素会成为 @code{expression} 的后继值。其中 @code{if} 语句是可选的；如果给定的话 @code{expression} 只会在符合条件时计算并加入到结果中。

生成器表达式总是写在圆括号里面，不过也可以算上调用函数时用的括号。如果你想即时创建一个传递给函数的迭代器，可以这么写:

@example
obj_total = sum(obj.count for obj in list_all_objects())
@end example

其中 @code{for...in} 语句包含了将要遍历的序列。这些序列并不必须同样长，因为它们会从左往右开始遍历，而 @strong{不是} 同时执行。对每个 @code{sequence1} 中的元素，@code{sequence2} 会从头开始遍历。@code{sequence3} 会对每个 @code{sequence1} 和 @code{sequence2} 的元素对开始遍历。

换句话说，列表推导式器是和下面的 Python 代码等价:

@example
for expr1 in sequence1:
    if not (condition1):
        continue   # Skip this element
    for expr2 in sequence2:
        if not (condition2):
            continue   # Skip this element
        ...
        for exprN in sequenceN:
            if not (conditionN):
                continue   # Skip this element

            # Output the value of
            # the expression.
@end example

这说明，如果有多个 @code{for...in} 语句而没有 @code{if} 语句，输出结果的长度就是所有序列长度的乘积。如果你的两个列表长度为3，那么输出的列表长度就是9:

@example
>>> seq1 = 'abc'
>>> seq2 = (1, 2, 3)
>>> [(x, y) for x in seq1 for y in seq2]  
[('a', 1), ('a', 2), ('a', 3),
 ('b', 1), ('b', 2), ('b', 3),
 ('c', 1), ('c', 2), ('c', 3)]
@end example

为了不让 Python 语法变得含糊，如果 @code{expression} 会生成元组，那这个元组必须要用括号括起来。下面第一个列表推导式语法错误，第二个则是正确的:

@example
# Syntax error
[x, y for x in seq1 for y in seq2]
# Correct
[(x, y) for x in seq1 for y in seq2]
@end example

@node 生成器<2>,内置函数<2>,生成器表达式和列表推导式,函数式编程指引
@anchor{howto/functional generators}@anchor{40d8}
@subsection 生成器


生成器是一类用来简化编写迭代器工作的特殊函数。普通的函数计算并返回一个值，而生成器返回一个能返回数据流的迭代器。

毫无疑问，你已经对如何在 Python 和 C 中调用普通函数很熟悉了，这时候函数会获得一个创建局部变量的私有命名空间。当函数到达 @code{return} 表达式时，局部变量会被销毁然后把返回给调用者。之后调用同样的函数时会创建一个新的私有命名空间和一组全新的局部变量。但是，如果在退出一个函数时不扔掉局部变量会如何呢？如果稍后你能够从退出函数的地方重新恢复又如何呢？这就是生成器所提供的；他们可以被看成可恢复的函数。

这里有简单的生成器函数示例:

@example
>>> def generate_ints(N):
...    for i in range(N):
...        yield i
@end example

任何包含了 @ref{18f,,yield} 关键字的函数都是生成器函数；Python 的 @ref{60f,,bytecode} 编译器会在编译的时候检测到并因此而特殊处理。

当你调用一个生成器函数，它并不会返回单独的值，而是返回一个支持生成器协议的生成器对象。当执行 @code{yield} 表达式时，生成器会输出 @code{i} 的值，就像 @code{return} 表达式一样。@code{yield} 和 @code{return} 最大的区别在于，到达 @code{yield} 的时候生成器的执行状态会挂起并保留局部变量。在下一次调用生成器 @ref{126e,,__next__()} 方法的时候，函数会恢复执行。

这里有一个 @code{generate_ints()} 生成器的示例:

@example
>>> gen = generate_ints(3)
>>> gen  
<generator object generate_ints at ...>
>>> next(gen)
0
>>> next(gen)
1
>>> next(gen)
2
>>> next(gen)
Traceback (most recent call last):
  File "stdin", line 1, in <module>
  File "stdin", line 2, in generate_ints
StopIteration
@end example

同样，你可以写出 @code{for i in generate_ints(5)}，或者 @code{a, b, c = generate_ints(3)}。

在生成器函数里面，@code{return value} 会触发从 @ref{126e,,__next__()} 方法抛出 @code{StopIteration(value)} 异常。一旦抛出这个异常，或者函数结束，处理数据的过程就会停止，生成器也不会再生成新的值。

你可以手动编写自己的类来达到生成器的效果，把生成器的所有局部变量作为实例的成员变量存储起来。比如，可以这么返回一个整数列表：把 @code{self.count} 设为0，然后通过 @code{count`()}。然而，对于一个中等复杂程度的生成器，写出一个相应的类可能会相当繁杂。

包含在 Python 库中的测试套件 Lib/test/test_generators.py@footnote{https://github.com/python/cpython/tree/3.8/Lib/test/test_generators.py} 里有很多非常有趣的例子。这里是一个用生成器实现树的递归中序遍历示例。:

@example
# A recursive generator that generates Tree leaves in in-order.
def inorder(t):
    if t:
        for x in inorder(t.left):
            yield x

        yield t.label

        for x in inorder(t.right):
            yield x
@end example

另外两个 @code{test_generators.py} 中的例子给出了 N 皇后问题（在 NxN 的棋盘上放置 N 个皇后，任何一个都不能吃掉另一个），以及马的遍历路线（在NxN 的棋盘上给马找出一条不重复的走过所有格子的路线）的解。

@menu
* 向生成器传递值:: 

@end menu

@node 向生成器传递值,,,生成器<2>
@anchor{howto/functional passing-values-into-a-generator}@anchor{40d9}
@subsubsection 向生成器传递值


在 Python 2.4 及之前的版本中，生成器只产生输出。一旦调用生成器的代码创建一个迭代器，就没有办法在函数恢复执行的时候向它传递新的信息。你可以设法实现这个功能，让生成器引用一个全局变量或者一个调用者可以修改的可变对象，但是这些方法都很繁杂。

在 Python 2.5 里有一个简单的将值传递给生成器的方法。@ref{18f,,yield} 变成了一个表达式，返回一个可以赋给变量或执行操作的值:

@example
val = (yield i)
@end example

我建议你在处理 @code{yield} 表达式返回值的时候， @strong{总是} 两边写上括号，就像上面的例子一样。括号并不总是必须的，但是比起记住什么时候需要括号，写出来会更容易一点。

（
@geindex Python 提高建议; PEP 342
PEP 342@footnote{https://www.python.org/dev/peps/pep-0342} 解释了具体的规则，也就是 @code{yield} 表达式必须括起来，除非是出现在最顶级的赋值表达式的右边。这意味着你可以写 @code{val = yield i}，但是必须在操作的时候加上括号，就像`@w{`}val = (yield i) + 12`@w{`}）

可以调用 @code{send(value)()} <generator.send> 方法向生成器发送值。这个方法会恢复执行生成器的代码，然后 @code{yield} 表达式返回特定的值。如果调用普通的 @code{__next__`方法，`@w{`}yield`()} 会返回 @code{None}.

这里有一个简单的每次加1的计数器，并允许改变内部计数器的值。

@example
def counter(maximum):
    i = 0
    while i < maximum:
        val = (yield i)
        # If value provided, change counter
        if val is not None:
            i = val
        else:
            i += 1
@end example

这是改变计数器的一个示例

@example
>>> it = counter(10)  
>>> next(it)  
0
>>> next(it)  
1
>>> it.send(8)  
8
>>> next(it)  
9
>>> next(it)  
Traceback (most recent call last):
  File "t.py", line 15, in <module>
    it.next()
StopIteration
@end example

因为 @code{yield} 很多时候会返回 @code{None}，所以你应该总是检查这个情况。不要在表达式中使用 @code{yield} 的值，除非你确定 @ref{1427,,send()} 是唯一的用来恢复你的生成器函数的方法。

除了 @ref{1427,,send()} 之外，生成器还有两个其他的方法:


@itemize *

@item 
@ref{1429,,throw(type@comma{} value=None@comma{} traceback=None)} 用于在生成器内部抛出异常；这个异常会在生成器暂停执行的时候由 @code{yield} 表达式抛出。

@item 
@ref{142b,,generator.close()} 会在生成器内部抛出 @ref{d2b,,GeneratorExit} 异常来结束迭代。当接收到这个异常时，生成器的代码会抛出 @ref{d2b,,GeneratorExit} 或者 @ref{480,,StopIteration}；捕捉这个异常作其他处理是非法的，并会出发 @ref{2ba,,RuntimeError}。@ref{142b,,close()} 也会在 Python 垃圾回收器回收生成器的时候调用。

如果你要在 @ref{d2b,,GeneratorExit} 发生的时候清理代码，我建议使用 @code{try: ... finally:} 组合来代替 @ref{d2b,,GeneratorExit}。
@end itemize

这些改变的累积效应是，让生成器从单向的信息生产者变成了既是生产者，又是消费者。

生成器也可以成为 @strong{协程} ，一种更广义的子过程形式。子过程可以从一个地方进入，然后从另一个地方退出（从函数的顶端进入，从 @code{return} 语句退出），而协程可以进入，退出，然后在很多不同的地方恢复（@code{yield} 语句）。

@node 内置函数<2>,itertools 模块,生成器<2>,函数式编程指引
@anchor{howto/functional built-in-functions}@anchor{40da}
@subsection 内置函数


我们可以看看迭代器常常用到的函数的更多细节。

Python 内置的两个函数 @ref{c26,,map()} 和 @ref{c27,,filter()} 复制了生成器表达式的两个特性:


@table @asis

@item @ref{c26,,map(f@comma{} iterA@comma{} iterB@comma{} ...)} 返回一个遍历序列的迭代器

@code{f(iterA[0], iterB[0]), f(iterA[1], iterB[1]), f(iterA[2], iterB[2]), ...}.

@example
>>> def upper(s):
...     return s.upper()
@end example

@example
>>> list(map(upper, ['sentence', 'fragment']))
['SENTENCE', 'FRAGMENT']
>>> [upper(s) for s in ['sentence', 'fragment']]
['SENTENCE', 'FRAGMENT']
@end example
@end table

你当然也可以用列表推导式达到同样的效果。

@ref{c27,,filter(predicate@comma{} iter)} 返回一个遍历序列中满足指定条件的元素的迭代器，和列表推导式的功能相似。 @strong{predicate} （谓词）是一个在特定条件下返回真值的函数；要使用函数 @ref{c27,,filter()}，谓词函数必须只能接受一个参数。

@example
>>> def is_even(x):
...     return (x % 2) == 0
@end example

@example
>>> list(filter(is_even, range(10)))
[0, 2, 4, 6, 8]
@end example

这也可以写成列表推导式:

@example
>>> list(x for x in range(10) if is_even(x))
[0, 2, 4, 6, 8]
@end example

@ref{ddc,,enumerate(iter@comma{} start=0)} 计数可迭代对象中的元素，然后返回包含每个计数（从 @strong{start} 开始）和元素两个值的元组。:

@example
>>> for item in enumerate(['subject', 'verb', 'object']):
...     print(item)
(0, 'subject')
(1, 'verb')
(2, 'object')
@end example

@ref{ddc,,enumerate()} 常常用于遍历列表并记录达到特定条件时的下标:

@example
f = open('data.txt', 'r')
for i, line in enumerate(f):
    if line.strip() == '@w{'}:
        print('Blank line at line #%i' % i)
@end example

@ref{43e,,sorted(iterable@comma{} key=None@comma{} reverse=False)} 会将 iterable 中的元素收集到一个列表中，然后排序并返回结果。其中 @emph{key} 和 @emph{reverse} 参数会传递给所创建列表的 @ref{43f,,sort()} 方法。:

@example
>>> import random
>>> # Generate 8 random numbers between [0, 10000)
>>> rand_list = random.sample(range(10000), 8)
>>> rand_list  
[769, 7953, 9828, 6431, 8442, 9878, 6213, 2207]
>>> sorted(rand_list)  
[769, 2207, 6213, 6431, 7953, 8442, 9828, 9878]
>>> sorted(rand_list, reverse=True)  
[9878, 9828, 8442, 7953, 6431, 6213, 2207, 769]
@end example

（对排序更详细的讨论可参见 @ref{1599,,排序指南}。）

内置函数 @ref{d7d,,any(iter)} 和 @ref{d7e,,all(iter)} 会查看一个可迭代对象内容的逻辑值。@ref{d7d,,any()} 在可迭代对象中任意一个元素为真时返回 @code{True}，而 @ref{d7e,,all()} 在所有元素为真时返回 @code{True}:

@example
>>> any([0, 1, 0])
True
>>> any([0, 0, 0])
False
>>> any([1, 1, 1])
True
>>> all([0, 1, 0])
False
>>> all([0, 0, 0])
False
>>> all([1, 1, 1])
True
@end example

@ref{c2b,,zip(iterA@comma{} iterB@comma{} ...)} 从每个可迭代对象中选取单个元素组成列表并返回:

@example
zip(['a', 'b', 'c'], (1, 2, 3)) =>
  ('a', 1), ('b', 2), ('c', 3)
@end example

它并不会在内存创建一个列表并因此在返回前而耗尽输入的迭代器；相反，只有在被请求的时候元组才会创建并返回。（这种行为的技术术语叫惰性计算，参见 lazy evaluation@footnote{https://en.wikipedia.org/wiki/Lazy_evaluation}.）

这个迭代器设计用于长度相同的可迭代对象。如果可迭代对象的长度不一致，返回的数据流的长度会和最短的可迭代对象相同

@example
zip(['a', 'b'], (1, 2, 3)) =>
  ('a', 1), ('b', 2)
@end example

然而，你应该避免这种情况，因为所有从更长的迭代器中取出的元素都会被丢弃。这意味着之后你也无法冒着跳过被丢弃元素的风险来继续使用这个迭代器。

@node itertools 模块,functools 模块,内置函数<2>,函数式编程指引
@anchor{howto/functional the-itertools-module}@anchor{40db}
@subsection itertools 模块


@ref{a3,,itertools} 模块包含很多常用的迭代器以及用来组合迭代器的函数。本节会用些小的例子来介绍这个模块的内容。

这个模块里的函数大致可以分为几类：


@itemize *

@item 
从已有的迭代器创建新的迭代器的函数。

@item 
接受迭代器元素作为参数的函数。

@item 
选取部分迭代器输出的函数。

@item 
给迭代器输出分组的函数。
@end itemize

@menu
* 创建新的迭代器:: 
* 对元素使用函数:: 
* 选择元素:: 
* 组合函数:: 
* 为元素分组:: 

@end menu

@node 创建新的迭代器,对元素使用函数,,itertools 模块
@anchor{howto/functional creating-new-iterators}@anchor{40dc}
@subsubsection 创建新的迭代器


@ref{c14,,itertools.count(start@comma{} step)} 返回一个等分的无限数据流。初始值默认为0，间隔默认为1，你也选择可以指定初始值和间隔:

@example
itertools.count() =>
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ...
itertools.count(10) =>
  10, 11, 12, 13, 14, 15, 16, 17, 18, 19, ...
itertools.count(10, 5) =>
  10, 15, 20, 25, 30, 35, 40, 45, 50, 55, ...
@end example

@ref{1ad0,,itertools.cycle(iter)} 保存一份所提供的可迭代对象的副本，并返回一个能产生整个可迭代对象序列的新迭代器。新迭代器会无限重复这些元素。:

@example
itertools.cycle([1, 2, 3, 4, 5]) =>
  1, 2, 3, 4, 5, 1, 2, 3, 4, 5, ...
@end example

@ref{1045,,itertools.repeat(elem@comma{} [n])} 返回 @emph{n} 次所提供的元素，当 @emph{n} 不存在时，返回无数次所提供的元素。

@example
itertools.repeat('abc') =>
  abc, abc, abc, abc, abc, abc, abc, abc, abc, abc, ...
itertools.repeat('abc', 5) =>
  abc, abc, abc, abc, abc
@end example

@ref{159b,,itertools.chain(iterA@comma{} iterB@comma{} ...)} 接受任意数量的可迭代对象作为输入，首先返回第一个迭代器的所有元素，然后是第二个的所有元素，如此一直进行下去，直到消耗掉所有输入的可迭代对象。

@example
itertools.chain(['a', 'b', 'c'], (1, 2, 3)) =>
  a, b, c, 1, 2, 3
@end example

@ref{39a,,itertools.islice(iter@comma{} [start]@comma{} stop@comma{} [step])} 返回一个所输入的迭代器切片的数据流。如果只单独给定 @emph{stop} 参数的话，它会返回从起始算起 @emph{stop} 个数量的元素。如果你提供了起始下标 @emph{start}，你会得到 @emph{stop-start} 个元素；如果你给定了 @emph{step} 参数，数据流会跳过相应的元素。和 Python 里的字符串和列表切片不同，你不能在 @emph{start}, @emph{stop} 或者 @emph{step} 这些参数中使用负数。:

@example
itertools.islice(range(10), 8) =>
  0, 1, 2, 3, 4, 5, 6, 7
itertools.islice(range(10), 2, 8) =>
  2, 3, 4, 5, 6, 7
itertools.islice(range(10), 2, 8, 2) =>
  2, 4, 6
@end example

@ref{1ad5,,itertools.tee(iter@comma{} [n])} 可以复制一个迭代器；它返回 @emph{n} 个能够返回源迭代器内容的独立迭代器。如果你不提供参数 @emph{n}，默认值为 2。复制迭代器需要保存源迭代器的一部分内容，因此在源迭代器比较大的时候会显著地占用内存；同时，在所有新迭代器中，有一个迭代器会比其他迭代器占用更多的内存。

@example
itertools.tee( itertools.count() ) =>
   iterA, iterB

where iterA ->
   0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ...

and   iterB ->
   0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ...
@end example

@node 对元素使用函数,选择元素,创建新的迭代器,itertools 模块
@anchor{howto/functional calling-functions-on-elements}@anchor{40dd}
@subsubsection 对元素使用函数


@ref{c2,,operator} 模块包含一组对应于 Python 操作符的函数。比如 @ref{1af7,,operator.add(a@comma{} b)} （把两个数加起来），@ref{1ae7,,operator.ne(a@comma{} b)} （和 @code{a != b} 相同），以及 @ref{715,,operator.attrgetter('id')} （返回获取 @code{.id} 属性的可调用对象）。

@ref{a23,,itertools.starmap(func@comma{} iter)} 假定可迭代对象能够返回一个元组的流，并且利用这些元组作为参数来调用 @emph{func}:

@example
itertools.starmap(os.path.join,
                  [('/bin', 'python'), ('/usr', 'bin', 'java'),
                   ('/usr', 'bin', 'perl'), ('/usr', 'bin', 'ruby')])
=>
  /bin/python, /usr/bin/java, /usr/bin/perl, /usr/bin/ruby
@end example

@node 选择元素,组合函数,对元素使用函数,itertools 模块
@anchor{howto/functional selecting-elements}@anchor{40de}
@subsubsection 选择元素


另外一系列函数根据谓词选取一个迭代器中元素的子集。

@ref{1584,,itertools.filterfalse(predicate@comma{} iter)} 和  @ref{c27,,filter()} 相反，返回所有让 predicate 返回 false 的元素:

@example
itertools.filterfalse(is_even, itertools.count()) =>
  1, 3, 5, 7, 9, 11, 13, 15, ...
@end example

@ref{1ad4,,itertools.takewhile(predicate@comma{} iter)} 返回一直让 predicate 返回 true 的元素。一旦 predicate 返回 false，迭代器就会发出终止结果的信号。:

@example
def less_than_10(x):
    return x < 10

itertools.takewhile(less_than_10, itertools.count()) =>
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9

itertools.takewhile(is_even, itertools.count()) =>
  0
@end example

@ref{1ad2,,itertools.dropwhile(predicate@comma{} iter)} 在 predicate 返回 true 的时候丢弃元素，并且返回可迭代对象的剩余结果。:

@example
itertools.dropwhile(less_than_10, itertools.count()) =>
  10, 11, 12, 13, 14, 15, 16, 17, 18, 19, ...

itertools.dropwhile(is_even, itertools.count()) =>
  1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ...
@end example

@ref{c13,,itertools.compress(data@comma{} selectors)} 接受两个迭代器，然后返回 @emph{data} 中使相应地 @emph{selector} 中的元素为真的元素；它会在任一个迭代器耗尽的时候停止:

@example
itertools.compress([1, 2, 3, 4, 5], [True, True, False, False, True]) =>
   1, 2, 5
@end example

@node 组合函数,为元素分组,选择元素,itertools 模块
@anchor{howto/functional combinatoric-functions}@anchor{40df}
@subsubsection 组合函数


@ref{c9f,,itertools.combinations(iterable@comma{} r)} 返回一个迭代器，它能给出输入迭代器中所包含的元素的所有可能的 @emph{r} 元元组的组合。:

@example
itertools.combinations([1, 2, 3, 4, 5], 2) =>
  (1, 2), (1, 3), (1, 4), (1, 5),
  (2, 3), (2, 4), (2, 5),
  (3, 4), (3, 5),
  (4, 5)

itertools.combinations([1, 2, 3, 4, 5], 3) =>
  (1, 2, 3), (1, 2, 4), (1, 2, 5), (1, 3, 4), (1, 3, 5), (1, 4, 5),
  (2, 3, 4), (2, 3, 5), (2, 4, 5),
  (3, 4, 5)
@end example

每个元组中的元素保持着 @emph{可迭代对象} 返回他们的顺序。例如，在上面的例子中数字 1 总是会在 2, 3, 4 或 5 前面。一个类似的函数，@ref{1ad6,,itertools.permutations(iterable@comma{} r=None)}，取消了保持顺序的限制，返回所有可能的长度为 @emph{r} 的排列:

@example
itertools.permutations([1, 2, 3, 4, 5], 2) =>
  (1, 2), (1, 3), (1, 4), (1, 5),
  (2, 1), (2, 3), (2, 4), (2, 5),
  (3, 1), (3, 2), (3, 4), (3, 5),
  (4, 1), (4, 2), (4, 3), (4, 5),
  (5, 1), (5, 2), (5, 3), (5, 4)

itertools.permutations([1, 2, 3, 4, 5]) =>
  (1, 2, 3, 4, 5), (1, 2, 3, 5, 4), (1, 2, 4, 3, 5),
  ...
  (5, 4, 3, 2, 1)
@end example

如果你不提供 @emph{r} 参数的值，它会使用可迭代对象的长度，也就是说会排列所有的元素。

注意这些函数会输出所有可能的位置组合，并不要求 @emph{可迭代对象} 的内容不重复:

@example
itertools.permutations('aba', 3) =>
  ('a', 'b', 'a'), ('a', 'a', 'b'), ('b', 'a', 'a'),
  ('b', 'a', 'a'), ('a', 'a', 'b'), ('a', 'b', 'a')
@end example

同一个元组 @code{('a', 'a', 'b')} 出现了两次，但是两个 'a' 字符来自不同的位置。

@ref{c12,,itertools.combinations_with_replacement(iterable@comma{} r)} 函数放松了一个不同的限制：元组中的元素可以重复。从概念讲，为每个元组第一个位置选取一个元素，然后在选择第二个元素前替换掉它。:

@example
itertools.combinations_with_replacement([1, 2, 3, 4, 5], 2) =>
  (1, 1), (1, 2), (1, 3), (1, 4), (1, 5),
  (2, 2), (2, 3), (2, 4), (2, 5),
  (3, 3), (3, 4), (3, 5),
  (4, 4), (4, 5),
  (5, 5)
@end example

@node 为元素分组,,组合函数,itertools 模块
@anchor{howto/functional grouping-elements}@anchor{40e0}
@subsubsection 为元素分组


我要讨论的最后一个函数，@ref{1ad3,,itertools.groupby(iter@comma{}key_func=None)}，是最复杂的函数。 @code{key_func(elem)} 是一个可以对迭代器返回的每个元素计算键值的函数。 如果你不提供这个键值函数，它就会简化成每个元素自身。

@ref{1ad3,,groupby()} 从所依据的可迭代对象中连续地收集具有相同值的元素，然后返回一个长度为2的元组的数据流, 每个元组包含键值以及对应这个键值的元素所组成的迭代器。

@example
city_list = [('Decatur', 'AL'), ('Huntsville', 'AL'), ('Selma', 'AL'),
             ('Anchorage', 'AK'), ('Nome', 'AK'),
             ('Flagstaff', 'AZ'), ('Phoenix', 'AZ'), ('Tucson', 'AZ'),
             ...
            ]

def get_state(city_state):
    return city_state[1]

itertools.groupby(city_list, get_state) =>
  ('AL', iterator-1),
  ('AK', iterator-2),
  ('AZ', iterator-3), ...

where
iterator-1 =>
  ('Decatur', 'AL'), ('Huntsville', 'AL'), ('Selma', 'AL')
iterator-2 =>
  ('Anchorage', 'AK'), ('Nome', 'AK')
iterator-3 =>
  ('Flagstaff', 'AZ'), ('Phoenix', 'AZ'), ('Tucson', 'AZ')
@end example

@ref{1ad3,,groupby()} 假定了所依据的可迭代对象的内容已经根据键值排序。注意，返回的迭代器也会使用所依据的可迭代对象，所以在请求迭代器 2和相应的键之前你必须先消耗迭代器 1 的结果。

@node functools 模块,小函数和 lambda 表达式,itertools 模块,函数式编程指引
@anchor{howto/functional the-functools-module}@anchor{40e1}
@subsection functools 模块


Python 2.5 中的 @ref{85,,functools} 模块包含了一些高阶函数。 @strong{高阶函数} 接受一个或多个函数作为输入，返回新的函数。 这个模块中最有用的工具是 @ref{7c2,,functools.partial()} 函数。

对于用函数式风格编写的程序，有时你会希望通过给定部分参数，将已有的函数构变形称新的函数。考虑一个 Python 函数 @code{f(a, b, c)}；你希望创建一个和 @code{f(1, b, c)} 等价的新函数 @code{g(b, c)}；也就是说你给定了 @code{f()} 的一个参数的值。这就是所谓的“部分函数应用”。

@ref{7c2,,partial()} 接受参数 @code{(function, arg1, arg2, ..., kwarg1=value1, kwarg2=value2)}。它会返回一个可调用的对象，所以你能够直接调用这个结果以使用给定参数的 @code{function}。

这里有一个很小但很现实的例子:

@example
import functools

def log(message, subsystem):
    """Write the contents of 'message' to the specified subsystem."""
    print('%s: %s' % (subsystem, message))
    ...

server_log = functools.partial(log, subsystem='server')
server_log('Unable to open socket')
@end example

@ref{c68,,functools.reduce(func@comma{} iter@comma{} [initial_value])} 持续地在可迭代对象的所有元素上执行操作，因此它不能够用在无限的可迭代对象上。@emph{func} 必须是一个接受两个元素并返回一个值的函数。@ref{c68,,functools.reduce()} 接受迭代器返回的前两个元素 A 和 B 并计算 @code{func(A, B)} 。然后它会请求第三个元素，C，计算 @code{func(func(A, B), C)}，然后把这个结果再和第四个元素组合并返回，如此继续下去直到消耗整个可迭代对象。如果输入的可迭代对象完全不返回任何值，@ref{192,,TypeError} 异常就会抛出。如果提供了初值(initial value)，它会被用作起始值，也就是先计算 @code{func(initial_value, A)} 。:

@example
>>> import operator, functools
>>> functools.reduce(operator.concat, ['A', 'BB', 'C'])
'ABBC'
>>> functools.reduce(operator.concat, [])
Traceback (most recent call last):
  ...
TypeError: reduce() of empty sequence with no initial value
>>> functools.reduce(operator.mul, [1, 2, 3], 1)
6
>>> functools.reduce(operator.mul, [], 1)
1
@end example

如果你在 @ref{c68,,functools.reduce()} 中使用 @ref{1af7,,operator.add()}，你就会把可迭代对象中的所有元素加起来.这种情况非常常见, 所以 Python 有一个特殊的内置函数 @ref{1e5,,sum()}:

@example
>>> import functools, operator
>>> functools.reduce(operator.add, [1, 2, 3, 4], 0)
10
>>> sum([1, 2, 3, 4])
10
>>> sum([])
0
@end example

不过, 对于很多使用 @ref{c68,,functools.reduce()} 的情形, 使用明显的 @ref{c29,,for} 循环会更清晰:

@example
import functools
# Instead of:
product = functools.reduce(operator.mul, [1, 2, 3], 1)

# You can write:
product = 1
for i in [1, 2, 3]:
    product *= i
@end example

一个相关的函数是 @ref{1dd,,itertools.accumulate(iterable@comma{} func=operator.add)} 。它执行同样的计算, 不过相对于只返回最终结果，@code{accumulate()} 会返回一个迭代器来输出所有中间结果:

@example
itertools.accumulate([1, 2, 3, 4, 5]) =>
  1, 3, 6, 10, 15

itertools.accumulate([1, 2, 3, 4, 5], operator.mul) =>
  1, 2, 6, 24, 120
@end example

@menu
* operator 模块:: 

@end menu

@node operator 模块,,,functools 模块
@anchor{howto/functional the-operator-module}@anchor{40e2}
@subsubsection operator 模块


前面已经提到了 @ref{c2,,operator} 模块。它包含一系列对应于 Python 操作符的函数。在函数式风格的代码中，这些函数通常很有用，可以帮你省下不少时间，避免写一些琐碎的仅仅执行一个简单操作的函数。

这个模块里的一些函数：


@itemize *

@item 
数学运算： @code{add()}，@code{sub()}，@code{mul()}，@code{floordiv()}，@code{abs()}， ...

@item 
逻辑运算： @code{not_()}，@code{truth()}。

@item 
位运算： @code{and_()}，@code{or_()}，@code{invert()}。

@item 
比较： @code{eq()}，@code{ne()}，@code{lt()}，@code{le()}，@code{gt()}，和 @code{ge()}。

@item 
确认对象： @code{is_()}，@code{is_not()}。
@end itemize

全部函数列表可以参考 operator 模块的文档。

@node 小函数和 lambda 表达式,修订记录和致谢,functools 模块,函数式编程指引
@anchor{howto/functional small-functions-and-the-lambda-expression}@anchor{40e3}
@subsection 小函数和 lambda 表达式


编写函数式风格程序时，你会经常需要很小的函数，作为谓词函数或者以某种方式来组合元素。

如果合适的 Python 内置的或者其他模块中的函数，你就一点也不需要定义新的函数:

@example
stripped_lines = [line.strip() for line in lines]
existing_files = filter(os.path.exists, file_list)
@end example

如果不存在你需要的函数，你就必须自己编写。一个编写小函数的方式是使用 @ref{c28,,lambda} 表达式。@code{lambda} 接受一组参数以及组合这些参数的表达式，它会创建一个返回表达式值的匿名函数:

@example
adder = lambda x, y: x+y

print_assign = lambda name, value: name + '=' + str(value)
@end example

另一种替代方案就是通常的使用 @code{def} 语句来定义函数:

@example
def adder(x, y):
    return x + y

def print_assign(name, value):
    return name + '=' + str(value)
@end example

哪一种更受青睐呢？这是一个风格问题；我通常的做法是避免使用 @code{lambda}。

我这么偏好的一个原因是，@code{lambda} 能够定义的函数非常受限。函数的结果必须能够作为单独的表达式来计算，这意味着你不能使用多路 @code{if... elif... else} 比较，或者 @code{try... except} 语句。如果你尝试在 @code{lambda} 语句中做太多事情，你最终会把表达式过于复杂以至于难以阅读。你能快速的说出下面的代码做了什么事情吗？:

@example
import functools
total = functools.reduce(lambda a, b: (0, a[1] + b[1]), items)[1]
@end example

你可以弄明白，不过要花上时间来理清表达式来搞清楚发生了什么。使用一个简短的嵌套的 @code{def} 语句可以让情况变得更好:

@example
import functools
def combine(a, b):
    return 0, a[1] + b[1]

total = functools.reduce(combine, items)[1]
@end example

如果我仅仅使用一个 @code{for} 循环会更好:

@example
total = 0
for a, b in items:
    total += b
@end example

或者使用内置的 @ref{1e5,,sum()} 和一个生成器表达式:

@example
total = sum(b for a, b in items)
@end example

许多使用 @ref{c68,,functools.reduce()} 的情形可以更清晰地写成 @code{for} 循环的形式。

Fredrik Lundh 曾经建议以下一组规则来重构 @code{lambda} 的使用:


@enumerate 

@item 
写一个 lambda 函数。

@item 
写一句注释来说明这个 lambda 究竟干了什么。

@item 
研究一会这个注释，然后想出一个抓住注释本质的名字。

@item 
用这个名字，把这个 lambda 改写成 def 语句。

@item 
把注释去掉。
@end enumerate

我非常喜欢这些规则，不过你完全有权利争辩这种消除 lambda 的风格是不是更好。

@node 修订记录和致谢,参考文献<2>,小函数和 lambda 表达式,函数式编程指引
@anchor{howto/functional revision-history-and-acknowledgements}@anchor{40e4}
@subsection 修订记录和致谢


作者要感谢以下人员对本文各种草稿给予的建议，更正和协助：Ian Bicking,Nick Coghlan, Nick Efford, Raymond Hettinger, Jim Jewett, Mike Krell,Leandro Lameiro, Jussi Salmela, Collin Winter, Blake Winton。

0.1 版: 2006 年 6 月 30 日发布。

0.11 版: 2006 年 7 月 1 日发布。 修正拼写错误。

0.2 版: 2006 年 7 月 10 日发布。 将 genexp 与 listcomp 两节合二为一。 修正拼写错误。

0.21 版: 加入了 tutor 邮件列表中建议的更多参考文件。

0.30 版: 添加了有关 @code{functional} 模块的小节，由 Collin Winter 撰写；添加了有关 operator 模块的简短小节；其他少量修改。

@node 参考文献<2>,,修订记录和致谢,函数式编程指引
@anchor{howto/functional references}@anchor{40e5}
@subsection 参考文献


@menu
* 通用文献:: 
* Python 相关:: 
* Python 文档:: 

@end menu

@node 通用文献,Python 相关,,参考文献<2>
@anchor{howto/functional general}@anchor{40e6}
@subsubsection 通用文献


@strong{Structure and Interpretation of Computer Programs}, Harold Abelson, Gerald Jay Sussman 和 Julie Sussman 著。全文可见 @indicateurl{https://mitpress.mit.edu/sicp/} 。在这部计算机科学的经典教科书中，第二和第三章讨论了使用序列和流来组织程序内部的数据传递。书中的示例采用 Scheme 语言，但其中这些章节中描述的很多设计方法同样适用于函数式风格的 Python 代码。

@indicateurl{http://www.defmacro.org/ramblings/fp.html}: 一个使用 Java 示例的函数式编程的总体介绍，有很长的历史说明。

@indicateurl{https://en.wikipedia.org/wiki/Functional_programming}: 一般性的函数式编程的 Wikipedia 条目。

@indicateurl{https://en.wikipedia.org/wiki/Coroutine}: 协程条目。

@indicateurl{https://en.wikipedia.org/wiki/Currying}: 函数柯里化条目。

@node Python 相关,Python 文档,通用文献,参考文献<2>
@anchor{howto/functional python-specific}@anchor{40e7}
@subsubsection Python 相关


@indicateurl{http://gnosis.cx/TPiP/}：David Mertz 书中的第一章 @cite{Text Processing in Python}，"Utilizing Higher-Order Functions in Text Processing" 标题部分讨论了文本处理的函数式编程。

Mertz 还在 IBM 的 DeveloperWorks 站点上针对函数式编程撰写了一系列共 3 篇文章；参见 part 1@footnote{https://developer.ibm.com/articles/l-prog/}, part 2@footnote{https://developer.ibm.com/tutorials/l-prog2/} 和 part 3@footnote{https://developer.ibm.com/tutorials/l-prog3/},

@node Python 文档,,Python 相关,参考文献<2>
@anchor{howto/functional python-documentation}@anchor{40e8}
@subsubsection Python 文档


@ref{a3,,itertools} 模块文档。

@ref{85,,functools} 模块文档。

@ref{c2,,operator} 模块文档。

@geindex Python 提高建议; PEP 289
PEP 289@footnote{https://www.python.org/dev/peps/pep-0289}: "Generator Expressions"

@geindex Python 提高建议; PEP 342
PEP 342@footnote{https://www.python.org/dev/peps/pep-0342}: "Coroutines via Enhanced Generators" 描述了 Python 2.5 中新的生成器特性。

@c comment
@c 
@c Handy little function for printing part of an iterator -- used
@c while writing this document.
@c 
@c import itertools
@c def print_iter(it):
@c      slice = itertools.islice(it, 10)
@c      for elem in slice[:-1]:
@c          sys.stdout.write(str(elem))
@c          sys.stdout.write(', ')
@c     print(elem[-1])

@node 日志常用指引,日志操作手册,函数式编程指引,Python 常用指引
@anchor{howto/logging doc}@anchor{40e9}@anchor{howto/logging logging-howto}@anchor{40ea}
@section 日志常用指引


@*作者: 
Vinay Sajip <vinay_sajip at red-dove dot com>


@menu
* 日志基础教程:: 
* 进阶日志教程:: 
* 日志级别: 日志级别<2>. 
* 有用的处理程序:: 
* 记录日志中引发的异常:: 
* 使用任意对象作为消息:: 
* 优化:: 

@end menu

@node 日志基础教程,进阶日志教程,,日志常用指引
@anchor{howto/logging basic-logging-tutorial}@anchor{40eb}@anchor{howto/logging logging-basic-tutorial}@anchor{b6b}
@subsection 日志基础教程


日志是对软件执行时所发生事件的一种追踪方式。软件开发人员对他们的代码添加日志调用，借此来指示某事件的发生。一个事件通过一些包含变量数据的描述信息来描述（比如：每个事件发生时的数据都是不同的）。开发者还会区分事件的重要性，重要性也被称为 @emph{等级} 或 @emph{严重性}

@menu
* 什么时候使用日志:: 
* 一个简单的例子: 一个简单的例子<2>. 
* 记录日志到文件:: 
* 从多个模块记录日志:: 
* 记录变量数据:: 
* 更改显示消息的格式:: 
* 在消息中显示日期/时间:: 
* 后续步骤:: 

@end menu

@node 什么时候使用日志,一个简单的例子<2>,,日志基础教程
@anchor{howto/logging when-to-use-logging}@anchor{40ec}
@subsubsection 什么时候使用日志


对于简单的日志使用来说日志功能提供了一系列便利的函数。它们是 @ref{2020,,debug()}，@ref{204b,,info()}，@ref{205d,,warning()}，@ref{205e,,error()} 和 @ref{205f,,critical()}。想要决定何时使用日志，请看下表，其中显示了对于每个通用任务集合来说最好的工具。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

你想要执行的任务

@tab

此任务最好的工具

@item

对于命令行或程序的应用，结果显示在控制台。

@tab

@ref{880,,print()}

@item

在对程序的普通操作发生时提交事件报告(比如：状态监控和错误调查)

@tab

@ref{204b,,logging.info()} 函数(当有诊断目的需要详细输出信息时使用 @ref{2020,,logging.debug()} 函数)

@item

提出一个警告信息基于一个特殊的运行时事件

@tab

@ref{e51,,warnings.warn()} 位于代码库中，该事件是可以避免的，需要修改客户端应用以消除告警

@ref{205d,,logging.warning()} 不需要修改客户端应用，但是该事件还是需要引起关注

@item

对一个特殊的运行时事件报告错误

@tab

引发异常

@item

报告错误而不引发异常(如在长时间运行中的服务端进程的错误处理)

@tab

@ref{205e,,logging.error()}, @ref{2060,,logging.exception()} 或 @ref{205f,,logging.critical()} 分别适用于特定的错误及应用领域

@end multitable


日志功能应以所追踪事件级别或严重性而定。各级别适用性如下（以严重性递增）：


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

级别

@tab

何时使用

@item

@code{DEBUG}

@tab

细节信息，仅当诊断问题时适用。

@item

@code{INFO}

@tab

确认程序按预期运行

@item

@code{WARNING}

@tab

表明有已经或即将发生的意外（例如：磁盘空间不足）。程序仍按预期进行

@item

@code{ERROR}

@tab

由于严重的问题，程序的某些功能已经不能正常执行

@item

@code{CRITICAL}

@tab

严重的错误，表明程序已不能继续执行

@end multitable


默认的级别是`@w{`}WARNING`@w{`}，意味着只会追踪该级别及以上的事件，除非更改日志配置。

所追踪事件可以以不同形式处理。最简单的方式是输出到控制台。另一种常用的方式是写入磁盘文件。

@node 一个简单的例子<2>,记录日志到文件,什么时候使用日志,日志基础教程
@anchor{howto/logging a-simple-example}@anchor{40ed}@anchor{howto/logging howto-minimal-example}@anchor{40ee}
@subsubsection 一个简单的例子


一个非常简单的例子：

@example
import logging
logging.warning('Watch out!')  # will print a message to the console
logging.info('I told you so')  # will not print anything
@end example

如果你在命令行中输入这些代码并运行，你将会看到：

@example
WARNING:root:Watch out!
@end example

输出到命令行。@code{INFO} 消息并没有出现，因为默认级别是 @code{WARNING} 。打印的信息包含事件的级别以及在日志调用中的对于事件的描述，例如“Watch out!”。暂时不用担心“root”部分：之后会作出解释。输出格式可按需要进行调整，格式化选项同样会在之后作出解释。

@node 记录日志到文件,从多个模块记录日志,一个简单的例子<2>,日志基础教程
@anchor{howto/logging logging-to-a-file}@anchor{40ef}
@subsubsection 记录日志到文件


一种非常常见的情况是将日志事件记录到文件，让我们继续往下看。请确认启动新的Python 解释器，不要在上一个环境中继续操作:

@example
import logging
logging.basicConfig(filename='example.log',level=logging.DEBUG)
logging.debug('This message should go to the log file')
logging.info('So should this')
logging.warning('And this, too')
@end example

现在，如果我们打开日志文件，我们应当能看到日志信息：

@example
DEBUG:root:This message should go to the log file
INFO:root:So should this
WARNING:root:And this, too
@end example

该示例同样展示了如何设置日志追踪级别的阈值。该示例中，由于我们设置的阈值是 @code{DEBUG}，所有信息全部打印

如果你想从命令行设置日志级别，例如：

@example
--log=INFO
@end example

并且在一些 @emph{loglevel} 变量中你可以获得 @code{--log} 命令的参数，你可以使用：

@example
getattr(logging, loglevel.upper())
@end example

通过 @emph{level} 参数获得你将传递给 @ref{1e0,,basicConfig()} 的值。你需要对用户输入数据进行错误排查，可如下例：

@example
# assuming loglevel is bound to the string value obtained from the
# command line argument. Convert to upper case to allow the user to
# specify --log=DEBUG or --log=debug
numeric_level = getattr(logging, loglevel.upper(), None)
if not isinstance(numeric_level, int):
    raise ValueError('Invalid log level: %s' % loglevel)
logging.basicConfig(level=numeric_level, ...)
@end example

对 @ref{1e0,,basicConfig()} 的调用应该在  @ref{2020,,debug()} ， @ref{204b,,info()} 等的前面。因为它被设计为一次性的配置，只有第一次调用会进行操作，随后的调用不会产生有效操作。

如果多次运行上述脚本，则连续运行的消息将追加到文件 @emph{example.log} 。 如果你希望每次运行重新开始，而不是记住先前运行的消息，则可以通过将上例中的调用更改为来指定 @emph{filemode} 参数:

@example
logging.basicConfig(filename='example.log', filemode='w', level=logging.DEBUG)
@end example

输出将与之前相同，但不再追加进日志文件，因此早期运行的消息将丢失。

@node 从多个模块记录日志,记录变量数据,记录日志到文件,日志基础教程
@anchor{howto/logging logging-from-multiple-modules}@anchor{40f0}
@subsubsection 从多个模块记录日志


如果你的程序包含多个模块，这里有一个如何组织日志记录的示例:

@example
# myapp.py
import logging
import mylib

def main():
    logging.basicConfig(filename='myapp.log', level=logging.INFO)
    logging.info('Started')
    mylib.do_something()
    logging.info('Finished')

if __name__ == '__main__':
    main()
@end example

@example
# mylib.py
import logging

def do_something():
    logging.info('Doing something')
@end example

如果你运行 @emph{myapp.py} ，你应该在 @emph{myapp.log} 中看到：

@example
INFO:root:Started
INFO:root:Doing something
INFO:root:Finished
@end example

这是你期待看到的。 你可以使用 @emph{mylib.py} 中的模式将此概括为多个模块。 请注意，对于这种简单的使用模式，除了查看事件描述之外，你不能通过查看日志文件来了解应用程序中消息的 @emph{来源} 。 如果要跟踪消息的位置，则需要参考教程级别以外的文档 - 请参阅 @ref{b6c,,进阶日志教程} 。

@node 记录变量数据,更改显示消息的格式,从多个模块记录日志,日志基础教程
@anchor{howto/logging logging-variable-data}@anchor{40f1}
@subsubsection 记录变量数据


要记录变量数据，请使用格式字符串作为事件描述消息，并将变量数据作为参数附加。 例如:

@example
import logging
logging.warning('%s before you %s', 'Look', 'leap!')
@end example

将显示：

@example
WARNING:root:Look before you leap!
@end example

如你所见，将可变数据合并到事件描述消息中使用旧的 %-s形式的字符串格式化。 这是为了向后兼容：logging 包的出现时间早于较新的格式化选项例如 @ref{4d4,,str.format()} 和 @ref{3e3,,string.Template}。 这些较新格式化选项 @emph{是} 受支持的，但探索它们超出了本教程的范围：有关详细信息，请参阅 @ref{2043,,Using particular formatting styles throughout your application}。

@node 更改显示消息的格式,在消息中显示日期/时间,记录变量数据,日志基础教程
@anchor{howto/logging changing-the-format-of-displayed-messages}@anchor{40f2}
@subsubsection 更改显示消息的格式


要更改用于显示消息的格式，你需要指定要使用的格式:

@example
import logging
logging.basicConfig(format='%(levelname)s:%(message)s', level=logging.DEBUG)
logging.debug('This message should appear on the console')
logging.info('So should this')
logging.warning('And this, too')
@end example

这将输出：

@example
DEBUG:This message should appear on the console
INFO:So should this
WARNING:And this, too
@end example

请注意，前面示例中出现的“root”已消失。 对于可以出现在格式字符串中的全部内容，你可以参考以下文档 @ref{2041,,LogRecord 属性} ，但为了简单使用，你只需要 @emph{levelname} （严重性）， @emph{message} （事件描述，包括可变数据），也许在事件发生时显示。 这将在下一节中介绍。

@node 在消息中显示日期/时间,后续步骤,更改显示消息的格式,日志基础教程
@anchor{howto/logging displaying-the-date-time-in-messages}@anchor{40f3}
@subsubsection 在消息中显示日期/时间


要显示事件的日期和时间，你可以在格式字符串中放置 '%(asctime)s'

@example
import logging
logging.basicConfig(format='%(asctime)s %(message)s')
logging.warning('is when this event was logged.')
@end example

应该打印这样的东西：

@example
2010-12-12 11:41:42,612 is when this event was logged.
@end example

日期/时间显示的默认格式（如上所示）类似于 ISO8601 或 
@geindex RFC; RFC 3339
RFC 3339@footnote{https://tools.ietf.org/html/rfc3339.html} 。 如果你需要更多地控制日期/时间的格式，请为 @code{basicConfig} 提供 @emph{datefmt} 参数，如下例所示:

@example
import logging
logging.basicConfig(format='%(asctime)s %(message)s', datefmt='%m/%d/%Y %I:%M:%S %p')
logging.warning('is when this event was logged.')
@end example

这会显示如下内容：

@example
12/12/2010 11:46:36 AM is when this event was logged.
@end example

@emph{datefmt} 参数的格式与 @ref{b5e,,time.strftime()} 支持的格式相同。

@node 后续步骤,,在消息中显示日期/时间,日志基础教程
@anchor{howto/logging next-steps}@anchor{40f4}
@subsubsection 后续步骤


基本教程到此结束。 它应该足以让你启动并运行日志记录。 日志包提供了更多功能，但为了充分利用它，你需要花更多的时间来阅读以下部分。 如果你准备好了，可以拿一些你最喜欢的饮料然后继续。

如果你的日志记录需求很简单，那么使用上面的示例将日志记录合并到你自己的脚本中，如果你遇到问题或者不理解某些内容，请在 comp.lang.python Usenet 组上发布一个问题（在 @indicateurl{https://groups.google.com/forum/#!forum/comp.lang.python} ） ，你应该在短时间内得到帮助。

还不够？ 你可以继续阅读接下来的几个部分，这些部分提供了比上面基本部分更高级或深入的教程。 之后，你可以看一下 @ref{b6d,,日志操作手册} 。

@node 进阶日志教程,日志级别<2>,日志基础教程,日志常用指引
@anchor{howto/logging advanced-logging-tutorial}@anchor{40f5}@anchor{howto/logging logging-advanced-tutorial}@anchor{b6c}
@subsection 进阶日志教程


日志库采用模块化方法，并提供几类组件：记录器、处理程序、过滤器和格式化程序。


@itemize *

@item 
记录器暴露了应用程序代码直接使用的接口。

@item 
处理器将日志记录（由记录器创建）发送到适当的目标。

@item 
过滤器提供了更精细的附加功能，用于确定要输出的日志记录。

@item 
格式器指定最终输出中日志记录的样式。
@end itemize

日志事件信息在 @ref{900,,LogRecord} 实例中的记录器、处理程序、过滤器和格式化程序之间传递。

通过调用 @ref{39f,,Logger} 类（以下称为 @emph{loggers}  ， 记录器）的实例来执行日志记录。 每个实例都有一个名称，它们在概念上以点（句点）作为分隔符排列在命名空间的层次结构中。 例如，名为 'scan' 的记录器是记录器 'scan.text' ，'scan.html' 和 'scan.pdf' 的父级。 记录器名称可以是你想要的任何名称，并指示记录消息源自的应用程序区域。

在命名记录器时使用的一个好习惯是在每个使用日志记录的模块中使用模块级记录器，命名如下:

@example
logger = logging.getLogger(__name__)
@end example

这意味着记录器名称跟踪包或模块的层次结构，并且直观地从记录器名称显示记录事件的位置。

记录器层次结构的根称为根记录器。 这是函数 @ref{2020,,debug()} 、 @ref{204b,,info()} 、 @ref{205d,,warning()} 、 @ref{205e,,error()} 和 @ref{205f,,critical()} 使用的记录器，它们只调用根记录器的同名方法。 功能和方法具有相同的签名。 根记录器的名称在记录的输出中打印为 'root' 。

当然，可以将消息记录到不同的地方。 软件包中的支持包含，用于将日志消息写入文件、 HTTP GET/POST 位置、通过 SMTP 发送电子邮件、通用套接字、队列或特定于操作系统的日志记录机制（如 syslog 或 Windows NT 事件日志）。 目标由 @emph{handler} 类提供。 如果你有任何内置处理程序类未满足的特殊要求，则可以创建自己的日志目标类。

默认情况下，没有为任何日志记录消息设置目标。 你可以使用 @ref{1e0,,basicConfig()} 指定目标（例如控制台或文件），如教程示例中所示。 如果你调用函数 @ref{2020,,debug()} 、 @ref{204b,,info()} 、 @ref{205d,,warning()} 、 @ref{205e,,error()} 和 @ref{205f,,critical()} ，他们将检查是否有设置目的地；如果没有设置，它们将在委托给根记录器进行实际的消息输出之前设置目标为控制台（ @code{sys.stderr} ）和默认格式的显示消息。

由 @ref{1e0,,basicConfig()} 设置的消息默认格式为：

@example
severity:logger name:message
@end example

你可以通过使用 @emph{format} 参数将格式字符串传递给 @ref{1e0,,basicConfig()} 来更改此设置。有关如何构造格式字符串的所有选项，请参阅 @ref{203f,,格式器对象} 。

@menu
* 记录流程:: 
* 记录器:: 
* 处理程序:: 
* 格式化程序:: 
* 配置日志记录:: 
* 如果没有提供配置会发生什么:: 
* 配置库的日志记录:: 

@end menu

@node 记录流程,记录器,,进阶日志教程
@anchor{howto/logging logging-flow}@anchor{40f6}
@subsubsection 记录流程


记录器和处理程序中的日志事件信息流程如下图所示。

@image{python-figures/logging_flow,,,,png}

@node 记录器,处理程序,记录流程,进阶日志教程
@anchor{howto/logging loggers}@anchor{40f7}
@subsubsection 记录器


@ref{39f,,Logger} 对象有三重任务。首先，它们向应用程序代码公开了几种方法，以便应用程序可以在运行时记录消息。其次，记录器对象根据严重性（默认过滤工具）或过滤器对象确定要处理的日志消息。第三，记录器对象将相关的日志消息传递给所有感兴趣的日志处理程序。

记录器对象上使用最广泛的方法分为两类：配置和消息发送。

这些是最常见的配置方法：


@itemize *

@item 
@ref{2019,,Logger.setLevel()} 指定记录器将处理的最低严重性日志消息，其中 debug 是最低内置严重性级别， critical 是最高内置严重性级别。 例如，如果严重性级别为 INFO ，则记录器将仅处理 INFO 、 WARNING 、 ERROR 和 CRITICAL 消息，并将忽略 DEBUG 消息。

@item 
@ref{2026,,Logger.addHandler()} 和 @ref{2027,,Logger.removeHandler()} 从记录器对象中添加和删除处理程序对象。处理程序在以下内容中有更详细的介绍 @ref{40f8,,处理程序} 。

@item 
@ref{2023,,Logger.addFilter()} 和 @ref{2024,,Logger.removeFilter()} 可以添加或移除记录器对象中的过滤器。 @ref{2048,,Filter 对象} 包含更多的过滤器细节。
@end itemize

你不需要始终在你创建的每个记录器上调用这些方法。 请参阅本节的最后两段。

配置记录器对象后，以下方法将创建日志消息：


@itemize *

@item 
@ref{70a,,Logger.debug()} 、 @ref{201f,,Logger.info()} 、 @ref{2021,,Logger.warning()} 、 @ref{2022,,Logger.error()} 和 @ref{709,,Logger.critical()} 都创建日志记录，包含消息和与其各自方法名称对应的级别。该消息实际上是一个格式化字符串，它可能包含标题字符串替换语法 @code{%s} 、 @code{%d} 、 @code{%f} 等等。其余参数是与消息中的替换字段对应的对象列表。关于 @code{**kwargs} ，日志记录方法只关注 @code{exc_info} 的关键字，并用它来确定是否记录异常信息。

@item 
@ref{708,,Logger.exception()} 创建与 @ref{2022,,Logger.error()} 相似的日志信息。 不同之处是， @ref{708,,Logger.exception()} 同时还记录当前的堆栈追踪。仅从异常处理程序调用此方法。

@item 
@ref{707,,Logger.log()} 将日志级别作为显式参数。对于记录消息而言，这比使用上面列出的日志级别方便方法更加冗长，但这是自定义日志级别的方法。
@end itemize

@ref{2017,,getLogger()} 返回对具有指定名称的记录器实例的引用（如果已提供），或者如果没有则返回 @code{root} 。名称是以句点分隔的层次结构。多次调用 @ref{2017,,getLogger()} 具有相同的名称将返回对同一记录器对象的引用。在分层列表中较低的记录器是列表中较高的记录器的子项。例如，给定一个名为 @code{foo} 的记录器，名称为 @code{foo.bar} 、 @code{foo.bar.baz} 和 @code{foo.bam} 的记录器都是 @code{foo} 子项。

记录器具有 @emph{有效等级} 的概念。如果未在记录器上显式设置级别，则使用其父级别作为其有效级别。如果父级没有明确的级别设置，则检查 @emph{其} 父级。依此类推，搜索所有上级元素，直到找到明确设置的级别。根记录器始终具有显式级别集（默认情况下为 @code{WARNING} ）。在决定是否处理事件时，记录器的有效级别用于确定事件是否传递给记录器的处理程序。

子记录器将消息传播到与其上级记录器关联的处理程序。因此，不必为应用程序使用的所有记录器定义和配置处理程序。为顶级记录器配置处理程序并根据需要创建子记录器就足够了。（但是，你可以通过将记录器的 @emph{propagate} 属性设置 @code{False} 来关闭传播。）

@node 处理程序,格式化程序,记录器,进阶日志教程
@anchor{howto/logging handler-basic}@anchor{40f8}@anchor{howto/logging handlers}@anchor{40f9}
@subsubsection 处理程序


@ref{201e,,Handler} 对象负责将适当的日志消息（基于日志消息的严重性）分派给处理程序的指定目标。 @ref{39f,,Logger} 对象可以使用 @ref{2026,,addHandler()} 方法向自己添加零个或多个处理程序对象。作为示例场景，应用程序可能希望将所有日志消息发送到日志文件，将错误或更高的所有日志消息发送到标准输出，以及将所有关键消息发送至一个邮件地址。 此方案需要三个单独的处理程序，其中每个处理程序负责将特定严重性的消息发送到特定位置。

标准库包含很多处理程序类型（参见 @ref{40fa,,有用的处理程序} ）；教程主要使用 @ref{b6e,,StreamHandler} 和 @ref{2083,,FileHandler} 。

处理程序中很少有方法可供应用程序开发人员使用。与使用内置处理程序对象（即不创建自定义处理程序）的应用程序开发人员相关的唯一处理程序方法是以下配置方法：


@itemize *

@item 
@code{setLevel()} 方法，就像在记录器对象中一样，指定将被分派到适当目标的最低严重性。为什么有两个 @code{setLevel()} 方法？记录器中设置的级别确定将传递给其处理程序的消息的严重性。每个处理程序中设置的级别确定处理程序将发送哪些消息。

@item 
@ref{2034,,setFormatter()} 选择一个该处理程序使用的 Formatter 对象。

@item 
@ref{2035,,addFilter()} 和 @ref{2036,,removeFilter()} 分别在处理程序上配置和取消配置过滤器对象。
@end itemize

应用程序代码不应直接实例化并使用 @ref{201e,,Handler} 的实例。 相反， @ref{201e,,Handler} 类是一个基类，它定义了所有处理程序应该具有的接口，并建立了子类可以使用（或覆盖）的一些默认行为。

@node 格式化程序,配置日志记录,处理程序,进阶日志教程
@anchor{howto/logging formatters}@anchor{40fb}
@subsubsection 格式化程序


格式化程序对象配置日志消息的最终顺序、结构和内容。 与 @ref{201e,,logging.Handler} 类不同，应用程序代码可以实例化格式化程序类，但如果应用程序需要特殊行为，则可能会对格式化程序进行子类化。构造函数有三个可选参数 —— 消息格式字符串、日期格式字符串和样式指示符。

@geindex __init__() (logging.logging.Formatter 方法)
@anchor{howto/logging logging logging Formatter __init__}@anchor{40fc}
@deffn {方法} logging.Formatter.__init__ (fmt=None, datefmt=None, style='%')
@end deffn

如果没有消息格式字符串，则默认使用原始消息。如果没有日期格式字符串，则默认日期格式为：

@example
%Y-%m-%d %H:%M:%S
@end example

最后加上毫秒数。 @code{style} 是 @cite{％}，'@{ ' 或 '$' 之一。 如果未指定其中一个，则将使用 '％'。

如果 @code{style} 是 '％'，则消息格式字符串使用 @code{%(<dictionary key>)s} 样式字符串替换；可能的键值在 @ref{2041,,LogRecord 属性} 中。 如果样式为 '@{'，则假定消息格式字符串与 @ref{4d4,,str.format()} （使用关键字参数）兼容，而如果样式为 '$' ，则消息格式字符串应符合 @ref{1293,,string.Template.substitute()} 。


在 3.2 版更改: 添加 @code{style} 形参。


以下消息格式字符串将以人类可读的格式记录时间、消息的严重性以及消息的内容，按此顺序:

@example
'%(asctime)s - %(levelname)s - %(message)s'
@end example

格式化程序使用用户可配置的函数将记录的创建时间转换为元组。 默认情况下，使用 @ref{edc,,time.localtime()} ；要为特定格式化程序实例更改此项，请将实例的 @code{converter} 属性设置为具有相同签名的函数 @ref{edc,,time.localtime()} 或 @ref{b38,,time.gmtime()} 。 要为所有格式化程序更改它，例如，如果你希望所有记录时间都以 GMT 显示，请在格式化程序类中设置 @code{converter} 属性（对于 GMT 显示，设置为 @code{time.gmtime} ）。

@node 配置日志记录,如果没有提供配置会发生什么,格式化程序,进阶日志教程
@anchor{howto/logging configuring-logging}@anchor{40fd}
@subsubsection 配置日志记录


开发者可以通过三种方式配置日志记录：


@enumerate 

@item 
使用调用上面列出的配置方法的 Python 代码显式创建记录器、处理程序和格式化程序。

@item 
创建日志配置文件并使用 @ref{3a1,,fileConfig()} 函数读取它。

@item 
创建配置信息字典并将其传递给 @ref{b24,,dictConfig()} 函数。
@end enumerate

有关最后两个选项的参考文档，请参阅 @ref{c81,,配置函数} 。 以下示例使用 Python 代码配置一个非常简单的记录器/一个控制台处理程序和一个简单的格式化程序:

@example
import logging

# create logger
logger = logging.getLogger('simple_example')
logger.setLevel(logging.DEBUG)

# create console handler and set level to debug
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)

# create formatter
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')

# add formatter to ch
ch.setFormatter(formatter)

# add ch to logger
logger.addHandler(ch)

# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warning('warn message')
logger.error('error message')
logger.critical('critical message')
@end example

从命令行运行此模块将生成以下输出：

@example
$ python simple_logging_module.py
2005-03-19 15:10:26,618 - simple_example - DEBUG - debug message
2005-03-19 15:10:26,620 - simple_example - INFO - info message
2005-03-19 15:10:26,695 - simple_example - WARNING - warn message
2005-03-19 15:10:26,697 - simple_example - ERROR - error message
2005-03-19 15:10:26,773 - simple_example - CRITICAL - critical message
@end example

以下 Python 模块创建的记录器、处理程序和格式化程序几乎与上面列出的示例中的相同，唯一的区别是对象的名称:

@example
import logging
import logging.config

logging.config.fileConfig('logging.conf')

# create logger
logger = logging.getLogger('simpleExample')

# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warning('warn message')
logger.error('error message')
logger.critical('critical message')
@end example

这是 logging.conf 文件：

@example
[loggers]
keys=root,simpleExample

[handlers]
keys=consoleHandler

[formatters]
keys=simpleFormatter

[logger_root]
level=DEBUG
handlers=consoleHandler

[logger_simpleExample]
level=DEBUG
handlers=consoleHandler
qualname=simpleExample
propagate=0

[handler_consoleHandler]
class=StreamHandler
level=DEBUG
formatter=simpleFormatter
args=(sys.stdout,)

[formatter_simpleFormatter]
format=%(asctime)s - %(name)s - %(levelname)s - %(message)s
datefmt=
@end example

输出几乎与不基于配置文件的示例相同：

@example
$ python simple_logging_config.py
2005-03-19 15:38:55,977 - simpleExample - DEBUG - debug message
2005-03-19 15:38:55,979 - simpleExample - INFO - info message
2005-03-19 15:38:56,054 - simpleExample - WARNING - warn message
2005-03-19 15:38:56,055 - simpleExample - ERROR - error message
2005-03-19 15:38:56,130 - simpleExample - CRITICAL - critical message
@end example

你可以看到配置文件方法比 Python 代码方法有一些优势，主要是配置和代码的分离以及非开发者轻松修改日志记录属性的能力。

@cartouche
@quotation 警告 
@ref{3a1,,fileConfig()} 函数接受一个默认参数 @code{disable_existing_loggers} ，出于向后兼容的原因，默认为 @code{True} 。这可能是你想要的，也可能不是你想要的，因为除非在配置中明确命名它们（或一个上级节点中），否则它将导致在 @ref{3a1,,fileConfig()} 调用之前存在的任何非 root 记录器被禁用。有关更多信息，请参阅参考文档，如果需要，请为此参数指定 @code{False} 。

传递给 @ref{b24,,dictConfig()} 的字典也可以用键 @code{disable_existing_loggers} 指定一个布尔值，如果没有在字典中明确指定，也默认被解释为 @code{True} 。这会导致上面描述的记录器禁用行为，这可能不是你想要的——在这种情况下，明确地为键提供 @code{False} 值。
@end quotation
@end cartouche

请注意，配置文件中引用的类名称需要相对于日志记录模块，或者可以使用常规导入机制解析的绝对值。因此，你可以使用 @ref{2094,,WatchedFileHandler} （相对于日志记录模块）或 @code{mypackage.mymodule.MyHandler} （对于在 @code{mypackage} 包中定义的类和模块 @code{mymodule} ，其中 @code{mypackage} 在Python导入路径上可用）。

在 Python 3.2 中，引入了一种新的配置日志记录的方法，使用字典来保存配置信息。 这提供了上述基于配置文件方法的功能的超集，并且是新应用程序和部署的推荐配置方法。 因为 Python 字典用于保存配置信息，并且由于你可以使用不同的方式填充该字典，因此你有更多的配置选项。 例如，你可以使用 JSON 格式的配置文件，或者如果你有权访问 YAML 处理功能，则可以使用 YAML 格式的文件来填充配置字典。当然，你可以在 Python 代码中构造字典，通过套接字以 pickle 形式接收它，或者使用对你的应用程序合理的任何方法。

以下是与上述相同配置的示例，采用 YAML 格式，用于新的基于字典的方法：

@example
version: 1
formatters:
  simple:
    format: '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
handlers:
  console:
    class: logging.StreamHandler
    level: DEBUG
    formatter: simple
    stream: ext://sys.stdout
loggers:
  simpleExample:
    level: DEBUG
    handlers: [console]
    propagate: no
root:
  level: DEBUG
  handlers: [console]
@end example

有关使用字典进行日志记录的更多信息，请参阅 @ref{c81,,配置函数} 。

@node 如果没有提供配置会发生什么,配置库的日志记录,配置日志记录,进阶日志教程
@anchor{howto/logging what-happens-if-no-configuration-is-provided}@anchor{40fe}
@subsubsection 如果没有提供配置会发生什么


如果未提供日志记录配置，则可能出现需要输出日志记录事件但无法找到输出事件的处理程序的情况。 在这些情况下，日志包的行为取决于 Python 版本。

对于3.2之前的Python版本，行为如下：


@itemize *

@item 
如果 @emph{logging.raiseExceptions} 为 @code{False} （生产模式），则会以静默方式丢弃该事件。

@item 
如果 @emph{logging.raiseExceptions} 为 @code{True} （开发模式），则会打印一条消息“无法找到记录器 X.Y.Z 的处理程序”。
@end itemize

在 Python 3.2 及更高版本中，行为如下：


@itemize *

@item 
事件使用“最后的处理程序”输出，存储在 @code{logging.lastResort} 中。 这个内部处理程序与任何记录器都没有关联，它的作用类似于 @ref{b6e,,StreamHandler} ，它将事件描述消息写入 @code{sys.stderr} 的当前值（因此服从任何可能的重定向影响）。 没有对消息进行格式化——只打印裸事件描述消息。处理程序的级别设置为“警告”，因此将输出此级别和更高级别的所有事件。
@end itemize

要获得 3.2 之前的行为， @code{logging.lastResort} 可以设置为 @code{None} 。

@node 配置库的日志记录,,如果没有提供配置会发生什么,进阶日志教程
@anchor{howto/logging configuring-logging-for-a-library}@anchor{40ff}@anchor{howto/logging library-config}@anchor{2091}
@subsubsection 配置库的日志记录


在开发使用日志记录的库时，你应该注意记录库如何使用日志记录——例如，使用的记录器的名称。还需要考虑其日志记录配置。如果应用程序不使用日志记录，并且库代码进行日志记录调用，那么（如上一节所述）严重性为“WARNING”及更高级别的事件将打印到 @code{sys.stderr} 。这被认为是最好的默认行为。

如果由于某种原因，你 @emph{不} 希望在没有任何日志记录配置的情况下打印这些消息，则可以将无操作处理程序附加到库的顶级记录器。这样可以避免打印消息，因为将始终为库的事件找到处理程序：它不会产生任何输出。如果库用户配置应用程序使用的日志记录，可能是配置将添加一些处理程序，如果级别已适当配置，则在库代码中进行的日志记录调用将正常地将输出发送给这些处理程序。

日志包中包含一个不做任何事情的处理程序： @ref{c15,,NullHandler} （自 Python 3.1 起）。可以将此处理程序的实例添加到库使用的日志记录命名空间的顶级记录器中（ @emph{如果} 你希望在没有日志记录配置的情况下阻止库的记录事件输出到 @code{sys.stderr} ）。如果库 @emph{foo} 的所有日志记录都是使用名称匹配 'foo.x' ， 'foo.x.y' 等的记录器完成的，那么代码:

@example
import logging
logging.getLogger('foo').addHandler(logging.NullHandler())
@end example

应该有预计的效果。如果一个组织生成了许多库，则指定的记录器名称可以是 “orgname.foo” 而不仅仅是 “foo” 。

@cartouche
@quotation 注解 
强烈建议你 @emph{不要将} @ref{c15,,NullHandler} @emph{以外的任何处理程序添加到库的记录器中} 。这是因为处理程序的配置是使用你的库的应用程序开发人员的权利。应用程序开发人员了解他们的目标受众以及哪些处理程序最适合他们的应用程序：如果你在“底层”添加处理程序，则可能会干扰他们执行单元测试和提供符合其要求的日志的能力。
@end quotation
@end cartouche

@node 日志级别<2>,有用的处理程序,进阶日志教程,日志常用指引
@anchor{howto/logging logging-levels}@anchor{4100}
@subsection 日志级别


日志记录级别的数值在下表中给出。如果你想要定义自己的级别，并且需要它们具有相对于预定义级别的特定值，那么这些内容可能是你感兴趣的。如果你定义具有相同数值的级别，它将覆盖预定义的值; 预定义的名称丢失。


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} 
@headitem

级别

@tab

数值

@item

@code{CRITICAL}

@tab

50

@item

@code{ERROR}

@tab

40

@item

@code{WARNING}

@tab

30

@item

@code{INFO}

@tab

20

@item

@code{DEBUG}

@tab

10

@item

@code{NOTSET}

@tab

0

@end multitable


级别也可以与记录器相关联，由开发人员设置或通过加载已保存的日志记录配置。在记录器上调用日志记录方法时，记录器会将其自己的级别与与方法调用关联的级别进行比较。如果记录器的级别高于方法调用的级别，则实际上不会生成任何记录消息。这是控制日志记录输出详细程度的基本机制。

记录消息被编码为 @ref{900,,LogRecord} 类的实例。当记录器决定实际记录事件时，从记录消息创建 @ref{900,,LogRecord} 实例。

记录消息通过使用 @emph{handlers} 进行调度机制，它们是 @ref{201e,,Handler} 类的子类的实例。处理程序负责确保记录的消息（以 @ref{900,,LogRecord} 的形式）最终位于特定位置（或一组位置），这对该消息的目标受众（例如最终用户、 支持服务台员工、系统管理员、开发人员）。传递处理程序用于特定目标的 @ref{900,,LogRecord} 实例。 每个记录器可以有零个、一个或多个与之关联的处理程序（通过 @ref{39f,,Logger} 的 @ref{2026,,addHandler()} 方法）。除了与记录器直接关联的任何处理程序之外，还调用与记录器的 @emph{所有祖先相关联的所有处理程序来分派消息（除非记录器的 *propagate} 标志设置为false值，这将停止传递到上级处理程序）。

就像记录器一样，处理程序可以具有与它们相关联的级别。处理程序的级别作为过滤器，其方式与记录器级别相同。如果处理程序决定调度一个事件，则使用 @code{emit()} 方法将消息发送到其目标。大多数用户定义的 @ref{201e,,Handler} 子类都需要重载 @code{emit()} 。

@menu
* 自定义级别:: 

@end menu

@node 自定义级别,,,日志级别<2>
@anchor{howto/logging custom-levels}@anchor{2064}@anchor{howto/logging id1}@anchor{4101}
@subsubsection 自定义级别


定义你自己的级别是可能的，但不一定是必要的，因为现有级别是根据实践经验选择的。但是，如果你确信需要自定义级别，那么在执行此操作时应特别小心，如果你正在开发库，则 @emph{定义自定义级别可能是一个非常糟糕的主意} 。 这是因为如果多个库作者都定义了他们自己的自定义级别，那么使用开发人员很难控制和解释这些多个库的日志记录输出，因为给定的数值可能意味着不同的东西 对于不同的库。

@node 有用的处理程序,记录日志中引发的异常,日志级别<2>,日志常用指引
@anchor{howto/logging id2}@anchor{4102}@anchor{howto/logging useful-handlers}@anchor{40fa}
@subsection 有用的处理程序


作为 @ref{201e,,Handler} 基类的补充，提供了很多有用的子类：


@enumerate 

@item 
@ref{b6e,,StreamHandler} 实例发送消息到流（类似文件对象）。

@item 
@ref{2083,,FileHandler} 实例将消息发送到硬盘文件。

@item 
@ref{2098,,BaseRotatingHandler} 是轮换日志文件的处理程序的基类。它并不应该直接实例化。而应该使用 @ref{2074,,RotatingFileHandler} 或 @ref{868,,TimedRotatingFileHandler} 代替它。

@item 
@ref{2074,,RotatingFileHandler} 实例将消息发送到硬盘文件，支持最大日志文件大小和日志文件轮换。

@item 
@ref{868,,TimedRotatingFileHandler} 实例将消息发送到硬盘文件，以特定的时间间隔轮换日志文件。

@item 
@ref{869,,SocketHandler} 实例将消息发送到 TCP/IP 套接字。从 3.4 开始，也支持 Unix 域套接字。

@item 
@ref{86a,,DatagramHandler} 实例将消息发送到 UDP 套接字。从 3.4 开始，也支持 Unix 域套接字。

@item 
@ref{20c4,,SMTPHandler} 实例将消息发送到指定的电子邮件地址。

@item 
@ref{a19,,SysLogHandler} 实例将消息发送到 Unix syslog 守护程序，可能在远程计算机上。

@item 
@ref{20bc,,NTEventLogHandler} 实例将消息发送到 Windows NT/2000/XP 事件日志。

@item 
@ref{207d,,MemoryHandler} 实例将消息发送到内存中的缓冲区，只要满足特定条件，缓冲区就会刷新。

@item 
@ref{70b,,HTTPHandler} 实例使用 @code{GET} 或 @code{POST} 方法将消息发送到 HTTP 服务器。

@item 
@ref{2094,,WatchedFileHandler} 实例会监视他们要写入日志的文件。如果文件发生更改，则会关闭该文件并使用文件名重新打开。此处理程序仅在类 Unix 系统上有用； Windows 不支持依赖的基础机制。

@item 
@ref{20d7,,QueueHandler} 实例将消息发送到队列，例如在 @ref{da,,queue} 或 @ref{b7,,multiprocessing} 模块中实现的队列。

@item 
@ref{c15,,NullHandler} 实例对错误消息不执行任何操作。它们由想要使用日志记录的库开发人员使用，但是想要避免如果库用户没有配置日志记录，则显示 "无法找到记录器XXX的消息处理器" 消息的情况。有关更多信息，请参阅 @ref{2091,,配置库的日志记录} 。
@end enumerate


3.1 新版功能: @ref{c15,,NullHandler} 类。



3.2 新版功能: @ref{20d7,,QueueHandler} 类。


The @ref{c15,,NullHandler} 、 @ref{b6e,,StreamHandler} 和 @ref{2083,,FileHandler} 类在核心日志包中定义。其他处理程序定义在 @ref{ac,,logging.handlers} 中。（还有另一个子模块 @ref{ab,,logging.config} ，用于配置功能）

记录的消息被格式化为通过 @ref{201d,,Formatter} 类的实例进行呈现。 它们使用适合与 ％ 运算符一起使用的格式字符串和字典进行初始化。

对于批量格式化多个消息，可以使用 @code{BufferingFormatter} 的实例。除了格式字符串（应用于批处理中的每个消息）之外，还提供了标题和尾部格式字符串。

当基于记录器级别和处理程序级别的过滤不够时，可以将 @ref{b70,,Filter} 的实例添加到 @ref{39f,,Logger} 和 @ref{201e,,Handler} 实例（通过它们的 @ref{2035,,addFilter()} 方法）。在决定进一步处理消息之前，记录器和处理程序都会查询其所有过滤器以获得许可。如果任何过滤器返回 false 值，则不会进一步处理该消息。

基本 @ref{b70,,Filter} 的功能允许按特定的记录器名称进行过滤。如果使用此功能，则允许通过过滤器发送到指定记录器及其子项的消息，并丢弃所有消息。

@node 记录日志中引发的异常,使用任意对象作为消息,有用的处理程序,日志常用指引
@anchor{howto/logging exceptions-raised-during-logging}@anchor{4103}@anchor{howto/logging logging-exceptions}@anchor{4104}
@subsection 记录日志中引发的异常


日志包设计为忽略记录日志生产时发生的异常。这样，处理日志记录事件时发生的错误（例如日志记录错误配置、网络或其他类似错误）不会导致使用日志记录的应用程序过早终止。

@ref{5f7,,SystemExit} 和 @ref{197,,KeyboardInterrupt} 异常永远不会被忽略。 在 @ref{201e,,Handler} 子类的 @code{emit()} 方法中发生的其他异常被传递给它的 @code{handleError()} 方法。

@ref{201e,,Handler} 中默认实现的 @code{handleError()} 检查是否设置了模块级变量 @code{raiseExceptions} 。如果有设置，则会将跟踪打印到 @ref{308,,sys.stderr} 。如果未设置，则忽略异常。

@cartouche
@quotation 注解 
@code{raiseExceptions} 默认值是 @code{True}。 这是因为在开发期间，你通常希望收到任何发生异常的通知。建议你将 @code{raiseExceptions} 设置为 @code{False} 以供生产环境使用。
@end quotation
@end cartouche

@node 使用任意对象作为消息,优化,记录日志中引发的异常,日志常用指引
@anchor{howto/logging arbitrary-object-messages}@anchor{2054}@anchor{howto/logging using-arbitrary-objects-as-messages}@anchor{4105}
@subsection 使用任意对象作为消息


在前面的部分和示例中，都假设记录事件时传递的消息是字符串。 但是，这不是唯一的可能性。你可以将任意对象作为消息传递，并且当日志记录系统需要将其转换为字符串表示时，将调用其 @code{__ str__()} 方法。实际上，如果你愿意，你可以完全避免计算字符串表示。例如， @ref{869,,SocketHandler} 通过 pickle 并网络发送来发出事件。

@node 优化,,使用任意对象作为消息,日志常用指引
@anchor{howto/logging optimization}@anchor{4106}
@subsection 优化


消息参数的格式化将被推迟，直到无法避免。但是，计算传递给日志记录方法的参数也可能很消耗资源，如果记录器只是丢弃你的事件，你可能希望避免这样做。要决定做什么，可以调用 @ref{201c,,isEnabledFor()} 方法，该方法接受一个 level 参数，如果记录器为该级别的调用创建了该事件，则返回 true 。 你可以写这样的代码:

@example
if logger.isEnabledFor(logging.DEBUG):
    logger.debug('Message with %s, %s', expensive_func1(),
                                        expensive_func2())
@end example

因此，如果记录器的阈值设置在“DEBUG”以上，则永远不会调用 @code{expensive_func1()} 和 @code{expensive_func2()} 。

@cartouche
@quotation 注解 
在某些情况下， @ref{201c,,isEnabledFor()} 本身可能比你想要的更消耗资源（例如，对于深度嵌套的记录器，其中显式级别仅在记录器层次结构中设置为高）。在这种情况下（或者如果你想避免在紧密循环中调用方法），你可以在本地或实例变量中将调用的结果缓存到 @ref{201c,,isEnabledFor()} ，并使用它而不是调用每次方法。只在日志记录配置在应用程序运行时动态更改（这不常见）时需重新计算这样的缓存值。
@end quotation
@end cartouche

对于需要对收集的日志信息进行更精确控制的特定应用程序，还可以进行其他优化。 以下是你可以执行的操作列表，以避免在你不需要的日志记录期间进行处理：


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

你不想收集的内容

@tab

如何避免收集它

@item

有关调用来源的信息

@tab

将 @code{logging._srcfile} 设置为 @code{None} 。这避免了调用 @ref{e5d,,sys._getframe()} ，如果 PyPy 支持 Python 3.x ,这可能有助于加速 PyPy （无法加速使用 @ref{e5d,,sys._getframe()} 的代码）等环境中的代码.

@item

线程信息

@tab

将 @code{logging.logThreads} 置为 @code{0} 。

@item

进程信息

@tab

将 @code{logging.logProcesses} 置为 @code{0} 。

@end multitable


另请注意，核心日志记录模块仅包含基本处理程序。如果你不导入 @ref{ac,,logging.handlers} 和 @ref{ab,,logging.config} ，它们将不会占用任何内存。


@subsubheading 参见



@table @asis

@item 模块 @ref{aa,,logging}

日志记录模块的 API 参考。

@item @ref{ab,,logging.config} 模块

日志记录模块的配置 API 。

@item @ref{ac,,logging.handlers} 模块

日志记录模块附带的有用处理器。
@end table

@ref{b6d,,日志操作手册}


@node 日志操作手册,正则表达式HOWTO,日志常用指引,Python 常用指引
@anchor{howto/logging-cookbook doc}@anchor{4107}@anchor{howto/logging-cookbook id1}@anchor{4108}@anchor{howto/logging-cookbook logging-cookbook}@anchor{b6d}
@section 日志操作手册


@*作者: 
Vinay Sajip <vinay_sajip at red-dove dot com>


本页包含了许多日志记录相关的概念，这些概念在过去一直被认为很有用。

@menu
* 在多个模块中记录日志:: 
* 在多个线程中记录日志:: 
* 多个日志处理器以及多种格式化器:: 
* 在多个地方记录日志:: 
* 日志服务器配置示例:: 
* 处理日志处理器的阻塞:: 
* 通过网络发送和接收日志:: 
* 在日志记录中添加上下文信息:: 
* 从多个进程记录至单个文件:: 
* 轮换日志文件:: 
* 使用其他日志格式化方式:: 
* Customizing LogRecord:: 
* Subclassing QueueHandler - a ZeroMQ example:: 
* Subclassing QueueListener - a ZeroMQ example:: 
* An example dictionary-based configuration:: 
* Using a rotator and namer to customize log rotation processing:: 
* A more elaborate multiprocessing example:: 
* Inserting a BOM into messages sent to a SysLogHandler:: 
* Implementing structured logging:: 
* Customizing handlers with dictConfig(): Customizing handlers with dictConfig. 
* Using particular formatting styles throughout your application:: 
* Configuring filters with dictConfig(): Configuring filters with dictConfig. 
* Customized exception formatting:: 
* Speaking logging messages:: 
* 缓冲日志消息并有条件地输出它们:: 
* 通过配置使用UTC (GMT) 格式化时间: 通过配置使用UTC GMT 格式化时间. 
* 使用上下文管理器的可选的日志记录:: 
* A CLI application starter template:: 
* A Qt GUI for logging:: 

@end menu

@node 在多个模块中记录日志,在多个线程中记录日志,,日志操作手册
@anchor{howto/logging-cookbook using-logging-in-multiple-modules}@anchor{4109}
@subsection 在多个模块中记录日志


多次调用 @code{logging.getLogger('someLogger')} 时会返回对同一个 logger 对象的引用。 这不仅是在同一个模块中，在其他模块调用也是如此，只要是在同一个 Python 解释器进程中。 是应该引用同一个对象，此外，应用程序也可以在一个模块中定义和配置父 logger，而在单独的模块中创建（但不配置）子 logger，对子 logger 的所有调用都将传给父 logger。 这里是主模块:

@example
import logging
import auxiliary_module

# create logger with 'spam_application'
logger = logging.getLogger('spam_application')
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('spam.log')
fh.setLevel(logging.DEBUG)
# create console handler with a higher log level
ch = logging.StreamHandler()
ch.setLevel(logging.ERROR)
# create formatter and add it to the handlers
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
fh.setFormatter(formatter)
ch.setFormatter(formatter)
# add the handlers to the logger
logger.addHandler(fh)
logger.addHandler(ch)

logger.info('creating an instance of auxiliary_module.Auxiliary')
a = auxiliary_module.Auxiliary()
logger.info('created an instance of auxiliary_module.Auxiliary')
logger.info('calling auxiliary_module.Auxiliary.do_something')
a.do_something()
logger.info('finished auxiliary_module.Auxiliary.do_something')
logger.info('calling auxiliary_module.some_function()')
auxiliary_module.some_function()
logger.info('done with auxiliary_module.some_function()')
@end example

这里是辅助模块:

@example
import logging

# create logger
module_logger = logging.getLogger('spam_application.auxiliary')

class Auxiliary:
    def __init__(self):
        self.logger = logging.getLogger('spam_application.auxiliary.Auxiliary')
        self.logger.info('creating an instance of Auxiliary')

    def do_something(self):
        self.logger.info('doing something')
        a = 1 + 1
        self.logger.info('done doing something')

def some_function():
    module_logger.info('received a call to "some_function"')
@end example

输出结果会像这样:

@example
2005-03-23 23:47:11,663 - spam_application - INFO -
   creating an instance of auxiliary_module.Auxiliary
2005-03-23 23:47:11,665 - spam_application.auxiliary.Auxiliary - INFO -
   creating an instance of Auxiliary
2005-03-23 23:47:11,665 - spam_application - INFO -
   created an instance of auxiliary_module.Auxiliary
2005-03-23 23:47:11,668 - spam_application - INFO -
   calling auxiliary_module.Auxiliary.do_something
2005-03-23 23:47:11,668 - spam_application.auxiliary.Auxiliary - INFO -
   doing something
2005-03-23 23:47:11,669 - spam_application.auxiliary.Auxiliary - INFO -
   done doing something
2005-03-23 23:47:11,670 - spam_application - INFO -
   finished auxiliary_module.Auxiliary.do_something
2005-03-23 23:47:11,671 - spam_application - INFO -
   calling auxiliary_module.some_function()
2005-03-23 23:47:11,672 - spam_application.auxiliary - INFO -
   received a call to 'some_function'
2005-03-23 23:47:11,673 - spam_application - INFO -
   done with auxiliary_module.some_function()
@end example

@node 在多个线程中记录日志,多个日志处理器以及多种格式化器,在多个模块中记录日志,日志操作手册
@anchor{howto/logging-cookbook logging-from-multiple-threads}@anchor{410a}
@subsection 在多个线程中记录日志


在多个线程中记录日志并不需要特殊的处理，以下示例展示了如何在主（初始）线程和另一个线程中记录日志:

@example
import logging
import threading
import time

def worker(arg):
    while not arg['stop']:
        logging.debug('Hi from myfunc')
        time.sleep(0.5)

def main():
    logging.basicConfig(level=logging.DEBUG, format='%(relativeCreated)6d %(threadName)s %(message)s')
    info = @{'stop': False@}
    thread = threading.Thread(target=worker, args=(info,))
    thread.start()
    while True:
        try:
            logging.debug('Hello from main')
            time.sleep(0.75)
        except KeyboardInterrupt:
            info['stop'] = True
            break
    thread.join()

if __name__ == '__main__':
    main()
@end example

脚本会运行输出类似下面的内容:

@example
   0 Thread-1 Hi from myfunc
   3 MainThread Hello from main
 505 Thread-1 Hi from myfunc
 755 MainThread Hello from main
1007 Thread-1 Hi from myfunc
1507 MainThread Hello from main
1508 Thread-1 Hi from myfunc
2010 Thread-1 Hi from myfunc
2258 MainThread Hello from main
2512 Thread-1 Hi from myfunc
3009 MainThread Hello from main
3013 Thread-1 Hi from myfunc
3515 Thread-1 Hi from myfunc
3761 MainThread Hello from main
4017 Thread-1 Hi from myfunc
4513 MainThread Hello from main
4518 Thread-1 Hi from myfunc
@end example

这表明不同线程的日志像期望的那样穿插输出，当然更多的线程也会像这样输出。

@node 多个日志处理器以及多种格式化器,在多个地方记录日志,在多个线程中记录日志,日志操作手册
@anchor{howto/logging-cookbook multiple-handlers-and-formatters}@anchor{410b}
@subsection 多个日志处理器以及多种格式化器


日志记录器是普通的Python对象。@ref{2026,,addHandler()} 方法对可以添加的日志处理器的数量没有限制。有时候，应用程序需要将所有严重性的所有消息记录到一个文本文件，而将错误或更高等级的消息输出到控制台。要进行这样的设定，只需配置适当的日志处理器即可。在应用程序代码中，记录日志的调用将保持不变。以下是对之前基于模块的简单配置示例的略微修改:

@example
import logging

logger = logging.getLogger('simple_example')
logger.setLevel(logging.DEBUG)
# create file handler which logs even debug messages
fh = logging.FileHandler('spam.log')
fh.setLevel(logging.DEBUG)
# create console handler with a higher log level
ch = logging.StreamHandler()
ch.setLevel(logging.ERROR)
# create formatter and add it to the handlers
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
ch.setFormatter(formatter)
fh.setFormatter(formatter)
# add the handlers to logger
logger.addHandler(ch)
logger.addHandler(fh)

# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warning('warn message')
logger.error('error message')
logger.critical('critical message')
@end example

需要注意的是，'应用程序' 代码并不关心是否有多个日志处理器。示例中所做的改变只是添加和配置了一个新的名为 @emph{fh} 的日志处理器。

在编写和测试应用程序时，能够创建带有更高或更低消息等级的过滤器的日志处理器是非常有用的。为了避免过多地使用 @code{print} 语句去调试，请使用 @code{logger.debug} ：它不像 @code{print} 语句需要你不得不在调试结束后注释或删除掉，logger.debug 语句可以在源代码中保持不变，在你再一次需要它之前保持无效。那时，唯一需要改变的是修改日志记录器和/或日志处理器的消息等级，以进行调试。

@node 在多个地方记录日志,日志服务器配置示例,多个日志处理器以及多种格式化器,日志操作手册
@anchor{howto/logging-cookbook logging-to-multiple-destinations}@anchor{410c}@anchor{howto/logging-cookbook multiple-destinations}@anchor{410d}
@subsection 在多个地方记录日志


假设有这样一种情况，你需要将日志按不同的格式和不同的情况存储在控制台和文件中。比如说想把日志等级为DEBUG或更高的消息记录于文件中，而把那些等级为INFO或更高的消息输出在控制台。而且记录在文件中的消息格式需要包含时间戳，打印在控制台的不需要。以下示例展示了如何做到:

@example
import logging

# set up logging to file - see previous section for more details
logging.basicConfig(level=logging.DEBUG,
                    format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s',
                    datefmt='%m-%d %H:%M',
                    filename='/temp/myapp.log',
                    filemode='w')
# define a Handler which writes INFO messages or higher to the sys.stderr
console = logging.StreamHandler()
console.setLevel(logging.INFO)
# set a format which is simpler for console use
formatter = logging.Formatter('%(name)-12s: %(levelname)-8s %(message)s')
# tell the handler to use this format
console.setFormatter(formatter)
# add the handler to the root logger
logging.getLogger('@w{'}).addHandler(console)

# Now, we can log to the root logger, or any other logger. First the root...
logging.info('Jackdaws love my big sphinx of quartz.')

# Now, define a couple of other loggers which might represent areas in your
# application:

logger1 = logging.getLogger('myapp.area1')
logger2 = logging.getLogger('myapp.area2')

logger1.debug('Quick zephyrs blow, vexing daft Jim.')
logger1.info('How quickly daft jumping zebras vex.')
logger2.warning('Jail zesty vixen who grabbed pay from quack.')
logger2.error('The five boxing wizards jump quickly.')
@end example

当运行后，你会看到控制台如下所示

@example
root        : INFO     Jackdaws love my big sphinx of quartz.
myapp.area1 : INFO     How quickly daft jumping zebras vex.
myapp.area2 : WARNING  Jail zesty vixen who grabbed pay from quack.
myapp.area2 : ERROR    The five boxing wizards jump quickly.
@end example

而在文件中会看到像这样

@example
10-22 22:19 root         INFO     Jackdaws love my big sphinx of quartz.
10-22 22:19 myapp.area1  DEBUG    Quick zephyrs blow, vexing daft Jim.
10-22 22:19 myapp.area1  INFO     How quickly daft jumping zebras vex.
10-22 22:19 myapp.area2  WARNING  Jail zesty vixen who grabbed pay from quack.
10-22 22:19 myapp.area2  ERROR    The five boxing wizards jump quickly.
@end example

正如你所看到的，DEBUG级别的消息只展示在文件中，而其他消息两个地方都会输出。

这个示例只演示了在控制台和文件中去记录日志，但你也可以自由组合任意数量的日志处理器。

@node 日志服务器配置示例,处理日志处理器的阻塞,在多个地方记录日志,日志操作手册
@anchor{howto/logging-cookbook configuration-server-example}@anchor{410e}
@subsection 日志服务器配置示例


以下是在一个模块中使用日志服务器配置的示例:

@example
import logging
import logging.config
import time
import os

# read initial config file
logging.config.fileConfig('logging.conf')

# create and start listener on port 9999
t = logging.config.listen(9999)
t.start()

logger = logging.getLogger('simpleExample')

try:
    # loop through logging calls to see the difference
    # new configurations make, until Ctrl+C is pressed
    while True:
        logger.debug('debug message')
        logger.info('info message')
        logger.warning('warn message')
        logger.error('error message')
        logger.critical('critical message')
        time.sleep(5)
except KeyboardInterrupt:
    # cleanup
    logging.config.stopListening()
    t.join()
@end example

然后如下的脚本，它接收文件名做为命令行参数，并将该文件以二进制编码的方式传给服务器，做为新的日志服务器配置:

@example
#!/usr/bin/env python
import socket, sys, struct

with open(sys.argv[1], 'rb') as f:
    data_to_send = f.read()

HOST = 'localhost'
PORT = 9999
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print('connecting...')
s.connect((HOST, PORT))
print('sending config...')
s.send(struct.pack('>L', len(data_to_send)))
s.send(data_to_send)
s.close()
print('complete')
@end example

@node 处理日志处理器的阻塞,通过网络发送和接收日志,日志服务器配置示例,日志操作手册
@anchor{howto/logging-cookbook dealing-with-handlers-that-block}@anchor{410f}
@subsection 处理日志处理器的阻塞


有时候需要让日志处理程序在不阻塞当前正在记录线程的情况下完成工作。 这在Web应用程序中很常见，当然也会在其他场景中出现。

一个常见的缓慢行为是 @ref{20c4,,SMTPHandler}: 由于开发者无法控制的多种原因（例如，性能不佳的邮件或网络基础架构），发送电子邮件可能需要很长时间。 其实几乎所有基于网络的处理程序都可能造成阻塞：即便是 @ref{869,,SocketHandler} 也可能在底层进行 DNS 查询，这太慢了（这个查询会深入至套接字代码，位于 Python 层之下，这是不受开发者控制的）。

一种解决方案是分成两部分去处理。第一部分，针对那些对性能有要求的关键线程的日志记录附加一个 @ref{20d7,,QueueHandler}。 日志记录器只需简单写入队列，该队列可以设置一个足够大的容量甚至不设置容量上限。通常写入队列是一个快速的操作，即使可能需要在代码中去捕获例如 @ref{2351,,queue.Full} 等异常。 如果你是一名处理关键线程的开发者，请务必记录这些信息 (包括建议只为日志处理器附加 @code{QueueHandlers}) 以便于其他开发者使用你的代码。

解决方案的另一部分是 @ref{70c,,QueueListener}，它被设计用来作为 @ref{20d7,,QueueHandler} 的对应。 @ref{70c,,QueueListener} 非常简单：向其传入一个队列和一些处理句柄，它会启动一个内部线程来监听从 @code{QueueHandlers} (或任何其他可用的 @code{LogRecords} 源) 发送过来的 LogRecords 队列。 @code{LogRecords} 会从队列中被移除，并被传递给句柄进行处理。

使用一个单独的类 @ref{70c,,QueueListener} 优点是可以使用同一个实例去服务于多个`@w{`}QueueHandlers`@w{`}。这样会更节省资源，否则每个处理程序都占用一个线程没有任何益处。

以下是使用了这样两个类的示例(省略了导入语句):

@example
que = queue.Queue(-1)  # no limit on size
queue_handler = QueueHandler(que)
handler = logging.StreamHandler()
listener = QueueListener(que, handler)
root = logging.getLogger()
root.addHandler(queue_handler)
formatter = logging.Formatter('%(threadName)s: %(message)s')
handler.setFormatter(formatter)
listener.start()
# The log output will display the thread which generated
# the event (the main thread) rather than the internal
# thread which monitors the internal queue. This is what
# you want to happen.
root.warning('Look out!')
listener.stop()
@end example

在运行后会产生:

@example
MainThread: Look out!
@end example


在 3.5 版更改: 在 Python 3.5 之前，@ref{70c,,QueueListener} 总是把从队列中接收的每个消息都传给它初始化的日志处理程序。(这是因为它会假设过滤级别总是在队列的另一侧去设置的。) 从 Python 3.5 开始，可以通过在监听器构造函数中添加一个参数 @code{respect_handler_level=True} 改变这种情况。当这样设置时，监听器会比较每条消息的等级和日志处理器中设置的等级，只把需要传递的消息传给对应的日志处理器。


@node 通过网络发送和接收日志,在日志记录中添加上下文信息,处理日志处理器的阻塞,日志操作手册
@anchor{howto/logging-cookbook network-logging}@anchor{4110}@anchor{howto/logging-cookbook sending-and-receiving-logging-events-across-a-network}@anchor{4111}
@subsection 通过网络发送和接收日志


如果你想在网络上发送日志，并在接收端处理它们。一个简单的方式是通过附加一个 @ref{869,,SocketHandler} 的实例在发送端的根日志处理器中:

@example
import logging, logging.handlers

rootLogger = logging.getLogger('@w{'})
rootLogger.setLevel(logging.DEBUG)
socketHandler = logging.handlers.SocketHandler('localhost',
                    logging.handlers.DEFAULT_TCP_LOGGING_PORT)
# don't bother with a formatter, since a socket handler sends the event as
# an unformatted pickle
rootLogger.addHandler(socketHandler)

# Now, we can log to the root logger, or any other logger. First the root...
logging.info('Jackdaws love my big sphinx of quartz.')

# Now, define a couple of other loggers which might represent areas in your
# application:

logger1 = logging.getLogger('myapp.area1')
logger2 = logging.getLogger('myapp.area2')

logger1.debug('Quick zephyrs blow, vexing daft Jim.')
logger1.info('How quickly daft jumping zebras vex.')
logger2.warning('Jail zesty vixen who grabbed pay from quack.')
logger2.error('The five boxing wizards jump quickly.')
@end example

在接收端，你可以使用 @ref{f0,,socketserver} 模块设置一个接收器。这里是一个基础示例:

@example
import pickle
import logging
import logging.handlers
import socketserver
import struct


class LogRecordStreamHandler(socketserver.StreamRequestHandler):
    """Handler for a streaming logging request.

    This basically logs the record using whatever logging policy is
    configured locally.
    """

    def handle(self):
        """
        Handle multiple requests - each expected to be a 4-byte length,
        followed by the LogRecord in pickle format. Logs the record
        according to whatever policy is configured locally.
        """
        while True:
            chunk = self.connection.recv(4)
            if len(chunk) < 4:
                break
            slen = struct.unpack('>L', chunk)[0]
            chunk = self.connection.recv(slen)
            while len(chunk) < slen:
                chunk = chunk + self.connection.recv(slen - len(chunk))
            obj = self.unPickle(chunk)
            record = logging.makeLogRecord(obj)
            self.handleLogRecord(record)

    def unPickle(self, data):
        return pickle.loads(data)

    def handleLogRecord(self, record):
        # if a name is specified, we use the named logger rather than the one
        # implied by the record.
        if self.server.logname is not None:
            name = self.server.logname
        else:
            name = record.name
        logger = logging.getLogger(name)
        # N.B. EVERY record gets logged. This is because Logger.handle
        # is normally called AFTER logger-level filtering. If you want
        # to do filtering, do it at the client end to save wasting
        # cycles and network bandwidth!
        logger.handle(record)

class LogRecordSocketReceiver(socketserver.ThreadingTCPServer):
    """
    Simple TCP socket-based logging receiver suitable for testing.
    """

    allow_reuse_address = True

    def __init__(self, host='localhost',
                 port=logging.handlers.DEFAULT_TCP_LOGGING_PORT,
                 handler=LogRecordStreamHandler):
        socketserver.ThreadingTCPServer.__init__(self, (host, port), handler)
        self.abort = 0
        self.timeout = 1
        self.logname = None

    def serve_until_stopped(self):
        import select
        abort = 0
        while not abort:
            rd, wr, ex = select.select([self.socket.fileno()],
                                       [], [],
                                       self.timeout)
            if rd:
                self.handle_request()
            abort = self.abort

def main():
    logging.basicConfig(
        format='%(relativeCreated)5d %(name)-15s %(levelname)-8s %(message)s')
    tcpserver = LogRecordSocketReceiver()
    print('About to start TCP server...')
    tcpserver.serve_until_stopped()

if __name__ == '__main__':
    main()
@end example

首先运行服务端，然后是客户端。在客户端，没有什么内容会打印在控制台中；在服务端，你应该会看到如下内容：

@example
About to start TCP server...
   59 root            INFO     Jackdaws love my big sphinx of quartz.
   59 myapp.area1     DEBUG    Quick zephyrs blow, vexing daft Jim.
   69 myapp.area1     INFO     How quickly daft jumping zebras vex.
   69 myapp.area2     WARNING  Jail zesty vixen who grabbed pay from quack.
   69 myapp.area2     ERROR    The five boxing wizards jump quickly.
@end example

请注意，在某些情况下序列化会存在一些安全。如果这影响到你，那么你可以通过覆盖 @code{makePickle()} 方法，使用自己的实现来解决，并调整上述脚本也使用覆盖后的序列化方法。

@node 在日志记录中添加上下文信息,从多个进程记录至单个文件,通过网络发送和接收日志,日志操作手册
@anchor{howto/logging-cookbook adding-contextual-information-to-your-logging-output}@anchor{4112}@anchor{howto/logging-cookbook context-info}@anchor{2057}
@subsection 在日志记录中添加上下文信息


有时，除了传递给日志记录器调用的参数外，我们还希望日志记录中包含上下文信息。例如，有一个网络应用，可能需要记录一些特殊的客户端信息在日志中（比如客户端的用户名、IP地址等）。虽然你可以通过设置额外的参数去达到这个目的，但这种方式不一定方便。或者你可能想到在每个连接的基础上创建一个 @code{Logger} 的实例，但这些实例是不会被垃圾回收的，这在练习中也许不是问题，但当 @code{Logger} 的实例数量取决于你应用程序中想记录的细致程度时，如果 @code{Logger} 的实例数量不受限制的话，将会变得难以管理。

@menu
* 使用日志适配器传递上下文信息:: 
* 使用过滤器传递上下文信息:: 

@end menu

@node 使用日志适配器传递上下文信息,使用过滤器传递上下文信息,,在日志记录中添加上下文信息
@anchor{howto/logging-cookbook using-loggeradapters-to-impart-contextual-information}@anchor{4113}
@subsubsection 使用日志适配器传递上下文信息


一个传递上下文信息和日志事件信息的简单办法是使用类 @code{LoggerAdapter}。 这个类设计的像 @code{Logger}，所以可以直接调用 @code{debug()}、@code{info()}、 @code{warning()}、 @code{error()}、@code{exception()}、 @code{critical()} 和 @code{log()}。 这些方法在对应的 @code{Logger} 中使用相同的签名，所以可以交替使用两种类型的实例。

当你创建一个 @code{LoggerAdapter} 的实例时，你会传入一个 @code{Logger} 的实例和一个包含了上下文信息的字典对象。当你调用一个 @code{LoggerAdapter} 实例的方法时，它会把调用委托给内部的 @code{Logger} 的实例，并为其整理相关的上下文信息。这是 @code{LoggerAdapter} 的一个代码片段:

@example
def debug(self, msg, /, *args, **kwargs):
    """
    Delegate a debug call to the underlying logger, after adding
    contextual information from this adapter instance.
    """
    msg, kwargs = self.process(msg, kwargs)
    self.logger.debug(msg, *args, **kwargs)
@end example

@code{LoggerAdapter} 的 @code{process()} 方法是将上下文信息添加到日志的输出中。 它传入日志消息和日志调用的关键字参数，并传回（隐式的）这些修改后的内容去调用底层的日志记录器。此方法的默认参数只是一个消息字段，但留有一个 'extra' 的字段作为关键字参数传给构造器。当然，如果你在调用适配器时传入了一个 'extra' 字段的参数，它会被静默覆盖。

使用 'extra' 的优点是这些键值对会被传入 @code{LogRecord} 实例的 __dict__ 中，让你通过 @code{Formatter} 的实例直接使用定制的字符串，实例能找到这个字典类对象的键。 如果你需要一个其他的方法，比如说，想要在消息字符串前后增加上下文信息，你只需要创建一个 @code{LoggerAdapter} 的子类，并覆盖它的 @code{process()} 方法来做你想做的事情，以下是一个简单的示例:

@example
class CustomAdapter(logging.LoggerAdapter):
    """
    This example adapter expects the passed in dict-like object to have a
    'connid' key, whose value in brackets is prepended to the log message.
    """
    def process(self, msg, kwargs):
        return '[%s] %s' % (self.extra['connid'], msg), kwargs
@end example

你可以这样使用:

@example
logger = logging.getLogger(__name__)
adapter = CustomAdapter(logger, @{'connid': some_conn_id@})
@end example

然后，你记录在适配器中的任何事件消息前将添加`@w{`}some_conn_id`@w{`}的值。

@menu
* 使用除字典之外的其它对象传递上下文信息:: 

@end menu

@node 使用除字典之外的其它对象传递上下文信息,,,使用日志适配器传递上下文信息
@anchor{howto/logging-cookbook using-objects-other-than-dicts-to-pass-contextual-information}@anchor{4114}
@subsubsection 使用除字典之外的其它对象传递上下文信息


你不需要将一个实际的字典传递给 @code{LoggerAdapter}-你可以传入一个实现了`@w{`}__getitem__`@w{`} 和`@w{`}__iter__`@w{`}的类的实例，这样它就像是一个字典。这对于你想动态生成值（而字典中的值往往是常量）将很有帮助。

@node 使用过滤器传递上下文信息,,使用日志适配器传递上下文信息,在日志记录中添加上下文信息
@anchor{howto/logging-cookbook filters-contextual}@anchor{204c}@anchor{howto/logging-cookbook using-filters-to-impart-contextual-information}@anchor{4115}
@subsubsection 使用过滤器传递上下文信息


你也可以使用一个用户定义的类 @code{Filter} 在日志输出中添加上下文信息。@code{Filter} 的实例是被允许修改传入的 @code{LogRecords}，包括添加其他的属性，然后可以使用合适的格式化字符串输出，或者可以使用一个自定义的类 @code{Formatter}。

例如，在一个web应用程序中，正在处理的请求（或者至少是请求的一部分），可以存储在一个线程本地 (@ref{228e,,threading.local}) 变量中，然后从`@w{`}Filter`@w{`} 中去访问。请求中的信息，如IP地址和用户名将被存储在`@w{`}LogRecord`@w{`}中，使用上例 @code{LoggerAdapter} 中的 'ip' 和 'user' 属性名。在这种情况下，可以使用相同的格式化字符串来得到上例中类似的输出结果。这是一段示例代码:

@example
import logging
from random import choice

class ContextFilter(logging.Filter):
    """
    This is a filter which injects contextual information into the log.

    Rather than use actual contextual information, we just use random
    data in this demo.
    """

    USERS = ['jim', 'fred', 'sheila']
    IPS = ['123.231.231.123', '127.0.0.1', '192.168.0.1']

    def filter(self, record):

        record.ip = choice(ContextFilter.IPS)
        record.user = choice(ContextFilter.USERS)
        return True

if __name__ == '__main__':
    levels = (logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR, logging.CRITICAL)
    logging.basicConfig(level=logging.DEBUG,
                        format='%(asctime)-15s %(name)-5s %(levelname)-8s IP: %(ip)-15s User: %(user)-8s %(message)s')
    a1 = logging.getLogger('a.b.c')
    a2 = logging.getLogger('d.e.f')

    f = ContextFilter()
    a1.addFilter(f)
    a2.addFilter(f)
    a1.debug('A debug message')
    a1.info('An info message with %s', 'some parameters')
    for x in range(10):
        lvl = choice(levels)
        lvlname = logging.getLevelName(lvl)
        a2.log(lvl, 'A message at %s level with %d %s', lvlname, 2, 'parameters')
@end example

在运行时，产生如下内容:

@example
2010-09-06 22:38:15,292 a.b.c DEBUG    IP: 123.231.231.123 User: fred     A debug message
2010-09-06 22:38:15,300 a.b.c INFO     IP: 192.168.0.1     User: sheila   An info message with some parameters
2010-09-06 22:38:15,300 d.e.f CRITICAL IP: 127.0.0.1       User: sheila   A message at CRITICAL level with 2 parameters
2010-09-06 22:38:15,300 d.e.f ERROR    IP: 127.0.0.1       User: jim      A message at ERROR level with 2 parameters
2010-09-06 22:38:15,300 d.e.f DEBUG    IP: 127.0.0.1       User: sheila   A message at DEBUG level with 2 parameters
2010-09-06 22:38:15,300 d.e.f ERROR    IP: 123.231.231.123 User: fred     A message at ERROR level with 2 parameters
2010-09-06 22:38:15,300 d.e.f CRITICAL IP: 192.168.0.1     User: jim      A message at CRITICAL level with 2 parameters
2010-09-06 22:38:15,300 d.e.f CRITICAL IP: 127.0.0.1       User: sheila   A message at CRITICAL level with 2 parameters
2010-09-06 22:38:15,300 d.e.f DEBUG    IP: 192.168.0.1     User: jim      A message at DEBUG level with 2 parameters
2010-09-06 22:38:15,301 d.e.f ERROR    IP: 127.0.0.1       User: sheila   A message at ERROR level with 2 parameters
2010-09-06 22:38:15,301 d.e.f DEBUG    IP: 123.231.231.123 User: fred     A message at DEBUG level with 2 parameters
2010-09-06 22:38:15,301 d.e.f INFO     IP: 123.231.231.123 User: fred     A message at INFO level with 2 parameters
@end example

@node 从多个进程记录至单个文件,轮换日志文件,在日志记录中添加上下文信息,日志操作手册
@anchor{howto/logging-cookbook logging-to-a-single-file-from-multiple-processes}@anchor{4116}@anchor{howto/logging-cookbook multiple-processes}@anchor{4117}
@subsection 从多个进程记录至单个文件


尽管 logging 是线程安全的，将单个进程中的多个线程日志记录至单个文件也 @emph{是} 受支持的，但将 @emph{多个进程} 中的日志记录至单个文件则 @emph{不是} 受支持的，因为在 Python 中并没有在多个进程中实现对单个文件访问的序列化的标准方案。 如果你需要将多个进程中的日志记录至单个文件，有一个方案是让所有进程都将日志记录至一个 @code{SocketHandler}，然后用一个实现了套接字服务器的单独进程一边从套接字中读取一边将日志记录至文件。 （如果愿意的话，你可以在一个现有进程中专门开一个线程来执行此项功能。） @ref{4110,,这一部分} 文档对此方式有更详细的介绍，并包含一个可用的套接字接收器，你自己的应用可以在此基础上进行适配。

You could also write your own handler which uses the @ref{2331,,Lock}
class from the @ref{b7,,multiprocessing} module to serialize access to the
file from your processes. The existing @code{FileHandler} and subclasses do
not make use of @ref{b7,,multiprocessing} at present, though they may do so in the
future. Note that at present, the @ref{b7,,multiprocessing} module does not provide
working lock functionality on all platforms (see
@indicateurl{https://bugs.python.org/issue3770}).

或者，你也可以使用 @code{Queue} 和 @ref{20d7,,QueueHandler} 将所有的日志事件发送至你的多进程应用的一个进程中。 以下示例脚本演示了如何执行此操作。 在示例中，一个单独的监听进程负责监听其他进程的日志事件，并根据自己的配置记录。 尽管示例只演示了这种方法（例如你可能希望使用单独的监听线程而非监听进程 —— 它们的实现是类似的），但你也可以在应用程序的监听进程和其他进程使用不同的配置，它可以作为满足你特定需求的一个基础:

@example
# You'll need these imports in your own code
import logging
import logging.handlers
import multiprocessing

# Next two import lines for this demo only
from random import choice, random
import time

#
# Because you'll want to define the logging configurations for listener and workers, the
# listener and worker process functions take a configurer parameter which is a callable
# for configuring logging for that process. These functions are also passed the queue,
# which they use for communication.
#
# In practice, you can configure the listener however you want, but note that in this
# simple example, the listener does not apply level or filter logic to received records.
# In practice, you would probably want to do this logic in the worker processes, to avoid
# sending events which would be filtered out between processes.
#
# The size of the rotated files is made small so you can see the results easily.
def listener_configurer():
    root = logging.getLogger()
    h = logging.handlers.RotatingFileHandler('mptest.log', 'a', 300, 10)
    f = logging.Formatter('%(asctime)s %(processName)-10s %(name)s %(levelname)-8s %(message)s')
    h.setFormatter(f)
    root.addHandler(h)

# This is the listener process top-level loop: wait for logging events
# (LogRecords)on the queue and handle them, quit when you get a None for a
# LogRecord.
def listener_process(queue, configurer):
    configurer()
    while True:
        try:
            record = queue.get()
            if record is None:  # We send this as a sentinel to tell the listener to quit.
                break
            logger = logging.getLogger(record.name)
            logger.handle(record)  # No level or filter logic applied - just do it!
        except Exception:
            import sys, traceback
            print('Whoops! Problem:', file=sys.stderr)
            traceback.print_exc(file=sys.stderr)

# Arrays used for random selections in this demo

LEVELS = [logging.DEBUG, logging.INFO, logging.WARNING,
          logging.ERROR, logging.CRITICAL]

LOGGERS = ['a.b.c', 'd.e.f']

MESSAGES = [
    'Random message #1',
    'Random message #2',
    'Random message #3',
]

# The worker configuration is done at the start of the worker process run.
# Note that on Windows you can't rely on fork semantics, so each process
# will run the logging configuration code when it starts.
def worker_configurer(queue):
    h = logging.handlers.QueueHandler(queue)  # Just the one handler needed
    root = logging.getLogger()
    root.addHandler(h)
    # send all messages, for demo; no other level or filter logic applied.
    root.setLevel(logging.DEBUG)

# This is the worker process top-level loop, which just logs ten events with
# random intervening delays before terminating.
# The print messages are just so you know it's doing something!
def worker_process(queue, configurer):
    configurer(queue)
    name = multiprocessing.current_process().name
    print('Worker started: %s' % name)
    for i in range(10):
        time.sleep(random())
        logger = logging.getLogger(choice(LOGGERS))
        level = choice(LEVELS)
        message = choice(MESSAGES)
        logger.log(level, message)
    print('Worker finished: %s' % name)

# Here's where the demo gets orchestrated. Create the queue, create and start
# the listener, create ten workers and start them, wait for them to finish,
# then send a None to the queue to tell the listener to finish.
def main():
    queue = multiprocessing.Queue(-1)
    listener = multiprocessing.Process(target=listener_process,
                                       args=(queue, listener_configurer))
    listener.start()
    workers = []
    for i in range(10):
        worker = multiprocessing.Process(target=worker_process,
                                         args=(queue, worker_configurer))
        workers.append(worker)
        worker.start()
    for w in workers:
        w.join()
    queue.put_nowait(None)
    listener.join()

if __name__ == '__main__':
    main()
@end example

上面脚本的一个变种，仍然在主进程中记录日志，但使用一个单独的线程:

@example
import logging
import logging.config
import logging.handlers
from multiprocessing import Process, Queue
import random
import threading
import time

def logger_thread(q):
    while True:
        record = q.get()
        if record is None:
            break
        logger = logging.getLogger(record.name)
        logger.handle(record)


def worker_process(q):
    qh = logging.handlers.QueueHandler(q)
    root = logging.getLogger()
    root.setLevel(logging.DEBUG)
    root.addHandler(qh)
    levels = [logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR,
              logging.CRITICAL]
    loggers = ['foo', 'foo.bar', 'foo.bar.baz',
               'spam', 'spam.ham', 'spam.ham.eggs']
    for i in range(100):
        lvl = random.choice(levels)
        logger = logging.getLogger(random.choice(loggers))
        logger.log(lvl, 'Message no. %d', i)

if __name__ == '__main__':
    q = Queue()
    d = @{
        'version': 1,
        'formatters': @{
            'detailed': @{
                'class': 'logging.Formatter',
                'format': '%(asctime)s %(name)-15s %(levelname)-8s %(processName)-10s %(message)s'
            @}
        @},
        'handlers': @{
            'console': @{
                'class': 'logging.StreamHandler',
                'level': 'INFO',
            @},
            'file': @{
                'class': 'logging.FileHandler',
                'filename': 'mplog.log',
                'mode': 'w',
                'formatter': 'detailed',
            @},
            'foofile': @{
                'class': 'logging.FileHandler',
                'filename': 'mplog-foo.log',
                'mode': 'w',
                'formatter': 'detailed',
            @},
            'errors': @{
                'class': 'logging.FileHandler',
                'filename': 'mplog-errors.log',
                'mode': 'w',
                'level': 'ERROR',
                'formatter': 'detailed',
            @},
        @},
        'loggers': @{
            'foo': @{
                'handlers': ['foofile']
            @}
        @},
        'root': @{
            'level': 'DEBUG',
            'handlers': ['console', 'file', 'errors']
        @},
    @}
    workers = []
    for i in range(5):
        wp = Process(target=worker_process, name='worker %d' % (i + 1), args=(q,))
        workers.append(wp)
        wp.start()
    logging.config.dictConfig(d)
    lp = threading.Thread(target=logger_thread, args=(q,))
    lp.start()
    # At this point, the main process could do some useful work of its own
    # Once it's done that, it can wait for the workers to terminate...
    for wp in workers:
        wp.join()
    # And now tell the logging thread to finish up, too
    q.put(None)
    lp.join()
@end example

这段变种的代码展示了如何使用特定的日志记录配置 - 例如`@w{`}foo`@w{`}记录器使用了特殊的处理程序，将 @code{foo} 子系统中所有的事件记录至一个文件 @code{mplog-foo.log}。在主进程（即使是在工作进程中产生的日志事件）的日志记录机制中将直接使用恰当的配置。

@menu
* Using concurrent.futures.ProcessPoolExecutor: Using concurrent futures ProcessPoolExecutor. 

@end menu

@node Using concurrent futures ProcessPoolExecutor,,,从多个进程记录至单个文件
@anchor{howto/logging-cookbook using-concurrent-futures-processpoolexecutor}@anchor{4118}
@subsubsection Using concurrent.futures.ProcessPoolExecutor


If you want to use @ref{2a3,,concurrent.futures.ProcessPoolExecutor} to start
your worker processes, you need to create the queue slightly differently.
Instead of

@example
queue = multiprocessing.Queue(-1)
@end example

you should use

@example
queue = multiprocessing.Manager().Queue(-1)  # also works with the examples above
@end example

and you can then replace the worker creation from this:

@example
workers = []
for i in range(10):
    worker = multiprocessing.Process(target=worker_process,
                                     args=(queue, worker_configurer))
    workers.append(worker)
    worker.start()
for w in workers:
    w.join()
@end example

to this (remembering to first import @ref{22,,concurrent.futures}):

@example
with concurrent.futures.ProcessPoolExecutor(max_workers=10) as executor:
    for i in range(10):
        executor.submit(worker_process, queue, worker_configurer)
@end example

@node 轮换日志文件,使用其他日志格式化方式,从多个进程记录至单个文件,日志操作手册
@anchor{howto/logging-cookbook using-file-rotation}@anchor{4119}
@subsection 轮换日志文件


@c (see <https://pymotw.com/3/logging/>)

有时，你希望当日志文件不断记录增长至一定大小时，打开一个新的文件接着记录。 你可能希望只保留一定数量的日志文件，当不断的创建文件到达该数量时，又覆盖掉最开始的文件形成循环。 对于这种使用场景，日志包提供了 @code{RotatingFileHandler}:

@example
import glob
import logging
import logging.handlers

LOG_FILENAME = 'logging_rotatingfile_example.out'

# Set up a specific logger with our desired output level
my_logger = logging.getLogger('MyLogger')
my_logger.setLevel(logging.DEBUG)

# Add the log message handler to the logger
handler = logging.handlers.RotatingFileHandler(
              LOG_FILENAME, maxBytes=20, backupCount=5)

my_logger.addHandler(handler)

# Log some messages
for i in range(20):
    my_logger.debug('i = %d' % i)

# See what files are created
logfiles = glob.glob('%s*' % LOG_FILENAME)

for filename in logfiles:
    print(filename)
@end example

结果应该是6个单独的文件，每个文件都包含了应用程序的部分历史日志:

@example
logging_rotatingfile_example.out
logging_rotatingfile_example.out.1
logging_rotatingfile_example.out.2
logging_rotatingfile_example.out.3
logging_rotatingfile_example.out.4
logging_rotatingfile_example.out.5
@end example

最新的文件始终是:file:@cite{logging_rotatingfile_example.out}，每次到达大小限制时，都会使用后缀`@w{`}.1`@w{`}重命名。每个现有的备份文件都会被重命名并增加其后缀（例如`@w{`}.1`@w{`} 变为`@w{`}.2`@w{`}），而`@w{`}.6`@w{`}文件会被删除掉。

显然，这个例子将日志长度设置得太小，这是一个极端的例子。 你可能希望将 @emph{maxBytes} 设置为一个合适的值。

@node 使用其他日志格式化方式,Customizing LogRecord,轮换日志文件,日志操作手册
@anchor{howto/logging-cookbook format-styles}@anchor{411a}@anchor{howto/logging-cookbook use-of-alternative-formatting-styles}@anchor{411b}
@subsection 使用其他日志格式化方式


当日志模块被添加至 Python 标准库时，只有一种格式化消息内容的方法即 %-formatting。 在那之后，Python 又增加了两种格式化方法: @ref{3e3,,string.Template} (在 Python 2.4 中新增) 和 @ref{4d4,,str.format()} (在 Python 2.6 中新增)。

日志（从 3.2 开始）为这两种格式化方式提供了更多支持。@code{Formatter} 类可以添加一个额外的可选关键字参数 @code{style}。它的默认值是 @code{'%'}，其他的值 @code{'@{'} 和 @code{'$'} 也支持，对应了其他两种格式化样式。其保持了向后兼容（如您所愿），但通过显示指定样式参数，你可以指定格式化字符串的方式是使用 @ref{4d4,,str.format()} 或 @ref{3e3,,string.Template}。 这里是一个控制台会话的示例，展示了这些方式：

@example
>>> import logging
>>> root = logging.getLogger()
>>> root.setLevel(logging.DEBUG)
>>> handler = logging.StreamHandler()
>>> bf = logging.Formatter('@{asctime@} @{name@} @{levelname:8s@} @{message@}',
...                        style='@{')
>>> handler.setFormatter(bf)
>>> root.addHandler(handler)
>>> logger = logging.getLogger('foo.bar')
>>> logger.debug('This is a DEBUG message')
2010-10-28 15:11:55,341 foo.bar DEBUG    This is a DEBUG message
>>> logger.critical('This is a CRITICAL message')
2010-10-28 15:12:11,526 foo.bar CRITICAL This is a CRITICAL message
>>> df = logging.Formatter('$asctime $name $@{levelname@} $message',
...                        style='$')
>>> handler.setFormatter(df)
>>> logger.debug('This is a DEBUG message')
2010-10-28 15:13:06,924 foo.bar DEBUG This is a DEBUG message
>>> logger.critical('This is a CRITICAL message')
2010-10-28 15:13:11,494 foo.bar CRITICAL This is a CRITICAL message
>>>
@end example

请注意最终输出到日志的消息格式完全独立于单条日志消息的构造方式。 它仍然可以使用 %-formatting，如下所示:

@example
>>> logger.error('This is an%s %s %s', 'other,', 'ERROR,', 'message')
2010-10-28 15:19:29,833 foo.bar ERROR This is another, ERROR, message
>>>
@end example

Logging calls (@code{logger.debug()}, @code{logger.info()} etc.) only take
positional parameters for the actual logging message itself, with keyword
parameters used only for determining options for how to handle the actual
logging call (e.g. the @code{exc_info} keyword parameter to indicate that
traceback information should be logged, or the @code{extra} keyword parameter
to indicate additional contextual information to be added to the log). So
you cannot directly make logging calls using @ref{4d4,,str.format()} or
@ref{3e3,,string.Template} syntax, because internally the logging package
uses %-formatting to merge the format string and the variable arguments.
There would be no changing this while preserving backward compatibility, since
all logging calls which are out there in existing code will be using %-format
strings.

There is, however, a way that you can use @{@}- and $- formatting to construct
your individual log messages. Recall that for a message you can use an
arbitrary object as a message format string, and that the logging package will
call @code{str()} on that object to get the actual format string. Consider the
following two classes:

@example
class BraceMessage:
    def __init__(self, fmt, /, *args, **kwargs):
        self.fmt = fmt
        self.args = args
        self.kwargs = kwargs

    def __str__(self):
        return self.fmt.format(*self.args, **self.kwargs)

class DollarMessage:
    def __init__(self, fmt, /, **kwargs):
        self.fmt = fmt
        self.kwargs = kwargs

    def __str__(self):
        from string import Template
        return Template(self.fmt).substitute(**self.kwargs)
@end example

Either of these can be used in place of a format string, to allow @{@}- or
$-formatting to be used to build the actual "message" part which appears in the
formatted log output in place of "%(message)s" or "@{message@}" or "$message".
It's a little unwieldy to use the class names whenever you want to log
something, but it's quite palatable if you use an alias such as __ (double
underscore --- not to be confused with _, the single underscore used as a
synonym/alias for @ref{dc6,,gettext.gettext()} or its brethren).

The above classes are not included in Python, though they're easy enough to
copy and paste into your own code. They can be used as follows (assuming that
they're declared in a module called @code{wherever}):

@example
>>> from wherever import BraceMessage as __
>>> print(__('Message with @{0@} @{name@}', 2, name='placeholders'))
Message with 2 placeholders
>>> class Point: pass
...
>>> p = Point()
>>> p.x = 0.5
>>> p.y = 0.5
>>> print(__('Message with coordinates: (@{point.x:.2f@}, @{point.y:.2f@})',
...       point=p))
Message with coordinates: (0.50, 0.50)
>>> from wherever import DollarMessage as __
>>> print(__('Message with $num $what', num=2, what='placeholders'))
Message with 2 placeholders
>>>
@end example

While the above examples use @code{print()} to show how the formatting works, you
would of course use @code{logger.debug()} or similar to actually log using this
approach.

One thing to note is that you pay no significant performance penalty with this
approach: the actual formatting happens not when you make the logging call, but
when (and if) the logged message is actually about to be output to a log by a
handler. So the only slightly unusual thing which might trip you up is that the
parentheses go around the format string and the arguments, not just the format
string. That's because the __ notation is just syntax sugar for a constructor
call to one of the XXXMessage classes.

If you prefer, you can use a @code{LoggerAdapter} to achieve a similar effect
to the above, as in the following example:

@example
import logging

class Message:
    def __init__(self, fmt, args):
        self.fmt = fmt
        self.args = args

    def __str__(self):
        return self.fmt.format(*self.args)

class StyleAdapter(logging.LoggerAdapter):
    def __init__(self, logger, extra=None):
        super(StyleAdapter, self).__init__(logger, extra or @{@})

    def log(self, level, msg, /, *args, **kwargs):
        if self.isEnabledFor(level):
            msg, kwargs = self.process(msg, kwargs)
            self.logger._log(level, Message(msg, args), (), **kwargs)

logger = StyleAdapter(logging.getLogger(__name__))

def main():
    logger.debug('Hello, @{@}', 'world!')

if __name__ == '__main__':
    logging.basicConfig(level=logging.DEBUG)
    main()
@end example

The above script should log the message @code{Hello, world!} when run with
Python 3.2 or later.

@node Customizing LogRecord,Subclassing QueueHandler - a ZeroMQ example,使用其他日志格式化方式,日志操作手册
@anchor{howto/logging-cookbook custom-logrecord}@anchor{411c}@anchor{howto/logging-cookbook customizing-logrecord}@anchor{411d}
@subsection Customizing @code{LogRecord}


Every logging event is represented by a @ref{900,,LogRecord} instance.
When an event is logged and not filtered out by a logger's level, a
@ref{900,,LogRecord} is created, populated with information about the event and
then passed to the handlers for that logger (and its ancestors, up to and
including the logger where further propagation up the hierarchy is disabled).
Before Python 3.2, there were only two places where this creation was done:


@itemize *

@item 
@ref{202a,,Logger.makeRecord()}, which is called in the normal process of
logging an event. This invoked @ref{900,,LogRecord} directly to create an
instance.

@item 
@ref{204f,,makeLogRecord()}, which is called with a dictionary containing
attributes to be added to the LogRecord. This is typically invoked when a
suitable dictionary has been received over the network (e.g. in pickle form
via a @ref{869,,SocketHandler}, or in JSON form via an
@ref{70b,,HTTPHandler}).
@end itemize

This has usually meant that if you need to do anything special with a
@ref{900,,LogRecord}, you've had to do one of the following.


@itemize *

@item 
Create your own @ref{39f,,Logger} subclass, which overrides
@ref{202a,,Logger.makeRecord()}, and set it using @ref{205c,,setLoggerClass()}
before any loggers that you care about are instantiated.

@item 
Add a @ref{b70,,Filter} to a logger or handler, which does the
necessary special manipulation you need when its
@ref{204a,,filter()} method is called.
@end itemize

The first approach would be a little unwieldy in the scenario where (say)
several different libraries wanted to do different things. Each would attempt
to set its own @ref{39f,,Logger} subclass, and the one which did this last would
win.

The second approach works reasonably well for many cases, but does not allow
you to e.g. use a specialized subclass of @ref{900,,LogRecord}. Library
developers can set a suitable filter on their loggers, but they would have to
remember to do this every time they introduced a new logger (which they would
do simply by adding new packages or modules and doing

@example
logger = logging.getLogger(__name__)
@end example

at module level). It's probably one too many things to think about. Developers
could also add the filter to a @ref{c15,,NullHandler} attached to their
top-level logger, but this would not be invoked if an application developer
attached a handler to a lower-level library logger --- so output from that
handler would not reflect the intentions of the library developer.

In Python 3.2 and later, @ref{900,,LogRecord} creation is done through a
factory, which you can specify. The factory is just a callable you can set with
@ref{2052,,setLogRecordFactory()}, and interrogate with
@ref{2051,,getLogRecordFactory()}. The factory is invoked with the same
signature as the @ref{900,,LogRecord} constructor, as @ref{900,,LogRecord}
is the default setting for the factory.

This approach allows a custom factory to control all aspects of LogRecord
creation. For example, you could return a subclass, or just add some additional
attributes to the record once created, using a pattern similar to this:

@example
old_factory = logging.getLogRecordFactory()

def record_factory(*args, **kwargs):
    record = old_factory(*args, **kwargs)
    record.custom_attribute = 0xdecafbad
    return record

logging.setLogRecordFactory(record_factory)
@end example

This pattern allows different libraries to chain factories together, and as
long as they don't overwrite each other's attributes or unintentionally
overwrite the attributes provided as standard, there should be no surprises.
However, it should be borne in mind that each link in the chain adds run-time
overhead to all logging operations, and the technique should only be used when
the use of a @ref{b70,,Filter} does not provide the desired result.

@node Subclassing QueueHandler - a ZeroMQ example,Subclassing QueueListener - a ZeroMQ example,Customizing LogRecord,日志操作手册
@anchor{howto/logging-cookbook subclassing-queuehandler-a-zeromq-example}@anchor{411e}@anchor{howto/logging-cookbook zeromq-handlers}@anchor{411f}
@subsection Subclassing QueueHandler - a ZeroMQ example


You can use a @code{QueueHandler} subclass to send messages to other kinds
of queues, for example a ZeroMQ 'publish' socket. In the example below,the
socket is created separately and passed to the handler (as its 'queue'):

@example
import zmq   # using pyzmq, the Python binding for ZeroMQ
import json  # for serializing records portably

ctx = zmq.Context()
sock = zmq.Socket(ctx, zmq.PUB)  # or zmq.PUSH, or other suitable value
sock.bind('tcp://*:5556')        # or wherever

class ZeroMQSocketHandler(QueueHandler):
    def enqueue(self, record):
        self.queue.send_json(record.__dict__)


handler = ZeroMQSocketHandler(sock)
@end example

Of course there are other ways of organizing this, for example passing in the
data needed by the handler to create the socket:

@example
class ZeroMQSocketHandler(QueueHandler):
    def __init__(self, uri, socktype=zmq.PUB, ctx=None):
        self.ctx = ctx or zmq.Context()
        socket = zmq.Socket(self.ctx, socktype)
        socket.bind(uri)
        super().__init__(socket)

    def enqueue(self, record):
        self.queue.send_json(record.__dict__)

    def close(self):
        self.queue.close()
@end example

@node Subclassing QueueListener - a ZeroMQ example,An example dictionary-based configuration,Subclassing QueueHandler - a ZeroMQ example,日志操作手册
@anchor{howto/logging-cookbook subclassing-queuelistener-a-zeromq-example}@anchor{4120}
@subsection Subclassing QueueListener - a ZeroMQ example


You can also subclass @code{QueueListener} to get messages from other kinds
of queues, for example a ZeroMQ 'subscribe' socket. Here's an example:

@example
class ZeroMQSocketListener(QueueListener):
    def __init__(self, uri, /, *handlers, **kwargs):
        self.ctx = kwargs.get('ctx') or zmq.Context()
        socket = zmq.Socket(self.ctx, zmq.SUB)
        socket.setsockopt_string(zmq.SUBSCRIBE, '@w{'})  # subscribe to everything
        socket.connect(uri)
        super().__init__(socket, *handlers, **kwargs)

    def dequeue(self):
        msg = self.queue.recv_json()
        return logging.makeLogRecord(msg)
@end example


@subsubheading 参见



@table @asis

@item 模块 @ref{aa,,logging}

日志记录模块的 API 参考。

@item @ref{ab,,logging.config} 模块

日志记录模块的配置 API 。

@item @ref{ac,,logging.handlers} 模块

日志记录模块附带的有用处理器。
@end table

@ref{b6b,,A basic logging tutorial}

@ref{b6c,,A more advanced logging tutorial}


@node An example dictionary-based configuration,Using a rotator and namer to customize log rotation processing,Subclassing QueueListener - a ZeroMQ example,日志操作手册
@anchor{howto/logging-cookbook an-example-dictionary-based-configuration}@anchor{4121}
@subsection An example dictionary-based configuration


Below is an example of a logging configuration dictionary - it's taken from
the documentation on the Django project@footnote{https://docs.djangoproject.com/en/1.9/topics/logging/#configuring-logging}.
This dictionary is passed to @ref{b24,,dictConfig()} to put the configuration into effect:

@example
LOGGING = @{
    'version': 1,
    'disable_existing_loggers': True,
    'formatters': @{
        'verbose': @{
            'format': '%(levelname)s %(asctime)s %(module)s %(process)d %(thread)d %(message)s'
        @},
        'simple': @{
            'format': '%(levelname)s %(message)s'
        @},
    @},
    'filters': @{
        'special': @{
            '()': 'project.logging.SpecialFilter',
            'foo': 'bar',
        @}
    @},
    'handlers': @{
        'null': @{
            'level':'DEBUG',
            'class':'django.utils.log.NullHandler',
        @},
        'console':@{
            'level':'DEBUG',
            'class':'logging.StreamHandler',
            'formatter': 'simple'
        @},
        'mail_admins': @{
            'level': 'ERROR',
            'class': 'django.utils.log.AdminEmailHandler',
            'filters': ['special']
        @}
    @},
    'loggers': @{
        'django': @{
            'handlers':['null'],
            'propagate': True,
            'level':'INFO',
        @},
        'django.request': @{
            'handlers': ['mail_admins'],
            'level': 'ERROR',
            'propagate': False,
        @},
        'myproject.custom': @{
            'handlers': ['console', 'mail_admins'],
            'level': 'INFO',
            'filters': ['special']
        @}
    @}
@}
@end example

For more information about this configuration, you can see the relevant section@footnote{https://docs.djangoproject.com/en/1.9/topics/logging/#configuring-logging}
of the Django documentation.

@node Using a rotator and namer to customize log rotation processing,A more elaborate multiprocessing example,An example dictionary-based configuration,日志操作手册
@anchor{howto/logging-cookbook cookbook-rotator-namer}@anchor{209d}@anchor{howto/logging-cookbook using-a-rotator-and-namer-to-customize-log-rotation-processing}@anchor{4122}
@subsection Using a rotator and namer to customize log rotation processing


An example of how you can define a namer and rotator is given in the following
snippet, which shows zlib-based compression of the log file:

@example
def namer(name):
    return name + ".gz"

def rotator(source, dest):
    with open(source, "rb") as sf:
        data = sf.read()
        compressed = zlib.compress(data, 9)
        with open(dest, "wb") as df:
            df.write(compressed)
    os.remove(source)

rh = logging.handlers.RotatingFileHandler(...)
rh.rotator = rotator
rh.namer = namer
@end example

These are not "true" .gz files, as they are bare compressed data, with no
"container" such as you’d find in an actual gzip file. This snippet is just
for illustration purposes.

@node A more elaborate multiprocessing example,Inserting a BOM into messages sent to a SysLogHandler,Using a rotator and namer to customize log rotation processing,日志操作手册
@anchor{howto/logging-cookbook a-more-elaborate-multiprocessing-example}@anchor{4123}
@subsection A more elaborate multiprocessing example


The following working example shows how logging can be used with multiprocessing
using configuration files. The configurations are fairly simple, but serve to
illustrate how more complex ones could be implemented in a real multiprocessing
scenario.

In the example, the main process spawns a listener process and some worker
processes. Each of the main process, the listener and the workers have three
separate configurations (the workers all share the same configuration). We can
see logging in the main process, how the workers log to a QueueHandler and how
the listener implements a QueueListener and a more complex logging
configuration, and arranges to dispatch events received via the queue to the
handlers specified in the configuration. Note that these configurations are
purely illustrative, but you should be able to adapt this example to your own
scenario.

Here's the script - the docstrings and the comments hopefully explain how it
works:

@example
import logging
import logging.config
import logging.handlers
from multiprocessing import Process, Queue, Event, current_process
import os
import random
import time

class MyHandler:
    """
    A simple handler for logging events. It runs in the listener process and
    dispatches events to loggers based on the name in the received record,
    which then get dispatched, by the logging system, to the handlers
    configured for those loggers.
    """

    def handle(self, record):
        if record.name == "root":
            logger = logging.getLogger()
        else:
            logger = logging.getLogger(record.name)

        if logger.isEnabledFor(record.levelno):
            # The process name is transformed just to show that it's the listener
            # doing the logging to files and console
            record.processName = '%s (for %s)' % (current_process().name, record.processName)
            logger.handle(record)

def listener_process(q, stop_event, config):
    """
    This could be done in the main process, but is just done in a separate
    process for illustrative purposes.

    This initialises logging according to the specified configuration,
    starts the listener and waits for the main process to signal completion
    via the event. The listener is then stopped, and the process exits.
    """
    logging.config.dictConfig(config)
    listener = logging.handlers.QueueListener(q, MyHandler())
    listener.start()
    if os.name == 'posix':
        # On POSIX, the setup logger will have been configured in the
        # parent process, but should have been disabled following the
        # dictConfig call.
        # On Windows, since fork isn't used, the setup logger won't
        # exist in the child, so it would be created and the message
        # would appear - hence the "if posix" clause.
        logger = logging.getLogger('setup')
        logger.critical('Should not appear, because of disabled logger ...')
    stop_event.wait()
    listener.stop()

def worker_process(config):
    """
    A number of these are spawned for the purpose of illustration. In
    practice, they could be a heterogeneous bunch of processes rather than
    ones which are identical to each other.

    This initialises logging according to the specified configuration,
    and logs a hundred messages with random levels to randomly selected
    loggers.

    A small sleep is added to allow other processes a chance to run. This
    is not strictly needed, but it mixes the output from the different
    processes a bit more than if it's left out.
    """
    logging.config.dictConfig(config)
    levels = [logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR,
              logging.CRITICAL]
    loggers = ['foo', 'foo.bar', 'foo.bar.baz',
               'spam', 'spam.ham', 'spam.ham.eggs']
    if os.name == 'posix':
        # On POSIX, the setup logger will have been configured in the
        # parent process, but should have been disabled following the
        # dictConfig call.
        # On Windows, since fork isn't used, the setup logger won't
        # exist in the child, so it would be created and the message
        # would appear - hence the "if posix" clause.
        logger = logging.getLogger('setup')
        logger.critical('Should not appear, because of disabled logger ...')
    for i in range(100):
        lvl = random.choice(levels)
        logger = logging.getLogger(random.choice(loggers))
        logger.log(lvl, 'Message no. %d', i)
        time.sleep(0.01)

def main():
    q = Queue()
    # The main process gets a simple configuration which prints to the console.
    config_initial = @{
        'version': 1,
        'handlers': @{
            'console': @{
                'class': 'logging.StreamHandler',
                'level': 'INFO'
            @}
        @},
        'root': @{
            'handlers': ['console'],
            'level': 'DEBUG'
        @}
    @}
    # The worker process configuration is just a QueueHandler attached to the
    # root logger, which allows all messages to be sent to the queue.
    # We disable existing loggers to disable the "setup" logger used in the
    # parent process. This is needed on POSIX because the logger will
    # be there in the child following a fork().
    config_worker = @{
        'version': 1,
        'disable_existing_loggers': True,
        'handlers': @{
            'queue': @{
                'class': 'logging.handlers.QueueHandler',
                'queue': q
            @}
        @},
        'root': @{
            'handlers': ['queue'],
            'level': 'DEBUG'
        @}
    @}
    # The listener process configuration shows that the full flexibility of
    # logging configuration is available to dispatch events to handlers however
    # you want.
    # We disable existing loggers to disable the "setup" logger used in the
    # parent process. This is needed on POSIX because the logger will
    # be there in the child following a fork().
    config_listener = @{
        'version': 1,
        'disable_existing_loggers': True,
        'formatters': @{
            'detailed': @{
                'class': 'logging.Formatter',
                'format': '%(asctime)s %(name)-15s %(levelname)-8s %(processName)-10s %(message)s'
            @},
            'simple': @{
                'class': 'logging.Formatter',
                'format': '%(name)-15s %(levelname)-8s %(processName)-10s %(message)s'
            @}
        @},
        'handlers': @{
            'console': @{
                'class': 'logging.StreamHandler',
                'formatter': 'simple',
                'level': 'INFO'
            @},
            'file': @{
                'class': 'logging.FileHandler',
                'filename': 'mplog.log',
                'mode': 'w',
                'formatter': 'detailed'
            @},
            'foofile': @{
                'class': 'logging.FileHandler',
                'filename': 'mplog-foo.log',
                'mode': 'w',
                'formatter': 'detailed'
            @},
            'errors': @{
                'class': 'logging.FileHandler',
                'filename': 'mplog-errors.log',
                'mode': 'w',
                'formatter': 'detailed',
                'level': 'ERROR'
            @}
        @},
        'loggers': @{
            'foo': @{
                'handlers': ['foofile']
            @}
        @},
        'root': @{
            'handlers': ['console', 'file', 'errors'],
            'level': 'DEBUG'
        @}
    @}
    # Log some initial events, just to show that logging in the parent works
    # normally.
    logging.config.dictConfig(config_initial)
    logger = logging.getLogger('setup')
    logger.info('About to create workers ...')
    workers = []
    for i in range(5):
        wp = Process(target=worker_process, name='worker %d' % (i + 1),
                     args=(config_worker,))
        workers.append(wp)
        wp.start()
        logger.info('Started worker: %s', wp.name)
    logger.info('About to create listener ...')
    stop_event = Event()
    lp = Process(target=listener_process, name='listener',
                 args=(q, stop_event, config_listener))
    lp.start()
    logger.info('Started listener')
    # We now hang around for the workers to finish their work.
    for wp in workers:
        wp.join()
    # Workers all done, listening can now stop.
    # Logging in the parent still works normally.
    logger.info('Telling listener to stop ...')
    stop_event.set()
    lp.join()
    logger.info('All done.')

if __name__ == '__main__':
    main()
@end example

@node Inserting a BOM into messages sent to a SysLogHandler,Implementing structured logging,A more elaborate multiprocessing example,日志操作手册
@anchor{howto/logging-cookbook inserting-a-bom-into-messages-sent-to-a-sysloghandler}@anchor{4124}
@subsection Inserting a BOM into messages sent to a SysLogHandler


@geindex RFC; RFC 5424
RFC 5424@footnote{https://tools.ietf.org/html/rfc5424.html} requires that a
Unicode message be sent to a syslog daemon as a set of bytes which have the
following structure: an optional pure-ASCII component, followed by a UTF-8 Byte
Order Mark (BOM), followed by Unicode encoded using UTF-8. (See the
@geindex RFC; RFC 5424#section-6
relevant section of the specification@footnote{https://tools.ietf.org/html/rfc5424.html#section-6}.)

In Python 3.1, code was added to
@ref{a19,,SysLogHandler} to insert a BOM into the message, but
unfortunately, it was implemented incorrectly, with the BOM appearing at the
beginning of the message and hence not allowing any pure-ASCII component to
appear before it.

As this behaviour is broken, the incorrect BOM insertion code is being removed
from Python 3.2.4 and later. However, it is not being replaced, and if you
want to produce 
@geindex RFC; RFC 5424
RFC 5424@footnote{https://tools.ietf.org/html/rfc5424.html}-compliant messages which include a BOM, an optional
pure-ASCII sequence before it and arbitrary Unicode after it, encoded using
UTF-8, then you need to do the following:


@enumerate 

@item 
Attach a @ref{201d,,Formatter} instance to your
@ref{a19,,SysLogHandler} instance, with a format string
such as:

@example
'ASCII section\ufeffUnicode section'
@end example

The Unicode code point U+FEFF, when encoded using UTF-8, will be
encoded as a UTF-8 BOM -- the byte-string @code{b'\xef\xbb\xbf'}.

@item 
Replace the ASCII section with whatever placeholders you like, but make sure
that the data that appears in there after substitution is always ASCII (that
way, it will remain unchanged after UTF-8 encoding).

@item 
Replace the Unicode section with whatever placeholders you like; if the data
which appears there after substitution contains characters outside the ASCII
range, that's fine -- it will be encoded using UTF-8.
@end enumerate

The formatted message @emph{will} be encoded using UTF-8 encoding by
@code{SysLogHandler}. If you follow the above rules, you should be able to produce
@geindex RFC; RFC 5424
RFC 5424@footnote{https://tools.ietf.org/html/rfc5424.html}-compliant messages. If you don't, logging may not complain, but your
messages will not be RFC 5424-compliant, and your syslog daemon may complain.

@node Implementing structured logging,Customizing handlers with dictConfig,Inserting a BOM into messages sent to a SysLogHandler,日志操作手册
@anchor{howto/logging-cookbook implementing-structured-logging}@anchor{4125}
@subsection Implementing structured logging


Although most logging messages are intended for reading by humans, and thus not
readily machine-parseable, there might be circumstances where you want to output
messages in a structured format which @emph{is} capable of being parsed by a program
(without needing complex regular expressions to parse the log message). This is
straightforward to achieve using the logging package. There are a number of
ways in which this could be achieved, but the following is a simple approach
which uses JSON to serialise the event in a machine-parseable manner:

@example
import json
import logging

class StructuredMessage:
    def __init__(self, message, /, **kwargs):
        self.message = message
        self.kwargs = kwargs

    def __str__(self):
        return '%s >>> %s' % (self.message, json.dumps(self.kwargs))

_ = StructuredMessage   # optional, to improve readability

logging.basicConfig(level=logging.INFO, format='%(message)s')
logging.info(_('message 1', foo='bar', bar='baz', num=123, fnum=123.456))
@end example

If the above script is run, it prints:

@example
message 1 >>> @{"fnum": 123.456, "num": 123, "bar": "baz", "foo": "bar"@}
@end example

Note that the order of items might be different according to the version of
Python used.

If you need more specialised processing, you can use a custom JSON encoder,
as in the following complete example:

@example
from __future__ import unicode_literals

import json
import logging

# This next bit is to ensure the script runs unchanged on 2.x and 3.x
try:
    unicode
except NameError:
    unicode = str

class Encoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, set):
            return tuple(o)
        elif isinstance(o, unicode):
            return o.encode('unicode_escape').decode('ascii')
        return super(Encoder, self).default(o)

class StructuredMessage:
    def __init__(self, message, /, **kwargs):
        self.message = message
        self.kwargs = kwargs

    def __str__(self):
        s = Encoder().encode(self.kwargs)
        return '%s >>> %s' % (self.message, s)

_ = StructuredMessage   # optional, to improve readability

def main():
    logging.basicConfig(level=logging.INFO, format='%(message)s')
    logging.info(_('message 1', set_value=@{1, 2, 3@}, snowman='\u2603'))

if __name__ == '__main__':
    main()
@end example

When the above script is run, it prints:

@example
message 1 >>> @{"snowman": "\u2603", "set_value": [1, 2, 3]@}
@end example

Note that the order of items might be different according to the version of
Python used.

@node Customizing handlers with dictConfig,Using particular formatting styles throughout your application,Implementing structured logging,日志操作手册
@anchor{howto/logging-cookbook custom-handlers}@anchor{4126}@anchor{howto/logging-cookbook customizing-handlers-with-dictconfig}@anchor{4127}
@subsection Customizing handlers with @code{dictConfig()}


There are times when you want to customize logging handlers in particular ways,
and if you use @ref{b24,,dictConfig()} you may be able to do this without
subclassing. As an example, consider that you may want to set the ownership of a
log file. On POSIX, this is easily done using @ref{a71,,shutil.chown()}, but the file
handlers in the stdlib don't offer built-in support. You can customize handler
creation using a plain function such as:

@example
def owned_file_handler(filename, mode='a', encoding=None, owner=None):
    if owner:
        if not os.path.exists(filename):
            open(filename, 'a').close()
        shutil.chown(filename, *owner)
    return logging.FileHandler(filename, mode, encoding)
@end example

You can then specify, in a logging configuration passed to @ref{b24,,dictConfig()},
that a logging handler be created by calling this function:

@example
LOGGING = @{
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': @{
        'default': @{
            'format': '%(asctime)s %(levelname)s %(name)s %(message)s'
        @},
    @},
    'handlers': @{
        'file':@{
            # The values below are popped from this dictionary and
            # used to create the handler, set the handler's level and
            # its formatter.
            '()': owned_file_handler,
            'level':'DEBUG',
            'formatter': 'default',
            # The values below are passed to the handler creator callable
            # as keyword arguments.
            'owner': ['pulse', 'pulse'],
            'filename': 'chowntest.log',
            'mode': 'w',
            'encoding': 'utf-8',
        @},
    @},
    'root': @{
        'handlers': ['file'],
        'level': 'DEBUG',
    @},
@}
@end example

In this example I am setting the ownership using the @code{pulse} user and group,
just for the purposes of illustration. Putting it together into a working
script, @code{chowntest.py}:

@example
import logging, logging.config, os, shutil

def owned_file_handler(filename, mode='a', encoding=None, owner=None):
    if owner:
        if not os.path.exists(filename):
            open(filename, 'a').close()
        shutil.chown(filename, *owner)
    return logging.FileHandler(filename, mode, encoding)

LOGGING = @{
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': @{
        'default': @{
            'format': '%(asctime)s %(levelname)s %(name)s %(message)s'
        @},
    @},
    'handlers': @{
        'file':@{
            # The values below are popped from this dictionary and
            # used to create the handler, set the handler's level and
            # its formatter.
            '()': owned_file_handler,
            'level':'DEBUG',
            'formatter': 'default',
            # The values below are passed to the handler creator callable
            # as keyword arguments.
            'owner': ['pulse', 'pulse'],
            'filename': 'chowntest.log',
            'mode': 'w',
            'encoding': 'utf-8',
        @},
    @},
    'root': @{
        'handlers': ['file'],
        'level': 'DEBUG',
    @},
@}

logging.config.dictConfig(LOGGING)
logger = logging.getLogger('mylogger')
logger.debug('A debug message')
@end example

To run this, you will probably need to run as @code{root}:

@example
$ sudo python3.3 chowntest.py
$ cat chowntest.log
2013-11-05 09:34:51,128 DEBUG mylogger A debug message
$ ls -l chowntest.log
-rw-r--r-- 1 pulse pulse 55 2013-11-05 09:34 chowntest.log
@end example

Note that this example uses Python 3.3 because that's where @ref{a71,,shutil.chown()}
makes an appearance. This approach should work with any Python version that
supports @ref{b24,,dictConfig()} - namely, Python 2.7, 3.2 or later. With pre-3.3
versions, you would need to implement the actual ownership change using e.g.
@ref{a2f,,os.chown()}.

In practice, the handler-creating function may be in a utility module somewhere
in your project. Instead of the line in the configuration:

@example
'()': owned_file_handler,
@end example

you could use e.g.:

@example
'()': 'ext://project.util.owned_file_handler',
@end example

where @code{project.util} can be replaced with the actual name of the package
where the function resides. In the above working script, using
@code{'ext://__main__.owned_file_handler'} should work. Here, the actual callable
is resolved by @ref{b24,,dictConfig()} from the @code{ext://} specification.

This example hopefully also points the way to how you could implement other
types of file change - e.g. setting specific POSIX permission bits - in the
same way, using @ref{a2e,,os.chmod()}.

Of course, the approach could also be extended to types of handler other than a
@ref{2083,,FileHandler} - for example, one of the rotating file handlers,
or a different type of handler altogether.

@node Using particular formatting styles throughout your application,Configuring filters with dictConfig,Customizing handlers with dictConfig,日志操作手册
@anchor{howto/logging-cookbook formatting-styles}@anchor{2043}@anchor{howto/logging-cookbook using-particular-formatting-styles-throughout-your-application}@anchor{4128}
@subsection Using particular formatting styles throughout your application


In Python 3.2, the @ref{201d,,Formatter} gained a @code{style} keyword
parameter which, while defaulting to @code{%} for backward compatibility, allowed
the specification of @code{@{} or @code{$} to support the formatting approaches
supported by @ref{4d4,,str.format()} and @ref{3e3,,string.Template}. Note that this
governs the formatting of logging messages for final output to logs, and is
completely orthogonal to how an individual logging message is constructed.

Logging calls (@ref{70a,,debug()}, @ref{201f,,info()} etc.) only take
positional parameters for the actual logging message itself, with keyword
parameters used only for determining options for how to handle the logging call
(e.g. the @code{exc_info} keyword parameter to indicate that traceback information
should be logged, or the @code{extra} keyword parameter to indicate additional
contextual information to be added to the log). So you cannot directly make
logging calls using @ref{4d4,,str.format()} or @ref{3e3,,string.Template} syntax,
because internally the logging package uses %-formatting to merge the format
string and the variable arguments. There would no changing this while preserving
backward compatibility, since all logging calls which are out there in existing
code will be using %-format strings.

There have been suggestions to associate format styles with specific loggers,
but that approach also runs into backward compatibility problems because any
existing code could be using a given logger name and using %-formatting.

For logging to work interoperably between any third-party libraries and your
code, decisions about formatting need to be made at the level of the
individual logging call. This opens up a couple of ways in which alternative
formatting styles can be accommodated.

@menu
* Using LogRecord factories:: 
* Using custom message objects:: 

@end menu

@node Using LogRecord factories,Using custom message objects,,Using particular formatting styles throughout your application
@anchor{howto/logging-cookbook using-logrecord-factories}@anchor{4129}
@subsubsection Using LogRecord factories


In Python 3.2, along with the @ref{201d,,Formatter} changes mentioned
above, the logging package gained the ability to allow users to set their own
@ref{900,,LogRecord} subclasses, using the @ref{2052,,setLogRecordFactory()} function.
You can use this to set your own subclass of @ref{900,,LogRecord}, which does the
Right Thing by overriding the @ref{2050,,getMessage()} method. The base
class implementation of this method is where the @code{msg % args} formatting
happens, and where you can substitute your alternate formatting; however, you
should be careful to support all formatting styles and allow %-formatting as
the default, to ensure interoperability with other code. Care should also be
taken to call @code{str(self.msg)}, just as the base implementation does.

Refer to the reference documentation on @ref{2052,,setLogRecordFactory()} and
@ref{900,,LogRecord} for more information.

@node Using custom message objects,,Using LogRecord factories,Using particular formatting styles throughout your application
@anchor{howto/logging-cookbook using-custom-message-objects}@anchor{412a}
@subsubsection Using custom message objects


There is another, perhaps simpler way that you can use @{@}- and $- formatting to
construct your individual log messages. You may recall (from
@ref{2054,,使用任意对象作为消息}) that when logging you can use an arbitrary
object as a message format string, and that the logging package will call
@ref{329,,str()} on that object to get the actual format string. Consider the
following two classes:

@example
class BraceMessage:
    def __init__(self, fmt, /, *args, **kwargs):
        self.fmt = fmt
        self.args = args
        self.kwargs = kwargs

    def __str__(self):
        return self.fmt.format(*self.args, **self.kwargs)

class DollarMessage:
    def __init__(self, fmt, /, **kwargs):
        self.fmt = fmt
        self.kwargs = kwargs

    def __str__(self):
        from string import Template
        return Template(self.fmt).substitute(**self.kwargs)
@end example

Either of these can be used in place of a format string, to allow @{@}- or
$-formatting to be used to build the actual "message" part which appears in the
formatted log output in place of “%(message)s” or “@{message@}” or “$message”.
If you find it a little unwieldy to use the class names whenever you want to log
something, you can make it more palatable if you use an alias such as @code{M} or
@code{_} for the message (or perhaps @code{__}, if you are using @code{_} for
localization).

Examples of this approach are given below. Firstly, formatting with
@ref{4d4,,str.format()}:

@example
>>> __ = BraceMessage
>>> print(__('Message with @{0@} @{1@}', 2, 'placeholders'))
Message with 2 placeholders
>>> class Point: pass
...
>>> p = Point()
>>> p.x = 0.5
>>> p.y = 0.5
>>> print(__('Message with coordinates: (@{point.x:.2f@}, @{point.y:.2f@})', point=p))
Message with coordinates: (0.50, 0.50)
@end example

Secondly, formatting with @ref{3e3,,string.Template}:

@example
>>> __ = DollarMessage
>>> print(__('Message with $num $what', num=2, what='placeholders'))
Message with 2 placeholders
>>>
@end example

One thing to note is that you pay no significant performance penalty with this
approach: the actual formatting happens not when you make the logging call, but
when (and if) the logged message is actually about to be output to a log by a
handler. So the only slightly unusual thing which might trip you up is that the
parentheses go around the format string and the arguments, not just the format
string. That’s because the __ notation is just syntax sugar for a constructor
call to one of the @code{XXXMessage} classes shown above.

@node Configuring filters with dictConfig,Customized exception formatting,Using particular formatting styles throughout your application,日志操作手册
@anchor{howto/logging-cookbook configuring-filters-with-dictconfig}@anchor{412b}@anchor{howto/logging-cookbook filters-dictconfig}@anchor{412c}
@subsection Configuring filters with @code{dictConfig()}


You @emph{can} configure filters using @ref{b24,,dictConfig()}, though it
might not be obvious at first glance how to do it (hence this recipe). Since
@ref{b70,,Filter} is the only filter class included in the standard
library, and it is unlikely to cater to many requirements (it's only there as a
base class), you will typically need to define your own @ref{b70,,Filter}
subclass with an overridden @ref{204a,,filter()} method. To do this,
specify the @code{()} key in the configuration dictionary for the filter,
specifying a callable which will be used to create the filter (a class is the
most obvious, but you can provide any callable which returns a
@ref{b70,,Filter} instance). Here is a complete example:

@example
import logging
import logging.config
import sys

class MyFilter(logging.Filter):
    def __init__(self, param=None):
        self.param = param

    def filter(self, record):
        if self.param is None:
            allow = True
        else:
            allow = self.param not in record.msg
        if allow:
            record.msg = 'changed: ' + record.msg
        return allow

LOGGING = @{
    'version': 1,
    'filters': @{
        'myfilter': @{
            '()': MyFilter,
            'param': 'noshow',
        @}
    @},
    'handlers': @{
        'console': @{
            'class': 'logging.StreamHandler',
            'filters': ['myfilter']
        @}
    @},
    'root': @{
        'level': 'DEBUG',
        'handlers': ['console']
    @},
@}

if __name__ == '__main__':
    logging.config.dictConfig(LOGGING)
    logging.debug('hello')
    logging.debug('hello - noshow')
@end example

This example shows how you can pass configuration data to the callable which
constructs the instance, in the form of keyword parameters. When run, the above
script will print:

@example
changed: hello
@end example

which shows that the filter is working as configured.

A couple of extra points to note:


@itemize *

@item 
If you can't refer to the callable directly in the configuration (e.g. if it
lives in a different module, and you can't import it directly where the
configuration dictionary is), you can use the form @code{ext://...} as described
in @ref{207a,,Access to external objects}. For example, you could have used
the text @code{'ext://__main__.MyFilter'} instead of @code{MyFilter} in the above
example.

@item 
As well as for filters, this technique can also be used to configure custom
handlers and formatters. See @ref{2073,,用户定义对象} for more
information on how logging supports using user-defined objects in its
configuration, and see the other cookbook recipe @ref{4126,,Customizing handlers with dictConfig()} above.
@end itemize

@node Customized exception formatting,Speaking logging messages,Configuring filters with dictConfig,日志操作手册
@anchor{howto/logging-cookbook custom-format-exception}@anchor{412d}@anchor{howto/logging-cookbook customized-exception-formatting}@anchor{412e}
@subsection Customized exception formatting


There might be times when you want to do customized exception formatting - for
argument's sake, let's say you want exactly one line per logged event, even
when exception information is present. You can do this with a custom formatter
class, as shown in the following example:

@example
import logging

class OneLineExceptionFormatter(logging.Formatter):
    def formatException(self, exc_info):
        """
        Format an exception so that it prints on a single line.
        """
        result = super(OneLineExceptionFormatter, self).formatException(exc_info)
        return repr(result)  # or format into one line however you want to

    def format(self, record):
        s = super(OneLineExceptionFormatter, self).format(record)
        if record.exc_text:
            s = s.replace('\n', '@w{'}) + '|'
        return s

def configure_logging():
    fh = logging.FileHandler('output.txt', 'w')
    f = OneLineExceptionFormatter('%(asctime)s|%(levelname)s|%(message)s|',
                                  '%d/%m/%Y %H:%M:%S')
    fh.setFormatter(f)
    root = logging.getLogger()
    root.setLevel(logging.DEBUG)
    root.addHandler(fh)

def main():
    configure_logging()
    logging.info('Sample message')
    try:
        x = 1 / 0
    except ZeroDivisionError as e:
        logging.exception('ZeroDivisionError: %s', e)

if __name__ == '__main__':
    main()
@end example

When run, this produces a file with exactly two lines:

@example
28/01/2015 07:21:23|INFO|Sample message|
28/01/2015 07:21:23|ERROR|ZeroDivisionError: integer division or modulo by zero|'Traceback (most recent call last):\n  File "logtest7.py", line 30, in main\n    x = 1 / 0\nZeroDivisionError: integer division or modulo by zero'|
@end example

While the above treatment is simplistic, it points the way to how exception
information can be formatted to your liking. The @ref{113,,traceback} module may be
helpful for more specialized needs.

@node Speaking logging messages,缓冲日志消息并有条件地输出它们,Customized exception formatting,日志操作手册
@anchor{howto/logging-cookbook speaking-logging-messages}@anchor{412f}@anchor{howto/logging-cookbook spoken-messages}@anchor{4130}
@subsection Speaking logging messages


There might be situations when it is desirable to have logging messages rendered
in an audible rather than a visible format. This is easy to do if you have
text-to-speech (TTS) functionality available in your system, even if it doesn't have
a Python binding. Most TTS systems have a command line program you can run, and
this can be invoked from a handler using @ref{f9,,subprocess}. It's assumed here
that TTS command line programs won't expect to interact with users or take a
long time to complete, and that the frequency of logged messages will be not so
high as to swamp the user with messages, and that it's acceptable to have the
messages spoken one at a time rather than concurrently, The example implementation
below waits for one message to be spoken before the next is processed, and this
might cause other handlers to be kept waiting. Here is a short example showing
the approach, which assumes that the @code{espeak} TTS package is available:

@example
import logging
import subprocess
import sys

class TTSHandler(logging.Handler):
    def emit(self, record):
        msg = self.format(record)
        # Speak slowly in a female English voice
        cmd = ['espeak', '-s150', '-ven+f3', msg]
        p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT)
        # wait for the program to finish
        p.communicate()

def configure_logging():
    h = TTSHandler()
    root = logging.getLogger()
    root.addHandler(h)
    # the default formatter just returns the message
    root.setLevel(logging.DEBUG)

def main():
    logging.info('Hello')
    logging.debug('Goodbye')

if __name__ == '__main__':
    configure_logging()
    sys.exit(main())
@end example

When run, this script should say "Hello" and then "Goodbye" in a female voice.

The above approach can, of course, be adapted to other TTS systems and even
other systems altogether which can process messages via external programs run
from a command line.

@node 缓冲日志消息并有条件地输出它们,通过配置使用UTC GMT 格式化时间,Speaking logging messages,日志操作手册
@anchor{howto/logging-cookbook buffered-logging}@anchor{4131}@anchor{howto/logging-cookbook buffering-logging-messages-and-outputting-them-conditionally}@anchor{4132}
@subsection 缓冲日志消息并有条件地输出它们


在某些情况下，你可能希望在临时区域中记录日志消息，并且只在发生某种特定的情况下才输出它们。 例如，你可能希望起始在函数中记录调试事件，如果函数执行完成且没有错误，你不希望输出收集的调试信息以避免造成日志混乱，但如果出现错误，那么你希望所有调试以及错误消息被输出。

下面是一个示例，展示如何在你的日志记录函数上使用装饰器以实现这一功能。该示例使用 @ref{207d,,logging.handlers.MemoryHandler} ，它允许缓冲已记录的事件直到某些条件发生，缓冲的事件才会被刷新（@code{flushed}） - 传递给另一个处理程序（ @code{target} handler）进行处理。 默认情况下， @code{MemoryHandler} 在其缓冲区被填满时被刷新，或者看到一个级别大于或等于指定阈值的事件。 如果想要自定义刷新行为，你可以通过更专业的 @code{MemoryHandler} 子类来使用这个秘诀。

这个示例脚本有一个简单的函数 @code{foo} ，它只是在所有的日志级别中循环运行，写到 @code{sys.stderr} ，说明它要记录在哪个级别上，然后在这个级别上实际记录一个消息。你可以给 @code{foo} 传递一个参数，如果为 true ，它将在ERROR和CRITICAL级别记录，否则，它只在DEBUG、INFO和WARNING级别记录。

脚本只是使用了一个装饰器来装饰 @code{foo}，这个装饰器将记录执行所需的条件。装饰器使用一个记录器作为参数，并在调用被装饰的函数期间附加一个内存处理程序。装饰器可以使用目标处理程序、记录级别和缓冲区的容量（缓冲记录的数量）来附加参数。这些参数分别默认为写入`@w{`}sys.stderr`@w{`} 的 @ref{b6e,,StreamHandler} ， @code{logging.ERROR} 和 @code{100}。

以下是脚本：

@example
import logging
from logging.handlers import MemoryHandler
import sys

logger = logging.getLogger(__name__)
logger.addHandler(logging.NullHandler())

def log_if_errors(logger, target_handler=None, flush_level=None, capacity=None):
    if target_handler is None:
        target_handler = logging.StreamHandler()
    if flush_level is None:
        flush_level = logging.ERROR
    if capacity is None:
        capacity = 100
    handler = MemoryHandler(capacity, flushLevel=flush_level, target=target_handler)

    def decorator(fn):
        def wrapper(*args, **kwargs):
            logger.addHandler(handler)
            try:
                return fn(*args, **kwargs)
            except Exception:
                logger.exception('call failed')
                raise
            finally:
                super(MemoryHandler, handler).flush()
                logger.removeHandler(handler)
        return wrapper

    return decorator

def write_line(s):
    sys.stderr.write('%s\n' % s)

def foo(fail=False):
    write_line('about to log at DEBUG ...')
    logger.debug('Actually logged at DEBUG')
    write_line('about to log at INFO ...')
    logger.info('Actually logged at INFO')
    write_line('about to log at WARNING ...')
    logger.warning('Actually logged at WARNING')
    if fail:
        write_line('about to log at ERROR ...')
        logger.error('Actually logged at ERROR')
        write_line('about to log at CRITICAL ...')
        logger.critical('Actually logged at CRITICAL')
    return fail

decorated_foo = log_if_errors(logger)(foo)

if __name__ == '__main__':
    logger.setLevel(logging.DEBUG)
    write_line('Calling undecorated foo with False')
    assert not foo(False)
    write_line('Calling undecorated foo with True')
    assert foo(True)
    write_line('Calling decorated foo with False')
    assert not decorated_foo(False)
    write_line('Calling decorated foo with True')
    assert decorated_foo(True)
@end example

运行此脚本时，应看到以下输出：

@example
Calling undecorated foo with False
about to log at DEBUG ...
about to log at INFO ...
about to log at WARNING ...
Calling undecorated foo with True
about to log at DEBUG ...
about to log at INFO ...
about to log at WARNING ...
about to log at ERROR ...
about to log at CRITICAL ...
Calling decorated foo with False
about to log at DEBUG ...
about to log at INFO ...
about to log at WARNING ...
Calling decorated foo with True
about to log at DEBUG ...
about to log at INFO ...
about to log at WARNING ...
about to log at ERROR ...
Actually logged at DEBUG
Actually logged at INFO
Actually logged at WARNING
Actually logged at ERROR
about to log at CRITICAL ...
Actually logged at CRITICAL
@end example

如你所见，实际日志记录输出仅在消息等级为ERROR或更高的事件时发生，但在这种情况下，任何之前较低消息等级的事件还会被记录。

你当然可以使用传统的装饰方法:

@example
@@log_if_errors(logger)
def foo(fail=False):
    ...
@end example

@node 通过配置使用UTC GMT 格式化时间,使用上下文管理器的可选的日志记录,缓冲日志消息并有条件地输出它们,日志操作手册
@anchor{howto/logging-cookbook formatting-times-using-utc-gmt-via-configuration}@anchor{4133}@anchor{howto/logging-cookbook utc-formatting}@anchor{4134}
@subsection 通过配置使用UTC (GMT) 格式化时间


有时候，你希望使用UTC来格式化时间，这可以通过使用一个类来实现，例如`UTCFormatter`，如下所示：

@example
import logging
import time

class UTCFormatter(logging.Formatter):
    converter = time.gmtime
@end example

然后你可以在你的代码中使用 @code{UTCFormatter}，而不是 @ref{201d,,Formatter}。 如果你想通过配置来实现这一功能，你可以使用 @ref{b24,,dictConfig()} API 来完成，该方法在以下完整示例中展示:

@example
import logging
import logging.config
import time

class UTCFormatter(logging.Formatter):
    converter = time.gmtime

LOGGING = @{
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': @{
        'utc': @{
            '()': UTCFormatter,
            'format': '%(asctime)s %(message)s',
        @},
        'local': @{
            'format': '%(asctime)s %(message)s',
        @}
    @},
    'handlers': @{
        'console1': @{
            'class': 'logging.StreamHandler',
            'formatter': 'utc',
        @},
        'console2': @{
            'class': 'logging.StreamHandler',
            'formatter': 'local',
        @},
    @},
    'root': @{
        'handlers': ['console1', 'console2'],
   @}
@}

if __name__ == '__main__':
    logging.config.dictConfig(LOGGING)
    logging.warning('The local time is %s', time.asctime())
@end example

脚本会运行输出类似下面的内容:

@example
2015-10-17 12:53:29,501 The local time is Sat Oct 17 13:53:29 2015
2015-10-17 13:53:29,501 The local time is Sat Oct 17 13:53:29 2015
@end example

展示了如何将时间格式化为本地时间和UTC两种形式，其中每种形式对应一个日志处理器 。

@node 使用上下文管理器的可选的日志记录,A CLI application starter template,通过配置使用UTC GMT 格式化时间,日志操作手册
@anchor{howto/logging-cookbook context-manager}@anchor{4135}@anchor{howto/logging-cookbook using-a-context-manager-for-selective-logging}@anchor{4136}
@subsection 使用上下文管理器的可选的日志记录


有时候，我们需要暂时更改日志配置，并在执行某些操作后将其还原。为此，上下文管理器是实现保存和恢复日志上下文的最明显的方式。这是一个关于上下文管理器的简单例子，它允许你在上下文管理器的作用域内更改日志记录等级以及增加日志处理器：

@example
import logging
import sys

class LoggingContext:
    def __init__(self, logger, level=None, handler=None, close=True):
        self.logger = logger
        self.level = level
        self.handler = handler
        self.close = close

    def __enter__(self):
        if self.level is not None:
            self.old_level = self.logger.level
            self.logger.setLevel(self.level)
        if self.handler:
            self.logger.addHandler(self.handler)

    def __exit__(self, et, ev, tb):
        if self.level is not None:
            self.logger.setLevel(self.old_level)
        if self.handler:
            self.logger.removeHandler(self.handler)
        if self.handler and self.close:
            self.handler.close()
        # implicit return of None => don't swallow exceptions
@end example

如果指定上下文管理器的日志记录等级属性，则在上下文管理器的with语句所涵盖的代码中，日志记录器的记录等级将临时设置为上下文管理器所配置的日志记录等级。 如果指定上下文管理的日志处理器属性，则该句柄在进入上下文管理器的上下文时添加到记录器中，并在退出时被删除。 如果你再也不需要该日志处理器时，你可以让上下文管理器在退出上下文管理器的上下文时关闭它。

为了说明它是如何工作的，我们可以在上面添加以下代码块:

@example
if __name__ == '__main__':
    logger = logging.getLogger('foo')
    logger.addHandler(logging.StreamHandler())
    logger.setLevel(logging.INFO)
    logger.info('1. This should appear just once on stderr.')
    logger.debug('2. This should not appear.')
    with LoggingContext(logger, level=logging.DEBUG):
        logger.debug('3. This should appear once on stderr.')
    logger.debug('4. This should not appear.')
    h = logging.StreamHandler(sys.stdout)
    with LoggingContext(logger, level=logging.DEBUG, handler=h, close=True):
        logger.debug('5. This should appear twice - once on stderr and once on stdout.')
    logger.info('6. This should appear just once on stderr.')
    logger.debug('7. This should not appear.')
@end example

我们最初设置日志记录器的消息等级为 @code{INFO}，因此消息#1出现，消息#2没有出现。在接下来的 @code{with`@w{`}代码块中我们暂时将消息等级变更为 `@w{`}DEBUG}，从而消息 #3 出现。在这一代码块退出后，日志记录器的消息等级恢复为 @code{INFO}，从而消息 #4 没有出现。在下一个 @code{with} 代码块中，我们再一次将设置消息等级设置为 @code{DEBUG}，同时添加一个将消息写入 @code{sys.stdout} 的日志处理器。因此，消息#5在控制台出现两次 (分别通过 @code{stderr} 和 @code{stdout})。在 @code{with} 语句完成后，状态与之前一样，因此消息 #6 出现（类似消息 #1），而消息 #7 没有出现（类似消息 #2）。

如果我们运行生成的脚本，结果如下：

@example
$ python logctx.py
1. This should appear just once on stderr.
3. This should appear once on stderr.
5. This should appear twice - once on stderr and once on stdout.
5. This should appear twice - once on stderr and once on stdout.
6. This should appear just once on stderr.
@end example

我们将`@w{`}stderr`@w{`}标准错误重定向到`@w{`}/dev/null`@w{`}，我再次运行生成的脚步，唯一被写入`@w{`}stdout`@w{`}标准输出的消息，即我们所能看见的消息，如下：

@example
$ python logctx.py 2>/dev/null
5. This should appear twice - once on stderr and once on stdout.
@end example

再一次，将 @code{stdout} 标准输出重定向到 @code{/dev/null}，我获得如下结果：

@example
$ python logctx.py >/dev/null
1. This should appear just once on stderr.
3. This should appear once on stderr.
5. This should appear twice - once on stderr and once on stdout.
6. This should appear just once on stderr.
@end example

在这种情况下，与预期一致，打印到 @code{stdout} 标准输出的消息＃5不会出现。

当然，这里描述的方法可以被推广，例如临时附加日志记录过滤器。 请注意，上面的代码适用于Python 2以及Python 3。

@node A CLI application starter template,A Qt GUI for logging,使用上下文管理器的可选的日志记录,日志操作手册
@anchor{howto/logging-cookbook a-cli-application-starter-template}@anchor{4137}@anchor{howto/logging-cookbook starter-template}@anchor{4138}
@subsection A CLI application starter template


Here's an example which shows how you can:


@itemize *

@item 
Use a logging level based on command-line arguments

@item 
Dispatch to multiple subcommands in separate files, all logging at the same
level in a consistent way

@item 
Make use of simple, minimal configuration
@end itemize

Suppose we have a command-line application whose job is to stop, start or
restart some services. This could be organised for the purposes of illustration
as a file @code{app.py} that is the main script for the application, with individual
commands implemented in @code{start.py}, @code{stop.py} and @code{restart.py}. Suppose
further that we want to control the verbosity of the application via a
command-line argument, defaulting to @code{logging.INFO}. Here's one way that
@code{app.py} could be written:

@example
import argparse
import importlib
import logging
import os
import sys

def main(args=None):
    scriptname = os.path.basename(__file__)
    parser = argparse.ArgumentParser(scriptname)
    levels = ('DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL')
    parser.add_argument('--log-level', default='INFO', choices=levels)
    subparsers = parser.add_subparsers(dest='command',
                                       help='Available commands:')
    start_cmd = subparsers.add_parser('start', help='Start a service')
    start_cmd.add_argument('name', metavar='NAME',
                           help='Name of service to start')
    stop_cmd = subparsers.add_parser('stop',
                                     help='Stop one or more services')
    stop_cmd.add_argument('names', metavar='NAME', nargs='+',
                          help='Name of service to stop')
    restart_cmd = subparsers.add_parser('restart',
                                        help='Restart one or more services')
    restart_cmd.add_argument('names', metavar='NAME', nargs='+',
                             help='Name of service to restart')
    options = parser.parse_args()
    # the code to dispatch commands could all be in this file. For the purposes
    # of illustration only, we implement each command in a separate module.
    try:
        mod = importlib.import_module(options.command)
        cmd = getattr(mod, 'command')
    except (ImportError, AttributeError):
        print('Unable to find the code for command \'%s\'@w{'} % options.command)
        return 1
    # Could get fancy here and load configuration from file or dictionary
    logging.basicConfig(level=options.log_level,
                        format='%(levelname)s %(name)s %(message)s')
    cmd(options)

if __name__ == '__main__':
    sys.exit(main())
@end example

And the @code{start}, @code{stop} and @code{restart} commands can be implemented in
separate modules, like so for starting:

@example
# start.py
import logging

logger = logging.getLogger(__name__)

def command(options):
    logger.debug('About to start %s', options.name)
    # actually do the command processing here ...
    logger.info('Started the \'%s\' service.', options.name)
@end example

and thus for stopping:

@example
# stop.py
import logging

logger = logging.getLogger(__name__)

def command(options):
    n = len(options.names)
    if n == 1:
        plural = '@w{'}
        services = '\'%s\'@w{'} % options.names[0]
    else:
        plural = 's'
        services = ', '.join('\'%s\'@w{'} % name for name in options.names)
        i = services.rfind(', ')
        services = services[:i] + ' and ' + services[i + 2:]
    logger.debug('About to stop %s', services)
    # actually do the command processing here ...
    logger.info('Stopped the %s service%s.', services, plural)
@end example

and similarly for restarting:

@example
# restart.py
import logging

logger = logging.getLogger(__name__)

def command(options):
    n = len(options.names)
    if n == 1:
        plural = '@w{'}
        services = '\'%s\'@w{'} % options.names[0]
    else:
        plural = 's'
        services = ', '.join('\'%s\'@w{'} % name for name in options.names)
        i = services.rfind(', ')
        services = services[:i] + ' and ' + services[i + 2:]
    logger.debug('About to restart %s', services)
    # actually do the command processing here ...
    logger.info('Restarted the %s service%s.', services, plural)
@end example

If we run this application with the default log level, we get output like this:

@example
$ python app.py start foo
INFO start Started the 'foo' service.

$ python app.py stop foo bar
INFO stop Stopped the 'foo' and 'bar' services.

$ python app.py restart foo bar baz
INFO restart Restarted the 'foo', 'bar' and 'baz' services.
@end example

The first word is the logging level, and the second word is the module or
package name of the place where the event was logged.

If we change the logging level, then we can change the information sent to the
log. For example, if we want more information:

@example
$ python app.py --log-level DEBUG start foo
DEBUG start About to start foo
INFO start Started the 'foo' service.

$ python app.py --log-level DEBUG stop foo bar
DEBUG stop About to stop 'foo' and 'bar'
INFO stop Stopped the 'foo' and 'bar' services.

$ python app.py --log-level DEBUG restart foo bar baz
DEBUG restart About to restart 'foo', 'bar' and 'baz'
INFO restart Restarted the 'foo', 'bar' and 'baz' services.
@end example

And if we want less:

@example
$ python app.py --log-level WARNING start foo
$ python app.py --log-level WARNING stop foo bar
$ python app.py --log-level WARNING restart foo bar baz
@end example

In this case, the commands don't print anything to the console, since nothing
at @code{WARNING} level or above is logged by them.

@node A Qt GUI for logging,,A CLI application starter template,日志操作手册
@anchor{howto/logging-cookbook a-qt-gui-for-logging}@anchor{4139}@anchor{howto/logging-cookbook qt-gui}@anchor{413a}
@subsection A Qt GUI for logging


A question that comes up from time to time is about how to log to a GUI
application. The Qt@footnote{https://www.qt.io/} framework is a popular
cross-platform UI framework with Python bindings using PySide2@footnote{https://pypi.org/project/PySide2/} or PyQt5@footnote{https://pypi.org/project/PyQt5/} libraries.

The following example shows how to log to a Qt GUI. This introduces a simple
@code{QtHandler} class which takes a callable, which should be a slot in the main
thread that does GUI updates. A worker thread is also created to show how you
can log to the GUI from both the UI itself (via a button for manual logging)
as well as a worker thread doing work in the background (here, just logging
messages at random levels with random short delays in between).

The worker thread is implemented using Qt's @code{QThread} class rather than the
@ref{109,,threading} module, as there are circumstances where one has to use
@code{QThread}, which offers better integration with other @code{Qt} components.

The code should work with recent releases of either @code{PySide2} or @code{PyQt5}.
You should be able to adapt the approach to earlier versions of Qt. Please
refer to the comments in the code snippet for more detailed information.

@example
import datetime
import logging
import random
import sys
import time

# Deal with minor differences between PySide2 and PyQt5
try:
    from PySide2 import QtCore, QtGui, QtWidgets
    Signal = QtCore.Signal
    Slot = QtCore.Slot
except ImportError:
    from PyQt5 import QtCore, QtGui, QtWidgets
    Signal = QtCore.pyqtSignal
    Slot = QtCore.pyqtSlot


logger = logging.getLogger(__name__)


#
# Signals need to be contained in a QObject or subclass in order to be correctly
# initialized.
#
class Signaller(QtCore.QObject):
    signal = Signal(str, logging.LogRecord)

#
# Output to a Qt GUI is only supposed to happen on the main thread. So, this
# handler is designed to take a slot function which is set up to run in the main
# thread. In this example, the function takes a string argument which is a
# formatted log message, and the log record which generated it. The formatted
# string is just a convenience - you could format a string for output any way
# you like in the slot function itself.
#
# You specify the slot function to do whatever GUI updates you want. The handler
# doesn't know or care about specific UI elements.
#
class QtHandler(logging.Handler):
    def __init__(self, slotfunc, *args, **kwargs):
        super(QtHandler, self).__init__(*args, **kwargs)
        self.signaller = Signaller()
        self.signaller.signal.connect(slotfunc)

    def emit(self, record):
        s = self.format(record)
        self.signaller.signal.emit(s, record)

#
# This example uses QThreads, which means that the threads at the Python level
# are named something like "Dummy-1". The function below gets the Qt name of the
# current thread.
#
def ctname():
    return QtCore.QThread.currentThread().objectName()


#
# Used to generate random levels for logging.
#
LEVELS = (logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR,
          logging.CRITICAL)

#
# This worker class represents work that is done in a thread separate to the
# main thread. The way the thread is kicked off to do work is via a button press
# that connects to a slot in the worker.
#
# Because the default threadName value in the LogRecord isn't much use, we add
# a qThreadName which contains the QThread name as computed above, and pass that
# value in an "extra" dictionary which is used to update the LogRecord with the
# QThread name.
#
# This example worker just outputs messages sequentially, interspersed with
# random delays of the order of a few seconds.
#
class Worker(QtCore.QObject):
    @@Slot()
    def start(self):
        extra = @{'qThreadName': ctname() @}
        logger.debug('Started work', extra=extra)
        i = 1
        # Let the thread run until interrupted. This allows reasonably clean
        # thread termination.
        while not QtCore.QThread.currentThread().isInterruptionRequested():
            delay = 0.5 + random.random() * 2
            time.sleep(delay)
            level = random.choice(LEVELS)
            logger.log(level, 'Message after delay of %3.1f: %d', delay, i, extra=extra)
            i += 1

#
# Implement a simple UI for this cookbook example. This contains:
#
# * A read-only text edit window which holds formatted log messages
# * A button to start work and log stuff in a separate thread
# * A button to log something from the main thread
# * A button to clear the log window
#
class Window(QtWidgets.QWidget):

    COLORS = @{
        logging.DEBUG: 'black',
        logging.INFO: 'blue',
        logging.WARNING: 'orange',
        logging.ERROR: 'red',
        logging.CRITICAL: 'purple',
    @}

    def __init__(self, app):
        super(Window, self).__init__()
        self.app = app
        self.textedit = te = QtWidgets.QPlainTextEdit(self)
        # Set whatever the default monospace font is for the platform
        f = QtGui.QFont('nosuchfont')
        f.setStyleHint(f.Monospace)
        te.setFont(f)
        te.setReadOnly(True)
        PB = QtWidgets.QPushButton
        self.work_button = PB('Start background work', self)
        self.log_button = PB('Log a message at a random level', self)
        self.clear_button = PB('Clear log window', self)
        self.handler = h = QtHandler(self.update_status)
        # Remember to use qThreadName rather than threadName in the format string.
        fs = '%(asctime)s %(qThreadName)-12s %(levelname)-8s %(message)s'
        formatter = logging.Formatter(fs)
        h.setFormatter(formatter)
        logger.addHandler(h)
        # Set up to terminate the QThread when we exit
        app.aboutToQuit.connect(self.force_quit)

        # Lay out all the widgets
        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(te)
        layout.addWidget(self.work_button)
        layout.addWidget(self.log_button)
        layout.addWidget(self.clear_button)
        self.setFixedSize(900, 400)

        # Connect the non-worker slots and signals
        self.log_button.clicked.connect(self.manual_update)
        self.clear_button.clicked.connect(self.clear_display)

        # Start a new worker thread and connect the slots for the worker
        self.start_thread()
        self.work_button.clicked.connect(self.worker.start)
        # Once started, the button should be disabled
        self.work_button.clicked.connect(lambda : self.work_button.setEnabled(False))

    def start_thread(self):
        self.worker = Worker()
        self.worker_thread = QtCore.QThread()
        self.worker.setObjectName('Worker')
        self.worker_thread.setObjectName('WorkerThread')  # for qThreadName
        self.worker.moveToThread(self.worker_thread)
        # This will start an event loop in the worker thread
        self.worker_thread.start()

    def kill_thread(self):
        # Just tell the worker to stop, then tell it to quit and wait for that
        # to happen
        self.worker_thread.requestInterruption()
        if self.worker_thread.isRunning():
            self.worker_thread.quit()
            self.worker_thread.wait()
        else:
            print('worker has already exited.')

    def force_quit(self):
        # For use when the window is closed
        if self.worker_thread.isRunning():
            self.kill_thread()

    # The functions below update the UI and run in the main thread because
    # that's where the slots are set up

    @@Slot(str, logging.LogRecord)
    def update_status(self, status, record):
        color = self.COLORS.get(record.levelno, 'black')
        s = '<pre><font color="%s">%s</font></pre>' % (color, status)
        self.textedit.appendHtml(s)

    @@Slot()
    def manual_update(self):
        # This function uses the formatted message passed in, but also uses
        # information from the record to format the message in an appropriate
        # color according to its severity (level).
        level = random.choice(LEVELS)
        extra = @{'qThreadName': ctname() @}
        logger.log(level, 'Manually logged!', extra=extra)

    @@Slot()
    def clear_display(self):
        self.textedit.clear()


def main():
    QtCore.QThread.currentThread().setObjectName('MainThread')
    logging.getLogger().setLevel(logging.DEBUG)
    app = QtWidgets.QApplication(sys.argv)
    example = Window(app)
    example.show()
    sys.exit(app.exec_())

if __name__=='__main__':
    main()
@end example

@node 正则表达式HOWTO,套接字编程指南,日志操作手册,Python 常用指引
@anchor{howto/regex doc}@anchor{413b}@anchor{howto/regex regex-howto}@anchor{16e5}@anchor{howto/regex regular-expression-howto}@anchor{413c}
@section 正则表达式HOWTO


@*作者: 
A.M. Kuchling <@email{amk@@amk.ca}>


@c TODO:
@c Document lookbehind assertions
@c Better way of displaying a RE, a string, and what it matches
@c Mention optional argument to match.groups()
@c Unicode (at least a reference)

@subsubheading 摘要



本文档是在Python中使用 @ref{dd,,re} 模块使用正则表达式的入门教程。 它提供了比“标准库参考”中相应部分更平和的介绍。

@menu
* 概述: 概述<18>. 
* 简单模式:: 
* 使用正则表达式:: 
* 更多模式能力:: 
* 修改字符串:: 
* 常见问题: 常见问题<2>. 
* 反馈:: 

@end menu

@node 概述<18>,简单模式,,正则表达式HOWTO
@anchor{howto/regex introduction}@anchor{413d}
@subsection 概述


正则表达式（称为RE，或正则，或正则表达式模式）本质上是嵌入在Python中的一种微小的、高度专业化的编程语言，可通过 @ref{dd,,re} 模块获得。 使用这种小语言，你可以为要匹配的可能字符串集指定规则；此集可能包含英语句子，电子邮件地址，TeX命令或你喜欢的任何内容。 然后，您可以询问诸如“此字符串是否与模式匹配？”或“此字符串中的模式是否匹配？”等问题。 你还可以使用正则修改字符串或以各种方式将其拆分。

正则表达式模式被编译成一系列字节码，然后由用 C 编写的匹配引擎执行。对于高级用途，可能需要特别注意引擎如何执行给定的正则，并将正则写入以某种方式生成运行速度更快的字节码。 本文档未涉及优化，因为它要求你充分了解匹配引擎的内部结构。

正则表达式语言相对较小且受限制，因此并非所有可能的字符串处理任务都可以使用正则表达式完成。 还有一些任务 @emph{可以} 用正则表达式完成，但表达式变得非常复杂。 在这些情况下，你最好编写 Python 代码来进行处理；虽然 Python 代码比精心设计的正则表达式慢，但它也可能更容易理解。

@node 简单模式,使用正则表达式,概述<18>,正则表达式HOWTO
@anchor{howto/regex simple-patterns}@anchor{413e}
@subsection 简单模式


我们首先要了解最简单的正则表达式。 由于正则表达式用于对字符串进行操作，因此我们将从最常见的任务开始：匹配字符。

有关正则表达式（确定性和非确定性有限自动机）的计算机科学的详细解释，你可以参考几乎所有有关编写编译器的教科书。

@menu
* 匹配字符:: 
* 重复:: 

@end menu

@node 匹配字符,重复,,简单模式
@anchor{howto/regex matching-characters}@anchor{413f}
@subsubsection 匹配字符


大多数字母和字符只会匹配自己。 例如，正则表达式 @code{test} 将完全匹配字符串 @code{test} 。 （你可以启用一个不区分大小写的模式，让这个正则匹配 @code{Test} 或 @code{TEST}，稍后会详细介绍。）

这条规则有例外；一些字符是特殊的 @emph{metacharacters} ，并且不匹配自己。 相反，它们表示应该匹配一些与众不同的东西，或者通过重复它们或改变它们的含义来影响正则的其他部分。 本文档的大部分内容都致力于讨论各种元字符及其功能。

这是元字符的完整列表；它们的意思将在本HOWTO的其余部分讨论。

@example
. ^ $ * + ? @{ @} [ ] \ | ( )
@end example

我们将看到的第一个元字符是 @code{[} 和 @code{]} 。 它们用于指定字符类，它是你希望匹配的一组字符。 可以单独列出字符，也可以通过给出两个字符并用 @code{'-'} 标记将它们分开来表示一系列字符。 例如， @code{[abc]} 将匹配任何字符 @code{a}、 @code{b} 或 @code{c} ；这与 @code{[a-c]} 相同，它使用一个范围来表示同一组字符。 如果你只想匹配小写字母，你的正则是 @code{[a-z]} 。

字符类中的元字符不生效。 例如，@code{[akm$]} 将匹配 @code{'a'} ， @code{'k'} 、 @code{'m'} 或 @code{'$'} 中的任意字符； @code{'$'} 通常是一个元字符，但在一个字符类中它被剥夺了特殊性。

你可以通过以下方式匹配 @emph{complementing} 设置的字符类中未列出的字符。这通过包含一个 @code{'^'} 作为该类的第一个字符来表示。 例如，@code{[^5]} 将匹配除 @code{'5'} 之外的任何字符。 如果插入符出现在字符类的其他位置，则它没有特殊含义。 例如：@code{[5^]} 将匹配 @code{'5'} 或 @code{'^'}。

也许最重要的元字符是反斜杠，@code{\}。 与 Python 字符串文字一样，反斜杠后面可以跟各种字符，以指示各种特殊序列。它也用于转义所有元字符，因此您仍然可以在模式中匹配它们；例如，如果你需要匹配 @code{[} 或 @code{\}，你可以在它们前面加一个反斜杠来移除它们的特殊含义：@code{\[} 或 @code{\\}。

一些以 @code{'\'} 开头的特殊序列表示通常有用的预定义字符集，例如数字集、字母集或任何非空格的集合。

让我们举一个例子：@code{\w} 匹配任何字母数字字符。 如果正则表达式模式以字节类表示，这相当于类 @code{[a-zA-Z0-9_]}。如果正则表达式是一个字符串，@code{\w} 将匹配由 @ref{11a,,unicodedata} 模块提供的 Unicode 数据库中标记为字母的所有字符。 通过在编译正则表达式时提供 @ref{3c0,,re.ASCII} 标志，可以在字符串模式中使用更为受限制的 @code{\w} 定义。

以下特殊序列列表不完整。 有关 Unicode 字符串模式的序列和扩展类定义的完整列表，请参阅标准库参考中的最后一部分 @ref{16e2,,正则表达式语法} 。通常，Unicode 版本匹配 Unicode 数据库中相应类别中的任何字符。


@table @asis

@item @code{\d}

匹配任何十进制数字；这等价于类 @code{[0-9]}。

@item @code{\D}

匹配任何非数字字符；这等价于类 @code{[^0-9]}。

@item @code{\s}

匹配任何空白字符；这等价于类 @code{[ \t\n\r\f\v]}。

@item @code{\S}

匹配任何非空白字符；这相当于类 @code{[^ \t\n\r\f\v]}。

@item @code{\w}

匹配任何字母与数字字符；这相当于类 @code{[a-zA-Z0-9_]}。

@item @code{\W}

匹配任何非字母与数字字符；这相当于类 @code{[^a-zA-Z0-9_]}。
@end table

这些序列可以包含在字符类中。 例如，@code{[\s,.]} 是一个匹配任何空格字符的字符类或者 @code{','} ，或 @code{'.'}。

本节的最后一个元字符是 @code{.} 。 它匹配除换行符之外的任何内容，并且有一个可选模式（ @ref{16e6,,re.DOTALL} ）甚至可以匹配换行符。 @code{.} 常用于你想匹配“任何字符”的地方。

@node 重复,,匹配字符,简单模式
@anchor{howto/regex repeating-things}@anchor{4140}
@subsubsection 重复


能够匹配不同的字符集合是正则表达式可以做的第一件事，这对于字符串可用方法来说是不可能的。 但是，如果这是正则表达式的唯一额外功能，那么它们就不会有太大的优势。 另一个功能是你可以指定正则的某些部分必须重复一定次数。

重复中我们要了解的第一个元字符是 @code{*}。 @code{*} 与字面字符 @code{'*'} 不匹配；相反，它指定前一个字符可以匹配零次或多次，而不是恰好一次。

例如，@code{ca*t} 将匹配 @code{'ct'} (0个 @code{'a'} 字符)，@code{'cat'} (1个 @code{'a'} )， @code{'caaat'} (3个 @code{'a'} 字符)，等等。

类似 @code{*} 这样的重复是 @emph{贪婪的}；当重复正则时，匹配引擎将尝试尽可能多地重复它。 如果模式的后续部分不匹配，则匹配引擎将回退并以较少的重复次数再次尝试。

一个逐步的例子将使这更加明显。 让我们考虑表达式 @code{a[bcd]*b}。 这个正则匹配字母 @code{'a'}，类 @code{[bcd]} 中的零或多个字母，最后以 @code{'b'} 结尾。 现在想象一下这个正则与字符串 @code{'abcbd'} 匹配。


@multitable {xxxxxxxx} {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

步骤

@tab

匹配

@tab

说明

@item

1

@tab

@code{a}

@tab

正则中的 @code{a} 匹配。

@item

2

@tab

@code{abcbd}

@tab

引擎尽可能多地匹配 @code{[bcd]*} ，直到字符串结束。

@item

3

@tab

@emph{失败}

@tab

引擎尝试匹配 @code{b} ，但是当前位置位于字符串结束，所以匹配失败。

@item

4

@tab

@code{abcb}

@tab

回退一次，@code{[bcd]*} 少匹配一个字符。

@item

5

@tab

@emph{失败}

@tab

再次尝试匹配 @code{b} ， 但是当前位置是最后一个字符 @code{'d'} 。

@item

6

@tab

@code{abc}

@tab

再次回退，所以 @code{[bcd]*} 只匹配 @code{bc} 。

@item

6

@tab

@code{abcb}

@tab

再试一次 @code{b} 。 这次当前位置的字符是 @code{'b'} ，所以它成功了。

@end multitable


正则现在已经结束了，它已经匹配了 @code{'abcb'}。 这演示了匹配引擎最初如何进行，如果没有找到匹配，它将逐步回退并一次又一次地重试正则的其余部分。 它将回退，直到它为 @code{[bcd]*} 尝试零匹配，如果随后失败，引擎将断定该字符串与正则完全不匹配。

另一个重复的元字符是 @code{+}，它匹配一次或多次。 要特别注意 @code{*} 和 @code{+} 之间的区别；@code{*} 匹配 @emph{零次} 或更多次，因此重复的任何东西都可能根本不存在，而 @code{+} 至少需要 @emph{一次}。 使用类似的例子，@code{ca+t} 将匹配 @code{'cat'} (1 个 @code{'a'})，@code{'caaat'} (3 个 @code{'a'})，但不会匹配 @code{'ct'}。

还有两个重复限定符。 问号字符 @code{?} 匹配一次或零次；你可以把它想象成是可选的。 例如，@code{home-?brew} 匹配 @code{'homebrew'} 或 @code{'home-brew'}。

最复杂的重复限定符是 @code{@{m,n@}}，其中 @emph{m} 和 @emph{n} 是十进制整数。 这个限定符意味着必须至少重复 @emph{m} 次，最多重复 @emph{n} 次。 例如，@code{a/@{1,3@}b} 将匹配 @code{'a/b'} ，@code{'a//b'} 和 @code{'a///b'} 。 它不匹配没有斜线的 @code{'ab'}，或者有四个的 @code{'a////b'}。

你可以省略 @emph{m} 或 @emph{n}; 在这种情况下，将假定缺失值的合理值。 省略 @emph{m} 被解释为 0 下限，而省略 @emph{n} 则为无穷大的上限。

还原论者的读者可能会注意到其他三个限定符都可以用这种表示法表达。 @code{@{0,@}} 与 @code{*} 相同， @code{@{1,@}} 相当于 @code{+} ， @code{@{0,1@}} 和 @code{?} 相同。 最好使用 @code{*} ， @code{+} 或 @code{?} ，只要因为它们更短更容易阅读。

@node 使用正则表达式,更多模式能力,简单模式,正则表达式HOWTO
@anchor{howto/regex using-regular-expressions}@anchor{4141}
@subsection 使用正则表达式


现在我们已经看了一些简单的正则表达式，我们如何在 Python 中实际使用它们？ @ref{dd,,re} 模块提供了正则表达式引擎的接口，允许你将正则编译为对象，然后用它们进行匹配。

@menu
* 编译正则表达式:: 
* 反斜杠灾难:: 
* 应用匹配:: 
* 模块级别函数: 模块级别函数<2>. 
* 编译标志:: 

@end menu

@node 编译正则表达式,反斜杠灾难,,使用正则表达式
@anchor{howto/regex compiling-regular-expressions}@anchor{4142}
@subsubsection 编译正则表达式


正则表达式被编译成模式对象，模式对象具有各种操作的方法，例如搜索模式匹配或执行字符串替换。:

@example
>>> import re
>>> p = re.compile('ab*')
>>> p
re.compile('ab*')
@end example

@ref{444,,re.compile()} 也接受一个可选的 @emph{flags} 参数，用于启用各种特殊功能和语法变体。 我们稍后将介绍可用的设置，但现在只需一个例子

@example
>>> p = re.compile('ab*', re.IGNORECASE)
@end example

正则作为字符串传递给 @ref{444,,re.compile()} 。 正则被处理为字符串，因为正则表达式不是核心Python语言的一部分，并且没有创建用于表达它们的特殊语法。 （有些应用程序根本不需要正则，因此不需要通过包含它们来扩展语言规范。）相反，@ref{dd,,re} 模块只是Python附带的C扩展模块，就类似于 @ref{ef,,socket} 或 @ref{144,,zlib} 模块。

将正则放在字符串中可以使 Python 语言更简单，但有一个缺点是下一节的主题。

@node 反斜杠灾难,应用匹配,编译正则表达式,使用正则表达式
@anchor{howto/regex id1}@anchor{4143}@anchor{howto/regex the-backslash-plague}@anchor{4144}
@subsubsection 反斜杠灾难


如前所述，正则表达式使用反斜杠字符 (@code{'\'}) 来表示特殊形式或允许使用特殊字符而不调用它们的特殊含义。 这与 Python 在字符串文字中用于相同目的的相同字符的使用相冲突。

假设你想要编写一个与字符串 @code{\section} 相匹配的正则，它可以在 LaTeX 文件中找到。 要找出在程序代码中写入的内容，请从要匹配的字符串开始。 接下来，您必须通过在反斜杠前面添加反斜杠和其他元字符，从而产生字符串 @code{\\section}。 必须传递给 @ref{444,,re.compile()} 的结果字符串必须是 @code{\\section}。 但是，要将其表示为 Python 字符串文字，必须 @emph{再次} 转义两个反斜杠。


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

字符

@tab

阶段

@item

@code{\section}

@tab

被匹配的字符串

@item

@code{\\section}

@tab

为 @ref{444,,re.compile()} 转义的反斜杠

@item

@code{"\\\\section"}

@tab

为字符串字面转义的反斜杠

@end multitable


简而言之，要匹配文字反斜杠，必须将 @code{'\\\\'} 写为正则字符串，因为正则表达式必须是 @code{\\}，并且每个反斜杠必须表示为 @code{\\} 在常规Python字符串字面中。 在反复使用反斜杠的正则中，这会导致大量重复的反斜杠，并使得生成的字符串难以理解。

解决方案是使用 Python 的原始字符串表示法来表示正则表达式；反斜杠不以任何特殊的方式处理前缀为 @code{'r'} 的字符串字面，因此 @code{r"\n"} 是一个包含 @code{'\'} 和 @code{'n'} 的双字符字符串，而 @code{"\n"} 是一个包含换行符的单字符字符串。 正则表达式通常使用这种原始字符串表示法用 Python 代码编写。

此外，在正则表达式中有效但在 Python 字符串文字中无效的特殊转义序列现在导致 @ref{278,,DeprecationWarning} 并最终变为 @ref{452,,SyntaxError}。 这意味着如果未使用原始字符串表示法或转义反斜杠，序列将无效。


@multitable {xxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} 
@headitem

常规字符串

@tab

原始字符串

@item

@code{"ab*"}

@tab

@code{r"ab*"}

@item

@code{"\\\\section"}

@tab

@code{r"\\section"}

@item

@code{"\\w+\\s+\\1"}

@tab

@code{r"\w+\s+\1"}

@end multitable


@node 应用匹配,模块级别函数<2>,反斜杠灾难,使用正则表达式
@anchor{howto/regex performing-matches}@anchor{4145}
@subsubsection 应用匹配


一旦你有一个表示编译正则表达式的对象，你用它做什么？ 模式对象有几种方法和属性。 这里只介绍最重要的内容；请参阅 @ref{dd,,re} 文档获取完整列表。


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

方法 / 属性

@tab

目的

@item

@code{match()}

@tab

确定正则是否从字符串的开头匹配。

@item

@code{search()}

@tab

扫描字符串，查找此正则匹配的任何位置。

@item

@code{findall()}

@tab

找到正则匹配的所有子字符串，并将它们作为列表返回。

@item

@code{finditer()}

@tab

找到正则匹配的所有子字符串，并将它们返回为一个 @ref{fce,,iterator}。

@end multitable


如果没有找到匹配， @ref{16f1,,match()} 和 @ref{16f2,,search()} 返回 @code{None} 。如果它们成功， 一个 @ref{897,,匹配对象} 实例将被返回，包含匹配相关的信息：起始和终结位置、匹配的子串以及其它。

你可以通过交互式实验 @ref{dd,,re} 模块来了解这一点。 如果你有 @ref{10c,,tkinter}，你可能还想查看 Tools/demo/redemo.py@footnote{https://github.com/python/cpython/tree/3.8/Tools/demo/redemo.py}，这是 Python 发行附带的演示程序。 它允许你输入正则和字符串，并显示RE是匹配还是失败。  @code{redemo.py} 在尝试调试复杂的正则时非常有用。

本 HOWTO 使用标准 Python 解释器作为示例。 首先，运行 Python 解释器，导入 @ref{dd,,re} 模块，然后编译一个正则

@example
>>> import re
>>> p = re.compile('[a-z]+')
>>> p
re.compile('[a-z]+')
@end example

现在，你可以尝试匹配正则 @code{[a-z]+} 的各种字符串。 空字符串根本不匹配，因为 @code{+} 表示“一次或多次重复”。 @ref{16f1,,match()} 在这种情况下应返回 @code{None}，这将导致解释器不打印输出。 你可以显式打印 @code{match()} 的结果，使其清晰。:

@example
>>> p.match("")
>>> print(p.match(""))
None
@end example

现在，让我们尝试一下它应该匹配的字符串，例如 @code{tempo}。在这个例子中 @ref{16f1,,match()} 将返回一个 @ref{897,,匹配对象}，因此你应该将结果储存到一个变量中以供稍后使用。

@example
>>> m = p.match('tempo')
>>> m
<re.Match object; span=(0, 5), match='tempo'>
@end example

现在你可以检查 @ref{897,,匹配对象} 以获取有关匹配字符串的信息。 匹配对象实例也有几个方法和属性；最重要的是：


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

方法 / 属性

@tab

目的

@item

@code{group()}

@tab

返回正则匹配的字符串

@item

@code{start()}

@tab

返回匹配的开始位置

@item

@code{end()}

@tab

返回匹配的结束位置

@item

@code{span()}

@tab

返回包含匹配 (start, end) 位置的元组

@end multitable


尝试这些方法很快就会清楚它们的含义:

@example
>>> m.group()
'tempo'
>>> m.start(), m.end()
(0, 5)
>>> m.span()
(0, 5)
@end example

@ref{1706,,group()} 返回正则匹配的子字符串。 @ref{170a,,start()} 和 @ref{170b,,end()} 返回匹配的起始和结束索引。 @ref{170c,,span()} 在单个元组中返回开始和结束索引。 由于 @ref{16f1,,match()} 方法只检查正则是否在字符串的开头匹配，所以 @code{start()} 将始终为零。 但是，模式的 @ref{16f2,,search()} 方法会扫描字符串，因此在这种情况下匹配可能不会从零开始。:

@example
>>> print(p.match('::: message'))
None
>>> m = p.search('::: message'); print(m)
<re.Match object; span=(4, 11), match='message'>
>>> m.group()
'message'
>>> m.span()
(4, 11)
@end example

在实际程序中，最常见的样式是在变量中存储 @ref{897,,匹配对象}，然后检查它是否为 @code{None}。 这通常看起来像:

@example
p = re.compile( ... )
m = p.match( 'string goes here' )
if m:
    print('Match found: ', m.group())
else:
    print('No match')
@end example

两种模式方法返回模式的所有匹配项。 @ref{16fc,,findall()} 返回匹配字符串的列表:

@example
>>> p = re.compile(r'\d+')
>>> p.findall('12 drummers drumming, 11 pipers piping, 10 lords a-leaping')
['12', '11', '10']
@end example

在这个例子中需要 @code{r} 前缀，使字面为原始字符串字面，因为普通的“加工”字符串字面中的转义序列不能被 Python 识别为正则表达式，导致 @ref{278,,DeprecationWarning} 并最终产生 @ref{452,,SyntaxError}。 请参阅 @ref{4144,,反斜杠灾难}。

@ref{16fc,,findall()} 必须先创建整个列表才能返回结果。 @ref{16fd,,finditer()} 方法将一个 @ref{897,,匹配对象} 的序列返回为一个 @ref{fce,,iterator}

@example
>>> iterator = p.finditer('12 drummers drumming, 11 ... 10 ...')
>>> iterator  
<callable_iterator object at 0x...>
>>> for match in iterator:
...     print(match.span())
...
(0, 2)
(22, 24)
(29, 31)
@end example

@node 模块级别函数<2>,编译标志,应用匹配,使用正则表达式
@anchor{howto/regex module-level-functions}@anchor{4146}
@subsubsection 模块级别函数


你不必创建模式对象并调用其方法；@ref{dd,,re} 模块还提供了顶级函数 @ref{bac,,match()}，@ref{bab,,search()}，@ref{95d,,findall()}，@ref{475,,sub()} 等等。 这些函数采用与相应模式方法相同的参数，并将正则字符串作为第一个参数添加，并仍然返回 @code{None} 或  @ref{897,,匹配对象} 实例。:

@example
>>> print(re.match(r'From\s+', 'Fromage amk'))
None
>>> re.match(r'From\s+', 'From amk Thu May 14 19:12:10 1998')  
<re.Match object; span=(0, 5), match='From '>
@end example

本质上，这些函数只是为你创建一个模式对象，并在其上调用适当的方法。 它们还将编译对象存储在缓存中，因此使用相同的未来调用将不需要一次又一次地解析该模式。

你是否应该使用这些模块级函数，还是应该自己获取模式并调用其方法？ 如果你正在循环中访问正则表达式，预编译它将节省一些函数调用。 在循环之外，由于有内部缓存，没有太大区别。

@node 编译标志,,模块级别函数<2>,使用正则表达式
@anchor{howto/regex compilation-flags}@anchor{4147}
@subsubsection 编译标志


编译标志允许你修改正则表达式的工作方式。 标志在 @ref{dd,,re} 模块中有两个名称，长名称如 @code{IGNORECASE} 和一个简短的单字母形式，例如 @code{I}。 （如果你熟悉 Perl 的模式修饰符，则单字母形式使用和其相同的字母；例如， @ref{16f5,,re.VERBOSE} 的缩写形式为 @ref{16ed,,re.X}。）多个标志可以 通过按位或运算来指定它们；例如，@code{re.I | re.M} 设置 @code{I} 和 @code{M} 标志。

这是一个可用标志表，以及每个标志的更详细说明。


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Flag

@tab

含义

@item

@code{ASCII}, @code{A}

@tab

使几个转义如 @code{\w}、@code{\b}、@code{\s} 和 @code{\d} 匹配仅与具有相应特征属性的 ASCII 字符匹配。

@item

@code{DOTALL}, @code{S}

@tab

使 @code{.} 匹配任何字符，包括换行符。

@item

@code{IGNORECASE}, @code{I}

@tab

进行大小写不敏感匹配。

@item

@code{LOCALE}, @code{L}

@tab

进行区域设置感知匹配。

@item

@code{MULTILINE}, @code{M}

@tab

多行匹配，影响 @code{^} 和 @code{$}。

@item

@code{VERBOSE}, @code{X} （为 '扩展'）

@tab

启用详细的正则，可以更清晰，更容易理解。

@end multitable



@deffn {数据} I

@deffnx {数据} IGNORECASE

执行不区分大小写的匹配；字符类和字面字符串将通过忽略大小写来匹配字母。 例如，@code{[A-Z]} 也匹配小写字母。 除非使用 @code{ASCII} 标志来禁用非ASCII匹配，否则完全 Unicode 匹配也有效。 当 Unicode 模式 @code{[a-z]} 或 @code{[A-Z]} 与 @code{IGNORECASE} 标志结合使用时，它们将匹配 52 个 ASCII 字母和 4 个额外的非 ASCII 字母：'İ' (U+0130，拉丁大写字母 I，带上面的点)，'ı' (U+0131，拉丁文小写字母无点 i)，'s' (U+017F，拉丁文小写字母长 s) 和'K' (U+212A，开尔文符号)。 @code{Spam} 将匹配 @code{'Spam'}，@code{'spam'}，@code{'spAM'} 或 @code{'ſpam'} (后者仅在 Unicode 模式下匹配)。 此小写不考虑当前区域设置；如果你还设置了 @code{LOCALE} 标志，则将考虑。
@end deffn


@deffn {数据} L

@deffnx {数据} LOCALE

使 @code{\w}、@code{\W}、@code{\b}、@code{\B} 和大小写敏感匹配依赖于当前区域而不是 Unicode 数据库。

区域设置是 C 库的一个功能，旨在帮助编写考虑到语言差异的程序。例如，如果你正在处理编码的法语文本，那么你希望能够编写 @code{\w+} 来匹配单词，但 @code{\w} 只匹配字符类 @code{[A-Za-z]} 字节模式；它不会匹配对应于 @code{é} 或 @code{ç} 的字节。如果你的系统配置正确并且选择了法语区域设置，某些C函数将告诉程序对应于 @code{é} 的字节也应该被视为字母。在编译正则表达式时设置 @code{LOCALE} 标志将导致生成的编译对象将这些C函数用于 @code{\w}；这比较慢，但也可以使 @code{\w+} 匹配你所期望的法语单词。在 Python 3 中不鼓励使用此标志，因为语言环境机制非常不可靠，它一次只处理一个“文化”，它只适用于 8 位语言环境。默认情况下，Python 3 中已经为 Unicode（str）模式启用了 Unicode 匹配，并且它能够处理不同的区域/语言。
@end deffn


@deffn {数据} M

@deffnx {数据} MULTILINE

(@code{^} 和 @code{$} 还没有解释；它们将在以下部分介绍 @ref{4148,,更多元字符}。)

通常 @code{^} 只匹配字符串的开头，而 @code{$} 只匹配字符串的结尾，紧接在字符串末尾的换行符（如果有的话）之前。 当指定了这个标志时，@code{^} 匹配字符串的开头和字符串中每一行的开头，紧跟在每个换行符之后。 类似地，@code{$} 元字符匹配字符串的结尾和每行的结尾（紧接在每个换行符之前）。
@end deffn


@deffn {数据} S

@deffnx {数据} DOTALL

使 @code{'.'} 特殊字符匹配任何字符，包括换行符；没有这个标志，@code{'.'} 将匹配任何字符 @emph{除了} 换行符。
@end deffn


@deffn {数据} A

@deffnx {数据} ASCII

使 @code{\w}、@code{\W}、@code{\b}、@code{\B}、@code{\s} 和 @code{\S} 执行仅 ASCII 匹配而不是完整匹配 Unicode 匹配。 这仅对 Unicode 模式有意义，并且对于字节模式将被忽略。
@end deffn


@deffn {数据} X

@deffnx {数据} VERBOSE

此标志允许你编写更易读的正则表达式，方法是为您提供更灵活的格式化方式。 指定此标志后，将忽略正则字符串中的空格，除非空格位于字符类中或前面带有未转义的反斜杠；这使你可以更清楚地组织和缩进正则。 此标志还允许你将注释放在正则中，引擎将忽略该注释；注释标记为 @code{'#'} 既不是在字符类中，也不是在未转义的反斜杠之前。

例如，这里的正则使用 @ref{16f5,,re.VERBOSE}；看看阅读有多容易？:

@example
charref = re.compile(r"""
 &[#]                # Start of a numeric entity reference
 (
     0[0-7]+         # Octal form
   | [0-9]+          # Decimal form
   | x[0-9a-fA-F]+   # Hexadecimal form
 )
 ;                   # Trailing semicolon
""", re.VERBOSE)
@end example

如果没有详细设置，正则将如下所示:

@example
charref = re.compile("&#(0[0-7]+"
                     "|[0-9]+"
                     "|x[0-9a-fA-F]+);")
@end example

在上面的例子中，Python的字符串文字的自动连接已被用于将正则分解为更小的部分，但它仍然比以下使用 @ref{16f5,,re.VERBOSE} 版本更难理解。
@end deffn

@node 更多模式能力,修改字符串,使用正则表达式,正则表达式HOWTO
@anchor{howto/regex more-pattern-power}@anchor{4149}
@subsection 更多模式能力


到目前为止，我们只介绍了正则表达式的一部分功能。 在本节中，我们将介绍一些新的元字符，以及如何使用组来检索匹配的文本部分。

@menu
* 更多元字符:: 
* 分组:: 
* 非捕获和命名组:: 
* 前向断言:: 

@end menu

@node 更多元字符,分组,,更多模式能力
@anchor{howto/regex id2}@anchor{414a}@anchor{howto/regex more-metacharacters}@anchor{4148}
@subsubsection 更多元字符


我们还没有涉及到一些元字符。 其中大部分内容将在本节中介绍。

要讨论的其余一些元字符是 @emph{零宽度断言} 。 它们不会使解析引擎在字符串中前进一个字符；相反，它们根本不占用任何字符，只是成功或失败。例如，@code{\b} 是一个断言，指明当前位置位于字边界；这个位置根本不会被 @code{\b} 改变。这意味着永远不应重复零宽度断言，因为如果它们在给定位置匹配一次，它们显然可以无限次匹配。


@table @asis

@item @code{|}

或者“or”运算符。 如果 @emph{A} 和 @emph{B} 是正则表达式，@code{A|B} 将匹配任何与 @emph{A} 或 @emph{B} 匹配的字符串。 @code{|} 具有非常低的优先级，以便在交替使用多字符字符串时使其合理地工作。 @code{Crow|Servo} 将匹配 @code{'Crow'} 或 @code{'Servo'}，而不是 @code{'Cro'}、@code{'w'} 或 @code{'S'} 和 @code{'ervo'}。

要匹配字面 @code{'|'}，请使用 @code{\|}，或将其括在字符类中，如 @code{[|]}。

@item @code{^}

在行的开头匹配。 除非设置了 @code{MULTILINE} 标志，否则只会在字符串的开头匹配。 在 @code{MULTILINE} 模式下，这也在字符串中的每个换行符后立即匹配。

例如，如果你希望仅在行的开头匹配单词 @code{From}，则要使用的正则 @code{^From}。:

@example
>>> print(re.search('^From', 'From Here to Eternity'))  
<re.Match object; span=(0, 4), match='From'>
>>> print(re.search('^From', 'Reciting From Memory'))
None
@end example

要匹配字面 @code{'^'}，使用 @code{\^}。

@item @code{$}

匹配行的末尾，定义为字符串的结尾，或者后跟换行符的任何位置。:

@example
>>> print(re.search('@}$', '@{block@}'))  
<re.Match object; span=(6, 7), match='@}'>
>>> print(re.search('@}$', '@{block@} '))
None
>>> print(re.search('@}$', '@{block@}\n'))  
<re.Match object; span=(6, 7), match='@}'>
@end example

以匹配字面 @code{'$'}，使用 @code{\$} 或者将其包裹在一个字符类中，例如 @code{[$]}。

@item @code{\A}

仅匹配字符串的开头。 当不在 @code{MULTILINE} 模式时，@code{\A} 和 @code{^} 实际上是相同的。 在 @code{MULTILINE} 模式中，它们是不同的: @code{\A} 仍然只在字符串的开头匹配，但 @code{^} 可以匹配在换行符之后的字符串内的任何位置。

@item @code{\Z}

只匹配字符串尾。

@item @code{\b}

字边界。 这是一个零宽度断言，仅在单词的开头或结尾处匹配。 单词被定义为一个字母数字字符序列，因此单词的结尾由空格或非字母数字字符表示。

以下示例仅当它是一个完整的单词时匹配 @code{class}；当它包含在另一个单词中时将不会匹配。

@example
>>> p = re.compile(r'\bclass\b')
>>> print(p.search('no class at all'))
<re.Match object; span=(3, 8), match='class'>
>>> print(p.search('the declassified algorithm'))
None
>>> print(p.search('one subclass is'))
None
@end example

使用这个特殊序列时，你应该记住两个细微之处。 首先，这是 Python 的字符串文字和正则表达式序列之间最严重的冲突。 在 Python 的字符串文字中，@code{\b} 是退格字符，ASCII 值为8。 如果你没有使用原始字符串，那么 Python 会将 @code{\b} 转换为退格，你的正则不会按照你的预期匹配。 以下示例与我们之前的正则看起来相同，但省略了正则字符串前面的 @code{'r'}。:

@example
>>> p = re.compile('\bclass\b')
>>> print(p.search('no class at all'))
None
>>> print(p.search('\b' + 'class' + '\b'))
<re.Match object; span=(0, 7), match='\x08class\x08'>
@end example

其次，在一个字符类中，这个断言没有用处，@code{\b} 表示退格字符，以便与 Python 的字符串文字兼容。

@item @code{\B}

另一个零宽度断言，这与 @code{\b} 相反，仅在当前位置不在字边界时才匹配。
@end table

@node 分组,非捕获和命名组,更多元字符,更多模式能力
@anchor{howto/regex grouping}@anchor{414b}
@subsubsection 分组


通常，你需要获取更多信息，而不仅仅是正则是否匹配。 正则表达式通常用于通过将正则分成几个子组来解析字符串，这些子组匹配不同的感兴趣组件。 例如，RFC-822 标题行分为标题名称和值，用 @code{':'} 分隔，如下所示：

@example
From: author@@example.com
User-Agent: Thunderbird 1.5.0.9 (X11/20061227)
MIME-Version: 1.0
To: editor@@example.com
@end example

这可以通过编写与整个标题行匹配的正则表达式来处理，并且具有与标题名称匹配的一个组，以及与标题的值匹配的另一个组。

组由 @code{'('}，@code{')'} 元字符标记。 @code{'('} 和 @code{')'} 与数学表达式的含义大致相同；它们将包含在其中的表达式组合在一起，你可以使用重复限定符重复组的内容，例如 @code{*}，@code{+}，@code{?} 或 @code{@{m,n@}}。 例如，@code{(ab)*} 将匹配 @code{ab} 的零次或多次重复。:

@example
>>> p = re.compile('(ab)*')
>>> print(p.match('ababababab').span())
(0, 10)
@end example

用 @code{'('}，@code{')'} 表示的组也捕获它们匹配的文本的起始和结束索引；这可以通过将参数传递给 @ref{1706,,group()}、@ref{170a,,start()}、@ref{170b,,end()} 以及 @ref{170c,,span()}。 组从 0 开始编号。组 0 始终存在；它表示整个正则，所以 @ref{897,,匹配对象} 方法都将组 0 作为默认参数。 稍后我们将看到如何表达不捕获它们匹配的文本范围的组。:

@example
>>> p = re.compile('(a)b')
>>> m = p.match('ab')
>>> m.group()
'ab'
>>> m.group(0)
'ab'
@end example

子组从左到右编号，从 1 向上编号。 组可以嵌套；要确定编号，只需计算从左到右的左括号字符。:

@example
>>> p = re.compile('(a(b)c)d')
>>> m = p.match('abcd')
>>> m.group(0)
'abcd'
>>> m.group(1)
'abc'
>>> m.group(2)
'b'
@end example

@ref{1706,,group()} 可以一次传递多个组号，在这种情况下，它将返回一个包含这些组的相应值的元组。:

@example
>>> m.group(2,1,2)
('b', 'abc', 'b')
@end example

@ref{1708,,groups()} 方法返回一个元组，其中包含所有子组的字符串，从1到最后一个子组。:

@example
>>> m.groups()
('abc', 'b')
@end example

模式中的后向引用允许你指定还必须在字符串中的当前位置找到先前捕获组的内容。 例如，如果可以在当前位置找到组 1 的确切内容，则 @code{\1} 将成功，否则将失败。 请记住，Python 的字符串文字也使用反斜杠后跟数字以允许在字符串中包含任意字符，因此正则中引入反向引用时务必使用原始字符串。

例如，以下正则检测字符串中的双字。:

@example
>>> p = re.compile(r'\b(\w+)\s+\1\b')
>>> p.search('Paris in the the spring').group()
'the the'
@end example

像这样的后向引用通常不仅仅用于搜索字符串 —— 很少有文本格式以这种方式重复数据 —— 但是你很快就会发现它们在执行字符串替换时 @emph{非常} 有用。

@node 非捕获和命名组,前向断言,分组,更多模式能力
@anchor{howto/regex non-capturing-and-named-groups}@anchor{414c}
@subsubsection 非捕获和命名组


精心设计的正则可以使用许多组，既可以捕获感兴趣的子串，也可以对正则本身进行分组和构建。 在复杂的正则中，很难跟踪组号。 有两个功能可以帮助解决这个问题。 它们都使用常用语法进行正则表达式扩展，因此我们首先看一下。

Perl 5 以其对标准正则表达式的强大补充而闻名。 对于这些新功能，Perl 开发人员无法选择新的单键击元字符或以 @code{\} 开头的新特殊序列，否则 Perl 的正则表达式与标准正则容易混淆。 例如，如果他们选择 @code{&} 作为一个新的元字符，旧的表达式将假设 @code{&} 是一个普通字符，并且不会编写 @code{\&} 或 @code{[&]}。

Perl 开发人员选择的解决方案是使用 @code{(?...)} 作为扩展语法。 括号后面的 @code{?} 是一个语法错误，因为 @code{?} 没有什么可重复的，所以这并没有引入任何兼容性问题。 紧跟在 @code{?} 之后的字符表示正在使用什么扩展名，所以 @code{(?=foo)} 是一个东西（一个正向的先行断言）和 @code{(?:foo)} 是其它东西（ 包含子表达式 @code{foo} 的非捕获组）。

Python 支持一些 Perl 的扩展，并增加了新的扩展语法用于 Perl 的扩展语法。 如果在问号之后的第一个字符为 @code{P}，即表明其为 Python 专属的扩展。

现在我们已经了解了一般的扩展语法，我们可以回到简化复杂正则中组处理的功能。

有时你会想要使用组来表示正则表达式的一部分，但是对检索组的内容不感兴趣。 你可以通过使用非捕获组来显式表达这个事实: @code{(?:...)}，你可以用任何其他正则表达式替换 @code{...}。:

@example
>>> m = re.match("([abc])+", "abc")
>>> m.groups()
('c',)
>>> m = re.match("(?:[abc])+", "abc")
>>> m.groups()
()
@end example

除了你无法检索组匹配内容的事实外，非捕获组的行为与捕获组完全相同；你可以在里面放任何东西，用重复元字符重复它，比如 @code{*}，然后把它嵌入其他组（捕获或不捕获）。 @code{(?:...)} 在修改现有模式时特别有用，因为你可以添加新组而不更改所有其他组的编号方式。 值得一提的是，捕获和非捕获组之间的搜索没有性能差异；两种形式没有一种更快。

更重要的功能是命名组：不是通过数字引用它们，而是可以通过名称引用组。

命名组的语法是Python特定的扩展之一: @code{(?P<name>...)}。 @emph{name} 显然是该组的名称。 命名组的行为与捕获组完全相同，并且还将名称与组关联。 处理捕获组的 @ref{897,,匹配对象} 方法都接受按编号引用组的整数或包含所需组名的字符串。 命名组仍然是给定的数字，因此你可以通过两种方式检索有关组的信息:

@example
>>> p = re.compile(r'(?P<word>\b\w+\b)')
>>> m = p.search( '(((( Lots of punctuation )))' )
>>> m.group('word')
'Lots'
>>> m.group(1)
'Lots'
@end example

此外，你可以通过 @ref{1709,,groupdict()} 将命名分组提取为一个字典:

@example
>>> m = re.match(r'(?P<first>\w+) (?P<last>\w+)', 'Jane Doe')
>>> m.groupdict()
@{'first': 'Jane', 'last': 'Doe'@}
@end example

命名组很有用，因为它们允许你使用容易记住的名称，而不必记住数字。 这是来自 @ref{98,,imaplib} 模块的示例正则

@example
InternalDate = re.compile(r'INTERNALDATE "'
        r'(?P<day>[ 123][0-9])-(?P<mon>[A-Z][a-z][a-z])-'
        r'(?P<year>[0-9][0-9][0-9][0-9])'
        r' (?P<hour>[0-9][0-9]):(?P<min>[0-9][0-9]):(?P<sec>[0-9][0-9])'
        r' (?P<zonen>[-+])(?P<zoneh>[0-9][0-9])(?P<zonem>[0-9][0-9])'
        r'"')
@end example

检索 @code{m.group('zonem')} 显然要容易得多，而不必记住检索第 9 组。

表达式中的后向引用语法，例如 @code{(...)\1}，指的是组的编号。 当然有一种变体使用组名而不是数字。 这是另一个 Python 扩展: @code{(?P=name)} 表示在当前点再次匹配名为 @emph{name} 的组的内容。 用于查找双字的正则表达式，@code{\b(\w+)\s+\1\b} 也可以写为 @code{\b(?P<word>\w+)\s+(?P=word)\b}:

@example
>>> p = re.compile(r'\b(?P<word>\w+)\s+(?P=word)\b')
>>> p.search('Paris in the the spring').group()
'the the'
@end example

@node 前向断言,,非捕获和命名组,更多模式能力
@anchor{howto/regex lookahead-assertions}@anchor{414d}
@subsubsection 前向断言


另一个零宽度断言是前向断言。 前向断言以正面和负面形式提供，如下所示：


@table @asis

@item @code{(?=…)}

正向前向断言。 如果包含的正则表达式，由 @code{...} 表示，在当前位置成功匹配，则成功，否则失败。 但是，一旦尝试了包含的表达式，匹配的引擎就不会前进；模式其余的部分会在在断言开始的地方尝试。

@item @code{(?!…)}

负向前向断言。 这与积正向断言相反；如果包含的表达式在字符串中的当前位置 @emph{不} 匹配，则成功。
@end table

更具体一些，让我们看看前向是有用的情况。 考虑一个简单的模式来匹配文件名并将其拆分为基本名称和扩展名，用 @code{.} 分隔。 例如，在 @code{news.rc} 中，@code{news} 是基本名称，@code{rc} 是文件名的扩展名。

与此匹配的模式非常简单：

@code{.*[.].*$}

请注意，@code{.} 需要特别处理，因为它是元字符，所以它在字符类中只能匹配特定字符。 还要注意尾随的 @code{$}；添加此项以确保扩展名中的所有其余字符串都必须包含在扩展名中。 这个正则表达式匹配 @code{foo.bar}、@code{autoexec.bat}、@code{sendmail.cf} 和 @code{printers.conf}。

现在，考虑使更复杂一点的问题；如果你想匹配扩展名不是 @code{bat} 的文件名怎么办？ 一些错误的尝试：

@code{.*[.][^b].*$} 上面的第一次尝试试图通过要求扩展名的第一个字符不是 @code{b} 来排除 @code{bat}。 这是错误的，因为模式也与 @code{foo.bar} 不匹配。

@code{.*[.]([^b]..|.[^a].|..[^t])$}

当你尝试通过要求以下一种情况匹配来修补第一个解决方案时，表达式变得更加混乱：扩展的第一个字符不是 @code{b}。 第二个字符不 @code{a}；或者第三个字符不是 @code{t}。 这接受 @code{foo.bar} 并拒绝 @code{autoexec.bat}，但它需要三个字母的扩展名，并且不接受带有两个字母扩展名的文件名，例如 @code{sendmail.cf}。 为了解决这个问题，我们会再次使模式复杂化。

@code{.*[.]([^b].?.?|.[^a]?.?|..?[^t]?)$}

在第三次尝试中，第二个和第三个字母都是可选的，以便允许匹配的扩展名短于三个字符，例如 @code{sendmail.cf}。

模式现在变得非常复杂，这使得它难以阅读和理解。 更糟糕的是，如果问题发生变化并且你想要将 @code{bat} 和 @code{exe} 排除为扩展，那么该模式将变得更加复杂和混乱。

负面前向消除了所有这些困扰：

@code{.*[.](?!bat$)[^.]*$} 负向前向意味着：如果表达式 @code{bat} 此时不匹配，请尝试其余的模式；如果 @code{bat$} 匹配，整个模式将失败。 尾随的 @code{$} 是必需的，以确保允许像 @code{sample.batch} 这样的扩展只以 @code{bat} 开头的文件能通过。 @code{[^.]*} 确保当文件名中有多个点时，模式有效。

现在很容易排除另一个文件扩展名；只需在断言中添加它作为替代。  以下模块排除以 @code{bat} 或 @code{exe}:

@code{.*[.](?!bat$|exe$)[^.]*$}

@node 修改字符串,常见问题<2>,更多模式能力,正则表达式HOWTO
@anchor{howto/regex modifying-strings}@anchor{414e}
@subsection 修改字符串


到目前为止，我们只是针对静态字符串执行搜索。 正则表达式通常也用于以各种方式修改字符串，使用以下模式方法：


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

方法 / 属性

@tab

目的

@item

@code{split()}

@tab

将字符串拆分为一个列表，在正则匹配的任何地方将其拆分

@item

@code{sub()}

@tab

找到正则匹配的所有子字符串，并用不同的字符串替换它们

@item

@code{subn()}

@tab

与 @code{sub()} 相同，但返回新字符串和替换次数

@end multitable


@menu
* 分割字符串:: 
* 搜索和替换:: 

@end menu

@node 分割字符串,搜索和替换,,修改字符串
@anchor{howto/regex splitting-strings}@anchor{414f}
@subsubsection 分割字符串


模式的 @ref{16fb,,split()} 方法在正则匹配的任何地方拆分字符串，返回一个片段列表。 它类似于 @ref{79b,,split()} 字符串方法，但在分隔符的分隔符中提供了更多的通用性；字符串的 @code{split()} 仅支持按空格或固定字符串进行拆分。 正如你所期望的那样，还有一个模块级 @ref{3c2,,re.split()} 函数。


@deffn {方法} .split (string[, maxsplit=0])

通过正则表达式的匹配拆分 @emph{字符串}。 如果在正则中使用捕获括号，则它们的内容也将作为结果列表的一部分返回。 如果 @emph{maxsplit} 非零，则最多执行 @emph{maxsplit} 次拆分。
@end deffn

你可以通过传递 @emph{maxsplit} 的值来限制分割的数量。 当 @emph{maxsplit} 非零时，将最多进行 @emph{maxsplit} 次拆分，并且字符串的其余部分将作为列表的最后一个元素返回。 在以下示例中，分隔符是任何非字母数字字符序列。:

@example
>>> p = re.compile(r'\W+')
>>> p.split('This is a test, short and sweet, of split().')
['This', 'is', 'a', 'test', 'short', 'and', 'sweet', 'of', 'split', '@w{'}]
>>> p.split('This is a test, short and sweet, of split().', 3)
['This', 'is', 'a', 'test, short and sweet, of split().']
@end example

有时你不仅对分隔符之间的文本感兴趣，而且还需要知道分隔符是什么。 如果在正则中使用捕获括号，则它们的值也将作为列表的一部分返回。 比较以下调用:

@example
>>> p = re.compile(r'\W+')
>>> p2 = re.compile(r'(\W+)')
>>> p.split('This... is a test.')
['This', 'is', 'a', 'test', '@w{'}]
>>> p2.split('This... is a test.')
['This', '... ', 'is', ' ', 'a', ' ', 'test', '.', '@w{'}]
@end example

模块级函数 @ref{3c2,,re.split()} 添加要正则作为第一个参数，但在其他方面是相同的。:

@example
>>> re.split(r'[\W]+', 'Words, words, words.')
['Words', 'words', 'words', '@w{'}]
>>> re.split(r'([\W]+)', 'Words, words, words.')
['Words', ', ', 'words', ', ', 'words', '.', '@w{'}]
>>> re.split(r'[\W]+', 'Words, words, words.', 1)
['Words', 'words, words.']
@end example

@node 搜索和替换,,分割字符串,修改字符串
@anchor{howto/regex search-and-replace}@anchor{4150}
@subsubsection 搜索和替换


另一个常见任务是找到模式的所有匹配项，并用不同的字符串替换它们。 @ref{16fe,,sub()} 方法接受一个替换值，可以是字符串或函数，也可以是要处理的字符串。


@deffn {方法} .sub (replacement, string[, count=0])

返回通过替换 @emph{replacement} 替换 @emph{string} 中正则的最左边非重叠出现而获得的字符串。 如果未找到模式，则 @emph{string} 将保持不变。

可选参数 @emph{count} 是要替换的模式最大的出现次数；@emph{count} 必须是非负整数。 默认值 0 表示替换所有。
@end deffn

这是一个使用 @ref{16fe,,sub()} 方法的简单示例。 它用 @code{colour} 这个词取代颜色名称:

@example
>>> p = re.compile('(blue|white|red)')
>>> p.sub('colour', 'blue socks and red shoes')
'colour socks and colour shoes'
>>> p.sub('colour', 'blue socks and red shoes', count=1)
'colour socks and red shoes'
@end example

@ref{16ff,,subn()} 方法完成相同的工作，但返回一个包含新字符串值和已执行的替换次数的 2 元组:

@example
>>> p = re.compile('(blue|white|red)')
>>> p.subn('colour', 'blue socks and red shoes')
('colour socks and colour shoes', 2)
>>> p.subn('colour', 'no colours at all')
('no colours at all', 0)
@end example

仅当空匹配与前一个空匹配不相邻时，才会替换空匹配。:

@example
>>> p = re.compile('x*')
>>> p.sub('-', 'abxd')
'-a-b--d-'
@end example

如果 @emph{replacement} 是一个字符串，则处理其中的任何反斜杠转义。 也就是说，@code{\n} 被转换为单个换行符，@code{\r} 被转换为回车符，依此类推。 诸如 @code{\&} 之类的未知转义是孤立的。 后向引用，例如 @code{\6}，被替换为正则中相应组匹配的子字符串。 这使你可以在生成的替换字符串中合并原始文本的部分内容。

这个例子匹配单词 @code{section} 后跟一个用 @code{@{}，@code{@}} 括起来的字符串，并将 @code{section} 改为 @code{subsection}

@example
>>> p = re.compile('section@{ ( [^@}]* ) @}', re.VERBOSE)
>>> p.sub(r'subsection@{\1@}','section@{First@} section@{second@}')
'subsection@{First@} subsection@{second@}'
@end example

还有一种语法用于引用由 @code{(?P<name>...)} 语法定义的命名组。 @code{\g<name>} 将使用名为 @code{name} 的组匹配的子字符串，@code{\g<number>} 使用相应的组号。 因此 @code{\g<2>} 等同于 @code{\2}，但在诸如 @code{\g<2>0} 之类的替换字符串中并不模糊。 (@code{\20} 将被解释为对组 20 的引用，而不是对组 2 的引用，后跟字面字符 @code{'0'}。) 以下替换都是等效的，但使用所有三种变体替换字符串。:

@example
>>> p = re.compile('section@{ (?P<name> [^@}]* ) @}', re.VERBOSE)
>>> p.sub(r'subsection@{\1@}','section@{First@}')
'subsection@{First@}'
>>> p.sub(r'subsection@{\g<1>@}','section@{First@}')
'subsection@{First@}'
>>> p.sub(r'subsection@{\g<name>@}','section@{First@}')
'subsection@{First@}'
@end example

@emph{replacement} 也可以是一个函数，它可以为你提供更多控制。 如果 @emph{replacement} 是一个函数，则为 @emph{pattern} 的每次非重叠出现将调用该函数。 在每次调用时，函数都会传递一个匹配的 @ref{897,,匹配对象} 参数，并可以使用此信息计算所需的替换字符串并将其返回。

在以下示例中，替换函数将小数转换为十六进制:

@example
>>> def hexrepl(match):
...     "Return the hex string for a decimal number"
...     value = int(match.group())
...     return hex(value)
...
>>> p = re.compile(r'\d+')
>>> p.sub(hexrepl, 'Call 65490 for printing, 49152 for user code.')
'Call 0xffd2 for printing, 0xc000 for user code.'
@end example

使用模块级别 @ref{475,,re.sub()} 函数时，模式作为第一个参数传递。 图案可以作为对象或字符串提供；如果需要指定正则表达式标志，则必须使用模式对象作为第一个参数，或者在模式字符串中使用嵌入式修饰符，例如: @code{sub("(?i)b+", "x", "bbbb BBBB")} 返回 @code{'x x'}。

@node 常见问题<2>,反馈,修改字符串,正则表达式HOWTO
@anchor{howto/regex common-problems}@anchor{4151}
@subsection 常见问题


正则表达式对于某些应用程序来说是一个强大的工具，但在某些方面，它们的行为并不直观，有时它们的行为方式与你的预期不同。 本节将指出一些最常见的陷阱。

@menu
* 使用字符串方法:: 
* match() 和 search(): match 和 search. 
* 贪婪与非贪婪:: 
* 使用 re.VERBOSE: 使用 re VERBOSE. 

@end menu

@node 使用字符串方法,match 和 search,,常见问题<2>
@anchor{howto/regex use-string-methods}@anchor{4152}
@subsubsection 使用字符串方法


有时使用 @ref{dd,,re} 模块是一个错误。 如果你匹配固定字符串或单个字符类，并且你没有使用任何 @ref{dd,,re} 功能，例如 @ref{16f4,,IGNORECASE} 标志，那么正则表达式的全部功能可能不是必需的。 字符串有几种方法可以使用固定字符串执行操作，它们通常要快得多，因为实现是一个针对此目的而优化的单个小 C 循环，而不是大型、更通用的正则表达式引擎。

一个例子可能是用另一个固定字符串替换一个固定字符串；例如，你可以用 @code{deed} 替换 @code{word} 。 @ref{475,,re.sub()} 看起来像是用于此的函数，但请考虑 @ref{15ed,,replace()} 方法。 注意 @code{replace()} 也会替换单词里面的 @code{word} ，把 @code{swordfish} 变成 @code{sdeedfish} ，但简单的正则 @code{word} 也会这样做。 （为了避免对单词的部分进行替换，模式必须是 @code{\bword\b}，以便要求 @code{word} 在任何一方都有一个单词边界。这使得工作超出了 @code{replace()} 的能力。）

另一个常见任务是从字符串中删除单个字符的每个匹配项或将其替换为另一个字符。 你可以用 @code{re.sub('\n', ' ', S)} 之类的东西来做这件事，但是 @ref{15ec,,translate()} 能够完成这两项任务，并且比任何正则表达式都快。

简而言之，在转向 @ref{dd,,re} 模块之前，请考虑是否可以使用更快更简单的字符串方法解决问题。

@node match 和 search,贪婪与非贪婪,使用字符串方法,常见问题<2>
@anchor{howto/regex match-versus-search}@anchor{4153}
@subsubsection match() 和 search()


The @ref{bac,,match()} function only checks if the RE matches at the beginning of the
string while @ref{bab,,search()} will scan forward through the string for a match.
It's important to keep this distinction in mind.  Remember,  @code{match()} will
only report a successful match which will start at 0; if the match wouldn't
start at zero,  @code{match()} will @emph{not} report it.

@example
>>> print(re.match('super', 'superstition').span())
(0, 5)
>>> print(re.match('super', 'insuperable'))
None
@end example

另一方面， @ref{bab,,search()} 将向前扫描字符串，报告它找到的第一个匹配项。:

@example
>>> print(re.search('super', 'superstition').span())
(0, 5)
>>> print(re.search('super', 'insuperable').span())
(2, 7)
@end example

有时你会被诱惑继续使用 @ref{bac,,re.match()} ，只需在你的正则前面添加 @code{.*} 。抵制这种诱惑并使用 @ref{bab,,re.search()} 代替。 正则表达式编译器对正则进行一些分析，以加快寻找匹配的过程。 其中一个分析可以确定匹配的第一个特征必须是什么；例如，以 @code{Crow} 开头的模式必须与 @code{'C'} 匹配。 分析让引擎快速扫描字符串，寻找起始字符，只在找到 @code{'C'} 时尝试完全匹配。

添加 @code{.*} 会使这个优化失效，需要扫描到字符串的末尾，然后回溯以找到正则的其余部分的匹配。 使用 @ref{bab,,re.search()} 代替。

@node 贪婪与非贪婪,使用 re VERBOSE,match 和 search,常见问题<2>
@anchor{howto/regex greedy-versus-non-greedy}@anchor{4154}
@subsubsection 贪婪与非贪婪


当重复一个正则表达式时，就像在 @code{a*} 中一样，最终的动作就是消耗尽可能多的模式。 当你尝试匹配一对对称分隔符，例如 HTML 标记周围的尖括号时，这个事实经常会让你感到困惑。因为 @code{.*} 的贪婪性质， 用于匹配单个 HTML 标记的简单模式不起作用。

@example
>>> s = '<html><head><title>Title</title>'
>>> len(s)
32
>>> print(re.match('<.*>', s).span())
(0, 32)
>>> print(re.match('<.*>', s).group())
<html><head><title>Title</title>
@end example

正则匹配 @code{'<'} 中的 @code{'<html>'} 和 @code{.*} 消耗字符串的其余部分。 正则中还有更多的剩余东西，并且 @code{>} 在字符串的末尾不能匹配，所以正则表达式引擎必须逐个字符地回溯，直到它找到匹配 @code{>} 。最终匹配从 @code{'<html>'} 中的 @code{'<'} 扩展到 @code{'</title>'} 中的 @code{'>'} ，而这并不是你想要的结果。

在这种情况下，解决方案是使用非贪婪的限定符 @code{*?} 、 @code{+?} 、 @code{??} 或 @code{@{m,n@}?} ，匹配为尽可能 @emph{少} 的文字。 在上面的例子中，在第一次 @code{'<'} 匹配后立即尝试 @code{'>'} ，当它失败时，引擎一次前进一个字符，每一步都重试 @code{'>'} 。 这产生了正确的结果:

@example
>>> print(re.match('<.*?>', s).group())
<html>
@end example

（请注意，使用正则表达式解析 HTML 或 XML 很痛苦。快而脏的模式将处理常见情况，但 HTML 和 XML 有特殊情况会破坏明显的正则表达式；当你编写正则表达式处理所有可能的情况时，模式将非常复杂。使用 HTML 或 XML 解析器模块来执行此类任务。）

@node 使用 re VERBOSE,,贪婪与非贪婪,常见问题<2>
@anchor{howto/regex using-re-verbose}@anchor{4155}
@subsubsection 使用 re.VERBOSE


到目前为止，你可能已经注意到正则表达式是一种非常紧凑的表示法，但它们并不是非常易读。 具有中等复杂度的正则可能会成为反斜杠、括号和元字符的冗长集合，使其难以阅读和理解。

对于这样的正则，在编译正则表达式时指定 @ref{16f5,,re.VERBOSE} 标志可能会有所帮助，因为它允许你更清楚地格式化正则表达式。

@code{re.VERBOSE} 标志有几种效果。 正则表达式中的 @emph{不是} 在字符类中的空格将被忽略。 这意味着表达式如 @code{dog | cat} 等同于不太可读的 @code{dog|cat} ，但 @code{[a b]} 仍将匹配字符 @code{'a'} 、 @code{'b'} 或空格。 此外，你还可以在正则中放置注释；注释从 @code{#} 字符扩展到下一个换行符。 当与三引号字符串一起使用时，这使正则的格式更加整齐:

@example
pat = re.compile(r"""
 \s*                 # Skip leading whitespace
 (?P<header>[^:]+)   # Header name
 \s* :               # Whitespace, and a colon
 (?P<value>.*?)      # The header's value -- *? used to
                     # lose the following trailing whitespace
 \s*$                # Trailing whitespace to end-of-line
""", re.VERBOSE)
@end example

这更具有可读性:

@example
pat = re.compile(r"\s*(?P<header>[^:]+)\s*:(?P<value>.*?)\s*$")
@end example

@node 反馈,,常见问题<2>,正则表达式HOWTO
@anchor{howto/regex feedback}@anchor{4156}
@subsection 反馈


正则表达式是一个复杂的主题。 这份文档是否有助于你理解它们？ 是否存在不清楚的部分，或者你遇到的问题未在此处涉及？ 如果是，请向作者发送改进建议。

关于正则表达式的最完整的书几乎肯定是由 O'Reilly 出版的 Jeffrey Friedl 的 Mastering Regular Expressions 。 不幸的是，它专注于 Perl 和 Java 的正则表达式，并且根本不包含任何 Python 材料，因此它不能用作 Python 编程的参考。 （第一版涵盖了 Python 现在删除的 @code{regex} 模块，这对你没有多大帮助。）考虑从你的图书馆中查找它。

@node 套接字编程指南,排序指南,正则表达式HOWTO,Python 常用指引
@anchor{howto/sockets doc}@anchor{4157}@anchor{howto/sockets socket-howto}@anchor{263a}@anchor{howto/sockets socket-programming-howto}@anchor{4158}
@section 套接字编程指南


@*作者: 
Gordon McMillan


@subsubheading 摘要



套接字几乎无处不在，但是它却是被误解最严重的技术之一。这是一篇简单的套接字概述。并不是一篇真正的教程 —— 你需要做更多的事情才能让它工作起来。其中也并没有涵盖细节（细节会有很多），但是我希望它能提供足够的背景知识，让你像模像样的开始使用套接字

@menu
* 套接字:: 
* 创建套接字: 创建套接字<2>. 
* 使用一个套接字:: 
* 断开连接:: 
* 非阻塞的套接字:: 

@end menu

@node 套接字,创建套接字<2>,,套接字编程指南
@anchor{howto/sockets sockets}@anchor{4159}
@subsection 套接字


我将只讨论关于 INET（比如：IPv4 地址族）的套接字，但是它将覆盖几乎 99% 的套接字使用场景。并且我将仅讨论 STREAM（比如：TCP）类型的套接字 - 除非你真的知道你在做什么（那么这篇 HOWTO 可能并不适合你），使用 STREAM 类型的套接字将会得到比其它类型更好的表现与性能。我将尝试揭开套接字的神秘面纱，也会讲到一些阻塞与非阻塞套接字的使用。但是我将以阻塞套接字为起点开始讨论。只有你了解它是如何工作的以后才能处理非阻塞套接字。

理解这些东西的难点之一在于「套接字」可以表示很多微妙差异的东西，这取决于上下文。所以首先，让我们先分清楚「客户端」套接字和「服务端」套接字之间的不同，客户端套接字表示对话的一端，服务端套接字更像是总机接线员。客户端程序只能（比如：你的浏览器）使用「客户端」套接字；网络服务器则可以使用「服务端」套接字和「客户端」套接字来会话

@menu
* 历史:: 

@end menu

@node 历史,,,套接字
@anchor{howto/sockets history}@anchor{415a}
@subsubsection 历史


目前为止，在各种形式的 @abbr{IPC,进程间通信} 中，套接字是最流行的。在任何指定的平台上，可能会有其它更快的 IPC 形式，但是就跨平台通信来说，套接字大概是唯一的玩法

套接字做为 BSD Unix 操作系统的一部分在伯克利诞生，像野火一样在因特网传播。有一个很好的原因 —— 套接字与 INET 的结合使得与世界各地的任意机器间通信变得令人难以置信的简单（至少对比与其他方案来说）

@node 创建套接字<2>,使用一个套接字,套接字,套接字编程指南
@anchor{howto/sockets creating-a-socket}@anchor{415b}
@subsection 创建套接字


简略地说，当你点击带你来到这个页面的链接时，你的浏览器就已经做了下面这几件事情:

@example
# create an INET, STREAMing socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# now connect to the web server on port 80 - the normal http port
s.connect(("www.python.org", 80))
@end example

当连接完成，套接字可以用来发送请求来接收页面上显示的文字。同样是这个套接字也会用来读取响应，最后再被销毁。是的，被销毁了。客户端套接字通常用来做一次交换（或者说一小组序列的交换）。

网络服务器发生了什么这个问题就有点复杂了。首页，服务器创建一个「服务端套接字」:

@example
# create an INET, STREAMing socket
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# bind the socket to a public host, and a well-known port
serversocket.bind((socket.gethostname(), 80))
# become a server socket
serversocket.listen(5)
@end example

有几件事需要注意：我们使用了 @code{socket.gethostname()}，所以套接字将外网可见。如果我们使用的是 @code{s.bind(('localhost', 80))} 或者 @code{s.bind(('127.0.0.1', 80))}，也会得到一个「服务端」套接字，但是后者只在同一机器上可见。@code{s.bind(('@w{'}, 80))} 则指定套接字可以被机器上的任何地址碰巧连接

第二个需要注点是：低端口号通常被一些「常用的」服务（HTTP, SNMP 等）所保留。如果你想把程序跑起来，最好使用一个高位端口号（通常是4位的数字）。

最后，@code{listen} 方法的参数会告诉套接字库，我们希望在队列中累积多达 5 个（通常的最大值）连接请求后再拒绝外部连接。 如果所有其他代码都准确无误，这个队列长度应该是足够的。

现在我们已经有一个「服务端」套接字，监听了 80 端口，我们可以进入网络服务器的主循环了:

@example
while True:
    # accept connections from outside
    (clientsocket, address) = serversocket.accept()
    # now do something with the clientsocket
    # in this case, we'll pretend this is a threaded server
    ct = client_thread(clientsocket)
    ct.run()
@end example

事际上，通常有 3 种方法可以让这个循环工作起来 - 调度一个线程来处理 @code{客户端套接字}，或者把这个应用改成使用非阻塞模式套接字，亦或是使用 @code{select} 库来实现「服务端」套接字与任意活动 @code{客户端套接字} 之间的多路复用。稍后会详细介绍。现在最重要的是理解：这就是一个 @emph{服务端} 套接字做的 @emph{所有} 事情。它并没有发送任何数据。也没有接收任何数据。它只创建「客户端」套接字。每个 @code{客户端套接字} 都是为了响应某些其它客户端套接字 @code{connect()} 到我们绑定的主机。一旦创建 @code{客户端套接字} 完成，就会返回并监听更多的连接请求。现个客户端可以随意通信 - 它们使用了一些动态分配的端口，会话结束时端口才会被回收

@menu
* 进程间通信:: 

@end menu

@node 进程间通信,,,创建套接字<2>
@anchor{howto/sockets ipc}@anchor{415c}
@subsubsection 进程间通信


如果你需要在同一台机器上进行两个进程间的快速 IPC 通信，你应该了解管道或者共享内存。如果你决定使用 AF_INET 类型的套接字，绑定「服务端」套接字到 @code{'localhost'} 。在大多数平台，这将会使用一个许多网络层间的通用快捷方式（本地回环地址）并且速度会快很多


@subsubheading 参见


@ref{b7,,multiprocessing} 模块使跨平台 IPC 通信成为一个高层的 API


@node 使用一个套接字,断开连接,创建套接字<2>,套接字编程指南
@anchor{howto/sockets using-a-socket}@anchor{415d}
@subsection 使用一个套接字


首先需要注意，浏览器的「客户端」套接字和网络服务器的「客户端」套接字是极为相似的。即这种会话是「点对点」的。或者也可以说 @emph{你作为设计师需要自行决定会话的规则和礼节} 。通常情况下，@code{连接} 套接字通过发送一个请求或者信号来开始一次会话。但这属于设计决定，并不是套接字规则。

现在有两组用于通信的动词。你可以使用 @code{send} 和 @code{recv} ，或者你可以把客户端套接字改成文件类型的形式来使用  @code{read} 和 @code{write} 方法。后者是 Java 语言中表示套接字的方法，我将不会在这儿讨论这个，但是要提醒你需要调用套接字的 @code{flush} 方法。这些是“缓冲”的文件，一个经常出现的错误是 @code{write} 一些东西，然后就直接开始 @code{read} 一个响应。如果不调用 @code{flush} ，你可能会一直等待这个响应，因为请求可能还在你的输出缓冲中。

现在我来到了套接字的两个主要的绊脚石 - @code{send} 和 @code{recv} 操作网络缓冲区。它们并不一定可以处理所有你想要（期望）的字节，因为它们主要关注点是处理网络缓冲。通常，它们在关联的网络缓冲区 @code{send} 或者清空 @code{recv} 时返回。然后告诉你处理了多少个字节。@emph{你} 的责任是一直调用它们直到你所有的消息处理完成。

当 @code{recv} 方法返回 0 字节时，就表示另一端已经关闭（或者它所在的进程关闭）了连接。你再也不能从这个连接上获取到任何数据了。你可以成功的发送数据；我将在后面讨论这一点。

像 HTTP 这样的协议只使用一个套接字进行一次传输。客户端发送一个请求，然后读取响应。就这么简单。套接字会被销毁。 表示客户端可以通过接收 0 字节序列表示检测到响应的结束。

但是如果你打算在随后来的传输中复用套接字的话，你需要明白 @emph{套接字里面是不存在 :abbr:`EOT (传输结束)`} 的。重复一下：套接字 @code{send} 或者 @code{recv} 完 0 字节后返回，连接会中断。如果连接没有被断开，你可能会永远处于等待 @code{recv} 的状态，因为（就目前来说）套接字 @emph{不会} 告诉你不用再读取了。现在如果你细心一点，你可能会意识到套接字基本事实：@emph{消息必须要么具有固定长度，要么可以界定，要么指定了长度（比较好的做法），要么以关闭连接为结束}。选择完全由你而定（这比让别人定更合理）。

假定你不希望结束连接，那么最简单的解决方案就是使用定长消息:

@example
class MySocket:
    """demonstration class only
      - coded for clarity, not efficiency
    """

    def __init__(self, sock=None):
        if sock is None:
            self.sock = socket.socket(
                            socket.AF_INET, socket.SOCK_STREAM)
        else:
            self.sock = sock

    def connect(self, host, port):
        self.sock.connect((host, port))

    def mysend(self, msg):
        totalsent = 0
        while totalsent < MSGLEN:
            sent = self.sock.send(msg[totalsent:])
            if sent == 0:
                raise RuntimeError("socket connection broken")
            totalsent = totalsent + sent

    def myreceive(self):
        chunks = []
        bytes_recd = 0
        while bytes_recd < MSGLEN:
            chunk = self.sock.recv(min(MSGLEN - bytes_recd, 2048))
            if chunk == b'@w{'}:
                raise RuntimeError("socket connection broken")
            chunks.append(chunk)
            bytes_recd = bytes_recd + len(chunk)
        return b'@w{'}.join(chunks)
@end example

发送分部代码几乎可用于任何消息传递方案 —— 在 Python 中你发送字符串，可以使用 @code{len()} 方法来确定它的长度（即使它嵌入了 @code{\0} 字符），主要是接收代码变得更复杂。（在 C 语言中，并没有更糟糕，除非消息嵌入了 @code{\0} 字符而且你又无法使用 @code{strlen} ）

最简单的改进是让消息的第一个字符表示消息类型，由类型决定长度。现在你需要两次 @code{recv}- 第一次取（至少）第一个字符来知晓长度，第二次在循环中获取剩余所有的消息。如果你决定到分界线，你将收到一些任意大小的块，（4096 或者 8192 通常是比较合适的网络缓冲区大小），扫描你接收到的分界符

一个需要意识到的复杂情况是：如果你的会话协议允许多个消息被发送回来（没有响应），调用 @code{recv} 传入任意大小的块，你可能会因为读到后续接收的消息而停止读取。你需要将它放在一边并保存，直到它需要为止。

以其长度（例如，作为5个数字字符）作为消息前缀时会变得更复杂，因为（信不信由你）你可能无法在一个 @code{recv} 中获得所有5个字符。在一般使用时，你会侥幸避免该状况；但是在高网络负载中，除非你使用两个 @code{recv} 循环，否则你的代码将很快中断 —— 第一个用于确定长度，第二个用于获取消息的数据部分。这很讨厌。当你发现 @code{send} 并不总是设法在支持搞定一切时，你也会有这种感觉。 尽管已经阅读过这篇文章，但最终还是会有所了解！

限于篇幅，建立你的角色，（保持与我的竞争位置），这些改进将留给读者做为练习。现在让我们继续。

@menu
* 二进制数据:: 

@end menu

@node 二进制数据,,,使用一个套接字
@anchor{howto/sockets binary-data}@anchor{415e}
@subsubsection 二进制数据


通过套接字传送二进制数据是可行的。主要问题在于并非所有机器都用同样的二进制数据格式。比如 Motorola 芯片用两个十六进制字节 00 01 来表示一个 16 位整数值 1。而 Intel 和 DEC 则会做字节反转 —— 即用 01 00 来表示 1。套接字库要求转换 16 位和 32 位整数 —— @code{ntohl, htonl, ntohs, htons} 其中的「n」表示 @emph{network}，「h」表示 @emph{host}，「s」表示 @emph{short}，「l」表示 @emph{long}。在网络序列就是主机序列时它们什么都不做，但是如果机器是字节反转的则会适当地交换字节序。

在现今的 32 位机器中，二进制数据的 ascii 表示往往比二进制表示要小。这是因为在非常多的时候所有 long 的值均为 0 或者 1。字符串形式的 "0" 为两个字节，而二进制形式则为四个。当然这不适用于固定长度的信息。自行决定，请自行决定。

@node 断开连接,非阻塞的套接字,使用一个套接字,套接字编程指南
@anchor{howto/sockets disconnecting}@anchor{415f}
@subsection 断开连接


严格地讲，你应该在 @code{close} 它之前将套接字 @code{shutdown} 。 @code{shutdown} 是发送给套接字另一端的一种建议。调用时参数不同意义也不一样，它可能意味着「我不会再发送了，但我仍然会监听」，或者「我没有监听了，真棒！」。然而，大多数套接字库或者程序员都习惯了忽略使用这种礼节，因为通常情况下 @code{close} 与 @code{shutdown(); close()} 是一样的。所以在大多数情况下，不需要显式的 @code{shutdown} 。

高效使用 @code{shutdown} 的一种方法是在类似 HTTP 的交换中。客户端发送请求，然后执行 @code{shutdown(1)} 。 这告诉服务器“此客户端已完成发送，但仍可以接收”。服务器可以通过接收 0 字节来检测 “EOF” 。它可以假设它有完整的请求。服务器发送回复。如果 @code{send} 成功完成，那么客户端仍在接收。

Python 进一步自动关闭，并说当一个套接字被垃圾收集时，如果需要它会自动执行 @code{close} 。但依靠这个机制是一个非常坏的习惯。如果你的套接字在没有 @code{close} 的情况下就消失了，那么另一端的套接字可能会无限期地挂起，以为你只是慢了一步。完成后 @emph{请} @code{close} 你的套接字。

@menu
* 套接字何时销毁:: 

@end menu

@node 套接字何时销毁,,,断开连接
@anchor{howto/sockets when-sockets-die}@anchor{4160}
@subsubsection 套接字何时销毁


使用阻塞套接字最糟糕的事情可能就是当另一边下线时（没有 @code{close} ）会发生什么。你的套接字可能会挂起。 TCP 是一种可靠的协议，它会在放弃连接之前等待很长时间。如果你正在使用线程，那么整个线程基本上已经死了。你无能为力。只要你没有做一些愚蠢的事情，比如在进行阻塞读取时持有一个锁，那么线程并没有真正消耗掉资源。 @emph{不要} 尝试杀死线程 —— 线程比进程更有效的部分原因是它们避免了与自动回收资源相关的开销。换句话说，如果你设法杀死线程，你的整个进程很可能被搞坏。

@node 非阻塞的套接字,,断开连接,套接字编程指南
@anchor{howto/sockets non-blocking-sockets}@anchor{4161}
@subsection 非阻塞的套接字


如果你已理解上述内容，那么你已经了解了使用套接字的机制所需了解的大部分内容。你仍将以相同的方式使用相同的函数调用。 只是，如果你做得对，你的应用程序几乎是由内到外的。

在 Python 中是使用 @code{socket.setblocking(0)} 来使其为非阻塞。 在 C 中做法更为复杂（例如，你需要在 BSD 风格的 @code{O_NONBLOCK} 和几乎无区别的 POSIX 风格的 @code{O_NDELAY} 之间作出选择，这与 @code{TCP_NODELAY} 完全不一样。）。 但其思路是完全相同的。 你要在创建套拼字之后但在使用它之前执行此操作。 （实际上，除非你是疯子才会反复切换。）

主要的机制差异是 @code{send} 、 @code{recv} 、 @code{connect} 和 @code{accept} 可以在没有做任何事情的情况下返回。 你（当然）有很多选择。你可以检查返回代码和错误代码，通常会让自己发疯。如果你不相信我，请尝试一下。你的应用程序将变得越来越大、越来越 Bug 、吸干 CPU。因此，让我们跳过脑死亡的解决方案并做正确的事。

使用 @code{select} 库

在 C 中，编码 @code{select} 相当复杂。 在 Python 中，它是很简单，但它与 C 版本足够接近，如果你在 Python 中理解 @code{select} ，那么在 C 中你会几乎不会遇到麻烦:

@example
ready_to_read, ready_to_write, in_error = \
               select.select(
                  potential_readers,
                  potential_writers,
                  potential_errs,
                  timeout)
@end example

你传递给 @code{select} 三个列表：第一个包含你可能想要尝试读取的所有套接字；第二个是你可能想要尝试写入的所有套接字，以及要检查错误的最后一个（通常为空）。你应该注意，套接字可以进入多个列表。 @code{select} 调用是阻塞的，但你可以给它一个超时。这通常是一件明智的事情 —— 给它一个很长的超时（比如一分钟），除非你有充分的理由不这样做。

作为返回，你将获得三个列表。它们包含实际可读、可写和有错误的套接字。 这些列表中的每一个都是你传入的相应列表的子集（可能为空）。

如果一个套接字在输出可读列表中，那么你可以像我们一样接近这个业务，那个套接字上的 @code{recv} 将返回 @emph{一些内容} 。可写列表的也相同，你将能够发送 @emph{一些内容} 。 也许不是你想要的全部，但 @emph{有些东西} 比没有东西更好。 （实际上，任何合理健康的套接字都将以可写方式返回 —— 它只是意味着出站网络缓冲区空间可用。）

如果你有一个“服务器”套接字，请将其放在 potential_readers 列表中。如果它出现在可读列表中，那么你的 @code{accept} （几乎肯定）会起作用。如果你已经创建了一个新的套接字 @code{connect} 其他人，请将它放在 potential_writers 列表中。如果它出现在可写列表中，那么它有可能已连接。

实际上，即使使用阻塞套接字， @code{select} 也很方便。这是确定是否阻塞的一种方法 —— 当缓冲区中存在某些内容时，套接字返回为可读。然而，这仍然无助于确定另一端是否完成或者只是忙于其他事情的问题。

@strong{可移植性警告} ：在 Unix 上， @code{select} 适用于套接字和文件。 不要在 Windows 上尝试。在 Windows 上， @code{select} 仅适用于套接字。另请注意，在 C 中，许多更高级的套接字选项在 Windows 上的执行方式不同。事实上，在 Windows 上我通常在使用我的套接字使用线程（非常非常好）。

@node 排序指南,Unicode 指南,套接字编程指南,Python 常用指引
@anchor{howto/sorting doc}@anchor{4162}@anchor{howto/sorting sorting-how-to}@anchor{4163}@anchor{howto/sorting sortinghowto}@anchor{1599}
@section 排序指南


@*作者: 
Andrew Dalke 和 Raymond Hettinger


@*发布版本: 
0.1


Python 列表有一个内置的 @ref{43f,,list.sort()} 方法可以直接修改列表。还有一个 @ref{43e,,sorted()} 内置函数，它会从一个可迭代对象构建一个新的排序列表。

在本文档中，我们将探索使用Python对数据进行排序的各种技术。

@menu
* 基本排序:: 
* 关键函数:: 
* Operator 模块函数:: 
* 升序和降序:: 
* 排序稳定性和排序复杂度:: 
* 使用装饰-排序-去装饰的旧方法:: 
* 使用 cmp 参数的旧方法:: 
* 其它:: 

@end menu

@node 基本排序,关键函数,,排序指南
@anchor{howto/sorting sorting-basics}@anchor{4164}
@subsection 基本排序


简单的升序排序非常简单：只需调用 @ref{43e,,sorted()} 函数即可。它会返回一个新的已排序列表。

@example
>>> sorted([5, 2, 3, 1, 4])
[1, 2, 3, 4, 5]
@end example

你也可以使用 @ref{43f,,list.sort()} 方法，它会直接修改原列表（并返回 @code{None} 以避免混淆），通常来说它不如 @ref{43e,,sorted()} 方便 ——— 但如果你不需要原列表，它会更有效率。

@example
>>> a = [5, 2, 3, 1, 4]
>>> a.sort()
>>> a
[1, 2, 3, 4, 5]
@end example

另外一个区别是， @ref{43f,,list.sort()} 方法只是为列表定义的，而 @ref{43e,,sorted()} 函数可以接受任何可迭代对象。

@example
>>> sorted(@{1: 'D', 2: 'B', 3: 'B', 4: 'E', 5: 'A'@})
[1, 2, 3, 4, 5]
@end example

@node 关键函数,Operator 模块函数,基本排序,排序指南
@anchor{howto/sorting key-functions}@anchor{4165}
@subsection 关键函数


@ref{43f,,list.sort()} 和 @ref{43e,,sorted()} 都有一个 @emph{key} 形参来指定在进行比较之前要在每个列表元素上进行调用的函数。

例如，下面是一个不区分大小写的字符串比较：

@example
>>> sorted("This is a test string from Andrew".split(), key=str.lower)
['a', 'Andrew', 'from', 'is', 'string', 'test', 'This']
@end example

@emph{key} 形参的值应该是一个函数，它接受一个参数并并返回一个用于排序的键。这种技巧速度很快，因为对于每个输入记录只会调用一次 key 函数。

一种常见的模式是使用对象的一些索引作为键对复杂对象进行排序。例如：

@example
>>> student_tuples = [
...     ('john', 'A', 15),
...     ('jane', 'B', 12),
...     ('dave', 'B', 10),
... ]
>>> sorted(student_tuples, key=lambda student: student[2])   # sort by age
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
@end example

同样的技术也适用于具有命名属性的对象。例如：

@example
>>> class Student:
...     def __init__(self, name, grade, age):
...         self.name = name
...         self.grade = grade
...         self.age = age
...     def __repr__(self):
...         return repr((self.name, self.grade, self.age))
@end example

@example
>>> student_objects = [
...     Student('john', 'A', 15),
...     Student('jane', 'B', 12),
...     Student('dave', 'B', 10),
... ]
>>> sorted(student_objects, key=lambda student: student.age)   # sort by age
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
@end example

@node Operator 模块函数,升序和降序,关键函数,排序指南
@anchor{howto/sorting operator-module-functions}@anchor{4166}
@subsection Operator 模块函数


上面显示的键函数模式非常常见，因此 Python 提供了便利功能，使访问器功能更容易，更快捷。  @ref{c2,,operator} 模块有 @ref{261,,itemgetter()} 、 @ref{715,,attrgetter()} 和 @ref{716,,methodcaller()} 函数。

使用这些函数，上述示例变得更简单，更快捷：

@example
>>> from operator import itemgetter, attrgetter
@end example

@example
>>> sorted(student_tuples, key=itemgetter(2))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
@end example

@example
>>> sorted(student_objects, key=attrgetter('age'))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
@end example

Operator 模块功能允许多级排序。 例如，按 @emph{grade} 排序，然后按 @emph{age} 排序：

@example
>>> sorted(student_tuples, key=itemgetter(1,2))
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)]
@end example

@example
>>> sorted(student_objects, key=attrgetter('grade', 'age'))
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)]
@end example

@node 升序和降序,排序稳定性和排序复杂度,Operator 模块函数,排序指南
@anchor{howto/sorting ascending-and-descending}@anchor{4167}
@subsection 升序和降序


@ref{43f,,list.sort()} 和 @ref{43e,,sorted()} 接受布尔值的 @emph{reverse} 参数。这用于标记降序排序。 例如，要以反向 @emph{age} 顺序获取学生数据：

@example
>>> sorted(student_tuples, key=itemgetter(2), reverse=True)
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]
@end example

@example
>>> sorted(student_objects, key=attrgetter('age'), reverse=True)
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]
@end example

@node 排序稳定性和排序复杂度,使用装饰-排序-去装饰的旧方法,升序和降序,排序指南
@anchor{howto/sorting sort-stability-and-complex-sorts}@anchor{4168}
@subsection 排序稳定性和排序复杂度


排序保证是 稳定@footnote{https://en.wikipedia.org/wiki/Sorting_algorithm#Stability} 的。 这意味着当多个记录具有相同的键值时，将保留其原始顺序。

@example
>>> data = [('red', 1), ('blue', 1), ('red', 2), ('blue', 2)]
>>> sorted(data, key=itemgetter(0))
[('blue', 1), ('blue', 2), ('red', 1), ('red', 2)]
@end example

注意 @emph{blue} 的两个记录如何保留它们的原始顺序，以便 @code{('blue', 1)} 保证在 @code{('blue', 2)} 之前。

这个美妙的属性允许你在一系列排序步骤中构建复杂的排序。例如，要按 @emph{grade} 降序然后 @emph{age} 升序对学生数据进行排序，请先 @emph{age} 排序，然后再使用 @emph{grade} 排序：

@example
>>> s = sorted(student_objects, key=attrgetter('age'))     # sort on secondary key
>>> sorted(s, key=attrgetter('grade'), reverse=True)       # now sort on primary key, descending
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
@end example

这可以被抽象为一个包装函数，该函数能接受一个列表以及字段和顺序的元组，以对它们进行多重排序。

@example
>>> def multisort(xs, specs):
...     for key, reverse in reversed(specs):
...         xs.sort(key=attrgetter(key), reverse=reverse)
...     return xs
@end example

@example
>>> multisort(list(student_objects), (('grade', True), ('age', False)))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
@end example

Python 中使用的 Timsort@footnote{https://en.wikipedia.org/wiki/Timsort} 算法可以有效地进行多种排序，因为它可以利用数据集中已存在的任何排序。

@node 使用装饰-排序-去装饰的旧方法,使用 cmp 参数的旧方法,排序稳定性和排序复杂度,排序指南
@anchor{howto/sorting the-old-way-using-decorate-sort-undecorate}@anchor{4169}
@subsection 使用装饰-排序-去装饰的旧方法


这个三个步骤被称为 Decorate-Sort-Undecorate ：


@itemize *

@item 
首先，初始列表使用控制排序顺序的新值进行修饰。

@item 
然后，装饰列表已排序。

@item 
最后，删除装饰，创建一个仅包含新排序中初始值的列表。
@end itemize

例如，要使用DSU方法按 @emph{grade} 对学生数据进行排序：

@example
>>> decorated = [(student.grade, i, student) for i, student in enumerate(student_objects)]
>>> decorated.sort()
>>> [student for grade, i, student in decorated]               # undecorate
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]
@end example

这方法语有效是因为元组按字典顺序进行比较，先比较第一项；如果它们相同则比较第二个项目，依此类推。

不一定在所有情况下都要在装饰列表中包含索引 @emph{i} ，但包含它有两个好处：


@itemize *

@item 
排序是稳定的——如果两个项具有相同的键，它们的顺序将保留在排序列表中。

@item 
原始项目不必具有可比性，因为装饰元组的排序最多由前两项决定。 因此，例如原始列表可能包含无法直接排序的复数。
@end itemize

这个方法的另一个名字是 Randal L. Schwartz 在 Perl 程序员中推广的 Schwartzian transform@footnote{https://en.wikipedia.org/wiki/Schwartzian_transform}。

既然 Python 排序提供了键函数，那么通常不需要这种技术。

@node 使用 cmp 参数的旧方法,其它,使用装饰-排序-去装饰的旧方法,排序指南
@anchor{howto/sorting the-old-way-using-the-cmp-parameter}@anchor{416a}
@subsection 使用 @emph{cmp} 参数的旧方法


本 HOWTO 中给出的许多结构都假定为 Python 2.4 或更高版本。在此之前，没有内置 @ref{43e,,sorted()} ， @ref{43f,,list.sort()} 也没有关键字参数。相反，所有 Py2.x 版本都支持 @emph{cmp} 参数来处理用户指定的比较函数。

在 Py3.0 中， @emph{cmp} 参数被完全删除（作为简化和统一语言努力的一部分，消除了丰富的比较与 @code{__cmp__()} 魔术方法之间的冲突）。

在 Py2.x 中， sort 允许一个可选函数，可以调用它来进行比较。该函数应该采用两个参数进行比较，然后返回负值为小于，如果它们相等则返回零，或者返回大于大于的正值。例如，我们可以这样做：

@example
>>> def numeric_compare(x, y):
...     return x - y
>>> sorted([5, 2, 4, 1, 3], cmp=numeric_compare) 
[1, 2, 3, 4, 5]
@end example

或者你可反转比较的顺序：

@example
>>> def reverse_numeric(x, y):
...     return y - x
>>> sorted([5, 2, 4, 1, 3], cmp=reverse_numeric) 
[5, 4, 3, 2, 1]
@end example

将代码从 Python 2.x 移植到 3.x 时，如果用户提供比较功能并且需要将其转换为键函数，则会出现这种情况。 以下包装器使这很容易：

@example
def cmp_to_key(mycmp):
    'Convert a cmp= function into a key= function'
    class K:
        def __init__(self, obj, *args):
            self.obj = obj
        def __lt__(self, other):
            return mycmp(self.obj, other.obj) < 0
        def __gt__(self, other):
            return mycmp(self.obj, other.obj) > 0
        def __eq__(self, other):
            return mycmp(self.obj, other.obj) == 0
        def __le__(self, other):
            return mycmp(self.obj, other.obj) <= 0
        def __ge__(self, other):
            return mycmp(self.obj, other.obj) >= 0
        def __ne__(self, other):
            return mycmp(self.obj, other.obj) != 0
    return K
@end example

要转换为键函数，只需包装旧的比较函数：

@c from functools import cmp_to_key

@example
>>> sorted([5, 2, 4, 1, 3], key=cmp_to_key(reverse_numeric))
[5, 4, 3, 2, 1]
@end example

在 Python 3.2 中， @ref{b4f,,functools.cmp_to_key()} 函数被添加到标准库中的 @ref{85,,functools} 模块中。

@node 其它,,使用 cmp 参数的旧方法,排序指南
@anchor{howto/sorting odd-and-ends}@anchor{416b}
@subsection 其它



@itemize *

@item 
对于区域相关的排序，请使用 @ref{3024,,locale.strxfrm()} 作为键函数，或者 @ref{3022,,locale.strcoll()} 作为比较函数。

@item 
@emph{reverse} 参数仍然保持排序稳定性（因此具有相等键的记录保留原始顺序）。 有趣的是，通过使用内置的 @ref{18e,,reversed()} 函数两次，可以在没有参数的情况下模拟该效果：

@example
>>> data = [('red', 1), ('blue', 1), ('red', 2), ('blue', 2)]
>>> standard_way = sorted(data, key=itemgetter(0), reverse=True)
>>> double_reversed = list(reversed(sorted(reversed(data), key=itemgetter(0))))
>>> assert standard_way == double_reversed
>>> standard_way
[('red', 1), ('red', 2), ('blue', 1), ('blue', 2)]
@end example

@item 
在两个对象之间进行比较时，保证排序例程使用 @ref{c2d,,__lt__()} 。 因此，通过定义 @ref{c2d,,__lt__()} 方法，可以很容易地为类添加标准排序顺序:

@example
>>> Student.__lt__ = lambda self, other: self.age < other.age
>>> sorted(student_objects)
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
@end example

@item 
键函数不需要直接依赖于被排序的对象。键函数还可以访问外部资源。例如，如果学生成绩存储在字典中，则可以使用它们对单独的学生姓名列表进行排序：

@example
>>> students = ['dave', 'john', 'jane']
>>> newgrades = @{'john': 'F', 'jane':'A', 'dave': 'C'@}
>>> sorted(students, key=newgrades.__getitem__)
['jane', 'dave', 'john']
@end example
@end itemize

@node Unicode 指南,HOWTO 使用 urllib 包获取网络资源,排序指南,Python 常用指引
@anchor{howto/unicode doc}@anchor{416c}@anchor{howto/unicode id1}@anchor{416d}@anchor{howto/unicode unicode-howto}@anchor{c35}
@section Unicode 指南


@*发布版本: 
1.12


本指南讨论了 Python 对于表达文本数据的 Unicode 规范的支持，并且解释了人们试图使用 Unicode 时经常遇到的问题。

@menu
* Unicode 概述:: 
* Python's Unicode Support:: 
* Reading and Writing Unicode Data:: 
* 致谢: 致谢<10>. 

@end menu

@node Unicode 概述,Python's Unicode Support,,Unicode 指南
@anchor{howto/unicode introduction-to-unicode}@anchor{416e}
@subsection Unicode 概述


@menu
* 定义:: 
* 编码:: 
* 参考文献: 参考文献<3>. 

@end menu

@node 定义,编码,,Unicode 概述
@anchor{howto/unicode definitions}@anchor{416f}
@subsubsection 定义


如今的程序需要具有处理许多不同类型字符的能力。应用程序常常需要国际化以便以用户可选择的不同语言显示信息和输出。同一个程序可能需要以英语、法语、日语、希伯来语或俄语输出错误信息。网页内容可能由任何语言写成，并且可能包含不同的表情符号。Python 的字符串类型使用 Unicode 标准来表示字符，这使 Python 程序能够正常处理所有这些可能的字符。

Unicode 规范 (@indicateurl{https://www.unicode.org/}) 旨在列出人类语言中用到的每个字符，并赋予每个字符唯一的编码。该规范持续进行修订和更新以添加新的语言和符号。

一个**字符**是文本的最小可能部件。‘A’、‘B’、‘C’ 等都是不同的字符。‘È’ 和 ‘Í’ 也一样。字符会随着语言或者上下文的变化而变化。比如，‘Ⅰ’ 是一个表示 “罗马数字 1” 的字符，它与大写字母 ‘I’ 不同。它们常常看起来相同，但这是两个有着不同含义的不同字符。

Unicode 标准描述了**码位**如何表示字符。一个码位的值是在 0 到 0x10FFFF （大约 110 万个值，目前有其中 11 万个被指派）。在这一标准中并且在这一文档中，一个码位写作 @code{U+265E} 来表示拥有值 @code{0x265e} 的字符（十进制下为 9,822）。

Unicode 标准包含了许多表格来列出字符和对应的码位。

@example
0061    'a'; LATIN SMALL LETTER A
0062    'b'; LATIN SMALL LETTER B
0063    'c'; LATIN SMALL LETTER C
...
007B    '@{'; LEFT CURLY BRACKET
...
2167    'Ⅷ'; ROMAN NUMERAL EIGHT
2168    'Ⅸ'; ROMAN NUMERAL NINE
...
265E    '♞'; BLACK CHESS KNIGHT
265F    '♟'; BLACK CHESS PAWN
...
1F600   '😀'; GRINNING FACE
1F609   '😉'; WINKING FACE
...
@end example

严格地说，这些定义暗示了这样的说法是没有意义的：“这是字符 @code{U+265E}”。@code{U+265E} 是一个码位，其代表了某特定的字符 —— 在这一情形下，它代表了字符 “国际象棋黑方骑士（黑马）” ‘♞’。在非正式上下文中，码位和字符的差异有时会被忽略。

一个字符在屏幕上或在纸上被表示为一组图形元素，被称为**字形**。比如，大写字母 A 的字形，是斜向的两笔和水平的一笔，而具体的细节取决于所使用的字体。大部分 Python 代码不必担心字形，找到应被显示的正确字形一般来说是用户图形界面工具箱或者终端的字体渲染器的工作。

@node 编码,参考文献<3>,定义,Unicode 概述
@anchor{howto/unicode encodings}@anchor{4170}
@subsubsection 编码


上一段可以归结为：一个 Unicode 字符串是一系列码位（从 0 到 @code{0x10FFFF} 或者说十进制的 1,114,111 的数字）组成的序列。这一序列在内存中需要被表示为一组**码元**，然后**码元** 会对应到包含八个二进制位的字节。将 Unicode 字符串翻译成字节序列的规则被称为**字符编码**，或者**编码**。

你可能会想到的第一种编码是使用一个 32 位的整数来代表一个代码位，然后使用 CPU 对 32 位整数的表达方式。在这一表达方式中，字符串 “Python” 可能看起来像是这样：

@example
   P           y           t           h           o           n
0x50 00 00 00 79 00 00 00 74 00 00 00 68 00 00 00 6f 00 00 00 6e 00 00 00
   0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
@end example

这个表达方式非常直接，但同时也存在 一些问题。


@enumerate 

@item 
不够方便；不同的处理器对字节的排序不同。

@item 
非常浪费空间。多数编码都小于127，或者255，所以很多空间都是 @code{0x00}。上面的字符串takes 24 bytes compared to the 6 bytes needed for an ASCII representation. Increased RAM usage doesn't matter too much (desktop computers have gigabytes of RAM, and strings aren't usually that large), but expanding our usage of disk and network bandwidth by a factor of 4 is intolerable.

@item 
It's not compatible with existing C functions such as @code{strlen()}, so a new
family of wide string functions would need to be used.
@end enumerate

Therefore this encoding isn't used very much, and people instead choose other
encodings that are more efficient and convenient, such as UTF-8.

UTF-8 is one of the most commonly used encodings, and Python often
defaults to using it.  UTF stands for "Unicode Transformation Format",
and the '8' means that 8-bit values are used in the encoding.  (There
are also UTF-16 and UTF-32 encodings, but they are less frequently
used than UTF-8.)  UTF-8 uses the following rules:


@enumerate 

@item 
If the code point is < 128, it's represented by the corresponding byte value.

@item 
If the code point is >= 128, it's turned into a sequence of two, three, or
four bytes, where each byte of the sequence is between 128 and 255.
@end enumerate

UTF-8 has several convenient properties:


@enumerate 

@item 
It can handle any Unicode code point.

@item 
A Unicode string is turned into a sequence of bytes that contains embedded
zero bytes only where they represent the null character (U+0000). This means
that UTF-8 strings can be processed by C functions such as @code{strcpy()} and sent
through protocols that can't handle zero bytes for anything other than
end-of-string markers.

@item 
A string of ASCII text is also valid UTF-8 text.

@item 
UTF-8 is fairly compact; the majority of commonly used characters can be
represented with one or two bytes.

@item 
If bytes are corrupted or lost, it's possible to determine the start of the
next UTF-8-encoded code point and resynchronize.  It's also unlikely that
random 8-bit data will look like valid UTF-8.

@item 
UTF-8 is a byte oriented encoding. The encoding specifies that each
character is represented by a specific sequence of one or more bytes. This
avoids the byte-ordering issues that can occur with integer and word oriented
encodings, like UTF-16 and UTF-32, where the sequence of bytes varies depending
on the hardware on which the string was encoded.
@end enumerate

@node 参考文献<3>,,编码,Unicode 概述
@anchor{howto/unicode references}@anchor{4171}
@subsubsection 参考文献


The Unicode Consortium site@footnote{http://www.unicode.org} has character charts, a
glossary, and PDF versions of the Unicode specification.  Be prepared for some
difficult reading.  A chronology@footnote{http://www.unicode.org/history/} of the
origin and development of Unicode is also available on the site.

On the Computerphile Youtube channel, Tom Scott briefly
discusses the history of Unicode and UTF-8@footnote{https://www.youtube.com/watch?v=MijmeoH9LT4}
(9 minutes 36 seconds).

To help understand the standard, Jukka Korpela has written an introductory guide@footnote{http://jkorpela.fi/unicode/guide.html} to reading the
Unicode character tables.

Another good introductory article@footnote{https://www.joelonsoftware.com/2003/10/08/the-absolute-minimum-every-software-developer-absolutely-positively-must-know-about-unicode-and-character-sets-no-excuses/}
was written by Joel Spolsky.
If this introduction didn't make things clear to you, you should try
reading this alternate article before continuing.

Wikipedia entries are often helpful; see the entries for "character encoding@footnote{https://en.wikipedia.org/wiki/Character_encoding}" and UTF-8@footnote{https://en.wikipedia.org/wiki/UTF-8}, for example.

@node Python's Unicode Support,Reading and Writing Unicode Data,Unicode 概述,Unicode 指南
@anchor{howto/unicode python-s-unicode-support}@anchor{4172}
@subsection Python's Unicode Support


Now that you've learned the rudiments of Unicode, we can look at Python's
Unicode features.

@menu
* The String Type:: 
* Converting to Bytes:: 
* Unicode Literals in Python Source Code:: 
* Unicode Properties:: 
* Comparing Strings:: 
* Unicode Regular Expressions:: 
* 参考文献: 参考文献<4>. 

@end menu

@node The String Type,Converting to Bytes,,Python's Unicode Support
@anchor{howto/unicode the-string-type}@anchor{4173}
@subsubsection The String Type


Since Python 3.0, the language's @ref{329,,str} type contains Unicode
characters, meaning any string created using @code{"unicode rocks!"}, @code{'unicode
rocks!'}, or the triple-quoted string syntax is stored as Unicode.

The default encoding for Python source code is UTF-8, so you can simply
include a Unicode character in a string literal:

@example
try:
    with open('/tmp/input.txt', 'r') as f:
        ...
except OSError:
    # 'File not found' error message.
    print("Fichier non trouvé")
@end example

Side note: Python 3 also supports using Unicode characters in identifiers:

@example
répertoire = "/tmp/records.log"
with open(répertoire, "w") as f:
    f.write("test\n")
@end example

If you can't enter a particular character in your editor or want to
keep the source code ASCII-only for some reason, you can also use
escape sequences in string literals. (Depending on your system,
you may see the actual capital-delta glyph instead of a u escape.)

@example
>>> "\N@{GREEK CAPITAL LETTER DELTA@}"  # Using the character name
'\u0394'
>>> "\u0394"                          # Using a 16-bit hex value
'\u0394'
>>> "\U00000394"                      # Using a 32-bit hex value
'\u0394'
@end example

In addition, one can create a string using the @ref{c31,,decode()} method of
@ref{32a,,bytes}.  This method takes an @emph{encoding} argument, such as @code{UTF-8},
and optionally an @emph{errors} argument.

The @emph{errors} argument specifies the response when the input string can't be
converted according to the encoding's rules.  Legal values for this argument are
@code{'strict'} (raise a @ref{1fd,,UnicodeDecodeError} exception), @code{'replace'} (use
@code{U+FFFD}, @code{REPLACEMENT CHARACTER}), @code{'ignore'} (just leave the
character out of the Unicode result), or @code{'backslashreplace'} (inserts a
@code{\xNN} escape sequence).
The following examples show the differences:

@example
>>> b'\x80abc'.decode("utf-8", "strict")  
Traceback (most recent call last):
    ...
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 0:
  invalid start byte
>>> b'\x80abc'.decode("utf-8", "replace")
'\ufffdabc'
>>> b'\x80abc'.decode("utf-8", "backslashreplace")
'\\x80abc'
>>> b'\x80abc'.decode("utf-8", "ignore")
'abc'
@end example

Encodings are specified as strings containing the encoding's name.  Python
comes with roughly 100 different encodings; see the Python Library Reference at
@ref{689,,标准编码} for a list.  Some encodings have multiple names; for
example, @code{'latin-1'}, @code{'iso_8859_1'} and @code{'8859}' are all synonyms for
the same encoding.

One-character Unicode strings can also be created with the @ref{13bf,,chr()}
built-in function, which takes integers and returns a Unicode string of length 1
that contains the corresponding code point.  The reverse operation is the
built-in @ref{13be,,ord()} function that takes a one-character Unicode string and
returns the code point value:

@example
>>> chr(57344)
'\ue000'
>>> ord('\ue000')
57344
@end example

@node Converting to Bytes,Unicode Literals in Python Source Code,The String Type,Python's Unicode Support
@anchor{howto/unicode converting-to-bytes}@anchor{4174}
@subsubsection Converting to Bytes


The opposite method of @ref{c31,,bytes.decode()} is @ref{c30,,str.encode()},
which returns a @ref{32a,,bytes} representation of the Unicode string, encoded in the
requested @emph{encoding}.

The @emph{errors} parameter is the same as the parameter of the
@ref{c31,,decode()} method but supports a few more possible handlers. As well as
@code{'strict'}, @code{'ignore'}, and @code{'replace'} (which in this case
inserts a question mark instead of the unencodable character), there is
also @code{'xmlcharrefreplace'} (inserts an XML character reference),
@code{backslashreplace} (inserts a @code{\uNNNN} escape sequence) and
@code{namereplace} (inserts a @code{\N@{...@}} escape sequence).

The following example shows the different results:

@example
>>> u = chr(40960) + 'abcd' + chr(1972)
>>> u.encode('utf-8')
b'\xea\x80\x80abcd\xde\xb4'
>>> u.encode('ascii')  
Traceback (most recent call last):
    ...
UnicodeEncodeError: 'ascii' codec can't encode character '\ua000' in
  position 0: ordinal not in range(128)
>>> u.encode('ascii', 'ignore')
b'abcd'
>>> u.encode('ascii', 'replace')
b'?abcd?'
>>> u.encode('ascii', 'xmlcharrefreplace')
b'&#40960;abcd&#1972;'
>>> u.encode('ascii', 'backslashreplace')
b'\\ua000abcd\\u07b4'
>>> u.encode('ascii', 'namereplace')
b'\\N@{YI SYLLABLE IT@}abcd\\u07b4'
@end example

The low-level routines for registering and accessing the available
encodings are found in the @ref{1c,,codecs} module.  Implementing new
encodings also requires understanding the @ref{1c,,codecs} module.
However, the encoding and decoding functions returned by this module
are usually more low-level than is comfortable, and writing new encodings
is a specialized task, so the module won't be covered in this HOWTO.

@node Unicode Literals in Python Source Code,Unicode Properties,Converting to Bytes,Python's Unicode Support
@anchor{howto/unicode unicode-literals-in-python-source-code}@anchor{4175}
@subsubsection Unicode Literals in Python Source Code


In Python source code, specific Unicode code points can be written using the
@code{\u} escape sequence, which is followed by four hex digits giving the code
point.  The @code{\U} escape sequence is similar, but expects eight hex digits,
not four:

@example
>>> s = "a\xac\u1234\u20ac\U00008000"
... #     ^^^^ two-digit hex escape
... #         ^^^^^^ four-digit Unicode escape
... #                     ^^^^^^^^^^ eight-digit Unicode escape
>>> [ord(c) for c in s]
[97, 172, 4660, 8364, 32768]
@end example

Using escape sequences for code points greater than 127 is fine in small doses,
but becomes an annoyance if you're using many accented characters, as you would
in a program with messages in French or some other accent-using language.  You
can also assemble strings using the @ref{13bf,,chr()} built-in function, but this is
even more tedious.

Ideally, you'd want to be able to write literals in your language's natural
encoding.  You could then edit Python source code with your favorite editor
which would display the accented characters naturally, and have the right
characters used at runtime.

Python supports writing source code in UTF-8 by default, but you can use almost
any encoding if you declare the encoding being used.  This is done by including
a special comment as either the first or second line of the source file:

@example
#!/usr/bin/env python
# -*- coding: latin-1 -*-

u = 'abcdé'
print(ord(u[-1]))
@end example

The syntax is inspired by Emacs's notation for specifying variables local to a
file.  Emacs supports many different variables, but Python only supports
'coding'.  The @code{-*-} symbols indicate to Emacs that the comment is special;
they have no significance to Python but are a convention.  Python looks for
@code{coding: name} or @code{coding=name} in the comment.

If you don't include such a comment, the default encoding used will be UTF-8 as
already mentioned.  See also 
@geindex Python 提高建议; PEP 263
PEP 263@footnote{https://www.python.org/dev/peps/pep-0263} for more information.

@node Unicode Properties,Comparing Strings,Unicode Literals in Python Source Code,Python's Unicode Support
@anchor{howto/unicode unicode-properties}@anchor{4176}
@subsubsection Unicode Properties


The Unicode specification includes a database of information about
code points.  For each defined code point, the information includes
the character's name, its category, the numeric value if applicable
(for characters representing numeric concepts such as the Roman
numerals, fractions such as one-third and four-fifths, etc.).  There
are also display-related properties, such as how to use the code point
in bidirectional text.

The following program displays some information about several characters, and
prints the numeric value of one particular character:

@example
import unicodedata

u = chr(233) + chr(0x0bf2) + chr(3972) + chr(6000) + chr(13231)

for i, c in enumerate(u):
    print(i, '%04x' % ord(c), unicodedata.category(c), end=" ")
    print(unicodedata.name(c))

# Get numeric value of second character
print(unicodedata.numeric(u[1]))
@end example

When run, this prints:

@example
0 00e9 Ll LATIN SMALL LETTER E WITH ACUTE
1 0bf2 No TAMIL NUMBER ONE THOUSAND
2 0f84 Mn TIBETAN MARK HALANTA
3 1770 Lo TAGBANWA LETTER SA
4 33af So SQUARE RAD OVER S SQUARED
1000.0
@end example

The category codes are abbreviations describing the nature of the character.
These are grouped into categories such as "Letter", "Number", "Punctuation", or
"Symbol", which in turn are broken up into subcategories.  To take the codes
from the above output, @code{'Ll'} means 'Letter, lowercase', @code{'No'} means
"Number, other", @code{'Mn'} is "Mark, nonspacing", and @code{'So'} is "Symbol,
other".  See
the General Category Values section of the Unicode Character Database documentation@footnote{http://www.unicode.org/reports/tr44/#General_Category_Values} for a
list of category codes.

@node Comparing Strings,Unicode Regular Expressions,Unicode Properties,Python's Unicode Support
@anchor{howto/unicode comparing-strings}@anchor{4177}
@subsubsection Comparing Strings


Unicode adds some complication to comparing strings, because the same
set of characters can be represented by different sequences of code
points.  For example, a letter like 'ê' can be represented as a single
code point U+00EA, or as U+0065 U+0302, which is the code point for
'e' followed by a code point for 'COMBINING CIRCUMFLEX ACCENT'.  These
will produce the same output when printed, but one is a string of
length 1 and the other is of length 2.

One tool for a case-insensitive comparison is the
@ref{6aa,,casefold()} string method that converts a string to a
case-insensitive form following an algorithm described by the Unicode
Standard.  This algorithm has special handling for characters such as
the German letter 'ß' (code point U+00DF), which becomes the pair of
lowercase letters 'ss'.

@example
>>> street = 'Gürzenichstraße'
>>> street.casefold()
'gürzenichstrasse'
@end example

A second tool is the @ref{11a,,unicodedata} module's
@ref{1042,,normalize()} function that converts strings to one
of several normal forms, where letters followed by a combining
character are replaced with single characters.  @code{normalize()} can
be used to perform string comparisons that won't falsely report
inequality if two strings use combining characters differently:

@example
import unicodedata

def compare_strs(s1, s2):
    def NFD(s):
        return unicodedata.normalize('NFD', s)

    return NFD(s1) == NFD(s2)

single_char = 'ê'
multiple_chars = '\N@{LATIN SMALL LETTER E@}\N@{COMBINING CIRCUMFLEX ACCENT@}'
print('length of first string=', len(single_char))
print('length of second string=', len(multiple_chars))
print(compare_strs(single_char, multiple_chars))
@end example

When run, this outputs:

@example
$ python3 compare-strs.py
length of first string= 1
length of second string= 2
True
@end example

The first argument to the @ref{1042,,normalize()} function is a
string giving the desired normalization form, which can be one of
'NFC', 'NFKC', 'NFD', and 'NFKD'.

The Unicode Standard also specifies how to do caseless comparisons:

@example
import unicodedata

def compare_caseless(s1, s2):
    def NFD(s):
        return unicodedata.normalize('NFD', s)

    return NFD(NFD(s1).casefold()) == NFD(NFD(s2).casefold())

# Example usage
single_char = 'ê'
multiple_chars = '\N@{LATIN CAPITAL LETTER E@}\N@{COMBINING CIRCUMFLEX ACCENT@}'

print(compare_caseless(single_char, multiple_chars))
@end example

This will print @code{True}.  (Why is @code{NFD()} invoked twice?  Because
there are a few characters that make @code{casefold()} return a
non-normalized string, so the result needs to be normalized again. See
section 3.13 of the Unicode Standard for a discussion and an example.)

@node Unicode Regular Expressions,参考文献<4>,Comparing Strings,Python's Unicode Support
@anchor{howto/unicode unicode-regular-expressions}@anchor{4178}
@subsubsection Unicode Regular Expressions


The regular expressions supported by the @ref{dd,,re} module can be provided
either as bytes or strings.  Some of the special character sequences such as
@code{\d} and @code{\w} have different meanings depending on whether
the pattern is supplied as bytes or a string.  For example,
@code{\d} will match the characters @code{[0-9]} in bytes but
in strings will match any character that's in the @code{'Nd'} category.

The string in this example has the number 57 written in both Thai and
Arabic numerals:

@example
import re
p = re.compile(r'\d+')

s = "Over \u0e55\u0e57 57 flavours"
m = p.search(s)
print(repr(m.group()))
@end example

When executed, @code{\d+} will match the Thai numerals and print them
out.  If you supply the @ref{3c0,,re.ASCII} flag to
@ref{444,,compile()}, @code{\d+} will match the substring "57" instead.

Similarly, @code{\w} matches a wide variety of Unicode characters but
only @code{[a-zA-Z0-9_]} in bytes or if @ref{3c0,,re.ASCII} is supplied,
and @code{\s} will match either Unicode whitespace characters or
@code{[ \t\n\r\f\v]}.

@node 参考文献<4>,,Unicode Regular Expressions,Python's Unicode Support
@anchor{howto/unicode id2}@anchor{4179}
@subsubsection 参考文献


@c comment should these be mentioned earlier, e.g. at the start of the "introduction to Unicode" first section?

Some good alternative discussions of Python's Unicode support are:


@itemize *

@item 
Processing Text Files in Python 3@footnote{http://python-notes.curiousefficiency.org/en/latest/python3/text_file_processing.html}, by Nick Coghlan.

@item 
Pragmatic Unicode@footnote{https://nedbatchelder.com/text/unipain.html}, a PyCon 2012 presentation by Ned Batchelder.
@end itemize

The @ref{329,,str} type is described in the Python library reference at
@ref{11b7,,文本序列类型 --- str}.

The documentation for the @ref{11a,,unicodedata} module.

The documentation for the @ref{1c,,codecs} module.

Marc-André Lemburg gave a presentation titled "Python and Unicode" (PDF slides)@footnote{https://downloads.egenix.com/python/Unicode-EPC2002-Talk.pdf} at
EuroPython 2002.  The slides are an excellent overview of the design of Python
2's Unicode features (where the Unicode string type is called @code{unicode} and
literals start with @code{u}).

@node Reading and Writing Unicode Data,致谢<10>,Python's Unicode Support,Unicode 指南
@anchor{howto/unicode reading-and-writing-unicode-data}@anchor{417a}
@subsection Reading and Writing Unicode Data


Once you've written some code that works with Unicode data, the next problem is
input/output.  How do you get Unicode strings into your program, and how do you
convert Unicode into a form suitable for storage or transmission?

It's possible that you may not need to do anything depending on your input
sources and output destinations; you should check whether the libraries used in
your application support Unicode natively.  XML parsers often return Unicode
data, for example.  Many relational databases also support Unicode-valued
columns and can return Unicode values from an SQL query.

Unicode data is usually converted to a particular encoding before it gets
written to disk or sent over a socket.  It's possible to do all the work
yourself: open a file, read an 8-bit bytes object from it, and convert the bytes
with @code{bytes.decode(encoding)}.  However, the manual approach is not recommended.

One problem is the multi-byte nature of encodings; one Unicode character can be
represented by several bytes.  If you want to read the file in arbitrary-sized
chunks (say, 1024 or 4096 bytes), you need to write error-handling code to catch the case
where only part of the bytes encoding a single Unicode character are read at the
end of a chunk.  One solution would be to read the entire file into memory and
then perform the decoding, but that prevents you from working with files that
are extremely large; if you need to read a 2 GiB file, you need 2 GiB of RAM.
(More, really, since for at least a moment you'd need to have both the encoded
string and its Unicode version in memory.)

The solution would be to use the low-level decoding interface to catch the case
of partial coding sequences.  The work of implementing this has already been
done for you: the built-in @ref{4ea,,open()} function can return a file-like object
that assumes the file's contents are in a specified encoding and accepts Unicode
parameters for methods such as @ref{1f9d,,read()} and
@ref{1fa0,,write()}.  This works through @ref{4ea,,open()}'s @emph{encoding} and
@emph{errors} parameters which are interpreted just like those in @ref{c30,,str.encode()}
and @ref{c31,,bytes.decode()}.

Reading Unicode from a file is therefore simple:

@example
with open('unicode.txt', encoding='utf-8') as f:
    for line in f:
        print(repr(line))
@end example

It's also possible to open files in update mode, allowing both reading and
writing:

@example
with open('test', encoding='utf-8', mode='w+') as f:
    f.write('\u4500 blah blah blah\n')
    f.seek(0)
    print(repr(f.readline()[:1]))
@end example

The Unicode character @code{U+FEFF} is used as a byte-order mark (BOM), and is often
written as the first character of a file in order to assist with autodetection
of the file's byte ordering.  Some encodings, such as UTF-16, expect a BOM to be
present at the start of a file; when such an encoding is used, the BOM will be
automatically written as the first character and will be silently dropped when
the file is read.  There are variants of these encodings, such as 'utf-16-le'
and 'utf-16-be' for little-endian and big-endian encodings, that specify one
particular byte ordering and don't skip the BOM.

In some areas, it is also convention to use a "BOM" at the start of UTF-8
encoded files; the name is misleading since UTF-8 is not byte-order dependent.
The mark simply announces that the file is encoded in UTF-8.  For reading such
files, use the 'utf-8-sig' codec to automatically skip the mark if present.

@menu
* Unicode filenames:: 
* Tips for Writing Unicode-aware Programs:: 
* 参考文献: 参考文献<5>. 

@end menu

@node Unicode filenames,Tips for Writing Unicode-aware Programs,,Reading and Writing Unicode Data
@anchor{howto/unicode unicode-filenames}@anchor{417b}
@subsubsection Unicode filenames


Most of the operating systems in common use today support filenames
that contain arbitrary Unicode characters.  Usually this is
implemented by converting the Unicode string into some encoding that
varies depending on the system.  Today Python is converging on using
UTF-8: Python on MacOS has used UTF-8 for several versions, and Python
3.6 switched to using UTF-8 on Windows as well.  On Unix systems,
there will only be a filesystem encoding if you've set the @code{LANG} or
@code{LC_CTYPE} environment variables; if you haven't, the default
encoding is again UTF-8.

The @ref{4f0,,sys.getfilesystemencoding()} function returns the encoding to use on
your current system, in case you want to do the encoding manually, but there's
not much reason to bother.  When opening a file for reading or writing, you can
usually just provide the Unicode string as the filename, and it will be
automatically converted to the right encoding for you:

@example
filename = 'filename\u4500abc'
with open(filename, 'w') as f:
    f.write('blah\n')
@end example

Functions in the @ref{c4,,os} module such as @ref{1f1,,os.stat()} will also accept Unicode
filenames.

The @ref{a3c,,os.listdir()} function returns filenames, which raises an issue: should it return
the Unicode version of filenames, or should it return bytes containing
the encoded versions?  @ref{a3c,,os.listdir()} can do both, depending on whether you
provided the directory path as bytes or a Unicode string.  If you pass a
Unicode string as the path, filenames will be decoded using the filesystem's
encoding and a list of Unicode strings will be returned, while passing a byte
path will return the filenames as bytes.  For example,
assuming the default filesystem encoding is UTF-8, running the following
program:

@example
fn = 'filename\u4500abc'
f = open(fn, 'w')
f.close()

import os
print(os.listdir(b'.'))
print(os.listdir('.'))
@end example

will produce the following output:

@example
$ python listdir-test.py
[b'filename\xe4\x94\x80abc', ...]
['filename\u4500abc', ...]
@end example

The first list contains UTF-8-encoded filenames, and the second list contains
the Unicode versions.

Note that on most occasions, you should can just stick with using
Unicode with these APIs.  The bytes APIs should only be used on
systems where undecodable file names can be present; that's
pretty much only Unix systems now.

@node Tips for Writing Unicode-aware Programs,参考文献<5>,Unicode filenames,Reading and Writing Unicode Data
@anchor{howto/unicode tips-for-writing-unicode-aware-programs}@anchor{417c}
@subsubsection Tips for Writing Unicode-aware Programs


This section provides some suggestions on writing software that deals with
Unicode.

The most important tip is:

@quotation

Software should only work with Unicode strings internally, decoding the input
data as soon as possible and encoding the output only at the end.
@end quotation

If you attempt to write processing functions that accept both Unicode and byte
strings, you will find your program vulnerable to bugs wherever you combine the
two different kinds of strings.  There is no automatic encoding or decoding: if
you do e.g. @code{str + bytes}, a @ref{192,,TypeError} will be raised.

When using data coming from a web browser or some other untrusted source, a
common technique is to check for illegal characters in a string before using the
string in a generated command line or storing it in a database.  If you're doing
this, be careful to check the decoded string, not the encoded bytes data;
some encodings may have interesting properties, such as not being bijective
or not being fully ASCII-compatible.  This is especially true if the input
data also specifies the encoding, since the attacker can then choose a
clever way to hide malicious text in the encoded bytestream.

@menu
* Converting Between File Encodings:: 
* Files in an Unknown Encoding:: 

@end menu

@node Converting Between File Encodings,Files in an Unknown Encoding,,Tips for Writing Unicode-aware Programs
@anchor{howto/unicode converting-between-file-encodings}@anchor{417d}
@subsubsection Converting Between File Encodings


The @ref{f5d,,StreamRecoder} class can transparently convert between
encodings, taking a stream that returns data in encoding #1
and behaving like a stream returning data in encoding #2.

For example, if you have an input file @emph{f} that's in Latin-1, you
can wrap it with a @ref{f5d,,StreamRecoder} to return bytes encoded in
UTF-8:

@example
new_f = codecs.StreamRecoder(f,
    # en/decoder: used by read() to encode its results and
    # by write() to decode its input.
    codecs.getencoder('utf-8'), codecs.getdecoder('utf-8'),

    # reader/writer: used to read and write to the stream.
    codecs.getreader('latin-1'), codecs.getwriter('latin-1') )
@end example

@node Files in an Unknown Encoding,,Converting Between File Encodings,Tips for Writing Unicode-aware Programs
@anchor{howto/unicode files-in-an-unknown-encoding}@anchor{417e}
@subsubsection Files in an Unknown Encoding


What can you do if you need to make a change to a file, but don't know
the file's encoding?  If you know the encoding is ASCII-compatible and
only want to examine or modify the ASCII parts, you can open the file
with the @code{surrogateescape} error handler:

@example
with open(fname, 'r', encoding="ascii", errors="surrogateescape") as f:
    data = f.read()

# make changes to the string 'data'

with open(fname + '.new', 'w',
          encoding="ascii", errors="surrogateescape") as f:
    f.write(data)
@end example

The @code{surrogateescape} error handler will decode any non-ASCII bytes
as code points in a special range running from U+DC80 to
U+DCFF.  These code points will then turn back into the
same bytes when the @code{surrogateescape} error handler is used to
encode the data and write it back out.

@node 参考文献<5>,,Tips for Writing Unicode-aware Programs,Reading and Writing Unicode Data
@anchor{howto/unicode id3}@anchor{417f}
@subsubsection 参考文献


One section of Mastering Python 3 Input/Output@footnote{http://pyvideo.org/video/289/pycon-2010--mastering-python-3-i-o},
a PyCon 2010 talk by David Beazley, discusses text processing and binary data handling.

The PDF slides for Marc-André Lemburg's presentation "Writing Unicode-aware Applications in Python"@footnote{https://downloads.egenix.com/python/LSM2005-Developing-Unicode-aware-applications-in-Python.pdf}
discuss questions of character encodings as well as how to internationalize
and localize an application.  These slides cover Python 2.x only.

The Guts of Unicode in Python@footnote{http://pyvideo.org/video/1768/the-guts-of-unicode-in-python}
is a PyCon 2013 talk by Benjamin Peterson that discusses the internal Unicode
representation in Python 3.3.

@node 致谢<10>,,Reading and Writing Unicode Data,Unicode 指南
@anchor{howto/unicode acknowledgements}@anchor{4180}
@subsection 致谢


The initial draft of this document was written by Andrew Kuchling.
It has since been revised further by Alexander Belopolsky, Georg Brandl,
Andrew Kuchling, and Ezio Melotti.

Thanks to the following people who have noted errors or offered
suggestions on this article: Éric Araujo, Nicholas Bastin, Nick
Coghlan, Marius Gedminas, Kent Johnson, Ken Krugler, Marc-André
Lemburg, Martin von Löwis, Terry J. Reedy, Serhiy Storchaka,
Eryk Sun, Chad Whitacre, Graham Wideman.

@node HOWTO 使用 urllib 包获取网络资源,Argparse 教程,Unicode 指南,Python 常用指引
@anchor{howto/urllib2 doc}@anchor{4181}@anchor{howto/urllib2 howto-fetch-internet-resources-using-the-urllib-package}@anchor{4182}@anchor{howto/urllib2 urllib-howto}@anchor{2c4e}
@section HOWTO 使用 urllib 包获取网络资源


@*作者: 
Michael Foord@footnote{http://www.voidspace.org.uk/python/index.shtml}


@cartouche
@quotation 注解 
这份 HOWTO 文档的早期版本有一份法语的译文，可在 urllib2 - Le Manuel manquant@footnote{http://www.voidspace.org.uk/python/articles/urllib2_francais.shtml} 处查阅。
@end quotation
@end cartouche

@menu
* 概述: 概述<19>. 
* 提取URL:: 
* 处理异常: 处理异常<2>. 
* info and geturl:: 
* Openers and Handlers:: 
* 基本认证:: 
* 代理:: 
* Sockets and Layers:: 
* 备注:: 

@end menu

@node 概述<19>,提取URL,,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 introduction}@anchor{4183}
@subsection 概述


@subsubheading Related Articles



关于使用 Python 获取网页资源，你或许还可以找到下列有用的文章：


@itemize *

@item 
基本的验证@footnote{http://www.voidspace.org.uk/python/articles/authentication.shtml}

@quotation

关于 @emph{基本的验证} 的入门指南，带有一些 Python 的示例。
@end quotation
@end itemize

@strong{urllib.request} 是一个用于获取 URL （统一资源定位地址）的 Python 模块。它以 @emph{urlopen} 函数的形式提供了一个非常简单的接口。该接口能够使用不同的协议获取 URL。同时它也提供了一个略微复杂的接口来处理常见情形——如：基本验证、cookies、代理等等。这些功能是通过叫做 handlers 和 opener 的对象来提供的。

urllib.request 支持多种  "URL 网址方案" （通过 URL中 @code{":"} 之前的字符串加以区分——如 URL 地址 @code{"ftp://python.org/"` 中的 `@w{`}"ftp"`}） ，使用与之相关的网络协议（如：FTP、 HTTP）来获取 URL 资源。本指南重点关注最常用的情形—— HTTP。

For straightforward situations @emph{urlopen} is very easy to use. But as soon as you
encounter errors or non-trivial cases when opening HTTP URLs, you will need some
understanding of the HyperText Transfer Protocol. The most comprehensive and
authoritative reference to HTTP is 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html}. This is a technical document and
not intended to be easy to read. This HOWTO aims to illustrate using @emph{urllib},
with enough detail about HTTP to help you through. It is not intended to replace
the @ref{120,,urllib.request} docs, but is supplementary to them.

@node 提取URL,处理异常<2>,概述<19>,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 fetching-urls}@anchor{4184}
@subsection 提取URL


下面是使用 urllib.request 最简单的方式：

@example
import urllib.request
with urllib.request.urlopen('http://python.org/') as response:
   html = response.read()
@end example

如果你想通过 URL 获取资源并保存某个临时的地方，你可以通过 @ref{25d,,shutil.copyfileobj()} 和 @ref{d42,,tempfile.NamedTemporaryFile()} 函数:

@example
import shutil
import tempfile
import urllib.request

with urllib.request.urlopen('http://python.org/') as response:
    with tempfile.NamedTemporaryFile(delete=False) as tmp_file:
        shutil.copyfileobj(response, tmp_file)

with open(tmp_file.name) as html:
    pass
@end example

urllib很易于使用（注意 URL 不仅仅可以以'http:'开头，也可以是'ftp:'，'file:'等）。但是，这篇教程的目的是介绍更加复杂的用法，大多数以HTTP举例。

HTTP基于请求和回应——客户端像服务器请求，服务器回应。urllib.request将你的HTTP请求保存为一个`@w{`}Request`@w{`}对象。在最简单的情况下，一个Request对象里包含你所请求的特定URL。以当前的Request对象作为参数调用`@w{`}urlopen`@w{`}返回服务器对你正在请求的URL的回应。回应是个文件类对象，所以你可以调用如`@w{`}.read()`@w{`}等命令。

@example
import urllib.request

req = urllib.request.Request('http://www.voidspace.org.uk')
with urllib.request.urlopen(req) as response:
   the_page = response.read()
@end example

注意urllib.request中的Request接口也支持处理所有的互联网协议。比如，你可以像这样做一个 FTP 请求：

@example
req = urllib.request.Request('ftp://example.com/')
@end example

在 HTTP 的情况下，Request 对象允许你做两件额外的事：一，你可以向服务器发送数据。二，你可以向服务器发送额外的信息（“元数据”）： @emph{关于} 数据或请求本身的。信息将以“HTTP头”的方式发过去。让我们一个个看过去。

@menu
* 数据:: 
* Headers:: 

@end menu

@node 数据,Headers,,提取URL
@anchor{howto/urllib2 data}@anchor{4185}
@subsubsection 数据


Sometimes you want to send data to a URL (often the URL will refer to a CGI
(Common Gateway Interface) script or other web application). With HTTP,
this is often done using what's known as a @strong{POST} request. This is often what
your browser does when you submit a HTML form that you filled in on the web. Not
all POSTs have to come from forms: you can use a POST to transmit arbitrary data
to your own application. In the common case of HTML forms, the data needs to be
encoded in a standard way, and then passed to the Request object as the @code{data}
argument. The encoding is done using a function from the @ref{11f,,urllib.parse}
library.

@example
import urllib.parse
import urllib.request

url = 'http://www.someserver.com/cgi-bin/register.cgi'
values = @{'name' : 'Michael Foord',
          'location' : 'Northampton',
          'language' : 'Python' @}

data = urllib.parse.urlencode(values)
data = data.encode('ascii') # data should be bytes
req = urllib.request.Request(url, data)
with urllib.request.urlopen(req) as response:
   the_page = response.read()
@end example

Note that other encodings are sometimes required (e.g. for file upload from HTML
forms - see HTML Specification@comma{} Form Submission@footnote{https://www.w3.org/TR/REC-html40/interact/forms.html#h-17.13} for more
details).

If you do not pass the @code{data} argument, urllib uses a @strong{GET} request. One
way in which GET and POST requests differ is that POST requests often have
"side-effects": they change the state of the system in some way (for example by
placing an order with the website for a hundredweight of tinned spam to be
delivered to your door).  Though the HTTP standard makes it clear that POSTs are
intended to @emph{always} cause side-effects, and GET requests @emph{never} to cause
side-effects, nothing prevents a GET request from having side-effects, nor a
POST requests from having no side-effects. Data can also be passed in an HTTP
GET request by encoding it in the URL itself.

具体操作如下:

@example
>>> import urllib.request
>>> import urllib.parse
>>> data = @{@}
>>> data['name'] = 'Somebody Here'
>>> data['location'] = 'Northampton'
>>> data['language'] = 'Python'
>>> url_values = urllib.parse.urlencode(data)
>>> print(url_values)  # The order may differ from below.  
name=Somebody+Here&language=Python&location=Northampton
>>> url = 'http://www.example.com/example.cgi'
>>> full_url = url + '?' + url_values
>>> data = urllib.request.urlopen(full_url)
@end example

Notice that the full URL is created by adding a @code{?} to the URL, followed by
the encoded values.

@node Headers,,数据,提取URL
@anchor{howto/urllib2 headers}@anchor{4186}
@subsubsection Headers


We'll discuss here one particular HTTP header, to illustrate how to add headers
to your HTTP request.

Some websites @footnote{@w{(1)} 
例如 Google。
} dislike being browsed by programs, or send different versions
to different browsers @footnote{@w{(2)} 
Browser sniffing is a very bad practice for website design - building
sites using web standards is much more sensible. Unfortunately a lot of
sites still send different versions to different browsers.
}. By default urllib identifies itself as
@code{Python-urllib/x.y} (where @code{x} and @code{y} are the major and minor version
numbers of the Python release,
e.g. @code{Python-urllib/2.5}), which may confuse the site, or just plain
not work. The way a browser identifies itself is through the
@code{User-Agent} header @footnote{@w{(3)} 
The user agent for MSIE 6 is
@emph{'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)'}
}. When you create a Request object you can
pass a dictionary of headers in. The following example makes the same
request as above, but identifies itself as a version of Internet
Explorer @footnote{@w{(4)} 
For details of more HTTP request headers, see
@uref{http://jkorpela.fi/http.html,Quick Reference to HTTP Headers}.
}.

@example
import urllib.parse
import urllib.request

url = 'http://www.someserver.com/cgi-bin/register.cgi'
user_agent = 'Mozilla/5.0 (Windows NT 6.1; Win64; x64)'
values = @{'name': 'Michael Foord',
          'location': 'Northampton',
          'language': 'Python' @}
headers = @{'User-Agent': user_agent@}

data = urllib.parse.urlencode(values)
data = data.encode('ascii')
req = urllib.request.Request(url, data, headers)
with urllib.request.urlopen(req) as response:
   the_page = response.read()
@end example

The response also has two useful methods. See the section on @ref{4187,,info and geturl}
which comes after we have a look at what happens when things go wrong.

@node 处理异常<2>,info and geturl,提取URL,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 handling-exceptions}@anchor{4188}
@subsection 处理异常


@emph{urlopen} raises @code{URLError} when it cannot handle a response (though as
usual with Python APIs, built-in exceptions such as @ref{1fb,,ValueError},
@ref{192,,TypeError} etc. may also be raised).

@code{HTTPError} is the subclass of @code{URLError} raised in the specific case of
HTTP URLs.

异常类从 @ref{11e,,urllib.error} 模块中导出。

@menu
* URLError:: 
* HTTPError:: 
* 包装起来:: 

@end menu

@node URLError,HTTPError,,处理异常<2>
@anchor{howto/urllib2 urlerror}@anchor{4189}
@subsubsection URLError


通常，引发 URLError 的原因是没有网络连接（或者没有到指定服务器的路由），或者指定的服务器不存在。该情况下，将会引发该异常，并带有一个 'reason' 属性，该属性是一个包含错误代码和文本错误信息的元组。

例如

@example
>>> req = urllib.request.Request('http://www.pretend_server.org')
>>> try: urllib.request.urlopen(req)
... except urllib.error.URLError as e:
...     print(e.reason)      
...
(4, 'getaddrinfo failed')
@end example

@node HTTPError,包装起来,URLError,处理异常<2>
@anchor{howto/urllib2 httperror}@anchor{418a}
@subsubsection HTTPError


从服务器返回的每个 HTTP 响应都包含一个数字的 “状态码”。有时该状态码表明服务器无法完成该请求。默认的处理器（函数？）将会为你处理这其中的一些响应。（例如，如果响应包含了 "redirection"，将会要求客户端去向另外的 URL 获取文档，urllib 将会为你处理该情形）。对于那些它无法处理的（状态代码），urlopen 将会引发一个  @code{HTTPError} 。典型的错误包括：‘404’（页面无法找到）、‘403’（请求遭拒绝）和 ’401‘ （需要身份验证）。

See section 10 of 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html} for a reference on all the HTTP error codes.

The @code{HTTPError} instance raised will have an integer 'code' attribute, which
corresponds to the error sent by the server.

@menu
* 错误代码:: 

@end menu

@node 错误代码,,,HTTPError
@anchor{howto/urllib2 error-codes}@anchor{418b}
@subsubsection 错误代码


Because the default handlers handle redirects (codes in the 300 range), and
codes in the 100--299 range indicate success, you will usually only see error
codes in the 400--599 range.

@ref{2c72,,http.server.BaseHTTPRequestHandler.responses} is a useful dictionary of
response codes in that shows all the response codes used by 
@geindex RFC; RFC 2616
RFC 2616@footnote{https://tools.ietf.org/html/rfc2616.html}. The
dictionary is reproduced here for convenience

@example
# Table mapping response codes to messages; entries have the
# form @{code: (shortmessage, longmessage)@}.
responses = @{
    100: ('Continue', 'Request received, please continue'),
    101: ('Switching Protocols',
          'Switching to new protocol; obey Upgrade header'),

    200: ('OK', 'Request fulfilled, document follows'),
    201: ('Created', 'Document created, URL follows'),
    202: ('Accepted',
          'Request accepted, processing continues off-line'),
    203: ('Non-Authoritative Information', 'Request fulfilled from cache'),
    204: ('No Content', 'Request fulfilled, nothing follows'),
    205: ('Reset Content', 'Clear input form for further input.'),
    206: ('Partial Content', 'Partial content follows.'),

    300: ('Multiple Choices',
          'Object has several resources -- see URI list'),
    301: ('Moved Permanently', 'Object moved permanently -- see URI list'),
    302: ('Found', 'Object moved temporarily -- see URI list'),
    303: ('See Other', 'Object moved -- see Method and URL list'),
    304: ('Not Modified',
          'Document has not changed since given time'),
    305: ('Use Proxy',
          'You must use proxy specified in Location to access this '
          'resource.'),
    307: ('Temporary Redirect',
          'Object moved temporarily -- see URI list'),

    400: ('Bad Request',
          'Bad request syntax or unsupported method'),
    401: ('Unauthorized',
          'No permission -- see authorization schemes'),
    402: ('Payment Required',
          'No payment -- see charging schemes'),
    403: ('Forbidden',
          'Request forbidden -- authorization will not help'),
    404: ('Not Found', 'Nothing matches the given URI'),
    405: ('Method Not Allowed',
          'Specified method is invalid for this server.'),
    406: ('Not Acceptable', 'URI not available in preferred format.'),
    407: ('Proxy Authentication Required', 'You must authenticate with '
          'this proxy before proceeding.'),
    408: ('Request Timeout', 'Request timed out; try again later.'),
    409: ('Conflict', 'Request conflict.'),
    410: ('Gone',
          'URI no longer exists and has been permanently removed.'),
    411: ('Length Required', 'Client must specify Content-Length.'),
    412: ('Precondition Failed', 'Precondition in headers is false.'),
    413: ('Request Entity Too Large', 'Entity is too large.'),
    414: ('Request-URI Too Long', 'URI is too long.'),
    415: ('Unsupported Media Type', 'Entity body in unsupported format.'),
    416: ('Requested Range Not Satisfiable',
          'Cannot satisfy request range.'),
    417: ('Expectation Failed',
          'Expect condition could not be satisfied.'),

    500: ('Internal Server Error', 'Server got itself in trouble'),
    501: ('Not Implemented',
          'Server does not support this operation'),
    502: ('Bad Gateway', 'Invalid responses from another server/proxy.'),
    503: ('Service Unavailable',
          'The server cannot process the request due to a high load'),
    504: ('Gateway Timeout',
          'The gateway server did not receive a timely response'),
    505: ('HTTP Version Not Supported', 'Cannot fulfill request.'),
    @}
@end example

When an error is raised the server responds by returning an HTTP error code
@emph{and} an error page. You can use the @code{HTTPError} instance as a response on the
page returned. This means that as well as the code attribute, it also has read,
geturl, and info, methods as returned by the @code{urllib.response} module:

@example
>>> req = urllib.request.Request('http://www.python.org/fish.html')
>>> try:
...     urllib.request.urlopen(req)
... except urllib.error.HTTPError as e:
...     print(e.code)
...     print(e.read())  
...
404
b'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">\n\n\n<html
  ...
  <title>Page Not Found</title>\n
  ...
@end example

@node 包装起来,,HTTPError,处理异常<2>
@anchor{howto/urllib2 wrapping-it-up}@anchor{418c}
@subsubsection 包装起来


So if you want to be prepared for @code{HTTPError} @emph{or} @code{URLError} there are two
basic approaches. I prefer the second approach.

@menu
* 数字1:: 
* Number 2:: 

@end menu

@node 数字1,Number 2,,包装起来
@anchor{howto/urllib2 number-1}@anchor{418d}
@subsubsection 数字1


@example
from urllib.request import Request, urlopen
from urllib.error import URLError, HTTPError
req = Request(someurl)
try:
    response = urlopen(req)
except HTTPError as e:
    print('The server couldn\'t fulfill the request.')
    print('Error code: ', e.code)
except URLError as e:
    print('We failed to reach a server.')
    print('Reason: ', e.reason)
else:
    # everything is fine
@end example

@cartouche
@quotation 注解 
The @code{except HTTPError} @emph{must} come first, otherwise @code{except URLError}
will @emph{also} catch an @code{HTTPError}.
@end quotation
@end cartouche

@node Number 2,,数字1,包装起来
@anchor{howto/urllib2 number-2}@anchor{418e}
@subsubsection Number 2


@example
from urllib.request import Request, urlopen
from urllib.error import URLError
req = Request(someurl)
try:
    response = urlopen(req)
except URLError as e:
    if hasattr(e, 'reason'):
        print('We failed to reach a server.')
        print('Reason: ', e.reason)
    elif hasattr(e, 'code'):
        print('The server couldn\'t fulfill the request.')
        print('Error code: ', e.code)
else:
    # everything is fine
@end example

@node info and geturl,Openers and Handlers,处理异常<2>,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 info-and-geturl}@anchor{4187}
@subsection info and geturl


由 urlopen （或者 @code{HTTPError} 实例）所返回的响应包含两个有用的方法： @code{info()} 和 @code{geturl()}，该响应由模块 @ref{121,,urllib.response} 定义。

@strong{geturl} - 返回所获取页面的真实 URL。该方法很有用，因为 @code{urlopen} （或者所使用的 opener 对象）可能回包括一次重定向。所获取页面的 URL 未必就是所请求的 URL 。

@strong{info} - 该方法返回一个类似字典的对象，描述了所获取的页面，特别是由服务器送出的头部信息（headers） 。目前它是一个 @code{http.client.HTTPMessage} 实例。

Typical headers include 'Content-length', 'Content-type', and so on. See the
Quick Reference to HTTP Headers@footnote{http://jkorpela.fi/http.html}
for a useful listing of HTTP headers with brief explanations of their meaning
and use.

@node Openers and Handlers,基本认证,info and geturl,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 openers-and-handlers}@anchor{418f}
@subsection Openers and Handlers


When you fetch a URL you use an opener (an instance of the perhaps
confusingly-named @ref{2bd5,,urllib.request.OpenerDirector}). Normally we have been using
the default opener - via @code{urlopen} - but you can create custom
openers. Openers use handlers. All the "heavy lifting" is done by the
handlers. Each handler knows how to open URLs for a particular URL scheme (http,
ftp, etc.), or how to handle an aspect of URL opening, for example HTTP
redirections or HTTP cookies.

You will want to create openers if you want to fetch URLs with specific handlers
installed, for example to get an opener that handles cookies, or to get an
opener that does not handle redirections.

To create an opener, instantiate an @code{OpenerDirector}, and then call
@code{.add_handler(some_handler_instance)} repeatedly.

Alternatively, you can use @code{build_opener}, which is a convenience function for
creating opener objects with a single function call.  @code{build_opener} adds
several handlers by default, but provides a quick way to add more and/or
override the default handlers.

Other sorts of handlers you might want to can handle proxies, authentication,
and other common but slightly specialised situations.

@code{install_opener} can be used to make an @code{opener} object the (global) default
opener. This means that calls to @code{urlopen} will use the opener you have
installed.

Opener objects have an @code{open} method, which can be called directly to fetch
urls in the same way as the @code{urlopen} function: there's no need to call
@code{install_opener}, except as a convenience.

@node 基本认证,代理,Openers and Handlers,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 id5}@anchor{4190}
@subsection 基本认证


To illustrate creating and installing a handler we will use the
@code{HTTPBasicAuthHandler}. For a more detailed discussion of this subject --
including an explanation of how Basic Authentication works - see the Basic Authentication Tutorial@footnote{http://www.voidspace.org.uk/python/articles/authentication.shtml}.

When authentication is required, the server sends a header (as well as the 401
error code) requesting authentication.  This specifies the authentication scheme
and a 'realm'. The header looks like: @code{WWW-Authenticate: SCHEME
realm="REALM"}.

例如

@example
WWW-Authenticate: Basic realm="cPanel Users"
@end example

The client should then retry the request with the appropriate name and password
for the realm included as a header in the request. This is 'basic
authentication'. In order to simplify this process we can create an instance of
@code{HTTPBasicAuthHandler} and an opener to use this handler.

The @code{HTTPBasicAuthHandler} uses an object called a password manager to handle
the mapping of URLs and realms to passwords and usernames. If you know what the
realm is (from the authentication header sent by the server), then you can use a
@code{HTTPPasswordMgr}. Frequently one doesn't care what the realm is. In that
case, it is convenient to use @code{HTTPPasswordMgrWithDefaultRealm}. This allows
you to specify a default username and password for a URL. This will be supplied
in the absence of you providing an alternative combination for a specific
realm. We indicate this by providing @code{None} as the realm argument to the
@code{add_password} method.

The top-level URL is the first URL that requires authentication. URLs "deeper"
than the URL you pass to .add_password() will also match.

@example
# create a password manager
password_mgr = urllib.request.HTTPPasswordMgrWithDefaultRealm()

# Add the username and password.
# If we knew the realm, we could use it instead of None.
top_level_url = "http://example.com/foo/"
password_mgr.add_password(None, top_level_url, username, password)

handler = urllib.request.HTTPBasicAuthHandler(password_mgr)

# create "opener" (OpenerDirector instance)
opener = urllib.request.build_opener(handler)

# use the opener to fetch a URL
opener.open(a_url)

# Install the opener.
# Now all calls to urllib.request.urlopen use our opener.
urllib.request.install_opener(opener)
@end example

@cartouche
@quotation 注解 
In the above example we only supplied our @code{HTTPBasicAuthHandler} to
@code{build_opener}. By default openers have the handlers for normal situations
-- @code{ProxyHandler} (if a proxy setting such as an 
@geindex http_proxy
@geindex 环境变量; http_proxy
@code{http_proxy}
environment variable is set), @code{UnknownHandler}, @code{HTTPHandler},
@code{HTTPDefaultErrorHandler}, @code{HTTPRedirectHandler}, @code{FTPHandler},
@code{FileHandler}, @code{DataHandler}, @code{HTTPErrorProcessor}.
@end quotation
@end cartouche

@code{top_level_url} is in fact @emph{either} a full URL (including the 'http:' scheme
component and the hostname and optionally the port number)
e.g. @code{"http://example.com/"} @emph{or} an "authority" (i.e. the hostname,
optionally including the port number) e.g. @code{"example.com"} or @code{"example.com:8080"}
(the latter example includes a port number).  The authority, if present, must
NOT contain the "userinfo" component - for example @code{"joe:password@@example.com"} is
not correct.

@node 代理,Sockets and Layers,基本认证,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 proxies}@anchor{4191}
@subsection 代理


@strong{urllib} will auto-detect your proxy settings and use those. This is through
the @code{ProxyHandler}, which is part of the normal handler chain when a proxy
setting is detected.  Normally that's a good thing, but there are occasions
when it may not be helpful @footnote{@w{(5)} 
In my case I have to use a proxy to access the internet at work. If you
attempt to fetch @emph{localhost} URLs through this proxy it blocks them. IE
is set to use the proxy, which urllib picks up on. In order to test
scripts with a localhost server, I have to prevent urllib from using
the proxy.
}. One way to do this is to setup our own
@code{ProxyHandler}, with no proxies defined. This is done using similar steps to
setting up a @ref{4192,,Basic Authentication} handler:

@example
>>> proxy_support = urllib.request.ProxyHandler(@{@})
>>> opener = urllib.request.build_opener(proxy_support)
>>> urllib.request.install_opener(opener)
@end example

@cartouche
@quotation 注解 
Currently @code{urllib.request} @emph{does not} support fetching of @code{https} locations
through a proxy.  However, this can be enabled by extending urllib.request as
shown in the recipe @footnote{@w{(6)} 
urllib opener for SSL proxy (CONNECT method): @uref{https://code.activestate.com/recipes/456195/,ASPN Cookbook Recipe}.
}.
@end quotation
@end cartouche

@cartouche
@quotation 注解 
@code{HTTP_PROXY} will be ignored if a variable @code{REQUEST_METHOD} is set; see
the documentation on @ref{2be3,,getproxies()}.
@end quotation
@end cartouche

@node Sockets and Layers,备注,代理,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 sockets-and-layers}@anchor{4193}
@subsection Sockets and Layers


The Python support for fetching resources from the web is layered.  urllib uses
the @ref{94,,http.client} library, which in turn uses the socket library.

As of Python 2.3 you can specify how long a socket should wait for a response
before timing out. This can be useful in applications which have to fetch web
pages. By default the socket module has @emph{no timeout} and can hang. Currently,
the socket timeout is not exposed at the http.client or urllib.request levels.
However, you can set the default timeout globally for all sockets using

@example
import socket
import urllib.request

# timeout in seconds
timeout = 10
socket.setdefaulttimeout(timeout)

# this call to urllib.request.urlopen now uses the default timeout
# we have set in the socket module
req = urllib.request.Request('http://www.voidspace.org.uk')
response = urllib.request.urlopen(req)
@end example


__________________________________________________________________


@node 备注,,Sockets and Layers,HOWTO 使用 urllib 包获取网络资源
@anchor{howto/urllib2 footnotes}@anchor{4194}
@subsection 备注


这篇文档由 John Lee 审订。

@node Argparse 教程,ipaddress模块介绍,HOWTO 使用 urllib 包获取网络资源,Python 常用指引
@anchor{howto/argparse doc}@anchor{4195}@anchor{howto/argparse argparse-tutorial}@anchor{4196}
@section Argparse 教程


@*作者: 
Tshepang Lekhonkhobe

@anchor{howto/argparse id1}@anchor{1fc1}
这篇教程旨在作为 @ref{6,,argparse} 的入门介绍，此模块是 Python 标准库中推荐的命令行解析模块。

@cartouche
@quotation 注解 
还有另外两个模块可以完成同样的任务，称为 @ref{87,,getopt} (对应于 C 语言中的 @code{getopt()} 函数) 和被弃用的 @ref{c3,,optparse}。还要注意 @ref{6,,argparse} 是基于 @ref{c3,,optparse} 的，因此用法与其非常相似。
@end quotation
@end cartouche

@menu
* 概念:: 
* 基础: 基础<2>. 
* 位置参数介绍:: 
* 可选参数介绍:: 
* 结合位置参数和可选参数:: 
* 进行一些小小的改进:: 
* 后记:: 

@end menu

@node 概念,基础<2>,,Argparse 教程
@anchor{howto/argparse concepts}@anchor{4197}
@subsection 概念


让我们利用 @code{ls} 命令来展示我们将要在这篇入门教程中探索的功能：

@example
$ ls
cpython  devguide  prog.py  pypy  rm-unused-function.patch
$ ls pypy
ctypes_configure  demo  dotviewer  include  lib_pypy  lib-python ...
$ ls -l
total 20
drwxr-xr-x 19 wena wena 4096 Feb 18 18:51 cpython
drwxr-xr-x  4 wena wena 4096 Feb  8 12:04 devguide
-rwxr-xr-x  1 wena wena  535 Feb 19 00:05 prog.py
drwxr-xr-x 14 wena wena 4096 Feb  7 00:59 pypy
-rw-r--r--  1 wena wena  741 Feb 18 01:01 rm-unused-function.patch
$ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
...
@end example

我们可以从这四个命令中学到几个概念：


@itemize *

@item 
@code{ls} 是一个即使在运行的时候没有提供任何选项，也非常有用的命令。在默认情况下他会输出当前文件夹包含的文件和文件夹。

@item 
如果我们想要使用比它默认提供的更多功能，我们需要告诉该命令更多信息。在这个例子里，我们想要查看一个不同的目录，@code{pypy}。我们所做的是指定所谓的位置参数。之所以这样命名，是因为程序应该如何处理该参数值，完全取决于它在命令行出现的位置。更能体现这个概念的命令如 @code{cp}，它最基本的用法是 @code{cp SRC DEST}。第一个位置参数指的是*你想要复制的*，第二个位置参数指的是*你想要复制到的位置*。

@item 
现在假设我们想要改变这个程序的行为。在我们的例子中，我们不仅仅只是输出每个文件的文件名，还输出了更多信息。在这个例子中，@code{-l} 被称为可选参数。

@item 
这是一段帮助文档的文字。它是非常有用的，因为当你遇到一个你从未使用过的程序时，你可以通过阅读它的帮助文档来弄清楚它是如何运行的。
@end itemize

@node 基础<2>,位置参数介绍,概念,Argparse 教程
@anchor{howto/argparse the-basics}@anchor{4198}
@subsection 基础


让我们从一个简单到（几乎）什么也做不了的例子开始：

@example
import argparse
parser = argparse.ArgumentParser()
parser.parse_args()
@end example

以下是该代码的运行结果：

@example
$ python3 prog.py
$ python3 prog.py --help
usage: prog.py [-h]

optional arguments:
  -h, --help  show this help message and exit
$ python3 prog.py --verbose
usage: prog.py [-h]
prog.py: error: unrecognized arguments: --verbose
$ python3 prog.py foo
usage: prog.py [-h]
prog.py: error: unrecognized arguments: foo
@end example

程序运行情况如下：


@itemize *

@item 
在没有任何选项的情况下运行脚本不会在标准输出显示任何内容。这没有什么用处。

@item 
第二行代码开始展现出 @ref{6,,argparse} 模块的作用。我们几乎什么也没有做，但已经得到一条很好的帮助信息。

@item 
@code{--help} 选项，也可缩写为 @code{-h}，是唯一一个可以直接使用的选项（即不需要指定该选项的内容）。指定任何内容都会导致错误。即便如此，我们也能直接得到一条有用的用法信息。
@end itemize

@node 位置参数介绍,可选参数介绍,基础<2>,Argparse 教程
@anchor{howto/argparse introducing-positional-arguments}@anchor{4199}
@subsection 位置参数介绍


举个例子：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("echo")
args = parser.parse_args()
print(args.echo)
@end example

运行此程序：

@example
$ python3 prog.py
usage: prog.py [-h] echo
prog.py: error: the following arguments are required: echo
$ python3 prog.py --help
usage: prog.py [-h] echo

positional arguments:
  echo

optional arguments:
  -h, --help  show this help message and exit
$ python3 prog.py foo
foo
@end example

程序运行情况如下：


@itemize *

@item 
我们增加了 @code{add_argument()} 方法，该方法用于指定程序能够接受哪些命令行选项。在这个例子中，我将选项命名为 @code{echo}，与其功能一致。

@item 
现在调用我们的程序必须要指定一个选项。

@item 
The @code{parse_args()} method actually returns some data from the
options specified, in this case, @code{echo}.

@item 
这一变量是 @ref{6,,argparse} 免费施放的某种 “魔法”（即是说，不需要指定哪个变量是存储哪个值的）。你也可以注意到，这一名称与传递给方法的字符串参数一致，都是  @code{echo}。
@end itemize

然而请注意，尽管显示的帮助看起来清楚完整，但它可以比现在更有帮助。比如我们可以知道 @code{echo} 是一个位置参数，但我们除了靠猜或者看源代码，没法知道它是用来干什么的。所以，我们可以把它改造得更有用：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("echo", help="echo the string you use here")
args = parser.parse_args()
print(args.echo)
@end example

然后我们得到：

@example
$ python3 prog.py -h
usage: prog.py [-h] echo

positional arguments:
  echo        echo the string you use here

optional arguments:
  -h, --help  show this help message and exit
@end example

现在，来做一些更有用的事情：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", help="display a square of a given number")
args = parser.parse_args()
print(args.square**2)
@end example

以下是该代码的运行结果：

@example
$ python3 prog.py 4
Traceback (most recent call last):
  File "prog.py", line 5, in <module>
    print(args.square**2)
TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'int'
@end example

进展不太顺利。那是因为 @ref{6,,argparse} 会把我们传递给它的选项视作为字符串，除非我们告诉它别这样。所以，让我们来告诉 @ref{6,,argparse} 来把这一输入视为整数：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", help="display a square of a given number",
                    type=int)
args = parser.parse_args()
print(args.square**2)
@end example

以下是该代码的运行结果：

@example
$ python3 prog.py 4
16
$ python3 prog.py four
usage: prog.py [-h] square
prog.py: error: argument square: invalid int value: 'four'
@end example

做得不错。当这个程序在收到错误的无效的输入时，它甚至能在执行计算之前先退出，还能显示很有帮助的错误信息。

@node 可选参数介绍,结合位置参数和可选参数,位置参数介绍,Argparse 教程
@anchor{howto/argparse introducing-optional-arguments}@anchor{419a}
@subsection 可选参数介绍


到目前为止，我们一直在研究位置参数。让我们看看如何添加可选的：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("--verbosity", help="increase output verbosity")
args = parser.parse_args()
if args.verbosity:
    print("verbosity turned on")
@end example

和输出：

@example
$ python3 prog.py --verbosity 1
verbosity turned on
$ python3 prog.py
$ python3 prog.py --help
usage: prog.py [-h] [--verbosity VERBOSITY]

optional arguments:
  -h, --help            show this help message and exit
  --verbosity VERBOSITY
                        increase output verbosity
$ python3 prog.py --verbosity
usage: prog.py [-h] [--verbosity VERBOSITY]
prog.py: error: argument --verbosity: expected one argument
@end example

程序运行情况如下：


@itemize *

@item 
这一程序被设计为当指定 @code{--verbosity} 选项时显示某些东西，否则不显示。

@item 
不添加这一选项时程序没有提示任何错误而退出，表明这一选项确实是可选的。注意，如果一个可选参数没有被使用时，相关变量被赋值为 @code{None}，在此例中是 @code{args.verbosity}，这也就是为什么它在 @ref{de0,,if} 语句中被当作逻辑假。

@item 
帮助信息有点不同。

@item 
使用 @code{--verbosity} 选项时，必须指定一个值，但可以是任何值。
@end itemize

上述例子接受任何整数值作为 @code{--verbosity} 的参数，但对于我们的简单程序而言，只有两个值有实际意义：@code{True} 或者 @code{False}。让我们据此修改代码：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("--verbose", help="increase output verbosity",
                    action="store_true")
args = parser.parse_args()
if args.verbose:
    print("verbosity turned on")
@end example

和输出：

@example
$ python3 prog.py --verbose
verbosity turned on
$ python3 prog.py --verbose 1
usage: prog.py [-h] [--verbose]
prog.py: error: unrecognized arguments: 1
$ python3 prog.py --help
usage: prog.py [-h] [--verbose]

optional arguments:
  -h, --help  show this help message and exit
  --verbose   increase output verbosity
@end example

程序运行情况如下：


@itemize *

@item 
现在，这一选项更多地是一个标志，而非需要接受一个值的什么东西。我们甚至改变了选项的名字来符合这一思路。注意我们现在指定了一个新的关键词 @code{action}，并赋值为 @code{"store_true"}。这意味着，当这一选项存在时，为 @code{args.verbose} 赋值为 @code{True}。没有指定时则隐含地赋值为 @code{False}。

@item 
当你为其指定一个值时，它会报错，符合作为标志的真正的精神。

@item 
留意不同的帮助文字。
@end itemize

@menu
* 短选项:: 

@end menu

@node 短选项,,,可选参数介绍
@anchor{howto/argparse short-options}@anchor{419b}
@subsubsection 短选项


如果你熟悉命令行的用法，你会发现我还没讲到这一选项的短版本。这也很简单：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("-v", "--verbose", help="increase output verbosity",
                    action="store_true")
args = parser.parse_args()
if args.verbose:
    print("verbosity turned on")
@end example

效果就像这样：

@example
$ python3 prog.py -v
verbosity turned on
$ python3 prog.py --help
usage: prog.py [-h] [-v]

optional arguments:
  -h, --help     show this help message and exit
  -v, --verbose  increase output verbosity
@end example

可以注意到，这一新的能力也反映在帮助文本里。

@node 结合位置参数和可选参数,进行一些小小的改进,可选参数介绍,Argparse 教程
@anchor{howto/argparse combining-positional-and-optional-arguments}@anchor{419c}
@subsection 结合位置参数和可选参数


我们的程序变得越来越复杂了：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbose", action="store_true",
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbose:
    print("the square of @{@} equals @{@}".format(args.square, answer))
else:
    print(answer)
@end example

接着是输出：

@example
$ python3 prog.py
usage: prog.py [-h] [-v] square
prog.py: error: the following arguments are required: square
$ python3 prog.py 4
16
$ python3 prog.py 4 --verbose
the square of 4 equals 16
$ python3 prog.py --verbose 4
the square of 4 equals 16
@end example


@itemize *

@item 
我们带回了一个位置参数，结果发生了报错。

@item 
注意顺序无关紧要。
@end itemize

给我们的程序加上接受多个冗长度的值，然后实际来用用：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", type=int,
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity == 2:
    print("the square of @{@} equals @{@}".format(args.square, answer))
elif args.verbosity == 1:
    print("@{@}^2 == @{@}".format(args.square, answer))
else:
    print(answer)
@end example

和输出：

@example
$ python3 prog.py 4
16
$ python3 prog.py 4 -v
usage: prog.py [-h] [-v VERBOSITY] square
prog.py: error: argument -v/--verbosity: expected one argument
$ python3 prog.py 4 -v 1
4^2 == 16
$ python3 prog.py 4 -v 2
the square of 4 equals 16
$ python3 prog.py 4 -v 3
16
@end example

除了最后一个，看上去都不错。最后一个暴露了我们的程序中有一个 bug。我们可以通过限制 @code{--verbosity} 选项可以接受的值来修复它：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", type=int, choices=[0, 1, 2],
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity == 2:
    print("the square of @{@} equals @{@}".format(args.square, answer))
elif args.verbosity == 1:
    print("@{@}^2 == @{@}".format(args.square, answer))
else:
    print(answer)
@end example

和输出：

@example
$ python3 prog.py 4 -v 3
usage: prog.py [-h] [-v @{0,1,2@}] square
prog.py: error: argument -v/--verbosity: invalid choice: 3 (choose from 0, 1, 2)
$ python3 prog.py 4 -h
usage: prog.py [-h] [-v @{0,1,2@}] square

positional arguments:
  square                display a square of a given number

optional arguments:
  -h, --help            show this help message and exit
  -v @{0,1,2@}, --verbosity @{0,1,2@}
                        increase output verbosity
@end example

注意这一改变同时反应在错误信息和帮助信息里。

现在，让我们使用另一种的方式来改变冗长度。这种方式更常见，也和 CPython 的可执行文件处理它自己的冗长度参数的方式一致（参考 @code{python --help} 的输出）：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display the square of a given number")
parser.add_argument("-v", "--verbosity", action="count",
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity == 2:
    print("the square of @{@} equals @{@}".format(args.square, answer))
elif args.verbosity == 1:
    print("@{@}^2 == @{@}".format(args.square, answer))
else:
    print(answer)
@end example

我们引入了另一种动作 @code{count}，来数某一个可选参数出现了几次：

@example
$ python3 prog.py 4
16
$ python3 prog.py 4 -v
4^2 == 16
$ python3 prog.py 4 -vv
the square of 4 equals 16
$ python3 prog.py 4 --verbosity --verbosity
the square of 4 equals 16
$ python3 prog.py 4 -v 1
usage: prog.py [-h] [-v] square
prog.py: error: unrecognized arguments: 1
$ python3 prog.py 4 -h
usage: prog.py [-h] [-v] square

positional arguments:
  square           display a square of a given number

optional arguments:
  -h, --help       show this help message and exit
  -v, --verbosity  increase output verbosity
$ python3 prog.py 4 -vvv
16
@end example


@itemize *

@item 
是的，它现在比前一版本更像是一个标志（和 @code{action="store_true"} 相似）。这能解释它为什么报错。

@item 
它也表现得与 “store_true” 的行为相似。

@item 
这给出了一个关于 @code{count} 动作的效果的演示。你之前很可能应该已经看过这种用法。

@item 
如果你不添加 @code{-v} 标志，这一标志的值会是 @code{None}。

@item 
如期望的那样，添加该标志的长形态能够获得相同的输出。

@item 
可惜的是，对于我们的脚本获得的新能力，我们的帮助输出并没有提供很多信息，但我们总是可以通过改善文档来修复这一问题（比如通过 @code{help} 关键字参数）。

@item 
最后一个输出暴露了我们程序中的一个 bug。
@end itemize

让我们修复一下：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", action="count",
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2

# bugfix: replace == with >=
if args.verbosity >= 2:
    print("the square of @{@} equals @{@}".format(args.square, answer))
elif args.verbosity >= 1:
    print("@{@}^2 == @{@}".format(args.square, answer))
else:
    print(answer)
@end example

这是它给我们的输出：

@example
$ python3 prog.py 4 -vvv
the square of 4 equals 16
$ python3 prog.py 4 -vvvv
the square of 4 equals 16
$ python3 prog.py 4
Traceback (most recent call last):
  File "prog.py", line 11, in <module>
    if args.verbosity >= 2:
TypeError: '>=' not supported between instances of 'NoneType' and 'int'
@end example


@itemize *

@item 
第一组输出很好，修复了之前的 bug。也就是说，我们希望任何 >= 2 的值尽可能详尽。

@item 
第三组输出并不理想。
@end itemize

让我们修复那个 bug：

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", action="count", default=0,
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity >= 2:
    print("the square of @{@} equals @{@}".format(args.square, answer))
elif args.verbosity >= 1:
    print("@{@}^2 == @{@}".format(args.square, answer))
else:
    print(answer)
@end example

我们刚刚引入了又一个新的关键字 @code{default}。我们把它设置为 @code{0} 来让它可以与其他整数值相互比较。记住，默认情况下如果一个可选参数没有被指定，它的值会是 @code{None}，并且它不能和整数值相比较（所以产生了 @ref{192,,TypeError} 异常）。

然后：

@example
$ python3 prog.py 4
16
@end example

凭借我们目前已学的东西你就可以做到许多事情，而我们还仅仅学了一些皮毛而已。 @ref{6,,argparse} 模块是非常强大的，在结束篇教程之前我们将再探索更多一些内容。

@node 进行一些小小的改进,后记,结合位置参数和可选参数,Argparse 教程
@anchor{howto/argparse getting-a-little-more-advanced}@anchor{419d}
@subsection 进行一些小小的改进


如果我们想扩展我们的简短程序来执行其他幂次的运算，而不仅是乘方:

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
parser.add_argument("-v", "--verbosity", action="count", default=0)
args = parser.parse_args()
answer = args.x**args.y
if args.verbosity >= 2:
    print("@{@} to the power @{@} equals @{@}".format(args.x, args.y, answer))
elif args.verbosity >= 1:
    print("@{@}^@{@} == @{@}".format(args.x, args.y, answer))
else:
    print(answer)
@end example

输出：

@example
$ python3 prog.py
usage: prog.py [-h] [-v] x y
prog.py: error: the following arguments are required: x, y
$ python3 prog.py -h
usage: prog.py [-h] [-v] x y

positional arguments:
  x                the base
  y                the exponent

optional arguments:
  -h, --help       show this help message and exit
  -v, --verbosity
$ python3 prog.py 4 2 -v
4^2 == 16
@end example

请注意到目前为止我们一直在使用详细级别来 @emph{更改} 所显示的文本。 以下示例则使用详细级别来显示 @emph{更多的} 文本:

@example
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
parser.add_argument("-v", "--verbosity", action="count", default=0)
args = parser.parse_args()
answer = args.x**args.y
if args.verbosity >= 2:
    print("Running '@{@}'".format(__file__))
if args.verbosity >= 1:
    print("@{@}^@{@} == ".format(args.x, args.y), end="")
print(answer)
@end example

输出：

@example
$ python3 prog.py 4 2
16
$ python3 prog.py 4 2 -v
4^2 == 16
$ python3 prog.py 4 2 -vv
Running 'prog.py'
4^2 == 16
@end example

@menu
* 矛盾的选项:: 

@end menu

@node 矛盾的选项,,,进行一些小小的改进
@anchor{howto/argparse conflicting-options}@anchor{419e}
@subsubsection 矛盾的选项


到目前为止，我们一直在使用 @ref{68f,,argparse.ArgumentParser} 实例的两个方法。 让我们再介绍第三个方法 @code{add_mutually_exclusive_group()}。 它允许我们指定彼此相互冲突的选项。 让我们再更改程序的其余部分以便使用新功能更有意义：我们将引入 @code{--quiet} 选项，它将与 @code{--verbose} 正好相反:

@example
import argparse

parser = argparse.ArgumentParser()
group = parser.add_mutually_exclusive_group()
group.add_argument("-v", "--verbose", action="store_true")
group.add_argument("-q", "--quiet", action="store_true")
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
args = parser.parse_args()
answer = args.x**args.y

if args.quiet:
    print(answer)
elif args.verbose:
    print("@{@} to the power @{@} equals @{@}".format(args.x, args.y, answer))
else:
    print("@{@}^@{@} == @{@}".format(args.x, args.y, answer))
@end example

我们的程序现在变得更简洁了，我们出于演示需要略去了一些功能。 无论如何，输出是这样的:

@example
$ python3 prog.py 4 2
4^2 == 16
$ python3 prog.py 4 2 -q
16
$ python3 prog.py 4 2 -v
4 to the power 2 equals 16
$ python3 prog.py 4 2 -vq
usage: prog.py [-h] [-v | -q] x y
prog.py: error: argument -q/--quiet: not allowed with argument -v/--verbose
$ python3 prog.py 4 2 -v --quiet
usage: prog.py [-h] [-v | -q] x y
prog.py: error: argument -q/--quiet: not allowed with argument -v/--verbose
@end example

这应该很容易理解。 我添加了末尾的输出这样你就可以看到其所达到的灵活性，即混合使用长和短两种形式的选项。

在我们收尾之前，你也许希望告诉你的用户这个程序的主要目标，以免他们还不清楚:

@example
import argparse

parser = argparse.ArgumentParser(description="calculate X to the power of Y")
group = parser.add_mutually_exclusive_group()
group.add_argument("-v", "--verbose", action="store_true")
group.add_argument("-q", "--quiet", action="store_true")
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
args = parser.parse_args()
answer = args.x**args.y

if args.quiet:
    print(answer)
elif args.verbose:
    print("@{@} to the power @{@} equals @{@}".format(args.x, args.y, answer))
else:
    print("@{@}^@{@} == @{@}".format(args.x, args.y, answer))
@end example

请注意用法文本中有细微的差异。 注意 @code{[-v | -q]}，它的意思是说我们可以使用 @code{-v} 或 @code{-q}，但不能同时使用两者：

@example
$ python3 prog.py --help
usage: prog.py [-h] [-v | -q] x y

calculate X to the power of Y

positional arguments:
  x              the base
  y              the exponent

optional arguments:
  -h, --help     show this help message and exit
  -v, --verbose
  -q, --quiet
@end example

@node 后记,,进行一些小小的改进,Argparse 教程
@anchor{howto/argparse conclusion}@anchor{419f}
@subsection 后记


除了这里显示的内容，@ref{6,,argparse} 模块还提供了更多功能。 它的文档相当详细和完整，包含大量示例。 完成这个教程之后，你应该能毫不困难地阅读该文档。

@c import ipaddress

@node ipaddress模块介绍,Argument Clinic How-To,Argparse 教程,Python 常用指引
@anchor{howto/ipaddress doc}@anchor{41a0}@anchor{howto/ipaddress an-introduction-to-the-ipaddress-module}@anchor{41a1}@anchor{howto/ipaddress ipaddress-howto}@anchor{2ea5}
@section ipaddress模块介绍


@*作者: 
Peter Moody


@*作者: 
Nick Coghlan


@subsubheading 概述



本文档旨在简要介绍 @ref{a2,,ipaddress} 模块。 它主要针对那些不熟悉 IP 网络术语的用户，但也可能对想要速览 @ref{a2,,ipaddress} 如何代表IP网络寻址概念的网络工程师有用。

@menu
* 创建 Address/Network/Interface 对象:: 
* 审查 Address/Network/Interface 对象:: 
* Network 作为 Address 列表:: 
* 比较运算: 比较运算<4>. 
* 将IP地址与其他模块一起使用:: 
* 实例创建失败时获取更多详细信息:: 

@end menu

@node 创建 Address/Network/Interface 对象,审查 Address/Network/Interface 对象,,ipaddress模块介绍
@anchor{howto/ipaddress creating-address-network-interface-objects}@anchor{41a2}
@subsection 创建 Address/Network/Interface 对象


因为 @ref{a2,,ipaddress} 是一个用于检查和操作 IP 地址的模块，你要做的第一件事就是创建一些对象。 您可以使用 @ref{a2,,ipaddress} 从字符串和整数创建对象。

@menu
* 关于IP版本的说明:: 
* IP主机地址:: 
* 定义网络:: 
* 主机接口:: 

@end menu

@node 关于IP版本的说明,IP主机地址,,创建 Address/Network/Interface 对象
@anchor{howto/ipaddress a-note-on-ip-versions}@anchor{41a3}
@subsubsection 关于IP版本的说明


对于不太熟悉 IP 寻址的读者，重要的是要知道 Internet 协议当前正在从协议的版本4转移到版本6。转换很大程度上是因为协议的版本4没有提供足够的地址来满足整个世界的需求，特别是考虑到越来越多的设备直接连接到互联网。

解释协议的两个版本之间的差异的细节超出了本介绍的范围，但读者需要至少知道存在这两个版本，并且有时需要强制使用一个版本或其他版本。

@node IP主机地址,定义网络,关于IP版本的说明,创建 Address/Network/Interface 对象
@anchor{howto/ipaddress ip-host-addresses}@anchor{41a4}
@subsubsection IP主机地址


通常称为“主机地址”的地址是使用IP寻址时最基本的单元。 创建地址的最简单方法是使用 @ref{2ea7,,ipaddress.ip_address()} 工厂函数，该函数根据传入的值自动确定是创建 IPv4 还是 IPv6 地址：

@example
>>> ipaddress.ip_address('192.0.2.1')
IPv4Address('192.0.2.1')
>>> ipaddress.ip_address('2001:DB8::1')
IPv6Address('2001:db8::1')
@end example

地址也可以直接从整数创建，适配32位的值并假定为IPv4地址:

@example
>>> ipaddress.ip_address(3221225985)
IPv4Address('192.0.2.1')
>>> ipaddress.ip_address(42540766411282592856903984951653826561)
IPv6Address('2001:db8::1')
@end example

要强制使用IPv4或IPv6地址，可以直接调用相关的类。 这对于强制为小整数创建IPv6地址特别有用:

@example
>>> ipaddress.ip_address(1)
IPv4Address('0.0.0.1')
>>> ipaddress.IPv4Address(1)
IPv4Address('0.0.0.1')
>>> ipaddress.IPv6Address(1)
IPv6Address('::1')
@end example

@node 定义网络,主机接口,IP主机地址,创建 Address/Network/Interface 对象
@anchor{howto/ipaddress defining-networks}@anchor{41a5}
@subsubsection 定义网络


主机地址通常组合在一起形成IP网络，因此 @ref{a2,,ipaddress} 提供了一种创建、检查和操作网络定义的方法。 IP网络对象由字符串构成，这些字符串定义作为该网络一部分的主机地址范围。 该信息的最简单形式是“网络地址/网络前缀”对，其中前缀定义了比较的前导比特数，以确定地址是否是网络的一部分，并且网络地址定义了那些位的预期值。

对于地址，提供了一个自动确定正确IP版本的工厂函数:

@example
>>> ipaddress.ip_network('192.0.2.0/24')
IPv4Network('192.0.2.0/24')
>>> ipaddress.ip_network('2001:db8::0/96')
IPv6Network('2001:db8::/96')
@end example

网络对象不能设置任何主机位。 这样做的实际效果是`@w{`}192.0.2.1/24`@w{`}没有描述网络。 这种定义被称为接口对象，因为网络上IP表示法通常用于描述给定网络上的计算机的网络接口，并在下一节中进一步描述。

默认情况下，尝试创建一个设置了主机位的网络对象将导致 @ref{1fb,,ValueError} 被引发。 要请求将附加位强制为零，可以将标志`@w{`}strict=False`@w{`} 传递给构造函数:

@example
>>> ipaddress.ip_network('192.0.2.1/24')
Traceback (most recent call last):
   ...
ValueError: 192.0.2.1/24 has host bits set
>>> ipaddress.ip_network('192.0.2.1/24', strict=False)
IPv4Network('192.0.2.0/24')
@end example

虽然字符串形式提供了更大的灵活性，但网络也可以用整数定义，就像主机地址一样。 在这种情况下，网络被认为只包含由整数标识的单个地址，因此网络前缀包括整个网络地址:

@example
>>> ipaddress.ip_network(3221225984)
IPv4Network('192.0.2.0/32')
>>> ipaddress.ip_network(42540766411282592856903984951653826560)
IPv6Network('2001:db8::/128')
@end example

与地址一样，可以通过直接调用类构造函数而不是使用工厂函数来强制创建特定类型的网络。

@node 主机接口,,定义网络,创建 Address/Network/Interface 对象
@anchor{howto/ipaddress host-interfaces}@anchor{41a6}
@subsubsection 主机接口


如上所述，如果您需要描述特定网络上的地址，则地址和网络类都不够。 像 @code{192.0.2.1/24} 这样的表示法通常被网络工程师和为防火墙和路由器编写工具的人用作“ @code{192.0.2.0/24} 网络上的主机 @code{192.0.2.1} ”的简写。因此，@ref{a2,,ipaddress} 提供了一组将地址与特定网络相关联的混合类。用于创建的接口与用于定义网络对象的接口相同，除了地址部分不限于是网络地址。

@example
>>> ipaddress.ip_interface('192.0.2.1/24')
IPv4Interface('192.0.2.1/24')
>>> ipaddress.ip_interface('2001:db8::1/96')
IPv6Interface('2001:db8::1/96')
@end example

接受整数输入（与网络一样），并且可以通过直接调用相关构造函数来强制使用特定IP版本。

@node 审查 Address/Network/Interface 对象,Network 作为 Address 列表,创建 Address/Network/Interface 对象,ipaddress模块介绍
@anchor{howto/ipaddress inspecting-address-network-interface-objects}@anchor{41a7}
@subsection 审查 Address/Network/Interface 对象


你已经遇到了创建IPv(4|6)(Address|Network|Interface) 对象的麻烦，因此你可能希望获得有关它的信息。 @ref{a2,,ipaddress} 试图让这个过程变得简单直观。

提取 IP 版本:

@example
>>> addr4 = ipaddress.ip_address('192.0.2.1')
>>> addr6 = ipaddress.ip_address('2001:db8::1')
>>> addr6.version
6
>>> addr4.version
4
@end example

从接口获取网络:

@example
>>> host4 = ipaddress.ip_interface('192.0.2.1/24')
>>> host4.network
IPv4Network('192.0.2.0/24')
>>> host6 = ipaddress.ip_interface('2001:db8::1/96')
>>> host6.network
IPv6Network('2001:db8::/96')
@end example

找出网络中有多少独立地址:

@example
>>> net4 = ipaddress.ip_network('192.0.2.0/24')
>>> net4.num_addresses
256
>>> net6 = ipaddress.ip_network('2001:db8::0/96')
>>> net6.num_addresses
4294967296
@end example

迭代网络上的“可用”地址:

@example
>>> net4 = ipaddress.ip_network('192.0.2.0/24')
>>> for x in net4.hosts():
...     print(x)  
192.0.2.1
192.0.2.2
192.0.2.3
192.0.2.4
...
192.0.2.252
192.0.2.253
192.0.2.254
@end example

获取网络掩码（即对应于网络前缀的设置位）或主机掩码（不属于网络掩码的任何位）：

@example
>>> net4 = ipaddress.ip_network('192.0.2.0/24')
>>> net4.netmask
IPv4Address('255.255.255.0')
>>> net4.hostmask
IPv4Address('0.0.0.255')
>>> net6 = ipaddress.ip_network('2001:db8::0/96')
>>> net6.netmask
IPv6Address('ffff:ffff:ffff:ffff:ffff:ffff::')
>>> net6.hostmask
IPv6Address('::ffff:ffff')
@end example

展开或压缩地址:

@example
>>> addr6.exploded
'2001:0db8:0000:0000:0000:0000:0000:0001'
>>> addr6.compressed
'2001:db8::1'
>>> net6.exploded
'2001:0db8:0000:0000:0000:0000:0000:0000/96'
>>> net6.compressed
'2001:db8::/96'
@end example

虽然IPv4不支持展开或压缩，但关联对象仍提供相关属性，因此版本中性代码可以轻松确保最简洁或最详细的形式用于IPv6地址，同时仍能正确处理IPv4地址。

@node Network 作为 Address 列表,比较运算<4>,审查 Address/Network/Interface 对象,ipaddress模块介绍
@anchor{howto/ipaddress networks-as-lists-of-addresses}@anchor{41a8}
@subsection Network 作为 Address 列表


将网络视为列表有时很有用。 这意味着它可以像这样索引它们:

@example
>>> net4[1]
IPv4Address('192.0.2.1')
>>> net4[-1]
IPv4Address('192.0.2.255')
>>> net6[1]
IPv6Address('2001:db8::1')
>>> net6[-1]
IPv6Address('2001:db8::ffff:ffff')
@end example

它还意味着网络对象可以使用像这样的列表成员测试语法:

@example
if address in network:
    # do something
@end example

根据网络前缀有效地完成包含性测试:

@example
>>> addr4 = ipaddress.ip_address('192.0.2.1')
>>> addr4 in ipaddress.ip_network('192.0.2.0/24')
True
>>> addr4 in ipaddress.ip_network('192.0.3.0/24')
False
@end example

@node 比较运算<4>,将IP地址与其他模块一起使用,Network 作为 Address 列表,ipaddress模块介绍
@anchor{howto/ipaddress comparisons}@anchor{41a9}
@subsection 比较运算


@ref{a2,,ipaddress} 有意义地提供了一些简单、希望直观的比较对象的方法:

@example
>>> ipaddress.ip_address('192.0.2.1') < ipaddress.ip_address('192.0.2.2')
True
@end example

如果你尝试比较不同版本或不同类型的对象，则会引发 @ref{192,,TypeError} 异常。

@node 将IP地址与其他模块一起使用,实例创建失败时获取更多详细信息,比较运算<4>,ipaddress模块介绍
@anchor{howto/ipaddress using-ip-addresses-with-other-modules}@anchor{41aa}
@subsection 将IP地址与其他模块一起使用


其他使用IP地址的模块（例如 @ref{ef,,socket} ）通常不会直接接受来自该模块的对象。 相反，它们必须被强制转换为另一个模块可接受的整数或字符串:

@example
>>> addr4 = ipaddress.ip_address('192.0.2.1')
>>> str(addr4)
'192.0.2.1'
>>> int(addr4)
3221225985
@end example

@node 实例创建失败时获取更多详细信息,,将IP地址与其他模块一起使用,ipaddress模块介绍
@anchor{howto/ipaddress getting-more-detail-when-instance-creation-fails}@anchor{41ab}
@subsection 实例创建失败时获取更多详细信息


使用与版本无关的工厂函数创建 address/network/interface 对象时，任何错误都将报告为 @ref{1fb,,ValueError} ，带有一般错误消息，只是说传入的值未被识别为该类型的对象。 缺少特定错误是因为有必要知道该值是*假设*是IPv4还是IPv6，以便提供有关其被拒绝原因的更多详细信息。

为了支持访问这些额外细节的用例，各个类构造函数实际上引发了 @ref{1fb,,ValueError} 子类 @ref{2eb0,,ipaddress.AddressValueError} 和 @ref{2ed5,,ipaddress.NetmaskValueError} 以准确指示定义的哪一部分无法正确解析。

直接使用类构造函数时，错误消息更加详细。 例如:

@example
>>> ipaddress.ip_address("192.168.0.256")
Traceback (most recent call last):
  ...
ValueError: '192.168.0.256' does not appear to be an IPv4 or IPv6 address
>>> ipaddress.IPv4Address("192.168.0.256")
Traceback (most recent call last):
  ...
ipaddress.AddressValueError: Octet 256 (> 255) not permitted in '192.168.0.256'

>>> ipaddress.ip_network("192.168.0.1/64")
Traceback (most recent call last):
  ...
ValueError: '192.168.0.1/64' does not appear to be an IPv4 or IPv6 network
>>> ipaddress.IPv4Network("192.168.0.1/64")
Traceback (most recent call last):
  ...
ipaddress.NetmaskValueError: '64' is not a valid netmask
@end example

但是，两个模块特定的异常都有 @ref{1fb,,ValueError} 作为它们的父类，所以如果你不关心特定类型的错误，你仍然可以编写如下代码:

@example
try:
    network = ipaddress.IPv4Network(address)
except ValueError:
    print('address/netmask is invalid for IPv4:', address)
@end example

@node Argument Clinic How-To,使用 DTrace 和 SystemTap 检测CPython,ipaddress模块介绍,Python 常用指引
@anchor{howto/clinic doc}@anchor{41ac}@anchor{howto/clinic argument-clinic-how-to}@anchor{41ad}
@section Argument Clinic How-To


@*作者: 
Larry Hastings


@subsubheading 摘要



Argument Clinic is a preprocessor for CPython C files.
Its purpose is to automate all the boilerplate involved
with writing argument parsing code for "builtins".
This document shows you how to convert your first C
function to work with Argument Clinic, and then introduces
some advanced topics on Argument Clinic usage.

Currently Argument Clinic is considered internal-only
for CPython.  Its use is not supported for files outside
CPython, and no guarantees are made regarding backwards
compatibility for future versions.  In other words: if you
maintain an external C extension for CPython, you're welcome
to experiment with Argument Clinic in your own code.  But the
version of Argument Clinic that ships with the next version
of CPython @emph{could} be totally incompatible and break all your code.

@menu
* The Goals Of Argument Clinic:: 
* Basic Concepts And Usage:: 
* Converting Your First Function:: 
* Advanced Topics:: 

@end menu

@node The Goals Of Argument Clinic,Basic Concepts And Usage,,Argument Clinic How-To
@anchor{howto/clinic the-goals-of-argument-clinic}@anchor{41ae}
@subsection The Goals Of Argument Clinic


Argument Clinic's primary goal
is to take over responsibility for all argument parsing code
inside CPython.  This means that, when you convert a function
to work with Argument Clinic, that function should no longer
do any of its own argument parsing—the code generated by
Argument Clinic should be a "black box" to you, where CPython
calls in at the top, and your code gets called at the bottom,
with @code{PyObject *args} (and maybe @code{PyObject *kwargs})
magically converted into the C variables and types you need.

In order for Argument Clinic to accomplish its primary goal,
it must be easy to use.  Currently, working with CPython's
argument parsing library is a chore, requiring maintaining
redundant information in a surprising number of places.
When you use Argument Clinic, you don't have to repeat yourself.

Obviously, no one would want to use Argument Clinic unless
it's solving their problem—and without creating new problems of
its own.
So it's paramount that Argument Clinic generate correct code.
It'd be nice if the code was faster, too, but at the very least
it should not introduce a major speed regression.  (Eventually Argument
Clinic @emph{should} make a major speedup possible—we could
rewrite its code generator to produce tailor-made argument
parsing code, rather than calling the general-purpose CPython
argument parsing library.  That would make for the fastest
argument parsing possible!)

Additionally, Argument Clinic must be flexible enough to
work with any approach to argument parsing.  Python has
some functions with some very strange parsing behaviors;
Argument Clinic's goal is to support all of them.

Finally, the original motivation for Argument Clinic was
to provide introspection "signatures" for CPython builtins.
It used to be, the introspection query functions would throw
an exception if you passed in a builtin.  With Argument
Clinic, that's a thing of the past!

One idea you should keep in mind, as you work with
Argument Clinic: the more information you give it, the
better job it'll be able to do.
Argument Clinic is admittedly relatively simple right
now.  But as it evolves it will get more sophisticated,
and it should be able to do many interesting and smart
things with all the information you give it.

@node Basic Concepts And Usage,Converting Your First Function,The Goals Of Argument Clinic,Argument Clinic How-To
@anchor{howto/clinic basic-concepts-and-usage}@anchor{41af}
@subsection Basic Concepts And Usage


Argument Clinic ships with CPython; you'll find it in @code{Tools/clinic/clinic.py}.
If you run that script, specifying a C file as an argument:

@example
$ python3 Tools/clinic/clinic.py foo.c
@end example

Argument Clinic will scan over the file looking for lines that
look exactly like this:

@example
/*[clinic input]
@end example

When it finds one, it reads everything up to a line that looks
exactly like this:

@example
[clinic start generated code]*/
@end example

Everything in between these two lines is input for Argument Clinic.
All of these lines, including the beginning and ending comment
lines, are collectively called an Argument Clinic "block".

When Argument Clinic parses one of these blocks, it
generates output.  This output is rewritten into the C file
immediately after the block, followed by a comment containing a checksum.
The Argument Clinic block now looks like this:

@example
/*[clinic input]
... clinic input goes here ...
[clinic start generated code]*/
... clinic output goes here ...
/*[clinic end generated code: checksum=...]*/
@end example

If you run Argument Clinic on the same file a second time, Argument Clinic
will discard the old output and write out the new output with a fresh checksum
line.  However, if the input hasn't changed, the output won't change either.

You should never modify the output portion of an Argument Clinic block.  Instead,
change the input until it produces the output you want.  (That's the purpose of the
checksum—to detect if someone changed the output, as these edits would be lost
the next time Argument Clinic writes out fresh output.)

For the sake of clarity, here's the terminology we'll use with Argument Clinic:


@itemize *

@item 
The first line of the comment (@code{/*[clinic input]}) is the @emph{start line}.

@item 
The last line of the initial comment (@code{[clinic start generated code]*/}) is the @emph{end line}.

@item 
The last line (@code{/*[clinic end generated code: checksum=...]*/}) is the @emph{checksum line}.

@item 
In between the start line and the end line is the @emph{input}.

@item 
In between the end line and the checksum line is the @emph{output}.

@item 
All the text collectively, from the start line to the checksum line inclusively,
is the @emph{block}.  (A block that hasn't been successfully processed by Argument
Clinic yet doesn't have output or a checksum line, but it's still considered
a block.)
@end itemize

@node Converting Your First Function,Advanced Topics,Basic Concepts And Usage,Argument Clinic How-To
@anchor{howto/clinic converting-your-first-function}@anchor{41b0}
@subsection Converting Your First Function


The best way to get a sense of how Argument Clinic works is to
convert a function to work with it.  Here, then, are the bare
minimum steps you'd need to follow to convert a function to
work with Argument Clinic.  Note that for code you plan to
check in to CPython, you really should take the conversion farther,
using some of the advanced concepts you'll see later on in
the document (like "return converters" and "self converters").
But we'll keep it simple for this walkthrough so you can learn.

Let's dive in!


@enumerate 0

@item 
Make sure you're working with a freshly updated checkout
of the CPython trunk.

@item 
Find a Python builtin that calls either @ref{26a,,PyArg_ParseTuple()}
or @ref{5c5,,PyArg_ParseTupleAndKeywords()}, and hasn't been converted
to work with Argument Clinic yet.
For my example I'm using @code{_pickle.Pickler.dump()}.

@item 
If the call to the @code{PyArg_Parse} function uses any of the
following format units:

@example
O&
O!
es
es#
et
et#
@end example

or if it has multiple calls to @ref{26a,,PyArg_ParseTuple()},
you should choose a different function.  Argument Clinic @emph{does}
support all of these scenarios.  But these are advanced
topics—let's do something simpler for your first function.

Also, if the function has multiple calls to @ref{26a,,PyArg_ParseTuple()}
or @ref{5c5,,PyArg_ParseTupleAndKeywords()} where it supports different
types for the same argument, or if the function uses something besides
PyArg_Parse functions to parse its arguments, it probably
isn't suitable for conversion to Argument Clinic.  Argument Clinic
doesn't support generic functions or polymorphic parameters.

@item 
Add the following boilerplate above the function, creating our block:

@example
/*[clinic input]
[clinic start generated code]*/
@end example

@item 
Cut the docstring and paste it in between the @code{[clinic]} lines,
removing all the junk that makes it a properly quoted C string.
When you're done you should have just the text, based at the left
margin, with no line wider than 80 characters.
(Argument Clinic will preserve indents inside the docstring.)

If the old docstring had a first line that looked like a function
signature, throw that line away.  (The docstring doesn't need it
anymore—when you use @code{help()} on your builtin in the future,
the first line will be built automatically based on the function's
signature.)

Sample:

@example
/*[clinic input]
Write a pickled representation of obj to the open file.
[clinic start generated code]*/
@end example

@item 
If your docstring doesn't have a "summary" line, Argument Clinic will
complain.  So let's make sure it has one.  The "summary" line should
be a paragraph consisting of a single 80-column line
at the beginning of the docstring.

(Our example docstring consists solely of a summary line, so the sample
code doesn't have to change for this step.)

@item 
Above the docstring, enter the name of the function, followed
by a blank line.  This should be the Python name of the function,
and should be the full dotted path
to the function—it should start with the name of the module,
include any sub-modules, and if the function is a method on
a class it should include the class name too.

Sample:

@example
/*[clinic input]
_pickle.Pickler.dump

Write a pickled representation of obj to the open file.
[clinic start generated code]*/
@end example

@item 
If this is the first time that module or class has been used with Argument
Clinic in this C file,
you must declare the module and/or class.  Proper Argument Clinic hygiene
prefers declaring these in a separate block somewhere near the
top of the C file, in the same way that include files and statics go at
the top.  (In our sample code we'll just show the two blocks next to
each other.)

The name of the class and module should be the same as the one
seen by Python.  Check the name defined in the @ref{3aed,,PyModuleDef}
or @ref{2d6,,PyTypeObject} as appropriate.

When you declare a class, you must also specify two aspects of its type
in C: the type declaration you'd use for a pointer to an instance of
this class, and a pointer to the @ref{2d6,,PyTypeObject} for this class.

Sample:

@example
/*[clinic input]
module _pickle
class _pickle.Pickler "PicklerObject *" "&Pickler_Type"
[clinic start generated code]*/

/*[clinic input]
_pickle.Pickler.dump

Write a pickled representation of obj to the open file.
[clinic start generated code]*/
@end example

@item 
Declare each of the parameters to the function.  Each parameter
should get its own line.  All the parameter lines should be
indented from the function name and the docstring.

The general form of these parameter lines is as follows:

@example
name_of_parameter: converter
@end example

If the parameter has a default value, add that after the
converter:

@example
name_of_parameter: converter = default_value
@end example

Argument Clinic's support for "default values" is quite sophisticated;
please see @ref{41b1,,the section below on default values}
for more information.

Add a blank line below the parameters.

What's a "converter"?  It establishes both the type
of the variable used in C, and the method to convert the Python
value into a C value at runtime.
For now you're going to use what's called a "legacy converter"—a
convenience syntax intended to make porting old code into Argument
Clinic easier.

For each parameter, copy the "format unit" for that
parameter from the @code{PyArg_Parse()} format argument and
specify @emph{that} as its converter, as a quoted
string.  ("format unit" is the formal name for the one-to-three
character substring of the @code{format} parameter that tells
the argument parsing function what the type of the variable
is and how to convert it.  For more on format units please
see @ref{2d0,,解析参数并构建值变量}.)

For multicharacter format units like @code{z#}, use the
entire two-or-three character string.

Sample:

@example
 /*[clinic input]
 module _pickle
 class _pickle.Pickler "PicklerObject *" "&Pickler_Type"
 [clinic start generated code]*/

 /*[clinic input]
 _pickle.Pickler.dump

    obj: 'O'

Write a pickled representation of obj to the open file.
[clinic start generated code]*/
@end example

@item 
If your function has @code{|} in the format string, meaning some
parameters have default values, you can ignore it.  Argument
Clinic infers which parameters are optional based on whether
or not they have default values.

If your function has @code{$} in the format string, meaning it
takes keyword-only arguments, specify @code{*} on a line by
itself before the first keyword-only argument, indented the
same as the parameter lines.

(@code{_pickle.Pickler.dump} has neither, so our sample is unchanged.)

@item 
If the existing C function calls @ref{26a,,PyArg_ParseTuple()}
(as opposed to @ref{5c5,,PyArg_ParseTupleAndKeywords()}), then all its
arguments are positional-only.

To mark all parameters as positional-only in Argument Clinic,
add a @code{/} on a line by itself after the last parameter,
indented the same as the parameter lines.

Currently this is all-or-nothing; either all parameters are
positional-only, or none of them are.  (In the future Argument
Clinic may relax this restriction.)

Sample:

@example
/*[clinic input]
module _pickle
class _pickle.Pickler "PicklerObject *" "&Pickler_Type"
[clinic start generated code]*/

/*[clinic input]
_pickle.Pickler.dump

    obj: 'O'
    /

Write a pickled representation of obj to the open file.
[clinic start generated code]*/
@end example

@item 
It's helpful to write a per-parameter docstring for each parameter.
But per-parameter docstrings are optional; you can skip this step
if you prefer.

Here's how to add a per-parameter docstring.  The first line
of the per-parameter docstring must be indented further than the
parameter definition.  The left margin of this first line establishes
the left margin for the whole per-parameter docstring; all the text
you write will be outdented by this amount.  You can write as much
text as you like, across multiple lines if you wish.

Sample:

@example
/*[clinic input]
module _pickle
class _pickle.Pickler "PicklerObject *" "&Pickler_Type"
[clinic start generated code]*/

/*[clinic input]
_pickle.Pickler.dump

    obj: 'O'
        The object to be pickled.
    /

Write a pickled representation of obj to the open file.
[clinic start generated code]*/
@end example

@item 
Save and close the file, then run @code{Tools/clinic/clinic.py} on
it.  With luck everything worked---your block now has output, and
a @code{.c.h} file has been generated! Reopen the file in your
text editor to see:

@example
/*[clinic input]
_pickle.Pickler.dump

    obj: 'O'
        The object to be pickled.
    /

Write a pickled representation of obj to the open file.
[clinic start generated code]*/

static PyObject *
_pickle_Pickler_dump(PicklerObject *self, PyObject *obj)
/*[clinic end generated code: output=87ecad1261e02ac7 input=552eb1c0f52260d9]*/
@end example

Obviously, if Argument Clinic didn't produce any output, it's because
it found an error in your input.  Keep fixing your errors and retrying
until Argument Clinic processes your file without complaint.

For readability, most of the glue code has been generated to a @code{.c.h}
file.  You'll need to include that in your original @code{.c} file,
typically right after the clinic module block:

@example
#include "clinic/_pickle.c.h"
@end example

@item 
Double-check that the argument-parsing code Argument Clinic generated
looks basically the same as the existing code.

First, ensure both places use the same argument-parsing function.
The existing code must call either
@ref{26a,,PyArg_ParseTuple()} or @ref{5c5,,PyArg_ParseTupleAndKeywords()};
ensure that the code generated by Argument Clinic calls the
@emph{exact} same function.

Second, the format string passed in to @ref{26a,,PyArg_ParseTuple()} or
@ref{5c5,,PyArg_ParseTupleAndKeywords()} should be @emph{exactly} the same
as the hand-written one in the existing function, up to the colon
or semi-colon.

(Argument Clinic always generates its format strings
with a @code{:} followed by the name of the function.  If the
existing code's format string ends with @code{;}, to provide
usage help, this change is harmless—don't worry about it.)

Third, for parameters whose format units require two arguments
(like a length variable, or an encoding string, or a pointer
to a conversion function), ensure that the second argument is
@emph{exactly} the same between the two invocations.

Fourth, inside the output portion of the block you'll find a preprocessor
macro defining the appropriate static @ref{e14,,PyMethodDef} structure for
this builtin:

@example
#define __PICKLE_PICKLER_DUMP_METHODDEF    \
@{"dump", (PyCFunction)__pickle_Pickler_dump, METH_O, __pickle_Pickler_dump__doc__@},
@end example

This static structure should be @emph{exactly} the same as the existing static
@ref{e14,,PyMethodDef} structure for this builtin.

If any of these items differ in @emph{any way},
adjust your Argument Clinic function specification and rerun
@code{Tools/clinic/clinic.py} until they @emph{are} the same.

@item 
Notice that the last line of its output is the declaration
of your "impl" function.  This is where the builtin's implementation goes.
Delete the existing prototype of the function you're modifying, but leave
the opening curly brace.  Now delete its argument parsing code and the
declarations of all the variables it dumps the arguments into.
Notice how the Python arguments are now arguments to this impl function;
if the implementation used different names for these variables, fix it.

Let's reiterate, just because it's kind of weird.  Your code should now
look like this:

@example
static return_type
your_function_impl(...)
/*[clinic end generated code: checksum=...]*/
@{
...
@end example

Argument Clinic generated the checksum line and the function prototype just
above it.  You should write the opening (and closing) curly braces for the
function, and the implementation inside.

Sample:

@example
/*[clinic input]
module _pickle
class _pickle.Pickler "PicklerObject *" "&Pickler_Type"
[clinic start generated code]*/
/*[clinic end generated code: checksum=da39a3ee5e6b4b0d3255bfef95601890afd80709]*/

/*[clinic input]
_pickle.Pickler.dump

    obj: 'O'
        The object to be pickled.
    /

Write a pickled representation of obj to the open file.
[clinic start generated code]*/

PyDoc_STRVAR(__pickle_Pickler_dump__doc__,
"Write a pickled representation of obj to the open file.\n"
"\n"
...
static PyObject *
_pickle_Pickler_dump_impl(PicklerObject *self, PyObject *obj)
/*[clinic end generated code: checksum=3bd30745bf206a48f8b576a1da3d90f55a0a4187]*/
@{
    /* Check whether the Pickler was initialized correctly (issue3664).
       Developers often forget to call __init__() in their subclasses, which
       would trigger a segfault without this check. */
    if (self->write == NULL) @{
        PyErr_Format(PicklingError,
                     "Pickler.__init__() was not called by %s.__init__()",
                     Py_TYPE(self)->tp_name);
        return NULL;
    @}

    if (_Pickler_ClearBuffer(self) < 0)
        return NULL;

    ...
@end example

@item 
Remember the macro with the @ref{e14,,PyMethodDef} structure for this
function?  Find the existing @ref{e14,,PyMethodDef} structure for this
function and replace it with a reference to the macro.  (If the builtin
is at module scope, this will probably be very near the end of the file;
if the builtin is a class method, this will probably be below but relatively
near to the implementation.)

Note that the body of the macro contains a trailing comma.  So when you
replace the existing static @ref{e14,,PyMethodDef} structure with the macro,
@emph{don't} add a comma to the end.

Sample:

@example
static struct PyMethodDef Pickler_methods[] = @{
    __PICKLE_PICKLER_DUMP_METHODDEF
    __PICKLE_PICKLER_CLEAR_MEMO_METHODDEF
    @{NULL, NULL@}                /* sentinel */
@};
@end example

@item 
Compile, then run the relevant portions of the regression-test suite.
This change should not introduce any new compile-time warnings or errors,
and there should be no externally-visible change to Python's behavior.

Well, except for one difference: @code{inspect.signature()} run on your function
should now provide a valid signature!

Congratulations, you've ported your first function to work with Argument Clinic!
@end enumerate

@node Advanced Topics,,Converting Your First Function,Argument Clinic How-To
@anchor{howto/clinic advanced-topics}@anchor{41b2}
@subsection Advanced Topics


Now that you've had some experience working with Argument Clinic, it's time
for some advanced topics.

@menu
* Symbolic default values:: 
* Renaming the C functions and variables generated by Argument Clinic:: 
* Converting functions using PyArg_UnpackTuple:: 
* Optional Groups:: 
* Using real Argument Clinic converters@comma{} instead of "legacy converters": Using real Argument Clinic converters instead of "legacy converters". 
* Py_buffer:: 
* Advanced converters:: 
* Parameter default values:: 
* The NULL default value:: 
* Expressions specified as default values:: 
* Using a return converter:: 
* Cloning existing functions:: 
* Calling Python code:: 
* Using a "self converter":: 
* Writing a custom converter:: 
* Writing a custom return converter:: 
* METH_O and METH_NOARGS:: 
* tp_new and tp_init functions:: 
* Changing and redirecting Clinic's output:: 
* The #ifdef trick:: 
* Using Argument Clinic in Python files:: 

@end menu

@node Symbolic default values,Renaming the C functions and variables generated by Argument Clinic,,Advanced Topics
@anchor{howto/clinic symbolic-default-values}@anchor{41b3}
@subsubsection Symbolic default values


The default value you provide for a parameter can't be any arbitrary
expression.  Currently the following are explicitly supported:


@itemize *

@item 
Numeric constants (integer and float)

@item 
字符串常量

@item 
@code{True}, @code{False}, and @code{None}

@item 
Simple symbolic constants like @code{sys.maxsize}, which must
start with the name of the module
@end itemize

In case you're curious, this is implemented in  @code{from_builtin()}
in @code{Lib/inspect.py}.

(In the future, this may need to get even more elaborate,
to allow full expressions like @code{CONSTANT - 1}.)

@node Renaming the C functions and variables generated by Argument Clinic,Converting functions using PyArg_UnpackTuple,Symbolic default values,Advanced Topics
@anchor{howto/clinic renaming-the-c-functions-and-variables-generated-by-argument-clinic}@anchor{41b4}
@subsubsection Renaming the C functions and variables generated by Argument Clinic


Argument Clinic automatically names the functions it generates for you.
Occasionally this may cause a problem, if the generated name collides with
the name of an existing C function.  There's an easy solution: override the names
used for the C functions.  Just add the keyword @code{"as"}
to your function declaration line, followed by the function name you wish to use.
Argument Clinic will use that function name for the base (generated) function,
then add @code{"_impl"} to the end and use that for the name of the impl function.

For example, if we wanted to rename the C function names generated for
@code{pickle.Pickler.dump}, it'd look like this:

@example
/*[clinic input]
pickle.Pickler.dump as pickler_dumper

...
@end example

The base function would now be named @code{pickler_dumper()},
and the impl function would now be named @code{pickler_dumper_impl()}.

Similarly, you may have a problem where you want to give a parameter
a specific Python name, but that name may be inconvenient in C.  Argument
Clinic allows you to give a parameter different names in Python and in C,
using the same @code{"as"} syntax:

@example
/*[clinic input]
pickle.Pickler.dump

    obj: object
    file as file_obj: object
    protocol: object = NULL
    *
    fix_imports: bool = True
@end example

Here, the name used in Python (in the signature and the @code{keywords}
array) would be @code{file}, but the C variable would be named @code{file_obj}.

You can use this to rename the @code{self} parameter too!

@node Converting functions using PyArg_UnpackTuple,Optional Groups,Renaming the C functions and variables generated by Argument Clinic,Advanced Topics
@anchor{howto/clinic converting-functions-using-pyarg-unpacktuple}@anchor{41b5}
@subsubsection Converting functions using PyArg_UnpackTuple


To convert a function parsing its arguments with @ref{e3f,,PyArg_UnpackTuple()},
simply write out all the arguments, specifying each as an @code{object}.  You
may specify the @code{type} argument to cast the type as appropriate.  All
arguments should be marked positional-only (add a @code{/} on a line by itself
after the last argument).

Currently the generated code will use @ref{26a,,PyArg_ParseTuple()}, but this
will change soon.

@node Optional Groups,Using real Argument Clinic converters instead of "legacy converters",Converting functions using PyArg_UnpackTuple,Advanced Topics
@anchor{howto/clinic optional-groups}@anchor{41b6}
@subsubsection Optional Groups


Some legacy functions have a tricky approach to parsing their arguments:
they count the number of positional arguments, then use a @code{switch} statement
to call one of several different @ref{26a,,PyArg_ParseTuple()} calls depending on
how many positional arguments there are.  (These functions cannot accept
keyword-only arguments.)  This approach was used to simulate optional
arguments back before @ref{5c5,,PyArg_ParseTupleAndKeywords()} was created.

While functions using this approach can often be converted to
use @ref{5c5,,PyArg_ParseTupleAndKeywords()}, optional arguments, and default values,
it's not always possible.  Some of these legacy functions have
behaviors @ref{5c5,,PyArg_ParseTupleAndKeywords()} doesn't directly support.
The most obvious example is the builtin function @code{range()}, which has
an optional argument on the @emph{left} side of its required argument!
Another example is @code{curses.window.addch()}, which has a group of two
arguments that must always be specified together.  (The arguments are
called @code{x} and @code{y}; if you call the function passing in @code{x},
you must also pass in @code{y}—and if you don't pass in @code{x} you may not
pass in @code{y} either.)

In any case, the goal of Argument Clinic is to support argument parsing
for all existing CPython builtins without changing their semantics.
Therefore Argument Clinic supports
this alternate approach to parsing, using what are called @emph{optional groups}.
Optional groups are groups of arguments that must all be passed in together.
They can be to the left or the right of the required arguments.  They
can @emph{only} be used with positional-only parameters.

@cartouche
@quotation 注解 
Optional groups are @emph{only} intended for use when converting
functions that make multiple calls to @ref{26a,,PyArg_ParseTuple()}!
Functions that use @emph{any} other approach for parsing arguments
should @emph{almost never} be converted to Argument Clinic using
optional groups.  Functions using optional groups currently
cannot have accurate signatures in Python, because Python just
doesn't understand the concept.  Please avoid using optional
groups wherever possible.
@end quotation
@end cartouche

To specify an optional group, add a @code{[} on a line by itself before
the parameters you wish to group together, and a @code{]} on a line by itself
after these parameters.  As an example, here's how @code{curses.window.addch}
uses optional groups to make the first two parameters and the last
parameter optional:

@example
/*[clinic input]

curses.window.addch

    [
    x: int
      X-coordinate.
    y: int
      Y-coordinate.
    ]

    ch: object
      Character to add.

    [
    attr: long
      Attributes for the character.
    ]
    /

...
@end example

注释:


@itemize *

@item 
For every optional group, one additional parameter will be passed into the
impl function representing the group.  The parameter will be an int named
@code{group_@{direction@}_@{number@}},
where @code{@{direction@}} is either @code{right} or @code{left} depending on whether the group
is before or after the required parameters, and @code{@{number@}} is a monotonically
increasing number (starting at 1) indicating how far away the group is from
the required parameters.  When the impl is called, this parameter will be set
to zero if this group was unused, and set to non-zero if this group was used.
(By used or unused, I mean whether or not the parameters received arguments
in this invocation.)

@item 
If there are no required arguments, the optional groups will behave
as if they're to the right of the required arguments.

@item 
In the case of ambiguity, the argument parsing code
favors parameters on the left (before the required parameters).

@item 
Optional groups can only contain positional-only parameters.

@item 
Optional groups are @emph{only} intended for legacy code.  Please do not
use optional groups for new code.
@end itemize

@node Using real Argument Clinic converters instead of "legacy converters",Py_buffer,Optional Groups,Advanced Topics
@anchor{howto/clinic using-real-argument-clinic-converters-instead-of-legacy-converters}@anchor{41b7}
@subsubsection Using real Argument Clinic converters, instead of "legacy converters"


To save time, and to minimize how much you need to learn
to achieve your first port to Argument Clinic, the walkthrough above tells
you to use "legacy converters".  "Legacy converters" are a convenience,
designed explicitly to make porting existing code to Argument Clinic
easier.  And to be clear, their use is acceptable when porting code for
Python 3.4.

However, in the long term we probably want all our blocks to
use Argument Clinic's real syntax for converters.  Why?  A couple
reasons:


@itemize *

@item 
The proper converters are far easier to read and clearer in their intent.

@item 
There are some format units that are unsupported as "legacy converters",
because they require arguments, and the legacy converter syntax doesn't
support specifying arguments.

@item 
In the future we may have a new argument parsing library that isn't
restricted to what @ref{26a,,PyArg_ParseTuple()} supports; this flexibility
won't be available to parameters using legacy converters.
@end itemize

Therefore, if you don't mind a little extra effort, please use the normal
converters instead of legacy converters.

In a nutshell, the syntax for Argument Clinic (non-legacy) converters
looks like a Python function call.  However, if there are no explicit
arguments to the function (all functions take their default values),
you may omit the parentheses.  Thus @code{bool} and @code{bool()} are exactly
the same converters.

All arguments to Argument Clinic converters are keyword-only.
All Argument Clinic converters accept the following arguments:

@quotation


@table @asis

@item @code{c_default}

The default value for this parameter when defined in C.
Specifically, this will be the initializer for the variable declared
in the "parse function".  See @ref{41b1,,the section on default values}
for how to use this.
Specified as a string.

@item @code{annotation}

The annotation value for this parameter.  Not currently supported,
because 
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008} mandates that the Python library may not use
annotations.
@end table
@end quotation

In addition, some converters accept additional arguments.  Here is a list
of these arguments, along with their meanings:

@quotation


@table @asis

@item @code{accept}

A set of Python types (and possibly pseudo-types);
this restricts the allowable Python argument to values of these types.
(This is not a general-purpose facility; as a rule it only supports
specific lists of types as shown in the legacy converter table.)

To accept @code{None}, add @code{NoneType} to this set.

@item @code{bitwise}

Only supported for unsigned integers.  The native integer value of this
Python argument will be written to the parameter without any range checking,
even for negative values.

@item @code{converter}

Only supported by the @code{object} converter.  Specifies the name of a
@ref{3c25,,C "converter function"}
to use to convert this object to a native type.

@item @code{encoding}

Only supported for strings.  Specifies the encoding to use when converting
this string from a Python str (Unicode) value into a C @code{char *} value.

@item @code{subclass_of}

Only supported for the @code{object} converter.  Requires that the Python
value be a subclass of a Python type, as expressed in C.

@item @code{type}

Only supported for the @code{object} and @code{self} converters.  Specifies
the C type that will be used to declare the variable.  Default value is
@code{"PyObject *"}.

@item @code{zeroes}

Only supported for strings.  If true, embedded NUL bytes (@code{'\\0'}) are
permitted inside the value.  The length of the string will be passed in
to the impl function, just after the string parameter, as a parameter named
@code{<parameter_name>_length}.
@end table
@end quotation

Please note, not every possible combination of arguments will work.
Usually these arguments are implemented by specific @code{PyArg_ParseTuple}
@emph{format units}, with specific behavior.  For example, currently you cannot
call @code{unsigned_short} without also specifying @code{bitwise=True}.
Although it's perfectly reasonable to think this would work, these semantics don't
map to any existing format unit.  So Argument Clinic doesn't support it.  (Or, at
least, not yet.)

下表显示了传统转换器映射到实参转换器的情况。左边是传统转换器，右边是要替换它的文本。


@multitable {xxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@item

@code{'B'}

@tab

@code{unsigned_char(bitwise=True)}

@item

@code{'b'}

@tab

@code{unsigned_char}

@item

@code{'c'}

@tab

@code{char}

@item

@code{'C'}

@tab

@code{int(accept=@{str@})}

@item

@code{'d'}

@tab

@code{double}

@item

@code{'D'}

@tab

@code{Py_complex}

@item

@code{'es'}

@tab

@code{str(encoding='name_of_encoding')}

@item

@code{'es#'}

@tab

@code{str(encoding='name_of_encoding', zeroes=True)}

@item

@code{'et'}

@tab

@code{str(encoding='name_of_encoding', accept=@{bytes, bytearray, str@})}

@item

@code{'et#'}

@tab

@code{str(encoding='name_of_encoding', accept=@{bytes, bytearray, str@}, zeroes=True)}

@item

@code{'f'}

@tab

@code{float}

@item

@code{'h'}

@tab

@code{short}

@item

@code{'H'}

@tab

@code{unsigned_short(bitwise=True)}

@item

@code{'i'}

@tab

@code{int}

@item

@code{'I'}

@tab

@code{unsigned_int(bitwise=True)}

@item

@code{'k'}

@tab

@code{unsigned_long(bitwise=True)}

@item

@code{'K'}

@tab

@code{unsigned_long_long(bitwise=True)}

@item

@code{'l'}

@tab

@code{long}

@item

@code{'L'}

@tab

@code{long long}

@item

@code{'n'}

@tab

@code{Py_ssize_t}

@item

@code{'O'}

@tab

@code{object}

@item

@code{'O!'}

@tab

@code{object(subclass_of='&PySomething_Type')}

@item

@code{'O&'}

@tab

@code{object(converter='name_of_c_function')}

@item

@code{'p'}

@tab

@code{bool}

@item

@code{'S'}

@tab

@code{PyBytesObject}

@item

@code{'s'}

@tab

@code{str}

@item

@code{'s#'}

@tab

@code{str(zeroes=True)}

@item

@code{'s*'}

@tab

@code{Py_buffer(accept=@{buffer, str@})}

@item

@code{'U'}

@tab

@code{unicode}

@item

@code{'u'}

@tab

@code{Py_UNICODE}

@item

@code{'u#'}

@tab

@code{Py_UNICODE(zeroes=True)}

@item

@code{'w*'}

@tab

@code{Py_buffer(accept=@{rwbuffer@})}

@item

@code{'Y'}

@tab

@code{PyByteArrayObject}

@item

@code{'y'}

@tab

@code{str(accept=@{bytes@})}

@item

@code{'y#'}

@tab

@code{str(accept=@{robuffer@}, zeroes=True)}

@item

@code{'y*'}

@tab

@code{Py_buffer}

@item

@code{'Z'}

@tab

@code{Py_UNICODE(accept=@{str, NoneType@})}

@item

@code{'Z#'}

@tab

@code{Py_UNICODE(accept=@{str, NoneType@}, zeroes=True)}

@item

@code{'z'}

@tab

@code{str(accept=@{str, NoneType@})}

@item

@code{'z#'}

@tab

@code{str(accept=@{str, NoneType@}, zeroes=True)}

@item

@code{'z*'}

@tab

@code{Py_buffer(accept=@{buffer, str, NoneType@})}

@end multitable


As an example, here's our sample @code{pickle.Pickler.dump} using the proper
converter:

@example
/*[clinic input]
pickle.Pickler.dump

    obj: object
        The object to be pickled.
    /

Write a pickled representation of obj to the open file.
[clinic start generated code]*/
@end example

One advantage of real converters is that they're more flexible than legacy
converters.  For example, the @code{unsigned_int} converter (and all the
@code{unsigned_} converters) can be specified without @code{bitwise=True}.  Their
default behavior performs range checking on the value, and they won't accept
negative numbers.  You just can't do that with a legacy converter!

Argument Clinic will show you all the converters it has
available.  For each converter it'll show you all the parameters
it accepts, along with the default value for each parameter.
Just run @code{Tools/clinic/clinic.py --converters} to see the full list.

@node Py_buffer,Advanced converters,Using real Argument Clinic converters instead of "legacy converters",Advanced Topics
@anchor{howto/clinic py-buffer}@anchor{41b8}
@subsubsection Py_buffer


When using the @code{Py_buffer} converter
(or the @code{'s*'}, @code{'w*'}, @code{'*y'}, or @code{'z*'} legacy converters),
you @emph{must} not call @ref{d4d,,PyBuffer_Release()} on the provided buffer.
Argument Clinic generates code that does it for you (in the parsing function).

@node Advanced converters,Parameter default values,Py_buffer,Advanced Topics
@anchor{howto/clinic advanced-converters}@anchor{41b9}
@subsubsection Advanced converters


Remember those format units you skipped for your first
time because they were advanced?  Here's how to handle those too.

The trick is, all those format units take arguments—either
conversion functions, or types, or strings specifying an encoding.
(But "legacy converters" don't support arguments.  That's why we
skipped them for your first function.)  The argument you specified
to the format unit is now an argument to the converter; this
argument is either @code{converter} (for @code{O&}), @code{subclass_of} (for @code{O!}),
or @code{encoding} (for all the format units that start with @code{e}).

When using @code{subclass_of}, you may also want to use the other
custom argument for @code{object()}: @code{type}, which lets you set the type
actually used for the parameter.  For example, if you want to ensure
that the object is a subclass of @code{PyUnicode_Type}, you probably want
to use the converter @code{object(type='PyUnicodeObject *', subclass_of='&PyUnicode_Type')}.

One possible problem with using Argument Clinic: it takes away some possible
flexibility for the format units starting with @code{e}.  When writing a
@code{PyArg_Parse} call by hand, you could theoretically decide at runtime what
encoding string to pass in to @ref{26a,,PyArg_ParseTuple()}.   But now this string must
be hard-coded at Argument-Clinic-preprocessing-time.  This limitation is deliberate;
it made supporting this format unit much easier, and may allow for future optimizations.
This restriction doesn't seem unreasonable; CPython itself always passes in static
hard-coded encoding strings for parameters whose format units start with @code{e}.

@node Parameter default values,The NULL default value,Advanced converters,Advanced Topics
@anchor{howto/clinic default-values}@anchor{41b1}@anchor{howto/clinic parameter-default-values}@anchor{41ba}
@subsubsection Parameter default values


Default values for parameters can be any of a number of values.
At their simplest, they can be string, int, or float literals:

@example
foo: str = "abc"
bar: int = 123
bat: float = 45.6
@end example

They can also use any of Python's built-in constants:

@example
yep:  bool = True
nope: bool = False
nada: object = None
@end example

There's also special support for a default value of @code{NULL}, and
for simple expressions, documented in the following sections.

@node The NULL default value,Expressions specified as default values,Parameter default values,Advanced Topics
@anchor{howto/clinic the-null-default-value}@anchor{41bb}
@subsubsection The @code{NULL} default value


For string and object parameters, you can set them to @code{None} to indicate
that there's no default.  However, that means the C variable will be
initialized to @code{Py_None}.  For convenience's sakes, there's a special
value called @code{NULL} for just this reason: from Python's perspective it
behaves like a default value of @code{None}, but the C variable is initialized
with @code{NULL}.

@node Expressions specified as default values,Using a return converter,The NULL default value,Advanced Topics
@anchor{howto/clinic expressions-specified-as-default-values}@anchor{41bc}
@subsubsection Expressions specified as default values


The default value for a parameter can be more than just a literal value.
It can be an entire expression, using math operators and looking up attributes
on objects.  However, this support isn't exactly simple, because of some
non-obvious semantics.

Consider the following example:

@example
foo: Py_ssize_t = sys.maxsize - 1
@end example

@code{sys.maxsize} can have different values on different platforms.  Therefore
Argument Clinic can't simply evaluate that expression locally and hard-code it
in C.  So it stores the default in such a way that it will get evaluated at
runtime, when the user asks for the function's signature.

What namespace is available when the expression is evaluated?  It's evaluated
in the context of the module the builtin came from.  So, if your module has an
attribute called "@code{max_widgets}", you may simply use it:

@example
foo: Py_ssize_t = max_widgets
@end example

If the symbol isn't found in the current module, it fails over to looking in
@code{sys.modules}.  That's how it can find @code{sys.maxsize} for example.  (Since you
don't know in advance what modules the user will load into their interpreter,
it's best to restrict yourself to modules that are preloaded by Python itself.)

Evaluating default values only at runtime means Argument Clinic can't compute
the correct equivalent C default value.  So you need to tell it explicitly.
When you use an expression, you must also specify the equivalent expression
in C, using the @code{c_default} parameter to the converter:

@example
foo: Py_ssize_t(c_default="PY_SSIZE_T_MAX - 1") = sys.maxsize - 1
@end example

Another complication: Argument Clinic can't know in advance whether or not the
expression you supply is valid.  It parses it to make sure it looks legal, but
it can't @emph{actually} know.  You must be very careful when using expressions to
specify values that are guaranteed to be valid at runtime!

Finally, because expressions must be representable as static C values, there
are many restrictions on legal expressions.  Here's a list of Python features
you're not permitted to use:


@itemize *

@item 
Function calls.

@item 
Inline if statements (@code{3 if foo else 5}).

@item 
Automatic sequence unpacking (@code{*[1, 2, 3]}).

@item 
List/set/dict comprehensions and generator expressions.

@item 
Tuple/list/set/dict literals.
@end itemize

@node Using a return converter,Cloning existing functions,Expressions specified as default values,Advanced Topics
@anchor{howto/clinic using-a-return-converter}@anchor{41bd}
@subsubsection Using a return converter


By default the impl function Argument Clinic generates for you returns @code{PyObject *}.
But your C function often computes some C type, then converts it into the @code{PyObject *}
at the last moment.  Argument Clinic handles converting your inputs from Python types
into native C types—why not have it convert your return value from a native C type
into a Python type too?

That's what a "return converter" does.  It changes your impl function to return
some C type, then adds code to the generated (non-impl) function to handle converting
that value into the appropriate @code{PyObject *}.

The syntax for return converters is similar to that of parameter converters.
You specify the return converter like it was a return annotation on the
function itself.  Return converters behave much the same as parameter converters;
they take arguments, the arguments are all keyword-only, and if you're not changing
any of the default arguments you can omit the parentheses.

(If you use both @code{"as"} @emph{and} a return converter for your function,
the @code{"as"} should come before the return converter.)

There's one additional complication when using return converters: how do you
indicate an error has occurred?  Normally, a function returns a valid (non-@code{NULL})
pointer for success, and @code{NULL} for failure.  But if you use an integer return converter,
all integers are valid.  How can Argument Clinic detect an error?  Its solution: each return
converter implicitly looks for a special value that indicates an error.  If you return
that value, and an error has been set (@code{PyErr_Occurred()} returns a true
value), then the generated code will propagate the error.  Otherwise it will
encode the value you return like normal.

Currently Argument Clinic supports only a few return converters:

@example
bool
int
unsigned int
long
unsigned int
size_t
Py_ssize_t
float
double
DecodeFSDefault
@end example

None of these take parameters.  For the first three, return -1 to indicate
error.  For @code{DecodeFSDefault}, the return type is @code{const char *}; return a @code{NULL}
pointer to indicate an error.

(There's also an experimental @code{NoneType} converter, which lets you
return @code{Py_None} on success or @code{NULL} on failure, without having
to increment the reference count on @code{Py_None}.  I'm not sure it adds
enough clarity to be worth using.)

To see all the return converters Argument Clinic supports, along with
their parameters (if any),
just run @code{Tools/clinic/clinic.py --converters} for the full list.

@node Cloning existing functions,Calling Python code,Using a return converter,Advanced Topics
@anchor{howto/clinic cloning-existing-functions}@anchor{41be}
@subsubsection Cloning existing functions


If you have a number of functions that look similar, you may be able to
use Clinic's "clone" feature.  When you clone an existing function,
you reuse:


@itemize *

@item 
its parameters, including


@itemize *

@item 
their names,

@item 
their converters, with all parameters,

@item 
their default values,

@item 
their per-parameter docstrings,

@item 
their @emph{kind} (whether they're positional only,
positional or keyword, or keyword only), and
@end itemize

@item 
its return converter.
@end itemize

The only thing not copied from the original function is its docstring;
the syntax allows you to specify a new docstring.

Here's the syntax for cloning a function:

@example
/*[clinic input]
module.class.new_function [as c_basename] = module.class.existing_function

Docstring for new_function goes here.
[clinic start generated code]*/
@end example

(The functions can be in different modules or classes.  I wrote
@code{module.class} in the sample just to illustrate that you must
use the full path to @emph{both} functions.)

Sorry, there's no syntax for partially-cloning a function, or cloning a function
then modifying it.  Cloning is an all-or nothing proposition.

Also, the function you are cloning from must have been previously defined
in the current file.

@node Calling Python code,Using a "self converter",Cloning existing functions,Advanced Topics
@anchor{howto/clinic calling-python-code}@anchor{41bf}
@subsubsection Calling Python code


The rest of the advanced topics require you to write Python code
which lives inside your C file and modifies Argument Clinic's
runtime state.  This is simple: you simply define a Python block.

A Python block uses different delimiter lines than an Argument
Clinic function block.  It looks like this:

@example
/*[python input]
# python code goes here
[python start generated code]*/
@end example

All the code inside the Python block is executed at the
time it's parsed.  All text written to stdout inside the block
is redirected into the "output" after the block.

As an example, here's a Python block that adds a static integer
variable to the C code:

@example
/*[python input]
print('static int __ignored_unused_variable__ = 0;')
[python start generated code]*/
static int __ignored_unused_variable__ = 0;
/*[python checksum:...]*/
@end example

@node Using a "self converter",Writing a custom converter,Calling Python code,Advanced Topics
@anchor{howto/clinic using-a-self-converter}@anchor{41c0}
@subsubsection Using a "self converter"


Argument Clinic automatically adds a "self" parameter for you
using a default converter.  It automatically sets the @code{type}
of this parameter to the "pointer to an instance" you specified
when you declared the type.  However, you can override
Argument Clinic's converter and specify one yourself.
Just add your own @code{self} parameter as the first parameter in a
block, and ensure that its converter is an instance of
@code{self_converter} or a subclass thereof.

What's the point?  This lets you override the type of @code{self},
or give it a different default name.

How do you specify the custom type you want to cast @code{self} to?
If you only have one or two functions with the same type for @code{self},
you can directly use Argument Clinic's existing @code{self} converter,
passing in the type you want to use as the @code{type} parameter:

@example
/*[clinic input]

_pickle.Pickler.dump

  self: self(type="PicklerObject *")
  obj: object
  /

Write a pickled representation of the given object to the open file.
[clinic start generated code]*/
@end example

On the other hand, if you have a lot of functions that will use the same
type for @code{self}, it's best to create your own converter, subclassing
@code{self_converter} but overwriting the @code{type} member:

@example
/*[python input]
class PicklerObject_converter(self_converter):
    type = "PicklerObject *"
[python start generated code]*/

/*[clinic input]

_pickle.Pickler.dump

  self: PicklerObject
  obj: object
  /

Write a pickled representation of the given object to the open file.
[clinic start generated code]*/
@end example

@node Writing a custom converter,Writing a custom return converter,Using a "self converter",Advanced Topics
@anchor{howto/clinic writing-a-custom-converter}@anchor{41c1}
@subsubsection Writing a custom converter


As we hinted at in the previous section... you can write your own converters!
A converter is simply a Python class that inherits from @code{CConverter}.
The main purpose of a custom converter is if you have a parameter using
the @code{O&} format unit—parsing this parameter means calling
a @ref{26a,,PyArg_ParseTuple()} "converter function".

Your converter class should be named @code{*something*_converter}.
If the name follows this convention, then your converter class
will be automatically registered with Argument Clinic; its name
will be the name of your class with the @code{_converter} suffix
stripped off.  (This is accomplished with a metaclass.)

You shouldn't subclass @code{CConverter.__init__}.  Instead, you should
write a @code{converter_init()} function.  @code{converter_init()}
always accepts a @code{self} parameter; after that, all additional
parameters @emph{must} be keyword-only.  Any arguments passed in to
the converter in Argument Clinic will be passed along to your
@code{converter_init()}.

There are some additional members of @code{CConverter} you may wish
to specify in your subclass.  Here's the current list:


@table @asis

@item @code{type}

The C type to use for this variable.
@code{type} should be a Python string specifying the type, e.g. @code{int}.
If this is a pointer type, the type string should end with @code{' *'}.

@item @code{default}

The Python default value for this parameter, as a Python value.
Or the magic value @code{unspecified} if there is no default.

@item @code{py_default}

@code{default} as it should appear in Python code,
as a string.
Or @code{None} if there is no default.

@item @code{c_default}

@code{default} as it should appear in C code,
as a string.
Or @code{None} if there is no default.

@item @code{c_ignored_default}

The default value used to initialize the C variable when
there is no default, but not specifying a default may
result in an "uninitialized variable" warning.  This can
easily happen when using option groups—although
properly-written code will never actually use this value,
the variable does get passed in to the impl, and the
C compiler will complain about the "use" of the
uninitialized value.  This value should always be a
non-empty string.

@item @code{converter}

The name of the C converter function, as a string.

@item @code{impl_by_reference}

A boolean value.  If true,
Argument Clinic will add a @code{&} in front of the name of
the variable when passing it into the impl function.

@item @code{parse_by_reference}

A boolean value.  If true,
Argument Clinic will add a @code{&} in front of the name of
the variable when passing it into @ref{26a,,PyArg_ParseTuple()}.
@end table

Here's the simplest example of a custom converter, from @code{Modules/zlibmodule.c}:

@example
/*[python input]

class ssize_t_converter(CConverter):
    type = 'Py_ssize_t'
    converter = 'ssize_t_converter'

[python start generated code]*/
/*[python end generated code: output=da39a3ee5e6b4b0d input=35521e4e733823c7]*/
@end example

This block adds a converter to Argument Clinic named @code{ssize_t}.  Parameters
declared as @code{ssize_t} will be declared as type @code{Py_ssize_t}, and will
be parsed by the @code{'O&'} format unit, which will call the
@code{ssize_t_converter} converter function.  @code{ssize_t} variables
automatically support default values.

More sophisticated custom converters can insert custom C code to
handle initialization and cleanup.
You can see more examples of custom converters in the CPython
source tree; grep the C files for the string @code{CConverter}.

@node Writing a custom return converter,METH_O and METH_NOARGS,Writing a custom converter,Advanced Topics
@anchor{howto/clinic writing-a-custom-return-converter}@anchor{41c2}
@subsubsection Writing a custom return converter


Writing a custom return converter is much like writing
a custom converter.  Except it's somewhat simpler, because return
converters are themselves much simpler.

Return converters must subclass @code{CReturnConverter}.
There are no examples yet of custom return converters,
because they are not widely used yet.  If you wish to
write your own return converter, please read @code{Tools/clinic/clinic.py},
specifically the implementation of @code{CReturnConverter} and
all its subclasses.

@node METH_O and METH_NOARGS,tp_new and tp_init functions,Writing a custom return converter,Advanced Topics
@anchor{howto/clinic meth-o-and-meth-noargs}@anchor{41c3}
@subsubsection METH_O and METH_NOARGS


To convert a function using @code{METH_O}, make sure the function's
single argument is using the @code{object} converter, and mark the
arguments as positional-only:

@example
/*[clinic input]
meth_o_sample

     argument: object
     /
[clinic start generated code]*/
@end example

To convert a function using @code{METH_NOARGS}, just don't specify
any arguments.

You can still use a self converter, a return converter, and specify
a @code{type} argument to the object converter for @code{METH_O}.

@node tp_new and tp_init functions,Changing and redirecting Clinic's output,METH_O and METH_NOARGS,Advanced Topics
@anchor{howto/clinic tp-new-and-tp-init-functions}@anchor{41c4}
@subsubsection tp_new and tp_init functions


You can convert @code{tp_new} and @code{tp_init} functions.  Just name
them @code{__new__} or @code{__init__} as appropriate.  Notes:


@itemize *

@item 
The function name generated for @code{__new__} doesn't end in @code{__new__}
like it would by default.  It's just the name of the class, converted
into a valid C identifier.

@item 
No @code{PyMethodDef} @code{#define} is generated for these functions.

@item 
@code{__init__} functions return @code{int}, not @code{PyObject *}.

@item 
Use the docstring as the class docstring.

@item 
Although @code{__new__} and @code{__init__} functions must always
accept both the @code{args} and @code{kwargs} objects, when converting
you may specify any signature for these functions that you like.
(If your function doesn't support keywords, the parsing function
generated will throw an exception if it receives any.)
@end itemize

@node Changing and redirecting Clinic's output,The #ifdef trick,tp_new and tp_init functions,Advanced Topics
@anchor{howto/clinic changing-and-redirecting-clinic-s-output}@anchor{41c5}
@subsubsection Changing and redirecting Clinic's output


It can be inconvenient to have Clinic's output interspersed with
your conventional hand-edited C code.  Luckily, Clinic is configurable:
you can buffer up its output for printing later (or earlier!), or write
its output to a separate file.  You can also add a prefix or suffix to
every line of Clinic's generated output.

While changing Clinic's output in this manner can be a boon to readability,
it may result in Clinic code using types before they are defined, or
your code attempting to use Clinic-generated code before it is defined.
These problems can be easily solved by rearranging the declarations in your file,
or moving where Clinic's generated code goes.  (This is why the default behavior
of Clinic is to output everything into the current block; while many people
consider this hampers readability, it will never require rearranging your
code to fix definition-before-use problems.)

Let's start with defining some terminology:


@table @asis

@item @emph{field}

A field, in this context, is a subsection of Clinic's output.
For example, the @code{#define} for the @code{PyMethodDef} structure
is a field, called @code{methoddef_define}.  Clinic has seven
different fields it can output per function definition:

@example
docstring_prototype
docstring_definition
methoddef_define
impl_prototype
parser_prototype
parser_definition
impl_definition
@end example

All the names are of the form @code{"<a>_<b>"},
where @code{"<a>"} is the semantic object represented (the parsing function,
the impl function, the docstring, or the methoddef structure) and @code{"<b>"}
represents what kind of statement the field is.  Field names that end in
@code{"_prototype"}
represent forward declarations of that thing, without the actual body/data
of the thing; field names that end in @code{"_definition"} represent the actual
definition of the thing, with the body/data of the thing.  (@code{"methoddef"}
is special, it's the only one that ends with @code{"_define"}, representing that
it's a preprocessor #define.)

@item @emph{destination}

A destination is a place Clinic can write output to.  There are
five built-in destinations:


@table @asis

@item @code{block}

The default destination: printed in the output section of
the current Clinic block.

@item @code{buffer}

A text buffer where you can save text for later.  Text sent
here is appended to the end of any existing text.  It's an
error to have any text left in the buffer when Clinic finishes
processing a file.

@item @code{file}

A separate "clinic file" that will be created automatically by Clinic.
The filename chosen for the file is @code{@{basename@}.clinic@{extension@}},
where @code{basename} and @code{extension} were assigned the output
from @code{os.path.splitext()} run on the current file.  (Example:
the @code{file} destination for @code{_pickle.c} would be written to
@code{_pickle.clinic.c}.)

@strong{Important: When using a} @code{file} @strong{destination, you}
@emph{must check in} @strong{the generated file!}

@item @code{two-pass}

A buffer like @code{buffer}.  However, a two-pass buffer can only
be dumped once, and it prints out all text sent to it during
all processing, even from Clinic blocks @emph{after} the dumping point.

@item @code{suppress}

The text is suppressed—thrown away.
@end table
@end table

Clinic defines five new directives that let you reconfigure its output.

The first new directive is @code{dump}:

@example
dump <destination>
@end example

This dumps the current contents of the named destination into the output of
the current block, and empties it.  This only works with @code{buffer} and
@code{two-pass} destinations.

The second new directive is @code{output}.  The most basic form of @code{output}
is like this:

@example
output <field> <destination>
@end example

This tells Clinic to output @emph{field} to @emph{destination}.  @code{output} also
supports a special meta-destination, called @code{everything}, which tells
Clinic to output @emph{all} fields to that @emph{destination}.

@code{output} has a number of other functions:

@example
output push
output pop
output preset <preset>
@end example

@code{output push} and @code{output pop} allow you to push and pop
configurations on an internal configuration stack, so that you
can temporarily modify the output configuration, then easily restore
the previous configuration.  Simply push before your change to save
the current configuration, then pop when you wish to restore the
previous configuration.

@code{output preset} sets Clinic's output to one of several built-in
preset configurations, as follows:

@quotation


@table @asis

@item @code{block}

Clinic's original starting configuration.  Writes everything
immediately after the input block.

Suppress the @code{parser_prototype}
and @code{docstring_prototype}, write everything else to @code{block}.

@item @code{file}

Designed to write everything to the "clinic file" that it can.
You then @code{#include} this file near the top of your file.
You may need to rearrange your file to make this work, though
usually this just means creating forward declarations for various
@code{typedef} and @code{PyTypeObject} definitions.

Suppress the @code{parser_prototype}
and @code{docstring_prototype}, write the @code{impl_definition} to
@code{block}, and write everything else to @code{file}.

The default filename is @code{"@{dirname@}/clinic/@{basename@}.h"}.

@item @code{buffer}

Save up most of the output from Clinic, to be written into
your file near the end.  For Python files implementing modules
or builtin types, it's recommended that you dump the buffer
just above the static structures for your module or
builtin type; these are normally very near the end.  Using
@code{buffer} may require even more editing than @code{file}, if
your file has static @code{PyMethodDef} arrays defined in the
middle of the file.

Suppress the @code{parser_prototype}, @code{impl_prototype},
and @code{docstring_prototype}, write the @code{impl_definition} to
@code{block}, and write everything else to @code{file}.

@item @code{two-pass}

Similar to the @code{buffer} preset, but writes forward declarations to
the @code{two-pass} buffer, and definitions to the @code{buffer}.
This is similar to the @code{buffer} preset, but may require
less editing than @code{buffer}.  Dump the @code{two-pass} buffer
near the top of your file, and dump the @code{buffer} near
the end just like you would when using the @code{buffer} preset.

Suppresses the @code{impl_prototype}, write the @code{impl_definition}
to @code{block}, write @code{docstring_prototype}, @code{methoddef_define},
and @code{parser_prototype} to @code{two-pass}, write everything else
to @code{buffer}.

@item @code{partial-buffer}

Similar to the @code{buffer} preset, but writes more things to @code{block},
only writing the really big chunks of generated code to @code{buffer}.
This avoids the definition-before-use problem of @code{buffer} completely,
at the small cost of having slightly more stuff in the block's output.
Dump the @code{buffer} near the end, just like you would when using
the @code{buffer} preset.

Suppresses the @code{impl_prototype}, write the @code{docstring_definition}
and @code{parser_definition} to @code{buffer}, write everything else to @code{block}.
@end table
@end quotation

The third new directive is @code{destination}:

@example
destination <name> <command> [...]
@end example

This performs an operation on the destination named @code{name}.

There are two defined subcommands: @code{new} and @code{clear}.

The @code{new} subcommand works like this:

@example
destination <name> new <type>
@end example

This creates a new destination with name @code{<name>} and type @code{<type>}.

There are five destination types:

@quotation


@table @asis

@item @code{suppress}

Throws the text away.

@item @code{block}

Writes the text to the current block.  This is what Clinic
originally did.

@item @code{buffer}

A simple text buffer, like the "buffer" builtin destination above.

@item @code{file}

A text file.  The file destination takes an extra argument,
a template to use for building the filename, like so:

@quotation

destination <name> new <type> <file_template>
@end quotation

The template can use three strings internally that will be replaced
by bits of the filename:

@quotation


@table @asis

@item @{path@}

The full path to the file, including directory and full filename.

@item @{dirname@}

The name of the directory the file is in.

@item @{basename@}

Just the name of the file, not including the directory.

@item @{basename_root@}

Basename with the extension clipped off
(everything up to but not including the last '.').

@item @{basename_extension@}

The last '.' and everything after it.  If the basename
does not contain a period, this will be the empty string.
@end table
@end quotation

If there are no periods in the filename, @{basename@} and @{filename@}
are the same, and @{extension@} is empty.  "@{basename@}@{extension@}"
is always exactly the same as "@{filename@}"."

@item @code{two-pass}

A two-pass buffer, like the "two-pass" builtin destination above.
@end table
@end quotation

The @code{clear} subcommand works like this:

@example
destination <name> clear
@end example

It removes all the accumulated text up to this point in the destination.
(I don't know what you'd need this for, but I thought maybe it'd be
useful while someone's experimenting.)

The fourth new directive is @code{set}:

@example
set line_prefix "string"
set line_suffix "string"
@end example

@code{set} lets you set two internal variables in Clinic.
@code{line_prefix} is a string that will be prepended to every line of Clinic's output;
@code{line_suffix} is a string that will be appended to every line of Clinic's output.

Both of these support two format strings:

@quotation


@table @asis

@item @code{@{block comment start@}}

Turns into the string @code{/*}, the start-comment text sequence for C files.

@item @code{@{block comment end@}}

Turns into the string @code{*/}, the end-comment text sequence for C files.
@end table
@end quotation

The final new directive is one you shouldn't need to use directly,
called @code{preserve}:

@example
preserve
@end example

This tells Clinic that the current contents of the output should be kept, unmodified.
This is used internally by Clinic when dumping output into @code{file} files; wrapping
it in a Clinic block lets Clinic use its existing checksum functionality to ensure
the file was not modified by hand before it gets overwritten.

@node The #ifdef trick,Using Argument Clinic in Python files,Changing and redirecting Clinic's output,Advanced Topics
@anchor{howto/clinic the-ifdef-trick}@anchor{41c6}
@subsubsection The #ifdef trick


If you're converting a function that isn't available on all platforms,
there's a trick you can use to make life a little easier.  The existing
code probably looks like this:

@example
#ifdef HAVE_FUNCTIONNAME
static module_functionname(...)
@{
...
@}
#endif /* HAVE_FUNCTIONNAME */
@end example

And then in the @code{PyMethodDef} structure at the bottom the existing code
will have:

@example
#ifdef HAVE_FUNCTIONNAME
@{'functionname', ... @},
#endif /* HAVE_FUNCTIONNAME */
@end example

In this scenario, you should enclose the body of your impl function inside the @code{#ifdef},
like so:

@example
#ifdef HAVE_FUNCTIONNAME
/*[clinic input]
module.functionname
...
[clinic start generated code]*/
static module_functionname(...)
@{
...
@}
#endif /* HAVE_FUNCTIONNAME */
@end example

Then, remove those three lines from the @code{PyMethodDef} structure,
replacing them with the macro Argument Clinic generated:

@example
MODULE_FUNCTIONNAME_METHODDEF
@end example

(You can find the real name for this macro inside the generated code.
Or you can calculate it yourself: it's the name of your function as defined
on the first line of your block, but with periods changed to underscores,
uppercased, and @code{"_METHODDEF"} added to the end.)

Perhaps you're wondering: what if @code{HAVE_FUNCTIONNAME} isn't defined?
The @code{MODULE_FUNCTIONNAME_METHODDEF} macro won't be defined either!

Here's where Argument Clinic gets very clever.  It actually detects that the
Argument Clinic block might be deactivated by the @code{#ifdef}.  When that
happens, it generates a little extra code that looks like this:

@example
#ifndef MODULE_FUNCTIONNAME_METHODDEF
    #define MODULE_FUNCTIONNAME_METHODDEF
#endif /* !defined(MODULE_FUNCTIONNAME_METHODDEF) */
@end example

That means the macro always works.  If the function is defined, this turns
into the correct structure, including the trailing comma.  If the function is
undefined, this turns into nothing.

However, this causes one ticklish problem: where should Argument Clinic put this
extra code when using the "block" output preset?  It can't go in the output block,
because that could be deactivated by the @code{#ifdef}.  (That's the whole point!)

In this situation, Argument Clinic writes the extra code to the "buffer" destination.
This may mean that you get a complaint from Argument Clinic:

@example
Warning in file "Modules/posixmodule.c" on line 12357:
Destination buffer 'buffer' not empty at end of file, emptying.
@end example

When this happens, just open your file, find the @code{dump buffer} block that
Argument Clinic added to your file (it'll be at the very bottom), then
move it above the @code{PyMethodDef} structure where that macro is used.

@node Using Argument Clinic in Python files,,The #ifdef trick,Advanced Topics
@anchor{howto/clinic using-argument-clinic-in-python-files}@anchor{41c7}
@subsubsection Using Argument Clinic in Python files


It's actually possible to use Argument Clinic to preprocess Python files.
There's no point to using Argument Clinic blocks, of course, as the output
wouldn't make any sense to the Python interpreter.  But using Argument Clinic
to run Python blocks lets you use Python as a Python preprocessor!

Since Python comments are different from C comments, Argument Clinic
blocks embedded in Python files look slightly different.  They look like this:

@example
#/*[python input]
#print("def foo(): pass")
#[python start generated code]*/
def foo(): pass
#/*[python checksum:...]*/
@end example

@node 使用 DTrace 和 SystemTap 检测CPython,,Argument Clinic How-To,Python 常用指引
@anchor{howto/instrumentation doc}@anchor{41c8}@anchor{howto/instrumentation instrumentation}@anchor{506}@anchor{howto/instrumentation instrumenting-cpython-with-dtrace-and-systemtap}@anchor{41c9}
@section 使用 DTrace 和 SystemTap 检测CPython


@*作者: 
David Malcolm


@*作者: 
Łukasz Langa


DTrace和SystemTap是监控工具，它们都提供了一种检查计算机系统上的进程的方法。 它们都使用特定领域的语言，允许用户编写脚本，其中：

@quotation


@itemize -

@item 
进程监视的过滤器

@item 
从感兴趣的进程中收集数据

@item 
生成有关数据的报告
@end itemize
@end quotation

从Python 3.6开始，CPython可以使用嵌入式“标记”构建，也称为“探测器”，可以通过DTrace或SystemTap脚本观察，从而更容易监视系统上的CPython进程正在做什么。

@strong{CPython implementation detail:} DTrace标记是CPython解释器的实现细节。 不保证CPython版本之间的探针兼容性。 更改CPython版本时，DTrace脚本可能会停止工作或无法正常工作而不会发出警告。

@menu
* 启用静态标记:: 
* 静态DTrace探针:: 
* 静态SystemTap标记:: 
* 可用的静态标记:: 
* SystemTap Tapsets:: 
* 例子: 例子<36>. 

@end menu

@node 启用静态标记,静态DTrace探针,,使用 DTrace 和 SystemTap 检测CPython
@anchor{howto/instrumentation enabling-the-static-markers}@anchor{41ca}
@subsection 启用静态标记


macOS内置了对DTrace的支持。 在Linux上，为了使用SystemTap的嵌入式标记构建CPython，必须安装SystemTap开发工具。

在Linux机器上，这可以通过：

@example
$ yum install systemtap-sdt-devel
@end example

或者：

@example
$ sudo apt-get install systemtap-sdt-dev
@end example

然后必须将CPython配置为`@w{`}--with-dtrace`@w{`}：

@example
checking for --with-dtrace... yes
@end example

在macOS上，您可以通过在后台运行Python进程列出可用的DTrace探测器，并列出Python程序提供的所有探测器：

@example
$ python3.6 -q &
$ sudo dtrace -l -P python$!  # or: dtrace -l -m python3.6

   ID   PROVIDER            MODULE                          FUNCTION NAME
29564 python18035        python3.6          _PyEval_EvalFrameDefault function-entry
29565 python18035        python3.6             dtrace_function_entry function-entry
29566 python18035        python3.6          _PyEval_EvalFrameDefault function-return
29567 python18035        python3.6            dtrace_function_return function-return
29568 python18035        python3.6                           collect gc-done
29569 python18035        python3.6                           collect gc-start
29570 python18035        python3.6          _PyEval_EvalFrameDefault line
29571 python18035        python3.6                 maybe_dtrace_line line
@end example

在Linux上，您可以通过查看是否包含“.note.stapsdt”部分来验证构建的二进制文件中是否存在SystemTap静态标记。

@example
$ readelf -S ./python | grep .note.stapsdt
[30] .note.stapsdt        NOTE         0000000000000000 00308d78
@end example

如果您已将Python构建为共享库（使用--enable-shared），则需要在共享库中查找。 例如：

@example
$ readelf -S libpython3.3dm.so.1.0 | grep .note.stapsdt
[29] .note.stapsdt        NOTE         0000000000000000 00365b68
@end example

足够现代的readelf命令可以打印元数据：

@example
$ readelf -n ./python

Displaying notes found at file offset 0x00000254 with length 0x00000020:
    Owner                 Data size          Description
    GNU                  0x00000010          NT_GNU_ABI_TAG (ABI version tag)
        OS: Linux, ABI: 2.6.32

Displaying notes found at file offset 0x00000274 with length 0x00000024:
    Owner                 Data size          Description
    GNU                  0x00000014          NT_GNU_BUILD_ID (unique build ID bitstring)
        Build ID: df924a2b08a7e89f6e11251d4602022977af2670

Displaying notes found at file offset 0x002d6c30 with length 0x00000144:
    Owner                 Data size          Description
    stapsdt              0x00000031          NT_STAPSDT (SystemTap probe descriptors)
        Provider: python
        Name: gc__start
        Location: 0x00000000004371c3, Base: 0x0000000000630ce2, Semaphore: 0x00000000008d6bf6
        Arguments: -4@@%ebx
    stapsdt              0x00000030          NT_STAPSDT (SystemTap probe descriptors)
        Provider: python
        Name: gc__done
        Location: 0x00000000004374e1, Base: 0x0000000000630ce2, Semaphore: 0x00000000008d6bf8
        Arguments: -8@@%rax
    stapsdt              0x00000045          NT_STAPSDT (SystemTap probe descriptors)
        Provider: python
        Name: function__entry
        Location: 0x000000000053db6c, Base: 0x0000000000630ce2, Semaphore: 0x00000000008d6be8
        Arguments: 8@@%rbp 8@@%r12 -4@@%eax
    stapsdt              0x00000046          NT_STAPSDT (SystemTap probe descriptors)
        Provider: python
        Name: function__return
        Location: 0x000000000053dba8, Base: 0x0000000000630ce2, Semaphore: 0x00000000008d6bea
        Arguments: 8@@%rbp 8@@%r12 -4@@%eax
@end example

上述元数据包含SystemTap的信息，描述如何修补策略性放置的机器代码指令以启用SystemTap脚本使用的跟踪钩子。

@node 静态DTrace探针,静态SystemTap标记,启用静态标记,使用 DTrace 和 SystemTap 检测CPython
@anchor{howto/instrumentation static-dtrace-probes}@anchor{41cb}
@subsection 静态DTrace探针


下面的 DTrace 脚本示例可以用来显示一个 Python 脚本的调用/返回层次结构，只在调用名为 "start" 的函数内进行跟踪。换句话说，导入时的函数调用不会被列出。

@example
self int indent;

python$target:::function-entry
/copyinstr(arg1) == "start"/
@{
        self->trace = 1;
@}

python$target:::function-entry
/self->trace/
@{
        printf("%d\t%*s:", timestamp, 15, probename);
        printf("%*s", self->indent, "");
        printf("%s:%s:%d\n", basename(copyinstr(arg0)), copyinstr(arg1), arg2);
        self->indent++;
@}

python$target:::function-return
/self->trace/
@{
        self->indent--;
        printf("%d\t%*s:", timestamp, 15, probename);
        printf("%*s", self->indent, "");
        printf("%s:%s:%d\n", basename(copyinstr(arg0)), copyinstr(arg1), arg2);
@}

python$target:::function-return
/copyinstr(arg1) == "start"/
@{
        self->trace = 0;
@}
@end example

它可以这样调用:

@example
$ sudo dtrace -q -s call_stack.d -c "python3.6 script.py"
@end example

输出结果会像这样:

@example
156641360502280  function-entry:call_stack.py:start:23
156641360518804  function-entry: call_stack.py:function_1:1
156641360532797  function-entry:  call_stack.py:function_3:9
156641360546807 function-return:  call_stack.py:function_3:10
156641360563367 function-return: call_stack.py:function_1:2
156641360578365  function-entry: call_stack.py:function_2:5
156641360591757  function-entry:  call_stack.py:function_1:1
156641360605556  function-entry:   call_stack.py:function_3:9
156641360617482 function-return:   call_stack.py:function_3:10
156641360629814 function-return:  call_stack.py:function_1:2
156641360642285 function-return: call_stack.py:function_2:6
156641360656770  function-entry: call_stack.py:function_3:9
156641360669707 function-return: call_stack.py:function_3:10
156641360687853  function-entry: call_stack.py:function_4:13
156641360700719 function-return: call_stack.py:function_4:14
156641360719640  function-entry: call_stack.py:function_5:18
156641360732567 function-return: call_stack.py:function_5:21
156641360747370 function-return:call_stack.py:start:28
@end example

@node 静态SystemTap标记,可用的静态标记,静态DTrace探针,使用 DTrace 和 SystemTap 检测CPython
@anchor{howto/instrumentation static-systemtap-markers}@anchor{41cc}
@subsection 静态SystemTap标记


使用 SystemTap 集成的底层方法是直接使用静态标记。 这需要你显式地说明包含它们的二进制文件。

例如，这个SystemTap脚本可以用来显示Python脚本的调用/返回层次结构：

@example
probe process("python").mark("function__entry") @{
     filename = user_string($arg1);
     funcname = user_string($arg2);
     lineno = $arg3;

     printf("%s => %s in %s:%d\\n",
            thread_indent(1), funcname, filename, lineno);
@}

probe process("python").mark("function__return") @{
    filename = user_string($arg1);
    funcname = user_string($arg2);
    lineno = $arg3;

    printf("%s <= %s in %s:%d\\n",
           thread_indent(-1), funcname, filename, lineno);
@}
@end example

它可以这样调用:

@example
$ stap \
  show-call-hierarchy.stp \
  -c "./python test.py"
@end example

输出结果会像这样:

@example
11408 python(8274):        => __contains__ in Lib/_abcoll.py:362
11414 python(8274):         => __getitem__ in Lib/os.py:425
11418 python(8274):          => encode in Lib/os.py:490
11424 python(8274):          <= encode in Lib/os.py:493
11428 python(8274):         <= __getitem__ in Lib/os.py:426
11433 python(8274):        <= __contains__ in Lib/_abcoll.py:366
@end example

其中的列是：

@quotation


@itemize -

@item 
脚本开始后经过的微秒数

@item 
可执行文件的名字

@item 
进程的PID
@end itemize
@end quotation

其余部分则表示脚本执行时的调用/返回层次结构。

对于 @cite{--enable-shared} 构建的CPython来说，这些标记是包含在libpython共享库中的，探针的点状路径需要反映这一点。比如上面例子中的这一行：

@example
probe process("python").mark("function__entry") @{
@end example

应改为：

@example
probe process("python").library("libpython3.6dm.so.1.0").mark("function__entry") @{
@end example

（假设是 CPython 3.6 的调试构建）

@node 可用的静态标记,SystemTap Tapsets,静态SystemTap标记,使用 DTrace 和 SystemTap 检测CPython
@anchor{howto/instrumentation available-static-markers}@anchor{41cd}
@subsection 可用的静态标记


@c I'm reusing the "c:function" type for markers

@geindex function__entry (C 函数)
@anchor{howto/instrumentation c function__entry}@anchor{41ce}
@deffn {C 函数} function__entry (str@w{ }filename, str@w{ }funcname, int@w{ }lineno)

这个标记表示一个Python函数的执行已经开始。它只对纯 Python （字节码）函数触发。

文件名、函数名和行号作为位置参数提供给跟踪脚本，必须使用 @code{$arg1}, @code{$arg2}, @code{$arg3} 访问：

@quotation


@itemize *

@item 
@code{$arg1} : @code{(const char *)} 文件名，使用  @code{user_string($arg1)} 访问

@item 
@code{$arg2} : @code{(const char *)} 函数名，使用 @code{user_string($arg2)} 访问

@item 
@code{$arg3} : @code{int} 行号
@end itemize
@end quotation
@end deffn

@geindex function__return (C 函数)
@anchor{howto/instrumentation c function__return}@anchor{41cf}
@deffn {C 函数} function__return (str@w{ }filename, str@w{ }funcname, int@w{ }lineno)

这个标记与 @ref{41ce,,function__entry()} 相反，表示Python函数的执行已经结束 (通过 @code{return} 或者异常)。 它只对纯Python (字节码) 函数触发。

参数和 @ref{41ce,,function__entry()} 相同
@end deffn

@geindex line (C 函数)
@anchor{howto/instrumentation c line}@anchor{41d0}
@deffn {C 函数} line (str@w{ }filename, str@w{ }funcname, int@w{ }lineno)

这个标记表示一个 Python 行即将被执行。它相当于用 Python 分析器逐行追踪。它不会在C函数中触发。

参数和 @ref{41ce,,function__entry()} 相同
@end deffn

@geindex gc__start (C 函数)
@anchor{howto/instrumentation c gc__start}@anchor{41d1}
@deffn {C 函数} gc__start (int@w{ }generation)

当Python解释器启动一个垃圾回收循环时被触发。 @code{arg0} 是要扫描的生成器，如 @ref{22e,,gc.collect()}。
@end deffn

@geindex gc__done (C 函数)
@anchor{howto/instrumentation c gc__done}@anchor{41d2}
@deffn {C 函数} gc__done (long@w{ }collected)

当Python解释器完成一个垃圾回收循环时被触发。@code{arg0} 是收集到的对象的数量。
@end deffn

@geindex import__find__load__start (C 函数)
@anchor{howto/instrumentation c import__find__load__start}@anchor{41e}
@deffn {C 函数} import__find__load__start (str@w{ }modulename)

在 @ref{9b,,importlib} 试图查找并加载模块之前被触发。@code{arg0} 是模块名称。


3.7 新版功能.

@end deffn

@geindex import__find__load__done (C 函数)
@anchor{howto/instrumentation c import__find__load__done}@anchor{41f}
@deffn {C 函数} import__find__load__done (str@w{ }modulename, int@w{ }found)

在 @ref{9b,,importlib} 的 find_and_load 函数被调用后被触发 。@code{arg0} 是模块名称， @code{arg1} 表示模块是否成功加载。


3.7 新版功能.

@end deffn

@geindex audit (C 函数)
@anchor{howto/instrumentation c audit}@anchor{41d3}
@deffn {C 函数} audit (str@w{ }event, void@w{ }*tuple)

当 @ref{eb7,,sys.audit()} 或 @ref{ec5,,PySys_Audit()} 被调用时启动。 @code{arg0} 是事件名称的 C 字符串，@code{arg1} 是一个指向元组对象的 @ref{4b5,,PyObject} 指针。


3.8 新版功能.

@end deffn

@node SystemTap Tapsets,例子<36>,可用的静态标记,使用 DTrace 和 SystemTap 检测CPython
@anchor{howto/instrumentation systemtap-tapsets}@anchor{41d4}
@subsection SystemTap Tapsets


使用SystemTap集成的更高层次的方法是使用 "tapset" 。SystemTap 的等效库，它隐藏了静态标记的一些底层细节。

这里是一个基于 CPython 的非共享构建的 tapset 文件。

@example
/*
   Provide a higher-level wrapping around the function__entry and
   function__return markers:
 \*/
probe python.function.entry = process("python").mark("function__entry")
@{
    filename = user_string($arg1);
    funcname = user_string($arg2);
    lineno = $arg3;
    frameptr = $arg4
@}
probe python.function.return = process("python").mark("function__return")
@{
    filename = user_string($arg1);
    funcname = user_string($arg2);
    lineno = $arg3;
    frameptr = $arg4
@}
@end example

如果这个文件安装在 SystemTap 的 tapset 目录下（例如`@w{`}/usr/share/systemtap/tapset`@w{`} ），那么这些额外的探测点就会变得可用。

@geindex python.function.entry (C 函数)
@anchor{howto/instrumentation c python function entry}@anchor{41d5}
@deffn {C 函数} python.function.entry (str@w{ }filename, str@w{ }funcname, int@w{ }lineno, frameptr)

这个探针点表示一个Python函数的执行已经开始。它只对纯Python （字节码）函数触发。
@end deffn

@geindex python.function.return (C 函数)
@anchor{howto/instrumentation c python function return}@anchor{41d6}
@deffn {C 函数} python.function.return (str@w{ }filename, str@w{ }funcname, int@w{ }lineno, frameptr)

这个探针点是 @ref{41d6,,python.function.return()} 的反义操作，表示一个Python函数的执行已经结束（通过 @code{return} 或者异常）。 它只对纯Python （字节码）函数触发。
@end deffn

@node 例子<36>,,SystemTap Tapsets,使用 DTrace 和 SystemTap 检测CPython
@anchor{howto/instrumentation examples}@anchor{41d7}
@subsection 例子


这个SystemTap脚本使用上面的tapset来更清晰地实现上面给出的跟踪Python函数调用层次结构的例子，而不需要直接命名静态标记。

@example
probe python.function.entry
@{
  printf("%s => %s in %s:%d\n",
         thread_indent(1), funcname, filename, lineno);
@}

probe python.function.return
@{
  printf("%s <= %s in %s:%d\n",
         thread_indent(-1), funcname, filename, lineno);
@}
@end example

下面的脚本使用上面的tapset提供了所有运行中的CPython代码的顶部视图，显示了整个系统中每一秒钟最频繁输入的前20个字节码帧。

@example
global fn_calls;

probe python.function.entry
@{
    fn_calls[pid(), filename, funcname, lineno] += 1;
@}

probe timer.ms(1000) @{
    printf("\033[2J\033[1;1H") /* clear screen \*/
    printf("%6s %80s %6s %30s %6s\n",
           "PID", "FILENAME", "LINE", "FUNCTION", "CALLS")
    foreach ([pid, filename, funcname, lineno] in fn_calls- limit 20) @{
        printf("%6d %80s %6d %30s %6d\n",
            pid, filename, lineno, funcname,
            fn_calls[pid, filename, funcname, lineno]);
    @}
    delete fn_calls;
@}
@end example

@node Python 常见问题,术语对照表,Python 常用指引,Top
@anchor{faq/index doc}@anchor{41d8}@anchor{faq/index faq-index}@anchor{12ad}@anchor{faq/index python-frequently-asked-questions}@anchor{41d9}
@chapter Python 常见问题


@menu
* Python常见问题:: 
* 编程常见问题:: 
* 设计和历史常见问题:: 
* 代码库和插件 FAQ:: 
* 扩展/嵌入常见问题:: 
* Python在Windows上的常见问题:: 
* 图形用户界面（GUI）常见问题:: 
* “为什么我的电脑上安装了 Python ？”:: 

@end menu

@node Python常见问题,编程常见问题,,Python 常见问题
@anchor{faq/general doc}@anchor{41da}@anchor{faq/general general-python-faq}@anchor{41db}
@section Python常见问题



@menu
* 一般信息:: 
* 现实世界中的 Python:: 

@end menu

@node 一般信息,现实世界中的 Python,,Python常见问题
@anchor{faq/general general-information}@anchor{41dc}
@subsection 一般信息


@menu
* 什么是 Python？:: 
* 什么是 Python 软件基金会？:: 
* 使用 Python 是否存在版权限制？:: 
* 创造 Python 的最初理由是什么？:: 
* Python 适合做什么？:: 
* Python 版本的编号形式是怎样的？:: 
* 我应如何获取一份 Python 源代码的副本？:: 
* 我应如何获取 Python 的文档？:: 
* 我之前从未接触过编程。 哪里有 Python 的教程？:: 
* 是否有专门针对 Python 的新闻组或邮件列表？:: 
* 我应如何获取 Python 的公开测试版本？:: 
* 我应如何为 Python 提交错误报告和补丁？:: 
* 是否有任何公开发表的 Python 相关文章可以供我参考引用？:: 
* 是否有任何 Python 相关的书籍？:: 
* www.python.org 具体位于世界上的哪个地点？: www python org 具体位于世界上的哪个地点？. 
* 为何命名为 Python？:: 
* 我必须喜欢 "Monty Python 的飞行马戏团" 吗？:: 

@end menu

@node 什么是 Python？,什么是 Python 软件基金会？,,一般信息
@anchor{faq/general what-is-python}@anchor{41dd}
@subsubsection 什么是 Python？


Python 是一种解释型、交互式、面向对象的编程语言。 它包含了模块、异常、动态类型、高层级动态数据类型以及类等特性。 在面向对象编程以外它还支持多种编程范式，例如过程式和函数式编程等。 Python 结合了超强的功能和极清晰的语法。 它带有许多系统调用和库以及多种窗口系统的接口，并且能用 C 或 C++ 来进行扩展。 它还可用作需要可编程接口的应用程序的扩展语言。 最后，Python 非常易于移植：它可以在包括 Linux 和 macOS 在内的许多 Unix 变种以及 Windows 上运行。

要了解更多详情，请先查看 @ref{118e,,Python 教程}。 Python 新手指南@footnote{https://wiki.python.org/moin/BeginnersGuide} 提供了学习 Python 的其他入门教程及资源的链接。

@node 什么是 Python 软件基金会？,使用 Python 是否存在版权限制？,什么是 Python？,一般信息
@anchor{faq/general what-is-the-python-software-foundation}@anchor{41de}
@subsubsection 什么是 Python 软件基金会？


Python 软件基金会（Python Software Foundation，简称 PSF）是一个独立的非盈利组织，它拥有 Python 2.1 及以上各版本的版权。 PSF 的使命是推进与 Python 编程语言相关的开源技术，并推广 Python 的使用。 PSF 的主页是 @indicateurl{https://www.python.org/psf/}。

向 PSF 提供捐助在美国是免税的。 如果你在使用 Python 并且感觉它对你很有帮助，可以通过 PSF 捐助页@footnote{https://www.python.org/psf/donations/} 进行捐助。

@node 使用 Python 是否存在版权限制？,创造 Python 的最初理由是什么？,什么是 Python 软件基金会？,一般信息
@anchor{faq/general are-there-copyright-restrictions-on-the-use-of-python}@anchor{41df}
@subsubsection 使用 Python 是否存在版权限制？


你可以任意使用源码，只要你保留版权信息并在你基于 Python 的产品文档中显示该版权信息。 如果你遵守此版权规则，就可以将 Python 用于商业领域，以源码或二进制码的形式（不论是否经过修改）销售 Python 的副本，或是以某种形式包含了 Python 的产品。 当然，我们仍然希望获知所有对 Python 的商业使用。

请参阅 PSF 许可页@footnote{https://www.python.org/psf/license/} 以查看进一步的说明以及许可的完整文本内容的链接。

Python 的徽标是注册商标，在某些情况下需要获得允许方可使用。 请参阅 商标使用政策@footnote{https://www.python.org/psf/trademarks/} 了解详情。

@node 创造 Python 的最初理由是什么？,Python 适合做什么？,使用 Python 是否存在版权限制？,一般信息
@anchor{faq/general why-was-python-created-in-the-first-place}@anchor{41e0}
@subsubsection 创造 Python 的最初理由是什么？


以下是有关最初缘起的一份 @emph{非常} 简短的摘要，由 Guido van Rossum 本人撰写:

@quotation

我在 CWI 的 ABC 部门时在实现解释型语言方面积累了丰富经验，通过与这个部门成员的协同工作，我学到了大量有关语言设计的知识。 这是许多 Python 特性的最初来源，包括使用缩进来组织语句以及包含非常高层级的数据结构（虽然在 Python 中具体的实现细节完全不同）。

我对 ABC 语言有过许多抱怨，但同时也很喜欢它的许多特性。 没有可能通过扩展 ABC 语言（或它的实现）来弥补我的不满 —— 实际上缺乏可扩展性就是它最大的问题之一。 我也有一些使用 Modula-2+ 的经验，并曾与 Modula-3 的设计者进行交流，还阅读了 Modula-3 的报告。 Modula-3 是 Python 中异常机制所用语法和语义，以及其他一些语言特性的最初来源。

我还曾在 CWI 的 Amoeba 分布式操作系统部门工作。 当时我们需要有一种比编写 C 程序或 Bash 脚本更好的方式来进行系统管理，因为 Amoeba 有它自己的系统调用接口，并且无法方便地通过 Bash 来访问。 我在 Amoeba 中处理错误的经验令我深刻地意识到异常处理在编程语言特性当中的重要地位。

我发现，某种具有 ABC 式的语法而又能访问 Amoeba 系统调用的脚本语言将可满足需求。 我意识到编写一种 Amoeba 专属的语言是愚蠢的，所以我决定编写一种具有全面可扩展性的语言。

在 1989 年的圣诞假期中，我手头的时间非常充裕，因此我决定开始尝试一下。 在接下来的一年里，虽然我仍然主要用我的业余时间来做这件事，但 Python 在 Amoeba 项目中的使用获得了很大的成功，来自同事的反馈让我得以增加了许多早期的改进。

到 1991 年 2 月，经过一年多的开发，我决定将其发布到 USENET。 之后的事情就都可以在 @code{Misc/HISTORY} 文件里面看了。
@end quotation

@node Python 适合做什么？,Python 版本的编号形式是怎样的？,创造 Python 的最初理由是什么？,一般信息
@anchor{faq/general what-is-python-good-for}@anchor{41e1}
@subsubsection Python 适合做什么？


Python 是一种高层级的多用途编程语言，可用于解决许多不同门类的问题。

该语言附带一个庞大的标准库，涵盖了字符串处理（正则表达式，Unicode，比较文件间的差异等），因特网协议（HTTP，FTP，SMTP，XML-RPC，POP，IMAP，CGI 编程等），软件工程（单元测试，日志记录，性能分析，Python 代码解析等），以及操作系统接口（系统调用，文件系统，TCP/IP 套接字等）。 请查看 @ref{118f,,Python 标准库} 的目录以了解所有可用的内容。 此外还可以获取到各种各样的第三方扩展。 请访问 Python 包索引@footnote{https://pypi.org} 来查找你感兴趣的软件包。

@node Python 版本的编号形式是怎样的？,我应如何获取一份 Python 源代码的副本？,Python 适合做什么？,一般信息
@anchor{faq/general how-does-the-python-version-numbering-scheme-work}@anchor{41e2}
@subsubsection Python 版本的编号形式是怎样的？


Python 版本的编号形式是 A.B.C 或 A.B。 A 称为大版本号 —— 它仅在对语言特性进行非常重大改变时才会递增。 B 称为小版本号，它会在语言特性发生较小改变时递增。 C 称为微版本号 —— 它会在每次发布问题修正时递增。 请参阅 
@geindex Python 提高建议; PEP 6
PEP 6@footnote{https://www.python.org/dev/peps/pep-0006} 了解有关问题修正发布版的详情。

发布版本并非都是问题修正版本。 在新的主要发布版本开发过程中，还会发布一系列的开发版，它们以 alpha (a), beta (b) 或 release candidate (rc) 来标示。 其中 alpha 版是早期发布的测试版，它的接口并未最终确定；在两个 alpha 发布版本间出现接口的改变并不意外。 而 beta 版更为稳定，它会保留现有的接口，但也可能增加新的模块，release candidate 版则会保持冻结状态不会再进行改变，除非有重大问题需要修正。

以上 alpha, beta 和 release candidate 版本会附加一个后缀。 用于 alpha 版本的后缀是带有一个小数字 N 的 “aN”，beta 版本的后缀是带有一个小数字 N 的“bN”，release candidate 版本的后缀是带有一个小数字 N 的“cN”。 换句话说，所有标记为 2.0aN 的版本都早于标记为 2.0bN 的版本，后者又都早于标记为 2.0cN 的版本，而 @emph{这些版本} 全都早于 2.0。

你还可能看到带有“+”后缀的版本号，例如“2.2+”。 这表示未发布版本，直接基于 CPython 开发代码仓库构建。 在实际操作中，当一个小版本最终发布后，未发布版本号会递增到下一个小版本号，成为“a0”版本，例如“2.4a0”。

另请参阅 @ref{5ce,,sys.version}, @ref{35da,,sys.hexversion} 以及 @ref{b13,,sys.version_info} 的文档。

@node 我应如何获取一份 Python 源代码的副本？,我应如何获取 Python 的文档？,Python 版本的编号形式是怎样的？,一般信息
@anchor{faq/general how-do-i-obtain-a-copy-of-the-python-source}@anchor{41e3}
@subsubsection 我应如何获取一份 Python 源代码的副本？


最新的 Python 发布版源代码总能从 python.org 获取，下载页链接为 @indicateurl{https://www.python.org/downloads/}。 最新的开发版源代码可以在 @indicateurl{https://github.com/python/cpython/} 获取。

发布版源代码是一个以 gzip 压缩的 tar 文件，其中包含完整的 C 源代码、Sphinx 格式的文档、Python 库模块、示例程序以及一些有用的自由分发软件。 该源代码将可在大多数 UNIX 类平台上直接编译并运行。

请参阅 Python 开发者指南的初步上手部分@footnote{https://devguide.python.org/setup/} 了解有关获取源代码并进行编译的更多信息。

@node 我应如何获取 Python 的文档？,我之前从未接触过编程。 哪里有 Python 的教程？,我应如何获取一份 Python 源代码的副本？,一般信息
@anchor{faq/general how-do-i-get-documentation-on-python}@anchor{41e4}
@subsubsection 我应如何获取 Python 的文档？


@c XXX mention py3k

当前的 Python 稳定版本的标准文档可在 @indicateurl{https://docs.python.org/3/} 查看。 也可在 @indicateurl{https://docs.python.org/3/download.html} 获取PDF、纯文本以及可下载的 HTML 版本。

文档以 reStructuredText 格式撰写，并使用 Sphinx 文档工具@footnote{http://sphinx-doc.org/} 生成。 文档的 reStructuredText 源文件是 Python 源代码发布版的一部分。

@node 我之前从未接触过编程。 哪里有 Python 的教程？,是否有专门针对 Python 的新闻组或邮件列表？,我应如何获取 Python 的文档？,一般信息
@anchor{faq/general i-ve-never-programmed-before-is-there-a-python-tutorial}@anchor{41e5}
@subsubsection 我之前从未接触过编程。 哪里有 Python 的教程？


有许多可选择的教程和书籍。 标准文档中也包含有 @ref{118e,,Python 教程}。

请参阅 新手指南@footnote{https://wiki.python.org/moin/BeginnersGuide} 以获取针对 Python 编程初学者的信息，包括教程的清单。

@node 是否有专门针对 Python 的新闻组或邮件列表？,我应如何获取 Python 的公开测试版本？,我之前从未接触过编程。 哪里有 Python 的教程？,一般信息
@anchor{faq/general is-there-a-newsgroup-or-mailing-list-devoted-to-python}@anchor{41e6}
@subsubsection 是否有专门针对 Python 的新闻组或邮件列表？


有一个新闻组 @code{comp.lang.python} 和一个邮件列表 python-list@footnote{https://mail.python.org/mailman/listinfo/python-list}。 新闻组和邮件列表是彼此互通的 —— 如果你可以阅读新闻就不必再订阅邮件列表。 @code{comp.lang.python} 的流量很大，每天会收到数以百计的发帖，Usenet 使用者通常更擅长处理这样大的流量。

有关新软件发布和活动的公告可以在 comp.lang.python.announce 中找到，这是个严格管理的低流量列表，每天会收到五个左右的发帖。 可以在 Python 公告邮件列表@footnote{https://mail.python.org/mailman/listinfo/python-announce-list} 页面进行订阅。

有关其他邮件列表和新闻组的更多信息可以在 @indicateurl{https://www.python.org/community/lists/} 找到。

@node 我应如何获取 Python 的公开测试版本？,我应如何为 Python 提交错误报告和补丁？,是否有专门针对 Python 的新闻组或邮件列表？,一般信息
@anchor{faq/general how-do-i-get-a-beta-test-version-of-python}@anchor{41e7}
@subsubsection 我应如何获取 Python 的公开测试版本？


可以从 @indicateurl{https://www.python.org/downloads/} 下载 alpha 和 beta 发布版。 所有发布版都会在 comp.lang.python 和 comp.lang.python.announce 新闻组以及 Python 主页 @indicateurl{https://www.python.org/} 上进行公告；并会推送到 RSS 新闻源。

你还可以通过 Git 访问 Python 的开发版。 请参阅 Python 开发者指南@footnote{https://devguide.python.org/} 了解详情。

@node 我应如何为 Python 提交错误报告和补丁？,是否有任何公开发表的 Python 相关文章可以供我参考引用？,我应如何获取 Python 的公开测试版本？,一般信息
@anchor{faq/general how-do-i-submit-bug-reports-and-patches-for-python}@anchor{41e8}
@subsubsection 我应如何为 Python 提交错误报告和补丁？


要报告错误或提交补丁，请使用安装于 @indicateurl{https://bugs.python.org/} 上的 Roundup。

你必须拥有一个 Roundup 账号才能报告错误；这样我们就可以在有后续问题时与你联系。 这也使得 Roundup 能在我们处理所报告的错误时向你发送更新消息。 如果你之前使用过 SourceForge 向 Python 报告错误，你可以通过 Roundup 的 密码重置操作@footnote{https://bugs.python.org/user?@@template=forgotten} 来获取你的 Roundup 密码。

有关 Python 开发流程的更多信息，请参阅 Python 开发者指南@footnote{https://devguide.python.org/}。

@node 是否有任何公开发表的 Python 相关文章可以供我参考引用？,是否有任何 Python 相关的书籍？,我应如何为 Python 提交错误报告和补丁？,一般信息
@anchor{faq/general are-there-any-published-articles-about-python-that-i-can-reference}@anchor{41e9}
@subsubsection 是否有任何公开发表的 Python 相关文章可以供我参考引用？


可能作为参考文献的最好方式还是引用你喜欢的 Python 相关书籍。

第一篇有关 Python 的文章写于 1991 年，现在其内容已经相当过时了。

@quotation

Guido van Rossum 与 Jelke de Boer, "使用 Python 编程语言交互式地测试远程服务器", CWI 季刊, 第 4 卷, 第 4 期 (1991 年 12 月), 阿姆斯特丹, 第 283--303 页。
@end quotation

@node 是否有任何 Python 相关的书籍？,www python org 具体位于世界上的哪个地点？,是否有任何公开发表的 Python 相关文章可以供我参考引用？,一般信息
@anchor{faq/general are-there-any-books-on-python}@anchor{41ea}
@subsubsection 是否有任何 Python 相关的书籍？


是的，相关的书籍很多，还有更多即将发行。 请访问 python.org 的 wiki 页面 @indicateurl{https://wiki.python.org/moin/PythonBooks} 获取一份清单。

你也可以到各大在线书店搜索 "Python" 并过滤掉对 Monty Python 的引用；或者也可以搜索 "Python" 加 "language"。

@node www python org 具体位于世界上的哪个地点？,为何命名为 Python？,是否有任何 Python 相关的书籍？,一般信息
@anchor{faq/general where-in-the-world-is-www-python-org-located}@anchor{41eb}
@subsubsection www.python.org 具体位于世界上的哪个地点？


Python 项目的基础架构分布于世界各地并由 Python 基础架构团队负责管理。 详情请访问 这里@footnote{http://infra.psf.io}。

@node 为何命名为 Python？,我必须喜欢 "Monty Python 的飞行马戏团" 吗？,www python org 具体位于世界上的哪个地点？,一般信息
@anchor{faq/general why-is-it-called-python}@anchor{41ec}
@subsubsection 为何命名为 Python？


在着手编写 Python 实现的时候，Guido van Rossum 同时还阅读了刚出版的 "Monty Python 的飞行马戏团"@footnote{https://en.wikipedia.org/wiki/Monty_Python} 剧本，这是一部自 1970 年代开始播出的 BBC 系列喜剧。 Van Rossum 觉得他需要选择一个简短、独特而又略显神秘的名字，于是他决定将这个新语言命名为 Python。

@node 我必须喜欢 "Monty Python 的飞行马戏团" 吗？,,为何命名为 Python？,一般信息
@anchor{faq/general do-i-have-to-like-monty-python-s-flying-circus}@anchor{41ed}
@subsubsection 我必须喜欢 "Monty Python 的飞行马戏团" 吗？


不必，但这对学习会有帮助。 :)

@node 现实世界中的 Python,,一般信息,Python常见问题
@anchor{faq/general python-in-the-real-world}@anchor{41ee}
@subsection 现实世界中的 Python


@menu
* Python 有多稳定？:: 
* 有多少人在使用 Python？:: 
* 有哪些重要的项目是用 Python 开发的？:: 
* 在未来可以期待 Python 将有什么新进展？:: 
* 提议对 Python 加入不兼容的更改是否合理？:: 
* Python 是一种对编程初学者友好的语言吗？:: 

@end menu

@node Python 有多稳定？,有多少人在使用 Python？,,现实世界中的 Python
@anchor{faq/general how-stable-is-python}@anchor{41ef}
@subsubsection Python 有多稳定？


非常稳定。 自 1991 年起大约每隔 6 到 18 个月就会推出新的稳定发布版，这种状态看来还还持续。 从 3.9 版开始，Python 将会每隔 12 个月推出一个新的主要发布版 (
@geindex Python 提高建议; PEP 602
PEP 602@footnote{https://www.python.org/dev/peps/pep-0602})。

开发者也会推出旧版本的“问题修正”发布版，因此现有发布版的稳定性还会逐步提升。 问题修正发布版会以版本号第三部分的数字来标示（例如 3.5.3, 3.6.2），用于稳定性的管理；只有对已知问题的修正会包含在问题修正发布版中，同一系列的问题修正发布版中的接口确定将会始终保持一致。

最新的稳定版本总是可以在 Python 下载页面@footnote{https://www.python.org/downloads/} 上找到。有两个生产环境可用的 Python 版本： 2.x 和 3.x。 推荐的版本是 3.x，大多数广泛使用的库都支持它。 虽然 2.x 仍然被广泛使用，但它 在 2020 年 1 月 1 日之后将不再维护@footnote{https://www.python.org/dev/peps/pep-0373/}。

@node 有多少人在使用 Python？,有哪些重要的项目是用 Python 开发的？,Python 有多稳定？,现实世界中的 Python
@anchor{faq/general how-many-people-are-using-python}@anchor{41f0}
@subsubsection 有多少人在使用 Python？


使用者应该数以百万计，但很难获得一个精确的数字。

Python 可以免费下载，因此并不存在销量数据，此外它也可以从许多不同网站获取，并且包含于许多 Linux 发行版之中，因此下载量统计同样无法完全说明问题。

comp.lang.python 新闻组非常活跃，但不是所有 Python 用户都会在新闻组发帖，许多人甚至不会阅读新闻组。

@node 有哪些重要的项目是用 Python 开发的？,在未来可以期待 Python 将有什么新进展？,有多少人在使用 Python？,现实世界中的 Python
@anchor{faq/general have-any-significant-projects-been-done-in-python}@anchor{41f1}
@subsubsection 有哪些重要的项目是用 Python 开发的？


请访问 @indicateurl{https://www.python.org/about/success} 查看使用了 Python 的项目列表。 阅览 历次 Python 会议@footnote{https://www.python.org/community/workshops/} 的日程纪要可以看到许多不同公司和组织所做的贡献。

高水准的 Python 项目包括 Mailman 邮件列表管理器@footnote{http://www.list.org} 和 Zope 应用服务器@footnote{http://www.zope.org}。 多个 Linux 发行版，其中最著名的有 Red Hat@footnote{https://www.redhat.com} 均已使用 Python 来编写部分或全部的安装程序和系统管理软件。 在内部使用 Python 的大公司包括了 Google, Yahoo 以及 Lucasfilm 等。

@node 在未来可以期待 Python 将有什么新进展？,提议对 Python 加入不兼容的更改是否合理？,有哪些重要的项目是用 Python 开发的？,现实世界中的 Python
@anchor{faq/general what-new-developments-are-expected-for-python-in-the-future}@anchor{41f2}
@subsubsection 在未来可以期待 Python 将有什么新进展？


请访问 @indicateurl{https://www.python.org/dev/peps/} 查看 Python 增强提议（PEP）。 PEP  是为 Python 加入某种新特性的提议进行描述的设计文档，其中会提供简明的技术规格说明与基本原理。 可以查找标题为“Python X.Y Release Schedule”的 PEP，其中 X.Y 是某个尚未公开发布的版本。

新版本的开发会在 python-dev 邮件列表@footnote{https://mail.python.org/mailman/listinfo/python-dev/} 中进行讨论。

@node 提议对 Python 加入不兼容的更改是否合理？,Python 是一种对编程初学者友好的语言吗？,在未来可以期待 Python 将有什么新进展？,现实世界中的 Python
@anchor{faq/general is-it-reasonable-to-propose-incompatible-changes-to-python}@anchor{41f3}
@subsubsection 提议对 Python 加入不兼容的更改是否合理？


通常来说是不合理的。 世界上已存在的 Python 代码数以亿计，因此，任何对该语言的更改即便仅会使得现有程序中极少的一部分失效也是难以令人接受的。 就算你可以提供一个转换程序，也仍然存在需要更新全部文档的问题；另外还有大量已出版的 Python 书籍，我们不希望让它们在一瞬间全部变成废纸。

如果必须更改某个特性，则应该提供渐进式的升级路径。 
@geindex Python 提高建议; PEP 5
PEP 5@footnote{https://www.python.org/dev/peps/pep-0005} 描述了引入向后不兼容的更改所需遵循的流程，以尽可能减少对用户的干扰。

@node Python 是一种对编程初学者友好的语言吗？,,提议对 Python 加入不兼容的更改是否合理？,现实世界中的 Python
@anchor{faq/general is-python-a-good-language-for-beginning-programmers}@anchor{41f4}
@subsubsection Python 是一种对编程初学者友好的语言吗？


有的。

从过程式、静态类型的编程语言例如 Pascal, C 或者 C++ 以及 Java 的某一子集开始引导学生入门仍然是常见的做法。 但以  Python 作为第一种编程语言进行学习对学生可能更有利。Python 具有非常简单和一致的语法和庞大的标准库，而且最重要的是，在编程入门教学中使用 Python 可以让学生专注于更重要的编程技能，例如问题分解与数据类型设计。 使用 Python，可以快速向学生介绍基本概念例如循环与过程等。 他们甚至有可能在第一次课里就开始接触用户自定义对象。

对于之前从未接触过编程的学生来说，使用静态类型语言会感觉不够自然。 这会给学生带来必须掌握的额外复杂性，并减慢教学的进度。 学生需要尝试像计算机一样思考，分解问题，设计一致的接口并封装数据。 虽然从长远来看，学习和使用一种静态类型语言是很重要的，但这并不是最适宜在学生的第一次编程课上就进行探讨的主题。

还有许多其他方面的特点使得 Python 成为很好的入门语言。 像 Java 一样，Python 拥有一个庞大的标准库，因此可以在课程非常早期的阶段就给学生布置一些 @emph{实用} 的编程项目。 编程作业不必仅限于标准四则运算和账目检查程序。 通过使用标准库，学生可以在学习编程基础知识的同时开发真正的应用，从而获得更大的满足感。 使用标准库还能使学生了解代码重用的概念。 而像 PyGame 这样的第三方模块同样有助于扩大学生的接触领域。

Python 的解释器使学生能够在编程时测试语言特性。 他们可以在一个窗口中输入程序源代码的同时开启一个解释器运行窗口。 如果他们不记得列表有哪些方法，他们这以这样做:

@example
>>> L = []
>>> dir(L) 
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
'__dir__', '__doc__', '__eq__', '__format__', '__ge__',
'__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__',
'__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__',
'__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__',
'__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__',
'__sizeof__', '__str__', '__subclasshook__', 'append', 'clear',
'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove',
'reverse', 'sort']
>>> [d for d in dir(L) if '__' not in d]
['append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

>>> help(L.append)
Help on built-in function append:

append(...)
    L.append(object) -> None -- append object to end

>>> L.append(1)
>>> L
[1]
@end example

通过使用解释器，学生编写程序时参考文档总是能伴随在他们身边。

Python 还拥有很好的 IDE。 IDLE 是一个跨平台的 Python IDE，它基于 Tkinter 库，使用 Python 语言编写。  PythonWin 是一个 Windows 专属的 IDE。 Emacs 用户将高兴地了解到 Emacs 具有非常好的 Python 模式。  所有这些编程环境都提供语法高亮，自动缩进以及在编写代码时使用交互式解释器等功能。 请访问 Python wiki@footnote{https://wiki.python.org/moin/PythonEditors} 查看 Python 编程环境的完整列表。

如果你想要讨论 Python 在教育中的使用，你可能会有兴趣加入 edu-sig 邮件列表@footnote{https://www.python.org/community/sigs/current/edu-sig}。

@node 编程常见问题,设计和历史常见问题,Python常见问题,Python 常见问题
@anchor{faq/programming doc}@anchor{41f5}@anchor{faq/programming programming-faq}@anchor{41f6}
@section 编程常见问题



@menu
* 一般问题:: 
* 核心语言:: 
* 数字和字符串:: 
* 性能: 性能<4>. 
* 序列（元组/列表）:: 
* 对象:: 
* 模块: 模块<3>. 

@end menu

@node 一般问题,核心语言,,编程常见问题
@anchor{faq/programming general-questions}@anchor{41f7}
@subsection 一般问题


@menu
* Python 有没有提供断点与单步调试等功能的，源码层次的调试器？:: 
* 有没有工具来帮助找寻漏洞或进行静态分析？:: 
* 我如何能够通过一个 Python 脚本创建一个独立运行的二进制文件？:: 
* 是否有 Python 程序规范代码标准或风格指南？:: 

@end menu

@node Python 有没有提供断点与单步调试等功能的，源码层次的调试器？,有没有工具来帮助找寻漏洞或进行静态分析？,,一般问题
@anchor{faq/programming is-there-a-source-code-level-debugger-with-breakpoints-single-stepping-etc}@anchor{41f8}
@subsubsection Python 有没有提供断点与单步调试等功能的，源码层次的调试器？


有的。

以下介绍了一些 Python 的调试器，内置函数 @ref{2f2,,breakpoint()} 允许你使用其中的任何一种。

pdb 模块是一个简单但是够用的控制台模式 Python 调试器。 它是标准 Python 库的一部分，并且 @ref{c9,,已收录于库参考手册}。 你也可以通过使用 pdb 代码作为样例来编写你自己的调试器。

作为标准 Python 发行版附带组件的 IDLE 交互式环境（通常位于 Tools/scripts/idle）中包含一个图形化的调试器。

PythonWin 是一个包含有基于 pdb 的 GUI 调试器的 Python IDE。 Pythonwin 调试器会为断点加上颜色，并具有许多很棒的特性，例如也可以非 Pythonwin 程序。 Pythonwin 是 Python for Windows Extensions@footnote{https://sourceforge.net/projects/pywin32/} 项目的一部分，也是 ActivePython 发行版的一部分（参见 @indicateurl{https://www.activestate.com/activepython}）。

Boa Constructor@footnote{http://boa-constructor.sourceforge.net/} 是一个使用wxWidgets的IDE和GUI构建器。它提供可视化框架创建和操作，对象检查器，源对象浏览器上的许多视图，继承层次结构，doc字符串生成的html文档，高级调试器，集成帮助和Zope支持。

Eric@footnote{http://eric-ide.python-projects.org/} 是一个基于PyQt和Scintilla编辑组件构建的IDE。

Pydb是标准Python调试器pdb的一个版本，经过修改后可与DDD（数据显示调试器）一起使用，DDD是一种流行的图形化调试器前端。 Pydb可以在 @indicateurl{http://bashdb.sourceforge.net/pydb/} 找到，DDD可以在 @indicateurl{https://www.gnu.org/software/ddd} 找到。

有许多商业Python IDE包括图形调试器。他们包括：


@itemize *

@item 
Wing IDE (@indicateurl{https://wingware.com/})

@item 
Komodo IDE (@indicateurl{https://komodoide.com/})

@item 
PyCharm (@indicateurl{https://www.jetbrains.com/pycharm/})
@end itemize

@node 有没有工具来帮助找寻漏洞或进行静态分析？,我如何能够通过一个 Python 脚本创建一个独立运行的二进制文件？,Python 有没有提供断点与单步调试等功能的，源码层次的调试器？,一般问题
@anchor{faq/programming is-there-a-tool-to-help-find-bugs-or-perform-static-analysis}@anchor{41f9}
@subsubsection 有没有工具来帮助找寻漏洞或进行静态分析？


有的。

PyChecker 是一个寻找Python代码漏洞以及对代码复杂性和风格给出警告的工具。你可以从这里获得PyChecker: @indicateurl{http://pychecker.sourceforge.net/} 。

Pylint@footnote{https://www.pylint.org/} 是另一个检查模块是否满足编码标准的工具，也可以编写插件来添加自定义功能。除了PyChecker 执行的错误检查之外， Pylint 还提供了一些额外的功能，例如检查行长度，变量名称是否根据您的编码标准格式良好，声明的接口是否完全实现等等。 @indicateurl{https://docs.pylint.org/} 提供了Pylint功能的完整列表。

静态类型检查器，例如 Mypy@footnote{http://mypy-lang.org/} 、 Pyre@footnote{https://pyre-check.org/} 和 Pytype@footnote{https://github.com/google/pytype} 可以检查Python源代码中的类型提示。

@node 我如何能够通过一个 Python 脚本创建一个独立运行的二进制文件？,是否有 Python 程序规范代码标准或风格指南？,有没有工具来帮助找寻漏洞或进行静态分析？,一般问题
@anchor{faq/programming how-can-i-create-a-stand-alone-binary-from-a-python-script}@anchor{41fa}
@subsubsection 我如何能够通过一个 Python 脚本创建一个独立运行的二进制文件？


如果你想要的只是一个独立的程序，用户可以下载和运行而不必先安装Python发行版，你就不需要将Python编译成C代码。有许多工具可以确定程序所需的模块集，并将这些模块与Python二进制文件绑定在一起以生成单个可执行文件。

一种是使用冻结工具，它包含在Python源代码树 @code{Tools/freeze} 中。它将Python字节代码转换为C数组；一个C编译器，你可以将所有模块嵌入到一个新程序中，然后将其与标准Python模块链接。

它的工作原理是递归扫描源代码以获取import语句（两种形式），并在标准Python路径和源目录（用于内置模块）中查找模块。 然后，它将用Python编写的模块的字节码转换为C代码（可以使用编组模块转换为代码对象的数组初始化器），并创建一个定制的配置文件，该文件仅包含程序中实际使用的内置模块。 然后，它编译生成的C代码并将其与Python解释器的其余部分链接，以形成一个独立的二进制文件，其行为与你的脚本完全相同。

显然， freeze 需要一个C编译器。有几个其他实用工具不需要。 一个是Thomas Heller的py2exe（仅限Windows）

@quotation

@indicateurl{http://www.py2exe.org/}
@end quotation

另一个工具是 Anthony Tuininga 的 cx_Freeze@footnote{https://anthony-tuininga.github.io/cx_Freeze/}。

@node 是否有 Python 程序规范代码标准或风格指南？,,我如何能够通过一个 Python 脚本创建一个独立运行的二进制文件？,一般问题
@anchor{faq/programming are-there-coding-standards-or-a-style-guide-for-python-programs}@anchor{41fb}
@subsubsection 是否有 Python 程序规范代码标准或风格指南？


有的。 请参阅标准库模块所要求的代码风格描述文档 
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008} 。

@node 核心语言,数字和字符串,一般问题,编程常见问题
@anchor{faq/programming core-language}@anchor{41fc}
@subsection 核心语言


@menu
* 当变量有值时，为什么会出现UnboundLocalError？:: 
* Python中的局部变量和全局变量有哪些规则？:: 
* 为什么在具有不同值的循环中定义的lambdas都返回相同的结果？:: 
* 如何跨模块共享全局变量？:: 
* 导入模块的“最佳实践”是什么？:: 
* 为什么对象之间会共享默认值？:: 
* 如何将可选参数或关键字参数从一个函数传递到另一个函数？:: 
* 形参和实参之间有什么区别？:: 
* 为什么更改列表 'y' 也会更改列表 'x'？:: 
* 如何编写带输出参数的函数（通过引用调用）？:: 
* 如何在Python中创建高阶函数？:: 
* 如何在Python中复制对象？:: 
* 如何找到对象的方法或属性？:: 
* 我的代码如何才能发现对象的名称？:: 
* 逗号运算符的优先级是什么？:: 
* 是否有与 C 的 "?;" 三目运算符等价的东西？: 是否有与 C 的 "? " 三目运算符等价的东西？. 
* 是否可以用Python编写混淆的单行程序?:: 
* 函数参数列表中的斜杠（/）是什么意思？:: 

@end menu

@node 当变量有值时，为什么会出现UnboundLocalError？,Python中的局部变量和全局变量有哪些规则？,,核心语言
@anchor{faq/programming why-am-i-getting-an-unboundlocalerror-when-the-variable-has-a-value}@anchor{41fd}
@subsubsection 当变量有值时，为什么会出现UnboundLocalError？


通过在函数体中的某处添加赋值语句，导致以前正常工作的代码被修改而得到 UnboundLocalError 会令人感到意外。

以下代码：

@example
>>> x = 10
>>> def bar():
...     print(x)
>>> bar()
10
@end example

正常工作，但是以下代码

@example
>>> x = 10
>>> def foo():
...     print(x)
...     x += 1
@end example

会得到一个 UnboundLocalError ：

@example
>>> foo()
Traceback (most recent call last):
  ...
UnboundLocalError: local variable 'x' referenced before assignment
@end example

这是因为当你对作用域中的变量进行赋值时，该变量将成为该作用域的局部变量，并在外部作用域中隐藏任何类似命名的变量。由于foo中的最后一个语句为 @code{x} 分配了一个新值，编译器会将其识别为局部变量。因此，当先前的 @code{print(x)} 尝试打印未初始化的局部变量时会导致错误。

在上面的示例中，你可以通过将其声明为全局来访问外部作用域变量：

@example
>>> x = 10
>>> def foobar():
...     global x
...     print(x)
...     x += 1
>>> foobar()
10
@end example

这个显式声明是必需的，以便提醒你（与类和实例变量的表面类似情况不同），你实际上是在外部作用域中修改变量的值

@example
>>> print(x)
11
@end example

你可以使用 @ref{c38,,nonlocal} 关键字在嵌套作用域中执行类似的操作：

@example
>>> def foo():
...    x = 10
...    def bar():
...        nonlocal x
...        print(x)
...        x += 1
...    bar()
...    print(x)
>>> foo()
10
11
@end example

@node Python中的局部变量和全局变量有哪些规则？,为什么在具有不同值的循环中定义的lambdas都返回相同的结果？,当变量有值时，为什么会出现UnboundLocalError？,核心语言
@anchor{faq/programming what-are-the-rules-for-local-and-global-variables-in-python}@anchor{41fe}
@subsubsection Python中的局部变量和全局变量有哪些规则？


在Python中，仅在函数内引用的变量是隐式全局变量。如果在函数体内的任何位置为变量赋值，则除非明确声明为全局，否则将其视为局部值。

虽然起初有点令人惊讶，但片刻考虑就可以解释。一方面，要求 @ref{11d8,,global} 表示已分配的变量可以防止意外的副作用。另一方面，如果所有全局引用都需要 @code{global} ，那么你一直都在使用 @code{global} 。你必须将对内置函数或导入模块的组件的每个引用声明为全局。这种杂乱会破坏 @code{global} 声明用于识别副作用的有用性。

@node 为什么在具有不同值的循环中定义的lambdas都返回相同的结果？,如何跨模块共享全局变量？,Python中的局部变量和全局变量有哪些规则？,核心语言
@anchor{faq/programming why-do-lambdas-defined-in-a-loop-with-different-values-all-return-the-same-result}@anchor{41ff}
@subsubsection 为什么在具有不同值的循环中定义的lambdas都返回相同的结果？


假设你使用for循环来定义几个不同的 lambda （甚至是普通函数），例如：:

@example
>>> squares = []
>>> for x in range(5):
...     squares.append(lambda: x**2)
@end example

这给你一个包含5个lambdas的列表，它们计算 @code{x**2} 。你可能会期望，当它们被调用时，它们将分别返回 @code{0} 、 @code{1} 、 @code{4} 、 @code{9} 和 @code{16} 。但是，当你真正尝试时，你会看到它们都返回 @code{16} 。:

@example
>>> squares[2]()
16
>>> squares[4]()
16
@end example

发生这种情况是因为 @code{x} 不是lambdas的内部变量，而是在外部作用域中定义，并且在调用lambda时访问它 - 而不是在定义它时。 在循环结束时， @code{x} 的值是 @code{4} ，所以所有的函数现在返回 @code{4**2} ，即 @code{16} 。你还可以通过更改 @code{x} 的值来验证这一点，并查看lambdas的结果如何变化:

@example
>>> x = 8
>>> squares[2]()
64
@end example

为了避免这种情况，你需要将值保存在lambdas的局部变量中，这样它们就不依赖于全局`@w{`}x`@w{`} 的值

@example
>>> squares = []
>>> for x in range(5):
...     squares.append(lambda n=x: n**2)
@end example

这里， @code{n=x} 在lambda本地创建一个新的变量 @code{n} ，并在定义lambda时计算，使它具有与 @code{x} 在循环中该点相同的值。这意味着 @code{n} 的值在第一个lambda中为 @code{0} ，在第二个lambda中为 @code{1} ，在第三个中为 @code{2} ，依此类推。因此每个lambda现在将返回正确的结果:

@example
>>> squares[2]()
4
>>> squares[4]()
16
@end example

请注意，这种行为并不是lambda所特有的，但也适用于常规函数。

@node 如何跨模块共享全局变量？,导入模块的“最佳实践”是什么？,为什么在具有不同值的循环中定义的lambdas都返回相同的结果？,核心语言
@anchor{faq/programming how-do-i-share-global-variables-across-modules}@anchor{4200}
@subsubsection 如何跨模块共享全局变量？


在单个程序中跨模块共享信息的规范方法是创建一个特殊模块（通常称为config或cfg）。只需在应用程序的所有模块中导入配置模块；然后该模块可用作全局名称。因为每个模块只有一个实例，所以对模块对象所做的任何更改都会在任何地方反映出来。 例如：

config.py:

@example
x = 0   # Default value of the 'x' configuration setting
@end example

mod.py:

@example
import config
config.x = 1
@end example

main.py:

@example
import config
import mod
print(config.x)
@end example

请注意，出于同样的原因，使用模块也是实现Singleton设计模式的基础。

@node 导入模块的“最佳实践”是什么？,为什么对象之间会共享默认值？,如何跨模块共享全局变量？,核心语言
@anchor{faq/programming what-are-the-best-practices-for-using-import-in-a-module}@anchor{4201}
@subsubsection 导入模块的“最佳实践”是什么？


通常，不要使用 @code{from modulename import *} 。这样做会使导入器的命名空间变得混乱，并且使得连接器更难以检测未定义的名称。

在文件的顶部导入模块。这样做可以清楚地了解代码所需的其他模块，并避免了模块名称是否在范围内的问题。每行导入一个模块可以轻松添加和删除导入的模块，但每行导入多个模块会占用更少的屏幕空间。

如果按以下顺序导入模块，这是一种很好的做法：


@enumerate 

@item 
标准库模块 -- 例如： @code{sys}, @code{os}, @code{getopt}, @code{re}

@item 
第三方库模块（安装在Python的site-packages目录中的任何内容） --  例如mx.DateTime，ZODB，PIL.Image等

@item 
本地开发的模块
@end enumerate

有时需要将模块导入语句移动到函数或类里面，以避免循环导入问题。Gordon McMillan 说：

@quotation

当两个模块都使用  "import <module>" 的导入形式时，循环导入就可以了。但是当第 2 个模块想从第 1 个模块中获取一个名称 ("from module import name") 并且导入位于顶层时，就会出错。 这是因为第 1 个模块中的名称还不可用，因为第 1 个模块正在忙着导入第 2 个模块。
@end quotation

在这种情况下，如果第二个模块仅用于一个函数，则可以轻松地将模块导入语句移动到该函数中。调用导入时，第一个模块将完成初始化，第二个模块可以进行导入。

如果某些模块是特定于平台的，则可能还需要将模块导入语句移出顶级代码。在这种情况下，甚至可能无法导入文件顶部的所有模块。在这种情况下，在相应的特定于平台的代码中导入正确的模块是一个很好的选择。

只有当需要解决诸如避免循环导入或试图减少模块初始化时间的问题时，才可以将导入移动到本地范围，例如在函数定义中。如果根据程序的执行方式，许多导入是不必要的，这种技术尤其有用。如果仅在某个函数中使用模块，您还可能希望将导入移到该函数中。请注意，第一次加载模块可能会因为模块的一次初始化而代价高昂，但多次加载模块实际上是免费的，只需进行几次字典查找。即使模块名称超出了作用域，模块也可能在 @ref{eb5,,sys.modules} 中可用。

@node 为什么对象之间会共享默认值？,如何将可选参数或关键字参数从一个函数传递到另一个函数？,导入模块的“最佳实践”是什么？,核心语言
@anchor{faq/programming why-are-default-values-shared-between-objects}@anchor{4202}
@subsubsection 为什么对象之间会共享默认值？


这种类型的缺陷通常会惹恼新手程序员。考虑这个函数

@example
def foo(mydict=@{@}):  # Danger: shared reference to one dict for all calls
    ... compute something ...
    mydict[key] = value
    return mydict
@end example

第一次调用此函数时，@code{mydict} 包含一项。第二次，@code{mydict} 包含两项，因为当 @code{foo()} 开始执行时， @code{mydict} 中已经有一项了。

函数调用经常被期望为默认值创建新的对象。 但实际情况并非如此。 默认值会在函数定义时一次性地创建。 如果对象发生改变，就如本示例中的字典那样，则对函数的后续调用将会引用这个被改变的对象。

按照定义，不可变对象例如数字、字符串、元组和 @code{None} 因为不可变所以是安全的。 对可变对象例如字典、列表和类实例的改变则可能造成迷惑。

由于这一特性，在编程中应遵循的一项好习惯是不使用可变对象作为默认值。 而应使用 @code{None} 作为默认值和函数中的值，检查值为 @code{None} 的形参并创建相应的列表、字典或其他可变对象。 例如，不要这样写:

@example
def foo(mydict=@{@}):
    ...
@end example

而要这样写:

@example
def foo(mydict=None):
    if mydict is None:
        mydict = @{@}  # create a new dict for local namespace
@end example

这一特性有时会很有用处。 当你有一个需要进行大量耗时计算的函数时，一个常见技巧是将每次调用函数的参数和结果值缓存起来，并在同样的值被再次请求时返回缓存的值。 这称为“记忆”，具体实现方式可以是这样的:

@example
# Callers can only provide two parameters and optionally pass _cache by keyword
def expensive(arg1, arg2, *, _cache=@{@}):
    if (arg1, arg2) in _cache:
        return _cache[(arg1, arg2)]

    # Calculate the value
    result = ... expensive computation ...
    _cache[(arg1, arg2)] = result           # Store result in the cache
    return result
@end example

你也可以使用包含一个字典的全局变量而不使用参数默认值；这完全取决于个人偏好。

@node 如何将可选参数或关键字参数从一个函数传递到另一个函数？,形参和实参之间有什么区别？,为什么对象之间会共享默认值？,核心语言
@anchor{faq/programming how-can-i-pass-optional-or-keyword-parameters-from-one-function-to-another}@anchor{4203}
@subsubsection 如何将可选参数或关键字参数从一个函数传递到另一个函数？


使用函数参数列表中的 @code{*} 和 @code{**} 说明符收集参数;这会将位置参数作为元组，将关键字参数作为字典。然后，您可以使用 @code{*} 和 @code{**} 调用另一个函数时传递这些参数：

@example
def f(x, *args, **kwargs):
    ...
    kwargs['width'] = '14.3c'
    ...
    g(x, *args, **kwargs)
@end example

@geindex argument; difference from parameter
@geindex parameter; difference from argument

@node 形参和实参之间有什么区别？,为什么更改列表 'y' 也会更改列表 'x'？,如何将可选参数或关键字参数从一个函数传递到另一个函数？,核心语言
@anchor{faq/programming faq-argument-vs-parameter}@anchor{4204}@anchor{faq/programming what-is-the-difference-between-arguments-and-parameters}@anchor{4205}
@subsubsection 形参和实参之间有什么区别？


@ref{14c4,,形参} 是指出现在函数定义中的名称，而 @ref{14bb,,实参} 则是在调用函数时实际传入的值。 形参定义了一个函数能接受何种类型的实参。 例如，对于以下函数定义:

@example
def func(foo, bar=None, **kwargs):
    pass
@end example

@emph{foo}, @emph{bar} 和 @emph{kwargs} 是 @code{func} 的形参。 但是，在调用 @code{func} 时，例如：

@example
func(42, bar=314, extra=somevar)
@end example

实际的值 @code{42}, @code{314} 和 @code{somevar} 则是实参。

@node 为什么更改列表 'y' 也会更改列表 'x'？,如何编写带输出参数的函数（通过引用调用）？,形参和实参之间有什么区别？,核心语言
@anchor{faq/programming why-did-changing-list-y-also-change-list-x}@anchor{4206}
@subsubsection 为什么更改列表 'y' 也会更改列表 'x'？


如果你编写的代码就像下面一样：

@example
>>> x = []
>>> y = x
>>> y.append(10)
>>> y
[10]
>>> x
[10]
@end example

你可能想知道为什么追加一个元素也改变了x。

产生这种结果有两个因素：


@enumerate 

@item 
变量只是指向具体对象的名称。 执行 @code{y = x} 并不会为列表创建一个副本 —— 它只是创建了一个新变量 @code{y} 指向 @code{x} 所指向的同一对象。 这意味着只存在一个对象（列表），@code{x} 和 @code{y} 都是对它的引用。

@item 
列表属于 @ref{11be,,mutable} 对象，这意味着你可以改变它的内容。
@end enumerate

在调用 @code{append()} 之后，这个可变对象的内容由 @code{[]} 变为 @code{[10]}。 由于两个变量都指向同一对象，因此使用任何一个名称所访问到的都是修改后的值 @code{[10]}。

如果我们改为将不可变对象赋值给 @code{x}:

@example
>>> x = 5  # ints are immutable
>>> y = x
>>> x = x + 1  # 5 can't be mutated, we are creating a new object here
>>> x
6
>>> y
5
@end example

我们可以看到在此情况下 @code{x} 和 @code{y} 就不再相等了。 这是因为整数是 @ref{11b6,,immutable} 对象，当我们执行 @code{x = x + 1} 时我们并不是改变了 @code{5} 这个对象的值；而是创建了一个新的对象 (整数 @code{6}) 并将其赋值给 @code{x} (也就是改变了 @code{x} 所指向的对象)。 在赋值之后我们就有了两个对象 (整数 @code{6} 和 @code{5}) 以及分别指向它们的两个变量 (@code{x} 现在指向 @code{6} 而 @code{y} 仍然指向 @code{5})。

某些操作 (例如 @code{y.append(10)} 和 @code{y.sort()}) 是改变原对象，而看上去相似的另一些操作 (例如 @code{y = y + [10]} 和 @code{sorted(y)}) 则是创建新对象。 通常在 Python 中 (以及在标准库的所有代码中) 会改变原对象的方法将返回 @code{None} 以帮助避免混淆这两种不同类型的操作。 因此如果你错误地使用了 @code{y.sort()} 并期望它将返回一个经过排序的 @code{y} 的副本，你得到的结果将会是 @code{None}，这将导致你的程序产生一个容易诊断的错误。

但是，还存在一类操作，不同的类型执行相同的操作会有不同的行为：那就是增强赋值运算符。 例如，@code{+=} 会原地改变列表，但不会改变元组或整数 (@code{a_list += [1, 2, 3]} 与 @code{a_list.extend([1, 2, 3])} 一样都会改变 @code{a_list}，而 @code{some_tuple += (1, 2, 3)} 和 @code{some_int += 1} 则会创建新的对象)。

换而言之：


@itemize *

@item 
如果我们有一个可变对象 (@ref{262,,list}, @ref{1b8,,dict}, @ref{b68,,set} 等等)，我们可以使用某些特定的操作来改变它，所有指向它的变量都会显示它的改变。

@item 
如果我们有一个不可变对象 (@ref{329,,str}, @ref{184,,int}, @ref{478,,tuple} 等等)，所有指向它的变量都将显示相同样的值，但凡是会改变这个值的操作将总是返回一个新对象。
@end itemize

如果你想知道两个变量是否指向相同的对象，你可以使用 @ref{13b6,,is} 运算符，或内置函数 @ref{d7f,,id()}。

@node 如何编写带输出参数的函数（通过引用调用）？,如何在Python中创建高阶函数？,为什么更改列表 'y' 也会更改列表 'x'？,核心语言
@anchor{faq/programming how-do-i-write-a-function-with-output-parameters-call-by-reference}@anchor{4207}
@subsubsection 如何编写带输出参数的函数（通过引用调用）？


请记住在 Python 中参数是通过赋值来传递的。 由于赋值只是创建了对象的引用，因此在调用者和被调用者的参数名称之间没有别名，所以本身是没有按引用调用的。 你可以通过多种方式实现所需的效果。


@enumerate 

@item 
通过返回一个结果元组:

@example
def func2(a, b):
    a = 'new-value'        # a and b are local names
    b = b + 1              # assigned to new objects
    return a, b            # return new values

x, y = 'old-value', 99
x, y = func2(x, y)
print(x, y)                # output: new-value 100
@end example

这几乎总是最清晰明了的解决方案。

@item 
通过使用全局变量。 这种方式不是线程安全的，而且也不受推荐。

@item 
通过传递一个可变 (即可原地修改的) 对象:

@example
def func1(a):
    a[0] = 'new-value'     # 'a' references a mutable list
    a[1] = a[1] + 1        # changes a shared object

args = ['old-value', 99]
func1(args)
print(args[0], args[1])    # output: new-value 100
@end example

@item 
通过传递一个会被改变的字典:

@example
def func3(args):
    args['a'] = 'new-value'     # args is a mutable dictionary
    args['b'] = args['b'] + 1   # change it in-place

args = @{'a': 'old-value', 'b': 99@}
func3(args)
print(args['a'], args['b'])
@end example

@item 
或者在一个类实例中捆绑值:

@example
class callByRef:
    def __init__(self, /, **args):
        for key, value in args.items():
            setattr(self, key, value)

def func4(args):
    args.a = 'new-value'        # args is a mutable callByRef
    args.b = args.b + 1         # change object in-place

args = callByRef(a='old-value', b=99)
func4(args)
print(args.a, args.b)
@end example

几乎没有任何适当理由将问题如此复杂化。
@end enumerate

你的最佳选择是返回一个包含多个结果的元组。

@node 如何在Python中创建高阶函数？,如何在Python中复制对象？,如何编写带输出参数的函数（通过引用调用）？,核心语言
@anchor{faq/programming how-do-you-make-a-higher-order-function-in-python}@anchor{4208}
@subsubsection 如何在Python中创建高阶函数？


你有两种选择：使用嵌套作用域，或者使用可调用对象。 例如，假设你想要定义 @code{linear(a,b)} 使其返回一个函数 @code{f(x)} 来设计 @code{a*x+b} 的值。 可以使用以下嵌套作用域:

@example
def linear(a, b):
    def result(x):
        return a * x + b
    return result
@end example

或使用一个可调用对象:

@example
class linear:

    def __init__(self, a, b):
        self.a, self.b = a, b

    def __call__(self, x):
        return self.a * x + self.b
@end example

在两种情况下，:

@example
taxes = linear(0.3, 2)
@end example

都会给出一个可调用对象，使得 @code{taxes(10e6) == 0.3 * 10e6 + 2}.

可调用对象方式的缺点是速度略慢且生成的代码略长。 但是，请注意一组可调用对象能够通过继承来共享签名:

@example
class exponential(linear):
    # __init__ inherited
    def __call__(self, x):
        return self.a * (x ** self.b)
@end example

对象可以封装多个方法的状态:

@example
class counter:

    value = 0

    def set(self, x):
        self.value = x

    def up(self):
        self.value = self.value + 1

    def down(self):
        self.value = self.value - 1

count = counter()
inc, dec, reset = count.up, count.down, count.set
@end example

这里 @code{inc()}, @code{dec()} 和 @code{reset()} 将表现为共享同一计数变量的多个函数。

@node 如何在Python中复制对象？,如何找到对象的方法或属性？,如何在Python中创建高阶函数？,核心语言
@anchor{faq/programming how-do-i-copy-an-object-in-python}@anchor{4209}
@subsubsection 如何在Python中复制对象？


一般来说，通常情况下请尝试 @ref{3c3,,copy.copy()} 或 @ref{3c4,,copy.deepcopy()}。 不是所有对象都可以复制，但多数都是可以的。

某些对象可以方便地复制。 例如字典具有 @ref{440,,copy()} 方法:

@example
newdict = olddict.copy()
@end example

序列可以通过切片来复制:

@example
new_l = l[:]
@end example

@node 如何找到对象的方法或属性？,我的代码如何才能发现对象的名称？,如何在Python中复制对象？,核心语言
@anchor{faq/programming how-can-i-find-the-methods-or-attributes-of-an-object}@anchor{420a}
@subsubsection 如何找到对象的方法或属性？


对于一个用户自定义类的实例 x，@code{dir(x)} 将返回一个按字母顺序排序的包含实例属性和方法及其类所定义的属性名称的列表。

@node 我的代码如何才能发现对象的名称？,逗号运算符的优先级是什么？,如何找到对象的方法或属性？,核心语言
@anchor{faq/programming how-can-my-code-discover-the-name-of-an-object}@anchor{420b}
@subsubsection 我的代码如何才能发现对象的名称？


通常来说是做不到的，因为对象并不真正具有名称。 在本质上，赋值总是会将一个名称绑定到某个值；@code{def} 和 @code{class} 语句也是如此，但在这种情况下该值是一个可调用对象。 考虑以下代码:

@example
>>> class A:
...     pass
...
>>> B = A
>>> a = B()
>>> b = a
>>> print(b)
<__main__.A object at 0x16D07CC>
>>> print(a)
<__main__.A object at 0x16D07CC>
@end example

不严谨地讲，该类有一个名称：虽然它是绑定了两个名称并通过名称 B 发起调用，所创建的实例仍然被视为类 A 的一个实例。 但是实例的名称则无法确定地说是 a 或是 b，因为有两个名称被绑定到了同一个值。

一般来说你的代码应该没有必要“知道”特定值的名称。 除非你是在编写特殊的内省程序，出现这样的问题通常表明如果改变方式可能会更有利。

在 comp.lang.python 中，Fredrik Lundh 在回答这样的问题时曾经给出过一个绝佳的类比：

@quotation

跟你找出在你家门廊见到的某只猫的名字所用的办法一样：猫（对象）自己无法告诉你它的名字，它根本就不在乎 —— 所以找出它叫什么名字的唯一办法是问你的所有邻居（命名空间）那是不是他们的猫（对象）……

……并且如果你发现它有很多名字或根本没有名字也不必觉得惊讶！
@end quotation

@node 逗号运算符的优先级是什么？,是否有与 C 的 "? " 三目运算符等价的东西？,我的代码如何才能发现对象的名称？,核心语言
@anchor{faq/programming what-s-up-with-the-comma-operator-s-precedence}@anchor{420c}
@subsubsection 逗号运算符的优先级是什么？


逗号在 Python 中不是运算符。 考虑这个例子:

@example
>>> "a" in "b", "a"
(False, 'a')
@end example

由于逗号不是运算符而是表达式之间的分隔符，以上代码的含义就相当于:

@example
("a" in "b"), "a"
@end example

而不是:

@example
"a" in ("b", "a")
@end example

对于各种赋值运算符 (@code{=}, @code{+=} 等) 来说同样如此。 它们并不是真正的运算符而是赋值语句中的语法分隔符。

@node 是否有与 C 的 "? " 三目运算符等价的东西？,是否可以用Python编写混淆的单行程序?,逗号运算符的优先级是什么？,核心语言
@anchor{faq/programming is-there-an-equivalent-of-c-s-ternary-operator}@anchor{420d}
@subsubsection 是否有与 C 的 "?:" 三目运算符等价的东西？


有的。 相应语法如下:

@example
[on_true] if [expression] else [on_false]

x, y = 50, 25
small = x if x < y else y
@end example

在 Python 2.5 引入此语法之前，常见的做法是使用逻辑运算符:

@example
[expression] and [on_true] or [on_false]
@end example

然而这种做法并不保险，因为当 @emph{on_true} 具有布尔假值时将会给出错误的结果。 所以，使用 @code{... if ... else ...} 形式总是会更好。

@node 是否可以用Python编写混淆的单行程序?,函数参数列表中的斜杠（/）是什么意思？,是否有与 C 的 "? " 三目运算符等价的东西？,核心语言
@anchor{faq/programming is-it-possible-to-write-obfuscated-one-liners-in-python}@anchor{420e}
@subsubsection 是否可以用Python编写混淆的单行程序?


可以。通常是在 @ref{c28,,lambda} 中嵌套 @code{lambda} 来实现的。请参阅以下三个来自 Ulf Bartelt 的示例代码：

@example
from functools import reduce

# Primes < 1000
print(list(filter(None,map(lambda y:y*reduce(lambda x,y:x*y!=0,
map(lambda x,y=y:y%x,range(2,int(pow(y,0.5)+1))),1),range(2,1000)))))

# First 10 Fibonacci numbers
print(list(map(lambda x,f=lambda x,f:(f(x-1,f)+f(x-2,f)) if x>1 else 1:
f(x,f), range(10))))

# Mandelbrot set
print((lambda Ru,Ro,Iu,Io,IM,Sx,Sy:reduce(lambda x,y:x+y,map(lambda y,
Iu=Iu,Io=Io,Ru=Ru,Ro=Ro,Sy=Sy,L=lambda yc,Iu=Iu,Io=Io,Ru=Ru,Ro=Ro,i=IM,
Sx=Sx,Sy=Sy:reduce(lambda x,y:x+y,map(lambda x,xc=Ru,yc=yc,Ru=Ru,Ro=Ro,
i=i,Sx=Sx,F=lambda xc,yc,x,y,k,f=lambda xc,yc,x,y,k,f:(k<=0)or (x*x+y*y
>=4.0) or 1+f(xc,yc,x*x-y*y+xc,2.0*x*y+yc,k-1,f):f(xc,yc,x,y,k,f):chr(
64+F(Ru+x*(Ro-Ru)/Sx,yc,0,0,i)),range(Sx))):L(Iu+y*(Io-Iu)/Sy),range(Sy
))))(-2.1, 0.7, -1.2, 1.2, 30, 80, 24))
#    \___ ___/  \___ ___/  |   |   |__ lines on screen
#        V          V      |   |______ columns on screen
#        |          |      |__________ maximum of "iterations"
#        |          |_________________ range on y axis
#        |____________________________ range on x axis
@end example

请不要在家里尝试，骚年！

@node 函数参数列表中的斜杠（/）是什么意思？,,是否可以用Python编写混淆的单行程序?,核心语言
@anchor{faq/programming faq-positional-only-arguments}@anchor{158b}@anchor{faq/programming what-does-the-slash-in-the-parameter-list-of-a-function-mean}@anchor{420f}
@subsubsection 函数参数列表中的斜杠（/）是什么意思？


函数参数列表中的斜杠表示在它之前的形参是仅限位置形参。 仅限位置形参没有外部可用的名称。  在调用接受仅限位置形参的函数时，参数只会基于它们的位置被映射到形参。 例如，@ref{152,,divmod()} 是一个接受仅限位置形参的函数。 它的文档是这样的:

@example
>>> help(divmod)
Help on built-in function divmod in module builtins:

divmod(x, y, /)
    Return the tuple (x//y, x%y).  Invariant: div*y + mod == x.
@end example

在形参列表末尾的斜杠意味着两个形参都是仅限位置形参。 因此，附带关键字参数调用 @ref{152,,divmod()} 将会导致报错:

@example
>>> divmod(x=3, y=4)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: divmod() takes no keyword arguments
@end example

@node 数字和字符串,性能<4>,核心语言,编程常见问题
@anchor{faq/programming numbers-and-strings}@anchor{4210}
@subsection 数字和字符串


@menu
* 如何指定十六进制和八进制整数？:: 
* 为什么-22 // 10返回-3？:: 
* 如何将字符串转换为数字？:: 
* 如何将数字转换为字符串？:: 
* 如何修改字符串？:: 
* 如何使用字符串调用函数/方法？:: 
* 是否有与Perl 的chomp() 等效的方法，用于从字符串中删除尾随换行符？: 是否有与Perl 的chomp 等效的方法，用于从字符串中删除尾随换行符？. 
* 是否有 scanf() 或 sscanf() 的对应物？: 是否有 scanf 或 sscanf 的对应物？. 
* 'UnicodeDecodeError' 或 'UnicodeEncodeError' 错误是什么意思？:: 

@end menu

@node 如何指定十六进制和八进制整数？,为什么-22 // 10返回-3？,,数字和字符串
@anchor{faq/programming how-do-i-specify-hexadecimal-and-octal-integers}@anchor{4211}
@subsubsection 如何指定十六进制和八进制整数？


要指定一个八进制数码，则在八进制值之前加一个零和一个小写或大写字母 "o" 作为前缀。 例如，要将变量 "a" 设为八进制的 "10" (十进制的 8)，就输入:

@example
>>> a = 0o10
>>> a
8
@end example

十六进制数也同样简单。 只要在十六进制数之前加一个零和一个小写或大写字母 "x"。 十六进制数码中的字母可以为大写或小写。 例如在 Python 解释器中输入:

@example
>>> a = 0xa5
>>> a
165
>>> b = 0XB2
>>> b
178
@end example

@node 为什么-22 // 10返回-3？,如何将字符串转换为数字？,如何指定十六进制和八进制整数？,数字和字符串
@anchor{faq/programming why-does-22-10-return-3}@anchor{4212}
@subsubsection 为什么-22 // 10返回-3？


这主要是为了让 @code{i % j} 的正负与 @code{j} 一致，如果你想要这样的结果，并且又想要:

@example
i == (i // j) * j + (i % j)
@end example

那么整除就必须向下取整。 C 同样要求保持一致，并且编译器在截短 @code{i // j} 的结果值时需要使 @code{i % j} 的正负与 @code{i} 一致。

对于 @code{i % j} 来说 @code{j} 为负值的应用场景实际上是非常少的。 而 @code{j} 为正值的情况则非常多，并且实际上在所有情况下让 @code{i % j} 的结果为 @code{>= 0} 会更有用处。 如果现在时间为 10 时，那么 200 小时前应是几时？ @code{-190 % 12 == 2} 是有用处的；@code{-190 % 12 == -10} 则是会导致意外的漏洞。

@node 如何将字符串转换为数字？,如何将数字转换为字符串？,为什么-22 // 10返回-3？,数字和字符串
@anchor{faq/programming how-do-i-convert-a-string-to-a-number}@anchor{4213}
@subsubsection 如何将字符串转换为数字？


对于整数，可使用内置的 @ref{184,,int()} 类型构造器，例如 @code{int('144') == 144}。 类似地，可使用 @ref{187,,float()} 转换为浮点数，例如 @code{float('144') == 144.0}。

默认情况下，这些操作会将数字按十进制来解读，因此 @code{int('0144') == 144} 而 @code{int('0x144')} 会引发 @ref{1fb,,ValueError}。 @code{int(string, base)} 接受第二个可选参数指定转换的基数，例如 @code{int('0x144', 16) == 324}。 如果指定基数为 0，则按 Python 规则解读数字：前缀 '0o' 表示八进制，而 '0x' 表示十六进制。

如果你只是想将字符串转为数字，请不要使用内置函数 @ref{b89,,eval()}。 @ref{b89,,eval()} 的速度会慢很多并且有安全风险：别人可能会传入具有你不想要的附带效果的 Python 表达式。 例如，别人可以传入 @code{__import__('os').system("rm -rf $HOME")} 这将删除你的家目录。

@ref{b89,,eval()} 还具有将数字解读为 Python 表达式的效果，这样 @code{eval('09')} 将会导致语法错误，因为 Python 不允许十进制数的首位是 '0' ('0' 除外)。

@node 如何将数字转换为字符串？,如何修改字符串？,如何将字符串转换为数字？,数字和字符串
@anchor{faq/programming how-do-i-convert-a-number-to-a-string}@anchor{4214}
@subsubsection 如何将数字转换为字符串？


例如要将数字 144 转换为字符串 '144'，可使用内置类型构造器 @ref{329,,str()}。 如果想要表示为十六进制或八进制数，可使用内置函数 @ref{c5f,,hex()} 或 @ref{c5e,,oct()}。 想要更好地格式化，请参阅 @ref{15c,,格式化字符串字面值} 和 @ref{d13,,格式字符串语法} 等小节，例如 @code{"@{:04d@}".format(144)} 生成 @code{'0144'} 而 @code{"@{:.3f@}".format(1.0/3.0)} 生成 @code{'0.333'}。

@node 如何修改字符串？,如何使用字符串调用函数/方法？,如何将数字转换为字符串？,数字和字符串
@anchor{faq/programming how-do-i-modify-a-string-in-place}@anchor{4215}
@subsubsection 如何修改字符串？


无法修改，因为字符串是不可变对象。 在大多数情况下，你应该使用你想要的各种部分来构造一个新字符串。 但是，如果你想要一个可以原地修改 Unicode 数据的对象，可尝试使用 @ref{827,,io.StringIO} 对象或 @ref{7,,array} 模块:

@example
>>> import io
>>> s = "Hello, world"
>>> sio = io.StringIO(s)
>>> sio.getvalue()
'Hello, world'
>>> sio.seek(7)
7
>>> sio.write("there!")
6
>>> sio.getvalue()
'Hello, there!'

>>> import array
>>> a = array.array('u', s)
>>> print(a)
array('u', 'Hello, world')
>>> a[0] = 'y'
>>> print(a)
array('u', 'yello, world')
>>> a.tounicode()
'yello, world'
@end example

@node 如何使用字符串调用函数/方法？,是否有与Perl 的chomp 等效的方法，用于从字符串中删除尾随换行符？,如何修改字符串？,数字和字符串
@anchor{faq/programming how-do-i-use-strings-to-call-functions-methods}@anchor{4216}
@subsubsection 如何使用字符串调用函数/方法？


有多种技巧可供选择。


@itemize *

@item 
最好的做法是使用一个将字符串映射到函数的字典。 这一技巧的主要优势在于字符串不必与函数名称一致。 这也是用于模拟其他语言中 case 结构的主要技巧:

@example
def a():
    pass

def b():
    pass

dispatch = @{'go': a, 'stop': b@}  # Note lack of parens for funcs

dispatch[get_input()]()  # Note trailing parens to call function
@end example

@item 
使用内置函数 @ref{443,,getattr()}

@example
import foo
getattr(foo, 'bar')()
@end example

请注意 @ref{443,,getattr()} 可用于任何对象，包括类、类实例、模块等等。

在标准库中多次使用了这个技巧，例如:

@example
class Foo:
    def do_foo(self):
        ...

    def do_bar(self):
        ...

f = getattr(foo_instance, 'do_' + opname)
f()
@end example

@item 
使用 @ref{44f,,locals()} 或 @ref{b89,,eval()} 来解析出函数名:

@example
def myFunc():
    print("hello")

fname = "myFunc"

f = locals()[fname]
f()

f = eval(fname)
f()
@end example

注意：使用 @ref{b89,,eval()} 速度慢而且危险。 如果你不能绝对掌控字符串的内容，别人将能传入可被解析为任意函数直接执行的字符串。
@end itemize

@node 是否有与Perl 的chomp 等效的方法，用于从字符串中删除尾随换行符？,是否有 scanf 或 sscanf 的对应物？,如何使用字符串调用函数/方法？,数字和字符串
@anchor{faq/programming is-there-an-equivalent-to-perl-s-chomp-for-removing-trailing-newlines-from-strings}@anchor{4217}
@subsubsection 是否有与Perl 的chomp() 等效的方法，用于从字符串中删除尾随换行符？


可以使用 @code{S.rstrip("\r\n")} 从字符串 @code{S} 的末尾删除所有的换行符，而不删除其他尾随空格。如果字符串 @code{S} 表示多行，且末尾有几个空行，则将删除所有空行的换行符：

@example
>>> lines = ("line 1 \r\n"
...          "\r\n"
...          "\r\n")
>>> lines.rstrip("\n\r")
'line 1 '
@end example

由于通常只在一次读取一行文本时才需要这样做，所以使用 @code{S.rstrip()} 这种方式工作得很好。

@node 是否有 scanf 或 sscanf 的对应物？,'UnicodeDecodeError' 或 'UnicodeEncodeError' 错误是什么意思？,是否有与Perl 的chomp 等效的方法，用于从字符串中删除尾随换行符？,数字和字符串
@anchor{faq/programming is-there-a-scanf-or-sscanf-equivalent}@anchor{4218}
@subsubsection 是否有 scanf() 或 sscanf() 的对应物？


没有这样的对应物。

对于简单的输入解析，最方便的做法通常是使用字符串对象的 @ref{79b,,split()} 方法将一行内容拆解为以空格分隔的单词，然后使用 @ref{184,,int()} 或 @ref{187,,float()} 将表示十进制数的字符串转换为数值。 @code{split()} 支持可选的 "sep" 形参，适用于内容行使用空格符以外的分隔符的情况。

以于更复杂的输入解析，正则表达式会比 C 的 @code{sscanf()} 更强大，也更适合此类任务。

@node 'UnicodeDecodeError' 或 'UnicodeEncodeError' 错误是什么意思？,,是否有 scanf 或 sscanf 的对应物？,数字和字符串
@anchor{faq/programming what-does-unicodedecodeerror-or-unicodeencodeerror-error-mean}@anchor{4219}
@subsubsection 'UnicodeDecodeError' 或 'UnicodeEncodeError' 错误是什么意思？


见 @ref{c35,,Unicode 指南}

@node 性能<4>,序列（元组/列表）,数字和字符串,编程常见问题
@anchor{faq/programming performance}@anchor{421a}
@subsection 性能


@menu
* 我的程序太慢了。该如何加快速度？:: 
* 将多个字符串连接在一起的最有效方法是什么？:: 

@end menu

@node 我的程序太慢了。该如何加快速度？,将多个字符串连接在一起的最有效方法是什么？,,性能<4>
@anchor{faq/programming my-program-is-too-slow-how-do-i-speed-it-up}@anchor{421b}
@subsubsection 我的程序太慢了。该如何加快速度？


总的来说，这是个棘手的问题。首先，下面列出了深入了解前需要记住的事情：


@itemize *

@item 
不同的 Python 实现具有不同的性能特点。 本 FAQ 着重解答的是 @ref{13ce,,CPython}。

@item 
行为可能因操作系统而异，尤其是在谈论 I / O 或多线程时。

@item 
在尝试优化任何代码 @emph{前} ，应始终找到程序中的热点（请参阅 @ref{d3,,profile} 模块）。

@item 
编写基准脚本将允许您在搜索改进时快速迭代（请参阅 @ref{10b,,timeit} 模块）。

@item 
强烈建议在可能引入隐藏在复杂优化中的回归之前，要有良好的代码覆盖率（通过单元测试或任何其他技术）。
@end itemize

话虽如此，加速Python代码有很多技巧。以下是一些可以达到可接受的性能水平的一般原则：


@itemize *

@item 
使您的算法更快（或更改为更快的算法）可以产生比尝试在代码中使用微优化技巧更大的好处。

@item 
使用正确的数据结构。参考文档 @ref{15ac,,内置类型} 和 @ref{1e,,collections} 模块。

@item 
当标准库提供用于执行某些操作的原语时，可能（尽管不能保证）比您可能提出的任何替代方案更快。对于用C编写的原语，例如内置函数和一些扩展类型，这是真的。例如，请确保使用 @ref{43f,,list.sort()} 内置方法或相关的 @ref{43e,,sorted()} 函数进行排序（有关适度高级用法的示例，请参阅 @ref{1599,,排序指南} ）。

@item 
抽象倾向于创造间接性并迫使翻译更多地工作。如果间接级别超过完成的有用工作量，则程序将变慢。你应该避免过度抽象，特别是在微小的功能或方法的形式下（这通常也会对可读性产生不利影响）。
@end itemize

如果你已经达到纯 Python 允许的限制，那么有一些工具可以让你走得更远。 例如， Cython@footnote{http://cython.org} 可以将稍微修改的 Python 代码版本编译为 C 扩展，并且可以在许多不同的平台上使用。 Cython 可以利用编译（和可选的类型注释）来使代码明显快于解释运行时的速度。 如果您对 C 编程技能有信心，也可以自己 @ref{1191,,编写 C 扩展模块} 。


@subsubheading 参见


专门介绍 性能提示@footnote{https://wiki.python.org/moin/PythonSpeed/PerformanceTips} 的wiki页面。


@node 将多个字符串连接在一起的最有效方法是什么？,,我的程序太慢了。该如何加快速度？,性能<4>
@anchor{faq/programming efficient-string-concatenation}@anchor{421c}@anchor{faq/programming what-is-the-most-efficient-way-to-concatenate-many-strings-together}@anchor{421d}
@subsubsection 将多个字符串连接在一起的最有效方法是什么？


@ref{329,,str} 和 @ref{32a,,bytes} 对象是不可变的，因此将多个字符串连接在一起效率很低，因为每个连接都会创建一个新对象。在一般情况下，总运行时间是总字符串长度的二次方。

要连接多个 @ref{329,,str} 对象，通常推荐的用法是将它们放入一个列表中并在结尾处调用 @ref{15ca,,str.join()} ：

@example
chunks = []
for s in my_strings:
    chunks.append(s)
result = '@w{'}.join(chunks)
@end example

（另一个合理有效的惯用方法是 @ref{827,,io.StringIO} ）

要连接多个 @ref{329,,str} 对象，建议使用本地连接（ @code{+=} 运算符）扩展 @ref{32b,,bytearray} 对象：

@example
result = bytearray()
for b in my_bytes_objects:
    result += b
@end example

@node 序列（元组/列表）,对象,性能<4>,编程常见问题
@anchor{faq/programming sequences-tuples-lists}@anchor{421e}
@subsection 序列（元组/列表）


@menu
* 如何在元组和列表之间进行转换？:: 
* 什么是负数序号？:: 
* 如何以相反的顺序迭代序列？:: 
* 如何从列表中删除重复项？:: 
* 如何在Python中创建数组？:: 
* 如何创建多维列表？:: 
* 如何将方法应用于一系列对象？:: 
* 为什么 a_tuple[i] += ['item'] 会在执行加法时引发异常？:: 
* 我想做一个复杂的排序：你能用Python做一个Schwartzian变换吗？:: 
* 如何按其他列表中的值对一个列表进行排序？:: 

@end menu

@node 如何在元组和列表之间进行转换？,什么是负数序号？,,序列（元组/列表）
@anchor{faq/programming how-do-i-convert-between-tuples-and-lists}@anchor{421f}
@subsubsection 如何在元组和列表之间进行转换？


类型构造器 @code{tuple(seq)} 可将任意序列（实际上是任意可迭代对象）转换为具有相同排列顺序的相同条目的元组。

例如，@code{tuple([1, 2, 3])} 产生 @code{(1, 2, 3)} 而 @code{tuple('abc')} 产生 @code{('a', 'b', 'c')}。 如果参数为一个元组，它不会创建副本而是返回同一对象，因此如果你不确定某个对象是否为元组时也可简单地调用 @ref{478,,tuple()}。

类型构造器 @code{list(seq)} 可将任意序列或可迭代对象转换为具有相同排列顺序的相同条目的列表。 例如，@code{list((1, 2, 3))} 产生 @code{[1, 2, 3]} 而 @code{list('abc')} 产生 @code{['a', 'b', 'c']}。 如果参数为一个列表，它会像 @code{seq[:]} 那样创建一个副本。

@node 什么是负数序号？,如何以相反的顺序迭代序列？,如何在元组和列表之间进行转换？,序列（元组/列表）
@anchor{faq/programming what-s-a-negative-index}@anchor{4220}
@subsubsection 什么是负数序号？


Python 序列使用正数或负数作为序号或称索引号。 对于正数序号，第一个序号为 0 而 1 为第二个序号，依此类推。 对于负数序号，倒数第一个序号为 -1 而倒数第二个序号为 -2，依此类推。 可以认为 @code{seq[-n]} 就相当于 @code{seq[len(seq)-n]}。

使用负数序号有时会很方便。 例如 @code{S[:-1]} 就是原字符串去掉最后一个字符，这可以用来移除某个字符串末尾的换行符。

@node 如何以相反的顺序迭代序列？,如何从列表中删除重复项？,什么是负数序号？,序列（元组/列表）
@anchor{faq/programming how-do-i-iterate-over-a-sequence-in-reverse-order}@anchor{4221}
@subsubsection 如何以相反的顺序迭代序列？


使用 @ref{18e,,reversed()} 内置函数，这是Python 2.4中的新功能:

@example
for x in reversed(sequence):
    ...  # do something with x ...
@end example

这不会修改您的原始序列，而是构建一个反向顺序的新副本以进行迭代。

在 Python 2.3 里，您可以使用扩展切片语法:

@example
for x in sequence[::-1]:
    ...  # do something with x ...
@end example

@node 如何从列表中删除重复项？,如何在Python中创建数组？,如何以相反的顺序迭代序列？,序列（元组/列表）
@anchor{faq/programming how-do-you-remove-duplicates-from-a-list}@anchor{4222}
@subsubsection 如何从列表中删除重复项？


有关执行此操作的许多方法的详细讨论，请参阅 Python Cookbook:

@quotation

@indicateurl{https://code.activestate.com/recipes/52560/}
@end quotation

如果您不介意重新排序列表，请对其进行排序，然后从列表末尾进行扫描，删除重复项：

@example
if mylist:
    mylist.sort()
    last = mylist[-1]
    for i in range(len(mylist)-2, -1, -1):
        if last == mylist[i]:
            del mylist[i]
        else:
            last = mylist[i]
@end example

如果列表的所有元素都可以用作设置键（即：它们都是 @ref{13c0,,hashable} ），这通常会更快:

@example
mylist = list(set(mylist))
@end example

这会将列表转换为集合，从而删除重复项，然后返回到列表中。

@node 如何在Python中创建数组？,如何创建多维列表？,如何从列表中删除重复项？,序列（元组/列表）
@anchor{faq/programming how-do-you-make-an-array-in-python}@anchor{4223}
@subsubsection 如何在Python中创建数组？


使用列表:

@example
["this", 1, "is", "an", "array"]
@end example

列表在时间复杂度方面相当于C或Pascal数组；主要区别在于，python列表可以包含许多不同类型的对象。

@code{array} 模块还提供了创建具有紧凑表示的固定类型的数组的方法，但它的索引速度比列表慢。还要注意，数字扩展和其他扩展还定义了具有各种特性的类似数组的结构。

要获取Lisp样式的列表，可以使用元组模拟cons单元：

@example
lisp_list = ("like",  ("this",  ("example", None) ) )
@end example

如果需要可变性，可以使用列表而不是元组。这里模拟lisp car的是 @code{lisp_list[0]} ，模拟cdr的是 @code{lisp_list[1]} 。只有在你确定真的需要的时候才这样做，因为它通常比使用Python列表慢得多。

@node 如何创建多维列表？,如何将方法应用于一系列对象？,如何在Python中创建数组？,序列（元组/列表）
@anchor{faq/programming faq-multidimensional-list}@anchor{15c9}@anchor{faq/programming how-do-i-create-a-multidimensional-list}@anchor{4224}
@subsubsection 如何创建多维列表？


你可能试图制作一个像这样的多维数组:

@example
>>> A = [[None] * 2] * 3
@end example

如果你打印它，看起来是正确的：

@c A = [[None] * 2] * 3

@example
>>> A
[[None, None], [None, None], [None, None]]
@end example

但是，当你给某一项赋值时，会同时在多个位置显示变化：

@c A = [[None] * 2] * 3

@example
>>> A[0][0] = 5
>>> A
[[5, None], [5, None], [5, None]]
@end example

其中的原因在于使用 @code{*} 对列表执行重复操作并不是创建副本，它只是创建现有对象的引用。 @code{*3} 创建了对长度为二的同一列表的 3 个引用。 对某一行的改变会作用于所有行，通常这一定不是你所希望的。

建议的做法是先创建一个所需长度的列表，然后其中的元素再以一个新创建的列表来填充:

@example
A = [None] * 3
for i in range(3):
    A[i] = [None] * 2
@end example

这样就生成了一个包含 3 个长度为二的不同列表的列表。 你也可以使用列表推导式:

@example
w, h = 2, 3
A = [[None] * w for i in range(h)]
@end example

或者你还可以使用提供矩阵类型的扩展包；其中最著名的是 NumPy@footnote{http://www.numpy.org/}。

@node 如何将方法应用于一系列对象？,为什么 a_tuple[i] += ['item'] 会在执行加法时引发异常？,如何创建多维列表？,序列（元组/列表）
@anchor{faq/programming how-do-i-apply-a-method-to-a-sequence-of-objects}@anchor{4225}
@subsubsection 如何将方法应用于一系列对象？


可以使用列表推导式：

@example
result = [obj.method() for obj in mylist]
@end example

@node 为什么 a_tuple[i] += ['item'] 会在执行加法时引发异常？,我想做一个复杂的排序：你能用Python做一个Schwartzian变换吗？,如何将方法应用于一系列对象？,序列（元组/列表）
@anchor{faq/programming faq-augmented-assignment-tuple-error}@anchor{1414}@anchor{faq/programming why-does-a-tuple-i-item-raise-an-exception-when-the-addition-works}@anchor{4226}
@subsubsection 为什么 a_tuple[i] += ['item'] 会在执行加法时引发异常？


这是由两个事实共同导致的结果，一是增强赋值运算符属于 @emph{赋值} 运算符，二是在 Python 中存在可变和不可变两种不同的对象。

此处的讨论在任何对元组中指向可变对象的元素使用增强赋值运算符的情况都是普遍成立的，但在此我们只以 @code{list} 和 @code{+=} 来举例。

如果你写成这样:

@example
>>> a_tuple = (1, 2)
>>> a_tuple[0] += 1
Traceback (most recent call last):
   ...
TypeError: 'tuple' object does not support item assignment
@end example

发生异常的原因是显而易见的: @code{1} 会与对象 @code{a_tuple[0]} 相加，而该对象为 (@code{1})，得到结果对象 @code{2}，但当我们试图将运算结果 @code{2} 赋值给元组的 @code{0} 号元素时就将报错，因为我们不能改变元组的元素所指向的对象。

在表层之处，以上增强赋值语句所做的大致是这样:

@example
>>> result = a_tuple[0] + 1
>>> a_tuple[0] = result
Traceback (most recent call last):
  ...
TypeError: 'tuple' object does not support item assignment
@end example

由于元组是不可变的，因此操作的赋值部分会引发错误。

当你这样写的时候:

@example
>>> a_tuple = (['foo'], 'bar')
>>> a_tuple[0] += ['item']
Traceback (most recent call last):
  ...
TypeError: 'tuple' object does not support item assignment
@end example

发生异常会令人略感吃惊，还有一个更为令人吃惊的事实：虽然有报错，但是添加操作却生效了:

@example
>>> a_tuple[0]
['foo', 'item']
@end example

要明白为何会这样，你需要知道 (a) 如果一个对象实现了 @code{__iadd__} 魔术方法，它会在执行 @code{+=} 增强赋值时被调用，并且其返回值将用于该赋值语句； (b) 对于列表来说，@code{__iadd__} 等价于在列表上调用 @code{extend} 并返回该列表。 因此对于列表我们可以说 @code{+=} 就是 @code{list.extend} 的“快捷方式”:

@example
>>> a_list = []
>>> a_list += [1]
>>> a_list
[1]
@end example

这相当于:

@example
>>> result = a_list.__iadd__([1])
>>> a_list = result
@end example

a_list 所引用的对象已被修改，而引用被修改对象的指针又重新被赋值给 @code{a_list}。 赋值的最终结果没有变化，因为它是引用 @code{a_list} 之前所引用的同一对象的指针，但仍然发生了赋值操作。

因此，在我们的元组示例中，发生的事情等同于：

@example
>>> result = a_tuple[0].__iadd__(['item'])
>>> a_tuple[0] = result
Traceback (most recent call last):
  ...
TypeError: 'tuple' object does not support item assignment
@end example

@code{__iadd__} 成功执行，因此列表得到了扩充，但是虽然 @code{result} 指向了 @code{a_tuple[0]} 已经指向的同一对象，最后的赋值仍然导致了报错，因为元组是不可变的。

@node 我想做一个复杂的排序：你能用Python做一个Schwartzian变换吗？,如何按其他列表中的值对一个列表进行排序？,为什么 a_tuple[i] += ['item'] 会在执行加法时引发异常？,序列（元组/列表）
@anchor{faq/programming i-want-to-do-a-complicated-sort-can-you-do-a-schwartzian-transform-in-python}@anchor{4227}
@subsubsection 我想做一个复杂的排序：你能用Python做一个Schwartzian变换吗？


该技术归功于Perl社区的 Randal Schwartz，它通过将每个元素映射到其 "排序值（sort value）" 的度量对列表中的元素进行排序。在Python中，使用 @ref{43f,,list.sort()} 方法的 @code{key} 参数：

@example
Isorted = L[:]
Isorted.sort(key=lambda s: int(s[10:15]))
@end example

@node 如何按其他列表中的值对一个列表进行排序？,,我想做一个复杂的排序：你能用Python做一个Schwartzian变换吗？,序列（元组/列表）
@anchor{faq/programming how-can-i-sort-one-list-by-values-from-another-list}@anchor{4228}
@subsubsection 如何按其他列表中的值对一个列表进行排序？


将它们合并到元组的迭代器中，对结果列表进行排序，然后选择所需的元素。

@example
>>> list1 = ["what", "I'm", "sorting", "by"]
>>> list2 = ["something", "else", "to", "sort"]
>>> pairs = zip(list1, list2)
>>> pairs = sorted(pairs)
>>> pairs
[("I'm", 'else'), ('by', 'sort'), ('sorting', 'to'), ('what', 'something')]
>>> result = [x[1] for x in pairs]
>>> result
['else', 'sort', 'to', 'something']
@end example

最后一步的替代方案是:

@example
>>> result = []
>>> for p in pairs: result.append(p[1])
@end example

如果你觉得这个更容易读懂，那么你可能更喜欢使用这个而不是前面的列表推导。然而，对于长列表来说，它的速度几乎是原来的两倍。为什么？首先， @code{append()} 操作必须重新分配内存，虽然它使用了一些技巧来避免每次都这样做，但它仍然偶尔需要这样做，而且代价相当高。第二，表达式 "result.append" 需要额外的属性查找。第三，必须执行所有这些函数调用会降低速度。

@node 对象,模块<3>,序列（元组/列表）,编程常见问题
@anchor{faq/programming objects}@anchor{4229}
@subsection 对象


@menu
* 什么是类？:: 
* 什么是方法？:: 
* 什么是 self ？:: 
* 如何检查对象是否为给定类或其子类的一个实例？:: 
* 什么是委托？:: 
* 如何从覆盖基类的派生类调用基类中定义的方法?:: 
* 如何组织代码以便更改基类？:: 
* 如何创建静态类数据和静态类方法？:: 
* 如何在Python中重载构造函数（或方法）？:: 
* 我尝试使用 __spam ，但是得到一个关于 _SomeClassName__spam 的错误信息。:: 
* 类定义了 __del__ 方法，但是删除对象时没有调用它。:: 
* 如何获取给定类的所有实例的列表？:: 
* 为什么 id() 的结果看起来不是唯一的？: 为什么 id 的结果看起来不是唯一的？. 

@end menu

@node 什么是类？,什么是方法？,,对象
@anchor{faq/programming what-is-a-class}@anchor{422a}
@subsubsection 什么是类？


@code{类} 是通过执行类语句创建的特定对象类型。@code{类对象} 被当作模板来创建实例对象，实例对象包含了特定于数据类型的数据（属性）和代码（方法）。

类可以基于一个或多个的其他类，称之为基类（ES），它继承基类的属性和方法，这样就可以通过继承来连续地细化对象模型。例如：您可能有一个 @code{Mailbox} 类提供邮箱的基本访问方法.，它的子类 @code{MboxMailbox}, @code{MaildirMailbox}, @code{OutlookMailbox} 用于处理各种特定邮箱格式。

@node 什么是方法？,什么是 self ？,什么是类？,对象
@anchor{faq/programming what-is-a-method}@anchor{422b}
@subsubsection 什么是方法？


@code{方法} 实际上就是类定义中的函数。对于某个对象 @code{x} 上的方法，通常称为 @code{x.name(arguments...)} 。

@example
class C:
    def meth(self, arg):
        return arg * 2 + self.attribute
@end example

@node 什么是 self ？,如何检查对象是否为给定类或其子类的一个实例？,什么是方法？,对象
@anchor{faq/programming what-is-self}@anchor{422c}
@subsubsection 什么是 self ？


Self 只是 @code{方法} 的第一个参数的常规名称。例如：对于某个类的某个实例 @code{x} ，其方法 @code{meth(self, a, b, c)} 实际上应该被称为 @code{x.meth(a, b, c)} ；对于被调用的方法会被称为 @code{meth(x, a, b, c)} 。

另请参阅 @ref{422d,,为什么必须在方法定义和调用中显式使用“self”？} 。

@node 如何检查对象是否为给定类或其子类的一个实例？,什么是委托？,什么是 self ？,对象
@anchor{faq/programming how-do-i-check-if-an-object-is-an-instance-of-a-given-class-or-of-a-subclass-of-it}@anchor{422e}
@subsubsection 如何检查对象是否为给定类或其子类的一个实例？


可使用内置函数 @code{isinstance(obj, cls)}。 你可以提供一个元组而不是单个类来检查某个对象是否为任意多个类当中某一个类的实例，例如 @code{isinstance(obj, (class1, class2, ...))}，也可以检查某个对象是否为 Python 内置类型当中某一个类型的对象，例如 @code{isinstance(obj, str)} 或 @code{isinstance(obj, (int, float, complex))}。

请注意大多数程序不会经常对用户自定义类使用 @ref{449,,isinstance()}。 如果是你自已开发的类，更正确的面向对象风格是在类中定义方法来封装特定的行为，而不是检查对象的类并根据它属于什么类来做不同的事。 例如，如果你有一个执行某些操作的函数:

@example
def search(obj):
    if isinstance(obj, Mailbox):
        ...  # code to search a mailbox
    elif isinstance(obj, Document):
        ...  # code to search a document
    elif ...
@end example

更好的方法是在所有类上定义一个 @code{search()} 方法，然后调用它：

@example
class Mailbox:
    def search(self):
        ...  # code to search a mailbox

class Document:
    def search(self):
        ...  # code to search a document

obj.search()
@end example

@node 什么是委托？,如何从覆盖基类的派生类调用基类中定义的方法?,如何检查对象是否为给定类或其子类的一个实例？,对象
@anchor{faq/programming what-is-delegation}@anchor{422f}
@subsubsection 什么是委托？


委托是一种面向对象的技巧（也称为设计模式）。 假设您有一个对象 @code{x} 并且想要改变其中一个方法的行为。 您可以创建一个新类，它提供您感兴趣的方法的新实现，并将所有其他方法委托给 @code{x} 的相应方法。

Python程序员可以轻松实现委托。 例如，以下类实现了一个类，该类的行为类似于文件，但将所有写入的数据转换为大写：

@example
class UpperOut:

    def __init__(self, outfile):
        self._outfile = outfile

    def write(self, s):
        self._outfile.write(s.upper())

    def __getattr__(self, name):
        return getattr(self._outfile, name)
@end example

在这里 @code{UpperOut} 类重新定义了 @code{write()} 方法在调用下层的 @code{self._outfile.write()} 方法之前将参数字符串转换为大写形式。 所有其他方法都被委托给下层的 @code{self._outfile} 对象。 委托是通过 @code{__getattr__} 方法来完成的；请参阅 @ref{13d1,,语言参考} 了解有关控制属性访问的更多信息。

请注意对于更一般的情况来说，委托可能包含更多细节问题。 当某些属性既需要读取又需要设置时，类还必须定义 @ref{e25,,__setattr__()} 方法，并且这样做必须小心谨慎。 @ref{e25,,__setattr__()} 的基本实现大致相当于以下代码:

@example
class X:
    ...
    def __setattr__(self, name, value):
        self.__dict__[name] = value
    ...
@end example

大多数 @ref{e25,,__setattr__()} 实现必须修改 @code{self.__dict__} 来为自身保存局部状态而又不至于造成无限递归。

@node 如何从覆盖基类的派生类调用基类中定义的方法?,如何组织代码以便更改基类？,什么是委托？,对象
@anchor{faq/programming how-do-i-call-a-method-defined-in-a-base-class-from-a-derived-class-that-overrides-it}@anchor{4230}
@subsubsection 如何从覆盖基类的派生类调用基类中定义的方法?


使用内置的 @ref{4dc,,super()} 函数：

@example
class Derived(Base):
    def meth(self):
        super(Derived, self).meth()
@end example

对于 Python 3.0之前的版本，您可能正在使用经典类：对于诸如 @code{class Derived(Base): ...} 之类的类定义，可以将在 @code{Base} (或 @code{Base} 中的一个的基类）中定义的方法 @code{meth()} 调用为 @code{Base.meth(self, arguments...)} 。这里， @code{Base.meth} 是一个未绑定的方法，因此您需要提供 @code{self} 参数。

@node 如何组织代码以便更改基类？,如何创建静态类数据和静态类方法？,如何从覆盖基类的派生类调用基类中定义的方法?,对象
@anchor{faq/programming how-can-i-organize-my-code-to-make-it-easier-to-change-the-base-class}@anchor{4231}
@subsubsection 如何组织代码以便更改基类？


可以为基类定义别名，在类定义之前为其分配实际基类，并在整个类中使用别名。然后更改分配给别名的值，就能实现上述要求。顺便提一下，如果你想动态决定（例如，取决于资源的可用性）要使用哪个基类，这个技巧也很方便。例如：

@example
BaseAlias = <real base class>

class Derived(BaseAlias):
    def meth(self):
        BaseAlias.meth(self)
        ...
@end example

@node 如何创建静态类数据和静态类方法？,如何在Python中重载构造函数（或方法）？,如何组织代码以便更改基类？,对象
@anchor{faq/programming how-do-i-create-static-class-data-and-static-class-methods}@anchor{4232}
@subsubsection 如何创建静态类数据和静态类方法？


Python支持静态数据和静态方法（在C ++或Java的意义上）。

对于静态数据，只需定义一个类属性。要为属性分配新值，就必须在赋值中显式使用类名：

@example
class C:
    count = 0   # number of times C.__init__ called

    def __init__(self):
        C.count = C.count + 1

    def getcount(self):
        return C.count  # or return self.count
@end example

对于任意 @code{c} 来说只要 @code{isinstance(c, C)} 为真，则 @code{c.count} 同样也指向 @code{C.count}，除非被 @code{c} 自身，或者从 @code{c.__class__} 回到 @code{C} 的基类搜索路径上的某个类所重载。

注意：在 C 的某个方法内部，像 @code{self.count = 42} 这样的赋值将在 @code{self} 自身的字典中新建一个名为 "count" 的不相关实例。 想要重新绑定类静态数据名称就必须总是指明类名，无论是在方法内部还是外部:

@example
C.count = 314
@end example

静态方法是可行的：

@example
class C:
    @@staticmethod
    def static(arg1, arg2, arg3):
        # No 'self' parameter!
        ...
@end example

然而，获得静态方法效果的更直接的方法是通过一个简单的模块级函数：

@example
def getcount():
    return C.count
@end example

如果您的代码是结构化的，以便为每个模块定义一个类（或紧密相关的类层次结构），那么这就提供了所需的封装。

@node 如何在Python中重载构造函数（或方法）？,我尝试使用 __spam ，但是得到一个关于 _SomeClassName__spam 的错误信息。,如何创建静态类数据和静态类方法？,对象
@anchor{faq/programming how-can-i-overload-constructors-or-methods-in-python}@anchor{4233}
@subsubsection 如何在Python中重载构造函数（或方法）？


这个答案实际上适用于所有方法，但问题通常首先出现在构造函数的上下文中。

在C ++中，你会这样写

@example
class C @{
    C() @{ cout << "No arguments\n"; @}
    C(int i) @{ cout << "Argument is " << i << "\n"; @}
@}
@end example

在Python中，您必须编写一个构造函数，使用默认参数捕获所有情况。例如：

@example
class C:
    def __init__(self, i=None):
        if i is None:
            print("No arguments")
        else:
            print("Argument is", i)
@end example

这不完全等同，但在实践中足够接近。

你也可以尝试一个可变长度的参数列表，例如:

@example
def __init__(self, *args):
    ...
@end example

相同的方法适用于所有方法定义。

@node 我尝试使用 __spam ，但是得到一个关于 _SomeClassName__spam 的错误信息。,类定义了 __del__ 方法，但是删除对象时没有调用它。,如何在Python中重载构造函数（或方法）？,对象
@anchor{faq/programming i-try-to-use-spam-and-i-get-an-error-about-someclassname-spam}@anchor{4234}
@subsubsection 我尝试使用 __spam ，但是得到一个关于 _SomeClassName__spam 的错误信息。


以双下划线打头的变量会被“更名”以提供一种定义类私有变量的简单而有效的方式。 任何形式为 @code{__spam} 的标识符（至少前缀两个下划线，至多后缀一个下划线）文本会被替换为 @code{_classname__spam}，其中 @code{classname} 为去除了全部前缀下划线的当前类名称。

这并不能保证私密性：外部用户仍然可以访问 "_classname__spam" 属性，私有变量值也在对象的 @code{__dict__} 中可见。 许多 Python 程序员从来都不使用这种私有变量名称。

@node 类定义了 __del__ 方法，但是删除对象时没有调用它。,如何获取给定类的所有实例的列表？,我尝试使用 __spam ，但是得到一个关于 _SomeClassName__spam 的错误信息。,对象
@anchor{faq/programming my-class-defines-del-but-it-is-not-called-when-i-delete-the-object}@anchor{4235}
@subsubsection 类定义了 __del__ 方法，但是删除对象时没有调用它。


这有几个可能的原因。

del 语句不一定调用 @ref{919,,__del__()} —— 它只是减少对象的引用计数，如果（引用计数）达到零，才会调用 @ref{919,,__del__()}。

如果数据结构包含循环链接（例如，每个子级都有一个父级引用，每个父级都有一个子级列表的树），则引用计数将永远不会返回零。尽管Python 偶尔会运行一个算法来检测这样的循环，但在数据结构的引用计数清零后，垃圾收集器可能需要一段时间来运行，因此 @ref{919,,__del__()} 方法可能会在不方便和随机的时间被调用。这对于重现一个问题，是非常不方便的。更糟糕的是，对象 @ref{919,,__del__()} 的方法执行顺序是任意的。虽然可以运行 @ref{22e,,gc.collect()} 来强制回收，但在一些病态的情况下，对象永远不会被回收。

尽管有循环收集器，但在对象上定义一个显式的 @code{close()} 方法以便在用完之后调用它仍然是一个好主意。 这样 @code{close()} 方法可以随即删除引用子对象的属性。 不要直接调用 @ref{919,,__del__()} —— 应该由 @ref{919,,__del__()} 调用 @code{close()}，并且 @code{close()} 能确保可以被同一对象多次地调用。

另一种避免循环引用的方法是使用 @ref{128,,weakref} 模块，该模块允许您指向对象而不增加其引用计数。例如，树状数据结构应该对其父级和同级引用使用弱引用（如果需要的话！）

@c XXX relevant for Python 3?
@c 
@c If the object has ever been a local variable in a function that caught an
@c expression in an except clause, chances are that a reference to the object
@c still exists in that function's stack frame as contained in the stack trace.
@c Normally, calling :func:`sys.exc_clear` will take care of this by clearing
@c the last recorded exception.

最后，如果 @ref{919,,__del__()} 方法引发异常，会将警告消息打印到 @ref{308,,sys.stderr} 。

@node 如何获取给定类的所有实例的列表？,为什么 id 的结果看起来不是唯一的？,类定义了 __del__ 方法，但是删除对象时没有调用它。,对象
@anchor{faq/programming how-do-i-get-a-list-of-all-instances-of-a-given-class}@anchor{4236}
@subsubsection 如何获取给定类的所有实例的列表？


Python不跟踪类（或内置类型）的所有实例。您可以对类的构造函数进行编程，以通过保留每个实例的弱引用列表来跟踪所有实例。

@node 为什么 id 的结果看起来不是唯一的？,,如何获取给定类的所有实例的列表？,对象
@anchor{faq/programming why-does-the-result-of-id-appear-to-be-not-unique}@anchor{4237}
@subsubsection 为什么 @code{id()} 的结果看起来不是唯一的？


@ref{d7f,,id()} 返回一个整数，该整数在对象的生命周期内保证是唯一的。因为在CPython中，这是对象的内存地址，所以经常发生在从内存中删除对象之后，下一个新创建的对象被分配在内存中的相同位置。这个例子说明了这一点：

@example
>>> id(1000) 
13901272
>>> id(2000) 
13901272
@end example

这两个id属于之前创建的不同整数对象，并在执行 @code{id()} 调用后立即删除。要确保要检查其id的对象仍处于活动状态，请创建对该对象的另一个引用：

@example
>>> a = 1000; b = 2000
>>> id(a) 
13901272
>>> id(b) 
13891296
@end example

@node 模块<3>,,对象,编程常见问题
@anchor{faq/programming modules}@anchor{4238}
@subsection 模块


@menu
* 如何创建 .pyc 文件？: 如何创建 pyc 文件？. 
* 如何找到当前模块名称？:: 
* 如何让模块相互导入？:: 
* __import__('x.y.z') 返回 <module 'x'>; 如何获取z?: __import__ 'x y z' 返回 <module 'x'>; 如何获取z?. 
* 当我编辑了导入过的模块并重新导入它时，这些变化没有显示出来。为什么会这样？:: 

@end menu

@node 如何创建 pyc 文件？,如何找到当前模块名称？,,模块<3>
@anchor{faq/programming how-do-i-create-a-pyc-file}@anchor{4239}
@subsubsection 如何创建 .pyc 文件？


当一个模块首次被导入时（或自当前已编译文件创建后源文件被修改时），将会在对应 @code{.py} 文件所在目录的 @code{__pycache__} 子目录下创建一个包含已编译代码的 @code{.pyc} 文件。 该 @code{.pyc} 文件的文件名的开头部分将与对应 @code{.py} 文件名相同，并以 @code{.pyc} 为后缀，中间部门则是基于创建它的特定 @code{python} 二进制代码版本。 （详情参见 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147}。）

无法创建 @code{.pyc} 文件的可能原因是包含源文件的目录存在权限问题，这意味着 @code{__pycache__} 子目录无法被创建。 举例来说，如果你以某一用户来开发程序但以另一用户身份来运行程序时就可能发生问题，测试 Web 服务器就属于这种情况。

除非设置了 
@geindex PYTHONDONTWRITEBYTECODE
@geindex 环境变量; PYTHONDONTWRITEBYTECODE
@ref{d32,,PYTHONDONTWRITEBYTECODE} 环境变量，否则当你导入模块并且 Python 具有创建 @code{__pycache__} 子目录并将已编译模块写入该子目录的能力（权限、存储空间等等）时就会自动创建 .pyc 文件。

在最高层级运行的 Python 脚本不被视为导入，因此不会创建 @code{.pyc} 文件。 例如，如果你有一个最高层级模块文件 @code{foo.py}，它又导入了另一个模块 @code{xyz.py}，当你运行 @code{foo} 模块 (通过输入终端命令 @code{python foo.py})，则将为 @code{xyz} 创建一个 @code{.pyc}，因为 @code{xyz} 是被导入的，但不会为 @code{foo} 创建 @code{.pyc} 文件，因为 @code{foo.py} 不是被导入的。

如果你需要为 @code{foo} 创建 @code{.pyc} 文件 —— 即为不是被导入的模块创建 @code{.pyc} 文件 —— 你可以使用 @ref{d7,,py_compile} 和 @ref{21,,compileall} 模块。

@ref{d7,,py_compile} 模块能够手动编译任意模块。 一种做法是交互式地使用该模块中的 @code{compile()} 函数:

@example
>>> import py_compile
>>> py_compile.compile('foo.py')                 
@end example

这将会将  @code{.pyc} 文件写入与 @code{foo.py} 相同位置下的 @code{__pycache__} 子目录（或者你也可以通过可选参数 @code{cfile} 来重载该行为）。

你还可以使用 @ref{21,,compileall} 模块自动编译一个目录或多个目录下的所有文件。 具体做法可以是在命令行提示符中运行 @code{compileall.py} 并提供包含要编译 Python 文件的目录路径:

@example
python -m compileall .
@end example

@node 如何找到当前模块名称？,如何让模块相互导入？,如何创建 pyc 文件？,模块<3>
@anchor{faq/programming how-do-i-find-the-current-module-name}@anchor{423a}
@subsubsection 如何找到当前模块名称？


模块可以通过查看预定义的全局变量 @code{__name__} 找到自己的模块名称。如果它的值为 @code{'__main__'} ，程序将作为脚本运行。通常，通过导入使用的许多模块也提供命令行界面或自检，并且只在检查 @code{__name__} 之后，才执行之后的代码:

@example
def main():
    print('Running test...')
    ...

if __name__ == '__main__':
    main()
@end example

@node 如何让模块相互导入？,__import__ 'x y z' 返回 <module 'x'>; 如何获取z?,如何找到当前模块名称？,模块<3>
@anchor{faq/programming how-can-i-have-modules-that-mutually-import-each-other}@anchor{423b}
@subsubsection 如何让模块相互导入？


假设您有以下模块：

foo.py:

@example
from bar import bar_var
foo_var = 1
@end example

bar.py:

@example
from foo import foo_var
bar_var = 2
@end example

问题是解释器将执行以下步骤：


@itemize *

@item 
首先导入foo

@item 
创建用于foo的空全局变量

@item 
foo被编译并开始执行

@item 
foo 导入 bar

@item 
创建了用于bar 的空全局变量

@item 
bar被编译并开始执行

@item 
bar导入foo（这是一个空操作（no-op ），因为已经有一个名为foo的模块）

@item 
bar.foo_var = foo.foo_var
@end itemize

最后一步失败了，因为Python还没有解释foo，而foo的全局符号字典仍然是空的。

当你使用 @code{import foo} ，然后尝试在全局代码中访问 @code{foo.foo_var} 时，会发生同样的事情。

这个问题有（至少）三种可能的解决方法。

Guido van Rossum 建议避免使用 @code{from <module> import ...} ，并将所有代码放在函数中。全局变量和类变量的初始化只能使用常量或内置函数。这意味着导入模块中的所有内容都被引用为 @code{<module>.<name>} 。

Jim Roskind建议在每个模块中按以下顺序执行步骤：


@itemize *

@item 
导出（全局变量，函数和不需要导入基类的类）

@item 
@code{导入} 声明

@item 
活动代码（包括从导入值初始化的全局变量）。
@end itemize

van Rossum不喜欢这种方法，因为导入出现在一个陌生的地方，但这种方法确实有效。

Matthias Urlichs建议重构代码，以便首先不需要递归导入。

这些解决方案并不相互排斥。

@node __import__ 'x y z' 返回 <module 'x'>; 如何获取z?,当我编辑了导入过的模块并重新导入它时，这些变化没有显示出来。为什么会这样？,如何让模块相互导入？,模块<3>
@anchor{faq/programming import-x-y-z-returns-module-x-how-do-i-get-z}@anchor{423c}
@subsubsection __import__('x.y.z') 返回 <module 'x'>; 如何获取z?


考虑使用 @ref{9b,,importlib} 中的函数 @ref{b0c,,import_module()} ：

@example
z = importlib.import_module('x.y.z')
@end example

@node 当我编辑了导入过的模块并重新导入它时，这些变化没有显示出来。为什么会这样？,,__import__ 'x y z' 返回 <module 'x'>; 如何获取z?,模块<3>
@anchor{faq/programming when-i-edit-an-imported-module-and-reimport-it-the-changes-don-t-show-up-why-does-this-happen}@anchor{423d}
@subsubsection 当我编辑了导入过的模块并重新导入它时，这些变化没有显示出来。为什么会这样？


出于效率和一致性的原因，Python仅在第一次导入模块时读取模块文件。如果不这么做，在一个由许多模块组成的程序中，每个模块都会导入相同的基本模块，那么基本模块将被解析和重新解析多次。要强制重新读取已更改的模块，请执行以下操作:

@example
import importlib
import modname
importlib.reload(modname)
@end example

警告：这种技术不是100％万无一失。特别是包含如下语句的模块

@example
from modname import some_objects
@end example

将继续使用旧版本的导入对象。如果模块包含类定义，则不会更新现有的类实例以使用新的类定义。这可能导致以下矛盾行为:

@example
>>> import importlib
>>> import cls
>>> c = cls.C()                # Create an instance of C
>>> importlib.reload(cls)
<module 'cls' from 'cls.py'>
>>> isinstance(c, cls.C)       # isinstance is false?!?
False
@end example

如果打印出类对象的“标识”，问题的本质就会明确：

@example
>>> hex(id(c.__class__))
'0x7352a0'
>>> hex(id(cls.C))
'0x4198d0'
@end example

@node 设计和历史常见问题,代码库和插件 FAQ,编程常见问题,Python 常见问题
@anchor{faq/design doc}@anchor{423e}@anchor{faq/design design-and-history-faq}@anchor{423f}
@section 设计和历史常见问题



@menu
* 为什么Python使用缩进来分组语句？:: 
* 为什么简单的算术运算得到奇怪的结果？:: 
* 为什么浮点计算不准确？:: 
* 为什么Python字符串是不可变的？:: 
* 为什么必须在方法定义和调用中显式使用“self”？:: 
* 为什么不能在表达式中赋值？:: 
* 为什么Python对某些功能（例如list.index()）使用方法来实现，而其他功能（例如len(List)）使用函数实现？: 为什么Python对某些功能（例如list index ）使用方法来实现，而其他功能（例如len List ）使用函数实现？. 
* 为什么 join()是一个字符串方法而不是列表或元组方法？: 为什么 join 是一个字符串方法而不是列表或元组方法？. 
* 异常有多快？:: 
* 为什么Python中没有switch或case语句？:: 
* 难道不能在解释器中模拟线程，而非得依赖特定于操作系统的线程实现吗？:: 
* 为什么lambda表达式不能包含语句？:: 
* 可以将Python编译为机器代码，C或其他语言吗？:: 
* Python如何管理内存？:: 
* 为什么CPython不使用更传统的垃圾回收方案？:: 
* CPython退出时为什么不释放所有内存？:: 
* 为什么有单独的元组和列表数据类型？:: 
* 列表是如何在CPython中实现的？:: 
* 字典是如何在CPython中实现的？:: 
* 为什么字典key必须是不可变的？:: 
* 为什么 list.sort() 没有返回排序列表？: 为什么 list sort 没有返回排序列表？. 
* 如何在Python中指定和实施接口规范？:: 
* 为什么没有goto？:: 
* 为什么原始字符串（r-strings）不能以反斜杠结尾？:: 
* 为什么Python没有属性赋值的“with”语句？:: 
* 为什么 if/while/def/class语句需要冒号？:: 
* 为什么Python在列表和元组的末尾允许使用逗号？:: 

@end menu

@node 为什么Python使用缩进来分组语句？,为什么简单的算术运算得到奇怪的结果？,,设计和历史常见问题
@anchor{faq/design why-does-python-use-indentation-for-grouping-of-statements}@anchor{4240}
@subsection 为什么Python使用缩进来分组语句？


Guido van Rossum 认为使用缩进进行分组非常优雅，并且大大提高了普通Python程序的清晰度。大多数人在一段时间后就学会并喜欢上这个功能。

由于没有开始/结束括号，因此解析器感知的分组与人类读者之间不会存在分歧。偶尔C程序员会遇到像这样的代码片段:

@example
if (x <= y)
        x++;
        y--;
z++;
@end example

如果条件为真，则只执行 @code{x++} 语句，但缩进会使你认为情况并非如此。即使是经验丰富的C程序员有时会长时间盯着它，想知道为什么即使 @code{x > y} ， @code{y} 也在减少。

因为没有开始/结束括号，所以Python不太容易发生编码式冲突。在C中，括号可以放到许多不同的位置。如果您习惯于阅读和编写使用一种风格的代码，那么在阅读（或被要求编写）另一种风格时，您至少会感到有些不安。

许多编码风格将开始/结束括号单独放在一行上。这使得程序相当长，浪费了宝贵的屏幕空间，使得更难以对程序进行全面的了解。理想情况下，函数应该适合一个屏幕（例如，20--30行）。 20行Python可以完成比20行C更多的工作。这不仅仅是由于缺少开始/结束括号 -- 缺少声明和高级数据类型也是其中的原因  -- 但缩进基于语法肯定有帮助。

@node 为什么简单的算术运算得到奇怪的结果？,为什么浮点计算不准确？,为什么Python使用缩进来分组语句？,设计和历史常见问题
@anchor{faq/design why-am-i-getting-strange-results-with-simple-arithmetic-operations}@anchor{4241}
@subsection 为什么简单的算术运算得到奇怪的结果？


请看下一个问题。

@node 为什么浮点计算不准确？,为什么Python字符串是不可变的？,为什么简单的算术运算得到奇怪的结果？,设计和历史常见问题
@anchor{faq/design why-are-floating-point-calculations-so-inaccurate}@anchor{4242}
@subsection 为什么浮点计算不准确？


用户经常对这样的结果感到惊讶:

@example
>>> 1.2 - 1.0
0.19999999999999996
@end example

并且认为这是 Python中的一个 bug。其实不是这样。这与 Python 关系不大，而与底层平台如何处理浮点数字关系更大。

CPython 中的 @ref{187,,float} 类型使用C语言的 @code{double} 类型进行存储。 @ref{187,,float} 对象的值是以固定的精度（通常为 53 位）存储的二进制浮点数，由于 Python 使用 C 操作，而后者依赖于处理器中的硬件实现来执行浮点运算。 这意味着就浮点运算而言，Python 的行为类似于许多流行的语言，包括 C 和 Java。

许多可以轻松地用十进制表示的数字不能用二进制浮点表示。例如，在输入以下语句后:

@example
>>> x = 1.2
@end example

为 @code{x} 存储的值是与十进制的值 @code{1.2} (非常接近) 的近似值，但不完全等于它。 在典型的机器上，实际存储的值是：

@example
1.0011001100110011001100110011001100110011001100110011 (binary)
@end example

它对应于十进制数值:

@example
1.1999999999999999555910790149937383830547332763671875 (decimal)
@end example

典型的 53 位精度为 Python 浮点数提供了 15-16 位小数的精度。

要获得更完整的解释，请参阅 Python 教程中的 @ref{12b7,,浮点算术}  一章。

@node 为什么Python字符串是不可变的？,为什么必须在方法定义和调用中显式使用“self”？,为什么浮点计算不准确？,设计和历史常见问题
@anchor{faq/design why-are-python-strings-immutable}@anchor{4243}
@subsection 为什么Python字符串是不可变的？


有几个优点。

一个是性能：知道字符串是不可变的，意味着我们可以在创建时为它分配空间，并且存储需求是固定不变的。这也是元组和列表之间区别的原因之一。

另一个优点是，Python 中的字符串被视为与数字一样“基本”。 任何动作都不会将值 8 更改为其他值，在 Python 中，任何动作都不会将字符串 "8" 更改为其他值。

@node 为什么必须在方法定义和调用中显式使用“self”？,为什么不能在表达式中赋值？,为什么Python字符串是不可变的？,设计和历史常见问题
@anchor{faq/design why-must-self-be-used-explicitly-in-method-definitions-and-calls}@anchor{4244}@anchor{faq/design why-self}@anchor{422d}
@subsection 为什么必须在方法定义和调用中显式使用“self”？


这个想法借鉴了 Modula-3 语言。 出于多种原因它被证明是非常有用的。

首先，更明显的显示出，使用的是方法或实例属性而不是局部变量。 阅读 @code{self.x} 或 @code{self.meth()} 可以清楚地表明，即使您不知道类的定义，也会使用实例变量或方法。在 C++ 中，可以通过缺少局部变量声明来判断（假设全局变量很少见或容易识别） —— 但是在 Python 中没有局部变量声明，所以必须查找类定义才能确定。 一些 C++ 和 Java 编码标准要求实例属性具有 @code{m_} 前缀，因此这种显式性在这些语言中仍然有用。

其次，这意味着如果要显式引用或从特定类调用该方法，不需要特殊语法。 在 C++ 中，如果你想使用在派生类中重写基类中的方法，你必须使用 @code{::} 运算符 -- 在 Python 中你可以编写 @code{baseclass.methodname(self, <argument list>)}。 这对于 @ref{d57,,__init__()} 方法非常有用，特别是在派生类方法想要扩展同名的基类方法，而必须以某种方式调用基类方法时。

最后，它解决了变量赋值的语法问题：为了 Python 中的局部变量（根据定义！）在函数体中赋值的那些变量（并且没有明确声明为全局）赋值，就必须以某种方式告诉解释器一个赋值是为了分配一个实例变量而不是一个局部变量，它最好是通过语法实现的（出于效率原因）。 C++ 通过声明来做到这一点，但是 Python 没有声明，仅仅为了这个目的而引入它们会很可惜。 使用显式的 @code{self.var} 很好地解决了这个问题。 类似地，对于使用实例变量，必须编写 @code{self.var} 意味着对方法内部的非限定名称的引用不必搜索实例的目录。 换句话说，局部变量和实例变量存在于两个不同的命名空间中，您需要告诉 Python 使用哪个命名空间。

@node 为什么不能在表达式中赋值？,为什么Python对某些功能（例如list index ）使用方法来实现，而其他功能（例如len List ）使用函数实现？,为什么必须在方法定义和调用中显式使用“self”？,设计和历史常见问题
@anchor{faq/design id2}@anchor{4245}@anchor{faq/design why-can-t-i-use-an-assignment-in-an-expression}@anchor{120c}
@subsection 为什么不能在表达式中赋值？


自 Python 3.8 开始，你能做到的！

赋值表达式使用海象运算符 @cite{:=} 在表达式中为变量赋值:

@example
while chunk := fp.read(200):
   print(chunk)
@end example

请参阅 
@geindex Python 提高建议; PEP 572
PEP 572@footnote{https://www.python.org/dev/peps/pep-0572} 了解详情。

@node 为什么Python对某些功能（例如list index ）使用方法来实现，而其他功能（例如len List ）使用函数实现？,为什么 join 是一个字符串方法而不是列表或元组方法？,为什么不能在表达式中赋值？,设计和历史常见问题
@anchor{faq/design why-does-python-use-methods-for-some-functionality-e-g-list-index-but-functions-for-other-e-g-len-list}@anchor{4246}
@subsection 为什么Python对某些功能（例如list.index()）使用方法来实现，而其他功能（例如len(List)）使用函数实现？


正如Guido所说：

@quotation

(a) 对于某些操作，前缀表示法比后缀更容易阅读 -- 前缀（和中缀！）运算在数学中有着悠久的传统，就像在视觉上帮助数学家思考问题的记法。比较一下我们将 x*(a+b) 这样的公式改写为 x*a+x*b 的容易程度，以及使用原始OO符号做相同事情的笨拙程度。

(b)  当读到写有len(X)的代码时，就知道它要求的是某件东西的长度。这告诉我们两件事：结果是一个整数，参数是某种容器。相反，当阅读x.len()时，必须已经知道x是某种实现接口的容器，或者是从具有标准len()的类继承的容器。当没有实现映射的类有get()或key()方法，或者不是文件的类有write()方法时，我们偶尔会感到困惑。


@center --- @indicateurl{https://mail.python.org/pipermail/python-3000/2006-November/004643.html}

@end quotation

@node 为什么 join 是一个字符串方法而不是列表或元组方法？,异常有多快？,为什么Python对某些功能（例如list index ）使用方法来实现，而其他功能（例如len List ）使用函数实现？,设计和历史常见问题
@anchor{faq/design why-is-join-a-string-method-instead-of-a-list-or-tuple-method}@anchor{4247}
@subsection 为什么 join()是一个字符串方法而不是列表或元组方法？


从Python 1.6开始，字符串变得更像其他标准类型，当添加方法时，这些方法提供的功能与始终使用String模块的函数时提供的功能相同。这些新方法中的大多数已被广泛接受，但似乎让一些程序员感到不舒服的一种方法是：

@example
", ".join(['1', '2', '4', '8', '16'])
@end example

结果如下:

@example
"1, 2, 4, 8, 16"
@end example

反对这种用法有两个常见的论点。

第一条是这样的：“使用字符串文本(String Constant)的方法看起来真的很难看”，答案是也许吧，但是字符串文本只是一个固定值。如果在绑定到字符串的名称上允许使用这些方法，则没有逻辑上的理由使其在文字上不可用。

第二个异议通常是这样的：“我实际上是在告诉序列使用字符串常量将其成员连接在一起”。遗憾的是并非如此。出于某种原因，把 @ref{79b,,split()} 作为一个字符串方法似乎要容易得多，因为在这种情况下，很容易看到:

@example
"1, 2, 4, 8, 16".split(", ")
@end example

是对字符串文本的指令，用于返回由给定分隔符分隔的子字符串（或在默认情况下，返回任意空格）。

@ref{15ca,,join()} 是字符串方法，因为在使用该方法时，您告诉分隔符字符串去迭代一个字符串序列，并在相邻元素之间插入自身。此方法的参数可以是任何遵循序列规则的对象，包括您自己定义的任何新的类。对于字节和字节数组对象也有类似的方法。

@node 异常有多快？,为什么Python中没有switch或case语句？,为什么 join 是一个字符串方法而不是列表或元组方法？,设计和历史常见问题
@anchor{faq/design how-fast-are-exceptions}@anchor{4248}
@subsection 异常有多快？


如果没有引发异常，则try/except块的效率极高。实际上捕获异常是昂贵的。在2.0之前的Python版本中，通常使用这个习惯用法:

@example
try:
    value = mydict[key]
except KeyError:
    mydict[key] = getvalue(key)
    value = mydict[key]
@end example

只有当你期望dict在任何时候都有key时，这才有意义。如果不是这样的话，你就是应该这样编码：

@example
if key in mydict:
    value = mydict[key]
else:
    value = mydict[key] = getvalue(key)
@end example

对于这种特定的情况，您还可以使用 @code{value = dict.setdefault(key, getvalue(key))}，但前提是调用 @code{getvalue()} 足够便宜，因为在所有情况下都会对其进行评估。

@node 为什么Python中没有switch或case语句？,难道不能在解释器中模拟线程，而非得依赖特定于操作系统的线程实现吗？,异常有多快？,设计和历史常见问题
@anchor{faq/design why-isn-t-there-a-switch-or-case-statement-in-python}@anchor{4249}
@subsection 为什么Python中没有switch或case语句？


你可以通过一系列 @code{if... elif... elif... else}.轻松完成这项工作。对于switch语句语法已经有了一些建议，但尚未就是否以及如何进行范围测试达成共识。有关完整的详细信息和当前状态，请参阅 
@geindex Python 提高建议; PEP 275
PEP 275@footnote{https://www.python.org/dev/peps/pep-0275} 。

对于需要从大量可能性中进行选择的情况，可以创建一个字典，将case 值映射到要调用的函数。例如：

@example
def function_1(...):
    ...

functions = @{'a': function_1,
             'b': function_2,
             'c': self.method_1, ...@}

func = functions[value]
func()
@end example

对于对象调用方法，可以通过使用 @ref{443,,getattr()} 内置检索具有特定名称的方法来进一步简化：

@example
def visit_a(self, ...):
    ...
...

def dispatch(self, value):
    method_name = 'visit_' + str(value)
    method = getattr(self, method_name)
    method()
@end example

建议对方法名使用前缀，例如本例中的 @code{visit_} 。如果没有这样的前缀，如果值来自不受信任的源，攻击者将能够调用对象上的任何方法。

@node 难道不能在解释器中模拟线程，而非得依赖特定于操作系统的线程实现吗？,为什么lambda表达式不能包含语句？,为什么Python中没有switch或case语句？,设计和历史常见问题
@anchor{faq/design can-t-you-emulate-threads-in-the-interpreter-instead-of-relying-on-an-os-specific-thread-implementation}@anchor{424a}
@subsection 难道不能在解释器中模拟线程，而非得依赖特定于操作系统的线程实现吗？


答案1： 不幸的是，解释器为每个Python堆栈帧推送至少一个C堆栈帧。此外，扩展可以随时回调Python。因此，一个完整的线程实现需要对C的线程支持。

答案2： 幸运的是， Stackless Python@footnote{https://github.com/stackless-dev/stackless/wiki} 有一个完全重新设计的解释器循环，可以避免C堆栈。

@node 为什么lambda表达式不能包含语句？,可以将Python编译为机器代码，C或其他语言吗？,难道不能在解释器中模拟线程，而非得依赖特定于操作系统的线程实现吗？,设计和历史常见问题
@anchor{faq/design why-can-t-lambda-expressions-contain-statements}@anchor{424b}
@subsection 为什么lambda表达式不能包含语句？


Python的 lambda表达式不能包含语句，因为Python的语法框架不能处理嵌套在表达式内部的语句。然而，在Python中，这并不是一个严重的问题。与其他语言中添加功能的lambda表单不同，Python的 lambdas只是一种速记符号，如果您懒得定义函数的话。

函数已经是Python中的第一类对象，可以在本地范围内声明。 因此，使用lambda而不是本地定义的函数的唯一优点是你不需要为函数创建一个名称 -- 这只是一个分配了函数对象(与lambda表达式生成的对象类型完全相同)的局部变量！

@node 可以将Python编译为机器代码，C或其他语言吗？,Python如何管理内存？,为什么lambda表达式不能包含语句？,设计和历史常见问题
@anchor{faq/design can-python-be-compiled-to-machine-code-c-or-some-other-language}@anchor{424c}
@subsection 可以将Python编译为机器代码，C或其他语言吗？


Cython@footnote{http://cython.org/} 将带有可选注释的Python修改版本编译到C扩展中。 Nuitka@footnote{http://www.nuitka.net/} 是一个将Python编译成 C++ 代码的新兴编译器，旨在支持完整的Python语言。要编译成Java，可以考虑 VOC@footnote{https://voc.readthedocs.io} 。

@node Python如何管理内存？,为什么CPython不使用更传统的垃圾回收方案？,可以将Python编译为机器代码，C或其他语言吗？,设计和历史常见问题
@anchor{faq/design how-does-python-manage-memory}@anchor{424d}
@subsection Python如何管理内存？


Python 内存管理的细节取决于实现。 Python 的标准实现 @ref{13ce,,CPython} 使用引用计数来检测不可访问的对象，并使用另一种机制来收集引用循环，定期执行循环检测算法来查找不可访问的循环并删除所涉及的对象。 @ref{86,,gc} 模块提供了执行垃圾回收、获取调试统计信息和优化收集器参数的函数。

但是，其他实现(如  Jython@footnote{http://www.jython.org}  或  PyPy@footnote{http://www.pypy.org} )，)可以依赖不同的机制，如完全的垃圾回收器 。如果你的Python代码依赖于引用计数实现的行为，则这种差异可能会导致一些微妙的移植问题。

在一些Python实现中，以下代码（在CPython中工作的很好）可能会耗尽文件描述符:

@example
for file in very_long_list_of_files:
    f = open(file)
    c = f.read(1)
@end example

实际上，使用CPython的引用计数和析构函数方案， 每个新赋值的 @emph{f} 都会关闭前一个文件。然而，对于传统的GC，这些文件对象只能以不同的时间间隔（可能很长的时间间隔）被收集（和关闭）。

如果要编写可用于任何python实现的代码，则应显式关闭该文件或使用  @ref{6e3,,with} 语句；无论内存管理方案如何，这都有效：

@example
for file in very_long_list_of_files:
    with open(file) as f:
        c = f.read(1)
@end example

@node 为什么CPython不使用更传统的垃圾回收方案？,CPython退出时为什么不释放所有内存？,Python如何管理内存？,设计和历史常见问题
@anchor{faq/design why-doesn-t-cpython-use-a-more-traditional-garbage-collection-scheme}@anchor{424e}
@subsection 为什么CPython不使用更传统的垃圾回收方案？


首先，这不是C标准特性，因此不能移植。(是的，我们知道Boehm GC库。它包含了 @emph{大多数} 常见平台（但不是所有平台）的汇编代码，尽管它基本上是透明的，但也不是完全透明的; 要让Python使用它，需要使用补丁。)

当Python嵌入到其他应用程序中时，传统的GC也成为一个问题。在独立的Python中，可以用GC库提供的版本替换标准的malloc()和free()，嵌入Python的应用程序可能希望用 @emph{它自己} 替代malloc()和free()，而可能不需要Python的。现在，CPython可以正确地实现malloc()和free()。

@node CPython退出时为什么不释放所有内存？,为什么有单独的元组和列表数据类型？,为什么CPython不使用更传统的垃圾回收方案？,设计和历史常见问题
@anchor{faq/design why-isn-t-all-memory-freed-when-cpython-exits}@anchor{424f}
@subsection CPython退出时为什么不释放所有内存？


当Python退出时，从全局命名空间或Python模块引用的对象并不总是被释放。 如果存在循环引用，则可能发生这种情况 C库分配的某些内存也是不可能释放的（例如像Purify这样的工具会抱怨这些内容）。 但是，Python在退出时清理内存并尝试销毁每个对象。

如果要强制 Python 在释放时删除某些内容，请使用 @ref{c,,atexit} 模块运行一个函数，强制删除这些内容。

@node 为什么有单独的元组和列表数据类型？,列表是如何在CPython中实现的？,CPython退出时为什么不释放所有内存？,设计和历史常见问题
@anchor{faq/design why-are-there-separate-tuple-and-list-data-types}@anchor{4250}
@subsection 为什么有单独的元组和列表数据类型？


虽然列表和元组在许多方面是相似的，但它们的使用方式通常是完全不同的。可以认为元组类似于Pascal记录或C结构；它们是相关数据的小集合，可以是不同类型的数据，可以作为一个组进行操作。例如，笛卡尔坐标适当地表示为两个或三个数字的元组。

另一方面，列表更像其他语言中的数组。它们倾向于持有不同数量的对象，所有对象都具有相同的类型，并且逐个操作。例如， @code{os.listdir('.')} 返回表示当前目录中的文件的字符串列表。如果向目录中添加了一两个文件，对此输出进行操作的函数通常不会中断。

元组是不可变的，这意味着一旦创建了元组，就不能用新值替换它的任何元素。列表是可变的，这意味着您始终可以更改列表的元素。只有不变元素可以用作字典的key，因此只能将元组和非列表用作key。

@node 列表是如何在CPython中实现的？,字典是如何在CPython中实现的？,为什么有单独的元组和列表数据类型？,设计和历史常见问题
@anchor{faq/design how-are-lists-implemented-in-cpython}@anchor{4251}
@subsection 列表是如何在CPython中实现的？


CPython的列表实际上是可变长度的数组，而不是lisp风格的链表。该实现使用对其他对象的引用的连续数组，并在列表头结构中保留指向该数组和数组长度的指针。

这使得索引列表 @code{a[i]} 的操作成本与列表的大小或索引的值无关。

当添加或插入项时，将调整引用数组的大小。并采用了一些巧妙的方法来提高重复添加项的性能; 当数组必须增长时，会分配一些额外的空间，以便在接下来的几次中不需要实际调整大小。

@node 字典是如何在CPython中实现的？,为什么字典key必须是不可变的？,列表是如何在CPython中实现的？,设计和历史常见问题
@anchor{faq/design how-are-dictionaries-implemented-in-cpython}@anchor{4252}
@subsection 字典是如何在CPython中实现的？


CPython的字典实现为可调整大小的哈希表。与B-树相比，这在大多数情况下为查找（目前最常见的操作）提供了更好的性能，并且实现更简单。

字典的工作方式是使用 @ref{9be,,hash()} 内置函数计算字典中存储的每个键的hash代码。hash代码根据键和每个进程的种子而变化很大；例如，"Python" 的hash值为-539294296，而"python"(一个按位不同的字符串)的hash值为1142331976。然后，hash代码用于计算内部数组中将存储该值的位置。假设您存储的键都具有不同的hash值，这意味着字典需要恒定的时间 -- O(1)，用Big-O表示法 -- 来检索一个键。

@node 为什么字典key必须是不可变的？,为什么 list sort 没有返回排序列表？,字典是如何在CPython中实现的？,设计和历史常见问题
@anchor{faq/design why-must-dictionary-keys-be-immutable}@anchor{4253}
@subsection 为什么字典key必须是不可变的？


字典的哈希表实现使用从键值计算的哈希值来查找键。如果键是可变对象，则其值可能会发生变化，因此其哈希值也会发生变化。但是，由于无论谁更改键对象都无法判断它是否被用作字典键值，因此无法在字典中修改条目。然后，当你尝试在字典中查找相同的对象时，将无法找到它，因为其哈希值不同。如果你尝试查找旧值，也不会找到它，因为在该哈希表中找到的对象的值会有所不同。

如果你想要一个用列表索引的字典，只需先将列表转换为元组；用函数 @code{tuple(L)} 创建一个元组，其条目与列表 @code{L} 相同。 元组是不可变的，因此可以用作字典键。

已经提出的一些不可接受的解决方案：


@itemize -

@item 
哈希按其地址（对象ID）列出。这不起作用，因为如果你构造一个具有相同值的新列表，它将无法找到；例如:

@example
mydict = @{[1, 2]: '12'@}
print(mydict[[1, 2]])
@end example

会引发一个 @ref{2c7,,KeyError} 异常，因为第二行中使用的 @code{[1, 2]} 的 id 与第一行中的 id 不同。换句话说，应该使用 @code{==} 来比较字典键，而不是使用 @ref{13b6,,is} 。

@item 
使用列表作为键时进行复制。这没有用的，因为作为可变对象的列表可以包含对自身的引用，然后复制代码将进入无限循环。

@item 
允许列表作为键，但告诉用户不要修改它们。当你意外忘记或修改列表时，这将产生程序中的一类难以跟踪的错误。它还使一个重要的字典不变量无效： @code{d.keys()} 中的每个值都可用作字典的键。

@item 
将列表用作字典键后，应标记为其只读。问题是，它不仅仅是可以改变其值的顶级对象；你可以使用包含列表作为键的元组。将任何内容作为键关联到字典中都需要将从那里可到达的所有对象标记为只读 —— 并且自引用对象可能会导致无限循环。
@end itemize

如果需要，可以使用以下方法来解决这个问题，但使用它需要你自担风险：你可以将一个可变结构包装在一个类实例中，该实例同时具有 @ref{338,,__eq__()} 和 @ref{339,,__hash__()} 方法。然后，你必须确保驻留在字典（或其他基于 hash 的结构）中的所有此类包装器对象的哈希值在对象位于字典（或其他结构）中时保持固定。:

@example
class ListWrapper:
    def __init__(self, the_list):
        self.the_list = the_list

    def __eq__(self, other):
        return self.the_list == other.the_list

    def __hash__(self):
        l = self.the_list
        result = 98767 - len(l)*555
        for i, el in enumerate(l):
            try:
                result = result + (hash(el) % 9999999) * 1001 + i
            except Exception:
                result = (result % 7777777) + i * 333
        return result
@end example

注意，哈希计算由于列表的某些成员可能不可用以及算术溢出的可能性而变得复杂。

此外，必须始终如此，如果 @code{o1 == o2} （即 @code{o1.__eq__(o2) is True} ）则 @code{hash(o1) == hash(o2)`@w{`}（即 `@w{`}o1.__hash__() == o2.__hash__()} ），无论对象是否在字典中。 如果你不能满足这些限制，字典和其他基于 hash 的结构将会出错。

对于 ListWrapper ，只要包装器对象在字典中，包装列表就不能更改以避免异常。除非你准备好认真考虑需求以及不正确地满足这些需求的后果，否则不要这样做。请留意。

@node 为什么 list sort 没有返回排序列表？,如何在Python中指定和实施接口规范？,为什么字典key必须是不可变的？,设计和历史常见问题
@anchor{faq/design why-doesn-t-list-sort-return-the-sorted-list}@anchor{4254}
@subsection 为什么 list.sort() 没有返回排序列表？


在性能很重要的情况下，仅仅为了排序而复制一份列表将是一种浪费。因此， @ref{43f,,list.sort()} 对列表进行了适当的排序。为了提醒您这一事实，它不会返回已排序的列表。这样，当您需要排序的副本，但也需要保留未排序的版本时，就不会意外地覆盖列表。

如果要返回新列表，请使用内置 @ref{43e,,sorted()} 函数。此函数从提供的可迭代列表中创建新列表，对其进行排序并返回。例如，下面是如何迭代遍历字典并按keys排序:

@example
for key in sorted(mydict):
    ...  # do whatever with mydict[key]...
@end example

@node 如何在Python中指定和实施接口规范？,为什么没有goto？,为什么 list sort 没有返回排序列表？,设计和历史常见问题
@anchor{faq/design how-do-you-specify-and-enforce-an-interface-spec-in-python}@anchor{4255}
@subsection 如何在Python中指定和实施接口规范？


由C++和Java等语言提供的模块接口规范描述了模块的方法和函数的原型。许多人认为接口规范的编译时强制执行有助于构建大型程序。

Python 2.6添加了一个 @ref{4,,abc} 模块，允许定义抽象基类 (ABCs)。然后可以使用 @ref{449,,isinstance()} 和 @ref{44a,,issubclass()} 来检查实例或类是否实现了特定的ABC。 @ref{1f,,collections.abc} 模块定义了一组有用的ABCs 例如 @ref{18e7,,Iterable} ， @ref{18e5,,Container} , 和 @ref{9e9,,MutableMapping}

对于Python，通过对组件进行适当的测试规程，可以获得接口规范的许多好处。还有一个工具PyChecker，可用于查找由于子类化引起的问题。

一个好的模块测试套件既可以提供回归测试，也可以作为模块接口规范和一组示例。许多Python模块可以作为脚本运行，以提供简单的“自我测试”。即使是使用复杂外部接口的模块，也常常可以使用外部接口的简单“桩代码（stub）”模拟进行隔离测试。可以使用 @ref{67,,doctest} 和 @ref{11b,,unittest} 模块或第三方测试框架来构造详尽的测试套件，以运行模块中的每一行代码。

适当的测试规程可以帮助在Python中构建大型的、复杂的应用程序以及接口规范。事实上，它可能会更好，因为接口规范不能测试程序的某些属性。例如， @code{append()} 方法将向一些内部列表的末尾添加新元素；接口规范不能测试您的 @code{append()} 实现是否能够正确执行此操作，但是在测试套件中检查这个属性是很简单的。

编写测试套件非常有用，您可能希望设计代码时着眼于使其易于测试。一种日益流行的技术是面向测试的开发，它要求在编写任何实际代码之前，首先编写测试套件的各个部分。当然，Python允许您草率行事，根本不编写测试用例。

@node 为什么没有goto？,为什么原始字符串（r-strings）不能以反斜杠结尾？,如何在Python中指定和实施接口规范？,设计和历史常见问题
@anchor{faq/design why-is-there-no-goto}@anchor{4256}
@subsection 为什么没有goto？


可以使用异常捕获来提供 “goto结构” ，甚至可以跨函数调用工作的 。许多人认为异常捕获可以方便地模拟C，Fortran和其他语言的 "go" 或 "goto" 结构的所有合理用法。例如:

@example
class label(Exception): pass  # declare a label

try:
    ...
    if condition: raise label()  # goto label
    ...
except label:  # where to goto
    pass
...
@end example

但是不允许你跳到循环的中间，这通常被认为是滥用goto。谨慎使用。

@node 为什么原始字符串（r-strings）不能以反斜杠结尾？,为什么Python没有属性赋值的“with”语句？,为什么没有goto？,设计和历史常见问题
@anchor{faq/design why-can-t-raw-strings-r-strings-end-with-a-backslash}@anchor{4257}
@subsection 为什么原始字符串（r-strings）不能以反斜杠结尾？


更准确地说，它们不能以奇数个反斜杠结束：结尾处的不成对反斜杠会转义结束引号字符，留下未结束的字符串。

原始字符串的设计是为了方便想要执行自己的反斜杠转义处理的处理器(主要是正则表达式引擎)创建输入。此类处理器将不匹配的尾随反斜杠视为错误，因此原始字符串不允许这样做。反过来，允许通过使用引号字符转义反斜杠转义字符串。当r-string用于它们的预期目的时，这些规则工作的很好。

如果您正在尝试构建Windows路径名，请注意所有Windows系统调用都使用正斜杠:

@example
f = open("/mydir/file.txt")  # works fine!
@end example

如果您正在尝试为DOS命令构建路径名，请尝试以下示例

@example
dir = r"\this\is\my\dos\dir" "\\"
dir = r"\this\is\my\dos\dir\ "[:-1]
dir = "\\this\\is\\my\\dos\\dir\\"
@end example

@node 为什么Python没有属性赋值的“with”语句？,为什么 if/while/def/class语句需要冒号？,为什么原始字符串（r-strings）不能以反斜杠结尾？,设计和历史常见问题
@anchor{faq/design why-doesn-t-python-have-a-with-statement-for-attribute-assignments}@anchor{4258}
@subsection 为什么Python没有属性赋值的“with”语句？


Python有一个 'with' 语句，它封装了块的执行，在块的入口和出口调用代码。有些语言的结构是这样的:

@example
with obj:
    a = 1               # equivalent to obj.a = 1
    total = total + 1   # obj.total = obj.total + 1
@end example

在Python中，这样的结构是不明确的。

其他语言，如ObjectPascal、Delphi和C++ 使用静态类型，因此可以毫不含糊地知道分配给什么成员。这是静态类型的要点 -- 编译器 @emph{总是} 在编译时知道每个变量的作用域。

Python使用动态类型。事先不可能知道在运行时引用哪个属性。可以动态地在对象中添加或删除成员属性。这使得无法通过简单的阅读就知道引用的是什么属性：局部属性、全局属性还是成员属性？

例如，采用以下不完整的代码段:

@example
def foo(a):
    with a:
        print(x)
@end example

该代码段假设 "a" 必须有一个名为 "x" 的成员属性。然而，Python中并没有告诉解释器这一点。假设 "a" 是整数，会发生什么？如果有一个名为 "x" 的全局变量，它是否会在with块中使用？如您所见，Python的动态特性使得这样的选择更加困难。

然而，Python 可以通过赋值轻松实现 "with" 和类似语言特性（减少代码量）的主要好处。代替:

@example
function(args).mydict[index][index].a = 21
function(args).mydict[index][index].b = 42
function(args).mydict[index][index].c = 63
@end example

写成这样:

@example
ref = function(args).mydict[index][index]
ref.a = 21
ref.b = 42
ref.c = 63
@end example

这也具有提高执行速度的副作用，因为Python在运行时解析名称绑定，而第二个版本只需要执行一次解析。

@node 为什么 if/while/def/class语句需要冒号？,为什么Python在列表和元组的末尾允许使用逗号？,为什么Python没有属性赋值的“with”语句？,设计和历史常见问题
@anchor{faq/design why-are-colons-required-for-the-if-while-def-class-statements}@anchor{4259}
@subsection 为什么 if/while/def/class语句需要冒号？


冒号主要用于增强可读性(ABC语言实验的结果之一)。考虑一下这个:

@example
if a == b
    print(a)
@end example

与

@example
if a == b:
    print(a)
@end example

注意第二种方法稍微容易一些。请进一步注意，在这个FAQ解答的示例中，冒号是如何设置的；这是英语中的标准用法。

另一个次要原因是冒号使带有语法突出显示的编辑器更容易工作；他们可以寻找冒号来决定何时需要增加缩进，而不必对程序文本进行更精细的解析。

@node 为什么Python在列表和元组的末尾允许使用逗号？,,为什么 if/while/def/class语句需要冒号？,设计和历史常见问题
@anchor{faq/design why-does-python-allow-commas-at-the-end-of-lists-and-tuples}@anchor{425a}
@subsection 为什么Python在列表和元组的末尾允许使用逗号？


Python 允许您在列表，元组和字典的末尾添加一个尾随逗号:

@example
[1, 2, 3,]
('a', 'b', 'c',)
d = @{
    "A": [1, 5],
    "B": [6, 7],  # last trailing comma is optional but good style
@}
@end example

有几个理由允许这样做。

如果列表，元组或字典的字面值分布在多行中，则更容易添加更多元素，因为不必记住在上一行中添加逗号。这些行也可以重新排序，而不会产生语法错误。

不小心省略逗号会导致难以诊断的错误。例如:

@example
x = [
  "fee",
  "fie"
  "foo",
  "fum"
]
@end example

这个列表看起来有四个元素，但实际上包含三个 : "fee", "fiefoo" 和 "fum" 。总是加上逗号可以避免这个错误的来源。

允许尾随逗号也可以使编程代码更容易生成。

@node 代码库和插件 FAQ,扩展/嵌入常见问题,设计和历史常见问题,Python 常见问题
@anchor{faq/library doc}@anchor{425b}@anchor{faq/library library-and-extension-faq}@anchor{425c}
@section 代码库和插件 FAQ



@menu
* 通用的代码库问题:: 
* 通用任务:: 
* 线程相关:: 
* 输入输出: 输入输出<2>. 
* 网络 / Internet 编程:: 
* 数据库:: 
* 数学和数字:: 

@end menu

@node 通用的代码库问题,通用任务,,代码库和插件 FAQ
@anchor{faq/library general-library-questions}@anchor{425d}
@subsection 通用的代码库问题


@menu
* 如何找到可以用来做 XXX 的模块或应用？:: 
* math.py（socket.py，regex.py 等）的源文件在哪？: math py（socket py，regex py 等）的源文件在哪？. 
* 在 Unix 中怎样让 Python 脚本可执行？:: 
* Python 中有 curses/termcap 包吗？:: 
* Python 中存在类似 C 的 onexit() 函数的东西吗？: Python 中存在类似 C 的 onexit 函数的东西吗？. 
* 为什么我的信号处理函数不能工作？:: 

@end menu

@node 如何找到可以用来做 XXX 的模块或应用？,math py（socket py，regex py 等）的源文件在哪？,,通用的代码库问题
@anchor{faq/library how-do-i-find-a-module-or-application-to-perform-task-x}@anchor{425e}
@subsubsection 如何找到可以用来做 XXX 的模块或应用？


在 @ref{118f,,代码库参考} 中查找是否有适合的标准库模块。（如果你已经了解标准库的内容，可以跳过这一步）

对于第三方软件包，请搜索 Python Package Index@footnote{https://pypi.org} 或是 Google@footnote{https://www.google.com} 等其他搜索引擎。用“Python”加上一两个你需要的关键字通常会找到有用的东西。

@node math py（socket py，regex py 等）的源文件在哪？,在 Unix 中怎样让 Python 脚本可执行？,如何找到可以用来做 XXX 的模块或应用？,通用的代码库问题
@anchor{faq/library where-is-the-math-py-socket-py-regex-py-etc-source-file}@anchor{425f}
@subsubsection math.py（socket.py，regex.py 等）的源文件在哪？


如果找不到模块的源文件，可能它是一个内建的模块，或是使用 C，C++ 或其他编译型语言实现的动态加载模块。这种情况下可能是没有源码文件的，类似 @code{mathmodule.c} 这样的文件会存放在 C 代码目录中（但不在 Python 目录中）。

Python 中（至少）有三类模块：


@enumerate 

@item 
使用 Python 编写的模块（.py)；

@item 
使用 C 编写的动态加载模块（.dll，.pyd，.so，.sl 等）；

@item 
使用 C 编写并链接到解释器的模块，要获取此列表，输入：

@example
import sys
print(sys.builtin_module_names)
@end example
@end enumerate

@node 在 Unix 中怎样让 Python 脚本可执行？,Python 中有 curses/termcap 包吗？,math py（socket py，regex py 等）的源文件在哪？,通用的代码库问题
@anchor{faq/library how-do-i-make-a-python-script-executable-on-unix}@anchor{4260}
@subsubsection 在 Unix 中怎样让 Python 脚本可执行？


你需要做两件事：文件必须是可执行的，并且第一行需要以 @code{#!} 开头，后面跟上 Python 解释器的路径。

第一点可以用执行 @code{chmod +x scriptfile} 或是 @code{chmod 755 scriptfile} 做到。

第二点有很多种做法，最直接的方式是：

@example
#!/usr/local/bin/python
@end example

在文件第一行，使用你所在平台上的 Python 解释器的路径。

如果你希望脚本不依赖 Python 解释器的具体路径，你也可以使用 @code{env} 程序。假设你的 Python 解释器所在目录已经添加到了 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 环境变量中，几乎所有的类 Unix 系统都支持下面的写法：

@example
#!/usr/bin/env python
@end example

@emph{不要} 在 CGI 脚本中这样做。CGI 脚本的 
@geindex PATH
@geindex 环境变量; PATH
@code{PATH} 环境变量通常会非常精简，所以你必须使用解释器的完整绝对路径。

有时候，用户的环境变量如果太长，可能会导致 @code{/usr/bin/env} 执行失败；又或者甚至根本就不存在 env 程序。在这种情况下，你可以尝试使用下面的 hack 方法（来自 Alex Rezinsky）：

@example
#! /bin/sh
""":"
exec python $0 $@{1+"$@@"@}
"""
@end example

这样做有一个小小的缺点，它会定义脚本的 __doc__ 字符串。不过可以这样修复：

@example
__doc__ = """...Whatever..."""
@end example

@node Python 中有 curses/termcap 包吗？,Python 中存在类似 C 的 onexit 函数的东西吗？,在 Unix 中怎样让 Python 脚本可执行？,通用的代码库问题
@anchor{faq/library is-there-a-curses-termcap-package-for-python}@anchor{4261}
@subsubsection Python 中有 curses/termcap 包吗？


@c XXX curses *is* built by default, isn't it?

对于类 Unix 系统：标准 Python 源码发行版会在 Modules@footnote{https://github.com/python/cpython/tree/3.8/Modules} 子目录中附带 curses 模块，但默认并不会编译。（注意：在 Windows 平台下不可用 —— Windows 中没有 curses 模块。）

@ref{2c,,curses} 模块支持基本的 curses 特性，同时也支持 ncurses 和 SYSV curses 中的很多额外功能，比如颜色、不同的字符集支持、填充和鼠标支持。这意味着这个模块不兼容只有 BSD curses 模块的操作系统，但是目前仍在维护的系统应该都不会存在这种情况。

对于 Windows 平台：使用 consolelib 模块@footnote{http://effbot.org/zone/console-index.htm}.

@node Python 中存在类似 C 的 onexit 函数的东西吗？,为什么我的信号处理函数不能工作？,Python 中有 curses/termcap 包吗？,通用的代码库问题
@anchor{faq/library is-there-an-equivalent-to-c-s-onexit-in-python}@anchor{4262}
@subsubsection Python 中存在类似 C 的 onexit() 函数的东西吗？


@ref{c,,atexit} 模块提供了一个与 C 的 @code{onexit()} 函数类似的注册函数。

@node 为什么我的信号处理函数不能工作？,,Python 中存在类似 C 的 onexit 函数的东西吗？,通用的代码库问题
@anchor{faq/library why-don-t-my-signal-handlers-work}@anchor{4263}
@subsubsection 为什么我的信号处理函数不能工作？


最常见的问题是信号处理函数没有正确定义参数列表。它会被这样调用：

@example
handler(signum, frame)
@end example

因此函数应该定义两个参数：

@example
def handler(signum, frame):
    ...
@end example

@node 通用任务,线程相关,通用的代码库问题,代码库和插件 FAQ
@anchor{faq/library common-tasks}@anchor{4264}
@subsection 通用任务


@menu
* 怎样测试 Python 程序或组件？:: 
* 怎样用 docstring 创建文档？:: 
* 怎样一次只获取一个按键？:: 

@end menu

@node 怎样测试 Python 程序或组件？,怎样用 docstring 创建文档？,,通用任务
@anchor{faq/library how-do-i-test-a-python-program-or-component}@anchor{4265}
@subsubsection 怎样测试 Python 程序或组件？


Python 带有两个测试框架。@ref{67,,doctest} 模块从模块的 docstring 中寻找示例并执行，对比输出是否与 docstring 中给出的是否一致。

@ref{11b,,unittest} 模块是一个模仿 Java 和 Smalltalk 测试框架的更棒的测试框架。

为了使测试更容易，你应该在程序中使用良好的模块化设计。程序中的绝大多数功能都应该用函数或类方法封装 —— 有时这样做会有额外惊喜，程序会运行得更快（因为局部变量比全局变量访问要快）。除此之外，程序应该避免依赖可变的局部变量，这会使得测试困难许多。

程序的“全局主逻辑”应该尽量简单：

@example
if __name__ == "__main__":
    main_logic()
@end example

并放置在程序主模块的最后面。

一旦你的程序已经用函数和类完善地组织起来，你就应该编写测试函数来测试其行为。可以使用自动执行一系列测试函数的测试集与每个模块进行关联。听起来似乎需要大量的工作，但是因为 Python 非常简洁和灵活，所以实际上会相当简单。在编写“生产代码”的同时别忘了也要编写测试函数，你会发现编程会变得更愉快、更有趣，因为这样会使得发现 bug 和设计缺陷更加容易。

程序主模块之外的其他“辅助模块”中可以增加自测试的入口。

@example
if __name__ == "__main__":
    self_test()
@end example

通过使用 Python 实现的“假”接口，即使是需要与复杂的外部接口交互的程序也可以在外部接口不可用时进行测试。

@node 怎样用 docstring 创建文档？,怎样一次只获取一个按键？,怎样测试 Python 程序或组件？,通用任务
@anchor{faq/library how-do-i-create-documentation-from-doc-strings}@anchor{4266}
@subsubsection 怎样用 docstring 创建文档？


@ref{d9,,pydoc} 模块可以用 Python 源码中的 docstring 创建 HTML 文件。也可以使用 epydoc@footnote{http://epydoc.sourceforge.net/} 来只通过 docstring 创建 API 文档。Sphinx@footnote{http://sphinx-doc.org} 也可以引入 docstring 的内容。

@node 怎样一次只获取一个按键？,,怎样用 docstring 创建文档？,通用任务
@anchor{faq/library how-do-i-get-a-single-keypress-at-a-time}@anchor{4267}
@subsubsection 怎样一次只获取一个按键？


在类 Unix 系统中有多种方案。最直接的方法是使用 curses，但是 curses 模块太大了，难以学习。

@c XXX this doesn't work out of the box, some IO expert needs to check why
@c 
@c Here's a solution without curses::
@c 
@c import termios, fcntl, sys, os
@c fd = sys.stdin.fileno()
@c 
@c oldterm = termios.tcgetattr(fd)
@c newattr = termios.tcgetattr(fd)
@c newattr[3] = newattr[3] & ~termios.ICANON & ~termios.ECHO
@c termios.tcsetattr(fd, termios.TCSANOW, newattr)
@c 
@c oldflags = fcntl.fcntl(fd, fcntl.F_GETFL)
@c fcntl.fcntl(fd, fcntl.F_SETFL, oldflags | os.O_NONBLOCK)
@c 
@c try:
@c     while True:
@c         try:
@c             c = sys.stdin.read(1)
@c             print("Got character", repr(c))
@c         except OSError:
@c             pass
@c finally:
@c     termios.tcsetattr(fd, termios.TCSAFLUSH, oldterm)
@c     fcntl.fcntl(fd, fcntl.F_SETFL, oldflags)
@c 
@c You need the :mod:`termios` and the :mod:`fcntl` module for any of this to
@c work, and I've only tried it on Linux, though it should work elsewhere.  In
@c this code, characters are read and printed one at a time.
@c 
@c :func:`termios.tcsetattr` turns off stdin's echoing and disables canonical
@c mode.  :func:`fcntl.fnctl` is used to obtain stdin's file descriptor flags
@c and modify them for non-blocking mode.  Since reading stdin when it is empty
@c results in an :exc:`OSError`, this error is caught and ignored.
@c 
@c .. versionchanged:: 3.3
@c    *sys.stdin.read* used to raise :exc:`IOError`. Starting from Python 3.3
@c    :exc:`IOError` is alias for :exc:`OSError`.

@node 线程相关,输入输出<2>,通用任务,代码库和插件 FAQ
@anchor{faq/library threads}@anchor{4268}
@subsection 线程相关


@menu
* 程序中怎样使用线程？:: 
* 我的线程都没有运行，为什么？:: 
* 如何将任务分配给多个工作线程？:: 
* 怎样修改全局变量是线程安全的？:: 
* 不能删除全局解释器锁吗？:: 

@end menu

@node 程序中怎样使用线程？,我的线程都没有运行，为什么？,,线程相关
@anchor{faq/library how-do-i-program-using-threads}@anchor{4269}
@subsubsection 程序中怎样使用线程？


一定要使用 @ref{109,,threading} 模块，不要使用 @ref{3,,_thread} 模块。@ref{109,,threading} 模块对 @ref{3,,_thread} 模块提供的底层线程原语做了更易用的抽象。

Aahz 的非常实用的 threading 教程中有一些幻灯片；可以参阅 @indicateurl{http://www.pythoncraft.com/OSCON2001/} 。

@node 我的线程都没有运行，为什么？,如何将任务分配给多个工作线程？,程序中怎样使用线程？,线程相关
@anchor{faq/library none-of-my-threads-seem-to-run-why}@anchor{426a}
@subsubsection 我的线程都没有运行，为什么？


一旦主线程退出，所有的子线程都会被杀掉。你的主线程运行得太快了，子线程还没来得及工作。

简单的解决方法是在程序中加一个时间足够长的 sleep，让子线程能够完成运行。

@example
import threading, time

def thread_task(name, n):
    for i in range(n):
        print(name, i)

for i in range(10):
    T = threading.Thread(target=thread_task, args=(str(i), i))
    T.start()

time.sleep(10)  # <---------------------------!
@end example

但目前（在许多平台上）线程不是并行运行的，而是按顺序依次执行！原因是系统线程调度器在前一个线程阻塞之前不会启动新线程。

简单的解决方法是在运行函数的开始处加一个时间很短的 sleep。

@example
def thread_task(name, n):
    time.sleep(0.001)  # <--------------------!
    for i in range(n):
        print(name, i)

for i in range(10):
    T = threading.Thread(target=thread_task, args=(str(i), i))
    T.start()

time.sleep(10)
@end example

比起用 @ref{67a,,time.sleep()} 猜一个合适的等待时间，使用信号量机制会更好些。有一个办法是使用 @ref{da,,queue} 模块创建一个 queue 对象，让每一个线程在运行结束时 append 一个令牌到 queue 对象中，主线程中从 queue 对象中读取与线程数量一致的令牌数量即可。

@node 如何将任务分配给多个工作线程？,怎样修改全局变量是线程安全的？,我的线程都没有运行，为什么？,线程相关
@anchor{faq/library how-do-i-parcel-out-work-among-a-bunch-of-worker-threads}@anchor{426b}
@subsubsection 如何将任务分配给多个工作线程？


最简单的方法是使用新的 @ref{22,,concurrent.futures} 模块，尤其是其中的 @ref{27a,,ThreadPoolExecutor} 类。

或者，如果你想更好地控制分发算法，你也可以自己写逻辑实现。使用 @ref{da,,queue} 模块来创建任务列表队列。@ref{d11,,Queue} 类维护一个了一个存有对象的列表，提供了 @code{.put(obj)} 方法添加元素，并且可以用 @code{.get()} 方法获取元素。这个类会使用必要的加锁操作，以此确保每个任务只会执行一次。

这是一个简单的例子：

@example
import threading, queue, time

# The worker thread gets jobs off the queue.  When the queue is empty, it
# assumes there will be no more work and exits.
# (Realistically workers will run until terminated.)
def worker():
    print('Running worker')
    time.sleep(0.1)
    while True:
        try:
            arg = q.get(block=False)
        except queue.Empty:
            print('Worker', threading.currentThread(), end=' ')
            print('queue empty')
            break
        else:
            print('Worker', threading.currentThread(), end=' ')
            print('running with argument', arg)
            time.sleep(0.5)

# Create queue
q = queue.Queue()

# Start a pool of 5 workers
for i in range(5):
    t = threading.Thread(target=worker, name='worker %i' % (i+1))
    t.start()

# Begin adding work to the queue
for i in range(50):
    q.put(i)

# Give threads time to run
print('Main thread sleeping')
time.sleep(5)
@end example

运行时会产生如下输出：

@example
Running worker
Running worker
Running worker
Running worker
Running worker
Main thread sleeping
Worker <Thread(worker 1, started 130283832797456)> running with argument 0
Worker <Thread(worker 2, started 130283824404752)> running with argument 1
Worker <Thread(worker 3, started 130283816012048)> running with argument 2
Worker <Thread(worker 4, started 130283807619344)> running with argument 3
Worker <Thread(worker 5, started 130283799226640)> running with argument 4
Worker <Thread(worker 1, started 130283832797456)> running with argument 5
...
@end example

查看模块的文档以获取更多信息；@ref{d11,,Queue} 类提供了多种接口。

@node 怎样修改全局变量是线程安全的？,不能删除全局解释器锁吗？,如何将任务分配给多个工作线程？,线程相关
@anchor{faq/library what-kinds-of-global-value-mutation-are-thread-safe}@anchor{426c}
@subsubsection 怎样修改全局变量是线程安全的？


Python VM 内部会使用 @ref{500,,global interpreter lock} （GIL）来确保同一时间只有一个线程运行。通常 Python 只会在字节码指令之间切换线程；切换的频率可以通过设置 @ref{be4,,sys.setswitchinterval()} 指定。从 Python 程序的角度来看，每一条字节码指令以及每一条指令对应的 C 代码实现都是原子的。

理论上说，具体的结果要看具体的 PVM 字节码实现对指令的解释。而实际上，对内建类型（int，list，dict 等）的共享变量的“类原子”操作都是原子的。

举例来说，下面的操作是原子的（L、L1、L2 是列表，D、D1、D2 是字典，x、y 是对象，i，j 是 int 变量）：

@example
L.append(x)
L1.extend(L2)
x = L[i]
x = L.pop()
L1[i:j] = L2
L.sort()
x = y
x.field = y
D[x] = y
D1.update(D2)
D.keys()
@end example

这些不是原子的：

@example
i = i+1
L.append(L[-1])
L[i] = L[j]
D[x] = D[x] + 1
@end example

覆盖其他对象的操作会在其他对象的引用计数变成 0 时触发其 @ref{919,,__del__()} 方法，这可能会产生一些影响。对字典和列表进行大量操作时尤其如此。如果有疑问的话，使用互斥锁！

@node 不能删除全局解释器锁吗？,,怎样修改全局变量是线程安全的？,线程相关
@anchor{faq/library can-t-we-get-rid-of-the-global-interpreter-lock}@anchor{426d}
@subsubsection 不能删除全局解释器锁吗？


@c XXX link to dbeazley's talk about GIL?

@ref{500,,global interpreter lock} （GIL）通常被视为 Python 在高端多核服务器上开发时的阻力，因为（几乎）所有 Python 代码只有在获取到 GIL 时才能运行，所以多线程的 Python 程序只能有效地使用一个 CPU。

在 Python 1.5 时代，Greg Stein 开发了一个完整的补丁包（“free threadings” 补丁），移除了 GIL，并用粒度更合适的锁来代替。Adam Olsen 最近也在他的 python-safethread@footnote{https://code.google.com/archive/p/python-safethread} 项目里做了类似的实验。不幸的是，由于为了移除 GIL 而使用了大量细粒度的锁，这两个实验在单线程测试中的性能都有明显的下降（至少慢 30%）。

但这并意味着你不能在多核机器上很好地使用 Python！你只需将任务划分为多*进程*，而不是多*线程*。新的 @ref{22,,concurrent.futures} 模块中的 @ref{2a3,,ProcessPoolExecutor} 类提供了一个简单的方法；如果你想对任务分发做更多控制，可以使用 @ref{b7,,multiprocessing} 模块提供的底层 API。

恰当地使用 C 拓展也很有用；使用 C 拓展处理耗时较久的任务时，拓展可以在线程执行 C 代码时释放 GIL，让其他线程执行。@ref{144,,zlib} 和 @ref{8d,,hashlib} 等标准库模块已经这样做了。

也有建议说 GIL 应该是解释器状态锁，而不是完全的全局锁；解释器不应该共享对象。不幸的是，这也不可能发生。由于目前许多对象的实现都有全局的状态，因此这是一个艰巨的工作。举例来说，小整型数和短字符串会缓存起来，这些缓存将不得不移动到解释器状态中。其他对象类型都有自己的自由变量列表，这些自由变量列表也必须移动到解释器状态中。等等。

我甚至怀疑这些工作是否可能在优先的时间内完成，因为同样的问题在第三方拓展中也会存在。第三方拓展编写的速度可比你将它们转换为把全局状态存入解释器状态中的速度快得多。

最后，假设多个解释器不共享任何状态，那么这样做比每个进程一个解释器好在哪里呢？

@node 输入输出<2>,网络 / Internet 编程,线程相关,代码库和插件 FAQ
@anchor{faq/library input-and-output}@anchor{426e}
@subsection 输入输出


@menu
* 怎样删除文件？（以及其他文件相关的问题……）:: 
* 怎样复制文件？:: 
* 怎样读取（或写入）二进制数据？:: 
* 似乎 os.popen() 创建的管道不能使用 os.read()，这是为什么？: 似乎 os popen 创建的管道不能使用 os read ，这是为什么？. 
* 怎样访问（RS232）串口？:: 
* 为什么关闭 sys.stdout（stdin，stderr）并不会真正关掉它？: 为什么关闭 sys stdout（stdin，stderr）并不会真正关掉它？. 

@end menu

@node 怎样删除文件？（以及其他文件相关的问题……）,怎样复制文件？,,输入输出<2>
@anchor{faq/library how-do-i-delete-a-file-and-other-file-questions}@anchor{426f}
@subsubsection 怎样删除文件？（以及其他文件相关的问题……）


使用 @code{os.remove(filename)} 或 @code{os.unlink(filename)}。查看 @ref{c4,,os} 模块以获取更多文档。这两个函数是一样的，@ref{a37,,unlink()} 是这个函数在 Unix 系统调用中的名字。

如果要删除目录，应该使用 @ref{a35,,os.rmdir()}；使用 @ref{a31,,os.mkdir()} 创建目录。@code{os.makedirs(path)} 会创建 @code{path} 中任何不存在的目录。@code{os.removedirs(path)} 则会删除其中的目录，只要它们都是空的；如果你想删除整个目录以及其中的内容，可以使用 @ref{21c,,shutil.rmtree()}。

重命名文件可以使用 @code{os.rename(old_path, new_path)}。

如果需要截断文件，使用 @code{f = open(filename, "rb+")} 打开文件，然后使用 @code{f.truncate(offset)}；offset 默认是当前的搜索位置。也可以对使用 @ref{65f,,os.open()} 打开的文件使用 @code{os.ftruncate(fd, offset)}，其中 @emph{fd} 是文件描述符（一个小的整型数）。

@ref{e9,,shutil} 模块也包含了一些处理文件的函数，包括 @ref{258,,copyfile()}，@ref{21a,,copytree()} 和 @ref{21c,,rmtree()}。

@node 怎样复制文件？,怎样读取（或写入）二进制数据？,怎样删除文件？（以及其他文件相关的问题……）,输入输出<2>
@anchor{faq/library how-do-i-copy-a-file}@anchor{4270}
@subsubsection 怎样复制文件？


@ref{e9,,shutil} 模块有一个 @ref{258,,copyfile()} 函数。注意在 MacOS 9  中不会复制 resource fork 和 Finder info。

@node 怎样读取（或写入）二进制数据？,似乎 os popen 创建的管道不能使用 os read ，这是为什么？,怎样复制文件？,输入输出<2>
@anchor{faq/library how-do-i-read-or-write-binary-data}@anchor{4271}
@subsubsection 怎样读取（或写入）二进制数据？


要读写复杂的二进制数据格式，最好使用 @ref{f8,,struct} 模块。该模块可以读取包含二进制数据（通常是数字）的字符串并转换为 Python 对象，反之亦然。

举例来说，下面的代码会从文件中以大端序格式读取一个 2 字节的整型和一个 4 字节的整型：

@example
import struct

with open(filename, "rb") as f:
    s = f.read(8)
    x, y, z = struct.unpack(">hhl", s)
@end example

格式字符串中的 ‘>’ 强制以大端序读取数据；字母 ‘h’ 从字符串中读取一个“短整型”（2 字节），字母 ‘l’ 读取一个“长整型”（4 字节）。

对于更常规的数据（例如整型或浮点类型的列表），你也可以使用 @ref{7,,array} 模块。

@cartouche
@quotation 注解 
要读写二进制数据的话，需要强制以二进制模式打开文件（这里为 @ref{4ea,,open()} 函数传入 @code{"rb"}）。如果（默认）传入 @code{"r"} 的话，文件会以文本模式打开，@code{f.read()} 会返回 @ref{329,,str} 对象，而不是 @ref{32a,,bytes} 对象。
@end quotation
@end cartouche

@node 似乎 os popen 创建的管道不能使用 os read ，这是为什么？,怎样访问（RS232）串口？,怎样读取（或写入）二进制数据？,输入输出<2>
@anchor{faq/library i-can-t-seem-to-use-os-read-on-a-pipe-created-with-os-popen-why}@anchor{4272}
@subsubsection 似乎 os.popen() 创建的管道不能使用 os.read()，这是为什么？


@ref{662,,os.read()} 是一个底层函数，它接收的是文件描述符 —— 用小整型数表示的打开的文件。@ref{2a9,,os.popen()} 创建的是一个高级文件对象，和内建的 @ref{4ea,,open()} 方法返回的类型一样。因此，如果要从 @ref{2a9,,os.popen()} 创建的管道 @emph{p} 中读取 @emph{n} 个字节的话，你应该使用 @code{p.read(n)}。

@c XXX update to use subprocess. See the :ref:`subprocess-replacements` section.
@c 
@c How do I run a subprocess with pipes connected to both input and output?
@c ------------------------------------------------------------------------
@c 
@c Use the :mod:`popen2` module.  For example::
@c 
@c    import popen2
@c    fromchild, tochild = popen2.popen2("command")
@c    tochild.write("input\n")
@c    tochild.flush()
@c    output = fromchild.readline()
@c 
@c Warning: in general it is unwise to do this because you can easily cause a
@c deadlock where your process is blocked waiting for output from the child
@c while the child is blocked waiting for input from you.  This can be caused
@c by the parent expecting the child to output more text than it does or
@c by data being stuck in stdio buffers due to lack of flushing.
@c The Python parent can of course explicitly flush the data it sends to the
@c child before it reads any output, but if the child is a naive C program it
@c may have been written to never explicitly flush its output, even if it is
@c interactive, since flushing is normally automatic.
@c 
@c Note that a deadlock is also possible if you use :func:`popen3` to read
@c stdout and stderr. If one of the two is too large for the internal buffer
@c (increasing the buffer size does not help) and you ``read()`` the other one
@c first, there is a deadlock, too.
@c 
@c Note on a bug in popen2: unless your program calls ``wait()`` or
@c ``waitpid()``, finished child processes are never removed, and eventually
@c calls to popen2 will fail because of a limit on the number of child
@c processes.  Calling :func:`os.waitpid` with the :data:`os.WNOHANG` option can
@c prevent this; a good place to insert such a call would be before calling
@c ``popen2`` again.
@c 
@c In many cases, all you really need is to run some data through a command and
@c get the result back.  Unless the amount of data is very large, the easiest
@c way to do this is to write it to a temporary file and run the command with
@c that temporary file as input.  The standard module :mod:`tempfile` exports a
@c :func:`~tempfile.mktemp` function to generate unique temporary file names. ::
@c 
@c    import tempfile
@c    import os
@c 
@c    class Popen3:
@c        """
@c        This is a deadlock-safe version of popen that returns
@c        an object with errorlevel, out (a string) and err (a string).
@c        (capturestderr may not work under windows.)
@c        Example: print(Popen3('grep spam','\n\nhere spam\n\n').out)
@c        """
@c        def __init__(self,command,input=None,capturestderr=None):
@c            outfile=tempfile.mktemp()
@c            command="( %s ) > %s" % (command,outfile)
@c            if input:
@c                infile=tempfile.mktemp()
@c                open(infile,"w").write(input)
@c                command=command+" <"+infile
@c            if capturestderr:
@c                errfile=tempfile.mktemp()
@c                command=command+" 2>"+errfile
@c            self.errorlevel=os.system(command) >> 8
@c            self.out=open(outfile,"r").read()
@c            os.remove(outfile)
@c            if input:
@c                os.remove(infile)
@c            if capturestderr:
@c                self.err=open(errfile,"r").read()
@c                os.remove(errfile)
@c 
@c Note that many interactive programs (e.g. vi) don't work well with pipes
@c substituted for standard input and output.  You will have to use pseudo ttys
@c ("ptys") instead of pipes. Or you can use a Python interface to Don Libes'
@c "expect" library.  A Python extension that interfaces to expect is called
@c "expy" and available from http://expectpy.sourceforge.net.  A pure Python
@c solution that works like expect is `pexpect
@c <https://pypi.org/project/pexpect/>`_.

@node 怎样访问（RS232）串口？,为什么关闭 sys stdout（stdin，stderr）并不会真正关掉它？,似乎 os popen 创建的管道不能使用 os read ，这是为什么？,输入输出<2>
@anchor{faq/library how-do-i-access-the-serial-rs232-port}@anchor{4273}
@subsubsection 怎样访问（RS232）串口？


对于 Win32，POSIX（Linux，BSD 等），Jython：

@quotation

@indicateurl{http://pyserial.sourceforge.net}
@end quotation

对于 Unix，查看 Mitch Chapman 发布的帖子：

@quotation

@indicateurl{https://groups.google.com/groups?selm=34A04430.CF9@@ohioee.com}
@end quotation

@node 为什么关闭 sys stdout（stdin，stderr）并不会真正关掉它？,,怎样访问（RS232）串口？,输入输出<2>
@anchor{faq/library why-doesn-t-closing-sys-stdout-stdin-stderr-really-close-it}@anchor{4274}
@subsubsection 为什么关闭 sys.stdout（stdin，stderr）并不会真正关掉它？


Python @ref{b3b,,文件对象} 是一个对底层 C 文件描述符的高层抽象。

对于在 Python 中通过内建的 @ref{4ea,,open()} 函数创建的多数文件对象来说，@code{f.close()} 从 Python 的角度将其标记为已关闭，并且会关闭底层的 C 文件描述符。在 @code{f} 被垃圾回收的时候，析构函数中也会自动处理。

但由于 stdin，stdout 和 stderr 在 C 中的特殊地位，在 Python 中也会对它们做特殊处理。运行 @code{sys.stdout.close()} 会将 Python 的文件对象标记为已关闭，但是*不会*关闭与之关联的文件描述符。

要关闭这三者的 C 文件描述符的话，首先你应该确认确实需要关闭它（比如，这可能会影响到处理 I/O 的拓展）。如果确实需要这么做的话，使用 @ref{3ca,,os.close()}：

@example
os.close(stdin.fileno())
os.close(stdout.fileno())
os.close(stderr.fileno())
@end example

或者也可以使用常量 0，1，2 代替。

@node 网络 / Internet 编程,数据库,输入输出<2>,代码库和插件 FAQ
@anchor{faq/library network-internet-programming}@anchor{4275}
@subsection 网络 / Internet 编程


@menu
* Python 中的 WWW 工具是什么？:: 
* 怎样模拟发送 CGI 表单（METHOD=POST）？:: 
* 生成 HTML 需要使用什么模块？:: 
* 怎样使用 Python 脚本发送邮件？:: 
* socket 的 connect() 方法怎样避免阻塞？: socket 的 connect 方法怎样避免阻塞？. 

@end menu

@node Python 中的 WWW 工具是什么？,怎样模拟发送 CGI 表单（METHOD=POST）？,,网络 / Internet 编程
@anchor{faq/library what-www-tools-are-there-for-python}@anchor{4276}
@subsubsection Python 中的 WWW 工具是什么？


参阅代码库参考手册中 @ref{2b69,,互联网协议和支持} 和 @ref{276f,,互联网数据处理} 这两章的内容。Python 有大量模块来帮助你构建服务端和客户端 web 系统。

@c XXX check if wiki page is still up to date

Paul Boddie 维护了一份可用框架的概览，见 @indicateurl{https://wiki.python.org/moin/WebProgramming} 。

Cameron Laird 维护了一份关于 Python web 技术的实用网页的集合，见 @indicateurl{http://phaseit.net/claird/comp.lang.python/web_python} 。

@node 怎样模拟发送 CGI 表单（METHOD=POST）？,生成 HTML 需要使用什么模块？,Python 中的 WWW 工具是什么？,网络 / Internet 编程
@anchor{faq/library how-can-i-mimic-cgi-form-submission-method-post}@anchor{4277}
@subsubsection 怎样模拟发送 CGI 表单（METHOD=POST）？


我需要通过 POST 表单获取网页，有什么代码能简单做到吗？

是的，这里有一个使用 urllib.request 的简单例子：

@example
#!/usr/local/bin/python

import urllib.request

# build the query string
qs = "First=Josephine&MI=Q&Last=Public"

# connect and send the server a path
req = urllib.request.urlopen('http://www.some-server.out-there'
                             '/cgi-bin/some-cgi-script', data=qs)
with req:
    msg, hdrs = req.read(), req.info()
@end example

注意，通常在百分号编码的 POST 操作中，查询字符串必须使用 @ref{785,,urllib.parse.urlencode()} 处理一下。举个例子，如果要发送 @code{name=Guy Steele, Jr.} 的话：

@example
>>> import urllib.parse
>>> urllib.parse.urlencode(@{'name': 'Guy Steele, Jr.'@})
'name=Guy+Steele%2C+Jr.'
@end example


@subsubheading 参见


查看 @ref{2c4e,,HOWTO 使用 urllib 包获取网络资源} 获取更多示例。


@node 生成 HTML 需要使用什么模块？,怎样使用 Python 脚本发送邮件？,怎样模拟发送 CGI 表单（METHOD=POST）？,网络 / Internet 编程
@anchor{faq/library what-module-should-i-use-to-help-with-generating-html}@anchor{4278}
@subsubsection 生成 HTML 需要使用什么模块？


@c XXX add modern template languages

你可以在 Web 编程 wiki 页面@footnote{https://wiki.python.org/moin/WebProgramming} 找到许多有用的链接。

@node 怎样使用 Python 脚本发送邮件？,socket 的 connect 方法怎样避免阻塞？,生成 HTML 需要使用什么模块？,网络 / Internet 编程
@anchor{faq/library how-do-i-send-mail-from-a-python-script}@anchor{4279}
@subsubsection 怎样使用 Python 脚本发送邮件？


使用 @ref{ed,,smtplib} 标准库模块。

下面是一个很简单的交互式发送邮件的代码。这个方法适用于任何支持 SMTP 协议的主机。

@example
import sys, smtplib

fromaddr = input("From: ")
toaddrs  = input("To: ").split(',')
print("Enter message, end with ^D:")
msg = '@w{'}
while True:
    line = sys.stdin.readline()
    if not line:
        break
    msg += line

# The actual mail send
server = smtplib.SMTP('localhost')
server.sendmail(fromaddr, toaddrs, msg)
server.quit()
@end example

在 Unix 系统中还可以使用 sendmail。sendmail 程序的位置在不同系统中不一样，有时是在 @code{/usr/lib/sendmail}，有时是在 @code{/usr/sbin/sendmail}。sendmail 手册页面会对你有所帮助。以下是示例代码：

@example
import os

SENDMAIL = "/usr/sbin/sendmail"  # sendmail location
p = os.popen("%s -t -i" % SENDMAIL, "w")
p.write("To: receiver@@example.com\n")
p.write("Subject: test\n")
p.write("\n")  # blank line separating headers from body
p.write("Some text\n")
p.write("some more text\n")
sts = p.close()
if sts != 0:
    print("Sendmail exit status", sts)
@end example

@node socket 的 connect 方法怎样避免阻塞？,,怎样使用 Python 脚本发送邮件？,网络 / Internet 编程
@anchor{faq/library how-do-i-avoid-blocking-in-the-connect-method-of-a-socket}@anchor{427a}
@subsubsection socket 的 connect() 方法怎样避免阻塞？


通常会用 @ref{e5,,select} 模块处理 socket 异步 I/O。

要避免 TCP 连接阻塞，你可以设置将 socket 设置为非阻塞模式。此时当调用 @code{connect()} 时，要么连接会立刻建立好（几乎不可能），要么会收到一个包含了错误码 @code{.error} 的异常。@code{errno.EINPROGRESS} 表示连接正在进行，但还没有完成。不同的系统会返回不同的值，所以你需要确认你使用的系统会返回什么。

你可以使用 @code{connect_ex()} 方法来避免产生异常。这个方法只会返回错误码。如果需要轮询的话，你可以再次调用 @code{connect_ex()} —— @code{0} 或 @code{errno.EISCONN} 表示连接已建立，或者你也可以用 select 检查这个 socket 是否可写。

@cartouche
@quotation 注解 
@ref{b,,asyncore} 模块提供了编写非阻塞网络代码框架性的方法。第三方的 Twisted@footnote{https://twistedmatrix.com/trac/} 库也很常用且功能强大。
@end quotation
@end cartouche

@node 数据库,数学和数字,网络 / Internet 编程,代码库和插件 FAQ
@anchor{faq/library databases}@anchor{427b}
@subsection 数据库


@menu
* Python 中有数据库包的接口吗？:: 
* 在 Python 中如何实现持久化对象？:: 

@end menu

@node Python 中有数据库包的接口吗？,在 Python 中如何实现持久化对象？,,数据库
@anchor{faq/library are-there-any-interfaces-to-database-packages-in-python}@anchor{427c}
@subsubsection Python 中有数据库包的接口吗？


有的。

标准 Python 还包含了基于磁盘的哈希接口例如 @ref{35,,DBM} 和 @ref{34,,GDBM} 。除此之外还有 @ref{f2,,sqlite3} 模块，该模块提供了一个轻量级的基于磁盘的关系型数据库。

大多数关系型数据库都已经支持。查看 数据库编程 wiki 页面@footnote{https://wiki.python.org/moin/DatabaseProgramming} 获取更多信息。

@node 在 Python 中如何实现持久化对象？,,Python 中有数据库包的接口吗？,数据库
@anchor{faq/library how-do-you-implement-persistent-objects-in-python}@anchor{427d}
@subsubsection 在 Python 中如何实现持久化对象？


@ref{ca,,pickle} 库模块以一种非常通用的方式解决了这个问题（虽然你依然不能用它保存打开的文件、套接字或窗口之类的东西），此外 @ref{e7,,shelve} 库模块可使用 pickle 和 (g)dbm 来创建包含任意 Python 对象的持久化映射。

@node 数学和数字,,数据库,代码库和插件 FAQ
@anchor{faq/library mathematics-and-numerics}@anchor{427e}
@subsection 数学和数字


@menu
* Python 中怎样生成随机数？:: 

@end menu

@node Python 中怎样生成随机数？,,,数学和数字
@anchor{faq/library how-do-i-generate-random-numbers-in-python}@anchor{427f}
@subsubsection Python 中怎样生成随机数？


@ref{dc,,random} 标准库模块实现了随机数生成器，使用起来非常简单：

@example
import random
random.random()
@end example

这个函数会返回 [0, 1) 之间的随机浮点数。

该模块中还有许多其他的专门的生成器，例如：


@itemize *

@item 
@code{randrange(a, b)} 返回 [a, b) 区间内的一个整型数。

@item 
@code{uniform(a, b)} 返回 [a, b) 区间之间的浮点数。

@item 
@code{normalvariate(mean, sdev)} 使用正态（高斯）分布采样。
@end itemize

还有一些高级函数直接对序列进行操作，例如：


@itemize *

@item 
@code{choice(S)} 从给定的序列中随机选择一个元素。

@item 
@code{shuffle(L)} 对列表进行原地重排，也就是说随机打乱。
@end itemize

还有 @code{Random} 类，你可以将其实例化，用来创建多个独立的随机数生成器。

@node 扩展/嵌入常见问题,Python在Windows上的常见问题,代码库和插件 FAQ,Python 常见问题
@anchor{faq/extending doc}@anchor{4280}@anchor{faq/extending extending-embedding-faq}@anchor{4281}
@section 扩展/嵌入常见问题



@c XXX need review for Python 3.

@menu
* 可以使用 C 语言创建自己的函数吗？:: 
* 可以使用 C++ 语言创建自己的函数吗？:: 
* C很难写，有没有其他选择？:: 
* 如何在 C 中执行任意 Python 语句？:: 
* 如何在 C 中对任意 Python 表达式求值？:: 
* 如何从Python对象中提取C的值？:: 
* 如何使用Py_BuildValue()创建任意长度的元组？: 如何使用Py_BuildValue 创建任意长度的元组？. 
* 如何从C调用对象的方法？:: 
* 如何捕获PyErr_Print()（或打印到stdout / stderr的任何内容）的输出？: 如何捕获PyErr_Print （或打印到stdout / stderr的任何内容）的输出？. 
* 如何从C访问用Python编写的模块？:: 
* 如何在 Python 中对接 C ++ 对象？:: 
* 我使用Setup文件添加了一个模块，为什么make失败了？:: 
* 如何调试扩展？:: 
* 我想在Linux系统上编译一个Python模块，但是缺少一些文件。为什么?:: 
* 如何区分“输入不完整”和“输入无效”？:: 
* 如何找到未定义的g++符号__builtin_new或__pure_virtual？:: 
* 能否创建一个对象类，其中部分方法在C中实现，而其他方法在Python中实现（例如通过继承）？:: 

@end menu

@node 可以使用 C 语言创建自己的函数吗？,可以使用 C++ 语言创建自己的函数吗？,,扩展/嵌入常见问题
@anchor{faq/extending can-i-create-my-own-functions-in-c}@anchor{4282}
@subsection 可以使用 C 语言创建自己的函数吗？


是的，您可以在C中创建包含函数、变量、异常甚至新类型的内置模块。在文档 @ref{1191,,扩展和嵌入 Python 解释器} 中有说明。

大多数中级或高级的Python书籍也涵盖这个主题。

@node 可以使用 C++ 语言创建自己的函数吗？,C很难写，有没有其他选择？,可以使用 C 语言创建自己的函数吗？,扩展/嵌入常见问题
@anchor{faq/extending id2}@anchor{4283}
@subsection 可以使用 C++ 语言创建自己的函数吗？


是的，可以使用C ++中兼容C的功能。 在Python include文件周围放置` @cite{extern“C”@{...@}`} ，并在Python解释器调用的每个函数之前放置 @code{extern“C”} 。 具有构造函数的全局或静态C ++对象可能不是一个好主意。

@node C很难写，有没有其他选择？,如何在 C 中执行任意 Python 语句？,可以使用 C++ 语言创建自己的函数吗？,扩展/嵌入常见问题
@anchor{faq/extending c-wrapper-software}@anchor{4284}@anchor{faq/extending writing-c-is-hard-are-there-any-alternatives}@anchor{4285}
@subsection C很难写，有没有其他选择？


编写自己的C扩展有很多选择，具体取决于您要做的事情。

@c XXX make sure these all work

Cython@footnote{http://cython.org} 及其相关的 Pyrex@footnote{https://www.cosc.canterbury.ac.nz/greg.ewing/python/Pyrex/} 是接受稍微修改过的Python形式并生成相应C代码的编译器。 Cython和Pyrex可以编写扩展而无需学习Python的C API。

如果需要连接到某些当前不存在Python扩展的C或C ++库，可以尝试使用 SWIG@footnote{http://www.swig.org} 等工具包装库的数据类型和函数。  SIP@footnote{https://riverbankcomputing.com/software/sip/intro} ， CXX@footnote{http://cxx.sourceforge.net/} Boost@footnote{http://www.boost.org/libs/python/doc/index.html} , 或 Weave@footnote{https://github.com/scipy/weave} 也是包装C ++库的替代方案。

@node 如何在 C 中执行任意 Python 语句？,如何在 C 中对任意 Python 表达式求值？,C很难写，有没有其他选择？,扩展/嵌入常见问题
@anchor{faq/extending how-can-i-execute-arbitrary-python-statements-from-c}@anchor{4286}
@subsection 如何在 C 中执行任意 Python 语句？


执行此操作的最高层级函数为 @ref{3b2c,,PyRun_SimpleString()}，它接受单个字符串参数用于在模块 @code{__main__} 的上下文中执行并在成功时返回 @code{0} 而在发生异常 (包括 @ref{452,,SyntaxError}) 时返回 @code{-1}。 如果你想要更多可控性，可以使用 @ref{f43,,PyRun_String()}；请在 @code{Python/pythonrun.c} 中查看 @ref{3b2c,,PyRun_SimpleString()} 的源码。

@node 如何在 C 中对任意 Python 表达式求值？,如何从Python对象中提取C的值？,如何在 C 中执行任意 Python 语句？,扩展/嵌入常见问题
@anchor{faq/extending how-can-i-evaluate-an-arbitrary-python-expression-from-c}@anchor{4287}
@subsection 如何在 C 中对任意 Python 表达式求值？


可以调用前一问题中介绍的函数 @ref{f43,,PyRun_String()} 并附带起始标记符 @ref{3b88,,Py_eval_input}；它会解析表达式，对其求值并返回结果值。

@node 如何从Python对象中提取C的值？,如何使用Py_BuildValue 创建任意长度的元组？,如何在 C 中对任意 Python 表达式求值？,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-extract-c-values-from-a-python-object}@anchor{4288}
@subsection 如何从Python对象中提取C的值？


这取决于对象的类型。 如果是元组，@ref{3de6,,PyTuple_Size()} 可返回其长度而 @ref{3ac1,,PyTuple_GetItem()} 可返回指定序号上的项。 对于列表也有类似的函数 @code{PyListSize()} 和 @ref{3ac2,,PyList_GetItem()}。

对于字节串，@ref{3d6e,,PyBytes_Size()} 可返回其长度而 @ref{3d72,,PyBytes_AsStringAndSize()} 提供一个指向其值和长度的指针。 请注意 Python 字节串可能为空，因此 C 的 @code{strlen()} 不应被使用。

要检测一个对象的类型，首先要确保它不为 @code{NULL}，然后使用 @ref{d18,,PyBytes_Check()}, @ref{3de2,,PyTuple_Check()}, @ref{3df7,,PyList_Check()} 等等。

还有一个针对 Python 对象的高层级 API，通过所谓的‘抽象’接口提供 —— 请参阅 @code{Include/abstract.h} 了解详情。 它允许使用 @ref{3c9a,,PySequence_Length()}, @ref{fe1,,PySequence_GetItem()} 这样的调用来与任意种类的 Python 序列进行对接，此外还可使用许多其他有用的协议例如数字 (@ref{3c94,,PyNumber_Index()} 等) 以及 PyMapping API 中的各种映射等等。

@node 如何使用Py_BuildValue 创建任意长度的元组？,如何从C调用对象的方法？,如何从Python对象中提取C的值？,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-use-py-buildvalue-to-create-a-tuple-of-arbitrary-length}@anchor{4289}
@subsection 如何使用Py_BuildValue()创建任意长度的元组？


不可以。应该使用 @ref{3de5,,PyTuple_Pack()} 。

@node 如何从C调用对象的方法？,如何捕获PyErr_Print （或打印到stdout / stderr的任何内容）的输出？,如何使用Py_BuildValue 创建任意长度的元组？,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-call-an-object-s-method-from-c}@anchor{428a}
@subsection 如何从C调用对象的方法？


可以使用 @ref{3c65,,PyObject_CallMethod()} 函数来调用某个对象的任意方法。 形参为该对象、要调用的方法名、类似 @ref{2ce,,Py_BuildValue()} 所用的格式字符串以及要传给方法的参数值:

@example
PyObject *
PyObject_CallMethod(PyObject *object, const char *method_name,
                    const char *arg_format, ...);
@end example

这适用于任何具有方法的对象 —— 不论是内置方法还是用户自定义方法。 你需要负责对返回值进行最终的 @ref{266,,Py_DECREF()} 处理。

例如调用某个文件对象的 "seek" 方法并传入参数 10, 0 (假定文件对象的指针为 "f"):

@example
res = PyObject_CallMethod(f, "seek", "(ii)", 10, 0);
if (res == NULL) @{
        ... an exception occurred ...
@}
else @{
        Py_DECREF(res);
@}
@end example

请注意由于 @ref{3ab4,,PyObject_CallObject()} @emph{总是} 接受一个元组作为参数列表，要调用不带参数的函数，则传入格式为 "()"，要调用只带一个参数的函数，则应将参数包含于圆括号中，例如 "(i)"。

@node 如何捕获PyErr_Print （或打印到stdout / stderr的任何内容）的输出？,如何从C访问用Python编写的模块？,如何从C调用对象的方法？,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-catch-the-output-from-pyerr-print-or-anything-that-prints-to-stdout-stderr}@anchor{428b}
@subsection 如何捕获PyErr_Print()（或打印到stdout / stderr的任何内容）的输出？


在 Python 代码中，定义一个支持 @code{write()} 方法的对象。 将此对象赋值给 @ref{307,,sys.stdout} 和 @ref{308,,sys.stderr}。 调用 print_error 或者只是允许标准回溯机制生效。 在此之后，输出将转往你的 @code{write()} 方法所指向的任何地方。

做到这一点的最简单方式是使用 @ref{827,,io.StringIO} 类：

@example
>>> import io, sys
>>> sys.stdout = io.StringIO()
>>> print('foo')
>>> print('hello world!')
>>> sys.stderr.write(sys.stdout.getvalue())
foo
hello world!
@end example

实现同样效果的自定义对象看起来是这样的：

@example
>>> import io, sys
>>> class StdoutCatcher(io.TextIOBase):
...     def __init__(self):
...         self.data = []
...     def write(self, stuff):
...         self.data.append(stuff)
...
>>> import sys
>>> sys.stdout = StdoutCatcher()
>>> print('foo')
>>> print('hello world!')
>>> sys.stderr.write('@w{'}.join(sys.stdout.data))
foo
hello world!
@end example

@node 如何从C访问用Python编写的模块？,如何在 Python 中对接 C ++ 对象？,如何捕获PyErr_Print （或打印到stdout / stderr的任何内容）的输出？,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-access-a-module-written-in-python-from-c}@anchor{428c}
@subsection 如何从C访问用Python编写的模块？


你可以通过如下方式获得一个指向模块对象的指针:

@example
module = PyImport_ImportModule("<modulename>");
@end example

如果模块尚未被导入（即它还不存在于 @ref{eb5,,sys.modules} 中），这会初始化该模块；否则它只是简单地返回 @code{sys.modules["<modulename>"]} 的值。 请注意它并不会将模块加入任何命名空间 —— 它只是确保模块被初始化并存在于 @ref{eb5,,sys.modules} 中。

之后你就可以通过如下方式来访问模块的属性（即模块中定义的任何名称）:

@example
attr = PyObject_GetAttrString(module, "<attrname>");
@end example

调用 @ref{3c5c,,PyObject_SetAttrString()} 为模块中的变量赋值也是可以的。

@node 如何在 Python 中对接 C ++ 对象？,我使用Setup文件添加了一个模块，为什么make失败了？,如何从C访问用Python编写的模块？,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-interface-to-c-objects-from-python}@anchor{428d}
@subsection 如何在 Python 中对接 C ++ 对象？


根据你的需求，可以选择许多方式。 手动的实现方式请查阅 @ref{1191,,"扩展与嵌入" 文档} 来入门。 需要知道的是对于 Python 运行时系统来说，C 和 C++ 并不没有太大的区别 —— 因此围绕一个 C 结构（指针）类型构建新 Python 对象的策略同样适用于 C++ 对象。

有关C ++库，请参阅 @ref{4284,,C很难写，有没有其他选择？}

@node 我使用Setup文件添加了一个模块，为什么make失败了？,如何调试扩展？,如何在 Python 中对接 C ++ 对象？,扩展/嵌入常见问题
@anchor{faq/extending i-added-a-module-using-the-setup-file-and-the-make-fails-why}@anchor{428e}
@subsection 我使用Setup文件添加了一个模块，为什么make失败了？


安装程序必须以换行符结束，如果没有换行符，则构建过程将失败。 （修复这个需要一些丑陋的shell脚本编程，而且这个bug很小，看起来不值得花这么大力气。)

@node 如何调试扩展？,我想在Linux系统上编译一个Python模块，但是缺少一些文件。为什么?,我使用Setup文件添加了一个模块，为什么make失败了？,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-debug-an-extension}@anchor{428f}
@subsection 如何调试扩展？


将GDB与动态加载的扩展名一起使用时，在加载扩展名之前，不能在扩展名中设置断点。

在您的 @code{.gdbinit} 文件中（或交互式）添加命令：

@example
br _PyImport_LoadDynamicModule
@end example

然后运行GDB：

@example
$ gdb /local/bin/python
gdb) run myscript.py
gdb) continue # repeat until your extension is loaded
gdb) finish   # so that your extension is loaded
gdb) br myfunction.c:50
gdb) continue
@end example

@node 我想在Linux系统上编译一个Python模块，但是缺少一些文件。为什么?,如何区分“输入不完整”和“输入无效”？,如何调试扩展？,扩展/嵌入常见问题
@anchor{faq/extending i-want-to-compile-a-python-module-on-my-linux-system-but-some-files-are-missing-why}@anchor{4290}
@subsection 我想在Linux系统上编译一个Python模块，但是缺少一些文件。为什么?


大多数打包的Python版本不包含 @code{/usr/lib/python2.@emph{x}/config/} 目录，该目录中包含编译Python扩展所需的各种文件。

对于Red Hat，安装python-devel RPM以获取必要的文件。

对于Debian，运行 @code{apt-get install python-dev} 。

@node 如何区分“输入不完整”和“输入无效”？,如何找到未定义的g++符号__builtin_new或__pure_virtual？,我想在Linux系统上编译一个Python模块，但是缺少一些文件。为什么?,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-tell-incomplete-input-from-invalid-input}@anchor{4291}
@subsection 如何区分“输入不完整”和“输入无效”？


有时，希望模仿Python交互式解释器的行为，在输入不完整时(例如，您键入了“if”语句的开头，或者没有关闭括号或三个字符串引号)，给出一个延续提示，但当输入无效时，立即给出一条语法错误消息。

在Python中，您可以使用 @ref{1d,,codeop} 模块，该模块非常接近解析器的行为。例如，IDLE就使用了这个。

在C中执行此操作的最简单方法是调用 @ref{3b6f,,PyRun_InteractiveLoop()} （可能在单独的线程中）并让Python解释器为您处理输入。您还可以设置 @ref{966,,PyOS_ReadlineFunctionPointer()} 指向您的自定义输入函数。有关更多提示，请参阅 @code{Modules/readline.c} 和 @code{Parser/myreadline.c} 。

但是，有时必须在与其他应用程序相同的线程中运行嵌入式Python解释器，并且不能允许 @ref{3b6f,,PyRun_InteractiveLoop()} 在等待用户输入时停止。那么另一个解决方案是调用 @code{PyParser_ParseString()} 并测试 @code{e.error} 等于 @code{E_EOF} ，如果等于，就意味着输入不完整。这是一个示例代码片段，未经测试，灵感来自Alex Farber的代码:

@example
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <node.h>
#include <errcode.h>
#include <grammar.h>
#include <parsetok.h>
#include <compile.h>

int testcomplete(char *code)
  /* code should end in \n */
  /* return -1 for error, 0 for incomplete, 1 for complete */
@{
  node *n;
  perrdetail e;

  n = PyParser_ParseString(code, &_PyParser_Grammar,
                           Py_file_input, &e);
  if (n == NULL) @{
    if (e.error == E_EOF)
      return 0;
    return -1;
  @}

  PyNode_Free(n);
  return 1;
@}
@end example

另一个解决方案是尝试使用 @ref{3b80,,Py_CompileString()} 编译接收到的字符串。如果编译时没有出现错误，请尝试通过调用 @ref{3b84,,PyEval_EvalCode()} 来执行返回的代码对象。否则，请将输入保存到以后。如果编译失败，找出是错误还是只需要更多的输入-从异常元组中提取消息字符串，并将其与字符串 “分析时意外的EOF” 进行比较。下面是使用GNUreadline库的完整示例(您可能希望在调用readline()时忽略 @strong{SIGINT} )：

@example
#include <stdio.h>
#include <readline.h>

#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <object.h>
#include <compile.h>
#include <eval.h>

int main (int argc, char* argv[])
@{
  int i, j, done = 0;                          /* lengths of line, code */
  char ps1[] = ">>> ";
  char ps2[] = "... ";
  char *prompt = ps1;
  char *msg, *line, *code = NULL;
  PyObject *src, *glb, *loc;
  PyObject *exc, *val, *trb, *obj, *dum;

  Py_Initialize ();
  loc = PyDict_New ();
  glb = PyDict_New ();
  PyDict_SetItemString (glb, "__builtins__", PyEval_GetBuiltins ());

  while (!done)
  @{
    line = readline (prompt);

    if (NULL == line)                          /* Ctrl-D pressed */
    @{
      done = 1;
    @}
    else
    @{
      i = strlen (line);

      if (i > 0)
        add_history (line);                    /* save non-empty lines */

      if (NULL == code)                        /* nothing in code yet */
        j = 0;
      else
        j = strlen (code);

      code = realloc (code, i + j + 2);
      if (NULL == code)                        /* out of memory */
        exit (1);

      if (0 == j)                              /* code was empty, so */
        code[0] = '\0';                        /* keep strncat happy */

      strncat (code, line, i);                 /* append line to code */
      code[i + j] = '\n';                      /* append '\n' to code */
      code[i + j + 1] = '\0';

      src = Py_CompileString (code, "<stdin>", Py_single_input);

      if (NULL != src)                         /* compiled just fine - */
      @{
        if (ps1  == prompt ||                  /* ">>> " or */
            '\n' == code[i + j - 1])           /* "... " and double '\n' */
        @{                                               /* so execute it */
          dum = PyEval_EvalCode (src, glb, loc);
          Py_XDECREF (dum);
          Py_XDECREF (src);
          free (code);
          code = NULL;
          if (PyErr_Occurred ())
            PyErr_Print ();
          prompt = ps1;
        @}
      @}                                        /* syntax error or E_EOF? */
      else if (PyErr_ExceptionMatches (PyExc_SyntaxError))
      @{
        PyErr_Fetch (&exc, &val, &trb);        /* clears exception! */

        if (PyArg_ParseTuple (val, "sO", &msg, &obj) &&
            !strcmp (msg, "unexpected EOF while parsing")) /* E_EOF */
        @{
          Py_XDECREF (exc);
          Py_XDECREF (val);
          Py_XDECREF (trb);
          prompt = ps2;
        @}
        else                                   /* some other syntax error */
        @{
          PyErr_Restore (exc, val, trb);
          PyErr_Print ();
          free (code);
          code = NULL;
          prompt = ps1;
        @}
      @}
      else                                     /* some non-syntax error */
      @{
        PyErr_Print ();
        free (code);
        code = NULL;
        prompt = ps1;
      @}

      free (line);
    @}
  @}

  Py_XDECREF(glb);
  Py_XDECREF(loc);
  Py_Finalize();
  exit(0);
@}
@end example

@node 如何找到未定义的g++符号__builtin_new或__pure_virtual？,能否创建一个对象类，其中部分方法在C中实现，而其他方法在Python中实现（例如通过继承）？,如何区分“输入不完整”和“输入无效”？,扩展/嵌入常见问题
@anchor{faq/extending how-do-i-find-undefined-g-symbols-builtin-new-or-pure-virtual}@anchor{4292}
@subsection 如何找到未定义的g++符号__builtin_new或__pure_virtual？


要动态加载g ++扩展模块，必须重新编译Python，要使用g ++重新链接（在Python Modules Makefile中更改LINKCC），及链接扩展模块（例如： @code{g++ -shared -o mymodule.so mymodule.o} ）。

@node 能否创建一个对象类，其中部分方法在C中实现，而其他方法在Python中实现（例如通过继承）？,,如何找到未定义的g++符号__builtin_new或__pure_virtual？,扩展/嵌入常见问题
@anchor{faq/extending can-i-create-an-object-class-with-some-methods-implemented-in-c-and-others-in-python-e-g-through-inheritance}@anchor{4293}
@subsection 能否创建一个对象类，其中部分方法在C中实现，而其他方法在Python中实现（例如通过继承）？


是的，您可以继承内置类，例如 @ref{184,,int} ， @ref{262,,list} ， @ref{1b8,,dict} 等。

Boost Python库（BPL，http：//www.boost.org/libs/python/doc/index.html）提供了一种从C ++执行此操作的方法（即，您可以使用BPL继承自C ++编写的扩展类 ）。

@node Python在Windows上的常见问题,图形用户界面（GUI）常见问题,扩展/嵌入常见问题,Python 常见问题
@anchor{faq/windows doc}@anchor{4294}@anchor{faq/windows python-on-windows-faq}@anchor{4295}@anchor{faq/windows windows-faq}@anchor{4296}
@section Python在Windows上的常见问题



@c XXX need review for Python 3.
@c XXX need review for Windows Vista/Seven?

@menu
* 我怎样在Windows下运行一个Python程序？:: 
* 我怎么让 Python 脚本可执行？:: 
* 为什么有时候 Python 程序会启动缓慢？:: 
* 我怎样使用Python脚本制作可执行文件？:: 
* *.pyd 文件和DLL文件相同吗？: * pyd 文件和DLL文件相同吗？. 
* 我怎样将Python嵌入一个Windows程序？:: 
* 如何让编辑器不要在我的 Python 源代码中插入 tab ？:: 
* 如何在不阻塞的情况下检查按键？:: 

@end menu

@node 我怎样在Windows下运行一个Python程序？,我怎么让 Python 脚本可执行？,,Python在Windows上的常见问题
@anchor{faq/windows faq-run-program-under-windows}@anchor{4297}@anchor{faq/windows how-do-i-run-a-python-program-under-windows}@anchor{4298}
@subsection 我怎样在Windows下运行一个Python程序？


这不一定是一个简单的问题。如果你已经熟悉在Windows的命令行中运行程序的方法，一切都显而易见；不然的话，你也许需要额外获得些许指导。

除非你在使用某种集成开发环境，否则你将会在被称为“DOS 窗口”或“命令提示符窗口”的地方 @emph{输入} Windows 命令。 通常你可以在搜索栏搜索 @code{cmd} 来创建这种窗口。 你应该能够识别你何时打开了这样的窗口，因为你将看到一个 Windows“命令提示符”，通常看起来是这样：

@example
C:\>
@end example

前面的字母可能会不同，而且后面有可能会有其他东西，所以你也许会看到类似这样的东西：

@example
D:\YourName\Projects\Python>
@end example

出现的内容具体取决与你的电脑如何设置和最近用它做的事。 当你启动了这样一个窗口后，就可以开始运行Python程序了。

Python 脚本需要被另外一个叫做 Python @emph{解释器} 的程序来处理。 解释器读取脚本，把它编译成字节码，然后执行字节码来运行你的程序。 所以怎样安排解释器来处理你的 Python 脚本呢？

首先，确保命令窗口能够将“py”识别为指令来开启解释器。 如果你打开过一个命令窗口， 尝试输入命令 @code{py} 然后按回车：

@example
C:\Users\YourName> py
@end example

然后你应当看见类似类似这样的东西：

@example
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>
@end example

解释器已经以“交互模式”打开。这意味着你可以交互输入Python语句或表达式，并在等待时执行或评估它们。这是Python最强大的功能之一。输入几个表达式并看看结果：

@example
>>> print("Hello")
Hello
>>> "Hello" * 3
'HelloHelloHello'
@end example

许多人把交互模式当作方便和高度可编程的计算器。 想结束交互式Python会话时，调用 @ref{15a7,,exit()} 函数，或者按住 @code{Ctrl} 键时输入 @code{Z}  ，之后按 @code{Enter} 键返回Windows命令提示符。

你可能发现在开始菜单有一个这样的选项 开始 ‣ 所有程序 ‣ Python 3.x ‣ Python (command line) ， 运行它后会出现一个有着 @code{>>>} 提示的想不出来口。 如果这样的话，在调用 @ref{15a7,,exit()} 函数或按 @code{Ctrl-Z} 组合键后窗口会消失。Windows在这个窗口中运行一个 "python" 命令，并且在你终止解释器的时候关闭它。

现在我们知道 @code{py} 命令已经被识别，可以输入Python脚本了。 你需要提供Python脚本的绝对路径或相对路径。 假设Python脚本位于桌面上并命名为 @code{hello.py}，并且命令提示符在用户主目录打开，那么可以看到类似于这样的东西:

@example
C:\Users\YourName>
@end example

那么现在可以让 @code{py} 命令执行你的脚本，只需要输入 @code{py} 和脚本路径:

@example
C:\Users\YourName> py Desktop\hello.py
hello
@end example

@node 我怎么让 Python 脚本可执行？,为什么有时候 Python 程序会启动缓慢？,我怎样在Windows下运行一个Python程序？,Python在Windows上的常见问题
@anchor{faq/windows how-do-i-make-python-scripts-executable}@anchor{4299}
@subsection 我怎么让 Python 脚本可执行？


在Windows上，标准Python安装程序已将.py扩展名与文件类型(Python.File) 相关联，并为该文件类型提供运行解释器的打开命令(@code{D:\Program Files\Python\python.exe "%1" %*}) 。 这足以使脚本在命令提示符下作为 'foo.py' 命令被执行。 如果希望通过简单地键入“foo”而无需输入文件扩展名来执行脚本，则需要将.py添加到PATHEXT环境变量中。

@node 为什么有时候 Python 程序会启动缓慢？,我怎样使用Python脚本制作可执行文件？,我怎么让 Python 脚本可执行？,Python在Windows上的常见问题
@anchor{faq/windows why-does-python-sometimes-take-so-long-to-start}@anchor{429a}
@subsection 为什么有时候 Python 程序会启动缓慢？


通常，Python 在 Windows 上启动得很快，但偶尔会有错误报告说 Python 突然需要很长时间才能启动。更令人费解的是，在其他配置相同的 Windows 系统上，Python 却可以工作得很好。

该问题可能是由于计算机上的杀毒软件配置错误造成的。当将病毒扫描配置为监视文件系统中所有读取行为时，一些杀毒扫描程序会导致两个数量级的启动开销。请检查你系统安装的杀毒扫描程序的配置，确保两台机它们是同样的配置。已知的， McAfee 杀毒软件在将它设置为扫描所有文件系统访问时，会产生这个问题。

@node 我怎样使用Python脚本制作可执行文件？,* pyd 文件和DLL文件相同吗？,为什么有时候 Python 程序会启动缓慢？,Python在Windows上的常见问题
@anchor{faq/windows how-do-i-make-an-executable-from-a-python-script}@anchor{429b}
@subsection 我怎样使用Python脚本制作可执行文件？


请参阅 cx_Freeze@footnote{https://anthony-tuininga.github.io/cx_Freeze/} 了解 distutils 扩展，它允许你从 Python 代码创建控制台和 GUI 可执行文件。 py2exe@footnote{http://www.py2exe.org/} ，是构建基于 Python 2.x 的可执行文件的最流行扩展，它还不支持 Python 3 ，但这个版本正在开发。

@node * pyd 文件和DLL文件相同吗？,我怎样将Python嵌入一个Windows程序？,我怎样使用Python脚本制作可执行文件？,Python在Windows上的常见问题
@anchor{faq/windows is-a-pyd-file-the-same-as-a-dll}@anchor{429c}
@subsection @code{*.pyd} 文件和DLL文件相同吗？


是的， .pyd 文件也是 dll ，但有一些差异。如果你有一个名为 @code{foo.pyd} 的DLL，那么它必须有一个函数 @code{PyInit_foo()} 。 然后你可以编写 Python 代码 “import foo” ，Python 将搜索 foo.pyd （以及 foo.py 、 foo.pyc ）。如果找到它，将尝试调用 @code{PyInit_foo()} 来初始化它。你不应将 .exe 与 foo.lib 链接，因为这会导致 Windows 要求存在 DLL 。

请注意， foo.pyd 的搜索路径是 PYTHONPATH ，与 Windows 用于搜索 foo.dll 的路径不同。此外， foo.pyd 不需要存在来运行你的程序，而如果你将程序与 dll 链接，则需要 dll 。 当然，如果你想 @code{import foo} ，则需要 foo.pyd 。在 DLL 中，链接在源代码中用 @code{__declspec(dllexport)} 声明。 在 .pyd 中，链接在可用函数列表中定义。

@node 我怎样将Python嵌入一个Windows程序？,如何让编辑器不要在我的 Python 源代码中插入 tab ？,* pyd 文件和DLL文件相同吗？,Python在Windows上的常见问题
@anchor{faq/windows how-can-i-embed-python-into-a-windows-application}@anchor{429d}
@subsection 我怎样将Python嵌入一个Windows程序？


在 Windows 应用程序中嵌入 Python 解释器可以总结如下：


@enumerate 

@item 
请 _不要_ 直接在你的 .exe 文件中内置 Python 。在 Windows 上， Python 必须是一个 DLL ，这样才可以处理导入的本身就是 DLL 的模块。（这是第一个未记录的关键事实。）相反，链接到 @code{python@emph{NN}.dll} ；它通常安装在 @code{C:\Windows\System} 中。 @emph{NN} 是 Python 版本，如数字“33”代表 Python 3.3 。

你可以通过两种不同的方式链接到 Python 。加载时链接意味着链接到 @code{python@emph{NN}.lib} ，而运行时链接意味着链接 @code{python@emph{NN}.dll} 。（一般说明： @code{python @emph{NN}.lib} 是所谓的“import lib”，对应于 @code{python@emph{NN}.dll} 。它只定义了链接器的符号。）

运行时链接极大地简化了链接选项，一切都在运行时发生。你的代码必须使用 Windows 的 @code{LoadLibraryEx()} 程序加载 @code{python@emph{NN}.dll} 。代码还必须使用使用 Windows 的 @code{GetProcAddress()} 例程获得的指针访问 @code{python@emph{NN}.dll} 中程序和数据（即 Python 的 C API ）。宏可以使这些指针对任何调用 Python C API 中的例程的 C 代码都是透明的。

Borland 提示：首先使用 Coff2Omf.exe 将 @code{python@emph{NN}.lib} 转换为 OMF 格式。

@c XXX what about static linking?

@item 
如果你使用 SWIG ，很容易创建一个 Python “扩展模块”，它将使应用程序的数据和方法可供 Python 使用。SWIG将为你处理所有蹩脚的细节。结果是你将链接到 .exe 文件 @emph{中} 的C代码 (!) 你不必创建 DLL 文件，这也简化了链接。

@item 
SWIG 将创建一个 init 函数（一个 C 函数），其名称取决于扩展模块的名称。例如，如果模块的名称是 leo ，则 init 函数将被称为 initleo() 。 如果您使用 SWIG 阴影类，则 init 函数将被称为 initleoc() 。这初始化了一个由阴影类使用的隐藏辅助类。

你可以将步骤 2 中的 C 代码链接到 .exe 文件的原因是调用初始化函数等同于将模块导入 Python ！ （这是第二个关键的未记载事实。）

@item 
简而言之，你可以用以下代码使用扩展模块初始化 Python 解释器。

@example
#include "python.h"
...
Py_Initialize();  // Initialize Python.
initmyAppc();  // Initialize (import) the helper class.
PyRun_SimpleString("import myApp");  // Import the shadow class.
@end example

@item 
Python C API 存在两个问题，如果你使用除 MSVC 之外的编译器用于构建 python.dll ，这将会变得明显。

问题1：采用 FILE* 参数的所谓“极高级”函数在多编译器环境中不起作用，因为每个编译器的FILE结构体概念都不同。从实现的角度来看，这些是非常 _低_ 级的功能。

问题2：在为void函数生成包装器时，SWIG会生成以下代码：

@example
Py_INCREF(Py_None);
_resultobj = Py_None;
return _resultobj;
@end example

Py_None 是一个宏，它扩展为对 pythonNN.dll 中名为 _Py_NoneStruct 的复杂数据结构的引用。同样，此代码将在多编译器环境中失败。将此类代码替换为：

@example
return Py_BuildValue("");
@end example

有可能使用 SWIG 的 @code{%typemap} 命令自动进行更改，但我无法使其工作（我是一个完全的SWIG新手）。

@item 
使用 Python shell 脚本从 Windows 应用程序内部建立 Python 解释器窗口并不是一个好主意；生成的窗口将独立于应用程序的窗口系统。相反，你（或 wxPythonWindow 类）应该创建一个“本机”解释器窗口。将该窗口连接到Python解释器很容易。你可以将 Python的 i/o 重定向到支持读写的 _任意_ 对象，因此你只需要一个包含 read() 和 write() 方法的 Python 对象（在扩展模块中定义）。
@end enumerate

@node 如何让编辑器不要在我的 Python 源代码中插入 tab ？,如何在不阻塞的情况下检查按键？,我怎样将Python嵌入一个Windows程序？,Python在Windows上的常见问题
@anchor{faq/windows how-do-i-keep-editors-from-inserting-tabs-into-my-python-source}@anchor{429e}
@subsection 如何让编辑器不要在我的 Python 源代码中插入 tab ？


本 FAQ 不建议使用制表符， Python 样式指南 
@geindex Python 提高建议; PEP 8
PEP 8@footnote{https://www.python.org/dev/peps/pep-0008} ，为发行的 Python 代码推荐 4 个空格；这也是 Emacs python-mode 默认值。

在任何编辑器下，混合制表符和空格都是一个坏主意。 MSVC 在这方面没有什么不同，并且很容易配置为使用空格： 点击 Tools ‣ Options ‣ Tabs，对于文件类型“Default”，设置“Tab size”和“Indent size”为 4 ，并选择“插入空格”单选按钮。

如果混合制表符和空格导致前导空格出现问题， Python 会引发 @ref{e71,,IndentationError} 或 @ref{e70,,TabError} 。你还可以运行 @ref{100,,tabnanny} 模块以批处理模式检查目录树。

@node 如何在不阻塞的情况下检查按键？,,如何让编辑器不要在我的 Python 源代码中插入 tab ？,Python在Windows上的常见问题
@anchor{faq/windows how-do-i-check-for-a-keypress-without-blocking}@anchor{429f}
@subsection 如何在不阻塞的情况下检查按键？


使用 msvcrt 模块。 是标准的 Windows 特定扩展模块。它定义了一个函数 @code{kbhit()} 来检查是否存在键盘命中，而 @code{getch()} 来获取一个字符而不回显它。

@node 图形用户界面（GUI）常见问题,“为什么我的电脑上安装了 Python ？”,Python在Windows上的常见问题,Python 常见问题
@anchor{faq/gui doc}@anchor{42a0}@anchor{faq/gui graphic-user-interface-faq}@anchor{42a1}
@section 图形用户界面（GUI）常见问题



@c XXX need review for Python 3.

@menu
* 图形界面常见问题:: 
* Python 是否有平台无关的图形界面工具包？:: 
* 有哪些Python的GUI工具是某个平台专用的？:: 
* 有关Tkinter的问题:: 

@end menu

@node 图形界面常见问题,Python 是否有平台无关的图形界面工具包？,,图形用户界面（GUI）常见问题
@anchor{faq/gui general-gui-questions}@anchor{42a2}
@subsection 图形界面常见问题


@node Python 是否有平台无关的图形界面工具包？,有哪些Python的GUI工具是某个平台专用的？,图形界面常见问题,图形用户界面（GUI）常见问题
@anchor{faq/gui what-platform-independent-gui-toolkits-exist-for-python}@anchor{42a3}
@subsection Python 是否有平台无关的图形界面工具包？


针对不同的（操作系统或）平台，有多种工具包可供选择。虽然有些工具包还没有移植到 Python 3 上，但至少目前 @ref{42a4,,Tkinter} 以及 @ref{42a5,,Qt} 是兼容 Python 3 的。

@c XXX check links

@menu
* Tkinter:: 
* wxWidgets:: 
* Qt:: 
* Gtk+:: 
* Kivy:: 
* FLTK:: 
* OpenGL:: 

@end menu

@node Tkinter,wxWidgets,,Python 是否有平台无关的图形界面工具包？
@anchor{faq/gui tkinter}@anchor{42a4}
@subsubsection Tkinter


Python 的标准编译包含了 @ref{310f,,tkinter}。这是一个面向对象的接口，指向  Tcl/Tk 微件包。 该接口大概是最容易安装（因为该接口包含在 Python 的大部分 二进制发行版@footnote{https://www.python.org/downloads/} 中）和使用的工具包。要了解 Tk 的详情，比如源代码等，可访问 Tcl/Tk 项目主页@footnote{https://www.tcl.tk}。 Tcl/Tk 可完整移植至 Mac OS X，Windows 和 Unix 操作系统上。

@node wxWidgets,Qt,Tkinter,Python 是否有平台无关的图形界面工具包？
@anchor{faq/gui wxwidgets}@anchor{42a6}
@subsubsection wxWidgets


wxWidgets (@indicateurl{https://www.wxwidgets.org}) 是一个自由、可移植的 GUI 图形用户界面类库，使用 C++ 编写。它可以在多个操作系统平台上提供原生自然的界面观感。包括Windows、Mac OS X、 GTK 和 X11 平台在内，都是wxWidgets 当前稳定支持的平台。在语言绑定适配方面，wxWidgets 类库可用于较多语言，包括 Python，Perl，Ruby等。

wxPython@footnote{https://www.wxpython.org} 是 wxWidgets 的 Python 适配。虽然该绑定在更新进度上经常会稍稍落后于 wxWidgets，但它利用纯 Python 扩展，提供了许多其他语言绑定没有实现的特性。wxPython 有一个活跃的用户和开发者社区。

wxWidgets 和 wxPython 都是自由开源库。宽松的许可证允许人们在商业软件、自由软件和共享软件中使用它们。

@node Qt,Gtk+,wxWidgets,Python 是否有平台无关的图形界面工具包？
@anchor{faq/gui qt}@anchor{42a5}
@subsubsection Qt


Qt 工具包 (可使用 PyQt@footnote{https://riverbankcomputing.com/software/pyqt/intro} 或 PySide@footnote{https://wiki.qt.io/PySide}) 及 KDE (PyKDE4@footnote{https://techbase.kde.org/Languages/Python/Using_PyKDE_4}) 有多个绑定适配可供选择。 PyQt 当前相较 PySide 更成熟，但如果你想编写专有软件，就必须要从 Riverbank Computing@footnote{https://www.riverbankcomputing.com/commercial/license-faq} 购买 PyQt 许可证。 PySide 则可以自由使用于各类软件。

Qt 4.5 以上版本使用 LGPL 进行许可；此外，商业许可证可从 Qt 公司@footnote{https://www.qt.io/licensing/} 那里获得。

@node Gtk+,Kivy,Qt,Python 是否有平台无关的图形界面工具包？
@anchor{faq/gui gtk}@anchor{42a7}
@subsubsection Gtk+


针对 Python 的 GObject 内省绑定@footnote{https://wiki.gnome.org/Projects/PyGObject} 可以用于编写 GTK+ 3 应用。 另请参阅 Python GTK+ 3 教程@footnote{https://python-gtk-3-tutorial.readthedocs.io}。

更早的、针对 Gtk+ 2 工具包@footnote{https://www.gtk.org} 的 PyGtk 绑定，是由 James Henstridge 实现的。具体请参考 <@indicateurl{http://www.pygtk.org}>。

@node Kivy,FLTK,Gtk+,Python 是否有平台无关的图形界面工具包？
@anchor{faq/gui kivy}@anchor{42a8}
@subsubsection Kivy


Kivy@footnote{https://kivy.org/} 是一种跨平台图形用户界面库，同时支持桌面操作系统（Windows，macOS 和 Linux）以及移动设备（Android，iOS）。该库使用 Python 和 Cython 编写，可以使用一系列窗口后端。

Kivy 是自由的开源软件，使用 MIT 许可证分发。

@node FLTK,OpenGL,Kivy,Python 是否有平台无关的图形界面工具包？
@anchor{faq/gui fltk}@anchor{42a9}
@subsubsection FLTK


the FLTK toolkit@footnote{http://www.fltk.org} 的Python绑定是简单却功能强大且成熟的跨平台窗口系统，可以在  the PyFLTK project@footnote{http://pyfltk.sourceforge.net} 里获得相关信息。

@node OpenGL,,FLTK,Python 是否有平台无关的图形界面工具包？
@anchor{faq/gui opengl}@anchor{42aa}
@subsubsection OpenGL


对于OpenGL绑定，请参阅 PyOpenGL@footnote{http://pyopengl.sourceforge.net}。

@node 有哪些Python的GUI工具是某个平台专用的？,有关Tkinter的问题,Python 是否有平台无关的图形界面工具包？,图形用户界面（GUI）常见问题
@anchor{faq/gui what-platform-specific-gui-toolkits-exist-for-python}@anchor{42ab}
@subsection 有哪些Python的GUI工具是某个平台专用的？


通过安装 PyObjc Objective-C bridge@footnote{https://pypi.org/project/pyobjc/}，Python程序可以使用Mac OS X的Cocoa库。

Mark Hammond的 @ref{4296,,Pythonwin} 包括一个微软基础类(MFC)的接口和一个绝大多数由使用MFC类的Python写成的Python编程环境。

@node 有关Tkinter的问题,,有哪些Python的GUI工具是某个平台专用的？,图形用户界面（GUI）常见问题
@anchor{faq/gui tkinter-questions}@anchor{42ac}
@subsection 有关Tkinter的问题


@menu
* 我怎样“冻结”Tkinter程序？:: 
* 在等待 I/O 操作时能够处理 Tk 事件吗？:: 
* 在Tkinter中键绑定不工作：为什么？:: 

@end menu

@node 我怎样“冻结”Tkinter程序？,在等待 I/O 操作时能够处理 Tk 事件吗？,,有关Tkinter的问题
@anchor{faq/gui how-do-i-freeze-tkinter-applications}@anchor{42ad}
@subsubsection 我怎样“冻结”Tkinter程序？


Freeze （意为 “冻结”）是一个用来创建独立应用程序的工具。 当 “冻结” Tkinter 程序时，程序并不是真的能够独立运行，因为程序仍然需要 Tcl 和 Tk 库。

一种解决方法是将程序与 Tcl 和 Tk 库一同发布，并且在运行时使用环境变量 
@geindex TCL_LIBRARY
@geindex 环境变量; TCL_LIBRARY
@code{TCL_LIBRARY} 和 
@geindex TK_LIBRARY
@geindex 环境变量; TK_LIBRARY
@code{TK_LIBRARY} 指向他们的位置。

为了获得真正能独立运行的应用程序，来自库里的 Tcl 脚本也需要被整合进应用程序。 一个做这种事情的工具叫 SAM (stand-alone modules，独立模块) ，它是 Tix distribution (@indicateurl{http://tix.sourceforge.net/}) 的一部分。

在启用 SAM 时编译 Tix ，在 Python 文件  @code{Modules/tkappinit.c} 中执行对 @code{Tclsam_init()} 等的适当调用，并且将程序与 libtclsam 和 libtksam 相链接（可能也要包括 Tix 的库）。

@node 在等待 I/O 操作时能够处理 Tk 事件吗？,在Tkinter中键绑定不工作：为什么？,我怎样“冻结”Tkinter程序？,有关Tkinter的问题
@anchor{faq/gui can-i-have-tk-events-handled-while-waiting-for-i-o}@anchor{42ae}
@subsubsection 在等待 I/O 操作时能够处理 Tk 事件吗？


在 Windows 以外的其他平台上可以，你甚至不需要使用线程！ 但是你必须稍微修改一下你的 I/O 代码。 Tk 有与 Xt 的 @code{XtAddInput()} 对应的调用，它允许你注册一个回调函数，当一个文件描述符可以进行 I/O 操作的时候，Tk 主循环将会调用这个回调函数。 参见 @ref{3129,,File Handlers}。

@node 在Tkinter中键绑定不工作：为什么？,,在等待 I/O 操作时能够处理 Tk 事件吗？,有关Tkinter的问题
@anchor{faq/gui i-can-t-get-key-bindings-to-work-in-tkinter-why}@anchor{42af}
@subsubsection 在Tkinter中键绑定不工作：为什么？


经常听到的抱怨是：已经通过  @code{bind()} 方法绑定了事件的处理程序，但是，当按下相关的按键后，这个处理程序却没有执行。

最常见的原因是，那个绑定的控件没有“键盘焦点”。请在 Tk 文档中查找 focus 指令。通常一个控件要获得“键盘焦点”，需要点击那个控件（而不是标签；请查看 takefocus 选项）。

@node “为什么我的电脑上安装了 Python ？”,,图形用户界面（GUI）常见问题,Python 常见问题
@anchor{faq/installed doc}@anchor{42b0}@anchor{faq/installed why-is-python-installed-on-my-computer-faq}@anchor{42b1}
@section “为什么我的电脑上安装了 Python ？”


@menu
* 什么是 Python？: 什么是 Python？<2>. 
* 为什么我的电脑上安装了 Python ？:: 
* 我能删除 Python 吗？:: 

@end menu

@node 什么是 Python？<2>,为什么我的电脑上安装了 Python ？,,“为什么我的电脑上安装了 Python ？”
@anchor{faq/installed what-is-python}@anchor{42b2}
@subsection 什么是 Python？


Python 是一种程序语言，被许多应用程序使用。它不仅因易学而在许多高校用于编程入门，还被工作于 Google、NASA 和卢卡斯影业等公司的软件开发人员使用。

如果你想学习更多 Python，看看 Beginner's Guide to Python@footnote{https://wiki.python.org/moin/BeginnersGuide}.

@node 为什么我的电脑上安装了 Python ？,我能删除 Python 吗？,什么是 Python？<2>,“为什么我的电脑上安装了 Python ？”
@anchor{faq/installed why-is-python-installed-on-my-machine}@anchor{42b3}
@subsection 为什么我的电脑上安装了 Python ？


如果你不记得你曾主动安装过 Python，但它却出现在了你的电脑上，这里有一些可能的原因。


@itemize *

@item 
可能是这台电脑的其他用户因想学习编程而安装了它，你得琢磨一下谁用过这台电脑并安装了 Python。

@item 
电脑上安装的第三方应用程序可能由 Python 写成并附带了一份 Python。这样的应用程序有很多，例如GUI程序、网络服务器、管理脚本等。

@item 
一些 Windows 可能预装了 Python。在撰写本文时，我们了解到 Hewlett-Packard 和 Compaq 的计算机包含Python。显然，HP/Compaq 的一些管理工具是用 Python 编写的。

@item 
许多 Unix 兼容的操作系统，例如 Mac OS X 和一些 Linux 发行版，默认安装了Python；它被包含在基本安装套件中。
@end itemize

@node 我能删除 Python 吗？,,为什么我的电脑上安装了 Python ？,“为什么我的电脑上安装了 Python ？”
@anchor{faq/installed can-i-delete-python}@anchor{42b4}
@subsection 我能删除 Python 吗？


这取决于所安装 Python 的来源

如果有人主动安装了 Python，你可以在不影响其它程序的情况下安全移除它。在 Windows 中，可使用“控制面板”中的“添加/删除程序”卸载。

如果 Python 来源于第三方应用程序，你也能删除它，但那些程序将不能正常工作。你应该使用那些应用程序的卸载器而不是直接删除 Python。

如果 Python 来自于你的操作系统，不推荐删除！如果删除了它，任何用 Python 写成的工具将无法工作，其中某些工具对于你来说可能十分重要。你甚至可能需要重装整个系统来修复因删除 Python 留下的烂摊子。

@node 术语对照表,文档说明,Python 常见问题,Top
@anchor{glossary doc}@anchor{42b5}@anchor{glossary glossary}@anchor{1193}@anchor{glossary id1}@anchor{42b6}
@chapter 术语对照表


@c if you add new entries, keep the alphabetical sorting!


@table @asis
@anchor{glossary term-0}@anchor{11ac}
@geindex >>>

@item @code{>>>}

交互式终端中默认的 Python 提示符。往往会显示于能以交互方式在解释器里执行的样例代码之前。
@anchor{glossary term-1}@anchor{11ad}
@geindex ...

@item @code{...}

可以是指：


@itemize *

@item 
交互式终端中输入特殊代码行时默认的 Python 提示符，包括：缩进的代码块，成对的分隔符之内（圆括号、方括号、花括号或三重引号），或是指定一个装饰器之后。

@item 
@ref{15a4,,Ellipsis} 内置常量。
@end itemize
@anchor{glossary term-2to3}@anchor{fb5}
@geindex 2to3

@item 2to3

一个将 Python 2.x 代码转换为 Python 3.x 代码的工具，能够处理大部分通过解析源码并遍历解析树可检测到的不兼容问题。

2to3 包含在标准库中，模块名为 @ref{a7,,lib2to3}；并提供一个独立入口点 @code{Tools/scripts/2to3}。参见 @ref{c6f,,2to3 - 自动将 Python 2 代码转为 Python 3 代码}。
@anchor{glossary term-abstract-base-class}@anchor{b2c}
@geindex abstract base class -- 抽象基类

@item abstract base class -- 抽象基类

抽象基类简称 ABC，是对 @ref{42b7,,duck-typing} 的补充，它提供了一种定义接口的新方式，相比之下其他技巧例如 @ref{442,,hasattr()} 显得过于笨拙或有微妙错误（例如使用 @ref{13d4,,魔术方法}）。ABC 引入了虚拟子类，这种类并非继承自其他类，但却仍能被 @ref{449,,isinstance()} 和 @ref{44a,,issubclass()} 所认可；详见 @ref{4,,abc} 模块文档。Python 自带许多内置的 ABC 用于实现数据结构（在 @ref{1f,,collections.abc} 模块中）、数字（在 @ref{c1,,numbers} 模块中）、流（在 @ref{a1,,io} 模块中）、导入查找器和加载器（在 @ref{9c,,importlib.abc} 模块中）。你可以使用 @ref{4,,abc} 模块来创建自己的 ABC。
@anchor{glossary term-annotation}@anchor{42b8}
@geindex annotation -- 标注

@item annotation -- 标注

关联到某个变量、类属性、函数形参或返回值的标签，被约定作为 @ref{42b9,,type hint} 来使用。

局部变量的标注在运行时不可访问，但全局变量、类属性和函数的标注会分别存放模块、类和函数的 @code{__annotations__} 特殊属性中。

参见 @ref{61a,,variable annotation}、@ref{11f1,,function annotation}、
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} 和 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526}，对此功能均有介绍。
@anchor{glossary term-argument}@anchor{14bb}
@geindex argument -- 参数

@item argument -- 参数

在调用函数时传给 @ref{14bc,,function} （或 @ref{42ba,,method} ）的值。参数分为两种：


@itemize *

@item 
@emph{关键字参数}: 在函数调用中前面带有标识符（例如 @code{name=}）或者作为包含在前面带有 @code{**} 的字典里的值传入。举例来说，@code{3} 和 @code{5} 在以下对 @ref{189,,complex()} 的调用中均属于关键字参数:

@example
complex(real=3, imag=5)
complex(**@{'real': 3, 'imag': 5@})
@end example

@item 
@emph{位置参数}: 不属于关键字参数的参数。位置参数可出现于参数列表的开头以及/或者作为前面带有 @code{*} 的 @ref{ba5,,iterable} 里的元素被传入。举例来说，@code{3} 和 @code{5} 在以下调用中均属于位置参数:

@example
complex(3, 5)
complex(*(3, 5))
@end example
@end itemize

参数会被赋值给函数体中对应的局部变量。有关赋值规则参见 @ref{646,,调用} 一节。根据语法，任何表达式都可用来表示一个参数；最终算出的值会被赋给对应的局部变量。

另参见 @ref{14c4,,parameter} 术语表条目，常见问题中 @ref{4204,,参数与形参的区别} 以及 
@geindex Python 提高建议; PEP 362
PEP 362@footnote{https://www.python.org/dev/peps/pep-0362}。
@anchor{glossary term-asynchronous-context-manager}@anchor{63b}
@geindex asynchronous context manager -- 异步上下文管理器

@item asynchronous context manager -- 异步上下文管理器

此种对象通过定义 @ref{1430,,__aenter__()} 和 @ref{1431,,__aexit__()} 方法来对 @ref{63d,,async with} 语句中的环境进行控制。由 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} 引入。
@anchor{glossary term-asynchronous-generator}@anchor{149c}
@geindex asynchronous generator -- 异步生成器

@item asynchronous generator -- 异步生成器

返回值为 @ref{35d9,,asynchronous generator iterator} 的函数。它与使用 @ref{284,,async def} 定义的协程函数很相似，不同之处在于它包含 @ref{18f,,yield} 表达式以产生一系列可在 @ref{2e3,,async for} 循环中使用的值。

此术语通常是指异步生成器函数，但在某些情况下则可能是指 @emph{异步生成器迭代器}。如果需要清楚表达具体含义，请使用全称以避免歧义。

一个异步生成器函数可能包含 @ref{1a3,,await} 表达式或者 @ref{2e3,,async for} 以及 @ref{63d,,async with} 语句。
@anchor{glossary term-asynchronous-generator-iterator}@anchor{35d9}
@geindex asynchronous generator iterator -- 异步生成器迭代器

@item asynchronous generator iterator -- 异步生成器迭代器

@ref{149c,,asynchronous generator} 函数所创建的对象。

此对象属于 @ref{63f,,asynchronous iterator}，当使用 @ref{142d,,__anext__()} 方法调用时会返回一个可等待对象来执行异步生成器函数的代码直到下一个 @ref{18f,,yield} 表达式。

每个 @ref{18f,,yield} 会临时暂停处理，记住当前位置执行状态 (包括局部变量和挂起的 try 语句)。当该 @emph{异步生成器迭代器} 与其他 @ref{142d,,__anext__()} 返回的可等待对象有效恢复时，它会从离开位置继续执行。参见 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} 和 
@geindex Python 提高建议; PEP 525
PEP 525@footnote{https://www.python.org/dev/peps/pep-0525}。
@anchor{glossary term-asynchronous-iterable}@anchor{63a}
@geindex asynchronous iterable -- 异步可迭代对象

@item asynchronous iterable -- 异步可迭代对象

可在 @ref{2e3,,async for} 语句中被使用的对象。必须通过它的 @ref{481,,__aiter__()} 方法返回一个 @ref{63f,,asynchronous iterator}。由 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} 引入。
@anchor{glossary term-asynchronous-iterator}@anchor{63f}
@geindex asynchronous iterator -- 异步迭代器

@item asynchronous iterator -- 异步迭代器

实现了 @ref{481,,__aiter__()} 和 @ref{142d,,__anext__()} 方法的对象。@code{__anext__} 必须返回一个 @ref{513,,awaitable} 对象。@ref{2e3,,async for} 会处理异步迭代器的 @ref{142d,,__anext__()} 方法所返回的可等待对象，直到其引发一个 @ref{fa5,,StopAsyncIteration} 异常。由 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} 引入。
@anchor{glossary term-attribute}@anchor{42bb}
@geindex attribute -- 属性

@item attribute -- 属性

关联到一个对象的值，可以使用点号表达式通过其名称来引用。例如，如果一个对象 @emph{o} 具有一个属性 @emph{a}，就可以用 @emph{o.a} 来引用它。
@anchor{glossary term-awaitable}@anchor{513}
@geindex awaitable -- 可等待对象

@item awaitable -- 可等待对象

能在 @ref{1a3,,await} 表达式中使用的对象。可以是 @ref{1a6,,coroutine} 或是具有 @ref{63c,,__await__()} 方法的对象。参见 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492}。
@anchor{glossary term-bdfl}@anchor{42bc}
@geindex BDFL

@item BDFL

“终身仁慈独裁者”的英文缩写，即 Guido van Rossum@footnote{https://gvanrossum.github.io/}，Python 的创造者。
@anchor{glossary term-binary-file}@anchor{1c37}
@geindex binary file -- 二进制文件

@item binary file -- 二进制文件

@ref{b3b,,file object} 能够读写 @ref{5e3,,字节类对象}。二进制文件的例子包括以二进制模式（@code{'rb'}, @code{'wb'} or @code{'rb+'}）打开的文件、@code{sys.stdin.buffer}、@code{sys.stdout.buffer} 以及 @ref{795,,io.BytesIO} 和 @ref{6d7,,gzip.GzipFile} 的实例。

另请参见 @ref{1239,,text file} 了解能够读写 @ref{329,,str} 对象的文件对象。
@anchor{glossary term-bytes-like-object}@anchor{5e3}
@geindex bytes-like object -- 字节类对象

@item bytes-like object -- 字节类对象

支持 @ref{15d6,,缓冲协议} 并且能导出 C-@ref{164e,,contiguous} 缓冲的对象。这包括所有 @ref{32a,,bytes}、@ref{32b,,bytearray} 和 @ref{44b,,array.array} 对象，以及许多普通 @ref{25c,,memoryview} 对象。字节类对象可在多种二进制数据操作中使用；这些操作包括压缩、保存为二进制文件以及通过套接字发送等。

某些操作需要可变的二进制数据。这种对象在文档中常被称为“可读写字节类对象”。可变缓冲对象的例子包括 @ref{32b,,bytearray} 以及 @ref{32b,,bytearray} 的 @ref{25c,,memoryview}。其他操作要求二进制数据存放于不可变对象 ("只读字节类对象")；这种对象的例子包括 @ref{32a,,bytes} 以及 @ref{32a,,bytes} 对象的 @ref{25c,,memoryview}。
@anchor{glossary term-bytecode}@anchor{60f}
@geindex bytecode -- 字节码

@item bytecode -- 字节码

Python 源代码会被编译为字节码，即 CPython 解释器中表示 Python 程序的内部代码。字节码还会缓存在 @code{.pyc} 文件中，这样第二次执行同一文件时速度更快（可以免去将源码重新编译为字节码）。这种 "中间语言" 运行在根据字节码执行相应机器码的 @ref{2723,,virtual machine} 之上。请注意不同 Python 虚拟机上的字节码不一定通用，也不一定能在不同 Python 版本上兼容。

字节码指令列表可以在 @ref{384a,,dis 模块} 的文档中查看。
@anchor{glossary term-callback}@anchor{253e}
@geindex callback -- 回调

@item callback -- 回调

一个作为参数被传入以用以在未来的某个时刻被调用的子例程函数。
@anchor{glossary term-class}@anchor{159a}
@geindex class -- 类

@item class -- 类

用来创建用户定义对象的模板。类定义通常包含对该类的实例进行操作的方法定义。
@anchor{glossary term-class-variable}@anchor{42bd}
@geindex class variable -- 类变量

@item class variable -- 类变量

在类中定义的变量，并且仅限在类的层级上修改 (而不是在类的实例中修改)。
@anchor{glossary term-coercion}@anchor{42be}
@geindex coercion -- 强制类型转换

@item coercion -- 强制类型转换

在包含两个相同类型参数的操作中，一种类型的实例隐式地转换为另一种类型。例如，@code{int(3.15)} 是将原浮点数转换为整型数 @code{3}，但在 @code{3+4.5} 中，参数的类型不一致（一个是 int, 一个是 float），两者必须转换为相同类型才能相加，否则将引发 @ref{192,,TypeError}。如果没有强制类型转换机制，程序员必须将所有可兼容参数归一化为相同类型，例如要写成 @code{float(3)+4.5} 而不是 @code{3+4.5}。
@anchor{glossary term-complex-number}@anchor{42bf}
@geindex complex number -- 复数

@item complex number -- 复数

对普通实数系统的扩展，其中所有数字都被表示为一个实部和一个虚部的和。虚数是虚数单位（@code{-1} 的平方根）的实倍数，通常在数学中写为 @code{i}，在工程学中写为 @code{j}。Python 内置了对复数的支持，采用工程学标记方式；虚部带有一个 @code{j} 后缀，例如 @code{3+1j}。如果需要 @ref{b1,,math} 模块内对象的对应复数版本，请使用 @ref{19,,cmath}，复数的使用是一个比较高级的数学特性。如果你感觉没有必要，忽略它们也几乎不会有任何问题。
@anchor{glossary term-context-manager}@anchor{563}
@geindex context manager -- 上下文管理器

@item context manager -- 上下文管理器

在 @ref{6e3,,with} 语句中使用，通过定义 @ref{c8e,,__enter__()} 和 @ref{c8f,,__exit__()} 方法来控制环境状态的对象。参见 
@geindex Python 提高建议; PEP 343
PEP 343@footnote{https://www.python.org/dev/peps/pep-0343}。
@anchor{glossary term-context-variable}@anchor{42c0}
@geindex context variable -- 上下文变量

@item context variable -- 上下文变量

一种根据其所属的上下文可以具有不同的值的变量。 这类似于在线程局部存储中每个执行线程可以具有不同的变量值。 不过，对于上下文变量来说，一个执行线程中可能会有多个上下文，而上下文变量的主要用途是对并发异步任务中变量进行追踪。 参见 @ref{25,,contextvars}。
@anchor{glossary term-contiguous}@anchor{164e}
@geindex contiguous -- 连续

@item contiguous -- 连续

@geindex C-contiguous
@geindex Fortran contiguous

一个缓冲如果是 @emph{C 连续} 或 @emph{Fortran 连续} 就会被认为是连续的。零维缓冲是 C 和 Fortran 连续的。在一维数组中，所有条目必须在内存中彼此相邻地排列，采用从零开始的递增索引顺序。在多维 C-连续数组中，当按内存地址排列时用最后一个索引访问条目时速度最快。但是在 Fortran 连续数组中则是用第一个索引最快。
@anchor{glossary term-coroutine}@anchor{1a6}
@geindex coroutine -- 协程

@item coroutine -- 协程

协程是子例程的更一般形式。  子例程可以在某一点进入并在另一点退出。 协程则可以在许多不同的点上进入、退出和恢复。 它们可通过 @ref{284,,async def} 语句来实现。 参见 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492}。
@anchor{glossary term-coroutine-function}@anchor{639}
@geindex coroutine function -- 协程函数

@item coroutine function -- 协程函数

返回一个 @ref{1a6,,coroutine} 对象的函数。协程函数可通过 @ref{284,,async def} 语句来定义，并可能包含 @ref{1a3,,await}、@ref{2e3,,async for} 和 @ref{63d,,async with} 关键字。这些特性是由 
@geindex Python 提高建议; PEP 492
PEP 492@footnote{https://www.python.org/dev/peps/pep-0492} 引入的。
@anchor{glossary term-cpython}@anchor{13ce}
@geindex CPython

@item CPython

Python 编程语言的规范实现，在 python.org@footnote{https://www.python.org} 上发布。"CPython" 一词用于在必要时将此实现与其他实现例如 Jython 或 IronPython 相区别。
@anchor{glossary term-decorator}@anchor{283}
@geindex decorator -- 装饰器

@item decorator -- 装饰器

返回值为另一个函数的函数，通常使用 @code{@@wrapper} 语法形式来进行函数变换。 装饰器的常见例子包括 @ref{1d8,,classmethod()} 和 @ref{1d9,,staticmethod()}。

装饰器语法只是一种语法糖，以下两个函数定义在语义上完全等价:

@example
def f(...):
    ...
f = staticmethod(f)

@@staticmethod
def f(...):
    ...
@end example

同的样概念也适用于类，但通常较少这样使用。有关装饰器的详情可参见 @ref{11f0,,函数定义} 和 @ref{c63,,类定义} 的文档。
@anchor{glossary term-descriptor}@anchor{159e}
@geindex descriptor -- 描述器

@item descriptor -- 描述器

任何定义了 @ref{13d3,,__get__()}, @ref{13d7,,__set__()} 或 @ref{13d8,,__delete__()} 方法的对象。当一个类属性为描述器时，它的特殊绑定行为就会在属性查找时被触发。通常情况下，使用 @emph{a.b} 来获取、设置或删除一个属性时会在 @emph{a} 的类字典中查找名称为 @emph{b} 的对象，但如果 @emph{b} 是一个描述器，则会调用对应的描述器方法。理解描述器的概念是更深层次理解 Python 的关键，因为这是许多重要特性的基础，包括函数、方法、属性、类方法、静态方法以及对超类的引用等等。

有关描述符的方法的详情可参看 @ref{4e3,,实现描述器}。
@anchor{glossary term-dictionary}@anchor{42c1}
@geindex dictionary -- 字典

@item dictionary -- 字典

一个关联数组，其中的任意键都映射到相应的值。键可以是任何具有 @ref{339,,__hash__()} 和 @ref{338,,__eq__()} 方法的对象。在 Perl 语言中称为 hash。
@anchor{glossary term-dictionary-view}@anchor{18da}
@geindex dictionary view -- 字典视图

@item dictionary view -- 字典视图

从 @ref{c23,,dict.keys()}, @ref{c25,,dict.values()} 和 @ref{c24,,dict.items()} 返回的对象被称为字典视图。它们提供了字典条目的一个动态视图，这意味着当字典改变时，视图也会相应改变。要将字典视图强制转换为真正的列表，可使用 @code{list(dictview)}。参见 @ref{166f,,字典视图对象}。
@anchor{glossary term-docstring}@anchor{154e}
@geindex docstring -- 文档字符串

@item docstring -- 文档字符串

作为类、函数或模块之内的第一个表达式出现的字符串字面值。它在代码执行时会被忽略，但会被解释器识别并放入所在类、函数或模块的 @code{__doc__} 属性中。由于它可用于代码内省，因此是对象存放文档的规范位置。
@anchor{glossary term-duck-typing}@anchor{42b7}
@geindex duck-typing -- 鸭子类型

@item duck-typing -- 鸭子类型

指一种编程风格，它并不依靠查找对象类型来确定其是否具有正确的接口，而是直接调用或使用其方法或属性（“看起来像鸭子，叫起来也像鸭子，那么肯定就是鸭子。”）由于强调接口而非特定类型，设计良好的代码可通过允许多态替代来提升灵活性。鸭子类型避免使用 @ref{603,,type()} 或 @ref{449,,isinstance()} 检测。(但要注意鸭子类型可以使用 @ref{b2c,,抽象基类} 作为补充。)  而往往会采用 @ref{442,,hasattr()} 检测或是 @ref{1ee2,,EAFP} 编程。
@anchor{glossary term-eafp}@anchor{1ee2}
@geindex EAFP

@item EAFP

“求原谅比求许可更容易”的英文缩写。这种 Python 常用代码编写风格会假定所需的键或属性存在，并在假定错误时捕获异常。这种简洁快速风格的特点就是大量运用 @ref{d6b,,try} 和 @ref{b37,,except} 语句。于其相对的则是所谓 @ref{42c2,,LBYL} 风格，常见于 C 等许多其他语言。
@anchor{glossary term-expression}@anchor{35cd}
@geindex expression -- 表达式

@item expression -- 表达式

可以求出某个值的语法单元。 换句话说，一个表达式就是表达元素例如字面值、名称、属性访问、运算符或函数调用的汇总，它们最终都会返回一个值。 与许多其他语言不同，并非所有语言构件都是表达式。 还存在不能被用作表达式的 @ref{1b24,,statement}，例如 @ref{11c1,,while}。 赋值也是属于语句而非表达式。
@anchor{glossary term-extension-module}@anchor{42c3}
@geindex extension module -- 扩展模块

@item extension module -- 扩展模块

以 C 或 C++ 编写的模块，使用 Python 的 C API 来与语言核心以及用户代码进行交互。
@anchor{glossary term-f-string}@anchor{15b}
@geindex f-string -- f-字符串

@item f-string -- f-字符串

带有 @code{'f'} 或 @code{'F'} 前缀的字符串字面值通常被称为“f-字符串”即 @ref{15c,,格式化字符串字面值} 的简写。参见 
@geindex Python 提高建议; PEP 498
PEP 498@footnote{https://www.python.org/dev/peps/pep-0498}。
@anchor{glossary term-file-object}@anchor{b3b}
@geindex file object -- 文件对象

@item file object -- 文件对象

对外提供面向文件 API 以使用下层资源的对象（带有 @code{read()} 或 @code{write()} 这样的方法）。根据其创建方式的不同，文件对象可以处理对真实磁盘文件，对其他类型存储，或是对通讯设备的访问（例如标准输入/输出、内存缓冲区、套接字、管道等等）。文件对象也被称为 @emph{文件类对象} 或 @emph{流}。

实际上共有三种类别的文件对象: 原始 @ref{1c37,,二进制文件}, 缓冲 @ref{1c37,,二进制文件} 以及 @ref{1239,,文本文件}。它们的接口定义均在 @ref{a1,,io} 模块中。创建文件对象的规范方式是使用 @ref{4ea,,open()} 函数。
@anchor{glossary term-file-like-object}@anchor{1bfc}
@geindex file-like object -- 文件类对象

@item file-like object -- 文件类对象

@ref{b3b,,file object} 的同义词。
@anchor{glossary term-finder}@anchor{1452}
@geindex finder -- 查找器

@item finder -- 查找器

一种会尝试查找被导入模块的 @ref{1453,,loader} 的对象。

从 Python 3.3 起存在两种类型的查找器: @ref{9ab,,元路径查找器} 配合 @ref{5e1,,sys.meta_path} 使用，以及 @ref{9ac,,path entry finders} 配合 @ref{956,,sys.path_hooks} 使用。

更多详情可参见 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}, 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} 和 
@geindex Python 提高建议; PEP 451
PEP 451@footnote{https://www.python.org/dev/peps/pep-0451}。
@anchor{glossary term-floor-division}@anchor{11b2}
@geindex floor division -- 向下取整除法

@item floor division -- 向下取整除法

向下舍入到最接近的整数的数学除法。向下取整除法的运算符是 @code{//} 。例如，表达式 @code{11 // 4} 的计算结果是 @code{2} ，而与之相反的是浮点数的真正除法返回 @code{2.75} 。注意 @code{(-11) // 4} 会返回 @code{-3} 因为这是 @code{-2.75} @emph{向下} 舍入得到的结果。见 
@geindex Python 提高建议; PEP 238
PEP 238@footnote{https://www.python.org/dev/peps/pep-0238} 。
@anchor{glossary term-function}@anchor{14bc}
@geindex function -- 函数

@item function -- 函数

可以向调用者返回某个值的一组语句。还可以向其传入零个或多个 @ref{14bb,,参数} 并在函数体执行中被使用。另见 @ref{14c4,,parameter}, @ref{42ba,,method} 和 @ref{11f0,,函数定义} 等节。
@anchor{glossary term-function-annotation}@anchor{11f1}
@geindex function annotation -- 函数标注

@item function annotation -- 函数标注

即针对函数形参或返回值的 @ref{42b8,,annotation} 。

函数标注通常用于 @ref{42b9,,类型提示}：例如以下函数预期接受两个 @ref{184,,int} 参数并预期返回一个 @ref{184,,int} 值:

@example
def sum_two_numbers(a: int, b: int) -> int:
   return a + b
@end example

函数标注语法的详解见 @ref{11f0,,函数定义} 一节。

请参看 @ref{61a,,variable annotation} 和 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} 对此功能的描述。
@anchor{glossary term-future}@anchor{67d}
@geindex __future__

@item __future__

一种伪模块，可被程序员用来启用与当前解释器不兼容的新语言特性。

通过导入 @ref{0,,__future__} 模块并对其中的变量求值，你可以查看新特性何时首次加入语言以及何时成为默认:

@example
>>> import __future__
>>> __future__.division
_Feature((2, 2, 0, 'alpha', 2), (3, 0, 0, 'alpha', 0), 8192)
@end example
@anchor{glossary term-garbage-collection}@anchor{129e}
@geindex garbage collection -- 垃圾回收

@item garbage collection -- 垃圾回收

释放不再被使用的内存空间的过程。Python 是通过引用计数和一个能够检测和打破循环引用的循环垃圾回收器来执行垃圾回收的。可以使用 @ref{86,,gc} 模块来控制垃圾回收器。

@geindex generator
@anchor{glossary term-generator}@anchor{99c}
@geindex generator -- 生成器

@item generator -- 生成器

返回一个 @ref{451,,generator iterator} 的函数。它看起来很像普通函数，不同点在于其包含 @ref{18f,,yield} 表达式以便产生一系列值供给 for-循环使用或是通过 @ref{67c,,next()} 函数逐一获取。

通常是指生成器函数，但在某些情况下也可能是指 @emph{生成器迭代器}。如果需要清楚表达具体含义，请使用全称以避免歧义。
@anchor{glossary term-generator-iterator}@anchor{451}
@geindex generator iterator -- 生成器迭代器

@item generator iterator -- 生成器迭代器

@ref{99c,,generator} 函数所创建的对象。

每个 @ref{18f,,yield} 会临时暂停处理，记住当前位置执行状态（包括局部变量和挂起的 try 语句）。当该 @emph{生成器迭代器} 恢复时，它会从离开位置继续执行（这与每次调用都从新开始的普通函数差别很大）。

@geindex generator expression
@anchor{glossary term-generator-expression}@anchor{42c4}
@geindex generator expression -- 生成器表达式

@item generator expression -- 生成器表达式

返回一个迭代器的表达式。 它看起来很像普通表达式后面带有定义了一个循环变量、范围的 @code{for} 子句，以及一个可选的 @code{if} 子句。 以下复合表达式会为外层函数生成一系列值:

@example
>>> sum(i*i for i in range(10))         # sum of squares 0, 1, 4, ... 81
285
@end example
@anchor{glossary term-generic-function}@anchor{1cb}
@geindex generic function -- 泛型函数

@item generic function -- 泛型函数

为不同的类型实现相同操作的多个函数所组成的函数。在调用时会由调度算法来确定应该使用哪个实现。

另请参见 @ref{1ca,,single dispatch} 术语表条目、@ref{382,,functools.singledispatch()} 装饰器以及 
@geindex Python 提高建议; PEP 443
PEP 443@footnote{https://www.python.org/dev/peps/pep-0443}。
@anchor{glossary term-gil}@anchor{be3}
@geindex GIL

@item GIL

参见 @ref{500,,global interpreter lock}。
@anchor{glossary term-global-interpreter-lock}@anchor{500}
@geindex global interpreter lock -- 全局解释器锁

@item global interpreter lock -- 全局解释器锁

@ref{13ce,,CPython} 解释器所采用的一种机制，它确保同一时刻只有一个线程在执行 Python @ref{60f,,bytecode}。此机制通过设置对象模型（包括 @ref{1b8,,dict} 等重要内置类型）针对并发访问的隐式安全简化了 CPython 实现。给整个解释器加锁使得解释器多线程运行更方便，其代价则是牺牲了在多处理器上的并行性。

不过，某些标准库或第三方库的扩展模块被设计为在执行计算密集型任务如压缩或哈希时释放 GIL。此外，在执行 I/O 操作时也总是会释放 GIL。

创建一个（以更精细粒度来锁定共享数据的）“自由线程”解释器的努力从未获得成功，因为这会牺牲在普通单处理器情况下的性能。据信克服这种性能问题的措施将导致实现变得更复杂，从而更难以维护。
@anchor{glossary term-hash-based-pyc}@anchor{42c5}
@geindex hash-based pyc -- 基于哈希的 pyc

@item hash-based pyc -- 基于哈希的 pyc

使用对应源文件的哈希值而非最后修改时间来确定其有效性的字节码缓存文件。 参见 @ref{322,,已缓存字节码的失效}。
@anchor{glossary term-hashable}@anchor{13c0}
@geindex hashable -- 可哈希

@item hashable -- 可哈希

一个对象的哈希值如果在其生命周期内绝不改变，就被称为 @emph{可哈希} （它需要具有 @ref{339,,__hash__()} 方法），并可以同其他对象进行比较（它需要具有 @ref{338,,__eq__()} 方法）。可哈希对象必须具有相同的哈希值比较结果才会相同。

可哈希性使得对象能够作为字典键或集合成员使用，因为这些数据结构要在内部使用哈希值。

大多数 Python 中的不可变内置对象都是可哈希的；可变容器（例如列表或字典）都不可哈希；不可变容器（例如元组和 frozenset）仅当它们的元素均为可哈希时才是可哈希的。 用户定义类的实例对象默认是可哈希的。 它们在比较时一定不相同（除非是与自己比较），它们的哈希值的生成是基于它们的 @ref{d7f,,id()}。
@anchor{glossary term-idle}@anchor{42c6}
@geindex IDLE

@item IDLE

Python 的 IDE，“集成开发与学习环境”的英文缩写。是 Python 标准发行版附带的基本编程器和解释器环境。
@anchor{glossary term-immutable}@anchor{11b6}
@geindex immutable -- 不可变

@item immutable -- 不可变

具有固定值的对象。不可变对象包括数字、字符串和元组。这样的对象不能被改变。如果必须存储一个不同的值，则必须创建新的对象。它们在需要常量哈希值的地方起着重要作用，例如作为字典中的键。
@anchor{glossary term-import-path}@anchor{1455}
@geindex import path -- 导入路径

@item import path -- 导入路径

由多个位置（或 @ref{1468,,路径条目}）组成的列表，会被模块的 @ref{1458,,path based finder} 用来查找导入目标。在导入时，此位置列表通常来自 @ref{482,,sys.path}，但对次级包来说也可能来自上级包的 @code{__path__} 属性。
@anchor{glossary term-importing}@anchor{1446}
@geindex importing -- 导入

@item importing -- 导入

令一个模块中的 Python 代码能为另一个模块中的 Python 代码所使用的过程。
@anchor{glossary term-importer}@anchor{1454}
@geindex importer -- 导入器

@item importer -- 导入器

查找并加载模块的对象；此对象既属于 @ref{1452,,finder} 又属于 @ref{1453,,loader}。
@anchor{glossary term-interactive}@anchor{42c7}
@geindex interactive -- 交互

@item interactive -- 交互

Python 带有一个交互式解释器，即你可以在解释器提示符后输入语句和表达式，立即执行并查看其结果。只需不带参数地启动 @code{python} 命令（也可以在你的计算机开始菜单中选择相应菜单项）。在测试新想法或检验模块和包的时候用这种方式会非常方便（请记得使用 @code{help(x)}）。
@anchor{glossary term-interpreted}@anchor{42c8}
@geindex interpreted -- 解释型

@item interpreted -- 解释型

Python 一是种解释型语言，与之相对的是编译型语言，虽然两者的区别由于字节码编译器的存在而会有所模糊。这意味着源文件可以直接运行而不必显式地创建可执行文件再运行。解释型语言通常具有比编译型语言更短的开发/调试周期，但是其程序往往运行得更慢。参见 @ref{42c7,,interactive}。
@anchor{glossary term-interpreter-shutdown}@anchor{75d}
@geindex interpreter shutdown -- 解释器关闭

@item interpreter shutdown -- 解释器关闭

当被要求关闭时，Python 解释器将进入一个特殊运行阶段并逐步释放所有已分配资源，例如模块和各种关键内部结构等。它还会多次调用 @ref{129e,,垃圾回收器}。这会触发用户定义析构器或弱引用回调中的代码执行。在关闭阶段执行的代码可能会遇到各种异常，因为其所依赖的资源已不再有效（常见的例子有库模块或警告机制等）。

解释器需要关闭的主要原因有 @code{__main__} 模块或所运行的脚本已完成执行。
@anchor{glossary term-iterable}@anchor{ba5}
@geindex iterable -- 可迭代对象

@item iterable -- 可迭代对象

能够逐一返回其成员项的对象。可迭代对象的例子包括所有序列类型（例如 @ref{262,,list}、@ref{329,,str} 和 @ref{478,,tuple}）以及某些非序列类型例如 @ref{1b8,,dict}、@ref{b3b,,文件对象} 以及定义了 @ref{509,,__iter__()} 方法或是实现了 @ref{11bc,,Sequence} 语义的 @ref{27f,,__getitem__()} 方法的任意自定义类对象。

可迭代对象被可用于 @ref{c29,,for} 循环以及许多其他需要一个序列的地方（@ref{c2b,,zip()}、@ref{c26,,map()} ...）。当一个可迭代对象作为参数传给内置函数 @ref{d20,,iter()} 时，它会返回该对象的迭代器。这种迭代器适用于对值集合的一次性遍历。在使用可迭代对象时，你通常不需要调用 @ref{d20,,iter()} 或者自己处理迭代器对象。@code{for} 语句会为你自动处理那些操作，创建一个临时的未命名变量用来在循环期间保存迭代器。参见 @ref{fce,,iterator}、@ref{11bc,,sequence} 以及 @ref{99c,,generator}。
@anchor{glossary term-iterator}@anchor{fce}
@geindex iterator -- 迭代器

@item iterator -- 迭代器

用来表示一连串数据流的对象。重复调用迭代器的 @ref{c5d,,__next__()} 方法（或将其传给内置函数 @ref{67c,,next()}）将逐个返回流中的项。当没有数据可用时则将引发 @ref{480,,StopIteration} 异常。到这时迭代器对象中的数据项已耗尽，继续调用其 @code{__next__()} 方法只会再次引发 @ref{480,,StopIteration} 异常。迭代器必须具有 @ref{509,,__iter__()} 方法用来返回该迭代器对象自身，因此迭代器必定也是可迭代对象，可被用于其他可迭代对象适用的大部分场合。一个显著的例外是那些会多次重复访问迭代项的代码。容器对象（例如 @ref{262,,list}）在你每次向其传入 @ref{d20,,iter()} 函数或是在 @ref{c29,,for} 循环中使用它时都会产生一个新的迭代器。如果在此情况下你尝试用迭代器则会返回在之前迭代过程中被耗尽的同一迭代器对象，使其看起来就像是一个空容器。

更多信息可查看 @ref{13f4,,迭代器类型}。
@anchor{glossary term-key-function}@anchor{6da}
@geindex key function -- 键函数

@item key function -- 键函数

键函数或称整理函数，是能够返回用于排序或排位的值的可调用对象。例如，@ref{3024,,locale.strxfrm()} 可用于生成一个符合特定区域排序约定的排序键。

Python 中有许多工具都允许用键函数来控制元素的排位或分组方式。其中包括 @ref{803,,min()}, @ref{804,,max()}, @ref{43e,,sorted()}, @ref{43f,,list.sort()}, @ref{6d9,,heapq.merge()}, @ref{18f9,,heapq.nsmallest()}, @ref{18f8,,heapq.nlargest()} 以及 @ref{1ad3,,itertools.groupby()}。

要创建一个键函数有多种方式。例如，@ref{15dc,,str.lower()} 方法可以用作忽略大小写排序的键函数。另外，键函数也可通过 @ref{c28,,lambda} 表达式来创建，例如 @code{lambda r: (r[0], r[2])}。还有 @ref{c2,,operator} 模块提供了三个键函数构造器：@ref{715,,attrgetter()}、@ref{261,,itemgetter()} 和 @ref{716,,methodcaller()}。请查看 @ref{1599,,如何排序} 一节以获取创建和使用键函数的示例。
@anchor{glossary term-keyword-argument}@anchor{5bf}
@geindex keyword argument -- 关键字参数

@item keyword argument -- 关键字参数

参见 @ref{14bb,,argument}。
@anchor{glossary term-lambda}@anchor{3674}
@geindex lambda

@item lambda

由一个单独 @ref{35cd,,expression} 构成的匿名内联函数，表达式会在调用时被求值。创建 lambda 函数的句法为 @code{lambda [parameters]: expression}
@anchor{glossary term-lbyl}@anchor{42c2}
@geindex LBYL

@item LBYL

“先查看后跳跃”的英文缩写。这种代码编写风格会在进行调用或查找之前显式地检查前提条件。此风格与 @ref{1ee2,,EAFP} 方式恰成对比，其特点是大量使用 @ref{de0,,if} 语句。

在多线程环境中，LBYL 方式会导致“查看”和“跳跃”之间发生条件竞争风险。例如，以下代码 @code{if key in mapping: return mapping[key]} 可能由于在检查操作之后其他线程从 @emph{mapping} 中移除了 @emph{key} 而出错。这种问题可通过加锁或使用 EAFP 方式来解决。
@anchor{glossary term-list}@anchor{42c9}
@geindex list -- 列表

@item list -- 列表

Python 内置的一种 @ref{11bc,,sequence}。虽然名为列表，但更类似于其他语言中的数组而非链接列表，因为访问元素的时间复杂度为 O(1)。
@anchor{glossary term-list-comprehension}@anchor{42ca}
@geindex list comprehension -- 列表推导式

@item list comprehension -- 列表推导式

处理一个序列中的所有或部分元素并返回结果列表的一种紧凑写法。@code{result = ['@{:#04x@}'.format(x) for x in range(256) if x % 2 == 0]} 将生成一个 0 到 255 范围内的十六进制偶数对应字符串（0x..）的列表。其中 @ref{de0,,if} 子句是可选的，如果省略则 @code{range(256)} 中的所有元素都会被处理。
@anchor{glossary term-loader}@anchor{1453}
@geindex loader -- 加载器

@item loader -- 加载器

负责加载模块的对象。它必须定义名为 @code{load_module()} 的方法。加载器通常由一个 @ref{1452,,finder} 返回。详情参见 
@geindex Python 提高建议; PEP 302
PEP 302@footnote{https://www.python.org/dev/peps/pep-0302}，对于 @ref{b2c,,abstract base class} 可参见 @ref{7bc,,importlib.abc.Loader}。
@anchor{glossary term-magic-method}@anchor{42cb}
@geindex magic method -- 魔术方法

@item magic method -- 魔术方法

@geindex magic; method

@ref{3608,,special method} 的非正式同义词 。
@anchor{glossary term-mapping}@anchor{b32}
@geindex mapping -- 映射

@item mapping -- 映射

一种支持任意键查找并实现了 @ref{18d9,,Mapping} 或 @ref{9e9,,MutableMapping} @ref{18bc,,抽象基类} 中所规定方法的容器对象。 此类对象的例子包括 @ref{1b8,,dict}, @ref{b33,,collections.defaultdict}, @ref{1b9,,collections.OrderedDict} 以及 @ref{9d4,,collections.Counter}。
@anchor{glossary term-meta-path-finder}@anchor{9ab}
@geindex meta path finder -- 元路径查找器

@item meta path finder -- 元路径查找器

@ref{5e1,,sys.meta_path} 的搜索所返回的 @ref{1452,,finder}。元路径查找器与 @ref{9ac,,path entry finders} 存在关联但并不相同。

请查看 @ref{9ad,,importlib.abc.MetaPathFinder} 了解元路径查找器所实现的方法。
@anchor{glossary term-metaclass}@anchor{22c5}
@geindex metaclass -- 元类

@item metaclass -- 元类

一种用于创建类的类。类定义包含类名、类字典和基类列表。元类负责接受上述三个参数并创建相应的类。大部分面向对象的编程语言都会提供一个默认实现。Python 的特别之处在于可以创建自定义元类。大部分用户永远不需要这个工具，但当需要出现时，元类可提供强大而优雅的解决方案。它们已被用于记录属性访问日志、添加线程安全性、跟踪对象创建、实现单例，以及其他许多任务。

更多详情参见 @ref{13e0,,元类}。
@anchor{glossary term-method}@anchor{42ba}
@geindex method -- 方法

@item method -- 方法

在类内部定义的函数。如果作为该类的实例的一个属性来调用，方法将会获取实例对象作为其第一个 @ref{14bb,,argument} (通常命名为 @code{self})。参见 @ref{14bc,,function} 和 @ref{1583,,nested scope}。
@anchor{glossary term-method-resolution-order}@anchor{159c}
@geindex method resolution order -- 方法解析顺序

@item method resolution order -- 方法解析顺序

方法解析顺序就是在查找成员时搜索全部基类所用的先后顺序。请查看 Python 2.3 方法解析顺序@footnote{https://www.python.org/download/releases/2.3/mro/} 了解自 2.3 版起 Python 解析器所用相关算法的详情。
@anchor{glossary term-module}@anchor{1445}
@geindex module -- 模块

@item module -- 模块

此对象是 Python 代码的一种组织单位。各模块具有独立的命名空间，可包含任意 Python 对象。模块可通过 @ref{1446,,importing} 操作被加载到 Python 中。

另见 @ref{1449,,package}。
@anchor{glossary term-module-spec}@anchor{35dd}
@geindex module spec -- 模块规格

@item module spec -- 模块规格

一个命名空间，其中包含用于加载模块的相关导入信息。是 @ref{145e,,importlib.machinery.ModuleSpec} 的实例。
@anchor{glossary term-mro}@anchor{281c}
@geindex MRO

@item MRO

参见 @ref{159c,,method resolution order}。
@anchor{glossary term-mutable}@anchor{11be}
@geindex mutable -- 可变

@item mutable -- 可变

可变对象可以在其 @ref{d7f,,id()} 保持固定的情况下改变其取值。另请参见 @ref{11b6,,immutable}。
@anchor{glossary term-named-tuple}@anchor{a9e}
@geindex named tuple -- 具名元组

@item named tuple -- 具名元组

术语“具名元组”可用于任何继承自元组，并且其中的可索引元素还能使用名称属性来访问的类型或类。 这样的类型或类还可能拥有其他特性。

有些内置类型属于具名元组，包括 @ref{edc,,time.localtime()} 和 @ref{1f1,,os.stat()} 的返回值。 另一个例子是 @ref{f51,,sys.float_info}:

@example
>>> sys.float_info[1]                   # indexed access
1024
>>> sys.float_info.max_exp              # named field access
1024
>>> isinstance(sys.float_info, tuple)   # kind of tuple
True
@end example

有些具名元组是内置类型（例如上面的例子）。 此外，具名元组还可通过常规类定义从 @ref{478,,tuple} 继承并定义名称字段的方式来创建。 这样的类可以手工编写，或者使用工厂函数 @ref{1b6,,collections.namedtuple()} 创建。 后一种方式还会添加一些手工编写或内置具名元组所没有的额外方法。
@anchor{glossary term-namespace}@anchor{42cc}
@geindex namespace -- 命名空间

@item namespace -- 命名空间

命名空间是存放变量的场所。命名空间有局部、全局和内置的，还有对象中的嵌套命名空间（在方法之内）。命名空间通过防止命名冲突来支持模块化。例如，函数 @ref{4ea,,builtins.open} 与 @ref{65f,,os.open()} 可通过各自的命名空间来区分。命名空间还通过明确哪个模块实现那个函数来帮助提高可读性和可维护性。例如，@ref{c01,,random.seed()} 或 @ref{39a,,itertools.islice()} 这种写法明确了这些函数是由 @ref{dc,,random} 与 @ref{a3,,itertools} 模块分别实现的。
@anchor{glossary term-namespace-package}@anchor{144c}
@geindex namespace package -- 命名空间包

@item namespace package -- 命名空间包

@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420} 所引入的一种仅被用作子包的容器的 @ref{1449,,package}，命名空间包可以没有实体表示物，其描述方式与 @ref{144b,,regular package} 不同，因为它们没有 @code{__init__.py} 文件。

另可参见 @ref{1445,,module}。
@anchor{glossary term-nested-scope}@anchor{1583}
@geindex nested scope -- 嵌套作用域

@item nested scope -- 嵌套作用域

在一个定义范围内引用变量的能力。例如，在另一函数之内定义的函数可以引用前者的变量。请注意嵌套作用域默认只对引用有效而对赋值无效。局部变量的读写都受限于最内层作用域。类似的，全局变量的读写则作用于全局命名空间。通过 @ref{c38,,nonlocal} 关键字可允许写入外层作用域。
@anchor{glossary term-new-style-class}@anchor{1c3f}
@geindex new-style class -- 新式类

@item new-style class -- 新式类

对于目前已被应于所有类对象的类形式的旧称谓。在早先的 Python 版本中，只有新式类能够使用 Python 新增的更灵活特性，例如 @ref{e26,,__slots__}、描述符、特征属性、@ref{441,,__getattribute__()}、类方法和静态方法等。
@anchor{glossary term-object}@anchor{42cd}
@geindex object -- 对象

@item object -- 对象

任何具有状态（属性或值）以及预定义行为（方法）的数据。object 也是任何 @ref{1c3f,,new-style class} 的最顶层基类名。
@anchor{glossary term-package}@anchor{1449}
@geindex package -- 包

@item package -- 包

一种可包含子模块或递归地包含子包的 Python @ref{1445,,module}。从技术上说，包是带有 @code{__path__} 属性的 Python 模块。

另参见 @ref{144b,,regular package} 和 @ref{144c,,namespace package}。
@anchor{glossary term-parameter}@anchor{14c4}
@geindex parameter -- 形参

@item parameter -- 形参

@ref{14bc,,function} （或方法）定义中的命名实体，它指定函数可以接受的一个 @ref{14bb,,argument} （或在某些情况下，多个实参）。有五种形参：


@itemize *

@item 
@emph{positional-or-keyword}：位置或关键字，指定一个可以作为 @ref{14bb,,位置参数} 传入也可以作为 @ref{14bb,,关键字参数} 传入的实参。这是默认的形参类型，例如下面的 @emph{foo} 和 @emph{bar}:

@example
def func(foo, bar=None): ...
@end example
@end itemize
@anchor{glossary positional-only-parameter}@anchor{2a7}

@itemize *

@item 
@emph{positional-only}：仅限位置，指定一个只能通过位置传入的参数。 仅限位置形参可通过在函数定义的形参列表中它们之后包含一个 @code{/} 字符来定义，例如下面的 @emph{posonly1} 和 @emph{posonly2}:

@example
def func(posonly1, posonly2, /, positional_or_keyword): ...
@end example
@end itemize
@anchor{glossary keyword-only-parameter}@anchor{2ac}

@itemize *

@item 
@emph{keyword-only}：仅限关键字，指定一个只能通过关键字传入的参数。仅限关键字形参可通过在函数定义的形参列表中包含单个可变位置形参或者在多个可变位置形参之前放一个 @code{*} 来定义，例如下面的 @emph{kw_only1} 和 @emph{kw_only2}:

@example
def func(arg, *, kw_only1, kw_only2): ...
@end example

@item 
@emph{var-positional}：可变位置，指定可以提供由一个任意数量的位置参数构成的序列（附加在其他形参已接受的位置参数之后）。这种形参可通过在形参名称前加缀 @code{*} 来定义，例如下面的 @emph{args}:

@example
def func(*args, **kwargs): ...
@end example

@item 
@emph{var-keyword}：可变关键字，指定可以提供任意数量的关键字参数（附加在其他形参已接受的关键字参数之后）。这种形参可通过在形参名称前加缀 @code{**} 来定义，例如上面的 @emph{kwargs}。
@end itemize

形参可以同时指定可选和必选参数，也可以为某些可选参数指定默认值。

另参见 @ref{14bb,,argument} 术语表条目、@ref{4204,,参数与形参的区别} 中的常见问题、@ref{6ee,,inspect.Parameter} 类、@ref{11f0,,函数定义} 一节以及 
@geindex Python 提高建议; PEP 362
PEP 362@footnote{https://www.python.org/dev/peps/pep-0362}。
@anchor{glossary term-path-entry}@anchor{1468}
@geindex path entry -- 路径入口

@item path entry -- 路径入口

@ref{1455,,import path} 中的一个单独位置，会被 @ref{1458,,path based finder} 用来查找要导入的模块。
@anchor{glossary term-path-entry-finder}@anchor{9ac}
@geindex path entry finder -- 路径入口查找器

@item path entry finder -- 路径入口查找器

任一可调用对象使用 @ref{956,,sys.path_hooks} (即 @ref{146a,,path entry hook}) 返回的 @ref{1452,,finder}，此种对象能通过 @ref{1468,,path entry} 来定位模块。

请参看 @ref{9ae,,importlib.abc.PathEntryFinder} 以了解路径入口查找器所实现的各个方法。
@anchor{glossary term-path-entry-hook}@anchor{146a}
@geindex path entry hook -- 路径入口钩子

@item path entry hook -- 路径入口钩子

一种可调用对象，在知道如何查找特定 @ref{1468,,path entry} 中的模块的情况下能够使用 @code{sys.path_hook} 列表返回一个 @ref{9ac,,path entry finder}。
@anchor{glossary term-path-based-finder}@anchor{1458}
@geindex path based finder -- 基于路径的查找器

@item path based finder -- 基于路径的查找器

默认的一种 @ref{9ab,,元路径查找器}，可在一个 @ref{1455,,import path} 中查找模块。
@anchor{glossary term-path-like-object}@anchor{363}
@geindex path-like object -- 路径类对象

@item path-like object -- 路径类对象

代表一个文件系统路径的对象。类路径对象可以是一个表示路径的 @ref{329,,str} 或者 @ref{32a,,bytes} 对象，还可以是一个实现了 @ref{4e5,,os.PathLike} 协议的对象。一个支持 @ref{4e5,,os.PathLike} 协议的对象可通过调用 @ref{4e7,,os.fspath()} 函数转换为 @ref{329,,str} 或者 @ref{32a,,bytes} 类型的文件系统路径；@ref{4e8,,os.fsdecode()} 和 @ref{4e9,,os.fsencode()} 可被分别用来确保获得 @ref{329,,str} 或 @ref{32a,,bytes} 类型的结果。此对象是由 
@geindex Python 提高建议; PEP 519
PEP 519@footnote{https://www.python.org/dev/peps/pep-0519} 引入的。
@anchor{glossary term-pep}@anchor{42ce}
@geindex PEP

@item PEP

“Python 增强提议”的英文缩写。一个 PEP 就是一份设计文档，用来向 Python 社区提供信息，或描述一个 Python 的新增特性及其进度或环境。PEP 应当提供精确的技术规格和所提议特性的原理说明。

PEP 应被作为提出主要新特性建议、收集社区对特定问题反馈以及为必须加入 Python 的设计决策编写文档的首选机制。PEP 的作者有责任在社区内部建立共识，并应将不同意见也记入文档。

参见 
@geindex Python 提高建议; PEP 1
PEP 1@footnote{https://www.python.org/dev/peps/pep-0001}。
@anchor{glossary term-portion}@anchor{144e}
@geindex portion -- 部分

@item portion -- 部分

构成一个命名空间包的单个目录内文件集合（也可能存放于一个 zip 文件内），具体定义见 
@geindex Python 提高建议; PEP 420
PEP 420@footnote{https://www.python.org/dev/peps/pep-0420}。
@anchor{glossary term-positional-argument}@anchor{5c0}
@geindex positional argument -- 位置参数

@item positional argument -- 位置参数

参见 @ref{14bb,,argument}。
@anchor{glossary term-provisional-api}@anchor{341}
@geindex provisional API -- 暂定 API

@item provisional API -- 暂定 API

暂定 API 是指被有意排除在标准库的向后兼容性保证之外的应用编程接口。虽然此类接口通常不会再有重大改变，但只要其被标记为暂定，就可能在核心开发者确定有必要的情况下进行向后不兼容的更改（甚至包括移除该接口）。此种更改并不会随意进行 -- 仅在 API 被加入之前未考虑到的严重基础性缺陷被发现时才可能会这样做。

即便是对暂定 API 来说，向后不兼容的更改也会被视为“最后的解决方案” —— 任何问题被确认时都会尽可能先尝试找到一种向后兼容的解决方案。

这种处理过程允许标准库持续不断地演进，不至于被有问题的长期性设计缺陷所困。详情见 
@geindex Python 提高建议; PEP 411
PEP 411@footnote{https://www.python.org/dev/peps/pep-0411}。
@anchor{glossary term-provisional-package}@anchor{97a}
@geindex provisional package -- 暂定包

@item provisional package -- 暂定包

参见 @ref{341,,provisional API}。
@anchor{glossary term-python-3000}@anchor{42cf}
@geindex Python 3000

@item Python 3000

Python 3.x 发布路线的昵称（这个名字在版本 3 的发布还遥遥无期的时候就已出现了）。有时也被缩写为“Py3k”。
@anchor{glossary term-pythonic}@anchor{42d0}
@geindex Pythonic

@item Pythonic

指一个思路或一段代码紧密遵循了 Python 语言最常用的风格和理念，而不是使用其他语言中通用的概念来实现代码。例如，Python 的常用风格是使用 @ref{c29,,for} 语句循环来遍历一个可迭代对象中的所有元素。许多其他语言没有这样的结构，因此不熟悉 Python 的人有时会选择使用一个数字计数器:

@example
for i in range(len(food)):
    print(food[i])
@end example

而相应的更简洁更 Pythonic 的方法是这样的:

@example
for piece in food:
    print(piece)
@end example
@anchor{glossary term-qualified-name}@anchor{13c2}
@geindex qualified name -- 限定名称

@item qualified name -- 限定名称

一个以点号分隔的名称，显示从模块的全局作用域到该模块中定义的某个类、函数或方法的“路径”，相关定义见 
@geindex Python 提高建议; PEP 3155
PEP 3155@footnote{https://www.python.org/dev/peps/pep-3155}。对于最高层级的函数和类，限定名称与对象名称一致:

@example
>>> class C:
...     class D:
...         def meth(self):
...             pass
...
>>> C.__qualname__
'C'
>>> C.D.__qualname__
'C.D'
>>> C.D.meth.__qualname__
'C.D.meth'
@end example

当被用于引用模块时，@emph{完整限定名称} 意为标示该模块的以点号分隔的整个路径，其中包含其所有的父包，例如 @code{email.mime.text}:

@example
>>> import email.mime.text
>>> email.mime.text.__name__
'email.mime.text'
@end example
@anchor{glossary term-reference-count}@anchor{3ad9}
@geindex reference count -- 引用计数

@item reference count -- 引用计数

对特定对象的引用的数量。当一个对象的引用计数降为零时，所分配资源将被释放。引用计数对 Python 代码来说通常是不可见的，但它是 @ref{13ce,,CPython} 实现的一个关键元素。@ref{fd,,sys} 模块定义了一个 @ref{35d7,,getrefcount()} 函数，程序员可调用它来返回特定对象的引用计数。
@anchor{glossary term-regular-package}@anchor{144b}
@geindex regular package -- 常规包

@item regular package -- 常规包

传统型的 @ref{1449,,package}，例如包含有一个 @code{__init__.py} 文件的目录。

另参见 @ref{144c,,namespace package}。
@anchor{glossary term-slots}@anchor{3742}
@geindex __slots__

@item __slots__

一种写在类内部的声明，通过预先声明实例属性等对象并移除实例字典来节省内存。虽然这种技巧很流行，但想要用好却并不容易，最好是只保留在少数情况下采用，例如极耗内存的应用程序，并且其中包含大量实例。
@anchor{glossary term-sequence}@anchor{11bc}
@geindex sequence -- 序列

@item sequence -- 序列

一种 @ref{ba5,,iterable}，它支持通过 @ref{27f,,__getitem__()} 特殊方法来使用整数索引进行高效的元素访问，并定义了一个返回序列长度的 @ref{dc4,,__len__()} 方法。内置的序列类型有 @ref{262,,list}、@ref{329,,str}、@ref{478,,tuple} 和 @ref{32a,,bytes}。注意虽然 @ref{1b8,,dict} 也支持 @ref{27f,,__getitem__()} 和 @ref{dc4,,__len__()}，但它被认为属于映射而非序列，因为它查找时使用任意的 @ref{11b6,,immutable} 键而非整数。

@ref{15c8,,collections.abc.Sequence} 抽象基类定义了一个更丰富的接口，它超越了 @ref{27f,,__getitem__()} 和 @ref{dc4,,__len__()}，添加了 @code{count()}, @code{index()}, @ref{d21,,__contains__()} 和 @ref{529,,__reversed__()} 。 可以使用 @code{register()} 显式注册实现此扩展接口的类型。
@anchor{glossary term-single-dispatch}@anchor{1ca}
@geindex single dispatch -- 单分派

@item single dispatch -- 单分派

一种 @ref{1cb,,generic function} 分派形式，其实现是基于单个参数的类型来选择的。
@anchor{glossary term-slice}@anchor{1598}
@geindex slice -- 切片

@item slice -- 切片

通常只包含了特定 @ref{11bc,,sequence} 的一部分的对象。切片是通过使用下标标记来创建的，在 @code{[]} 中给出几个以冒号分隔的数字，例如 @code{variable_name[1:3:5]}。方括号（下标）标记在内部使用 @ref{dfd,,slice} 对象。
@anchor{glossary term-special-method}@anchor{3608}
@geindex special method -- 特殊方法

@item special method -- 特殊方法

@geindex special; method

一种由 Python 隐式调用的方法，用来对某个类型执行特定操作例如相加等等。这种方法的名称的首尾都为双下划线。特殊方法的文档参见 @ref{508,,特殊方法名称}。
@anchor{glossary term-statement}@anchor{1b24}
@geindex statement -- 语句

@item statement -- 语句

语句是程序段（一个代码“块”）的组成单位。一条语句可以是一个 @ref{35cd,,expression} 或某个带有关键字的结构，例如 @ref{de0,,if}、@ref{11c1,,while} 或 @ref{c29,,for}。
@anchor{glossary term-text-encoding}@anchor{1593}
@geindex text encoding -- 文本编码

@item text encoding -- 文本编码

用于将Unicode字符串编码为字节串的编码器。
@anchor{glossary term-text-file}@anchor{1239}
@geindex text file -- 文本文件

@item text file -- 文本文件

一种能够读写 @ref{329,,str} 对象的 @ref{b3b,,file object}。通常一个文本文件实际是访问一个面向字节的数据流并自动处理 @ref{1593,,text encoding}。文本文件的例子包括以文本模式（@code{'r'} 或 @code{'w'}）打开的文件、@ref{306,,sys.stdin}、@ref{307,,sys.stdout} 以及 @ref{827,,io.StringIO} 的实例。

另请参看 @ref{1c37,,binary file} 了解能够读写 @ref{5e3,,字节类对象} 的文件对象。
@anchor{glossary term-triple-quoted-string}@anchor{42d1}
@geindex triple-quoted string -- 三引号字符串

@item triple-quoted string -- 三引号字符串

首尾各带三个连续双引号（"）或者单引号（'）的字符串。它们在功能上与首尾各用一个引号标注的字符串没有什么不同，但是有多种用处。它们允许你在字符串内包含未经转义的单引号和双引号，并且可以跨越多行而无需使用连接符，在编写文档字符串时特别好用。
@anchor{glossary term-type}@anchor{42d2}
@geindex type -- 类型

@item type -- 类型

类型决定一个 Python 对象属于什么种类；每个对象都具有一种类型。要知道对象的类型，可以访问它的 @ref{e03,,__class__} 属性，或是通过 @code{type(obj)} 来获取。
@anchor{glossary term-type-alias}@anchor{42d3}
@geindex type alias -- 类型别名

@item type alias -- 类型别名

一个类型的同义词，创建方式是把类型赋值给特定的标识符。

类型别名的作用是简化 @ref{42b9,,类型提示}。例如:

@example
from typing import List, Tuple

def remove_gray_shades(
        colors: List[Tuple[int, int, int]]) -> List[Tuple[int, int, int]]:
    pass
@end example

可以这样提高可读性:

@example
from typing import List, Tuple

Color = Tuple[int, int, int]

def remove_gray_shades(colors: List[Color]) -> List[Color]:
    pass
@end example

参见 @ref{119,,typing} 和 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484}，其中有对此功能的详细描述。
@anchor{glossary term-type-hint}@anchor{42b9}
@geindex type hint -- 类型提示

@item type hint -- 类型提示

@ref{42b8,,annotation} 为变量、类属性、函数的形参或返回值指定预期的类型。

类型提示属于可选项，Python 不要求提供，但其可对静态类型分析工具起作用，并可协助 IDE 实现代码补全与重构。

全局变量、类属性和函数的类型提示可以使用 @ref{303,,typing.get_type_hints()} 来访问，但局部变量则不可以。

参见 @ref{119,,typing} 和 
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484}，其中有对此功能的详细描述。
@anchor{glossary term-universal-newlines}@anchor{5ef}
@geindex universal newlines -- 通用换行

@item universal newlines -- 通用换行

一种解读文本流的方式，将以下所有符号都识别为行结束标志：Unix 的行结束约定 @code{'\n'}、Windows 的约定 @code{'\r\n'} 以及旧版 Macintosh 的约定 @code{'\r'}。参见 
@geindex Python 提高建议; PEP 278
PEP 278@footnote{https://www.python.org/dev/peps/pep-0278} 和 
@geindex Python 提高建议; PEP 3116
PEP 3116@footnote{https://www.python.org/dev/peps/pep-3116} 和 @ref{163c,,bytes.splitlines()} 了解更多用法说明。
@anchor{glossary term-variable-annotation}@anchor{61a}
@geindex variable annotation -- 变量标注

@item variable annotation -- 变量标注

对变量或类属性的 @ref{42b8,,annotation}。

在标注变量或类属性时，还可选择为其赋值:

@example
class C:
    field: 'annotation'
@end example

变量标注通常被用作 @ref{42b9,,类型提示}：例如以下变量预期接受 @ref{184,,int} 类型的值:

@example
count: int = 0
@end example

变量标注语法的详细解释见 @ref{150f,,带标注的赋值语句} 一节。

请参看 @ref{11f1,,function annotation}、
@geindex Python 提高建议; PEP 484
PEP 484@footnote{https://www.python.org/dev/peps/pep-0484} 和 
@geindex Python 提高建议; PEP 526
PEP 526@footnote{https://www.python.org/dev/peps/pep-0526}，其中对此功能有详细描述。
@anchor{glossary term-virtual-environment}@anchor{12a7}
@geindex virtual environment -- 虚拟环境

@item virtual environment -- 虚拟环境

一种采用协作式隔离的运行时环境，允许 Python 用户和应用程序在安装和升级 Python 分发包时不会干扰到同一系统上运行的其他 Python 应用程序的行为。

另参见 @ref{125,,venv}。
@anchor{glossary term-virtual-machine}@anchor{2723}
@geindex virtual machine -- 虚拟机

@item virtual machine -- 虚拟机

一台完全通过软件定义的计算机。Python 虚拟机可执行字节码编译器所生成的 @ref{60f,,bytecode}。
@anchor{glossary term-zen-of-python}@anchor{42d4}
@geindex Zen of Python -- Python 之禅

@item Zen of Python -- Python 之禅

列出 Python 设计的原则与哲学，有助于理解与使用这种语言。查看其具体内容可在交互模式提示符中输入 "@code{import this}"。
@end table

@node 文档说明,处理错误,术语对照表,Top
@anchor{about doc}@anchor{42d5}@anchor{about about-these-documents}@anchor{42d6}
@chapter 文档说明


这些文档是用 Sphinx@footnote{http://sphinx-doc.org/} 从 reStructuredText@footnote{http://docutils.sourceforge.net/rst.html} 源生成的，@cite{Sphinx} 是一个专为处理 Python 文档而编写的文档生成器。

@c In the online version of these documents, you can submit comments and suggest
@c changes directly on the documentation pages.

本文档及其工具链之开发，皆在于志愿者之努力，亦恰如 Python 本身。如果您想为此作出贡献，请阅读 @ref{3b3b,,处理错误} 了解如何参与。我们随时欢迎新的志愿者！

特别鸣谢：


@itemize *

@item 
Fred L. Drake, Jr.，原始 Python 文档工具集之创造者，众多文档之作者；

@item 
Docutils@footnote{http://docutils.sourceforge.net/} 项目，该项目孕育了 reStructuredText 及 Docutils 套件；

@item 
Fredrik Lundh 的项目 Alternative Python Reference@footnote{http://effbot.org/zone/pyref.htm}，Sphinx 从中得到了很多不错的点子
@end itemize

@menu
* Python 文档的贡献者:: 

@end menu

@node Python 文档的贡献者,,,文档说明
@anchor{about contributors-to-the-python-documentation}@anchor{42d7}
@section Python 文档的贡献者


有很多对 Python 语言，Python 标准库和 Python 文档有贡献的人，随 Python 源代码发布的 Misc/ACKS@footnote{https://github.com/python/cpython/tree/3.8/Misc/ACKS} 文件列出了部分贡献者。

仅通过 Python 社区的输入和贡献，Python 就拥有了如此出色的文档——谢谢你们！

@node 处理错误,版权所有,文档说明,Top
@anchor{bugs doc}@anchor{42d8}@anchor{bugs dealing-with-bugs}@anchor{42d9}@anchor{bugs reporting-bugs}@anchor{3b3b}
@chapter 处理错误


Python 是一门成熟的编程语言，以稳定著称。为维持其美誉，开发者希望获悉所有您在 Python 中发现的缺陷。

有时候自己修复漏洞并将补丁提交给 Python 能更快地解决问题，因为它简化了流程并且减少了参与的人力。 请参阅如何 @ref{42da,,提交补丁}。

@menu
* 文档 Bug:: 
* 使用 Python 的问题追踪系统:: 
* 开始为 Python 贡献您的知识:: 

@end menu

@node 文档 Bug,使用 Python 的问题追踪系统,,处理错误
@anchor{bugs documentation-bugs}@anchor{42db}
@section 文档 Bug


如果您在本文档中发现了错误并打算帮助我们改进，请将错误提交到 @ref{42dc,,追踪系统}。 如果您有相应的修正建议，请一并提交。 （译者注：如果是中文文档翻译相关的错误，请务必提交到 @indicateurl{https://github.com/python/python-docs-zh-cn/issues}。如果将翻译问题反馈到了其他地方，可能会因为语言不通而不能及时处理。）

如果您时间有限，还可以通过电子邮件将文档的错误报告发送至 @email{docs@@python}.org（代码运行错误请发送至 @email{python-list@@python.org}）。“docs@@”是一个由志愿者运作的邮件列表；您的请求会得到关注，但可能需要一些时间才会被处理。


@subsubheading 参见



@table @asis

@item Documentation bugs@footnote{https://bugs.python.org/issue?@@filter=status&@@filter=components&components=4&status=1&@@columns=id@comma{}activity@comma{}title@comma{}status&@@sort=-activity}

已提交给 Python 问题追踪系统的文档错误列表。

@item 问题跟踪@footnote{https://devguide.python.org/tracker/}

在追踪系统上参与问题改进的过程概述。

@item 改进文档@footnote{https://devguide.python.org/docquality/#helping-with-documentation}

给有兴趣为 Python 文档做出贡献的人。
@end table


@node 使用 Python 的问题追踪系统,开始为 Python 贡献您的知识,文档 Bug,处理错误
@anchor{bugs using-the-python-issue-tracker}@anchor{42dd}@anchor{bugs using-the-tracker}@anchor{42dc}
@section 使用 Python 的问题追踪系统


对于 Python 本身的错误报告应当通过 Python 错误追踪系统（@indicateurl{https://bugs.python.org/}）进行提交。该错误追踪系统提供了一个可以输入并提交相关信息给开发者的网页表单。

第一步是确认是否有重复的报告。这样做除了可以节省开发者的时间，也能让您从中了解到我们做出了怎样的努力；我们有可能已经在下个版本中修复了这个问题，也有可能需要更详细的信息（在这种情况下，非常欢迎您提供！）。要查找重复的报告，请使用顶部的搜索栏进行搜索。

如果您没有搜索到您想报告的问题，请返回并登录 Python 错误追踪系统。如果您没有账号，请点击“注册（Register）”链接，或者在侧边栏中选择任何一个 OpenID 登录方式。您不能匿名提交一份错误报告。

如果已经登录， 那您就可以提交错误报告了。请点击侧边栏中的“新建（Create New）”链接，打开报告表单。

表单中有几个空栏（译者注：请用英语填写）。请在 “标题（Title）”栏填入对问题 @emph{非常} 简短的描述；一个好的描述应当少于十个单词。在 “类型（Type）”栏，选择您的问题的类型；同样地，选择 bug 相对应的“组件（Component）”和“版本（Versions）”。

在“说明（Comment）”栏，请详细描述问题，包括您预期的情况和实际的情况。请确保包含任何涉及的拓展模块，以及您当时所使用的硬件和软件平台（如果可能，请附上版本信息）。

每一份错误报告将被分派给一名开发者，并由这名开发者决定如何修正这个问题。每当有相关的进展时，您都会收到通知。


@subsubheading 参见



@table @asis

@item 如何有效地报告错误@footnote{https://www.chiark.greenend.org.uk/~sgtatham/bugs.html}

该文章详细介绍了如何创建一份有用的错误报告。它描述了什么样的信息是有用的，以及为什么是有用的。

@item 错误报告编写指南@footnote{https://developer.mozilla.org/en-US/docs/Mozilla/QA/Bug_writing_guidelines}

关于写一份好的错误报告。部分仅针对 Mozilla 项目，不过其描述了通用的恰当做法。
@end table


@node 开始为 Python 贡献您的知识,,使用 Python 的问题追踪系统,处理错误
@anchor{bugs contributing-to-python}@anchor{42da}@anchor{bugs getting-started-contributing-to-python-yourself}@anchor{42de}
@section 开始为 Python 贡献您的知识


除了仅仅报告您所发现的错误之外，同样欢迎您提交修复它们的补丁。您可以在 Python 开发者指引@footnote{https://devguide.python.org/} 中找到更多为 Python 打补丁的信息。如果您有任何问题，核心导师邮件列表@footnote{https://mail.python.org/mailman3/lists/core-mentorship.python.org/} 是一个友好的去处，在那里， 你可以寻求修复 Python 相关问题的答案。

@node 版权所有,历史和许可证,处理错误,Top
@anchor{copyright doc}@anchor{42df}@anchor{copyright copyright}@anchor{42e0}@anchor{copyright core-mentorship-mailing-list}@anchor{42e1}
@chapter 版权所有


Python 与这份文档：

版权所有 © 2001-2020 Python 软件基金会。保留所有权利。

版权所有 © 2000 BeOpen.com。保留所有权利。

版权所有 © 1995-2000 Corporation for National Research Initiatives。保留所有权利。

版权所有 © 1991-1995 Stichting Mathematisch Centrum。保留所有权利。


__________________________________________________________________


有关完整的许可证和许可信息，参见 @ref{42e2,,历史和许可证}。

@node 历史和许可证,分发 Python 模块（遗留版本）,版权所有,Top
@anchor{license doc}@anchor{42e3}@anchor{license history-and-license}@anchor{42e2}@anchor{license id1}@anchor{42e4}
@chapter 历史和许可证


@menu
* 该软件的历史:: 
* 获取或以其他方式使用 Python 的条款和条件:: 
* 收录软件的许可与鸣谢:: 

@end menu

@node 该软件的历史,获取或以其他方式使用 Python 的条款和条件,,历史和许可证
@anchor{license history-of-the-software}@anchor{42e5}
@section 该软件的历史


Python 由荷兰数学和计算机科学研究学会（CWI，见 @indicateurl{https://www.cwi.nl/} ）的 Guido van Rossum 于 1990 年代初设计，作为一门叫做 ABC 的语言的替代品。尽管 Python 包含了许多来自其他人的贡献，Guido 仍是其主要作者。

1995 年，Guido 在弗吉尼亚州的国家创新研究公司（CNRI，见 @indicateurl{https://www.cnri.reston.va.us/} ）继续他在 Python 上的工作，并在那里发布了该软件的多个版本。

2000 年五月，Guido 和 Python 核心开发团队转到 BeOpen.com 并组建了 BeOpen PythonLabs 团队。 同年十月，PythonLabs 团队转到 Digital Creations (现为 Zope Corporation；见 @indicateurl{https://www.zope.org/})。 2001 年，Python 软件基金会 (PSF，见 @indicateurl{https://www.python.org/psf/}) 成立，这是一个专为拥有 Python 相关知识产权而创建的非营利组织。 Zope Corporation 现在是 PSF 的赞助成员。

所有的 Python 版本都是开源的（有关开源的定义参阅 @indicateurl{https://opensource.org/} ）。历史上，绝大多数 Python 版本是 GPL 兼容的；下表总结了各个版本情况。


@multitable {xxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxx} 
@headitem

发布版本

@tab

源自

@tab

年份

@tab

所有者

@tab

GPL 兼容？

@item

0.9.0 至 1.2

@tab

n/a

@tab

1991-1995

@tab

CWI

@tab

是

@item

1.3 至 1.5.2

@tab

1.2

@tab

1995-1999

@tab

CNRI

@tab

是

@item

1.6

@tab

1.5.2

@tab

2000

@tab

CNRI

@tab

否

@item

2.0

@tab

1.6

@tab

2000

@tab

BeOpen.com

@tab

否

@item

1.6.1

@tab

1.6

@tab

2001

@tab

CNRI

@tab

否

@item

2.1

@tab

2.0+1.6.1

@tab

2001

@tab

PSF

@tab

否

@item

2.0.1

@tab

2.0+1.6.1

@tab

2001

@tab

PSF

@tab

是

@item

2.1.1

@tab

2.1+2.0.1

@tab

2001

@tab

PSF

@tab

是

@item

2.1.2

@tab

2.1.1

@tab

2002

@tab

PSF

@tab

是

@item

2.1.3

@tab

2.1.2

@tab

2002

@tab

PSF

@tab

是

@item

2.2 及更高

@tab

2.1.1

@tab

2001 至今

@tab

PSF

@tab

是

@end multitable


@cartouche
@quotation 注解 
GPL 兼容并不意味着 Python 在 GPL 下发布。与 GPL 不同，所有 Python 许可证都允许您分发修改后的版本，而无需开源所做的更改。GPL 兼容的许可证使得 Python 可以与其它在 GPL 下发布的软件结合使用；但其它的许可证则不行。
@end quotation
@end cartouche

感谢众多在 Guido 指导下工作的外部志愿者，使得这些发布成为可能。

@node 获取或以其他方式使用 Python 的条款和条件,收录软件的许可与鸣谢,该软件的历史,历史和许可证
@anchor{license terms-and-conditions-for-accessing-or-otherwise-using-python}@anchor{42e6}
@section 获取或以其他方式使用 Python 的条款和条件


@menu
* 用于 PYTHON 3.8.4 的 PSF 许可协议: 用于 PYTHON 3 8 4 的 PSF 许可协议. 
* 用于 PYTHON 2.0 的 BEOPEN.COM 许可协议: 用于 PYTHON 2 0 的 BEOPEN COM 许可协议. 
* 用于 PYTHON 1.6.1 的 CNRI 许可协议: 用于 PYTHON 1 6 1 的 CNRI 许可协议. 
* 用于 PYTHON 0.9.0 至 1.2 的 CWI 许可协议: 用于 PYTHON 0 9 0 至 1 2 的 CWI 许可协议. 

@end menu

@node 用于 PYTHON 3 8 4 的 PSF 许可协议,用于 PYTHON 2 0 的 BEOPEN COM 许可协议,,获取或以其他方式使用 Python 的条款和条件
@anchor{license psf-license-agreement-for-python-release}@anchor{42e7}
@subsection 用于 PYTHON 3.8.4 的 PSF 许可协议


@example
1. This LICENSE AGREEMENT is between the Python Software Foundation ("PSF"), and
   the Individual or Organization ("Licensee") accessing and otherwise using Python
   3.8.4 software in source or binary form and its associated documentation.

2. Subject to the terms and conditions of this License Agreement, PSF hereby
   grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
   analyze, test, perform and/or display publicly, prepare derivative works,
   distribute, and otherwise use Python 3.8.4 alone or in any derivative
   version, provided, however, that PSF's License Agreement and PSF's notice of
   copyright, i.e., "Copyright © 2001-2020 Python Software Foundation; All Rights
   Reserved" are retained in Python 3.8.4 alone or in any derivative version
   prepared by Licensee.

3. In the event Licensee prepares a derivative work that is based on or
   incorporates Python 3.8.4 or any part thereof, and wants to make the
   derivative work available to others as provided herein, then Licensee hereby
   agrees to include in any such work a brief summary of the changes made to Python
   3.8.4.

4. PSF is making Python 3.8.4 available to Licensee on an "AS IS" basis.
   PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY WAY OF
   EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND DISCLAIMS ANY REPRESENTATION OR
   WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE
   USE OF PYTHON 3.8.4 WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON 3.8.4
   FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF
   MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 3.8.4, OR ANY DERIVATIVE
   THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.

6. This License Agreement will automatically terminate upon a material breach of
   its terms and conditions.

7. Nothing in this License Agreement shall be deemed to create any relationship
   of agency, partnership, or joint venture between PSF and Licensee.  This License
   Agreement does not grant permission to use PSF trademarks or trade name in a
   trademark sense to endorse or promote products or services of Licensee, or any
   third party.

8. By copying, installing or otherwise using Python 3.8.4, Licensee agrees
   to be bound by the terms and conditions of this License Agreement.
@end example

@node 用于 PYTHON 2 0 的 BEOPEN COM 许可协议,用于 PYTHON 1 6 1 的 CNRI 许可协议,用于 PYTHON 3 8 4 的 PSF 许可协议,获取或以其他方式使用 Python 的条款和条件
@anchor{license beopen-com-license-agreement-for-python-2-0}@anchor{42e8}
@subsection 用于 PYTHON 2.0 的 BEOPEN.COM 许可协议


BEOPEN PYTHON 开源许可协议第 1 版

@example
1. This LICENSE AGREEMENT is between BeOpen.com ("BeOpen"), having an office at
   160 Saratoga Avenue, Santa Clara, CA 95051, and the Individual or Organization
   ("Licensee") accessing and otherwise using this software in source or binary
   form and its associated documentation ("the Software").

2. Subject to the terms and conditions of this BeOpen Python License Agreement,
   BeOpen hereby grants Licensee a non-exclusive, royalty-free, world-wide license
   to reproduce, analyze, test, perform and/or display publicly, prepare derivative
   works, distribute, and otherwise use the Software alone or in any derivative
   version, provided, however, that the BeOpen Python License is retained in the
   Software, alone or in any derivative version prepared by Licensee.

3. BeOpen is making the Software available to Licensee on an "AS IS" basis.
   BEOPEN MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY WAY OF
   EXAMPLE, BUT NOT LIMITATION, BEOPEN MAKES NO AND DISCLAIMS ANY REPRESENTATION OR
   WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE
   USE OF THE SOFTWARE WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

4. BEOPEN SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF THE SOFTWARE FOR
   ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF USING,
   MODIFYING OR DISTRIBUTING THE SOFTWARE, OR ANY DERIVATIVE THEREOF, EVEN IF
   ADVISED OF THE POSSIBILITY THEREOF.

5. This License Agreement will automatically terminate upon a material breach of
   its terms and conditions.

6. This License Agreement shall be governed by and interpreted in all respects
   by the law of the State of California, excluding conflict of law provisions.
   Nothing in this License Agreement shall be deemed to create any relationship of
   agency, partnership, or joint venture between BeOpen and Licensee.  This License
   Agreement does not grant permission to use BeOpen trademarks or trade names in a
   trademark sense to endorse or promote products or services of Licensee, or any
   third party.  As an exception, the "BeOpen Python" logos available at
   @indicateurl{http://www.pythonlabs.com/logos.html} may be used according to the permissions
   granted on that web page.

7. By copying, installing or otherwise using the software, Licensee agrees to be
   bound by the terms and conditions of this License Agreement.
@end example

@node 用于 PYTHON 1 6 1 的 CNRI 许可协议,用于 PYTHON 0 9 0 至 1 2 的 CWI 许可协议,用于 PYTHON 2 0 的 BEOPEN COM 许可协议,获取或以其他方式使用 Python 的条款和条件
@anchor{license cnri-license-agreement-for-python-1-6-1}@anchor{42e9}
@subsection 用于 PYTHON 1.6.1 的 CNRI 许可协议


@example
1. This LICENSE AGREEMENT is between the Corporation for National Research
   Initiatives, having an office at 1895 Preston White Drive, Reston, VA 20191
   ("CNRI"), and the Individual or Organization ("Licensee") accessing and
   otherwise using Python 1.6.1 software in source or binary form and its
   associated documentation.

2. Subject to the terms and conditions of this License Agreement, CNRI hereby
   grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
   analyze, test, perform and/or display publicly, prepare derivative works,
   distribute, and otherwise use Python 1.6.1 alone or in any derivative version,
   provided, however, that CNRI's License Agreement and CNRI's notice of copyright,
   i.e., "Copyright © 1995-2001 Corporation for National Research Initiatives; All
   Rights Reserved" are retained in Python 1.6.1 alone or in any derivative version
   prepared by Licensee.  Alternately, in lieu of CNRI's License Agreement,
   Licensee may substitute the following text (omitting the quotes): "Python 1.6.1
   is made available subject to the terms and conditions in CNRI's License
   Agreement.  This Agreement together with Python 1.6.1 may be located on the
   Internet using the following unique, persistent identifier (known as a handle):
   1895.22/1013.  This Agreement may also be obtained from a proxy server on the
   Internet using the following URL: @indicateurl{http://hdl.handle.net/1895.22/1013}."

3. In the event Licensee prepares a derivative work that is based on or
   incorporates Python 1.6.1 or any part thereof, and wants to make the derivative
   work available to others as provided herein, then Licensee hereby agrees to
   include in any such work a brief summary of the changes made to Python 1.6.1.

4. CNRI is making Python 1.6.1 available to Licensee on an "AS IS" basis.  CNRI
   MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY WAY OF EXAMPLE,
   BUT NOT LIMITATION, CNRI MAKES NO AND DISCLAIMS ANY REPRESENTATION OR WARRANTY
   OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF
   PYTHON 1.6.1 WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

5. CNRI SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON 1.6.1 FOR
   ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF
   MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 1.6.1, OR ANY DERIVATIVE
   THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.

6. This License Agreement will automatically terminate upon a material breach of
   its terms and conditions.

7. This License Agreement shall be governed by the federal intellectual property
   law of the United States, including without limitation the federal copyright
   law, and, to the extent such U.S. federal law does not apply, by the law of the
   Commonwealth of Virginia, excluding Virginia's conflict of law provisions.
   Notwithstanding the foregoing, with regard to derivative works based on Python
   1.6.1 that incorporate non-separable material that was previously distributed
   under the GNU General Public License (GPL), the law of the Commonwealth of
   Virginia shall govern this License Agreement only as to issues arising under or
   with respect to Paragraphs 4, 5, and 7 of this License Agreement.  Nothing in
   this License Agreement shall be deemed to create any relationship of agency,
   partnership, or joint venture between CNRI and Licensee.  This License Agreement
   does not grant permission to use CNRI trademarks or trade name in a trademark
   sense to endorse or promote products or services of Licensee, or any third
   party.

8. By clicking on the "ACCEPT" button where indicated, or by copying, installing
   or otherwise using Python 1.6.1, Licensee agrees to be bound by the terms and
   conditions of this License Agreement.
@end example

@node 用于 PYTHON 0 9 0 至 1 2 的 CWI 许可协议,,用于 PYTHON 1 6 1 的 CNRI 许可协议,获取或以其他方式使用 Python 的条款和条件
@anchor{license cwi-license-agreement-for-python-0-9-0-through-1-2}@anchor{42ea}
@subsection 用于 PYTHON 0.9.0 至 1.2 的 CWI 许可协议


@example
Copyright © 1991 - 1995, Stichting Mathematisch Centrum Amsterdam, The
Netherlands.  All rights reserved.

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided that
the above copyright notice appear in all copies and that both that copyright
notice and this permission notice appear in supporting documentation, and that
the name of Stichting Mathematisch Centrum or CWI not be used in advertising or
publicity pertaining to distribution of the software without specific, written
prior permission.

STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE FOR ANY SPECIAL, INDIRECT
OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.
@end example

@node 收录软件的许可与鸣谢,,获取或以其他方式使用 Python 的条款和条件,历史和许可证
@anchor{license licenses-and-acknowledgements-for-incorporated-software}@anchor{42eb}
@section 收录软件的许可与鸣谢


本节是Python发行版中收录的第三方软件的许可和致谢清单，该清单是不完整且不断增长的。

@menu
* Mersenne Twister:: 
* 套接字: 套接字<2>. 
* 异步套接字服务:: 
* Cookie 管理:: 
* 执行追踪:: 
* UUencode 与 UUdecode 函数:: 
* XML 远程过程调用:: 
* test_epoll:: 
* Select kqueue:: 
* SipHash24:: 
* strtod 和 dtoa:: 
* OpenSSL:: 
* expat:: 
* libffi:: 
* zlib: zlib<3>. 
* cfuhash:: 
* libmpdec:: 
* W3C C14N 测试套件:: 

@end menu

@node Mersenne Twister,套接字<2>,,收录软件的许可与鸣谢
@anchor{license mersenne-twister}@anchor{42ec}
@subsection Mersenne Twister


@code{_random} 模块包含基于 @indicateurl{http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/emt19937ar.html} 下载的代码。以下是原始代码的完整注释（声明）：

@example
A C-program for MT19937, with initialization improved 2002/1/26.
Coded by Takuji Nishimura and Makoto Matsumoto.

Before using, initialize the state by using init_genrand(seed)
or init_by_array(init_key, key_length).

Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

 1. Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

 2. Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

 3. The names of its contributors may not be used to endorse or promote
    products derived from this software without specific prior written
    permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


Any feedback is very welcome.
http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
email: m-mat @@ math.sci.hiroshima-u.ac.jp (remove space)
@end example

@node 套接字<2>,异步套接字服务,Mersenne Twister,收录软件的许可与鸣谢
@anchor{license sockets}@anchor{42ed}
@subsection 套接字


@ref{ef,,socket} 模块使用 @code{getaddrinfo()} 和 @code{getnameinfo()} 函数，这些函数源代码在WIDE项目（@indicateurl{http://www.wide.ad.jp/}）的单独源文件中。

@example
Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. Neither the name of the project nor the names of its contributors
   may be used to endorse or promote products derived from this software
   without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS `@w{`}AS IS'@w{'} AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
@end example

@node 异步套接字服务,Cookie 管理,套接字<2>,收录软件的许可与鸣谢
@anchor{license asynchronous-socket-services}@anchor{42ee}
@subsection 异步套接字服务


@ref{9,,asynchat} 和 @ref{b,,asyncore} 模块包含以下声明:

@example
Copyright 1996 by Sam Rushing

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and
its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that copyright notice and this permission
notice appear in supporting documentation, and that the name of Sam
Rushing not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.

SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL, INDIRECT OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
@end example

@node Cookie 管理,执行追踪,异步套接字服务,收录软件的许可与鸣谢
@anchor{license cookie-management}@anchor{42ef}
@subsection Cookie 管理


@ref{96,,http.cookies} 模块包含以下声明:

@example
Copyright 2000 by Timothy O'Malley <timo@@alum.mit.edu>

               All Rights Reserved

Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
copies and that both that copyright notice and this permission
notice appear in supporting documentation, and that the name of
Timothy O'Malley  not be used in advertising or publicity
pertaining to distribution of the software without specific, written
prior permission.

Timothy O'Malley DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS, IN NO EVENT SHALL Timothy O'Malley BE LIABLE FOR
ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
@end example

@node 执行追踪,UUencode 与 UUdecode 函数,Cookie 管理,收录软件的许可与鸣谢
@anchor{license execution-tracing}@anchor{42f0}
@subsection 执行追踪


@ref{112,,trace} 模块包含以下声明:

@example
portions copyright 2001, Autonomous Zones Industries, Inc., all rights...
err...  reserved and offered to the public under the terms of the
Python 2.2 license.
Author: Zooko O'Whielacronx
http://zooko.com/
mailto:zooko@@zooko.com

Copyright 2000, Mojam Media, Inc., all rights reserved.
Author: Skip Montanaro

Copyright 1999, Bioreason, Inc., all rights reserved.
Author: Andrew Dalke

Copyright 1995-1997, Automatrix, Inc., all rights reserved.
Author: Skip Montanaro

Copyright 1991-1995, Stichting Mathematisch Centrum, all rights reserved.


Permission to use, copy, modify, and distribute this Python software and
its associated documentation for any purpose without fee is hereby
granted, provided that the above copyright notice appears in all copies,
and that both that copyright notice and this permission notice appear in
supporting documentation, and that the name of neither Automatrix,
Bioreason or Mojam Media be used in advertising or publicity pertaining to
distribution of the software without specific, written prior permission.
@end example

@node UUencode 与 UUdecode 函数,XML 远程过程调用,执行追踪,收录软件的许可与鸣谢
@anchor{license uuencode-and-uudecode-functions}@anchor{42f1}
@subsection UUencode 与 UUdecode 函数


@ref{123,,uu} 模块包含以下声明:

@example
Copyright 1994 by Lance Ellinghouse
Cathedral City, California Republic, United States of America.
                       All Rights Reserved
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of Lance Ellinghouse
not be used in advertising or publicity pertaining to distribution
of the software without specific, written prior permission.
LANCE ELLINGHOUSE DISCLAIMS ALL WARRANTIES WITH REGARD TO
THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS, IN NO EVENT SHALL LANCE ELLINGHOUSE CENTRUM BE LIABLE
FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Modified by Jack Jansen, CWI, July 1995:
- Use binascii module to do the actual line-by-line conversion
  between ascii and binary. This results in a 1000-fold speedup. The C
  version is still 5 times faster, though.
- Arguments more compliant with Python standard
@end example

@node XML 远程过程调用,test_epoll,UUencode 与 UUdecode 函数,收录软件的许可与鸣谢
@anchor{license xml-remote-procedure-calls}@anchor{42f2}
@subsection XML 远程过程调用


@ref{13f,,xmlrpc.client} 模块包含以下声明:

@example
    The XML-RPC client interface is

Copyright (c) 1999-2002 by Secret Labs AB
Copyright (c) 1999-2002 by Fredrik Lundh

By obtaining, using, and/or copying this software and/or its
associated documentation, you agree that you have read, understood,
and will comply with the following terms and conditions:

Permission to use, copy, modify, and distribute this software and
its associated documentation for any purpose and without fee is
hereby granted, provided that the above copyright notice appears in
all copies, and that both that copyright notice and this permission
notice appear in supporting documentation, and that the name of
Secret Labs AB or the author not be used in advertising or publicity
pertaining to distribution of the software without specific, written
prior permission.

SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
OF THIS SOFTWARE.
@end example

@node test_epoll,Select kqueue,XML 远程过程调用,收录软件的许可与鸣谢
@anchor{license test-epoll}@anchor{42f3}
@subsection test_epoll


@code{test_epoll} 模块包含以下声明:

@example
Copyright (c) 2001-2006 Twisted Matrix Laboratories.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
@end example

@node Select kqueue,SipHash24,test_epoll,收录软件的许可与鸣谢
@anchor{license select-kqueue}@anchor{42f4}
@subsection Select kqueue


@ref{e5,,select} 模块关于 kqueue 的接口包含以下声明:

@example
Copyright (c) 2000 Doug White, 2006 James Knight, 2007 Christian Heimes
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS `@w{`}AS IS'@w{'} AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
@end example

@node SipHash24,strtod 和 dtoa,Select kqueue,收录软件的许可与鸣谢
@anchor{license siphash24}@anchor{42f5}
@subsection SipHash24


@code{Python/pyhash.c} 文件包含 Marek Majkowski' 对 Dan Bernstein 的SipHash24 算法的实现。它包含以下声明:

@example
<MIT License>
Copyright (c) 2013  Marek Majkowski <marek@@popcount.org>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
</MIT License>

Original location:
   https://github.com/majek/csiphash/

Solution inspired by code from:
   Samuel Neves (supercop/crypto_auth/siphash24/little)
   djb (supercop/crypto_auth/siphash24/little2)
   Jean-Philippe Aumasson (https://131002.net/siphash/siphash24.c)
@end example

@node strtod 和 dtoa,OpenSSL,SipHash24,收录软件的许可与鸣谢
@anchor{license strtod-and-dtoa}@anchor{42f6}
@subsection strtod 和 dtoa


@code{Python/dtoa.c} 文件提供了C语言的 dtoa 和 strtod 函数，用于将C语言的 双精度型和字符串进行转换，由David M. Gay的同名文件派生而来，该文件当前可从http://www.netlib.org/fp/ 下载。2009年3月16日检索到的原始文件包含以下版权和许可声明:

@example
/****************************************************************
 *
 * The author of this software is David M. Gay.
 *
 * Copyright (c) 1991, 2000, 2001 by Lucent Technologies.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 *
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHOR NOR LUCENT MAKES ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 *
 ***************************************************************/
@end example

@node OpenSSL,expat,strtod 和 dtoa,收录软件的许可与鸣谢
@anchor{license openssl}@anchor{42f7}
@subsection OpenSSL


如果操作系统可用，则 @ref{8d,,hashlib}, @ref{d1,,posix}, @ref{f3,,ssl}, @ref{29,,crypt} 模块使用OpenSSL库来提高性能。此外，适用于Python的Windows和Mac OS X安装程序可能包括OpenSSL库的拷贝，所以在此处也列出了OpenSSL许可证的拷贝:

@example
 LICENSE ISSUES
 ==============

 The OpenSSL toolkit stays under a dual license, i.e. both the conditions of
 the OpenSSL License and the original SSLeay license apply to the toolkit.
 See below for the actual license texts. Actually both licenses are BSD-style
 Open Source licenses. In case of any license issues related to OpenSSL
 please contact openssl-core@@openssl.org.

 OpenSSL License
 ---------------

   /* ====================================================================
    * Copyright (c) 1998-2008 The OpenSSL Project.  All rights reserved.
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions
    * are met:
    *
    * 1. Redistributions of source code must retain the above copyright
    *    notice, this list of conditions and the following disclaimer.
    *
    * 2. Redistributions in binary form must reproduce the above copyright
    *    notice, this list of conditions and the following disclaimer in
    *    the documentation and/or other materials provided with the
    *    distribution.
    *
    * 3. All advertising materials mentioning features or use of this
    *    software must display the following acknowledgment:
    *    "This product includes software developed by the OpenSSL Project
    *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
    *
    * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
    *    endorse or promote products derived from this software without
    *    prior written permission. For written permission, please contact
    *    openssl-core@@openssl.org.
    *
    * 5. Products derived from this software may not be called "OpenSSL"
    *    nor may "OpenSSL" appear in their names without prior written
    *    permission of the OpenSSL Project.
    *
    * 6. Redistributions of any form whatsoever must retain the following
    *    acknowledgment:
    *    "This product includes software developed by the OpenSSL Project
    *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
    *
    * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT `@w{`}AS IS'@w{'} AND ANY
    * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
    * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
    * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
    * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
    * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
    * OF THE POSSIBILITY OF SUCH DAMAGE.
    * ====================================================================
    *
    * This product includes cryptographic software written by Eric Young
    * (eay@@cryptsoft.com).  This product includes software written by Tim
    * Hudson (tjh@@cryptsoft.com).
    *
    */

Original SSLeay License
-----------------------

   /* Copyright (C) 1995-1998 Eric Young (eay@@cryptsoft.com)
    * All rights reserved.
    *
    * This package is an SSL implementation written
    * by Eric Young (eay@@cryptsoft.com).
    * The implementation was written so as to conform with Netscapes SSL.
    *
    * This library is free for commercial and non-commercial use as long as
    * the following conditions are aheared to.  The following conditions
    * apply to all code found in this distribution, be it the RC4, RSA,
    * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
    * included with this distribution is covered by the same copyright terms
    * except that the holder is Tim Hudson (tjh@@cryptsoft.com).
    *
    * Copyright remains Eric Young's, and as such any Copyright notices in
    * the code are not to be removed.
    * If this package is used in a product, Eric Young should be given attribution
    * as the author of the parts of the library used.
    * This can be in the form of a textual message at program startup or
    * in documentation (online or textual) provided with the package.
    *
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions
    * are met:
    * 1. Redistributions of source code must retain the copyright
    *    notice, this list of conditions and the following disclaimer.
    * 2. Redistributions in binary form must reproduce the above copyright
    *    notice, this list of conditions and the following disclaimer in the
    *    documentation and/or other materials provided with the distribution.
    * 3. All advertising materials mentioning features or use of this software
    *    must display the following acknowledgement:
    *    "This product includes cryptographic software written by
    *     Eric Young (eay@@cryptsoft.com)"
    *    The word 'cryptographic' can be left out if the rouines from the library
    *    being used are not cryptographic related :-).
    * 4. If you include any Windows specific code (or a derivative thereof) from
    *    the apps directory (application code) you must include an acknowledgement:
    *    "This product includes software written by Tim Hudson (tjh@@cryptsoft.com)"
    *
    * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG `@w{`}AS IS'@w{'} AND
    * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
    * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    * SUCH DAMAGE.
    *
    * The licence and distribution terms for any publically available version or
    * derivative of this code cannot be changed.  i.e. this code cannot simply be
    * copied and put under another distribution licence
    * [including the GNU Public Licence.]
    */
@end example

@node expat,libffi,OpenSSL,收录软件的许可与鸣谢
@anchor{license expat}@anchor{42f8}
@subsection expat


除非使用 @code{--with-system-expat} 配置了构建，否则 @code{pyexpat} 扩展都是用包含 expat源的拷贝构建的:

@example
Copyright (c) 1998, 1999, 2000 Thai Open Source Software Center Ltd
                               and Clark Cooper

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
@end example

@node libffi,zlib<3>,expat,收录软件的许可与鸣谢
@anchor{license libffi}@anchor{42f9}
@subsection libffi


除非使用 @code{--with-system-libffi} 配置了构建，否则 @code{_ctypes} 扩展都是包含 libffi源的拷贝构建的:

@example
Copyright (c) 1996-2008  Red Hat, Inc and others.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
`@w{`}Software'@w{'}), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED `@w{`}AS IS'@w{'}, WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
@end example

@node zlib<3>,cfuhash,libffi,收录软件的许可与鸣谢
@anchor{license zlib}@anchor{42fa}
@subsection zlib


如果系统上找到的zlib版本太旧而无法用于构建，则使用包含 zlib源代码的拷贝来构建 @ref{144,,zlib} 扩展:

@example
Copyright (C) 1995-2011 Jean-loup Gailly and Mark Adler

This software is provided 'as-is', without any express or implied
warranty.  In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
   claim that you wrote the original software. If you use this software
   in a product, an acknowledgment in the product documentation would be
   appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

3. This notice may not be removed or altered from any source distribution.

Jean-loup Gailly        Mark Adler
jloup@@gzip.org          madler@@alumni.caltech.edu
@end example

@node cfuhash,libmpdec,zlib<3>,收录软件的许可与鸣谢
@anchor{license cfuhash}@anchor{42fb}
@subsection cfuhash


@ref{114,,tracemalloc} 使用的哈希表的实现基于 cfuhash项目:

@example
Copyright (c) 2005 Don Owens
All rights reserved.

This code is released under the BSD license:

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

  * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

  * Redistributions in binary form must reproduce the above
    copyright notice, this list of conditions and the following
    disclaimer in the documentation and/or other materials provided
    with the distribution.

  * Neither the name of the author nor the names of its
    contributors may be used to endorse or promote products derived
    from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
OF THE POSSIBILITY OF SUCH DAMAGE.
@end example

@node libmpdec,W3C C14N 测试套件,cfuhash,收录软件的许可与鸣谢
@anchor{license libmpdec}@anchor{42fc}
@subsection libmpdec


除非使用 @code{--with-system-libmpdec} 配置了构建，否则 @code{_decimal} 模块都是用包含 libmpdec 库的拷贝构建的。

@example
Copyright (c) 2008-2016 Stefan Krah. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
@end example

@node W3C C14N 测试套件,,libmpdec,收录软件的许可与鸣谢
@anchor{license w3c-c14n-test-suite}@anchor{42fd}
@subsection W3C C14N 测试套件


@ref{105,,test} 包（lib/test/xmltestdata/c14n-20/）中的 C14N2.0测试套件来源于W3C网站 @indicateurl{https://www.w3.org/TR/xml-c14n2-testcases/} ，并根据 BSD许可证（三条款版）发行：

@quotation

Copyright (c) 2013 W3C(R) (MIT, ERCIM, Keio, Beihang),
All Rights Reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:


@itemize *

@item 
Redistributions of works must retain the original copyright notice,
this list of conditions and the following disclaimer.

@item 
Redistributions in binary form must reproduce the original copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

@item 
Neither the name of the W3C nor the names of its contributors may be
used to endorse or promote products derived from this work without
specific prior written permission.
@end itemize

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
@end quotation

@c to include legacy packaging docs in build

@node 分发 Python 模块（遗留版本）,安装Python模块（旧版）,历史和许可证,Top
@anchor{distutils/index doc}@anchor{42fe}@anchor{distutils/index distributing-python-modules-legacy-version}@anchor{42ff}@anchor{distutils/index distutils-index}@anchor{7f2}
@chapter 分发 Python 模块（遗留版本）


@*作者: 
Greg Ward ， Anthony Baxter


@*电子邮箱: 
@email{distutils-sig@@python.org}



@subsubheading 参见



@table @asis

@item @ref{7f0,,分发 Python 模块}

最新的模块分发文档
@end table


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
本指南仅介绍构建和分发扩展的基本工具，这些扩展是作为此Python版本的一部分提供的。 第三方工具提供更易于使用和更安全的替代方案。有关详细信息，请参阅 Python 打包用户指南中的 快速推荐部分@footnote{https://packaging.python.org/guides/tool-recommendations/} 。
@end quotation
@end cartouche

本文档从模块开发人员的角度描述了 Python Distribution Utilities ("Distutils")。 描述了 @code{setuptools} 构建所依赖的下层功能，以允许 Python 开发者方便地为更广泛的受众编写 Python 模块和扩展。

@menu
* An Introduction to Distutils:: 
* 编写安装脚本:: 
* 编写设置脚本的配置文件:: 
* Creating a Source Distribution:: 
* Creating Built Distributions:: 
* Distutils 示例:: 
* 扩展 Distutils:: 
* 命令参考:: 
* API参考引用:: 

@end menu

@node An Introduction to Distutils,编写安装脚本,,分发 Python 模块（遗留版本）
@anchor{distutils/introduction doc}@anchor{4300}@anchor{distutils/introduction an-introduction-to-distutils}@anchor{4301}@anchor{distutils/introduction distutils-intro}@anchor{4302}
@section An Introduction to Distutils


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

This document covers using the Distutils to distribute your Python modules,
concentrating on the role of developer/distributor: if you're looking for
information on installing Python modules, you should refer to the
@ref{7f1,,安装Python模块（旧版）} chapter.

@menu
* 概念和术语:: 
* 一个简单的例子: 一个简单的例子<3>. 
* General Python terminology:: 
* Distutils-specific terminology:: 

@end menu

@node 概念和术语,一个简单的例子<3>,,An Introduction to Distutils
@anchor{distutils/introduction concepts-terminology}@anchor{4303}@anchor{distutils/introduction distutils-concepts}@anchor{4304}
@subsection 概念和术语


Using the Distutils is quite simple, both for module developers and for
users/administrators installing third-party modules.  As a developer, your
responsibilities (apart from writing solid, well-documented and well-tested
code, of course!) are:


@itemize *

@item 
编写一个设置脚本 (@code{setup.py} by convention)

@item 
(可选)编写设置脚本的配置文件

@item 
create a source distribution

@item 
(optional) create one or more built (binary) distributions
@end itemize

每个这些任务均已在此文档覆盖.

Not all module developers have access to a multitude of platforms, so it's not
always feasible to expect them to create a multitude of built distributions.  It
is hoped that a class of intermediaries, called @emph{packagers}, will arise to
address this need.  Packagers will take source distributions released by module
developers, build them on one or more platforms, and release the resulting built
distributions.  Thus, users on the most popular platforms will be able to
install most popular Python module distributions in the most natural way for
their platform, without having to run a single setup script or compile a line of
code.

@node 一个简单的例子<3>,General Python terminology,概念和术语,An Introduction to Distutils
@anchor{distutils/introduction a-simple-example}@anchor{4305}@anchor{distutils/introduction distutils-simple-example}@anchor{4306}
@subsection 一个简单的例子


The setup script is usually quite simple, although since it's written in Python,
there are no arbitrary limits to what you can do with it, though you should be
careful about putting arbitrarily expensive operations in your setup script.
Unlike, say, Autoconf-style configure scripts, the setup script may be run
multiple times in the course of building and installing your module
distribution.

If all you want to do is distribute a module called @code{foo}, contained in a
file @code{foo.py}, then your setup script can be as simple as this:

@example
from distutils.core import setup
setup(name='foo',
      version='1.0',
      py_modules=['foo'],
      )
@end example

一些观察:


@itemize *

@item 
most information that you supply to the Distutils is supplied as keyword
arguments to the @code{setup()} function

@item 
those keyword arguments fall into two categories: package metadata (name,
version number) and information about what's in the package (a list of pure
Python modules, in this case)

@item 
modules are specified by module name, not filename (the same will hold true
for packages and extensions)

@item 
it's recommended that you supply a little more metadata, in particular your
name, email address and a URL for the project (see section @ref{4307,,编写安装脚本}
for an example)
@end itemize

To create a source distribution for this module, you would create a setup
script, @code{setup.py}, containing the above code, and run this command from a
terminal:

@example
python setup.py sdist
@end example

Windows用户, 打开命令行窗口 (Start ‣ Accessories) 并且更改命令为:

@example
setup.py sdist
@end example

@code{sdist} 将创建一个归档文件（例如在 Unix 中为 tarball，在 Windows 中为 ZIP 文件），其中包含你的配置脚本 @code{setup.py} 以及你的模块 @code{foo.py}。 此归档文件将被命名为 @code{foo-1.0.tar.gz} (或 @code{.zip})，并将解包到目录 @code{foo-1.0} 当中。

If an end-user wishes to install your @code{foo} module, all they have to do is
download @code{foo-1.0.tar.gz} (or @code{.zip}), unpack it, and---from the
@code{foo-1.0} directory---run

@example
python setup.py install
@end example

which will ultimately copy @code{foo.py} to the appropriate directory for
third-party modules in their Python installation.

This simple example demonstrates some fundamental concepts of the Distutils.
First, both developers and installers have the same basic user interface, i.e.
the setup script.  The difference is which Distutils @emph{commands} they use: the
@code{sdist} command is almost exclusively for module developers, while
@code{install} is more often for installers (although most developers will
want to install their own code occasionally).

If you want to make things really easy for your users, you can create one or
more built distributions for them.  For instance, if you are running on a
Windows machine, and want to make things easy for other Windows users, you can
create an executable installer (the most appropriate type of built distribution
for this platform) with the @code{bdist_wininst} command.  For example:

@example
python setup.py bdist_wininst
@end example

will create an executable installer, @code{foo-1.0.win32.exe}, in the current
directory.

Other useful built distribution formats are RPM, implemented by the
@code{bdist_rpm} command, Solaris @code{pkgtool}
(@code{bdist_pkgtool}), and HP-UX @code{swinstall}
(@code{bdist_sdux}).  For example, the following command will create an RPM
file called @code{foo-1.0.noarch.rpm}:

@example
python setup.py bdist_rpm
@end example

(The @code{bdist_rpm} command uses the @code{rpm} executable, therefore
this has to be run on an RPM-based system such as Red Hat Linux, SuSE Linux, or
Mandrake Linux.)

You can find out what distribution formats are available at any time by running

@example
python setup.py bdist --help-formats
@end example

@node General Python terminology,Distutils-specific terminology,一个简单的例子<3>,An Introduction to Distutils
@anchor{distutils/introduction general-python-terminology}@anchor{4308}@anchor{distutils/introduction python-terms}@anchor{4309}
@subsection General Python terminology


If you're reading this document, you probably have a good idea of what modules,
extensions, and so forth are.  Nevertheless, just to be sure that everyone is
operating from a common starting point, we offer the following glossary of
common Python terms:


@table @asis

@item module

the basic unit of code reusability in Python: a block of code imported by some
other code.  Three types of modules concern us here: pure Python modules,
extension modules, and packages.

@item pure Python module

a module written in Python and contained in a single @code{.py} file (and
possibly associated @code{.pyc} files).  Sometimes referred to as a
"pure module."

@item extension module -- 扩展模块

a module written in the low-level language of the Python implementation: C/C++
for Python, Java for Jython. Typically contained in a single dynamically
loadable pre-compiled file, e.g. a shared object (@code{.so}) file for Python
extensions on Unix, a DLL (given the @code{.pyd} extension) for Python
extensions on Windows, or a Java class file for Jython extensions.  (Note that
currently, the Distutils only handles C/C++ extensions for Python.)

@item package -- 包

a module that contains other modules; typically contained in a directory in the
filesystem and distinguished from other directories by the presence of a file
@code{__init__.py}.

@item root package

the root of the hierarchy of packages.  (This isn't really a package, since it
doesn't have an @code{__init__.py} file.  But we have to call it something.)
The vast majority of the standard library is in the root package, as are many
small, standalone third-party modules that don't belong to a larger module
collection. Unlike regular packages, modules in the root package can be found in
many directories: in fact, every directory listed in @code{sys.path} contributes
modules to the root package.
@end table

@node Distutils-specific terminology,,General Python terminology,An Introduction to Distutils
@anchor{distutils/introduction distutils-specific-terminology}@anchor{430a}@anchor{distutils/introduction distutils-term}@anchor{430b}
@subsection Distutils-specific terminology


The following terms apply more specifically to the domain of distributing Python
modules using the Distutils:


@table @asis

@item module distribution

a collection of Python modules distributed together as a single downloadable
resource and meant to be installed @emph{en masse}.  Examples of some well-known
module distributions are NumPy, SciPy, Pillow,
or mxBase.  (This would be called a @emph{package}, except that term is
already taken in the Python context: a single module distribution may contain
zero, one, or many Python packages.)

@item pure module distribution

a module distribution that contains only pure Python modules and packages.
Sometimes referred to as a "pure distribution."

@item non-pure module distribution

a module distribution that contains at least one extension module.  Sometimes
referred to as a "non-pure distribution."

@item distribution root

the top-level directory of your source tree (or  source distribution); the
directory where @code{setup.py} exists.  Generally  @code{setup.py} will be
run from this directory.
@end table

@node 编写安装脚本,编写设置脚本的配置文件,An Introduction to Distutils,分发 Python 模块（遗留版本）
@anchor{distutils/setupscript doc}@anchor{430c}@anchor{distutils/setupscript setup-script}@anchor{4307}@anchor{distutils/setupscript writing-the-setup-script}@anchor{430d}
@section 编写安装脚本


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

The setup script is the centre of all activity in building, distributing, and
installing modules using the Distutils.  The main purpose of the setup script is
to describe your module distribution to the Distutils, so that the various
commands that operate on your modules do the right thing.  As we saw in section
@ref{4306,,一个简单的例子} above, the setup script consists mainly of a call to
@code{setup()}, and most information supplied to the Distutils by the module
developer is supplied as keyword arguments to @code{setup()}.

Here's a slightly more involved example, which we'll follow for the next couple
of sections: the Distutils' own setup script.  (Keep in mind that although the
Distutils are included with Python 1.6 and later, they also have an independent
existence so that Python 1.5.2 users can use them to install other module
distributions.  The Distutils' own setup script, shown here, is used to install
the package into Python 1.5.2.)

@example
#!/usr/bin/env python

from distutils.core import setup

setup(name='Distutils',
      version='1.0',
      description='Python Distribution Utilities',
      author='Greg Ward',
      author_email='gward@@python.net',
      url='https://www.python.org/sigs/distutils-sig/',
      packages=['distutils', 'distutils.command'],
     )
@end example

There are only two differences between this and the trivial one-file
distribution presented in section @ref{4306,,一个简单的例子}: more metadata, and the
specification of pure Python modules by package, rather than by module.  This is
important since the Distutils consist of a couple of dozen modules split into
(so far) two packages; an explicit list of every module would be tedious to
generate and difficult to maintain.  For more information on the additional
meta-data, see section @ref{430e,,Additional meta-data}.

Note that any pathnames (files or directories) supplied in the setup script
should be written using the Unix convention, i.e. slash-separated.  The
Distutils will take care of converting this platform-neutral representation into
whatever is appropriate on your current platform before actually using the
pathname.  This makes your setup script portable across operating systems, which
of course is one of the major goals of the Distutils.  In this spirit, all
pathnames in this document are slash-separated.

This, of course, only applies to pathnames given to Distutils functions.  If
you, for example, use standard Python functions such as @ref{5c1,,glob.glob()} or
@ref{a3c,,os.listdir()} to specify files, you should be careful to write portable
code instead of hardcoding path separators:

@example
glob.glob(os.path.join('mydir', 'subdir', '*.html'))
os.listdir(os.path.join('mydir', 'subdir'))
@end example

@menu
* Listing whole packages:: 
* Listing individual modules:: 
* Describing extension modules:: 
* Relationships between Distributions and Packages:: 
* Installing Scripts:: 
* Installing Package Data:: 
* Installing Additional Files:: 
* Additional meta-data:: 
* Debugging the setup script:: 

@end menu

@node Listing whole packages,Listing individual modules,,编写安装脚本
@anchor{distutils/setupscript listing-packages}@anchor{430f}@anchor{distutils/setupscript listing-whole-packages}@anchor{4310}
@subsection Listing whole packages


The @code{packages} option tells the Distutils to process (build, distribute,
install, etc.) all pure Python modules found in each package mentioned in the
@code{packages} list.  In order to do this, of course, there has to be a
correspondence between package names and directories in the filesystem.  The
default correspondence is the most obvious one, i.e. package @ref{39,,distutils} is
found in the directory @code{distutils} relative to the distribution root.
Thus, when you say @code{packages = ['foo']} in your setup script, you are
promising that the Distutils will find a file @code{foo/__init__.py} (which
might be spelled differently on your system, but you get the idea) relative to
the directory where your setup script lives.  If you break this promise, the
Distutils will issue a warning but still process the broken package anyway.

If you use a different convention to lay out your source directory, that's no
problem: you just have to supply the @code{package_dir} option to tell the
Distutils about your convention.  For example, say you keep all Python source
under @code{lib}, so that modules in the "root package" (i.e., not in any
package at all) are in @code{lib}, modules in the @code{foo} package are in
@code{lib/foo}, and so forth.  Then you would put

@example
package_dir = @{'@w{'}: 'lib'@}
@end example

in your setup script.  The keys to this dictionary are package names, and an
empty package name stands for the root package.  The values are directory names
relative to your distribution root.  In this case, when you say @code{packages =
['foo']}, you are promising that the file @code{lib/foo/__init__.py} exists.

Another possible convention is to put the @code{foo} package right in
@code{lib}, the @code{foo.bar} package in @code{lib/bar}, etc.  This would be
written in the setup script as

@example
package_dir = @{'foo': 'lib'@}
@end example

A @code{package: dir} entry in the @code{package_dir} dictionary implicitly
applies to all packages below @emph{package}, so the @code{foo.bar} case is
automatically handled here.  In this example, having @code{packages = ['foo',
'foo.bar']} tells the Distutils to look for @code{lib/__init__.py} and
@code{lib/bar/__init__.py}.  (Keep in mind that although @code{package_dir}
applies recursively, you must explicitly list all packages in
@code{packages}: the Distutils will @emph{not} recursively scan your source tree
looking for any directory with an @code{__init__.py} file.)

@node Listing individual modules,Describing extension modules,Listing whole packages,编写安装脚本
@anchor{distutils/setupscript listing-individual-modules}@anchor{4311}@anchor{distutils/setupscript listing-modules}@anchor{4312}
@subsection Listing individual modules


For a small module distribution, you might prefer to list all modules rather
than listing packages---especially the case of a single module that goes in the
"root package" (i.e., no package at all).  This simplest case was shown in
section @ref{4306,,一个简单的例子}; here is a slightly more involved example:

@example
py_modules = ['mod1', 'pkg.mod2']
@end example

This describes two modules, one of them in the "root" package, the other in the
@code{pkg} package.  Again, the default package/directory layout implies that
these two modules can be found in @code{mod1.py} and @code{pkg/mod2.py}, and
that @code{pkg/__init__.py} exists as well. And again, you can override the
package/directory correspondence using the @code{package_dir} option.

@node Describing extension modules,Relationships between Distributions and Packages,Listing individual modules,编写安装脚本
@anchor{distutils/setupscript describing-extension-modules}@anchor{4313}@anchor{distutils/setupscript describing-extensions}@anchor{4314}
@subsection Describing extension modules


Just as writing Python extension modules is a bit more complicated than writing
pure Python modules, describing them to the Distutils is a bit more complicated.
Unlike pure modules, it's not enough just to list modules or packages and expect
the Distutils to go out and find the right files; you have to specify the
extension name, source file(s), and any compile/link requirements (include
directories, libraries to link with, etc.).

@c XXX read over this section

All of this is done through another keyword argument to @code{setup()}, the
@code{ext_modules} option.  @code{ext_modules} is just a list of
@ref{4315,,Extension} instances, each of which describes a
single extension module.
Suppose your distribution includes a single extension, called @code{foo} and
implemented by @code{foo.c}.  If no additional instructions to the
compiler/linker are needed, describing this extension is quite simple:

@example
Extension('foo', ['foo.c'])
@end example

The @code{Extension} class can be imported from @ref{54,,distutils.core} along
with @code{setup()}.  Thus, the setup script for a module distribution that
contains only this one extension and nothing else might be:

@example
from distutils.core import setup, Extension
setup(name='foo',
      version='1.0',
      ext_modules=[Extension('foo', ['foo.c'])],
      )
@end example

The @code{Extension} class (actually, the underlying extension-building
machinery implemented by the @code{build_ext} command) supports a great deal
of flexibility in describing Python extensions, which is explained in the
following sections.

@menu
* 扩展名和软件包:: 
* Extension source files:: 
* Preprocessor options:: 
* Library options:: 
* 其他选项: 其他选项<2>. 

@end menu

@node 扩展名和软件包,Extension source files,,Describing extension modules
@anchor{distutils/setupscript extension-names-and-packages}@anchor{4316}
@subsubsection 扩展名和软件包


The first argument to the @ref{4315,,Extension} constructor is
always the name of the extension, including any package names.  For example,

@example
Extension('foo', ['src/foo1.c', 'src/foo2.c'])
@end example

describes an extension that lives in the root package, while

@example
Extension('pkg.foo', ['src/foo1.c', 'src/foo2.c'])
@end example

describes the same extension in the @code{pkg} package.  The source files and
resulting object code are identical in both cases; the only difference is where
in the filesystem (and therefore where in Python's namespace hierarchy) the
resulting extension lives.

If you have a number of extensions all in the same package (or all under the
same base package), use the @code{ext_package} keyword argument to
@code{setup()}.  For example,

@example
setup(...,
      ext_package='pkg',
      ext_modules=[Extension('foo', ['foo.c']),
                   Extension('subpkg.bar', ['bar.c'])],
     )
@end example

will compile @code{foo.c} to the extension @code{pkg.foo}, and @code{bar.c} to
@code{pkg.subpkg.bar}.

@node Extension source files,Preprocessor options,扩展名和软件包,Describing extension modules
@anchor{distutils/setupscript extension-source-files}@anchor{4317}
@subsubsection Extension source files


The second argument to the @ref{4315,,Extension} constructor is
a list of source
files.  Since the Distutils currently only support C, C++, and Objective-C
extensions, these are normally C/C++/Objective-C source files.  (Be sure to use
appropriate extensions to distinguish C++ source files: @code{.cc} and
@code{.cpp} seem to be recognized by both Unix and Windows compilers.)

However, you can also include SWIG interface (@code{.i}) files in the list; the
@code{build_ext} command knows how to deal with SWIG extensions: it will run
SWIG on the interface file and compile the resulting C/C++ file into your
extension.

@c XXX SWIG support is rough around the edges and largely untested!

This warning notwithstanding, options to SWIG can be currently passed like
this:

@example
setup(...,
      ext_modules=[Extension('_foo', ['foo.i'],
                             swig_opts=['-modern', '-I../include'])],
      py_modules=['foo'],
     )
@end example

Or on the commandline like this:

@example
> python setup.py build_ext --swig-opts="-modern -I../include"
@end example

On some platforms, you can include non-source files that are processed by the
compiler and included in your extension.  Currently, this just means Windows
message text (@code{.mc}) files and resource definition (@code{.rc}) files for
Visual C++. These will be compiled to binary resource (@code{.res}) files and
linked into the executable.

@node Preprocessor options,Library options,Extension source files,Describing extension modules
@anchor{distutils/setupscript preprocessor-options}@anchor{4318}
@subsubsection Preprocessor options


Three optional arguments to @ref{4315,,Extension} will help if
you need to specify include directories to search or preprocessor macros to
define/undefine: @code{include_dirs}, @code{define_macros}, and @code{undef_macros}.

For example, if your extension requires header files in the @code{include}
directory under your distribution root, use the @code{include_dirs} option:

@example
Extension('foo', ['foo.c'], include_dirs=['include'])
@end example

You can specify absolute directories there; if you know that your extension will
only be built on Unix systems with X11R6 installed to @code{/usr}, you can get
away with

@example
Extension('foo', ['foo.c'], include_dirs=['/usr/include/X11'])
@end example

You should avoid this sort of non-portable usage if you plan to distribute your
code: it's probably better to write C code like

@example
#include <X11/Xlib.h>
@end example

If you need to include header files from some other Python extension, you can
take advantage of the fact that header files are installed in a consistent way
by the Distutils @code{install_headers} command.  For example, the Numerical
Python header files are installed (on a standard Unix installation) to
@code{/usr/local/include/python1.5/Numerical}. (The exact location will differ
according to your platform and Python installation.)  Since the Python include
directory---@code{/usr/local/include/python1.5} in this case---is always
included in the search path when building Python extensions, the best approach
is to write C code like

@example
#include <Numerical/arrayobject.h>
@end example

If you must put the @code{Numerical} include directory right into your header
search path, though, you can find that directory using the Distutils
@ref{62,,distutils.sysconfig} module:

@example
from distutils.sysconfig import get_python_inc
incdir = os.path.join(get_python_inc(plat_specific=1), 'Numerical')
setup(...,
      Extension(..., include_dirs=[incdir]),
      )
@end example

Even though this is quite portable---it will work on any Python installation,
regardless of platform---it's probably easier to just write your C code in the
sensible way.

You can define and undefine pre-processor macros with the @code{define_macros} and
@code{undef_macros} options. @code{define_macros} takes a list of @code{(name, value)}
tuples, where @code{name} is the name of the macro to define (a string) and
@code{value} is its value: either a string or @code{None}.  (Defining a macro @code{FOO}
to @code{None} is the equivalent of a bare @code{#define FOO} in your C source: with
most compilers, this sets @code{FOO} to the string @code{1}.)  @code{undef_macros} is
just a list of macros to undefine.

例如

@example
Extension(...,
          define_macros=[('NDEBUG', '1'),
                         ('HAVE_STRFTIME', None)],
          undef_macros=['HAVE_FOO', 'HAVE_BAR'])
@end example

is the equivalent of having this at the top of every C source file:

@example
#define NDEBUG 1
#define HAVE_STRFTIME
#undef HAVE_FOO
#undef HAVE_BAR
@end example

@node Library options,其他选项<2>,Preprocessor options,Describing extension modules
@anchor{distutils/setupscript library-options}@anchor{4319}
@subsubsection Library options


You can also specify the libraries to link against when building your extension,
and the directories to search for those libraries.  The @code{libraries} option is
a list of libraries to link against, @code{library_dirs} is a list of directories
to search for libraries at  link-time, and @code{runtime_library_dirs} is a list of
directories to  search for shared (dynamically loaded) libraries at run-time.

For example, if you need to link against libraries known to be in the standard
library search path on target systems

@example
Extension(...,
          libraries=['gdbm', 'readline'])
@end example

If you need to link with libraries in a non-standard location, you'll have to
include the location in @code{library_dirs}:

@example
Extension(...,
          library_dirs=['/usr/X11R6/lib'],
          libraries=['X11', 'Xt'])
@end example

(Again, this sort of non-portable construct should be avoided if you intend to
distribute your code.)

@c XXX Should mention clib libraries here or somewhere else!

@node 其他选项<2>,,Library options,Describing extension modules
@anchor{distutils/setupscript other-options}@anchor{431a}
@subsubsection 其他选项


There are still some other options which can be used to handle special cases.

The @code{optional} option is a boolean; if it is true,
a build failure in the extension will not abort the build process, but
instead simply not install the failing extension.

The @code{extra_objects} option is a list of object files to be passed to the
linker. These files must not have extensions, as the default extension for the
compiler is used.

@code{extra_compile_args} and @code{extra_link_args} can be used to
specify additional command line options for the respective compiler and linker
command lines.

@code{export_symbols} is only useful on Windows.  It can contain a list of
symbols (functions or variables) to be exported. This option is not needed when
building compiled extensions: Distutils  will automatically add @code{initmodule}
to the list of exported symbols.

The @code{depends} option is a list of files that the extension depends on
(for example header files). The build command will call the compiler on the
sources to rebuild extension if any on this files has been modified since the
previous build.

@node Relationships between Distributions and Packages,Installing Scripts,Describing extension modules,编写安装脚本
@anchor{distutils/setupscript relationships-between-distributions-and-packages}@anchor{431b}
@subsection Relationships between Distributions and Packages


A distribution may relate to packages in three specific ways:


@enumerate 

@item 
It can require packages or modules.

@item 
It can provide packages or modules.

@item 
It can obsolete packages or modules.
@end enumerate

These relationships can be specified using keyword arguments to the
@ref{3b1c,,distutils.core.setup()} function.

Dependencies on other Python modules and packages can be specified by supplying
the @emph{requires} keyword argument to @code{setup()}. The value must be a list of
strings.  Each string specifies a package that is required, and optionally what
versions are sufficient.

To specify that any version of a module or package is required, the string
should consist entirely of the module or package name. Examples include
@code{'mymodule'} and @code{'xml.parsers.expat'}.

If specific versions are required, a sequence of qualifiers can be supplied in
parentheses.  Each qualifier may consist of a comparison operator and a version
number.  The accepted comparison operators are:

@example
<    >    ==
<=   >=   !=
@end example

These can be combined by using multiple qualifiers separated by commas (and
optional whitespace).  In this case, all of the qualifiers must be matched; a
logical AND is used to combine the evaluations.

Let's look at a bunch of examples:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Requires Expression

@tab

说明

@item

@code{==1.0}

@tab

Only version @code{1.0} is compatible

@item

@code{>1.0, !=1.5.1, <2.0}

@tab

Any version after @code{1.0} and before @code{2.0}
is compatible, except @code{1.5.1}

@end multitable


Now that we can specify dependencies, we also need to be able to specify what we
provide that other distributions can require.  This is done using the @emph{provides}
keyword argument to @code{setup()}. The value for this keyword is a list of
strings, each of which names a Python module or package, and optionally
identifies the version.  If the version is not specified, it is assumed to match
that of the distribution.

Some examples:


@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

Provides Expression

@tab

说明

@item

@code{mypkg}

@tab

Provide @code{mypkg}, using the distribution
version

@item

@code{mypkg (1.1)}

@tab

Provide @code{mypkg} version 1.1, regardless of
the distribution version

@end multitable


A package can declare that it obsoletes other packages using the @emph{obsoletes}
keyword argument.  The value for this is similar to that of the @emph{requires}
keyword: a list of strings giving module or package specifiers.  Each specifier
consists of a module or package name optionally followed by one or more version
qualifiers.  Version qualifiers are given in parentheses after the module or
package name.

The versions identified by the qualifiers are those that are obsoleted by the
distribution being described.  If no qualifiers are given, all versions of the
named module or package are understood to be obsoleted.

@node Installing Scripts,Installing Package Data,Relationships between Distributions and Packages,编写安装脚本
@anchor{distutils/setupscript distutils-installing-scripts}@anchor{431c}@anchor{distutils/setupscript installing-scripts}@anchor{431d}
@subsection Installing Scripts


So far we have been dealing with pure and non-pure Python modules, which are
usually not run by themselves but imported by scripts.

Scripts are files containing Python source code, intended to be started from the
command line.  Scripts don't require Distutils to do anything very complicated.
The only clever feature is that if the first line of the script starts with
@code{#!} and contains the word "python", the Distutils will adjust the first line
to refer to the current interpreter location. By default, it is replaced with
the current interpreter location.  The @code{--executable} (or @code{-e})
option will allow the interpreter path to be explicitly overridden.

The @code{scripts} option simply is a list of files to be handled in this
way.  From the PyXML setup script:

@example
setup(...,
      scripts=['scripts/xmlproc_parse', 'scripts/xmlproc_val']
      )
@end example


在 3.1 版更改: All the scripts will also be added to the @code{MANIFEST} file if no template is
provided.  See @ref{3b1f,,Specifying the files to distribute}.


@node Installing Package Data,Installing Additional Files,Installing Scripts,编写安装脚本
@anchor{distutils/setupscript distutils-installing-package-data}@anchor{431e}@anchor{distutils/setupscript installing-package-data}@anchor{431f}
@subsection Installing Package Data


Often, additional files need to be installed into a package.  These files are
often data that's closely related to the package's implementation, or text files
containing documentation that might be of interest to programmers using the
package.  These files are called @emph{package data}.

Package data can be added to packages using the @code{package_data} keyword
argument to the @code{setup()} function.  The value must be a mapping from
package name to a list of relative path names that should be copied into the
package.  The paths are interpreted as relative to the directory containing the
package (information from the @code{package_dir} mapping is used if appropriate);
that is, the files are expected to be part of the package in the source
directories. They may contain glob patterns as well.

The path names may contain directory portions; any necessary directories will be
created in the installation.

For example, if a package should contain a subdirectory with several data files,
the files can be arranged like this in the source tree:

@example
setup.py
src/
    mypkg/
        __init__.py
        module.py
        data/
            tables.dat
            spoons.dat
            forks.dat
@end example

The corresponding call to @code{setup()} might be:

@example
setup(...,
      packages=['mypkg'],
      package_dir=@{'mypkg': 'src/mypkg'@},
      package_data=@{'mypkg': ['data/*.dat']@},
      )
@end example


在 3.1 版更改: All the files that match @code{package_data} will be added to the @code{MANIFEST}
file if no template is provided.  See @ref{3b1f,,Specifying the files to distribute}.


@node Installing Additional Files,Additional meta-data,Installing Package Data,编写安装脚本
@anchor{distutils/setupscript distutils-additional-files}@anchor{4320}@anchor{distutils/setupscript installing-additional-files}@anchor{4321}
@subsection Installing Additional Files


The @code{data_files} option can be used to specify additional files needed
by the module distribution: configuration files, message catalogs, data files,
anything which doesn't fit in the previous categories.

@code{data_files} specifies a sequence of (@emph{directory}, @emph{files}) pairs in the
following way:

@example
setup(...,
      data_files=[('bitmaps', ['bm/b1.gif', 'bm/b2.gif']),
                  ('config', ['cfg/data.cfg'])],
     )
@end example

Each (@emph{directory}, @emph{files}) pair in the sequence specifies the installation
directory and the files to install there.

Each file name in @emph{files} is interpreted relative to the @code{setup.py}
script at the top of the package source distribution. Note that you can
specify the directory where the data files will be installed, but you cannot
rename the data files themselves.

The @emph{directory} should be a relative path. It is interpreted relative to the
installation prefix (Python's @code{sys.prefix} for system installations;
@code{site.USER_BASE} for user installations). Distutils allows @emph{directory} to be
an absolute installation path, but this is discouraged since it is
incompatible with the wheel packaging format. No directory information from
@emph{files} is used to determine the final location of the installed file; only
the name of the file is used.

You can specify the @code{data_files} options as a simple sequence of files
without specifying a target directory, but this is not recommended, and the
@code{install} command will print a warning in this case. To install data
files directly in the target directory, an empty string should be given as the
directory.


在 3.1 版更改: All the files that match @code{data_files} will be added to the @code{MANIFEST}
file if no template is provided.  See @ref{3b1f,,Specifying the files to distribute}.


@node Additional meta-data,Debugging the setup script,Installing Additional Files,编写安装脚本
@anchor{distutils/setupscript additional-meta-data}@anchor{4322}@anchor{distutils/setupscript meta-data}@anchor{430e}
@subsection Additional meta-data


The setup script may include additional meta-data beyond the name and version.
This information includes:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxx} 
@headitem

元数据

@tab

描述

@tab

值

@tab

注释

@item

@code{name}

@tab

包名称

@tab

短字符串

@tab

(1)

@item

@code{version}

@tab

此发布的版本

@tab

短字符串

@tab

(1)(2)

@item

@code{author}

@tab

软件包作者的姓名

@tab

短字符串

@tab

(3)

@item

@code{author_email}

@tab

软件包的作者的电子邮件地址

@tab

电子邮件地址

@tab

(3)

@item

@code{maintainer}

@tab

软件包维护者的名字

@tab

短字符串

@tab

(3)

@item

@code{maintainer_email}

@tab

软件包维护者的电子邮件地址

@tab

电子邮件地址

@tab

(3)

@item

@code{url}

@tab

软件包的网址

@tab

网址

@tab

(1)

@item

@code{description}

@tab

软件包的简短摘要说明

@tab

短字符串

@tab

@item

@code{long_description}

@tab

软件包的详细说明

@tab

长字符串

@tab

(4)

@item

@code{download_url}

@tab

可以下载软件包的网址

@tab

网址

@tab

@item

@code{classifiers}

@tab

分类列表

@tab

字符串列表

@tab

(6)(7)

@item

@code{platforms}

@tab

平台清单

@tab

字符串列表

@tab

(6)(8)

@item

@code{keywords}

@tab

关键字列表

@tab

字符串列表

@tab

(6)(8)

@item

@code{license}

@tab

软件包许可证

@tab

短字符串

@tab

(5)

@end multitable


注释:


@enumerate 

@item 
These fields are required.

@item 
It is recommended that versions take the form @emph{major.minor[.patch[.sub]]}.

@item 
Either the author or the maintainer must be identified. If maintainer is
provided, distutils lists it as the author in @code{PKG-INFO}.

@item 
The @code{long_description} field is used by PyPI when you publish a package,
to build its project page.

@item 
The @code{license} field is a text indicating the license covering the
package where the license is not a selection from the "License" Trove
classifiers. See the @code{Classifier} field. Notice that
there's a @code{licence} distribution option which is deprecated but still
acts as an alias for @code{license}.

@item 
This field must be a list.

@item 
The valid classifiers are listed on
PyPI@footnote{https://pypi.org/classifiers}.

@item 
To preserve backward compatibility, this field also accepts a string. If
you pass a comma-separated string @code{'foo, bar'}, it will be converted to
@code{['foo', 'bar']}, Otherwise, it will be converted to a list of one
string.
@end enumerate


@table @asis

@item 'short string'

A single line of text, not more than 200 characters.

@item 'long string'

Multiple lines of plain text in reStructuredText format (see
@indicateurl{http://docutils.sourceforge.net/}).

@item 'list of strings'

See below.
@end table

Encoding the version information is an art in itself. Python packages generally
adhere to the version format @emph{major.minor[.patch][sub]}. The major number is 0
for initial, experimental releases of software. It is incremented for releases
that represent major milestones in a package. The minor number is incremented
when important new features are added to the package. The patch number
increments when bug-fix releases are made. Additional trailing version
information is sometimes used to indicate sub-releases.  These are
"a1,a2,...,aN" (for alpha releases, where functionality and API may change),
"b1,b2,...,bN" (for beta releases, which only fix bugs) and "pr1,pr2,...,prN"
(for final pre-release release testing). Some examples:


@table @asis

@item 0.1.0

the first, experimental release of a package

@item 1.0.1a2

the second alpha release of the first patch version of 1.0
@end table

@code{classifiers} must be specified in a list:

@example
setup(...,
      classifiers=[
          'Development Status :: 4 - Beta',
          'Environment :: Console',
          'Environment :: Web Environment',
          'Intended Audience :: End Users/Desktop',
          'Intended Audience :: Developers',
          'Intended Audience :: System Administrators',
          'License :: OSI Approved :: Python Software Foundation License',
          'Operating System :: MacOS :: MacOS X',
          'Operating System :: Microsoft :: Windows',
          'Operating System :: POSIX',
          'Programming Language :: Python',
          'Topic :: Communications :: Email',
          'Topic :: Office/Business',
          'Topic :: Software Development :: Bug Tracking',
          ],
      )
@end example


在 3.7 版更改: @ref{3b1c,,setup} now warns when @code{classifiers}, @code{keywords}
or @code{platforms} fields are not specified as a list or a string.


@node Debugging the setup script,,Additional meta-data,编写安装脚本
@anchor{distutils/setupscript debug-setup-script}@anchor{4323}@anchor{distutils/setupscript debugging-the-setup-script}@anchor{4324}
@subsection Debugging the setup script


Sometimes things go wrong, and the setup script doesn't do what the developer
wants.

Distutils catches any exceptions when running the setup script, and print a
simple error message before the script is terminated.  The motivation for this
behaviour is to not confuse administrators who don't know much about Python and
are trying to install a package.  If they get a big long traceback from deep
inside the guts of Distutils, they may think the package or the Python
installation is broken because they don't read all the way down to the bottom
and see that it's a permission problem.

On the other hand, this doesn't help the developer to find the cause of the
failure. For this purpose, the 
@geindex DISTUTILS_DEBUG
@geindex 环境变量; DISTUTILS_DEBUG
@code{DISTUTILS_DEBUG} environment variable can be set
to anything except an empty string, and distutils will now print detailed
information about what it is doing, dump the full traceback when an exception
occurs, and print the whole command line when an external program (like a C
compiler) fails.

@node 编写设置脚本的配置文件,Creating a Source Distribution,编写安装脚本,分发 Python 模块（遗留版本）
@anchor{distutils/configfile doc}@anchor{4325}@anchor{distutils/configfile setup-config}@anchor{4326}@anchor{distutils/configfile writing-the-setup-configuration-file}@anchor{4327}
@section 编写设置脚本的配置文件


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

通常，在 @emph{事前} 就写出构建发布包所需的一切是不可能的：你可能需要从用户或者用户的系统获取一些信息，才能继续下去。 只要这些信息相当简单 —— 例如一个用于搜索 C 头文件或库的目录列表 —— 那么提供配置文件 @code{setup.cfg} 供用户配置就是一个低成本且方便的解决方式。 配置文件还允许你为任何命令选项提供默认值，而安装器可以通过命令行或编辑配置文件来覆盖这些默认值。

安装配置文件是在安装脚本和安装脚本命令行之间一个适当的折衷方式 --- 安装脚本在理想情况下应当不受安装者的控制 @footnote{@w{(1)} 
在 Distutils 完全支持自动配置之前，这一理想可能是无法实现的。
} --- 而安装脚本命令行则在你的控制范围之外且完全取决于安装者的选择。 实际上，@code{setup.cfg} (以及目标系统上的其他任何 Distutils 配置文件) 是在配置脚本之后、命令行之前被处理。 这导致了几个有用的后果:

@c % (If you have more advanced needs, such as determining which extensions

@c % to build based on what capabilities are present on the target system,

@c % then you need the Distutils ``auto-configuration'' facility.  This

@c % started to appear in Distutils 0.9 but, as of this writing, isn't mature

@c % or stable enough yet for real-world use.)


@itemize *

@item 
安装者可以通过编辑 @code{setup.cfg} 来覆盖你放在 @code{setup.py} 中的配置

@item 
你可以为无法在 @code{setup.py} 中方便设置的选项提供非标准的默认值

@item 
安装者可以使用 @code{setup.py} 的命令行选项来覆盖 @code{setup.cfg} 中的一切
@end itemize

配置文件的基本语法很简单:

@example
[command]
option=value
...
@end example

其中 @emph{command} 是一个 Distutils 命令 (例如 @code{build_py}, @code{install})，而 @emph{option} 是该命令所支持的某个选项。 可以为每个命令提供任意数量的选项，并且可以在文件中包括任意数量的命令组。 空白行会被忽略，以一个 @code{'#'} 开始的注释行也是如此。 长选项值可以简单地通过缩进后续行的方式被拆分为多行。

你可以用通用的 @code{--help} 选项找出特定命令所支持的选项列表，例如

@example
$ python setup.py --help build_ext
[...]
Options for 'build_ext' command:
  --build-lib (-b)     directory for compiled extension modules
  --build-temp (-t)    directory for temporary files (build by-products)
  --inplace (-i)       ignore build-lib and put compiled extensions into the
                       source directory alongside your pure Python modules
  --include-dirs (-I)  list of directories to search for header files
  --define (-D)        C preprocessor macros to define
  --undef (-U)         C preprocessor macros to undefine
  --swig-opts          list of SWIG command line options
[...]
@end example

请注意在命令行中拼写为 @code{--foo-bar} 的选项在配置文件中会拼写为 @code{foo_bar}。
@anchor{distutils/configfile distutils-build-ext-inplace}@anchor{4328}
例如，假设你希望你的扩展在“原地”构建 --- 就是说你有一个扩展 @code{pkg.ext}，你希望编译出的扩展文件 (例如在 Unix 上为 @code{ext.so}) 放在与你的纯 Python 模块 @code{pkg.mod1} 和 @code{pkg.mod2} 相同的源目录中。 你总是可以在命令行中使用 @code{--inplace} 选项来确保这一点:

@example
python setup.py build_ext --inplace
@end example

但是这要求你总是显式地指定 @code{build_ext} 命令，并且记得提供 @code{--inplace}。 一个更容易的方式是通过将其编码在此发布包的配置文件 @code{setup.cfg} 中，“设置并忘记”该选项。

@example
[build_ext]
inplace=1
@end example

这将影响此模块发布包的所有构建，不论你是否显式指定 @code{build_ext}。 如果你在你的源发布包中包括了 @code{setup.cfg}，它还将影响最终用户的构建 --- 对此选项来说这可能不是个好主意，因为总是原地构建扩展会破坏模块发布包的安装。 不过在某些特殊情况下，模块是在其安装目录中被构建的，因此这可能会是个有用的功能。 （但是，发布预期在其安装目录中被构建的扩展几乎总是一个坏主意。）

另一个例子：特定的命令会接受许多在多次运行中都不发生变化的选项；例如，@code{bdist_rpm} 需要知道为创建 RPM 发布包生成 "spec" 文件所要求的所有信息。 这些信息有的来自安装脚本，有的由 Distutils 自动生成（例如已安装文件列表）。 但有的则必须作为 @code{bdist_rpm} 的选项提供，每次运行时都在命令行中完成将会非常繁琐。 因此，这里提供 Distutils 本身的 @code{setup.cfg} 中的一段代码:

@example
[bdist_rpm]
release = 1
packager = Greg Ward <gward@@python.net>
doc_files = CHANGES.txt
            README.txt
            USAGE.txt
            doc/
            examples/
@end example

请注意 @code{doc_files} 选项只是一个空格分隔以提高可读性的多行字符串。


@subsubheading 参见



@table @asis

@item "安装 Python 模块" 中的 @ref{4329,,Syntax of config files}

有关配置文件的更多信息可在系统管理员手册中查看。
@end table


@subsubheading 备注


@node Creating a Source Distribution,Creating Built Distributions,编写设置脚本的配置文件,分发 Python 模块（遗留版本）
@anchor{distutils/sourcedist doc}@anchor{432a}@anchor{distutils/sourcedist creating-a-source-distribution}@anchor{432b}@anchor{distutils/sourcedist source-dist}@anchor{432c}
@section Creating a Source Distribution


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

As shown in section @ref{4306,,一个简单的例子}, you use the @code{sdist} command
to create a source distribution.  In the simplest case,

@example
python setup.py sdist
@end example

(assuming you haven't specified any @code{sdist} options in the setup script
or config file), @code{sdist} creates the archive of the default format for
the current platform.  The default format is a gzip'ed tar file
(@code{.tar.gz}) on Unix, and ZIP file on Windows.

You can specify as many formats as you like using the @code{--formats}
option, for example:

@example
python setup.py sdist --formats=gztar,zip
@end example

to create a gzipped tarball and a zip file.  The available formats are:


@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxx} 
@headitem

格式

@tab

描述

@tab

注释

@item

@code{zip}

@tab

zip 文件 (@code{.zip})

@tab

(1),(3)

@item

@code{gztar}

@tab

gzip'ed tar 文件 (@code{.tar.gz})

@tab

(2)

@item

@code{bztar}

@tab

bzip2'ed tar 文件 (@code{.tar.bz2})

@tab

@item

@code{xztar}

@tab

xz'ed tar 文件 (@code{.tar.xz})

@tab

@item

@code{ztar}

@tab

压缩 tar 文件 (@code{.tar.Z})

@tab

(4)

@item

@code{tar}

@tab

tar 文件 (@code{.tar})

@tab

@end multitable



在 3.5 版更改: 添加了对 @code{xztar} 格式的支持


注释:


@enumerate 

@item 
默认Windows

@item 
默认 Unix

@item 
requires either external @code{zip} utility or @ref{142,,zipfile} module (part
of the standard Python library since Python 1.6)

@item 
requires the @code{compress} program. Notice that this format is now
pending for deprecation and will be removed in the future versions of Python.
@end enumerate

When using any @code{tar} format (@code{gztar}, @code{bztar}, @code{xztar}, @code{ztar} or
@code{tar}), under Unix you can specify the @code{owner} and @code{group} names
that will be set for each member of the archive.

For example, if you want all files of the archive to be owned by root:

@example
python setup.py sdist --owner=root --group=root
@end example

@menu
* Specifying the files to distribute:: 
* Manifest-related options:: 

@end menu

@node Specifying the files to distribute,Manifest-related options,,Creating a Source Distribution
@anchor{distutils/sourcedist manifest}@anchor{3b1f}@anchor{distutils/sourcedist specifying-the-files-to-distribute}@anchor{432d}
@subsection Specifying the files to distribute


If you don't supply an explicit list of files (or instructions on how to
generate one), the @code{sdist} command puts a minimal default set into the
source distribution:


@itemize *

@item 
all Python source files implied by the @code{py_modules} and
@code{packages} options

@item 
all C source files mentioned in the @code{ext_modules} or
@code{libraries} options

@c XXX getting C library sources currently broken---no
@c :meth:`get_source_files` method in :file:`build_clib.py`!

@item 
scripts identified by the @code{scripts} option
See @ref{431c,,Installing Scripts}.

@item 
anything that looks like a test script: @code{test/test*.py} (currently, the
Distutils don't do anything with test scripts except include them in source
distributions, but in the future there will be a standard for testing Python
module distributions)

@item 
Any of the standard README files (@code{README}, @code{README.txt},
or @code{README.rst}), @code{setup.py} (or whatever you called your setup
script), and @code{setup.cfg}.

@item 
all files that matches the @code{package_data} metadata.
See @ref{431e,,Installing Package Data}.

@item 
all files that matches the @code{data_files} metadata.
See @ref{4320,,Installing Additional Files}.
@end itemize

Sometimes this is enough, but usually you will want to specify additional files
to distribute.  The typical way to do this is to write a @emph{manifest template},
called @code{MANIFEST.in} by default.  The manifest template is just a list of
instructions for how to generate your manifest file, @code{MANIFEST}, which is
the exact list of files to include in your source distribution.  The
@code{sdist} command processes this template and generates a manifest based
on its instructions and what it finds in the filesystem.

If you prefer to roll your own manifest file, the format is simple: one filename
per line, regular files (or symlinks to them) only.  If you do supply your own
@code{MANIFEST}, you must specify everything: the default set of files
described above does not apply in this case.


在 3.1 版更改: An existing generated @code{MANIFEST} will be regenerated without
@code{sdist} comparing its modification time to the one of
@code{MANIFEST.in} or @code{setup.py}.



在 3.1.3 版更改: @code{MANIFEST} files start with a comment indicating they are generated.
Files without this comment are not overwritten or removed.



在 3.2.2 版更改: @code{sdist} will read a @code{MANIFEST} file if no @code{MANIFEST.in}
exists, like it used to do.



在 3.7 版更改: @code{README.rst} is now included in the list of distutils standard READMEs.


The manifest template has one command per line, where each command specifies a
set of files to include or exclude from the source distribution.  For an
example, again we turn to the Distutils' own manifest template:

@example
include *.txt
recursive-include examples *.txt *.py
prune examples/sample?/build
@end example

The meanings should be fairly clear: include all files in the distribution root
matching @code{*.txt}, all files anywhere under the @code{examples} directory
matching @code{*.txt} or @code{*.py}, and exclude all directories matching
@code{examples/sample?/build}.  All of this is done @emph{after} the standard
include set, so you can exclude files from the standard set with explicit
instructions in the manifest template.  (Or, you can use the
@code{--no-defaults} option to disable the standard set entirely.)  There are
several other commands available in the manifest template mini-language; see
section @ref{432e,,创建源码发行包; sdist 命令}.

The order of commands in the manifest template matters: initially, we have the
list of default files as described above, and each command in the template adds
to or removes from that list of files.  Once we have fully processed the
manifest template, we remove files that should not be included in the source
distribution:


@itemize *

@item 
all files in the Distutils "build" tree (default @code{build/})

@item 
all files in directories named @code{RCS}, @code{CVS}, @code{.svn},
@code{.hg}, @code{.git}, @code{.bzr} or @code{_darcs}
@end itemize

Now we have our complete list of files, which is written to the manifest for
future reference, and then used to build the source distribution archive(s).

You can disable the default set of included files with the
@code{--no-defaults} option, and you can disable the standard exclude set
with @code{--no-prune}.

Following the Distutils' own manifest template, let's trace how the
@code{sdist} command builds the list of files to include in the Distutils
source distribution:


@enumerate 

@item 
include all Python source files in the @code{distutils} and
@code{distutils/command} subdirectories (because packages corresponding to
those two directories were mentioned in the @code{packages} option in the
setup script---see section @ref{4307,,编写安装脚本})

@item 
include @code{README.txt}, @code{setup.py}, and @code{setup.cfg} (standard
files)

@item 
include @code{test/test*.py} (standard files)

@item 
include @code{*.txt} in the distribution root (this will find
@code{README.txt} a second time, but such redundancies are weeded out later)

@item 
include anything matching @code{*.txt} or @code{*.py} in the sub-tree
under @code{examples},

@item 
exclude all files in the sub-trees starting at directories matching
@code{examples/sample?/build}---this may exclude files included by the
previous two steps, so it's important that the @code{prune} command in the manifest
template comes after the @code{recursive-include} command

@item 
exclude the entire @code{build} tree, and any @code{RCS}, @code{CVS},
@code{.svn}, @code{.hg}, @code{.git}, @code{.bzr} and @code{_darcs}
directories
@end enumerate

Just like in the setup script, file and directory names in the manifest template
should always be slash-separated; the Distutils will take care of converting
them to the standard representation on your platform. That way, the manifest
template is portable across operating systems.

@node Manifest-related options,,Specifying the files to distribute,Creating a Source Distribution
@anchor{distutils/sourcedist manifest-options}@anchor{432f}@anchor{distutils/sourcedist manifest-related-options}@anchor{4330}
@subsection Manifest-related options


The normal course of operations for the @code{sdist} command is as follows:


@itemize *

@item 
if the manifest file (@code{MANIFEST} by default) exists and the first line
does not have a comment indicating it is generated from @code{MANIFEST.in},
then it is used as is, unaltered

@item 
if the manifest file doesn't exist or has been previously automatically
generated, read @code{MANIFEST.in} and create the manifest

@item 
if neither @code{MANIFEST} nor @code{MANIFEST.in} exist, create a manifest
with just the default file set

@item 
use the list of files now in @code{MANIFEST} (either just generated or read
in) to create the source distribution archive(s)
@end itemize

There are a couple of options that modify this behaviour.  First, use the
@code{--no-defaults} and @code{--no-prune} to disable the standard
"include" and "exclude" sets.

Second, you might just want to (re)generate the manifest, but not create a source
distribution:

@example
python setup.py sdist --manifest-only
@end example

@code{-o} is a shortcut for @code{--manifest-only}.

@node Creating Built Distributions,Distutils 示例,Creating a Source Distribution,分发 Python 模块（遗留版本）
@anchor{distutils/builtdist doc}@anchor{4331}@anchor{distutils/builtdist built-dist}@anchor{4332}@anchor{distutils/builtdist creating-built-distributions}@anchor{4333}
@section Creating Built Distributions


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

A "built distribution" is what you're probably used to thinking of either as a
"binary package" or an "installer" (depending on your background).  It's not
necessarily binary, though, because it might contain only Python source code
and/or byte-code; and we don't call it a package, because that word is already
spoken for in Python.  (And "installer" is a term specific to the world of
mainstream desktop systems.)

A built distribution is how you make life as easy as possible for installers of
your module distribution: for users of RPM-based Linux systems, it's a binary
RPM; for Windows users, it's an executable installer; for Debian-based Linux
users, it's a Debian package; and so forth.  Obviously, no one person will be
able to create built distributions for every platform under the sun, so the
Distutils are designed to enable module developers to concentrate on their
specialty---writing code and creating source distributions---while an
intermediary species called @emph{packagers} springs up to turn source distributions
into built distributions for as many platforms as there are packagers.

Of course, the module developer could be their own packager; or the packager could
be a volunteer "out there" somewhere who has access to a platform which the
original developer does not; or it could be software periodically grabbing new
source distributions and turning them into built distributions for as many
platforms as the software has access to.  Regardless of who they are, a packager
uses the setup script and the @code{bdist} command family to generate built
distributions.

As a simple example, if I run the following command in the Distutils source
tree:

@example
python setup.py bdist
@end example

then the Distutils builds my module distribution (the Distutils itself in this
case), does a "fake" installation (also in the @code{build} directory), and
creates the default type of built distribution for my platform.  The default
format for built distributions is a "dumb" tar file on Unix, and a simple
executable installer on Windows.  (That tar file is considered "dumb" because it
has to be unpacked in a specific location to work.)

Thus, the above command on a Unix system creates
@code{Distutils-1.0.@emph{plat}.tar.gz}; unpacking this tarball from the right place
installs the Distutils just as though you had downloaded the source distribution
and run @code{python setup.py install}.  (The "right place" is either the root of
the filesystem or  Python's @code{@emph{prefix}} directory, depending on the options
given to the @code{bdist_dumb} command; the default is to make dumb
distributions relative to @code{@emph{prefix}}.)

Obviously, for pure Python distributions, this isn't any simpler than just
running @code{python setup.py install}---but for non-pure distributions, which
include extensions that would need to be compiled, it can mean the difference
between someone being able to use your extensions or not.  And creating "smart"
built distributions, such as an RPM package or an executable installer for
Windows, is far more convenient for users even if your distribution doesn't
include any extensions.

The @code{bdist} command has a @code{--formats} option, similar to the
@code{sdist} command, which you can use to select the types of built
distribution to generate: for example,

@example
python setup.py bdist --format=zip
@end example

would, when run on a Unix system, create
@code{Distutils-1.0.@emph{plat}.zip}---again, this archive would be unpacked
from the root directory to install the Distutils.

The available formats for built distributions are:


@multitable {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxx} 
@headitem

格式

@tab

描述

@tab

注释

@item

@code{gztar}

@tab

gzipped tar 文件 (@code{.tar.gz})

@tab

(1)

@item

@code{bztar}

@tab

bzipped tar 文件 (@code{.tar.bz2})

@tab

@item

@code{xztar}

@tab

xzipped tar 文件 (@code{.tar.xz})

@tab

@item

@code{ztar}

@tab

压缩 tar 文件 (@code{.tar.Z})

@tab

(3)

@item

@code{tar}

@tab

tar 文件 (@code{.tar})

@tab

@item

@code{zip}

@tab

zip 文件 (@code{.zip})

@tab

(2),(4)

@item

@code{rpm}

@tab

RPM

@tab

(5)

@item

@code{pkgtool}

@tab

Solaris @code{pkgtool}

@tab

@item

@code{sdux}

@tab

HP-UX @code{swinstall}

@tab

@item

@code{wininst}

@tab

Windows的自解压ZIP文件

@tab

(4)

@item

@code{msi}

@tab

Microsoft安装程序。

@tab

@end multitable



在 3.5 版更改: 添加了对 @code{xztar} 格式的支持


注释:


@enumerate 

@item 
默认 Unix

@item 
默认Windows

@item 
requires external @code{compress} utility.

@item 
requires either external @code{zip} utility or @ref{142,,zipfile} module (part
of the standard Python library since Python 1.6)

@item 
requires external @code{rpm} utility, version 3.0.4 or better (use @code{rpm
--version} to find out which version you have)
@end enumerate

You don't have to use the @code{bdist} command with the @code{--formats}
option; you can also use the command that directly implements the format you're
interested in.  Some of these @code{bdist} "sub-commands" actually generate
several similar formats; for instance, the @code{bdist_dumb} command
generates all the "dumb" archive formats (@code{tar}, @code{gztar}, @code{bztar},
@code{xztar}, @code{ztar}, and @code{zip}), and @code{bdist_rpm} generates both
binary and source RPMs.  The @code{bdist} sub-commands, and the formats
generated by each, are:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

命令

@tab

格式

@item

@code{bdist_dumb}

@tab

tar, gztar, bztar, xztar, ztar, zip

@item

@code{bdist_rpm}

@tab

rpm, srpm

@item

@code{bdist_wininst}

@tab

wininst

@item

@code{bdist_msi}

@tab

msi

@end multitable


@cartouche
@quotation 注解 
从Python 3.8开始不推荐使用 bdist_wininst
@end quotation
@end cartouche

The following sections give details on the individual @code{bdist_*}
commands.

@c .. _creating-dumb:

@c Creating dumb built distributions

@c =================================

@c XXX Need to document absolute vs. prefix-relative packages here, but first
@c I have to implement it!

@menu
* 创建RPM软件包:: 
* Creating Windows Installers:: 
* Cross-compiling on Windows:: 
* Vista User Access Control (UAC): Vista User Access Control UAC. 

@end menu

@node 创建RPM软件包,Creating Windows Installers,,Creating Built Distributions
@anchor{distutils/builtdist creating-rpm-packages}@anchor{4334}@anchor{distutils/builtdist creating-rpms}@anchor{4335}
@subsection 创建RPM软件包


The RPM format is used by many popular Linux distributions, including Red Hat,
SuSE, and Mandrake.  If one of these (or any of the other RPM-based Linux
distributions) is your usual environment, creating RPM packages for other users
of that same distribution is trivial. Depending on the complexity of your module
distribution and differences between Linux distributions, you may also be able
to create RPMs that work on different RPM-based distributions.

The usual way to create an RPM of your module distribution is to run the
@code{bdist_rpm} command:

@example
python setup.py bdist_rpm
@end example

or the @code{bdist} command with the @code{--format} option:

@example
python setup.py bdist --formats=rpm
@end example

The former allows you to specify RPM-specific options; the latter allows  you to
easily specify multiple formats in one run.  If you need to do both, you can
explicitly specify multiple @code{bdist_*} commands and their options:

@example
python setup.py bdist_rpm --packager="John Doe <jdoe@@example.org>" \
                bdist_wininst --target-version="2.0"
@end example

Creating RPM packages is driven by a @code{.spec} file, much as using the
Distutils is driven by the setup script.  To make your life easier, the
@code{bdist_rpm} command normally creates a @code{.spec} file based on the
information you supply in the setup script, on the command line, and in any
Distutils configuration files.  Various options and sections in the
@code{.spec} file are derived from options in the setup script as follows:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

RPM @code{.spec} 文件配置或选项

@tab

Distutils安装脚本选项

@item

名称

@tab

@code{name}

@item

摘要（在序言中）

@tab

@code{description}

@item

版本

@tab

@code{version}

@item

供应商

@tab

@code{author} 和 @code{author_email}, 或 --- & @code{maintainer} 和 @code{maintainer_email}

@item

版权所有

@tab

@code{license}

@item

Url

@tab

@code{url}

@item

%d描述（部分）

@tab

@code{long_description}

@end multitable


Additionally, there are many options in @code{.spec} files that don't have
corresponding options in the setup script.  Most of these are handled through
options to the @code{bdist_rpm} command as follows:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

RPM @code{.spec} 文件配置或选项

@tab

@code{bdist_rpm} 选项

@tab

默认值

@item

发布版本

@tab

@code{release}

@tab

"1"

@item

组织

@tab

@code{group}

@tab

"Development/Libraries"

@item

供应商

@tab

@code{vendor}

@tab

（同上）

@item

打包

@tab

@code{packager}

@tab

(none)

@item

提供

@tab

@code{provides}

@tab

(none)

@item

需求

@tab

@code{requires}

@tab

(none)

@item

冲突

@tab

@code{conflicts}

@tab

(none)

@item

淘汰

@tab

@code{obsoletes}

@tab

(none)

@item

Distribution

@tab

@code{distribution_name}

@tab

(none)

@item

构建要求

@tab

@code{build_requires}

@tab

(none)

@item

Icon

@tab

@code{icon}

@tab

(none)

@end multitable


Obviously, supplying even a few of these options on the command-line would be
tedious and error-prone, so it's usually best to put them in the setup
configuration file, @code{setup.cfg}---see section @ref{4326,,编写设置脚本的配置文件}.  If
you distribute or package many Python module distributions, you might want to
put options that apply to all of them in your personal Distutils configuration
file (@code{~/.pydistutils.cfg}).  If you want to temporarily disable
this file, you can pass the @code{--no-user-cfg} option to @code{setup.py}.

There are three steps to building a binary RPM package, all of which are
handled automatically by the Distutils:


@enumerate 

@item 
create a @code{.spec} file, which describes the package (analogous  to the
Distutils setup script; in fact, much of the information in the  setup script
winds up in the @code{.spec} file)

@item 
create the source RPM

@item 
create the "binary" RPM (which may or may not contain binary code, depending
on whether your module distribution contains Python extensions)
@end enumerate

Normally, RPM bundles the last two steps together; when you use the Distutils,
all three steps are typically bundled together.

If you wish, you can separate these three steps.  You can use the
@code{--spec-only} option to make @code{bdist_rpm} just create the
@code{.spec} file and exit; in this case, the @code{.spec} file will be
written to the "distribution directory"---normally @code{dist/}, but
customizable with the @code{--dist-dir} option.  (Normally, the @code{.spec}
file winds up deep in the "build tree," in a temporary directory created by
@code{bdist_rpm}.)

@c % \XXX{this isn't implemented yet---is it needed?!}

@c % You can also specify a custom \file{.spec} file with the

@c % \longprogramopt{spec-file} option; used in conjunction with

@c % \longprogramopt{spec-only}, this gives you an opportunity to customize

@c % the \file{.spec} file manually:

@c %

@c % \ begin{verbatim}

@c % > python setup.py bdist_rpm --spec-only

@c % # ...edit dist/FooBar-1.0.spec

@c % > python setup.py bdist_rpm --spec-file=dist/FooBar-1.0.spec

@c % \ end{verbatim}

@c %

@c % (Although a better way to do this is probably to override the standard

@c % \command{bdist\_rpm} command with one that writes whatever else you want

@c % to the \file{.spec} file.)

@node Creating Windows Installers,Cross-compiling on Windows,创建RPM软件包,Creating Built Distributions
@anchor{distutils/builtdist creating-windows-installers}@anchor{4336}@anchor{distutils/builtdist creating-wininst}@anchor{4337}
@subsection Creating Windows Installers


@cartouche
@quotation 警告 
从Python 3.8开始不推荐使用 bdist_wininst
@end quotation
@end cartouche

Executable installers are the natural format for binary distributions on
Windows.  They display a nice graphical user interface, display some information
about the module distribution to be installed taken from the metadata in the
setup script, let the user select a few options, and start or cancel the
installation.

Since the metadata is taken from the setup script, creating Windows installers
is usually as easy as running:

@example
python setup.py bdist_wininst
@end example

or the @code{bdist} command with the @code{--formats} option:

@example
python setup.py bdist --formats=wininst
@end example

If you have a pure module distribution (only containing pure Python modules and
packages), the resulting installer will be version independent and have a name
like @code{foo-1.0.win32.exe}. Note that creating @code{wininst} binary
distributions in only supported on Windows systems.

If you have a non-pure distribution, the extensions can only be created on a
Windows platform, and will be Python version dependent. The installer filename
will reflect this and now has the form @code{foo-1.0.win32-py2.0.exe}.  You
have to create a separate installer for every Python version you want to
support.

The installer will try to compile pure modules into @ref{60f,,bytecode} after installation
on the target system in normal and optimizing mode.  If you don't want this to
happen for some reason, you can run the @code{bdist_wininst} command with
the @code{--no-target-compile} and/or the @code{--no-target-optimize}
option.

By default the installer will display the cool "Python Powered" logo when it is
run, but you can also supply your own 152x261 bitmap which must be a Windows
@code{.bmp} file with the @code{--bitmap} option.

The installer will also display a large title on the desktop background window
when it is run, which is constructed from the name of your distribution and the
version number.  This can be changed to another text by using the
@code{--title} option.

The installer file will be written to the "distribution directory" --- normally
@code{dist/}, but customizable with the @code{--dist-dir} option.

@node Cross-compiling on Windows,Vista User Access Control UAC,Creating Windows Installers,Creating Built Distributions
@anchor{distutils/builtdist cross-compile-windows}@anchor{4338}@anchor{distutils/builtdist cross-compiling-on-windows}@anchor{4339}
@subsection Cross-compiling on Windows


Starting with Python 2.6, distutils is capable of cross-compiling between
Windows platforms.  In practice, this means that with the correct tools
installed, you can use a 32bit version of Windows to create 64bit extensions
and vice-versa.

To build for an alternate platform, specify the @code{--plat-name} option
to the build command.  Valid values are currently 'win32', and  'win-amd64'.
For example, on a 32bit version of Windows, you could execute:

@example
python setup.py build --plat-name=win-amd64
@end example

to build a 64bit version of your extension.  The Windows Installers also
support this option, so the command:

@example
python setup.py build --plat-name=win-amd64 bdist_wininst
@end example

would create a 64bit installation executable on your 32bit version of Windows.

To cross-compile, you must download the Python source code and cross-compile
Python itself for the platform you are targeting - it is not possible from a
binary installation of Python (as the .lib etc file for other platforms are
not included.)  In practice, this means the user of a 32 bit operating
system will need to use Visual Studio 2008 to open the
@code{PCbuild/PCbuild.sln} solution in the Python source tree and build the
"x64" configuration of the 'pythoncore' project before cross-compiling
extensions is possible.

Note that by default, Visual Studio 2008 does not install 64bit compilers or
tools.  You may need to reexecute the Visual Studio setup process and select
these tools (using Control Panel->[Add/Remove] Programs is a convenient way to
check or modify your existing install.)

@menu
* The Postinstallation script:: 

@end menu

@node The Postinstallation script,,,Cross-compiling on Windows
@anchor{distutils/builtdist postinstallation-script}@anchor{433a}@anchor{distutils/builtdist the-postinstallation-script}@anchor{433b}
@subsubsection The Postinstallation script


Starting with Python 2.3, a postinstallation script can be specified with the
@code{--install-script} option.  The basename of the script must be
specified, and the script filename must also be listed in the scripts argument
to the setup function.

This script will be run at installation time on the target system after all the
files have been copied, with @code{argv[1]} set to @code{-install}, and again at
uninstallation time before the files are removed with @code{argv[1]} set to
@code{-remove}.

The installation script runs embedded in the windows installer, every output
(@code{sys.stdout}, @code{sys.stderr}) is redirected into a buffer and will be
displayed in the GUI after the script has finished.

Some functions especially useful in this context are available as additional
built-in functions in the installation script.

@geindex directory_created() (內置函数)
@geindex file_created() (內置函数)
@anchor{distutils/builtdist directory_created}@anchor{433c}
@deffn {函数} directory_created (path)
@anchor{distutils/builtdist file_created}@anchor{433d}
@deffnx {函数} file_created (path)

These functions should be called when a directory or file is created by the
postinstall script at installation time.  It will register @emph{path} with the
uninstaller, so that it will be removed when the distribution is uninstalled.
To be safe, directories are only removed if they are empty.
@end deffn

@geindex get_special_folder_path() (內置函数)
@anchor{distutils/builtdist get_special_folder_path}@anchor{433e}
@deffn {函数} get_special_folder_path (csidl_string)

This function can be used to retrieve special folder locations on Windows like
the Start Menu or the Desktop.  It returns the full path to the folder.
@emph{csidl_string} must be one of the following strings:

@example
"CSIDL_APPDATA"

"CSIDL_COMMON_STARTMENU"
"CSIDL_STARTMENU"

"CSIDL_COMMON_DESKTOPDIRECTORY"
"CSIDL_DESKTOPDIRECTORY"

"CSIDL_COMMON_STARTUP"
"CSIDL_STARTUP"

"CSIDL_COMMON_PROGRAMS"
"CSIDL_PROGRAMS"

"CSIDL_FONTS"
@end example

If the folder cannot be retrieved, @ref{1d3,,OSError} is raised.

Which folders are available depends on the exact Windows version, and probably
also the configuration.  For details refer to Microsoft's documentation of the
@code{SHGetSpecialFolderPath()} function.
@end deffn

@geindex create_shortcut() (內置函数)
@anchor{distutils/builtdist create_shortcut}@anchor{433f}
@deffn {函数} create_shortcut (target, description, filename[, arguments[, workdir[, iconpath[, iconindex]]]])

This function creates a shortcut. @emph{target} is the path to the program to be
started by the shortcut. @emph{description} is the description of the shortcut.
@emph{filename} is the title of the shortcut that the user will see. @emph{arguments}
specifies the command line arguments, if any. @emph{workdir} is the working directory
for the program. @emph{iconpath} is the file containing the icon for the shortcut,
and @emph{iconindex} is the index of the icon in the file @emph{iconpath}.  Again, for
details consult the Microsoft documentation for the @code{IShellLink}
interface.
@end deffn

@node Vista User Access Control UAC,,Cross-compiling on Windows,Creating Built Distributions
@anchor{distutils/builtdist vista-user-access-control-uac}@anchor{4340}
@subsection Vista User Access Control (UAC)


Starting with Python 2.6, bdist_wininst supports a @code{--user-access-control}
option.  The default is 'none' (meaning no UAC handling is done), and other
valid values are 'auto' (meaning prompt for UAC elevation if Python was
installed for all users) and 'force' (meaning always prompt for elevation).

@cartouche
@quotation 注解 
从Python 3.8开始不推荐使用 bdist_wininst
@end quotation
@end cartouche

@node Distutils 示例,扩展 Distutils,Creating Built Distributions,分发 Python 模块（遗留版本）
@anchor{distutils/examples doc}@anchor{4341}@anchor{distutils/examples distutils-examples}@anchor{4342}@anchor{distutils/examples id1}@anchor{4343}
@section Distutils 示例


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

本章节提供几个基础示例，来帮助用户入门 distutils。关于使用 distutils 的额外信息可以参考 Distutils Cookbook。


@subsubheading 参见



@table @asis

@item Distutils Cookbook@footnote{https://wiki.python.org/moin/Distutils/Cookbook}

一套展示如何更好地控制和使用 distutils 的方法。
@end table


@menu
* 纯 Python 分发（通过 module）:: 
* 纯 Python 分发（通过 包）:: 
* 单个扩展模块:: 
* 检查一个包:: 
* 读取元数据:: 

@end menu

@node 纯 Python 分发（通过 module）,纯 Python 分发（通过 包）,,Distutils 示例
@anchor{distutils/examples pure-mod}@anchor{4344}@anchor{distutils/examples pure-python-distribution-by-module}@anchor{4345}
@subsection 纯 Python 分发（通过 module）


如果你要分发一组模块，特别是它们不在特定的包中，你可以在配置脚本中使用 @code{py_modules} 选项单独指定它们。

最简单的情况下，你只用关心两个文件：一个配置脚本，和单个你要分发的模块，这个示例中的 @code{foo.py}: ：

@example
<root>/
        setup.py
        foo.py
@end example

（在本章节的所有图中，@emph{<root>} 表示分发根目录。）这种情况下的一个最小配置脚本是：

@example
from distutils.core import setup
setup(name='foo',
      version='1.0',
      py_modules=['foo'],
      )
@end example

注意分发的包名用 @code{name} 选项单独指定，没有规定它必须和包中单独的模块同名（虽然这也是个可以遵循的好习惯）。然而，分发名用来生成文件名，所以你应该坚持用字母、数字、下划线和连词号。

因为 @code{py_modules} 是个列表，你当然可以指定多个模块，比如，如果你要分发模块 @code{foo} 和 @code{bar}，你的配置可能是这样：

@example
<root>/
        setup.py
        foo.py
        bar.py
@end example

并且配置脚本是：

@example
from distutils.core import setup
setup(name='foobar',
      version='1.0',
      py_modules=['foo', 'bar'],
      )
@end example

你可以把模块源文件放进另一个目录，但是如果你有足够的模块，也许用包指定模块更简单，而不是单独列出它们。

@node 纯 Python 分发（通过 包）,单个扩展模块,纯 Python 分发（通过 module）,Distutils 示例
@anchor{distutils/examples pure-pkg}@anchor{4346}@anchor{distutils/examples pure-python-distribution-by-package}@anchor{4347}
@subsection 纯 Python 分发（通过 包）


如果你有超过一组模块要分发，特别是它们在不同的包中，也许指定整个包更简单，而不是指定单独的模块。这样即使你的模块不在一个包中也有效；你可以直接令 Distutils 来从根包来处理模块，并且这样对任何其他包也有效（除非你不需要 @code{__init__.py} 文件）。

上一个示例的配置脚本也可以写成：

@example
from distutils.core import setup
setup(name='foobar',
      version='1.0',
      packages=['@w{'}],
      )
@end example

（空字符串表示根包。）

如果两个文件移动到子目录，但是依然在根包中，如：

@example
<root>/
        setup.py
        src/      foo.py
                  bar.py
@end example

那么你依然需要指定根包，但是你还需要告诉 Distutils 根包中的源文件在哪：

@example
from distutils.core import setup
setup(name='foobar',
      version='1.0',
      package_dir=@{'@w{'}: 'src'@},
      packages=['@w{'}],
      )
@end example

更一般地，你要分发多个在同一个包（或者子包）中的模块。举个例子，假设 @code{foo} 和 @code{bar} 模块属于 @code{foobar} 包，排布源文件树的一种方式是：

@example
<root>/
        setup.py
        foobar/
                 __init__.py
                 foo.py
                 bar.py
@end example

这其实是 Distutils 默认的排布，也是你的配置脚本中需要的工作量最小的。

@example
from distutils.core import setup
setup(name='foobar',
      version='1.0',
      packages=['foobar'],
      )
@end example

如果你要把模块放到没有按照它们的包名命名的目录里，那你需要再次使用 @code{package_dir} 选项。比如，如果 @code{src} 目录包含包 @code{foobar} 中的模块：

@example
<root>/
        setup.py
        src/
                 __init__.py
                 foo.py
                 bar.py
@end example

一个合适的配置脚本可以是：

@example
from distutils.core import setup
setup(name='foobar',
      version='1.0',
      package_dir=@{'foobar': 'src'@},
      packages=['foobar'],
      )
@end example

或者，你可以把主包中的模块直接放到分发根目录：

@example
<root>/
        setup.py
        __init__.py
        foo.py
        bar.py
@end example

这样你的配置文件是：

@example
from distutils.core import setup
setup(name='foobar',
      version='1.0',
      package_dir=@{'foobar': '@w{'}@},
      packages=['foobar'],
      )
@end example

（空字符串同样表示当前目录。）

如果你有子包，则它们必须显式列在 @code{packages} 中，但是 @code{package_dir} 中的任何条目会自动扩展到子包。（也就是说，Distutils @emph{不会} 扫描你的源码树，而是尝试通过查找 @code{__init__.py} 文件，来弄清哪些目录与 Python 包关联。）这样，如果默认排布产生一个子包：

@example
<root>/
        setup.py
        foobar/
                 __init__.py
                 foo.py
                 bar.py
                 subfoo/
                           __init__.py
                           blah.py
@end example

则相应的配置脚本是：

@example
from distutils.core import setup
setup(name='foobar',
      version='1.0',
      packages=['foobar', 'foobar.subfoo'],
      )
@end example

@node 单个扩展模块,检查一个包,纯 Python 分发（通过 包）,Distutils 示例
@anchor{distutils/examples single-ext}@anchor{4348}@anchor{distutils/examples single-extension-module}@anchor{4349}
@subsection 单个扩展模块


扩展模块用 @code{ext_modules} 选项指定。@code{package_dir} 对在哪寻找扩展源文件无效；它只对纯 Python 模块的源文件有效。最简单的，一个用单个C源文件写的单扩展模块是：

@example
<root>/
        setup.py
        foo.c
@end example

如果 @code{foo} 扩展属于根包，则配置脚本可以是：

@example
from distutils.core import setup
from distutils.extension import Extension
setup(name='foobar',
      version='1.0',
      ext_modules=[Extension('foo', ['foo.c'])],
      )
@end example

如果扩展在包中，比如 @code{foopkg}，那么

使用完全相同的源文件树排布，通过改变扩展的名字，这个扩展很容易放入 @code{foopkg} 包中：

@example
from distutils.core import setup
from distutils.extension import Extension
setup(name='foobar',
      version='1.0',
      ext_modules=[Extension('foopkg.foo', ['foo.c'])],
      )
@end example

@node 检查一个包,读取元数据,单个扩展模块,Distutils 示例
@anchor{distutils/examples checking-a-package}@anchor{434a}
@subsection 检查一个包


@code{check} 命令允许你校验你的包的元数据是否满足生成分发的最低要求。

直接使用你的 @code{setup.py} 脚本来运行它。如果缺了一些东西，@code{check} 会显示警告。

我们来用单个脚本举例：

@example
from distutils.core import setup

setup(name='foobar')
@end example

运行 @code{check} 命令会显示一些警告：

@example
$ python setup.py check
running check
warning: check: missing required meta-data: version, url
warning: check: missing meta-data: either (author and author_email) or
         (maintainer and maintainer_email) must be supplied
@end example

如果你在 @code{long_description} 域中使用 reStructuredText 语法，并且安装了 docutils@footnote{http://docutils.sourceforge.net} ，你可以用 @code{check} 命令，和 @code{restructuredtext} 选项检查语法是否正确。

比如，如果 @code{setup.py} 脚本改成：

@example
from distutils.core import setup

desc = """\
My description
==============

This is the description of the `@w{`}foobar`@w{`} package.
"""

setup(name='foobar', version='1', author='tarek',
    author_email='tarek@@ziade.org',
    url='http://example.com', long_description=desc)
@end example

长描述中有问题的地方，通过使用 @code{docutils} 解析器，@code{check} 能进行删除：

@example
$ python setup.py check --restructuredtext
running check
warning: check: Title underline too short. (line 2)
warning: check: Could not finish the parsing.
@end example

@node 读取元数据,,检查一个包,Distutils 示例
@anchor{distutils/examples reading-the-metadata}@anchor{434b}
@subsection 读取元数据


@ref{3b1c,,distutils.core.setup()} 函数提供一个通过项目的 @code{setup.py}  脚本，来查询项目的元数据的域的命令行接口：

@example
$ python setup.py --name
distribute
@end example

这个调用通过运行 @ref{3b1c,,distutils.core.setup()} 函数读取 @code{name} 元数据。然而，当源文件或者二进制分发用 Distutils 创建时，元数据域写入一个名为 @code{PKG-INFO} 的静态文件。当一个基于Distutils的项目安装在 Python 中时，@code{PKG-INFO} 文件随着分发的模块和包一起复制到 @code{NAME-VERSION-pyX.X.egg-info} 中，其中 @code{NAME} 是项目的名字，@code{VERSION} 是元数据中定义的版本， @code{pyX.X} 则是 Python 的大版本和小版本，如 @code{2.7} 或者 @code{3.2}。

你可以读回静态文件，使用 @code{distutils.dist.DistributionMetadata} 类和它的 @code{read_pkg_file()} 方法：

@example
>>> from distutils.dist import DistributionMetadata
>>> metadata = DistributionMetadata()
>>> metadata.read_pkg_file(open('distribute-0.6.8-py2.7.egg-info'))
>>> metadata.name
'distribute'
>>> metadata.version
'0.6.8'
>>> metadata.description
'Easily download, build, install, upgrade, and uninstall Python packages'
@end example

注意类也可以用元数据文件载入值来实例化：

@example
>>> pkg_info_path = 'distribute-0.6.8-py2.7.egg-info'
>>> DistributionMetadata(pkg_info_path).name
'distribute'
@end example

@c % \section{Multiple extension modules}

@c % \label{multiple-ext}

@c % \section{Putting it all together}

@node 扩展 Distutils,命令参考,Distutils 示例,分发 Python 模块（遗留版本）
@anchor{distutils/extending doc}@anchor{434c}@anchor{distutils/extending docutils}@anchor{434d}@anchor{distutils/extending extending-distutils}@anchor{132f}@anchor{distutils/extending id1}@anchor{434e}
@section 扩展 Distutils


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

Distutils 可以通过各种方式扩展。 大多数扩展都采用新命令或现有命令的替换形式。 例如，可以编写新命令以支持新的特定于平台的包格式，但是可以修改现有命令的替换，以修改命令在包上的操作细节。

distutils 的大多数扩展都在想要修改现有命令的 @code{setup.py} 脚本中编写；其中许多只是简单地在 @code{.py} 文件以外添加了一些应当被拷贝到包中的文件后缀以便使用。

大多部 distutils 命令的实现都是 @ref{434f,,distutils.cmd.Command} 类的子类。 新增命令可直接继承自 @code{Command}，而替换命令往往间接派生自 @code{Command}， 直接子类化它们所替换的命令。 所有命令都要求自 @code{Command} 派生。

@c % \section{Extending existing commands}

@c % \label{extend-existing}

@c % \section{Writing new commands}

@c % \label{new-commands}

@c % \XXX{Would an uninstall command be a good example here?}

@menu
* 集成新的命令:: 
* 添加新的发布类型:: 

@end menu

@node 集成新的命令,添加新的发布类型,,扩展 Distutils
@anchor{distutils/extending integrating-new-commands}@anchor{4350}
@subsection 集成新的命令


有多种方法可将新的命令实现集成到 distutils 中。 最困难的一种是鼓动在 distutils 自身内部包含新特性，并等待（以及要求）某个 Python 版本提供该支持。 出于多种原因，这确实是相当难的。

对于大多数需求来说最为常见并且可能最为合理的一种则是通过你自己的 @code{setup.py} 脚本来包含新的实现，然后让 @ref{3b1c,,distutils.core.setup()} 函数使用它们:

@example
from distutils.command.build_py import build_py as _build_py
from distutils.core import setup

class build_py(_build_py):
    """Specialized Python source builder."""

    # implement whatever needs to be different...

setup(cmdclass=@{'build_py': build_py@},
      ...)
@end example

如果新的实现必须通过特定的包来使用则此方式最为适宜，因为每个对这个包感兴趣的人都将会需要有新的命令实现。

从 Python 2.4 开始，还有第三个选项可用，其目标是允许添加支持现有 @code{setup.py} 脚本的新命令，而不需要修改 Python 安装包。 这预计可允许第三方扩展提供对附加打包系统的支持，而相应命令又可用于任何 distutils 命令可被使用的地方。 新的配置选项 @code{command_packages} (命令行选项为 @code{--command-packages}) 可用来指定附加包，以在其中查找实现新增命令的模块。 像所有 distutils 选项一样，这可以通过命令行或配置文件来指定。 此选项只能在配置文件的 @code{[global]} 小节之中或在命令行的任何命令之前设置。 如果是设置在配置文件中，则它可被命令行设置重载；如果在命令行中将其设为空字符串则将会使用默认值。 此选项绝不应当在随特定包提供的配置文件中设置。

这个新选项可被用来添加任意数量的包到查找命令实现的包列表；多个包名应当以逗号分隔。 当未指明时，查找将只在 @ref{3e,,distutils.command} 包中进行。 但是当 @code{setup.py} 附带 @code{--command-packages distcmds,buildcmds} 选项运行时，@ref{3e,,distutils.command}, @code{distcmds} 和 @code{buildcmds} 包将按此顺序被查找。 新的命令应当在与命名同名的模块中由同名的类来实现。 给定上述示例命令行选项，则命令 @code{bdist_openpkg} 可由类 @code{distcmds.bdist_openpkg.bdist_openpkg} 或 @code{buildcmds.bdist_openpkg.bdist_openpkg} 来实现。

@node 添加新的发布类型,,集成新的命令,扩展 Distutils
@anchor{distutils/extending adding-new-distribution-types}@anchor{4351}
@subsection 添加新的发布类型


创建发布（在 @code{dist/} 目录中的文件）的命令需要将 @code{(command, filename)} 二元组添加到 @code{self.distribution.dist_files} 以便 @code{upload} 可以将其上传到 PyPI。 二元组中的 @emph{filename} 不包含路径信息而只有文件名本身。 在 dry-run 模式下，二元组仍然应当被添加以表示必须创建的内容。

@node 命令参考,API参考引用,扩展 Distutils,分发 Python 模块（遗留版本）
@anchor{distutils/commandref doc}@anchor{4352}@anchor{distutils/commandref command-reference}@anchor{4353}@anchor{distutils/commandref reference}@anchor{4354}
@section 命令参考


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

@c % \section{Building modules: the \protect\command{build} command family}

@c % \label{build-cmds}

@c % \subsubsection{\protect\command{build}}

@c % \label{build-cmd}

@c % \subsubsection{\protect\command{build\_py}}

@c % \label{build-py-cmd}

@c % \subsubsection{\protect\command{build\_ext}}

@c % \label{build-ext-cmd}

@c % \subsubsection{\protect\command{build\_clib}}

@c % \label{build-clib-cmd}

@menu
* 安装模块; install 命令族: 安装模块 install 命令族. 
* 创建源码发行包; sdist 命令: 创建源码发行包 sdist 命令. 

@end menu

@node 安装模块 install 命令族,创建源码发行包 sdist 命令,,命令参考
@anchor{distutils/commandref install-cmd}@anchor{4355}@anchor{distutils/commandref installing-modules-the-install-command-family}@anchor{4356}
@subsection 安装模块: @code{install} 命令族


install 命令会确保 build 命令已经运行，然后运行子命令 @code{install_lib}, @code{install_data} 和 @code{install_scripts}。

@c % \subsubsection{\protect\command{install\_lib}}

@c % \label{install-lib-cmd}

@menu
* install_data:: 
* install_scripts:: 

@end menu

@node install_data,install_scripts,,安装模块 install 命令族
@anchor{distutils/commandref install-data}@anchor{4357}@anchor{distutils/commandref install-data-cmd}@anchor{4358}
@subsubsection @code{install_data}


此命令会安装随发行包一同提供的所有数据文件。

@node install_scripts,,install_data,安装模块 install 命令族
@anchor{distutils/commandref install-scripts}@anchor{4359}@anchor{distutils/commandref install-scripts-cmd}@anchor{435a}
@subsubsection @code{install_scripts}


此命令会安装发行包中的所有（Python）脚本。

@c % \subsection{Cleaning up: the \protect\command{clean} command}

@c % \label{clean-cmd}

@node 创建源码发行包 sdist 命令,,安装模块 install 命令族,命令参考
@anchor{distutils/commandref creating-a-source-distribution-the-sdist-command}@anchor{435b}@anchor{distutils/commandref sdist-cmd}@anchor{432e}
@subsection 创建源码发行包: @code{sdist} 命令


@c XXX fragment moved down from above: needs context!

列出的模板命令有:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

命令

@tab

描述

@item

@code{include pat1 pat2 ...}

@tab

包括与列出的模式匹配的所有文件

@item

@code{exclude pat1 pat2 ...}

@tab

排除与列出的模式匹配的所有文件

@item

@code{recursive-include dir pat1 pat2
...}

@tab

包括 @emph{dir} 下与列出的模式匹配的所有文件

@item

@code{recursive-exclude dir pat1 pat2
...}

@tab

排除 @emph{dir} 下与列出的模式匹配的所有文件

@item

@code{global-include pat1 pat2 ...}

@tab

包括与源树匹配的所有文件---和任何列出的模式

@item

@code{global-exclude pat1 pat2 ...}

@tab

排除与源树匹配的所有文件---和任何列出的模式

@item

@code{prune dir}

@tab

排除 @emph{dir} 下的所有文件

@item

@code{graft dir}

@tab

包括 @emph{dir} 下的所有文件

@end multitable


此处的模式是 Unix 风格的 "glob" 模式: @code{*} 匹配任意的常规文件名字符序列，@code{?} 匹配任意单个常规文件名字符，而 @code{[range]} 匹配 @emph{range} 范围内的任意字符 (例如 @code{a-z}, @code{a-zA-Z}, @code{a-f0-9_.})。 “常规文件名字符”的定义取决于具体平台：在 Unix 上是指正斜杠以外的任何字符；在 Windows 则是指反斜杠或冒号以外的任何字符。

@c XXX Windows support not there yet

@c % \section{Creating a built distribution: the

@c % \protect\command{bdist} command family}

@c % \label{bdist-cmds}

@c % \subsection{\protect\command{bdist}}

@c % \subsection{\protect\command{bdist\_dumb}}

@c % \subsection{\protect\command{bdist\_rpm}}

@c % \subsection{\protect\command{bdist\_wininst}}

@node API参考引用,,命令参考,分发 Python 模块（遗留版本）
@anchor{distutils/apiref doc}@anchor{435c}@anchor{distutils/apiref api-reference}@anchor{435d}@anchor{distutils/apiref id1}@anchor{435e}
@section API参考引用



@subsubheading 参见



@table @asis

@item New and changed setup.py arguments in setuptools@footnote{https://setuptools.readthedocs.io/en/latest/setuptools.html#new-and-changed-setup-keywords}

The @code{setuptools} project adds new capabilities to the @code{setup} function
and other APIs, makes the API consistent across different Python versions,
and is hence recommended over using @code{distutils} directly.
@end table


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

@menu
* distutils.core: distutils core --- 分发包功能的核心. 分发包功能的核心
* distutils.ccompiler: distutils ccompiler --- CCompiler基类. CCompiler基类
* distutils.unixccompiler: distutils unixccompiler --- Unix C Compiler. Unix C Compiler
* distutils.msvccompiler: distutils msvccompiler --- Microsoft Compiler. Microsoft Compiler
* distutils.bcppcompiler: distutils bcppcompiler --- Borland Compiler. Borland Compiler
* distutils.cygwincompiler: distutils cygwincompiler --- Cygwin Compiler. Cygwin Compiler
* distutils.archive_util: distutils archive_util --- Archiving utilities. Archiving utilities
* distutils.dep_util: distutils dep_util --- Dependency checking. Dependency checking
* distutils.dir_util: distutils dir_util --- Directory tree operations. Directory tree operations
* distutils.file_util: distutils file_util --- Single file operations. Single file operations
* distutils.util: distutils util --- Miscellaneous other utility functions. Miscellaneous other utility functions
* distutils.dist: distutils dist --- The Distribution class. The Distribution class
* distutils.extension: distutils extension --- The Extension class. The Extension class
* distutils.debug: distutils debug --- Distutils debug mode. Distutils debug mode
* distutils.errors: distutils errors --- Distutils exceptions. Distutils exceptions
* distutils.fancy_getopt: distutils fancy_getopt --- Wrapper around the standard getopt module. Wrapper around the standard getopt module
* distutils.filelist: distutils filelist --- The FileList class. The FileList class
* distutils.log: distutils log --- Simple PEP 282-style logging. Simple PEP 282-style logging
* distutils.spawn: distutils spawn --- Spawn a sub-process. Spawn a sub-process
* distutils.sysconfig: distutils sysconfig --- System configuration information. System configuration information
* distutils.text_file: distutils text_file --- The TextFile class. The TextFile class
* distutils.version: distutils version --- Version number classes. Version number classes
* distutils.cmd: distutils cmd --- Abstract base class for Distutils commands. Abstract base class for Distutils commands
* Creating a new Distutils command:: 
* distutils.command: distutils command --- Individual Distutils commands. Individual Distutils commands
* distutils.command.bdist: distutils command bdist --- Build a binary installer. Build a binary installer
* distutils.command.bdist_packager: distutils command bdist_packager --- Abstract base class for packagers. Abstract base class for packagers
* distutils.command.bdist_dumb: distutils command bdist_dumb --- Build a "dumb" installer. Build a "dumb" installer
* distutils.command.bdist_msi: distutils command bdist_msi --- Build a Microsoft Installer binary package. Build a Microsoft Installer binary package
* distutils.command.bdist_rpm: distutils command bdist_rpm --- Build a binary distribution as a Redhat RPM and SRPM. Build a binary distribution as a Redhat RPM and
                               SRPM
* distutils.command.bdist_wininst: distutils command bdist_wininst --- Build a Windows installer. Build a Windows installer
* distutils.command.sdist: distutils command sdist --- Build a source distribution. Build a source distribution
* distutils.command.build: distutils command build --- Build all files of a package. Build all files of a package
* distutils.command.build_clib: distutils command build_clib --- Build any C libraries in a package. Build any C libraries in a package
* distutils.command.build_ext: distutils command build_ext --- Build any extensions in a package. Build any extensions in a package
* distutils.command.build_py: distutils command build_py --- Build the py/ pyc files of a package. Build the .py/.pyc files of a package
* distutils.command.build_scripts: distutils command build_scripts --- Build the scripts of a package. Build the scripts of a package
* distutils.command.clean: distutils command clean --- Clean a package build area. Clean a package build area
* distutils.command.config: distutils command config --- Perform package configuration. Perform package configuration
* distutils.command.install: distutils command install --- Install a package. Install a package
* distutils.command.install_data: distutils command install_data --- Install data files from a package. Install data files from a package
* distutils.command.install_headers: distutils command install_headers --- Install C/C++ header files from a package. Install C/C++ header files from a package
* distutils.command.install_lib: distutils command install_lib --- Install library files from a package. Install library files from a package
* distutils.command.install_scripts: distutils command install_scripts --- Install script files from a package. Install script files from a package
* distutils.command.register: distutils command register --- Register a module with the Python Package Index. Register a module with the Python Package Index
* distutils.command.check: distutils command check --- Check the meta-data of a package. Check the meta-data of a package

@end menu

@node distutils core --- 分发包功能的核心,distutils ccompiler --- CCompiler基类,,API参考引用
@anchor{distutils/apiref distutils-core-core-distutils-functionality}@anchor{435f}@anchor{distutils/apiref module-distutils core}@anchor{54}
@subsection @code{distutils.core} --- 分发包功能的核心


@geindex distutils.core (模块)

The @ref{54,,distutils.core} 是为了使用 Distutils 工具唯一要安装的模块。它提供函数 @ref{3b1c,,setup()} （该函数被 setup 脚本调用）。间接提供了类  @code{distutils.dist.Distribution} 和 @ref{434f,,distutils.cmd.Command}.

@geindex setup() (在 distutils.core 模块中)
@anchor{distutils/apiref distutils core setup}@anchor{3b1c}
@deffn {函数} distutils.core.setup (arguments)

The basic do-everything function that does most everything you could ever ask
for from a Distutils method.

The setup function takes a large number of arguments. These are laid out in the
following table.


@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

参数名称

@tab

值

@tab

type

@item

@emph{name}

@tab

包的名字

@tab

字符串

@item

@emph{version}

@tab

包的版本号；参见 @ref{66,,distutils.version}

@tab

字符串

@item

@emph{description}

@tab

单行的包的描述

@tab

字符串

@item

@emph{long_description}

@tab

更长的包描述

@tab

字符串

@item

@emph{author}

@tab

包的作者

@tab

字符串

@item

@emph{author_email}

@tab

包的作者的电子邮件

@tab

字符串

@item

@emph{maintainer}

@tab

The name of the current
maintainer, if different from
the author. Note that if
the maintainer is provided,
distutils will use it as the
author in @code{PKG-INFO}

@tab

字符串

@item

@emph{maintainer_email}

@tab

当前维护者的电子邮件地址，如果不同与作者

@tab

字符串

@item

@emph{url}

@tab

包的URL（主页）

@tab

字符串

@item

@emph{download_url}

@tab

包的下载地址

@tab

字符串

@item

@emph{packages}

@tab

A list of Python packages that
distutils will manipulate

@tab

字符串列表

@item

@emph{py_modules}

@tab

distutils 会操作的 Python 模块列表

@tab

字符串列表

@item

@emph{scripts}

@tab

要构建和安装的独立脚本文件的列表

@tab

字符串列表

@item

@emph{ext_modules}

@tab

要构建的 Python 扩展的列表

@tab

类 @ref{4315,,distutils.core.Extension} 的实例的列表

@item

@emph{classifiers}

@tab

包的类别列表

@tab

a list of strings; valid classifiers are listed on PyPI@footnote{https://pypi.org/classifiers}.

@item

@emph{distclass}

@tab

要使用的类 @ref{4360,,Distribution} 类

@tab

@ref{4360,,distutils.core.Distribution} 的子类

@item

@emph{script_name}

@tab

setup.py 脚本名称 —— 默认为 @code{sys.argv[0]}

@tab

字符串

@item

@emph{script_args}

@tab

提供给安装脚本的参数

@tab

字符串列表

@item

@emph{options}

@tab

安装脚本的默认选项

@tab

字典

@item

@emph{license}

@tab

包的许可证

@tab

字符串

@item

@emph{keywords}

@tab

Descriptive meta-data, see
@geindex Python 提高建议; PEP 314
PEP 314@footnote{https://www.python.org/dev/peps/pep-0314}

@tab

字符串列表或逗号分隔的字符串

@item

@emph{platforms}

@tab

@tab

字符串列表或逗号分隔的字符串

@item

@emph{cmdclass}

@tab

A mapping of command names to
@ref{4361,,Command} subclasses

@tab

字典

@item

@emph{data_files}

@tab

要安装的数据文件列表

@tab

列表

@item

@emph{package_dir}

@tab

A mapping of package to
directory names

@tab

字典

@end multitable

@end deffn

@geindex run_setup() (在 distutils.core 模块中)
@anchor{distutils/apiref distutils core run_setup}@anchor{4362}
@deffn {函数} distutils.core.run_setup (script_name[, script_args=None, stop_after='run'])

Run a setup script in a somewhat controlled environment, and return  the
@code{distutils.dist.Distribution} instance that drives things.   This is
useful if you need to find out the distribution meta-data  (passed as keyword
args from @emph{script} to @ref{3b1c,,setup()}), or  the contents of the config files or
command-line.

@emph{script_name} is a file that will be read and run with @ref{c3d,,exec()}.  @code{sys.argv[0]}
will be replaced with @emph{script} for the duration of the call.  @emph{script_args} is a
list of strings; if supplied, @code{sys.argv[1:]} will be replaced by @emph{script_args}
for the duration  of the call.

@emph{stop_after} tells @ref{3b1c,,setup()} when to stop processing; possible  values:


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

值

@tab

描述

@item

@emph{init}

@tab

Stop after the @ref{4360,,Distribution}
instance has been created  and populated
with the keyword arguments to @ref{3b1c,,setup()}

@item

@emph{config}

@tab

Stop after config files have been parsed
(and their data stored in the
@ref{4360,,Distribution} instance)

@item

@emph{commandline}

@tab

Stop after the command-line
(@code{sys.argv[1:]} or  @emph{script_args}) have
been parsed (and the data stored in the
@ref{4360,,Distribution} instance.)

@item

@emph{run}

@tab

Stop after all commands have been run (the
same as  if @ref{3b1c,,setup()} had been called
in the usual way). This is the default
value.

@end multitable

@end deffn

In addition, the @ref{54,,distutils.core} module exposed a number of  classes that
live elsewhere.


@itemize *

@item 
@code{Extension} from @ref{5b,,distutils.extension}

@item 
@ref{434f,,Command} from @ref{3d,,distutils.cmd}

@item 
@code{Distribution} from @ref{59,,distutils.dist}
@end itemize

A short description of each of these follows, but see the relevant module for
the full reference.

@geindex Extension (distutils.core 中的类)
@anchor{distutils/apiref distutils core Extension}@anchor{4315}
@deffn {类} distutils.core.Extension

The Extension class describes a single C or C++ extension module in a setup
script. It accepts the following keyword arguments in its constructor:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

参数名称

@tab

值

@tab

type

@item

@emph{name}

@tab

the full name of the
extension, including any
packages --- ie. @emph{not} a
filename or pathname, but
Python dotted name

@tab

字符串

@item

@emph{sources}

@tab

list of source filenames,
relative to the distribution
root (where the setup script
lives), in Unix form
(slash-separated) for
portability.
Source files may be C, C++,
SWIG (.i), platform-specific
resource files, or whatever
else is recognized by the
@code{build_ext} command
as source for a Python
extension.

@tab

字符串列表

@item

@emph{include_dirs}

@tab

list of directories to search
for C/C++ header files (in
Unix form for portability)

@tab

字符串列表

@item

@emph{define_macros}

@tab

list of macros to define; each
macro is defined using a
2-tuple @code{(name, value)},
where @emph{value} is
either the string to define it
to or @code{None} to define it
without a particular value
(equivalent of @code{#define FOO}
in source or @code{-DFOO}
on Unix C compiler command
line)

@tab

元组列表

@item

@emph{undef_macros}

@tab

要明确取消定义的宏列表

@tab

字符串列表

@item

@emph{library_dirs}

@tab

list of directories to search
for C/C++ libraries at link
time

@tab

字符串列表

@item

@emph{libraries}

@tab

要链接的库名列表（不是文件名或路径）

@tab

字符串列表

@item

@emph{runtime_library_dirs}

@tab

list of directories to search
for C/C++ libraries at run
time (for shared extensions,
this is when the extension is
loaded)

@tab

字符串列表

@item

@emph{extra_objects}

@tab

list of extra files to link
with (eg. object files not
implied by 'sources', static
library that must be
explicitly specified, binary
resource files, etc.)

@tab

字符串列表

@item

@emph{extra_compile_args}

@tab

any extra platform- and
compiler-specific information
to use when compiling the
source files in 'sources'. For
platforms and compilers where
a command line makes sense,
this is typically a list of
command-line arguments, but
for other platforms it could
be anything.

@tab

字符串列表

@item

@emph{extra_link_args}

@tab

any extra platform- and
compiler-specific information
to use when linking object
files together to create the
extension (or to create a new
static Python interpreter).
Similar interpretation as for
'extra_compile_args'.

@tab

字符串列表

@item

@emph{export_symbols}

@tab

list of symbols to be exported
from a shared extension. Not
used on all platforms, and not
generally necessary for Python
extensions, which typically
export exactly one symbol:
@code{init} + extension_name.

@tab

字符串列表

@item

@emph{depends}

@tab

扩展名依赖的文件列表

@tab

字符串列表

@item

@emph{language}

@tab

extension language (i.e.
@code{'c'}, @code{'c++'},
@code{'objc'}). Will be detected
from the source extensions if
not provided.

@tab

字符串

@item

@emph{optional}

@tab

指定扩展中的构建失败不应中止构建过程，而只是跳过扩展。

@tab

布尔

@end multitable



在 3.8 版更改: On Unix, C extensions are no longer linked to libpython except on
Android and Cygwin.

@end deffn

@geindex Distribution (distutils.core 中的类)
@anchor{distutils/apiref distutils core Distribution}@anchor{4360}
@deffn {类} distutils.core.Distribution

A @ref{4360,,Distribution} describes how to build, install and package up a Python
software package.

See the @ref{3b1c,,setup()} function for a list of keyword arguments accepted  by the
Distribution constructor. @ref{3b1c,,setup()} creates a Distribution instance.


在 3.7 版更改: @ref{4360,,Distribution} now warns if @code{classifiers},
@code{keywords} and @code{platforms} fields are not specified as a list or
a string.

@end deffn

@geindex Command (distutils.core 中的类)
@anchor{distutils/apiref distutils core Command}@anchor{4361}
@deffn {类} distutils.core.Command

A @ref{4361,,Command} class (or rather, an instance of one of its subclasses)
implement a single distutils command.
@end deffn

@node distutils ccompiler --- CCompiler基类,distutils unixccompiler --- Unix C Compiler,distutils core --- 分发包功能的核心,API参考引用
@anchor{distutils/apiref distutils-ccompiler-ccompiler-base-class}@anchor{4363}@anchor{distutils/apiref module-distutils ccompiler}@anchor{3c}
@subsection @code{distutils.ccompiler} --- CCompiler基类


@geindex distutils.ccompiler (模块)

This module provides the abstract base class for the @ref{4364,,CCompiler}
classes.  A @ref{4364,,CCompiler} instance can be used for all the compile  and
link steps needed to build a single project. Methods are provided to  set
options for the compiler --- macro definitions, include directories,  link path,
libraries and the like.

This module provides the following functions.

@geindex gen_lib_options() (在 distutils.ccompiler 模块中)
@anchor{distutils/apiref distutils ccompiler gen_lib_options}@anchor{4365}
@deffn {函数} distutils.ccompiler.gen_lib_options (compiler, library_dirs, runtime_library_dirs, libraries)

Generate linker options for searching library directories and linking with
specific libraries.  @emph{libraries} and @emph{library_dirs} are, respectively, lists of
library names (not filenames!) and search directories.  Returns a list of
command-line options suitable for use with some compiler (depending on the two
format strings passed in).
@end deffn

@geindex gen_preprocess_options() (在 distutils.ccompiler 模块中)
@anchor{distutils/apiref distutils ccompiler gen_preprocess_options}@anchor{4366}
@deffn {函数} distutils.ccompiler.gen_preprocess_options (macros, include_dirs)

Generate C pre-processor options (@code{-D}, @code{-U}, @code{-I}) as
used by at least two types of compilers: the typical Unix compiler and Visual
C++. @emph{macros} is the usual thing, a list of 1- or 2-tuples, where @code{(name,)}
means undefine (@code{-U}) macro @emph{name}, and @code{(name, value)} means define
(@code{-D}) macro @emph{name} to @emph{value}.  @emph{include_dirs} is just a list of
directory names to be added to the header file search path (@code{-I}).
Returns a list of command-line options suitable for either Unix compilers or
Visual C++.
@end deffn

@geindex get_default_compiler() (在 distutils.ccompiler 模块中)
@anchor{distutils/apiref distutils ccompiler get_default_compiler}@anchor{4367}
@deffn {函数} distutils.ccompiler.get_default_compiler (osname, platform)

Determine the default compiler to use for the given platform.

@emph{osname} should be one of the standard Python OS names (i.e. the ones returned
by @code{os.name}) and @emph{platform} the common value returned by @code{sys.platform} for
the platform in question.

The default values are @code{os.name} and @code{sys.platform} in case the parameters
are not given.
@end deffn

@geindex new_compiler() (在 distutils.ccompiler 模块中)
@anchor{distutils/apiref distutils ccompiler new_compiler}@anchor{4368}
@deffn {函数} distutils.ccompiler.new_compiler (plat=None, compiler=None, verbose=0, dry_run=0, force=0)

Factory function to generate an instance of some CCompiler subclass for the
supplied platform/compiler combination. @emph{plat} defaults to @code{os.name} (eg.
@code{'posix'}, @code{'nt'}), and @emph{compiler}  defaults to the default compiler for
that platform. Currently only @code{'posix'} and @code{'nt'} are supported, and the
default compilers are "traditional Unix interface" (@code{UnixCCompiler}
class) and Visual C++ (@code{MSVCCompiler} class).  Note that it's perfectly
possible to ask for a Unix compiler object under Windows, and a Microsoft
compiler object under Unix---if you supply a value for @emph{compiler}, @emph{plat} is
ignored.

@c % Is the posix/nt only thing still true? Mac OS X seems to work, and

@c % returns a UnixCCompiler instance. How to document this... hmm.
@end deffn

@geindex show_compilers() (在 distutils.ccompiler 模块中)
@anchor{distutils/apiref distutils ccompiler show_compilers}@anchor{4369}
@deffn {函数} distutils.ccompiler.show_compilers ()

Print list of available compilers (used by the @code{--help-compiler} options
to @code{build}, @code{build_ext}, @code{build_clib}).
@end deffn

@geindex CCompiler (distutils.ccompiler 中的类)
@anchor{distutils/apiref distutils ccompiler CCompiler}@anchor{4364}
@deffn {类} distutils.ccompiler.CCompiler ([verbose=0, dry_run=0, force=0])

The abstract base class @ref{4364,,CCompiler} defines the interface that  must be
implemented by real compiler classes.  The class also has  some utility methods
used by several compiler classes.

The basic idea behind a compiler abstraction class is that each instance can be
used for all the compile/link steps in building a single project.  Thus,
attributes common to all of those compile and link steps --- include
directories, macros to define, libraries to link against, etc. --- are
attributes of the compiler instance.  To allow for variability in how individual
files are treated, most of those attributes may be varied on a per-compilation
or per-link basis.

The constructor for each subclass creates an instance of the Compiler object.
Flags are @emph{verbose} (show verbose output), @emph{dry_run} (don't actually execute the
steps) and @emph{force} (rebuild everything, regardless of dependencies). All of
these flags default to @code{0} (off). Note that you probably don't want to
instantiate @ref{4364,,CCompiler} or one of its subclasses directly - use the
@code{distutils.CCompiler.new_compiler()} factory function instead.

The following methods allow you to manually alter compiler options for  the
instance of the Compiler class.

@geindex add_include_dir() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler add_include_dir}@anchor{436a}
@deffn {方法} add_include_dir (dir)

Add @emph{dir} to the list of directories that will be searched for header files.
The compiler is instructed to search directories in the order in which they are
supplied by successive calls to @ref{436a,,add_include_dir()}.
@end deffn

@geindex set_include_dirs() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler set_include_dirs}@anchor{436b}
@deffn {方法} set_include_dirs (dirs)

Set the list of directories that will be searched to @emph{dirs} (a list of strings).
Overrides any preceding calls to @ref{436a,,add_include_dir()}; subsequent calls to
@ref{436a,,add_include_dir()} add to the list passed to @ref{436b,,set_include_dirs()}.
This does not affect any list of standard include directories that the compiler
may search by default.
@end deffn

@geindex add_library() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler add_library}@anchor{436c}
@deffn {方法} add_library (libname)

Add @emph{libname} to the list of libraries that will be included in all links driven
by this compiler object.  Note that @emph{libname} should *not* be the name of a
file containing a library, but the name of the library itself: the actual
filename will be inferred by the linker, the compiler, or the compiler class
(depending on the platform).

The linker will be instructed to link against libraries in the order they were
supplied to @ref{436c,,add_library()} and/or @ref{436d,,set_libraries()}.  It is perfectly
valid to duplicate library names; the linker will be instructed to link against
libraries as many times as they are mentioned.
@end deffn

@geindex set_libraries() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler set_libraries}@anchor{436d}
@deffn {方法} set_libraries (libnames)

Set the list of libraries to be included in all links driven by this compiler
object to @emph{libnames} (a list of strings).  This does not affect any standard
system libraries that the linker may include by default.
@end deffn

@geindex add_library_dir() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler add_library_dir}@anchor{436e}
@deffn {方法} add_library_dir (dir)

Add @emph{dir} to the list of directories that will be searched for libraries
specified to @ref{436c,,add_library()} and @ref{436d,,set_libraries()}.  The linker will be
instructed to search for libraries in the order they are supplied to
@ref{436e,,add_library_dir()} and/or @ref{436f,,set_library_dirs()}.
@end deffn

@geindex set_library_dirs() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler set_library_dirs}@anchor{436f}
@deffn {方法} set_library_dirs (dirs)

Set the list of library search directories to @emph{dirs} (a list of strings).  This
does not affect any standard library search path that the linker may search by
default.
@end deffn

@geindex add_runtime_library_dir() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler add_runtime_library_dir}@anchor{4370}
@deffn {方法} add_runtime_library_dir (dir)

Add @emph{dir} to the list of directories that will be searched for shared libraries
at runtime.
@end deffn

@geindex set_runtime_library_dirs() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler set_runtime_library_dirs}@anchor{4371}
@deffn {方法} set_runtime_library_dirs (dirs)

Set the list of directories to search for shared libraries at runtime to @emph{dirs}
(a list of strings).  This does not affect any standard search path that the
runtime linker may search by default.
@end deffn

@geindex define_macro() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler define_macro}@anchor{4372}
@deffn {方法} define_macro (name[, value=None])

Define a preprocessor macro for all compilations driven by this compiler object.
The optional parameter @emph{value} should be a string; if it is not supplied, then
the macro will be defined without an explicit value and the exact outcome
depends on the compiler used.

@c XXX true? does ANSI say anything about this?
@end deffn

@geindex undefine_macro() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler undefine_macro}@anchor{4373}
@deffn {方法} undefine_macro (name)

Undefine a preprocessor macro for all compilations driven by this compiler
object.  If the same macro is defined by @ref{4372,,define_macro()} and
undefined by @ref{4373,,undefine_macro()} the last call takes precedence
(including multiple redefinitions or undefinitions).  If the macro is
redefined/undefined on a per-compilation basis (ie. in the call to
@ref{1b4,,compile()}), then that takes precedence.
@end deffn

@geindex add_link_object() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler add_link_object}@anchor{4374}
@deffn {方法} add_link_object (object)

Add @emph{object} to the list of object files (or analogues, such as explicitly named
library files or the output of "resource compilers") to be included in every
link driven by this compiler object.
@end deffn

@geindex set_link_objects() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler set_link_objects}@anchor{4375}
@deffn {方法} set_link_objects (objects)

Set the list of object files (or analogues) to be included in every link to
@emph{objects}.  This does not affect any standard object files that the linker may
include by default (such as system libraries).
@end deffn

The following methods implement methods for autodetection of compiler  options,
providing some functionality similar to GNU @code{autoconf}.

@geindex detect_language() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler detect_language}@anchor{4376}
@deffn {方法} detect_language (sources)

Detect the language of a given file, or list of files. Uses the  instance
attributes @code{language_map} (a dictionary), and  @code{language_order} (a
list) to do the job.
@end deffn

@geindex find_library_file() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler find_library_file}@anchor{4377}
@deffn {方法} find_library_file (dirs, lib[, debug=0])

Search the specified list of directories for a static or shared library file
@emph{lib} and return the full path to that file.  If @emph{debug} is true, look for a
debugging version (if that makes sense on the current platform).  Return
@code{None} if @emph{lib} wasn't found in any of the specified directories.
@end deffn

@geindex has_function() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler has_function}@anchor{4378}
@deffn {方法} has_function (funcname[, includes=None, include_dirs=None, libraries=None, library_dirs=None])

Return a boolean indicating whether @emph{funcname} is supported on the current
platform.  The optional arguments can be used to augment the compilation
environment by providing additional include files and paths and libraries and
paths.
@end deffn

@geindex library_dir_option() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler library_dir_option}@anchor{4379}
@deffn {方法} library_dir_option (dir)

Return the compiler option to add @emph{dir} to the list of directories searched for
libraries.
@end deffn

@geindex library_option() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler library_option}@anchor{437a}
@deffn {方法} library_option (lib)

Return the compiler option to add @emph{lib} to the list of libraries linked into the
shared library or executable.
@end deffn

@geindex runtime_library_dir_option() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler runtime_library_dir_option}@anchor{437b}
@deffn {方法} runtime_library_dir_option (dir)

Return the compiler option to add @emph{dir} to the list of directories searched for
runtime libraries.
@end deffn

@geindex set_executables() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler set_executables}@anchor{437c}
@deffn {方法} set_executables (**args)

Define the executables (and options for them) that will be run to perform the
various stages of compilation.  The exact set of executables that may be
specified here depends on the compiler class (via the 'executables' class
attribute), but most will have:


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

attribute -- 属性

@tab

描述

@item

@emph{compiler}

@tab

C/C++ 编译器

@item

@emph{linker_so}

@tab

用于创建共享对象和库的链接器

@item

@emph{linker_exe}

@tab

用于创建二进制可执行文件的链接器

@item

@emph{archiver}

@tab

静态库创建者

@end multitable


On platforms with a command-line (Unix, DOS/Windows), each of these is a string
that will be split into executable name and (optional) list of arguments.
(Splitting the string is done similarly to how Unix shells operate: words are
delimited by spaces, but quotes and backslashes can override this.  See
@ref{437d,,distutils.util.split_quoted()}.)
@end deffn

The following methods invoke stages in the build process.

@geindex compile() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler compile}@anchor{437e}
@deffn {方法} compile (sources[, output_dir=None, macros=None, include_dirs=None, debug=0, extra_preargs=None, extra_postargs=None, depends=None])

Compile one or more source files. Generates object files (e.g.  transforms a
@code{.c} file to a @code{.o} file.)

@emph{sources} must be a list of filenames, most likely C/C++ files, but in reality
anything that can be handled by a particular compiler and compiler class (eg.
@code{MSVCCompiler} can handle resource files in @emph{sources}).  Return a list of
object filenames, one per source filename in @emph{sources}.  Depending on the
implementation, not all source files will necessarily be compiled, but all
corresponding object filenames will be returned.

If @emph{output_dir} is given, object files will be put under it, while retaining
their original path component.  That is, @code{foo/bar.c} normally compiles to
@code{foo/bar.o} (for a Unix implementation); if @emph{output_dir} is @emph{build}, then
it would compile to @code{build/foo/bar.o}.

@emph{macros}, if given, must be a list of macro definitions.  A macro definition is
either a @code{(name, value)} 2-tuple or a @code{(name,)} 1-tuple. The former defines
a macro; if the value is @code{None}, the macro is defined without an explicit
value.  The 1-tuple case undefines a macro.  Later
definitions/redefinitions/undefinitions take precedence.

@emph{include_dirs}, if given, must be a list of strings, the directories to add to
the default include file search path for this compilation only.

@emph{debug} is a boolean; if true, the compiler will be instructed to output debug
symbols in (or alongside) the object file(s).

@emph{extra_preargs} and @emph{extra_postargs} are implementation-dependent. On platforms
that have the notion of a command-line (e.g. Unix, DOS/Windows), they are most
likely lists of strings: extra command-line arguments to prepend/append to the
compiler command line.  On other platforms, consult the implementation class
documentation.  In any event, they are intended as an escape hatch for those
occasions when the abstract compiler framework doesn't cut the mustard.

@emph{depends}, if given, is a list of filenames that all targets depend on.  If a
source file is older than any file in depends, then the source file will be
recompiled.  This supports dependency tracking, but only at a coarse
granularity.

Raises @code{CompileError} on failure.
@end deffn

@geindex create_static_lib() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler create_static_lib}@anchor{437f}
@deffn {方法} create_static_lib (objects, output_libname[, output_dir=None, debug=0, target_lang=None])

Link a bunch of stuff together to create a static library file. The "bunch of
stuff" consists of the list of object files supplied as @emph{objects}, the extra
object files supplied to @ref{4374,,add_link_object()} and/or
@ref{4375,,set_link_objects()}, the libraries supplied to @ref{436c,,add_library()} and/or
@ref{436d,,set_libraries()}, and the libraries supplied as @emph{libraries} (if any).

@emph{output_libname} should be a library name, not a filename; the filename will be
inferred from the library name.  @emph{output_dir} is the directory where the library
file will be put.

@c XXX defaults to what?

@emph{debug} is a boolean; if true, debugging information will be included in the
library (note that on most platforms, it is the compile step where this matters:
the @emph{debug} flag is included here just for consistency).

@emph{target_lang} is the target language for which the given objects are being
compiled. This allows specific linkage time treatment of certain languages.

Raises @code{LibError} on failure.
@end deffn

@geindex link() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler link}@anchor{4380}
@deffn {方法} link (target_desc, objects, output_filename[, output_dir=None, libraries=None, library_dirs=None, runtime_library_dirs=None, export_symbols=None, debug=0, extra_preargs=None, extra_postargs=None, build_temp=None, target_lang=None])

Link a bunch of stuff together to create an executable or shared library file.

The "bunch of stuff" consists of the list of object files supplied as @emph{objects}.
@emph{output_filename} should be a filename.  If @emph{output_dir} is supplied,
@emph{output_filename} is relative to it (i.e. @emph{output_filename} can provide
directory components if needed).

@emph{libraries} is a list of libraries to link against.  These are library names,
not filenames, since they're translated into filenames in a platform-specific
way (eg. @emph{foo} becomes @code{libfoo.a} on Unix and @code{foo.lib} on
DOS/Windows).  However, they can include a directory component, which means the
linker will look in that specific directory rather than searching all the normal
locations.

@emph{library_dirs}, if supplied, should be a list of directories to search for
libraries that were specified as bare library names (ie. no directory
component).  These are on top of the system default and those supplied to
@ref{436e,,add_library_dir()} and/or @ref{436f,,set_library_dirs()}.  @emph{runtime_library_dirs}
is a list of directories that will be embedded into the shared library and used
to search for other shared libraries that *it* depends on at run-time.  (This
may only be relevant on Unix.)

@emph{export_symbols} is a list of symbols that the shared library will export.
(This appears to be relevant only on Windows.)

@emph{debug} is as for @ref{1b4,,compile()} and @ref{437f,,create_static_lib()},  with the
slight distinction that it actually matters on most platforms (as opposed to
@ref{437f,,create_static_lib()}, which includes a @emph{debug} flag mostly for form's
sake).

@emph{extra_preargs} and @emph{extra_postargs} are as for @ref{1b4,,compile()}  (except of
course that they supply command-line arguments for the particular linker being
used).

@emph{target_lang} is the target language for which the given objects are being
compiled. This allows specific linkage time treatment of certain languages.

Raises @code{LinkError} on failure.
@end deffn

@geindex link_executable() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler link_executable}@anchor{4381}
@deffn {方法} link_executable (objects, output_progname[, output_dir=None, libraries=None, library_dirs=None, runtime_library_dirs=None, debug=0, extra_preargs=None, extra_postargs=None, target_lang=None])

Link an executable.  @emph{output_progname} is the name of the file executable, while
@emph{objects} are a list of object filenames to link in. Other arguments  are as for
the @ref{4380,,link()} method.
@end deffn

@geindex link_shared_lib() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler link_shared_lib}@anchor{4382}
@deffn {方法} link_shared_lib (objects, output_libname[, output_dir=None, libraries=None, library_dirs=None, runtime_library_dirs=None, export_symbols=None, debug=0, extra_preargs=None, extra_postargs=None, build_temp=None, target_lang=None])

Link a shared library. @emph{output_libname} is the name of the output  library,
while @emph{objects} is a list of object filenames to link in.  Other arguments are
as for the @ref{4380,,link()} method.
@end deffn

@geindex link_shared_object() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler link_shared_object}@anchor{4383}
@deffn {方法} link_shared_object (objects, output_filename[, output_dir=None, libraries=None, library_dirs=None, runtime_library_dirs=None, export_symbols=None, debug=0, extra_preargs=None, extra_postargs=None, build_temp=None, target_lang=None])

Link a shared object. @emph{output_filename} is the name of the shared object that
will be created, while @emph{objects} is a list of object filenames  to link in.
Other arguments are as for the @ref{4380,,link()} method.
@end deffn

@geindex preprocess() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler preprocess}@anchor{4384}
@deffn {方法} preprocess (source[, output_file=None, macros=None, include_dirs=None, extra_preargs=None, extra_postargs=None])

Preprocess a single C/C++ source file, named in @emph{source}. Output will be written
to file named @emph{output_file}, or @emph{stdout} if @emph{output_file} not supplied.
@emph{macros} is a list of macro definitions as for @ref{1b4,,compile()}, which will
augment the macros set with @ref{4372,,define_macro()} and @ref{4373,,undefine_macro()}.
@emph{include_dirs} is a list of directory names that will be added to the  default
list, in the same way as @ref{436a,,add_include_dir()}.

Raises @code{PreprocessError} on failure.
@end deffn

The following utility methods are defined by the @ref{4364,,CCompiler} class, for
use by the various concrete subclasses.

@geindex executable_filename() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler executable_filename}@anchor{4385}
@deffn {方法} executable_filename (basename[, strip_dir=0, output_dir='@w{'}])

Returns the filename of the executable for the given @emph{basename}.  Typically for
non-Windows platforms this is the same as the basename,  while Windows will get
a @code{.exe} added.
@end deffn

@geindex library_filename() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler library_filename}@anchor{4386}
@deffn {方法} library_filename (libname[, lib_type='static', strip_dir=0, output_dir='@w{'}])

Returns the filename for the given library name on the current platform. On Unix
a library with @emph{lib_type} of @code{'static'} will typically  be of the form
@code{liblibname.a}, while a @emph{lib_type} of @code{'dynamic'}  will be of the form
@code{liblibname.so}.
@end deffn

@geindex object_filenames() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler object_filenames}@anchor{4387}
@deffn {方法} object_filenames (source_filenames[, strip_dir=0, output_dir='@w{'}])

Returns the name of the object files for the given source files.
@emph{source_filenames} should be a list of filenames.
@end deffn

@geindex shared_object_filename() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler shared_object_filename}@anchor{4388}
@deffn {方法} shared_object_filename (basename[, strip_dir=0, output_dir='@w{'}])

Returns the name of a shared object file for the given file name @emph{basename}.
@end deffn

@geindex execute() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler execute}@anchor{4389}
@deffn {方法} execute (func, args[, msg=None, level=1])

Invokes @ref{438a,,distutils.util.execute()}. This method invokes a  Python function
@emph{func} with the given arguments @emph{args}, after  logging and taking into account
the @emph{dry_run} flag.
@end deffn

@geindex spawn() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler spawn}@anchor{438b}
@deffn {方法} spawn (cmd)

Invokes @code{distutils.util.spawn()}. This invokes an external  process to run
the given command.
@end deffn

@geindex mkpath() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler mkpath}@anchor{438c}
@deffn {方法} mkpath (name[, mode=511])

Invokes @ref{438d,,distutils.dir_util.mkpath()}. This creates a directory  and any
missing ancestor directories.
@end deffn

@geindex move_file() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler move_file}@anchor{438e}
@deffn {方法} move_file (src, dst)

Invokes @ref{438f,,distutils.file_util.move_file()}. Renames @emph{src} to  @emph{dst}.
@end deffn

@geindex announce() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler announce}@anchor{4390}
@deffn {方法} announce (msg[, level=1])

Write a message using @code{distutils.log.debug()}.
@end deffn

@geindex warn() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler warn}@anchor{4391}
@deffn {方法} warn (msg)

Write a warning message @emph{msg} to standard error.
@end deffn

@geindex debug_print() (distutils.ccompiler.CCompiler 方法)
@anchor{distutils/apiref distutils ccompiler CCompiler debug_print}@anchor{4392}
@deffn {方法} debug_print (msg)

If the @emph{debug} flag is set on this @ref{4364,,CCompiler} instance, print  @emph{msg} to
standard output, otherwise do nothing.
@end deffn
@end deffn

@c % \subsection{Compiler-specific modules}

@c %

@c % The following modules implement concrete subclasses of the abstract

@c % \class{CCompiler} class. They should not be instantiated directly, but should

@c % be created using \function{distutils.ccompiler.new_compiler()} factory

@c % function.

@node distutils unixccompiler --- Unix C Compiler,distutils msvccompiler --- Microsoft Compiler,distutils ccompiler --- CCompiler基类,API参考引用
@anchor{distutils/apiref distutils-unixccompiler-unix-c-compiler}@anchor{4393}@anchor{distutils/apiref module-distutils unixccompiler}@anchor{64}
@subsection @code{distutils.unixccompiler} --- Unix C Compiler


@geindex distutils.unixccompiler (模块)

This module provides the @code{UnixCCompiler} class, a subclass of
@code{CCompiler} that handles the typical Unix-style command-line  C compiler:


@itemize *

@item 
macros defined with @code{-Dname[=value]}

@item 
macros undefined with @code{-Uname}

@item 
include search directories specified with @code{-Idir}

@item 
libraries specified with @code{-llib}

@item 
library search directories specified with @code{-Ldir}

@item 
compile handled by @code{cc} (or similar) executable with @code{-c}
option: compiles @code{.c} to @code{.o}

@item 
link static library handled by @code{ar} command (possibly with
@code{ranlib})

@item 
link shared library handled by @code{cc} @code{-shared}
@end itemize

@node distutils msvccompiler --- Microsoft Compiler,distutils bcppcompiler --- Borland Compiler,distutils unixccompiler --- Unix C Compiler,API参考引用
@anchor{distutils/apiref distutils-msvccompiler-microsoft-compiler}@anchor{4394}@anchor{distutils/apiref module-distutils msvccompiler}@anchor{60}
@subsection @code{distutils.msvccompiler} --- Microsoft Compiler


@geindex distutils.msvccompiler (模块)

@c XXX: This is *waaaaay* out of date!

This module provides @code{MSVCCompiler}, an implementation of the abstract
@code{CCompiler} class for Microsoft Visual Studio. Typically, extension
modules need to be compiled with the same compiler that was used to compile
Python. For Python 2.3 and earlier, the compiler was Visual Studio 6. For Python
2.4 and 2.5, the compiler is Visual Studio .NET 2003.

@code{MSVCCompiler} will normally choose the right compiler, linker etc. on
its own. To override this choice, the environment variables @emph{DISTUTILS_USE_SDK}
and @emph{MSSdk} must be both set. @emph{MSSdk} indicates that the current environment has
been setup by the SDK's @code{SetEnv.Cmd} script, or that the environment variables
had been registered when the SDK was installed; @emph{DISTUTILS_USE_SDK} indicates
that the distutils user has made an explicit choice to override the compiler
selection by @code{MSVCCompiler}.

@node distutils bcppcompiler --- Borland Compiler,distutils cygwincompiler --- Cygwin Compiler,distutils msvccompiler --- Microsoft Compiler,API参考引用
@anchor{distutils/apiref distutils-bcppcompiler-borland-compiler}@anchor{4395}@anchor{distutils/apiref module-distutils bcppcompiler}@anchor{3b}
@subsection @code{distutils.bcppcompiler} --- Borland Compiler


@geindex distutils.bcppcompiler (模块)

This module provides @code{BorlandCCompiler}, a subclass of the abstract
@code{CCompiler} class for the Borland C++ compiler.

@node distutils cygwincompiler --- Cygwin Compiler,distutils archive_util --- Archiving utilities,distutils bcppcompiler --- Borland Compiler,API参考引用
@anchor{distutils/apiref distutils-cygwincompiler-cygwin-compiler}@anchor{4396}@anchor{distutils/apiref module-distutils cygwinccompiler}@anchor{55}
@subsection @code{distutils.cygwincompiler} --- Cygwin Compiler


@geindex distutils.cygwinccompiler (模块)

This module provides the @code{CygwinCCompiler} class, a subclass of
@code{UnixCCompiler} that handles the Cygwin port of the GNU C compiler to
Windows.  It also contains the Mingw32CCompiler class which handles the mingw32
port of GCC (same as cygwin in no-cygwin mode).

@node distutils archive_util --- Archiving utilities,distutils dep_util --- Dependency checking,distutils cygwincompiler --- Cygwin Compiler,API参考引用
@anchor{distutils/apiref distutils-archive-util-archiving-utilities}@anchor{4397}@anchor{distutils/apiref module-distutils archive_util}@anchor{3a}
@subsection @code{distutils.archive_util} ---  Archiving utilities


@geindex distutils.archive_util (模块)

This module provides a few functions for creating archive files, such as
tarballs or zipfiles.

@geindex make_archive() (在 distutils.archive_util 模块中)
@anchor{distutils/apiref distutils archive_util make_archive}@anchor{4398}
@deffn {函数} distutils.archive_util.make_archive (base_name, format[, root_dir=None, base_dir=None, verbose=0, dry_run=0])

Create an archive file (eg. @code{zip} or @code{tar}).  @emph{base_name}  is the name of
the file to create, minus any format-specific extension;  @emph{format} is the
archive format: one of @code{zip}, @code{tar}, @code{gztar}, @code{bztar}, @code{xztar}, or
@code{ztar}. @emph{root_dir} is a directory that will be the root directory of the
archive; ie. we typically @code{chdir} into @emph{root_dir} before  creating the
archive.  @emph{base_dir} is the directory where we start  archiving from; ie.
@emph{base_dir} will be the common prefix of all files and directories in the
archive.  @emph{root_dir} and @emph{base_dir} both default to the current directory.
Returns the name of the archive file.


在 3.5 版更改: 添加了对 @code{xztar} 格式的支持

@end deffn

@geindex make_tarball() (在 distutils.archive_util 模块中)
@anchor{distutils/apiref distutils archive_util make_tarball}@anchor{4399}
@deffn {函数} distutils.archive_util.make_tarball (base_name, base_dir[, compress='gzip', verbose=0, dry_run=0])

'Create an (optional compressed) archive as a tar file from all files in and
under @emph{base_dir}. @emph{compress} must be @code{'gzip'} (the default),
@code{'bzip2'}, @code{'xz'}, @code{'compress'}, or @code{None}.  For the @code{'compress'}
method the compression utility named by @code{compress} must be on the
default program search path, so this is probably Unix-specific.  The output
tar file will be named @code{base_dir.tar}, possibly plus the appropriate
compression extension (@code{.gz}, @code{.bz2}, @code{.xz} or @code{.Z}).  Return the
output filename.


在 3.5 版更改: Added support for the @code{xz} compression.

@end deffn

@geindex make_zipfile() (在 distutils.archive_util 模块中)
@anchor{distutils/apiref distutils archive_util make_zipfile}@anchor{439a}
@deffn {函数} distutils.archive_util.make_zipfile (base_name, base_dir[, verbose=0, dry_run=0])

Create a zip file from all files in and under @emph{base_dir}.  The output zip file
will be named @emph{base_name} + @code{.zip}.  Uses either the  @ref{142,,zipfile} Python
module (if available) or the InfoZIP @code{zip}  utility (if installed and
found on the default search path).  If neither  tool is available, raises
@code{DistutilsExecError}.   Returns the name of the output zip file.
@end deffn

@node distutils dep_util --- Dependency checking,distutils dir_util --- Directory tree operations,distutils archive_util --- Archiving utilities,API参考引用
@anchor{distutils/apiref distutils-dep-util-dependency-checking}@anchor{439b}@anchor{distutils/apiref module-distutils dep_util}@anchor{57}
@subsection @code{distutils.dep_util} --- Dependency checking


@geindex distutils.dep_util (模块)

This module provides functions for performing simple, timestamp-based
dependency of files and groups of files; also, functions based entirely  on such
timestamp dependency analysis.

@geindex newer() (在 distutils.dep_util 模块中)
@anchor{distutils/apiref distutils dep_util newer}@anchor{439c}
@deffn {函数} distutils.dep_util.newer (source, target)

Return true if @emph{source} exists and is more recently modified than @emph{target}, or
if @emph{source} exists and @emph{target} doesn't. Return false if both exist and @emph{target}
is the same age or newer  than @emph{source}. Raise @code{DistutilsFileError} if
@emph{source} does not exist.
@end deffn

@geindex newer_pairwise() (在 distutils.dep_util 模块中)
@anchor{distutils/apiref distutils dep_util newer_pairwise}@anchor{439d}
@deffn {函数} distutils.dep_util.newer_pairwise (sources, targets)

Walk two filename lists in parallel, testing if each source is newer than its
corresponding target.  Return a pair of lists (@emph{sources}, @emph{targets}) where
source is newer than target, according to the semantics of @ref{439c,,newer()}.

@c % % equivalent to a listcomp...
@end deffn

@geindex newer_group() (在 distutils.dep_util 模块中)
@anchor{distutils/apiref distutils dep_util newer_group}@anchor{439e}
@deffn {函数} distutils.dep_util.newer_group (sources, target[, missing='error'])

Return true if @emph{target} is out-of-date with respect to any file listed in
@emph{sources}.  In other words, if @emph{target} exists and is newer than every file in
@emph{sources}, return false; otherwise return true. @emph{missing} controls what we do
when a source file is missing; the default (@code{'error'}) is to blow up with an
@ref{1d3,,OSError} from  inside @ref{1f1,,os.stat()}; if it is @code{'ignore'}, we silently
drop any missing source files; if it is @code{'newer'}, any missing source files
make us assume that @emph{target} is out-of-date (this is handy in "dry-run" mode:
it'll make you pretend to carry out commands that wouldn't work because inputs
are missing, but that doesn't matter because you're not actually going to run
the commands).
@end deffn

@node distutils dir_util --- Directory tree operations,distutils file_util --- Single file operations,distutils dep_util --- Dependency checking,API参考引用
@anchor{distutils/apiref distutils-dir-util-directory-tree-operations}@anchor{439f}@anchor{distutils/apiref module-distutils dir_util}@anchor{58}
@subsection @code{distutils.dir_util} --- Directory tree operations


@geindex distutils.dir_util (模块)

This module provides functions for operating on directories and trees of
directories.

@geindex mkpath() (在 distutils.dir_util 模块中)
@anchor{distutils/apiref distutils dir_util mkpath}@anchor{438d}
@deffn {函数} distutils.dir_util.mkpath (name[, mode=0o777, verbose=0, dry_run=0])

Create a directory and any missing ancestor directories.  If the directory
already exists (or if @emph{name} is the empty string, which means the current
directory, which of course exists), then do nothing.  Raise
@code{DistutilsFileError} if unable to create some directory along the way (eg.
some sub-path exists, but is a file rather than a directory).  If @emph{verbose} is
true, print a one-line summary of each mkdir to stdout.  Return the list of
directories actually created.
@end deffn

@geindex create_tree() (在 distutils.dir_util 模块中)
@anchor{distutils/apiref distutils dir_util create_tree}@anchor{43a0}
@deffn {函数} distutils.dir_util.create_tree (base_dir, files[, mode=0o777, verbose=0, dry_run=0])

Create all the empty directories under @emph{base_dir} needed to put @emph{files} there.
@emph{base_dir} is just the name of a directory which doesn't necessarily exist
yet; @emph{files} is a list of filenames to be interpreted relative to @emph{base_dir}.
@emph{base_dir} + the directory portion of every file in @emph{files} will be created if
it doesn't already exist.  @emph{mode}, @emph{verbose} and @emph{dry_run} flags  are as for
@ref{438d,,mkpath()}.
@end deffn

@geindex copy_tree() (在 distutils.dir_util 模块中)
@anchor{distutils/apiref distutils dir_util copy_tree}@anchor{43a1}
@deffn {函数} distutils.dir_util.copy_tree (src, dst[, preserve_mode=1, preserve_times=1, preserve_symlinks=0, update=0, verbose=0, dry_run=0])

Copy an entire directory tree @emph{src} to a new location @emph{dst}.  Both @emph{src} and
@emph{dst} must be directory names.  If @emph{src} is not a directory, raise
@code{DistutilsFileError}.  If @emph{dst} does  not exist, it is created with
@ref{438d,,mkpath()}.  The end result of the  copy is that every file in @emph{src} is
copied to @emph{dst}, and  directories under @emph{src} are recursively copied to @emph{dst}.
Return the list of files that were copied or might have been copied, using their
output name. The return value is unaffected by @emph{update} or @emph{dry_run}: it is
simply the list of all files under @emph{src}, with the names changed to be under
@emph{dst}.

@emph{preserve_mode} and @emph{preserve_times} are the same as for
@ref{43a2,,distutils.file_util.copy_file()}; note that they only apply to
regular files, not to
directories.  If @emph{preserve_symlinks} is true, symlinks will be copied as
symlinks (on platforms that support them!); otherwise (the default), the
destination of the symlink will be copied.  @emph{update} and @emph{verbose} are the same
as for @code{copy_file()}.

Files in @emph{src} that begin with @code{.nfs} are skipped (more information on
these files is available in answer D2 of the NFS FAQ page@footnote{http://nfs.sourceforge.net/#section_d}).


在 3.3.1 版更改: NFS files are ignored.

@end deffn

@geindex remove_tree() (在 distutils.dir_util 模块中)
@anchor{distutils/apiref distutils dir_util remove_tree}@anchor{43a3}
@deffn {函数} distutils.dir_util.remove_tree (directory[, verbose=0, dry_run=0])

Recursively remove @emph{directory} and all files and directories underneath it. Any
errors are ignored (apart from being reported to @code{sys.stdout} if @emph{verbose} is
true).
@end deffn

@node distutils file_util --- Single file operations,distutils util --- Miscellaneous other utility functions,distutils dir_util --- Directory tree operations,API参考引用
@anchor{distutils/apiref distutils-file-util-single-file-operations}@anchor{43a4}@anchor{distutils/apiref module-distutils file_util}@anchor{5d}
@subsection @code{distutils.file_util} --- Single file operations


@geindex distutils.file_util (模块)

This module contains some utility functions for operating on individual files.

@geindex copy_file() (在 distutils.file_util 模块中)
@anchor{distutils/apiref distutils file_util copy_file}@anchor{43a2}
@deffn {函数} distutils.file_util.copy_file (src, dst[, preserve_mode=1, preserve_times=1, update=0, link=None, verbose=0, dry_run=0])

Copy file @emph{src} to @emph{dst}. If @emph{dst} is a directory, then @emph{src} is copied there
with the same name; otherwise, it must be a filename. (If the file exists, it
will be ruthlessly clobbered.) If @emph{preserve_mode} is true (the default), the
file's mode (type and permission bits, or whatever is analogous on the
current platform) is copied. If @emph{preserve_times} is true (the default), the
last-modified and last-access times are copied as well. If @emph{update} is true,
@emph{src} will only be copied if @emph{dst} does not exist, or if @emph{dst} does exist but
is older than @emph{src}.

@emph{link} allows you to make hard links (using @ref{a30,,os.link()}) or symbolic links
(using @ref{a36,,os.symlink()}) instead of copying: set it to @code{'hard'} or
@code{'sym'}; if it is @code{None} (the default), files are copied. Don't set @emph{link}
on systems that don't support it: @ref{43a2,,copy_file()} doesn't check if hard or
symbolic linking is available.  It uses @code{_copy_file_contents()} to copy file
contents.

Return a tuple @code{(dest_name, copied)}: @emph{dest_name} is the actual  name of the
output file, and @emph{copied} is true if the file was copied  (or would have been
copied, if @emph{dry_run} true).

@c % XXX if the destination file already exists, we clobber it if

@c % copying, but blow up if linking.  Hmmm.  And I don't know what

@c % macostools.copyfile() does.  Should definitely be consistent, and

@c % should probably blow up if destination exists and we would be

@c % changing it (ie. it's not already a hard/soft link to src OR

@c % (not update) and (src newer than dst)).
@end deffn

@geindex move_file() (在 distutils.file_util 模块中)
@anchor{distutils/apiref distutils file_util move_file}@anchor{438f}
@deffn {函数} distutils.file_util.move_file (src, dst[, verbose, dry_run])

Move file @emph{src} to @emph{dst}. If @emph{dst} is a directory, the file will be moved into
it with the same name; otherwise, @emph{src} is just renamed to @emph{dst}.  Returns the
new full name of the file.

@cartouche
@quotation 警告 
Handles cross-device moves on Unix using @ref{43a2,,copy_file()}.  What about
other systems?
@end quotation
@end cartouche
@end deffn

@geindex write_file() (在 distutils.file_util 模块中)
@anchor{distutils/apiref distutils file_util write_file}@anchor{43a5}
@deffn {函数} distutils.file_util.write_file (filename, contents)

Create a file called @emph{filename} and write @emph{contents} (a sequence of strings
without line terminators) to it.
@end deffn

@node distutils util --- Miscellaneous other utility functions,distutils dist --- The Distribution class,distutils file_util --- Single file operations,API参考引用
@anchor{distutils/apiref distutils-util-miscellaneous-other-utility-functions}@anchor{43a6}@anchor{distutils/apiref module-distutils util}@anchor{65}
@subsection @code{distutils.util} --- Miscellaneous other utility functions


@geindex distutils.util (模块)

This module contains other assorted bits and pieces that don't fit into  any
other utility module.

@geindex get_platform() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util get_platform}@anchor{43a7}
@deffn {函数} distutils.util.get_platform ()

Return a string that identifies the current platform.  This is used mainly to
distinguish platform-specific build directories and platform-specific built
distributions.  Typically includes the OS name and version and the
architecture (as supplied by 'os.uname()'), although the exact information
included depends on the OS; e.g., on Linux, the kernel version isn't
particularly important.

返回值的示例：


@itemize *

@item 
@code{linux-i586}

@item 
@code{linux-alpha}

@item 
@code{solaris-2.6-sun4u}
@end itemize

For non-POSIX platforms, currently just returns @code{sys.platform}.

For Mac OS X systems the OS version reflects the minimal version on which
binaries will run (that is, the value of @code{MACOSX_DEPLOYMENT_TARGET}
during the build of Python), not the OS version of the current system.

For universal binary builds on Mac OS X the architecture value reflects
the universal binary status instead of the architecture of the current
processor. For 32-bit universal binaries the architecture is @code{fat},
for 64-bit universal binaries the architecture is @code{fat64}, and
for 4-way universal binaries the architecture is @code{universal}. Starting
from Python 2.7 and Python 3.2 the architecture @code{fat3} is used for
a 3-way universal build (ppc, i386, x86_64) and @code{intel} is used for
a universal build with the i386 and x86_64 architectures

Examples of returned values on Mac OS X:


@itemize *

@item 
@code{macosx-10.3-ppc}

@item 
@code{macosx-10.3-fat}

@item 
@code{macosx-10.5-universal}

@item 
@code{macosx-10.6-intel}
@end itemize
@end deffn

@geindex convert_path() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util convert_path}@anchor{43a8}
@deffn {函数} distutils.util.convert_path (pathname)

Return 'pathname' as a name that will work on the native filesystem, i.e. split
it on '/' and put it back together again using the current directory separator.
Needed because filenames in the setup script are always supplied in Unix style,
and have to be converted to the local convention before we can actually use them
in the filesystem.  Raises @ref{1fb,,ValueError} on non-Unix-ish systems if
@emph{pathname} either  starts or ends with a slash.
@end deffn

@geindex change_root() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util change_root}@anchor{43a9}
@deffn {函数} distutils.util.change_root (new_root, pathname)

Return @emph{pathname} with @emph{new_root} prepended.  If @emph{pathname} is relative, this is
equivalent to @code{os.path.join(new_root,pathname)} Otherwise, it requires making
@emph{pathname} relative and then joining the two, which is tricky on DOS/Windows.
@end deffn

@geindex check_environ() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util check_environ}@anchor{43aa}
@deffn {函数} distutils.util.check_environ ()

Ensure that 'os.environ' has all the environment variables we guarantee that
users can use in config files, command-line options, etc.  Currently this
includes:


@itemize *

@item 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME} - user's home directory (Unix only)

@item 
@geindex PLAT
@geindex 环境变量; PLAT
@code{PLAT} - description of the current platform, including hardware and
OS (see @ref{43a7,,get_platform()})
@end itemize
@end deffn

@geindex subst_vars() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util subst_vars}@anchor{43ab}
@deffn {函数} distutils.util.subst_vars (s, local_vars)

Perform shell/Perl-style variable substitution on @emph{s}.  Every occurrence of
@code{$} followed by a name is considered a variable, and variable is substituted
by the value found in the @emph{local_vars} dictionary, or in @code{os.environ} if it's
not in @emph{local_vars}. @emph{os.environ} is first checked/augmented to guarantee that
it contains certain values: see @ref{43aa,,check_environ()}.  Raise @ref{1fb,,ValueError}
for any variables not found in either @emph{local_vars} or @code{os.environ}.

Note that this is not a fully-fledged string interpolation function. A valid
@code{$variable} can consist only of upper and lower case letters, numbers and an
underscore. No @{ @} or ( ) style quoting is available.
@end deffn

@geindex split_quoted() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util split_quoted}@anchor{437d}
@deffn {函数} distutils.util.split_quoted (s)

Split a string up according to Unix shell-like rules for quotes and backslashes.
In short: words are delimited by spaces, as long as those spaces are not escaped
by a backslash, or inside a quoted string. Single and double quotes are
equivalent, and the quote characters can be backslash-escaped.  The backslash is
stripped from any two-character escape sequence, leaving only the escaped
character.  The quote characters are stripped from any quoted string.  Returns a
list of words.

@c % Should probably be moved into the standard library.
@end deffn

@geindex execute() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util execute}@anchor{438a}
@deffn {函数} distutils.util.execute (func, args[, msg=None, verbose=0, dry_run=0])

Perform some action that affects the outside world (for instance, writing to the
filesystem).  Such actions are special because they are disabled by the
@emph{dry_run} flag.  This method takes  care of all that bureaucracy for you; all
you have to do is supply the function to call and an argument tuple for it (to
embody the "external action" being performed), and an optional message to print.
@end deffn

@geindex strtobool() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util strtobool}@anchor{43ac}
@deffn {函数} distutils.util.strtobool (val)

Convert a string representation of truth to true (1) or false (0).

True values are @code{y}, @code{yes}, @code{t}, @code{true}, @code{on}  and @code{1}; false values
are @code{n}, @code{no}, @code{f}, @code{false},  @code{off} and @code{0}.  Raises
@ref{1fb,,ValueError} if @emph{val}  is anything else.
@end deffn

@geindex byte_compile() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util byte_compile}@anchor{43ad}
@deffn {函数} distutils.util.byte_compile (py_files[, optimize=0, force=0, prefix=None, base_dir=None, verbose=1, dry_run=0, direct=None])

Byte-compile a collection of Python source files to @code{.pyc} files in a
@code{__pycache__} subdirectory (see 
@geindex Python 提高建议; PEP 3147
PEP 3147@footnote{https://www.python.org/dev/peps/pep-3147} and 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488}).
@emph{py_files} is a list of files to compile; any files that don't end in
@code{.py} are silently skipped.  @emph{optimize} must be one of the following:


@itemize *

@item 
@code{0} - don't optimize

@item 
@code{1} - normal optimization (like @code{python -O})

@item 
@code{2} - extra optimization (like @code{python -OO})
@end itemize

If @emph{force} is true, all files are recompiled regardless of timestamps.

The source filename encoded in each @ref{60f,,bytecode} file defaults to the filenames
listed in @emph{py_files}; you can modify these with @emph{prefix} and @emph{basedir}.
@emph{prefix} is a string that will be stripped off of each source filename, and
@emph{base_dir} is a directory name that will be prepended (after @emph{prefix} is
stripped).  You can supply either or both (or neither) of @emph{prefix} and
@emph{base_dir}, as you wish.

If @emph{dry_run} is true, doesn't actually do anything that would affect the
filesystem.

Byte-compilation is either done directly in this interpreter process with the
standard @ref{d7,,py_compile} module, or indirectly by writing a temporary script
and executing it.  Normally, you should let @ref{43ad,,byte_compile()} figure out to
use direct compilation or not (see the source for details).  The @emph{direct} flag
is used by the script generated in indirect mode; unless you know what you're
doing, leave it set to @code{None}.


在 3.2.3 版更改: Create @code{.pyc} files with an @ref{3a89,,import magic tag} in their name, in a @code{__pycache__} subdirectory
instead of files without tag in the current directory.



在 3.5 版更改: Create @code{.pyc} files according to 
@geindex Python 提高建议; PEP 488
PEP 488@footnote{https://www.python.org/dev/peps/pep-0488}.

@end deffn

@geindex rfc822_escape() (在 distutils.util 模块中)
@anchor{distutils/apiref distutils util rfc822_escape}@anchor{43ae}
@deffn {函数} distutils.util.rfc822_escape (header)

Return a version of @emph{header} escaped for inclusion in an 
@geindex RFC; RFC 822
RFC 822@footnote{https://tools.ietf.org/html/rfc822.html} header, by
ensuring there are 8 spaces space after each newline. Note that it does no other
modification of the string.

@c % this _can_ be replaced
@end deffn

@c % \subsection{Distutils objects}

@node distutils dist --- The Distribution class,distutils extension --- The Extension class,distutils util --- Miscellaneous other utility functions,API参考引用
@anchor{distutils/apiref distutils-dist-the-distribution-class}@anchor{43af}@anchor{distutils/apiref module-distutils dist}@anchor{59}
@subsection @code{distutils.dist} --- The Distribution class


@geindex distutils.dist (模块)

This module provides the @ref{4360,,Distribution} class, which
represents the module distribution being built/installed/distributed.

@node distutils extension --- The Extension class,distutils debug --- Distutils debug mode,distutils dist --- The Distribution class,API参考引用
@anchor{distutils/apiref distutils-extension-the-extension-class}@anchor{43b0}@anchor{distutils/apiref module-distutils extension}@anchor{5b}
@subsection @code{distutils.extension} --- The Extension class


@geindex distutils.extension (模块)

This module provides the @code{Extension} class, used to describe C/C++
extension modules in setup scripts.

@c % \subsection{Ungrouped modules}

@c % The following haven't been moved into a more appropriate section yet.

@node distutils debug --- Distutils debug mode,distutils errors --- Distutils exceptions,distutils extension --- The Extension class,API参考引用
@anchor{distutils/apiref distutils-debug-distutils-debug-mode}@anchor{43b1}@anchor{distutils/apiref module-distutils debug}@anchor{56}
@subsection @code{distutils.debug} --- Distutils debug mode


@geindex distutils.debug (模块)

本模块提供DEBUG标识。

@node distutils errors --- Distutils exceptions,distutils fancy_getopt --- Wrapper around the standard getopt module,distutils debug --- Distutils debug mode,API参考引用
@anchor{distutils/apiref distutils-errors-distutils-exceptions}@anchor{43b2}@anchor{distutils/apiref module-distutils errors}@anchor{5a}
@subsection @code{distutils.errors} --- Distutils exceptions


@geindex distutils.errors (模块)

Provides exceptions used by the Distutils modules.  Note that Distutils modules
may raise standard exceptions; in particular, SystemExit is usually raised for
errors that are obviously the end-user's fault (eg. bad command-line arguments).

This module is safe to use in @code{from ... import *} mode; it only exports
symbols whose names start with @code{Distutils} and end with @code{Error}.

@node distutils fancy_getopt --- Wrapper around the standard getopt module,distutils filelist --- The FileList class,distutils errors --- Distutils exceptions,API参考引用
@anchor{distutils/apiref distutils-fancy-getopt-wrapper-around-the-standard-getopt-module}@anchor{43b3}@anchor{distutils/apiref module-distutils fancy_getopt}@anchor{5c}
@subsection @code{distutils.fancy_getopt} --- Wrapper around the standard getopt module


@geindex distutils.fancy_getopt (模块)

This module provides a wrapper around the standard @ref{87,,getopt}  module that
provides the following additional features:


@itemize *

@item 
short and long options are tied together

@item 
options have help strings, so @ref{43b4,,fancy_getopt()} could potentially  create a
complete usage summary

@item 
options set attributes of a passed-in object

@item 
boolean options can have "negative aliases" --- eg. if @code{--quiet} is
the "negative alias" of @code{--verbose}, then @code{--quiet} on the
command line sets @emph{verbose} to false.
@end itemize

@geindex fancy_getopt() (在 distutils.fancy_getopt 模块中)
@anchor{distutils/apiref distutils fancy_getopt fancy_getopt}@anchor{43b4}
@deffn {函数} distutils.fancy_getopt.fancy_getopt (options, negative_opt, object, args)

Wrapper function. @emph{options} is a list of @code{(long_option, short_option,
help_string)} 3-tuples as described in the constructor for
@ref{43b5,,FancyGetopt}. @emph{negative_opt} should be a dictionary mapping option names
to option names, both the key and value should be in the @emph{options} list.
@emph{object} is an object which will be used to store values (see the @ref{87,,getopt()}
method of the @ref{43b5,,FancyGetopt} class). @emph{args} is the argument list. Will use
@code{sys.argv[1:]} if you  pass @code{None} as @emph{args}.
@end deffn

@geindex wrap_text() (在 distutils.fancy_getopt 模块中)
@anchor{distutils/apiref distutils fancy_getopt wrap_text}@anchor{43b6}
@deffn {函数} distutils.fancy_getopt.wrap_text (text, width)

Wraps @emph{text} to less than @emph{width} wide.
@end deffn

@geindex FancyGetopt (distutils.fancy_getopt 中的类)
@anchor{distutils/apiref distutils fancy_getopt FancyGetopt}@anchor{43b5}
@deffn {类} distutils.fancy_getopt.FancyGetopt ([option_table=None])

The option_table is a list of 3-tuples: @code{(long_option, short_option,
help_string)}

If an option takes an argument, its @emph{long_option} should have @code{'='} appended;
@emph{short_option} should just be a single character, no @code{':'} in any case.
@emph{short_option} should be @code{None} if a @emph{long_option}  doesn't have a
corresponding @emph{short_option}. All option tuples must have long options.
@end deffn

The @ref{43b5,,FancyGetopt} class provides the following methods:

@geindex getopt() (distutils.fancy_getopt.FancyGetopt 方法)
@anchor{distutils/apiref distutils fancy_getopt FancyGetopt getopt}@anchor{43b7}
@deffn {方法} FancyGetopt.getopt ([args=None, object=None])

Parse command-line options in args. Store as attributes on @emph{object}.

If @emph{args} is @code{None} or not supplied, uses @code{sys.argv[1:]}.  If @emph{object} is
@code{None} or not supplied, creates a new @code{OptionDummy} instance, stores
option values there, and returns a tuple @code{(args, object)}.  If @emph{object} is
supplied, it is modified in place and @ref{87,,getopt()} just returns @emph{args}; in
both cases, the returned @emph{args} is a modified copy of the passed-in @emph{args} list,
which is left untouched.

@c % and args returned are?
@end deffn

@geindex get_option_order() (distutils.fancy_getopt.FancyGetopt 方法)
@anchor{distutils/apiref distutils fancy_getopt FancyGetopt get_option_order}@anchor{43b8}
@deffn {方法} FancyGetopt.get_option_order ()

Returns the list of @code{(option, value)} tuples processed by the previous run of
@ref{87,,getopt()}  Raises @ref{2ba,,RuntimeError} if @ref{87,,getopt()} hasn't been called
yet.
@end deffn

@geindex generate_help() (distutils.fancy_getopt.FancyGetopt 方法)
@anchor{distutils/apiref distutils fancy_getopt FancyGetopt generate_help}@anchor{43b9}
@deffn {方法} FancyGetopt.generate_help ([header=None])

Generate help text (a list of strings, one per suggested line of output) from
the option table for this @ref{43b5,,FancyGetopt} object.

If supplied, prints the supplied @emph{header} at the top of the help.
@end deffn

@node distutils filelist --- The FileList class,distutils log --- Simple PEP 282-style logging,distutils fancy_getopt --- Wrapper around the standard getopt module,API参考引用
@anchor{distutils/apiref distutils-filelist-the-filelist-class}@anchor{43ba}@anchor{distutils/apiref module-distutils filelist}@anchor{5e}
@subsection @code{distutils.filelist} --- The FileList class


@geindex distutils.filelist (模块)

This module provides the @code{FileList} class, used for poking about the
filesystem and building lists of files.

@node distutils log --- Simple PEP 282-style logging,distutils spawn --- Spawn a sub-process,distutils filelist --- The FileList class,API参考引用
@anchor{distutils/apiref distutils-log-simple-pep-282-style-logging}@anchor{43bb}@anchor{distutils/apiref module-distutils log}@anchor{5f}
@subsection @code{distutils.log} --- Simple @strong{PEP 282}-style logging


@geindex Python 提高建议; PEP 282

@geindex distutils.log (模块)

@node distutils spawn --- Spawn a sub-process,distutils sysconfig --- System configuration information,distutils log --- Simple PEP 282-style logging,API参考引用
@anchor{distutils/apiref distutils-spawn-spawn-a-sub-process}@anchor{43bc}@anchor{distutils/apiref module-distutils spawn}@anchor{61}
@subsection @code{distutils.spawn} --- Spawn a sub-process


@geindex distutils.spawn (模块)

This module provides the @code{spawn()} function, a front-end to  various
platform-specific functions for launching another program in a  sub-process.
Also provides @code{find_executable()} to search the path for a given executable
name.

@node distutils sysconfig --- System configuration information,distutils text_file --- The TextFile class,distutils spawn --- Spawn a sub-process,API参考引用
@anchor{distutils/apiref distutils-sysconfig-system-configuration-information}@anchor{43bd}@anchor{distutils/apiref module-distutils sysconfig}@anchor{62}
@subsection @code{distutils.sysconfig} --- System configuration information


@geindex distutils.sysconfig (模块)

The @ref{62,,distutils.sysconfig} module provides access to Python's low-level
configuration information.  The specific configuration variables available
depend heavily on the platform and configuration. The specific variables depend
on the build process for the specific version of Python being run; the variables
are those found in the @code{Makefile} and configuration header that are
installed with Python on Unix systems.  The configuration header is called
@code{pyconfig.h} for Python versions starting with 2.2, and @code{config.h}
for earlier versions of Python.

Some additional functions are provided which perform some useful manipulations
for other parts of the @ref{39,,distutils} package.

@geindex PREFIX() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig PREFIX}@anchor{43be}
@deffn {数据} distutils.sysconfig.PREFIX

The result of @code{os.path.normpath(sys.prefix)}.
@end deffn

@geindex EXEC_PREFIX() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig EXEC_PREFIX}@anchor{43bf}
@deffn {数据} distutils.sysconfig.EXEC_PREFIX

The result of @code{os.path.normpath(sys.exec_prefix)}.
@end deffn

@geindex get_config_var() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig get_config_var}@anchor{43c0}
@deffn {函数} distutils.sysconfig.get_config_var (name)

Return the value of a single variable.  This is equivalent to
@code{get_config_vars().get(name)}.
@end deffn

@geindex get_config_vars() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig get_config_vars}@anchor{43c1}
@deffn {函数} distutils.sysconfig.get_config_vars (...)

Return a set of variable definitions.  If there are no arguments, this returns a
dictionary mapping names of configuration variables to values.  If arguments are
provided, they should be strings, and the return value will be a sequence giving
the associated values. If a given name does not have a corresponding value,
@code{None} will be included for that variable.
@end deffn

@geindex get_config_h_filename() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig get_config_h_filename}@anchor{43c2}
@deffn {函数} distutils.sysconfig.get_config_h_filename ()

Return the full path name of the configuration header.  For Unix, this will be
the header generated by the @code{configure} script; for other platforms the
header will have been supplied directly by the Python source distribution.  The
file is a platform-specific text file.
@end deffn

@geindex get_makefile_filename() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig get_makefile_filename}@anchor{43c3}
@deffn {函数} distutils.sysconfig.get_makefile_filename ()

Return the full path name of the @code{Makefile} used to build Python.  For
Unix, this will be a file generated by the @code{configure} script; the
meaning for other platforms will vary.  The file is a platform-specific text
file, if it exists. This function is only useful on POSIX platforms.
@end deffn

@geindex get_python_inc() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig get_python_inc}@anchor{43c4}
@deffn {函数} distutils.sysconfig.get_python_inc ([plat_specific[, prefix]])

Return the directory for either the general or platform-dependent C include
files.  If @emph{plat_specific} is true, the platform-dependent include directory is
returned; if false or omitted, the platform-independent directory is returned.
If @emph{prefix} is given, it is used as either the prefix instead of
@ref{43be,,PREFIX}, or as the exec-prefix instead of @ref{43bf,,EXEC_PREFIX} if
@emph{plat_specific} is true.
@end deffn

@geindex get_python_lib() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig get_python_lib}@anchor{43c5}
@deffn {函数} distutils.sysconfig.get_python_lib ([plat_specific[, standard_lib[, prefix]]])

Return the directory for either the general or platform-dependent library
installation.  If @emph{plat_specific} is true, the platform-dependent include
directory is returned; if false or omitted, the platform-independent directory
is returned.  If @emph{prefix} is given, it is used as either the prefix instead of
@ref{43be,,PREFIX}, or as the exec-prefix instead of @ref{43bf,,EXEC_PREFIX} if
@emph{plat_specific} is true.  If @emph{standard_lib} is true, the directory for the
standard library is returned rather than the directory for the installation of
third-party extensions.
@end deffn

The following function is only intended for use within the @ref{39,,distutils}
package.

@geindex customize_compiler() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig customize_compiler}@anchor{43c6}
@deffn {函数} distutils.sysconfig.customize_compiler (compiler)

Do any platform-specific customization of a
@ref{4364,,distutils.ccompiler.CCompiler} instance.

This function is only needed on Unix at this time, but should be called
consistently to support forward-compatibility.  It inserts the information that
varies across Unix flavors and is stored in Python's @code{Makefile}.  This
information includes the selected compiler, compiler and linker options, and the
extension used by the linker for shared objects.
@end deffn

This function is even more special-purpose, and should only be used from
Python's own build procedures.

@geindex set_python_build() (在 distutils.sysconfig 模块中)
@anchor{distutils/apiref distutils sysconfig set_python_build}@anchor{43c7}
@deffn {函数} distutils.sysconfig.set_python_build ()

Inform the @ref{62,,distutils.sysconfig} module that it is being used as part of
the build process for Python.  This changes a lot of relative locations for
files, allowing them to be located in the build area rather than in an installed
Python.
@end deffn

@node distutils text_file --- The TextFile class,distutils version --- Version number classes,distutils sysconfig --- System configuration information,API参考引用
@anchor{distutils/apiref distutils-text-file-the-textfile-class}@anchor{43c8}@anchor{distutils/apiref module-distutils text_file}@anchor{63}
@subsection @code{distutils.text_file} --- The TextFile class


@geindex distutils.text_file (模块)

This module provides the @ref{43c9,,TextFile} class, which gives an interface  to
text files that (optionally) takes care of stripping comments, ignoring  blank
lines, and joining lines with backslashes.

@geindex TextFile (distutils.text_file 中的类)
@anchor{distutils/apiref distutils text_file TextFile}@anchor{43c9}
@deffn {类} distutils.text_file.TextFile ([filename=None, file=None, **options])

This class provides a file-like object that takes care of all  the things you
commonly want to do when processing a text file  that has some line-by-line
syntax: strip comments (as long as @code{#}  is your comment character), skip blank
lines, join adjacent lines by escaping the newline (ie. backslash at end of
line), strip leading and/or trailing whitespace.  All of these are optional and
independently controllable.

The class provides a @ref{43ca,,warn()} method so you can generate  warning messages
that report physical line number, even if the  logical line in question spans
multiple physical lines.  Also  provides @ref{43cb,,unreadline()} for implementing
line-at-a-time lookahead.

@ref{43c9,,TextFile} instances are create with either @emph{filename}, @emph{file}, or both.
@ref{2ba,,RuntimeError} is raised if both are @code{None}. @emph{filename} should be a
string, and @emph{file} a file object (or something that provides @ref{de,,readline()}
and @ref{43cc,,close()}  methods).  It is recommended that you supply at least
@emph{filename},  so that @ref{43c9,,TextFile} can include it in warning messages.  If
@emph{file} is not supplied, @ref{43c9,,TextFile} creates its own using the
@ref{4ea,,open()} built-in function.

The options are all boolean, and affect the values returned by @ref{de,,readline()}


@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxx} 
@headitem

选项名称

@tab

描述

@tab

默认值

@item

@emph{strip_comments}

@tab

strip from @code{'#'} to
end-of-line, as well as any
whitespace leading up to the
@code{'#'}---unless it is
escaped by a backslash

@tab

true

@item

@emph{lstrip_ws}

@tab

strip leading whitespace from
each line before returning it

@tab

false

@item

@emph{rstrip_ws}

@tab

strip trailing whitespace
(including line terminator!)
from each line before
returning it.

@tab

true

@item

@emph{skip_blanks}

@tab

skip lines that are empty
*after* stripping comments
and whitespace.  (If both
lstrip_ws and rstrip_ws are
false, then some lines may
consist of solely whitespace:
these will *not* be skipped,
even if @emph{skip_blanks} is
true.)

@tab

true

@item

@emph{join_lines}

@tab

if a backslash is the last
non-newline character on a
line after stripping comments
and whitespace, join the
following line to it to form
one logical line; if N
consecutive lines end with a
backslash, then N+1 physical
lines will be joined to form
one logical line.

@tab

false

@item

@emph{collapse_join}

@tab

strip leading whitespace from
lines that are joined to their
predecessor; only matters if
@code{(join_lines and not
lstrip_ws)}

@tab

false

@end multitable


Note that since @emph{rstrip_ws} can strip the trailing newline, the semantics of
@ref{de,,readline()} must differ from those of the built-in file object's
@ref{de,,readline()} method!  In particular, @ref{de,,readline()}  returns @code{None} for
end-of-file: an empty string might just be a  blank line (or an all-whitespace
line), if @emph{rstrip_ws} is true  but @emph{skip_blanks} is not.

@geindex open() (distutils.text_file.TextFile 方法)
@anchor{distutils/apiref distutils text_file TextFile open}@anchor{43cd}
@deffn {方法} open (filename)

Open a new file @emph{filename}.  This overrides any @emph{file} or @emph{filename}
constructor arguments.
@end deffn

@geindex close() (distutils.text_file.TextFile 方法)
@anchor{distutils/apiref distutils text_file TextFile close}@anchor{43cc}
@deffn {方法} close ()

Close the current file and forget everything we know about it (including the
filename and the current line number).
@end deffn

@geindex warn() (distutils.text_file.TextFile 方法)
@anchor{distutils/apiref distutils text_file TextFile warn}@anchor{43ca}
@deffn {方法} warn (msg[, line=None])

Print (to stderr) a warning message tied to the current logical line in the
current file.  If the current logical line in the file spans multiple physical
lines, the warning refers to the whole range, such as @code{"lines 3-5"}.  If
@emph{line} is supplied,  it overrides the current line number; it may be a list or
tuple  to indicate a range of physical lines, or an integer for a  single
physical line.
@end deffn

@geindex readline() (distutils.text_file.TextFile 方法)
@anchor{distutils/apiref distutils text_file TextFile readline}@anchor{43ce}
@deffn {方法} readline ()

Read and return a single logical line from the current file (or from an internal
buffer if lines have previously been "unread" with @ref{43cb,,unreadline()}).  If the
@emph{join_lines} option  is true, this may involve reading multiple physical lines
concatenated into a single string.  Updates the current line number,  so calling
@ref{43ca,,warn()} after @ref{de,,readline()} emits a warning  about the physical line(s)
just read.  Returns @code{None} on end-of-file,  since the empty string can occur
if @emph{rstrip_ws} is true but  @emph{strip_blanks} is not.
@end deffn

@geindex readlines() (distutils.text_file.TextFile 方法)
@anchor{distutils/apiref distutils text_file TextFile readlines}@anchor{43cf}
@deffn {方法} readlines ()

Read and return the list of all logical lines remaining in the current file.
This updates the current line number to the last line of the file.
@end deffn

@geindex unreadline() (distutils.text_file.TextFile 方法)
@anchor{distutils/apiref distutils text_file TextFile unreadline}@anchor{43cb}
@deffn {方法} unreadline (line)

Push @emph{line} (a string) onto an internal buffer that will be checked by future
@ref{de,,readline()} calls.  Handy for implementing a parser with line-at-a-time
lookahead. Note that lines that are "unread" with @ref{43cb,,unreadline()} are not
subsequently re-cleansed (whitespace  stripped, or whatever) when read with
@ref{de,,readline()}. If multiple calls are made to @ref{43cb,,unreadline()} before a call
to @ref{de,,readline()}, the lines will be returned most in most recent first order.
@end deffn
@end deffn

@node distutils version --- Version number classes,distutils cmd --- Abstract base class for Distutils commands,distutils text_file --- The TextFile class,API参考引用
@anchor{distutils/apiref distutils-version-version-number-classes}@anchor{43d0}@anchor{distutils/apiref module-distutils version}@anchor{66}
@subsection @code{distutils.version} --- Version number classes


@geindex distutils.version (模块)

@c % todo

@c % \section{Distutils Commands}

@c %

@c % This part of Distutils implements the various Distutils commands, such

@c % as \code{build}, \code{install} \&c. Each command is implemented as a

@c % separate module, with the command name as the name of the module.

@node distutils cmd --- Abstract base class for Distutils commands,Creating a new Distutils command,distutils version --- Version number classes,API参考引用
@anchor{distutils/apiref distutils-cmd-abstract-base-class-for-distutils-commands}@anchor{43d1}@anchor{distutils/apiref module-distutils cmd}@anchor{3d}
@subsection @code{distutils.cmd} --- Abstract base class for Distutils commands


@geindex distutils.cmd (模块)

This module supplies the abstract base class @ref{434f,,Command}.

@geindex Command (distutils.cmd 中的类)
@anchor{distutils/apiref distutils cmd Command}@anchor{434f}
@deffn {类} distutils.cmd.Command (dist)

Abstract base class for defining command classes, the "worker bees" of the
Distutils.  A useful analogy for command classes is to think of them as
subroutines with local variables called @emph{options}.  The options are declared
in @ref{43d2,,initialize_options()} and defined (given their final values) in
@ref{43d3,,finalize_options()}, both of which must be defined by every command
class.  The distinction between the two is necessary because option values
might come from the outside world (command line, config file, ...), and any
options dependent on other options must be computed after these outside
influences have been processed --- hence @ref{43d3,,finalize_options()}.  The body
of the subroutine, where it does all its work based on the values of its
options, is the @ref{43d4,,run()} method, which must also be implemented by every
command class.

The class constructor takes a single argument @emph{dist}, a
@ref{4360,,Distribution} instance.
@end deffn

@node Creating a new Distutils command,distutils command --- Individual Distutils commands,distutils cmd --- Abstract base class for Distutils commands,API参考引用
@anchor{distutils/apiref creating-a-new-distutils-command}@anchor{43d5}
@subsection Creating a new Distutils command


This section outlines the steps to create a new Distutils command.

A new command lives in a module in the @ref{3e,,distutils.command} package. There
is a sample template in that directory called @code{command_template}.  Copy
this file to a new module with the same name as the new command you're
implementing.  This module should implement a class with the same name as the
module (and the command).  So, for instance, to create the command
@code{peel_banana} (so that users can run @code{setup.py peel_banana}), you'd copy
@code{command_template} to @code{distutils/command/peel_banana.py}, then edit
it so that it's implementing the class @code{peel_banana}, a subclass of
@ref{434f,,distutils.cmd.Command}.

Subclasses of @ref{434f,,Command} must define the following methods.

@geindex initialize_options() (distutils.cmd.Command 方法)
@anchor{distutils/apiref distutils cmd Command initialize_options}@anchor{43d2}
@deffn {方法} Command.initialize_options ()

Set default values for all the options that this command supports.  Note that
these defaults may be overridden by other commands, by the setup script, by
config files, or by the command-line.  Thus, this is not the place to code
dependencies between options; generally, @ref{43d2,,initialize_options()}
implementations are just a bunch of @code{self.foo = None} assignments.
@end deffn

@geindex finalize_options() (distutils.cmd.Command 方法)
@anchor{distutils/apiref distutils cmd Command finalize_options}@anchor{43d3}
@deffn {方法} Command.finalize_options ()

Set final values for all the options that this command supports. This is
always called as late as possible, ie.  after any option assignments from the
command-line or from other commands have been done.  Thus, this is the place
to code option dependencies: if @emph{foo} depends on @emph{bar}, then it is safe to
set @emph{foo} from @emph{bar} as long as @emph{foo} still has the same value it was
assigned in @ref{43d2,,initialize_options()}.
@end deffn

@geindex run() (distutils.cmd.Command 方法)
@anchor{distutils/apiref distutils cmd Command run}@anchor{43d4}
@deffn {方法} Command.run ()

A command's raison d'etre: carry out the action it exists to perform, controlled
by the options initialized in @ref{43d2,,initialize_options()}, customized by other
commands, the setup script, the command-line, and config files, and finalized in
@ref{43d3,,finalize_options()}.  All terminal output and filesystem interaction should
be done by @ref{43d4,,run()}.
@end deffn

@geindex sub_commands (distutils.cmd.Command 属性)
@anchor{distutils/apiref distutils cmd Command sub_commands}@anchor{43d6}
@deffn {属性} Command.sub_commands

@emph{sub_commands} formalizes the notion of a "family" of commands,
e.g. @code{install} as the parent with sub-commands @code{install_lib},
@code{install_headers}, etc.  The parent of a family of commands defines
@emph{sub_commands} as a class attribute; it's a list of 2-tuples @code{(command_name,
predicate)}, with @emph{command_name} a string and @emph{predicate} a function, a
string or @code{None}.  @emph{predicate} is a method of the parent command that
determines whether the corresponding command is applicable in the current
situation.  (E.g. @code{install_headers} is only applicable if we have any C
header files to install.)  If @emph{predicate} is @code{None}, that command is always
applicable.

@emph{sub_commands} is usually defined at the @emph{end} of a class, because
predicates can be methods of the class, so they must already have been
defined.  The canonical example is the @code{install} command.
@end deffn

@node distutils command --- Individual Distutils commands,distutils command bdist --- Build a binary installer,Creating a new Distutils command,API参考引用
@anchor{distutils/apiref distutils-command-individual-distutils-commands}@anchor{43d7}@anchor{distutils/apiref module-distutils command}@anchor{3e}
@subsection @code{distutils.command} --- Individual Distutils commands


@geindex distutils.command (模块)

@c % \subsubsection{Individual Distutils commands}

@c % todo

@node distutils command bdist --- Build a binary installer,distutils command bdist_packager --- Abstract base class for packagers,distutils command --- Individual Distutils commands,API参考引用
@anchor{distutils/apiref distutils-command-bdist-build-a-binary-installer}@anchor{43d8}@anchor{distutils/apiref module-distutils command bdist}@anchor{3f}
@subsection @code{distutils.command.bdist} --- Build a binary installer


@geindex distutils.command.bdist (模块)

@c % todo

@node distutils command bdist_packager --- Abstract base class for packagers,distutils command bdist_dumb --- Build a "dumb" installer,distutils command bdist --- Build a binary installer,API参考引用
@anchor{distutils/apiref distutils-command-bdist-packager-abstract-base-class-for-packagers}@anchor{43d9}@anchor{distutils/apiref module-distutils command bdist_packager}@anchor{42}
@subsection @code{distutils.command.bdist_packager} --- Abstract base class for packagers


@geindex distutils.command.bdist_packager (模块)

@c % todo

@node distutils command bdist_dumb --- Build a "dumb" installer,distutils command bdist_msi --- Build a Microsoft Installer binary package,distutils command bdist_packager --- Abstract base class for packagers,API参考引用
@anchor{distutils/apiref distutils-command-bdist-dumb-build-a-dumb-installer}@anchor{43da}@anchor{distutils/apiref module-distutils command bdist_dumb}@anchor{40}
@subsection @code{distutils.command.bdist_dumb} --- Build a "dumb" installer


@geindex distutils.command.bdist_dumb (模块)

@c % todo

@node distutils command bdist_msi --- Build a Microsoft Installer binary package,distutils command bdist_rpm --- Build a binary distribution as a Redhat RPM and SRPM,distutils command bdist_dumb --- Build a "dumb" installer,API参考引用
@anchor{distutils/apiref distutils-command-bdist-msi-build-a-microsoft-installer-binary-package}@anchor{43db}@anchor{distutils/apiref module-distutils command bdist_msi}@anchor{41}
@subsection @code{distutils.command.bdist_msi} --- Build a Microsoft Installer binary package


@geindex distutils.command.bdist_msi (模块)

@geindex bdist_msi (distutils.command.bdist_msi 中的类)
@anchor{distutils/apiref distutils command bdist_msi bdist_msi}@anchor{43dc}
@deffn {类} distutils.command.bdist_msi.bdist_msi

Builds a Windows Installer@footnote{https://msdn.microsoft.com/en-us/library/cc185688(VS.85).aspx} (.msi) binary package.

In most cases, the @code{bdist_msi} installer is a better choice than the
@code{bdist_wininst} installer, because it provides better support for
Win64 platforms, allows administrators to perform non-interactive
installations, and allows installation through group policies.
@end deffn

@node distutils command bdist_rpm --- Build a binary distribution as a Redhat RPM and SRPM,distutils command bdist_wininst --- Build a Windows installer,distutils command bdist_msi --- Build a Microsoft Installer binary package,API参考引用
@anchor{distutils/apiref distutils-command-bdist-rpm-build-a-binary-distribution-as-a-redhat-rpm-and-srpm}@anchor{43dd}@anchor{distutils/apiref module-distutils command bdist_rpm}@anchor{43}
@subsection @code{distutils.command.bdist_rpm} --- Build a binary distribution as a Redhat RPM and SRPM


@geindex distutils.command.bdist_rpm (模块)

@c % todo

@node distutils command bdist_wininst --- Build a Windows installer,distutils command sdist --- Build a source distribution,distutils command bdist_rpm --- Build a binary distribution as a Redhat RPM and SRPM,API参考引用
@anchor{distutils/apiref distutils-command-bdist-wininst-build-a-windows-installer}@anchor{43de}@anchor{distutils/apiref module-distutils command bdist_wininst}@anchor{44}
@subsection @code{distutils.command.bdist_wininst} --- Build a Windows installer


@geindex distutils.command.bdist_wininst (模块)


3.8 版后已移除: Use bdist_wheel (wheel packages) instead.


@c % todo

@node distutils command sdist --- Build a source distribution,distutils command build --- Build all files of a package,distutils command bdist_wininst --- Build a Windows installer,API参考引用
@anchor{distutils/apiref distutils-command-sdist-build-a-source-distribution}@anchor{43df}@anchor{distutils/apiref module-distutils command sdist}@anchor{53}
@subsection @code{distutils.command.sdist} --- Build a source distribution


@geindex distutils.command.sdist (模块)

@c % todo

@node distutils command build --- Build all files of a package,distutils command build_clib --- Build any C libraries in a package,distutils command sdist --- Build a source distribution,API参考引用
@anchor{distutils/apiref distutils-command-build-build-all-files-of-a-package}@anchor{43e0}@anchor{distutils/apiref module-distutils command build}@anchor{45}
@subsection @code{distutils.command.build} --- Build all files of a package


@geindex distutils.command.build (模块)

@c % todo

@node distutils command build_clib --- Build any C libraries in a package,distutils command build_ext --- Build any extensions in a package,distutils command build --- Build all files of a package,API参考引用
@anchor{distutils/apiref distutils-command-build-clib-build-any-c-libraries-in-a-package}@anchor{43e1}@anchor{distutils/apiref module-distutils command build_clib}@anchor{46}
@subsection @code{distutils.command.build_clib} --- Build any C libraries in a package


@geindex distutils.command.build_clib (模块)

@c % todo

@node distutils command build_ext --- Build any extensions in a package,distutils command build_py --- Build the py/ pyc files of a package,distutils command build_clib --- Build any C libraries in a package,API参考引用
@anchor{distutils/apiref distutils-command-build-ext-build-any-extensions-in-a-package}@anchor{43e2}@anchor{distutils/apiref module-distutils command build_ext}@anchor{47}
@subsection @code{distutils.command.build_ext} --- Build any extensions in a package


@geindex distutils.command.build_ext (模块)

@c % todo

@node distutils command build_py --- Build the py/ pyc files of a package,distutils command build_scripts --- Build the scripts of a package,distutils command build_ext --- Build any extensions in a package,API参考引用
@anchor{distutils/apiref distutils-command-build-py-build-the-py-pyc-files-of-a-package}@anchor{43e3}@anchor{distutils/apiref module-distutils command build_py}@anchor{48}
@subsection @code{distutils.command.build_py} --- Build the .py/.pyc files of a package


@geindex distutils.command.build_py (模块)

@geindex build_py (distutils.command.build_py 中的类)
@anchor{distutils/apiref distutils command build_py build_py}@anchor{43e4}
@deffn {类} distutils.command.build_py.build_py
@end deffn

@geindex build_py_2to3 (distutils.command.build_py 中的类)
@anchor{distutils/apiref distutils command build_py build_py_2to3}@anchor{43e5}
@deffn {类} distutils.command.build_py.build_py_2to3

Alternative implementation of build_py which also runs the
2to3 conversion library on each .py file that is going to be
installed. To use this in a setup.py file for a distribution
that is designed to run with both Python 2.x and 3.x, add:

@example
try:
    from distutils.command.build_py import build_py_2to3 as build_py
except ImportError:
    from distutils.command.build_py import build_py
@end example

to your setup.py, and later:

@example
cmdclass = @{'build_py': build_py@}
@end example

to the invocation of setup().
@end deffn

@node distutils command build_scripts --- Build the scripts of a package,distutils command clean --- Clean a package build area,distutils command build_py --- Build the py/ pyc files of a package,API参考引用
@anchor{distutils/apiref distutils-command-build-scripts-build-the-scripts-of-a-package}@anchor{43e6}@anchor{distutils/apiref module-distutils command build_scripts}@anchor{49}
@subsection @code{distutils.command.build_scripts} --- Build the scripts of a package


@geindex distutils.command.build_scripts (模块)

@c % todo

@node distutils command clean --- Clean a package build area,distutils command config --- Perform package configuration,distutils command build_scripts --- Build the scripts of a package,API参考引用
@anchor{distutils/apiref distutils-command-clean-clean-a-package-build-area}@anchor{43e7}@anchor{distutils/apiref module-distutils command clean}@anchor{4b}
@subsection @code{distutils.command.clean} --- Clean a package build area


@geindex distutils.command.clean (模块)

This command removes the temporary files created by @code{build}
and its subcommands, like intermediary compiled object files.  With
the @code{--all} option, the complete build directory will be removed.

Extension modules built @ref{4328,,in place}
will not be cleaned, as they are not in the build directory.

@node distutils command config --- Perform package configuration,distutils command install --- Install a package,distutils command clean --- Clean a package build area,API参考引用
@anchor{distutils/apiref distutils-command-config-perform-package-configuration}@anchor{43e8}@anchor{distutils/apiref module-distutils command config}@anchor{4c}
@subsection @code{distutils.command.config} --- Perform package configuration


@geindex distutils.command.config (模块)

@c % todo

@node distutils command install --- Install a package,distutils command install_data --- Install data files from a package,distutils command config --- Perform package configuration,API参考引用
@anchor{distutils/apiref distutils-command-install-install-a-package}@anchor{43e9}@anchor{distutils/apiref module-distutils command install}@anchor{4d}
@subsection @code{distutils.command.install} --- Install a package


@geindex distutils.command.install (模块)

@c % todo

@node distutils command install_data --- Install data files from a package,distutils command install_headers --- Install C/C++ header files from a package,distutils command install --- Install a package,API参考引用
@anchor{distutils/apiref distutils-command-install-data-install-data-files-from-a-package}@anchor{43ea}@anchor{distutils/apiref module-distutils command install_data}@anchor{4e}
@subsection @code{distutils.command.install_data} --- Install data files from a package


@geindex distutils.command.install_data (模块)

@c % todo

@node distutils command install_headers --- Install C/C++ header files from a package,distutils command install_lib --- Install library files from a package,distutils command install_data --- Install data files from a package,API参考引用
@anchor{distutils/apiref distutils-command-install-headers-install-c-c-header-files-from-a-package}@anchor{43eb}@anchor{distutils/apiref module-distutils command install_headers}@anchor{4f}
@subsection @code{distutils.command.install_headers} --- Install C/C++ header files from a package


@geindex distutils.command.install_headers (模块)

@c % todo

@node distutils command install_lib --- Install library files from a package,distutils command install_scripts --- Install script files from a package,distutils command install_headers --- Install C/C++ header files from a package,API参考引用
@anchor{distutils/apiref distutils-command-install-lib-install-library-files-from-a-package}@anchor{43ec}@anchor{distutils/apiref module-distutils command install_lib}@anchor{50}
@subsection @code{distutils.command.install_lib} --- Install library files from a package


@geindex distutils.command.install_lib (模块)

@c % todo

@node distutils command install_scripts --- Install script files from a package,distutils command register --- Register a module with the Python Package Index,distutils command install_lib --- Install library files from a package,API参考引用
@anchor{distutils/apiref distutils-command-install-scripts-install-script-files-from-a-package}@anchor{43ed}@anchor{distutils/apiref module-distutils command install_scripts}@anchor{51}
@subsection @code{distutils.command.install_scripts} --- Install script files from a package


@geindex distutils.command.install_scripts (模块)

@c % todo

@node distutils command register --- Register a module with the Python Package Index,distutils command check --- Check the meta-data of a package,distutils command install_scripts --- Install script files from a package,API参考引用
@anchor{distutils/apiref distutils-command-register-register-a-module-with-the-python-package-index}@anchor{43ee}@anchor{distutils/apiref module-distutils command register}@anchor{52}
@subsection @code{distutils.command.register} --- Register a module with the Python Package Index


@geindex distutils.command.register (模块)

The @code{register} command registers the package with the Python Package  Index.
This is described in more detail in 
@geindex Python 提高建议; PEP 301
PEP 301@footnote{https://www.python.org/dev/peps/pep-0301}.

@c % todo

@node distutils command check --- Check the meta-data of a package,,distutils command register --- Register a module with the Python Package Index,API参考引用
@anchor{distutils/apiref distutils-command-check-check-the-meta-data-of-a-package}@anchor{43ef}@anchor{distutils/apiref module-distutils command check}@anchor{4a}
@subsection @code{distutils.command.check} --- Check the meta-data of a package


@geindex distutils.command.check (模块)

The @code{check} command performs some tests on the meta-data of a package.
For example, it verifies that all required meta-data are provided as
the arguments passed to the @code{setup()} function.

@c % todo

@node 安装Python模块（旧版）,Python 模块索引,分发 Python 模块（遗留版本）,Top
@anchor{install/index doc}@anchor{43f0}@anchor{install/index install-index}@anchor{7f1}@anchor{install/index installing-python-modules-legacy-version}@anchor{43f1}
@chapter 安装Python模块（旧版）


@*作者: 
Greg Ward


@c TODO: Fill in XXX comments


@subsubheading 参见



@table @asis

@item @ref{7ef,,安装 Python 模块}

最新的模块安装文档。对于常规Python使用，你几乎肯定像使用该文档而非这个。
@end table


@cartouche
@quotation 注解 
这篇文档只有在 @indicateurl{https://setuptools.readthedocs.io/en/latest/setuptools.html} 上的 @code{setuptools} 文档独立涵盖此处包含的所有相关信息之前，才会单独保留。
@end quotation
@end cartouche

@cartouche
@quotation 注解 
本指南仅介绍构建和分发扩展的基本工具，这些扩展是作为此Python版本的一部分提供的。 第三方工具提供更易于使用和更安全的替代方案。有关详细信息，请参阅 Python 打包用户指南中的 快速推荐部分@footnote{https://packaging.python.org/guides/tool-recommendations/} 。
@end quotation
@end cartouche

@menu
* 概述: 概述<20>. 
* Standard Build and Install:: 
* Alternate Installation:: 
* 自定义安装:: 
* Distutils Configuration Files:: 
* Building Extensions; Tips and Tricks: Building Extensions Tips and Tricks. 

@end menu

@node 概述<20>,Standard Build and Install,,安装Python模块（旧版）
@anchor{install/index inst-intro}@anchor{43f2}@anchor{install/index introduction}@anchor{43f3}
@section 概述


在Python 2.0中，@code{distutils} API 首次被添加到标准库中。这向Linux发行版维护者提供了一个将Python项目转换为发行版软件包的标准方法，以及向系统管理员们提供了直接将这些软件包安装到目标系统的标准方法。

In the many years since Python 2.0 was released, tightly coupling the build
system and package installer to the language runtime release cycle has turned
out to be problematic, and it is now recommended that projects use the
@code{pip} package installer and the @code{setuptools} build system, rather than
using @code{distutils} directly.

See @ref{7ef,,安装 Python 模块} and @ref{7f0,,分发 Python 模块} for more details.

This legacy documentation is being retained only until we're confident that the
@code{setuptools} documentation covers everything needed.

@menu
* Distutils based source distributions:: 

@end menu

@node Distutils based source distributions,,,概述<20>
@anchor{install/index distutils-based-source-distributions}@anchor{43f4}@anchor{install/index inst-new-standard}@anchor{43f5}
@subsection Distutils based source distributions


If you download a module source distribution, you can tell pretty quickly if it
was packaged and distributed in the standard way, i.e. using the Distutils.
First, the distribution's name and version number will be featured prominently
in the name of the downloaded archive, e.g. @code{foo-1.0.tar.gz} or
@code{widget-0.9.7.zip}.  Next, the archive will unpack into a similarly-named
directory: @code{foo-1.0} or @code{widget-0.9.7}.  Additionally, the
distribution will contain a setup script @code{setup.py}, and a file named
@code{README.txt} or possibly just @code{README}, which should explain that
building and installing the module distribution is a simple matter of running
one command from a terminal:

@example
python setup.py install
@end example

For Windows, this command should be run from a command prompt window
(Start ‣ Accessories):

@example
setup.py install
@end example

If all these things are true, then you already know how to build and install the
modules you've just downloaded:  Run the command above. Unless you need to
install things in a non-standard way or customize the build process, you don't
really need this manual.  Or rather, the above command is everything you need to
get out of this manual.

@node Standard Build and Install,Alternate Installation,概述<20>,安装Python模块（旧版）
@anchor{install/index inst-standard-install}@anchor{43f6}@anchor{install/index standard-build-and-install}@anchor{43f7}
@section Standard Build and Install


As described in section @ref{43f5,,Distutils based source distributions}, building and installing a module
distribution using the Distutils is usually one simple command to run from a
terminal:

@example
python setup.py install
@end example

@menu
* Platform variations:: 
* Splitting the job up:: 
* How building works:: 
* How installation works:: 

@end menu

@node Platform variations,Splitting the job up,,Standard Build and Install
@anchor{install/index inst-platform-variations}@anchor{43f8}@anchor{install/index platform-variations}@anchor{43f9}
@subsection Platform variations


You should always run the setup command from the distribution root directory,
i.e. the top-level subdirectory that the module source distribution unpacks
into.  For example, if you've just downloaded a module source distribution
@code{foo-1.0.tar.gz} onto a Unix system, the normal thing to do is:

@example
gunzip -c foo-1.0.tar.gz | tar xf -    # unpacks into directory foo-1.0
cd foo-1.0
python setup.py install
@end example

On Windows, you'd probably download @code{foo-1.0.zip}.  If you downloaded the
archive file to @code{C:\Temp}, then it would unpack into
@code{C:\Temp\foo-1.0}; you can use either an archive manipulator with a
graphical user interface (such as WinZip) or a command-line tool (such as
@code{unzip} or @code{pkunzip}) to unpack the archive.  Then, open a
command prompt window and run:

@example
cd c:\Temp\foo-1.0
python setup.py install
@end example

@node Splitting the job up,How building works,Platform variations,Standard Build and Install
@anchor{install/index inst-splitting-up}@anchor{43fa}@anchor{install/index splitting-the-job-up}@anchor{43fb}
@subsection Splitting the job up


Running @code{setup.py install} builds and installs all modules in one run.  If you
prefer to work incrementally---especially useful if you want to customize the
build process, or if things are going wrong---you can use the setup script to do
one thing at a time.  This is particularly helpful when the build and install
will be done by different users---for example, you might want to build a module
distribution and hand it off to a system administrator for installation (or do
it yourself, with super-user privileges).

For example, you can build everything in one step, and then install everything
in a second step, by invoking the setup script twice:

@example
python setup.py build
python setup.py install
@end example

If you do this, you will notice that running the @code{install} command
first runs the @code{build} command, which---in this case---quickly notices
that it has nothing to do, since everything in the @code{build} directory is
up-to-date.

You may not need this ability to break things down often if all you do is
install modules downloaded off the 'net, but it's very handy for more advanced
tasks.  If you get into distributing your own Python modules and extensions,
you'll run lots of individual Distutils commands on their own.

@node How building works,How installation works,Splitting the job up,Standard Build and Install
@anchor{install/index how-building-works}@anchor{43fc}@anchor{install/index inst-how-build-works}@anchor{43fd}
@subsection How building works


As implied above, the @code{build} command is responsible for putting the
files to install into a @emph{build directory}.  By default, this is @code{build}
under the distribution root; if you're excessively concerned with speed, or want
to keep the source tree pristine, you can change the build directory with the
@code{--build-base} option. For example:

@example
python setup.py build --build-base=/path/to/pybuild/foo-1.0
@end example

(Or you could do this permanently with a directive in your system or personal
Distutils configuration file; see section @ref{43fe,,Distutils Configuration Files}.)  Normally, this
isn't necessary.

The default layout for the build tree is as follows:

@example
--- build/ --- lib/
or
--- build/ --- lib.<plat>/
               temp.<plat>/
@end example

where @code{<plat>} expands to a brief description of the current OS/hardware
platform and Python version.  The first form, with just a @code{lib} directory,
is used for "pure module distributions"---that is, module distributions that
include only pure Python modules.  If a module distribution contains any
extensions (modules written in C/C++), then the second form, with two @code{<plat>}
directories, is used.  In that case, the @code{temp.@emph{plat}} directory holds
temporary files generated by the compile/link process that don't actually get
installed.  In either case, the @code{lib} (or @code{lib.@emph{plat}}) directory
contains all Python modules (pure Python and extensions) that will be installed.

In the future, more directories will be added to handle Python scripts,
documentation, binary executables, and whatever else is needed to handle the job
of installing Python modules and applications.

@node How installation works,,How building works,Standard Build and Install
@anchor{install/index how-installation-works}@anchor{43ff}@anchor{install/index inst-how-install-works}@anchor{4400}
@subsection How installation works


After the @code{build} command runs (whether you run it explicitly, or the
@code{install} command does it for you), the work of the @code{install}
command is relatively simple: all it has to do is copy everything under
@code{build/lib} (or @code{build/lib.@emph{plat}}) to your chosen installation
directory.

If you don't choose an installation directory---i.e., if you just run @code{setup.py
install}---then the @code{install} command installs to the standard
location for third-party Python modules.  This location varies by platform and
by how you built/installed Python itself.  On Unix (and Mac OS X, which is also
Unix-based), it also depends on whether the module distribution being installed
is pure Python or contains extensions ("non-pure"):


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

平台

@tab

标准安装位置

@tab

默认值

@tab

注释

@item

（单一）Unix

@tab

@code{@emph{prefix}/lib/python@emph{X.Y}/site-packages}

@tab

@code{/usr/local/lib/python@emph{X.Y}/site-packages}

@tab

(1)

@item

（类）Unix

@tab

@code{@emph{exec-prefix}/lib/python@emph{X.Y}/site-packages}

@tab

@code{/usr/local/lib/python@emph{X.Y}/site-packages}

@tab

(1)

@item

Windows

@tab

@code{@emph{prefix}\Lib\site-packages}

@tab

@code{C:\Python@emph{XY}\Lib\site-packages}

@tab

(2)

@end multitable


注释:


@enumerate 

@item 
Most Linux distributions include Python as a standard part of the system, so
@code{@emph{prefix}} and @code{@emph{exec-prefix}} are usually both @code{/usr} on
Linux.  If you build Python yourself on Linux (or any Unix-like system), the
default @code{@emph{prefix}} and @code{@emph{exec-prefix}} are @code{/usr/local}.

@item 
The default installation directory on Windows was @code{C:\Program
Files\Python} under Python 1.6a1, 1.5.2, and earlier.
@end enumerate

@code{@emph{prefix}} and @code{@emph{exec-prefix}} stand for the directories that Python
is installed to, and where it finds its libraries at run-time.  They are always
the same under Windows, and very often the same under Unix and Mac OS X.  You
can find out what your Python installation uses for @code{@emph{prefix}} and
@code{@emph{exec-prefix}} by running Python in interactive mode and typing a few
simple commands. Under Unix, just type @code{python} at the shell prompt.  Under
Windows, choose Start ‣ Programs ‣ Python X.Y ‣
Python (command line).   Once the interpreter is started, you type Python code
at the prompt.  For example, on my Linux system, I type the three Python
statements shown below, and get the output as shown, to find out my
@code{@emph{prefix}} and @code{@emph{exec-prefix}}:

@example
Python 2.4 (#26, Aug  7 2004, 17:19:02)
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.prefix
'/usr'
>>> sys.exec_prefix
'/usr'
@end example

A few other placeholders are used in this document: @code{@emph{X.Y}} stands for the
version of Python, for example @code{3.2}; @code{@emph{abiflags}} will be replaced by
the value of @ref{264,,sys.abiflags} or the empty string for platforms which don't
define ABI flags; @code{@emph{distname}} will be replaced by the name of the module
distribution being installed.  Dots and capitalization are important in the
paths; for example, a value that uses @code{python3.2} on UNIX will typically use
@code{Python32} on Windows.

If you don't want to install modules to the standard location, or if you don't
have permission to write there, then you need to read about alternate
installations in section @ref{4401,,Alternate Installation}.  If you want to customize your
installation directories more heavily, see section @ref{4402,,自定义安装} on
custom installations.

@node Alternate Installation,自定义安装,Standard Build and Install,安装Python模块（旧版）
@anchor{install/index alternate-installation}@anchor{4403}@anchor{install/index inst-alt-install}@anchor{4401}
@section Alternate Installation


Often, it is necessary or desirable to install modules to a location other than
the standard location for third-party Python modules.  For example, on a Unix
system you might not have permission to write to the standard third-party module
directory.  Or you might wish to try out a module before making it a standard
part of your local Python installation.  This is especially true when upgrading
a distribution already present: you want to make sure your existing base of
scripts still works with the new version before actually upgrading.

The Distutils @code{install} command is designed to make installing module
distributions to an alternate location simple and painless.  The basic idea is
that you supply a base directory for the installation, and the
@code{install} command picks a set of directories (called an @emph{installation
scheme}) under this base directory in which to install files.  The details
differ across platforms, so read whichever of the following sections applies to
you.

Note that the various alternate installation schemes are mutually exclusive: you
can pass @code{--user}, or @code{--home}, or @code{--prefix} and @code{--exec-prefix}, or
@code{--install-base} and @code{--install-platbase}, but you can't mix from these
groups.

@menu
* Alternate installation; the user scheme: Alternate installation the user scheme. 
* Alternate installation; the home scheme: Alternate installation the home scheme. 
* Alternate installation; Unix (the prefix scheme): Alternate installation Unix the prefix scheme. 
* Alternate installation; Windows (the prefix scheme): Alternate installation Windows the prefix scheme. 

@end menu

@node Alternate installation the user scheme,Alternate installation the home scheme,,Alternate Installation
@anchor{install/index alternate-installation-the-user-scheme}@anchor{4404}@anchor{install/index inst-alt-install-user}@anchor{12ef}
@subsection Alternate installation: the user scheme


This scheme is designed to be the most convenient solution for users that don't
have write permission to the global site-packages directory or don't want to
install into it.  It is enabled with a simple option:

@example
python setup.py install --user
@end example

Files will be installed into subdirectories of @ref{12ee,,site.USER_BASE} (written
as @code{@emph{userbase}} hereafter).  This scheme installs pure Python modules and
extension modules in the same location (also known as @ref{12dc,,site.USER_SITE}).
Here are the values for UNIX, including Mac OS X:


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

文件类型

@tab

安装目录

@item

模块

@tab

@code{@emph{userbase}/lib/python@emph{X.Y}/site-packages}

@item

脚本

@tab

@code{@emph{userbase}/bin}

@item

数据

@tab

@code{@emph{userbase}}

@item

C 头文件

@tab

@code{@emph{userbase}/include/python@emph{X.Y}@emph{abiflags}/@emph{distname}}

@end multitable


以下是Windows上使用的值：


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

文件类型

@tab

安装目录

@item

模块

@tab

@code{@emph{userbase}\Python@emph{XY}\site-packages}

@item

脚本

@tab

@code{@emph{userbase}\Python@emph{XY}\Scripts}

@item

数据

@tab

@code{@emph{userbase}}

@item

C 头文件

@tab

@code{@emph{userbase}\Python@emph{XY}\Include@{distname@}}

@end multitable


The advantage of using this scheme compared to the other ones described below is
that the user site-packages directory is under normal conditions always included
in @ref{482,,sys.path} (see @ref{eb,,site} for more information), which means that
there is no additional step to perform after running the @code{setup.py} script
to finalize the installation.

The @code{build_ext} command also has a @code{--user} option to add
@code{@emph{userbase}/include} to the compiler search path for header files and
@code{@emph{userbase}/lib} to the compiler search path for libraries as well as to
the runtime search path for shared C libraries (rpath).

@node Alternate installation the home scheme,Alternate installation Unix the prefix scheme,Alternate installation the user scheme,Alternate Installation
@anchor{install/index alternate-installation-the-home-scheme}@anchor{4405}@anchor{install/index inst-alt-install-home}@anchor{4406}
@subsection Alternate installation: the home scheme


The idea behind the "home scheme" is that you build and maintain a personal
stash of Python modules.  This scheme's name is derived from the idea of a
"home" directory on Unix, since it's not unusual for a Unix user to make their
home directory have a layout similar to @code{/usr/} or @code{/usr/local/}.
This scheme can be used by anyone, regardless of the operating system they
are installing for.

Installing a new module distribution is as simple as

@example
python setup.py install --home=<dir>
@end example

where you can supply any directory you like for the @code{--home} option.  On
Unix, lazy typists can just type a tilde (@code{~}); the @code{install} command
will expand this to your home directory:

@example
python setup.py install --home=~
@end example

To make Python find the distributions installed with this scheme, you may have
to @ref{4407,,modify Python's search path} or edit
@code{sitecustomize} (see @ref{eb,,site}) to call @ref{36b6,,site.addsitedir()} or edit
@ref{482,,sys.path}.

The @code{--home} option defines the installation base directory.  Files are
installed to the following directories under the installation base as follows:


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

文件类型

@tab

安装目录

@item

模块

@tab

@code{@emph{home}/lib/python}

@item

脚本

@tab

@code{@emph{home}/bin}

@item

数据

@tab

@code{@emph{home}}

@item

C 头文件

@tab

@code{@emph{home}/include/python/@emph{distname}}

@end multitable


(Mentally replace slashes with backslashes if you're on Windows.)

@node Alternate installation Unix the prefix scheme,Alternate installation Windows the prefix scheme,Alternate installation the home scheme,Alternate Installation
@anchor{install/index alternate-installation-unix-the-prefix-scheme}@anchor{4408}@anchor{install/index inst-alt-install-prefix-unix}@anchor{4409}
@subsection Alternate installation: Unix (the prefix scheme)


The "prefix scheme" is useful when you wish to use one Python installation to
perform the build/install (i.e., to run the setup script), but install modules
into the third-party module directory of a different Python installation (or
something that looks like a different Python installation).  If this sounds a
trifle unusual, it is---that's why the user and home schemes come before.  However,
there are at least two known cases where the prefix scheme will be useful.

First, consider that many Linux distributions put Python in @code{/usr}, rather
than the more traditional @code{/usr/local}.  This is entirely appropriate,
since in those cases Python is part of "the system" rather than a local add-on.
However, if you are installing Python modules from source, you probably want
them to go in @code{/usr/local/lib/python2.@emph{X}} rather than
@code{/usr/lib/python2.@emph{X}}.  This can be done with

@example
/usr/bin/python setup.py install --prefix=/usr/local
@end example

Another possibility is a network filesystem where the name used to write to a
remote directory is different from the name used to read it: for example, the
Python interpreter accessed as @code{/usr/local/bin/python} might search for
modules in @code{/usr/local/lib/python2.@emph{X}}, but those modules would have to
be installed to, say, @code{/mnt/@emph{@@server}/export/lib/python2.@emph{X}}.  This could
be done with

@example
/usr/local/bin/python setup.py install --prefix=/mnt/@@server/export
@end example

In either case, the @code{--prefix} option defines the installation base, and
the @code{--exec-prefix} option defines the platform-specific installation
base, which is used for platform-specific files.  (Currently, this just means
non-pure module distributions, but could be expanded to C libraries, binary
executables, etc.)  If @code{--exec-prefix} is not supplied, it defaults to
@code{--prefix}.  Files are installed as follows:


@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

文件类型

@tab

安装目录

@item

Python 模块

@tab

@code{@emph{prefix}/lib/python@emph{X.Y}/site-packages}

@item

扩展模块

@tab

@code{@emph{exec-prefix}/lib/python@emph{X.Y}/site-packages}

@item

脚本

@tab

@code{@emph{prefix}/bin}

@item

数据

@tab

@code{@emph{prefix}}

@item

C 头文件

@tab

@code{@emph{prefix}/include/python@emph{X.Y}@emph{abiflags}/@emph{distname}}

@end multitable


There is no requirement that @code{--prefix} or @code{--exec-prefix}
actually point to an alternate Python installation; if the directories listed
above do not already exist, they are created at installation time.

Incidentally, the real reason the prefix scheme is important is simply that a
standard Unix installation uses the prefix scheme, but with @code{--prefix}
and @code{--exec-prefix} supplied by Python itself as @code{sys.prefix} and
@code{sys.exec_prefix}.  Thus, you might think you'll never use the prefix scheme,
but every time you run @code{python setup.py install} without any other options,
you're using it.

Note that installing extensions to an alternate Python installation has no
effect on how those extensions are built: in particular, the Python header files
(@code{Python.h} and friends) installed with the Python interpreter used to run
the setup script will be used in compiling extensions.  It is your
responsibility to ensure that the interpreter used to run extensions installed
in this way is compatible with the interpreter used to build them.  The best way
to do this is to ensure that the two interpreters are the same version of Python
(possibly different builds, or possibly copies of the same build).  (Of course,
if your @code{--prefix} and @code{--exec-prefix} don't even point to an
alternate Python installation, this is immaterial.)

@node Alternate installation Windows the prefix scheme,,Alternate installation Unix the prefix scheme,Alternate Installation
@anchor{install/index alternate-installation-windows-the-prefix-scheme}@anchor{440a}@anchor{install/index inst-alt-install-prefix-windows}@anchor{440b}
@subsection Alternate installation: Windows (the prefix scheme)


Windows has no concept of a user's home directory, and since the standard Python
installation under Windows is simpler than under Unix, the @code{--prefix}
option has traditionally been used to install additional packages in separate
locations on Windows.

@example
python setup.py install --prefix="\Temp\Python"
@end example

to install modules to the @code{\Temp\Python} directory on the current drive.

The installation base is defined by the @code{--prefix} option; the
@code{--exec-prefix} option is not supported under Windows, which means that
pure Python modules and extension modules are installed into the same location.
Files are installed as follows:


@multitable {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

文件类型

@tab

安装目录

@item

模块

@tab

@code{@emph{prefix}\Lib\site-packages}

@item

脚本

@tab

@code{@emph{prefix}\Scripts}

@item

数据

@tab

@code{@emph{prefix}}

@item

C 头文件

@tab

@code{@emph{prefix}\Include@{distname@}}

@end multitable


@node 自定义安装,Distutils Configuration Files,Alternate Installation,安装Python模块（旧版）
@anchor{install/index custom-installation}@anchor{440c}@anchor{install/index inst-custom-install}@anchor{4402}
@section 自定义安装


Sometimes, the alternate installation schemes described in section
@ref{4401,,Alternate Installation} just don't do what you want.  You might want to tweak just
one or two directories while keeping everything under the same base directory,
or you might want to completely redefine the installation scheme.  In either
case, you're creating a @emph{custom installation scheme}.

To create a custom installation scheme, you start with one of the alternate
schemes and override some of the installation directories used for the various
types of files, using these options:


@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} 
@headitem

文件类型

@tab

覆盖选项

@item

Python 模块

@tab

@code{--install-purelib}

@item

扩展模块

@tab

@code{--install-platlib}

@item

所有模块

@tab

@code{--install-lib}

@item

脚本

@tab

@code{--install-scripts}

@item

数据

@tab

@code{--install-data}

@item

C 头文件

@tab

@code{--install-headers}

@end multitable


These override options can be relative, absolute,
or explicitly defined in terms of one of the installation base directories.
(There are two installation base directories, and they are normally the
same---they only differ when you use the Unix "prefix scheme" and supply
different @code{--prefix} and @code{--exec-prefix} options; using @code{--install-lib}
will override values computed or given for @code{--install-purelib} and
@code{--install-platlib}, and is recommended for schemes that don't make a
difference between Python and extension modules.)

For example, say you're installing a module distribution to your home directory
under Unix---but you want scripts to go in @code{~/scripts} rather than
@code{~/bin}. As you might expect, you can override this directory with the
@code{--install-scripts} option; in this case, it makes most sense to supply
a relative path, which will be interpreted relative to the installation base
directory (your home directory, in this case):

@example
python setup.py install --home=~ --install-scripts=scripts
@end example

Another Unix example: suppose your Python installation was built and installed
with a prefix of @code{/usr/local/python}, so under a standard  installation
scripts will wind up in @code{/usr/local/python/bin}.  If you want them in
@code{/usr/local/bin} instead, you would supply this absolute directory for the
@code{--install-scripts} option:

@example
python setup.py install --install-scripts=/usr/local/bin
@end example

(This performs an installation using the "prefix scheme", where the prefix is
whatever your Python interpreter was installed with--- @code{/usr/local/python}
in this case.)

If you maintain Python on Windows, you might want third-party modules to live in
a subdirectory of @code{@emph{prefix}}, rather than right in @code{@emph{prefix}}
itself.  This is almost as easy as customizing the script installation
directory---you just have to remember that there are two types of modules
to worry about, Python and extension modules, which can conveniently be both
controlled by one option:

@example
python setup.py install --install-lib=Site
@end example

The specified installation directory is relative to @code{@emph{prefix}}.  Of
course, you also have to ensure that this directory is in Python's module
search path, such as by putting a @code{.pth} file in a site directory (see
@ref{eb,,site}).  See section @ref{4407,,Modifying Python's Search Path} to find out how to modify
Python's search path.

If you want to define an entire installation scheme, you just have to supply all
of the installation directory options.  The recommended way to do this is to
supply relative paths; for example, if you want to maintain all Python
module-related files under @code{python} in your home directory, and you want a
separate directory for each platform that you use your home directory from, you
might define the following installation scheme:

@example
python setup.py install --home=~ \
                        --install-purelib=python/lib \
                        --install-platlib=python/lib.$PLAT \
                        --install-scripts=python/scripts
                        --install-data=python/data
@end example

或者，等价于

@example
python setup.py install --home=~/python \
                        --install-purelib=lib \
                        --install-platlib='lib.$PLAT' \
                        --install-scripts=scripts
                        --install-data=data
@end example

@code{$PLAT} is not (necessarily) an environment variable---it will be expanded by
the Distutils as it parses your command line options, just as it does when
parsing your configuration file(s).

Obviously, specifying the entire installation scheme every time you install a
new module distribution would be very tedious.  Thus, you can put these options
into your Distutils config file (see section @ref{43fe,,Distutils Configuration Files}):

@example
[install]
install-base=$HOME
install-purelib=python/lib
install-platlib=python/lib.$PLAT
install-scripts=python/scripts
install-data=python/data
@end example

或者，等价于，

@example
[install]
install-base=$HOME/python
install-purelib=lib
install-platlib=lib.$PLAT
install-scripts=scripts
install-data=data
@end example

Note that these two are @emph{not} equivalent if you supply a different installation
base directory when you run the setup script.  For example,

@example
python setup.py install --install-base=/tmp
@end example

would install pure modules to @code{/tmp/python/lib} in the first case, and
to @code{/tmp/lib} in the second case.  (For the second case, you probably
want to supply an installation base of @code{/tmp/python}.)

You probably noticed the use of @code{$HOME} and @code{$PLAT} in the sample
configuration file input.  These are Distutils configuration variables, which
bear a strong resemblance to environment variables. In fact, you can use
environment variables in config files on platforms that have such a notion but
the Distutils additionally define a few extra variables that may not be in your
environment, such as @code{$PLAT}.  (And of course, on systems that don't have
environment variables, such as Mac OS 9, the configuration variables supplied by
the Distutils are the only ones you can use.) See section @ref{43fe,,Distutils Configuration Files}
for details.

@cartouche
@quotation 注解 
When a @ref{359e,,virtual environment} is activated, any options
that change the installation path will be ignored from all distutils configuration
files to prevent inadvertently installing projects outside of the virtual
environment.
@end quotation
@end cartouche

@c XXX need some Windows examples---when would custom installation schemes be
@c needed on those platforms?

@c XXX Move this to Doc/using

@menu
* Modifying Python's Search Path:: 

@end menu

@node Modifying Python's Search Path,,,自定义安装
@anchor{install/index inst-search-path}@anchor{4407}@anchor{install/index modifying-python-s-search-path}@anchor{440d}
@subsection Modifying Python's Search Path


When the Python interpreter executes an @ref{c16,,import} statement, it searches
for both Python code and extension modules along a search path.  A default value
for the path is configured into the Python binary when the interpreter is built.
You can determine the path by importing the @ref{fd,,sys} module and printing the
value of @code{sys.path}.

@example
$ python
Python 2.2 (#11, Oct  3 2002, 13:31:27)
[GCC 2.96 20000731 (Red Hat Linux 7.3 2.96-112)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.path
['@w{'}, '/usr/local/lib/python2.3', '/usr/local/lib/python2.3/plat-linux2',
 '/usr/local/lib/python2.3/lib-tk', '/usr/local/lib/python2.3/lib-dynload',
 '/usr/local/lib/python2.3/site-packages']
>>>
@end example

The null string in @code{sys.path} represents the current working directory.

The expected convention for locally installed packages is to put them in the
@code{@emph{...}/site-packages/} directory, but you may want to install Python
modules into some arbitrary directory.  For example, your site may have a
convention of keeping all software related to the web server under @code{/www}.
Add-on Python modules might then belong in @code{/www/python}, and in order to
import them, this directory must be added to @code{sys.path}.  There are several
different ways to add the directory.

The most convenient way is to add a path configuration file to a directory
that's already on Python's path, usually to the @code{.../site-packages/}
directory.  Path configuration files have an extension of @code{.pth}, and each
line must contain a single path that will be appended to @code{sys.path}.  (Because
the new paths are appended to @code{sys.path}, modules in the added directories
will not override standard modules.  This means you can't use this mechanism for
installing fixed versions of standard modules.)

Paths can be absolute or relative, in which case they're relative to the
directory containing the @code{.pth} file.  See the documentation of
the @ref{eb,,site} module for more information.

A slightly less convenient way is to edit the @code{site.py} file in Python's
standard library, and modify @code{sys.path}.  @code{site.py} is automatically
imported when the Python interpreter is executed, unless the @ref{b1d,,-S} switch
is supplied to suppress this behaviour.  So you could simply edit
@code{site.py} and add two lines to it:

@example
import sys
sys.path.append('/www/python/')
@end example

However, if you reinstall the same major version of Python (perhaps when
upgrading from 2.2 to 2.2.2, for example) @code{site.py} will be overwritten by
the stock version.  You'd have to remember that it was modified and save a copy
before doing the installation.

There are two environment variables that can modify @code{sys.path}.
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} sets an alternate value for the prefix of the Python
installation.  For example, if 
@geindex PYTHONHOME
@geindex 环境变量; PYTHONHOME
@ref{4d0,,PYTHONHOME} is set to @code{/www/python},
the search path will be set to @code{['@w{'}, '/www/python/lib/pythonX.Y/',
'/www/python/lib/pythonX.Y/plat-linux2', ...]}.

The 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} variable can be set to a list of paths that will be
added to the beginning of @code{sys.path}.  For example, if 
@geindex PYTHONPATH
@geindex 环境变量; PYTHONPATH
@ref{94d,,PYTHONPATH} is
set to @code{/www/python:/opt/py}, the search path will begin with
@code{['/www/python', '/opt/py']}.  (Note that directories must exist in order to
be added to @code{sys.path}; the @ref{eb,,site} module removes paths that don't
exist.)

Finally, @code{sys.path} is just a regular Python list, so any Python application
can modify it by adding or removing entries.

@node Distutils Configuration Files,Building Extensions Tips and Tricks,自定义安装,安装Python模块（旧版）
@anchor{install/index distutils-configuration-files}@anchor{440e}@anchor{install/index inst-config-files}@anchor{43fe}
@section Distutils Configuration Files


As mentioned above, you can use Distutils configuration files to record personal
or site preferences for any Distutils options.  That is, any option to any
command can be stored in one of two or three (depending on your platform)
configuration files, which will be consulted before the command-line is parsed.
This means that configuration files will override default values, and the
command-line will in turn override configuration files.  Furthermore, if
multiple configuration files apply, values from "earlier" files are overridden
by "later" files.

@menu
* Location and names of config files:: 
* Syntax of config files:: 

@end menu

@node Location and names of config files,Syntax of config files,,Distutils Configuration Files
@anchor{install/index inst-config-filenames}@anchor{440f}@anchor{install/index location-and-names-of-config-files}@anchor{4410}
@subsection Location and names of config files


The names and locations of the configuration files vary slightly across
platforms.  On Unix and Mac OS X, the three configuration files (in the order
they are processed) are:


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

文件类型

@tab

位置和文件名

@tab

注释

@item

system

@tab

@code{@emph{prefix}/lib/python@emph{ver}/distutils/distutils.cfg}

@tab

(1)

@item

personal

@tab

@code{$HOME/.pydistutils.cfg}

@tab

(2)

@item

local

@tab

@code{setup.cfg}

@tab

(3)

@end multitable


And on Windows, the configuration files are:


@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxx} 
@headitem

文件类型

@tab

位置和文件名

@tab

注释

@item

system

@tab

@code{@emph{prefix}\Lib\distutils\distutils.cfg}

@tab

(4)

@item

personal

@tab

@code{%HOME%\pydistutils.cfg}

@tab

(5)

@item

local

@tab

@code{setup.cfg}

@tab

(3)

@end multitable


On all platforms, the "personal" file can be temporarily disabled by
passing the @cite{--no-user-cfg} option.

注释:


@enumerate 

@item 
Strictly speaking, the system-wide configuration file lives in the directory
where the Distutils are installed; under Python 1.6 and later on Unix, this is
as shown. For Python 1.5.2, the Distutils will normally be installed to
@code{@emph{prefix}/lib/python1.5/site-packages/distutils}, so the system
configuration file should be put there under Python 1.5.2.

@item 
On Unix, if the 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME} environment variable is not defined, the user's
home directory will be determined with the @code{getpwuid()} function from the
standard @ref{d6,,pwd} module. This is done by the @ref{1fe,,os.path.expanduser()}
function used by Distutils.

@item 
I.e., in the current directory (usually the location of the setup script).

@item 
(See also note (1).)  Under Python 1.6 and later, Python's default "installation
prefix" is @code{C:\Python}, so the system configuration file is normally
@code{C:\Python\Lib\distutils\distutils.cfg}. Under Python 1.5.2, the
default prefix was @code{C:\Program Files\Python}, and the Distutils were not
part of the standard library---so the system configuration file would be
@code{C:\Program Files\Python\distutils\distutils.cfg} in a standard Python
1.5.2 installation under Windows.

@item 
On Windows, if the 
@geindex HOME
@geindex 环境变量; HOME
@code{HOME} environment variable is not defined,
@geindex USERPROFILE
@geindex 环境变量; USERPROFILE
@code{USERPROFILE} then 
@geindex HOMEDRIVE
@geindex 环境变量; HOMEDRIVE
@code{HOMEDRIVE} and 
@geindex HOMEPATH
@geindex 环境变量; HOMEPATH
@code{HOMEPATH} will
be tried. This is done by the @ref{1fe,,os.path.expanduser()} function used
by Distutils.
@end enumerate

@node Syntax of config files,,Location and names of config files,Distutils Configuration Files
@anchor{install/index inst-config-syntax}@anchor{4329}@anchor{install/index syntax-of-config-files}@anchor{4411}
@subsection Syntax of config files


The Distutils configuration files all have the same syntax.  The config files
are grouped into sections.  There is one section for each Distutils command,
plus a @code{global} section for global options that affect every command.  Each
section consists of one option per line, specified as @code{option=value}.

For example, the following is a complete config file that just forces all
commands to run quietly by default:

@example
[global]
verbose=0
@end example

If this is installed as the system config file, it will affect all processing of
any Python module distribution by any user on the current system.  If it is
installed as your personal config file (on systems that support them), it will
affect only module distributions processed by you.  And if it is used as the
@code{setup.cfg} for a particular module distribution, it affects only that
distribution.

You could override the default "build base" directory and make the
@code{build*} commands always forcibly rebuild all files with the
following:

@example
[build]
build-base=blib
force=1
@end example

which corresponds to the command-line arguments

@example
python setup.py build --build-base=blib --force
@end example

except that including the @code{build} command on the command-line means
that command will be run.  Including a particular command in config files has no
such implication; it only means that if the command is run, the options in the
config file will apply.  (Or if other commands that derive values from it are
run, they will use the values in the config file.)

You can find out the complete list of options for any command using the
@code{--help} option, e.g.:

@example
python setup.py build --help
@end example

and you can find out the complete list of global options by using
@code{--help} without a command:

@example
python setup.py --help
@end example

See also the "Reference" section of the "Distributing Python Modules" manual.

@node Building Extensions Tips and Tricks,,Distutils Configuration Files,安装Python模块（旧版）
@anchor{install/index building-extensions-tips-and-tricks}@anchor{4412}@anchor{install/index inst-building-ext}@anchor{4413}
@section Building Extensions: Tips and Tricks


Whenever possible, the Distutils try to use the configuration information made
available by the Python interpreter used to run the @code{setup.py} script.
For example, the same compiler and linker flags used to compile Python will also
be used for compiling extensions.  Usually this will work well, but in
complicated situations this might be inappropriate.  This section discusses how
to override the usual Distutils behaviour.

@menu
* Tweaking compiler/linker flags:: 
* Using non-Microsoft compilers on Windows:: 

@end menu

@node Tweaking compiler/linker flags,Using non-Microsoft compilers on Windows,,Building Extensions Tips and Tricks
@anchor{install/index inst-tweak-flags}@anchor{4414}@anchor{install/index tweaking-compiler-linker-flags}@anchor{4415}
@subsection Tweaking compiler/linker flags


Compiling a Python extension written in C or C++ will sometimes require
specifying custom flags for the compiler and linker in order to use a particular
library or produce a special kind of object code. This is especially true if the
extension hasn't been tested on your platform, or if you're trying to
cross-compile Python.

In the most general case, the extension author might have foreseen that
compiling the extensions would be complicated, and provided a @code{Setup} file
for you to edit.  This will likely only be done if the module distribution
contains many separate extension modules, or if they often require elaborate
sets of compiler flags in order to work.

A @code{Setup} file, if present, is parsed in order to get a list of extensions
to build.  Each line in a @code{Setup} describes a single module.  Lines have
the following structure:

@example
module ... [sourcefile ...] [cpparg ...] [library ...]
@end example

Let's examine each of the fields in turn.


@itemize *

@item 
@emph{module} is the name of the extension module to be built, and should be a
valid Python identifier.  You can't just change this in order to rename a module
(edits to the source code would also be needed), so this should be left alone.

@item 
@emph{sourcefile} is anything that's likely to be a source code file, at least
judging by the filename.  Filenames ending in @code{.c} are assumed to be
written in C, filenames ending in @code{.C}, @code{.cc}, and @code{.c++} are
assumed to be C++, and filenames ending in @code{.m} or @code{.mm} are assumed
to be in Objective C.

@item 
@emph{cpparg} is an argument for the C preprocessor,  and is anything starting with
@code{-I}, @code{-D}, @code{-U} or @code{-C}.

@item 
@emph{library} is anything ending in @code{.a} or beginning with @code{-l} or
@code{-L}.
@end itemize

If a particular platform requires a special library on your platform, you can
add it by editing the @code{Setup} file and running @code{python setup.py build}.
For example, if the module defined by the line

@example
foo foomodule.c
@end example

must be linked with the math library @code{libm.a} on your platform, simply add
@code{-lm} to the line:

@example
foo foomodule.c -lm
@end example

Arbitrary switches intended for the compiler or the linker can be supplied with
the @code{-Xcompiler} @emph{arg} and @code{-Xlinker} @emph{arg} options:

@example
foo foomodule.c -Xcompiler -o32 -Xlinker -shared -lm
@end example

The next option after @code{-Xcompiler} and @code{-Xlinker} will be
appended to the proper command line, so in the above example the compiler will
be passed the @code{-o32} option, and the linker will be passed
@code{-shared}.  If a compiler option requires an argument, you'll have to
supply multiple @code{-Xcompiler} options; for example, to pass @code{-x c++}
the @code{Setup} file would have to contain @code{-Xcompiler -x -Xcompiler c++}.

Compiler flags can also be supplied through setting the 
@geindex CFLAGS
@geindex 环境变量; CFLAGS
@code{CFLAGS}
environment variable.  If set, the contents of 
@geindex CFLAGS
@geindex 环境变量; CFLAGS
@code{CFLAGS} will be added to
the compiler flags specified in the  @code{Setup} file.

@node Using non-Microsoft compilers on Windows,,Tweaking compiler/linker flags,Building Extensions Tips and Tricks
@anchor{install/index inst-non-ms-compilers}@anchor{4416}@anchor{install/index using-non-microsoft-compilers-on-windows}@anchor{4417}
@subsection Using non-Microsoft compilers on Windows


@menu
* Borland/CodeGear C++:: 
* GNU C / Cygwin / MinGW:: 

@end menu

@node Borland/CodeGear C++,GNU C / Cygwin / MinGW,,Using non-Microsoft compilers on Windows
@anchor{install/index borland-codegear-c}@anchor{4418}
@subsubsection Borland/CodeGear C++


This subsection describes the necessary steps to use Distutils with the Borland
C++ compiler version 5.5.  First you have to know that Borland's object file
format (OMF) is different from the format used by the Python version you can
download from the Python or ActiveState Web site.  (Python is built with
Microsoft Visual C++, which uses COFF as the object file format.) For this
reason you have to convert Python's library @code{python25.lib} into the
Borland format.  You can do this as follows:

@c Should we mention that users have to create cfg-files for the compiler?

@c see also http://community.borland.com/article/0,1410,21205,00.html

@example
coff2omf python25.lib python25_bcpp.lib
@end example

The @code{coff2omf} program comes with the Borland compiler.  The file
@code{python25.lib} is in the @code{Libs} directory of your Python
installation.  If your extension uses other libraries (zlib, ...) you have to
convert them too.

The converted files have to reside in the same directories as the normal
libraries.

How does Distutils manage to use these libraries with their changed names?  If
the extension needs a library (eg. @code{foo}) Distutils checks first if it
finds a library with suffix @code{_bcpp} (eg. @code{foo_bcpp.lib}) and then
uses this library.  In the case it doesn't find such a special library it uses
the default name (@code{foo.lib}.) @footnote{@w{(1)} 
This also means you could replace all existing COFF-libraries with OMF-libraries
of the same name.
}

To let Distutils compile your extension with Borland C++ you now have to type:

@example
python setup.py build --compiler=bcpp
@end example

If you want to use the Borland C++ compiler as the default, you could specify
this in your personal or system-wide configuration file for Distutils (see
section @ref{43fe,,Distutils Configuration Files}.)


@subsubheading 参见



@table @asis

@item C++Builder Compiler@footnote{https://www.embarcadero.com/products}

Information about the free C++ compiler from Borland, including links to the
download pages.

@item Creating Python Extensions Using Borland's Free Compiler@footnote{http://www.cyberus.ca/~g_will/pyExtenDL.shtml}

Document describing how to use Borland's free command-line C++ compiler to build
Python.
@end table


@node GNU C / Cygwin / MinGW,,Borland/CodeGear C++,Using non-Microsoft compilers on Windows
@anchor{install/index gnu-c-cygwin-mingw}@anchor{4419}
@subsubsection GNU C / Cygwin / MinGW


This section describes the necessary steps to use Distutils with the GNU C/C++
compilers in their Cygwin and MinGW distributions. @footnote{@w{(2)} 
欲了解更多信息，请查阅 @indicateurl{https://www.sourceware.org/cygwin/} 和 @indicateurl{http://www.mingw.org/}
} For a Python interpreter
that was built with Cygwin, everything should work without any of these
following steps.

Not all extensions can be built with MinGW or Cygwin, but many can.  Extensions
most likely to not work are those that use C++ or depend on Microsoft Visual C
extensions.

To let Distutils compile your extension with Cygwin you have to type:

@example
python setup.py build --compiler=cygwin
@end example

and for Cygwin in no-cygwin mode @footnote{@w{(3)} 
Then you have no POSIX emulation available, but you also don't need
@code{cygwin1.dll}.
} or for MinGW type:

@example
python setup.py build --compiler=mingw32
@end example

If you want to use any of these options/compilers as default, you should
consider writing it in your personal or system-wide configuration file for
Distutils (see section @ref{43fe,,Distutils Configuration Files}.)

@menu
* Older Versions of Python and MinGW:: 

@end menu

@node Older Versions of Python and MinGW,,,GNU C / Cygwin / MinGW
@anchor{install/index older-versions-of-python-and-mingw}@anchor{441a}
@subsubsection Older Versions of Python and MinGW


The following instructions only apply if you're using a version of Python
inferior to 2.4.1 with a MinGW inferior to 3.0.0 (with
binutils-2.13.90-20030111-1).

These compilers require some special libraries.  This task is more complex than
for Borland's C++, because there is no program to convert the library.  First
you have to create a list of symbols which the Python DLL exports. (You can find
a good program for this task at
@indicateurl{https://sourceforge.net/projects/mingw/files/MinGW/Extension/pexports/}).

@c I don't understand what the next line means. --amk

@c (inclusive the references on data structures.)

@example
pexports python25.dll >python25.def
@end example

The location of an installed @code{python25.dll} will depend on the
installation options and the version and language of Windows.  In a "just for
me" installation, it will appear in the root of the installation directory.  In
a shared installation, it will be located in the system directory.

Then you can create from these information an import library for gcc.

@example
/cygwin/bin/dlltool --dllname python25.dll --def python25.def --output-lib libpython25.a
@end example

The resulting library has to be placed in the same directory as
@code{python25.lib}. (Should be the @code{libs} directory under your Python
installation directory.)

If your extension uses other libraries (zlib,...) you might  have to convert
them too. The converted files have to reside in the same directories as the
normal libraries do.


@subsubheading 参见



@table @asis

@item Building Python modules on MS Windows platform with MinGW@footnote{http://old.zope.org/Members/als/tips/win32_mingw_modules}

Information about building the required libraries for the MinGW environment.
@end table


@subsubheading 备注


@node Python 模块索引,索引,安装Python模块（旧版）,Top
@unnumbered Python 模块索引


@menu
* __future__: 0. Future statement definitions
* __main__: 1. The environment where the top-level script is run.
* _dummy_thread: 2. Drop-in replacement for the _thread module.
* _thread: 3. Low-level threading API.
* abc: 4. Abstract base classes according to :pep:`3119`.
* aifc: 5. Read and write audio files in AIFF or AIFC format.
* argparse: 6. Command-line option and argument parsing library.
* array: 7. Space efficient arrays of uniformly typed numeric
                        values.
* ast: 8. Abstract Syntax Tree classes and manipulation.
* asynchat: 9. Support for asynchronous command/response protocols.
* asyncio: a. Asynchronous I/O.
* asyncore: b. A base class for developing asynchronous socket
                        handling services.
* atexit: c. Register and execute cleanup functions.
* audioop: d. Manipulate raw audio data.
* base64: e. RFC 3548: Base16@comma{} Base32@comma{} Base64 Data
                        Encodings; Base85 and Ascii85
* bdb: f. Debugger framework.
* binascii: 10. Tools for converting between binary and various ASCII-
                        encoded binary representations.
* binhex: 11. Encode and decode files in binhex4 format.
* bisect: 12. Array bisection algorithms for binary searching.
* builtins: 13. The module that provides the built-in namespace.
* bz2: 14. Interfaces for bzip2 compression and decompression.
* calendar: 15. Functions for working with calendars@comma{} including
                        some emulation of the Unix cal program.
* cgi: 16. Helpers for running Python scripts via the Common
                        Gateway Interface.
* cgitb: 17. Configurable traceback handler for CGI scripts.
* chunk: 18. Module to read IFF chunks.
* cmath: 19. Mathematical functions for complex numbers.
* cmd: 1a. Build line-oriented command interpreters.
* code: 1b. Facilities to implement read-eval-print loops.
* codecs: 1c. Encode and decode data and streams.
* codeop: 1d. Compile (possibly incomplete) Python code.
* collections: 1e. Container datatypes
* collections.abc: 1f. Abstract base classes for containers
* colorsys: 20. Conversion functions between RGB and other color
                        systems.
* compileall: 21. Tools for byte-compiling all Python source files in a
                        directory tree.
* concurrent.futures: 22. Execute computations concurrently using threads or
                        processes.
* configparser: 23. Configuration file parser.
* contextlib: 24. Utilities for with-statement contexts.
* contextvars: 25. Context Variables
* copy: 26. Shallow and deep copy operations.
* copyreg: 27. Register pickle support functions.
* cProfile: 28. 
* crypt: 29. The crypt() function used to check Unix passwords.
* csv: 2a. Write and read tabular data to and from delimited
                        files.
* ctypes: 2b. A foreign function library for Python.
* curses: 2c. An interface to the curses library@comma{} providing
                        portable terminal handling.
* curses.ascii: 2d. Constants and set-membership functions for ASCII
                        characters.
* curses.panel: 2e. A panel stack extension that adds depth to curses
                        windows.
* curses.textpad: 2f. Emacs-like input editing in a curses window.
* dataclasses: 30. Generate special methods on user-defined classes.
* datetime: 31. Basic date and time types.
* dbm: 32. Interfaces to various Unix "database" formats.
* dbm.dumb: 33. Portable implementation of the simple DBM interface.
* dbm.gnu: 34. GNU's reinterpretation of dbm.
* dbm.ndbm: 35. The standard "database" interface@comma{} based on
                        ndbm.
* decimal: 36. Implementation of the General Decimal Arithmetic
                        Specification.
* difflib: 37. Helpers for computing differences between objects.
* dis: 38. Disassembler for Python bytecode.
* distutils: 39. Support for building and installing Python modules
                        into an existing Python installation.
* distutils.archive_util: 3a. Utility functions for creating archive files
                          (tarballs@comma{} zip files@comma{} ...)
* distutils.bcppcompiler: 3b. 
* distutils.ccompiler: 3c. Abstract CCompiler class
* distutils.cmd: 3d. Provides the abstract base class
                        :class:`~distutils.cmd.Command`. This class is
                        subclassed by the modules in the distutils.command
                        subpackage.
* distutils.command: 3e. Contains one module for each standard Distutils
                        command.
* distutils.command.bdist: 3f. Build a binary installer for a package
* distutils.command.bdist_dumb: 40. Build a "dumb" installer - a simple archive of
                                files
* distutils.command.bdist_msi: 41. Build a binary distribution as a Windows MSI
                               file
* distutils.command.bdist_packager: 42. Abstract base class for packagers
* distutils.command.bdist_rpm: 43. Build a binary distribution as a Redhat RPM and
                               SRPM
* distutils.command.bdist_wininst: 44. Build a Windows installer
* distutils.command.build: 45. Build all files of a package
* distutils.command.build_clib: 46. Build any C libraries in a package
* distutils.command.build_ext: 47. Build any extensions in a package
* distutils.command.build_py: 48. Build the .py/.pyc files of a package
* distutils.command.build_scripts: 49. Build the scripts of a package
* distutils.command.check: 4a. Check the meta-data of a package
* distutils.command.clean: 4b. Clean a package build area
* distutils.command.config: 4c. Perform package configuration
* distutils.command.install: 4d. Install a package
* distutils.command.install_data: 4e. Install data files from a package
* distutils.command.install_headers: 4f. Install C/C++ header files from a package
* distutils.command.install_lib: 50. Install library files from a package
* distutils.command.install_scripts: 51. Install script files from a package
* distutils.command.register: 52. Register a module with the Python Package Index
* distutils.command.sdist: 53. Build a source distribution
* distutils.core: 54. The core Distutils functionality
* distutils.cygwinccompiler: 55. 
* distutils.debug: 56. Provides the debug flag for distutils
* distutils.dep_util: 57. Utility functions for simple dependency checking
* distutils.dir_util: 58. Utility functions for operating on directories and
                        directory trees
* distutils.dist: 59. Provides the Distribution class@comma{} which
                        represents the module distribution being
                        built/installed/distributed
* distutils.errors: 5a. Provides standard distutils exceptions
* distutils.extension: 5b. Provides the Extension class@comma{} used to describe
                        C/C++ extension modules in setup scripts
* distutils.fancy_getopt: 5c. Additional getopt functionality
* distutils.file_util: 5d. Utility functions for operating on single files
* distutils.filelist: 5e. The FileList class@comma{} used for poking about the
                        file system and building lists of files.
* distutils.log: 5f. A simple logging mechanism@comma{} :pep:`282`-style
* distutils.msvccompiler: 60. Microsoft Compiler
* distutils.spawn: 61. Provides the spawn() function
* distutils.sysconfig: 62. Low-level access to configuration information of the
                        Python interpreter.
* distutils.text_file: 63. Provides the TextFile class@comma{} a simple interface
                        to text files
* distutils.unixccompiler: 64. UNIX C Compiler
* distutils.util: 65. Miscellaneous other utility functions
* distutils.version: 66. Implements classes that represent module version
                        numbers.
* doctest: 67. Test pieces of code within docstrings.
* dummy_threading: 68. Drop-in replacement for the threading module.
* email: 69. Package supporting the parsing@comma{}
                        manipulating@comma{} and generating email messages.
* email.charset: 6a. Character Sets
* email.contentmanager: 6b. Storing and Retrieving Content from MIME Parts
* email.encoders: 6c. Encoders for email message payloads.
* email.errors: 6d. The exception classes used by the email package.
* email.generator: 6e. Generate flat text email messages from a message
                        structure.
* email.header: 6f. Representing non-ASCII headers
* email.headerregistry: 70. Automatic Parsing of headers based on the field name
* email.iterators: 71. Iterate over a message object tree.
* email.message: 72. The base class representing email messages.
* email.mime: 73. Build MIME messages.
* email.parser: 74. Parse flat text email messages to produce a message
                        object structure.
* email.policy: 75. Controlling the parsing and generating of messages
* email.utils: 76. Miscellaneous email package utilities.
* encodings.idna: 77. Internationalized Domain Names implementation
* encodings.mbcs: 78. Windows ANSI codepage
* encodings.utf_8_sig: 79. UTF-8 codec with BOM signature
* ensurepip: 7a. Bootstrapping the "pip" installer into an existing
                        Python installation or virtual environment.
* enum: 7b. Implementation of an enumeration class.
* errno: 7c. Standard errno system symbols.
* faulthandler: 7d. Dump the Python traceback.
* fcntl: 7e. The fcntl() and ioctl() system calls.
* filecmp: 7f. Compare files efficiently.
* fileinput: 80. Loop over standard input or a list of files.
* fnmatch: 81. Unix shell style filename pattern matching.
* formatter: 82. Generic output formatter and device interface.
* fractions: 83. Rational numbers.
* ftplib: 84. FTP protocol client (requires sockets).
* functools: 85. Higher-order functions and operations on callable
                        objects.
* gc: 86. Interface to the cycle-detecting garbage collector.
* getopt: 87. Portable parser for command line options; support both
                        short and long option names.
* getpass: 88. Portable reading of passwords and retrieval of the
                        userid.
* gettext: 89. Multilingual internationalization services.
* glob: 8a. Unix shell style pathname pattern expansion.
* grp: 8b. The group database (getgrnam() and friends).
* gzip: 8c. Interfaces for gzip compression and decompression
                        using file objects.
* hashlib: 8d. Secure hash and message digest algorithms.
* heapq: 8e. Heap queue algorithm (a.k.a. priority queue).
* hmac: 8f. Keyed-Hashing for Message Authentication (HMAC)
                        implementation
* html: 90. Helpers for manipulating HTML.
* html.entities: 91. Definitions of HTML general entities.
* html.parser: 92. A simple parser that can handle HTML and XHTML.
* http: 93. HTTP status codes and messages
* http.client: 94. HTTP and HTTPS protocol client (requires sockets).
* http.cookiejar: 95. Classes for automatic handling of HTTP cookies.
* http.cookies: 96. Support for HTTP state management (cookies).
* http.server: 97. HTTP server and request handlers.
* imaplib: 98. IMAP4 protocol client (requires sockets).
* imghdr: 99. Determine the type of image contained in a file or
                        byte stream.
* imp: 9a. Access the implementation of the import statement.
* importlib: 9b. The implementation of the import machinery.
* importlib.abc: 9c. Abstract base classes related to import
* importlib.machinery: 9d. Importers and path hooks
* importlib.resources: 9e. Package resource reading@comma{} opening@comma{} and
                        access
* importlib.util: 9f. Utility code for importers
* inspect: a0. Extract information and source code from live objects.
* io: a1. Core tools for working with streams.
* ipaddress: a2. IPv4/IPv6 manipulation library.
* itertools: a3. Functions creating iterators for efficient looping.
* json: a4. Encode and decode the JSON format.
* json.tool: a5. A command line to validate and pretty-print JSON.
* keyword: a6. Test whether a string is a keyword in Python.
* lib2to3: a7. The 2to3 library
* linecache: a8. Provides random access to individual lines from text
                        files.
* locale: a9. Internationalization services.
* logging: aa. Flexible event logging system for applications.
* logging.config: ab. Configuration of the logging module.
* logging.handlers: ac. Handlers for the logging module.
* lzma: ad. A Python wrapper for the liblzma compression library.
* mailbox: ae. Manipulate mailboxes in various formats
* mailcap: af. Mailcap file handling.
* marshal: b0. Convert Python objects to streams of bytes and back
                        (with different constraints).
* math: b1. Mathematical functions (sin() etc.).
* mimetypes: b2. Mapping of filename extensions to MIME types.
* mmap: b3. Interface to memory-mapped files for Unix and Windows.
* modulefinder: b4. Find modules used by a script.
* msilib: b5. Creation of Microsoft Installer files@comma{} and CAB
                        files.
* msvcrt: b6. Miscellaneous useful routines from the MS VC++
                        runtime.
* multiprocessing: b7. Process-based parallelism.
* multiprocessing.connection: b8. API for dealing with sockets.
* multiprocessing.dummy: b9. Dumb wrapper around threading.
* multiprocessing.managers: ba. Share data between process with shared objects.
* multiprocessing.pool: bb. Create pools of processes.
* multiprocessing.shared_memory: bc. Provides shared memory for direct access
                                 across processes.
* multiprocessing.sharedctypes: bd. Allocate ctypes objects from shared memory.
* netrc: be. Loading of .netrc files.
* nis: bf. Interface to Sun's NIS (Yellow Pages) library.
* nntplib: c0. NNTP protocol client (requires sockets).
* numbers: c1. Numeric abstract base classes (Complex@comma{}
                        Real@comma{} Integral@comma{} etc.).
* operator: c2. Functions corresponding to the standard operators.
* optparse: c3. Command-line option parsing library.
* os: c4. Miscellaneous operating system interfaces.
* os.path: c5. Operations on pathnames.
* ossaudiodev: c6. Access to OSS-compatible audio devices.
* parser: c7. Access parse trees for Python source code.
* pathlib: c8. Object-oriented filesystem paths
* pdb: c9. The Python debugger for interactive interpreters.
* pickle: ca. Convert Python objects to streams of bytes and back.
* pickletools: cb. Contains extensive comments about the pickle protocols
                        and pickle-machine opcodes@comma{} as well as some
                        useful functions.
* pipes: cc. A Python interface to Unix shell pipelines.
* pkgutil: cd. Utilities for the import system.
* platform: ce. Retrieves as much platform identifying data as
                        possible.
* plistlib: cf. Generate and parse Mac OS X plist files.
* poplib: d0. POP3 protocol client (requires sockets).
* posix: d1. The most common POSIX system calls (normally used via
                        module os).
* pprint: d2. Data pretty printer.
* profile: d3. Python source profiler.
* pstats: d4. Statistics object for use with the profiler.
* pty: d5. Pseudo-Terminal Handling for Linux.
* pwd: d6. The password database (getpwnam() and friends).
* py_compile: d7. Generate byte-code files from Python source files.
* pyclbr: d8. Supports information extraction for a Python module
                        browser.
* pydoc: d9. Documentation generator and online help system.
* queue: da. A synchronized queue class.
* quopri: db. Encode and decode files using the MIME quoted-
                        printable encoding.
* random: dc. Generate pseudo-random numbers with various common
                        distributions.
* re: dd. Regular expression operations.
* readline: de. GNU readline support for Python.
* reprlib: df. Alternate repr() implementation with size limits.
* resource: e0. An interface to provide resource usage information on
                        the current process.
* rlcompleter: e1. Python identifier completion@comma{} suitable for the
                        GNU readline library.
* runpy: e2. Locate and run Python modules without importing them
                        first.
* sched: e3. General purpose event scheduler.
* secrets: e4. Generate secure random numbers for managing secrets.
* select: e5. Wait for I/O completion on multiple streams.
* selectors: e6. High-level I/O multiplexing.
* shelve: e7. Python object persistence.
* shlex: e8. Simple lexical analysis for Unix shell-like languages.
* shutil: e9. High-level file operations@comma{} including copying.
* signal: ea. Set handlers for asynchronous events.
* site: eb. Module responsible for site-specific configuration.
* smtpd: ec. A SMTP server implementation in Python.
* smtplib: ed. SMTP protocol client (requires sockets).
* sndhdr: ee. Determine type of a sound file.
* socket: ef. Low-level networking interface.
* socketserver: f0. A framework for network servers.
* spwd: f1. The shadow password database (getspnam() and friends).
* sqlite3: f2. A DB-API 2.0 implementation using SQLite 3.x.
* ssl: f3. TLS/SSL wrapper for socket objects
* stat: f4. Utilities for interpreting the results of
                        os.stat()@comma{} os.lstat() and os.fstat().
* statistics: f5. Mathematical statistics functions
* string: f6. Common string operations.
* stringprep: f7. String preparation@comma{} as per RFC 3453
* struct: f8. Interpret bytes as packed binary data.
* subprocess: f9. Subprocess management.
* sunau: fa. Provide an interface to the Sun AU sound format.
* symbol: fb. Constants representing internal nodes of the parse
                        tree.
* symtable: fc. Interface to the compiler's internal symbol tables.
* sys: fd. Access system-specific parameters and functions.
* sysconfig: fe. Python's configuration information
* syslog: ff. An interface to the Unix syslog library routines.
* tabnanny: 100. Tool for detecting white space related problems in
                        Python source files in a directory tree.
* tarfile: 101. Read and write tar-format archive files.
* telnetlib: 102. Telnet client class.
* tempfile: 103. Generate temporary files and directories.
* termios: 104. POSIX style tty control.
* test: 105. Regression tests package containing the testing suite
                        for Python.
* test.support: 106. Support for Python's regression test suite.
* test.support.script_helper: 107. Support for Python's script execution tests.
* textwrap: 108. Text wrapping and filling
* threading: 109. Thread-based parallelism.
* time: 10a. Time access and conversions.
* timeit: 10b. Measure the execution time of small code snippets.
* tkinter: 10c. Interface to Tcl/Tk for graphical user interfaces
* tkinter.scrolledtext: 10d. Text widget with a vertical scroll bar.
* tkinter.tix: 10e. Tk Extension Widgets for Tkinter
* tkinter.ttk: 10f. Tk themed widget set
* token: 110. Constants representing terminal nodes of the parse
                        tree.
* tokenize: 111. Lexical scanner for Python source code.
* trace: 112. Trace or track Python statement execution.
* traceback: 113. Print or retrieve a stack traceback.
* tracemalloc: 114. Trace memory allocations.
* tty: 115. Utility functions that perform common terminal control
                        operations.
* turtle: 116. An educational framework for simple graphics
                        applications
* turtledemo: 117. A viewer for example turtle scripts
* types: 118. Names for built-in types.
* typing: 119. Support for type hints (see :pep:`484`).
* unicodedata: 11a. Access the Unicode Database.
* unittest: 11b. Unit testing framework for Python.
* unittest.mock: 11c. Mock object library.
* urllib: 11d. 
* urllib.error: 11e. Exception classes raised by urllib.request.
* urllib.parse: 11f. Parse URLs into or assemble them from components.
* urllib.request: 120. Extensible library for opening URLs.
* urllib.response: 121. Response classes used by urllib.
* urllib.robotparser: 122. Load a robots.txt file and answer questions about
                        fetchability of other URLs.
* uu: 123. Encode and decode files in uuencode format.
* uuid: 124. UUID objects (universally unique identifiers)
                        according to RFC 4122
* venv: 125. Creation of virtual environments.
* warnings: 126. Issue warning messages and control their disposition.
* wave: 127. Provide an interface to the WAV sound format.
* weakref: 128. Support for weak references and weak dictionaries.
* webbrowser: 129. Easy-to-use controller for Web browsers.
* winreg: 12a. Routines and objects for manipulating the Windows
                        registry.
* winsound: 12b. Access to the sound-playing machinery for Windows.
* wsgiref: 12c. WSGI Utilities and Reference Implementation.
* wsgiref.handlers: 12d. WSGI server/gateway base classes.
* wsgiref.headers: 12e. WSGI response header tools.
* wsgiref.simple_server: 12f. A simple WSGI HTTP server.
* wsgiref.util: 130. WSGI environment utilities.
* wsgiref.validate: 131. WSGI conformance checker.
* xdrlib: 132. Encoders and decoders for the External Data
                        Representation (XDR).
* xml: 133. Package containing XML processing modules
* xml.dom: 134. Document Object Model API for Python.
* xml.dom.minidom: 135. Minimal Document Object Model (DOM) implementation.
* xml.dom.pulldom: 136. Support for building partial DOM trees from SAX
                        events.
* xml.etree.ElementTree: 137. Implementation of the ElementTree API.
* xml.parsers.expat: 138. An interface to the Expat non-validating XML parser.
* xml.parsers.expat.errors: 139. 
* xml.parsers.expat.model: 13a. 
* xml.sax: 13b. Package containing SAX2 base classes and convenience
                        functions.
* xml.sax.handler: 13c. Base classes for SAX event handlers.
* xml.sax.saxutils: 13d. Convenience functions and classes for use with SAX.
* xml.sax.xmlreader: 13e. Interface which SAX-compliant XML parsers must
                        implement.
* xmlrpc.client: 13f. XML-RPC client access.
* xmlrpc.server: 140. Basic XML-RPC server implementations.
* zipapp: 141. Manage executable Python zip archives
* zipfile: 142. Read and write ZIP-format archive files.
* zipimport: 143. Support for importing Python modules from ZIP
                        archives.
* zlib: 144. Low-level interface to compression and decompression
                        routines compatible with gzip.
@end menu


@node 索引,,Python 模块索引,Top
@unnumbered 索引


@printindex ge

@anchor{library/types CodeType}@w{                              }
@anchor{346e}@w{                              }
@anchor{library/ctypes ctype-foreign-functions}@w{                              }
@anchor{howto/urllib2 basic-authentication}@w{                              }
@anchor{3469}@w{                              }
@anchor{using/cmdline PYTHONSTARTUP}@w{                              }
@anchor{library/poplib popplib POP3_SSL}@w{                              }
@anchor{346f}@w{                              }
@anchor{346c}@w{                              }
@anchor{3475}@w{                              }
@anchor{using/cmdline audit_event_cpython_run_file_0}@w{                              }
@anchor{4192}@w{                              }
@anchor{using/cmdline audit_event_cpython_run_stdin_0}@w{                              }
@anchor{346d}@w{                              }

@c %**end of body
@bye
